High-performance battery positive electrode slurry and preparation method thereof

Abstract

The invention discloses high-performance battery positive electrode slurry and a preparation method thereof. The method comprises the following steps: adding a surface modifier into a binder, atomizing the surface modifier, carrying out solid-liquid dispersion mixing on atomized mixed glue liquid drops and suspended and dispersed positive electrode material particles, fully contacting the mixed glue liquid drops with residual alkali on the surface of the positive electrode material, and carrying out an acid-base neutralization reaction; a uniform fast ion conductor coating layer is formed on the surface of the positive electrode material in situ, and the coating layer not only can improve the ionic conductivity, reduce polarization and facilitate improvement of rate performance, but also can effectively isolate side reactions on an electrode-electrolyte interface under high voltage, and more importantly, when lithium / sodium ions are deeply delaminated under high voltage, the lithium / sodium ion battery can be effectively prevented from being damaged. The coating layer enhances the diffusion of lithium / sodium ions on an electrode / electrolyte interface, inhibits the generation of microcracks in the cycle process, improves the stability of the positive electrode material, and further improves the cycle performance and high-temperature storage performance of the battery.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of secondary batteries, in particular to a high-performance battery positive electrode slurry and a preparation method thereof. BACKGROUND

[0002] High-nickel positive electrode materials have the advantages of high capacity, low cost and rich raw material sources, and are a kind of secondary battery material with extremely promising application prospects. However, the surface of the high-nickel positive electrode material contains a large amount of residual alkali (LiO2, LiOH, Li2CO3, etc.). The existence of these residual alkalis increases the surface polarization of the positive electrode material, and affects the cycle performance, safety performance and the like of the positive electrode material. In addition, during the preparation of the positive electrode slurry, these residual alkalis will trigger the elimination reaction of the binder polyvinylidene fluoride (PVDF), and the double bonds after defluorination combine with each other to cause the gelling of the slurry and the inability to coat, thereby affecting the manufacturing of the pole piece.

[0003] At present, the water washing process is mainly adopted in the industry to reduce the residual alkali on the surface of the positive electrode material. However, during the water washing process, lithium / sodium in the surface layer of the positive electrode material will undergo proton exchange with water, leading to the deterioration of the capacity and cycle performance of the material. At the same time, the water washing destroys the surface structure of the material, increases the specific surface area of the material, and causes the increase of the side reaction of the material with the electrolyte, thereby accelerating the attenuation of the battery. In order to reduce the negative effects of water washing, the product after water washing usually needs to be subjected to heat treatment or coating to repair the surface structure of the material, but this measure will increase the process difficulty and processing cost.

[0004] In addition, some residual alkali scavengers are added during the mechanical stirring of the positive electrode slurry to reduce the residual alkali on the surface of the positive electrode material, such as acid conductive agents (acid conductive carbon black, such as the invention application with the publication number CN111710868A), organic acids (at least one of propenoic acid, butenoic acid, trans-butenoic acid, maleic acid, fumaric acid, itaconic acid, 3-pentenoic acid, 3-hexenoic acid, octenoic acid, 2-octenoic acid, 2-methyl-2-hexenoic acid, such as the invention application with the publication number CN113937249A), acid additives (at least one of oxalic acid, LiPF6, citric acid, tetraethyl silicate, such as the invention application with the publication number CN112510192A) or mixed additives (dispersion type additives and acid buffer type additives, such as the invention application with the publication number CN106571468A) and the like. Although the addition of the above residual alkali scavengers can improve the gelling phenomenon of the positive electrode slurry and eliminate the residual alkali on the surface of the positive electrode material to a certain extent, the reaction products themselves do not have the property of fast ion conductor, and the covering on the surface of the positive electrode material will hinder the conduction of lithium ions, thereby affecting the electrochemical performance of the lithium ion battery.

[0005] The application with the publication number CN109119632A discloses a positive electrode slurry with a solid content of 50-70%, which reduces the impurity lithium content on the surface of the positive electrode material by adding boric acid with a mass ratio of 0.1-1% during mechanical stirring of the slurry, forms a lithium fast ion conductor on the surface of the positive electrode material, and improves the conductivity of the positive electrode material. However, the biggest problem of this process is that lithium borate generated by acid-base neutralization reaction will self-agglomerate in the solvent and will not uniformly adhere to the surface of the material, and the slurry has very limited improvement on the performance of the battery.

