Preparation method of sodium ion battery negative plate and sodium ion battery

Abstract

The embodiment of the invention provides a preparation method of a sodium-ion battery negative plate and a sodium-ion battery. The preparation method comprises the following steps: soaking a pretreated light aluminum foil in an acidic mixed aqueous solution of hydroxypropyl chitosan and a pyrrole monomer; adding an oxidizing agent into the acidic mixed aqueous solution to form a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating on the surface of the optical aluminum foil to obtain a negative electrode current collector; the method comprises the following steps: dissolving hard carbon, a conductive agent and a binder in a solvent according to a preset proportion to prepare slurry; and coating the slurry on the surface of the negative current collector, and baking and drying to obtain the negative plate. According to the method, the hydroxypropyl chitosan can be applied to the negative electrode binder so as to at least partially replace a traditional binder system; the technical scheme of'bonding-interface collaborative optimization 'is formed, the adhesion of hard carbon and the aluminum foil is improved, the internal resistance of an electrode plate is reduced, the structural stability of the electrode is improved, and the cycle life of the battery is prolonged.

Description

TECHNICAL FIELD

[0001] Embodiments of the present specification relate to the technical field of sodium ion battery, in particular to a preparation method of sodium ion battery negative electrode sheet and a sodium ion battery. BACKGROUND

[0002] Nowadays, energy shortage caused by a large number of chemical fuels has become a global focus; therefore, it is necessary to develop new energy to solve the energy and environmental crisis. Sodium ion batteries are widely studied due to long service life, high safety, low theoretical cost and abundant resources. The negative electrode of the sodium ion battery plays an important role in loading and releasing sodium ions, which directly affects the kinetic performance of the battery. At present, the negative electrode material mainly includes carbon-based materials, alloy materials, titanium-based materials, organic compounds and the like; among them, carbon-based materials have excellent comprehensive performance and high cost performance, and are the mainstream development direction. Carbon-based materials include graphite, graphene, amorphous carbon and the like. Hard carbon in amorphous carbon has attracted widespread attention due to its high sodium storage specific capacity, low swelling effect and cost.

[0003] At present, the preparation of hard carbon negative electrode of sodium ion battery mainly uses the traditional binder system of lithium ion battery, such as the composite system of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), and usually uses aluminum foil as the current collector. However, the CMC+SBR system relies on physical adsorption, and the binding force between hard carbon particles is weak. In the charging and discharging process, it is difficult to effectively inhibit the displacement between particles, which easily leads to the destruction of the electrode structure, causes the pulverization and shedding of active materials, and results in the short cycle life of the battery. At the same time, the molecular structure of CMC and SBR is dense, which hinders the conduction of sodium ions, resulting in poor rate performance (high current charging and discharging ability) of the electrode, and it is difficult to meet the demand of high-power energy storage.

[0004] Therefore, the present specification aims to provide a preparation method of sodium ion battery negative electrode sheet and a sodium ion battery. SUMMARY

[0005] In view of the above problems of the prior art, the purpose of the embodiments of the present specification is to provide a preparation method of sodium ion battery negative electrode sheet and a sodium ion battery to solve the problem of the adhesion of the binder on the negative electrode side of the sodium ion battery in the prior art.

[0006] In order to solve the above technical problems, the specific technical solutions of the embodiments of the present specification are as follows:

[0007] In a first aspect, the embodiments of the present specification provide a preparation method of sodium ion battery negative electrode sheet, which comprises the following steps:

[0008] The pretreated aluminum foil is immersed in an acidic mixed aqueous solution of hydroxypropyl chitosan and pyrrole monomer;

[0009] An oxidant is added to an acidic mixed aqueous solution to form a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating on the surface of the light aluminum foil through an in-situ oxidative polymerization reaction, thereby obtaining a negative electrode current collector;

[0010] Hard carbon, conductive agent, and binder are dissolved in a solvent in a predetermined ratio to form a slurry;

[0011] The slurry is coated onto the surface of the negative electrode current collector and baked dry to obtain a negative electrode sheet.

[0012] In a preferred embodiment, the mass concentration of the hydroxypropyl chitosan is 0.1-5%; the mass concentration of the pyrrole monomer is 0.01-1%.

[0013] The pretreatment of the aluminum foil includes at least degreasing and cleaning, rinsing with deionized water, and drying.

