High voltage resistant dispersion polymer, conductive paste dispersion polymer, conductive paste and electrode paste, and methods of making same

Abstract

The application discloses a high-voltage-resistant dispersion polymer, conductive paste dispersion polymer, conductive paste and electrode paste and a preparation method thereof. The high-voltage-resistant dispersion polymer comprises at least two components, including an A component as an anchor point and an alkane B component for reducing the rigidity of the polymer; the energy level difference between the HOMO energy level and the LUMO energy level of the A component is not less than 0.1, the energy level difference between the HOMO energy level and the LUMO energy level of the B component is not less than 0.2, and the molecular weight of the B component is 120-200. The A component is used for enhancing the combination function of the dispersion polymer and CNT; the B component reduces the rigidity of the dispersion polymer and is better dissolved in a solvent. The energy levels of the A component and the B component are controlled, the CNT can exist under the premise of the acting force, and the dispersion polymer can also be dissolved in the solvent of the conductive paste. The battery prepared by using the carbon nanotube conductive paste containing the dispersion polymer has excellent high-voltage resistance and electrical cycle performance.

Description

Technical Field

[0001] This invention relates to the field of battery applications, and in particular to a high-voltage resistant dispersion polymer, a conductive slurry dispersion polymer, a conductive slurry and an electrode slurry, and a method for preparing the same. Background Technology

[0002] Conductive agents are a crucial component of lithium-ion batteries, primarily functioning to improve electronic conductivity. To ensure good charge-discharge performance of the electrodes, a certain amount of conductive agent is typically added during electrode fabrication. This provides additional contact points for the active electrode particles, reducing contact resistance between electrode materials. It plays a vital role in improving battery cycle performance, capacity, and rate performance. Furthermore, conductive agents can improve electrode processability, promote electrolyte wetting of the electrodes, and effectively increase the migration rate of lithium ions in the electrode materials, reducing polarization and thus improving charge-discharge efficiency and the lifespan of the lithium-ion battery. Like lithium-ion battery electrode materials, conductive agents are constantly evolving. From the earliest carbon black materials, characterized by point-like conductive agents (also known as zero-dimensional conductive agents), which primarily improve conductivity through point contact between particles; to later developments such as conductive carbon fibers and carbon nanotubes, which possess one-dimensional structures. Due to their fibrous structure, these agents increase contact with electrode material particles, significantly improving electrode conductivity and reducing electrode resistance.

[0003] Compared to traditional particulate conductive agents (carbon black, graphite, acetylene black, etc.), carbon nanotubes (CNTs), as typical one-dimensional carbon nanomaterials, possess excellent electrical and thermal conductivity, a high aspect ratio, and a mesoporous structure that facilitates lithium-ion shuttle passage. They can form an effective three-dimensional highly conductive network between battery active materials at relatively low addition amounts, thus holding promise as a replacement for traditional particulate conductive agents in the design and manufacturing of high-end lithium batteries. However, due to the strong π-π interactions and van der Waals forces between CNT bundles, currently commercially available CNTs need to be used in conjunction with polymers that provide dispersion, prepared into various slurries through processes such as milling and ultrasonication, and ultimately applied to lithium batteries in slurry form. Therefore, the various physicochemical properties of the dispersant polymer will directly or indirectly affect the cycle life and stability of lithium batteries.

[0004] Currently, physical dispersants for CNTs can be broadly classified into two categories: polymers and amphiphilic small molecule compounds. Amphiphilic small molecule compounds, such as sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfate (SDBS), sterol activators, porphyrins, and ammonium bromide-modified aromatic small molecule compounds, often contain charged or active groups (-OH, -COOH, etc.) in their structures. These active groups are unstable under electrochemical reactions due to redox reactions, and therefore are rarely used in lithium batteries. High molecular weight polymers, such as polyvinylpyrrolidone (PVPK30) and carboxymethyl cellulose (CMC), exhibit better stability in electrochemical reactions and are therefore widely used.

