Enhancing the pseudocapacitance of carbon electrodes by doping them with heteroatoms becomes one promising way for fabricating high energy density supercapacitors. Nevertheless, rich doping with heteroatoms often arouses an inevitable contradiction between pseudocapacitance and conductivity. In this paper, inspired by the surface structure of the lotus leaf, a novel “plains–hills” model of carbon structure is proposed to solve this problem. For achieving this plains–hills structure, CaCl₂ is employed as both a complexing agent and an oxygen scavenger in Ca²⁺–biogels via host–guest complexation, resulting in an ultrathin carbon unstacked nanosheet (“plains” domain) with numerous protuberances (“hills” domain) by a facile one-step pyrolysis. The obtained plains–hills architecture containing the defect-rich hills and the ordered plains achieves a harmonious coexistence of high pseudocapacitance and good conductivity in heteroatom-doped carbon materials. As expected, this kind of plains–hills carbon electrode exhibits a reversible capacity of 147.2 mAh g^–1 at 10 A g^–1 after 5000 cycles, leading to an obvious energy density enhancement of potassium ion hybrid supercapacitors.

中文翻译：

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“平原-丘陵”：一种设计用于高性能钾离子混合超级电容器的生物质衍生碳电极材料的新模型

通过用杂原子掺杂碳电极来提高碳电极的伪电容成为制造高能量密度超级电容器的一种有前途的方法。然而，富含杂原子的掺杂通常会引起伪电容与电导率之间不可避免的矛盾。在本文中，受荷叶表面结构的启发，提出了一种新颖的碳素结构“平原－丘陵”模型来解决这一问题。为了实现这种平原-丘陵结构，CaCl ₂在Ca ^2+中既用作络合剂又用作除氧剂通过宿主-客体复合产生的生物凝胶，通过简便的一步热解作用就可以形成具有许多突起（“丘陵”域）的超薄碳纳米管未堆叠纳米片（“平原”域）。所获得的平原-丘陵结构包含缺陷丰富的丘陵和有序的平原，从而在杂原子掺杂碳材料中实现了高假电容和良好电导率的和谐共存。不出所料，这种平地-希尔斯碳电极在5000次循环后在10 A g ^–1处表现出147.2 mAh g ^–1的可逆容量，从而显着提高了钾离子混合超级电容器的能量密度。