Highly N-doped carbon with low graphitic-N content as anode material for enhanced initial Coulombic efficiency of lithium-ion batteries

Abstract

N-doped carbons as one of the most prominent anode materials to replace standard graphite exhibit outstanding Li+ storage performance. However, N-doped carbon anodes still suffer from low N-doping levels and low initial Coulombic efficiency (ICE). In this study, high N-doped and low graphitic-N carbons (LGNCs) with enhanced ICE were synthesized by taking advantage of a denitrification strategy for graphitic carbon nitride (g-C3N4). In brief, more than 14.5 at% of N from g-C3N4 (55.1 at% N) was retained by reacting graphitic-N with lithium, which was subsequently removed. As graphitic-N is largely responsible for the irreversible capacity, the anode's performance was significantly increased. Compared to general N-doped carbons with high graphitic-N proportion (>50%) and low N content (<15 at%), LGNCs delivered a low proportion of 10.8%–17.2% within the high N-doping content of 14.5–42.7 at%, leading to an enhanced specific capacity of 1499.9 mAh g−1 at an ICE of 93.7% for the optimal sample of LGNC (4:1). This study provides a facile strategy to control the N content and speciation, achieving both high Li+ storage capacity and high ICE, and thus promoting research and application of N-doped carbon materials.