Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device, the secondary battery comprises a positive pole piece and a negative pole piece, the positive pole piece comprises a positive pole material layer, the positive pole material layer comprises a positive pole active material, and the positive pole active material comprises a manganese-containing material; the manganese-containing material comprises at least one of lithium manganate, lithium iron manganese phosphate, a lithium-rich manganese-based material or nickel cobalt lithium manganate. The negative pole piece comprises a first additive, the first additive comprises at least one of carboxylate, sulfonate or a metal organic framework compound, carboxylate comprises at least one of lithium oxalate, sodium citrate, sodium maleate or sodium tartrate, sulfonate comprises at least one of sodium benzenesulfonate, sodium dodecyl benzene sulfonate or sodium methanesulfonate, and metal organic framework compound comprises at least one of lithium oxalate, sodium citrate, sodium maleate or sodium tartrate. The metal organic framework compound is prepared from at least one of Zn (C4H7N2) 2, C48H28O32Zr6 or C14H16N2O8Mg2. The invention further discloses a preparation method of the metal organic framework compound. The secondary battery meets the characteristics, and the cycle performance of the secondary battery can be improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical technologies, and particularly to a secondary battery and an electronic device. Background Art

[0002] Manganese-containing materials (such as lithium manganate, lithium iron manganese phosphate, etc.) are widely used in lithium-ion batteries. Taking lithium manganate as an example, after the service life of the lithium-ion battery ends, the Mn ions deposited on the negative electrode material layer are as high as 3000 ppm, and the Mn ions are deposited on the surface of the negative electrode active material particles, that is, on the SEI film. The deposition of Mn ions will cause problems such as increased impedance, capacity loss, and gas generation of the lithium-ion battery.

[0003] To alleviate the damage of Mn ions to the negative electrode material layer, the commonly used technical method is to optimize the positive electrode material to reduce Mn dissolution. However, due to the physical properties of the positive electrode material itself, it is difficult to completely solve the problem. Adsorbing Mn ions with a separator coating is also another solution, but it requires the development of a special separator, and the process is complex and the cost is high. Therefore, there is an urgent need to provide a lithium-ion battery that can reduce the damage of Mn ions to the negative electrode material layer and improve the cycle performance of the lithium-ion battery. Summary of the Invention

[0004] The purpose of this application is to provide a secondary battery and an electronic device that can reduce the damage of Mn ions to the negative electrode material layer and improve the cycle performance of the secondary battery. The specific technical solutions are as follows:

[0005] In the first aspect of this application, a secondary battery is provided, which includes a positive electrode tab and a negative electrode tab. The positive electrode tab 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 the positive electrode active material includes a manganese-containing material. The manganese-containing material includes at least one of lithium manganate, lithium iron manganese phosphate, lithium-rich manganese-based material, or nickel cobalt manganeseate. The negative electrode tab includes a first additive, and the first additive includes at least one of carboxylate, sulfonate, or metal-organic framework compound. The carboxylate includes at least one of lithium oxalate, sodium citrate, sodium maleate, or sodium tartrate. The sulfonate includes at least one of sodium benzenesulfonate, sodium dodecylbenzenesulfonate, or sodium methylsulfonate. The metal-organic framework compound includes Zn(C4H7N2)2, C 48 H 28 O 32 Zr6 or C 14 H 16At least one of N2O8Mg2. In a secondary battery, when the positive electrode active material of the positive electrode material layer includes a manganese-containing material and the above-mentioned first additive is used in the negative electrode sheet, the first additive can be used as a negative electrode Mn ion adsorption additive. The first additive can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, so as to fix Mn ions and reduce the damage of Mn ions to the negative electrode material layer, and can improve the cycle performance of the secondary battery.

[0006] In one or more embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes a first additive. Based on the mass of the negative electrode material layer, the mass percentage content of the first additive is W1%, and 0.2 ≤ W1 ≤ 2. By adjusting the negative electrode material layer to include the first additive and the value of W1 within the above range, the first additive in the negative electrode material layer has an appropriate mass percentage content. The first additive can adsorb more Mn ions dissolved from the positive electrode and form chemical bonds with free Mn ions, so as to fix Mn ions and further reduce the damage of Mn ions to the negative electrode material layer, and can further improve the cycle performance of the secondary battery.

[0007] In one or more embodiments of the present application, in the infrared spectrum of the negative electrode material layer, there is a first characteristic peak in the range of 2500 cm -1 to 3300 cm -1 , 1650 cm -1 to 1740 cm -1 , 1000 cm -1 to 1400 cm -1 ; and / or, there is a second characteristic peak in the range of 1090 cm -1 to 1290 cm -1 , 968 cm -1 to 1168 cm -1 , 520 cm -1 to 720 cm -1 , 430 cm -1 to 630 cm -1 ; and / or, there is a third characteristic peak in the range of 500 cm -1 to 600 cm -1 , 1000 cm -1 to 1400 cm -1 , 1600 cm -1 to 1700 cm -1 , 2800 cm -1 to 3000 cm -1 , 3200 cm -1 to 3600 cm -1There is a third characteristic peak within the range. The infrared spectrum of the negative electrode material layer satisfies the above characteristics and can improve the cycling performance of the secondary battery.

[0008] In one or more embodiments of the present application, the negative electrode tab includes a negative electrode current collector, a negative electrode material layer, and a first coating layer. The negative electrode material layer is disposed between the negative electrode current collector and the first coating layer. The first coating layer includes a first additive. Based on the mass of the first coating layer, the mass percentage content of the first additive is W2%, and 84 ≤ W2 ≤ 98. The negative electrode tab further includes a first coating layer. The first coating layer includes a first additive and the value of W2 is adjusted within the above range. The first coating layer serves as an Mn ion adsorption layer. The first additive in the first coating layer has a suitable mass percentage content. The first additive can adsorb more Mn ions dissolved from the positive electrode and form chemical bonds with free Mn ions, so as to achieve the purpose of fixing Mn ions and further reducing the damage of Mn ions to the negative electrode material layer, and can further improve the cycling performance of the secondary battery.

[0009] In one or more embodiments of the present application, the surface of the negative electrode material layer away from the negative electrode current collector includes a plurality of coating regions and non-coating regions. Each coating region is provided with a first coating layer. The plurality of coating regions are spaced apart along the length direction after the negative electrode tab is unfolded and extend along the width direction after the negative electrode tab is unfolded. Along the length direction after the negative electrode tab is unfolded, the distance between two adjacent coating regions is D1 mm, and 1 ≤ D1 ≤ 10. The first coating layer is arranged in a stripe shape on the surface of the negative electrode material layer, and the distance between two adjacent coating regions is adjusted within the above range, which can effectively increase the exposed area of the negative electrode material, improve the wetting performance of the negative electrode tab of the secondary battery, and further improve the cycling performance of the secondary battery.

[0010] In one or more embodiments of the present application, the surface of the negative electrode material layer away from the negative electrode current collector includes a plurality of coating regions and non-coating regions. Each coating region is provided with a first coating layer. The plurality of coating regions are distributed in a grid pattern. The first coating layer is arranged in a grid shape on the surface of the negative electrode material layer. While having a large area, it can also improve the wetting ability of each position of the negative electrode tab, improve the wetting performance of the negative electrode tab of the secondary battery; at the same time, the first additive in the first coating layer can adsorb more Mn ions dissolved from the positive electrode and form chemical bonds with free Mn ions, achieving the purpose of fixing Mn ions and further reducing the damage of Mn ions to the negative electrode material layer, and further improving the cycling performance of the secondary battery.

