Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Patent
1991-05-02
1993-04-13
Niebling, John
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
20419215, 20419229, 359265, 359273, 428689, 428698, 428701, 429218, C23C 1434, H01M 458, H01M 618
Patent
active
052022013
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a composite element having a titanium chalcogenide or oxychalcogenide layer, more particularly usable as the positive electrode in a thin film electrochemical cell, such as an electrochemical generator or an electrochromic cell.
More specifically, it relates to the production of electrochemical cells with solid electrolytes and electrodes and in particular thin film electrochemical cells, whose operating principle is based on the insertion and disinsertion (or intercalation or disintercalation) of an alkali metal ion or a proton in the positive electrode.
Electrochemical cells of this type have numerous applications, e.g. in the form of microgenerators having a total thickness of a few micrometers, in systems for protecting the memories of microsystems during power failures or as integrated systems in smart cards of the bank card type.
These electrochemical cells can also be used as an electrochromic system when the positive electrode changes colour during insertion, which makes them interesting for the display of information or even better, when the negative electrode is transparent, for windows which change colour according to needs (smart windows).
Numerous embodiments of "all-solid" electrochemical cells, optionally of the thin film type and with solid electrodes and electrolyte are known. Thus, French patent FR-A-2 581 483 describes a solid battery or pile successively incorporating an alkali metal coating such as lithium, constituting an ion source, an ionic solid conductive electrolyte coating and a lamellar intercalation composite coating able to receive and accumulate the ions from said alkali metal coating. The lamellar compound can be a substance of formula MX.sub.2, e.g. TiS.sub.2 and can be deposited by epitaxy.
French patent FR-A-2 550 015 also describes an "all-solid" electrochemical generator constituted by a positive electrode of an insertion compound of lithium, such as crystallized TiS.sub.2, an ionic conductive electrolyte by Li.sup.+ ions and a negative lithium electrode.
European patent EP-A-0127373 describes a thin film battery having a positive, crystallized TiS.sub.2 electrode deposited on a current collector with an amorphous TiO.sub.2 intermediate coating, an ionic conductive glass electrolyte and a negative lithium electrode.
Consideration has also been given to the production of generators having solid positive electrodes of amorphous transition metal chalcogenide by chemical processes in the manner described in U.S. Pat. No. 4,299,892 and WO-88/00172.
In the case of positive, crystallized TiS.sub.2 electrodes, the insertion and disinsertion of lithium are made more difficult due to the anisotropic character of the electrode. Moreover, these electrodes have a poor resistance to insertions and disinsertions and have an inadequate stability.
In the case of chemically prepared, amorphous, positive electrodes, the electrode preparation procedure is not suitable for the production of thin films.
"All-solid" generators are not entirely satisfactory, because the current densities which can be obtained remain below 20 .mu.A/cm.sup.2. In addition, the use of a solid electrolyte with amorphous electrodes causes certain problems, because these electrolytes are not very good ionic conductors. Therefore, the performance characteristics of the generator are limited, because the surface state of the electrodes does not make it possible to use a solid electrolyte thickness below 20 .mu.m in order to avoid any risk of direct contact between the positive electrode and the negative electrode.
The present invention specifically relates to a composite element usable as the positive electrode and in particular in thin film form, in an "all-solid" electrochemical cell, which makes it possible to obtain better results and obviate the aforementioned disadvantages.
The composite element according to the invention is constituted by a substrate coated by cathodic sputtering with an isotropic, amorphous material coating complying with the formula: such that 0<a.ltoreq.2,
REFERENCES:
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patent: 4555456 (1985-11-01), Kanehori et al.
patent: 4730383 (1988-03-01), Balkanski
patent: 4816356 (1989-03-01), Balkanski
patent: 4889414 (1989-12-01), Ranh et al.
patent: 4945014 (1990-07-01), Miyabayashi et al.
Chemical Abstracts, vol. III, No. 15, Oct. 9, 1989, Abstract No. 11:137484R.
Mater. Sci. Eng., B 1989, B3(1-2), 19-23.
Dormoy Richard
Levasseur Alain
Meunier Georges
Centre National de la Recherche Scientifique
Leader William T.
Niebling John
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