Composite cathode active material and method of making, and related devices comprising the same

Abstract

The present application relates to a composite positive electrode active material and a preparation method thereof, and a related device comprising the same. The composite positive electrode active material comprises an electrically conductive tubular body and an active material layer arranged on the surface of the electrically conductive tubular body, wherein the active material layer comprises a compound with a molecular formula of Li 1+x Mn y Ni z Co (1‑x‑y‑z) O2, wherein 0 The composite positive electrode active material of the present application can improve the rate performance of a battery cell when applied to the battery cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, and more particularly, to a composite positive electrode active material and a preparation method thereof, and a related device comprising the same. BACKGROUND

[0002] Battery cells have reliable working performance, and no pollution, no memory effect, and other advantages, and are widely used. For example, as environmental protection issues are increasingly valued, new energy vehicles are increasingly popular, and the demand for power battery cells will show explosive growth.

[0003] However, as the application range of battery cells becomes more and more extensive, the performance of battery cells has also been severely challenged. In order to improve the performance of battery cells, the positive electrode active material in the battery cell is usually optimized and improved. However, the rate performance of the positive electrode active material for battery cells is poor. SUMMARY

[0004] The present application provides a composite positive electrode active material and a preparation method thereof, and a related device comprising the same. The composite positive electrode active material of the present application can improve the rate performance of battery cells when applied to battery cells.

[0005] In a first aspect, the present application provides a composite positive electrode active material, which comprises a conductive tubular body and an active material layer arranged on the surface of the conductive tubular body, the active material layer comprises a compound with a molecular formula of Li 1+ x Mn y Ni z Co (1-x-y-z) O2, wherein 0

[0006] Thus, the present application sets a conductive tubular body, so that the compound is attached to the surface of the conductive tubular body to form an active material layer. The composite positive electrode active material takes the conductive tubular body as a support substrate, which can improve the overall structural strength of the composite positive electrode active material and is conducive to stabilizing the structure of the active material layer. Moreover, due to the limitation of the conductive tubular body, the thickness of the active material layer is relatively small, and the thickness of the active material layer is nanoscale, which is conducive to shortening the migration path of active ions in the active material layer, improving the migration rate of active ions, improving the ion transmission capacity, and improving the rate performance of battery cells using the composite positive electrode active material, i.e. improving the ability to charge and discharge under large current. Moreover, the conductive tubular body has excellent electrical conductivity, the electron transmission capacity is improved, the overall electrical conductivity of the composite positive electrode active material is improved, and the capacity is relatively larger, thereby further improving the rate performance of battery cells.

[0007] In some embodiments, the average tube diameter of the composite positive electrode active material is L0, in units of nm, and 200≤L0≤430; optionally, 200≤L0≤330. When the average tube diameter of the composite positive electrode active material is within the above range, the size of the composite positive electrode active material as a whole is small, which can further shorten the migration path of active ions and improve the rate performance of the battery cell.

[0008] In some embodiments, the thickness of the active material layer is A, in units of nm, and 80≤A≤200; optionally, 80≤A≤150. When the thickness of the active material layer is within the above range, the thickness of the active material layer is relatively small, which can further shorten the migration path of active ions and further improve the rate performance of the battery cell.

[0009] In some embodiments, 0.2≤x≤0.6; optionally, 0.2≤x≤0.3.

[0010] In some embodiments, 0.2≤y≤0.6.

[0011] In some embodiments, 0.1≤z≤0.5; optionally, 0.1≤z≤0.45;

[0012] In some embodiments, the compound comprises Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, Li 1.3 Mn 0.23 Ni 0.23 Co 0.24 O2, Li 1.2 Mn 0.6 Ni 0.2 O2, Li 1.2 Mn 0.4 Ni 0.4 O2, and Li 1.2 Mn 0.54 Ni 0.2 Co 0.06 O2. When the compound in the composite positive electrode active material of the embodiments satisfies the above range, the rate performance of the battery cell can be improved on the basis of improving the specific capacity of the composite positive electrode active material.

[0013] In some embodiments, the average tube diameter of the conductive tubular body is L, in units of nm, and 20≤L≤70; and / or the average length of the conductive tubular body is H, in units of μm, and 1≤H≤5. When the size of the conductive tubular body of the embodiments satisfies the above range, the size of the active material layer in the tube diameter direction can be better controlled, the migration path of active ions can be shortened, and the rate performance of the battery cell can be improved.

[0014] In some embodiments, the conductive tubular body comprises carbon nanotubes and / or carbon fibers. When the material of the conductive tubular body in the composite positive electrode active material of the embodiments satisfies the above range, the conductive tubular body can better support the active material layer and control the size of the active material layer in the direction of the tube diameter, thereby improving the rate performance of the battery cell.

[0015] In some embodiments, the mass percentage of the active material layer based on the mass of the composite positive electrode active material is W1%, and the mass percentage of the conductive tubular body based on the mass of the composite positive electrode active material is W2%, wherein 9≤W1 / W2≤33; optionally, 9≤W1 / W2≤25. Further optionally, 90≤W1≤97; and / or 3≤W2≤10. When the mass percentages of the active material layer and the conductive tubular body satisfy the above relationship, the thickness of the active material layer is relatively small on the basis of the support of the conductive tubular body to the active material layer, which can further shorten the migration path of the active ions and improve the rate performance of the battery cell.

