Surface-engineered mesoporous silicon microparticles as high-Coulombic-efficiency anodes for lithium-ion batteries

• Published in: Nano energy Vol. 61; no. C; pp. 404 - 410
• Main Authors: Wang, Jiangyan, Liao, Lei, Lee, Hye Ryoung, Shi, Feifei, Huang, William, Zhao, Jie, Pei, Allen, Tang, Jing, Zheng, Xueli, Chen, Wei, Cui, Yi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.07.2019; Elsevier
• Subjects: Coulombic efficiency; ENERGY STORAGE; Lithium-ion battery; Mesoporous microparticle; Silicon anode; Surface-engineering; Coulombic efficiency; Lithium-ion battery; Surface-engineering; Mesoporous microparticle; Silicon anode
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2019.04.070

High-capacity silicon anodes suffer from rapid capacity decay due to large volume expansion, which causes mechanical fracture, electrical contact loss and unstable solid electrolyte interphase (SEI). Nanostructuring has proved to be effective in addressing these problems over the past decade; however, new issues such as poor initial Coulombic efficiencies due to increased surface area remain unsolved. Here we develop a surface-engineering strategy by depositing a dense silicon skin onto each mesoporous silicon microparticle and further encapsulating it with a conformal graphene cage, which improves both the initial and later-cycle Coulombic efficiencies. The silicon skin lowers the unfavorable electrolyte/electrode contact area and minimizes SEI formation, resulting in an initial Coulombic efficiency over twice as high as that without silicon skin coating. The graphene cage combined with the inner void space of mesoporous silicon allow for silicon expansion, which guarantees structural integrity and SEI stability, resulting in high later-cycle Coulombic efficiencies (99.8–100% for later cycles) and impressive cycling stability. [Display omitted] •Si skin coating lowers the unfavorable electrolyte/electrode interface and minimizes SEI formation.•The initial Coulombic efficiency is doubled after silicon skin coating.•The reserved internal void space buffers the volume expansion, guaranteeing good cycling stability.•The graphene cage endows Si microparticles electrochemically active surfaces.•The stable SEI formation on graphene cage guarantees high later-cycle Coulombic efficiencies.