Short for lithium-ion and sometimes abbreviated as Li-on, Li-ion is a fragile technology requiring a protector circuit. It is used where very high energy density is needed and cost is secondary. Li-ion batteries are more expensive, but perform without the memory issues that affect other types of batteries.
Pioneering work for the lithium battery began in 1912 by G. N. Lewis but it was not until the early 1970's that the first non-rechargeable lithium batteries became commercially available. Attempts to develop rechargeable lithium batteries followed in the eighties, but failed due to safety concerns.
Lithium is the lightest of all metals, has the greatest electrochemical potential, and provides the largest energy content. Rechargeable batteries using lithium metal as an electrode are capable of providing both high voltage and excellent capacity, resulting in an extraordinary energy density.
After much research during the eighties, it was found that occasional shorts from lithium dendrites could cause thermal run-away. The cell temperature approaches the melting temperature of lithium, which results in violent reactions. A large quantity of rechargeable lithium batteries sent to Japan had to be recalled in 1991 after a battery in a cellular phone exploded and inflicted burns to a man's face.
With an inherent instability of lithium metal, research shifted to a non-metallic lithium battery using lithium ions from chemicals such as LiCoO2 (lithium-cobalt dioxide). Although slightly lower in energy density than with lithium metal, the Li-ion is safe, provided certain precautions are met when charging and discharging. In 1991, Sony commercialized the Li-ion and is presently the largest supplier of this battery.