[0011] In one or more embodiments of the present application, the thickness of the first coating is H μm, where 1 ≤ H ≤ 10. By regulating the thickness of the first coating within the above range, the weight content per unit area of the first additive in the first coating is appropriate. The first additive can adsorb more Mn ions dissolved from the positive electrode, further reducing the damage of Mn ions to the negative electrode material layer, and can further improve the cycling performance of the secondary battery. At the same time, the secondary battery also has a high energy density.

[0012] In one or more embodiments of the present application, the porosity of the first coating is P%, where 10 ≤ P ≤ 40. By regulating the porosity of the first coating within the above range, the first coating has an appropriate porosity. The first additive can adsorb the Mn ions dissolved from the positive electrode faster through the pores and form chemical bonds with the free Mn ions, so as to achieve the purpose of fixing the Mn ions and further reducing the damage of Mn ions to the negative electrode material layer, and can further improve the cycling performance of the secondary battery.

[0013] In one or more embodiments of the present application, in the infrared spectrum of the first coating, a fourth characteristic peak exists in the range of 2500 cm -1 to 3300 cm -1 、1650 cm -1 to 1740 cm -1 、1000 cm -1 to 1400 cm -1 ; and / or, a fifth characteristic peak exists in the range of 1090 cm -1 to 1290 cm -1 、968 cm -1 to 1168 cm -1 、520 cm -1 to 720 cm -1 、430 cm -1 to 630 cm -1 ; and / or, a sixth characteristic peak exists in the range of 500 cm -1 to 600 cm -1 、1000 cm -1 to 1400 cm -1 、1600 cm -1 to 1700 cm -1 、2800 cm -1 to 3000 cm -1 、3200 cm -1 to 3600 cm -1 . The infrared spectrum of the first coating satisfies the above characteristics, which can improve the cycling performance of the secondary battery.

[0014] In one or more embodiments of the present application, the first coating further includes a binder and a dispersant. The binder includes at least one of polymethyl methacrylate, styrene-butadiene rubber, or polyacrylic acid. The dispersant includes at least one of carboxymethyl cellulose, polyvinylpyrrolidone, hydroxypropyl methylcellulose, or polyethylene glycol. Based on the mass of the first coating, the mass percentage of the binder is W3%, and the mass percentage of the dispersant is W4%, where 1 ≤ W3 ≤ 10 and 1 ≤ W4 ≤ 6. By controlling the types and mass percentages of the binder and the dispersant in the first coating within the above ranges, the first additive can be better dispersed, which is beneficial to preparing a relatively stable first coating slurry and is beneficial to the coating of the first coating.

[0015] A 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 cycling performance.

[0016] Advantages of the present application:

[0017] The present application provides a secondary battery and an electronic device. The secondary battery includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive current collector and a positive electrode material layer provided on at least one surface of the positive current collector. The positive electrode material layer includes a positive electrode active material. The positive electrode active material includes a manganese-containing material. The manganese-containing material includes at least one of lithium manganate, lithium iron phosphate manganese, lithium-rich manganese-based material, or lithium nickel cobalt manganese oxide. The negative electrode plate includes a first additive. The first additive includes at least one of carboxylate, sulfonate, or metal-organic framework compound. The carboxylate includes at least one of lithium oxalate, sodium citrate, sodium maleate, or sodium tartrate. The sulfonate includes at least one of sodium benzenesulfonate, sodium dodecylbenzenesulfonate, or sodium methylsulfonate. The metal-organic framework compound includes at least one of Zn(C4H7N2)2, C 48 H 28 O 32 Zr6 or C 14 H 16 N2O8Mg2. When the secondary battery meets the above characteristics, it can reduce the damage of Mn ions to the negative electrode material layer and improve the cycling performance of the secondary battery.

[0018] Of course, it is not necessary for any product or method implementing the present application to simultaneously achieve all the above-mentioned advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other embodiments can also be obtained based on these drawings.

[0020] Figure 1 Schematic diagram of the structure of the negative electrode sheet along the thickness direction of an embodiment of the present application;

[0021] Figure 2 Schematic diagram of the structure of the first coating along the length and width directions of an embodiment of the present application;

[0022] Figure 3 Schematic diagram of the structure of the first coating along the length and width directions of another embodiment of the present application;

[0023] Figure 4 Schematic diagram of the structure of the first coating along the length and width directions of yet another embodiment of the present application;

[0024] Figure 5 Infrared spectrum diagram of the negative electrode material layer of Examples 1-2 of the present application;

[0025] Figure 6 Infrared spectrum diagram of the first coating of Example 2-1 of the present application. Detailed implementation manners

[0026] Next, the technical solutions in the present application will be clearly and completely described in conjunction with the embodiments and drawings of the present application. 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 implementation manners of the present application, lithium-ion batteries are taken as examples of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries.

[0028] Manganese-containing materials (such as lithium manganate, lithium iron manganese phosphate, etc.) are widely used in lithium-ion batteries and have the advantages of low cost and high platform voltage. However, the dissolution of Mn ions, passing through the separator and depositing on the surface of the negative electrode material layer, will damage the solid electrolyte interface (SEI) film. Taking lithium manganate as an example, after the service life of the lithium-ion battery ends, the Mn deposited on the negative electrode material layer is as high as 3000 ppm, and the Mn ions are deposited on the surface of the negative electrode active material particles, that is, on the SEI film. The deposition of Mn ions will cause problems such as increased impedance, capacity loss, and gas generation of the lithium-ion battery.

[0029] A first aspect of the present application provides a secondary battery, which includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet 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, the positive electrode active material includes a manganese-containing material, and the manganese-containing material includes at least one of lithium manganate, lithium iron manganese phosphate, lithium-rich manganese-based material, or lithium nickel cobalt manganate. The above 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 0.6 Co 0.1 Mn 0.3 O2 (NCM613), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523) or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM111). 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 may be provided on one surface of the positive electrode current collector along its own thickness direction, or may be provided on both surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here may 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. The present application has no special limitation on the mass percentage content of the positive electrode active material in the positive electrode material layer as long as the purpose of the present application can be achieved. For example, based on the mass of the positive electrode material layer, the mass percentage content of the positive electrode active material is 90% to 97%.

[0030] The negative electrode sheet includes a first additive, and the first additive includes at least one of carboxylate, sulfonate, or metal-organic framework compound (MOF). The carboxylate includes at least one of lithium oxalate, sodium citrate, sodium maleate, or sodium tartrate. The sulfonate includes at least one of sodium benzenesulfonate, sodium dodecylbenzenesulfonate, or sodium methylsulfonate. The metal-organic framework compound includes Zn(C4H7N2)2 (ZIF-8), C 48 H 28 O 32 Zr6 (UiO-66) or C14 H 16 At least one of N2O8Mg2(MOF-74(Mg)).

[0031] The inventors' research found that in a secondary battery, when the positive electrode active material of the positive electrode material layer includes a manganese-containing material, and the above-mentioned first additive is used in the negative electrode sheet, the first additive can be used as a negative electrode Mn ion adsorption additive. The first additive can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, so as to achieve the purpose of fixing Mn ions and reducing the damage of Mn ions to the negative electrode material layer, and can improve the cycle performance of the secondary battery.

