LiFePO4 nanoparticles growth with preferential (010) face modulated by Tween-80

Abstract

Small grain size combined with large I₍₀₂₀₎/I₍₁₁₁₎ ratio have been proven to be an effective strategy to improve the electrochemical properties of LiFePO₄ material due to increased Li-ion diffusion. In view of this, we use Tween-80 as the surfactant in hydrothermal synthesis to modulate both crystal size and orientation of LiFePO₄. It is indicated that the LiFePO₄ particles synthesized via the Tween-80 modified hydrothermal method exhibited a small mean diameter of 100 nm and a large I₍₀₂₀₎/I₍₁₁₁₎ ratio of 1.19. Whereas in the surfactant-free hydrothermal system, the obtained LiFePO₄ particles exhibit a relatively large mean diameter of 200 nm and a low I₍₀₂₀₎/I₍₁₁₁₎ ratio of 0.84. LiFePO₄ particles with small grain size and a large I₍₀₂₀₎/I₍₁₁₁₎ ratio can be easily brought into contact with electrolyte, facilitating electric and Li-ion diffusion. After being coated with conductive carbon, the synthesized LiFePO₄/C nanoparticles perform a high Li-ion diffusion coefficient of 1.79 × 10⁻¹³ cm² s⁻¹. It presents a large reversible capacity of 166.5 mA h g⁻¹ at 0.1 C and even a high rate capacity of 119.6 mA h g⁻¹ at 20 C.