Synergistic effects of P-functionalization and localized graphitization in sustainable hard carbon for enhanced...

Hard carbon is a promising anode due to economy and high plateau capacity at low voltages. However, the low reversible capacity is limited by the lack of active sites and the unstable solid electrolyte interphase (SEI). P-doped hard carbon (NOP-1400) is synthesized from camphor leaf residue by the element doping and temperature optimization. The temperature optimization promotes the rearrangement between carbon layers and affects local graphitization. Local graphitization enhances the structural stability and conductivity. P doping improves the layer spacing of local graphite domain, introduces more functional groups, and increases the number of active sites. This improves the electronic structure of NOP-1400, facilitating the formation of a uniform and inorganic-rich SEI, thereby enhancing cycling stability. The NOP-1400 achieves 445.65 mAh g^-1 at 0.1 A g^-1 after 500 cycles in sodium ion batteries and 223.19 mAh g^-1 in potassium ion batteries. This work provides insights for the rational construction and interface chemical regulation of P-doped biomass hard carbon.