RU205771U1 - PRISMATIC LITHIUM-ION BATTERY - Google Patents

Abstract

The utility model relates to electrochemical power engineering, in particular, to lithium-ion batteries (LIB). One of the urgent problems of LIB is the problem of increasing the safety of their operation. The technical result of the utility model is to increase the thermal and mechanical resistance of the battery to the flow of short-circuit current in it. The specified technical result is achieved by the design of a prismatic lithium-ion battery. The lithium-ion battery contains a two-layer polymer evacuated housing with an outer layer, an inner layer and inside which an electrode block of positive and negative electrodes is located; on one side of the housing, current leads of positive and negative electrodes are hermetically sealed, consisting of current collectors with an active mass deposited on them, between the electrodes there is a separator tape impregnated with electrolyte, the current collectors of the electrodes are welded to the current leads of the charge-discharge controller, the arrangement of the electrodes and the separator is made by the Z-stacking method, the separator tape is made of three-layer, consisting of an inner layer of polypropylene and two layers of polyvinylidene difluoride, directly in contact with the surface of the negative and positive electrodes. A three-layer sulfonated rubber film is applied to the current leads of the electrodes, and the inner layer of the body is equipped with protective plasters on the side surfaces. 2 c.p. f-ly, 4 dwg.

Description

The utility model relates to electrochemical power engineering, in particular, to lithium-ion batteries (LIB). One of the urgent problems of LIB is the problem of increasing the safety of their operation.

Known is a cylindrical lithium-ion battery with a cathode based on LiCoO ₂ , a three-layer separator and a self-healing fuse. electrodes made of a roll-type design, consisting of a positive electrode based on LiCoO ₂ and a negative electrode based on artificial graphite, separated by a porous three-layer separator (polypropylene / polyethylene / polypropylene) 25 μm thick, the separator is moistened with an electrolyte based on LiPF ₆ salt and solvents ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, vinyl carbonate, the positive terminal is spot-welded to the cover, the negative terminal is spot-welded to the battery case, the cover has a safety diaphragm and a self-healing fuse in the form rings, sealing and fastening of the cover to the body are made by bending, preliminary and final rolling.

The disadvantage of this technical solution is the lack of resistance to ignition with a short circuit of the electrodes. The fuse does not sufficiently solve this problem, since the short circuit occurs inside the battery case, and the fuse only opens the electrodes.

Known prismatic lithium-ion battery Patent RU No. 190339, published 06/27/2019, IPC H01M 10/0525, H01M 4/131, adopted as a prototype containing a two-layer polymer housing with an outer layer and an inner layer, inside which is placed an electrode block of positive and negative electrodes, on one side of the case, the current leads of the positive and negative electrodes, consisting of current collectors with an active mass applied to them, are hermetically sealed, a separator impregnated with electrolyte is located between the electrodes, the current collectors of the electrodes are welded to the corresponding current leads.

The disadvantage of the prototype is insufficient resistance to mechanical damage, as a result of which a short circuit of the electrodes occurs, as a result of which the temperature inside the block of electrodes rises and a fire occurs.

A problem in the design of lithium-ion batteries is their low resistance to ignition due to the formation of flammable gaseous products during short circuit of the electrodes, which occurs both during operation and during mechanical damage.

The technical result of the utility model is to increase the thermal and mechanical resistance of the battery to the flow of short-circuit current in it.

The specified technical result is achieved by the design of a prismatic lithium-ion battery. The lithium-ion battery contains a two-layer polymer evacuated housing with an outer layer, an inner layer and inside which an electrode block of positive and negative electrodes is located; on one side of the housing, current leads of positive and negative electrodes are hermetically sealed, consisting of current collectors with an active mass deposited on them, between the electrodes there is a separator tape impregnated with electrolyte, the current collectors of the electrodes are welded to the current leads of the charge-discharge controller, and the arrangement of the electrodes and the separator is made by the Z-stacking method, the separator tape is made of three-layer, consisting of an inner layer of polypropylene and two layers of polyvinylidene difluoride, directly contacting with the surface of the negative and positive electrodes. A three-layer sulfonated rubber film is applied to the current leads of the electrodes, and the inner layer of the body is equipped with protective plasters on the side surfaces.

