Binder-free Boron-doped Si nanowires Toward the Enhancement of Lithium- ion capacitor.

Abstract
Lithium-ion capacitors (LICs) are next-generation electrochemical storage devices that combine the benefits of both supercapacitors and lithium-ion batteries. Silicon materials have attracted attention for the development of high-performance LICs owing to their high theoretical capacity and low delithiation potential (~0.5 V vs. Li/Li+). However, sluggish ion diffusion has severely restricted the development of LICs. Herein, a binder-free anode of boron-doped silicon nanowires (B-doped SiNWs) on a copper substrate was reported as an anode for LICs. B-doping could significantly improve the conductivity of the SiNW anode, which could enhance electron/ion transfer in LICs. As expected, the B-doped SiNWs//Li half-cell delivered a higher initial discharge capacity of 454 mAh g-1 with excellent cycle stability (capacity retention of 96% after 100 cycles). Furthermore, the near-lithium reaction plateau of Si endows the LICs with a high voltage window (1.5-4.2V), and the as-fabricated B-doped SiNWs//AC LIC possesses the maximum energy density value of 155.8 Wh kg-1) at a battery-inaccessible power density of 275W kg-1. This study provides a new strategy for using Si-based composites to develop high-performance LIC. &#xD.