There are several reports available on the Web describing the Safety of Lithium Ion batteries and battery Packs.
In particular a Sandia National Laboratory Safety Study Report published in 2008 (read on energy.gov (pdf)).
In Summary, Lithium Iron Phosphate (LFP) Cell Chemistry, is safer and more abuse tolerant
Lithium ion batteries are not all the same
There are a wide number of chemistries used in Li-Ion batteries.
- Oxide Base Lithium ion: Conventional lithium ion battery cathodes have been transition metal oxides that use cobalt (Co), manganese (Mn), or nickel (Ni) based oxides
- Lithium Iron Phosphate (LFP): Safest Chemistry uses chemically stable LFP which does not exhibit the energetic thermal runaway that metal oxide lithium ion cells experience.
There are a wide number of chemistries used in Li-Ion batteries. LFP batteries avoid the reactivity, safety, and abuse sensitivity issues involved with the use of lithium metal cathodes by using phosphate for its cathode; no metallic lithium is present in the cell. Li-Ion batteries with liquid electrolyte are rechargeable batteries and have a cathode of various classes of materials that include layered LiMO2 (M = Co, Ni, Mn or combinations of these or other metals, i.e. Al, Mg, etc.), olivines (LiFePO4), or spinels such as manganese oxides. The anode is usually a form of carbon, namely, coke, natural and synthetic graphites, mesophase carbon micro beads (MCMB) or carbon fibers. The electrolyte in these cells is made up of a combination of organic carbonates and a salt. The most commonly used salt is LiPF6 (lithium hexafluorophosphate). Other salts such as LiBOB (Lithium bisoxalatoborate) or LiBF4 (lithium tetrafluoroborate) have also been used.