[0032] In one or more embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes a first additive. Based on the mass of the negative electrode material layer, the mass percentage content of the first additive is W1%, and 0.2 ≤ W1 ≤ 2. Exemplarily, the value of W1 can be 0.2, 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.4, 1.5, 1.6, 1.8, 2, or a range composed of any two of the above numerical values. The above-mentioned "negative electrode material layer provided on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be provided on one surface of the negative electrode current collector along its own thickness direction, or can be provided on two surfaces of the negative electrode current collector along its own 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. By adjusting the negative electrode material layer to include the first additive and the value of W1 within the above range, the first additive in the negative electrode material layer has an appropriate mass percentage content. The first additive can adsorb more Mn ions dissolved from the positive electrode and form chemical bonds with free Mn ions, so as to achieve the purpose of fixing Mn ions and further reducing the damage of Mn ions to the negative electrode material layer, and can further improve the cycle performance of the secondary battery.

[0033] The present application has no special limitation on the negative electrode current collector, 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 (such as lithium-copper composite current collector, carbon-copper composite current collector, nickel-copper composite current collector, titanium-copper composite current collector, etc.).

[0034] In one or more embodiments of the present application, the negative electrode material layer includes a first additive, and the negative electrode material layer further includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The present application places no particular limitation on the negative electrode active material, as long as the object of the present application can be achieved. For example, the negative electrode active material may include at least one of 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, lithium titanate with a spinel structure Li4Ti5O 12 , Li-Al alloy, or metallic lithium, etc. The present application places no particular limitation on the type of the negative electrode binder, as long as the object of the present application can be achieved. For example, the negative electrode binder may include, but is not limited to, at least one of polyvinylidene fluoride (PVDF), copolymer of vinylidene fluoride and hexafluoropropylene, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyamide, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber (SBR), 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. The present application places no particular limitation on the type of the negative electrode conductive agent, as long as the object of the present application can be achieved. For example, the negative electrode conductive agent may include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fiber, flake graphite, graphene, metal material, or conductive polymer. The above conductive carbon black may include, but is not limited to, at least one of Super P, acetylene black, or Ketjen black. The above carbon nanotubes may include, but is not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above carbon fiber may include, but is not limited to, vapor-grown carbon fiber (VGCF) and / or nanofiber. The above metal material may include, but is not limited to, metal powder and / or metal fiber. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The above conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The present application places no particular limitation on the mass percentage contents of the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent in the negative electrode material 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. [[ID=~]]

[0035] The present application places no particular limitation on the thickness of the negative electrode current collector, as long as the object of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 20 μm. The present application places no particular limitation on the thickness of the negative electrode material layer, as long as the object 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.

[0036] In one or more embodiments of the present application, in the infrared spectrum of the negative electrode material layer, at 2500 cm -1 to 3300cm -1 、1650cm -1 to 1740cm -1 , 1000cm -1 to 1400cm -1 The presence of a first characteristic peak within the range. The infrared spectrum of the negative electrode material layer meets the aforementioned characteristics, indicating that the negative electrode material layer includes the aforementioned carboxylate. Simultaneously, the positive electrode active material of the secondary battery's positive electrode material layer includes a manganese-containing material. The carboxylate can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, thereby reducing damage to the negative electrode material layer caused by Mn ions and improving the cycle performance of the secondary battery.

[0037] In one or more embodiments of the present application, in the infrared spectrum of the negative electrode material layer, at 1090 cm -1 to 1290cm -1 、968cm -1 to 1168cm -1 , 520cm -1 Up to 720cm -1 、430cm -1 Up to 630cm -1 The presence of a second characteristic peak within the range. The infrared spectrum of the negative electrode material layer meets the aforementioned characteristics, indicating that the negative electrode material layer includes the aforementioned sulfonate. Simultaneously, the positive electrode active material of the secondary battery's positive electrode material layer includes a manganese-containing material. The sulfonate preferentially adsorbs Mn ions and forms chemical bonds with free Mn ions, thereby reducing damage to the negative electrode material layer caused by Mn ions and improving the cycle performance of the secondary battery.

[0038] In one or more embodiments of the present application, in the infrared spectrum of the negative electrode material layer, at 500 cm -1 Up to 600cm -1 , 1000cm -1 to 1400cm -1 , 1600cm -1 to 1700cm -1 , 2800cm -1 Up to 3000cm -1 3200cm -1 to 3600cm -1There is a third characteristic peak within the range. The infrared spectrum of the negative electrode material layer satisfies the above characteristics, indicating that the negative electrode material layer includes the above metal-organic framework compound. At the same time, the positive electrode active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The metal-organic framework compound can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can reduce the damage of Mn ions to the negative electrode material layer and improve the cycling performance of the secondary battery.

[0039] In one or more embodiments of the present application, in the infrared spectrum of the negative electrode material layer, there is a first characteristic peak in the range of 2500 cm -1 to 3300 cm -1 , 1650 cm -1 to 1740 cm -1 , 1000 cm -1 to 1400 cm -1 ; and, there is a second characteristic peak in the range of 1090 cm -1 to 1290 cm -1 , 968 cm -1 to 1168 cm -1 , 520 cm -1 to 720 cm -1 , 430 cm -1 to 630 cm -1 The infrared spectrum of the negative electrode material layer satisfies the above characteristics, indicating that the negative electrode material layer includes the above carboxylate and sulfonate. At the same time, the positive electrode active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The carboxylate and sulfonate can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can further reduce the damage of Mn ions to the negative electrode material layer and further improve the cycling performance of the secondary battery.

[0040] In one or more embodiments of the present application, in the infrared spectrum of the negative electrode material layer, there is a first characteristic peak in the range of 2500 cm -1 to 3300 cm -1 , 1650 cm -1 to 1740 cm -1 , 1000 cm -1 to 1400 cm -1 ; and, there is a second characteristic peak in the range of 500 cm -1 to 600 cm -1 , 1000 cm -1 to 1400 cm -1 , 1600 cm -1 to 1700 cm -1 , 2800 cm -1 to 3000 cm -1 , 3200 cm -1To 3600 cm -1 There is a third characteristic peak within the range. The infrared spectrum of the negative electrode material layer satisfies the above characteristics, indicating that the negative electrode material layer includes the above carboxylate salt and metal-organic framework compound. At the same time, the positive active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The carboxylate salt and metal-organic framework compound can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can further reduce the damage of Mn ions to the negative electrode material layer and further improve the cycle performance of the secondary battery.

[0041] In one or more embodiments of the present application, in the infrared spectrum of the negative electrode material layer, there is a second characteristic peak in the range of 1090 cm -1 to 1290 cm -1 、968 cm -1 to 1168 cm -1 、520 cm -1 to 720 cm -1 、430 cm -1 to 630 cm -1 ; and, there is a third characteristic peak in the range of 500 cm -1 to 600 cm -1 、1000 cm -1 to 1400 cm -1 、1600 cm -1 to 1700 cm -1 、2800 cm -1 to 3000 cm -1 、3200 cm -1 to 3600 cm -1 There is a third characteristic peak within the range. The infrared spectrum of the negative electrode material layer satisfies the above characteristics, indicating that the negative electrode material layer includes the above sulfonate salt and metal-organic framework compound. At the same time, the positive active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The sulfonate salt and metal-organic framework compound can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can further reduce the damage of Mn ions to the negative electrode material layer and further improve the cycle performance of the secondary battery.

