Secondary battery, method for manufacturing the same, and power consumption device

Abstract

The present application provides a secondary battery including a positive electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer contains a conductive agent, and the conductive agent includes a first conductive carbon black and a second conductive carbon black. The specific surface area of the second conductive carbon black is larger than the specific surface area of the first conductive carbon black. In addition, the present application further provides a method for manufacturing the secondary battery and a power consumption device. The secondary battery of the present application realizes a low internal resistance and improves the energy density and cycle performance of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to secondary batteries, their manufacturing methods, and power-consuming devices.

Background Art

[0002] In recent years, secondary batteries have been very widely applied in many fields such as energy storage systems such as wind power, thermal power, hydropower, and solar power plants, and electric tools and electric bicycles.

[0003] A secondary battery generally includes positive and negative electrode plates, an electrolytic solution, and a separator disposed between the positive and negative electrode plates. When manufacturing the electrode plate, in order to make the electrode plate satisfy a certain conductivity, generally a conductive agent is added to the electrode plate. However, the addition of the conductive agent reduces the occupancy rate of the active material in the electrode plate, thereby causing a decrease in the energy density.

[0004] Therefore, how to develop a secondary battery that can achieve a low internal resistance and at the same time achieve a high energy density and electrical performance is one of the problems that researchers should quickly solve.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present application has been made in view of the above problems, and its purpose is to provide a secondary battery for realizing a low internal resistance and improving the energy density and cycle performance of the battery.

Means for Solving the Problems

[0006] To achieve the above object, a first aspect of the present application provides a secondary battery. This secondary battery includes a positive electrode plate, and the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer contains a conductive agent, and the conductive agent includes a first conductive carbon black and a second conductive carbon black. The specific surface area of the second conductive carbon black is larger than the specific surface area of the first conductive carbon black.

[0007] By using two types of conductive carbon blacks with different specific surface areas, it is possible to improve the internal resistance and cycle performance of the battery without increasing the usage amount of the conductive agent.

[0008] In any embodiment, when the specific surface area of the first conductive carbon black is S1 and the specific surface area of the second conductive carbon black is S2, S2 / S1≧4, and optionally, 5≦S2 / S1≦17.

[0009] By setting the ratio of the specific surface areas of the first conductive carbon black and the second conductive carbon black within the above range, the improvement of the internal resistance and cycle performance of the battery can be realized better.

[0010] In any embodiment, the specific surface area of the first conductive carbon black ≦140m 2 / g, and optionally 50m 2 / g~130m 2 / g, and / or, the specific surface area of the second conductive carbon black is 200m 2 / g~1200m 2 / g, and optionally 300m 2 / g~1000m 2 / g.

[0011] In any embodiment, the conductive agent (1) The mass occupancy rate of the conductive agent in the positive electrode film layer ≦5%, and optionally 0.8%~3.0%, (2) The mass occupancy of the first conductive carbon black in the positive electrode film layer is ≤ 4.2%, optionally 0.4% - 3%; (3) The mass occupancy of the second conductive carbon black in the positive electrode film layer is ≤ 2.5%, optionally 0.1% - 2%; and (4) The mass ratio of the first conductive carbon black to the second conductive carbon black is (0.4 - 8):1, optionally (0.5 - 7):1, and at least one of the above is satisfied.

[0012] In any embodiment, the oil absorption amount of the first conductive carbon black is ≤ 260, and / or the oil absorption amount of the second conductive carbon black is ≤ 300.

[0013] In any embodiment, the water content of the first conductive carbon black is ≤ 5000 ppm, and / or the water content of the second conductive carbon black is ≤ 10000 ppm.

[0014] In any embodiment, the conductive agent further includes carbon nanotubes. Optionally, the tube diameter of the carbon nanotubes is 4 - 10 nm. Optionally, the tube length of the carbon nanotubes is 0.3 - 50 μm. Optionally, the aspect ratio of the carbon nanotubes is 50 - 12500. Optionally, the carbon nanotubes include multi - wall carbon nanotubes. Optionally, the mass occupancy of the carbon nanotubes in the positive electrode film layer is ≤ 1.2%. Optionally, the mass ratio of the second conductive carbon black to the carbon nanotubes is (0.1 - 10):1.

[0015] In any embodiment, the first conductive carbon black and the second conductive carbon black are each independently selected from at least one of furnace carbon black, acetylene black, Super p, and ketjen black.

[0016] The second aspect of the present application further provides a method for manufacturing the secondary battery described in the first aspect of the present application. This method includes manufacturing a positive electrode plate by adopting the following steps. S1. A step of dry-mixing a first conductive carbon, a second conductive carbon, and a first dispersant in a stirring tank to obtain a powder mixture. Here, the specific surface area of the second conductive carbon black is larger than that of the first conductive carbon black. S2. A step of adding a solvent to the powder mixture, uniformly mixing, and then obtaining slurry 1. S3. A step of adding a second dispersant to slurry 1, uniformly mixing, and then obtaining slurry 2. S4. A step of adding a positive electrode active material to the slurry 2 and uniformly mixing to obtain a positive electrode material slurry. S5. A step of coating the positive electrode material slurry on at least one surface of a positive electrode current collector, drying, and then forming a positive electrode film layer.

[0017] In any embodiment, the first dispersant includes a vinylidene fluoride-based polymer. Optionally, the first dispersant includes a vinylidene fluoride homopolymer or a compound of a first dispersant obtained by copolymerizing vinylidene fluoride and an active group-containing vinylidene fluoride. Here, the active group includes at least one of a carboxyl group, an epoxy group, a hydroxy group, or a sulfonic acid group, and is optionally a carboxyl group or an epoxy group.

