Can the safety problem of lithium batteries really not be solved?

Can the safety problem of lithium batteries really not be solved? In recent years, the burning and explosion of mobile phone batteries and laptop batteries has become less worrying. Recently, the battery of Samsung Galaxy Note 7 caught fire and exploded, and the safety of lithium batteries has become the focus of attention. In addition to the application status of external factors, the safety of lithium batteries depends on the underlying electrochemical system and underlying elements, such as electrode/cell structure, planning and processing procedures, and the selection of electrochemical system cells are the most basic elements that determine battery safety. The author will analyze the safety of lithium batteries from several different perspectives. Thermodynamic point of view: Studies have shown that not only the cathode, the appearance of the anode material is also covered with a thin passivation film, and the lithium battery that covers the passivation film function of the electrode will attack a very important influence and special interface The problem, as long as it does not exist in the non-aqueous organic electrolyte system. What I want to emphasize here is that from the perspective of the Fermi level, the existing lithium battery system is thermodynamically unstable. The work can proceed smoothly because the passivation film on the surface of the positive electrode and the negative electrode is dynamically isolated from the further reaction between the positive electrode and the negative electrode and the electrolyte. Therefore, the safety of lithium batteries is directly related to the integrity and fineness of the passive film on the anode and cathode surfaces. From the perspective of heat transfer: Unsafe behaviors of lithium batteries (including charging and discharging, rapid charging and discharging, short circuits, mechanical abuse conditions and high temperature thermal shocks, etc.) can easily trigger dangerous side reactions in batteries and thermal attacks. Directly destroy the negative and positive electrodes on the outer surface of the passivation film. When the temperature of the battery rises to 130°C, the difference in the SEI film on the surface of the negative electrode leads to the violent resuscitation of the highly active lithium carbon negative electrode electrolyte contact, and the heat of the attack makes the battery enter a high-risk state. When the internal temperature of the battery rises above 200°C, the passivation film on the anode surface separates the anode area from oxygen, and continues to react violently with the electrolyte to generate a large amount of heat, forming a higher internal pressure. When the battery temperature reaches above 240°C, the lithium-carbon positive electrode and the binder undergo a strong exothermic reaction. It can be seen that the damage of the SEI film to the appearance of the negative electrode leads to a strong exothermic reaction between the highly active lithium-intercalation negative electrode and the electrolyte, which is the direct cause of the increase in battery temperature and thermal runaway of the battery. The differential of the positive electrode data is only a part of the thermal runaway reaction, not even the most important factor. Lithium iron phosphate (LFP) has a very stable structure and usually does not undergo thermal differentiation, but LFP batteries also have other dangerous side uses, so the safety of LFP batteries is only relative. It can be seen from the above analysis that temperature control is of great significance to the safety of lithium batteries. Compared with small 3C batteries, high-power batteries are more difficult to dissipate due to factors such as battery structure, working mode, and environment. Therefore, thermal management planning for high-power battery systems is very important. Electrode flammability: The organic solvent used in lithium batteries is flammable and has a low flash point. Thermal runaway caused by unsafe behavior can easily ignite combustible liquid components with a low ignition point and cause the battery to burn. Lithium cathode carbon data, the gap and cathode carbon are also flammable. The probability of lithium burning is higher than the probability of battery explosion, but battery explosion must be accompanied by incineration. In addition, when the battery ruptures and the humidity of the external environment is high, the water and oxygen in the air can easily react violently with the carbon negative electrode embedded with lithium, releasing a large amount of heat and causing the battery to burn. The flammability of electrode data is one of the important differences between lithium batteries and water secondary batteries. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Analysis of the impact of low temperature on lithium iron phosphate batteries