HK1238412A1 - A separator for a rechargeable battery - Google Patents

Description

Isolating membrane for rechargeable battery

[ technical field ] A method for producing a semiconductor device

The present invention relates to the field of rechargeable batteries, and in particular, but not exclusively, to a separator for rechargeable batteries such as lithium ion batteries.

[ background of the invention ]

Various kinds of rechargeable batteries, such as lead-acid batteries, nickel cadmium (NiCd) batteries, nickel metal hydride (NiMH) batteries, and lithium ion (Li-ion) batteries, have been developed and widely used. Among these various kinds of rechargeable batteries, lithium ion batteries are commonly used in consumer electronics products such as portable electronic devices due to their small size, portability, and high energy density. However, lithium ion batteries also have safety concerns, and are even dangerous during events such as thermal runaway, which can result in the battery burning or exploding. For example, internal short-circuiting of the battery is caused by external impact or collision, thereby causing malfunction of the rechargeable battery until thermal runaway. Internal short circuits can cause heat to shrink the battery separator, which can create more severe short circuits. Overcharging the rechargeable battery also generates excess heat, which can also lead to thermal runaway. Generally, thermal runaway of a rechargeable battery can be avoided, minimized, or reduced by avoiding heat generation due to short circuits, and/or providing a heat-resistant layer on a separator of the rechargeable battery.

[ summary of the invention ]

It is an object of the present invention to provide a coating or separator for a separator of a rechargeable battery.

It is another object of the present invention to provide a separator for a rechargeable battery.

It is another object of the present invention to mitigate or eliminate to some extent one or more of the problems associated with coatings or films and separators for known separators for rechargeable batteries.

It is another object of the present invention to provide a rechargeable battery having a novel separator, which is capable of reducing overheating of the battery.

The above object of the invention is met by the combination of features of the independent claims of the invention; the dependent claims disclose further advantageous embodiments of the invention.

Other objects of the present invention will be derived from the following description by those skilled in the art. Accordingly, the above object statements are not exhaustive, but merely serve to illustrate some of the objects of the present invention.

In general, the present invention provides a separator coating or film, and/or a separator having such a coating or film, for use in rechargeable batteries, such as, but not limited to, lithium ion rechargeable batteries. The present invention may be provided in the following manner: a coating disposed or applied on one or more surfaces of a battery separator film, and/or a prepared film layer disposed or disposed between one or more surfaces of a separator film and one or more battery electrodes, i.e., an anode or a cathode. A separator is an ion-permeable member such as a membrane disposed between the anode and cathode of a battery. In particular, the separator coating or film provides a "self-shutdown" mechanism in response to temperature changes to stop reactions within the cell. To achieve this, the coating or membrane comprises a porous layer of the first material, on which pores can melt in response to a temperature increase caused by overheating. In particular, the pores are open at normal operating temperatures, allowing ionic charge carriers (e.g., lithium ions between the anode and cathode) to pass through, for example, during discharge and charge of a rechargeable battery. Under abnormal operating conditions, such as during a short circuit of a rechargeable battery, overheating and/or excessive heat build-up may occur, and the pores of the porous layer of the first material may close automatically when the temperature reaches or exceeds a certain predetermined threshold temperature. As a result, the reduction minimizes, or even prevents, the passage of ions, thereby stopping the chemical reaction and reducing, minimizing, or preventing further heat generation. The coating or film may also include a second material for adhering the porous layer of the first material to the separator and/or electrode, thereby reducing, minimizing or preventing thermal shrinkage of the separator. The present invention provides an automatic, temperature-responsive shutdown mechanism that effectively reduces, prevents, or minimizes overheating due to short-circuiting or overcharging of a rechargeable battery, thereby reducing the chances of potential safety hazards (e.g., thermal runaway) associated with operation of the rechargeable battery.

In a first broad aspect, the present invention provides a coating or film disposed between a separator and at least one electrode of a rechargeable battery. Preferably, the coating or membrane comprises a first material capable of forming a porous layer allowing ions to pass therethrough, wherein the first material is configured to close pores in the porous layer of the first material as a function of temperature, thereby reducing, minimizing or preventing ions from passing through the layer.

