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Galvanic cells are fascinating systems that offer us insight into the conversion of chemical energy into electrical energy – a principle that drives many aspects of our modern lives. Whether in batteries, accumulators, or fuel cells, galvanic cells are at the heart of numerous applications that shape everyday life. But how exactly do they work? What happens on the atomic level when chemical reactions suddenly generate electricity? These questions lead us directly into the fascinating realm of electrochemistry, where electron flow and chemical reactions work in perfect symbiosis.
What is a galvanic cell?
A galvanic cell is a device that converts chemical energy into electrical energy through a redox reaction. It consists of two different half-cells, each made up of a metal and an electrolyte solution. These cells are connected by a salt bridge or porous partition, allowing ion flow while keeping the two half-cells electrically separated.
Daniell Cell: An example of a galvanic cell
The Daniell cell is a classic example of a galvanic cell and vividly illustrates how chemical energy is converted into electrical energy. This cell consists of two half-cells: a zinc half-cell and a copper half-cell. In the zinc half-cell, zinc serves as the anode where oxidation occurs: Zn → Zn²⁺ + 2e⁻. The released electrons travel through the external circuit to the copper half-cell, which serves as the cathode. Here, the reduction occurs: Cu²⁺ + 2e⁻ → Cu. The Daniell cell is not only an important representative of galvanic cells but also a commonly used teaching example to explain the basic principles of electrochemistry.
Difference between galvanic cells and electrolytic cells
Galvanic cells and electrolytic cells are both electrochemical cells, but they differ in how they operate and the processes they use. A galvanic cell converts chemical energy into electrical energy. It is based on a redox system, where a spontaneous redox reaction causes electrons to flow from the anode (where oxidation occurs) to the cathode (where reduction occurs). This electron flow generates electric current. In a galvanic cell, the reaction occurs spontaneously without external energy input. The anode is negative as it releases electrons, and the cathode is positive as it accepts electrons.
In contrast, an electrolytic cell uses electrical energy to drive a non-spontaneous chemical reaction. Here, current from an external source is applied to the cell to trigger the redox reaction. The anode is positive because it is connected to the positive side of the power source, and the cathode is negative as it is connected to the negative side. Electrolytic cells are often used in processes like electrolysis, such as the decomposition of water into hydrogen and oxygen or the extraction of metals from their ores.
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4 Main Types of Galvanic Cells
There are various types of galvanic cells that differ in structure, function, and application. The main types are primary cells, secondary cells, concentration cells, and fuel cells.
Primary cells are non-rechargeable cells that convert chemical energy into electrical energy until the reactive substances are depleted. They are mainly used for low-power devices such as remote controls and clocks. A well-known example is the alkaline battery, which uses zinc as the anode and manganese dioxide as the cathode. The chemical reaction in primary cells is not reversible, meaning they cannot be recharged once discharged.
A special form of the galvanic cell is the concentration cell, where two identical electrodes are immersed in solutions of different concentrations. The resulting voltage difference is due to the ion concentration difference in the electrolytes. These cells are useful for demonstrating theoretical concepts in electrochemistry and find rare practical applications.
Secondary cells, on the other hand, are rechargeable and find widespread use in devices that require regular recharging, such as smartphones or electric vehicles. A classic example is the lead-acid battery, used in cars. In this type of cell, the reactions are reversible, allowing the chemical energy to be restored after discharge by applying electrical energy. Another popular example is the lithium-ion battery, which is used in many modern applications due to its high energy density.
Fuel cells are a special type of galvanic cell that continuously feed fuels such as hydrogen and oxygen to convert chemical energy into electrical energy. Unlike the other cell types, the energy here is not generated by a stored reaction but by the continuous supply of reactants. Hydrogen fuel cells are an example, where hydrogen is oxidized at the anode and oxygen is reduced at the cathode, producing electricity and water as by-products. These cells hold great potential for environmentally friendly energy applications, especially in the field of electromobility.
Structure of a Galvanic Cell
The structure of a galvanic cell consists of two main components: the half-cells and the connection system (e.g., a salt bridge or porous membrane), which together enable the conversion of chemical energy into electrical energy.
1. Two Half-Cells
Each galvanic cell consists of two half-cells where a redox reaction occurs:
- Anode (oxidation half-cell): This is where oxidation occurs. A metal atom gives off electrons and is released into the solution as an ion. The anode is negative in galvanic cells.
