A dual-component lithium ion battery cathode material and a preparation method thereof

Abstract

The application discloses a kind of two-component lithium ion battery positive electrode material and preparation method thereof, it is related to the field of battery material.Therein, two-component lithium ion battery positive electrode material includes A component and B component, the A component includes 2-10 weight parts first binder, 1-4 weight parts second binder, 0.05-1 weight parts dispersing agent, 80-90 weight parts active substance, 1-10 weight parts conductive agent and 20-100 weight parts first solvent;The first binder selects hydroxyl resin, the second binder selects polyurethane resin, polyester resin, organic silicon resin, organic fluorine resin any one or several combinations thereof;The B component is isocyanate curing agent;The weight ratio of A component and B component is (20-55):1.The positive electrode material of the application has the advantages of strong adhesion with aluminum foil, capacity cycle stability and high safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery materials, and in particular to a dual-component lithium ion battery positive electrode material and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries have the advantages of high working voltage, large energy density, small self-discharge, no memory effect, etc., and are currently a commonly used portable ideal battery, which can be applied to electronic devices such as camcorders, mobile phones, notebook computers, etc., and is also the preferred power source for electric vehicles, aerospace, satellites, submarines, underwater robots, etc.

[0003] The positive and negative electrode materials are the most core components of lithium ion batteries and are the focus of research. However, there are relatively few reports on the auxiliary binder in the electrode.

[0004] Among them, in the preparation process of the positive electrode sheet, the binder mainly plays the role of bonding the active material, bonding the active material and the current collector, and buffering the volume expansion of the electrode during use. Although the amount of binder in the electrode is small, it plays a crucial role in battery performance.

[0005] At present, the common positive electrode binder is a fluorine-containing polymer. For example, patent application No. CN107958997A discloses a positive electrode slurry, a positive electrode sheet and a lithium ion battery. The positive electrode slurry comprises a positive electrode active material, a conductive agent and a binder. The positive electrode active material comprises first positive electrode active material particles with a pH value of ≥11.5. The binder comprises a fluorine-containing polymer selected from one or more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, vinylidene fluoride-trifluorochloroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. Among them, according to the test data, the adhesion of the positive electrode sheet is only 180 N / m at most.

[0006] That is, when a fluorine-containing polymer is used as a binder, the adhesion between the binder and the active material or the aluminum foil current collector is still less than 200 N / m, which can easily cause problems such as cracking and peeling of the active material, and there is a certain safety hazard. Therefore, it is of great significance to further effectively improve the adhesion between the binder and the active material or the aluminum foil current collector. SUMMARY

[0007] In order to improve the problem of poor adhesion between the binder and the active material or the aluminum foil current collector in the related art, the present application provides a dual-component lithium ion battery positive electrode material and a preparation method thereof.

[0008] The application provides a two-component lithium ion battery positive electrode material.

[0009] A two-component lithium ion battery positive electrode material comprises an A component and a B component, wherein the A component comprises 2-10 parts by weight of a first binder, 1-4 parts by weight of a second binder, 0.05-1 part by weight of a dispersing agent, 80-90 parts by weight of an active substance, 1-10 parts by weight of a conductive agent and 20-100 parts by weight of a first solvent.

[0010] The first binder is selected from hydroxyl resins, and the second binder is selected from any one or combination of polyurethane resins, polyester resins, silicone resins and organic fluorine resins.

[0011] The B component is an isocyanate curing agent.

[0012] The weight ratio of the A component to the B component is (20-55):1.

[0013] The main difference between the application and the related art positive electrode material is that the positive electrode material comprises the A component and the B component, wherein the B component promotes the curing of the slurry, is added into the A component before use, can effectively prevent the thickening or local gelation of the positive electrode material during storage, and effectively improves the processability of the positive electrode material.

[0014] Secondly, compared with the single-component binder, the hydroxyl resin and the isocyanate in the application react to form new chemical bonds, which can effectively improve the bonding performance between the binder and the active substance and the bonding performance between the positive electrode material and the aluminum foil, and promote the bonding stability of the positive electrode material and the capacity retention rate of the lithium ion battery after cyclic charging and discharging.