[0018] In any embodiment, the second dispersant is selected from a copolymer of ethylene and maleic anhydride or a copolymer of styrene and maleic anhydride.

[0019] In any embodiment, the mass ratio of the sum of the masses of the first conductive carbon black and the second conductive carbon black to the first dispersant is (0.4 to 2.0):1, and optionally (0.75 to 1.8):1.

[0020] In any embodiment, the mass ratio of the sum of the masses of the first conductive carbon black and the second conductive carbon black to the second dispersant is (8 to 30):1, and optionally (9 to 25):1.

[0021] In any embodiment, in step S3, a second dispersant and carbon nanotubes (CNTs) are added to slurry 1, uniformly mixed, and then slurry 2 is obtained.

[0022] In any embodiment, the content a of the first conductive carbon black, the content b of the second conductive carbon black, and the content c of the carbon nanotubes satisfy 0.2 ≤ ((a + b) × c) / (a × b) ≤ 10, and optionally 0.4 ≤ ((a + b) × c) / (a × b) ≤ 6. Here, a, b, and c are based on the total weight based on the dry weight of the conductive slurry.

[0023] A third aspect of the present application provides a power consumption device including at least one of the secondary battery according to the first aspect of the present application and the secondary battery manufactured by the method according to the second aspect of the present application.

[0024] Since the power consumption device of the present application includes the secondary battery according to the present application, it has at least the same advantages as the secondary battery.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

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Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0026] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the secondary battery, its manufacturing method, and the power consumption device of the present application will be described in detail. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of structures that are actually the same may be omitted. This is to avoid making the following description unnecessarily long and to enable those skilled in the art to easily understand. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and do not limit the theme described in the claims.

[0027] The "ranges" disclosed in this application are limited in the form of a lower limit and an upper limit. A given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a specific range. The ranges thus defined may or may not include the end values, and any combination is possible. That is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, it is understood that ranges of 60 - 110 and 80 - 120 are also conceivable. In addition, if 1 and 2 are listed as the minimum range values and 3, 4, and 5 are listed as the maximum range values, all of the ranges 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are conceivable. In this application, unless otherwise specified, the numerical range "a - b" represents a shortened expression of any combination of real numbers from a to b, where both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are listed in this specification, and "0 - 5" is only a shortened expression of combinations of these numbers. Also, when a certain parameter is expressed as an integer ≧ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] Unless otherwise specified, all embodiments and alternative embodiments of this application can be combined with each other to form a new technical solution.

[0029] Unless otherwise specified, all technical features and alternative technical features of this application can be combined with each other to form a new technical solution.

[0030] Unless otherwise specified, all steps of this application may be performed in order or randomly, and preferably, they are performed in order. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, the fact that the method mentioned above may further include step (c) means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0031] Unless otherwise specified, "comprising" and "including" mentioned in this application represent an open type, but may also be a closed type. For example, the above "comprising" and "including" may further include or encompass other components not listed, or may include or encompass only the components listed.

[0032] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the conditions where A is true (or exists) and B is false (or does not exist), where A is false (or does not exist) but B is true (or exists), and where both A and B are true (or exist) satisfy "A or B".

[0033] The inventors have found the following in their research. The conductive performance of the conductive slurries used in the prior art is low, and in order to meet the demand for the conductive performance of the electrode plates, it is necessary to use many conductive slurries. However, this reduces the occupancy rate of the active material in the positive electrode film layer, which is disadvantageous for improving the energy density. For this reason, those skilled in the art generally add graphene with a higher conductivity to the conductive slurry. However, graphene is expensive and does not have a cost advantage.

[0034] As a result of intensive research, the inventors have found the following. By manufacturing a positive electrode active slurry using a first conductive carbon black and a second conductive carbon black having different specific surface areas, the internal resistance of a secondary battery can be effectively improved, the amount of conductive agent used can be reduced, the occupancy rate of the active material can be increased, thereby improving the energy density. At the same time, compared with graphene, carbon black has a lower price, cost advantages, and higher dispersibility. In addition, by further optimizing the blending ratio of each substance in the system, the internal resistance of the secondary battery can be further improved, thereby improving the energy density of the corresponding secondary battery and contributing to the improvement of cycle performance.

[0035] For this reason, a first aspect of the present application provides a secondary battery, which includes a positive electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. The positive electrode film layer contains a conductive agent, and the conductive agent contains a first conductive carbon black and a second conductive carbon black. The specific surface area of the second conductive carbon black is larger than the specific surface area of the first conductive carbon black.

[0036] By using two types of conductive carbon blacks with different specific surface areas, it is possible to improve the internal resistance and cycle performance of the battery without increasing the amount of conductive agent used.

[0037] In some embodiments, if the specific surface area of the first conductive carbon black is S1 and the specific surface area of the second conductive carbon black is S2, then S2 / S1≧4, and optionally, 5≦S2 / S1≦17.

[0038] By setting the ratio of the specific surface areas of the first conductive carbon black and the second conductive carbon black within the above range, the improvement of the internal resistance and cycle performance of the battery can be better realized.