[0016] In a second aspect, the present application provides a method for preparing a composite positive electrode active material, comprising:

[0017] adding the conductive tubular body and the first polymer into a first solvent to mix a first spinning solution;

[0018] dissolving the lithium source, the transition metal source, and the second polymer in a second solvent to mix a second spinning solution;

[0019] coaxially electrospinning the first spinning solution and the second spinning solution to prepare a precursor;

[0020] sequentially drying and calcining the precursor to obtain a composite positive electrode active material,

[0021] wherein the composite positive electrode active material comprises a conductive tubular body and an active material layer arranged on the surface of the conductive tubular body, and the active material layer comprises a compound with a molecular formula of Li 1+x Mn y Ni z Co (1-x-y-z) O2, wherein 0

[0022] In some embodiments, the lithium source comprises one or more of lithium hydroxide, lithium acetate, lithium chloride, lithium nitrate; and / or the transition metal source comprises a manganese source, a nickel source, and a cobalt source; optionally, the manganese source comprises one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese acetate, manganese carbonate; and / or the nickel source comprises one or more of nickel nitrate, nickel sulfate, nickel chloride, nickel acetate, nickel hydroxide; and / or the cobalt source comprises one or more of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, cobalt hydroxide.

[0023] In a third aspect, the present application provides a battery cell, comprising a positive electrode sheet, wherein the positive electrode sheet comprises the composite positive electrode active material according to any one of the embodiments of the first aspect of the present application or prepared by the method according to any one of the embodiments of the second aspect of the present application.

[0024] In a fourth aspect, the present application provides a battery, comprising the battery cell according to the third aspect of the present application.

[0025] In a fifth aspect, the present application provides an electric device, comprising the battery according to the fourth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained according to the drawings without creative labor for those skilled in the art.

[0027] Figure 1 is a schematic diagram of an embodiment of the battery cell of the present application.

[0028] Figure 2 is an exploded schematic diagram of the embodiment of the battery cell of Figure 1

[0029] Figure 3 is a schematic diagram of an embodiment of the battery module of the present application.

[0030] Figure 4 is a schematic diagram of an embodiment of the battery pack of the present application.

[0031] Figure 5 is an exploded schematic diagram of the embodiment of the battery pack of Figure 4

[0032] Figure 6 is a schematic diagram of an embodiment of the electric device comprising the battery cell of the present application as a power supply.

[0033] The drawings are not necessarily drawn according to the actual proportions.​​

[0034] Reference signs are explained as follows:

[0035] 1: battery pack; 2: upper case; 3: lower case; 4: battery module

[0036] 5: battery cell; 51: case; 52: electrode assembly

[0037] 53: cover plate

[0038] 6: power consuming device DETAILED DESCRIPTION

[0039] Hereinafter, specific embodiments of the composite positive electrode active material and the method for producing the same, the battery cell, the battery, and the power consuming device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters that are already well known, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0040] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise specified, a numerical range "a-b" represents a shorthand manner of describing the arbitrary real number combinations between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all the real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not otherwise specified.

[0042] If not particularly specified, all the technical features of the present application and optional technical features can be combined with each other to form new technical solutions.

[0043] If not particularly specified, all the steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method mentioned can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0044] If not particularly specified, the "comprise" and "include" mentioned in the present application are open-ended, and can also be closed. For example, the "comprise" and "include" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0045] If not particularly specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, either of the following conditions satisfies the condition "A or B": 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).

[0046] The battery cell comprises a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprises a positive electrode film layer containing a positive electrode active material, and the negative electrode sheet comprises a negative electrode film layer containing a negative electrode active material. The electronic conduction path and the ionic conduction path of the battery cell are separated from each other, and active ions such as lithium ions, sodium ions, etc. migrate inside the battery cell, for example, during charging and discharging of the battery cell, the electrolyte with ion conductivity provides a path for the active ions, so that the active ions are deintercalated in the positive and negative electrode materials; electrons are transmitted in the external circuit to form a charging and discharging current, ensuring the balance of total charge.

[0047] The positive electrode active material comprises at least one of a variety of substances, such as a lithium-rich manganese-based material, a polyanion material, etc.; since the transition metal layer of the lithium-rich manganese-based material contains lithium, it can release relatively more lithium ions, has a high specific capacity, and has the advantages of high voltage platform, large energy density, low price, environmental friendliness, etc., so that the lithium-rich manganese-based material has a significant advantage in the positive electrode active material.

[0048] However, the first coulombic efficiency of the lithium-rich manganese-based material is low, the irreversible capacity loss is large, the conductivity is relatively poor, and the active ion diffusion is difficult, resulting in that the cycle performance and rate performance of the battery cell are not ideal when the lithium-rich manganese-based material is applied to the battery cell. In order to improve the conductivity of the lithium-rich manganese-based material, in the related technology, the conductive material and the lithium-rich manganese-based material are usually compounded into a composite positive electrode active material, and the lithium-rich manganese-based material is coated with the conductive material to improve the overall conductivity of the composite positive electrode active material. However, the lithium-rich manganese-based material prepared by the above coating method has a large particle size and a long lithium ion transmission path, so even if the surface of the lithium-rich manganese-based material is coated with a carbon layer with excellent conductivity, the improvement of the rate performance of the material is still very limited.

