Negative electrode slurry, method for preparing the same, and sodium-ion battery

Abstract

The application discloses a negative electrode slurry, a preparation method thereof and a sodium ion battery. The negative electrode slurry comprises a thickening agent and a negative electrode material, the thickening agent comprises a high-molecular polymer with a structural unit shown in formula (I): wherein R1 is a branched structure with 1-10 C atoms and a terminal -COOH; R2 is a branched structure with 1-10 C atoms and a terminal acid group; R3 is a branched structure with 1-10 C atoms and a terminal -COOR4 ester group; R4 is a saturated alkane with 1-5 carbon atoms; 70%<=x<=95%, 0%<=y<=10%, 5%<=z<=30%. The negative electrode slurry has high viscosity stability and low preparation cost.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a negative electrode slurry and its preparation method, and a sodium-ion battery. Background Technology

[0002] The rapid development of new energy vehicles has increased the huge demand for rechargeable batteries. However, global lithium resources are scarce and unevenly distributed, leading to a supply shortage of upstream lithium ore and a year-on-year increase in the price of lithium salt raw materials. Sodium-ion batteries, on the other hand, not only have low raw material costs and abundant sources, but also outperform lithium-ion batteries in terms of fast-charging performance, high and low temperature performance, and safety. Furthermore, sodium-ion battery production can utilize the same production lines and equipment as lithium-ion batteries, resulting in low conversion costs. Therefore, research on sodium-ion batteries is gradually increasing.

[0003] Due to the small interlayer spacing of graphite, larger sodium ions require greater energy to embed into the graphite layers, making reversible insertion / extraction within the effective potential window impossible. Therefore, researchers believe that traditional graphite is unsuitable as the negative electrode for sodium-ion batteries. Consequently, hard carbon is currently the primary negative electrode material in sodium-ion batteries. However, the high energy density of hard carbon materials results in high alkalinity (pH = 10.0–11.0) due to its unique microstructure. During the sodium-ion battery negative electrode slurry homogenization process, the high alkalinity of hard carbon easily leads to chain scission of the commonly used thickener, sodium carboxymethyl cellulose (CMC), resulting in unstable viscosity of the negative electrode slurry system. Simultaneously, it easily causes demulsification of the solid binder (SBR), leading to sedimentation of the negative electrode slurry. This can easily cause slurry over-flow and spoilage, reducing the overall yield of the production line. Summary of the Invention

[0004] One of the objectives of this invention is to provide a negative electrode slurry and its preparation method, and a sodium-ion battery, which can improve the viscosity stability of the negative electrode slurry and avoid sedimentation.

[0005] To achieve the above objectives, the present invention provides a negative electrode slurry comprising a thickener, said thickener comprising a polymer with structural units shown in formula (I):

[0006]

[0007] Wherein, R1 is a branched structure with 1-10 C atoms ending in -COOH, R2 is a branched structure with 1-10 C atoms ending in an acidic group, R3 is a branched structure with 1-10 C atoms ending in an ester group (-COOR4), and R4 is a saturated alkane with 1-5 carbon atoms, and 70%≤x≤95%, 0%≤y≤10%, and 5%≤z≤30%.

[0008] The acidic group includes -SO3H.

[0009] The negative electrode slurry also includes a negative electrode material and a binder;

[0010] The thickener comprises 0.3-2.0 parts by weight, the negative electrode material comprises 20-50 parts by weight, and the binder comprises 0.5-3.5 parts by weight.

[0011] The negative electrode slurry further includes deionized water and a conductive agent, wherein the deionized water is 40-60 parts by weight and the conductive agent is 0.5-3.0 parts by weight.

[0012] The negative electrode material includes hard carbon;

[0013] And / or, the adhesive comprises any one or more of polyvinylidene fluoride, acrylonitrile copolymer, perfluorosulfonic acid resin, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polymethyl methacrylate;

[0014] And / or, the conductive agent includes any one or more of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, conductive graphite, and carbon fiber.

[0015] To achieve the above objectives, the present invention also provides a method for preparing a negative electrode slurry, comprising:

[0016] A thickener, a conductive agent, and a negative electrode material are mixed to obtain a premix; wherein the thickener comprises a polymer with structural units shown in formula (I):

[0017]

[0018] Wherein, R1 is a branched structure with 1-10 carbon atoms ending in -COOH, R2 is a branched structure with 1-10 carbon atoms ending in an acidic group, R3 is a branched structure with 1-10 carbon atoms ending in an ester group (-COOR4), and R4 is a saturated alkane with 1-5 carbon atoms, and 70% ≤ x ≤ 95%, 0% ≤ y ≤ 10%, and 5% ≤ z ≤ 30%.

[0019] The premix is ​​mixed with deionized water, and the thickener and the negative electrode material are kneaded together to obtain an intermediate mixture.

[0020] The intermediate mixture, the thickener, and the deionized water are mixed to obtain a slurry.

[0021] The slurry and binder are mixed to obtain the negative electrode slurry.

[0022] The thickener (0.3-2.0 parts by weight), the negative electrode material (20-50 parts by weight), and the binder (0.5-3.5 parts by weight) are mixed to obtain a premix.

[0023] And / or, add 23-35 parts by weight of the deionized water to the premix and mix to obtain the intermediate mixture;

[0024] And / or, add 0.1-1.0 parts by weight of the thickener and 17-25 parts by weight of the deionized water to the intermediate mixture and mix to obtain the slurry;

[0025] And / or, add 0.5-3.5 parts of binder to the slurry and mix to obtain the negative electrode slurry.

[0026] The thickener, the conductive agent, and the negative electrode material are mixed for 5-10 minutes at a revolution speed of 10-25 rpm and a rotation speed of 500-1000 rpm to obtain the premix.

[0027] And / or, the premix and the deionized water undergo a kneading reaction at a speed of 5-20 rpm revolution and 0 rpm rotation for 30-90 min to obtain the intermediate mixture;

[0028] And / or, the intermediate mixture, the thickener, and the deionized water are mixed at a speed of 15-30 rpm for 30-90 min and a rotation speed of 1200-2000 rpm to obtain the slurry;

[0029] And / or, the slurry and the binder are mixed at a speed of 15-30 rpm for revolution and 500-1500 rpm for 15-60 minutes to obtain the negative electrode slurry.

