Session 1 - WordPress.com presentation Introduction to Battery Technology Page 3 Dr. B.H.S....

Session – 1

Session Name: Introduction to Battery Technology

Author Name: Dr. B. H. S. Thimmappa

Department: Chemistry

Subject/Course: Engineering Chemistry

Page 2 Ver: 1.01 Introduction to Battery Technology

Dr. B.H.S. Thimmappa Manipal Institute of Technology

Session Objectives

At the end of this session, the learner will be able to:

Illustrate the importance of batteries in life.

Define the following terms:

Cell

Battery

Charging

Recharging

Separator

Relate battery to different facts of daily life with suitable examples.

Describe the major features of commercial cells.

List the two major types of batteries.

Distinguish between primary and secondary battery.

Describe the working principle of dry cell.

List the various applications of dry cell.

Identify the advantages and disadvantages dry cell.

Teaching Learning Material

Board

Slide presentation

Introduction to Battery Technology Page 3 Dr. B.H.S. Thimmappa Manipal Institute of Technology

Session Plan

Time (in min)

Content Methodology Faculty

Approach Typical Student

Activity

Learning Outcomes (Blooms + Gardner’s)

15 Introduction to

Battery Technology

Questioning Brainstorming

Questions Facilitates

Participates Understands

Discusses

Understanding

Intrapersonal Interpersonal

Linguistic

05 Classification of Commercial Cells

Group Discussion Facilitates Questions

Understands Discusses

Understanding


Linguistic

10

Difference between Primary and Secondary

Batteries

Chalk and Talk Explains Understands

Observes

Understanding


Linguistic

15 Working of Dry Cell Presentation Explains Visualises Analyses

Analysis


Visual

10

Applications, Advantages and Disadvantages of

Dry Cell

Chalk and Talk Explains

Questions Understands

Understanding


Linguistic

05 Conclusion Recall the Keywords

Lists Facilitates

Recalls Answers Explains

Remembering Understanding

Interpersonal

Linguistic



Session Inputs

Introduction to Battery Technology

We can begin the session the introduction to battery

technology. This can be done by conducting an activity which

will help the learners understand the need for battery usage in

everyday life. We can also have a brainstorming session to

discuss the importance and properties of batteries.

Suggested Activity: Questioning

The faculty can divide the learners into two groups and ask them a

question which is as follows:

What is the justification of the blind man to carry a torch?

Expected answers can be:

For the people with their eyes wide open, who can fall on the blind man

during night time.

The faculty can summarise the above response and conclude that:

For a blind man, night and day are the same. But for person with all his

senses intact can still be ‘blind’. Blind person needs a torch, not because

he can see in the dark but because others should not dash him on the way.

Suggested Activity: Brainstorming

Brainstorming can be carried out to understand the importance and

properties of batteries expected for different applications.

We can choose one learner from each bench to represent learners in that

bench and ask these selected individual learners to list the various

applications of batteries they see in everyday life. The faculty can ask them

to think individually and come up with different features that are important

in specific applications within two minutes. The following set of questions

can be posed:

1. Name a few things that use battery?

2. Name a few properties of batteries for different applications?

We can write some of the interesting responses on the board and

consolidate the appropriate uses and different properties that play


important role in selected applications. Finally, the learners can be asked

to note down these examples and their expected features for particular

applications.

Responses from the learners may include the following:

Wall clock, wrist watch.

Motor vehicles, electronic vehicles.

Uninterruptible Power Supply (UPS) for computers, lawnmower.

Remote control, camcorders.

Laptop computers, calculators.

Cameras, battery operated gas lighter/bell.

Cell phones, children toys.

Cardiac pacemaker, hearing aids.

Key chain laser, emergency lighting.

Battery:

It is one of the key functional devices used in daily life for an

individual. It is a miniature chemical reactor that converts

chemical energy into electrical energy on demand or a device

that stores chemical energy that can be used as a source of

direct current when required. Battery is a combination of two or

more electrochemical cells arranged in series or parallel to

produce higher voltages.

Following are some pictures on various kinds of batteries.



Batteries come in many sizes reflecting their wide range of uses from

cars to computers

Creative visualization


The different manufacturers of batteries are Eveready, Duracell, Panasonic,

Exide, Sanyo and Toshiba.

Cell: A cell is a single arrangement of two electrodes and an electrolyte

capable of providing electricity due to redox reaction/free energy change

within the cell.

Discharging: It is an operation in which a battery delivers electrical energy to

an external load.

Charging: It is an operation in which the battery is restored to its original

charged condition by reversal of the current flow.

