Unveiling the Microscopic Origin of Irreversible Capacity Loss of Hard Carbon for Sodium-Ion Batteries |
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Authors: | Jingqiang Zheng Chaohong Guan Huangxu Li Danjun Wang Yanqing Lai Simin Li Jie Li Zhian Zhang |
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Institution: | 1. School of Metallurgy and Environment, Hunan Provincial Key Laboratory of Nonferrous Value-Added Metallurgy, Engineering Research Center of the Ministry of Education for Advanced Battery Materials, Central South University, Changsha, 410083 P.R. China;2. University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240 P.R. China;3. Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, 999077 P.R. China |
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Abstract: | The primary bottleneck hindering the application of hard carbon in sodium-ion batteries (SIBs) anodes lies in its inadequate initial Coulombic efficiency (ICE). Unclear causes of capacity loss at the microscopic level restrict the improvement of hard carbon anodes. Here, two pivotal stages that influence the structure and composition of hard carbon, namely synthesis, and storage are evaluated; subsequently identifying crucial determinants contributing to irreversible capacity loss. The results suggest that undergrown carbon layers allowing the intrusion of solvent molecules into the interior of the hard carbon is a key factor during the synthesis stage, while the gradual formation of oxygen-containing functional groups on the surface of the hard carbon is another factor leading to irreversible loss of capacity during storage stage. This research microscopically clarifies the irreversible capacity loss mechanism on hard carbon and provides guidelines for designing and applying high ICE hard carbon for SIBs. |
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Keywords: | air stability carbon surface chemistry coulomb efficiency external surface areas Na-ion batteries |
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