Rate performance enhancement in lithium-ion batteries using TiNb2-xAlxO7 anodes with self-generated protective layers

Abstract

Lithium titanate oxides, i.e. Li4Ti5O12 (LTO), and titanium niobium oxides, i.e. TiNb2O7 (TNO), are promising anodes for lithium-ion batteries (LIBs). In comparison to LTO anodes, TNO anodes have zero-strain characteristics but with a higher specific capacity (about 387 mAh g-1). However, the reactions leading to gas generation during high-rate cycling impedes the practical use of TNO anodes. The incorporation of aluminum into TNO by partial replacement of niobium atoms is proposed to address these issues. This Al-incorporation enables self- generation of a protective shell through the solute drag effect by annealing process. The generated protective layer is conducive to the formation of a solid electrolyte interphase (SEI) layer with enhanced lithium-ion conductivity during reaction with electrolyte. In addition, this SEI layer can effectively reduce side reactions and polarization during high-rate cycling, thereby suppressing the possibility of gas generation and enhancing the overall electrochemical performances. As a result, TiNb1.95Al0.05O(TNAO-0.05) anode exhibits a high specific capacity of about 223 mAh g-1 for over 100 cycles at 0.1C. Even at a higher rate of about 5C, it maintains a specific capacity as high as 176 mAh g-1, and holding up a capacity retention of 96.4 % after 300 cycles at 1C. This report demonstrates the potential of TNAO-0.05 anode for industrial battery applications.