Batteries: Types, Cells, Functions & Uses

Batteries are electrochemical devices, which contain one or more electrochemical cells and can be charged with an electric current. Batteries can be discharged whenever required.

• Batteries are devices composed of multiple electrochemical cells connected to external inputs and outputs.
• It is widely used to power small electric devices, including mobile phones, remotes and flashlights.
• Historically, the term ‘battery’ has been used to refer to a combination of two or more electrochemical cells.
• However, the modern battery definition only applies to accommodate devices featuring a single cell.
• Batteries can be classified into two types, namely primary batteries and secondary batteries. 
• Alessandro Volta is responsible to create the first electric battery.

Key Terms: Nernst Equation, Standard Electrode Potential, Temperature, Electricity, Metals, Oxidation, Reduction, Cell, Battery, Electrochemistry

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What is a Battery?

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A battery is a collection of electrochemical cells that serves as a source of energy. An oxidation-reduction reaction is the foundation of an electrochemical cell.

The following properties must be present in a practical or useful battery:

• It has to be light-weight and small in size.
• A consistent voltage must be provided by the cell or battery. Furthermore, while using, the battery or cell's voltage must not change.

Terms Related to Batteries

Some important terms related to batteries include:

• Power Capacity: It is the energy stored in a battery and can be measured in Watt-hour.
• Power Capability: It can be defined as the maximum amount of current a battery is capable of delivering. It is also termed C-rating.
• Nominal Voltage: Nominal voltage is when the voltage of the battery is constant and is not variable.
• Charging Current: Charging Current can be defined as the maximum amount of current which can be applied to a battery to charge.
• Charging Voltage: It can be defined as the maximum amount of voltage which needs to be applied to the battery to charge it effectively.
• Discharging Current: It is the maximum current which can be drawn out of the battery, thus delivering to load. In case the current drawn overextends the stated discharging current, the battery might start to drain up fast, causing it to heat up.
• Shelf Life: The shelf-life can be expressed as the time for which the battery can stay powered up and usable. It can be found in non-rechargeable batteries since they are for single usage.
• Cut-off Voltage: The voltage for which the battery might get considered as completely discharged is the cut-off voltage.
• Cycle Life: In case a battery is completely charged but discharges to 80% of its original capacity, then it had a complete cycle. The number of cycles a battery is seen to complete is defined as the cycle life.

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Types of Batteries

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There are two types of batteries or practical cells used in commercial values. These are the following:

• Primary battery
• Secondary battery

Primary Cell

Power is generated via a chemical reaction in the primary cells. The reaction is only one-way in this case. We will not be able to reverse this phenomenon. As a result, these cells die after a certain period. A primary cell cannot be reused or recharged. Daniell cell, Dry cell, and Mercury cell are examples of primary cells.

Daniell Cell

A copper vessel holds a concentrated solution of copper sulphate in the Daniell cell. In the copper vessel containing copper sulphate solution, a porous pot containing dilute sulphuric acid is placed.

Daniell Cell

Dilute sulphuric acid is used to dip a zinc rod. Here, the Zinc electrode acts as an anode, while the copper container acts as a cathode. The following are the reactions that occur in the cell:

At anode: Zn(s) →Zn²⁺(aq) + 2e-

At cathode: Cu²⁺(aq) + 2e- →Cu(s)

Net cell reaction: Zn(s) + Cu²⁺(aq) →Cu(s) + Zn²⁺(aq)

The cell may be represented as,

Zn(s) | Zn²⁺(aq) || Cu2+(aq) | Cu(s)

   (anode)                        (cathode)

The emf of a Daniell cell is 1.1 V.

Dry Cell

The dry cell is a compact version of the LeClanche cell. It comprises a zinc outer container that serves as an anode. A porous insulating paper is used to line the zinc content of the cell from the inside. A carbon rod with a brass cover serves as the cathode.

Dry Cell

Between the cathode and the anode, a gap is filled with a mixture of MnO₂, a thick paste of ammonium chloride (NH₄Cl), zinc chloride (ZnCl₂), and charcoal. The porous paper lining keeps the zinc container from coming into direct contact with the paste. It performs the function of a salt bridge. Pitch or wax is used to seal the cell from the top.

