Wide-temperature-range sodium-ion battery negative electrode carbon-coated current collector, conductive slurry, and preparation method and application of negative electrode carbon-coated current collector and conductive slurry

Abstract

The invention relates to the field of secondary batteries, and particularly discloses a wide-temperature-range sodium-ion battery negative electrode carbon-coated current collector, conductive slurry and a preparation method and application of the wide-temperature-range sodium-ion battery negative electrode carbon-coated current collector and the conductive slurry. The conductive paste is composed of a modified cross-linked nano conductive adhesive, a conductive agent, a dispersing agent and a solvent. Wherein the modified cross-linked nano conductive adhesive is obtained by mixing a water-based binder and an MXene material according to a mass ratio of (2-3): 1 and performing low-temperature cross-linking. By introducing the modified cross-linked nano conductive adhesive, the modified cross-linked nano conductive adhesive not only can be used as a complexing agent to form a complex with metal ions in the battery, change the properties of the surface of an electrode and prevent the surface of a negative pole piece from being oxidized, but also can be compounded with a conductive agent to form a multi-dimensional conductive network, increase conductive sites and enhance the wide temperature range and corrosion-resistant adaptability of the sodium-ion battery; and the overall performance of the battery is improved, so that the sodium ion battery can be applied in a wider range of scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of secondary batteries, more particularly, to a wide-temperature-range sodium-ion battery negative electrode carbon-coated current collector, conductive paste and preparation method and application thereof. BACKGROUND

[0002] As a new energy storage technology, sodium-ion batteries have become a hot research topic in the energy field in recent years due to their advantages of abundant resources, low cost and environmental friendliness. In the secondary battery system, sodium-ion batteries not only meet the demand for large-scale energy storage, but also have broad application prospects. As one of the key components of the battery, the performance of the negative electrode material directly affects the overall performance of the battery, and the current collector, as an important part of the negative electrode material, plays a crucial role in the conductivity, cycle life, corrosion resistance and wide-temperature-range adaptability of the battery. With the continuous expansion of the application range of sodium-ion batteries, especially the increasing demand for application in extreme temperature environments, the performance requirements for the current collector are becoming increasingly stringent.

[0003] Currently, in order to improve the conductivity and wide-temperature-range adaptability of the negative electrode material of sodium-ion batteries, various means are usually used for optimization in the industry. For example, a conductive coating is coated on the surface of the current collector to enhance the conductivity, common methods include using carbon materials, metal oxides or conductive polymer materials for coating; by adding conductive agents such as carbon black, graphene, etc. to build a conductive network; or using a water-based binder to mix with conductive materials to prepare a paste, which is then coated on the surface of the current collector. In addition, there are also methods to improve the corrosion resistance of the current collector through chemical modification or physical deposition. These means improve the conductivity and stability of the current collector to some extent.

[0004] However, the conductive coating materials commonly used in the prior art can improve the conductivity to some extent, but there are still obvious deficiencies in corrosion resistance and wide-temperature-range adaptability. Especially under extreme temperature conditions, the performance of the coating material tends to decay, which manifests as a decrease in conductivity, a decrease in interfacial adhesion, and a decrease in corrosion resistance, etc., thereby seriously affecting the overall performance and service life of the battery. The existence of these problems limits the application of sodium-ion batteries in a wider range of scenarios, and there is an urgent need to develop new conductive coating materials to solve the above-mentioned defects. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a wide-temperature-range sodium-ion battery negative electrode carbon-coated current collector, conductive paste and preparation method and application thereof.

[0006] The technical scheme adopted by the present application is as follows: In a first aspect, the present application provides a conductive paste for a wide-temperature-range sodium-ion battery current collector, the conductive paste having a solid content of 10-20 wt%, and a viscosity of ≤150 mPa·s; The conductive paste is composed of the following components by weight percentage: modified cross-linked nano-conductive glue 60%-70%, conductive agent 5%-10%, dispersant 5%-20%, and the balance being solvent. The modified cross-linked nano-conductive glue is obtained by mixing the aqueous binder and the MXene material at a mass ratio of 2-3:1, and stirring at a low speed for 5-8 hours at a temperature of 8-25℃.