[0039] In some embodiments, the specific surface area of the first conductive carbon black is ≤ 140 m 2 / g, optionally 50 m 2 / g to 130 m 2 / g, and further optionally 55 m 2 / g to 80 m 2 / g. And / or, the specific surface area of the second conductive carbon black is 200 m 2 / g to 1200 m 2 / g, optionally 300 m 2 / g to 1000 m 2 / g, also optionally 400 m 2 / g to 900 m 2 / g, and further optionally 500 m 2 / g to 800 m 2 / g.

[0040] In some embodiments, the conductive agent (1) The mass occupancy rate of the conductive agent in the positive electrode film layer is ≤ 5%, optionally 0.8% to 3.0%, and further optionally 0.9% to 2.5%; (2) The mass occupancy rate of the first conductive carbon black in the positive electrode film layer is ≤ 4.2%, optionally 0.4% to 3%, and further optionally 0.5% to 2.5%; (3) The mass occupancy rate of the second conductive carbon black in the positive electrode film layer is ≤ 2.5%, optionally 0.1% to 2%, and further optionally 0.4% to 1%; and (4) The mass ratio of the first conductive carbon black to the second conductive carbon black is (0.4 to 8):1, optionally (0.5 to 7):1, and at least one of them is satisfied.

[0041] In some embodiments, the oil absorption amount of the first conductive carbon black is ≤ 260, and / or the oil absorption amount of the second conductive carbon black is ≤ 300.

[0042] The oil absorption amount has the meaning known in the art and can be measured by adopting instruments and methods known in the art. For example, referring to the ASTM D2414 oil absorption test standard, an oil absorption test instrument (such as HiTEC Keithley SourceMeter) can be adopted for measurement.

[0043] In some embodiments, the water content of the first conductive carbon black ≤ 5000 ppm, and / or the water content of the second conductive carbon black ≤ 10000 ppm.

[0044] The water content can be measured by adopting instruments and methods known in the art. For example, referring to the GB / T 11133-2015 Karl Fischer method, a coulometric moisture titrator (such as 774 Test method) can be adopted for measurement.

[0045] In some embodiments, the conductive agent further includes carbon nanotubes. Optionally, the tube diameter of the carbon nanotubes is 4 - 10 nm, and further optionally 5 - 8 nm. Optionally, the tube length of the carbon nanotubes is 0.3 - 50 μm, and further optionally 0.8 - 40 μm. Optionally, the aspect ratio of the carbon nanotubes is 50 - 12500, and further optionally 100 - 8000. Optionally, the carbon nanotubes include multi-walled carbon nanotubes. Optionally, the mass occupancy rate of the carbon nanotubes in the positive electrode film layer ≤ 1.2%, and optionally ≤ 0.6%. Optionally, the mass ratio of the second conductive carbon black to the carbon nanotubes is (0.1 - 10):1, optionally (0.2 - 6):1, and further optionally (0.3 - 4):1.

[0046] In this application, the tube diameter of the carbon nanotube is measured according to GB / T 26826-2011, and the tube length of the carbon nanotube is measured by the scanning electron microscope statistical method.

[0047] In some embodiments, the first conductive carbon black and the second conductive carbon black are each independently selected from at least one of furnace carbon black, acetylene black, Super p, and ketjen black. Optionally, the first conductive carbon black and the second conductive carbon black may be the same type of carbon black or different types of carbon black, but optionally they are the same type of carbon black.

[0048] In some embodiments, the positive electrode film layer further contains a dispersant, and the dispersant includes a first dispersant and a second dispersant.

[0049] In some embodiments, the first dispersant includes a vinylidene fluoride-based polymer. Optionally, the first dispersant includes a vinylidene fluoride homopolymer or a compound of a first dispersant obtained by copolymerizing vinylidene fluoride and a vinylidene fluoride containing an active group. Here, the active group includes at least one of a carboxyl group, an epoxy group, a hydroxy group, or a sulfonic acid group, and optionally a carboxyl group or an epoxy group.

[0050] In some embodiments, the number average molecular weight of the first dispersant is 100,000 to 5,000,000, and optionally 500,000 to 3,000,000.

[0051] In some embodiments, the second dispersant is selected from a copolymer of ethylene and maleic anhydride and a copolymer of styrene and maleic anhydride. Optionally, its number average molecular weight is 10,000 to 200,000, and optionally 50,000 to 150,000.

[0052] In this application, the number average molecular weight is measured by adopting gel permeation chromatography (GPC) in accordance with GB / T 21863-2008 "Gel Permeation Chromatography (GPC) with Tetrahydrofuran as Eluent" (which is equivalent to adopting DIN 55672-1:2007 "Gel Permeation Chromatography (GPC) - Part 1: Using Tetrahydrofuran (THF) as Eluent Solvent", a German standard).

[0053] In this application, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on one or both of the two opposite surfaces of the positive electrode current collector.

[0054] In some embodiments, the positive electrode current collector may adopt a metal foil sheet or a composite current collector. For example, as the metal foil sheet, aluminum foil may be adopted. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as substrates like polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0055] In this application, the positive electrode material is a compound that can reversibly occlude and release Li + .

[0056] In some embodiments, the positive electrode active material may employ a positive electrode active material for batteries well known in the art. By way of example, the positive electrode active material may include at least one material selected from among lithium-containing phosphates having an olivine structure, lithium transition metal oxides, and modified compounds thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of a battery may be used. These positive electrode active materials may be used alone, or two or more of them may be used in combination. Here, examples of the lithium transition metal oxide include lithium cobalt oxide (e.g., LiCoO 2 ), lithium nickel oxide (e.g., LiNiO 2 ), lithium manganese oxide (e.g., LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which may be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which may be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which may be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which may be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which may be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O 2It may include, but is not limited to, at least one of them and its modified compounds, etc. Examples of the lithium-containing phosphate with an olivine structure include lithium iron phosphate (for example, LiFePO 4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (for example, LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon, but is not limited thereto.