[0015] In addition, the second binder is also added in the application, and the second binder can be selected according to different performance requirements. The addition of the polyurethane resin can further adjust the flexibility of the binder, and the addition of the silicone resin or the organic fluorine resin can further adjust the high-temperature resistance of the binder. The specific selection can be made according to the actual scene requirements.

[0016] Optionally, the first binder comprises hydroxyl acrylic resin and hydroxyl silicone resin, and the weight ratio of the hydroxyl acrylic resin to the hydroxyl silicone resin is (3.8-4.2):1.

[0017] When the first binder is selected from the combination of the hydroxyl acrylic resin and the hydroxyl silicone resin with a weight ratio of (3.8-4.2):1, the bonding stability between the positive electrode material and the aluminum foil and the dimensional stability of the positive electrode material in a high-temperature environment are improved, which is conducive to improving the capacity retention rate of the lithium ion battery after cyclic charging and discharging and the capacity retention rate in a high-temperature environment.

[0018] Optionally, the hydroxyl acrylate resin comprises the following raw materials by weight:

[0019] Structural monomer: 30-33 parts

[0020] Acid monomer: 5-22 parts

[0021] Functional monomer: 23-26 parts

[0022] Chain transfer agent: 1-3 parts

[0023] Initiator: 0.4-0.6 parts

[0024] Catalyst: 0.1-0.3 parts

[0025] Second solvent: 100 parts

[0026] The structural monomer is selected from any one or combination of methyl methacrylate, butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-isooctyl acrylate, dodecyl acrylate, tetradecyl acrylate, octadecyl acrylate, acrylonitrile, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, N,N-dimethyl acrylamide, and styrene;

[0027] The acid monomer is selected from any one or combination of acrylic acid, methacrylic acid, butenoic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and anhydrides of the above acid monomers;

[0028] The functional monomer is selected from any one or combination of hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate;

[0029] The chain transfer agent is selected from any one or combination of n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, mercaptoethanol, ethylene glycol, and isopropyl alcohol; the initiator is selected from any one or combination of benzoyl peroxide and azobisisobutyronitrile; and the catalyst is selected from any one or combination of zinc glutarate and zinc iso-octoate;

[0030] The second solvent is selected from any one or combination of toluene, o-xylene, p-xylene, m-xylene, ethyl acetate, butyl acetate, pentyl acetate, isoamyl acetate, cyclohexanone, N-methyl pyrrolidone, N-ethyl pyrrolidone, ethylene glycol ethyl ether acetate, ethylene glycol methyl ether, ethylene glycol methyl ether acetate, dipropylene glycol, and dipropylene glycol methyl ether.

[0031] Optionally, the structural monomer is selected from styrene and dodecyl acrylate, and the weight ratio of the styrene and dodecyl acrylate is 3: (4.5-5.5).

[0032] When the structural monomer is selected from a composition of styrene and dodecyl acrylate with a weight ratio of 3: (4.5-5.5), the temperature resistance of the positive electrode material is further improved, and the dimensional stability of the positive electrode material in a high-temperature environment is effectively improved.

[0033] Optionally, the acidic monomer is selected from a composition of maleic acid and itaconic anhydride, and the weight ratio of the maleic acid and itaconic anhydride is (1-2):3.

[0034] When the acidic monomer is selected from a composition of maleic acid and itaconic anhydride with a weight ratio of (1-2):3, the bonding stability between the positive electrode material and the aluminum foil is greatly improved, so that the capacity retention rate of the lithium ion battery prepared by using the positive electrode material is still maintained at more than 88% after 1000 cycles of charging and discharging. The reason may be that when the above-mentioned combined acidic monomer is used, the interfacial bonding force between the binder and the active material and the conductive agent is greatly enhanced. At the same time, the binder also has high elasticity and high adhesion, which can maintain the bonding stability between the positive electrode material and the aluminum foil after multiple charging and discharging cycles, and maintain the stability of the active material and the conductive agent in the positive electrode material.

[0035] Optionally, the second binder includes polyurethane resin and organic fluorine resin, and the weight ratio of the polyurethane resin and the organic fluorine resin is (2.5-3.5):1.

