Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device, the secondary battery comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode active material and a conductive agent, and the conductive agent comprises carbon black particles; the coating rate of the carbon black particles to the positive electrode active material particles is C%, and C is not less than 60 and not more than 98. According to the present invention, by regulating the type of the conductive agent and the coating rate of the carbon black particles on the positive electrode active material particles in the application range, the dynamic performance of the secondary battery is improved, the secondary battery further has good high temperature performance, and the internal resistance of the secondary battery can be reduced.

Description

Technical Field

[0001] The present application relates to the field of electrochemistry technology, and particularly to a secondary battery and an electronic device. Background Art

[0002] Reducing the internal resistance of lithium-ion batteries has always been the pursuit of customers. During the cycling process of lithium-ion batteries, the positive electrode impedance dominates. Selecting a new type of conductive agent and building a good conductive network are the main directions for reducing the internal resistance of lithium-ion batteries.

[0003] In the prior art, generally, the internal resistance of lithium-ion batteries is reduced by increasing the content of the conductive agent or reducing the content of the binder. However, increasing the content of the conductive agent will lead to a decrease in the content of the positive electrode active material and a decrease in the energy density of the lithium-ion battery; reducing the content of the binder will lead to a decrease in the adhesion between the positive electrode material layer and the positive electrode current collector and a decrease in the internal cohesion of the positive electrode material layer itself, resulting in problems such as film peeling and thickness swelling during the use of the lithium-ion battery. Summary of the Invention

[0004] The purpose of the present application is to provide a secondary battery and an electronic device, which can improve the kinetic performance of the secondary battery while the secondary battery also has good high-temperature performance and can reduce the internal resistance of the secondary battery. The specific technical solutions are as follows:

[0005] In the first aspect of the present application, a secondary battery is provided, which includes a positive electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The positive electrode material layer includes a positive electrode active material and a conductive agent. The conductive agent includes carbon black particles, and the coating rate of the carbon black particles on the positive electrode active material particles is C%, and 60 ≤ C ≤ 98. When the positive electrode material layer includes a positive electrode active material and a conductive agent, and the conductive agent includes carbon black particles, after the carbon black particles are stacked, there is still a certain gap, which is more conducive to storing the electrolyte. And after the carbon black particle units are uniformly distributed on the surface of the positive electrode active material particles in a smaller size, the surface area of the positive electrode active material particles can be cut into smaller and more uniform areas, which is beneficial to reducing the Li + and electron diffusion paths and reducing the Li + concentration polarization, thereby improving the kinetic performance of the secondary battery; at the same time, the carbon black particles are thinly coated on the surface of the positive electrode active material particles, and the appropriate thickness is beneficial to the Li + transport, and can also improve the kinetic performance of the secondary battery. And when the coating rate of the carbon black particles on the positive electrode active material particles is within the scope of the present application, while reducing the Li + concentration polarization and improving the kinetic performance of the secondary battery, the possibility of direct contact between the surface of the positive electrode active material and the electrolyte is reduced, the secondary battery also has good high-temperature performance, and can also reduce the internal resistance of the secondary battery.

[0006] In an embodiment of the present application, 80 ≤ C ≤ 95. By controlling the coating rate of carbon black particles on the cathode active material particles within the above range, while reducing the Li + concentration polarization and further improving the kinetic performance of the secondary battery, the possibility of direct contact between the surface of the cathode active material and the electrolyte is reduced. The secondary battery also has better high-temperature performance and can further reduce the internal resistance of the secondary battery.

[0007] In an embodiment of the present application, the stacking thickness of carbon black particles on the surface of the cathode active material particles is H nm, 20 ≤ H ≤ 60. By controlling the stacking thickness of carbon black particles on the surface of the cathode active material particles within the above range, the stacking thickness of carbon black particles on the surface of the cathode active material particles is appropriate, which is beneficial to Li + transport and can further improve the kinetic performance of the secondary battery.

[0008] In an embodiment of the present application, the particle size of the primary particles of carbon black particles is d1 nm, 5 ≤ d1 ≤ 40. In an embodiment of the present application, the particle size of the primary particles of carbon black particles is d1 nm, 10 ≤ d1 ≤ 30. By controlling the particle size of the primary particles of carbon black particles within the above range, the particle size of the primary particles of carbon black particles is small. The small-sized carbon black particles are thinly coated on the surface of the cathode active material, and the thickness is appropriate, which is beneficial to Li + transport and can further improve the kinetic performance of the secondary battery.

[0009] In an embodiment of the present application, the particle size Dv50 of the cathode material layer particles satisfies: 200d1 ≤ Dv50 ≤ 5000d1. When the particle size Dv50 of the cathode material layer particles satisfies the above characteristics, the carbon black particles can be more closely coated on the surface of the cathode active material, and there can be appropriate gaps between the cathode active materials. The cathode active materials are filled more tightly, reducing the possibility of broken bridges between the cathode active materials, which is beneficial to the construction of the conductive network and can further improve the kinetic performance of the secondary battery.

[0010] In an embodiment of the present application, 3 μm ≤ Dv50 ≤ 30 μm. By controlling the particle size Dv50 of the cathode material layer particles within the above range, the cathode active material can have good kinetic performance and good high-temperature performance, so that the secondary battery has good kinetic performance and high-temperature performance.

[0011] In an embodiment of the present application, the carbon black particles contain oxygen element. Based on the mass of the carbon black particles, the mass percentage content of the oxygen element is W O %, 0.3 ≤ W O≤3. The carbon black particles contain oxygen element, and regulating the mass percentage of oxygen element within the above range can improve the self-dispersibility of the carbon black particles, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + and further reduce the concentration polarization of Li + , thereby further enhancing the kinetic performance of the secondary battery.

[0012] In an embodiment of the present application, the carbon black particles contain hydrogen element, and based on the mass of the carbon black particles, the mass percentage of hydrogen element is W H %, 0.1 ≤ W H ≤ 0.5. The carbon black particles contain hydrogen element, and regulating the mass percentage of hydrogen element within the above range can improve the self-dispersibility of the carbon black particles, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + and further reduce the concentration polarization of Li + , thereby further enhancing the kinetic performance of the secondary battery.

[0013] In an embodiment of the present application, the positive electrode material layer further includes an organic polymer, and the molecular weight distribution range of the organic polymer is from 20000 to 2500000. The molecular weight distribution range of the organic polymer satisfies the above characteristics. On the one hand, it can make the carbon black particles have good dispersibility, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + and further reduce the concentration polarization of Li + , thereby further enhancing the kinetic performance of the secondary battery; on the other hand, it can make the substances in the positive electrode material layer and between the positive electrode material layer and the positive electrode current collector have good adhesiveness, and can reduce the expansion of the electrode sheet and the increase amplitude of the contact impedance during the cycling of the secondary battery, and improve the cycling performance of the secondary battery.

[0014] In an embodiment of the present application, the weight-average molecular weight of the organic polymer is Mw, 300000 ≤ Mw ≤ 1500000. By regulating the weight-average molecular weight of the organic polymer within the above range, on the one hand, it can make the carbon black particles have good dispersibility, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + and further reduce the concentration polarization of Li + , thereby further enhancing the kinetic performance of the secondary battery; on the other hand, it can make the substances in the positive electrode material layer and between the positive electrode material layer and the positive electrode current collector have good adhesiveness, and can reduce the expansion of the electrode sheet and the increase amplitude of the contact impedance during the cycling of the secondary battery, and improve the cycling performance of the secondary battery.

[0015] In an embodiment of the present application, the mass ratio of the conductive agent to the organic polymer is 0.5 to 1.0. By adjusting the mass ratio of the conductive agent to the organic polymer within the above range, the conductive agent and the organic polymer have appropriate mass percentages, which is beneficial to Li + transport, and can further improve the kinetic performance of the secondary battery; it can also make the positive electrode material layer and the positive electrode current collector have good adhesion, reduce the expansion of the electrode sheet and the increase amplitude of the contact impedance during the cycling of the secondary battery, and improve the cycling performance of the secondary battery; and can improve the thermal stability of the positive electrode.