[0006] The above technical solutions can remove the residual alkali on the surface of the positive electrode material to a certain extent, and improve the processability of the positive electrode slurry, but also have certain limitations, such as high cost, long production cycle, and limited improvement on the electrochemical performance. SUMMARY

[0007] In order to overcome the limitations of the prior art and meet the needs of reducing cost, efficiently and quickly reducing residual alkali content, improving the processability of the positive electrode material, electrochemical performance, and large-scale production, the present application provides a low-cost high-performance positive electrode slurry, a preparation method and its application. In the dispersion and mixing process of the electrode material, the conductive agent and the binder, a surface modifier is added. The droplets of the atomized surface modifier adhere to the surface of the positive electrode material, and an acid-base neutralization reaction occurs between the surface modifier and the residual alkali on the surface of the positive electrode material. A fast ion conductor is formed in situ on the surface of the material, improving the conductivity and structural stability of the positive electrode material, and improving the rate performance, cycle performance and high-temperature storage performance of the battery.

[0008] The present application first provides a preparation method of a high-performance battery positive electrode slurry. The formula of the high-performance battery positive electrode slurry includes a binder, a surface modifier, a conductive agent, a solvent and a positive electrode material. The binder is a solid powder or an emulsion containing part of the solvent. The conductive agent is a solid powder or a dispersion liquid dispersed in part of the solvent. The surface modifier and the positive electrode material are solid powders.

[0009] The preparation method includes the following steps:

[0010] (1) preparing a mixed solution and atomizing and dispersing into suspension droplets:

[0011] The mixed solution is one or two. When the mixed solution is one, the mixed solution is a mixture of the binder, the surface modifier, the solvent and part or all of the conductive agent. When the mixed solution is two, one of the mixed solutions contains part or all of the conductive agent and part of the solvent, and the other mixed solution contains the binder and part of the solvent. The surface modifier is mixed in one of the mixed solutions or each has a part in the two mixed solutions, and the two mixed solutions are atomized and dispersed into suspension droplets respectively.

[0012] (2) suspending and dispersing the positive electrode material into suspension particles:

[0013] If only part of the conductive agent is added to the mixed solution, the remaining part of the conductive agent is added to the positive electrode material to be suspended and dispersed into suspended particles;

[0014] (3) If the mixed solution is one, the mixing of the suspended droplets and the suspended particles forms a slurry, which is the high-performance battery positive electrode slurry;

[0015] If the mixed solution is two, the suspended droplets of one of the mixed solutions are mixed with the suspended particles first, and then the suspended droplets of the other mixed solution are mixed, wherein at least part of the surface modifier is added to the mixed solution that is mixed first.

[0016] In the above steps, the preparation of suspended droplets and suspended particles is independent and has no sequence. After being prepared separately, they are mixed together through pipelines.

[0017] Preferably, the components include, by weight:

[0018] Positive electrode material 94-99.8 parts, conductive agent 0.001-4 parts, binder 0.1-4 parts;

[0019] Surface modifier 0.1%-0.8% of the total weight of all other solid powders;

[0020] Solvent, so that the solid content of the high-performance battery positive electrode slurry is 75%-98%.

[0021] More preferably, the surface modifier accounts for 0.1%-0.4% of the total mass of all other solid powders.

[0022] If the content of the surface modifier is too low, it cannot effectively eliminate the residual alkali on the surface of the positive electrode material and form a uniform fast ion conductor layer, thereby improving the electrochemical performance of the battery. If the content is too high, it can easily reduce the energy density of the battery and worsen the rate, cycle, and high-temperature storage performance of the battery.

[0023] Preferably, the method of atomization and dispersion is selected from at least one of the following: electrostatic charge atomization, magnetization charge atomization, pressure atomization, supersonic atomization, rotary atomization, vortex atomization, thermal atomization, vibration atomization, pneumatic atomization, and bubble atomization.

[0024] Preferably, the method of suspension and dispersion is selected from at least one of the following: airflow impact, electrostatic dispersion, ultrasonic dispersion, mechanical dispersion. The mechanical dispersion can be at least one of the following: grinding dispersion, colloid mill dispersion, ball mill dispersion, sand mill dispersion, high-speed stirring.

[0025] Preferably, the positive electrode material is treated before dispersion to improve the dispersibility and / or surface energy of the positive electrode material, so that it is easy to adhere to the binder and the conductive agent. The treatment method is at least one of heating, microwave irradiation, corona, ultraviolet, mechanical vibration, mechanical stirring, grinding, air flow impact, ultrasonic impact and plasma treatment. Among them, "and / or" means alternative selection or coexistence of both. After improving the dispersibility and / or surface energy of the electrode material by the above treatment, the active material can be better contacted and coated with the conductive glue solution. When the positive electrode material is a mixture of multiple materials, the mixture can be mixed by stirring, grinding and other treatments.