[0007] By adopting the above technical solution, the modified cross-linked nano-conductive glue, the conductive agent, and the dispersant synergistically form a stable conductive network structure. The MXene material in the modified cross-linked nano-conductive glue has excellent conductivity and chemical stability, which can significantly enhance the corrosion resistance of the coating. At the same time, the low-temperature cross-linking process of the aqueous binder and the MXene material optimizes the microstructure of the coating, so that it maintains good adhesion and conductivity in a wide temperature range. In addition, the reasonable proportion of each component effectively reduces the interfacial resistance, further improving the adaptability of the coating under extreme temperature conditions, thereby greatly improving the overall performance of the sodium-ion battery negative material.

[0008] Further, the aqueous binder is sodium alginate, and the aqueous solution of the sodium alginate has a viscosity of less than 1500 mPa·s at room temperature and a pH of 3-8.

[0009] By adopting the above technical solution, the aqueous binder in the modified cross-linked nano-conductive glue is selected as sodium alginate, and the aqueous solution of the sodium alginate has a relatively low viscosity at room temperature and a moderate pH value. This makes the conductive paste have good dispersibility and stability during preparation, thereby facilitating the improvement of the uniformity of the conductive coating. At the same time, the appropriate pH range also helps to be compatible with other materials, avoiding adverse effects on performance caused by chemical reactions, and ultimately improving the overall performance of the conductive coating.

[0010] Further, the MXene material is Ti3C2T x , and the flake diameter of the Ti3C2T x is 2-6 um, and the microhardness is 60HV-70HV.

[0011] By adopting the above technical solution, the MXene material is selected as Ti3C2T x , which can significantly improve the conductivity and wide-temperature-range adaptability of the conductive paste. It mainly enhances the stability of the conductive network, reduces the interfacial resistance, and improves the adhesion with the substrate, thereby improving the overall performance of the sodium-ion battery negative material.

[0012] Further, the preparation method of the MXene material comprises: adding NaF with a proportion of 5-15wt% in hydrochloric acid solution, and after complete dissolution, obtaining solution I; slowly adding Ti3AlC2 with a proportion of 3-10wt% into solution I, and stirring at 25-40℃ for 12-18h to obtain solution II; ultrasonicating solution II in an argon environment and ice bath for 10-20min to obtain a suspension, and obtaining the MXene material after centrifugal separation.

[0013] By adopting the above technical scheme, Ti3C2T x material with high conductivity and wide temperature range adaptability is prepared by selective etching and peeling of Ti3AlC2. In this method, NaF with a specific concentration is used in combination with hydrochloric acid solution to ensure the selective etching effect of Ti3AlC2, thereby improving the purity and performance stability of the material. Ultrasonicating in an argon environment and ice bath further promotes the peeling of the layered structure to obtain uniformly dispersed MXene material. The finally obtained MXene material can significantly improve the conductivity and corrosion resistance of the conductive coating, and enhance the adaptability of the sodium ion battery negative electrode current collector in a wide temperature range environment.

[0014] Further, the dispersant comprises any one or a combination of at least two of carboxymethyl cellulose and its lithium salt or sodium salt, polyvinylpyrrolidone, polyalkylene oxide unsaturated monomer, DIS-730A, isopropyl alcohol and SDS-720; Preferably, the dispersant is polyvinylpyrrolidone.

[0015] Further, the conductive agent comprises any one of conductive carbon black, acetylene black, conductive graphite, graphene, carbon fiber, carbon nanotube; Preferably, the conductive agent is carbon black SP with a particle size D50≤20um; In a second aspect, the application provides a preparation method of the above conductive paste, which comprises: After mixing and dispersing the dispersant with the solvent, the conductive agent is added and dispersed to obtain a conductive liquid; Mixing the modified cross-linked nano conductive adhesive with water to obtain a modified cross-linked nano conductive adhesive liquid; Slowly adding the modified cross-linked nano conductive adhesive liquid into the conductive liquid, and after sanding treatment, a dispersion mixed liquid is obtained; the dispersion mixed liquid is treated by vacuumizing and demagnetizing to obtain the conductive paste.