[0016] In an embodiment of the present application, the organic polymer includes at least one of polyvinylidene fluoride, polyvinylpyrrolidone, hydrogenated nitrile rubber, copolymer of vinylidene fluoride - hexafluoropropylene, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyamide, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene - butadiene rubber, polypropylene, polyethylene, polyetherimide, copolymer of olefin derivatives or carboxymethyl cellulose salt. Selecting the above organic polymer can make the carbon black particles have good dispersibility, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the Li + distribution area, further reduce the Li + concentration polarization, and further improve the kinetic performance of the secondary battery; it can also make the substances in the positive electrode material layer and between the positive electrode material layer and the positive electrode current collector have good adhesion, reduce the expansion of the electrode sheet and the increase amplitude of the contact impedance during the cycling of the secondary battery, and improve the cycling performance of the secondary battery.

[0017] In an embodiment of the present application, based on the mass of the positive electrode material layer, the mass percentage of the positive electrode active material is W1%, the mass percentage of the conductive agent is W2%, and the mass percentage of the organic polymer is W3%, 95.0 ≤ W1 ≤ 99.0, 0.5 ≤ W2 ≤ 2.0, 0.5 ≤ W3 ≤ 3.0. By adjusting the mass percentages of the positive electrode active material, the conductive agent, and the organic polymer within the above range, while improving the kinetic performance of the secondary battery, the secondary battery also has good high - temperature performance, and can also reduce the internal resistance of the secondary battery.

[0018] In an embodiment of the present application, the conductive agent further includes carbon nanotubes, and the diameter of the carbon nanotubes is d2 nm, 3 ≤ d2 ≤ 15. The conductive agent further includes carbon nanotubes, and by adjusting the diameter of the carbon nanotubes within the above range, while making the positive electrode slurry have good processing performance, it can provide a higher effective conductive area and can further reduce the internal resistance of the secondary battery.

[0019] In an embodiment of the present application, based on the mass of the positive electrode material layer, the mass percentage of the positive electrode active material is W1%, the mass percentage of the carbon black particles is W21%, the mass percentage of the carbon nanotubes is W22%, and the mass percentage of the organic polymer is W3%. 95.0 ≤ W1 ≤ 99.0, 0.3 ≤ W21 ≤ 1.5, 0.2 ≤ W22 ≤ 0.8, 0.5 ≤ W3 ≤ 3.0. By adjusting the mass percentages of the positive electrode active material, carbon black particles, carbon nanotubes, and organic polymer within the above ranges, while further improving the kinetic performance of the secondary battery, the secondary battery also has better high-temperature performance and can further reduce the internal resistance of the secondary battery.

[0020] In an embodiment of the present application, the adhesion force between the positive electrode material layer and the positive electrode current collector is F N / m, 5 ≤ F ≤ 25. By adjusting the adhesion force between the positive electrode material layer and the positive electrode current collector within the above range, the positive electrode material layer and the positive electrode current collector have a high adhesion force, which can reduce the pole piece swelling and the increase in contact impedance during the cycling of the secondary battery and improve the cycling performance of the secondary battery.

[0021] In an embodiment of the present application, the positive electrode active material includes at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium-rich manganese-based material, or lithium titanate. By selecting the above positive electrode active material, the secondary battery has good kinetic performance and good high-temperature performance, and the secondary battery also has a low internal resistance.

[0022] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the foregoing embodiments. Therefore, the electronic device provided by the present application has good kinetic performance and high-temperature performance, and at the same time also has a low internal resistance.

[0023] Advantages of the present application:

[0024] The present application provides a secondary battery and an electronic device. The secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The positive electrode material layer includes a positive electrode active material and a conductive agent. The conductive agent includes carbon black particles, and the coating rate of the carbon black particles on the positive electrode active material particles is C%. 60 ≤ C ≤ 98. By adjusting the type of the conductive agent and the coating rate of the carbon black particles on the positive electrode active material particles within the scope of the present application, while improving the kinetic performance of the secondary battery, the secondary battery also has good high-temperature performance and can reduce the internal resistance of the secondary battery.

[0025] Of course, it is not necessary for any product or method implementing the present application to achieve all the above-mentioned advantages simultaneously. Detailed implementation manners

[0026] Next, in combination with the embodiments of the present application, the technical solutions in the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0027] It should be noted that in the specific embodiments of the present application, a lithium-ion battery is used as an example of a secondary battery to explain the present application. However, the secondary battery of the present application is not limited to lithium-ion batteries.

[0028] The 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 material layer provided on at least one surface of the positive electrode current collector. The positive electrode material layer includes a positive electrode active material and a conductive agent. The conductive agent includes carbon black particles, and the coating rate of the carbon black particles on the positive electrode active material particles is C%, where 60 ≤ C ≤ 98. Exemplarily, the value of C can be 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98 or a range composed of any two of the above values. In the present application, the carbon black particles include at least one of Super P, acetylene black, or Ketjen black. The above "positive electrode material layer provided on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be provided on one surface of the positive electrode current collector along its own thickness direction, or can be provided on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of the positive electrode current collector or a partial area of the positive electrode current collector. The present application has no special limitation as long as the purpose of the present application can be achieved.

[0029] The inventors have found through research that when the positive electrode material layer includes a positive electrode active material and a conductive agent, and the conductive agent includes carbon black particles, there are still certain gaps after the carbon black particles are stacked, which is more conducive to storing the electrolyte. Moreover, after the carbon black particle units are small and evenly distributed on the surface of the positive electrode active material particles, the surface area of the positive electrode active material particles can be cut into smaller and more uniform areas, which is beneficial to reducing the + diffusion paths of Li + and electrons, reducing the + concentration polarization, and improving the kinetic performance of the secondary battery; at the same time, the carbon black particles are thinly coated on the surface of the positive electrode active material particles, and a moderate thickness is beneficial to the + transport of Li +Concentration polarization and extend the migration path of Li when combined with electrons on the surface of the positive electrode active material, resulting in poor kinetic performance of the secondary battery; when the coating rate of carbon black particles on the positive electrode active material particles is too large, for example, greater than 98%, and the exposed surface of the positive electrode active material is too small, it will also lead to poor kinetic performance of the secondary battery. When the coating rate of carbon black particles on the positive electrode active material particles is within the scope of this application, while reducing Li + concentration polarization and improving the kinetic performance of the secondary battery, it reduces the possibility of the surface of the positive electrode active material directly contacting the electrolyte. The secondary battery also has good high-temperature performance and can also reduce the internal resistance of the secondary battery. In this application, high temperature means a temperature greater than or equal to 60 °C. + Concentration polarization, while improving the kinetic performance of the secondary battery, reduces the possibility of the surface of the positive electrode active material directly contacting the electrolyte. The secondary battery also has good high-temperature performance and can also reduce the internal resistance of the secondary battery. In this application, high temperature means a temperature greater than or equal to 60 °C.

[0030] In an embodiment of this application, 80 ≤ C ≤ 95. Exemplarily, the value of C can be 80, 82, 84, 86, 88, 90, 92, 94, 95 or the range composed of any two of the above numerical values. By controlling the coating rate of carbon black particles on the positive electrode active material particles within the above range, while reducing Li + concentration polarization and further improving the kinetic performance of the secondary battery, it reduces the possibility of the surface of the positive electrode active material directly contacting the electrolyte. The secondary battery also has better high-temperature performance and can also further reduce the internal resistance of the secondary battery.

[0031] In an embodiment of this application, the stacking thickness of carbon black particles on the surface of the positive electrode active material particles is H nm, 20 ≤ H ≤ 60. Exemplarily, the value of H can be 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60 or the range composed of any two of the above numerical values. By controlling the stacking thickness of carbon black particles on the surface of the positive electrode active material particles within the above range, the stacking thickness of carbon black particles on the surface of the positive electrode active material particles is appropriate, which is beneficial to Li + transport and can further improve the kinetic performance of the secondary battery.

[0032] In an embodiment of this application, the particle size of the primary particles of carbon black particles is d1 nm, 5 ≤ d1 ≤ 40. Exemplarily, the value of d1 can be 5, 7, 8, 10, 13, 15, 17, 20, 23, 25, 27, 30, 33, 35, 37, 40 or the range composed of any two of the above numerical values. In an embodiment of this application, the particle size of the primary particles of carbon black particles is d1 nm, 10 ≤ d1 ≤ 30. By controlling the particle size of the primary particles of carbon black particles within the above range, the particle size of the primary particles of carbon black particles is small. The small-sized carbon black particles are thinly coated on the surface of the positive electrode active material, and the appropriate thickness is beneficial to Li +Transport can further improve the kinetic performance of the secondary battery.

