Battery monomer, battery device, power utilization device and positive pole piece

Abstract

The invention discloses a battery monomer, a battery device, a power utilization device and a positive pole piece. A positive pole piece of the battery monomer comprises a positive current collector and a positive film layer positioned on at least one side of the positive current collector, and the positive film layer comprises a first lithium supplement additive and a second lithium supplement additive; the first lithium supplement additive comprises a lithium-rich metal oxide; the second lithium supplement additive comprises one or more of compounds shown as LiaNi < 1-b > M < 1 > O < c >; the molar content of Li in the first lithium supplement additive is greater than that of Li in the second lithium supplement additive; the average long diameter of the first lithium supplement additive particles is 2-10 [mu] m, the average long diameter of the second lithium supplement additive particles is 2-10 [mu] m, and the ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles is 0.3-4. The battery monomer has long cycle life.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of battery technology, in particular to a battery cell, a battery device, a power utilization device, and a positive electrode sheet. BACKGROUND

[0002] Battery cells are widely used in mobile phones, notebook computers, electric vehicles, electric aircraft, electric ships, electric toys, and electric tools. In the development of battery cells, how to improve the cycle life of battery cells is one of the problems to be solved at present. SUMMARY

[0003] To solve the above technical problems, the present disclosure provides a battery cell, a battery device, a power utilization device, and a positive electrode sheet, which has a long cycle life.

[0004] In a first aspect, the embodiments of the present disclosure provide a battery cell, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer comprising a first lithium supplementing additive and a second lithium supplementing additive; the first lithium supplementing additive comprising a lithium-rich metal oxide; the second lithium supplementing additive comprising Li a Ni 1-b M 1 b O c one or more of the compounds shown in the formula, wherein 0 < a ≤ 2.2, 0 ≤ b < 1, 0.8 ≤ c ≤ 2.2, M 1 comprising one or more of Cu, Mg, Zn, Mn, Al, Zr, or Ti; the molar content of Li elements in the first lithium supplementing additive is greater than the molar content of Li elements in the second lithium supplementing additive; the average length-diameter of the first lithium supplementing additive particles is 2 μm-10 μm, the average length-diameter of the second lithium supplementing additive particles is 2 μm-10 μm, and the ratio of the average length-diameter of the first lithium supplementing additive particles to the average length-diameter of the second lithium supplementing additive particles is 0.3-4.

[0005] In the battery cell of the embodiments of the present disclosure, the positive electrode film layer of the positive electrode sheet comprises the first lithium supplementing additive and the second lithium supplementing additive. The first lithium supplementing additive comprises a lithium-rich metal oxide, and the molar content of Li elements is high, thereby being able to provide a high capacity and compensate for the irreversible loss of active lithium ions in the charging and discharging process. However, in the delithiation process of the first lithium supplementing additive, part of the lattice oxygen of the lithium supplementing metal oxide will be oxidized to produce superoxide anions O ² or O . O ² and O RH +The intermediates such as the above can cause continuous decomposition of the electrolyte and gas production, and affect the cycle life of the battery cell. According to the experimental results, when the second lithium supplement additive is included in the positive electrode film layer, and the ratio of the average length diameter of the first lithium supplement additive particles to the average length diameter of the second lithium supplement additive particles is between 0.3 and 4, the gas production of the battery cell during storage and cycling can be effectively reduced.

[0006] The researchers speculate that the second lithium supplement additive can react with the RH + and capture the hydrogen ions that are easily reduced. When the particle size of the first lithium supplement additive and the second lithium supplement additive meets the range of the embodiments of the present disclosure, the reaction rate of the lattice oxygen of the first lithium supplement additive with the electrolyte to generate intermediates and the reaction rate of the second lithium supplement additive with the intermediates are close, so that the second lithium supplement additive can quickly consume the intermediates, thereby effectively reducing the side reactions of the intermediates in the electrolyte and the negative electrode, and further reducing the gas production of the battery cell during storage and cycling.

[0007] The embodiments of the present disclosure can improve the lithium supplement capacity and reduce the gas production of the battery cell during storage and cycling, thereby improving the cycle life of the battery cell, by regulating the composition and particle size of the first lithium supplement additive and the second lithium supplement additive.

[0008] In some embodiments, the ratio of the average length diameter of the first lithium supplement additive particles to the average length diameter of the second lithium supplement additive particles is 0.4-2, which can be 0.6-1.8. In this way, the gas production of the battery cell during storage and cycling can be reduced, and the lithium supplement uniformity of the positive electrode film layer can be improved.

[0009] In some embodiments, the average length diameter of the first lithium supplement additive particles is 4-7 μm. In this way, the lithium supplement capacity of the first lithium supplement additive can be improved, thereby improving the cycle performance of the battery cell.

[0010] In some embodiments, the average length diameter of the second lithium supplement additive particles is 4-7 μm. In this way, the cycle life of the battery cell can be prolonged, and the second lithium supplement additive can be used in a smaller amount, thereby improving the average lithium supplement capacity of the first lithium supplement additive and the second lithium supplement additive as a whole.

[0011] In some embodiments, the mass ratio of the first lithium supplement additive to the second lithium supplement additive is 0.5:1-3.5:1. In this way, the lithium supplement capacity can be improved, and the gas production of the battery cell during storage and cycling can be reduced, thereby improving the cycle life of the battery cell.

[0012] In some embodiments, the first lithium supplement additive accounts for 0.1%-3% of the mass of the positive electrode film layer, and can alternatively account for 0.1%-2%. In this way, a suitable additional lithium source can be provided in the positive electrode to compensate for the irreversible lithium loss during the first charging process of the battery cell, thereby improving the first coulomb efficiency, energy density, and cycle life of the battery cell.

[0013] In some embodiments, the second lithium supplement additive accounts for 0.01%-2% of the mass of the positive electrode film layer, and can alternatively account for 0.03%-1.2%. In this way, the gas production of the battery cell during storage and cycling can be reduced.

[0014] In some embodiments, the first lithium supplement additive comprises a core and a coating layer located on the surface of the core.

[0015] The core comprises lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles.

[0016] The coating layer comprises a first coating layer and a second coating layer, the first coating layer is located on the surface of the core, and the second coating layer is located on the surface of the first coating layer away from the core; wherein the first coating layer comprises an oxide containing M 2 elements, the M 2 elements include one or more of Al, Zn, W, Zr, Mg, Ti, and Co; and the second coating layer comprises a carbon material.

[0017] In this way, under the condition of large-rate activation, the first lithium supplement additive can have a faster delithiation rate, a higher delithiation capacity, and fewer side reactions, thereby enabling the battery cell to have both long cycle life and high productivity.

[0018] In some embodiments, the average thickness of the first coating layer is 0.1 nm-10 nm, and can alternatively be 0.1 nm-5 nm. In this way, the delithiation capacity of the first lithium supplement additive can be effectively exerted, especially under the condition of large-rate activation.

[0019] In some embodiments, the average thickness of the second coating layer is 5 nm-20 nm, and can alternatively be 10 nm-20 nm. In this way, the second coating layer can have better coating uniformity, and can also have good electronic conductivity and smaller lithium ion diffusion resistance.

[0020] In some embodiments, the first coating layer is formed by an atomic layer deposition process. In this way, the compactness of the first coating layer can be improved, thereby effectively reducing the direct contact between the core and the electrolyte, reducing the occurrence of side reactions, and further improving the cycle performance of the battery cell.

[0021] In some embodiments, the first coating layer comprises aluminum oxide, zinc oxide, tungsten oxide, zirconium oxide, magnesium oxide, titanium oxide, cobalt oxide, and Li-M2 one or more of oxides represented by -O. Thereby, the cycle performance of the battery cell is improved.

[0022] In some embodiments, the I of the first lithium supplementing additive is 0.1-1, I D / I G 0.1-1, I D represents the intensity of the D peak of the Raman spectrum at 1350±50 cm -1 represents the intensity of the G peak of the Raman spectrum at 1580±50 cm G represents the intensity of the G peak of the Raman spectrum at 1580±50 cm -1 represents the intensity of the G peak of the Raman spectrum at 1580±50 cm. Thereby, the rate of lithium ion extraction in the lithium supplementing additive is improved, and the lithium supplementing efficiency is improved.

[0023] In some embodiments, the carbon material includes one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers.

[0024] In some embodiments, the mass content of the carbon element in the first lithium supplementing additive is 1%-5%, which can be 2.5%-3.5%. Thereby, the lithium supplementing additive can have both high electronic conductivity and high lithium supplementing capacity.

[0025] In some embodiments, the mass content of the M 2 element in the first lithium supplementing additive is 0.01%-2%, which can be 0.01%-0.1%. Thereby, the first lithium supplementing additive has good kinetics, so that the first lithium supplementing additive has high lithium supplementing efficiency.

