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What is the impact of storage conditions on Nmc Pouch Cell?

by josefa•

As a supplier of NMC pouch cells, I’ve witnessed firsthand the pivotal role storage conditions play in maintaining the quality and performance of these advanced energy storage solutions. NMC (Nickel Manganese Cobalt) pouch cells are widely used in various applications, from electric vehicles to portable electronics, due to their high energy density, long cycle life, and excellent power output. However, improper storage can significantly degrade these cells, leading to reduced performance, shortened lifespan, and even safety risks. In this blog, I’ll delve into the impact of storage conditions on NMC pouch cells and share some best practices to ensure their optimal performance. Nmc Pouch Cell

Temperature

Temperature is one of the most critical factors affecting the storage of NMC pouch cells. Extreme temperatures can accelerate the chemical reactions within the cells, leading to capacity degradation, increased self-discharge rate, and even thermal runaway in severe cases.

  • High Temperature Storage: When NMC pouch cells are stored at high temperatures (above 45°C), the electrochemical reactions within the cells become more active. This leads to the decomposition of the electrolyte, the growth of solid electrolyte interphase (SEI) layer on the anode, and the dissolution of the cathode material. As a result, the capacity of the cells decreases, and the internal resistance increases, reducing the overall performance of the cells. Moreover, high temperatures can cause the separator to shrink, increasing the risk of short circuits and thermal runaway.

  • Low Temperature Storage: On the other hand, storing NMC pouch cells at low temperatures (below -20°C) can also have a negative impact on their performance. At low temperatures, the mobility of lithium ions in the electrolyte decreases, leading to a significant increase in internal resistance. This can cause the cells to lose power rapidly, especially during high-rate discharge. Additionally, low temperatures can cause the formation of lithium metal deposits on the anode, which can penetrate the separator and cause short circuits, posing a serious safety hazard.

To ensure the optimal performance and safety of NMC pouch cells, it is recommended to store them at a moderate temperature range of 20°C to 25°C. If it is necessary to store the cells at higher or lower temperatures, appropriate measures should be taken to control the temperature and minimize the exposure time.

State of Charge (SOC)

The state of charge (SOC) of NMC pouch cells during storage also has a significant impact on their performance and lifespan. Storing the cells at a high SOC can accelerate the aging process, while storing them at a low SOC can cause the electrolyte to freeze and damage the cells.

  • High SOC Storage: When NMC pouch cells are stored at a high SOC (above 80%), the higher voltage leads to increased stress on the cathode and anode materials. This can cause the cathode material to degrade more rapidly, leading to a decrease in capacity and cycle life. Additionally, high SOC storage can increase the risk of lithium plating on the anode, especially at low temperatures or high charging rates. Lithium plating can cause short circuits and thermal runaway, which are serious safety concerns.

  • Low SOC Storage: Storing NMC pouch cells at a low SOC (below 20%) can also be detrimental to their performance. At low SOC, the electrolyte may freeze, especially at low temperatures, which can damage the internal structure of the cells. Moreover, low SOC storage can cause the formation of irreversible lithium compounds, leading to a permanent loss of capacity.

To maximize the lifespan and performance of NMC pouch cells, it is recommended to store them at a moderate SOC of around 40% to 60%. This can help to minimize the stress on the electrode materials and reduce the risk of lithium plating and electrolyte freezing.

Humidity

Humidity is another important factor that can affect the storage of NMC pouch cells. High humidity can cause the electrolyte to absorb moisture, leading to the formation of hydrofluoric acid (HF) and other corrosive substances. These substances can corrode the electrodes and the current collectors, reducing the performance and lifespan of the cells. Additionally, high humidity can increase the risk of short circuits due to the formation of conductive paths on the surface of the cells.

To prevent the negative effects of humidity, it is recommended to store NMC pouch cells in a dry environment with a relative humidity of less than 40%. If necessary, desiccants can be used to absorb the moisture in the storage environment.

Storage Time

The storage time of NMC pouch cells also has an impact on their performance. Even under ideal storage conditions, the cells will still experience some degree of self-discharge and aging over time. The longer the cells are stored, the more significant the degradation will be.

To minimize the degradation of NMC pouch cells during storage, it is recommended to keep the storage time as short as possible. If the cells need to be stored for an extended period, they should be periodically charged and discharged to maintain their performance.

Best Practices for Storage

Based on the above analysis, here are some best practices for storing NMC pouch cells:

  • Temperature Control: Store the cells at a moderate temperature range of 20°C to 25°C. If necessary, use temperature-controlled storage facilities to maintain the optimal temperature.
  • SOC Management: Store the cells at a moderate SOC of around 40% to 60%. Avoid storing the cells at a high or low SOC for an extended period.
  • Humidity Protection: Store the cells in a dry environment with a relative humidity of less than 40%. Use desiccants if necessary to absorb the moisture in the storage environment.
  • Regular Inspection: Periodically inspect the cells for any signs of damage, such as swelling, leakage, or discoloration. If any damage is found, the cells should be removed from storage immediately and disposed of properly.
  • Short-Term Storage: Keep the storage time as short as possible. If the cells need to be stored for an extended period, charge and discharge them periodically to maintain their performance.

Conclusion

Floor Standing Lithium Batteries In conclusion, storage conditions have a significant impact on the performance, lifespan, and safety of NMC pouch cells. By carefully controlling the temperature, state of charge, humidity, and storage time, we can minimize the degradation of the cells and ensure their optimal performance. As a supplier of NMC pouch cells, I am committed to providing high-quality products and technical support to our customers. If you have any questions or need further information about the storage of NMC pouch cells, please feel free to contact us for a procurement discussion.

References

  • Arora, P., & White, R. E. (1998). Comparative study of the different separator shutdown behaviors. Journal of the Electrochemical Society, 145(11), 4167-4174.
  • Xu, K. (2004). Nonaqueous liquid electrolytes for lithium-based rechargeable batteries. Chemical Reviews, 104(10), 4303-4417.
  • Zhang, J.-G., & Xu, K. (2007). Lithium ion battery safety: a key hurdle for large scale applications. Journal of Power Sources, 174(1), 1-9.

Dongguan Ritano New Energy Co., Ltd.
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