Positive electrode paste, positive electrode plate, electrochemical device comprising positive electrode paste, and electronic device comprising positive electrode plate

Abstract

The invention provides positive electrode slurry, a positive electrode plate, an electrochemical device comprising the positive electrode plate and an electronic device. The positive electrode slurry comprises an active material and a conductive agent, and meets the formula: # imgabs0 #, and theta represents the volume percentage of particles with the particle size of less than 300nm in the active material; x1 represents the percentage of the mass of the active material to the solid mass of the positive electrode slurry; x2 represents the percentage of the mass of the conductive agent to the solid mass of the positive electrode slurry; s1 represents the specific surface area of the active material in unit of m < 2 > / g; s2 represents the specific surface area of the conductive agent with the unit of m < 2 > / g; d1 represents the particle size distribution coefficient of the active material; d2 represents the particle size distribution coefficient of the conductive agent. According to the positive electrode slurry meeting the limited conditions, a good dispersion system can be formed among the components in the slurry, the solid content of the positive electrode slurry is increased, and the dispersity and stability of the positive electrode slurry are effectively maintained, so that the rate and cycle performance of a battery cell are improved, and the impedance is reduced.

Description

Technical Field

[0001] The present application relates to the field of energy storage, and particularly to a positive electrode slurry, a positive electrode sheet, an electrochemical device including the same, and an electronic device. Background Art

[0002] With the continuous and rapid growth of the new energy electric vehicle market, the demand for power batteries is also expanding rapidly. Lithium iron phosphate (LFP) materials have surpassed traditional ternary materials to become one of the mainstream materials for lithium-ion power batteries due to their relatively low price and higher safety.

[0003] However, the particle size distribution of lithium iron phosphate materials is relatively wide, and the distribution of large and small particles is uneven. Nano-sized small particles have a relatively large specific surface area, which enhances the intermolecular force and adsorption effect, causing the particles to attract each other and easily resulting in particle agglomeration. In addition, the conductive agent added to the slurry has a small particle size and a large specific surface area, and contains various polar functional groups on its surface. Due to the interaction between particles, the conductive agent is also difficult to stably disperse in the slurry, so the conductive agent is also prone to agglomeration. These agglomeration phenomena lead to poor processability of the slurry. Slurry gel may occur in the front-stage homogenization process, and the viscosity increases rapidly, affecting the coating consistency, and further having an adverse impact on the electrical performance and cycle performance of the battery cell. To address these problems, solutions need to be found to ensure the uniform dispersion of lithium iron phosphate materials and conductive agents in the slurry, improve the stability of the slurry, as well as the rate performance and cycle performance of the battery cell. Summary of the Invention

[0004] In view of the above problems existing in the prior art, the present application provides a positive electrode slurry, a positive electrode sheet, an electrochemical device including the same, and an electronic device. By matching the mass percentage, particle size distribution coefficient, specific surface area of the active material and the conductive agent in the positive electrode slurry, and the volume percentage of particles with a particle size less than 300 nm in the active material, the dispersion and stability of the positive electrode slurry are effectively improved, thereby improving the electrochemical performance and cycle performance of the electrochemical device.

[0005] The first aspect of the present application provides a positive electrode slurry, which includes an active material and a conductive agent, and the positive electrode slurry satisfies:

[0006]

[0007] where θ represents the volume percentage of particles with a particle size less than 300 nm in the active material; X1 represents the percentage of the mass of the active material in the solid mass of the positive electrode slurry; X2 represents the percentage of the mass of the conductive agent in the solid mass of the positive electrode slurry; S1 represents the specific surface area of the active material, in units of m 2 / g; S2 represents the specific surface area of the conductive agent, in units of m 2 / g; D1 represents the particle size distribution coefficient of the active material; D1 = (D901 - D101) / D501, where D101 represents the particle size at which the volume fraction of the active material in the particle size distribution based on volume is 10%, D501 represents the particle size at which the volume fraction of the active material in the particle size distribution based on volume is 50%, D901 represents the particle size at which the volume fraction of the active material in the particle size distribution based on volume is 90%, and the units of D101, D501, and D901 are all μm; D2 represents the particle size distribution coefficient of the conductive agent; D2 = (D902 - D102) / D502, where D102 represents the particle size at which the volume fraction of the conductive agent in the particle size distribution based on volume is 10%, D502 represents the particle size at which the volume fraction of the conductive agent in the particle size distribution based on volume is 50%, D902 represents the particle size at which the volume fraction of the conductive agent in the particle size distribution based on volume is 90%, and the units of D102, D502, and D902 are all μm.

[0008] The second aspect of the present application provides a method for preparing a positive electrode slurry for preparing the aforementioned positive electrode slurry.

[0009] The third aspect of the present application provides a positive electrode sheet solidified from the aforementioned positive electrode slurry or the positive electrode slurry prepared according to the aforementioned preparation method.

[0010] The fourth aspect of the present application provides an electrochemical device including the aforementioned positive electrode sheet.

[0011] The fifth aspect of the present application provides an electronic device including the aforementioned electrochemical device.

[0012] The technical solution of the present application can achieve the following beneficial effects:

[0013] By regulating the distribution relationship among the mass percentage, specific surface area, particle size distribution coefficient of the active material and the conductive agent in the positive electrode slurry, and the volume percentage of particles with a particle size less than 300 nm in the active material, the present application makes it meet specific limiting conditions. For the positive electrode slurry that meets these limiting conditions, a good dispersion system can be formed among the components in the slurry. While increasing the solid content of the positive electrode slurry, the dispersibility and stability of the positive electrode slurry can be effectively maintained, thereby improving the electrochemical performance and cycling performance of the electrochemical device and reducing the impedance. Specific Embodiments

[0014] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. The described embodiments herein are illustrative in nature and are used to provide a basic understanding of the present application. The embodiments of the present application should not be construed as a limitation of the present application.

[0015] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recited.

[0016] In the description herein, unless otherwise specified, "above" and "below" include the recited number.

[0017] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured by various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0018] The list of items connected by the terms "at least one of", "at least one", "at least one kind of" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.