[0026] In some embodiments, the powder resistivity of the first lithium supplementing additive under 12 MPa is 5 Ω•cm or less, which can be 0.5 Ω•cm-2 Ω•cm. Thereby, the rate of lithium ion extraction in the first lithium supplementing additive is accelerated, and the lithium supplementing efficiency of the first lithium supplementing additive is improved, especially under high-rate activation conditions.

[0027] In some embodiments, the lithium-rich metal oxide includes one or more of lithium-rich metal oxides containing A elements, the A elements including one or more of Co, Fe, V, Nb, Cr, Mo.

[0028] Optionally, the lithium-rich metal oxide includes one or more of Li3A 1 O4, Li5A 2 O4, and Li6A 3 O4, wherein A 1 includes one or more of V, Nb, Cr, Mo, A 2 includes one or more of Fe, Cr, V, Mo, A 3one or more of Co, V, Cr, Mo.

[0029] In a second aspect, the embodiments of the present disclosure provide a battery device, comprising a plurality of the battery cell of the first aspect.

[0030] In a third aspect, the embodiments of the present disclosure provide a power consumption device, comprising the battery cell of the first aspect or the battery device of the second aspect.

[0031] In a fourth aspect, the embodiments of the present disclosure provide a positive electrode tab, comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer comprising a first lithium supplementing additive and a second lithium supplementing additive; the first lithium supplementing additive comprising a lithium-rich metal oxide; the second lithium supplementing additive comprising Li a Ni 1-b M 1 b O c one or more of the compounds shown in the formula, wherein 0 1 one or more of Cu, Mg, Zn, Mn, Al, Zr or Ti; the molar content of Li element in the first lithium supplementing additive is greater than the molar content of Li element in the second lithium supplementing additive; the average length-diameter of the first lithium supplementing additive particles is 2-10 μm, the average length-diameter of the second lithium supplementing additive particles is 2-10 μm, and the ratio of the average length-diameter of the first lithium supplementing additive particles to the average length-diameter of the second lithium supplementing additive particles is 0.3-4.

[0032] In some embodiments, the ratio of the average length-diameter of the first lithium supplementing additive particles to the average length-diameter of the second lithium supplementing additive particles is 0.4-2, which can be 0.6-1.8.

[0033] In some embodiments, the average length-diameter of the first lithium supplementing additive particles is 4-7 μm.

[0034] In some embodiments, the average length-diameter of the second lithium supplementing additive particles is 4-7 μm.

[0035] In some embodiments, the mass ratio of the first lithium supplementing additive to the second lithium supplementing additive is 0.5:1-3.5:1.

[0036] In some embodiments, the first lithium supplementing additive comprises a core and a coating layer located on the surface of the core; The core comprises lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles; The coating layer comprises a first coating layer and a second coating layer, the first coating layer is located on the surface of the core, and the second coating layer is located on the surface of the first coating layer away from the core; wherein the first coating layer comprises M 2an oxide of an element, M 2 The element includes one or more of Al, Zn, W, Zr, Mg, Ti, Co; and the second coating layer includes a carbon material.

[0037] In some embodiments, the lithium-rich metal oxide includes one or more of a lithium-rich metal oxide including an element A, the element A including one or more of Co, Fe, V, Nb, Cr, Mo.

[0038] Optionally, the lithium-rich metal oxide includes one or more of Li3A 1 O4, Li5A 2 O4, and Li6A 3 O4, wherein A 1 includes one or more of V, Nb, Cr, Mo, A 2 includes one or more of Fe, Cr, V, Mo, A 3 includes one or more of Co, V, Cr, Mo. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments of the present disclosure will be briefly introduced below. Obviously, the drawings described below are only some of the embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the drawings.

[0040] Figure 1 A schematic diagram of a battery cell provided by some embodiments of the present disclosure is shown.

[0041] Figure 2 A schematic diagram of an electrical device provided by some embodiments of the present disclosure is shown.

[0042] In the drawings, the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0043] Hereinafter, the battery cell, the battery device, the electrical device, and the positive electrode sheet of the present disclosure are specifically disclosed, but unnecessary detailed descriptions will be omitted as appropriate with reference to the drawings. For example, there are cases where detailed descriptions of matters that are well known and repeated descriptions of actually 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 drawings and the following description are provided so that those skilled in the art can fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0044] The ranges disclosed herein are defined by their lower and upper limit. Any range defined by a lower limit and an upper limit can be approximated by any number of smaller ranges within the defined range. For example, a range of 60-120 is approximated by any number of ranges between 60 and 120, e.g., 60-64, 65-70, 71-80, 81-90, 91-100, 101-110, 111-120, etc. Any number of these smaller ranges can be defined as desired or necessary in order to depict the entire range implicitly defined. For example, a range of 60-120 can be approximated by any number of ranges between 60 and 120, e.g., 60-120, 60-80, 80-100, 100-120, etc. In the present disclosure, unless otherwise indicated, a numerical range "a-b" means and is equivalent to the range of any real combinations of values between "a" and "b", wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" means and is equivalent to the entire set of real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand for these value combinations. In addition, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present disclosure.

[0046] Unless otherwise specified, all technical features and optional technical features of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present disclosure.

[0047] Unless otherwise specified, all steps of the present disclosure 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) in sequence, or steps (b) and (a) in sequence. For example, it is mentioned that the method 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.

[0048] Unless otherwise specified, in the present disclosure, the terms "first", "second", etc. are used to distinguish different objects, and are not used to describe a specific order or primary and secondary relationship.

[0049] In the present disclosure, the terms "a plurality of", "a plurality of" refer to two or more.

[0050] In the description of the embodiments of the present disclosure, if there is no special indication, the first feature is "on" or "under" the second feature, which can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature can be "above", "over" and "on" the second feature, which can be that the first feature is directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature can be "under", "below" and "under" the second feature, which can be that the first feature is directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is less than that of the second feature.

[0051] Unless otherwise specified, the test temperature of each parameter mentioned in the present disclosure is 25°C.

[0052] The battery cell mentioned in the embodiments of the present disclosure can realize the function of charging and discharging alone, and can continue to be used by activating the active material through charging after discharging. The battery cell can be in the shape of a cylinder, a cuboid or other shapes, which are not limited in the embodiments of the present disclosure. For example, Figure 1 The battery cell 5 in the cuboid structure is taken as an example.

[0053] The battery apparatus mentioned in the embodiments of the present disclosure can include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can include a plurality of battery cells connected in series, in parallel or in a mixed connection through a busbar component.

[0054] In some embodiments, the battery cell assembly is usually formed by arranging a plurality of battery cells.

[0055] As an example, the battery cell assembly can be a battery module formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with a cable tie.

[0056] In some embodiments, the battery apparatus can be a battery pack including a box body and one or more battery cell assemblies accommodated in the box body.

[0057] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be accommodated in the box body by fixing the battery module in the box body.

[0058] As an example, the battery cell assembly can also be accommodated in the box body by directly fixing a plurality of battery cells in the box body.

[0059] As an example, the case can include a first case and a second case. The first case and the second case are fastened so that an inside of the case forms a closed space to accommodate the battery cell assembly. The closed here means covered or closed, which can be sealed or unsealed. The first case can be a top cover or a bottom plate.

[0060] As an example, the case can include a top cover, a frame and a bottom plate. The top cover and the bottom plate are connected with the frame respectively so that an inside of the case forms a closed space to accommodate the battery cell assembly.

[0061] In some embodiments, the case can be part of a chassis structure of a vehicle. For example, part of the case can be at least part of a floor of the vehicle, or part of the case can be at least part of a cross beam and a longitudinal beam of the vehicle.

[0062] The technical solutions described in the embodiments of the present disclosure are applicable to various electric devices using battery cells and battery devices, such as mobile devices (e.g., mobile phones, tablet computers, notebook computers, 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. The battery cells and battery devices are used to store or provide electric energy.

[0063] Figure 2 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0064] The battery cell provided by the embodiments of the present disclosure can include but is not limited to a lithium battery cell, such as a lithium ion battery cell, a lithium metal battery cell, etc.

[0065] The battery cell provided by the embodiments of the present disclosure includes an electrode assembly. The electrode assembly can be a jelly-roll structure or a stacked structure, and the embodiments of the present disclosure are not limited in this regard. The battery cell further includes an outer package, which can be used to encapsulate the electrode assembly. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as one or more of aluminum plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0066] The electrode assembly generally includes a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet, which serves to insulate the positive and negative electrodes to prevent short circuit.

