Indium doping: An effective route to optimize the electrochemical performance of LiFePO4 cathode material

This study aimed to develop In-doped LiFePO4 cathode materials for lithium ion power batteries in electric vehicles that meet the requirements of both fast acceleration and long-term reversible charge-discharge stability. We focused on investigating the role of indium doping in enhancing high-rate capability. Density functional theory (DFT) calculations revealed that successful substitution of In at Fe site exhibits distinct features for both LiFe1-xInxPO4 and Fe1-xInxPO4. The results showed that the presence of In in unlithiated Fe1-xInxPO4 can lower the diffusion energy barrier of lithium ions. On the other hand, the introduction of In in lithiated LiFe1-xInxPO4 creates an impurity energy band at the Fermi energy level, which enhances electron conductivity of the active material. Experimental data demonstrated that with 2% In doping, the 2% In3+-LFP/C electrode delivers 160 mAh g−1 at 0.1C, and 150 mAh g−1 at 1C (with excellent retention rate of 98% after 700 cycles). Additionally, the In-doped electrode provided higher discharge capacity at high-rates (5C and 10C) due to improved electron conductivity and lithium ion diffusion properties. These findings prove that indium doping is an effective approach to reinforcing the electrochemical capabilities of high-rate LiFePO4 cathode material for lithium storage.