Edge coating adhesive and method of making and use thereof

Abstract

The application belongs to the field of new energy, and discloses a kind of edge coating glue, which is made of the following reaction raw materials: polyurethane prepolymer, diisocyanate, crosslinking agent, dibasic anhydride; The polyurethane prepolymer is equivalent to 20-60wt% of the total weight of all reaction raw materials; The crosslinking agent is equivalent to 0.01-0.3wt% of the total weight of all reaction raw materials; The polyurethane prepolymer contains polyether segment; The polyurethane prepolymer contains polyether segment; The total molar amount of isocyanate groups in polyurethane prepolymer and diisocyanate is X; The molar amount of dibasic anhydride is Y, the functionality of crosslinking agent is n; The molar amount of crosslinking agent is Z; X=m*(2*Y+Z*n); m=0.95-1.05. The coating glue of the application uses the combination of diisocyanate and crosslinking agent modified by polyether segment, and prepares polyimide by using diisocyanate and dibasic anhydride, so that the edge coating glue has excellent flexibility and permeation resistance under the premise of having initial bonding performance. Meanwhile, the application also provides the preparation method and application of the edge coating glue.

Description

Technical Field

[0001] This invention belongs to the field of new energy, and more specifically, relates to an edge coating adhesive, its preparation method and uses. Background Technology

[0002] Lithium crystals can form in lithium-ion batteries during repeated cycles, potentially puncturing the separator and causing direct contact between the positive and negative electrodes, leading to a short circuit. Therefore, an edge-coated adhesive layer is needed for protection. Simultaneously, during the cutting process, the equipment needs to identify and cut the electrode edges. Traditional direct cutting methods may result in misalignment or damage to the negative electrode material area. The edge-coated adhesive ensures proper cutting. Furthermore, the bonding with the separator guarantees a stable bond between the electrode and the separator, preventing the risk of misalignment.

[0003] In existing technologies, edge coating adhesives based on polyimide are difficult to simultaneously achieve both flexibility and impermeability. The technical problem to be solved in this case is: how to improve the flexibility and impermeability of polyimide-based edge coating adhesives. Summary of the Invention

[0004] The main objective of this invention is to provide an edge coating adhesive. The coating adhesive of this invention uses a combination of polyether segment modified diisocyanate and crosslinking agent, and combines diisocyanate and diacid anhydride to prepare polyimide, so that the edge coating adhesive maintains excellent flexibility and impermeability while having preliminary bonding properties.

[0005] In addition, the present invention also provides a method for preparing the edge coating adhesive and its application.

[0006] The specific solution of the present invention is as follows:

[0007] An edge coating adhesive is made from the following reactive raw materials: polyurethane prepolymer, diisocyanate, crosslinking agent, and dicarboxylic anhydride;

[0008] The polyurethane prepolymer comprises 20–60 wt% of the total weight of all reactants; the crosslinking agent comprises 0.01–0.3 wt% of the total weight of all reactants; the polyurethane prepolymer contains polyether segments.

[0009] The total molar amount of isocyanate groups in polyurethane prepolymer and diisocyanate is X;

[0010] The molar amount of the dicarboxylic acid anhydride is Y, the functionality of the crosslinking agent is n, the molar amount of the crosslinking agent is Z, and m is the ratio of the molar amount of isocyanate groups, hydroxyl groups, and the total molar amount of anhydride groups.

[0011] X=m*(2*Y+Z*n); m=0.95~1.05.

[0012] Implicitly, the use of polyurethane prepolymer, diisocyanate, crosslinking agent, and diacid anhydride as raw materials to copolymerize and prepare edge coating adhesive indicates that the preparation method is a random copolymerization method.

[0013] In a preferred embodiment of the present invention, the polyurethane prepolymer is equivalent to 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 55 wt%, and 60 wt% of the total weight of all reactants; the crosslinking agent is equivalent to 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, and 0.3 wt% of the total weight of all reactants.

