Zeolitic imidazolate framework upgrading polyethylene oxide composite electrolyte for high-energy solid-state lithium batteries

The energy density of solid-state lithium batteries (SSLBs) has been primarily limited by the low ionic conductivity of solid electrolyte and poor interface compatibility between electrolyte and electrodes. Herein, a multifunctional composite solid polymer electrolyte (CSPE) based on polyethylene oxide (PEO) embedded with zeolitic imidazolate framework-8 deposited on carboxymethyl cellulose (ZIF@CMC) is reported. The ZIF@CMC interpenetrated in PEO matrix creates a continuous Li+ conductive network by combining Zn2+ in ZIF with the unsaturated group in PEO to boost the Li+ transport through the PEO chain segment. On the other hand, Zn2+ can bond with bis(trifluoromethane)sulfonimide (TFSI-) anion, thus promoting the dissolution of lithium salt and releasing more lithium ions. This CSPE demonstrates brilliant electrochemical properties, including a high ionic conductivity of 1.8 × 10-4 S cm-1 at room temperature and a wide electrochemical window of 5 V. The integrated LiFePO4/CSPE/Li batteries using 20 wt.% ZIF-8@CMC show excellent reversible capacity of 145.6 mAh g-1 with a capacity retention of 88.95 % after 200 cycles at a high current density of 0.5C. Our study proposed a novel and effective strategy to construct high-performance solid-state lithium batteries.