Chinese battery manufacturer CATL’s new battery energy storage system (BESS), ‘Tener’ has raised questions about its claim that the LFP batteries will not suffer any degradation during the first five years.
CATL explained that the new ultra-low degradation level has been achieved thanks to biomimetic SEI (solid electrolyte interphase) and self-assembled electrolyte technologies. The company said this has “cleared roadblocks for the movement of lithium ions”.
The battery management system (BMS) combined with new technology should allow up to 15,000 cycles ‘without significant degradation’. CATL also said that the new LFP battery offers 30% better energy density than the common industry range.
The BESS has a stated capacity of 6.25MWh per 20’ container. The capacity lies significantly above the 5MWh-per-unit that appears to have become the standard for BESS products from China.
As BESS is a large investment for many power companies, less degradation is a strong sales argument.
Emily Feijen Farbod of Iben Energy in the Netherlands told BEST that dynamic BMS has been used in EV batteries offering an 8% degradation rate per year. While adaptive BMS and SEI technology can significantly mitigate battery degradation, they cannot completely stop it. Battery degradation is a natural process including chemical reactions within the battery, mechanical stress, temperature fluctuations, and usage patterns, she said.
Marek Kubik of energy company Enowa has analysed the information and said to BEST he thought the given capacity fade is quite significant for LFP in the early years. The zero-degradation claim is likely largely down to a breakthrough in the use of pre-lithiated LFP cells, he said.
Pre-lithiation limits the initial breakdown and high initial active lithium loss that occurs in the first cycles of a cell’s use, thus avoiding the initial capacity fade that usually appears. However, in a low lithium price world, this can still look attractive, especially considering total cost of ownership of the ESS, he said.
