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Lithium (Li)-rich transition metal oxide cathodes with a cation disordered rock salt structure (DRX) are increasingly gaining popularity for advanced Li batteries as they offer high capacity and cost benefits over the commonly used layered Li transition metal oxide cathodes. However, the performance of DRX cathodes and their applications are limited by severe side reactions between the cathode and the state-of-the-art carbonate-based electrolytes at high voltage of 4.8 V, transition metal dissolution, and structural instability of the cathode particles. In this work, an advanced localized high-concentration electrolyte (LHCE) is developed to form a stable cathode-electrolyte interphase and mitigate structural instability of the Li1.13Mn0.66Ti0.21O2 (LMTO) DRX during electrochemical cycling. Li||LMTO half cells with the LHCE demonstrate increased capacity, cycling stability, and superior rate capability compared with cells containing a conventional carbonate electrolyte. For instance, the Li||LMTO cells cycled in LHCE show a higher initial capacity of 205.2 mAh g−1 and a better capacity retention of 72.5% after 200 cycles at a current density of 20 mA g−1 than those with the conventional electrolyte (initial capacity of 187.7 mAh g−1 and capacity retention of 19.9%). This work paves the way to the development of practical DRX cathode-based high-energy Li batteries.

Vehicle electrification is a critical application of lithium-ion batteries (LIBs), and it is essential to develop LIBs that can operate at sub-ambient temperatures with satisfying performance. Conventional LIBs have performance deficits at low temperatures which hinder their use in extreme environments. One approach to address this problem is to rationally engineer the electrode/electrolyte interface with electrolyte additives to improve the electrochemical kinetics at sub-ambient temperatures. In this work, silicic acid (SiAc) is incorporated into standard LIB electrolyte as an additive to enhance the capacity and energy density of LIBs at temperatures down to −20 °C. Full-cell impedance analysis and X-ray photoelectron spectroscopy of cycled electrodes point towards an additive-induced change in surface chemistry which alters the charge transfer process. It is proposed that the SiAc additive participated in the formation of solid electrolyte interphase (SEI) and lowered the activation energy of the interface impedance, assisting lithium ion transport across the interface at lower temperatures.

Monitoring real-world battery degradation is crucial for the widespread application of batteries in different scenarios. However, acquiring quantitative degradation information in operating commercial cells is challenging due to the complex, embedded, and/or qualitative nature of most existing sensing techniques. This process is essentially limited by the type of signals used for detection. Here, we report the use of effective battery thermal conductivity (keff) as a quantitative indicator of battery degradation by leveraging the strong dependence of keff on battery-structure changes. A measurement scheme based on attachable thermal-wave sensors is developed for non-embedded detection and quantitative assessment. A proof-of-concept study of battery degradation during fast charging demonstrates that the amount of lithium plating and electrolyte consumption associated with the side reactions on the graphite anode and deposited lithium can be quantitatively distinguished using our method. Therefore, this work opens the door to the quantitative evaluation of battery degradation using simple non-embedded thermal-wave sensors.

The mass adoption of electric vehicles is hindered by the inadequate extreme fast charging (XFC) performance (i.e., less than 15 min charging time to reach 80% state of charge) of commercial high-specific-energy (i.e., >200 Wh/kg) lithium-ion batteries (LIBs). Here, to enable the XFC of commercial LIBs, we propose the regulation of the battery's self-generated heat via active thermal switching. We demonstrate that retaining the heat during XFC with the switch OFF boosts the cell's kinetics while dissipating the heat after XFC with the switch ON reduces detrimental reactions in the battery. Without modifying cell materials or structures, the proposed XFC approach enables reliable battery operation by applying

Although the two active redox centers in Li-rich cathodes, including the anionic and cationic contributions, can enable Li-ion batteries to achieve outstanding specific energy, their behaviors at different current densities have not been clarified. Here, we provide a comparative study of transition metals (TMs) and oxygen redox activities by directly accessing their oxidation states in Li-rich materials operated at very different current rates. Our data reveal that the oxidation of oxygen in the near-surface region is at the same level for electrodes cycled with a wide range of current rates, indicating a reaction gradient of lattice oxygen redox reactions. The oxidation process of lattice oxygen is found to be dynamically compatible with that of the TMs. Combining the results of first principles calculations and complementary experimental findings, we propose a detailed mechanism of structural distortion from octahedral Li to tetrahedral Li and the role of oxygen vacancy in Li+ diffusion. It is found that fast delithiation occurring at high current densities can easily cause local structural transformation, leading to a limited Li+ diffusion rate and consequently suppressing rate capability.

