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Low temperatures severely impair the performance of lithium-ion batteries, which demand powerful electrolytes with wide liquidity ranges, facilitated ion diffusion, and lower desolvation energy. The keys lie in establishing mild interactions between Li+ and solvent molecules internally, which are hard to achieve in commercial ethylene-carbonate based electrolytes. Herein, we tailor the solvation structure with low-ε solvent-dominated coordination, and unlock ethylene-carbonate via electronegativity regulation of carbonyl oxygen. The modified electrolyte exhibits high ion conductivity (1.46 mS·cm−1) at −90 °C, and remains liquid at −110 °C. Consequently, 4.5 V graphite-based pouch cells achieve ~98% capacity over 200 cycles at −10 °C without lithium dendrite. These cells also retain ~60% of their room-temperature discharge capacity at −70 °C, and miraculously retain discharge functionality even at ~−100 °C after being fully charged at 25 °C. This strategy of disrupting solvation dominance of ethylene-carbonate through molecular charge engineering, opens new avenues for advanced electrolyte design. Low-temperature operation remains challenging for batteries. Here, the authors report an electrolyte solvation structure design strategy to break solvation dominance of ethylene carbonate to facilitate the desolvation process that improves the low-temperature performance of lithium-ion batteries even below −100 °C. [ABSTRACT FROM AUTHOR]

It is challenging to efficiently and economically recycle many lithium‐ion batteries (LIBs) because of the low valuation of commodity metals and materials, such as LiFePO4. There are millions of tons of spent LIBs where the barrier to recycling is economical, and to make recycling more feasible, it is required that the value of the processed recycled material exceeds the value of raw commodity materials. The presented research illustrates improved profitability and economics for recycling spent LIBs by utilizing the surplus energy in lithiated graphite to drive the preparation of organolithiums to add value to the recycled lithium materials. This study methodology demonstrates that the surplus energy of lithiated graphite obtained from spent LIBs can be utilized to prepare high‐value organolithiums, thereby significantly improving the economic profitability of LIB recycling. Organolithiums (R–O–Li and R–Li) were prepared using alkyl alcohol (R–OH) and alkyl bromide (R–Br) as substrates, where R includes varying hindered alkyl hydrocarbons. The organolithiums extracted from per kilogram of recycled LIBs can increase the economic value between $29.5 and $226.5 kg−1 cell. The value of the organolithiums is at least 5.4 times the total theoretical value of spent materials, improving the profitability of recycling LIBs over traditional pyrometallurgical ($0.86 kg−1 cell), hydrometallurgical ($1.00 kg−1 cell), and physical direct recycling methods ($5.40 kg−1 cell). [ABSTRACT FROM AUTHOR]

Nickel‐rich LiNi1−x−yCoxMnyO2 (NCM, 1−x−y ≥ 0.6) is known as a promising cathode material for lithium‐ion batteries since its superiority of high voltage and large capacity. However, polycrystalline Ni‐rich NCMs suffer from poor cycle stability, limiting its further application. Herein, single crystal and polycrystalline LiNi0.84Co0.07Mn0.09O2 cathode materials are compared to figure out the relation of the morphology and the electrochemical storage performance. According to the Li+ diffusion coefficient, the lower capacity of single crystal samples is mainly ascribed to the limited Li+ diffusion in the large bulk. In situ XRD illustrates that the polycrystalline and single crystal NCMs show a virtually identical manner and magnitude in lattice contraction and expansion during cycling. Also, the electrochemically active surface area (ECSA) measurement is employed in lithium‐ion battery study for the first time, and these two cathodes show huge discrepancy in the ECSA after the initial cycle. These results suggest that the single crystal sample exhibits reduced cracking, surface side reaction, and Ni/Li mixing but suffers the lower Li+ diffusion kinetics. This work offers a view of how the morphology of Ni‐rich NCM effects the electrochemical performance, which is instructive for developing a promising strategy to achieve good rate performance and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Rechargeable sodium metal batteries (SMBs) have emerged as promising alternatives to commercial Li‐ion batteries because of the natural abundance and low cost of sodium resources. However, the overuse of metallic sodium in conventional SMBs limits their energy densities and leads to severe safety concerns. Herein, we propose a sodium‐free‐anode SMB (SFA‐SMB) configuration consisting of a sodium‐rich Na superionic conductor‐structured cathode and a bare Al/C current collector to address the above challenges. Sodiated Na3V2(PO4)3 in the form of Na5V2(PO4)3 was investigated as a cathode to provide a stable and controllable sodium source in the SFA‐SMB. It provides not only remarkable Coulombic efficiencies of Na plating/stripping cycles but also a highly reversible three‐electron redox reaction within 1.0–3.8 V versus Na/Na+ confirmed by structural/electrochemical measurements. Consequently, an ultrahigh energy density of 400 Wh kg−1 was achieved for the SFA‐SMB with fast Na storage kinetics and impressive capacity retention of 93% after 130 cycles. A narrowed voltage window (3.0–3.8 V vs. Na/Na+) further increased the lifespan to over 300 cycles with a high retained specific energy of 320 Wh kg−1. Therefore, the proposed SFA‐SMB configuration opens a new avenue for fabricating next‐generation batteries with high energy densities and long lifetimes. [ABSTRACT FROM AUTHOR]

The current Li-based battery technology is limited in terms of energy contents. Therefore, several approaches are considered to improve the energy density of these energy storage devices. Here, we report the combination of a heteroatom-based gel polymer electrolyte with a hybrid cathode comprising of a Li-rich oxide active material and graphite conductive agent to produce a high-energy "shuttle-relay" Li metal battery, where additional capacity is generated from the electrolyte's anion shuttling at high voltages. The gel polymer electrolyte, prepared via in situ polymerization in an all-fluorinated electrolyte, shows adequate ionic conductivity (around 2 mS cm−1 at 25 °C), oxidation stability (up to 5.5 V vs Li/Li+), compatibility with Li metal and safety aspects (i.e., non-flammability). The polymeric electrolyte allows for a reversible insertion of hexafluorophosphate anions into the conductive graphite (i.e., dual-ion mechanism) after the removal of Li ions from Li-rich oxide (i.e., rocking-chair mechanism). The energy content increase is of paramount importance for the development of future Li-based batteries. Here, the authors propose a gel polymer electrolyte in combination with a positive electrode comprising of a Li-rich oxide active material and graphite to produce a high-energy Li metal cell. [ABSTRACT FROM AUTHOR]

