battery is a device consisting of one or more electrochemical cells with external connections[1] for powering electrical devices such as flashlightsmobile phones, and electric cars. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal. When a battery is connected to an external electric load, a redox reaction converts high-energy reactants to lower-energy products, and the free-energy difference is delivered to the external circuit as electrical energy. Historically the term “battery” specifically referred to a device composed of multiple cells, however the usage has evolved to include devices composed of a single cell.


Categories and types of batteries


Batteries are classified into primary and secondary forms:

  • Primarybatteries are designed to be used until exhausted of energy then discarded. Their chemical reactions are generally not reversible, so they cannot be recharged. When the supply of reactants in the battery is exhausted, the battery stops producing current and is useless.[22]
  • Secondarybatteries can be recharged; that is, they can have their chemical reactions reversed by applying electric current to the cell. This regenerates the original chemical reactants, so they can be used, recharged, and used again multiple times.[23]

Some types of primary batteries used, for example, for telegraph circuits, were restored to operation by replacing the electrodes.[24] Secondary batteries are not indefinitely rechargeable due to dissipation of the active materials, loss of electrolyte and internal corrosion.



Primary batteries, or primary cells, can produce current immediately on assembly. These are most commonly used in portable devices that have low current drain, are used only intermittently, or are used well away from an alternative power source, such as in alarm and communication circuits where other electric power is only intermittently available. Disposable primary cells cannot be reliably recharged, since the chemical reactions are not easily reversible and active materials may not return to their original forms. Battery manufacturers recommend against attempting to recharge primary cells.[25] In general, these have higher energy densities than rechargeable batteries,[26] but disposable batteries do not fare well under high-drain applications with loads under 75 ohms (75 Ω). Common types of disposable batteries include zinc–carbon batteries and alkaline batteries.



Secondary batteries, also known as secondary cells, or rechargeable batteries, must be charged before first use; they are usually assembled with active materials in the discharged state. Rechargeable batteries are (re)charged by applying electric current, which reverses the chemical reactions that occur during discharge/use. Devices to supply the appropriate current are called chargers.

The oldest form of rechargeable battery is the lead–acid battery, which are widely used in automotive and boating applications. This technology contains liquid electrolyte in an unsealed container, requiring that the battery be kept upright and the area be well ventilated to ensure safe dispersal of the hydrogen gas it produces during overcharging. The lead–acid battery is relatively heavy for the amount of electrical energy it can supply. Its low manufacturing cost and its high surge current levels make it common where its capacity (over approximately 10 Ah) is more important than weight and handling issues. A common application is the modern car battery, which can, in general, deliver a peak current of 450 amperes.

20th Century Rechargeable Batteries

In the 1970s, COMSAT developed the nickel-hydrogen battery for use in communication satellites. These batteries store hydrogen in a pressurized, gaseous form. Many man-made satellites, like the International Space Station, still rely on nickel-hydrogen batteries.

The research of several companies since the late 1960s resulted in the createion of the nickel-metal hydride (NiMH) battery. NiMH batteries were released to the consumer market in 1989, and provided a smaller, cheaper alternative to the rechargeable nickel-hydrogen cells.

Asahi Chemical of Japan built the first lithium-ion battery in 1985, and Sony created the first commercial lithium-ion battery in 1991. In the late 1990s, a soft, flexible casing was created for lithium-ion batteries and gave rise to the “lithium polymer” or “LiPo” battery.

How they work ?


Batteries generally require several chemical reactions in order to operate. At least one reaction occurs in or around the anode and one or more reactions occur in or around the cathode. In all cases, the reaction at the anode produces extra electrons in a process called oxidation, and the reaction at the cathode uses the extra electrons during a process known as reduction.

When the switch is closed, the circuit is complete, and electrons can flow from the anode to the cathode. These electrons enable the chemical reations at the anode and cathode.

In essence, we are separating a certain kind of chemical reaction, a reduction-oxidation reaction or redox reaction, into two separate parts. Redox reactions occur when electrons are transferred between chemicals. We can harness the movement of electrons in this reaction to flow outside the battery to power our circuit.

Anode Oxidation

This first part of the redox reaction, oxidation, occurs between the anode and electrolyte, and it produces electrons (marked as e).

Some oxidation reactions produce ions, such as in a lithium-ion battery. In other chemistries, the reaction consumes ions, like in the common alkaline battery. In either case, ions are able to flow freely through the electrolyte where electrons cannot.

Cathode Reduction

The other half of the redox reaction, reduction, occurs in or near the cathode. Electrons produced by the oxidation reaction are consumed during reduction.

In some cases, like lithium-ion batteries, positively charged lithium ions produced during the oxidation reaction are consumed during reduction. In other cases, like alkaline batteries, negatively charged ions are produced during reduction.

