Composite positive electrode material and preparation method thereof, positive plate, secondary battery and electric device

Abstract

The invention relates to a composite positive electrode material and a preparation method thereof, a positive plate, a battery and a power utilization device, the composite positive electrode material comprises a nickel-containing positive electrode material and a functional film layer arranged on the surface of the nickel-containing positive electrode material, and the functional film layer comprises Li2MO4 and an organic lithium phosphonate compound; wherein M is selected from at least one of sulfur, selenium and tellurium; the organic lithium phosphonate compound contains a structure shown in a formula (1), wherein * represents a site where the structure shown in the formula (1) is connected with other structures in the organic lithium phosphonate compound.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a composite positive electrode material and a preparation method thereof, a positive electrode sheet, a secondary battery and an electrical device. Background Art

[0002] Secondary batteries are increasingly widely used due to their clean and renewable characteristics. They mainly rely on the movement of active ions such as lithium ions between the positive and negative electrodes to generate electricity. They have been widely used in electric vehicles, portable electronic devices, energy storage systems and other fields.

[0003] In recent years, with the rapid development of the new energy industry, people's demand for new energy vehicles such as electric cars and electric bicycles has increased, and their performance requirements have become higher and higher.

[0004] As demand increases, the performance of traditional secondary batteries is increasingly unable to meet people's needs and needs further improvement. Summary of the invention

[0005] Based on this, it is necessary to provide a composite positive electrode material and a preparation method thereof, a positive electrode sheet, a battery and an electrical device, aiming to improve the cycle performance and kinetic performance of secondary batteries.

[0006] In a first aspect of the present application, a composite positive electrode material is provided, characterized in that the composite positive electrode material comprises a nickel-containing positive electrode material and a functional film layer provided on the surface of the nickel-containing positive electrode material, wherein components of the functional film layer include Li2MO4 and an organic lithium phosphonate compound;

[0007] Wherein, M is selected from at least one of sulfur, selenium and tellurium; and the organic lithium phosphonate compound has a structure shown in formula (1):

[0008]

[0009] * represents the site where the structure represented by formula (1) is connected to other structures in the organic lithium phosphonate compound.

[0010] In the above-mentioned composite positive electrode material, a functional film layer with specific components is formed on the surface of the positive electrode material, and the components of the functional film layer include an inorganic component Li2MO4 and an organic component organic lithium phosphonate compound. The specific organic and inorganic components synergistically improve the strength and stability of the functional film layer, thereby reducing the probability of positive electrode material particle breakage; and, on the one hand, Li2MO4 and the organic component organic lithium phosphonate compound can effectively improve the kinetic properties of the positive electrode material as fast ion conductors; on the other hand, the organic lithium phosphonate compound has good thermal stability and good flame retardant function, which can improve the thermal stability of the battery; all aspects work together to improve the cycle stability and kinetic performance of the battery when the composite positive electrode material is used to prepare the battery.

[0011] In some embodiments, in the functional film layer, MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound is (0.6-5):1;

[0012] Optionally, in the functional film layer, MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound is (1-5):1.

[0013] The ratio of each component in the functional membrane layer is regulated to synergistically form a structurally stable organic-inorganic hybrid functional membrane layer while reducing the negative impact on the battery cycle performance.

[0014] In some of the embodiments, in the composite positive electrode material, the content of the single substance of the M element is ≤0.1%.

[0015] The content of the residual M element in the functional film layer is regulated to reduce its negative impact on the conductive properties of the positive electrode material.

[0016] In some embodiments, the thickness of the functional film layer is 5 nm to 20 nm;

[0017] Optionally, the thickness of the functional film layer is 5nm to 10nm.

[0018] By regulating the thickness of the functional film layer, the stability of the positive electrode material can be further improved while reducing the negative impact on its cycle performance.

