A water-based hard carbon negative electrode slurry, a preparation method and application thereof

Abstract

The present application relates to a kind of water-based hard carbon negative electrode slurry and its preparation method and application, its composition includes the following components: hard carbon: 55~70 parts;20~30 parts sodium polyacrylate modified alkali lignin;Sodium carboxymethylcellulose: 1.5~5 parts;Water: fixed as 100 parts.With water as solvent, by sodium carboxymethylcellulose and sodium polyacrylate modified alkali lignin composition water-based slurry, change traditional organic solvent-based slurry, avoid the volatilization of organic matter in the preparation of slurry and coating process, production does not need additional removal of volatile organic matter.At the same time, the water-based slurry can also effectively improve the poor flowability problem of traditional slurry caused by hard carbon, with good uniformity when coating.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to an aqueous hard carbon anode slurry, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries are gaining increasing market attention due to their low raw material cost, abundant sources, and high safety. Hard carbon materials in sodium-ion batteries have excellent sodium storage performance, minimal volume expansion after sodium intercalation, good safety, and structural stability, and are often used as key materials for sodium-ion anodes. However, hard carbon materials also have significant drawbacks. They have poor flowability and coating uniformity when coated with slurry, which may cause electrode detachment, affecting battery performance and potentially leading to safety accidents.

[0003] In addition, during the preparation of electrode paste, organic systems are commonly used, and organic solvents such as N-methylpyrrolidone (NMP) are volatile. Especially in industrial production, absorption devices are usually required to remove the volatile organic compounds in order to meet environmental protection requirements. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide an aqueous hard carbon anode slurry, its preparation method, and its application, thereby improving the slurry system and simultaneously addressing the problems of poor slurry flowability and organic matter volatilization during the production process.

[0005] First aspect:

[0006] An aqueous hard carbon anode slurry, comprising the following components by mass parts: Hard carbon: 55-70 parts; Sodium polyacrylate modified alkali lignin, 20-30 parts; Sodium carboxymethyl cellulose: 1.5 to 5 parts; Water: fixed at 100 portions.

[0007] This invention uses water as a solvent and combines sodium carboxymethyl cellulose and sodium polyacrylate-modified alkali lignin to form an aqueous slurry, which changes the traditional organic solvent-based slurry. This avoids the volatilization of organic matter during slurry preparation and coating, eliminating the need for additional removal of volatile organic matter during production. Simultaneously, this aqueous slurry effectively improves the poor flowability of traditional slurries caused by hard carbon, resulting in better coating uniformity. Furthermore, both sodium carboxymethyl cellulose and sodium polyacrylate-modified alkali lignin contain sodium, which can serve as an additional sodium source during the first charge-discharge cycle, compensating for the low coulombic efficiency of hard carbon during the initial charge-discharge cycle.

[0008] As a preferred embodiment, the sodium polyacrylate-modified alkali lignin is obtained by graft copolymerization of sodium polyacrylate and alkali lignin.

[0009] As a preferred embodiment, the average molecular weight of the sodium carboxymethyl cellulose is 20,000 to 120,000. Controlling the molecular weight of sodium carboxymethyl cellulose can prevent hard carbon in the slurry from settling and causing stratification, while also preventing excessive viscosity from causing the slurry to lose its fluidity. Furthermore, although sodium carboxymethyl cellulose exhibits relatively weak water retention and binding strength at this molecular weight, sodium polyacrylate-modified alkali lignin has strong water retention and provides a certain degree of binding strength. Therefore, the synergistic effect of sodium carboxymethyl cellulose and sodium polyacrylate-modified alkali lignin achieves a balance between viscosity, binding strength, and water retention in the slurry.

[0010] As a preferred embodiment, the mass of the sodium hydroxymethyl cellulose is 8-12% of the mass of the sodium polyacrylate-modified alkali lignin.

[0011] As a preferred option, the slurry viscosity is 3000-6000 mPa·s at 25°C. This viscosity range is suitable for coating.

[0012] The second aspect: A method for preparing the aqueous hard carbon anode slurry as described in the first aspect includes the following steps: First, the sodium hydroxymethyl cellulose is mixed with 60 parts of water and stirred at 100-300 rpm for 1-10 minutes. Then, the stirring speed is adjusted to 60-120 rpm, and the sodium polyacrylate-modified alkali lignin is added. After the addition is complete, stirring is continued for 30-60 minutes. Finally, the hard carbon and 40 parts of water are added simultaneously, and the mixture is stirred at 250-500 rpm for 1-3 hours to obtain the aqueous hard carbon negative electrode slurry.

