Slurry, current collector structure, pole piece, battery cell and preparation method

Abstract

The invention provides slurry, a current collector structure, a pole piece, a battery cell and a preparation method. Mixing the solid and a solvent, wherein the mass ratio of the solvent is 25-50%; wherein the mixed solid comprises a polymer matrix, the mass of the polymer matrix accounts for 1-80% of the mass of the mixed solid, and the polymer matrix is configured to improve the viscosity of the current collector and the active matter layer; the mass of the conductive agent accounts for 5-70% of the mass of the mixed solid; the mass of the functional material accounts for 1-94% of the mass of the mixed solid, the functional material comprises a first functional material and a second functional material, the first functional material is configured to reduce the internal resistance of the lithium ion battery, and the second functional material is configured to improve the safety of the lithium ion battery. According to the slurry disclosed by the invention, the binding force between the current collector and the active material is enhanced, and the cohesiveness of the positive pole piece can be improved; during needling, the short-circuit resistance can be increased, and the contact area between the current collector and the needle is reduced, so that the safety performance of the battery cell is improved; and burrs generated during slitting of the current collector can be effectively wrapped, so that the safety performance of the battery cell is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of ion batteries, and in particular to a slurry, a current collector structure, a pole piece, a battery cell, and a preparation method thereof. Background Art

[0002] With the continuous development of new energy sources, the demand for lithium battery energy density is increasing, and the accompanying safety issues are also growing. Lithium batteries often experience thermal runaway when subjected to mechanical impact forces such as squeezing, collision, or puncture. This is mainly because in such situations, a short circuit occurs inside the lithium battery, instantly generating a large amount of heat, which can cause fire and explosion. Summary of the Invention

[0003] The purpose of this disclosure is to provide a slurry, current collector structure, electrode, battery cell, and preparation method that can solve at least one of the above-mentioned technical problems. The specific solution is as follows:

[0004] According to a specific embodiment of the present disclosure, on the one hand, the present disclosure provides a slurry for a lithium-ion battery, the slurry comprising: a mixed solid and a solvent, the mass ratio of the solvent being 25-50%; wherein the mixed solid comprises: a polymer matrix, the mass of the polymer matrix accounting for 1-80% of the mass of the mixed solid, and the polymer matrix being configured to improve the adhesion between the current collector and the active material layer; a conductive agent, the mass of the conductive agent accounting for 5-70% of the mass of the mixed solid; a functional material, the mass of the functional material accounting for 1-94% of the mass of the mixed solid, the functional material comprising a first functional material and a second functional material, the first functional material being configured to reduce the internal resistance of the lithium-ion battery, and the second functional material being configured to and / or improve the safety of the lithium-ion battery.

[0005] In an optional embodiment, the mass of the polymer matrix accounts for 50-70% of the mass of the mixed solid.

[0006] In an optional embodiment, the mass of the conductive agent accounts for 20-40% of the mass of the mixed solid.

[0007] In an optional embodiment, the mass of the functional material accounts for 10-30% of the mass of the mixed solid.

[0008] In an optional embodiment, the first functional material includes: a lithium salt, and the lithium salt is configured to reduce internal resistance.

[0009] In an optional embodiment, the second functional material includes: inorganic particles, and the inorganic particles are configured to improve the safety of the lithium-ion battery.

[0010] In an optional embodiment, the lithium salt is one or more of lithium nickelate, lithium manganate, lithium nickel manganate, lithium phosphate and lithium borate.

[0011] In an optional embodiment, the inorganic particles are one or more of aluminum oxide, silicon oxide, zinc oxide, manganese oxide, calcium oxide, barium titanate and aluminum hydroxide.

[0012] In an optional embodiment, the lithium salt is one or more of LiMPO4, LiFeMPO4 and Li2MP2O7; wherein M is Mn, Co or Ni.

[0013] In an optional embodiment, the polymer matrix is ​​one or more of polybutene, polyethylene, polyamide, polycarbonate, polyvinyl chloride, epoxy resin, acrylate resin, oily polyvinylidene fluoride, polyvinylidene fluoride copolymer, polystyrene, polyacrylic acid, polyacrylonitrile, polyimide, water-based PVDF, polyurethane, polyvinyl alcohol, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer and phenolic resin.

[0014] In an optional embodiment, the conductive agent is one or more of a conductive carbon material, a metal powder, and a conductive polymer.

[0015] In an optional embodiment, the conductive carbon material is one or more of acetylene black, conductive carbon black, carbon nanotubes, conductive graphite and graphene;

[0016] In an optional embodiment, the metal powder is one or more of aluminum powder, nickel powder and silver powder.

[0017] In an optional embodiment, the conductive polymer is one or more of conductive polythiophene, conductive polypyrrolidone and conductive polyaniline.

[0018] In an optional embodiment, the solvent is one or more of N-methylpyrrolidone, N-dimethylformamide, dimethyl sulfoxide, dimethylformamide, toluene, acetone, ethanol, propanol, isopropanol and ethylene glycol.

[0019] According to a specific embodiment of the present disclosure, on the other hand, the present disclosure provides a current collector structure, which includes: a current collector and a coating layer coated with the slurry as described in any one of the above technical solutions.

[0020] In an optional embodiment, the current collector includes: a support layer; a conductive layer, the conductive layer covering the support layer; and a coating layer, the coating layer covering the conductive layer; wherein the coating layer adopts the slurry as described in any one of the above technical solutions.

