Composite elastic separator, and preparation method therefor and use thereof

Abstract

A composite elastic separator, and a preparation method therefor and the use thereof. The composite elastic separator comprises an elastic layer, an interface layer and a flame-retardant layer, wherein the interface layer is located between the elastic layer and the flame-retardant layer; the material of the elastic layer comprises an elastic polymer; the material of the flame-retardant layer comprises aramid fibers; the material of the interface layer comprises an elastic polymer and aramid fibers; and the interface layer is of a network-like structure. The composite elastic separator can effectively solve the problem of expansion during charging and discharging, and can also improve the safety of a battery.

Description

Composite elastic diaphragm and preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202410448944.9, filed on April 15, 2024 in the China Patent Office and entitled "Composite elastic diaphragm and preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, in particular to a composite elastic diaphragm, a preparation method of the composite elastic diaphragm and a lithium battery. BACKGROUND

[0003] A lithium ion battery mainly consists of a positive electrode, a negative electrode, a diaphragm and an electrolyte. Among them, the diaphragm is a thin film used to separate the positive and negative electrodes during electrolytic reaction to prevent direct reaction between the two in the electrolytic cell.

[0004] The lithium ion battery will produce different degrees of swelling and gas generation during normal temperature cycling, high temperature cycling and high temperature storage. There are two main solutions at present. The first solution is physical restriction. If the battery cell is pressed too tightly (the module shell has too much rigidity), the diaphragm will also be squeezed, which may accelerate the capacity decay of the battery cell and is more likely to cause safety risks. The second solution is to reserve an expansion gap. If the gap between the battery cells is too large, on the one hand, it will cause waste of space volume, and on the other hand, it will increase the thickness of the battery cell, thereby increasing the distance between the positive and negative electrodes of the battery cell.

[0005] The main material of the existing diaphragm is polyethylene and polypropylene and other polyolefin base materials. The diaphragm has poor resilience and cannot solve the swelling problem during charging and discharging. TECHNICAL SOLUTION

[0006] Therefore, the present application provides a composite elastic diaphragm to solve the problem that the existing diaphragm cannot solve the swelling problem during charging and discharging.

[0007] In the embodiments of the present application, a composite elastic diaphragm includes an elastic layer, an interface layer and a flame-retardant layer. The interface layer is located between the elastic layer and the flame-retardant layer. The material of the elastic layer includes an elastic polymer. The material of the flame-retardant layer includes aramid fiber. The material of the interface layer includes the elastic polymer and the aramid fiber. The interface layer has a reticular structure.

[0008] Optionally, in some embodiments, the aramid fiber includes one or more of meta-aramid fiber and para-aramid fiber; and / or

[0009] The elastic polymer includes one or more of polystyrene, ethylene-vinyl acetate copolymer, polyurethane-based polymer, thermoplastic polyether ester elastomer, and thermoplastic vulcanized rubber.

[0010] Optionally, in some embodiments, the elastic layer further includes a ceramic material; and / or

[0011] The material of the interface layer further includes the ceramic material.

[0012] Optionally, in some embodiments, the ceramic material includes one or more of alumina, boehmite, silica, magnesium oxide, and calcium oxide.

[0013] Optionally, in some embodiments, the ceramic material is ceramic particles, and the average particle size of the ceramic particles is 0.3-1.0 μm.

[0014] Optionally, in some embodiments, in the elastic layer, the mass ratio of the elastic polymer to the ceramic material is (0.6-2):(0.001-1).

[0015] Optionally, in some embodiments, the flame-retardant layer is a porous structure.

[0016] Optionally, in some embodiments, the thickness of the composite elastic diaphragm is 12-35 μm.

[0017] Optionally, in some embodiments, the thickness of the elastic layer is 5-14 μm.

[0018] Optionally, in some embodiments, the thickness of the flame-retardant layer is 1-4 μm.

[0019] Optionally, in some embodiments, the thickness of the interface layer is 100-200 nm.

[0020] Optionally, in some embodiments, the composite elastic diaphragm further includes a base film, and the base film is arranged on the side of the elastic layer away from the interface layer.

[0021] Optionally, in some embodiments, the material of the base film includes one or more of polyethylene and polypropylene; and / or

[0022] The thickness of the base film is 6-15 μm.

[0023] Correspondingly, the embodiments of the present application further provide a preparation method of a composite elastic diaphragm, including:

[0024] providing a pre-prepared elastic layer, and the material of the pre-prepared elastic layer includes an elastic polymer;

[0025] providing a first mixture solution including aramid, a cosolvent and a first solvent; and

[0026] disposing the first mixture solution on the pre-elastic layer, wherein part of the first mixture solution penetrates into the upper surface of the pre-elastic layer to form an elastic layer and an interface layer combined with the elastic layer, and the first mixture solution not penetrating into the pre-elastic layer forms a flame-retardant layer on the interface layer, thereby obtaining a composite elastic separator.

[0027] Optionally, in some embodiments, the method for preparing the pre-elastic layer comprises:

[0028] providing an elastic polymer and a second solvent, and first mixing to obtain a second mixture solution; and

[0029] providing a base film, and disposing the second mixture solution on the base film to obtain a pre-elastic layer.

[0030] Optionally, in some embodiments, the elastic polymer comprises one or more of polystyrene, ethylene-vinyl acetate copolymer, polyurethane-based polymer, thermoplastic polyether ester elastomer, and thermoplastic vulcanized rubber.

[0031] Optionally, in some embodiments, the second solvent comprises one or more of methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, toluene, ethyl acetate, butanone, and acetone.

[0032] Optionally, in some embodiments, the base film comprises one or more of polyethylene and polypropylene.

[0033] Optionally, in some embodiments, the mass concentration of the elastic polymer in the second mixture solution is 94.8-316 mg / mL.