Separator: It is a physical barrier between anodes and cathodes in a battery

to prevent internal short-circuiting. Separators must be ionically conducting

but electronically insulating and inert in the battery environment.

A separator and a salt bridge have similar functions like:

i) To enable the populations of ions to stay electrically neutral.

ii) To make sure that no contact is made between reactants.

Importance of battery

Can you imagine a life without batteries? The wrist-watch or a wall clock

requires battery for them to work. The automobile starts with a battery to take

you to your workplace. As you know, battery is the backbone of UPS to run

your computers without interruption. The battery inside a remote control

helps you to change channels of a television. Similarly, laptops, cameras,

mobile sets, children toys, etc. need battery for their operation. Likewise, the

battery powers the heart pacemaker or key chain laser used as a teaching

aid. The lawnmower has a small engine that is electrically ignited by a

battery and spark plug.

The battery required to start a car must be capable of delivering a large

current for a short period of time which means short bursts of high energy. The

cardiac pace maker battery must be very small to provide minimal weight,

leak-proof, non-toxic and capable of delivering a small but steady current for

a long period of time. Longer and consistent back up is required in UPS

systems. A battery in the form of a flat flexible sheet is required for laptop

computers. The compact mass of the battery dictates much of the design for

portable electronic items. The ideal battery for every purpose would be

dependable, economical, lightweight, more efficient, flexibility of design,



longer design life and environmentally safe. We have to realise that the

perfect battery does not exist.

Classification of Commercial Cells

As we have had a detailed discussion on the introduction of

batteries, its importance and various applications, we can now

deal with the classification of commercial cells. This can be

done with the help of a group discussion.

Suggested Activity: Group Discussion

We can form four groups in the class and ask them to think of a few basic

requirements of the primary and secondary battery systems to generate

number of ideas. We can assign each group one type of device and ask

one representative from each group to present their list. The groups can be

asked to discuss the features of each type of device, compile the

responses in two minutes and present them to the rest of the class.

The responses from the learners can be written on the board without

repetitions. We can select those requirements that are relevant and

appropriate while incorrect ones can be erased. The activity can be

concluded by providing a comparative account of primary and

secondary batteries.

Primary Cells (Throw-away batteries or irreversible batteries):

These are galvanic Cells which produce electricity from chemicals that are

sealed into it when it is made. They cannot be recharged as the cell reaction

cannot be reversed efficiently by recharging. Once cell reaction has

reached equilibrium, cell must be discarded (‘dead’). These are used once

and then thrown away.

Example: Zinc–manganese dioxide cell, mercuric oxide–zinc cell and silver

oxide-zinc cell.

Secondary Cells (Rechargeable cells, storage cells, accumulators):

These are rechargeable by passing current through it. During charging, an

external source of energy reverses the spontaneous cell reaction and restores

the non-equilibrium mixture of reactants. After charging, cell can be used for

supplying current as the reaction sinks toward equilibrium again. We can

have large number of charge-discharge cycles. These can be recharged

and reused several times.


Example: Lead acid storage cell, nickel-cadmium cell, lithium ion battery

and nickel-metal hydride battery.

Basic requirements of primary cell:

• Compactness and lightweight.

• Fabricated from easily available raw materials.

• Cheaper cost of production (budget-friendly).

• High energy density and constant voltage.

• Being environmental properties (eco-friendly).

• Longer shelf life and discharge period.

• Leak proof containers and variety of design options.

• Colour and attractive appearance (cosmetic requirements).

Basic requirements of secondary cell:

• Long shelf-life in both charged and discharged conditions.

• Longer cycle-life and design-life.

• High power to weight ratio—low weight.

• Short time for recharging (quick recharge).

(Very quick charger, < 90minutes, X-Press charger, 90 minutes to 6 hours,

slow charger > 6 hours).

• Tolerance to service conditions (shock resistance).

• High voltage and high energy density.

• Aesthetically appealing design.

• Cause negligible pollution (leakage, gassing and toxicity).

• Explosion-resistant- some Li-ion batteries heat up very fast in laptops.

• Substantially lower maintenance.

• High operational reliability.

From the above discussion, we understand that, it is better to adopt as many

features as possible in the design of an ideal battery system for every

purpose. The composition of the battery changes as per the predetermined

characteristics and it is important to know the various types of battery

systems. The main challenges to watch out for in both the types can be

summarised in the form of 3Cs namely: Cost, Capital and Capacity.

Differences between Primary and Secondary Batteries

After the classification of commercial cells into primary and

secondary cells, we can now study the difference between

primary and secondary batteries. The facilitator can highlight the

similarities between the two types with suitable explanation.



