For many years, nickel-cadmium has been the only suitable battery for portable devices ranging from wireless communications to mobile computing. The emergence of nickel hydride and lithium ion was in the early 1990s, from nose to nose to strive for customer recognition. Today, lithium ion is the fastest growing and most promising battery chemistry.
Lithium Ion Battery
The pioneer work of lithium batteries began in 1912 by GN Lewis, but it was not until the early 1970s that the first non-rechargeable lithium batteries began to be commercialized. Lithium is the lightest of all metals, has the largest electrochemical potential, and provides the largest weight energy density.
Due to safety issues, attempts to develop rechargeable lithium batteries failed. Due to the inherent instability of lithium metal, especially during the charging process, research has turned to non-metallic lithium batteries using lithium ions. Although the energy density is slightly lower than that of metallic lithium, lithium ion is safe, as long as certain precautions are met during charging and discharging. In 1991, Sony commercialized the first lithium-ion battery. Other manufacturers followed suit.
The energy density of lithium ions is usually twice that of standard nickel-cadmium. There is a potential for higher energy density. The load characteristics are quite good, and the discharge performance is similar to that of nickel-cadmium. The high battery voltage of 3.6 volts allows the design of a battery pack that uses only one battery. Most mobile phones today run on a single unit. The nickel-based battery pack requires three 1.2-volt batteries connected in series.
Lithium-ion batteries have low maintenance costs, which is an advantage that most other chemical methods cannot claim. Without memory, there is no need to cycle regularly to extend battery life. In addition, the self-discharge is less than half that of Ni-Cd, which makes Li-ion ideal for modern fuel gauge applications. Lithium-ion batteries cause almost no harm when they are disposed of.
Despite the overall advantages, lithium ion also has its disadvantages. It is fragile and requires a protective circuit to maintain safe operation. The protection circuit built into each battery pack can limit the peak voltage of each battery during charging and prevent the battery voltage from dropping too low during discharge. In addition, the battery temperature is monitored to prevent the temperature from becoming too high. The maximum charge and discharge current of most battery packs is limited to between 1C and 2C. By taking these precautions, the possibility of metal lithium plating due to overcharging is virtually eliminated.
Most lithium-ion batteries are worried about aging, and many manufacturers remain silent on this issue. Regardless of whether the battery is used or not, the capacity will drop significantly after one year. Batteries usually fail after two or three years. It should be noted that other chemicals also have age-related degeneration effects. This is especially true for nickel hydride metal if exposed to high ambient temperatures. At the same time, it is known that lithium-ion battery packs have been used for five years in certain applications.
Manufacturers are constantly improving lithium ion. New and enhanced chemical combinations are introduced every six months or so. With such rapid progress, it is difficult to assess the degree of aging of the revised battery.
Storage in a cool place will slow down the aging process of lithium ions (and other chemicals). The manufacturer's recommended storage temperature is 15°C (59°F). In addition, the battery should be partially charged during storage. The manufacturer recommends a 40% fee.
In terms of cost-to-energy ratio, the most economical lithium-ion battery is the cylindrical 18650 (dimensions 18mm x 65.2mm). This unit is used for mobile computing and other applications that do not require ultra-thin geometric shapes. If slim packaging is required, prismatic lithium-ion batteries are the best choice. The energy storage cost of these batteries is relatively high.
High energy density-greater potential.
It does not need to be started for a long time when brand new. Just charge it regularly.
Relatively low self-discharge-self-discharge is less than half of nickel-based batteries.
Low maintenance-no need for regular discharge; no memory.
Special batteries can provide high currents for applications such as power tools.
A protection circuit is needed to keep the voltage and current within a safe range.
Even if it is not used, it will age-40% charge storage in a cool place will reduce the aging effect.
Transportation restrictions-shipments of larger quantities may be subject to regulations. This restriction does not apply to batteries that are carried on the body.
Expensive to manufacture-the cost is 40% higher than nickel-cadmium.
Not yet fully mature-metals and chemicals are constantly changing.