EP4078714A1

EP4078714A1 - Electrochemical cell with three-dimensional electrode structure

Info

Publication number: EP4078714A1
Application number: EP20824934.2A
Authority: EP
Inventors: Nicolas Besnard; Victor CHAUDOY; David Leray
Original assignee: Renault SAS
Current assignee: Ampere Sas
Priority date: 2019-12-17
Filing date: 2020-12-15
Publication date: 2022-10-26
Also published as: WO2021122606A1; JP2023506817A; FR3104820A1; KR20220116236A; US20230021008A1; FR3104820B1; CN114902463A

Abstract

The present invention relates to an electric electrochemical cell (10), characterized in that it comprises a casing (12) that comprises a vessel (14), the internal surface of which is at least partially covered by a layer (15) of copper so as to form a current collector for the negative electrode (60) and an upper cover (18), which houses a three-dimensional positive electrode (+) structure and which contains a solid electrolyte, and in that the three-dimensional positive electrode structure comprises a series of positive electrodes (50), each of which is a vertical bar (50).

Description

DESCRIPTION

TITLE: ELECTROCHEMICAL CELL WITH THREE-DIMENSIONAL ELECTRODE STRUCTURE

Technical field of the invention

The present invention relates to an electrochemical cell having a three-dimensional electrode structure.

The invention relates in particular to an electrochemical cell with a three-dimensional electrode structure and a solid electrolyte.

Technical background

Battery systems - also called electric batteries and / or accumulators - are broken down into different elements or sense-sets of different scales such as: materials; electrodes; cells; modules; packs.

The passage from one scale to another leads to losses of volume and mass which have a direct consequence on the mass capacity of storage of electrical energy of a system - also called energy density of the system - because of the '' addition of packaging, electrical connection components, etc.

The size of a cell is limited by its assembly process, which consists of the superposition of layers of electrodes and separators. The electrodes are thin and the number of layers remains limited because it is necessary to take into account and solve the alignment problems in particular.

In fact, the more the number of layers increases, the more the risks of loss of alignment increase, which limits the dimensions (thickness, length, width) of the cells.

The technical problem to be solved is to be able to increase the volume of the cells, which is dependent on the shaping and assembly processes. conventional cells. The increase in the volume of the cells makes it possible to increase the filling rate of the packs, by removing some of the non-active materials and reducing the number of cells.

It has already been proposed in document EP-A1 -3.157.090 a cell with a three-dimensional structure of nested and intercalated electrodes.

Such a design allows multiple negative and positive electrodes to be simultaneously nested in a single step. However, the electrodes are flat and are obtained by conventional coating techniques. The electrode size scale remains small, which causes the possibility of faults in the alignment of the electrodes.

In addition, the precise sizing of the electrodes is critical because, during insertion, the electrodes must precisely fill the available vacuum, at the risk of causing false contacts. The thickness homogeneity of the electrodes is critical and difficult to guarantee.

The invention aims to provide a new design of an electrochemical cell with a three-dimensional structure of electrode (s) which overcomes the aforementioned drawbacks.

Summary of the invention

The invention provides an electrochemical cell, characterized in that it comprises a housing which:

- Has a first lower element in the form of a tank, the internal surface of which is at least partially covered with a layer of conductive material to constitute the current collector of the first electrode of a first polarity;

- Has a second upper element in the form of a cover for closing the tank;

- houses a three-dimensional electrode structure of a first electrical polarity;

- Houses a three-dimensional electrode structure of a second electrical polarity opposite to the first electrical polarity and nested in the three-dimensional electrode structure of a first polarity; - and contains an electrolyte as an ionic conductive medium, and in that the three-dimensional electrode structure of second polarity comprises a series of electrodes of second polarity each of which is an elongated body of vertical orientation.

