Negative electrode slurry, method for preparing the same, negative electrode sheet, and cylindrical battery
By introducing anionic and cationic surfactant composite micelles into cylindrical batteries, the problem of uneven electrode wetting was solved, achieving synergistic enhancement of electrode morphology uniformity and interfacial wettability, thereby improving the electrochemical performance of the battery.
Patent Information
- Application Number
- CN202610757567.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-29
- Publication Date
- 2026-08-25
AI Technical Summary
Cylindrical batteries, due to their wound structure, have a large number of electrode layers and dense pores, resulting in a long electrolyte penetration path. This leads to insufficient and uneven electrode wetting, affecting the battery's rate performance and cycle life.
A composite surfactant consisting of anionic and cationic surfactants is introduced into the porous current collector negative electrode system. Through electrostatic interaction, a stable composite micelle is formed, which synergistically enhances the uniformity of electrode morphology and interfacial wettability.
It significantly improves electrode wettability and uniformity, shortens electrolyte penetration time, and enhances battery rate performance and cycle life.
Smart Images
Figure CN122638481A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion cylindrical battery technology, and particularly relates to a negative electrode slurry and its preparation method, a negative electrode sheet and a cylindrical battery. Background Technology
[0002] Cylindrical batteries occupy an important position in electric vehicles, energy storage systems, and other fields due to their high structural strength, high production efficiency, and good consistency. However, the winding structure of cylindrical batteries results in a large number of electrode layers and dense pores. This leads to a long and difficult electrolyte penetration path from the cell ends into the interior, resulting in insufficient and uneven electrode wetting. Insufficient and uneven wetting not only prolongs formation time and reduces production efficiency, but also obstructs lithium-ion transport paths and increases interfacial impedance, severely affecting the battery's rate performance and cycle life.
[0003] Existing technologies attempt to improve the situation through the following approaches: first, using porous current collectors (such as copper foam) to construct capillary channels using their three-dimensional network structure; second, adding a single surfactant to the slurry to reduce the surface tension of the electrolyte; and third, using a mixture of anionic and nonionic surfactants in the slurry to reduce the surface tension of the electrolyte and enhance the wetting performance of the negative electrode. However, the above solutions still have the following technical shortcomings: 1) Although porous current collectors provide space for the expansion of active materials and can quickly and fully wet the battery cell, they cannot improve the uniformity of electrode wetting.
[0004] 2) Single surfactants have a limited mechanism of action, which can only reduce the surface tension of the electrolyte and has limited effect on improving wettability. Moreover, when cationic surfactants are added alone, the surfactant molecules are prone to agglomeration, resulting in uneven electrode morphology and affecting electrochemical performance.
[0005] 3) When anionic surfactants and nonionic surfactants are mixed, phase separation, micelle aggregation, and excessive foaming are likely to occur, which will affect the wettability of the electrolyte and the uniformity of the electrodes. Summary of the Invention
[0006] In view of this, this application provides a negative electrode slurry and its preparation method, a negative electrode sheet, and a cylindrical battery. By introducing a composite surfactant consisting of anionic and cationic surfactants into a porous current collector negative electrode system, the electrostatic interaction and synergistic effect between the two surfactants are utilized to achieve synergistic enhancement of electrode morphology uniformity and interfacial wettability while maintaining the advantages of the three-dimensional network of the porous current collector.
[0007] To achieve the above objectives, this application adopts the following solution: The first aspect of this application provides a negative electrode slurry, comprising an active material, a conductive agent, a binder, a composite surfactant, and water; the composite surfactant comprises anionic surfactant and cationic surfactant, preferably, the anionic surfactant is one or more of sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS); the cationic surfactant is one or more of hexadecyltrimethylammonium bromide (CTAB) and hexadecyltrimethylammonium chloride (CTAC). It should be noted that the -OSO3 in the anionic surfactant SDS molecule... - Or the sulfonate group -SO3 in the SDBS molecule - With cationic surfactants quaternary ammonium cationic head-N + (CH3)3 forms ion pairs through electrostatic attraction, and the hydrophobic chains of the two surfactants intertwine to form stable composite micelles. While CTAB or CTAC tends to agglomerate when added alone, the addition of SDS / SDBS "anchors" CTAB / CTAC molecules within the composite micelles, significantly improving the dispersibility of CTAB / CTAC in the slurry and avoiding uneven morphology caused by localized agglomeration.
