Liu Guiyu, Wang Zhiqiang, Yuan Huimin, Yan Chunliu, Hao Rui, Zhang Fangchang, Luo Wen, Wang Hongzhi, Cao Yulin, Gu Shuai, Zeng Chun, Li Yingzhi, Wang Zhenyu, Qin Ning, Luo Guangfu, Lu Zhouguang
Department of Materials Science and Engineering, Shenzhen Key Laboratory of Interfacial Science and Engineering of Materials, Southern University of Science and Technology, Shenzhen, 518055, China.
Guangdong Provincial Key Laboratory of Computational Science and Material Design, Southern University of Science and Technology, Shenzhen, 518055, China.
Adv Sci (Weinh). 2023 Dec;10(36):e2305414. doi: 10.1002/advs.202305414. Epub 2023 Oct 24.
Although hard carbon (HC) demonstrates superior initial Coulombic efficiency, cycling durability, and rate capability in ether-based electrolytes compared to ester-based electrolytes for sodium-ion batteries (SIBs), the underlying mechanisms responsible for these disparities remain largely unexplored. Herein, ex situ electron paramagnetic resonance (EPR) spectra and in situ Raman spectroscopy are combined to investigate the Na storage mechanism of HC under different electrolytes. Through deconvolving the EPR signals of Na in HC, quasi-metallic-Na is successfully differentiated from adsorbed-Na. By monitoring the evolution of different Na species during the charging/discharging process, it is found that the initial adsorbed-Na in HC with ether-based electrolytes can be effectively transformed into intercalated-Na in the plateau region. However, this transformation is obstructed in ester-based electrolytes, leading to the predominant storage of Na in HC as adsorbed-Na and pore-filled-Na. Furthermore, the intercalated-Na in HC within the ether-based electrolytes contributes to the formation of a uniform, dense, and stable solid-electrolyte interphase (SEI) film and eventually enhances the electrochemical performance of HC. This work successfully deciphers the electrolyte-dominated Na storage mechanisms in HC and provides fundamental insights into the industrialization of HC in SIBs.
尽管与钠离子电池（SIBs）的酯基电解质相比，硬碳（HC）在醚基电解质中表现出优异的初始库仑效率、循环耐久性和倍率性能，但造成这些差异的潜在机制在很大程度上仍未得到探索。在此，结合非原位电子顺磁共振（EPR）光谱和原位拉曼光谱来研究不同电解质下HC的钠存储机制。通过对HC中钠的EPR信号进行去卷积，成功区分了准金属钠和吸附钠。通过监测充放电过程中不同钠物种的演变，发现使用醚基电解质时HC中初始吸附的钠在平台区可有效转化为嵌入钠。然而，这种转化在酯基电解质中受到阻碍，导致HC中钠主要以吸附钠和孔填充钠的形式存储。此外，醚基电解质中HC内的嵌入钠有助于形成均匀、致密且稳定的固体电解质界面（SEI）膜，并最终提高HC的电化学性能。这项工作成功破译了HC中由电解质主导的钠存储机制，并为HC在SIBs中的工业化提供了基本见解。
