Modified metal foil material and preparation method thereof, pole piece and battery

Abstract

The present invention relates to the field of new energy batteries, and specifically to a modified metal foil material and a preparation method thereof, a pole piece and a battery, wherein the modified metal foil material comprises a substrate and a modified layer arranged on the surface of the substrate; wherein the material of the substrate comprises a metal foil containing hydroxyl groups on the surface; and the material of the modified layer comprises polyurethane. In the modified metal foil material of the present invention, the polyurethane is directly generated on the surface of the substrate, which can effectively avoid the inevitable capacity loss caused by the hot melt adhesive having fluidity flowing to the active material area during the coating process.

Description

Technical Field

[0001] The present invention relates to the field of new energy batteries, and in particular to a modified metal foil material and a preparation method thereof, a pole piece and a battery. Background Art

[0002] At present, the manufacturing process of batteries usually involves combining two or more winding cores, and ultrasonically welding the tabs of the two or more winding cores to the adapter. During the ultrasonic welding process, in order to meet the requirements of a greater fault tolerance, people often reserve a sufficient length of tabs to meet the ultrasonic welding operation requirements of the tabs and the adapter, which will cause the tabs to move in an inconsistent direction during the battery cell assembly process, causing some tabs to be inserted upside down into the bare battery cell, causing the positive and negative poles to contact each other and cause a short circuit, which may cause very serious safety risks.

[0003] Patent document CN116014083A discloses that the tab hot melt adhesive improves the tab inversion phenomenon; however, it does not consider whether the fluidity of the adhesive on the foil will affect welding, and if the adhesive flows to the welding point for welding, how to reduce the resistance of the tab adhesive (consistent with the internal resistance of the uncoated battery) is not considered. This patent mainly improves the above-mentioned directions for improvement, mainly modifying the surface functional groups of the foil and the hot melt adhesive, and adding highly conductive substances with corresponding functional groups to them, which effectively reduces the fluidity and the welding resistance even if the adhesive flows to the welding point. Summary of the invention

[0004] In view of this, the present invention is committed to providing a modified metal foil and its preparation method, a pole piece and a battery, so as to solve the problem in the prior art that the pole tabs have inconsistent directions during the battery cell assembly process, resulting in some pole tabs being inserted upside down into the bare battery cell, causing the positive and negative poles to contact each other and cause a short circuit, thereby causing safety risks.

[0005] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0006] A first aspect of the present invention provides a modified metal foil, the modified metal foil comprising a substrate and a modified layer disposed on the surface of the substrate;

[0007] Wherein, the material of the substrate includes a metal foil having hydroxyl groups on the surface;

[0008] The material of the modified layer includes polyurethane.

[0009] Optionally, the metal foil is selected from copper foil and / or aluminum foil; the mass ratio of the substrate to the modified layer is 1:0.04-0.1; the thickness of the metal foil is 8-15 μm; and the thickness of the modified layer is 0.1-1 nm.

[0010] A second aspect of the present invention provides a method for preparing a modified metal foil, the method comprising the following steps:

[0011] S1, mixing a metal foil, a borohydride, an ammonium salt and a first organic solvent and performing a first heating reflux treatment to obtain a first product;

[0012] S2, mixing the first product, water, an oxidant, a hydroxide and the first organic solvent and performing an oxidation reaction to obtain a second product;

[0013] S3, filtering, washing and first drying the second product to obtain a metal foil having a hydroxyl group on its surface;

[0014] S4, mixing the metal foil having a hydroxyl group on the surface, the isocyanate raw material, the conductive agent and the second organic solvent and performing a second heating reflux treatment to obtain a third product;

[0015] S5, mixing the third product, the polytetrahydrofuran raw material and the second organic solvent and performing a polymerization reaction to obtain a precipitate; and performing a second drying treatment on the precipitate.

[0016] Optionally, in step S1, the mass ratio of the metal foil, the borohydride and the ammonium salt is (3-9): (2-6): (4-8); the amount of the first organic solvent per gram of the metal foil is 50-170 mL; optionally, the metal foil is selected from copper foil and / or aluminum foil; optionally, the borohydride is selected from at least one of sodium borohydride, potassium borohydride, calcium borohydride, magnesium borohydride and lithium borohydride; optionally, the ammonium salt is selected from at least one of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium bisulfate, ammonium fluoride, ammonium carbonate and ammonium bicarbonate; optionally, the first organic solvent is selected from at least one of tetrahydrofuran, acetonitrile, formamide and acetone.

[0017] Optionally, in step S2, the mass ratio of the first product and the hydroxide is (3~20):(5~15); the amount of the first organic solvent is 25~160mL per gram of the first product; the amount of water is 25~160mL per gram of the first product; the amount of the oxidant is 0.5~25mL per gram of the first product; optionally, the oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite and sodium peroxide; optionally, the hydroxide is selected from at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide; optionally, the second organic solvent is selected from at least one of toluene, xylene and benzene.