[0005] With the rapid development of the lithium battery industry, the market is placing increasingly higher demands on the cycle life and high voltage resistance of lithium batteries. Commonly used polyvinylpyrrolidone (PVPK30) is not suitable for high voltage, and current application requirements place higher demands on the high voltage resistance and cycle life of CNT dispersants. However, developing a qualified CNT polymer dispersant involves many technical barriers, requiring consideration of numerous factors during development, such as solvent solubility, CNT encapsulation, compatibility with cathode materials, and contact with cathode materials. Based on these factors, there is currently a lack of commercially available technologies that utilize CNTs as conductive agents to achieve high cycle life and are capable of mass production, necessitating urgent improvement. Summary of the Invention

[0006] In order to enable the battery to have high cycle characteristics, this application provides a high-voltage resistant dispersion polymer, a conductive slurry and an electrode slurry, and a method for preparing the same.

[0007] In a first aspect, this application provides a high-voltage resistant dispersion polymer, the polymer comprising at least two components, wherein the two components include an A component as an anchor point and an alkane B component to reduce the rigidity of the polymer; the energy level difference between the HOMO and LUMO levels of the A component is not less than 0.1, the energy level difference between the HOMO and LUMO levels of the B component is not less than 0.2, and the molecular weight of the B component is 120-200.

[0008] Those skilled in the art are well aware that there are many technical barriers to developing qualified CNT dispersion polymers. Numerous factors need to be considered during development, such as solvent solubility, CNT encapsulation, compatibility with electrode active materials, and contactability with electrode active materials. In reality, the sheer number of factors has led to development stagnation and created many technical barriers. The technical solution of this application divides the carbon nanotube dispersion polymer into two modules. Component A of module 1 can adsorb CNTs, enhancing the binding function between the dispersion polymer and CNTs. Component B of module 2 reduces the rigidity of the dispersion polymer, allowing it to dissolve better in the solvent of the conductive slurry. Furthermore, the energy level difference between the HOMO and LUMO levels of component A is controlled to be no less than 0.1, and the energy level difference of component B is no less than 0.2, with a molecular weight of 120-200, thereby improving the high-voltage resistance of the dispersion polymer. The carefully selected small-molecule synthesized dispersion polymer, while maintaining interaction with CNTs, also dissolves in the solvent of the conductive slurry. Batteries made using this dispersion polymer exhibit excellent high-voltage resistance and electrocycle performance.

[0009] Preferably, component A has an aromatic ring structure with a large π electron cloud or a cyano compound structure, and component B has an organic small molecule structure with a branched alkane or a long straight-chain alkane.

[0010] Preferably, the aromatic ring structure of the large π electron cloud includes a benzene ring, biphenyl, naphthalene ring, anthracene ring, perylene ring, ester-based five-membered ring, or oxygen-containing six-membered ring; the organic small molecule structure includes a long-chain alkane molecule structure with carbon-carbon double bonds.

[0011] Furthermore, component A is composed of

[0012] Preferably, the flexible molecule of component B is an oxygen-containing long-chain alkane, and the repeating unit is methylene (-CH2-) or bis(ethoxy) (-CH2-CH2-O-).

[0013] Furthermore, component B is

[0014] The development of CNT polymer dispersants faces numerous challenges, such as solubility, chemical stability, and CNT encapsulation. To meet these requirements, researchers need to experiment extensively with various organic molecules and combinations with different functional groups, resulting in a massive workload. For companies with current R&D capabilities, verifying these features through numerous experiments is difficult, both in terms of human and financial resources and the operational efficiency of manufacturing companies. However, through further optimization of the functional groups, the inventors have achieved good solubility of the aforementioned monomer compounds and polymers in conductive paste solvents, further improving the battery's electrocycle performance.

[0015] Furthermore, the energy level difference between the HOMO and LUMO levels of component A is 0.1-0.24, and the energy level difference between the HOMO and LUMO levels of component B is 0.2-0.23.

