Water-soluble binder, battery electrode pieces, and their applications

Abstract

This application provides a water-soluble binder, battery electrodes, and applications thereof. The water-soluble binder comprises a copolymer, the polymerizable monomers of the copolymer comprising a combination of double-bond-containing nitrile monomers, double-bond-containing amide monomers, double-bond-containing carboxylic acid monomers, optionally double-bond-containing sulfonic acid monomers, and optionally a fifth type monomer, the water-soluble binder is in powder form, and the mass percentage content of the copolymer in the water-soluble binder is ≥92%. Through the design of the polymerizable monomers and copolymers and their combination with powder form, this application makes it possible to improve the cycle performance of electrodes and lithium-ion batteries by providing a water-soluble binder with excellent adhesive strength and effectively suppressing volume expansion during charge-discharge cycles of the electrodes.

Description

[Technical Field]

[0001] This application belongs to the field of battery materials technology, and more specifically, relates to water-soluble binders, battery electrodes, and their applications. [Background technology]

[0002] Lithium-ion batteries, with their high energy density and excellent cycle performance, are currently widely used in mobile electronics, electric vehicle industries, and energy storage fields. Currently, commercially available lithium-ion batteries primarily use graphite negative electrodes. However, the theoretical capacity of graphite-based batteries is relatively low, making it difficult to meet the demands of rapidly developing energy technologies. Silicon-based materials offer clear advantages in terms of capacity and are considered the most promising negative electrode active material. However, silicon-based materials undergo very large volume expansion and contraction during charging and discharging, leading to rapid decay of electrode capacity and poor battery cycle performance. Therefore, developing high-performance negative electrodes is a crucial step in improving lithium-ion battery performance.

[0003] The negative electrode includes a negative electrode active material that participates in the electrochemical reaction, and auxiliary materials that do not participate in the electrochemical reaction, such as current collectors, conductive agents, and binders. The electrochemical performance of a battery is related not only to the type and properties of the active material, but also to the performance of auxiliary materials such as binders. Currently, the main binders commonly used in negative electrodes include SBR (styrene-butadiene copolymer and its modified copolymer) systems and PAA (acrylic acid and its derivative copolymer) systems. Here, SBR binders are usually used in combination with carboxymethylcellulose (CMC), but because SBR itself has low strength, poor adhesive strength, and insufficient suppression of electrode piece expansion, silicon negative electrodes using SBR binders have clear cycle performance defects.

[0004] PAA-based binders have advantages over SBR-based binders, such as requiring relatively less material, having strong expansion suppression capabilities, and exhibiting good cycle performance, and are therefore increasingly being applied to lithium-ion battery anodes. For example, CN105633411A discloses a composite binder applicable to silicon-based anode materials for lithium-ion batteries, comprising a main binder and a compounding binder, wherein the main binder is partially neutralized polyacrylic acid, the compounding binder is styrene-butadiene rubber, and the mass ratio of the main binder to the composite binder is 50% or more. This composite binder has good dispersibility and mechanical properties and helps improve the electrochemical performance of silicon-based anode materials. CN109037689A discloses a polymer binder for lithium-ion silicon anode material, mainly composed of polyacrylic acid with 2% to 10% by weight of styrene-acrylic acid copolymer added. This polymer binder forms a gel structure during the anode manufacturing process, forming an integrated structure with the conductive agent and silicon powder, thereby improving the performance of the anode. CN111139002A discloses a polymer binder containing 5% to 75% of the monomer CHR of formula 1. 11 =CHR 12 -CN and 1% to 35% of the monomer CHR of formula 2. 21 =CHR 22 -CONR 23 R 24 And, 5% to 65% of the monomer CHR of formula 3 31 =COOR 32 We disclose a water-soluble binder for lithium-ion batteries, which is a water-soluble emulsion containing a multi-copolymer formed from and can provide good adhesive performance.

[0005] Although the performance of the above-mentioned PAA-based binders has improved compared to SBR, problems still remain in terms of flexibility, adhesion, and processability in the manufacture of anodes. Furthermore, all PAA-based binders currently used in the industry are aqueous solutions, and in order to maintain good suspension dispersion ability and adhesion, the molecular weight of the polymer is generally very high, and therefore the solid content of PAA-based aqueous solutions is generally relatively low. Currently, the solid content of available PAA-based binders is between 5% and 15%, and the relatively low solid content of liquid binders significantly increases both the transportation and packaging costs of PAA-based binders. At the same time, aqueous polymerization systems cannot effectively remove unpolymerized monomers and low molecular weight polymer portions, so there is considerable room for improvement in terms of adhesion and expansion suppression. Therefore, the development of binders with high adhesion and effective expansion suppression, as well as the reduction of transportation and packaging costs, are urgent issues that need to be addressed in this field.

[0006] On the one hand, most conventional solid binders have a relatively high content of hydrophobic monomers and are not water-soluble, which limits their applications in the field of aqueous anode binders. Therefore, there is a need for the development of a solid binder that can solve the above technical problems while simultaneously possessing water solubility. [Overview of the Initiative]

[0007] The following is an overview of the topics described in detail herein. This overview is not intended to limit the scope of the claims.

[0008] This application provides a water-soluble binder, a battery electrode, and applications thereof. The water-soluble binder has higher adhesive strength and flexibility, effectively suppresses the expansion of the active material, and can improve the cycle performance of lithium-ion batteries.

[0009] In a first embodiment, the present application provides a water-soluble binder comprising a copolymer, wherein the polymerizable 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, a selectable double-bond-containing sulfonic acid monomer, and a selectable fifth monomer, the water-soluble binder is in the form of a powder, and the mass percentage content of the copolymer in the water-soluble binder is ≥ 92%.