[0036] When the second binder is selected from a composition of polyurethane resin and organic fluorine resin with a weight ratio of (2.5-3.5):1, the temperature resistance of the positive electrode material can be further improved while maintaining the bonding stability between the positive electrode material and the aluminum foil, which promotes the capacity retention rate of the lithium ion battery prepared by using the positive electrode material in a high-temperature environment.

[0037] Optionally, the dispersant is selected from any one or a combination of VOK-Disper 3031 dispersant and YTF003 dispersant.

[0038] The VOK-Disper 3031 dispersant and the YTF003 dispersant can effectively promote the dispersion performance of the active material and the positive material in the binder of the present application.

[0039] Optionally, the active material includes lithium cobaltate and ternary nickel-cobalt-manganese material, and the weight ratio of the lithium cobaltate and the ternary nickel-cobalt-manganese material is 5: (10-15).

[0040] The active substance is selected from a combination of lithium cobaltate and ternary nickel-cobalt-manganese material in a weight ratio of 5: (10-15), which can further improve the capacity retention rate of the lithium ion battery after cyclic charging and discharging and in a high temperature environment.

[0041] Optionally, the conductive agent is selected from any one or a combination of acetylene black, superconducting carbon black, conductive graphite and conductive carbon fiber.

[0042] The acetylene black, superconducting carbon black, conductive graphite and conductive carbon fiber all have good conductivity, can form a conductive network on the surface of the active substance, accelerate the electron transmission rate, and can absorb and retain electrolyte to provide more electrolyte cross section for lithium ions, thereby improving the charging efficiency of the battery and prolonging the service life of the battery.

[0043] In a second aspect, the application provides a preparation method of a two-component lithium ion battery positive electrode material, which adopts the following technical scheme:

[0044] A preparation method of a two-component lithium ion battery positive electrode material, comprising the following steps:

[0045] (1) mixing and stirring the first binder, part of the first solvent, the active substance and part of the conductive agent to obtain a first mixture;

[0046] (2) adding the remaining conductive agent to the first mixture obtained in step (1) and mixing and stirring to obtain a second mixture;

[0047] (3) adding the second binder to the second mixture obtained in step (2) and mixing and stirring to obtain a third mixture;

[0048] (4) adding the remaining first solvent to the third mixture obtained in step (3) and mixing uniformly, and then filtering to obtain the A component;

[0049] (5) when used, the B component is added to the A component obtained in step (4) according to the proportion, and then mixed uniformly to obtain the lithium ion battery positive electrode material.

[0050] The first solvent and the conductive agent are added in batches, which is beneficial to shorten the stirring time and improve the dispersion efficiency.

[0051] In summary, the technical scheme of the application has the following beneficial effects:

[0052] 1. The positive electrode material in the application has the advantages of strong interfacial bonding force between the binder and the active substance and strong adhesion to aluminum foil;

[0053] 2. The positive electrode material in the application has good size stability and high capacity retention rate after cyclic charging and discharging in a high temperature environment. DETAILED DESCRIPTION

[0054] The present application will be further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0055] A hydroxyl acrylic resin, comprising the following raw materials in parts by weight:

[0056] Structural monomers: 30-33 parts

[0057] Acidic monomers: 5-22 parts

[0058] Functional monomers: 23-26 parts

[0059] Chain transfer agent: 1-3 parts

[0060] Initiator: 0.4-0.6 parts

[0061] Catalyst: 0.1-0.3 parts

[0062] Second solvent: 100 parts

[0063] The structural monomer is selected from any one or a combination of several of the following: methyl methacrylate, butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-isooctyl acrylate, dodecyl acrylate, tetradecyl acrylate, octadecyl acrylate, acrylonitrile, acrylamide, methacrylamide, N-hydroxymethylacrylamide, N,N-dimethylacrylamide, and styrene.

[0064] The acidic monomer is selected from any one or a combination of several of the following: acrylic acid, methacrylic acid, butenoic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and acid anhydrides of the above acidic monomers.

