CZ36155U1 - Lithium battery safety system - Google Patents

Description

In the registration procedure, the Industrial Property Office does not determine whether the subject of the utility model meets the conditions of eligibility for protection according to § 1 of Act. E. 478/1992 Coll.

CZ 36155 UI

Lithium battery cell safety system

Field of technology

The technical solution relates to the safety system of a lithium battery cell, which contains at least one container with emergency liquid, which in an emergency situation floods the space of the electrodes with emergency liquid. The safety system ensures safe operation of the cell by protecting the cell from catching fire or exploding. Basically, every type of lithium cell known from the state of the art can be provided with the system according to the technical solution. The solution is applicable both for individual lithium cells and for an accumulator consisting of several cells.

Current state of the art

Lithium accumulators belong to modern sources of electrical energy, particularly suitable for mobile purposes and as "reservoirs" of electrical energy obtained, for example, from alternative sources. The current and still unsolved problem of lithium batteries is their safety. Lithium has the highest energy density and specific capacity compared to other metals, i.e. the highest energy per volume. Lithium batteries can therefore provide very high currents, which is often desirable (electric cars), but accompanied by the problem of overheating. In the event of a short circuit, the cell can overheat very quickly and explode. The materials of the positive electrodes are usually substances with a high proportion of chemically bound oxygen and therefore support combustion, and at the same time the materials of the negative electrodes are self-igniting substances in air and moisture. This is accompanied by an electrolyte consisting of a lithium salt solution in an organic and therefore flammable liquid. The challenge for researchers in the field, in addition to striving for the highest possible efficiency and capacity, is above all operational safety.

According to the state of the art, active protection of the cell typically consists of the use of protective electronic circuits, which, in addition to voltage and current, also monitor an unreasonable increase in temperature and, when it is exceeded, disconnect the cell electrically.

European patent EP 2 619 836 presents one possible solution for temperature regulation of a large-capacity lithium battery, in which a battery module suitable for a cooling system is described, including a variant using a liquid electrolyte as a cooling medium.

Patent No. 306,913 described a solution where the lithium battery consists of mutually separable negative and positive electrode modules, which can be mechanically separated in the event of an emergency, while at the same time the electrolyte from the negative electrode module is displaced by the emergency liquid, thus preventing an unwanted chemical reaction and possible fire or explosion of the battery.

Utility Model No. 31,991 addresses the safety of a coiled lithium battery with a special design of the battery where the electrode strip is wound into a coil around a central glass container with emergency liquid. The emergency liquid is mineral oil. In an emergency situation, the detonator, which is connected to the safety electronic circuit, ensures the destruction of the container with the emergency liquid.

Utility Model No. 33,343 contributed to the safety of the lithium battery by using an inert vacuum oil (ie, vacuum pump oil) of the perfluoropolyether (PFPE) oil type as the emergency fluid. These oils have advantageous properties in terms of emergency liquid requirements, as they are a non-flammable and non-explosive liquid, with low surface tension, which is also biologically inert and ecologically sound.

The presented technical solution relates in particular to the new construction of the lithium battery cell safety system, which overcomes the disadvantages of existing systems and provides a high

- 1 CZ 36155 UI degree of safety and protection against explosion, while it is universally usable for lithium accumulators known from the state of the art.

The essence of the technical solution

The presented technical solution mainly relates to the safety system of a lithium battery cell, which contains at least one emergency space with emergency liquid, while the term "space" means any closed internal space located together with the electrodes (electrode module) in the solid housing of the accumulator. The basic feature of the crash area is that it is completely or at least partially defined by a layer of thermoplastic material with a low melting point or a low glass transition temperature.

This thermoplastic material can be coated on one or both sides with a thin aluminum foil (to prevent possible interaction between the organic electrolyte and the thermoplastic and/or between the emergency liquid and the thermoplastic). The term "partially" means that, for example, only one wall of the emergency room or part of the wall of the emergency room is made of thermoplastic material. If an emergency situation occurs and the temperature of the cell rises above a safe level, at least one wall of the emergency compartment will be disturbed by the high temperature and the emergency liquid will flood the electrodes, expel the electrolyte from the separators and stop the flow of ions and therefore the passage of electric current, thus preventing ignition/ cell explosion.