[0010] In this application, the water-soluble binder contains a multi-copolymer formed by polymerizing specific monomers, and as a powder (solid) material, it significantly reduces the transportation and packaging costs of PAA-based binders. Furthermore, in the powder formation process, unpolymerized monomers and low molecular weight polymer portions are removed, resulting in a copolymer with an even higher molecular weight and an appropriate molecular weight distribution. As a result, the water-soluble binder can simultaneously possess copolymer adhesion, water solubility, and dispersibility compared to solution-type PAA-based binders in related technologies, and has significantly improved adhesive strength and expansion suppression ability. Based on the design of polymerizable monomers and copolymers and their combination with powder form, the water-soluble binder not only has good dispersibility and paste stability but also excellent adhesive strength. Compared to solution-type binders in related technologies, the adhesive strength is improved by at least 20%, the amount added is reduced by 20%, a better adhesive effect is achieved with less binder usage, and the expansion of active material volume during charge-discharge cycles can be effectively suppressed, thereby improving the cycle performance of electrodes and lithium-ion batteries.

[0011] The following are preferred embodiments of the present application, but are not limitations on the technical solutions provided herein. Rather, the objectives and beneficial effects of the present application can be better achieved and realized by these preferred embodiments.

[0012] In the present application, the mass percentage content of the copolymer in the water-soluble binder is ≥ 92%, for example, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%, and may also be a specific point value between the above point values. Considering the limitations of the paper surface and conciseness, the present application does not comprehensively list the specific point values included in the above range.

[0013] Preferably, the solid content of the water-soluble binder is ≥ 92%, for example, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%, and may also be a specific point value between the above point values. Considering the limitations of the paper surface and conciseness, the present application does not comprehensively list the specific point values included in the above range.

[0014] Preferably, the mass percentage content of water in the water-soluble binder is ≤ 8%, for example, 0, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7% or 8%, and may also be a specific point value between the above point values. Considering the limitations of the paper surface and conciseness, the present application does not comprehensively list the specific point values included in the above range. By controlling the water content ≤ 8%, excellent water-soluble ability can be further imparted to the binder, and when manufacturing the electrode sheet, the binder can be dissolved in water faster, improving the process efficiency.

[0015] As a further preferred embodiment of the present application, the water-soluble binder contains only the copolymer and water, does not contain other additives, the mass percentage content of the copolymer is ≥ 92%, and the mass percentage content of the water is ≤ 8%.

[0016] Preferably, the D of the water-soluble binder 50The particle size is 1 to 100 μm, and may be, 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, and specific point values ​​between the above point values. Considering the limitations of space and conciseness, this application does not comprehensively list specific point values ​​included in the above range. Binders within the above particle size range have superior dissolving ability. More preferably, the D of the water-soluble binder is 50 The particle size is 10-80 μm.

[0017] Preferably, the water-soluble binder is prepared as 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 to 20000 cps, and may be, for example, 500 cps, 800 cps, 1000 cps, 3000 cps, 5000 cps, 8000 cps, 10000 cps, 12000 cps, 15000 cps, or 18000 cps, as well as specific point values ​​between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range.

[0018] In a further preferred embodiment of the present invention, the viscosity of the first aqueous solution at 25.0 ± 0.1°C is 500 to 10000 cps.

[0019] 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%, and in some other preferred embodiments of the present application, the light transmittance of the first aqueous solution is ≥ 92%.

[0020] Generally, a water-soluble binder is considered to have a light transmittance of ≥85% in an aqueous solution. The water-soluble binder provided by 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 may be 92% to 98%.

[0021] Preferably, the above water-soluble binder is prepared as a second aqueous solution with a solid content of 0.5%, and the pH value of the second aqueous solution is 6.0 to 9.0, and may be, 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, and specific point values ​​between the above point values. Considering the limitations of space and conciseness, this application does not comprehensively list specific point values ​​included in the above range.

[0022] Preferably, the weight-average molecular weight of the copolymer is 200,000 to 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, 1,000,000, 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, 1,800,000, 1,850,000, 1,900,000 These could be 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 points. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range. In some preferred embodiments of the present application, the weight-average molecular weight of the copolymer is 600,000 to 2,000,000; in some other preferred embodiments of the present application, the weight-average molecular weight of the copolymer is 600,000 to 1,500,000; in some other preferred embodiments of the present application, the weight-average molecular weight of the copolymer is 200,000 to 2,000,000; in some other preferred embodiments of the present application, the weight-average molecular weight of the copolymer is 500,000 to 3,000,000; and in some other preferred embodiments of the present application, the weight-average molecular weight of the copolymer is 200,000 to 2,500,000.

[0023] Preferably, the molecular weight distribution of the copolymer is 2 to 8, and may be, for example, 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 specific point values ​​between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range. By controlling the molecular weight distribution of the copolymer to 2 to 8, this application can simultaneously provide adhesion, water solubility, and dispersibility of the copolymer; that is, the high molecular weight portion helps to improve adhesion, and the small amount of medium and low molecular weight portion helps to improve water solubility and improve graphite dispersibility. In some preferred embodiments of this application, the molecular weight distribution of the copolymer is 2 to 6.

[0024] In a preferred embodiment of the present invention, the weight-average molecular weight (Mw) of the copolymer is 200,000 to 3,000,000, and the molecular weight distribution of the copolymer is 2 to 8. Depending on the molecular weight and molecular weight distribution of the copolymer, the water-soluble binder achieves excellent technical effects in terms of adhesion, dispersibility, water solubility, and suppression of volume expansion.

[0025] Specifically, the above double-bond-containing nitrile monomer has the structure shown in formula I, the above double-bond-containing amide monomer has the structure shown in formula II, the above double-bond-containing carboxylic acid monomer has the structure shown in formula III, and the above double-bond-containing sulfonic acid monomer has the structure shown in formula IV;

[0026] [ka]

[0027] Here, R 11 is one of H, Cl, Br, or a methyl group.

[0028] R 12is one of H, Cl, Br, or a C1-C6 (e.g., C1, C2, C3, C4, C5, or C6) linear or branched alkyl group.

[0029] R 21 , R 31 Each of these is independently selected from either an H group or a methyl group.