[0033] In an embodiment of the present application, the particle size Dv50 of the positive electrode material layer particles satisfies: 200d1 ≤ Dv50 ≤ 5000d1. When the particle size Dv50 of the positive electrode material layer particles satisfies the above characteristics, it can not only make the carbon black particles adhere to the surface of the positive electrode active material more closely, but also make there be appropriate gaps between the positive electrode active materials, and the positive electrode active materials are filled more tightly, reducing the possibility of broken bridges between the positive electrode active materials, which is beneficial to the construction of the conductive network and can further improve the kinetic performance of the secondary battery.

[0034] In the present application, Dv50 refers to the particle size that reaches 50% of the cumulative volume when measured from the small particle size in the particle size distribution based on the volume of the material.

[0035] In an embodiment of the present application, 3μm ≤ Dv50 ≤ 30μm. Exemplarily, Dv50 can be 3μm, 5μm, 7μm, 9μm, 10μm, 13μm, 15μm, 17μm, 19μm, 20μm, 23μm, 25μm, 27μm, 29μm, 30μm or a range composed of any two of the above values. By controlling the particle size Dv50 of the positive electrode material layer particles within the above range, it can not only make the positive electrode active material have good kinetic performance, but also make the positive electrode active material have good high-temperature performance, so that the secondary battery has good kinetic performance and high-temperature performance.

[0036] In an embodiment of the present application, the carbon black particles contain oxygen element, and based on the mass of the carbon black particles, the mass percentage content of the oxygen element is W O %, 0.3 ≤ W O ≤ 3. Exemplarily, the value of W O can be 0.3, 0.5, 0.7, 0.9, 1, 1.3, 1.5, 1.7, 1.9, 2, 2.3, 2.5, 2.7, 2.9, 3 or a range composed of any two of the above values. The carbon black particles contain oxygen element, and by controlling the mass percentage content of the oxygen element within the above range, the self-dispersibility of the carbon black particles can be improved, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + , further reduce the Li + concentration polarization, and further improve the kinetic performance of the secondary battery.

[0037] In an embodiment of the present application, the carbon black particles contain hydrogen element, and based on the mass of the carbon black particles, the mass percentage content of the hydrogen element is W H %, 0.1 ≤ W H ≤ 0.5. Exemplarily, the value of W HThe value can be 0.1, 0.15, 0.19, 0.2, 0.25, 0.29, 0.3, 0.35, 0.39, 0.4, 0.45, 0.49, 0.5 or a range composed of any two of the above numerical values. The carbon black particles contain hydrogen elements, and by controlling the mass percentage content of hydrogen elements within the above range, the self-dispersibility of the carbon black particles can be improved, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + and further reduce the Li + concentration polarization, and further improve the kinetic performance of the secondary battery.

[0038] In an embodiment of the present application, the positive electrode material layer further includes an organic polymer, and the molecular weight distribution range of the organic polymer is from 20,000 to 2,500,000. Exemplarily, the molecular weight distribution range of the organic polymer can be 20,000, 100,000, 500,000, 1,000,000, 1,500,000, 2,000,000, 2,500,000 or a range composed of any two of the above numerical values. The above molecular weight distribution range refers to the overall distribution range of the molecular weight of the organic polymer. In the present application, the organic polymer can be used as a binder in the positive electrode material layer. The binder is usually a high molecular polymer, which has both a binding effect and a dispersing effect, that is, it disperses these materials through steric hindrance by attaching to the surface of other materials. Carbon black particles with a high specific surface area are not easy to disperse and require more binder molecules to attach to their surface to disperse them. Under the same content, the smaller the molecular weight of the polymer, the larger the number, and the better the dispersing effect; but binding requires a polymer with a higher molecular weight. Therefore, a polymer with a blended small molecular weight and large molecular weight is selected as the binder. The molecular weight distribution range of the organic polymer satisfies the above characteristics. The molecular weight distribution range of the organic polymer is relatively wide, including small molecular weight and large molecular weight. The small molecular weight and large molecular weight organic polymers are applied to the positive electrode material layer. On the one hand, it can make the carbon black particles have good dispersibility, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + and further reduce the Li + concentration polarization, and further improve the kinetic performance of the secondary battery; on the other hand, it can make the substances in the positive electrode material layer and between the positive electrode material layer and the positive electrode current collector have good adhesion, and can reduce the pole piece swelling and the growth rate of contact impedance during the cycling of the secondary battery, and improve the cycling performance of the secondary battery. In the present application, the small molecular weight organic polymer can refer to an organic polymer with a molecular weight distribution range of 20,000 to 250,000; the large molecular weight organic polymer can refer to an organic polymer with a molecular weight distribution range of 250,000 to 2,500,000.

[0039] In an embodiment of the present application, the weight-average molecular weight of the organic polymer is Mw, and 300,000 ≤ Mw ≤ 1,500,000. Exemplarily, the value of Mw can be 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000, 1,500,000 or a range composed of any two of the above numerical values. The above weight-average molecular weight refers to the statistical average molecular weight by mass. The molecular weight distribution range of the organic polymer will affect the weight-average molecular weight of the organic polymer. By regulating the weight-average molecular weight of the organic polymer within the above range, the molecular weight of the organic polymer includes both small molecular weights and large molecular weights. When the small-molecular-weight and large-molecular-weight organic polymers are applied to the positive electrode material layer, on the one hand, it can make the carbon black particles have good dispersibility, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + and further reduce the concentration polarization of Li + , and further improve the kinetic performance of the secondary battery; on the other hand, it can make the substances in the positive electrode material layer and between the positive electrode material layer and the positive electrode current collector have good adhesion, and can reduce the pole piece swelling and the growth rate of contact impedance during the cycling of the secondary battery, and improve the cycling performance of the secondary battery.

[0040] In an embodiment of the present application, the mass ratio of the conductive agent to the organic polymer is 0.5 to 1.0. Exemplarily, the mass ratio of the conductive agent to the organic polymer can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0 or a range composed of any two of the above numerical values. By regulating the mass ratio of the conductive agent to the organic polymer within the above range, the conductive agent and the organic polymer have appropriate mass percentages, which is beneficial to the transmission of Li + , can further improve the kinetic performance of the secondary battery; can also make the positive electrode material layer and the positive electrode current collector have good adhesion, can reduce the pole piece swelling and the growth rate of contact impedance during the cycling of the secondary battery, and improve the cycling performance of the secondary battery; and can improve the thermal stability of the positive electrode.

[0041] In an embodiment of the present application, the organic polymer includes at least one of polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), hydrogenated nitrile butadiene rubber (HNBR), copolymer of vinylidene fluoride and hexafluoropropylene, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyamide, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber, polypropylene, polyethylene, polyetherimide, copolymer of propylene hydrocarbon derivatives or carboxymethyl cellulose salt. The above carboxymethyl cellulose salt may include but is not limited to at least one of sodium carboxymethyl cellulose, potassium carboxymethyl cellulose or lithium carboxymethyl cellulose. By selecting the above organic polymer, the organic polymer has good dispersion and bonding effects, can make the carbon black particles have good dispersibility, and the carbon black particles are more evenly distributed on the surface of the positive electrode active material particles, which can further increase the distribution area of Li + and further reduce the concentration polarization of Li + , and further improve the kinetic performance of the secondary battery; it can also make the substances in the positive electrode material layer and between the positive electrode material layer and the positive electrode current collector have good adhesiveness, can reduce the pole piece swelling and the growth rate of contact impedance during the cycling of the secondary battery, and improve the cycling performance of the secondary battery.

[0042] In an embodiment of the present application, based on the mass of the positive electrode material layer, the mass percentage content of the positive electrode active material is W1%, the mass percentage content of the conductive agent is W2%, and the mass percentage content of the organic polymer is W3%, where 95.0 ≤ W1 ≤ 99.0, 0.5 ≤ W2 ≤ 2.0, and 0.5 ≤ W3 ≤ 3.0. Exemplarily, the value of W1 can be 95.0, 95.5, 95.9, 96.0, 96.5, 96.9, 97.0, 97.5, 97.9, 98.0, 98.5, 98.9, 99.0 or a range composed of any two of the above values; the value of W2 can be 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, 1.7, 1.9, 2.0 or a range composed of any two of the above values; the value of W3 can be 0.5, 0.7, 0.9, 1.0, 1.5, 1.7, 1.9, 2.0, 2.5, 2.7, 2.9, 3.0 or a range composed of any two of the above values. By adjusting the mass percentage contents of the positive electrode active material, the conductive agent, and the organic polymer within the above ranges, while improving the kinetic performance of the secondary battery, the secondary battery also has good high-temperature performance and can also reduce the internal resistance of the secondary battery.

