N/O/P-rich three-dimensional carbon network for fast sodium storage

Heteroatom doping is an effective strategy to improve the sodium storage capacity of carbon materials. However, the current heteroatom doping preparation method is complicated and it is difficult to achieve large-scale industrial production. In this paper, starch is used as precursor to obtain N, O, P co-doped carbon network (NOP–CN) through a simple calcination. Experimental and theoretical calculations were used to systematically analyze the effect of N, O, P co-doping on the sodium storage capacity of the carbon material. Compared with diatomic (N, O) doping, the introduction of P atoms further enhances the conductivity of the carbon structure, while distorting the graphite layer, generating more active sites and defects, increasing the graphite layer spacing. At the same time, the unique three-dimensional network of NOP–CN provides a fast transmission channel for sodium ions. Therefore, NOP–CN exhibits excellent electrochemical performance. The reversible capacity can reach 341.3 mA h g−1 at 0.05 A g−1. After 2000 cycles at 5 A g−1, the capacity can remain 119.1 mA h g−1. The excellent sodium storage capacity and simple synthesis strategy in this study provide an efficient and convenient method for the design of heteroatom-doped carbon materials.