[0034] Optionally, in some embodiments, the rotation speed of the first mixing is 500-3000 r / min.

[0035] Optionally, in some embodiments, the time of the first mixing is 1-6 h.

[0036] Optionally, in some embodiments, after disposing the second mixture solution on the base film, the method further comprises first phase inversion and first drying; the temperature of the first drying is 40-80 °C, and the time of the first drying is 1-5 h.

[0037] Optionally, in some embodiments, the second mixture solution further comprises one or more of ceramic material and pore-forming agent.

[0038] Optionally, in some embodiments, the ceramic material comprises one or more of alumina, boehmite, silicon dioxide, magnesium oxide, and calcium oxide.

[0039] Optionally, in some embodiments, the pore-forming agent comprises one or more of dimethyl carbonate, tripropylene glycol, and polyethylene glycol.

[0040] Optionally, in some embodiments, the mass ratio of the elastic polymer to the ceramic material is (0.6-2):(0.001-1).

[0041] Optionally, in some embodiments, the mass ratio of the elastic polymer to the pore-forming agent is 1:(0.05-0.2).

[0042] Optionally, in some embodiments, the disposing the first mixed solution on the pre-prepared elastic layer comprises: providing aramid, a cosolvent, and a first solvent, second mixing to obtain a first mixed solution, and depositing the first mixed solution.

[0043] Optionally, in some embodiments, the aramid comprises one or more of meta-aramid and para-aramid.

[0044] Optionally, in some embodiments, the cosolvent comprises one or more of sodium chloride, lithium chloride, and potassium chloride.

[0045] Optionally, in some embodiments, the first solvent comprises one or more of methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, toluene, ethyl acetate, butanone, and acetone.

[0046] Optionally, in some embodiments, the mass ratio of the aramid to the cosolvent is 1:(0.5-3).

[0047] Optionally, in some embodiments, the mass concentration of the aramid in the first mixed solution is 15-25 mg / mL.

[0048] Optionally, in some embodiments, the rotation speed of the second mixing is 500-3000 r / min.

[0049] Optionally, in some embodiments, the time of the second mixing is 1-6 h.

[0050] Optionally, in some embodiments, the disposing the first mixed solution on the pre-prepared elastic layer further comprises second phase inversion and second drying; the temperature of the second drying is 40-80 °C, and the time of the second drying is 1-5 h.

[0051] Correspondingly, the application further provides a battery, wherein the battery comprises a composite elastic separator, the composite elastic separator comprises an elastic layer, an interface layer and a flame-retardant layer, the interface layer is located between the elastic layer and the flame-retardant layer, the material of the elastic layer comprises an elastic polymer, the material of the flame-retardant layer comprises aramid fiber, the material of the interface layer comprises the elastic polymer and the aramid fiber, and the interface layer has a reticular structure.

[0052] Optionally, in some embodiments, the aramid fiber comprises one or more of meta-aramid fiber and para-aramid fiber; and / or

[0053] The elastic polymer comprises one or more of polystyrene, ethylene-vinyl acetate copolymer, polyurethane-based polymer, thermoplastic polyether ester elastomer and thermoplastic vulcanized rubber.

[0054] Optionally, in some embodiments, the elastic layer further comprises a ceramic material; and / or

[0055] The material of the interface layer further comprises the ceramic material.

[0056] Optionally, in some embodiments, the ceramic material comprises one or more of aluminum oxide, boehmite, silicon dioxide, magnesium oxide and calcium oxide.

[0057] Optionally, in some embodiments, the ceramic material is ceramic particles, and the average particle size of the ceramic particles is 0.3-1.0 μm.

[0058] Optionally, in some embodiments, in the elastic layer, the mass ratio of the elastic polymer to the ceramic material is (0.6-2):(0.001-1).

[0059] Optionally, in some embodiments, the flame-retardant layer has a porous structure.

[0060] Optionally, in some embodiments, the thickness of the composite elastic separator is 12-35 μm.

[0061] Optionally, in some embodiments, the thickness of the elastic layer is 5-14 μm.

[0062] Optionally, in some embodiments, the thickness of the flame-retardant layer is 1-4 μm.

[0063] Optionally, in some embodiments, the thickness of the interface layer is 100-200 nm.

[0064] Optionally, in some embodiments, the composite elastic separator further comprises a base film, and the base film is arranged on the side of the elastic layer away from the interface layer. Advantages

[0065] The composite elastic diaphragm provided by the application has good resilience of the elastic polymer in the elastic layer, and the composite elastic diaphragm is compressed when subjected to pressure, and returns to the initial state after the pressure is removed. In addition, the elastic layer has excellent elasticity, and the problem of charging and discharging expansion is well solved. In addition, the aramid fiber in the flame-retardant layer has good high-temperature resistance and good flame-retardant effect. In addition, the aramid fiber serves as the first line of defense against lithium dendrites, and can prevent the composite elastic diaphragm from being punctured. In addition, the elastic layer has excellent elasticity, and the elastic layer can cover the part after the lithium dendrites puncture the flame-retardant layer, so as to prevent the positive and negative electrodes from being in contact to cause short circuit. In addition, the part of the elastic polymer in the elastic layer close to the flame-retardant layer and the part of the aramid fiber in the flame-retardant layer close to the elastic layer form an interfacial layer in a network structure, so that the elastic layer and the flame-retardant layer are firmly connected. The composite elastic diaphragm formed by the elastic layer, the interfacial layer and the flame-retardant layer not only has good resilience, but also has good flame-retardant effect. In addition, the mechanical properties are excellent, and the elastic layer has adhesion, so that the diaphragm and the electrode plate are well bonded together. The cooperation of the flame-retardant layer, the interfacial layer and the elastic layer in the application well solves the problem of charging and discharging expansion, and improves the safety of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can be obtained without creative labor based on these drawings.