[0019] In some embodiments, the organic lithium phosphonate compound contains a group represented by formula (1-1):

[0020]

[0021] Among them, R1 is selected from any one of -OR2, substituted or unsubstituted alkyl having 1 to 10 carbon atoms, substituted or unsubstituted alkenyl having 2 to 10 carbon atoms, and substituted or unsubstituted alkynyl having 2 to 10 carbon atoms; R2 is selected from any one of H, Li, substituted or unsubstituted alkyl having 1 to 10 carbon atoms, substituted or unsubstituted alkenyl having 2 to 10 carbon atoms, substituted or unsubstituted alkynyl having 2 to 10 carbon atoms, and substituted or unsubstituted alkylcarboxylic acid having 2 to 10 carbon atoms.

[0022] In some embodiments, the organic lithium phosphonate compound includes at least one of (a) to (c):

[0023]

[0024] Wherein, in (a), each R2 is not simultaneously selected from H;

[0025] Each R3 is independently selected from any one of a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group, and a group represented by formula (1-1), and at least one R3 is selected from a group represented by formula (1-1); L1 is selected from a substituted or unsubstituted alkane subunit having 1 to 10 carbon atoms and a substituted or unsubstituted alkene subunit having 2 to 10 carbon atoms;

[0026] Each L2 is independently selected from any one of a single bond, a substituted or unsubstituted alkane subunit having 1 to 10 carbon atoms, and a substituted or unsubstituted alkene subunit having 2 to 10 carbon atoms; each R4 is independently selected from a substituted or unsubstituted alkyl subunit having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl subunit having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl subunit having 2 to 10 carbon atoms, and -L 21 At least one of R5;

[0027] Each L 21 They are independently selected from a single bond, a substituted or unsubstituted alkane subunit with 1 to 10 carbon atoms, R5 is selected from -N(R6)2, and each R6 is independently selected from H, a substituted or unsubstituted alkane subunit with 1 to 10 carbon atoms, a phosphonic acid group and any one of the groups represented by formula (1-1); and (c) contains at least one group represented by formula (1-1).

[0028] In some embodiments, the organic lithium phosphonate compound satisfies at least one of the following conditions (3) to (5):

[0029] (3) each R2 is independently selected from any one of H, Li, an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by a halogen, an alkyl group having 1 to 10 carbon atoms substituted by a hydroxyl group, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkylcarboxylic acid having 2 to 10 carbon atoms, and an alkylcarboxylic acid having 2 to 10 carbon atoms substituted by a hydroxyl group;

[0030] (4) Each R3 is independently selected from any one of an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by a halogen, an alkyl group having 1 to 10 carbon atoms substituted by a hydroxyl group, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group, and a group represented by formula (1-1);

[0031] (5) Each R4 is independently selected from an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and -L 21At least one of R5; each R6 is independently selected from any one of an alkane subunit having 1 to 10 carbon atoms, a phosphonic acid group and a group represented by formula (1-1).

[0032] In some embodiments, the components of the functional film layer also include a metal oxide type rock salt phase;

[0033] Optionally, the metal in the metal oxide type rock salt phase includes at least one of Ni, Co and Mn.

[0034] The metal oxide rock salt phase can further protect the nickel-containing positive electrode material, reduce the chance of it being corroded by organic phosphate compounds, and further improve the cycle stability of the composite positive electrode material.

[0035] In some embodiments, the composition of the nickel-containing positive electrode material satisfies: Li t Ni x Co y A h O z ;

[0036] Among them, A is selected from at least one of manganese, aluminum, copper, zinc, tin, magnesium and iron, 0<x<1, 0<y<1, 1.5≤y≤2.5, 0<h<1, 0.8≤t≤1.5, 1.5≤z≤2.5.

[0037] In some of the embodiments, the mass proportion of residual lithium in the composite positive electrode material is ≤2%, and the residual lithium includes Li2CO3, LiOH and Li2O.