[0014] This invention employs a combination of polyether segment-modified diisocyanate and a crosslinking agent to prepare polyimide using diisocyanate and diacid anhydride. This allows the edge coating adhesive to maintain excellent flexibility and impermeability while possessing preliminary adhesion properties. Using an appropriate amount of crosslinking agent imparts a certain thickening property to the coating adhesive, ensuring a clear boundary between it and the electrode slurry when applied to the electrode sheet. Simultaneously, the use of the crosslinking agent in conjunction with the polyether segments allows the flexibility of the coating adhesive to be controlled within a suitable range.

[0015] More specifically, the control of the application performance of this invention is closely related to the following factors:

[0016] 1. Using random copolymerization helps maintain a clear interface and improves the anti-permeability effect; the main difference between front-end copolymerization and random copolymerization lies in the anti-permeability effect, while the two have no significant impact on mechanical properties such as adhesion performance.

[0017] 2. Control of free functional groups: The formula X = m*(2*Y+Z*n) and m = 0.95~1.05 means that the free monomers and / or functional groups in the edge coating adhesive within the system are completely reacted; when they cannot be completely reacted, excessive free monomers and / or functional groups have a significant impact on the anti-permeability performance of the product.

[0018] When the value of m is adjusted to 0.95 and 1.05, the anti-permeability effect is still acceptable, but it is significantly weaker than the formula with m=1. At the same time, when the value of m is 0.95, 1, and 1.05, the three values ​​have no significant impact on the mechanical properties such as bonding performance.

[0019] 3. The amount of crosslinking agent needs to be controlled within a suitable range to avoid poor thickening performance, unclear boundaries, and excessive softness of the edge coating due to insufficient crosslinking agent, and to avoid brittleness and low elongation at break of the edge coating due to excessive crosslinking agent.

[0020] Meanwhile, the crosslinking agent must be used in conjunction with polyether segment modified diisocyanate. If polyether segment modified diisocyanate is not used, the edge coating adhesive will become brittle and lack flexibility. At the same time, controlling the amount of polyether segment modified diisocyanate in an appropriate ratio can effectively improve the clarity of the boundary and keep the edge coating adhesive within a suitable swelling range.

[0021] 4. The amount of polyurethane prepolymer used needs to be controlled within a suitable range. When the prepolymer accounts for more than 65% of the total weight of all reactants, its anti-swelling properties deteriorate significantly, its elongation at break increases significantly, and its anti-permeability properties deteriorate significantly. When the prepolymer accounts for less than 20% of the total weight of all reactants, although the bonding properties are improved, the affinity between the edge coating adhesive and the electrolyte is low, which is not conducive to improving electrochemical performance. At the same time, its anti-permeability properties deteriorate significantly.

[0022] By controlling the above four factors, an edge coating adhesive with good adhesion, swelling properties, flexibility, and impermeability can be obtained. This not only enables it to exhibit good electrochemical performance when applied to batteries, but also meets the basic requirements of machine image recognition and improves the accuracy of cutting processes.

[0023] In the aforementioned edge coating adhesive, the polyurethane prepolymer is polymerized from polyether glycol and diisocyanate; the molar ratio of polyether glycol to diisocyanate is 1:2 to 3.

[0024] In some embodiments of the present invention, the molar ratio of polyether diol to diisocyanate is 1:2, 1:2.2, 1:2.4, 1:2.5, 1:2.6, or 1:3;

[0025] The isocyanate index of the polyurethane prepolymer of the present invention is 2 to 3, indicating that the prepolymer is a semi-prepolymer with isocyanate groups at both ends and free diisocyanate in the system; that is, the polyurethane prepolymer of the present invention is essentially a polyether-modified diisocyanate.

[0026] This invention constructs a polyurethane prepolymer in the form of a semi-prepolymer, in which PEG segments (polyethylene glycol segments), diisocyanate, and diacid anhydride form a random copolymer. Compared with traditional block copolymer products, the biggest advantage of this polymer form is that it can effectively prevent permeation. This may be because the more uniform copolymerization gives the edge coating adhesive better consistency and mechanical stability, so as to maintain a stable interface with the positive electrode slurry.