[0030] R 22 , R 32 Each of these is independently selected from H, a C1-C20 (e.g., C1, C2, C3, C4, C5, C6, C8, C10, C12, C15, or C18) linear or branched alkyl group, or a phenyl group; R 23 , R 24 Each of these is independently selected from H, a substituted or unsubstituted C1-C20 (e.g., C1, C2, C3, C4, C5, C6, C8, C10, C12, C15, or C18) linear or branched alkyl group, or a substituted or unsubstituted phenyl group, and the substituted substituent is at least one selected from a C1-C6 (e.g., C1, C2, C3, C4, C5, or C6) linear or branched alkyl group, a phenyl group, a sulfonic acid group, or a sulfonic acid base.

[0031] M is one of the following: H, Li, Na, or K.

[0032] R 41 It is selected from H or a methyl group.

[0033] R 42 is one selected from H, a C1-C6 (e.g., C1, C2, C3, C4, C5, or C6) linear or branched alkyl group, or a phenyl group.

[0034] R 43 This is one selected from C1-C6 (e.g., C1, C2, C3, C4, C5, or C6) linear or branched alkylene groups, or phenylene groups.

[0035] X is one of the following: H, Li, Na, or K.

[0036] In this application, the term "C1-C20 linear or branched alkyl group" is preferably a C1-C16 linear or branched alkyl group, more preferably a C1-C10 linear or branched alkyl group, and even more preferably a C1-C6 linear or branched alkyl group, and includes, but is not limited to, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a 2-methylbutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a neohexyl group, a 2-ethylhexyl group, an n-octyl group, an n-heptyl group, an n-nonyl group, or an n-decyl group.

[0037] Preferably, in formula I, the above R 11 H is H.

[0038] Preferably, in formula I, the above R 12 It is selected from H or a methyl group.

[0039] Preferably, the double-bond-containing nitrile monomer includes acrylonitrile and / or methacrylonitrile.

[0040] Preferably, the mass percentage content of the double-bond-containing nitrile monomer in the polymerizable monomer of the copolymer is 1% to 60%, and may be, for example, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55%, as well as specific point values ​​between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range, and more preferably it is 20% to 55%, and even more preferably 30% to 55%.

[0041] Preferably, in formula II, the above R 21 H is H.

[0042] Preferably, in formula II, the above R 22 This is selected from H or a methyl group.

[0043] Preferably, in formula II, the above R 23 , R 24 Each of these is independently selected from H, a substituted or unsubstituted C1-C6 linear, or branched alkyl group.

[0044] Preferably, R 23 , R 24 The substituted substituent in is at least one selected from a C1-C3 linear or branched alkyl group, a phenyl group, and a sulfonic acid group.

[0045] Preferably, the double bond-containing amide monomer includes one or at least two of the following: 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.

[0046] Preferably, the mass percentage content of the double-bond-containing amide monomer in the polymerizable monomer of the copolymer is 1% to 40%, and may be, for example, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, or 38%, as well as specific point values ​​between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range, and more preferably it is 5% to 30%, and even more preferably 5% to 20%.

[0047] Preferably, the double bond-containing carboxylic acid monomer comprises one or at least two of the following: acrylic acid, methacrylic acid, sodium acrylate, sodium methacrylate, lithium acrylate, or lithium methacrylate.

[0048] Preferably, the mass percentage content of the double-bond-containing carboxylic acid monomer in the polymerizable monomer of the copolymer is 5% to 95%, and may be, for example, 10%, 15%, 20%, 25%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%, as well as specific point values ​​between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range, and more preferably it is 20% to 65%, and even more preferably 30% to 60%.

[0049] Preferably, in formula IV, the above R 41 H is H.

[0050] Preferably, in formula IV, the above R 42 It is selected from H or a methyl group.

[0051] Preferably, in formula IV, the above R 43 This is a methylene group.

[0052] Preferably, the double bond-containing sulfonic acid monomer comprises one or at least two of the following: methacrylic sulfonic acid, acrylic sulfonic acid, sodium methacrylic sulfonate, sodium acrylic sulfonate, lithium methacrylic sulfonate, or lithium acrylic sulfonate.

[0053] Preferably, the mass percentage content of the double-bond-containing sulfonic acid monomer in the polymerizable monomer of the copolymer is 0 to 15%, and may be, for example, 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, or 14%, as well as specific point values ​​between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range, and more preferably it is 0 to 10%.

[0054] Preferably, the fifth monomer includes a double bond-containing ester monomer and / or a double bond-containing ether monomer.

[0055] Preferably, the fifth monomer includes one or at least two of the following: 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.

[0056] Preferably, the mass percentage content of the fifth monomer in the polymerizable monomer of the copolymer is 0 to 20%, and may be, for example, 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. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range, and more preferably it is 0 to 15%, and even more preferably 0 to 10%.

[0057] Exemplary, a method for producing a water-soluble binder provided by the present invention includes polymerizing a polymerizable monomer in the presence of an initiator and a solvent, and then post-treating and drying the resulting polymerization product to obtain the water-soluble binder in powder form.

[0058] Preferably, the initiator comprises one or at least two of the following: an organic peroxide, an inorganic peroxide, or a redox initiator.

[0059] Preferably, the initiator comprises one or at least two of the following: benzoyl peroxide, diisopropylbenzene peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, or tert-butyl peroxide.

[0060] Preferably, when calculated with a mass of 100 parts of the polymerizable monomer, the mass of the initiator is 0.01 to 2 parts, and may be, for example, 0.03 parts, 0.05 parts, 0.08 parts, 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.5 parts, or 1.8 parts, as well as specific point values ​​between the above point values. Considering the limitations of space and conciseness, this application does not comprehensively list specific point values ​​included in the above range.

[0061] Preferably, the solvent may be an organic solvent, water, or a composition of both. The organic solvent may include, but is not limited to, methanol, ethanol, acetonitrile, or N-methylpyrrolidone (NMP). If the solvent is a composition of an organic solvent and water, the two may be mixed in any mass ratio, for example, in the range of 1:99 to 99:1, and can be selected according to actual requirements.

[0062] Preferably, if the mass of the polymerizable monomer is calculated as 100 parts, the mass of the solvent is 100 to 500 parts, and may be, for example, 150 parts, 200 parts, 250 parts, 300 parts, 350 parts, 400 parts, or 450 parts, as well as a specific point value between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list the specific point values ​​included in the above range.