[0021] In an optional embodiment, the current collector includes a composite current collector or a metal foil, and the metal foil is preferably an aluminum foil or a copper foil.

[0022] According to a specific embodiment of the present disclosure, on another aspect, the present disclosure provides a positive electrode plate, and the positive electrode plate includes: a current collector structure as described in any one of the above technical solutions.

[0023] According to a specific embodiment of the present disclosure, on another aspect, the present disclosure provides a battery cell, which includes: a positive electrode sheet as described in the above technical solution.

[0024] According to a specific embodiment of the present disclosure, on another aspect, the present disclosure provides a method for preparing a current collector structure, which comprises: coating a slurry as described in any one of the above technical solutions on the surface of the current collector; placing the slurry in a temperature-controlled environment for drying, the drying temperature being 60-120°C and the drying time being 10-30 minutes; after drying, obtaining the current collector structure.

[0025] In an optional embodiment, the coating thickness of the slurry is 3-20 μm.

[0026] In an optional embodiment, the coating thickness of the slurry is preferably 7-10 μm.

[0027] In an optional embodiment, the method for preparing the current collector structure also includes: preparing the slurry; wherein, preparing the slurry includes: mixing a mixed solid and a solvent, stirring evenly, and obtaining the slurry; wherein, the mixed solid includes: a polymer matrix, the mass of the polymer matrix accounts for 1-80% of the mass of the mixed solid, and the polymer matrix is ​​configured to improve the adhesion between the current collector and the active material layer; a conductive agent, the mass of the conductive agent accounts for 5-70% of the mass of the mixed solid; a functional material, the mass of the functional material accounts for 1-94% of the mass of the mixed solid, and the functional material includes a first functional material and a second functional material, the first functional material is configured to reduce the internal resistance of the lithium-ion battery, and the second functional material is configured to improve the safety of the lithium-ion battery.

[0028] According to a specific embodiment of the present disclosure, on another aspect, the present disclosure provides a method for preparing a positive electrode sheet, including a method for preparing a current collector structure as described in any one of the above technical solutions.

[0029] In an optional embodiment, the method for preparing the positive electrode sheet further includes: preparing a positive electrode slurry, including dissolving the positive electrode material, positive electrode conductor, and positive electrode binder in a positive electrode solvent, stirring and dispersing them evenly to obtain a positive electrode slurry; and coating the positive electrode slurry on the outer surface of the current collector structure.

[0030] According to a specific embodiment of the present disclosure, on another aspect, the present disclosure provides a method for preparing a battery cell, including a method for preparing a positive electrode sheet as described in any one of the above technical solutions.

[0031] Compared with the prior art, the above solution of the embodiment of the present disclosure has at least the following beneficial effects:

[0032] The present disclosure provides a slurry that can form a layer of glue when applied to the surface of the current collector, thereby reducing the exposed area of ​​the empty foil and improving safety. At the same time, the slurry of the present disclosure enhances the bonding force between the current collector and the active material, which can improve the adhesion of the positive electrode plate; during acupuncture, it will increase the short-circuit resistance and reduce the contact area between the current collector and the acupuncture, thereby improving the safety performance of the battery cell; it can also effectively wrap the metal burrs that may be generated when the current collector is cut, thereby improving the safety performance of the battery cell. In addition, the electrode coated with the slurry of the present disclosure plays a buffering role during the rolling process, effectively protecting the conductive layer in the current collector, thereby improving the cycle performance of the battery cell; the battery cell assembled with this electrode has improved energy density, cycle performance and safety performance; the battery cell assembled with this electrode has improved energy density, cycle performance and safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic structural diagram of a current collector structure according to an embodiment of the present disclosure is shown.

[0034] Figure 2 A flow chart of a method for preparing a current collector structure according to an embodiment of the present disclosure is shown.

[0035] Reference numerals:

[0036] 100: current collector structure; 110: support layer; 120: conductive layer; 130: coating layer; 140: protective layer. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the present disclosure more clear, the present disclosure will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present disclosure, rather than all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present disclosure without creative effort are intended to fall within the scope of protection of the present disclosure.

[0038] The terms used in the embodiments of the present disclosure are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. The singular forms "a," "an," "the," and "the" used in the embodiments of the present disclosure and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0039] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0040] It should be understood that although the terms "first," "second," "third," etc. may be used to describe structures in the embodiments of the present disclosure, these structures should not be limited to these terms. These terms are merely used to distinguish different structures. For example, a first component may also be referred to as a second component, and similarly, a second component may also be referred to as a first component without departing from the scope of the embodiments of the present disclosure.

[0041] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0042] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

[0043] In the related art, lithium batteries will experience thermal runaway when they encounter mechanical impact forces such as extrusion, collision or puncture. This is mainly because in such cases, a short circuit occurs inside the lithium battery, and a large amount of heat is generated instantly, which causes fire and explosion. In some related technologies, some functional materials that reduce internal resistance are added. The internal resistance reduced by adding functional materials is not enough to compensate for the impact of the increase in thickness, which will greatly reduce the performance of the battery. In addition, the glue used in the related art is not optimal in terms of raw materials, ratios and coating thickness. The preparation process of the glue is complicated, which leads to problems such as increased internal resistance, reduced energy density, and deterioration of the cycle in the battery. In addition, the preparation process of the glue is complicated, which leads to the improvement of battery safety performance while reducing its electrical performance, and does not completely and effectively improve the safety performance of the battery.