[0026] Preferably, the binder is at least one of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, acrylic resin, nitrile rubber, polymethyl methacrylate, polyethylene oxide, polyethylene, polypropylene, polyacrylonitrile, styrene butadiene rubber, gum arabic, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, sodium polyacrylate, lithium polyacrylate, polymethacrylic acid, carboxymethyl chitosan, polyvinyl alcohol, polyacrylamide, acryloyl polymer, diene polymer, natural rubber;

[0027] The surface modifier is at least one of boric acid (H3BO3), metasilicic acid (H2SiO3), phosphoric acid (H3PO4).

[0028] Preferably, the positive electrode material is at least one of:

[0029] Lithium-containing phosphate with olivine structure or modified compound thereof, lithium transition metal oxide or modified compound thereof, sodium transition metal oxide with layered structure or tunnel structure, prussian sodium material, phosphate sodium material, sulfate sodium material.

[0030] Among them, the lithium transition metal oxide is lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium-rich manganese-based material xLi2MnO3·(1-x)LiMO2(0 l / 3 Co 1 / 3 Mn 1 / 3 O2(also referred to as NCM111), LiNi 0.5 Co 0.2 Mn 0.3 O2(also referred to as NCM523), LiNi0.5 Co 0.25 Mn 0.25 O2(also can be referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Mn 0.05 O2) or modified compounds of the above compounds.

[0031] The lithium-containing phosphate with olivine structure or modified compounds thereof are at least one of lithium iron phosphate (such as LiFePO4), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0032] The sodium transition metal oxide with a layered structure or a tunnel structure has a chemical formula of Na x M y O z , 0 < x < 1, 0 < y < 1, 1 < z < 2, M is selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V; preferably, the layered transition metal oxide is NaNi m Fe n Mn p O2(m + n + p = 1, 0 < m < 1, 0 < n < 1, 0 < p < 1) or NaNi m Co n Mn p O2(m + n + p = 1, 0 < m < 1, 0 < n < 1, 0 < p < 1).

[0033] The Prussian-type sodium battery material has a molecular formula of Na x M[M(CN)6] y ·zH2O, M and M are transition metals, 0 < x < 2, 0 < y < 1, 0 < z < 20; preferably, the Prussian-type sodium battery material is Na x Mn[Fe(CN)6] y ·zH2O (0 < x < 2, 0 < y < 1, 0 < z < 20) or Na x Fe[Fe(CN)6] y ·zH2O (0 < x < 2, 0 < y < 1, 0 < z < 20).

[0034] The phosphate-based sodium battery material has a chemical formula of Na3(MO 1-x PO4)2F 1+2x , 0≤x≤1, M is selected from at least one of Al, V, Ge, Fe, Ga, preferably, the phosphate-based sodium battery material is at least one of Na3(VPO4)2F3 or Na3(VOPO4)2F; or, the phosphate-based sodium battery material has a chemical formula of Na2MPO4F, M is selected from at least one of Fe, Mn, preferably, the phosphate-based sodium battery material is at least one of Na2FePO4F or Na2MnPO4F.

[0035] The sulfate-based sodium battery material has a chemical formula of Na2M(SO4)2·2H2O, M is selected from at least one of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V.

[0036] More preferably, the positive electrode material is further mixed with a solid-state electrolyte, the content of the solid-state electrolyte is not more than 10% of the mass of the positive electrode material;

[0037] The solid-state electrolyte is at least one of:

[0038] Polymer electrolyte: polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polypropylene oxide (PPO), polyvinylidene chloride (PVDC), single-ion polymer electrolyte;

[0039] Sulfide electrolyte: NASICON, LISICON;

[0040] Oxide electrolyte: LLZO type, NaPON type, LiPON type, garnet type, glassy type.

[0041] However, the present application is not limited to these materials, and other conventional materials that can be used as solid-state electrolytes can also be used. These solid-state electrolytes can be used alone or in combination of two or more.

[0042] Preferably, the adhesive is at least one of the following: polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, acrylic resin, nitrile rubber, polymethyl methacrylate, polyethylene oxide, polyethylene, polypropylene, polyacrylonitrile, styrene-butadiene rubber, gum arabic, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, sodium polyacrylate, lithium polyacrylate, polymethacrylic acid, carboxymethyl chitosan, polyvinyl alcohol, polyacrylamide, acryloyl polymers, diene polymers, and natural rubber.