[0030] The thickener is obtained through the following steps:

[0031] Deionized water, surfactants, and monomer materials are mixed to obtain a pre-emulsion;

[0032] Remove oxygen from the pre-emulsion;

[0033] The initiator is added dropwise to the deoxygenated pre-emulsion to carry out a polymerization reaction, and the thickener particles are precipitated.

[0034] The thickener particles are processed to obtain the thickener.

[0035] The surfactant includes one or more of sodium dodecylbenzenesulfonate, allyl ether sulfonates, and polyether ammonium phosphate containing double bonds;

[0036] The monomer material includes one or more of acrylate, acrylic acid, and propylene sulfonic acid;

[0037] The initiator includes one or more of ammonium sulfate, sodium persulfate, dialkyl peroxide, and ester peroxide.

[0038] The mass ratio of the surfactant to the monomer material is 1:0.001-0.15.

[0039] The mass ratio of the surfactant to the initiator is 1:0.005-0.015;

[0040] The deionized water, the surfactant, and the monomer material are mixed at room temperature;

[0041] Oxygen in the pre-emulsion is removed at a temperature of 60-90°C in an inert gas atmosphere;

[0042] The pre-emulsion polymerization reaction takes 1-4 hours, during which the thickener particles are precipitated.

[0043] To achieve the above objectives, the present invention also provides a sodium-ion battery, comprising a positive electrode, a separator, and a negative electrode, wherein the positive electrode, the separator, and the negative electrode are stacked or nested in sequence.

[0044] The negative electrode sheet is made from the negative electrode slurry provided in the first aspect of this application.

[0045] The negative electrode slurry provided by this invention includes a thickener and a negative electrode material. In the polymer of the thickener, R1 is a branched structure with 1-10 C atoms ending in -COOH, R2 is a branched structure with 1-10 C atoms ending in acidic groups, R3 is a branched structure with 1-10 C atoms ending in -COOR4 ester groups, and R4 is a saturated alkane with 1-5 carbon atoms. Furthermore, 70%≤x≤95%, 0%≤y≤10%, and 5%≤z≤30%, that is, the main chain structure of the thickener is a stable organic hydrocarbon chain, which will not undergo chain-breaking reaction when exposed to high alkali, thereby ensuring the stability of the entire macromolecular chain and thus ensuring the stability of the dispersion system of the negative electrode slurry. Currently, the thickener used in the negative electrode slurry of sodium-ion batteries is carboxymethyl cellulose (CMC), which is an anionic water-soluble cellulose ether. Its main chain structure contains ether bonds -CHR4-O-CHR5-. These ether bonds are prone to chain scission under high alkalinity, which leads to the breakage of polymer macromolecular chains, resulting in a decrease in the viscosity of the negative electrode slurry and easy disruption of the stable state of the solid-liquid mixture.

[0046] Furthermore, the pH value of a 1 wt% aqueous solution of the thickener in the negative electrode slurry provided by the present invention is 1.0 to 3.0, while the pH value of a 1 wt% aqueous solution of carboxymethyl cellulose (CMC) containing -COOH acidic groups is 6.5 to 8.0. Therefore, the ester groups in the thickener provided by the present invention can enhance the compatibility with hard carbon negative electrodes, eliminating the need for additional acid neutralizers. It can neutralize alkaline negative electrode materials, keeping the alkalinity of the slurry in the negative electrode slurry preparation process at a normal level (pH = 7.5 to 9.0). This avoids demulsification and agglomeration of the binder due to high alkalinity, thereby preventing abnormalities in the processing caused by sedimentation of the negative electrode slurry.

[0047] Because no additional acid neutralizer is used, the production process of the negative electrode slurry can be simplified, and the elimination of the acid neutralizer reduces the production cost of the negative electrode slurry. At the same time, it increases the proportion of negative electrode material, thereby improving the energy density of sodium-ion batteries. Furthermore, a thickener with a certain degree of acidity can neutralize the alkalinity of the slurry to a normal level, thus increasing the range of binders that can be selected, further reducing the manufacturing cost of sodium-ion batteries and promoting their industrial application. Attached Figure Description

[0048] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0049] Figure 1 A flowchart illustrating a method for preparing a negative electrode slurry according to an embodiment of the present invention;

[0050] Figure 2 The results show the viscosity stability of the negative electrode slurries prepared according to Examples 1 to 4, Comparative Examples 1 and 2. Detailed Implementation

[0051] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can be practiced without requiring some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention.

[0052] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0053] In a first aspect, embodiments of the present invention provide a negative electrode slurry that can be used to prepare negative electrode sheets for sodium-ion batteries.

[0054] The negative electrode slurry includes a binder, a thickener, and a negative electrode material. The thickener includes a polymer with the structural unit shown in formula (I):

[0055]

[0056] Wherein, R1 is a branched structure with 1-10 C atoms ending in -COOH, R2 is a branched structure with 1-10 C atoms ending in an acidic group, R3 is a branched structure with 1-10 C atoms ending in an ester group (-COOR4), and R4 is a saturated alkane with 1-5 carbon atoms, and 70%≤x≤95%, 0%≤y≤10%, and 5%≤z≤30%.

[0057] Currently, carboxymethyl cellulose (CMC) is used as a thickener in the negative electrode slurry of sodium-ion batteries. CMC is an anionic, water-soluble cellulose ether, and its main chain structure contains ether bonds -CHR4-O-CHR5-. These ether bonds are prone to chain scission under high alkalinity, leading to the breakage of the polymer macromolecular chain, which in turn causes a decrease in the viscosity of the negative electrode slurry and easily disrupts the stability of the solid-liquid mixture. In contrast, the thickener provided in this application has a stable organic hydrocarbon chain main chain structure that does not undergo chain scission under high alkalinity, ensuring the stability of the entire macromolecular chain and thus ensuring the stability of the negative electrode slurry dispersion system.

[0058] Furthermore, the 1wt% aqueous solution of the thickener in the negative electrode slurry provided by this invention has a pH value of 1.0 to 3.0, while the commonly used thickener, due to the presence of -COOH acidic groups in the 1wt% aqueous solution of carboxymethyl cellulose (CMC), has a pH value of 6.5 to 8.0. Therefore, the ester groups in the thickener provided by this invention can enhance the compatibility with negative electrode materials (such as hard carbon), eliminating the need for additional acid neutralizers. It can neutralize alkaline negative electrode materials, ensuring that the alkalinity of the slurry during the preparation of the negative electrode slurry is at a normal level (pH = 7.5 to 9.0), preventing the binder from demulsifying and agglomerating due to high alkalinity, thereby avoiding abnormalities in the processing caused by sedimentation of the negative electrode slurry.

