A rigid-flexible gel polymer electrolytes with long cycle life and dendrite-free in lithium metal batteries

Abstract

Gel polymer electrolytes (GPEs) in lithium-ion batteries (LIBs) are promising alternatives to liquid electrolytes due to their higher safety and energy density. However, GPE suffers from low ionic conductivity and poor interfacial compatibility. Here, we demonstrate a rigid-flexible GPE (CPE(PVAc)) of the PVDF-HFP/LAGP/PVAc/LiTFSI was prepared by a simple solution casting method. A fast route and efficient for the transport of lithium ions had been constructed by dripping a small amount of LEF (1 M LiTFSI/EC-DMC-FEC (1:1:0.2 v/v/v)) on both sides of the membrane. Moreover, a stable LiF-rich SEI layer was formed on the Li anode, effectively inhibited the growth of lithium dendrites. The CPE(PVAc) possesses high ionic conductivity (1.47 mS cm−1 at 30 °C) and robust mechanical properties (230 % fracture length and 3.4 MPa fracture strength). The Li-symmetric cell with CPE(PVAc) can operate for >1500 h of stable operation at 0.1 mA cm−2 and 25 °C. The assembled LiFePO4|CPE(PVAc)|Li coin cells presented excellent initial discharge specific capacity (135.4 mAh g−1 at 2C and 25 °C, and 157.5 mAh g−1 at 1C and 55 °C) and long-term cycling stability (97.6 % capacity retention after 500 cycles at 2C and 25 °C, and 80 % capacity retention after 400 cycles at 1C and 55 °C). The advantages of CPE(PVAc) electrolyte have shown great potential for application in high-performance lithium metal batteries.