Aqueous binder, preparation method and application thereof, and sodium ion battery

Abstract

The invention relates to a water-based binder, a preparation method and application thereof, and a sodium ion battery. The preparation method of the water-based binder comprises the following steps: grafting a P-containing group on a polyanionic binder; and then adding a cross-linking agent and nano inorganic particles for cross-linking, and drying to obtain the water-based binder. By selecting the polyanionic binder and grafting the high-polarity P-containing group and the cross-linked composite nano inorganic particles, the flame retardance of the water-based binder can be effectively improved, and after the water-based binder is applied to the electrode plate, the wettability of the electrolyte on the electrode plate can be effectively improved; in addition, when the material and a layered oxide positive electrode material are cooperated to prepare the positive electrode plate of the sodium-ion battery, lattice oxygen release can be inhibited, and an oxygen diffusion path can be blocked, so that the thermal runaway risk of the sodium-ion battery can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an aqueous binder, a preparation method and application thereof, and a sodium ion battery. Background Art

[0002] Due to the hydrophobic properties of commonly used binders such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), sodium alginate, styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC), the interfacial contact angle between the electrode sheet and the electrolyte is large, which in turn leads to poor wettability of the electrolyte to the electrode sheet and poor ion transmission efficiency; at the same time, these commonly used binders are not flame retardant enough and it is difficult to meet high safety requirements.

[0003] Furthermore, sodium-ion batteries (SIBs) are considered an important alternative to lithium-ion batteries due to their abundant sodium resources and low cost. However, the layered oxide cathodes used in SIBs are susceptible to lattice oxygen release at high temperatures, and currently used binders are unable to inhibit oxygen evolution, increasing the risk of thermal runaway. Summary of the Invention

[0004] Based on this, it is necessary to provide an aqueous binder, a preparation method and application thereof, and a sodium ion battery to address the above problems.

[0005] A method for preparing a water-based binder comprises the following steps:

[0006] Grafting P-containing groups onto the polyanionic binder;

[0007] Then, a cross-linking agent and nano inorganic particles are added to perform cross-linking, and a water-based adhesive is obtained after drying.

[0008] In one embodiment, the P-containing group is selected from at least one of a phosphate group, a phosphonic acid group, and a phosphazene group;

[0009] And / or, the polyanionic binder is at least one selected from polyacrylic acid, sodium polyacrylate, sodium alginate, and sodium carboxymethyl cellulose;

[0010] And / or, the cross-linking agent is selected from at least one of polyethylene oxide and polyethylene glycol diacrylate;

[0011] And / or, the nano inorganic particles are selected from at least one of titanium dioxide, boron nitride, and aluminum oxide.

[0012] In one embodiment, in the step of grafting the P-containing group onto the polyanionic binder, the grafting rate is 5%-30%;

[0013] And / or, the mass fraction of the nano inorganic particles in the aqueous binder is 1%-10%;

[0014] And / or, the mass ratio of the cross-linking agent to the polyanionic binder is 1:5-1:20.

[0015] In one embodiment, the particle size of the nano inorganic particles is 10 nm-100 nm.

[0016] In one embodiment, the step of grafting the P-containing group onto the polyanionic binder includes: dissolving the polyanionic binder in a solvent, then adding a P-containing monomer and an initiator, and reacting at 60° C.-90° C. for 2 hours-6 hours to complete the grafting.

[0017] In one embodiment, the P-containing monomer is selected from at least one of hydroxyethyl acrylate phosphate, vinyl phosphonate, vinyl phosphonic acid, hexachlorocyclotriphosphazene, and hydroxyalkoxyphosphazene.

[0018] A water-based adhesive prepared by the preparation method.

[0019] The aqueous binder is used in batteries.

[0020] A sodium ion battery, wherein the positive electrode sheet of the sodium ion battery uses the aqueous binder.

[0021] In one embodiment, the negative electrode sheet of the sodium ion battery uses the aqueous binder;

[0022] And / or, the separator of the sodium ion battery uses the aqueous binder.

[0023] The present invention has the following beneficial effects:

[0024] 1. First, the excellent ionic conductivity of the polyanionic binder is conducive to ion transmission. Secondly, the present invention can reduce the contact angle between the electrode sheet and the electrolyte and improve the liquid absorption rate of the electrolyte by grafting highly polar P-containing groups on the polyanionic binder. Furthermore, a porous network structure can be formed by cross-linking. The porous network structure can provide capillary channels and promote uniform penetration of the electrolyte. Therefore, when the electrode sheet uses the aqueous binder of the present invention, the electrolyte wettability can be effectively improved, thereby effectively improving the ion transmission efficiency.