[0059] Because no additional acid neutralizer is used, the production process of the negative electrode slurry can be simplified, and the elimination of the acid neutralizer reduces the production cost of the negative electrode slurry. At the same time, it increases the proportion of negative electrode material, thereby improving the energy density of sodium-ion batteries. Furthermore, a thickener with a certain degree of acidity can neutralize the alkalinity of the slurry to a normal level, thus increasing the range of binders that can be selected, further reducing the manufacturing cost of sodium-ion batteries and promoting their industrial application.

[0060] In some embodiments, the acidic group in R2 includes -SO3H, or other acidic groups may be used.

[0061] In some embodiments, the negative electrode material includes hard carbon.

[0062] In some embodiments, the negative electrode slurry further includes a binder, i.e., the negative electrode slurry includes a thickener, a negative electrode material and a binder, wherein the thickener is 0.3-2.0 parts by weight, the negative electrode material is 20-50 parts by weight, and the binder is 0.5-3.5 parts by weight.

[0063] In some embodiments, the adhesive includes one or more of polyvinylidene fluoride, acrylonitrile copolymer, perfluorosulfonic acid resin, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polymethyl methacrylate.

[0064] In this embodiment, the thickener can be used to change the dispersion stability of the negative electrode slurry components, and the binder can be used to change the interaction forces between the negative electrode slurry components and between the negative electrode slurry components and the substrate, thereby improving the stability and uniformity of the negative electrode slurry coating and the electrode sheet in subsequent processes. Since the thickener provided by this invention has a certain degree of acidity, it can neutralize alkaline negative electrode materials, ensuring that the alkalinity of the quasi-slurry during the preparation of the negative electrode slurry is at a normal level (pH = 7.5–9.0). This prevents the binder from demulsifying and agglomerating due to high alkalinity, thus avoiding abnormalities in the processing caused by the sedimentation of the negative electrode slurry.

[0065] In some embodiments, the negative electrode slurry further includes deionized water and a conductive agent, wherein the deionized water is 40-60 parts by weight and the conductive agent is 0.5-3.0 parts by weight.

[0066] In some embodiments, the conductive agent includes one or more of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, conductive graphite, and carbon fiber.

[0067] The negative electrode slurry provided by this invention includes a thickener and a negative electrode material. In the polymer of the thickener, R1 is a branched structure with 1-10 C atoms ending in -COOH, R2 is a branched structure with 1-10 C atoms ending in acidic groups, R3 is a branched structure with 1-10 C atoms ending in -COOR4 ester groups, and R4 is a saturated alkane with 1-5 carbon atoms. Furthermore, 70%≤x≤95%, 0%≤y≤10%, and 5%≤z≤30%, that is, the main chain structure of the thickener is a stable organic hydrocarbon chain, which will not undergo chain-breaking reaction when exposed to high alkali, thereby ensuring the stability of the entire macromolecular chain and thus ensuring the stability of the dispersion system of the negative electrode slurry.

[0068] Furthermore, the pH value of a 1 wt% aqueous solution of the thickener in the negative electrode slurry provided by the present invention is 1.0 to 3.0, while the pH value of a 1 wt% aqueous solution of carboxymethyl cellulose containing -COOH acidic groups is 6.5 to 8.0. Therefore, the ester groups in the thickener provided by the present invention can enhance the compatibility with hard carbon negative electrodes. No additional acid neutralizing agent is needed, and it can undergo a neutralization reaction with alkaline negative electrode materials, so that the alkalinity of the quasi-slurry in the preparation of negative electrode slurry is at a normal level (pH = 7.5 to 9.0), avoiding demulsification and agglomeration of the binder due to high alkalinity, thereby avoiding abnormalities in the processing caused by sedimentation of the negative electrode slurry.

[0069] Furthermore, since no additional acid neutralizer is used, the production process of the negative electrode slurry can be simplified, and the elimination of the acid neutralizer reduces the production cost of the negative electrode slurry while increasing the proportion of negative electrode material, thereby improving the energy density of sodium-ion batteries. Moreover, thickeners with a certain degree of acidity can neutralize the alkalinity of the slurry to a normal level, thus increasing the range of binders that can be selected, further reducing the manufacturing cost of sodium-ion batteries and promoting their industrial application.

[0070] Secondly, embodiments of the present invention provide a method for preparing a negative electrode slurry. Figure 1 This is a flowchart illustrating a method for preparing a negative electrode slurry according to an embodiment of the present invention.

[0071] See Figure 1 The preparation methods of negative electrode slurry include:

[0072] S10, the thickener, conductive agent, and negative electrode material are mixed to obtain a premix; wherein the thickener comprises a polymer with the structural unit shown in formula (I):

[0073]

[0074] Wherein, R1 is a branched structure with 1-10 C atoms ending in -COOH, R2 is a branched structure with 1-10 C atoms ending in an acidic group, R3 is a branched structure with 1-10 C atoms ending in an ester group (-COOR4), and R4 is a saturated alkane with 1-5 carbon atoms, and 70%≤x≤95%, 0%≤y≤10%, and 5%≤z≤30%.

[0075] In some embodiments, 0.3-2.0 parts by weight of thickener, 20-50 parts by weight of negative electrode material, and 0.5-3.5 parts by weight of binder are mixed to obtain a premix.

[0076] In some embodiments, the thickener, conductive agent, and negative electrode material are mixed at a speed of 10-25 rpm for 5-10 minutes and a rotation speed of 500-1000 rpm to obtain a premix.

[0077] In some embodiments of the present invention, the thickener is obtained through the following steps:

[0078] S11, deionized water, surfactant and monomer material are mixed to obtain a pre-emulsion.

[0079] The surfactants include one or more of sodium dodecylbenzenesulfonate, allyl ether sulfonates, and polyether ammonium phosphate containing double bonds;

[0080] The monomer materials include one or more of acrylates, acrylic acid, and propylene sulfonic acid.

[0081] In some embodiments, deionized water, surfactant, and monomer material are mixed at room temperature, with the mass ratio of surfactant to monomer material being 1:0.001-0.15.

[0082] S12 removes oxygen from the pre-emulsion.

[0083] In some embodiments, oxygen in the pre-emulsion is removed at a temperature of 60-90°C in an inert gas (such as nitrogen) atmosphere.

