Aqueous cross-linking binder and preparation method thereof, lithium-ion battery negative electrode material and preparation method thereof, and a secondary lithium battery

Abstract

The present invention belongs to the technical field of lithium-ion battery materials. The present invention provides an aqueous cross-linked binder and a preparation method thereof, a lithium-ion battery negative electrode material and a preparation method thereof, and a secondary lithium battery. The preparation method of the aqueous cross-linked binder comprises the following steps: mixing a natural polysaccharide solution, a linear long-chain binder solution, and a titanate coupling agent, and then reacting to obtain an aqueous cross-linked binder. The preparation method of the aqueous cross-linked binder provided by the present invention does not require a post-processing purification step, thereby overcoming the difficulties of traditional cross-linked binders such as difficult purification and poor reactivity. In addition, the prepared aqueous cross-linked binder has better mechanical properties and battery performance than traditional two-dimensional linear binders.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery materials, and in particular to an aqueous cross-linking binder and a preparation method thereof, a lithium ion battery negative electrode material and a preparation method thereof, and a secondary lithium battery. Background Art

[0002] The recent boom in mobile electronic devices, such as smartphones and laptops, has driven a surge in demand for batteries. Simultaneously, the commercialization of the electric vehicle industry and the expansion of large-scale power grids are driving the development of lithium-ion batteries toward larger capacity and higher energy density.

[0003] The theoretical specific capacity of traditional graphite anode is 372mAh / g, which cannot meet the market demand for high-capacity batteries. Silicon has attracted extensive attention from Chinese and foreign scholars due to its extremely high theoretical specific capacity (4200mAh / g). Compared with graphite anode, silicon has obvious advantages in capacity and lower electrode potential (vsLi / Li + ≤0.4V) makes it difficult for lithium to precipitate on the surface of the silicon negative electrode, and the safety performance is better. Although silicon has the above advantages as the negative electrode of lithium-ion batteries, there are still some difficulties that have not been overcome. There are mainly two points: (1) The lithium storage capacity of silicon is reflected through alloying. During the lithium insertion process, amorphous Li first appears on the outer layer of crystalline silicon. x Si, the interior still maintains the form of crystalline silicon, so there will be a huge stress difference between the inside and outside, causing particle pulverization. And silicon is fully embedded with lithium (forming Li 4.4 After the silicon particles are pulverized, the volume will expand by 300-400% compared to crystalline silicon, resulting in a drastic change in the stress between silicon particles and the pulverization of the electrode active material. The pulverization of silicon particles will cause cracks in the conductive network formed between the silicon particles and the conductive agent, which will prevent lithium from being released, causing a decrease in capacity and affecting the cycle performance. (2) The pulverization of silicon particles will produce new surfaces, leading to the repeated generation of solid electrolyte membrane (SEI), repeated consumption of electrolyte, affecting the cycle performance of the battery, and ultimately causing the battery to short circuit.

[0004] To address these issues, designing a three-dimensional network binder with excellent mechanical properties can effectively alleviate a series of problems faced during the lithiation process of silicon anodes. Currently, commonly used crosslinkers include organic peroxides, anhydrides, glycidyl ethers, polyacids, polyols, or small-molecule monomers containing unsaturated bonds. However, these crosslinkers often encounter problems such as difficulty in initiation, poor reactivity with polymer chains, environmentally unfriendly solvents, difficulty in post-processing and purification, and difficulty in controlling the degree of crosslinking during the reaction process. The electrolyte in lithium-ion batteries is very sensitive to the water content of the electrode and the electrochemical stability of the additives, so choosing the right crosslinker is extremely important.

[0005] Therefore, how to provide a three-dimensional network adhesive with excellent mechanical properties has become a problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a water-based cross-linking binder and a preparation method thereof, a lithium-ion battery negative electrode material and a preparation method thereof, and a secondary lithium battery, the purpose of which is to solve the technical problems existing in the reaction process of existing cross-linking agents, such as difficulty in initiation, poor reactivity with polymer chains, environmentally unfriendly solvents, difficulty in post-processing purification, and difficulty in controlling the degree of cross-linking.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing a water-based cross-linking binder, comprising the following steps:

[0009] A water-based cross-linking binder is obtained by mixing a natural polysaccharide solution, a linear long-chain binder solution and a titanate coupling agent and reacting the mixture.

