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Leclanché cell

April 11, 2024

The Leclanché cell is a battery invented and patented by the French scientist Georges Leclanché in 1866.[1][2][3] The battery contained a conducting solution (electrolyte) of ammonium chloride, a cathode (positive terminal) of carbon, a depolarizer of manganese dioxide (oxidizer), and an anode (negative terminal) of zinc (reductant).[4][5] The chemistry of this cell was later successfully adapted to manufacture a dry cell.

A 1919 illustration of a Leclanché cell

History edit

In 1866, Georges Leclanché invented a battery that consisted of a zinc anode and a manganese dioxide cathode wrapped in a porous material, dipped in a jar of ammonium chloride solution. The manganese dioxide cathode had a little carbon mixed into it as well, which improved conductivity and absorption.[6] It provided a voltage of 1.4 volts.[7] This cell achieved very quick success in telegraphy, signalling and electric bell work.

The dry cell form was used to power early telephones—usually from an adjacent wooden box affixed to the wall—before telephones could draw power from the telephone line itself. The Leclanché cell could not provide a sustained current for very long; in lengthy conversations, the battery would run down, rendering the conversation inaudible.[8] This is because certain chemical reactions in the cell increase its internal resistance and, thus, lower its voltage. These reactions reverse themselves when the battery is left idle, making it good for many short periods of use with idle time between them, but not long periods of use.[9]

Construction edit

The original form of the cell used a porous pot. This gave it a relatively high internal resistance, and various modifications were made to reduce the resistance. These included the "Agglomerate block cell" and the "Sack cell". Leclanché first, and Carl Gassner later, both strived to transform the original wet cell into a more portable and more efficient dry cell.

Porous pot cell
In Leclanché's original cell the depolarizer (in fact, the oxidizing agent in the cell), consisting of crushed manganese dioxide, is packed into a pot, and a carbon rod is inserted to act as the cathode (reduction reaction). The anode (oxidation reaction), which is a zinc rod, is then immersed along with the pot in a solution of ammonium chloride. The liquid solution acts as the electrolyte, permeating through the porous pot to make contact with the cathode.
Agglomerate block cell
In 1871 Leclanché dispensed with the porous pot and replaced it with a pair of "agglomerate blocks", attached to the carbon plate by rubber bands. These blocks were made by mixing the manganese dioxide with binding agents and pressing the mixture into moulds.
Sack cell
In this cell the porous pot is replaced by a wrapping of canvas or sacking. In addition, the zinc rod is replaced by a zinc cylinder to give a larger surface area. It has a lower internal resistance than either of the above (porous and agglomerate).
Starch addition
In 1876, Georges Leclanché added starch to the ammonium chloride electrolyte in an effort to better jellify it.
Improved dry cell
In 1888, a German physician, Carl Gassner, improved the jellification process and produced a more portable dry cell by mixing plaster and hydrophilic chemicals with the ammonium chloride electrolyte.

Chemistry edit

The redox reaction in a Leclanché cell involves the two following half-reactions:

– anode (oxidation of Zn): Zn → Zn2+ + 2e− | E0 = −0.76 volts
– cathode (reduction of Mn(IV)): 2 MnO2 + 2NH4+ + 2e− → 2 MnO(OH) + 2 NH3 | E0 = 1.23 volts

The chemical process which produces electricity in a Leclanché cell begins when zinc atoms on the surface of the anode oxidize, i.e. they give up both their valence electrons to become positively charged Zn2+ ions. As the Zn2+ ions move away from the anode, leaving their electrons on its surface, the anode becomes more negatively charged than the cathode. When the cell is connected in an external electrical circuit, the excess electrons on the zinc anode flow through the circuit to the carbon rod, the movement of electrons forming an electric current. The potential difference in charge over the anode and cathode is equal to the difference of the two half-reaction potentials, producing a theoretical voltage of 1.99v of potential energy across the terminals. A variety of factors, such as internal resistance, lower this output value to the 1.4 volts measured from these cells in practice.

As the current travels around the circuit, when the electrons enter the cathode (carbon rod), they combine with manganese dioxide (MnO2) and water (H2O), which react with each other to produce manganese oxide (Mn2O3) and negatively charged hydroxide ions. This is accompanied by a secondary acid-base reaction in which the hydroxide ions (OH–) accept a proton (H+) from the ammonium ions present in the ammonium chloride electrolyte to produce molecules of ammonia and water.[10]

Zn(s) + 2 MnO2(s) + 2 NH4Cl(aq) → ZnCl2(aq) + Mn2O3(s) + 2 NH3(aq) + H2O(l),

or if one also considers the hydration of the Mn2O3(s) sesquioxide into Mn(III) oxy-hydroxide:

Zn(s) + 2 MnO2(s) + 2 NH4Cl(aq) → ZnCl2(aq) + 2 MnO(OH)(s) + 2 NH3(aq)


Alternately, the reduction reaction of Mn(IV) can proceed further, forming Mn(II) hydroxide.