In a second main aspect, the present invention provides a rechargeable battery having a novel separator film comprising a coating or film according to the first aspect.

In a third broad aspect, the present invention provides a method of making a rechargeable battery. The method comprises the following steps: a layer of a coating or film according to the first aspect is provided between a separator and at least one electrode of a rechargeable battery.

Summary of the inventionthe present invention is not necessarily defined by all features disclosed. The invention may reside in a combination of the features disclosed.

[ description of the drawings ]

The above and other features of the present invention will be described in connection with the accompanying drawings and exemplary preferred embodiments.

Fig. 1 shows a side cross-sectional view of a portion of a rechargeable battery including a separator coating or film according to a first embodiment of the present invention;

FIG. 2 is a top view of a release film coating or film of a second embodiment of the present invention;

FIG. 3 is a top view of the release film coating or film shown in FIG. 1;

FIG. 4 is an enlarged view of one particle of the coating or film shown in FIG. 3;

FIG. 5 is a side cross-sectional view of the configuration and arrangement of the coating or film on the release film shown in FIG. 3;

FIG. 6 is a side cross-sectional view of a third embodiment of a coating or film configuration and arrangement of the present invention;

FIG. 7 is a side cross-sectional view of a fourth embodiment of a coating or film configuration and arrangement of the present invention;

FIG. 8 is a side cross-sectional view of a fifth embodiment of a coating or film configuration and arrangement of the present invention;

FIG. 9 is a side cross-sectional view of a coating or film configuration and arrangement of a sixth embodiment of the present invention;

FIG. 10 is a flow chart of the synthesis and preparation process of the separator film and its coating or film of the present invention;

FIG. 11 shows the adhesive strength between each electrode and the separator of the present invention;

FIG. 12 shows the relationship between specific heat capacity and temperature for a coating or film material according to one embodiment of the present invention.

[ detailed description ] embodiments

The following describes preferred embodiments of the invention by way of example, but without limiting the implementation of the invention by combining the necessary features.

Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Also, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may apply to some embodiments but not necessarily to others.

Referring to fig. 1, there is shown a partial view of a rechargeable battery 10, such as but not limited to a lithium ion rechargeable battery 10, having an anode 12 and a cathode 14 separated by a separator or membrane 20 to allow ionic charge carriers or liquid electrolyte ions to pass through and be transported between the two electrodes to form a closed circuit within the electrochemical cell. The separator 20 is important with respect to the chemical or electrochemical stability of the electrolyte and electrodes, and has sufficient mechanical strength to withstand some mechanical damage. Suitable materials for the separator 20 may be, but are not limited to, nylon, polyester, fiberglass, polypropylene (PP), Polyethylene (PE), Polytetrafluoroethylene (PTFE), and/or polyvinyl chloride (PVC).

Specifically, there is at least one coating or film 30 between the separator 20 and one or more of the electrodes 12, 14. In one embodiment, the coating or film 30 may be prepared as a coating that is deposited or coated on one or more surfaces of the separator film 20. Alternatively, the coating or film 30 may be prepared as a separate barrier film layer and then placed or disposed between one or more surfaces of the barrier film 20 and one or more respective electrodes 12, 14.

As best shown in fig. 2, the coating or membrane 30 comprises a porous layer 32 of a first material having pores or channels 34 therethrough for allowing ions to pass therethrough. In response to a change in temperature, such as a sudden increase in temperature due to overheating, the first material 32 may adapt to close the pores 34 in the porous layer 32 of the first material, thereby reducing, minimizing, or preventing the passage of ions through the porous layer 32 of the first material. As a result, the electrical circuit is interrupted to some extent, causing the electrochemical cell to shut down, thereby preventing further heat generation. Thus, safety hazards such as thermal runaway are avoided, or the probability of occurrence of similar events is reduced. In one embodiment, closing the pores of the porous layer 32 of the first material may be achieved by arranging for the first material 32 to undergo at least one phase change upon a temperature change during which the pores 34 of the porous layer 32 of the first material are adapted to close, thereby reducing, minimizing or preventing the passage of ions through the porous layer 32 of the first material.