[0065] The functional monomer is selected from any one or a combination of several of hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

[0066] The chain transfer agent is selected from any one or a combination of several of the following: n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butanethiol, mercaptoethanol, ethylene glycol, and isopropanol.

[0067] The initiator is selected from benzoyl peroxide and azobisisobutyronitrile, or a combination of two of them; the catalyst is selected from zinc glutarate and zinc isooctanoate, or a combination of several of them.

[0068] The second solvent is selected from any one or combination of toluene, o-xylene, p-xylene, m-xylene, ethyl acetate, butyl acetate, amyl acetate, isoamyl acetate, cyclohexanone, N-methyl pyrrolidone, N-ethyl pyrrolidone, ethylene glycol ethyl ether acetate, ethylene glycol methyl ether, ethylene glycol methyl ether acetate, dipropylene glycol, and dipropylene glycol methyl ether.

[0069] The following is described with specific preparation examples 1-8, wherein the raw material ratio of the hydroxyl acrylic resin in preparation examples 1-8 is as follows in Table 1:

[0070] Table 1 Raw material ratio of the hydroxyl acrylic resin in preparation examples 1-8 (unit / g)

[0071]

[0072] The preparation method of the hydroxyl acrylic resin in preparation examples 1-8 includes the following steps:

[0073] The structural monomer, functional monomer, acidic monomer, catalyst, and chain transfer agent are added to 70 g of the second solvent, nitrogen is introduced to remove air, the temperature is raised to 60°C at a rate of 1.5°C / min, and refluxed for 1 h to obtain the reaction material;

[0074] The initiator is dissolved in 30 g of the second solvent to obtain an initiator solution;

[0075] The initiator solution is added to the reaction material at a rate of 1-2 drops / s, and reacted at 75°C for 3 h to obtain the hydroxyl acrylic resin. Embodiment

[0076] A two-component lithium ion battery positive electrode material includes an A component and a B component, and the weight ratio of the A component to the B component is (20-55):1; wherein the A component contains 2-10 parts by weight of a first binder, 1-4 parts by weight of a second binder, 0.05-1 part by weight of a dispersant, 80-90 parts by weight of an active material, 1-10 parts by weight of a conductive agent, and 20-100 parts by weight of a first solvent.

[0077] The first binder is selected from any one or combination of hydroxyl resin, polyurethane resin, polyester resin, silicone resin, and organic fluorine resin.

[0078] The dispersant is selected from any one or combination of VOK-Disper 3031 dispersant and YTF003 dispersant; the VOK-Disper 3031 dispersant is from Germany Voker, and the YTF003 dispersant is from Shenzhen Yite Technology Co., Ltd.

[0079] The active material is selected from any one or combination of lithium cobaltate, ternary nickel-cobalt-manganese material; preferably, the active material comprises lithium cobaltate and ternary nickel-cobalt-manganese material, and the weight ratio of lithium cobaltate to ternary nickel-cobalt-manganese material is 5: (10-15).

[0080] The conductive agent is selected from any one or combination of acetylene black, superconducting carbon black, conductive graphite, conductive carbon fiber; preferably, the acetylene black or superconducting carbon black or conductive graphite has a surface area of 500-1000 square meters per gram.

[0081] The first solvent is selected from any one or combination of tetrahydrofuran, pyridine, N-methyl pyrrolidone.

[0082] The B component is an isocyanate curing agent; the isocyanate curing agent can be selected from any one or combination of hexamethylene diisocyanate, isophorone diisocyanate, and other diisocyanates.

[0083] The application is further described below with specific examples 1-18.

[0084] Examples 1-2

[0085] A two-component lithium ion battery positive electrode material comprises A component and B component, the ratio of raw materials of the A component is shown in Table 2 below, and the B component is selected from isophorone diisocyanate.

[0086] Table 2 Ratio of A component of two-component lithium ion battery positive electrode material in examples 1-2 (unit: kg)

[0087]

[0088] In the above examples 1-2, the A component:

[0089] The hydroxyl acrylate resin is prepared by the hydroxyl acrylate resin prepared in Preparation Example 1;

[0090] The hydroxyl value of the hydroxyl silicone resin is 9 mgKOH / g, and the viscosity is 80 cps;

[0091] The melt flow rate of the polyurethane resin is 56 g / 10 min

[0092] The surface area of the acetylene black is 500 square meters per gram.

