Separator, preparation method therefor, battery and electrical apparatus

Abstract

The present disclosure provides a separator, a preparation method therefor, a battery, and an electrical apparatus. The separator comprises a base film and an adhesive layer at least located on one side of the base film. The adhesive layer comprises a polymer, the loss modulus of the polymer at 10°C being 5×106Pa-9×108Pa.

Description

Isolation film and preparation method thereof, battery, and electrical device Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular, to an isolation membrane and a preparation method thereof, a battery, and an electrical device. Background Art

[0002] In recent years, with the advancement of battery technology, the market demand for high-power output and fast charge and discharge power batteries has become more urgent, and higher performance requirements have been placed on batteries. Although separators do not participate in the electrochemical reaction in the battery, they play a key role in improving the battery's structural stability and dynamic performance. However, current separators still face many challenges in industrial production and application.

[0003] It should be noted that the above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art.

[0004] Application Contents

[0005] In a first aspect of the present application, a separator is provided, comprising a base film and an adhesive layer at least on one side of the base film, wherein the adhesive layer comprises a polymer having a loss modulus of 5×10 6 Pa-9×10 8 Pa. As a result, the separator has excellent adhesion and anti-swelling properties.

[0006] In some embodiments, the crosslinking degree of the polymer is a, and a≥75%, thereby helping to make the polymer have a suitable loss modulus.

[0007] In some embodiments, the mass swelling degree of the polymer at 70° C. is b, and 36%≤b≤75%. This helps to improve the anti-swelling performance of the polymer.

[0008] In some embodiments, 80%≤a≤90%, and 43%≤b≤60%. This helps to further improve the anti-swelling performance of the polymer.

[0009] In some embodiments, the polymer has a loss modulus of 1×10 6 Pa-9×10 7 Pa. Therefore, the separator has excellent adhesion at room temperature.

[0010] In some embodiments, the monomers of the polymer and the derivatives of the monomers of the polymer include at least a first monomer, and the structure of the first monomer is shown in Formula 1:

[0011] Wherein, R1 includes hydrogen atom or C1-C4 alkyl, R2 includes substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C3-C4 isobornyl, -CH2(CH2) n1 -O-benzene ring, -CH2(CH2) n2 -O epoxy group, wherein the substituent of the substituted C1-C4 alkyl group includes a hydroxyl group or a C1-C6 alkyl group, and the n1 and n2 are independently 1 to 3. This helps to improve the adhesive properties of the polymer.

[0012] In some embodiments, the first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, vinyl acetate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, and 2-phenoxyethyl acrylate. This helps to further improve the adhesive properties of the polymer.

[0013] In some embodiments, the monomer of the polymer and the derivative of the monomer of the polymer further include a second monomer, and the structure of the second monomer is shown in Formula 2 and / or Formula 3:

[0014] and / or,

[0015] Wherein, R3 comprises a hydrogen atom or a C1-C8 alkyl group, and R4 comprises a hydrogen atom or a C1-C8 alkyl group. Thus, the second monomer can improve the rigidity of the polymer.

[0016] In some embodiments, the second monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid. Thus, the second monomer can further increase the rigidity of the polymer.

[0017] In some embodiments, the monomer of the polymer and the derivative of the monomer of the polymer further include a third monomer, and the structure of the third monomer is shown in Formula 4:

[0018] Wherein, R5 includes a hydrogen atom, a C1-C6 alkyl group substituted with a hydroxyl group, or a C1-C6 alkoxy group, and R6 includes a hydrogen atom or a C1-C6 alkyl group. Thus, the third monomer can improve the adhesion and anti-swelling properties of the polymer.

[0019] In some embodiments, the third monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide. Thus, the third monomer can further improve the adhesion and anti-swelling properties of the polymer.

[0020] In some embodiments, the base film includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, and polyethylene naphthalene. This helps to improve the adhesion of the polymer to the base film.

[0021] In a second aspect of the present application, a method for preparing the aforementioned isolation film is proposed, wherein a polymer is disposed on at least one side of a base film to form an adhesive layer to obtain the isolation film. Thus, the aforementioned isolation film can be prepared in a simple manner.

[0022] In some embodiments, providing the polymer includes: mixing and stirring the constituent monomers of the polymer, an emulsifier, and an initiator in a molar ratio of 100:(2-10):(0.2-1), heating and reacting to obtain a polymer emulsion, and spray-drying the polymer emulsion to obtain the polymer. This can increase the yield of the polymer.

[0023] In some embodiments, the polymer comprises a first monomer, a second monomer, and a third monomer, wherein the mass ratio of the first monomer, the second monomer, and the third monomer is 100:(1-50):(10-40). This can improve the adhesion and anti-swelling properties of the polymer.

[0024] In some embodiments, the polymer has a loss modulus of 6×10 7 Pa-1.4×10 8 Pa. As a result, the separator has excellent adhesion and anti-swelling properties.

[0025] In a third aspect of the present application, a battery is provided, comprising the aforementioned separator and / or a separator obtained by the aforementioned method. Thus, the battery has all the features and advantages of the aforementioned separator and method for preparing the separator, which will not be further elaborated here.

[0026] In some embodiments, the battery is a lithium-ion battery, and at 10° C., the lithium precipitation window of the battery is 0.7° C. to 1.5° C. Therefore, the battery has excellent low-temperature cycle performance.

[0027] In a fourth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0029] FIG1 is a schematic structural diagram of an isolation membrane according to an embodiment of the present application;

[0030] FIG2 is a schematic structural diagram of an isolation membrane according to another embodiment of the present application;

[0031] FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0032] FIG4 is an exploded view of the battery cell according to an embodiment of the present application shown in FIG3 ;

[0033] FIG5 is a schematic diagram of a battery module according to an embodiment of the present application;

[0034] FIG6 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0035] FIG7 is an exploded view of the battery pack shown in FIG6 according to an embodiment of the present application;

[0036] FIG8 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0037] Explanation of reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 11 base film; 12 polymer; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0038] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0039] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0040] The terms "include" and "have" in the description and claims of this application and any variations thereof are open expressions, that is, including the contents specified in this application but not excluding other contents.

[0041] In the description of this application, regardless of whether the word "about" or "approximately" is used, all numbers disclosed herein are approximate values. The value of each number may vary by less than 10% or by a reasonable difference considered by a person skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0042] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the technical features indicated. "First feature" and "second feature" may include one or more of the features.