[0013] This invention first adds sodium carboxymethyl cellulose to water to act as a preliminary thickener, thereby improving the stability of the subsequent pulping process; then, sodium polyacrylate-modified alkali lignin is added to form a hydrogel-like substance, which on the one hand helps to retain water and prevents excessive evaporation of water during stirring, and on the other hand helps to uniformly disperse the hard carbon, thus preparing a more uniform slurry; finally, the remaining water and hard carbon are added at the same time to fully disperse the hard carbon and regulate the flowability of the slurry, which facilitates the subsequent coating process.

[0014] As a preferred embodiment, the method further includes the following steps: adding the sodium polyacrylate-modified alkali lignin in 1 to 3 portions, stirring for 5 to 20 minutes after each addition, and continuing to stir for 30 to 60 minutes after all the lignin has been added. Adding the sodium polyacrylate-modified alkali lignin in portions can avoid particle agglomeration caused by adding a large amount in a short time.

[0015] Third aspect: A method for preparing a sodium-ion battery anode material includes the following steps: The aqueous hard carbon anode slurry described in the first aspect is coated onto the current collector, and then the coated current collector is dried in an environment of 100~120℃ for 1~10h; then, in an oxygen-containing environment, the temperature is increased to 220~280℃ at a heating rate of 1~5℃ / min and held for 1~3h; finally, in an inert atmosphere, the temperature is increased to 450~600℃ at a heating rate of 0.5~2℃ / min and held for 0.5~6h to obtain the sodium-ion battery anode material. The current collector includes copper foil.

[0016] In preparing the sodium-ion battery anode material according to this invention, the temperature is first raised to 100-120°C to initially dry the moisture, avoiding violent evaporation of moisture during subsequent heating, which could cause the slurry surface to break. Then, the temperature is raised to 220-280°C, which on the one hand pre-oxidizes the sodium polyacrylate-modified alkali lignin, and on the other hand oxidizes and decomposes sodium hydroxymethyl cellulose. At this time, the sodium polyacrylate-modified alkali lignin acts as a binder, keeping the slurry stable and preventing collapse and deformation. Finally, the temperature is raised to 450-600°C to carbonize the sodium polyacrylate-modified alkali lignin, forming an integrated electrode with hard carbon.

[0017] During carbonization, sodium polyacrylate-modified alkali lignin acts as both a conductive agent and a binder, forming an integrated framework at the microscale. The hard carbon and alkali lignin are uniformly bonded, resulting in high mechanical strength and facilitating rapid electron transport, thus improving the high-rate performance of the battery.

[0018] In addition, if the carbonization temperature is too low, the sodium polyacrylate-modified alkali lignin will not be carbonized sufficiently and will not form an integrated framework, resulting in reduced conductivity. If the temperature is too high, graphitized carbon may be formed, which is not conducive to the insertion and extraction of sodium ions during charging and discharging.

[0019] As a preferred embodiment, the coating thickness of the aqueous hard carbon negative electrode slurry on the current collector is 20~100μm, and the coating speed is 1~40m / min.

[0020] Fourth aspect: A sodium-ion battery, comprising the sodium-ion battery negative electrode material described in the third aspect. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] An aqueous hard carbon anode slurry, comprising the following components by mass parts: Hard carbon: 55-70 parts; Sodium polyacrylate modified alkali lignin, 20-30 parts; Sodium carboxymethyl cellulose: 1.5 to 5 parts; Water: fixed at 100 portions.

[0025] Sodium polyacrylate-modified alkali lignin is obtained through graft copolymerization of sodium polyacrylate and alkali lignin. The graft copolymerization method is a conventional existing approach and specifically may include the following steps: Raw material preparation: Dissolve alkali lignin in a solvent (such as dimethylformamide).

[0026] Initiation reaction: Under nitrogen protection, an initiator (such as ammonium persulfate) is added and stirred at 50~70℃ to generate free radical active sites on alkali lignin molecules.

[0027] Graft copolymerization: Acrylic acid monomers are added dropwise to an alkali lignin solution. The acrylic acid monomers undergo polymerization at the active sites to form polyacrylic acid branches. At the same time, sodium hydroxide is used to neutralize part of the acrylic acid during the reaction to form sodium acrylate, thereby improving the water solubility of the product.

