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•Define a battery
•State five practical applications of batteries
•What is electrolysis?
•What is an electrolyte?
•What are positive and negative terminal are
called?
•Make a labelled sketch of a simple cell
•What is a difference between primary and a
secondary cell? name two types and three
applications of each.
Secondary (Rechargeable)
Batteries
• Nickel cadmium
• Nickel metal hydride
• Alkaline
• Lithium ion
• Lithium ion polymer
• Lead acid
Lead acid battery;
• Invented by French physicist GASTAN PLANTE
• Oldest rechargeable battery
• Nominal cell voltage is 2.105v
• Second lowest energy-to-weight ratio (next to the nickel-iron battery)
Construction;
• consist of Lead &Lead Oxide
electrodes
• Which are dipped in Sulphuric
acid
• Normal Lead acid battery is
six cell battery
• Separators are present in between electrodes
Separators
• wood
• rubber
• glass fiber mat
• cellulose
• sintered PVC
• micro porous PVC/polyethylene.
Construction of lead-acid battery (cont....)
Cells and Batteries
Working of Lead-acid battery (cont….)
Discharging reactions
Anode reaction:
Cathode reaction:
Cells and Batteries
Working of Lead-acid battery (cont….)
Recharging reactions
Anode reaction:
Cathode reaction:
Cells and Batteries
Figure 7 One of the Cells in a 12-V Lead Storage Battery (LSM 14.1C)
applications
• Submarines
• Motor car ignition
• Industries
• To maintain required
voltages in sub stations
Limitations of Lead acid battery
• More amounts of materials should be taken. Because,
the products lead sulphate and water are poor
conductors of electricity. Moreover, acid gets
progressively diluted.
• Optimal charging and discharging should be done to
avoid the loss of efficiency.
• Wrong polarity connection should be avoided.
• Acid concentration and proper connections should be
monitored /checked frequently.
Cells and Batteries
ALKALINE BATTERIES
Description
• Alkaline batteries and alkaline cells (a battery being a
collection of multiple cells) are a type of disposable battery
or rechargeable battery dependent upon the reaction
between zinc and manganese(IV) oxide (Zn/MnO2).
• Alkaline battery is an improved dry cell.
• The alkaline battery gets its name because it has an alkaline
electrolyte of potassium hydroxide, as opposed to the
acidic electrolyte of the zinc-carbon batteries
• Zinc in a powdered form increases the surface area of the
anode, allowing more particle interaction. This lowers the
internal resistance and increases the power density
Construction
• A cylindrical cell is contained in a drawn steel can, which is the
cathode current collector.
• The cathode mixture is a compressed paste of manganese
dioxide with carbon powder added for increased conductivity.
• The hollow center of the cathode is lined with a separator,
which prevents mixing of the anode and cathode materials and
short-circuiting of the cell.
• The separator is made of a non-woven layer of cellulose or a
synthetic polymer. The separator must conduct ions and
remain stable in the highly alkaline electrolyte solution.
• The anode is composed of a dispersion of zinc powder in a gel
containing the potassium hydroxide electrolyte. To prevent
gassing of the cell at the end of its life, more manganese
dioxide is used than required to react with all the zinc.
Chemistry
Anode : Zinc Powder
Cathode : Manganese dioxide(MnO2)
powder
Electrolyte : Potassium hydroxide(KOH)
Half
cell reactions
• Anode(Oxidation) :
Zn (s) + 2OH− (aq) → ZnO(s) + H2O (l) + 2e−
• Cathode(Reduction) :
2MnO2 (s) + H2O (l) + 2e− →Mn2O3 (s) + 2OH− (aq)
• The overall reaction is:
Zn + 2MnO2 —> ZnO + Mn2O3 ;E=1.5 V
Advantages
• Better low temperature performance than zinc carbon.
Continue to function in sub-zero temperatures.
• Available in a wide range of sizes including AAA, AA, C, D
and 9Volt sizes.
• Suitable for a wide range of consumer applications
• Made from non toxic chemicals
• No voltage drop and longer shell life than dry cell because
of alkaline electrolyte
• Up to ten times the service life of regular zinc-carbon cells.
