Moderately concentrated electrolyte enabling high-performance lithium metal batteries with a wide working temperature range

The electrolyte integrated with lithium metal anodes is subjected to the issues of interfacial compatibility and stability,which strongly influence the performances of high-energy lithium metal batteries.Here,we report a new electrolyte recipe viz.a moderately concentrated electrolyte comprising of 2.4 M lithium bis(fluorosulfonyl)imide(LiFSI)in a cosolvent mixture of fluorinated ethylene carbonate(FEC)and dimethyl carbonate(DMC)with relatively high ion conductivity.Owing to the preferential decomposition of LiFSI and FEC,an inorganic-rich interphase with abundant Li_(2)O and LiF nanocrystals is formed on lithium metal with improved robustness and ion transfer kinetics,enabling lithium plating/stripping with an extremely low overpotential of~8 mV and the average CE of 97%.When tested in Li||LiFePO_(4) cell,this electrolyte provides long-term cycling with a capacity retention of 98.3%after 1000 cycles at 1 C and an excellent rate performance of 20 C,as well as an areal capacity of 1.35 mA h cm^(-2)at the cathode areal loading of 9 mg cm^(-2).Moreover,the Li||LiFePO_(4) cell exhibits excellent wide-temperature performances(-40~60℃),including long-term cycling stability over 2600 cycles without visible capacity fading at 0℃,as well as extremely high average CEs of 99.6%and 99.8% over 400 cycles under-20℃ and 45℃.

Mesoscale interplay among composition heterogeneity,lattice deformation,and redox stratification in single-crystalline layered oxide cathode

Single-crystalline layered oxide materials for lithium-ion batteries are featured by their excellent capacity retention over their polycrystalline counterparts,making them sought-after cathode candidates.Their capacity degradation,however,becomes more severe under high-voltage cycling,hindering many high-energy applications.It has long been speculated that the interplay among composition heterogeneity,lattice deformation,and redox stratification could be a driving force for the performance decay.The underlying mechanism,however,is not well-understood.In this study,we use X-ray microscopy to systematically examine single-crystalline NMC particles at the mesoscale.This technique allows us to capture detailed signals of diffraction,spectroscopy,and fluorescence,offering spatially resolved multimodal insights.Focusing on early high-voltage charging cycles,we uncover heterogeneities in valence states and lattice structures that are inherent rather than caused by electrochemical abuse.These heterogeneities are closely associated with compositional variations within individual particles.Our findings provide useful insights for refining material synthesis and processing for enhanced battery longevity and efficiency.

Air-stable inorganic solid-state electrolytes for high energy density lithium batteries: Challenges, strategies, and prospects

Solid-state batteries have been considered as promising next-generation energy storage devices for potentially higher energy density and better safety compared with commercial lithium-ion batteries that are based on organic liquid electrolytes.However,in terms of indispensable solid-state electrolytes,there are remaining issues to be solved before entering the market.Most solid-state electrolytes are air-sensitive,which causes a complex and expensive cell assembly and impressible interface.Therefore,the solid-state electrolytes are expected to be atmosphere-stable,which will undoubtedly bring significant benefits to solid-state battery manufacturing.This review covers air-stabilityrelated issues of different types of inorganic solid-state electrolytes and the corresponding strategies.First,we provide an overview of solid-state electrolytes and solid-state batteries,including their history and advantages/disadvantages.Then,different types of solid-state electrolytes are selected as examples to illustrate the unfavorable interactions in air and the corresponding adverse effects.Next,according to recent advances,we summarize the effective strategies of constructing different types of air-stable inorganic solid-state electrolytes.Finally,perspectives on designing accessible air-stable solid-state electrolytes are provided,aiming to achieve the assembly of high-performance solid-state batteries in the atmosphere.

Data-Driven Lithium-Ion Battery Cathode Research with State-of-the-Art Synchrotron X-ray Techniques

CONSPECTUS:The lithium-ion battery(LIB)is a tremendously successful technology for energy storage thanks to its favorable characteristics including high energy density,long lifespan,affordability,and safety.It has been widely adopted in sectors including consumer electronics and electric vehicles,which are featured by an enormous market value.To meet the ever-increasing demands for energy density and cycle life,industry and academia are continuously devoting efforts to improve the current LIB technology.This requires an in-depth understanding of the electrochemical reaction processes and degradation/failure mech-anisms,to which advanced characterization is pivotal.Combining advanced synchrotron X-ray techniques with machine learning(ML)methods has been demonstrated as a powerful tool for uncovering the fundamental reaction and aging mechanisms in LIB and is emerging as an important research frontier.Our group’s research has been focusing on the battery cathode,which is a major limiting factor in today’s LIB technology.The degradation and failure of cathode materials in LIB are multiscale.The chemo mechanical processes at these different length scales are intertwined and mutually modulated.Therefore,it is crucial to understand the underlying mechanisms of charge−lattice−morphology−kinetics interactions in battery cathodes as a function of the electrochemical states.Synchrotron X-ray technology has unique advantages.It can detect lattice structure,electronic structure,chemical valence state,and multiscale morphology in different experimental modes,with high resolution and high efficiency.However,the large-scale experimental data bring great challenges in terms of reduction,analysis,and interpretation.Data-driven methods based on ML can greatly assist researchers to understand,control,and predict the electrochemical behavior of the complex battery cathode systems.In this Account,we focus on showcasing the integration of synchrotron and ML techniques for LIB cathode research.We review our recent findings on charge−lattice−morphology−kinetics in LIB cathode materials via this approach.First,the ML-based morphological study of cathode materials is discussed,highlighting a ML-assisted automatic feature recognition,particle identification,and statistical analysis of the prolonged cycling-induced particle damage and detachment from the carbon matrix.Second,we discuss the chemical heterogeneity and lattice deformation in cathode materials revealed by ML-assisted multimodal synchrotron characterizations.The role of ML tools in identifying and understanding chemical outliers and lattice defects in NCM cathodes is highlighted.Third,we provide our perspective on a future“dream”experiment for investigating the spatial distribution of cation−anion redox coupling effects in the battery cathode by means of resonant inelastic X-ray scattering(RIXS)imaging with ML.We anticipate that this new approach will provide new horizons for the development of novel high-energy and high-power-density LIB cathode materials.With an emphasis on the data-driven approaches for researching battery materials with synchrotron X-ray techniques,we hope that this Account will lead to more endeavors in this research field.