Aqueous compound slurry and preparation method thereof, and lithium ion battery negative electrode material

Abstract

The invention belongs to the technical field of lithium battery negative electrode slurry, and particularly relates to water-based compound slurry and a preparation method thereof and a lithium ion battery negative electrode material.The preparation method comprises the following steps that S1, amino alcohol and CMC are dissolved in deionized water, and a dispersed glue solution is obtained; s2, respectively adding the SWCNT and the MWCNT into independent dispersion glue solutions for wetting, and carrying out pre-dispersion by using a high-pressure homogenizer, so as to obtain an SWCNT pre-dispersion solution and an MWCNT pre-dispersion solution; s3, the SWCNT pre-dispersion liquid and the MWCNT pre-dispersion liquid are dispersed through a high-pressure jet flow homogenizer, and SWCNT slurry and MWCNT slurry are obtained; s4, the SWCNT slurry and the MWCNT slurry are mixed, and water-based compound slurry is obtained; according to the preparation method, the agglomeration structure of the carbon nanotubes is preliminarily scattered by utilizing shearing force and a hole effect through a high-pressure homogenizer, and then secondary dispersion is carried out by utilizing a high-pressure jet homogenizer, so that the SWCNT and the MWCNT are further dispersed into fibrous conductive carbon tubes which are high in length-diameter ratio and not easy to agglomerate, and the MWCNT with the high length-diameter ratio can achieve the conductivity and the cycle performance superior to those of traditional MWCNTs.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery anode slurries, and specifically relates to an aqueous compound slurry, a preparation method thereof, and a lithium ion battery anode material. Background Art

[0002] In the front-end process of lithium ion battery manufacturing, pulping is one of the most important processes. Pulping refers to uniformly dispersing the main materials of the positive and negative electrodes of a lithium ion battery, a conductive agent, a binder, etc. in water or a certain organic solvent (mainly NMP) by means of stirring, centrifugation, ball milling, etc.

[0003] SWCNT (single-walled carbon nanotube) is a commonly used conductive agent for silicon anode batteries in the prior art. It has excellent performance but high cost. Traditional MWCNT (multi-walled carbon nanotube) is an aggregated small particle, and its long-range conductive effect is average. Although it is easy to obtain, it is not suitable for the silicon anode slurry of lithium ion batteries.

[0004] Therefore, how to improve the long-range conductive effect of MWCNT in the anode slurry is a technical problem that needs to be solved urgently in this field.

[0005] It should be noted that the above information disclosed in this background art part is only used to understand the background art of the concept of this application. Therefore, the above description is not considered as information of the prior art. Summary of the Invention

[0006] The embodiments of the present disclosure at least provide an aqueous compound slurry, a preparation method thereof, and a lithium ion battery anode material.

[0007] In a first aspect, the embodiments of the present disclosure provide a preparation method of an aqueous compound slurry, including the following steps: S1, dissolving amino alcohol and CMC in deionized water to obtain a dispersion colloid solution; S2, respectively adding SWCNT and MWCNT into independent dispersion colloid solutions to be wetted, and using a high-pressure homogenizer for pre-dispersion to obtain a SWCNT pre-dispersion solution and a MWCNT pre-dispersion solution; S3, dispersing the SWCNT pre-dispersion solution and the MWCNT pre-dispersion solution through a high-pressure jet homogenizer to obtain a SWCNT slurry and a MWCNT slurry; S4, mixing the SWCNT slurry and the MWCNT slurry to obtain an aqueous compound slurry.

[0008] In an optional embodiment, the sum of the mass fractions of amino alcohol and CMC in the dispersion colloid solution in step S1 is 0.4%-0.8%.

[0009] In an optional embodiment, the pre-dispersion by the high-pressure homogenizer in step S2 specifically includes:

[0010] When the temperature is 24 ± 4 °C, the input energy required for the pre-dispersed slurry is set to 0.3 kWh / kg, and the duration T of homogenization is calculated; the T satisfies the following relationship: In the formula, T is the required homogenization time, in hours; E is the input energy, in kWh / kg; M total is the total output, in kg; P is the power of the high-pressure homogenizer, in kW.

