Attempts to develop lithium secondary batteries have failed due to safety concerns. In particular, because of the inherent instability of lithium metal during charging, research has shifted to non-metallic lithium batteries that use lithium ions. Although it has a slightly lower energy density than lithium metal, lithium ion is safe when certain precautions are met during charging and discharging. In 1991, Sony Corporation commercialized the first lithium-ion battery. Other manufacturers followed suit.
The energy density of lithium ions is typically twice that of standard nickel cadmium. Possibility of higher energy density. The load characteristics are quite good and it behaves similarly to nickel-cadmium in terms of discharge. The high cell voltage of 3.6 volts enables battery pack designs with only one cell. Most cell phones today run on a single cell. A nickel-based pack requires three 1.2 volt cells connected in series.
Lithium-ion is a low-maintenance battery, an advantage that most other chemicals cannot claim. No memory and no scheduled cycling to extend battery life. In addition, self-discharge is less than half that of nickel-cadmium, making lithium ion well-suited for modern fuel gauge applications. Lithium-ion batteries do little damage when disposed of.
Despite its overall advantages, lithium-ion has its drawbacks. They are fragile and require protection circuitry to maintain safe operation. A protection circuit built into each pack limits the peak voltage of each cell during charging and prevents the cell voltage from dropping too low during discharge. The cell temperature is also monitored to avoid temperature extremes. The maximum charge and discharge current of most packs is limited between 1C and 2C. Taking these precautions virtually eliminates the chance of metal lithium plating due to overcharging.
Aging is a concern for most lithium-ion batteries, and many manufacturers remain silent on the issue. A slight drop in capacity is noticeable after a year with or without the battery. Batteries often fail after 2-3 years. It’s important to note that other chemicals also have age-related degenerative effects. This is especially true for nickel-metal-hydride when exposed to high ambient temperatures. At the same time, it is known that lithium-ion packs have been used for 5 years in some applications.
Manufacturers are constantly improving lithium-ion. About every six months, new and improved chemical combinations are introduced. This rapid progression makes it difficult to assess how well modified batteries will age.
Storing in a cool place slows the aging process of lithium ions (and other chemicals). The manufacturer recommends a storage temperature of 15°C (59°F). Batteries should also be partially charged during storage. The manufacturer recommends a 40% charge.
The most economical lithium-ion battery in terms of cost-to-energy ratio is the cylindrical 18650 (size 18mm x 65.2mm). These cells are used in mobile computing and other applications that do not require ultra-thin geometries. If you need a slim pack, the prismatic lithium ion battery is your best choice. These cells are more expensive in terms of stored energy.
- High Energy Density – Possibility of higher capacity.
- No need for prolonged priming when new. Only one regular charge is required.
- Relatively low self-discharge – self-discharge is less than half that of nickel-based batteries.
- Low maintenance – no regular discharge required. I don’t remember.
- Specialty cells can provide very high current for applications such as power tools.