Graphene has excellent electrical conductivity, huge specific surface area and good chemical stability, making it an ideal electrode material for lithium-ion batteries. Graphene is a single layer of carbon atoms with a hexagonal grid structure. Graphene
The electronic structure of carbon atoms is similar to that of graphite. Because of its strong sp2 hybridization, it has very excellent electrical conductivity. It is the thinnest known in the world but has the highest strength and hardness, almost completely transparent crystalline material, the strength of the ideal state is about 20 times that of steel. The thermal conductivity of graphene is as high as 5300 W/(m·K), which is higher than that of carbon nanotubes and diamond. At room temperature, its electron mobility is higher than ordinary silicon and carbon nanotubes, up to 15000 cm2
/(V·s) or more; at the same time, it is currently the lowest impedance material in the world, with a resistivity of only 10-6Ω·m. Graphene has been widely used in lithium-ion batteries due to its excellent electron mobility and extremely low impedance
1 Application in anode materials
The negative electrode of a lithium ion battery is mainly used as the main body of lithium storage, which is suitable for
The performance of the battery plays a decisive role. Usually by judging whether the negative electrode material has a good lithium ion transmission channel and electron transmission channel to determine its pros and cons. Graphene not only has the ability to provide good electron transmission channels, but also has excellent lithium ion transmission
performance. Graphene not only has excellent electrical conductivity, but the interlayer spacing of graphene is very small, only on the order of micro-nano, which makes the diffusion path of lithium ions shorter; the combination of graphene and lithium ions is on the whole outside of graphene. The surface is carried out at the same time, thus improving the transmission performance.
The porous graphene was prepared by hydrothermal reaction of graphite oxide and strong alkali etching.
And 10 C rate, its discharge capacity can reach 2207 mAh/g,
220 mAh/g and 147 mAh/g, after being discharged at a rate of 10 C and cycling 40 times at a discharge rate of 0.5 C, the specific capacity is still as high as 672 mAh/g. From the above data, it can be seen that the graphene table
Exhibited excellent cycle performance.
Graphene is prepared by oxidation-reduction method, and
Applying it to the negative electrode material of lithium-ion battery, the experimental data shows that the specific capacity of the first cycle is significantly improved, and the specific capacity value can reach 540 mAh/g. Because of its huge specific surface area, excellent electrical properties and stable chemical properties, graphene has been widely used in the negative electrode material of lithium ion batteries. Graphene not only has the same interlayer lithium insertion as graphite, but also because of its huge surface area, lithium ions can be inserted at both ends of the graphene sheet, which greatly increases the specific capacity of graphene. The theoretical value can reach two levels of traditional graphite materials. Times
2 Application in cathode materials
Research in recent years has found that graphene not only has excellent performance in the application of negative electrode materials for lithium-ion batteries, it also has excellent performance in the two-dimensional high
It has a special structure on the specific surface area and is used in lithium-ion batteries
In the cathode material. This feature of graphene further improves the electron transport capability, thereby improving the conductivity of the cathode material.
Comprehensive improvement, and enhance the transmission capacity of lithium ions. The energy density of a lithium-ion battery is determined by the energy density of the cathode material. Therefore, the cathode material is a single component of the lithium-ion battery.
A very critical part of the yuan. Current research shows that the composite cathode material formed by the combination of graphene and LiFePO4, LiNi1/3Co1/3Mn1/3O2 and LiMn2O4 can improve the electrochemical performance of the material.
Olivine-type LiFePO4 is a widely used cathode material for lithium-ion batteries. Its theoretical specific capacity is 170 mAh/g. However, problems such as low electronic conductivity and lithium ion diffusion limit its application in high-rate applications. After compounding it with graphene, the graphene fully encapsulates the surface of LiFePO4, and uses the tough mesh conductive structure in graphene to maintain electrical conductivity, thereby improving the entire surface.
The electrical conductivity of the material.
3 Graphene-based conductive agent
At present, the most commonly used conductive agent in lithium ion batteries is conductive
Graphite, conductive carbon black and new conductive agent. Conductive graphite is basically artificial graphite; conductive carbon black mainly uses organic matter (natural gas, heavy oil
Etc.) It is obtained by incomplete combustion or thermal decomposition, which is the most used
A wide range of conductive agents; new conductive agents include carbon fiber (VGCF), carbon nanotube (CNT), etc. or a mixture of the above conductive agents . Due to its high electronic conductivity and low resistance, graphene can be used as a conductive agent in lithium-ion batteries to improve the cycle and effectively increase the lithium insertion rate of lithium ions. In addition, due to the graphene crystal phase
Freely moving electrons and ultra-thin particle size, and "face
The “point” contact method makes the powder conductivity of graphene as high as
100 times that of conductive carbon black. Therefore, the graphene conductive agent is different from the traditional
Compared with conductive agent, it has obvious advantages in discharge and conductivity. 3 Summary and outlook
Graphene is widely used in lithium-ion batteries due to its stable chemical properties, large specific surface area and excellent electrical conductivity. In order to alleviate environmental problems, new energy vehicles may become a major trend in the development of transportation tools in the future, but at present, new energy vehicles still urgently need to solve the problems of increasing cruising range and fast charging. Graphene as
A new type of electrode and conductive agent material is expected to play a greater value and role in the application of lithium-ion batteries for new energy vehicles in the future.
To learn more about Li-ion batteries, please refer to https://www.junleepower.com/