[0018] Optionally, in step S4, the mass ratio of the metal foil containing hydroxyl groups on the surface, the isocyanate raw material and the conductive agent is (5-25): (5-10): (2-8); the amount of the second organic solvent is 1-15 mL per gram of the metal foil containing hydroxyl groups on the surface; optionally, the isocyanate raw material is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate and naphthalene 1,5-diisocyanate; optionally, the conductive agent is selected from at least one of carbon nanotubes, graphite, graphene and MXene materials.

[0019] Optionally, in step S5, the mass ratio of the third product and the polytetrahydrofuran raw material is (5-25): (1-5); the amount of the second organic solvent is 1-15 mL per gram of the third product; optionally, the polytetrahydrofuran raw material is selected from at least one of polytetrahydrofuran, poly-2-methyltetrahydrofuran and poly-2-ethyltetrahydrofuran.

[0020] Optionally, in step S1, the conditions for the first heating reflux treatment include: a heating reflux temperature of 80-100°C, and a heating reflux time of 8-16 hours; and / or, in step S2, the conditions for the oxidation reaction include: an oxidation temperature of 20-60°C, and an oxidation time of 6-10 hours; and / or, in step S3, the washing liquid used in the filtration and washing treatment includes at least one of water, ethanol and acetone; the conditions for the first drying treatment include: a drying temperature of 40-80°C, and a drying time of 8-16 hours; and / or, in step S4, the conditions for the second heating reflux treatment include: a heating reflux temperature of 100-120°C, and a heating reflux time of 4-10 hours; and / or, in step S5, the conditions for the polymerization reaction include: a polymerization temperature of 80-120°C, and a polymerization time of 8-16 hours; the conditions for the second drying treatment include: a drying temperature of 40-80°C, and a drying time of 10-16 hours.

[0021] A third aspect of the present invention provides a pole piece, comprising a pole ear and a foil material disposed on the pole ear, wherein the foil material comprises the modified metal foil material mentioned above and / or the modified metal foil material prepared according to the above preparation method.

[0022] A fourth aspect of the present invention provides a battery, comprising a pole piece, wherein the pole piece is the pole piece described above.

[0023] Through the above technical solution, the beneficial technical effects of the present invention are:

[0024] (1) In the modified metal foil of the present invention, the material of the modified layer includes polyurethane, wherein the polyurethane is directly generated on the substrate (metal foil) and connected by a chemical bond -NHCOO-, which can effectively avoid the inevitable capacity loss caused by the hot melt adhesive flowing to the active material area during the coating process due to its fluidity.

[0025] (2) The preparation method of the modified metal foil of the present invention comprises first mixing a metal foil, a borohydride, an ammonium salt and a first organic solvent and performing a first heating reflux treatment to obtain a first product (a metal foil containing a dehydrogenation product on the surface); then mixing the first product, water, an oxidant, a hydroxide and the first organic solvent and performing an oxidation reaction, and after filtering, washing and drying, obtaining a metal foil containing a hydroxyl group on the surface; then reacting a polyurethane with the hydroxyl group at the end of the metal foil to allow the polyurethane to be self-synthesized on the foil. In this process, a conductive agent is added to improve the conductivity of the polyurethane after being connected to the hydroxyl group at the end of the metal foil.

[0026] (3) In the present invention, the foil material on the tab is modified so that the tab can be kneaded after hot pressing, and the tab is not easily inverted during ultrasonic welding. The modified metal foil material arranged on the tab in the present invention includes a substrate and a modified layer material, wherein the modified layer material includes polyurethane and a small amount of conductive agent, has strong conductivity, and can reduce the change in resistance caused by ultrasonic welding.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0029] Figure 1 Shown is a schematic diagram of the positive electrode sheet prepared in Example 1.

[0030] Figure 2 Shown is a schematic diagram of the transfer welding device in Example 1.

[0031] Figure 3 Shown are the relevant reaction equations involved in the preparation process of metal foil (taking aluminum foil as an example) containing hydroxyl groups on the surface.

[0032] Figure 4 Shown are the relevant reaction equations involved in the modification process.

[0033] Figure 2The reference numerals in the figure are explained as follows: 1-first unwinding roller; 2-second unwinding roller; 3-roll welding head; 4-Al-CNT-PU; 5-pole piece conveying device; 6-welding seat; 7-welding teeth. DETAILED DESCRIPTION

[0034] The present invention discloses a modified metal foil and a preparation method thereof, a pole piece and a battery. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0035] In the description of the present invention, a list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A, B are listed, the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, C are listed, the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0036] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0037] If not otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0038] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0039] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0040] In order to solve the problem in the prior art that the tabs are not aligned in the same direction during the cell assembly process, which results in some tabs being inserted upside down into the bare cell, causing the positive and negative electrodes to contact each other and cause a short circuit, thereby causing safety risks, the present invention adopts the following technical solution:

[0041] A first aspect of the present invention provides a modified metal foil, the modified metal foil comprising a substrate and a modified layer disposed on the surface of the substrate;

[0042] Wherein, the material of the substrate includes a metal foil having hydroxyl groups on the surface;

[0043] The material of the modified layer includes polyurethane.