[0016] By adopting the technical scheme, the preparation method can ensure the uniformity and stability of the conductive paste. Specifically, the dispersant is mixed with the solvent in advance and then the conductive agent is added, which effectively prevents the agglomeration of the conductive agent and forms a uniform conductive liquid; the modified cross-linked nano conductive glue is mixed with water and then gradually added into the conductive liquid, and the particle distribution is further refined through the sanding treatment to enhance the continuity of the conductive network; finally, through vacuum extraction and magnetic field removal, bubbles and impurities are removed, which significantly improves the overall performance of the conductive paste, thereby providing a more reliable conductive coating material for the carbon-coated current collector of the wide-temperature-range sodium ion battery negative electrode.

[0017] Further, in the process of preparing the dispersion mixed liquid, the sanding treatment is recycled for 3-6 times of grinding, the temperature is 15-25℃, and the time is 30-60min.

[0018] In a third aspect, the application provides a carbon-coated current collector for a wide-temperature-range sodium ion battery negative electrode, which comprises a foil body and a conductive coating arranged on the surface of the foil; the conductive coating is obtained by coating the conductive paste on the surface of the foil body and drying.

[0019] Further, the thickness of the foil body is 7-20μm, and the coating thickness of the conductive paste is 0.5-1μm.

[0020] In a fourth aspect, the application provides a sodium ion battery negative electrode sheet, which uses the carbon-coated current collector for a wide-temperature-range sodium ion battery negative electrode.

[0021] Further, it further comprises a negative electrode slurry, which comprises, by weight fraction: 92-96wt% of negative electrode active material, 1-3wt% of conductive agent, 0.3-0.6wt% of porous medium, 0.05-0.5wt% of dispersant, 3-7wt% of modified cross-linked nano conductive glue, and the balance is solvent.

[0022] Further, the porous medium is porous anatase titanium dioxide or porous aluminum oxide, preferably porous aluminum oxide, with a particle size D50≤6μm. The porous structure of the medium itself is easy to form a stable large surface, which can form a stable adsorption of sodium ions and achieve excellent results.

[0023] Further, the negative electrode active material is one or more of hard carbon, soft carbon, and silicon-carbon composite, preferably the negative electrode active material is hard carbon.

[0024] Further, the conductive agent includes any one of conductive carbon black, acetylene black, conductive graphite, graphene, carbon fiber, and carbon nanotube. Further, the dispersant includes any one of carboxymethyl cellulose and lithium salt or sodium salt thereof, polyvinylpyrrolidone, polyalkylene oxide unsaturated monomer, DIS-730A, isopropyl alcohol solution, or SDS-720 or a combination of at least two of them; To sum up, the present application has the following beneficial effects: 1. By introducing modified cross-linked nano-conductive glue, not only can it form a complex with metal ions in the battery as a complexing agent, change the properties of the electrode surface, prevent the surface of the negative electrode sheet from oxidizing, but also can form a multi-dimensional conductive network with the conductive agent, increase the conductive sites, enhance the wide temperature range and corrosion resistance of the sodium ion battery, and improve the overall performance of the battery.

[0025] 2. The modified cross-linked nano-conductive glue and the conductive agent synergistically build an efficient conductive network, reduce the interface resistance, improve the conductive performance, and at the same time enhance the adhesion between the coating and the substrate, ensuring that the excellent conductive effect can still be maintained under extreme temperature conditions.

[0026] 3. The formulation optimization and preparation process design of the conductive slurry ensure that the slurry has moderate solid content and viscosity, and forms a uniform and dense conductive coating after coating, further improving the adaptability of the current collector in a wide temperature range environment, meeting the needs of sodium ion batteries in diversified application scenarios.

[0027] 4. In the preferred scheme of the present application, during the preparation process of the negative electrode slurry in the negative electrode sheet, by optimizing the material formula and process parameters, a non-uniform porous system is formed in the slurry, effectively solving the agglomeration problem of carbon materials, improving the uniformity and stability of the negative electrode materials. And by introducing a porous medium into the traditional hard carbon negative electrode system, the hard carbon material is dispersed around the porous medium, increasing the channel for hard carbon to contact with sodium ions, and improving the rate performance of the hard carbon negative electrode in the sodium ion battery. DETAILED DESCRIPTION

[0028] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustration of the present application, and should not be regarded as limiting the scope of the present application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer, and the reagents or instruments not mentioned by the manufacturer are all conventional products that can be purchased on the market.