In one embodiment, the porous layer 32 of the first material may include a plurality of particles 36 interconnected to form a porous network that contains the pores 34 of the first material 32. The plurality of particles 36 are configured to fuse together in response to temperature changes, thereby reducing the size of the pores 34, closing or blocking the pores 34 of the porous network.

For example, first material 32 is configured to undergo a first phase change at a first temperature. The first temperature may be a glass transition temperature (T) of the first material 32_g) At the first temperature, the first material 32 begins to soften or deform to close the aperture 34. First material 32 may also be configured to undergo a second phase change at a second temperature, higher than the first temperature, such as a melting temperature (T @)_m) At the second temperature, the porous layer 32 of the first material begins to melt and disintegrates. This applies to first material 32 comprising, for example, one or more amorphous and semi-crystalline polymers.

In one embodiment, the first temperature and the second temperature may be related to the melting temperature (T) of the first material 32_m) Is covered by the scope of (1). E.g. melting temperature (T)_m) May include an initial melting temperature (T)_m1) As a first temperature, at the initial melting temperature, the porous layer 32 of the first material begins to melt. As the temperature continues to rise, melting continues until the orifice 32 closes. Eventually, the first material 32 will reach a melt down temperature (T)_m2) As a second temperature, at the meltdown temperature, the porous layer 32 of the first material is melted down and disintegrates. This applies to first material 32 comprising, for example, one or more semi-crystalline polymers.

Preferably, the second temperature and the first temperature differ by at least 20 ℃. In a particular embodiment, the glass transition temperature (T)_g) Is in the range of about 80 ℃ to about 150 ℃, and a melting temperature (T)_m) Is in the range of about 100 c to about 250 c.

In one embodiment, the plurality of particles 36 of the porous layer 32 of the first material may comprise one or more polymeric materials consisting of at least one of the following monomeric materials: methyl methacrylate, methyl acrylate, ethyl methacrylate, butyl acrylate, isobutyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, isooctyl acrylate, isooctyl methacrylate, lauryl acrylate, lauryl methacrylate, isodecyl acrylate, or mixtures thereof, Acrylate (acrylic salt), methacrylate (methacrylic salt), acrylonitrile (acrylonitrite), methacrylonitrile (methacrylonitrile), acrylamide (acrylamide), methacrylamide (methacrylamide), styrene (styrene), divinylbenzene (divinyl benzene), epoxy resin (epoxide resin), bisphenol a (bisphenola), ethylene oxide (ethylene oxide), fluorine-containing monomer (fluorine-containing monomer), and the like. Those skilled in the art will be able to select and apply any other material to achieve the stated objectives without departing from the spirit and scope of the present invention. Depending on the synthesis and preparation process, the plurality of particles 36 may be configured in one or more shapes including, but not limited to, spheres, rods, cuboids, needles, cubes, ellipsoids, prisms, cones, tetrahedrons, irregularities, and combinations thereof.

Referring to fig. 3, another embodiment of the invention is shown wherein the coating or film 30 comprises a second material 38 deposited on one or more surfaces of the porous layer 32 of the first material for adhering the first material 32 to the separator film 20 and one or more corresponding surfaces of the respective electrodes 12, 14 while binding the particles of the first material 32 to form an interconnected porous network. Second material 38 may comprise one or more polymeric materials composed of at least one of the following monomeric materials: methyl methacrylate, methyl acrylate, ethyl methacrylate, butyl acrylate, isobutyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, isooctyl acrylate, isooctyl methacrylate, lauryl acrylate, isodecyl acrylate, methacrylic acid, acrylate (acrylic salt), methacrylate (methacrylic salt), acrylonitrile (acrylonitrite), methacrylonitrile (methacrylonitrile), acrylamide (acrylamide), methacrylamide (methacrylamide), styrene (styrene), divinylbenzene (divinyl benzene), epoxy resin (epoxide resin), bisphenol a (bisphenol a), ethylene oxide (ethyleneoxide), fluorine-containing monomer, and the like (fluorinated-contacting monomer). Those skilled in the art will be able to select and apply any other material to achieve the stated objectives without departing from the spirit and scope of the present invention.