[0044] In order to solve at least one of the technical problems mentioned above, the present disclosure provides a slurry, a current collector structure 100, a pole piece, a battery cell and a preparation method; the slurry is used for lithium-ion batteries, and the slurry includes: a mixed solid and a solvent, and the mass ratio of the solvent is 25-50%; wherein the mixed solid includes: a polymer matrix, the mass of the polymer matrix accounts for 1-80% of the mass of the mixed solid, and the polymer matrix is ​​configured to improve the adhesion between the current collector and the active material layer; a conductive agent, the mass of the conductive agent accounts for 5-70% of the mass of the mixed solid; a functional material, the mass of the functional material accounts for 1-94% of the mass of the mixed solid, and the functional material is configured to reduce internal resistance and / or improve safety. The slurry involved in the present disclosure mainly relates to the field of lithium-ion batteries, and can also be used in the fields of other metal ion batteries, such as sodium ion batteries, potassium ion batteries, magnesium ion batteries, calcium ion batteries, aluminum ion batteries, zinc ion batteries, etc., and more broadly, it can also be used in the fields of metal-sulfur based batteries. This disclosure optimizes the raw materials and ratios of the primer functional adhesive (slurry), using a composite current collector + primer functional adhesive (coating the slurry on the current collector surface) to improve the adhesion of the electrode sheet. Battery cells assembled using electrode sheets made from this current collector structure 100 have improved cycle performance and safety. This disclosure considers the material composition and the ratios of each component, comprehensively considering multiple factors such as cost, performance, and safety, to achieve an optimal match, ensuring battery safety while improving overall battery performance.

[0045] Optional embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0046] According to a specific embodiment of the present disclosure, on the one hand, a slurry is provided for use in lithium-ion batteries, the slurry comprising: a mixed solid and a solvent, the mass ratio of the solvent being 25-50%; wherein the mixed solid comprises: a polymer matrix, the mass of the polymer matrix accounting for 1-80% of the mass of the mixed solid, the polymer matrix being configured to improve the adhesion between the current collector and the active material layer; a conductive agent, the mass of the conductive agent accounting for 5-70% of the mass of the mixed solid; and a functional material, the mass of the functional material accounting for 1-94% of the mass of the mixed solid, the functional material comprising a first functional material and a second functional material, the first functional material being configured to reduce the internal resistance of the lithium-ion battery, and the second functional material being configured to improve the safety of the lithium-ion battery. The present disclosure provides a slurry that can form a layer of glue when applied to the surface of the current collector, thereby reducing the exposed area of ​​the empty foil and thereby improving safety. At the same time, the slurry disclosed herein enhances the bonding force between the current collector and the active material, which can improve the adhesion of the positive electrode sheet; during acupuncture, the short-circuit resistance will be increased, and the contact area between the current collector and the needle will be reduced, thereby improving the safety performance of the battery cell; it can also effectively wrap the metal burrs that may be generated when the current collector is cut, thereby improving the safety performance of the battery cell. In addition, the electrode sheet coated with the slurry disclosed herein acts as a buffer during the rolling process, effectively protecting the conductive layer 120 in the current collector, thereby improving the cycle performance of the battery cell; the battery cell assembled with this electrode sheet has improved energy density, cycle performance and safety performance; the battery cell assembled with this electrode sheet has improved energy density, cycle performance and safety performance. Furthermore, the mass of the polymer matrix accounts for 50-70% of the mass of the mixed solid; the mass of the conductive agent accounts for 20-40% of the mass of the mixed solid; and the mass of the functional material accounts for 10-30% of the mass of the mixed solid.

[0047] It should be noted that the slurry disclosed in the present invention mainly relates to the field of lithium-ion batteries, and can also be used in the fields of other metal-ion batteries, such as sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, calcium-ion batteries, aluminum-ion batteries, zinc-ion batteries, etc. More broadly, it can also be used in fields such as metal-sulfur-based batteries. In actual use, the slurry can not only be used in current collector batteries, but can also be directly applied on metal foils, such as aluminum foil, copper foil, etc., and then coated with positive electrode slurry to obtain positive electrode sheets. The slurry disclosed in the present invention is applied to the surface of the current collector, and the resulting current collector structure 100 can enhance the bonding force between the current collector and the active material, improve the adhesion of the positive electrode sheet, improve the safety performance of the battery cell, and also improve the cycle performance of the battery cell. The method for preparing the slurry is: mixing the polymer matrix, the conductive agent, the functional material and the solvent, and stirring them evenly to obtain the slurry.

[0048] In some embodiments, the polymer matrix is ​​one or more of polybutene, polyethylene, polyamide, polycarbonate, polyvinyl chloride, epoxy resin, acrylate resin, oily polyvinylidene fluoride, polyvinylidene fluoride copolymer, polystyrene, polyacrylic acid, polyacrylonitrile, polyimide, water-based PVDF, polyurethane, polyvinyl alcohol, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer and phenolic resin. In actual use, the support layer in the composite current collector is usually a polymer material, so the slurry disclosed herein uses the polymer matrix as a base material to increase viscosity, which can be well bonded to the composite current collector, thereby improving the viscosity of the current collector and the active material layer, and then improving the peel strength of the pole piece. In a preferred embodiment, the polymer matrix is ​​oily polyvinylidene fluoride (PVDF), polyvinylidene fluoride copolymer (such as PVDF-HFP copolymer, PVDF-TFE copolymer). It should be noted that lithium ion batteries themselves contain PVDF. Therefore, in the selection of the polymer matrix, selecting a material with PVDF can improve the compatibility of the slurry with the lithium ion battery.

