Lithium ion battery positive electrode slurry and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a lithium ion battery positive electrode slurry and a preparation method thereof, the slurry comprises nickel cobalt lithium manganate, a polypyrrole-polyacrylate composite binder, amino functionalized graphene, an ionic liquid and deionized water, the preparation method comprises the following steps: synthesizing a polypyrrole-polyacrylate core-shell composite binder, performing ultrasonic pre-activation on a high-nickel positive electrode material and ionic liquid to form homogeneous slurry, synchronously introducing the composite binder and amino graphene, and adopting a shearing-ultrasonic coupling process to realize nano-dispersion. And dynamically regulating and controlling the alkalescence pH, and completing viscosity optimization through stage-by-stage water replenishing and low-speed stirring to obtain the high-nickel positive electrode slurry. Through collaborative optimization of the core-shell binder, ionic liquid collaborative passivation, amino graphene directional modification and gradient dispersion process, the defects of high-nickel slurry sedimentation, side reaction and conductive network are overcome, rheological-stress characteristics are balanced, and slurry stability, electrochemical performance and process suitability are synchronously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium ion battery positive electrode slurry and a preparation method thereof. Background Art

[0002] With the growing demand for high-energy-density lithium-ion batteries, high-nickel layered oxides have become a research hotspot as cathode materials due to their high specific capacity. However, high-nickel materials have high residual lithium content on their surfaces and a strong tendency for particle agglomeration, which leads to problems such as sedimentation, viscosity fluctuations, and uneven coating during slurry preparation, seriously restricting battery performance and process stability. Existing technologies mainly improve slurry properties by optimizing binder type, conductive agent dispersion, or process parameters. However, the stringent requirements of high-nickel systems on component synergy and process timing have not yet been systematically addressed.

[0003] Currently, traditional binders (such as PVDF) are unable to achieve both conductive network construction and particle bonding due to their insulating properties. Physically blended conductive agents (such as carbon black) are prone to forming localized insulating regions due to uneven dispersion in high-solids slurries, leading to increased electrode resistivity. Furthermore, conventional dispersion processes are insufficiently able to regulate the surface energy of high-nickel particles. After the slurry is left to stand, the side reactions between residual lithium and the solvent intensify, generating gas and accelerating the degradation of the active material. While ionic liquids or functionalized additives can partially alleviate these issues, their interfacial compatibility with binders and conductive agents is poor, and their process adaptability is difficult to meet the needs of large-scale production.

[0004] In summary, the existing technology has multi-dimensional contradictions in the stability, conductive network uniformity and side reaction inhibition of high-nickel positive electrode slurry. In this regard, the present invention proposes a lithium-ion battery positive electrode slurry and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide a lithium-ion battery positive electrode slurry and a preparation method thereof, which solves the problems of poor dispersibility, low stability and electrochemical performance degradation caused by particle agglomeration, residual lithium side reactions and uneven conductive network in high-nickel positive electrode slurry.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A lithium-ion battery positive electrode slurry comprises the following components in percentage by weight: Lithium nickel cobalt manganese oxide 90.0-95.0%; Polypyrrole-polyacrylate composite binder 2.0-4.0%; Amino-functionalized graphene 0.5-1.5%; Ionic liquid 0.3-1.0%; The balance was deionized water.

[0007] The binder is a core-shell structure formed by in-situ oxidative polymerization of polypyrrole and polyacrylate. The polyacrylate backbone provides flexible support, inhibiting the volume expansion of the high-nickel material during charge and discharge, while the polypyrrole shell forms a continuous electron conduction path through a π-π conjugated structure, replacing some of the functions of traditional conductive agents (such as SuperP).

[0008] The molecular-level combination of polypyrrole and polyacrylate is achieved through chemical bonding (rather than physical blending), avoiding interfacial impedance issues between the two phases. The redox properties of polypyrrole can dynamically adjust the pH of the slurry, neutralizing the LiOH / Li2CO3 residue on the surface of lithium nickel cobalt manganese oxide and inhibiting gelation.

[0009] Amino-functionalized graphene is modified via a two-step process: vapor-phase silanization pretreatment to enhance graphene edge reactivity, followed by liquid-phase amino grafting (γ-aminopropyltriethoxysilane modification) to introduce amino groups. The amino groups form coordination bonds with oxygen vacancies on the surface of lithium nickel cobalt manganese oxide, enhancing interfacial bonding and reducing the "dead zone" of the conductive agent.

[0010] Amino modification directionally optimizes the interfacial compatibility between graphene and high-nickel materials, reducing contact resistance; silanization pretreatment prevents graphene sheet stacking and ensures nanoscale dispersion.

