Electrode material, electrode plate and preparation method thereof, and secondary battery

Abstract

The present invention provides an electrode material, an electrode plate, a preparation method thereof, and a secondary battery. The electrode material includes an electrode active material, a conductive agent, and a binder; wherein the binder includes a first binder and a second binder (mass ratio of 0 to 0.2:1), or a first binder and a third binder (mass ratio of 0.05 to 0.3:1); the first binder includes one or more of polytetrafluoroethylene, polytrifluorochloroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and ethylene-chlorotrifluoroethylene copolymer; the second binder includes a copolymer of two or more of acrylic acid, acrylic ester, acrylonitrile, and acrylamide; and the third binder includes one or more of polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and a fluorine-containing acrylate resin.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to an electrode material, an electrode plate and a preparation method thereof, and a secondary battery. Background Art

[0002] Secondary batteries, such as lithium-ion batteries, are primarily composed of a positive electrode, a negative electrode, and an electrolyte. Charge and discharge occur through the movement of lithium ions between the positive and negative electrodes. Due to their high energy density and capacity, they are widely used as power sources for mobile devices. In recent years, they have also been widely used in electric and hybrid vehicles.

[0003] Currently, the typical industrial manufacturing method for secondary batteries involves wet coating a mixed slurry containing electrode active materials and a binder onto the electrode current collector. Furthermore, conventional techniques often incorporate organic additives during electrode sheet preparation. These additives are difficult to volatilize during drying and tend to remain in the electrode sheet, leading to increased interfacial impedance and the risk of degradation.

[0004] The commonly used binder for positive electrode is polyvinylidene fluoride (PVDF), and the commonly used binder for negative electrode is styrene-butadiene rubber (SBR) and / or sodium carboxymethyl cellulose (CMC). After coating, an oven is needed to dry the electrode to remove the solvent. The oven occupies a large area (50~60m 2 ), high energy consumption; and the slurry gel is easy to clog the filter element due to large viscosity rebound, viscosity fluctuation, and poor filtration, and cause particle scratches, fluid thinning and other problems due to poor dispersion; the binder floats and migrates during the drying process, resulting in uneven distribution in the thickness direction, reduced porosity in the upper layer, and rapid cycle attenuation. Summary of the Invention

[0005] The object of the present invention is to provide an electrode material, an electrode plate and a preparation method thereof, and a secondary battery. The electrode material has good adhesion and material fusion properties, and can be prepared into electrode plates by a quasi-dry method, avoiding the technical problems currently encountered in the preparation of electrode plates, such as solvent residue, large slurry viscosity rebound, easy clogging of filter elements during filtration, uneven dispersion of electrode materials, easy cracking of thick plates, and reduced energy density of secondary batteries.

[0006] To this end, a first aspect of the present invention provides an electrode material, comprising an electrode active material, a conductive agent, and a binder; the binder comprises a first binder, the first binder comprising one or a combination of two or more of the following: polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene and perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene and hexafluoropropylene copolymer, ethylene and chlorotrifluoroethylene copolymer; the binder further comprises a second binder or a third binder;

[0007] The second binder comprises one or a combination of two or more of the following: a copolymer of two or more of acrylic acid, acrylic ester, acrylonitrile, and acrylamide; the mass ratio of the first binder to the second binder is 0-0.2:1;

[0008] The third binder includes one or a combination of two or more of the following groups: polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and fluorine-containing acrylate resin. The mass ratio of the first binder to the third binder is 0.05~0.3:1.

[0009] Therefore, the present invention, by applying the above-mentioned electrode material, especially the binder therein, makes the electrode material have good adhesion and material fusion, avoiding the floating of the binder and the easy cracking of thick electrode sheets during the preparation process, avoiding the delamination phenomenon and the risk of demolding, thereby enabling the preparation of thick electrode sheets. When this electrode material is used in the electrode sheets of secondary batteries, it can increase the proportion of main materials, increase the energy density of the battery cell, and have the advantages of improving lithium ion transmission capacity, reducing impedance, and improving rate performance.

[0010] In any embodiment, in the electrode material, the mass percentage of the binder is 0.15-5%.

[0011] In any embodiment, the mass ratio of the first binder to the second binder is 0.01-0.2:1; the mass ratio of the first binder to the third binder is 0.1-0.3:1.

[0012] In any embodiment, in the electrode material, the mass percentage of the electrode active material is 91-99.65%, the mass percentage of the conductive agent is 0.2-4%, and the mass percentage of the binder is 0.15-5%.

[0013] In any embodiment, the copolymer included in the second binder has a weight average molecular weight greater than or equal to 300,000.

[0014] In any embodiment, the copolymer included in the second binder forms a three-dimensional cross-linked network structure through hydrogen bonding between polar groups.

[0015] In any embodiment, the conductive agent includes one or a combination of two or more of the following: conductive carbon black Super P (SP), acetylene black, Ketjen black (KB), carbon fiber, carbon nanotubes (CNTs), graphene, conductive graphite (such as KS-6, KS-15, SFG-6, MX-15, etc.).

[0016] In any embodiment, the electrode material is an electrode material for a positive electrode, which includes a positive electrode active material, a conductive agent, and a binder; the binder includes a first binder and a third binder.

[0017] In any embodiment, in the electrode material, the mass percentage of the positive electrode active material is 93-99.65%, the mass percentage of the conductive agent is 0.2-4%, and the mass percentage of the binder is 0.15-3.3%.

[0018] In any embodiment, in the electrode material, the mass ratio of the first binder to the third binder is 0.05-0.3:1.

[0019] In any embodiment, in the electrode material, the mass percentage of the first binder is 0.1-0.3%, and the mass percentage of the third binder is 0.3-3%.

[0020] In any embodiment, the positive electrode active material includes one or a combination of two or more of the following: lithium transition metal oxides, lithium-containing phosphates, Prussian blue, and layered oxides.

[0021] In any embodiment, the lithium transition metal oxide comprises one or a combination of two or more selected from the group consisting of lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi1 / 3Co1 / 3Mn1 / 3O2, referred to as NCM333; LiNi 0.5 Co 0.2 Mn 0.3 O2, which is referred to as NCM523; LiNi 0.5 Co 0.25 Mn 0.25 O2, which is referred to as NCM211; LiNi 0.6 Co 0.2 Mn 0.2 O2, which is referred to as NCM622; LiNi 0.8 Co 0.1 Mn 0.1 O2, which is referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds.