[0029] The specific embodiments of the present application will be described in detail below. It should be understood that the specific embodiments described herein are only for illustration and explanation of the present application, and are not intended to limit the present application.

[0030] Preparation example of modified cross-linked nano-conductive glue Preparation example 1 The preparation example provides a modified cross-linked nano conductive glue, and a preparation method thereof comprises the following steps: 1. Preparation of MXene material: A mixed solution is prepared by using a certain amount of deionized water and 15wt% of 12M HCl, 10wt% of NaF is added to the mixed hydrochloric acid solution, and after complete dissolution, solution I is obtained; 7wt% of Ti3AlC2 is slowly added to solution I, and stirred at 30°C for 15h to obtain solution II; The above solution II is ultrasonically treated in an argon environment and an ice bath for 15min to obtain a suspension, and then separated by centrifugation at a speed of 3000rpm for 7min to obtain Ti3C2T x material, Ti3C2T x The flake diameter of which is about 4um, and the microhardness is 68HV.

[0031] (2) Preparation of modified cross-linked nano conductive glue: Sodium alginate SA with a molecular weight of less than 200000 is used as an aqueous binder to prepare a sodium alginate aqueous solution, the viscosity of which at room temperature is 1400mPa·s, and the pH is 3-8; The MXene material prepared in step (1) is added to the sodium alginate aqueous solution, and the mass ratio of the MXene material to the sodium alginate is 30:70, and after uniform mixing, the cross-linking reaction is carried out in a low-temperature environment to obtain the modified cross-linked nano conductive glue.

[0032] Preparation Example 2 The difference between the present preparation example and Preparation Example 1 is that in step (2), the mass ratio of the MXene material to the sodium alginate is 30:90.

[0033] Preparation Example 3 The difference between the present preparation example and Preparation Example 1 is that in step (2), the mass ratio of the MXene material to the sodium alginate is 30:60.

[0034] Preparation Example 4 The difference between the present preparation example and Preparation Example 1 is that in step (1), the proportion of Ti3AlC2 is 3wt%.

[0035] Preparation Example 5 The difference between the present preparation example and Preparation Example 1 is that in step (1), the proportion of Ti3AlC2 is 10wt%.

[0036] Preparation Example 6 The difference between the present preparation example and Preparation Example 1 is that the mass ratio of the MXene material to the sodium alginate is 50:50.

[0037] Preparation Example 7 The preparation example is different from preparation example 1 in that a commercially available Ti3AlC2 material is used as the MXene material. Embodiment

[0038] Embodiment 1 The embodiment provides a carbon-coated current collector for a wide-temperature-range sodium ion battery, and a preparation method thereof comprises the following steps: (1) preparing a conductive slurry: a. preparing raw materials in percentage by weight: 65% of modified cross-linked nano conductive adhesive (provided in preparation example 1), 7.5% of conductive agent (carbon black), 15% of dispersing agent (polyvinylpyrrolidone), and the rest is solvent; b. mixing and dispersing the dispersing agent with the solvent (water), adding the conductive agent, and stirring and dispersing by using a double-planetary stirrer (stirring speed is 20 rpm, dispersing speed is 1500 rpm, temperature is 20 DEG C, and time is 40 min) to obtain a conductive liquid; c. mixing the modified cross-linked nano conductive adhesive with water, and stirring and dispersing by using a double-planetary stirrer (stirring speed is 70 rpm, dispersing speed is 1500 rpm, temperature is 20 DEG C, and time is 45 min) to obtain a modified cross-linked nano conductive adhesive liquid; d. slowly adding the modified cross-linked nano conductive adhesive liquid into the conductive liquid to obtain a dispersion mixture; e. vacuumizing and removing the magnetic treatment of the dispersion mixture to obtain a conductive slurry.

[0039] (2) preparing a current collector The conductive slurry prepared in step (1) is coated on the surface of a foil material with a thickness of 12 μm by using a coating machine, the coating thickness is 0.8 μm, and the carbon-coated current collector is obtained after drying.