The arrangement of the electrodes and the separator strip by the Z-laying method provides more reliable insulation of the electrode ends from direct electrical contact than other methods of mounting the separator strip, since during the Z-laying the separator strip is not cut, not welded, but retains its mechanical integrity. When assembling the electrode block, microprotrusions of the collector or unevenness of the active mass are leveled by the lateral pressure of the separating tape without breaking it. In case of mechanical damage to the electrode block and a corresponding displacement of the planes of the electrodes, the lateral insulation prevents additional short circuits of the electrodes by the end sections. The use of a three-layer separation tape, consisting of layers of polyvinylidene difluoride (PVDF), directly contacting the surfaces of the electrodes and the inner layer of polypropylene, increases the separation resistance to rupture due to the greater mechanical strength of PVDF, and also due to its greater thermal stability (melting point 123-127 ° C, softening temperature 140 ° C), the separator retains its structure longer during thermal runaway caused by a short circuit. PVDF also has an increased fire resistance due to the presence of fluorine-substituted fragments in its structure, which reduces the amount of substances hazardous for the development of combustion when the electrodes are short-circuited. The inner layer of polypropylene, as a more low-melting component, ensures that the pores of the PVDF layers are melted at an increase in temperature and prevents the emergence of new points of short circuit by rapidly growing lithium dendrites, thereby limiting the increase in the rate of temperature rise.

The essence of the utility model is illustrated by drawings.

FIG. 1 shows the arrangement of the electrodes and the separator in the Z-arrangement.

FIG. 2 is a frontal cutaway sketch of a prismatic lithium-ion battery.

FIG. 3 is a cross-sectional side view of the structure of a prismatic lithium-ion battery.

FIG. 4 shows the arrangement of the separator layers in the accumulator.

The figures show:

1 - inner layer of a two-layer polymer body,

2 - outer layer of a two-layer polymer body,

3 - negative electrode,

4 - positive electrode,

5 - current collector of negative electrode 3,

6 - current collector of the positive electrode 4,

7 - separator,

8 - negative current output,

9 - positive current output,

10 - protective plasters,

11 - three-layer sulfonated rubber film,

12 - charge-discharge controller,

13 - current supply wires,

14 - layer of separation from polyvinylidene difluoride,

15 - polypropylene separation layer.

A prismatic lithium-ion battery consists of a two-layer body, including an inner layer 1 and an outer layer 2. In the inner layer 1 of the body there is a block of negative 3 and positive 4 electrodes, consisting of current collectors: 5 negative electrode 3 and 6 positive electrode 4 with deposited on current collectors with active mass, between the electrodes there is a separator 7 impregnated with electrolyte. Separator 7 is three-layer, consisting of two layers of polyvinylidene difluoride 14, contacting the surface of negative electrode 3 and positive electrode 4, and a layer of polypropylene 15 located between layers of polyvinylidene difluoride 14. The arrangement of electrodes of positive 4, negative 3 and separator tape 7 is made by the Z-stacking method ... Current collectors 5 and 6 of electrodes 3 and 4 are welded to the corresponding current leads 8 and 9, current leads 8 and 9 are located on one side of the case, the case is evacuated, the inner layer 1 of the case is equipped with protective patches 10 on the side surfaces, a three-layer sulfonated rubber film 11, electrodes 3 and 4 are pressed with a force of 5-6 MPa in the filled state, at the end of the outer layer 2 of the case there is a charge-discharge controller 12, to which current leads 8 and 9 and current supply wires 13 are connected.

The battery is assembled by placing the positive electrode 4 on the tape of the three-layer separator 7, the tape of the separator 7 is placed on the upper side of the positive electrode 4, the negative electrode 3 is placed on the surface of the tape of the separator 7, and the tape of the three-layer separator 7 is again laid on its upper surface 7. The operation is repeated the required amount times until the electrode package is obtained, current collectors 6 of positive electrodes 4 are welded, current collectors 5 of negative electrodes 3, the electrode package is placed on a two-layer sheet of the body, the free edge of the sheet is wrapped so that the electrode package is completely closed and sealed around the perimeter, except for the side opposite fold the web, so that the three-layer sulfonated rubber film 11 of each of the current leads 8 and 9 falls into the soldering zone. An electrolyte is poured into the inner layer of the two-layer polymer body 1, evacuated, the remaining side is sealed, leaving an additional pocket and a force is created on the outer part of the body 2 of 5-6 MPa. To the current collectors 5 and 6 of the negative and positive electrodes, respectively, located outside the case, the charge-discharge controller 12, the current supply wires 13 are soldered and the protective plasters 10 are glued, after which the formation is carried out, the pocket is sealed and removed.