[0010] Furthermore, the concentration of the natural polysaccharide solution is 0.01 to 0.05 g / mL, and the natural polysaccharide is any one of sodium carboxymethyl cellulose, sodium alginate, alginic acid, gum arabic and chitosan;

[0011] The concentration of the linear long-chain binder solution is 0.01 to 0.05 g / mL, the molecular weight of the linear long-chain binder is 200,000 to 1.25 million, and the general structural formula of the linear long-chain binder is as follows:

[0012]

[0013] The R1 is independently -COOH or -OH, and R2 is independently -COOH or -OH.

[0014] Furthermore, the general structural formula of the titanate coupling agent is as follows:

[0015] n (RO)-Ti-(OXR'Y) 4-n ,

[0016] Wherein, RO is a group generated by hydrolysis of a titanate coupling agent, X is a P or N atom, R′ is an aliphatic hydrocarbon, Y is a multifunctional functional group, and n≤4.

[0017] Furthermore, the mass ratio of the natural polysaccharide to the linear long-chain binder is 1-9:1-9, and the mass of the titanate coupling agent is 1-15% of the total reactants;

[0018] The reaction temperature is 60-100° C., and the reaction time is 4-10 hours.

[0019] The present invention provides a water-based cross-linking adhesive prepared by the above preparation method.

[0020] The present invention provides a method for preparing a negative electrode material for a lithium ion battery using the above-mentioned aqueous cross-linked binder, comprising the following steps:

[0021] Silicon powder, conductive additives and water-based cross-linking binder are mixed to obtain electrode slurry, which is then coated on a current collector copper foil and dried to obtain a negative electrode material for a lithium-ion battery.

[0022] Furthermore, the particle size of the silicon powder is 50 to 150 nm; the conductive additive is one or more of acetylene black, Ketjen black, Super P, carbon nanotubes and graphene;

[0023] The mass ratio of the silicon powder, the conductive additive and the water-based cross-linking binder is 50-80:10-30:10-30.

[0024] Furthermore, the mixing is carried out in a stirring manner, and the mixing time is 6 to 12 hours; the drying temperature is 80 to 120° C., and the drying time is 6 to 12 hours.

[0025] The present invention provides a lithium ion battery negative electrode material prepared by the above method.

[0026] The present invention provides a secondary lithium battery comprising a lithium metal pole piece, an electrolyte, a diaphragm, a battery casing and the above-mentioned lithium ion battery negative electrode material.

[0027] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The raw materials used in the present invention are widely available, and the reaction solvent is non-toxic and pollution-free. Different natural polysaccharides and titanate coupling agents can be selected to undergo various reactions such as esterification, amidation, and coordination. The by-products of the reactions are water or alcohols, which can be automatically removed during the drying process, eliminating the need for post-processing and purification steps. This overcomes the difficulties of traditional cross-linked binders in purification and poor reactivity, and achieves the overall goal of low pollution, easy reaction, and high performance.

[0029] 2. The present invention forms a covalent bonding network by esterification, amidation, coordination and other reactions between functional groups such as carboxyl and hydroxyl groups on the polymer chain and titanate coupling agents. Compared with traditional two-dimensional linear binders, the water-based cross-linked binder prepared by the present invention has better mechanical properties and battery performance.

[0030] 3. The mechanical properties of the secondary lithium battery prepared by the present invention are improved by more than 60% compared with ordinary lithium batteries; the first-cycle coulombic efficiency of the secondary lithium battery prepared by the present invention is above 93%, and the capacity retention rate is as high as 68% after 100 cycles at a current density of 2.1A / g, which has great commercial value and good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a reaction process diagram for preparing a water-based cross-linking adhesive according to the present invention;

[0032] Figure 2 The cyclic voltammetry curve of the secondary lithium battery prepared in Example 1 at a scan rate of 0.05 mV;

[0033] Figure 3 The AC impedance spectra of the secondary lithium battery prepared in Example 1 before and after cycling;

[0034] Figure 4 The battery rate performance diagram of the lithium batteries prepared in Example 1 and Comparative Example 1 at different current densities;

[0035] Figure 5 This is a comparison chart of the cycling results of the lithium batteries prepared in Example 1 and Comparative Examples 1 to 3 at a current density of 2.1 A / g. DETAILED DESCRIPTION

[0036] The present invention provides a method for preparing a water-based cross-linking binder, comprising the following steps:

[0037] A water-based cross-linking binder is obtained by mixing a natural polysaccharide solution, a linear long-chain binder solution and a titanate coupling agent and reacting the mixture.