[0049] To solve the above problems, the application provides a composite positive electrode active material. The lithium-rich manganese-based material with a specific molecular formula is arranged outside a conductive tubular body, the conductive tubular body constitutes a core part, the lithium-rich manganese-based material constitutes a shell layer, and the two constitute a core-shell structure. The conductive tubular body can improve the overall conductivity of the composite positive electrode active material, and because the conductive tubular body limits the thickness of the shell layer to a certain extent, that is, limits the material size in the radial direction, the migration path of the active ion is relatively short, so the rate performance of the battery cell using the composite positive electrode active material can be improved.

[0050] Composite cathode active material

[0051] The application provides a composite positive electrode active material. The composite positive electrode active material comprises a conductive tubular body and an active material layer arranged on the surface of the conductive tubular body, the active material layer comprises a compound with a molecular formula of Li 1+ x Mn y Ni z Co (1-x-y-z) O2, wherein 0 < x < 1, 0 < y < 1, 0 < z < 1, and 0 < x + y + z ≤ 1.

[0052] Although the mechanism is not very clear, the composite positive electrode active material of the application can significantly improve the rate performance of the battery cell when applied to the battery cell.

[0053] The conductive tubular body can be understood as a tubular structure, which can be a hollow structure or a solid structure. The hollow structure can be a structure with both ends open or at least one end closed. The conductive tubular body can be compared to a cylindrical structure, and the average pipe diameter of the conductive tubular body is equivalent to the average pipe diameter of the cylinder. The length of the conductive tubular body is equivalent to the length of the cylinder.

[0054] The active material layer is located on the outer surface of the conductive tubular body, and the active material layer is a whole layer structure, which can be understood as a hollow tubular structure arranged outside the conductive tubular body. The active material layer is a shell layer, and the conductive tubular body is a core part, and the two constitute a core-shell structure.

[0055] Compound Li 1+x Mn y Ni z Co (1-x-y-z) The lithium and transition metal in O2 respectively occupy the position of the center of the octahedron formed by surrounding six oxygen, and are arranged alternately in the direction of c-axis according to O-Li-O-transition metal atom layer. The lithium in the compound will additionally occupy the transition metal layer and orderly arrange with the manganese Mn, forming a special lattice structure, which makes the lithium content in the compound relatively high, so that the specific capacity of the compound is relatively high. However, the above-mentioned compound has relatively poor rate performance due to its special crystal structure.

[0056] The present application sets the conductive tubular body, so that the compound is attached to the surface of the conductive tubular body to form an active material layer, and the composite positive electrode active material takes the conductive tubular body as the supporting substrate, which can improve the overall structural strength of the composite positive electrode active material and is conducive to stabilizing the structure of the active material layer. And due to the limitation of the conductive tubular body, the thickness of the active material layer is relatively small, and the thickness of the active material layer is nanoscale, which is conducive to shortening the migration path of active ions in the active material layer, improving the migration rate of active ions, improving the ion transmission capacity, and improving the rate performance of the battery monomer using the composite positive electrode active material, that is, improving the ability of charging and discharging under large current. Moreover, the conductive tubular body has excellent conductivity, the electron transmission capacity is improved, the overall conductivity of the composite positive electrode active material is improved, and the capacity is relatively larger, so as to further improve the rate performance of the battery monomer.

[0057] In some embodiments, the average tube diameter of the composite positive electrode active material is L0, and the unit is nm, 200≤L0≤430. When the average tube diameter of the composite positive electrode active material is in the above range, the size of the overall composite positive electrode active material is small, which can further shorten the migration path of active ions and improve the rate performance of the battery monomer. Alternatively, 200≤L0≤330.

[0058] For example, the average tube diameter of the composite positive electrode active material is 200 nm, 210 nm, 220 nm, 230 nm, 250 nm, 260 nm, 280 nm, 300 nm, 320 nm, 330 nm, 350 nm, 360 nm, 380 nm, 400 nm, 430 nm, or a range composed of any two of the above values.

[0059] In some embodiments, the thickness of the active material layer is A, in nm, and 80≤A≤200; alternatively, 80≤A≤150. When the thickness of the active material layer is within the above range, the thickness of the active material layer is relatively small, which can further shorten the migration path of the active ions, and can further improve the rate performance of the battery cell.

[0060] For example, the thickness of the active material layer is 80 nm, 100 nm, 120 nm, 150 nm, 160 nm, 180 nm, 200 nm, or a range defined by any two of the above values.

[0061] In the present application, the thickness of the active material layer has the meaning known in the art, and can be measured by using the devices and methods known in the art, for example, by transmission electron microscopy (TEM) or ion polishing section (CP).

[0062] The compound in the composite positive electrode active material of the embodiments of the present application is further selected to better play a synergistic effect with the conductive tubular body, and on the basis of improving the specific capacity of the composite positive electrode active material, the rate performance of the battery cell is improved.