[0040] Embodiments 2-5 The difference between the embodiments and embodiment 1 is that the modified cross-linked nano conductive adhesive in the conductive slurry is different. Embodiment 2: the modified cross-linked nano conductive adhesive is provided in preparation example 2; Embodiment 3: the modified cross-linked nano conductive adhesive is provided in preparation example 3; Embodiment 4: the modified cross-linked nano conductive adhesive is provided in preparation example 4; Embodiment 5: the modified cross-linked nano conductive adhesive is provided in preparation example 5.

[0041] Embodiments 6-10 The difference between the embodiments and embodiment 1 is that the raw materials and their proportions in the conductive slurry are different, and the specific contents are shown in Table 1: Table 1. Note: the balance is solvent water.

[0042] Example 10 The difference between this example and Example 1 is that during the preparation of the conductive slurry, the modified cross-linked nano-conductive glue solution is slowly added to the conductive liquid, and after 3-6 cycles of grinding (temperature 20°C, time 40 min) the sanding treatment is obtained. The dispersion mixed liquid is obtained.

[0043] Comparative Example Comparative Example 1 The difference between this comparative example and Example 1 is that sodium alginate is directly used as a binder to replace the modified cross-linked nano-conductive glue. (The sodium alginate solution is consistent with Preparation Example 1) Comparative Example 2 The difference between this comparative example and Example 1 is that during the preparation of the conductive slurry, the modified cross-linked nano-conductive glue provided by Preparation Example 6 is used.

[0044] Comparative Example 3 The difference between this comparative example and Example 1 is that during the preparation of the conductive slurry, the modified cross-linked nano-conductive glue used is 80wt%.

[0045] Comparative Example 4 The difference between this comparative example and Example 1 is that during the preparation of the conductive slurry, the modified cross-linked nano-conductive glue provided by Preparation Example 7 is used.

[0046] Performance test The carbon-coated current collectors provided by the examples and comparative examples were subjected to peel strength test and corrosion resistance test: (1) Peel strength test: MTS electronic tensile testing machine was used to test the peel strength according to GB / T2792-2014 "Test method for peel strength of adhesive tape"; (2) Acid resistance test: a simulated electrolyte (NaPF6-containing carbonate solution) with pH = 1 was prepared, and the carbon-coated current collector was immersed in the above electrolyte at 25°C for 48 hours. The liquid absorption rate of the carbon-coated current collector was calculated according to the following formula: Liquid absorption rate = (m2-m1 / m1) x 100%; Wherein, the weight of the carbon-coated aluminum foil before soaking in the electrolyte is m1, and the weight of the composite current collector after soaking in the electrolyte is m2.

[0047] The test results are shown in Table 2: Table 2. Peeling force (N) Liquid absorption rate (%) Example 1 33.15 2.45 Example 2 36.27 2.34 Example 3 33.08 2.49 Example 4 32.81 2.51 Example 5 32.17 2.33 Example 6 32.04 2.87 Example 7 33.27 2.41 Example 8 31.45 2.74 Example 9 32.04 2.83 Example 10 31.78 2.76 Comparative Example 1 18.47 5.32 Comparative Example 2 26.78 4.23 Comparative Example 3 33.24 3.12 Comparative Example 4 29.45 4.67 As can be seen from Table 2, the carbon-coated current collector provided by the application examples 1-10 has high peeling force and low liquid absorption rate in strong acidic electrolyte, indicating that it has strong adhesion, which can ensure the long-term effectiveness and stability of the conductive layer; at the same time, it has acid resistance, can be applied to acidic electrolyte scenes, and can effectively prevent electrochemical corrosion.

[0048] As can be seen from examples 1-3 and comparative example 1, compared with directly using sodium alginate as the binder, the carbon-coated current collector using the modified cross-linked nano conductive adhesive not only improves the adhesion, but also enhances the acid resistance.

[0049] As can be seen from examples 1-3 and comparative example 2, in the process of preparing the modified cross-linked nano conductive adhesive, if the proportion of MXene material is too large, the adhesion and acid resistance of the current collector will be weakened to different degrees, which is mainly because the mutual influence between the functional groups on the surface of the MXene material, and the -OH groups contained therein release different degrees of H + .

