Class 12 Chemistry Electrochemistry Secondary Battery

Secondary Battery

  • The reaction in a secondary battery occurs many times.
  • Once it exhausts it can be recharged and used again.
  • They are recharged by passing electric current through it in opposite direction.
  • Example of secondary cell is lead and nickel cadmium cell.

Fig. Lead storage battery

Fig. Nickel-Cadmium cell

  • It is used extensively in automobiles and invertors.
  • The lead cell contains a lead anode and a lead dioxide (PbO2) cathode and sulphuric acid is used as an electrolyte.
    Anode: Pb(s) + SO42–(aq) --> PbSO4(s) + 2e
    Cathode: PbO2(s) + SO42–(aq) + 4H+(aq) + 2e --> PbSO4 (s) + 2H2O (l)
  • The net cell reaction is:
    Pb(s)+PbO2(s)+2H2SO4(aq) --> 2PbSO4(s) + 2H2O(l)
  • While charging, the reaction within the battery is reversed and PbSO4(s) on anode and cathode is converted into Pb and PbO2, respectively.
  • It has a longer life thanlead storage cell and it requires more expenses to
  • The net reaction is:
    Cd (s)+2Ni(OH)3 (s) --> CdO (s) +2Ni(OH)2 (s) +H2O(l)

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