Water-soluble binder, battery electrode sheet and use thereof

Abstract

A water-soluble binder, a battery electrode sheet and the use thereof. The water-soluble binder comprises a copolymer. Polymeric monomers of the copolymer comprise a combination of a double-bond-containing nitrile monomer, a double-bond-containing amide monomer, a double-bond-containing carboxylic acid monomer, optionally a double-bond-containing sulfonic acid monomer and optionally a fifth monomer. The water-soluble binder is in the form of powder, and the mass percentage content of the copolymer in the water-soluble binder is greater than or equal to 92%. By means of the design of the polymeric monomers and the copolymer and the combination of the copolymer and the powder form, the water-soluble binder has excellent binding power, and can effectively inhibit the volume expansion of an electrode sheet during charge and discharge cycles, thereby improving the cycle performance of the electrode sheet and a lithium-ion battery.

Description

Water-soluble adhesive, battery pole piece and its application Technical Field

[0001] The present application belongs to the field of battery material technology, and specifically relates to a water-soluble adhesive, a battery pole piece and applications thereof. Background Art

[0002] Lithium-ion batteries are widely used in mobile electronics, the electric vehicle industry, and energy storage due to their high energy density and excellent cycle performance. Currently, the negative electrode system of commercial lithium-ion batteries is mainly based on graphite. However, the theoretical capacity of graphite as an active material is relatively low, making it difficult to meet the needs of the rapid development of energy technology. Silicon-based materials have significant advantages in capacity and are considered the most promising negative electrode active materials. However, silicon-based materials experience significant volume expansion and contraction during charge and discharge, resulting in rapid electrode capacity decay and poor battery cycle performance. Therefore, developing high-performance negative electrodes is a key approach to improving the performance of lithium-ion batteries.

[0003] The negative electrode includes the negative electrode active material that participates in the electrochemical reaction, as well as auxiliary materials such as the current collector, conductive agent, and binder that do not participate in the electrochemical reaction. The electrochemical performance of the battery is not only related to the type and properties of the active material, but also to the performance of auxiliary materials such as the binder. The main binders commonly used in negative electrodes at present include SBR (styrene-butadiene copolymer and its modified copolymer) and PAA (copolymer of acrylic acid and its derivatives); among them, SBR binder is usually used in combination with carboxymethyl cellulose (CMC). SBR itself has low strength and poor bonding force, and its inhibitory effect on the expansion of the electrode is insufficient. Therefore, the silicon negative electrode using SBR binder has obvious cycle performance defects.

[0004] Compared to SBR binders, PAA binders have the advantages of lower dosage, stronger expansion suppression, and better cycle performance, and are therefore increasingly widely used in lithium-ion battery negative electrodes. For example, CN105633411A discloses a composite binder suitable for lithium-ion battery silicon-based negative electrode materials, comprising a main binder and a complementary binder, wherein the main binder is partially neutralized polyacrylic acid, the complementary binder is styrene-butadiene rubber, and the main binder accounts for 50% or more of the composite binder by mass. The composite binder has good dispersibility and mechanical properties, which helps to improve the electrochemical performance of silicon-based negative electrode materials. CN109037689A discloses a polymer binder for lithium-ion silicon-based negative electrode materials, which is mainly composed of polyacrylic acid and contains 2%-10% by weight of a styrene-acrylate copolymer. The polymer binder forms a gel structure during the preparation of the negative electrode, which can form an integral structure with the conductive agent and silicon powder, thereby improving the negative electrode performance. CN111139002A discloses a water-soluble adhesive for lithium-ion batteries, which contains 5%-75% of a monomer CHR of formula 1.11 =CHR 12 -CN, 1%-35% of the monomer CHR of formula 2 21 =CHR 22 -CONR 23 R 24 With 5%-65% of the monomer CHR of formula 3 31 =COOR 32 The water-soluble emulsion of the formed multi-polymer can provide good bonding performance.

[0005] While the aforementioned PAA binders offer improved performance compared to SBR, they still face challenges with flexibility, adhesion, and processability in negative electrode preparation. Furthermore, the PAA binders commonly used in the industry are all aqueous solutions. To maintain good suspension and dispersion capabilities and adhesion, the polymer molecular weight is often very high, resulting in relatively low solids contents in PAA aqueous solutions. Currently available PAA binders have solid contents ranging from 5% to 15%. This low solids content significantly increases the transportation and packaging costs of PAA binders. Furthermore, because aqueous polymerization systems fail to effectively remove unpolymerized monomers and low-molecular-weight polymers, significant room for improvement in adhesion and swelling suppression remains. Therefore, developing binders with high adhesion and effective swelling suppression, while reducing transportation and packaging costs, remains an urgent challenge in this field.

[0006] On the other hand, most existing solid binders have a high content of hydrophobic monomers and are water-insoluble, which limits their application in the field of aqueous negative electrode binders. Therefore, there is an urgent need to develop a solid binder that can solve the above technical problems and is also water-soluble.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The present application provides a water-soluble adhesive, a battery pole piece and applications thereof. The water-soluble adhesive has higher bonding strength and flexibility, can effectively inhibit the expansion of active materials, and improve the cycle performance of lithium-ion batteries.

[0010] In the first aspect, the present application provides a water-soluble adhesive, which includes a copolymer, and the polymerization monomers of the copolymer include a double-bond nitrile monomer, a double-bond amide monomer, a double-bond carboxylic acid monomer, optionally a double-bond sulfonic acid monomer, and optionally a combination of a fifth type of monomer; the water-soluble adhesive is in the form of a powder, and the mass percentage of the copolymer in the water-soluble adhesive is ≥92%.

[0011] In the present application, the water-soluble binder comprises a multi-component copolymer formed by polymerizing specific monomers. As a powder (solid) material, this significantly reduces the transportation and packaging costs of PAA-type binders. Furthermore, during the powder formation process, unpolymerized monomers and low-molecular-weight polymers are removed, resulting in the copolymer having a higher molecular weight and an appropriate molecular weight distribution. This allows the water-soluble binder to achieve significantly improved adhesion and expansion suppression compared to solution-based PAA-type binders in the related art, while maintaining the copolymer's adhesiveness, water solubility, and dispersibility. Based on the design of the polymerized monomers and copolymer and their integration with the powder form, the water-soluble binder not only exhibits good dispersibility and slurry stability, but also exhibits excellent adhesion. Compared to solution-based binders in the related art, the adhesion is increased by at least 20% while the added amount is reduced by more than 20%. This achieves superior adhesion with a lower binder dosage, effectively suppressing the volume expansion of the active material during charge and discharge cycles, thereby improving the cycling performance of electrodes and lithium-ion batteries.

