Gluing slurry, battery diaphragm and battery using same

Abstract

The invention relates to the technical field of battery diaphragms, and particularly discloses gluing slurry, a battery diaphragm and a battery applying the gluing slurry, the battery diaphragm is composed of a ceramic or solid electrolyte base membrane and a cross-linking functional coating on the base membrane, the cross-linking functional coating is formed by dispensing or coating the gluing slurry on the ceramic or solid electrolyte base membrane and drying, and the ceramic or solid electrolyte base membrane is coated with the cross-linking functional coating. The salinized polymer and the flexible polymer in the gluing slurry form a cross-linked network under the action of the cross-linking agent and are subjected to secondary cross-linking on the surface of the particle polymer to form uniformly dispersed polymer particles with controllable size and morphology, so that the battery diaphragm can be ensured to have the properties of good ionic conductivity, liquid absorption and retention capability, bonding force and the like, the structure is stable, and the service life of the battery diaphragm is prolonged. And the diaphragm can stably exist on the surface of the diaphragm.

Description

Technical Field

[0001] The invention relates to the technical field of battery separators, in particular to a coating slurry, a battery separator and a battery using the same. Background Art

[0002] In order to reduce the internal resistance of the battery and improve the battery performance, it is very important to improve the adhesion between the diaphragm and the pole piece so that the diaphragm and the pole piece fit more closely. Therefore, the market demand for glue-coated diaphragms is increasing day by day. The glue layer made of suitable materials can improve the processability, liquid absorption and retention, and adhesion of the diaphragm. However, due to the phenomenon of infiltration caused by the characteristics of the polymer, as well as the price of the representative raw material PVDF, the further development of glue-coated diaphragms is limited.

[0003] Among the glue-coated diaphragms, the lithium-ion battery diaphragms made by glue-coating machines have the characteristics of high thermal stability, mechanical strength, puncture resistance, high liquid retention and wettability, and are an emerging technical route in the glue-coating process. The glue-coating process has high requirements for the morphology of the glue particles, the dispersion of the particles in the slurry, and the adhesion of the material itself.

[0004] The coated diaphragm mainly uses PVDF as the raw material. PVDF has a wide electrochemical window and can provide good electrolyte wettability. However, on the one hand, PVDF has a high cost due to problems such as the synthesis process. Although some manufacturers use cheaper PMMA instead of PVDF, PMMA has a large gap compared to PVDF in terms of processing performance and heat resistance, and it is difficult to completely replace PVDF in the coated diaphragm. On the other hand, the electrode bonding performance and ion conductivity provided by PVDF are poor, and the PVDF structure is single, which makes it difficult to further modify and give additional functions, such as providing additional lithium ions, increasing the ionic conductivity of the battery diaphragm and electrolyte, thereby improving the overall performance of the lithium battery cycle performance, capacity and other properties. In the face of the above problems, the use of salted polymers to replace PVDF, PMMA and other materials is a feasible solution.

[0005] At present, salted polymers such as lithium polyacrylate and sodium carboxymethyl cellulose have been used in battery negative electrodes, and it has been proven that after using salted polymers in the negative electrode, the first-cycle coulombic efficiency and reversible capacity of the battery are increased by about 10% compared with PVDF, and the number of battery cycles is increased to 3 times that of PVDF. On the other hand, most salted polymers represented by PAALi are easy to form films but have good fluidity. If used in diaphragm coating, structural infiltration and collapse are prone to occur, blocking the pores and causing the diaphragm permeability to increase significantly, limiting the use of the diaphragm. Therefore, if salted polymers are to be used on a large scale in lithium battery diaphragms, it is necessary to solve the problem of whether they can stably exist in a specific morphology on the diaphragm surface.