[0043] Preferably, the conductive agent is at least one of the following: superconducting carbon, carbon nanotubes, graphene, graphite powder, conductive carbon black, acetylene black, carbon dots, Ketjen black, carbon fiber powder or dispersion.

[0044] Preferably, the solvent is at least one of the following: water, ethanol, isopropanol, acetone, N-methylpyrrolidone, N,N-dimethylformamide, dimethylacetamide, dimethylthionylurea, trichloroacetic acid, methylamine, methanol, ethyl acetate, tetramethylurea, or trimethyl phosphate.

[0045] In this application, the binder and conductive agent are used as raw materials and can be commercially available. The purchased binder and conductive agent may be solid powders or dispersed in a solvent. The binder dispersed in the solvent forms an emulsion, and the conductive agent dispersed in the solvent forms a dispersion. The solvent introduced into the system by these binder and conductive agents also needs to be included in the total solvent content. Furthermore, the solvents added at various points can be the same type or different types. This invention also provides a high-performance battery cathode slurry prepared by the aforementioned method.

[0046] The present invention also provides a positive electrode sheet, which is obtained by laminating the high-performance battery positive electrode slurry onto a current collector. The positive electrode current collector can be selected from aluminum current collectors, carbon current collectors, composite current collectors, carbon foil-coated current collectors, or titanium-nickel shape memory alloy current collectors.

[0047] This invention also provides a secondary battery comprising the aforementioned positive electrode. The secondary battery further includes a negative electrode, an electrolyte, and a packaging shell. The types of electrolyte and packaging shell are not limited and can be selected according to actual needs. The electrolyte can be a liquid electrolyte or a solid electrolyte, such as an inorganic solid electrolyte or a polymer electrolyte. The negative electrode includes a negative current collector and a negative electrode film disposed thereon. The negative electrode film may include a negative electrode material, a conductive agent, and a binder. The type of negative electrode material is not limited and can be selected according to actual needs; for example, the negative electrode material can be commonly used natural graphite, artificial graphite, silicon, silicon oxide, silicon alloy, tin, tin alloy, lithium titanate, etc.

[0048] The present invention also provides a method for preparing a positive electrode sheet, wherein a high-performance battery positive electrode slurry is prepared by the method, and the high-performance battery positive electrode slurry is then composited onto a current collector to obtain the positive electrode sheet.

[0049] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0050] This invention presents a method for preparing high-performance battery cathode slurry that differs from existing techniques such as water washing of raw materials to remove residual alkali and direct addition of residual alkali removers during mechanical stirring of the slurry. This invention involves adding surface modifiers boric acid, phosphoric acid, and metasilicic acid to a binder and atomizing it. The atomized mixed slurry droplets are then mixed with suspended cathode material particles in a solid-liquid dispersion. The mixed slurry droplets fully contact the residual alkali on the cathode material surface, undergoing an acid-base neutralization reaction. This forms a uniform fast-ion conductor coating layer in situ on the cathode material surface. This coating layer not only improves ionic conductivity and reduces polarization, thus enhancing rate performance, but also effectively isolates side reactions at the electrode-electrolyte interface under high voltage. More importantly, when lithium / sodium ions undergo deep delamination under high voltage, the coating layer enhances the diffusion of lithium / sodium ions at the electrode / electrolyte interface, suppresses the generation of microcracks during cycling, and improves the stability of the cathode material, thereby improving the battery's cycle performance and high-temperature storage performance. This method achieves the removal and modification of residual alkali on the surface of the cathode material while simultaneously preparing the cathode slurry, thereby improving the electrochemical performance of the battery. Attached Figure Description

[0051] Figure 1 The slurry with a solid content of 90% prepared in Example 1 is an example.

[0052] Figure 2 The positive electrode sheet prepared in Example 1.

[0053] Figure 3 The test data for the battery cells obtained in Example 1 and Comparative Example 1 are as follows: Figure 3 In this context, A represents the rate performance test. Figure 3 B in the figure represents the ambient temperature cycling performance test. Detailed Implementation

[0054] Example 1

[0055] In this embodiment, the cathode slurry contains the cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2, conductive agent single-arm carbon nanotubes, binder polyvinylidene fluoride (PVDF), and surface modifier boric acid (H3BO3), among which LiNi 0.9 Co 0.05 Mn 0.05The mass ratio of O2, single-arm carbon nanotubes and PVDF solid powder is 98:0.5:1.5. The surface modifier boric acid accounts for 0.4% of the total mass of the above three substances in the solid powder. The solid content of the positive electrode slurry is 90%.