Zn(s) + MnO2(s) + 2 NH4Cl(aq) → ZnCl2(aq) + Mn(OH)2(s) + 2 NH3(aq)

Uses edit

The electromotive force (e.m.f.) produced by a Leclanche cell is 1.4 volts, with a resistance of several ohms where a porous pot is used.[7] It saw extensive usage in telegraphy, signaling, electric bells and similar applications where intermittent current was required and it was desirable that a battery should require little maintenance.

The Leclanché battery wet cell was the forerunner of the modern zinc–carbon battery (a dry cell). The addition of zinc chloride to the electrolyte paste raises the e.m.f. to 1.5 volts. Later developments dispensed with the ammonium chloride completely, giving a cell that can endure more sustained discharge without its internal resistance rising as quickly (the zinc chloride cell).

See also edit

References edit

  1. ^ Leclanché, "une pile à oxyde insoluble" [an insoluble oxide battery], French patent no. 71,865 (issued: 8 June 1866) in: French Ministry of Agriculture and Commerce (1881). Description des machines et procédés pour lesquels des brevets d'invention ont été pris … [Descriptions of machines and procedures for which patents have been taken …] (in French). Vol. 98. Paris, France: Imprimerie Nationale. pp. 33–34.
  2. ^ Leclanché, Georges (1868). "Quelques observations sur l'emploi des piles électriques. Pile constante au peroxyde de manganèse à un seul liquide". Les Mondes. 16: 532.
  3. ^ Jensen, William B. (January 2014). "The Leclanché Cell. Museum Notes, Oesper Collections". hdl:2374.UC/731246.
  4. ^ Leclanché, Georges (1867). Notes sur l'emploi des piles électriques en télégraphie, pile constante au peroxyde de manganèse à un seul liquide. Paris: Impr. de Hennuyer et fils.
  5. ^ Leclanché, Georges (1869). Notice sur la pile Leclanché : précédée de quelques considérations sur l'emploi des piles électriques en télégraphie. Paris: Jamin, Bailly et cie, Burndy Library.
  6. ^ Zinc–Carbon Batteries, Molecular Expressions. magnet.fsu.edu
  7. ^ a b Morgan, Alfred P. (1913). The Boy Electrician. Boston: Lothrop, Lee & Separd Co. p. 58.
  8. ^ Battery Facts. "Leclanché Cell". Retrieved 2007-01-09.
  9. ^ Calvert, James B. (2000-04-07). . du.edu. Archived from the original on 2007-01-12. Retrieved 2007-01-12.
  10. ^ "Commercial galvanic cells: Leclanché Dry Cell". 26 November 2013. Retrieved 2017-12-26.

Bibliography edit

  • Practical Electricity by W. E. Ayrton and T. Mather, published by Cassell and Company, London, 1911, pp 188–193