Reactions that occur during the discharge:

At anode: Zn(s) →Zn²⁺+ 2e-

Zn²⁺ ions move towards the carbon electrode (cathode). At the cathode, the reaction is

At cathode: MnO₂+ NH⁴⁺+ e- → MnO (OH) + NH₃MnO₂

It has a depolarizing effect. In a cathodic reaction, the state of manganese is lowered from + 4 to + 3. The ammonia molecules generated at the cathode combine with Zn²⁺ ions from the anode to form Zn(NH₃)₄²⁺, a complex ion. The absorption of Zn²⁺ by NH₃ molecules lowers the concentration of free Zn²⁺, causing the cell's voltage to rise. The potential of a dry cell is roughly 1.5 volts.

Mercury Cell

The mercury cell is a relatively new product available in the market. It provides a more consistent voltage. The Mercury Cell's emf is 1.35 V. The mercury cell is usually more expensive. This is why they are only found in high-tech devices such as cameras, hearing aids, and wristwatches.

Mercury Cell

In a Mercury cell, an amalgamated zinc plate with a steel top plate serves as the anode. The cathode is a mixture of mercury, mercury oxide, and carbon powder. The outer steel case comes into contact with it. The electrolyte is a KOH paste containing Zn(OH)₂.

This paste is carried by an inert porous substance. A neoprene rubber insulating seal separates the two electrodes. During discharge, the following reactions occur:

At anode: Zn(Hg) + 2OH^- →Zn (OH)₂ + 2e-

At cathode: HgO + H₂O + 2e- →Hg + 2OH^-

Overall reaction: Zn(Hg) + HgO(s) →Zn(OH)₂+ Hg(l)

Secondary Cell

The secondary cells, on the other hand, are the cells that perform repeated actions. After each use, these batteries can be recharged. The cells are recharged by passing electricity through them.

As a result, you can reuse these cells multiple times. Secondary cells include the lead-acid cell (or lead-acid battery), nickel-cadmium cell, and others.

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Lead Acid Battery

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Each battery is made up of several voltaic cells that are connected in series. A 6 to 12-volt battery is usually made up of three to six of these cells.

• The cathode is a grid of lead packed with PbO₂ and the anode is a grid of lead packed with finely divided spongy lead.
• The electrolyte is a sulphuric acid aqueous solution.
• At the anode, lead is oxidized to Pb²⁺ ions, resulting in the formation of insoluble PbSO₄. PbO₂ is reduced to Pb²⁺ ions and PbSO₄ is formed at the cathode.

Lead acid battery

The lead acid battery undergoes the following reactions:

At Anode

The lead oxidizes to Pb²⁺ ions after losing two Electrons.

Pb(s)→ Pb₂+ (aq) +2e-

Pb₂+ (aq) + SO₄^2- (aq) → PbSO₄(s)

The anode reaction as a whole can be written as:

Pb(s) + SO₄^2- (aq) → PbSO₄(s) + 2e-

At Cathode

The PbO₂ is reduced as the following:

PbO₂ (s) + 4H⁺ +2 e¯¯ ———-> Pb²⁺ (aq) + 2 H₂O

PbO₂ (s) + SO₄^2- (aq) →PbSO₄(s)

The cathode reaction as a whole can be written as :

PbO₂ (s) + 4H⁺ +2e- + SO₄^2- (aq) → PbSO4(s) + 2 H₂O

Pb(s) + SO₄^2- (aq)→ PbSO₄(s) + 2e-

PbO₂ (s) + 4H⁺ +2e- + SO4^2- (aq) → PbSO₄(s) + 2H₂O

Pb(s) +PbO₂(s) + 2 H2_SO₄ (aq) → 2 PbSO₄(s) + 2H₂O

PbSO₄ is generated at each electrode during the operation of the cell, and sulphuric acid is consumed. As a result, the density of the solution falls, and the concentration of H₂SO₄ decreases.

Recharging the Battery

By passing an electric current of an appropriate voltage in the opposite direction, the cell can be charged. The reaction between the electrodes is reversible. As a result, the electron flow is reversed, and lead is deposited on the anode while PbO₂ is deposited on the cathode. Sulphuric acid's density rises as well.

The reaction could be written as follows:

2PbSO₄ (s)+2H₂O →Pb(s) + PbO₂ (s) +2H₂SO₄

It functions as a voltaic cell and generates electric energy when used to start an automobile's engine. It functions as an electrolytic cell when recharging.

