Ni₃S₂ Nanoparticles Anchored on d-Ti₃C₂ Nanosheets with Enhanced Sodium Storage

To enhance structural stability and explore energy storage mechanisms for sodium-ion batteries, Ni3S2 nanoparticles anchored on d-Ti3C2 nanosheets (Ni3S2/d-Ti3C2) are designed and synthesized through the hydrothermal method followed by sulfurization reaction. Ni3S2/d-Ti3C2 provides abundant active sites and reduces the Na+ diffusion path, leading to high sodium storage performance. The d-Ti3C2 nanosheets work as a conductive framework, providing high ion- and electron-conductive pathways and buffer volume change in Ni3S2 nanoparticles, while Ni3S2 nanoparticles exhibit high sodium storage and are applied as the spacer to suppress the restacking of d-Ti3C2 nanosheets. The synergistic effect effectively improves sodium storage performance of the obtained electrode and shows a special capacitive and diffusive dual-model energy storage mechanism for sodium-ion batteries. Specifically, Ni3S2 nanoparticles are battery-type components with high capacity, and the d-Ti3C2 nanosheets are pseudocapacitive components with a high pseudocapacitive value and fast energy storage. Consequently, the Ni3S2/d-Ti3C2 electrode provides enhanced performance (234.4 mA h g–1 at 0.1A g–1), almost 5.5 times that of the d-Ti3C2 electrode (∼42.4 mA h g–1). The results show that this metal sulfide incorporation strategy presents a prospective way to heighten sodium storage performance of d-Ti3C2 MXene.