[0038] In a second aspect of the present application, a method for preparing a composite positive electrode material is provided, comprising the following steps:

[0039] The nickel-containing positive electrode material, M element and an organic phosphonic acid compound are mixed to prepare a prefabricated positive electrode material;

[0040] The prefabricated positive electrode material is subjected to a chemical formation treatment to prepare the composite positive electrode material;

[0041] The M element includes at least one of sulfur, selenium and tellurium; the organic phosphonic acid compound has a structure shown in formula (2):

[0042]

[0043] * represents the site where the structure represented by formula (2) is connected to other structures in the organic phosphonic acid compound.

[0044] During the preparation of the above-mentioned composite positive electrode material, the M element reacts with the layered oxide in the nickel-containing positive electrode material to form Li2M2O3, and at the same time forms a metal oxide-type rock salt phase to protect the surface of the positive electrode material particles, so that the organic phosphonic acid compound preferentially reacts with the residual lithium such as LiOH and Li2CO3 on the surface of the positive electrode material to form an organic phosphonate lithium compound, thereby absorbing the residual lithium on the surface of the nickel-containing positive electrode material and initially forming a coating layer on the surface of the positive electrode material; in the further formation process, Li2M2O3 further reacts with the residual lithium to be oxidized to Li2MO4, and finally forms a functional film layer whose components include inorganic component Li2MO4 and organic component organic phosphonate lithium compound, and the specific organic and inorganic components synergistically improve the strength and stability of the functional film layer, thereby reducing the probability of breakage of the positive electrode material particles, and the organic-inorganic hybrid functional film layer generated in situ on the particle surface improves the material's kinetic properties, cycle stability and thermal stability.

[0045] Furthermore, in the process of M single substance reaction to form Li2MO4, Li + The released Li ions can be used to compensate for the loss of Li ions caused by the formation of the functional film layer. Taking the organic lithium phosphonate compound as hydroxyethylidene diphosphonic acid C2H8O7P2 (HEDP) and the M element as sulfur as an example, the main reaction processes that may be involved in the above preparation process are explained:

[0046] (1)4LiM1O2+2S→4M1O+Li2S2O3+Li2O;

[0047] (2)2Li2O+C2H8O7P2→Li4C2H4O7P2+2H2O;

[0048] (3)2Li2CO3+C2H8O7P2→Li4C2H4O7P2+2H2O+2CO2;

[0049] In reaction (1), the M element reacts with the layered oxide LiM1O2 in the nickel-containing positive electrode material to form Li2M2O3, and simultaneously generates a metal oxide-type rock salt phase M1O, where M1 is the metal in the nickel-containing positive electrode material, including but not limited to: Ni, Co or Mn; at the same time, the organic phosphonic acid compound preferentially reacts with residual lithium such as LiOH and Li2CO3 on the surface of the positive electrode material to form an organic lithium phosphonate compound.

[0050] (4)2LiMO2+S+2Li2O-4e - →2MO+Li2SO4+4Li + ;

[0051] (5)2LiMO2+S+2Li2CO3-4e - →2MO+Li2SO4+2CO2+4Li+ ;

[0052] (6)Li2S2O3+5Li2O-8e - →2Li2SO4+8Li + ;

[0053] (7)Li2S2O3+Li2CO3-8e - →2Li2SO4+5CO2+8Li + ;

[0054] During the formation process, reactions (4) to (7) mainly occur. Li2M2O3 further reacts with residual lithium and is oxidized to Li2MO4, ultimately forming a functional membrane layer composed of inorganic component Li2MO4 and organic component lithium phosphonate compound, which further absorbs residual lithium and converts Li in the residual lithium into Li2MO4. + Release it.

[0055] In some embodiments, the mixing process comprises the following steps:

[0056] The nickel-containing positive electrode material and the M element are subjected to a first mixing treatment, and then the organic phosphonic acid compound is added to perform a second mixing treatment;

[0057] Optionally, the first mixing treatment time is 0.5h to 6h;

[0058] Optionally, the second mixing treatment time is 0.5h to 3h.