[0014] In a preferred embodiment, the acidic mixed aqueous solution is obtained by adding hydrochloric acid and / or acetic acid, and the pH value of the acidic mixed aqueous solution is 2-6.

[0015] In a preferred embodiment, the oxidant is at least one of ferric chloride, ammonium persulfate, or hydrogen peroxide;

[0016] The molar amount of the oxidant is 1-3 times the molar amount of the pyrrole monomer.

[0017] In a preferred embodiment, the reaction temperature of the in-situ oxidative polymerization reaction is 20-25°C, and the reaction time is 5-50 minutes.

[0018] In a preferred embodiment, the thickness of the hydroxypropyl chitosan / polypyrrole composite conductive polymer coating is 1-10 μm.

[0019] In a preferred embodiment, the conductive agent comprises one or a mixture of at least two of conductive carbon black, acetylene black, conductive graphite, Ketjen black, graphene, and carbon nanotubes.

[0020] The binder includes sodium carboxymethyl cellulose, styrene-butadiene rubber, and hydroxypropyl chitosan.

[0021] In a preferred embodiment, the preset ratio of the hard carbon fiber, conductive agent, and binder is 92-96%: 2-5%: 1-3%, and the sum of the preset ratios of the hard carbon fiber, conductive agent, and binder is 100%.

[0022] In a preferred embodiment, the amount of hydroxypropyl chitosan added is 0.5-1%;

[0023] The anode sheet has an areal density of 30 g / m³. 2 -100 g / m2 .

[0024] Secondly, embodiments of this specification provide a sodium-ion battery, comprising a sodium-ion positive electrode, an inorganic porous film, a sodium-ion electrolyte, and a negative electrode prepared by a method for preparing a sodium-ion battery negative electrode as described above.

[0025] Using the above technical solution, the sodium-ion battery negative electrode preparation method and sodium-ion battery provided in the embodiments of this specification use hydroxypropyl chitosan as part of the binder, which is used in combination with sodium carboxymethyl cellulose and styrene-butadiene rubber. This allows the abundant hydroxyl and amino functional groups of hydroxypropyl chitosan to form hydrogen bonds and intermolecular interactions with hard carbon particles, sodium carboxymethyl cellulose and styrene-butadiene rubber, replacing part of the traditional binder (such as part of CMC or SBR). This enhances the bonding strength between hard carbon particles while ensuring the flexibility of the electrode, and improves the structural stability of the electrode during charging and discharging. Furthermore, the hydroxypropyl chitosan / polypyrrole (HPCS / PPy) composite conductive polymer layer formed on the surface of the aluminum foil utilizes hydroxypropyl chitosan (HPCS) as a dispersant and stabilizer to promote the uniform dispersion of pyrrole monomers on the aluminum foil surface. The PPy layer generated through in-situ polymerization has excellent conductivity, which can significantly reduce the contact resistance at the interface between hard carbon and aluminum foil. Moreover, the synergistic effect between HPCS and PPy (such as hydrogen bonding and electrostatic interaction) can enhance the adhesion between the coating and the aluminum foil, making the hard carbon negative electrode slurry more uniformly distributed during the coating process. This solves the problem of active material detachment caused by insufficient adhesion and helps to further reduce the internal resistance of the electrode.

[0026] To make the above and other objects, features and advantages of the embodiments of this specification more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic flowchart of the steps for preparing a sodium-ion battery negative electrode sheet according to an embodiment of this specification is shown. Detailed Implementation

[0029] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this specification.

[0030] It should be noted that the terms "first," "second," etc., used in this specification, claims, and the foregoing drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0031] This specification provides an embodiment of a method for preparing a sodium-ion battery negative electrode sheet, such as... Figure 1 As shown, the following steps may be included:

[0032] S110: Pretreated aluminum foil is impregnated in an acidic mixed aqueous solution of hydroxypropyl chitosan and pyrrole monomer.

[0033] The hydroxypropyl chitosan has a mass concentration of 0.1-5%; the pyrrole monomer has a mass concentration of 0.01-1%; and the pretreatment of the aluminum foil includes at least degreasing, rinsing with deionized water, and drying. The acidic mixed aqueous solution is obtained by adding hydrochloric acid and / or acetic acid, and the pH value of the acidic mixed aqueous solution is 2-6.