[0063] In some embodiments, 0.2≤x≤0.6; alternatively, 0.2≤x≤0.5; 0.2≤x≤0.4; 0.2≤x≤0.3; for example, 0.2≤x≤0.6, 0

[0064] In some embodiments, 0.2≤y≤0.6; alternatively, 0.2≤y≤0.55; 0.3≤y≤0.55; 0.4≤y≤0.6; for example, 0

[0065] In some embodiments, 0.1≤z≤0.5; alternatively, 0.1≤z≤0.45; 0.1≤z≤0.4; 0.15≤z≤0.4; 0.1≤z≤0.35; 0.15≤z≤0.35; for example, 0

[0066] In some embodiments, the compound comprises Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, Li 1.3 Mn 0.23 Ni 0.23 Co 0.24 O2, Li 1.2 Mn 0.6 Ni 0.2 O2, Li 1.2 Mn 0.4Ni 0.4 O2and Li 1.2 Mn 0.54 Ni 0.2 Co 0.06 one or more of O2and Li.

[0067] At least one of the material and the size of the conductive tubular body in the composite positive electrode active material of the embodiments of the present application is further selected, so as to better play a synergistic effect with the active material layer, on the basis of improving the specific capacity of the composite positive electrode active material, the rate performance of the battery cell is improved.

[0068] In some embodiments, the conductive tubular body comprises carbon nanotubes and / or carbon fibers.

[0069] In some embodiments, the average tube diameter of the conductive tubular body is L, the unit is nm, and 20≤L≤70. Exemplarily, the average tube diameter of the conductive tubular body is 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, or a range composed of any two of the above values.

[0070] In some embodiments, the average length of the conductive tubular body is H, the unit is μm, and 1≤H≤5. Exemplarily, the average length of the conductive tubular body is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range composed of any two of the above values.

[0071] In the present application, the average tube diameter and the average length of the conductive tubular body are the meanings known in the art, which can be detected by using the devices and methods known in the art, for example, can be measured by scanning electron microscope (SEM) or transmission electron microscope (TEM).

[0072] In the embodiments of the present application, the active material layer can improve the specific capacity of the composite positive electrode active material, and as the mass content of the active material layer increases, the specific capacity of the composite positive electrode active material also increases; the conductive tubular body can improve the electrical conductivity of the composite positive electrode active material, but the effect of the conductive tubular body on the specific capacity is small, and as the mass content of the conductive tubular body increases, the electrical conductivity of the composite positive electrode active material also increases, but the specific capacity of the composite positive electrode active material may have a downward trend. In order to improve the specific capacity and electrical conductivity of the composite positive electrode active material, in some embodiments, the mass percentage content of the active material layer is W1% based on the mass of the composite positive electrode active material; the mass percentage content of the conductive tubular body is W2% based on the mass of the composite positive electrode active material, wherein 9≤W1 / W2≤33. Optionally, 9≤W1 / W2≤25. For example, W1 / W2 can be 9, 10, 12, 15, 16, 18, 19, 20, 22, 25, 28, 30, 31, 32, 32.5, 33 or a range formed by any two of the above values.

[0073] When the mass percentage contents of the active material layer and the conductive tubular body satisfy the above relationship, on the basis of the conductive tubular body providing support for the active material layer, the thickness of the active material layer is relatively small, which can further shorten the migration path of active ions and improve the rate performance of the battery cell.

[0074] In some embodiments, 90≤W1≤97. Optionally, 90≤W1≤95. For example, the mass percentage content of the active material layer can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or a range formed by any two of the above values.

[0075] In some embodiments, 3≤W2≤10. Optionally, 3≤W2≤5. For example, the mass percentage content of the conductive tubular body can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range formed by any two of the above values.

[0076] In the present application, the mass percentage content of the active material layer has the meaning known in the art and can be detected by using the devices and methods known in the art, for example, the mass percentage content of the active material layer can be detected by thermogravimetric analysis (TGA) in view of the relatively large difference in thermal decomposition temperature between the active material layer and the conductive tubular body; specifically, the sample is placed in an oxygen atmosphere and heat treated to decompose the conductive tubular body (for example, the conductive carbon nanotube is decomposed at 600°C, while the lithium-rich manganese-based material will not be decomposed due to the thermal decomposition temperature greater than 900°C), and the remaining substance is weighed and calculated to obtain the mass percentage content of the active material layer. Accordingly, the mass percentage content of the conductive tubular body is calculated.

[0077] Method of producing a composite cathode active material

[0078] The application also provides a method for preparing a composite positive electrode active material, the method comprising:

[0079] In step S100, a conductive tubular body and a first polymer are added to a first solvent and mixed into a first spinning solution;

[0080] In step S200, a lithium source, a transition metal source and a second polymer are dissolved in a second solvent and mixed into a second spinning solution;

[0081] In step S300, the first spinning solution and the second spinning solution are coaxially electrospun to prepare a precursor;

[0082] In step S400, the precursor is sequentially dried and calcined to obtain a composite positive electrode active material,

[0083] The composite positive electrode active material comprises a conductive tubular body and an active material layer arranged on the surface of the conductive tubular body, and the active material layer comprises a compound with a molecular formula of Li 1+x Mn y Ni z Co (1-x-y-z) O2, wherein 0 < x < 1, 0 < y < 1, 0 < z < 1, and 0 < x + y + z ≤ 1.