[0043] In an embodiment of the present application, the conductive agent further includes carbon nanotubes, and the diameter of the carbon nanotubes is d2 nm, where 3 ≤ d2 ≤ 15. Exemplarily, the value of d2 can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range composed of any two of the above numerical values. The above carbon nanotubes include single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The conductive agent further includes carbon nanotubes, and by regulating the diameter of the carbon nanotubes within the above range, while enabling the positive electrode slurry to have good processing performance, it can provide a relatively large effective conductive area and can further reduce the internal resistance of the secondary battery.

[0044] In an embodiment of the present application, based on the mass of the positive electrode material layer, the mass percentage content of the positive electrode active material is W1%, the mass percentage content of the carbon black particles is W21%, the mass percentage content of the carbon nanotubes is W22%, and the mass percentage content of the organic polymer is W3%, where 95.0 ≤ W1 ≤ 99.0, 0.3 ≤ W21 ≤ 1.5, 0.2 ≤ W22 ≤ 0.8, and 0.5 ≤ W3 ≤ 3.0. Exemplarily, the value of W1 can be 95.0, 95.5, 95.9, 96.0, 96.5, 96.9, 97.0, 97.5, 97.9, 98.0, 98.5, 98.9, 99.0, or a range composed of any two of the above numerical values; the value of W21 can be 0.3, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, or a range composed of any two of the above numerical values; the value of W22 can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or a range composed of any two of the above numerical values; the value of W3 can be 0.5, 0.7, 0.9, 1.0, 1.5, 1.7, 1.9, 2.0, 2.5, 2.7, 2.9, 3.0, or a range composed of any two of the above numerical values. By regulating the mass percentage content of the positive electrode active material, carbon black particles, carbon nanotubes, and organic polymer within the above range, while further improving the kinetic performance of the secondary battery, the secondary battery also has better high-temperature performance and can further reduce the internal resistance of the secondary battery.

[0045] In an embodiment of the present application, the adhesion between the positive electrode material layer and the positive electrode current collector is F N / m, where 5 ≤ F ≤ 25. Exemplarily, the value of F can be 5, 7, 9, 10, 11, 13, 15, 17, 19, 20, 21, 23, 25, or a range composed of any two of the above numerical values. By regulating the adhesion between the positive electrode material layer and the positive electrode current collector within the above range, the positive electrode material layer and the positive electrode current collector have relatively high adhesion, which can reduce the pole piece swelling and the growth amplitude of the contact impedance during the cycling of the secondary battery and improve the cycling performance of the secondary battery.

[0046] In one embodiment of the present application, the positive electrode active material includes at least one of lithium cobaltate (LiCoO2), lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium-rich manganese-based material, or lithium titanate. The above-mentioned lithium nickel cobalt manganate may include LiNi 0.95 Co 0.03 Mn 0.02 O2 (Ni95), LiNi 0.91 Co 0.03 Mn 0.06 O2 (Ni91), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523) or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM111). By selecting the above positive electrode active material, the secondary battery has good kinetic performance and good high-temperature performance, and the secondary battery also has a low internal resistance.

[0047] In one embodiment of the present application, when the capacity of the secondary battery is from 3000 mAh to 6000 mAh, the 1s DC resistance (DCR) at 25°C and 20% state of charge (SOC) is from 20 mΩ to 60 mΩ, and the internal resistance growth rate R1 after 800 cycles at 25°C is from 10% to 40%. The DC resistance of the secondary battery and the internal resistance growth rate after 800 cycles are within the above ranges, indicating that the secondary battery has good kinetic performance and a low internal resistance.

[0048] The present application does not particularly limit the preparation method of carbon black particles, as long as the purpose of the present application can be achieved. For example, the preparation method of carbon black particles may include the following steps: selecting acetylene or tar as the raw material; performing a high-temperature pyrolysis reaction on the raw material, the temperature of the high-temperature pyrolysis reaction is from 1000°C to 1500°C, and the time of the high-temperature pyrolysis reaction is from 0.1 s to 3 s to obtain carbon black particles; blowing out, cooling, and collecting the above carbon black particles from the furnace tube to obtain the required carbon black particles. By using the above preparation method, -COOH, -OH, and -CO can be introduced onto the surface of the carbon black particles, which can improve the self-dispersibility of the carbon black particles.

[0049] The present application has no particular limitation on the method for regulating the coating rate of carbon black particles on the positive electrode active material particles, as long as the object of the present application can be achieved. For example, the coating rate of carbon black particles on the positive electrode active material particles can be regulated by regulating the mass percentage content of oxygen element, hydrogen element in the carbon black particles or the mass percentage content of carbon black particles in the positive electrode material layer.

[0050] The present application has no particular limitation on the method for regulating the stacking thickness of carbon black particles on the surface of the positive electrode active material particles, as long as the object of the present application can be achieved. For example, the stacking thickness of carbon black particles on the surface of the positive electrode active material particles can be regulated by regulating the mass percentage content of carbon black particles.

[0051] The present application has no particular limitation on the method for regulating the particle size of the primary particles of carbon black particles, as long as the object of the present application can be achieved. For example, the particle size of the primary particles of carbon black particles can be regulated by regulating the reaction time of the high-temperature cracking reaction. For example, commercially available carbon black particles with different particle sizes of primary particles can be selected.

[0052] The present application has no particular limitation on the method for regulating the particle size Dv50 of the positive electrode material layer particles, as long as the object of the present application can be achieved. For example, the particle size Dv50 of the positive electrode material layer particles can be regulated by regulating the particle size Dv50 of the positive electrode active material and / or the conductive agent.

[0053] The present application has no particular limitation on the method for regulating the mass percentage content of oxygen element, as long as the object of the present application can be achieved. For example, the mass percentage content of oxygen element can be regulated by regulating the content of oxygen element in the synthesis gas introduced during the high-temperature cracking reaction.

[0054] The present application has no particular limitation on the method for regulating the mass percentage content of hydrogen element, as long as the object of the present application can be achieved. For example, the mass percentage content of hydrogen element can be regulated by regulating the content of hydrogen element in the synthesis gas introduced during the high-temperature cracking reaction.

[0055] The present application has no particular limitation on the method for regulating the mass ratio of the conductive agent to the organic polymer, as long as the object of the present application can be achieved. For example, the mass ratio of the conductive agent to the organic polymer can be regulated by regulating the mass of the added conductive agent and / or organic polymer. Exemplarily, when other conditions remain unchanged, increasing the addition amount of the conductive agent increases the mass ratio of the conductive agent to the organic polymer; decreasing the addition amount of the conductive agent decreases the mass ratio of the conductive agent to the organic polymer. Exemplarily, when other conditions remain unchanged, decreasing the addition amount of the organic polymer increases the mass ratio of the conductive agent to the organic polymer; increasing the addition amount of the organic polymer decreases the mass ratio of the conductive agent to the organic polymer.

[0056] The present application has no particular limitation on the method for regulating the mass percentages of the positive electrode active material, the conductive agent, and the organic polymer, as long as the object of the present application can be achieved. For example, the mass percentage of the positive electrode active material can be regulated by regulating the mass of the added positive electrode active material; the mass percentage of the conductive agent can be regulated by regulating the mass of the added conductive agent; the mass percentage of the organic polymer can be regulated by regulating the mass of the added organic polymer.

[0057] The present application has no particular limitation on the method for regulating the diameter of the carbon nanotubes, as long as the object of the present application can be achieved. For example, the diameter of the carbon nanotubes can be regulated by regulating the synthesis temperature of the carbon nanotubes. For example, commercially available carbon nanotubes with different diameters can be selected.

[0058] The present application has no particular limitation on the method for regulating the adhesion between the positive electrode material layer and the positive electrode current collector, as long as the object of the present application can be achieved. For example, the adhesion between the positive electrode material layer and the positive electrode current collector can be regulated by regulating the mass percentage of the organic polymer in the positive electrode material layer.

