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This paper provides a holistic view of the different studies related to gassing in NMC/graphite lithium-ion batteries over the past couple of decades of scientific development. It underlines the difficulty of predicting the concentration and the proportion of gas released upon cycling and storage and to get a clear mechanistic insight into the reduction and oxidation pathways of electrolyte solvents, the thermal electrolyte degradation, as well as the reactions that involve secondary sources such as water, NMC surface species and cross-talk reactions. Though many relevant experiments such as operando gas analysis using isotope-labeled solvents or two-compartment cells have been conducted, they failed, for instance, to determine the exact mechanism leading to the generation of CO and CO2 gas. Last but not least, this paper discusses different strategies that are currently proposed to reduce or eliminate gassing such as the use of electrolyte additives that enable singlet oxygen quenching or scavenging, NMC coatings that limit the contact with electrolyte and different lithium salts to prevent thermal electrolyte degradation.

Lithium-ion batteries (LIBs) have become ubiquitous power sources for small electronic devices, electric vehicles, and stationary energy storage systems. Despite the success of LIBs which is acknowledged by their increasing commodity market, the historical evolution of the chemistry behind the LIB technologies is laden with obstacles and yet to be unambiguously documented. This Viewpoint outlines chronologically the most essential findings related to today's LIBs, including commercial electrode and electrolyte materials, but furthermore also depicts how the today popular and widely emerging solid-state batteries were instrumental at very early stages in the development of LIBs.

With the aim of establishing a data simultaneous comparison, the Principal Component Analysis (PCA) statistical tool was applied to LiNi0.6Mn0.2Co0.2O2/graphite Li-ion cells electrolyte’s decomposition products detected by UHPLC-ESI-HRMS. Herein, we illustrate how the chemometric tool associated with mass spectrometry data can be relevant to provide information about the presence of unusual molecules. Indeed, pristine Triton X-100 surfactant molecules used in the electrode elaboration process were detected after the impregnation stage. However, as they chemically react and oxidize at a potential lower than 4.5 V vs Li/Li+, only surfactant derivatives and classical ageing molecules were observed, respectively, after storage and cycling stages at 55 °C, leading to a triangle-type correlation circle. On the other hand, global schemes of LiPF6-based electrolyte degradation pathways were elaborated from a comparative study with literature to help interpret results in future electrolyte ageing studies.

Motivated by the request to build shape-conformable flexible, wearable and customizable batteries while maximizing the energy storage and electrochemical performances, additive manufacturing (AM) appears as a revolutionary discipline. Battery components such as electrodes, separator, electrolyte, current collectors and casing can be tailored with any shape, allowing the direct incorporation of batteries and all electronics within the final three-dimensional object. AM also paves the way toward the implementation of complex 3D electrode architectures that could enhance significantly the power battery performances. Transitioning from conventional 2D to complex 3D lithium-ion battery (LIB) architectures will increase the electrochemically active surface area, enhance the Li+ diffusion paths, thus leading to improved specific capacity and power performance [1]. Our recent modeling studies [2] involving the simulation of a classical Ragone plot illustrated that a gyroid 3D battery architecture has +158% performance at a high current density of 6C, in comparison to planar geometry. In this presentation, an overview of current trends in energy storage 3D printing will be discussed [3-11]. A summary of our recent works on lithium-ion battery 3D printing via Thermoplastic Material Extrusion / Fused Deposition Modeling will be presented [12-16]. The development of printable composite filaments (Graphite-, LiFePO4-, Li2TP-, PEO/LiTFSI-, SiO2-, Ag/Cu-based) corresponding to each part of a LIB (electrodes, electrolyte, separator, current collectors), and the importance of introducing a plasticizer (polyethylene glycol dimethyl ether average Mn 500 for polylactic acid) as an additive to enhance the printability will be addressed. Printing of the complete LIB in a single step using multi-material printing options, and the implementation of a solvent-free protocol [14] will also be discussed. Second part of this presentation will be dedicated to AM of batteries by means of Vat Photopolymerization (VPP) processes, including stereolithography, digital light processing and two-photon polymerization (offering a greater resolution down to 0.1μm), to print high resolution battery components [10]. Composite resins formulation approaches based on the introduction of solid battery particles or precursor salts will be introduced [17, 18]. Finally, an overview of our ongoing project dedicated to AM of sodium-ion batteries from resources available on the Moon and Mars will be presented. Due to its relative abundance in the Lunar regolith, the development of a composite photocurable resin loaded with TiO2 negative electrode material and conductive additives, to feed a VPP printer, will be discussed [18]. [1] Long et al., Three-dimensional battery architectures, Chemical Reviews 104(10) (2004) 4463-4492. [2] Maurel et al., Considering lithium-ion battery 3D-printing via thermoplastic material extrusion and polymer powder bed fusion, Additive Manufacturing (2020) 101651. [3] Maurel et al., Overview on Lithium-Ion Battery 3D-Printing By Means of Material Extrusion, ECS Transactions 98(13) (2020) 3-21. [4] Ragones et al., Towards smart free form-factor 3D printable batteries, Sustainable Energy & Fuels 2(7) (2018) 1542-1549. [5] Reyes et al., Three-Dimensional Printing of a Complete Lithium Ion Battery with Fused Filament Fabrication, ACS Applied Energy Materials 1(10) (2018) 5268-5279. [6] Yee et al., Hydrogel-Based Additive Manufacturing of Lithium Cobalt Oxide, Advanced Materials Technologies 6(2) (2021). [7] Saccone et al., Understanding and mitigating mechanical degradation in lithium–sulfur batteries: additive manufacturing of Li2S composites and nanomechanical particle compressions, Journal of Materials Research (2021). [8] Tagliaferri et al., Direct ink writing of energy materials, Materials Advances 2(2) (2021) 25. [9] Sun et al., 3D Printing of Interdigitated Li-Ion Microbattery Architectures, Advanced Materials 25(33) (2013) 4539-4543. [10] Maurel et al., Toward High Resolution 3D Printing of Shape-Conformable Batteries via Vat Photopolymerization: Review and Perspective, IEEE Access 9 (2021) 140654-140666. [11] Seol et al., All-Printed In-Plane Supercapacitors by Sequential Additive Manufacturing Process, Acs Applied Energy Materials 3(5) (2020) 4965-4973. [12] Maurel et al., Highly Loaded Graphite-Polylactic Acid Composite-Based Filaments for Lithium-Ion Battery Three-Dimensional Printing, Chemistry of Materials 30(21) (2018) 7484-7493. [13] Maurel et al., Three-Dimensional Printing of a LiFePO4/Graphite Battery Cell via Fused Deposition Modeling, Scientific Reports 9(1) (2019) 18031. [14] Maurel et al., Environmentally Friendly Lithium-Terephthalate/Polylactic Acid Composite Filament Formulation for Lithium-Ion Battery 3D-Printing via Fused Deposition Modeling, ECS Journal of Solid State Science and Technology 10(3) (2021) 037004. [15] Maurel et al., Poly(Ethylene Oxide)-LiTFSI Solid Polymer Electrolyte Filaments for Fused Deposition Modeling Three-Dimensional Printing, Journal of the Electrochemical Society 167(7) (2020). [16] Maurel et al., Ag-Coated Cu/Polylactic Acid Composite Filament for Lithium and Sodium-Ion Battery Current Collector Three-Dimensional Printing via Thermoplastic Material Extrusion, Frontiers in Energy Research 9(70) (2021). [17] Martinez et al., Additive Manufacturing of LiNi1/3Mn1/3Co1/3O2 battery electrode material via vat photopolymerization precursor approach, (submitted). [18] Maurel et al., Vat Photopolymerization Additive Manufacturing of Sodium-Ion Battery TiO2 Negative Electrodes from Lunar In-Situ Resources, (submitted).

