What are the ways to solve the safety problem of large-capacity lithium-ion batteries?

How to solve the safety problem of large-capacity lithium batteries The safety problem of lithium batteries is not a peripheral problem, but an essential problem based on material technology. Breakthroughs in material technology: 1. Choose safe cathode materials. The current cathodes include two mass-produced material products: lithium cobalt oxide and lithium manganate. Lithium cobalt oxide is a very mature system for small batteries. Due to the characteristics of lithium cobalt oxide (LiCo) in terms of molecular structure: after fully charged, there are still a large amount of lithium ions left in the positive electrode, and when overcharged, it remains in the positive electrode. Lithium ions will rush to the negative electrode, and the formation of dendrites on the negative electrode is an inevitable result of the overcharge of the battery using lithium cobalt oxide material. Even in the normal charging and discharging process, there may be excess lithium ions free to form on the negative electrode. Dendrite. Therefore, the frequent explosions of mobile phone batteries are due to the failure of the protection circuit on the one hand, but more importantly, there is no fundamental solution to the problem in terms of materials. At the same time, lithium cobalt oxide is highly oxidizing, it will decompose at 175 degrees, the shell will leak, and it will burn and explode in contact with air. 2. The choice of lithium manganate material ensures that in the fully charged state, the lithium ions of the positive electrode have been completely embedded in the carbon pores of the negative electrode in terms of molecular structure, which fundamentally prevents the appearance of dendrites. At the same time, the stable structure of lithium manganese oxide makes its oxidation performance far lower than that of lithium cobalt oxide, and its decomposition temperature exceeds 100 degrees of lithium cobalt oxide. Even if an internal short circuit (needle puncture), external short circuit, or overcharge occurs due to external forces, it can be completely Prevent the danger of burning and explosion caused by the precipitation of metallic lithium. 3. Choose a separator with good thermal shutdown performance. The purpose of the separator is to allow lithium ions to pass through while isolating the positive and negative electrodes of the battery. When the temperature rises, the diaphragm is closed before melting, so that the internal resistance rises to 2000 ohms and the internal reaction stops. 4. Explosion-proof valve: When the internal pressure or temperature reaches the preset standard, the explosion-proof valve will open and begin pressure relief to prevent excessive internal gas accumulation and deformation, which will eventually cause the shell to burst. 5. Protection circuit: Usually, the protection circuit needs to prevent overcharging, overdischarging, and super-high current. The important principle is to control the switching circuit to turn off the entire loop by measuring the voltage and total current of each cell. There is no excessive difficulty in circuit design. However, whether the design of the protection circuit is reasonable and whether the reliability is high enough is a test of the processing manufacturer's ability. The protection circuit is based on a pCB circuit composed of about dozens of resistors, capacitors, switch MOS tubes and other electronic components, and each component has the possibility of failure. A failed protection circuit will appear in two states: open circuit or conduction. When it is open, the user cannot use the battery pack, and the conduction state will test the battery's ability to resist overcharge. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.