[0049] In some embodiments, the conductive agent is one or more of a conductive carbon material, a metal powder, and a conductive polymer. In an optional embodiment, the conductive carbon material is one or more of acetylene black, conductive carbon black, carbon nanotubes, conductive graphite, and graphene. In an optional embodiment, the metal powder is one or more of aluminum powder, nickel powder, and silver powder. In an optional embodiment, the conductive polymer is one or more of conductive polythiophene, conductive polypyrrolidone, and conductive polyaniline. It should be noted that the conductive agent, as a conductive material, is usually selected from materials with good electrical conductivity, such as graphite and metal, followed by conductive polymers, or a combination thereof. Acetylene black, conductive carbon black, carbon nanotubes, conductive graphite, and graphene are common and very stable conductive carbon materials, and are also often used in the field of batteries. Therefore, the present disclosure prefers them as the conductive agent.

[0050] In some embodiments, the first functional material comprises a lithium salt configured to reduce the internal resistance of a lithium-ion battery. In an alternative embodiment, the second functional material comprises inorganic particles configured to improve the safety of the lithium-ion battery. In an alternative embodiment, the lithium salt is one or more of lithium nickelate, lithium manganate, lithium nickel manganate, lithium phosphate, and lithium borate. In an alternative embodiment, the inorganic particles are one or more of aluminum oxide, silicon oxide, zinc oxide, manganese oxide, calcium oxide, barium titanate, and aluminum hydroxide. In a preferred embodiment, the lithium salt is one or more of LiMPO4, LiFeMPO4, and Li2MP2O7, where M is Mn, Co, or Ni. The present disclosure reduces the internal resistance of a lithium-ion battery by adding the first functional material. The lithium salt can interact with the lithium ions in the battery, improving conductivity and lithium ion flow, thereby reducing the internal resistance of the lithium-ion battery. The addition of the second functional material primarily increases friction and overall roughness through the inorganic salt particles, improving the pass rate of the needle penetration test, thereby increasing the resistance of the lithium-ion battery to external force damage and improving safety.

[0051] In some embodiments, the solvent is one or more of N-methylpyrrolidone, N-dimethylamide, dimethyl sulfoxide, dimethylformamide, toluene, acetone, ethanol, propanol, isopropanol and ethylene glycol. During use, the solvent disclosed herein is preferably an organic solvent, that is, the mixed solid (the polymer matrix, the conductive agent and the functional material) is dissolved as much as possible. The solvent selected by the present disclosure not only has high solubility, but also can make certain insoluble compounds and simple substances form a uniform suspension in the solvent, and is stable in state and is not easy to react chemically with the mixed fixation. In addition, the solvent selected by the present disclosure has good viscosity, can reasonably control the viscosity of the adhesive, is beneficial to environmental protection and makes the mixed solid easier to diffuse in the adhesive to form a uniform adhesive after adding the granular mixed solid, so that the welding layer after coating is more uniform.

[0052] Figure 1 FIG. 1 shows a schematic structural diagram of a current collector structure 100 according to an embodiment of the present disclosure. Figure 1 As shown, according to a specific embodiment of the present disclosure, on the other hand, a current collector structure 100 is provided, comprising: a current collector and a coating layer 130 coated with a slurry as described in any of the above embodiments. In an optional embodiment, the current collector comprises a composite current collector or a metal foil, preferably an aluminum foil or a copper foil.

[0053] In some embodiments, the current collector includes: a support layer 110; a conductive layer 120, wherein the conductive layer 120 covers the support layer 110; and a coating layer 130, wherein the coating layer 130 uses a slurry as described in any one of the above embodiments.

[0054] In some embodiments, the material of the support layer 110 is one or more of polyethylene terephthalate, polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene dicarboxamide, acrylonitrile-butadiene-styrene copolymer, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyphenylene sulfide, polyvinylidene fluoride, silicone rubber, and polycarbonate. In an optional embodiment, the thickness of the support layer 110 is 4-10 μm. In a preferred embodiment, the thickness of the support layer 110 is 4-8 μm.

[0055] In some embodiments, the conductive layer 120 is made of aluminum or aluminum alloy. In an optional embodiment, the conductive layer 120 has a thickness of 0.8-3 μm. In a preferred embodiment, the conductive layer 120 has a thickness of 1-2.5 μm.

[0056] In some embodiments, a protective layer 140 is provided on a side of the conductive layer 120 away from the support layer 110. In some embodiments, the protective layer 140 is made of a metal, an alloy, or a metal oxide. In some embodiments, the protective layer 140 is made of one or more of nickel, chromium, a nickel-based alloy, a copper-based alloy, aluminum oxide, cobalt oxide, chromium oxide, and nickel oxide.

[0057] Figure 2 FIG. 1 shows a flow chart of a method for preparing a current collector structure 100 according to an embodiment of the present disclosure. Figure 2 As shown, according to the specific embodiment of the present disclosure, on the other hand, a method for preparing a current collector structure 100 is provided, and the method for preparing the current collector structure 100 includes: S100, coating the surface of the current collector with a slurry as described in any one of the above embodiments; S200, placing it in a temperature-controlled environment for drying, the drying temperature is 60-120°C, and the drying time is 10-30min; S300, after drying, obtaining the current collector structure 100.

[0058] In some embodiments, the coating thickness of the slurry is 3-20 μm. In a preferred embodiment, the coating thickness of the slurry is 7-10 μm.

[0059] In an optional embodiment, the drying temperature is 60-120° C. and the drying time is 10-30 minutes.