[0059] The study found that when organic phosphonic acid compounds come into direct contact with the layered oxides in the nickel-containing positive electrode material, a redox reaction will occur to release oxygen, thereby damaging the structure of the positive electrode material. Taking hydroxyethylidene diphosphonic acid C2H8O7P2 (HEDP) as an example, the reaction is as follows:

[0060] 4LiMO2+C2H8O7P2→Li4C2H4O7P2+4MO+2H2O+O2

[0061] Therefore, the nickel-containing positive electrode material and the M element are first mixed to deposit a metal oxide rock salt phase MO on the surface of the nickel-containing positive electrode material, which is equivalent to a "protective barrier" to reduce the probability of oxygen release due to redox reaction when the organic phosphonic acid compound directly contacts the layered oxide in the nickel-containing positive electrode material.

[0062] In some embodiments, the mixing process satisfies at least one of the following conditions (6) to (7):

[0063] (6) The mass ratio of the M element to the nickel-containing positive electrode material is (0.01-1):100;

[0064] Optionally, the mass ratio of the M element to the nickel-containing positive electrode material is (0.1-0.4):100;

[0065] (7) The mass ratio of the organic phosphonic acid compound to the nickel-containing positive electrode material is (0.01-1):100;

[0066] Optionally, the mass ratio of the organic phosphonic acid compound to the nickel-containing positive electrode material is (0.1-0.5):100.

[0067] The mass ratio of the M element, the organic phosphonic acid compound and the nickel-containing positive electrode material is controlled to absorb the residual lithium while forming a stable inorganic-organic hybrid functional membrane layer, and further avoid the negative impact on the battery cycle performance.

[0068] According to a third aspect of the present application, a positive electrode sheet is provided, wherein the positive electrode sheet comprises the composite positive electrode material according to the first aspect or a composite positive electrode material prepared by the method for preparing the composite positive electrode material according to the second aspect.

[0069] In a fourth aspect of the present application, a secondary battery is provided, wherein the secondary battery comprises the composite positive electrode material of the first aspect or the composite positive electrode material prepared by the preparation method of the composite positive electrode material of the second aspect or the positive electrode sheet of the third aspect.

[0070] According to a fifth aspect of the present application, there is provided an electrical device, wherein the electrical device comprises the secondary battery according to the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0072] Figure 1 is a schematic diagram of one embodiment of a battery cell;

[0073] Figure 2 yes Figure 1 Exploded diagram of

[0074] Figure 3 is a schematic diagram of an embodiment of a battery pack;

[0075] Figure 4 yes Figure 3 Exploded diagram of

[0076] Figure 5 is a schematic diagram of an embodiment of an electric device using a secondary battery as a power source;

[0077] Figure 6 This is an electron microscope image of a composite positive electrode material according to one embodiment.

[0078] Description of reference numerals:

[0079] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery cell; 41. Shell; 42. Electrode assembly; 43. Cover plate; 5. Electrical device. DETAILED DESCRIPTION

[0080] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0081] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0082] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0083] In the present application, the term "alkyl" refers to a group formed when an alkane loses a hydrogen, such as methane loses a hydrogen to form a methyl group; "alkenyl or alkynyl" refers to a group formed when an alkene or alkyne loses a hydrogen, such as ethylene loses a hydrogen to form vinyl, and acetylene loses a hydrogen to form ethynyl.

[0084] The term "chain alkane" refers to an alkane in which the carbon atoms are connected by single carbon-carbon bonds and do not form a ring, and the remaining valence bonds are all bonded to hydrogen, including straight-chain alkanes and branched-chain alkanes.

[0085] In the present application, the carbon number of “chain alkyl group having 1 to 10 carbon atoms” can be 1 to 30, including 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Non-limiting examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, 2-ethylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, 1-methylpentyl, 3-methylpentyl, 2-ethylpentyl, 4-methyl-2-pentyl, n-hexyl, 1-methylhexyl, 2-ethylhexyl, 2-butylhexyl, n-heptyl, 1-methylheptyl, 2,2-dimethylheptyl, 2-ethylheptyl, n-octyl, n-nonyl, and n-decyl.

