A positive electrode non-fluorine lithium battery binder, its preparation method and application

Abstract

The present application belongs to the technical field of polymer, and particularly relates to a positive electrode non-fluorine lithium ion battery binder. The binder is a copolymer containing several monomer polymerization units, the monomer polymerization units include acrylic monomer polymerization units, acrylonitrile monomer polymerization units and oil-soluble monomer polymerization units; at least part of the acrylic monomers in the acrylic monomer polymerization units are pre-neutralized; and no emulsifier remains in the binder. The binder has excellent bonding performance and anti-swelling performance. When the binder is applied to a positive electrode material, the battery system has excellent cycle performance, small internal resistance and less gas generation. Meanwhile, the present application also discloses a preparation method and application of the binder.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymers, and particularly relates to a positive electrode binder for non-fluorine lithium ion batteries with excellent performance, and a preparation method and application thereof. BACKGROUND

[0002] In recent years, lithium ion batteries (LIB) are closely related to our life, and have broad application prospects and market value in small portable electronic devices, large electric vehicles and other large energy storage systems. Nowadays, lithium ion batteries are developed towards the direction of prolonging cycle stability, high energy density, high transmission rate, low cost and safety. The energy density of lithium ion batteries is affected by many factors. In addition to starting from the active material as the main component, the performance of non-active substances can also be improved to reduce the component ratio, thereby indirectly improving the energy density of the battery.

[0003] In lithium ion batteries, the binder is an important non-active material, which has a small proportion but plays an important role. It plays a binding role between the active material, the conductive agent and the current collector, stabilizes the SEI film, and makes them have overall connectivity, thereby reducing the ion transmission resistance of the electrode, and at the same time making the electrode sheet have good mechanical properties and processing properties to meet the needs of industrial production.

[0004] Polyvinylidene fluoride (PVDF) is the most commonly used positive electrode binder, and its dosage accounts for 3% of the positive electrode material. In 2016, the total output of positive electrode material was 160,000 tons, corresponding to the need for PVDF of 4.8 million tons, and the market space of PVDF with a unit price of 10-20 million tons was about 500-1000 million yuan. In addition, styrene-butadiene rubber (SBR) is the most commonly used negative electrode binder, and 98% of lithium battery negative electrode binders use SBR, which accounts for about 3% of the negative electrode dosage. According to the total output of 7Gwh of lithium batteries in China in 2016 and the need for 680kg of graphite negative electrode per Gwh of battery, the total demand for SBR is 1700kg, and according to the price of 10-15 million yuan per ton in 2016, the market space is 200-300 million yuan. According to the prediction of Gaogong Lithium, the total demand for lithium batteries in China will reach 151.7Gwh by 2020, and the demand for SBR binder will reach 1948 tons. According to the market size estimated at the same price, the market size is 400 million yuan, and the annual compound growth rate is as high as 30.87%.

[0005] But since entering 2021, with the rapid growth of global new energy, the price of polyvinylidene fluoride (PVDF) has entered a rapid upward cycle since early 2021. Since more than 90% of the positive electrode adhesive in lithium battery auxiliary materials uses PVDF, lithium electronic giants have been competing for PVDF resin worldwide, and the overall market is in short supply. And according to market forecasts, by 2025, the global demand for battery-grade PVDF will exceed 70,000 tons; At present, the market is mainly supplied by foreign capital such as Solvay and Arkema, and only a few domestic enterprises have successfully introduced the lithium battery industry chain. According to our industry chain research, in addition to foreign capital enterprises such as Solvay, Arkema, and Wu Yu, there is also a small amount of capacity from Dongyue, Funolin, Dongyangguang, and China Blue Sky, but it is difficult to meet the rapid growth of the lithium battery field, and it is expected that the shortage will not improve. In view of the above problems, we need to develop a product with performance comparable to PVDF and reasonable price.

[0006] The positive electrode adhesive is widely prepared using acrylonitrile as a reaction monomer. Specifically, the following patents are involved:

[0007] D1: CN1167161C discloses a positive electrode for a non-aqueous electrolyte secondary battery and a battery using the same. The specification records that the particle-like binder is preferably composed of an elastic copolymer containing a 2-ethylhexyl acrylate monomer, an acrylic acid monomer, and an acrylonitrile monomer. The particle-like binder can also have a cross-linked structure. The examples record that the particle-like binder uses an elastic copolymer containing an acrylonitrile monomer, a 2-ethylhexyl acrylate monomer, and an acrylic acid monomer (BM500B (trade name) produced by Japan Zeon Corporation).

[0008] D2: CN112500817B discloses a positive electrode adhesive and a preparation method thereof, as well as a battery positive electrode and a lithium battery. The adhesive is a copolymer of acrylonitrile and methyl acrylate monomers. The large amount of cyano groups contained therein can interact with metal ions in the positive electrode material, alleviating the interface side reaction between the positive electrode material and the electrolyte at high temperatures, reducing the interface impedance, inhibiting the dissolution of metal ions, stabilizing the surface structure of the positive electrode material, improving the electrical performance of the battery at high temperatures, and improving the flexibility of the polymer. The introduction of the methyl acrylate monomer enhances the processability of the electrode sheet, reduces the possibility of adhesive failure at high temperatures, and maintains the integrity of the electrode structure and conductive network at high temperatures.

[0009] This scheme uses organic phase solution polymerization and precipitation in a water-alcohol system. Although this scheme does not contain emulsifiers, it is a reaction in a homogeneous phase.

[0010] D3: CN106220779B discloses an acrylonitrile copolymer adhesive comprising the following weight percentage of structural units: acrylonitrile unit 78-95%, acrylic ester unit 1-10%, acrylamide unit 2-15%. Acrylonitrile monomer is used as the main body, and acrylate monomer, strong polar acrylamide monomer or acrylic acid salt monomer is added to acrylonitrile for copolymerization, so as to impart flexibility, electrolyte affinity and appropriate swelling degree in electrolyte to the polymer film while maintaining the strong adhesion or intermolecular force of the acrylonitrile polymer, so as to adapt to the volume periodic change of the electrode active material with the intercalation\deintercalation of lithium ions in the charging and discharging process, thereby improving the energy density and cycle performance of the lithium ion battery.