[0028] Product separation: After the reaction is complete, the pH is adjusted to acidic (e.g., pH 2-3), taking advantage of the insolubility of alkali lignin under acidic conditions, causing the graft copolymer to precipitate. The unreacted sodium polyacrylate homopolymer remains dissolved in the solution, and can be separated and purified by centrifugation.

[0029] Furthermore, the average molecular weight of sodium hydroxymethyl cellulose is 20,000 to 120,000, and the mass of sodium hydroxymethyl cellulose is 8 to 12% of the mass of sodium polyacrylate-modified alkali lignin. At 25°C, the viscosity of the slurry is 3,000 to 6,000 mPa·s.

[0030] A method for preparing an aqueous hard carbon anode slurry includes the following steps: First, mix sodium hydroxymethyl cellulose with 60 parts of water and stir at 100-300 rpm for 1-10 minutes. Then, adjust the speed to 60-120 rpm and add sodium polyacrylate-modified alkali lignin in 1-3 portions, stirring for 5-20 minutes after each addition. After all the lignin has been added, continue stirring for 30-60 minutes. Finally, add hard carbon and 40 parts of water at the same time and stir at 250-500 rpm for 1-3 hours to obtain an aqueous hard carbon anode slurry.

[0031] A method for preparing a sodium-ion battery anode material includes the following steps: Aqueous hard carbon anode slurry is coated onto a current collector, and the coated current collector is dried in an environment of 100~120℃ for 1~10h. Then, in an oxygen-containing environment, the temperature is increased to 220~280℃ at a heating rate of 1~5℃ / min and held for 1~3h. Finally, in an inert atmosphere, the temperature is increased to 450~600℃ at a heating rate of 0.5~2℃ / min and held for 0.5~6h to obtain the sodium-ion battery anode material.

[0032] The current collector includes copper foil. The coating thickness of the aqueous hard carbon negative electrode slurry on the current collector is 20~100μm, and the coating speed is 1~40m / min. When the current collector is initially dried in an environment of 100~120℃, it can be a forced-air drying oven or a vacuum drying, preferably a vacuum drying.

[0033] A sodium-ion battery, comprising a sodium-ion battery negative electrode material.

[0034] Example 1 A water-based hard carbon anode slurry and its preparation method: The formulation of aqueous hard carbon anode slurry, by mass parts, includes the following components: Hard carbon: 60 parts; Sodium polyacrylate modified alkali lignin, 20 parts; Sodium carboxymethyl cellulose with an average molecular weight of 80,000: 2 parts; Water: 100 portions.

[0035] The preparation method includes the following steps: First, 2 parts of sodium carboxymethyl cellulose were mixed with 60 parts of water and stirred at 200 rpm for 3 minutes. Then, the stirring speed was adjusted to 60 rpm, and 10 parts of sodium polyacrylate-modified alkali lignin were added and stirred for 10 minutes. Then, another 10 parts of sodium polyacrylate-modified alkali lignin were added, and stirring was continued for 30 minutes after the addition was complete. Finally, 60 parts of hard carbon and 40 parts of water were added simultaneously, and the mixture was stirred at 400 rpm for 1 hour to obtain an aqueous hard carbon anode slurry. The viscosity was measured to be 3300 mPa·s at 25°C.

[0036] A method for preparing a sodium-ion battery anode material includes the following steps: Aqueous hard carbon anode slurry was coated onto copper foil to a thickness of 40 μm at a coating speed of 20 m / min. The coated current collector was then vacuum-dried at 100 °C for 3 h. Next, in an oxygen-containing environment, the temperature was increased to 220 °C at a rate of 1 °C / min and held for 3 h. Finally, in an inert atmosphere, the temperature was increased to 550 °C at a rate of 1 °C / min and held for 3 h to obtain the sodium-ion battery anode material.

[0037] Example 2 A water-based hard carbon anode slurry and its preparation method: The formulation of aqueous hard carbon anode slurry, by mass parts, includes the following components: Hard carbon: 65 parts; 25 parts of sodium polyacrylate-modified alkali lignin; Sodium carboxymethyl cellulose with an average molecular weight of 60,000: 2.4 parts; Water: 100 portions.

