FWIW, LiFePO4 is generally used these days vs li-ion, better temperature range, more robust and immune to overcharge, cycle life, etc. They are in very widespread use, so it is probably worth ensuring that is the base chemistry if you are looking into 12v drop-ins.
Edit: here is a "typical" lifepO4 cell in an EV these days, -25C to 75C
http://liionbms.com/pdf/thundersky/TS-LFP100.pdf