Disadvantages
A unique drawback of the Li-ion battery is that its life span is dependent upon aging from time of manufacturing (shelf life) regardless of whether it was charged, and not just on the number of charge/discharge cycles. So an older battery will not last as long as a new battery due solely to its age, unlike other batteries. This drawback is not widely publicised.[6]
At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 degrees Celsius or 77 degrees Fahrenheit will irreversibly lose approximately 20% capacity per year. However, a battery stored inside a poorly ventilated laptop may be subject to a prolonged exposure to much higher temperatures than 25 °C, which will significantly shorten its life. The capacity loss begins from the time the battery was manufactured, and occurs even when the battery is unused. Different storage temperatures produce different loss results: 6% loss at 0 °C(32 °F), 20% at 25 °C(77 °F), and 35% at 40 °C(104 °F). When stored at 40% charge level, these figures are reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively.[7]
Li-ion batteries can even go into a state that is known as deep discharge. At this point, the battery may take a very long time to recharge. For example, a laptop battery that normally charges fully in 3 hours may take up to 42 hours to recharge. Or the deep discharge state may be so severe that the battery will never come back to life. Deep discharging only takes place when products with rechargeable batteries are left unused for extended periods of time (often 2 or more years) or when they are recharged so often that they can no longer hold a charge. This makes Li-ion batteries unsuitable for back-up applications compared to lead-acid batteries, or even to nickel metal hydride batteries.
Because the maximum power that can be continuously drawn from the battery depends on its capacity, in high-powered (relative to C, the battery capacity in A·h) applications, like portable computers and video cameras, rather than showing a gradual shortening of the running time of the equipment, Li-ion batteries may often just abruptly fail.