[0084] S13, the initiator is dripped into the deoxygenated pre-emulsion to allow the surfactant and monomer materials to undergo a polymerization reaction, precipitating thickener particles.

[0085] The initiators include one or more of ammonium sulfate, sodium persulfate, dialkyl peroxide, and ester peroxide.

[0086] In some embodiments, the mass ratio of surfactant to initiator is 1:0.005-0.015, the pre-emulsion polymerization reaction is carried out for 1-4 hours, and thickener particles are precipitated.

[0087] S14, The thickener particles are processed to obtain a thickener.

[0088] In some embodiments, the thickener particles are subjected to pressure filtration, drying, and pulverization to obtain the finished thickener product. The specific methods of pressure filtration, drying, and pulverization are not limited in the embodiments of the present invention.

[0089] S20 involves mixing the premix and deionized water, and then kneading the thickener and negative electrode material to obtain an intermediate mixture.

[0090] In some embodiments, 23-35 parts by weight of deionized water are added to the premix and mixed to obtain an intermediate mixture.

[0091] In some embodiments, the premix and deionized water undergo a kneading reaction at a speed of 5-20 rpm and 0 rpm for 30-90 min to obtain an intermediate mixture.

[0092] It should be noted that in S20, while the thickener, conductive agent, and negative electrode material are dispersed and coated, the thickener and negative electrode material undergo a kneading reaction.

[0093] S30, mix the intermediate mixture, thickener and deionized water to obtain a slurry.

[0094] In some embodiments, 0.1-1.0 parts by weight of thickener and 17-25 parts by weight of deionized water are added to the intermediate mixture and mixed to obtain a slurry.

[0095] In some embodiments, the intermediate mixture, thickener, and deionized water are mixed at a speed of 15-30 rpm for 30-90 minutes and a rotation speed of 1200-2000 rpm to obtain a slurry.

[0096] Because the thickener can neutralize the alkaline negative electrode material, the alkalinity of the slurry in the preparation of the negative electrode slurry is kept at a normal level (pH = 7.5-9.0), which avoids the binder from demulsifying and agglomerating due to high alkalinity, thereby avoiding abnormalities in the processing caused by the sedimentation of the negative electrode slurry.

[0097] S40, mix the slurry and binder to obtain the negative electrode slurry.

[0098] In some embodiments, 0.5-3.5 parts of binder are added to the slurry and mixed to obtain a negative electrode slurry.

[0099] In some embodiments, the slurry and binder are mixed at a speed of 15-30 rpm for revolution and 500-1500 rpm for 15-60 minutes to obtain a negative electrode slurry.

[0100] In the negative electrode slurry, the binder exists stably and is uniformly dispersed, resulting in a negative electrode slurry with stable viscosity and that is not prone to sedimentation.

[0101] In some embodiments, after S40, the following may also be included:

[0102] The negative electrode slurry is coated, dried, and sheeted to obtain the negative electrode of a sodium-ion secondary battery.

[0103] The method for preparing the negative electrode slurry provided in this embodiment of the invention ensures the stability of the entire macromolecular chain by ensuring that the main chain structure of the thickener is a stable organic hydrocarbon chain. This chain will not undergo chain breaking reaction when exposed to high alkali, thus ensuring the stability of the negative electrode slurry dispersion system. Furthermore, the thickener's polymer structure includes R1 (1-10 C atoms with -COOH terminal branches), R2 (1-10 C atoms with acidic terminal branches), R3 (1-10 C atoms with -COOR4 ester terminal branches), and R4 (1-5 carbon atoms in a saturated alkali).

[0104] Furthermore, the pH value of a 1 wt% aqueous solution of the thickener in the negative electrode slurry provided by the present invention is 1.0 to 3.0, while the pH value of a 1 wt% aqueous solution of carboxymethyl cellulose (CMC) containing -COOH acidic groups is 6.5 to 8.0. Therefore, the ester groups in the thickener provided by the present invention can enhance the compatibility with hard carbon negative electrodes, eliminating the need for additional acid neutralizers. It can neutralize alkaline negative electrode materials, keeping the alkalinity of the slurry in the negative electrode slurry preparation process at a normal level (pH = 7.5 to 9.0). This avoids demulsification and agglomeration of the binder due to high alkalinity, thereby preventing abnormalities in the processing caused by sedimentation of the negative electrode slurry.

[0105] Furthermore, since no additional acid neutralizer is used, the production process of the negative electrode slurry can be simplified, and the elimination of the acid neutralizer reduces the production cost of the negative electrode slurry while increasing the proportion of negative electrode material, thereby improving the energy density of sodium-ion batteries. Moreover, thickeners with a certain degree of acidity can neutralize the alkalinity of the slurry to a normal level, thus increasing the range of binders that can be selected, further reducing the manufacturing cost of sodium-ion batteries and promoting their industrial application.

[0106] Thirdly, embodiments of the present invention provide a sodium-ion battery, comprising a positive electrode, a separator, and a negative electrode, wherein the positive electrode, the separator, and the negative electrode are stacked or nested in sequence; the material of the negative electrode is any of the negative electrode slurry provided in the embodiments of this application.

[0107] In some embodiments, the positive electrode active material used in the positive electrode sheet includes layered oxides; the negative electrode material used in the negative electrode sheet includes hard carbon.

[0108] In some embodiments, the positive electrode sheet can be prepared by the following steps: the positive electrode active material layered oxide, binder PVDF, and conductive agent SP are thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 92:4:4, and then coated onto aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0109] In some embodiments, the negative electrode sheet can be prepared by the following steps: coating, drying and sheeting the negative electrode slurry provided in the embodiments of this application to obtain the negative electrode sheet.

[0110] The negative and positive electrode sheets are then stacked (or wound), packaged, injected with electrolyte, activated, formed, volume-controlled, degassing and encapsulation, edge-folded, glued or dripped, and inspected for appearance to obtain a sodium-ion battery. This application does not limit the specific processes for preparing sodium-ion batteries from negative and positive electrode sheets.

[0111] To better understand the present invention, the preparation method of the negative electrode slurry provided by the present invention will be described in detail below with several embodiments.

[0112] Example 1

[0113] Step 100: Sodium dodecyl sulfonate and acrylate are added to deionized water at a weight ratio of 0.001:1 and mixed at room temperature to obtain a uniform pre-emulsion; oxygen in the pre-emulsion is removed at 60°C under a nitrogen atmosphere; then, an aqueous solution of ammonium persulfate is added dropwise at a mass ratio of 1:0.005 to allow the sodium dodecyl sulfonate and acrylate to undergo a polymerization reaction for 1 hour, precipitating thickener particles, which are then filtered, dried, and pulverized to obtain the finished thickener product.

