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.

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.

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.

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.

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.

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.

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.

“Polymer-in-ceramic” based poly(ε-caprolactone)/ceramic composite electrolyte for all-solid-state batteries

Inspired by the concept of "polymer-in-ceramic",a composite poly(ε-caprolactone)(PCL)/ceramic containing LiTFSI is prepared and investigated as a solid electrolyte for all-solid-state batteries.The composite with the optimum concentration of 45 wt% LiTFSI and 75 wt% Li1.5Al0.5Ge1.5(PO4)3(LAGP,NASICON-type structure) exhibits a high ionic conductivity(σi=0.17 mS cm-1) at 30℃,a transference number of 0.30,and is stable up to 5.0 V.The composite electrolyte is a flexible and self-standing membrane.Solid-state LiFePO4//Li batteries with this composite electrolyte demonstrate excellent cycling stability with high discharge capacity of 157 mA h g-1,high capacity retention of 96% and coulombic efficiency of 98.5% after 130 cycles at 30℃ and 0.1 C rate.These electrochemical properties are better than other PCL-based allsolid-lithium batteries,and validate the concept of "polymer-in-ceramic" by avoiding the drawback of lower conductivity in prior "polymer-in-ceramic" electrolyte at high concentration of the ceramic.

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.

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.

Stable Cycling of All-Solid-State Lithium Batteries Enabled by Cyano-Molecular Diamond Improved Polymer Electrolytes

The interfacial instability of the poly(ethylene oxide)(PEO)-based electrolytes impedes the long-term cycling and further application of all-solid-state lithium metal batter-ies.In this work,we have shown an effective additive 1-adaman-tanecarbonitrile,which con-tributes to the excellent per-formance of the poly(ethylene oxide)-based electrolytes.Owing to the strong interaction of the 1-Adamantanecarboni-trile to the polymer matrix and anions,the coordination of the Li^(+)-EO is weakened,and the binding effect of anions is strengthened,thereby improving the Li^(+)conductivity and the electrochemical stability.The diamond building block on the surface of the lithium anode can sup-press the growth of lithium dendrites.Importantly,the 1-Adamantanecarbonitrile also regulates the formation of LiF in the solid electrolyte interface and cathode electrolyte interface,which contributes to the interfacial stability(especially at high voltages)and protects the electrodes,enabling all-solid-state batteries to cycle at high voltages for long periods of time.Therefore,the Li/Li symmetric cell undergoes long-term lithium plating/stripping for more than 2000 h.1-Adamantanecarbonitrile-poly(ethylene oxide)-based LFP/Li and 4.3 V Ni_(0.8)Mn_(0.1)Co_(0.1)O_(2)/Li all-solid-state batteries achieved stable cycles for 1000 times,with capacity retention rates reaching 85%and 80%,respectively.

Solid polymer electrolyte-based high areal capacity all-solid-state batteries enabled with ceramic interlayers

Solid polymer electrolytes(SPEs)based all-solid-state batteries(ASSBs)have attracted extensive attention as a promising candidate for next-generation energy storage systems.Typical ASSBs require high fabrication pressure to achieve high areal capacity,under which,however,SPEs struggle and risk damage or failure due to their low mechanical strength.There is also a lack of study on complex stress and strain SPEs experience during ASSB cell assembly processes.Here,ceramic solid electrolytes are selected as interlayers to address the stress-strain conditions during assembling.As a result,high areal capacity ASSBs with a LiCoO2 loading of 12 mg·cm^(-2) were assembled with SPE-based composite electrolytes.Around 200 cycles were carried out for these cells at a current density of 1 mA·cm^(-2) under room temperature.The capacity decay of the battery at 200 cycles is observed to be as low as 0.06% per cycle.This work identifies a critical issue for application of SPEs in ASSBs and provides a potential strategy for the design of SPE-based ASSBs with high specific energy and long cycle life.

