Lithium ion secondary battery and electric equipment

Abstract

The invention relates to the technical field of batteries, in particular to a lithium ion secondary battery and electric equipment, a positive pole piece of the lithium ion secondary battery comprises a manganese-containing positive active material, the positive pole piece further comprises a first substance layer, and / or a negative pole piece further comprises a second substance layer, the first substance layer is arranged on the side, away from the positive current collector, of the positive active material layer and comprises a first substance; the second substance layer is arranged on the side, away from the negative electrode current collector, of the negative electrode active material layer, the second substance layer comprises a second substance, and the mass ratio of the first substance to the manganese-containing positive electrode active material and the mass ratio of the second substance to the manganese-containing positive electrode active material are independently (1.1-15): 100; the first substance and the second substance respectively comprise one or more than two of a first compound, a carbon material and a halogenated compound, the first compound comprises a compound containing one or two of a polyoxygen group and an N element, and the specific surface area of the carbon material is greater than or equal to 200m < 2 > / g and less than or equal to 3000m < 2 > / g. The first substance layer and / or the second substance layer can capture manganese dissolved out of the positive pole piece, the amount of manganese directly deposited on the surface of the negative pole piece is reduced, damage to an SEI film is reduced, the loss of active lithium is reduced, and the cycling stability of the lithium ion secondary battery is improved.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to lithium-ion secondary batteries and electrical equipment. Background Technology

[0002] In recent years, lithium-ion batteries have made great strides and can be widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in electric vehicles, power tools, and aerospace. However, manganese-containing cathode active materials, such as manganese-rich cathode materials, tend to cause rapid capacity decay in lithium-ion secondary batteries. Summary of the Invention

[0003] In view of this, the main technical problem solved by this application is that the capacity decay of batteries assembled with manganese-containing positive electrode active materials is relatively fast. Therefore, this application provides lithium-ion secondary batteries and electrical equipment that can improve the capacity decay of lithium-ion secondary batteries and enhance their electrochemical performance.

[0004] The first aspect of this application provides a lithium-ion secondary battery, including a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive active material layer disposed on the positive current collector, the positive active material including a manganese-containing positive active material. The negative electrode includes a negative current collector and a negative active material layer disposed on the negative current collector. The positive electrode further includes a first material layer, and / or the negative electrode further includes a second material layer. The first material layer is disposed on the side of the positive active material layer away from the positive current collector. The first material layer includes a first substance, the mass ratio of the first substance to the manganese-containing positive active material is (1.1-15):100, the first substance includes one or more of a first compound, a carbon material, and a halogenated compound, the first compound including one or two of a polyoxygen group and nitrogen element; the specific surface area of ​​the carbon material is greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 / g; The second material layer is disposed on the side of the negative electrode active material layer away from the negative electrode current collector. The second material layer includes a second material, and the mass ratio of the second material to the manganese-containing positive electrode active material is (1.1~15):100. The first material includes one or more of a first compound, carbon material, and halogenated compound. The first compound includes one or two of a compound containing a polyoxy group and nitrogen element. The specific surface area of ​​the carbon material is greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 / g.

[0005] In the technical solution of this application's embodiments, the first substance and the second substance each comprise substances with a specific surface area greater than or equal to 200m². 2 / g and less than or equal to 3000m2 The lithium-ion secondary battery comprises one or more of the following: carbon material, a first compound containing polyoxygen groups and / or nitrogen, and a halogenated compound. The carbon material has a large specific surface area, enabling it to adsorb manganese ions dissolved from the positive electrode active material. The first compound containing polyoxygen groups and / or nitrogen, and the halogenated compound, can adsorb manganese ions or / and react with manganese ions. This allows the first and second substances to capture manganese ions. The positive electrode active material layer of the lithium-ion secondary battery includes a manganese-containing positive electrode active material. By setting a first material layer on the positive electrode sheet, or setting a second material layer on the negative electrode sheet, or simultaneously setting both the first and second material layers on the positive and negative electrode sheets, the first and / or second material layers can capture Mn dissolved from the manganese-containing positive electrode active material. 2+ By controlling the mass ratio of the first substance to the manganese-containing positive electrode active material and the mass ratio of the second substance to the manganese-containing positive electrode active material, the first and second substances can effectively capture the manganese ions dissolved from the positive electrode active material, reducing the amount of manganese ions reaching the negative electrode active material layer, reducing the amount of manganese ions directly deposited on the surface of the negative electrode active material layer, reducing the damage to the SEI film (solid electrolyte interface film) on the surface of the negative electrode active material, and reducing the loss of active lithium ions. This can improve the capacity decay of lithium-ion secondary batteries and enhance the cycle stability of lithium-ion secondary batteries.

[0006] In any embodiment, the mass ratio of the first substance to the manganese-containing positive electrode active material is (3-10):100, and / or, the mass ratio of the second substance to the manganese-containing positive electrode active material is (3-10):100. In the embodiments of this application, by controlling the mass ratio of the first substance to the manganese-containing positive electrode active material within the above range, and / or the mass ratio of the second substance to the manganese-containing positive electrode active material within the above range, the specific capacity of the lithium-ion secondary battery is optimized, and the cycle stability of the lithium-ion secondary battery can be improved.

[0007] In any embodiment, the carbon material includes one or more of carbon nanotubes, Ketjen black, and activated carbon, which can adsorb manganese ions to achieve the effect of capturing manganese ions.

