Due to their excellent physical and chemical stability and long-term cycling, insertion anodes are becoming increasingly important in energy storage. However, insertion anodes still suffer from low energy density and large irreversible capacity. Systematically controlling the macroscopic structure and microscopic crystal parameters are effective ways of improving the energy density, cycle capacity, and rate performance of carbonaceous materials. In this work, a series of nonporous, microporous, and mesoporous carbon nanosheets was designed and fabricated from balsa waste by thermal infiltration, and displayed high disorder and abundant surface functional groups. The sample with the best performance (BC-8) had a large pore size centred at 2.5–4.5 nm, accompanied by a highly disordered crystallite structure, expanded carbon interlayers, a large number of active sites, and small particle sizes. The results revealed that mesoporous carbon nanosheets deliver a large capacity, and that the ion storage capacity of carbon nanosheets could be increased by optimizing the pore size. As an ion storage anode, sample BC-8 exhibited higher reversible capacity (630 mA h g⁻¹ at a rate of 0.2 A g⁻¹ after 100 cycles), longer cycling stability, and better rate performance (150 mA h g⁻¹ at 5 A g⁻¹ after 1000 cycles) than the other samples. Kinetic analysis confirmed that porous carbon nanosheet materials show a synergistic effect between capacitor-like and diffusion-controlled behavior; the excellent electrochemical properties of mesoporous carbon nanosheets are dominated by diffusion-controlled behavior; and the capacity of the micropores is mainly governed by surface capacitance-controlled contributions. Our work helps explain the improved ion storage behavior of carbon with a two-dimensional nanosheet structure and provides an effective strategy for designing higher energy density carbon materials for advanced energy storage systems.

中文翻译：

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来自生物质废物的碳纳米片：洞察可控孔结构在能量存储中的作用

由于其优异的物理和化学稳定性以及长期循环，插入式阳极在储能方面变得越来越重要。但是，插入式阳极仍具有能量密度低和不可逆容量大的缺点。系统地控制宏观结构和微观晶体参数是提高碳质材料的能量密度，循环容量和速率性能的有效方法。在这项工作中，由轻木废物通过热渗透设计和制造了一系列无孔，微孔和中孔碳纳米片，并显示出高无序性和丰富的表面官能团。性能最佳的样品（BC-8）的孔尺寸大，集中在2.5-4.5 nm，并伴有高度无序的微晶结构，扩展的碳夹层，大量的活性位点，并且粒径小。结果表明，介孔碳纳米片具有大的容量，并且可以通过优化孔径来增加碳纳米片的离子存储容量。作为离子存储阳极，样品BC-8具有更高的可逆容量（630 mA汞柱）^-1在0.2 A g的速率^-1 100次循环后），较长的循环稳定性，以及更好的倍率性能（150毫安汞柱^-1在5 A G ^-11000次循环后）。动力学分析证实，多孔碳纳米片材料在电容器样行为和扩散控制行为之间表现出协同作用。介孔碳纳米片的优异电化学性能主要由扩散控制行为决定。而微孔的容量主要由表面电容控制的贡献所决定。我们的工作有助于解释二维二维纳米片结构改善的碳离子存储行为，并为设计用于高级能量存储系统的更高能量密度的碳材料提供了有效的策略。