Primary Batteries Secondary Batteries

1. Cell reaction is irreversible.

2. Must be discarded after its

active elements have been

consumed.

3. Have relatively short shelf life.

4. Function only as galvanic cells.

5. They cannot be used as energy

storage devices.

6. They cannot be recharged.

7. Gives low voltage during usage.

8. Example: Dry cell, Li

MnO2battery.

1. Cell reaction is reversible.

2. May be recharged several time

from an external Direct Current

(DC) source during its useful life.

3. Have very long shelf life.

4. Functions both as galvanic cells

and as electrolytic cells during

charging process.

5. They can be used as energy

storage devices (Example:

solar/thermal energy converted

to electrical energy).

6. They can be recharged.

7. Stable discharge profile.

8. Example: Lead acid battery, Ni-

Cd battery.

Similarities between Primary and Secondary Batteries

• Rechargeable batteries are available in exactly the same sizes

as disposable ones and replace them in all devices-

AA/AAA/C/D/9v.

• Chemical energy is stored in the form of electro-active

materials (High energy anodic and cathode materials).

• Produce electrical energy at the expense of stored-up

chemical energy.

• Both types are commercially exploited (available easily in the

market).

Working of Dry Cell

We have already understood the differences and similarities

between the primary and secondary batteries. We shall now deal

with the working of a dry cell. We can present some diagrams and

explain the concept to the learners in detail.

The faculty can describe the different components of a dry cell in the

construction section and explain the anode, cathode and net reactions in

the actual working of dry cell using slides. The images can help the learners


to have a dimensional visualisation and provide a link between pictures and

theoretical explanation.

Dry Cell (Leclanche’ Cell)…….Zn-MnO2 cell/Zinc-carbon batteries



Description:

• Anode: Cylindrical zinc metal container.

• Cathode: Graphite rod at the center.

• Electrolyte: Aqueous paste of NH4Cl and ZnCl2.

• Separator: Gel coated paper membrane.

• Nominal Cell Potential = 1.5 V.

NH4Cl used as a paste rather than as a dry solid

Solid ionic compounds do not conduct electricity-ions are firmly held by

strong electrostatic forces and cannot move. When NH4Cl is dissolved in

water-loosens its structure-ions are free to move and can carry an electric

current. The electrolyte is made mobile by having it as a paste.

How dry cell works?

Primary Electrode Reactions

Anode: Zn(s)→Zn2+(aq)+ 2e-

Cathode: 2MnO2(s) + H2O (l) + 2e- → Mn2O3 (s) + 2OH-(aq)

Net Reaction: Zn(s) + 2MnO2(s) + H2O (l) → Zn2+(aq)+Mn2O3(s)+2OH-(aq)

Secondary Reactions:

NH4+(aq)+ OH-(aq) → NH3(g) + H2O(l)

Zn2+(aq) + 2NH3(g) + 2Cl - → [Zn(NH3)2Cl2]

Cell Reaction: Zn + 2MnO2 + 2NH4Cl → [Zn(NH3)2Cl2] + H2O + Mn2O3

(Overall discharge reaction)

Explanation: At the anode, zinc atoms give up two electrons and become

positively charged zinc ions (Zn2+) as the cell discharges. At the cathode,

electrons reduce manganese from +4 oxidation state to +3 state (tetravalent

to the trivalent state) and hydroxyl ions react with ammonium chloride to

produce ammonia. The ammonia released at the cathode diffuses to the

anode where it reacts with zinc ions to form the stable complex, [Zn (NH3)2

Cl2]. It cannot be recharged as the primary product Zn2+ is irretrievably

converted into a stable complex. The dry cell delivers a nominal voltage of

1.5 V due to primary electrode reactions and falls to 0.8 V as the reaction

products accumulate inside.


Applications, Advantages and Disadvantages of Dry Cell

Having learnt the construction and working of a dry cell it is time

to list several actual applications along with specific advantages

and disadvantages of a dry cell.

Applications

1. In small portable appliances where small amount of current is needed

such as flashlights, transistor radios, calculators and children toys.

2. In consumer electronic devices where the power drain is not too heavy

such as quarts wall clocks, walkman, remote controls and flashlights.

