Research progress on molybdenum- and tungsten-based materials for sodium-ion batteries: fundamental mechanisms and optimization strategies

Abstract

In sodium-ion battery (SIB) anode systems, molybdenum (Mo)- and tungsten (W)-based materials have shown great potential in the field of energy storage due to their high theoretical capacity, adjustable layered structure, and multi-electron characteristics. However, their practical applications are limited by challenges such as structural collapse caused by volume expansion, instability of the solid electrolyte interface (SEI) due to interface side reactions, and poor conductivity. To date, many reports have shown that through strategies such as structural design, compounding and hybridization, defect and interface engineering, their conductivity can be significantly improved, mechanical stress alleviated and ion transport paths optimized, achieving a breakthrough in cycling stability. In this review, we first analyze the challenges faced by Mo- and W-based materials in SIB anodes. Then, we systematically focus on the sodium storage mechanisms and performance optimization strategies for Mo- and W-based materials, as well as research progress on Mo- and W-based oxides/chalcogenides, carbon composites and polymetallic molybdenum/tungstate. Finally, we discuss the bottlenecks they face and provide an outlook for the future development of Mo- and W-based materials in the SIB field.