[0050] As can be seen from examples 1, 6 and 7 and comparative example 3, when the proportion of the modified cross-linked nano conductive adhesive in the conductive slurry formulation exceeds 70%, although it has little effect on the adhesion of the current collector, it will reduce the acid resistance to a certain extent. This is mainly because a large amount of H+ is accumulated in the material cross-linking reaction, which locally reduces the pH of the system.

[0051] As can be seen from examples 1-3 and comparative example 4, compared with the commercially available Ti3C2T x material, the adhesion and acid resistance of the current collector are enhanced to different degrees when the Ti3C2T x material prepared by the specific method of the application is used to prepare the modified cross-linked nano conductive adhesive.

[0052] Application Example 1 The application example provides a negative electrode sheet, which comprises: 1. Prepare a negative electrode slurry: a. Prepare materials by weight fraction: hard carbon 93wt%, conductive carbon black 2wt%, porous medium is porous anatase titanium dioxide with particle size D50≤6μm 0.5wt%, dispersing agent is carboxymethyl cellulose sodium powder 0.2wt%, the modified cross-linked nano conductive adhesive (provided by preparation example 1) 3wt%, and the balance is solvent.

[0053] b. Prepare glue A: a certain amount of dispersing agent and solvent are placed in a double planetary stirrer, vacuum dispersion stirring for 2 hours, and standing for 8 hours to prepare glue A. Circulating cooling water is introduced during stirring to prevent the glue temperature from being too high; c. Preparation of glue liquid B: the conductive agent is added to glue liquid A, vacuum stirring for 0.8h; then the negative active material is added, vacuum stirring for 1.5h; then the porous medium is added, low-speed vacuum stirring for 1h, finally the modified cross-linked nano-conductive glue liquid is added, low-speed vacuum stirring for 1.5h; d. Vacuum degassing: the slurry obtained after dispersion is placed in an environment with a vacuum degree of -85 to -60 kPa for 40 min, filtered through a 100-200 mesh screen, to obtain a negative electrode slurry for sodium ion batteries.

[0054] 2. The above negative electrode slurry is coated on the negative electrode carbon-coated current collector provided in Example 1, with a coating thickness of 120 μm.

[0055] Application Comparative Example 1: The difference from Application Example 1 is that the negative electrode current collector provided in Application Comparative Example 1 is used. Application Comparative Example 2: The difference from Application Example 1 is that the negative electrode current collector provided in Application Comparative Example 2 is used. Application Comparative Example 3: The difference from Application Example 1 is that the negative electrode current collector provided in Application Comparative Example 3 is used. Application Comparative Example 4: The difference from Application Example 1 is that the negative electrode current collector provided in Application Comparative Example 4 is used. Application Comparative Example 5: The difference from Application Example 1 is that an equal amount of aqueous sodium alginate is directly used instead of the modified cross-linked nano-conductive glue in the preparation of the negative electrode slurry.

[0056] Application Comparative Example 6 The difference from Application Example 1 is that no porous medium (porous anatase titanium dioxide) is added to the negative electrode material.

[0057] Application Comparative Example 7 The difference from Application Example 1 is that the porous medium added to the negative electrode material is porous carbon with a particle size D50≤6 μm.

[0058] Application Comparative Example 8 The difference from Application Example 1 is that the proportion of the porous medium added to the negative electrode material is 0.8 wt%.

[0059] Performance detection test The negative electrode sheet provided in the application example is used to test the wide temperature range adaptability: The test method is as follows: The ST2253 digital four-probe tester is used to test the resistivity of the negative electrode sheet, with a test accuracy of ±0.1%.

[0060] The test results are shown in Table 3: Table 3. As can be seen from Table 3: It can be seen from the combination of application example 1 and comparative application examples 1-4 that the conductive performance and adhesion of the negative electrode current collector have a great influence on the wide-temperature-range adaptability of the negative electrode sheet. This is mainly because the negative electrode current collector in application example 1 of the present application adds a specific modified cross-linked nano-conductive adhesive solution or Ti3C2T x material (prepared by a special process), the conductive performance and adhesion of the negative electrode current collector are improved.