[0034] The purpose of step S110 is to allow hydroxypropyl chitosan to be adsorbed onto the surface of the aluminum foil.

[0035] S120: An oxidant is added to an acidic mixed aqueous solution to form a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating on the surface of the light aluminum foil through an in-situ oxidative polymerization reaction, thereby obtaining a negative electrode current collector.

[0036] The oxidant is at least one of ferric chloride, ammonium persulfate, or hydrogen peroxide, and the molar amount of the oxidant is 1-3 times the molar amount of the pyrrole monomer.

[0037] The in-situ oxidative polymerization reaction is carried out at a temperature of 20-25°C for 5-50 minutes. The thickness of the hydroxypropyl chitosan / polypyrrole composite conductive polymer coating formed by the in-situ oxidative polymerization reaction is 1-10 μm.

[0038] S130: Dissolve hard carbon, conductive agent, and binder in a solvent according to a preset ratio to make a slurry.

[0039] The conductive agent includes one or a mixture of at least two of conductive carbon black, acetylene black, conductive graphite, Ketjen black, graphene, and carbon nanotubes; the binder includes sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and hydroxypropyl chitosan (HPCS), and the preset ratio of hard carbon, conductive agent, and binder is 92-96%: 2-5%: 1-3%, and the sum of the preset ratios of hard carbon, conductive agent, and binder is 100%.

[0040] S140: The slurry is coated on the surface of the negative electrode current collector and baked dry to obtain a negative electrode sheet.

[0041] The amount of hydroxypropyl chitosan added to the binder is 0.5-1%; the final negative electrode sheet density is 30 g / m³. 2 -100 g / m 2

[0042] This specification provides a method for preparing a sodium-ion battery negative electrode sheet, using hydroxypropyl chitosan (HPCS) as a partial binder in combination with sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). HPCS, with its abundant hydroxyl and amino functional groups, can form hydrogen bonds and intermolecular interactions with hard carbon particles, CMC, and SBR, replacing some traditional binders (such as some CMC or SBR). This enhances the bonding strength between hard carbon particles while maintaining electrode flexibility, improving the structural stability of the electrode during charge and discharge processes.

[0043] A hydroxypropyl chitosan / polypyrrole (HPCS / PPy) composite conductive polymer layer is formed on the surface of the aluminum foil. Hydroxypropyl chitosan (HPCS) acts as a dispersant and stabilizer, promoting the uniform dispersion of pyrrole monomers on the aluminum foil surface. The PPy layer generated by in-situ polymerization has excellent conductivity, which can significantly reduce the contact resistance at the interface between hard carbon and aluminum foil. At the same time, the synergistic effect of HPCS and PPy (such as hydrogen bonding and electrostatic interaction) can enhance the adhesion between the coating and the aluminum foil, making the hard carbon negative electrode slurry more uniformly distributed during the coating process, reducing the shedding of active material due to insufficient adhesion, and further reducing the internal resistance of the electrode.

[0044] In summary, by simultaneously applying HPCS to the negative electrode binder (partially replacing CMC / SBR) and aluminum foil surface treatment (constructing an HPCS / PPy composite layer), a technical solution of "bonding-interface synergistic optimization" is formed, which increases the adhesion between hard carbon and aluminum foil and further reduces the internal resistance of the electrode.

[0045] Based on this, the embodiments of this specification also provide a sodium-ion battery, including a sodium-ion positive electrode sheet, an inorganic porous film, a sodium-ion electrolyte, and a sodium-ion battery negative electrode sheet prepared as described above. The sodium-ion battery is prepared by processes such as rolling, die cutting, stacking, assembly, baking, electrolyte injection, standing, formation, and capacity testing.

[0046] The sodium-ion battery negative electrode preparation method and sodium-ion battery provided in the embodiments of this specification partially replace the traditional CMC / SBR binder system with hydroxypropyl chitosan (HPCS). HPCS's abundant hydroxyl / amino groups form a hydrogen bond network with hard carbon and SBR, enhancing the mechanical bonding and structural stability between electrode particles. Simultaneously, the HPCS / polypyrrole (PPy) composite conductive polymer coating significantly improves the adhesion between hard carbon and aluminum foil and reduces interfacial contact resistance through both chemical bonding and physical anchoring. This solves the core problems of insufficient mechanical strength and high interfacial resistance of existing binder systems. Furthermore, the bio-based properties and water solubility of HPCS are more in line with the trend of green manufacturing.

