Nickel-Metal-Hydride (Ni-MH) Technology, applications and forecast

The world's need for energy storage is growing rapidly. Electrochemical storage is one of the key components. The market for rechargeable batteries has almost doubled in 15 years, notably with the multiplication of nomadic applications, such as cell phones, laptops, tablets... At present, growth is being driven more by the development of electric, hybrid and rechargeable hybrid vehicles. Demand in this sector is creating strong pressure on production volumes for lithium-ion batteries, which are the key technology for the automotive sector thanks to their greater energy density than other rechargeable technologies. Lithium-ion technologies enable much higher mass and volume energy densities than other types (in excess of 200 Wh · kg ^–1 and 500 Wh · L ^–1 ). However, despite all the excitement surrounding lithium-ion technology, it has to be said that the "old" technologies still play an important role.

To illustrate this, it is interesting to analyze the different types of use. Electrochemical storage applications can be divided into several categories : starter battery, traction battery, on-board battery, stationary battery and portable battery. For each type of application, one or more technologies are used, depending above all on the characteristics required for the application: voltage (V), capacity (Ah), energy density (Wh · kg ^–1 or Wh · L ^–1 ), power requirement (W · kg ^–1 ), service life (number of cycles or duration of use for standby applications), temperature conditions (– 40 to + 80°C) and, of course, cost in €/kWh. Cost is an important component, but safety must never be overlooked. From this point of view, lithium technologies are by far the most sensitive, and require great care in system design.

In this context, the main technologies (figure 1 ) are :