FR3054727A1 - ELECTROCHEMICAL DEVICE, SUCH AS A MICROBATTERY OR ELECTROCHROME DEVICE, AND METHOD FOR PRODUCING THE SAME - Google Patents

Abstract

The electrochemical device comprises a first stack (1) of solid thin layers formed on a substrate (2), said first stack (1) forming a battery and comprising: - a first electrode (4a) and a second electrode (4b) separate by an electrically insulating and ionically conductive electrolyte layer (3), the electrolyte layer ensuring the transit of ions between the first and second electrodes (4a and 4b), - a first current collector (5a) in contact with the first electrode (4a), - a second current collector (5b) in contact with the second electrode (4b), the first current collector (5a) and the second current collector (5b) being electronically isolated by the second electrode (5b). an electrolyte (3); - a first cohesion layer (6) disposed between the first electrode (4a) and the electrolyte layer (3), the first cohesion layer (6) being configured to be permeable to said ions and adapting the stresses between the electrolyte layer (3) and the first electrode (4a) and devoid of electrochemical property with the electrolyte.

Description

Holder (s): COMMISSIONER OF ATOMIC ENERGY AND ALTERNATIVE ENERGIES Public establishment.

Extension request (s)

Agent (s): CABINET HECKE Société anonyme.

ELECTROCHEMICAL DEVICE, SUCH AS A MICROBATTERY OR AN ELECTROCHROMIC DEVICE, AND ITS MANUFACTURING METHOD.

FR 3 054 727 - A1

The electrochemical device comprises a first stack (1) of solid thin layers formed on a substrate (2), said first stack (1) forming a battery and comprising:

- a first electrode (4a) and a second electrode (4b) separated by an electronically insulating and ionically conductive electrolyte layer (3), the electrolyte layer ensuring the transit of ions between the first and second electrodes (4a and 4b),

- a first current collector (5a) in contact with the first electrode (4a),

- a second current collector (5b) in contact with the second electrode (4b), the first current collector (5a) and second the current collector (5b) being electronically isolated by the electrolyte layer (3),

- a first cohesion layer (6) disposed between the first electrode (4a) and the electrolyte layer (3), the first cohesion layer (6) being configured to be permeable to said ions and to adapt the stresses between the layer electrolyte (3) and the first electrode (4a) and devoid of electrochemical property with the electrolyte.

Electrochemical device, such as a microbattery or an electrochromic device, and its production method.

Technical field of the invention

The invention relates to an all solid electrochemical device, such as an all solid microbattery or an electrochromic device, and to its production method.

State of the art

Microbatteries are defined as all solid-state electrochemical generators formed by a stack of thin layers which comprises at least two electrodes (positive and negative) separated by an electrolyte. These microbatteries make it possible in particular to adapt energy sources to new nomadic applications which are offered regularly and which integrate electronic microcircuits.

The batteries are more and more efficient and smaller and smaller. To achieve such results, batteries use materials capable of storing atoms of an element, for example a metal ion of M ⁺ type, such as H ⁺ , Li ⁺ , Na ⁺ , K ⁺ , in ionic, alloyed form, or even monoatomic. These batteries then release these atoms in the form of ions.

In the case of lithium batteries, various mechanisms can be brought into play, and in particular the insertion of lithium within a host structure, the formation of metal-lithium alloy or even the formation of defined compounds.

It is recognized that the formation of alloys or of compounds defined with lithium induces a significant volume expansion, for example an increase in volume of the order of 400% for the lithiation of silicon. During the lithiation, significant stresses are present in the battery and more specifically at the level of the electrode.

This significant volume expansion can result in delamination or sputtering phenomena of the electrodes used. This mechanical degradation inevitably results in a rapid drop in the electrical performance of the battery.

In the case of batteries with liquid electrolyte, in order to partially remedy these problems, various solutions have been proposed.

The publication by Polat et al. (“Improving Si Anode Performance by Forming Copper Capped Copper-Silicon Thin Film Anodes for Rechargeable Lithium Ion Bateries” Electrochimica Acta 170 (2015) 63-71) proposes the production of an anode formed by a copper substrate covered with a layer CuSi obtained by spraying copper and silicon atoms which will form a uniformly dispersed structure of copper silicide.

As a variant, the preceding stack is covered with a layer of copper to improve the physical, mechanical and surface properties of the Cu / CuSi film. Two different stacks are therefore available

Cu / CuSi and Cu / CuSi / Cu with a layer of CuSi which has a thickness slightly less than 3μΐτι. In the second embodiment, the top layer of copper has a thickness of less than 100 nm.

This document proposes the realization of a copper collector covered by a specific CuSi electrode. The use of CuSi in the Cu3Si form makes it possible to suppress volume variations in silicon-based anodes. This teaching proposes a very particular alloy to form the anode which remains particularly difficult for industrial integration.

It also appears that the copper layer in contact with the liquid electrolyte makes it possible to increase the performance of the anode by increasing the conductivity and by presenting a ductile material.

The electrolyte being in liquid form, in the event of slight deterioration of the electrode, for example due to volume expansion or cracks, the liquid electrolyte is in contact with the electrode. Indeed, the liquid electrolyte will interfere in the interstices of the electrode and thus ensure continuity of contact between the electrolyte and the electrode.

However, when too large a volume expansion occurs, problems of electronic continuity can appear and in particular because of the significant cracks in the electrode. The use of upper and lower copper layers improves electronic continuity by removing some of the volume expansion constraints of the electrode.

However, it appears that the solutions proposed in the prior art for a liquid electrolyte do not make it possible to completely solve the problems of degradation of the performance of the battery and in particular in the case of batteries with solid electrolyte because the solid electrolyte cannot deform to fill the cracks in the electrode.