[0011] In an alternative embodiment, the particle size of the pretreated MWCNT is not greater than 20 um.

[0012] In an alternative embodiment, in step S2, the mass fraction of SWCNT is 0.4% - 0.8%, and the mass fraction of MWCNT is 0.4% - 0.8%.

[0013] In an alternative embodiment, the dispersion by the high-pressure jet homogenizer in step S3 specifically includes: dispersing the SWCNT pre-dispersed liquid and the MWCNT pre-dispersed liquid through the high-pressure jet homogenizer to form fibrous conductive carbon tubes with some SWCNT and all MWCNT; wherein, the dispersion pressure of the SWCNT is 200 - 1000 bar, and the number of homogenization times is 10 - 20 times; the dispersion pressure of the MWCNT is 200 - 500 bar, and the number of homogenization times is 10 - 20 times.

[0014] In an alternative embodiment, the outer diameter OD value of the fibrous conductive carbon tube is not less than 0.45 abs.

[0015] In an alternative embodiment, the nozzle aperture used by the high-pressure jet homogenizer is not greater than φ0.5 mm.

[0016] In a second aspect, the embodiments of the present disclosure further provide an aqueous composite slurry, obtained by the method as described above, and including the following components by mass fraction: SWCNT 0.4% - 0.8%, fibrous conductive carbon tube 0.4% - 0.8%; wherein, the outer diameter OD value of the fibrous conductive carbon tube is not less than 0.45 abs.

[0017] In a third aspect, the embodiments of the present disclosure further provide a negative electrode material for a lithium-ion battery, obtained by coating the above-mentioned aqueous composite slurry on a current collector.

[0018] The beneficial effects of the present invention are as follows. The aqueous composite slurry, its preparation method, and the anode material of the lithium-ion battery use a high-pressure homogenizer to initially disperse the agglomerated structure of carbon nanotubes by means of shear force and cavitation effect. Subsequently, a high-pressure jet homogenizer is used for secondary dispersion, so that SWCNT and MWCNT are further dispersed into fibrous conductive carbon tubes with a high aspect ratio and not easily agglomerated. The application of this part of fibrous conductive carbon tubes in the slurry can avoid the agglomeration effect brought by traditional MWCNT and significantly improve the long-range conductive effect. At the same time, in the silicon-based anode, MWCNT with a high aspect ratio can also exhibit better conductive performance and cycling performance than traditional MWCNT.

[0019] Other features and advantages of the present invention will be described in the following specification, and in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention are achieved and obtained by the structure specifically pointed out in the specification and the drawings.

[0020] To make the above objectives, features, and advantages of the present invention more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, is described in detail as follows. Brief Description of the Drawings

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a 100-fold enlarged view of an SWCNT slurry provided by an embodiment of the present disclosure. Detailed Embodiments

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0024] As used herein, phrases such as "in one embodiment", "according to one embodiment", "in some embodiments", etc. generally refer to the fact that the specific feature, structure, or characteristic after such phrase can be included in at least one embodiment of the present disclosure. Thus, a specific feature, structure, or characteristic can be included in more than one embodiment of the present disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example", "exemplary", etc. are used "as an example, instance, or illustration. Any embodiment, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or superior to other embodiments, aspects, or designs. Instead, the use of the terms "example", "exemplary", etc. is intended to present concepts in a concrete manner.

[0025] In this document, example embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as "at least one of..." modify the entire list of elements when following a list of elements, rather than modifying an individual element in the list. For example, the expression "at least one of a, b, and c" should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0026] The terms used herein are only for describing specific exemplary configurations and are not intended to be limiting. As used herein, the singular articles "a", "an", and "the" may also be intended to include the plural forms, unless it is clearly stated otherwise herein. The terms "comprising", "including", and "having" are inclusive and thus specify the presence of the specified features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as necessarily requiring them to be performed in the particular order discussed or shown, unless specifically identified as an order of performance. Additional or alternative steps may be employed.