[0038] In the present invention, the reaction process is as follows Figure 1 As shown, the characteristic functional groups of natural polysaccharides form a covalent and coordinated structure with titanate coupling agents, and then undergo esterification and amidation reactions with linear binders such as acrylic acid. Then, they are further dehydrated during the vacuum drying process of electrode sheet preparation to form a stable covalent structure.

[0039] In the present invention, the concentration of the natural polysaccharide solution is 0.01 to 0.05 g / mL, preferably 0.02 to 0.04 g / mL, and more preferably 0.03 g / mL; the natural polysaccharide is any one of sodium carboxymethyl cellulose, sodium alginate, alginic acid, gum arabic, and chitosan, preferably any one of sodium carboxymethyl cellulose, sodium alginate, alginic acid, and chitosan, and more preferably sodium carboxymethyl cellulose, sodium alginate, or chitosan;

[0040] The concentration of the linear long-chain binder solution is 0.01 to 0.05 g / mL, preferably 0.02 to 0.04 g / mL, and more preferably 0.03 g / mL; the molecular weight of the linear long-chain binder is 200,000 to 1.25 million, preferably 400,000 to 1.2 million, and more preferably 600,000 to 1,000,000; the general structural formula of the linear long-chain binder is as follows:

[0041]

[0042] The R1 is independently -COOH or -OH, preferably -COOH; R2 is independently -COOH or -OH, preferably -COOH.

[0043] In the present invention, the general structural formula of the titanate coupling agent is as follows:

[0044] n (RO)-Ti-(OXR'Y) 4-n ,

[0045] Wherein, RO is a group produced by hydrolysis of a titanate coupling agent; X is a P or N atom, preferably a N atom; R′ is an aliphatic hydrocarbon, preferably an alkane, an alkene or an alkyne, more preferably an alkane; Y is a multifunctional functional group, preferably any one of an amino group, an epoxy group, a thiol group and a hydroxyl group, more preferably an amino group or a hydroxyl group; n≤4, preferably ≤3, more preferably 1 or 2.

[0046] In the present invention, the mass ratio of natural polysaccharide to linear long-chain binder is 1-9:1-9, preferably 2-8:2-7, and more preferably 3-5:5-6; the mass of titanate coupling agent is 1-15% of the total reactants, preferably 3-12%, and more preferably 5-10%.

[0047] In the present invention, the reaction temperature is 60-100° C., preferably 65-90° C., more preferably 70-80° C.; the reaction time is 4-10 h, preferably 5-9 h, more preferably 7-8 h.

[0048] The present invention provides a water-based cross-linking adhesive prepared by the above preparation method.

[0049] The present invention provides a method for preparing a negative electrode material for a lithium ion battery using the above-mentioned aqueous cross-linked binder, comprising the following steps:

[0050] Silicon powder, conductive additives and water-based cross-linking binder are mixed to obtain electrode slurry, which is then coated on a current collector copper foil and dried to obtain a negative electrode material for a lithium-ion battery.

[0051] In the present invention, the particle size of the silicon powder is 50 to 150 nm, preferably 60 to 120 nm, and more preferably 80 to 100 nm; the conductive additive is one or more of acetylene black, Ketjen black, SuperP, carbon nanotubes and graphene, preferably one or more of acetylene black, SuperP, carbon nanotubes and graphene, and more preferably acetylene black and / or SuperP.

[0052] In the present invention, the mass ratio of the silicon powder, the conductive additive and the aqueous cross-linking binder is 50-80:10-30:10-30, preferably 55-75:15-26:12-25, and more preferably 60-70:20-25:15-20.

[0053] In the present invention, the mixing is carried out in a stirring manner, and the mixing time is 6 to 12 hours, preferably 7 to 11 hours, and more preferably 8 to 10 hours; the drying temperature is 80 to 120°C, preferably 85 to 110°C, and more preferably 90 to 100°C; the drying time is 6 to 12 hours, preferably 7 to 11 hours, and more preferably 8 to 10 hours.

[0054] The present invention provides a lithium ion battery negative electrode material prepared by the above method.

[0055] The present invention provides a secondary lithium battery comprising a lithium metal pole piece, an electrolyte, a diaphragm, a battery casing and the above-mentioned lithium ion battery negative electrode material.