[0027] In the aforementioned edge coating adhesive, the molecular weight of the polyether glycol is 400–2000.

[0028] In some embodiments of the present invention, the molecular weight of the polyether glycol is 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, or 2000.

[0029] The experimental results show that using polyether glycols with different molecular weights did not produce significant changes. It can be inferred that if the molecular weight of the polyether glycol is too small, it may lead to problems such as poor product flexibility and excessive viscosity increase; if the molecular weight of the polyether glycol is too large, it may lead to an increase in the overall molecular weight of the polymer, resulting in a sparse crosslinking network and reduced viscosity when the amount of crosslinking agent is the same. Both of these performance degradations will lead to poor interface clarity and reduced industrial applicability.

[0030] In the aforementioned edge coating adhesive, the crosslinking agent is one or more combinations of trimethylolpropane, glycerol, 2,3,4-trihydroxytoluene, 2,4,6-trihydroxytoluene, 3,5,3'-trihydroxybibenzyl, 3,4,4'-triaminodiphenyl ether, 4,4',4”-triaminotriphenylmethane, and 2,3,4-triaminopyridine.

[0031] In the aforementioned edge coating adhesive, the diacid anhydride is one or more combinations of 4,4'-terephthalodioxydiphthalic anhydride, pyromellitic dianhydride, 3,3'-biphenyltetracarboxylic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 4,4'-terephthalodioxydiphthalic anhydride, 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)hexafluoropropane dianhydride, and 2,2-bis(4-(3,4-dicarboxybenzoyloxy)phenyl)hexafluoropropane dianhydride.

[0032] In the aforementioned edge coating adhesive, the diisocyanate is one or more combinations of terephthalic diisocyanate, 1,5-naphthalene diisocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 3,3-dichlorobiphenyl-4,4-diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, phenylmethylene diisocyanate, and dimethylbiphenyl diisocyanate.

[0033] In the aforementioned edge coating adhesive, the polyurethane prepolymer accounts for 45-55 wt% of the total weight of all reactants; the crosslinking agent accounts for 0.1-0.25 wt% of the total weight of all reactants.

[0034] Meanwhile, the present invention also discloses a method for preparing the edge coating adhesive as described above, wherein the reactants and solvents are subjected to a polymerization reaction at 80-100°C.

[0035] In some embodiments of the present invention, the polymerization temperature is 80°C, 85°C, 90°C, or 100°C;

[0036] In the above preparation method, the reaction time is 2 to 6 hours;

[0037] In some embodiments of the present invention, the reaction time of the polymerization reaction is 2h, 3h, 4h, 5h, or 6h.

[0038] The ratio of the total amount of reactants to the weight of solvent is 100:10 to 300.

[0039] In some embodiments of the present invention, the ratio of the total amount of reactants to the weight of solvent is 100:10, 100:50, 100:100, 100:150, 100:200, 100:250, or 100:300.

[0040] In the above preparation method, the polyurethane prepolymer is prepared by mixing polyether diol and diisocyanate and reacting at 60-80°C for 3-10 hours.

[0041] Finally, the present invention also discloses the use of edge-coated adhesives as described above in the preparation of battery electrodes.

[0042] One of the above-described technical solutions of the present invention has at least one of the following advantages or beneficial effects:

[0043] This invention employs a combination of polyether segment-modified diisocyanate and a crosslinking agent to prepare polyimide using diisocyanate and diacid anhydride. This allows the edge coating adhesive to maintain excellent flexibility and impermeability while possessing preliminary adhesion properties. Using an appropriate amount of crosslinking agent imparts a certain thickening property to the coating adhesive, ensuring a clear boundary between it and the electrode slurry when applied to the electrode sheet. Simultaneously, the use of the crosslinking agent in conjunction with the polyether segments allows the flexibility of the coating adhesive to be controlled within a suitable range.

[0044] More specifically, the control of the application performance of this invention is closely related to the following factors:

[0045] 1. Using random copolymerization helps maintain a clear interface and improves the anti-permeability effect; the main difference between front-end copolymerization and random copolymerization lies in the anti-permeability effect, while the two have no significant impact on mechanical properties such as adhesion performance.