[0008] In any embodiment, the first compound includes one or more of the following: silicon dioxide, lithium phosphate, lithium silicate, lithium sulfate, polyacrylic acid, lithium polyacrylate, sodium para-aminosalicylate, lithium nitride, and lanthanum nitrate. In the embodiments of this application, silicon dioxide has a porous structure, which allows it to physically adsorb Mn. 2+ On the other hand, the Si-O bonds of silicon dioxide can react with manganese ions. 2+ When manganese ions form chemical bonds, they can simultaneously achieve the effects of physical adsorption and chemical reaction, capturing Mn. 2+The same manganese ion effect. Lithium phosphate, lithium silicate, lithium sulfate, polyacrylic acid, lithium polyacrylate, sodium para-aminosalicylic acid, lithium nitride, and lanthanum nitrate can also react with Mn. 2+ When manganese ions form chemical bonds, they can be captured.

[0009] In any embodiment, the halogenated compound includes one or more compounds formed from Group 1 and Group 7, and compounds formed from Group 2 and Group 7. In embodiments of this application, the halogenated compound includes halides from Group 1 or Group 2, and the halogenated compound can react with Mn... 2+ The reaction with manganese ions achieves the effect of capturing manganese ions.

[0010] In any embodiment, the halogenated compound includes one or more of potassium fluoride, lithium fluoride, and calcium chloride. In embodiments of this application, the above-mentioned halogenated compound is combined with Mn... 2+ Manganese ions readily form chemical bonds, thus exhibiting a good effect in capturing manganese ions.

[0011] In any embodiment, the volume average particle size DV50 of the first substance is 100 nm to 10 μm; the volume average particle size DV50 of the second substance is 100 nm to 10 μm. In the embodiments of this application, by controlling the volume average particle size DV50 of the first and second substances within the above range, the first and second substances have a larger specific surface area, resulting in better adsorption of manganese ions or reaction with manganese ions; in addition, the volume average particle size DV50 of the first and second substances within the above range results in better film-forming properties of the first and second substance layers.

[0012] In any embodiment, the volume average particle size DV50 of the first substance is 100 nm to 1 μm; the volume average particle size DV50 of the second substance is 100 nm to 1 μm. In the embodiments of this application, the volume average particle size DV50 of the first and second substances is relatively small, resulting in a larger specific surface area for both substances, thus improving the adsorption or reaction with manganese ions.

[0013] In any embodiment, the mass fraction of the first substance is 70% to 100% based on the total mass of the first substance layer; and / or, the mass fraction of the second substance is 70% to 100% based on the total mass of the second substance layer. In the embodiments of this application, the first substance is the main material of the first substance layer, and the second substance is the main material of the second substance layer.

[0014] In any embodiment, the first material layer further includes a first adhesive, and / or the second material layer further includes a second adhesive. By providing the first and second adhesives, the fabrication of the first and second material layers is facilitated, resulting in better film-forming properties.

[0015] In any embodiment, the manganese-containing positive electrode active material includes spinel lithium nickel manganese oxide. Spinel lithium nickel manganese oxide has a relatively high average charging voltage, and the electrolyte is prone to HF corrosion under high voltage, leading to material structural instability and significant manganese ion dissolution. The first and / or second substances in the lithium-ion secondary battery of this application can effectively capture manganese ions, significantly improving the rapid capacity decay of the lithium-ion secondary battery and enhancing its long-term cycle stability.

[0016] In any embodiment, the manganese-containing positive electrode active material includes the structure Li a Mn b T c O d The material, wherein T includes one or more of Ni, Na, Si, P, Nb, Mo, Te, Ta, Al, K, V, Cr, Fe, Cu, Co, Zr, Ge, F, Cl, Br, and I, with 0.8 ≤ a ≤ 2, 0.5 ≤ b ≤ 2, 0 ≤ c ≤ 1, and 1.5 ≤ d ≤ 4. In the embodiments of this application, the manganese-containing positive electrode active material includes the material with the above-mentioned structural formula, and the manganese-containing positive electrode active material has good charge-discharge performance.

[0017] A second aspect of this application provides an electrical device including the lithium-ion secondary battery of the first aspect. In embodiments of this application, the battery device possesses at least the same advantages as the lithium-ion secondary battery of the first aspect.

[0018] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a battery cell according to one embodiment of this application.

[0020] Figure 2 This is an exploded structural diagram of a battery according to one embodiment of this application.

[0021] Figure 3 This is a partial structural schematic diagram of an electrical device according to one embodiment of this application.

[0022] Figure 4a This is a scanning electron microscope image of a cross-section of the positive electrode sheet according to one embodiment of this application.

[0023] Figure 4b This is an X-ray electron spectrum of a cross-section of the positive electrode sheet according to an embodiment of this application. Detailed Implementation

[0024] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0025] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0027] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0028] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0029] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0030] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0031] During the charging and discharging process, manganese-containing positive electrode active materials, especially those rich in manganese, are prone to manganese ions dissolving from the manganese-rich positive electrode active material and depositing onto the negative electrode sheet due to the Jahn-Teller effect (JT effect) or side reactions between the manganese-rich positive electrode active material and the electrolyte. The manganese ions continuously damage the SEI film on the negative electrode sheet, causing the lithium ions in the manganese-containing positive electrode active material to be continuously consumed in order to repair the SEI film, which aggravates the loss of active lithium ions and results in a faster capacity decay of lithium-ion secondary batteries.

[0032] The first aspect of this application provides a lithium-ion secondary battery, including a positive electrode and a negative electrode. The positive electrode includes a current collector and a positive active material layer disposed on the current collector, the positive active material including a manganese-containing positive active material. The negative electrode includes a negative current collector and a negative active material layer disposed on the current collector. The positive electrode further includes a first material layer, and / or the negative electrode further includes a second material layer. The first material layer is disposed on the side of the positive active material layer away from the positive current collector. The first material layer includes a first substance, the mass ratio of the first substance to the manganese-containing positive active material is (1.1-15):100, the first substance includes one or more of a first compound, a carbon material, and a halogenated compound, the first compound including one or two of a polyoxygen group and nitrogen element; the specific surface area of ​​the carbon material is greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 / g; The second material layer is disposed on the side of the negative electrode active material layer away from the negative electrode current collector. The second material layer includes a second material, and the mass ratio of the second material to the manganese-containing positive electrode active material is (1.1~15):100. The first material includes one or more of a first compound, carbon material, and halogenated compound. The first compound includes one or two of a compound containing a polyoxy group and nitrogen element. The specific surface area of ​​the carbon material is greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 / g.

