Binderless Electrodeposited NiCo₂S₄-MWCNT as a Potential Anode Material for Sodium-Ion Batteries

Abstract

Conversion type ternary NiCo2S4, exhibiting high electrical conductivity (~1.25 × 106 S m-1) and high theoretical capacity (703 mAh g-1), has gained interest as an anode material for sodium-ion batteries (SIBs). Despite its potential, NiCo2S4 (NCS) has extensive volume expansion during cycling. This study introduces the NCS-multi-walled carbon nanotube (MWCNT) onto a carbon fiber (CF) electrode (NCS and NCS-MWCNT@CF), developed through electrodeposition, which addresses these limitations. The unique sheet-like morphology of NCS, featuring abundant pores, ensures good access to the electrolyte. Incorporating a three-dimensional conductive CF framework that acts as a free-standing current collector helps prevent the agglomeration of NCS particles and mitigates volume expansion by providing enough buffer space in the layers of the CF matrix. Our findings reveal that NCS on CF electrodes deliver a second cycle capacity of 620 mA g-1 at 30 mA g-1 and retain 72 % capacity after 200 cycles. At 200 mA g-1, the NCS@CF electrodes deliver 378 mAh g-1 in the second cycle with 68% capacity retention in the 200th cycle, whereas NCS-MWCNT@CF delivers 538 mAh g-1 at 200 mA g-1, maintaining 86 % capacity after 100 cycles, making it a potential anode for SIBs.