Enhancement of the Electrochemical Performances of Composite Solid-State Electrolytes by Doping with Graphene

With high safety and good flexibility, polymer-based composite solid electrolytes are considered to be promising electrolytes and are widely investigated in solid lithium batteries. However, the low conductivity and high interfacial impedance of polymer-based solid electrolytes hinder their industrial applications. Herein, a composite solid-state electrolyte containing graphene (PVDF-LATP-LiClO4-Graphene) with structurally stable and good electrochemical performance is explored and enables excellent electrochemical properties for lithium-ion batteries. The ionic conductivity of the composite electrolyte membrane containing 5 wt% graphene reaches 2.00 × 10^-3 S cm^-1 at 25 °C, which is higher than that of the composite electrolyte membrane without graphene (2.67 × 10^-4 S cm^-1). The electrochemical window of the composite electrolyte membrane containing 5 wt% graphene reaches 4.6 V, and its Li⁺ transference numbers reach 0.84. Assembling this electrolyte into the battery, the LFP/PVDF-LATP-LiClO4-Graphene /Li battery has a specific discharge capacity of 107 mAh g^-1 at 0.2 C, and the capacity retention rate was 91.58% after 100 cycles, higher than that of the LiFePO₄/PVDF-LATP-LiClO₄/Li (LFP/PLL/Li) battery, being 94 mAh g^-1 and 89.36%, respectively. This work provides a feasible solution for the potential application of composite solid electrolytes.