[0006] In terms of the spot coating diaphragm process, if salted polymers are directly used instead of PVDF to develop spot coating diaphragms, the gel-like polymer properties formed by salted polymers will make it more difficult to control the morphology and defects of the glue dots than PVDF. Therefore, if salted polymers are to be used in the spot coating process, it is particularly important whether the polymers can be well dispersed and assembled into regular particles. Summary of the invention

[0007] The purpose of the present invention is to provide a coating slurry, a battery separator and a battery using the same, so as to avoid the infiltration and collapse of the coating functional layer in the structure, realize the introduction of new functions and the improvement of existing indicators, assemble the polymer into regular particles, and solve the problem that the salted polymer cannot stably exist in a specific morphology on the surface of the separator.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] A coating slurry for lithium-ion batteries, wherein the amounts of the components in the coating slurry are as follows, by weight: 75-99 parts of deionized water, 0.01-1 parts of dispersants, 0.1-3 parts of salted polymers, 0.1-3 parts of flexible polymers, 1-15 parts of granular polymers, 0.1-1 parts of crosslinking agents, 0.01-1 parts of crosslinking initiators, and 0.01-1 parts of wetting agents; the granular polymers are synthesized from functional monomers by solution polymerization or emulsion polymerization, the particle size of the synthesized granular polymers is 0.5-10 μm, and the weight-average molecular weight is 2000-2000000; the flexible polymers are composed of short polymer segments with a molecular weight of 100-50000; the salted polymers are prepared by solution or emulsion polymerization in an aqueous phase, and the weight-average molecular weight of the salted polymers is 2000-1000000.

[0010] As a limitation of the present invention, the functional monomers of the synthetic particle polymer include any three or more of vinylidene chloride, vinylidene fluoride, vinylidene fluoride-hexafluoropropylene, acrylic acid, acrylate, acrylonitrile, carboxymethyl cellulose, styrene-butadiene rubber, vinyl pyrrolidone, lithium acrylate, sodium acrylate, vinyl alcohol, acryl alcohol, sodium alginate, and acrylamide.

[0011] The weight average molecular weight of the particle polymer is 2000-2000000, preferably 100000-500000. The cross-linked coating functional layer supports the gel component, so that the gel component can function while avoiding spreading on the membrane surface, thereby infiltrating and plugging the pores to increase the membrane permeability.

[0012] As a limitation of the present invention, the salified polymer is one or more combinations of polyacrylate, polycarboxymethyl cellulose salt, polylactic acid salt, polyalginate, poly(p-phenylene sulfonate), polybutenoate, polycarboxyethyl cellulose salt, and polymethacrylate; the salt ions of the salified polymer are one or more ions of lithium ion, sodium ion, calcium ion, potassium ion, magnesium ion, zinc ion, barium ion, and ammonium ion.

[0013] The weight average molecular weight of the salted polymer is 2000-1000000, preferably 20000-200000. The cross-linked coating functional layer is the functional main body of the coating layer, and the side chain groups and salt ions contained therein can provide the coating layer with the required adhesion, electrolyte absorption and retention, ion conduction efficiency and other functions required by the diaphragm.

[0014] As a limitation of the present invention, the flexible polymer is one or more combinations of polystyrene butadiene copolymer, polyvinyl alcohol, polyethylene glycol, polypropylene alcohol, and polyethylene oxide.

[0015] The weight average molecular weight of the flexible polymer is 100 to 50000, preferably 1000 to 5000. The role of the cross-linked coating functional layer is to act as a flexible component, fill the gap between components, and improve the toughness of the coating layer.

[0016] As a limitation of the present invention, the crosslinking agent is one or more combinations of propylene diamine, tetrahydropyridine, trimethylamine, triethylamine, tert-butylamine, tetramethylguanidine, tetraethylguanidine, N,N'-dimethylethylenediamine, polyisocyanate, and di-o-chlorodiphenylamine.

[0017] As a limitation of the present invention, the crosslinking initiator is one or more combinations of diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, di-tert-butyl peroxide, diisopropyl peroxide, benzoyl peroxide, potassium persulfate, sodium persulfate, azobisisobutyronitrile, and dimethyl azobisisobutyrate.