[0033] In the technical solution of this application's embodiments, the first substance and the second substance each comprise substances with a specific surface area greater than or equal to 200m². 2 / g, and less than or equal to 3000m 2 The lithium-ion secondary battery comprises one or more of the following: carbon material, a first compound containing polyoxygen groups and / or nitrogen, and a halogenated compound. The carbon material has a large specific surface area, enabling it to adsorb manganese ions dissolved from the positive electrode active material. The first compound containing polyoxygen groups and / or nitrogen, and the halogenated compound, can adsorb manganese ions or / and react with manganese ions. This allows the first and second substances to capture manganese ions. The positive electrode active material layer of the lithium-ion secondary battery includes a manganese-containing positive electrode active material. By setting a first material layer on the positive electrode sheet, or setting a second material layer on the negative electrode sheet, or simultaneously setting both the first and second material layers on the positive and negative electrode sheets, the first and / or second material layers can capture Mn dissolved from the manganese-containing positive electrode active material. 2+ The first and second material layers have a layered structure, and their relatively dense formation effectively reduces manganese ion leakage and improves manganese ion capture. By controlling the mass ratio of the first material to the manganese-containing positive electrode active material and the mass ratio of the second material to the manganese-containing positive electrode active material, the first and second materials can effectively capture manganese ions dissolved from the positive electrode active material, reducing the amount of manganese ions reaching the negative electrode active material layer, reducing the amount of manganese ions directly deposited on the surface of the negative electrode active material layer, reducing damage to the SEI film (solid electrolyte interface film) on the surface of the negative electrode active material, and reducing the loss of active lithium ions. This can improve the capacity decay of lithium-ion secondary batteries and enhance their cycle stability.

[0034] In this application, carbon materials refer to all-carbon or mixtures containing all-carbon, such as diamond, graphite, carbon black, carbon nanotubes, carbon fibers, carbon nanospheres, etc.

[0035] In this embodiment, the first compound contains one or both of the following: a polyoxygen group and nitrogen (N). A polyoxygen group refers to a compound with two or more oxygen-containing covalent bonds. Because the first compound contains two or more oxygen-containing covalent bonds, it exhibits strong electronegativity, allowing oxygen ions to form coordinate bonds with manganese ions, or / and the compound to adsorb manganese ions. The anion of the polyoxygen group includes oxygen ions, which have strong electronegativity, while the cation has weak electronegativity; for example, the cation may include elements from Group 1 or Group 2. The first compound contains nitrogen (N), which has lone pairs of electrons and can form coordinate bonds with manganese ions, resulting in a chemical reaction and the chemical adsorption of manganese ions. In this embodiment, the first compound preferably does not contain manganese ions to avoid the negative impact of manganese ions from the first compound on the lithium-ion secondary battery.

[0036] In this embodiment, the halogenated compound is a halogenated compound. The halide ions are highly electronegative and can form coordinate bonds with manganese ions, thus capturing manganese ions. In the embodiments of this application, the weaker the electronegativity of the cation in the halogenated compound, the more favorable it is for the halide ions to form coordinate bonds with manganese ions.

[0037] In one embodiment of this application, the lithium-ion secondary battery includes a first material layer but does not include a second material layer. In this embodiment, by controlling the mass ratio of the first material to the manganese-containing positive electrode active material to be (1.1-15):100, manganese ions dissolved from the positive electrode active material can be initially captured, reducing the amount of manganese ions reaching the negative electrode. The mass ratio of the first material to the manganese-containing positive electrode active material is 1.1:100, 1.5:100, 1.8:100, 2:100, 5:100, 7:100, 10:100, 11:100, 13:100, 15:100, etc., or a range of any two of the above values, such as (1.1-1.8):100, (1.8-7):100, (7-15):100, etc.

[0038] In another embodiment of this application, the lithium-ion secondary battery includes a second material layer but does not include a first material layer. The mass ratio of the second material to the manganese-containing positive electrode active material is (1.1-15):100. The second material layer can capture the Mn dissolved from the positive electrode active material layer. 2+The manganese ions are reduced by controlling the mass ratio of the second substance to the manganese-containing positive electrode active material within the above-mentioned range, thereby achieving a better effect in capturing manganese ions. The mass ratio of the second substance to the manganese-containing positive electrode active material is 1.1:100, 1.5:100, 1.7:100, 2:100, 5:100, 8:100, 10:100, 12:100, 13:100, 15:100, or any range of two of the above values, such as (1.1–1.7):100, (1.7–8):100, (8–15):100, etc.

[0039] In another embodiment of this application, the lithium-ion secondary battery includes a first material layer and a second material layer. The mass ratio of the first material to the manganese-containing positive electrode active material is (1.1–15):100. The mass ratio of the second material to the manganese-containing positive electrode active material is also (1.1–15):100. The amounts of the first and second materials may be the same or different. The manganese positive electrode active material dissolves Mn... 2+ After manganese ions are captured by the first material layer, during the charging and discharging process of the lithium-ion secondary battery, some manganese ions will still move towards the negative electrode under the action of the driving voltage; the second material layer can capture the Mn dissolved from the positive electrode active material layer. 2+ The manganese ions are reduced to decrease the amount of manganese ions reaching the negative electrode active material layer. By controlling the mass ratio of the first substance and the second substance to the positive electrode active material within the above range, the manganese ions can be captured, while simultaneously improving the properties of the positive electrode active material. The mass ratio of the first substance to the manganese-containing positive electrode active material is 1.1:100, 1.5:100, 1.8:100, 2:100, 5:100, 7:100, 10:100, 11:100, 13:100, 15:100, etc., or any range of two of the above values, such as (1.1~1.8):100, (1.8~7):100, (7~15):100, etc. The mass ratio of the second substance to the manganese-containing positive electrode active material is 1.1:100, 1.5:100, 1.7:100, 2:100, 5:100, 8:100, 10:100, 12:100, 13:100, 15:100, etc., or a range of any two of the above values, such as (1.1~1.7):100, (1.7~8):100, (8~15):100, etc.