[0019] I. Positive electrode slurry

[0020] One or more embodiments of the present application provide a positive electrode slurry, which includes an active material and a conductive agent, and the positive electrode slurry satisfies:

[0021]

[0022] Wherein, θ represents the volume percentage of particles in the active material with a particle size less than 300 nm; X1 represents the percentage of the mass of the active material in the solid mass of the positive electrode slurry; X2 represents the percentage of the mass of the conductive agent in the solid mass of the positive electrode slurry; S1 represents the specific surface area of the active material, with the unit m 2 / g; S2 represents the specific surface area of the conductive agent, with the unit m 2 / g; D1 represents the particle size distribution coefficient of the active material; D1 = (D901 - D101) / D501, where D101 represents the particle size at which the volume fraction of the active material in the particle size distribution on a volume basis is 10%, D501 represents the particle size at which the volume fraction of the active material in the particle size distribution on a volume basis is 50%, D901 represents the particle size at which the volume fraction of the active material in the particle size distribution on a volume basis is 90%, and the units of D101, D501, and D901 are all μm; D2 represents the particle size distribution coefficient of the conductive agent; D2 = (D902 - D102) / D502, where D102 represents the particle size at which the volume fraction of the conductive agent in the particle size distribution on a volume basis is 10%, D502 represents the particle size at which the volume fraction of the conductive agent in the particle size distribution on a volume basis is 50%, D902 represents the particle size at which the volume fraction of the conductive agent in the particle size distribution on a volume basis is 90%, and the units of D102, D502, and D902 are all μm.

[0023] In this application, by regulating the distribution relationship among the mass percentage, specific surface area, particle size distribution coefficient of the active material and the conductive agent in the positive electrode paste, and the volume percentage of particles with a particle size less than 300 nm in the active material, so as to satisfy the above specific limiting conditions. For the positive electrode paste that meets these limiting conditions, a good dispersion system can be formed among the components in the paste. While increasing the solid content of the positive electrode paste, the dispersibility and stability of the positive electrode paste can be effectively maintained, thereby improving the electrochemical performance and cycling performance of the electrochemical device and reducing the impedance.

[0024] In some embodiments, it is 0.15, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.6, 4.8, 5.0, 5.2, 5.4, 5.58 or the range composed of any two of the above values.

[0025] In some embodiments, Within this limiting range, the components in the paste are uniformly dispersed, which is beneficial to improving the stability of the paste and reducing the film resistance of the electrode sheet, and further beneficial to the performance of the lithium-ion battery and the improvement of the cycling performance.

[0026] In some embodiments, the volume percentage θ of the particle size less than 300 nm in the active material satisfies: 0 < θ ≤ 10%. If the volume percentage of the particle size less than 300 nm in the active material is too high, the agglomeration phenomenon of the active material is more serious, resulting in poor dispersibility and stability of the slurry, an increase in the film resistance of the corresponding electrode sheet, and further affecting the electrochemical performance and cycling performance. In some embodiments, the volume percentage θ of the particle size less than 300 nm in the active material satisfies: 5% ≤ θ ≤ 10%. In some embodiments, the volume percentage θ of the particle size less than 300 nm in the active material is 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or the range composed of any two of the above values.

[0027] In some embodiments, the percentage X1 of the mass of the active material in the solid mass of the positive electrode slurry satisfies: 92% ≤ X1 ≤ 97%. If the percentage X1 of the mass of the active material in the solid mass of the positive electrode slurry is too high, the proportion of the corresponding conductive agent or binder is too low, resulting in too large a film resistance or too low a bonding force of the electrode sheet, and further resulting in poor electrical performance or film peeling and powder falling of the battery cell; if the percentage X1 of the mass of the active material in the solid mass of the positive electrode slurry is too low, the energy density of the battery cell will be severely reduced; controlling the percentage X1 of the mass of the active material in the solid mass of the positive electrode slurry within this range is beneficial to the electrical performance and energy density improvement of the battery cell. In some embodiments, the percentage X1 of the mass of the active material in the solid mass of the positive electrode slurry is 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.50%, 97% or the range composed of any two of the above values. In some embodiments, the percentage X1 of the mass of the active material in the solid mass of the positive electrode slurry satisfies: 95% ≤ X1 ≤ 97%.

[0028] In some embodiments, the percentage X2 of the mass of the conductive agent in the solid mass of the positive electrode slurry satisfies: 0.25% ≤ X2 ≤ 3%. If the percentage of the mass of the conductive agent in the solid mass of the positive electrode slurry is too high, the proportion of the active material will decrease, which will in turn affect the energy density of the battery cell and is also not conducive to the improvement of the dispersion and stability of the slurry. If the percentage of the mass of the conductive agent in the solid mass of the positive electrode slurry is too low, the film resistance of the electrode sheet is too high, resulting in a decrease in the electrical performance of the battery cell. Controlling the percentage of the mass of the conductive agent in the solid mass of the positive electrode slurry within this range is beneficial to both the performance of the battery cell's electrical properties and the improvement of the energy density of the battery cell and the dispersion stability of the slurry. In some embodiments, the mass percentage X2 of the conductive agent in the positive electrode slurry is 0.25%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0% or the range composed of any two of the above values. In some embodiments, the percentage X2 of the mass of the conductive agent in the solid mass of the positive electrode slurry satisfies: 0.8% ≤ X2 ≤ 2%.

[0029] In some embodiments, the specific surface area S1 of the active material satisfies: 10 ≤ S1 ≤ 15. If the specific surface area of the active material is too large, the agglomeration phenomenon of the active material is more serious, resulting in poor dispersion and stability of the slurry, affecting the electrochemical performance and cycling performance. If the specific surface area of the active material is too small, it is not conducive to the improvement of the compaction density of the electrode sheet, and thus affects the improvement of the volume energy density of the battery cell. Therefore, it is necessary to limit the specific surface area of the active material within the above range. In some embodiments, the specific surface area S1 of the active material is 10.0, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8, 12.0, 12.2, 12.4, 12.6, 12.8, 13.0, 13.2, 13.4, 13.6, 13.8, 14.0, 14.2, 14.4, 14.6, 14.8, 15.0 or the range composed of any two of the above values. In some embodiments, the specific surface area S1 of the active material satisfies: 11 ≤ S1 ≤ 14.

