Interesting. That would really make sense in small motor applications where less weight is a real advantage. Saw a guy using a Stihl polesaw using batteries. Already much lighter than the petrol alternative.
Auto is a really hard market to crack - unless you can get Elon Musk interested.
https://www.stihl.com.au/STIHL-Products/01608/Battery-Power-By-STIHL.aspx