Novel multiphase nano Ni3Bi2S2/NiS anchored on graphite nanosheet for high-capacity sodium-ion battery anodes

In the context of scalable electrode production via ball-milling, achieving high cycling stability and electrochemical performance in bifunctional anodes for sodium ion batteries (SIBs) is crucial yet remains a significant challenge. To address these objectives, we have developed a unique hybrid anode nanocomposite characterized by its local multiphase nature. This composite involves the incorporation of novel ternary-Ni-Bi-S/binary-Ni-S nanomaterials onto exfoliated graphite nanosheets (Ni3Bi2S2/NiS-G) through a facile ball-milling process. Our combined experimental and theoretical investigations suggest that the interactions between graphite nanosheets and the layered structure of Ni3Bi2S2/NiS, along with the discharge products of Na2S, play pivotal roles in enhancing the Na+ diffusion rate and stability of the hierarchical configuration anode. Upon testing, the novel Ni3Bi2S2/NiS-G shows overwhelmingly higher electrochemical performance compared to the Ni3Bi2S2/NiS counterpart, the Ni3Bi2S2/NiS-G delivered a reversible capacity of 489.9 mAh/g at 0.2 A/g after 400 cycles, and displayed a high capacity of 387.3 and 339.6 mAh/g after 500 cycles at 1 A/g and 2 A/g, respectively, yielding a high capacity retention ratio of 84.8 % and 82.8 % of the 1st cycle. This work provided a novel approach for developing new bifunctional anode electrodes with high capacity and rate performance as well as superior cycling stability.