[0016] Secondly, this application provides a method for preparing a high-voltage resistant dispersed polymer, wherein the above-mentioned component A, the above-mentioned component B, and the initiator are mixed evenly in a molar ratio of 1:(0.1-3):(0.0005-0.01), and then reacted under a nitrogen atmosphere for 7-20 hours, with the reaction temperature controlled at 50-110℃.

[0017] Furthermore, the reaction temperature is controlled between 50-90℃.

[0018] By controlling the molar ratio of component A, component B, and initiator, and by limiting the reaction atmosphere, temperature, and reaction time, the resulting dispersed polymer has good purity, which further improves the battery's electric cycle performance and high voltage resistance.

[0019] The initiator can be selected from photoinitiators, thermal initiators, or ionic initiators depending on the actual situation.

[0020] Thirdly, this application provides a method for preparing a conductive paste dispersion polymer, wherein the above-mentioned component A, the above-mentioned component B, and the initiator are mixed in a molar ratio of 1:(0.5-2):(0.0005-0.005) and then a solvent is added, and the reaction is carried out under a nitrogen atmosphere for 7-20 hours, with the reaction temperature controlled at 50-90℃.

[0021] When preparing conductive slurry dispersion polymers, components A and B, along with an initiator, are added in a specific molar ratio for polymerization, followed by the addition of a solvent—the solvent used in lithium batteries. Adding a solvent during the preparation of the dispersion polymer allows for a rapid determination of whether the polymer dissolves in the solvent and is suitable for dispersion in lithium batteries. Utilizing the principle of "like dissolves like," the solubility of the prepared dispersion polymer in the solvent can be quickly identified during the reaction process, enabling the rapid selection of a suitable dispersion polymer and determining whether the ratio of components A and B is appropriate.

[0022] Preferably, the solvent is NMP (pyrrolidone).

[0023] NMP solvent is a common solvent used in lithium battery cathodes and slurries, which can quickly determine whether the above-mentioned dispersion polymer is suitable for lithium battery cathodes.

[0024] Fourthly, this application provides a conductive slurry containing the above-mentioned dispersing polymer, comprising the high-voltage resistant dispersant, carbon nanotubes and solvent, wherein the mass ratio of the carbon nanotubes to the high-voltage resistant dispersant is (1-5):1.

[0025] By rationally controlling the ratio between the dispersing polymer and CNTs in this application, the polymer can generate interaction forces with the CNTs, while ensuring that the polymer molecules have sufficient flexibility so that they can be adsorbed or wrapped around the CNT surface in the solvent to achieve the dispersion effect.

[0026] Preferably, the conductive slurry is obtained by grinding and dispersing the dispersion polymer and CNTs.

[0027] During grinding, the relatively high-speed rotation causes the dispersed polymer and CNTs to be processed to be pressurized by external pressure (which can be generated by a pump) to generate a downward spiral impact force. As they pass through the gap between the colloid mill teeth, they are subjected to strong shearing force, friction, high-frequency vibration and other physical effects, which effectively emulsifies, disperses and pulverizes the carbon nanotubes. This allows the dispersed polymer and carbon nanotubes to combine more fully and uniformly to form a conductive slurry with stable conductivity.

[0028] Fifthly, this application provides an electrode paste containing the above-mentioned conductive paste, which is composed of the conductive paste, a conductive active material and a binder; wherein the amount of carbon nanotube conductive paste added is 0.5-2%.

[0029] When the conductive slurry prepared in this application is used in electrode slurry, it can be well dispersed in the electrode active material, and the resulting electrode slurry has a uniform texture. When applied to a battery, it enables the battery to have excellent high voltage resistance and electric cycle performance.

[0030] In summary, this application, through ingenious design of polymer units, synthesizes polymers that can generate interaction forces with CNTs, while ensuring sufficient flexibility of the polymer molecules, enabling them to adsorb or entangle on the CNT surface in a solvent to achieve dispersion. The battery pouch prepared using this method showed no capacity decay after 500 cycles at room temperature with high voltages of 2.8-4.35V; at 45℃, the capacity retention rate after 500 cycles was approximately 95%, with an expected cycle life of 1500-2000 cycles, demonstrating excellent high-voltage resistance and electrocycling performance.