[0022] In any embodiment, the lithium-containing phosphate includes one or a combination of two or more selected from the following groups: lithium iron phosphate (e.g., LiFePO4, referred to as LFP), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0023] In any embodiment, the electrode material is an electrode material for a negative electrode, which includes a negative electrode active material, a conductive agent, and a binder; the binder includes a first binder and a second binder.

[0024] In any embodiment, in the electrode material, the mass percentage of the negative electrode active material is 91.7-98.8%, the mass percentage of the conductive agent is 0.2-4%, and the mass percentage of the binder is 1-4.3%.

[0025] In any embodiment, in the electrode material, the mass ratio of the first binder to the second binder is 0-0.2:1.

[0026] In any embodiment, in the electrode material, the mass percentage of the first binder is 0-0.3%, and the mass percentage of the second binder is 1-4%.

[0027] In any embodiment, the negative electrode active material includes one or a combination of two or more selected from the group consisting of natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, and silicon-carbon composite.

[0028] A second aspect of the present invention provides a battery pole piece, which includes the electrode material and a current collector according to the first aspect of the present invention, wherein the electrode material is arranged on the current collector.

[0029] In any embodiment, on the electrode plate, the material layer formed by the electrode active material has a porosity of 10-45%.

[0030] In any embodiment, on the electrode plate, the mass per unit area of ​​the electrode material is 150-600 mg / 1540.25 mm 2 .

[0031] In any embodiment, the electrode plate is an electrode plate for a positive electrode, and the mass per unit area of ​​the electrode material on the electrode plate is 350-600 mg / 1540.25 mm 2 .

[0032] In any embodiment, the electrode plate is an electrode plate for a positive electrode, and the electrode active material is a positive electrode active material; wherein the porosity of the material layer formed by the positive electrode active material is 10-45%.

[0033] In any embodiment, the electrode plate is an electrode plate for a negative electrode, and the mass per unit area of ​​the electrode material on the electrode plate is 150-400 mg / 1540.25 mm 2 .

[0034] In any embodiment, the electrode plate is an electrode plate for a negative electrode, and the electrode active material is a negative electrode active material; wherein the porosity of the material layer formed by the negative electrode active material is 20-45%.

[0035] The third aspect of the present invention provides a method for preparing the electrode plate described in the second aspect of the present invention, which comprises: uniformly mixing the solvent, the electrode active material, the conductive agent and the binder in proportion to obtain an electrode slurry; kneading the electrode slurry to obtain a lump material; and sequentially extruding, thinning and compounding the lump material with the current collector.

[0036] In any embodiment, the preparation method does not include a drying step.

[0037] In any embodiment, the solid content of the electrode slurry is 65-90%.

[0038] According to the technical solution of the present invention, a high-solid content electrode slurry can be used, which not only reduces the manufacturing cost by reducing the amount of solvent used, but also avoids the need to use drying to remove the solvent, thereby avoiding the upward migration of the binder during the upward volatilization of the drying solvent, resulting in uneven distribution in the thickness direction, reduced porosity in the upper layer, and rapid cycle attenuation.

[0039] In any embodiment, the preparation method of the electrode slurry includes: mixing the electrode active material, the conductive agent and the first binder in proportion to obtain a powder particle mixture; and mixing the powder particle mixture with the second binder or the third binder and the solvent in proportion to obtain an electrode slurry.

[0040] In any embodiment, the electrode plate is an electrode plate for a positive electrode, and the electrode active material is a positive electrode active material; the preparation method of the electrode slurry comprises: mixing the positive electrode active material, the conductive agent and the first binder in proportion to obtain a powder particle mixture; and mixing the powder particle mixture with the third binder and the solvent in proportion to obtain the electrode slurry.

[0041] In any embodiment, the electrode plate is an electrode plate for a positive electrode, and the solvent includes one or a combination of two selected from the following group: N-methylpyrrolidone (NMP) and small molecule alcohol.

[0042] According to the technical solution of the present invention, the small molecule alcohol is a polyol with a carbon chain length of less than 10; for example, it can be selected from one or a combination of two or more of 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,3-hexanediol.

[0043] In any embodiment, the electrode plate is an electrode plate for a positive electrode, and the solid content of the electrode slurry is 70-85%.

[0044] In any embodiment, the electrode plate is an electrode plate for a negative electrode, and the electrode active material is a negative electrode active material; the preparation method of the electrode slurry comprises: uniformly mixing the negative electrode active material, the conductive agent and the first binder in proportion to obtain a powder particle mixture; and uniformly mixing the powder particle mixture with the second binder and the solvent in proportion to obtain the electrode slurry.

[0045] In any embodiment, the electrode plate is an electrode plate for a negative electrode, and the solvent includes one or a combination of two selected from the following groups: deionized water, N-methylpyrrolidone (NMP), small molecule alcohol, and ester.

[0046] In any embodiment, the electrode plate is an electrode plate for a negative electrode, and the solvent is deionized water.

[0047] In any embodiment, the electrode plate is an electrode plate for a negative electrode, and the solid content of the electrode slurry is 65-90%.

[0048] In any embodiment, the preparation method of the electrode slurry includes: mixing the electrode active material, the conductive agent and the first binder in proportion to obtain a powder particle mixture; and mixing the powder particle mixture with the second binder or the third binder and the solvent in proportion to obtain an electrode slurry.

[0049] In any embodiment, the kneading equipment may be a kneader, an internal mixer, a screw extruder, etc.

[0050] In any embodiment, the kneading temperature is 25-100°C.

[0051] In any embodiment, the agglomerated material is extruded to obtain a thick sheet material, and the extrusion equipment can be a screw extruder, a hydraulic extruder, etc.

[0052] In any embodiment, the thinning is performed by rolling.

[0053] In any embodiment, the thinning process parameters include: A / B roller speed ratio of 1:1-2; roller A is a mirror roller; roller B is a rough roller with a roughness of 0.2-0.5 μm; roller pressure of 2-30T.

[0054] In any embodiment, the thick sheet material is thinned by rolling once or multiple times and then compounded with a current collector to obtain an electrode sheet.

[0055] In any embodiment, the compounding is performed by rolling.

[0056] In any embodiment, the composite process parameters include: B / C roller speed ratio of 1:1-2; B roller is a rough roller with a roughness of 0.2-0.5 μm; C roller is a rough roller with a roughness of 0.6-0.9 μm; roller pressure is 2-50T.

[0057] A fourth aspect of the present invention provides a secondary battery comprising the electrode plate and an electrolyte according to the second aspect of the present invention.

