Reduced titanium oxide Ti₃O₅ powder as a promising conductive additive for LiFePO₄-based lithium-ion batteries

Abstract

Reduced titanium oxide Ti₃O₅ powder which was fabricated by a sol–gel process was added to lithium iron phosphate (LiFePO₄) cathode electrodes for use in lithium-ion batteries and its performance was investigated. First discharging of the cathode electrode with Ti₃O₅ powder as the conductive additive keeps the capacity of 170.9 mAh g⁻¹ at 0.1 C, 150.8 mAh g⁻¹ at 0.5 C, 134.6 mAh g⁻¹ at 1 C, and 107 mAh g⁻¹ at 2 C, respectively, which is higher than that of the cathode electrode with acetylene black as the conductive additive, who keeps the capacity of 162 mAh g⁻¹ at 0.1 C, 142.8 mAh g⁻¹ at 0.5 C, 126.9 mAh g⁻¹ at 1 C, and 105.8 mAh g⁻¹ at 2 C, respectively. Over 100 cycles at 0.5 C, the LiFePO₄ cathode electrode with Ti₃O₅ powder can maintain 77.5 % of its initial capacity, and the electrode with acetylene black shows 73.6 % capacity retention. The reason why the electrode with Ti₃O₅ additive shows better rate capability is that the Ti₃O₅ powder exhibits a relatively good electrical conductivity and shows a more homogeneous dispersion than acetylene black among the LiFePO₄ particles during the cycles, in the investigation, a layer of suspected titanium oxide yarn-like thin film is discovered coating on the LiFePO₄ particles of the cathode electrode with Ti₃O₅ powder after 100 cycles at 0.5 C.