N-Enriched Porous Carbon/SiO2 Composites Derived from Biomass Rice Husks for Boosting Li-Ion Storage: Insight into the Effect of N-Doping.

N-enriched porous carbon/SiO 2 (SiO 2 /NC) composite from rice husks was prepared by ball mill and tested as 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 N-doping influence on a series of SiO 2 /NC has been systematically studied, which proves 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 mill to reach a desirable balance of high capacity, long-term cyclability and rate property. The optimized SiO 2 /NC composite delivers stably reversible capacity of 581 mA h g -1 at high current load of 1.0 A g -1 at 1000 th . The novel Li-storage mechanism of active silica in composite has been firstly proposed upon N-doping effect that redox reaction between SiO 2 and Li + is accelerated to transform into alloying reaction of Si generated and Li + , enhancing reversible capacity. Besides, kinetics analysis confirms that there is combined Li-storage mechanism of battery-capacitive pattern in composite, which contributes to fast charge transfer and ion diffusion during cycle.