[0067] During the first charging process of the battery cell, a solid electrolyte interface (SEI) film is formed on the negative electrode surface, which causes irreversible consumption of lithium ions. The rupture and repair of the SEI film during subsequent charging and discharging processes also continuously consumes active lithium ions. The introduction of a lithium supplement additive into the positive electrode can provide additional lithium ions to compensate for the irreversible loss of active lithium ions during charging and discharging, effectively improving the energy density and cycle life of the battery cell. Lithium-rich metal oxide lithium supplement additives represented by Li5FeO4 have the advantages of high theoretical capacity, simple synthesis, and low decomposition potential.

[0068] However, the kinetic performance of lithium-rich metal oxides is poor. To meet the needs of industrialization, lithium-rich metal oxides need to be activated at a higher voltage to quickly release lithium ions and exert the lithium supplement effect. However, during the delithiation process of lithium-rich metal oxides, lattice oxygen (O 2- ) in the structure participates in the oxidation reaction, and part of the lattice oxygen is oxidized to produce superoxide anions O ² or O . O ² and O have strong nucleophilicity and will attack non-aqueous organic solvents such as carbonate solvents in the electrolyte, producing intermediate products (such as RH + ), which will initiate a chain decomposition reaction, leading to electrolyte decomposition and hydrogen gas production. Moreover, during the storage or cyclic charging and discharging of the battery cell, the SEI film may be damaged, and the intermediate products, such as RH + , resulting from the reaction of O ² and O with the electrolyte, will contact the negative electrode and be reduced, leading to continuous electrolyte decomposition and gas production during storage or cyclic charging and discharging, affecting the cycle life of the battery cell.

[0069] In view of this, the battery cell provided by the embodiments of the present disclosure includes specific first and second lithium supplement additives in the positive electrode sheet, which can improve the cycle life of the battery cell.

[0070] The battery cell of the embodiments of the present disclosure includes a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector. For example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector. The positive electrode film layer includes a first lithium supplement additive and a second lithium supplement additive.

[0071] The first lithium supplement additive of the embodiments of the present disclosure includes a lithium-rich metal oxide.

[0072] The second lithium supplement additive of the present disclosure includes Li a Ni 1-b M 1 b O c one or more of the compounds shown in the formula, wherein 0 1 includes one or more of Cu, Mg, Zn, Mn, Al, Zr or Ti.

[0073] The molar content of Li element in the first lithium supplement additive is greater than the molar content of Li element in the second lithium supplement additive. The molar content of Li element refers to the number of moles of Li element contained in the supplement additive per amount of substance. For example, in the case that the amount of substance of the first lithium supplement additive and the second lithium supplement additive is the same, the number of Li + in the first lithium supplement additive is greater than the number of Li + in the second lithium supplement additive.

[0074] The average long diameter of the first lithium supplement additive particles is 2-10 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range consisting of any of the above values.

[0075] The average long diameter of the second lithium supplement additive particles is 2-10 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range consisting of any of the above values.

[0076] The ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles is 0.3-4, for example, it can be 0.3, 0.5, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.5, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, or a range consisting of any of the above values.

[0077] In the battery cell of the embodiments of the present disclosure, the positive film layer of the positive electrode sheet includes the first lithium supplement additive and the second lithium supplement additive. The first lithium supplement additive includes lithium-rich metal oxide, and the molar content of Li element is high, thereby being able to provide high capacity and compensate for the irreversible loss of active lithium ions in the charging and discharging process. However, in the process of delithiation of the first lithium supplement additive, part of the lattice oxygen of the lithium supplement metal oxide will be oxidized to produce superoxide anion O ² or O . O ² and O react with the electrolyte to produce RH+ The intermediate products such as the above can cause continuous decomposition of the electrolyte and gas production, affecting the cycle life of the battery cell. According to the experimental results, when the second lithium supplement additive is included in the positive electrode film layer and the ratio of the average length-diameter of the first lithium supplement additive particles to the average length-diameter of the second lithium supplement additive particles is between 0.3 and 4, the gas production of the battery cell during storage and cycling can be effectively reduced. The researchers speculate that the second lithium supplement additive can react with the intermediate products such as RH + and capture the easily-reduced hydrogen ions. When the particle size of the first lithium supplement additive and the second lithium supplement additive meets the range of the embodiments of the present disclosure, the rate of the side reaction of the lattice oxygen of the first lithium supplement additive with the electrolyte to generate intermediate products and the reaction rate of the second lithium supplement additive with the intermediate products are close, so that the second lithium supplement additive can quickly consume the intermediate products, thereby effectively reducing the side reaction of the intermediate products in the electrolyte and the negative electrode, and further reducing the gas production of the battery cell during storage and cycling.

[0078] The embodiments of the present disclosure can improve the cycle life of the battery cell by regulating the composition and particle size of the first lithium supplement additive and the second lithium supplement additive, thereby effectively reducing the gas production of the battery cell during storage and cycling.

[0079] The average length-diameter of the first lithium supplement additive particles and the average length-diameter of the second lithium supplement additive particles can be tested by ion polishing cross-section morphology analysis (CP) and scanning electron microscopy (SEM). Multiple test surfaces can be taken and the average value is taken as the test result. For example, the positive electrode film layer can be subjected to ion polishing cross-section morphology analysis (CP), and then the particle size, morphology, or combined element analysis results of different particles in the cross-section can be analyzed by SEM to distinguish the first lithium supplement additive particles and the second lithium supplement additive particles in the test surface. The two-dimensional projection image of the first lithium supplement additive particles and the second lithium supplement additive particles in the test surface is obtained, the longest straight line distance between two points on the particle contour in the projection image is measured to obtain the length-diameter of the particle. The average value of the length-diameter of the first lithium supplement additive particles and the average value of the length-diameter of the second lithium supplement additive particles in the test surface are calculated to obtain the average length-diameter of the first lithium supplement additive particles and the average length-diameter of the second lithium supplement additive particles.

[0080] In some embodiments, 0≤b≤0.5, for example, b can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a range consisting of any of the above values. In this way, the second lithium supplement additive can have a suitable rate of consuming intermediate products.

[0081] Alternatively, 0≤b≤0.2, for example, b can be 0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, or a range consisting of any of the above values.

[0082] In case b is 0, Li a Ni 1-b M 1 b O c The transition metal element in the compound shown as Li a Ni 1-b M 1 b O c The compound shown as is further doped with other transition metal elements, such as one or more of Cu, Mg, Zn, Mn, Al, Zr or Ti.

[0083] In some embodiments, the ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles can be 0.4-2, for example, can be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range consisting of any of the aforementioned numerical values.

[0084] Thus, it is beneficial to match the generation rate of the intermediate product with the reaction rate of the second lithium supplement additive with the intermediate product, to improve the rate of consumption of the intermediate product by the second lithium supplement additive, thereby effectively reducing the side reactions of the intermediate product in the electrolyte and the negative electrode, and further reducing the gas production of the battery cell during storage and cycling. The particle size of the first lithium supplement additive and the second lithium supplement additive meets the given range, which also allows the delithiation rates of the first lithium supplement additive and the second lithium supplement additive to be close, thereby improving the uniformity of lithium supplement of the positive electrode film.

[0085] Alternatively, the ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles can be 0.6-1.8, for example, can be 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or a range consisting of any of the aforementioned numerical values.

[0086] In some embodiments, the average long diameter of the first lithium supplement additive particles is 4-7 pm, for example, can be 4 pm, 4.2 pm, 4.4 pm, 4.6 pm, 4.8 pm, 5 pm, 5.2 pm, 5.4 pm, 5.6 pm, 5.8 pm, 6 pm, 6.2 pm, 6.4 pm, 6.6 pm, 6.8 pm, 7 pm, or a range consisting of any of the aforementioned numerical values.

[0087] The particle size of the first lithium supplement additive is within the above range, which can shorten the ion transmission path of the lithium-rich metal oxide and improve the kinetic performance of the lithium-rich metal oxide. Thus, the lithium supplement capacity of the first lithium supplement additive can be improved, thereby improving the cycle performance of the battery cell.

[0088] In some embodiments, the average long diameter of the second lithium supplement additive particle can be 4-7 μm, for example, can be 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5 μm, 5.2 μm, 5.4 μm, 5.6 μm, 5.8 μm, 6 μm, 6.2 μm, 6.4 μm, 6.6 μm, 6.8 μm, 7 μm, or a range consisting of any of the above values.