[0063] Preferably, the polymerization reaction is carried out in a protective atmosphere.

[0064] Preferably, the protective atmosphere contains nitrogen gas.

[0065] Preferably, the temperature of the polymerization reaction is 50 to 90°C, and may be, for example, 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. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range.

[0066] Preferably, the time for the polymerization reaction is 2 to 24 hours, and may be, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, 20 hours, or 22 hours, as well as specific point values ​​between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range.

[0067] Preferably, the post-treatment includes, in order, removal of residual monomers, adjustment of pH, and solid-liquid separation.

[0068] Preferably, the method for removing the residual monomers includes reduced pressure, where the vacuum level of the reduced pressure (vacuum drawing) is ≤ 0.1 MPa, and may be, for example, 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, and a specific point value between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range.

[0069] Preferably, the reagent for adjusting the pH includes one or at least two of the following: an aqueous solution of sodium hydroxide, an aqueous solution of lithium hydroxide, or an aqueous solution of potassium hydroxide.

[0070] Preferably, the temperature used to adjust the pH is 30 to 70°C, and may be, for example, 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. Considering the limitations of space and brevity, this application does not exhaustively list specific point values ​​included in the above range, and more preferably, it is 40 to 60°C.

[0071] Preferably, the above pH is adjusted to a pH value of 6.0 to 9.0, and may be, 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, and specific point values ​​between the above point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range, and more preferably it is 7.0 to 8.5.

[0072] Preferably, the above solid-liquid separation method includes solid pressure filtration.

[0073] Preferably, the process further includes grinding and sieving steps after the drying described above.

[0074] Preferably, the above manufacturing method is: The polymerizable monomer, initiator, and solvent are mixed and the polymerization reaction is carried out in a protective atmosphere at 50-90°C for 2-24 hours to obtain the polymerization product; The process includes removing residual monomers by vacuuming the polymerization product to ≤0.1 MPa, then adjusting the pH of the system to 7.0-8.5, and obtaining the above water-soluble binder in powder form through solid-liquid separation, drying, grinding, and sieving.

[0075] To further improve the dispersion and wetting performance of the powder binder manufactured above, a wetting dispersant in an amount of 0.01% to 5% by mass can be added to the above water-soluble binder in powder form.

[0076] Preferably, the wetting dispersant may be one or at least two of the following: polycarboxylic acid-based, modified polycarboxylic acid-based, polyether-based, or modified polyether-based dispersants.

[0077] In a second embodiment, the present application provides an electrode material composition comprising the water-soluble binder described in the first embodiment.

[0078] Preferably, the electrode material composition comprises a combination of an active material, a conductive agent, and the water-soluble binder.

[0079] Preferably, the mass percentage content of the water-soluble binder in the electrode material composition is 0.3% to 3%, and may be, for example, 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. Considering the limitations of space and conciseness, this application does not comprehensively list specific point values ​​included in the above range.

[0080] It should be explained that the mass of the electrode material composition described above 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 based on its solid content.

[0081] Preferably, the electrode material composition is a negative electrode material composition, and the active material is a negative electrode active material.

[0082] Preferably, the negative electrode active material includes a carbon-based material and / or a silicon-based material.

[0083] Preferably, the carbon-based material includes one or at least two of the following: graphite, carbon black, carbon nanotubes, carbon fibers, mesocarbon microbeads, or petroleum coke.

[0084] Preferably, the silicon-based material includes one or at least two of the following: nanosilicon, micron silicon, porous silicon, amorphous silicon, or silicon oxide.

[0085] Preferably, when the mass of the negative electrode active material is calculated in units of 100 parts, the mass of the conductive agent is 0.1 to 5.0 parts, and may be, for example, 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 point values. Considering the limitations of space and brevity, this application does not comprehensively list specific point values ​​included in the above range.

[0086] In a third embodiment, the present application provides a battery electrode piece comprising a current collector and a coating installed on the current collector, wherein the material of the coating comprises the electrode material composition described in the second embodiment.

[0087] Preferably, the battery electrode piece is the negative electrode piece.

[0088] In a preferred embodiment of the present invention, the peel strength of the negative electrode piece is ≥ 17.8 N / mm, and may be between 17.8 and 20.14 N / mm.

[0089] In a preferred embodiment of the present invention, the water-soluble binder has excellent adhesive strength and flexibility, can suppress volume expansion, and causes the full-charge expansion of the negative electrode piece containing it to be ≤25.3%, which may be 24.65% to 25.23%, and the capacity retention rate of the lithium-ion battery containing it after 500 cycles at 60°C to be ≥86.5%, which may be 86.87% to 88.25%.

[0090] In a fourth aspect, the present application provides an electrochemical energy storage device comprising the water-soluble binder described in the first aspect and at least one of the electrode material composition described in the second aspect or the battery electrode piece described in the third aspect.

[0091] Preferably, the electrochemical energy storage device includes 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.

[0092] Compared to related technologies, this invention has the following beneficial effects.

[0093] The water-soluble powder binder provided by this application contains a multi-component copolymer formed by polymerizing specific types of monomers. As a powder material, it not only significantly reduces the transportation and packaging costs of PAA-based binders, but also, by removing unpolymerized monomers and low molecular weight polymer portions during the powder formation process, the powder form of the water-soluble binder has significantly improved adhesion and expansion suppression capabilities compared to solution-type PAA-based binders in related technologies. Based on the design of polymerizable monomers and copolymers and their combination with powder form, the water-soluble binder has excellent adhesion, improving it by at least ≥20% compared to conventional solution-type binders, reducing the amount added by ≥20%, and effectively suppressing volume expansion during the charge-discharge cycle of the electrode pieces, thereby improving the cycle performance of the electrode pieces and lithium-ion batteries. On the other hand, compared to liquid binder products, powder products adhere more easily to the graphite surface during kneading, forming a denser coating effect, thereby improving processing performance and further enhancing electrical performance.

