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Sustainable Tech Fundamentals > Batteries > Flashcards

Batteries Flashcards

1
Q

fWhat is the negative terminal called… what occurs there

A

Anode, Oxidisation (electrons are lost)

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2
Q

What is the positive terminal called… what occurs there

A

Cathode, Reduction (electrons are gained)

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3
Q

In a Lead Acid Battery, what is on the negative and positive terminal and what electrolyte is used

A

Negative -> Lead (Pb)
Positive -> Lead Dioxide (PbO2)
Electrolyte -> Sulfuric Acid (H2SO4)

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4
Q

What is the reaction on the negative terminal (anode) of a Lead Acid Battery

A

Pb + H2SO4 -> PbSO4 + 2H+ + 2e-

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5
Q

What is the reaction on the positive terminal (cathode) of a Lead Acid Battery

A

PbO2 + SO4 + 4H+ + 2e- -> PbSO4 + H2O

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6
Q

What is the overall voltage of a Lead Acid Battery

A

2V… (1.68V from cathode - -0.36V from anode)

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7
Q

What is the formula for capacity of an electrode

A

Capacity = (Amount of Electrons) / (Mass of Active material)

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8
Q

What is Sulphation and what does it do

A

PbSO (lead sulfite) grows on the electrode, it has the potential to block active material in the battery causing the battery to ‘die’

It occurs during charging and thus builds up when the battery is not being used (car battery).

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9
Q

What are the side reactions in a Lead Acid Battery… are they good or bad

A

When charging, if material is depleted then electrolysis of water occurs.

Good -> allows battery to self balance (no BMS)

Bad -> causes battery to self discharge

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10
Q

What is acceptance current

A

The current that results in only the main process occurring (no side process)

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11
Q

What is faradaic efficiency

A

Acceptance current / total current

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12
Q

Name 3 causes of degradation of Lead Acid Batteries

A

Sulphation -> black access to active material

Stratification -> no flow in battery causes bottom of electrode to corrode more than the top, solve by shaking battery

Corrosion of grid collector -> grid connects the electrodes, if it corrodes then the electrodes are not connected (no conduction)

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13
Q

In a Nickle Cadmium Battery, what is on the negative and positive terminal

A

Negative -> Cadmium (Cd)
Positive -> Nickle Oxide Hydroxide (NiOOH)
Electrolyte -> Not really… is a separator

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14
Q

What is the reaction on the negative terminal (anode) of a NiCd Battery

A

Cd + 2OH- -> Cd(OH)2 + 2e-

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15
Q

What is the reaction on the positive terminal (cathode) of a NiCd Battery

A

NiOOH + e- + H2O -> Ni(OH)2 + OH-

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16
Q

What is the overall voltage of a NiCd Battery

A

Approx 1.3V

17
Q

Explain the memory effect briefly, what batteries experience this

A

Battery remembers how it was last used, if it was only drained to 50% then the next time it is charged it will only discharge to 50%.

Can fix this by fully discharging at a lower voltage.

18
Q

In a Nickle Hydride Battery, what is on the negative and positive terminals and what is the electrolyte used

A

Negative -> Metal Hydroxide (MH)
Positive -> Nickle (NiOOH)
Electrolyte -> Potassium Hydroxide

19
Q

What is the reaction on the positive terminal (cathode) of a Nickle Hydride Battery

A

NiOOH + e- + H2O -> Ni(OH)2 + OH-

20
Q

What is the reaction on the negative terminal (anode) of a Nickle Hydride Battery

A

MH- + OH- -> M + H2O

Where M = Metal, can be several

21
Q

What is the overall reaction of a lithium ion battery

A

LiC6 + LiCoC2 = C6 + LiCoO2

22
Q

What is on the positive terminal of a LIB and what is the reaction

A

Positive -> LiCoO2

LiCoO2 -> LiCoO2 + xLi + xe-

23
Q

What is on the negative terminal of a LIB and what is the reaciton

A

Negative -> Graphite

xLi + xe- + 6C -> LixC6

24
Q

Advantages of LIB

A

Fast charging to 400 mAh/g

Wide choice of negative electrode carbons, can be hard and soft

Possible for 1000 mAh/g (large power)

25
Q

What is SEI formation

A

Surface Electrolyte Interface formation (SEI) -> film forms on the electrode, this prevents ion transfer and increases résistance, is not reversible.

26
Q

Disadvantages of LIB

A

SEI formation

Low diffusion rates of lithium ions

High voltage differences

27
Q

What is the positive terminal in a LIB made up of, and what do they do

A

Active Material (LCoO2) - 80%

Carbon Black - 10%
Increases the conductivity of the electrode

Binder - 10%
Acts as a glue in the electrode (holds it together)

28
Q

During overcharge of a Lead Acid Battery, what occurs

A

electrolysis of water, helps balance the battery

29
Q

During deep discharge of a Lead Acid Battery, what occurs

A

Material is depleted, leads to sulphation where active material is blocked.

30
Q

what are the 3 problems that occur in batteries that are operating in crucial damage regions

A

Conductivity where there should be resistance

Resistance where there should be conductivity

Loss of capacity

31
Q

Explain how conductivity can arise were there should be resistance

A

Dendrites can form on the negative electrode. Dendrites have lower resistance than the rest of the electrode and thus dendritic growth is promoted in a positive feedback loop.

Eventually the dendrite will grow enough to touch the positive electrode which results in a short circuit and the battery dies.

32
Q

Explain how resistance can arise were there should be conductivity

A

SEI (surface electrode interface formation) occurs when the electrolyte decomposes and a film grows on the electrode. preventing the transfer of ions and increases resistance… is not reversible

33
Q

What are the key design requirements when manufacturing a battery

A

Uniform current
Large surface area (for reaction)
Good electrical connections on active material
Insulation
Strong and wear resistant casing

34
Q

What are the key safety factors when manufacturing a battery

A

Shut down separator (PE)
Designing with a positive temperature coefficient
Current interrupt device

Sustainable Tech Fundamentals (2 decks)

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