[0057] In some embodiments, optionally, the positive electrode active material is a lithium-containing composite oxide having a layered structure or a spinel structure, such as LiCoO 2 , LiMn 2 O 4 , LiNiO 2 , LiNi 1 / 2 Mn 1 / 2 O 2 and other lithium manganese nickel composite oxides represented by, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 and other lithium manganese nickel cobalt composite oxides represented by, or LiNi 1-x-y-z Co x Al y Mg z O 2 (in the formula, 0≦x≦1, 0≦y≦0.1, 0≦z≦0.1, 0≦1 - x - y - z≦1) and other lithium-containing composite oxides. Note that lithium-containing composite oxides in which some of the constituent elements in the above lithium-containing composite oxides are substituted by additive elements such as Ge, Ti, Zr, Mg, Al, Mo, Sn, etc. are also included within the scope of this application.

[0058] In addition to the above-mentioned positive electrode active material, other conventional materials that can be used as the positive electrode active material of the battery may also be used. These positive electrode active materials may be used alone, or two or more of them may be used in combination. For example, by using a layered lithium-containing composite oxide and a spinel-structured lithium-containing composite oxide in combination, it is possible to achieve both an increase in capacity and an improvement in safety.

[0059] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium cobaltate, lithium nickel cobaltate, lithium nickel manganate, lithium iron phosphate and lithium titanate, and derivatives or combinations thereof in which the element positions are substituted or doped with transition metals or non-transition metals.

[0060] In some embodiments, the mass occupancy of the positive electrode active material in the positive electrode film layer is 90% to 97.1%, optionally 95% to 97.1%.

[0061] In some embodiments, the positive electrode film layer optionally further includes an adhesive. The adhesive is, for example, an adhesive commonly used in the battery field such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide.

[0062] In some embodiments, the dry weight of the adhesive accounts for 0.1% to 3.5% of the total weight of the positive electrode film layer based on the dry weight, optionally 0.5% to 2.5%.

[0063] The second aspect of the present application further provides a method for manufacturing the secondary battery described in the first aspect of the present application. This method includes manufacturing a positive electrode plate by adopting the following steps. Step S1: Dry-mix the first conductive carbon, the second conductive carbon, and the first dispersant in a stirring tank to obtain a powder mixture. Here, the specific surface area of the second conductive carbon black is larger than that of the first conductive carbon black. Step S2: Add a solvent to the powder mixture, mix uniformly, and then obtain Slurry 1. Step S3: Add the second dispersant to Slurry 1, mix uniformly, and then obtain Slurry 2. Step S4: Add the positive electrode active material to the Slurry 2, mix uniformly, and obtain a positive electrode material slurry. Step S5: Coat the positive electrode material slurry on at least one surface of the positive electrode current collector, dry it, and then form a positive electrode film layer.

[0064] In some embodiments, the first dispersant includes a vinylidene fluoride-based polymer. Optionally, the first dispersant includes a vinylidene fluoride homopolymer or a compound of a first dispersant obtained by copolymerizing vinylidene fluoride and a vinylidene fluoride containing an active group. Here, the active group includes at least one of a carboxyl group, an epoxy group, a hydroxy group, or a sulfonic acid group, and is optionally a carboxyl group or an epoxy group.

[0065] In some embodiments, the second dispersant is selected from a copolymer of ethylene and maleic anhydride or a copolymer of styrene and maleic anhydride.

[0066] In some embodiments, the mass ratio of the sum of the masses of the first conductive carbon black and the second conductive carbon black to the first dispersant is (0.4 to 2.0):1, and optionally (0.75 to 1.8):1.

[0067] In some embodiments, the mass ratio of the sum of the masses of the first conductive carbon black and the second conductive carbon black to the second dispersant is (8 to 30):1, and optionally (9 to 25):1.

[0068] In some embodiments, in steps S1 to S4, each mixing may be performed by adopting the following operations. The stirring linear velocity is 5 m / s to 25 m / s, optionally 8 m / s to 20 m / s, the stirring time is 10 minutes to 60 minutes, and optionally 13 minutes to 40 minutes.

[0069] In some embodiments, the solvent is selected from at least one of N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and dimethyl sulfoxide.

[0070] In some embodiments, in step S3, a second dispersant and carbon nanotubes (CNT) are added to slurry 1, uniformly mixed, and then slurry 2 is obtained.

[0071] In some embodiments, the content a of the first conductive carbon black, the content b of the second conductive carbon black, and the content c of the carbon nanotubes satisfy 0.2 ≦ ((a + b) × c) / (a × b) ≦ 10, and optionally 0.4 ≦ ((a + b) × c) / (a × b) ≦ 6. Here, a, b, and c are based on the total weight based on the dry weight of the conductive slurry.

[0072] Hereinafter, the secondary battery of the present application will be described with appropriate reference to the drawings. The secondary battery may include the form of a battery cell, the form of a battery module, or the form of a battery pack.

[0073] In one embodiment of the present application, a battery cell is provided.

[0074] Generally, a battery cell includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge of the battery, active ions shuttle back and forth between the positive electrode plate and the negative electrode plate for intercalation and deintercalation. The electrolyte serves to conduct ions between the positive electrode plate and the negative electrode plate. The separator is installed between the positive electrode plate and the negative electrode plate, mainly serving to prevent short circuit between the positive and negative electrodes and allowing ions to pass through.