[0043] " scope " disclosed in the application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0047] In this application, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0048] In a battery, the separator can promote the diffusion of electrolyte in the battery between the positive and negative electrodes, thereby facilitating the cyclical intercalation and deintercalation of metal active ions between the positive and negative electrodes. At the end of the battery cycle, the electrolyte in the battery is relatively scarce, and the promoting effect of the separator is more prominent at this time. In order to improve the bonding strength between the separator and the electrode, the separator may include a base film and an adhesive layer located on the surface of the base film. The provision of the adhesive layer can effectively improve the bonding strength between the separator and the electrode, thereby promoting the cyclical intercalation and deintercalation of metal active ions between the positive and negative electrodes, and improving the structural stability of the battery. The constituent material of the adhesive layer located on the surface of the base film is usually a polymer. Due to the large size difference between the macromolecular segments in the polymer and the small molecule solvent in the electrolyte, the small solvent molecules in the electrolyte will first penetrate and diffuse between the macromolecular segments of the polymer, weakening the interaction force between the macromolecular segments, causing the polymer to expand in volume, that is, the polymer will swell in the electrolyte. When the polymer swells excessively in the electrolyte, on the one hand, it can lead to problems such as increased volume expansion and electrode pulverization during battery charge and discharge, and even cause the precipitation of residual polymer oligomers, leading to blockage of the separator pores. On the other hand, the swelling will further consume the already scarce electrolyte. Ultimately, the polymer swells excessively, significantly reducing the adhesion between the electrode and the separator. The separator is unable to effectively suppress the volume expansion of the negative electrode during cyclic overcharge, especially the volume expansion of silicon-based negative electrode systems (silicon content in the negative electrode active material is greater than 10%wt), causing wrinkling at the electrode interface, further accelerating the reversible capacity decay, and deteriorating the battery's cycling dynamics.

[0049] The swelling of a polymer is closely related to its monomer composition. When the degree of crosslinking is low and / or the polymer contains more flexible monomers, the molecular segments of the polymer are more likely to move, which in turn exacerbates the swelling of the polymer in the electrolyte. Furthermore, the motion of the polymer molecular segments is also affected by temperature. The higher the temperature, the faster the polymer molecular chains move, making it difficult to clearly identify the cause of excessive polymer swelling even at room temperature. Furthermore, because polymers hardly swell at low temperatures, and the degree of swelling and crosslinking of polymers at low temperatures is difficult to test, the anti-swelling properties of the polymer cannot be effectively adjusted based on swelling behavior.

[0050] In this application, the loss modulus of a polymer at low temperatures is defined. The loss modulus reflects the energy lost as heat during deformation under stress, and can directly reflect the viscous components in the polymer. The viscous components in the polymer are directly related to the polymer's degree of crosslinking and molecular segment rigidity. Furthermore, since polymer molecular segments move more slowly at low temperatures, the loss modulus of the polymer at low temperatures can directly reflect the polymer's degree of crosslinking and molecular segment rigidity. Therefore, by optimizing the loss modulus of the polymer at low temperatures, a polymer with an appropriate degree of crosslinking and molecular segment rigidity can be obtained, thereby improving the polymer's adhesion and anti-swelling properties, and thereby improving the adhesion and anti-swelling properties between the isolation membrane and the adjacent electrode.

[0051] Loss modulus, also known as viscous modulus, refers to the amount of energy lost due to viscous deformation (irreversible) when a material is deformed, reflecting the viscosity of the material.

[0052] In the first aspect of the present application, the present application proposes an isolation film, referring to FIG1 , comprising a base film 11 and an adhesive layer 12 located at least on one side of the base film 11, wherein the adhesive layer comprises a polymer having a loss modulus of 5×10 6 Pa-9×10 8 Pa.

[0053] The loss modulus of a polymer has a strong correlation with its adhesion. When the loss modulus of a polymer is within an appropriate range, the polymer has higher adhesion and better anti-swelling performance.

[0054] When the loss modulus of the polymer at 10°C is within the aforementioned range, the polymer contains an appropriate amount of rigid monomers and has an appropriate degree of cross-linking, so that the molecular chain segments in the polymer have poor mobility and are not prone to excessive swelling in the electrolyte. At the same time, the polymer with the aforementioned loss modulus at 10°C also has excellent low-temperature adhesion, which is beneficial to improving the adhesion effect between the isolation membrane and the adjacent pole pieces, improving the low-temperature dynamics of the battery using the aforementioned isolation membrane, and thereby improving the cycle performance of the battery.

[0055] In this application, the loss modulus of a polymer at 10°C can be tested using methods known in the art. For example, it can be obtained by the following method:

[0056] (1) Film preparation: Prepare a 50% solids solution of the polymer emulsion and place it on a Petri dish at 25°C for 24 hours to form a 1 mm thick film. (2) Place the prepared film on an Anton Paar instrument (MCR302). (3) Press the film from above with an 8 mm diameter rotor. (4) Set the pressure to 1.0 N. (5) Raise the temperature at a rate of 1°C / min and a frequency of 1 Hz. Measure the temperature from -25°C to 50°C, recording the value at 10°C to obtain the polymer loss modulus at 10°C.

[0057] In some embodiments, referring to FIG2 , the base film 11 has two opposite surfaces in its own thickness direction, and the adhesive layer 12 is provided on two opposite surfaces of the base film 12 . Thus, when the isolation film is provided between the positive electrode sheet and the negative electrode sheet, the isolation film has a good bonding effect with both the positive electrode sheet and the negative electrode sheet.

[0058] In some embodiments, the polymer has a degree of cross-linking a, where a≥75%.

[0059] As an example, the degree of cross-linking of the polymer can be 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%.

[0060] When the degree of cross-linking of the polymer is within the aforementioned range, the molecular segments in the polymer move slowly in the electrolyte, and the small molecule solvents in the electrolyte are not easy to penetrate between the molecular segments, which helps to improve the excessive swelling of the polymer in the electrolyte and at the same time reduces the situation where the base membrane pores are blocked due to excessive volume expansion of the polymer particles.

