The big competitors to lithium ion right now are LFP (lithium iron phosphate) and LTO (lithium titanate oxide). Neither have quite the power density of current lithium ion cells, but they're not that far off. LFP is quite popular right now for home storage and RVs. It is not nearly as prone to fire as lithium ion. LTO is even safer yet, it usually doesn't even pop the case if you abuse it to the point of destruction. LFP is improving density so it may be viable soon for EVs (in the US; in China they already use LFP), which manufacturers would love. Making the news for fires is really undesirable.