[0056] (1) Preparation of positive electrode slurry

[0057] A mixture with a solid content of 17.8% was prepared by mixing surface modifier boric acid with a PVDF aqueous emulsion with a solid content of 32.5% and a single-arm carbon nanotube dispersion with a solid content of 5.9% (solvent is water). The mixture was then dispersed into suspended droplets by a bubble atomization dispersion method.

[0058] Using airflow impact to process the positive electrode material LiNi 0.9 Co 0.05 Mn 0.05 O2 particles are dispersed in dry air;

[0059] Atomized and dispersed mixed liquid droplets and suspended and dispersed LiNi 0.9 Co 0.05 Mn 0.05 O2 particles were mixed to prepare a positive electrode slurry with a solid content of 90%. A photograph of the slurry is shown below. Figure 1 As shown.

[0060] (2) Preparation of secondary batteries

[0061] The positive electrode slurry was evenly spread on the surface of a 10μm aluminum foil, with a double-sided areal density of 280g / m². 2 After drying, the positive electrode sheet is obtained through rolling and punching. A photograph of the positive electrode sheet is shown below. Figure 2 As shown.

[0062] Using the above-mentioned positive electrode and lithium sheet, a button cell is assembled in a glove box. The separator is a polyethylene film (PE), the electrolyte is a 1 mol / L LiPF6 solution, and the organic solvent is a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1.

[0063] Example 2

[0064] The difference between this embodiment and Embodiment 1 is that the surface modifier in the positive electrode slurry accounts for 0.1% of the total mass of the positive electrode material, conductive agent, and binder solid powder. Other parameters and conditions are exactly the same as in Embodiment 1.

[0065] Example 3

[0066] The difference between this embodiment and Embodiment 1 is that the surface modifier in the positive electrode slurry accounts for 0.8% of the total mass of the positive electrode material, conductive agent, and binder solid powder. Other parameters and conditions are exactly the same as in Embodiment 1.

[0067] Example 4

[0068] The difference between this embodiment and Embodiment 1 is that the surface modifier H3BO3 is replaced with H2SiO3 in equal quantities, while the other parameters and conditions are exactly the same as in Embodiment 1.

[0069] Example 5

[0070] The difference between this embodiment and Embodiment 1 is that the surface modifier H3BO3 is replaced with H3PO4 in equal amounts, while the other parameters and conditions are exactly the same as in Embodiment 1.

[0071] Example 6

[0072] In this embodiment, the cathode slurry contains the cathode material LiNi. 0.7 Co 0.2 Mn 0.1 The cathode slurry consists of O2 (NCM721), conductive agent single-arm carbon nanotubes, binder styrene-butadiene rubber (SBR), and surface modifier H3BO3. The mass ratio of the cathode material, conductive agent, and binder solid powder is 99.8:0.1:0.1. The surface modifier boric acid accounts for 0.1% of the total mass of the above three solid powders. The solid content of the cathode slurry is 98%.

[0073] Single-arm carbon nanotube powder and surface modifier H3BO3 were added to an SBR aqueous emulsion with a solid content of 4.9%, and stirred for 2 hours at a revolution speed of (25±5) r / min and a rotation speed of (200±50) r / min. After stirring, the mixed emulsion containing the surface modifier and conductive agent was atomized and dispersed using electrostatic charge spraying, and the cathode material was suspended and dispersed using airflow impact dispersion. The suspended cathode material particles were mixed with the atomized droplets to obtain a cathode slurry with a solid content of 98%. Other parameters and conditions were exactly the same as in Example 1.

[0074] Example 7

[0075] In this embodiment, the positive electrode slurry contains the positive electrode material Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 0.99 Zr 0.01 O2, garnet-type solid electrolyte Li 6.5 La3Zr 1.5 Ta 0.5 O 12The slurry comprises (LLZTO) powder, conductive carbon black, PVDF binder, and H3PO4 surface modifier. The mass ratio of the positive electrode material, solid electrolyte, conductive agent, and binder solid powder is 88:8.8:2:1.2. Phosphoric acid, the surface modifier, accounts for 0.4% of the total mass of the above four solid powders. The solid content of the positive electrode slurry is 90%.

