Li₄Ti₅O₁₂ coated with ultrathin aluminum-doped zinc oxide films as an anode material for lithium-ion batteries

Aluminum-doped zinc oxide (AZO) films were coated on the surface of Li₄Ti₅O₁₂ (LTO) particles via atomic layer deposition (ALD) in a fluidized bed reactor. The electrochemical characterization results indicated that the coating of AZO significantly improved the electrochemical performance of LTO between 0.1 V and 3.0 V with a proper coating thickness. Among all AZO-coated LTO samples, 250-10AZO (nine cycles of ZnO ALD followed by one cycle of Al₂O₃ ALD at a deposition temperature of 250 °C) showed the best performance. After 250 cycles of charge/discharge at a 1 C rate (1 C = 175 mA g⁻¹), the capacity decreased from 203 to 190 mAh g⁻¹ with a capacity retention of ~94% at room temperature and from 224 to 216 mAh g⁻¹ with a capacity retention of ~96% at 55 °C. The AZO coating layer with an appropriate thickness not only increased the capacity of LTO by enhancing conductivity, but also assisted the LTO electrodes to form a beneficial interface layer to protect the LTO from the continuous attack by harmful components in the electrolyte, especially under extreme conditions, such as high temperature and high current rates.