Panasonic is one of those power tool companies that do their own thing. They recently released a new line of 18V cordless power tools that are bundled with 4.2Ah Li-ion battery packs. 4.2Ah? It doesn’t seem that this capacity is an attempt to best the recent de-facto high-capacity standard of 4.0Ah, but that it was just a convenient capacity given the Li-ion cells they use.
Within the battery packs, the battery cells are separated with a special heat-resistant ceramic coating layer to protect them from heat buildup, and internal heat sensors further protect against heat buildup that can decrease their batteries’ usable lifetimes.