[0011] The cations in the ionic liquid occupy the active sites on the surface of lithium nickel cobalt manganese oxide through electrostatic adsorption, inhibiting the side reactions between residual lithium and water (such as gas production); the hydrophobic anions form a steric hindrance layer to prevent water molecules from penetrating into the material interface.

[0012] Ionic liquids have both dispersing and passivating functions, breaking through the limitations of traditional dispersants (such as PVP) that rely solely on steric hindrance, while solving the problems of slurry stability and battery safety.

[0013] Preferably, the ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

[0014] Preferably, the amino-functionalized graphene is prepared by the following steps: Silane gas is used to vapor-deposit graphene at 250-350°C for 0.5-1.5 hours; The silanized graphene is reacted with γ-aminopropyltriethoxysilane in a buffer solution of pH 8.0-9.0, with a mass ratio of γ-aminopropyltriethoxysilane to graphene of 1:8-1:12, a reaction temperature of 50-70°C, and a reaction time of 3-5h; After centrifugal drying, amino-functionalized graphene with an amino loading of 0.8-1.2 mmol / g was obtained.

[0015] Preferably, the silane gas is a mixture of SiH4 and N2.

[0016] The present invention also provides a method for preparing a positive electrode slurry for a lithium ion battery, which is used to prepare the positive electrode slurry for a lithium ion battery described above, comprising the following steps: S1. preparing a polypyrrole-polyacrylate composite binder: mixing a pyrrole monomer with a polyacrylate emulsion, reacting the mixture under the action of an oxidant, centrifugally drying the mixture, and then crushing the mixture; S2. Preactivation: Mix lithium nickel cobalt manganese oxide, ionic liquid and deionized water, and treat under 30-50 kHz ultrasound for 20-40 minutes to form a pre-dispersed slurry with an initial viscosity of 300-600 mPa·s; S3, dynamic compounding: adding the composite binder and amino-functionalized graphene to the slurry of step S2, and dispersing them using a rotary shear-ultrasonic coupling device; S4. pH control: within 3-8 minutes after the dynamic compounding is completed, add 5-15 wt% citric acid aqueous solution to adjust the slurry pH to 9.3-9.7; S5. Viscosity balance: add the remaining deionized water and stir at a revolution speed of 10-20 rpm and a rotation speed of 400-600 rpm for 8-12 minutes to obtain the final slurry.

[0017] Pre-activation stage: Ultrasonic treatment is used to preferentially adsorb the ionic liquid on the surface of lithium nickel cobalt manganese oxide, reducing the van der Waals force between particles and laying the foundation for the subsequent dispersion of functional materials; Dynamic compounding stage: Using rotational shear and ultrasonic coupling, nanoscale dispersion of the binder and amino-functionalized graphene is achieved under normal pressure. Shear forces dominate the macroscopic flow, while ultrasonic cavitation breaks up nanoaggregates. pH control stage: Citric acid is added within 3-8 minutes after dynamic compounding to dynamically adjust the pH using the carboxylic acid groups of polypyrrole-polyacrylate to avoid binder degradation caused by alkaline environment; Viscosity balance stage: Low-speed homogenization eliminates bubbles and internal stress introduced by high-speed dispersion, ensuring that the rheological properties of the slurry are suitable for the coating process.

[0018] The binder is synthesized using in-situ oxidative polymerization. The thickness of the polypyrrole shell and the grafting density are adjusted by controlling the molar ratio of pyrrole to polyacrylate and the reaction temperature. Ammonium persulfate is used as an oxidant, and its addition ratio (molar ratio of 1.0:1 to 1.5:1 with pyrrole) influences the degree of polymerization and conductivity.

[0019] In-situ polymerization ensures that polypyrrole uniformly coats the polyacrylate particles to form a stable core-shell structure; too low a grafting density leads to insufficient conductivity, while too high a grafting density reduces the elastic modulus.

[0020] Silanization pretreatment is performed at 250-350°C. A mixture of SiH₄ and N₂ introduces silane groups to the graphene edges, enhancing the positioning accuracy of subsequent amino grafting. The pH value of the γ-aminopropyltriethoxysilane modification controls the degree of amino protonation, optimizing its interfacial bonding with lithium nickel cobalt manganese oxide.

[0021] Preferably, the specific steps of preparing the polypyrrole-polyacrylate composite binder in step S1 are as follows: Mix the pyrrole monomer and the polyacrylate emulsion in a molar ratio of 1:3-1:5 and stir under nitrogen protection; Add 5-10 wt% ammonium persulfate aqueous solution dropwise, control the reaction temperature at 35-45°C, and the reaction time for 5-8 hours; The product was centrifuged and washed until neutral, dried, and then crushed into powder with a particle size of 1-5 μm.

