Regulation of nano FePO4 precursors and exploration of influencing mechanisms in LiFePO4/C cathode

Abstract

The iron phosphate (FePO₄) process route has become the predominant method for synthesizing lithium iron phosphate (LiFePO₄) due to its established technology and controllability. And the performance of LiFePO₄ is significantly influenced by the quality of the FePO₄ precursor. In this study, we strategically utilized Fe₂O₃ and H₃PO₄ as raw materials to produce nano-flake FePO₄ precursors through two distinct methods: hydrothermal and chemical precipitation. These precursors were generated with varying sizes, dispersions, and morphologies, which significantly impacted the properties of the synthesized LiFePO₄/C composites. A thorough comparison was conducted between LiFePO₄/C composites derived from these nano-flake FePO₄ precursors and those synthesized from commercial FePO₄. It was observed that LiFePO₄/C materials produced from hydrothermally synthesized nano-flake FePO₄ exhibited superior uniformity and dispersion, resulting in a desirable nanosheet morphology. In contrast, LiFePO₄/C materials derived from the precursors obtained via chemical precipitation showed a nanoparticle morphology, attributed to precursor aggregation during dehydration. The study conclusively demonstrated that the LiFePO₄/C sample with a nanosheet-like morphology exhibited the best performance, delivering an impressive discharge capacity of 158.24 mA h g⁻¹ at 0.2C, along with exceptional rate capability and the high Li⁺ diffusion coefficient of 2.17 × 10⁻¹¹ cm² s⁻¹. These findings underscore the critical role of precursor synthesis methods in determining the electrochemical performance of LiFePO₄/C materials, providing valuable insights for the optimization of lithium-ion battery technology.