A suitable thermoplastic material can be polyolefin thermoplastics, e.g. low-density polyethylene, PE-LD (melting temperature 105 °C - 115 °C), especially cycloolefin copolymers (COC) or polymers (COP) (glass transition temperature 100 °C - 163 °C), commercially available e.g. under the names Apel, Arton, Topas, Zeonex and Zeonor. Styrene plastics can also be used, such as polystyrene, PS, or styrene-acrylonitrile, SAN (glass transition temperature 105 °C). Particularly advantageous are cycloolefin polymers available under the name Zeonor from spol. Zeon Corporation, Tokyo, Japan. The most advantageous material is specifically Zeonor 1020R, which exhibits very suitable physical-chemical, mechanical and electrical properties and a glass transition temperature of 102 °C. The glass transition temperature characterizes the transition state between the glassy and liquid state for amorphous polymers, at this temperature there is a sudden decrease in the modulus of elasticity.

The emergency fluid is mineral oil or vacuum oil.

In one embodiment, the emergency liquid contains at least one reagent that reacts with lithium, especially at temperatures that can reach hundreds of °C in the event of a short circuit of the cell, to form compounds that do not decompose water (in contrast, pure lithium, or dendrites formed in current Li cells at temperatures above 80 °C, react violently with water to form hydroxide and hydrogen). A preferred reagent is sulfur, especially in the form of nanoparticles. The reaction of sulfur and lithium produces lithium sulfide, LÍ2S.

In another embodiment, the security system includes another space, possibly a container, containing an inert gas, preferably nitrogen. The space for inert gas is separated from the emergency space by a layer made at least partially of thermoplastic material. In an emergency situation, the gas pressure will help the emergency liquid to quickly penetrate into the spaces between the electrodes and mix with the electrolyte. In addition, the reaction of nitrogen and lithium produces lithium nitride, LÍ3N, a compound that does not decompose water.

The safety system according to the presented technical solution ensures the safe operation of the cell/accumulator, among other things, by protecting it from ignition by a chemical reaction between lithium and a reagent, e.g. sulfur, and/or nitrogen, which leads to the conversion of lithium into compounds that do not decompose water. A lithium cell or a multi-cell accumulator equipped with the safety system described above will be able to be extinguished with water in the event of a fire.

-2CZ 36155 UI

The security system according to the presented technical solution can be used essentially for any (in terms of electrode material) lithium cells or accumulators known from the state of the art.

The presented technical solution also relates to a lithium battery cell equipped with the safety system described above.

The cell in which the safety system is applied typically comprises an electrode module containing at least one negative electrode and at least one positive electrode, separated by a separator and surrounded by an electrolyte, enclosed in a rigid housing.

In one embodiment, the emergency space is made up of an emergency container, which can be of essentially any shape, which is adapted so that the container can be placed in the fixed case of the cell in close proximity to the electrode module. In one embodiment, the emergency container may be in the shape of a cylinder or an elliptical cylinder, the cell being formed in such a way that the electrodes are pressed in the form of a strip and are helically wound on the emergency container. The emergency container is entirely or at least partially made of thermoplastic material.

In another embodiment, the safety system is implemented in such a way that an emergency space is defined in the cell of the usual construction, which contains an electrode module containing at least one negative electrode and at least one positive electrode, separated by a separator saturated with electrolyte, which has at least one wall formed by a thermoplastic material. In one such embodiment, the thermoplastic material forms a partition between the electrode module and the emergency space filled with emergency liquid.

In another embodiment, a space for nitrogen is also defined outside the emergency space inside the solid case. The space for nitrogen is separated from the emergency space by a layer made at least partially of thermoplastic material.

In one embodiment, a suitable emergency fluid is mineral oil.

In another embodiment, a suitable emergency fluid is an inert vacuum oil (vacuum pump oil) of the perfluoropolyether (PFPE) oil type as described in Utility Model No. 33,343.

The safety system of lithium cells from the state of the art includes as standard a safety electronic module enabling the electrical disconnection of the cell and contains at least one electronic sensor, such as a temperature, current or possibly an impact/shock sensor. The safety electronic module preferably contains all three of the aforementioned sensors. The safety electronic module is therefore designed to monitor the current and temperature inside the cell, as well as possible shocks/shocks, and to disconnect the battery electrically in the event of an emergency.

The presented technical solution is advantageously applied to a cell that includes an electrode module containing a negative electrode made of lithium metal and a positive electrode containing vanadium oxides, which provides a high capacity and specific energy of the cell.