According to other characteristics of the invention:

- the electrodes of the second polarity are distributed inside the housing in a regular pattern;

- the vessel houses a series of conductive elements of first polarity which are electrically connected to said layer of conductive material and each of which is an elongate element of vertical orientation;

- The conductive elements of the first polarity are distributed inside the housing in a regular pattern;

- The conductive elements of first polarity are distributed equidistantly between the electrodes of second polarity;

- each electrode of second polarity is a vertical bar which has a central core of conductive material which is covered with a layer of active material of electrode of second polarity;

- the upper end section of each central core made of conductive material extends vertically through the closing cover of the tank, and all the upper end sections of the central cores made of conductive material are electrically connected to each other by a plate collector arranged above the cover;

- the negative electrode (electrode of first polarity) is cast in the tank of the housing;

- the layer of active material of the electrode of the second polarity is covered with a peripheral layer of solid electrolyte;

- the lower end section of each electrode of second polarity is fixed in a complementary electrically insulated housing which is formed in the lower wall of the housing of the housing;

- the first polarity is negative and the second polarity is positive;

- the layer of conductive material as the current collector of the electrode of the first polarity is a layer of copper;

- the layer of conductive material to constitute the current collector of the electrode of the second polarity is an aluminum layer;

- the active material of each of the second polarity is a material which can belong to the category of NMC (LiNixMnyCoz02);

the active material of each electrode of first polarity is a material which may belong to the category of graphites;

- the electrolyte is a polymer electrolyte or a hybrid electrolyte / cast ceramic polymer;

- the positive electrode contains an electronic conductor to ensure electronic percolation.

- the negative electrode contains an electronic conductor to ensure electronic percolation;

- the electrochemical cell is characterized in that:

- the mixture which forms the electrode of the first polarity is a mixture based on an active material, an electrically conductive agent and a solid electrolyte on the conductive elements of the first polarity covered with a copper coating;

- a mixture which forms the electrode of the second polarity is a mixture of active material, electronic conductor and solid electrolyte on the central cores of conductive material covered with an aluminum coating;

- an electrically insulating film between the electrodes of the first and second polarity is solid electrolyte;

- the solid electrolyte is a polymer electrolyte or a hybrid material / ceramic polymer

Brief description of the figures

Other characteristics and advantages of the invention will become apparent on reading the detailed description which follows, for the understanding of which reference is made to the appended drawings in which:

[F ig .1] - Figure 1 is a schematic perspective view of an exemplary embodiment of an electrochemical cell according to the invention; [Fig.2] - Figure 2 is a partial exploded perspective view of some of the components of the electrochemical cell shown in Figure 1;

[Fig.3] - Figure 3 is a partial perspective view along a horizontal sectional plane of the electrochemical cell shown in Figure 1;

[Fig.4] - Figure 4 is a partial sectional view along the vertical and longitudinal section plane 4-4 of Figure 3;

[Fig.5] - Figure 5 is a partial sectional view along the vertical and longitudinal sectional plane 5-5 of Figure 3;

[Fig.6] - Figure 6 is a partial sectional view along the vertical and longitudinal sectional plane 6-6 of Figure 3;

[Fig.7] - Figure 7 is a perspective view which shows a portion of the vessel of the housing of the electrochemical cell of Figures 1 and 2;

[Fig.8] - Figure 8 is a view on a larger scale of the corner portion of the portion of the tank shown in Figure 7;

[Fig.9] - Figure 9 is a view similar to that of Figure 8 which shows a first manufacturing step for the fixing in the bottom of the tank of one of the positive rod-shaped electrodes;

[Fig.10] - and Figure 10 is a view similar to those of Figures 8 and 9 which shows the electrode in the mounted position and fixed in its housing formed in the bottom of the tank.

Detailed description of the invention

For the description of the invention and the understanding of the claims, the vertical, longitudinal and transverse orientations will be adopted without limitation and without limiting reference to the earth's gravity according to the reference mark V, L, T indicated in the figures, the longitudinal axes of which L and transverse T extend in a horizontal plane.

By convention, the transverse axis is oriented from the rear to the front and the longitudinal axis is oriented from the left to the right. In the description which follows, identical, similar or analogous elements will be designated by the same reference numerals.

Unless otherwise indicated, in the description which follows, the terms conductor, conductor, insulator, polarity, polarized, etc. will be used with reference to the laws of electricity.

There is shown in Figures 1 and 2 an electrochemical cell 10 which, without limitation, is here of generally rectangular parallelepiped shape.

