Alkaline rechargeable batteries are batteries using alkaline electrolyte mainly composed of potassium hydroxide (KOH), and in almost all battery systems, the nickel positive electrode excellent in charge and discharge cycle performance is used. In the negative electrode, iron (Fe), zinc (Zn), cadmium (Cd) and others are used as active material, but because of the long charge and discharge cycle life and high reliability of sealed batteries, the main stream of alkaline batteries was nickel-cadmium (NiCd) batteries using cadmium negative electrode. Nickel-cadmium batteries (NiCd) provide one of the few sources of rechargeable portable electric power. Nickel-cadmium batteries comprise a plurality of nickel-cadmium voltaic cells connected in series. The cadmium electrode is used as a cathode almost exclusively in nickel-cadmium storage batteries. The nickel oxide electrode serves as positive electrode and an aqueous KOH solution as electrolyte. Although a variety of rechargeable battery technologies have been developed, rechargeable nickel-cadmium (NiCd) batteries have several advantageous properties. Nickel-cadmium batteries have a relatively high capacity to weight ratio, a relatively flat voltage to percent of discharge curve, good performance at low temperatures, the capability of delivering high amperage currents for engine starting and similar purposes, and a relatively high recharge recycling capacity. NiCd cells may be hermetically sealed which permits operation in any position and in inaccessible locations. They are also fairly inexpensive relative to some other high performance battery technologies. While rechargeable NiCad batteries can be used to supply such clean power, NiCad batteries have a number of problems. In particular, they require periodic recharging in order to provide power.
Nickel metal hydride (NiMH) battery Alkaline storage batteries having a wide application in various portable appliances include nickel-cadmium (NiCd) storage batteries, nickel-metal hydride (NiMH) storage batteries and the like. Among them, the nickel-metal hydride storage batteries have recently been used widely as small-size sealed storage batteries, because they can be expected to have a higher capacity density. Nickel cadmium cells have long been the standard for high discharge applications such as power tools. However, increasing emphasis is being placed on nickel metal hydride electrochemical cells as replacements for nickel cadmium cells. NiMH cells avoid environmental concerns relating to cadmium and have improved energy density. A nickel-metal hydride storage battery is a secondary battery comprising a positive electrode formed from an active material composed mainly of nickel hydroxide and a negative electrode composed mainly of a hydrogen storage alloy. In general, nickel-metal hydride batteries comprise a negative electrode of hydrogen absorbing alloy, a positive electrode of nickel hydroxide, an alkaline electrolyte, a separator, etc. Nickel metal-hydride storage batteries have positive electrodes including an active material containing nickel hydroxide as a principal component and negative electrodes including a hydrogen-absorbing alloy as a principal material. Therefore, they have rapidly spread as secondary batteries having high energy densities and high reliability. A nickel positive electrode for use in a nickel-metal hydride storage cell can be either a sintered type or a paste type (nonsintered type). NiMH batteries are widely used in laptop computers, cellular phones, electrical vehicles (EV), hybride electric vehicles (HEV) and different tools. For further details Click here