A prismatic lithium-ion battery works as follows. When charging, the current supply wires 13 are connected to the terminals of the same name of the charger (not shown in the figure), which ensures the flow through the current leads 8 and 9, as well as the current collectors 5 and 6 of the electrodes 3 and 4 and the anode and cathode masses of the current, which provides the processes of intercalation from the electrolyte lithium ions into graphite at negative electrode 3 and deintercalation of lithium ions from cobaltite into lithium at positive electrode 4. As a result, the battery goes into a charged state. During the discharge, the current supply wires 13 are connected to the same terminals of the consumer (not shown in the figure), when the circuit is closed, the current flows through the current leads 8 and 9 of the electrodes 3 and 4, the current collectors of the electrodes 5 and 6 of the electrodes 3 and 4, the anode and cathodic active mass, which provides deintercalation of lithium from graphite and intercalation of lithium into delithium cobalt oxide. When the voltage reaches 2.97 V, the charge-discharge controller 12, fixed at the end of the outer layer 2 of the multilayer polymer body, turns off the discharge current. If during the discharge process mechanical damage occurs, leading to a point short circuit of the positive 4 and negative 3 electrodes with their simultaneous deformation, the tape of the three-layer separator 7 prevents the closure of electrodes 3 and 4 along the outer edge due to reliable shielding of the edges of electrodes 3 and 4 by the fold of the separator tape 7. In the process of thermal runaway accompanying the short circuit, the polyvinylidene difluoride layer 14 retains its mechanical integrity up to 140 ° C, while the polypropylene layer 15 melts, closing the pores of the separator tape 7 and isolating electrodes 3 and 4 from each other, increasing the internal resistance and reducing the short-circuit current. This prevents ignition and the formation of flammable gaseous products, thereby increasing the thermal and mechanical stability of the battery.

The achievement of the declared technical result is also proved by the tests carried out. For verification tests, two versions of prismatic lithium-ion batteries were assembled: the proposed version and a battery using a PP / PE / PP three-layer separator.

The tests were as follows:

1. Checking the performance of batteries during charging and discharging with increased currents.

2. Checking the performance of batteries at elevated temperatures plus 50 ° C.

3. Checking the performance of batteries during tests for fire and explosion safety:

3.1. Mechanical damage to charged batteries with internal shorting of electrodes;

3.2. Mechanical damage to discharged batteries with internal shorting of electrodes.

To carry out tests for fire and explosion safety, the battery was fixed on the base of the headframe, temperature measurement sensors were fixed on the battery case; a metal punch pierced the battery case through and through, resulting in a short circuit of the electrodes with depressurization; using a temperature sensor, the temperature on the external battery case was recorded.

As a result of tests (table 1), it was found that: a battery assembled using a three-layer separator of the PVDF / PE / PVDF type provides greater battery safety during operation with increased charge and discharge currents, is more resistant to high temperatures, as indicated by a lower internal resistance, more resistant to mechanical stress, this is indicated by a lower degree of heating and less significant smoke.

Based on the foregoing, it can be concluded that the proposed utility model can be implemented in practice with the achievement of the claimed technical result.

Claims (3)

1. A prismatic lithium-ion battery contains a two-layer polymer evacuated housing with an outer layer, an inner layer and an electrode block made of positive and negative electrodes inside; active mass, between the electrodes there is a separator tape impregnated with electrolyte, the current collectors of the electrodes are welded to the current leads of the charge-discharge controller, characterized in that the arrangement of the electrodes and the separator is made by the Z-stacking method, the separator tape is made of three-layer, consisting of an inner layer of polypropylene and two layers of polyvinylidene difluoride in direct contact with the surface of the negative and positive electrodes. 2. A prismatic lithium-ion battery according to claim 1, characterized in that a three-layer sulfonated rubber film is applied to the current leads of the electrodes. 3. A prismatic lithium-ion battery according to claim 1, characterized in that the inner layer of the body is provided with protective patches on the side surfaces.

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