[0061] The crosslinking degree a of a polymer can be tested using methods known in the art. As an example, the test method can use the following steps:

[0062] (1) Weigh 6 g of polymer particles using two layers of weighing paper (Uni Bloc SHIMADZU AUY2200000 balance is used for weighing);

[0063] (2) The weighed polymer particles were placed in a vacuum oven at 105°C (the vacuum oven used was Lijia LDZF-6090, size 450*450*450RT~250°C) and dried for 6 hours;

[0064] (3) Stack two layers of medium-speed filter paper (using Xinxing quantitative medium-speed filter paper for medium-speed filter paper) and number them, and place them in a 105°C vacuum oven (using Lijia LDZF-6090 vacuum oven, size 450*450*450, RT~250°C) to dry for 6 hours;

[0065] (4) After taking the polymer particles and weighing paper out of the vacuum oven, immediately seal them in a sealed bag to prevent water absorption;

[0066] (5) After taking the medium-speed filter paper out of the vacuum oven, immediately place it in a ziplock bag and weigh it. Record the total weight of the medium-speed filter paper and ziplock bag m1, and keep the weight value to 4 decimal places;

[0067] (6) Pour the polymer particles obtained in step (4) into a small crusher (Baixin LG-01 crusher, power 350W, fineness 30-300 mesh, speed 2500r / m, crushing amount 500g / m), cover with a lid, and tighten;

[0068] (7) Plug in the power supply, turn on the power switch, count for 30 seconds with a stopwatch, and then turn off the power switch;

[0069] (8) The crusher is left to stand for 5 minutes. After the powder in the crusher has settled, the crusher cover is unscrewed and the sample is in a uniform powder state.

[0070] (9) Use a brush to transfer the crushed sample into a ziplock bag and seal it immediately;

[0071] (10) After taring the centrifuge tube and the centrifuge tube cap on a balance, remove the sample bag from the drying dish, pour about 2 ± 0.2 g of sample into the centrifuge tube, immediately cover the centrifuge tube cap, and weigh the actual weight of the sample m2;

[0072] (11) Add 50 ml of dimethyl carbonate (DMC) according to the scale on the 50 ml centrifuge tube;

[0073] (12) Transfer the centrifuge tube to a 60°C oven (Boxun GZX-9146MBE oven, capacity 129L, RT + 5°C ~ 300°C) and keep warm for 12 h;

[0074] (13) After taking the centrifuge tube out of the oven, pour the sample onto medium-speed filter paper, filter the solution, and retain the supernatant;

[0075] (14) Rinse the centrifuge tube with a large amount of DMC solution to prevent sample residue in the centrifuge tube;

[0076] (15) Dry the filtered material in an oven at 105°C for 2 h;

[0077] (16) After the sample is baked, put the sample into the corresponding ziplock bag and weigh it;

[0078] (17) Reset the scale to zero, weigh the total mass of the filtered material, medium-speed filter paper, and ziplock bag, and record the mass m3;

[0079] The crosslinking degree a of the polymer particles was calculated.

[0080] In some embodiments, the mass swelling degree of the polymer at 70° C. is b, and 36%≤b≤75%.

[0081] In some embodiments, when 36%≤b≤75%, a / b may be greater than or equal to 1.

[0082] When a / b is within the aforementioned range, the polymer particles have a suitable loss modulus, which can improve the adhesion of the polymer. At the same time, the polymer particles will not swell too much in the electrolyte and consume too much electrolyte, while reducing the situation where the volume of the polymer particles expands too much and blocks the pores of the base film.

[0083] In some embodiments, 80%≤a≤90%, and 43%≤b≤60%.

[0084] In some embodiments, when 80%≤a≤90% and 43%≤b≤60%, a / b may be 1-2.1, which helps to further improve the anti-swelling performance of the polymer.

[0085] As an example, a / b may be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or 2.1.

[0086] The mass swelling degree b of the polymer at 70° C. can be tested using methods known in the art. For example, the testing method can use the following steps:

[0087] (1) Dissolution: Mix 10 g of polymer particle powder with 90 g of N-methylpyrrolidone (NMP) and stir to dissolve at 40°C for 7 h;

[0088] (2) Film preparation: The stirred polymer particle powder solution was placed in a 250 mL beaker and baked at 70°C for 8 days to obtain a dry film;

[0089] (3) Swelling rate test: Take a dry film of about 3g, with a thickness of 2mm, weigh its exact mass and record it as M1, soak it in electrolyte (the mass ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in the electrolyte solvent is 3:5:2, and the electrolyte solvent is mixed with lithium hexafluorophosphate (LiPF6) to form a 1mol / L electrolyte), place it in a 70℃ oven and bake it for 24h. After taking out the sample and letting it stand for 1h, wipe it clean and weigh its mass M2. Calculate the mass swelling degree b of the polymer particles.

[0090] In some embodiments, the polymer has a loss modulus of 1×10 6 Pa-9×10 7 Pa.

[0091] The loss modulus of a polymer is inversely proportional to its temperature. When the loss modulus of a polymer at 25°C is within the aforementioned range, the polymer has excellent adhesion and anti-swelling properties at 25°C. At the same time, the loss modulus of the polymer at 10°C is within the aforementioned range.

[0092] By adopting appropriate polymer monomers, the polymer can have a better cross-linking degree and molecular segment rigidity, thereby making the polymer have a suitable loss modulus.

[0093] In this application, the loss modulus of a polymer at 25°C can be tested using methods known in the art. For example, it can be obtained by the following method:

[0094] (1) Film preparation: Prepare a 50% solids solution of the polymer emulsion and place it on a Petri dish at 25°C for 24 hours to form a 1 mm thick film. (2) Place the prepared film on an Anton Paar instrument (MCR302). (3) Press the film from above with an 8 mm diameter rotor. (4) Set the pressure to 1.0 N. (5) Raise the temperature at a rate of 1°C per minute and test at a frequency of 1 Hz. From -25°C to 50°C, record the value at 25°C to obtain the loss modulus of the polymer at 25°C.

[0095] In some embodiments, polymer monomers containing hydroxyl groups can serve as internal crosslinking agents to improve the crosslinking degree of the polymer.

[0096] In some embodiments, the monomers of the polymer and the derivatives of the monomers of the polymer include at least a first monomer, and the structure of the first monomer is shown in Formula 1:

[0097] Wherein, R1 includes hydrogen atom or C1-C4 alkyl, R2 includes substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C3-C4 isobornyl, -CH2(CH2) n1 -O-benzene ring, -CH2(CH2) n2 -O epoxy group, wherein the substituent of the substituted C1-C4 alkyl group includes a hydroxyl group or a C1-C6 alkyl group, and n1 and n2 are independently 1-3.

[0098] In some embodiments, when R2 is -CH2(CH2)n1 -O-benzene ring or -CH2(CH2) n2 In the case of -O epoxy group, the R2 group is connected to the oxygen atom through a methylene group.