[0084] The method of the application uses a spinning process to prepare a composite positive electrode active material, which can form a core-shell structure of the conductive tubular body and the active material layer, and the thickness of the active material layer is uniform, and the performance of the composite positive electrode active material is uniform and stable.

[0085] In step S100, in some embodiments, the first solvent can include one or more of N,N-dimethylformamide, anhydrous ethanol, and N-methyl pyrrolidone.

[0086] In some embodiments, the first polymer can include one or more of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polypyrrolidone (PVP).

[0087] In step S200, in some embodiments, the second solvent can include one or more of N,N-dimethylformamide, anhydrous ethanol, and N-methyl pyrrolidone. The first solvent and the second solvent can be selected from the same material or different materials. When the same material is selected, the compatibility of the first spinning solution and the second spinning solution is better, which can further improve the bonding interface between the active material layer and the conductive tubular body.

[0088] In some embodiments, the second polymer can include one or more of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polypyrrolidone (PVP). The first polymer and the second polymer can be made of the same material or different materials. When the first polymer and the second polymer are made of the same material, the first spinning solution and the second spinning solution have better compatibility, which can further improve the bonding interface between the active material layer and the conductive tubular body.

[0089] In some embodiments, the transition metal source can be a transition metal salt. Specifically, the transition metal source includes at least one of a manganese source, a nickel source, and a cobalt source.

[0090] In some embodiments, the lithium source includes one or more of lithium hydroxide, lithium acetate, lithium chloride, and lithium nitrate.

[0091] In some embodiments, the manganese source includes one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese acetate, and manganese carbonate.

[0092] In some embodiments, the nickel source includes one or more of nickel nitrate, nickel sulfate, nickel chloride, nickel acetate, and nickel hydroxide.

[0093] In some embodiments, the cobalt source includes one or more of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt hydroxide.

[0094] In step S300, in some embodiments, the temperature for spinning is 20-30°C; and / or the voltage is 8-10 kV.

[0095] In some embodiments, the injection speed during the spinning process is 0.02-0.06 mL / h.

[0096] In step S400, in some embodiments, the drying can remove the first solvent and the second solvent in the precursor, and the drying temperature can be greater than or equal to the boiling point temperature of the first solvent and the second solvent, for example, 70°C.

[0097] In some embodiments, the calcination can be performed in multiple steps. Specifically, a pre-calcination can be performed in an oxygen or air atmosphere, and the sintering temperature is 450-550°C, and the holding time is 4-6 h. The pre-calcination can make the transition metal source and the lithium source form a stoichiometric ratio of the active material layer.

[0098] After being cooled to room temperature, the crucible containing the material is transferred to an argon furnace (inert atmosphere) for high-temperature sintering, and the sintering temperature is 800-900°C, and the holding time is 8-10 h. The high-temperature sintering can enhance ion diffusion and control the crystal structure of the material.

[0099] Prior to step S100, the method further includes step S500, pretreating the conductive structure. Specifically, impurities on the surface of the conductive structure are removed in a concentrated acid mixture. The concentrated acid mixture is composed of concentrated sulfuric acid and concentrated nitric acid, with a volume ratio of 3:1.

[0100] Battery cell

[0101] This application also provides a battery cell.

[0102] A battery cell, also known as a rechargeable battery or accumulator, is a battery that can be recharged after discharge to activate its active materials and continue to be used. Typically, a battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is positioned between the positive and negative electrodes, primarily serving to prevent short circuits between them while allowing active ions to pass through.

[0103] The battery cell of this application includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes the composite positive electrode active material of the first aspect of this application. Therefore, the battery cell of this application can improve cycle performance and rate performance.

[0104] [Positive electrode plate]

[0105] In some embodiments, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0106] In some embodiments, the positive electrode film layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the positive electrode film layer, the mass percentage content of the positive electrode conductive agent is ≤5 wt%.

[0107] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass percentage of the positive electrode binder is ≤5 wt% based on the total weight of the positive electrode film layer.

[0108] In some embodiments, the positive current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymeric material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0109] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing a composite positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0110] [Negative electrode plate]

[0111] A single battery cell also includes a negative electrode plate.

[0112] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0113] The negative electrode active material may be any negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy materials.

[0114] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage content of the negative electrode conductive agent is ≤5 wt%.

[0115] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder is ≤5 wt% based on the total weight of the negative electrode film layer.

[0116] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc. In some embodiments, the mass percentage of the other additives is ≤2 wt% based on the total weight of the negative electrode film.

[0117] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0118] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0119] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0120] Electrolyte

[0121] In some implementations, the battery cell also includes an electrolyte.

[0122] During the charging and discharging process of a single battery cell, active ions repeatedly insert and extract between the positive and negative electrode plates, while the electrolyte acts as a conductor for these active ions. The embodiments of this application do not impose any particular restrictions on the type of electrolyte; it can be selected according to actual needs.

[0123] The electrolyte comprises an electrolyte salt and a solvent. The types of electrolyte salt and solvent are not specifically limited and can be selected according to actual needs.