[0044] In the modified metal foil of the present invention, the material of the modified layer includes polyurethane, wherein the polyurethane is directly generated on the aluminum foil and connected by a chemical bond -NHCOO-, which can effectively avoid the inevitable capacity loss caused by the hot melt adhesive flowing to the active material area during the coating process due to its fluidity.

[0045] Exemplarily, the metal foil may be selected from copper foil and / or aluminum foil.

[0046] According to the present invention, a suitable mass ratio of the substrate material and the modified layer material can have the effect of enhancing the adhesion of the foil. If the ratio of the modified layer material is too high, it may cause the foil to have a larger resistance, thereby affecting electronic conduction; if the ratio of the modified layer material is too low, it may cause the adhesion of the foil to decrease. In the present invention, the mass ratio of the substrate to the modified layer can be 1:0.04~0.1. Exemplarily, the mass ratio of the substrate to the modified layer can be any of 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09 and 1:0.1 or any value within the range of any two of the above values.

[0047] According to the present invention, the thickness of the metal foil may be 8 to 15 μm. For example, the thickness of the metal foil may be any value among 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm and 15 μm, or any value within the range formed by any two of the above values.

[0048] According to the present invention, the thickness of the modified layer can have the effect of enhancing the adhesion of the foil. If the thickness of the modified layer is too large, it may cause the foil to have a large resistance, thereby affecting electronic conduction; if the thickness of the modified layer is too small, it may cause the adhesion of the foil to decrease. In the present invention, the thickness of the modified layer can be 0.1~1nm. Exemplarily, the thickness of the modified layer can be any value among 0.1nm, 0.3nm, 0.5nm, 0.7nm, 0.9nm and 1nm, or any value within the range of any two of the above values.

[0049] In the present invention, the material of the modified layer also includes a conductive agent, and the conductive ability of the polyurethane and Al-OH after connection is improved by adding the conductive agent. Exemplarily, the conductive agent can be one of carbon nanotubes (CNT), conductive carbon black (SP), graphene and MXene.

[0050] A second aspect of the present invention provides a method for preparing a modified metal foil, the method comprising the following steps:

[0051] S1, mixing a metal foil, a borohydride, an ammonium salt and a first organic solvent and performing a first heating reflux treatment to obtain a first product;

[0052] S2, mixing the first product, water, an oxidant, a hydroxide and the first organic solvent and performing an oxidation reaction to obtain a second product;

[0053] S3, filtering, washing and first drying the second product to obtain a metal foil having a hydroxyl group on its surface;

[0054] S4, mixing the metal foil having a hydroxyl group on the surface, the isocyanate raw material, the conductive agent and the second organic solvent and performing a second heating reflux treatment to obtain a third product;

[0055] S5, mixing the third product, the polytetrahydrofuran raw material and the second organic solvent and performing a polymerization reaction to obtain a precipitate; and performing a second drying treatment on the precipitate.

[0056] The preparation method of the modified metal foil of the present invention comprises the following steps: firstly mixing metal foil, borohydride, ammonium salt and a first organic solvent and performing a first heating reflux treatment to obtain a first product (a metal foil containing a dehydrogenation product on the surface); then mixing the first product, water, an oxidant, a hydroxide and the first organic solvent and performing an oxidation reaction, and after filtering, washing and drying, obtaining a metal foil containing a hydroxyl group on the surface; then reacting polyurethane with the hydroxyl group at the end of the metal foil to allow the polyurethane to be self-synthesized on the foil, and in this process, by adding a conductive agent, the conductivity of the polyurethane after being connected with the hydroxyl group at the end of the metal foil is improved.

[0057] In an exemplary embodiment of the present invention, the preparation process of the metal foil (taking aluminum foil as an example) containing hydroxyl groups on the surface involves the following reaction equations: Figure 3 shown.

[0058] Illustratively, in the preparation process of Al foil containing hydroxyl groups on the surface, borohydride and ammonium salt (such as NaBH4 and (NH4)2SO4) react in a first organic solvent to generate BH3-NH3, which is then refluxed on the Al foil to obtain dehydrogenated BH-NH2, and finally hydroxyl groups are generated on the surface of the Al foil under the action of hydroxide and oxidant (NaOH and H2O2) to obtain Al-OH.

[0059] In an exemplary embodiment of the present invention, the modified metal foil can be polyurethane and CNT modified Al foil, denoted as Al-CNT-PU. The relevant reaction equations involved in the modification process are as follows: Figure 4 shown.

[0060] According to the present invention, in step S1, the mass ratio of the metal foil, the borohydride and the ammonium salt can be (3-9): (2-6): (4-8).