[0058] In any embodiment, the electrode plate is an electrode plate for a positive electrode, and the thickness of the electrode plate is 50-500 μm and the compaction density is 2.0-3.8 g / cm 3 and / or

[0059] The electrode plate is an electrode plate for a negative electrode, and the thickness of the electrode plate is 50-500 μm, and the compaction density is 1.4-1.75 g / cm 3 .

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The present invention provides an electrode material that uses a specific combination of binders, has good adhesion and material fusion properties, and avoids delamination and the risk of demolding. When the electrode material provided by the present invention is prepared into electrode plates, it is not necessary to add additional organic additives such as esters and petroleum ether, thereby avoiding solvent residues during the processing process; and it is not necessary to perform a drying step, thereby avoiding problems such as uneven thickness due to the upward migration of the binder during the drying process, and easy cracking of thick plates.

[0062] (2) The present invention also provides corresponding electrode plates. The electrode material provided by the present invention can be used to prepare thick plates with good uniformity, which can be combined into secondary batteries to improve the energy density of the battery cell. In addition, since the binder content in the electrode plates is low, the proportion of the main material is increased, further increasing the energy density.

[0063] (3) The present invention provides a method for preparing an electrode plate. The method adopts a quasi-dry method to prepare the electrode plate. The solid content of the electrode slurry is relatively high. The preparation can be completed by only using processes such as kneading, extrusion, thinning, and compounding with a current collector (for example, by roller pressing). The method avoids problems such as large viscosity rebound of the slurry during wet coating and easy clogging of the filter element during filtration. The method does not require the use of an oven with a large floor space, thereby effectively reducing energy consumption.

[0064] (4) The secondary battery prepared using the electrode material provided by the present invention has good ion transport capability, rate performance, and low impedance. In addition, it has the advantages of low solvent content and low cost, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiment below. The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention. In the accompanying drawings:

[0066] Figure 1 : The battery capacity retention rate of the lithium ion battery provided by the present invention during multiple charge and discharge cycles at 25°C. DETAILED DESCRIPTION

[0067] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0068] The "ranges" disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner are inclusive and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range.

[0069] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0070] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0071] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, "the method comprises steps (a) and (b)" means that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially.

[0072] In a specific embodiment provided by the present invention, an electrode material is provided, which includes an electrode active material, a conductive agent and a binder; the binder includes a first binder, and the first binder includes one or a combination of two or more of the following: polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene and perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene and hexafluoropropylene copolymer, ethylene and chlorotrifluoroethylene copolymer; the binder also includes a second binder or a third binder;

[0073] The second binder comprises one or a combination of two or more of the following: a copolymer of two or more of acrylic acid, acrylic ester, acrylonitrile, and acrylamide; the mass ratio of the first binder to the second binder is 0-0.2:1;

[0074] The third binder includes one or a combination of two or more of the following groups: polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, fluorine-containing acrylate resin (such as trifluoroethyl acrylate homopolymer, trifluoroethyl methacrylate homopolymer, pentafluoropropyl acrylate homopolymer, etc.), and the mass ratio of the first binder to the third binder is 0.05~0.3:1.

[0075] The above technical solution, particularly the application of a binder with a specific ratio, provides the electrode material with excellent adhesion and material fusion properties, avoiding binder floating during the preparation process, cracking of thick electrode sheets, delamination, and the risk of demolding, thereby enabling the production of thick electrode sheets. Using this electrode material in secondary battery electrode sheets can increase the proportion of the main material, enhance the energy density of the battery cell, and have the advantages of improving lithium ion transmission capacity, reducing impedance, and improving rate performance.

[0076] In some embodiments, the mass ratio of the first binder to the second binder is 0~0.2:1; for example, in some specific embodiments, the first binder does not exist; in other specific embodiments, the mass ratio of the first binder to the second binder can be selected from 0.01:1, 0.02:1, 0.05:1, 0.1:1, 0.15:1, 0.2:1, etc.

[0077] Compared with using only the second binder, using the first binder and the second binder at the same time is more conducive to improving the wettability of the electrode plate prepared from the electrode material to the electrolyte under reasonable proportions.

[0078] In some embodiments, the mass ratio of the first binder to the third binder is 0.05-0.3:1, for example, it can be selected from 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, etc.

[0079] By selecting a specific ratio of the first binder to the second binder and the first binder to the third binder, the present invention effectively improves the adhesion of the electrode material, the material fusion, etc.; if it is not within the ratio range, for example, increasing the content of the first binder will reduce the material fusion and the adhesion between the membrane and the current collector, and increase the risk of demolding during the cycle; increasing the content of the second / third binder will increase the viscosity of the material, resulting in the inability of the sticking roller to complete the transfer and the recombination with the current collector; reducing the content of the first binder will reduce the strength of the membrane, and reducing the content of the second / third binder will cause the adhesion of the membrane to decrease.

[0080] In some embodiments, the weight percentage of the binder in the electrode material is 0.15-5%, for example, 0.15%, 0.5%, 1%, 1.1%, 1.15%, 1.25%, 1.3%, 2%, 2.7%, 3%, 3.5%, 4%, 4.5%, 5%, etc. If the weight percentage of the binder is less than 0.15%, agglomerated material cannot be prepared and insufficient bonding force is provided; if the weight percentage is greater than 5%, the material viscosity is high, and it is easy to stick to the roller during the thinning process, making film transfer impossible.

[0081] The mass percentage of the electrode active material is 91~99.65%, such as 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.65%, etc.; the mass percentage of the conductive agent is 0.2~4%, such as 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc. Among them, when the electrode active material and the conductive agent are in the above mass percentage range, it is beneficial to the conductive performance of the electrode, while increasing the proportion of active materials and increasing energy density. If it exceeds the above range, for example, the conductive agent exceeds the upper limit, the content of the active main material will be reduced, and the energy density of the battery cell will be reduced; if the conductive agent exceeds the lower limit, the conductive ability of the electrode will be insufficient, resulting in an increase in the impedance of the battery cell and a decrease in the rate performance.

[0082] In some embodiments, the copolymer included in the second binder has a weight average molecular weight greater than or equal to 300,000; and the copolymer included in the second binder forms a three-dimensional cross-linked network structure through hydrogen bonding between polar groups.

[0083] By using a copolymer with a network cross-linking structure and a weight average molecular weight greater than or equal to 300,000, sufficient capacity is provided to bind the graphite particles to form a network structure, and the pole piece is made flexible and does not crack during the winding and reeling process.

[0084] In some embodiments, the conductive agent in the electrode material includes one or a combination of two or more of the following: conductive carbon black Super P (SP), acetylene black, Ketjen black (KB), carbon fiber, carbon nanotubes (CNTs), graphene, conductive graphite (e.g., KS-6, KS-15, SFG-6, MX-15, etc.).