[0124] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0125] As an example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0126] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0127] [Isolation membrane]

[0128] In some implementations, the battery cell also includes a separator.

[0129] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0130] 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.

[0131] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process and / or a stacking process.

[0132] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0133] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a soft package, such as a pouch. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0134] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 The example shown is a square-structured battery cell 5.

[0135] In some implementations, such as Figure 2As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process and / or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted according to requirements.

[0136] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0137] In some embodiments of this application, the battery cells according to this application can be assembled into a battery module. The number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0138] Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0139] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0140] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0141] Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0142] The battery in this application includes one or more battery cells. When the battery includes multiple battery cells, the battery may include a battery module and a battery pack.

[0143] Electric device

[0144] This application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack described in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0145] The electrical device can be configured to use individual battery cells, battery modules, or battery packs according to its usage requirements.

[0146] Figure 6 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0147] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0148] Examples

[0149] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0150] Example

[0151] Example A-1

[0152] Carbon nanotube / active material layer Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 preparation

[0153] (1) Remove impurities from the surface of carbon nanotubes in a mixed solution of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1);

[0154] (2) The purified carbon nanotubes and polyacrylonitrile were dissolved in N,N-dimethylformamide to form spinning solution A;

[0155] (3) Lithium hydroxide, manganese sulfate, nickel sulfate and cobalt sulfate are dissolved in N,N-dimethylformamide in stoichiometric ratio, polyacrylonitrile is added and mixed evenly to form spinning solution B, wherein the molar ratio of lithium ions, manganese ions, nickel ions and cobalt ions is 1.2:0.54:0.13:0.13;

[0156] (4) The inner shaft uses spinning solution A and the outer shaft uses spinning solution B. The spinning precursor is prepared by coaxial electrospinning.

[0157] (5) The spinning precursor was dried at 70℃ for 5 hours and then calcined in stages. The first stage was pre-calcined in a muffle furnace at 500℃ for 5 hours. After the muffle furnace cooled to room temperature, the crucible was transferred to an argon furnace for sintering at 850℃ for 10 hours. After cooling, the carbon nanotube / active material layer Li was obtained. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, in which the carbon nanotubes are hollow carbon nanotubes.

[0158] Examples A-21 to Examples A-37

[0159] The carbon nanotube / active material layer Li was prepared using a method similar to that used in Example A-1. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, unlike Example A-1, Examples A-21 to A-33 adjusted the mass ratio of carbon nanotubes and active material layers.

[0160] Example B

[0161] Carbon nanotube / active material layer Li 1.3 Mn 0.23 Ni 0.23 Co 0.24 O2 preparation

[0162] (1) Remove impurities from the surface of carbon nanotubes in a mixed solution of concentrated sulfuric acid and concentrated nitric acid;

[0163] (2) The purified carbon nanotubes and polyacrylonitrile were dissolved in N,N-dimethylformamide to form spinning solution A;

[0164] (3) Lithium hydroxide, manganese nitrate, nickel nitrate and cobalt nitrate are dissolved in N,N-dimethylformamide in stoichiometric ratio, polyacrylonitrile is added and mixed evenly to form spinning solution B, wherein the molar ratio of lithium ions, manganese ions, nickel ions and cobalt ions is 1.3:0.23:0.23:0.24;

[0165] (4) The inner shaft uses spinning solution A and the outer shaft uses spinning solution B. The spinning precursor is prepared by coaxial electrospinning.

[0166] (5) The spinning precursor was dried at 70℃ for 5 hours, and then calcined in stages. The first stage was pre-calcined in a muffle furnace at 500℃ for 5 hours. After the muffle furnace cooled to room temperature, the crucible was transferred to an argon furnace for sintering at 850℃ for 10 hours. After cooling, a hollow tubular carbon nanotube / active material layer Li was obtained. 1.3 Mn 0.23 Ni 0.23 Co 0.24 O2.

[0167] Example C

[0168] Carbon nanotube / active material layer Li 1.2 Mn 0.6 Ni 0.2 O2 preparation

[0169] (1) Remove impurities from the surface of carbon nanotubes in a mixed solution of concentrated sulfuric acid and concentrated nitric acid;

[0170] (2) The purified carbon nanotubes and polyacrylonitrile were dissolved in N,N-dimethylformamide to form spinning solution A;

[0171] (3) Lithium acetate, manganese acetate, and nickel acetate are dissolved in N,N-dimethylformamide in stoichiometric ratio, and polyacrylonitrile is added and mixed evenly to form spinning solution B, wherein the molar ratio of lithium ions, manganese ions, and nickel ions is 1.2:0.6:0.2;

[0172] (4) The inner shaft uses spinning solution A and the outer shaft uses spinning solution B. The spinning precursor is prepared by coaxial electrospinning.

[0173] (5) The spinning precursor was dried at 70℃ for 5 hours, and then calcined in stages. The first stage was pre-calcined in a muffle furnace at 450℃ for 4.5 hours. After the muffle furnace cooled to room temperature, the crucible was transferred to an argon furnace for sintering at 900℃ for 10 hours. After cooling, a hollow tubular carbon nanotube / active material layer Li was obtained. 1.2 Mn 0.6 Ni 0.2 O2.