The electrochemical cell 10 thus comprises a rectangular parallelepipedal housing 12 which essentially consists of a lower tank 14, the upper face 16 of which is open vertically upwards, and an upper cover 18 for sealing the lower tank 14, here with the interposition of an annular seal 20 of rectangular outline.

The lower tank 14 has a horizontal bottom wall 22, two vertical and transverse side walls on the left 24 and on the right 26, and two vertical and longitudinal side walls, front 28 and rear 30.

Like the upper cover 18, the lower tank 14 is made of an insulating synthetic material, in particular of plastic or of a composite material.

Without limitation, the entire internal surface of the lower tank 14, and in particular the upper face 23 of the bottom wall 22, is covered with a conductive metal layer 15, for example copper, to constitute the collector. current of the negative electrode of the electrochem ical cell 10.

The copper layer 15 is for example produced by vapor phase deposition.

The upper cover 18 is in the general form of a rectangular plate and its lower face 17 is not coated with a conductive material. The upper cover 18 is thus an insulating element. In addition, the lower face 17 is coated with a layer of electrically insulating material.

In its upper face 19, the upper cover 18 defines a housing 32 of rectangular outline which receives and houses an upper collecting plate or sheet 34 of complementary shape and thickness which is here made of aluminum.

The upper cover 18 and the manifold 34 are pierced with a series of vertical through holes, 36 and 38 respectively, which are distributed over the entire available horizontal surface of the manifold 32 in a regular pattern here formed by transverse parallel alignments of lines of holes aligned longitudinally.

As can be seen in particular in Figure 7, the horizontal bottom wall 22 of the lower housing 14 comprises a series of housings 40 which extend over a reduced depth and each of which is delimited by a generally cylindrical side wall 42 and by a horizontal flat bottom wall 44.

The walls 42, 44 of each housing 40 are devoid of any copper coating layer so that each housing 40 is an insulating housing.

The housings 40 are for example made by molding during the manufacture of the bottom wall 22. In order to prevent them from being coated with copper during the deposition of the copper layer on the rest of the internal surface of the tank. lower 14, a housing protection mask 40 can be used during the operation of depositing the layer of copper in the vapor phase.

The entire available internal surface of the bottom wall 22 is provided with a series of housings 40 which are staggered in a regular pattern in the form of offset longitudinal and transverse alignments.

The lower tank 14 which constitutes the negative electrode of the electrochemical cell 10 comprises a series of elements conductors 46 each of which here consists of a vertical rod which extends from the bottom wall 22 to which it is fixed. As can be seen in Figure 4, each rod 46 serving as a current collector of the negative electrode does not extend to the height of the top cover 18 and there is a vertical clearance between the upper end of each rod 46 serving as a current collector of the negative electrode and the portion facing the underside 17 of the upper cover 18 Each rod 46 serving as a current collector of the negative electrode can be made of an insulating material and it can also be coated with a layer of copper which can be produced by deposition at the same time as the layer of copper which coats the internal surface of the lower tank 14.

The rods 46 serving as a current collector of the negative electrode made of conductive material or coated with a conductive material such as the copper layer are electrically connected to the conductive coating, here copper, of the internal surface of the lower tank 14 for constitute "extensions" of the negative electrode which is inside the lower tank 14.

The rods 46 serving as a current collector of the negative electrode are arranged over the entire available surface area of the internal face of the bottom wall 22 and they are distributed in a regular pattern, each here between three adjacent housings 40 in a triangle.

As can be seen in particular in FIG. 7, each housing 40 is surrounded directly by four rods 46 arranged in a square or else, depending on the longitudinal line to which the housing 40 belongs, it is surrounded by two rods 46 aligned transversely, and this equidistant from the housings 40.

Other geometric patterns and arrangements of the housings 40, of the rods 46 serving as the current collector of the electrode negative and vertical holes 36 and 38 are possible without departing from the scope of the invention.

In accordance with the teachings of the invention, the positive electrode structure is a three-dimensional structure which consists of a series of electrodes each of which is in the form of a bar 50 of vertical orientation.

In a non-limiting way, each bar 50 is here a cylindrical bar with a circular section.