[0046] 2. Control of free functional groups: The formula X = m*(2*Y+Z*n) and m = 0.95~1.05 means that the free monomers and / or functional groups in the edge coating adhesive within the system are completely reacted; when they cannot be completely reacted, excessive free monomers and / or functional groups have a significant impact on the anti-permeability performance of the product.

[0047] When the value of m is adjusted to 0.95 and 1.05, the anti-permeability effect is still acceptable, but it is significantly weaker than the formula with m=1. At the same time, when the value of m is 0.95, 1, and 1.05, the three values ​​have no significant impact on the mechanical properties such as bonding performance.

[0048] 3. The amount of crosslinking agent needs to be controlled within a suitable range to avoid poor thickening performance, unclear boundaries, and excessive softness of the edge coating due to insufficient crosslinking agent, and to avoid brittleness and low elongation at break of the edge coating due to excessive crosslinking agent.

[0049] Meanwhile, the crosslinking agent must be used in conjunction with polyether segment modified diisocyanate. If polyether segment modified diisocyanate is not used, the edge coating adhesive will become brittle and lack flexibility. At the same time, controlling the amount of polyether segment modified diisocyanate in an appropriate ratio can effectively improve the clarity of the boundary and keep the edge coating adhesive within a suitable swelling range.

[0050] 4. The amount of polyurethane prepolymer used needs to be controlled within a suitable range. When the prepolymer accounts for more than 65% of the total weight of all reactants, its anti-swelling properties deteriorate significantly, its elongation at break increases significantly, and its anti-permeability properties deteriorate significantly. When the prepolymer accounts for less than 20% of the total weight of all reactants, although the bonding properties are improved, the affinity between the edge coating adhesive and the electrolyte is low, which is not conducive to improving electrochemical performance. At the same time, its anti-permeability properties deteriorate significantly.

[0051] By controlling the above four factors, an edge coating adhesive with good adhesion, swelling properties, flexibility, and impermeability can be obtained. This not only enables it to exhibit good electrochemical performance when applied to batteries, but also meets the basic requirements of machine image recognition and improves the accuracy of cutting processes. Attached Figure Description

[0052] Figure 1 This is a test diagram of the anti-permeability performance of Embodiment 1 of the present invention;

[0053] Figure 2 This is a test diagram of the anti-permeability performance of Embodiment 2 of the present invention;

[0054] Figure 3 This is a test diagram of the anti-permeability performance of Embodiment 3 of the present invention;

[0055] Figure 4 This is a test diagram of the anti-permeability performance of Embodiment 4 of the present invention;

[0056] Figure 5 This is a test diagram of the anti-permeability performance of Embodiment 5 of the present invention;

[0057] Figure 6 This is a test diagram of the anti-permeability performance of Embodiment 6 of the present invention;

[0058] Figure 7 This is a test diagram of the anti-permeability performance of Embodiment 7 of the present invention;

[0059] Figure 8 This is a test diagram of the anti-permeability performance of Embodiment 8 of the present invention;

[0060] Figure 9 This is a test diagram of the anti-permeability performance of Embodiment 9 of the present invention;

[0061] Figure 10 This is a test diagram of the anti-permeability performance of Embodiment 10 of the present invention;

[0062] Figure 11 This is a test diagram of the anti-permeability performance of Embodiment 11 of the present invention;

[0063] Figure 12 This is a test diagram of the anti-permeability performance of Embodiment 12 of the present invention;

[0064] Figure 13 This is a test diagram of the anti-permeability performance of Embodiment 13 of the present invention;

[0065] Figure 14 This is a test diagram of the anti-permeability performance of Embodiment 14 of the present invention;

[0066] Figure 15 This is a test diagram of the anti-permeability performance of Embodiment 15 of the present invention;

[0067] Figure 16 This is a test diagram of the anti-permeability performance of Embodiment 16 of the present invention;

[0068] Figure 17 This is a test diagram of the anti-permeability performance of Embodiment 17 of the present invention;

