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Sustainable > Energy Storage & Batteries > Flashcards

Energy Storage & Batteries Flashcards

1
Q

What does more energy from renewable sources provide, and what are the key components in achieving this goals?

A

The transition to zero-carbon economy.
Key:
1. Increased electrification rates
2. Increased storage

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2
Q

What is the problem with energy supply from renewables, and why is energy storage important?

A

Problem: more difficult to control due to intermittence of supply (weather changes etc.)

Significance: excess energy produces can be stored, and used when renewable sources are insufficient.

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3
Q

What is a battery, give an example?

A

An electrochemical cell using two different metals (Zn and Cu) in contact with an electrolyte.
Example: hybrid cars / fully electric cars.

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4
Q

What does the voltage produced by the cell depend on?

A

The type of electrodes used and electrolyte.

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5
Q

How does the separator in the battery operate?

A

Allows ions to move selectively.
Prevents other species of moving.

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6
Q

How do batteries work?

A
  1. Cu deposits on Cu cathode.
    Cu(2+) (aq) + 2e- => Cu (s)
  2. Ion transport charge equivalent to electron flow.
  3. Porous barrier allows (SO4)2- to pass, blocks Zn and Cu ions.
  4. Zn gives 2e -> goes into aq.
    Zn (s) => Zn2+ (aq) + 2e-
  5. Zn loses e more readily than Cu.
  6. Electrode with oxidation : anode.

CuSO4 => (SO4)2- => ZnSO4

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7
Q

What does the potential of batteries determine?

A

=> determines the potential of the cell.

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8
Q

What is the order of the reactivity of metals?

A

Highest
1. K
2. Na
3. Ca
4. Mg
5. Al
6. C
7. Zn
8. Fe
9. Pb
10. H
11. Cu
12. Ag
13. Au
Lowest

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9
Q

What are the two types of batteries?

A
  1. Primary - disposable, electrochemical reaction cannot be reversed.
  2. Secondary - rechargeable, electrochemical reaction can be reversed by applying certain voltage to the battery (in opposite direction of the discharge).
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10
Q

Which are common disposable commercial batteries?

A

DISPOSABLE

  1. Zinc-Carbon: in all drycell batteries, cheap.
    Electrodes are Zn & C, with acidic paste serving as the electrolyte.
  2. Alkaline: in duracell and energizer batteries.
    Electrodes are Zn & MnO2, with alkaline electrolyte.
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11
Q

Which are common rechargeable batteries?

A
  1. Nickel-Cadmium: NiCd
  2. Nickel-metal hydride: NiMH (Less stable than NiCd)
  3. Lead-Acid: used in cars.
    Electrodes are Pb & PbO2, with an acidic (H2SO4) electrolyte.
  4. Lithium-ion: Li-ion
    High energy density, power rate, cycle life.
    BUT, more expensive.
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12
Q

Give a brief explanation about Zinc-Carbon batteries.

A
  • Electrodes are Zn & C, with an acidic paste serving as the electrolyte.
  • disposable.
  • Zinc as anode, MnO2 as cathode.
  • Redox chemistry takes place in the battery.
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13
Q

How does a Zn-C battery operate? Give the overall reaction.

A
  1. The C added to cathode increasing conductivity & retaining moisture.
    = non-conducting tube
    = separating layer
    = C electrode surrounded by carbon black.
    = Manganese dioxide - cathode
    = Zinc metal sleeve - anode
    = Ion transfer accomplished in a paste of ammonium chloride and zinc chloride.
  2. Reaction:
    Zn + 2MnO2 -> ZnO + Mn2O3
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14
Q

Give a brief explanation about Alkaline batteries.

A
  • Used in Duracell and Energizer batteries.
  • Electrodes are Zn & MnO, with alkaline electrolyte (e.g. KOH).
  • disposable.
  • Zinc as anode, MnO2 as cathode.
  • Redox chemistry takes place in the battery.
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15
Q

Write the redox reactions, at the cathode and anode, and the overall reaction.

A

Anode: Zn + 2OH- => Zn(OH)2 + 2e-
Cathode: MnO2 + 2H2O + 2e- => Mn(OH)2 + 2OH-
Full discharge: Zn + MnO2 + 2H2O => Mn(OH)2 + Zn(OH)2

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16
Q

Give a brief explanation about NiCd batteries.

A
  • rechargeable.
  • Cd as anode, Ni as cathode (discharge)
  • Ni as anode, Cd as cathode (charging)
  • Advantage: stability, long life.
  • Problem: toxicity of Cd.
17
Q

Write the reactions of the anode and cathode upon discharge for NiCd.

A

Anode: Cd + 2OH- => Cd(OH)2 + 2e-
Cathode: Ni(OH)4 + 2K+ + 2e- => 2KOH + Ni(OH)2

18
Q

Write the reactions of the anode and cathode upon charging for NiCd.

A

Cathode: Ni(OH)2 + 2OH- => Ni(OH)4 + 2e-
Anode: Cd(OH)2 + 2K+ + 2e- => Cd + 2KOH

19
Q

Give a brief explanation about Lead-Acid batteries.

A
  • used in cars.
  • Electrodes are Pb & PbO2, with an acidic (H2SO4) electrolyte.
  • Rechargeable.
20
Q

Write the reactions of the anode and cathode upon discharge for Lead-Acid along with the overall reaction.

A

Anode: Pb + HSO4- => PbSO4 + H+ + 2e-
Cathode: PbO2 + 3H+ + HSO4- + 2e- => PbSO4 + 2H2O
Overall: Pb + PbO2 + 2H2SO4 => 2PbSO4 + 2H2O

21
Q

Give a brief explanation about Lithium-ion batteries.

A
  • High energy density.
  • High power rate.
  • High cycle life.
  • Rechargeable.
22
Q

Write the reactions of the anode and cathode for Lithium-ion along with the overall reaction.

A

Cathode: Reduction, with CoO2 combines with Li-ions, forming LiCoO2.
Half reaction is CoO2 + Li+ + e- => LiCoO2
Co(IV) => Co(III)

Anode: Oxidation, with graphite intercalation compound LiC6 forming graphite C6, and Li-ions.
Half reaction is LiC6 => C6 + Li+ + e-
Li(0) => Li(I)

Full Reaction: LiC6 + CoO2 <=> C6 + LiCoO2
- Left to Right = discharging
- Right to Left = charging

23
Q

Charging and discharging of batteries.

A

Page 29.

24
Q

What are the improvements required to replace the internal combustion engine by electric engine?

A
  1. Reduce price of batteries.
  2. Improve energy density.
  3. Increase power density.
  4. Improve their lifetimes.
25
Q

What is the problem of Li-ion batteries and suggest an alternative?

A

Eventhough ideal for automotive industry, it is too expensive.
Cheaper alternatives: Na-ion batteries.

Sustainable (8 decks)

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