A Look into Batteries, Powering Everything from Devices to Renewable Energy

Batteries are a basic part of modern life, powering everything from smartphones and laptops to electric vehicles and large renewable energy storage systems. Batteries and similar devices accept, store, and release electricity on demand.

Modern batteries are classified into two main types: Primary Batteries and Secondary Batteries.

Primary batteries are single-use cells that cannot be recharged and must be disposed of once their lifespan is over. They typically have a high energy density and discharge more slowly. Primary batteries are the most common batteries available today because they are cheap and simple to use. Some examples of primary batteries are:

Dry Cell: dry cell is a type of electric battery, commonly used for portable electrical devices. Unlike wet cell batteries, which have a liquid electrolyte, dry cells use an electrolyte in the form of a paste, and are thus less susceptible to leakage.

Alkaline batteries: An alkaline battery is a type of disposable battery that generates energy through a chemical reaction between zinc metal and manganese dioxide. It gets its name from the alkaline electrolyte it contains, typically potassium hydroxide (KOH). Alkaline batteries are among the most commonly used batteries today, powering devices such as digital cameras, toys, and flashlights.

Silver-zinc batteries: These use a silver oxide cathode and a powdered zinc anode. These batteries are known for their long operational life and low self-discharge rate, meaning they lose their charge slowly over time. Silver-zinc batteries are often found in the form of button cells and are commonly used in devices like watches, cameras, and hearing aids.

Secondary Batteries are multicycle batteries, meaning we can recharge these batteries and use them many times. These kinds of batteries are mostly used in EVs, Phones, Automobiles, and Energy Storage Applications. Some examples of primary batteries are:

Lead Acid Battery: A lead-acid battery is a rechargeable battery that relies on lead and sulfuric acid to generate electricity. The lead plates are immersed in sulfuric acid, where a controlled chemical reaction occurs, producing electrical energy. When the battery is recharged, this chemical reaction is reversed, restoring the battery's charge. These batteries are commonly used in the starting system of cars, and home inverter battery applications.

Li-ion Battery: A lithium-ion battery is a type of rechargeable battery that is charged and discharged by lithium ions moving between the negative (anode) and positive (cathode) electrodes. Lithium-ion batteries are one of the most widely used types of rechargeable batteries in modern electronics. Found in everything from smartphones and laptops to electric vehicles and energy storage systems.

Solid-State Battery: Unlike traditional liquid-based batteries, solid-state batteries use solid electrolytes, which are safer and less prone to leakage or combustion. They promise higher energy densities, longer lifespans, and improved safety features. Solid-state batteries are still in the research and development stage, but they hold great potential for use in everything from consumer electronics to electric vehicles.

How do they Work?

The battery consists of four basic parts, the anode, cathode, electrolyte, and separator.

The anode is the electrode where electricity flows in. The cathode is the electrode where electricity flows out. An electrolyte is usually a liquid that an electric current can pass through and the separator is the membrane that separates the battery's anode and cathode.

To explain this, let's look at the most important battery technology in today’s world, lithium-ion battery.

Anode: Stores lithium, and releases lithium-ions when the battery is discharging (in-use). Graphite is the most commercially successful anode material for lithium-ion batteries.

Cathode: Stores lithium, and releases lithium-ions when the battery is charging.

Electrolyte: A liquid that acts as the transporter of lithium ions.

Separator: Allows the flow of lithium ions freely from anode to cathode while prohibiting the flow of electrons in the battery.

The basic working of the system is as follows: The anode and cathode store the lithium. The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator. The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered (cell phone, computer, etc.) to the negative current collector. The separator blocks the flow of electrons inside the battery.

While the battery is discharging and providing an electric current, the anode releases lithium ions to the cathode, generating a flow of electrons from one side to the other. When plugging in the device, the opposite happens: Lithium ions are released by the cathode and received by the anode.

Two key concepts related to batteries are energy density and power density. Energy density, measured in watt-hours per kilogram (Wh/kg), refers to the amount of energy a battery can store relative to its mass. Power density, measured in watts per kilogram (W/kg), indicates the amount of power a battery can deliver relative to its mass. To better understand these terms, imagine draining a pool: energy density is the size of the pool, while power density is how quickly you can empty it.