Composite polymer electrolytes reinforced by a three‐dimensional polyacrylonitrile/Li 0.33 La 0.557 TiO 3 nanofiber framework for room‐temperature dendrite‐free all‐solid‐state lithium metal battery

Abstract Substituting liquid electrolytes with solid electrolytes is considered as an important strategy to solve the problem of flammability and explosion for traditional lithium‐ion batteries (LIB). However, neither inorganic solid electrolytes (ISE) nor solid polymer electrolytes (SPE) alone can meet the operating requirements for room‐temperature (RT) all‐solid‐state lithium metal batteries (ASSLMB). Here, we report a three‐dimensional (3D) nanofiber framework reinforced polyethylene oxide (PEO)‐based composite polymer electrolytes (CPE) through constructing a nanofiber framework combining polyacrylonitrile (PAN) and fast Li‐ion conductor Li 0.33 La 0.557 TiO 3 (LLTO) framework by electrospinning method. Meanwhile, the PEO electrolyte filled in the pores of the PAN/LLTO nanofiber framework can effectively isolate the direct contact between the chemically active Ti 4+ in LLTO with lithium metal, thereby avoiding the occurrence of interfacial reactions. Enhanced electrochemical stability makes a wide electrochemical window up to 4.8 V with an ionic conductivity of about 9.87 × 10 –5 S·cm −1 at RT. Benefiting from the excellent lithium dendrite growth inhibition ability of 3D PAN/LLTO nanofiber framework, especially when the mass of LLTO reaches twice that of the PAN, Li/Li symmetric cell could cycle stably for 1000 h without a short circuit. In addition, under 30 °C, the LiFePO 4 /Li ASSLMB using such CPE delivers large capacities of 156.2 and 140 mAh·g −1 at 0.2C and 0.5C, respectively. These results provide a new insight for the development of the next generation of safe, high‐performance ASSLMBs.