Tailoring the Ionic Conductivity of Composite Electrolyte by La-Doping Regulated Li4ti5o12 for Solid State Lithium Metal Batteries

Abstract

It is urgently required that polyethylene oxide (PEO) based electrolytes exhibit high Li+ conductivity and exceptional interfacial compatibility at wide temperature. In this study, La-doped two-dimensional (2D) Li4Ti5O12 nanosheets (La-LTO NSs) are firstly introduced into PEO (La-LTO/PL) to achieve composite polymer electrolytes (CPEs). The La doping can regulate the micro-structure of LTO NSs for realizing high aspect ratio and introducing rich oxygen vacancy, which significantly enhance the amorphous region and anchor adequate TFSI-. Furthermore, the DFT calculation reveals that enrichment of charge density gather around La element and oxygen vacancies, indicating the stronger interaction between La-LTO NSs and PEO/TFSI-. Therefore, the CPEs deliver multiple ion-transport channels including the interface between the La-LTO NSs and PEO, PEO chains and La-LTO NSs, enabling fast Li-ion transport and highly stable interface. As a result, the CPEs exhibit impressive ionic conductivity (2×10-4 S cm-1 under 30°C, 1×10-3 S cm-1 under 60°C) and steady electrochemical impedance value during 22 days. While the all-solid-state Li|LiFePO4 (Li|LFP) batteries deliver remarkable cycle stability for 400 cycles with high-capacity retention of 80% at 0.2 C under 30°C. Moreover, the pouch cell of Li|LFP maintains approximately 100% capacity retention after 100 cycles. This work promotes the applications of CPEs in high-performance solid-state Li batteries.

Keywords: La doped Li4Ti5O12 nanosheets, composite solid polymer electrolyte, multiple ion-transport channels, interfacial stability, all-solid-state Li metal batterie