[0114] Step 200: Add 0.2 parts by weight of thickener, 0.5 parts by weight of conductive carbon black and 20 parts by weight of hard carbon to a mixing tank and mix for 5 minutes. During mixing, the mixing tank revolves at 10 rpm and rotates at 500 rpm to obtain a premix.

[0115] Thickeners include those with the molecular formula -(CH2-CHCOOH). 0.95 -(CH2-CHCOOCH3) 0.05 - Organic high molecular polymers.

[0116] Step 300: Add 23 parts by weight of deionized water to the premix and mix for 30 minutes at a speed of 5 rpm revolution and 0 rpm rotation. This allows the thickener, conductive carbon black, and hard carbon to disperse and coat the mixture, while the acidic thickener and alkaline hard carbon can undergo a neutralization reaction to obtain an intermediate mixture.

[0117] Step 400: Add 0.1 parts by weight of thickener and 17 parts by weight of deionized water to the intermediate mixture and mix for 30 minutes at a speed of 15 rpm revolution and 1200 rpm rotation. The components are further dispersed evenly to form a fluid solid-liquid suspension system. At the same time, the acidic thickener and the alkaline hard carbon continue to neutralize and react to obtain a slurry.

[0118] Through steps 300 and 400, the thickener can maintain its thickening properties and also complete a neutralization reaction with the hard carbon, thus preparing a slurry with uniform component dispersion, stable solid and liquid phases, and normal alkalinity (pH = 7.5–9.0).

[0119] In step 500, 0.5 parts by weight of styrene-butadiene rubber are added to the slurry obtained in step 400, and the mixture is stirred for 15 minutes at a speed of 15 rpm revolution and 500 rpm rotation to ensure that the binder is stable and uniformly dispersed, thereby preparing a negative electrode slurry with stable viscosity and not easy to settle.

[0120] Step 600: The negative electrode slurry obtained in step 500 is coated, dried, and formed into a negative electrode sheet.

[0121] Step 700: The negative electrode sheet is stacked (or wound), packaged, injected with electrolyte, activated, formed, capacitated, degassed and packaged, folded, and glued or dripped to obtain a sodium-ion battery.

[0122] Example 2

[0123] Step 100: Sodium dodecyl sulfonate and acrylate are added to deionized water at a weight ratio of 0.005:1 and mixed at room temperature to obtain a uniform pre-emulsion; oxygen in the pre-emulsion is removed at 65°C under a nitrogen atmosphere; then, an aqueous solution of ammonium persulfate is added dropwise at a mass ratio of ammonium persulfate to acrylate of 0.008:1 to allow the sodium dodecyl sulfonate and acrylate to undergo a polymerization reaction for 1.5 hours, precipitating thickener particles, which are then filtered, dried, and pulverized to obtain the finished thickener product.

[0124] Step 200: Add 0.3 parts by weight of thickener, 1.0 parts by weight of conductive carbon black and 25 parts by weight of hard carbon to a mixing tank and mix for 6 minutes. During mixing, the mixing tank revolves at 12 rpm and rotates at 550 rpm to obtain a premix.

[0125] Thickeners include those with the molecular formula -(CH2-CHCOOH). 0.95 -(CH2-CHCOOCH3) 0.05 - Organic high molecular polymers.

[0126] Step 300: Add 25 parts by weight of deionized water to the premix and mix for 40 minutes at a speed of 8 rpm and 0 rpm. This allows the thickener, conductive carbon black, and hard carbon to disperse and coat the mixture, while the acidic thickener and alkaline hard carbon can undergo a neutralization reaction to obtain an intermediate mixture.

[0127] Step 400: Add 0.3 parts by weight of thickener and 18 parts by weight of deionized water to the intermediate mixture and mix for 40 minutes at a speed of 18 rpm revolution and 1300 rpm rotation. The components are further dispersed evenly to form a fluid solid-liquid suspension system. At the same time, the acidic thickener and the alkaline hard carbon continue to neutralize and react to obtain a slurry.

[0128] Through steps 300 and 400, the thickener can maintain its thickening properties and also complete a neutralization reaction with the hard carbon, thus preparing a slurry with uniform component dispersion, stable solid and liquid phases, and normal alkalinity (pH = 7.5–9.0).

[0129] In step 500, 1.0 part by weight of styrene-butadiene rubber is added to the slurry obtained in step 400, and the mixture is mixed for 20 minutes at a speed of 18 rpm revolution and 600 rpm rotation to ensure that the binder is stable and uniformly dispersed, thus preparing a negative electrode slurry with stable viscosity and not easy to settle.

[0130] Step 600: The negative electrode slurry obtained in step 500 is coated, dried, and formed into a negative electrode sheet.

[0131] Step 700: The negative electrode sheet is stacked (or wound), packaged, injected with electrolyte, activated, formed, capacitated, degassed and packaged, folded, and glued or dripped to obtain a sodium-ion battery.

[0132] Example 3

[0133] Step 100: Sodium dodecyl sulfonate and acrylate are added to deionized water at a weight ratio of 0.01:1 and mixed at room temperature to obtain a uniform pre-emulsion; oxygen in the pre-emulsion is removed at 70°C under a nitrogen atmosphere; then, an aqueous solution of ammonium persulfate is added dropwise, with a mass ratio of ammonium persulfate to acrylate of 0.01:1, to allow the sodium dodecyl sulfonate and acrylate to undergo a polymerization reaction for 2 hours, precipitating thickener particles, which are then filtered, dried, and pulverized to obtain the finished thickener product.

[0134] Step 200: Add 0.5 parts by weight of thickener, 1.5 parts by weight of conductive agent and 30 parts by weight of hard carbon to a mixing tank and mix for 7 minutes. During mixing, the mixing tank revolves at 15 rpm and rotates at 600 rpm to obtain a premix.

[0135] Thickeners include those with the molecular formula -(CH2-CHCOOH).0.80 -(CH2-CHCOOCH3) 0.20 - Organic high molecular polymers.

