The biggest trouble is that a lithium battery that will last 8 years, and the one that will puff up in a year and lose 80% of capacity, all look the same when you buy them. It's all about the purity of materials, quality control, and other things you don't see without a microscope.

Big players like Ford play it very safe with their own cell manufacturers, but a random smaller-scale startup might be forced to buy the cells from the lowest bidder on Aliexpress, and that won't fare well.