[0076] A mixed solution was prepared by mixing H3PO4 with an aqueous PVDF emulsion containing 10.8% solids. The positive electrode material, solid electrolyte, and conductive carbon black were then dry-mixed and suspended and dispersed. The suspended and dispersed mixed materials were then mixed with droplets of the mixed solution dispersed by bubble atomization to prepare a slurry. Other parameters and conditions were exactly the same as in Example 1.

[0077] Example 8

[0078] In this embodiment, the positive electrode slurry contains Prussian blue as the positive electrode material, multi-walled carbon nanotubes as the conductive agent, conductive carbon black as the conductive agent, PVDF as the binder, and H2SiO3 and H3BO3 as surface modifiers. The mass ratio of the positive electrode material, solid electrolyte, conductive agent, and binder solid powder is 94:4:2, the mass ratio of multi-walled carbon nanotubes to conductive carbon black powder is 1:3, and the surface modifiers silicic acid and boric acid account for 0.1% and 0.4% of the total mass of the above three solid powders, respectively. The solid content of the positive electrode slurry is 75%.

[0079] A mixed colloid was prepared by mixing H2SiO3 with an aqueous PVDF emulsion containing 12.2% solids. A mixed conductive agent dispersion was prepared by mixing H3BO3 with a multi-walled carbon nanotube dispersion containing 5% solids (water as solvent). The positive electrode material and conductive carbon black were dry-mixed and then suspended and dispersed by electrostatic dispersion. The suspended and dispersed mixture particles were then mixed sequentially with droplets of the mixed colloid dispersed by supersonic atomization and droplets of the mixed conductive agent dispersion dispersed by electrostatic charge atomization to prepare a slurry. Other parameters and conditions were exactly the same as in Example 1.

[0080] Example 9

[0081] In this embodiment, the cathode slurry contains the cathode material LiNi. 0.8 Co 0.1 Mn 0.1 The cathode material consists of (NCM811), conductive agent single-arm carbon nanotubes, binder PVDF, and surface modifier H3BO3. The mass ratio of the cathode material, conductive agent, and binder solid powder is 95.999:0.001:4. The surface modifier boric acid accounts for 0.4% of the total mass of the above three solid powders. The solid content of the cathode slurry is 75%.

[0082] A mixed conductive agent dispersion was prepared by mixing H3BO3 with a multi-walled carbon nanotube dispersion (solvent being water) containing 2% solids. The cathode material particles were then suspended and dispersed using electrostatic dispersion. This dispersion was subsequently mixed with droplets of the mixed conductive agent dispersion dispersed by bubble atomization and droplets of a PVDF aqueous emulsion (10.7% solids) dispersed by supersonic atomization to prepare a slurry. All other parameters and conditions were identical to those in Example 1.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that the positive electrode slurry does not contain surface modifiers. All other parameters and conditions are exactly the same as in Example 1.

[0085] Comparative Example 2

[0086] The difference from Example 1 is that the surface modifier in the positive electrode slurry accounts for 0.05% of the total mass of the positive electrode material, conductive agent, and binder solid powder. Other parameters and conditions are exactly the same as in Example 1.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that the surface modifier in the positive electrode slurry accounts for 1% of the total mass of the positive electrode material, conductive agent, and binder solid powder. Other parameters and conditions are exactly the same as in Example 1.

[0089] Comparative Example 4

[0090] The difference from Example 1 is that the solid content of the positive electrode slurry is 65%. All other parameters and conditions are exactly the same as in Example 1.

[0091] A mixture with a solid content of 4.3% was prepared by mixing surface modifier boric acid with a PVDF aqueous emulsion with a solid content of 32.5%, a single-arm carbon nanotube dispersion with a solid content of 5.9% (solvent is water) and water. The mixture was then dispersed into suspended droplets by a bubble atomization dispersion method.

[0092] Using airflow impact to process the positive electrode material LiNi 0.9 Co 0.05 Mn 0.05 O2 particles are dispersed in dry air;

[0093] Atomized and dispersed mixed liquid droplets and suspended and dispersed LiNi 0.9 Co 0.05 Mn 0.05 A positive electrode slurry with a solid content of 65% was prepared by mixing O2 particles.

[0094] Comparative Example 5

[0095] The difference from Example 1 is that the positive electrode slurry was prepared using a conventional wet process, and the solid content of the positive electrode slurry was 75%. Other parameters and conditions were exactly the same as in Example 1.

[0096] After stirring PVDF binder powder with NMP solvent for 2 hours, a PVDF solution with a solid content of 10% was obtained. Boric acid, a surface modifier, was added to the PVDF solution and stirring was continued for 30 minutes to obtain a mixture.