Subject of the invention

The invention aims to remedy the drawbacks of the prior art and, in particular, to provide an electrochemical device having a solid electrolyte having better management of internal stresses and / or improved electrical performance.

We tend to reach this object by an electrochemical device such as a battery or an electrochromic device, comprising a stack of thin solid layers formed on a substrate, said first stack comprising:

a first electrode and a second electrode separated by an electronically insulating and ionically conductive solid electrolyte layer, the electrolyte layer ensuring the transit of ions between the first and second electrodes,

- a first current collector in contact with the first electrode,

- a second current collector in contact with the second electrode, the first current collector and the second current collector being electronically isolated by the electrolyte layer,

- At least one first cohesion layer disposed between one of the first and second electrodes and the electrolyte layer, the at least one cohesion layer being configured to have a permeation rate for said ions greater than 50% and to adapt the stresses between the electrolyte layer and one of the first and second electrodes.

In a development, the first cohesion layer is disposed between the electrolyte layer and the first electrode and a second cohesion layer is disposed between the electrolyte layer and the second electrode.

In a particular embodiment, the first cohesion layer and / or the second cohesion layer are continuous layers respectively covering at least one face of the first electrode and / or of the second electrode to prevent direct contact between the layer electrolyte and the first electrode and / or the second electrode.

It is advantageous to provide that a device in which the first cohesion layer and / or the second cohesion layer are continuous layers covering respectively several faces of the first electrode and / or of the second electrode to prevent direct contact between the layer electrolyte and the first electrode and / or the second electrode.

In a particular embodiment, the first cohesion layer and / or the second cohesion layer are layers respectively covering at least one face of the first electrode and / or of the second electrode and io defining holes allowing direct contact between the electrolyte layer and respectively the first electrode and / or the second electrode.

Alternatively, the first cohesion layer and / or the second cohesion layer are formed by a plurality of disjointed patterns preventing direct contact between the electrolyte layer and the first electrode and / or the second electrode respectively.

Preferably, the first current collector and / or the second current collector are made from a material chosen from Cu, Ni, Ti,

Al, Au, Ag, Ta, Ba, Cr, W, Pt.

It is advantageous to provide that the first electrode and / or the second electrode is made of a material chosen from LiCoO ₂ , LiFeO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , UCOPO4, LiFePO ₄ , Li ₄ Ti ₅ 0i ₂ , LiTiOS, LiM _x Mn ₂ - _x with 0 <x <0.5 and with

M chosen from Ni, Co, Fe and Ti or an oxide of formula MxOy with M a metal or a sulfide of formula MxSy with M a metal, or in a material chosen from Bi, Sb, Si, Sn, Zn, Ni, Cd , Ce, Fe, Mg, Ge, Li or an alloy of these materials.

In an advantageous embodiment, the electrolyte layer is made of a material comprising ions chosen from lithium, sodium and manganese.

In another development, the first cohesion layer and / or the second cohesion layer are made of a material chosen from Pt, Ti, W, Ag, Cu, Ni, Al, Au, Ta, Ba, Cr, an alloy of these materials or an oxide of these materials.

It is also advantageous to provide that the first cohesion layer and / or the second cohesion layer are devoid of electrochemical property with the electrolyte layer.

Preferably, the permeation rate for said ions is greater than 90% and preferably greater than 98%.

In a particular device, one of the first electrode and of the second electrode is a lithium metal electrode and the at least first cohesion layer is disposed between the electrolyte layer and the other of the first electrode and the second electrode.

Advantageously, one of the first electrode and of the second electrode is an electrode made of CuSi alloy and in which the at least first cohesion layer is disposed between the electrolyte layer and the other of the first electrode and the second electrode

Brief description of the drawings

Other advantages and characteristics will emerge more clearly from the description which follows of particular embodiments of the invention given by way of examples, without limitation, and represented in the appended drawings, in which:

FIGS. 1, 2 and 3 schematically represent, in section, three stacks of thin layers forming electrochemical devices such as microbatteries or electrochromic devices, with continuous cohesion layers,

FIGS. 4 and 5 schematically represent, in section, two io stacks of thin layers forming electrochemical devices such as microbatteries or electrochromic devices, with continuous and discontinuous cohesion layers,

FIGS. 6 and 7 schematically represent a top view of different forms of cohesion layer,

FIG. 8 schematically represents, in section, a stack of thin layers forming an electrochemical device such as a microbattery or an electrochromic device, with continuous and discontinuous cohesion layers and a discontinuous electrode,

- Figures 9 and 10 show the evolution of the internal resistance and the loss of capacity as a function of the number of charge / discharge cycles for a battery according to the prior art and a battery according to the invention.

Description of a preferred embodiment of the invention

As illustrated in FIGS. 1, 2 and 3, the electrochemical device comprises a first stack 1 of thin solid layers formed on a substrate 2. The first stack 1 forms an electrochromic device or a battery, advantageously a microbattery.

δ

A microbattery is an all-solid-state electrochemical generator which is advantageously rechargeable. The thickness of a microbattery is small, for example between 30μΐτι and 200μΐτι. The microbattery occupies an area between a few μιτι ² and a few cm ² .

The electrochemical device is produced on a substrate 2. In an advantageous embodiment, the substrate 2 is electrically insulating. The substrate 2 can be made of an insulating material or it can comprise electrically conductive layers covered, on the surface, by an electrically insulating layer. The electrically insulating layer can be produced by a layer or by a stack of several layers. For example, the electrically insulating layer is made of silicon oxide.

The substrate 2 is provided with a first face and a second face.

The stack is deposited on the first face of the substrate 2, that is to say on the electrically insulating face.