[0031] Technical effects:

[0032] 1. The dispersion polymer described in this application has a good adsorption force with carbon nanotubes through the anchoring effect of component A, and the dispersion polymer has better flexibility by using component B to reduce the rigidity of the polymer, so that it can adsorb or wrap around the surface of carbon nanotubes in the solvent to achieve the dispersion effect.

[0033] 2. The dispersion polymer designed in this application has high voltage resistance, which better meets market demand.

[0034] 3. By adding commonly used lithium battery solvents when preparing conductive slurry dispersion polymers, it is possible to more quickly select the appropriate conductive slurry dispersion polymer for lithium batteries. At the same time, it is possible to determine whether the ratio of A and B is appropriate. If it is not appropriate, it will be difficult to dissolve in the solvent.

[0035] 4. The lithium battery electrode sheet uses an electrode slurry prepared with the dispersed polymer described in this application, which has good high voltage resistance. Compared with the prior art, the battery can still have a high retention rate after 500 cycles in a voltage window of 2.8-4.35V. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the internal structure of a battery.

[0037] Figures 2-4 The images show GPC test data for polymer PSD11 from Example 1, polymer AN1821 from Example 4, and polymer PNA308 from Example 5.

[0038] Figures 5-10 The images show the state diagrams of the carbon nanotube-dispersed polymer solutions in Examples 1-5 and Comparative Example 1, respectively.

[0039] Figure 11-13 The images shown are, in order, the state diagrams of the conductive paste LB108-44-PSD11 prepared in Example 1, the conductive paste LBCNT-PS prepared in Comparative Example 2, and the conductive paste LBCNT-PD prepared in Comparative Example 3 after grinding.

[0040] Figure 14-16 The images shown are, in order, electron microscope images of the conductive pastes LB108-44-PSD11, LB108-44-AN1821, and LB108-44-PNA308 prepared in Examples 6-8, magnified at 25,000x and 10,000x respectively.

[0041] Figures 17-19 The figures are, respectively, the positive electrode resistivity box plot, the bulk resistivity box plot, and the full cell internal resistance box plot prepared in Example 11 (LB108-44-PSD11) and Comparative Example 4 (LB108-44-PVP).

[0042] Figure 20 and Figure 21 The graphs show the cycle capacity retention rate and battery capacity of the pouch cells prepared in Example 11 and Comparative Example 4 at 25°C, respectively. The solid and dashed lines at the top of the graphs represent Example 11, and the solid and dashed lines at the bottom represent Comparative Example 4.

[0043] Figure 22 and Figure 23The graphs show the cycle capacity retention rate and battery capacity of the pouch cells prepared in Example 11 and Comparative Example 4 at 45°C, respectively. The solid and dashed lines at the top of the graphs represent Example 11, and the solid and dashed lines at the bottom represent Comparative Example 4.

[0044] Figure 24 and Figure 25 The figures are charge-discharge curves of the pouch cells prepared in Example 11 and Comparative Example 4, respectively, after 500 cycles at high voltage and 25°C and 45°C.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1. Shell; 2. Positive tab; 3. Negative tab; 4. Cell; 41. Positive electrode plate; 42. Separator; 43. Negative electrode plate. Detailed Implementation

[0047] Example

[0048] Example 1

[0049] This embodiment provides a carbon nanotube dispersant polymer: Under nitrogen protection, styrene (4.0 g, 38.5 mmol), butyl methacrylate (BM, 5.5 g, 38.5 mmol), and 10 mg of azobisisobutyronitrile (AIB) were dissolved in 15 mL of NMP. The solution was purged with nitrogen three times, sealed with adhesive tape, and reacted at 60°C for 16 h to obtain polymer PSD11. See the GPC detection chart for details. Figure 2 For a detailed polymer solution state diagram, please refer to [link / reference]. Figure 5 The solution was homogeneous and clear, indicating that the polymer PSD has excellent solubility in the organic solvent NMP, further demonstrating that the polymer dispersant can dissolve better in conductive slurry.