[0012] The following are preferred implementations of the present application, but are not intended to limit the technical solutions provided by the present application. Through the following preferred implementations, the objectives and beneficial effects of the present application can be better achieved and realized.

[0013] In the present application, the mass percentage of the copolymer in the water-soluble adhesive is ≥92%, for example, it can be 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0014] Preferably, the solid content of the water-soluble binder is ≥92%, for example, it can be 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0015] Preferably, the water content of the water-soluble binder is ≤8% by weight, for example, 0, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application does not exhaustively list the specific values ​​included in the above range. By controlling the water content to ≤8%, the binder can be further endowed with excellent water solubility, which can enable the binder to dissolve in water more quickly during the preparation of the sheet, thereby improving process efficiency.

[0016] As a further preferred embodiment of the present application, the water-soluble binder contains only a copolymer and water without other additives, the mass percentage of the copolymer is ≥92%, and the mass percentage of the water is ≤8%.

[0017] Preferably, the D of the water-soluble binder 50 The particle size is 1-100 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 70 μm, 80 μm or 90 μm, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific values ​​included in the range. The binder within the particle size range has better solubility. Further preferably, the D of the water-soluble binder 50 The particle size is 10-80μm.

[0018] Preferably, the water-soluble binder is formulated into a first aqueous solution with a solid content of 1.0%, and the viscosity of the first aqueous solution at 25.0±0.1°C is 200-20,000 cps, for example, 500 cps, 800 cps, 1,000 cps, 3,000 cps, 5,000 cps, 8,000 cps, 10,000 cps, 12,000 cps, 15,000 cps or 18,000 cps, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0019] As a further preferred embodiment of the present application, the viscosity of the first aqueous solution at 25.0±0.1° C. is 500-10000 cps.

[0020] Preferably, the light transmittance of the first aqueous solution is ≥85%. In some preferred embodiments of the present application, the light transmittance of the first aqueous solution is ≥90%. In other preferred embodiments of the present application, the light transmittance of the first aqueous solution is ≥92%.

[0021] It is generally believed that an aqueous solution with a light transmittance of ≥85% is a water-soluble binder; the water-soluble binder provided in this application has excellent water solubility, and the light transmittance of the first aqueous solution prepared with a solid content of 1.0% is ≥90%, and can be 92%-98%.

[0022] Preferably, the water-soluble binder is formulated into a second aqueous solution with a solid content of 0.5%, and the pH value of the second aqueous solution is 6.0-9.0, for example, it can be 6.2, 6.5, 6.8, 7.0, 7.2, 7.5, 7.8, 8.0, 8.2, 8.5 or 8.8, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0023] Preferably, the weight average molecular weight of the copolymer is 200,000-3,000,000, for example, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 650,000, 700,000, 750,000, 800,000, 850,000, 900,000, 950,000, 1,050,000, 1,100,000, 1,150,000, 1,200,000, 1,250,000, 1,300,000, 1,350,000, 1,400,000, 1,450,000, 1,500,000, 1,550,000, 1,600,000, 1,650,000, 1,700,000, 1,750,000, 1,050,000, 1,100,000, 1,150,000, 1,200,000, 1,250,000, 1,350,000, 1,400,000, 1,450,000, 1,500,000, 1,550,000, 1,600,000, 1,650,000, 1,700,000, 1,750,000, 1, Due to space limitations and for the sake of brevity, this application no longer exhaustively lists the specific point values ​​included in the range: 800,000, 1.85 million, 1.9 million, 1.95 million, 2 million, 2.05 million, 2.1 million, 2.15 million, 2.2 million, 2.25 million, 2.3 million, 2.35 million, 2.4 million, 2.45 million, 2.5 million, 2.55 million, 2.6 million, 2.65 million, 2.7 million, 2.75 million, 2.8 million, 2.85 million, 2.9 million or 2.95 million, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application no longer exhaustively lists the specific point values ​​included in the said range. As some preferred embodiments of the present application, the weight average molecular weight of the copolymer is 600,000-2 million; as some other preferred embodiments of the present application, the weight average molecular weight of the copolymer is 600,000-1.5 million; as some other preferred embodiments of the present application, the weight average molecular weight of the copolymer is 200,000-2 million; as some other preferred embodiments of the present application, the weight average molecular weight of the copolymer is 500,000-3 million; as some other preferred embodiments of the present application, the weight average molecular weight of the copolymer is 200,000-2.5 million.

[0024] Preferably, the molecular weight distribution of the copolymer is 2-8, for example, it can be 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.2, 7.5 or 8, and the specific point values ​​between the above-mentioned point values, limited to space and for simplicity, the application no longer exhaustively enumerates the specific point values ​​included in the scope. The application is 2-8 by controlling the molecular weight distribution of the copolymer, which can take into account the cohesiveness, water solubility and dispersibility of the copolymer, that is, the high molecular weight part helps to improve cohesive force, and a small amount of medium and low molecular weight parts help to improve water solubility, and help to improve the dispersibility of graphite. As some preferred embodiments of the application, the molecular weight distribution of the copolymer is 2-6.

[0025] As a preferred embodiment of the present application, the weight average molecular weight (Mw) of the copolymer is 200,000-3,000,000, and the molecular weight distribution of the copolymer is 2-8. Through the molecular weight and molecular weight distribution of the copolymer, the water-soluble adhesive achieves excellent technical effects in terms of adhesion, dispersibility, water solubility and inhibition of volume expansion.

[0026] Specifically, the double-bond-containing nitrile monomer has a structure shown in Formula I, the double-bond-containing amide monomer has a structure shown in Formula II, the double-bond-containing carboxylic acid monomer has a structure shown in Formula III, and the double-bond-containing sulfonic acid monomer has a structure shown in Formula IV;

[0027] Among them, R 11 Any one selected from H, Cl, Br or methyl.

[0028] R 12 Any one selected from H, Cl, Br, C1-C6 (e.g., C1, C2, C3, C4, C5 or C6) linear or branched alkyl.

[0029] R 21 、R 31 are each independently selected from H or methyl.