Advantageously, the substrate 2 and preferably the electrically insulating face have barrier characteristics. Preferably, the substrate and / or the electrically insulating face are a barrier to the diffusion of lithium or to the material to be inserted / removed from the electrochemical device.

The electrochemical device comprises a first layer of electrolyte 3 which separates the first and second electrodes of the battery 4a and 4b. In this way, the electrodes 4a / 4b are electrically insulated by means of the first electrolyte layer 3. The first and second electrodes 4a and 4b are formed by electrically conductive materials. At least one of the electrodes 4a / 4b is formed by a material which has electrochemical properties with respect to the electrolyte layer 3, that is to say which is electrochemically active for the ion to be displaced. The two electrodes 4a and 4b are separated by the electrolyte 3 which is ionically conductive and electronically insulating. The electrolyte layer 3 ensures the transit of the ions between the electrodes 4a and 4b.

The electrochemical device also includes first and second current collectors 5a and 5b. The first current collector 5a is electrically connected to the first electrode 4a. The second current collector 5b is electrically connected to the second electrode 4b. The first and second current collectors 5a and 5b are electrically isolated from each other and in particular by means of the electrolyte layer 3.

The materials forming the current collectors 5a and 5b are advantageously different from the materials forming the electrodes 4a and 4b. The materials forming the current collectors 5a and 5b are electrically conductive and are advantageously devoid of electrochemical property with respect to the electrolyte layer 3. Preferably, the current collectors are formed from materials which conduct the current best than the electrodes. Current collectors are formed by electronic conductive materials and preferably exclusively in electronic conductive materials. The electrodes 4a and 4b are formed by materials which participate in the electrochemical mechanisms of the battery and for example in the phenomena of insertion and deinsertion of ions, for example Li ⁺ ions.

In an alternative embodiment, the current collectors 5a and 5b can be formed from electrode materials. These materials can be identical or different from the materials used to form the electrodes 4a and 4b.

According to the embodiments, the first electrode 4a is formed before or after the electrolyte 3 and the second electrode 4b can be formed after or before the electrolyte. Figures 1 and 2 show two similar structures where the electrodes 4a and 4b are inverted. It can for example be the same for a structure shown in FIG. 3.

The first electrode 4a exhibits a volume expansion during the charging or discharging phases of the electrochemical device. As a variant, the first electrode 4a and the second electrode 4b have a volume expansion during the charging or discharging phases of the electrochemical device.

io All solid-state electrochemical devices undergo significant mechanical stresses during the successive stages of charging and discharging. Indeed, the migration of ions from one electrode to the other electrode will cause significant volume variations inside the electrochemical device and more precisely in the first electrode and / or in the second electrode which will induce mechanical stresses strong throughout the device.

The inventors have observed that the volume variations of the electrodes result in a fracturing of the interface between the first electrode 4a and the solid electrolyte 3 and / or a fracturing of the interface between the second electrode 4b and the solid electrolyte 3 . This fracturing results in a partial or total loss of contact between the electrode 4a / 4b and the electrolyte 3 which will cause a significant increase in the internal resistance of the electrochemical device. This loss of contact can also prevent the migration of ions, which implies a significant reduction in the service life of the battery as well as its electrical capacity.

It is important to note that these various problems are not present in an electrochemical device provided with a liquid electrolyte. Indeed, the electrolyte being in liquid form, the different volume variations inside the electrochemical device do not result in a loss of contact between the electrolyte and the electrode.

In order to produce an all solid electrochemical device which better supports the successive charge and discharge cycles, the inventors propose to place a cohesion layer 6 between the first electrode 4a and the solid electrolyte 3 as shown in FIG. 1. In a preferred embodiment, the cohesion layer 6 can also be deposited on one or more side walls of the first electrode 4a. the cohesion layer 6 can also be placed between the electrolyte 3 and the second electrode 4b.

Preferably, the cohesion layer 6 is disposed between the positive electrode and the electrolyte 3. As a variant, it is also possible to use the cohesion layer 6 between the negative electrode and the electrolyte 3. It is still possible to use a cohesion layer 6 between the electrolyte 3 and each of the positive and negative electrodes.

The cohesion layer 6 ensures good contact between the electrode 4a / 4b and the electrolyte 3 despite the variations in volume during the multiple charging and discharging phases. The cohesion layer 6 is made of a material different from the electrolyte 3. If the cohesion layer 6 is in contact with the first electrode 4a, the layer 6 is made of a material different from that forming the first electrode 4a. If the cohesion layer 6 is in contact with the second electrode 4b, the layer 6 is produced from a material different from that forming the second electrode 4b.

Against all expectations, the addition of this cohesion layer 6 which is made of a passive material, that is to say which is advantageously devoid of electrochemical property with the electrolyte 3 does not degrade the performance of the electrochemical device. The cohesion layer 6 does not participate in the electrochemical reactions between the electrode 4a or 4b and the electrolyte 3 while making it possible to improve the operation of the electrochemical device.

The cohesion layer 6 is arranged on at least one of the electrodes, that is to say on the positive electrode and / or on the negative electrode so that the first electrode 4a is separated from the electrolyte 3 at least partially at by means of the cohesion layer 6. The cohesion layer 6 can also be arranged so that the second electrode 4b is separated from the electrolyte 3 at least partially by means of the cohesion layer 6

FIG. 3 represents an embodiment where first and second cohesion layers 6a and 6b are disposed respectively between the first electrode 4a and the electrolyte 3 and between the second electrode 4b and the electrolyte 3.

The two cohesion layers 6a and 6b are different from the electrolyte 3. The two cohesion layers 6a and 6b are different from the materials forming the two electrodes 4a and 4b with which they are in contact. According to the embodiments, the first and second cohesion layers 6a and 6b can be made from identical or different materials.

