Effect of Li₄Ti₅O₁₂ particle size on the performance of lithium ion battery electrodes at high C-rates and low temperatures

Two different Li₄Ti₅O₁₂ materials were investigated: smaller primary particle size forming large secondary particle aggregates (LTO-SP, surface area 22 m²/g) and larger primary particle size with less secondary particle aggregates (LTO-LP, surface area 7 m²/g). Both samples were synthesized using the same high temperature solid state synthesis but different end processing, resulting in the same crystalline structure but different particle morphology. At 0.1C measured discharge capacities were close to the theoretical capacity of Li₄Ti₅O₁₂ (175 mAh/g), and similar capacities were obtained at low C-rates and room temperature for both LTO-SP and LTO-LP. However, higher capacities were obtained with LTO-SP at high C-rates and -20 °C indicating beneficial effect of small particle size and large surface area. Shapes of the charge/discharge curves were different for LTO-SP and LTO-LP, and this is attributed to the large surface area of LTO-SP which affects the electrochemical performance because of different reaction potentials at surface sites versus bulk.