[0067] FIG. 1 is a flow chart of a preparation method of a composite elastic diaphragm according to an embodiment of the application.

[0068] FIG. 2 is an SEM diagram of the composite elastic diaphragm prepared in Example 1 of the application.

[0069] Embodiments of the application

[0070] The technical solutions in the embodiments of the application will be described clearly and completely in the following with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only some embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the application, and are not used to limit the application.

[0071] In the present application, the orientation words such as "upper" and "lower" refer to the upper and lower positions of the device in the actual use or working state, and the "inner" and "outer" refer to the outline of the device, unless otherwise specified. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as markers and do not impose a numerical requirement or establish an order.

[0072] In the present application, the association relationship of the associated objects is described by "and / or", which means that there can be three kinds of relationships, for example, A and / or B can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.

[0073] In the present application, "at least one" means one or more, and "multiple" means two or more. "One or more", "at least one of the following" or the like means any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0074] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present application, it refers to any cited number (fraction or integer) within the indicated range.

[0075] Lithium dendrite refers to the dendritic metallic lithium element formed when lithium ions are reduced during charging of lithium batteries using liquid electrolyte. Metallic lithium is not used as a negative active material because metallic lithium will crystallize on the negative electrode to form dendritic metallic lithium-"lithium dendrite". The performance of the existing separator is not good, and the lithium dendrite will pierce the separator to a certain extent, causing internal short circuit of the lithium battery. In addition, the connection between the film layers of the existing composite separator is not good and is easy to fall off.

[0076] The technical solutions of the present application are as follows:

[0077] In a first aspect, the embodiments of the present application provide a composite elastic diaphragm, comprising an elastic layer, an interface layer and a flame-retardant layer, wherein the interface layer is located between the elastic layer and the flame-retardant layer. The material of the elastic layer comprises an elastic polymer, the material of the flame-retardant layer comprises aramid, the material of the interface layer comprises the elastic polymer and the aramid, and the interface layer has a network structure.

[0078] In the embodiments of the present application, the elastic polymer in the elastic layer has good resilience. When the composite elastic diaphragm is subjected to pressure, it will be compressed, and after the pressure is removed, it will return to the initial state. Due to the excellent elasticity of the elastic layer, the charging and discharging expansion problem is well solved. In addition, the aramid in the flame-retardant layer has good flame-retardant effect and high-temperature resistance. Furthermore, the aramid serves as the first line of defense against lithium dendrites, preventing the composite elastic diaphragm from being punctured. After the lithium dendrites pierce the flame-retardant layer, the elastic layer will cover this part, preventing the positive and negative electrodes from contacting and causing short circuit. In addition, the part of the elastic polymer in the elastic layer close to the flame-retardant layer and the part of the aramid in the flame-retardant layer close to the elastic layer form the interface layer with a network structure, making the elastic layer and the flame-retardant layer firmly connected. The composite elastic diaphragm formed by the elastic layer, the interface layer and the flame-retardant layer not only has good resilience, but also has good flame-retardant effect. In addition, the mechanical properties are excellent. Moreover, the elastic layer has adhesion, which can make the diaphragm and the electrode piece well bonded together. The cooperation of the flame-retardant layer, the interface layer and the elastic layer in the present application well solves the charging and discharging expansion problem, and improves the safety of the battery.

[0079] In some embodiments, the flame-retardant layer has a porous structure. Due to the porous structure inside the flame-retardant layer and the connection between the pores, the composite elastic diaphragm has high wettability in the electrolyte.

[0080] In some embodiments, the aramid comprises one or more of meta-aramid and para-aramid.

[0081] In some embodiments, the elastic polymer comprises one or more of polystyrene (TPS), ethylene-vinyl acetate copolymer (EVA), polyurethane (TPU) polymer, thermoplastic polyether ester elastomer (TPEE), and thermoplastic vulcanized rubber (TPV).

[0082] In some embodiments, the elastic layer further comprises a ceramic material, and the material of the interface layer further comprises the ceramic material.

[0083] Further, the ceramic material comprises one or more of aluminum oxide, boehmite, silicon dioxide, magnesium oxide and calcium oxide.

[0084] Further, the ceramic material is ceramic particles, and the average particle size of the ceramic particles is 0.3-1.0 μm, for example, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm. Within the range of the average particle size, the ceramic particles can be uniformly distributed in the elastic layer and can improve the strength of the elastic layer.

[0085] In some embodiments, the mass ratio of the elastic polymer to the ceramic material in the elastic layer is (0.6-2):(0.001-1), for example, 0.6:0.001, 0.6:0.1, 0.6:0.2, 0.6:0.3, 0.8:0.001, 0.8:0.1, 0.8:0.2, 0.8:0.3, 0.8:0.4, 0.9:0.001, 0.9:0.1, 0.9:0.2, 0.9:0.3, 0.9:0.4, 1:0.001, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1.2:0.001, 1.2:0.1, 1.2:0.2, 1.2:0.3, 1.2:0.4, 1.2:0.5, 1.2:0.6, 1.5:0.001, 1.5:0.1, 1.5:0.2, 1.5:0.3, 1.5:0.4, 1.5:0.5, 1.5:0.6, 1.5:0.7, 1.8:0.001, 1.8:0.1, 1.8:0.2, 1.8:0.3, 1.8:0.4, 1.8:0.5, 1.8:0.6, 1.8:0.7, 1.8:0.8, 1.8:0.9, 2:0.001, 2:0.1, 2:0.2, 2:0.3, 2:0.4, 2:0.5, 2:0.6, 2:0.7, 2:0.8, 2:0.9, 2:1, etc. Within the range of the mass ratio, the elastic layer can provide the swelling gap of the battery and has good mechanical strength.