According to the embodiments, the first electrode 4a is partially or totally separated from the electrolyte 3 by means of the cohesion layer. In a partial separation, at least one direct contact zone exists between the first electrode 4a and the electrolyte 3. In a total separation (not shown), there is no direct contact between the electrolyte 3 and the first electrode 4a. It can be the same for the second electrode 4b by means of the second cohesion layer 6b.

The cohesion layer 6 is configured to be permeable to ions so as not to interfere with the operation of the electrochemical device.

The composition and / or the thickness of the cohesion layer 6 are chosen so that the cohesion layer 6 is permeable to ions, preferably to lithium ions. An ion permeable layer is a layer that has a permeation rate greater than 50%. Advantageously, the permeation rate is between 90% and 100%. Preferably, the permeation rate is between 98% and 100%.

The permeation rate corresponds to the ratio between the number of ions crossing the cohesion layer to reach the electrode, over a predetermined period, and the number of ions reaching the electrode in an equivalent structure devoid of the cohesion layer 6.

The material forming the cohesion layer 6 can be intrinsically permeable to ions. It is advantageous to use a porous material. Preferably, the porous material has a through porosity and even more preferably a through nanometric porosity. For example, it is advantageous to use a porous copper layer to facilitate obtaining a permeable copper layer.

It is advantageous to use a material which has an ion diffusion coefficient which is greater than or equal to 1.10 ' ⁶ S.cm' ¹ at 25 ° C. In this way, the cohesion layer 6 also has good ionic conductivity.

The thickness of the cohesion layer 6 is advantageously between 5 nm and 100 nm, preferably between 20 nm and 50 nm. The inventors have observed that if the thickness of the layer is less than 5 nm, there is a risk of naming in certain operating modes. On the contrary, if the thickness is very large, it is difficult to produce a cohesion layer 6 which is permeable to ions.

As a variant which can be combined with the previous embodiment, the cohesion layer 6 can define preferred permeation channels for the ions between the electrolyte 3 and the electrode 4a or 4b. These permeation channels can be produced by using different thicknesses and / or different materials in the cohesion layer 6. It is also possible to form permeation channels by modifying the porosity rate in the cohesion layer 6.

It is also advantageous to provide a cohesion layer 6 which has a density less than the density of the material forming the associated electrode. The use of a sparse cohesion layer 6 makes it possible to obtain good ion permeation properties more easily.

In a particularly advantageous embodiment, the cohesion layer 6 is a porous layer. Advantageously, the porosity is open and emerging so as to facilitate the transit of ions. The diameter of the pores or the maximum transverse dimension is advantageously less than 1 micron.

The first cohesion layer 6a is configured to adapt the constraints between the electrolyte layer 3 and the first electrode 4a so as to maintain contact between the electrolyte layer 3 and the first electrode 4a regardless of the volume of the electrode 4a.

It is also advantageous to use a cohesion layer 6 in a material having a modulus of elasticity of the same order of magnitude as that of the electrode layer 4a and / or that of the electrolyte layer 3. This precaution does not stiffen the interface too much and reduce the risk of delamination. Advantageously, two moduli of elasticity are considered to have the same order of magnitude if the ratio between the moduli of elasticity is between 0.5 and 2.

In a particular embodiment, the thickness of the cohesion layer 6 and the material forming the cohesion layer 6 are configured to reduce the risks of delamination with the electrode and / or with the electrolyte. By limiting the risks of delamination, it is possible to reduce the increase in impedance to less than 5% and to maintain a capacity greater than 80% of the initial capacity after 200 to 300 cycles.

The inventors have also observed that the use of a cohesion layer 6 whose thickness is less than 50 nm is particularly advantageous since it makes it possible not to degrade the properties of electronic and ionic exchanges of the interface between the electrode 4 and the electrolyte 3 in comparison with a direct contact between the electrolyte 3 and the first electrode 4. Preferably, the thickness of the cohesion layer 6 is between 5 and 20 nanometers.

The inventors have observed that if the cohesion layer 6 is too thick, for example a thickness greater than 50 nm, the passage of ions is limited and a larger shaping phase is preferable for cycling the electrochemical device.

On the other hand, when using a cohesion layer 6 having a very thin thickness, advantageously less than 5 nm, problems of interface cohesion and delamination can be observed during charge and discharge cycles in certain conditions.

The cohesion layer 6 is electronically conductive. Advantageously, the cohesion layer 6 is a metal layer, that is to say that it is made of pure metal or a metal alloy. By pure metal is meant that the layer contains at least 90% by mass of the same metallic element or even 99% by mass of the same metallic element.

In a preferred embodiment, the cohesion layer 6 comprises or is constituted by a copper layer, that is to say containing at least 90% by mass of copper and advantageously 99% by mass of copper. In a particular embodiment, the copper layer is not in contact with the electrolyte.

Advantageously, the cohesion layer is made of a material containing copper. The copper-based layer is for example made of CuO or AlCu. Good results have been obtained for an AlCu alloy containing 5% by mass of copper or less than 5% by mass of copper.

Advantageously, the copper layer does not contain silicon, that is to say less than 1% of silicon.

Instead of a layer of copper or in addition to a layer of copper, it is for example possible to use a layer made of one of the following materials Pt, Ti, W, Ag, Cu, Ni, Al , Au, Ta, Ba, Cr to form the cohesion layer 6. The material used does not exhibit electrochemical properties with the electrodes. Advantageously, the cohesion layer 6 in one of the preceding materials is made of a material based respectively on Pt, Ti, W, Ag, Cu, Ni, Al, Au, Ta, Ba, Cr that is that is to say which comprises at least 20 atomic% of said element, preferably at least 50 atomic%.