[0025] 2. The PO· free radicals generated by the decomposition of P groups at high temperatures can capture active oxygen free radicals in the gas phase to achieve chemical flame retardancy. At the same time, nano-inorganic fillers can achieve physical flame retardancy. Therefore, through the synergistic effect of chemistry and physics, its flame retardancy can be effectively improved, thereby improving the safety performance of the electrode sheet using this water-based binder.

[0026] 3. When aqueous binders and layered oxide positive electrode materials are used together to prepare the positive electrode sheets of sodium ion batteries, the P-containing groups in the aqueous binders can form coordination bonds with the surface oxygen vacancies of the layered oxide positive electrode materials, inhibiting the release of lattice oxygen. At the same time, nano-inorganic fillers can form a physical barrier on the surface of the electrode sheet, blocking the oxygen diffusion path, thereby reducing the risk of thermal runaway of the sodium ion battery. DETAILED DESCRIPTION

[0027] To facilitate understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments or embodiments and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or the combination of all related listed items.

[0029] In the present invention, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Furthermore, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0030] The preparation method of the water-based binder provided by the present invention comprises the following steps:

[0031] S1, grafting P groups onto the polyanionic binder;

[0032] S2, then adding a crosslinking agent and nano inorganic particles for crosslinking, and drying to obtain a water-based adhesive.

[0033] In step S1, the method of grafting P-containing groups on the polyanionic binder is not preferred. In the present invention, a step of grafting P-containing groups on the polyanionic binder is provided, which mainly includes: dissolving the polyanionic binder in a solvent, then adding a P-containing monomer and an initiator, and reacting at 60°C-90°C for 2 hours-6 hours to complete the grafting.

[0034] The solvent is preferably a mixture of deionized water and ethanol. After dissolving the polyanionic binder in the solvent, the mass fraction of the polyanionic binder in the solution is preferably controlled to be 5%-15%. Furthermore, the P-containing monomer and initiator are selected based on the desired P-containing group to be grafted. For example, the P-containing monomer is selected from at least one of hydroxyethyl acrylate phosphate, vinyl phosphonate, vinyl phosphonic acid, hexachlorocyclotriphosphazene, and hydroxyalkoxyphosphazene. The initiator is selected from at least one of ammonium persulfate (APS) and azobisisobutyronitrile (AIBN).

[0035] Optionally, the P-containing group is selected from at least one of a phosphate group, a phosphonic acid group, and a phosphazene group. Phosphate groups, phosphonic acid groups, and phosphazene groups are highly polar groups and, after grafting, can significantly improve the wettability of the aqueous adhesive to the electrolyte. When the P-containing group is selected from a phosphate group, the P-containing monomer is preferably selected from at least one of hydroxyethyl acrylate phosphate and vinyl phosphonate. When the P-containing group is selected from a phosphonic acid group, the P-containing monomer is preferably selected from vinyl phosphonic acid. When the P-containing group is selected from a phosphazene group, the P-containing monomer is preferably selected from at least one of hexachlorocyclotriphosphazene and hydroxyalkoxyphosphazene.

[0036] Optionally, the polyanionic binder is selected from at least one of polyacrylic acid, sodium polyacrylate, sodium alginate, and sodium carboxymethyl cellulose.

[0037] Optionally, in the step of grafting P-containing groups onto the polyanionic binder, the grafting rate is preferably 5%-30%, further preferably 10%-30%, and more preferably 20%-30%, which can ensure that there are sufficient P-containing groups to achieve functionalization effects without reducing the flexibility of the water-based binder.

[0038] In step S2, the crosslinking agent is selected from at least one of polyethylene oxide and polyethylene glycol diacrylate. This crosslinking agent not only facilitates ion transport but also forms a strong interaction with the inorganic nanoparticles, ensuring tight crosslinking with the inorganic nanoparticles, thereby achieving physical flame retardancy using the inorganic nanoparticles. Preferably, the mass ratio of the crosslinking agent to the polyanionic binder is 1:5-1:20.

[0039] Optionally, the nano-inorganic particles are selected from at least one of titanium dioxide, boron nitride, and aluminum oxide, which not only have a thermal conductivity of more than 10W / mK, can quickly conduct heat to avoid the generation of local hot spots, but also have excellent electrochemical stability. Preferably, the particle size of the nano-inorganic particles is 10nm-100nm.