[0085] In some embodiments, the electrode material is a positive electrode material, which includes a positive electrode active material, a conductive agent, and a binder; the binder includes a first binder and a third binder; wherein the mass percentage of the positive electrode active material is 93-99.65%, for example, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.65%, etc.; the mass percentage of the conductive agent is 0.2-4%, for example, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.; the mass percentage of the binder is 0.15-3.3%, for example, 0.15%, 0.5%, 1%, 1.1%, 1.15%, 1.25%, 1.3%, 2%, 2.7%, 3%, 3.3%, etc. The mass percentages of the above raw materials are obtained after optimization for the positive electrode material.

[0086] In a preferred embodiment, the mass ratio of the first binder to the third binder in the positive electrode material is 0.05-0.3:1; for example, 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, etc.

[0087] In another preferred embodiment, the mass percentage of the first binder in the positive electrode material is 0.1~0.3%, for example, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.; the mass percentage of the third binder is 0.3~3%, for example, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0088] In some embodiments, the positive electrode active material includes a lithium transition metal oxide, such as lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi1 / 3Co1 / 3Mn1 / 3O2, which is abbreviated as NCM333; LiNi0.5 Co 0.2 Mn 0.3 O2, which is referred to as NCM523; LiNi 0.5 Co 0.25 Mn 0.25 O2, which is referred to as NCM211; LiNi 0.6 Co 0.2 Mn 0.2 O2, which is referred to as NCM622; LiNi 0.8 Co 0.1 Mn 0.1 O2, which is referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc.

[0089] In some embodiments, the positive electrode active material includes a lithium-containing phosphate, such as lithium iron phosphate (e.g., LiFePO4, abbreviated as LFP), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, etc.

[0090] In some embodiments, the positive electrode active material includes Prussian blue.

[0091] In some embodiments, the positive electrode active material includes a layered oxide.

[0092] In some embodiments, the electrode material is a negative electrode material, which includes a negative electrode active material, a conductive agent, and a binder; the binder includes a first binder and a second binder; wherein the mass percentage of the negative electrode active material is 91.7-98.8%, for example, 91.7%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.8%, etc.; the mass percentage of the conductive agent is 0.2-4%, for example, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.; the mass percentage of the binder is 1-4.3%, for example, 1%, 1.5%, 2%, 2.5%, 2.7%, 3%, 3.5%, 4%, 4.3%, etc. The mass percentages of the above raw materials are obtained after optimization for the negative electrode material.

[0093] In some embodiments, the binder for the negative electrode material includes the second binder but does not include the first binder.

[0094] In a preferred embodiment, the mass ratio of the first binder to the second binder in the negative electrode material is 0.01-0.2:1; for example, 0.01:1, 0.02:1, 0.05:1, 0.1:1, 0.15:1, 0.2:1, etc.

[0095] In another preferred embodiment, the mass percentage of the first binder in the negative electrode material is 0.05~0.3%, for example, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.; the mass percentage of the second binder is 1~4%, for example, 1%, 1.2%, 1.5%, 1.7%, 1.8%, 1.9%, 1.95%, 2%, 3%, 4%, etc.

[0096] In some embodiments, the negative electrode active material includes one or a combination of two or more selected from the group consisting of natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, and silicon-carbon composites.

[0097] In some embodiments, a battery electrode is provided, comprising a current collector and an electrode material provided by the present invention disposed on the current collector; wherein the porosity of the material layer formed by the electrode active material is 10 to 45%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc.

[0098] This porosity is beneficial to increasing the electrolyte infiltration rate, reducing the standing time after injection, improving production efficiency and reducing costs, while improving the diffusion ability of lithium ions in the electrode, reducing impedance, and improving the rate performance of the battery cell; if the porosity is not within the above range, the energy density of the battery cell will be reduced, and the rate and high and low temperature performance will be reduced.

[0099] In some embodiments, the mass per unit area of ​​the electrode material on the electrode plate is 150-600 mg / 1540.25 mm 2 , for example about 150mg / 1540.25mm 2 、197mg / 1540.25mm 2 , 200mg / 1540.25mm 2 、250mg / 1540.25mm 2 、300mg / 1540.25mm 2 , 400mg / 1540.25mm 2 、430mg / 1540.25mm 2 、450mg / 1540.25mm 2 、480mg / 1540.25mm 2 、500mg / 1540.25mm 2、550mg / 1540.25mm 2 、600mg / 1540.25mm 2 wait.

[0100] In a preferred embodiment, the electrode plate is a positive electrode plate, the porosity of the material layer formed by the electrode active material is 10-45%; the unit area mass of the electrode material on the electrode plate is 350-600 mg / 1540.25 mm 2 .

[0101] In another preferred embodiment, the electrode plate is a negative electrode plate, the porosity of the material layer formed by the electrode active material is 20-45%; the unit area mass of the electrode material on the electrode plate is 150-400 mg / 1540.25 mm 2 .

[0102] In some embodiments, a method for preparing the above-mentioned electrode plate is provided, which includes: uniformly mixing a solvent, the electrode active material, a conductive agent and a binder in proportion to obtain an electrode slurry; kneading the electrode slurry to obtain a lump material; and sequentially extruding, thinning and compounding the lump material with the current collector.

[0103] In a preferred embodiment, the preparation method does not include a drying step; preferably, the solids content of the electrode slurry is 65-90%, for example, 65%, 70%, 75%, 80%, 85%, 90%, etc. When the electrode material provided by the present invention is used, and in particular the binder component with a specific ratio thereof, the amount of solvent used in the preparation of the electrode sheet can be significantly reduced, thereby avoiding the need for a drying step to remove the solvent. This further avoids the upward migration of the binder during the drying solvent volatilization process, resulting in uneven thickness distribution, reduced porosity in the upper layer, and rapid cycle decay.

[0104] In some embodiments, a kneader, an internal mixer or a screw extruder is used as a kneading device, and the kneading temperature is 25~100°C; a screw extruder or a hydraulic extruder is used for extrusion to extrude the lump material into a thick sheet; the thick sheet is then thinned by rolling, and the thinning process is preferably a A / B roller speed ratio of 1:1~2; the A roller is a mirror roller; the B roller is a rough roller with a roughness of 0.2~0.5μm; the roller pressure is 2~30T; then, after the thick sheet is thinned, it is compounded with the collector, and the compounding is carried out by rolling, and the process is preferably a B / C roller speed ratio of 1:1~2; the B roller is a rough roller with a roughness of 0.2~0.5μm; the C roller is a rough roller with a roughness of 0.6~0.9μm; and the roller pressure is 2~50T.