The cohesion layer 6 can be an alloy of the above materials. It is also possible to provide that the cohesion layer 6 is an oxide of the preceding materials.

The cohesion layer can also be made of transparent conductive oxide.

The deposition of a copper layer on an electrode has already been carried out in the prior art for electrochemical devices having a liquid electrolyte, that is to say in a device where the mechanical stresses are very different.

Indeed, Gao et al. ("Preparation of Cu coating on graphite electrode foil and its suppressive effect on PC decomposition", Solid State lonics 178 (2007) 1225-1229) propose to deposit nanometric particles of copper on the surface of graphite electrodes in order to avoid the decomposition of the liquid electrolyte which is directly in contact with the graphite electrode.

Guo et al. (“Nano-scale copper-coated graphite as anode material for lithiumion batteries”, Journal of Applied Electrochemistry 32, 679-685, 2002) also propose to cover a graphite electrode with copper. An improvement in the electronic conductivity of the electrode is observed as well as in the capacities for accepting Li ⁺ ions between the carbon sheets. Here again, the problem of managing constraints is ignored.

It is advantageous to form a cohesion layer 6 which has good electronic conduction so as to reduce or even eliminate the influence of the cohesion layer 6 on the electronic exchanges between the electrode 4a / 4b and the electrolyte 3. Preferably , the material of the cohesion layer 6 has a conductivity greater than 10 ⁵ S.cm ' ¹ at 25 ° C.

The cohesion layer 6 can be, for example, in granular or columnar form with grains oriented perpendicular to the surface of the electrode 4. This configuration promotes permeation, and in particular the appearance of through porosity, between the electrolyte 3 and electrode 4 which are arranged on two opposite faces.

In a first embodiment, the cohesion layer 6 is a continuous layer which separates the electrode 4 and the electrolyte 3.

In another embodiment illustrated in FIG. 4, the cohesion layer

6b is a discontinuous layer, that is to say that it defines zones where the electrolyte 3 is in direct contact with the electrode 4b and zones where the electrolyte 3 is separated from the electrode 4b by the layer of cohesion 6b. It can be the same for layer 6a and electrode 4a.

In yet another embodiment illustrated in FIG. 5, the cohesion layer 6b is a discontinuous layer, that is to say that it defines zones where the cohesion layer 6b covers the electrolyte 3 and zones where the electrolyte 3 is not covered by the cohesion layer 6. However, in comparison with the previous embodiment, there is no direct contact between the electrolyte 3 and the electrode 4b or no direct contact between two adjacent patterns of the cohesion layer. This empty space allows the volume expansion of the electrode 4b during the charging or discharging phases. The volume of the empty space varies depending on the state of charge of the battery or the state of the electrochromic device.

According to the embodiments, it is possible to use an electrode 4a / 4b formed by a continuous layer or by several patterns separated from each other and physically distinct. It is also possible to use a monolithic electrode with holes.

Figures 4 and 5 show a continuous cohesion layer 6a and a discontinuous cohesion layer 6b. It is possible to invert the continuous layer and the discontinuous layer. It is also possible to use two discontinuous cohesion layers.

Figures 6 and 7 illustrate a top view of two embodiments of a discontinuous cohesion layer. In the embodiment of FIG. 6, the cohesion layer 6 is monolithic and defines empty zones. In the embodiment of Figure 7, the cohesion layer 6 has a plurality of patterns distinct from each other.

FIG. 8 represents an embodiment where the cohesion layer 6b is discontinuous and where the second electrode is also discontinuous. It can be the same for the cohesion layer 6a and the first electrode 4a.

FIG. 9 represents the evolution of the internal resistance (AR) for a microbattery provided with a continuous cohesion layer 6 and for an equivalent microbattery devoid of the cohesion layer. It appears that, as the different charge and discharge cycles progress, the microbattery provided with the cohesion layer shows practically no change in its internal resistance. On the contrary, the battery lacking a cohesion layer sees its internal resistance very greatly increased from the first charge and discharge cycles. Figure 9 also shows the evolution of the impedance spectrum for the two types of batteries.

The two batteries each have a LiCoO ₂ electrode and another Bi electrode. The electrolyte 3 is formed by LiPON. The first battery is provided with a copper layer which separates the electrolyte 3 and the Bi electrode.

It appears that in the battery devoid of copper layer, the increase in internal resistance is directly linked to the decrease in active surface, that is to say the decrease in contact surface between the electrolyte and the electrode. . This decrease in active surface seems to be caused by the detachment of the negative Bi electrode. On the contrary, the addition of the copper layer made it possible to avoid this delamination and therefore made it possible to maintain a constant internal resistance. The copper layer made it possible to maintain the integrity of the contact surface between the electrolyte 3 and the electrode 4, which improves the cyclability of the battery.

FIG. 10 represents the evolution of the loss of capacity (AC) as the charge and discharge cycles progress for the two batteries already represented in FIG. 9.

It appears that for the battery devoid of copper layer, the discharge capacity decreases strongly in relation to the increase of the internal resistance shown in FIG. 9. For the battery provided with the copper layer, the discharge capacity remains constant and a loss of capacity of less than 1.5% is observed after 35 cycles.

It is important to note that the configuration provided with a solid electrolyte does not exhibit a significant loss of capacity from the first charge / discharge cycles as is illustrated in the publication by Polat et al. The battery is more efficient than that of the prior art with a solid electrolyte. The use of a permeable cohesion layer 6 with a solid electrolyte makes it possible to avoid a significant loss of capacity.

In an alternative embodiment, if the electrochemical device is intended to undergo high temperatures, it is advantageous to replace the copper layer with a layer in another material. This other material is advantageously chosen so as to be less reactive than copper with the material forming the electrode.

