Revealing electrochemical performance of Ni doping LiFePO4 composite

Abstract

In this work, Ni²⁺ was doped into the crystal lattice of LiFePO₄ to improve the electrochemical performance. Lengths of the Li–O bonds in LiFe_0.98Ni_0.02PO₄/C (2% NiSO₄-doped LiFePO₄) is longer than that of the bare LiFePO₄ sample, the micromorphology of LiFe_0.98Ni_0.02PO₄/C sample becomes uniform, and the Ni²⁺ doped into LiFePO4 expands the crystal plane spacing, which is conducive to Li⁺ diffusion. Amongst all the doped samples, the Li⁺ diffusion coefffcient of LiFe_0.98Ni_0.02PO₄/C is the largest, and the redox peak of LiFe_0.98Ni_0.02PO₄/C is more symmetrical, sharper and narrower, indicating that the proper amount of Ni^2+-modified LiFePO₄ can improve the electrochemical performance. Specific discharge capacity at 1C is 152 mAh g⁻¹ when the doping amount is 2%. Additionally, after 200 cycles at 2C, the discharge specific capacity can be attained at 140 mAh g⁻¹ and capacity retention rate reached 98%.