In situ synthesis of cellulose/carbon nanotubes/molybdenum disulfide composite with ultrahigh capacity and enhanced coulombic efficiency for sodium ion battery

Abstract

Sodium ion batteries (SIBs) have wide application prospects due to their low cost, high capacity and extended cycling life. However, there is a critical need for anode materials that exhibit ultrahigh capacity and outstanding initial coulombic efficiency (ICE) to further enhance SIB performance. Herein, cellulose/carbon nanotubes/molybdenum disulfide (CM/CNTs/MoS₂) microspheres are initially synthesized via the in situ deposition of nano-MoS₂ onto cellulose/carbon nanotubes (CM/CNTs) microspheres. Subsequently, hard carbon/molybdenum disulfide (C/MoS₂) composite anode is obtained through direct calcination of CM/CNTs/MoS₂ microspheres at 1350 °C. The carbon framework effectively mitigates volume expansion and prevents structural collapse of the C/MoS₂ anode during electrochemical testing. To enhance the ICE of C/MoS₂ composite anode, a weakly solvating electrolyte (WSE) strategy is developed, involving one cycle of high current-density discharge/charge in LiPF₆ electrolyte. Electrochemical impedance spectroscopy (EIS) tests reveal that the thin and compact solid-electrolyte interface (SEI) formed on the C/MoS₂-WSE composite anode significantly reduce the reaction resistance (R_ct). When paired with Na₃V₂(PO₄)₃ (NVP) cathode, the C/MoS₂-SWE//NVP full cell demonstrates a reversible capacity of 276 mAh·g⁻¹ at a current density of 300 mA g⁻¹, along with an ultra-high capacity retention of 97.3 % after 100 cycles.