[0030] In some embodiments, the specific surface area S2 of the conductive agent satisfies: 120 ≤ S2 ≤ 200. If the specific surface area of the conductive agent is too large, the agglomeration phenomenon of the conductive agent is more serious, resulting in poor dispersibility and stability of the slurry, affecting the electrochemical performance and cycling performance. If the specific surface area of the conductive agent is too small, it is not conducive to improving the compaction density of the electrode sheet, and thus affects the improvement of the volumetric energy density of the battery cell. Therefore, the specific surface area of the conductive agent needs to be limited within the above range. In some embodiments, the specific surface area S2 of the conductive agent is 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200 or the range composed of any two of the above values. In some embodiments, the specific surface area S2 of the conductive agent satisfies: 150 ≤ S2 ≤ 200.

[0031] In some embodiments, the particle size distribution coefficient D1 of the active material satisfies: 2.5 ≤ D1 ≤ 18. The larger the particle size distribution coefficient of the active material, the more difficult it is to disperse evenly, affecting the electrochemical performance and cycling performance; the smaller the particle size distribution coefficient of the active material, the less conducive to improving the compaction density of the electrode sheet, and thus affects the improvement of the volumetric energy density of the battery cell. Controlling the particle size distribution coefficient of the active material within this range is conducive to the performance of the battery cell's electrical properties and the improvement of the volumetric energy density. In some embodiments, the particle size distribution coefficient D1 of the active material is 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or the range composed of any two of the above values. In some embodiments, the particle size distribution coefficient D1 of the active material satisfies: 5 ≤ D1 ≤ 15.

[0032] In some embodiments, the particle size distribution coefficient D2 of the conductive agent satisfies: 1.2 ≤ D2 ≤ 2.0. The larger the particle size distribution coefficient of the conductive agent, the more difficult it is to disperse evenly, affecting the electrochemical performance and cycling performance; the smaller the particle size distribution coefficient of the conductive agent, the less conducive to improving the compaction density of the electrode sheet; controlling the particle size distribution coefficient of the conductive agent within this range is conducive to the performance of the battery cell's electrical properties and the improvement of the volumetric energy density. In some embodiments, the particle size distribution coefficient D2 of the conductive agent is 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or the range composed of any two of the above values. In some embodiments, the particle size distribution coefficient D2 of the conductive agent satisfies: 1.5 ≤ D2 ≤ 2.0.

[0033] In some embodiments, the D501 of the active material satisfies: 0.8 ≤ D501 ≤ 1.8. In some embodiments, the D501 of the active material is 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or the range composed of any two of the above values.

[0034] In some embodiments, D901 of the active material satisfies: 10 ≤ D901 ≤ 14.5. In some embodiments, D901 of the active material is 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, or a range composed of any two of the above values.

[0035] In some embodiments, D101 of the active material satisfies: 0.3 ≤ D101 ≤ 0.6. In some embodiments, D101 of the active material is 0.3, 0.4, 0.5, 0.6, or a range composed of any two of the above values.

[0036] In some embodiments, the active material includes a lithium iron phosphate material; the lithium iron phosphate material includes at least one of Li x Fe y A (1-y) PO4 materials, where A includes at least one of the elements Mn, Co, Ti, Mg, Ca, Cr, Cu, Ni, V, Mo, Zn, Al, B, and Nb, 0.05 ≤ x ≤ 1.2, 0 < y ≤ 1.

[0037] In some embodiments, the dispersant includes at least one of polyester, polyacrylate, amino alcohol, polyolefin, and polyether.

[0038] In some embodiments, the polyester includes polyphosphate.

[0039] In some embodiments, the phosphate includes at least one of the compounds shown in Formula I,

[0040]

[0041] In Formula I, R 1 、R 2 、R 3 are each independently selected from H, C1-C8 alkyl, fluorine-substituted C1-C8 alkyl, C1-C8 alkenyl, fluorine-substituted C1-C8 alkenyl, C1-C8 alkoxy, fluorine-substituted C1-C8 alkoxy, SO3 - 、COO - 、NT2 or NT 3+ ; where T is selected from H, C1-C8 alkyl, fluorine-substituted C1-C8 alkyl, C1-C8 alkenyl, fluorine-substituted C1-C8 alkenyl, C1-C8 alkoxy, or fluorine-substituted C1-C8 alkoxy.

[0042] Exemplarily, the above phosphates include at least one of phosphate or polyphosphate. Exemplarily, the polyphosphates include at least one of sodium hexametaphosphate, sodium polyphosphate (Calgon N), potassium tripolyphosphate (KTPP), and tetrapotassium pyrophosphate (TKPP).

[0043] In some embodiments, the polyesters may be polyester compounds formed by the reaction of carboxyl-terminated polyesters with polyamines or amino alcohol substances, with -C-NH- or -C-O- as the bridging group and amine as the anchoring group.

[0044] In some embodiments, the polyacrylate compounds include at least one of the compounds shown in Formula II,

[0045]

[0046] In Formula II, R is selected from H, C1-C8 alkyl, fluorine-substituted C1-C8 alkyl, C1-C6 alkenyl, fluorine-substituted C1-C8 alkenyl, C1-C8 alkoxy, fluorine-substituted C1-C8 alkoxy, SO3 - , COO - , NT2 or NT 3+ ; wherein, T is selected from H, C1-C8 alkyl, fluorine-substituted C1-C8 alkyl, C1-C8 alkenyl, fluorine-substituted C1-C8 alkenyl, C1-C8 alkoxy or fluorine-substituted C1-C8 alkoxy;

[0047] R' is selected from H, C1-C8 alkyl, fluorine-substituted C1-C8 alkyl, C1-C6 alkenyl, fluorine-substituted C1-C8 alkenyl, C1-C8 alkoxy, fluorine-substituted C1-C8 alkoxy;

[0048] n is a natural number greater than 1.

[0049] Exemplarily, the above polyacrylates include at least one of carboxyl-terminated polyacrylate, hydroxyl-terminated polyacrylate, polyacrylic acid, and polyurethane-modified acrylic acid.

[0050] Exemplarily, the above polyolefins include end-group polyisobutene.