[0075] [Secondary battery] The second aspect of the present application provides a secondary battery, which includes the separator described in the first aspect of the present application. Generally, in addition to the separator, the secondary battery further includes a positive electrode plate, a negative electrode plate, and an electrolytic solution.

[0076] In particular, the present application may be used in a lithium metal battery as an alternative to a conventional separator. The negative electrode may be lithium metal or a lithium alloy, or there may be no negative electrode. The corresponding positive electrode material is as described above. In the case of a lithium metal battery without a negative electrode, the positive electrode material needs to provide a lithium source.

[0077] The manufacturing of the secondary battery may be carried out by methods commonly used in the art. For example, an electrode assembly may be manufactured by a winding process or a lamination process using a positive electrode plate, a negative electrode plate, and a separator, and then an electrolytic solution may be injected into the electrode assembly and sealed to manufacture the secondary battery.

[0078] It should be noted that the secondary battery described in the present application includes button-type batteries. When the secondary battery is a button-type battery, the materials of the positive electrode plate and the negative electrode plate may be the same or different. In addition, a button-type battery may be manufactured by methods commonly used by those skilled in the art. As an example, a positive electrode plate, a separator, and a negative electrode plate may be assembled as an electrode assembly, and then an electrolytic solution may be injected into the electrode assembly and sealed to manufacture the button-type battery.

[0079] Hereinafter, the above-mentioned members of the secondary battery will be described respectively.

[0080] Negative electrode plate The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. As an example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is disposed on either one or both of the two opposing surfaces of the negative electrode current collector.

[0081] In some embodiments, the negative electrode current collector may employ a metal foil sheet or a composite current collector. For example, as the metal foil sheet, a copper foil may be employed. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0082] In the present application, the negative electrode material is a lithium metal or a compound capable of occluding and releasing lithium.

[0083] In some embodiments, the negative electrode active material may employ a negative electrode active material for batteries well known in the art. As an example, various materials such as alloys or oxides of aluminum, silicon, tin, etc., and carbon materials may be used as the negative electrode active material. Optionally, the oxide may include titanium dioxide, etc., and the carbon material may include graphite, pyrolytic carbon-based, coke-based, glassy carbon-based, fired bodies of organic polymer compounds, mesocarbon microbeads, etc. The tin-based material may be selected from at least one of tin alone, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0084] In some embodiments, optionally, the dry weight of the negative electrode active material accounts for 75% to 99% of the total weight of the negative electrode film layer based on the dry weight, and optionally accounts for 80% to 97%.

[0085] In some embodiments, the negative electrode film layer optionally further includes an adhesive. The adhesive is an adhesive commonly used in the battery field, such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, etc.

[0086] In some embodiments, optionally, the dry weight of the adhesive accounts for 0.1% to 3.5% of the total weight of the negative electrode film layer based on the dry weight, and optionally accounts for 0.5% to 2.5%.

[0087] In some embodiments, the negative electrode film layer optionally further includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, optionally, the dry weight of the conductive agent accounts for 0.05% to 5% of the total weight of the negative electrode film layer based on the dry weight, and optionally accounts for 0.5% to 3%.

[0089] In some embodiments, the negative electrode film layer optionally further includes other auxiliaries, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0090] In some embodiments, the negative electrode plate may be manufactured by the following method. The above components for manufacturing the negative electrode plate, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (for example, deionized water) to form a negative electrode slurry. The negative electrode slurry is coated on the negative electrode current collector, and through processes such as drying and cold pressing, a negative electrode plate is obtained.

[0091] [Electrolyte] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. The present application does not specifically limit the type of the electrolyte, and it can be selected according to the needs. For example, the electrolyte may be liquid, gel-like, or all-solid.

[0092] In some embodiments, the electrolyte employs an electrolytic solution. The electrolytic solution contains an electrolyte salt and a solvent.

[0093] In some embodiments, a non-aqueous solvent (organic solvent) is used as the non-aqueous electrolytic solution. The non-aqueous solvent includes carbonate-based, ether-based, etc.

[0094] In some embodiments, the carbonate-based includes cyclic carbonates and chain carbonates. Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, sulfur-based esters (ethylene glycol sulfide), etc. Examples of chain carbonates include low-viscosity polar chain carbonates represented by dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc., and aliphatic branched carbonate-based compounds. A mixed solvent of cyclic carbonate (especially ethylene carbonate) and chain carbonate is particularly preferred.

[0095] Examples of ether-based include dimethyl ether tetraethylene glycol (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), etc.

[0096] In addition to the above non-aqueous solvents, chain alkyl ester solvents such as methyl propionate, chain triphosphate esters such as trimethyl phosphate, nitrile solvents such as 3-methoxypropionitrile, and non-aqueous solvents (organic solvents) such as branched compounds having ether bonds represented by dendrimer compounds may be further employed.

[0097] Moreover, a fluorine-based solvent may be employed.

[0098] Examples of the fluorine-based solvent include, for example, H(CF 2 ) 2 OCH 3 , C 4 F 9 OCH 3 , H(CF 2 ) 2 OCH 2 CH 3 , H(CF 2 ) 2 OCH 2 CF 3 , H(CF 2 ) 2 CH 2 O(CF 2 ) 2 H, etc., or CF 3 CHFCF 2 OCH 3 , CF 3 CHFCF 2 OCH 2 CH 3(Perfluoroalkyl)alkyl ethers having a linear structure such as 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyl decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecafluorohexyl methyl ether, 5-trifluoromethyl dodecafluorohexyl ethyl ether, 5-trifluoromethyl dodecafluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecafluorooctyl methyl ether, 7-trifluoromethyl hexadecafluorooctyl ethyl ether, 7-trifluoromethyl hexadecafluorooctyl propyl ether, etc. may be mentioned.