In a particular embodiment, to form the cohesion layer 6, it is possible to combine a copper-based layer which covers or which is covered by a layer in another material. For example, the copper layer can be formed by a stack comprising a copper layer and a nickel layer. It appears that this particular stack makes it possible to dampen the volume expansion in the electrode and to present better temperature resistance of the assembly. In one embodiment, the nickel layer is in contact with the electrolyte 3.

In a particular embodiment, the cohesion layer 6 is formed by a monolithic pattern which defines a plurality of holes. For example, the cohesion layer 6 defines a grid-shaped pattern as shown in FIG. 6.

In a preferred embodiment, the holes are configured to form privileged permeation paths for lithium ions between the electrolyte 3 and the electrode 4a.

In an alternative embodiment, the holes are empty and allow a volume expansion of the electrode 4a which at least partially fills the hole. In this way, the stresses are reduced and the risks of detachment are reduced.

In this particular configuration with a cohesion layer 6 provided with holes, it is possible to deposit greater thicknesses of material to form the cohesion layer 6. The holes can be of any shape, for example in the form of squares, of diamonds, triangles, discs ... The width and length of the holes are advantageously between 0.5 μίτι and 5 μίτι.

In an alternative embodiment, the cohesion layer 6 is formed by a plurality of distinct patterns which are physically separated from each other as shown in FIG. 7. As for the previous embodiment, the use of several separate patterns by empty areas allows the use of a layer having a greater thickness.

In these latter two embodiments, the surface area occupied by the cohesion layer with the uncovered electrode surface makes it possible to optimize the ion transfer flux.

In another embodiment, the cohesion layer 6a / 6b defines a first pattern with solid areas and hollow areas. The electrode 4a / 4b also defines a second pattern which includes solid areas and hollow areas.

The first current collector 5a and the electrolyte 3 are successively separated by the electrode 4a and the cohesion layer 6. The cohesion layer 6 and the electrode 4a are arranged so that the empty areas are terminated by a side by the current collector and on the other side by the electrolyte 3.

Advantageously, the cohesion layer 6 and the electrode 4a / 4b define exactly the same patterns, for example a grid in the form of a grid or of separate studs. Cohesion layer 6 and the electrode

4a / 4b are arranged so that they form pillars separating the current collector 5a / 5b and the electrolyte 3. These pillars are spaced from each other. As a variant, the grids define empty zones between the current collector 5a / 5b and the electrolyte 3.

In another embodiment, the cohesion layer 6 and the electrode 4a / 4b have different shapes. The cohesion layer 6 is in the form of a grid shown in Figure 5 and the electrode 4a / 4b is in the form of several patterns shown in Figure 6. An opposite arrangement is also possible.

These hollow zones allow a volume expansion in a direction parallel to the surface of the electrolyte 3, in directions perpendicular to the axis Z. This embodiment is particularly advantageous when the volume expansion is very large during the different cycles of charge and discharge. The definition of the exposed areas and of the covered areas makes it possible to reduce the interface surface between the electrode 4a / 4b and the electrolyte 3, that is to say the surface subjected to the volume expansion.

It is particularly advantageous to provide that the spacing between two patterns is such that the lateral walls of the patterns meet only in the extreme cases of charges or discharges, that is to say when the volume variation is maximum, for example when the volume expansion is maximum.

io For example, in the case of a material having a maximum volume expansion equal to 300% and if the cohesion layer and the associated electrode form multiple pillars of square section, these pillars will see their side increase by an equal value at 44%. Consequently, it is particularly advantageous to provide that the spacing between two consecutive patterns is greater than or equal to 44% of the dimension of the sides of the patterns of the pillars.

In the embodiment illustrated in FIG. 1, the first stack comprises:

the first and second current collectors 5a and 5b formed on the substrate 2,

the first electrode 4a in electrical contact with the first current collector 5a,

- the electrolyte layer 3 covering the first electrode 4a and possibly the first current collector 5a,

the second electrode 4b in contact with the electrolyte layer 3 and separated from the first electrode 4a by the electrolyte layer 3, the second electrode 4b being in electrical contact with the second current collector 5b,

- the cohesion layer 6 formed between the first electrode 4a and the electrolyte layer 3 and / or between the second electrode 4b and the electrolyte layer 3.

Advantageously, the solid electrolyte 3 can be based on lithium, for example, in lithium nitride (Li ₃ N), LiPON (lithium phosphorus oxynitride), U2S-P2S5, LiGeP ₂ Si2, LiSiPON (lithium Silicon phosphorus) , LISICON (Ι_ί ₂ + 2χΖηι5 _x GeO ₄ ), LiPONB (Boron doped lithium phosphorous oxynitride), LiBSO (lithium borate sulfate) or even LiBON (Li boron-oxynitride) etc ... It is also possible to use other electrolytes and preferably based on sodium such as, for example, Na ₃ PS ₄ or NaSiCON having the chemical formula Nai + xZr2Si _x P ₃ -xOi2, with 0 <x <3.

In an alternative embodiment, the solid electrolyte 3 can also be used in the form of a gel or a polymer. Electrolyte 3 is made up of a polymer matrix which gives it its structural properties and a liquid which gives it its electrical and electrochemical properties.

The polymer matrix may be formed by a material chosen from Polyethylene glycol (PEO), ethoxylated bisphenol A dimethacrylate (BEMA, bisphenol A ethoxylate dimethacrylate), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride - hexafluoropropylene (PVDF-HFP, poly (vinylidene fluoride-cohexafluoropropylene)).

It is also possible to use a silica-type polymer matrix chosen from tetraethyl orthosilicate (TEOS), vinyltrimethoxysilane (NTMS, vinyltrimethoxysilane), tetramethyl orthosilicate (TMOS).