[0086] In the present application, the term "substituted or unsubstituted" means that the functional group described after the term may or may not have a substituent.

[0087] In the present application, the halogen group includes chlorine, fluorine, bromine, and iodine.

[0088] In this application, when two groups are connected by a connection point, for example When R is selected from a single bond, it means that the two groups do not need to be connected through a specific group, but are directly connected by a single bond, that is,

[0089] In one embodiment of the present application, a composite positive electrode material is provided, characterized in that the composite positive electrode material comprises a nickel-containing positive electrode material and a functional film layer provided on the surface of the nickel-containing positive electrode material, and components of the functional film layer include Li2MO4 and an organic lithium phosphonate compound.

[0090] Wherein, M is selected from at least one of sulfur, selenium and tellurium; the organic lithium phosphonate compound has a structure shown in formula (1):

[0091]

[0092] * represents the site where the structure represented by formula (1) is connected to other structures in the organic lithium phosphonate compound.

[0093] In the above-mentioned composite positive electrode material, a functional film layer with specific components is formed on the surface of the positive electrode material, and the components of the functional film layer include an inorganic component Li2MO4 and an organic component organic lithium phosphonate compound. The specific organic and inorganic components synergistically improve the strength and stability of the functional film layer, thereby reducing the probability of positive electrode material particle breakage; and, on the one hand, Li2MO4 and the organic component organic lithium phosphonate compound can effectively improve the kinetic properties of the positive electrode material as fast ion conductors; on the other hand, the organic lithium phosphonate compound has good thermal stability and good flame retardant function, which can improve the thermal stability of the battery; all aspects work together to improve the cycle stability and kinetic performance of the battery when the composite positive electrode material is used to prepare the battery.

[0094] It can be understood that "*" represents the site where the group represented by formula (1) is connected to other structures in the organic lithium phosphonate compound. In other words, at least one electron in the group represented by formula (1) will form a covalent bond with an electron in other structures in the organic lithium phosphonate compound.

[0095] In the functional film layer, MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound is (0.6-5):1.

[0096] In some embodiments, in the functional film layer, MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound is (1 to 5):1.

[0097] In some embodiments, in the functional film layer, MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound is (1.5 to 5):1.

[0098] The ratio of each component in the functional membrane layer is regulated to synergistically form a structurally stable organic-inorganic hybrid functional membrane layer while reducing the negative impact on the battery cycle performance.

[0099] It is understandable that the MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound directly reacts with the molar ratio of the structure represented by formula (1) in the Li2MO4 organic lithium phosphonate compound.

[0100] Specifically, the functional film layer can be directly tested by using X-ray photoelectron spectroscopy (XPS) to obtain an energy spectrum diagram and mark MO4 accordingly. 2- The ratio of the peak intensities of the characteristic peaks of the group and the group of the structure shown in formula (1) is MO4 2-The molar ratio of the group to the group of the structure represented by formula (1).

[0101] In the above “(0.6~5):1”, the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 , 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4:1, 5:1; or a range consisting of any two values, for example: "(1.5-4):1, (1.5-3.5):1, (1.5-3):1, (1.5-2.5):1, (1.5-2):1, (2-4):1, (2-3.5):1, (2-3):1, (2-2.5):1, (2.5-4):1, (2.5-3.5):1, (2.5-3):1.

[0102] In some embodiments, the MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound is 2:1.

[0103] In some of the embodiments, in the composite positive electrode material, the content of the single substance of the M element is ≤0.1%.

[0104] The content of the residual M element in the functional film layer is regulated to reduce its negative impact on the conductive properties of the positive electrode material.

[0105] In some embodiments, the thickness of the functional film layer is 5 nm to 20 nm;

[0106] Optionally, the thickness of the functional film layer is 5 nm to 10 nm.

[0107] By regulating the thickness of the functional film layer, the stability of the positive electrode material can be further improved while reducing the negative impact on its cycle performance.