[0030] R 22 、R 32 Each is independently selected from any one of H, C1-C20 (e.g., C1, C2, C3, C4, C5, C6, C8, C10, C12, C15 or C18, etc.) linear or branched alkyl, and phenyl;

[0031] R 23 、R 24 Each is independently selected from any one of H, substituted or unsubstituted C1-C20 (such as C1, C2, C3, C4, C5, C6, C8, C10, C12, C15 or C18, etc.) straight chain or branched alkyl, and substituted or unsubstituted phenyl; the substituted substituent is selected from at least one of C1-C6 (such as C1, C2, C3, C4, C5 or C6) straight chain or branched alkyl, phenyl, sulfonic acid group, and sulfonate group.

[0032] M is selected from any one of H, Li, Na and K.

[0033] R 41 Selected from H or methyl.

[0034] R 42 Any one selected from H, C1-C6 (such as C1, C2, C3, C4, C5 or C6) straight chain or branched chain alkyl, and phenyl.

[0035] R 43 Any one selected from C1-C6 (e.g., C1, C2, C3, C4, C5 or C6) linear or branched alkylene and phenylene.

[0036] X is selected from any one of H, Li, Na and K.

[0037] In the present application, the term "C1-C20 straight chain or branched alkyl" is preferably a C1-C16 straight chain or branched alkyl, further preferably a C1-C10 straight chain or branched alkyl, and even more preferably a C1-C6 straight chain or branched alkyl, including but not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, 2-methylbutyl, n-pentyl, isopentyl, neopentyl, n-hexyl, neohexyl, 2-ethylhexyl, n-octyl, n-heptyl, n-nonyl or n-decyl, etc.

[0038] Preferably, in Formula I, the R 11 For H.

[0039] Preferably, in Formula I, the R 12 Selected from H or methyl.

[0040] Preferably, the double bond-containing nitrile monomer includes acrylonitrile and / or methacrylonitrile.

[0041] Preferably, the mass percentage of the double-bond nitrile monomer in the polymerization monomer of the copolymer is 1%-60%, for example, it can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or 55%, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific points included in the range. It is further preferred to be 20%-55%, and even more preferred to be 30%-55%.

[0042] Preferably, in Formula II, the R 21 For H.

[0043] Preferably, in Formula II, the R 22 Selected from H or methyl.

[0044] Preferably, in Formula II, the R 23 、R 24 Each is independently selected from any one of H, substituted or unsubstituted C1-C6 linear or branched alkyl.

[0045] Preferably, R 23 、R 24 The substituted substituent is selected from at least one of a C1-C3 straight or branched alkyl group, a phenyl group, and a sulfonic acid group.

[0046] Preferably, the double bond-containing amide monomer includes any one of acrylamide, methacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide or 2-acrylamide-2-phenylethanesulfonic acid, or a combination of at least two thereof.

[0047] Preferably, the mass percentage of the double bond amide monomer in the polymerization monomer of the copolymer is 1%-40%, for example, it can be 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35% or 38%, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific points included in the range. It is further preferred to be 5%-30%, and even more preferred to be 5%-20%.

[0048] Preferably, the double bond-containing carboxylic acid monomer includes any one or a combination of at least two of acrylic acid, methacrylic acid, sodium acrylate, sodium methacrylate, lithium acrylate or lithium methacrylate.

[0049] Preferably, the mass percentage of the double bond carboxylic acid monomer in the polymerization monomer of the copolymer is 5%-95%, for example, it can be 10%, 15%, 20%, 25%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific points included in the range. It is further preferred to be 20%-65%, and even more preferred to be 30%-60%.

[0050] Preferably, in Formula IV, the R 41 For H.

[0051] Preferably, in Formula IV, the R 42 Selected from H or methyl.

[0052] Preferably, in Formula IV, the R 43 For methylene.

[0053] Preferably, the double-bond-containing sulfonic acid monomer includes any one of methacrylic acid, propylene sulfonic acid, sodium methacrylic acid sulfonate, sodium propylene sulfonate, lithium methacrylic acid sulfonate or lithium propylene sulfonate, or a combination of at least two thereof.

[0054] Preferably, the mass percentage of the double-bond sulfonic acid monomer in the polymerized monomers of the copolymer is 0-15%, for example, it can be 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13% or 14%, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific values ​​included in the range, and 0-10% is further preferred.

[0055] Preferably, the fifth type of monomers includes double bond-containing ester monomers and / or double bond-containing ether monomers.

[0056] Preferably, the fifth type of monomer includes any one or a combination of at least two of ethyl acrylate, hydroxyethyl acrylate, butyl acrylate, hydroxybutyl acrylate, lauryl acrylate, octadecyl acrylate, ethyl methacrylate, hydroxyethyl methacrylate, butyl methacrylate, hydroxybutyl methacrylate, lauryl methacrylate, octadecyl methacrylate, alkyl polyoxyethylene ether acrylate, alkyl polyoxyethylene ether methacrylate, diethylene glycol vinyl ether, triethylene glycol vinyl ether or polyethylene glycol vinyl ether;

[0057] Preferably, the mass percentage of the fifth monomer in the polymerization monomer of the copolymer is 0-20%, for example, it can be 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or 19%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range, and 0-15% is further preferred, and 0-10% is even more preferred.

[0058] Illustratively, the preparation method of the water-soluble binder provided in the present application includes: subjecting a polymerizable monomer to a polymerization reaction in the presence of an initiator and a solvent, and subjecting the obtained polymer product to post-treatment and drying to obtain the water-soluble binder in powder form.

[0059] Preferably, the initiator comprises any one of an organic peroxide, an inorganic peroxide or a redox initiator, or a combination of at least two thereof.

[0060] Preferably, the initiator includes any one of benzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane or tert-butyl peroxide, or a combination of at least two thereof.

[0061] Preferably, based on 100 parts by mass of the polymerized monomer, the mass of the initiator is 0.01-2 parts, for example, it can be 0.03 parts, 0.05 parts, 0.08 parts, 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, 1 parts, 1.2 parts, 1.5 parts or 1.8 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific points included in the range.

[0062] Preferably, the solvent may be an organic solvent or water, or a combination of the two. The organic solvent includes, but is not limited to, methanol, ethanol, acetonitrile, or N-methylpyrrolidone (NMP). When the solvent is a combination of an organic solvent and water, the two may be mixed in any mass ratio, for example, in a mass ratio ranging from 1:99 to 99:1, and the mixture may be selected according to actual needs.

