Study On Cycling And Rate Performance With Silicon/Carbon Composite Anode For Lithium-ion Batteries

With the development of science and technologies,especially information technology,portable electronic equipment and electric traffic tools have been widely used,and the requirement for high-performance energy storage and supply devices is urgent.Lithium-ion batteries play an important role in energy systems due to their high capacity,long cycle life and good rate capability.At present,the capacity of carbonaceous material based anode of lithium ion batteries has been developed to the theoretical limit,and the research of new high-capacity metarials is increasing.The silicon/carbon composite,which combines the high specific capacity of silicon and the good conductivity,easy ductility of carbonaceous materials,improves the cycle life and rate capability of the silicon-based anode electrode with high specific capacity.And the silicon/carbon composite has great potential to be used as the lithium ion battery anode.The cycle life of amorphous carbon coated silicon nanoparticles composite is first improved by ball milling and rolling pre-designed silicon/carbon composite material in this thesis.And then,this thesis design and fabricate silicon/carbon composites with high strength carbon/silicon layer structure and graphene coated silicon strucutre.First,in order to reduce the loss of silicon in the cycle process,which existed in the amorphous carbon coated silicon nanoparticles,the materials are dealed with ball milling and roll processing.Measurements demonstrate that the treated composite has good cycling performance.In order to maintain the long cycle life and further enhance the specific capacity of silicon/carbon composites,a "shell-like" graphene/CNT/SiNPs laminated composite is designed and fabricated in this thesis.The "shell-like" graphene layer is realized by vacuum filtration to accommodate a large number of SiNPs,and a high efficient electron transport network is built by CNTs.This structure can avoid the consumption of silicon materials during the cycle and improve the rate capability of the material.The test results show that this silicon/carbon composite retain high specific capacity with good cycling performance.In order to further improve the rate capabilities of silicon/carbon composity,the high strength graphene sheets are designed to wrap SiNPs.In this thesis,the lyophilization method is introduced to achieve graphene coated SiNPs composite anode,and fabricate the rGO@void@SiNPs structure.By reaction between the functional groups on the GO surface and the functional groups of the silica coated on the SiNPs,the SiNPs can be coated with the cross-linked graphene spheres.The cross-linked graphene network improves the rate capability of this material and protect the silicon from consuming.The tests show that this silicon/carbon composite has not only good cycle life and high specific capacity,but also excellent rate performance.