[0108] In the above-mentioned "5nm~20nm", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm; or a range consisting of any two numerical values, for example: 5nm~20nm, 5nm~15nm, 5nm~10nm, 7nm~20nm, 7nm~20nm, 7nm~15nm, 7nm~10nm, 10nm~20nm, 10nm~15nm, 15nm~20nm.

[0109] In some embodiments, the organic lithium phosphonate compound contains a group represented by formula (1-1):

[0110]

[0111] Among them, R1 is selected from any one of -OR2, substituted or unsubstituted alkyl having 1 to 10 carbon atoms, substituted or unsubstituted alkenyl having 2 to 10 carbon atoms, and substituted or unsubstituted alkynyl having 2 to 10 carbon atoms; R2 is selected from any one of H, Li, substituted or unsubstituted alkyl having 1 to 10 carbon atoms, substituted or unsubstituted alkenyl having 2 to 10 carbon atoms, substituted or unsubstituted alkynyl having 2 to 10 carbon atoms, and substituted or unsubstituted alkylcarboxylic acid having 2 to 10 carbon atoms.

[0112] In some embodiments, R1 is selected from any one of -OR2, an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by a halogen, an alkyl group having 1 to 10 carbon atoms substituted by a hydroxyl group, an alkenyl group having 2 to 10 carbon atoms, and an alkynyl group having 2 to 10 carbon atoms.

[0113] In some embodiments, R1 is selected from any one of -OR2, a chain alkyl group with 1 to 10 carbon atoms, a chain alkyl group with 1 to 10 carbon atoms substituted by halogen, a chain alkyl group with 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group with 2 to 10 carbon atoms, and an alkynyl group with 2 to 10 carbon atoms.

[0114] In some embodiments, R1 is selected from any one of -OR2, an alkyl group with 1 to 5 carbon atoms, an alkyl group with 1 to 5 carbon atoms substituted by a halogen, an alkyl group with 1 to 5 carbon atoms substituted by a hydroxyl group, an alkenyl group with 2 to 5 carbon atoms, and an alkynyl group with 2 to 5 carbon atoms.

[0115] In some embodiments, R1 is selected from any one of -OR2, a chain alkyl group with 1 to 5 carbon atoms, a chain alkyl group with 1 to 5 carbon atoms substituted by halogen, a chain alkyl group with 1 to 5 carbon atoms substituted by hydroxyl, an alkenyl group with 2 to 5 carbon atoms, and an alkynyl group with 2 to 5 carbon atoms.

[0116] In some embodiments, R1 is selected from any one of -OR2, a chain alkyl group with 1 to 3 carbon atoms, a chain alkyl group with 1 to 3 carbon atoms substituted by halogen, a chain alkyl group with 1 to 3 carbon atoms substituted by hydroxyl, an alkenyl group with 2 to 5 carbon atoms, and an alkynyl group with 2 to 5 carbon atoms.

[0117] In some embodiments, R2 is selected from any one of H, Li, an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by halogen, an alkyl group having 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and an alkyl carboxylic acid having 2 to 10 carbon atoms.

[0118] It is understood that: "alkyl carboxylic acid" refers to a group formed after at least one hydrogen in the alkyl group is replaced by a carboxylic acid group.

[0119] In some embodiments, R2 is selected from any one of H, Li, a chain alkyl group having 1 to 10 carbon atoms, a chain alkyl group having 1 to 10 carbon atoms substituted by halogen, a chain alkyl group having 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a chain alkyl carboxylic acid having 2 to 10 carbon atoms.

[0120] In some embodiments, R2 is selected from any one of H, Li, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, an alkyl group having 1 to 5 carbon atoms substituted by a hydroxyl group, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, and an alkyl carboxylic acid having 2 to 5 carbon atoms.

[0121] In some embodiments, R2 is selected from any one of H, Li, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by halogen, an alkyl group having 1 to 5 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, and an alkylcarboxylic acid having 2 to 5 carbon atoms.

