Structure and electrochemical performances of LiFe1−2xTixPO4/C cathode doped with high valence Ti4+ by carbothermal reduction method

• LiFePO4/C and LiFe1−2xTixPO4/C are prepared by carbothermal reduction method.
• Phenol–formaldehyde resin is used as reducing agent and carbon source.
• Mechanism of carbothermal reduction reaction is presented on the basis of TG–DSC.
• The electrochemical performances of samples are systematically investigated.

LiFePO4/C (LFPC) and LiFe1−2xTixPO4/C (LFTPC) were prepared by carbothermal reduction method using FePO4·2H2O as iron source and phenol–formaldehyde resin as reducing agent and carbon source. Different ratios of TiO2 (IV) with high valence and small radius were applied to dope LiFePO4 to enhance its electrochemical performances. Results show that LFPC and LFTPC are synthesized successfully by carbothermal reduction method. The optimal carbon content in LFPC is 5 wt.% and its discharge capacity at 0.1 C is 150.8 mA h g−1. The crystallite structure of LFTPC becomes stable. They possess the smaller particle size compared with LiFePO4. LFTPC-2 possesses the best C-rate and cycle performances among all the samples. Its discharge capacities at 0.1 C, 1 C and 3 C are 132.7 mA h g−1, 98.7 mA h g−1 and 83.1 mA h g−1. The discharge curve can maintain its stable and flat platform of 3.3 V at 3 C. The electronic conductivity of LFTPC, which is coated with carbon and doped with Ti, can reach ∼10−4 S cm−1. The charge transfer resistance of LFTPC-2 is 33.68 Ω, which is much lower than that of other samples.