PVDF-HFP/BP nanosheets composite gel electrolyte with high ionic conductivity for lithium batteries

Abstract

In this work, polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) /phosphorene (BP) nanosheets composite gel electrolytes with high ionic conductivity are prepared by macrophase separation method to address the problems of low ionic conductivity of pure PVDF electrolyte. The ionic conductivity of the gel electrolyte reaches 1.34 × 10−3 S/cm at room temperature when the BP content is 0.3 wt%, and the electrochemical window was stable up to 6.0 V. The discharge capacity of the anode at 0.1 C for the first cycle of Li//PVDF-HFP/BP//LiFePO4 battery raises to 142 mA h/g, reaching 83.5% of the theoretical capacity, and retains 94.9% of capacity and 97.8% of charge/discharge efficiency after 100 cycles at 0.2 C. The microscopic morphology shows that the lithium deposition is transformed from dendrites to spheres, which greatly improves the stability of the SEI film. And the DFT calculations indicate that the binding energy of Li+ to the BP surface is − 0.811 eV, and the diffusion potential barrier is only 0.380 eV when Li+ migrates along the (100) crystal plane of BP nanosheets.