Liquid metal as an efficient protective layer for lithium metal anodes in all-solid-state batteries

Lithium metal batteries with inorganic solid-state electrolytes have emerged as strong and attractive candidates for electrochemical energy storage devices because of their high-energy content and safety.Nonetheless,inherent challenges of deleterious lithium dendrite growth and poor interfacial stability hinder their commercial application.Herein,we report a liquid metal-coated lithium metal(LM@Li)anode strategy to improve the contact between lithium metal and a Li6PS5Cl inorganic electrolyte.The LM@Li symmetric cell shows over 1000 h of stable lithium plating/stripping cycles at 2mA cm^(-2) and a significantly higher critical current density of 9.8 mAcm^(-2) at 25°C.In addition,a full battery assembled with a high-capacity composite LiNbO3@-LiNi_(0.7)Co_(0.2)Mn_(0.1)O_(2)(LNO@NCM721)cathode shows stable cycling performance.Experimental and computational results have demonstrated that dendrite growth tolerance and physical contact in solid-state batteries can be reinforced by using LM interlayers for interfacial modification.

Interface and mechanical degradation mechanisms of the silicon anode in sulfide-based solid-state batteries at high temperatures

Silicon(Si)is a competitive anode material owing to its high theoretical capacity and low electrochemical potential.Recently,the prospect of Si anodes in solid-state batteries(SSBs)has been proposed due to less solid electrolyte interphase(SEI)formation and particle pulverization.However,major challenges arise for Si anodes in SSBs at elevated temperatures.In this work,the failure mechanisms of Si-Li_(6)PS_(5)Cl(LPSC)composite anodes above 80℃are thoroughly investigated from the perspectives of interface stability and(electro)chemo-mechanical effect.The chemistry and growth kinetics of Lix Si|LPSC interphase are demonstrated by combining electrochemical,chemical and computational characterizations.Si and/or Si–P compound formed at Lix Si|LPSC interface prove to be detrimental to interface stability at high temperatures.On the other hand,excessive volume expansion and local stress caused by Si lithiation at high temperatures damage the mechanical structure of Si-LPSC composite anodes.This work elucidates the behavior and failure mechanisms of Si-based anodes in SSBs at high temperatures and provides insights into upgrading Si-based anodes for application in SSBs.

A dynamic database of solid-state electrolyte(DDSE)picturing all-solid-state batteries

All-solid-state batteries(ASSBs)are a class of safer and higher-energy-density materials compared to conventional devices,from which solid-state electrolytes(SSEs)are their essential components.To date,investigations to search for high ion-conducting solid-state electrolytes have attracted broad concern.However,obtaining SSEs with high ionic conductivity is challenging due to the complex structural information and the less-explored structure-performance relationship.To provide a solution to these challenges,developing a database containing typical SSEs from available experimental reports would be a new avenue to understand the structureperformance relationships and find out new design guidelines for reasonable SSEs.Herein,a dynamic experimental database containing>600 materials was developed in a wide range of temperatures(132.40–1261.60 K),including mono-and divalent cations(e.g.,Li^(+),Na^(+),K^(+),Ag^(+),Ca^(2+),Mg^(2+),and Zn^(2+))and various types of anions(e.g.,halide,hydride,sulfide,and oxide).Data-mining was conducted to explore the relationships among different variates(e.g.,transport ion,composition,activation energy,and conductivity).Overall,we expect that this database can provide essential guidelines for the design and development of high-performance SSEs in ASSB applications.This database is dynamically updated,which can be accessed via our open-source online system.