[0099] During battery manufacturing, hot or cold pressing is required to securely bond the separator to the electrode, ensuring sufficient rigidity for quick and efficient battery cell assembly. The unsaturated ester group in the first monomer facilitates polymerization and forms the backbone of the polymer chain, imparting superior molecular rigidity and adhesion to the polymer. This improves the polymer's anti-swelling properties, which in turn enhances the separator's contribution to kinetics in the lean state during the later stages of the battery cycle.

[0100] In some embodiments, the first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, vinyl acetate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, and 2-phenoxyethyl acrylate.

[0101] By using any one or more of the above first monomers, the adhesive properties and anti-swelling properties of the polymer can be adjusted.

[0102] In some embodiments, the polymer monomer and the derivative of the polymer monomer further include a second monomer, and the structure of the second monomer is shown in Formula 2 and / or Formula 3:

[0103] and / or,

[0104] Wherein, R3 includes a hydrogen atom or a C1-C8 alkyl group, and R4 includes a hydrogen atom or a C1-C8 alkyl group.

[0105] The second monomer contains carboxyl and / or cyano functional groups. These groups not only improve the adhesion between the polymer and the electrode, but also enhance the polymer's crosslinking activity. These groups act as internal crosslinkers, entering the macromolecular chain during monomer polymerization, thereby increasing the polymer's crosslinking degree, rigidity, and anti-swelling properties. Furthermore, both carboxyl and cyano functional groups are polar, enhancing the solvation and desolvation of lithium ions, thereby increasing the separator's ion conductivity and improving battery kinetics.

[0106] In some embodiments, the second monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

[0107] By using any one or more of the above-mentioned second monomers, the adhesive properties of the polymer can be adjusted. Among them, the monomer containing a cyano group can also increase the ionic conductivity of the polymer and improve the dynamic properties of the polymer.

[0108] In some embodiments, the polymer monomer and the derivative of the polymer monomer further include a third monomer, and the structure of the third monomer is shown in Formula 4:

[0109] Wherein, R5 includes a hydrogen atom, a C1-C6 alkyl group substituted with a hydroxyl group, or a C1-C6 alkoxy group, and R6 includes a hydrogen atom or a C1-C6 alkyl group.

[0110] The unsaturated amide group in the third monomer's structure facilitates polymerization, regulating molecular weight while also providing excellent adhesion and anti-swelling properties. The amide group can also form bonds with functional groups on the base film, improving adhesion between the polymer and the base film.

[0111] In some embodiments, the third monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide.

[0112] The use of any one or more third monomers mentioned above can play a role in regulating the molecular weight, so as to adjust the molecular weight of the polymer. The molecular weight of the polymer is helpful to improve the adhesion within a certain range.

[0113] In some embodiments, the base film includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, and polyethylene naphthalene. This helps to improve the adhesion of the polymer to the base film.

[0114] By adopting the base film made of the above materials, the adhesion of the polymer on the base film can be effectively improved, thereby improving the structural stability of the isolation film.

[0115] The base membrane is a porous membrane material with good chemical and mechanical stability. In some embodiments, the base membrane can be a single-layer membrane material or a multi-layer composite membrane material. When the base membrane is a multi-layer composite membrane material, the materials of each layer can be the same or different.

[0116] In some embodiments, the base membrane has a porosity of 10%-95%, for example, 15%-90%, 20%-85%, 25%-80%, 30%-75%, 35%-70%, 40%-65%, 45%-60%, 50%-55%. Thus, the probability of direct contact between the positive electrode and the negative electrode can be reduced while improving the ion conductivity of the isolation membrane.

[0117] In some embodiments, the base film has a pore diameter of 0.1 μm to 50 μm, for example, 0.5 μm to 50 μm, 1 μm to 45 μm, 5 μm to 40 μm, 10 μm to 35 μm, 15 μm to 30 μm, or 20 μm to 25 μm. Selecting a base film with such a pore structure allows the separator to have good ion conductivity, reducing the probability of direct contact between the positive and negative electrode sheets, thereby improving battery dynamics.

[0118] In some embodiments, the polymer has a loss modulus of 6×10 7 Pa-1.4×10 8 Therefore, the separator has better adhesion and anti-swelling properties.

[0119] In a second aspect of the present application, the present application proposes a method for preparing the aforementioned isolation membrane, comprising:

[0120] S1: Provide base film

[0121] In some embodiments, the relevant parameters of the base film can refer to part or all of the technical features in the aforementioned embodiment. The parts not described in this embodiment can also refer to the aforementioned embodiment and related drawings, and will not be repeated here.

[0122] S2: Disposing a polymer on at least one side of the base film

[0123] In some embodiments, the aforementioned isolation film may be manufactured in a simple manner by disposing a polymer on one side of the base film to form an adhesive layer.

[0124] In some embodiments, S2 can be performed by the following steps: (S2-1) providing an adhesive layer slurry, wherein the adhesive layer slurry includes a polymer; (S2-2) coating the adhesive layer slurry on at least one side of the base film and drying it to obtain a separator.

[0125] In some embodiments, in step (S2-1), the solvent in the bonding layer slurry may be water, such as deionized water.

[0126] In some embodiments, in step (2-1), the bonding layer slurry may further include other organic compounds, for example, a polymer for improving heat resistance, a dispersant, a wetting agent, etc.

[0127] In some embodiments, in step (2-2), coating can be performed using a coater.

[0128] In some embodiments, in step (2-2), coating may be performed by at least one of transfer coating, spin spray coating, and dip coating.

[0129] In some embodiments, the coater includes a gravure roller; the gravure roller is used to transfer the tie layer slurry to the base film.

[0130] In some embodiments, the polymer in the bonding layer slurry can be provided by the following method: the constituent monomers of the polymer, the emulsifier, and the initiator are mixed and stirred according to a molar ratio of 100:(2-10):(0.2-1), heated to react to obtain a polymer emulsion, and the polymer emulsion is spray-dried to obtain a polymer, thereby obtaining a polymer emulsion through emulsion polymerization and improving the yield of the polymer.

[0131] Emulsion polymerization is a process in which monomers are dispersed in water with the help of emulsifiers and mechanical stirring to form an emulsion, and then an initiator is added to initiate monomer polymerization.

[0132] Emulsifiers are substances that can transform mutually incompatible oil and water into an emulsion that is difficult to separate. Emulsifiers are usually surfactants that have both hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups.

[0133] An initiator is a substance that can initiate polymerization of monomers. For example, free radical initiators, which are compounds that readily decompose into free radicals (i.e., primary free radicals) upon exposure to heat, can be used to initiate free radical polymerization and copolymerization of olefinic and diene monomers.