[0011] The experimental method of the scheme is: adding 900 parts of distilled water in a reaction container, starting stirring, purging high-purity nitrogen for 1 hour to remove oxygen, then adding 4 parts of methyl acrylate, 12 parts of acrylamide and 84 parts of acrylonitrile, heating to 60℃ under inert atmosphere and constant temperature; then adding 5 parts of 20% ammonium persulfate initiator solution to initiate the reaction, and ending after 4 hours of reaction. After filtration, drying, crushing and sieving, the adhesive is obtained.

[0012] Although the case also uses a suspension polymerization method, it lacks a hydrophilic ionic monomer.

[0013] D4: CN114242938A discloses an ion battery positive electrode sheet and a preparation method and application thereof. The raw materials of the slurry of the positive electrode sheet include a water-based binder, a dispersant, a conductive agent, a positive electrode active material and deionized water; the raw materials of the water-based binder include polyacrylonitrile and polyacrylate-methyl methacrylate, and the mass ratio of the polyacrylonitrile to the polyacrylate-methyl methacrylate is (6-8):(2-4).

[0014] The scheme records: first mixing polyacrylonitrile, dispersant and part of deionized water, then second mixing polyacrylate-methyl methacrylate to obtain a water-based binder solution;

[0015] It can be seen that the scheme contains a dispersant.

[0016] D5: CN112952092A discloses a positive electrode binder, the binder comprising a first component and a second component; the first component is a copolymer of vinylidene fluoride and a first monomer, the first monomer being one or several of C2-C8 olefins and C2-C4 halogenated olefins other than vinylidene fluoride; the second component is a copolymer of acrylonitrile monomer and a second monomer, the acrylonitrile monomer being acrylonitrile and / or methacrylonitrile, and the second monomer being one or several of acrylamide monomers, acrylic acid monomers and nitrogen heterocyclic monomers; the weight ratio of the first component and the second component is (1:4)-(4:1).

[0017] The scheme is described as follows:

[0018] The method comprises:

[0019] (1) a first polymerization reaction of vinylidene fluoride and the first monomer in a first solvent in the presence of a first chain transfer agent, a first initiator and a dispersant, and removing the first solvent to obtain the first component;

[0020] (2) a second polymerization reaction of acrylonitrile monomer and the second monomer in a second solvent in the presence of a second chain transfer agent, a second initiator and an emulsifier, and removing the second solvent to obtain the second component;

[0021] (3) mixing the first component and the second component.

[0022] It can be seen that the scheme contains a dispersant.

[0023] D6: CN1795578A discloses a lithium ion secondary battery, which is composed of a positive electrode capable of embedding / extruding lithium ions, a negative electrode capable of inserting / extruding lithium ions, a porous membrane between the positive electrode and the negative electrode, and a non-aqueous electrolyte; wherein the porous membrane is adhered to the surface of at least one of the positive electrode and the negative electrode; the porous membrane is composed of a filler and a resin binder; the content of the resin binder in the porous membrane is 1.5-8 parts by weight per 100 parts by weight of the filler; and the resin binder contains acrylonitrile units, acrylic ester units or methacrylic ester units.

[0024] D7: CN114447338A discloses a positive electrode sheet slurry and its preparation method, a lithium ion battery, and a vehicle, the positive electrode sheet slurry comprising a positive electrode active material, a first binder, a second binder, a conductive agent, and a first solvent; wherein the first binder comprises a polyacrylic binder, the second binder comprises a polyacrylate binder, and the first solvent comprises deionized water; the mass ratio of the first binder and the second binder to the positive electrode active material is 2-5:90-96. By adding two different binders in the positive electrode sheet slurry, the two can work synergistically, so that the binder has good adhesion strength and flexibility at the same time. The adhesion performance can be maintained while reducing the amount of binder. The positive electrode sheet slurry can be tightly attached to the surface of the positive electrode sheet, and the positive electrode sheet prepared can have good flexibility, and can improve the specific capacity of the lithium ion battery to a certain extent, and improve the performance of the lithium ion battery; the specification book records that the polyacrylic binder comprises a polyacrylonitrile multi-copolymer, and / or a copolymer of acrylic acid and acrylonitrile.

[0025] However, neither D6 nor D7 discloses the ratio of acrylic acid and acrylonitrile and the synthesis method.

[0026] D8: CN114736632A discloses a kind of acrylonitrile binder powder and its preparation method, with soft monomer, hard monomer, polar monomer, functional monomer, crosslinking monomer, reactive anionic emulsifier, initiator, buffer, oxidizing agent, reducing agent as raw material, first polyacrylonitrile binder emulsion is prepared, then powder is made by drying process, acrylonitrile binder powder is obtained. The preparation of acrylonitrile binder powder takes (methyl) acrylonitrile as main monomer and water as solvent, which is green and environmentally friendly, and easy to operate. It is mainly used for the adhesion of lithium battery positive active material and current collector. By using a reactive emulsifier, the influence of free emulsifier in the binder on battery charging and discharging is reduced. The acrylonitrile binder powder has excellent electrolyte resistance, low swelling rate, and excellent adhesion.

[0027] The specification book records that the functional monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, hydroxyethyl acrylate, β-acryloyloxy propionic acid, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate and hydroxybutyl methacrylate; the polar monomer is one or more of acrylonitrile and methacrylonitrile;

[0028] The amount of polar monomer is 50-90%, and the amount of functional monomer is 2-25%;

[0029] Its example 1 records:

[0030] (1) Preparation of pre-emulsion: 2.5 parts of sodium allyloxy hydroxypropyl sulfonate, 1.5 parts of lithium hydroxide were added into 350 parts of deionized water, and stirred to dissolve to obtain an emulsifier aqueous solution. A mixture of 50 parts of methyl methacrylate, 37.5 parts of butyl acrylate, 150 parts of acrylonitrile, 7.5 parts of methacrylic acid and 5 parts of acrylamide was used as a mixed monomer, and the mixed monomer was added into the emulsifier aqueous solution, and stirred at a speed of 400 revolutions per minute for 30 minutes to prepare a pre-emulsion;

[0031] (2) Preparation of initiator solution: 0.75 parts of ammonium persulfate was added into 25 parts of deionized water, and stirred to dissolve to obtain an initiator solution;