[0086] In some embodiments, the composite elastic separator further comprises a base film, and the base film is disposed on the side of the elastic layer away from the interface layer.

[0087] Further, the material of the base film comprises one or more of polyethylene (PE) and polypropylene (PP).

[0088] In some embodiments, the thickness of the composite elastic separator is 12-35 μm, for example, 12 μm, 12.1 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 25 μm, 26 μm, 28 μm, 29 μm, 30 μm, 32 μm, 33.15 μm, 33.2 μm, 34 μm, 35 μm, etc.

[0089] Further, the thickness of the elastic layer is 5-14 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, etc.

[0090] Further, the thickness of the flame-retardant layer is 1-4 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, etc.

[0091] Further, the thickness of the interface layer is 100-200 nm, for example, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm, 200 nm, etc.

[0092] Further, the thickness of the base film is 6-15 μm, for example, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc.

[0093] In a second aspect, referring to FIG. 1, the application also provides a preparation method of the composite elastic diaphragm, comprising:

[0094] S01, providing a pre-prepared elastic layer, the material of the pre-prepared elastic layer comprising an elastic polymer;

[0095] S02, providing a first mixed solution, the first mixed solution comprising aramid, a cosolvent and a first solvent;

[0096] S03, disposing the first mixed solution on the pre-prepared elastic layer, wherein part of the first mixed solution penetrates into the upper surface of the pre-prepared elastic layer, forming an elastic layer and an interface layer combined with the elastic layer, and the first mixed solution not penetrating into the pre-prepared elastic layer forms a flame-retardant layer on the interface layer, obtaining a composite elastic diaphragm.

[0097] In the S01,

[0098] The preparation method of the pre-prepared elastic layer comprises:

[0099] S011, providing an elastic polymer and a second solvent, and mixing to obtain a second mixed solution;

[0100] S012, providing a base film, and disposing the second mixed solution on the base film to obtain a pre-prepared elastic layer.

[0101] In the S011:

[0102] In some embodiments, the elastic polymer includes one or more of polystyrene (TPS), ethylene vinyl acetate copolymer (EVA), polyurethane (TPU) polymer, thermoplastic polyether ester elastomer (TPEE), and thermoplastic vulcanizate (TPV).

[0103] In some embodiments, the second solvent comprises one or more of methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, toluene, ethyl acetate, butanone, and acetone.

[0104] In some embodiments, in the second mixed solution, the mass concentration of the elastic polymer is 94.8-316 mg / mL, for example, 94.8 mg / mL, 95 mg / mL, 98 mg / mL, 100 mg / mL, 105 mg / mL, 110 mg / mL, 115 mg / mL, 120 mg / mL, 130 mg / mL, 140 mg / mL, 150 mg / mL, 160 mg / mL, 170 mg / mL, 180 mg / mL, 190 mg / mL, 200 mg / mL, 210 mg / mL, 220 mg / mL, 230 mg / mL, 240 mg / mL, 250 mg / mL, 260 mg / mL, 270 mg / mL, 280 mg / mL, 290 mg / mL, 300 mg / mL, 310 mg / mL, 316 mg / mL, etc., which is conducive to uniform dissolution and dispersion of the elastic polymer within the mass concentration range.

[0105] Furthermore, the rotation speed of the first mixing is 500-3000 r / min, for example, it can be 500 r / min, 600 r / min, 800 r / min, 1000 r / min, 1100 r / min, 1200 r / min, 1500 r / min, 1800 r / min, 2000 r / min, 2100 r / min, 2200 r / min, 2500 r / min, 2600 r / min, 2800 r / min, 3000 r / min, etc.

[0106] Furthermore, the first mixing time is 1 to 6 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc. Within the range of the first mixing speed and time, the elastic polymer is facilitated to be fully dissolved and mixed.

[0107] In said S012:

[0108] In some embodiments, the base film includes one or more of polyethylene (PE) and polypropylene (PP).

[0109] In some embodiments, the method of disposing the second mixed liquid on the base film includes a first coating.

[0110] Furthermore, the first coating method includes one or more of spin coating, spray coating, wire rod coating, and dip coating.

[0111] After the second mixed liquid is disposed on the base film, the method further includes a first phase inversion and a first drying.

[0112] It can be understood that the first phase conversion is a conventional technology in this field. The second mixed liquid is a slurry. After the second mixed liquid is set on the base film, it is washed with water. The first solvent is dissolved in water. The purpose of the first phase conversion is to remove the first solvent and quickly form a film.

[0113] Furthermore, the first drying temperature is 40-80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc., and the first drying time is 1-5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, etc. Within this temperature and time range, the second mixed liquid after the first phase transformation is dried to obtain the prefabricated elastic layer.

[0114] In some embodiments, the second mixed liquid further comprises one or more of a ceramic material and a pore-forming agent. It should be noted that when the second mixed liquid further comprises the pore-forming agent, the pore-forming agent dissolves in water during the first phase inversion process. The pore-forming agent is then removed by the phase inversion process, thereby promoting film formation and pore formation in the prefabricated elastic layer.

[0115] In some embodiments, the ceramic material includes one or more of alumina, boehmite, silica, magnesium oxide, and calcium oxide. The ceramic material provides support within the elastic layer, increasing its strength. Furthermore, the ceramic material in the interface layer, along with the elastic material and aramid, forms a mesh structure, which is interspersed with the ceramic material, further enhancing the bonding strength of the interface layer.

[0116] In some embodiments, the pore-forming agent includes one or more of dimethyl carbonate, tripropylene glycol, and polyethylene glycol. The pore-forming agent can form pores, promoting the formation of a prefabricated elastic layer with a porous structure, allowing electrolyte infiltration, and facilitating efficient lithium ion transmission.