[0042] In one or more embodiments of the present application, in the infrared spectrum of the negative electrode material layer, there is a first characteristic peak in the range of 2500 cm -1 to 3300 cm -1 、1650 cm -1 to 1740 cm -1 、1000 cm -1 to 1400 cm -1 ; and, there is a second characteristic peak in the range of 1090 cm -1 to 1290 cm -1 、968 cm -1from 0 to 1168 cm -1 and 520 cm -1 from 520 to 720 cm -1 and 430 cm -1 from 430 to 630 cm -1 There is a second characteristic peak in the range; and, at 500 cm -1 from 500 to 600 cm -1 and 1000 cm -1 from 1000 to 1400 cm -1 and 1600 cm -1 from 1600 to 1700 cm -1 and 2800 cm -1 from 2800 to 3000 cm -1 and 3200 cm -1 from 3200 to 3600 cm -1 There is a third characteristic peak in the range. The infrared spectrogram of the negative electrode material layer satisfies the above characteristics, indicating that the negative electrode material layer includes the above carboxylates, sulfonates and metal-organic framework compounds. At the same time, the positive electrode active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The carboxylates, sulfonates and metal-organic framework compounds can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can further reduce the damage of Mn ions to the negative electrode material layer and further improve the cycle performance of the secondary battery.

[0043] In one or more embodiments of the present application, as Figure 1 shown, the negative electrode tab 10 includes a negative electrode current collector 101, a negative electrode material layer 102 and a first coating layer 103. The negative electrode material layer 102 is disposed between the negative electrode current collector 101 and the first coating layer 103. The first coating layer is disposed on the entire surface of the negative electrode material layer away from the negative electrode current collector. For the convenience of understanding, a two-dimensional rectangular coordinate system is established with the length direction after the negative electrode tab is unfolded as the X direction and the width direction after the negative electrode tab is unfolded as the Y direction. As Figure 2As shown, a first coating is provided on the entire surface of the negative electrode material layer away from the negative electrode current collector, and the first coating is a continuous coating. The first coating includes a first additive, and based on the mass of the first coating, the mass percentage content of the first additive is W2%, where 84 ≤ W2 ≤ 98. Exemplarily, the value of W2 can be 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98 or a range composed of any two of the above values. The negative electrode plate also includes a first coating, the first coating includes a first additive and the value of W2 is adjusted within the above range. The first coating serves as a Mn ion adsorption layer, and the first additive in the first coating has an appropriate mass percentage content. The first additive can adsorb more Mn ions dissolved from the positive electrode and form chemical bonds with free Mn ions, thereby achieving the purpose of fixing Mn ions and further reducing the damage of Mn ions to the negative electrode material layer, and can further improve the cycling performance of the secondary battery.

[0044] In one or more embodiments of the present application, as Figure 3 shown, the surface of the negative electrode material layer away from the negative electrode current collector (not shown in the figure) includes a plurality of coating regions 110 and non-coating regions 111. Each coating region 110 is provided with a first coating. The plurality of coating regions are arranged at intervals along the length direction (i.e., the X direction) after the negative electrode plate is unfolded and extend along the width direction (i.e., the Y direction) after the negative electrode plate is unfolded. Along the length direction after the negative electrode plate is unfolded, the distance between two adjacent coating regions 110 is D1 mm, where 1 ≤ D1 ≤ 10. Exemplarily, the value of D1 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a range composed of any two of the above values. The first coating is provided on the surface of the negative electrode material layer in a stripe shape, and by adjusting the distance between two adjacent coating regions within the above range, the exposed area of the negative electrode material can be effectively increased, the wetting performance of the negative electrode plate of the secondary battery can be improved, and the cycling performance of the secondary battery can be further improved. It can be understood that the size of a single coating region along the X direction is the length of a single coating region, and the size of a single coating region along the Y direction is the width of a single coating region; the size of a single non-coating region along the Y direction is the width of a single non-coating region. In the present application, the length of a single coating region can be 3 mm to 50 mm; the width of a single coating region can be the width after the negative electrode plate is unfolded; the width of a single non-coating region can be the width after the negative electrode plate is unfolded. The present application does not particularly limit the width after the negative electrode plate is unfolded, as long as the purpose of the present application can be achieved.

[0045] In one or more embodiments of the present application, as Figure 4As shown, the surface of the negative electrode material layer away from the negative electrode current collector (not shown in the figure) includes a plurality of coating regions 110 and non-coating regions 111. Each coating region 110 is provided with a first coating, and the plurality of coating regions 110 are distributed in a grid pattern. The first coating is arranged in a grid pattern on the surface of the negative electrode material layer. While enabling the first coating to have a relatively large area, it can also improve the wetting ability of each position of the negative electrode plate, thereby improving the wetting performance of the negative electrode plate of the secondary battery. At the same time, the first additive in the first coating can adsorb more Mn ions dissolved from the positive electrode and form chemical bonds with the free Mn ions, achieving the purpose of fixing the Mn ions and further reducing the damage of the Mn ions to the negative electrode material layer, and further improving the cycle performance of the secondary battery. In the present application, the plurality of coating regions are distributed in a grid pattern. Along the length direction of the negative electrode plate after unfolding, the distance between two adjacent coating regions can be 1 mm to 50 mm, and the length of a single coating region can be 1 mm to 10 mm. Along the width direction of the negative electrode plate after unfolding, the distance between two adjacent coating regions can be 1 mm to 10 mm, and the width of a single coating region can be 1 mm to 10 mm.

[0046] In one or more embodiments of the present application, the thickness of the first coating is H μm, where 1 ≤ H ≤ 10. Exemplarily, the value of H can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or a range composed of any two of the above values. By adjusting the thickness of the first coating within the above range, the weight content per unit area of the first additive in the first coating is relatively appropriate. The first additive can adsorb more Mn ions dissolved from the positive electrode, further reducing the damage of the Mn ions to the negative electrode material layer, and further improving the cycle performance of the secondary battery. At the same time, the secondary battery also has a relatively high energy density.

[0047] In one or more embodiments of the present application, the porosity of the first coating is P%, where 10 ≤ P ≤ 40. Exemplarily, the value of P can be 10, 13, 15, 16, 19, 20, 23, 25, 26, 29, 30, 33, 35, 36, 39, 40, or a range composed of any two of the above values. By adjusting the porosity of the first coating within the above range, the first coating has an appropriate porosity. The first additive can adsorb the Mn ions dissolved from the positive electrode faster through the pores and form chemical bonds with the free Mn ions, thereby achieving the purpose of fixing the Mn ions and further reducing the damage of the Mn ions to the negative electrode material layer, and further improving the cycle performance of the secondary battery.

[0048] In one or more embodiments of the present application, in the infrared spectrum of the first coating, at 2500 cm -1 to 3300 cm -1 、1650 cm -1 to 1740 cm -1 、1000 cm-1 to 1400 cm -1 There is a fourth characteristic peak within the range. The infrared spectrum of the first coating satisfies the above characteristics, indicating that the first coating includes the above carboxylate salt. At the same time, the positive electrode active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The carboxylate salt can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can reduce the damage of Mn ions to the negative electrode material layer and improve the cycle performance of the secondary battery.

[0049] In one or more embodiments of the present application, in the infrared spectrum of the first coating, at 1090 cm -1 to 1290 cm -1 and 968 cm -1 to 1168 cm -1 and 520 cm -1 to 720 cm -1 and 430 cm -1 to 630 cm -1 There is a fifth characteristic peak within the range. The infrared spectrum of the first coating satisfies the above characteristics, indicating that the first coating includes the above sulfonate salt. At the same time, the positive electrode active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The sulfonate salt can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can reduce the damage of Mn ions to the negative electrode material layer and improve the cycle performance of the secondary battery.

[0050] In one or more embodiments of the present application, in the infrared spectrum of the first coating, at 500 cm -1 to 600 cm -1 and 1000 cm -1 to 1400 cm -1 and 1600 cm -1 to 1700 cm -1 and 2800 cm -1 to 3000 cm -1 and 3200 cm -1 to 3600 cm -1 There is a sixth characteristic peak within the range. The infrared spectrum of the first coating satisfies the above characteristics, indicating that the first coating includes the above metal-organic framework compound. At the same time, the positive electrode active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The metal-organic framework compound can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can reduce the damage of Mn ions to the negative electrode material layer and improve the cycle performance of the secondary battery.