[0093] Secondly, the weight ratio of the A component to the B component in Example 1 is 20:1; and the weight ratio of the A component to the B component in Examples 2-5 is 55:1.

[0094] In addition, the preparation method of the two-component lithium ion battery positive electrode material in Examples 1-2 comprises the following steps:

[0095] (1) The first binder, 50wt% of the first solvent, the active substance, and 50wt% of the conductive agent are stirred at a stirring speed of 50r / min for 30min to obtain a first mixture;

[0096] (2) The remaining conductive agent is added into the first mixture obtained in step (1) and stirred at a stirring speed of 50r / min for 30min to obtain a second mixture;

[0097] (3) The second binder is added into the second mixture obtained in step (2) and stirred at a stirring speed of 50r / min for 30min to obtain a third mixture;

[0098] (4) The remaining first solvent is added into the third mixture obtained in step (3) and stirred at a stirring speed of 50r / min for 30min, and then filtered to obtain component A;

[0099] (5) When used, the component B is added into the component A obtained in step (4) and stirred at a stirring speed of 50r / min for 30min to obtain a lithium ion battery positive electrode material.

[0100] Example 6

[0101] A two-component lithium ion battery positive electrode material, which is different from example 4 in that:

[0102] The second binder is selected by using equal amounts of organic fluorine resin instead of polyurethane resin, and the organic fluorine resin is selected by using polyvinylidene fluoride, and the molecular weight of the polyvinylidene fluoride is 1 million.

[0103] Example 7

[0104] A two-component lithium ion battery positive electrode material, which is different from example 4 in that:

[0105] The second binder includes polyurethane resin and organic fluorine resin, and the weight ratio of the polyurethane resin to the organic fluorine resin is 1:1.

[0106] The melt flow rate of the polyurethane resin is 56g / 10min;

[0107] The organic fluorine resin is selected by using polyvinylidene fluoride, and the molecular weight of the polyvinylidene fluoride is 1 million.

[0108] Example 8

[0109] A two-component lithium ion battery positive electrode material, which is different from example 4 in that:

[0110] The second binder includes polyurethane resin and organic fluorine resin, and the weight ratio of the polyurethane resin to the organic fluorine resin is 3:1.

[0111] The melt flow rate of the polyurethane is 56 g / 10 min.

[0112] The organic fluorine resin is polyvinylidene fluoride, and the molecular weight of the polyvinylidene fluoride is 1 million.

[0113] Example 9

[0114] A dual-component lithium ion battery cathode material, which is different from example 8 in that:

[0115] The active material is replaced by an equal amount of ternary nickel-cobalt-manganese material instead of lithium cobaltate.

[0116] Example 10

[0117] A dual-component lithium ion battery cathode material, which is different from example 8 in that:

[0118] The active material includes a combination of lithium cobaltate and ternary nickel-cobalt-manganese material, and the weight ratio of lithium cobaltate to ternary nickel-cobalt-manganese material is 1:1.

[0119] Example 11

[0120] A dual-component lithium ion battery cathode material, which is different from example 8 in that:

[0121] The active material includes a combination of lithium cobaltate and ternary nickel-cobalt-manganese material, and the weight ratio of lithium cobaltate to ternary nickel-cobalt-manganese material is 5:13.

[0122] Example 12

[0123] A dual-component lithium ion battery cathode material, which is different from example 11 in that:

[0124] The hydroxyl acrylic resin is the hydroxyl acrylic resin prepared in Preparation Example 2.

[0125] Example 13

[0126] A dual-component lithium ion battery cathode material, which is different from example 11 in that:

[0127] The hydroxyl acrylic resin is the hydroxyl acrylic resin prepared in Preparation Example 3.

[0128] Example 14

[0129] A dual-component lithium ion battery cathode material, which is different from example 11 in that:

[0130] The hydroxyl acrylic resin is the hydroxyl acrylic resin prepared in Preparation Example 4.