[0059] The present application has no particular limitation on the positive electrode current collector, as long as the object of the present application can be achieved. For example, it can include aluminum foil, aluminum alloy foil, or a composite current collector (such as an aluminum-carbon composite current collector), etc.

[0060] The present application has no particular limitation on the thickness of the positive electrode current collector, as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 6 μm to 16 μm. The present application has no particular limitation on the thickness of the positive electrode material layer, as long as the object of the present application can be achieved. For example, the thickness of the single-sided positive electrode material layer is 25 μm to 250 μm.

[0061] Optionally, the positive electrode tab can further include a conductive layer, and the conductive layer is located between the positive electrode current collector and the positive electrode material layer. The present application has no particular limitation on the composition of the conductive layer, and it can be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular limitation on the conductive agent and the binder in the conductive layer, and it can be at least one of the above-mentioned conductive agents and the above-mentioned organic polymers. The present application has no particular limitation on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art can select according to actual needs as long as the object of the present application can be achieved.

[0062] In the present application, the secondary battery further includes a negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The above "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or can be disposed on both surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of the negative electrode current collector or a partial area of the negative electrode current collector. There is no special limitation in the present application, as long as the purpose of the present application can be achieved. There is no special limitation on the negative electrode current collector in the present application, as long as the purpose of the present application can be achieved. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector, etc.

[0063] The negative electrode material layer of the present application includes a negative electrode active material. There is no special limitation on the negative electrode active material in the present application, as long as the purpose of the present application can be achieved. For example, the negative electrode active material can include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5 < x < 1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12 , Li-Al alloy or metallic lithium, etc. The negative electrode material layer of the present application further includes a negative electrode binder and a negative electrode conductive agent. There is no special limitation on the negative electrode binder and the negative electrode conductive agent in the negative electrode material layer of the present application, as long as the purpose of the present application can be achieved. For example, the negative electrode binder can be at least one of the above organic polymers, and the negative electrode conductive agent can be at least one of the above conductive agents. There is no special limitation on the mass ratio of the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent in the negative electrode material layer in the present application, and those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0064] There is no special limitation on the thickness of the negative electrode current collector in the present application, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm. There is no special limitation on the thickness of the negative electrode material layer in the present application, as long as the purpose of the present application can be achieved. For example, the thickness of the single-sided negative electrode material layer is 30 μm to 250 μm.

[0065] Optionally, the negative electrode sheet may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular limitation on the composition of the conductive layer, and it may be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular limitation on the conductive agent and the binder in the conductive layer, and they may be at least one of the above-mentioned negative electrode conductive agents and the above-mentioned negative electrode binders. The present application has no particular limitation on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved.

[0066] In the present application, the secondary battery further includes an electrolyte. The electrolyte includes a lithium salt and a non-aqueous solvent. The lithium salt may include various lithium salts commonly used in the art, such as at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. The present application has no particular limitation on the non-aqueous solvent, as long as the object of the present application can be achieved. For example, it may include but is not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds, or other organic solvents. The above carbonate compounds may include but are not limited to at least one of linear carbonate compounds, cyclic carbonate compounds, or fluorinated carbonate compounds. The above linear carbonate compounds may include but are not limited to at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or ethyl methyl carbonate (EMC). The above cyclic carbonate compounds may include but are not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylene ethylene carbonate (VEC). The above fluorinated carbonate compounds may include but are not limited to at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethyl ethylene carbonate. The above carboxylate compounds may include but are not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, or caprolactone. The above ether compounds may include but are not limited to at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The above other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The present application has no particular limitation on the mass percentage content of the lithium salt and the non-aqueous solvent, as long as the object of the present application can be achieved.

[0067] In the present application, the secondary battery further includes a separator. The separator is used to separate the positive electrode sheet and the negative electrode sheet, prevent internal short circuit of the secondary battery, allow electrolyte ions to pass through freely, and does not affect the progress of the electrochemical charge and discharge process. There is no particular limitation on the separator in the present application, as long as the object of the present application can be achieved. For example, the material of the separator may include, but is not limited to, at least one of polyolefins (PO) mainly composed of polyethylene (PE) and polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of the separator may include at least one of a woven film, a non-woven film, a microporous film, a composite film, a rolled film or a spun film.

[0068] In the present application, the separator may include a base film and a surface treatment layer. The base film may be a non-woven fabric or a composite film having a porous structure, and the material of the base film may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the base film, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a separator binder, and there is no particular limitation on the above-mentioned inorganic particles in the present application. For example, it may include at least one of alumina, silica, magnesia, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. There is no particular limitation on the above-mentioned separator binder in the present application. For example, it may be at least one of the aforementioned negative electrode binders. The polymer layer contains a first polymer, and the material of the first polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0069] The secondary battery of the present application further includes a packaging bag for accommodating the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte, as well as other components known in the art in the secondary battery, and the present application does not limit the above-mentioned other components. There is no particular limitation on the packaging bag in the present application, and it may be a packaging bag well-known in the art, as long as the object of the present application can be achieved.

[0070] There is no particular limitation on the type of the secondary battery in the present application, and it may include any device that generates an electrochemical reaction. In the present application, the secondary battery may include, but is not limited to: lithium metal secondary battery, lithium ion secondary battery (lithium ion battery), lithium polymer secondary battery or lithium ion polymer secondary battery, etc.

[0071] The preparation process of the secondary battery of the present application is well-known to those skilled in the art, and the present application has no special limitations. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and performing operations such as winding and folding as needed to obtain a wound structure electrode assembly, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag and sealing it to obtain a secondary battery; or, stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and then fixing the four corners of the entire laminated structure with tape to obtain a laminated structure electrode assembly, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, an overcurrent protection element, a guide plate, etc. may be placed in the packaging bag as needed to prevent the pressure inside the secondary battery from rising and overcharge / discharge. Among them, the packaging bag is a known packaging bag in the art, and the present application does not limit this.

[0072] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the foregoing embodiments. Therefore, the electronic device provided by the present application has good kinetic performance and high-temperature performance, and also has a low internal resistance.

[0073] The present application does not particularly limit the type of the electronic device, and it can be any electronic device known in the prior art. In some embodiments, the electronic device may include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal TV, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a moped, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, a large household battery, and a lithium-ion capacitor, etc.

[0074] Examples

[0075] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0076] Testing methods and equipment:

[0077] Test on the coating rate of carbon black particles on the positive electrode active material particles:

[0078] (1) Disassemble the lithium-ion battery to obtain the positive electrode sheet; (2) Immerse the above positive electrode sheet in dimethyl carbonate (DMC) at room temperature for 30 minutes, take it out, and then dry it; (3) Take the positive electrode sheet obtained in step (2), obtain the cross-section of the positive electrode material layer on the positive electrode sheet by brittle fracture with liquid nitrogen, and observe the surface of the positive electrode active material particles in the above cross-section through a scanning electron microscope (SEM, model: Thermo Fisher FEI-ApreoS) at a magnification of 10,000 times. The area covered by carbon black particles is S1, and the area not covered by carbon black particles is S2. Then the coating rate C (%) of carbon black particles on the positive electrode active material particles = S1 / (S1 + S2)×100%, where the sum of S1 + S2 is at least 2 mm 2 。

[0079] Measurement of the stacking thickness of carbon black particles on the surface of positive electrode active material particles:

[0080] (1) Under the condition of 25±2°C, discharge the lithium-ion battery at a constant current of 0.5C to 3.0V, let it stand for 5 minutes, and then disassemble it to obtain the positive electrode sheet; (2) Immerse the above positive electrode sheet in DMC at 65±5°C for 30 minutes, take it out, and then dry it; (3) Take the positive electrode sheet obtained in step (2), obtain the cross-section of the positive electrode material layer on the positive electrode sheet by plasma cutting, and observe and measure the stacking thickness of carbon black particles on the surface of the positive electrode active material particles through SEM at a magnification of 10,000 times. Test 40 different positions, and take the average value of all test values as the final result.