International audience; Aiming at a more comprehensive understanding of the solid electrolyte interphase (SEI) in sodium ion batteries (NIBs), a detailed X-ray photoelectron spectroscopy (XPS) investigation of the few-nanometer thick passivation film formed on hard carbon (HC) in contact with various Na+-ion conducting electrolytes is reported. The electrolytes investigated include 1 M solutions of NaPF6, NaClO4, NaTFSI, NaFSI, and NaFTFSI, all dissolved in a common mixture of ethylene carbonate (EC) and diethylene carbonate (DEC) (EC/DEC = 1/1 wt. ratio). For comparison, the study of analogous Li-based electrolytes containing LiPF6 and LiFSI as representative electrolyte salts is also reported. The anion and cation of the electrolyte salt appear to play a key role in determining the overall SEI layer composition, including its depth evolution and thickness. The SEI building species formed on hard carbon by solvent reduction upon sodiation are found to decrease with the various salts in the order: NaPF6 > NaClO4 ≈ NaTFSI > NaFTFSI > NaFSI. The comparison of lithiated and sodiated HC electrodes shows that the SEI layer is more homogeneous and richer in organic species upon the use of Na-based electrolytes. Surface and depth-profiling XPS analysis on HC electrodes charged in the various electrolyte formulations provides in-depth insights on the differences and similarities of the SEI (composition, thickness, depth evolution, etc.) evolving from the variation in the chemical structure of the cations and anions of the respective salts.

International audience; From the literature overview, lithium difluorophosphate salt, LiPO2F2, is considered a powerful electrolyte additive capable of enhancing lithium-ion batteries' capacity retention. Lower cell impedance associated with SEI and/or CEI layers composition and texture modifications had been widely demonstrated, but without providing clear mechanisms. This paper sheds light on the reactivity of LiPO2F2 by combining electrochemical measurements and analyzes of electrolyte degradation products at the interphases and in the electrolytes by means of infrared and mass spectrometry techniques. Fluorine substitution reaction by electrochemically formed anions leads to a mitigation of electrolyte solvents degradation and to the enrichment of the SEI layer with LiF and lithium organofluorophosphates. Furthermore, a discussion on the composition of the CEI layer that enables the prevention of the transition metals dissolution from positive electrode layered oxides materials is also presented.

In parallel with the considerable investigations on renewable energy sources, electrical energy storage systems used to store the energy produced now and to provide it when needed have received much attention lately.1 Amongst them, lithium-ion batteries (LIB) are today the most employed in a huge range of purposes including cellphones, laptops or even electric vehicles. Current LIB consists in a planar arrangement (2D) in which the different parts of the battery (positive and negative electrodes, separator, current collectors) are rolled or stacked. Unfortunately, in this type of 2D configuration, lithium ions diffuse only along one dimension. Additive manufacturing (AM) technologies, also called 3D-printing processes, could enable the production of much more complex 3D architectures thus allowing diffusion of the lithium cations towards two or three-dimensions. Advantage of those 3D designs is that the electrochemical active surface area is expected to increase as well as the battery specific capacity and power.2 On the other hand, AM could also allow the direct incorporation of LIB within the final object, thus enabling the possibility to maximize the energy storage capabilities while reducing the dead volume and weight. Amongst the various AM available technologies, we focused our work on the Fused Deposition Modeling (FDM) process using a thermoplastic filament as material source for the 3D-printer. In this presentation, the formulation of composite PLA-based filaments specially designed to print each parts of the LIB (with liquid electrolyte) will be described.3,4 The active material composition within the negative and positive electrodes (graphite and lithium iron phosphate (LiFePO4) respectively), was increased as high as possible in order to enhance the electrochemical performances. Furthermore, the addition of a plasticizer was required to maintain enough mechanical strength while, in the meantime, carbon black was added to confer adequate electrical properties. The impact of ceramic additives on ionic conductivity in the separator was also investigated. From the optimized filaments compositions, stepwise and then “one-shot” 3D-printing of complete LiFePO4/graphite battery cells of any shapes were carried out (Figure 1). In order to prevent short-circuits, classical 3D-printing parameters such as the infill patterns and infill density were investigated for the LIB separator improvement. Finally, this presentation will introduce our latest results5 regarding the printability of a polyethylene oxide/lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI) filament (2.18 × 10−3 S cm−1 at 90 °C) optimized to be used as solid polymer electrolyte in a lithium-ion battery. This presentation, by combining both battery and 3D-printing understandings, will tackle various electrochemical (thickness, electronic and ionic conductivity, liquid electrolyte uptake) and 3D-printing parameters (infill density, infill pattern, perimeters, over and under-extrusion, retraction), which clearly paves the way for enhanced 3D-printed LIB. References: [1] Tarascon, J. M. & Armand, M. Issues and challenges facing rechargeable lithium batteries. Nature 414, 359-367, doi:10.1038/35104644 (2001). [2] Long, J. W., Dunn, B., Rolison, D. R. & White, H. S. Three-dimensional battery architectures. Chemical Reviews 104, 4463-4492, doi:10.1021/cr020740l (2004). [3] Maurel, A. et al. Highly Loaded Graphite-Polylactic Acid Composite-Based Filaments for Lithium-Ion Battery Three-Dimensional Printing. Chemistry of Materials 30, 7484-7493, doi:10.1021/acs.chemmater.8b02062 (2018). [4] Maurel, A. et al. Three-Dimensional Printing of a LiFePO4/Graphite Battery Cell via Fused Deposition Modeling. Scientific Reports 9, 18031, doi:10.1038/s41598-019-54518-y (2019). [5] Maurel, A. et al. Poly(Ethylene Oxide)−LiTFSI Solid Polymer Electrolyte Filaments for Fused Deposition Modeling Three-Dimensional Printing. Journal of The Electrochemical Society 167, 070536, doi:10.1149/1945-7111/ab7c38 (2020). Figure 1

Storage of nickel-rich LiNi1-x-yMnxCoyO2 positive active materials under improper environmental conditions brings about undesirable surface reactions causing poor Li-ion cell electrochemical performances and gas generation. In this paper, a detailed stepwise investigation of the increasing reactivity of 532, 622, 811 and 901 NMC materials towards a specific H2O/CO2 atmosphere is reported. Water-soluble salts as lithium carbonate, hydroxide and sulfates are accurately quantified thanks to acid-base titration and inductively coupled plasma atomic emission spectroscopy techniques. On the other hand, the presence of insoluble species as transition metal oxyhydroxides and oxides is unveiled through a thermal decomposition study using thermogravimetric mass spectrometer coupling technique. Their formation and thermal decomposition mechanisms are proposed after careful analysis of the characteristic mass loss and O2, CO2 and H2O evolution profile in the 50–500 °C region. Interestingly, the results also highlight an in situ lithiated layered oxide material reformation reaction. To assess their chemical reactivity towards LiPF6-based electrolyte, the latter was analyzed through 19F nuclear magnetic resonance after storage with various reference salts and 811 NMC. LiPO2F2 is detected from storage tests with Li2CO3, Li2O and Li2SO4, and fluorophosphate-type molecules are detected from LiOH; this experiment can help discriminate between LiOH and Li2O as NMC surface species.

