Batteries power much of our modern lives, from phones to laptops to electric vehicles. Secondary batteries, also known as rechargeable batteries, allow us to use and reuse the same battery multiple times by recharging it through an external power source.

Types of Secondary Batteries

Secondary batteries come in different types based on their chemistry. Some of the most common types are:

Lead-Acid Batteries

The lead-acid battery is one of the earliest rechargeable batteries invented in 1859. It uses lead for the negative electrode and lead dioxide for the positive electrode with sulfuric acid as the electrolyte. Lead-acid batteries are commonly used to start engines in vehicles due to their high current delivery ability. These batteries also find applications as backup power sources. However, they have low energy densities and require regular maintenance.

Nickel-Cadmium (NiCad) Batteries

Developed in 1899, NiCad batteries use nickel oxide hydroxide and metallic cadmium for positive and negative electrodes respectively with an alkaline electrolyte. They have high energy densities, long life cycles and can deliver high currents. However, their use has reduced due to environmental concerns over toxic heavy metals like cadmium.

Nickel-Metal Hydride (NiMH) Batteries

NiMH batteries were commercialized as an alternative to NiCad batteries in 1989. They use nickel hydroxide for the positive electrode and an alloy of metallic hydrogen absorbing for the negative electrode with potassium hydroxide as electrolyte. NiMH batteries have higher energy densities than NiCad but lower than lithium-ion batteries. They are commonly used in hybrid electric vehicles, mobile phones and cameras due to their design simplicity.

Lithium-ion Batteries

Lithium-ion batteries are currently the most widely used Secondary Battery technology. First commercialized in 1991, they use a lithium-ion intercalated into carbon as the negative electrode and lithium-ion intercalated into a metal oxide or polymer as the positive electrode with a non-aqueous liquid electrolyte. Li-ion batteries have very high energy densities, no memory effect and low self-discharge. This has made them ideal for consumer electronics and electric vehicles. Continuous research is trying to improve their capacities, lifecycles and reduce costs.