[0134] In some embodiments, the emulsifier may include at least one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium laurate, sodium stearate, and sodium palmitoleate.

[0135] In some embodiments, the initiator may meet at least one of the following conditions: the persulfate initiator includes at least one of potassium persulfate and ammonium persulfate; the acyl peroxide initiator includes at least one of benzoyl peroxide and dioctanoyl peroxide; the azo initiator includes at least one of azobisisobutyronitrile and dimethyl azobisisobutyrate.

[0136] In some embodiments, the constituent monomers of the polymer may include the aforementioned first monomer, second monomer, and third monomer, wherein the mass ratio of the first monomer, the second monomer, and the third monomer may be 100:(1-50):(10-40), so that the polymer has the advantages of the first monomer, the second monomer, and the third monomer while also having better adhesion and anti-swelling properties.

[0137] In some embodiments, the adhesive layer is disposed on only one surface of the base film. In other embodiments, the adhesive layer is disposed on both surfaces of the base film.

[0138] In a third aspect of the present application, a battery is provided, comprising the aforementioned separator and / or a separator obtained by the aforementioned method. Thus, the battery has all the features and advantages of the aforementioned separator and method for preparing the separator, which will not be further elaborated here.

[0139] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts the active ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0140] In some embodiments, the battery is a lithium ion battery, and at 10° C., the lithium deposition window of the battery is 0.7C-1.5C.

[0141] At low temperatures, the mobility of lithium ions in lithium batteries decreases significantly, resulting in a sharp increase in the internal resistance of the battery, serious loss of discharge capacity, and a reduction in the battery charging lithium deposition window. A slightly larger charging current may cause lithium deposition, and the deposited metallic lithium dendrites may pierce the isolation membrane, causing thermal runaway.

[0142] The lithium deposition window refers to the maximum current that the battery can achieve without lithium deposition (there are no white spots on the surface of the negative electrode), also known as the maximum non-lithium deposition rate of the battery.

[0143] When the aforementioned isolation membrane is used in the battery, since the isolation membrane still has good adhesion at low temperatures, it is beneficial to improve the adhesion effect between the isolation membrane and the adjacent pole pieces, improve the low-temperature dynamics of the battery using the aforementioned isolation membrane, and widen the lithium plating window of the battery, which is consistent with the lithium plating window of the battery at room temperature, thereby improving the cycle performance of the battery.

[0144] The lithium plating window of the battery can be tested by methods known in the art. As an example, the test method can be carried out in the following steps: the sample preparation step includes: (1) taking a bare cell that has not been rolled, placing three or more copper wires in the middle position of the separator corresponding to the second outer negative electrode sheet, and fixing them with tape at the upper edge of the anode sheet; (2) applying a small piece of separator on the copper wires to ensure that the copper wires are covered and do not touch each other, and fixing the separator with tape; if it is a four-electrode cell, one or more copper wires (SE) must not be covered by the separator and marked to distinguish them from the other copper wires; (3) re-rolling the bare cell, being careful not to shift the copper wires, and paying attention to keeping the length and width of the negative electrode sheet larger than the positive electrode sheet; (4) continuing the rolling process, first cold pressing (25°C, 3MPa, 10s), and then hot pressing (55°C, 5MPa, 15s) to obtain the cell to be tested.

[0145] The test steps include capacity test and continuous charge window test. Taking the positive electrode active material as nickel-cobalt-manganese ternary material as an example, the capacity test includes: (1) letting the battery cell to be tested stand for 30 minutes; (2) charging the battery cell to 2.8V at a rate of 0.33C; (3) letting the battery cell stand for 5 minutes; (4) charging the battery cell to 4.35V at a rate of 0.33C, and then charging the battery cell at a constant voltage to a current of ≤0.05C; (5) letting the battery cell stand for 5 minutes; (6) discharging the battery cell to 2.8V at a rate of 0.33C, and recording the battery capacity C n (7) Let it stand for 5 minutes. During the entire capacity test, the test temperature is 25°C and the test sampling interval is 10S / mA / mV.

[0146] The continuous charge window test includes: (1) letting the battery cell to be tested stand for 30 minutes; (2) charging it to 2.8V at a rate of 0.33C; (3) stopping the current supply and placing it at -10℃; (4) letting it stand for 2 hours; (5) charging it to 4.35V at different rates, reading the capacity C1 before the jump (the jump point is when the negative electrode potential reaches -10mV or the voltage reaches 4.35V), and then testing the next rate. The test rates include: 0.08C, 0.1C, 0.2C, 0.4C, 0.6C, 0.8C, 1C, 1.5C, 2C, 3C. C1 / C n The SOC at the time of jump is taken as the X-axis and the rate as the Y-axis to obtain the rate-SOC curve at the temperature. The charging rate corresponding to 50% SOC can be obtained through the rate-SOC curve. The C1 corresponding to 50% SOC is the unreasonable rate at this temperature.

[0147] In the continuous charge window test, the test temperature of steps (1) and (2) is 25°C, and the test sampling interval is 60S / mA / mV; the test temperature of steps (3) and (4) is -10°C, and the test sampling interval is 60S / mA / mV; the test temperature of step (5) is -10°C, and the test sampling interval is 10S / mA / mV.

[0148] [Positive electrode]

[0149] As an example, referring to FIG. 2 , the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer 22 is provided on either or both of the two facing surfaces of the positive electrode current collector 21 .

[0150] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one side of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0151] In some embodiments, when the battery is a lithium ion battery, the positive electrode active material may be a positive electrode active material for lithium ion batteries known in the art.

[0152] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. The modified compounds of the above materials may be modified by doping and / or surface coating the materials.

[0153] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for the positive electrode active materials refer to the initial state of the material, i.e., the state before addition. When the positive electrode active material is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0154] In some embodiments, when the battery is a sodium ion battery, the positive electrode active material may be a positive electrode active material for sodium ion batteries known in the art.

[0155] As an example, the positive electrode active material may include at least one of the following materials: a sodium transition metal oxide, a polyanion compound, a Prussian blue-type sodium compound, and their respective modified compounds. However, this application is not limited to these materials; other conventional materials that can be used as battery positive electrode active materials may also be used. The modified compounds of the above materials may be modified by doping and / or surface coating.

[0156] In some embodiments, the transition metal in the sodium transition metal oxide may be at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu. The chemical formula of the sodium transition metal oxide may satisfy Na x MO2, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu, and 0<x≤1.

