Graphene in Lithium Battery Anode Materials
Graphene is a carbonaceous material discovered by the physicists Geim and Novoselov of the University of Manchester in 2004.Two scientists in the laboratory used a sticky strip of adhesive tape to separate the graphene from the graphite. The advent of graphene broke the graphene that the scientific community guessed at the time could not exist alone, but needed Graphite exists as a carrier,Graphene is used as a negative electrode material to exhibit superior effects. It quickly attracted the attention of the negative materials science community and became another research direction for lithium ion battery anode materials in the early 21st century.
Graphene can be directly used as a negative electrode material for lithium ion batteries. Yoo et al. first reported in 2008 that graphene is directly used as a negative electrode material for lithium ion batteries with a specific capacity of 540 mAh/g.
When the graphene nanosheet prepared by Guo et al. was used for lithium battery anode materials, the first reversible capacity was 672 mAh/g. After 30 cycles, the reversible capacity was maintained at 502 mAh/g.
However, graphene has a high irreversible capacity for the first time, which is mainly due to the reaction of lithium ions with oxygen-containing functional groups on the surface of graphene and the large specific surface area of graphene.
Graphene can also be used as a negative electrode material for lithium ion batteries by compounding with metal oxide or alloy materials, such as tin-based, silicon-based oxide and other materials.Wang et al. prepared a nano-Mn3O4-graphene composite with a two-step solution phase reaction method with a specific capacity of 900 mAh/g.
The SnO2-graphene nanopore electrode prepared by Paek et al. has a three-dimensional layered flexible structure with a reversible specific capacity of 810 mAh/g, and the cycle performance is remarkably enhanced.
Choi et al. used graphite oxide and ferric chloride as raw materials to synthesize a Fe3O4 modified hollow graphene sphere by spray pyrolysis. The content of graphene in the material was 27wt.%, which showed quite good high current charge and discharge performance and long cycle performance.
Su et al. prepared a graphene-coated silicon/graphite composite from graphene oxide. The mass ratio of silicon, graphite and graphene oxide was 2:8:5, and the composite exhibited good electrochemical performance.
A composite material of graphene and carbon materials such as graphite, carbon nanotubes, and fullerene is also used as a lithium negative electrode material.
Yoo et al. incorporated fullerenes and carbon nanotubes into graphene. The specific capacity of graphene/C60 composites was 784 mAh/g, and the specific capacity of graphene/CNT composites was 730 mAh/g, while the ratio of graphene electrodes. The capacity is only 540mAh/g.
Song et al. prepared a graphene-coated graphitized hollow carbon sphere from polystyrene. The initial discharge specific capacity of the material was 2007 mAh/g, and the first coulombic efficiency was 50.4%.
Liu et al. prepared a large-size nitrogen-doped graphene-coated graphite material using hydrazine hydrate as a nitrogen source. When the amount of graphene is 1wt%, the reversible capacity of the material reaches 390mAh/g at a current density of 0.1C. At 5C, the current density is still 164mAh/g reversible capacity, showing good electrochemical performance.
Zhang et al. studied the electrochemical performance of graphene as a conductive agent for lithium titanate anode materials. The lithium titanate electrode with a graphene content of 5% has better rate performance than a lithium titanate electrode with 15% carbon black conductive agent.