[0117] In some embodiments, the mass ratio of the elastic polymer to the ceramic material is (0.6-2):(0.001-1), for example, it can be 0.6:0.001, 0.6:0.1, 0.6:0.2, 0.6:0.3, 0.8:0.001, 0.8:0.1, 0.8:0.2, 0.8:0.3, 0.8:0.4, 0.9:0.001, 0.9:0.1, 0.9:0.2, 0.9:0.3, 0.9:0.4, 1:0.001, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1.2:0.001, 1.2:0.1, 1.2:0.2, 1.2:0.3, 1.2:0.4, 1.2:0.5, 1.2:0.6, 1.5:0.001, 1.5:0.1, 1.5:0.2, 1.5:0.3, 1.5:0.4, 1.5:0.5, 1.5:0.6, 1.5:0.7, 1.8:0.001, 1.8:0.1, 1.8:0.2, 1.8:0.3, 1.8:0.4, 1.8:0.5, 1.8:0.6, 1.8:0.7, 1.8:0.8, 1.8:0.9, 2:0.001, 2:0.1, 2:0.2, 2:0.3, 2:0.4, 2:0.5, 2:0.6, 2:0.7, 2:0.8, 2:0.9, 2:1, etc. Within the range of the mass ratio, it is beneficial to obtain a pre-prepared elastic layer with good elasticity and strength.

[0118] In some embodiments, the mass ratio of the elastic polymer to the pore-forming agent is 1:(0.05-0.2), for example, it can be 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1, 1:0.12, 1:0.14, 1:0.15, 1:0.16, 1:0.18, 1:0.19, 1:0.2, etc. Within the range of the mass ratio, it is beneficial to form a pre-prepared elastic layer with a porous structure.

[0119] In the S03, the first mixture is prepared by mixing the first solvent, the aramid fiber, and the auxiliary solvent.

[0120] In some embodiments, the first mixture is prepared by providing the aramid fiber, the auxiliary solvent, and the first solvent, mixing the aramid fiber, the auxiliary solvent, and the first solvent to obtain the first mixture, and depositing the first mixture.

[0121] In some embodiments, the aramid fiber includes one or more of meta-aramid fiber and para-aramid fiber.

[0122] In some embodiments, the auxiliary solvent includes one or more of sodium chloride, lithium chloride, and potassium chloride. The auxiliary solvent serves to fully dissolve the aramid fiber in the first solvent.

[0123] In some embodiments, the first solvent comprises one or more of methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, toluene, ethyl acetate, butanone, acetone.

[0124] In some embodiments, the mass ratio of the aramid fiber to the cosolvent is 1:(0.5-3), for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.1, 1:2.3, 1:2.5, 1:2.8, 1:3, etc. Within the range of the mass ratio, it is beneficial for the rapid dissolution of the aramid fiber.

[0125] In some embodiments, the mass concentration of the aramid fiber in the first mixed solution is 15-25 mg / mL, for example, it can be 15 mg / mL, 16 mg / mL, 16.5 mg / mL, 17 mg / mL, 17.236 mg / mL, 18 mg / mL, 18.2 mg / mL, 18.4 mg / mL, 18.6 mg / mL, 18.8 mg / mL, 19 mg / mL, 19.2 mg / mL, 19.4 mg / mL, 19.6 mg / mL, 19.8 mg / mL, 20 mg / mL, 21 mg / mL, 22 mg / mL, 23 mg / mL, 23.8 mg / mL, 24 mg / mL, 24.5 mg / mL, 25 mg / mL, etc. Within the range of the mass concentration, it is beneficial for the coating.

[0126] In some embodiments, the rotation speed of the second mixing is 500-3000 r / min, for example, it can be 500 r / min, 600 r / min, 800 r / min, 1000 r / min, 1100 r / min, 1200 r / min, 1500 r / min, 1800 r / min, 2000 r / min, 2100 r / min, 2200 r / min, 2500 r / min, 2600 r / min, 2800 r / min, 3000 r / min, etc.

[0127] In some embodiments, the time of the second mixing is 1-6 h, for example, it can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, etc. Within the range of the rotation speed and time of the second mixing, it is beneficial for the sufficient dissolution and mixing of the aramid fiber.

[0128] In some embodiments, the method of disposing the first mixed solution on the pre-prepared elastic layer comprises a second coating.

[0129] Further, the second coating method comprises one or more of spin coating, spray coating, wire bar coating, dip coating.

[0130] In some embodiments, the disposing the first mixture on the pre-prepared elastic layer further comprises phase inversion and second drying.

[0131] It can be understood that the second phase inversion is a routine technique in the art, the first mixture slurry, the second phase inversion specifically refers to slurry passing water, the cosolvent and the second solvent are easily soluble in water, and the purpose of the second phase inversion is to remove the cosolvent and the second solvent.

[0132] Further, the temperature of the second drying is 40-80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, etc., and the time of the second drying is 1-5h, for example, it can be 1h, 2h, 3h, 4h, 5h, etc. Within the temperature and time range of the second drying, the first mixture after the second phase inversion is dried and the flame-retardant layer is obtained.

[0133] In the embodiments of the present application, part of the second solvent in the first mixture has a dissolving effect on the elastic polymer in the pre-prepared elastic layer, and after coating, this part of the second solvent will dissolve a small amount of elastic polymer. The dissolved elastic polymer is a flexible polymer, and the aramid is a zigzag-shaped macromolecule. By utilizing the flexibility of the elastic polymer and the aramid, the two are mixed and staggered, and are arranged in a random flexible manner. After the second solvent volatilizes, the elastic polymer and the aramid are intertwined to form a network structure, that is, an interfacial layer is formed between the elastic layer and the flame-retardant layer, so that the elastic layer and the flame-retardant layer are closely combined.