[0157] In some embodiments, the polyanionic compound may be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Among them, the transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si; n represents (YO4) n- valence.

[0158] In some embodiments, the polyanionic compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds of anion units and halogen anions. The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si, and n represents (YO4) n- The halogen may include at least one of F, Cl, and Br.

[0159] In some embodiments, the polyanionic compound may also be a compound having sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. M may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, Y may include at least one of P, S and Si, and n represents (YO4) n- valence state, Z represents a transition metal, m represents (ZO y ) m+ The halogen may include at least one of F, Cl, and Br.

[0160] As an example, the polyanionic compound may satisfy the chemical formula NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' includes at least one of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0161] In some embodiments, the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN - The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.

[0162] As an example, a Prussian blue-like compound may satisfy the chemical formula Na a Me b Me' c (CN)6, wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0<a≤2, 0<b<1, and 0<c<1.

[0163] The battery's charge and discharge processes are accompanied by the deintercalation and consumption of Na, resulting in different molar contents of Na at different discharge states. The molar contents of Na in the positive electrode active materials listed in this application refer to the initial state of the material, i.e., the state before the materials are added. The molar contents of Na will change after the positive electrode active materials are applied to the battery system and undergo charge and discharge cycles.

[0164] In the list of positive electrode active materials in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0165] In some embodiments, the positive electrode active material layer may further optionally include a binder.

[0166] As an example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0167] In some embodiments, the positive active material layer may further optionally include a conductive agent.

[0168] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0169] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0170] [Negative electrode]

[0171] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0172] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0173] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0174] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials include at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0175] In some embodiments, the negative electrode active material layer may further include a conductive agent, which includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0176] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0177] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0178] [Electrolytes]

[0179] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0180] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0181] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0182] In some embodiments, the solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0183] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0184] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0185] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0186] In some embodiments, the battery outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the battery outer packaging may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0187] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG3 shows a battery cell 5 with a square structure as an example.

[0188] In some embodiments, referring to Figure 4, the outer packaging may include a shell 51 and a top cover assembly 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0189] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0190] Figure 5 shows an example battery module 4. Referring to Figure 5 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0191] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0192] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0193] Figures 6 and 7 illustrate an example battery pack 1. Referring to Figures 6 and 7 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0194] In a fourth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here.

[0195] The electrical device includes at least one of the batteries, battery modules, or battery packs provided in this application. The battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (see Figure 8, such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0196] As an electrical device, a battery, battery module or battery pack can be selected according to its usage requirements.

[0197] The present invention will be described below by way of specific examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are determined according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments not specified by manufacturer are all commercially available conventional products.

[0198] Example 1

[0199] 1. Preparation of polymer

[0200] (1) Preparation of polymer emulsion

[0201] Methyl acrylate (the first monomer), methacrylic acid (the second monomer), and acrylamide (the third monomer) were weighed and mixed uniformly in a mass ratio of 80:5:15. In a 5L four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser, 1000g of the mixed monomers, 30g of sodium lauryl sulfate (an emulsifier), 10g of ammonium persulfate (an initiator), and 1200g of deionized water were added. Emulsification was carried out at high speed stirring for 30 minutes. Under nitrogen protection, the temperature was raised to 75°C and the reaction was allowed to proceed for 4 hours. The temperature was then lowered to below 40°C, the pH was adjusted to neutral, and the product was filtered to obtain a polymer emulsion.

[0202] (2) The polymer emulsion was subjected to a spray drying process to obtain an adhesive for an isolation film. The conditions of the spray drying process were: an inlet air temperature of 110° C., an outlet air temperature of 50° C., and an air pressure of 0.5 kPa.

[0203] 2. Preparation of batteries:

[0204] (1) Preparation of isolation membrane

[0205] A commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (from Zhuo Gao Electronic Technology Co., Ltd.) was used as the base membrane. The polymer prepared above was stirred and mixed uniformly in deionized water to obtain a slurry (solid content of 20%). The slurry was sprayed onto both surfaces of the base membrane and dried to remove the solvent. The polymer coating density on the base membrane was 1.5 g / m2. 2 , and obtain an isolation film.

[0206] (2) Preparation of positive electrode sheet

[0207] Polyvinylidene fluoride (PVDF), NCM811, conductive agent carbon black, and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 1.2:58.38:0.42:40, and then stirred and mixed to prepare a positive electrode slurry. 2 The loading amount is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0208] (3) Preparation of negative electrode sheet

[0209] Artificial graphite, conductive agent acetylene black, adhesive styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) were added into deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and stirred thoroughly to prepare a negative electrode slurry (solid content of 63%). 2 The loading amount is coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain the negative electrode sheet.

[0210] (4) Preparation of electrolyte

[0211] At 25°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 is dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0212] (5) Battery assembly

[0213] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence, and cold-pressed (during which the separator is bonded to the electrode sheet) to obtain a bare cell; the bare cell is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging and other processes, a battery is obtained.

[0214] The difference between Examples 2-9 and Comparative Examples 1-2 and Example 1 is as shown in Table 1.

[0215] Table 1

[0216] The polymers in the above examples and comparative examples were tested as follows. The test results are shown in Table 2:

[0217] Loss modulus: Prepare a 50% solids solution of the polymer emulsion and place it on a Petri dish at 25°C for 24 hours to form a 1 mm thick film. (2) Place the film on an Anton Paar instrument (MCR302). (3) Press the film from above with an 8 mm diameter rotor. (4) Set the pressure to 1.0 N. (5) Raise the temperature at a rate of 1°C / min and a frequency of 1 Hz. Record the values ​​at 10°C and 25°C from -25°C to 50°C. This gives the loss modulus of the polymer at 10°C and 25°C.