[0018] A coated diaphragm for lithium-ion batteries, the diaphragm having at least one ceramic coating layer or a solid electrolyte coating layer, and a cross-linked coated functional layer formed by cross-linking the coated slurry for lithium-ion batteries described in any one of the above items, the cross-linked coated functional layer being coated on the ceramic coating layer or the solid electrolyte coating layer.

[0019] As a limitation of the present invention, the cross-linked coating functional layer comprises a cross-linked network formed by a salted polymer initiated by the cross-linking agent and the flexible polymer, and spherical composite polymer particles are formed on the surface of the particle polymer through secondary cross-linking.

[0020] The polymer composite particles in the coating layer can meet the functions of the coated diaphragm, such as adhesion, electrolyte absorption and retention, and high ion conductivity, while avoiding the problem of increased air permeability caused by polymer infiltration.

[0021] As a limitation of the present invention, the cross-linked coating functional layer is coated on the ceramic coating layer or the solid electrolyte coating layer by spot coating and then drying. When spot coating, the diameter range of the glue spots formed by the cross-linked coating functional layer is 0.5 to 5 mm, the spacing between the glue spots is 0.25 to 2.5 mm, and the thickness of the cross-linked coating functional layer is 0.2 to 2 μm.

[0022] A lithium ion battery comprises the above-mentioned glue-coated diaphragm for lithium ion battery.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention constructs composite polymer particles containing salted polymers and corresponding coating slurries through cross-linking of functional components. Structurally, the granular polymer serves as the matrix of the coating functional layer and provides the basic morphology for the coating functional layer; the salted polymer and the flexible polymer serve as the skeleton and the filler, respectively, and form a cross-linked network under the action of the cross-linking agent, and produce secondary cross-linking on the surface of the granular polymer, adhering to the surface of the granular polymer, so that the coating functional layer as a whole forms particles that are approximately spherical. The formed composite particles are evenly dispersed between particles under the electrostatic repulsion of the salted polymer, and the particle size and morphology are controllable, which is suitable for the point coating process, and helps to improve the process problem of glue point defects that are prone to occur in the point coating process. Functionally, the granular polymer provides the basic physical properties required for the diaphragm coating layer, the salted polymer provides high adhesion and ionic conductivity, and the flexible polymer increases the toughness of the system. Through the synergistic effect of structure and function, excellent bonding performance (peeling force with the pole piece after hot pressing is greater than or equal to 15N / m) and ionic conductivity can be increased to 10 can be achieved while ensuring that the air permeability increment of the coating is less than 100s / 100mL. -3 S / cm level. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a partial schematic diagram of the evaluation criteria for dispensing glue, in which the circular marked part is the standard perfect dispensing particle;

[0026] Figure 2 This is a partial schematic diagram of the evaluation standard for spot coating, in which the circular marked part on the left is the standard ineffective spot coating particles, and the circular marked part on the right is the standard defective spot coating particles. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In each embodiment provided by the present invention, unless otherwise specified, the particle polymer used in the embodiment is a copolymer formed by emulsion polymerization of acrylic acid, acrylic ester, and acrylonitrile monomers (the molar ratio of acrylic acid, acrylic ester, and acrylonitrile is 2:3:1), with a weight average molecular weight of 500,000 and an average particle size of 2 to 5 μm; the salted polymer is lithium polyacrylate with a weight average molecular weight of 150,000; the flexible polymer is polyvinyl alcohol with a weight average molecular weight of 2,400, the cross-linking initiator is dimethyl azobisisobutyrate, and the cross-linking agent is N,N'-dimethylpropylenediamine. The coated diaphragm is a base film containing a single-sided aluminum oxide coating or a single-sided lithium titanium aluminum phosphate coating (the base film is a polyethylene film with a thickness of 9 μm), and the dispersant is an acrylate copolymer ammonium salt solution (BYK LP-C22092, 1.16 kg / m 3 ), the wetting agent is an alkylammonium salt of a copolymer with an acidic group (BYK-ET3004, acid value: 94 mgKOH / g, 1.08 g / mL).

