Lithium-ion Battery





                    
      Lithium-ion batteries are common rechargeable batteries for portable electronics, with a high energy density, tiny memory effect and low self-discharge. Lithium-ion batteries are also growing in popularity for military, electric vehicle and aerospace applications.
Invention


       
            Lithium batteries were first proposed by British chemist M Stanley Whittingham, now at Binghamton University, while working for Exxon in the 1970s. He proposed a lithium-titanium disulfide battery, which was discontinued because of the high cost of titanium disulfide also when exposed to air, titanium disulfide reacts to form hydrogen sulfide compounds, which have an unpleasant odor and are toxic to most animals. As well as Batteries with metallic lithium electrodes presented safety issues, as lithium is a highly reactive element; it auto ignites exposed to normal atmospheric conditions because of spontaneous reactions with water and oxygen. As a result, research moved to develop batteries in which, instead of metallic lithium, only lithium compounds are present, being capable of accepting and releasing lithium ions. Which developed in the form of Lithium-ion batteries, commonly used today.
Construction
                    
          The three primary functional components of a lithium-ion battery are the positive and negative electrodes and electrolyte. Generally, the negative electrode of a conventional lithium-ion cell is made from carbon. The positive electrode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent. The electro-chemical roles of the electrodes reverse between anode and cathode, depending on the direction of current flow through the cell.
         Depending on materials choices of electrodes and electrolytes, the voltage, energy density, life, and safety of a lithium-ion battery can change dramatically. Recently, novel architectures using nanotechnology have been employed to improve performance.
Pure lithium is highly reactive. It reacts vigorously with water to form lithium hydroxide and hydrogen gas. Thus, a non-aqueous electrolyte is typically used, and a sealed container rigidly excludes moisture from the battery pack.

Advantage
·        High energy density - potential for yet higher capacities.
 
·        Does not need prolonged priming when new. One regular charge is all that's needed.
 
·        Relatively low self-discharge - self-discharge is less than half that of nickel-based batteries.
 
·        Low Maintenance - no periodic discharge is needed; there is no memory.
 
·        Specialty cells can provide very high current to applications such as power tools.

Disadvantage
  • Requires protection circuit to maintain voltage and current within safe limits.
     
  • Subject to aging, even if not in use - storage in a cool place at 40% charge reduces the aging effect.
     
  • Transportation restrictions - shipment of larger quantities may be subject to regulatory control. This restriction does not apply to personal carry-on batteries.
     
  • Expensive to manufacture - about 40 percent higher in cost than nickel-cadmium.
     
  • Not fully mature - metals and chemicals are changing on a continuing basis.

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