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Nickel-Cadmium Battery Cell

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This is a rechargeable cell as well. It has a longer life than a lead acid battery, but it is more expensive. However, because it is smaller and lighter, it offers some advantages. It can be found in cordless and portable devices.

• It is made up of a cadmium anode and a metal grid with NiO₂ as a cathode.
• KOH is the electrolyte in this cell.

During discharge and charge, the following reactions occur:

Anode

Cd(s)+2OH - CdO(s) +H₂O(l) + 2e-

Cathode

2NI(OH₃) (s) + 2e- → 2Ni(OH)₂(s) +2OH- (aq)

Cd(s) + 2Ni(OH₃) (s) → CdO(s) + 2Ni(OH)₂(s) + H₂O(l)

Recharging the cell allows the reaction products to adhere to the electrodes and be reconverted. The charging procedure is comparable to that of a lead-acid battery.

It generates a potential of around 1.4 volts.

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Lithium-Ion Battery

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The lithium-ion battery, which is also called LIB, can be defined as a type of secondary battery that can be recharged. 

• During the discharging process, the lithium ions pass from the negative electrode to the positive electrode (via the help of an electrolyte).
• These lithium ions travel back while charging. Lithium-ion batteries use intercalated lithium compounds in the positive electrode.
• In the negative electrode (as fuel) graphite is used.

Some characteristics of LIBs include:

• The lithium-ion battery is very stable and safe. It also has a very high energy capacity.
• LIBs can be used in mobile phones and portable laptops and tablets.
• It has a very slow self-discharge.

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Fuel Cells

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The Fuel cells are voltaic cells with a constant supply of reactants to the electrodes. These are intended to immediately transform the energy generated by the combustion of fuels such as H, CO, CH₄, and others into electrical energy.

1) In this cell, hydrogen and oxygen are bubbled into concentrated aqueous sodium hydroxide or potassium hydroxide via a porous carbon electrode.

2) The fuel (hydrogen) is supplied into the anode compartment and oxidized.

3) The oxygen is supplied into the cathode chamber and reduced there.

The following reaction takes place:

Anode

2[H₂(g) + 2OH^-(aq) →2H₂O(1)+2^e-]

Cathode

O₂(g) + 2H₂O(l) + 4^e-  →4OH^-(aq)

2H₂(g) +O₂(g) → 2H₂O (l)

Each electrode is constructed of porous compressed carbon with a small amount of catalyst embedded in it (Pt, Ag, or CoO). These fuel cells are more efficient than traditional methods of generating electricity on a wide scale by burning hydrogen and carbon fuels. The energy of the fuel is instantly converted into electricity via cells.

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Function of battery

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The storage of energy in a battery, along with its transformation from one form to another one is called electrochemistry. An electrochemical cell supports the battery's functioning.

The functions of the battery include:

• A battery helps to supply electricity to a variety of electronic devices.
• It helps to store chemical energy and converts it to electrical energy.
• It functions as a voltage regulator.

Facts Related to Batteries

Batteries are of different forms, sizes, and voltages. Thus, some facts about it are:

• Batteries are relatively more expensive than mains power. However, the main power does not suit for mobile devices.
• Bicycles feature taillights that are seen to be powered by batteries
• Hand and foot generators can potentially be used as a replacement for batteries. However, they are extremely demanding.
• Fuel cells and solar cells do not fall under the category of batteries because they do not store energy,
• A Capacitor should not be confused with a battery. It is because it does not store energy in the chemical process.

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Uses of Battery 

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Some of the uses of batteries include"

• It is used in home appliances as well as medical devices
• It is also widely used in Construction.
• It is used in a variety of places, including military operations and firefighting.
• The battery is most prevalently used in automobiles.

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Things to Remember

• Batteries are devices that are made up of several electrochemical cells connected to external inputs and outputs.
• Batteries are widely used to offer power to small electric devices, which extensively include mobile phones, remotes, and flashlights.
• The battery is used in automobiles,  home appliances and medical devices.
• Batteries are mainly of two types, namely primary batteries and secondary batteries. 
• Fuel cells and solar cells are not batteries because they do not store energy,

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Previous Year Questions

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2. 1C electricity deposits​
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4. Which of the following processes occurs in the electrolysis of an aqueous solution of nickel chloride at nickel anode...?​
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7. The value of the dissociation constant of the acid at the given concentration at 25∘C is...​
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