Air Stability of Solid‑State Sulfide Batteries and Electrolytes

Sulfides have been widely acknowledged as one of the most promising solid electrolytes(SEs)for all-solid-state batteries(ASSBs)due to their superior ionic conductivity and favourable mechanical properties.However,the extremely poor air stability of sulfide SEs leads to destroyed structure/performance and release of toxic H_(2)S gas,which greatly limits mass-production/practical application of sulfide SEs and ASSBs.This review is designed to serve as an all-inclusive handbook for studying this critical issue.First,the research history and milestone breakthroughs of this field are reviewed,and this is followed by an in-depth elaboration of the theoretical paradigms that have been developed thus far,including the random network theory of glasses,hard and soft acids and bases(HSAB)theory,thermodynamic analysis and kinetics of interfacial reactions.Moreover,the characterization of air stability is reviewed from the perspectives of H2S generation,morphology evolution,mass change,component/structure variations and electrochemical performance.Furthermore,effective strategies for improving the air stabilities of sulfide SEs are highlighted,including H_(2)S absorbents,elemental substitution,design of new materials,surface engineering and sulfide-polymer composite electrolytes.Finally,future research directions are proposed for benign development of air stability for sulfide SEs and ASSBs.

Stable Ni-rich layered oxide cathode for sulfide-based all-solid-state lithium battery

Sulfide-based all-solid-state lithium-ion batteries(ASSLIBs)are one of the most promising energy storage technologies due to their high safety and ionic conductivity.To achieve greater energy density,a Ni-rich layered oxide LiNi_(x)Co_(y)M_(1-x-y)O_(2)(NCM,MMn/Al,x≥0.6)is desirable due to its relatively high voltage and large capacity.However,interfacial side reactions between the NCM and sulfide solid electrolytes lead to undesirable interfacial passivation layers and low ionic conductivity,thereby degrading the electrochemical performance of NCM sulfide all-solid-state batteries.Herein,a time-/cost-effective sulfidation strategy is exploited to sulfidize a Ni-rich NCM_(88) cathode in a mixed gas atmosphere of N_(2) and CS_(2).A new type of cathode(NCM88-S)with an ultrathin(∼2nm)surface layer is obtained,which significantly reduces the interfacial side reactions/resistance and improves the interfacial stability.The resulting NCM_(88)-S/Li_(6)PS_(5)Cl/Li_(4)Ti_(5)O_(12) ASSLIB exhibits superior performance,including a high discharge specific capacity(200.7 mAh g−1)close to that of liquid batteries,excellent cycling performance(a capacity retention of 87%after 500 cycles),and satisfactory rate performance(158.3 mAh g^(−1) at 1C).