[0056] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0057] Example 1

[0058] The titanate coupling agent used in this embodiment is diisopropyl di(triethanolamine) titanate;

[0059] The preparation process of the water-based cross-linking adhesive is as follows:

[0060] Take 0.0200g of sodium alginate in a 5mL beaker, add 1mL of deionized water and fully dissolve it at 60°C under a heated magnetic stirrer to obtain a sodium alginate solution; take 10μL of di(triethanolamine)diisopropyl titanate and add it to the sodium alginate solution, heat it at 80°C until the coordination reaction is completed and the solution is light yellow; take 0.0200g of polyacrylic acid in a 5mL beaker, add 1mL of deionized water and fully dissolve it on a magnetic stirrer, then pour it into the solution in the previous step and continue stirring for 4h to obtain a water-based cross-linked adhesive.

[0061] The preparation process of lithium-ion battery negative electrode materials is as follows:

[0062] 0.1200 g of nano-silicon powder, 0.0400 g of Super P and 0.0400 g of the above-mentioned aqueous cross-linking binder were dispersed in deionized water to form a slurry. The slurry was coated on a 9 μm copper foil using a coating machine and dried at 120° C. for 12 h to obtain a lithium-ion battery negative electrode material.

[0063] The preparation process of secondary lithium batteries is as follows:

[0064] The lithium-ion battery negative electrode material prepared above was assembled into a CR2025 button cell, wherein: the counter electrode was a metal lithium sheet, the separator was a polypropylene film (PP film), the electrolyte solution was a 1 mol / L LiPF6 solution, and the solvent was a mixed solution of EC and 10% FEC in a volume ratio of 1:1.

[0065] Example 2

[0066] The titanate coupling agent used in this embodiment is diisopropyl di(triethanolamine) titanate;

[0067] The preparation process of the water-based cross-linking adhesive is as follows:

[0068] Take 0.0200g of sodium carboxymethyl cellulose in a 5mL beaker, add 1mL of deionized water and fully dissolve it at 60°C under a heated magnetic stirrer to obtain a carboxymethyl cellulose solution; take 10μL of di(triethanolamine)diisopropyl titanate and add it to the sodium carboxymethyl cellulose solution, and heat it at 80°C until the coordination reaction is completed; take 0.0200g of polyethylene maleic anhydride in a 5mL beaker, add 1mL of deionized water and fully dissolve it on a magnetic stirrer, then pour it into the solution in the previous step and continue stirring for 4h to obtain a water-based cross-linked binder.

[0069] The preparation process of lithium-ion battery negative electrode materials is as follows:

[0070] 0.1200 g of nano-silicon powder, 0.0400 g of Super P and 0.0400 g of the above-mentioned aqueous cross-linking binder were dispersed in deionized water to form a slurry. The slurry was coated on a 9 μm copper foil using a coating machine and dried at 120° C. for 12 h to obtain a lithium-ion battery negative electrode material.

[0071] The preparation process of secondary lithium batteries is as follows:

[0072] The lithium-ion battery negative electrode material prepared above was assembled into a CR2025 button cell, wherein: the counter electrode was a metal lithium sheet, the separator was a polypropylene film (PP film), the electrolyte solution was a 1 mol / L LiPF6 solution, and the solvent was a mixed solution of DMC and 5% FEC in a volume ratio of 1:1.

[0073] Example 3

[0074] The titanate coupling agent used in this embodiment is tetraisopropyl orthotitanate;

[0075] The preparation process of the water-based cross-linking adhesive is as follows:

[0076] Take 0.0400g of sodium alginate in a 10mL beaker, add 2mL of deionized water and fully dissolve it at 60°C under a heated magnetic stirrer to obtain a sodium alginate solution; take 10μL of tetraisopropyl orthotitanate and add it to the sodium alginate solution, heat it at 80°C until the coordination reaction is completed and the solution is light yellow; take 0.0400g of polyacrylic acid in a 10mL beaker, add 2mL of deionized water and fully dissolve it on a magnetic stirrer, then pour it into the solution in the previous step and continue stirring for 6h to obtain a water-based cross-linked adhesive.

[0077] The preparation process of lithium-ion battery negative electrode materials is as follows:

[0078] 0.1200 g of nano-silicon powder, 0.0400 g of Super P and 0.0400 g of the above-mentioned aqueous cross-linking binder were dispersed in deionized water to form a slurry. The slurry was coated on a 9 μm copper foil using a coating machine and dried at 120° C. for 12 h to obtain a lithium-ion battery negative electrode material.

