Structure Design Of LLTO-based Composite Solid Electrolyte For Enhancing Ion Conduction And Stability

All-solid-state lithium batteries,featuring high energy density and security,have been regarded as promising next-generation energy storage devices.As the core component of the battery,the properties and physical parameters of solid electrolyte directly affect the electrochemical performance of the battery.However,the design and development of solid electrolyte with stable structure and efficient ion transfer ability have become a problem that limits their development and application.Thus,focusing on the imbalance of ion transfer and stability of solid electrolyte,this study proposes the strategy of organic-inorganic composite to strengthen ion transfer and stability.The microstructure-property relationship among microstructure,ion transfer and stability could be comprehensively elucidated by structural design and regulation,in order to offer some guidances to the thin stable electrolyte design and ion transfer characteristics intensification.The details are summarized as follows:（1）Design of composite electrolyte with bicontinuous phase structure for enhancing ion conduction and stability.The interconnected porous lithium lanthanum titanate（LLTO）framework was synthesized by sintering the gel permeated nylon template.Then,poly（ethylene oxide）（PEO）was incorporated in the LLTO framework by solution-dripping method to produce PEO-LLTO framework solid electrolyte（PLLF electrolyte）with vertically bicontinuous phase.LLTO framework,as the transfer subject,fast transports lithium ions through the intrinsic vacancy or defect,meanwhile the confined PEO with low crystallization provides fast Li⁺transfer channel depending on chain motion,thus synergistically enhancing Li⁺conduction ability.The results indicate that PLLF electrolyte with bicontinuous phase structure exhibits an excellent ionic conductivity of 2.04×10^-4 S cm^-1 at 25 ℃.The interconnected structure obtained by organic-inorganic composite endows PLLF electrolyte with excellent structural stability.In addition,the thin PEO layer on the electrolyte surface would avoid the side reaction with the lithium anode and effectively reduce the interfacial resistance.The assembled all-solid-state lithium battery（LiFePO4/Li）achieves excellent battery performance:the initial discharge specific capacity of 159.2 m Ah g^-1 and the capacity retention of 97.2%after 150cycles at 60 ℃ and 1 C.（2）Design of thin electrolyte with concrete structure for enhancing ion conduction and stability.Based on the co-sintering method,porous and continuous Vr-LLTO framework was synthesized by composite rigid vermiculite nanosheets（Vr）and LLTO nanoparticles,followed by solution-dripping method to prepare concrete structured and thin Vr-LLTO/PEO electrolyte.Stable and continuous Li⁺transport channels were constructed by LLTO phase attached to the interface of nanosheets.Meanwhile,the reduction of electrolyte thickness shortens the ion transfer distance and strengthens the ion transfer ability.Thus,Vr-LLTO/PEO electrolyte exhibits excellent ionic conductivity of 1.04×10^-4 S cm^-1 at room temperature,higher than that of traditional ceramic electrolytes.In addition,the interaction between Vr and LLTO nanoparticles combined with the composite PEO synergically exerts the advantages of organic-inorganic components,which effectively enhances the stability of solid electrolyte.Furthermore,the optimized electrode-electrolyte interface and electrolyte internal interface improves the compatibility.The all-solid-state lithium battery equipped with Vr-LLTO/PEO electrolyte exhibits extraordinary cycling stability:the high coulomb efficiency（～95%）after 200 cycles at 1 C and the capacity retention rate of 84.4%.