LiFePO4/C nanoparticle with fast ion/electron transfer capability obtained by adjusting pH values

Olivine-structure LiFePO4 is considered as promising cathode materials for lithium-ion batteries. However, the material always sustains poor electron conductivity and restricted lithium-ion diffusion channel, severely hindering its further commercial application. In this work, adjusting the synthesis condition on pH value is a practical approach to reduce the nanoparticle size, which vastly boosts its performance. The pH = 6 sample exhibits the highest specific capacity (149.7 mAh/g at 0.1 C) and capacity retention (96.3% after 50 cycles at 0.1 C, 89.7% after 200 cycles at 1 C) among the other LiFePO4/C powders. Compared to pH = 8 electrode, cyclic voltammetry and electrochemical impedance analysis disclose the reduced charge transfer resistance from 1492 to 993 Ω. Lithium-ion diffusion coefficient from 1.13 × 10–14 to 4.24 × 10–14 cm2s−1suggests that the optimal pH value can effectively minimize particle size, improve contact area, and buffer the diffusion barrier, including electron and ion, thus including the electrochemical property. Our study provides a simple and efficient strategy to design and optimize promising olivine-structural cathodes for lithium-ion batteries.