[0061] In the present invention, the amount of the first organic solvent used per gram of the metal foil may be 50 to 170 mL. For example, the amount of the first organic solvent used per gram of the metal foil may be any value among 50 mL, 70 mL, 90 mL, 110 mL, 130 mL, 150 mL and 170 mL, or any value within the range of any two of the above values.

[0062] Exemplarily, the metal foil may be selected from copper foil and / or aluminum foil.

[0063] Illustratively, the borohydride may be selected from at least one of sodium borohydride, potassium borohydride, calcium borohydride, magnesium borohydride and lithium borohydride.

[0064] Illustratively, the ammonium salt may be selected from at least one of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium bisulfate, ammonium fluoride, ammonium carbonate and ammonium bicarbonate.

[0065] Illustratively, the first organic solvent may be selected from at least one of tetrahydrofuran, acetonitrile, formamide and acetone.

[0066] According to the present invention, in step S2, the mass ratio of the first product and the hydroxide can be (3-20): (5-15).

[0067] In the present invention, the amount of the first organic solvent per gram of the first product may be 25 to 160 mL. Exemplarily, the amount of the first organic solvent per gram of the first product may be any value among 25 mL, 50 mL, 70 mL, 90 mL, 110 mL, 130 mL, 150 mL and 160 mL, or any value within the range of any two of the above values.

[0068] In the present invention, the amount of water per gram of the first product can be 25 to 160 mL. Exemplarily, the amount of water per gram of the first product can be any value among 25 mL, 50 mL, 70 mL, 90 mL, 110 mL, 130 mL, 150 mL and 160 mL, or any value within the range of any two of the above values.

[0069] In the present invention, the amount of the oxidant can be 0.5 to 25 mL per gram of the first product. For example, the amount of the oxidant can be any value among 0.5 mL, 1 mL, 5 mL, 10 mL, 15 mL, 20 mL and 25 mL per gram of the first product, or any value within the range of any two of the above values.

[0070] Exemplarily, the oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite and sodium peroxide.

[0071] Illustratively, the hydroxide is selected from at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0072] Illustratively, the second organic solvent is selected from at least one of toluene, xylene and benzene.

[0073] According to the present invention, in step S4, the mass ratio of the metal foil containing hydroxyl groups on the surface, the isocyanate raw material and the conductive agent can be (5-25): (5-10): (2-8).

[0074] In the present invention, the amount of the second organic solvent can be 1 to 15 mL per gram of the metal foil containing hydroxyl groups on the surface. For example, the amount of the second organic solvent can be any value among 1 mL, 5 mL, 10 mL and 15 mL per gram of the metal foil containing hydroxyl groups on the surface, or any value within the range of any two of the above values.

[0075] Illustratively, the isocyanate raw material may be selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, and naphthalene 1,5-diisocyanate.

[0076] Exemplarily, the conductive agent may be selected from at least one of carbon nanotubes, graphite, graphene and MXene materials.

[0077] According to the present invention, in step S5, the mass ratio of the third product and the polytetrahydrofuran raw material can be (5-25): (1-5).

[0078] In the present invention, the amount of the second organic solvent can be 1 to 15 mL per gram of the third product. For example, the amount of the second organic solvent can be any one of 1 mL, 5 mL, 10 mL and 15 mL per gram of the third product, or any value within the range of any two of the above values.

[0079] Illustratively, the polytetrahydrofuran raw material may be selected from at least one of polytetrahydrofuran, poly-2-methyltetrahydrofuran and poly-2-ethyltetrahydrofuran.

[0080] According to the present invention, in step S1, the conditions of the first heating reflux treatment may include: a heating reflux temperature of 80-100° C. and a heating reflux time of 8-16 hours.

[0081] According to the present invention, in step S2, the conditions of the oxidation reaction may include: an oxidation temperature of 20-60° C. and an oxidation time of 6-10 h.

[0082] According to the present invention, in step S3, the washing liquid used in the filter washing treatment may include at least one of water, ethanol and acetone; the conditions of the first drying treatment may include: a drying temperature of 40-80°C and a drying time of 8-16h.

[0083] According to the present invention, in step S4, the conditions of the second heating reflux treatment may include: a heating reflux temperature of 100-120° C., and a heating reflux time of 4-10 hours.

[0084] According to the present invention, in step S5, the conditions of the polymerization reaction may include: a polymerization temperature of 80-120° C., and a polymerization time of 8-16 hours; the conditions of the second drying treatment may include: a drying temperature of 40-80° C., and a drying time of 10-16 hours.

[0085] A third aspect of the present invention provides a pole piece, comprising a pole ear and a foil material disposed on the pole ear, wherein the foil material comprises the modified metal foil material mentioned above and / or the modified metal foil material prepared according to the above preparation method.