Each positive electrode bar 50 comprises a central core or heart 52 which is here a vertical central aluminum rod whose upper section 54 extends vertically beyond the horizontal upper face 49 of the cylindrical bar to be received vertically through the aligned holes 36 and 38 of the top cover 18 and the aluminum plate 34 forming a collector for all of the positive electrodes 50 of the three-dimensional positive electrode structure of the electrochemical cell 10.

As a variant, each central core 52 can be made of an insulating material coated on the outside with a layer of aluminum. Each central core 52 connected to the plate 34 acting as a current collector.

The diameter of each central core 52 is for example equal to about two millimeters and it is coated on the outside with a layer 56 which is a mixture of positive electrode material and solid electrolyte and which is produced by dipping.

The positive electrode material and for example a material belonging to the so-called “NMC” category of which the general definition of the composition is (LiNixMnyCoz02), in which x, y and z correspond to the stoichiometric proportions of the various components.

The radial thickness of the tubular layer of positive electrode material 56 is for example equal to four millimeters. By way of example, the height of each positive electrode bar 50, which is delimited by its upper 49 and lower 51 opposite horizontal faces, and for example equal to two hundred millimeters.

Without limitation, the layer of positive electrode material 56 is coated on the outside with a thin complementary layer of solid electrolyte coating which is preferably the same as the solid electrolyte of the electrochemical cell 10, the composition and size of which. implementation will be described below.

The peripheral layer of solid electrolyte coating which is formed on each positive electrode bar 50 is for example produced by dipping the bar consisting of its central core 52 and of its layer of positive electrode material 56, consisting of the active material and of the electrolyte which has previously been heated and melted and then soaked in the electrolyte, also previously heated and melted.

Once cooled, the solid electrolyte coating film is formed over the entire outer peripheral surface of the positive electrode bar 50. This film acts as a separator, electrically insulating the positive and negative electrodes. Its thickness is variable depending on the viscosity of the chosen mixture containing the electrolyte in polymer form.

The thickness is for example of the order of twenty microns to ensure good mechanical strength as well as sufficient electrical insulation between the positive 50 and negative 60 electrodes.

For mounting and fixing each positive electrode bar 50, the free lower end section 58 of each positive electrode bar 50 is received and is fixed in an associated housing 40 of the bottom wall 22 of the tank. lower 14.

Fixing is for example ensured by a gluing operation by means of a drop of insulating adhesive or by means of a drop molten polymer electrolyte 59 deposited in the bottom 44 of the associated housing 40.

As can be seen in particular in FIG. 6, each positive electrode bar 50 extends substantially over the entire internal height of the housing 12 and its upper end face 49 is adjacent to the internal face 17 of the upper cover 18. .

The electrochemical cell 10 finally comprises a mixture of negative electrode 60, comprising an electrolyte which is here a solid electrolyte and the active material, for example graphite. The mixture 60 is poured into the lower tank 14, in particular around the bars 50 of the positive electrode and the rods 46 serving as a current collector for the negative electrode.

After being poured and cooled, the mixture 60 is set. The mixture completely fills the space available inside the lower tank 14.

The lower vessel 14 is then sealed by the upper cover 18 with the upper free end sections 54 of the cores 52 of the positive electrode bars 50 which pass through the upper cover 18 and the external aluminum plate 34.

The whole of the aluminum outer plate 34 and the upper free end sections 54 for connecting the positive electrode bars 50 can then be hermetically protected from the external environment.

The electrical connection of the positive electrodes with an external electrical circuit is made by means of a conductive aluminum connection end piece 70 which is connected to the plate 34 and which is arranged in the upper part of the right side wall 26.

The electrical connection of the negative electrode with an external electrical circuit is made by means of a conductive end piece 72 of copper connection which is connected to the layer 15 of copper and which is arranged in the lower part of the right side wall 26.

Advantageously, the design according to the invention makes it possible to produce a “solid” electrochemical cell 10 which is produced and used without any solvent, which has the advantage of avoiding the formation of porosities.

The dimensions of the positive electrodes 50 and of the negative electrode housing 12 can vary within wide ranges. Depending on the application and for example to maximize the energy capacity stored, for example in application to a supply battery of a motor vehicle with an electric traction motor, it is possible to choose a box of several tens of centimeters of length with very thick electrodes of a few meters unlimited.