[0008] Furthermore, the mass ratio of the anionic surfactant to the cationic surfactant is 1:(0.5-2), preferably, the mass ratio of the anionic surfactant to the cationic surfactant is 1:2.
[0009] Furthermore, the active material includes one or more of the following: natural graphite, artificial graphite, mesophase carbon microspheres, silicon suboxide, soft carbon, and hard carbon. Preferably, the conductive agent includes one or more of graphene, Ketjen black, conductive carbon black, acetylene black, and carbon nanotubes. Preferably, the adhesive includes one or more of styrene-butadiene rubber, polyacrylic acid, sodium carboxymethyl cellulose, and polyacrylonitrile.
[0010] The second aspect of this application provides a method for preparing a negative electrode slurry, comprising the following steps: first, adding a quantitative amount of anionic surfactant to water to dissolve and disperse evenly; then adding active material, conductive agent and binder for thorough mixing; finally adding cationic surfactant and continuing to mix evenly to obtain a negative electrode active slurry.
[0011] It is important to note that, to prevent precipitation and aggregation from the mixing of anions and cations, the anionic surfactants SDS / SDBS are first dissolved in water and added to the slurry. Due to their excellent dispersibility, SDS / SDBS preferentially disperses in the slurry, uniformly adsorbing onto the surfaces of solid particles such as carbon materials and conductive agents, effectively coating all solid particles with a negatively charged template. When the cationic surfactants CTAB / CTAC are subsequently added slowly, they do not aggregate randomly but are attracted by the uniformly dispersed SDS / SDBS in the system. Because SDS / SDBS is already uniformly distributed on every particle surface, the precipitation process is no longer chaotic but proceeds along the "template" set by SDS / SDBS, ultimately resulting in a uniform microstructure.
[0012] Furthermore, the mass ratio of the active material, conductive agent, binder and composite surfactant is (90-96.5):(1-3):(2-6):(0.5-1).
[0013] A third aspect of this application provides a negative electrode sheet, comprising a porous current collector and a negative electrode slurry obtained by the above preparation method coated on the upper and lower surfaces of the porous current collector, wherein the solid content of the negative electrode slurry is 9% to 60%.
[0014] Furthermore, a negative electrode sheet, wherein the porous current collector comprises one or more of copper foam and nickel foam.
[0015] Furthermore, the porosity of the porous current collector is 85-95%, preferably with a specific surface area of 1500-2500 cm². 2 / g, with a pore size of 100–500 μm and a thickness of 20–100 μm.
[0016] Furthermore, the compaction density of the negative electrode sheet is 0.8–1.8 g / cm³. 3 .
[0017] The fourth aspect of this application provides a cylindrical battery, including a battery casing, a battery cell, and an electrolyte. The battery cell is made by a winding process, comprising a positive electrode, a separator, and the aforementioned negative electrode sheet.
[0018] Compared with the prior art, the beneficial effects of this application are: This application introduces anionic and cationic surfactants into a porous current collector anode system and adjusts the ratio of anionic to cationic surfactants to achieve synergistic optimization and form stable composite micelles, thereby obtaining a uniform electrode morphology. The three-dimensional network structure of the porous current collector, such as copper foam, plays a dual role in capillary driving and interface modification, significantly improving electrode wettability. Specifically: 1) Enhanced interfacial activity First, anionic surfactants SDS / SDBS are added to the slurry and uniformly dispersed. Then, cationic surfactants CTAB / CTAC are added and uniformly adsorbed. The resulting composite micelles are oriented at the gas-liquid interface, with their hydrophobic chains facing the gas phase and their hydrophilic head groups facing the liquid phase, which can more effectively reduce the surface tension of the electrolyte. At the same time, the composite micelles can form a more stable adsorption layer at the solid-liquid interface, making the interface modification effect more durable and stable.
