Improved lithium storage capacity and high rate capability of nitrogen-doped graphite-like electrode materials prepared from thermal pyrolysis of graphene quantum dots

Abstract

Adopting a solid-phase microwave-assisted technique followed by thermal pyrolysis of N-functionalized graphene quantum dots, novel nitrogen-doped graphite-like (NGL) electrode materials were synthesized and served as the anode for Li-ion batteries. The NGL anode demonstrated reversible capacity of 530 mAh g(-1) at 0.1C, superior rate capability at high C rate operation (420 mAh g(-1) at 5C), remarkable initial coulombic efficiency (>95.7%), and excellent cyclic stability along with high efficiency (>99.1%) during entire cycling. The NGL anode nanostructure enables improved lithium ion mobility and reversible Li+ storage during cycling. The analysis of the Ragone plots revealed that the specific energy of NGL anode reaches to ca. 840 Wh kg(-1) at the power density of 4200 W kg(-1). The diffusion coefficient of Li ions was measured as 1.69 x 10(-9) cm(2) s(-1) for the NGL anode material, substantially improving over commonly used graphite electrodes (15-26 times higher Li+ diffusivity). The high-rate cyclability as well as the cyclic stability of the NGL anodes were also confirmed via long-term cycling of full pouch cells assembled with ternary cathode and NGL anode. The robust design of the NGL anode materials introduced in this work, paves the way for designing next-generation lithium-ion batteries operating at ultrahigh C rates. (C) 2020 Elsevier Ltd. All rights reserved.