Interfacial post-heterojunction construction in Mn-doped NiS2 for realizing fast and stable sodium storage

Abstract

Sodium-ion batteries (SIBs) are considered as ideal energy storage devices. However, sluggish kinetics and mechanical instability of electrode materials hinder the development of SIBs in practical application. It is necessary to design a high-performance anode material for fast and stable sodium storage. Herein, Mn-doped NiS2 with a post-heterojunction (M−NS/C-2) is prepared. The electrochemical performance is improved by the synergistic effect of Mn-doping and post-heterojunction interface construction. On the one hand, Mn-doping enlarges the lattice spacing of NiS2 to accommodate sodium ions, moreover, the stacked morphology with interlamellar void influenced by doping provides a structural buffer and dominant pseudo-capacity. On the other hand, Cu7.2S4 is formed in ether electrolyte for the reaction of polysulfide and copper current collector, which grafts active material onto the copper current collector, reinforcing mechanical supporting. Further, the post-heterojunction interface formation between NiS2 and Cu7.2S4 in the cyclic process can be promoted by Mn-doping, boosting electron transfer to facilitate rapid kinetics. Thus, M−NS/C-2 displays good rate performance (497.9 mAh/g even at 10 A/g) and superior cycling stability (390.4 mAh/g after 20,000 cycles at 10 A/g with 0.0013 % attenuation per cycle). The M−NS/C-2|| Na3V2(PO4)3 full cell shows cyclic performance of 241.5 mAh/g after 100 cycles at 1 A/g.