A low-impedance cylindrical battery negative electrode slurry, a preparation method and application thereof

Abstract

The application discloses a kind of low impedance cylindrical battery negative electrode slurry and its preparation method and application, the method is by first pre-dispersion with part of binder, constructs stable conductive network framework, ensures that conductive agent is fully depolymerized and dispersed, to construct uniform conductive network, significantly reduce the overall and local resistance of negative electrode sheet, fundamentally eliminate the local high impedance point caused by conductive agent agglomeration.The application is by step adding binder and introducing NMP organic solvent, form a unique hybrid solvent system.The system can more effectively wet active material, promote the rearrangement of binder molecular chain, to form more uniform, more firm bonding structure between active material, conductive agent and current collector.This not only greatly enhances the mechanical integrity of sheet, reduces the risk of active material peeling during the cycle, also further guarantees the long-term stability of conductive network.

Description

Technical Field

[0001] This invention belongs to the field of cylindrical lithium-ion battery technology, specifically relating to a low-impedance cylindrical battery negative electrode slurry, its preparation method, and its application. Background Technology

[0002] Cylindrical lithium-ion batteries (such as 18650, 21700, and 26650) are widely used in consumer electronics and energy storage due to their high standardization, good mechanical strength, high energy density, and cost advantages. However, the wound structure of cylindrical batteries results in a longer internal current path, placing extremely high demands on the conductivity and consistency of the electrodes. As the core component of the battery, the internal resistance of the negative electrode is a key factor affecting the rate performance, cycle life, and thermal stability of cylindrical batteries.

[0003] Currently, most negative electrode slurries use aqueous systems. However, conventional preparation processes often lead to uneven dispersion of conductive agents (such as Super P), forming localized high-resistivity points on the electrode. During high-current charge and discharge of cylindrical batteries, these high-resistivity points exacerbate localized heat generation, becoming a potential hazard for battery performance degradation and thermal runaway. Therefore, optimizing the slurry process to construct an extremely uniform conductive network and significantly reduce the overall and localized internal resistance of the negative electrode is crucial for improving the electrochemical performance of cylindrical batteries. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a low-impedance cylindrical battery negative electrode slurry.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including,

[0008] Polyacrylic acid solution and conductive agent, accounting for 70-80 wt% of the total mass of polyacrylic acid solution raw materials, are added to a mixer and stirred to obtain slurry I;

[0009] Add graphite and 40-50 wt% deionized water (based on the total mass of the deionized water raw material) to slurry I, and stir to obtain slurry II;

[0010] Add the remaining polyacrylic acid solution, deionized water, and N-methylpyrrolidone from the raw materials to slurry II, and stir to obtain slurry III;

[0011] Add styrene-butadiene rubber latex to slurry III and stir to obtain negative electrode slurry;

[0012] The weight ratio of graphite, conductive agent, deionized water, polyacrylic acid solution, styrene-butadiene rubber latex, and N-methylpyrrolidone in the negative electrode slurry raw material is 46~50:0.5~1:2~6:44~48:1~5:2~6.

[0013] In a preferred embodiment of the method for preparing the low-impedance cylindrical battery negative electrode slurry of the present invention, the mass concentration of the polyacrylic acid solution is 20~25wt%, and the solid content of the styrene-butadiene rubber emulsion is 55~65%.

[0014] In a preferred embodiment of the method for preparing the low-impedance cylindrical battery negative electrode slurry of the present invention, the stirring speed of the slurry I obtained by stirring is 32~35 rpm and the stirring time is 1~1.5 h.

[0015] In a preferred embodiment of the method for preparing the low-impedance cylindrical battery negative electrode slurry of the present invention, the stirring speed of the slurry II obtained by stirring is 32~35 rpm and the stirring time is 2~2.5 h.

[0016] In a preferred embodiment of the method for preparing the low-impedance cylindrical battery negative electrode slurry of the present invention, the stirring speed of the slurry III obtained by stirring is 28~35 rpm and the stirring time is 1~1.5 h.

[0017] In a preferred embodiment of the method for preparing the low-impedance cylindrical battery negative electrode slurry of the present invention, the stirring speed for obtaining the negative electrode slurry is 16~18 rpm and the stirring time is 1~1.2h.

[0018] Another object of the present invention is to provide a low-resistivity cylindrical battery negative electrode slurry, wherein the slurry has a viscosity of 3100~3200 mPa·s and an adhesion force >9.2 N.

