Humic acid resin-based amorphous porous carbon as high rate and cycle performance anode for sodium-ion batteries

We developed amorphous porous carbon (i.e. humic acid resin-based amorphous porous carbon, HARC800) with the controlled porosity in the ordered structure as anode material for sodium-ion batteries (SIBs) through the optimized annealing process supported by functional lignite and sodium alginate precursors. HARC800 has well-developed interconnected mesoporous and micropores, accounting for 85.7% and 14.3%, respectively. The porous characteristic of amorphous carbon materials can curtail the diffusion path of Na⁺, and promote the penetration of electrolyte in the material, which is very instrumental in intensify the dynamic property of the material, thereby promoting the storage of Na⁺. When it is applied to the anode for SIBs, the HARC800 provides an initial reversible capacity of 260 mA h g⁻¹ at 30 mA g⁻¹. Even at 2000 mA g⁻¹, it appears 99 mA h g⁻¹, indicating that it has excellent rate performance. It could be yielded 133 mA h g⁻¹ after 200 cycles at 500 mA g⁻¹, and maintain 119 mA h g⁻¹ after 1000 cycles at 1000 mA g⁻¹, suggesting its outstanding long-life cycle performance. This research proposes that reasonable control of the ratio of mesoporous and micropores can promote the Na⁺ storage performance of amorphous porous carbon materials.