Zinc-based Batteries: A Better Alternative to Li-ion?

Lithium-ion batteries are the primary energy storage devices utilized in portable electronics and electric vehicles. Lithium, an alkali metal, has a soft, silver-white texture and the lowest density among all metals. Its high reactivity renders it valuable for various applications, especially in the battery industry. However, it is highly combustible and poses significant environmental hazards if not handled with care. To address this environmental concern, researchers are actively exploring alternative options that are eco-friendly and readily available in the Earth's crust. One such alternative is zinc, an abundant metal that has demonstrated promising results in Zn-based electrochemistry as a substitute for Li-based batteries.

 

Ecofriendly battery versus traditional batteries. Image used courtesy of Freepik

 

Zinc is a metallic element belonging to the transition metal group 12 of the periodic table, including cadmium and mercury. With an atomic number of 30, atomic radius of 135 pm, and atomic weight of 65.39, zinc has a density of 7.14 g/cm3. In its pure form, zinc appears silvery-grey, but upon exposure to air, it undergoes oxidation and acquires a dull grey color. Zinc is the 24th most abundant element and is widely used in galvanization, which involves coating iron and steel surfaces to prevent corrosion. Recent research indicates that zinc may also have the potential as a key component in Zn-based batteries.

 

Differences Between Li-ion and Zinc Batteries

Following are the key differences between lithium-based batteries and zinc-based batteries.

 

Chemistry

Lithium-based batteries use lithium compounds as the anode and cathode's active material. In contrast, zinc-based batteries use zinc in the anode and manganese dioxide in the cathode.

Lithium-based batteries, including lithium-ion and polymer batteries, utilize lithium compounds as the active material in both the anode and cathode. Typically, the anode is made of graphite coated with a lithium-containing compound, while the cathode is typically composed of a metal oxide such as lithium cobalt, lithium iron phosphate, or lithium manganese. On the other hand, zinc-based batteries, such as zinc-carbon and alkaline, use zinc as the anode and manganese dioxide as the cathode, with an alkaline solution like potassium hydroxide serving as the electrolyte.  

While the generalization that lithium-based and zinc-based batteries use specific materials in their anodes and cathodes is typically accurate, there may be deviations or variations within these categories. Other types of batteries may have entirely different materials in their anodes and cathodes, and it is critical to consider the distinctive properties of each type of battery when examining their characteristics and potential applications.

 

Battery chemistry. Image used courtesy of Pixabay

 

Energy Density

Lithium-based batteries typically have higher energy density than zinc-based batteries, enabling them to store more energy. This is due to the use of lightweight and highly reactive materials in lithium-based batteries, which can store a significant amount of energy in a small space. On the other hand, zinc-based batteries have lower energy density as zinc is a heavier and less reactive material than lithium, which limits the amount of energy that can be stored. 

However, the energy density of a battery is not the only factor that determines its performance. The battery's capacity, voltage, and internal resistance also play important roles in determining how much energy it can deliver and how quickly it can deliver it. Moreover, different battery types may have varying trade-offs between energy density, power output, and other performance factors, making the suitability of a specific battery for a particular application depends on several factors beyond just its chemistry.

 

Battery Lifespan

Lithium-based batteries generally have a longer lifespan than zinc-based batteries, as they can withstand more charge and discharge cycles without degrading.

Lithium-based batteries' lifespan is generally longer than zinc-based batteries due to their ability to endure more charge and discharge cycles without deteriorating due to the nature of the materials used in the battery's anode and cathode, which are more robust and resilient in lithium-based batteries. Zinc-based batteries, on the other hand, are more prone to deterioration when subjected to high-stress conditions such as deep discharge or overcharging. It is important to note that the lifespan of a battery is affected by various factors such as usage, temperature, and storage conditions. Therefore, proper battery management and maintenance can significantly enhance the lifespan of both lithium-based and zinc-based batteries.

 

Power Output

Zinc-based batteries have a lower power output than lithium-based batteries, making them more suitable for low-power applications such as remote controls or flashlights.

Zinc-based batteries are known to have a lower power output compared to lithium-based batteries. Power output, measured in watts or milliwatts, is the rate at which a battery can deliver energy. The higher energy density and lower internal resistance of lithium-based batteries enable them to provide energy more quickly and efficiently, resulting in higher power output. However, power output is not the only factor that determines a battery's performance, as its capacity, voltage, and internal resistance also play significant roles. For instance, a higher-capacity zinc-based battery may provide more total energy than a lower-capacity lithium-based battery, despite having a lower power output. Therefore, selecting the appropriate battery for a specific application requires considering all relevant aspects of its performance and not solely its chemistry.

