What are the common low-temperature heating technologies for lithium-ion batteries

At present, lithium-ion batteries are divided into two categories: external heating and internal heating. The external heating can be divided into two types: one is the integration of heating and cooling, and the other is to directly use electric heaters for heating. The internal heating can also be divided into two categories: self-heating and electrically excited heating. 1. External heating 1. Integrated heating and cooling design can be divided into three categories: air, liquid and phase change materials according to the different working media of the temperature control system. The working principle of the temperature control system using air as the medium is that the outside air is first heated by the heating system and then enters the battery pack under the use of a fan, thereby heating the battery. The noise and efficiency of this method are difficult to solve. Compared with air, liquid has a higher thermal conductivity and heat capacity, so the heat conduction efficiency is higher. According to whether the battery is in contact with the heat-conducting liquid during heating, liquid heating can be divided into two categories: non-contact heating and immersion heating. The phase change material provides a simpler method for preheating the battery pack. This method is important to achieve the purpose of heating and cooling the battery pack through the heat released or absorbed by the phase change material during the phase change process. The thermal conductivity of variable materials is usually relatively low, which is not conducive to the rapid transfer of heat to the battery. At present, this method is still in the laboratory stage and has not yet been applied in practice. 2. Electric heaters Electric heaters can be divided into: 1. Peltier effect heater; 2. Electric heating sheet; 3. Electric heating jacket; 4. Electric heating film. The Peltier effect heater uses the Peltier effect of the semiconductor to form a hot surface and a cold surface on its two surfaces. The position of the hot and cold surfaces can be controlled by controlling the direction of the current, so as to achieve the purpose of cooling or heating the battery, and the temperature is high or low. It can be controlled by controlling the current amplitude. In the heating method using electric heaters, the electric heaters are usually placed on the top or lower end of the battery, and the heat generated by the electric heaters is directly transferred to the battery. Generally speaking, the electric heaters are made of positive temperature coefficient material (PTC). , As the temperature increases, the resistance increases, so as to achieve the purpose of autonomous temperature control. The electric heating jacket was first proposed by Chery Automobile Company. The method is to use a thermal resistance to make a protective jacket around the battery, and monitor the temperature change of the battery pack through the BMS system of the battery pack to control the preheating of the battery. The electric heating film is generally made of a composite of metal foil and insulating material, and it is pasted on the surface of the battery during use. The advantage of this heating method is that the heating film is relatively thin (1-2mm), so it takes up less battery space. 2. Internal heating 1. Self-heating Put a Ni foil inside the battery, and then lead out the poles outside the battery, and control the heating of the battery through an external circuit. 2. Direct current preheating. This method is important to directly apply a direct current discharge current to the battery, and heat the battery through the heat generated by the battery during the discharge process. 3. Alternating current preheating Alternating current heating method is to apply an alternating current at both ends of the battery, and use the internal impedance of the lithium ion battery to realize the battery heating. Since the direction of the alternating current is always changing rapidly, it prevents the battery from the heating process caused by the large current discharge of the direct current Decline in capacity. 4. Pulse current preheating The pulse current preheating method is to preheat the lithium-ion battery through the discontinuous high-current discharge method through the heat generated by the ohmic resistance inside the lithium-ion battery. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.