Kirkendall effect-assisted synthesis of hollow MoS2 nanospheres with interlayer expansion for improved magnesium diffusion kinetics and durability

Abstract

Due to its unique interlayer structure, MoS₂ is considered as one of the optimal cathode materials for magnesium-ion batteries. However, the intrinsic state of MoS₂ exhibits a small interlayer spacing and poor electrical conductivity, posing challenges in achieving reversible interlayer intercalation/deintercalation of Mg²⁺. As a result, this leads to limited energy density and inadequate cycling stability. Herein, we developed a universal strategy based on the Kirkendall effect to synthesize hollow MoS₂ nanospheres with a 1T phase and expanded interplanar distance. During the vulcanization process, the inward diffusion rate of the Mo atom surpasses that of the external S atom, leading to the progressive formation of a hollow structure within the MoS₂ sphere. In addition, the hollow structure can increase the specific surface area and mitigates volume expansion; while the presence of the 1T phase and expanded interlayer spacing (from 0.615 nm to 0.727 nm) can improve electrode conductivity, reduce the diffusion barrier for ions, and alleviate lattice breathing-induced volume changes. As a result, the synthesized electrode exhibits superior electrochemical performance and structural stability with a reversible capacity of 331.3 mA h g⁻¹ at 20 mA g⁻¹ after 200 cycles, and 129.2 mA h g⁻¹ at 1000 mA g⁻¹ after 2000 cycles.