A reliable heating device coupled with a FTIR gas analyzer has been tailored with the aim of evaluating the role of state-of-the-art lithium-ion battery components and environmental conditions on thermal and toxic hazards. Here, we demonstrate its effectiveness in accurately assessing the role of fully charged 0.6 Ah pouch cells confinement, electrolyte composition and separator coating on heat release and toxic gas generation-related risks. The fire safety international standards developed by the ISO TC92 SC3 subcommittee were used to determine the asphyxiant and irritant gases toxicity. Cells tighting confinement proves to be a very efficient way to diminish and delay (from 180 to 245 °C) the thermal runaway phenomenon occurrence and relating toxic gas release. Vinylene carbonate as electrolyte additive is able to shift (+20 °C) the onset temperature, while substitution of 1/3 M LiPF6 by LiFSI does not modify the thermal behavior, nor the toxic risks. The coating of a tri-layer separator influences the irritant gas toxicity related risk, by decreasing fluorinated components release. This study highlights that some improvements regarding LIB safety can be achieved through appropriate component selection and cells integration design at a module/pack level.

Actual parallel-plate architecture of lithium-ion batteries consists of lithium-ion diffusion in one dimension between the electrodes. To achieve higher performances in terms of specific capacity and power, configurations enabling lithium-ion diffusion in two or three dimensions is considered. With a view to build these complex three-dimensional (3D) battery architectures avoiding the electrodes interpenetration issues, this work is focused on fused deposition modeling (FDM). In this study, the formulation and characterization of a 3D-printable graphite/polylactic acid (PLA) filament, specially designed to be used as negative electrode in a lithium-ion battery and to feed a conventional commercially available FDM 3D printer, is reported. The graphite active material loading in the produced filament is increased as high as possible to enhance the electrochemical performance, while the addition of various amounts of plasticizers such as propylene carbonate, poly(ethylene glycol) dimethyl ether average Mn ∼ 2000, poly(ethylene glycol) dimethyl ether average Mn ∼ 500, and acetyl tributyl citrate is investigated to provide the necessary flexibility to the filament to be printed. Considering the optimized plasticizer composition, an in-depth study is carried out to identify the electrical and electrochemical impact of carbon black and carbon nanofibers as conductive additives. © 2018 American Chemical Society.

International audience; Li4Ti5O12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process, due to interfacial reactions between active material and electrolyte solution. In the same time, the electronic and ionic conductivity of pristine LTO is very poor and induces the use of nanoparticles which increase the outgassing phenomena. The coating of LTO particles could be a solution. For this the LTO spinel particles are modified with ionic conductor Li3PO4 coating using a spray-drying method. For the first time a homogeneous thin dense layer phosphate based conductor is obtained without nanoparticles, as a thin film material. It is so possible to study the influence of ionic conductor deposited on the negative electrode material on performances by the controlled layer thickness. This coating was characterized by XRD, SEM, XPS and TEM. The electrochemical performance of Li3PO4 coated Li4Ti5O12 is improved at high C-rate by the surface modification (improvement of 30 mAh g(-1) at 5 C-rate compared to pristine LTO for 5 nm of coating), inducing by a modification of surface energy. An optimum coating thickness was studied. This type of coating allows a significant decrease of outgassing phenomena due the conformal coating and opens the way to a great number of studies and new technologies. (C) 2016 Elsevier B.V. All rights reserved.

Among the 3D-printing technologies, fused deposition modeling (FDM) represents a promising route to enable direct incorporation of the battery within the final 3D object. Here, the preparation and characterization of lithium iron phosphate/polylactic acid (LFP/PLA) and SiO2/PLA 3D-printable filaments, specifically conceived respectively as positive electrode and separator in a lithium-ion battery is reported. By means of plasticizer addition, the active material loading within the positive electrode is raised as high as possible (up to 52 wt.%) while still providing enough flexibility to the filament to be printed. A thorough analysis is performed to determine the thermal, electrical and electrochemical effect of carbon black as conductive additive in the positive electrode and the electrolyte uptake impact of ceramic additives in the separator. Considering both optimized filaments composition and using our previously reported graphite/PLA filament for the negative electrode, assembled and “printed in one-shot” complete LFP/Graphite battery cells are 3D-printed and characterized. Taking advantage of the new design capabilities conferred by 3D-printing, separator patterns and infill density are discussed with a view to enhance the liquid electrolyte impregnation and avoid short-circuits.

The main safety issue pertaining to operating lithium-ion batteries (LIBs) relates to their sensitivity to thermal runaway. This complex multiphysics phenomenon was observed in two commercial 18650 Ni-rich LIBs, namely a Panasonic NCR GA and a LG HG2, which were based on L i ( N i 0.8 C o 0.15 A l 0.05 ) O 2 (NCA) and L i ( N i 0.8 M n 0.1 C o 0.1 ) O 2 (NMC811), respectively, for positive electrodes, in combination with graphite-SiOx composite negative electrodes. At pristine state, the batteries were charged to different levels of state of charge (SOC) (100% and 50%) and were investigated through thermal abuse tests in quasi-adiabatic conditions of accelerating rate calorimetry (ARC). The results confirmed the proposed complete thermal runaway of exothermic chain reactions. The different factors impacting the thermal runaway kinetics were also studied by considering the intertwined impacts of SOC and the related properties of these highly reactive Ni-rich technologies. All tested cells started their accelerated thermal runaway stage at the same self-heating temperature rate of ~48 &deg, C/min. Regardless of technology, cells at reduced SOC are less reactive. Regardless of SOC levels, the Panasonic NCR GA battery technology had a wider safe region than that of the LG HG2 battery. This technology also delayed the hard internal short circuit and shifted the final venting to a higher temperature. However, above this critical temperature, it exhibited the most severe irreversible self-heating stage, with the highest self-heating temperature rate over the longest duration.

Here two chemical reduction pathways to synthesize the vinylene carbonate (VC) and poly(VC) reduction products are investigated, with the precise aim of further deciphering the lithium-ion battery solid electrolyte interphase (SEI) layer composition and the associated reduction mechanisms. The liquid synthesis pathway offers the opportunity of varying the concentration of Li-4,4′-Di-tert-butylbiphenyl reducing agent, whereas the dry synthesis pathway by ball milling allows to solve issues related to solvent-induced side reactions and washing procedure. As a result, the two syntheses do not unveil the same reduction mechanisms, favouring either carboxylate or carbonate salts as the major end product. The latter pathway is very efficient in terms of providing SEI-layers products resulting in well-defined IR spectra and comparisons with simulated spectra enable us to obtain IR fingerprints of the Li di-vinylene di-carbonate (LDVD) compound. Taken together the synthesis procedures provide information on conditions favouring radical polymerization and further poly(VC) reduction into Li2CO3 and polyacetylene. Overall, this chemical simulation of SEI-layers formation assists in a proper characterization of the SEI-layers created on graphite surfaces by their IR spectra showing that Li2CO3, LDVD and poly(VC) are all present in different proportions dependent on the VC content in the electrolyte.