[0027] It should be noted that like reference numerals and letters denote like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

[0028] Some embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments may be combined with each other.

[0029] Embodiments of the present disclosure provide a method for preparing an aqueous composite slurry, comprising the following steps: S1, dissolving amino alcohol and CMC (sodium carboxymethyl cellulose) in deionized water to obtain a dispersion glue solution; S2, respectively adding SWCNT and MWCNT to independent dispersion glue solutions for wetting, and using a high-pressure homogenizer for pre-dispersion to obtain a SWCNT pre-dispersion solution and a MWCNT pre-dispersion solution; S3, dispersing the SWCNT pre-dispersion solution and the MWCNT pre-dispersion solution through a high-pressure jet homogenizer to obtain a SWCNT slurry and a MWCNT slurry; S4, mixing the SWCNT slurry and the MWCNT slurry to obtain an aqueous composite slurry.

[0030] In an alternative embodiment, the sum of the mass fractions of amino alcohol and CMC in the dispersion glue solution in step S1 is 0.4% - 0.8%.

[0031] In an alternative embodiment, the pre-dispersion by the high-pressure homogenizer in step S2 specifically includes: at a temperature of 24 ± 4 °C, setting the input energy required for the pre-dispersed slurry to 0.3 kWh / kg, and calculating the duration T of homogenization; the T satisfies the following relationship: In the formula, T is the required homogenization time, in hours; E is the input energy, in kWh / kg; M total is the total output, in kg; P is the power of the high-pressure homogenizer, in kW.

[0032] Specifically, for example, for 10 kg of dispersed material, under the condition of using a homogenizer with a power of 4 kW, using the above formula: T = (kWh / kg * 10 kg) / 4 kWh = 0.75 hours.

[0033] Specifically, the purpose of pre-dispersion is to deagglomerate the CNT powder. Currently, the SWCNT produced by the current process are all high-wound flocs. Pre-dispersion can enable them to absorb a certain amount of energy, thereby reducing their winding state, enabling them to be dispersed after passing through the nozzle, so as to avoid clogging of the nozzle in the equipment during the high-pressure jet homogenization process; however, excessive dispersion will lead to a decrease in long-range conductivity. Therefore, by calculating the duration of homogenization, the dispersion effect and the long-range conductivity performance can be balanced. Similarly, although the winding of SWCNT is not as serious as that of MWCNT, it can also be pre-dispersed better through the high-pressure homogenizer, thereby improving the efficiency of high-pressure jet homogenization.

[0034] In an alternative embodiment, the particle size of the pretreated MWCNT is not greater than 20 μm.

[0035] In an alternative embodiment, the mass fraction of SWCNT in step S2 is 0.4% - 0.8%, and the mass fraction of MWCNT is 0.4% - 0.8%.

[0036] In an alternative embodiment, the dispersion by the high-pressure jet homogenizer in step S3 specifically includes: dispersing the SWCNT pre-dispersion liquid and the MWCNT pre-dispersion liquid through the high-pressure jet homogenizer to form fibrous conductive carbon tubes from part (not less than 10%) of the SWCNT and all of the MWCNT; wherein, the dispersion pressure of the SWCNT is 200 - 1000 bar, and the number of homogenization times is 10 - 20 times; the dispersion pressure of the MWCNT is 200 - 500 bar, and the number of homogenization times is 10 - 20 times.

[0037] Specifically, the carbon nanotubes are dispersed by the cavitation, impact, and shear effects of the high-pressure jet homogenizer. Especially for the dispersion of MWCNT, the strength of its carbon tubes is lower than that of SWCNT. Therefore, a nozzle with a smaller aperture needs to be used for homogenization to make it more subject to the cavitation impact effect, so as to be dispersed into fibrous carbon tubes, and a smaller homogenization pressure is adopted to reduce its shear effect, thereby obtaining MWCNT with a high aspect ratio and avoiding the fracture of MWCNT with weak carbon tube strength and the formation of secondary agglomeration.

