N‐Enriched Porous Carbon/SiO<sub>2</sub> Composites Derived from Biomass Rice Husks for Boosting Li‐Ion Storage: Insight into the Effect of N‐Doping
Yi Feng, Li Liu, Xiaoyang Liu, Yixin Li, Yunpeng Wu, Yanchao Zhu, Xiaofeng Wang
Abstract
Abstract A N‐enriched porous carbon/SiO 2 (SiO 2 /NC) composite from rice husks was prepared by ball milling and tested as a stable anode for lithium ion batteries (LIBs), in which the homogeneous dispersion of SiO 2 nanoparticles and carbon matrix, and high level of N‐doping can be realized simultaneously. The influence of N‐doping on a series of SiO 2 /NCs was systematically studied; this proved that the porosity, N‐doping content, and electronic conductivity of SiO 2 /NC can be controlled by adjusting common nitrogen sources (urea and melamine) and doping routes, including dry and wet milling, to reach a desirable balance of high capacity, long‐term cyclability, and rate property. The optimized SiO 2 /NC composite delivers a stably reversible capacity of 581 mA h g −1 at the high current load of 1.0 A g −1 at the 1000th cycle. The novel Li‐storage mechanism of active silica in a composite was first proposed after observation of the N‐doping effect that the redox reaction between SiO 2 and Li + is accelerated to transform into an alloying reaction of generated Si and Li + , thus enhancing the reversible capacity. Moreover, kinetics analysis confirms that there is a combined Li‐storage mechanism of battery‐capacitive pattern in composite that contributes to fast charge transfer and ion diffusion during cycle.