In this paper, the development of an environmentally-friendly lithium-terephtalate/polylactic acid (Li2TP/PLA) composite filament, for its use, once 3D-printed via Fused Deposition Modeling (FDM), as negative electrode of a lithium-ion battery is reported. Solvent-free formulation of the 3D-printable filament is achieved through the direct introduction of synthesized Li2TP particles and PLA polymer powder within an extruder. Printability is improved through the incorporation of poly(ethylene glycol) dimethyl ether average Mn∼500 (PEGDME500) as plasticizer, while electrical performances are enhanced through the introduction of carbon black (CB). Thermal, electrical, morphological, electrochemical and printability characteristics are discussed thoroughly. By taking advantage of the 3D-printing slicer software capabilities, an innovative route is proposed to improve the liquid electrolyte impregnation within the 3D-printed electrodes.

In this paper, the ability to 3D print lithium-ion batteries through Pmnbspace thermoplastic material extrusion and polymer powder bed fusion is considered. Focused on the formulation of positive electrodes composed of polypropylene, LiFePO4 as active material, and conductive additives, advantages and drawbacks of both additive manufacturing technologies, are thoroughly discussed from the electrochemical, electrical, morphological and mechanical perspectives. Based on these preliminary results, strategies to further optimize the electrochemical performances are proposed. Through a comprehensive modeling study, the enhanced electrochemical suitability at high current densities of various complex three-dimensional lithium-ion battery architectures, in comparison with classical two-dimensional planar design, is highlighted. Finally, the direct printing capability of the complete lithium-ion battery by means of multi-materials printing options processes is examined.

In the last years, LiNixMnyCozO2 (x+y+z = 1) layered materials have been widely used as positive electrode materials in lithium-ion batteries for electric car applications, because of their high energy density given by the nickel content. Unfortunately, their stability towards H2O and CO2 is compromised when x>0.5, favoring the formation of surface species commonly called soluble bases (SB). The presence of SB has shown to increase the cell’s impedance, decrease the capacity retention and evolve gas during functioning1-4. Therefore, in this work, accurate SB quantification methods were implemented on four high-nickel layered materials with the aim of further deciphering their formation mechanisms and reactivity towards electrolyte. The optimization of a procedure that allows the quantification of SB in the as-received and after H2O/CO2storage of the NMC532, 622, 811 and LiNi0.9Co0.1O2, will be shown through the complementary use of acid-base titration and inductively coupled plasma (ICP) techniques. We unveiled the presence and quantified different lithium and sodium salts. Moreover, thanks to additional TGA/MS analysis, we propose a novel NMC surface degradation mechanism upon H2O/CO2 storage that involves the presence of lithium and nickel-based surface species. Finally, through nuclear magnetic resonance technique (19F and 31P NMR), the chemical reactivity of these surface species towards a commercial LiPF6-based liquid electrolyte was studied at room and at high temperature, evidencing the presence of lithium fluorophosphate as major decomposition product. 1. Liu, H. S., et al. (2006). "Investigation and improvement on the storage property of LiNi0.8Co0.2O2 as a cathode material for lithium-ion batteries." Journal of Power Sources 162(1): 644-650. 2. Bi, Y. J., et al. (2016). "Stability of Li2CO3 in cathode of lithium ion battery and its influence on electrochemical performance." Rsc Advances 6(23): 19233-19237. 3. Renfrew, S. E. and B. D. McCloskey (2017). "Residual Lithium Carbonate Predominantly Accounts for First Cycle CO2 and CO Outgassing of Li-Stoichiometric and Li-Rich Layered Transition-Metal Oxides." Journal of the American Chemical Society 139(49): 17853-17860. 4. Mahne, N., et al. (2018). "Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen." Angewandte Chemie-International Edition 57(19): 5529-5533.

Since the commercialization of Lithium-Ion Battery (LIB) by Sony Inc. in 1991 until today, recurrent incidents involving LIBs have been reported worldwide. During these incidents, the most energetic catastrophic failure of a LIB system is a cascading thermal runaway event. It is characterized by a deficit of energy dissipation versus energy accumulation in the cells leading to uncontrollable overheating of the battery system [1,2]. This complex event involves multi-scale phenomena ranging from internal parallel or cascading physico-chemical to battery components reactions (electrodes, electrolytes & separator) and further to the thermal propagation of cell core & safety features. Complexity of the comprehensive understanding of the thermal runaway hazard also lies in the fact that both normal operation (through aging and relating medium/long term degradation effects) and abuse conditions can contribute to a thermal runaway event, as recently discussed by [2] or [3]. Battery safety is becoming even more critical with the emergence of highly reactive Ni-rich LIBs in the market. These batteries are commercialized to meet novel energy- or power-demanding applications and are expected to dominate the market in the coming years, likely until the occurrence of a new technological breakthrough. Therefore, these newly introduced LIBs presenting such high energy density characteristics and integrating more intrinsically reactive materials could possibly lead to more catastrophic events subsequent to the thermal runaway. Therefore, there is a clear need to better understand the underlying specific electrochemical and thermal behaviors of these technologies in both normal and abuse conditions across their lifetime. Inspired by the former collaborative IFPEN/INERIS research works on the thermal runaway of LIBs (essentially focused on LFP/Graphite and relating batteries) [2], this work aims to go deeper into the understanding & modeling of this complex phenomenon at cell scale, taking into account the influence of novel highly reactive technologies and the influence of aging with 2 target degradation mechanisms: SEI growth and Li Plating, in order to understand what the keys are towards inherently safer design and operation of highly reactive LIBs. It is a matter of establishing the link between the materials used (electrodes, electrolytes) in high energy density & intrinsically reactive LIB technologies, the degradation products during cell calendar and cycling aging (mainly analyzed through SEI evolution during cell lifetime and Li deposition during cold recharges) as well as the thermal runaway kinetics. The selected technologies studied in this research are two commercial 18650 Ni-rich LIBs, namely a Panasonic NCR GA and a LG HG2, which were based on Li(Ni0.8Co0.15Al0.05)O2 (NCA) and Li(Ni0.8Mn0.1Co0.1)O2 (NMC811), respectively, for positive electrodes, in combination with graphite-SiOx composite negative electrodes. With the goal of finding the keys factors that can improve the safety of these highly reactive LIBs during usage, the research strategy relies on the achievements of the previous projects and on the synergism offered by combined experimental and modeling studies as illustrated in Figure 1. The experimental study includes the 3 interconnected experimental processes here after specified: a complete multi-scale cell analysis in order to analyze the pristine, aged and thermally abused cells; a safety-focused aging campaign in order to artificially age battery samples, focusing on each target mechanism (SEI growth, Lithium plating) in a controlled and measurable way; accelerating rate calorimetry (ARC)thermal abuse tests in quasi-adiabatic conditions at cell level in order to qualifying the thermal runaway phenomenon as well as calibrating the thermal runaway model. The modeling study leads to the development of an extended thermal runaway model in order to predict the behaviors of different LIBs nearby and during thermal runaway under field conditions. This coupled multi-physics model will improve and extend the initial thermal runaway model built by [2] by integrating the impact of Li plating & SEI-driven cycling aging. The final result will be a multi-dimensional multiphysical model of LIB capable of accounting for the triggering of runaway under different thermal and electrical conditions and as a function of the state of aging. The predictions of the models will be validated based on other thermal abuse tests. This model will further be implemented to understand the electrical or thermal initiation of the phenomenon of thermal runaway and its propagation within a battery pack regarding its design. They will eventually be transposed into tools enabling the best design of the packs and avoidance of this undesirable phenomenon. References 1. S. Abada et al, Journal of Power Sources, 306, 178–192 (2016). 2. S. Abada et al, Journal of Power Sources, 399, 264–273 (2018). 3. F. H. Gandoman et al, Applied Energy, 251, 113343 (2019). Figure 1