[0040] In some embodiments, the mass ratio of the first substance to the manganese-containing positive electrode active material is (3-10):100, and / or, the mass ratio of the second substance to the manganese-containing positive electrode active material is (3-10):100. In the embodiments of this application, by controlling the mass ratio of the first substance to the manganese-containing positive electrode active material within the above range, and / or the mass ratio of the second substance to the manganese-containing positive electrode active material within the above range, the specific capacity of the lithium-ion secondary battery is optimized, and the cycle stability of the lithium-ion secondary battery can be improved. The mass ratio of the first substance to the manganese-containing positive electrode active material is 3:100, 5:100, 7:100, 10:100, etc., or a range of any two of the above values, such as (3-5):100, (5-7):100, (7-10):100, etc. The mass ratio of the second substance to the manganese-containing positive electrode active material is 3:100, 4:100, 5:100, 8:100, 10:100, or any range of two of the above values, such as (3-4):100, (4-8):100, (8-10):100, etc.

[0041] In the embodiments of this application, the first substance and the second substance may be the same or different. In one embodiment of this application, the first substance includes substances with a specific surface area greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 In other embodiments, the first substance may also be one or more of a first compound containing a polyoxygen group and / or nitrogen element, or a halogenated compound. The second substance includes the first compound containing a polyoxygen group; in other embodiments, the second substance may also include a compound with a specific surface area greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 The carbon material can have a specific surface area of ​​200 m² / g, and can be composed of one or more of the following: a carbon material containing a polyoxygen group and nitrogen, a first compound containing nitrogen, or a halogenated compound. 2 / g、500m 2 / g、800m 2 / g, 1000m 2 / g、1200m 2 / g、2000m 2 / g、2500m 2 / g、3000m 2 / g, or a range of values ​​consisting of any two of the above values, such as 200m. 2 / g-500 m 2 / g、500m 2 / g-1200 m 2 / g、1200m 2 / g-3000 m 2 / g、、

[0042] In some embodiments, the carbon material includes one or more of carbon nanotubes, Ketjen black, and activated carbon. In the embodiments of this application, the carbon nanotubes have a large specific surface area and strong adsorption capacity; the specific surface area is greater than or equal to 200 m². 2 / g and less than or equal to 3000m 2 / g of Ketjen black and activated carbon have strong adsorption capacity and can adsorb Mn dissolved from the positive electrode active material. 2+ Manganese ions. In one embodiment of this application, the carbon material is activated carbon. In other embodiments, the carbon material may also be carbon nanotubes or Ketjen black, or two or three of carbon nanotubes, Ketjen black, and activated carbon.

[0043] In some embodiments, the first compound includes one or more of silicon dioxide, lithium phosphate, lithium silicate, lithium sulfate, polyacrylic acid, lithium polyacrylate, sodium para-aminosalicylate, lithium nitride, and lanthanum nitrate. In the embodiments of this application, silicon dioxide has a porous structure, which allows it to physically adsorb Mn. 2+ On the other hand, the Si-O bonds of silicon dioxide can react with manganese ions. 2+ When manganese ions form chemical bonds, they can simultaneously achieve the effects of physical adsorption and chemical reaction, capturing Mn. 2+ The same manganese ion effect. Lithium phosphate, lithium silicate, lithium sulfate, polyacrylic acid, lithium polyacrylate, sodium para-aminosalicylic acid, lithium nitride, and lanthanum nitrate can also react with Mn. 2+ When manganese ions form chemical bonds, they can be captured.

[0044] In some embodiments, the halogenated compound includes one or more compounds formed from Group 1 and Group 7 compounds, and compounds formed from Group 2 and Group 7 compounds. In embodiments of this application, the halogenated compound includes halides from Group 1 or Group 2 compounds, and the halogenated compound can react with Mn... 2+ The reaction with manganese ions achieves the effect of capturing manganese ions. Compounds formed between Group I and Group VII include one or more of LiF, NaF, KF, LiCl, LiI, LiBr, NaBr, KBr, NaCl, KCl, NaI, and KI. Compounds formed between Group II and Group VII include one or more of MgF₂, CaF₂, MgCl₂, CaCl₂, MgBr₂, and CaBr₂.

[0045] In some embodiments, the halogenated compound includes one or more of potassium fluoride, lithium fluoride, and calcium chloride. In embodiments of this application, the above-mentioned halogenated compound is combined with Mn... 2+Manganese ions readily form chemical bonds, thus exhibiting a good effect in capturing manganese ions.

[0046] In some embodiments, the volume average particle size (DV50) of the first substance and the second substance is 100 nm to 10 μm, respectively. In this embodiment, by controlling the volume average particle size (DV50) of the first substance and the second substance within the above range, the first substance and the second substance have a larger specific surface area, resulting in better adsorption of manganese ions or reaction with manganese ions. Furthermore, the volume average particle size (DV50) of the first substance and the second substance within the above range results in better film-forming properties of the first substance layer and the second substance layer. Specifically, the volume average particle size (DV50) of the first substance is 100 nm, 500 nm, 800 nm, 1 μm, 2 μm, 5 μm, 7 μm, 10 μm, etc., or a range consisting of any two of the above values, such as 100 nm to 800 nm, 800 nm to 2 μm, 2 μm to 10 μm, etc. The volume average particle size (DV50) of the first substance is 100nm, 500nm, 700nm, 1μm, 2μm, 5μm, 8μm, 10μm, etc., or a range of any two of the above values, such as 100nm~700nm, 700nm~2μm, 2μm~10μm, etc.