[0050] The reaction equation is:

[0051]

[0052] Example 2

[0053] Under nitrogen protection, styrene (6.0 g, 57.7 mmol), butyl methacrylate (5.5 g, 38.5 mmol), and 11 mg of azobisisobutyronitrile (AIB) were dissolved in 15 mL of NMP. The solution was purged with nitrogen three times, sealed with adhesive tape, and reacted at 60 °C for 16 h to obtain polymer PSD32. See the polymer solution phase diagram for details. Figure 6 The solution was homogeneous and clear, indicating that polymer PSD32 has excellent solubility in the organic solvent NMP, further demonstrating that the polymer dispersant can dissolve better in conductive slurry.

[0054] Example 3

[0055] Under nitrogen protection, styrene (4.0 g, 38.5 mmol), butyl methacrylate (8.2 g, 57.7 mmol), and 12 mg of azobisisobutyronitrile (AIB) were dissolved in 15 mL of NMP. The solution was purged with nitrogen three times, sealed with adhesive tape, and reacted at 60 °C for 16 h to obtain polymer PSD23. See the polymer solution phase diagram for details. Figure 7 The solution was homogeneous and clear, indicating that polymer PSD23 has excellent solubility in the organic solvent NMP, further demonstrating that the polymer dispersant can dissolve better in conductive slurry.

[0056] Example 4

[0057] Under nitrogen protection, acrylonitrile (2.0 g, 37.7 mmol), octadecyl methacrylate (6.38 g, 18.8 mmol), and 10 mg of azobisisobutyronitrile (AIB) were dissolved in 15 mL of NMP. The solution was purged with nitrogen three times, sealed with adhesive tape, and reacted at 60 °C for 16 h to obtain polymer AN1821. See the GPC chromatogram for details. Figure 3 For a detailed polymer solution state diagram, please refer to [link / reference]. Figure 8 The solution was homogeneous and clear, indicating that polymer AN1821 has excellent solubility in the organic solvent NMP, further demonstrating that the polymer dispersant can dissolve better in conductive slurry.

[0058] The reaction equation is:

[0059]

[0060] Example 5

[0061] This embodiment provides a carbon nanotube dispersant polymer: Under nitrogen protection, acrylonitrile (3.0 g, 56.5 mmol), N-vinylpyrrolidone (6.3 g, 56.5 mmol), and 9 mg of azobisisobutyronitrile (AIB) were dissolved in 30 mL of NMP. The solution was purged with nitrogen three times, sealed with adhesive tape, and reacted at 60°C for 8 h to obtain polymer PNA308. See the GPC detection chart for details. Figure 4 For a detailed polymer solution state diagram, please refer to [link / reference]. Figure 9 This indicates that polymer PNA308 has excellent solubility in the organic solvent NMP, further demonstrating that the polymer dispersant can dissolve better in conductive slurries.

[0062] The reaction equation is:

[0063]

[0064] Example 6

[0065] This embodiment provides a conductive paste: 4.0 g of polymer PSD11, 16.0 g of carbon nanotubes FT6812 (Tiannai Technology Co., Ltd.), and 315 g of NMP from Example 1 were placed in a sand mill. The milling speed was adjusted to 3000 rpm / min, and after milling for 2 hours, the conductive paste LB108-44-PSD11 was collected. The CNT content was 4 wt%. The particle size and viscosity of the conductive paste are shown in Table 1. The state diagram of the conductive paste after milling is shown in [Figure 1]. Figure 11 With the addition of PSD11, CNTs in the conductive paste can be ground to a particle size D50 < 0.07 μm, and the conductive paste is fine and uniform, indicating that CNTs have good dispersibility in the conductive paste under the action of polymer PSD11.

[0066] Example 7

[0067] This embodiment provides a conductive paste, which differs from Embodiment 6 in that: polymer PSD11 is replaced by an equal mass of polymer PSD32 from Embodiment 2 to obtain conductive paste LB108-44-PSD32 (CNT content is 4wt%).

