Nickel cadmium (NiCd) batteries
A nickel cadmium (NiCd) battery consists of a nickel hydroxide cathode and a cadmium hydroxide anode. Advantages include the batteries being light weight, efficient, reliable, robust, able to operate over a wide temperature range, and feature a higher energy density than lead-acid batteries. However, the major drawbacks of NiCd batteries are their low energy density, and environmental hazards. For this reason, NiCd batteries have been banned in consumer electronics in the EU since 2006.
Nickel-metal hydride (NMH) batteries
Advantages: Higher capacity, compactness and energy density than nickel cadmium batteries; can operate at a wide temperature range; reliable and safe; and high performance
A nickel-metal hydride (NMH) battery consists of a nickel hydroxide cathode and a hydrogen-absorbing alloy anode. The mostly commonly used metal is AB5, where A represents a mixture of four rare earth metals (lanthanum, cerium, neodymium and praseodymium) and B represents nickel, cobalt, manganese and/or aluminium.
These batteries have been used in hybrid vehicles such as the Toyota Prius and Honda Civic.
Sodium sulphur (NaS) batteries
This battery technology has the advantages of: high energy density, long lifetimes and they can operate under extreme conditions including high temperatures. This does have the drawback that the batteries need a constant temperature of around 300°C.
These batteries have a wide range of both output and discharge times compared to other storage technologies. A competitor to sodium sulphur batteries are lithium-ion batteries as the anticipated cost savings for mass production of sodium sulphur has not occurred.
Sodium Nickel Chloride (NaNiCl) batteries
Sodium nickel batteries have been used in BEVs and PHEVs and are being expanded to applications in the telecommunications sector, back-up power in the electric grid and on and off-grid energy storage.
When the battery is being charged sodium atoms in the nickel chloride (NiCl2) cathode become ions and move through a ceramic electrolyte (e.g. NaAlCl4) to the anode made of sodium. Then this process is reversed during discharging.