[0136] Step 300: Add 28 parts by weight of deionized water to the premix and mix for 50 minutes at a speed of 10 rpm revolution and 0 rpm rotation. This allows the thickener, conductive carbon black and hard carbon to disperse and coat the mixture, while the acidic thickener and alkaline hard carbon can undergo a neutralization reaction to obtain an intermediate mixture.

[0137] Step 400: Add 0.5 parts by weight of thickener and 20 parts by weight of deionized water to the intermediate mixture and mix for 60 minutes at a speed of 20 rpm revolution and 1500 rpm rotation. The components are further dispersed evenly to form a fluid solid-liquid suspension system. At the same time, the acidic thickener and the alkaline hard carbon continue to neutralize and react to obtain a slurry.

[0138] Through steps 300 and 400, the thickener can maintain its thickening properties and also complete a neutralization reaction with the hard carbon, thus preparing a slurry with uniform component dispersion, stable solid and liquid phases, and normal alkalinity (pH = 7.5–9.0).

[0139] In step 500, 1.5 parts by weight of styrene-butadiene rubber are added to the slurry obtained in step 400, and the mixture is stirred for 30 minutes at a speed of 20 rpm revolution and 800 rpm rotation to ensure that the binder is stable and uniformly dispersed, thus preparing a negative electrode slurry with stable viscosity and not easy to settle.

[0140] Step 600: The negative electrode slurry obtained in step 500 is coated, dried, and formed into a negative electrode sheet.

[0141] Step 700: The negative electrode sheet is stacked (or wound), packaged, injected with electrolyte, activated, formed, capacitated, degassed and packaged, folded, and glued or dripped to obtain a sodium-ion battery.

[0142] Example 4

[0143] Step 100: Sodium dodecyl sulfonate and acrylate are added to deionized water at a weight ratio of 0.1:1 and mixed at room temperature to obtain a uniform pre-emulsion; oxygen in the pre-emulsion is removed at 80°C under a nitrogen atmosphere; then, an aqueous solution of ammonium persulfate is added dropwise, with a mass ratio of ammonium persulfate to acrylate of 0.012:1, to allow sodium dodecyl sulfonate and acrylate to undergo a polymerization reaction for 3 hours, precipitating thickener particles, which are then filtered, dried, and pulverized to obtain the finished thickener product.

[0144] Step 200: Add 0.8 parts by weight of thickener, 2.0 parts by weight of conductive carbon black and 40 parts by weight of hard carbon to a mixing tank and mix for 8 minutes. During mixing, the mixing tank revolves at 18 rpm and rotates at 700 rpm to obtain a premix.

[0145] The thickener contains components with the structural unit -(CH2-CHCOOH) in its molecular formula. 0.80 -(CH2-CHCOOCH3) 0.20 - Organic high molecular polymers.

[0146] Step 300: Add 30 parts by weight of deionized water to the premix and mix for 70 minutes at a speed of 12 rpm and 0 rpm. This allows the thickener, conductive carbon black, and hard carbon to disperse and coat the mixture, while the acidic thickener and alkaline hard carbon can undergo a neutralization reaction to obtain an intermediate mixture.

[0147] Step 400: Add 0.7 parts by weight of thickener and 21 parts by weight of deionized water to the intermediate mixture and mix for 70 minutes at a speed of 23 rpm revolution and 1600 rpm rotation. The components are further dispersed evenly to form a fluid solid-liquid suspension system. At the same time, the acidic thickener and the alkaline hard carbon continue to neutralize and react to obtain a slurry.

[0148] Through steps 300 and 400, the thickener can maintain its thickening properties and also complete a neutralization reaction with the hard carbon, thus preparing a slurry with uniform component dispersion, stable solid and liquid phases, and normal alkalinity (pH = 7.5–9.0).

[0149] In step 500, 2.5 parts by weight of styrene-butadiene rubber are added to the slurry obtained in step 400, and the mixture is stirred for 40 minutes at a speed of 25 rpm revolution and 1000 rpm rotation to ensure that the binder is stable and uniformly dispersed, thereby preparing a negative electrode slurry with stable viscosity and not easy to settle.

[0150] Step 600: The negative electrode slurry obtained in step 500 is coated, dried, and formed into a negative electrode sheet.

[0151] Step 700: The negative electrode sheet is stacked (or wound), packaged, injected with electrolyte, activated, formed, capacitated, degassed and packaged, folded, and glued or dripped to obtain a sodium-ion battery.

[0152] Example 5

[0153] Step 100: Sodium dodecyl sulfonate and acrylate are added to deionized water at a weight ratio of 0.1:1 and mixed at room temperature to obtain a uniform pre-emulsion; oxygen in the pre-emulsion is removed at 85°C under a nitrogen atmosphere; then, an aqueous solution of ammonium persulfate is added dropwise, with a mass ratio of ammonium persulfate to acrylate of 0.013:1, to allow sodium dodecyl sulfonate and acrylate to undergo a polymerization reaction for 3.5 hours, precipitating thickener particles, which are then filtered, dried, and pulverized to obtain the finished thickener product.

[0154] Step 200: Add 0.9 parts by weight of thickener, 2.5 parts by weight of conductive carbon black and 45 parts by weight of hard carbon to a mixing tank and mix for 9 minutes. During mixing, the mixing tank revolves at 20 rpm and rotates at 800 rpm to obtain a premix.

[0155] Thickeners include those with the molecular formula -(CH2-CHCOOH). 0.70 -(CH2-CHSO3H) 0.10 -(CH2-CHCOOCH3) 0.20 - Organic high molecular polymers.

[0156] Step 300: Add 32 parts by weight of deionized water to the premix and mix for 80 minutes at a speed of 15 rpm revolution and 0 rpm rotation. This allows the thickener, conductive carbon black and hard carbon to disperse and coat the mixture, while the acidic thickener and alkaline hard carbon can undergo a neutralization reaction to obtain an intermediate mixture.

[0157] Step 400: Add 0.9 parts by weight of thickener and 23 parts by weight of deionized water to the intermediate mixture and mix for 80 minutes at a speed of 25 rpm revolution and 1800 rpm rotation. The components are further dispersed evenly to form a fluid solid-liquid suspension system. At the same time, the acidic thickener and the alkaline hard carbon continue to neutralize and react to obtain a slurry.

[0158] Through steps 300 and 400, the thickener can maintain its thickening properties and also complete a neutralization reaction with the hard carbon, thus preparing a slurry with uniform component dispersion, stable solid and liquid phases, and normal alkalinity (pH = 7.5–9.0).