[0063] Preferably, based on 100 parts by mass of the polymerized monomer, the mass of the solvent is 100-500 parts, for example, it can be 150 parts, 200 parts, 250 parts, 300 parts, 350 parts, 400 parts or 450 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0064] Preferably, the polymerization reaction is carried out in a protective atmosphere.

[0065] Preferably, the protective atmosphere comprises nitrogen.

[0066] Preferably, the temperature of the polymerization reaction is 50-90°C, for example, it can be 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 78°C, 82°C, 85°C or 88°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0067] Preferably, the polymerization reaction time is 2-24h, for example, it can be 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 12h, 15h, 16h, 18h, 20h or 22h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0068] Preferably, the post-treatment comprises removing residual monomers, adjusting pH and solid-liquid separation performed in sequence.

[0069] Preferably, the method for removing residual monomers includes reducing pressure, and the vacuum degree of the reduced pressure (vacuuming) is ≤0.1 MPa, for example, it can be 0, 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa or 0.09 MPa, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0070] Preferably, the reagent used to adjust the pH includes any one of a sodium hydroxide aqueous solution, a lithium hydroxide aqueous solution or a potassium hydroxide aqueous solution, or a combination of at least two thereof.

[0071] Preferably, the temperature for adjusting the pH is 30-70°C, for example, it can be 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C or 68°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range, and 40-60°C is further preferred.

[0072] Preferably, the pH is adjusted to a pH value of 6.0-9.0, for example, 6.2, 6.5, 6.8, 7.0, 7.2, 7.5, 7.8, 8.0, 8.2, 8.5 or 8.8, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific points included in the range, and 7.0-8.5 is further preferred.

[0073] Preferably, the solid-liquid separation method comprises solid filter press.

[0074] Preferably, the drying step further includes crushing and screening steps.

[0075] Preferably, the preparation method comprises:

[0076] The polymerization monomer, initiator and solvent are mixed, and polymerization reaction is carried out at 50-90° C. for 2-24 hours in a protective atmosphere to obtain a polymerization product;

[0077] The polymerized product is vacuumed to ≤0.1 MPa to remove residual monomers, and then the pH value of the system is adjusted to 7.0-8.5. After solid-liquid separation, drying, crushing and screening, the water-soluble binder in powder form is obtained.

[0078] In order to further improve the dispersibility and wetting properties of the powder binder prepared above, 0.01% to 5% by weight of a wetting dispersant may be added to the water-soluble binder in powder form.

[0079] Preferably, the wetting and dispersing agent may be any one of polycarboxylic acid, modified polycarboxylic acid, polyether or modified polyether dispersants, or a combination of at least two thereof.

[0080] In a second aspect, the present application provides an electrode material composition, which includes the water-soluble binder as described in the first aspect.

[0081] Preferably, the electrode material composition comprises a combination of an active material, a conductive agent and the water-soluble binder.

[0082] Preferably, the mass percentage of the water-soluble binder in the electrode material composition is 0.3%-3%, for example, it can be 0.4%, 0.5%, 0.7%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2.0%, 2.3%, 2.5%, 2.8% or 3.0%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0083] It should be noted that the mass of the electrode material composition is the sum of the masses of the active material, the conductive agent and the water-soluble binder, and the mass of the water-soluble binder is calculated in terms of solid content.

[0084] Preferably, the electrode material composition is a negative electrode material composition, and the active material is a negative electrode active material.

[0085] Preferably, the negative electrode active material includes carbon-based materials and / or silicon-based materials.

[0086] Preferably, the carbon-based material includes any one of graphite, carbon black, carbon nanotubes, carbon fibers, mesocarbon microbeads or petroleum coke, or a combination of at least two thereof.

[0087] Preferably, the silicon-based material includes any one of nano-silicon, micro-silicon, porous silicon, amorphous silicon or silicon oxide, or a combination of at least two thereof.

[0088] Preferably, based on 100 parts by mass of the negative electrode active material, the mass of the conductive agent is 0.1-5.0 parts, for example, it can be 0.1 parts, 0.3 parts, 0.5 parts, 0.7 parts, 0.9 parts, 1.0 parts, 1.2 parts, 1.5 parts, 1.8 parts, 2.0 parts, 2.2 parts, 2.5 parts, 2.8 parts, 3.0 parts, 3.2 parts, 3.5 parts, 3.8 parts, 4.0 parts, 4.2 parts, 4.5 parts or 4.8 parts, as well as specific point values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0089] In a third aspect, the present application provides a battery electrode, comprising a current collector and a coating disposed on the current collector, wherein the material of the coating comprises the electrode material composition as described in the second aspect.

[0090] Preferably, the battery electrode is a negative electrode.

[0091] As a preferred embodiment of the present application, the peel strength of the negative electrode sheet is ≥17.8 N / mm, and can be 17.8-20.14 N / mm.

[0092] As a preferred embodiment of the present application, the water-soluble binder has excellent bonding strength and flexibility, can inhibit volume expansion, and makes the full-charge expansion of the negative electrode plate containing it ≤25.3%, which can be 24.65%-25.23%; the capacity retention rate of the lithium-ion battery containing it after 500 cycles at 60°C is ≥86.5%, which can be 86.87%-88.25%.

[0093] In a fourth aspect, the present application provides an electrochemical energy storage device, which includes at least one of the water-soluble binder as described in the first aspect, the electrode material composition as described in the second aspect, or the battery electrode as described in the third aspect.

[0094] Preferably, the electrochemical energy storage device comprises any one of a lithium-ion battery, a sodium-ion battery, a supercapacitor, a fuel cell or a solar cell, and more preferably a lithium-ion battery.

[0095] Compared with the related art, this application has the following beneficial effects.

[0096] The water-soluble powder binder provided in this application includes a multi-component copolymer formed by the polymerization of specific types of monomers. As a powder material, it not only greatly reduces the transportation and packaging costs of PAA-type binders, but also removes unpolymerized monomers and low-molecular-weight polymers during the powder formation process, thereby making the water-soluble binder in powder form have significantly improved adhesion and expansion inhibition capabilities compared to the solution-type PAA-type binders in the related art. Based on the design of the polymerized monomers and copolymers and their combination with the powder form, the water-soluble binder has excellent adhesion, which is at least 20% higher than the adhesion of existing solution-type binders and the addition amount is reduced by 20%. It can effectively inhibit the volume expansion of the electrode during the charge and discharge cycle, thereby improving the cycle performance of the electrode and lithium-ion battery. On the other hand, compared with the glue product, the powder product is more easily pressed tightly onto the graphite surface during kneading, forming a denser coating effect, thereby improving processing performance and further improving electrical performance.

