Configuration design toward sustainably-released polymer electrolytes for enhancing ionic transport and cycle stability of solid lithium batteries

Abstract

Poly(vinylidene difluoride) (PVDF)-based solid polymer electrolytes (SPEs) hold great promise in the practical deployment of solid lithium batteries (SLBs), but suffer from low ionic conductivity, poor interfacial compatibility, and unstable anode interface, especially without liquid wetting. Herein, we utilize poly (propylene carbonate) (PPC), which degrades into propylene carbonate (PC) when being contacted with alkaline Li-metal to construct the PVDF-based composite SPEs. Blended and bi-layered PVDF/PPC configurations are designed, of which the sustain-release effect of PPC, the ionic transport, and the cycle stability are compared. The evenly swelling of PC on PVDF enables a high ionic conductivity (1.2 × 10−4 S cm−1) and a low interfacial resistance (42 Ω cm−2) of bi-layered SPEs at 30 °°C and contributes to the homogeneous distribution of high current density inside electrolytes. Besides, the produced PC can accelerate the dissociation and decomposition of Li-salts, leading to the generation of a stable and uniform solid electrolyte interface. Consequently, the Li/LiFePO4 and Li/LiNi0.6Co0.2Mn0.2O2 cells with bi-layered SPEs deliver a capacity of 163.1 and 151.4 mAh g−1 for 100 cycles at 0.2 C and 30 °C. This study provides a rational protocol for the design of PVDF SPEs and promotes the practical application of PVDF-based SLBs with desirable performances.