[0019] Another object of the present invention is to provide an application of a low-impedance cylindrical battery negative electrode slurry in the preparation of cylindrical lithium-ion batteries.

[0020] Another object of the present invention is to provide a cylindrical lithium-ion battery using the aforementioned low-impedance cylindrical battery negative electrode slurry.

[0021] Beneficial effects of this invention:

[0022] The low-impedance cylindrical battery negative electrode slurry of the present invention, through a unique step-by-step processing sequence and hybrid solvent system, ensures the extreme dispersion of conductive agents and active materials, forming a highly uniform conductive network, thereby significantly reducing the resistivity of the negative electrode sheet, improving the uniformity and heat dissipation of the cylindrical battery during cycling, and greatly enhancing its fast charging performance and cycle life. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0024] Figure 1 The charge-discharge curve of the cylindrical battery prepared by the negative electrode slurry in Example 3 of this invention at a rate of 0.2C is shown.

[0025] Figure 2 The charge-discharge curve of the cylindrical battery prepared by the negative electrode slurry in Example 3 of this invention at a rate of 0.5C is shown.

[0026] Figure 3 This is a photograph of a cylindrical battery made using the negative electrode slurry prepared according to Example 3 of the present invention. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0030] Unless otherwise specified, all raw materials used in this invention are commercially available in the field. The corresponding models of the raw materials used in specific embodiments are shown in Table 1.

[0031] Table 1

[0032] Raw material name Manufacturer / Model Conductive carbon black Griffith N-Methylpyrrolidone Yusheng graphite Deepwater CMC Dongguan Jinna Carbon black (SP) Griffith Styrene-butadiene latex (SBR) (60% solids content) Dao Ying Polyacrylic acid Solute mass fraction 20% ethanol 99% concentration

[0033] The viscosity and adhesion of the negative electrode slurry prepared in the examples / comparative examples were determined according to the following method:

[0034] Viscosity testing methods:

[0035] 1) After the slurry to be tested is removed from the mixing equipment, it should be allowed to stand for 10-15 minutes at a test temperature of 25℃. If necessary, vacuum degassing or gentle shaking can be used to remove air bubbles from the slurry.

[0036] 2) Turn on the viscometer to preheat and calibrate using standard silicone oil. Select the matching rotor model and sample cup according to the estimated viscosity range. Tighten the rotor clockwise onto the connecting rod.

[0037] 3) Slowly pour the prepared slurry into the sample cup to the specified scale, place it on the constant temperature sample platform of the viscometer, set and maintain the test temperature at 25℃, and keep it at the constant temperature for at least 5 minutes to ensure that the internal temperature of the sample is uniform.

[0038] 4) Rotate the instrument's lifting knob to slowly immerse the rotor into the slurry at an inclined angle until the liquid level reaches the marked line on the rotor rod. After immersion, let it stand for 1-2 minutes to allow the slurry structure to stabilize before the test begins.

[0039] 5) Rotate the speed control knob to set the speed to 10 rpm. Start the measurement. After the viscosity reading stabilizes for approximately 30-60 seconds, record the stable viscosity value (mPa·s).

[0040] Adhesion force test method:

[0041] The prepared slurry was uniformly coated on a 14μm copper foil, dried in an oven at 135℃ for 1 hour, and then a peel test was performed.

[0042] Prepare a 25mm*100mm stainless steel plate, cut out a 25mm*100mm electrode sample, and tear off 2-3mm of the upper part of the sample to be tested with high temperature adhesive and clamp it on the fixing fixture.

[0043] Rotate the speed control knob to set the test speed to 300 mm / min for vertical peeling of the tape, and record the maximum force value during the peeling process.

[0044] The electrochemical performance of the negative electrode slurry prepared in the examples / comparative examples for the preparation of cylindrical lithium-ion batteries was determined according to the following methods:

[0045] 1) The obtained negative electrode slurry is coated, dried, and rolled to obtain a negative electrode sheet;

[0046] 2) Prepare a positive electrode slurry by mixing 95 parts of lithium cobalt oxide positive electrode material, 3.5 parts of conductive agent (conductive carbon black), 1.5 parts of binder PVDF and an appropriate amount of N-methylpyrrolidone, and then obtain a positive electrode sheet by coating, drying and rolling.

