RU2737037C1 - Electrochemical device and battery - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to the field of electrical engineering, namely to electrochemical current sources. Electrochemical device and battery comprise electroconductive plates (1), electric insulating frame (2) and electrochemical cell (3) made in form of pile or flat roll of electrodes and separators and having anode (7) and cathode (8) current leads with end parts located on opposite sides of electrochemical cell (3). Current leads are connected via buses (9) to electroconductive plates (1) forming together with electric insulating frame (2) a shell around electrochemical cell (3). Electric insulating frame (2) is equipped with heat carrier pumping channel with inlet (11) and outlet (12) holes.EFFECT: technical result is increase in specific capacity of electrochemical device.7 cl, 7 dwg

Description

The invention relates to the field of electrical engineering, namely, to electrochemical current sources, for example, batteries and capacitors with a double electric layer.

Electrochemical power sources are widely used. In particular, on transport vehicles with electric power plants, batteries of such electrochemical cells as lithium-ion batteries and capacitors with a double electric layer (supercapacitors) are used, while the electrochemical cells experience short-term overloads that are many times higher than the average level of electrical power they give or receive. Overloads lead to heating of electrochemical cells. Effective cooling of the latter is one of the key technical challenges.

A battery of electrochemical cells is known, the leads of which are used for connection with cooling equipment (US 8 962 172 B2). In this device, heat transfer from electrochemical cells is carried out mainly along the down conductors, made, for example, of metal foil; heat transfer in the direction perpendicular to the surface of the down conductors (from the electrodes to the walls of the elements) is used ineffectively. In addition, thermal conductivity is limited by the small contact area between the cooling equipment and the terminals of the electrochemical cells.

Known battery of electrochemical cells with ribbed walls and placed in a common housing (RU 2 564 509 C2); thermal stabilization is carried out by washing the walls with a coolant along the channels formed by the walls. In this case, heat transfer from electrochemical cells is carried out mainly in the direction perpendicular to the surface of the down conductors (from the electrodes to the walls). A similar approach is used in devices with channels from tubes embedded in plates (WO 2010/044553; KR 2019 0123 309A; KR 2019 0133 689 A). The channels for the circulation of the coolant increase the volume of the battery, which reduces its specific energy.

Known battery of electrochemical cells, which contains cooling plates with tubes located around the perimeter of the plates for the circulation of the coolant (US 10 340 565 B2). Cooling plates adjoin the surface of the walls of the electrochemical cells - in this case, heat transfer from the electrochemical cells is carried out mainly in the direction perpendicular to the surface of the down conductors (from the electrodes to the walls); heat transfer along the down conductors is insignificant. A similar approach is used in a number of other devices (US 10 038 226 B2; US 10 454 083 B2; US 10 514 209 B2; JP 5 621 111 B2; KR 101 326 086 B1).

The closest to the claimed invention in terms of a set of essential features is an electrochemical device (RU 2 608 762 C1), which contains housing elements, electrically conductive plates, electrical insulating frames and a prefabricated package of electrochemical cells, each of which is made in the form of a stack or flat roll of electrodes and separators , and has anode and cathode current leads with end parts located on opposite sides of the electrochemical cell, and the anode and cathode current leads are connected to the electrically conductive plates, and the electrical insulating frames are located between the electrically conductive plates and form, assembled with them, a shell around each electrochemical cell. The disadvantage of this device is the lack of thermal stabilization means designed both for its cooling (when heating from the influence of electrical loads) and for heating (when the temperature drops in winter). This disadvantage is the reason for the low specific power SP, measured by the ratio of the permissible output electrical power of the electrochemical device to its volume.

The objective of the claimed invention is to increase the specific power of the electrochemical device.

Technical results to solve the problem:

- ensuring the possibility of pumping the coolant through the electrochemical device without significantly increasing its volume;

- ensuring the minimum thermal resistance between the coolant and the electrodes of the electrochemical device.

