Rechargeable Batteries

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Rechargeable Batteries

• by
• Thomas Hargest

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What Are Rechargeable Batteries?

• Rechargeable batteries are batteries that can be
  restored to full charge by the application of
  electrical energy.
• Rechargeable batteries come in different designs
  using different chemical reactions.
• Rechargeable batteries are also called storage
  batteries or secondary cells.

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Examples of Rechargeable Batteries

• Lead-acid battery This battery is used in
  automobiles. The electrodes are made of lead and
  lead-oxide with a strong acidic electrolyte.

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Lead-acid Battery

• Lead-acid batteries are the most commonly used
  rechargeable batteries today.
• The chemical reactions are (charged to
  discharged)
• Anode (oxidation)
• Pb(s) SO42- (aq) ? PbSO4 (s) 2e-
• Cathode (reduction)
• PbO2(s) SO42- (aq) 4H 2e- ? PbSO4
  (s) 2H2O (l)

A sealed lead acid battery
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Examples of Rechargeable Batteries (continued)

• Nickel-cadmium battery The electrodes are
  nickel-hydroxide and cadmium, with
  potassium-hydroxide as the electrolyte.

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Nickel-cadmium Battery

• Cross-section of a classic NiCd cell.

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Examples of Rechargeable Batteries (continued)

• Nickel-metal hydride battery This battery does
  not contain cadmium and is used in hybrid or
  electric vehicles. The electrodes are
  nickel-hydroxide and rare earth metals, with
  potassium-hydroxide as the electrolyte.

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Nickel-metal Hydride Battery

• The reaction occurring in a NiMH battery is as
  follows H2O Mm 2e- ? OH- ½ H2 (stored as
  Mm-Hx)
• The battery is charged in the right direction of
  this equation and discharged in the left
  direction.
• Mm stands for mischmetal (from German "mixed
  metals") is an unintentional alloy of rare earth
  elements in various naturally-occurring
  proportions.

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Examples of Rechargeable Batteries (continued)

• Lithium-ion battery This battery has a large
  ratio of power to weight and is used in high-end
  laptop computers and cell phones.

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Lithium-ion Battery

• The anode is made from carbon.
• The cathode is a metal oxide such as CoO2.
• The electrolyte is a lithium salt in an organic
  solvent, such as ether.
• Since the lithium metal is very reactive and
  explosive, Li-ion cells usually have built-in
  protective electronics and/or fuses to prevent
  polarity reversal, over-voltage and over-heating.

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Non-rechargeable vs Rechargeable

• Non-rechargeable (primary) batteries, such as
  zinc-carbon batteries, are based on irreversible
  chemical changes that use up the materials in one
  or both of their electrodes.

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Non-rechargeable Batteries

• Cross-section of a zinc-carbon battery

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Non-rechargeable vs Rechargeable (continued)

• Rechargeable batteries are able to undergo the
  reverse chemical reaction changes efficiently to
  allow them to be restored to almost the same
  fully charged condition on each recharging.

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• http//science.howstuffworks.com/battery.htm
• http//en.wikipedia.org/wiki/Rechargeable_battery
• http//www.sciam.com/askexpert_question
• http//www.buchmann.ca
• http//www.batteryuniversity.com/index.htm