 

Cost of Battery Materials

Zinc-based batteries are generally less expensive than lithium-based batteries, as zinc is a more abundant and less expensive material than lithium.

 

Materials mining. Image used courtesy of Pixabay

 

Zinc-based batteries are generally more affordable than lithium-based batteries. The abundance and common use of zinc make it less costly than lithium, a rare and more expensive material. However, it's important to note that the cost of a battery depends on various factors beyond just the raw materials. The manufacturing cost, battery design complexity, and mass production economies of scale also influence the price of a battery. Furthermore, advances in manufacturing processes and increased production volumes have significantly reduced the cost of lithium-based batteries in recent years, which has closed the cost gap between lithium-based and zinc-based batteries.

 

Battery Safety

Lithium-based batteries are more prone to overheating and catching fire than zinc-based batteries, although both types of batteries can pose safety risks if mishandled.

Lithium-based batteries are more susceptible to overheating and catching fire than zinc-based batteries due to the reactive nature of the materials used in their chemistry that can generate heat when exposed to certain conditions, such as overcharging or high temperatures. The result of overheating is a thermal runaway reaction that could lead to an explosion or fire.  

Nonetheless, both types of batteries can present safety risks if abused or mishandled. While zinc-based batteries are generally less prone to overheating, they can also catch fire if subjected to extreme conditions or damaged. To mitigate the potential safety hazards of any type of battery, it is vital to follow the manufacturer's instructions, charge and discharge batteries correctly, avoid subjecting them to harsh conditions, and dispose of them per local regulations.

 

Environmental Impact

Zinc-based batteries are generally considered more environmentally friendly than lithium-based batteries, as zinc is more readily recyclable and less toxic than lithium.

Recycling zinc-based batteries are relatively simple and cost-effective as zinc is abundant, widely used, and readily recyclable, with a lower environmental impact than lithium. Lithium-based batteries, however, pose more significant challenges due to their complex chemistry and specialized recycling processes, making recycling them more difficult. The mining and production of lithium can cause adverse environmental effects such as water depletion and soil degradation. Nevertheless, there is an ongoing effort to develop sustainable and efficient production and recycling methods for lithium-based batteries. While zinc-based batteries are generally considered more environmentally friendly than lithium-based batteries, the overall environmental impact of any battery depends on various factors, including the battery's specific design and chemistry, the materials used, and the manufacturing and recycling processes employed.

 

Advances in Zinc-based Batteries

Zinc-based batteries have been the focus of much research in recent years due to their potential to offer a more cost-effective and sustainable alternative to lithium-ion batteries. Here are some of the current advancements in zinc-based batteries:

 

Zinc-air Batteries

Zinc-air batteries are a type of metal-air battery that use zinc as the anode, oxygen from the air as the cathode, and an electrolyte to facilitate the transfer of ions between the two. These batteries have high energy density and are promising for electric vehicles and other applications. Figure 1 provides a diagram of the construction zinc-air battery. 

 

Figure 1. Construction of zinc-air battery. Image used courtesy of Chetan Kumbhar

 

Zinc-ion Batteries

Zinc-ion batteries use zinc ions instead of lithium ions to store and release energy. They are considered a promising alternative to lithium-ion batteries because zinc is abundant, low-cost, and environmentally friendly. Zinc-ion batteries are also more stable than lithium-ion batteries and have a longer lifespan. Figure 2 illustrates the construction of zinc-ion batteries.

 

Figure 2. Construction of zinc-ion battery. Image used courtesy of Chetan Kumbhar

 

Zinc-manganese Batteries

Zinc-manganese batteries are a type of alkaline battery that use zinc as the anode, manganese dioxide as the cathode, and an alkaline electrolyte. They are commonly used in household appliances like flashlights and remote controls. Figure 3 depicts a zinc-based battery with manganese dioxide as a cathode.

 

Zinc-carbon Batteries

Zinc-carbon batteries are one of the oldest and most common types of primary batteries. They use a zinc anode, a carbon cathode, and an electrolyte to generate electricity. Although they have low energy density and are not rechargeable, they are widely used in low-drain devices such as clocks and remote controls. Figure 3 provides a diagram of the zinc-carbon battery.

 

Figure 3. Construction of zinc-carbon battery. IImage used courtesy of Chetan Kumbhar

 

Overall, the current advancements in zinc-based batteries are focused on improving their energy density, cycle life, and safety. Researchers are also exploring new materials and designs to enhance their performance and reduce costs.