[0038] In an alternative embodiment, the outer diameter OD value of the fibrous conductive carbon tube is not less than 0.45 abs.

[0039] Specifically, the slurry is diluted for the measurement of the optical density, that is, the optical density value is measured by multiplying the mass fraction of the powder in the slurry by 100,000 times. For example: the 0.4% SWCNT slurry is diluted 0.4% * 100,000 times and then the optical density value is measured. The higher the optical density value, the higher the degree of its dispersion.

[0040] In an alternative embodiment, the aperture diameter of the nozzle used in the high-pressure jet homogenizer is not greater than φ0.5 mm.

[0041] Specifically, due to the agglomerated powder in the pre-dispersed slurry, a smaller nozzle is not conducive to the dispersion of the agglomerated powder and may cause blockage. A larger nozzle will reduce the cavitation and impact effects, and more of the dispersion method is the shear effect between the valve bodies, resulting in the fracture and re-agglomeration of MWCNT.

[0042] In a second aspect, the embodiments of the present disclosure further provide an aqueous composite slurry, which is obtained by the method described above, and includes the following components by mass fraction: 0.4% - 0.8% of SWCNT, 0.4% - 0.8% of fibrous conductive carbon tubes; wherein, the OD value of the fibrous conductive carbon tube is not less than 0.45 abs (optical density value).

[0043] In a third aspect, the embodiments of the present disclosure further provide a negative electrode material for a lithium-ion battery, which is obtained by coating the above-mentioned aqueous composite slurry on a current collector.

[0044] Example 1:

[0045] Preparation of aqueous compound slurry:

[0046] S1. Dissolve 10 g of amino alcohol and 40 g of CMC in 4950 g of deionized water to obtain a dispersion colloidal solution;

[0047] S2. Add SWCNT and MWCNT to separate dispersion colloidal solutions for wetting respectively, and use a high-pressure homogenizer for pre-dispersion. Among them, SWCNT is homogenized at 24 °C for 0.375 h, and MWCNT is homogenized at 24 °C for 0.375 h to obtain a SWCNT pre-dispersed solution and a MWCNT pre-dispersed solution;

[0048] S3. Disperse the SWCNT pre-dispersed solution and the MWCNT pre-dispersed solution through a high-pressure jet homogenizer. Among them, the dispersion pressure of the SWCNT pre-dispersed solution is 700 bar, and the number of homogenization times is 10 times. The dispersion pressure of the MWCNT pre-dispersed solution is 300 bar, and the number of homogenization times is 10 times, to obtain a SWCNT slurry and the Figure 1 MWCNT slurry as shown;

[0049] As Figure 1 shown, the SWCNT after high-pressure jet dispersion presents a fibrous structure, and the aspect ratio is significantly increased.

[0050] S4. Mix the SWCNT slurry and the MWCNT slurry to obtain an aqueous compound slurry, hereinafter referred to as compound CNT.

[0051] Prepare a negative electrode slurry according to the solid mass ratio of graphite, silicon negative electrode, CMC, carbon black, PAA, SBR, and compound CNT of 81.2:14.3:1:0.6:1.6:1.2:0.1. Among them, the compound CNT includes 1 part of SWCNT and 40 parts of MWCNT;

[0052] First, make a glue with CMC and deionized water, and the solid content of the glue is 2%. The subsequent addition sequence is carbon black, graphite, silicon negative electrode, CNT, PAA, SBR in turn, and finally add deionized water to adjust the solid content to 50%;

[0053] Before adding SBR, the revolution speed is 3500 RPM and the rotation speed is 50 RPM. After adding SBR, the revolution speed is 500 RPM and the rotation speed is 10 RPM. After homogenizing for 120 minutes, it is coated on the current collector, dried at 80 °C, and then the pole piece is cut into a negative electrode. Using NCM as the positive electrode, a soft-pack battery is prepared and tested on a Neware test system. The charge and discharge conditions are set as: 1C charge and discharge for 200 cycles. As shown in Table 1, the results show that: the first-week discharge capacity is 1864 mAh, and the first-week efficiency is 76.3%.