[0040] Optionally, the mass fraction of the nano inorganic particles in the aqueous binder is 1%-10%.

[0041] It is understood that after cross-linking, vacuum drying and other operations may be performed to obtain a powdered aqueous binder. Furthermore, the aqueous binder may be crushed to a particle size of less than 50 μm.

[0042] Furthermore, the present invention also provides a water-based adhesive prepared by the preparation method.

[0043] In the present invention, by grafting highly polar P-containing groups onto a polyanionic binder, the contact angle between the electrode sheet and the electrolyte can be reduced after the aqueous binder is applied to the electrode sheet, thereby improving the electrolyte absorption rate. At the same time, a porous network structure can be formed through crosslinking, and the porous network structure can provide capillary channels, thereby promoting uniform electrolyte penetration after the aqueous binder is applied to the electrode sheet. In addition, the polyanionic binder itself has excellent ionic conductivity, which is conducive to ion transmission. Therefore, when the aqueous binder of the present invention is used in the electrode sheet, the electrolyte wettability can be effectively improved, and thus the ion transmission efficiency can be effectively improved.

[0044] In addition, the PO· free radicals generated by the decomposition of P-containing groups at high temperatures can capture active oxygen free radicals in the gas phase to achieve chemical flame retardancy. At the same time, the nano-inorganic filler can achieve physical flame retardancy. Therefore, through the synergistic effect of chemistry and physics, its flame retardant performance can be effectively improved. Furthermore, when the electrode sheet uses the water-based adhesive of the present invention, the safety performance of the electrode sheet can be effectively improved.

[0045] In addition, when the aqueous binder of the present invention is applied to a sodium ion battery and used in conjunction with a layered oxide positive electrode material as a positive electrode active material layer, the P-containing groups in the aqueous binder can form coordination bonds with the surface oxygen vacancies of the layered oxide positive electrode material, thereby inhibiting the release of its lattice oxygen. At the same time, the nano-inorganic filler can form a physical barrier on the surface of the electrode sheet, blocking the oxygen diffusion path, thereby reducing the risk of thermal runaway of the sodium ion battery.

[0046] Furthermore, the present invention also provides a use of the aqueous binder in a battery. The aqueous binder of the present invention can be used in secondary batteries such as lithium-ion batteries, sodium-ion batteries, and solid-state batteries.

[0047] Specifically, the aqueous binder can be used in positive electrode sheets, negative electrode sheets and separators, and can effectively improve the wettability and safety of the electrolyte. When used in positive electrode sheets and negative electrode sheets, it can completely replace binders such as PVDF, CMC, SBR, etc., and can also be mixed with binders such as PVDF, CMC, SBR, etc. When used in separators, it can be coated on the separator to form a aqueous binder coating.

[0048] Furthermore, the present invention also provides a sodium ion battery, wherein the positive electrode sheet of the sodium ion battery uses the aqueous binder.

[0049] It can be understood that the positive electrode sheet also includes a sodium ion battery positive electrode material and a conductive agent. The present invention has no special requirements for the mass ratio of the sodium ion battery positive electrode material, the conductive agent and the aqueous binder in the positive electrode sheet. It can be selected and controlled according to conventional methods. There are no special requirements for the selection of the sodium ion battery positive electrode material and the conductive agent. For example, the sodium ion battery positive electrode material is selected from a layered oxide positive electrode material, a polyanion positive electrode material or Prussian blue, and the conductive agent is selected from carbon nanotubes (CNTs), conductive carbon black (Super P), acetylene black, Ketjen black and conductive graphite, etc. The present invention will not be repeated here.

[0050] Among them, when the positive electrode material of the sodium ion battery is selected from layered oxide positive electrode materials, such as NaNiO2, NaCoO2, NaMnO2, etc., the P-containing groups in the aqueous binder can form coordination bonds with the surface oxygen vacancies of the layered oxide positive electrode material, inhibiting the release of its lattice oxygen. At the same time, the nano-inorganic filler can form a physical barrier on the surface of the electrode sheet to block the oxygen diffusion path, thereby reducing the risk of thermal runaway of the sodium ion battery.