[0079] The preparation process of secondary lithium batteries is as follows:

[0080] The lithium-ion battery negative electrode material prepared above was assembled into a CR2025 button cell, wherein: the counter electrode was a metal lithium sheet, the separator was a polypropylene film (PP film), the electrolyte solution was a 1 mol / L LiPF6 solution, and the solvent was a mixed solution of EC and 5% FEC in a volume ratio of 1:1.

[0081] Example 4

[0082] The titanate coupling agent used in this embodiment is tetra-n-butyl titanate;

[0083] The preparation process of the water-based cross-linking adhesive is as follows:

[0084] Take 0.0200g of sodium alginate in a 5mL beaker, add 1mL of deionized water and fully dissolve it at 60°C under a heated magnetic stirrer to obtain a sodium alginate solution; take 10μL of tetrabutyl titanate and add it to the sodium alginate solution, heat it at 80°C until the coordination reaction is completed and the solution is light yellow; take 0.0200g of polyacrylic acid in a 5mL beaker, add 1mL of deionized water and fully dissolve it on a magnetic stirrer, then pour it into the solution in the previous step and continue stirring for 6h to obtain a water-based cross-linked binder.

[0085] The preparation process of lithium-ion battery negative electrode materials is as follows:

[0086] 0.1200 g of nano-silicon powder, 0.0400 g of Super P and 0.0400 g of the above-mentioned aqueous cross-linking binder were dispersed in deionized water to form a slurry. The slurry was coated on a 9 μm copper foil using a coating machine and dried at 100° C. for 10 h to obtain a lithium-ion battery negative electrode material.

[0087] The preparation process of secondary lithium batteries is as follows:

[0088] The lithium-ion battery negative electrode material prepared above was assembled into a CR2025 button cell, wherein: the counter electrode was a metal lithium sheet, the separator was a polypropylene film (PP film), the electrolyte solution was a 1 mol / L LiPF6 solution, and the solvent was a mixed solution of EC and 5% FEC in a volume ratio of 1:1.

[0089] Comparative Example 1

[0090] The preparation process of lithium-ion battery negative electrode materials is as follows:

[0091] 0.1200 g of nano-silicon powder, 0.0400 g of SuperP and 0.0400 g of sodium alginate were dispersed in deionized water to form a slurry, which was coated on a 9 μm copper foil using a coating machine and dried at 120° C. for 12 h to obtain a lithium-ion battery negative electrode material.

[0092] The preparation process of secondary lithium batteries is as follows:

[0093] The lithium-ion battery negative electrode material prepared above was assembled into a CR2025 button battery, wherein: the counter electrode was a metal lithium sheet, the separator was a polypropylene film (PP film), the electrolyte solution was a 1 mol / L LiPF6 solution, and the solvent was a mixed solution of EC and DEC in a volume ratio of 1:1.

[0094] Comparative Example 2

[0095] The preparation process of lithium-ion battery negative electrode materials is as follows:

[0096] 0.1200 g of nano-silicon powder, 0.0400 g of SuperP and 0.0400 g of polyacrylic acid were dispersed in deionized water to form a slurry, which was coated on a 9 μm copper foil using a coating machine and dried at 120° C. for 12 h to obtain a lithium-ion battery negative electrode material.

[0097] The preparation process of secondary lithium batteries is as follows:

[0098] The lithium-ion battery negative electrode material prepared above was assembled into a CR2025 button cell, wherein: the counter electrode was a metal lithium sheet, the separator was a polypropylene film (PP film), the electrolyte solution was a 1 mol / L LiPF6 solution, and the solvent was a mixed solution of EC and 10% FEC in a volume ratio of 1:1.

[0099] Comparative Example 3

[0100] The preparation process of lithium-ion battery negative electrode materials is as follows:

[0101] 0.1200 g of nano-silicon powder, 0.0400 g of Super P, 0.0200 g of polyacrylic acid and 0.0200 g of sodium alginate were dispersed in deionized water to form a slurry. The slurry was coated on a 9 μm copper foil using a coating machine and dried at 120° C. for 12 h to obtain a lithium-ion battery negative electrode material.

[0102] The preparation process of secondary lithium batteries is as follows:

[0103] The lithium-ion battery negative electrode material prepared above was assembled into a CR2025 button cell, wherein: the counter electrode was a metal lithium sheet, the separator was a polypropylene film (PP film), the electrolyte solution was a 1 mol / L LiPF6 solution, and the solvent was a mixed solution of EC and 10% FEC in a volume ratio of 1:1.

