Electrochemical Performance Research Of Modified Mesocarbon Microbeads

Mesocarbon microbeads has been used widely as the anode material of lithium-ion batteries. But, as the upgrading of the digital products and the emergence of new energy vehicles, the specific capacity of mesophase carbon microspheres have been difficult to meet the energy requirements of the products, improving the existing specific capacity of anode materials, is the key to solve this problem. In this paper, we used MCMB as raw material, modified through three methods, oxidation modification, load SnO2 nanorods and nitrogen doping to increase the charge and discharge specific capacity of the MCMB.The OMCMB was modified through Hummers method, and annealed in two ways, experiment results shows that the oxidizing modified MCMBs present Fluffy sponge structure, the specific capacity of two oxidizing modified MCMB samples increased obviously, between the two OMCMBs, the 1050-OMCMB shows a better electrochemical performance, the specific capacity of 1050-OMCMB up to 852 mAh/g, after 50 cycles, the specific capacity still keeps 450 mAh/g.We uesd hydrothermal growth method to load SnO2 nanorods on the surface of MCMB, got a sea urchin shaped composite material. The highest specific capacity of this composite material can reach 616.5 mAh/g. In addition, We researched the influence of different reaction conditions on the micro structure and electrochemical performance of MCMB/SnO2 composite materials. As the increase of concentration and reaction time, the SnO2 nanorods increased diameter and length, at the same time, the increase of concentration and reaction time can make the samples specific capacity increased, but also led to a decline in their cycle performance. Graphene coating of MCMB/SnO2 composite can significantly improve the cycle performance, after 50 cycles, the specific capacity of graphene coating MCMB can be 400mAh/g.When it comes to N doped MCMBs, we used melamine and ammonia as nitrogen source. The N elements doped into the MCMB in three types, pyrrolic N, pyridinic N and graphitic N.The electrochemical performance of NR-OMCMB-2 sample is better, compared with the raw MCMB, its specific capacity increased 50 mAh/g, and with the increase of cycling times, there is no obvious decrease on its specific capacity.