[0051] It is understood that sodium-ion batteries also include a negative electrode sheet, a separator, and an electrolyte. The present invention does not have any special requirements for the negative electrode sheet, separator, and electrolyte of the sodium-ion battery, and conventional designs can be used. For example, the active material of the negative electrode sheet is selected from hard carbon materials, soft carbon materials, graphite, etc. The conductive agent is selected from carbon nanotubes (CNTs), conductive carbon black (Super P), acetylene black, Ketjen black, and conductive graphite, etc. The binder is selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), sodium alginate, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), etc. The separator is selected from polypropylene separator (PP), polyimide separator (PI), polyethylene separator (PE), ceramic coated separator, etc. The electrolyte contains a sodium salt and an organic solvent, wherein the sodium salt is selected from NaPF6, etc., and the organic solvent is selected from ethylene carbonate (EC), dimethyl carbonate (DMC), etc. The present invention will not be repeated here.

[0052] Optionally, in the negative electrode sheet of the sodium ion battery, the aqueous binder is used to replace conventional binders such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), sodium alginate, styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC);

[0053] Optionally, the sodium ion battery diaphragm uses the aqueous binder, specifically by coating the aqueous binder on the surface of the diaphragm to form a coating with a thickness of 2 μm-20 μm.

[0054] The present invention does not impose any requirements on the shape of the sodium ion battery, which can be a cylindrical battery, a square battery, etc.

[0055] Below, the technical solution of the present invention will be further described by the following specific examples. However, it will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, the procedures were carried out according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0056] Example 1

[0057] Sodium polyacrylate with a molecular weight of 500,000 was dissolved in a 3:1 (volume ratio) mixture of deionized water and ethanol. The mixture was stirred magnetically at 60°C until completely dissolved, maintaining a sodium polyacrylate mass fraction of 10%. Hydroxyethyl acrylate phosphate monomer (HEA-P, purity ≥99%) was then added at a molar ratio of 12:1. After nitrogen protection, ammonium persulfate (APS) was added as an initiator at a concentration of 0.5% by weight. The reaction was continued at 80°C for 4 hours to form a graft copolymer containing phosphate groups with a grafting efficiency of 10%.

[0058] Titanium dioxide with a particle size of 20 nm and boron nitride nanosheets with a particle size of 20 nm were weighed at a ratio of 5% by mass of the nano-inorganic particles in the aqueous binder. The titanium dioxide and boron nitride nanosheets were dispersed in a solution of the above-mentioned graft copolymer of phosphate groups at a mass ratio of 3:1. The mixture was ultrasonically treated at a power of 300 W for 30 minutes, and then a polyethylene oxide (PEO) cross-linker was added. The mass of the polyethylene oxide (PEO) cross-linker was 10% of the mass of the sodium polyacrylate. The mixture was allowed to stand for cross-linking for 24 hours, and then the gel-like product was vacuum dried at 60°C for 8 hours and crushed into a powder with a particle size of 1 μm to obtain an aqueous binder.

[0059] D 50 10μm NaNi 0.3 Mn 0.5 Co 0.2O2, acetylene black and the aqueous binder prepared above were mixed in a mass ratio of 95:3:2, and deionized water was added to prepare a slurry with a solid content of 65%. The slurry was coated on the surface of aluminum foil, then dried at 120°C for 12 hours, rolled to a compaction density of 3.2g / cm³, and cut into positive electrode sheets with a diameter of 14mm.

[0060] Example 2

[0061] Sodium polyacrylate with a molecular weight of 500,000 was dissolved in a 3:1 (volume ratio) mixture of deionized water and ethanol at 60°C with magnetic stirring until completely dissolved, maintaining a 10% mass fraction of sodium polyacrylate. Vinylphosphonic acid was then added at a 6:1 molar ratio. After nitrogen protection, ammonium persulfate (APS) was added as an initiator at a concentration of 0.5% by weight. The reaction was continued at 80°C for 4 hours to form a graft copolymer containing phosphonic acid groups, with a grafting efficiency of 20%.

[0062] Titanium dioxide with a particle size of 20 nm and boron nitride nanosheets with a particle size of 100 nm were weighed so that the mass fraction of the nano-inorganic particles in the binder was 10%. The titanium dioxide and boron nitride nanosheets were dispersed in the solution of the above-mentioned graft copolymer of phosphate groups at a mass ratio of 3:1. The mixture was ultrasonically treated at a power of 300 W for 30 minutes, and then a polyethylene oxide (PEO) cross-linker was added. The mass of the polyethylene oxide (PEO) cross-linker was 10% of the mass of the sodium polyacrylate. The mixture was allowed to stand for cross-linking for 24 hours, and then the gel-like product was vacuum dried at 60°C for 8 hours and crushed into a powder with a particle size of 1 μm to obtain a water-based binder.