[0081] Measurement of the particle size of the primary particles of carbon black particles:

[0082] (1) Disassemble the lithium-ion battery to obtain the positive electrode sheet; (2) Immerse the above positive electrode sheet in DMC at room temperature for 30 minutes, take it out, and then dry it; (3) Take the positive electrode sheet obtained in step (2), corrode it with concentrated sulfuric acid, filter to obtain the conductive agent, dry it, and then test the particle size of the primary particles of carbon black particles under a transmission electron microscope (TEM) at a magnification of 80,000 times. Test the particle size of the primary particles of 50 carbon black particles, and take the average value of all test values as the final result.

[0083] Measurement of the particle size Dv50 of the particles in the positive electrode material layer:

[0084] (1) Disassemble the lithium-ion battery to obtain the positive electrode plate; (2) Immerse the above positive electrode plate in N-methylpyrrolidone (NMP) at 45 ± 5 °C until the positive electrode material layer film peels off from the positive electrode current collector, then remove the positive electrode current collector, dissolve the positive electrode material layer film in NMP, and use a disperser to disperse evenly to obtain the positive electrode material layer slurry; (3) Use a Malvern particle size tester (model MasterSizer 2000) to test the above positive electrode material layer slurry to obtain the particle size Dv50 of the positive electrode material layer particles.

[0085] Test for mass percentage content of elements:

[0086] Use a German Elementar elemental analyzer to test the types of elements in the carbon black particles and the mass percentage content of the elements in the carbon black particles.

[0087] Test for weight-average molecular weight and molecular weight distribution range:

[0088] (1) Disassemble the lithium-ion battery to obtain the positive electrode plate; (2) Take the above positive electrode plate and immerse it in the solvent NMP to remove the film, dissolve the positive electrode material layer film in the solvent, and use a disperser to disperse evenly to obtain the slurry; (3) Take the above slurry, use the centrifugation method to separate the binder in the slurry, and use gel permeation chromatography (GPC) to determine the weight-average molecular weight and molecular weight distribution range of the binder. The model of the gel chromatography instrument used is PL-GPC220.

[0089] Test for the diameter of carbon nanotubes:

[0090] (1) Disassemble the lithium-ion battery to obtain the positive electrode plate; (2) Immerse the above positive electrode plate in DMC at room temperature for 60 min, take it out, and dry it at room temperature; (3) Take the positive electrode plate obtained in step (2) and use liquid nitrogen embrittlement to obtain the cross-section of the positive electrode material layer on the positive electrode plate; (4) Observe the above cross-section through SEM, test the diameters of no less than 30 carbon nanotubes in 10 regions, and take the average value as the diameter of the carbon nanotubes.

[0091] Adhesion test:

[0092] (1) Disassemble the lithium-ion battery to obtain the positive electrode sheet; (2) Immerse the above positive electrode sheet in DMC at 25 ± 5 °C for 30 min, and then dry it; (3) Take the positive electrode sheet obtained in step (2), and use a high-speed tensile testing machine (model: GT-7010-EP) and the 90° angle method to test the adhesion between the positive electrode material layer and the positive electrode current collector, that is: make the part of the positive electrode sheet coated with the positive electrode material layer into a strip (size: 80 mm × 20 mm), and adhesively attach a part of the positive electrode sheet to the steel plate from one end of the positive electrode sheet along the length direction through double-sided tape; then fix the steel plate at the corresponding position of the high-speed tensile testing machine, lift the positive electrode sheet that is not adhered to the steel plate, directly put the positive electrode sheet into the chuck and clamp it. When the clamping force is greater than 0 kgf and less than 0.02 kgf, the high-speed tensile testing machine can be used to perform the test at a speed of 5 mm / min. Finally, the average value of the tensile force in the stable region is recorded as the adhesion between the positive electrode material layer and the positive electrode current collector. It is required that the ratio of the standard deviation to the average value of the adhesion data in this stable region does not exceed 10%.

[0093] 1s DC internal resistance (DCR) test:

[0094] Take the lithium-ion battery in the example or comparative example and perform the following tests at 25 ± 2 °C: (1) Stand still for 2 h; (2) Then charge at a constant current of 1.0C to 4.50 V, and charge at a constant voltage of 4.50 V until the current is less than or equal to 0.025C; stand still for 2 h; (3) Then discharge at a constant current of 0.2C to 3.0 V, and take the discharge capacity of this step as C1, and stand still for 5 h; (4) Then charge at a constant current of 1.0C1 to 4.50 V, and charge at a constant voltage of 4.50 V until the current is less than or equal to 0.025C1; stand still for 10 min; (5) Then discharge at a constant current of 0.1C1 until the capacity is 0.2C1, stand still for 15 min, record the voltage at this time as V0, and then discharge at a constant current of 1.0C1 for 1 s, and record the voltage at this time as V1. Then the 1s DCR at 25 °C and 20% SOC is (V0 - V1) / 1.0C1.

[0095] Internal resistance growth rate test after 800 cycles at 25 °C:

[0096] Take the lithium-ion battery in the example or comparative example and perform the following tests at 25 ± 2 °C:

[0097] (1) Stand still for 2 h, discharge at a constant current of 0.7C to 3.0 V, and stand still for 5 min;

[0098] (2) Charge at a constant current of 1.0C to 4.50V, then charge at a constant voltage of 4.50V until the current is less than or equal to 0.05C; let it stand for 5 min; then discharge at a constant current of 0.5C to 3.0V, and test the internal resistance of the lithium-ion battery at this time with a sine current of 1000Hz and record it as IMP1; let it stand for 5 min; cycle 49 times according to the above steps, and record the internal resistances of the lithium-ion battery as IMP1, IMP2, ……, IMP49 in sequence; then perform the 50th cycle. In the 50th cycle, charge at a constant current of 1.0C to 4.50V, then charge at a constant voltage of 4.50V until the current is less than or equal to 0.05C; let it stand for 5 min; then discharge at a constant current of 0.2C to 3.0V, and record the internal resistance of the lithium-ion battery at this time as IMP50;

[0099] (3) Then cycle the above step (2) 16 times, and then charge at a constant current of 1.0C to 4.50V, then charge at a constant voltage of 4.50V until the current is less than or equal to 0.05C; let it stand for 5 min; then discharge at a constant current of 0.5C to 3.0V, and record the internal resistance of the lithium-ion battery in the 801st cycle as IMP801; then the internal resistance growth rate R1(%) of the lithium-ion battery after 800 cycles at 25℃ = IMP801 / IMP1 - 100%.

[0100] High-temperature performance test:

[0101] In an environment of 25±3℃, charge the lithium-ion battery at a constant current of 0.5C to 4.50V, and then charge at a constant voltage of 4.50V until the current is less than or equal to 0.025C, and test the initial thickness of the lithium-ion battery and record it as T1. Then put the lithium-ion battery into a high-temperature furnace at 85±3℃ and store it for 8h, and then in-situ test the thickness of the lithium-ion battery and record it as T2. Then the high-temperature storage thickness expansion rate T(%) of the lithium-ion battery = (T2 - T1) / T1 × 100%.

[0102] In this application, the high-temperature performance of the lithium-ion battery is characterized by the high-temperature storage thickness expansion rate of the lithium-ion battery. The smaller the high-temperature storage thickness expansion rate of the lithium-ion battery, the better the high-temperature performance of the lithium-ion battery.

[0103] Example 1-1

[0104] <Preparation of the positive electrode sheet>

[0105] The cathode active material lithium cobalt oxide (LiCoO₂), the conductive agent carbon black particles, the conductive agent carbon nanotubes, and the organic polymer polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.6:0.4:0.5:1.5, and then NMP is added as a solvent and stirred and mixed evenly to obtain a cathode slurry, where the solid content of the cathode slurry is 70 wt%; the particle size Dv50 of the cathode active material is 17 μm; the carbon black particles are acetylene black, and the carbon nanotubes are multi-walled carbon nanotubes. The cathode slurry is evenly coated on one surface of a cathode current collector aluminum foil with a thickness of 12 μm and dried at 120 °C for 1 h to obtain a cathode plate with a cathode material layer with a thickness of 100 μm coated on one side. The above steps are repeated on the other surface of the aluminum foil to obtain a cathode plate with a cathode material layer coated on both sides. It is dried under vacuum conditions at 120 °C for 1 h, and then after cold pressing, slicing, and slitting, a cathode plate with a specification of 74 mm × 867 mm is obtained. Among them, the compaction density in the cold pressing process is 4.2 g / cm 3 .