[0174] Comparative Example N

[0175] Composite cathode active material (carbon nanotubes and spherical Li) 1.2 Mn 0.54 Ni 0.13 Co 0.13 Preparation of O2 composite materials

[0176] High-temperature ball milling was used to process spherical Li particles. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 and carbon nanotubes (mass ratio 93:7) are mechanically mixed and ball-milled at 500 r / min for at least 6 hours. The carbon nanotubes are then incorporated into the Li... 1.2 Mn 0.54 Ni 0.13 Co 0.13 In the O2 material, the size of the carbon nanotubes is the same as that in Example A-1.

[0177] Comparative Example M

[0178] Composite positive electrode active material (active material layer Li) 1.2 Mn 0.54 Ni 0.13 Co 0.13 Preparation of O2

[0179] The specific preparation steps are as follows:

[0180] (1) Remove impurities from the surface of carbon nanotubes in a mixed solution of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1);

[0181] (2) The purified carbon nanotubes and polyacrylonitrile were dissolved in N,N-dimethylformamide to form spinning solution A;

[0182] (3) Lithium hydroxide, manganese sulfate, nickel sulfate and cobalt sulfate are dissolved in N,N-dimethylformamide in stoichiometric ratio, polyacrylonitrile is added and mixed evenly to form spinning solution B, wherein the molar ratio of lithium ions, manganese ions, nickel ions and cobalt ions is 1.2:0.54:0.13:0.13;

[0183] (4) The inner shaft uses spinning solution A and the outer shaft uses spinning solution B. The spinning precursor is prepared by coaxial electrospinning.

[0184] (5) The spinning precursor was dried at 70℃ for 5 hours, and then calcined in stages. The first stage was pre-calcined in a muffle furnace at 500℃ for 5 hours, then heated to 850℃ for 10 hours to burn off the carbon nanotubes. After cooling, the hollow tubular active material layer Li was obtained. 1.2 Mn 0.54 Ni0.13 Co 0.13 O2.

[0185] Example 1

[0186] Preparation of lithium-ion batteries

[0187] 1. Preparation of positive electrode sheet

[0188] Aluminum foil with a thickness of 12μm was used as the positive electrode current collector.

[0189] The composite positive electrode active material prepared in Example A-1, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an appropriate amount of solvent NMP at a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry. The positive electrode slurry was uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0190] 2. Preparation of negative electrode sheet

[0191] A copper foil with a thickness of 8μm was used as the negative electrode current collector.

[0192] The negative electrode active material graphite, the binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na), and the conductive agent carbon black (Super P) are mixed in an appropriate amount of deionized water at a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly coated onto the surface of the negative electrode current collector copper foil. After drying and cold pressing, the negative electrode sheet is obtained.

[0193] 3. Separating membrane

[0194] Porous polyethylene (PE) membrane is used as the separator.

[0195] 4. Preparation of electrolyte

[0196] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC) and diethyl carbonate (DMC) are mixed at a volume ratio of 1:1 to obtain an electrolyte solvent. Subsequently, lithium hexafluorophosphate is mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0197] 5. Preparation of lithium-ion batteries

[0198] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrode assembly is then wound up. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0199] Examples 2-1 to 4-2

[0200] Lithium-ion batteries were prepared using a method similar to that of Example 1. The difference from Example 1 is that the types of composite positive electrode active materials were adjusted in Examples 2-1 to 4-2.

[0201] Comparative Example 1

[0202] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 is that Comparative Example 1 used the composite active material prepared by Comparative Example N.

[0203] Comparative Example 2

[0204] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 is that Comparative Example 2 used the composite active material prepared by Comparative Example M.

[0205] The data for the examples and comparative examples are shown in Table 1.

[0206] Test section

[0207] 1. Battery cell rate performance test

[0208] At 25°C, the battery cell is charged at a constant current of 0.5C to 4.6V, then charged at a constant voltage of 4.6V until the current is less than 0.05C. The battery cell is then discharged at a constant current of 2C to 3.0V to obtain the discharge capacity at 2C.

[0209] 2. First Coulombic Efficiency Test of Battery Cells

[0210] After formation, the battery cells are first charged to 4.6V at 25℃ and 0.5C, then charged to 0.05C at a constant voltage of 4.6V. After resting for 10 minutes, they are discharged at a constant current of 0.5C with a cutoff voltage of 3.0V (5 cells per group). The first-cycle charging capacity and first-cycle discharging capacity of the battery cells are obtained. The first coulombic efficiency of the battery cells is then calculated according to the following formula.

[0211] First-week coulombic efficiency (%) = (first-week discharge capacity / first-week charge capacity) × 100%.

[0212] Test results

[0213] Table 1

[0214]

[0215] As shown in Table 1, Comparative Example 1 uses a high-temperature ball milling process to mix lithium-rich manganese-based materials and carbon nanotubes to form a composite positive electrode active material. The lithium-rich manganese-based material consists of multiple particles, and the carbon nanotubes are mainly dispersed in the gaps formed by the multiple particles of the lithium-rich manganese-based material. Since carbon nanotubes are conductive, the introduction of carbon nanotubes can improve the overall conductivity of the composite positive electrode active material. However, carbon nanotubes have little effect on the performance of the lithium-rich manganese-based material. Therefore, although this material can improve the overall conductivity of the composite positive electrode active material to a certain extent, the improvement on rate performance is limited.