[0068] Example 8

[0069] This embodiment provides a conductive paste, which differs from Embodiment 6 in that: polymer PSD11 is replaced by an equal mass of polymer PSD23 from Embodiment 3 to obtain conductive paste LB108-44-PSD23 (CNT content is 4wt%).

[0070] Example 9

[0071] This embodiment provides a conductive paste, which differs from Embodiment 6 in that: polymer PSD11 is replaced by an equal mass of polymer AN1821 from Embodiment 4 to obtain conductive paste LB108-44-AN821 (CNT content is 4wt%).

[0072] Example 10

[0073] This embodiment provides a conductive paste containing polymer PNA308. The difference from Example 6 is that polymer PNA308 from Example 5 is used to replace polymer PSD11 by the same mass to obtain conductive paste LB108-44-PNA308 (CNT content is 4wt%).

[0074] Examples 11-15

[0075] This embodiment provides a soft-pack battery, including a casing 1, a positive electrode tab 2, a negative electrode tab 3, and an electrolyte. The casing 1 contains a battery cell 4 that is fixedly connected to the positive electrode tab 2 and the negative electrode tab 3. The battery cell 4 is formed by stacking the positive electrode plate 41, the separator 42, and the negative electrode plate 43 sequentially according to a specified height.

[0076] The positive electrode sheet 41 is prepared as follows: a conductive paste (CNT, 4 wt%) is mixed with a positive electrode material (lithium nickel cobalt manganese oxide NMC532, 97.8 wt%) and a binder (polyvinylidene fluoride PVDF5130, 1.5 wt%), and stirred at high speed for 40 min to disperse evenly, thereby obtaining a positive electrode paste (CNT, 0.7 wt%). The positive electrode paste is then uniformly coated onto an aluminum foil and baked dry to obtain the positive electrode sheet 41.

[0077] The negative electrode sheet 43 is prepared as follows: conductive paste (CNT, 4wt%) is mixed with negative electrode material (artificial graphite FSNC-1:SP:CMC:SBR = 95.5:1:1.1:2.4) and binder, and stirred at high speed for 40 minutes to disperse evenly, thereby obtaining a negative electrode paste (CNT, 0.5wt%). The negative electrode paste is then uniformly coated onto aluminum foil and baked dry to obtain the negative electrode sheet 43.

[0078] The processing method of the soft-pack battery is as follows: the cut positive and negative electrode sheets and separator 42 are stacked layer by layer. After stacking to the specified height, the stacked battery cell 4 is covered with separator 42. The positive electrode tabs 2 and negative electrode tabs 3 on both sides of the battery cell 4 are welded, and the top and side seals are completed using aluminum-plastic film. After the electrolyte (Tienci TC-8633) is injected for formation, the battery is sealed and vented to complete the preparation.

[0079] The conductive pastes used in Examples 11-15 are the conductive pastes prepared in Examples 6-10, respectively.

[0080] The box plots of resistivity of the positive electrode sheet, the bulk resistivity of the positive electrode sheet, and the internal resistance of the full cell prepared in Example 11 (LB108-44-PSD11) are as follows: Figures 17-19 The battery's cycle capacity retention and battery capacity at 25°C were tested, and the results are detailed in [link to test results]. Figure 20 and Figure 21 The battery's cycle capacity retention and capacity at 45℃ were tested; the results are detailed in [link to results]. Figure 22 and Figure 23 .

[0081] Comparative Example

[0082] Comparative Example 1

[0083] The difference from Example 1 is that an equimolar amount of octadecyl methacrylate was used instead of butyl methacrylate in the carbon nanotube dispersion polymer, resulting in dispersion polymer PSD1811. See the polymer solution state diagram for details. Figure 10 The solution directly separates into layers, indicating that the polymer PSD1811 is insoluble in the organic solvent NMP, further demonstrating that PSD1811 is difficult to dissolve in conductive pastes.

