This new battery looks like becoming the lighter and safer replacement for both lithium-ion batteries and ultracapacitors - it cannot explode or burst into flames :

https://www.itri.org.tw/eng/Content/MSGPic01/contents.aspx?&SiteID=1&MmmID=620651711540203650&CatID=620653256325611005&MSID=654276522356353763

Tony G