[0051] Exemplarily, the above amino alcohol compounds include at least one of polymer polyol compounds and amino alcohol compounds. Exemplarily, the amino alcohol compounds are preferably ethanolamine or 2-amino-2-methyl-1-propanol.

[0052] Exemplarily, the above polyether compounds include, but are not limited to, perfluoropolyether compounds and polyetherimide compounds.

[0053] The common feature of the above dispersants is that the main chain is a saturated hydrocarbon polymer with high oxidation resistance, and at least one anchoring group such as an ester group, a carboxyl group, a phosphate group, an amino group, and a hydroxyl group is linked to the main chain. This anchoring group has good affinity for carbon-coated lithium iron phosphate nanoparticles and conductive agent nanoparticles. In addition, a side chain is introduced into the main chain, and this side chain is a flexible solvation chain that can extend into the dispersion medium, inhibiting the agglomeration between carbon-coated lithium iron phosphate nanoparticles and conductive agent nanoparticles through steric hindrance effects, effectively solving the dispersion problem of lithium iron phosphate and conductive agent in the slurry, and maintaining the stability of the slurry viscosity.

[0054] In some embodiments, based on the solid mass of the positive electrode slurry, the mass percentage content of the dispersant is represented as F, satisfying: 0.2% ≤ F ≤ 1.0%. In some embodiments, the mass percentage content F of the dispersant is 0.2%, 0.4%, 0.6%, 0.8%, 1.0% or the range composed of any two of the above values.

[0055] In some embodiments, the conductive agent includes at least one of carbon black, carbon nanotubes, nanofibrous carbon, Ketjen black, acetylene black, and graphene.

[0056] In some embodiments, the conductive agent includes carbon black and carbon nanotubes, and the mass ratio of carbon black to carbon nanotubes is 1:1 to 5:1. The ratio of carbon black to carbon nanotubes can be adjusted, and the embodiments of the present application do not make specific limitations on this.

[0057] In some embodiments, the solid content of the positive electrode slurry is 50% to 68%. In some embodiments, the solid content of the positive electrode slurry is 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68% or the range composed of any two of the above values. In some embodiments, the solid content of the positive electrode slurry is 52% to 64%.

[0058] In some embodiments, the viscosity value of the positive electrode slurry is 3000 mPa·s to 15000 mPa·s. In some embodiments, the viscosity value of the positive electrode slurry is 3000 mPa·s, 4000 mPa·s, 5000 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 11000 mPa·s, 12000 mPa·s, 13000 mPa·s, 14000 mPa·s, 15000 mPa·s or the range composed of any two of the above values. In some embodiments, the viscosity value of the positive electrode slurry is 4000 mPa·s to 10000 mPa·s.

[0059] In some embodiments, the positive electrode paste further includes a binder, and the binder includes, but is not limited to: at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon. In some embodiments, the binder is preferably polyvinylidene fluoride (PVDF).

[0060] In some embodiments, based on the solid mass of the positive electrode paste, the mass percentage content of the binder is represented as E, and satisfies: 1.5% ≤ E ≤ 5%. In some embodiments, the mass percentage content E of the binder is 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% or a range composed of any two of the above values.

[0061] One or more embodiments of the present application further provide a preparation method of the above positive electrode paste, including the following steps:

[0062] S1. Dispersing and stirring a dispersant, a conductive agent, and a solvent to obtain a first mixed paste;

[0063] S2. High-viscosity stirring an active material, a binder, a solvent, and the first mixed paste to obtain a second mixed paste;

[0064] S3. High-speed dispersing and stirring a solvent and the second mixed paste to obtain the positive electrode paste.

[0065] In some embodiments, the revolution speed of the stirring in S1 is 5 rmp to 30 rmp. In some embodiments, the revolution speed of the stirring is 5 rmp, 10 rmp, 15 rmp, 20 rmp, 25 rmp, 30 rmp, or a range composed of any two of the above values.

[0066] In some embodiments, the dispersion speed in S1 is 300 rmp to 3000 rmp. In some embodiments, the dispersion speed is 300 rmp, 500 rmp, 1000 rmp, 1500 rmp, 2000 rmp, 2500 rmp, 3000 rmp, or a range composed of any two of the above values.

[0067] In some embodiments, the stirring time in S1 is 30 min to 60 min. In some embodiments, the stirring time is 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or a range composed of any two of the above values.

[0068] In some embodiments, the stirring temperature of S1 is 15°C to 45°C. In some embodiments, the stirring and mixing temperature is 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or the range composed of any two of the above values.

[0069] In S1, the dispersant and the conductive agent are first mixed with a part of the solvent to prepare the first mixed slurry, and the relatively difficult-to-disperse conductive agent can be pre-dispersed into a uniform and stable slurry.

[0070] In some embodiments, the stirring revolution speed of S2 is 10 rmp to 25 rmp. In some embodiments, the stirring revolution speed is 10 rmp, 15 rmp, 20 rmp, 25 rmp or the range composed of any two of the above values.

[0071] In some embodiments, the dispersion speed of S2 is 0 to 100 rmp. In some embodiments, the dispersion speed is 0, 20 rmp, 40 rmp, 60 rmp, 80 rmp, 100 rmp or the range composed of any two of the above values.

[0072] In some embodiments, the stirring time of S2 is 30 min to 75 min. In some embodiments, the stirring time is 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min or the range composed of any two of the above values.

[0073] In some embodiments, the stirring temperature of S2 is 25°C to 70°C. In some embodiments, the stirring and mixing temperature is 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or the range composed of any two of the above values.

[0074] The high-viscosity kneading and stirring in S2 is beneficial to both the shear dispersion of nano-aggregated particles and the coating and depolymerization of the dispersant on the aggregated particles.

[0075] In some embodiments, the stirring revolution speed of S3 is 10 rmp to 30 rmp. In some embodiments, the stirring revolution speed is 10 rmp, 15 rmp, 20 rmp, 25 rmp, 30 rmp or the range composed of any two of the above values.

[0076] In some embodiments, the dispersion speed of S3 is 500 rmp to 3000 rmp. In some embodiments, the dispersion speed is 500 rmp, 1000 rmp, 1500 rmp, 2000 rmp, 2500 rmp, 3000 rmp or the range composed of any two of the above values.