[0047] Example 1

[0048] The aluminum foil, which has been degreased, rinsed with deionized water and dried, is immersed in a mixed aqueous solution containing 0.1% hydroxypropyl chitosan and 0.01% pyrrole monomer by mass, so that the hydroxypropyl chitosan is adsorbed onto the surface of the aluminum foil. The pH of the mixed aqueous solution is 2, which is adjusted by adding hydrochloric acid or acetic acid.

[0049] Subsequently, an oxidant with a molar amount equal to that of the pyrrole monomer is added to the mixed aqueous solution. Through in-situ oxidative polymerization, the pyrrole monomer is polymerized on the surface of the aluminum foil adsorbed with hydroxypropyl chitosan, forming a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating, thereby obtaining the negative electrode current collector. The thickness of the hydroxypropyl chitosan / polypyrrole composite conductive polymer coating is 1 μm, the in-situ oxidative polymerization reaction temperature is 20°C, and the reaction time is 50 minutes; wherein the oxidant is ferric chloride.

[0050] Then, hard carbon, conductive agent, and binder are dissolved in a solvent in a ratio of 92%:5%:3% to prepare a slurry.

[0051] Finally, the slurry is coated onto the surface of the negative electrode current collector, and after baking and drying, a negative electrode sheet is obtained.

[0052] The conductive agent is conductive carbon black; the binder includes sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and hydroxypropyl chitosan (HPCS), with HPCS added at 0.5%, CMC at 1.2%, and SBR at 1.3%. The final prepared negative electrode sheet has an areal density of 30 g / m³. 2 .

[0053] The negative electrode sheet prepared by the above method, along with the sodium ion positive electrode sheet, inorganic porous film, and sodium ion electrolyte, are processed into a sodium ion battery through processes such as rolling, die cutting, stacking, assembly, baking, electrolyte injection, settling, formation, and capacity testing.

[0054] Example 2

[0055] The aluminum foil, which has been degreased, rinsed with deionized water and dried, is immersed in a mixed aqueous solution containing 5% hydroxypropyl chitosan and 1% pyrrole monomer by mass concentration, so that the hydroxypropyl chitosan is adsorbed onto the surface of the aluminum foil. The pH of the mixed aqueous solution is 6, which is adjusted by adding hydrochloric acid or acetic acid.

[0056] Subsequently, an oxidant with a molar amount three times that of the pyrrole monomer was added to the mixed aqueous solution. Through in-situ oxidative polymerization, the pyrrole monomer was polymerized on the surface of the aluminum foil adsorbed with hydroxypropyl chitosan, forming a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating, thus obtaining the negative electrode current collector. The thickness of the formed hydroxypropyl chitosan / polypyrrole composite conductive polymer coating was 10 μm, the in-situ oxidative polymerization reaction temperature was 25°C, and the reaction time was 60 minutes; wherein the oxidant was ammonium persulfate.

[0057] Then, the hard carbon, conductive agent, and binder are dissolved in a solvent in a ratio of 96%:2%:2% to form a slurry.

[0058] Finally, the slurry is coated onto the surface of the negative electrode current collector, and after baking and drying, a negative electrode sheet is obtained.

[0059] The conductive agent includes acetylene black; the binder includes sodium carboxymethyl cellulose (CMC) + styrene-butadiene rubber (SBR) + hydroxypropyl chitosan (HPCS), wherein the addition amount of HPCS is 1%, the addition amount of CMC is 0.5%, and the addition amount of SBR is 0.5%; the anode sheet density is 100 g / m³. 2 .

[0060] The negative electrode sheet prepared by the above method, along with the sodium ion positive electrode sheet, inorganic porous film, and sodium ion electrolyte, are processed into a sodium ion battery through processes such as rolling, die cutting, stacking, assembly, baking, electrolyte injection, settling, formation, and capacity testing.

[0061] Example 3

[0062] The aluminum foil, which has been degreased, rinsed with deionized water and dried, is immersed in a mixed aqueous solution containing 2.5% hydroxypropyl chitosan and 0.5% pyrrole monomer by mass, so that the hydroxypropyl chitosan is adsorbed onto the surface of the aluminum foil. The pH of the mixed aqueous solution is 4, which is adjusted by adding hydrochloric acid or acetic acid.

