Batteries

Question 1

fWhat is the negative terminal called… what occurs there

Answer 1

Anode, Oxidisation (electrons are lost)

Question 2

What is the positive terminal called… what occurs there

Answer 2

Cathode, Reduction (electrons are gained)

Question 3

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

Answer 3

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

Question 4

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

Answer 4

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

Question 5

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

Answer 5

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

Question 6

What is the overall voltage of a Lead Acid Battery

Answer 6

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

Question 7

What is the formula for capacity of an electrode

Answer 7

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

Question 8

What is Sulphation and what does it do

Answer 8

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).

Question 9

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

Answer 9

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

Question 10

What is acceptance current

Answer 10

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

Question 11

What is faradaic efficiency

Answer 11

Acceptance current / total current

Question 12

Name 3 causes of degradation of Lead Acid Batteries

Answer 12

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)

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

What is the overall voltage of a NiCd Battery

Answer 16

Approx 1.3V

Question 17

Explain the memory effect briefly, what batteries experience this

Answer 17

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.

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

Answer 20

MH- + OH- -> M + H2O

Where M = Metal, can be several

Question 21

What is the overall reaction of a lithium ion battery

Answer 21

LiC6 + LiCoC2 = C6 + LiCoO2

Question 22

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

Answer 22

Positive -> LiCoO2

LiCoO2 -> LiCoO2 + xLi + xe-

Question 23

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

Answer 23

Negative -> Graphite

xLi + xe- + 6C -> LixC6

Question 24

Advantages of LIB

Answer 24

Fast charging to 400 mAh/g

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

Possible for 1000 mAh/g (large power)

Question 25

What is SEI formation

Answer 25

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

Question 26

Disadvantages of LIB

Answer 26

SEI formation Low diffusion rates of lithium ions High voltage differences

Question 27

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

Answer 27

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)

Question 28

During overcharge of a Lead Acid Battery, what occurs

Answer 28

electrolysis of water, helps balance the battery

Question 29

During deep discharge of a Lead Acid Battery, what occurs

Answer 29

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

Question 30

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

Answer 30

Conductivity where there should be resistance Resistance where there should be conductivity Loss of capacity

Question 31

Explain how conductivity can arise were there should be resistance

Answer 31

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.

Question 32

Explain how resistance can arise were there should be conductivity

Answer 32

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

Question 33

What are the key design requirements when manufacturing a battery

Answer 33

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

Question 34

What are the key safety factors when manufacturing a battery

Answer 34

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