Efforts on enhancing the Li-ion diffusion coefficient and electronic conductivity of titanate-based anode materials for advanced Li-ion batteries

Titanate-based compounds have been considered as a hopeful family of anode materials for high-performance lithium-ion batteries due to the "zero-strain" characteristics, low cost, excellent safety and high potential plateau, and free generation of metallic Li and solid electrolyte interphase film. Nonetheless, the large-scale applications of titanate-based compounds are limited by the intrinsically low Li-ion diffusion coefficient and poor electronic conductivity. Considerable efforts have been devoted to solving these challenges towards practical applications, and some crucial progresses have been made. In this review, we present a comprehensive overview of the structural features, transport properties, and modification strategies of titanate-based compounds. The research progress of various effective strategies for enhancing Li-ion diffusion coefficient, electronic conductivity and electrochemical performance are emphatically summarized, including ion-doping, surface modifications, particle morphology control, construction of composite electrodes, etc. This review also gives a compendious summary of gassing mechanism of Li4Ti5O12-based battery and the solution. Designing delicate architectures of carbon coating is an efficient strategy to obtain high-performance titanate-based materials, which can restrain gassing behavior and achieve the high electronic conductivity simultaneously. At last, an insight into the future research directions and further developments of titanate-based compounds is prospected so as to promote their wide application. The review will offer significant comprehension for design and optimization of high performance of the titanate-based compounds.