As we all know, whether it is LFP, NCM, LCO or silicon-oxygen materials, the conductivity is very poor. The carbon black or graphite conductive agents that have been used before can no longer meet the requirements of lithium batteries for internal resistance. Therefore, we are thinking about how to further reduce the internal resistance of the battery and improve the battery performance?
We began to try graphene and carbon nanotubes as positive electrode conductive agents, and the effect was very good, which opened up the large-scale application of graphene and carbon nanotubes in lithium batteries; the aqueous single-walled carbon tube slurry of the negative electrode has also been introduced into the silicon negative electrode in the past two years.
Application of Graphene conductive paste in positive electrode
Graphene positive electrode material was first used in LFP positive electrode. Studies have shown that graphene in LFP positive electrode can improve the compaction density of the positive electrode, the low temperature performance of the battery and the electronic conductivity, but it has a certain impact on the ionic conductivity. Some scholars explain that large-area graphene sheets may hinder the insertion and extraction of lithium ions to a certain extent during rate charging and discharging. It is generally preferred to mix graphene, acetylene black or carbon nanotube conductive agents to give full play to their respective strengths. For NCM or NCA positive electrodes, it is generally preferred to use carbon nanotubes and carbon black composite conductive agents.
Application of carbon nanotube conductive slurry in batteries
Carbon nanotubes have the advantages of high aspect ratio, good conductivity, and better contact with active materials. They are now widely used in lithium batteries. The difference between carbon tubes and graphene is that they have different contact points with active materials. Graphene cannot fully contact with the positive electrode material due to its large thickness, but carbon tubes can achieve multi-point contact with active materials. Generally, carbon tubes are compounded with carbon black conductive agents and added to the positive electrode. The various performances are better than those of pure carbon tubes.
Application of single-walled carbon nanotube aqueous slurry in silicon negative electrode
As we all know, silicon negative electrode materials have high specific capacity, but they are more likely to expand during charging and discharging. In order to improve the energy density of lithium batteries, silicon negative electrodes have to be used. People suppress its expansion by redeveloping negative electrode binders and carbon coating silicon. But this problem still cannot be solved. After the single-walled carbon nanotube aqueous slurry was launched, domestic power battery companies began to try to use the advantages of carbon nanotubes' ultra-high mechanical properties to try to further suppress the expansion of silicon. Judging from the prepared battery cycle performance, the solution of using single-walled carbon tubes and carbon black as a conductive agent is better than simply using multi-walled carbon tubes or carbon black.
Single-walled carbon nanotube aqueous slurry was first developed by a foreign carbon tube manufacturer and promoted by its agent. Two new slurry dispersion plants have been built in China. The tube diameter can reach less than 2nm, and the aspect ratio is larger than that of domestic multi-walled carbon tubes. However, due to the very large specific surface area, the concentration of carbon tubes can only be increased to less than one percent, and the price is relatively expensive. However, since its actual usage in the silicon negative electrode is less than 1‰, it has little impact on the cost of the battery cell, and it is now used in batches in domestic power battery factories.
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