[0131] Example 15

[0132] A dual-component lithium ion battery cathode material, which is different from example 11 in that:

[0133] The hydroxyl acrylic resin is the hydroxyl acrylic resin prepared in Preparation Example 5.

[0134] Example 16

[0135] A two-component lithium ion battery cathode material, which is different from Example 11 in that:

[0136] The hydroxyl acrylic resin is the hydroxyl acrylic resin prepared in Preparation Example 6.

[0137] Example 17

[0138] A two-component lithium ion battery cathode material, which is different from Example 11 in that:

[0139] The hydroxyl acrylic resin is the hydroxyl acrylic resin prepared in Preparation Example 7.

[0140] Example 18

[0141] A two-component lithium ion battery cathode material, which is different from Example 11 in that:

[0142] The hydroxyl acrylic resin is the hydroxyl acrylic resin prepared in Preparation Example 8.

[0143] Comparative Example 1

[0144] A lithium ion battery cathode material, comprising the following raw materials:

[0145] Polyvinylidene fluoride: 10 kg

[0146] Dispersant VOK-Disper 3031: 1 kg

[0147] Lithium cobaltate: 90 kg

[0148] Acetylene black: 10 kg

[0149] 1. Methyl pyrrolidone: 100 kg.

[0150] The molecular weight of the polyvinylidene fluoride is 1 million.

[0151] In this comparative example, the lithium ion battery cathode material is prepared as follows:

[0152] The polyvinylidene fluoride, the dispersant VOK-Disper, the lithium cobaltate, and the acetylene black are added to the N-methyl pyrrolidone, stirred uniformly, and then the lithium ion battery cathode material is obtained.

[0153] Comparative Example 2

[0154] A two-component lithium ion battery cathode material, which is different from Example 2 in that:

[0155] The hydroxy acrylate resin is replaced by an equivalent amount of carboxyl acrylate resin, and the acid value of the carboxyl acrylate resin is 80.

[0156] Preparation of the positive electrode sheet: Select an aluminum foil with a thickness of 14 μm as the positive current collector, and uniformly coat the positive electrode slurry of Comparative Example 1-2 and Examples 1-18 on both surfaces of the aluminum foil, with a coating surface density of 2 mg / cm 2 Then vacuum drying at 120°C, cold pressing, cutting, and slitting to obtain the positive electrode sheet. Among them, the positive electrode sheet of Example 1-18 will not appear powdering during the slitting process, and the positive electrode sheet of Comparative Example 1-2 will have powdering problems during the slitting process.

[0157] Preparation of the lithium ion battery: The positive electrode sheet corresponding to Example 1-18 and Comparative Example 1-2 is wound with a separator (polypropylene film) and a graphite negative electrode sheet (graphite: SP: SBR: CMC mass ratio is 97: 1: 1.5: 0.5, and the negative current collector is a copper foil) to form a 426080 type battery with a capacity of 2 Ah, and the electrolyte is injected into the battery. The electrolyte uses 1 mol / L of LiPF6 as a lithium salt and EC / EMC=3:7 (V / V) as a non-aqueous organic solvent. After that, the battery is formed and tested for capacity, and a lithium ion battery 1-18 prepared by using the positive electrode material of Example 1-18 and a lithium ion battery 1#-2# prepared by using the positive electrode material of Comparative Example 1-2 are obtained.

[0158] Test 1, peel strength of the battery positive electrode material and the positive current collector aluminum foil:

[0159] (1) Test of the adhesion of the positive electrode sheet before cyclic charging and discharging

[0160] The cold-pressed positive electrode sheet is cut into a size of 20 mm*200 mm, and a 180° tensile test is performed to test the adhesion between the positive electrode sheet and the aluminum foil.

[0161] (2) Test of the adhesion of the positive electrode sheet after 1000 cycles of cyclic charging and discharging

[0162] At 45°C, the lithium ion battery is charged at 1.5C constant current to 4.35V, then charged at constant voltage to a current of 0.05C, then discharged at 1.5C constant current to 3.0V, which is one cycle. After 1000 cycles of charging / discharging, the positive electrode sheet of the lithium ion battery is removed, and the adhesion between the positive electrode sheet and the aluminum foil is tested.