[0038] The preparation method includes the following steps: First, 2.4 parts of sodium carboxymethyl cellulose were mixed with 60 parts of water and stirred at 100 rpm for 10 minutes. Then, the stirring speed was adjusted to 80 rpm, and 10 parts of sodium polyacrylate-modified alkali lignin were added and stirred for 5 minutes. Then, another 10 parts of sodium polyacrylate-modified alkali lignin were added and stirred for 10 minutes. Then, another 5 parts of sodium polyacrylate-modified alkali lignin were added, and after all the additions were completed, stirring was continued for 40 minutes. Finally, 65 parts of hard carbon and 40 parts of water were added simultaneously, and the mixture was stirred at 500 rpm for 2 hours to obtain an aqueous hard carbon anode slurry. The viscosity was measured to be 4100 mPa·s at 25°C.

[0039] A method for preparing a sodium-ion battery anode material includes the following steps: Aqueous hard carbon anode slurry was coated onto copper foil to a thickness of 60 μm at a coating speed of 10 m / min. The coated current collector was then vacuum-dried at 100 °C for 5 h. Next, in an oxygen-containing environment, the temperature was increased to 260 °C at a rate of 3 °C / min and held for 2 h. Finally, in an inert atmosphere, the temperature was increased to 600 °C at a rate of 2 °C / min and held for 1 h to obtain the sodium-ion battery anode material.

[0040] Example 3 A water-based hard carbon anode slurry and its preparation method: The formulation of aqueous hard carbon anode slurry, by mass parts, includes the following components: Hard carbon: 70 parts; 30 parts of sodium polyacrylate-modified alkali lignin; Sodium carboxymethyl cellulose with an average molecular weight of 40,000: 3.6 parts; Water: 100 portions.

[0041] The preparation method includes the following steps: First, 3.6 parts of sodium carboxymethyl cellulose were mixed with 60 parts of water and stirred at 300 rpm for 1 minute. Then, the stirring speed was adjusted to 120 rpm, and 30 parts of sodium polyacrylate-modified alkali lignin were added. After the addition was complete, stirring was continued for 60 minutes. Finally, 70 parts of hard carbon and 40 parts of water were added simultaneously, and the mixture was stirred at 500 rpm for 3 hours to obtain an aqueous hard carbon anode slurry. The viscosity was measured to be 4300 mPa·s at 25°C.

[0042] A method for preparing a sodium-ion battery anode material includes the following steps: Aqueous hard carbon anode slurry was coated onto copper foil to a thickness of 20 μm at a coating speed of 40 m / min. The coated current collector was then vacuum-dried at 105 °C for 10 h. Next, in an oxygen-containing environment, the temperature was increased to 270 °C at a rate of 5 °C / min and held for 1 h. Finally, in an inert atmosphere, the temperature was increased to 450 °C at a rate of 0.5 °C / min and held for 5 h to obtain the sodium-ion battery anode material.

[0043] Example 4 A water-based hard carbon anode slurry and its preparation method: The formulation of aqueous hard carbon anode slurry, by mass parts, includes the following components: Hard carbon: 55 parts; 28 parts of sodium polyacrylate-modified alkali lignin; Sodium carboxymethyl cellulose with an average molecular weight of 120,000: 2.4 parts; Water: 100 portions.

[0044] The preparation method includes the following steps: First, 2.4 parts of sodium carboxymethyl cellulose were mixed with 60 parts of water and stirred at 250 rpm for 10 minutes. Then, the stirring speed was adjusted to 100 rpm, and 14 parts of sodium polyacrylate-modified alkali lignin were added. The mixture was stirred for 20 minutes, followed by the addition of another 14 parts of sodium polyacrylate-modified alkali lignin. After the addition was complete, the mixture was stirred for another 50 minutes. Finally, 55 parts of hard carbon and 40 parts of water were added simultaneously, and the mixture was stirred at 400 rpm for 1 hour to obtain an aqueous hard carbon anode slurry. The viscosity was measured to be 5600 mPa·s at 25°C.

[0045] A method for preparing a sodium-ion battery anode material includes the following steps: Aqueous hard carbon anode slurry was coated onto copper foil to a thickness of 100 μm at a coating speed of 1 m / min. The coated current collector was then vacuum-dried at 120 °C for 2 h. Next, in an oxygen-containing environment, the temperature was increased to 280 °C at a rate of 1.5 °C / min and held for 1 h. Finally, in an inert atmosphere, the temperature was increased to 500 °C at a rate of 1.5 °C / min and held for 6 h to obtain the sodium-ion battery anode material.

[0046] Example 5 A water-based hard carbon anode slurry and its preparation method: The formulation of aqueous hard carbon anode slurry, by mass parts, includes the following components: Hard carbon: 60 parts; Sodium polyacrylate modified alkali lignin, 24 parts; Sodium carboxymethyl cellulose with an average molecular weight of 20,000: 2.5 parts; Water: 100 portions.