[0032] (3) Preparation of seed emulsion: 0.75 parts of sodium allyloxy hydroxypropyl sulfonate, 0.5 parts of lithium hydroxide and 0.25 parts of ammonium persulfate were added into 225 parts of deionized water, and stirred to dissolve. 5% of the pre-emulsion was added, and slowly heated to 70°C, and reacted for 25 minutes. A blue fluorescence phenomenon appeared, and a seed emulsion was obtained;

[0033] (4) 0.075 parts of tert-butyl hydroperoxide was added into 10 parts of deionized water, and stirred to obtain an oxidizing agent aqueous solution;

[0034] (5) 0.1 parts of erythorbic acid was added into 15 parts of deionized water, and stirred to dissolve to obtain a reducing agent aqueous solution;

[0035] (6) The remaining pre-emulsion and the initiator solution of step (2) were simultaneously added into the seed emulsion of step (3) at 70°C, and the dropping time was 3.5 hours. After the dropping was completed, the temperature was maintained for 0.5 hours. Then the oxidizing agent aqueous solution of step (4) and the reducing agent aqueous solution of step (5) were simultaneously added, and the dropping time was 10 minutes. The temperature was maintained for 2 hours, and then vacuum was applied for 30 minutes. After the vacuum was applied, the temperature was lowered, and the product was filtered to obtain a polyacrylonitrile binder emulsion;

[0036] (7) The polyacrylonitrile binder emulsion obtained in step (6) was subjected to spray drying to obtain an acrylonitrile binder powder.

[0037] It can be seen that the case adopts a reactive emulsifier for dispersion.

[0038] D9: CN103190022B discloses a secondary battery positive electrode water-based adhesive composition, a secondary battery positive electrode slurry composition, a secondary battery positive electrode and a secondary battery; the ratio of each monomer unit in the adhesive is that the (meth) acrylate monomer unit is preferably 50-95 mass%, more preferably 60-90 mass%, the vinyl monomer unit with an acidic group is preferably 0.1-10 mass%, more preferably 1.0-7.0 mass%, the α, β-unsaturated nitrile monomer unit is preferably 3-40 mass%, more preferably 5-30 mass%, and the other monomer units that can be copolymerized with them are preferably 0.05-47 mass%, more preferably 0.1-37 mass%. It should be noted that when the cross-linkable monomer is used as the other monomer that can be copolymerized, the ratio of the cross-linkable monomer unit is preferably 0.05-2.0 mass%, more preferably 0.1-1.0 mass%.

[0039] The case embodiment 8 explicitly records that it needs an emulsifier to participate in the reaction.

[0040] From the above literature, we can draw the following preliminary conclusions:

[0041] Conclusion 1: The positive electrode binder is divided into oil-based and water-based; the binders in the above-mentioned literature are water-based, such as CN103190022B, CN103811802A, etc.; we found in subsequent research that using a water-based binder is not conducive to the performance of the positive electrode, as the positive electrode will undergo very intense electrochemical reactions, resulting in bulging and gas production.

[0042] Conclusion 2: Most of the polymerization monomers are acrylonitrile and acrylate; in some literature, acrylonitrile is the main body, such as CN114736632A, CN106220779B, and in some literature, acrylate is the main body, such as CN103190022B.

[0043] Conclusion 3: Some polymers are involved in emulsifiers, whether they are represented by self-emulsifying monomers or non-reactive emulsifiers, in most reaction systems, there are emulsifiers.

[0044] Conclusion 4: Some literature records that acrylate is used to improve the processing performance, such as CN112500817B; we also verified this in subsequent experiments.

[0045] During the research of this project, the following difficulties were encountered:

[0046] 1. The oil-based polymerization product binder is not good, and the anti-swelling property is not good;

[0047] 2. It is difficult to balance the electrochemical performance such as cycle performance, internal resistance, gas production, etc.

[0048] 3. The polymer reaction system is unstable, and the granular product is difficult to precipitate.

[0049] The present application is proposed to solve the above problems. SUMMARY

[0050] The present application aims to provide a positive electrode non-fluorine lithium battery binder with excellent binding performance and swelling resistance, and when applied to a positive electrode material, the battery system exhibits excellent cycle performance, small internal resistance and less gas generation.

[0051] The present application also provides a preparation method and application of the binder.

[0052] Unless otherwise specified in the present application: nM represents nanomole / liter, μM represents micromole / liter, mM represents millimole / liter, and M represents mole / liter;

[0053] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0054] A positive electrode non-fluorine lithium ion battery binder, the binder is a copolymer containing several monomer polymerization units, the monomer polymerization units include acrylic monomer polymerization units, acrylonitrile monomer polymerization units, and oil-soluble monomer polymerization units; at least part of the acrylic monomers in the acrylic monomer polymerization units are pre-neutralized;

[0055] The binder contains 3-10wt% of acrylic monomer polymerization units, 75-90wt% of acrylonitrile monomer polymerization units, and 5-20wt% of oil-soluble monomer polymerization units.

[0056] No emulsifier residue or less than 0.01wt% of emulsifier residue is contained in the binder.

[0057] In the above-mentioned positive electrode non-fluorine lithium ion battery binder, 0-10wt% of water-soluble monomer polymerization units are further contained.

[0058] Preferably, 0-9wt% of water-soluble monomer polymerization units are further contained.

[0059] Further preferably, 0-7wt% of water-soluble monomer polymerization units are further contained.

[0060] Further preferably, 0-6wt% of water-soluble monomer polymerization units are further contained.

[0061] In the above-mentioned positive electrode non-fluorine lithium ion battery binder, the binder contains 4-10wt% of acrylic monomer polymerization units, 75-90wt% of acrylonitrile monomer polymerization units, and 10-20wt% of oil-soluble monomer polymerization units.

[0062] Preferably, the binder contains 4-10 wt% of acrylic monomer polymerized units, 75-90 wt% of acrylonitrile monomer polymerized units, and 10 wt% of oil-soluble monomer polymerized units.

[0063] In the above positive electrode non-fluorine lithium ion battery binder, 4-10 wt% of acrylic monomer polymerized units, 78-90 wt% of acrylonitrile monomer polymerized units, and 8-12 wt% of oil-soluble monomer polymerized units, and 0-6 wt% of water-soluble monomer polymerized units.

