N-doped graphene/graphite composite as a conductive agent-free anode material for lithium ion batteries with greatly enhanced electrochemical performance

Present graphite anode cannot meet the increasing requirement of electronic devices and electric vehicles due to its low specific capacity, poor cycle stability and low rate capability. The study reported a promising N-doped graphene/graphite composite as a conductive agent-free anode material for lithium ion batteries. Herein, graphite oxide and urea were dispersed in ultrapure water and partly reduced by ascorbic acid. Followed by mixing with graphite and hydrothermal treatment to produce graphene oxide/graphite hydrogel. The hydrogel was dried and finally annealed in Ar/H-2 to obtain N-doped graphene/graphite composite. The result shows that all of graphite particles was dispersed in three-dimensional graphene framework with a rich of open pores. The open pore accelerates the electrolyte transport. The graphene framework works as a conductive agent and graphite particle connector and improves the electron transfer. Electrical conductivity of the composite reaches 5912 S m(-1), which is much better than that of the pristine graphite (4018 S m(-1)). The graphene framework also acts as an expansion absorber in the anodes of lithium ion battery to relieve the large strains developed at high discharge rates. As a result, the N-doped G/C electrode provides an excellent electrochemical performance for lithium ion battery, including high specific capacity (781 mA h g(-1)), outstanding rate capability (351 mA h g(-1) at 10 C) and intriguing cycling stability (98.1% capacity retention at 10 C after 1000 cycles). (C) 2015 Elsevier Ltd. All rights reserved.