[0094] After reading and understanding the detailed explanation, other aspects will become clear. [Modes for carrying out the invention]

[0095] The technical solutions of this application will be further described below with reference to specific embodiments. Those skilled in the art should understand that the above embodiments are merely to aid in understanding this application and do not specifically limit it.

[0096] The terms “include,” “contain,” “have,” “contain,” or any other variation thereof as used in this application are intended to cover non-exclusive inclusion. For example, a composition, step, method, product, or apparatus containing the enumerated elements is not necessarily limited to those elements and may further include other elements not expressly enumerated or elements specific to such composition, step, method, product, or apparatus.

[0097] The phrases "optional," "selectable," and "any one" mean that the matters or events described thereafter may or may not occur, and the description includes both cases where the event occurs and cases where it does not.

[0098] The indefinite articles "one kind" and "one" preceding an element or component in this application do not limit the number requirement (i.e., the number of occurrences) of the element or component. Therefore, "one" or "one kind" should be interpreted as including one or at least one, and singular elements or components also include plural forms unless the number clearly means singular only.

[0099] The use of terms such as “one embodiment,” “several embodiments,” “exemplary examples,” “specific examples,” or “several examples” in this application means that the specific features, structures, materials, or properties described in accordance with the embodiment or example are included in at least one embodiment or example of this application. In this specification, exemplary descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0100] Furthermore, the technical features relating to each embodiment of this application can be combined with each other, as long as they do not contradict each other.

[0101] In the following specific embodiments of this application, the polymerizable monomers, initiators, and solvents used are all commercially available products.

[0102] The test method for the following specific embodiments of the present invention is as follows:

[0103] (1) Solid content of water-soluble binder: Take 2-3 g of the powdered or liquid binder awaiting measurement, bake it in a 120°C forced-air oven for 2 hours, and record the mass before and after baking as m0 and m1, respectively. The solid content is calculated as m1 / m0 × 100%.

[0104] (2) Water-soluble binder D 50 Particle size: The test was performed using a laser particle size analyzer with the model number RODOT T4.1+VIBRI.

[0105] (3) Weight-average molecular weight and molecular weight distribution of water-soluble binders: The weight-average molecular weight (Mw) and molecular weight distribution of the water-soluble binder (copolymer) were obtained by testing using gel permeation chromatography (GPC).

[0106] The specific test conditions are as follows: Analytical instrument: Agilent 1260 Infinity II, Mobile phase: 0.1 Mol / L NaNO3 aqueous solution, Column: Waters Ultrastyragel 1000 and Waters Ultrastyragel 120 connected in series, Detector: Agilent 1260 RID, Standard: PEG, Flow rate: 0.8 mL / min, Column temperature: 40°C, Detector temperature: 40°C.

[0107] (4) Viscosity of aqueous solution of water-soluble binder: Deionized water was added to dissolve the powdered binder to the required solid content. After confirming that it was completely dissolved, the mixture was kept at a constant temperature of 25°C, and the viscosity of the liquid binder was tested using an NDJ-5S digital rotational viscometer.

[0108] (5) Light transmittance of aqueous solution of water-soluble binder: A UV spectrophotometer was used. 10 g of powder binder was accurately weighed to 0.1 g, water was added to a 20 mL volumetric flask, and the mixture was uniformly stirred to prepare the test solution, which was then kept at a constant temperature of 25°C. A 10 mm cuvette, thoroughly washed with pure water, was taken and tested at a wavelength of 430 nm. First, the light transmittance was adjusted to zero with pure water for the specified volume, and then the light transmittance of the test solution was measured.

[0109] (6) pH value of the aqueous solution of the water-soluble binder: Using a Mettler pH meter, deionized water was added to dissolve the powder binder to a solid content of 0.5%, and the mixture was thoroughly stirred and dispersed until clear, ensuring that the sample was uniformly diluted and dispersed without aggregation. The pH was then measured using a pH meter.

[0110] Example 1 The water-soluble binder was in powder form and contained a copolymer, wherein the polymerizable monomer of the copolymer consisted of 55 parts by mass of acrylic acid, 5 parts by mass of N,N-diethylacrylamide, and 40 parts by mass of acrylonitrile. The method for producing the water-soluble binder was as follows.

[0111] 350 parts of a mixed solvent of pure water and acetonitrile were added to a reaction vessel and stirred at 100 rpm. Each polymerizable monomer was added in the above proportions, nitrogen gas was continuously passed through, and the mixture was stirred for 3 hours to obtain a solution. The temperature was raised to 80°C, and 0.5 parts of benzoyl peroxide solution (10% by mass) was added to the solution. The mixture was reacted at 80°C for 10 hours to obtain a polymerization product. The polymerization product was then depressurized to less than 0.1 MPa at 60°C using a vacuum pump to remove residual monomers. Next, the mixture was neutralized to pH 7.5 using an aqueous lithium hydroxide solution at 50°C, and the resulting water-soluble binder was obtained in powder form through solid pressure filtration, drying, grinding, and sieving.

[0112] The solids content of the water-soluble binder provided by this embodiment is 92%, D 50 The particle size was 50 μm.

[0113] The Mw of the above water-soluble binder (copolymer) is 8.96 × 10 5 The molecular weight distribution was 2.72.

[0114] The above water-soluble binder was redispersed and dissolved in a 1.0% solids aqueous solution, resulting in a viscosity of 1000 cps and a light transmittance of 98%.

[0115] The above water-soluble binder was redispersed and dissolved in a 0.5% aqueous solution, and the pH value was 7.5.

[0116] Example 2 The water-soluble binder was in powder form and contained a copolymer, wherein the polymerizable monomer of the copolymer consisted of 30 parts by mass of acrylic acid, 10 parts by mass of N,N-diethylacrylamide, 55 parts by mass of acrylonitrile, and 5 parts by mass of sodium methacrylate. The method for producing the water-soluble binder was as follows.

