In recent years, sodium ion batteries (SIBs) have been widely investigated due to limited lithium resources. Though sodium and lithium elements have similar physical and chemical properties, some decently performing anodes of lithium ion batteries are problematic in SIBs. Hence, it is of great importance to develop suitable anodes for SIBs. In recent works, doped amorphous carbon has been considered a prospective and serviceable anode for the storage of sodium. Nevertheless, there is no commonly accepted explanation for the sodium storage mechanism and doping effect of doped carbon to explain why doping can improve the sodium-storage performance in SIBs. In this study, sodium-storage behavior in electron-rich, element-modified, amorphous carbon is addressed, considering N and P. The affinity of N-doped amorphous carbon is identified by calculating the electron distributions of the N-doped structures. Furthermore, the adsorption energies of sodium in the P-doped amorphous carbon systems are analyzed to elucidate the storage behavior of doping. From the above analysis, the internal structure of co-doped carbon is characterized and pyrrolic N and P-O structures reveal excellent sodium-storage performance. Consequently, hydrothermal treatment is designed to build the precursor of the required P-O structure. Based on the sodium-storage theory, a carbon anode doped with dual electron-rich elements is synthesized successfully, which shows enhanced electrochemical performances in terms of cycle life and capacity in batteries. As a result, these research results fill the theoretical gap of the sodium-storage behavior of electron-rich, element-doped, amorphous carbon and provide the experimental basis for its application.

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