[0163] Test 2, 45°C cycle test of the lithium ion battery:

[0164] The prepared lithium ion battery 1-18 and lithium ion battery 1#-2# are tested according to the following methods respectively:

[0165] The lithium ion battery was charged at 45 °C with 1.5C constant current to 4.35V, then constant voltage charged to 0.05C, then discharged with 1.5C constant current to 3.0V, which was one cycle, after 1000 cycles of charging / discharging, the thickness expansion rate and capacity retention rate of the lithium ion battery after 1000 cycles were calculated.

[0166] Test three, high temperature storage performance:

[0167] The prepared lithium ion batteries 1-18 and lithium ion batteries 1#-2# were tested according to the following methods respectively:

[0168] The lithium ion battery was placed at 25 °C for 30 minutes, then charged with 0.5C constant current to 4.35V, then constant voltage charged to 0.05C at 4.35V and placed for 5 minutes, then stored at 60 °C for 30 days, and the thickness expansion rate and capacity retention rate of the lithium ion battery after 30 days of storage were measured respectively.

[0169] Table 3 Performance test of positive electrode sheet and lithium ion battery

[0170]

[0171] Result analysis

[0172] According to the data in Table 3, combining Example 2 and Comparative Example 1, compared with directly using polyvinylidene fluoride as the binder, the two-component binder composed of the hydroxyl resin and the isocyanate curing agent in the application is more conducive to improving the adhesion between the positive electrode material and the aluminum foil, and the positive electrode sheet prepared by using the two-component binder will not appear powdering during slitting, indicating that the adhesion between the binder and the active material is also significantly improved.

[0173] According to the data in Table 3, combining Example 2 and Comparative Example 2, when the carboxyl acrylic resin is used instead of the hydroxyl acrylic resin, the adhesion between the positive electrode material and the aluminum foil is greatly reduced, and the dimensional stability of the positive electrode material in a high temperature environment is also significantly reduced. The reason is that after using the carboxyl acrylic resin instead of the hydroxyl acrylic resin, the binder has pores, which reduces the adhesion strength between the active material and the conductive agent and the binder.

[0174] According to the data in Table 3, combining Examples 2-5, when the first binder is selected from a composition with a weight ratio of hydroxyl acrylic resin to hydroxyl silicone resin in the range of (3.8-4.2):1, the adhesion stability between the positive electrode material and the aluminum foil and the dimensional stability of the positive electrode material in a high temperature environment are improved.

[0175] Based on Examples 4 and 6-8 and the data in Table 3, it can be seen that when the second binder is a composition of polyurethane resin and organic fluorine resin in a weight ratio of (2.5-3.5):1, it can further improve the temperature resistance of the positive electrode material while maintaining the bonding stability between the positive electrode material and the aluminum foil, and promote the capacity retention rate of the lithium-ion battery made with this positive electrode material in a high-temperature environment.

[0176] Based on Examples 8-11 and the data in Table 3, it can be seen that when the active material is selected from a composition of lithium cobalt oxide and ternary nickel-cobalt-manganese materials in a weight ratio of 5:(10-15), the capacity retention rate of lithium-ion batteries after cyclic charging and discharging and in high-temperature environments can be further improved.

[0177] Based on Examples 11-13 and the data in Table 3, it can be seen that when the structural monomer of the hydroxyl acrylic resin is selected from a composition in which the weight ratio of styrene to dodecyl acrylate is in the range of 3:(4.5-5.5), it is beneficial to further improve the temperature resistance of the cathode material, effectively improve the dimensional stability of the cathode material in a high-temperature environment, and improve the capacity retention rate of the lithium-ion battery made with the cathode material in a high-temperature environment.

[0178] Based on Examples 13-18 and the data in Table 3, it can be seen that when the acidic monomer of the hydroxyl acrylic resin is selected from a composition with a weight ratio of maleic acid to itaconic anhydride in the range of (1-2):3, the bonding stability between the positive electrode material and the aluminum foil is greatly improved, enabling the lithium-ion battery made with this positive electrode material to maintain a capacity retention rate of over 88% after 1000 charge-discharge cycles.