[0019] 2) Porous current collectors synergistically improve wettability For example, the three-dimensional interconnected pore network of porous copper current collector foam guides the rapid penetration of electrolyte under capillary force. The composite surfactant further reduces the surface tension of the electrolyte and decreases the contact angle, making it easier for the electrolyte to enter the micron-sized pores. The synergistic effect of both significantly shortens the wetting time.
[0020] In summary, the negative electrode slurry of this application contains a combination of cationic and anionic surfactants, which form ordered composite micelles through electrostatic interactions. These micelles reduce the surface tension of the system and improve wettability on the one hand, and construct a dense and stable composite adsorption layer on the other hand, thus stabilizing the interface. Finally, the negative electrode slurry is coated on the surface of a porous current collector, resulting in a negative electrode sheet with better wetting, more stable dispersion, uniform morphology, and no agglomeration. Attached Figure Description
[0021] Figure 1 The images shown are scanning electron microscope (SEM) images of the negative electrode sheets prepared for Comparative Examples 1, 2, and 2 of this application. a is Comparative Example 2, b is Comparative Example 1, and c is Example 2. Detailed Implementation
[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0023] Example 1 Preparation of the negative electrode slurry: First, the anionic surfactant SDS is fully dissolved in deionized water and dispersed evenly. Then, artificial graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber are added and thoroughly mixed. Finally, the cationic surfactant CTAB is added and mixed evenly to obtain the negative electrode active slurry. The mass ratio of SDS to CTAB in the composite surfactant is 1:1. The mass ratio of artificial graphite, conductive carbon black, sodium carboxymethyl cellulose, styrene-butadiene rubber, and composite surfactant is 95.8:1:1.2:1.4:0.6. The resulting negative electrode slurry has a solid content of 57% and its viscosity is adjusted to 4920 mPa·s.
[0024] The prepared negative electrode slurry was coated onto the copper foam. The vacuum system was activated, and the pressure was evacuated to -0.1 MPa and maintained for 10 minutes to allow the negative electrode slurry to fully penetrate into the pores of the copper foam. The copper foam current collector has a porosity of 90%, a pore size of 300 μm, and a specific surface area of 2000 cm². 2 / g, with a thickness of 20μm. The vacuum was then slowly released. This process was repeated three times. The coated negative electrode was then dried and rolled to obtain a compacted density of 1.65mg / cm³. 3 The negative electrode plate.
[0025] Example 2 The difference between this embodiment and Embodiment 1 is that the composite surfactant uses an SDS:CTAB mass ratio of 1:2, while the rest is the same as in Embodiment 1.
[0026] Example 3 The difference between this embodiment and Embodiment 1 is that the composite surfactant uses an SDS:CTAB mass ratio of 2:1, while the rest is the same as in Embodiment 1.
[0027] Example 4 The difference between this embodiment and Embodiment 1 is that the composite surfactant is SDBS and CTAC in a mass ratio of 1:2, and the rest is the same as in Embodiment 1.
[0028] Comparative Example 1 The difference between this embodiment and Embodiment 1 is that the composite surfactant is replaced with SDS and CTAB is not added; otherwise, it is the same as Embodiment 1.
[0029] Comparative Example 2 The difference between this embodiment and Embodiment 1 is that the composite surfactant is replaced with CTAB and SDS is not added; otherwise, it is the same as Embodiment 1.
[0030] Comparative Example 3 The difference between this embodiment and Embodiment 1 is that no composite surfactant is added, and the mass ratio of artificial graphite, conductive carbon black, sodium polymethyl cellulose, and styrene-butadiene rubber is 96.4:1:1.2:1.4. The rest is the same as in Embodiment 1.
[0031] Comparative Example 4 The difference between this embodiment and Embodiment 1 is that traditional copper foil is used instead of foamed copper current collector; otherwise, they are the same as in Embodiment 1.
