Batteries can be sorted into 3 categories: lithium-ion battery, nickel–metal hydride battery and alkaline battery.
A lithium-ion battery (sometimes Li-ion battery or LIB) is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types. Unlike lithium primary batteries (which are disposable), lithium-ion electrochemical cells use an intercalated lithium compound as the electrode material instead of metallic lithium.
Lithium-ion batteries are common in consumer electronics. They are one of the most popular types of rechargeable battery for portable electronics, with one of the best energy densities, no memory effect, and only a slow loss of charge when not in use. Beyond consumer electronics, LIBs are also growing in popularity for electric vehicle, and aerospace applications. Research is yielding a stream of improvements to traditional LIB technology, focusing on energy density, durability, cost, and intrinsic safety.
Alkaline batteries are a type of primary batteries dependent upon the reaction between zinc and manganese dioxide(Zn/MnO2). A rechargeable alkaline battery allows reuse of specially designed cells.
Compared with zinc-carbon batteries of the Leclanché or zinc chloride types, alkaline batteries have a higher energy density and longer shelf-life, with the same voltage. Button cell silver-oxide batteries have higher energy density and capacity but also higher cost than similar-size alkaline cells.
The alkaline battery gets its name because it has an alkaline electrolyte of potassium hydroxide, instead of the acidic ammonium chloride or zinc chloride electrolyte of the zinc-carbon batteries. Other battery systems also use alkaline electrolytes, but they use different active materials for the electrodes.
3A nickel–metal hydride cell, abbreviated NiMH or Ni-MH, is a type of rechargeable battery. It is very similar to the nickel–cadmium cell (Ni-Cd). NiMH use positive electrodes of nickel oxyhydroxide (Ni-OOH), like the Ni-Cd, but the negative electrode uses a hydrogen-absorbing alloy instead of cadmium. A NiMH battery can have two to three times the capacity of an equivalent size Ni-Cd, and their energy density approaches that of a lithium-ion cell.
The typical specific energy for small NiMH cells is about 100 Wh/kg, and for larger NiMH cells about 75 Wh/kg (270 kJ/kg). This is significantly better than the typical 40–60 Wh/kg for Ni–Cd, and similar to the 100-160 Wh/kg for Li-ion. NiMH has a volumetric energy density of about 300 Wh/L (1080 MJ/m³), significantly better than nickel–cadmium at 50–150 Wh/L, and about the same as li-ion at 250-360 Wh/L.
NiMH batteries have replaced Ni-Cd for many roles, notably small rechargeable batteries. NiMH batteries are very common for AA (penlight-size) batteries, which have nominal charge capacities (C) ranging from 1100 mAh to 3100 mAh at 1.2 V, measured at the rate that discharges the cell in five hours. Useful discharge capacity is a decreasing function of the discharge rate, but up to a rate of around 1×C (full discharge in one hour), it does not differ significantly from the nominal capacity.
NiMH batteries normally operate at 1.2 V per cell, somewhat lower than conventional 1.5 V cells, but will operate most devices designed for that voltage.
About 22% of portable rechargeable batteries sold in Japan in 2010 were Ni-MH. In Switzerland in 2009, the equivalent statistic was approximately 60%. This percentage has fallen over time due to the increase in manufacture of Li-ion batteries: in 2000, almost half of all portable rechargeable batteries sold in Japan were NiMH.
One significant disadvantage of NiMH batteries is a high rate of self-discharge; a Ni-HM battery will lose as much as 3% of its charge per week of storage. In 2005 a low self-discharge NiMH battery (LSD) was developed. LSD Ni-MH batteries significantly lower self-discharge, but at the cost of lowering capacity by about 20%.