Synergistic Coupling of Sulfide Electrolyte and Integrated 3D FeS_(2)Electrode Toward Long-Cycling All-Solid-State Lithium Batteries

FeS_(2)cathode is promising for all-solid-state lithium batteries due to its ultra-high capacity,low cost,and environmental friendliness.However,the poor performances,induced by limited electrode-electrolyte interface,severe volume expansion,and polysulfide shuttle,hinder the application of FeS_(2)in all-solid-state lithium batteries.Herein,an integrated 3D FeS_(2)electrode with full infiltration of Li6PS5Cl sulfide electrolytes is designed to address these challenges.Such a 3D integrated design not only achieves intimate and maximized interfacial contact between electrode and sulfide electrolytes,but also effectively buffers the inner volume change of FeS_(2)and completely eliminates the polysulfide shuttle through direct solid-solid conversion of Li2S/S.Besides,the vertical 3D arrays guarantee direct electron transport channels and horizontally shortened ion diffusion paths,endowing the integrated electrode with a remarkably reduced interfacial impedance and enhanced reaction kinetics.Benefiting from these synergies,the integrated all-solid-state lithium battery exhibits the largest reversible capacity(667 mAh g^(-1)),best rate performance,and highest capacity retention of 82%over 500 cycles at 0.1 C compared to both a liquid battery and non-integrated all-solid-state lithium battery.The cycling performance is among the best reported for FeS_(2)-based all-solid-state lithium batteries.This work presents an innovative synergistic strategy for designing long-cycling high-energy all-solid-state lithium batteries,which can be readily applied to other battery systems,such as lithium-sulfur batteries.

Recent advances and future perspectives of Ruddlesden–Popper perovskite oxides electrolytes for all-solid-state batteries

All-solid-state batteries equipped with solid-state electrolytes(SSEs)havegained significant interest due to their enhanced safety,energy density,andlongevity in comparison to traditional liquid organic electrolyte-based batteries.However,many SSEs,such as sulfides and hydrides,are highly sensitiveto water,limiting their practical use.As one class of important perovskites,theRuddlesden–Popper perovskite oxides(RPPOs),show great promise as SSEsdue to their exceptional stability,particularly in terms of water resistance.Inthis review,the crystal structure and synthesis methods of RPPOs SSEs are firstintroduced in brief.Subsequently,the mechanisms of ion transportation,including oxygen anions and lithium-ions,and the relevant strategies forenhancing their ionic conductivity are described in detail.Additionally,theprogress made in developing flexible RPPOs SSEs,which are critical for flexibleand wearable electronic devices,has also been summarized.Furthermore,thekey challenges and prospects for exploring and developing RPPOs SSEs in allsolid-state batteries are suggested.This review presents in detail the synthesismethods,the ion transportation mechanism,and strategies to enhance theroom temperature ionic conductivity of RPPOs SSEs,providing valuableinsights on enhancing their ionic conductivity and thus for their practicalapplication in solid-state batteries.

Monophase-homointerface electrodes intrinsically stabilize high-voltage all-solid-state batteries

The electrochemical stability and contact reliability of heterointerfaces between the solid electrolyte(SE) and electrode are critical for all-solid-state batteries(ASSBs), particularly much more challenging for high-voltage ASSBs, owing to the limited thermodynamically electrochemical window and mechanical inflexibility of SE, aggravating interfacial side reactions and contact failure. Considering all those issues originating from intrinsic heterogeneity in physicochemical features between the cathode material and SE, we are thinking about simplifying the heterointerfaces into a homointerface as a permanent cure to solve all electrochemical-mechanical interfacial failure. Herein, we propose monophase cathodes to construct thermodynamically stable all-in-one homointerfaces in ASS electrodes, removing unstable heterointerfaces by excluding SEs and intrinsically eliminating the Li chemical potential gap to avoid the formation of lithium-depleted space-charge layer and highly resistive mixed ion–electron conductor interphase. Our conception is successfully validated in the layered transition-metal oxide cathodes, which display outstanding stability no matter the MH-LiCoO_(2) cathode charging to 4.7 V or MH-Li_(1.2)Mn_(0.54)Ni_(0.13)-Co_(0.13)O_(2) cathode charging to 5.3 V. It is undeniable that our current version of above-illustrated MH-cathodes would bring out some new challenges for the practical application due to abandoning the SE. However, we believe our work also offers a brandnew direction to ultimately address the electrochemical–mechanical interfacial issues that would be promising for high-energy ASSBs with more discoveries of advanced monophase cathodes in the future.