[0216] In Comparative Example 2, the lithium-rich manganese-based material was prepared as a hollow tubular active material by electrospinning, but this active material had little effect on improving the rate performance and first coulombic efficiency of lithium-ion batteries.

[0217] In Embodiment 1 of this application, a conductive tubular body is formed as the core and a lithium-rich manganese-based material is formed as the shell through electrospinning. The two components form a core-shell structure, which works synergistically to significantly improve the overall conductivity of the composite cathode active material and shorten the migration path of active ions, thereby improving the rate performance of the battery cell using the composite cathode active material. Furthermore, Embodiments 2 to 4 further improve the rate performance of the battery cell by adjusting the structural dimensions of the shell and core. The structural forms of the embodiments of this application are applicable to lithium-rich manganese-based materials with different molecular formulas, such as Embodiments B and C, all of which can improve the rate performance of the battery cell.

[0218] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A composite positive electrode active material, comprising a conductive tubular body and an active material layer disposed on the surface of the conductive tubular body, wherein the active material layer comprises materials with the molecular formula Li 1+x Mn y Ni z Co (1-x-y-z) Compounds of O2, among which, 0<x<1, 0<y<1, 0<z<1, 0<x+y+z≤1.

2. The composite positive electrode active material according to claim 1, wherein, The average diameter of the composite positive electrode active material is L0, and its unit is nm, where 200≤L0≤430.

3. The composite positive electrode active material according to claim 2, wherein, 200≤L0≤330。 4. The composite positive electrode active material according to claim 1 or 2, wherein, The thickness of the active material layer is A, and its unit is nm, where 80≤A≤200.

5. The composite positive electrode active material according to claim 4, wherein, 80≤A≤150。 6. The composite positive electrode active material according to claim 1, wherein, 0.2≤x≤0.6; and / or 0.2≤y≤0.6; and / or 0.1≤z≤0.

5.

7. The composite positive electrode active material according to claim 6, wherein, 0.2≤x≤0.3。 8. The composite positive electrode active material according to claim 6, wherein, 0.1≤z≤0.45。 9. The composite positive electrode active material according to claim 1, wherein, The compound includes Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, Li 1.3 Mn 0.23 Ni 0.23 Co 0.24 O2, Li 1.2 Mn 0.6 Ni 0.2 O2, Li 1.2 Mn 0.4 Ni 0.4 O2 and Li 1.2 Mn 0.54 Ni 0.2 Co 0.06 One or more of O2.

10. The composite positive electrode active material according to claim 1, wherein, The average diameter of the conductive tubular body is L, with units of nm, where 20 ≤ L ≤ 70; and / or the average length of the conductive tubular body is H, with units of μm, where 1 ≤ H ≤ 5.

11. The composite positive electrode active material according to claim 1, wherein, The conductive tubular body includes carbon nanotubes and / or carbon fibers.

12. The composite positive electrode active material according to claim 1, wherein, Based on the mass of the composite positive electrode active material, the mass percentage of the active material layer is W1%; based on the mass of the composite positive electrode active material, the mass percentage of the conductive tubular body is W2%, wherein 9≤W1 / W2≤33.

13. The composite positive electrode active material according to claim 12, wherein, 9≤W1 / W2≤25.

14. The composite positive electrode active material according to claim 12, wherein, 90≤W1≤97; and / or 3≤W2≤10.

15. A method for preparing a composite positive electrode active material, comprising: The conductive tubular body and the first polymer are added to the first solvent and mixed to form the first spinning solution; The lithium source, the transition metal source, and the second polymer are dissolved in the second solvent and mixed to form the second spinning solution; The first spinning solution and the second spinning solution are coaxially electrospun to prepare a precursor. The precursors were sequentially dried and calcined to obtain a composite positive electrode active material. The composite positive electrode active material comprises a conductive tubular body and an active material layer disposed on the surface of the conductive tubular body, wherein the active material layer comprises Li 1+x Mn y Ni z Co (1-x-y-z) Compounds of O2, wherein 0 < x < 1, 0 < y < 1, 0 < z < 1, 0 < x + y + z ≤ 1.

16. The method according to claim 15, wherein, The lithium source includes one or more of lithium hydroxide, lithium acetate, lithium chloride, and lithium nitrate; and / or the transition metal source includes a manganese source, a nickel source, and a cobalt source.

17. The method according to claim 16, wherein, The manganese source includes one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese acetate, and manganese carbonate; and / or The nickel source includes one or more of nickel nitrate, nickel sulfate, nickel chloride, nickel acetate, and nickel hydroxide; and / or The cobalt source includes one or more of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt hydroxide.

18. A battery cell comprising a positive electrode, said positive electrode comprising a composite positive electrode active material as described in any one of claims 1 to 14 or a composite positive electrode active material prepared by any one of claims 15 to 17.

19. A battery comprising a battery cell as described in claim 18.

20. An electrical device comprising the battery as claimed in claim 19.

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