[0064] In the above positive electrode non-fluorine lithium ion battery binder, the oil-soluble monomer is one or more of methyl (meth)acrylate, ethyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, C13-C16 (meth)acrylate, butyl (meth)acrylate, isooctyl (meth)acrylate, isobornyl methacrylate, styrene, vinyl acetate, alkoxyphenol acrylate, and glycidyl (meth)acrylate.

[0065] The acrylic monomer is an alkenoic acid or a methacrylic acid.

[0066] The acrylonitrile monomer is one or more of acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-ethylacrylonitrile.

[0067] In the above positive electrode non-fluorine lithium ion battery binder, the water-soluble monomer is one or more of acrylamide, methacrylamide, N-methylolacrylamide, N-hydroxyethylacrylamide, N-methylacrylamide and N,N-dimethylacrylamide, itaconic acid, hydroxyethyl (meth)acrylate, and hydroxyethyl methacrylate.

[0068] In the above positive electrode non-fluorine lithium ion battery binder, the neutralization degree of the acrylic monomer is 10-100%.

[0069] In the above positive electrode non-fluorine lithium ion battery binder, the neutralization degree of the acrylic monomer is 70-100%.

[0070] In the above positive electrode non-fluorine lithium ion battery binder, the binder is a linear or cross-linked polymer.

[0071] If the binder is a cross-linked polymer, the binder further contains 0-1 wt% of cross-linked monomer polymerized units; in some embodiments, the amount of the cross-linked monomer is 0.1-0.9 wt%; preferably, the amount of the cross-linked monomer is 0.1-0.6 wt%; preferably, the amount of the cross-linked monomer is 0.1-0.4 wt%.

[0072] The cross-linking monomer is one or more of divinyl benzene, polyethylene glycol (200) bisacrylate, polyethylene glycol (400) bisacrylate, polyethylene glycol (600) bisacrylate, polyethylene glycol (200) bismethacrylate, polyethylene glycol (400) bismethacrylate, polyethylene glycol (600) bismethacrylate / N,N-methylene bismethacrylamide, pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, trimethylolpropane tri(3-aziridinyl propionate), polyurethane acrylate, dipentaerythritol diacrylate, dipropylene glycol diacrylate, ethoxylated (30) bisphenol A diacrylate.

[0073] Meanwhile, the application also discloses a preparation method of the positive electrode non-fluorine lithium ion battery adhesive as described above, which comprises the following steps: adding acrylate monomers, acrylonitrile monomers, oil-soluble monomers, or acrylate monomers, acrylonitrile monomers, oil-soluble monomers and water-soluble monomers into water and stirring to obtain a suspension; heating to an initiation temperature, adding an initiator dropwise to react to obtain a product; and filtering, washing and drying the product to obtain the positive electrode non-fluorine lithium ion battery adhesive.

[0074] In the preparation method described above, the method specifically comprises the following steps:

[0075] The acrylonitrile monomers, the oil-soluble monomers, the at least partially neutralized acrylate monomers are added into water and stirred to obtain a suspension; or the acrylonitrile monomers, the oil-soluble monomers, the water-soluble monomers and the at least partially neutralized acrylate monomers are added into water and stirred to obtain a suspension.

[0076] The water is heated to an initiation temperature, and an initiator is added dropwise to react to obtain a product; and the product is filtered, washed and dried to obtain the adhesive.

[0077] The amount of water is 0.5-5 times the total weight of the acrylonitrile monomers, the oil-soluble monomers and the acrylate monomers.

[0078] Preferably, the amount of water is 1-4 times the total weight of the acrylonitrile monomers, the oil-soluble monomers and the acrylate monomers.

[0079] Preferably, the amount of water is 1.5-3.5 times the total weight of the acrylonitrile monomers, the oil-soluble monomers and the acrylate monomers.

[0080] The stirring speed is 200-1000 rpm; preferably, the stirring speed is 200-500 rpm.

[0081] In the preparation method described above, the initiator is ammonium sulfate, potassium persulfate, sodium persulfate, azobisdimethylaminoformamide hydrochloride, or a redox initiator composed of persulfate and sodium sulfite, hydrogen peroxide.

[0082] The initiator corresponds to 0.1 to 2 wt% of the total weight of the acrylonitrile-based monomer, the oil-soluble monomer, and the at least partially neutralized acrylic monomer;

[0083] The initiation temperature is 30 to 100°C;

[0084] The reaction time is 2 to 24 hours.

[0085] Preferably, the initiator corresponds to 0.3 to 0.9 wt% of the total weight of the acrylonitrile-based monomer, the oil-soluble monomer, and the at least partially neutralized acrylic monomer;

[0086] The initiation temperature is 50 to 80°C;

[0087] The reaction time is 3 to 12 hours.

[0088] Finally, the present application also discloses a positive electrode non-fluorine lithium battery binder as described above for use in positive electrode conductive slurry homogenization and electrode sheet processing applications. It exhibits excellent electrochemical cycle performance in battery performance, faster dissolution speed compared to PVDF in dissolution time, and greater advantage in adhesion.

[0089] Specifically, the electrode sheet is used in a battery, and the electrode sheet is a positive electrode sheet. The positive electrode includes a current collector and a positive electrode active material layer. The current collector can be any conductor, such as aluminum, stainless steel, nickel-coated steel, etc.

[0090] The positive electrode active material layer can include a positive electrode active material, and optionally include a conductive agent and a positive electrode binder. The positive electrode active material is not specifically limited, as long as it is a solid-solution oxide including lithium, such as a material capable of electrochemically intercalating and deintercalating lithium ions. The solid-solution oxide can include, for example, LiaMn x Co y Ni z O2(1.15≤a≤1.43, 0.45≤x≤0.6, 0.10≤y≤0.15, 0.20≤z≤0.28), LiMn x Co y Ni z O2(0.3≤x≤0.85, 0.10≤y≤0.3, 0.10≤z≤0.3), LiMn 1.5 Ni 0.5 O4, etc.

[0091] The conductive agent can be, for example, carbon black such as Ketjen black or acetylene black, natural graphite, artificial graphite, etc., but is not specifically limited, as long as it is intended to improve the conductivity of the positive electrode.

[0092] The positive electrode binder adheres the positive electrode active material layer to the current collector, as described above.