[0089] The particle size of the second lithium supplement additive is within the above range, which has good kinetic performance and large specific surface area, thereby not only having high lithium supplement efficiency, but also providing more active sites for reaction with intermediate products, accelerating the consumption rate of intermediate products, and reducing the side reactions of intermediate products in the electrolyte and the negative electrode. Thus, it is helpful to prolong the cycle life of the battery cell. The second lithium supplement additive has more active sites for reaction with intermediate products, and the unit mass of the second lithium supplement additive can consume more intermediate products, thereby also allowing the second lithium supplement additive to have less dosage, thereby improving the average lithium supplement gram capacity of the first lithium supplement additive and the second lithium supplement additive as a whole.

[0090] In some embodiments, the mass ratio of the first lithium supplement additive to the second lithium supplement additive is 0.5:1-3.5:1, for example, can be 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, or a range consisting of any of the above values.

[0091] The mass ratio of the first lithium supplement additive to the second lithium supplement additive meets the given range, on the one hand, the second lithium supplement additive can consume part of the lattice oxygen of the first lithium supplement additive and the side reaction intermediate products of the electrolyte, and on the other hand, the first lithium supplement additive and the second lithium supplement additive as a whole have high average lithium supplement gram capacity. Thus, the lithium supplement capacity can be improved while reducing the gas production of the battery cell during storage and cycling, thereby improving the cycle life of the battery cell.

[0092] In some embodiments, the first lithium supplement additive comprises a core and a coating layer located on the surface of the core.

[0093] The core comprises lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles.

[0094] The coating layer includes a first coating layer and a second coating layer, the first coating layer is located on the surface of the core, and the second coating layer is located on the surface of the first coating layer away from the core; wherein the first coating layer includes an oxide containing M 2 an element, M 2 The element includes one or more of Al, Zn, W, Zr, Mg, Ti and Co; and the second coating layer includes a carbon material.

[0095] The lithium-rich metal oxide is prone to polarization at a large activation rate, resulting in an actual delithiation capacity much lower than a theoretical value. In addition, after lithium ions are stripped at a large activation rate, the lithium-rich metal oxide has a large volume change, which intensifies the risk of dissolution of transition metal ions in the delithiation product of the lithium-rich metal oxide. The dissolved transition metal ions migrate to the negative electrode and are reduced, which not only damages the stability of the SEI film, but also catalyzes the decomposition of the electrolyte, thereby causing consumption of the electrolyte and affecting the cycle life of the battery cell.

[0096] The lithium-rich metal oxide particles with a single crystal or single crystal-like structure have high structural stability and a small volume change after lithium ions are stripped, which can reduce the dissolution of metal ions. The lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide single crystal-like particles with a small particle size are used as the lithium supplement agent, which can shorten the ion transport path, reduce the hindering effect of the grain boundary on lithium ion diffusion, improve the kinetic performance of the lithium-rich metal oxide, and also improve the structural stability of the delithiation product of the lithium-rich metal oxide and reduce the dissolution of metal ions in the delithiation product. However, the specific surface area of the lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide single crystal-like particles with a small particle size is large, and the contact area with the electrolyte is large. The lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide single crystal-like particles with a small particle size will undergo side reactions after contacting with the electrolyte. At a large activation rate, the side reactions of the lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide single crystal-like particles with a small particle size with the electrolyte will intensify, thereby affecting the lithium supplement capacity of the lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide single crystal-like particles with a small particle size and the cycle performance of the battery cell.

[0097] The first lithium supplement additive of the embodiment of the present disclosure includes a lithium-rich metal oxide single crystal particle and / or lithium-rich metal oxide single crystal-like particle core, and a first coating layer is coated on the surface of the core, the first coating layer includes an oxide containing M 2 an element, M 2The elements include one or more of Al, Zn, W, Zr, Mg, Ti, Co, which have good compactness, can reduce the contact between the lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles and the electrolyte, thereby reducing the side reaction of the lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles with the electrolyte. The electronic conduction performance of the above-mentioned type of metal oxide is poor, and the first lithium supplement additive of the embodiment of the present disclosure is coated with a second coating layer on the surface away from the core of the first coating layer, and the second coating layer includes a carbon material, which can improve the electronic conductivity of the first lithium supplement additive, thereby accelerating the rate of lithium ion extraction from the first lithium supplement additive and improving the lithium supplement efficiency of the first lithium supplement additive.

[0098] The first lithium supplement additive of the above-mentioned embodiment is less likely to have a side reaction with the electrolyte, and its delithiation product structure is stable and has less metal ion dissolution. Under large rate activation conditions, the first lithium supplement additive can have a faster delithiation rate, a higher delithiation capacity, and fewer side reactions. Thus, the battery cell can have both long cycle life and high capacity.

[0099] The terms "single crystal particles" and "single crystal-like particles" have the meanings known in the art. "Single crystal-like particles" are also known as quasi-single crystal particles, and generally refer to particles formed by agglomeration of a small number, for example less than 10, of highly consistent primary particles with crystallographic orientation.

[0100] In some embodiments, the average particle size of the core can be 2 μm-10 μm, and optionally 2 μm-7 μm.

[0101] In some embodiments, the average particle size of the lithium-rich metal oxide single crystal particles can be 2 μm-10 μm, and optionally 2 μm-7 μm.

[0102] In some embodiments, the average particle size of the lithium-rich metal oxide single crystal particles can be 2 μm-10 μm, and optionally 2 μm-7 μm.

[0103] In some embodiments, the average thickness of the first coating layer can be 0.1 nm-10 nm, for example, 0.1 nm, 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or a range consisting of any of the above values.

[0104] The average thickness of the first coating layer is between 0.1 nm and 10 nm, which can reduce the influence of the first coating layer on the electronic conduction performance of the first lithium supplement additive, and also allows the first coating layer to have a smaller lithium ion diffusion path. Thus, it is beneficial to the delithiation capacity of the first lithium supplement additive, especially under large rate activation conditions.

[0105] Optionally, the average thickness of the first coating layer can be 0.1 nm-5 nm, for example, can be 0.1 nm, 0.3 nm, 0.5 nm, 0.8 nm, 1 nm, 1.5 nm, 2 m, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, or a range consisting of any of the above values.

[0106] In some embodiments, the average thickness of the second coating layer can be 5 nm-20 nm, for example, can be 5 nm, 7 nm, 9 nm, 10 nm, 12 nm, 14 nm, 15 nm, 16 nm, 18 nm, 20 nm, or a range consisting of any of the above values.

[0107] In the first lithium supplement additive, the average thickness of the second coating layer is between 5 nm and 20 nm, which can make the second coating layer have better coating uniformity while making the second coating layer have good electronic conductivity and smaller lithium ion diffusion resistance.

[0108] Optionally, the average thickness of the second coating layer can be 10 nm-20 nm, for example, can be 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, or a range consisting of any of the above values.

[0109] The average thickness of the coating layer can be tested by transmission electron microscopy (TEM) pictures and EDS composition analysis charts. For example, after determining the boundary between the second coating layer and the first coating layer by the composition analysis result of EDS, 5 test points can be selected in different areas of the first coating layer and the second coating layer respectively, and the average thickness is calculated as the average thickness of the first coating layer and the second coating layer.

[0110] In some embodiments, the first coating layer can be formed by an atomic layer deposition (ALD) process. Thus, it is helpful to improve the density of the first coating layer, thereby effectively reducing the direct contact between the core and the electrolyte, reducing the occurrence of side reactions, and thereby improving the cycle performance of the battery cell.

[0111] In some embodiments, the first coating layer includes one or more of aluminum oxide, zinc oxide, tungsten oxide, zirconium oxide, magnesium oxide, titanium oxide, cobalt oxide, and Li-M 2 -O indicated oxides.

[0112] Li-M 2 -O indicates a metal oxide formed by the elements Li, a metal element M 2 and the element O.

[0113] The aforementioned metal oxides exhibit good chemical and thermal stability, and are not easily reacted in the electrolyte. During battery cell formation and cycling, even at high temperatures and high charge / discharge rates, the first coating layer can maintain an intact and dense coating structure, effectively reducing direct contact between the core and the electrolyte and minimizing side reactions. This contributes to improving the cycle performance of the battery cell.

[0114] In some embodiments, the lithium supplement additive I D / I G For 0.1-1, I D This indicates that the Raman spectrum is at 1350±50 cm⁻¹. -1 D peak intensity at I G This indicates that the Raman spectrum is at 1580±50 cm⁻¹. -1 The intensity of the G peak at that location.

[0115] I of lithium supplementation additive D / I G When the conductivity is 0.1-1, the second coating layer exhibits good electronic conductivity, which can improve the electron transport performance of the lithium replenishment additive. This, in turn, helps to increase the extraction rate of active lithium ions from the lithium replenishment additive, thereby improving the lithium replenishment efficiency.