While electrical vehicles (EVs) are expanding rapidly and getting more and more popular in the market, researchers have started to leverage the remaining capacity of used or to‐be‐retired batteries for their second‐life applications. It is crucial to develop a fast and efficient technology to first sort them and then extend their life while delivering energy, waste reduction, and economic benefits. In this work, a pulse clustering model embedded with improved bisecting K‐means algorithm is developed to effectively sort retired batteries with life cycles ranging from new to an end‐of‐life state. The relevance of selected variables is rigorously validated, reaching the accuracy as high as 88% compared with the traditional full charge–discharge test. To note, the test time has largely reduced from hours to minutes. This data‐driven clustering modeling with fast pulse test is a promising approach for clustering lithium‐ion batteries, which is demonstrated with a home‐built and high throughput intelligent clustering machine. In general, the technology opens a new generation of battery clustering, improving the efficiency and accuracy over the past semiempirical approaches. [ABSTRACT FROM AUTHOR]

Spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode candidate for the next‐generation high energy‐density lithium‐ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site‐selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fd3‾ m structure. This site‐selective doping not only suppresses unfavorable two‐phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg‐doped LNMOs exhibit extraordinarily stable electrochemical performance in both half‐cells and prototype full‐batteries with novel TiNb2O7 counter‐electrodes. This work pioneers an atomic‐doping engineering strategy for electrode materials that could be extended to other energy materials to create high‐performance devices. [ABSTRACT FROM AUTHOR]

The electrode surface of aqueous lithium‐ion batteries has been studied with alternating‐current scanning electrochemical microscopy (AC‐SECM), which enables the visualization of microscopic domains with different topography. An equivalent circuit was proposed to analyze the appropriate frequency for the interface image. In addition, AC signals (impedance, current, and phase shift) and measurement conditions, including the tip position, step size, and excitation voltage amplitude, were discussed and statistically treated to optimize the interface visualization parameter. This work not only provides some fundamental knowledge for obtaining high‐resolution AC‐SECM images of the electrode surface in lithium‐ion batteries, but also paves way for the solid electrolyte interphase studies in other battery systems. [ABSTRACT FROM AUTHOR]

Abstract: The lithium‐ion capacitor (LIC) has been regarded as a promising device that combines the merits of lithium‐ion batteries and supercapacitors, and that meets the requirements for both high energy and high power density. The development of advanced electrode materials is the key requirement. Herein, we report the bottom‐up synthesis of activated carbon nanofiber (a‐PANF) with a hierarchical porous structure and a high degree of graphitization. Electrospinning has been employed to prepare an interconnected fiber network with macropores, and ferric acetylacetonate has been introduced as both a mesopore‐creating agent and a graphitic catalyst to increase the degree of graphitization. Furthermore, chemical activation enlarges the specific surface area by producing abundant micropores. Half‐cell evaluation of the as‐prepared a‐PANF gave a discharge capacity of 80 mA h g−1 at 0.1 A g−1 within 2–4.5 V and no capacity fading after 1000 cycles at 2 A g−1, which represents a significant improvement compared to conventional activated carbon (AC). Furthermore, an as‐assembled LIC with a‐PANF cathode and Fe3O4 anode showed a superior energy density of 124.6 W h kg−1 at a specific power of 93.8 W kg−1, which remained at 103.7 W h kg−1 at 4687.5 W kg−1. This indicates promising application potential of a‐PANF as an electrode material for efficient energy storage systems. [ABSTRACT FROM AUTHOR]

Abstract: The development of lithium (Li) metal anodes Li metal batteries faces huge challenges such as uncontrolled Li dendrite growth and large volume change during Li plating/stripping, resulting in severe capacity decay and high safety hazards. A 3D porous copper (Cu) current collector as a host for Li deposition can effectively settle these problems. However, constructing a uniform and compact 3D porous Cu structure is still an enormous challenge. Herein, an electrochemical etching method for Cu–Zinc (Zn) alloy is reported to precisely engrave a 3D Cu structure with uniform, smooth, and compact porous network. Such a continuous structure endows 3D Cu excellent mechanical properties and high electrical conductivity. The uniform and smooth pores with a large internal surface area ensures well dispersed current density for homogeneous Li metal deposition and accommodation. A smooth and stable solid electrolyte interphase is formed and meanwhile Li dendrites and dead Li are effectively suppressed. The Li metal anode conceived 3D Cu current collector can stably cycle for 400 h under an Li plating/stripping capacity of 1 mA h cm−2 and a current density of 1 mA cm−2. The Li@3D Cu||LiFePO4 full cells present excellent cycling and rate performances. The electrochemical dealloying is a robust method to construct 3D Cu current collectors for dendrite‐free Li metal anodes. [ABSTRACT FROM AUTHOR]

How to compute the lithium concentration in Li-ion battery electrode particles fast and accurately is crucial in the study of physics-based Li-ion battery models. When computing the lithium concentration in Li-ion battery electrode particles with a high fidelity model, whether it can be achieved depends on the algorithm used. In this work, an algorithm for computing the lithium concentration in Li-ion battery electrode particles with the lithium concentration-stress coupling model is developed. Theoretically, providing that the parameters of the lithium concentration-stress coupling model are given, the lithium concentration in Li-ion battery electrode particles under any load current of Li-ion batteries whose amplitude is no higher than the given limit can be computed fast and accurately with the algorithm. To verify this, the algorithm is used in the State of Charge (SOC) estimation of two types of Li-ion batteries under different load currents. By timing the estimating processes and comparing the estimated results with the measured results, it can be concluded that the algorithm is effective. • Modify the deriving process of the lithium concentration-stress coupling model. • Develop an algorithm for the lithium concentration-stress coupling model. • Develop a program as the embodiment of the theoretical part in this paper. [ABSTRACT FROM AUTHOR]

Abstract: This study is trying to demonstrate whether graphene is able to construct an effective conducting network for both electron and ion transports in cathode system of a high-power lithium ion battery (LIB), not based on a coin cell, but by employing a commercial soft-packaged 10Ah battery pack as a model system. Compared with the cells using commercial conductive additive (7wt% carbon black and 3wt% conductive graphite), a 10Ah cell using only 1wt% graphene and 1wt% carbon black shows lower internal resistance and higher energy density due to the excellent conductivity of graphene. However, owing to the fact that the planar structure of the graphene sheets blocks fast Li+ ion transport, the steric effect resulted heavy polarization occurs at a relatively high charge/discharge rate (>3C). That is, although flexible and planar graphene helps construct an effective electron transfer network, it retards Li+ ion transport. Thus, for an energy-storing LIB with a low working charge/discharge rate, graphene additive shows apparent superiority over commercial ones even with much less addition fraction and may find its real commercial applications; while, for a high-power LIB which works at higher charge/discharge rate, fast ion transport path is required to be effectively constructed before a real application. Simulation results indicate that further work should be focused on the adjustment of electrode pore structure and modification of graphene steric structure accordingly to construct an unimpeded ion conducting network and provide high speed path for Li+ ion transport. [Copyright &y& Elsevier]