[0047] Among them, the volume average particle size DV50 is common knowledge in the field and has a common meaning in the field. It can be measured by methods and instruments in the field.

[0048] In some embodiments, the volume average particle size (DV50) of the first substance and the second substance is 100 nm to 1 μm. In the embodiments of this application, the relatively small volume average particle size (DV50) of the first substance and the second substance results in a larger specific surface area for both substances, leading to better adsorption of manganese ions or better reaction with manganese ions. Specifically, the volume average particle size (DV50) of the first substance is 100 nm, 500 nm, 800 nm, 1 μm, or any range of any two of the above values, such as 100 nm to 800 nm, 500 nm to 800 nm, 800 nm to 1 μm, etc. The volume average particle size (DV50) of the first substance is 100 nm, 500 nm, 700 nm, 1 μm, or any range of any two of the above values, such as 100 nm to 500 nm, 500 nm to 700 nm, 700 nm to 1 μm, etc.

[0049] In some embodiments, the mass fraction of the first substance is 70% to 100% based on the total mass of the first material layer; and / or, the mass fraction of the second substance is 70% to 100% based on the total mass of the second material layer. In the embodiments of this application, the first substance is the main material of the first material layer, and the second substance is the main material of the second material layer. The first and second material layers can be manufactured by spraying, roller coating, or magnetron sputtering, etc. The first material layer may include only the first substance, or it may also include an adhesive, etc. The second material layer may include only the second substance, or it may also include an adhesive, etc. Wherein, based on the total mass of the first material layer, the mass fraction of the first substance can be 70%, 80%, 83%, 88%, 90%, 96%, 100%, etc., or a range of any two of the above values, such as 70% to 83%, 83% to 88%, 88% to 100%, etc. Based on the total mass of the second material layer, the mass fraction of the second material can be 70%, 80%, 81%, 86%, 93%, 97%, 100%, etc., or a range of any two of the above values, such as 70%–81%, 81%–93%, 93%–100%, etc.

[0050] In some embodiments, the first material layer further includes a first adhesive, and / or the second material layer further includes a second adhesive. By providing the first and second adhesives, the fabrication of the first and second material layers is facilitated, resulting in better film-forming properties. The first and second adhesives can be the same or different. The first adhesive may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. The second adhesive includes one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0051] In some embodiments, the manganese-containing positive electrode active material includes spinel lithium nickel manganese oxide. In this application embodiment, the average charging voltage of spinel lithium nickel manganese oxide is relatively high. Under high voltage, the electrolyte is prone to HF corrosion, leading to material instability and significant manganese ion dissolution. The first and / or second substances in the lithium-ion secondary battery of this application embodiment can effectively capture manganese ions, significantly improving the rapid capacity decay of the lithium-ion secondary battery and enhancing its stability. In this application embodiment, the spinel lithium nickel manganese oxide may also be doped with other metal elements, such as one or more of Ta, Al, V, Fe, Cu, Co, P, Nb, Mo, and Na, or coated with other coating layers.

[0052] The average voltage value of the first charge cycle is common knowledge in the field and has a common meaning in the field. It can be measured by methods and instruments in the field.

[0053] In some embodiments, the manganese-containing positive electrode active material includes materials with the structural formula Li. a Mn b T c O d The material, wherein T includes one or more of Ni, Na, Si, P, Nb, Mo, Te, Ta, Al, K, V, Cr, Fe, Cu, Co, Zr, Ge, F, Cl, Br, and I, with 0.8 ≤ a ≤ 2, 0.5 ≤ b ≤ 2, 0 ≤ c ≤ 1, and 1.5 ≤ d ≤ 4. In the embodiments of this application, the manganese-containing positive electrode active material includes the material with the above-mentioned structural formula, and the manganese-containing positive electrode active material has good charge-discharge performance. The manganese-containing positive electrode active material may also include a coating layer, which coats a material with the structural formula Li. a Mn b T c O d The surface of the material can be coated with materials such as carbon, and the embodiments of this application do not limit the specific material of the coating. For example, manganese-containing positive electrode active materials include spinel lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 Lithium manganese oxide (LiMn2O4), spinel lithium manganese oxide (Li2MnO3), layered lithium-rich manganese oxide (Li2MnO3), lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, olivine manganese iron phosphate (LiMn2O4), etc. 0.9 Fe 0.1 PO4, LiMn 0.6 Fe 0.4 PO4), lithium manganese iron phosphate and carbon composites, etc.

[0054] This application also provides a positive electrode sheet, comprising a positive current collector, a positive active material layer, and a first material layer; the positive active material includes a manganese-containing positive active material, and the positive active material layer is disposed on at least one side of the positive current collector; the first material layer is disposed on the side of the positive active material layer opposite to the positive current collector, and the mass ratio of the first material to the manganese-containing positive active material is (1.1-15):100, wherein the first material includes one or more of carbon materials, polyoxygenated compounds, halogenated compounds, and nitrogen-containing compounds, and the specific surface area of ​​the carbon material is greater than or equal to 200 m². 2 / g and less than or equal to 3000m 2 / g. In this embodiment of the application, the positive electrode sheet is provided with a first material layer, so that after the positive electrode sheet is assembled into a lithium-ion secondary battery, the first material layer can capture the Mn dissolved from the positive electrode active material layer. 2+ Manganese ions are present. By controlling the mass ratio of the first substance to the manganese-containing positive electrode active material within the above range, it is possible to capture manganese ions and, on the other hand, to achieve a larger specific capacity in the lithium-ion secondary battery assembled from the positive electrode.