[0116] Material I D / I G The test can be performed using a Raman spectrometer. D I represents the intensity of the D peak in the Raman spectrum of the material at 1350 ± 50 cm⁻¹. G This represents the intensity of the G peak in the Raman spectrum of the material at 1580±50 cm⁻¹. The testing conditions were: excitation wavelength 532 nm, grating 600 lines, objective lens 50x, integration time 10 s, cumulative scans 3 times, area scan, obtaining the D and G peak intensities at 100 points, and calculating the I intensity at 100 points. D / I G Remove the largest and smallest 30 I's. D / I G The average of the remaining 40 points is the material's I. D / I G The testing instrument can be a Horiba Lab RAMHR800 Raman spectrometer.

[0117] In some embodiments, carbon materials may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] In some embodiments, the mass content of carbon element in the lithium supplement additive can be 1%-5%, for example, can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any of the above values.

[0119] By making the content of carbon element in the above range, the lithium supplement additive can have both high electronic conductivity and high lithium supplement capacity.

[0120] Alternatively, in some embodiments, the mass content of carbon element in the lithium supplement additive can be 2.5%-3.5%, for example, can be 2.5%, 2.8%, 3%, 3.2%, 3.4%, 3.5%, or a range consisting of any of the above values.

[0121] In some embodiments, the mass content of M 2 element in the first lithium supplement additive can be 0.01%-2%, for example, can be 0.01%, 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.3%, 1.5%, 1.7%, 1.9%, 2%, or a range consisting of any of the above values.

[0122] By making the content of M 2 element in the above range, the first lithium supplement additive can have good kinetic performance, so that the first lithium supplement additive has high lithium supplement efficiency.

[0123] Alternatively, in some embodiments, the mass content of M 2 element in the first lithium supplement additive can be 0.01%-0.1%, for example, can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or a range consisting of any of the above values.

[0124] In some embodiments, the first coating layer is located on the surface of more than 80% of the core, for example, the first coating layer is located on the surface of more than 80% of the core, more than 85% of the surface, more than 88% of the surface, more than 90% of the surface, more than 91% of the surface, more than 92% of the surface, more than 93% of the surface, more than 94% of the surface, more than 95% of the surface, more than 96% of the surface, more than 97% of the surface, more than 98% of the surface, more than 99% of the surface, or 100% of the surface.

[0125] By locating the first coating layer on the surface of the core of 80% or more, the first coating layer can more completely coat the lithium-rich metal oxide single crystal particles or lithium-rich metal oxide-like single crystal particles in the core, reduce the contact of the lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles with the electrolyte, and thus reduce the side reaction of the lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles with the electrolyte. In this way, the risk of side reaction of the core with the electrolyte under large rate activation conditions can be reduced, and the delithiation capacity of the first lithium supplementing additive under large rate activation conditions can be improved. The first coating layer more completely coats the lithium-rich metal oxide single crystal particles or lithium-rich metal oxide-like single crystal particles in the core, which can also reduce the contact of the lithium-rich metal oxide with air and reduce the side reaction of the lithium-rich metal oxide with H2O and CO2 in the air. In this way, the residual alkali content in the first lithium supplementing additive can be reduced, thereby reducing the risk of side reaction of the residual alkali with the electrolyte, and further improving the cycle performance of the battery cell.

[0126] Optionally, the first coating layer is located on the surface of the core of 95% or more.

[0127] More optionally, the first coating layer is located on the surface of the core of 100%.

[0128] In some embodiments, the second coating layer is located on the surface of the core with the first coating layer of 80% or more, for example, the second coating layer is located on the surface of the core with the first coating layer of 80% or more, 85% or more, 88% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, or 100%.

[0129] By locating the second coating layer on the surface of the core with the first coating layer of 90% or more, the second coating layer can more completely coat the core with the first coating layer. In this way, not only can the contact of the lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles in the core with the electrolyte be further reduced, but a more complete electronic conduction network can also be formed on the surface of the first lithium supplementing additive. In this way, the side reaction of the first lithium supplementing additive under large rate activation conditions can be reduced, and the delithiation rate and higher delithiation capacity of the first lithium supplementing additive under large rate activation conditions can be improved, thereby helping to improve the cycle life and capacity of the battery cell.

[0130] Optionally, the second coating layer is located on the surface of the core with the first coating layer of 95% or more.

[0131] More optionally, the second coating layer is located on the surface of the core with the first coating layer of 100%.

[0132] In some embodiments, the lithium-rich metal oxide can include one or more of lithium-rich metal oxides containing an A element, the A element including one or more of Co, Fe, V, Nb, Cr, Mo.

[0133] Optionally, the lithium-rich metal oxide includes Li3A 1 O4, Li5A 2 O4, and Li6A 3 O4, wherein A 1 includes one or more of V, Nb, Cr, Mo, A 2 includes one or more of Fe, Cr, V, Mo, A 3 includes one or more of Co, V, Cr, Mo.

[0134] In some embodiments, the first lithium supplement additive can have a powder resistivity of 5 Ω•cm or less at 12 MPa.

[0135] When the first lithium supplement additive has a powder resistivity of 5 Ω•cm or less at 12 MPa, the first lithium supplement additive has good electronic conductivity, which helps to accelerate the rate of lithium ion extraction in the first lithium supplement additive and improve the lithium supplement efficiency of the first lithium supplement additive, especially under large rate activation conditions.

[0136] Optionally, in some embodiments, the first lithium supplement additive can have a powder resistivity of 0.5 Ω•cm to 2 Ω•cm at 12 MPa.

[0137] The powder resistivity of the first lithium supplement additive at 12 MPa can be tested by a method known in the art, for example, a powder resistivity tester can be used for testing. The testing temperature can be 25°C.

[0138] In the single body of the embodiments of the present disclosure, the first lithium supplement additive can be prepared by the following steps: providing a core, the core including lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles; coating an oxide containing an M 2 element on the surface of the core to form a first coating layer, the M 2 element including one or more of Al, Zn, W, Zr, Mg, Ti, Co; coating a carbon material on the surface of the core coated with the first coating layer to form a second coating layer, to obtain a lithium supplement additive, the lithium supplement additive including the core and the coating layer on the surface of the core, the core including lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles; the coating layer including the first coating layer and the second coating layer, the first coating layer being on the surface of the core, and the second coating layer being on the surface of the first coating layer away from the core; wherein the first coating layer includes an oxide containing an M 2 element, the M 2The element comprises one or more of Al, Zn, W, Zr, Mg, Ti, Co; and the second coating layer comprises a carbon material.

[0139] Optionally, the inner core surface is coated with a M 2 The step of oxidizing the element can comprise the step of depositing a M 2 source on the inner core surface by an atomic layer deposition process; and placing the intermediate in an atmosphere containing ozone to cause the M 2 source to react with the ozone to form an oxide of the M 2 element.

[0140] Optionally, the M 2 source can comprise a soluble M 2 salt and / or an alkyl M 2 compound.

[0141] The alkyl M 2 compound can represent an organic compound comprising M 2 atoms and an alkyl group in a molecular structure. 2

[0142] Optionally, the M 2 source comprises one or more of aluminum oxalate, zinc oxalate, tungsten oxalate, zirconium oxalate, magnesium oxalate, titanium oxalate, cobalt oxalate, aluminum nitrate, zinc nitrate, tungsten nitrate, zirconium nitrate, magnesium nitrate, titanium nitrate, cobalt nitrate, trimethylaluminum, trimethylzinc, trimethyltungsten, trimethylzirconium, trimethylmagnesium, trimethyltitanium, trimethylcobalt.

[0143] Optionally, the step of coating the inner core surface coated with the first coating layer with a carbon material to form the second coating layer can comprise the step of mixing the inner core coated with the first coating layer with an organic carbon source and heat treating the mixture in a protective atmosphere at 350-750°C to cause the organic carbon source to carbonize and form the second coating layer.

[0144] Optionally, the mixing can comprise mixing at a rotation speed of 20-50 r / min, and the mixing time can be 3-5 min.

[0145] Optionally, the heat treating can be performed for 4-10 h.

[0146] Optionally, the organic carbon source can comprise one or more of sucrose, glucose, citric acid, pitch, polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), phenol formaldehyde resin, and polyethylene glycol (PEG).

[0147] ​In some embodiments, the core can be prepared by the following steps: mixing the Li source and the metal source according to stoichiometric ratio to obtain core raw materials; mixing and refining the core raw materials by a ball milling method, controlling the ball milling time to be 12-24 hours, so that the average particle size of the obtained powder is less than 1 μm; vacuum drying the obtained powder at 60-80 °C for 12 hours after ball milling, and then calcining in an inert atmosphere (such as argon or nitrogen) after removing the moisture, the calcination temperature is 500-600 °C, and the holding time is 2-4 hours to obtain a precursor powder; mixing the precursor powder with the Li source, and sintering to obtain the core.