[0047] 3) The positive electrode, separator, and negative electrode are stacked in sequence and wound into a compact cylindrical bare cell by a fully automatic winding machine;

[0048] 4) Place the prepared battery cell into the battery case and weld the negative electrode tab to the bottom of the case. After baking at high temperature to remove moisture, inject electrolyte in a dry environment and finally seal the case to ensure that the battery is completely sealed, thus obtaining a 2000mAh cylindrical battery.

[0049] Test its internal resistance and cycling performance under high-rate cycling conditions: the cell is charged to 4.2V at 0.5C constant current and constant voltage, rested for 5 minutes, discharged to 2.75V at 3C constant current, rested for 5 minutes, and cycled 300 times. The initial capacity is compared with the capacity at the 300th cycle, and the capacity retention rate is calculated.

[0050] Low-rate cycling conditions: The cell is charged to 4.2V at a constant current and constant voltage of 0.5C, discharged to 2.75V at a constant current of 1.5C, and cycled for 300 cycles. The initial capacity is compared with the capacity after the 300th cycle to calculate the capacity retention rate.

[0051] Example 1

[0052] This embodiment provides a method for preparing a low-impedance cylindrical battery negative electrode slurry, specifically:

[0053] 1) Weigh the raw materials according to the following mass proportions:

[0054] Graphite (negative electrode active material) 48 parts, conductive agent (conductive carbon black) 1 part, deionized water 2 parts, polyacrylic acid solution (PAA, water-based adhesive, solute mass fraction 20%) 44 parts, styrene-butadiene rubber latex (SBR, solute mass fraction 60%) 3 parts, N-methylpyrrolidone (NMP, organic solvent) 2 parts.

[0055] The weight ratio of graphite, conductive agent, deionized water, PPA solution, SBR emulsion, and N-methylpyrrolidone is 48:1:2:44:3:2.

[0056] 2) Add 75wt% of the PAA solution and conductive agent to a mixer and stir at 33 rpm for 1.2 h to fully pre-disperse the conductive agent and form a conductive network skeleton to obtain slurry I;

[0057] 3) Add graphite and 45wt% of deionized water to slurry I, stir at 33 rpm for 2.2 h to fully mix the active material with the conductive network, and obtain slurry II;

[0058] 4) Add the remaining PAA solution raw material, deionized water raw material, and N-methylpyrrolidone to slurry II, stir at 32 rpm for 1.2 h to fully mix the aqueous and organic solution systems, and obtain slurry III;

[0059] 5) Add SBR emulsion to slurry III and stir at a low speed of 17 rpm for 1.1 h until the slurry is uniform, has good fluidity and is free of lumps, thus obtaining the negative electrode slurry of this embodiment.

[0060] Example 2

[0061] The difference between this embodiment and Embodiment 1 lies in adjusting the proportion of PAA solution in slurry I, the proportion of deionized water in slurry II, and the slurry mixing conditions. Specifically:

[0062] 1) Weigh the raw materials according to the formula in step 1) of Example 1;

[0063] 2) Add 70wt% of the PAA solution and conductive agent to a mixer and stir at 32rpm for 1.2h to fully pre-disperse the conductive agent and form a conductive network skeleton to obtain slurry I;

[0064] 3) Add graphite and 40wt% of deionized water to slurry I, stir at 32 rpm for 2.2 h to fully mix the active material with the conductive network, and obtain slurry II;

[0065] 4) Add the remaining PAA solution raw material, deionized water raw material, and N-methylpyrrolidone to slurry II, stir at 28 rpm for 1.2 h to fully mix the aqueous and organic solution systems, and obtain slurry III;

[0066] 5) Add SBR emulsion to slurry III and stir at a low speed of 16 rpm for 1.1 h until the slurry is uniform, has good fluidity and is free of lumps, thus obtaining the negative electrode slurry of this embodiment.

[0067] Example 3

[0068] The difference between this embodiment and Embodiment 1 lies in adjusting the proportion of PAA solution in slurry I, the proportion of deionized water in slurry II, and the slurry mixing conditions. Specifically:

[0069] 1) Weigh the raw materials according to the formula in step 1) of Example 1;

[0070] 2) Take 80wt% of the total amount of PAA solution raw materials and the conductive agent and add them to the mixer. Stir at 35rpm for 1.2h to fully pre-disperse the conductive agent and form a conductive network skeleton to obtain slurry I;

[0071] 3) Add graphite and 50wt% of deionized water to slurry I, stir at 35 rpm for 2.2 h to fully mix the active material with the conductive network, and obtain slurry II;

[0072] 4) Add the remaining PAA solution raw material, deionized water raw material, and N-methylpyrrolidone to slurry II, stir at 35 rpm for 1.2 h to fully mix the aqueous and organic solution systems, and obtain slurry III;

[0073] 5) Add styrene-butadiene rubber (SBR) emulsion to slurry III and stir at a low speed of 18 rpm for 1.1 h until the slurry is uniform, has good fluidity and is free of lumps, thus obtaining the negative electrode slurry of this embodiment.

