Lithium Battery Safety

Work for the lithium battery began in 1912, but is was not until the early 1970’s when the first non-rechargeable lithium batteries hit the shelves. In the 1980’s work began to develop rechargeable lithium batteries. These early models were based on metallic lithium and offered very high energy density. However, inherent instabilities of lithium metal, especially during charging, put a damper on the development. The cell had the potential of a thermal run-away. The temperature would quickly rise to the melting point of the metallic lithium and cause a violent reaction. A large quantity of rechargeable lithium batteries had to be recalled in 1991 after the pack in a cellular phone released hot gases and inflicted burns to a man’s face.

The inherent instability of lithium metal caused research to be shifted to a non-metallic lithium battery using lithium ions. Although slightly lower in energy density, the lithium-ion system is safe, providing certain precautions are met when charging and discharging. Today, lithium-ion is one of the most successful and safe battery chemistries available. Two billion cells are produced every year. The high energy density and light weight of lithium-ion batteries make them the power source of choice for cell phones, laptops, and of course electric vehicles.

All lithium-ion batteries used in consumer products have a built in circuit board that monitors the battery during charging and discharging. It can see and offer the following:

  • Reverse polarity protection
  • Charge temperature–must not be charged when temperature is lower than 0° C or above 45° C
  • Charge current must not be too high, typically below 0.7 C
  • Discharge current protection to prevent damage due to short circuits
  • Charge voltage–a permanent fuse opens if too much voltage is applied to the battery terminals
  • Overcharge protection–stops charge when voltage per cell rises above 4.30 volts
  • Overdischarge protection–stops discharge when battery voltage falls below 2.3 volts per cell (varies with manufacturer)
  • A fuse opens if the battery is ever exposed to temperatures above 100° C

Without it, the battery may end up like the one seen below.