It was popular for pro power tools for a while. Those get a lot of abuse, and people are constantly changing battery packs so they max out on charging cycles. DeWalt used LiFePO4 from A123 Systems. But they seem to have given that up.
I honestly wonder why. I developed a portable small-quantity project a few years ago and designed in a 20AH LiFePO4 battery pack; it seemed like the only sane choice. The cost was slightly higher and density was slightly lower, but the difference was less than 10%. Not having to be concerned with battery failure modes was a huge advantage. But those factors must be different at larger scales; the largest scale I can think of where density matters would be for a commercial electric 18-wheeler tractor; what chemistry do those use?