[0093] For example, the positive electrode active material layer can be manufactured by the following manufacturing method. The positive electrode active material, the conductive agent, and the positive electrode binder are dry-mixed to prepare a positive electrode material mixture. Subsequently, the positive electrode material mixture is dispersed in a suitable organic solvent to prepare a positive electrode material mixture slurry, and the prepared positive electrode material mixture slurry is coated on a current collector, which is dried and pressed to prepare the positive electrode active material layer.

[0094] In practical applications, the battery further includes a negative electrode, a separator, and an electrolyte, which are common in the art, and the use of commercially available products does not affect the performance trend of the present application, for example:

[0095] Negative electrode

[0096] The negative electrode includes a current collector and a negative electrode active material layer. The current collector can be any material as long as it is a conductor, and examples of the material can include aluminum, stainless steel, and nickel-plated steel. The negative electrode active material layer includes a negative electrode-specific binder (generally aqueous) and a negative electrode active material.

[0097] Separator

[0098] The separator is not specifically limited as long as it is used as a separator for a lithium-ion rechargeable battery. As the separator, it is desirable to use a porous film, a nonwoven fabric, or the like that exhibits improved high-rate discharge performance, and they can be used alone or in combination. The resin constituting the separator can be, for example, a polyolefin-based resin such as polyethylene or polypropylene, a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, polyvinylidene fluoride, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-perfluoro vinyl ether copolymer, a vinylidene fluoride-tetrafluoroethylene copolymer, a vinylidene fluoride-trifluoroethylene copolymer, a vinylidene fluoride-fluoroethylene copolymer, a vinylidene fluoride-hexafluoroacetone copolymer, a vinylidene fluoride-ethylene copolymer, a vinylidene fluoride-propylene copolymer, a vinylidene fluoride-trifluoropropylene copolymer, a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, a vinylidene fluoride-ethylene-tetrafluoroethylene copolymer, or the like.

[0099] Non-aqueous electrolyte

[0100] The non-aqueous electrolyte is not specifically limited as long as it is a non-aqueous electrolyte that can be conventionally used in a lithium-ion rechargeable battery. The non-aqueous electrolyte can include an electrolyte salt in a non-aqueous solvent.

[0101] The advantageous effects of the present application are as follows:

[0102] The core innovation point of the present application is:

[0103] 1. The use of ionized neutralized acrylic monomers, acrylonitrile monomers improves the hydration performance of the oil droplet surface in the suspension polymerization process, which can ensure the uniformity and stability of the liquid, and make each droplet become a small bulk polymerization environment during the reaction process, and the produced product has better adhesion, high and low temperature cycle effect, etc.

[0104] 2. The present case does not use any form of emulsifier (including non-reactive and reactive emulsifiers), the introduction of emulsifiers will cause the emulsification of the system, and after emulsification, the monomers will react in the micron-sized emulsion capsules. The present case uses a suspension system, and the monomers will react in a system of hundreds of microns or millimeters. The performance of the reaction product is significantly different. At the same time, the emulsifier used in the traditional method will remain on the surface of the particles, affecting the particle peeling force, anti-settling ability, and high and low temperature cycle performance.

[0105] The advantage of using a suspension system to prepare the positive electrode binder of the present application is that:

[0106] 2.1 The binder in the positive electrode material is generally selected as an oily material, because the positive electrode active material in the positive electrode material, such as ternary material, lithium cobaltate, lithium manganate, etc. is prone to react with water, which damages the electrochemical performance of the positive electrode active material. Therefore, the use of an oily binder can reduce the probability of contact between water and the positive electrode active material. The present application uses a suspension polymerization system with water as the continuous phase. After formula optimization, the oily droplets can exist independently in the water phase, which has almost all the advantages of oily binders, such as excellent hydrophobicity, processing performance, and resistance to decomposition under oxidative conditions, etc.

[0107] 2.2 The binder in the positive electrode material undergoes an oxidation reaction, which not only requires strong oxidation resistance, but also requires good oxidation resistance at high voltage. The excessive hydrophilic groups in the water-based material easily interact with the oxidation and electron loss process during the electrochemical reaction, causing the molecular structure of the water-based material to be destroyed. The oily material of the present application mainly contains nitrile groups, which interact with metal ions in the positive electrode material through coordination, thereby alleviating the interface side reaction between the positive electrode material and the electrolyte at high temperature, reducing the interface impedance, inhibiting the dissolution of metal ions, stabilizing the surface structure of the positive electrode material, and improving the electrical performance of the battery at high temperature. The use of oil-soluble monomers improves the processing performance, and the use of acrylic monomers and nitrile monomers improves the hydration performance of the oil droplet surface, making the droplets uniform and stable, and ultimately stabilizing the performance of the product.

[0108] 2.3 Although fine oil powder with uniform particle size can still be obtained by traditional emulsion polymerization, emulsion polymerization is not only affected by the emulsifier described above, but also by the externally introduced electrolyte salt for demulsification; generally, electrolyte (such as Mg salt) needs to be added after emulsion polymerization to collect solid particles, and metal ions will affect the performance of the positive active material. Therefore, the suspension polymerization with water as the continuous phase of the present application can perfectly avoid such problems.

[0109] Based on the above basic principles and actual detection, the present application has the following beneficial effects:

[0110] (1) The non-fluorine positive electrode binder of the present application has excellent thickening and suspension performance, and the obtained slurry has excellent stability and anti-settling performance;

[0111] (2) The non-fluorine positive electrode binder of the present application has good dispersibility and operability, which only needs to be directly added to NMP for dissolution, and then conductive fillers are added, without additional pretreatment or post-neutralization, and without adding CMC, the operation is simple, and the NMP dispersion time is 1-1.5h, which is faster.

[0112] (3) It has excellent bonding performance, and has better performance than the PVDF system;

[0113] (4) The electrochemical performance of the material is basically equivalent to that of PVDF;

[0114] Compared with the existing PVDF positive electrode binder, the present application has better bonding force, and through the structure design of the polymer, the initial effect of the product is also more excellent, and the dissolution time is reduced by half compared with PVDF when used, which simplifies the processing technology and has obvious advantages, and the electrical performance is equivalent to that of PVDF.

