Investigation of the electrochemical performance of polyvinylidene fluoride-derived LiFePO₄/C composite nanospheres

Abstract

The wide application of LiFePO₄ (LFP) in high-power lithium-ion batteries is limited due to its two main drawbacks: poor electronic conductivity and low lithium-ion diffusivity, which can be greatly improved through a combination of reducing the LFP crystallites to nanoscale and introducing a conductive carbon coating layer. It is well accepted that the choice of carbon precursors has a significant impact on the ultimate lithium storage property of the LiFePO₄/carbon (LFP/C) composite. In this work, LFP/C core–shell composite nanospheres using polyvinylidene fluoride (PVDF) as carbon source (LFP/C-PVDF) were prepared and the electrochemical performances in lithium half cells were investigated. The electrochemical properties of LFP/C composite derived from glucose (LFP/C-GLU) and the bare LFP without carbon coating were also investigated for comparison. It was found that LFP/C-PVDF displayed a higher capacity, better rate capability and smaller polarization than its LFP/C-GLU and LFP counterparts, which could be ascribed to lower surface and charge-transfer impedances, and an enhanced lithium-ion diffusivity, as revealed by electrochemical impedance spectroscopy analysis. Our study demonstrates that PVDF is a facile and potential carbon precursor for LiFePO₄ in high-performance lithium-ion battery application.