The second adhesive material 38 is configured to inhibit thermal contraction of the porous network of the first material 32, and therefore also of the separator 20. As best shown in fig. 4, first material 32 and second material 38 are arranged in a core-shell configuration. In a particular embodiment, the second material 38 is configured to adhere the first material 32 to at least one surface of the separator 20 and the respective electrodes 12, 14 with an adhesive strength in a range of 5N/m to 50N/m.

Different arrangements and configurations of the coating or film 30 having the first and second materials 32, 38 are depicted in fig. 5-9. For example, spherical particles 40 having a core-shell structure, i.e., a core formed with first material 32 and a shell formed with second material 38, are shown in fig. 5. The embodiment of fig. 6 shows regularly shaped particles 36 of the first material 32, with the second material 38 dispersed between the particles 36 of the first material 32. Fig. 7 shows another embodiment where the surface of irregularly shaped particles 36 of first material 32 are partially or completely covered by second material 38. Another embodiment of fig. 8 shows irregularly shaped particles 36 of first material 32 with second material 38 randomly dispersed among the particles 36 of first material 32. Another embodiment of fig. 9 shows irregularly shaped particles 36 of first material 32, with second material 38 not only randomly dispersed between particles 36, but also forming a top porous layer over first material 32 and adjacent to each electrode 12, 14, with the top porous layer of second material 38 acting as a bonding layer between the porous network of first material 32 and each electrode 12, 14.

Fig. 10 shows the synthesis and preparation of a coating or film 30 comprising first and second materials 32, 38, and the subsequent application to a release film 20. First, seed particles 36 of first material 32 may be synthesized by known polymerization techniques, such as emulsion polymerization in the presence of one or more surfactants and monomers. Examples of surfactants may be, but are not limited to: ethoxylated ammonium alkyl sulfates (ammonium ethoxylated alkyl sulfates) and/or polyethylene oxide (PEO); examples of monomers may be, but are not limited to: methyl methacrylate, acrylic acid, methacrylic acid, acrylamide, styrene and/or divinylbenzene. After the seed particles 36 are synthesized, further polymerization, such as seed emulsion polymerization, is performed in the presence of one or more surfactants and monomers to provide a coating of the second material 38 on the seed particles of the first material 32 to form the bonded particles 40 having a core-shell structure. Examples of surfactants may be, but are not limited to: ethoxylated ammonium alkyl sulfates (ammonium ethoxylated alkyl sulfates) and/or polyethylene oxide (PEO); examples of monomers may be, but are not limited to: methyl methacrylate, butyl acrylate, and/or lauryl acrylate.

The adhesive granules 40 may then be dispersed in one or more solvents, optionally together with one or more additives such as tackifiers, to form a slurry-like coating material. The slurry may then be applied to the separator 20 by one or more processes such as gravure coating (grain), dip coating (taping), and/or slot-die coating (slot-die).

In order to show the inventionAnd various analytical techniques are also used to characterize the coating or film 30 comprising the first material 32 and the second bonding material 38. For example, fig. 11 shows the adhesive strength of a release film coating or film 30 comprising core-shell structured adhesive particles 40. In this particular embodiment, the bond strength between separator coating or film 30 and anode 12 is about 24N/m and the bond strength between separator coating or film 30 and cathode 14 is about 20N/m. FIG. 12 shows a Differential Scanning Calorimetry (DSC) analysis of a barrier film coating or film 30, which shows a glass transition temperature (T) of about 100 deg.C_g). The invention also relates to a separator for rechargeable batteries, such as lithium-ion batteries, comprising a coating or film as described above. The invention also relates to a rechargeable battery, such as a lithium ion battery, having a separator, and to a method of making a rechargeable battery by providing said coating or film between a separator of the rechargeable battery and at least one electrode.

An advantage of the present invention is to provide a rechargeable battery separator having an automatic, temperature-responsive, automatic shutdown mechanism, thereby effectively avoiding, minimizing or reducing overheating caused by short-circuiting of the rechargeable battery, and further reducing, minimizing or avoiding the occurrence of potential hidden troubles, such as thermal runaway, associated with the operation of the rechargeable battery. In particular, the coating or membrane is configured to allow transfer of ions at temperatures below 80 ℃, but to begin closing pores by melting the particles at temperatures between 80 ℃ and 150 ℃, thereby stopping the reaction of the electrochemical cell. Preferably. The melting of the particles occurs at or above a first temperature, which is typically the glass transition temperature (T) of the first material_g) Or initial melting temperature (T)_m1) The first material begins to melt at a first temperature. Preferably, the difference between the first temperature and the second temperature is at least 20 ℃, the second temperature typically being the disintegration temperature of the first material layer, and this temperature difference being such that there is sufficient time to close the pores before the coating or film melts and disintegrates.