[0115] (5) The material has better high-voltage resistance performance. BRIEF DESCRIPTION OF DRAWINGS

[0116] Figure 1 is a sample picture of the binder of Example 1 of the present application; Figure 1 Figure 2 is a picture of the application effect of the binder of Example 1 of the present application in the positive electrode homogenate;

[0117] Figure 2 Figure 3 is the electrolyte swelling resistance of the adhesive film of the binder of Example 1 of the present application and PVDF;

[0118] Figure 4 is the LSV curve of the binder of Example 1 of the present application and PVDF; Figure 3 Figure 4 is the LSV curve of the binder of Example 1 of the present application and PVDF;

[0119] Figure 4 Figure 4 is the LSV curve of the binder of Example 1 of the present application and PVDF; ​​

[0120] Appendix Figure 5 This is a graph showing the test results of the adhesion force between the adhesive and the PVDF electrode in Example 1 of the present invention;

[0121] Appendix Figure 6 This is a low-temperature discharge plateau curve of the adhesive and PVDF in Example 1 of the present invention;

[0122] Appendix Figure 7 This is a graph showing the room temperature cycling data of the adhesive and PVDF in Example 1 of the present invention;

[0123] Appendix Figure 8 This is a high-temperature cycling data curve of the adhesive and PVDF in Example 1 of the present invention;

[0124] Appendix Figure 9 These are comparative photographs showing the solubility of the adhesive and the PVDF adhesive in Example 1 of the present invention. Detailed Implementation

[0125] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this does not constitute any limitation on the present invention.

[0126] Example 1

[0127] Acrylic acid was dissolved in water, and lithium hydroxide was added dropwise under a chilled water circulation system for neutralization. Then, acrylonitrile (AN) and methyl acrylate (MA) were added, followed by deionized water and rapid stirring (300 rpm) to form a stable suspension. Nitrogen gas was then introduced to remove oxygen for about 1 hour. After nitrogen purging for a certain period, the temperature was raised to 60°C, and an initiator was added to initiate polymerization, which lasted for 12 hours. After the reaction was completed, the product was milky white granules. The crude product was obtained by centrifugation and filtration. The product was washed and dried to obtain a high-performance positive electrode non-fluorinated lithium battery binder.

[0128] The preparation methods for Examples 2-16 are the same as those for Example 1; the formulations for Examples 1-16 are shown in Table 1.

[0129] Table 1 Formulation Table (Weight in g, Neutralization in %)

[0130]

[0131]

[0132] Example 17

[0133] The difference from Example 1 is that the monomer phase also contains a crosslinking agent;

[0134] In this embodiment, divinylbenzene is selected as the crosslinking agent, and the amount of crosslinking agent used is 0.2g.

[0135] Example 18

[0136] Reference Example 1, except that the monomer phase also contains a crosslinking agent;

[0137] The crosslinking agent in this example is selected to be divinyl benzene, and the amount of crosslinking agent used is 0.5 g.

[0138] Example 19

[0139] Reference Example 1, except that the monomer phase also contains a crosslinking agent;

[0140] The crosslinking agent in this example is selected to be divinyl benzene, and the amount of crosslinking agent used is 0.8 g.

[0141] Example 20

[0142] Reference Example 1, except that the monomer phase also contains a crosslinking agent;

[0143] The crosslinking agent in this example is selected to be pentaerythritol triacrylate, and the amount of crosslinking agent used is 0.2 g.

[0144] Comparative Example 1

[0145] Generally the same as Example 1, except that the amount of acrylic acid is 14 g, and there is no methyl acrylate.

[0146] Comparative Example 2

[0147] Generally the same as Example 1, except that the amount of methyl acrylate is 14 g, and there is no acrylic acid.

[0148] Comparative Example 3

[0149] Generally the same as Example 1, except that the acrylic acid is replaced by acrylamide.

[0150] Comparative Example 4

[0151] Generally the same as Example 1, except that the amounts of monomers are respectively 20 g of acrylic acid, 74 g of acrylonitrile, and 10 g of methyl acrylate.

[0152] Comparative Example 5

[0153] Generally the same as Example 1, except that the amounts of monomers are respectively 2 g of acrylic acid, 92 g of acrylonitrile, and 10 g of methyl acrylate.

[0154] Comparative Example 6

[0155] Generally the same as Example 1, except that 1 g of sodium dodecyl sulfonate is added to the deionized water in advance.

[0156] Comparative Example 7

[0157] Generally the same as Example 1, except that 1 g of 2-acrylamido-2-methylpropanesulfonic acid was added in advance in the deionized water.

[0158] Comparative Example 8

[0159] A comparative sample was prepared using commercially available battery-grade PVDF.

[0160] Performance test

[0161] Physical test of the polymer: including 5% glue solution viscosity test and processability test;

[0162] The method of 5% glue solution viscosity test is as follows: the powder is put into a certain amount of NMP at a mass ratio of 5 wt%, and then uniformly dispersed and stirred to prepare a uniform transparent glue solution; after the glue solution is placed in a 25°C constant temperature box, a rotary viscometer is used for viscosity test.

[0163] The method of processability test is as follows: the binder is mixed with conductive main material, NMP, etc. according to a certain proportion, and then homogenized to a certain viscosity and fineness, filtered, and then coated, and the flexibility of the pole piece and the state of the pole piece are observed.

[0164] The test results can be referred to Table 2.

[0165] Table 2: Comparison of polymerization state and product performance in examples

[0166]

[0167]

[0168] Battery physical and electrochemical performance characterization

[0169] The binder and its application performance in the positive electrode pole piece are characterized / tested by the following method:

[0170] Battery pole piece preparation test: the binder is mixed with conductive main material, NMP, etc. according to a certain proportion, and then homogenized to a certain viscosity and fineness, filtered, and then coated, and a soft package battery is prepared for performance evaluation.

[0171] Viscosity test: a digital rotary viscometer is used for test, the rotation speed is 20 rpm, and the viscosity data is obtained by test.

[0172] Pole piece peeling force test: after the pole piece is prepared and rolled, a 180° peeling force test is performed.

