Self-purification and surface-coordination dual-polymer/Li6.4La3Zr1.4Ta0.6O12 interphase achieves Li+-transport-enhanced composite solid-state electrolyte

Abstract

Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) is one of the most widely used solid electrolytes for solid-state lithium-ion batteries (SSLIBs). However, this ceramics-type solid electrolyte suffers from poor interfacial contact and impure surface phase, causing large interfacial resistance and hindering Li⁺ transport. In this study, a binary polymer solution acting as a self-purification and surface-coordination agent, consisting of polyacrylonitrile (PAN) and poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PC), are mixed with LLZTO to form a Li⁺-transport-enhanced solid-state composite electrolyte. PC effectively eliminates the Li₂CO₃ impurity to form in-situ LiF coating on LLZTO particles. Simultaneously, the –CN groups in PAN establish coordination bonds with LLZTO, creating fast Li⁺ transport channels at the polymer/ceramic interphase. In addition, the introduced flexible polymer phase enhances the interfacial contact between electrodes and electrolyte. The optimized polymer/LLZTO interphase enables the as-prepared solid-state composite electrolyte to deliver excellent electrochemical performances. The assembled quasi-solid-state Li||LiFePO₄ cells stably work at 0.5 C (1 C = 170 mA g⁻¹) for >300 cycles at 60 °C and >600 cycles at room temperature, respectively. The Li||Li cell also shows a cycling life of >2000 h at 0.1 mA cm⁻² and 0.1 mAh cm⁻². This strategy effectively improves Li ⁺ migration on the polymer/LLZTO interphase, providing a new approach for next-generation SSLIBs.