[0077] In some embodiments, the stirring time of S3 is from 60 min to 180 min. In some embodiments, the stirring time is 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, or the range composed of any two of the above values.

[0078] In some embodiments, the stirring temperature of S3 is from 15 °C to 45 °C. In some embodiments, the stirring and mixing temperature is 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, or the range composed of any two of the above values.

[0079] II. Positive electrode tab

[0080] One or more embodiments of the present application further provide a positive electrode tab, which includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer is cured from the aforementioned positive electrode paste or the positive electrode paste prepared by the aforementioned preparation method.

[0081] In some embodiments, the positive electrode current collector includes, but is not limited to, a metal foil or a composite current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0082] III. Electrochemical device

[0083] One or more embodiments of the present application further provide an electrochemical device, including the aforementioned positive electrode tab.

[0084] The electrochemical device of the present application further includes a negative electrode tab, an electrolyte, and a separator.

[0085] In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material. The negative electrode active material includes at least one of a silicon-based material, a carbon-based material, a tin-based material, a phosphorus-based material, and metallic lithium. The silicon-based material includes at least one of silicon, a silicon alloy, a silicon oxide compound, and a silicon carbide compound. The carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon nanotubes, and graphene. The tin-based material includes at least one of tin, a tin oxide, and a tin alloy. The negative electrode current collector includes at least one of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.

[0086] In some embodiments, the negative electrode sheet further includes a binder and a conductive agent. The binder includes, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon. The conductive agent includes, but is not limited to, at least one of carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based materials include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based materials include metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer includes polyphenylene derivatives.

[0087] The electrochemical device of the present application further includes an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.

[0088] In some embodiments of the present application, the lithium salt includes, but is not limited to, one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, or lithium difluoroborate. Exemplarily, the lithium salt can be LiPF6.

[0089] The non-aqueous solvent includes, but is not limited to, one or more of carbonate compounds, carboxylate compounds, or ether compounds.

[0090] Exemplarily, the carbonate compounds include, but are not limited to, one or more of linear carbonate compounds or cyclic carbonate compounds. Specifically, the linear carbonate compounds include, but are not limited to, one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC); the cyclic carbonate compounds include, but are not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylene carbonate (VEC).

[0091] Exemplarily, the carboxylate compounds include, but are not limited to, one or more of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, or caprolactone.

[0092] Exemplarily, the ether compounds include, but are not limited to, one or more of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran.

[0093] In some embodiments, a separator is provided between the positive electrode sheet and the negative electrode sheet to prevent short circuit. There are no particular limitations on the material and shape of the separator that can be used in the embodiments of the present application, and it can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer, an inorganic substance, etc. formed of a material that is stable to the electrolyte of the present application.

[0094] The electrochemical device of the present application includes, but is not limited to: all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to: lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries.

[0095] In a specific example of the present invention, the electrochemical device is a lithium ion battery, and the present application does not specifically limit the type of the lithium ion battery, and it can be any type of lithium ion battery, such as a button type, a cylindrical type, a soft package type lithium ion battery, etc.

[0096] IV. Electronic Device

[0097] One or more embodiments of the present application further provide an electronic device, and the electronic device includes the aforementioned electrochemical device.

[0098] In some embodiments, the electronic device of the present application includes, but is not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, hand-held cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, or lithium ion capacitors, etc.

[0099] Hereinafter, the electrochemical device of the present application will be further elaborated with specific examples and comparative examples.

[0100] Examples and Comparative Examples

[0101] Hereinafter, examples and comparative examples are given to further specifically illustrate the present application, but the present application is not limited to these examples as long as it does not deviate from its gist.

[0102] The active materials, dispersants, conductive agents, binders, solvents, etc. used in the following examples were all obtained commercially.

[0103] Example 1

[0104] Preparation of the positive electrode slurry:

[0105] S1. 15 kg of the solvent N-methylpyrrolidone (NMP), 0.406 kg of the dispersant (end-capped polyisobutylene), 0.649 kg of super conductive carbon, and 8.114 kg of multi-walled carbon nanotubes (solid content 4%) were successively added to a 100 L double planetary mixer. The mixer was mixed and dispersed according to the parameters of 20 rmp for revolution, 1800 rmp for dispersion, 60 min for stirring time, and 30 °C for temperature to obtain a first mixed slurry;

[0106] S2. 78.142 kg of the active material LiFePO4, 1.623 kg of the binder polyvinylidene fluoride (PVDF), and 4.258 kg of the solvent N-methylpyrrolidone (NMP) were successively added to the double planetary mixer containing the first mixture, and the solid content of the mixture was controlled to be 75%; the mixer was highly viscous stirred according to the parameters of 10 rmp for revolution, 50 rmp for dispersion, 45 min for stirring time, and 45 °C for temperature to obtain a second mixed slurry;

[0107] S3. 36.578 kg of the solvent N-methylpyrrolidone (NMP) was added to the second mixed slurry. The mixer was subjected to high-speed dispersion stirring according to the parameters of 20 rmp for revolution, 2000 rmp for dispersion, 170 min for stirring time, and 30 °C for temperature to obtain a positive electrode slurry with a solid content of 56% and a viscosity value of 8000 mPa·s.

[0108] In the positive electrode active material, the volume percentage θ of the particles with a particle size less than 300 nm in the active material was 8%; the specific surface area S1 of the active material was 12.5 m 2 / g; the particle size distribution coefficient D1 of the active material was 7.5. In the positive electrode slurry, the solid mass of the positive electrode slurry was 81.144 kg; the mass percentage X1 of the active material was 96.3%; the mass percentage X2 of the conductive agent was 1.2%; the mass percentage of the dispersant was 0.5%; the mass percentage of the binder was 2.0%; the specific surface area S2 of the conductive agent was 180 m 2 / g; the particle size distribution coefficient D2 of the conductive agent was 1.6.

[0109] Preparation of the positive electrode plate: The positive electrode slurry prepared by the foregoing method was uniformly coated on both surfaces of a positive electrode current collector aluminum foil with a thickness of 12 μm, dried, and roll-pressed to obtain a positive electrode plate.