Technical results are achieved by the fact that in an electrochemical device containing two electrically conductive plates located in parallel to one another at a distance of H, an electrical insulating frame and an electrochemical cell made in the form of a stack or a flat roll of electrodes and separators, and having anode and cathode current leads with end parts located on opposite sides of the electrochemical cell at a distance W, and the anode current collector is connected to one electrically conductive plate, the cathode current collector is connected to another electrically conductive plate, and the electrical insulating frame is located between the electrically conductive plates and forms, assembled with them, a shell around the electrochemical cell, according to the invention the frame is equipped with a channel for pumping the coolant, and the distances H and W satisfy the condition:

7 <W / H <14.

The insulating frame can be made of a metal covered with a dielectric layer, or of plastic with a high thermal conductivity.

An elastic compensator for changing the thickness of the electrodes can be placed inside the electrochemical cell. The specified expansion joint can be made in the form of a sealed shell filled with gas or porous material. The specified compensator can be in the form of a rectangular prism, located so that the electrodes and separators in a stack or flat roll are evenly pressed against each other and against the electrically conductive plates.

The end parts of the anode and cathode down conductors can be welded to the electrically conductive plates directly or through adapter busbars.

Electrochemical devices can be assembled into a package, forming a battery, while each electrochemical device contains two electrically conductive plates located in parallel opposite one another, an electrical insulating frame and an electrochemical cell made in the form of a stack or flat roll of electrodes and separators, and having an anode and cathodic down conductors with end parts located on opposite sides of the electrochemical cell, and the anode down conductor is connected to one electrically conductive plate, the cathode current collector is connected to another electrically conductive plate, and the electrical insulating frame is located between the electrically conductive plates and forms, assembled with them, a shell around the electrochemical cell; electrochemical devices are connected in series in a package and pressed against each other by the outer surfaces of the electrically conductive plates; According to the invention, the electrical insulating frames are equipped with channels for pumping the coolant with openings, into which collector taps are inserted, which combine these channels into a common network with an inlet and outlet.

The collector taps can be made in the form of a comb.

The collector bends can be T-shaped, with gaskets and plugs placed at their joints. It is preferable to place the gaskets and plugs in such an order that provides a parallel-serial connection of the channels for pumping the coolant.

It is preferable that the end portions of the anode and cathode current collectors in adjacent electrochemical devices of the stack are mirrored to one another.

Contact pads can be located on the outer surface of the electrically conductive plates opposite the junction with the down conductors. The contact pads can be a plurality of micro-notched protrusions.

Electrically conductive plates may have areas that protrude beyond the contours of the insulating frames. The protruding sections of the electrically conductive plates can be used for additional connections, in particular for connecting voltage balancing circuits of electrochemical cells in a battery.

The essential features of the proposed solution affect the achievement of the technical result as follows:

The implementation of the electrochemical cell in the form of a stack or a flat roll of electrodes and separators and its location inside the shell of electrically conductive plates and an electrical insulating frame provides efficient heat transfer from the electrodes of the electrochemical cell to the above shell in the transverse direction - perpendicular to the surface of the down conductors.

The connection of the down conductors of the electrochemical cell with the electrically conductive plates ensures efficient heat transfer from the electrodes of the electrochemical cell to the above shell in the longitudinal direction - parallel to the surface of the down conductors.

The choice of the distances H and W so that they satisfy the condition:

7 <W / H <14

allows you to provide a minimum thermal resistance between the above shell and the electrodes of the electrochemical cell, since in this case the optimal ratio of transverse and longitudinal heat fluxes is ensured.

Equipping the electrical insulating frame with a channel for pumping the coolant makes it possible not to introduce additional assembly units, that is, the volume and complexity of the electrochemical device increase insignificantly.

The electrical insulating frame is made of metal coated with a dielectric layer to minimize the thermal resistance between the coolant and the above-mentioned shell.

The placement of an elastic compensator inside the electrochemical element allows stabilizing the transverse thermal resistance when the thickness of the electrodes changes during the discharge / charge of the electrochemical cell.

The assembly of these electrochemical devices into a package and the installation of collector taps provide the possibility of pumping the coolant through the battery of electrochemical cells without significantly increasing its volume and complexity.

The rest of the features of the proposed solution are explanatory.