[0060] In some embodiments, the method for preparing the current collector structure 100 further includes: preparing the slurry; wherein the preparing the slurry includes: mixing a mixed solid and a solvent, stirring evenly, to obtain the slurry; wherein the mixed solid includes: a polymer matrix, the mass of the polymer matrix accounts for 1-80% of the mass of the mixed solid, and the polymer matrix is ​​configured to improve the adhesion between the current collector and the active material layer; a conductive agent, the mass of the conductive agent accounts for 5-70% of the mass of the mixed solid; a functional material, the mass of the functional material accounts for 1-94% of the mass of the mixed solid, and the functional material includes a first functional material and a second functional material, the first functional material is configured to reduce the internal resistance of the lithium-ion battery, and the second functional material is configured to improve the safety of the lithium-ion battery. In an optional embodiment, the method for preparing the current collector structure 100 further includes: S10, mixing the polymer matrix, the conductive agent, the functional material and the solvent, stirring evenly, to obtain the slurry. In some embodiments, the preparation method of the current collector structure 100 also includes: preparing the current collector; wherein, preparing the current collector includes: S20, forming a conductive layer 120 on the surface of the support layer 110; forming a protective layer 140 on the surface of the conductive layer 120 to obtain the current collector.

[0061] In some embodiments, the method for preparing the current collector structure 100 further includes: preparing the current collector; wherein, preparing the current collector includes: forming a conductive layer 120 on the surface of the support layer 110; forming a protective layer 140 on the surface of the conductive layer 120 to obtain the current collector.

[0062] Example 1:

[0063] 50 wt% of PVDF (the polymer matrix), 30 wt% of graphite (the conductive agent), 10 wt% of LiMnPO4 (lithium manganese phosphate - the first functional material) and 10 wt% of aluminum oxide (the second functional material) are mixed to form a mixed solid; the mixed solid is then dissolved in NMP (the solvent, the mass of which accounts for 35 wt% of the mass of the mixed solid), mixed, and stirred to be uniformly dispersed to obtain slurry 1 (the coating slurry in the present disclosure);

[0064] 96 wt % of NCM (the positive electrode material), 2 wt % of SP (conductive carbon black - the positive electrode conductor), 0.5 wt % of CNTs (carbon nanotubes - the positive electrode conductor), and 1.5 wt % of PVDF (the binder) were dissolved in NMP (N-methylpyrrolidone - the positive electrode solvent), and the mixture was stirred and dispersed uniformly to obtain a positive electrode active material layer slurry 1;

[0065] The prepared slurry 1 is coated on both surfaces of the positive electrode composite current collector (the current collector) with a coating thickness of 10 μm, and dried to obtain a positive electrode current collector with a primer slurry (i.e., the current collector structure 1); then the prepared positive electrode active material layer slurry 1 is coated on both surfaces of the current collector structure 1, dried, and rolled to obtain a positive electrode sheet 1.

[0066] Comparative Example 1:

[0067] 50 wt% of PVDF (polymer matrix), 30 wt% of graphite (conductive agent), and 20 wt% of NMP (solvent) were mixed and stirred to obtain slurry 2 (coating slurry in the related art);

[0068] The preparation of the positive electrode active material layer slurry is the same as in Example 1 to obtain positive electrode active material layer slurry 2;

[0069] The prepared positive electrode active material layer slurry 2 is coated on both surfaces of the positive electrode composite current collector (the current collector), dried, and rolled to obtain a positive electrode sheet 2. Comparative Example 2:

[0070] The preparation of the positive electrode active material layer slurry is the same as in Example 1 to obtain positive electrode active material layer slurry 3;

[0071] The prepared positive electrode active material layer slurry 3 is coated on both surfaces of the positive electrode composite current collector (the current collector), dried, and roll-pressed to obtain a positive electrode sheet 3 .

[0072] Preparation of negative electrode sheet:

[0073] 94.9wt% of artificial graphite (negative electrode active material - the negative electrode material), 1.5wt% of SP (conductive carbon black - the conductive agent), 0.5wt% of CNTs (carbon nanotubes - the negative electrode conductor), 1.8wt% of SBR (hydroxystyrene-butadiene rubber - the binder) and 1.3wt% of CMC (sodium carboxymethyl cellulose - the negative electrode binder) are dissolved in deionized water (the negative electrode solvent), stirred and dispersed evenly to obtain a negative electrode active layer slurry; the negative electrode active layer slurry is coated on the surface of the negative electrode collector (current collector), dried and rolled to obtain a negative electrode sheet.

[0074] Battery cell preparation:

[0075] 1. The positive electrode sheet 1, the separator and the negative electrode sheet are stacked and assembled in sequence; baking, packaging, liquid injection, high temperature pressure forming, liquid extraction, packaging and volume determination are carried out in sequence to obtain a battery cell 1.

[0076] 2. The positive electrode sheet 2, the separator and the negative electrode sheet are stacked and assembled in sequence; baking, packaging, liquid injection, high temperature pressure forming, liquid extraction, packaging and constant volume are carried out in sequence to obtain the battery cell 2.

[0077] 3. The positive electrode sheet 3, the separator and the negative electrode sheet are stacked and assembled in sequence; baking, packaging, liquid injection, high temperature pressure forming, liquid extraction, packaging and volume determination are carried out in sequence to obtain the battery cell 3.

[0078] Ion battery preparation:

[0079] 1. Assemble the battery cells 1 into a lithium-ion battery 1.

[0080] 2. Assemble the battery cells 2 into a lithium-ion battery 2.

