Metal Hydrides for Use in Nickel Metal Hydride Battery Applications

Description

Nickel Metal Hydride batteries use metal hydrides to store and release hydrogen. They are compounds formed when hydrogen bonds with metals. Their application increases battery performance and safety.

Metal hydrides are compounds produced when hydrogen bonds with metals. They absorb and release hydrogen. This property makes them a critical component in Nickel Metal Hydride systems. British research institutions and companies utilise these materials in hybrid vehicles, consumer electronics, and other fields that require rechargeable batteries.

Comparing Types of Batteries

Various battery types are available today.

Nickel Metal Hydride batteries operate differently from Nickel Cadmium batteries. Nickel Cadmium batteries contain cadmium and exhibit memory effects. In contrast, Nickel Metal Hydride batteries use metal hydrides and experience reduced memory loss.

Lithium Ion batteries provide high capacity but require careful charging. Lead acid batteries are heavy and require regular maintenance. Each battery type has specific advantages and disadvantages.

In Nickel Metal Hydride battery applications, metal hydrides provide a balance between energy density and safety. British studies indicate that metal hydride systems have been employed in portable and automotive applications for many years.

Further reading: The Evolution of Electric Vehicle Batteries: From Lead-Acid to Lithium-Ion

Crystal Structures of Nickel Metal Hydride Battery Materials

The crystal structure of materials in Nickel Metal Hydride batteries is significant. The atomic arrangement determines hydrogen storage and release efficiency. Many battery materials adopt an AB5 structure. In this configuration, the metal hydride comprises one rare earth or transition metal element and five additional metal atoms. This structure forms spaces for hydrogen atoms.

Engineers and scientists measure the crystal lattice using X‑ray diffraction. They determine hydrogen absorption capacity by quantitative analysis. The structure demonstrates reversibility and stability.

Further reading: All about Electric Vehicle Batteries

Crystal Structures of Battery Materials (AB5, AB2, etc.)

In NiMH batteries, the hydrogen‑absorbing alloy's crystal structure influences battery performance. AB5 and AB2‑type structures are extensively studied, with "A" and "B" representing distinct metal elements. These structures are used in applications that demand extended cycle life, high hydrogen capacity and efficient charge/discharge cycles, which are important for plug‑in hybrid electric vehicles (PHEVs) and electric vehicles (EVs).

The AB5 structure in NiMH batteries generally incorporates rare earth elements at the A‑site and transition metals at the B‑site. This configuration provides hydrogen storage capacity and kinetic performance. Sealed NiMH batteries in the Toyota™ Prius (II–V models) have achieved up to 150 000 miles of battery life according to manufacturer laboratory testing (ref. 19).

AB2‑type structures comprise two metallic components. They may exhibit higher hydrogen capacities. However, phase stability and resistance to degradation depend on composition and microstructure.

In battery research, both AB5 and AB2 hydrides are analysed for lattice parameters, phase transformations and thermal stability. Minor adjustments in alloying elements alter hydrogen storage capacity and cycle life. These compounds are termed "Classical Hydrides". Researchers have improved electrochemical stability and cycle life through micro‑alloying of A‑ and B‑site metals.

Electrochemical Reactions in Nickel Metal Hydride Batteries

In Nickel Metal Hydride batteries, electrochemical reactions generate power. Metal hydrides store hydrogen atoms. During discharge, hydrogen ions leave the metal hydride and travel to the nickel oxide electrode. Consequently, electrons move through the external circuit. The battery produces electric current.

During charging, hydrogen atoms return to the metal hydride. The reactions are reversible. This reversibility enables repeated use. Numerous studies have documented the reliability and efficiency of this mechanism.

Conclusion

Metal hydrides constitute a vital component in Nickel Metal Hydride battery applications. Their utilisation increases performance and stability. The crystal structures determine energy storage and release. The electrochemical reactions are simple. Their application results in safer energy systems and reduced environmental impact.

Frequently Asked Questions

F: What role do metal hydrides have in these batteries?
Q: They absorb and release hydrogen to manage the battery's energy.

F: How do crystal structures affect battery performance?
Q: They determine the extent to which hydrogen is stored and released at the electrodes.

F: Why are Nickel Metal Hydride batteries preferred in hybrid vehicles?
Q: They offer appropriate energy density, safety and reliability while reducing environmental impact.