How Do Batteries Work?

By Stefano Tommasone Ph.D.Reviewed by Lexie CornerMar 3 2025

Batteries store and convert chemical energy into electrical energy through electrochemical reactions. They are a critical power source for modern electronics, from smartphones and laptops to electric vehicles.

Their widespread use supports portable electronics, grid energy storage, and transportation electrification, making them essential in reducing fossil fuel reliance and advancing clean energy solutions. Understanding battery operation and performance factors is key to improving efficiency, durability, and energy output.^[1]

Image Credit: gunawand3570/Shuttestock.com

How Batteries Generate Electricity

A battery consists of four main components:

• Anode – Typically made of reactive materials like lithium or zinc, the anode undergoes oxidation, releasing electrons.
• Cathode – A material capable of accepting electrons, the cathode undergoes reduction during battery discharge.
• Electrolyte – A chemical medium (e.g., potassium hydroxide, ammonium chloride) that enables ion movement to maintain charge balance.
• Separator – A porous barrier that prevents direct contact between the anode and cathode while allowing ions to pass through, ensuring safe battery operation.

During discharge, electrons move from the anode to the cathode through an external circuit, creating an electric current that powers devices. This process relies on redox (reduction-oxidation) reactions: the anode reacts with the electrolyte, releasing electrons, while the cathode simultaneously accepts them, completing the circuit.

The specific electrode and electrolyte materials determine a battery’s voltage, capacity, and efficiency. For example, in common alkaline batteries, the zinc anode oxidizes into zinc oxide, while manganese dioxide at the cathode is reduced to manganese oxide, with potassium hydroxide acting as the electrolyte.^[2]

Types of Batteries and Their Functioning

Batteries fall into two main categories: primary (single-use) and secondary (rechargeable).

Primary batteries cannot be recharged once depleted. These include:

• Alkaline batteries: Commonly found in remote controls, wall clocks, and flashlights.
• Lithium metal batteries: Used in medical implants and smoke detectors. They offer higher voltage (3.0V vs. 1.5V), lower self-discharge rates, and a longer lifespan than alkaline and zinc-carbon batteries.

In contrast, secondary batteries are rechargeable, allowing multiple charge-discharge cycles. These include: 

• Lithium-ion batteries (LIBs): Widely used in smartphones, laptops, and electric vehicles, LIBs have revolutionized portable electronics due to their high energy density and long cycle life.
• Lead-acid batteries: Common in automotive applications, they provide reliable power but are bulkier and have a shorter lifespan than LIBs.
• Nickel-metal hydride (NiMH) batteries: These are found in hybrid vehicles and rechargeable AA batteries. They offer a more environmentally friendly alternative to older nickel-cadmium (NiCd) batteries.
• Lithium-sulfur batteries: They use sulfur-based cathodes, offering a lower environmental impact since sulfur is widely available, inexpensive, and more sustainable than critical metals like cobalt or nickel. As a result, they are being explored for future energy storage applications.
• Solid-state batteries: Featuring a lithium metal anode, a layered oxide cathode, and a solid electrolyte, these batteries promise higher energy density and improved safety. They are a strong candidate for electric vehicles and portable electronics, though mass production costs and scalability remain challenges.

Charging and Discharging

During discharge, a battery converts stored chemical energy into electrical energy. Electrons move from the anode to the cathode through an external circuit, while ions in the electrolyte maintain charge balance.

For rechargeable batteries, this process is reversed during charging. Electrical energy forces electrons back to the anode, restoring the battery’s original chemical state. This cycle is crucial for lithium-ion and lead-acid batteries, which are widely used in energy storage and transportation.

Factors Affecting Battery Performance

Several factors influence battery performance and lifespan. Temperature fluctuations are among the most significant, as extreme heat accelerates chemical degradation, while low temperatures slow ion movement, reducing efficiency and capacity.^[3]

Battery capacity—the amount of charge a battery can store—declines over time due to repeated charge cycles. This degradation is also influenced by electrode materials and design, which directly impact overall performance. Charging speed and depth of discharge play a critical role as well. Overcharging or deep discharging can degrade battery materials, while charging at excessively high rates shortens lifespan. Similarly, rapid discharge reduces a battery’s energy storage capacity and long-term stability.

Batteries naturally lose charge over time through self-discharge, caused by internal chemical reactions.^[4] Additionally, internal resistance leads to energy loss as heat, further reducing efficiency. Minimizing internal resistance is crucial for maximizing battery performance and durability.

As demand for more efficient and longer-lasting batteries grows, researchers are exploring new materials, electrode compositions, and battery designs. Shirley Meng, Liew Family Professor at the Pritzker School of Molecular Engineering at the University of Chicago, highlights the importance of often-overlooked factors in battery performance, stating:

There is a gap in understanding the grain orientation, also known as texture, and how such a factor impacts rechargeable metal battery performance.

Recent research has shown that adjusting the texture of soft metal anodes, such as lithium and sodium, can improve charge and discharge efficiency. Minghao Zhang, a Research Associate Professor and lead author of a recent study, explains:

In our work, we discovered that adding a thin layer of silicon between lithium metal and the current collector helps create the desired texture. This change improved the battery’s rate capability by nearly ten times in all-solid-state batteries using lithium metal.

These insights are driving innovation in next-generation battery materials, with a focus on faster charging, improved energy storage, and increased lifespan.

Additionally, researchers are working on eco-friendly battery designs and more efficient recycling methods to enhance sustainability and reduce environmental impact.^[6]

For more information on recent battery advancements, please see:

• Gelatin–Organic Acid-Based Biodegradable Batteries for Stretchable Electronics
• What Are Proton Batteries and How Do They Work?
• Understanding and Mitigating Silicon Anode Swelling in Modern Batteries
• Advanced AFM Techniques Revolutionize Battery Research: ResiScope Takes Center Stage
• High-Performance Aqueous Zinc-Ion Batteries with Mo1.74CTz MXene Cathode
• Nanoporous Helium-Silicon Co-Deposited Anodes for Lithium-Ion Batteries

References and Further Reading

1. Njema, GG., Ouma, RB. O., Kibet, JK. (2024). A Review on the Recent Advances in Battery Development and Energy Storage Technologies. Journal of Renewable Energy.https://doi.org/10.1155/2024/2329261. Available: https://onlinelibrary.wiley.com/doi/abs/10.1155/2024/2329261
2. Nzereogu, PU., Omah, AD., Ezema, FI., Iwuoha, EI., Nwanya, A. C. (2022). Anode materials for lithium-ion batteries: A review. Applied Surface Science Advances. https://doi.org/10.1016/j.apsadv.2022.100233. Available: https://www.sciencedirect.com/science/article/pii/S2666523922000253
3. Battery Degradation [Online]. Exro Technologies Inc. Available: https://www.exro.com/industry-insights/battery-degradation-explained [Accessed 11/02/2025].
4. Bruj, O., Calborean, A. (2025). Lifecycle Evaluation of Lithium-Ion Batteries Under Fast Charging and Discharging Conditions. Batteries. Available: https://www.mdpi.com/2313-0105/11/2/65
5. Zhang, M., et al. (2025). Grain Selection Growth of Soft Metal in Electrochemical Processes. Joule. doi.org/10.1016/j.joule.2025.101847
6. Itani, K., De Bernardinis, A. (2023). Review on New-Generation Batteries Technologies: Trends and Future Directions. Energies. Available: https://www.mdpi.com/1996-1073/16/22/7530

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