[0069] Figure 18 This is a test chart of the anti-permeability performance of Comparative Example 1;

[0070] Figure 19 This is a test chart of the anti-permeability performance of Comparative Example 2;

[0071] Figure 20 This is a test chart of the anti-permeability performance of Comparative Example 3;

[0072] Figure 21 This is a test chart of the anti-permeability performance of Comparative Example 4;

[0073] Figure 22 This is a test chart of the anti-permeability performance of Comparative Example 5. Detailed Implementation

[0074] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0075] Part 1: Preparation of Prepolymer

[0076] Preparation method of prepolymer

[0077] A mixture of polyether glycol and isocyanate is obtained, wherein the molar ratio of polyether glycol to isocyanate is 1:2.0 to 3.0. The mixture is further polymerized at 50 to 150°C for 1 to 10 hours to obtain a prepolymer.

[0078] The formulations of the prepolymers of the present invention are shown in Table 1 below;

[0079] Table 1 Formula Table

[0080]

[0081] Part Two: Preparation of Polyimide

[0082] 2.1 Adjustment of raw material usage

[0083] While keeping all prepolymer 3 stirred, the crosslinking agent, diisocyanate, dicarboxylic anhydride, and N-methylpyrrolidone were heated to 120°C and reacted for 10 hours to obtain the product.

[0084] The crosslinking agent is trimethylolpropane; the diisocyanate is toluene diisocyanate; and the diacid anhydride is pyromellitic dianhydride.

[0085] The specific formula is shown in Table 2;

[0086] Table 2 Formula Table Unit: g

[0087]

[0088] 2.2 Adjustment of prepolymer and reaction process parameters

[0089] The amounts of crosslinking agent and dicarboxylic anhydride are the same as in Example 1. The difference lies in the selection of the prepolymer, the selection of the diisocyanate, and the adjustment of temperature and time in the process parameters. The solvent is replaced with an equal amount of N,N-dimethylacetamide.

[0090] See Table 3 for details;

[0091] Table 3 Formula and Process Table

[0092]

[0093] In Table 3, m = 1.

[0094] 2.3 Adjustment of the types of crosslinking agents, diisocyanates, and dicarboxylic anhydrides

[0095] The preparation process and formulation dosage are the same as in Example 1, except that the types of crosslinking agent and diacid anhydride have been adjusted, as detailed in Table 4.

[0096] Table 4 Formula Table

[0097]

[0098]

[0099] In Table 4, m = 1.

[0100] Comparative Example 4

[0101] 2 mol of diisocyanate MDI (diphenylmethane diisocyanate) was dissolved in 1000 g of solvent NMP (N-methylpyrrolidone), heated to 50 °C, and 1 mol of the monomer polytetrahydrofuran ether diol 1000 was gradually added dropwise (the addition was completed in 0.5 h), and 150.5 g of solvent NMP was added to maintain the concentration of the solution at 50 wt%. The reaction was carried out at 50 °C for 2 h to obtain isocyanate-terminated soft segment oligomer M1.

[0102] 2 mol of the monomer diaminodiphenyl ether was dissolved in 900 g of solvent NMP, heated to 50 °C, and 1 mol of diisocyanate MDI was gradually added dropwise (the addition was completed in 0.5 h). 76.1 g of solvent NMP was added to maintain the overall concentration of the solution at 40 wt%. The reaction was carried out at 50 °C for 2 h to obtain amino-terminated hard oligomer M2.

[0103] Mix M1 and M2 thoroughly and react at 80°C for 3 hours. Then add 5078.3g of NMP at once to obtain a polymer solution (concentration 20wt%) of alternating soft and hard segments copolymerized, which is the finished product.

[0104] Comparative Example 5

[0105] 2 mol of diisocyanate MDI was dissolved in 1000 g of solvent NMP, heated to 50 °C, and 1 mol of polymeric monomer polytetrahydrofuran ether diol 1000 was gradually added (the addition was completed in 0.5 h), and 150.5 g of solvent NMP was added to maintain the concentration of the solution at 50 wt%. The reaction was carried out at 50 °C for 2 h to obtain isocyanate-terminated soft segment oligomer M1.