[0097] LiNi 0.9 Co 0.05 Mn 0.05 O2 and conductive single-arm carbon nanotube powder are dry-mixed, and then NMP is added and mixed to obtain a pre-wetting material.

[0098] The mixture containing the surface modifier was kneaded with the pre-wetting material to obtain a slurry with a solid content of 75%. The positive electrode slurry was then coated onto aluminum foil. Other parameters and conditions were exactly the same as in Example 1.

[0099] Detection Example 1

[0100] The following describes the battery testing process.

[0101] (1) Rate test: At room temperature, constant current and constant voltage charging at 2.8-4.3V and 0.3C rate, and discharge at 0.5C, 1C, 2C and 3C rates respectively. After the rate test is completed, each battery is cycled at 0.3C / 0.3C rate for two weeks.

[0102] (2) Cyclic test: At room temperature, 2.8-4.3V, cycle for 500 cycles at 0.5C / 0.5C rate. After the test, each battery is cycled for two weeks at 0.3C / 0.3C rate.

[0103] (3) High-temperature storage test: At room temperature, charge to 4.3V at a constant current and constant voltage of 0.3C. Store at 45℃ for 90 days. After the test, each battery is cycled at 0.3C / 0.3C rate for two weeks.

[0104] The test results are shown in Table 1 and Figure 3 As shown.

[0105] Table 1 shows the test results of Examples 1-5 and Comparative Examples 1-4.

[0106]

[0107]

[0108] From Table 1 and Figure 3As can be seen, in Examples 1-5, the rate performance, cycle life, and high-temperature storage performance of the obtained batteries are significantly improved compared to Comparative Example 1. This is because the atomized surface modifiers boric acid (H3BO3), metasilicic acid (H2SiO3), and phosphoric acid (H3PO4) neutralize with the residual alkali on the surface of the cathode material, forming in-situ Li3BO3, LiBO2, Li2Si2O5, and Li3PO4 fast ion conductor coating layers on the material surface. These coating layers improve ionic conductivity and reduce polarization, which is beneficial for improving rate performance. Furthermore, the coating layers effectively isolate side reactions at the electrode-electrolyte interface under high voltage, improving the battery's high-temperature storage performance. More importantly, when lithium ions undergo deep delamination under high voltage, the coating layers enhance lithium ion diffusion at the electrode / electrolyte interface, suppress the generation of microcracks during cycling, and improve the stability of the cathode material, thereby improving the battery's cycle performance and high-temperature storage performance. Comparing Examples 1-3, it can be seen that the surface modifier of the present invention preferably accounts for 0.1%-0.4% of the total mass of the solid components in the positive electrode slurry. Within the above proportion range, the battery has the best rate performance, cycle life and high temperature storage performance.

[0109] In Comparative Example 2, the surface modifier content was too low, failing to effectively eliminate lithium impurities on the cathode material surface, resulting in limited improvement in the battery's rate, cycle, and high-temperature storage performance. In Comparative Example 3, the surface modifier content was too high; excess surface modifier corroded the aluminum current collector, leading to poor contact between the electrode coating and the current collector, and deteriorating the battery's electrochemical performance. In Comparative Example 4, adjusting the slurry solid content to 65% improved the battery's rate, cycle, and high-temperature storage performance to some extent, but the improvement was not significant. This was because a large amount of solvent formed a continuous phase, causing the fast lithium-ion conductors generated by the acid-base neutralization reaction to move freely in the large amount of solvent, resulting in self-aggregation rather than uniform adhesion to the material surface. This led to uneven coating of the fast ion conductors on the cathode surface, thus affecting the electrochemical performance. In Comparative Example 5, the direct addition of surface modifiers during the mechanical stirring of the slurry improved the rate, cycle and high-temperature storage performance of the battery to some extent, but the improvement effect was not significant. This is because the traditional mechanical stirring method in the high solids content system cannot ensure that the surface modifiers are evenly dispersed and fully contacted with the cathode material, resulting in insufficient reaction between the residual alkali of the cathode material and the surface modifiers. The fast ion conductors generated by the acid-base neutralization reaction are unevenly distributed on the cathode surface, thus affecting the electrochemical performance.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance battery cathode slurry, characterized in that, The formulation of the high-performance battery cathode slurry includes a binder, a surface modifier, a conductive agent, a solvent, and a cathode material. The binder is a solid powder or an emulsion containing a portion of the solvent. The conductive agent is a solid powder or a dispersion dispersed in a portion of the solvent. The surface modifier and the cathode material are solid powders. The preparation method includes the following steps: (1) Prepare the mixture and atomize it into a suspension of droplets: The mixture may be one or two types. When the mixture is one type, it is a mixture of binder, surface modifier, solvent, and some or all of conductive agent. When the mixture is two types, one type contains some or all of conductive agent and some solvent, and the other type contains binder and some solvent. The surface modifier is mixed in one type of mixture or in each of the two mixtures, and each mixture is atomized and dispersed into suspended droplets. (2) The positive electrode material is suspended and dispersed into suspended particles: If only a portion of the conductive agent is added to the mixture, the remaining conductive agent is added to the positive electrode material and suspended and dispersed together into suspended particles. (3) If the mixture is of one type, then the slurry formed by mixing the suspended droplets with the suspended particles is the high-performance battery cathode slurry. If the mixture consists of two types of liquids, the suspended droplets formed by atomizing one type of liquid are first mixed with the suspended particles, and then mixed with the suspended droplets formed by atomizing the other type of liquid. The first mixed liquid contains at least a portion of a surface modifier.