[0173] Battery assembly:

[0174] Positive electrode: NCM811 / Ronsel S85E, negative electrode: graphite / Betrayer S360-L1, separator: Xingyuan separator, electrolyte: ternary electrolyte;

[0175] The method for testing the room temperature cycle performance of the battery is as follows: using an electrochemical workstation to perform high temperature cycle test on the batteries of the above examples and comparative examples (temperature is 25°C, 1C constant current and constant voltage charging, cutoff current is 0.05C, 30min rest after charging, 1C constant current discharging, 30min rest after discharging; cycle test is performed according to the above steps until the capacity attenuation is 80% of the initial capacity;

[0176] The method for testing the high temperature cycle performance of the battery is as follows: using an electrochemical workstation to perform high temperature cycle test on the batteries of the above examples and comparative examples (temperature is 45°C, 1C constant current and constant voltage charging, cutoff current is 0.05C, 30min rest after charging, 1C constant current discharging, 30min rest after discharging; cycle test is performed according to the above steps until the capacity attenuation is 80% of the initial capacity

[0177] The method for testing the DCR of the battery is as follows: ensure that the surface temperature of the battery reaches 25±2°C; 1C constant current discharging to 2.5V, 1C constant current discharging to 2.5V; then 1C constant current and constant voltage charging to 3.65V, current to 0.05C cutoff, 30min rest and the surface temperature of the battery reaches 25±2°C; 1C constant current discharging to 2.5V, the discharge capacity is recorded as C0, 1C constant current discharging to 2.5V; 1C constant current and constant voltage charging to 3.65V, 30min rest; 1C constant current discharging for 30min, 30min rest, the terminal voltage is recorded as U1; 1C constant current discharging for 10s, the terminal voltage is recorded as U2. The above results can be obtained by the DCR calculation formula.

[0178] Resistant to electrolyte swelling: the binder is made into a film, then soaked in electrolyte and tested for swelling rate at 60°C for 3D.

[0179] The characterization / test results are as follows:

[0180] Figure 2 The self-made binder is used for positive electrode application and the coating photo thereof, the binder has excellent flexibility and processing performance, the addition amount is 1.0-1.2%, and no additional plasticizer is needed, and no adverse phenomena such as powder falling, cracking, etc. occur during coating and baking of the prepared electrode sheet.

[0181] Several different binders are used for testing, experiment 1 uses the self-made binder (example 1), experiment 2 uses comparative example 6, and experiment 3 uses comparative example 8, the proportions of the materials used in the three binders in the positive electrode slurry formula are the same, and the preparation process is also the same, and three groups of parallel experiments are designed, and the viscosity obtained is averaged. The slurry formula and the obtained formula viscosity are shown in Table 3. As shown in Table 3, compared with the others, the self-made binder has excellent suspension and dispersion performance.

[0182] Table 3 slurry formula

[0183] Color paste Experiment 1 Experiment 2 Experiment 3 Use of binder Homemade sample Comparative example 6 Comparative example 8 Binder amount 1.2％ 1.2％ 1.2％ Conductive carbon 2.0％ 2.0％ 2.0％ LCO 96.8％ 96.8％ 96.8％ Paste viscosity 8500 mPa.s 6850 mPa.s 6180 mPa.s Paste stability 24 h stable 24 h stable 24 h stable

[0184] Figure 3 is the electrolyte solution resistance of the adhesive film, and it is found through the test that the electrolyte solution resistance of the self-made sample (Example 1) is better than that of PVDF (Comparative Example 8).

[0185] Figure 4 is the LSV curve, and it is found through the test that the self-made sample (Example 1) has better high-voltage resistance performance than PVDF (Comparative Example 8).

[0186] Figure 5 is the adhesion test, and it is found through the test that the self-made sample (Example 1) has better adhesion than PVDF (Comparative Example 8), which is increased by 110% compared with PVDF.

[0187] Figure 6 is the low-temperature performance of the binder, and it is found through the experiment that the self-made sample (Example 1) is better than PVDF (Comparative Example 8) at-20℃ low-temperature discharge platform, and the low-temperature discharge performance is obviously better than that of conventional PVDF.

[0188] Figure 7 and Figure 8 is the normal temperature and high temperature cycle performance test of the binder, and it is found through the test that the cycle data of the self-made sample (Example 1) is equivalent to that of PVDF (Comparative Example 8).

[0189] Figure 9 is the solubility comparison of the binder, and it can be found through the solubility comparison that the self-made sample (Example 1) can shorten the dissolution time by 50% compared with PVDF (Comparative Example 8).

[0190] Table 4 is the test results of the peel strength and electrical properties of each example and comparative example;

[0191] Table 4 is the test results of the peel strength and electrical properties of each example and comparative example

[0192]

[0193]

[0194] It should be noted that Examples 7, 19, Comparative Examples 1, 3 and 4 have poor processing performance, and the electrochemical performance test performance is too poor, which is not shown in the above table.

[0195] Result analysis:

[0196] 1. It can be seen from Examples 1-20 and Comparative Examples 1-8 that the selection of the formula and the suspension system of the present application can ensure that the battery has more excellent basic performance.

[0197] 2. From Examples 1, 4 and 5, it can be seen that the change of oil-soluble monomer species has no significant effect on performance; from Examples 1, 11 and 12, it can be seen that after the oil-soluble monomer contains a long-chain hydrophobic group, the processing performance becomes better, but the electrochemical performance is not significantly improved or even worse.

[0198] 3. From Examples 1 and 13-16, it can be seen that the neutralization degree has a relatively obvious effect on the performance of the product. Generally, the higher the neutralization degree, the better the battery capacity and internal resistance performance.

[0199] 4. From Examples 1 and 17-19, it can be seen that the viscosity first increases and then decreases with the increase of the crosslinking agent, and the peel force also follows this rule. It is suggested that the crosslinking agent should not exceed 0.5%, and most preferably should not exceed 0.4%, otherwise the processing performance and internal resistance will be significantly deteriorated.

[0200] 5. From Examples 1, 6-9, it can be seen that the introduction of hydrophilic monomers can effectively improve the adhesion of the battery pole piece and the dispersion performance of the main material, but has an adverse effect on the processing performance.

[0201] 6. From the comparison of Examples 1 and Comparative Example 1, it can be seen that the absence of oil-soluble monomers results in poor processing performance, and the introduction of oil-soluble monomers can improve the toughness and other related processing performance of the product. From the comparison of Examples 1 and Comparative Examples 2 and 3, it can be seen that the absence of acrylic acid, even if a large amount of water-soluble acrylonitrile is present, can easily cause particle adhesion during the reaction process, which affects the performance of the product.

[0202] 7. From Examples 1, Comparative Examples 4 and 5, it can be seen that an excessive amount of acrylic acid after neutralization has an adverse effect on the peel force, impedance and processing performance, and an insufficient amount of acrylic acid after neutralization can easily lead to particle adhesion, which affects the performance (peel force, impedance) of the product.