[0106] 2 mol of the monomers diaminodiphenyl ether and 0.2 mol of 3,4,4'-triaminodiphenyl ether were dissolved in 900 g of solvent NMP. The mixture was heated to 50 °C, and 1.1 mol of diisocyanate MDI was gradually added (the addition was completed in 0.5 h). 76.1 g of solvent NMP was added to maintain the overall concentration of the solution at 40 wt%. The mixture was reacted at 50 °C for 2 h to obtain amino-terminated hard oligomer M2.

[0107] Mix M1 and M2 thoroughly and react at 80°C for 3 hours. Then add 5078.3g of NMP at once to obtain a polymer solution (concentration 20wt%) of alternating soft and hard segments, which is the finished product.

[0108] Part Three: Performance Testing

[0109] The embodiments and comparative examples of the present invention have undergone basic adhesion performance testing, elongation at break testing, and thickening performance testing.

[0110] Test methods are given for basic adhesion performance testing, elongation at break testing, and thickening performance testing.

[0111] Thickening performance test: The adhesive, borax, and solvent NMP were blended to prepare a slurry with an adhesive: borax ratio of 15:85 (by weight) and a solid content of 40 wt%.

[0112] Viscosity test: The adhesive solution was kept at 25℃ for 6 hours and then tested using a digital rotational viscometer at a rotation speed of 20 rpm. The viscosity data was obtained from the test.

[0113] Elongation at break test: The adhesive solution is dried into a film, and its mechanical properties are tested using a universal testing machine.

[0114] Adhesion performance test: The adhesive was applied to aluminum foil, dried to form a film with a thickness of 20μm, and then a 180° peel force test was performed.

[0115] Anti-permeability test: One drop of the prepared Boehmite slurry and one drop of the positive electrode lithium iron phosphate slurry were dropped onto aluminum foil, and the permeation of the two slurries was observed.

[0116] The test results are shown in Table 5.

[0117] Table 5 Test Results

[0118]

[0119]

[0120]

[0121] Results analysis:

[0122] 1. As can be seen from Examples 1 to 14, the edge coating adhesive, using the technical solution of the present invention, meets the basic requirements in terms of mechanical properties such as adhesive viscosity, slurry viscosity, and adhesion strength; through Figures 1 to 14 It is evident that the product of this invention has good anti-permeability performance;

[0123] in, Figure 2 Representative Example 2 and Figure 3 The performance of Example 3 is not as good as that of Example 1 because m≠1. This further illustrates that the equimolar amounts of isocyanate groups, anhydride groups, and crosslinking agent functional groups are important. When m≠1, it means that there are free functional groups or monomers in the polymer, and these free functional groups or monomers have a certain impact on the anti-permeability performance of the product.

[0124] Figure 4 Compared to Example 1, Example 4 showed a slightly worse interface clarity and a significantly weakened swelling degree, indicating that the prepolymer's specific gravity is a crucial parameter. If it falls below 20%, the interface clarity will further deteriorate, and the swelling performance will disappear.

[0125] Figure 9 The interface clarity of Example 9 is relatively poor compared to Example 1, indicating that the use of crosslinking agent is a very important factor in maintaining interface clarity.

[0126] Figure 13 The interface is relatively clear, but during the verification, the droplets were not added properly, resulting in the droplets not being round.

[0127] 2. As can be seen from Example 1 and Comparative Example 1, when no crosslinking agent is used, the viscosity of the adhesive, the viscosity of the slurry, and the anti-permeability performance are all significantly deteriorated. As can be seen from Example 1 and Comparative Example 2, when the prepolymer accounts for more than 65% of the total weight of all reactants, its anti-swelling performance is significantly deteriorated, its elongation at break is significantly increased, and its anti-permeability performance is significantly deteriorated. As can be seen from Comparative Example 1 and Comparative Example 3, when the prepolymer accounts for less than 20% of the total weight of all reactants, although the bonding performance is improved, the affinity between the edge coating adhesive and the electrolyte is low, which is not conducive to improving the electrochemical performance, and its anti-permeability performance is significantly deteriorated.