[0134] Further, the second solvent also dissolves a small amount of part of the ceramic material, which is in a granular form and is distributed in the elastic polymer and the aramid. At the same time, by utilizing the flexibility of the elastic polymer and the aramid, the ceramic material, the elastic polymer and the aramid are intertwined together, and after drying, the second solvent volatilizes to form a network structure.

[0135] In a third aspect, the embodiments of the present application also provide a battery, which comprises the composite elastic separator of the first aspect or is prepared by the preparation method of the second aspect.

[0136] The present application will be described in detail through specific embodiments below. The following embodiments are only part of the embodiments of the present application and are not a limitation of the present application.

[0137] Embodiment 1

[0138] The present embodiment provides a composite elastic separator, and a preparation method thereof is as follows:

[0139] 52g of TPU, 20g of silicon dioxide, 5g of PEG, and 240g of DMF are mixed, and mixed at 1200r / min for 150min to obtain a second mixture;

[0140] The second mixed solution is coated on the PE base film using a coating machine, and after phase inversion and first drying, the temperature of the first drying is 60℃, and the time is 3h, to obtain a pre-elastic layer, wherein the thickness of the pre-elastic layer after removing the PE base film is 10μm;

[0141] 125g of sodium chloride, 100g of meta-aramid, and 4740g of DMF are mixed, mixed at 1000r / min for 120min to obtain a first mixed solution;

[0142] The first mixed solution is coated on the pre-elastic layer using a coating machine, and after phase inversion and second drying, the temperature of the second drying is 70℃, and the time is 2h, to obtain a composite elastic diaphragm, the thickness is 14μm.

[0143] Example 2

[0144] This example is basically the same as example 1, the only difference is that the mass of TPU is replaced by 40g, the mass of silicon dioxide is replaced by 20g, 8g of PEG, 400g of DMF; the mass of sodium chloride is replaced by 125g, the mass of meta-aramid is replaced by 42g, 2654.4g of DMF.

[0145] Example 3

[0146] This example is basically the same as example 1, the only difference is that the mass of TPU is replaced by 40g, the mass of silicon dioxide is replaced by 15g, 2g of PEG, 120g of DMF; the mass of sodium chloride is replaced by 21g, the mass of meta-aramid is replaced by 42g, 1592.64g of DMF.

[0147] Example 4

[0148] This example is basically the same as example 1, the only difference is that the meta-aramid is replaced by para-aramid.

[0149] Example 5

[0150] This example is basically the same as example 1, the only difference is that the TPU is replaced by EVA.

[0151] Example 6

[0152] This example is basically the same as example 1, the only difference is that the TPU is replaced by TPEE.

[0153] Example 7

[0154] This example is basically the same as example 1, the only difference is that the TPU is replaced by TPS.

[0155] Example 8

[0156] This example is basically the same as Example 1, except that sodium chloride is replaced by lithium chloride.

[0157] Example 9

[0158] This example is basically the same as Example 1, except that sodium chloride is replaced by potassium chloride.

[0159] Example 10

[0160] This example is basically the same as Example 1, except that silicon dioxide is replaced by magnesium oxide.

[0161] Example 11

[0162] This example is basically the same as Example 1, except that silicon dioxide is replaced by aluminum oxide.

[0163] Example 12

[0164] This example is basically the same as Example 1, except that the temperature of the first drying is 40°C, and the time is 5h, and the temperature of the second drying is 40°C, and the time is 5h.

[0165] Example 13

[0166] This example is basically the same as Example 1, except that the temperature of the first drying is 80°C, and the time is 1h, and the temperature of the second drying is 80°C, and the time is 1h.

[0167] Comparative Example 1

[0168] This comparative example is basically the same as Example 1, except that the second mixed solution does not contain TPU.

[0169] Comparative Example 2

[0170] This comparative example is basically the same as Example 1, except that the first mixed solution does not contain meta-aramid.

[0171] Comparative Example 3

[0172] This comparative example is basically the same as Example 1, except that the first mixed solution does not contain meta-aramid, and the second mixed solution does not contain TPU.

[0173] Comparative Example 4

[0174] This comparative example is basically the same as Example 1, except that the second mixed solution does not contain ceramic material silicon dioxide.

[0175] Figure 2 is an SEM image of the composite elastic diaphragm prepared in Embodiment 1 of the application. As can be seen from Figure 2, an interface layer is formed between the elastic layer and the flame-retardant layer, there are many ceramic particles interspersed in the elastic layer, which improves the strength of the composite elastic diaphragm, and the interface layer makes the elastic layer and the flame-retardant layer combine quite closely, and the aramid layer surface is relatively dense, which can be a good first line of defense against lithium dendrites.

[0176] The flame-retardant properties, elastic recovery rate and tensile strength of the composite elastic diaphragms of Examples 1-13 and Comparative Examples 1-4 were detected respectively, wherein the elastic recovery rate was tested by a press machine; the tensile strength was tested in accordance with GB / T10403-2006 "Test Method for Tensile Properties of Plastic Sheeting" and ASTM D882-10 "Standard Test Method for Tensile Properties of Thin Plastic Sheeting", and the test results are shown in Table 1.

[0177] Table 1

[0178] As can be seen from Table 1,

[0179] Examples 1-4 and Examples 8-13 are compared with Comparative Examples 1 and 3. The elastic recovery rate and tensile strength of the composite elastic diaphragms of Examples 1-4 and Examples 8-13 of the application are all better than those of Comparative Examples 1 and 3, which shows that the addition of the elastic polymer and aramid of the application can significantly improve the elastic recovery rate and tensile strength of the composite elastic diaphragm, and the prepared diaphragm has strong elastic ability and good mechanical properties.