[0159] In step 500, 3.0 parts by weight of styrene-butadiene rubber are added to the slurry obtained in step 400, and the mixture is stirred for 50 minutes at a speed of 28 rpm revolution and 1200 rpm rotation to ensure that the binder is stable and uniformly dispersed, thus preparing a negative electrode slurry with stable viscosity and not easy to settle.

[0160] Step 600: The negative electrode slurry obtained in step 500 is coated, dried, and formed into a negative electrode sheet.

[0161] Step 700: The negative electrode sheet is stacked (or wound), packaged, injected with electrolyte, activated, formed, capacitated, degassed and packaged, folded, and glued or dripped to obtain a sodium-ion battery.

[0162] Example 6

[0163] Step 100: Sodium dodecyl sulfonate and acrylate are added to deionized water at a weight ratio of 0.15:1 and mixed at room temperature to obtain a uniform pre-emulsion; oxygen in the pre-emulsion is removed at 90°C under a nitrogen atmosphere; then, an aqueous solution of ammonium persulfate is added dropwise at a mass ratio of ammonium persulfate to acrylate of 0.015:1 to allow the sodium dodecyl sulfonate and acrylate to undergo a polymerization reaction for 4 hours, precipitating thickener particles, which are then filtered, dried, and pulverized to obtain the finished thickener product.

[0164] Step 200: Add 1.0 part by weight of thickener, 3.0 parts by weight of conductive carbon black and 50 parts by weight of hard carbon to a mixing tank and mix for 10 minutes. During mixing, the mixing tank revolves at 25 rpm and rotates at 1000 rpm to obtain a premix.

[0165] Thickeners include those with the molecular formula -(CH2-CHCOOH). 0.70 -(CH2-CHSO3H) 0.10 -(CH2-CHCOOCH3) 0.20 - Organic high molecular polymers.

[0166] Step 300: Add 35 parts by weight of deionized water to the premix and mix for 90 minutes at a speed of 20 rpm revolution and 0 rpm rotation. This allows the thickener, conductive carbon black and hard carbon to disperse and coat the mixture, while the acidic thickener and alkaline hard carbon can undergo a neutralization reaction to obtain an intermediate mixture.

[0167] Step 400: Add 1.0 part by weight of thickener and 25 parts by weight of deionized water to the intermediate mixture and mix for 90 minutes at a speed of 30 rpm revolution and 2000 rpm rotation. The components are further dispersed evenly to form a fluid solid-liquid suspension system. At the same time, the acidic thickener and the alkaline hard carbon continue to neutralize and react to obtain a slurry.

[0168] Through steps 300 and 400, the thickener can maintain its thickening properties and also complete a neutralization reaction with the hard carbon, thus preparing a slurry with uniform component dispersion, stable solid and liquid phases, and normal alkalinity (pH = 7.5–9.0).

[0169] In step 500, 3.5 parts by weight of styrene-butadiene rubber are added to the slurry obtained in step 400, and the mixture is stirred for 60 minutes at a speed of 30 rpm revolution and 1500 rpm rotation to ensure that the binder is stable and uniformly dispersed, thus preparing a negative electrode slurry with stable viscosity and not easy to settle.

[0170] Step 600: The negative electrode slurry obtained in step 500 is coated, dried, and formed into a negative electrode sheet.

[0171] Step 700: The negative electrode sheet is stacked (or wound), packaged, injected with electrolyte, activated, formed, capacitated, degassed and packaged, folded, and glued or dripped to obtain a sodium-ion battery.

[0172] Comparative Example 1

[0173] Step 100: Add 1.0 part by weight of thickener, 3.0 parts by weight of conductive carbon black, and 50 parts by weight of hard carbon to a mixing tank and mix for 10 minutes. During mixing, the mixing tank revolves at 25 rpm and rotates at 1000 rpm to obtain a premix. The thickener used is a water-soluble cellulose ether—sodium carboxymethyl cellulose (CMC).

[0174] Step 200: Add 35 parts by weight of deionized water to the premix and mix for 90 minutes at a speed of 20 rpm revolution and 0 rpm rotation to disperse and coat the thickener, conductive carbon black and hard carbon to obtain an intermediate mixture.

[0175] Step 300: Add 1.0 part by weight of thickener and 25 parts by weight of deionized water to the intermediate mixture, and mix for 90 minutes at a speed of 30 rpm revolution and 2000 rpm rotation. The components are further dispersed evenly to form a fluid solid-liquid suspension system and obtain a slurry.

[0176] Step 400: Add 3.5 parts by weight of styrene-butadiene rubber to the slurry obtained in step 400, and mix for 60 minutes at a speed of 30 rpm revolution and 1500 rpm rotation to obtain the negative electrode slurry.

[0177] Comparative Example 2

[0178] Step 100: Add 1.0 part by weight of thickener, 3.0 parts by weight of conductive carbon black, and 50 parts by weight of hard carbon to a mixing tank and mix for 10 minutes. During mixing, the mixing tank revolves at 25 rpm and rotates at 1000 rpm to obtain a premix. The thickener has an organic hydrocarbon chain as its main chain—polyacrylic acid.

[0179] Step 200: Add 35 parts by weight of deionized water to the premix and mix for 90 minutes at a speed of 20 rpm revolution and 0 rpm rotation to obtain an intermediate mixture.

[0180] Step 300: Add 1.0 part by weight of thickener and 25 parts by weight of deionized water to the intermediate mixture, and mix for 90 minutes at a speed of 30 rpm revolution and 2000 rpm rotation to further disperse the components evenly and obtain a slurry.

[0181] Step 400: Add 3.5 parts by weight of styrene-butadiene rubber to the slurry obtained in step 400, and mix for 60 minutes at a speed of 30 rpm revolution and 1500 rpm rotation to obtain the negative electrode slurry.

[0182] The negative electrode slurries obtained in Examples 1 to 4, as well as the negative electrode slurries obtained in Comparative Examples 1 and 2, were selected for stability testing. The stability test results are shown in [reference needed]. Figure 2 .exist Figure 2 In the graph, the horizontal axis represents the length of time, in hours (h); the vertical axis represents the viscosity, in mPa·s.

[0183] It should be noted that the stability test results of Examples 5 and 6 are basically similar to those of Example 4. To more clearly represent the stability, only the stability results of Examples 1 to 4, Comparative Example 1 and Comparative Example 2 are shown.