[0061] It can be seen from the combination of application example 1 and comparative application example 5 that adding a modified cross-linked nano-conductive adhesive solution to the negative electrode slurry during preparation can improve the adaptability of the negative electrode sheet in a wide-temperature-range environment compared to directly using sodium alginate as the binder, thereby ensuring the conductive effect under extreme temperature conditions.

[0062] It can be seen from the combination of application example 1 and comparative application examples 6-8 that adding a certain proportion and specification of porous media to the negative electrode slurry helps to improve the wide-temperature-range adaptability of the negative electrode sheet, which indicates that the porous media can effectively solve the agglomeration problem of carbon materials, improve the uniformity and stability of the negative electrode material, and improve the rate performance of the hard carbon negative electrode in sodium ion batteries.

[0063] The specific embodiments are merely an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and the modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A conductive paste for current collectors in wide-temperature-range sodium-ion batteries, characterized in that, The conductive paste comprises the following components by weight percentage. Composition: 60%-70% modified cross-linked nano-conductive adhesive, 5%-10% conductive agent, 5%-20% dispersant, and the balance is solvent; The modified cross-linked nano-conductive adhesive is obtained by mixing an aqueous binder with MXene material at a mass ratio of 2-3:1 and then cross-linking at a low temperature of 8-25℃.

2. The conductive paste for a wide-temperature-range sodium-ion battery current collector according to claim 1, characterized in that, The aqueous adhesive is sodium alginate, and the aqueous solution of sodium alginate has a viscosity of less than 1500 mPa·s at room temperature and a pH of 3-8.

3. The conductive paste for a wide-temperature-range sodium-ion battery current collector according to claim 1, characterized in that, The MXene material is Ti3C2T x The Ti3C2T x The sheet diameter is 2-6 μm, and the microhardness is 60 HV-70 HV.

4. The conductive paste for a wide-temperature-range sodium-ion battery current collector according to claim 3, characterized in that, The preparation method of the MXene material includes: Add 5-15 wt% NaF to the hydrochloric acid solution and let it dissolve completely to obtain solution I; 3-10 wt% Ti3AlC2 was slowly added to solution I and stirred at 25-40℃ for 12-18 h to obtain solution II; The solution II was sonicated in an argon atmosphere and an ice bath for 10-20 minutes to obtain a suspension, which was then centrifuged to obtain the MXene material.

5. The conductive paste for a wide-temperature-range sodium-ion battery current collector according to claim 1, characterized in that, The dispersant includes any one or a combination of at least two of carboxymethyl cellulose and its lithium or sodium salts, polyvinylpyrrolidone, polyoxyalkylene unsaturated monomers, DIS-730A, isopropanol, and SDS-720.

6. A method for preparing a conductive paste according to any one of claims 1-5, characterized in that, It includes: After the dispersant is mixed and dispersed with the solvent, the conductive agent is added and dispersed again to obtain a conductive liquid; The modified cross-linked nano-conductive adhesive is mixed with water to obtain a modified cross-linked nano-conductive adhesive solution. The modified cross-linked nano-conductive adhesive was slowly added to the conductive liquid, and after grinding, a dispersion mixture was obtained. The dispersed mixture is subjected to vacuuming and demagnetization to obtain the conductive slurry.

7. The method for preparing the conductive paste according to claim 6, characterized in that, During the preparation of the dispersion mixture, the grinding process involves 3-6 cycles of grinding in a grinding mill at a temperature of 15-25°C for 30-60 minutes.

8. A carbon-coated current collector for the negative electrode of a wide-temperature-range sodium-ion battery, characterized in that, The negative electrode carbon-coated current collector includes a foil body and a conductive coating disposed on the surface of the foil; the conductive coating is obtained by coating the conductive paste as described in any one of claims 1-5 onto the surface of the foil body and then drying it.

9. The wide-temperature-range sodium-ion battery negative electrode carbon-coated current collector according to claim 8, characterized in that, The thickness of the foil body is 7-20 μm, and the coating thickness of the conductive paste is 0.5-1 μm.

10. A sodium-ion battery negative electrode sheet, characterized in that, It employs the wide-temperature-range sodium-ion battery negative electrode carbon-coated current collector as described in claim 8 or 9.

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