[0074] Example 4

[0075] The difference between this embodiment and Embodiment 1 is that the mixing conditions of the slurry are adjusted, specifically:

[0076] 1) Weigh the raw materials according to the formula in step 1) of Example 1;

[0077] 2) Add 75wt% of the PAA solution and conductive agent to a mixer and stir at 35rpm for 1.2h to fully pre-disperse the conductive agent and form a conductive network skeleton to obtain slurry I;

[0078] 3) Add graphite and 45wt% of deionized water to slurry I, stir at 35 rpm for 2.2 h to fully mix the active material with the conductive network, and obtain slurry II;

[0079] 4) Add the remaining PAA solution raw material, deionized water raw material, and N-methylpyrrolidone to slurry II, stir at 35 rpm for 1.2 h to fully mix the aqueous and organic solution systems, and obtain slurry III;

[0080] 5) Add SBR emulsion to slurry III and stir at a low speed of 18 rpm for 1.1 h until the slurry is uniform, has good fluidity and is free of lumps, thus obtaining the negative electrode slurry of this embodiment.

[0081] The relevant performance of the negative electrode slurry prepared in Examples 1 to 4 and the cylindrical lithium-ion batteries prepared therefrom were determined, and the results are shown in Table 2.

[0082] Table 2

[0083] Material Slurry viscosity (mPa·s) Electrode adhesion test (N) Internal resistance (mΩ) 3C high magnification 300 cycles (%) 1.5C low magnification, 300 cycles (%) Example 1 3156 9.58 14.133 83.56 92.46 Example 2 3189 9.45 14.139 82.46 91.23 Example 3 3174 9.39 13.157 83.89 93.19 Example 4 3164 9.26 13.897 83.46 92.55

[0084] As shown in Table 2, under the premise of keeping the slurry formulation and stepwise feeding process unchanged, adjusting parameters such as the pre-dispersion ratio of polyacrylic acid (PAA) solution, the staged addition of deionized water, and the stirring speed can all yield a negative electrode slurry with excellent comprehensive performance. A higher PAA pre-dispersion ratio and a suitable stirring speed are conducive to the full dispersion of the conductive agent, constructing a continuous conductive network, thereby significantly reducing the internal resistance of the electrode. Increasing the addition ratio of deionized water in step three can effectively adjust the rheological properties of the slurry, promote the uniform mixing of active materials and conductive network, and improve the uniformity of electrode structure and long-term cycling stability, especially the capacity retention rate at high rates. Finally, using a lower stirring speed to introduce the SBR emulsion can avoid excessive shearing that damages the integrity of the binder polymer chains, ensuring sufficient adhesion of the electrode sheet. Thus, by controlling the solid-liquid dispersion, homogenization, and bonding processes stepwise, a comprehensive balance of conductivity, mechanical strength, and electrochemical stability is achieved.

[0085] Appendix Figures 1-3 The images show charge-discharge curves and actual photos of the cylindrical battery prepared using the negative electrode slurry in Example 3 of this patent at 0.2C and 0.5C rates. Figure 1 , 2 The curves in the graph are smooth, with no abnormal voltage steps or fluctuations. This indicates that the slurry is uniformly dispersed, forming a stable conductive network and bonding structure, thus its charge-discharge curve is expected to be even smoother.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 1 is that the PAA solution raw material and deionized water raw material are added directly in one step. Specifically:

[0088] 1) Weigh the raw materials according to the formula in step 1) of Example 1;

[0089] 2) Add PAA solution and conductive agent to a mixer and stir at 33 rpm for 1.2 h to obtain slurry I;

[0090] 3) Add graphite to slurry I and stir at 33 rpm for 2.2 h to obtain slurry II;

[0091] 4) Add N-methylpyrrolidone and deionized water to slurry II, stir at 32 rpm for 1.2 h to fully mix the aqueous and organic solutions, and obtain slurry III;

[0092] 5) Add SBR emulsion to slurry III and stir at a low speed of 17 rpm for 1.1 h to obtain the negative electrode slurry of this comparative example.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 1 is that the proportion of PAA solution raw material in slurry I is adjusted. In step 2), 20 wt% of the total amount of PAA solution raw material is taken. The remaining steps are the same as in Example 1 to obtain the negative electrode slurry of this comparative example.