[0084] Reaction equation:

[0085]

[0086] Comparative Example 2

[0087] The difference from Example 1 is that the preparation method of the carbon nanotube dispersed polymer is as follows: under nitrogen protection, styrene (4.0 g) and 4 mg of azobisisobutyronitrile were dissolved in 15 mL of NMP, nitrogen was replaced 3 times, and after sealing with adhesive tape, the mixture was placed at 60 °C for 16 h to obtain polymer PS.

[0088] 16.0 g of carbon nanotubes FT6812 (Tiannai Technology Co., Ltd.), 4.0 g of PS, and 315 g of NMP were placed in a sand mill. The milling speed was adjusted to 3000 rpm / min, and after milling for 2 hours, the CNT conductive paste LBCNT-PS was collected to fabricate a soft-pack battery. The state diagram of the conductive paste after milling is shown below. Figure 12 When PS is added, CNTs in the conductive paste are not well dispersed, and the conductive paste has obvious coarse particles that are difficult to stir, indicating that CNTs are poorly dispersed in the conductive paste under the action of the polymer PS.

[0089] Comparative Example 3

[0090] The difference from Example 1 is that, under nitrogen protection, butyl methacrylate (4.0 g) and 4 mg of azobisisobutyronitrile were dissolved in 15 mL of NMP, purged with nitrogen three times, sealed with adhesive tape, and reacted at 60 °C for 16 h to obtain polymer PD.

[0091] Take 16.0g of carbon nanotubes FT6812 (Tiannai Technology Co., Ltd.), 4.0g of PD and 315g of NMP and place them in a sand mill. Adjust the sand mill speed to 3000rpm / min and grind for 2 hours. Then collect the CNT conductive paste LBCNT-PD to make a soft pack battery.

[0092] See the diagram of the conductive paste after grinding. Figure 13 When PD is added, CNTs in the conductive paste are not well dispersed, and the conductive paste has obvious coarse particles that are difficult to stir, indicating that CNTs are poorly dispersed in the conductive paste under the action of polymer PD.

[0093] Comparative Example 4

[0094] The only difference from Example 11 is that polyvinylpyrrolidone (PVP) is used in an equal molar amount to replace PSD11 to obtain LBCNT-PVP for making pouch cells.

[0095] The resistivity box plots of the positive electrode sheet, the bulk resistivity box plot, and the internal resistance box plot of the full cell prepared by Comparative Example 4 (LB108-44-PVP) are shown below. Figures 17-19 The battery's cycle capacity retention and capacity at 25°C were tested; the results are detailed in [link to results]. Figure 20 and Figure 21 The battery's cycle capacity retention and capacity at 45℃ were tested; the results are detailed in [link to results]. Figure 22 and Figure 23 .

[0096] experiment

[0097] Examples 6-10: Conductive paste testing (viscosity, particle size)

[0098] Viscosity testing method: Take 200ml of slurry prepared in Examples 1-5 and Comparative Examples 1-4 respectively, and use Brookfield viscometer to test the viscosity and read the data after the viscosity stabilizes.

[0099] Particle size testing method: Take a small amount of slurry prepared in Examples 1-5 and Comparative Examples 1-4 respectively, drop it into a Malvern laser particle size analyzer, and measure D50 and D90.

[0100] The test results are detailed in Table 1.

[0101] Table 1

[0102]

[0103] Effect Analysis: According to the data comparison in Table 1, it can be seen that Comparative Examples 1-3 are difficult to disperse in conductive pastes. However, the polymer synthesized in this application, composed of CNT-loving molecules (Component A) and low-polarity flexible molecules containing branched or long-chain alkanes (Component B), with energy levels of 0.1-0.24 for Component A and 0.2-0.23 for Component B, produces a conductive paste with a viscosity as low as 630 cp, particle size D50 ≤ 0.07 μm, and particle size D90 < 2.0 μm. This is close to the conductive pastes prepared using PVP as a dispersant in existing technologies. This indicates that the dispersing polymer synthesized by the technical solution of this application can basically meet the requirements for application in carbon nanotube conductive pastes and can basically reach the existing level.

