In situ interface engineering of NiSe with interlinked conductive networks for high energy density sodium-ion half/full batteries

Abstract

Transition metal selenides (TMSs) are compounds composed of transition metals and selenium, and they offer a range of chemical and structural diversities that can be exploited to optimize their performance as sodium-ion battery (SIB) electrodes. One of the most promising TMSs for SIBs is NiSe, which possesses a high theoretical capacity of 399 mA h g⁻¹. However, poor cycling stability and low overall energy density resulted from its structural instability, as well as the poor intrinsic conductivity, limiting its application in SIBs. In this work, in situ interface engineering of NiSe is proposed via chemically anchoring high doping and three-dimensional (3D) carbon nanotubes (CNTs) on the surface of NiSe nanofibers (NiSe@NC/CNTs). The CNTs, which in situ grow in multiple directions, form a connected conductive network that is good for electron transport. In addition, the nano-confined NiSe nanoparticles effectively inhibit the volume expansion of charge and discharge in SIBs. A NiSe@NC/CNT electrode is directly used as an anode for SIBs, showing an excellent long-term cycling stability of 225 mA h g⁻¹ after 1000 cycles and high rate capability. The sodium-ion full batteries with the NiSe@NC/CNT anode exhibit a high energy density of 147 W h kg⁻¹ at a power density of 244 W kg⁻¹, along with stable cycling performance. The sodium ion (de)intercalation process of the NiSe@NC/CNT anode material has been characterized, revealing its charging and discharging mechanism. Theoretical calculations were conducted to investigate the volume change produced by doped N buffer materials during Na⁺ embedding/desequestration, which provides more active sites for sodium ion storage. Our study provides a better understanding of the interface engineering of the TMS electrode and sheds light on the design and optimization of high-performance SIBs.