Rechargeable Batteries

The reactions in rechargeable cells can be reversed using electrical energy so the cell can be re-used. Examples are Ni-Cd (nickel-cadmium) batteries, lithium-ion batteries and lithium polymer batteries used in laptops. Lead-acid batteries are used in cars. Each cell has two lead plates. The cathode is coated with lead (IV) oxide. The electrolyte is concentrated sulfuric acid. At the anode:Pb(s) + SO₄^2-(aq) → PbSO₄(s) + 2e^-At the cathode:PbO₂(s) +4H⁺(aq) + SO₄^2-(aq) + 2e^- → PbSO₄(s) + 2H₂O(l)Overall:Pb(s) + PbO₂(s) + 4H⁺(aq) + 2SO₄^2-(aq) → 2PbSO₄(s) + 2H₂O(l)With rechargeable batteries the oxidised and reduced forms of the anode and cathode must be solid. Digital cameras and mobile phones use rechargeable Lithium cells that use a solid polymer electrolyte. One type of battery has a lithium anode and a titanium (IV) sulfide cathode. At the anode:Li ⇌ Li⁺ + e^-At the cathode:TiS₂ + e^- ⇌ TiS₂^-OverallLi(s) + TiS₂(s) → LiTiS₂(s)