[0063] D 50 10μm NaNi 0.3 Mn 0.5 Co 0.2 O2, acetylene black and the aqueous binder prepared above were mixed in a mass ratio of 95:3:2, and deionized water was added to prepare a slurry with a solid content of 65%. The slurry was coated on the surface of aluminum foil, then dried at 120°C for 12 hours, rolled to a compaction density of 3.2g / cm³, and cut into positive electrode sheets with a diameter of 14mm.

[0064] Example 3

[0065] Sodium alginate with a molecular weight of 300,000 was dissolved in a mixture of deionized water and ethanol in a 3:1 volume ratio at 60°C with magnetic stirring until completely dissolved. The mass fraction of the sodium alginate was controlled to be 10%. Hexachlorocyclotriphosphazene was then added at a molar ratio of 24:1. After nitrogen protection, ammonium persulfate (APS) was added as an initiator at a concentration of 0.5% by weight. The reaction was incubated at 80°C for 4 hours to form a graft copolymer containing phosphazene groups with a grafting efficiency of 5%.

[0066] Alumina with a particle size of 20 nm and boron nitride nanosheets with a particle size of 100 nm were weighed so that the mass fraction of the nano-inorganic particles in the binder was 10%. The alumina and boron nitride nanosheets were dispersed in the solution of the above-mentioned phosphazene-group graft copolymer in a mass ratio of 3:1. The solution was ultrasonically treated at a power of 300 W for 30 minutes. Subsequently, a polyethylene glycol diacrylate crosslinker was added, and the mass of the polyethylene glycol diacrylate crosslinker was 5% of the mass of the sodium alginate. The solution was allowed to stand for crosslinking for 24 hours. The gel-like product was then vacuum-dried at 60° C. for 8 hours and crushed into a powder with a particle size of 1 μm to obtain a water-based binder.

[0067] D 50 10μm NaNi 0.3 Mn 0.5 Co 0.2 O2, acetylene black and the aqueous binder prepared above were mixed in a mass ratio of 95:3:2, and deionized water was added to prepare a slurry with a solid content of 65%. The slurry was coated on the surface of aluminum foil, and then dried at 120°C for 12 hours. The slurry was rolled to a compaction density of 3.2g / cm³ and cut into positive electrode sheets with a diameter of 14mm.

[0068] Example 4

[0069] Polyacrylic acid (PA) with a molecular weight of 500,000 was dissolved in a 3:1 (volume ratio) mixture of deionized water and ethanol at 60°C with magnetic stirring until completely dissolved, maintaining a PA mass fraction of 10%. Hydroxyalkoxyphosphazene was then added at a molar ratio of 4:1. After nitrogen protection, ammonium persulfate (APS) was added as an initiator at a concentration of 0.5% by weight. The reaction was continued at 80°C for 4 hours to form a graft copolymer containing phosphazene groups with a grafting efficiency of 30%.

[0070] Alumina with a particle size of 20 nm and boron nitride nanosheets with a particle size of 10 nm were weighed so that the mass fraction of the nano-inorganic particles in the binder was 10%. The aluminum oxide and boron nitride nanosheets were dispersed in a solution of the above-mentioned phosphazene-group graft copolymer in a mass ratio of 3:1. The solution was ultrasonically treated at a power of 300 W for 30 minutes. Subsequently, a polyethylene glycol diacrylate cross-linker was added, and the mass of the polyethylene glycol diacrylate cross-linker was 10% of the mass of the polyacrylic acid. The solution was allowed to stand for cross-linking for 24 hours. The gel-like product was then vacuum-dried at 60° C. for 8 hours and crushed into a powder with a particle size of 1 μm to obtain a water-based binder.

[0071] D 50 10μm NaNi 0.3 Mn 0.5 Co 0.2O2, acetylene black and the aqueous binder prepared above were mixed in a mass ratio of 95:3:2, and deionized water was added to prepare a slurry with a solid content of 65%. The slurry was coated on the surface of aluminum foil, then dried at 120°C for 12 hours, rolled to a compaction density of 3.2g / cm³, and cut into positive electrode sheets with a diameter of 14mm.

[0072] Comparative Example 1

[0073] The difference between Comparative Example 1 and Example 1 is that D 50 10μm NaNi 0.3 Mn 0.5 Co 0.2 O2, acetylene black and sodium polyacrylate were mixed in a mass ratio of 95:3:2, and deionized water was added to form a slurry with a solid content of 65%. The slurry was coated on the surface of aluminum foil, then dried at 120°C for 12 hours, rolled to a compaction density of 3.2g / cm³, and cut into positive electrode sheets with a diameter of 14mm.