[0022] Preferably, in the step S3, the rotary shear-ultrasound coupling device is operated at a shear rate of 5000-8000s -1 , disperse for 15-25 minutes at an ultrasonic frequency of 20-40kHz.

[0023] Preferably, the addition rate of the citric acid solution in step S4 is 0.5-1.5 mL / min.

[0024] In summary, the present invention includes at least one of the following beneficial technical effects: 1. The present invention achieves a molecular-level combination of conductivity and viscoelasticity through the core-shell structure design of the polypyrrole-polyacrylate composite binder. The polypyrrole shell constructs a continuous conductive network, and the polyacrylate main chain regulates the rheological properties of the slurry through dynamic hydrogen bonds, effectively suppressing particle sedimentation and viscosity fluctuations, and adapting to the requirements of high-precision coating processes.

[0025] 2. The present invention uses the dual functional synergistic effect of the ionic liquid dispersant to passivate the residual lithium active sites on the surface of the high-nickel positive electrode, block the water penetration path, significantly reduce gas production and residual lithium enrichment during slurry storage and circulation, and extend the battery life.

[0026] 3. The directional interface modification of the amino-functionalized graphene of the present invention strengthens the electron transfer interface between the conductive agent and the positive electrode particles through silanization pretreatment and amino grafting, reducing the contact resistance; the shear-ultrasonic coupling effect of the dynamic composite process ensures the uniformity of the conductive network and improves the charge transfer efficiency at high rates.

[0027] 4. The flexible segments of the composite binder of the present invention interpenetrate with the rigid conductive units, dynamically adjusting the stress distribution of the electrode during the charge and discharge process, inhibiting the propagation of microcracks caused by the volume expansion of the high-nickel material, while maintaining the continuity of the conductive network, achieving a balance between mechanical strength and electrochemical performance.

[0028] 5. The phased energy input design of the gradient dispersion process of the present invention is adapted to the parameter window of industrial equipment, and the unification of slurry dispersion efficiency and stability is achieved through timing control, which reduces the process complexity and meets the large-scale production requirements of high-nickel systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0030] The following is combined with Figure 1 , the present invention is described in further detail.

[0031] The present invention provides a lithium ion battery positive electrode slurry and a preparation method thereof through the following three embodiments, the specific contents of which are as follows: Example 1-3: Example 1: Raw material ratio (parts by mass): Lithium nickel cobalt manganese oxide (D50 = 5 μm): 92.0 parts; Polypyrrole-polyacrylate composite binder: 3.0 parts; Amino-functionalized graphene: 1.0 part; Ionic liquid: 0.5 parts; Deionized water: balance.

[0032] Preparation steps: Synthesis of polypyrrole-polyacrylate composite binder: Pyrrole monomer and polyacrylate emulsion were mixed at a molar ratio of 1:4 and stirred at 200 rpm for 10 min under nitrogen protection; 8 wt% ammonium persulfate aqueous solution (pyrrole: oxidant = 1:1.2) was added dropwise, the reaction temperature was controlled at 40°C, and the reaction time was 6 h; The solution was washed by centrifugation until the pH value of the filtrate was 7.0, dried in vacuum (55°C, 8h), and pulverized into powder with a particle size of 3 μm.

[0033] Preparation of amino-functionalized graphene: Silanization pretreatment: introduce SiH4 / N2 mixed gas (flow ratio 1:7) at 300℃ for 1h; Amino modification: Silane-modified graphene was reacted with γ-aminopropyltriethoxysilane (mass ratio 1:10) in phosphate buffer at pH 8.5 at 60°C for 4 h. After centrifugal drying, the amino loading was measured to be 1.0 mmol / g.

[0034] Pre-activation: Lithium nickel cobalt manganese oxide, ionic liquid and deionized water were mixed and treated under 40 kHz ultrasound for 30 min, with an initial viscosity of 450 mPa·s.

[0035] Dynamic Compounding: Add binder and amino-functionalized graphene, and use a shear rate of 6500s -1 , ultrasonic frequency 30kHz (power density 50W / L) dispersion for 20min.

[0036] pH control: Within 5 minutes after dynamic compounding, a 10 wt % citric acid aqueous solution was added at a rate of 1.0 mL / min to adjust the pH of the slurry to 9.5.

[0037] Viscosity balance: The remaining deionized water (already included in the total amount of water) was added, and the mixture was stirred at 15 rpm and 500 rpm for 10 min, with a final viscosity of 4000 mPa·s.