[0110] Preparation of the negative electrode sheet: Artificial graphite was used as the negative electrode active material. The negative electrode active material, binder SBR, CMC, PAA, conductive carbon black, and carbon nanotubes were mixed according to the mass ratio of negative electrode active material:SBR:CMC:PAA:conductive carbon black:carbon nanotubes = 96:1:0.5:1:1:0.5. Ultra-pure water was added, and the negative electrode slurry was obtained through a high-speed mixer. The negative electrode slurry was uniformly coated on the surface of a negative electrode current collector copper foil with a thickness of 8 μm, dried and roll-pressed to obtain the negative electrode sheet.

[0111] Preparation of the electrolyte: Dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 1:1:1 as the solvent. Based on the volume of the solvent, 1 mol / L LiPF6 was added as the lithium salt. Based on the mass of the solvent, 5% vinylene carbonate (VC) was added as an additive to obtain the electrolyte.

[0112] Separator: A 11-μm-thick PE porous polymer separator was used.

[0113] Preparation of the lithium-ion battery: After cutting the negative electrode sheet and the positive electrode sheet into a size of 46 mm by 54 mm, they were stacked together with the separator to assemble a bare battery cell. Then, the electrode tabs were welded, and the cell was assembled into an aluminum-plastic film. After that, electrolyte injection, standing, formation, and grading were carried out to fabricate the lithium-ion battery.

[0114] Examples 2 to 11

[0115] Examples 2 to 11 were obtained by adjusting the mass percentages X1 and X2 of the active material and the conductive agent, specific surface areas S1 and S2, particle size distribution coefficients D1 and D2, volume percentage θ of particles with a particle size less than 300 nm in the active material, type and percentage of the dispersant in the positive electrode slurry on the basis of Example 1. The specific data are shown in Table 1. The other preparation methods of Examples 2 to 11 were the same as those of Example 1.

[0116] Comparative Example 1

[0117] Preparation of the positive electrode slurry:

[0118] 78.953 kg of the active material LiFePO4, 1.996 kg of the binder polyvinylidene fluoride (PVDF), 62.977 kg of the solvent N-methylpyrrolidone (NMP), 0.162 kg of super conductive carbon, and 0.8114 kg of multi-walled carbon nanotubes (solid content 4%) were successively added to a 100-L double planetary mixer. The mixer was mixed and dispersed according to the parameters of revolution at 20 rmp, dispersion at 2000 rmp, mixing time of 180 min, and temperature of 30 °C to obtain a positive electrode slurry with a solid content of 56% and a viscosity value of 8500 mPa·s.

[0119] In the positive electrode active material, the volume percentage θ of particles with a particle size less than 300 nm in the active material is 0.2%; the specific surface area S1 of the active material is 9.5 m 2 / g; the particle size distribution coefficient D1 of the active material is 2.4. In the positive electrode slurry, the solid mass of the positive electrode slurry is 81.14 kg; the mass percentage X1 of the active material is 97.3%; the mass percentage X2 of the conductive agent is 0.24%; the mass percentage of the binder is 2.46%; the specific surface area S2 of the conductive agent is 115 m 2 / g; the particle size distribution coefficient D2 of the conductive agent is 2.5.

[0120] Preparation of the positive electrode sheet: The positive electrode slurry prepared by the aforementioned method is uniformly coated on both surfaces of a positive electrode current collector aluminum foil with a thickness of 12 μm, dried and roll-pressed to obtain a positive electrode sheet.

[0121] Preparation of the negative electrode sheet: Artificial graphite is used as the negative electrode active material, and the negative electrode active material, binder SBR, CMC, PAA, conductive carbon black, and carbon nanotubes are mixed according to the mass ratio of negative electrode active material:SBR:CMC:PAA:conductive carbon black:carbon nanotubes = 96:1:0.5:1:1:0.5, and ultrapure water is added. The negative electrode slurry is obtained by a high-speed mixer, and the negative electrode slurry is uniformly coated on the surface of a negative electrode current collector copper foil with a thickness of 8 μm, dried and roll-pressed to obtain a negative electrode sheet.

[0122] Preparation of the electrolyte: Dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 1:1:1 as the solvent. Based on the volume of the solvent, 1 mol / L LiPF6 is added as the lithium salt, and based on the mass of the solvent, 5% vinylene carbonate (VC) is added as an additive to obtain the electrolyte.

[0123] Separator: An 11-μm-thick PE porous polymer separator is used.

[0124] Preparation of the lithium-ion battery: After cutting the negative electrode sheet and the positive electrode sheet into a size of 46 mm by 54 mm, they are stacked together with the separator. After assembling into a bare battery cell, the electrode tabs are welded and assembled into an aluminum-plastic film, and then liquid injection, standing, formation, and grading are carried out to manufacture the lithium-ion battery.

[0125] Comparative Example 2

[0126] Comparative Example 2 is obtained by adjusting the mass percentages X1 and X2 of the active material and the conductive agent, the specific surface areas S1 and S2, the particle size distribution coefficients D1 and D2, and the volume percentage θ of particles with a particle size less than 300 nm in the active material in Comparative Example 1. The specific data are shown in Table 1. The other preparation methods of Comparative Example 2 are the same as those of Comparative Example 1.

[0127] Comparative Example 3-4

[0128] Based on Example 1, Comparative Example 3-4 was obtained by adjusting the mass percentages X1 and X2 of the active material and the conductive agent, the specific surface areas S1 and S2, the particle size distribution coefficients D1 and D2, the volume percentage θ of particles with a particle size less than 300 nm in the active material, the type and percentage of the dispersant. The specific data are shown in Table 1. The other preparation methods of Comparative Example 3-4 are the same as those of Example 1.

[0129] Testing Method

[0130] 1. Particle Size Testing:

[0131] 1) Place the selected powder sample in the sample cup of the instrument, and place the sample cup at the measurement position of the laser particle size analyzer.

[0132] 2) Turn on the power of the laser particle size analyzer and start the measurement program. In the program interface, different measurement modes can be selected according to needs, such as single measurement, continuous measurement, etc.