[0184] Stability testing was conducted at room temperature, from Figure 2 It can be seen that the viscosity fluctuations of the negative electrode slurries obtained in Examples 1 to 4 are relatively small with the extension of time, indicating that these negative electrode slurries have good stability. The viscosity of Comparative Examples 1 and 2 decreases rapidly with the extension of time. Figure 2 The stability test results show that the negative electrode slurry provided in this embodiment of the invention has higher stability.

[0185] It should be clarified that the present invention is not limited to the specific configurations and processes described in the above embodiments and shown in the figures. For the sake of convenience and brevity, detailed descriptions of known methods are omitted here, and the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, which will not be repeated here.

[0186] The device embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separate. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any inventive effort.

[0187] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A negative electrode slurry, characterized in that, It includes a binder, a thickener, and a negative electrode material, wherein the thickener comprises a polymer with a structural unit shown in formula (I): （Ⅰ） Wherein, R1 is a branched structure with 1-10 C atoms ending in -COOH, R2 is a branched structure with 1-10 C atoms ending in acidic groups, R3 is a branched structure with 1-10 C atoms ending in -COOR4 ester groups, and R4 is a saturated alkane with 1-5 carbon atoms. Furthermore, 70%≤x≤95%, 0%<y≤10%, and 5%≤z≤30%, the main chain structure of the thickener is a stable organic hydrocarbon chain, the pH value of a 1wt% aqueous solution of the thickener is 1.0~3.0, the acidic groups include -SO3H, the negative electrode material includes hard carbon, and the thickener reacts with the hard carbon to neutralize and prevent the binder from demulsifying and agglomerating.

2. The negative electrode slurry according to claim 1, characterized in that, The thickener is 0.3-2.0 parts by weight, the negative electrode material is 20-50 parts by weight, and the binder is 0.5-3.5 parts by weight.

3. The negative electrode slurry according to claim 2, characterized in that, The negative electrode slurry also includes deionized water and a conductive agent, wherein the deionized water is 40-60 parts by weight and the conductive agent is 0.5-3.0 parts by weight.

4. The negative electrode slurry according to claim 3, characterized in that, The adhesive includes any one or more of polyvinylidene fluoride, acrylonitrile copolymer, perfluorosulfonic acid resin, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polymethyl methacrylate. And / or, the conductive agent includes any one or more of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, conductive graphite, and carbon fiber.

5. A method for preparing a negative electrode slurry, characterized in that, include: A thickener, a conductive agent, and a negative electrode material are mixed to obtain a premix; wherein the thickener comprises a polymer with structural units shown in formula (I): （Ⅰ） Wherein, R1 is a branched structure with 1-10 C atoms ending in -COOH, R2 is a branched structure with 1-10 C atoms ending in acidic groups, R3 is a branched structure with 1-10 C atoms ending in -COOR4 ester groups, R4 is a saturated alkane with 1-5 carbon atoms, and 70%≤x≤95%, 0%<y≤10%, 5%≤z≤30%, the main chain structure of the thickener is a stable organic hydrocarbon chain, the pH value of a 1wt% aqueous solution of the thickener is 1.0~3.0, the acidic groups include -SO3H, and the negative electrode material includes hard carbon; The premix is ​​mixed with deionized water, and the thickener and the negative electrode material are kneaded together to obtain an intermediate mixture. The intermediate mixture, the thickener, and the deionized water are mixed to obtain a slurry. The slurry and binder are mixed to obtain the negative electrode slurry.

6. The method for preparing the negative electrode slurry according to claim 5, characterized in that, Mix 0.3-1.0 parts by weight of the thickener, 20-50 parts by weight of the negative electrode material, and 0.5-3.0 parts by weight of the conductive agent to obtain the premix. And / or, add 23-35 parts by weight of the deionized water to the premix and mix to obtain the intermediate mixture; And / or, add 0.1-1.0 parts by weight of the thickener and 17-25 parts by weight of the deionized water to the intermediate mixture and mix to obtain the slurry; And / or, add 0.5-3.5 parts of binder to the slurry and mix to obtain the negative electrode slurry.

7. The method for preparing the negative electrode slurry according to claim 5, characterized in that, The thickener, the conductive agent, and the negative electrode material are mixed at a speed of 10-25 rpm for 5-10 minutes and a rotation speed of 500-1000 rpm to obtain the premix. And / or, the premix and the deionized water undergo a kneading reaction at a speed of 5-20 rpm revolution and 0 rpm rotation for 30-90 min to obtain the intermediate mixture; And / or, the intermediate mixture, the thickener, and the deionized water are mixed at a speed of 15-30 rpm for 30-90 min and a rotation speed of 1200-2000 rpm to obtain the slurry; And / or, the slurry and the binder are mixed at a speed of 15-30 rpm for revolution and 500-1500 rpm for 15-60 minutes to obtain the negative electrode slurry.

8. The method for preparing the negative electrode slurry according to claim 5, characterized in that, The thickener is obtained through the following steps: Deionized water, surfactants, and monomer materials are mixed to obtain a pre-emulsion; Remove oxygen from the pre-emulsion; The initiator is added dropwise to the deoxygenated pre-emulsion to carry out a polymerization reaction, and the thickener particles are precipitated. The thickener particles are processed to obtain the thickener.

9. The method for preparing the negative electrode slurry according to claim 8, characterized in that, The surfactant includes one or more of sodium dodecylbenzenesulfonate, allyl ether sulfonates, and polyether ammonium phosphate containing double bonds; The monomer material includes one or more of acrylate, acrylic acid, and propylene sulfonic acid; The initiator includes one or more of ammonium sulfate, sodium persulfate, dialkyl peroxide, and ester peroxide.

10. The method for preparing the negative electrode slurry according to claim 9, characterized in that, The deionized water, the surfactant, and the monomer material are mixed at room temperature, wherein the mass ratio of the surfactant to the monomer material is 1:0.001-0.

15. And / or, at a temperature of 60-90°C, remove oxygen from the pre-emulsion in an inert gas atmosphere; And / or, the mass ratio of the surfactant to the initiator is 1:0.005-0.015; And / or, the pre-emulsion polymerization reaction lasts for 1-4 hours, during which the thickener particles precipitate.

11. A sodium-ion battery, characterized in that, It includes a positive electrode, a separator, and a negative electrode, wherein the positive electrode, the separator, and the negative electrode are stacked or nested in sequence. The negative electrode sheet is made from the negative electrode slurry according to any one of claims 1-3.

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