Silicon-Nanowire-based 3D Anodes for High-Capacity Lithium-Ion Batteries

We report on the scalable synthesis and characterization of novel-architecture three-dimensional high-capacity amorphous SiNW-based anodes, with focus on the study of their electrochemical-degradation mechanisms. We achieved an unprecedented combination of remarkable performance characteristics: high loadings of 3-25 mAh/cm², a very low irreversible capacity (10% for the 3-4mAh/cm² anodes), current efficiency greater than 99.5%, cycle stability both in half cells and in a LiFePO₄ battery and fast charge–discharge rates (up to 2.7C at 20mA/cm²). These SiNW-based binder-free 3D anodes have been cycled for over 500 cycles, exhibiting a stable cycle life. Notably, it was found that the increase in the continuous SEI layer thickness, and the concomitant increase in resistivity, represents the major cause of the observed capacity loss of the SiNW-based anodes, as we demonstrated by cleaning and reusing cycled anodes. We also demonstrate the effects of different types of coatings on the SEI and on cycling stability of the cell. Our data reveal that NW-based anodes of novel architecture are expected to meet the requirements of lithium-ion batteries for both portable and electric-vehicle applications.