The reason why lithium batteries are afraid of cold is mainly related to their internal chemical reactions and physical properties.
1 Slow down of chemical reaction rate
During the charging and discharging process of lithium batteries, it involves the migration of lithium ions between the positive and negative electrodes, as well as the chemical reactions of electrode active materials. These reactions require a certain amount of energy to overcome the activation energy barrier, allowing for electron transfer and material conversion.
In low-temperature environments, the rate of these chemical reactions will significantly slow down because the molecular motion of reactants slows down, the collision frequency decreases, and the reactions become difficult to carry out. Therefore, the performance of lithium batteries at low temperatures will be affected, manifested as reduced capacity and decreased rate performance.
2 Decreased solubility of electrode active material
The solubility of electrode active materials inside lithium batteries will decrease at low temperatures. This means that under low temperature conditions, the concentration of electrode active substances in the electrolyte will decrease, thereby reducing the amount of active substances available for reaction. This further reduces the battery's charging and discharging capabilities, leading to a decline in battery performance.
3 Decreased electrolyte fluidity
The electrolyte in lithium batteries can become viscous and even partially solidified at low temperatures. This will lead to a decrease in the ion conductivity of the electrolyte, that is, the migration speed of ions in the electrolyte slows down.
Due to the crucial role of ion migration in battery charging and discharging processes, the decrease in electrolyte fluidity directly affects the output voltage and power of the battery.
4 The internal resistance of the battery increases
In low-temperature environments, the resistance of various materials inside lithium batteries, such as electrodes and electrolytes, will increase. This will lead to an increase in the internal resistance of the battery, thereby reducing its effective capacity and discharge time. Meanwhile, the increase in internal resistance will also generate more heat during the charging and discharging process of the battery, further affecting its performance and safety.
5 Negative electrode lithium deposition phenomenon
During low-temperature charging, lithium ions can easily form lithium dendrites on the negative electrode surface. These lithium dendrites may puncture the separator, causing internal short circuits in the battery and potentially leading to safety accidents. In addition, the precipitated lithium metal reacts with the electrolyte to form deposits, increasing the thickness of the solid electrolyte interface (SEI) and further affecting the low-temperature performance of the battery.
6 What are the solutions to deal with the fear of low temperature in lithium batteries
1. Improve battery materials and design
Optimize electrolyte: Use a non freezing electrolyte to ensure good ion transport capability at low temperatures. Improve electrode materials and battery structure design, rationally design the internal structure of the battery, reduce internal voids, and enhance the thermal conductivity of the battery.
2. Optimization of battery management system
Intelligent temperature control system: Add temperature sensors inside the battery to monitor real-time temperature changes.
Take heating or cooling measures according to the battery temperature to ensure that the battery can maintain a suitable working temperature in a low-temperature environment.
Battery preheating technology:
Preheat the battery to a suitable temperature before use to improve the low-temperature performance of the lithium battery.
This can be achieved through the preheating function of the car's preheating system or the home charging station.
Charging strategy adjustment:
Adopting slow charging in low-temperature environments to reduce the internal resistance and electrochemical reaction rate of the battery.
Protect the battery from damage caused by overcharging and discharging by controlling the current and voltage of the battery.
3. User suggestions and measures
Avoid long-term low-temperature parking: Try to avoid parking the vehicle in a low-temperature environment for a long time to reduce the rapid decrease in battery power.
Charge as needed: Follow the principle of "charge as needed" to avoid the battery being too low and affecting normal use.
Choose high-quality insulation materials: Wrap the lithium battery with specialized insulation materials to increase its temperature.
Pay attention to purchasing high-quality insulation materials to ensure insulation effectiveness.