Electrochemical device

Details Electrochemical device Electrochemical device

2001-12-26

2003-03-04

Epps, Georgia (Department: 2873)

Optical: systems and elements

Optical modulator

Light wave temporal modulation

C359S270000, C359S268000

Reexamination Certificate

active

06529308

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of electrochemical devices having at least one electrochemically active layer capable of reversibly and simultaneously inserting ions and electrons, in particular electrochromic devices. These electro-chemical devices are, in particular, used to manufacture windows whose optical and/or energy transmission or optical reflection can be modulated using an electric current. They can also be used to manufacture energy-storage elements such as batteries or, alternatively, gas sensors or display elements.
2. Description of the Background
Considering the particular example of electrochromic systems, it will be recalled that, as is known, they include a layer of a material capable of reversibly and simultaneously inserting ions, in particular cations, and electrons, and whose oxidation states corresponding to the inserted and deinserted states are of distinct coloration, one of the states generally being transparent. The insertion or deinsertion reaction is controlled by a suitable electrical power supply, in particular by applying an appropriate potential difference. The electrochromic material, in general based on tungsten oxide, thus needs to be brought into contact with a source of electrons, such as a transparent electroconductive layer, and a source of ions, such as an ionic-conductor electrolyte.
It is furthermore known that, in order to provide at least of the order of a hundred switching operations, a back electrode which is itself also capable of reversibly inserting cations, symmetrically with respect to the layer of electrochromic material, must be associated with the layer of electrochromic material, so that, macroscopically, the electrolyte appears as a simple ion medium.
The back electrode must be formed either by a layer which has neutral coloration, or one which is at least transparent when the electrochromic layer is in the uncoloured state. Since tungsten oxide is a cathodic electrochromic material, that is to say its coloured state corresponds to the most reduced state, an anodic electrochromic material such as nickel oxide, iridium oxide or vanadium oxide, without implying any limitation, is generally used for the back electrode. It has also been proposed to use a material which is optically neutral in the oxidation states in question, for example cerium oxide or organic materials such as electronic conducting polymers (polyaniline, etc.) or Prussian blue.
Such systems are described, for example, in European Patents EP-0,338,876, EP-0,408,427, EP-0,575,207 and EP-0,628,849.
These systems can currently be divided into two categories, according to the type of electrolyte which they use:
either the electrolyte is present in the form of a polymer or a gel, for example a protonic-conduction polymer such as those described in European Patents EP-0,253,713 and EP-0,670,346, or a polymer with lithium-ion conduction such as those described in Patents EP-0,382,623, EP-0,518,754 or EP-0,532,408
or the electrolyte is an inorganic layer which is an ionic conductor but electronically insulating, in which case the term “all solid” electrochromic systems is used.
Reference may be made to patents EP97/400702.3 of Mar. 27, 1997 and EP-0 831 360 for the description of an “all solid” system. It is principally to this type of system that the invention relates, because it has a clear advantage in terms of ease of manufacture. This is because, with such a configuration, all the layers of the system can be deposited successively on a single carrier substrate (whereas in the system in which the electrolyte is a polymer or a gel, it is normally necessary to manufacture two “half-cells” which are assembled together via the electrolyte, which actually requires the use of two carrier substrates and the running of two series of layer depositions in parallel on each of them).
Whatever the configuration adopted, one requirement with this type of electrochemical system consists in giving it a “memory effect” which is sufficient in terms of the application in question. This term is intended to mean the capacity which the system has to stay in a given state once the electrical power supply has been cut. In the case of an electrochromic window, this state is generally its coloured state. In the absence of an electrical power supply, it tends to revert to its uncoloured state. The aim is clearly for this memory effect to be able to last as long as possible so that, by means of the electrical power supply of the system, the user can actually control its state satisfactorily. In practice, it is for example desirable for the electrochromic window to be able to stay in the coloured state, with the power off, for several hours, for example 10 to 20 hours.
In practice, this goal is difficult to achieve because the system has to deal with a leakage current from one electroconductive layer to the other, in particular at the periphery of the system, which tends to make it revert to its equilibrium state, that is to say to its uncoloured state.
A first solution consisted in accepting the existence of these leakage currents, and in re-supplying the system with electricity when it is in its coloured state, with a given periodicity, in order to compensate for them. It is not, however, fully satisfactory, if only because these leakage currents can vary from one window to another, and in this case the coloration achieved by two similar windows supplied with electricity in the same way is different.
A second solution consisted in putting a margin on one of the two electroconductive layers, that is to say depositing the layers in such a way that they are offset at their periphery, and thus in eliminating/reducing the leakage current from one layer to another at their respective peripheries. The solution is effective but makes the process of manufacturing the system more complicated: in particular, it makes it necessary to deposit at least one of the two electroconductive layers by using a mask on the carrier substrate.
SUMMARY OF THE INVENTION
The object of the invention is therefore to overcome these drawbacks by providing, in particular, a novel method of processing the electrochemical devices described above in order to improve their performance, very particularly in order to limit/eliminate the risks of short-circuits, the so-called leakage currents and, thereby, in order to increase their “memory effect”, and to do so while favouring simplicity in its implementation.
The invention firstly relates to a method of processing an electrochemical device having at least one carrier substrate provided with a stack of functional layers comprising at least one electrochemically active layer which is capable of reversibly and simultaneously inserting ions and electrons and which is arranged between two electroconductive layers. It is, in particular, an electrochemical device of the electrochromic type, with a stack of functional layers including at least, successively:
a first electroconductive layer,
a first electrochemically active layer capable of reversibly inserting ions, for example cations such as H
+
, Li
+
or anions such as OH
−
, in particular of an anodic (or cathodic, respectively) electrochromic material,
an electrolyte layer,
a second electrochromically active layer capable of reversibly inserting the said ions, in particular of a cathodic (or anodic, respectively) electrochromic material,
a second electroconductive layer.
The method of the invention is characterized in that the functionality of at least one of the functional layers, with the exception of one of the electroconductive layers, in particular with the exception of the first (the one closest to the carrier substrate), is locally inhibited so as to delimit an inactive peripheral region in the stack.
In the context of the invention, the term “layer” is intended to mean either unitary layers or the superposition of a plurality of layers which jointly fulfil the same function. This is, in particular, the case with the electrolyte layer, wh

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