Low temperature lithium battery internal heating

Compared with external heating, internal heating has a faster heating rate and a higher heating rate. Therefore, methods for internal heating of lithium batteries have also received extensive attention. However, the control mechanism of internal heating is more complicated, and some internal heating methods still have certain safety risks. Internal heating methods can be divided into two categories: self-heating and current excitation. The following table is a comparison of several commonly used internal heating methods. 1. Automatic heating method As can be seen from the above table, the self-heating method has absolute advantages in the heating rate. This method is to put a nickel foil inside the battery, then pull out the poles outside the battery, and control the heating of the battery through an external circuit. Experiments show that when the battery is heated at -30°C to 0°C, the heating rate of this method can reach 60°C/min, and only 5.5% of the energy is consumed. In order to reduce the temperature gradient inside the battery during the heating process, more nickel foil can be added to heat the battery. Research has shown that the heating rate of the two batteries with nickel foil added to the battery increases from -20°C to 0°C. At 96°C/min, the energy consumption is only 2.9%, and the heating speed can only reach 60°C/min under the same conditions as a single piece of Ni, which consumes 4.1% of electricity. It can be seen that multiple Ni chips can not only effectively reduce the temperature gradient inside the battery, but also effectively increase the battery's heating rate. 2. External current excitation method This method can be divided into DC preheating method, AC preheating method and pulse preheating method. 3. DC preheating method This method is to directly apply a DC discharge current to the battery, and heat the battery by the heat that appears during the discharge process. Qu et al. proved that this method of preheating the 18650 battery can achieve a heating rate of 4.29°C/min (8, 9.5 and 11A discharge). However, in order to meet the requirement of rapid temperature rise, this method needs to use high current discharge. At this time, the battery has a larger polarization, which will lead to an increase in the battery capacity decay rate. Studies have shown that in this preheating mode, the cycle life of the battery may be only about 81 times. 4.Ac preheating method The alternating current heating method is to apply alternating current (ac) at both ends of the battery, using the internal impedance of the lithium battery to heat the battery, because the direction of the alternating current (ac) changes rapidly to prevent the heating process of the DC high current discharge from failing The battery capacity, at the same time, compared with the direct current heating method, the communication temperature rises faster and the efficiency is higher. Research shows that adding AC current and reducing AC frequency can effectively improve AC heating efficiency. 5. Pulse current preheating method Pulse current preheating is a method of preheating the lithium battery by using the large current intermittent discharge inside the lithium battery and the heat generated by the ohmic impedance. Compared with air preheating, the preheating method of pulse discharge can achieve a more uniform temperature distribution in the battery (temperature gradient is less than 2°C), and effectively reduce the failure problem caused by the ability of the internal temperature gradient of the battery. However, such battery preheating requires Adding an internal discharge circuit of the battery pack leads to an increase in battery cost, so this preheating method is still at the laboratory stage and has no commercial application. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: A brief analysis of the six advantages of lithium batteries