[0081] 3. Assemble the battery cells 3 into a lithium-ion battery 3.

[0082] Test method: Perform the following tests on cell 1, cell 2, and cell 3 (or positive electrode sheet 1, positive electrode sheet 2, and positive electrode sheet 3, or lithium-ion battery 1, lithium-ion battery 2, and lithium-ion battery 3), respectively, and record the experimental data:

[0083] 1. Peel strength: Cut the coated and dried positive electrode sheets 1, 2, and 3 into sample sizes, fix them on a steel plate, fold the free ends 180°, and then fix them on the fixture of a tensile testing machine for testing.

[0084] 2. Battery internal resistance: When the battery is at 70-90% SOC, use BT3562A voltage internal resistance tester to test the internal resistance of lithium-ion battery 1, lithium-ion battery 2 and lithium-ion battery 3 respectively;

[0085] 3. 2C Capacity Retention Rate: At room temperature, lithium-ion battery 1, lithium-ion battery 2, and lithium-ion battery 3 were tested using a charge and discharge test cabinet. The specific process was as follows: the batteries were charged at a current of 0.5C to a final voltage of 4.2V, then switched to constant voltage charging. Charging was stopped when the charging current dropped to 0.05C, and the battery was left standing for 30 minutes. Lithium-ion battery 1, lithium-ion battery 2, and lithium-ion battery 3 were each discharged at a current of 2C to a final voltage of 3.0V, and the battery was left standing for 30 minutes. The discharge capacity retention rate was recorded.

[0086] 4. 1C cycle: At room temperature, charge lithium-ion battery 1, lithium-ion battery 2, and lithium-ion battery 3 at 1C current to a final voltage of 4.2V, then switch to constant voltage charging. Stop charging when the charging current drops to 0.05C and let it sit for 30 minutes. Discharge lithium-ion battery 1, lithium-ion battery 2, and lithium-ion battery 3 at 1C current to a final voltage of 3.0V and let it sit for 30 minutes. Cycle again. Stop testing when the capacity retention rate reaches 80%. Record the number of cycles and discharge capacity retention rate.

[0087] 5. Needle Penetration Test: After fully charging the same number of lithium-ion batteries 1, 2, and 3, use a 5-8mm diameter needle with a 30°-60° angle to penetrate the batteries at a speed of 25±5mm / s in a direction perpendicular to the batteries. If the needle penetration is completed for more than 60 minutes, the batteries will pass the test if they do not catch fire or explode. The pass rate will be recorded.

[0088] The test results are as follows:

[0089]

[0090] The test results show that:

[0091] (1) The peeling strength of the electrode made of slurry is much greater than the peeling strength without adding the slurry coating layer. Therefore, the peeling strength of the electrode made of slurry is higher. At the same time, through the comparison between Example 1 and Comparative Example 1, the slurry disclosed in the present invention can further increase the viscosity brought by the polymer matrix, thereby improving the quality and safety of the electrode.

[0092] (2) After the current collector of the lithium-ion battery is replaced from pure foil to composite current collector, the internal resistance will increase slightly, the 2C rate performance will decrease slightly, but the safety performance will be greatly improved. The reason is that the conductivity of the composite current collector cannot be compared with that of metal foil. A large part of the material in the composite current collector is non-conductor, and the thickness of the composite current collector is much greater than that of the metal foil. Therefore, the internal resistance of the lithium-ion battery using the composite current collector is usually greater than that of the lithium-ion battery using the metal foil. The increase in internal resistance comes from the fact that the conductive layer of the composite current collector is thinner than that of the pure foil, so the conductivity decreases, and the rate is further slightly reduced. But it is precisely because of this that, during the needle puncture test, the polymer layer in the composite current collector can partially block the internal short circuit point caused by the steel needle, thereby greatly improving the safety performance. It can be seen from Example 1 and Comparative Example 1 that the internal resistance of the lithium-ion battery using slurry 1 (the coating slurry in the present disclosure) is much smaller than the internal resistance of the lithium-ion battery using slurry 2 (the coating slurry in the related art).

[0093] (3) The 2C-capacity retention test results show that the performance of Example 1 and Comparative Examples 1-2 are similar. Although the performance of Example 1 and Comparative Examples 1-2 is similar, it can be seen from the data that the performance of Example 1 using the slurry described in the present disclosure is superior.

[0094] (4) The 1C cycle-80% capacity retention test results show that the advantages of the current collector are demonstrated, and the capacity retention rate of the current collector is much higher than that of the metal foil. It can be clearly seen in Example 1 and Comparative Examples 1-2 that Example 1 has the highest capacity retention rate, proving that the lithium-ion battery using the slurry of the present disclosure has superior performance in this test.

[0095] (5) The pass rate of the needle puncture test reflects the safety performance of the lithium-ion battery under external force impact. It can be seen from the experimental results that the pass rate of the lithium-ion battery using slurry 1 (the coating slurry in the present disclosure) is much higher than the pass rate of the lithium-ion battery of Comparative Examples 1-2, proving that the safety performance of the lithium-ion battery using slurry 1 (the coating slurry in the present disclosure) is much higher than that of Comparative Examples 1-2.

[0096] Comparison between Example 1 and Comparative Example 1 shows that the addition of the primer layer further improves the cycling performance and safety of the battery. This indicates that the primer (the slurry disclosed herein) can mitigate the decrease in adhesion between the active material and the current collector during cycling, improving cycling performance. During the acupuncture process, the primer increases the short-circuit resistance and reduces the contact area between the current collector and the acupuncture point, thereby improving the safety performance of the battery cell.

