State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Dingxi Road, Changning District, Shanghai, 200050, P. R. China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.
Chem Asian J. 2023 Jun 1;18(11):e202300210. doi: 10.1002/asia.202300210. Epub 2023 Apr 27.
Hard carbon (HC) anode shows great potential due to its high capacity and excellent rate performance. However, state-of-the-art HC anode still suffers insufficient initial Coulomb efficiency (ICE) due to the abundant Li-trapping sites. Herein, we demonstrate a facile annealing engineering for HC anodes to improve the ICE and the mechanism is systematically studied. Accordingly, during the annealing process, metastable O- and N-containing functional groups are pyrolyzed, which cause the microstructure reconstruction of HC. Therefore, irreversible lithium ions adsorption is reduced significantly and the conversion of sp to sp C contributes to the localized graphitization of HC. Consequently, the optimized HC achieves ultra-high ICE of 90% from initial 61%. It is demonstrated that HC will adsorb H O and some organic species from environment gradually, causing conversion of some electrochemical stable functional groups to the irreversible Li-trapping sites. This work provides facile strategy and novel insight for high ICE HC anodes.
硬碳 (HC) 阳极由于其高容量和优异的倍率性能而具有巨大的潜力。然而，由于存在丰富的锂捕获位点，最先进的 HC 阳极的初始库仑效率 (ICE) 仍然不足。在此，我们展示了一种用于 HC 阳极的简便退火工程，以提高 ICE，并系统地研究了其机制。因此，在退火过程中，亚稳的 O 和 N 含官能团发生热解，导致 HC 的微结构重构。因此，不可逆的锂离子吸附显著减少，sp 到 sp^2 C 的转化有助于 HC 的局部石墨化。因此，优化后的 HC 的初始 ICE 可高达 90%，从 61%提高。实验表明，HC 会逐渐从环境中吸附 H_2O 和一些有机物质，导致一些电化学稳定的官能团转化为不可逆的锂捕获位点。这项工作为高 ICE HC 阳极提供了简便的策略和新的见解。