[0097] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0098] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0099] As used herein, the terms "comprises," "including," "having," "containing" or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a listed element is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0100] "Optionally", "optionally", and "either" means that the subsequently described matter or event can or cannot occur, and that the description includes instances where the event occurs and instances where it does not.

[0101] The indefinite articles "a" and "an" before an element or component of the present application do not limit the quantity requirement (i.e., the number of times the element or component appears). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the quantity clearly refers to only the singular form.

[0102] The terms "one embodiment," "some embodiments," "exemplarily," "specific examples," or "some examples" used herein mean that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present application. In this document, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0103] Moreover, the technical features involved in each embodiment of the present application can be combined with each other as long as they do not conflict with each other.

[0104] In the following specific embodiments of the present application, the polymerization monomers, initiators, solvents, etc. used are all commercially available products.

[0105] The testing methods involved in the following specific implementations of this application are as follows.

[0106] (1) Solid content of water-soluble binder:

[0107] Take 2-3g of the powder or glue to be tested, place it in a 120℃ forced air oven and bake it for 2h. Record the mass before and after baking as m0 and m1 respectively. Solid content = m1 / m0×100%.

[0108] (2) Water-soluble adhesive D 50 Particle size:

[0109] The test was carried out using a RODOT T4.1+VIBRI laser particle size analyzer.

[0110] (3) Weight average molecular weight and molecular weight distribution of water-soluble adhesives:

[0111] The weight average molecular weight (Mw) and molecular weight distribution of the water-soluble adhesive (copolymer) were obtained by gel permeation chromatography (GPC).

[0112] The specific test conditions are as follows: analytical instrument: Agilent 1260 Infinity II; mobile phase: 0.1 Mol / L NaNO3 aqueous solution; chromatographic column: Waters Ultrastyragel 1000 and Waters Ultrastyragel 120 in series; detector: Agilent 1260 RID; standard: PEG; flow rate: 0.8 mL / min; column temperature: 40°C; detector temperature: 40°C.

[0113] (4) Viscosity of water-soluble adhesive solution:

[0114] Add deionized water to dissolve the powder to the required solid content. After confirming that it is fully dissolved, keep the temperature at 25°C and use NDJ-5S digital rotational viscometer to test the viscosity of the glue.

[0115] (5) Transmittance of water-soluble adhesive solution:

[0116] Use a UV spectrophotometer. Weigh 10g of the adhesive solution to the nearest 0.1g, add water to a 20mL volumetric flask, stir thoroughly, and use this as the test solution. Maintain a constant temperature of 25°C. Rinse a clean 10mm cuvette with pure water and test at a wavelength of 430nm. First, adjust the transmittance to zero with the pure water used to adjust the volume, then measure the transmittance of the test solution.

[0117] (6) pH value of water-soluble adhesive solution:

[0118] Using a Mettler pH meter, add deionized water to dissolve the powder to a solid content of 0.5%, stir and disperse thoroughly until transparent, ensure that the sample is diluted and dispersed evenly without agglomeration, and test the pH with a pH meter.

[0119] Example 1

[0120] A water-soluble adhesive in powder form comprises a copolymer, wherein the monomers of the copolymer comprise, by weight, 55 parts of acrylic acid, 5 parts of N,N-diethylacrylamide, and 40 parts of acrylonitrile. The preparation method of the water-soluble adhesive is as follows:

[0121] A mixed solvent of 350 parts pure water and acetonitrile was added to a reaction kettle, stirred at 100 rpm, and each polymerization monomer was added according to the aforementioned formula. Nitrogen was continuously introduced and stirred for 3 hours to obtain a solution. The temperature was raised to 80° C., and 0.5 parts benzoyl peroxide solution (10% by mass) was added to the aforementioned solution. The mixture was reacted at 80° C. for 10 hours to obtain a polymerization product. The polymerization product was decompressed at 60° C. to a vacuum degree of less than 0.1 MPa using a vacuum pump to remove residual monomers. The product was then neutralized with a lithium hydroxide aqueous solution at 50° C. to a pH of 7.5. The solid was filter-pressed, dried, pulverized, and sieved to obtain the water-soluble binder in powder form.

[0122] The solid content of the water-soluble binder provided in this embodiment is 92%, D 50 The particle size is 50μm.

[0123] The Mw of the water-soluble binder (copolymer) is 8.96×10 5 , the molecular weight distribution is 2.72.

[0124] The water-soluble binder is redispersed and dissolved into an aqueous solution with a solid content of 1.0%, a viscosity of 1000 cps, and a light transmittance of 98%.

[0125] The water-soluble binder is redispersed and dissolved into a 0.5% aqueous solution with a pH value of 7.5.

[0126] Example 2

[0127] A water-soluble adhesive in powder form comprises a copolymer whose monomers, in parts by mass, include: 30 parts acrylic acid, 10 parts N,N-diethylacrylamide, 55 parts acrylonitrile, and 5 parts sodium methacrylate sulfonate. The preparation method of the water-soluble adhesive is as follows:

[0128] A mixed solvent of 350 parts pure water and acetonitrile was added to a reaction kettle, stirred at 100 rpm, and each polymerization monomer was added according to the aforementioned formula. Nitrogen was continuously introduced and stirred for 3 hours to obtain a solution. The temperature was raised to 80° C., and 0.5 parts benzoyl peroxide solution (10% by mass) was added to the aforementioned solution. The mixture was reacted at 80° C. for 10 hours to obtain a polymerization product. The polymerization product was decompressed at 60° C. to a vacuum degree of less than 0.1 MPa using a vacuum pump to remove residual monomers. The product was then neutralized with a lithium hydroxide aqueous solution at 50° C. to a pH of 7.8. The solid was filter-pressed, dried, pulverized, and sieved to obtain the water-soluble binder in powder form.

[0129] The solid content of the water-soluble binder provided in this embodiment is 95%, D 50 The particle size is 57μm.

[0130] The Mw of the water-soluble binder (copolymer) is 9.24×105 , the molecular weight distribution is 2.54.

[0131] The water-soluble binder is redispersed and dissolved into an aqueous solution with a solid content of 1.0%, a viscosity of 10,000 cps, and a light transmittance of 92%.

[0132] The water-soluble binder is redispersed and dissolved into a 0.5% aqueous solution with a pH value of 7.7.