[0074] Comparative Example 2

[0075] The difference between Comparative Example 2 and Example 1 is that D 50 10μm NaNi 0.3 Mn 0.5 Co 0.2 O2, acetylene black, and the phosphate-containing graft copolymer prepared in Example 1 were mixed in a mass ratio of 95:3:2, and deionized water was added to form a slurry with a solid content of 65%. The slurry was coated on the surface of aluminum foil, and then dried at 120°C for 12 hours. The slurry was rolled to a compaction density of 3.2 g / cm³ and cut into positive electrode sheets with a diameter of 14 mm.

[0076] Comparative Example 3

[0077] The only difference between Comparative Example 3 and Example 1 is that the sodium polyacrylate is not grafted with a P group, but is directly cross-linked with the cross-linking agent and the nano-inorganic particles.

[0078] D 50 10μm NaNi 0.3 Mn 0.5 Co 0.2 O2, acetylene black, and the above-prepared adhesive were mixed in a mass ratio of 95:3:2, and deionized water was added to form a slurry with a solid content of 65%. The slurry was coated on the surface of aluminum foil, then dried at 120°C for 12 hours, rolled to a compaction density of 3.2g / cm³, and cut into positive electrode sheets with a diameter of 14mm.

[0079] The adhesives and positive electrode sheets prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to performance tests, and the results are shown in Table 1.

[0080] Table 1 Binder and positive electrode performance test results

[0081]

[0082] The limiting oxygen index and self-extinguishing time in Table 1 indicate that the flame retardancy of the aqueous binder can be effectively improved by grafting highly polar P-containing groups and cross-linked composite nano-inorganic particles. The electrolyte absorption rate and electrode wetting angle indicate that the application of the aqueous binder to the positive electrode effectively improves the wettability of the electrolyte to the positive electrode. The DSC oxygen release exothermic peak temperature indicates that the synergistic use of the aqueous binder with the layered oxide positive electrode material to prepare the positive electrode for a sodium-ion battery can inhibit lattice oxygen release and block oxygen diffusion pathways, thereby reducing the risk of thermal runaway in the sodium-ion battery. Furthermore, Examples 1-4 indicate that a higher grafting rate of P-containing groups leads to better functionalization.

[0083] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a water-based binder, characterized in that: The following steps are involved: Grafting P-containing groups onto the polyanionic binder; Then, a cross-linking agent and nano inorganic particles are added to perform cross-linking, and a water-based adhesive is obtained after drying.

2. The method for preparing the water-based binder according to claim 1, wherein: The P-containing group is selected from at least one of a phosphate group, a phosphonic acid group, and a phosphazene group; And / or, the polyanionic binder is at least one selected from polyacrylic acid, sodium polyacrylate, sodium alginate, and sodium carboxymethyl cellulose; And / or, the cross-linking agent is selected from at least one of polyethylene oxide and polyethylene glycol diacrylate; And / or, the nano inorganic particles are selected from at least one of titanium dioxide, boron nitride, and aluminum oxide.

3. The method for preparing the water-based adhesive according to claim 1, wherein: In the step of grafting the P-containing group onto the polyanionic binder, the grafting rate is 5%-30%; And / or, the mass fraction of the nano inorganic particles in the aqueous binder is 1%-10%; And / or, the mass ratio of the cross-linking agent to the polyanionic binder is 1:5-1:

20.

4. The method for preparing the water-based adhesive according to claim 1, wherein: The particle size of the nano inorganic particles is 10nm-100nm.

5. The method for preparing a water-based binder according to any one of claims 1 to 4, characterized in that: The step of grafting the P-containing group on the polyanionic binder includes: dissolving the polyanionic binder in a solvent, then adding a P-containing monomer and an initiator, and reacting at 60° C.-90° C. for 2 hours-6 hours to complete the grafting.

6. The method for preparing the water-based adhesive according to claim 5, wherein: The P-containing monomer is selected from at least one of hydroxyethyl acrylate phosphate, vinyl phosphonate, vinyl phosphonic acid, hexachlorocyclotriphosphazene, and hydroxyalkoxyphosphazene.

7. A water-based adhesive prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the aqueous binder according to claim 7 in a battery.

9. A sodium ion battery, characterized in that: The positive electrode sheet of the sodium ion battery uses the aqueous binder according to claim 7.

10. The sodium ion battery according to claim 9, characterized in that The negative electrode sheet of the sodium ion battery uses the aqueous binder according to claim 7; And / or, the separator of the sodium ion battery uses the aqueous binder according to claim 7.

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