Thus, the technical result is achieved due to:

- the possibility of pumping the coolant without significant design complications;

- minimization of thermal resistances all the way from electrodes to coolant;

- the optimal ratio of transverse and longitudinal heat flows.

The technical result is provided by features, the totality of which is not known from the prior art, that is, the claimed technical solution meets the criteria of "novelty" and "inventive step".

An example of the implementation of the proposed technical solution is shown in the illustrations:

FIG. 1 - component parts of the device in the order of their assembly; designation of secant planes А-А and В-В.

FIG. 2 - section of A-A devices assembled in a package.

FIG. 3 - fragment of section А-А.

FIG. 4 - isotherms of the temperature field.

FIG. 5 is a graph reflecting the influence of the design parameters of the device on its specific energy and power.

FIG. 6 - section В-В of the electrical insulating frame with collector taps attached to it; designation of the secant plane C-C.

FIG. 7 - section C-C of devices assembled in a package.

The electrochemical device (figure 1, figure 3), contains two electrically conductive plates 1, an electrical insulating frame 2 and an electrochemical cell 3. Electrochemical cell 3 consists of electrodes 4, 5, separators 6, an anode current collector 7 and a cathode current collector 8. Down conductors 7, 8 are connected with their end parts to electrically conductive plates 1 through adapter busbars 9. The insulating frame 2 is equipped with a channel 10 for pumping the heat carrier. Channel 10 has an inlet 11 and an outlet 12. The insulating frame 2 is made of a metal coated with a dielectric layer 13. An elastic compensator 14 for changing the thickness of the electrodes is placed inside the electrochemical cell.

The battery (figure 2, figure 7) is made in the form of a prefabricated package 20 of electrochemical devices. Electrochemical devices in the package are pressed against each other by the outer surfaces of the electrically conductive plates 1.

In the holes 11, 12 are pressed collector taps 21 (Fig. 6, Fig. 7), which are made T-shaped. Sealing gaskets 22 and plugs 23 are placed at the joints of the collector taps 21 - the collectors 24 formed in this case combine the channels 10 into a common network with inlet 25 and outlet 26 (the direction of movement of the coolant is shown by arrows).

Contact pads 27 are located on the outer surfaces of the electrically conductive plates 1 (Fig. 1, Fig. 2) opposite the places where they are connected to the adapter buses 9 ...

One of the electrically conductive plates 1 (Fig. 1) has a protruding portion 28 that can be used to connect the voltage balancing circuit of the electrochemical cells in the battery.

Each electrode 4, 5 (figure 3) is a layer of a substance deposited on the surface of the corresponding current collector 7, 8 and impregnated with an electrolyte solution. Each down conductor 7, 8 is made in the form of a metal foil, for example, aluminum or copper - depending on the type of electrochemical cell 3. The substance layers are separated by separators 6. The end parts of the down conductors 7, 8 protrude beyond the boundaries of the separators 6.

For such electrochemical cells as supercapacitors or lithium-ion batteries, the following parameter ratios are characteristic:

where Df is the thickness of the foil from which the down conductors are made; Kf - coefficient of thermal conductivity of the foil; Dg is the distance between the foil layers; Kg - coefficient of thermal conductivity in the intervals between foil layers (average coefficient of thermal conductivity of the substance of electrodes and separators impregnated with electrolyte).

Electrochemical cell 3 is isolated from the external environment by a shell, which is formed by an electrical insulating frame 2 and electrically conductive plates 1. The latter are body parts, electrical terminals and a means of heat exchange between the electrochemical cell 3 and the coolant in the channel of the electrical insulating frame 2.

The heat transfer pattern is explained using a fragment of the cross-section of the electrochemical device (Fig. 3) and the corresponding isotherms (Fig. 4) with characteristic points:

- f - point inside channel 10 with a temperature equal to the temperature of the coolant;

- e, e '- points in the electrically conductive plates 1 opposite the junction with the adapter bus 9 (the fragment of Fig. 3 shows only one adapter bus 9 and the corresponding end part of the current collector 8);

- d, d '- points in the middle of the electrochemical cell 3 farthest from the coolant.

