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The history of the battery
3) Portable rechargeable batteries (secondary batteries)

[1] Nickel-cadmium battery (Ni-Cd)

The first nickel-cadmium battery was invented over 100 years ago in 1899 by a Swedish inventor named Waldemar Jungner. It was commercialized first at the beginning of 1960 in the USA, and in Japan, Sanyo Electric Co. Ltd., Matsushita Electric Industrial Co., Ltd. (currently Panasonic Corporation), and others began producing them in large quantities in 1963 and 1964.

This battery uses cadmium (Cd) as an active mass of negative electrode and nickel oxyhydroxide as an active mass of positive electrode (NiOOH), with an alkaline solution as an electrolyte. At about 1.2 volts, it provides about the same voltage as a dry-battery. Batteries for industrial use have an open label, but most of those for general consumer use are a sealed label type to eliminate any concern about leaks.

To put the sealed battery to practical use, it was necessary to find a way of preventing the battery from increasing inner pressure and exploding due to hydrogen and oxygen gases generated when discharging, oxygen at the positive electrode and hydrogen at the negative one. In the late 1940s, ideas proposed by a Frenchman named Neumann resulted in technological improvements, such as creating a larger negative electrode to suppress the amount of hydrogen gas produced and to increase the efficiency of oxygen absorption that enabled the commercialization of the sealed battery.

The nickel-cadmium battery is stable (its performance does not drop even when over-discharged or discharged over a long period of time), and it has great high current discharge characteristics (load characteristics), and thus it is used today in cordless telephones, electric tools, electric shavers, emergency lighting, and other applications.

[2] Nickel-metal hydride battery (Ni-MH)

In the 1990s, use of small electronic devices such as mobile phones, notebook computers, camcorders, and digital cameras (digital still cameras) quickly spread. One of the factors driving this trend was the emergence of world-first mass-produced, nickel-metal hydride batteries from Matsushita Battery Industries (Panasonic Energy) and Sanyo Electric Co., Ltd.

This battery replaced the negative electrode of the nickel-cadmium battery with one made of hydrogen absorbing alloys, and the voltage was about the same at around 1.2V. Using this high-tech material, the battery's energy density was greatly increased. In 1980, Toshiba Corporation lead the industry in the development of hydrogen absorbing alloys for negative electrodes, and Toshiba announced its consequent success in a report to a battery round-table discussion in 1984. Toshiba also announced the creation of a "super lattice alloy," a new alloy material with a completely different structure in 2000. A full 100 years after Waldemar Jungner's invention of nickel-cadmium batteries, a new rechargeable battery had emerged. The sealing of nickel-metal hydride batteries was based on the same concept as the nickel-cadmium battery.

For a time thereafter, this material structure was consistently improved upon, and taking over from Toshiba Battery's nickel-metal hydride operations, Sanyo Battery achieved its own "super lattice alloy" and the world's highest hydrogen adsorption capacity. So, technical innovation still continues today.

Because nickel-metal hydride batteries do not use cadmium, a hazardous substance, they are environmentally friendly and have been replacing nickel-cadmium batteries and are becoming more widely used in the small electronic devices mentioned earlier. For those types that are interchangeable with dry batteries, their capacity is increasing by about 10% each year, and they are contributing to the increased performance of digital cameras and other devices. In addition, nickel-metal hydride batteries are being used in the world's first mass-produced hybrid vehicles. Along with the growth of environmental awareness, the demand expansion for these batteries is expected.

[3] Lithium-ion battery (Li-ion)

The lithium ion battery appeared in answer to the higher energy density requirements of electronic devices as they increased in performance and functionality and exceeded the capacity of nickel-metal hydride batteries. In 1991, Sony Energy Devices Corporation was the world's first company to mass produce them. Today, they are available from many companies.

While these batteries are of the rechargeable lithium family with a high discharge voltage of about 3.7V, they use a positive and negative electrode set that can absorb and evolve lithium ions without the lithium dissolving or precipitating. The battery features good charge/discharge cycle characteristics of more than 500 cycles. Specifically, the positive electrode is made of lithium cobalt oxide (LiCo02), while the negative electrode is carbon (C); however, recently, positive electrode material that includes nickel and manganese, and negative electrode material that includes tin, are contributing to improve performance.

In comparison to nickel-cadmium batteries and nickel-metal hydride batteries, these batteries are light, have no memory effect, and have very low self-discharge rates, so they are quickly becoming the battery of choice for mobile devices, which are themselves becoming smaller and lighter with higher performance. In this processes, improvements in electrode materials and structures have more than doubled the energy density of these batteries in the decade since they first appeared on the market. Through the adoption of aluminum labels and advances in laminate technology, such as with lithium polymer batteries, they are becoming even lighter and thinner still.

Most recently, they are being used in high power output applications such as electric tools, power assisted bicycles, and electric vehicles, that have until now been the domain of nickel-cadmium and nickel-metal hydride batteries, and so the demand for lithium-ion batteries continues to grow.