[0086] In the pole piece of the present invention, the pole tab and the foil on the pole tab can be connected by transfer welding, and the self-synthesis of hot melt adhesive on the foil surface can be well achieved by transfer welding. Figure 2 As shown, the conventional foil passes through the unwinding mechanism to the circular welding head part, and then ultrasonic welding is performed after the contact with the pole piece and the pole ear brought by the belt. In the present invention, the foil on the pole ear is modified so that the pole ear can be kneaded after hot pressing, and it is not easy to cause the pole ear to be inverted during the ultrasonic welding process. The modified metal foil arranged on the pole ear in the present invention includes a substrate and a modified layer material, wherein the modified layer material includes polyurethane and a small amount of conductive agent, has strong conductivity, and can reduce the change in resistance value caused by ultrasonic welding.

[0087] A fourth aspect of the present invention provides a battery, comprising a pole piece, wherein the pole piece is the pole piece described above.

[0088] The present invention is further described in detail by way of examples. The raw materials used in the examples can be obtained through commercial sources.

[0089] Example 1

[0090] (1) Preparation of Al-OH

[0091] 6g of conventional aluminum foil is placed in a reaction vessel, and then 4g of sodium borohydride, 6g of ammonium sulfate, and then 500mL of the first solvent tetrahydrofuran are added thereto, and a mixture is obtained after mixing; the mixture is heated and refluxed at a temperature of 90°C for 12h, and cooled to room temperature to obtain a dehydrogenated product on the aluminum foil; then 500mL of deionized water is added, and an oxidation reaction is carried out with 30mL of hydrogen peroxide and 10g of sodium hydroxide in a mixture of the first solvent such as tetrahydrofuran and water, and the mixture is oxidized at about 40°C; then, the obtained substance is filtered, washed with hot water, and then washed with ethanol and acetone. The product is dried at 60°C in a vacuum oven for 12h to obtain a dried substance, i.e., Al foil containing hydroxyl groups, which can be recorded as Al-OH.

[0092] (2) Preparation of Al-CNT-PU

[0093] The prepared Al foil containing hydroxyl groups, 7 g of toluene diisocyanate and 5 g of carbon nanotubes (CNT) are added to a reaction container, and a second solvent, toluene, is added to mix to obtain a mixture; the reaction container is heated to 110°C, and heated under reflux for 7 hours under oil bath conditions. When all the Al foil containing hydroxyl groups and toluene diisocyanate (the mass ratio of aluminum foil to toluene diisocyanate is 0.86:1) are reacted completely, 3 g of polytetrahydrofuran and 40 mL of the second solvent, toluene, are added thereto, and the reactants are allowed to polymerize for 12 hours to completely polymerize to obtain a precipitate; the precipitate is dried in a vacuum oven at a drying temperature of 60°C for a drying time of 12 hours to obtain polyurethane and CNT-modified Al, which can be recorded as Al-CNT-PU.

[0094] (3) Preparation of positive electrode

[0095] The positive electrode active material ternary 6 series (LiNi 0.6 Co 0.2 Mn 0.2 O2) powder, conductive carbon and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 8:1:1 to obtain a mixed material, the mixed material is fully stirred in N-methylpyrrolidone (NMP) to obtain a positive electrode active slurry of the corresponding positive electrode sheet, the positive electrode active slurry is coated on a conventional aluminum foil to obtain a plate content of LiNi0.6Co0.2Mn0.2O2 with a mass fraction of 80wt%, and after drying and pressing, a first positive electrode plate is obtained.

[0096] The modified foil (Al-CNT-PU) is transferred to the ear of the first positive electrode plate by transfer welding, and then die-cut to obtain the final positive electrode plate. The transfer welding steps include: the conventional foil passes through the unwinding mechanism to the circular welding head part, and then contacts with the electrode plate ear brought by the conveyor belt and then ultrasonic welding is performed (such as Figure 2 As shown in Figure 7, the enlarged view of the welding head shows that the surface contains many welding teeth. Figure 1 shown.

[0097] (4) Preparation of negative electrode sheet

[0098] The negative electrode active material graphite powder, conductive carbon and PVDF were mixed in a mass ratio of 8:1:1 to obtain a mixed material, and the mixed material was fully stirred in deionized water to obtain a negative electrode active slurry of the corresponding negative electrode sheet. The negative electrode active slurry was coated on a conventional copper foil to obtain a main material graphite mass fraction of 80wt% and a negative electrode slurry surface density of 1.21mg / cm 2 The negative electrode slurry coating is dried and pressed into sheets to obtain a first negative electrode sheet.

[0099] The prepared modified foil (Al-CNT-PU) is transfer-welded to the tab of the first negative electrode plate, and then die-cut to obtain the final negative electrode plate.

[0100] (5) Preparation of lithium-ion batteries

[0101] Ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:2:1 to obtain a mixed organic solvent, and then fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare an electrolyte.

[0102] The prepared positive electrode sheet, negative electrode sheet and PE separator are wound to obtain the corresponding winding core, and then the main liquid injection, formation and capacity separation are carried out into the shell to obtain the corresponding aluminum shell battery.

[0103] Example 2

[0104] The preparation method of Al-OH in this embodiment is generally the same as that in Embodiment 1, except that the amount of sodium borohydride added is 2 g.