[0203] From the results of 6 and 7, it can be very determined that the suspension stability of oil droplets is related to the surface hydration performance, and the hydration performance is not only related to the nitrile group, but also related to the carboxyl group. The carboxyl group tends to be distributed on the surface of the oil droplets due to its hydrophilic characteristics, and therefore the amount of carboxyl group and the amount of nitrile group are the core factors for ensuring the hydration performance and the suspension stability of the oil droplets. In the case where the nitrile group cannot be reduced (to ensure the basic electrochemical performance), the amount of carboxyl group becomes a very important factor. At the same time, from Examples 13-16, it can be seen that the neutralization degree is also an important auxiliary factor, which is closely related to the adhesion and DCR. In the case where the carboxyl acid can be selected, it should be fully neutralized.

[0204] 8. As can be seen from Example 1, Comparative Examples 6 and 7, when the emulsifier is introduced into the system, regardless of whether it is a reactive or non-reactive emulsifier, it will emulsify the system, reduce the reaction particle size, and ultimately result in low material yield, poor viscosity, and poor peel strength performance. At the same time, the emulsifier remaining on the surface of the particles will affect the electrochemical properties of the battery, such as internal resistance and DCR.

[0205] In summary, the present application can maintain the synergy and unity of peel strength, DCR, processing performance, and other properties. It is necessary to use appropriate hydrated monomers (at least partially neutralized acrylic monomers, acrylonitrile monomers) in combination with an appropriate amount of oil-soluble monomers. In the suspension polymerization system, the hydrated monomers maintain the stability of the suspension system, while improving the stability of the bulk polymerization reaction within the suspended microspheres, improving the peel performance of the polymer, and reducing the DCR.

[0206] The present application excludes the use of any form of emulsifier to avoid emulsification of the system by the emulsifier, which reduces the particle size of the suspended particles. That is, the multiple independent bulk polymerization systems of the larger particle size suspended particles of the present application are a very important prerequisite for realizing the advantages of the present application.

[0207] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples. Any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included within the scope of protection of the present application.

Claims

1. A positive electrode non-fluorinated lithium-ion battery binder, characterized in that, The adhesive is a copolymer composed of several monomer polymerization units, wherein the monomer polymerization units consist of 4-10 wt% acrylic monomer polymerization units, 75-90 wt% acrylonitrile monomer polymerization units, 10-20 wt% oil-soluble monomer polymerization units, 0-10 wt% water-soluble monomer polymerization units, and 0-0.4 wt% crosslinking monomer polymerization units; at least a portion of the acrylic monomers in the acrylic monomer polymerization units are pre-neutralized. The total weight of the acrylic monomer polymerization unit, acrylonitrile monomer polymerization unit, oil-soluble monomer polymerization unit, water-soluble monomer polymerization unit, and crosslinking monomer polymerization unit is 100 wt%. The water-soluble monomer polymerization unit is one or both of hydroxyethyl methacrylate and hydroxyethyl acrylate; The adhesive contains no emulsifier residue or has an emulsifier residue of less than 0.01 wt%. The oil-soluble monomer is one or more of the following: ethyl methacrylate, lauryl methacrylate, octadecyl methacrylate, C13-C16 methacrylate, butyl methacrylate, isooctyl methacrylate, isobornyl methacrylate, styrene, vinyl acetate, alkoxyphenol acrylate, and glycidyl methacrylate. The degree of neutralization of the acrylic monomers is 70-100%.

2. The positive electrode non-fluorinated lithium-ion battery binder according to claim 1, characterized in that, The acrylic monomer is acrylic acid or methacrylic acid; The acrylonitrile monomer is one or more of acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-ethylacrylonitrile.

3. The positive electrode non-fluorinated lithium-ion battery binder according to claim 1, characterized in that, The adhesive is a linear or cross-linked polymer; If the adhesive is a crosslinked polymer, then the crosslinking monomer is one or more of the following: divinylbenzene, polyethylene glycol (200) diacrylate, polyethylene glycol (400) diacrylate, polyethylene glycol (600) diacrylate, polyethylene glycol (200) dimethacrylate, polyethylene glycol (400) dimethacrylate, polyethylene glycol (600) dimethacrylate, N,N-methylenebisacrylamide, pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, trimethylolpropane tri(3-acrylidinepropionate), tripropylene glycol diacrylate, dipropylene glycol diacrylate, and ethoxylated (30) bisphenol A diacrylate.

4. A method for preparing a positive electrode non-fluorinated lithium-ion battery binder as described in any one of claims 1-3, characterized in that, A positive electrode non-fluorinated lithium-ion battery binder is obtained by suspension polymerization with water as the continuous phase under free radical initiation conditions, using at least partially neutralized acrylic monomers, acrylonitrile monomers, and oil-soluble monomers as reactants, or using at least partially neutralized acrylic monomers, acrylonitrile monomers, oil-soluble monomers, and water-soluble monomers as reactants.

5. The preparation method according to claim 4, characterized in that, The method is specifically as follows: A suspension is obtained by adding acrylonitrile monomers, oil-soluble monomers, and at least partially neutralized acrylic monomers to water and stirring; or, a suspension is obtained by adding acrylonitrile monomers, oil-soluble monomers, water-soluble monomers, and at least partially neutralized acrylic monomers to water and stirring. Heat to the initiation temperature, add initiator dropwise to react and obtain the product. After filtering, washing and drying the sample, the binder can be obtained. The amount of water used is 0.5 to 5 times the total weight of the individual unit; The stirring speed is 200-1000 rpm.

6. The preparation method according to claim 5, characterized in that, The initiator is potassium persulfate, sodium persulfate, azobisisobutyramidine hydrochloride, or a redox initiator composed of persulfate, sodium sulfite, and hydrogen peroxide; The initiator is equivalent to 0.1 to 2 wt% of the total weight of acrylonitrile monomers, oil-soluble monomers, and at least partially neutralized acrylic monomers; The initiation temperature is 30–100℃; The reaction time is 2–24 h.

7. The positive electrode non-fluorinated lithium-ion battery binder as described in any one of claims 1-3 is used as a positive electrode conductive slurry homogenizer and electrode processing.

Images