A flexible solid polymer electrolyte enabled with lithiated zeolite for high performance lithium battery

Solid-state lithium batteries using composite polymer electrolytes (CPEs) have attracted much attention owing to their higher safety compared to liquid electrolytes and flexibility compared to ceramic electrolytes. However, their unsatisfactory lithium-ion conductivity still limits their development. Herein, a high ion conductive CPE with multiple continuous lithium pathways is designed. This new electrolyte consists of poly(vinylidene fluorideco-hexafluoropropylene) (PVDF-HFP) and lithiated X type zeolite (Li-X), which possesses a high ionic conductivity (1.98 × 10⁻⁴ S/cm), high lithium transference number (t ${}_{{\mathrm{L}\mathrm{i}}^{+}}$ = 0.55), wide electrochemical window (4.7 V), and excellent stability against the lithium anode. Density functional theory (DFT) calculation confirms that the Lewis acid sites in zeolite can graft with N,N-dimethylformamide (DMF) and PVDF-HFP chains, resulting in decreased crystallinity of polymer and providing rapid Li⁺ transmission channels. When used in a full cell, the solid Li|Li-X-3%|LiFePO₄ cell displays excellent cycling stability and rate performance at room temperature and 60 °C. Furthermore, pouch cells with the Li-X-3% electrolyte exhibit brilliant safety under extreme conditions, such as folding and cutting. Thus, this proposed zeolite-PVDF-HFP CPE represents a promising potential in the application of making a safer, higher performing, and flexible solid-state lithium battery.