The development of battery sensing techniques is crucial for safe, reliable, and fast operation of lithium-ion batteries (LIBs). There is a growing realization that the spatially averaged chemical information provided by existing battery diagnostic tools is insufficient for understanding degradation of LIBs. Here, we report the use of thermal waves for operando probing of the local lithium concentration as a function of depth inside battery electrodes. The dependence of the thermal conductivity of electrodes on lithiation is used for lithium detection for the first time. A proof-of-concept study of graphite anodes demonstrates that thermal-wave sensing provides spatial information of lithium concentration comparable with experimental results using synchrotron X-ray diffraction. Therefore, a valuable battery sensing technique based on thermal waves is developed for studying the lithium concentration and the degradation of electrodes during fast charge, which may lead to much cheaper and faster sensing techniques compared with synchrotron-based techniques.

The rapidly growing technological demand for lithium-ion batteries has prompted the development of novel cathode materials with high energy density, low cost, and improved safety. High voltage spinel, LiNi0.5Mn1.5O4 (LNMO), is one of the most promising candidates yet to be commercialized. The two primary obstacles for this material are the inferior electronic conductivity and fast capacity degradation in full cells due to the high operating voltage. By systematically addressing these limitations, we successfully develop a thick LNMO electrode with areal capacity loadings up to 3 mAh·cm−2. The optimized thick electrode is paired with a commercial graphite anode at both the coin cell and pouch cell level, achieving a full cell capacity retention as high as 72% and 78%, respectively, after 300 cycles. We attribute this superior cycling stability to careful optimizations of cell components and testing conditions, with a specific focus improving electronic conductivity and high voltage compatibility. These results suggest precise control of materials quality, electrode architecture and electrolyte optimization can soon support the development of a cobalt-free battery system based on a thick LNMO cathode (>4 mAh·cm2), which will eventually meet the needs of next-generation Li-ion batteries with reduced cost, improved safety, and assured sustainability.

Owing to the negative impact of the extensive utilization of batteries on the environment, sustainability of the cells needs to be included in the systemic research of batteries. Herein, a dissolvable ionic crosslinked polymer (DICP) is exploited as a binder for lithium–sulfur batteries by crosslinking the polyacrylic acid and polyethyleneimine through carboxy-amino ionic interaction. This interaction is pH-controlled, and therefore, the crosslinked binder network can be readily dissociated under basic conditions, providing a facile strategy enabling valuable components recycled through a convenient washing method. The sulfur cathode prepared using the recycled carbon–sulfur composite can deliver comparable capacity as that of fresh electrode. In addition, evidence from cell performance and characterizations, such as in situ X-ray absorption spectroscopy, in situ UV–visible spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculation, confirms that DICP is a more effective binder than its commercial counterpart on suppressing polysulfide dissolution in the electrolyte. Exploiting reversible crosslinked polymer binder for recyclable Li–S batteries with ameliorated electrochemical performance, this study illuminates sustainable development for large-scale energy storage systems.

The Li-S battery is a promising next-generation technology due to its high theoretical energy density (2600 Wh kg-1) and low active material cost. However, poor cycling stability and coulombic efficiency caused by polysulfide dissolution have proven to be major obstacles for a practical Li-S battery implementation. In this work, we develop a novel strategy to suppress polysulfide dissolution using hydrofluoroethers (HFEs) with bi-functional, amphiphlic surfactant-like design: a polar lithiophilic "head" attached to a fluorinated lithiophobic "tail." A unique solvation mechanism is proposed for these solvents whereby dissociated lithium ions are readily coordinated with lithiophilic "head" to induce self-assembly into micelle-like complex structures. Complex formation is verified experimentally by changing the additive structure and concentration using small angle X-ray scattering (SAXS). These HFE-based electrolytes are found to prevent polysulfide dissolution and to have excellent chemical compatibility with lithium metal: Li||Cu stripping/plating tests reveal high coulombic efficiency (>99.5%), modest polarization, and smooth surface morphology of the uniformly deposited lithium. Li-S cells are demonstrated with 1395 mAh g-1 initial capacity and 71.9% retention over 100 cycles at >99.5% efficiency-evidence that the micelle structure of the amphiphilic additives in HFEs can prohibit polysulfide dissolution while enabling facile Li+ transport and anode passivation.