The cell housing is a solid housing to provide mechanical protection for the cell. The case is standardly equipped with positive and negative pole contacts, on which the collectors of the respective electrodes are brought out. For reasons of mechanical protection, the case can still be lined inside with additional flexible material.

In another embodiment, the casing may be double, consisting of a solid casing and another outer casing, with the space between the rigid casing and the outer casing containing the extinguishing powder. The rigid case is then equipped with a safety valve, which is adapted to release the expanding electrolyte into the space with the fire-extinguishing powder. This solution can be particularly advantageously applied to a battery consisting of several cells, where the space between the cells and the battery case is filled with fire

-3 CZ 36155 UI powder. The fire extinguishing powder is able to absorb the leaked electrolyte and thus prevent it from igniting.

The electrode module comprises at least one negative and one positive electrode, separated by a separator, in any arrangement, e.g. preferably as a coil, bundle or column, The electrodes can be made of standard materials used for Li or Li-ion cells, as known to those skilled in the art . However, advantageously, the safety system according to the presented technical solution is applied in combination with a cell, where the negative electrode is made of metal lithium (Li), and at the same time the positive electrode contains vanadium oxides, preferably vanadium oxide (V2O5), and most preferably it is formed by a mixture ( composite) of V2O5 and graphene.

The electrode module is usually made of an electrode strip that is rolled into a coil or folded like an accordion. The electrode strip consists of at least one negative electrode strip and at least one positive electrode strip, between which a separator is inserted.

Preferably, the negative electrode strip is surrounded by positive electrode strips on both sides. The electrode strip in one advantageous embodiment therefore contains one negative and two positive electrodes. The actual material of the negative electrode and the material of the positive electrode is pressed between two layers of the current collector (from a perforated metal strip in the form of a metal mesh, expanded metal, perforated or porous metal foil). On the first, i.e. the inner side of the positive electrode strip, which adjoins the negative electrode, the inner separator strip is pressed, and on the second, i.e. the outer side, the outer separator is pressed. The separators are saturated with electrolyte during the pressing of the electrode strip.

In another embodiment, the electrode module contains plate electrodes, where the arrangement is such that the positive electrode is surrounded on each side by one negative electrode, the electrodes being separated by separators soaked in electrolyte. The negative electrode consists of a current collector, which is a Cu ductile iron, with a deposited layer of Li metal, the positive electrode contains V2O5 deposited on a current collector, which is an AI ductile iron.

The electrolyte for the lithium cell is any of the common electrolytes of the organic solvent type containing Li salts, which are known to the expert.

The material of the inner separator and the outer separator is preferably selected from the group of polyolefin porous film, porous strip of non-woven glass or ceramic, fibers based on ZrO2, AI2O3, or corundum, while the outer separator is provided with a layer of weak AI film on the outside.

The method of manufacturing the above-described lithium accumulator with an electrode module in the form of a coil was described in principle in EP 3 096 373 and further in utility models No. 31 991 and 33 343.

The features of the above-mentioned designs can be combined as desired. The expert is aware that it is possible to modify the described system by routine procedures in various ways while maintaining the principle of the safety system described here. The following images and examples of advantageous designs serve to better understand the essence of the presented technical solution. The scope of protection of the presented solution is defined by the attached protection claims.

Clarification of drawings

Giant. 1A schematically shows a coil lithium battery where the electrode strip is wound on a central emergency container (containing emergency liquid) and the entire coil is housed in a rigid housing. The emergency container is made of thermoplastic material.

Giant. 1B shows a cross-section of a pressed electrode strip comprising one strip of negative electrode surrounded on each side by a strip of positive electrode, showing the interposition of individual layers of electrode materials, current collectors and separators. The diagram demonstrates

-4CZ 36155 UI qualitative composition of the electrode strip, in the actual design the thicknesses of the individual layers are not the same.

Giant. 2 is a diagram of a device for producing an electrode strip.

Giant. 3A is a diagram of the implementation of the safety system in a standard type cell, where the emergency space containing the emergency liquid is defined inside the case of the cell, adjacent to the electrode module and separated from it by an envelope made of thermoplastic material. In addition, the system contains a space for nitrogen, separated from the emergency space also by an envelope made of thermoplastic material.

Giant. 3B is an enlarged section of FIG. 3A to show details of the embodiment.