An inorganic and non-toxic compounds combination of FeCl·4HO, LiCO and HPO was chosen to synthesize homogeneous nano-structured LiFePO/C composite material via a simplified sol-gel route. The dependency of the physicochemical properties and the corresponding electrochemical responses on the residual carbon content were investigated in details. Rietveld refinement of X-ray diffraction measurement and X-ray photoelectron spectroscopy analysis confirmed the feasibility of preparing pure LiFePO phase via this approach. With increasing amount of residual carbon, the particles size gradually decreased and the bulk electrical conductivity monotonically increased. However, the higher level of residual carbon would bring disadvantageous impact on the lithium ion diffusion. Due to high electrical conductivity, controlled particle size and suitable microstructure, the sample with 4.5 wt.% residual carbon exhibited stable cycling performance and delivered high discharge capacity of 163, 119 and 108 mA h g at 0.1 C, 5 C and 10 C, respectively. [ABSTRACT FROM AUTHOR]

The activation characteristics and the effects of current densities on the formation of a separate LiCoO and graphite electrode were investigated and the behavior also was compared with that of the full LiCoO/graphite batteries using various electrochemical techniques. The results showed that the formation current densities obviously influenced the electrochemical impedance spectrum of Li/graphite, LiCoO/Li, and LiCoO/graphite cells. The electrolyte was reduced on the surface of graphite anode between 2.5 and 3.6 V to form a preliminary solid electrolyte interphase (SEI) film of anode during the formation of the LiCoO/graphite batteries. The electrolyte was oxidized from 3.95 V vs Li/Li on the surface of LiCoO to form a SEI film of cathode. A highly conducting SEI film could be formed gradually on the surface of graphite anode, whereas the SEI film of LiCoO cathode had high resistance. The LiCoO cathode could be activated completely at the first cycle, while the activation of the graphite anode needed several cycles. The columbic efficiency of the first cycle increased, but that of the second decreased with the increase in the formation current of LiCoO/graphite batteries. The formation current influenced the cycling performance of batteries, especially the high-temperature cycling performance. Therefore, the batteries should be activated with proper current densities to ensure an excellent formation of SEI film on the anode surface. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline LiFe1−x Sn x PO4 (0≤ x ≤0.07) samples are synthesized using SnCl4·5H2O as dopant via an inorganic-based sol–gel method. The dependency of the physicochemical and electrochemical properties on the doping amount of tin are systemically worked out and regular changes are revealed. In the whole concentration range, the chemical valence of Fe2+ is not basically changed whereas tin is found in two different oxidation states, namely +2 and +4. The replacement of Fe2+ by supervalent Sn4+ would lead to electron compensation. Under the synergetic effects between the charge compensation and the crystal distortion, the electrical conductivities for the bulk samples first increase and then decrease with the increasing amount of Sn doping. Upon the doping amount, the apparent lithium-ion diffusion coefficient and the electrochemical performance also display the similar trends. The doping is beneficial to refine the particle size and narrow down the size distribution, however optimizing the doping amount is necessary. Compared with other samples, the sample with a doping amount of about 3mol% delivers the highest capacities at all C-rates and exhibits the excellent rate capability due to the high electrical conductivity and the fast lithium-ion diffusion velocity. [Copyright &y& Elsevier]

Li-ion batteries are used widely in electric vehicles and electronic devices. Pseudo 2-Dimensional model(P2D model) is a classical physics-based Li-ion battery model and it is used widely for its high accuracy. In this paper, P2D model is modified for application. To compute the parameters and outputs of the modified P2D model fast and accurately, algorithms for computing the parameters and outputs of the modified P2D model are developed. To assess the effectiveness of the modified P2D model and the algorithms for computing the parameters and outputs of the modified P2D model, experiments and simulations are conducted. The experiments are conducted to obtain the data for conducting the simulations and the simulations are conducted based on the modified P2D model and the algorithms for computing the parameters and outputs of the modified P2D model. According to the simulation results, the modified P2D model and the algorithms for computing the parameters and outputs of the modified P2D model are effective. The modified P2D model and the algorithms for computing the parameters and outputs of the modified P2D model can be used to develop Li-ion battery charging methods. • P2D model is modified for application. • An algorithm for computing the parameters of the modified P2D model is developed. • An algorithm for computing the outputs of the modified P2D model is developed. [ABSTRACT FROM AUTHOR]

Sn4P3 is a potential high‐capacity anode material for a Li‐ion battery; however, its practical application is hindered by the fast capacity decay due to insufficient electronic conductivity, large volume expansion, and progressive tin agglomeration upon cycling. Herein, it is demonstrated that the highly conductive but inactive TiC can serve as an efficient additive to address the aforementioned issues, thus resulting in largely enhanced cycle stability and rate capability of Sn4P3. More importantly, the incorporation of high‐density TiC does not result in sacrifice in the volumetric capacity of the electrode. The Sn4P3/30TiC electrode delivers an initial volumetric capacity of ≈953.7 Ah L−1. After 100 cycles, a capacity of ≈701.0 Ah L−1 is maintained, which corresponds to a retention of ≈73.5%. This finding provides a feasible and effective strategy for designing stable anode materials with a high volumetric capacity. [ABSTRACT FROM AUTHOR]

In this article, a novel lithium ion batteries thermal design to manage ultrahigh thermal shock of a commercial small four‐rotor electric unmanned aerial vehicle (UAV) is developed and optimized. The cooling relies on internal heat pipe and convective cooling of UAV body, so that the heat generated by the battery can reach exterior cooling through a dedicated thermal path. The thermal management system is passive and requires no additional energy consumption. Finite element simulation is established to model the system and advanced thermal materials, and the system is optimized by response surface method in a dual objectives approach: minimizing maximum battery temperature and weight of the UAV. Simulation results show that the new passive cooling system can keep the temperature of the lithium ion battery within a reasonable range. The effects of convective heat transfer coefficient, discharge rate, and fuselage thermal conductivity were studied. After optimizing the system, the highest temperature of battery discharging at 3C rate can be kept no more than 36°C in the cost of 32.18 g weight increment. [ABSTRACT FROM AUTHOR]