[0063] Subsequently, an oxidant with a molar amount twice that of the pyrrole monomer was added to the mixed aqueous solution. The pyrrole monomer was then polymerized on the surface of the aluminum foil adsorbed with hydroxypropyl chitosan through an in-situ oxidative polymerization reaction, forming a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating, thus obtaining the negative electrode current collector. The thickness of the formed hydroxypropyl chitosan / polypyrrole composite conductive polymer coating was 3 μm. The in-situ oxidative polymerization reaction was carried out at a temperature of 25°C for 60 minutes; the oxidant was hydrogen peroxide.

[0064] Subsequently, hard carbon, conductive agent, and binder are dissolved in a solvent in a ratio of 94%:3%:3% to prepare a slurry.

[0065] Finally, the slurry is coated onto the surface of the negative electrode current collector, and after baking and drying, a negative electrode sheet is obtained.

[0066] The conductive agent includes conductive graphite; the binder includes sodium carboxymethyl cellulose (CMC) + styrene-butadiene rubber (SBR) + hydroxypropyl chitosan (HPCS), with HPCS added at 0.7%, CMC at 1.3%, and SBR at 1%; the negative electrode sheet density is 70 g / m². 2 .

[0067] Sodium-ion batteries are prepared from the above-mentioned negative electrode sheet, sodium-ion positive electrode sheet, inorganic porous film and sodium-ion electrolyte through processes such as rolling, die cutting, stacking, assembly, baking, electrolyte injection, standing, formation and capacity testing.

[0068] Comparative Example

[0069] Hard carbon, conductive agent, and binder are dissolved in a solvent in a ratio of 96%:3%:1% to prepare a slurry.

[0070] The slurry is directly coated onto the surface of a smooth aluminum foil (i.e., the surface of the smooth aluminum foil does not have a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating), and after baking and drying, a negative electrode sheet is obtained.

[0071] The conductive agent is conductive carbon black; the binder is a traditional sodium carboxymethyl cellulose (CMC) styrene-butadiene rubber (SBR) system; the negative electrode sheet density is 50 g / m³. 2 .

[0072] Finally, the negative electrode sheet prepared by the above method, along with the sodium-ion positive electrode sheet, inorganic porous film, and sodium-ion electrolyte, are processed into a sodium-ion battery through processes such as rolling, die cutting, stacking, assembly, baking, electrolyte injection, settling, formation, and capacity testing.

[0073] The sodium-ion batteries prepared in Examples 1, 2, 3 and the comparative example were tested, and the performance parameters were compared as shown in Table 1 below.

[0074] Table 1 Comparison of performance parameters of sodium-ion batteries

[0075]

[0076] As can be seen from the table above, the negative electrode prepared using the method described in the embodiments of this specification has a significantly lower internal resistance than the negative electrode prepared using the traditional CMC+SBR binder system, and the internal resistance of the negative electrode is also significantly reduced. Consequently, the sodium-ion battery produced exhibits a certain reduction in AC internal resistance compared to traditional batteries, and a significant improvement in rate performance and cycle performance.

[0077] Therefore, by forming a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating on the surface of aluminum foil, and then coating the surface with a slurry made of hard carbon conductive agent and binder, it is possible to:

[0078] (1) Significantly improves electrode structure stability and extends battery cycle life: The abundant hydroxyl and amino groups in hydroxypropyl chitosan (HPCS) molecules form hydrogen bonds and intermolecular force networks with hard carbon particles, CMC and SBR, replacing some of the traditional binders, thereby more effectively suppressing the volume expansion of hard carbon during charging and discharging, and reducing particle displacement and shedding.

[0079] (2) Reduce the internal resistance of the electrode and improve the rate performance and energy efficiency of the battery: The HPCS / PPy composite conductive polymer layer has both high conductivity (PPy has a much better conductivity than the traditional aluminum foil surface) and strong adhesion (hydrogen bonding / electrostatic interaction between HPCS and aluminum foil and hard carbon), which reduces the contact resistance between hard carbon and aluminum foil.

[0080] (3) Enhance the adhesion between hard carbon and aluminum foil and reduce the shedding of active materials: The HPCS / PPy composite coating significantly enhances the bonding force between the coating and aluminum foil through a dual mechanism of chemical bonding (interaction between the amino group of HPCS and the pyrrole ring of PPy) and physical adsorption; at the same time, the hydrogen bonding between HPCS and hard carbon further enhances the anchoring effect of hard carbon particles on the coating.