Advantages

1. Dry cell is inexpensive, widely available (pent arch cell at 8 rupees).

2. Normally works without leaking (leak proof cells).

3. Has a high energy density.

4. It is not toxic and low environmental impact on disposal.

5. It contains no liquid electrolytes.

Disadvantages

1. Voltage drops during use due to build up of reaction products around the

electrodes when current is drawn rapidly from it. There is a drop in

electrolyte concentration around the cathode and the time required for

the Mn2O3 to diffuse away from the cathode. So it is not suitable for use in

a photoflash unit of a camera, that is, inefficient at high current drain.

2. It has limited shelf life because the zinc is corroded by the acidic

ammonium chloride. Consequently, zinc container disintegrates and the

paste leaks out through the outer covering (shelf-life is 6-8 months). So do

not forget to look at the manufacturing date before buying (check the

expiry date!).

3. They cannot be used once they get discharged. An attempt to recharge

results in explosion and fire hazards.

4. Its Electro Motive Force (EMF) decreases during use as the active material

is consumed and falls to 0.8V as the reaction products accumulate inside.

If unused for a while the cell spontaneously rejuvenates as we allow the

products to diffuse away from the electrodes.

5. The service life of the battery is short (approximately1.5 years).



Conclusion

As we have gone through the application, advantages and

disadvantages of a dry cell, we can now conclude the session

with the help of an activity called recall by keywords.

Suggested Activity: Recall by Keywords

The faculty can divide the class into three groups—Group 1, 2 and 3. The

groups will be allotted with some topics discussed in the session. Each

group can have a discussion among themselves and one person from

each group shall volunteer to come up on stage and explain the key points

of that topic to the rest of the class.

The group that covers all the key points of the topic shall be rewarded.

Some of the topics to be given can be as follows:

1. Battery

2. Examples of batteries used in everyday life.

3. Primary battery.

4. Secondary battery.

5. Advantages and disadvantages of a battery.

The expected answers can be:

1. A battery is a source of direct current, which flows in one direction

2. Examples of batteries in everyday life include the following:

Automobile—lead storage battery, flash lights, radios, camera,

calculators—dry cells, Space vehicles—fuel cells.

3. Primary batteries irreversibly transform chemical energy to electrical

energy. Once the initial supply of reactants is exhausted, energy cannot

be readily restored to the battery by electrical means.

4. Secondary batteries can have the chemical reactions reversed by

supplying electrical energy to the cell, restoring their original

composition.

5. As the electrochemical reactions are electrically reversible in a

secondary it should in principle be possible use it for ever. But a

rechargeable battery has limited design life because of the following

reasons.

Abuse—not used properly.

Separator failure—heat generated by charging current.

Degradation of the active material (swelling, shrinking and breaking

up) failures as a consequence of mechanical or thermo-mechanical

stresses—normal ageing process of cycling.

Corrosion of the metallic electrodes over a period of time.


Summary

In this session, we learnt to:

Illustrate the importance of batteries in life.

Define the following terms:

Cell

Battery

Charging

Recharging

Separator

Relate battery to different facts of daily life with suitable examples.

Describe the major features of commercial cells.

List the two major types of batteries.

Distinguish between primary and secondary battery.

Describe the working principle of dry cell.

List the various applications of dry cell.

Identify the advantages and disadvantages dry cell.



Assignment

1. What is the purpose of separator in a commercial cell?

2. What are the basic commercial requirements for a primary and

secondary cells?

3. Account for the following:

i) Primary cells should not be recharged.

ii) The dry cell has limited shelf life.

iii) Secondary battery has finite lifespan.

4. Distinguish between the following:

i) Cell and battery ii) Charging and discharging

5. Write the anode active material and cathode active material in the dry

cell.

6. Explain why a paste of ammonium chloride is used in a dry cell although

dry solid is an ionic compound.

7. Explain the meaning, importance and impacts of batteries in our day-to-

day lives.

8. Comment on the following statements, which may be either true or false.

(i) Dry cell cannot be used in the photoflash unit of a camera.

(ii) Secondary battery in practice has limited life.

9. State and explain the similarities and differences between the primary

and secondary batteries.

10. Construct a working cell model using the readily available materials and

measure the voltage output using voltmeter.


References

L. Dingrando, K. Tallman, N. Hainen, N. C. Wistrom, Chemistry: Matter and

Change, New York, McGraw-Hill, 2007, pp 662695.

Clive, D. S. Tuck, Modern Battery Technology, Ellis Horwood, New York,

1991

D. Linden, T.B. Reddy, Ed, Handbook of Batteries, 3rd edition, McGraw-Hill,

New York, 2002.

H.A. Kiehne, Battery Technology Handbook, CRC Press, McGraw-Hill, New

York, 2003.

www.tinhoahoc.com/Battery/cr020730k.pdf

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