[0051] In one or more embodiments of the present application, in the infrared spectrum of the first coating, at 2500 cm -1 to 3300 cm -1 and 1650 cm -1From 1740 cm -1 to 1000 cm -1 to 1400 cm -1 There is a fourth characteristic peak in the range; and, at 1090 cm -1 to 1290 cm -1 、968 cm -1 to 1168 cm -1 、520 cm -1 to 720 cm -1 、430 cm -1 to 630 cm -1 There is a fifth characteristic peak in the range. The infrared spectrogram of the first coating satisfies the above characteristics, indicating that the first coating includes the above carboxylate and sulfonate. At the same time, the positive active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The carboxylate and sulfonate can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can further reduce the damage of Mn ions to the negative electrode material layer and further improve the cycle performance of the secondary battery.

[0052] In one or more embodiments of the present application, in the infrared spectrogram of the first coating, in the range of 2500 cm -1 to 3300 cm -1 、1650 cm -1 to 1740 cm -1 、1000 cm -1 to 1400 cm -1 There is a fourth characteristic peak in the range; and, at 500 cm -1 to 600 cm -1 、1000 cm -1 to 1400 cm -1 、1600 cm -1 to 1700 cm -1 、2800 cm -1 to 3000 cm -1 、3200 cm -1 to 3600 cm -1 There is a sixth characteristic peak in the range. The infrared spectrogram of the first coating satisfies the above characteristics, indicating that the first coating includes the above carboxylate and metal-organic framework compound. At the same time, the positive active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The carboxylate and metal-organic framework compound can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can further reduce the damage of Mn ions to the negative electrode material layer and further improve the cycle performance of the secondary battery.

[0053] In one or more embodiments of the present application, in the infrared spectrogram of the first coating, at 1090 cm -1 to 1290 cm -1, 968 cm -1 to 1168 cm -1 , 520 cm -1 to 720 cm -1 , 430 cm -1 to 630 cm -1 There is a fifth characteristic peak in the range; and, at 500 cm -1 to 600 cm -1 , 1000 cm -1 to 1400 cm -1 , 1600 cm -1 to 1700 cm -1 , 2800 cm -1 to 3000 cm -1 , 3200 cm -1 to 3600 cm -1 There is a sixth characteristic peak in the range. The infrared spectrum of the first coating satisfies the above characteristics, indicating that the first coating includes the above sulfonate and metal-organic framework compound. At the same time, the positive electrode active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The sulfonate and metal-organic framework compound can preferentially adsorb Mn ions and form chemical bonds with free Mn ions, which can further reduce the damage of Mn ions to the negative electrode material layer and further improve the cycle performance of the secondary battery.

[0054] In one or more embodiments of the present application, in the infrared spectrum of the first coating, there is a fourth characteristic peak in the range of 2500 cm -1 to 3300 cm -1 , 1650 cm -1 to 1740 cm -1 , 1000 cm -1 to 1400 cm -1 There is a fourth characteristic peak in the range; and, at 1090 cm -1 to 1290 cm -1 , 968 cm -1 to 1168 cm -1 , 520 cm -1 [[ID=)]]to 720 cm -1 , 430 cm -1 to 630 cm -1 There is a fifth characteristic peak in the range; and, at 500 cm -1 to 600 cm -1 , 1000 cm -1 to 1400 cm -1 , 1600 cm -1 to 1700 cm -1 , 2800 cm -1 to 3000 cm -1 , 3200 cm-1 from 3600 cm -1 There is a sixth characteristic peak within the range. The infrared spectrogram of the first coating satisfies the above characteristics, indicating that the first coating includes the above carboxylates, sulfonates, and metal-organic framework compounds. At the same time, the positive electrode active material of the positive electrode material layer of the secondary battery includes a manganese-containing material. The carboxylates, sulfonates, and metal-organic framework compounds can preferentially adsorb Mn ions and form chemical bonds with the free Mn ions, which can further reduce the damage of Mn ions to the negative electrode material layer and further improve the cycling performance of the secondary battery.

[0055] In one or more embodiments of the present application, the first coating further includes a binder and a dispersant. The binder includes at least one of polymethyl methacrylate (PMMA), styrene-butadiene rubber, or polyacrylic acid. The dispersant includes at least one of carboxymethyl cellulose (CMC), polyvinylpyrrolidone, hydroxypropyl methylcellulose, or polyethylene glycol. Based on the mass of the first coating, the mass percentage content of the binder is W3%, and the mass percentage content of the dispersant is W4%, where 1 ≤ W3 ≤ 10 and 1 ≤ W4 ≤ 6. Exemplarily, the value of W3 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or a range composed of any two of the above numerical values; the value of W4 can be 1, 1.5, 1.7, 2, 2.5, 2.7, 3, 3.5, 3.7, 4, 4.5, 4.7, 5, 5.5, 5.7, 6, or a range composed of any two of the above numerical values. By regulating the types and mass percentage contents of the binder and the dispersant in the first coating within the above ranges, the first additive can be better dispersed, which is beneficial to preparing a relatively stable first coating slurry and is beneficial to the coating of the first coating.

[0056] In one or more embodiments of the present application, the negative electrode material layer includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The present application does not particularly limit the negative electrode active material, as long as the object of the present application can be achieved. For example, it can include at least one of the above negative electrode active materials. The present application does not particularly limit the type of the negative electrode binder, as long as the object of the present application can be achieved. For example, it can include at least one of the above negative electrode binders. The present application does not particularly limit the type of the negative electrode conductive agent, as long as the object of the present application can be achieved. For example, it can include at least one of the above negative electrode conductive agents. The present application does not particularly limit the mass percentage contents of the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent in the negative electrode material layer. Those skilled in the art can select according to actual needs as long as the object of the present application can be achieved.

[0057] The present application has no particular limitation on the method for regulating the mass percentage of the first additive in the negative electrode material layer, as long as the object of the present application can be achieved. For example, the mass percentage of the first additive in the negative electrode material layer can be regulated by regulating the mass of the first additive added when preparing the negative electrode slurry.

[0058] The present application has no particular limitation on the method for regulating the mass percentage of the first additive in the first coating layer, as long as the object of the present application can be achieved. For example, the mass percentage of the first additive in the first coating layer can be regulated by regulating the mass of the first additive added when preparing the first coating slurry.

[0059] The present application has no particular limitation on the method for regulating the thickness of the first coating layer, as long as the object of the present application can be achieved. For example, the thickness of the first coating layer can be regulated by regulating the coating weight of the first coating layer.

[0060] The present application has no particular limitation on the method for regulating the porosity of the first coating layer, as long as the object of the present application can be achieved. For example, when other conditions remain unchanged, the porosity of the first coating layer can be regulated by regulating the mass ratio of the first additive, the binder, and the dispersant.

[0061] The present application has no particular limitation on the method for regulating the mass percentage of the binder and the dispersant, as long as the object of the present application can be achieved. For example, the mass percentage of the binder can be regulated by regulating the mass of the added binder; the mass percentage of the dispersant can be regulated by regulating the mass of the added dispersant.

[0062] 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.