April 11, 2024
leclanché, cell, battery, invented, patented, french, scientist, georges, leclanché, 1866, battery, contained, conducting, solution, electrolyte, ammonium, chloride, cathode, positive, terminal, carbon, depolarizer, manganese, dioxide, oxidizer, anode, negativ. The Leclanche cell is a battery invented and patented by the French scientist Georges Leclanche in 1866 1 2 3 The battery contained a conducting solution electrolyte of ammonium chloride a cathode positive terminal of carbon a depolarizer of manganese dioxide oxidizer and an anode negative terminal of zinc reductant 4 5 The chemistry of this cell was later successfully adapted to manufacture a dry cell A 1919 illustration of a Leclanche cell Contents 1 History 2 Construction 3 Chemistry 4 Uses 5 See also 6 References 7 BibliographyHistory editIn 1866 Georges Leclanche invented a battery that consisted of a zinc anode and a manganese dioxide cathode wrapped in a porous material dipped in a jar of ammonium chloride solution The manganese dioxide cathode had a little carbon mixed into it as well which improved conductivity and absorption 6 It provided a voltage of 1 4 volts 7 This cell achieved very quick success in telegraphy signalling and electric bell work The dry cell form was used to power early telephones usually from an adjacent wooden box affixed to the wall before telephones could draw power from the telephone line itself The Leclanche cell could not provide a sustained current for very long in lengthy conversations the battery would run down rendering the conversation inaudible 8 This is because certain chemical reactions in the cell increase its internal resistance and thus lower its voltage These reactions reverse themselves when the battery is left idle making it good for many short periods of use with idle time between them but not long periods of use 9 Construction editThe original form of the cell used a porous pot This gave it a relatively high internal resistance and various modifications were made to reduce the resistance These included the Agglomerate block cell and the Sack cell Leclanche first and Carl Gassner later both strived to transform the original wet cell into a more portable and more efficient dry cell Porous pot cell In Leclanche s original cell the depolarizer in fact the oxidizing agent in the cell consisting of crushed manganese dioxide is packed into a pot and a carbon rod is inserted to act as the cathode reduction reaction The anode oxidation reaction which is a zinc rod is then immersed along with the pot in a solution of ammonium chloride The liquid solution acts as the electrolyte permeating through the porous pot to make contact with the cathode Agglomerate block cell In 1871 Leclanche dispensed with the porous pot and replaced it with a pair of agglomerate blocks attached to the carbon plate by rubber bands These blocks were made by mixing the manganese dioxide with binding agents and pressing the mixture into moulds Sack cell In this cell the porous pot is replaced by a wrapping of canvas or sacking In addition the zinc rod is replaced by a zinc cylinder to give a larger surface area It has a lower internal resistance than either of the above porous and agglomerate Starch addition In 1876 Georges Leclanche added starch to the ammonium chloride electrolyte in an effort to better jellify it Improved dry cell In 1888 a German physician Carl Gassner improved the jellification process and produced a more portable dry cell by mixing plaster and hydrophilic chemicals with the ammonium chloride electrolyte Chemistry editThe redox reaction in a Leclanche cell involves the two following half reactions anode oxidation of Zn Zn Zn2 2e E0 0 76 volts cathode reduction of Mn IV 2 MnO2 2NH4 2e 2 MnO OH 2 NH3 E0 1 23 voltsThe chemical process which produces electricity in a Leclanche cell begins when zinc atoms on the surface of the anode oxidize i e they give up both their valence electrons to become positively charged Zn2 ions As the Zn2 ions move away from the anode leaving their electrons on its surface the anode becomes more negatively charged than the cathode When the cell is connected in an external electrical circuit the excess electrons on the zinc anode flow through the circuit to the carbon rod the movement of electrons forming an electric current The potential difference in charge over the anode and cathode is equal to the difference of the two half reaction potentials producing a theoretical voltage of 1 99v of potential energy across the terminals A variety of factors such as internal resistance lower this output value to the 1 4 volts measured from these cells in practice As the current travels around the circuit when the electrons enter the cathode carbon rod they combine with manganese dioxide MnO2 and water H2O which react with each other to produce manganese oxide Mn2O3 and negatively charged hydroxide ions This is accompanied by a secondary acid base reaction in which the hydroxide ions OH accept a proton H from the ammonium ions present in the ammonium chloride electrolyte to produce molecules of ammonia and water 10 Zn s 2 MnO2 s 2 NH4Cl aq ZnCl2 aq Mn2O3 s 2 NH3 aq H2O l or if one also considers the hydration of the Mn2O3 s sesquioxide into Mn III oxy hydroxide Zn s 2 MnO2 s 2 NH4Cl aq ZnCl2 aq 2 MnO OH s 2 NH3 aq Alternately the reduction reaction of Mn IV can proceed further forming Mn II hydroxide Zn s MnO2 s 2 NH4Cl aq ZnCl2 aq Mn OH 2 s 2 NH3 aq Uses editThe electromotive force e m f produced by a Leclanche cell is 1 4 volts with a resistance of several ohms where a porous pot is used 7 It saw extensive usage in telegraphy signaling electric bells and similar applications where intermittent current was required and it was desirable that a battery should require little maintenance The Leclanche battery wet cell was the forerunner of the modern zinc carbon battery a dry cell The addition of zinc chloride to the electrolyte paste raises the e m f to 1 5 volts Later developments dispensed with the ammonium chloride completely giving a cell that can endure more sustained discharge without its internal resistance rising as quickly the zinc chloride cell See also editList of battery types History of the battery Alkaline battery a similar cell in which the NH4Cl electrolyte has been replaced by KOH This improved type of battery with a much higher charge density 5 was commercialised much later 1960 70 References edit Leclanche une pile a oxyde insoluble an insoluble oxide battery French patent no 71 865 issued 8 June 1866 in French Ministry of Agriculture and Commerce 1881 Description des machines et procedes pour lesquels des brevets d invention ont ete pris Descriptions of machines and procedures for which patents have been taken in French Vol 98 Paris France Imprimerie Nationale pp 33 34 Leclanche Georges 1868 Quelques observations sur l emploi des piles electriques Pile constante au peroxyde de manganese a un seul liquide Les Mondes 16 532 Jensen William B January 2014 The Leclanche Cell Museum Notes Oesper Collections hdl 2374 UC 731246 Leclanche Georges 1867 Notes sur l emploi des piles electriques en telegraphie pile constante au peroxyde de manganese a un seul liquide Paris Impr de Hennuyer et fils Leclanche Georges 1869 Notice sur la pile Leclanche precedee de quelques considerations sur l emploi des piles electriques en telegraphie Paris Jamin Bailly et cie Burndy Library Zinc Carbon Batteries Molecular Expressions magnet fsu edu a b Morgan Alfred P 1913 The Boy Electrician Boston Lothrop Lee amp Separd Co p 58 Battery Facts Leclanche Cell Retrieved 2007 01 09 Calvert James B 2000 04 07 The Electromagnetic Telegraph du edu Archived from the original on 2007 01 12 Retrieved 2007 01 12 Commercial galvanic cells Leclanche Dry Cell 26 November 2013 Retrieved 2017 12 26 Bibliography editPractical Electricity by W E Ayrton and T Mather published by Cassell and Company London 1911 pp 188 193 Retrieved from https en wikipedia org w index php title Leclanche cell amp oldid 1206662381, wikipedia, wiki, book, books, library,

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