[0218] Degree of cross-linking: (1) Weigh 6 g of polymer particles by stacking two layers of weighing paper (Uni Bloc SHIMADZU AUY2200000 balance is used for weighing); (2) Place the weighed polymer particles in a vacuum oven at 105°C (vacuum oven is Lijia LDZF-6090, size 450*450*450RT~250°C) and dry for 6 h; (3) Stack two layers of medium-speed filter paper (medium-speed filter paper is Xinxing quantitative medium-speed filter paper) and number them, and place them in a vacuum oven at 105°C (vacuum oven is Lijia LDZF-6090, size 450*450*450RT~250°C) and dry for 6 h; (4) Take the polymer particles and weighing paper out of the vacuum oven Immediately seal the medium-speed filter paper in a sealed bag to prevent water absorption; (5) Take the medium-speed filter paper out of the vacuum oven and immediately put it into a ziplock bag and weigh it, record the total weight of the medium-speed filter paper and the ziplock bag m1, and keep 4 decimal places; (6) Pour the polymer particles obtained in step (4) into a small crusher (the crusher uses Baixin LG-01, power 350W, fineness 30-300 mesh, speed 2500r / m, crushing amount 500g / m), cover it with a lid, and tighten it; (7) Plug in the power supply, turn on the power switch, count 30S with a stopwatch, and then turn off the power switch; (8) Crusher The crusher was left to stand for 5 minutes. After the powder in the crusher settled, the crusher cover was unscrewed and the sample was in a uniform powder state. (9) The crushed sample was transferred to a ziplock bag with a brush and sealed immediately. (10) After the centrifuge tube and the centrifuge tube cover were peeled on a balance, the sample bag was taken out from the drying dish, and about 2±0.2g of sample was poured into the centrifuge tube. The centrifuge tube cover was immediately closed and the actual weight of the sample was measured. (11) 50ml of dimethyl carbonate (DMC) was added according to the scale on the 50ml centrifuge tube. (12) The centrifuge tube was transferred to a 60℃ oven (the oven was equipped with a Bosch oven). GZX-9146MBE, capacity 129L, RT+5℃~300℃) for 12h; (13) After taking the centrifuge tube out of the oven, pour the sample onto medium-speed filter paper, filter the solution, and retain the filter material; (14) Rinse the centrifuge tube with a large amount of DMC solution to prevent the sample from remaining in the centrifuge tube; (15) Dry the filter material in a 105℃ oven for 2h; (16) After the sample is baked, put the sample into the corresponding self-sealing bag and weigh it; (17) Reset the scale, weigh the total mass of the filter material, medium-speed filter paper and self-sealing bag, and record the mass m3; according to The crosslinking degree a of the polymer particles was calculated.

[0219] Mass swelling degree: (1) Dissolution: Take 10g of polymer particle powder and 90g of N-methylpyrrolidone (NMP), mix them, and stir and dissolve them at 40℃ for 7h; (2) Film preparation: Place the stirred polymer particle powder glue solution in a 250mL beaker, bake it at 70℃ for 8 days to obtain a dry film; (3) Swelling rate test: Take a dry film of about 3g, with a thickness of 2mm, weigh its exact mass and record it as M1, soak it in an electrolyte (the mass ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in the electrolyte solvent is 3:5:2, and the electrolyte solvent is mixed with lithium hexafluorophosphate (LiPF6) to form a 1mol / L electrolyte), place it in a 70℃ oven and bake it for 24h. Take out the sample and let it stand for 1h, then wipe it clean and weigh its mass M2. According to Calculate the mass swelling degree b of the polymer particles.

[0220] Table 2

[0221] The batteries in the above examples and comparative examples were tested as follows. The test results are shown in Table 3:

[0222] 1. Low temperature bonding performance:

[0223] (1) Select the prepared 300 mm long × 100 mm wide separator and the positive electrode sheet and negative electrode sheet prepared above.

[0224] (2) Wrap the upper and lower surfaces of the release film with paper and use a die cutter and a punch to cut into 54.2 mm × 72.5 mm samples.

[0225] (3) Stack the punched separator sample and the positive electrode neatly, pad the upper and lower surfaces with 130mm×130mm Teflon, place the stacked sample in the middle of a 200mm×200mm cardboard, and cover it with a 150mm×160mm cardboard.

[0226] (4) Place the folded sample into the flat press and adjust the pressure. Adjust the air pressure to 3500KG±10KG (the contact area is about 50mm×100mm, and the actual pressure after conversion is about 7MPa). Set T=25℃ and the time to 10s for pressing.

[0227] (5) Use a die cutter and a punch to punch the hot-pressed sample into strips of 72.5 mm × 15 mm.

[0228] (6) One side of the positive electrode is fixed on the steel plate with double-sided tape, and the other side is adhered with an isolation film. Use double-sided tape to stick an A4 paper strip with a width of 15 mm to the isolation film to complete the test sample production.

[0229] (7) Turn on the high-speed rail tensile testing machine and set the parameters in sequence as follows: adhesion test, speed 50 mm / min, and starting clamp spacing 40 mm.

[0230] (8) Place the test sample between the clamps, fix the end of the steel plate to the lower clamp, and fix the A4 paper to the upper clamp. Clamp the upper and lower clamps with the clamps respectively.

[0231] (9) Click the stretching operation interface on the computer desktop, reset the force and displacement, and then click "Start" to pre-stretch for about 5mm. After pre-stretching, reset the force and displacement to zero again and start the test. During the test, fix the steel plate that fixes the electrode, and the tensile testing machine pulls the A4 paper strip upward to separate the separator from the positive electrode. After the test is completed, export and save the complete data.

[0232] (10) Each group of test samples should be measured for at least 5 samples. If the adhesion test curves of the 5 test samples have good repeatability, then the next group of tests should be carried out. Otherwise, the test should be repeated until the repeatability of the 5 test samples is good.

[0233] (11) After the test is completed, a bonding strength (N / m)-displacement curve is drawn, and the average value of the 100th to 300th data points is taken as the bonding force. The measured bonding force is recorded as F1.

[0234] 2. Capacity retention at 25℃:

[0235] At 25°C, the battery was fixed with a three-piece steel clamp with a 1mm single-sided thermal insulation pad between the clamp and the battery. A preload of 0.1MPa was applied. The battery was then charged at a constant current rate of 1C to a charge cut-off voltage of 3.65V. The battery was then charged at a constant voltage to a current of ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a discharge cut-off voltage of 2.8V. The battery was allowed to stand for 5 minutes, and the battery capacity at this time, C0, was recorded. The battery was charged and discharged 1500 times in this manner, and the battery capacity after 1500 cycles was recorded as C1.

[0236] Battery cycle capacity retention rate at 25°C = C1 / C0×100%

[0237] 3. Low-temperature three-electrode lithium deposition window:

[0238] The sample preparation steps include: (1) taking an unrolled bare cell, placing three or more copper wires in the middle position of the second outer negative electrode sheet corresponding to the isolation film, and fixing them at the upper edge of the anode sheet with tape; (2) applying a small piece of isolation film on the copper wires to ensure that the copper wires are covered and do not touch each other, and fixing the isolation film with tape; if it is a four-electrode, one or more copper wires (SE) must not be covered by the isolation film, and be marked to distinguish them from the remaining copper wires; (3) re-rolling the bare cell, being careful not to shift the copper wires, and paying attention to keeping the length and width dimensions of the negative electrode sheet larger than the positive electrode sheet; (4) continuing the rolling process, first cold pressing (25°C, 3MPa, 10s), and then hot pressing (55°C, 5MPa, 15s) to obtain the cell to be tested.

