Graphene is the lowest resistivity material currently found, only 10-8 Ω·m; electron mobility at room temperature is as high as 15000 cm2/V·s, which is an excellent conductive agent. In lithium-ion batteries, the use of graphene powder instead of conventional conductive carbon black (such as super P) and carbon nanotubes as a conductive agent can significantly improve the rate performance and cycle life of lithium-ion batteries, and at the same time, graphene super The high thermal conductivity also contributes to the heat dissipation of the battery. As a conductive agent for lithium ion batteries, graphene requires high purity, no impurity, uniform dispersion, and good batch consistency. According to the special requirements of lithium ion batteries for graphene conductive paste, the company has developed an arc method graphene conductive paste product. The project's routing includes two parts:
(1) Firstly, high-conductivity and zero-oxygen content high-conductivity nano-scale graphene powder materials are prepared by arc discharge technology;
(2) Dispersing the graphene powder material in a solvent such as NMP or water by using an "ultrasonic-emulsification" cycle technique to obtain a conductive paste for a lithium ion battery.
1. The preparation process of graphene powder is simple, and the raw materials are widely used. The preparation of graphene adopts arc discharge technology (physical method), that is, under a reducing atmosphere and a negative pressure condition, a large current is applied between two carbon rods (anode and cathode) to form a plasma arc discharge; the anode carbon rod is in the arc At the high temperature generated by the discharge, the gas is vaporized, and during the process of moving to the inner wall of the discharge chamber, the graphene powder material is formed through a series of chemical physical processes. The technology realizes one-step green preparation from carbon source to graphene, and the preparation process has no pollutant emission.
2. The arc method graphene powder material has excellent electrical conductivity and excellent performance in forming a conductive network in the electrode. Graphene, as a conductive agent for lithium ion batteries, requires sufficient contact with the electrode material to form a good conductive network during the preparation of the electrode, in order to exert the advantage of high conductivity of graphene. The preparation of graphene by arc method is first The reducing atmosphere (hydrogen + helium) is formed by the growth of gaseous carbon atoms, and its carbon content is above 99.5%, thereby ensuring that the performance of the lithium ion battery is not adversely affected; secondly, the conductivity of the graphene is high. Its conductivity is above 1000 S/m, which is much higher than that of redox graphene. Third, the sheet size of graphene is small (~200 nm or less), so it can be well in the preparation process of the electrode. The surface of the electrode material coated on the micron level and the void formed by the deposition of the electrode material particles constitute a good conductive network, which significantly improves the conductivity of the electrode.
3. The graphene dispersion process is simple and pollution-free, and the slurry composition is flexible and can be customized according to user requirements. At the same time, it is possible to produce an organic conductive paste or a water-based conductive paste, which is flexible and convenient, which is an advantage that it is difficult to prepare a graphene conductive paste by a liquid phase stripping method.
4. The entire conductive paste preparation process achieves zero emissions. The process is short, the product quality is reliable, the batch stability is good, and the product consistency is not caused by the change of raw materials (such as the origin of natural graphite, purification process, etc.), which is based on the liquid phase stripping technology of natural graphite. Has the advantage. Batch stability is a concern for battery manufacturers.
1. Reduce battery internal resistance, improve battery rate charge and discharge performance and cycle life
2. Reduce the amount of conductive agent and increase the energy density of the battery.
3. Improve the compaction density of the pole piece and improve the machining performance of the pole piece
4. Suppress the heating of the battery during the charging process and improve the safety of the battery.
5, good dispersion, compatibility with existing battery technology, can be directly added, tested for all types of positive and negative pole pieces.