Interlayer regulation of MoS₂ nano sheets for enhanced potassium storage in Ni₃S₄ nanospheres dispersed on N-doped graphene

The significant volume expansion resulting from potassium ion (K⁺) intercalation limits the development of promising electrode materials for PIBs. Herein, a facile self-propagating combustion synthesis (SPCS) strategy is proposed to obtain self-loading of MoS₂ layers around Ni₃S₄ nano-particles on a nitrogen-doped graphene (NG) matrix (MoS₂/Ni₃S₄@NG). This layered structure act as a boundary layer, regulating the direct insertion of K⁺ into Ni₃S₄, facilitating efficient K⁺ storage, and ultimately mitigating structural degradation and volume expansion during battery cycling. The resulting MoS₂/Ni₃S₄@NG electrode delivers a reversible specific capacity of 370.6 mAh/g and exhibits a rate capability of 240.8 mAh/g at 0.6 A g⁻¹ after 100 cycles, whereas maintained 75 % of its capacity even after 1000 cycles. Furthermore, the pseudocapacitive-controlled storage mechanism displays 81.9 % of the capacitive contribution at a scan rate of 1 mV s⁻¹. Density functional theory (DFT) analysis reveals that redistribution of electronic states near the fermi level (FL) in MoS₂/Ni₃S₄ heterostructure, driven by Ni 3d and Mo 4d orbitals hybridization, significantly enhances the density of state (DOS) at FL. This promotes efficient charge excitation, improves electrical conductivity, and mitigate structural distortion during K⁺ intercalation, ensuring the structural stability of Ni₃S₄. Overall, the current work has substantial potential to develop highly-performance anode electrodes for PIBs.