[0063] The positive electrode material layer of the present application further includes a positive electrode binder. The present application has no particular limitation on the positive electrode binder, as long as the object of the present application can be achieved. For example, the positive electrode binder can include at least one of the above-mentioned negative electrode binders. The positive electrode material layer of the present application further includes a positive electrode conductive agent. The present application has no particular limitation on the positive electrode conductive agent, as long as the object of the present application can be achieved. For example, the positive electrode conductive agent can include at least one of the above-mentioned negative electrode conductive agents. The present application has no particular limitation on the mass percentage of the positive electrode binder and the positive electrode conductive agent in the positive electrode material 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.

[0064] The present application does not particularly limit 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 does not particularly limit 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.

[0065] 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. There is no particular limitation on the non-aqueous solvent in the present application, 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. There is no particular limitation on the mass percentage content of the lithium salt and the non-aqueous solvent in the present application, as long as the object of the present application can be achieved.

[0066] 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 (e.g., 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.

[0067] 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 an adhesive layer or an inorganic layer, or may be a functional coating formed by mixing a first additive, a separator binder and inorganic particles. For example, the inorganic layer includes inorganic particles and a separator binder. 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. The adhesive layer includes a separator binder. The functional coating may further include a separator dispersant. There is no particular limitation on the separator dispersant in the present application, as long as the object of the present application can be achieved. For example, the separator dispersant may include at least one of the above-mentioned dispersants. 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.

[0068] 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. There is no limitation on the above-mentioned other components in the present application. 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.

[0069] 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.

[0070] The preparation process of the secondary battery of the present application is well-known to those skilled in the art, and there is no special limitation in the present application. 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 winding, folding, etc. 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 and discharge. Among them, the packaging bag is a known packaging bag in the art, and the present application does not limit this.

[0071] 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 cycle performance.

[0072] 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 laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, minidiscs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motor-assisted bicycles, bicycles, lighting appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, and lithium-ion capacitors, etc.

[0073] Examples

[0074] 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.

[0075] Testing methods and equipment:

[0076] Infrared spectrum test of the negative electrode material layer:

[0077] Disassemble the lithium-ion battery, take out the negative electrode plate, dry the negative electrode plate after cleaning it with DMC. Scrape off the powder of the negative electrode material layer with a small knife, and then use the Thermo Fisher Nicolet iS20 FTIR spectrometer to perform Fourier transform infrared spectroscopy on the powder of the negative electrode material layer. Reference standard: GB / T 21186-2007 "Fourier Transform Infrared Spectrometer" national standard. Use the method of potassium bromide tablet pressing to perform infrared spectroscopy and obtain the infrared spectrogram of the negative electrode material layer.

[0078] Infrared spectroscopy test of the first coating:

[0079] Disassemble the lithium-ion battery, take out the negative electrode plate, dry the negative electrode plate after cleaning it with DMC. Scrape off the powder of the first coating with a small knife, and then use the Thermo Fisher Nicolet iS20 FTIR spectrometer to perform Fourier transform infrared spectroscopy on the powder of the first coating. Reference standard: GB / T 21186-2007 "Fourier Transform Infrared Spectrometer" national standard. Use the method of potassium bromide tablet pressing to perform infrared spectroscopy and obtain the infrared spectrogram of the first coating.

[0080] Porosity test:

[0081] Place the negative electrode plate in liquid nitrogen for rapid freezing to embrittle the binder, and use a scraper to peel off the first coating from the edge of the negative electrode plate. Punch the first coating into small round pieces with a diameter d of 14 mm, measure the thickness h of the small round pieces, measure the weight m of the small round pieces, put the above small round pieces into a true density meter (model AccupycⅡ1340) for testing, and measure the true density of the small round pieces as V2. Then calculate the apparent density V1 of the small round pieces through the diameter d and thickness h. V1 = m / [π × (d / 2) 2 × h].

[0082] The porosity P (%) of the first coating = (V1 - V2) / V1 × 100%.

[0083] Cycling performance test:

[0084] At 45 °C, the lithium-ion batteries in the examples or comparative examples were charged at a constant current of 0.5C to 4.28V, then charged at a constant voltage of 4.28V until the current was less than 0.025C, allowed to stand for 5 min, and discharged at a constant current of 1C to 3.0V. The above is one charge-discharge cycle, and the discharge capacity of the first cycle was recorded. The lithium-ion batteries were cycled multiple times under the above conditions, and the discharge capacity of the lithium-ion battery was measured for each cycle. Taking the discharge capacity of the first cycle as 100%, the charge-discharge cycle was repeated until the discharge capacity retention rate decayed to 80% of the discharge capacity of the first cycle, at which point the test was stopped and the number of cycles was recorded as an index for evaluating the cycle performance of the lithium-ion battery. Discharge capacity retention rate (%) = (discharge capacity after each discharge cycle / discharge capacity of the first cycle) × 100%.

[0085] Example 1-1

[0086] <Preparation of negative electrode sheet>

[0087] The negative electrode active material artificial graphite, negative electrode conductive agent Super P, negative electrode binder polyacrylic acid, and first additive lithium oxalate were mixed at a weight ratio of 96.8:1.5:1.2:0.5, and deionized water (H2O) was added as a solvent to prepare a slurry with a solid content of 70 wt%, and the slurry was stirred evenly to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 10 μm and dried at 110 °C to obtain a negative electrode sheet with a single-sided coated negative electrode material layer. Then the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coated negative electrode material layer, and the coating weight of the negative electrode material layer was 95 g / m 2 After coating, the above negative electrode sheet was cold-pressed with a compaction density of 1.7 g / cm 3 Then, after cutting and welding the tabs, a negative electrode sheet with a specification of 78 mm × 875 mm was obtained for use.

[0088] <Preparation of positive electrode sheet>

[0089] The positive electrode active material manganese-containing material lithium manganate, positive electrode conductive agent Super P, and positive electrode binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 96:2:2, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%. After vacuum stirring evenly, a positive electrode slurry was obtained. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 15 μm and dried at 120 °C to obtain a positive electrode sheet with a single-sided coated positive electrode material layer. Then the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coated positive electrode material layer, and the coating weight of the positive electrode material layer was 180 g / m 2 After coating, the above positive electrode sheet was cold-pressed with a compaction density of 2.7 g / cm3 After cutting the pieces and welding the tabs, a positive electrode plate with a specification of 74 mm × 867 mm is obtained for standby use.

[0090] <Preparation of electrolyte>

[0091] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed evenly according to the mass ratio of EC:EMC:DEC = 3:5:2 to obtain a basic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the above basic solvent and mixed evenly to obtain an electrolyte. Among them, 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.

[0092] <Preparation of separator>

[0093] Dissolve lithium oxalate, the first additive, in water, add polymethyl methacrylate, the separator binder, alumina, and CMC, the separator dispersant, to prepare a functional coating slurry with a solid content of 80 wt%. The mass ratio of the separator binder, alumina, separator dispersant, and the first additive is 85:6:4:5. Use a manual doctor blade coater to scrape the above functional coating slurry on one side of a polypropylene (PP) separator with a thickness of 12 μm and dry it at 70 °C for 10 min to obtain a separator with a single-sided coated functional coating; among them, the thickness of the functional coating is 2 μm.

[0094] <Preparation of lithium-ion battery>

[0095] Stack the positive electrode plate, separator, negative electrode plate, and separator in sequence, so that the separator is between the positive electrode plate and the negative electrode plate to play an isolation role. During the stacking process, the functional coating of the separator is arranged opposite to the negative electrode plate, and then it is wound to obtain an electrode assembly; place the electrode assembly in an aluminum-plastic film, then inject the prepared electrolyte above, and through processes such as formation, degassing, and trimming, a lithium-ion battery is obtained.