[0029] Example 1: A glue-coated diaphragm for a lithium-ion battery, the preparation method being:

[0030] Step 1: Prepare the glue slurry

[0031] According to the mass percentage, 96 parts of deionized water and 0.02 parts of dispersant were accurately weighed and added to the container and stirred at 700 rpm for 2 minutes. Then, one raw material was added every 30 minutes. The order and amount of the materials were as follows: 3.25 parts of granular polymer, 0.36 parts of salted polymer, 0.36 parts of flexible polymer, 0.01 parts of crosslinking initiator, 0.1 parts of crosslinking agent, and 0.01 parts of wetting agent. After the materials were added, they were stirred at 350 rpm for 4 hours. After the raw materials were completely dispersed and mixed in the deionized water and the crosslinking of the polymer components was completed, the stirring was stopped to obtain a functional adhesive slurry with a solid content of 4%.

[0032] Step 2: Preparation of coated separator for lithium-ion batteries

[0033] A coated diaphragm with a 9 μm base film and a 2 μm single-sided aluminum oxide coating was used as the base film. The functional adhesive slurry was coated on the aluminum oxide coating surface of the base film using a micro-gravure roller to form an adhesive layer. The average thickness of the adhesive layer was 0.87 μm. ， The product is then dried at 80°C to obtain a coated diaphragm for a lithium-ion battery.

[0034] Example 2: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that the amount of the particulate polymer used in step 1 is 2 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0035] Example 3: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that the amount of the particulate polymer used in step 1 is 4.5 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0036] Example 4: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that the amount of salted polymer used in step 1 is 0.18 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0037] Example 5: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that the amount of salted polymer used in step 1 is 0.54 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0038] Example 6: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that the amount of flexible polymer used in step 1 is 0.18 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0039] Example 7: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that the amount of flexible polymer used in step 1 is 0.54 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0040] Example 8: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that in step 1, the amount of the granular polymer is 4.87 parts, the amount of the salified polymer is 0.54 parts, and the amount of the flexible polymer is 0.54 parts. The solid content of the functional glue-coated slurry obtained in step 1 is 6%. The amounts of the remaining substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0041] Example 9: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that in step 1, the amount of the granular polymer is 6.5 parts, the amount of the salified polymer is 0.72 parts, and the amount of the flexible polymer is 0.72 parts. The solid content of the functional glue-coated slurry obtained in step 1 is 8%. The amounts of the remaining substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0042] Example 10: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that a coated diaphragm of 9μm base film + 1μm single-sided lithium titanium aluminum phosphate coating is used as the base film, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0043] Example 11: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 1 is that in step 1, the particulate polymer is a copolymer formed by emulsion polymerization of acrylate, acrylamide and vinylidene fluoride monomers (the molar ratio of acrylate, acrylamide and vinylidene fluoride is 3:3:1), with a weight-average molecular weight of 350,000 and an average particle size of 2.7 μm. The salted polymer is a mixture of calcium polyacrylate and sodium polyacrylate in a mass ratio of 1:1. The flexible polymer is polypropylene alcohol. The amounts of the remaining substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0044] Based on Example 1, control experiments were carried out, specifically Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4, as described below:

[0045] Comparative Example 1: This comparative example relates to a glue-coated diaphragm for lithium-ion batteries. The difference from Example 1 is that no salted polymer and flexible polymer are added during the preparation process, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0046] Comparative Example 2: This comparative example relates to a glue-coated diaphragm for lithium-ion batteries. The difference from Example 1 is that no cross-linking agent and cross-linking initiator are added during the preparation process, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0047] Comparative Example 3: This comparative example relates to a glue-coated diaphragm for lithium-ion batteries. The difference from Example 1 is that no flexible polymer is added during the preparation process, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0048] Comparative Example 4: This comparative example relates to a glue-coated diaphragm for lithium-ion batteries. The difference from Example 1 is that no salted polymer is added during the preparation process, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 1.