For a system of smaller capacity and less bulk, the size of the housing can be reduced while maintaining electrodes of the same dimensions.

If you want to have a lot of available power, you can reduce the thicknesses of the electrodes in order to reduce the ion diffusion times in the electrolyte.

Thanks to the invention, all the negative and positive electrode subsets are connected in parallel, which makes it possible to increase the energy density of the battery system.

The techniques proposed for the production of the negative three-dimensional electrode constituted by the lower tank 14 which can be produced by molding, and of the three-dimensional positive electrode makes it possible to produce electrode thicknesses much greater than those obtained according to current techniques. conventional by coating in liquid process which are at most a hundred microns.

Being able to compartmentalize the electrodes in the form of a rigid tank containing a solid electrolyte makes it possible to reduce the risk of short circuits compared to conventional designs using a stack of flat electrodes.

Furthermore, the electrical configuration of the electrochemical cell system according to the invention can be modulated in the sense that it is possible to choose the value of the voltage.

Claims

1. Electrochemical cell (10), characterized in that it comprises a housing (12) which:

- comprises a first lower element in the form of a tank (14), the internal surface of which is at least partially covered with a layer (15) of conductive material to constitute the current collector of the first electrode of a first polarity (-) ;

- Has a second upper element in the form of a cover (18) for closing the tank (14);

- houses a three-dimensional electrode structure with a second electrical polarity (+) opposite to the first polarity;

- and contains an electrolyte as an ionic conductive medium, and characterized in that the three-dimensional electrode structure of second polarity (+) comprises a series of electrodes (50) of second polarity each of which is an elongated body of orientation vertical.

2. An electrochemical cell according to claim 1, characterized in that the electrodes (50) of second polarity are distributed inside the housing (12) in a regular pattern.

3. Electrochemical cell according to any one of the preceding claims, characterized in that the tank (14) houses a series of conductive elements (46) of first polarity (-) which are electrically connected to said layer (15) of material. conductor and each of which is an elongated element of vertical orientation.

4. An electrochemical cell according to claim 3, characterized in that the conductive elements (46) of first polarity are distributed inside the housing (12) in a regular pattern.

5. An electrochemical cell according to claim 3 taken in combination with claim 2, characterized in that the conductive elements (46) of first polarity (-) are distributed equidistantly between the electrodes (50) of second polarity (+).

6. Electrochemical cell according to any one of the preceding claims, characterized in that each electrode (50) of second polarity is a vertical bar which comprises a central core (52) of conductive material which is covered with a layer (56). electrolyte and electrode active material of second polarity.

7. An electrochemical cell according to claim 6, characterized in that the upper end section of each central core (52,

54) of conductive material extends vertically through the cover (18) for closing the vessel (14), and in that all the upper end sections (54) of the central cores (52) of conductive material are connected electrically between them by a collector plate (34) arranged above the cover (18).

8. Electrochemical cell according to any one of the preceding claims, characterized in that a mixture serving to form the electrode of first polarity (60) is a mixture based on solid electrolyte poured into the tank (14) of the housing. (12).

9. An electrochemical cell according to claim 8 taken in combination with claim 6, characterized in that the layer (56) of active material of the electrode (50) of the second polarity is covered with a peripheral layer of said solid electrolyte.

10. An electrochemical cell according to any one of the preceding claims, characterized in that the lower end section (58) of each electrode (50) of second polarity is fixed in a complementary electrically insulated housing (40) which is formed in the lower wall of the tank (14) of the housing (12).

11. An electrochemical cell according to any one of the preceding claims, characterized in that the first polarity is negative and the second polarity is positive.

12. An electrochemical cell according to claim 11 in combination with claims 6 and 8, characterized in that:

- the mixture (60) which forms the electrode of first polarity is a mixture based on active material, electrically conductive agent and solid electrolyte on the conductive elements (46) of first polarity covered with a copper coating (15);

- a mixture (56) which forms the electrode of second polarity (50) is a mixture based on active material, electronic conductive agent and solid electrolyte on the central cores (52) of conductive material covered with a aluminum coating;

- an electrically insulating film between the first and second polarity electrodes is solid electrolyte

- the solid electrolyte is a polymer electrolyte or a hybrid material / ceramic polymer.