Incorporation of Ionic Conductive Polymers into Sulfide Electrolyte-Based Solid-State Batteries to Enhance Electrochemical Stability and Cycle Life

Sulfide-based inorganic solid electrolytes are promising materials for high-performance safe solid-state batteries.The high ion conductivity,mechanical characteristics,and good processability of sulfide-based inorganic solid electrolytes are desirable properties for realizing high-performance safe solid-state batteries by replacing conventional liquid electrolytes.However,the low chemical and electrochemical stability of sulfide-based inorganic solid electrolytes hinder the commercialization of sulfide-based safe solid-state batteries.Particularly,the instability of sulfide-based inorganic solid electrolytes is intensified in the cathode,comprising various materials.In this study,carbonate-based ionic conductive polymers are introduced to the cathode to protect cathode materials and suppress the reactivity of sulfide electrolytes.Several instruments,including electrochemical spectroscopy,X-ray photoelectron spectroscopy,and scanning electron microscopy,confirm the chemical and electrochemical stability of the polymer electrolytes in contact with sulfide-based inorganic solid electrolytes.Sulfide-based solid-state cells show stable electrochemical performance over 100 cycles when the ionic conductive polymers were applied to the cathode.

Anion competition for Li^(+)solvated coordination environments in poly(1,3 dioxolane)electrolyte to enable high-voltage lithium metal solid-state batteries

Gel-based polymer electrolytes are limited by the polarity of the residual solvent,which restricts the coupling-breaking behaviour during Li^(+)conduction,resulting in the Li^(+)transport kinetics being greatly affected.Here,we designed anion competitive gel polymer electrolyte(ACPE)by introducing lithium difluoro(oxalato)borate(LiDFOB)anion into the 1,3-dioxolane(DOL)in situ polymerisation system.ACPE enhances the ionic dipole interaction between Li^(+)and the solvent molecules and synergizes with Li^(+)across the solvation site of the polymer ethylene oxide(EO)unit,combination that greatly improves the Li^(+)transport efficiency.As a result,ACPE exhibits 1.12 mS cm^(−1)ionic conductivity and 0.75 Li^(+)transfer number at room temperature.Additionally,this intra-polymer solvation sheath allows preferential desolvation of DFOB−,which contributes to the formation of kinetically stable anion-derived interphase and effectively mitigates side reactions.Our results demonstrate that the assembled Li||NCM622 solid-state battery exhibits lifespan of over 300 cycles with average Coulombic efficiency of 98.8%and capacity retention of 80.3%.This study introduces a novel approach for ion migration and interface design,paving the way for high-safety and high-energy-density batteries.

Pressure-Induced Pre-Lithiation Enables High-Performing Si Anodes in All-Solid-State Batteries

A commentary on pressure-induced pre-lithiation towards Si anodes in allsolid-state Li-ion batteries(ASSLIBs)using sulfide electrolytes(SEs)is presented.First,feasible pre-lithiation technologies for Si anodes in SE-based ASSLIBs especially the significant pressure-induced pre-lithiation strategies are briefly reviewed.Then,a recent achievement by Meng et al.in this field is elaborated in detail.Finally,the significance of Meng’s work is discussed.

Alleviating the sluggish kinetics of all-solid-state batteries via cathode single-crystallization and multi-functional interface modification

The application of Li-rich Mn-based cathodes, the most promising candidates for high-energy-density Liion batteries, in all-solid-state batteries can further enhance the safety and stability of battery systems.However, the utilization of high-capacity Li-rich cathodes has been limited by sluggish kinetics and severe interfacial issues in all-solid-state batteries. Here, a multi-functional interface modification strategy involving dispersed submicron single-crystal structure and multi-functional surface modification layer obtained through in-situ interfacial chemical reactions was designed to improve the electrochemical performance of Li-rich Mn-based cathodes in all-solid-state batteries. The design of submicron single-crystal structure promotes the interface contact between the cathode particles and the solid-state electrolyte,and thus constructs a more complete ion and electron conductive network in the composite cathode.Furthermore, the Li-gradient layer and the lithium molybdate coating layer constructed on the surface of single-crystal Li-rich particles accelerate the transport of Li ions at the interface, suppress the side reactions between cathodes and electrolyte, and inhibit the oxygen release on the cathode surface. The optimized Li-rich cathode materials exhibit excellent electrochemical performance in halide all-solid-state batteries. This study emphasizes the vital importance of reaction kinetics and interfacial stability of Lirich cathodes in all-solid-state batteries and provides a facile modification strategy to enhance the electrochemical performance of all-solid-state batteries based on Li-rich cathodes.

