Yin Bo, Liang Shuquan, Yu Dongdong, Cheng Boshi, Egun Ishioma L, Lin Jiande, Xie Xuefang, Shao Hezhu, He Haiyong, Pan Anqiang
School of Material Science and Engineering, Central South University, Changsha, 410083, China.
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China.
Adv Mater. 2021 Sep;33(37):e2100808. doi: 10.1002/adma.202100808. Epub 2021 Aug 1.
Numerous studies have reported that the enhancement of rate capability of carbonaceous anode by heteroatom doping is due to the increased diffusion-controlled capacity induced by expanding interlayer spacing. However, percentage of diffusion-controlled capacity is less than 30% as scan rate is larger than 1 mV s , suggesting there is inaccuracy in recognizing principle of improving rate capability of carbonaceous anode. In this paper, it is found that the heteroatom doping has little impact on interlayer spacing of carbon in bulk phase, meaning that diffusion-controlled capacity is hard to be enhanced by doping. After synergizing with tensile stress, however, the interlayer spacing in subsurface region is obviously expanded to 0.40 nm, which will increase the thickness of accessible subsurface region at high current density. So SRNDC-700 electrodes display a high specific capacity of 160.6 and 69.5 mAh g at 20 and 50 A g , respectively. Additionally, the high reversibility of carbon structure insures ultralong cycling stability and hence attenuation of SRNDC-700 is only 0.0025% per cycle even at 10 A g for 6000 cycles. This report sheds new insight into mechanism of improving electrochemical performance of carbonaceous anode by doping and provides a novel design concept for doping carbon.
众多研究报告称，杂原子掺杂提高碳质阳极倍率性能的原因是层间距扩大导致扩散控制容量增加。然而，当扫描速率大于1 mV s时，扩散控制容量的占比小于30%，这表明在认识碳质阳极倍率性能提升原理方面存在不准确之处。本文发现，杂原子掺杂对本体相中碳的层间距影响很小，这意味着通过掺杂难以提高扩散控制容量。然而，在与拉伸应力协同作用后，亚表面区域的层间距明显扩大至0.40 nm，这将增加高电流密度下可及亚表面区域的厚度。因此，SRNDC - 700电极在20和50 A g时分别显示出160.6和69.5 mAh g的高比容量。此外，碳结构的高可逆性确保了超长的循环稳定性，因此即使在10 A g下循环6000次，SRNDC - 700的衰减也仅为每循环0.0025%。本报告为通过掺杂改善碳质阳极电化学性能的机理提供了新的见解，并为掺杂碳提供了一种新颖的设计理念。
