Sodium‐ion capacitors (SICs) can effectively combine high energy density with high power density, and are especially appropriate for high‐power demanding applications of large‐scale stationary energy storage. Surface‐induced pseudocapacitive charge storage based on porous or nano carbon materials is regarded as the most promising candidate for SICs. Unfortunately, their ultralow packing densities severely restrict their practical applications. A novel approach toward ultrafast high‐volumetric SICs based on folded‐graphene electrodes has already been demonstrated and showed quite competitive performance. In this work, it is further proved that oxygen functional groups and folded texture are two key elements for high‐volumetric sodium storage of folded‐graphene electrodes. Through a simple and controllable method, of thermal treatment in inert atmosphere, both the oxygen functional groups and folded texture can be quantitatively manipulated to better investigate the individual contribution and mutual interplay. It is illustrated that oxygen functional groups are crucial to superior capacitive sodium storage while folded texture is not only the origin for high‐volumetric sodium storage but also beneficial for both capacitive and additional diffusion‐controlled sodium storage. Inspired by above‐mentioned conclusion, more rational designs and effective preparation of advanced structure and novel materials can be realized to better promote the development of high‐volumetric SICs.

中文翻译：

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紧凑型钠离子电容器的致密石墨烯电极中氧官能团与折叠结构的相互作用

钠离子电容器（SIC）可以有效地将高能量密度与高功率密度结合起来，特别适合于对大功率要求苛刻的大型固定式储能应用。基于多孔或纳米碳材料的表面感应伪电容电荷存储被认为是SIC的最有希望的候选者。不幸的是，它们的超低堆积密度严重限制了它们的实际应用。已经展示了一种基于折叠石墨烯电极的超快高容量SIC的新颖方法，并显示出相当有竞争力的性能。在这项工作中，进一步证明了氧官能团和折叠结构是折叠石墨烯电极高体积钠存储的两个关键元素。通过一种简单且可控的方法，在惰性气氛中进行热处理的过程中，可以对氧官能团和折叠结构进行定量控制，以更好地研究个体贡献和相互影响。说明了氧官能团对于出色的电容性钠存储至关重要，而折叠的纹理不仅是高体积钠存储的起源，而且对电容性和附加扩散控制的钠存储都有利。受到上述结论的启发，可以实现更合理的设计以及有效的先进结构和新颖材料的制备方法，以更好地促进高容量SIC的发展。说明了氧官能团对于出色的电容性钠存储至关重要，而折叠的纹理不仅是高体积钠存储的起源，而且对电容性和附加扩散控制的钠存储都有利。受到上述结论的启发，可以实现更合理的设计以及有效的先进结构和新颖材料的制备方法，以更好地促进高容量SIC的发展。说明了氧官能团对于出色的电容性钠存储至关重要，而折叠的纹理不仅是高体积钠存储的起源，而且对电容性和附加扩散控制的钠存储都有利。受到上述结论的启发，可以实现更合理的设计以及有效的先进结构和新颖材料的制备方法，以更好地促进高容量SIC的发展。