[0099] Further, the above-mentioned iso-(perfluoroalkyl)alkyl ether may be used in combination with the above-mentioned (perfluoroalkyl)alkyl ether having a linear structure.

[0100] As the electrolyte salt used in the non-aqueous electrolyte, lithium salts such as lithium perchlorate, lithium organic borate, lithium salt of a fluorine-containing compound, lithium imide salt, etc. are preferable.

[0101] Examples of such electrolyte salts include, for example, LiClO 4 、LiPF 6 、LiBF 4 、LiAsF 6 、LiSbF 6 、LiCF 3 SO 3 、LiCF3 CO 2 , LiC 2 F 4 (SO 3 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , LiC n F 2n+1 SO 3 (n ≧ 2), LiN(R f OSO 2 ) 2 (wherein R f is a fluoroalkyl group), etc. Among these lithium salts, fluorine-containing organic lithium salts are particularly preferred. Fluorine-containing organic lithium salts are easily dissolved in non-aqueous electrolytes because they have a large anionic property and are easily separated into ions.

[0102] The concentration of the electrolyte lithium salt in the non-aqueous electrolyte is, for example, 0.3 mol / L (moles / liter) or more, further optionally 0.7 mol / L or more, optionally 1.7 mol / L or less, and further optionally 1.2 mol / L or less. If the concentration of the electrolyte lithium salt is too low, the ionic conductivity becomes too small. If the concentration of the electrolyte lithium salt is too high, precipitation of undissolved electrolyte salts is a concern.

[0103] In some embodiments, the electrolyte further optionally contains an additive, but the present application is not particularly limited. For example, the additive may include a negative electrode film-forming additive and a positive electrode film-forming additive, and may further include additives that can improve some performances of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, etc.

[0104] [Separator] In some embodiments, the battery cell further includes a separator. This application is not particularly limited to the type of separator, and any known separator with good chemical stability and mechanical stability and having a porous structure may be selected.

[0105] In some embodiments, the material of the separator may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and there is no particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and there is no particular limitation.

[0106] In some embodiments, the battery cell may include an exterior body. The exterior body may be used to package the above electrode assembly and electrolyte.

[0107] In some embodiments, the exterior body of the battery cell may be a rigid case, such as a rigid plastic case, an aluminum case, a steel case, etc. The exterior body of the battery cell may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] This application is not particularly limited to the shape of the battery cell, and it may be cylindrical, square, or any other arbitrary shape. For example, FIG. 1 shows a battery cell 5 having a square structure as an example.

[0109] In some embodiments, referring to FIG. 2, the outer package may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates surround to form an accommodation cavity. The case 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can close the accommodation cavity by covering the opening. The positive electrode plate, the negative electrode plate, and the separator can form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodation cavity. The electrolytic solution infiltrates the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 may be one or more, and those skilled in the art can specifically select according to actual needs.

[0110] In some embodiments, the battery cell may be assembled into a battery module. The number of battery cells included in the battery module may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0111] FIG. 3 shows a battery module 4 as an example. Referring to FIG. 3, in the battery module 4, a plurality of battery cells 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged according to any other method. Further, the plurality of battery cells 5 may be fixed with a fastener.

[0112] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0113] In some embodiments, the above battery cell may be assembled into a battery pack. In some embodiments, the above battery module may further be assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0114] FIGS. 4 and 5 show a battery pack 1 as an example. Referring to FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3. The upper housing 2 is provided to cover the lower housing 3 and can form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box according to any method.

[0115] Further, the present application further provides a power consumption device, and the power consumption device includes a secondary battery according to the present application. The secondary battery may be used as a power source of the power consumption device or as an energy storage unit of the power consumption device. The power consumption device may include, but is not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, and satellites, energy storage systems, etc.

[0116] As the power consumption device, a secondary battery can be selected according to the requirements in its use.

[0117] FIG. 6 shows a power consumption device as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like. In order to meet the requirements of the power consumption device for high power and high energy density of the secondary battery, a battery pack or a battery module can be adopted.

[0118] Another example of the device may be a mobile phone, a tablet computer, a notebook computer, or the like. Generally, the device is required to be thinner and lighter, and a battery cell can be adopted as a power source.

[0119] Embodiment Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are merely for interpreting the present application, and should not be understood as limitations on the present application. When specific technologies or conditions are not specified in the embodiments, the technologies or conditions described in the literature of the technical field or the product instruction manual are followed. For the reagents or instruments used, those for which the manufacturer is not specified are all common products that can be purchased commercially. Unless otherwise specified, the masses of the substances used in the examples are all masses without crystal water.

[0120] Example 1 Manufacture of secondary battery 1. Manufacture of positive electrode plate The first conductive carbon black (Super P), the second conductive carbon black (Ketjen black), and the first dispersant (PVDF 5130) were dry-mixed at a mass ratio of 3:1:3 and dispersed in a stirring tank at a linear velocity of 10 m / s for 15 min. Here, the specific surface area SSA of the first conductive carbon black (i.e., S1) = 60 m 2 / g, the specific surface area SSA of the second conductive carbon black (i.e., S2) = 600 m 2 / g, and S2 / S1 = 10.