[0054] Comparative Example 1:

[0055] Prepare the negative electrode slurry according to the solid mass ratio of graphite, silicon negative electrode, CMC, carbon black, PAA, SBR, and SWCNT of 81.2:14.3:1:0.6:1.6:1.2:0.05;

[0056] First, prepare the glue by adding CMC to deionized water with a solid content of 2% in the glue solution. The subsequent addition sequence is carbon black, graphite, silicon negative electrode, CNT, PAA, SBR in turn, and finally add deionized water to adjust the solid content to 50%;

[0057] Before adding SBR, the revolution speed is 3500 RPM and the rotation speed is 50 RPM. After adding SBR, the revolution speed is 500 RPM and the rotation speed is 10 RPM. After homogenizing for 120 minutes, it is coated on the current collector and dried at 80°C. Then, cut the electrode sheet as the negative electrode, use NCM as the positive electrode, and prepare a soft-pack battery for testing on a Neware test system. The charge and discharge conditions are set as: charge and discharge at 1C for 200 cycles. As shown in Table 1, the results show that the first-week discharge capacity is 1807 mAh and the first efficiency is 75.7%.

[0058] Example 2:

[0059] Preparation of aqueous compound slurry:

[0060] S1. Dissolve 10 g of amino alcohol and 40 g of CMC in 4950 g of deionized water to obtain a dispersion glue solution;

[0061] S2. Add SWCNT and MWCNT to separate dispersion glue solutions for wetting respectively, and use a high-pressure homogenizer for pre-dispersion. Among them, SWCNT is homogenized at 24°C for 0.375 h, and MWCNT is homogenized at 24°C for 0.375 h to obtain SWCNT pre-dispersion liquid and MWCNT pre-dispersion liquid;

[0062] S3. Disperse the SWCNT pre-dispersion liquid and MWCNT pre-dispersion liquid through a high-pressure jet homogenizer. Among them, the dispersion pressure of the SWCNT pre-dispersion liquid is 700 bar and the homogenization times are 10 times. The dispersion pressure of the MWCNT pre-dispersion liquid is 300 bar and the homogenization times are 10 times to obtain SWCNT slurry and MWCNT slurry;

[0063] Prepare the negative electrode slurry according to the solid mass ratio of graphite, silicon negative electrode, CMC, carbon black, PAA, SBR, and compound CNT of 81.2:14.3:1:0.6:1.6:1.2:0.2, where the compound CNT includes 1 part of SWCNT and 40 parts of MWCNT;

[0064] First, prepare the glue by adding CMC and deionized water. The solid content of the glue solution is 2%. Subsequently, the addition sequence is carbon black, graphite, silicon negative electrode, CNT, PAA, SBR in turn, and finally add deionized water to adjust the solid content to 50%;

[0065] Before adding SBR, the revolution speed is 3500 RPM and the rotation speed is 50 RPM. After adding SBR, the revolution speed is 500 RPM and the rotation speed is 10 RPM. After homogenizing for 120 minutes, it is coated on the current collector and dried at 80 °C. Then, the electrode sheet is cut into the negative electrode, and NCM is used as the positive electrode to prepare a soft-pack battery, which is tested on a Neware test system. The charge-discharge conditions are set as: charge and discharge at 1C for 200 cycles. As shown in Table 1, the results show that the first-week discharge capacity is 1845 mAh and the first efficiency is 75.9%.

