What You Need To Know About Lithium Ion Batteries

Used for many popular handheld devices from iPods to iPAQs lithium-ion batteries are ideal for mobile electronics. They are lightweight, energy-dense, and have a chemistry composite allowing the battery to recharge fast. But what is lithium, where does it come from, how is it made into a battery, what does it look like, and where can I get it?

Here is a quick list of the chemical characteristics of lithium

  • Name: lithium
  • Symbol: Li
  • Atomic number: 3
  • Atomic weight: [6.941 (2)] g m r
  • Chemical Abstract Service Registry ID: 7439-93-2
  • Group number: 1
  • Group name: Alkali metal
  • Period number: 2
  • Block: s-block
  • Standard state: solid at 298 K
  • Color: silvery white/grey
  • Classification: Metallic

You will not find lithium lying around in the open as lithium does not occur as the free metal. Lithium however is a component of nearly all igneous rocks and many natural brines with large deposits located in California and Nevada both in the good ole USA. You will find lithium in the rock forms spodumene, lepidolite, petalite, and amblygonite.

Lithium is extracted, one way, from the rock by heating the rock to 1100°C, mixing with sulphuric acid, H2SO4, and heating to 250°C. Then it is followed by extracting into water to create a lithium sulphate solution, Li2SO4. At this point then it can be used for various manufacturing purposes.

Lithium has high electrochemical potential and thus is used as a battery anode material in dry cells and storage batteries. In fact the energy of some lithium-based cells can be five times greater than an equivalent-sized lead-acid cell and three times greater than alkaline batteries. Lithium cells often have a starting voltage of 3.0 V. This means that batteries can be lighter in weight, have lower per-use costs, and have higher and more stable voltage profiles.

Here are some facts for lithium-ion battery cells:

  • The lightest of all metals
  • The greatest electrochemical potential
  • The largest energy density for weight.
  • The load characteristics are reasonably good in terms of discharge.
  • The high cell voltage of 3.6 volts allows battery pack designs with only one cell versus three.
  • It is a low maintenance battery.
  • No memory and no scheduled cycling is required to prolong the battery's life.
  • Lithium-ion cells cause little harm when disposed.
  • It is fragile and requires a protection circuit to maintain safe operation.
  • Cell temperature is monitored to prevent temperature extremes.
  • Capacity deterioration is noticeable after one year (whether the battery is in use or not).

Here are some facts for Lithium Polymer Battery Cells:

  • The lithium-polymer differentiates itself from the conventional battery in the type of electrolyte used (a plastic-like film that does not conduct electricity but allows ion exchange – electrically charged atoms or groups of atoms).
  • The polymer electrolyte replaces the traditional porous separator, which is soaked with electrolyte.
  • The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and thin-profile geometry.
  • Cell thickness measures as little as one millimeter (0.039 inches).
  • Can be formed and shaped in any way imagined.
  • Commercial lithium-polymer batteries are hybrid cells that contain gelled electrolyte to enhane conductivity.
  • Gelled electrolyte added to the lithium-ion-polymer replaces the porous separator. The gelled electrolyte is simply added to enhance ion conductivity.
  • Capacity is slightly less than that of the standard lithium-ion battery.
  • Lithium-ion-polymer finds its market niche in wafer-thin geometries, such as PDA batteries.
  • Improved safety – more resistant to overcharge; less chance for electrolyte leakage.

Until next time, Dan Hagopian www.batteryship.com
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