[0148] Optionally, the Li source can include one or more of Li2O, Li2CO3, Li2C2O4, CH3COOLi, LiOH•H2O, and LiOH; and the metal source can include one or more of oxides, hydroxides, halides, sulfates, carbonates, nitrates, oxalates, acetates, sulfides, and nitrides of the metal.

[0149] Optionally, the sintering can include: heating at a rate of 4-8 °C / min to 500-600 °C, and holding for 4-6 hours to make the precursor powder and the Li source react preliminarily and form crystal nuclei; heating at a rate of 2-4 °C / min to 800-900 °C, and holding for 8-12 hours. The heat treatment at 800-900 °C can promote slow crystal growth and inhibit the formation of polycrystals.

[0150] In some embodiments, the mass fraction of the first lithium supplement additive in the positive electrode film layer can be 0.1-3%, based on the total mass of the positive electrode film layer being 100%. As an example, the mass fraction of the first lithium supplement additive in the positive electrode film layer can be 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, or a range consisting of any of the above values.

[0151] The mass fraction of the first lithium supplement additive in the positive electrode film layer within the above range can provide a suitable additional lithium source in the positive electrode, compensate for the irreversible lithium loss during the first charging process of the battery cell, and improve the first coulombic efficiency, energy density, and cycle life of the battery cell.

[0152] Optionally, the mass fraction of the first lithium supplement additive in the positive electrode film layer can be 0.1-2%, based on the total mass of the positive electrode film layer being 100%. As an example, the mass fraction of the first lithium supplement additive in the positive electrode film layer can be 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or a range consisting of any of the above values.

[0153] In some embodiments, the second lithium supplement additive in the cathode film layer can have a mass fraction of 0.01%-2%. As an example, the second lithium supplement additive in the cathode film layer can have a mass fraction of 0.01%, 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.2%, 1.5%, 1.8%, 2%, or a range consisting of any of the aforementioned values. This can reduce the amount of gas generated during storage and cycling of the battery cell.

[0154] Alternatively, the second lithium supplement additive in the cathode film layer can have a mass fraction of 0.01%-1.2%. As an example, the second lithium supplement additive in the cathode film layer can have a mass fraction of 0.01%, 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.2%, or a range consisting of any of the aforementioned values.

[0155] In some embodiments, the cathode film layer further comprises a cathode active material.

[0156] In some embodiments, the cathode active material can include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, and respective modifications thereof. Examples of lithium transition metal oxides can include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and respective modifications thereof. Examples of lithium-containing phosphates can include, but are not limited to, one or more of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and respective modifications thereof.

[0157] As an example, the cathode active material can include, but is not limited to, one or more of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.1 Al 0.05 O2, LiFePO4, LiMnPO4.

[0158] The battery cell will be accompanied by Li deintercalation and consumption during charging and discharging process, and the molar content of Li is different when the battery cell is discharged to different states. In the enumeration of the positive active material in the present disclosure, the molar content of Li is the initial state of the material, i.e. the state before feeding, and the positive active material is applied to the battery cell. After charging and discharging cycle, the molar content of Li will change. In the enumeration of the positive active material in the present disclosure, the molar content of O is only the theoretical state value, and the lattice oxygen release will cause the change of the molar content of O. The actual molar content of O will also appear to be floating.

[0159] The modification material of the positive active material of each lithium battery cell described above can be a doping modification and / or a surface coating modification of the positive active material.

[0160] In some embodiments, the positive electrode film layer can further include a positive electrode conductive agent. As an example, the positive electrode conductive agent can include, but is not limited to, one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0161] In some embodiments, the positive electrode film layer can further include a positive electrode binder. As an example, the positive electrode binder can include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0162] In some embodiments, the positive electrode current collector can adopt a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be adopted. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0163] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing the positive active material, the positive electrode conductive agent, the positive electrode binder, and any other components in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0164] [Negative electrode sheet] In some embodiments, the negative electrode tab can include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0165] The negative electrode active material can employ materials known in the art that are useful for battery cells. As an example, the negative electrode active material can include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials can include, but are not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based materials can include, but are not limited to, one or more of elemental tin, tin oxide, and tin alloy materials.

[0166] In some embodiments, the negative electrode film layer can further include a negative electrode conductive agent. As an example, the negative electrode conductive agent can include, but is not limited to, one or more of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In some embodiments, the negative electrode film layer can further include a negative electrode binder. As an example, the negative electrode binder can include, but is not limited to, one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0168] In some embodiments, the negative electrode film layer can further include other auxiliary agents. As an example, the other auxiliary agents can include thickening agents, such as sodium carboxymethyl cellulose (CMC), PTC thermistor material, and the like.

[0169] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0170] The negative electrode film layer is usually formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and other optional additives in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0171] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer.

[0172] In some embodiments, the negative electrode tab can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, etc. When the foamed metal is used as the negative electrode tab, the surface of the foamed metal can not be provided with a negative electrode active material, or of course can be provided with a negative electrode active material.

[0173] [Separator] The separator is disposed between the positive electrode tab and the negative electrode tab to insulate the positive and negative electrodes and prevent short circuiting.

[0174] In some embodiments, the separator includes a separator film. The present disclosure does not have a particular limitation on the type of separator film, and any publicly known porous structure film having good chemical stability and mechanical stability can be used.

[0175] In some embodiments, the material of the separator film can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited. The separator can be a separate component located between the positive and negative electrodes, or can be attached to the surface of the positive and negative electrodes. An inorganic particle coating layer, an organic particle coating layer, or an organic / inorganic composite coating layer can also be applied to the surface of the separator film.

[0176] In some embodiments, the separator is a solid-state electrolyte. The solid-state electrolyte is disposed between the positive electrode tab and the negative electrode tab, and simultaneously functions to transport ions and insulate the positive and negative electrodes.

[0177] In some embodiments, the battery cell can further include an outer package for accommodating the electrode assembly obtained by assembling the negative electrode tab, the separator film, and the positive electrode tab. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as one or more of an aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0178] [Electrolyte] The electrolyte serves to conduct ions between the positive electrode and the negative electrode.

[0179] In some embodiments, the electrolyte employs an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0180] Taking a lithium battery cell as an example, the electrolyte salt can include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bisoxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0181] In some embodiments, the organic solvent can include, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), 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), diethyl sulfone (ESE), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

[0182] In some embodiments, the electrolyte solution can further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive capable of improving certain performance of the battery cell, such as an additive capable of improving overcharge performance, an additive capable of improving high-temperature performance, an additive capable of improving low-temperature performance, and the like.

[0183] Optionally, the additive can include one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propane sultone (PS), and vinyl sulfate (DTD).

[0184] Methods for preparing battery cells are known. For example, battery cell assembly methods include, but are not limited to, button cells, jellyroll cells, prismatic cells, pouch cells, etc. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery cell. As an example, a positive electrode sheet, a separator, and a negative electrode sheet can be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly can be placed in an outer package, the electrolyte can be injected after drying, and the battery cell can be obtained through processes such as vacuum packaging, standing, and formation.

[0185] Embodiments The present disclosure is more particularly described in the following examples that are intended to be illustrative only, as numerous modifications and variations within the scope of the present disclosure will become apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported herein are based on mass, and all reagents used in the examples are commercially available or synthesized according to standard procedures and used without further purification, and the equipment used in the examples is commercially available.

[0186] Example 1 Positive electrode tab A positive electrode active material lithium iron phosphate (LFP), a first lithium supplement additive, a second lithium supplement additive, a positive electrode binder polyvinylidene fluoride, and a positive electrode conductive agent carbon black were dispersed in a solvent N-methyl pyrrolidone (NMP) at a mass ratio of 96:1.5:0.5:0.5:1.5, stirred uniformly, and a positive electrode slurry was prepared. The positive electrode slurry was uniformly coated on both surfaces of an aluminum foil, dried, cold-pressed, and cut to obtain a positive electrode sheet. The first lithium supplement additive includes a Li5FeO4 single crystal particle core and a coating layer, the coating layer includes a first coating layer and a second coating layer, the first coating layer is located on the surface of the core, and the second coating layer is located on the surface of the first coating layer away from the core. The first coating layer is an aluminum oxide coating layer deposited by ALD, M 2 The element is Al, and the second coating layer is an acetylene black carbon coating layer. The second lithium supplement additive is Li2NiO2. The average length diameter d1 of the first lithium supplement additive particles is 2 μm, and the average length diameter d2 of the second lithium supplement additive particles is 5 μm. The positive electrode sheet includes an aluminum foil and positive electrode film layers on both sides of the aluminum foil, and the mass content w1 of the first lithium supplement additive in the positive electrode film layer is 1.5%, and the mass content w2 of the second lithium supplement additive is 0.5%.