Heat exchange between the electrochemical cell 3 and the electrically conductive plates 1 goes in two ways:

1) Longitudinal path (along the x-axis in figure 4): from the electrodes 4, 5 through the current collector 8 to the transition bus 9; then, through the adapter bus 9, to point e.

2) Transverse path (along the y-axis in Fig. 4): from electrodes 4, 5 to electrically conductive plates 1.

Heat exchange between the electrically conductive plates 1 and the coolant goes from points e, e 'through the dielectric layer 13 and the electrical insulating frame 2 to point f.

Electrochemical cell 3 in the form of a stack or flat roll has anisotropic properties - its thermal conductivity in the transverse direction is lower than in the longitudinal direction, respectively, the distance between the temperature field isotherms (Fig. 4) in the y direction is less than in the x direction.

The design parameters H, W (Fig. 2) are chosen so that

where H is the distance between the electrically conductive plates 1, W is the distance between opposite sides of the electrochemical cell 3.

Taking into account (1), (2), (3), heat is transferred equally in both the transverse and longitudinal directions: in the regions located to the right of the diagonals de, d'-e '(Fig. 3), the longitudinal transfer prevails heat, and in the areas located to the left - transverse. This is optimal for the claimed device, which is explained below using the graphs.

In Fig. 5, the axes plotted (in relative units) the specific energy SE and the specific power SP, which depend on the design parameters of the electrochemical device: the graph (solid line) illustrates the changes in SE and SP when deviating from the optimal ratio (3); dashed lines show graphs for analog devices, in which the only type of heat transfer significantly predominates - transverse (Ry << Rx), or longitudinal (Rx << Ry). Thermal resistances are designated by Rx, Ry symbols.

As can be seen from the graphs, the proposed device significantly outperforms analogues at W / H = 10, which is optimal if relations (1), (2) are observed. These ratios can vary within certain limits for technological reasons - accordingly, the optimum also varies:

Thus, as shown in the graphs (figure 5), in comparison with analogs, the proposed solution allows you to increase the specific power of the electrochemical device and battery by 20-30%.

Claims (8)

1. An electrochemical device containing two electrically conductive plates located parallel to one another at a distance of H, an electrical insulating frame and an electrochemical cell made in the form of a stack or flat roll of electrodes and separators and having anode and cathode current leads with end parts located on opposite sides an electrochemical cell at a distance W, and the anode current collector is connected to one electrically conductive plate, the cathode current collector is connected to another electrically conductive plate, and the electrical insulating frame is located between the electrically conductive plates and forms, in assembly with them, a shell around the electrochemical cell, characterized in that the electrical insulating frame is equipped with a channel for pumping the coolant, and the distances H and W satisfy the condition 7 <W / H <14. 2. A device according to claim 1, characterized in that the insulating frame is made of metal coated with a dielectric layer. 3. The device according to claim 1, characterized in that an elastic compensator for changes in the thickness of the electrodes is placed inside the electrochemical cell. 4. A battery made in the form of a prefabricated package of electrochemical devices, each of which contains two electrically conductive plates arranged in parallel to one another, an electrical insulating frame and an electrochemical cell made in the form of a stack or a flat roll of electrodes and separators and having anode and cathodic down conductors with end parts located on opposite sides of the electrochemical cell, and the anode current collector is connected to one electrically conductive plate, the cathode current collector is connected to the other electrically conductive plate, and the electrical insulating frame is located between the electrically conductive plates and forms, assembled with them, a shell around the electrochemical cell; electrochemical devices are connected in series in a package and pressed against each other by the outer surfaces of the electrically conductive plates, characterized in that the electrical insulating frames are equipped with channels for pumping the coolant with holes, into which collector taps are inserted, which combine these channels into a common network with an inlet and outlet. 5. The battery according to claim 4, characterized in that the end parts of the anode and cathodic down conductors in adjacent electrochemical devices of the package are arranged in a mirror image relative to each other. 6. The battery according to claim 5, characterized in that the contact pads are located on the outer surfaces of the electrically conductive plates opposite the connection points with the down conductors. 7. The battery according to claim 4, characterized in that the electrically conductive plates have portions that protrude beyond the contours of the insulating frames.

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