[0032] The positive electrode sheet is prepared using the following method: Positive electrode preparation: Lithium iron phosphate (LiFePO4), conductive carbon black (SuperP), and polyvinylidene fluoride (PVDF) (binder) are dispersed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 95:2:3 and stirred until homogeneous to form a positive electrode slurry with a solid content controlled at 65–75%. The positive electrode slurry is then uniformly coated onto a 12 μm thick aluminum foil current collector. After drying, it is rolled to obtain the positive electrode sheet.
[0033] Electrolyte preparation: Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) are mixed in a volume ratio of 1:1:1 to form an organic solvent. Fluoroethylene carbonate (FEC) is added to the mixed solvent at a volume of 5%. Thoroughly dried lithium hexafluorophosphate (LiPF6) is dissolved in the above mixed solvent at a concentration of 1.0 mol / L.
[0034] The diaphragm is a polypropylene diaphragm with a thickness of 9 μm.
[0035] The above-described embodiments and comparative examples were combined with a positive electrode to fabricate LR46120 cylindrical lithium-ion batteries, and their electrochemical performance was tested. The test results are shown in Table 1.
[0036] Test method: 1. Wetting Test: Cut the prepared negative electrode sheet into 5cm×5cm squares, place them in 50mL of electrolyte, and record the time required for the electrolyte to completely wet the negative electrode sheet. The criterion for successful wetting is that the electrolyte is completely spread on the electrode surface without any dry spots.
[0037] 2. Rate performance test: Charge and discharge tests were conducted at 2C and 5C rates, and the capacity retention rate was recorded.
[0038] 3. Cyclic testing: Cyclic testing was conducted at a current density of 1C at a room temperature of 25±2℃, and the capacity retention rate after 500 cycles was calculated.
[0039] Table 1 shows the performance test results of Examples 1-4 and Comparative Examples 1-4.
[0040] Test Result Analysis: As shown in Table 1, the wetting time of Examples 1-4 was 10-12 seconds, which was significantly better than that of Comparative Example 4 (65 seconds) and Comparative Example 3 (48 seconds), and also better than that of Comparative Example 1 (16 seconds) and Comparative Example 2 (22 seconds). Among them, Example 2 (SDS:CTAB=1:2) had the shortest wetting time, at only 10 seconds. This indicates that the synergistic effect of the foamed copper current collector and the composite surfactant significantly accelerated the electrolyte penetration, and the optimal ratio was 1:2.
[0041] The initial coulombic efficiency of Examples 1-4 was 93-95%, which was higher than that of Comparative Example 1 (91%), Comparative Example 2 (89%) and Comparative Example 3 (87%), indicating that the composite surfactant reduced the irreversible capacity loss during the SEI film formation process.
[0042] Examples 1-4 exhibited capacity retention rates of 93-95% at 2C and 86-87% at 5C, both superior to the comparative examples. Example 2 showed the best retention rates at 95% at 2C and approximately 87% at 5C. This is attributed to the uniform conductive network and low interfacial impedance constructed by the composite surfactant.
[0043] Examples 1-4 showed a capacity retention rate of 92-95% after 500 cycles, which was significantly higher than that of Comparative Example 1 (90%), Comparative Example 2 (86%) and Comparative Example 3 (84%), indicating that the composite surfactant helps maintain the integrity of the electrode structure and the stability of the SEI film.
[0044] Test results show that the present invention, through the synergistic effect of the copper foam current collector and the SDS-CTAB composite surfactant, significantly shortens the wetting time (10-12 seconds), improves the initial coulombic efficiency (93-95%) and cycle stability (92-95% retention rate after 500 cycles), and its overall performance is superior to that of the comparative examples. Meanwhile, the combination of SDBS and CTAC (Example 4) also leverages the electrostatic attraction and synergistic effect between the anionic and cationic surfactants to achieve enhanced wettability and improved electrochemical performance. This indicates that the technical solution of the present invention has good universality.
[0045] To further verify that the combined use of cationic and anionic surfactants in the negative electrode slurry and their synergistic coating on porous copper current collector foam resulted in a negative electrode sheet with better wetting, more stable dispersion, uniform morphology, and no agglomeration, scanning electron microscopy (SEM) was used to characterize the morphology of negative electrode sheets prepared with different surfactant systems. Figure 1 As shown.
