Modification strategies and recent advances of sodium titanate anode materials for enhanced electrochemical performance in sodium ion batteries

Abstract

Sodium-ion batteries (SIBs) are prospective next-generation alternatives to lithium-ion batteries (LIBs). Recently, most research has focused on the sodium titanate (NTO) structure as a possible anode with a low operating potential for SIBs. Furthermore, NTO has excellent stability and safety, and a suitable sodium storage capability. Although there are various types of NTOs, such as NaTiO₂, Na₄Ti₅O₁₂, Na₂Ti₆O₁₃, and Na₂Ti₃O₇, the most common NTO with a low operating voltage of 0.3 V vs. Na/Na⁺ is layered Na₂Ti₃O₇. However, the sluggish ion insertion/extraction kinetics, substantial lattice expansion, low electronic conductivity, and the low Na⁺ ion diffusion limit the electrochemical performance of NTO. To address these challenges, several modification techniques have been developed, including nanostructure engineering, ion doping, the incorporation of carbon-based composites, carbon coating, and other surface modification techniques. Herein, the types of NTOs and the corresponding modification strategies that enhance the electrochemical performance of NTO anodes are outlined. The effects of these modification strategies on the NTO structure and their resulting electrochemical improvements are systematically summarized. Nanostructure engineering is widely employed in NTO anodes because the large surface area of the nanosized structures will accelerate surface processes, thereby improving the electrochemical properties. SIB research for stationary energy storage will be substantially aided by the use of modified NTO anode materials.