[0180] Examples 1-4 and Examples 8-13 are compared with Comparative Example 2. The difference in elastic recovery rate is not large, but the tensile strength of the diaphragm of the application is obviously better than that of Comparative Example 2, which shows that the addition of aramid significantly improves the mechanical properties of the composite elastic diaphragm.

[0181] Examples 5-7 are compared with Comparative Examples 1 and 3. The elastic recovery rate and tensile strength of the composite elastic diaphragms of Examples 5-7 of the application are all better than those of Comparative Examples 1 and 3. This shows that the EVA, TPEE and TPS of the application can all well improve the elastic properties of the composite elastic diaphragm of the application.

[0182] Examples 1-13 are compared with Comparative Example 4. The elastic recovery rate and tensile strength of the composite elastic diaphragms of Examples 1-13 of the application are all better than those of Comparative Example 4, which shows that the addition of ceramic material further improves the mechanical strength and elastic ability of the diaphragm.

[0183] Battery Example 1

[0184] This embodiment provides a battery, and the preparation method is as follows:

[0185] The lithium nickel cobalt manganese oxide, the conductive agent Super P and the binder PVDF were mixed in a mass ratio of 8:1:1, dispersed in an organic solvent NMP (N-methyl pyrrolidone), stirred until stable and uniform, to form a positive electrode slurry, the positive electrode slurry was coated on an aluminum foil with a thickness of 10 μm, dried at 80°C, then further vacuum dried at 120°C, and then rolled, sliced to form a positive electrode sheet;

[0186] Under an inert atmosphere in a glove box, a negative electrode shell | a spring | a gasket | a lithium sheet | an electrolyte | the composite elastic separator of Example 1 | a positive electrode sheet | a positive electrode shell were sequentially assembled, and a full coin type battery was obtained by pressing at 800 kPa for 5 s.

[0187] Battery Examples 2-13

[0188] Battery Examples 2-13 were basically the same as Battery Example 1, except that the composite elastic separator of Example 1 was replaced by the composite elastic separator of Examples 2-13 in Battery Examples 2-13.

[0189] Based on the test results of the composite elastic separator comparative examples, Battery Comparative Example 1, Battery Comparative Example 2 and Battery Comparative Example 4 were set.

[0190] Battery Comparative Example 1, Battery Comparative Example 2, Battery Comparative Example 3 and Battery Comparative Example 4

[0191] Battery Comparative Example 1, Battery Comparative Example 2, Battery Comparative Example 3 and Battery Comparative Example 4 were basically the same as Battery Example 1, except that the composite elastic separator of Example 1 was replaced by the composite elastic separator of Battery Comparative Example 1, Battery Comparative Example 2, Battery Comparative Example 3 and Battery Comparative Example 4 in Battery Comparative Example 1, Battery Comparative Example 2, Battery Comparative Example 3 and Battery Comparative Example 4.

[0192] The capacity retention rates of Battery Examples 1-13, Battery Comparative Example 1, Battery Comparative Example 2, Battery Comparative Example 3 and Battery Comparative Example 4 were tested, and the data results are shown in Table 2.

[0193] The test method of the capacity retention rate (cycle curve) was as follows: the battery was charged at 0.33C constant current and constant voltage to 4.2V at 25°C, and then discharged at 0.5C constant current to 3.0V, which was 1 cycle, and the remaining capacity was the capacity retention rate, and the cycle number and the capacity retention rate of each battery were compared.

[0194] Table 2

[0195] From Table 2, it can be seen that:

[0196] Compared with the battery comparative examples 1-4, the composite elastic separator prepared in the battery examples 1-13 is applied to the battery, the cycle number of the battery examples 1-13 is much higher than that of the battery comparative examples 1-4, which indicates that the battery of the application has a longer service life; the content retention rate of the battery examples 1-13 in 100 cycles is higher than that of the battery comparative examples 1-4, which indicates that the battery of the application has a better content retention rate in 100 cycles and a longer cycle life.

[0197] The composite elastic separator, the preparation method and the application thereof provided by the embodiments of the application are described in detail above, and the principles and implementation manners of the application are described by applying specific examples; the above examples are only used to help understand the method and the core idea of the application; meanwhile, according to the idea of the application, the specific implementation manners and application ranges will be changed by the person skilled in the art, and the above description should not be understood as a limitation on the application.

Claims

1. A composite elastomeric septum, wherein, The composite elastic diaphragm comprises: an elastic layer, an interface layer and a flame-retardant layer, the interface layer is located between the elastic layer and the flame-retardant layer, the material of the elastic layer comprises an elastic polymer, the material of the flame-retardant layer comprises aramid, the material of the interface layer comprises the elastic polymer and the aramid, and the interface layer has a reticular structure.

2. The composite elastic diaphragm according to claim 1, wherein the aramid comprises one or more of meta-aramid and para-aramid; and / or the elastic polymer comprises one or more of polystyrene, ethylene-vinyl acetate copolymer, polyurethane-based polymer, thermoplastic polyether ester elastomer, and thermoplastic vulcanized rubber.

3. The composite elastic diaphragm according to claim 1, wherein the elastic layer further comprises a ceramic material; and / or the material of the interface layer further comprises the ceramic material.

4. The composite elastomeric septum of claim 3 wherein, one or more of the following features (1) to (3): (1) the ceramic material comprises one or more of alumina, boehmite, silica, magnesium oxide, and calcium oxide; (2) the ceramic material is ceramic particles, and the average particle size of the ceramic particles is 0.3 to 1.0 μm; (3) in the elastic layer, the mass ratio of the elastic polymer to the ceramic material is (0.6 to 2):(0.001 to 1).

5. The composite elastomeric septum of claim 1 wherein, one or more of the following features (1) to (5): (1) the flame-retardant layer has a porous structure; (2) the thickness of the composite elastic diaphragm is 12 to 35 μm; (3) the thickness of the elastic layer is 5 to 14 μm; (4) the thickness of the flame-retardant layer is 1 to 4 μm; (5) the thickness of the interface layer is 100 to 200 nm.

