Suppressing vertical displacement of lithiated silicon particles in high volumetric capacity battery electrodes

Yu, Denis Y. W. and Zhou, Ming and Hoster, Harry (2015) Suppressing vertical displacement of lithiated silicon particles in high volumetric capacity battery electrodes. ChemElectroChem, 2 (8). pp. 1090-1095. ISSN 2196-0216

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Abstract

Silicon is a potential high-capacity anode material for lithium-ion batteries. However, the large volume expansion of the material remains a bottleneck to its commercialization. Many studies were devoted to nanostructured silicon composites with voids to accommodate the volume expansion. Yet, full capability of silicon cannot be utilized because of the low volumetric capacity of these nanostructured electrodes. Here, we re-design dense silicon electrodes with three times the volumetric capacity of graphite by monitoring and limiting thickness changes of the electrodes. In-situ electrochemical dilatometry reveals that volume change is typically non-linear with state of charge, and highly affected by electrode composition. One key problem is the vertical displacement of the silicon particles by many times their own diameter during lithiation, which leads to irreversible detachment of active particles and increased porosity of the overall electrode for a weak binder. Better reversibility in electrode thickness change is achieved by using polyimide with higher modulus and larger ultimate elongation as the binder, resulting in better cycle stability.