[0096] Examples 1-2 to Examples 1-13

[0097] Except for adjusting the relevant preparation parameters according to Table 1, the rest are the same as Example 1-1.

[0098] Example 2-1

[0099] Except for preparing the negative electrode plate according to the following method, the rest are the same as Example 1-1.

[0100] <Preparation of negative electrode plate>

[0101] (1) Mix artificial graphite as the anode active material, Super P as the anode conductive agent, and polyacrylic acid as the anode binder in a weight ratio of 97.3:1.5:1.2. Add deionized water (H2O) as a solvent to formulate a slurry with a solid content of 70 wt%, and stir evenly to obtain the anode slurry. Uniformly coat the anode slurry on one surface of the anode current collector copper foil with a thickness of 10 μm, and dry it at 110 °C to obtain an anode electrode sheet with a single-sided coated anode material layer. Then repeat the above steps on the other surface of the copper foil to obtain an anode electrode sheet with a double-sided coated anode material layer. The coating weight of the anode material layer is 95 g / m 2 .

[0102] (2) Mix polymethyl methacrylate as the binder, lithium oxalate as the first additive, and CMC as the dispersant, and add deionized water as a solvent to formulate the first coating slurry with a solid content of 80 wt%; among them, the mass ratio of the binder, dispersant, and first additive is 5:1:94.

[0103] (3) Uniformly coat the first coating slurry on one surface of the anode electrode sheet prepared in step (1), and dry it at 110 °C. Then repeat the above steps on the other surface of the anode electrode sheet to obtain an anode electrode sheet with both sides sequentially coated with the anode material layer and the first coating. The coating weight of the first coating is 0.51 g / m 2 . After the coating is completed, cold press the above anode electrode sheet, and the compaction density is 1.7 g / cm 3 . Then, after slitting and welding the tabs, an anode electrode sheet with a specification of 78 mm × 875 mm is obtained for use. Among them, the thickness H of the first coating is 2 μm; and the first coating is provided on all surfaces of the anode material layer away from the anode current collector, and the first coating is a continuous coating.

[0104] Examples 2-2 to 2-11

[0105] Except for adjusting the relevant preparation parameters according to Table 2, the rest are the same as in Example 2-1.

[0106] Examples 2-12 to 2-13

[0107] Except for adjusting the coating weight of the first coating so that the thickness of the first coating is as shown in Table 2, the rest are the same as in Example 2-2.

[0108] Example 3-1

[0109] Except for preparing the anode electrode sheet according to the following method, the rest are the same as in Example 2-2.

[0110] <Preparation of Anode Electrode Sheet>

[0111] Steps (1) and (2) are the same as steps (1) and (2) in Example 2-2.

[0112] (3) Using extrusion gap coating, the first coating slurry is coated on one surface of the negative electrode sheet prepared in step (1) in a gap and uniformly along the length direction after the negative electrode sheet is unfolded, and dried at 110 °C. As Figure 3 shown, the surface of the negative electrode material layer away from the negative electrode current collector includes multiple coating areas and non-coating areas. Each coating area is provided with a first coating. Along the length direction after the negative electrode sheet is unfolded, the distance D1 between two adjacent coating areas is 3 mm, and the length of a single coating area is 5 mm. Then repeat the above steps on the other surface of the negative electrode sheet to obtain a negative electrode sheet with double-sided striped coating of the first coating. The coating weight of the first coating is 0.51 g / m 2 . After coating, the above negative electrode sheet is cold-pressed, and the compaction density is 1.7 g / cm 3 . Then, after cutting and welding the tab, a negative electrode sheet with a specification of 78 mm × 875 mm is obtained for use.

[0113] Examples 3-2 to 3-3

[0114] Except for adjusting the relevant preparation parameters according to Table 3, the rest are the same as in Example 3-1.

[0115] Example 3-4

[0116] Except for preparing the negative electrode sheet according to the following method, the rest are the same as in Example 3-1.

[0117] <Preparation of Negative Electrode Sheet>

[0118] Steps (1) and (2) are the same as steps (1) and (2) in Example 3-1.

[0119] (3) Using extrusion gap coating, the first coating slurry is coated on one surface of the negative electrode sheet prepared in step (1) in a gap and uniformly along the length direction after the negative electrode sheet is unfolded, and dried at 110 °C, and then the first coating slurry is coated on the same surface of the negative electrode sheet in a gap and uniformly along the width direction after the negative electrode sheet is unfolded, and dried at 110 °C. As Figure 4As shown, the surface of the negative electrode material layer away from the negative electrode current collector includes multiple coating areas and non-coating areas. Each coating area is provided with a first coating, and the multiple coating areas are distributed in a grid pattern. Along the length direction of the negative electrode tab after unfolding, the distance between two adjacent coating areas is 3 mm, and the length of a single coating area is 5 mm; along the width direction of the negative electrode tab after unfolding, the distance between two adjacent coating areas is 3 mm, and the width of a single coating area is 3 mm. Then, repeat the above steps on the other surface of the negative electrode tab to obtain a negative electrode tab with a double-sided grid-like coating of the first coating. The coating weight of the first coating is 0.51 g / m 2 . After the coating is completed, cold press the above negative electrode tab, and the compaction density is 1.7 g / cm 3 . Then, after cutting and welding the tab, a negative electrode tab with a specification of 78 mm × 875 mm is obtained for use.

[0120] Comparative Examples 1-1 to 1-3

[0121] Except for adjusting the relevant preparation parameters according to Table 1, the rest are the same as in Example 1-1.

[0122] Comparative Examples 2-1 to 2-3

[0123] Except for adjusting the relevant preparation parameters according to Table 2, the rest are the same as in Example 2-1.

[0124] The preparation parameters and electrical performance parameters of each example and comparative example are shown in Tables 1 to 3.

[0125] Table 1

[0126]

[0127]

[0128] Note: (1) In Table 1, " / " indicates no relevant preparation parameters; (2) In Table 1, "ZIF-8" refers to the metal-organic framework compound Zn(C4H7N2)2; (3) In Examples 1-7, the "manganese-containing material" is "NCM613", which means the manganese-containing material is LiNi 0.6 Co 0.1 Mn 0.3 O2, and the same applies to other examples.

[0129] As can be seen from Examples 1-1 to 1-13 and Comparative Examples 1-1 to 1-3, when the positive active material of the positive electrode layer includes a manganese-containing material and the negative electrode material layer of the negative electrode tab includes a first additive, the prepared lithium-ion battery has a higher number of charge-discharge cycles, indicating that the cycle performance of the lithium-ion battery can be improved. In Comparative Examples 1-1 to 1-3, the negative electrode material layer of the negative electrode tab does not include the first additive, and the prepared lithium-ion battery has a lower number of charge-discharge cycles, indicating that the cycle performance of the lithium-ion battery is poor.

[0130] The mass percentage content of the first additive generally affects the cycle performance of the lithium-ion battery. As can be seen from Examples 1-2, 1-10 to 1-13, by adjusting the mass percentage content of the first additive within the scope of this application, the prepared lithium-ion battery has a higher number of charge-discharge cycles, indicating that the cycle performance of the lithium-ion battery can be improved.

[0131] It is known from Figure 5 that in the infrared spectrum of the negative electrode material layer of Example 1-2, there are second characteristic peaks in the ranges of 1090 cm -1 to 1290 cm -1 , 968 cm -1 to 1168 cm -1 , 520 cm -1 to 720 cm -1 , 430 cm -1 to 630 cm -1 .

