Tin Phosphide Hollow Nanospheres Enveloped by MXene as a Conversion-Type Anode Enabling Rapid and Stable Ion Storage in Diverse Energy Storage Systems

Abstract

The design of a single anode material compatible with both Li⁺ and Na⁺ storage represents a critical advancement in the development of advanced lithium-ion (LIBs) and sodium-ion batteries (SIBs), particularly from a cost-effectiveness perspective. Tin phosphide, a conversion-type anode material, presents an energy storage mechanism without specific constraints on ion size or alloy properties and can provide high capacity with respect to Li and Na ions, making it an ideal candidate for dual applications in both LIBs and SIBs. However, its large volumetric expansion during the conversion reaction and low electronic conductivity lead to rapid capacity degradation. Herein, a coated hollow Sn₄P₃ sphere structure is designed, wherein Sn₄P₃ hollow nanospheres (Sn₄P₃HNs) are tightly encapsulated by MXene nanosheets. The hollow nanosphere structure provides space for inward volumetric expansion, while the MXene coating prevents outward expansion and enhances conductivity, endowing the composite with excellent cyclic stability and rate capabilities. For lithium-ion storage and sodium-ion storage, it exhibits excellent capacity retention of 92.75% and 95% at 1 A g⁻¹ after 1200 and 1500 cycles, respectively. The remarkable electrochemical properties demonstrated in this study indicate that this composite is a highly competitive anode option for simultaneous application in lithium-ion and sodium-ion batteries.