Green energy harvesting (solar and wind) and storage along with electrification of transport sector could bring about a major transformation in the CO2 emission levels that we are currently experiencing. Lithium ion batteries provide an efficient energy storage system to realize this goal. The key developments in Li-ion battery technology starting from solid solution electrodes, intercalation electrodes, conversion electrodes, organic electrodes, and polymer electrolytes with a major focus on the contribution of Michel Armand, an eminent scientist who at a young age saw the future of energy storage, have been elaborated. Moreover, the direction of research that seems interesting to pursue for realizing our goals has also been outlined.

Additive manufacturing technologies open the way to the direct-integration of electronics and solid-state battery within the final 3D object. Here, a 3D printable polyethylene oxide/lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI) filament (2.18 × 10−3 S cm−1 at 90 °C) optimized to be used as solid polymer electrolyte in a lithium-ion battery is produced to feed a fused deposition modeling (FDM) 3D-printer. Due to its relatively poor mechanical properties compared to classical polymer filament such as polylactic acid (PLA), deep modifications of the 3D-printer were implemented in order to facilitate its printability. The solid polymer electrolyte thermal, structural, morphological, mechanical and electrical characterization is reported. Interestingly, using three different electrochemical impedance spectroscopy sample holders (lateral, sandwich and interdigitated-comb), we demonstrate that conductivity values differs for a same sample, highlighting the PEO chains orientation effect on the conductivity measurements.

International audience; Active materials in batteries suffer from deleterious chemical and structural evolutions during cycling. To follow these modifications, transmission electron microscopy and associated techniques (EELS, EDX) are of great use. However, these materials can undergo drastic changes under the electron beam. In this study the various microstructural and chemical evolutions induced by electron irradiation were thoroughly investigated at different charging states on a MnO material reacting through the conversion process leading to nanoparticles. During the electron irradiation, compounds pulverization, nanograins growth as well as the formation of manganese carbide were observed. Consequently, knowing the modifications the sample can undergo under electron irradiation and managing to the best the TEM parameters (spot size, aperture size…) to limit its effect can be of help to avoid misinterpretation and to fully understand the mechanisms, which occur during cycling.

The successful development of electrified vehicles is a key factor in the transition to a more environmentally friendly transportation sector. Li-ion batteries, which are today’s choice to power electrified vehicles, have to fulfill more stringent requirements in terms of ageing and need advanced tools to study the interfaces evolution upon cycling. This work is thus focused on understanding the impedance behavior of a commercial graphite-based negative electrode, which is used in a Li-ion battery designed for such vehicles. 3-electrode pouch cells were assembled with such negative electrode, a LMOlayered oxide-based positive electrode, a Celgard1type separator soaked with a carbonate solvents-LiPF6 mixture electrolyte and a LTO-based electrode as reference. Electrochemical Impedance Spectroscopy measurements were performed at different cell states of charge and ageing times. The impedance of the graphite-based anode is analyzed for first time with de Levie’s equation for porous electrodes. The analysis is supported by designed SEI layer formation experiments with vinylene carbonate and vinylene ethyl carbonate additives. The high frequency domain of the interfacial kinetic loop reflects porosity effects and the graphite particles–composite matrix electric tranfer. The SEI layer and charge transfer phenomena are reflected in the medium and medium to low frequency domains respectively, and their impedance contributions depend on the Li content of the graphite particles. Upon ageing, the interfacial impedance of the graphite-based electrode should increase due to SEI layer growing. However, from 100% to 80% of battery capacity retention, the impedance decreases. Our analysis backed by post-mortem characterizations allows to assign this unexpected behavior to porosity rise and slight Mn-contamination of the SEI layer.

International audience; A detailed investigation of the combustion behavior of LiPF6 or LiFSI-based carbonate electrolytes was conducted with the objective of getting better knowledge of lithium-ion battery system fire induced thermal and chemical threats. The well-controlled experimental conditions provided by the Tewarson calorimeter have enabled the accurate evaluation of fire hazard rating parameters such as heat release rate and effective heat of combustion and the quantification of toxic effluents (HF, SO2, NOx...). Results have shown that all the electrolytes tested burn in phases depending on the flammability nature of their mixture constituents. The first stage of combustion is solely governed by the more volatile solvent (linear carbonate) and the influence of adding salt comes into effect predominantly in the second stage. It has been also shown that combustion enthalpy of electrolytes lies in the solvent mixture, irrespective of the salt added. The fire induced toxicity in well-ventilated conditions is found to be mainly dictated by the salt and its chemical structure, showing very limited concerns that emanate from the organic solvents.

International audience; The risk of thermal runaway is, for Li-ion batteries, a critical issue for large-scale applications. This results in manufacturers and researchers placing great emphasis on minimizing the heat generation and thereby mitigating safety-related risks through the search for suitable materials or additives. To this end an in-depth stepwise investigation has been undertaken to provide a better understanding of the exothermic processes that take place at the negative electrode/electrolyte interface as well as an increased visibility of the role of the state-of-the-art electrode binders, additives and lithium salt by means of the classical DSC technique.A reliable experimental set up helped quantify the beneficial or harmful contribution of binder polymers to the exothermic behavior of the CMC/SBR containing graphite electrode film in contact with 1 M LiPF6 in EC:DMC:EMC (1:1:1 v/v/v) electrolyte. Further, the role of the VC, FEC and VEC electrolyte additives (2 wt.%) in reinforcing the protective SEI layer towards thermally induced electrolyte reduction is discussed in the light of infrared spectroscopy and transmission electron microscopy analyzes results.Moreover, after a preliminary corrosion study of LiPF6/LiFSI mixtures, we showed that the 0.66/0.33 molar composition can be used in commercial NMC-based LiBs with a positive effect on the thermal runaway.

International audience; The effect of the replacement of the carbonyl oxygen in VEC additive by =C(CN)2 in the analogous dicyano ketene vinyl ethylene acetal (DCKVEA) on the electrochemical reduction profile is significant. Yet, the additives were proven, through IR spectroscopy supported by DFT computations, by applying EELS techniques and performing synthesis of a reduction product, to reduce in a similar way. Interestingly, the reduction-induced capacities were found to be quite different and can be explained either by the different properties of the SEI, from lithium carbonate and its malononitrile homologue, or by thedifferent abilities of the two additives to solvate Li+.