[0121] The obtained product was added to an NMP solvent and dispersed at a linear velocity of 15 m / s for 30 min to obtain Slurry 1. The solid content was 10.5%.

[0122] After adding the second dispersant (copolymer of ethylene and maleic anhydride, Mn = 100000) to Slurry 1, it was dispersed at a linear velocity of 15 m / s for 15 min to obtain Slurry 2. The first conductive carbon black + the second conductive carbon black and the second dispersant were mixed at a mass ratio of 10:1, and LiNi 0.8 Co 0.1 Mn 0.1 O 2(NCM811) was added to the above mixture and mixing was continued to obtain a positive electrode active slurry. The added mass ratio of the positive electrode active material based on the weight of the positive electrode film layer after drying was 96.3%.

[0123] The positive electrode active slurry was coated on the aluminum foil of the positive electrode current collector, and through processes such as drying, cold pressing, slitting, and cutting, a positive electrode plate was obtained. The surface density of the positive electrode plate was 300 mg / mm 2 and the tap density was 3.3 g / cm 3 .

[0124] 2. Manufacture of negative electrode plate Artificial graphite as the negative electrode active material, carbon black (Super P) as the conductive agent, styrene-butadiene rubber (SBR) as the adhesive, and sodium carboxymethyl cellulose (CMC) were uniformly mixed in deionized water, which is an appropriate amount of solvent, at a mass ratio of 96:1:1.5:1.5 to obtain a negative electrode slurry. The negative electrode slurry was coated on the copper foil of the negative electrode current collector, and through processes such as drying, cold pressing, slitting, and cutting, a negative electrode plate was obtained. The surface density of the negative electrode plate was 185 mg / mm 2 and the tap density was 1.6 g / cm 3 .

[0125] 3. Manufacture of electrolyte Ethylene carbonate (EC) and methyl ethyl carbonate (EMC) were mixed at a mass ratio of 30:70 to obtain an organic solvent. Thoroughly dried LiPF 6 was dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0126] 4. Separator A polyethylene (PE) porous polymer film with a thickness of 13 μm was used as the separator.

[0127] 5. Manufacture of secondary battery A positive electrode plate, a separator, and a negative electrode plate were laminated and wound in order to obtain an electrode assembly. The electrode assembly was placed in an outer package, and after drying, an electrolytic solution was injected. Through processes such as vacuum packaging, standing, formation, and shaping, a secondary battery was obtained. The margin was 89%.

[0128] Examples 2 to 16 The method for manufacturing a secondary battery is the same as that of Example 1, but only the conductive agent in the positive electrode slurry was changed, and carbon nanotubes (CNTs) were optionally added. Specifically, refer to Table 1.

[0129] Comparative Example 1 The method for manufacturing a secondary battery is the same as that of Example 1, but when manufacturing the positive electrode slurry, only the first conductive carbon black was used.

[0130] Comparative Example 2 The method for manufacturing a secondary battery is the same as that of Example 1, but when manufacturing the positive electrode slurry, only the second conductive carbon black was used.

[0131] Test methods for related parameters 1. Specific surface area test Regarding the test of the specific surface area, refer to GB / T 19587-2017, and use the Tri-Star 3020 type specific surface area and pore size analysis test equipment of Micromeritics, USA, to perform the specific surface area analysis test by nitrogen gas adsorption, and calculate the specific surface area of the material by the BET (Brunauer Emmett Teller) method. Refer to Table 1 for the test results.

[0132] 2. DCR test at 25°C At 25°C, the battery was charged at a constant current to 4.25 V at 0.5 C, and then charged at a constant voltage until the current reached 0.05 C. Then, the battery was discharged at a constant current of 0.5 C for 30 minutes to adjust the battery to 50% SOC (State of Charge), and the voltage of the battery at this time was designated as U1. Then, the battery was discharged at a constant current of 4 C for 30 seconds, sampled at 0.1 seconds, and the voltage at the end of discharge was designated as U2. The initial DCR of the battery was represented using the discharge DCR of the battery at 50% SOC, and the initial DCR of the battery = (U1 - U2) / 4C.

[0133] 3.25°C Cycle Performance Test At 25°C, the secondary batteries manufactured in each example and comparative example were charged at a constant current to a charge cut-off voltage of 4.25 V at a rate of 1 C, then charged at a constant voltage until the current ≤ 0.05 C, and left standing for 5 min. Further, they were discharged at a constant current to a discharge cut-off voltage of 2.8 V at a rate of 0.33 C, left standing for 5 min, and this was taken as one charge-discharge cycle. According to this method, the battery was subjected to a cycle charge-discharge test until the battery capacity decayed to 80%. The number of cycles at this time was recorded and taken as the cycle life of the battery at 25°C.

[0134]

Table 1

[0135]

Table 2

[0136] As can be seen from Table 1 and Table 2, by using the two types of conductive carbon black of the present application, excellent conductive performance and improved battery cycle performance could be realized without increasing the amount of conductive agent used.

[0137] It should be noted that this application is not limited to the above embodiments. The above embodiments are illustrative, and embodiments that have substantially the same configuration as the technical idea within the scope of the technical solution of this application and exhibit the same effects are all included within the technical scope of this application. In addition, within the scope not departing from the spirit of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other forms constructed by combining some of the components in the embodiments are also included within the scope of this application.

Explanation of Reference Signs

[0138] 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Battery cell, 51 Case, 52 Electrode assembly, 53 Top cover assembly.