Open circuit voltage (OCV) is an important characteristic parameter of lithium-ion batteries, which is used to analyze the changes of electronic energy in electrode materials, and to estimate battery state of charge (SOC) and manage the battery pack. Therefore, accurate OCV modeling is a great significance for lithium-ion battery management. In this paper, the characteristics of high-capacity lithium-ion batteries at different temperatures were considered, and the OCV-SOC characteristic curves at different temperatures were studied by modeling, exponential, polynomial, sum of sin functions, and Gaussian model fitting method with pulse test data. The parameters of fitting OCV-SOC curves by exponential model (n = 2), polynomial model (n = 3~7), sum of sin functions model (n = 3), and Gaussian model (n = 4) at temperatures of 45 °C, 25 °C, 0 °C, and −20°C are obtained, and the errors are analyzed. The experimental results show that the operating temperature of the battery influences the OCV-SOC characteristic significantly. Therefore, these factors need to be considered in order to increase the accuracy of the model and improve the accuracy of battery state estimation. [ABSTRACT FROM AUTHOR]

The use of high-capacity batteries as the battery pack of electric vehicles is the current development trend. In order to better design battery packages and battery management systems and develop related battery estimation technology, the related characteristics of high capacity battery cells need to be studied in depth. Capacity and pulse tests of batteries at different temperatures are carried out in this paper. Through these experimental data, the electrical characteristics of different parameters of the high capacity battery, such as capacity characteristic data, internal resistance characteristic data, OCV-SOC characteristic relation curve, power data and temperature rise are analyzed. The specific parameters of the battery in the second order equivalent circuit model are obtained by using the off-line parameter identification method. These parameters results can be used as comparison data and reference data. It is beneficial to the on-line parameter identification of battery model and the estimation of battery state, so as to shorten the development time and improve the quality of the development. [ABSTRACT FROM AUTHOR]

Sate of charge (SOC) accurate estimation is one of the most important functions in a battery management system for battery packs used in electrical vehicles. This paper focuses on battery SOC estimation and its issues and challenges by exploring different existing estimation methodologies. The key technologies of lithium-ion battery state estimation methodologies of the electrical vehicles categorized under five groups, such as the conventional method, adaptive filter algorithm, learning algorithm, nonlinear observer, and the hybrid method, are explored in an in-depth analysis. Lithium-ion battery characteristic, battery model, estimation algorithm, and cell unbalancing are the most important factors that affect the accuracy and robustness of SOC estimation. Finally, this paper concludes with the challenges of SOC estimation and suggests other directions for possible research efforts. [ABSTRACT FROM AUTHOR]

In article number 1500353, Yan‐Bing He, Feiyu Kang, and co‐workers report the successful preparation of a hierarchical all‐solid‐state electrolyte based on nitrile materials via an in‐situ synthesis method. This electrolyte exhibits low flammability, excellent flexibility, and outstanding electrochemical performance, and has particular applications potential in wearable devices and electric vehicles. [ABSTRACT FROM AUTHOR]

Zn metal anodes that are compatible with aqueous electrolytes open the door to developing safe and cost-effective rechargeable Zinc based batteries (RZBs). However, the Commercialization of RZBs requires efforts from multiple dimensions. In this study, the temperature dependence of the Zn metal anode's lifespan is in reverse with the Li metal anode counterpart. key factors that affect the temperature sensibility of the metal anode were summarized. Based on that, we demonstrate that adjusting the electrolyte composition can customize the nominal operation temperature and balance the battery performance. [Display omitted] The operating temperature of batteries is an essential consideration in actual applications. Understanding the temperature dependence is conducive to battery design. The experience in lithium-ion batteries (LIBs) indicates that the dendrite issue is exacerbated at lower temperatures and suppressed at higher temperatures. In this study, we revealed the dendrite evolution in aqueous rechargeable zinc-based batteries (RZBs), for which the opposite temperature dependence was observed. Detailed investigations elucidate that the degree of matching of the interface reaction rate and ion diffusivity, together with side reactions, are the key factors that determine the cycling performance. The different properties of organic and aqueous electrolytes result in a reversed temperature dependence. We further conducted a detailed investigation of hybrid electrolytes (organic and aqueous) for balancing the ion diffusivity and side reactions to broaden the working temperature window for RZBs. This work reveals a completely opposite temperature dependence for LIBs and RZBs and discloses the underlying mechanism, reminding one of the differences between LIBs and RZBs in many aspects. [ABSTRACT FROM AUTHOR]

A novel Li 4 Ti 5 O 12 (LTO) electrode with a hierarchical carbon-based conducting network has been developed for high rate lithium ion battery. The unique network is constructed by graphene sheets (GS) that are not only dispersed among (inter-) but also inside (intra-) LTO particles, together with a thin carbon layer wrapping around the LTO particles. The intraparticle GS promotes the electron transfer inside LTO particles while the interparticle GS together with carbon coating bridges the particles guaranteeing fast electron transfer among LTO particles, which construct a highway throughout the whole electrode sheet. Quantitatively, only a trace amount of GS (∼ 0.4 wt%) synergistic with carbon coating (∼0.8 wt%) contributes to a more effective conducting network in the produced LTO electrode and as a result much better performance as compared to the LTO case with similar carbon coating but free of GS. Due to the effectiveness of the conducting network, even with a tap density as high as ∼1.0 g cm −3 , the novel LTO possesses both excellent rate performance and cycling behaviors. The capacity of 123.5 mA h g −1 is obtained at a charge/discharge rate as high as 30 C and a very high capacity of 144.8 mAh g −1 is maintained even after 100 cycles at 10 C. Due to such a low fraction of carbon and a high tape density, the novel LTO electrode has a great practical application value in both the power and energy storage lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: As an appealing storage system for electric vehicle application, the lithium-oxygen battery could theoretically provide ultrahigh energy density; however, its attractive implementation is overshadowed by unsatisfactory electrochemical characteristics of the poor rate capability and the short span life. Here, we put forward one kind of effective strategy to ameliorate these deficiencies. By embedding a novel air electrode, the utilization level of the electrochemically available active sites is effectively increased and meanwhile the mass transfer of oxygen is signally improved. The evaporation speed of the solvent is greatly slowed down to some degree. We demonstrate that a super P-based lithium-O2 battery could be operated over stable 50 cycles at the current density of 3000 (equivalent to 2.4 mA cm−2), corresponding to a discharge time of about 20 min to 1000 . Based on the weight of the super P and the resultant Li2O2, the specific power density could reach 4040 W kg−1; even so, a substantial specific energy density of 1350 Wh kg−1 still could be achieved. [Copyright &y& Elsevier]