[0104] according to Figure 17 and 18 It can be seen that the electrode resistivity and bulk resistivity of the battery described in Example 11 are significantly lower than those of the battery prepared using Comparative Example 4.

[0105] according to Figure 19It can be seen that the soft-pack battery described in Example 11 of the application is made using the LB108-44-PSD11 conductive paste described in Example 6, and its internal resistance is significantly lower than that of the soft-pack battery made using the LBCNT-PVP conductive paste described in Comparative Example 4.

[0106] Figure 20 and Figure 21 This indicates that the battery described in Example 11 did not experience significant capacity decay after 500 cycles at room temperature (25°C) within a voltage window of 2.8-4.35V. This demonstrates that the battery in Example 11 has a higher capacity retention rate than the battery prepared using the conductive paste LBCNT-PVP described in Comparative Example 4. The battery in Example 11 retains approximately 95% of its capacity after 500 cycles. Similarly, Figure 22 and Figure 23 This more intuitively demonstrates that the capacity retention of the battery described in Example 11 after 500 cycles at 45°C is superior to that of the battery prepared using the conductive paste LBCNT-PVP described in Comparative Example 4.

[0107] Figure 24 This indicates that at room temperature (25°C), the battery prepared using the dispersion polymer PSD11 described in Example 1 exhibits superior high-voltage performance compared to batteries using PVP as a dispersant in the prior art. Figure 25 It can be seen that the difference in high-voltage performance is more pronounced at 45℃. The battery prepared using PSD11 clearly exhibits excellent charge-discharge performance at high voltages, indicating that the battery made using the dispersion polymer of this application has better high-voltage performance and better meets market demands. Therefore, combined with the electrical performance tests, it is comprehensively demonstrated that the battery made using the dispersion polymer of this application has excellent high-voltage resistance and cycle performance, representing a significant improvement over existing batteries using PVP as a dispersant, which already has good performance.

[0108] The above-described embodiments are merely preferred embodiments of the present invention, used to explain and illustrate the invention, and not to limit the scope of the invention. The invention title has been described through specific embodiments. Those skilled in the art can refer to the content of the present invention to appropriately change the raw materials, process conditions, and other aspects to achieve other corresponding objectives. Such changes do not depart from the content of the present invention, and all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of the present invention.

Claims

1. A conductive paste, characterized in that: The product includes a high-voltage resistant dispersion polymer, carbon nanotubes, and a solvent. The high-voltage resistant dispersion polymer is polymerized from two components, A and B, wherein the mass ratio of the carbon nanotubes to the high-voltage resistant dispersion polymer is (1-5):

1. Component A is styrene, and component B is butyl methacrylate; Alternatively, component A may be acrylonitrile, and component B may be octadecyl methacrylate; Alternatively, component A may be acrylonitrile, and component B may be N-vinylpyrrolidone.

2. The conductive paste according to claim 1, characterized in that: The method for preparing the high voltage resistant dispersion polymer is as follows: Component A, Component B, and initiator are mixed evenly in a molar ratio of 1:(0.1-3):(0.0005-0.01), and then reacted under a nitrogen atmosphere for 7-20 h, with the reaction temperature controlled at 50-110℃.

3. The conductive paste according to claim 1, characterized in that: The method for preparing the high voltage resistant dispersion polymer is as follows: Component A, Component B, and initiator are mixed in a molar ratio of 1:(0.5-2):(0.0005-0.005), and then solvent is added and the mixture is homogenized. The reaction is carried out under a nitrogen atmosphere for 7-20 h, and the reaction temperature is controlled at 50-90℃.

4. The conductive paste according to claim 3, characterized in that: The solvent is N-methylpyrrolidone.

5. An electrode paste, characterized in that: It is composed of the conductive paste, conductive active material and binder as described in any one of claims 1-4; wherein the amount of the conductive paste added is 0.5-2%.

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