[0187] Negative electrode tab The negative active material artificial graphite, the negative conductive agent carbon black, the negative binder styrene-butadiene rubber (SBR), and the thickening agent sodium carboxymethyl cellulose are added into deionized water according to a mass ratio of 97.2:0.8:0.8:1.2, and a negative slurry is prepared after being fully stirred and mixed uniformly. The negative slurry is uniformly coated on both surfaces of the copper foil, and then the negative electrode sheet is obtained after drying, cold pressing, and slitting.

[0188] Separator film A polyethylene (PE) film with a thickness of 13 μm is selected.

[0189] Electrolyte Ethylene carbonate (EC) and methyl ethyl carbonate (EMC) are mixed according to a volume ratio of 3:7 to obtain a mixed solvent, and then LiPF6 is dissolved in the mixed solvent to obtain an electrolyte. The concentration of LiPF6 in the electrolyte is 1 mol / L.

[0190] Battery cell The positive electrode sheet, the separator, and the negative electrode sheet are sequentially stacked to assemble an electrode assembly, which is then packaged in an aluminum-plastic film and injected with an electrolyte to obtain a battery monomer. The battery monomer is formed according to the following steps: constant current charging at 0.1C rate to 3.65 V, standing for 60 s, and then constant current charging at 0.1C rate to 4.3 V.

[0191] Examples 2 to 4 The preparation method of the battery monomer is the same as that in Example 1, except that the average length-diameter of the first lithium supplement additive particles is adjusted. The core and the coating layer of the first lithium supplement additive, the second lithium supplement additive, w1, and w2 in Examples 2 to 4 are the same as those in Example 1.

[0192] Examples 5 to 7 The preparation method of the battery monomer is the same as that in Example 1, except that the average length-diameter of the second lithium supplement additive particles is adjusted. The first lithium supplement additive, the second lithium supplement additive, w1, and w2 in Examples 5 to 7 are the same as those in Example 1.

[0193] Examples 8 to 9 The preparation method of the battery monomer is the same as that in Example 1, except that the average length-diameter of the first lithium supplement additive and the second lithium supplement additive particles is adjusted. The composition of the first lithium supplement additive, the composition of the second lithium supplement additive, w1, and w2 in Examples 8 to 9 are the same as those in Example 1.

[0194] Comparative Examples 1 to 6 The preparation method of the battery cell is the same as that of Example 1, except that at least one of the core type of the first lithium supplement additive, the average length-diameter of the first lithium supplement additive particles, the average length-diameter of the second lithium supplement additive particles, and the mass content of the first lithium supplement additive and the second lithium supplement additive in the positive electrode film layer is adjusted according to Table 3. The composition of the coating layer of the first lithium supplement additive and the composition of the second lithium supplement additive of Comparative Examples 1 to 6 are the same as those of Example 1.

[0195] Test section (1) Cycle capacity retention rate test At 25°C, the battery cell is charged at 0.1C constant current to 3.65V, and then charged at 3.65V constant voltage until the current is less than or equal to 0.05C, and the first cycle charging capacity is recorded as D0; stand for 5 min; discharge at 0.1C constant current to 2.5V, and record the first cycle discharge capacity as C0; cycle the battery cell according to the above method, and record the discharge capacity of the 1000th cycle as Cn; The cycle capacity retention rate P of the battery cell after 1000 cycles 1000 (%) = Cn / C0 x 100%.

[0196] (2) Fe dissolution amount test At 25°C, the battery cell is charged at 0.1C constant current to 3.65V, and then charged at 3.65V constant voltage until the current is less than or equal to 0.05C; stand for 5 min; discharge at 0.1C constant current to 2.5V; cycle the battery cell according to the above method. After 1000 cycles, the battery cell is disassembled and the negative electrode sheet is taken out.

[0197] The negative electrode sheet is dissolved in concentrated nitric acid, the insoluble residue is taken out, and the remaining solution is sent into an atomizer by a peristaltic pump to form an aerosol, which is then sent into a high-temperature plasma by a carrier gas (argon). The sample is atomized, ionized and excited in the plasma, and different elements emit characteristic rays of different wavelengths. The detector confirms the element type and content according to the characteristic spectral line intensity. After the metal elements in the lithium supplement additive are dissolved, they are generally reduced to metal elements in the negative electrode by the electrolyte. Therefore, the content of the metal element (Fe) corresponding to the lithium supplement additive in the negative electrode is taken as the dissolution amount of the metal element (Fe) in the lithium supplement additive.

[0198] (3) Cycle gas production test At 25°C, the battery cell is charged at 0.1C constant current to 3.65V, and then charged at 3.65V constant voltage until the current is less than or equal to 0.05C; stand for 5 min; discharge at 0.1C constant current to 2.5V; cycle the battery cell according to the above method. The volume of the battery cell before cycling V0 and the volume of the battery cell after 1000 cycles V1 are recorded by the drainage method, respectively, V0= M0 / (p 液 x Q), V1= M1 / (p 液 x Q), wherein, M0 is the mass of the battery cell drainage before circulation, M1 is the mass of the battery cell drainage after 1000 cycles, p 液 is the density of the liquid, Q is the nominal capacity of the battery cell. The circulation gas production = V1-V0.

[0199] In Tables 1 to 3, " / " represents no corresponding parameter, and "C element mass content" represents the mass content of carbon elements in the first lithium supplement additive.

[0200] Table 1 Table 2 Table 3 Table 4 As can be seen from Tables 1 to 4, by making the positive electrode film layer include the first lithium supplement additive and the second lithium supplement additive, and the ratio of the average length diameter of the first lithium supplement additive particles to the average length diameter of the second lithium supplement additive particles is within the range of the embodiments of the present disclosure, the active lithium ions can be supplemented into the battery cell while reducing the gas production of the battery cell during the circulation process, thereby improving the cycle life of the battery cell.

[0201] The positive electrode film layer of Comparative Example 1 does not include the second lithium supplement additive, resulting in a higher gas production of the battery cell of Comparative Example 1. The gas production of the battery cell during the circulation process will affect the quality of the pole piece, such as causing black spots or lithium precipitation on the surface of the negative pole piece, etc., so that the side reaction inside the battery cell is intensified, the transition metal of the positive electrode is dissolved, and the cycle performance of the battery cell is poor.

[0202] The ratio of the average length diameter of the first lithium supplement additive particles to the average length diameter of the second lithium supplement additive particles of Comparative Example 2 is too small, the generation rate of the intermediate product and the reaction rate of the second lithium supplement additive and the intermediate product are not matched, the second lithium supplement additive cannot quickly consume the intermediate product, resulting in a higher gas production and poor cycle performance of the battery cell of Comparative Example 2.

[0203] The ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles of Comparative Example 3 is too large, and at this time, the average long diameter of the second lithium supplement additive particles is small, the generation rate of the intermediate product and the reaction rate of the second lithium supplement additive with the intermediate product are not matched, and the reaction rate of the second lithium supplement additive with the intermediate product is too fast, which may affect other reactions in the battery cell, such as the quality of SEI film formation, resulting in an increase in the internal resistance of the battery cell and affecting the cycle performance of the battery cell.

[0204] The ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles of Comparative Example 4 is too large, and at this time, the average long diameter of the first lithium supplement additive particles is large, the generation rate of the intermediate product and the reaction rate of the second lithium supplement additive with the intermediate product are not matched, resulting in a higher gas production and poorer cycle performance of the battery cell of Comparative Example 4.

[0205] The ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles of Comparative Example 5 is too small, and at this time, the generation rate of the intermediate product and the reaction rate of the second lithium supplement additive with the intermediate product are not matched, and the second lithium supplement additive cannot quickly consume the intermediate product, resulting in a higher gas production and poorer cycle performance of the battery cell of Comparative Example 5.

[0206] The ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles of Comparative Example 6 is too large, and at this time, the average long diameter of the first lithium supplement additive particles is large, the generation rate of the intermediate product and the reaction rate of the second lithium supplement additive with the intermediate product are not matched, resulting in a higher gas production and poorer cycle performance of the battery cell of Comparative Example 6. In addition, the core of the first lithium supplement additive of Comparative Example 6 is a Li5FeO4 polycrystal particle, and compared with a single crystal particle, the polycrystal particle has poor kinetic performance and poor structural stability, which further deteriorates the cycle performance of the battery cell of Comparative Example 6.

