We used to offer Li-ion AAA batteries. They are currently discontinued, and we do not plan to restock them for the time being. Our stock had a high percentage of defects because of the sensitivity of Li-ion battery chemistry. We found they did not handle the rigors and impacts of spinning as well as we needed them to.
While they work in the flowlight, Li-ion batteries can damage other electronics because they have 3x the voltage of regular AAA batteries. They can even damage a flowlight if inserted in the wrong direction and the button is held down too long! Because of these issues, we stopped offering Li-ions on our site.
If you need batteries for your lights, we offer NiMH AAA batteries which are optimized for usage in flowlights on our site directly: https://www.flowtoys.com/powerup/batteries/You are also welcome to use alkaline batteries - though they are not rechargeable - or other high quality rechargeable NiMHs like eneloops.
If you have any questions, please feel free to contact us!