[0095] Comparative Example 3

[0096] The difference between this comparative example and Example 1 is that the stirring speed in steps 2) to 5) is adjusted to 20 rpm, while the remaining steps are the same as in Example 1, to obtain the negative electrode slurry of this comparative example.

[0097] Comparative Example 4

[0098] The difference between this comparative example and Example 1 is that the organic solvent N-methylpyrrolidone in the raw material formulation is omitted, while the remaining steps and processes are the same as in Example 1, to obtain the negative electrode slurry of this comparative example.

[0099] Comparative Example 5

[0100] This comparative example provides another method for preparing negative electrode slurry, using traditional styrene-butadiene rubber (SBR) emulsion and sodium carboxymethyl cellulose (CMC) as both dispersant and binder. Specifically:

[0101] 1) Prepare a 1.7 wt% CMC solution:

[0102] Weigh 17 parts of CMC solid and 83 parts of deionized water. Slowly add the CMC to the deionized water while stirring at low speed to prevent it from agglomerating. After adding, stir at 35 rpm for 1.5 hours and let stand for 3 hours until all air bubbles are eliminated to form a stable gel.

[0103] 2) Take 48 parts of CMC slurry and add them to a mixing pot. Add 1 part of Super P and stir at full strength for 1.2 hours to make it fully mixed and obtain slurry A.

[0104] 3) Add 48 parts graphite and 2 parts deionized water to slurry A and stir vigorously for 2 hours to disperse the slurry evenly, thus obtaining slurry B;

[0105] 4) Add 2 parts NMP to slurry B and stir vigorously for 1.2 hours. Then add 3 parts SBR emulsion and continue stirring for 1 hour until the slurry is uniform and free of lumps, thus obtaining the final negative electrode slurry of this comparative example.

[0106] Comparative Example 6

[0107] The difference between this comparative example and Example 1 is that only the N-methylpyrrolidone (NMP) in the raw materials is replaced with an equal mass of ethanol, while the remaining steps and processes are the same as in Example 1, to obtain the negative electrode slurry of this comparative example.

[0108] Comparative Example 7

[0109] The difference between this comparative example and Example 1 is that the total amount of PAA solution is reduced to 40 parts, while the amount of graphite is increased to 50 parts. All other steps and processes are the same as in Example 1 to obtain the negative electrode slurry of this comparative example.

[0110] The performance of the negative electrode slurries prepared in Comparative Examples 1 to 7 and the cylindrical lithium-ion batteries prepared therefrom were measured and compared with that of Example 1. The results are shown in Table 3.

[0111] Table 3

[0112] Material Slurry viscosity (mPa·s) Electrode adhesion test (N) Internal resistance (mΩ) 3C high magnification 300 cycles (%) 1.5C low magnification, 300 cycles (%) Example 1 3156 9.58 14.133 83.56 92.46 Comparative Example 1 3328 9.14 15.814 72.52 81.46 Comparative Example 2 3445 8.79 15.213 71.46 82.45 Comparative Example 3 3480 6.89 15.468 70.88 81.49 Comparative Example 4 3654 7.67 16.489 72.28 86.47 Comparative Example 5 2769 7.79 14.897 74.26 85.46 Comparative Example 6 3565 8.23 15.546 75.67 80.64 Comparative Example 7 3587 6.54 15.897 75.54 78.86

[0113] Table 3 shows that in Comparative Example 1, adding PAA and deionized water in one step may have resulted in a significant increase in battery internal resistance and a decrease in cycle performance due to the inability to construct an effective initial conductive network. This demonstrates that the stepwise process of first constructing the conductive framework and then introducing the active material is crucial for obtaining a uniform electrode structure. In Comparative Example 2, using only 20% PAA for pre-dispersion resulted in insufficient colloidal material for framework construction, failing to form a stable conductive pathway and leading to a decrease in cycle performance. This highlights the necessity of a higher proportion of PAA during the pre-dispersion stage. In Comparative Example 3, the excessively low stirring speed throughout the process may have resulted in insufficient dispersion force, leading to uneven mixing of components and a significant decrease in slurry performance and electrode adhesion. This underscores the importance of a segmented, moderate stirring process.