2. The method for preparing the high-performance battery cathode slurry according to claim 1, characterized in that, The ingredients, by weight, include: Positive electrode material 94-99.8 parts, conductive agent 0.001-4 parts, binder 0.1-4 parts; Surface modifiers comprising 0.1%-0.8% of the weight of all other solid powders; The solvent is used to make the solid content of the high-performance battery cathode slurry 75%-98%.

3. The method for preparing the high-performance battery cathode slurry according to claim 1, characterized in that, The atomization dispersion method is selected from at least one of the following: electrostatic atomization, magnetized charged atomization, pressure atomization, supersonic atomization, rotary atomization, vortex atomization, thermal atomization, vibration atomization, pneumatic atomization, and bubble atomization. The suspension dispersion method is selected from at least one of the following: airflow impact, electrostatic dispersion, ultrasonic dispersion, and mechanical dispersion.

4. The method for preparing the high-performance battery cathode slurry according to claim 1, characterized in that, The adhesive is at least one of the following: polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, acrylic resin, nitrile rubber, polymethyl methacrylate, polyethylene oxide, polyethylene, polypropylene, polyacrylonitrile, styrene-butadiene rubber, gum arabic, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, polyacrylic acid, sodium polyacrylate, lithium polyacrylate, polymethacrylic acid, carboxymethyl chitosan, polyvinyl alcohol, polyacrylamide, acryloyl polymers, diene polymers, and natural rubber; The surface modifier is at least one of the following: boric acid, metasilicic acid, or phosphoric acid.

5. The method for preparing the high-performance battery cathode slurry according to claim 1, characterized in that, The conductive agent is at least one of the following: superconducting carbon, carbon nanotubes, graphene, graphite powder, conductive carbon black, acetylene black, carbon dots, Ketjen black, carbon fiber powder or dispersion. The solvent is at least one of the following: water, ethanol, isopropanol, acetone, N-methylpyrrolidone, N,N-dimethylformamide, dimethylacetamide, dimethylthionylurea, trichloroacetic acid, methylamine, methanol, ethyl acetate, tetramethylurea, or trimethyl phosphate.

6. The method for preparing the high-performance battery cathode slurry according to claim 1, characterized in that, The positive electrode material is at least one of the following: Lithium phosphates or their modified compounds with olivine structure, lithium transition metal oxides or their modified compounds, sodium transition metal oxides with layered or tunnel structures, Prussian-type sodium electrical materials, phosphate-based sodium electrical materials, and sulfate-based sodium electrical materials.

7. The method for preparing the high-performance battery cathode slurry according to claim 6, characterized in that, The cathode material also contains a solid electrolyte, and the content of the solid electrolyte does not exceed 10% of the mass of the cathode material by mass percentage. The solid electrolyte is at least one of the following: Polymer electrolytes: polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polypropylene oxide, polyvinylidene chloride, monoionic polymer electrolytes; Sulfide electrolytes: NASICON, LISICON; Oxide electrolytes: LLZO type, NaPON type, LiPON type, garnet type, glassy state.

8. The high-performance battery cathode slurry prepared by the preparation method according to any one of claims 1-7.

9. A positive electrode sheet, characterized in that, It is obtained by combining the high-performance battery cathode slurry of claim 8 onto the current collector.

10. A secondary battery, characterized in that, It includes the positive electrode sheet as described in claim 9.

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