The rheological properties of electrode slurries used in the manufacturing of lithium-ion batteries affect the manufacturing processes as well as the battery quality, such as electrochemical and durability performance. There is thus an urgent need to develop a physics-based model to describe the rheological properties of these electrode slurries to enable further optimization of battery electrode production. In this paper, we present a microrheological model for estimating the viscosity of electrode slurries that incorporates colloidal forces such as van der Waals and polymeric steric repulsion forces. The model shows good agreement with the experimentally determined viscosities of a graphite-based anode slurry and should be extendable to describe the rheological properties of cathode slurries.

A highly graphitized carbon on a silicon monoxide (SiO) surface coating at low temperature, based on polymer precursor π⁻π stacking, was developed. A novel conductive and electrochemically stable carbon coating was rationally designed to modify the SiO anode materials by controlling the sintering of a conductive polymer, a pyrene-based homopolymer poly (1-pyrenemethyl methacrylate; PPy), which achieved high graphitization of the carbon layers at a low temperature and avoided silicon carbide formation and possible SiO material transformation. When evaluated as the anode of a lithium-ion battery (LIB), the carbon-coated SiO composite delivered a high discharge capacity of 2058.6 mAh/g at 0.05 C of the first formation cycle with an initial Coulombic efficiency (ICE) of 62.2%. After 50 cycles at 0.1 C, this electrode capacity was 1090.2 mAh/g (~82% capacity retention, relative to the capacity of the second cycle at 0.1 °C rate), and a specific capacity of 514.7 mAh/g was attained at 0.3 C after 500 cycles. Furthermore, the coin-type full cell composed of the carbon coated SiO composite anode and the Li[Ni0.5Co0.2Mn0.3O₂] cathode attained excellent cycling performance. The results show the potential applications for using a π⁻π stacking polymer precursor to generate a highly graphitize coating for next-generation high-energy-density LIBs.

A highly graphitized carbon on a silicon monoxide (SiO) surface coating at low temperature, based on polymer precursor π⁻π stacking, was developed. A novel conductive and electrochemically stable carbon coating was rationally designed to modify the SiO anode materials by controlling the sintering of a conductive polymer, a pyrene-based homopolymer poly (1-pyrenemethyl methacrylate; PPy), which achieved high graphitization of the carbon layers at a low temperature and avoided silicon carbide formation and possible SiO material transformation. When evaluated as the anode of a lithium-ion battery (LIB), the carbon-coated SiO composite delivered a high discharge capacity of 2058.6 mAh/g at 0.05 C of the first formation cycle with an initial Coulombic efficiency (ICE) of 62.2%. After 50 cycles at 0.1 C, this electrode capacity was 1090.2 mAh/g (~82% capacity retention, relative to the capacity of the second cycle at 0.1 °C rate), and a specific capacity of 514.7 mAh/g was attained at 0.3 C after 500 cycles. Furthermore, the coin-type full cell composed of the carbon coated SiO composite anode and the Li[Ni0.5Co0.2Mn0.3O₂] cathode attained excellent cycling performance. The results show the potential applications for using a π⁻π stacking polymer precursor to generate a highly graphitize coating for next-generation high-energy-density LIBs.

The lithium-sulfur (Li-S) rechargeable battery has the benefit of high gravimetric energy density and low cost. Significant research currently focuses on increasing the sulfur loading and sulfur/inactive-materials ratio, to improve life and capacity. Inspired by nature's ant-nest structure, this research results in a novel Li-S electrode that is designed to meet both goals. With only three simple manufacturing-friendly steps, which include slurry ball-milling, doctor-blade-based laminate casting, and the use of the sacrificial method with water to dissolve away table salt, the ant-nest design has been successfully recreated in an Li-S electrode. The efficient capabilities of the ant-nest structure are adopted to facilitate fast ion transportation, sustain polysulfide dissolution, and assist efficient precipitation. High cycling stability in the Li-S batteries, for practical applications, has been achieved with up to 3 mg·cm(-2) sulfur loading. Li-S electrodes with up to a 85% sulfur ratio have also been achieved for the efficient design of this novel ant-nest structure.