[0105] The preparation method of Al-CNT-PU, the preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium-ion battery in this embodiment are the same as those in Example 1.

[0106] Example 3

[0107] The preparation method of Al-OH in this embodiment is generally the same as that in Embodiment 1, except that the amount of sodium borohydride added is 6 g.

[0108] The preparation method of Al-CNT-PU, the preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium-ion battery in this embodiment are the same as those in Example 1.

[0109] Example 4

[0110] The preparation method of Al-OH in this embodiment is generally the same as that in Embodiment 1, except that the amount of ammonium sulfate added is 4 g.

[0111] The preparation method of Al-CNT-PU, the preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium-ion battery in this embodiment are the same as those in Example 1.

[0112] Example 5

[0113] The preparation method of Al-OH in this embodiment is generally the same as that in Embodiment 1, except that the amount of ammonium sulfate added is 8 g.

[0114] The preparation method of Al-CNT-PU, the preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium-ion battery in this embodiment are the same as those in Example 1.

[0115] Example 6

[0116] The preparation method of Al-OH in this example is the same as that in Example 1.

[0117] The preparation method of Al-CNT-PU in this embodiment is generally the same as that in Embodiment 1, except that the amount of toluene diisocyanate added is 5 g (the mass ratio of aluminum foil to toluene diisocyanate is 1.2:1).

[0118] The preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium ion battery in this embodiment are the same as those in Embodiment 1.

[0119] Example 7

[0120] The preparation method of Al-OH in this example is the same as that in Example 1.

[0121] The preparation method of Al-CNT-PU in this embodiment is generally the same as that in Embodiment 1, except that the amount of toluene diisocyanate added is 10 g (the mass ratio of aluminum foil to toluene diisocyanate is 0.6:1).

[0122] The preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium ion battery in this embodiment are the same as those in Embodiment 1.

[0123] Example 8

[0124] The preparation method of Al-OH in this example is the same as that in Example 1.

[0125] The preparation method of Al-CNT-PU in this embodiment is generally the same as that in Embodiment 1, except that the amount of CNT added is 2 g.

[0126] The preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium ion battery in this embodiment are the same as those in Embodiment 1.

[0127] Example 9

[0128] The preparation method of Al-OH in this example is the same as that in Example 1.

[0129] The preparation method of Al-CNT-PU in this embodiment is generally the same as that in Embodiment 1, except that the amount of CNT added is 8 g.

[0130] The preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium ion battery in this embodiment are the same as those in Embodiment 1.

[0131] Example 10

[0132] The preparation method of Al-OH in this example is the same as that in Example 1.

[0133] The preparation method of Al-CNT-PU in this embodiment is generally the same as that in Embodiment 1, except that the amount of polytetrahydrofuran added is 1 g.

[0134] The preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium ion battery in this embodiment are the same as those in Embodiment 1.

[0135] Embodiment 11

[0136] The preparation method of Al-OH in this example is the same as that in Example 1.

[0137] The preparation method of Al-CNT-PU in this embodiment is generally the same as that in Embodiment 1, except that the amount of polytetrahydrofuran added is 5 g.

[0138] The preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium ion battery in this embodiment are the same as those in Embodiment 1.

[0139] Comparative Example 1

[0140] (1) Preparation of positive electrode

[0141] The positive electrode active material ternary 6 series (LiNi 0.6 Co 0.2 Mn 0.2 O2) powder, conductive carbon and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 8:1:1 to obtain a mixed material, and the mixed material is fully stirred in N-methylpyrrolidone (NMP) to obtain a positive electrode active slurry of the corresponding positive electrode sheet, and the positive electrode active slurry is coated on a conventional aluminum foil to obtain a LiNi electrode sheet with a content of 1.5 0.6 Co 0.2 Mn 0.2 The mass fraction of O2 is 80wt%, and after drying and tableting, the first positive electrode sheet is obtained.

[0142] The epoxy resin is coated on the tab of the first positive electrode plate to obtain the final positive electrode plate.

[0143] (2) Preparation of negative electrode

[0144] The negative electrode active material graphite powder, conductive carbon and PVDF were mixed in a mass ratio of 8:1:1 to obtain a mixed material, and the mixed material was fully stirred in deionized water to obtain a negative electrode active slurry of the corresponding negative electrode sheet. The negative electrode active slurry was coated on a conventional copper foil to obtain a main material graphite mass fraction of 80wt% and a negative electrode slurry surface density of 1.21mg / cm 2 The negative electrode slurry coating is dried and pressed into sheets to obtain a first negative electrode sheet.

[0145] The phenolic resin is coated on the tab of the first negative electrode plate, and then die-cut to obtain the final negative electrode plate.

[0146] (3) Preparation of lithium-ion batteries

[0147] The preparation method of the lithium ion battery in this comparative example is the same as that in Example 1.

[0148] Comparative Example 2

[0149] The preparation method of Al-OH in this comparative example is the same as that in Example 1.

