Layer-by-Layer-Structured Silicon-Based Electrode Design for Ultrafast Lithium-Ion Batteries

Silicon has attracted attention as a high-capacity material capable of replacing graphite as a battery anode material. However, silicon exhibits poor cycling stability owing to particle cracking and unstable SEI formation owing to large volume changes during charging and discharging. Therefore, we report the electrode design of lithium-ion batteries (LIBs) anode structure composed of laminated layers of silicon and carbon nanotubes (CNTs), which significantly increases the cycling life and delivers ultrafast performance. Unlike previously commercialized casting methods that use ultrasonic spraying, the Si- and CNT-layered architecture aims to solve engineering limitations that include non-uniform coatings, unclear active materials, conductive materials, and binder distribution. The laminated-Si/CNT electrode exhibited an excellent specific capacity of 157.58 mAh/g after 500 cycles at an ultrafast current density of 2000 mA/g; it also exhibited a cycling stability of 20.02% after 10 cycles at a current density of 100 mA/g and 190 cycles at 200 mA/g. This performance is due to the following effects that complement the shortcomings of the Si electrode through CNT layer stacking. First, the top CNT layer coating prevents direct contact between the Si-active material and the electrolyte, thereby reducing side reactions. Second, the laminated-Si/CNT electrode with its layer-by-layer structure suppresses the overall volume expansion of the electrode owing to the buffering effect of the CNT layer. Third, the CNT layers are highly electrically and ionically conductive, unlike silicon layers, thereby enhancing ultrafast cycling performance.