[0117] 350 parts of a mixed solvent of pure water and acetonitrile were added to a reaction vessel and stirred at 100 rpm. Each polymerizable monomer was added in the above proportions, nitrogen gas was continuously passed through, and the mixture was stirred for 3 hours to obtain a solution. The temperature was raised to 80°C, and 0.5 parts of benzoyl peroxide solution (10% by mass) was added to the solution. The mixture was reacted at 80°C for 10 hours to obtain a polymerization product. The polymerization product was then depressurized to less than 0.1 MPa at 60°C using a vacuum pump to remove residual monomers. Next, the mixture was neutralized to pH 7.8 using an aqueous lithium hydroxide solution at 50°C, and the water-soluble binder was obtained in powder form through solid pressure filtration, drying, grinding, and sieving.

[0118] The solids content of the water-soluble binder provided by this embodiment is 95%, D 50 The particle size was 57 μm.

[0119] The Mw of the above water-soluble binder (copolymer) is 9.24 × 10 5 The molecular weight distribution was 2.54.

[0120] The above water-soluble binder was redispersed and dissolved in a 1.0% solids aqueous solution, resulting in a viscosity of 10,000 cps and a light transmittance of 92%.

[0121] The above water-soluble binder was redispersed and dissolved in a 0.5% aqueous solution, and the pH value was 7.7.

[0122] Example 3 The water-soluble binder was in powder form and contained a copolymer, wherein the polymerizable monomer of the copolymer consisted of 35 parts by mass of acrylic acid, 15 parts by mass of N,N-diethylacrylamide, 40 parts by mass of acrylonitrile, and 10 parts by mass of sodium methacrylate. The method for producing the water-soluble binder was as follows.

[0123] 350 parts of a mixed solvent of pure water and acetonitrile were added to a reaction vessel and stirred at 100 rpm. Each polymerizable monomer was added in the above proportions, nitrogen gas was continuously passed through, and the mixture was stirred for 3 hours to obtain a solution. The temperature was raised to 80°C, and 0.5 parts of benzoyl peroxide solution (10% by mass) was added to the solution. The mixture was reacted at 80°C for 10 hours to obtain a polymerization product. The polymerization product was then depressurized to less than 0.1 MPa at 60°C using a vacuum pump to remove residual monomers. Next, the mixture was neutralized to pH 7.4 using an aqueous lithium hydroxide solution at 50°C, and the water-soluble binder was obtained in powder form through solid pressure filtration, drying, grinding, and sieving.

[0124] The solids content of the water-soluble binder provided by this embodiment is 94%, D 50 The particle size was 63 μm.

[0125] The Mw of the above water-soluble binder (copolymer) is 8.46 × 10 5 The molecular weight distribution was 2.83.

[0126] The above water-soluble binder was redispersed and dissolved in a 1.0% solids aqueous solution, resulting in a viscosity of 4500 cps and a light transmittance of 95%.

[0127] The above water-soluble binder was redispersed and dissolved in a 0.5% aqueous solution, and its pH value was 7.3.

[0128] Example 4 The water-soluble binder was in powder form and contained a copolymer, wherein the polymerizable monomer of the copolymer consisted of 60 parts by mass of acrylic acid, 10 parts by mass of N,N-diethylacrylamide, 20 parts by mass of acrylonitrile, and 10 parts by mass of sodium methacrylate. The method for producing the water-soluble binder was as follows.

[0129] 350 parts of a mixed solvent of pure water and acetonitrile were added to a reaction vessel and stirred at 100 rpm. Each polymerizable monomer was added in the above proportions, nitrogen gas was continuously passed through, and the mixture was stirred for 3 hours to obtain a solution. The temperature was raised to 80°C, and 0.5 parts of benzoyl peroxide solution (10% by mass) was added to the solution. The mixture was reacted at 80°C for 10 hours to obtain a polymerization product. The polymerization product was then depressurized to less than 0.1 MPa at 60°C using a vacuum pump to remove residual monomers. Next, the mixture was neutralized to pH 7.5 using an aqueous lithium hydroxide solution at 50°C, and the resulting water-soluble binder was obtained in powder form through solid pressure filtration, drying, grinding, and sieving.

[0130] The solids content of the water-soluble binder provided by this embodiment is 94%, D 50 The particle size was 60 μm.

[0131] The Mw of the above water-soluble binder (copolymer) is 11.65 × 10 5 The molecular weight distribution was 3.46.

[0132] The above water-soluble binder was redispersed and dissolved in a 1.0% solids aqueous solution, resulting in a viscosity of 550 cps and a light transmittance of 98%.

[0133] The above water-soluble binder was redispersed and dissolved in a 0.5% aqueous solution, and the pH value was 7.5.

[0134] Example 5 The water-soluble binder was in powder form and contained a copolymer, wherein the polymerizable monomer of the copolymer consisted of 55 parts by mass of acrylic acid, 5 parts by mass of N,N-diethylacrylamide, and 40 parts by mass of acrylonitrile. The method for producing the water-soluble binder was as follows.

[0135] 450 parts of a mixed solvent of pure water and acetonitrile were added to a reaction vessel and stirred at 100 rpm. Each polymerizable monomer was added in the above proportions, nitrogen gas was continuously passed through, and the mixture was stirred for 3 hours to obtain a solution. The temperature was raised to 80°C, and 0.7 parts of benzoyl peroxide solution (10% by mass) was added to the solution. The reaction was carried out at 80°C for 8 hours to obtain a polymerization product. The polymerization product was then depressurized to less than 0.1 MPa at 60°C using a vacuum pump to remove residual monomers. Next, the pH was neutralized to 7.7 using an aqueous lithium hydroxide solution at 50°C, and the mixture was subjected to solid pressure filtration, drying, grinding, and sieving to obtain the above water-soluble binder in powder form.

[0136] The solids content of the water-soluble binder provided by this embodiment is 95%, D 50 The particle size was 65 μm.

[0137] The Mw of the above water-soluble binder (copolymer) is 4.5 × 10 5 The molecular weight distribution was 4.38.

[0138] The above water-soluble binder was redispersed and dissolved in a 1.0% solids aqueous solution, resulting in a viscosity of 550 cps and a light transmittance of 94%.

[0139] The above water-soluble binder was redispersed and dissolved in a 0.5% aqueous solution, and the pH value was 7.7.