[0106] <Preparation of the negative electrode plate>

[0107] The anode active material artificial graphite, the anode binder sodium carboxymethyl cellulose (CMC-Na), and the anode binder styrene-butadiene rubber (SBR) are mixed in a weight ratio of 95:2:3, and then deionized water is added as a solvent and stirred and mixed evenly to obtain an anode slurry, where the solid content of the anode slurry is 75 wt%; the anode slurry is evenly coated on one surface of a negative current collector copper foil with a thickness of 12 μm and dried at 120 °C to obtain a negative electrode plate with a negative electrode material layer with a thickness of 120 μm coated on one side. The above steps are repeated on the other surface of the copper foil to obtain a negative electrode plate with a negative electrode material layer coated on both sides. It is dried under vacuum conditions at 120 °C for 1 h, and then after cold pressing, slicing, and slitting, a negative electrode plate with a specification of 78 mm × 875 mm is obtained. Among them, the compaction density in the cold pressing process is 1.75 g / cm 3 .

[0108] <Preparation of the electrolyte>

[0109] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed in a weight ratio of 1:1:1 to obtain a basic solvent, and then lithium hexafluorophosphate (LiPF₆) is added and mixed evenly to obtain an electrolyte. Based on the mass of the electrolyte, the mass percentage content of the lithium salt is 12.5%, and the balance is the basic solvent.

[0110] <Preparation of the separator>

[0111] A polyethylene (PE) film with a thickness of 15 μm is used.

[0112] <Preparation of Lithium-Ion Batteries>

[0113] Stack the above-prepared positive electrode sheet, separator, negative electrode sheet, and separator in sequence, with the separator placed in the middle of the positive electrode sheet and the negative electrode sheet to play an isolation role, and wind them to obtain an electrode assembly. After welding the electrode tabs, place the electrode assembly in an aluminum-plastic film packaging bag, inject the electrolyte after drying, and obtain the lithium-ion battery through processes such as vacuum packaging, standing, formation, degassing, and trimming.

[0114] Examples 1-2 to Examples 1-5

[0115] Except that the particle size of the primary particles of carbon black particles is as shown in Table 1 by controlling the reaction time of the high-temperature pyrolysis reaction, the rest is the same as in Example 1-1.

[0116] Examples 1-6 to Examples 1-9

[0117] Except that the mass percentage contents of oxygen element and hydrogen element are as shown in Table 1 by controlling the contents of oxygen element and hydrogen element in the synthetic gas introduced during the high-temperature pyrolysis reaction process, the rest is the same as in Example 1-3.

[0118] Examples 1-10 to Examples 1-11

[0119] Except that the diameter of the carbon nanotubes is as shown in Table 1 by controlling the synthesis temperature of the carbon nanotubes, the rest is the same as in Example 1-3.

[0120] Example 1-12

[0121] Except that the particle size Dv50 of the positive electrode active material is adjusted to 5 μm and the relevant preparation parameters are adjusted according to Table 1, the rest is the same as in Example 1-3.

[0122] Example 1-13

[0123] Except that the particle size Dv50 of the positive electrode active material is adjusted to 24 μm, the rest is the same as in Example 1-3.

[0124] Example 1-14

[0125] Except that the particle size Dv50 of the positive electrode active material is adjusted to 35 μm, the rest is the same as in Example 1-3.

[0126] Examples 1-15 to Examples 1-21

[0127] Except that the relevant preparation parameters are adjusted according to Table 1, the rest is the same as in Example 1-3.

[0128] Examples 2-1 to Examples 2-8

[0129] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as in Examples 1-3.

[0130] Comparative Examples 1-1 to 1-2

[0131] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0132] Comparative Example 1-3

[0133] Except for mixing the cathode active material lithium cobalt oxide (LiCoO₂), conductive agent graphene, conductive agent carbon nanotubes, and organic polymer polyvinylidene fluoride (PVDF) in a weight ratio of 97.6:0.4:0.5:1.5 in the <Preparation of Cathode Plate>, adding NMP as a solvent, and stirring and mixing evenly to obtain the cathode slurry, the rest is the same as in Example 1-1.

[0134] Comparative Example 1-4

[0135] Except for mixing the cathode active material lithium cobalt oxide (LiCoO₂), conductive agent carbon nanotubes, and organic polymer polyvinylidene fluoride (PVDF) in a weight ratio of 97.6:0.9:1.5 in the <Preparation of Cathode Plate>, adding NMP as a solvent, and stirring and mixing evenly to obtain the cathode slurry, the rest is the same as in Example 1-1.

[0136] Comparative Examples 2-1 to 2-2

[0137] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as in Examples 1-3.

[0138] The preparation parameters and electrical performance parameters of each example and comparative example are shown in Tables 1 to 2.

[0139] Table 1

[0140]

[0141]

[0142] Note: (1) In Table 1, " / " indicates no relevant preparation parameters; (2) In Table 1, taking Example 1-1 as an example, the "molecular weight distribution range of the organic polymer" is "5W~150W", indicating that the molecular weight distribution range of the organic polymer is from 50,000 to 1,500,000, and the same applies to other examples.

[0143] It can be seen from Examples 1-1 to 1-21 and Comparative Examples 1-1 to 1-4 that when the type of conductive agent and the coating rate of carbon black particles on the cathode active material particles are within the scope of the present application, the prepared lithium-ion battery has a lower 1sDCR at 25°C and 20% SOC, the internal resistance growth rate after 800 cycles at 25°C, and the thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has good kinetic performance, a lower internal resistance, and good high-temperature performance. In Comparative Examples 1-1 to 1-2, the coating rate of carbon black particles on the cathode active material particles is not within the scope of the present application, and the prepared lithium-ion battery has a higher 1sDCR at 25°C and 20% SOC, the internal resistance growth rate after 800 cycles at 25°C, and the thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has poor kinetic performance, a higher internal resistance, and poor high-temperature performance. In Comparative Examples 1-3 to 1-4, the type of conductive agent is not within the scope of the present application, and the prepared lithium-ion battery has a higher 1sDCR at 25°C and 20% SOC, the internal resistance growth rate after 800 cycles at 25°C, and the thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has poor kinetic performance, a higher internal resistance, and poor high-temperature performance.

[0144] The particle size of the primary particles of carbon black particles usually affects the kinetic performance of lithium-ion batteries. It can be seen from Examples 1-1 to 1-5 that by controlling the particle size of the primary particles of carbon black particles within the scope of the present application, the prepared lithium-ion battery has a lower 1sDCR at 25°C and 20% SOC, the internal resistance growth rate after 800 cycles at 25°C, and the thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has good kinetic performance, a lower internal resistance, and good high-temperature performance.

[0145] The mass percentage contents of oxygen element and hydrogen element usually affect the kinetic performance of lithium-ion batteries. It can be seen from Example 1-3 and Examples 1-6 to 1-9 that by controlling the mass percentage contents of oxygen element and hydrogen element within the scope of the present application, the prepared lithium-ion battery has a lower 1sDCR at 25°C and 20% SOC, the internal resistance growth rate after 800 cycles at 25°C, and the thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has good kinetic performance, a lower internal resistance, and good high-temperature performance.

[0146] The diameter of carbon nanotubes generally affects the internal resistance of lithium-ion batteries. It can be seen from Examples 1-3, Examples 1-10 to Examples 1-11 that by regulating the diameter of carbon nanotubes within the scope of this application, the prepared lithium-ion batteries have a lower 1sDCR at 25°C and 20% SOC, the internal resistance growth rate after 800 cycles at 25°C, and the thickness expansion rate during high-temperature storage, indicating that the internal resistance of lithium-ion batteries can be reduced. At the same time, the lithium-ion batteries also have good kinetic performance and high-temperature performance. In Examples 1-3, Examples 1-10 to Examples 1-11, as the diameter of carbon nanotubes increases, it is beneficial to improve the dispersibility of carbon nanotubes and carbon black particles, and the coating rate of carbon black particles on the positive active material particles increases. In addition, as the diameter of carbon nanotubes increases, the specific surface area of carbon nanotubes decreases, the amount of binder consumed decreases, and the adhesion between the positive electrode material layer and the positive electrode current collector increases.