[0207] Examples 1-1 to 1-3 The preparation method of the battery cell is the same as that of Example 3 except that the type of the second lithium supplement additive is adjusted. The first lithium supplement additive of Examples 1-1 to 1-3 is the same as that of Example 3, and the average long diameter of the second lithium supplement additive particles, d1 / d2, w1, and w2 are the same as those of Example 3.

[0208] Table 5 Table 6 As can be seen from Table 5 and Table 6, by adjusting the type of the second lithium supplement additive, the gas production and cycle performance of the battery cell can be adjusted.

[0209] Examples 2-1 to 2-4 The preparation method of the battery monomer is the same as that of Example 3, except that the mass content w1 of the first lithium supplement additive and the mass content w2 of the second lithium supplement additive in the positive electrode film layer are adjusted, and the mass content of the positive electrode active material in the positive electrode film layer is adjusted accordingly. The first lithium supplement additive and the second lithium supplement additive of Examples 2-1 to 2-4 are the same as those of Example 3.

[0210] Table 7 Table 8 As can be seen from Table 7 and Table 8, when the first lithium supplement additive and the second lithium supplement additive are the same, by adjusting the mass content of the first lithium supplement additive and the second lithium supplement additive in the positive electrode film layer, the gas production and the cycle performance of the battery monomer can be adjusted.

[0211] Examples 3-1 to 3-2 The preparation method of the battery monomer is the same as that of Example 3, except that the coating amount of aluminum oxide in the first lithium supplement additive is adjusted. The core of the first lithium supplement additive, the composition of the second coating layer, the mass content of carbon element in the first lithium supplement additive, the second lithium supplement additive, d1, d2, w1, w2 of Examples 3-1 to 3-2 are the same as those of Example 3.

[0212] Table 9 Table 10 As can be seen from Table 9 and Table 10, when other parameters are the same, by adjusting the mass content of M 2 element in the first coating layer, the first coating layer can have good barrier performance, and the influence of the first coating layer on the conductivity of the first lithium supplement additive can be reduced, thereby reducing the dissolution of metal ions in the first lithium supplement additive, and the contact of O ² or O with the electrolyte, and thus the battery monomer can have low gas production and good cycle performance.

[0213] Examples 4-1 to 4-3 The preparation method of the battery monomer is the same as that of Example 3, except that the coating amount of carbon material (acetylene black) in the first lithium supplement additive is adjusted. The core of the first lithium supplement additive, the composition and coating amount (M 2 element mass content) of the first coating layer, the second lithium supplement additive, d1, d2, w1, w2 of Examples 4-1 to 4-2 are the same as those of Example 3.

[0214] Table 11 Table 12 As can be seen from Table 11 and Table 12, when other parameters are the same, by adjusting the coating amount of the carbon material in the second coating layer, the second coating layer can have good barrier property and electrical conductivity, and the first lithium supplement additive can have high lithium supplement capacity, so that the dissolution of metal ions in the first lithium supplement additive can be reduced, and the contact with the electrolyte can also improve the kinetic performance of the first lithium supplement additive, thereby enabling the battery monomer to have low gas production and good cycle performance. ² or O with the electrolyte, and the kinetic performance of the first lithium supplement additive can also be improved, thereby enabling the battery monomer to have low gas production and good cycle performance.

[0215] Examples 5-1 to 5-6 In addition to adjusting the composition of the first coating layer in the first lithium supplement additive, the preparation method of the battery monomer is the same as that of Example 3. The core of the first lithium supplement additive, the composition and coating amount (mass content of carbon element) of the second coating layer, the second lithium supplement additive, d1, d2, w1, and w2 of Examples 5-1 to 5-2 are the same as those of Example 3.

[0216] Table 13 Table 14 As can be seen from Table 13 and Table 14, by making the first coating layer of the first lithium supplement additive include the above-mentioned kind of M 2 element, the first coating layer can have good barrier property, and thereby the battery monomer can have low gas production and good cycle performance.

[0217] It should be noted that the present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope of the main idea of the present disclosure, various modifications that can be thought of by those skilled in the art, and other ways constructed by combining part of the elements in the embodiments are also included in the scope of the present disclosure.

Claims

1. A battery cell, comprising a positive electrode tab, the positive electrode tab comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, characterized in that, the positive electrode film layer comprises a first lithium supplementing additive and a second lithium supplementing additive; the first lithium supplementing additive comprises a lithium-rich metal oxide; The second lithium supplement additive comprises Li a Ni 1-b M 1 b O c one or more of the compounds shown, wherein 0 < a < 2.2, 0 < b < 1, 0.8 < c < 2.2, M 1 one or more of Cu, Mg, Zn, Mn, Al, Zr or Ti; a molar content of Li element in the first lithium supplementing additive is greater than a molar content of Li element in the second lithium supplementing additive; an average length-diameter of the first lithium supplementing additive particles is 2 μm-10 μm, an average length-diameter of the second lithium supplementing additive particles is 2 μm-10 μm, and a ratio of the average length-diameter of the first lithium supplementing additive particles to the average length-diameter of the second lithium supplementing additive particles is 0.3-4.

2. The battery cell of claim 1, wherein, a ratio of the average length-diameter of the first lithium supplementing additive particles to the average length-diameter of the second lithium supplementing additive particles is 0.4-2. 3.The battery cell of claim 1, characterized in that, an average length-diameter of the first lithium supplementing additive particles is 4 μm-7 μm; and / or, an average length-diameter of the second lithium supplementing additive particles is 4 μm-7 μm.

4. The battery cell of claim 1, wherein, a mass ratio of the first lithium supplementing additive to the second lithium supplementing additive is 0.5:1-3.5:

1.

5. The battery cell of any one of claims 1-4, wherein, the first lithium supplementing additive comprises a core and a coating layer located on a surface of the core; the core comprises lithium-rich metal oxide single crystal particles and / or lithium-rich metal oxide-like single crystal particles; The coating layer comprises a first coating layer and a second coating layer, the first coating layer is located on the surface of the core, and the second coating layer is located on the surface of the first coating layer away from the core; wherein the first coating layer comprises M 2 Oxide of an element, M 2 The element comprises one or more of Al, Zn, W, Zr, Mg, Ti, Co; and the second coating layer comprises a carbon material.

6. The battery cell of claim 5, wherein, the first lithium supplementing additive satisfies at least one of the following conditions (1) to (9): (1) an average thickness of the first coating layer is 0.1 nm-10 nm; (2) the first coating layer is formed by an atomic layer deposition process; (3) the first cladding layer includes one or more of aluminum oxide, zinc oxide, tungsten oxide, zirconium oxide, magnesium oxide, titanium oxide, cobalt oxide, and Li-M 2 -O indicated oxides (4) an average thickness of the second coating layer is 5 nm-20 nm; (5) the carbon material comprises one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers; (6) in the first lithium supplementing additive, a mass content of carbon element is 1%-5%; (7) In the first lithium supplement additive, M 2 The mass content of the element is 0.01%-2%. (8) a powder resistivity of the first lithium supplementing additive under 12 MPa is 5 Ω·cm or less; (9) I D / I G is 0.1-1, I D represents the intensity of the D peak of the Raman spectrum at 1350±50 cm -1 -1. I G represents the intensity of the G peak of the Raman spectrum at 1580±50 cm -1 -1. 7.The battery cell of claim 1, characterized in that, the lithium-rich metal oxide comprises one or more of lithium-rich metal oxides containing element A, element A comprising one or more of Co, Fe, V, Nb, Cr, Mo.

8. A battery device characterized by comprising: a plurality of battery cells of any one of claims 1-7.

9. An electrical device, characterized by a battery device of claim 8.

10. A positive electrode sheet characterized by comprising: comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer comprises a first lithium supplementing additive and a second lithium supplementing additive; the first lithium supplementing additive comprises a lithium-rich metal oxide; The second lithium supplement additive comprises Li a Ni 1-b M 1 b O c one or more of the compounds shown, wherein 0 < a < 2.2, 0 < b < 1, 0.8 < c < 2.2, M 1 one or more of Cu, Mg, Zn, Mn, Al, Zr or Ti; a molar content of Li element in the first lithium supplementing additive is greater than a molar content of Li element in the second lithium supplementing additive; The average long diameter of the first lithium supplement additive particles is 2-10 μm, the average long diameter of the second lithium supplement additive particles is 2-10 μm, and the ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles is 0.3-4. The average long diameter of the first lithium supplement additive particles is 2-10 μm, the average long diameter of the second lithium supplement additive particles is 2-10 μm, and the ratio of the average long diameter of the first lithium supplement additive particles to the average long diameter of the second lithium supplement additive particles is 0.3-4. The average long diameter of the first lithium supplement additive particles is 2-10 μm, the average long diameter of the second lithium supplement additive particles is 2-10 μ

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