Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, China.
Novusilicon Co.Ltd., Changzhou, 213149, China.
Small Methods. 2023 Jun;7(6):e2201623. doi: 10.1002/smtd.202201623. Epub 2023 Feb 25.
Silicon-based anodes have been considered as ideal candidates for next-generation Li-ion batteries. However, the rapid cyclability decay due to significant volume expansion limits its commercialization. Besides, the instable interface further aggravates the degradation. Carbon coating is one effective way to improve the electrochemical performance.The coating integrity may be a critical index for core-shell structure electrode materials. Herein, the coating integrity of SiO @C composite is tested by a developed selective alkali dissolution, further quantitatively depicted by a proposed index of alkali solubility α. The effect of coating integrity on electrochemical performance reveals that SiO dissolution loss has a significant impact on the overall electrode structure stability and interface property. Because of the side reaction between uncoated active SiO and electrolyte, the quadratic decrease of initial coulombic efficiency and increase of solid electrolyte interphase thickness with the rise of alkali solubility are closely related to the generated F content induced by active material loss, further supported by the obvious linear rise of Li SiF fraction, leads to the linear increase of interface impedance and volume expansion rate, which may take primarily responsibility for the performance decay. This work propels the fundamental understanding on the interface failure mechnism and inspires rational high-performance electrode material design.
硅基阳极被认为是下一代锂离子电池的理想候选材料。然而，由于其显著的体积膨胀，其快速的循环稳定性衰减限制了其商业化应用。此外，不稳定的界面进一步加剧了降解。碳涂层是提高电化学性能的一种有效方法。涂层的完整性可能是核壳结构电极材料的一个关键指标。在此，通过开发的选择性碱溶解法对 SiO@C 复合材料的涂层完整性进行了测试，并通过提出的碱溶性指数α进一步定量描述。涂层完整性对电化学性能的影响表明，SiO 的溶解损失对整体电极结构稳定性和界面性能有重大影响。由于未涂层活性 SiO 与电解质之间的副反应，初始库仑效率的二次下降和固体电解质界面层厚度的增加与由于活性材料损失而产生的 F 含量密切相关，进一步得到了由活性材料损失引起的 Li-SiF 分数的明显线性增加的支持，导致界面阻抗和体积膨胀率的线性增加，这可能是导致性能衰减的主要原因。这项工作推动了对界面失效机制的基本理解，并为合理的高性能电极材料设计提供了启示。
