With the way technology is developing, it seems solid-state batteries shall dominate the broader applications in the future. There are already contemporary designs that have seen practical usage with cars and smartphones. Yet, there has been a less-known variant already in use at a smaller scale, and that is the nickel-cadmium battery.
If you’ve never given it much thought before, you are not alone. Most people would walk right past it or have it stored in their homes without even realizing it, even if it is the first practical step in developing solid-state batteries, which will still be around for decades. As such, here is your definitive guide on Ni-Cd batteries, their design, and the applications best suited for them.
What Is a Nickel Cadmium Battery?
A nickel-cadmium battery is a form of solid-state battery, much like lithium-ion batteries, given that none of the solid components transform from their state, even as the ions and electrons are exchanged among them. It was invented by Waldemar Jungner in Sweden in 1899. The battery uses nickelic hydroxide and cadmium as the cathode and anode, respectively. The primary electrolyte is an aqueous solution of potassium hydroxide.
Typically, a nickel-cadmium battery can be manufactured in small-sized units, thanks to the highly malleable metals and its surprising power output. A regular AA Ni-Cd battery can possess an electromotive force of 1.3 Volts. It can be recharged for over 3000 cycles and has less thermal runoff than its lead-acid equivalents.
Structure of a Nickel Cadmium Battery
You can buy a Ni-Cd battery in various forms. The maximum sales bracket is covered by rechargeable dry cells that you can use in remotes, electric toothbrushes, and other miniature devices. However, the basic structure is quite comparable, with the same chemicals just used in different quantities and shapes. You can study it in detail through the image below.
The nickelic hydroxide electrode is placed in layers congruent to the cadmium hydroxide plates. A porous separator maintains the potential difference and prevents short circuits. As for the electrolyte, it is a 30% concentrated potassium hydroxide solution shared by each layer of the electrodes.
The entire arrangement is encased in a nickel-plated steel case insulated at the bottom. It is done so that the nickel in the case can supply the relevant ions to the electrodes underneath, further extending the battery’s lifespan. In order to make the battery more secure, a spring-loaded cap and vent hole is added to the top to allow for excess heat to escape into the atmosphere.
How does a Ni-Cd battery function?
In the discharging state, the cadmium anode loses electrons and reacts with the hydroxide ions from the electrolyte to form cadmium hydroxide. On the cathode side, the nickelic hydroxide reduces to nickel hydroxide after consuming the electrons and reacting with the water in the solution. The process is reversed during the charging state. The flow of electrons from an external load causes the current to flow through the circuit.
Pros and Cons of Nickel Cadmium Battery
- Since the components of the battery never change their state, the loss in the transfer of hydroxide ions and electrons is minimal. Therefore, Ni-Cd batteries have more efficiency than lead-acid batteries.
- You can’t overcharge lead-acid batteries because the excess charges can cause electrolysis and break the sulfuric acid into water and sulfur dioxide, a gas that is lethal even in small quantities. It doesn’t happen with Ni-Cd batteries. Overcharging only produces extra hydroxide ions from the water that are quickly consumed once the battery needs to discharge.
- Due to high thermal stability, Ni-Cd batteries can function in temperatures ranging from -20°C (-4°F) to 65°C (149°F). You can also safely charge Ni-Cd batteries within a temperature range of 0°C (32°F) to 45°C (113°F).
- You can recharge a Ni-Cd battery for over 3000 cycles with minimal loss in efficiency.
- Nickel and cadmium are highly malleable metals. So, you can design a Ni-Cd battery with nearly any shape and size per your requirements.
- Ni-Cd batteries can withstand heavy impacts and millions of vibration cycles without detriment to performance.
- A Ni-Cd battery is expensive since both nickel and cadmium are expensive to mine and refine.
- It is hard to dispose of used batteries since cadmium is highly toxic to the environment. Later versions utilized nickel-metal hydrides and eventually lithium-ion, which are easier to recycle or dispose of.
- A nickel-cadmium battery can suffer from a memory effect. It occurs when a cell is discharged and recharged to the same level too many times. After a certain period, you can’t restore it to its full potential.
Nickel-Cadmium batteries are used in several real-life applications. Some of the most popular ones include:
- Handheld power tools
- Photography equipment
- Remote-controlled cars and civilian drones
- Solar lights
- Emergency backup power
- Limited-processing devices such as calculators and pregnancy test kits
Why are Ni-Cd batteries banned in some countries?
The disposal of cadmium is a complex process. It helps to have a concentrated waste pile to obtain 99% pure cadmium to recycle. If not contained appropriately, it can penetrate the soil and mix with the groundwater, making it highly toxic. Many developing countries may not have the infrastructure to handle that, which is why they prefer to ban Ni-Cd batteries entirely.
Is Ni-Cad better than a lithium-ion battery?
No. Lithium-ion batteries have a higher storage capacity by volume, are less expensive to manufacture, possess more recharging cycles, and prove more straightforward to recycle. Sure, they have thermal issues, but the correct electrolyte can hopefully solve the problem in the near future.
How many times can you recharge a Ni-Cd battery?
It depends upon the size and capacity of the battery in question. A small 1.3V Ni-Cd battery can be charged and discharged about 3000 times. You can recharge a larger 12V variant for more than 5000 cycles.
The nickel-cadmium battery may have limited applications in today’s world, yet it remains a crucial step forward in battery technology. Considering that it is still used after more than a century after its invention is a testament to its reliability. We hope this piece gave you new insights into the battery’s technology. Still, have a few burning questions. We would love to read and answer them in the comments below.
- Separators for nickel metal hydride and nickel-cadmium batteries designed to reduce self-discharge rates