Nickel-metal hydride batteries

Definition

Nickel-metal hydride (NiMH) batteries are a type of rechargeable battery that use a hydrogen-absorbing alloy for the negative electrode and nickel oxyhydroxide for the positive electrode. They are a popular alternative to traditional nickel-cadmium batteries, offering higher energy density and improved environmental friendliness.

5 Must Know Facts For Your Next Test

1. NiMH batteries have a higher energy density compared to traditional nickel-cadmium batteries, allowing for more compact and lightweight designs.
2. They are environmentally friendly as they do not contain the toxic cadmium found in nickel-cadmium batteries.
3. NiMH batteries can be recharged hundreds of times, making them a cost-effective and sustainable power source.
4. They have a relatively high self-discharge rate, meaning they can lose a significant amount of charge even when not in use.
5. NiMH batteries are commonly used in portable electronics, power tools, and hybrid electric vehicles due to their high energy density and long cycle life.

Review Questions

• Explain the key components and working principle of a nickel-metal hydride battery.
  • A nickel-metal hydride (NiMH) battery consists of a negative electrode made of a hydrogen-absorbing alloy and a positive electrode made of nickel oxyhydroxide. During charging, the negative electrode stores hydrogen, while the positive electrode is oxidized. During discharge, the stored hydrogen is released from the negative electrode, and the positive electrode is reduced, generating an electric current that can be used to power devices. The reversible storage and release of hydrogen in the negative electrode is the fundamental mechanism that allows NiMH batteries to be rechargeable.
• Describe the advantages of nickel-metal hydride batteries over traditional nickel-cadmium batteries.
  • Compared to nickel-cadmium batteries, nickel-metal hydride (NiMH) batteries offer several advantages. NiMH batteries have a higher energy density, allowing for more compact and lightweight designs. They are also more environmentally friendly, as they do not contain the toxic cadmium found in nickel-cadmium batteries. Additionally, NiMH batteries can be recharged hundreds of times, making them a cost-effective and sustainable power source. These advantages have led to the widespread use of NiMH batteries in portable electronics, power tools, and hybrid electric vehicles.
• Analyze the potential drawbacks of nickel-metal hydride batteries and how they impact their practical applications.
  • While nickel-metal hydride (NiMH) batteries offer several advantages, they also have some potential drawbacks that can impact their practical applications. One key drawback is their relatively high self-discharge rate, meaning they can lose a significant amount of charge even when not in use. This can be a concern for applications where the battery needs to maintain a consistent charge over extended periods. Additionally, NiMH batteries are susceptible to memory effect, where repeated partial discharges can reduce their overall capacity over time. These limitations need to be carefully considered when selecting NiMH batteries for specific applications, such as in portable electronics or electric vehicles, where reliable and consistent power delivery is crucial.

Related terms

Rechargeable batteries: Rechargeable batteries, also known as secondary batteries, are energy storage devices that can be repeatedly charged and discharged, unlike primary batteries which are disposable.

Hydrogen-absorbing alloy: The negative electrode in a NiMH battery is made of a hydrogen-absorbing alloy, which can reversibly store and release hydrogen during the charging and discharging process.

Nickel oxyhydroxide: The positive electrode in a NiMH battery is made of nickel oxyhydroxide, a compound that undergoes redox reactions during the battery's operation.