Surface engineering of nickel-rich single-crystal layered oxide cathode enables high-capacity and long cycle-life sulfide all-solid-state batteries

Sulfide all-solid-state lithium batteries(SASSLBs)with a single-crystal nickel-rich layered oxide cathode(LiNix-CoyMn_(1-x-y)O_(2),x≥0.8)are highly desirable for advanced power batteries owing to their excellent energy density and safety.Nevertheless,the cathode material's cracking issue and its severe interfacial problem with sulfide solid electrolytes have hindered the further development.This study proposes to employ surface modification engineering to produce B-NCM cathode materials coated with boride nanostructure stabilizer in situ by utilizing NCM encapsulated with residual lithium.This approach enhances the electrochemical performance of SASSLBs by effectively inhibiting electrochemical-mechanical degradation of the NCM cathode material on cycling and reducing deleterious side reactions with the solid sulfide electrolyte.The B-NCM/LPSCl/Gr SASSLBs demonstrate impressive cycling stability,retaining 84.19%of its capacity after 500 cycles at 0.2 C,which represents a 30.13%increase vs.NCM/LPSCl/Gr.It also exhibits a specific capacity of 170.4 mAh/g during its first discharge at 0.1 C.This work demonstrates an effective surface engineering strategy for enhancing capacity and cycle life,providing valuable insights into solving interfacial problems in SASSLBs.

Elucidating Ion Transport Phenomena in Sulfide/Polymer Composite Electrolytes for Practical Solid-State Batteries

Despite the enormous interest in inorganic/polymer composite solid-state electrolytes(CSEs)for solid-state batteries(SSBs),the underlying ion transport phenomena in CSEs have not yet been elucidated.Here,we address this issue by formulating a mechanistic understanding of bi-percolating ion channels formation and ion conduction across inorganic-polymer electrolyte interfaces in CSEs.A model CSE is composed of argyrodite-type Li_6PS_5Cl(LPSCl)and gel polymer electrolyte(GPE,including Li~+-glyme complex as an ion-conducting medium).The percolation threshold of the LPSCl phase in the CSE strongly depends on the elasticity of the GPE phase.Additionally,manipulating the solvation/desolvation behavior of the Li~+-glyme complex in the GPE facilitates ion conduction across the LPSCl-GPE interface.The resulting scalable CSE(area=8×6(cm×cm),thickness~40μm)can be assembled with a high-mass-loading LiNi_(0.7)Co_(0.15)Mn_(0.15)O_(2)cathode(areal-mass-loading=39 mg cm~(-2))and a graphite anode(negative(N)/positive(P)capacity ratio=1.1)in order to fabricate an SSB full cell with bi-cell configuration.Under this constrained cell condition,the SSB full cell exhibits high volumetric energy density(480 Wh L_(cell)~(-1))and stable cyclability at 25℃,far exceeding the values reported by previous CSE-based SSBs.

Surface-roughened current collectors for anode-free all-solid-state batteries

Anode-free all-solid-state batteries(AFASSBs), composed of a fully lithiated cathode and a bare current collector(CC) that eliminates excess lithium, can maximize the energy density(because of a compact cell configuration) and improve the safety of solid-state systems. Although significant progress has been made by modifying CCs in liquid-based anode-free batteries, the role of CCs and the mechanism of Li formation on CCs in AFASSBs are still unexplored. Here, we systematically investigate the effect of the surface roughness of the CCs on the Li plating/stripping behavior in AFASSBs. The results show that the moderately roughened CC substantially improves the Coulombic efficiency and cycle stability of AFASSBs owing to the increased contact points between the solid electrolyte and the roughened CC. In contrast, the excessively roughened CC deteriorates the performance owing to the contact loss.Moreover, an ex situ interface analysis reveals that the roughened surface of the CC could suppress the interfacial degradation during the Li ion extraction from a sulfide solid electrolyte to a CC. This provides an indication to the origin that hinders the electrochemical performance of AFASSBs. These findings show the potential for the application of surface-engineered CCs in AFASSBs and provide guidelines for designing advanced CCs.