[0133] Example 3

[0134] A water-soluble adhesive in powder form comprises a copolymer whose monomers, in parts by mass, include: 35 parts acrylic acid, 15 parts N,N-diethylacrylamide, 40 parts acrylonitrile, and 10 parts sodium methacrylate sulfonate. The preparation method of the water-soluble adhesive is as follows:

[0135] A mixed solvent of 350 parts pure water and acetonitrile was added to a reaction kettle, stirred at 100 rpm, and each polymerization monomer was added according to the aforementioned formula. Nitrogen was continuously introduced and stirred for 3 hours to obtain a solution. The temperature was raised to 80° C., and 0.5 parts benzoyl peroxide solution (10% by mass) was added to the aforementioned solution. The mixture was reacted at 80° C. for 10 hours to obtain a polymerization product. The polymerization product was decompressed at 60° C. to a vacuum degree of less than 0.1 MPa using a vacuum pump to remove residual monomers. The product was then neutralized with a lithium hydroxide aqueous solution at 50° C. to a pH of 7.4. The solid was filter-pressed, dried, pulverized, and sieved to obtain the water-soluble binder in powder form.

[0136] The solid content of the water-soluble binder provided in this embodiment is 94%, D 50 The particle size is 63μm.

[0137] The Mw of the water-soluble binder (copolymer) is 8.46×10 5 , the molecular weight distribution is 2.83.

[0138] The water-soluble binder is redispersed and dissolved into an aqueous solution with a solid content of 1.0%, a viscosity of 4500 cps, and a light transmittance of 95%.

[0139] The water-soluble binder is redispersed and dissolved into a 0.5% aqueous solution with a pH value of 7.3.

[0140] Example 4

[0141] A water-soluble adhesive in powder form comprises a copolymer whose monomers, in parts by mass, include: 60 parts acrylic acid, 10 parts N,N-diethylacrylamide, 20 parts acrylonitrile, and 10 parts sodium methacrylate sulfonate. The preparation method of the water-soluble adhesive is as follows:

[0142] A mixed solvent of 350 parts pure water and acetonitrile was added to a reaction kettle, stirred at 100 rpm, and each polymerization monomer was added according to the aforementioned formula. Nitrogen was continuously introduced and stirred for 3 hours to obtain a solution. The temperature was raised to 80° C., and 0.5 parts benzoyl peroxide solution (10% by mass) was added to the aforementioned solution. The mixture was reacted at 80° C. for 10 hours to obtain a polymerization product. The polymerization product was decompressed at 60° C. to a vacuum degree of less than 0.1 MPa using a vacuum pump to remove residual monomers. The product was then neutralized with a lithium hydroxide aqueous solution at 50° C. to a pH of 7.5. The solid was filter-pressed, dried, pulverized, and sieved to obtain the water-soluble binder in powder form.

[0143] The solid content of the water-soluble binder provided in this embodiment is 94%, D 50 The particle size is 60μm.

[0144] The Mw of the water-soluble binder (copolymer) is 11.65×10 5 , the molecular weight distribution is 3.46.

[0145] The water-soluble binder is redispersed and dissolved into an aqueous solution with a solid content of 1.0%, a viscosity of 550 cps, and a light transmittance of 98%.

[0146] The water-soluble binder is redispersed and dissolved into a 0.5% aqueous solution with a pH value of 7.5.

[0147] Example 5

[0148] A water-soluble adhesive in powder form comprises a copolymer, wherein the monomers of the copolymer comprise, by weight, 55 parts of acrylic acid, 5 parts of N,N-diethylacrylamide, and 40 parts of acrylonitrile. The preparation method of the water-soluble adhesive is as follows:

[0149] A mixed solvent of 450 parts pure water and acetonitrile was added to a reaction kettle, stirred at 100 rpm, and each polymerization monomer was added according to the aforementioned formula. Nitrogen was continuously introduced and stirred for 3 hours to obtain a solution. The temperature was raised to 80° C., and 0.7 parts benzoyl peroxide solution (10% by mass) was added to the aforementioned solution. The mixture was reacted at 80° C. for 8 hours to obtain a polymerization product. The polymerization product was decompressed at 60° C. to a vacuum degree of less than 0.1 MPa using a vacuum pump to remove residual monomers. The product was then neutralized with a lithium hydroxide aqueous solution at 50° C. to a pH of 7.7. The solid was filter-pressed, dried, crushed, and sieved to obtain the water-soluble binder in powder form.

[0150] The solid content of the water-soluble binder provided in this embodiment is 95%, D 50 The particle size is 65μm.

[0151] The Mw of the water-soluble binder (copolymer) is 4.5×10 5, the molecular weight distribution is 4.38.

[0152] The water-soluble binder is redispersed and dissolved into an aqueous solution with a solid content of 1.0%, a viscosity of 550 cps, and a light transmittance of 94%.

[0153] The water-soluble binder is redispersed and dissolved into a 0.5% aqueous solution with a pH value of 7.7.

[0154] Example 6

[0155] A water-soluble adhesive in powder form comprises a copolymer whose monomers, in parts by mass, include: 45 parts acrylic acid, 10 parts N,N-diethylacrylamide, 40 parts acrylonitrile, and 5 parts butyl acrylate. The preparation method of the water-soluble adhesive is as follows:

[0156] A mixed solvent of 350 parts pure water and acetonitrile was added to a reaction kettle, stirred at 100 rpm, and each polymerization monomer was added according to the aforementioned formula. Nitrogen was continuously introduced and stirred for 3 hours to obtain a solution. The temperature was raised to 75° C., and 0.5 parts benzoyl peroxide solution (10% by mass) was added to the aforementioned solution. The mixture was reacted at 75° C. for 12 hours to obtain a polymerization product. The polymerization product was decompressed at 60° C. to a vacuum degree of less than 0.1 MPa using a vacuum pump to remove residual monomers. The product was then neutralized with a lithium hydroxide aqueous solution at 50° C. to a pH of 7.7. The solid was filter-pressed, dried, pulverized, and sieved to obtain the water-soluble binder in powder form.

[0157] The solid content of the water-soluble binder provided in this embodiment is 93%, D 50 The particle size is 57μm.

[0158] The Mw of the water-soluble binder (copolymer) is 12.86×10 5 , the molecular weight distribution is 4.79.

[0159] The water-soluble binder is redispersed and dissolved into an aqueous solution with a solid content of 1.0%, a viscosity of 7000 cps, and a light transmittance of 94%.