[0097] According to a specific embodiment of the present disclosure, in another aspect, a positive electrode plate is provided, and the positive electrode plate includes: a current collector structure 100 as described in any one of the above embodiments.

[0098] In some embodiments, the positive electrode sheet further includes: a positive electrode active material layer, wherein the positive electrode active material layer covers the surface of the current collector structure 100 .

[0099] According to a specific embodiment of the present disclosure, on the other hand, a method for preparing a positive electrode sheet is provided, the method for preparing a positive electrode sheet comprising: coating a slurry as described in any one of the above embodiments on the surface of a current collector; obtaining a current collector structure 100 after drying; and forming a positive electrode active material layer on the surface of the current collector structure 100.

[0100] In some embodiments, forming the positive electrode active material layer on the surface of the current collector structure 100 includes: preparing a positive electrode active material layer slurry; and coating the positive electrode active material layer slurry on the surface of the current collector structure 100 .

[0101] In some embodiments, the preparation of the positive electrode active material layer slurry includes: dissolving the positive electrode material, the positive electrode conductor, and the positive electrode binder in a positive electrode solvent; and stirring the mixture to obtain the positive electrode active material layer slurry. In some embodiments, the positive electrode solvent is an N-methylpyrrolidone solution.

[0102] In some embodiments, the method for preparing the positive electrode plate further includes: preparing the slurry; wherein, the preparing the slurry includes: mixing a mixed solid and a solvent, stirring evenly, and obtaining the slurry; wherein, the mixed solid includes: a polymer matrix, the mass of the polymer matrix accounts for 1-80% of the mass of the mixed solid, and the polymer matrix is ​​configured to improve the adhesion between the current collector and the active material layer; a conductive agent, the mass of the conductive agent accounts for 5-70% of the mass of the mixed solid; a functional material, the mass of the functional material accounts for 1-94% of the mass of the mixed solid, and the functional material is configured to reduce internal resistance and / or improve safety.

[0103] According to a specific embodiment of the present disclosure, in another aspect, a negative electrode plate is provided, which includes: a negative electrode current collector structure and a negative electrode active material layer, wherein the negative electrode active material layer covers the surface of the current collector structure 100 .

[0104] According to a specific embodiment of the present disclosure, in another aspect, a method for preparing a negative electrode sheet is provided, the method for preparing a negative electrode sheet comprising: forming a negative electrode active material layer on the surface of the negative electrode current collector structure.

[0105] In some embodiments, forming the negative electrode active material layer on the surface of the negative electrode current collector structure includes: preparing a negative electrode active material layer slurry; and coating the negative electrode active material layer slurry on the surface of the negative electrode current collector structure.

[0106] In some embodiments, the preparation of the negative electrode active material layer slurry includes: dissolving the negative electrode material, the positive electrode conductor, and the negative electrode binder in a negative electrode solvent; and stirring the mixture to obtain the negative electrode active material layer slurry. In some embodiments, the negative electrode solvent is deionized water.

[0107] According to a specific embodiment of the present disclosure, on another aspect, a battery cell is provided, which includes: a positive electrode sheet as described in any one of the above embodiments and / or a negative electrode sheet as described in any one of the above embodiments.

[0108] According to a specific embodiment of the present disclosure, on the other hand, a method for preparing a battery cell is provided, which comprises: sequentially stacking and assembling the positive electrode sheet and the separator as described in any one of the above embodiments and the negative electrode sheet as described in any one of the above embodiments; and sequentially performing baking, packaging, liquid injection, high-temperature pressure forming, liquid extraction, packaging, and constant volume to obtain a battery cell.

[0109] According to a specific embodiment of the present disclosure, in another aspect, an ion battery is provided, comprising: a battery cell as described in any one of the above embodiments.

[0110] The present disclosure is intended to protect a slurry, a current collector structure 100, an electrode, a battery cell, and a preparation method. The slurry is used in lithium-ion batteries and includes: a mixed solid and a solvent, wherein the mass ratio of the solvent is 25-50%. The mixed solid includes: a polymer matrix, the mass of the polymer matrix accounting for 1-80% of the mass of the mixed solid, and the polymer matrix is ​​configured to improve the adhesion between the current collector and the active material layer; a conductive agent, the mass of the conductive agent accounting for 5-70% of the mass of the mixed solid; and a functional material, the mass of the functional material accounting for 1-94% of the mass of the mixed solid, wherein the functional material includes a first functional material and a second functional material, the first functional material being configured to reduce the internal resistance of the lithium-ion battery, and the second functional material being configured to improve the safety of the lithium-ion battery. The present disclosure provides a slurry that can form a layer of glue when applied to the surface of the current collector, thereby reducing the exposed area of ​​the empty foil and thus improving safety. At the same time, the slurry disclosed herein enhances the bonding force between the current collector and the active material, improving the adhesion of the positive electrode sheet; during acupuncture, it increases the short-circuit resistance and reduces the contact area between the current collector and the needle, thereby improving the safety performance of the battery cell; it can also effectively wrap the metal burrs that may be generated when the current collector is cut, thereby improving the safety performance of the battery cell. In addition, the electrode sheet coated with the slurry disclosed herein acts as a buffer during the rolling process, effectively protecting the conductive layer 120 in the current collector, thereby improving the cycle performance of the battery cell; the battery cell assembled with this electrode sheet has improved energy density, cycle performance, and safety performance; the battery cell assembled with this electrode sheet has improved energy density, cycle performance, and safety performance.