Giant. 4 is a diagram of a cell equipped with a safety system, where the emergency space is defined by the outer and inner shell of the electrode module, which shells are made of thermoplastic material, the space for nitrogen is between the outer shell of the electrode module and the solid case of the cell, and in addition, the cell is provided with an outer case , where the space between the solid case and the outer case contains the extinguishing powder. The rigid case is equipped with a safety valve, ensuring the connection of the space with nitrogen to the space with fire-extinguishing powder in an emergency situation.

Examples of implementing a technical solution

Example 1

Giant. 1A illustrates one embodiment of a lithium battery cell safety system. The article contains an electrode strip 1.1. wound into a coil on a core formed by a cylindrical emergency container 2.1 with an emergency liquid. Electrode strip 1.1 consists of one strip of negative electrode, which is surrounded on both sides by strips of positive electrode. The complete coil containing the electrode strip 1.1 and the emergency container 2.1 is placed in a solid case 3, which is equipped with a positive and negative pole, and which also contains a temperature, current and shock sensor. Emergency container 2.1 is made of thermoplastic material Zeonor 1020R (Zeon Corporation, Tokyo, Japan) coated on both sides with a thin AI film. The AI film protects the thermoplastic from possible negative effects of the emergency liquid (mineral oil) on one side and the electrolyte (contains an organic solvent) on the other. However, the strength of the AI film is so low that during the thermal degradation of the thermoplastic material of the walls of the emergency container 2.1, the degradation/tear of the AI film will occur and the emergency liquid may flood the electrode strip.

Fig. 1B shows a schematic cross-section of the pressed electrode strip 1,1, where the individual layers of the materials are placed against each other (while the thicknesses of the layers in the actual design are not the same. The material 5 of the negative electrode is a lithium (Li) foil that is pressed between two collectors 6 of the current of the negative electrode, which is a copper (Cu) drawn metal. The material of the 8 positive electrode, which is a mixture (composite) of V2O5 and graphene, is pressed between two collectors of the 9 current of the positive electrode, which is an aluminum (AI) drawn metal. On the first, i.e. on the inner side of the strip of the positive electrode, which is adjacent to the negative electrode, an inner separator 7 is pressed, and on the other side, i.e. the outer side, an outer separator 10 provided on the outer side with an aluminum (AI) foil is pressed. The separators 7, 10 are in saturated with electrolyte during the pressing of the electrode strip Current collectors 6, 9 are connected to the respective poles of the cell on the case 4 in the assembled state.

The emergency fluid is mineral oil.

In the event of an emergency situation, indicated e.g. by an increase in the temperature of the cell above a safe level, the walls of the emergency container 2.1 made of thermoplastic are completely disturbed due to the increase in temperature and the emergency liquid floods the electrodes and separators of the electrode strip 1.1. Standard security

-5CZ 36155 UI electronics simultaneously electrically disconnects the battery. This prevents the battery from catching fire or exploding.

Fig. 2 is a diagram of a device for the production of a lithium cell with a safety system according to Fig. 1A. In the illustrated pressing and forming device, the active material 5 of the negative electrode is pressed between two moving parallel strips of the negative electrode current collector 6, the active material 8 of the positive electrode is pressed between the two moving parallel strips of the positive electrode current collector 9, while on the first side of the strip the positive electrode is pressed by the inner separator 7 and the outer separator 10 is pressed on the other side. At the same time, one strip of positive electrode is pressed from each side to the central strip of the negative electrode, and the electrode strip 1.1 pressed in this way is wound onto the emergency container 2.1.

Example 2

Giant. 3A demonstrates a preferred embodiment of the safety system of a standard type lithium battery cell with plate electrodes. The electrode module 1 containing one positive electrode between two negative electrodes, placed between blank plates 12 made of AI, is placed in a fixed housing 3 containing the lower part 3,1 and the upper part 3,2 of the housing 3. The material 5 of the negative electrode is lithium (Li ) foil that is pressed onto the current collector 6 of the negative electrode, which is copper (Cu) ductile metal. The material 8 of the positive electrode, which is a mixture (composite) of V2O5 and graphene, is pressed onto the current collector 9 of the positive electrode, which is aluminum (AI) ductile metal (see Fig. 3B). The electrode module 1 containing the electrodes and the electrolyte is covered in the lower part with the inner cover 11.1, which is made of a layer of thermoplastic material Zeonor 1020R (Zeon Corporation, Tokyo, Japan) coated on both sides with a thin AI foil. Emergency space 2 occupying part of the space between the electrode module 1 and the lower part 3.1 of the fixed housing 3. The emergency liquid is mineral oil. In the lower part 3.1 of the fixed case 3, another space 13 filled with nitrogen is defined, separated from the emergency space 2 by another, outer envelope 11.2 made of thermoplastic material Zeonor 1020R (Zeon Corporation, Tokyo, Japan) coated on both sides with a thin AI foil.