• Low internal resistance.
• Good low temperature performance.
• Excellent leakage resistance.
• Alkaline batteries do not have a carbon rod cathode, which allow them to
be smaller.
CONSTRUCTION OF ALKALINE
BATTERIES
• http://www.youtube.com/watch?v=ksxSOwA933M
Nickel-Cadmium Battery
Cathode
NiO(OH)
Anode
Cd
Separator
NaOH
NICKEL CADMIUM BATTERIES
• NICKEL HYDROXIDE (POSITIVE ELCTRODE)
• CADMIUM HYDROXIDE (NEGATIVE ELECTRODE)
• POTASSIUM HYDROXIDE (ELECTROLYTE)
• SEPERATOR
• CHEMICAL REACTION:
• NORMALLY 19 TO 20 CELLS ARE USED
WORKING OF NiCd BATTERIES
• Nickel-Cadmium battery:- the reactions look something like this:
Oxidation:Cd(s) + 2 OH- (aq) → Cd(OH)2(s) + 2 eReduction:-
2NiO(OH)(s) + 2 H2O(l) + 2 e- → 2Ni(OH)2(s) + 2 OH- (aq)
Net:-
Cd(s) + 2NiO(OH)(s) + 2 H2O(l) → Cd(OH)2(s) + 2Ni(OH)2(s)
Electrons moving from one place to another – this is electricity
Numbers of electrons in oxidation and reduction must be same.
Nickel cadmium batteries
• Advantages
• Fast and simple charge even after prolonged storage.
• High number of charge/discharge cycles — if properly maintained,
the NiCd provides over 1000 charge/discharge cycles.
• Long shelf life – in any state-of-charge.
• Simple storage and transportation — most airfreight companies
accept the NiCd without special conditions.
• Good low temperature performance.
• Forgiving if abused — the NiCd is one of the most rugged
rechargeable batteries.
• Economically priced — the NiCd is the lowest cost battery in terms of
cost per cycle.
• Available in a wide range of sizes and performance options (most
NiCd cells are cylindrical.)
NICKEL
CADMIUM BATTERIES
• Limitations:
• Relatively low energy density compared with newer
systems.
• Memory effect: The NiCd must periodically be exercised to
prevent memory.
• Environmentally unfriendly: the NiCd contains toxic metals.
Some countries are limiting the use of the NiCd battery.
• Has relatively high self-discharge: needs recharging after
storage.
Lithium Manganese Dioxide
• Chemistry
Lithium (-), manganese dioxide (+)
Alkali metal salt in organic solvent electrolyte
• Features
+ High energy density
+ Long shelf life (20 years at 70°C)
+ Capable of high rate discharge
• Expensive
Nickel Metal Hydride (NiMH)
• The nickel-metal hydride battery chemistry is a hybrid of the
proven positive electrode chemistry of the sealed nickelcadmium battery with the energy storage features of metal
alloys developed for advanced hydrogen energy storage
concepts. This heritage in a positive-limited battery design
results in batteries providing enhanced capacities while
retaining the well-characterized electrical and physical
design features of the sealed nickel-cadmium battery
design.
Nickel Metal Hydride (NiMH)
• ADVANTAGES:
• 30 – 40 percent higher capacity over a standard NiCd. The
NiMH has potential for yet higher energy densities.
• Less prone to memory than the NiCd. Periodic exercise cycles
are required less often.
• Simple storage and transportation — transportation
conditions are not subject to regulatory control.
• Environmentally friendly — contains only mild toxins;
profitable for recycling.
• Elimination of the constraints on battery manufacture
• Simplified incorporation into products
• Greater service advantage over other primary battery types at
low temperature extremes operating at -20°C
limitations
• High self-discharge — the NiMH has about 50 percent
higher self-discharge compared to the NiCd. New chemical
additives improve the self-discharge but at the expense of
lower energy density.
• High maintenance — battery requires regular full discharge
to prevent crystalline formation.
• About 20 percent more expensive than NiCd — NiMH
batteries designed for high current draw are more
expensive than the regular version.