[0150] Preparation of Al-CNT-PU: Polyurethane reacts with the hydroxyl group at the end of Al foil (this polyurethane is self-synthesized on the foil): the prepared Al foil containing hydroxyl groups and 7g toluene diisocyanate are added to a reaction container, and a second solvent, toluene, is added to mix to obtain a mixture; the reaction container is heated to 110°C, and heated to reflux for 7 hours under oil bath conditions. When all the Al foil containing hydroxyl groups and toluene diisocyanate (the mass ratio of aluminum foil to toluene diisocyanate is 0.86:1) are reacted completely, 3g polytetrahydrofuran and 40mL of the second solvent toluene are added thereto, and the reactants are allowed to polymerize for 12 hours to obtain a precipitate; the precipitate is dried in a vacuum oven at a drying temperature of 60°C and a drying time of 12 hours to obtain polyurethane-modified Al, which can be recorded as Al-PU.

[0151] The preparation method of the positive electrode sheet, the preparation method of the negative electrode sheet and the preparation method of the lithium ion battery in this comparative example are the same as those in Example 1.

[0152] Comparative Example 3

[0153] (1) Preparation of positive electrode

[0154] The positive electrode active material ternary 6 series (LiNi 0.6 Co 0.2 Mn 0.2 O2) powder, conductive carbon and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 8:1:1 to obtain a mixed material, and the mixed material is fully stirred in N-methylpyrrolidone (NMP) to obtain a positive electrode active slurry of the corresponding positive electrode sheet, and the positive electrode active slurry is coated on a conventional aluminum foil to obtain a LiNi electrode sheet with a content of 1.5 0.6 Co 0.2 Mn 0.2 The mass fraction of O2 is 80wt%, and after drying and tableting, the first positive electrode sheet is obtained.

[0155] The untreated conventional aluminum foil is transfer welded to the tab of the first positive electrode sheet to obtain the final positive electrode sheet.

[0156] (2) Preparation of negative electrode

[0157] The negative electrode active material graphite powder, conductive carbon and PVDF were mixed in a mass ratio of 8:1:1 to obtain a mixed material, and the mixed material was fully stirred in deionized water to obtain a negative electrode active slurry of the corresponding negative electrode sheet. The negative electrode active slurry was coated on a conventional copper foil to obtain a main material graphite mass fraction of 80wt% and a negative electrode slurry surface density of 1.21mg / cm 2The negative electrode slurry coating is dried and pressed into sheets to obtain a first negative electrode sheet.

[0158] The untreated conventional aluminum foil is transferred and welded to the tab of the first negative electrode plate, and then die-cut to obtain the final negative electrode plate.

[0159] (3) Preparation of lithium-ion batteries

[0160] The preparation method of the lithium ion battery in this comparative example is the same as that in Example 1.

[0161] Test Example 1

[0162] The lithium ion batteries obtained in Examples 1 to 11 and Comparative Examples 1 to 3 were tested for initial coulombic efficiency, battery resistance, and cycle capacity retention rate. The test results are shown in Table 1.

[0163] (1) First coulombic efficiency (first efficiency) test method: First, the battery is charged to 3.75V at a constant current of 0.1C. This step is the formation stage of the battery SEI film, and the battery capacity C1 after formation is recorded. Secondly, the battery is fully charged at a constant current of 1C to 4.4V and a constant voltage of 4.4V to I≤0.05C, and the charge capacity C2 is recorded. Finally, the battery discharge capacity C3 is obtained by discharging at a constant current of 1C to 2.8V, and the first coulombic efficiency is calculated according to the formula C3 / (C1+C2).

[0164] (2) Battery internal resistance test method: The battery internal resistance is measured using a battery internal resistance meter.

[0165] (3) Cycle capacity retention rate test method: Test according to steps a. 1C constant current discharge to 2.8V; b. Stand for 30 minutes; c. 1C constant current charge to 4.4V; d. Stand for 30 minutes; e. 1C constant current discharge to 2.8V; f. Stand for 30 minutes. Repeat steps c to f, record the battery capacity C4 after 300 cycles, and calculate the capacity retention rate using C4 / C3.

[0166] Table 1

[0167]

[0168] It can be seen from Table 1 that in the embodiment of the present invention, by respectively arranging the modified metal foil on the tabs of the positive electrode sheet and the negative electrode sheet, the first coulombic efficiency and cycle capacity retention rate of the lithium-ion battery can be significantly improved, and the internal resistance of the battery can be reduced to a certain extent.

[0169] Test Example 2

[0170] 500 batteries were manufactured according to the corresponding preparation processes for Example 1, Comparative Example 1 and Comparative Example 3, and the tab inversion phenomenon was counted. The statistical results are shown in Table 2.

[0171] Table 2

[0172]

[0173] It can be seen from Table 2 that the number of inverted tabs in Example 1 is significantly reduced, and the quality rate is significantly improved. Therefore, the embodiments of the present invention can effectively solve the problem in the prior art that the tabs are inconsistent in direction during the battery cell assembly process, resulting in some tabs being inverted into the bare battery cell, causing the positive and negative electrodes to contact each other and cause a short circuit, thereby improving the safety performance of lithium-ion batteries.

