A hard carbon material with free-standing porous structure and high contents of heteroatom functional groups is considered to be a potential anode for potassium-ion batteries (PIBs). Herein, a free-standing phosphorus/nitrogen cofunctionalized porous carbon monolith (denoted as PN-PCM) anode for PIBs is successfully fabricated via a supercritical CO₂ foaming technology, followed by amidoximation, phosphorylation, and thermal treatment. Thanks to the synergistic effect of a three-dimensional macroporous open structure and high P/N contents of 6.19/5.74 at%, the PN-PCM anode delivers an excellent reversible specific capacity (396 mA h g^–1 at 0.1 A g^–1 after 300 cycles) with high initial Coulombic efficiency (63.6%), a great rate performance (168 mA h g^–1 at 5 A g^–1), and an ultralong cycling stability (218 mA h g^–1 at 1 A g^–1 after 3000 cycles). Theoretical calculations clarify that in a P/N cofunctionalized carbon, the P–C bonds devote more to enhancing the potassium storage via adsorption and improving electronic conductivity of carbon, while P–O bonds contribute more to enlarging the interlayer distance of carbon and reducing the ion diffusion barrier.

中文翻译：

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游离钾/氮共官能化多孔碳整料作为高性能钾离子电池阳极的可控磷酸化策略。

具有独立的多孔结构和高杂原子官能团含量的硬碳材料被认为是钾离子电池（PIB）的潜在阳极。在此，通过超临界CO ₂发泡技术成功地制造了用于PIB的独立式磷/氮共官能化多孔碳整料（表示为PN-PCM）阳极，然后进行了酰胺化，磷酸化和热处理。得益于三维大孔开放结构的协同效应和6.19 / 5.74 at％的高P / N含量，PN-PCM阳极具有出色的可逆比容量（396 mA hg ^–1在0.1 A g ^–1时后300个循环）以高的初始库仑效率（63.6％），很大的速度性能（168毫安汞柱^-1在5 A G ^-1），和一个超长循环稳定性（218毫安汞柱^-1 1 A G ^-1后3000个周期）。理论计算表明，在P / N共官能化碳中，P–C键更多地通过吸附和改善碳的电子电导率来提高钾的储存量，而P–O键则更多地扩大了碳的层间距离并减少了碳的形成。离子扩散阻挡层。