Integrated N, P co-doped and dense carbon networks produced by a chemical crosslinking strategy: Facilitating high gravimetric/volumetric performance sodium ion batteries

Low-cost sodium ion batteries (SIBs) have shown hopeful perspective for large-scale energy storage systems. However, the development of carbon anode materials with high gravimetric and volumetric capacity is still a challenge. Herein, we propose a novel dense and N, P co-doped carbon derived from high density crosslinked bacterial cellulose (BC) with hexachlorocyclotriphosphazene (HCCP), which simultaneously combines high gravimetric and volumetric capacity. The as-prepared electrode demonstrates a high reversible capacity of 223 mAh g−1 at 0.05 A g−1 and superior rate performance (145 mAh g−1 at 10 A g−1) based on the overall electrode materials. The full SIBs with this electrode show a high energy density (156.1 Wh kg−1) as well as a high Coulombic efficiency in the potential range of 0–4.2 V. Density functional theory (DFT) calculation and kinetic analysis reveals that the synergistic effect of N, P co-doped configurations contributes to the superior sodium storage performance. Moreover, this electrode possesses high pressing density of 1.40 g cm−3, which increases the volumetric capacity greatly (from 97.2 to 312.2 mAh cm−3). This work proposes a new idea towards the development of low-cost bacterial cellulose that can be used in practical applications for high gravimetric and volumetric performance SIBs.