Tuning Solid Interfaces via Varying Electrolyte Distributions Enables High-Performance Solid-State Batteries

Solid/solid interface is the major challenge for high-performance solid-state batteries.Solid electrolytes(SEs)play a crucial role in the fabrication of effective interfaces in solid-state batteries.Herein,the electrolyte distribution with varied particle sizes is tuned to construct solid-state batteries with excellent performance at different operating temperatures.Solid-state batteries with the configuration S/L(small-sized SE in composite cathode and large-sized SE in electrolyte layer)show the best performance at room temperature(168 mA h g^(−1) at 0.2 C,retention of 99%,100 cycles)and−20°C(89 mA h g^(−1) at 0.05 C),while the configuration S/S displays better performance at elevated temperature.The superior performance of S/L battery is associated with faster lithium-ion dynamics due to the better solid/solid interface between active materials and electrolytes.Moreover,the inferior performance at 60℃is caused by the formation of voids and cracks in the electrolyte layer during cycling.In contrast,the S/S battery delivers superior performance at elevated operating temperature because of the integrated structure.This work confirms that tailoring electrolyte size has significant effect on fabricating all-climate solid-state batteries.

First Principle Material Genome Approach for All Solid-State Batteries

Due to ever-increasing concern about safety issues in using alkali metal ionic batteries, all solid-state batteries (ASSBs) have attracted tremendous attention. The foundation to enable high-performance ASSBs lies in delivering ultra-fast ionic conductors that are compatible with both alkali anodes and high-voltage cathodes. Such a challenging task cannot be fulfilled, without solid understanding covering materials stability and properties, interfacial reactions, structural integrity, and electrochemical windows. Here in this work, we will review recent advances on fundamental modeling in the framework of material genome initiative based on the density functional theory (DFT), focusing on solid alkali batteries. Efforts are made in offering a dependable road chart to formulate competitive materials and construct "better" batteries.

Electro-chemo-mechanical design of polymer matrix in composited LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode endows solid-state batteries with superior performance

Nickel-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811) cathode material has been widely concerned due to its high voltage,high specific capacity and excellent rate performance,which is considered as one of the most promising cathode materials for the next generation of high-energy-density solid-state lithium batteries.However,serious electro-chemo-mechanical degradation of Nickel-rich cathode during cycling,especially at a high voltage(over 4.5 V),constrains their large-scale application.Here,using the multiphysical simulation,highly-conductive polymer matrix with spontaneous stress-buffering effect was uncovered theoretically for reinforcing the electrochemical performance of composited NCM81 1 cathode through the visualization of uniform concentration distribution of Li-ion coupled with improved stress field inside NCM811 cathode.Thereupon,polyacrylonitrile(PAN) and soft polyvinylidene fluoride(PVDF) were selected as the polymer matrix to fabricate the composited NCM811 cathode(PVDFPAN@NCM811) for improving the electrochemical performance of the solid-state NMC811|Li full cells,which can maintain high capacity over 146.2 mA h g^(-1)after 200 cycles at a high voltage of 4.5 V.Suggestively,designing a multifunctional polymer matrix with high ionic conductivity and mechanical property can buffer the stress and maintain the integrity of the structure,which can be regarded as the door-opening avenue to realize the high electrochemical performance of Ni-rich cathode for solidstate batteries.

Progress and perspective of interface design in garnet electrolyte-based all-solid-state batteries