[0038] Example 2: Raw material ratio (parts by mass): Lithium nickel cobalt manganese oxide: 90.0 parts; Polypyrrole-polyacrylate composite binder: 4.0 parts; Amino-functionalized graphene: 0.5 parts; Ionic liquid: 1.0 part; Deionized water: balance.

[0039] Preparation steps: Binder synthesis: Pyrrole:polyacrylate=1:3 (molar ratio), reaction temperature 35°C, time 8h; Ammonium persulfate concentration 5 wt% (pyrrole:oxidant=1:1.0); After centrifugation, the powder particle size was 1 μm.

[0040] Preparation of amino-functionalized graphene: Silanization: SiH4 / N2 flow ratio 1:9, 250℃ for 1.5h; Amino modification: γ-aminopropyltriethoxysilane:graphene = 1:8, pH = 8.0, 50 °C for 5 h; The amino group loading was 0.8 mmol / g.

[0041] Pre-activation: 30 kHz ultrasonic treatment for 40 min, initial viscosity 600 mPa·s.

[0042] Dynamic compounding: shear rate 5000s -1 , ultrasonic frequency 20kHz, dispersion 25min.

[0043] pH control: within 8 minutes after dynamic compounding, 5 wt% citric acid solution was added at 0.5 mL / min, pH = 9.7.

[0044] Viscosity balance: stirring at 10 rpm for revolution and 400 rpm for rotation for 12 min, the final viscosity is 3800 mPa·s.

[0045] Example 3: Raw material ratio (parts by mass): Lithium nickel cobalt manganese oxide: 95.0 parts; Polypyrrole-polyacrylate composite binder: 2.0 parts; Amino-functionalized graphene: 1.5 parts; Ionic liquid: 0.3 parts; Deionized water: balance.

[0046] Preparation steps: Binder synthesis: Pyrrole:polyacrylate=1:5 (molar ratio), reaction temperature 45°C, time 5h; Ammonium persulfate concentration 10 wt% (pyrrole:oxidant=1:1.5); The powder particle size after centrifugation was 5 μm.

[0047] Preparation of amino-functionalized graphene: Silanization: SiH4 / N2 flow ratio 1:5, 350℃ for 0.5h; Amino modification: γ-aminopropyltriethoxysilane:graphene = 1:12, pH = 9.0, 70 ° C for 3 h; The amino group loading was 1.2 mmol / g.

[0048] Pre-activation: 50 kHz ultrasonic treatment for 20 min, initial viscosity 300 mPa·s.

[0049] Dynamic compounding: shear rate 8000s -1 , ultrasonic frequency 40kHz, dispersion 15min.

[0050] pH control: within 3 minutes after dynamic compounding, 15 wt% citric acid solution was added at 1.5 mL / min, pH = 9.3.

[0051] Viscosity balance: stirring at 20 rpm for revolution and 600 rpm for rotation for 8 min, the final viscosity is 4200 mPa·s.

[0052] Comparative Examples 1-6: Comparative Example 1: Compared with Example 1, the difference is: The polypyrrole-polyacrylate composite binder was omitted and an equal amount of conventional polyvinylidene fluoride (PVDF) binder was used instead; the amino-functionalized graphene was replaced with unmodified ordinary graphene.

[0053] The remaining preparation steps and parameters are the same.

[0054] Comparative Example 2: Compared with Example 1, the difference is: Omit the ionic liquid and use an equal amount of deionized water instead; No ultrasonic coupling dispersion was performed in the dynamic compounding step, and only a shear rate of 6500s was used. -1 .

[0055] The remaining preparation steps and parameters are the same.

[0056] Comparative Example 3: Compared with Example 1, the difference is: The silanization pretreatment step was omitted in the preparation of amino-functionalized graphene, and untreated graphene was directly used to react with γ-aminopropyltriethoxysilane; The pH control step was delayed until 20 minutes after the end of dynamic compounding.

[0057] The remaining preparation steps and parameters are the same.

[0058] Comparative Example 4: Compared with Example 1, the difference is: The grafting molar ratio of polypyrrole-polyacrylate composite binder was adjusted to 2:1; Dynamic composite shear rate reduced to 4000s -1 .

[0059] The remaining preparation steps and parameters are the same.

[0060] Comparative Example 5: Compared with Example 1, the difference is: The pre-activation step is omitted, and lithium nickel cobalt manganese oxide, binder, amino-functionalized graphene, ionic liquid and all deionized water are directly mixed and dispersed at one time; No viscosity equilibration step was performed.

[0061] The remaining preparation steps and parameters are the same.

[0062] Comparative Example 6: Compared with Example 1, the difference is: A conventional conductive agent (SuperP) was used to replace amino-functionalized graphene in an amount of 1.0 part; In the composite adhesive, polypyrrole and polyacrylate are physically blended (non-in-situ polymerization grafting).