[0122] In some embodiments, R2 is selected from any one of H, Li, a chain alkyl group with 1 to 3 carbon atoms, a chain alkyl group with 1 to 3 carbon atoms substituted by halogen, a chain alkyl group with 1 to 3 carbon atoms substituted by hydroxyl, an alkenyl group with 2 to 5 carbon atoms, an alkynyl group with 2 to 5 carbon atoms, and a chain alkyl carboxylic acid with 2 to 5 carbon atoms.

[0123] In some embodiments, the organic lithium phosphonate compound includes at least one of (a) to (c):

[0124]

[0125] Wherein, in (a), each R2 is not selected from H at the same time.

[0126] In some of the embodiments, each R3 is independently selected from any one of a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group and a group shown in formula (1-1), and at least one R3 is selected from the group shown in formula (1-1); L1 is selected from a substituted or unsubstituted alkane subunit having 1 to 10 carbon atoms and a substituted or unsubstituted alkene subunit having 2 to 10 carbon atoms.

[0127] In some of the embodiments, each R3 is independently selected from an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by halogen, an alkyl group having 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group and any one of the groups shown in formula (1-1), and at least one R3 is selected from the group shown in formula (1-1).

[0128] In some of the embodiments, each R3 is independently selected from any one of a chain alkyl group having 1 to 10 carbon atoms, a chain alkyl group having 1 to 10 carbon atoms substituted by halogen, a chain alkyl group having 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group and a group shown in formula (1-1), and at least one R3 is selected from the group shown in formula (1-1).

[0129] In some of the embodiments, each R3 is independently selected from a chain alkyl group having 1 to 5 carbon atoms, a chain alkyl group having 1 to 5 carbon atoms substituted by halogen, a chain alkyl group having 1 to 5 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group and any one of the groups shown in formula (1-1), and at least one R3 is selected from the group shown in formula (1-1).

[0130] In some embodiments, each L2 is independently selected from any one of a single bond, an alkane subunit having 1 to 10 carbon atoms, an alkane subunit having 1 to 10 carbon atoms substituted by a hydroxyl group, an alkane subunit having 1 to 10 carbon atoms substituted by a halogen, and an alkene subunit having 2 to 10 carbon atoms.

[0131] In some embodiments, each L2 is independently selected from any one of a single bond, a chain alkane subunit having 1 to 10 carbon atoms, a chain alkane subunit having 1 to 10 carbon atoms substituted by a hydroxyl group, a chain alkane subunit having 1 to 10 carbon atoms substituted by a halogen, and an alkene subunit having 2 to 10 carbon atoms.

[0132] In some embodiments, each L2 is independently selected from any one of a single bond, an alkane subunit having 1 to 5 carbon atoms, an alkane subunit having 1 to 5 carbon atoms substituted by a hydroxyl group, an alkane subunit having 1 to 5 carbon atoms substituted by a halogen, and an alkene subunit having 2 to 5 carbon atoms.

[0133] In some embodiments, each L2 is independently selected from any one of a single bond, a chain alkane subunit with 1 to 5 carbon atoms, a chain alkane subunit with 1 to 5 carbon atoms substituted by a hydroxyl group, a chain alkane subunit with 1 to 5 carbon atoms substituted by a halogen, and a chain alkene subunit with 2 to 5 carbon atoms.

[0134] In some embodiments, each R4 is independently selected from a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, and -L 21 At least one of R5.

[0135] Each L 21 They are independently selected from a single bond, a substituted or unsubstituted alkane subunit with 1 to 10 carbon atoms, R5 is selected from -N(R6)2, and each R6 is independently selected from H, a substituted or unsubstituted alkane subunit with 1 to 10 carbon atoms, a phosphonic acid group and any one of the structures shown in formula (1-1); and (c) contains at least one group shown in formula (1-1).

