Electrospun core-shell fibers for robust silicon nanoparticle-based lithium ion battery anodes.

Because of its unprecedented theoretical capacity near 4000 mAh/g, which is approximately 10-fold larger compared to those of the current commercial graphite anodes, silicon has been the most promising anode for lithium ion batteries, particularly targeting large-scale energy storage applications including electrical vehicles and utility grids. Nevertheless, Si suffers from its short cycle life as well as the limitation for scalable electrode fabrication. Herein, we develop an electrospinning process to produce core-shell fiber electrodes using a dual nozzle in a scalable manner. In the core-shell fibers, commercially available nanoparticles in the core are wrapped by the carbon shell. The unique core-shell structure resolves various issues of Si anode operations, such as pulverization, vulnerable contacts between Si and carbon conductors, and an unstable sold-electrolyte interphase, thereby exhibiting outstanding cell performance: a gravimetric capacity as high as 1384 mAh/g, a 5 min discharging rate capability while retaining 721 mAh/g, and cycle life of 300 cycles with almost no capacity loss. The electrospun core-shell one-dimensional fibers suggest a new design principle for robust and scalable lithium battery electrodes suffering from volume expansion.