[0147] The particle size Dv50 of the positive electrode material layer particles generally affects the kinetic performance and high-temperature performance of lithium-ion batteries. It can be seen from Examples 1-3, Examples 1-12 to Examples 1-14 that by regulating the particle size Dv50 of the positive electrode material layer particles within the scope of this application, the prepared lithium-ion batteries have a lower 1sDCR at 25°C and 20% SOC, the internal resistance growth rate after 800 cycles at 25°C, and the thickness expansion rate during high-temperature storage, indicating that the lithium-ion batteries have good kinetic performance, low internal resistance, and good high-temperature performance. In Example 1-12, the particle size Dv50 of the positive electrode material layer particles is small, the dispersibility of the positive electrode material layer particles is relatively poor, the coating rate of carbon black particles on the positive active material particles is small, and the stacking thickness of carbon black particles on the surface of the positive active material particles is large. In Examples 1-3, Examples 1-13, and Examples 1-14, as the particle size Dv50 of the positive electrode material layer particles increases, the specific surface area of the positive electrode material layer particles decreases, the mass percentage content of carbon black particles remains unchanged, the coating rate of carbon black particles on the positive active material particles increases, and the stacking thickness of carbon black particles on the surface of the positive active material particles increases.

[0148] The molecular weight distribution range and weight-average molecular weight of the organic polymer generally affect the kinetic performance and cycling performance of lithium-ion batteries. It can be seen from Examples 1-3, Examples 1-15 to Examples 1-21 that by regulating the molecular weight distribution range and weight-average molecular weight of the organic polymer within the scope of this application, the prepared lithium-ion batteries have a lower 1sDCR at 25°C and 20% SOC, the internal resistance growth rate after 800 cycles at 25°C, and the thickness expansion rate during high-temperature storage, indicating that the lithium-ion batteries have good kinetic performance, low internal resistance, and good high-temperature performance.

[0149] Table 2

[0150]

[0151]

[0152] Note: (1) In Table 2, taking Examples 1-3 as an example, the type of the positive electrode active material is "LCO", which means the positive electrode active material is lithium cobalt oxide (LiCoO2), and the same applies to other examples.

[0153] It can be seen from Examples 2-1 to 2-8 and Comparative Examples 2-1 to 2-2 that when the type of the conductive agent and the coating rate of the carbon black particles on the positive electrode active material particles are within the scope of the present application, the prepared lithium-ion battery has a lower 1sDCR at 25°C and 20% SOC, an internal resistance growth rate after 800 cycles at 25°C, and a thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has good kinetic performance, a lower internal resistance, and good high-temperature performance. In Comparative Examples 2-1 to 2-2, the coating rate of the carbon black particles on the positive electrode active material particles is not within the scope of the present application, and the prepared lithium-ion battery has a higher 1sDCR at 25°C and 20% SOC, an internal resistance growth rate after 800 cycles at 25°C, and a thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has poor kinetic performance, a higher internal resistance, and poor high-temperature performance.

[0154] The mass percentage contents of the positive electrode active material, carbon black particles, carbon nanotubes, and organic polymer usually affect the kinetic performance, high-temperature performance, and internal resistance of the lithium-ion battery. It can be seen from Examples 1-3 and Examples 2-1 to 2-5 that by adjusting the mass percentage contents of the positive electrode active material, carbon black particles, carbon nanotubes, and organic polymer within the scope of the present application, the prepared lithium-ion battery has a lower 1sDCR at 25°C and 20% SOC, an internal resistance growth rate after 800 cycles at 25°C, and a thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has good kinetic performance, a lower internal resistance, and good high-temperature performance.

[0155] The type of the organic polymer usually affects the kinetic performance and cycle performance of the lithium-ion battery. It can be seen from Examples 1-3 and Example 2-6 that by adjusting the type of the organic polymer within the scope of the present application, the prepared lithium-ion battery has a lower 1sDCR at 25°C and 20% SOC, an internal resistance growth rate after 800 cycles at 25°C, and a thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has good kinetic performance, a lower internal resistance, and good high-temperature performance.

[0156] The types of the positive electrode active materials generally affect the kinetic performance, high-temperature performance and internal resistance of the lithium-ion battery. It can be seen from Examples 1-3, Examples 2-7 to Examples 2-8 that by regulating the types of the positive electrode active materials within the scope of the present application, the prepared lithium-ion battery has a lower 1sDCR at 25°C and 20% SOC, an internal resistance growth rate after 800 cycles at 25°C, and a thickness expansion rate during high-temperature storage, indicating that the lithium-ion battery has good kinetic performance, low internal resistance and good high-temperature performance.

[0157] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method or article.

[0158] Each embodiment in this specification is described in a related manner. For the same or similar parts among the embodiments, reference can be made to each other. The key points of each embodiment are the differences from other embodiments.

[0159] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of protection of the present application.

Claims

1. A secondary battery, which includes a positive electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The positive electrode material layer includes a positive electrode active material and a conductive agent. The conductive agent includes carbon black particles, and the coating rate of the carbon black particles on the positive electrode active material particles is C%, where 60 ≤ C ≤ 98.

2. The secondary battery according to claim 1, wherein, 80≤C≤95。 3. The secondary battery according to claim 1, wherein, The stacking thickness of the carbon black particles on the surface of the positive electrode active material particles is H nm, where 20 ≤ H ≤ 60.

4. The secondary battery according to claim 1, wherein, The particle size of the primary particles of the carbon black particles is d1 nm, where 5 ≤ d1 ≤ 40.

5. The secondary battery according to claim 4, wherein The particle size of the primary particles of the carbon black particles is d1 nm, where 10 ≤ d1 ≤ 30.

6. The secondary battery according to claim 4, wherein, The particle size Dv50 of the positive electrode material layer particles satisfies: 200d1 ≤ Dv50 ≤ 5000d1.

7. The secondary battery according to claim 6, wherein, 3μm ≤ Dv50 ≤ 30μm.

8. The secondary battery according to claim 1, wherein, The carbon black particles include oxygen. Based on the mass of the carbon black particles, the mass percentage of the oxygen element is W O %, 0.3≤W O ≤3.

9. The secondary battery according to claim 1, wherein The carbon black particles include hydrogen element, and based on the mass of the carbon black particles, the mass percentage of the hydrogen element is W H %, 0.1 ≤ W H ≤ 0.

5.

10. The secondary battery according to claim 1, wherein, The positive electrode material layer further includes an organic polymer, and the molecular weight distribution range of the organic polymer is from 20,000 to 2,500,000.

11. The secondary battery according to claim 10, which satisfies at least one of the following characteristics: (1) The weight-average molecular weight of the organic polymer is Mw, where 300,000 ≤ Mw ≤ 1,500,000; (2) The mass ratio of the conductive agent to the organic polymer is from 0.5 to 1.0; (3) The organic polymer includes at least one of polyvinylidene fluoride, polyvinylpyrrolidone, hydrogenated nitrile rubber, copolymer of vinylidene fluoride - hexafluoropropylene, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyamide, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene - butadiene rubber, polypropylene, polyethylene, polyetherimide, copolymer of olefin derivatives or carboxymethyl cellulose salt; (4) Based on the mass of the positive electrode material layer, the mass percentage content of the positive electrode active material is W1%, the mass percentage content of the conductive agent is W2%, and the mass percentage content of the organic polymer is W3%, where 95.0 ≤ W1 ≤ 99.0, 0.5 ≤ W2 ≤ 2.0, 0.5 ≤ W3 ≤ 3.

0.

12. The secondary battery according to claim 10, wherein, The conductive agent further includes carbon nanotubes, and the diameter of the carbon nanotubes is d2 nm, where 3 ≤ d2 ≤ 15.

13. The secondary battery according to claim 12, wherein, Based on the mass of the positive electrode material layer, the mass percentage content of the positive electrode active material is W1%, the mass percentage content of the carbon black particles is W21%, the mass percentage content of the carbon nanotubes is W22%, and the mass percentage content of the organic polymer is W3%, where 95.0 ≤ W1 ≤ 99.0, 0.3 ≤ W21 ≤ 1.5, 0.2 ≤ W22 ≤ 0.8, 0.5 ≤ W3 ≤ 3.

0.

14. The secondary battery according to claim 1, wherein The adhesion force between the positive electrode material layer and the positive electrode current collector is F N / m, where 5 ≤ F ≤ 25.

15. The secondary battery according to claim 1, wherein, The positive electrode active material includes at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium - rich manganese - based material or lithium titanate.

16. An electronic device, which includes the secondary battery according to any one of claims 1 to 15.

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