[0063] The remaining preparation steps and parameters are the same.

[0064] Test Example 1: Slurry stability test Test objects: Example 1, Comparative Example 1, Comparative Example 5.

[0065] Description of experimental steps: Step 1: Sample preparation Slurry samples (only one sample per group) were prepared according to the ratios and processes of Example 1, Comparative Example 1, and Comparative Example 5, respectively. The preparation was completed under the same environment (25° C., humidity ≤30%) and sealed for storage.

[0066] Step 2: Initial Viscosity Test A rotational viscometer (shear rate 10 s -1 The initial viscosity of the slurry was measured at 25°C using a spindle SC4-21. The data were collected at an interval of 10 s and the average value was taken after stabilization.

[0067] Step 3: Static stability test The slurry was placed in a 50 mL transparent glass bottle, sealed, and placed in a 25°C thermostat for 24 h. The slurry was slowly poured out to avoid disturbing the sediment.

[0068] Step 4: Viscosity test after standing Measure the viscosity after standing under the same conditions as in step 2 and calculate the viscosity change rate: Step 5: Sedimentation Rate Test After standing, the slurry was centrifuged at 3000 rpm for 10 min to separate the supernatant and the precipitate. The precipitate was dried at 105°C to a constant weight and the weight ratio of the precipitate was calculated as follows: Experimental data: Table 1: Slurry stability test data Summary: The viscosity change rate (3.36%) and sedimentation rate (0.91%) of the slurry of Example 1 after standing are significantly better than those of Comparative Example 1 (16.84%, 6.15%) and Comparative Example 5 (15.47%, 9.12%). This result directly reflects the synergistic optimization mechanism of component design and process of the present invention. The core-shell structure of the polypyrrole-polyacrylate composite binder stabilizes the rheological properties of the slurry while suppressing particle agglomeration through the continuous electron transport network of the polypyrrole conductive shell and the dynamic hydrogen bond regulation of the polyacrylate main chain, while the traditional physically blended binder causes conductive network breakage and viscosity fluctuations due to the lack of chemical bonding. The timing control of the gradient dispersion process, from the ionic liquid surface passivation in the pre-activation stage to the shear-ultrasonic coupled dispersion in the dynamic composite stage, accurately matches the surface energy regulation of the high nickel material and the nano-scale dispersion requirements of the conductive agent, avoiding particle agglomeration and local stress concentration caused by the one-step mixing process. The synergistic effect of the directional modification of amino-functionalized graphene and the ionic liquid strengthens the conductive agent-cathode particle interface through chemical coordination and electrostatic adsorption mechanisms, reducing the formation of "dead zones" while simultaneously blocking the water permeation pathway to inhibit residual lithium side reactions. Through molecular design, interface regulation, and closed-loop optimization of process parameters, the technical solution of this invention systematically addresses the challenges of achieving compatibility between dispersion stability and electrochemical performance in high-nickel slurries.

[0069] Test Example 2: Electrochemical Performance Test Test objects: Example 1, Comparative Example 1, Comparative Example 6.

[0070] Description of experimental steps Step 1: Pole preparation The slurries of Example 1, Comparative Example 1, and Comparative Example 6 were coated on aluminum foil (wet film thickness 200 μm), dried under vacuum at 80°C for 12 h, and rolled to a compacted density of 3.4 ± 0.1 g / cm 3 , cut into 50×50mm pole pieces.

[0071] Step 2: Surface resistance test The electrode sheet surface resistance was measured using a four-probe tester (probe pressure 100 g) at 25° C. and 40% humidity, and a single measurement value was taken.

[0072] Step 3: Battery assembly: Assemble CR2032 button cells (H2O≤0.5ppm) using the electrode as the positive electrode, the lithium sheet as the negative electrode, Celgard 2400 as the separator, and 1M LiPF6 / EC:DMC=1:1 as the electrolyte.

[0073] Step 4: Cycle Performance Test The battery was cycled 200 times at 1C (200 mA / g) between 3.0 and 4.3 V, and the capacity retention was calculated.