[0132] Table 2

[0133]

[0134]

[0135] Note: (1) In Table 2, " / " indicates no relevant preparation parameters; (2) In Table 2, "ZIF-8" refers to the metal-organic framework compound Zn(C4H7N2)2; (3) In Example 2-7, the "manganese-containing material" is "NCM613", which means the manganese-containing material is LiNi 0.6 Co 0.1 Mn 0.3 O2, and the same applies to other examples.

[0136] It can be seen from Examples 2-1 to 2-13 and Comparative Examples 2-1 to 2-3 that when the positive electrode active material of the positive electrode material layer includes a manganese-containing material and the first coating of the negative electrode sheet includes a first additive, the prepared lithium-ion battery has a higher number of cycle times, indicating that the cycle performance of the lithium-ion battery can be improved. In Comparative Examples 2-1 to 2-3, the first coating of the negative electrode sheet does not include the first additive, and the prepared lithium-ion battery has a lower number of cycle times, indicating that the cycle performance of the lithium-ion battery is poor.

[0137] The mass percentage content of the first additive usually affects the cycle performance of the lithium-ion battery. It can be seen from Examples 2-2, 2-10, and 2-11 that by adjusting the mass percentage content of the first additive within the scope of this application, the prepared lithium-ion battery has a higher number of cycle times, indicating that the cycle performance of the lithium-ion battery can be improved.

[0138] The thickness of the first coating usually affects the cycle performance and energy density of the lithium-ion battery. It can be seen from Examples 2-2 and 2-12 to 2-13 that by adjusting the thickness of the first coating within the scope of this application, the prepared lithium-ion battery has a higher number of cycle times, indicating that the cycle performance of the lithium-ion battery can be improved.

[0139] From Figure 6 it can be known that in the infrared spectrum of the first coating in Example 2-1, there are fourth characteristic peaks in the ranges of 2500 cm -1 to 3300 cm -1 , 1650 cm -1 to 1740 cm -1 , and 1000 cm -1 to 1400 cm -1 .

[0140] Table 3

[0141]

[0142] Note: In Table 3, " / " indicates no relevant preparation parameters.

[0143] It can be known from Examples 3-1 to 3-3 that the first coating is arranged on the surface of the negative electrode material layer in a striped shape, and by adjusting the distance between adjacent two coating areas within the above range, the prepared lithium-ion battery has a higher number of cycle times, indicating that the cycle performance of the lithium-ion battery can be improved.

[0144] It can be known from Example 3-4 that the first coating is arranged on the surface of the negative electrode material layer in a grid shape, and the prepared lithium-ion battery has a higher number of cycle times, indicating that the cycle performance of the lithium-ion battery can be improved.

[0145] It should be noted that, in this document, 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 comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method or article.

[0146] 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. Each embodiment focuses on the differences from other embodiments.

[0147] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A secondary battery, comprising a positive electrode plate and a negative electrode plate, the positive electrode plate comprising a positive current collector and a positive electrode material layer provided on at least one surface of the positive current collector, the positive electrode material layer comprising a positive electrode active material, the positive electrode active material comprising a manganese-containing material, the manganese-containing material comprising at least one of lithium manganate, lithium iron manganese phosphate, lithium-rich manganese-based material, or lithium nickel cobalt manganese oxide; The negative electrode sheet includes a first additive, and the first additive includes at least one of carboxylate, sulfonate or metal-organic framework compound. The carboxylate includes at least one of lithium oxalate, sodium citrate, sodium maleate or sodium tartrate. The sulfonate includes at least one of sodium benzenesulfonate, sodium dodecylbenzenesulfonate or sodium methylsulfonate. The metal-organic framework compound includes at least one of Zn(C4H7N2)2, C 48 H 28 O 32 Zr6 or C 14 H 16 at least one of N2O8Mg2.

2. The secondary battery according to claim 1, wherein, The negative electrode plate comprises a negative current collector and a negative electrode material layer provided on at least one surface of the negative current collector, the negative electrode material layer comprising a first additive, and based on the mass of the negative electrode material layer, the mass percentage content of the first additive is W1%, and 0.2 ≤ W1 ≤ 2.

3. The secondary battery according to claim 2, wherein, In the infrared spectrum of the negative electrode material layer, there are first characteristic peaks in the range of 2500 cm -1 to 3300 cm -1 、1650 cm -1 to 1740 cm -1 、1000 cm -1 to 1400 cm -1 ; and / or, there are second characteristic peaks in the range of 1090 cm -1 to 1290 cm -1 、968 cm -1 to 1168 cm -1 、520 cm -1 to 720 cm -1 、430 cm -1 to 630 cm -1 ; and / or, there are third characteristic peaks in the range of 500 cm -1 to 600 cm -1 、1000 cm -1 to 1400 cm -1 、1600 cm -1 to 1700 cm -1 、2800 cm -1 to 3000 cm -1 、3200 cm -1 to 3600 cm -1 .

4. The secondary battery according to claim 1, wherein, The negative electrode plate comprises a negative current collector, a negative electrode material layer, and a first coating layer, the negative electrode material layer being provided between the negative current collector and the first coating layer, the first coating layer comprising the first additive, and based on the mass of the first coating layer, the mass percentage content of the first additive is W2%, and 84 ≤ W2 ≤ 98.

5. The secondary battery according to claim 4, wherein, The surface of the negative electrode material layer away from the negative current collector comprises a plurality of coating regions and non-coating regions, each of the coating regions being provided with the first coating layer, the plurality of coating regions being spaced apart along the length direction after the negative electrode plate is unfolded and extending along the width direction after the negative electrode plate is unfolded, and along the length direction after the negative electrode plate is unfolded, the distance between two adjacent coating regions is D1 mm, and 1 ≤ D1 ≤ 10.

6. The secondary battery according to claim 4, wherein, The surface of the negative electrode material layer away from the negative current collector comprises a plurality of coating regions and non-coating regions, each of the coating regions being provided with the first coating layer, and the plurality of coating regions are distributed in a grid pattern.

7. The secondary battery according to any one of claims 4 to 6, wherein, The thickness of the first coating layer is H μm, and 1 ≤ H ≤ 10.

8. The secondary battery according to any one of claims 4 to 6, wherein, The porosity of the first coating layer is P%, and 10 ≤ P ≤ 40.

9. The secondary battery according to any one of claims 4 to 6, wherein, In the infrared spectrogram of the first coating, a fourth characteristic peak exists in the range of 2500 cm -1 to 3300 cm -1 、1650 cm -1 to 1740 cm -1 、1000 cm -1 to 1400 cm -1 ; and / or, a fifth characteristic peak exists in the range of 1090 cm -1 to 1290 cm -1 、968 cm -1 to 1168 cm -1 、520 cm -1 to 720 cm -1 、430 cm -1 to 630 cm -1 ; and / or, a sixth characteristic peak exists in the range of 500 cm -1 to 600 cm -1 、1000 cm -1 to 1400 cm -1 、1600 cm -1 to 1700 cm -1 、2800 cm -1 to 3000 cm -1 、3200 cm -1 to 3600 cm -1 .

10. The secondary battery according to any one of claims 4 to 6, wherein The first coating layer further comprises a binder and a dispersant, the binder comprising at least one of polymethyl methacrylate, styrene-butadiene rubber, or polyacrylic acid, the dispersant comprising at least one of carboxymethyl cellulose, polyvinylpyrrolidone, hydroxypropyl methylcellulose, or polyethylene glycol; based on the mass of the first coating layer, the mass percentage content of the binder is W3%, and the mass percentage content of the dispersant is W4%, and 1 ≤ W3 ≤ 10, 1 ≤ W4 ≤ 6.

11. An electronic device, comprising the secondary battery according to any one of claims 1 to 10.

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