A SiOSnCoC composite anode is assembled using a conductive polymer binder for the application in next-generation high energy density lithium-ion batteries. A specific capacity of 700 mAh/g is achieved at a 1C (900 mA/g) rate. A high active material loading anode with an areal capacity of 3.5 mAh/cm(2) is demonstrated by mixing SiOSnCoC with graphite. To compensate for the lithium loss in the first cycle, stabilized lithium metal powder (SLMP) is used for prelithiation; when paired with a commercial cathode, a stable full cell cycling performance with a 86% first cycle efficiency is realized. By achieving these important metrics toward a practical application, this conductive polymer binder/SiOSnCoC anode system presents great promise to enable the next generation of high-energy lithium-ion batteries.

A SiOSnCoC composite anode is assembled using a conductive polymer binder for the application in next-generation high energy density lithium-ion batteries. A specific capacity of 700 mAh/g is achieved at a 1C (900 mA/g) rate. A high active material loading anode with an areal capacity of 3.5 mAh/cm(2) is demonstrated by mixing SiOSnCoC with graphite. To compensate for the lithium loss in the first cycle, stabilized lithium metal powder (SLMP) is used for prelithiation; when paired with a commercial cathode, a stable full cell cycling performance with a 86% first cycle efficiency is realized. By achieving these important metrics toward a practical application, this conductive polymer binder/SiOSnCoC anode system presents great promise to enable the next generation of high-energy lithium-ion batteries.

High-tap-density silicon nanomaterials are highly desirable as anodes for lithium ion batteries, due to their small surface area and minimum first-cycle loss. However, this material poses formidable challenges to polymeric binder design. Binders adhere on to the small surface area to sustain the drastic volume changes during cycling; also the low porosities and small pore size resulting from this material are detrimental to lithium ion transport. This study introduces a new binder, poly(1-pyrenemethyl methacrylate-co-methacrylic acid) (PPyMAA), for a high-tap-density nanosilicon electrode cycled in a stable manner with a first cycle efficiency of 82%-a value that is further improved to 87% when combined with graphite material. Incorporating the MAA acid functionalities does not change the lowest unoccupied molecular orbital (LUMO) features or lower the adhesion performance of the PPy homopolymer. Our single-molecule force microscopy measurement of PPyMAA reveals similar adhesion strength between polymer binder and anode surface when compared with conventional polymer such as homopolyacrylic acid (PAA), while being electronically conductive. The combined conductivity and adhesion afforded by the MAA and pyrene copolymer results in good cycling performance for the high-tap-density Si electrode.

Lithium bis(trifluoromethane) sulfonamide (TFSI) is a promising electrolyte salt in lithium batteries, due to its good conductivity and high dissociation between the lithium cation and its anion. By tethering N-pentane trifluoromethane sulfonamide (C5NHTf), a TFSI analogue molecule, onto the surface of silica nanoparticle as a monolayer coverage should increase the Li(+) transference number to unity since anions bound to particles have reduced mobilities. Silica polymer composite has better mechanical property than that of the pure PEO. Analogously trifluoromethane sulfonic aminoethyl methacrylate (TfMA), a TFSI analogue vinyl monomer, was polymerized on silica nanoparticle surface as a multilayer coverage. Anchored polyelectrolytes to particle surfaces offer multiple sites for anions, and in principle the carrier concentration would increase arbitrarily and approach the carrier concentration of the bulk polyelectrolyte. Monolayer grafted nanoparticles have a lithium content of 1.2 × 10(-3) g Li/g, and multilayer grafted nanoparticles have a lithium content over an order higher at 2 × 10(-2) g Li/g. Electrolytes made from monolayer grafted particles exhibit a weak conductivity dependence on temperature, exhibiting an ionic conductivity in the range of 10(-6) S/cm when temperatures increase to 80 °C. While electrolytes made from multilayer grafted particles show a steep increase in conductivity with temperature with an ionic conductivity increase to 3 × 10(-5) S/cm at 80 °C, with an O/Li ratio of 32.