[0074] Experimental data: Table 2: Electrochemical performance test data Summary: The surface resistance of Example 1 (1.35Ω·cm 2 ) and capacity retention (90.2%) are significantly better than those of comparative example 1 (11.8Ω·cm 2 , 76.9%) and Comparative Example 6 (8.9Ω·cm 2 , 83.7%), this difference is due to the synergistic optimization mechanism of components and processes of the present invention: The core-shell structure of the composite binder forms a uniform electron transmission path in the electrode through the continuous conductive network of polypyrrole and the flexible chain segment of polyacrylate, which significantly reduces the interface resistance. Comparative Example 1 uses physically blended PVDF and ordinary graphene. The surface resistance increases (11.8Ω·cm) due to the breakage of the conductive network. 2 ) and rapid capacity decay (76.9%). The timing control of the gradient dispersion process ensures uniform coating of the conductive agent and the positive electrode particles through ionic liquid surface passivation in the pre-activation stage and shear-ultrasonic coupling dispersion in the dynamic composite stage, reducing local polarization; while in Comparative Example 6, due to the lack of directional modification of amino-functionalized graphene, the interface bonding force between the conductive agent and the particles is insufficient, resulting in a capacity retention rate (83.7%) lower than that in Example 1. The chemical grafting of amino-functionalized graphene strengthens the interface coordination effect through silanization pretreatment, reduces the conductive "dead zone", and the hydrophobic shielding effect of the ionic liquid further inhibits the corrosion of the electrolyte on the high-nickel material, synergistically improving the cycle stability.

[0075] Test Example 3: Process Suitability Test Test objects: Example 1, Comparative Example 2, Comparative Example 4.

[0076] Description of experimental steps Step 1: Pole preparation and coating The slurry was coated on aluminum foil (wet film thickness 200 μm), dried in vacuum at 80 °C for 12 h, and rolled to a compacted density of 3.4 ± 0.1 g / cm 3 , cut into 100mm wide pole pieces.

[0077] Step 2: Coating thickness uniformity test Use a laser thickness gauge to randomly select 10 measurement points along the horizontal direction of the pole piece, calculate the thickness standard deviation (σ), and the single measurement value is the final result.

[0078] Step 3: Pole cracking rate test Bend the pole piece 180° and hold it for 5 seconds. Count the surface crack area ratio using an optical microscope (50x magnification). The single measurement value is the final result.

[0079] Experimental data: Table 3: Process suitability test data In summary, the coating thickness uniformity (standard deviation of 0.51 μm) and cracking rate (3.8%) of Example 1 are significantly better than those of Comparative Example 2 (1.78 μm, 21.9%) and Comparative Example 4 (1.32 μm, 15.4%). This advantage is due to the coordinated design of components and processes of the present invention: The core-shell structure of the composite binder, through chemical bonding between the flexible polyacrylate segments and the rigid conductive network of polypyrrole, evenly disperses volume expansion stress during the drying process of the electrode, inhibiting the propagation of microcracks. The dynamic hydrogen bonding of the polyacrylate backbone adsorbs on the surface of the positive electrode particles, enhancing the cohesion of the slurry, while the interpenetrating conductive network of the polypyrrole shell and amino-functionalized graphene further enhances the toughness of the electrode. In Comparative Example 4, due to insufficient binder grafting rate, the polypyrrole coverage rate decreased, resulting in uneven particle coating. After rolling, internal stress concentration caused an increase in the cracking rate (15.4%).

[0080] The dual function of the ionic liquid dispersant is to preferentially adsorb and passivate residual lithium active sites on the surface of the high-nickel material through cationic groups, suppressing fluctuations in the slurry's rheological properties caused by side reactions. At the same time, the anionic hydrophobic layer blocks the water penetration path, improving the slurry's leveling. In Comparative Example 2, because the ionic liquid was not used, the particle surface energy was not effectively controlled. The slurry viscosity fluctuated dramatically during the coating process, resulting in a significant deterioration in the thickness standard deviation (1.78μm). After drying, the electrode exhibited large-scale cracks (21.9%) due to residual solvent and stress concentration.

[0081] The shear-ultrasound coupling of the dynamic composite process is achieved by high shear rate (5000-8000s -1 ) dominates the macroscopic flow to break up large-scale agglomerates, while the ultrasonic cavitation effect peels off nanoscale agglomerates, ensuring uniform dispersion of the conductive agent and binder. This spatiotemporal matching of energy input allows the slurry viscosity to be highly compatible with the coating process window, avoiding the residual submicron-scale agglomerates caused by the single shear dispersion in Comparative Example 2. The closed-loop process design of the present invention achieves precise control from molecular adsorption, interfacial bonding, to macroscopic rheological properties, ultimately achieving the high consistency and mechanical stability required for the industrial production of high-nickel positive electrode slurries.

[0082] Test Example 4: Side reaction inhibition test Test objects: Example 1, Comparative Example 2, Comparative Example 3.

[0083] Description of experimental steps: Step 1: Slurry preparation and standing Slurries were prepared according to the ratios and processes of Example 1, Comparative Example 2, and Comparative Example 3, 20 g of each slurry was put into a 50 mL sealed glass bottle, and allowed to stand at 25° C. for 24 h.