The liquid of electrolyte 3 contains a lithium salt chosen from lithium chloride (LiCI), lithium bromide (LiBr), lithium iodide (Lil), lithium perchlorate (LiCIO ₄ , Lithium perchlorate) , lithium tetrafluoroborate (LiBF ₄ ,

Lithium tetrafluoroborate), lithium hexafluorophosphate (LiPF ₆ , Lithium hexafluorophosphate), lithium hexafluoroarsenate (LiAsF ₆ , Lithium hexafluoro arsenate), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) (Bis (trifluoromethane) sulfonimide lithium) or a mixture of several of these salts together. The liquid of the electrolyte may also contain a carbonate solvent and advantageously a solvent chosen from ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC). Once solidified, the solvent will be part of a gel, that is to say of a solid electrolyte. in the event of an electrode crack, the risk of electrolyte 3 leaking is controlled.

The electrolyte 3, the electrodes 4a / 4b and the current collectors 5a / 5b can be deposited by the same deposition technique or by different techniques. It is possible to use for each of these layers a physical vapor deposition (PVD), a chemical vapor deposition (CVD), a low pressure chemical vapor deposition (LPCVD), a thermal evaporation deposition.

It is also possible to use other techniques, for example coating, spray, electrospray, electrolytic deposition, electrolytic deposition under hydrothermal conditions, electrophoresis or dipcoating.

Advantageously, the thicknesses of the current collectors are less than 500 nm, preferably less than 250 nm. In a preferred embodiment, the thicknesses of the other layers of the electrochemical device are less than 100 microns, preferably less than 20 microns. In an advantageous embodiment, the electrolyte has a thickness of between 1 and 3 microns.

In a particular embodiment, the thicknesses of the different layers of the electrochemical device are configured to obtain a capacity balance between the electrodes 4a and 4b.

Advantageously, the thicknesses of the different layers of the electrochemical device are configured to reduce the internal resistance.

The first electrode 4a or the second electrode 4b is a positive electrode. The positive electrode is cationically inserted to insert, for example, io Li ⁺ . To form the positive electrode, it is possible to use lithium intercalation materials and for example those of the LiMO group and more particularly: LiCoO ₂ , LiFeO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , and more generally the materials LiM _x Mn ₂ - _x O _{4 type} with 0 <x <0.5 and M = Ni, Co, Fe, Ti ....

The other electrode 4b or 4a is a negative electrode. The material used to form the negative electrode depends on the type of battery considered, that is to say on the type of electrolyte 3 used. The battery can be of the metallic lithium type with a metallic lithium electrode. In the case of a battery with a metallic lithium electrode, it is particularly advantageous not to use a cohesion layer between the electrolyte 3 and the metallic lithium electrode 4.

The negative electrode can also be of the lithium-ion type with materials capable of forming an alloy or a compound defined with lithium. These materials have a large volume expansion. The materials forming the electrode are advantageously chosen from the list consisting of: Bi, Sb, Si, Sn, Zn, Ni, Cd, Ce, Co, Fe, Mg, Ge. It may be advantageous not to use an electrode containing Cu3Si which is complicated to implement.

It is also possible to choose oxides of the Me _x O _{y type} or sulphides of the Me _x S _{y type} with Me representing a metal. It is also possible to produce the electrode by means of an MF, MF2 or MF3 type complex with M representing a metal and F representing fluorine. For example, it is possible to use the following complexes FeF3, VF3, CrF3, MnF2, CoF2, CoF3, AgF.

It is also possible to produce a lithium-free type battery and in this case the electrodes 4a and / or 4b are unalloyed. The negative electrode can be made of a non-electrochemically active material, for example in a material capable of forming a current collector, for example of copper. The same can be true for sodium-based batteries.

The cohesion layer 6 can be deposited by any of the techniques mentioned above. Using any of the previously mentioned techniques allows the cohesion layer to be deposited in a standard process for manufacturing an electrochemical device such as a microbattery or an electrochromic device.

The current collectors 5a and 5b can be formed by transparent conductive oxides, for example aluminum zinc oxide, indium tin oxide. It is also possible to produce the current collectors 5a and 5b from metal or metal alloy. The current collectors can be formed from a material chosen from Cu, Ni, Ti, Al, Au, Ag, Ta, Ba, Cr, W, Pt. Advantageously, the current collector is made of metal or made of a metal alloy and contains at least 90 atomic% of one of the preceding metals or of the sum of the preceding metals. It is also possible to produce the current collectors from one or more of the preceding materials.

In one embodiment, the different layers are deposited through a mask comprising recesses. In this way, the different layers can form patterns as soon as they are deposited.

As a variant, the layers are deposited continuously over the entire substrate, according to a technique known as full plate, then they are etched so as to shape them. The etching can be carried out by any suitable technique, for example by plasma using a mask or by means of a laser beam. The two stacks are formed at the same time io but they are dissociated as and when the etching steps.

It is also possible to combine these two embodiments between the different layers.

A first pattern of first electrode material is formed on the first current collector 5a to define the first electrode 4a. This first pattern can be formed by deposition through a mask or by deposition and then etching of the first electrode material. According to the embodiments, the first pattern can partially or completely cover the first current collector

5a. It is also possible to provide that the first pattern extends beyond the first current collector 5a. This first pattern forms the first electrode 4a.

The cohesion layer 6 is deposited on the first electrode.

The electrolyte material is then deposited. The electrolyte material may partially or completely cover the first pattern. The electrolyte material will form the electrolyte layer 3 It is also possible to provide that the electrolyte layer 3 extends beyond the first pattern, for example to cover the first current collector 5a or possibly the substrate 2. The electrolyte layer 3 covers the cohesion layer.

The electrolyte material can partially cover the second current collector 5b if the latter has already been partially formed before the deposition of the electrolyte or even before the deposition of the first electrode.