[0105] In some embodiments, a method for preparing a positive electrode plate is provided, comprising: uniformly mixing a positive electrode active material, a conductive agent, and a first binder in proportion to obtain a powder particle mixture; and uniformly mixing the powder particle mixture with the third binder and the solvent in proportion to obtain the electrode slurry; preferably, the solid content of the electrode slurry is 70-85%.

[0106] In the preparation method of the positive electrode plate, the solvent includes one or a combination of two selected from the following groups: N-methylpyrrolidone (NMP), a small molecule alcohol (a polyol with a carbon chain length of less than 10; for example, one or a combination of two or more selected from 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,3-hexanediol).

[0107] In some embodiments, a method for preparing a negative electrode plate is provided, comprising: uniformly mixing the negative electrode active material, the conductive agent, and the first binder in proportion to obtain a powder particle mixture; and uniformly mixing the powder particle mixture with the second binder and the solvent in proportion to obtain the electrode slurry. Preferably, the solid content of the electrode slurry is 65~90%.

[0108] In the preparation method of the negative electrode plate, the solvent includes one or a combination of two selected from the following groups: deionized water, N-methylpyrrolidone (NMP), a small molecule alcohol (a polyol with a carbon chain length of less than 10; for example, one or a combination of more than two selected from 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,3-hexanediol), and an ester; preferably deionized water.

[0109] In some embodiments, a secondary battery is provided, which includes the electrode plates provided by the present invention and an electrolyte; the positive electrode plates of the secondary battery are the plates provided by the present invention, and the negative electrode plates are conventional commercially available plates; or the negative electrode plates of the secondary battery are the plates provided by the present invention, and the positive electrode plates are conventional commercially available plates; preferably, both the positive electrode plates and the negative electrode plates of the secondary battery are the electrode plates provided by the present invention.

[0110] The secondary battery provided by the present invention has the advantages of high energy density, small cell impedance, high rate performance and cycle performance.

[0111] In some embodiments, the thickness of the positive electrode sheet in the secondary battery is 50-500 μm, and the compaction density is 2.0-3.8 g / cm 3 The thickness of the negative electrode sheet is 50~500μm, and the compaction density is 1.4~1.75g / cm 3 .

[0112] Example 1

[0113] A lithium-ion battery is provided, and its preparation method is as follows:

[0114] (1) Preparation of positive electrode

[0115] The raw materials were weighed according to the mass ratio of lithium iron phosphate, conductive carbon black Super P, polytetrafluoroethylene and polyvinylidene fluoride of 98.15:0.7:0.15:1. The positive electrode active materials lithium iron phosphate, conductive carbon black Super P and polytetrafluoroethylene were mixed evenly in a double planetary mixer to obtain solvent-free granular materials; polyvinylidene fluoride and N-methylpyrrolidone (NMP) were mixed into a glue solution and then kneaded with the solvent-free granular materials in an internal mixer to form a mass material (slurry solid content of 75%), which was then extruded into thick sheets by screw extrusion, thinned by roller pressing, and composited with the positive electrode current collector aluminum foil to obtain a positive electrode sheet. The unit area mass of the electrode material on this positive electrode sheet is 400mg / 1540.25mm 2 .

[0116] (2) Preparation of negative electrode sheet

[0117] The negative electrode active material artificial graphite, acetylene black, binder styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were dissolved in deionized water at a mass ratio of 96.6:0.7:1.5:1.2, and thoroughly stirred to obtain a negative electrode slurry (slurry solid content of 50%). The negative electrode slurry was coated on the negative electrode current collector copper foil, dried, and cold pressed to prepare the negative electrode sheet. The unit area mass of the electrode material on the negative electrode sheet is 197 mg / 1540.25 mm 2 .

[0118] (3) Secondary battery preparation

[0119] The positive electrode sheet, a 14μm thick polyethylene film serving as a separator, and the negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. The sheets are then wound to form a bare cell. The bare cell is placed in an outer package, dried, and then injected with electrolyte. The cell then undergoes vacuum packaging, resting, forming, and shaping to produce a lithium-ion battery.

[0120] Example 2

[0121] A lithium-ion battery is provided, and its preparation method is as follows:

[0122] (1) Preparation of positive electrode

[0123] The preparation method of the positive electrode sheet in step (1) of Example 1 is the same as that in Example 1 except for the following differences: the mass ratio of lithium iron phosphate, conductive carbon black Super P, polytetrafluoroethylene and polyvinylidene fluoride is 98.2:0.7:0.1:1.

[0124] (2) Preparation of negative electrode sheet

[0125] The raw materials were weighed according to the mass ratio of artificial graphite, conductive carbon black Super P, and acrylic acid-acrylamide-acrylonitrile copolymer of 97.3:0.7:2. The artificial graphite and conductive carbon black Super P were mixed evenly in a double planetary mixer to obtain solvent-free granules; acrylic acid-acrylamide-acrylonitrile copolymer, deionized water and the solvent-free granules were kneaded into a mass in an internal mixer (the slurry solid content was 70%), which was extruded into thick sheets by screw extrusion, thinned by rollers, and composited with the negative electrode current collector copper foil to obtain a negative electrode sheet. The unit area mass of the electrode material on the negative electrode sheet is 197mg / 1540.25mm 2 .

[0126] (3) Secondary battery preparation

[0127] The secondary battery preparation method is the same as step (3) in Example 1.

[0128] Example 3

[0129] A lithium-ion battery is provided, and its preparation method is as follows:

[0130] (1) Preparation of positive electrode

[0131] The preparation method of the positive electrode sheet in step (1) of Example 1 is the same as that in Example 1 except for the following differences: the mass ratio of lithium iron phosphate, conductive carbon black Super P, polytetrafluoroethylene and polyvinylidene fluoride is 98.2:0.7:0.15:1.

[0132] (2) Preparation of negative electrode sheet

[0133] The preparation method of the negative electrode sheet is the same as step (2) in Example 2.

[0134] (3) Secondary battery preparation

[0135] The secondary battery is prepared in the same manner as step (3) in Example 2.

[0136] Example 4

[0137] A lithium-ion battery is provided, and its preparation method is as follows:

[0138] (1) Preparation of positive electrode

[0139] The preparation method of the positive electrode sheet in step (1) of Example 1 is the same as that in Example 1 except for the following differences: the mass ratio of lithium iron phosphate, conductive carbon black Super P, polytetrafluoroethylene and polyvinylidene fluoride is 98.05:0.7:0.25:1.