[0066] Comparative Example 2

[0067] Preparation of aqueous compound slurry:

[0068] S1. Dissolve 10 g of amino alcohol and 40 g of CMC in deionized water to obtain a dispersion glue solution;

[0069] S2. Add SWCNT to the dispersion glue solution to wet it, and use a high-pressure homogenizer for pre-dispersion. Among them, SWCNT is homogenized at 24 °C for 0.375 h to obtain a SWCNT pre-dispersion solution;

[0070] S3. Disperse the SWCNT pre-dispersion solution through a high-pressure jet homogenizer. The dispersion pressure of the SWCNT pre-dispersion solution is 700 bar, and the homogenization times are 10 times to obtain a SWCNT slurry;

[0071] S4. Compound 1 part of the SWCNT slurry with 40 parts of the sand-milled and dispersed ordinary MWCNT slurry with a low aspect ratio to obtain a compound CNT slurry;

[0072] Prepare the negative electrode slurry according to the solid mass ratio of graphite, silicon negative electrode, CMC, carbon black, PAA, SBR, and compound CNT of 81.2:14.3:1:0.6:1.6:1.2:0.1. Among them, the compound CNT includes 1 part of SWCNT and 40 parts of MWCNT;

[0073] First, prepare the glue by adding CMC and deionized water. The solid content of the glue solution is 2%. Subsequently, the addition sequence is carbon black, graphite, silicon negative electrode, CNT, PAA, SBR in turn, and finally add deionized water to adjust the solid content to 50%;

[0074] Before adding SBR, the revolution speed was 3500 RPM and the rotation speed was 50 RPM. After adding SBR, the revolution speed was 500 RPM and the rotation speed was 10 RPM. After homogenizing for 120 minutes, it was coated on the current collector and dried at 80 °C, and then the electrode sheet was cut as the negative electrode, with NCM as the positive electrode, and a soft-pack battery was prepared and tested on a Neware test system. The charge-discharge conditions were set as follows: 1C charge-discharge cycle for 200 weeks. As shown in Table 1, the results showed that the first-week discharge capacity was 1801 mAh and the first efficiency was 73.6%.

[0075] Specifically, in terms of the total mass fraction in the soft-pack battery, the soft-pack batteries obtained in Examples 1-2 and Comparative Examples 1-2 were subjected to performance tests, and the following Table 1 was obtained.

[0076] Table 1

[0077] Group Viscosity Internal Resistance / mΩ Initial Week Discharge Capacity / mAh Initial Week Efficiency / % 1C Cycle 200 Weeks Efficiency / % Example 1: 0.1% Compound 4112 15.4 1864 76.3 89.5 Comparative Example 1: 0.05% SWCNT 4019 16.1 1807 75.7 89.7 Example 2: 0.2% Compound 4284 15.5 1845 75.9 90.2 Comparative Example 2: 0.1% Ordinary Compound 4112 17.1 1801 73.6 83.8

[0078] As can be seen from Table 1, the fibrous MWCNT slurry prepared by the method provided in the embodiments of the present application, after being configured with the SWCNT slurry into a compound slurry and applied in a silicon negative electrode battery system, has good first-week discharge capacity, first-week efficiency and cycle efficiency, can effectively reduce or replace the use of SWCNT in the silicon negative electrode system, and at the same time has better performance than traditional multi-walled dispersed slurries.

[0079] Specifically, in Comparative Example 2, SWCNT was only dispersed by ordinary processes, and the aspect ratio did not meet the specified requirements, and the performance that could be achieved in Example 1 could not be achieved synergistically at the same concentration. This is because the volume change of the silicon negative electrode material during charge and discharge can reach up to 300%-400%, which easily leads to the destruction of the material structure and electrode pulverization, affecting the cycle life. At the same time, the conductivity of silicon is relatively low, affecting electron transport and lithium ion diffusion. Therefore, fibrous MWCNT with a high aspect ratio can form a stable three-dimensional network structure in the silicon negative electrode material, improving conductivity and relieving volume expansion, thereby enhancing the cycle performance. That is, compared with Comparative Example 2, fibrous MWCNT with a high aspect ratio has higher efficiency after 200 cycles at 1C.