International audience; A comparative and in-depth investigation on the reactivity of various Li-based electrolytes and of the solid electrolyte interface (SEI) formed at graphite electrode is carried out using X-ray photoelectron spectroscopy (XPS), chemical simulation test, and differential scanning calorimetry (DSC). The electrolytes investigated include LiX (X = PF6, TFSI, TDI, FSI, and FTFSI), dissolved in EC-DMC. The reactivity and SEI nature of electrolytes containing the relatively new imide (LiFSI and LiFTFSI) and imidazole (LiTDI) salts are evaluated and compared to those of well-researched LiPF6− and LiTFSI-based electrolytes. The thermal reactivity of LixC6 in the various electrolytes is found to be in the order of LiFSI > LiTDI > LiTFSI > LiFTFSI > LiPF6 and LiFSI > LiFTFSI > LiPF6 > LiTFSI > LiTDI in terms of onset exothermic temperature and total heat generated, respectively. Surface and depth-profiling XPS analysis of the SEI formed with the diverse electrolyte formulations provide insight into the differences and similarities (composition, thickness, and evolution, etc.) emanating from the structure of the various salt anions.

The development of high energy Li-ion batteries with improved durability and increased safety mostly relies on the use of newly developed electrolytes. A detailed appraisal of fire-induced thermal and chemical threats on LiPF 6 - and LiFSI-based electrolytes by means of the so-called “fire propagation apparatus” had highlighted that the salt anion was responsible for the emission of a non negligible content of irritant gas as HF (PF 6 − ) or HF and SO 2 (FSI − ). A more thorough comparative investigation of the toxicity threat in the case of larger-size 0.4 kWh Li-ion modules was thus undertaken. A modeling approach that consists in extrapolating the experimental data obtained from 1.3Ah LiFePO 4 /graphite pouch cells under fire conditions and in using the state-of-the-art fire safety international standards for the evaluation of fire toxicity was applied under two different real-scale simulating scenarios. The obtained results reveal that critical thresholds are highly dependent on the nature of the salt, LiPF 6 or LiFSI, and on the cells state of charge. Hence, this approach can help define appropriate fire safety engineering measures for a given technology (different chemistry) or application (fully charged backup batteries or batteries subjected to deep discharge).

We report a systematic investigation of Na-based electrolytes that comprise various NaX [X=hexafluorophosphate (PF6 ), perchlorate (ClO4 ), bis(trifluoromethanesulfonyl)imide (TFSI), fluorosulfonyl-(trifluoromethanesulfonyl)imide (FTFSI), and bis(fluorosulfonyl)imide (FSI)] salts and solvent mixtures [ethylene carbonate (EC)/dimethyl carbonate (DMC), EC/diethyl carbonate (DEC), and EC/propylene carbonate (PC)] with respect to the Al current collector stability, formation of soluble degradation compounds, reactivity towards sodiated hard carbon (Nax -HC), and solid-electrolyte interphase (SEI) layer formation. Cyclic voltammetry demonstrates that the stability of Al is highly influenced by the nature of the anions, solvents, and additives. GC-MS analysis reveals that the formation of SEI telltales depends on the nature of the linear alkyl carbonates and the battery chemistry (Li(+) vs. Na(+) ). FTIR spectroscopy shows that double alkyl carbonates are the main components of the SEI layer on Nax -HC. In the presence of Na salts, EC/DMC and EC/DEC presented a higher reactivity towards Nax -HC than EC/PC. For a fixed solvent mixture, the onset temperature follows the sequence NaClO4

In recent years, greener transportation has become of major interest to limit air pollution and global warming. For this purpose, Li-ion batteries (LIBs) are considered as the most promising power source for electric vehicles (EV) and hybrid electric vehicles (HEV) due to their high energy density. The use of high-energy multi-cell battery packs imposes ever more stringent requirements on LIBs in term of safety and long-term cyclability. The formation of an effective SEI passivation layer at the negative electrode / electrolyte interface was found to be of paramount importance in order to enable LIB long-life cycling and controlling the threshold for thermal runaway. This is why SEI-forming additives have been used in the electrolyte to reinforce these protective properties, with the most common additives being vinylene carbonate (VC) (1), fluoroethylene carbonate (FEC) (2), and vinyl ethylene carbonate (VEC) (3). To our knowledge, the modification of EC and PC on the carbonyl group, rather than on the alkylene bridge as for VC, VEC, or FEC, has not previously been attempted.(4,5) It is known that the =C(CN)2 group is an “oxygen equivalent” being even slightly more electronegative than O itself and extending considerably the conjugation. Hence, we hypothesized that modified EC or PC, with C=C(CN)2 replacing the carbonyl groups, could lead to a more facile reduction at higher potentials and a stable SEI. The dicyanoketene propylene (and ethylene) acetal, DCKPA (DCKEA), have both been synthesized according to a simple procedure.(6) The reduction process has been investigated for DCKPA by means of GC/MS and IR analysis and the efficiency as a SEI-reinforcing additive demonstrated by the analysis of the soluble products using liquid GC/MS. The cycling tests using a pouch cell configuration at both 20 and 45°C were realized with only 0.5 wt.% of additive in the electrolyte and resulted in higher capacity retention. Moreover, a post-mortem analysis by DSC revealed an improvement in term of safety due to an improved lithiated graphite/electrolyte interface. [1] H.-H. Lee, Y.-Y. Wang, C.-C. Wan, M.-H. Yang, H.-C. Wu, D.-T. Shieh, Journal of Applied Electrochemistry. 35 (2005) 615–623. [2] I.A. Profatilova, S.-S. Kim, N.-S. Choi, Electrochimica Acta. 54 (2009) 4445–4450. [3] Y. Hu, W. Kong, H. Li, X. Huang, L. Chen, Electrochemistry Communications. 6 (2004) 126–131. [4] C. Forestier, P. Jankowski, L. Coser, G. Gachot, L. Sannier, P. Johansson, et al., Journal of Power Sources. 303 (2016) 1–9. [5] Pending patent [6] W.J. Middleton, V.A. Engelhardt, Journal of the American Chemical Society. 80 (1958) 2788–2795. Figure 1: Results of cycling tests at 45°C without and with 0.5 wt.% of DCKPA using a pouch cell configuration, and the post mortem DSC / liquid GC/MS analyses. Figure 1

International audience; The risk of thermal runaway is, for Li-ion batteries, a critical issue for large-scale applications. This compels manufacturers to find suitable materials or additives, which are able to minimize the heat generation and thereby mitigate safety-related risks. In an attempt to get more insight and understand the exothermic processes that take place at the negative electrode/electrolyte interface, we implemented GC/MS analytical technique to detect volatile compounds. Based on a mechanistic study, we propose a general electrolyte degradation scheme in the 100-250 ◦C temperature range, involving electrochemically driven carbonates reduction followed by chemical reactions. The mechanisms for decomposition deduced from these analyses shed new light on the processes involved in the formation of the precipitated (SEI layer) and soluble molecules upon cell formation cycles and ageing.