[0084] Step 2: Gas production test The syringe method was used to measure the gas volume increase after standing, and the gas production per unit mass of slurry (mL / g) was calculated.

[0085] Step 3: Pole residual lithium content test The slurry was dried after standing, and the active material powder was scraped off and dissolved with acid. The Li content was detected by ICP-OES and converted into the total content of LiOH and Li2CO3 (ppm).

[0086] Experimental data: Table 4: Side reaction inhibition test data sample Gas production (mL / g) Residual lithium content (ppm) Example 1 1.9 708 Comparative Example 2 13.7 2560 Comparative Example 3 6.3 1580 In summary, the gas production (1.9 mL / g) and residual lithium content (708 ppm) of Example 1 are significantly lower than those of Comparative Example 2 (13.7 mL / g, 2560 ppm) and Comparative Example 3 (6.3 mL / g, 1580 ppm). This difference is due to the component synergy and process control mechanism of the present invention: The dual passivation effect of ionic liquids is that the cationic groups preferentially adsorb on the oxygen vacancies on the surface of high nickel materials, forming a physical barrier to inhibit the side reaction of residual lithium (LiOH / Li2CO3) with electrolyte or water. At the same time, the anionic hydrophobic layer blocks the permeation path of water molecules, reducing Li + Reacts with water to generate gas. In Comparative Example 2, since no ionic liquid was added, the residual lithium on the surface was directly exposed to the environment, resulting in a surge in gas production (13.7mL / g) and residual lithium enrichment (2560ppm). The timeliness of dynamic pH regulation is achieved by injecting an acidic regulator (such as citric acid) in real time during the slurry compounding stage to stabilize the pH in the 6.5-7.5 window, thereby avoiding continuous lithium dissolution of the positive electrode material in a highly alkaline environment; while in Comparative Example 3, due to delayed pH regulation, the surface lattice oxygen release of the positive electrode particles was aggravated under the initial high pH conditions, and the residual lithium content increased (1580ppm). The interface modification of amino-functionalized graphene enhances the amino grafting density through silanization pretreatment, and its active sites form hydrogen bond anchoring with the residual LiOH on the positive electrode surface, reducing the free Li + The technical solution of the present invention forms multiple protections from surface passivation, pH window control to interface chemical bonding, systematically improving the chemical stability of high-nickel positive electrode slurry.

[0087] Test Example 5: Conductive Network Construction Efficiency Test Test objects: Example 1, Comparative Example 3, Comparative Example 6.

[0088] Description of experimental steps: Step 1: Pole preparation The slurry was coated on aluminum foil (wet film thickness 200 μm), dried in vacuum at 80 °C for 12 h, and rolled to a compacted density of 3.4 ± 0.1 g / cm 3 , cut into 14mm diameter pole pieces.

[0089] Step 2: Electrochemical Impedance Spectroscopy (EIS) Test The test was performed at open circuit potential (frequency range: 100 kHz-10 mHz, AC amplitude 10 mV), and the charge transfer resistance (Rct) was extracted by equivalent circuit fitting.

[0090] Step 3: Rate performance test Assemble a CR2032 battery, charge it to 4.3V at 1C, and discharge it at 1C, 2C, and 5C. Calculate the capacity retention rate (5C / 1C ratio).

[0091] Experimental data: Table 5: Conductive network construction efficiency test data sample <![CDATA[Rct(Ω·cm 2 )]]> Rate performance (%) Example 1 14.2 95.3 Comparative Example 3 52.4 82.6 Comparative Example 6 29.7 87.1 Summary: The charge transfer resistance of Example 1 (14.2Ω·cm 2 ) and rate performance (95.3%) are significantly better than those of comparative example 3 (52.4Ω·cm 2 , 82.6%) and Comparative Example 6 (29.7Ω·cm 2 , 87.1%), this result is due to the synergistic effect of the conductive network construction strategy and process of the present invention: The interface-oriented modification of amino-functionalized graphene introduces silanol groups at the edge of graphene through silanization pretreatment, providing chemical anchoring sites for amino grafting, forming stable coordination bonds with oxygen vacancies on the surface of the positive electrode particles, and significantly reducing the interface contact resistance. However, the unsilanized graphene in Comparative Example 3 has insufficient amino loading, loose interface bonding between the conductive network and the active material, and blocked electron transmission paths, resulting in an increase in Rct (52.4Ω·cm 2 ) and rate performance degradation (82.6%). The shear-ultrasonic coupling of the dynamic composite process is achieved through high shear rates (5000-8000s -1 ) breaks up the conductive agent agglomerates, and simultaneously uses the ultrasonic cavitation effect to peel off the π-π stacking between graphene sheets, achieving nano-scale dispersion and forming an interpenetrating conductive network; while Comparative Example 6 uses a physically blended spherical conductive agent (SuperP), whose random contact points cannot construct a continuous electron path, resulting in Rct (29.7Ω·cm 2 ) is significantly higher than Example 1.