Inorganic solid-state electrolytes(SSEs)are nonflammable alternatives to the commercial liquid-phase electrolytes.This enables the use of lithium(Li)metal as an anode,providing high-energy density and improved stability by avoiding unwanted liquid-phase chemical reactions.Among the different types of SSEs,the garnet-type electrolytes witness a rapid development and are considered as one of the top candidates to pair with Li metal due to their high ionic conductivity,thermal,and electrochemical stability.However,the large resistances at the interface between garnet-type electrolytes and cathode/anode are the major bottlenecks for delivering desirable electrochemical performances of all-solid-state batteries(SSBs).The electrolyte/anode interface also suffers from metallic dendrite formation,leading to rapid performance degradation.This is a fundamental material challenge due to the poor contact and wettability between garnet-type electrolytes with electrode materials.Here,we summarize and analyze the recent contributions in mitigating such materials challenges at the interface.Strategies used to address these challenges are divided into different categories with regard to their working principles.On one hand,progress has been made in the anode/garnet interface,such as the successful application of Li-alloy anode and different artificial interlayers,significantly improving interfacial performance.On the other hand,the desired cathode/garnet interface is still hard to reach due to the complex chemical and physical structure at the cathode.The common methods used are nanostructured cathode host and sintering additives for increasing the contact area.On the basis of this information,we present our views on the remaining challenges and future research of electrode/garnet interface.This review not only motivates the need for further understanding of the fundamentals,stability,and modifications of the garnet/electrode interfaces but also provides guidelines for the future design of the interface for SSB.

Space Charge Layer Eff ect in Sulfide Solid Electrolytes in All-Solid-State Batteries: In-situ Characterization and Resolution

All-solid-state lithium batteries(ASSLBs)have advantages of safety and high energy density,and they are expected to become the next generation of energy storage devices.Sulfide-based solid-state electrolytes(SSEs)with high ionic conduc-tivity and low grain boundary resistance exhibit remarkable practical application.However,the space charge layer(SCL)eff ect and high interfacial resistance caused by a mismatch with the current commercial oxide cathodes restrict the develop-ment of sulfide SSEs and ASSLBs.This review summarizes the research progress on the SCL eff ect of sulfide SSEs and oxide cathodes,including the mechanism and direct evidence from high performance in-situ characterizations,as well as recent progress on the interfacial modification strategies to alleviate the SCL eff ect.This study provides future direction to stabilize the high performance sulfide-based solid electrolyte/oxide cathode interface for state-of-the-art ASSLBs and future all-SSE storage devices.

In situ characterizations of solid-solid interfaces in solid-state batteries using synchrotron X-ray techniques

The solid-solid electrode-electrolyte interface represents an important component in solid-state batteries(SSBs),as ionic diffusion,reaction,transformation,and restructuring could all take place.As these processes strongly influence the battery performance,studying the evolution of the solid-solid interfaces,particularly in situ during battery operation,can provide insights to establish the structure-property relationship for SSBs.Synchrotron X-ray techniques,owing to their unique penetration power and diverse approaches,are suitable to investigate the buried interfaces and examine structural,compositional,and morphological changes.In this review,we will discuss various surface-sensitive synchrotron-based scattering,spectroscopy,and imaging methods for the in situ characterization of solid-solid interfaces and how this information can be correlated to the electrochemical properties of SSBs.The goal is to overview the advantages and disadvantages of each technique by highlighting representative examples,so that similar strategies can be applied by battery researchers and beyond to study similar solid-solid interface systems.

Review of the electrochemical performance and interfacial issues of high-nickel layered cathodes in inorganic all-solid-state batteries

All-solid-state batteries potentially exhibit high specific energy and high safety,which is one of the development directions for nextgeneration lithium-ion batteries.The compatibility of all-solid composite electrodes with high-nickel layered cathodes and inorganic solid electrolytes is one of the important problems to be solved.In addition,the interface and mechanical problems of high-nickel layered cathodes and inorganic solid electrolyte composite electrodes have not been thoroughly addressed.In this paper,the possible interface and mechanical problems in the preparation of high-nickel layered cathodes and inorganic solid electrolytes and their interface reaction during charge–discharge and cycling are reviewed.The mechanical contact problems from phenomena to internal causes are also analyzed.Uniform contact between the high-nickel cathode and solid electrolyte in space and the ionic conductivity of the solid electrolyte are the prerequisites for the good performance of a high-nickel layered cathode.The interface reaction and contact loss between the high-nickel layered cathode and solid electrolyte in the composite electrode directly affect the passage of ions and electrons into the active material.The buffer layer constructed on the high-nickel cathode surface can prevent direct contact between the active material and electrolyte and slow down their interface reaction.An appropriate protective layer can also slow down the interface contact loss by reducing the volume change of the high-nickel layered cathode during charge and discharge.Finally,the following recommendations are put forward to realize the development vision of high-nickel layered cathodes:(1)develop electrochemical systems for high-nickel layered cathodes and inorganic solid electrolytes;(2)elucidate the basic science of interface and electrode processes between high-nickel layered cathodes and inorganic solid electrolytes,clarify the mechanisms of the interfacial chemical and electrochemical reactions between the two materials,and address the intrinsic safety issues;(3)strengthen the development of research and engineering technologies and their preparation methods for composite electrodes with high-nickel layered cathodes and solid electrolytes and promote the industrialization of all-solid-state batteries.