[0239] The test steps include capacity test and continuous charge window test. The capacity test includes: (1) let the battery cell to be tested stand for 30 minutes; (2) DC charge to 2.8V at a rate of 0.33C; (3) let it stand for 5 minutes; (4) charge to 4.35V at a rate of 0.33C, and then charge at a constant voltage to a current of ≤0.05C; (5) let it stand for 5 minutes; (6) discharge to 2.8V at a rate of 0.33C, and record the battery capacity C n (7) Let it stand for 5 minutes. During the entire capacity test, the test temperature is 25°C and the test sampling interval is 10S / mA / mV.

[0240] The continuous charge window test includes: (1) letting the battery cell to be tested stand for 30 minutes; (2) charging it to 2.8V at a rate of 0.33C; (3) stopping the current supply and placing it at -10℃; (4) letting it stand for 2 hours; (5) charging it to 4.35V at different rates, reading the capacity C1 before the jump (the jump point is when the negative electrode potential reaches -10mV or the voltage reaches 4.35V), and then testing the next rate. The test rates include: 0.08C, 0.1C, 0.2C, 0.4C, 0.6C, 0.8C, 1C, 1.5C, 2C, 3C. C1 / C n The SOC at the time of the jump is taken as the X-axis and the rate as the Y-axis to obtain the rate-SOC curve at this temperature. The charge rate corresponding to 5% SOC and 50% SOC can be obtained through the rate-SOC curve. The C1 corresponding to the corresponding SOC is the irrational rate at this temperature. In the continuous charge window test, the test temperature of steps (1) and (2) is 25℃, and the test sampling interval is 60S / mA / mV; the test temperature of steps (3) and (4) is -10℃, and the test sampling interval is 60S / mA / mV; the test temperature of step (5) is -10℃, and the test sampling interval is 10S / mA / mV.

[0241] Table 3

[0242] The test results show that the loss modulus of the polymer in Comparative Example 1 at 10°C is less than 5×10 6 Pa, resulting in excessive swelling of the polymer, with a mass swelling of 120% at 70°C, which deteriorates the bonding effect of the battery and consumes too much electrolyte, resulting in a decrease in battery cycle performance. The loss modulus of the polymer in Comparative Example 2 at 10°C is greater than 9×10 8 Pa, which causes the bonding effect of the separator to deteriorate at low temperatures, the electrode to separate from the separator, and a significant decrease in battery cycle performance.

[0243] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An isolation film, wherein, It includes a base film and at least an adhesive layer on one side of the base film. The adhesive layer includes a polymer, and the loss modulus of the polymer at 10 °C is 5×10 6 Pa - 9×10 8 Pa.

2. The separator film according to claim 1, wherein, The crosslinking degree of the polymer is a, where a ≥ 75%.

3. The separator film according to claim 1 or 2, wherein The mass swelling degree of the polymer at 70°C is b, where 36% ≤ b ≤ 75%.

4. The separator according to claim 3, wherein 80% ≤ a ≤ 90%, and 43% ≤ b ≤ 60%.

5. The separator according to any one of claims 1-4, wherein, The loss modulus of the polymer at 25 °C is 1×10 6 Pa - 9×10 7 Pa.

6. The separator according to any one of claims 1-5, wherein The monomers of the polymer and derivatives of the monomers of the polymer at least include a first monomer, and the structure of the first monomer is shown in Formula 1: Among them, R1 includes a hydrogen atom or an alkyl group of C1-C4, and R2 includes a substituted or unsubstituted alkyl group of C1-C4, a substituted or unsubstituted isobornyl group of C3-C4, -CH2(CH2) n1 -O-phenyl ring, -CH2(CH2) n2 -O epoxy group, where the substituent of the substituted alkyl group of C1-C4 includes a hydroxyl group or an alkyl group of C1-C6, and n1 and n2 are each independently 1-3.

7. The separator film according to claim 6, wherein, The first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, vinyl acetate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, 2-phenoxyethyl acrylate.

8. The separator according to any one of claims 1-7, wherein, The monomers of the polymer and derivatives of the monomers of the polymer further include a second monomer, and the structure of the second monomer is as shown in Formula 2, and / or, Formula 3: and / or, Wherein, R3 includes a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R4 includes a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

9. The separator according to claim 8, wherein, The second monomer includes at least one of acrylonitrile, methacrylonitrile, ethylacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, heptenoic acid.

10. The separator film according to any one of claims 1-9, wherein, The monomers of the polymer and derivatives of the monomers of the polymer further include a third monomer, and the structure of the third monomer is as shown in Formula 4: Wherein, R5 includes a hydrogen atom, a C1-C6 alkyl group substituted by a hydroxyl group or a C1-C6 alkoxy group, and R6 includes a hydrogen atom or a C1-C6 alkyl group.

11. The separator film according to claim 10, wherein, The third monomer includes at least one of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide.

12. The separator according to any one of claims 1-11, wherein The base film includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cycloolefin copolymer, polyphenylene sulfide, polyvinylnaphthalene.

13. The separator film according to any one of claims 1-12, wherein, The loss modulus of the polymer at 10 °C is 6×10 7 Pa - 1.4×10 8 Pa.

14. A method for preparing the separator film according to any one of claims 1-13, wherein, The polymer is disposed on at least one side of the base film to form an adhesive layer, so as to obtain the separator film.

15. The method according to claim 14, wherein, Providing the polymer includes: Blending and stirring the constituent monomers, emulsifier, and initiator of the polymer in a molar ratio of 100:(2-10):(0.2-1), and heating and reacting to obtain a polymer emulsion. The polymer emulsion is spray-dried to obtain a polymer.

16. The method according to claim 14 or 15, wherein The constituent monomers of the polymer include a first monomer, a second monomer, and a third monomer, wherein the mass ratio of the first monomer, the second monomer, and the third monomer is 100:(1-50):(10-40).

17. A battery, wherein, Including the separator film according to any one of claims 1-13, and / or the separator film obtained by using the method according to any one of claims 14-16.

18. The battery according to claim 17, wherein, The battery is a lithium-ion battery, and at 10°C, the lithium plating window of the battery is 0.7C - 1.5C.

19. An electrical device, wherein, Including the battery according to claim 17 or 18.

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