Abstract: A novel LiFePO4/C composite with 3D carbon network was prepared using Cetyltrimethyl Ammonium Bromid (CTAB) and starch as carbon sources via a facile method. The 3D carbon network structure was composed of a full and uniform carbon coating and a continuous carbon film framework. Good conductive paths enhancing electrons transfer efficiency and porous structure facilitating diffusion of lithium ions have been constructed by the 3D conductive network structure, which contributes the high ionic and electrical conductivities. As a result, the LiFePO4/C composite possesses an excellent electrochemical performance especially the high-rate cyclic performance. It delivers a capacity of 95mAhg−1 at current density of 3.4Ag−1 (20C). After 1200 cycles, the discharge capacity of 74mAhg−1 can still be obtained, almost reaching a retention of 80%, which is higher than the best cyclic performance in previous investigations. [Copyright &y& Elsevier]

Abstract: The lithium ion batteries using Li4Ti5O12 as the anode material are easily being inflated during charge and discharge, which, however, does not occur in the batteries using graphite as the anode material. The high reduction reactivity of electrolyte on the Li4Ti5O12 material may be the main reason. In this work, the reduction reactivities of electrolyte on the uncoated and carbon-coated Li4Ti5O12 electrodes are compared for the first time. The results show that the reduction decomposition of electrolyte does occur on the uncoated Li4Ti5O12 electrode at around 0.7V, while it only takes place at the first cycle on the carbon-coated Li4Ti5O12 electrode. The carbon coating layers cover the catalytic active sites of Li4Ti5O12 particles and separate the Li4Ti5O12 particles from the electrolyte. A successive solid electrolyte interface (SEI) film is formed on the carbon layer during the formation process, which can prevent the further reduction decomposition of electrolyte at around 0.7V. The impurity phases of rutile and anatase TiO2 do not influence the reduction reactivity of electrolyte. This work is not only important to understand the reduction decomposition mechanism of electrolyte on the Li4Ti5O12 electrode, but also provides an effective solution to suppress the reduction decomposition of electrolyte in the batteries. [Copyright &y& Elsevier]

Abstract State-of-health evaluation of lithium ion batteries is one of the key challenges to construct efficient battery system with enhanced performance. In this paper, we demonstrate a facile evaluation method which is based on the voltage stabilization behaviour during relaxation. A second-order equivalent circuit is employed to describe the voltage relaxation. By simulating the voltage relaxation curves, the characteristic parameters that can distinguish the ohmic, activation and concentration depolarizations are acquired. The obtained parameters are sensitive to electrochemical states, which provide comprehensive evaluation to the state-of-health of batteries and aging mechanism analysis. As an example, the proposed method identifies two aging stages of Li(Ni 1/3 Co 1/3 Mn 1/3) O 2 /graphite pouch cells during accelerated aging. Namely, a loss of lithium inventory in the first stage of aging, and the loss of active material in the next stage. Postmodern analysis including X-ray diffraction and high-resolution transmission electron microscope well agrees with the voltage relaxation simulation. The proposed state-of-health evaluation method is non-destructive and accessible for on-board aging diagnosis, which is of great significance for developing better battery management system. Highlights • A facile and in-depth state-of-health (SOH) evaluation method is developed. • We accurately model the VR behaviour using a second-order RC model. • The VR method is non-destructive and accessible for on-board aging diagnosis. • The aging mechanisms are distinguished by VR method. [ABSTRACT FROM AUTHOR]

Abstract Lithium ion capacitor (LIC) has been regarded as a promising device to combine the merits of high-energy lithium ion battery and high-power supercapacitor. The key challenge in developing high performance LIC is to achieve synergy between the high capacity of battery anode and the fast non-Faradaic reaction rate of capacitive cathode without compromising energy density. Here, we report 3D interconnected Fe 3 O 4 @C core@shell nanocomposites with enhanced lithium storage reaction kinetics as an anode material of LIC. Chitosan, a renewable biopolymer with rich functional groups, has been utilized as both structural directing agent and carbon precursor to assist the synthesis of Fe 3 O 4 @C composites, which have small particle size and an in-situ formed carbon coating layer. The carbon coating can not only dramatically improve the electronic conductivity, but also buffer the large volume expansion/contraction of Fe 3 O 4 during lithiation/delithiation. The Fe 3 O 4 @C composites show a reversible capacity of 1116.1 mA h g−1 at 0.1 A g−1 and 587.2 mA h g−1 at 2 A g−1, as well as stable capacity retention over cycling. Furthermore, the hybrid device based on Fe 3 O 4 @C composites achieves a specific energy of 110.1 Wh kg−1 at a specific power of 250 W kg−1, demonstrating promising application of the reported hybrid systems. Graphical abstract A lithium ion battery and supercapacitor hybrid device has been constructed with novel designed 3D interconnected Fe 3 O 4 @C anode prepared using chiotsan biopolymer, which combines high energy density and high power density simultaneously. The hybrid device achieves an exceptional energy density of 110.1 Wh kg−1 at a specific power of 250 W kg−1 with outstanding capacity retention. Image 1 [ABSTRACT FROM AUTHOR]

The antimony oxide/reduced graphene oxide (Sb 2 O 3 /rGO) nanocomposites are used as anode of Li-ion and Na-ion batteries (LIBs and NIBs). However, it is unclear about Li-ion and Na-ion storage mechanism in Sb 2 O 3 /rGO nanocomposites. Herein, the conversion-alloying mechanisms of Sb 2 O 3 /rGO anodes for Na-ion and Li-ion storage are comparatively studied with a combined in-situ XRD and quasi in-situ XPS method. The distinct behaviours are monitored during (de)lithiation and (de)sodiation with respect to crystal structure and chemical composition evolution. It is evidenced that the Na-ion can be easily transported to the inner part of the Sb 2 O 3 , where the Li-ion almost cannot reach, leading to a fully transformation during sodiation. In addition, the conversion reaction product of amorphous Na 2 O display their better chemical stability than amorphous Li 2 O during electrochemical cycles, which contribute to a stable and long cycling life of NIBs. This work gain insight into the high-capacity anodes with conversation-alloying mechanism for NIBs. [ABSTRACT FROM AUTHOR]

Template method has been used as an important method to prepare porous materials. However, there are few reports about template method employing potassium chloride as template. Here, potassium chloride is employed as a template to prepare the porous carbon, and transition metal nitrates (Fe(NO 3 ) 2 ,d Co(NO 3 ) 2 , Ni(NO 3 ) 2 ) are introduced to catalyze graphitization and to result different carbon structure during carbonization (denoted as Fe@C, Co@C and Ni@C). The Fe@C shows a formicary-like structure with an about 20 nm pore diameter and the Co@C displays a completely compact structure. Whereas, the Ni@C exhibits a foam-like structure with hierarchical porous structure consisting of macroporous frameworks, mesopores and ultrathin porous walls (∼5 nm). Its macropore and mesopore diameter is around 100 nm and 4 nm, respectively, its specific surface area is 464.5 m 2  g −1 . When adopted as anode material, the Ni@C presents much outstanding rate and cycling capability for lithium and sodium storage than Fe@C and Co@C, the capacity for sodium storage is 260 mAh g −1 after 100 cycles at 100 mA g −1 and 92 mAh g −1 after 1000 cycles at 1A g −1 , and the capacity for lithium storage is 683 mAh g −1 after 1000 cycles at a current density of 1 A g −1 . [ABSTRACT FROM AUTHOR]