[0104] Figure 2 The cyclic voltammetry curve of the secondary lithium battery prepared in Example 1 at a sweep rate of 0.05 mV is shown in FIG. Figure 2 It can be seen that the lithiation peaks are at 0.01V, 0.19V and 0.34V, 0.52V, respectively. No other peaks appear during the scanning process, which proves that the binder cross-linked by the titanate coupling agent is stable within the operating voltage of the silicon negative electrode battery, and the overall peak shape tends to be stable after the fourth cycle, and the reversibility of the electrode is good.

[0105] Figure 3 The AC impedance spectrum of the secondary lithium battery prepared in Example 1 before and after cycling is shown in FIG. Figure 3 It can be seen that after one cycle, a solid electrolyte film (SEI) is formed on the surface of the electrode, which is reflected in the new SEI capacitance and resistance in the fitting circuit.

[0106] Figure 4 The battery rate performance diagrams of the lithium batteries prepared in Example 1 and Comparative Example 1 at 0.42A / g, 0.82A / g, 2.1A / g, 4.2A / g, and 8.2A / g, respectively, are shown in FIG. Figure 4 It can be seen that the secondary lithium battery prepared in the present invention maintains a specific capacity of at least 1054 mAh / g at a current density of 8.2 A / g, proving that the battery has the ability to perform long cycles at a high current density.

[0107] Figure 5 The results of the lithium battery prepared in Example 1 and Comparative Examples 1 to 3 were compared at a current density of 2.1 A / g. Figure 5 It can be seen that the secondary lithium battery prepared by the present invention has a specific capacity of 2208.3 mAh / g after 100 cycles, the first-cycle coulombic efficiency is as high as 93.8%, and the specific capacity retention rate after 100 cycles is above 68%, which has better cycle performance than the control example.

[0108] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0109] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a water-based cross-linking adhesive, characterized in that: The following steps are involved: A natural polysaccharide solution, a linear long-chain binder solution and a titanate coupling agent are mixed and reacted to obtain a water-based cross-linking binder; The reaction temperature is 60-100°C and the reaction time is 4-10 hours; The characteristic functional groups of natural polysaccharides form a covalent and coordinated structure with titanate coupling agents, and then undergo esterification and amidation reactions with linear long-chain binders; The linear long-chain binder is polyacrylic acid or polyethylene maleic anhydride.

2. The preparation method according to claim 1, characterized in that The concentration of the natural polysaccharide solution is 0.01 to 0.05 g / mL, and the natural polysaccharide is any one of sodium carboxymethyl cellulose, sodium alginate, alginic acid, gum arabic and chitosan; The concentration of the linear long-chain binder solution is 0.01-0.05 g / mL, and the molecular weight of the linear long-chain binder is 200,000-1.25 million.

3. The preparation method according to claim 2, characterized in that The general structural formula of the titanate coupling agent is as follows: n (RO)-Ti-(OXR′Y) 4-n , Wherein, RO is a group generated by hydrolysis of a titanate coupling agent, X is a P or N atom, R′ is an aliphatic hydrocarbon, Y is a multifunctional functional group, and n≤4.

4. The preparation method according to claim 3, characterized in that The mass ratio of the natural polysaccharide to the linear long-chain binder is 1-9:1-9, and the mass of the titanate coupling agent is 1-15% of the total reactants.

5. A water-based cross-linking adhesive prepared by the preparation method according to any one of claims 1 to 4.

6. A method for preparing a negative electrode material for a lithium ion battery using the aqueous cross-linking binder according to claim 5, characterized in that: The following steps are involved: Silicon powder, conductive additives and water-based cross-linking binder are mixed to obtain electrode slurry, which is then coated on a current collector copper foil and dried to obtain a negative electrode material for a lithium-ion battery.

7. The method according to claim 6, characterized in that The particle size of the silicon powder is 50 to 150 nm; the conductive additive is one or more of acetylene black, Ketjen black, Super P, carbon nanotubes and graphene; The mass ratio of the silicon powder, the conductive additive and the water-based cross-linking binder is 50-80:10-30:10-30.

8. The method according to claim 7, characterized in that The mixing is carried out in a stirring manner for 6 to 12 hours; the drying temperature is 80 to 120° C. for 6 to 12 hours.

9. A lithium-ion battery negative electrode material prepared by the method according to any one of claims 6 to 8.

10. A secondary lithium battery, characterized in that: The invention comprises a lithium metal pole piece, an electrolyte, a diaphragm, a battery shell and the lithium-ion battery negative electrode material according to claim 9.

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