- Cathode (reduction half-cell): The reduction occurs at the cathode. Ions from the solution gain electrons and deposit as solid metal at the cathode. The cathode is positive.
2. Electrodes
The electrodes are typically made of metals (e.g., zinc and copper). They are each immersed in an aqueous solution of their respective metal ions.
3. Electrolyte Solution:
Each half-cell contains a solution (electrolyte) with ions that participate in the redox reaction. For example, the zinc half-cell contains zinc sulfate (Zn2+), and the copper half-cell contains copper sulfate (Cu2+).
4. Salt Bridge or Porous Membrane:
This connection between the two half-cells allows ions to circulate freely between the solutions without mixing them directly. It maintains charge balance while electron flow occurs in the external circuit.
5. External Circuit:
The external circuit connects the two electrodes. Electrons flow from the anode to the cathode, generating usable electric current.
Where are galvanic cells found?
Galvanic cells are widely used in many areas of everyday life and in industry because they can efficiently generate electrical energy from chemical reactions. Their applications range from simple household devices to complex technologies. The main application areas include the following:
- Batteries for household devices: Primary cells such as alkaline batteries are widely used in everyday devices such as remote controls, flashlights, clocks, smoke detectors, and toys. These batteries provide a reliable power source for devices with low to medium energy demand. Button cells (small galvanic cells) are also commonly used in watches, calculators, and hearing aids.
- Rechargeable batteries (secondary cells): Lithium-ion batteries are widely used in mobile devices such as smartphones, laptops, tablets, and wearable devices (e.g., smartwatches). They are known for their high energy density and recharging capability. Nickel-metal hydride (NiMH) batteries, on the other hand, are used in cameras, cordless phones, and some hybrid vehicles.
- Electromobility: Electric vehicles (EVs) use lithium-ion batteries to power the electric motor. These batteries offer large storage capacity and are optimized for repeated recharging, making them ideal for electric cars and e-bikes. Hybrid vehicles also combine a conventional combustion engine with an electric motor powered by rechargeable batteries.
- Energy storage: Batteries for renewable energy storage: Lithium-ion batteries or other accumulators are used in solar and wind power systems to store excess energy and make it available when energy generation is not possible (e.g., at night or in calm conditions). Lead-acid batteries are used in uninterruptible power supplies (UPS) to provide short-term energy during power outages and protect systems.
- Medical devices: Hearing aids, pacemakers, and implantable defibrillators use specially adapted lithium batteries, which must have a long service life and operate safely. Portable medical devices such as blood pressure monitors and insulin pumps are also often powered by batteries.
- Industry and emergency power: In telecommunications and data centers, galvanic cells are used as backup power systems (UPS) to ensure continuous power supply during an outage. Lead-acid batteries are widely used in forklifts and other industrial equipment that require rechargeable batteries.
- Fuel cells: Fuel cells, a special type of galvanic cell, are used in hydrogen-powered vehicles, space exploration, and stationary power generators. They generate electricity by reacting hydrogen and oxygen and are promising low-emission energy sources for the future of electromobility and decentralized power supply.
- Corrosion protection: Galvanic cells also play a role in corrosion protection of metals. For example, sacrificial anodes made of zinc or magnesium are attached to ship hulls, pipelines, or other metal structures to protect them from corrosion. The sacrificial anode corrodes instead of the protected metal, acting as a galvanic cell.
- Sensors and measuring devices: Galvanic oxygen sensors are used to measure the oxygen content in air or liquids. They are found in many industrial and medical applications, such as ventilators and laboratory instruments.
DiLiCo: Measuring Technology for Your Energy Converters
As a leading company in the field of measurement technology for electrochemical energy converters, DiLiCo Engineering offers you innovative solutions for numerous applications in which galvanic cells play a crucial role. Our expertise includes the development of measuring devices for fuel cells, redox flow batteries, and electrolyzers – key technologies of the hydrogen economy and sustainable energy storage.
Our customized monitoring systems for cell voltage and current density play a key role in optimizing the lifespan and efficiency of galvanic cells. Whether in research or industry, our technologies help you develop durable and powerful energy converters. With DiLiCo as your partner, you benefit from optimized performance, innovative cost-saving solutions, and increased reliability of your systems.
Our measurement technologies are particularly essential for analyzing cell voltage in stationary fuel cell systems or PEM electrolyzers. We make a valuable contribution to improving the efficiency and longevity of these systems. Trust DiLiCo Engineering for top-class measurement and analysis solutions in the field of electrochemical energy storage and conversion.