[0081] (4) Improve electrode processing uniformity and increase yield: HPCS / PPy composite coating makes the aluminum foil surface more hydrophilic and has moderate roughness. The hard carbon negative electrode slurry has better fluidity and more uniform distribution during the coating process, reducing local defects (such as bubbles and thick edges) caused by slurry aggregation or uneven distribution.

[0082] (5) Significantly optimized environmental protection and economy: HPCS is derived from natural chitosan (such as shrimp shells, crab shells and other wastes), which is biodegradable and can replace part of CMC (which relies on petrochemical raw materials), in line with the trend of green manufacturing; PPy is generated on the surface of aluminum foil through in-situ polymerization, without the need to add additional adhesives, reducing the amount of materials used and process steps.

[0083] (6) Strong process compatibility and easy to scale up production: The water-soluble properties of HPCS allow it to be directly integrated into the existing aqueous homogenization process of sodium-ion battery negative electrode without changing equipment or significantly adjusting parameters; the preparation of HPCS / PPy composite coating only requires adding a coating step to the existing aluminum foil processing line, which has high compatibility.

[0084] It should be noted that the order of the embodiments provided in this specification is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, while specific embodiments have been described in this specification, other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired results. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous. The descriptions in this specification are merely several preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0085] This specification uses specific embodiments to illustrate the principles and implementation methods of this specification. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this specification. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this specification. Therefore, the content of this specification should not be construed as a limitation of this specification.

Claims

1. A method for preparing a sodium-ion battery negative electrode, characterized in that, Includes the following steps: Pretreated aluminum foil was impregnated in an acidic aqueous solution of hydroxypropyl chitosan and pyrrole monomer; An oxidant is added to an acidic mixed aqueous solution to form a hydroxypropyl chitosan / polypyrrole composite conductive polymer coating on the surface of the light aluminum foil through an in-situ oxidative polymerization reaction, thereby obtaining a negative electrode current collector; Hard carbon, conductive agent, and binder are dissolved in a solvent in a predetermined ratio to form a slurry; The slurry is coated onto the surface of the negative electrode current collector and baked dry to obtain a negative electrode sheet.

2. The method according to claim 1, characterized in that, The hydroxypropyl chitosan has a mass concentration of 0.1-5%; the pyrrole monomer has a mass concentration of 0.01-1%. The pretreatment of the aluminum foil includes at least degreasing and cleaning, rinsing with deionized water, and drying.

3. The method according to claim 2, characterized in that, The acidic mixed aqueous solution is obtained by adding hydrochloric acid and / or acetic acid, and the pH value of the acidic mixed aqueous solution is 2-6.

4. The method according to claim 1, characterized in that, The oxidant is at least one of ferric chloride, ammonium persulfate, or hydrogen peroxide; The molar amount of the oxidant is 1-3 times the molar amount of the pyrrole monomer.

5. The method according to claim 4, characterized in that, The in-situ oxidative polymerization reaction is carried out at a temperature of 20-25℃ for 5-50 minutes.

6. The method according to claim 5, characterized in that, The thickness of the hydroxypropyl chitosan / polypyrrole composite conductive polymer coating is 1-10 μm.

7. The method according to claim 1, characterized in that, The conductive agent includes one or a mixture of at least two of the following: conductive carbon black, acetylene black, conductive graphite, Ketjen black, graphene, and carbon nanotubes. The binder includes sodium carboxymethyl cellulose, styrene-butadiene rubber, and hydroxypropyl chitosan.

8. The method according to claim 7, characterized in that, The preset ratio of hard carbon, conductive agent, and binder is 92-96%: 2-5%: 1-3%, and the sum of the preset ratios of hard carbon, conductive agent, and binder is 100%.

9. The method according to claim 7, characterized in that, The amount of hydroxypropyl chitosan added is 0.5-1%; The anode sheet has an areal density of 30 g / m³. 2 -100 g / m 2 .

10. A sodium-ion battery, characterized in that, It includes sodium-ion positive electrode sheets, inorganic porous films, sodium-ion electrolytes, and negative electrode sheets prepared by the method for preparing sodium-ion battery negative electrode sheets as described in any one of claims 1 to 9.

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