Optimizing lithium-ion diffusion in LiFePO4: the impact of Ti4+ doping on high-rate capability and electrochemical stability

Abstract

This study aims to enhance the electrochemical performance of lithium iron phosphate (LiFePO₄) cathode materials through Ti⁴⁺ ion doping strategy, in order to address the challenges of low conductivity and slow lithium-ion diffusion rates. We synthesized iron phosphate precursors with different Ti⁴⁺ doping levels using the chemical precipitation method and successfully prepared LiFePO₄ material by the high-temperature solid-phase method, which improves the uniformity of ion doping. By systematically studying the effect of Ti⁴⁺ doping on material structure, morphology, and electrochemical properties, we found that Ti⁴⁺ successfully entered the LiFePO4, without affecting its morphology or lattice. This structural change had a positive impact on the electrochemical performance of the material. The discharge-specific capacities of 2% Ti⁴⁺-doped LiFePO₄ samples at 0.1, 1, 5, and 10 C reached 161.0, 132.4, 105.3, and 92.6 mAh g⁻¹, respectively, demonstrating excellent electrochemical performance. Its lithium-ion diffusion coefficient was also significantly better than that of other samples. The comprehensive analysis results from XRD, SEM, XPS, and electrochemical testing show that the appropriate amount of Ti⁴⁺ doping optimizes the diffusion path of lithium-ions and increases the charge transfer rate, thereby significantly improving the electrochemical performance of LiFePO₄. This discovery not only enriches the understanding of the modification mechanism of lithium-ion battery cathode materials, but also provides important scientific basis and practical guidance for the development of high-performance lithium-ion battery cathode materials.