[0160] The water-soluble binder is redispersed and dissolved into a 0.5% aqueous solution with a pH value of 7.7.

[0161] Example 7

[0162] A water-soluble adhesive in powder form comprises a copolymer whose monomers, in parts by mass, include: 40 parts acrylic acid, 10 parts N,N-diethylacrylamide, 45 parts acrylonitrile, and 5 parts butyl acrylate. The preparation method of the water-soluble adhesive is as follows:

[0163] A mixed solvent of 350 parts pure water and acetonitrile was added to a reaction kettle, stirred at 100 rpm, and each polymerization monomer was added according to the aforementioned formula. Nitrogen was continuously introduced and stirred for 3 hours to obtain a solution. The temperature was raised to 72° C., and 0.3 parts benzoyl peroxide solution (10% by mass) was added to the aforementioned solution. The mixture was reacted at 72° C. for 12 hours to obtain a polymerization product. The polymerization product was decompressed at 60° C. to a vacuum degree of less than 0.1 MPa using a vacuum pump to remove residual monomers. The product was then neutralized with a lithium hydroxide aqueous solution at 50° C. to a pH of 7.5. The solid was filter-pressed, dried, pulverized, and sieved to obtain the water-soluble binder in powder form.

[0164] The solid content of the water-soluble binder provided in this embodiment is 95%, D 50 The particle size is 50μm.

[0165] The Mw of the water-soluble binder (copolymer) is 19.88×10 5 , the molecular weight distribution is 5.33.

[0166] The water-soluble binder is redispersed and dissolved into an aqueous solution with a solid content of 1.0%, a viscosity of 10,000 cps, and a light transmittance of 93%.

[0167] The water-soluble binder is redispersed and dissolved into a 0.5% aqueous solution with a pH value of 7.5.

[0168] Comparative Example 1

[0169] The invention discloses a binder, which is prepared by combining commercially available styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) in a mass ratio of 1:1.

[0170] Comparative Example 2

[0171] The invention discloses an adhesive, which is a commercially available acrylic resin PAA adhesive and a solution-type adhesive.

[0172] Comparative Example 3

[0173] A water-soluble adhesive in solution form is prepared by the following method: adding 350 parts of pure water to a reaction kettle, stirring at 100 rpm, then adding 55 parts of acrylic acid, 5 parts of N,N-diethylacrylamide, and 40 parts of acrylonitrile, continuously purging with nitrogen, and stirring for 3 hours to obtain a solution; heating the reaction mixture to 80°C, adding 0.5 parts of a 10% by mass benzoyl peroxide solution to the solution, and reacting the mixture at 80°C for 10 hours to obtain a polymerized product. The polymerized product is then decompressed at 60°C using a vacuum pump to a vacuum degree of less than 0.1 MPa to remove residual monomers, then neutralized with a lithium hydroxide aqueous solution at 50°C to a pH of 7.5, and water is added to adjust the solids content to 5%, thereby obtaining the water-soluble adhesive.

[0174] The solid content of the water-soluble adhesive provided in this comparative example is 5%. When the water-soluble adhesive is diluted to a 1% aqueous solution, the viscosity is 600 cps and the light transmittance is 94%.

[0175] The Mw of the water-soluble binder (copolymer) is 5.34×10 5 , the molecular weight distribution is 3.67.

[0176] Application Examples 1-7, Comparative Application Examples 1-3

[0177] A negative electrode plate comprises a current collector (Cu foil) and a coating disposed on the current collector, wherein the coating is made of a negative electrode material composition; the negative electrode material composition comprises a negative electrode active material (graphite), a conductive agent (conductive carbon black SP) and a binder; wherein the binder is the binder provided in Examples 1-7 and Comparative Examples 1-3, respectively.

[0178] Preparation of the negative electrode sheet: The negative electrode active material, SP and the binder of Examples 1-7 were mixed in a mass ratio of 97.0:1:2.0, added to pure water at a ratio of 50% solid content of the system, and stirred thoroughly to form a uniform negative electrode slurry, which was coated on the negative electrode current collector Cu foil, dried, and roll-pressed to obtain a negative electrode sheet.

[0179] For the binder of Comparative Examples 1-3, the negative electrode active material, SP and the binder of Comparative Examples 1-3 were mixed in a mass ratio of 96.5:1:2.5, added to pure water at a ratio of 50% of the system solid content, and stirred and mixed thoroughly to prepare a uniform negative electrode slurry, which was coated on the negative electrode current collector Cu foil, dried, and roll-pressed to obtain a negative electrode sheet.

[0180] A lithium-ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the negative electrode sheet is the aforementioned negative electrode sheet; the preparation method of the lithium-ion battery is as follows:

[0181] (1) Preparation of positive electrode sheet: The positive electrode active material (nickel-cobalt-manganese ternary material NCM622), conductive agent (SP) and binder (polyvinylidene fluoride, PVDF) were mixed in a mass ratio of 95.5:2.0:2.5, added to N-methylpyrrolidone (NMP) at a solid content of 50%, and stirred thoroughly to prepare a uniform positive electrode slurry. The slurry was coated on the positive electrode current collector Al foil, dried, and rolled to obtain a positive electrode sheet.

[0182] (2) Preparation of negative electrode sheet: as described above;

[0183] (3) Diaphragm: PP porous polymer film;

[0184] (4) Assembly of lithium-ion batteries: The positive electrode sheet, the separator and the negative electrode sheet are wound in sequence to obtain a battery cell; the battery cell is encapsulated with an aluminum-plastic film, baked to remove water, and then injected with an electrolyte (LiPF6 electrolyte, 1 mol / L, the solvent is a mixture of ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a mass ratio of 3:2:5), and the lithium-ion battery is obtained through vacuum packaging, shelving, formation, secondary sealing, shaping and other processes.

[0185] The performance test of the negative electrode and lithium-ion battery is carried out as follows:

[0186] (1) Peel strength: The electrode sheets of the embodiment and comparative example were cut into 20 cm × 2.5 cm strips. A 1 mm thick steel plate was adhered to the current collector side with double-sided tape, and a transparent tape was attached to the coating layer side. The strips were peeled off in a 180° direction at a speed of 100 mm / min using a tensile testing machine, and the peel stress was measured.