[0047] The preparation method includes the following steps: First, 2.5 parts of sodium carboxymethyl cellulose were mixed with 60 parts of water and stirred at 240 rpm for 5 minutes. Then, the stirring speed was adjusted to 100 rpm, and 24 parts of sodium polyacrylate-modified alkali lignin were added. After the addition was complete, stirring was continued for 30 minutes. Finally, 60 parts of hard carbon and 40 parts of water were added simultaneously, and the mixture was stirred at 250 rpm for 1.5 hours to obtain an aqueous hard carbon anode slurry. The viscosity was measured to be 3100 mPa·s at 25°C.

[0048] A method for preparing a sodium-ion battery anode material includes the following steps: Aqueous hard carbon anode slurry was coated onto copper foil to a thickness of 50 μm at a coating speed of 25 m / min. The coated current collector was then vacuum-dried at 100 °C for 4 h. Next, in an oxygen-containing environment, the temperature was increased to 230 °C at a rate of 2 °C / min and held for 1.5 h. Finally, in an inert atmosphere, the temperature was increased to 600 °C at a rate of 2 °C / min and held for 0.5 h to obtain the sodium-ion battery anode material.

[0049] The above embodiments are merely illustrative of several implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the invention patent. For those skilled in the art, any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments without departing from the concept of the present invention are all within the protection scope of the present invention.

Claims

1. A water-based hard carbon anode slurry, characterized in that, By mass, it includes the following components: Hard carbon: 55-70 parts; Sodium polyacrylate modified alkali lignin, 20-30 parts; Sodium carboxymethyl cellulose: 1.5 to 5 parts; Water: fixed at 100 portions.

2. The aqueous hard carbon anode slurry according to claim 1, characterized in that, The sodium polyacrylate-modified alkali lignin is obtained by graft copolymerization of sodium polyacrylate and alkali lignin.

3. The aqueous hard carbon anode slurry according to claim 1, characterized in that, The average molecular weight of the sodium hydroxymethyl cellulose is 20,000 to 120,000.

4. The aqueous hard carbon anode slurry according to claim 3, characterized in that, The mass of the sodium hydroxymethyl cellulose is 8-12% of the mass of sodium polyacrylate-modified alkali lignin.

5. The aqueous hard carbon anode slurry according to claim 4, characterized in that, At 25℃, the slurry viscosity is 3000-6000 mPa·s.

6. A method for preparing the aqueous hard carbon anode slurry according to any one of claims 1 to 5, characterized in that, Includes the following steps: First, the sodium hydroxymethyl cellulose is mixed with 60 parts of water and stirred at 100-300 rpm for 1-10 minutes. Then, the stirring speed is adjusted to 60-120 rpm, and the sodium polyacrylate-modified alkali lignin is added. After the addition is complete, stirring is continued for 30-60 minutes. Finally, the hard carbon and 40 parts of water are added simultaneously, and the mixture is stirred at 250-500 rpm for 1-3 hours to obtain the aqueous hard carbon negative electrode slurry.

7. The method for preparing the aqueous hard carbon anode slurry according to claim 6, characterized in that, The process also includes the following steps: adding the sodium polyacrylate-modified alkali lignin in 1 to 3 portions, stirring for 5 to 20 minutes after each addition, and continuing to stir for 30 to 60 minutes after all the lignin has been added.

8. A method for preparing a sodium-ion battery anode material, characterized in that, Includes the following steps: The aqueous hard carbon anode slurry according to any one of claims 1 to 5 is coated onto the current collector, and then the coated current collector is dried in an environment of 100 to 120°C for 1 to 10 hours; then, in an oxygen-containing environment, the temperature is increased to 220 to 280°C at a heating rate of 1 to 5°C / min and held for 1 to 3 hours; finally, in an inert atmosphere, the temperature is increased to 450 to 600°C at a heating rate of 0.5 to 2°C / min and held for 0.5 to 6 hours to obtain the sodium-ion battery anode material; The current collector includes copper foil.

9. The method for preparing sodium-ion battery anode material according to claim 8, characterized in that, The coating thickness of the aqueous hard carbon negative electrode slurry on the current collector is 20~100μm, and the coating speed is 1~40m / min.

10. A sodium-ion battery, characterized in that, Includes the sodium-ion battery anode material as described in claim 8.