Silicon-embedded porous carbon microspheres with an exceptional conductive framework for ions and electrons were obtained by electrospraying a mixed polymer solution of polystyrene and polyvinylpyrrolidone, containing silicon nanoparticles, carbon nanotubes and carbon blacks, and subsequent heat treatment. In the composite microspheres, silicon particles were embedded in the porous carbon framework composed of interwoven carbon nanotubes, filled carbon blacks and interconnected amorphous carbon derived from polymers. The cage-like porous carbon microspheres could not only accommodate the volume expansion of silicon but also ensure a robust electrical contact, fast transport for electrons and ions. Therefore, the silicon/carbon anode exhibits a high capacity of 1325 mAh g −1 at 0.2 A g −1 after 60 cycles and superior rate capability with a capacity of 925 mAh g −1 at a large current density of 5 A g −1 . [ABSTRACT FROM AUTHOR]

Multicomponent composites with an atomic-scale distribution of different component and an integrated lattice structure may manifest an enhanced synergistic effect compared to the mechanical mixture. In this paper, multicomponent Zn 0.12 Co 0.88 CO 3 composite with high tap density (2.11 g cm −3 ) synthesized via one-step solvothermal method, which exhibits hexagonal structure similar to that of the monocomponent cobalt carbonate (CoCO 3 ). The Zn-substitution could significantly improve the charge and discharge capacity of CoCO 3 from 1001.6 mAh g −1 to 1253.7 mAh g −1 at 0.2 C. When the Zn-substituted CoCO 3 is embedded in carbon nanotubes (CNT) network, the rate performance of Zn 0.12 Co 0.88 CO 3 can be improved greatly. The resulting Zn 0.12 Co 0.88 CO 3 /CNT exhibits outstanding rate performance, delivering a reversible capacity of 1098.4, 840.8, and 610.7 mAh g −1 at 0.5, 1 and 2 C, respectively. The excellent performance of Zn 0.12 Co 0.88 CO 3 /CNT is ascribed to the unique micro-sphere structure with carbon nanotubes. The elastic CNT networks are introduced to wrap the Zn 0.12 Co 0.88 CO 3 , which can not only provide a highly conductive network for electron transfer, but also serve as a buffer to alleviate the aggregation and volume changes of Zn 0.12 Co 0.88 CO 3 nanoparticles. The Zn 0.12 Co 0.88 CO 3 /CNT composite may serve as a novel high-capacity LIBs anode material for practical application, and a facile strategic approach is introduced for the full-molar-ratio synthesis of multicomponent composites. [ABSTRACT FROM AUTHOR]

In this study, commercial Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 /graphite (NCM/C) lithium-ion batteries were cycled at −10 °C under different current rates ranging from 0.2 C to 1C. Electrochemical measurements and post-mortem analysis were performed to identify the root causes of the degradation in the electrochemical performance of the cells. The results reveal that apart from the increase of lithium plating on the anode, there is a considerable and abnormal capacity loss on the NCM cathode with the increase in current rate. The different degradation mechanisms including the loss of lithium inventory (LLI) and the specific capacity loss of NCM material (LAM) during cycling at −10 °C were analyzed quantitatively. It is shown that the evolution trend of LLI with the increase in current rate (8.6%, 35.0%, 55.8% for 0.2 C, 0.5 C and 1 C respectively) corresponds closely to that of the capacity loss of the full-cells (8.6%, 45.5%, 63.6% for 0.2 C, 0.5 C and 1 C, respectively), which is different to the trend of LAM (7.2%, 8.8%, 22.3% for 0.2 C, 0.5 C and 1 C, respectively). Further analysis by XRD and HR-TEM clearly indicates that the crystallinity of the hexagonal layered structure of NCM was greatly impaired after low-temperature cycling at −10 °C, and spinel phase can be observed among the layered structure. [ABSTRACT FROM AUTHOR]

Although silicon/carbon (Si/C) nanohybrid materials are promising to improve the energy density of lithium ion batteries, their nano-sized features severely hinder their practical application, as the current battery assembly process favors micron-sized electrode materials. In this work, to combine the merits of nano- and micron-sized materials together, micron-sized carbon coated graphene wrapped Si/carbon black (Si/CB@G@C) spherical hybrids are synthesized via a water-in-oil (W/O) emulsion system. In the obtained hierarchical structure, Si and CB nanoparticles (NPs) are embedded in the micron-sized graphene sphere, well encapsulated by the flexible graphene sheets, and these hybrids are further coated by an amorphous carbon layer. Thus, the graphene sphere can accommodate the volume expansion of Si NPs during lithiation, protect them from direct exposure to the electrolyte and enhance the electrical conductivity. Furthermore, the CB particles between Si NPs and graphene, together with the carbon coating layer can provide highly conductive network for the transport of electrons, also preventing Si NPs from directly contact with the electrolyte. As a result, the as-prepared Si/CB@G@C hybrids exhibit a significantly improved cycling stability compared with pure Si and Si@G hybrids, along with an excellent rate performance (728 mAh g −1 at 2 A g −1 ). [ABSTRACT FROM AUTHOR]

This work demonstrates how a very low fraction of graphene greatly enhances the usage efficiency of carbon-based conductive additive in LiCoO 2 -based lithium ion batteries (LIB) and develops a strategy using binary conductive additive to have a high performance battery, especially with excellent rate performance. With a much lower fraction of carbon additive for a commercial LIB, only 0.2 wt% graphene nanosheet (GN) together with 1 wt% Super-P (SP) constructing an effective conductive network, the prepared battery exhibits outstanding cycling stability (146 mAhg −1 at 1C with retention of 96.4% after 50 cycles) and rate capability (116.5 mAhg −1 even at 5C). In this battery, a composite conducting network is formed with a long-range electron pathway formed by a trace amount of GN and the short-range electron pathway by aggregation of SP particles. More interestingly, in micro-sized LiCoO 2 system, the GN additive does not present hindrance effect for lithium ion transport even in high rate discharge, which is entirely different from the nano-sized LiFePO 4 system. This study further demonstrates commercial potential of GN additive for high performance LIB and more importantly gives a well-designed recipe for its real application. [ABSTRACT FROM AUTHOR]