[0187] (2) Full charge expansion: The lithium-ion battery was charged and discharged at 0.5C in the voltage range of 2.5-4.2V at 25°C. The constant current method was used to test the initial coulombic efficiency of the charge and discharge cycle and the coulombic efficiency and capacity retention rate after 50 cycles. After 50 cycles of charge and discharge, when the electrode plate was fully charged and lithium-intercalated, the ratio of the increase in the electrode plate thickness to the thickness of the electrode plate before charge and discharge was recorded as full charge expansion.

[0188] (3) Cycle performance: The lithium-ion battery was placed directly in an oven at 60°C and charged and discharged at 1C in the voltage range of 2.5-4.2V. The cycle capacity retention rate after 500 cycles was measured.

[0189] The test results are shown in Table 1:

[0190] Table 1

[0191] According to the test results in Table 1, compared with the conventional SBR binder and solution-type PAA binder in Comparative Examples 1-3, the water-soluble binder provided in the present application as a powder material not only reduces the transportation cost and packaging cost of the solution-type binder, but also has significantly improved bonding strength and expansion inhibition ability compared to the solution-type PAA binder in the related art; by optimizing the design of the copolymer molecular weight, the water-soluble binder provided in the present application as a powder material not only reduces the transportation cost and packaging cost of the solution-type binder, but also has significantly improved bonding strength and expansion inhibition ability compared to the solution-type PAA binder in the related art;

[0192] The peel strength of the negative electrode sheets of the water-soluble binders described in Examples 1-3 and 6-7 was 17.8-20.14 N / mm, the full-charge expansion rate was 24.65%-26.78%, and the capacity retention rate of the lithium-ion battery after 500 cycles at 60°C was 86.87%-88.25%, effectively improving the cycle performance of the lithium-ion battery. Comparing Examples 1-3, 6-7 with Examples 4-5, it can be seen that the design of the comonomer of the copolymer and the design of the specific molecular weight can further optimize the water-soluble binder in terms of adhesion, dispersibility, water solubility, and inhibition of volume expansion. The slightly lower amount of nitrile monomer in Example 4 resulted in a decrease in the adhesion performance of the water-soluble binder; the lower molecular weight of the copolymer in Example 5 resulted in varying degrees of reduction in the adhesion, water solubility, and ability to inhibit volume expansion of the water-soluble binder.

[0193] The applicant declares that this application uses the above-mentioned embodiments to illustrate the water-soluble adhesive, battery electrode, and their applications. However, this application is not limited to the above-mentioned embodiments, which does not mean that this application must rely on the above-mentioned embodiments in order to be implemented. Those skilled in the art should understand that any improvements to this application, equivalent replacements for various raw materials in the products of this application, addition of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of this application.

Claims

1. A water-soluble binder comprising a copolymer, wherein the polymerization monomers of the copolymer comprise a combination of a double-bond nitrile monomer, a double-bond amide monomer, a double-bond carboxylic acid monomer, optionally a double-bond sulfonic acid monomer, and optionally a fifth monomer; the water-soluble binder is in the form of a powder, and the weight percentage of the copolymer in the water-soluble binder is ≥92%.

2. The water-soluble adhesive according to claim 1, wherein The D of the water-soluble binder 50 The particle size is 1-100μm.

3. The water-soluble adhesive according to claim 1, wherein The water-soluble binder is prepared into a first aqueous solution with a solid content of 1.0%, wherein the viscosity of the first aqueous solution at 25.0±0.1° C. is 200-20000 cps; The light transmittance of the first aqueous solution is ≥85%.

4. The water-soluble adhesive according to claim 1, wherein The water-soluble binder is prepared into a second aqueous solution with a solid content of 0.5%, and the pH value of the second aqueous solution is 6.0-9.

0.

5. The water-soluble adhesive according to claim 1, wherein The weight average molecular weight of the copolymer is 200,000-3,000,000. The water-soluble adhesive according to claim 1 , wherein: The molecular weight distribution of the copolymer is 2-8.

7. The water-soluble adhesive according to claim 1, wherein The double bond-containing nitrile monomers include acrylonitrile and / or methacrylonitrile; The double bond-containing amide monomers include any one or a combination of at least two of acrylamide, methacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide or 2-acrylamide-2-phenylethanesulfonic acid; The double bond-containing carboxylic acid monomer includes any one or a combination of at least two of acrylic acid, methacrylic acid, sodium acrylate, sodium methacrylate, lithium acrylate or lithium methacrylate; The double bond-containing sulfonic acid monomer includes any one of methacrylic acid, propylene sulfonic acid, sodium methacrylic acid sulfonate, sodium propylene sulfonate, lithium methacrylic acid sulfonate or lithium propylene sulfonate, or a combination of at least two thereof; The fifth type of monomers includes any one of ethyl acrylate, hydroxyethyl acrylate, butyl acrylate, hydroxybutyl acrylate, lauryl acrylate, octadecyl acrylate, ethyl methacrylate, hydroxyethyl methacrylate, butyl methacrylate, hydroxybutyl methacrylate, lauryl methacrylate, octadecyl methacrylate, alkyl polyoxyethylene ether acrylate, alkyl polyoxyethylene ether methacrylate, diethylene glycol vinyl ether, triethylene glycol vinyl ether or polyethylene glycol vinyl ether, or a combination of at least two thereof.

8. The water-soluble adhesive according to claim 1, wherein The mass percentage of the double-bond nitrile monomer in the polymerization monomers of the copolymer is 1%-60%, the mass percentage of the double-bond amide monomer is 1%-40%, the mass percentage of the double-bond carboxylic acid monomer is 5%-95%, the mass percentage of the double-bond sulfonic acid monomer is 0-15%, and the mass percentage of the fifth type of monomer is 0-20%.

9. An electrode material composition comprising the water-soluble binder according to any one of claims 1 to 8.

10. The electrode material composition according to claim 9, wherein The electrode material composition includes a combination of an active material, a conductive agent and the water-soluble binder; The mass percentage of the water-soluble binder in the electrode material composition is 0.3%-3.0%.

11. A battery pole piece, comprising a current collector and a coating disposed on the current collector, wherein the material of the coating comprises the electrode material composition according to claim 9 or 10.

12. An electrochemical energy storage device comprising at least one of the water-soluble binder according to any one of claims 1 to 8, the electrode material composition according to claim 9 or 10, or the battery electrode according to claim 11; The electrochemical energy storage device includes any one of a lithium ion battery, a sodium ion battery, a supercapacitor, a fuel cell or a solar cell.

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