[0140] (2) Preparation of negative electrode sheet

[0141] The preparation method of the negative electrode sheet is the same as step (2) in Example 2.

[0142] (3) Secondary battery preparation

[0143] The secondary battery is prepared in the same manner as step (3) in Example 2.

[0144] Example 5

[0145] A lithium-ion battery is provided, and its preparation method is as follows:

[0146] (1) Preparation of positive electrode

[0147] The preparation method of the positive electrode sheet is the same as that of step (1) in Example 1 except for the following differences: the mass ratio of lithium iron phosphate, conductive carbon black Super P, polytetrafluoroethylene and polyvinylidene fluoride is 98:0.7:0.3:1.

[0148] (2) Preparation of negative electrode sheet

[0149] The preparation method of the negative electrode sheet is the same as step (2) in Example 2.

[0150] (3) Secondary battery preparation

[0151] The secondary battery is prepared in the same manner as step (3) in Example 2.

[0152] Example 6

[0153] A lithium-ion battery is provided, and its preparation method is as follows:

[0154] (1) Preparation of positive electrode

[0155] Lithium iron phosphate, polyvinylidene fluoride, and acetylene black were dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 97.3:2:0.7, and thoroughly stirred to obtain a positive electrode slurry (slurry solid content of 63%). The positive electrode slurry was coated on the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet. The electrode material mass per unit area of ​​the positive electrode sheet is 400 mg / 1540.25 mm 2 .

[0156] (2) Preparation of negative electrode sheet

[0157] The preparation method of the negative electrode sheet is the same as step (2) in Example 2.

[0158] (3) Secondary battery preparation

[0159] The secondary battery is prepared in the same manner as step (3) in Example 2.

[0160] Example 7

[0161] A lithium-ion battery is provided, wherein the preparation method is the same as that of Example 6, except that the negative electrode is prepared according to the following steps:

[0162] The raw materials were weighed according to the mass ratio of artificial graphite, conductive carbon black Super P, polytetrafluoroethylene, and acrylic acid-acrylamide-acrylonitrile copolymer of 97.3:0.7:0.05:1.95. Artificial graphite, conductive carbon black Super P, and polytetrafluoroethylene were mixed evenly in a double planetary mixer to obtain solvent-free granular material; acrylic acid-acrylamide-acrylonitrile copolymer, deionized water and the solvent-free granular material were kneaded into a mass material in an internal mixer (the slurry solid content was 70%), which was extruded into thick sheets by screw extrusion, thinned by roller pressing, and composited with the negative electrode current collector copper foil to obtain a negative electrode plate. The unit area mass of the electrode material on the negative electrode plate is 197mg / 1540.25mm 2 .

[0163] Example 8

[0164] A lithium-ion battery is provided, and its preparation method is as follows:

[0165] (1) Preparation of positive electrode

[0166] The preparation method of the positive electrode sheet is the same as step (1) in Example 6.

[0167] (2) Preparation of negative electrode sheet

[0168] The preparation method of the negative electrode plate in step (2) of Example 7 is the same as that in Example 7 except for the following differences: the mass ratio of artificial graphite, conductive carbon black Super P, polytetrafluoroethylene, and acrylic acid-acrylamide-acrylonitrile copolymer is 97.3:0.7:0.1:1.9.

[0169] (3) Secondary battery preparation

[0170] The secondary battery is prepared in the same manner as step (3) in Example 6.

[0171] Example 9

[0172] A lithium-ion battery is provided, and its preparation method is as follows:

[0173] (1) Preparation of positive electrode

[0174] The preparation method of the positive electrode sheet is the same as step (1) in Example 6.

[0175] (2) Preparation of negative electrode sheet

[0176] The preparation method of the negative electrode plate in step (2) of Example 7 is the same as that in Example 7 except for the following differences: the mass ratio of artificial graphite, conductive carbon black Super P, polytetrafluoroethylene, and acrylic acid-acrylamide-acrylonitrile copolymer is 97.3:0.7:0.2:1.8.

[0177] (3) Secondary battery preparation

[0178] The secondary battery is prepared in the same manner as step (3) in Example 6.

[0179] Example 10

[0180] A lithium-ion battery is provided, and its preparation method is as follows:

[0181] (1) Preparation of positive electrode

[0182] The preparation method of the positive electrode sheet is the same as step (1) in Example 6.

[0183] (2) Preparation of negative electrode sheet

[0184] The preparation method of the negative electrode plate in step (2) of Example 7 is the same as that in Example 7 except for the following differences: the mass ratio of artificial graphite, conductive carbon black Super P, polytetrafluoroethylene, and acrylic acid-acrylamide-acrylonitrile copolymer is 97.3:0.7:0.3:1.7.

[0185] (3) Secondary battery preparation

[0186] The secondary battery is prepared in the same manner as step (3) in Example 6.

[0187] Example 11

[0188] A lithium-ion battery is provided, wherein the positive electrode sheet and the secondary battery preparation method thereof are the same as those in Example 1, and the negative electrode sheet preparation method is the same as those in Example 9.

[0189] Example 12

[0190] A lithium-ion battery is provided, and its preparation method is as follows:

[0191] (1) Preparation of positive electrode

[0192] The preparation method of the positive electrode sheet in step (1) of Example 1 is the same as that in Example 1 except for the following differences: the unit area mass of the electrode material is 430 mg / 1540.25 mm 2 .

[0193] (2) Preparation of negative electrode sheet

[0194] The preparation method of the negative electrode sheet in step (2) of Example 9 is the same as that in Example 9 except for the following differences: the unit area mass of the electrode material is 212 mg / 1540.25 mm 2 .

[0195] (3) Preparation of secondary batteries

[0196] The preparation method of the secondary battery is the same as step (3) in Example 1.

[0197] Example 13

[0198] A lithium-ion battery is provided, and its preparation method is as follows:

[0199] (1) Preparation of positive electrode

[0200] The preparation method of the positive electrode sheet in step (1) of Example 1 is the same as that in Example 1 except for the following differences: the unit area mass of the electrode material is 450 mg / 1540.25 mm 2 .

[0201] (2) Preparation of negative electrode sheet

[0202] The preparation method of the negative electrode sheet is the same as that of step (2) in Example 9 except for the following differences: the unit area mass of the electrode material is 222 mg / 1540.25 mm 2 .

[0203] (3) Preparation of secondary batteries

[0204] The preparation method of the secondary battery is the same as step (3) in Example 1.