• Limited service life
• Limited discharge current
Negative Electrode
• The basic concept of the nickel-metal hydride battery negative
electrode emanated from research on the storage of hydrogen for use
as an alternative energy source in the 1970s. Certain metallic alloys were
observed to form hydrides that could capture (and release) hydrogen in
volumes up to nearly a thousand times their own volume. By careful
selection of the alloy constituents and proportions, the
thermodynamics could be balanced to permit the absorption and
release process to proceed at room temperatures. The metal hydride
electrode has a theoretical capacity >40 percent higher than the
cadmium electrode in a nickel-cadmium couple. As a result, nickel-metal
hydride batteries provide energy densities that are >20 percent higher
than the equivalent nickel-cadmium battery.
• Battery Construction
• The nickel-metal hydride couple lends itself to the wound construction
shown in (Fig. 1), which is similar to that used by cylindrical nickelcadmium, LI ion and primary lithium batteries. The basic components
consist of the positive and negative electrodes insulated by separators.
The sandwiched electrodes are wound together and inserted into a
metallic can that is sealed after injection of electrolyte. Nickel-metal
hydride batteries are typically sealed designs with metallic cases and tops
that are electrically insulated from each other. The case serves, as the
negative terminal for the battery while the top is the positive terminal.
Finished battery designs may use a plastic insulating wrapper shrunk over
the case to provide electrical isolation between cells in typical battery
applications. Nickel-metal hydride batteries contain a resealable safety
vent built into the top, as shown in (Fig. 4). The nickel-metal hydride
battery is designed so the oxygen recombination cycle described earlier is
capable of recombining gases formed during overcharge under normal
operating conditions, thus maintaining pressure equilibrium within the
battery. However, in cases of extended overcharge or incompatible
battery/charger combinations for the operating environment, it is possible
that oxygen, and hydrogen, will be generated faster than it can be
recombined. In such cases the safety vent will open to reduce the
pressure and prevent battery rupture. The vent reseals once the pressure
is relieved. The expulsion of gas thru the resealable vent can carry
electrolyte, which may form crystals or rust once outside the can.
Electrochemistry:
• Discharge
• At the negative electrode, the hydrogen is desorbed and
combines with a hydroxyl ion to form water while also
• contributing an electron to the circuit.
Alloy (H) + OH`‹----------------› Alloy + H2O + e`
• At the positive electrode, nickel oxyhydroxide is reduced to
its lower valence state, nickel hydroxide.
NiOOH + H2O + e`‹------------------› Ni(OH)2 + OH`
Hazards: EXPLOSION
• A battery explosion is caused by the misuse or malfunction of a battery,
such as attempting to recharge a primary (non-rechargeable) battery,[70] or
short circuiting a battery.[71] With car batteries, explosions are most likely to
occur when a short circuit generates very large currents
• When a battery is recharged at an excessive rate, an explosive gas mixture
of hydrogen and oxygen may be produced faster than it can escape from
within the walls of the battery, leading to pressure build-up and the
possibility of bursting of the battery case. In extreme cases, the battery acid
may spray violently from the casing of the battery and cause injury.
Overcharging—
• That is, attempting to charge a battery beyond its electrical capacity—can
also lead to a battery explosion, leakage, or irreversible damage to the
battery. It may also cause damage to the charger or device in which the
overcharged battery is later used. In addition, disposing of a battery in fire
may cause an explosion as steam builds up within the sealed case of the
battery.[71]
Leakage
• Many battery chemicals are corrosive, poisonous, or both. If
leakage occurs, either spontaneously or through accident, the
chemicals released may be dangerous.
• For example, disposable batteries often use zinc "can" as both a
reactant and as the container to hold the other reagents. If this kind
of battery is run all the way down, or if it is recharged after running
down too far, the reagents can emerge through the cardboard and
plastic that forms the remainder of the container. The active
chemical leakage can then damage the equipment that the
batteries were inserted into. For this reason, many electronic device
manufacturers recommend removing the batteries from devices
that will not be used for extended periods of time.
Environmental concerns
• The widespread use of batteries has created many environmental
concerns, such as toxic metal pollution. Battery manufacture
consumes resources and often involves hazardous chemicals. Used
batteries also contribute to electronic waste.
Lithium v Alkaline Discharge