Diffusion-Free All-Solid-State Batteries Enabled by an Ionic/Electronic Dual-Conductive Anode

Silicon(Si)is one of the most promising anodes for enabling all-solid-state batteries(ASSBs)with high energy density and safety.However,the tremendous volume change and sluggish kinetics result in poor electrochemical performance.Herein,we proposed an ionic/electronic dual-conductive material of Li_(x)Si as a diffusion-rapid and all-active anode for ASSBs.Compared with pure Si anode,the as-fabricated Li_(x)Si showed dramatic promotions of 35 times electronic and 400 times ionic conductivities.The three-dimensional(3D)ionic-electronic transport system of Li_(x)Si enabled rapid kinetics and uniform volume change of electrode materials in the whole electrode,corresponding to a lower volumechange rate.As a result,the ASSBs with LiCoO_(2)cathode exhibited a reversible discharge capacity of 154.4 mAh g−1,corresponding to an initial Coulombic efficiency of 97.3%.Besides,the batteries delivered a high rate capacity of 99.3 mAh g^(−1)at 2 C and long-term cycle stability of 94.0%after 800 cycles at 1 C,which was much better than the pure Si anode.This study sheds light on a new understanding of the importance of ionic conductivity for Si-based anode and might help inspire the design of advanced anode materials for ASSBs.

Perspective on powder technology for all-solid-state batteries:How to pair sulfide electrolyte with high-voltage cathode

Sulfide solid electrolytes(SEs)have attracted ever-increasing attention due to their superior roomtemperature ionic conductivity(~10^(-2) S cm^(-1)).Additionally,the integration of sulfide SEs and highvoltage cathodes is promising to achieve higher energy density.However,the incompatible interfaces between sulfide SEs and high-voltage cathodes have been one of the key factors limiting their applications.Therefore,this review presents a critical summarization of the interfacial issues in all-solid-state lithium batteries based on sulfide SEs and high-voltage cathodes and proposes strategies to stabilize the electrolyte/cathode interfaces.Moreover,the future research direction of electrolyte/cathode interfaces and application prospects of powder technology in sulfide-based ASSLBs were also discussed.

Advances in All-Solid-State Lithium-Sulfur Batteries for Commercialization

Solid-state batteries are commonly acknowledged as the forthcoming evolution in energy storage technologies.Recent development progress for these rechargeable batteries has notably accelerated their trajectory toward achieving commercial feasibility.In particular,all-solid-state lithium-sulfur batteries(ASSLSBs)that rely on lithium-sulfur reversible redox processes exhibit immense potential as an energy storage system,surpassing conventional lithium-ion batteries.This can be attributed predominantly to their exceptional energy density,extended operational lifespan,and heightened safety attributes.Despite these advantages,the adoption of ASSLSBs in the commercial sector has been sluggish.To expedite research and development in this particular area,this article provides a thorough review of the current state of ASSLSBs.We delve into an in-depth analysis of the rationale behind transitioning to ASSLSBs,explore the fundamental scientific principles involved,and provide a comprehensive evaluation of the main challenges faced by ASSLSBs.We suggest that future research in this field should prioritize plummeting the presence of inactive substances,adopting electrodes with optimum performance,minimizing interfacial resistance,and designing a scalable fabrication approach to facilitate the commercialization of ASSLSBs.

Stable Cycling of All-Solid-State Lithium Metal Batteries Enabled by Salt Engineering of PEO-Based Polymer Electrolytes

Poly(ethylene oxide)(PEO)-based polymer electrolytes show the prospect in all-solid-state lithium metal batteries;however,they present limitations of low room-temperature ionic conductivity,and interfacial incompatibility with high voltage cathodes.Therefore,a salt engineering of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide lithium salt(LiHFDF)/LiTFSI system was developed in PEO-based electrolyte,demonstrating to effectively regulate Li ion transport and improve the interfacial stability under high voltage.We show,by manipulating the interaction between PEO matrix and TFSI^(-)-HFDF^(-),the optimized solid-state polymer electrolyte achieves maximum Li+conduction of 1.24×10^(-4)S cm^(-1)at 40℃,which is almost 3 times of the baseline.Also,the optimized polymer electrolyte demonstrates outstanding stable cycling in the LiFePO_(4)/Li and LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)/Li(3.0-4.4 V,200 cycles)based all-solid-state lithium batteries at 40℃.