[0049] Test experiment 1: Lithium-ion battery coated diaphragm samples were prepared according to the amounts and steps in the above examples 1-11 and comparative examples 1-4, and air permeability test, ion conductivity test, liquid absorption and retention rate test, and adhesion test were carried out.

[0050] Air permeability test: Cut 8cm×2cm strips from each lithium-ion battery coated separator sample and test using an Asahi Seiko air permeability tester in a 100cc test gas mode. Record the time it takes for all the test gas to pass through the strip, which is the air permeability value.

[0051] Ion conductivity test: record the membrane thickness D (μm) and membrane sample area S (cm 2 ), assembled button batteries, packaged and left to stand, and then tested the internal resistance R (Ω) of the diaphragm at room temperature using an electrochemical workstation, and calculated the ionic conductivity of each lithium-ion battery coated diaphragm sample.

[0052] Liquid absorption and retention rate test: Cut a 5cm×5cm glue-coated diaphragm sample from each lithium-ion battery glue-coated diaphragm sample, and weigh the initial weight of the sample using an analytical balance. Soak it in a 1:1 mixture of dimethyl carbonate and ethylene carbonate for 2 hours. After completion, take out the sample and wipe the residual liquid on the surface with dust-free paper, and weigh the sample. Calculate the liquid absorption and retention rate of each lithium-ion battery glue-coated diaphragm sample.

[0053] Adhesion test: Cut a 6cm×8cm glued diaphragm sample from each lithium-ion battery glued diaphragm sample, and then take a negative electrode sheet of the same size as the glued diaphragm sample. Stack the diaphragm sample and the negative electrode sheet, and hot press for 1 minute at 90℃ and 2MPa. Cut the hot-pressed diaphragm-electrode sheet sample into 1.5cm wide test strips, and peel them at a uniform speed of 50mm / min with a preload of 0.01N on a peel tester. After the test, read the peel strength value.

[0054]

[0055] Example 12: A glue-coated diaphragm for a lithium-ion battery, prepared by:

[0056] Step 1: Prepare the glue slurry

[0057] According to the mass percentage, 96 parts of deionized water and 0.02 parts of dispersant were accurately weighed and added to the container and stirred at 700 rpm for 2 minutes. Then, one raw material was added every 30 minutes. The order and amount of the materials were as follows: 3.25 parts of granular polymer, 0.36 parts of salted polymer, 0.36 parts of flexible polymer, 0.01 parts of crosslinking initiator, 0.1 parts of crosslinking agent, and 0.01 parts of wetting agent. After the materials were added, they were stirred at 350 rpm for 4 hours. After the raw materials were completely dispersed and mixed in the deionized water and the crosslinking of the polymer components was completed, the stirring was stopped to obtain a functional adhesive slurry with a solid content of 4%.

[0058] Step 2: Preparation of coated separator for lithium-ion batteries

[0059] A coated diaphragm with 9μm base film + 2μm single-sided aluminum oxide coating was used as the base membrane, and a dispensing machine was used to apply glue on the aluminum oxide coating of the base membrane to obtain a glue-coated diaphragm. The average diameter of the glue spots of the obtained spot-coated diaphragm was 3mm, the average spacing between the glue spots was 2mm, and the average thickness of the coating layer was 0.64μm. It was then dried at 80°C to obtain a glue-coated diaphragm for lithium-ion batteries.

[0060] Example 13: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 12 is that the amount of particulate polymer used in step 1 is 2 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 12.

[0061] Example 14: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 12 is that the amount of particulate polymer used in step 1 is 4.5 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 12.

