What is passivation for Li-SoCL2 battery? How to avoid the problem caused by passivation?

Passivation is a phenomenon that occurs in Li-SOCl2 (lithium thionyl chloride) batteries, where a layer of insulating material forms on the surface of the lithium anode. This layer inhibits the flow of ions and electrons, reducing the battery's performance and capacity. Passivation is mainly caused by side reactions that take place during battery operation, such as the oxidation of lithium metal.

To avoid the problems caused by passivation in Li-SOCl2 batteries, several strategies can be employed:

1.      Controlled Discharge: Passivation tends to occur more rapidly during high-current or high-rate discharges. To mitigate this, it is recommended to discharge the Li-SOCl2 battery at a controlled rate. Slow and steady discharges help minimize the formation of the passivation layer, allowing for improved battery performance.

2.      Proper Storage: If a Li-SOCl2 battery is not in use for an extended period, it is advisable to store it at low temperatures, typically between -20°C and -40°C. Lower temperatures reduce the rate of side reactions and passivation, helping to preserve the battery's capacity and performance.

3.      Temperature Management: Temperature has a significant impact on passivation. Excessively high temperatures can accelerate the passivation process, leading to reduced battery efficiency. It is crucial to operate Li-SOCl2 batteries within their recommended temperature range to minimize passivation. Similarly, avoiding extremely low temperatures is important as well, as it can increase the internal resistance and limit the battery's capacity.

4.      Battery Design: Improving the design of Li-SOCl2 batteries can help mitigate passivation-related issues. For example, using additives or coatings on the lithium anode can reduce the formation of the passivation layer. These additives or coatings can modify the surface properties of the anode, enhancing its stability and reducing the occurrence of passivation.

5.      Optimized Electrolyte Composition: The electrolyte used in Li-SOCl2 batteries plays a crucial role in passivation. Researchers are continuously exploring different electrolyte formulations to minimize passivation effects. Modifying the composition of the electrolyte, such as incorporating specific additives or optimizing the solvent mixture, can help mitigate passivation and improve battery performance.

It is important to note that passivation cannot be completely eliminated in Li-SOCl2 batteries, but by implementing these strategies, the negative effects of passivation can be reduced, thereby improving the battery's overall performance and longevity. As research and development continue in the field of Li-SOCl2 batteries, further advancements may provide more effective ways to mitigate passivation-related issues.