[0055] In some embodiments, the carbon material, polyoxyalkylene compound, halogenated compound, and nitrogen-containing compound are the same materials as the second manganese scavenger of the first aspect, and will not be described in detail here. The volume average particle size DV50 of the second manganese scavenger is also the same as that of the second manganese scavenger of the first aspect, and will not be described in detail here.

[0056] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0057] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0058] In some embodiments, the positive electrode active material includes the manganese-containing positive electrode active material of the first aspect described above. The positive electrode active material may also include positive electrode active materials known in the art for lithium-ion batteries. As an example, the positive electrode active material may also include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium nickel cobalt oxides, and LiNi... 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)) and composites of lithium iron phosphate and carbon.

[0059] In some embodiments, the positive electrode active material layer may optionally include a binder. The binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0060] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0061] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a positive current collector and drying it to obtain a positive active material layer; coating the positive active material layer with a slurry containing the first substance, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0062] This application also provides a negative electrode sheet, comprising a negative electrode current collector, a negative electrode active material layer, and a second material layer; the negative electrode active material layer is disposed on at least one side of the negative electrode current collector; the second material layer is disposed on the side of the negative electrode active material layer opposite to the negative electrode current collector, and the mass ratio of the second material to the manganese-containing positive electrode active material of the positive electrode sheet to be assembled is (1.1-15):100, the second material comprising one or more of carbon materials, polyoxyalkylene compounds, halogenated compounds, and nitrogen-containing compounds; the specific surface area of ​​the carbon material is greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 / g. In the embodiments of this application, the second substance can capture manganese ions, and the Mn dissolved from the manganese-containing positive electrode active material... 2+ After manganese ions are captured by the first material layer, a driving voltage exists during the charging and discharging process of the lithium-ion secondary battery. Under the action of the driving voltage, some manganese ions will still move towards the negative electrode. In the embodiment of this application, the negative electrode is provided with a second material layer, which can capture the Mn dissolved from the manganese-containing positive electrode active material layer. 2+ The amount of manganese ions reaching the negative electrode active material layer is reduced by controlling the mass ratio of the second substance to the manganese-containing positive electrode active material within the above range.

[0063] In some embodiments, the carbon material, polyoxyalkylene compound, halogenated compound, and nitrogen-containing compound are the same material as the second substance of the first aspect, and will not be described in detail here. The volume average particle size DV50 of the second substance is also the same as that of the second substance of the first aspect, and will not be described in detail here.

[0064] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0065] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0066] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0067] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0068] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0069] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0070] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0071] A second aspect of this application provides an electrical device including the lithium-ion secondary battery of the first aspect. In embodiments of this application, the battery device possesses at least the same advantages as the lithium-ion secondary battery of the first aspect.

[0072] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device according to an embodiment of this application.

[0073] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of one embodiment of the vehicle 1000 of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during starting, navigation, and driving.

[0074] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0075] Please refer to Figure 2 , Figure 2 This is an exploded structural diagram of an embodiment of the battery 100 of this application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, jointly defining a space for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 jointly define the space; alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0076] In battery 100, there can be multiple battery cells 20. These multiple battery cells 20 can be connected in series, in parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel. Multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and then the whole assembly of multiple battery cells 20 is housed in the housing 10. Alternatively, battery 100 can also be composed of multiple battery cells 20 first connected in series, in parallel, or in a mixed manner to form a battery module, and then multiple battery modules are connected in series, in parallel, or in a mixed manner to form a whole, which is then housed in the housing 10.

[0077] The battery cell 20 can be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes.

[0078] Please refer to Figure 3 , Figure 3 This is an exploded structural diagram of one embodiment of the battery cell 20 of this application. Figure 3 In this context, X, Y, and Z represent the directions of the three-dimensional spatial coordinate axes. A battery cell 20 refers to the smallest unit that makes up the battery 100. The battery cell 20 includes an end cap 21, a casing 22, a cell assembly 23, and other functional components.

[0079] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, allowing battery cell 20 to have higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with cell assembly 23 to output or input electrical energy to battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this application embodiment does not impose special limitations on this. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0080] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the cell assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 can be used to close the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the cell assembly 23. The material of the housing 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special limitations on this.

[0081] The cell assembly 23 is the component in the battery cell 20 where the electrochemical reaction occurs. The casing 22 may contain one or more cell assemblies 23. The cell assembly 23 is mainly formed by winding or stacking positive and negative electrode plates, and typically a separator is provided between the positive and negative electrode plates. The portions of the positive and negative electrode plates containing active material constitute the main body of the cell assembly, while the portions of the positive and negative electrode plates without active material each constitute a tab 23a. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery 100, the positive and negative active materials react with the electrolyte, and the tabs 23a connect to the electrode terminals 21a to form a current loop.

[0082] [Isolation membrane]

[0083] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0084] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0085] [Electrolytes]

[0086] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0087] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0088] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0089] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, ethylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone, dimethyl glycol ether (DME), tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethoxymethane, 1,2-dimethoxyethylene and diethylene glycol dimethyl ether.

[0090] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0091] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into a battery cell assembly using a winding or stacking process.

[0092] The beneficial effects of this application are further illustrated below with reference to the embodiments.

[0093] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0094] 1) Preparation of lithium-ion secondary batteries

[0095] 1.1) Preparation of positive electrode sheet.

[0096] The positive electrode active material, conductive carbon black (Super P), and PVDF were mixed at a mass ratio of 96:2.5:1.5. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added, and the mixture was stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was coated onto aluminum foil and dried to obtain a positive electrode active material layer. In this embodiment, the positive electrode active material is LiNi. 0.5 Mn 1.5 O4. The loading of positive electrode active material on both sides of the positive current collector is 0.017 g / cm³. 2 .