[0092] The conductive-viscoelastic synergistic mechanism of the composite binder maintains the structural stability of the conductive network during the charge and discharge process through the chemical bonding of the rigid conductive shell of polypyrrole and the flexible chain segment of polyacrylate. The continuous π-π conjugated chain of polypyrrole provides a fast electron transmission channel, while the dynamic hydrogen bonding of polyacrylate disperses the volume expansion stress and inhibits crack propagation under high-rate cycling. In Comparative Example 3, the unfunctionalized graphene is separated from the positive electrode particles under cyclic stress due to insufficient interfacial bonding force, forming a conductive "dead zone", which further aggravates the capacity decay. The technical solution of the present invention systematically improves the electron transmission efficiency and kinetic performance of the high-nickel positive electrode from molecular interface design, dispersion process optimization to binder function synergy.

[0093] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A positive electrode slurry for a lithium ion battery, characterized in that: The composition comprises the following components in weight percentage: Lithium nickel cobalt manganese oxide 90.0-95.0%; Polypyrrole-polyacrylate composite binder 2.0-4.0%; Amino-functionalized graphene 0.5-1.5%; Ionic liquid 0.3-1.0%; The balance was deionized water.

2. The positive electrode slurry for lithium-ion batteries according to claim 1, characterized in that: The ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

3. The positive electrode slurry for lithium-ion batteries according to claim 1, characterized in that: The amino-functionalized graphene is prepared by the following steps: Silane gas is used to vapor-deposit graphene at 250-350°C for 0.5-1.5 hours; The silanized graphene is reacted with γ-aminopropyltriethoxysilane in a buffer solution of pH 8.0-9.0, with a mass ratio of γ-aminopropyltriethoxysilane to graphene of 1:8-1:12, a reaction temperature of 50-70°C, and a reaction time of 3-5h; After centrifugal drying, amino-functionalized graphene with an amino loading of 0.8-1.2 mmol / g was obtained.

4. The positive electrode slurry for lithium-ion batteries according to claim 3, characterized in that: The silane gas is a mixture of SiH4 and N2.

5. A method for preparing a positive electrode slurry for a lithium ion battery, characterized in that: The method for preparing a positive electrode slurry for a lithium-ion battery according to any one of claims 1 to 4 comprises the following steps: S1. preparing a polypyrrole-polyacrylate composite binder: mixing a pyrrole monomer with a polyacrylate emulsion, reacting the mixture under the action of an oxidant, centrifugally drying the mixture, and then crushing the mixture; S2. Preactivation: Mix lithium nickel cobalt manganese oxide, ionic liquid and deionized water, and treat under 30-50 kHz ultrasound for 20-40 minutes to form a pre-dispersed slurry with an initial viscosity of 300-600 mPa·s; S3, dynamic compounding: adding the composite binder and amino-functionalized graphene to the slurry of step S2, and dispersing them using a rotary shear-ultrasonic coupling device; S4. pH control: within 3-8 minutes after the dynamic compounding is completed, add 5-15wt% citric acid aqueous solution to adjust the slurry pH to 9.3-9.7; S5. Viscosity balance: add the remaining deionized water and stir at a revolution speed of 10-20 rpm and a rotation speed of 400-600 rpm for 8-12 minutes to obtain the final slurry.

6. The method for preparing a positive electrode slurry for a lithium-ion battery according to claim 5, characterized in that: The specific steps for preparing the polypyrrole-polyacrylate composite binder in step S1 are as follows: Mix the pyrrole monomer and the polyacrylate emulsion in a molar ratio of 1:3-1:5 and stir under nitrogen protection; Add 5-10wt% ammonium persulfate aqueous solution dropwise, control the reaction temperature at 35-45°C, and the reaction time for 5-8h; The product was centrifuged and washed until neutral, dried, and then crushed into powder with a particle size of 1-5 μm.

7. The method for preparing a positive electrode slurry for a lithium ion battery according to claim 5, characterized in that: In the S3 step, the rotary shear-ultrasound coupling device is operated at a shear rate of 5000-8000s -1 , disperse for 15-25 minutes at an ultrasonic frequency of 20-40kHz.

8. The method for preparing a positive electrode slurry for a lithium ion battery according to claim 5, characterized in that: The addition rate of the citric acid solution in step S4 is 0.5-1.5 mL / min.

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