The silicon/carbon (Si/C) hybrid fibers with a hierarchical core–shell structure are prepared by encapsulating Si nanoparticles in the interconnected hollow carbon fibers (Si@IHCFs) based on a dual coaxial electrospinning technique. For the hierarchical structure, Si nanoparticles are embedded in the honeycomb-like carbon framework in the fiber core, which is further wrapped by the interlocked cobweb-like carbon shell network. As lithium-ion battery anode, the well-defined Si@IHCFs demonstrates a reversible capacity of 903 mAh g −1 and a capacity retention of 89% after 100 cycles with a current density of 0.2 A g −1 . With the current density gradually increasing to 2.0 A g −1 , the electrode shows a specific capacity of 743 mAh g −1 , exhibiting superior rate capability compared to the Si/C fibers with a core–shell but unconnected structure. The excellent electrochemical properties are attributed to the hierarchical core–shell structure and cross-linked network for the Si/C composite fibers. The carbon framework in the core region accommodates the volume expansion of Si by the honeycomb-like pores. And the interconnected carbon shell can not only prevent electrolyte from permeating into the core section, but also improve the electronic conductivity by the connections in the fiber network. [ABSTRACT FROM AUTHOR]

To boost the commercialization of high energy density lithium ion batteries (LIBs) used for electric vehicles, the development of electrode materials with high volumetric capacity is of great significance. In this work, a novel Si/slightly exfoliated graphite (SEG)/carbon composite used as anode for LIBs with high volumetric capacity is fabricated. The Si nanoparticles are uniformly intercalated in the squashed interlayers of SEG which are then further filled by amorphous carbon. The SEG acts as a conductivity skeleton, while the spaces between squashed interlayers(folds) in SEG function as buffer spaces for the expansion of Si nanoparticles during lithiation reactions. The amorphous carbon connects the Si nanoparticles with SEG to form a 3D conductive network. Owing to the high packing density (0.7 g cm −3 ) and unique structure, this material possesses a high volumetric capacity of 1050 mAh cm −3 . Meanwhile, the Si/SEG/C composite also exhibits excellent rate and cyclic performance, presenting a reversible capacities of 1456 and 1056 mAh g −1 at 100 and 500 mA g −1 with capacity retention of 84.7% after 50 cycles at 500 mA g −1 . This work opens up an avenue to craft the Si/C composite with high volumetric energy densities and rate performance. [ABSTRACT FROM AUTHOR]

Graphene and other carbon materials have been combined with various silicon (Si) nanostructures to accommodate the volume change of Si and enhance their electrical conductivity. However, for most of the formed hybrids, their low initial Coulombic efficiency (CE), fragile structures and poor stability cannot meet the practical application of battery. In this work, inspired by the structure and composition of reinforced concrete, a Si nanoparticles embedded in porous carbon/graphene (Si-C/G) electrode is fabricated through directly calcining a Si-polyacrylonitrile/graphene oxide precursor on a current collector. In this concrete-like structure, amorphous carbon, the carbonization product of polyacrylonitrile, acts as the “cement” and binds all components together. The flexible graphene network effectively enhances the strength, flexibility and conductivity of the electrode, as does the reinforcing rod framework in concrete. This carbon/graphene scaffold can accommodate the volume expansion of Si and isolate Si from electrolyte. Such Si-C/G electrode with small surface area and compact structure achieves a high initial CE of 78% and a reversible capacity of 1711 mAh g −1 , as well as outstanding rate and cycling performances. [ABSTRACT FROM AUTHOR]

In this paper, the degradation of LiFePO 4 /graphite batteries during 10 months of storage under different temperatures and states of charge (SOCs) is studied. The effects of SOC during storage process are systematically investigated using electrochemical methods and post-mortem analysis. The results show that at elevated temperature of 55 °C, higher stored SOC results in more significant increase in bulk resistance ( R b ) and charge-transfer resistance ( R ct ) of full battery, whereas the rate-discharge capability of stored battery is unchanged. The side reactions at the electrode/electrolyte interface caused by self-discharge are the main reasons for the performance fading during storage. For LiFePO 4 cathode, long-time storage does not influence the framework structure under various SOCs. The existence of little irreversible capacity loss and impedance increase indicates that side reactions also occur at the positive electrode. For graphite anode, only a little capacity loss is found upon storage. There is a significant increase in impedance and a small amount of Fe deposition on graphite anode after storage at 100% SOC and 55 °C. The lithium ion loss arises from side reactions taking place at the graphite anode, which is responsible for the capacity degradation of battery during the storage process. XPS analysis confirms that a deposit layer composed of Li 2 CO 3 and LiF is formed on the surface of anode. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 nanoparticles encapsulated in porous carbon fibers (Fe 3 O 4 @PCFs) as anode materials in lithium ion batteries are fabricated by a facile single-nozzle electrospinning technique followed by heat treatment. A mixed solution of polyacrylonitrile (PAN) and polystyrene (PS) containing Fe 3 O 4 nanoparticles is utilized to prepare hybrid precursor fibers of Fe 3 O 4 @PS/PAN. The resulted porous Fe 3 O 4 /carbon hybrid fibers composed of compact carbon shell and Fe 3 O 4 -embeded honeycomb-like carbon core are formed due to the thermal decomposition of PS and PAN. The Fe 3 O 4 @PCF composite demonstrates an initial reversible capacity of 1015 mAh g −1 with 84.4% capacity retention after 80 cycles at a current density of 0.2 A g −1 . This electrode also exhibits superior rate capability with current density increasing from 0.1 to 2.0 A g −1 , and capacity retention of 91% after 200 cycles at 2.0 A g −1 . The exceptionally high performances are attributed to the high electric conductivity and structural stability of the porous carbon fibers with unique structure, which not only buffers the volume change of Fe 3 O 4 with the internal space, but also acts as high-efficient transport pathways for ions and electrons. Furthermore, the compact carbon shell can promote the formation of stable solid electrolyte interphase on the fiber surface. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been regarded as one of the most attractive anode materials for the next generation lithium-ion batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, the architecture of Si-based anode material still needs to be well designed to overcome the structure degradation and instability of the solid-electrolyte interphase caused by a large volume change during cycling. Here we report the electrochemical performances of a novel binder-free Si/carbon composite film consisting of alternatively stacked Si-porous carbon layers and graphene layers, which is synthesized by electrostatic spray deposition followed by heat treatment. For this composite film, Si nanoparticles are embedded in the porous carbon layer composed of nitrogen-doped carbon framework, carbon black and carbon nanotubes. And the combined Si-porous carbon layer is further sandwiched by flexible and conductive graphene sheets. The multilayered Si-porous carbon/graphene electrode shows a maximum reversible capacity of 1020 mAh g −1 with 75% capacity retention after 100 cycles and a good rate capability on the basis of the total electrode weight. The excellent electrochemical performances are attributed to the fact that the layer-by-layer porous carbon matrix can accommodate the volume change of Si particles and maintain the structural and electrical integrities. [ABSTRACT FROM AUTHOR]