[0111] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. References to the common and similar parts between the various embodiments will be sufficient. For the systems or devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, their descriptions are relatively simple; for relevant details, refer to the descriptions of the methods.

[0112] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present disclosure.

Claims

1. A slurry for lithium-ion batteries, characterized in that: include: Mixing a solid and a solvent, wherein the mass ratio of the solvent is 25-50%; wherein the mixed solid comprises: A polymer matrix, the mass of the polymer matrix accounting for 1-80% of the mass of the mixed solid, and the polymer matrix is ​​configured to improve the adhesion between the current collector and the active material layer; A conductive agent, wherein the mass of the conductive agent accounts for 5-70% of the mass of the mixed solid; Functional material, the mass of the functional material accounts for 1-94% of the mass of the mixed solid, the functional material includes a first functional material and a second functional material, the first functional material is configured to reduce the internal resistance of the lithium-ion battery, and the second functional material is configured to improve the safety of the lithium-ion battery.

2. The slurry according to claim 1, characterized in that The mass of the polymer matrix accounts for 50-70% of the mass of the mixed solid; and / or The mass of the conductive agent accounts for 20-40% of the mass of the mixed solid; and / or The mass of the functional material accounts for 10-30% of the mass of the mixed solid.

3. The slurry according to claim 1, characterized in that The polymer matrix is ​​one or more of polybutene, polyethylene, polyamide, polycarbonate, polyvinyl chloride, epoxy resin, acrylate resin, oily polyvinylidene fluoride, polyvinylidene fluoride copolymer, polystyrene, polyacrylic acid, polyacrylonitrile, polyimide, water-based PVDF, polyurethane, polyvinyl alcohol, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer and phenolic resin; And / or, the first functional material includes: a lithium salt, wherein the lithium salt is configured to reduce the internal resistance of the lithium-ion battery; preferably, the lithium salt is one or more of lithium nickelate, lithium manganate, lithium nickel manganate, lithium phosphate and lithium borate; further preferably, the lithium salt is one or more of LiMPO4, LiFeMPO4 and Li2MP2O7; wherein M is Mn, Co or Ni; And / or, the second functional material comprises: inorganic particles, wherein the inorganic particles are configured to improve the safety of the lithium-ion battery; preferably, the inorganic particles are one or more of aluminum oxide, silicon oxide, zinc oxide, manganese oxide, calcium oxide, barium titanate and aluminum hydroxide; And / or, the conductive agent is one or more of a conductive carbon material, a metal powder, and a conductive polymer; preferably, the conductive carbon material is one or more of acetylene black, conductive carbon black, carbon nanotubes, conductive graphite, and graphene; preferably, the metal powder is one or more of aluminum powder, nickel powder, and silver powder; preferably, the conductive polymer is one or more of conductive polythiophene, conductive polypyrrolidone, and conductive polyaniline; And / or, the solvent is one or more of N-methylpyrrolidone, N-dimethylformamide, dimethyl sulfoxide, dimethylformamide, toluene, acetone, ethanol, propanol, isopropanol and ethylene glycol.

4. A current collector structure, characterized in that: include: A current collector and a coating layer coated with the slurry according to any one of claims 1 to 3.

5. The current collector structure according to claim 4, characterized in that: The current collector includes a composite current collector or a metal foil, and the metal foil is preferably an aluminum foil or a copper foil.

6. A positive electrode plate, characterized in that: include: The current collector structure according to any one of claims 4 to 5.

7. A battery cell, characterized in that: include: The positive electrode sheet as claimed in claim 6.

8. A method for preparing a current collector structure, characterized in that: include: Coating the slurry according to any one of claims 1 to 3 on the surface of the current collector; Place in a temperature-controlled environment for drying, the drying temperature is 60-120℃, and the drying time is 10-30min; After drying, a current collector structure is obtained.

9. The method for preparing the current collector structure according to claim 8, characterized in that: The coating thickness of the slurry is 3-20 μm, preferably 7-10 μm.

10. The method for preparing a current collector structure according to any one of claims 8 to 9, characterized in that: Also includes: Prepare the slurry; wherein the preparing the slurry comprises: Mixing the mixed solid and the solvent, stirring evenly to obtain the slurry; Wherein, the mixed solid includes: a polymer matrix, the mass of the polymer matrix accounts for 1-80% of the mass of the mixed solid, and the polymer matrix is ​​configured to improve the viscosity between the current collector and the active material layer; a conductive agent, the mass of the conductive agent accounts for 5-70% of the mass of the mixed solid; a functional material, the mass of the functional material accounts for 1-94% of the mass of the mixed solid, and the functional material includes a first functional material and a second functional material, the first functional material is configured to reduce the internal resistance of the lithium-ion battery, and the second functional material is configured to improve the safety of the lithium-ion battery.

11. A method for preparing a positive electrode sheet, characterized in that: The invention comprises a method for preparing the current collector structure according to any one of claims 8 to 10.

12. The method for preparing a positive electrode sheet according to claim 11, wherein: Also includes: Prepare the positive electrode slurry, including dissolving the positive electrode material, the positive electrode conductor, and the positive electrode binder in the positive electrode solvent, stirring and dispersing them uniformly to obtain the positive electrode slurry; The positive electrode slurry is coated on the outer surface of the current collector structure.

13. A method for preparing a battery cell, characterized in that: The invention comprises a method for preparing a positive electrode sheet according to any one of claims 11 to 12.

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