[0140] Example 6 The water-soluble binder was in powder form and contained a copolymer, wherein the polymerizable monomers of the copolymer consisted of 45 parts by mass of acrylic acid, 10 parts by mass of N,N-diethylacrylamide, 40 parts by mass of acrylonitrile, and 5 parts by mass of butyl acrylate. The method for producing the water-soluble binder was as follows.

[0141] 350 parts of a mixed solvent of pure water and acetonitrile were added to a reaction vessel and stirred at 100 rpm. Each polymerizable monomer was added in the above proportions, nitrogen gas was continuously passed through, and the mixture was stirred for 3 hours to obtain a solution. The temperature was raised to 75°C, and 0.5 parts of benzoyl peroxide solution (10% by mass) was added to the solution. The mixture was reacted at 75°C for 12 hours to obtain a polymerization product. The polymerization product was then depressurized to less than 0.1 MPa at 60°C using a vacuum pump to remove residual monomers. Next, the mixture was neutralized to pH 7.7 with an aqueous lithium hydroxide solution at 50°C, and the water-soluble binder was obtained in powder form through solid pressure filtration, drying, grinding, and sieving.

[0142] The solids content of the water-soluble binder provided by this embodiment is 93%, D 50 The particle size was 57 μm.

[0143] The Mw of the above water-soluble binder (copolymer) is 12.86 × 10 5 The molecular weight distribution was 4.79.

[0144] The above water-soluble binder was redispersed and dissolved in a 1.0% solids aqueous solution, resulting in a viscosity of 7000 cps and a light transmittance of 94%.

[0145] The above water-soluble binder was redispersed and dissolved in a 0.5% aqueous solution, and its pH value was 7.7.

[0146] Example 7 The water-soluble binder was in powder form and contained a copolymer, wherein the polymerizable monomers of the copolymer consisted of 40 parts by mass of acrylic acid, 10 parts by mass of N,N-diethylacrylamide, 45 parts by mass of acrylonitrile, and 5 parts by mass of butyl acrylate. The method for producing the water-soluble binder was as follows.

[0147] 350 parts of a mixed solvent of pure water and acetonitrile were added to a reaction vessel and stirred at 100 rpm. Each polymerizable monomer was added in the above proportions, nitrogen gas was continuously passed through, and the mixture was stirred for 3 hours to obtain a solution. The temperature was raised to 72°C, and 0.3 parts of benzoyl peroxide solution (10% by mass) was added to the solution. The reaction was carried out at 72°C for 12 hours to obtain a polymerization product. The polymerization product was then depressurized to less than 0.1 MPa at 60°C using a vacuum pump to remove residual monomers. Next, the pH was neutralized to 7.5 using an aqueous lithium hydroxide solution at 50°C, and the mixture was subjected to solid pressure filtration, drying, grinding, and sieving to obtain the above water-soluble binder in powder form.

[0148] The solids content of the water-soluble binder provided by this embodiment is 95%, D 50 The particle size was 50 μm.

[0149] The Mw of the above water-soluble binder (copolymer) is 19.88 × 10 5 The molecular weight distribution was 5.33.

[0150] The above water-soluble binder was redispersed and dissolved in a 1.0% solids aqueous solution, resulting in a viscosity of 10,000 cps and a light transmittance of 93%.

[0151] The above water-soluble binder was redispersed and dissolved in a 0.5% aqueous solution, and its pH value was 7.5.

[0152] Comparative Example 1 The binder used was a combination of commercially available styrene-butadiene rubber (SBR) and sodium carboxymethylcellulose (CMC) in a 1:1 mass ratio.

[0153] Comparative Example 2 It was a commercially available acrylic resin PAA binder, a solution-type binder.

[0154] Comparative Example 3 The product was a water-soluble binder in solution form, and the manufacturing method was as follows: 350 parts of pure water were added to a reaction vessel and stirred at 100 rpm. Then 55 parts of acrylic acid, 5 parts of N,N-diethylacrylamide, and 40 parts of acrylonitrile were added, and nitrogen gas was continuously passed through while stirring for 3 hours to obtain a solution. The temperature was raised to 80°C, and 0.5 parts of benzoyl peroxide solution (10% by mass) was added to the above solution. The reaction was carried out at 80°C for 10 hours to obtain a polymerization product. The polymerization product was then depressurized to less than 0.1 MPa at 60°C using a vacuum pump to remove residual monomers. Next, the pH was neutralized to 7.5 using an aqueous lithium hydroxide solution at 50°C, and water was added to adjust the solid content to 5% to obtain the water-soluble binder.

[0155] The water-soluble binder provided in this comparative example had a solid content of 5%, and when diluted in a 1% aqueous solution, its viscosity was 600 cps and its light transmittance was 94%.

[0156] The Mw of the above water-soluble binder (copolymer) is 5.34 × 10 5 The molecular weight distribution was 3.67.

[0157] Application Examples 1-7, Comparative Application Examples 1-3 The negative electrode piece includes a current collector (Cu foil) and a coating applied to the current collector, wherein the material of the coating is a negative electrode material composition, and the negative electrode material composition comprises a negative electrode active material (graphite), a conductive agent (conductive carbon black SP), and a binder, where the binder was the binder provided in Examples 1 to 7 and Comparative Examples 1 to 3, respectively.

[0158] Manufacturing of the above negative electrode pieces: The negative electrode active material, SP, and the binders of Examples 1 to 7 were mixed in a mass ratio of 97.0:1:2.0, and added to pure water at a ratio of 50% solid content of the system. The mixture was thoroughly stirred and mixed to prepare a uniform negative electrode paste, which was then applied to the negative electrode current collector Cu foil, dried, and roll-pressed to obtain the negative electrode pieces.

[0159] For the binders of Comparative Examples 1 to 3, the negative electrode active material, SP, and the binders of Comparative Examples 1 to 3 were mixed in a mass ratio of 96.5:1:2.5. This mixture was then added to pure water at a ratio of 50% solid content of the system, and thoroughly stirred to prepare a uniform negative electrode paste. This paste was then applied to a negative electrode current collector Cu foil, dried, and roll-pressed to obtain a negative electrode piece.