Li 4 Ti 5 O 12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process. The interfacial reactions between LTO and electrolyte solution may be the main reason. In this work, the LTO spinel particles are modified with ZnO coating using a chemical process to reduce the surface reactivity of LTO particles. Results show that the ZnO coating can effectively stabilize the electrode/electrolyte interface and suppress the formation of a solid electrolyte interface (SEI) film. Simultaneously, this ZnO modification can improve the electronic conductivity and lithium ion diffusion coefficient, which contributes to a great improvement in cyclic and high rate capabilities of LTO electrode. The ZnO coating on LTO may be an effective method to restrict the gassing behavior of LTO based battery. [ABSTRACT FROM AUTHOR]

During the cycling of Li-O2batteries thedischarge process gives rise to dynamically evolving agglomeratescomposed of lithium–oxygen nanostructures; however, littleis known about their composition. In this paper, we present resultsfor a Li-O2battery based on an activated carbon cathodethat indicate interfacial effects can suppress disproportionationof a LiO2component in the discharge product. High-intensityX-ray diffraction and transmission electron microscopy measurementsare first used to show that there is a LiO2component alongwith Li2O2in the discharge product. The stabilityof the discharge product was then probed by investigating the dependenceof the charge potential and Raman intensity of the superoxide peakwith time. The results indicate that the LiO2componentcan be stable for possibly up to days when an electrolyte is lefton the surface of the discharged cathode. Density functional calculationson amorphous LiO2reveal that the disproportionation processwill be slower at an electrolyte/LiO2interface comparedto a vacuum/LiO2interface. The combined experimental andtheoretical results provide new insight into how interfacial effectscan stabilize LiO2and suggest that these interfacial effectsmay play an important role in the charge and discharge chemistriesof a Li–O2battery. [ABSTRACT FROM AUTHOR]

Lithium iron phosphate/carbon (LiFePO 4 /C) microspheres with an excellent multiple conductive network are synthesized using iron (III) acrylate as both iron and carbon sources. The innermost network is constructed by a uniform carbon layer on the surface of LiFePO 4 primary nanoparticles, which derives from the carbonation of in-situ polymerized polyacrylic acid (PAA) layer. Moreover, the acetylene black added in spay drying process fills the voids among primary nanoparticles to construct the second conductive network. Finally, the carbon from optimized content sucrose used as binder and linker can interconnect primary nanoparticles together to form the third network. In addition, subtle mesoporous structure is formed inside the multiple carbon conductive network. The highly speed electron transfer and lithium ion transportation can be achieved simultaneously for LiFePO 4 /C microspheres. All these features contribute to their great rate performance (163.1 mAh g −1 at 0.1 C and 126.5 mAh g −1 at 5 C) and outstanding cycling stability (95.3% of capacity retention after 1000 cycles at 5 C/5C). The well-designed LiFePO 4 /C microspheres with unique structure are very promising cathode materials for rechargeable lithium ion power batteries. [ABSTRACT FROM AUTHOR]

A porous tin peroxide/carbon (SnO 2 /C) composite electrode coated with an amorphous carbon layer is prepared using a facile method. In this electrode, spherical graphite particles act as supporter of electrode framework, and the interspace among particles is filled with porous amorphous carbon derived from decomposition of polyvinylidene fluoride and polyacrylonitrile. SnO 2 nanoparticles are uniformly embedded in the porous amorphous carbon matrix. The pores in amorphous carbon matrix are able to buffer the huge volume expansion of SnO 2 during charge/discharge cycling, and the carbon framework can prevent the SnO 2 particles from pulverization and re-aggregation. The carbon coating layer on the outermost surface of electrode can further prevent porous SnO 2 /C electrode from contacting with electrolyte directly. As a result, the repeated formation of solid electrolyte interface is avoided and the cycling stability of electrode is improved. The obtained SnO 2 /C electrode presents an initial coulombic efficiency of 77.3% and a reversible capacity of 742 mA h g −1 after 130 cycles at a current density of 100 mA g −1 . Furthermore, a reversible capacity of 679 mA h g −1 is obtained at 1 A g −1 . [ABSTRACT FROM AUTHOR]

[Display omitted] • A uniform protective layer composed of Li x Al y SiO z /Li 2 O is formed by the chemical reaction of aluminum isopropoxide with Li x Si. • The modified Li x Si has high lithium reserves and great environmental adaptability. • The storage time under the condition of certain oxygen and water content can be prolonged. In recent years, lots of efforts have been applied to improve the initial Coulombic efficiency (ICE) of lithium-ion batteries (LIBs), among which prelithiation is considered to be one of the most promising schemes. Here we report a modified Li x Si with high lithium reserves and great environmental adaptability as the prelithiation reagent, which can make up for the capacity loss of the negative electrode in the first cycle. Through the chemical reaction between aluminum isopropoxide and Li x Si, a protective layer consisting of Li x Al y SiO z /Li 2 O is formed on the surface of Li x Si particles. This synthesized material provides a new idea for the actual industrial production of prelithiation. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the formation of SEI films on Li4Ti5O12 (LTO) anodes offers a major benefit to large-scale applications of lithium ion batteries made therefrom. This paper reveals that an SEI film is formed above 1 V due to the interfacial reaction between the electrode and electrolyte: LTO anodes are previously considered free from SEI films when cycled between 1 and 3 V. The reactivity and the formation of SEI films are much affected by the morphology and surface area of the electrode. To study the above, LTO powders with different morphologies are synthesized using lithium acetate (LA) and lithium hydroxide (LH) as the lithium sources. LTO–LH consisting of agglomerates of primary small particles with a large surface area has higher reactivity than LTO–LA with a cubic structure and small surface area. As a result, the LTO–LH anode with a smooth SEI film offers better cyclic performance than the LTO–LA anode with a porous SEI film. The addition of vinylene carbonate to the electrolyte facilitates rapid formation of a protective SEI film on LTO–LA, greatly improving the rate and cyclic performance: stable specific capacity of 155.6 mAh g−1 and remarkable 135.2 mAh g−1 after 500 cycles at 10 C are recorded. [Copyright &y& Elsevier]