[0205] Example 14

[0206] A lithium-ion battery is provided, and its preparation method is as follows:

[0207] (1) Preparation of positive electrode

[0208] The preparation method of the positive electrode sheet in step (1) of Example 1 is the same as that in Example 1 except for the following differences: the unit area mass of the electrode material is 480 mg / 1540.25 mm 2 .

[0209] (2) Preparation of negative electrode sheet

[0210] The preparation method of the negative electrode sheet in step (2) of Example 9 is the same as that in Example 9 except for the following differences: the unit area mass of the electrode material is 237 mg / 1540.25 mm 2 .

[0211] (3) Preparation of secondary batteries

[0212] The preparation method of the secondary battery is the same as step (3) in Example 1.

[0213] Comparative Example 1

[0214] A lithium-ion battery is provided, and its preparation method is as follows:

[0215] (1) Preparation of positive electrode

[0216] The preparation method of the positive electrode sheet in step (1) of Example 6 is the same as that in Example 6 except for the following differences: the unit area mass of the electrode material is 400 mg / 1540.25 mm 2 .

[0217] (2) Preparation of negative electrode sheet

[0218] The preparation method of the negative electrode sheet in step (2) of Example 1 is the same as that in Example 1 except for the following differences: the unit area mass of the electrode material is 197 mg / 1540.25 mm 2 .

[0219] (3) Preparation of secondary batteries

[0220] The preparation method of the secondary battery is the same as step (3) in Example 1.

[0221] Comparative Example 2

[0222] A lithium-ion battery is provided, and its preparation method is as follows:

[0223] (1) Preparation of positive electrode

[0224] The preparation method of the positive electrode sheet in step (1) of Example 6 is the same as that in Example 6 except for the following differences: the unit area mass of the electrode material is 430 mg / 1540.25 mm 2 .

[0225] (2) Preparation of negative electrode sheet

[0226] The preparation method of the negative electrode sheet in step (2) of Example 1 is the same as that in Example 1 except for the following differences: the unit area mass of the electrode material is 212 mg / 1540.25 mm 2 .

[0227] (3) Preparation of secondary batteries

[0228] The preparation method of the secondary battery is the same as step (3) in Example 1.

[0229] Comparative Example 3

[0230] A lithium-ion battery is provided, and its preparation method is as follows:

[0231] (1) Preparation of positive electrode

[0232] The preparation method of the positive electrode sheet in step (1) of Example 6 is the same as that in Example 6 except for the following differences: the unit area mass of the electrode material is 450 mg / 1540.25 mm 2 .

[0233] (2) Preparation of negative electrode sheet

[0234] The preparation method of the negative electrode sheet in step (2) of Example 1 is the same as that in Example 1 except for the following differences: the unit area mass of the electrode material is 222 mg / 1540.25 mm 2 .

[0235] (3) Preparation of secondary batteries

[0236] The preparation method of the secondary battery is the same as step (3) in Example 1.

[0237] Experimental example

[0238] The lithium-ion batteries prepared in the examples and comparative examples were tested as follows:

[0239] (1) Analytical test

[0240] The battery is charged at a constant current of 1C to 3.65 V, then charged at a constant voltage at 3.65 V to a current of 0.05C. After standing for 5 minutes, it is discharged at a constant current of 1C to 2.5 V. The above is one charge and discharge cycle of the battery. After 10 cycles, it is charged at a constant voltage at 3.65 V to a current of 0.05C. The battery is disassembled in a dry environment. The golden yellow surface of the negative electrode indicates no decomposition, and the appearance of a silvery white area indicates decomposition.

[0241] (2) Electrolyte infiltration rate test

[0242] Test method: Use a capillary tube (1mm diameter) to draw a certain amount of electrolyte (2cm height), bringing the capillary end into contact with the surface of the electrode plate. The electrode plate has a porous structure, and capillary force draws the electrolyte from the capillary tube. The time required for the electrolyte to be completely absorbed is recorded, and the electrolyte infiltration rate is calculated from this.

[0243] Calculation method of electrolyte infiltration rate: electrolyte density * electrolyte volume in capillary / time required for the electrolyte to be completely absorbed.

[0244] The test results are shown in Table 1.

[0245] Table 1 Lithium-ion battery positive and negative electrode analysis and electrolyte infiltration rate test results

[0246]

[0247] (3) Rate performance test

[0248] Rate discharge: 0.33C charge to 3.65V, constant voltage charge to current of 0.05C, stand for 5 minutes, 0.33C discharge to 2.5V and measure the discharge capacity during the period, stand for 30 minutes; 0.33C charge to 3.65V, constant voltage charge to current of 0.05C, stand for 5 minutes, 1C discharge to 2.5V and measure the discharge capacity during the period, stand for 30 minutes; 0.33C charge to 3.65V, constant voltage charge to current of 0.05C, stand for 5 minutes, 3C discharge to 2.8V and measure the discharge capacity during the period, stand for 30 minutes; 0.33C charge to 3.65V, constant voltage charge to current of 0.05C, stand for 5 minutes, 5C discharge to 2.5V and measure the discharge capacity during the period, stand for 30 minutes.

[0249] Rate charge: 0.33C charge to 3.65V, constant voltage charge to current of 0.05C, stand for 5 minutes, 0.33C discharge to 2.5V, and measure the charging capacity during the period, and stand for 30 minutes; 1C charge to 3.65V, constant voltage charge to current of 0.05C, stand for 30 minutes, 0.33C discharge to 2.5V and measure the charging capacity during the period, and stand for 30 minutes; 3C charge 3.65V, constant voltage charge to current of 0.05C, stand for 5 minutes, 0.33C discharge to 2.5V and measure the charging capacity during the period, and stand for 30 minutes; 5C charge to 4.2V, constant voltage charge to current of 0.05C, stand for 30 minutes, 0.33C discharge to 2.5V and measure the charging capacity during the period, and stand for 30 minutes.

[0250] The test results are shown in Table 2.

[0251] Table 2 Lithium-ion battery charge and discharge rate test results

[0252]

[0253] (4) DCR performance test

[0254] Test method:

[0255] (1) At 25°C, charge at 0.33C until fully charged, then discharge at 0.33C for 0.1Cn (Cn represents battery capacity) to adjust the secondary battery to 90% SOC, let it rest for 30 minutes, and end the resting voltage at V1. Then discharge at 3C for 30 seconds, and end the discharge voltage at V2. Let it rest for 40 seconds, and charge at 3C for 30 seconds.