[0160] A lithium-ion battery comprising a positive electrode piece, a negative electrode piece, a separator, and an electrolyte, wherein the negative electrode piece is the negative electrode piece described above, and the manufacturing method of the lithium-ion battery was as follows.

[0161] (1) Manufacturing of positive electrode pieces: 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, and N-methylpyrrolidone NMP was added to the mixture at a ratio of 50% of the system's solid content, and the mixture was thoroughly stirred to prepare a uniform positive electrode paste. This paste was then applied to the positive electrode current collector Al foil, dried, and roll-pressed to obtain positive electrode pieces.

[0162] (2) The manufacturing of the negative electrode pieces was as described above.

[0163] (3) A porous PP polymer film was used as the separator.

[0164] (4) Assembly of lithium-ion battery: The positive electrode piece, separator and negative electrode piece are wound in order to obtain a battery core. The battery core is packaged with an aluminum plastic film, and after firing to remove moisture, an electrolyte (LiPF6 electrolyte, 1 mol / L, solvent is a mixture of ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a mass ratio of 3:2:5) is injected. The lithium-ion battery is then obtained through processes such as vacuum packaging, standing, chemical conversion, secondary packaging, and shaping.

[0165] Performance tests were conducted on the negative electrode piece and lithium-ion battery, and the method was as follows.

[0166] (1) Peel strength: Electrode pieces from the examples and comparative examples were cut into long lengths of 20 cm x 2.5 cm. A 1 mm thick steel plate was attached to the current collector side with double-sided tape, and transparent tape was attached to the coated layer side. The pieces were then peeled in a 180° direction at a speed of 100 mm / min using a tensile testing machine, and the peel stress was measured.

[0167] (2) Fully charged expansion: A lithium-ion battery was subjected to charge-discharge cycles at 25°C, in a voltage range of 2.5 to 4.2V, at 0.5C. The initial Coulomb efficiency of the charge-discharge cycle, the Coulomb efficiency after 50 cycles, and the capacity retention rate were measured using the constant current method. After 50 charge-discharge cycles, with the electrode pieces fully charged and lithium-inserted, the ratio of the increase in electrode piece thickness to the electrode piece thickness before charge-discharge was recorded as fully charged expansion.

[0168] (3) Cycle performance: The lithium-ion battery was placed directly in an oven environment at 60°C and subjected to charge-discharge cycles at 1C in a voltage range of 2.5 to 4.2V. The cycle capacity retention rate after 500 cycles was measured.

[0169] The test results are shown in Table 1.

[0170] [Table 1]

[0171] As can be seen from the test results in Table 1, compared to the conventional SBR binder and solution-type PAA binder in Comparative Examples 1-3, the water-soluble binder provided in this application, as a powder material, not only reduces the transportation and packaging costs of solution-type binders, but also has significantly improved adhesive strength and expansion suppression ability compared to solution-type PAA-based binders in related technologies. Through the optimized design of the copolymer molecular weight, the peel strength of the negative electrode pieces 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 after 500 cycles at 60°C for lithium-ion batteries was 86.87%-88.25%, effectively improving the cycle performance of lithium-ion batteries. As can be seen by comparing Examples 1-3, 6-7 and Examples 4-5, the design of the copolymer monomers and the design of specific molecular weights allowed for further optimization of the water-soluble binder in terms of adhesion, dispersibility, water solubility, and suppression of volume expansion. In Example 4, the amount of nitrile monomer used was slightly low, which reduced the adhesion performance of the water-soluble binder. In Example 5, the copolymer molecular weight was relatively low, which reduced the adhesion, water solubility, and ability to suppress volume expansion of the water-soluble binder to varying degrees.

[0172] The applicant declared that while the present application illustrates the water-soluble binder, battery electrode pieces and their uses by the above-described embodiments, the present application is not limited to the above embodiments, and that this does not mean that one must rely on the above embodiments to carry out the present application. It will be apparent to those skilled in the art that any improvements to the present application, equivalent substitutions and additions of auxiliary components to the raw materials of the present product, and selection of specific forms are all included within the claims and disclosures of the present application.

Claims

1. A water-soluble binder containing a copolymer, wherein the polymerizable monomers of the copolymer include a combination of a double-bond-containing nitrile monomer, a double-bond-containing amide monomer, a double-bond-containing carboxylic acid monomer, a selectable double-bond-containing sulfonic acid monomer, and a selectable fifth monomer, the water-soluble binder is in the form of a powder, and the mass percentage content of the copolymer in the water-soluble binder is ≥ 92%.

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

3. The water-soluble binder is prepared as 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 to 20,000 cps; The water-soluble binder according to claim 1, wherein the light transmittance of the first aqueous solution is ≥ 85%.

4. The water-soluble binder 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 to 9.

0.

5. The water-soluble binder according to claim 1, wherein the weight-average molecular weight of the copolymer is 200,000 to 3,000,000.

6. The water-soluble binder according to claim 1, wherein the molecular weight distribution of the copolymer is 2 to 8.

7. The double bond-containing nitrile monomers include acrylonitrile and / or methacrylonitrile; The double bond-containing amide monomer comprises one or at least two of the following: 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-acrylamido-2-phenylethanesulfonic acid; The double bond-containing carboxylic acid monomer comprises one or at least two of the following: acrylic acid, methacrylic acid, sodium acrylate, sodium methacrylate, lithium acrylate, or lithium methacrylate; The double bond-containing sulfonic acid monomer comprises one or at least two of the following: methacrylic sulfonic acid, acrylic sulfonic acid, sodium methacrylic sulfonate, sodium acrylic sulfonate, lithium methacrylic sulfonate, or lithium acrylic sulfonate; The water-soluble binder according to claim 1, wherein the fifth monomer comprises one or at least two of the following: 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.

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

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

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

11. A battery electrode piece comprising a current collector and a coating applied to the current collector, wherein the material of the coating comprises the electrode material composition described in 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 piece according to claim 11; An electrochemical energy storage device comprising one of the following: a lithium-ion battery, a sodium-ion battery, a supercapacitor, a fuel cell, or a solar cell.

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