In the event of an emergency situation, when the temperature of the cell rises above a safe level and at the same time the electrolyte vapor expands, the nitrogen in space 13 will also be compressed, and as a result of the temperature increase, the thermoplastic casings 11.1 and 11.2 will completely break and the emergency liquid will flood the electrode module and diffuses between the electrodes, aided by nitrogen pressure. In addition, nitrogen reacting with lithium will form lithium nitride (L13N), which, unlike pure lithium, does not decompose water.

Example 3

In the embodiment shown in Fig. 4, there is a battery cell, which in a fixed case 3 contains an electrode module 1 containing a harmonically folded electrode strip 1.1 (arranged in the same way as the strip in example 1) and an electrolyte. The emergency space 2 between the inner casing 11.1 of thermoplastic material and the outer casing 11.2 of thermoplastic material (in both cases Zeonor 1020R, Zeon Corporation, Tokyo, Japan) coated on both sides with a thin AI film is filled with emergency liquid. The emergency liquid is mineral oil in which sulfur is dispersed in the form of nanoparticles. The cell is further equipped with an outer casing 4. The outer casing 11.2 made of thermoplastic together with the solid casing 3 define a space 13. which is filled with nitrogen. The space 14 between the fixed housing 3 and the outer housing 4 contains fire extinguishing powder. The rigid package 3 is equipped with at least one safety valve 15 to allow the expanding electrolyte to be discharged into the space 14 with the fire-extinguishing powder.

In the event of an emergency situation, when the temperature of the cell rises above a safe level and at the same time the electrolyte vapor expands, the nitrogen in space 13 will also be compressed, and as a result of the temperature increase, the thermoplastic casings 11.1 and 11.2 will completely break and the emergency liquid will flood the electrode module and diffuses between the electrodes, aided by nitrogen pressure. At least some of the lithium is converted to lithium nitride (LÍ3N) and, in addition, due to the presence of sulfur in the emergency liquid, at least some of the lithium is converted

-6CZ 36155 UI for lithium sulfide (L12S), which also does not decompose water. The expanding electrolyte with the emergency liquid will be released at overpressure using the safety valve 15 into the space 14 between the fixed housing 3 and the outer housing 4 containing the fire extinguishing powder.

Claims (9)

PROTECTION CLAIMS 1. A safety system for a lithium storage cell, wherein the cell comprises an electrode module (1) containing at least one negative and one positive electrode, where the electrodes are separated by a separator saturated with electrolyte, enclosed in a solid case (3) of the cell, characterized in that it is formed at least one emergency space (2) containing an emergency liquid, wherein the emergency space (2) is located inside a solid housing (3) and is separated from the electrode module (1) by a layer at least partially made of thermoplastic material. 2. Safety system according to claim 1, characterized in that the emergency space (2) is an emergency container (2.1) made at least partially of thermoplastic material, forming a core on which the electrode module (1) in the form of an electrode strip (1.1) is wound . 3. The safety system according to claim 1, characterized in that the emergency space (2) is located between the electrode module (1) and the fixed housing (3), while the electrode module (1) is separated from the emergency liquid by an inner casing (11.1) formed at least partly from a layer of thermoplastic material. 4. The safety system according to claim 3, characterized in that it further contains a space (13) filled with nitrogen, located inside a solid casing (3) and separated from the emergency space (2) by an outer casing (11.2) formed at least partially from a layer of thermoplastic material. 5. A security system according to any one of claims 1 to 4, characterized in that the thermoplastic material is a cycloolefin copolymer, or a cycloolefin polymer, with a glass transition temperature of 100°C - 163°C. 6. The security system according to any one of claims 1 to 5, characterized in that the thermoplastic material is a cycloolefin polymer with a glass transition temperature of 102°C. 7. A security system according to any one of claims 1 to 6, characterized in that the layer of thermoplastic material is coated on one side or both sides with a thin aluminum foil. 8. A safety system according to any one of claims 1 to 7, characterized in that the emergency liquid is mineral oil or vacuum oil. 9. The safety system according to claim 8, characterized in that the emergency liquid contains at least one reagent reacting with lithium to form a compound that does not decompose water, which is generally in the form of nanoparticles.