Will cold weather reduce the performance of lithium batteries?

　　In winter, when the temperature is low, lithium batteries are prone to polarization, crystallization and other phenomena, resulting in changes in the electrolyte, resulting in a decline in the cycle life of lithium batteries; The discharge function of lithium battery will decrease when the temperature of other batteries is lower than 5 ℃. Therefore, it is necessary to prevent the lithium battery from showing capacity decay and capacity decay during discharge in winter, which is the season with the fastest decline of lithium battery function. The main reason is that the internal resistance of lithium battery increases and the discharge current decreases as the temperature decreases, resulting in the reduction of active substances and the reduction of the activity of active substances. At low temperature, the redox reaction of the active material becomes more active, and the active material is more prone to live degradation, resulting in the reduction of battery capacity. At other low temperatures, the amount of ion generation decreases and the activity decreases, resulting in lithium ion aggregation at the active site. The active substance decomposes in the electrolyte and releases a lot of active substances, which leads to the decrease of the ion dispersion between the active substance and the electrolyte, which leads to the decrease of the activity of the active substance. All these will lead to the decrease of lithium ion activity, which will cause the electrolyte to fail to work normally. At low temperature, the capacitance of lithium ion will drop a lot. Therefore, lithium battery will not reduce its function in winter.

　　1. When the temperature is low, the charging current of lithium battery decreases and the capacity of lithium battery decreases.

　　The main reason is that during the storage of the battery, the water in the cell and electrolyte as well as the oxygen in the air have an oxidation reaction, which makes the lithium ion produce a reaction of lithium removal, releasing more positive material and reducing the activity. Therefore, the charging current of lithium battery is relatively small at low temperature. Because the internal temperature of the battery is relatively high at high temperature, this leads to the increase of the internal resistance of the lithium battery cell. The discharge current decreases. The charging current drops from 10-15 A to about 4 A, and the charging speed is significantly slower. However, it will not affect the function of lithium battery too much at this moment. In fact, it will not reduce the function, but increase the cell capacity and service life! What if we don't find it in time? Please be careful! We can improve it by the following ways: First, charge and care the lithium battery regularly to prevent the occurrence of over-discharge of lithium battery due to insufficient power. The second is to check whether the control charging current changes (especially the charging port). Prevent continuous charging of lithium battery in cold weather; Reduce the number of charges and discharges to maintain your lithium battery and prevent overcharge and discharge of lithium battery; And timely sorting out the electrolyte and other substances generated in the lithium battery to reduce the lithium capacity.

　　2. The activity of electrolyte decreases, resulting in the decrease of electricity

　　The electrolyte can generate many active substances at low temperature, and the decomposition of these active substances will release a lot of water and volatile gases, resulting in the electrolyte can not work normally. There is an imbalance of surface tension between lithium ion and active material. These active substances will disperse the active molecules to the surrounding, cause damage to the electrode structure, and cause chemical reaction and redox reaction between the active molecules and the electrolyte. The hydrogen bond effect between the active substances and the electrolyte is easy to occur, and generate many hydrophilic molecules. These molecules have many strong adsorption abilities. Once the adsorption of active molecules can be weakened, the charge transfer cannot be guaranteed. There is no stable adsorption effect between the active substance and the electrolyte. This leads to the electrolyte not being fully dissolved and many bubbles are produced. The more bubbles are accumulated, the more difficult it is to disperse and circulate, and the more electric charges will be. When they are gathered together to form a gel and slowly accumulated in the solid, they form a solid, which is the main component of the electrolyte; This kind of solid is difficult to disperse and absorb the external light. It will only make the water crystal containing water in the electrolyte condense to form ice crystal. The charge will be dispersed on the surface of the solid to form water insoluble substance, and then cause the current to be very small or the substrate can not discharge normally; As the temperature continues to drop, the voltage will stop after the discharge current decreases to zero. At this time, the electrolyte will have delamination, polarization, blockage and even electrolyte crystallization, and then lead to electrode structure damage, and the electrolyte will not work normally. When the ambient temperature is lower than 5 ℃, crystals and droplets will precipitate from the electrode to form liquid salt crystals floating on the surface of the electrolyte. This makes charging very difficult! Charging at low temperature will cause the temperature of the traction battery to be too low to start; When the discharge current disappears, because the electrode capacity continues to decline, the capacity may be reduced rapidly or lost, which is a very risky phenomenon for the battery pack. Therefore, to do a good job of lithium battery safety in winter, we should try to reduce the use of battery pack in winter; Do not use lithium battery charging equipment (charger) in winter. It is better not to use electric vehicle battery charging method or start mobile phone; Prevent charging at low temperature or discharging directly at room temperature below 5 ℃; For example, the oxidation reaction of active substances has become severe and gray, which is very harmful to lithium-ion batteries! If we take this kind of situation

　　3. Electrolyte precipitation and active substance activity decrease at low temperature

　　At low temperature, the ion density in the electrolyte decreases, the decomposition of active substances is accelerated, and the temperature of the active site is low, resulting in the reduction of lithium battery capacity. Low temperature of lithium battery will also lead to the reduction of activity, which will lead to the reduction of oxidation and decomposition of the active part. In addition, the battery will also produce many redox reactions during the discharge process. After the electrolyte freezes, it will precipitate the electrolyte and the ice crystals on the negative electrode to form the precipitation. These conditions will greatly prolong the decay period of lithium battery at low temperature and may have adverse effects in later use! Therefore, relevant protective measures should be taken in winter!

　　4. The lithium battery functions worse in winter.

　　Because the lithium battery will consume electricity when it is discharged, it will form battery attenuation when the electricity is reduced. When the temperature is lower than 5 ℃, the battery discharge function will deteriorate. How to maintain the battery in winter? The discharge function of the battery decreases the fastest in winter. We can take some measures to prevent it. First of all, ensure that the electric vehicle has sufficient power; Secondly, it is necessary to ensure that the battery system has sufficient power and that the maintenance system can supply more power when discharging; Again, we should pay attention to prevent the use of electrical products in winter; Before final use, check whether all electrical appliances are in normal condition and whether the battery is in abnormal condition. In particular, the battery must be well maintained. If the battery is overcharged or over-discharged, it will lead to battery failure, short circuit and even explosion and personal injury. Therefore, it is necessary to prevent the use of batteries in cold climates and the use of electric vehicles in low temperatures (the battery temperature is lower than 5 degrees) to speed up the function decline. Therefore, the use of electric vehicles in cold weather depends not only on the function of the vehicle, but also on whether there is leakage or short circuit. It is recommended that the battery and electric vehicles be placed indoors together. Don't drive the electric car in winter, put it in the car. Because the temperature change is relatively large, it will lead to a severe situation of reduced endurance. And if you are not careful to be stabbed, there will be a large area of severe burns. So it is very important to maintain the battery well; The other point is to pay attention to overcharge of the battery! Do not overcharge or discharge to cause safety incidents.

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