Duality of Li_(2)CO_(3) in Solid-State Batteries

Solid-state batteries(SSBs)have been considered the most promising technology because of their superior energy density and safety.Among all the solid-state electrolytes(SEs),Li_(7) La_(3) Zr_(2) O_(12)(LLZO)with high ionic conductivity(3×10^(−4) S/cm)has been widely investigated.However,its large-scale production in ambient air faces a challenge.After air exposure,the generated Li_(2)CO_(3) layer deteriorates the ionic conductivity and interfacial wettability,thus greatly compromising the electrochemical performance of SSBs.Many works aim to eliminate this layer to recover the pristine LLZO surface.Unfor-tunately,few articles have emphasized the merits of Li_(2)CO_(3).In this review,we focus on the two-sidedness of Li_(2)CO_(3).We discuss the various characteristics of Li_(2)CO_(3) that can be used and recapitulate the strategies that utilize Li_(2)CO_(3).Insulating Li_(2)CO_(3) is no longer an obstacle but an opportunity for realizing intimate interfacial contact,high air stability,and outstand-ing electrochemical performance.This review aims to off er insightful guidelines for treating air-induced Li_(2)CO_(3) and lead to developing the enhanced air stability and electrochemical performance of LLZO.

Inhomogeneous lithium-storage reaction triggering the inefficiency of all-solid-state batteries

All-solid-state batteries offer an attractive option for developing safe lithium-ion batteries.Among the various solid-state electrolyte candidates for their applications,sulfide solid electrolytes are the most suitable owing to their high ionic conductivity and facile processability.However,their performance is extensively lower compared with those of conventional liquid electrolyte-based batteries mainly because of interfacial reactions between the solid electrolytes and high capacity cathodes.Moreover,the kinetic evolution reaction in the composite cathode of all-solid-state lithium batteries has not been actively discussed.Here,electrochemical analyses were performed to investigate the differences between the organic liquid electrolyte-based battery and all-solid-state battery systems.Combined with electrochemical analyses and synchrotron-based in situ and ex situ X-ray analyses,it was confirmed that inhomogeneous reactions were due to physical contact.Loosely contacted and/or isolated active material particles account for the inhomogeneously charged regions,which further intensify the inhomogeneous reactions during extended cycles,thereby increasing the polarization of the system.This study highlighted the benefits of electrochemo-mechanical integrity for securing a smooth conduction pathway and the development of a reliable homogeneous reaction system for the success of solid-state batteries.

Chinese Scientists Discover a New Class of Viscoelastic Inorganic Glass(VIGLAS)Electrolytes for Solid-State Batteries

Solid-state batteries,often hailed as the next disruptive battery technology,offer a promising solution to the safety concerns associated with conventional liquid lithium-ion batteries while significantly enhancing energy density.This technological advancement holds the potential to revolutionize key industries,including electric vehicles,energy storage,and mobile devices.However,the practical implementation of solid-state batteries is hindered by several limitations related to interface stability and manufacturing costs.For instance,organic polymer solid-state batteries demonstrate impressive mechanical stability at the interface,but fall short of desirable chemical stability.This limitation restricts their energy density,primarily due to compatibility issues with high-voltage cathodes.On the other hand,commercially viable inorganic sulfide solid-state batteries,while showing promise,come with the drawback of high manufacturing costs.