A composite lithium electrolyte composed of polyelectrolyte-grafted nanoparticles and polyethylene glycol dimethyl ether (PEGDME) is synthesized and characterized. Polyanions immobilized by the silica nanoparticles have reduced anion mobility. Composite nanoparticles grafted by poly(lithium 4-styrenesulfonate) only have moderate conductivity at 60 °C. Almost an order increase of the conductivity to ∼10(-6) S/cm is achieved by co-polymerization of the poly(ethylene oxide) methacrylate with sodium 4-styrenesulfonate, which enhances dissociation between lithium cation and polyanion and facilitates lithium ion transfer from the inner part of the polyelectrolyte layer. This composite electrolyte has the potential to suppress lithium dendrite growth and enable the use of lithium metal anode in rechargeable batteries.

Sulfur species dissolution, precipitation and phase transformation during the charge and discharge process strongly affect the performance of lithium sulfur (Li-S) batteries. Interface properties between electrode and electrolyte play an important role in these batteries. In this work, four kinds of binders with different functionalities, which differs both in chemical and electrical properties, are employed to study how the interface properties affect the battery reaction mechanism. The phase transformation of sulfur species is studied in detail. Remarkable differences are observed among sulfur cathodes with different binders. More solid-phase sulfur species precipitation is observed with binders that have carbonyl functional groups, like poly(9, 9-dioctylfluorene-co-fluorenone-co-methylbenzoic ester) (PFM) and poly(vinylpyrrolidone) (PVP), in both fully charged and discharged states. Also, the improved conductivity from introducing conductive binders greatly promotes sulfur species precipitation. These findings suggest that the contributions from functional groups affinity and binder conductivity lead to more sulfur transformation into the solid phase, so the shuttle effect can be greatly reduced, and a better cell performance can be obtained.

The mechanical failure at the electrode interfaces (laminate/current collector and binder/particle interfaces) leads to particle isolation and delamination, which has been regarded as one of the main reasons for the capacity decay and cell failure of lithium-ion batteries (LIBs). Polymer binder provides the key function for a good interface property and for maintaining the electrode integrity of LIBs. Triethylene glycol monomethyl ether (TEG) moieties were incorporated into polymethacrylic acid (PMAA) to different extents at the molecular level. Microscratch tests of the graphite electrodes based on these binders indicate that the electrode is more flexible with 5 or 10% TEG in the polymer binders. Crack generation is inhibited by the flexible TEG-containing binder, compared to that of the unmodified PMAA-based electrode, leading to the better cycling performance of the flexible electrode. With a 10% TEG moiety in the binder, the graphite half-cell reaches a reversible capacity of >270 mAh/g at the 1C rate, compared to a value of ∼190 mAh/g for the unmodified PMAA binder.

Stabilized Lithium Metal Powder (SLMP®) was applied in graphite anode and the effects of this prelithiation method to cell performance were investigated. Performance of prelithiated cells was compared with that of regular graphite based cells. The first cycle capacity loss of SLMP prelithiated cell was largely reduced and the corresponding first cycle Coulombic efficiency was significantly improved. The graphite/NMC cell with SLMP prelithiation but without any standard cell formation process showed better cycle performance than that of none SLMP containing cell with standard formation process. Prelithiation of graphite electrode with SLMP promote stable solid electrolyte interface (SEI) formation on the surface of graphite anode. Application of SLMP in lithium-ion battery thus provides an effective method to enhance capacity, and promises a low cost SEI formation process. This also implies the potential use of other promising anode materials, such as Si and Sn that have large first cycle capacity loss, in commercial lithium-ion batteries. © 2014 Published by Elsevier Ltd.

A styrene butadiene rubber (SBR)-polyvinylidene difluoride (PVDF) based binder system has been developed for an electrochemical system that is not compatible with the conventional N-methyl pyrrolidinone (NMP) solvent used to cast most Li-ion electrode slurries. This polymer system's binding properties decouple the mechanical and ionic-transport properties. It demonstrates comparable mechanical properties to SBR-based electrodes and cell performance to traditional PVDF-based electrodes. This new binder design however enables the incorporation of stabilized lithium metal powder (SLMP) into a graphite anode to improve its first cycle coulombic efficiency. © The Royal Society of Chemistry 2013.