[0114] In Comparative Example 4, the system was reverted to a pure aqueous solution, resulting in increased slurry viscosity, decreased flowability, and a maximum internal resistance of 16.489 mΩ. This demonstrates that the introduction of NMP is indispensable for controlling slurry rheology and improving electrode uniformity. Comparative Example 6, which replaced NMP with an equal amount of ethanol, resulted in a significantly lower cycle retention rate at 1.5C compared to Example 1. Furthermore, Comparative Example 7, by reducing the total PAA content, directly led to a decrease in electrode adhesion to 6.54 N and a severe reduction in cycle life. Comparative Example 5, using a conventional CMC / SBR system, significantly outperformed the present invention in both electrode adhesion (7.79 N) and 3C high-rate cycle retention rate (74.26%).

[0115] This invention effectively solves the problem of uneven dispersion of conductive agents through its unique step-by-step processing sequence and hybrid solvent system. The method first pre-disperses the conductive agent with a portion of the binder to construct a stable conductive network framework, ensuring that the conductive agent is fully depolymerized and dispersed, thereby building a uniform conductive network. This significantly reduces the overall and local internal resistance of the negative electrode, fundamentally eliminating localized high impedance points caused by conductive agent agglomeration. This invention forms a unique hybrid solvent system by adding the binder step-by-step and introducing NMP organic solvent. This system can more effectively wet the active material and promote the rearrangement of the binder molecular chains, thereby forming a more uniform and robust bond structure between the active material, conductive agent, and current collector. This not only greatly enhances the mechanical integrity of the electrode and reduces the risk of active material peeling off during cycling, but also further ensures the long-term stability of the conductive network.

[0116] The reduction in electrode internal resistance and the uniformity of current distribution greatly mitigate the risks of localized overcharging and lithium deposition during high-current charging, thereby significantly improving battery charging performance. The uniform charge distribution and robust electrode structure work together to ensure slower capacity decay during long-term cycling, significantly extending battery cycle life.

[0117] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a low-impedance cylindrical battery negative electrode slurry, characterized in that: include, Polyacrylic acid solution and conductive agent, accounting for 70-80 wt% of the total mass of polyacrylic acid solution raw materials, are added to a mixer and stirred to obtain slurry I; Add graphite and 40-50 wt% deionized water (based on the total mass of the deionized water raw material) to slurry I, and stir to obtain slurry II; Add the remaining polyacrylic acid solution, deionized water, and N-methylpyrrolidone from the raw materials to slurry II, and stir to obtain slurry III; Add styrene-butadiene rubber latex to slurry III and stir to obtain negative electrode slurry; The weight ratio of graphite, conductive agent, deionized water, polyacrylic acid solution, styrene-butadiene rubber latex, and N-methylpyrrolidone in the negative electrode slurry raw material is 46~50:0.5~1:2~6:44~48:1~5:2~6.

2. The method for preparing the low-impedance cylindrical battery negative electrode slurry as described in claim 1, characterized in that: The polyacrylic acid solution has a mass concentration of 20-25 wt%, and the styrene-butadiene rubber latex has a solid content of 55-65%.

3. The method for preparing the low-impedance cylindrical battery negative electrode slurry as described in claim 1, characterized in that: The stirring speed for obtaining slurry I is 32~35 rpm, and the stirring time is 1~1.5 h.

4. The method for preparing the low-impedance cylindrical battery negative electrode slurry as described in claim 1, characterized in that: The stirring speed for obtaining slurry II is 32~35 rpm, and the stirring time is 2~2.5 h.

5. The method for preparing the low-impedance cylindrical battery negative electrode slurry as described in claim 1, characterized in that: The stirring speed for obtaining slurry III is 28~35 rpm, and the stirring time is 1~1.5 h.

6. The method for preparing the low-impedance cylindrical battery negative electrode slurry as described in claim 1, characterized in that: The stirring speed for obtaining the negative electrode slurry is 16~18 rpm, and the stirring time is 1~1.2h.

7. The low-impedance cylindrical battery negative electrode slurry prepared by any one of claims 1 to 6, characterized in that: The viscosity of the slurry is 3100~3200 mPa·s, and the adhesion force is >9.2 N.

8. The application of the low-impedance cylindrical battery negative electrode slurry as described in claim 7 in the preparation of cylindrical lithium-ion batteries.

9. A cylindrical lithium-ion battery, characterized in that: The negative electrode slurry according to claim 7 is used.

Images