Cottonseed cake-derived hard carbon anode with modulated carbon layer spacing and pores for highly reversible and durable sodium-ion batteries

Abstract

Biomass-derived hard carbon, as a type of highly promising anode material for sodium-ion batteries (SIBs), has garnered considerable interests due to the merits of wide sources, diverse structural features, desirable surface chemistry and low cost. However, the practical utilization of it has been hindered by the bottlenecks including unreasonable synthesis process, and unclear elucidation between Na-storage mechanism and specific microstructures. Herein, a novel cottonseed cake-derived hard carbon anode material was synthesized by a combined approach of pre-oxidization, acid-base treatment and carbonization. This approach effectively expands the carbon interlayer spacing and enables the formation of appealing pores for the hard carbon, promoting the achievement of high-performance Na-storage in SIBs. Consequently, the optimized APHC sample delivers an impressive initial reversible capacity of 302.1 mAh g⁻¹, a high initial Coulombic efficiency of 92.3%, and a remarkable capacity retention rate of 86.7% over 200 cycles at 100 mA g⁻¹. Besides, the assembled full cell with commercial NaNi₁/₃Fe₁/₃Mn₁/₃O₂ as cathode material displays a high reversible capacity of 136.1 mAh g⁻¹, retaining 72.2 % capacity after 200 cycles at 50 mA g⁻¹. This work provides a facile strategy for the design of advanced cottonseed cake-derived hard carbon anode material with modulated carbon layer spacing and pores for rechargeable SIBs.