[0174] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a modified metal foil, characterized in that: The preparation method comprises the following steps: S1, mixing a metal foil, a borohydride, an ammonium salt and a first organic solvent and performing a first heating reflux treatment to obtain a first product; S2, mixing the first product, water, an oxidant, a hydroxide and the first organic solvent and performing an oxidation reaction to obtain a second product; S3, filtering, washing and first drying the second product to obtain a metal foil having a hydroxyl group on its surface; S4, mixing the metal foil having a hydroxyl group on the surface, the isocyanate raw material, the conductive agent and the second organic solvent and performing a second heating reflux treatment to obtain a third product; S5, mixing the third product, the polytetrahydrofuran raw material and the second organic solvent and performing a polymerization reaction to obtain a precipitate; and performing a second drying treatment on the precipitate.

2. The preparation method according to claim 1, characterized in that: In step S1, the mass ratio of the metal foil, the borohydride and the ammonium salt is (3-9): (2-6): (4-8); The amount of the first organic solvent used is 50-170 mL per gram of the metal foil; The metal foil is selected from copper foil and / or aluminum foil; The borohydride is selected from at least one of sodium borohydride, potassium borohydride, calcium borohydride, magnesium borohydride and lithium borohydride; The ammonium salt is selected from at least one of ammonium sulfate, ammonium nitrate, ammonium chloride, ammonium bisulfate, ammonium fluoride, ammonium carbonate and ammonium bicarbonate; The first organic solvent is selected from at least one of tetrahydrofuran, acetonitrile, formamide and acetone.

3. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of the first product and the hydroxide is (3-20): (5-15); The amount of the first organic solvent is 25-160 mL per gram of the first product; The amount of water used is 25-160 mL per gram of the first product; The amount of the oxidant is 0.5-25 mL per gram of the first product; The oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite and sodium peroxide; The hydroxide is selected from at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide; The second organic solvent is selected from at least one of toluene, xylene and benzene.

4. The preparation method according to claim 1, characterized in that: In step S4, the metal foil having a hydroxyl group on the surface, the isocyanate raw material and the conductive agent are mixed in a mass ratio of (5-25): (5-10): (2-8); The amount of the second organic solvent is 1-15 mL per gram of the metal foil having hydroxyl groups on the surface; The isocyanate raw material is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate and naphthalene 1,5-diisocyanate; The conductive agent is selected from at least one of carbon nanotubes, graphite, graphene and MXene materials.

5. The preparation method according to claim 1, characterized in that: In step S5, the mass ratio of the third product and the polytetrahydrofuran raw material is (5-25): (1-5); The amount of the second organic solvent used is 1-15 mL per gram of the third product; The polytetrahydrofuran raw material is selected from at least one of polytetrahydrofuran, poly-2-methyltetrahydrofuran and poly-2-ethyltetrahydrofuran.

6. The preparation method according to claim 1, characterized in that: In step S1, the first heating reflux treatment conditions include: heating reflux temperature of 80-100° C., heating reflux time of 8-16 hours; and / or, In step S2, the conditions of the oxidation reaction include: oxidation temperature of 20-60° C., oxidation time of 6-10 h; and / or, In step S3, the washing liquid used in the filter washing treatment includes at least one of water, ethanol and acetone; the conditions of the first drying treatment include: a drying temperature of 40-80° C. and a drying time of 8-16 hours; and / or, In step S4, the conditions of the second heating reflux treatment include: the heating reflux temperature is 100-120° C., the heating reflux time is 4-10 hours; and / or, In step S5, the conditions of the polymerization reaction include: a polymerization temperature of 80-120° C., and a polymerization time of 8-16 hours; the conditions of the second drying treatment include: a drying temperature of 40-80° C., and a drying time of 10-16 hours.

7. A modified metal foil, characterized in that: The modified metal foil is prepared according to the preparation method according to any one of claims 1 to 6; The modified metal foil comprises a substrate and a modified layer arranged on the surface of the substrate; Wherein, the material of the substrate includes a metal foil having hydroxyl groups on the surface; The material of the modified layer includes polyurethane.

8. The modified metal foil according to claim 7, characterized in that: The metal foil is selected from copper foil and / or aluminum foil; The mass ratio of the substrate to the modified layer is 1:0.04-0.1; The thickness of the metal foil is 8-15 μm; The thickness of the modified layer is 0.1-1 nm.

9. A pole piece, characterized in that: The pole piece includes a pole ear and a foil material arranged on the pole ear, wherein the foil material includes a modified metal foil material prepared by the preparation method according to any one of claims 1 to 6 or a modified metal foil material according to claim 7 or 8.

10. A battery, characterized in that: The battery comprises a pole piece, wherein the pole piece is the pole piece according to claim 9.

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