Leclanché or dry cell : Zn|(ZnCl₂),NH₄Cl|MnO₂,C

• Anode (-): zinc case
  Zn(s) -----> Zn²⁺(aq) + 2e^-

• Cathode (+): carbon rod in contact with carbon & MnO₂
  NH₄⁺(aq) + MnO₂(s) + e^- -----> NH₃(aq) + MnO(OH)(s)

• Electrolyte: Paste of NH₄Cl, ZnCl₂ (acid electrolyte)

• Voltage: 1.5 volts

• Uses: low drain appliances such as radios, torches, liquid crystal calculators, toys

Alkaline cell : Zn,ZnO|KOH(paste)|MnO₂,C

• Anode (-): brass rod in contact with powdered zinc
  Zn(s) + 2OH^-(aq) -----> ZnO(s) + H₂O(l) + 2e^-

• Cathode (+): steel case in contact with carbon & MnO₂
  MnO₂(s) + H₂O(l) + e^- -----> MnO(OH)(s) + OH^-(aq)

• Electrolyte: paste of 7M KOH (alkaline electrolyte)

• Voltage: 1 volt

• Uses: High current or high total capacity appliances such as electronic photographic flash units, tape recorders, radios, shavers
  Can deliver higher current than Leclanché cell without severe voltage drop.

Mercury button cell

• Anode (-): steel cap in contact with powdered zinc
  Zn(s) + 2OH^-(aq) -----> ZnO(s) + H₂O(l) + 2e^-

• Cathode (+): steel case in contact with powdered HgO
  HgO(s) +H₂O(l) + 2e^- -----> Hg(l) + 2OH^-(aq)

• Electrolyte: paste of KOH (alkaline electrolyte)

• Voltage: 1.3 volts

• Uses: watches, pacemakers, hearing aids, microphones

Silver button cell: Zn,ZnO|KOH (paste)|Ag₂O,Ag

• Anode (-): steel cap in contact with powdered zinc
  Zn(s) + 2OH^-(aq) -----> ZnO(s) + H₂O(l) + 2e^-

• Cathode (+): steel case in contact with powdered Ag₂O
  Ag₂O(s) + H₂O(l) + 2e^- -----> 2Ag(s) + 2OH^-(aq)

• Electrolyte: paste of KOH (alkaline electrolyte)

• Voltage: 1.3 volts

• Uses: watches, pacemakers, hearing aids
  As cell discharges, concentrations do NOT change as reactants & products are solids.
  [OH^-] in electrolyte does NOT change.
  So, the voltage of this cell remains constant throughout its lifetime.

Lithium cell : Li|Li⁺(nonaqueous)|KOH(paste)|MnO₂,Mn(OH)₃,C

• Anode (-): lithium
  Li----->Li₊+e^-

• Cathode (+): carbon in contact with manganese(III),manganese(IV) electrode
  MnO₂+2H₂O+e^------>Mn(OH)₃+OH^-

• Electrolyte: paste of KOH (alkaline electrolyte)

• Voltage:  

• Uses: auto-wind, auto-focus cameras
  Can deliver high current.
  Have long shelf-life.

Lithium iodide solid state cell : Li|LiI(s)|I₂(in polymer)

• Anode (-): lithium
  Li(s) -----> Li⁺ + e^-

• Cathode (+): iodine
  ½I₂(s) + e^- -----> I^-

• Electrolyte: lithium iodide

• Voltage: 2 volts

• Uses: cardiac pacemaker, watches, calculators
  Lasts about 10 years

Lead-acid battery (or accumulator) : Pb,PbSO₄|H₂SO₄(aq)|PbO₂,Pb

• Anode (-): lead plates
  Pb(s)+HSO₄^-(aq) ----->PbSO₄(s)+H⁺(aq)+2e^-

• Cathode (+): lead plates covered with PbO₂
  PbO₂(s)+3H⁺(aq)+HSO₄^-(aq)+2e^- ----->PbSO₄(s)+2H₂O(l)

• Electrolyte: 4M H₂SO₄

• Voltage: 2.1 volts per cell (6 cells in series makes up a 12volt car battery)

• Uses: motor vehicle batteries
  As cell delivers current, lead sulfate deposits on electrodes & [H₂SO₄] falls.
  Six 2V cells connected in series make up a 12V battery.
  To obtain high current output from the battery, the surface area of the electrodes in contact with the electrolyte must be large & the plates close together.

Nickel-cadmium cell (NiCad) : Cd,Cd(OH)₂|KOH|NiO₂,Ni(OH)₂,Ni

• Anode (-): grid covered with cadmium
  Cd(s)+2OH^-(aq)----->Cd(OH)₂(s)+2e^-

• Cathode (+): grid covered with nickel(III)hydroxide
  NiO(OH)(s)+H₂O(l)+e^------>Ni(OH)₂(s)+OH^-(aq)

• Electrolyte: KOH

• Voltage: 1.25volts

• Uses: video cameras, phones, cordless drills, laptop computers

• promising future

• more efficient than coal or gas-fired power stations

• non-polluting

• porous electrodes lined with catalysts, eg, Ni or Pt, making it expensive

• systems required to continuously supply reactants & remove products

• CH₄, CH₃OH, C₃H₈ can be used instead of H₂(g)

Alkaline fuel cell

• Anode (-): porous carbon anode with catalyst in contact with H₂(g)
  H₂(g)+2OH^-(aq)----->2H₂O(l)+2e^-

• Cathode (+): porous carbon cathode with catalyst in contact with O₂(g)
  O₂(g)+2H₂O(l)+4e^------>4OH^-(aq)

• Electrolyte: hot KOH(aq)

• Voltage: ~1volt

Acid fuel cell

• Anode (-): porous carbon anode with catalyst in contact with H₂(g)
  H₂(g)----->2H⁺(aq)+2e^-

• Cathode (+): porous carbon cathode with catalyst in contact with O₂(g)
  O₂(g)+4H⁺(aq)+4e^------>2H₂O(l)

• Electrolyte: hot H₃PO₄(aq)

• Voltage: ~1volt