[0062] Example 15: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 12 is that the amount of salted polymer used in step 1 is 0.18 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 12.

[0063] Example 16: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 12 is that the amount of salted polymer used in step 1 is 0.54 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 12.

[0064] Example 17: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 12 is that the amount of flexible polymer used in step 1 is 0.18 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 12.

[0065] Example 18: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 12 is that the amount of flexible polymer used in step 1 is 0.54 parts, and the amounts of other substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 12.

[0066] Example 19: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 12 is that in step 1, the amount of the granular polymer is 4.87 parts, the amount of the salified polymer is 0.54 parts, and the amount of the flexible polymer is 0.54 parts. The solid content of the functional glue-coated slurry obtained in step 1 is 6%. The amounts of the remaining substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 12.

[0067] Example 20: This example relates to a glue-coated diaphragm for lithium-ion batteries. The only difference from Example 12 is that in step 1, the amount of the granular polymer is 6.5 parts, the amount of the salified polymer is 0.72 parts, and the amount of the flexible polymer is 0.72 parts. The solid content of the functional glue-coated slurry obtained in step 1 is 8%. The amounts of the remaining substances and the preparation steps of the glue-coated diaphragm for lithium-ion batteries are the same as those in Example 12.

[0068] Based on Example 12, control experiments were carried out, specifically Comparative Example 5, Comparative Example 6, and Comparative Example 7, as described below:

[0069] Comparative Example 5 This comparative example relates to a glue-coated diaphragm for a lithium-ion battery, which differs from Example 10 in that no salted polymer and flexible polymer are added during the preparation process, specifically:

[0070] Comparative Example 6: This comparative example relates to a glue-coated separator for lithium-ion batteries, which differs from Example 10 in that no cross-linking agent and cross-linking initiator are added during the preparation process, specifically:

[0071] Comparative Example 7: This comparative example relates to a glue-coated separator for lithium-ion batteries, which differs from Example 10 in that no particulate polymer is added during the preparation process, specifically:

[0072] Test experiment 2: According to the dosage and steps in the above-mentioned Examples 12-20 and Comparative Examples 5-7, the glue-coated separator samples for lithium-ion batteries were prepared, and the appearance of the glue-coated points was tested.

[0073] Appearance inspection of glue spots: At a longitudinal distance of not less than 0.5m, to avoid damaging the glue spots, randomly cut 5 2.5cm×2.5cm glue spots from each lithium-ion battery glue spot sample, and use a cold field emission scanning electron microscope to observe the morphology of the glue spots and count them. There are three evaluation criteria: Figure 1 Perfectly dotted particles as shown and Figure 2 The defective dot coating particles and the ineffective dot coating particles are shown. The number of three types of dot coating particles is counted to evaluate the dot coating effect of different slurries.

[0074]

[0075] Conclusion: It can be seen from the experimental data that the air permeability of the lithium ion battery coated diaphragm prepared by the steps of Example 1 is lower than that of the lithium ion battery coated diaphragm prepared by the steps of Comparative Examples 1-4, while the ionic conductivity, liquid absorption and retention rate and peel strength at room temperature are higher than those of the lithium ion battery coated diaphragm prepared by the steps of Comparative Examples 1-4; in the appearance inspection of the glue coating points, the number of perfect spot coating particles formed by the spot coating on the lithium ion battery coated diaphragm prepared by the steps of Example 12 is higher than that of the lithium ion battery coated diaphragm prepared by the steps of Comparative Examples 5-7, and the spot coating effect is excellent.

[0076] In summary, the glue-coated diaphragm for lithium-ion batteries provided by the present invention has good properties such as ionic conductivity, liquid absorption and retention capacity, and adhesion, and has a stable structure, is not prone to collapse, and can stably exist on the surface of the diaphragm.