[0133] 3) During the measurement, it is necessary to keep the sample cup stable and avoid vibration or shaking. At the same time, parameters of the measurement program need to be set, such as the measurement range, measurement time, volume distribution, etc.

[0134] 4) After starting the measurement, the laser particle size analyzer will start to measure the powder sample. By analyzing the scattered light intensity of the powder sample, the particle size volume distribution data of the powder sample can be obtained.

[0135] 5) After the measurement is completed, the experimental data need to be recorded and analyzed. The particle size distribution of the powder sample can be shown by plotting the particle size distribution curve to obtain the volume particle size data.

[0136] Read D10, D50, D90 and the volume percentage of particles with a particle size less than 300 nm using the above particle size data.

[0137] 2. Specific Surface Area Testing of Particles:

[0138] 1) Load the sample to be tested (30 - 500 mg, varying according to the specific surface area of the sample) into the sample tube.

[0139] 2) Install the sample tube onto the degassing station. When installing the sample tube, it must be aligned with the port, and the screws tightened to ensure secure sealing. Then, put the heating jacket on the sample tube, set parameters such as file information and degassing temperature, turn on the vacuum pump, and start heating and vacuum degassing the sample to remove the gas adsorbed on the material surface. After degassing is completed, turn off the heating power supply. After the sample has cooled to room temperature, backfill with helium gas. After filling the helium gas to atmospheric pressure, remove the sample tube and immediately cover it with a rubber stopper, weigh it to 0.1 mg, and record the weight of the sample tube filled with helium gas, the stopper, and the filling rod. This is the gross weight of the sample tube. Use the same sample tube, stopper, and filling rod for the following operations. The sample is weighed using the subtraction method: a. Place the bracket on the balance and tare it to zero; b. Put the sealed filter plug on the sample tube or place the stopper on the bracket and record the reading m1; c. Load the sample into the sample tube through a funnel, put on the sealed plug or stopper, weigh and record the reading m2; d. Install the sample tube into the degassing station for degassing; e. Place the cooled degassed sample tube on the bracket after zeroing the operation, weigh and record the reading m3; f. Subtract the reading m1 from the reading m3 to obtain the sample mass.

[0140] 3) Install the weighed sample tube onto the analysis station, add liquid nitrogen to the Dewar flask, and input the sample mass into the analysis file. Set the test parameters and start the adsorption and desorption test process.

[0141] 4) After the test is completed, take out the sample from the sample tube. Wash the sample tube and dry it for future use.

[0142] 3. Slurry solid content test:

[0143] 1) Use an infrared drying solid content meter for testing. Connect the instrument to the main power supply and turn the two horizontal adjustment feet of the balance until the bubble is at the center of the level indicator.

[0144] 2) When the solid content meter is in a stable state, place the standard weight on the tray. After the reading stabilizes, record the data and set the defined drying temperature to 140 °C.

[0145] 3) Place a copper foil or aluminum foil of the same size as the tray on the tray for weighing. After its reading stabilizes, press the zero key to zero it.

[0146] 4) Test the slurry solid content. Use a spoon to thinly and evenly spread 0.8 - 1.2 g of the sample on the copper foil or aluminum foil, close the top cover, and press the "Start" key to start the test.

[0147] 5) When the screen shows that the test reaction is over, read the percentage of the sample solid content and record the test result.

[0148] 4. Slurry viscosity test:

[0149] 1) Use a rotational viscometer. Screw the rotor into the connecting screw (screw in to install towards the left, screw out to remove towards the right).

[0150] 2) Place 450 - 500 mL of the sample to be tested directly below the head of the viscometer. Lower the head so that the rotor notch is level with the liquid surface of the sample to be tested and the rotor should be at the center of the beaker; the thermometer should be placed in the slurry; the rotor scale should be flush with the liquid level line of the sample to be tested.

[0151] 3) Click the "Start" button to start the test; you can monitor the progress of the test by clicking "View Data"; after the measurement timing ends, read the viscosity and temperature values of the sample to be tested from the display screen and record the test results.

[0152] 5. Impedance Test:

[0153] 1) Fully discharge, adjust the temperature to 25 °C, a. Rest for 10 min; b. 0.5C DC 2.5V; c. Rest for 5 min.

[0154] 2) 5 °C 2C DCR test from 10% - 100% SOC: a. 1C CC for 6 min; b. Rest for 3 h, ensure that the temperature deviation between the battery cell and the ambient temperature is < 2 °C, record the terminal voltage V0; c. 2C DC for 30 s (sampling every 0.1 s), record the voltages at 1 s / 5 s / 10 s / 30 s during discharge and calculate DCR (voltage sampling frequency is 0.1 s, lower cut-off voltage is 2.0 V); d. Rest for 40 s, record the terminal voltage V1; e. 1.5C CC for 30 s (sampling every 0.1 s), record the voltages at 1 s / 5 s / 10 s / 30 s during discharge and calculate DCR (voltage sampling frequency is 0.1 s, upper cut-off voltage is 3.75 V); f. Repeat steps a - e 9 times; g. Rest for 5 min.

[0155] 6. Cycle Performance Test:

[0156] 1) Adjust the temperature to 25 °C, rest for 10 min.

[0157] 2) 0.5C DC 2.5V.

[0158] 3) Rest for 5 min.

[0159] 4) 1C CC to 3.65V, 3.65V CV with a charge rate of 0.05C.

[0160] 5) Rest for 5 min.

[0161] 6) 1C DC to 2.5V (the capacity of this step is denoted as C).

[0162] 7) Repeat steps 4 - 7, 3 times in a loop (take the average of the 6th step for 3 times as the initial capacity C0);

[0163] 8) Rest for 5 min;

[0164] 9) Charge at 1C CC to 3.65V, then discharge at 3.65V CV to 0.05C;

[0165] 10) Rest for 5 min;

[0166] 11) Discharge at 1C DC to 2.5V;

[0167] 12) Repeat steps 8 - 11, 200 times in a loop (take the capacity C 200 ) at the 200th time of step 11;

[0168] 13) Calculate the capacity retention rate as C 200 / C0.

[0169] The test results are shown in Table 1 below.