6. The composite elastomeric septum of claim 1 wherein, The composite elastic diaphragm further comprises a base film, and the base film is arranged on the side of the elastic layer away from the interface layer.

7. The composite elastic diaphragm according to claim 6, wherein the material of the base film comprises one or more of polyethylene and polypropylene; and / or the thickness of the base film is 6 to 15 μm.

8. A method of making a composite elastomeric septum, wherein, The method comprises: providing a pre-prepared elastic layer, the material of the pre-prepared elastic layer comprising an elastic polymer; providing a first mixed solution, the first mixed solution comprising aramid, a cosolvent and a first solvent; and arranging the first mixed solution on the pre-prepared elastic layer, wherein part of the first mixed solution penetrates into the upper surface of the pre-prepared elastic layer to form an elastic layer and an interface layer combined with the elastic layer, and the first mixed solution that does not penetrate into the pre-prepared elastic layer forms a flame-retardant layer on the interface layer, thereby obtaining a composite elastic diaphragm.

9. The production method according to claim 8, wherein The preparation method of the pre-prepared elastic layer comprises: providing an elastic polymer and a second solvent, and mixing to obtain a second mixed solution; and providing a base film, and arranging the second mixed solution on the base film to obtain a pre-prepared elastic layer.

10. The production method according to claim 9, wherein one or more of the following features (1) to (7): (1) the elastic polymer comprises one or more of polystyrene, ethylene-vinyl acetate copolymer, polyurethane-based polymer, thermoplastic polyether ester elastomer, and thermoplastic vulcanized rubber. (2) the second solvent comprises one or more of methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, toluene, ethyl acetate, butanone, acetone; (3) the base film comprises one or more of polyethylene, polypropylene; (4) in the second mixed solution, the mass concentration of the elastic polymer is 94.8-316 mg / mL; (5) the rotation speed of the first mixing is 500-3000 r / min; (6) the time of the first mixing is 1-6 h; (7) after the second mixed solution is arranged on the base film, first phase inversion and first drying are further included; the temperature of the first drying is 40-80 °C, and the time is 1-5 h.

11. The production method according to claim 9, wherein The second mixed solution further comprises one or more of a ceramic material and a pore-forming agent.

12. The method of making according to claim 11, wherein, One or more of the following features (1) to (4) are included: (1) the ceramic material comprises one or more of alumina, boehmite, silicon dioxide, magnesium oxide, calcium oxide; (2) the pore-forming agent comprises one or more of dimethyl carbonate, tripropylene glycol, and polyethylene glycol; (3) the mass ratio of the elastic polymer to the ceramic material is (0.6-2):(0.001-1); (4) the mass ratio of the elastic polymer to the pore-forming agent is 1:(0.05-0.2).

13. The method of making according to claim 8, wherein, The arrangement of the first mixed solution on the pre-prepared elastic layer comprises: providing aramid, a cosolvent, and a first solvent, second mixing to obtain a first mixed solution, and depositing the first mixed solution.

14. The production method according to claim 13, wherein One or more of the following features (1) to (8) are included: (1) the aramid comprises one or more of meta-aramid and para-aramid; (2) the cosolvent comprises one or more of sodium chloride, lithium chloride, and potassium chloride; (3) the first solvent comprises one or more of methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, toluene, ethyl acetate, butanone, acetone; (4) the mass ratio of the aramid to the cosolvent is 1:(0.5-3); (5) in the first mixed solution, the mass concentration of the aramid is 15-25 mg / mL; (6) the rotation speed of the second mixing is 500-3000 r / min; (7) the time of the second mixing is 1-6 h; (8) after the first mixed solution is arranged on the pre-prepared elastic layer, second phase inversion and second drying are further included; the temperature of the second drying is 40-80 °C, and the time is 1-5 h.

15. A battery, wherein, The battery comprises a composite elastic separator, the composite elastic separator comprises an elastic layer, an interface layer, and a flame-retardant layer, the interface layer is located between the elastic layer and the flame-retardant layer, the material of the elastic layer comprises an elastic polymer, the material of the flame-retardant layer comprises aramid, the material of the interface layer comprises the elastic polymer and the aramid, and the interface layer has a reticular structure.

16. The battery according to claim 15, wherein, the aramid comprises one or more of meta-aramid and para-aramid; and / or The elastic polymer includes one or more of polystyrene, ethylene-vinyl acetate copolymer, polyurethane-based polymer, thermoplastic polyether ester elastomer, and thermoplastic vulcanizate.

17. The battery of claim 15, wherein, The elastic layer further includes a ceramic material; and / or The material of the interface layer further includes the ceramic material.

18. The battery of claim 17, wherein, One or more of the following features (1) to (3) is included: (1) The ceramic material includes one or more of alumina, boehmite, silica, magnesium oxide, and calcium oxide; (2) The ceramic material is ceramic particles, and the average particle size of the ceramic particles is 0.3 to 1.0 μm; (3) In the elastic layer, the mass ratio of the elastic polymer to the ceramic material is (0.6 to 2) : (0.001 to 1).

19. The battery of claim 15, wherein, One or more of the following features (1) to (5) is included: (1) The flame-retardant layer is a porous structure; (2) The thickness of the composite elastic separator is 12 to 35 μm; (3) The thickness of the elastic layer is 5 to 14 μm; (4) The thickness of the flame-retardant layer is 1 to 4 μm; (5) The thickness of the interface layer is 100 to 200 nm.

20. The battery of claim 15, wherein, The composite elastic separator further includes a base film disposed on the side of the elastic layer distal to the interface layer.

Images