Researcher Andreas Gutsch from the Karlsruhe Institute of Technology said at the PV Symposium in Germany recently that some lithium-ion cells working in storage systems experienced up to 30% capacity loss after 1,000 cycles, while some cells have a better capacity after 5,000 cycles. In other words, there can be quite a lot of variation in lithium-ion cell performance.
Testing conditions did not allow him to reveal the names of cell manufacturers. The cells were not easy to obtain for testing and he could not disclose that specific information. However, his test results did reveal that cells from China that were tested had the performance that decreased most rapidly. Cells from Japan and Germany did the best, while ones from South Korea and the US were in the middle of the performance range.
One battery type that was specifically mentioned was the Tesla battery. This battery was found to last 400 cycles and was indicated to have the ability to power a car for about 200,000 kilometers (124,000 miles): 400 cycles multiplied by 500 km per full charge. That said, Elon Musk has stated that Tesla has a Model S in the lab with 500,000 miles (805,000 kilometers) on it, and without excess degradation. So, it seems the tests have been conducted very differently or something funky is going on.
Gutsch previously noted that some energy storage battery types might have safety issues, such as thermal runaway. According to his research, safety standards for some batteries have not been met.
He does believe batteries will eventually be a great way to store electricity, though.
All, or most of us lay people are on a learning curve when it comes considering how to evaluate the best batteries for consumer technology performance. To engineers, it may not be surprising at all that there could be such a range in cell performance. It may be fairly dismaying to lay persons to find this out, though we may notice that some of our consumer devices (like smartphones and other rechargeables) have poor to very poor battery lives, with variation being rather large.
Battery storage for a home or business is quite another matter.