[0080] Furthermore, the cost of 0.05% concentration of SWCNT in Comparative Example 1 is much higher than that of 0.1% compounding in Example 1, but under the synergistic effect of the fibrous MWCNT slurry and the SWCNT slurry, the long-range conductive performance of Example 1 does not decrease but increases.

[0081] In summary, for the aqueous composite slurry, its preparation method, and the anode material of the lithium-ion battery, the high-pressure homogenizer is used to initially break up the agglomerated structure of carbon nanotubes by means of shear force and cavitation effect. Subsequently, the high-pressure jet homogenizer is used for secondary dispersion, so that SWCNT and MWCNT are further dispersed into fibrous conductive carbon tubes with a high aspect ratio and not easily agglomerated. The application of this part of fibrous conductive carbon tubes in the slurry can avoid the agglomeration effect brought by traditional MWCNT and significantly improve the long-range conductive effect. At the same time, in the silicon-based anode, MWCNT with a high aspect ratio also has better conductive performance and cycling performance than traditional MWCNT.

[0082] Taking the above-described ideal embodiments of the present invention as an inspiration, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing an aqueous composite slurry, characterized in that: The steps include: Step S1, dissolving amino alcohol and CMC in deionized water to obtain a dispersed rubber solution; Step S2, adding SWCNT and MWCNT into separate dispersion gel solutions for wetting, and pre-dispersing them using a high-pressure homogenizer to obtain SWCNT pre-dispersion solution and MWCNT pre-dispersion solution; Step S3, dispersing the SWCNT pre-dispersion liquid and the MWCNT pre-dispersion liquid by a high-pressure jet homogenizer to obtain SWCNT slurry and MWCNT slurry; as well as, Step S4, mixing the SWCNT slurry and the MWCNT slurry to obtain an aqueous composite slurry.

2. The preparation method according to claim 1, characterized in that The sum of the mass fractions of amino alcohol and CMC in the dispersed rubber solution of step S1 is 0.4%-0.8%.

3. The preparation method according to claim 1, characterized in that: The high pressure homogenizer pre-dispersion in step S2 specifically includes: At a temperature of 24±4°C, the input energy required for pre-dispersed slurry is set to 0.3 kWh / kg, and the duration T of homogenization is calculated; The T satisfies the following relationship: ; Where, T is the required homogenization time, in hours; E is the energy input, in kWh / kg; M total is the total output in kilograms; P is the power of the high pressure homogenizer in kilowatts.

4. The preparation method according to claim 3, characterized in that: The particle size of the pretreated MWCNT is no more than 20 um.

5. The preparation method according to claim 1, characterized in that: In the step S2, the mass fraction of SWCNT is 0.4%-0.8%, and the mass fraction of MWCNT is 0.4%-0.8%.

6. The preparation method according to claim 1, characterized in that: The high pressure jet homogenizer dispersion in step S3 specifically includes: Dispersing the SWCNT pre-dispersion liquid and the MWCNT pre-dispersion liquid by a high-pressure jet homogenizer to form fibrous conductive carbon tubes from the SWCNT and MWCNT; Wherein, the dispersion pressure of the SWCNT is 200-1000 bar, and the homogenization times are 10-20 times; The dispersion pressure of the MWCNT is 200-500 bar, and the homogenization times are 10-20 times.

7. The preparation method according to claim 6, characterized in that: The OD value of the fibrous conductive carbon tube is not less than 0.45 abs.

8. The preparation method according to claim 6, characterized in that: The nozzle aperture used by the high-pressure jet homogenizer is φ0.3-0.5 mm.

9. An aqueous composite slurry, characterized in that: Obtained by the method according to any one of claims 1 to 8, comprising the following components by mass fraction: SWCNT 0.4%-0.8%, fibrous conductive carbon tube 0.4%-0.8%; among them, The OD value of the fibrous conductive carbon tube is not less than 0.45 abs.

10. A negative electrode material for a lithium ion battery, characterized in that: The aqueous composite slurry as claimed in claim 9 is coated on a current collector.

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