[0097] N-methylpyrrolidone solvent was added to activated carbon and stirred until homogeneous. This mixture was then coated onto the positive electrode active material layer, dried, and used to form the first material layer. The material was then cold-pressed and slit to form the positive electrode sheet. The specific surface area of ​​the activated carbon was 200 m². 2 / g, the volume average particle size DV50 of activated carbon is 5μm; the mass ratio of activated carbon to positive electrode active material is 1.1:100.

[0098] 1.2) Preparation of negative electrode sheet.

[0099] Artificial graphite (anode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) were mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 96:1:1:2 to form a uniform negative electrode slurry. This slurry was then uniformly coated onto the surface of a copper foil current collector, and dried to obtain a layer of negative electrode active material. This yielded the negative electrode sheet. The loading of the negative electrode active material on one side of the current collector was 0.007 g / cm³. 2 .

[0100] Deionized water is added to activated carbon and stirred until homogeneous. This mixture is then coated onto the negative electrode active material layer, dried to form the second material layer, and cold-pressed and slit to produce the positive electrode sheet. The specific surface area of ​​the activated carbon is 200 m² / g. 2 / g, the volume average particle size DV50 of activated carbon is 5μm; the mass ratio of activated carbon to positive electrode active material is 1.1:100.

[0101] 1.3) Separation membrane.

[0102] A 12μm thick polypropylene film (16mm in diameter) was used as the separator.

[0103] 1.4) Electrolyte.

[0104] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then dissolved in this solution to obtain an electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L.

[0105] 1.5) Assembly of lithium-ion secondary batteries.

[0106] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the anode and cathode for isolation. These are then wound to obtain a bare cell. The bare cell is placed in outer packaging, injected with prepared electrolyte, and undergoes processes such as sealing, formation, and venting to obtain the battery.

[0107] The specific testing methods for the relevant parameters are as follows:

[0108] 2) Electrochemical performance testing.

[0109] 2.1) Initial discharge capacity test.

[0110] At 25°C, the lithium-ion secondary battery was charged at a constant current of 0.3C to a voltage of 4.9V, then charged at a constant voltage of 4.9V to a current of 0.05C. After resting for 5 minutes, the lithium-ion secondary battery was discharged at a constant current of 0.33C to a voltage of 3.0V. This discharge capacity is the first-cycle discharge capacity of the lithium-ion secondary battery. Dividing this capacity by the mass of the positive electrode active material in the lithium-ion secondary battery gives the initial discharge specific capacity of the positive electrode active material.

[0111] 2.2) High-temperature cycle performance test of lithium-ion secondary batteries.

[0112] At 45℃, the lithium-ion secondary battery is charged at a constant current of 0.5C to a voltage of 4.9V, then charged at a constant voltage of 4.9V to a current of 0.05C. After resting for 5 minutes, the lithium-ion secondary battery is discharged at a constant current of 0.5C to a voltage of 3.0V. This constitutes one charging cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. After performing the cycle charging test in the above manner, the cycle ends when the discharge capacity decays to 80% of the initial capacity. The total number of cycles is the high-temperature cycle life.

[0113] 3) Manganese leaching test.

[0114] The lithium-ion secondary battery, after cycling and degradation to 80% of its initial capacity, was discharged to 2.8V. The battery was disassembled, the negative electrode was removed, and the negative electrode was soaked in DMC for 15 minutes. The negative electrode was then removed and dried. Approximately 2g of powder from the dried negative electrode was scraped off, and inductively coupled plasma (ICP) spectroscopy was performed to determine the Mn mass content of the negative electrode.

[0115] 4) X-ray electron energy dispersive spectroscopy (EDS).

[0116] The electrode slices are placed on the scanning electron microscope (SEM) stage, and the samples are imaged under the electron beam generated by the electron gun to obtain the SEM microstructure of the samples.

[0117] After obtaining the SEM microstructure, the equipment is switched to scanning electron microscope X-ray energy dispersive spectroscopy (EDS) mode, and a full-field scan is performed within a specific field of view. When the electron beam interacts with the sample, the atoms in the sample are excited, emitting specific characteristic X-rays that are received by the EDS detector, allowing for analysis of the elemental composition of the corresponding region.

[0118] 5) Volume average particle size Dv50 test.

[0119] Equipment Model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer; Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009; Specific Test Procedure: Take an appropriate amount of the sample to be tested (the sample concentration should be 8%-12% light-blocking), add 20ml of deionized water, and simultaneously incubate for 5 minutes (53KHz / 120W) to ensure complete dispersion of the sample. Then, measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0120] Examples 2-12 are similar to Example 1, as detailed in Table 1.

[0121] Comparative Example 1

[0122] 1.1) Preparation of positive electrode sheet.

[0123] The positive electrode active material was mixed with conductive carbon black (Super P) and PVDF at a mass ratio of 96:2.5:1.5, and an appropriate amount of solvent N-methylpyrrolidone (NMP) was added. The mixture was stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was coated onto aluminum foil, dried, cold-pressed, and slit to obtain positive electrode sheets. The loading of the positive electrode active material on the positive electrode sheet was 0.016 g / cm³. 2 In this embodiment, the positive electrode active material is LiNi. 0.5 Mn 1.5 O4. The loading of positive electrode active material on both sides of the positive electrode current collector is 0.017 g / cm³. 2 .

[0124] 1.2) Preparation of negative electrode sheet.

[0125] Artificial graphite (anode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) were mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 96:1:1:2 to form a uniform negative electrode slurry. This slurry was then uniformly coated onto the surface of a copper foil current collector, and dried to obtain a layer of negative electrode active material. This yielded the negative electrode sheet. The loading of the negative electrode active material on one side of the current collector was 0.007 g / cm³. 2 .

[0126] Everything else is the same as in Example 1.