In a particular embodiment, the electrolyte layer 3 continuously covers the first and second current collectors 5a and 5b. The electrolyte layer can be deposited through a mask or be deposited over the entire substrate and then optionally etched.

A second pattern of second electrode material is then formed. This second pattern can be formed by deposition through a mask or by deposition and then etching of the second electrode material. According to the embodiments, the second pattern can partially or completely cover the first pattern. It is also possible to provide that the second pattern projects beyond the first current collector for example to come into contact with the substrate 4. The second pattern will advantageously form the second electrode 4b.

The second current collector material is deposited through a mask to form the second and fourth current collectors 5b and 5d. Alternatively, the second current collector material is deposited and then etched to form the second and fourth current collectors 5b and 5d.

As a variant, the cohesion layer is deposited after the electrolyte layer if the second electrode 4b is deposited before the electrolyte 3.

Claims (14)

Claims 1. Electrochemical device such as a battery or an electrochromic device, comprising at least a first stack (1) of layers 5 thin solids placed on a substrate ( 2), said first stack (1) comprising: - a first electrode (4a) and a second electrode (4b) separated by a layer of solid electrolyte ( 3) electronically insulating and ionically conductive, the electrolyte layer (3) ensuring transit 10 ions between the first and second electrodes (4a and 4b), - a first current collector (5a) in contact with the first electrode (4a), - a second current collector (5b) in contact with the second electrode (4b), the first current collector (5a) and the second 15 current collector (5b) being electronically isolated by the electrolyte layer (3), - at least a first cohesion layer (6a, 6b) disposed between one of the first and second electrodes (4a, 4b) and the electrolyte layer (3), the at least one cohesion layer (6) being configured for 20 have a permeation rate for said ions greater than 50% and a thickness at least equal to 5 nm so as to adapt the stresses between the electrolyte layer (3) and one of the first and second electrodes (4a, 4b). 2. Device (1) according to claim 1, in which the first cohesion layer (6a) is disposed between the electrolyte layer (3) and the first electrode (4a) and a second cohesion layer (6b) is disposed between the electrolyte layer (3) and the second electrode (4b). 3. Device (1) according to one of claims 1 and 2, in which the first cohesion layer (6a) and / or the second cohesion layer (6b) are continuous layers respectively covering at least one face of the first electrode (4a) and / or the second electrode (4b) to prevent direct contact between the electrolyte layer (3) and the first electrode (4a) and / or the second electrode (4b). 4. Device (1) according to claim 3, wherein the first cohesion layer (6a) and / or the second cohesion layer (6b) are continuous layers respectively covering several faces of the first electrode (4a) and / or of the second electrode (4b) to prevent direct contact between 10 the electrolyte layer (3) and the first electrode (4a) and / or the second electrode (4b). 5. Device (1) according to one of claims 1 and 2, wherein the first cohesion layer ( 6a) and / or the second cohesion layer (6b) 15 are layers respectively covering at least one face of the first electrode (4a) and / or of the second electrode (4b) and defining holes allowing direct contact between the electrolyte layer (3) and the first electrode respectively ( 4a) and / or the second electrode (4b). 6. Device (1) according to any one of claims 1 and 2, in which the first cohesion layer (6a) and / or the second cohesion layer (6b) are formed by a plurality of disjointed patterns preventing contact direct between the electrolyte layer (3) and respectively the first electrode (4a) and / or the second electrode (4b). 7. Device (1) according to any one of claims 1 to 6, in which the first current collector (5a) and / or the second current collector (5b) are made from a material chosen from Cu, Ni, Ti, Al, Au, Ag, Ta, Ba, Cr, W, Pt. 8. Device (1) according to any one of claims 1 to 7, in which the first electrode (4a) and / or the second electrode (4b) is made of a material chosen from UCoO ₂ , LiFeO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiFePO ₄ , Li ₄ Ti ₅ O ₁₂₎ LiTiOS, UM _x Mn ₂ - _x with 0 <x <0.5 and with M chosen from Ni, 5 Co, Fe and Ti or an oxide of formula MxOy with M a metal or a sulfide of formula MxSy with M a metal, or in a material chosen from Bi, Sb, Si, Sn, Zn, Ni, Cd, Ce, Fe , Mg, Ge, Li or an alloy of these materials. 9. Device (1) according to any one of claims 1 to 8, in 10 which the electrolyte layer (3) is made of a material comprising ions chosen from lithium, sodium and manganese. 10. Device (1) according to any one of claims 1 to 9, wherein the first cohesion layer (6a) and / or the second layer of 15 cohesion (6b) are made of a material chosen from Pt, Ti, W, Ag, Cu, Ni, Al, Au, Ta, Ba, Cr, an alloy of these materials or an oxide of these materials. 11. Device (1) according to any one of claims 1 to 10, in 20 which the first cohesion layer (6a) and / or the second cohesion layer (6b) are devoid of electrochemical property with the electrolyte layer (3). 12. Device (1) according to any one of claims 1 to 11, in 25 where the permeation rate to said ions is greater than 90% and preferably greater than 98%. 13. Device (1) according to any one of claims 1 to 12, wherein one of the first electrode (4a) and the second electrode (4b) is 30 a lithium metal electrode and in which the at least first cohesion layer (6a, 6b) is disposed between the electrolyte layer (3) and the other of the first electrode (4a) and the second electrode (4b ). 14. Device (1) according to any one of claims 1 to 12, in which one of the first electrode (4a) and of the second electrode (4b) is an electrode made of CuSi alloy and in which the at least first cohesion layer (6a, 6b) is arranged between the electrolyte layer (3) and the other of the first electrode (4a) and the second electrode (4b). 1/4 Z