[0179] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A two-component lithium-ion battery cathode material, characterized in that: The A component comprises 2-10 parts by weight of a first binder, 1-4 parts by weight of a second binder, 0.05-1 parts by weight of a dispersant, 80-90 parts by weight of an active material, 1-10 parts by weight of a conductive agent, and 20-100 parts by weight of a first solvent; The B component is an isocyanate curing agent; the weight ratio of the A component to the B component is (20-55):1; The first binder comprises a hydroxyl acrylic resin and a hydroxyl silicone resin, and the weight ratio of the hydroxyl acrylic resin to the hydroxyl silicone resin is (3.8-4.2):1; The hydroxyl acrylic resin comprises the following raw materials by weight: 30-33 parts of a structural monomer; 5-22 parts of an acidic monomer; 23-26 parts of a functional monomer; 1-3 parts of a chain transfer agent; 0.4-0.6 parts of an initiator; 0.1-0.3 parts of a catalyst; and 100 parts of a second solvent; The structural monomer is selected from styrene and dodecyl acrylate, and the weight ratio of the styrene to the dodecyl acrylate is 3:(4.5-5.5); The acidic monomer is selected from a combination of maleic acid and maleic anhydride in a weight ratio of 2:3, or a combination of maleic acid and itaconic acid in a weight ratio of 2:3; The second binder comprises a polyurethane resin and an organic fluorine resin, and the weight ratio of the polyurethane resin to the organic fluorine resin is (2.5-3.5):

1.

2. The bi-component lithium-ion battery cathode material of claim 1, wherein: The functional monomer is selected from any one or a combination of hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

3. The bi-component lithium-ion battery cathode material of claim 1, wherein: The chain transfer agent is selected from any one or a combination of n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, mercaptoethanol, ethylene glycol, and isopropyl alcohol.

4. The bi-component lithium-ion battery cathode material of claim 1, wherein: The initiator is selected from any one or a combination of benzoyl peroxide and azobisisobutyronitrile.

5. The bi-component lithium-ion battery cathode material of claim 1, wherein: The catalyst is selected from any one or a combination of zinc glutarate and zinc iso-octoate.

6. The bi-component lithium-ion battery cathode material of claim 1, wherein: The second solvent is selected from any one or a combination of toluene, o-xylene, p-xylene, m-xylene, ethyl acetate, butyl acetate, pentyl acetate, isoamyl acetate, cyclohexanone, N-methyl pyrrolidone, N-ethyl pyrrolidone, ethylene glycol ethyl ether acetate, ethylene glycol methyl ether, ethylene glycol methyl ether acetate, dipropylene glycol, and dipropylene glycol methyl ether.

7. The bi-component lithium-ion battery cathode material of claim 1, wherein: The dispersant is selected from any one or a combination of VOK-Disper 3031 dispersant and YTF003 dispersant.

8. The bi-component lithium-ion battery cathode material of claim 1, wherein: The active material comprises lithium cobaltate and ternary nickel-cobalt-manganese material, and the weight ratio of the lithium cobaltate to the ternary nickel-cobalt-manganese material is 5:(10-15).

9. The bi-component lithium-ion battery cathode material of claim 1, wherein: The conductive agent is selected from any one or a combination of acetylene black, superconducting carbon black, conductive graphite, and conductive carbon fiber.

10. The method of producing a two-component lithium-ion battery cathode material according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (1) mixing and stirring the first binder, part of the first solvent, the active material, and part of the conductive agent to obtain a first mixture; (2) adding the remaining conductive agent into the first mixture obtained in step (1) and mixing and stirring to obtain a second mixture; (3) adding the second binder into the second mixture obtained in step (2), mixing and stirring to obtain a third mixture; (4) adding the remaining first solvent into the third mixture obtained in step (3), mixing and stirring to obtain the A component; (5) when used, the B component is added into the A component obtained in step (4) according to the proportion, and mixed uniformly to obtain the lithium ion battery cathode material.

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