Wei Yaqing, Chen Jiajun, Wang Siqi, Zhong Xingguo, Xiong Rundi, Gan Lin, Ma Ying, Zhai Tianyou, Li Huiqiao
State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, Hubei P. R. China.
Shenzhen Huazhong University of Science and Technology Research Institute, Shenzhen 518057, Guangdong, P. R. China.
ACS Appl Mater Interfaces. 2020 Apr 8;12(14):16264-16275. doi: 10.1021/acsami.9b22346. Epub 2020 Mar 24.
Many recent efforts on the electrode design for advanced Li-ion batteries (LIBs) are often devoted to increasing the gravimetric capacity, but little attention is paid to the volumetric capacity which is more critical for practical application. Though the alloying-type anode materials are quite attractive, the challenge is that they must be composited with a large amount of carbon materials (e.g., GO, rGO, CNT) to buffer their large volume change, which would undoubtedly sacrifice the volumetric energy density of the whole electrode due to the carbon's low tap density (∼0.05 g/cm). Herein, we propose the unique layered SbTe, which possesses high conductivity and a large volumetric capacity (3419 mAh/cm), to be served as the alternative anode for LIBs. Furthermore, we introduce natural graphite, which is low price and with high density (2.25 g/cm), into SbTe to successfully build a novel SbTe@Gra composite in which the SbTe particles are wrapped by graphite layers. Interestingly, this modified SbTe@Gra exhibits much more superior cycle stability (570 mAh/g after 200 cycles, 96% retention) than pure SbTe (130 mAh/g after 200 cycles, 22% retention), while keeping its original large volumetric capacity output (∼3200 mAh/cm) at the same time. More specially, it enables a reversible structure recovery of SbTe, guaranteeing the electrode integrity and cyclability. These extraordinary phenomena are investigated in detail, whose results display that the outer graphite layer plays an important role by facilitating the intimate contact with SbTe particles and protecting them from pulverization. Besides, such graphite layer greatly promotes the electron-transfer during lithiation, helping to improve the rate capability (372 mAh/g at 2000 mA/g, 60% retention). Consequently, the assembled SbTe//LiCoO full cell delivers a large capacity of 500 mAh/g, with stable discharge plateau and cycle stability, revealing its high potential for practical application.
近期在先进锂离子电池（LIBs）电极设计方面的许多努力通常致力于提高重量容量，但对体积容量的关注较少，而体积容量对实际应用更为关键。尽管合金型负极材料颇具吸引力，但挑战在于它们必须与大量碳材料（如氧化石墨烯、还原氧化石墨烯、碳纳米管）复合以缓冲其巨大的体积变化，由于碳的振实密度低（约0.05 g/cm³），这无疑会牺牲整个电极的体积能量密度。在此，我们提出独特的层状SbTe，其具有高导电性和大体积容量（3419 mAh/cm³），作为LIBs的替代负极。此外，我们将价格低廉且密度高（2.25 g/cm³）的天然石墨引入SbTe中，成功构建了一种新型的SbTe@Gra复合材料，其中SbTe颗粒被石墨层包裹。有趣的是，这种改性的SbTe@Gra表现出比纯SbTe更优异的循环稳定性（200次循环后为570 mAh/g，保持率96%），而纯SbTe（200次循环后为130 mAh/g，保持率22%），同时保持其原有的大体积容量输出（约3200 mAh/cm³）。更特别的是，它能使SbTe实现可逆的结构恢复，确保电极的完整性和循环性能。对这些非凡现象进行了详细研究，结果表明外部石墨层通过促进与SbTe颗粒的紧密接触并保护它们不被粉碎而发挥重要作用。此外，这种石墨层极大地促进了锂化过程中的电子转移，有助于提高倍率性能（2000 mA/g时为372 mAh/g，保持率60%）。因此，组装的SbTe//LiCoO全电池具有500 mAh/g的大容量，放电平台稳定且循环稳定性良好，显示出其在实际应用中的巨大潜力。
