In the past decade, batteries have become indispensable in modern society, powering our cars, phones, homes, and more. The inner mechanisms, components, and classifications have evolved remarkably and shaped our daily lives.
What is a battery?
A battery is a storage container with one or more cells that, when react, create a flow of electrons in a circuit. The chemical process between the substances within these cells produces a charge transfer between them. This simultaneous oxidation and reduction reaction is called an electrochemical oxidation-reduction (Redox) reaction when one element loses electrons (oxidation), and the other gains them (reduction). The electron exchange converts chemical energy into electrical energy in batteries, creating sustainable energy storage solutions.
Three Essential Components of a Battery
Batteries comprise three main components; Anode, Cathode, and Electrolyte. The cathode refers to the electrode where the reduction occurs. In contrast, the anode relates to the electrode where oxidation occurs. An electrolyte separates these two. The electrolyte is a chemical allowing an electrical charge to pass between the two. The electrolyte puts the chemicals required for the reaction in contact with the anode and cathode, converting stored energy into electrical energy.
Anode (–)
The anode is the negative electrode in an electrochemical cell. It undergoes oxidation, releasing electrons to the circuit and allowing current to flow. In the case of Li-ion batteries, the anode materials, such as silicon and carbon (graphite), undergo oxidation, producing ions that can move through the electrolyte while preventing the passage of electrons.
Cathode (+)
The cathode is the positive (oxidizing) electrode that gains electrons from the circuit during the electrochemical reaction. The current flows out of the cathode. In the case of Li-ion batteries, positively charged lithium ions produced during oxidation are consumed during reduction. Examples of cathode materials in a battery are Lithium Nickel Manganese Cobalt Oxide (NMC batteries), Lithium Nickel Cobalt Aluminum Oxide (NCA batteries), and Lithium Manganese Oxide (LMO batteries).
Electrolyte
The battery electrolyte enables current flow between the anode and cathode. It is often a liquid or gel, including salts, acids, and bases. Electrons at the terminals cause chemical reactions, forming ion clouds. Anions (negative ions) move from the cathode to the anode. In contrast, cations (positive ions) move from the anode to the cathode. This bidirectional flow of charge through the electrolyte is vital for battery operation, converting stored energy into electrical energy.
Battery System Classification
Batteries are mainly classified into two categories: Primary and secondary. However, with advancements in science and technology, other energy supply sources have been developed and are currently evolving.
Primary batteries are single-use (disposable), commonly known as non-rechargeable batteries. Once the energy in a primary battery is depleted, it cannot be restored, and the battery needs to be replaced. Common examples of primary batteries include Zinc-Carbon (alkaline), such as AAA and coin cell batteries, often found in household items.
On the other hand, secondary batteries are rechargeable batteries. They are designed to be reused multiple times by restoring their energy through a charging process. When a secondary battery is depleted, it can be connected to a power source, such as a charger, to replenish its energy and be reused. Common types of secondary batteries, apart from lithium-ion batteries, are nickel-cadmium (NiCd) batteries and nickel-metal hydride (NiMH) batteries.
Fuel Cells – An Alternative Sustainable Energy Source
Fuel cells are electrochemical cells that use a fuel source (e.g., Hydrogen) and an oxidant to generate electricity from an electrochemical process. Fuel cells found in combustion vehicles are similar to batteries, as they generate an electrical current, except that they require a continuous addition of fuel and oxidizer. Both fuel cells and secondary batteries have advantages and disadvantages. Secondary batteries are more efficient but can take a long time to recharge depending on the charger; the approximate charging time can range from 30 minutes to 10 hours. Fuel cells will have the same power quality over time and run continuously, yet will only do so as long as reactants are supplied.
Fuel cells use Hydrogen and oxygen from the air to produce water and electricity. It is more efficient than internal combustion engines, with efficiencies exceeding 60%. A hydrogen fuel cell needs 2-3 times more energy to cover the same distance as an electric car, although this depends on the cell's type and size. Vehicles with hydrogen fuel cells and secondary battery cells are better for the environment than diesel and petrol cars since they emit fewer emissions. Nevertheless, the emissions from electric vehicles depend on the energy source used to charge the battery.
The future of batteries is bright, with ongoing research and development focused on creating more efficient, longer-lasting, and sustainable energy storage solutions. Materials, chemistry, and engineering advancements can revolutionize various industries, including electric vehicles, renewable energy, and consumer electronics. As we push the boundaries of technology, we can expect batteries to play a vital role in driving the transition toward a cleaner and more sustainable future.
Authors: Anna Sheridan & Saieesh Nayak