This specification describes the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise numerous different arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are thus within its spirit and scope.

Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, but which are structurally different.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only exemplary embodiments have been shown and described and do not limit the scope of the invention. It should be appreciated that any of the features described herein may be used with any of the embodiments. The embodiments are not exclusive of each other or of any other embodiment not described herein. Accordingly, the present invention also provides embodiments that comprise a combination of one or more of the above-described embodiments. Modifications and variations may be made to the invention as set forth herein without departing from the spirit and scope of the invention, and therefore, only such limitations should be interpreted as are indicated by the following claims.

In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example: a) a combination of circuit elements that performs that function or b) software in any format, including firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the same function. The invention as defined by the appended claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. Thus, any means that can provide the same functionality is considered equivalent to that shown herein.

In the claims which follow and in the preceding description of the invention, unless the context requires otherwise, the word "comprise" or "comprises" is used in an open-ended sense, i.e. to specify the presence of the stated features, but not to exclude or add other features from the various embodiments of the invention.

Claims (20)

1. A coating or film between a separator and at least one electrode of a rechargeable battery, said coating or film comprising:

a first material capable of forming a porous layer allowing ions to pass through;

wherein the first material is configured to substantially close pores on the porous layer of the first material as a function of temperature to substantially reduce or prevent ions from passing through the porous layer of the first material.

2. The coating or film of claim 1, wherein the first material is configured to undergo at least one phase change in accordance with the change in temperature during which pores of the porous layer of the first material are substantially closed, thereby reducing or preventing ions from passing through the first material.

3. The coating or film of claim 1 wherein the porous layer of the first material comprises a plurality of particles interconnected to form a porous network comprising pores of the porous layer of the first material.

4. The coating or film of claim 3, wherein the plurality of particles are configured to fuse together to substantially close or block pores of the porous network as a function of temperature.

5. The coating or film of claim 2, wherein the first material is configured to undergo a first phase change at a first temperature.

6. The coating or film of claim 5, wherein the first temperature is a glass transition temperature at which the first material begins to soften.

7. Coating or film according to claim 5, wherein the first temperature is a melting temperature at which the first material starts to melt.

8. The coating or film of claim 5, wherein the first material is configured to undergo a second phase change at a second temperature, the second temperature being higher than the first temperature.

9. The coating or film of claim 8, wherein the second temperature is a melting temperature at which the first material melts and disintegrates.

10. The coating or film of claim 6, wherein the glass transition temperature is in a range of about 80 ℃ to about 150 ℃.

11. The coating or film of claim 7, wherein the melting temperature is in a range of about 100 ℃ to about 250 ℃.

12. The coating or film of claim 8, wherein the second temperature and the first temperature differ by at least 20 ℃.

13. The coating or film of claim 1, wherein the plurality of particles are in one or more shapes comprising spheres, rods, cuboids, needles, cubes, ovals, prisms, cones, tetrahedra, irregularities, and combinations thereof.

14. The coating or film of claim 2, further comprising a second material deposited on the first material for adhering the first material to one or more surfaces of the separator and the at least one electrode.

15. The coating or film of claim 14, wherein the second material is configured to be dispersed between the first materials.

16. The coating or film of claim 14, wherein the second material is configured to cover the plurality of particles to form a core-shell structure.

17. The coating or film of claim 14, wherein the second material is configured to be deposited on at least one of the following junctions: a junction between the first material and a respective surface of the separator, a junction between the first material and a respective surface of the at least one electrode.

18. The coating or film of claim 14, wherein the plurality of particles are interconnected by the second material.

19. A rechargeable battery with a separator, characterized in that it comprises a coating or film according to claim 1.

20. A method of making a rechargeable battery, comprising the steps of:

between a separator and at least one electrode of said rechargeable battery, a coating or film according to claim 1 is provided.