[0128] 3. As can be seen from Comparative Examples 4 and 5, the product of the present invention has superior anti-permeation performance compared to the block copolymerization method.

[0129] In summary, to achieve good anti-permeability performance of a product, at least the following key factors are required:

[0130] 1. Appropriate degree of crosslinking; 2. Appropriate amount of flexible segments; 3. Product obtained by random copolymerization; 4. Reactive groups should react as completely as possible, without any free monomers.

[0131] Ultimately, we believe that the surface tension of the slurry is increased by the flexible segments, moderate cross-linking, and relatively uniform copolymerization, which prevents the positive electrode slurry with high surface tension from penetrating into the edge coating adhesive.

[0132] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, nor does it mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An edge coating adhesive, characterized in that, It is made from the following reactants: polyurethane prepolymer, diisocyanate, crosslinking agent, and dicarboxylic anhydride; The polyurethane prepolymer comprises 20–60 wt% of the total weight of all reactants; the crosslinking agent comprises 0.01–0.3 wt% of the total weight of all reactants; the polyurethane prepolymer contains polyether segments. The total molar amount of isocyanate groups in polyurethane prepolymer and diisocyanate is X; The molar amount of the dicarboxylic acid anhydride is Y, the functionality of the crosslinking agent is n, the molar amount of the crosslinking agent is Z, and m is the ratio of the molar amount of isocyanate groups, hydroxyl groups, and the total molar amount of anhydride groups. X=m*(2*Y+Z*n); m=0.95~1.

05.

2. The edge coating adhesive according to claim 1, characterized in that, The polyurethane prepolymer is polymerized from polyether glycol and diisocyanate; the molar ratio of polyether glycol to diisocyanate is 1:2 to 3.

3. The edge coating adhesive according to claim 2, characterized in that, The molecular weight of the polyether diol is 400 to 2000.

4. The edge coating adhesive according to claim 1, characterized in that, The crosslinking agent is one or more combinations of trimethylolpropane, glycerol, 2,3,4-trihydroxytoluene, 2,4,6-trihydroxytoluene, 3,5,3'-trihydroxybibenzyl, 3,4,4'-triaminodiphenyl ether, 4,4',4”-triaminotriphenylmethane, and 2,3,4-triaminopyridine.

5. The edge coating adhesive according to claim 1 or 2, characterized in that, The dicarboxylic anhydride is one or more combinations of 4,4'-terephthalodioxydiphthalic anhydride, pyromellitic dianhydride, 3,3'-biphenyltetracarboxylic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 4,4'-terephthalodioxydiphthalic anhydride, 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)hexafluoropropane dianhydride, and 2,2-bis(4-(3,4-dicarboxybenzoyloxy)phenyl)hexafluoropropane dianhydride.

6. The edge coating adhesive according to claim 1, characterized in that, The diisocyanate is one or more combinations of terephthalic diisocyanate, 1,5-naphthalene diisocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 3,3-dichlorobiphenyl-4,4-diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, phenylmethylene diisocyanate, and dimethylbiphenyl diisocyanate.

7. The edge coating adhesive according to any one of claims 1, 2, 4, and 6, characterized in that, The polyurethane prepolymer accounts for 45-55 wt% of the total weight of all reactants; the crosslinking agent accounts for 0.1-0.25 wt% of the total weight of all reactants.

8. A method for preparing an edge coating adhesive as described in any one of claims 1 to 7, characterized in that, The reactants and solvents are subjected to polymerization at 80–100°C.

9. The preparation method according to claim 8, characterized in that, The reaction time is 2–6 hours; The total amount of reactants and the weight ratio of solvent are 100:10 to 300. The polyurethane prepolymer is prepared by mixing polyether diol and diisocyanate and reacting at 60-80°C for 3-10 hours.

10. Use of the edge-coating adhesive as described in any one of claims 1 to 7 to prepare battery electrodes.

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