[0256] (2) At 25°C, charge at 0.33C until fully charged, then discharge at 0.33C for 0.5Cn (Cn represents battery capacity) to adjust the secondary battery to 50% SOC, let it rest for 30 minutes, and the resting voltage is V1. Then, discharge at 3C for 30 seconds, and the discharge cut-off voltage is V2. Then, discharge at 3C for 30 seconds, let it rest for 40 seconds, and charge at 3C for 30 seconds.

[0257] (3) At 25°C, charge at 0.33C to a fully charged state, then discharge at 0.33C for 0.9Cn (Cn represents the battery capacity) to adjust the secondary battery to 20% SOC, let it rest for 30 minutes, and the resting end voltage is V1. Then, discharge at 3C for 30 seconds, and the discharge cut-off voltage is V2. Then, discharge at 3C for 30 seconds, let it rest for 40 seconds, and charge at 3C for 30 seconds.

[0258] Calculation method: DCR = (V1 - V2) / I, where V1 is the static end voltage, V2 is the discharge cut-off voltage, and I is the discharge current. The test results are shown in Table 3.

[0259] Table 3 Lithium-ion battery DCR performance test results

[0260]

[0261] (5) Battery cycle life test

[0262] At 25°C, the lithium-ion batteries of all embodiments and comparative examples were subjected to charge and discharge tests. One charge and discharge cycle process is as follows: 1C constant current charging to 3.65 V, then constant voltage charging at 3.65 V to a current of 0.05C, standing for 5 minutes, and then 1C constant current discharging to 2.5 V. The battery capacity at this time is recorded as C1. The above is one charge and discharge cycle of the battery. The above process is repeated. The capacity retention rate of the lithium-ion battery during the cycle is shown in FIG. Figure 1 shown.

[0263] (6) Electrode porosity test

[0264] Place the sample cup in the true density tester, close the test system, and introduce helium according to the program. Measure the pressure of the gas in the sample chamber and expansion chamber, and then calculate the true volume V1 according to Bohr's law (PV=nRT). Use tweezers to select >20 discs with good appearance and no powder on the edges and place them in the sample cup. Record the number of discs and calculate the apparent volume V2, V2=S*H*A, where: S - area, cm 2 ;H - thickness, cm;A - number of samples, EA;

[0265] Porosity calculation method: Porosity P = (V2-V1) / V2*100%, where V1 is the true volume of the sample, cm 3, obtained by test; V2-apparent volume of sample, cm 3 The results of the electrode porosity test are shown in Table 4.

[0266] Table 4 Electrode porosity test results

[0267]

[0268] The foregoing description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed herein are intended to be encompassed within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. An electrode material, characterized in that The electrode material includes an electrode active material, a conductive agent and a binder; The electrode active material is a positive electrode active material, the binder includes a first binder and a third binder, the mass ratio of the first binder to the third binder is 0.1-0.3:1, and the unit area mass of the electrode material is 430-600 mg / 1540.25 mm 2 Alternatively, the electrode active material is a negative electrode active material, the binder comprises a first binder and a second binder, the mass ratio of the first binder to the second binder is 0.01 to 0.2:1, and the mass per unit area of ​​the electrode material is 212 to 400 mg / 1540.25 mm 2 ; The first binder comprises one or a combination of two or more of the following: polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-chlorotrifluoroethylene copolymer; The second binder comprises one or a combination of two or more of the following: a copolymer of two or more of acrylic acid, acrylate, acrylonitrile, and acrylamide; The third binder includes one or a combination of two or more of the following: polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and fluorine-containing acrylate resin.

2. The electrode material according to claim 1, wherein In the electrode material, the mass percentage of the binder is 0.15% to 5%.

3. The electrode material according to claim 1, wherein In the electrode material, the mass percentage of the electrode active material is 91% to 99.65%, the mass percentage of the conductive agent is 0.2% to 4%, and the mass percentage of the binder is 0.15% to 5%.

4. The electrode material according to claim 1, wherein The copolymer contained in the second binder has a weight average molecular weight greater than or equal to 300,000.

5. The electrode material according to claim 1, wherein The conductive agent includes one or a combination of two or more of the following: conductive carbon black Super P, acetylene black, Ketjen black, carbon fiber, carbon nanotube, graphene, and conductive graphite.

6. The electrode material according to claim 1, wherein The positive electrode active material includes one or a combination of two or more of the following: lithium transition metal oxide, lithium-containing phosphate, Prussian blue, and layered oxide.

7. The electrode material according to claim 6, wherein The lithium transition metal oxide includes one or a combination of two or more selected from the following group: lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof.

8. The electrode material according to claim 6, wherein The lithium-containing phosphate includes one or a combination of two or more selected from the following groups: lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

9. The electrode material according to claim 1, wherein The negative electrode active material includes one or a combination of two or more selected from the following group: natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, and silicon-carbon composite.

10. An electrode plate, characterized in that: The device comprises the electrode material and a current collector according to any one of claims 1 to 9, wherein the electrode material is arranged on the current collector.

11. The electrode plate according to claim 10, wherein: On the electrode plate, the porosity of the material layer formed by the electrode active material is 10% to 45%.

12. The electrode plate according to claim 11, wherein: The electrode active material is a positive electrode active material; wherein the porosity of the material layer formed by the positive electrode active material is 10% to 45%, and the unit area mass of the electrode material is 430 to 600 mg / 1540.25 mm 2 ;or, The electrode active material is a negative electrode active material; wherein the porosity of the material layer formed by the negative electrode active material is 20% to 45%, and the unit area mass of the electrode material is 212 to 400 mg / 1540.25 mm 2 .

13. The method for preparing an electrode sheet according to any one of claims 10 to 12, characterized in that: include: The solvent, the electrode active material, the conductive agent and the binder are mixed uniformly in proportion to prepare an electrode slurry; The electrode slurry is kneaded to obtain a mass material; the mass material is sequentially extruded, thinned, and compounded with the current collector.

14. The preparation method according to claim 13, wherein The solid content of the electrode slurry is 65% to 90%.

15. The preparation method according to claim 13, wherein The preparation method does not include a drying step.

16. The preparation method according to claim 13, wherein The electrode active material is a positive electrode active material, and the solvent comprises one or a combination of two selected from the following groups: N-methylpyrrolidone, small molecule alcohol; or The electrode active material is a negative electrode active material, and the solvent includes one or a combination of two selected from the following groups: deionized water, N-methylpyrrolidone, small molecule alcohol, and ester.

17. A secondary battery, characterized in that: The secondary battery comprises the electrode material according to any one of claims 1 to 9 or the electrode plate according to any one of claims 10 to 12.

Images