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Experiments and instruments

A series of short movies showing how neutron experiments are prepared or performed. Some of these movies have an historical interest since they captured important moments in the life of the ILL.

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Films and animations

D1B

Why can't alkaline batteries be recharged?

D1B is a high intensity powder diffractometer with an 80° PSD (position sensitive detector). One of its major use is for kinetic and real time experiments like the one shown here.

The video below was recorder in January 1995 by M6, the French TV  company, just before the restart of the High Flux Reactor of the ILL after a long refit. It shows the installation on the instrument of a sample alkaline battery and explains why such experiments are important. In fact the in situ neutron study of the charge/discharge process of alkaline batteries made it possible to understand why alkaline batteries are not rechargeable.

 

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Click here to download the 320x240 MPEG-4 movie (file size: 3 Mb,  duration 1'15")

Click here to download the 768x576 MPEG-4 movie (file size: 20.4 Mb, duration 1'37")

Movie by the French TV M6

©2002-2007, M6 and Institut Laue-Langevin, Grenoble, France.

To summarise:

When an alkaline battery discharges, electrolyte water decomposes into H+ and OH- ions. The H+ ion inserts itself into MnO2 forming an interstitial compound, transferring an electron at the same time (reduction).

    MnO2 + xH+ + xe-  <=>  HxMnO2

The OH- hydroxyl ion oxides zinc into zinc hydroxide, Zn(OH)2 and loses one electron e-.

    Zn+2OH-  <=>  Zn(OH)2 + 2e-

At the start of the discharge, when less than 40% has reacted (x<0.4), the intermediate component HxMnO2 has the same structure (ramsdellite) as MnO2. As the discharging continues, a new compound appears. It is MnOOH (groutite), whose structure is very different and which does not re-transform back into ramsdellite if H+ is taken out. This is why, beyond x = 0.4 discharge, the reaction is no longer reversible and the battery cannot be recharged.

A detailed explanation of the above structural transformation can be found in the CD-ROM "Exploring matter with neutrons".

Ref.: Y. Chabre and J. Pannetier (1995) Progress in Solid State Chem., 23, 1-150.

English translation of the French spoken text

> Journalist :
The nuclear reactor of the Institut Laue Langevin was restarted on 6th January after an interruption of 3 years for a major refit.  The normal research programme using this outstanding facility will continue from the following Monday.
Five years ago two Grenoble scientists were closely studying alcaline batteries.

> Jean Pannetier :
Alcaline batteries use an active component manganese dioxide which is cheap and creates little pollution.  The inconvenience of such batteries is that they are not rechargeable, and throughout the world there are studies going on to achieve their re-use.

> Journalist:
Since the invention of the battery in 1866 no-one has been able to explain why a battery cannot be recharged.  The reactor of the ILL has thrown new light on this problem.

> Jean Pannetier :
We direct neutrons across the battery while it is discharging, and these are then counted by this detector. The signal we obtain tells us of the changes occurring during discharge.

> Journalist :
In fact the ILL and CNRS researchers now have understood that, during discharging, the chemical reaction of the manganese was irreversible, hence the impossibility of re-use. Having
discovered the reason the next step, offering enormous financial rewards, is to work out how to recharge the battery.

Translation: Ronen Ghosh, ILL

Original spoken text in French

> Journaliste :
Remis en marche le 6 janvier après trois ans d'interruption, le réacteur nucléaire de l'Institut Laue Langevin sera opérationnel lundi, un outil formidable pour le recherche. Il y a cinq ans, deux scientifiques grenoblois se sont intéressés de près aux piles alcalines.

> Jean Pannetier :
Les piles alcalines contiennent comme matériau actif du dioxyde de manganèse, qui est un matériau peu cher et peu polluant. Ces piles présentent malheureusement l'inconvénient de ne pas être rechargeables, et de nombreuses recherches sont menées actuellement dans le monde entier pour essayer de les rendre chargeables.

> Journaliste :
Depuis l'invention de la pile en 1866, personne ne pouvait expliquer pourquoi une pile n'était pas rechargeable. Le réacteur de l'ILL a permis d'éclairer nos lanternes.

> Jean Pannetier:
Les neutrons traversent la pile pendant qu'elle se décharge, et ils sont comptés par ce détecteur. Le signal obtenu nous renseigne sur les transformations qui se produisent au cours de cette décharge.

> Journaliste :
Effectivement, chercheurs de l'ILL et du CNRS ont compris que, pendant l'utilisation d'une pile, la réaction chimique sur le manganèse était irréversible, impossible donc de la recharger. Après avoir découvert le pourquoi, il faut maintenant savoir comment recharger une pile, les enjeux financiers sont énormes.

D'après: Fabien Filhol
English checked by: Ronen Ghosh, ILL, April 2007.
Updates: A.Filhol, 17 Sept 2008, 9 Sept 2009.

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