Garnet Composite Solid Electrolyte with Cotton Modified by Metal Chelator as a Template for Flexible Solid-State Lithium Metal Batteries

Most current commercial lithium-ion batteries use organic electrolytes, which have considerable safety issues owing to their toxicity, easy combustion, degradation under high pressure, and corrosiveness. Therefore, safer lithium metal batteries with higher energy density have attracted considerable research attention. Composite solid-state electrolytes combining inorganic ceramics and organic polymers have superior performance; however, challenges such as low ionic conductivity, limited electrochemical windows, and low cycling stability remain to be addressed. Herein, we report a method of graft modification of cotton templates via the metal chelator EDTA (ethylenediaminetetraacetic acid). EDTA adsorbs metal ions from LLZO (Li7La3Zr2O12) precursors to prepare LLZO ceramic fabrics (LLZO CF) with cotton/EDTA as templates. Thus, LLZO ceramic fabric composite solid-state electrolytes (LLZO CF-CSE) with a double-layer cast structure are formed. This LLZO CF-CSE increases the lithium-ion conductivity (3.5 × 10–4 S cm–1 at 50 °C) and widens its electrochemical window (5.2 V). The initial specific capacity of a LiFePO4/Li battery with LLZO CF-CSE reaches 144.5 mAh g–1 at 50 °C, and the capacity remains at 117.6 mAh g–1 after 300 cycles, translating into a capacity retention rate of 99.44% under 1C charge/discharge conditions. Our work presents a method to prepare high-performance, safe, and stable cycling composite solid-state electrolytes.