Electron Flow

In most batteries, some or all of the chemical reactions can occur even when the battery is not connected to a circuit. These reactions can impact a battery’s shelf life.

For the most part, the reactions will only occur at full force when an electrically conductive circuit is completed between the anode and cathode. The less resistance between the anode and cathode, the more electrons are allowed to flow, and the quicker the chemical reactions occu






use-cases around us,

Uses of Battery includes providing backup power during power outage. At home, the batteries are typically wired to electrical appliances. If power goes down these appliances still receives power. For example, many customers have energy rates that changes based on the time of the day. Batteries can help these customers manage their energy by storing energy during low cost times and discharging energy during high cost times. Batteries can store energy from solar and wind and discharge it when it is needed the most.

Applications and uses of batteries are given below:

  • House
  • Health Instruments
  • Medical
  • Logistics and construction
  • Firefighting and Emergency
  • Military

Batteries are used inside the House

Disposable batteries power things like remote controls, torch lights etc. Rechargeable batteries such as alkaline batteries are used in digital cameras, handheld video game consoles, cellphones and many more. Advanced batteries like lithium batteries power appliances that draw too much power such as laptops and other devices.

It is used in Health Instruments

Artificial limbs, hearing aids, insulin pumps, valve assistance devices uses batteries. Mercury battery can be useful for photographic light meters and electronic devices such as real time clock of appliances.

Uses of Batteries in Medical

ECG heart monitor are hooked up with battery so that it can be moved with the patient and is always ON for showing the patient’s vitals. In hospitals, rechargeable batteries such as lithium- ion batteries and nickel-cadmium batteries are used.

These are used in Logistics and Construction

Heavy duty batteries are used to power devices such as forklift because exhaust fumes and carbon monoxide while combustion might prove dangerous in confined work areas. Lead acid battery is used for starting, lighting and ignition of automobiles.

These are used in Firefighting and Emergency Response

Batteries are used in radios which is very important for emergency response. These radios use large batteries in order to hold large charge. ECGs, flashlights and even metal or fire detectors use batteries. Everyday these devices help to save lives.

Batteries use in Military Operations

Batteries power the radios which are used to communicate. Even the night vision, infrared goggles are powered by batteries. Lithium provides much longer life to devices and silver oxide batteries are used in military and submarines.

These were some applications and uses of battery, if you wish to know more, download BYJU’S The Learning App.


Disposing of used batteries

The Environmental issues

The average household uses 21 batteries a year. The UK generates 20 – 30,000 tons of waste general purpose batteries every year, but less than 1,000 tons are recycled.

In 2001 we bought 680 million batteries in the UK.  Most of these (89%) were general-purpose batteries.  This amounted to almost 19,000 tonnes of waste general purpose batteries requiring disposal in the UK.

Currently, only a very small percentage of consumer disposable batteries are recycled (less than 2%) and most waste batteries are disposed of in landfill sites. The rate for recycling of consumer rechargeable batteries is estimated to be 5%.

Whilst the exact chemical make-up varies from type to type (see below), most batteries contain heavy metals, which are the main cause for environmental concern. When disposed of incorrectly, these heavy metals may leak into the ground when the battery casing corrodes.  This can contribute to soil and water pollution and endanger wildlife. Cadmium, for example, can be toxic to aquatic invertebrates and can bio-accumulate in fish, which damages ecosystems and makes them unfit for human consumption. Some batteries, such as button cell batteries, also contain mercury, which has similarly hazardous properties.  Mercury is no longer being used in the manufacture of non-rechargeable batteries, except button cells where it is a functional component.  The major European battery suppliers have been offering mercury-free disposable batteries since 1994.


Recycling batteries

An increasing number of householders recognize the residual value of spent batteries and separate them from their general household waste for recycling.  A number of local authorities now collect waste household batteries in curbside collections.  Rechargeable batteries can also be recycled once they have reached the end of their useful lives.

Batteries contain a range of metals which can be reused as a secondary raw material. There are well-established methods for the recycling of most batteries containing lead, nickel-cadmium, nickel hydride and mercury. For some, such as newer nickel-hydride and lithium systems, recycling is still in the early stages.

UK’s first battery dedicated recycling plant for household batteries was recently opened in West Bromwich. It is estimated it will be able to recycle up to 1800 tonnes per year; the opening of this plant is expected to stimulate a significant increase in domestic battery recycling rates in the UK.

What can we do to help?

  • Use the mains rather than batteries when possible.
  • Turn off battery-driven appliances when not in use
  • Use rechargeable batteries and a battery charger. This saves energy because the energy needed to manufacture a battery is on average 50 times greater than the energy it gives out.
  • However, rechargeable batteries are not suitable for smoke alarms as they tend to run out suddenly, preventing the alarm from warning when battery power is low.
  • Opt for appliances that can use power derived from the sun via solar panels or from a winding mechanism, e.g. radios, mobile phone wind-up chargers