[0077] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A coating slurry for lithium-ion batteries, characterized in that: The dosage of each component in the coating slurry is as follows: 75 to 99 parts of deionized water, 0.01 to 1 part of dispersant, 0.1 to 3 parts of salted polymer, 0.1 to 3 parts of flexible polymer, 1 to 15 parts of granular polymer, 0.1 to 1 part of crosslinking agent, 0.01 to 1 part of crosslinking initiator, and 0.01 to 1 part of wetting agent; the granular polymer is synthesized from functional monomers by solution polymerization or emulsion polymerization, and the particle size of the synthesized granular polymer is 0.5 to 10 μm, and the weight-average molecular weight is 2000 to 2000000; the flexible polymer is composed of short polymer chain segments with a molecular weight of 100 to 50000; the preparation method of the salted polymer is solution or emulsion polymerization in an aqueous phase, and the weight-average molecular weight of the salted polymer is 2000 to 1000000.

2. The coating slurry for lithium-ion batteries according to claim 1, characterized in that: The functional monomers of the synthetic particle polymer include any three or more of vinylidene chloride, vinylidene fluoride, vinylidene fluoride-hexafluoropropylene, acrylic acid, acrylate, acrylonitrile, carboxymethyl cellulose, styrene-butadiene rubber, vinyl pyrrolidone, lithium acrylate, sodium acrylate, vinyl alcohol, allyl alcohol, sodium alginate, and acrylamide.

3. The coating slurry for lithium-ion batteries according to claim 1, characterized in that: The salified polymer is one or more combinations of polyacrylate, polycarboxymethyl cellulose, polylactic acid, polyalginate, poly(p-phenylene sulfonate), polybutenoate, polycarboxyethyl cellulose, and polymethacrylate; the salt ions of the salified polymer are one or more ions of lithium, sodium, calcium, potassium, magnesium, zinc, barium, and ammonium.

4. The coating slurry for lithium-ion batteries according to claim 1, characterized in that: The flexible polymer is one or more combinations of polystyrene butadiene copolymer, polyvinyl alcohol, polyethylene glycol, polypropylene alcohol and polyethylene oxide.

5. The coating slurry for lithium-ion batteries according to claim 1, characterized in that: The crosslinking agent is one or more of propylene diamine, tetrahydropyridine, trimethylamine, triethylamine, tert-butylamine, tetramethylguanidine, tetraethylguanidine, N,N'-dimethylethylenediamine, polyisocyanate, and di-o-chlorodiphenylamine.

6. The coating slurry for lithium-ion batteries according to claim 1, characterized in that: The crosslinking initiator is one or more of diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, di-tert-butyl peroxide, diisopropyl peroxide, benzoyl peroxide, potassium persulfate, sodium persulfate, azobisisobutyronitrile and dimethyl azobisisobutyrate.

7. A glue-coated diaphragm for lithium-ion batteries, characterized in that: The diaphragm has at least one ceramic coating layer or a solid electrolyte coating layer, and a cross-linked coating functional layer formed by cross-linking the coating slurry for lithium ion batteries according to any one of claims 1 to 6, and the cross-linked coating functional layer is coated on the ceramic coating layer or the solid electrolyte coating layer.

8. The glue-coated diaphragm for lithium-ion battery according to claim 7, characterized in that: The cross-linked coating functional layer comprises a cross-linked network formed by a salted polymer initiated by the cross-linking agent and the flexible polymer, and spherical composite polymer particles are formed on the surface of the particle polymer through secondary cross-linking.

9. The glue-coated separator for lithium-ion batteries according to claim 8, characterized in that: The cross-linked coating functional layer is coated on the ceramic coating layer or the solid electrolyte coating layer by spot coating and then drying. When spot coating, the diameter range of the glue spots formed by the cross-linked coating functional layer is 0.5-5mm, the spacing between the glue spots is 0.25-2.5mm, and the thickness of the cross-linked coating functional layer is 0.2-2μm.

10. A lithium ion battery comprising the glue-coated separator for lithium ion battery according to claim 9.

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