A Lithium Ion (Li-Ion) battery is a rechargeable battery with twice the energy capacity of a Nickel-Cadmium battery and greater stability and safety. LiIon batteries use a liquid lithium-based material for one of their electrodes.
LiIon batteries are common in all kinds of devices, especially mobile. Uses of LiIon batteries include but are not limited to smartphones, tablets and more commonly notebooks, radio controlled hobby vehicles, portable vaporizers, UAV and drones. Some cleverly formatted LiIon batteries have also been used in wearables.
LiIon batteries are often compared to LiPo (lithium polymer) batteries. True LiPo batteries aren't commercially available due to poor room-temperature performance. What is referred to as LiPo in commercial use is really a LiIon-polymer hybrid or a standard liquid electrolyte in a polymerized foil pouch format. Pouch-formatted LiIon liquid batteries still require hard casing in the product to prevent expansion that would otherwise become a performance and safety issue.
There have been incidents of combustion or explosion in LiIon batteries in high-drain applications such as hoverboard and portable vaporizers. One cause may be the proliferation of low-quality and even counterfeit LiIon batteries. The LiIon cells used in the Tesla S high-performance electric car are based on safer new technologies, allowing for discharge down to zero volts without incident.
The best battery choice really depends on the particular application. LiIon have better low-temperature discharge performance, with operating ranges of -20'C-60'C. Some can suffer from aging, however, even when not in use. Although care must be exercised in sourcing the batteries, LiIon is better suited to very high-drain devices. Both LiPo and LiIon batteries require special smart chargers and often require circuit protection for safest use.
LiIon batteries were developed as early as 1912 but didn't become popularized until Sony adopted them in 1995.