International audience; The use of the high energy Li-ion battery technology for emerging markets like electromobility requires precise appraisal of their safety levels in abuse conditions. Combustion tests were performed on commercial pouch cells by means of the Fire Propagation Apparatus also called Tewarson calorimeter in the EU, so far used to study flammability parameters of polymers and chemicals. Well-controlled conditions for cell combustion are created in such an apparatus with the opportunity to analyse standard decomposition/combustion gases and therefore to quantify thermal and toxic threat parameters governing the fire risk namely the rate of heat release and the effective heat of combustion as well as the toxic product releases. Using the method of O2 consumption, total combustion heats and its kinetic of production were determined as a function of the cell state of charge unveiling an explosion risk in the case of a charged cell. The resulting combustion heat is revealed to be consistent with cumulated contribution values pertaining to each organic part of the cell (polymers and electrolytes) as calculated from thermodynamic data. The first order evaluation of the dangerousness of toxic gases resulting from fire induced combustion such as HF, CO, NO, SO2 and HCl was undertaken and stressed the fact that HF is the most critical gas originating from F-containing cell components in our test conditions.

There is urgent action required for replacing LiPF6 as a solute for Li-ion batteries electrolytes. This salt, prone to highly Lewis acidic PF5 release and hydrolysis to HF is responsible for deleterious reaction on carbonate solvents, corrosion of electrode materials leading to safety problems then release to toxic chemicals. A major advantage of LiPF6 is that it passivates aluminium. Most attempts to replace LiPF6 with hydrolytically-stable salts have been unsuccessful because of Al corrosion. We present here two “Huckel” type salts, namely lithium (2-fluoroalkyl-4,5-dicyano-imidazolate); fluoroalkyle = CF3 (TDI), C2F5 (PDI) with high charge delocalization. These thermally stable salts give both appreciably conductive solutions in EC/DMC (>6 mS cm−1 at 20 °C) with a lower decrease with temperature than LiPF6. Non fluorinated lithium (4,5-dicyano-1,2,3-triazolate) is comparatively less than half as conductive. The lithium transference number T+ measured by PFG-NMR is also higher. Voltammetry scans with either platinum or aluminium electrodes show an oxidation wall at 4.6 V versus Li+:Li°. These two salts are thus the first examples of strictly covalent, non-corroding salts allowing 4+ V electrode material operation. This is demonstrated with experimental Li/LiMn2O4 cells as beyond the third cycles, the fade of the three electrolytes were quasi-identical, though LiPF6 had a sharper initial decrease.

International audience; To allow electric vehicles to be powered by Li-ion batteries, scientists must understand further their aging processes in view to extend their cycle life and safety. For this purpose, we focused on the development of analytical techniques aiming at identifying organic species resulting from the degradation of carbonate-based electrolytes (ECDMC/ LiPF6) at low potential. As ESI-HRMS provided insightful information to the mechanism and chronological formation of ethylene oxide oligomers, we implemented "gas" GC/MS experiments to explore the lower mass range corresponding to highly volatile compounds. With the help of chemical simulation tests, we were able to discriminate their formation pathways (thermal and/or electrochemical) and found that most of the degradation compounds originate from the electrochemically driven linear alkyl carbonate reduction upon cycling and to a lesser extent from a two-step EC reduction. Deduced from these results, we propose an overall electrolyte degradation scheme spanning the entire mass range and the chemical or electrochemical type of processes.

Lithium salts enlisting azide, oxocarbons, dicarboxylates and hydrazides have been identified as a practical mean to compensate the irreversible capacity loss of LIBs negative electrodes. During the first charge, the anion loses electrons and converts to gaseous N2, CO or CO2, within an acceptable potential range (3 to 4.5 V). We report an electrochemical study on these easily accessible “sacrificial salts”. Keywords: Sacrificial salts, Overlithiation, Initial capacity loss, Lithium batteries, Negative electrodes

Actual parallel-plate architecture of lithium-ion batteries consists in lithium ion diffusion in one dimension between the electrodes. To achieve higher performances in terms of specific capacity and power, configurations enabling lithium ion diffusion in two or three dimensions have been considered (1-5). With a view to build these complex 3D battery architectures avoiding the electrodes interpenetration issues, this work was focused on the Fused Deposition Modeling (FDM). In this presentation, the formulation and characterization of a 3D-printing graphite/polylactic-acid (PLA) filament, specially designed to be used as negative electrode in a lithium-ion battery, and to feed a conventional FDM 3D-printer will be described (6). Graphite loading into the produced filament was increased as high as possible (up to 62.5%wt) to enhance the electrochemical performances while maintaining sufficient mechanical strength to be printed. Formulation process is displayed in Fig. 1a. With such a high ratio of active material, the graphite/PLA filament was found to be very brittle. To overcome this problem, a plasticizer has been added to the PLA matrix to improve its ductility and decrease its stiffness. Influence of the amount of various plasticizers such as propylene carbonate (PC), poly(ethylene glycol) dimethyl ether average Mn~2000 (PEGDME2000), poly(ethylene glycol) dimethyl ether average Mn~500 (PEGDME500) and acetyl tributyl citrate (ATBC) was investigated by performing both differential scanning calorimetry and tensile mechanical tests. On the other hand, printability behavior of the extruded composite filaments was tested by using a commercially available 3D printer. From the optimized plasticizer composition, two-dimensional discs but also high resolution complex three-dimensional structures, such as a semi-cube lattice and a “3Dbenchy” boat, were successfully 3D-printed. Finally, considering this optimized composite, an in-depth study was carried out to identify the electronic percolation (Fig. 1b) and electrochemical impact of carbon black SuperP and carbon nanofibers as conductive additives; electrical conductivities were determined from impedance measurements performed at various stabilized temperatures ranging from 20ºC to 50°C and, in parallel, capacity retention was investigated in detail at different current densities after the different elaboration steps (film before extrusion and disc after printing). Significant progress has been achieved regarding the capacity retention as compared to Foster et al. (7) who was the first group to use FDM technology to 3D-print a negative electrode disc. They were aware that the low specific capacity values reported (15.8 mAh.g-1 at current density of 10 mA.g-1) were unfortunately caused by the use of a filament containing only 8%wt of graphene as active material and 92%wt of PLA. In this work, by increasing the graphite loading up to 62.5%wt, a reversible capacity of 201 mAh.g- 1 at current density of 4 mA.g-1 was achieved for the 3D-printed negative electrode disc by using the most printable filament (Fig. 1c). References: J. W. Long, B. Dunn, D. R. Rolison and H. S. White, Chemical Reviews, 104, 4463 (2004). S. Ferrari, M. Loveridge, S. D. Beattie, M. Jahn, R. J. Dashwood and R. Bhagat, Journal of Power Sources, 286, 25 (2015). H. S. Min, B. Y. Park, L. Taherabadi, C. L. Wang, Y. Yeh, R. Zaouk, M. J. Madou and B. Dunn, Journal of Power Sources, 178, 795 (2008). L. Taberna, S. Mitra, P. Poizot, P. Simon and J. M. Tarascon, Nature Materials, 5, 567 (2006). K. Sun, T. S. Wei, B. Y. Ahn, J. Y. Seo, S. J. Dillon and J. A. Lewis, Advanced Materials, 25, 4539 (2013). A. Maurel, M. Courty, B. Fleutot, H. Tortajada, K. Prashantha, M. Armand, S. Grugeon, S. Panier and L. Dupont, Advanced Energy Materials, (submitted April 2018). C. W. Foster, M. P. Down, Y. Zhang, X. B. Ji, S. J. Rowley-Neale, G. C. Smith, P. J. Kelly and C. E. Banks, Scientific Reports, 7 (2017). Figure 1

With EV and HEV developments, battery monitoring systems have to meet the new requirements of car industry. This paper deals with one of them, the battery ability to start a vehicle, also called battery crankability. A fractional order model obtained by system identification is used to estimate the crankability of lead-acid batteries. Fractional order modelling permits an accurate simulation of the battery electrical behaviour with a low number of parameters. It is demonstrated that battery available power is correlated to the battery crankability and its resistance. Moreover, the high-frequency gain of the fractional model can be used to evaluate the battery resistance. Then, a battery crankability estimator using the battery resistance is proposed. Finally, this technique is validated with various battery experimental data measured on test rigs and vehicles.

