📖 This post is part of our Batteries 101 series 📖
1. What Are Nickel–Cadmium batteries? Quick Introduction
Although we see them less often nowadays, nickel–cadmium (Ni–Cd) batteries represent a major chapter in the story of rechargeable batteries. Besides being one of the first rechargeable battery types to witness widespread use in consumer products, Ni–Cd batteries offer a compelling blend of performance characteristics that have made them a staple in certain applications since their commercialization.
2. History of Nickel–Cadmium Batteries
Nickel-Cadmium Batteries Were First Created in 1899
The journey of Ni–Cd batteries began with the pioneering work of Swedish inventor Waldemar Jungner in 1899. Despite initial challenges, Jungner's creation laid the groundwork for future advancements in rechargeable battery technology. These batteries quickly outshined lead–acid counterparts due to their superior chemical robustness and higher energy density. Jungner's company, Ackumulator Aktiebolaget Jungner, faced obstacles but eventually evolved into Saft AB, a prominent manufacturer of Ni–Cd batteries today. Subsequent developments in the 1930s and 1940s further improved the performance and durability of these batteries, introducing innovations like coated electrodes and sealed designs for enhanced efficiency.
Widespread Adoption in the Late 20th Century
These developments helped establish Ni–Cd batteries as a viable option for a broad range of applications, leading to their extensive adoption in the following decades. In 2000, 1.5 billion Ni–Cd batteries were being manufactured each year. For many years, Ni–Cd batteries were a common power source for portable electronics, power tools, flashlights, and other devices, prior to their replacement by nickel–metal hydride batteries, which feature a higher capacity and avoid the use of toxic cadmium, and more recently by lithium-ion batteries.
3. How Do Nickel–Cadmium Batteries Work?
Ni–Cd batteries rely on reversible chemical reactions involving three main components:
- A nickel oxide hydroxide cathode
- A cadmium-based anode
- An alkaline electrolyte (typically potassium hydroxide)
Consumer Ni–Cd batteries nowadays use the "jelly-roll" design, where the electrodes are manufactured as thin sheets sandwiched around a separator layer then rolled up in a spiral and inserted inside a cylindrical casing. This increases the active surface area, leading to a much higher maximum current.
Here's a simplified overview of the electrochemical reactions:
- Discharging: During discharge, the cadmium metal of the anode reacts with hydroxide ions to form cadmium hydroxide and electrons, while the nickel oxide hydroxide of the cathode is reduced by these electrons into nickel hydroxide. These reactions generate a flow of electrons from the anode to the cathode through the external circuit, providing electrical power.
- Charging: During charging, these reactions are reversed. The application of an external electrical current converts nickel hydroxide back into nickel oxide hydroxide at the cathode and cadmium hydroxide back into metallic cadmium at the anode, thus making the battery ready for another discharge cycle.
4. Characteristics of Nickel–Cadmium Batteries
Like any technology, Ni–Cd batteries have their own set of advantages and disadvantages, which are important to consider when evaluating their use in specific contexts.
Advantages
- High charging/discharging rates: Because of their low internal resistance, Ni–Cd batteries are capable of supporting high charging and discharging rates without significant loss in performance. This makes them particularly useful in applications requiring a substantial power output in a short period.
- Durability and longevity: Ni–Cd batteries can withstand a large number of charge/discharge cycles and a high depth of discharge, even for prolonged periods. With proper care, these batteries can last for many years, making them a cost-effective solution.
- Performance at extreme temperatures: The low internal resistance of Ni–Cd batteries also means that they do not easily overheat, leading to rugged performance over a wide temperature range.
- Reliable output: Ni–Cd batteries have a nominal voltage of 1.2 V per cell. Although this is somewhat lower than the 1.5 V initially supplied by primary alkaline and zinc–carbon cells, Ni–Cd cells maintain this voltage relatively steadily for the duration of discharge, meaning that they are still suitable for the many (but not all) electronic devices designed to function at the lower voltages produced by other battery types toward the end of discharge. This reliability is crucial in applications where a predictable power output is necessary.
Disadvantages
- Environmental concerns: The presence of cadmium, a toxic heavy metal, in Ni–Cd batteries poses significant environmental and health risks, especially to aquatic life, if they are not disposed of properly. Indeed, these concerns played a major role in their widespread replacement by other battery chemistries. For example, the 2006 Battery Directive limited sales of Ni–Cd batteries in the European Union, albeit with some exemptions, and the new Batteries Regulation 2023 is set to make this even stricter by banning their use in all portable applications.
- Memory effect: Another notable drawback of Ni–Cd batteries is the so-called memory effect, where repeatedly recharging a battery after only partial discharge may cause it to lose its ability to utilize its full capacity in the future. Although this can be mitigated with proper charging techniques, it remains a concern in cases where batteries are not fully discharged on a regular basis.
- Energy density: Compared with newer battery technologies, Ni–Cd batteries are heavier and larger for a given capacity. This can be a limiting factor for portable applications where size and weight are crucial considerations.
- Cost and availability: While the cost of Ni–Cd batteries can be competitive, especially for applications that benefit from their unique advantages, the overall trend toward other battery technologies has decreased the availability of Ni–Cd batteries and caused them to become relatively niche products less able to benefit from the economies of scale provided by widespread utilization.
5. What Are Nickel-Cadmium Batteries Used For?
Ni–Cd batteries were at one point commonplace in consumer devices before they were superseded by newer technologies. Current applications of Ni–Cd batteries include the following:
- Emergency lighting and backup systems: The ability of Ni–Cd batteries to hold their charge, deliver stable power output, withstand deep discharge cycles, and operate under a broad range of conditions makes them ideal for emergency lighting systems and backup power applications in critical settings.
- Aerospace and military applications: The durability and performance of Ni–Cd batteries under extreme conditions also make them suitable for use in aerospace and military equipment, where reliability is paramount.
- Power tools: Ni–Cd batteries are still often used in cordless power tools because of their ability to deliver high surge currents and stable output while enduring rough handling and extreme conditions.
6. Conclusion
Ni–Cd batteries have had a lasting impact on the world of rechargeable batteries. Their development marked a significant technological advancement, offering a reliable and durable energy source for a wide range of devices and applications. Although newer technologies such as nickel–metal hydride and lithium-ion batteries now overshadow Ni–Cd batteries in many areas, their robustness, reliability, and unique characteristics have allowed them to remain valuable in specific niches.
As we continue to move toward greener and more efficient energy storage solutions, regulatory restrictions may mean that the future of Ni–Cd batteries hinges on advancements in recycling processes and material recovery to mitigate environment impact. While Ni–Cd batteries are no longer at the forefront of consumer electronics power solutions, their legacy as a pioneering rechargeable battery technology is undeniable.
The story of Ni–Cd batteries, from their inception to their widespread use to their replacement with preferred alternatives, reflects the broader narrative of technological progress, environmental responsibility, and the continual search for optimal energy storage solutions.
>> Check out the vendors in nickel–cadmium battery manufacturing on Qurator.com here