[0170] Table 1

[0171]

[0172] From the data comparison between Examples 1 - 11 and Comparative Examples 1 - 4, it can be seen that by regulating the distribution relationship among the mass percentage, specific surface area, particle size distribution coefficient of the active material and the conductive agent in the positive electrode slurry, and the volume percentage of particles with a particle size less than 300 nm in the active material, so that it meets The viscosity and solid content of the slurry are relatively stable, thus ensuring that the cycle capacity retention rate of the electrochemical device reaches more than 96% and the impedance is as low as below 0.3 ohm, showing a significant improvement compared with Comparative Examples 1 - 4. This is because, under this limited condition, a good dispersion system can be formed among the components in the slurry. While increasing the solid content of the positive electrode slurry, the dispersibility and stability of the positive electrode slurry are effectively maintained, thereby improving the electrochemical performance and cycle performance of the electrochemical device and reducing the impedance.

[0173] From the data comparison between Examples 1 - 9 and Examples 10 - 11, it can be seen that by regulating the distribution relationship among the mass percentage, specific surface area, particle size distribution coefficient of the active material and the conductive agent in the positive electrode slurry, and the volume percentage of particles with a particle size less than 300 nm in the active material, so that it further meets Under this limited condition, the components in the slurry are more uniformly dispersed, the viscosity and stability of the slurry are further improved, and thus the cycle capacity retention rate of the electrochemical device reaches 98% and above and the impedance is lower than 0.28 ohm.

[0174] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those of ordinary skill in the art will recognize that some modifications and changes can be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.

Claims

1. A positive electrode paste, characterized in that, The positive electrode paste includes an active material and a conductive agent, and the positive electrode paste satisfies: where θ represents the volume percentage of particles in the active material with a particle size less than 300 nm; X1 represents the percentage of the mass of the active material in the solid mass of the positive electrode paste; X2 represents the percentage of the mass of the conductive agent in the solid mass of the positive electrode paste; S1 represents the specific surface area of the active material, unit m 2 / g; S2 represents the specific surface area of the conductive agent, unit m 2 / g; D1 represents the particle size distribution coefficient of the active material; D1 = (D901 - D101) / D501, D101 represents the particle size at 10% volume cumulative in the particle size distribution of the active material on a volume basis, D501 represents the particle size at 50% volume cumulative in the particle size distribution of the active material on a volume basis, D901 represents the particle size at 90% volume cumulative in the particle size distribution of the active material on a volume basis, and the units of D101, D501, and D901 are all μm; D2 represents the particle size distribution coefficient of the conductive agent; D2 = (D902 - D102) / D502, D102 represents the particle size at 10% volume cumulative in the particle size distribution of the conductive agent on a volume basis, D502 represents the particle size at 50% volume cumulative in the particle size distribution of the conductive agent on a volume basis, D902 represents the particle size at 90% volume cumulative in the particle size distribution of the conductive agent on a volume basis, and the units of D102, D502, and D902 are all μm.

2. The positive electrode paste according to claim 1, characterized in that, The positive electrode paste also satisfies:

3. The positive electrode paste according to claim 1, characterized in that, The positive electrode paste also satisfies at least one of the following conditions: (1) 0% < θ ≤ 10%; (2)92％≤X1≤97％； (3)0.25％≤X2≤3％； (4)10≤S1≤15； (5)120≤S2≤200； (6)2.5≤D1≤18； (7)1.2≤D2≤2.0。 4. The positive electrode paste according to claim 1, characterized in that, The positive electrode paste also satisfies at least one of the following conditions: (1) 5% ≤ θ ≤ 10%; (2)95％≤X1≤97％； (3)0.8％≤X2≤2％； (4)11≤S1≤14； (5)150≤S2≤200； (6)5≤D1≤15； (7)1.5≤D2≤2.0。 5. The positive electrode paste according to claim 1, characterized in that, The positive electrode paste also satisfies at least one of the following conditions: (1) The active material includes a lithium iron phosphate material; the lithium iron phosphate material includes at least one of Li x Fe y A (1-y) PO4 materials, where A includes at least one of the elements Mn, Co, Ti, Mg, Ca, Cr, Cu, Ni, V, Mo, Zn, Al, B, and Nb, 0.05 ≤ x ≤ 1.2, 0 < y ≤ 1; (2)0.8≤D501≤1.8； (3)10≤D901≤14.5； (4)0.3≤D101≤0.6。 6. The positive electrode paste according to claim 1, characterized in that, The positive electrode paste also satisfies at least one of the following conditions: (1) The positive electrode material further includes a dispersant, and the dispersant includes at least one of polyester, polyacrylate, amino alcohol, polyolefin, and polyether; (2) The positive electrode material further includes a dispersant, and the mass percentage content of the dispersant based on the solid mass of the positive electrode paste is represented as F, satisfying: 0.2% ≤ F ≤ 1.0%; (3) The conductive agent includes at least one of carbon black, carbon nanotube, nanofiber carbon, Ketjen black, acetylene black, and graphene; (4) The conductive agent includes carbon black and carbon nanotubes, and the mass ratio of the carbon black to the carbon nanotubes is 1:1 to 5:1; (5) The positive electrode paste further includes a binder, and the mass percentage content of the binder based on the solid mass of the positive electrode paste is represented as E, satisfying: 1.5% ≤ E ≤ 5%.

7. A method for preparing a positive electrode paste according to any one of claims 1 to 6, characterized in that, Including the following steps: S1. Mix the dispersant, the conductive agent, and a solvent to obtain a first mixed paste; S2. Mix the active material, the binder, the solvent, and the first mixed paste to obtain a second mixed paste; S3. Mix the solvent and the second mixed paste to obtain the positive electrode paste.

8. A positive electrode sheet, characterized in that, It includes a positive current collector and a positive active material layer disposed on the positive current collector, and the positive active material layer is solidified from the positive electrode paste according to any one of claims 1 to 6 or the positive electrode paste prepared by the preparation method according to claim 7.

9. An electrochemical device, characterized in that, It includes a negative electrode sheet, a separator, an electrolyte, and the positive electrode sheet according to claim 8.

10. An electronic device, characterized in that, It includes the electrochemical device according to claim 9.

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