[0127] Comparative Example 2

[0128] The difference from Example 1 is that the mass ratio of the first substance to the manganese-containing positive electrode active material is 0.05:100, and the mass ratio of the second substance to the manganese-containing positive electrode active material is 0.05:100. Everything else is the same as in Example 1.

[0129]

[0130] Based on Comparative Examples 1 and 2, the lithium-ion secondary batteries of Examples 1-12 of this application have an initial discharge specific capacity of 102 mAh / g, which is a relatively good initial discharge specific capacity. The lithium-ion secondary batteries of Examples 1-12 of this application have 102-284 cycles when cycling to 80% of their initial capacity at 45°C. Compared to Comparative Examples 1 and 2, the number of cycles when cycling to 80% of their initial capacity at 45°C is increased for the lithium-ion secondary batteries of Examples 1-12 of this application. This indicates that by setting a first material layer and / or a second material layer, and controlling the mass ratio of the first material to the manganese-containing positive electrode active material to (1.1-15):100 and the mass ratio of the second material to the manganese-containing positive electrode active material to (1.1-15):100, the high-temperature cycle life of the lithium-ion secondary batteries can be improved. When the lithium-ion batteries of Examples 1 to 12 of this application are cycled to 80% of their initial capacity, the amount of Mn dissolved on the negative electrode side is 90ppm to 902ppm based on the total mass of the negative electrode active material layer. Compared with 970ppm and 1002ppm of Comparative Examples 1 and 2, the amount of Mn dissolved on the negative electrode side of Examples 1 to 12 of this application is significantly reduced.

[0131] like Figure 4a The image shown is a cross-sectional scanning electron microscope image of the positive electrode sheet of Embodiment 7 of this application. It can be seen from the image that a positive electrode active material layer is formed underneath, and a first material layer is formed on top of the active material layer. For example... Figure 4b The image shown is an X-ray electron spectrum of the positive electrode sheet of Embodiment 7 of this application, wherein... Figure 4b The cyan-blue color represents phosphorus.

[0132] The above are merely embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A lithium-ion secondary battery, characterized in that, It includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive active material layer disposed on the positive current collector. The positive active material includes a manganese-containing positive active material. The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector. The positive electrode further includes a first material layer, and / or the negative electrode further includes a second material layer; The first material layer is disposed on the side of the positive electrode active material layer away from the positive electrode current collector. The first material layer comprises a first substance, and the mass ratio of the first substance to the manganese-containing positive electrode active material is (1.1-15):

100. The first substance comprises one or more of a first compound, a carbon material, and a halogenated compound. The first compound comprises one or more of a compound containing a polyoxygen group and nitrogen element. The specific surface area of ​​the carbon material is greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 / g; The second material layer is disposed on the side of the negative electrode active material layer away from the negative electrode current collector. The second material layer includes a second substance, and the mass ratio of the second substance to the manganese-containing positive electrode active material is (1.1-15):

100. The first substance includes one or more of a first compound, a carbon material, and a halogenated compound. The first compound includes one or two of a compound containing a polyoxygen group and nitrogen element. The specific surface area of ​​the carbon material is greater than or equal to 200 m². 2 / g, and less than or equal to 3000m 2 / g.

2. The lithium-ion secondary battery according to claim 1, characterized in that, The mass ratio of the first substance to the manganese-containing positive electrode active material is (3-10):100, and / or the mass ratio of the second substance to the manganese-containing positive electrode active material is (3-10):

100.

3. The lithium-ion secondary battery according to claim 1 or 2, characterized in that, The carbon material includes one or more of carbon nanotubes, Ketjen black, and activated carbon; and / or, The first compound comprises one or more of the following: silicon dioxide, lithium phosphate, lithium silicate, lithium sulfate, polyacrylic acid, lithium polyacrylate, sodium para-aminosalicylic acid, lithium nitride, and lanthanum nitrate; and / or, The halogenated compounds include one or more of the compounds formed from Group I and Group VII, and the compounds formed from Group II and Group VII.

4. The lithium-ion secondary battery according to any one of claims 1-3, characterized in that, The halogenated compound includes one or more of potassium fluoride, lithium fluoride, and calcium chloride.

5. The lithium-ion secondary battery according to any one of claims 1 to 4, characterized in that, The volume average particle size (DV50) of the first substance is 100 nm to 10 μm; the volume average particle size (DV50) of the second substance is 100 nm to 10 μm.

6. The lithium-ion secondary battery according to any one of claims 1 to 5, characterized in that, The volume average particle size (DV50) of the first substance is 100 nm to 1 μm; the volume average particle size (DV50) of the second substance is 100 nm to 1 μm.

7. The lithium-ion secondary battery according to any one of claims 1 to 6, characterized in that, Based on the total mass of the first material layer, the mass fraction of the first material is 70% to 100%; and / or, based on the total mass of the second material layer, the mass fraction of the second material is 70% to 100%.

8. The lithium-ion secondary battery according to any one of claims 1 to 7, characterized in that, The first material layer further includes a first adhesive, and / or the second material layer further includes a second adhesive.

9. The lithium-ion secondary battery according to any one of claims 1 to 8, characterized in that, The manganese-containing positive electrode active material includes materials with the structural formula Li. a Mn b T c O d The material, wherein T includes one or more of Ni, Na, Si, P, Nb, Mo, Te, Ta, Al, K, V, Cr, Fe, Cu, Co, Zr, Ge, F, Cl, Br, and I, with 0.8≤a≤2, 0.5≤b≤2, 0≤c≤1, and 1.5≤d≤4.

10. The lithium-ion secondary battery according to any one of claims 1 to 9, characterized in that, The manganese-containing positive electrode active material includes spinel lithium nickel manganese oxide.

11. An electrical appliance, characterized in that, Includes the lithium-ion secondary battery as described in any one of claims 1 to 10.

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