Claims

1. A secondary battery, comprising a positive electrode plate, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer contains a conductive agent, wherein the conductive agent includes a first conductive carbon black and a second conductive carbon black, and a specific surface area of the second conductive carbon black is larger than a specific surface area of the first conductive carbon black. The secondary battery is as described above.

2. When a specific surface area of the first conductive carbon black is denoted as S1 and a specific surface area of the second conductive carbon black is denoted as S2, S2 / S1≥4, and optionally, 5≤S2 / S1≤17. The secondary battery according to Claim 1 is as described above.

3. The specific surface area of the first conductive carbon black ≤ 140 m ２ / g, and optionally 50 m ２ / g to 130 m ２ / g, and / or The specific surface area of the second conductive carbon black is 200 m ２ / g to 1200 m ２ / g, and optionally 300 m ２ / g to 1000 m ２ / g. The secondary battery according to claim 1 or 2.

4. The conductive agent, (1) a mass occupancy rate of the conductive agent in the positive electrode film layer is ≤5%, and optionally, is 0.8% - 3.0%; (2) a mass occupancy rate of the first conductive carbon black in the positive electrode film layer is ≤4.2%, and optionally, is 0.4% - 3%; (3) a mass occupancy rate of the second conductive carbon black in the positive electrode film layer is ≤2.5%, and optionally, is 0.1% - 2%; and (4) a mass ratio of the first conductive carbon black to the second conductive carbon black is (0.4 - 8):1, and optionally, is (0.5 - 7):

1. The secondary battery according to any one of Claims 1 to 3 satisfies at least one of the above conditions.

5. An absorption oil amount of the first conductive carbon black is ≤260, and / or an absorption oil amount of the second conductive carbon black is ≤300. The secondary battery according to any one of Claims 1 to 4 is as described above.

6. A water content of the first conductive carbon black is ≤5000 ppm, and / or a water content of the second conductive carbon black is ≤10000 ppm. The secondary battery according to any one of Claims 1 to 5 is as described above.

7. The conductive agent further includes carbon nanotubes, optionally, a tube diameter of the carbon nanotubes is 4 - 10 nm, optionally, a tube length of the carbon nanotubes is 0.3 - 50 μm, optionally, an aspect ratio of the carbon nanotubes is 50 - 12500, optionally, the carbon nanotubes include multi - walled carbon nanotubes. Optionally, the mass occupancy ratio of the carbon nanotubes in the positive electrode film layer is ≤ 1.2%, Optionally, the mass ratio of the second conductive carbon black to the carbon nanotubes is (0.1 - 10):

1. The secondary battery according to any one of claims 1 to 6.

8. The first conductive carbon black and the second conductive carbon black are each independently selected from at least one of furnace carbon black, acetylene black, and ketjen black. The secondary battery according to any one of claims 1 to 7.

9. A method for manufacturing a secondary battery, S1: A step of dry-mixing a first conductive carbon black, a second conductive carbon black, and a first dispersant in a stirring tank to obtain a powder mixture, wherein the specific surface area of the second conductive carbon black is larger than the specific surface area of the first conductive carbon black, S2: A step of adding a solvent to the powder mixture and uniformly mixing to obtain slurry 1, S3: A step of adding a second dispersant to slurry 1 and uniformly mixing to obtain slurry 2, S4: A step of adding a positive electrode active material to the slurry 2 and uniformly mixing to obtain a positive electrode material slurry, S5: A step of coating the positive electrode material slurry on at least one surface of a positive electrode current collector, drying, and then forming a positive electrode film layer, A method for manufacturing a secondary battery, including manufacturing a positive electrode plate by adopting the above steps.

10. The first dispersant includes a vinylidene fluoride-based polymer, Optionally, the first dispersant includes a vinylidene fluoride homopolymer or a compound of a first dispersant obtained by copolymerizing vinylidene fluoride and a vinylidene fluoride containing an active group, wherein the active group includes at least one of a carboxyl group, an epoxy group, a hydroxy group, or a sulfonic acid group, and optionally a carboxyl group or an epoxy group. The manufacturing method according to claim 9.

11. The second dispersant is selected from a copolymer of ethylene and maleic anhydride or a copolymer of styrene and maleic anhydride. The manufacturing method according to claim 9 or 10.

12. The mass ratio of the sum of the masses of the first conductive carbon black and the second conductive carbon black to the first dispersant is (0.4 to 2.0):1, and optionally (0.75 to 1.8):

1. The manufacturing method according to any one of claims 9 to 11.

13. The mass ratio of the sum of the masses of the first conductive carbon black and the second conductive carbon black to the second dispersant is (8 to 30):1, and optionally (9 to 25):

1. The manufacturing method according to any one of claims 9 to 12.

14. In step S3, a second dispersant and carbon nanotubes are added to slurry 1, uniformly mixed, and then slurry 2 is obtained. The manufacturing method according to any one of claims 9 to 13.

15. The content a of the first conductive carbon black, the content b of the second conductive carbon black, and the content c of the carbon nanotubes satisfy 0.2 ≤ ((a + b) × c) / (a × b) ≤ 10, and optionally 0.4 ≤ ((a + b) × c) / (a × b) ≤ 6. Here, a, b, and c are based on the total weight based on the dry weight of the conductive slurry. The manufacturing method according to claim 14.

16. A power consumption device including a secondary battery according to any one of claims 1 to 8, or a secondary battery manufactured by the method according to any one of claims 9 to 15.

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