Synergy of PVDF-HFP and ZIF-8 promotes PEO electrolyte towards all-solid-state lithium battery

Abstract

Polyethylene oxide (PEO)-based electrolytes are considered to be promising for all-solid-state battery, benefiting from the superior flexibility, excellent processability and well compatibility. However, the low ionic conductivity at room temperature and poor stability under high voltage limit their further application. Herein, ZIF-8@PVDF-HFP/PEO (PPZ) solid electrolyte was successfully prepared by facial electrospinning process. On one side, the cooperation of PVDF-HFP and ZIF-8 was benefit to decrease the crystallization degree of PEO and thus promoted the Li+ transfer. Moreover, the in-situ formed LiF layer derived from the decomposition of PVDF-HFP protected the electrolyte from contacting directly with the electrode, contributing to a stable electrode/electrolyte interface. The results demonstrated that the electrochemical stability and mechanical property of PPZ electrolyte were significantly improved when compared to the bare PEO electrolyte. The tensile strength increased from 0.5 to 6.7 MPa and the Li+ transference number enlarged from 0.17 to 0.48. More importantly, the assembled LCO(LiCoO2)||PPZ||Li all-solid-state battery delivered a discharge specific capacity of 144.7 mAh g-1 at 0.2 C, nearly 1.6 times than that of the LCO||PEO||Li (90.7 mAh g-1). Besides that, the retention maintained at 86.3 % even after 200 cycles, manifesting a long-term cycling stability. This work provides a new idea for the practical application of PEO under high voltage.