[0046] SEM image a of Comparative Example 2 (CTAB only) shows obvious surfactant aggregation on the electrode surface, with unevenly sized blocky aggregates appearing between graphite particles, resulting in an overall non-uniform morphology. This is due to the self-aggregation of CTAB molecules during the slurry drying process.
[0047] SEM image b of Comparative Example 1 (with only SDS added) shows that the electrode surface morphology is relatively uniform and there are no obvious agglomerates, indicating that SDS has good dispersion performance.
[0048] SEM image c of Example 2 (composite addition of SDS and CTAB) shows that the electrode surface morphology is further improved, exhibiting a uniform, dense, and continuous structural feature, and the aggregation of CTAB is significantly suppressed. This is attributed to the formation of stable composite micelles by SDS and CTAB through electrostatic attraction, which allows CTAB to be uniformly dispersed in the slurry.
[0049] In summary, SEM morphology analysis results indicate that the combined use of SDS and CTAB produces a synergistic effect between anions and cations. SDS effectively improves the dispersibility of CTAB in the slurry, avoiding the agglomeration phenomenon that occurs when CTAB is added alone, resulting in a uniform and dense electrode morphology. This provides a structural basis for rapid electrolyte wetting and uniform lithium-ion transport. This morphology improvement is one of the important reasons for the significant improvement in the wettability and electrochemical performance of the negative electrode in this application.
[0050] The foregoing has shown and described the preferred embodiments of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.
[0051] Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.
[0052] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A negative electrode slurry, characterized in that, It includes active materials, conductive agents, binders, composite surfactants, and water; the composite surfactants include anionic surfactants and cationic surfactants, preferably, the anionic surfactant is one or more of sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS); the cationic surfactant is one or more of hexadecyltrimethylammonium bromide (CTAB) and hexadecyltrimethylammonium chloride (CTAC).
2. The negative electrode slurry according to claim 1, characterized in that, The mass ratio of the anionic surfactant to the cationic surfactant is 1:(0.5-2), preferably 1:
2.
3. The negative electrode slurry according to claim 1, characterized in that, The active material includes one or more of the following: natural graphite, artificial graphite, mesophase carbon microspheres, silicon suboxide, soft carbon, and hard carbon. Preferably, the conductive agent includes one or more of graphene, Ketjen black, conductive carbon black, acetylene black, and carbon nanotubes. Preferably, the adhesive includes one or more of styrene-butadiene rubber, polyacrylic acid, sodium carboxymethyl cellulose, and polyacrylonitrile.
4. A method for preparing a negative electrode slurry, characterized in that, Includes the following steps: First, a certain amount of anionic surfactant is added to water to dissolve and disperse evenly. Then, active material, conductive agent and binder are added and mixed thoroughly. Finally, cationic surfactant is added and mixed evenly to obtain negative electrode active slurry.
5. The method for preparing the negative electrode slurry according to claim 4, characterized in that, The mass ratio of the active material, conductive agent, binder and composite surfactant is (90-96.5):(1-3):(2-6):(0.5-1).
6. A negative electrode sheet, characterized in that, The present invention includes a porous current collector and a negative electrode slurry prepared by the preparation method described in claim 5, which is coated on the upper and lower surfaces of the porous current collector, wherein the solid content of the negative electrode slurry is 9% to 60%.
7. The negative electrode sheet according to claim 6, characterized in that, The porous current collector includes one or more of copper foam and nickel foam.
8. The negative electrode sheet according to claim 6, characterized in that, The porous current collector has a porosity of 85-95%, preferably a specific surface area of 1500-2500 cm². 2 / g, with a pore size of 100–500 μm and a thickness of 20–100 μm.
9. The negative electrode sheet according to claim 6, characterized in that, The compacted density of the negative electrode sheet is 0.8–1.8 g / cm³. 3 .
10. A cylindrical battery, characterized in that, The battery includes a battery casing, a battery cell, and an electrolyte. The battery cell is manufactured by a winding process, comprising a positive electrode, a separator, and a negative electrode sheet as described in any one of claims 6-9.