How was the nickel-metal hydride battery invented?

Nickel-metal hydride (NiMH) batteries were developed as an improvement over earlier nickel-cadmium (NiCd) batteries, addressing environmental, safety, and energy density limitations. Their invention in the 1970s and 1980s stemmed from research into safer, high-capacity rechargeable batteries for various applications.

Here’s an overview of how NiMH batteries came about:

1. Early Research and Background: NiCd batteries, first developed in the early 20th century, were widely used but contained toxic cadmium, leading to environmental concerns and recycling challenges. Scientists aimed to develop a safer, more eco-friendly alternative that would also offer higher energy density.

2. Exploration of Hydrogen Storage: NiMH batteries emerged from the research into hydrogen storage and metal hydrides. In the 1960s and 1970s, scientists discovered that certain metal alloys could effectively store hydrogen by absorbing it to form a hydride. This property opened the door to using these alloys in batteries as a potential "hydrogen sponge" for storing electrical energy.

3. Development of Nickel-Metal Hydride Chemistry: Building on nickel battery chemistry, researchers looked into replacing the cadmium in NiCd batteries with a hydrogen-absorbing metal alloy. The breakthrough came when they combined nickel oxide hydroxide as the positive electrode with a hydrogen-absorbing metal alloy for the negative electrode. This pairing created a rechargeable battery with a better energy-to-weight ratio and no toxic cadmium.

4. Commercialization and Refinements: Ovonic Battery Company, led by scientist Stanford Ovshinsky, was instrumental in refining and commercializing NiMH technology in the 1980s. Ovshinsky’s work with metal hydrides and hydrogen storage contributed to making NiMH batteries practical for consumer use. The battery was introduced commercially in the 1990s, primarily in consumer electronics, power tools, and later in hybrid electric vehicles due to its energy density, environmental benefits, and safety profile.

5. Advantages Over NiCd: NiMH batteries offered several advantages over NiCd, including higher capacity, longer cycle life, and the absence of toxic cadmium. Although NiMH batteries self-discharge more quickly than NiCd, their improved capacity and eco-friendliness made them a preferable choice for many applications.

Today, while lithium-ion batteries have largely overtaken NiMH in consumer electronics, NiMH batteries are still used in applications that benefit from their stability and moderate energy density, such as hybrid vehicles and certain consumer devices.