The implementation of lithium ion batteries in various applications (electric vehicles, portable electric devices, …) led to the development of both anode and cathode materials with increasing lithium storage capacities1-2. Among the different analytical techniques available, few allow the investigation of both microstructural and chemical evolutions. Transmission electron microscopy (TEM) combined with energy dispersive spectroscopy (EDX) and Electron Energy Loss Spectroscopy (EELS) is one of those powerful tools. However, one of the main drawbacks in the battery field is the high reactivity of the majority of the cycled products to electron irradiation and few studies have been performed so far to fully understand and determine its impact on the microstructure and chemistry of cycled materials. Considering the development of in-situ TEM experiment3-5, knowing the evolution of these electrode materials under electron irradiation is becoming primordial to decipher the real mechanisms going on during cycling from the electron-induced artifacts6-8. Thus, we chose to investigate the microstructural and chemical evolutions during cycling and electron irradiation of a transition metal oxide material going through a conversion reaction by TEM and EELS9. In this aim, we performed electron irradiation under two ranges of electron dose rate (low dose: 5 -15 103 é.nm-2.s-1, high dose: 2 105 - 5 106 é.nm-2.s-1) on MnO powder at the charged (lithiated) and the discharged (delithiated) state. As expected after lithiation and using a low dose rate, the micro-sized MnO particles are transformed into agglomerates of nanoparticles (2-3 nm size) surrounded by a Solid Electrolyte Interphase (SEI) with a thickness up to 30 nm (figure 1a). The global shape of the former grains remains the same. The EELS analyses (figure 1e) are in agreement with the presence of Li2O and Mn metal. After increasing the electron dose rate, several microstructural changes were highlighted such as the increase of the nanoparticles size and crystallinity (figure 1b). The pulverization of the SEI coupled with the apparition of a phase on the TEM grid carbon film analyzed as Li2O by EELS (figure 1e) was also observed. The EELS investigation confirmed the presence of Li2O and metal Mn even after irradiation. After delithiation and using a low dose rate, the microstructure composed of nanoparticles of 2-3 nm size embedded in a matrix and surrounded by a thinner SEI (up to 20 nm) is still maintained (figure 1c). The EELS analyses (figure 1e) are in agreement with the presence of mixture of Li2O and MnO. After increasing the electron dose rate, the observed changes are similar to those observed in the lithiated sample. The EELS and electron diffraction investigation confirmed the presence of manganese oxide as well as Li2O and sometime metal Mn. Under really high irradiation, a new phase appears on the carbon film and was identified by EELS then confirmed by SAED as Mn7C3 (figure 1d and 1e). The apparition of this phase can be explained by an electrical breakdown of the sample. These irradiation-induced modifications highlight the high sensitivity of cycled materials reacting through conversion processes to the electron beam and how they can lead to misinterpretation in terms of structural and chemical evolution and thus of involved mechanisms. In order to decipher the modifications induced by cycling or irradiation, it is necessary to perform preliminary studies on the electron irradiation effect on the microstructure and chemistry. Then to limit the irradiation impact and perform representative studies of battery materials throughout the cycling, the investigation must be performed in a low dose configuration. In terms of characterization, the electron diffraction could not fully allow the phases determination due to their pseudo-amorphous character. Therefore, its combination with EELS to determine the oxidation states of transition metal was decisive. In conclusion, even if the battery materials are beam sensitive, the use of electron microscopy and associated techniques (EELS, EDX) can be a key to fully understand the mechanisms involved during cycling when carefully controlled. [1] J. Cabana et al., Adv. Mater., 22, E170-92 (2010) [2] M. Armand and J.-M. Tarascon, Nanotechnology, 451, 652–657 (2008) [3] M. E. Holtz et al., Microsc. Microanal., 19, 1027–1035 (2013). [4] J. Y. Huang et al., Science, 330, 1515–20 (2010) [5] H. Kim et al., Adv. Energy Mater., 5, 1–7 (2015). [6] F. Lin et al., Sci. Rep., 4, 5694 (2014) [7] A. Hightower et al., Appl. Phys. Lett., 77, 10–13 (2000). [8] M. Boniface et al., Nano Lett., 16, 7381–7388 (2016) [9] C. Davoisne et al., J. Electrochem. Soc., 164, A1520–A1525 (2017) Figure 1

Currently, batteries are being both considered and utilized in a variety of large-scale applications. Materials sustainability stands as a key issue for future generations of batteries. One alternative to the use of a finite supply of mined materials is the use of renewable organic materials. However, before addressing issues regarding the sustainability of a given organic electrode, fundamental questions relating to the structure-function relationships between organic components and battery performance must first be explored. Herein we report the synthesis, characterization, and device performance of an organic salt, lithium 2,6-bis(ethoxycarbonyl)-3,7-dioxo-3,7-dihydro-s-indacene-1,5-bis(olate), capable of reversibly intercalating with minimal polarization 1.8 Li per unit formula over two main voltage plateaus located at approximately 1.96 and approximately 1.67 V (vs. Li/Li(+)), leading to an overall capacity of 125 mAh/g. Proton NMR and in situ XRD analyses of battery cycling versus Li at room temperature reveal that the insertion-deinsertion process is fully reversible with the dips in the voltage-composition traces, which are associated with changes in the 3D structural packing of the electrochemically active molecules.

Oxidized stainless steel electrodes containing chromium oxides without any conducting additives or binder have been successfully cycled at high temperatures (up to 100 °C) in organic solvent-based electrolytes with high reversibility. Cycling at high temperature results in an enhancement of the capacity at lower voltages, which is maintained upon cycling. After studying different electrolyte candidates, the best results were obtained using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in ethylene carbonate.

The electrical signals generated by a vehicle cranking offer an interesting way to estimate the lead-acid battery resistance. Since resistance and power are correlated, the cranking signals can thus be used to evaluate the battery cranking capability, and possibly to define a new battery SOF (State Of Function). This paper shows how a simple fractional model is suitable for simulating the battery dynamical behavior and especially for measuring its resistance in high-frequencies. The application of the model validation technique to fractional systems is then presented to provide a resistance estimation solution. Finally, a simpler method, meeting the automotive requirements, has been developed and validated with experimental data.