There are 3 main components to a battery: the anode, the cathode, and the electrolyte. Lithium ion batteries shuttle lithium ions, positively charged lithium atoms, back and forth from the anode to the cathode depending on whether you are charging or discharging your battery. Most lithium ion batteries utilize a graphite anode and Lithium Cobalt Oxide cathode (LiCoO2).

There’s been a move to use pure lithium metal as the anode material which dramatically increases the energy density. There are a lot of hazards to doing so though. A really promising path towards safe incorporation of lithium metal anodes are solid state batteries (no liquid electrolyte) or polymer batteries (polymer electrolyte). What it looks like to me is this battery was running a lithium metal anode and when it was exposed to air ignited violently likely continuing to burn due to other flammable components being present in the cell.