[0136] It is understood that (c) contains at least one group represented by formula (1-1) means that at least one R4 in formula (c) is selected from -L 21 R5, and at least one L 21 is -N(R6)2, and at least one R6 is a group represented by formula (1-1).

[0137] In some embodiments, each L 21 Each of them is independently selected from any one of a single bond, an alkane substituent having 1 to 10 carbon atoms, an alkane substituent having 1 to 10 carbon atoms substituted by a halogen, and an alkane substituent having 1 to 10 carbon atoms substituted by a hydroxyl group.

[0138] In some embodiments, each L 21Each of them is independently selected from any one of a single bond, a paraffinic hydrocarbon substituent having 1 to 10 carbon atoms, a paraffinic hydrocarbon substituent having 1 to 10 carbon atoms substituted by a halogen, and a paraffinic hydrocarbon substituent having 1 to 10 carbon atoms substituted by a hydroxyl group.

[0139] In some embodiments, each L 21 Each of them is independently selected from any one of a single bond, an alkane substituent having 1 to 5 carbon atoms, an alkane substituent having 1 to 5 carbon atoms substituted by a halogen, and an alkane substituent having 1 to 5 carbon atoms substituted by a hydroxyl group.

[0140] In some embodiments, each L 21 Each of them is independently selected from any one of a single bond, a paraffinic hydrocarbon substituent having 1 to 5 carbon atoms, a paraffinic hydrocarbon substituent having 1 to 5 carbon atoms substituted by a halogen, and a paraffinic hydrocarbon substituent having 1 to 5 carbon atoms substituted by a hydroxyl group.

[0141] In some embodiments, each L 21 Each of them is independently selected from any one of a single bond, an alkanediyl group having 1 to 3 carbon atoms, an alkanediyl group having 1 to 3 carbon atoms substituted by a halogen, and an alkanediyl group having 1 to 3 carbon atoms substituted by a hydroxyl group.

[0142] In some of the embodiments, each R6 is independently selected from H, an alkane subunit having 1 to 10 carbon atoms, an alkane subunit having 1 to 10 carbon atoms substituted by halogen, an alkane subunit having 1 to 10 carbon atoms substituted by hydroxyl, a phosphonic acid group, and any one of the structures shown in formula (1-1).

[0143] In some of the embodiments, each R6 is independently selected from H, a chain alkane subunit with 1 to 10 carbon atoms, a chain alkane subunit with 1 to 10 carbon atoms substituted by halogen, a chain alkane subunit with 1 to 10 carbon atoms substituted by hydroxyl, a phosphonic acid group, and any one of the structures shown in formula (1-1).

[0144] In some of the embodiments, each R6 is independently selected from H, an alkane subunit with 1 to 5 carbon atoms, an alkane subunit with 1 to 5 carbon atoms substituted by halogen, an alkane subunit with 1 to 5 carbon atoms substituted by hydroxyl, a phosphonic acid group, and any one of the structures shown in formula (1-1).

[0145] In some of the embodiments, each R6 is independently selected from H, a chain alkane subunit with 1 to 5 carbon atoms, a chain alkane subunit with 1 to 5 carbon atoms substituted by halogen, a chain alkane subunit with 1 to 5 carbon atoms substituted by hydroxyl, a phosphonic acid group, and any one of the structures shown in formula (1-1).

[0146] In some of these embodiments, the components of the functional film layer also include a metal oxide type rock salt phase;

[0147] Optionally, the metal in the metal oxide type rock salt phase includes at least one of Ni, Co and Mn.

[0148] The metal oxide rock salt phase can further protect the nickel-containing positive electrode material, reduce the chance of it being corroded by organic phosphate compounds, and further improve the cycle stability of the composite positive electrode material.

[0149] It is understood that the above-mentioned nickel positive electrode material can be various types of nickel positive electrode materials commonly used in the art, such as lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc.

[0150] It should be noted that the lithium content in the positive electrode material mentioned in the above example refers to its content when it is not in use. During the use of the battery, it will be repeatedly used as a battery, and the Li in the positive electrode active material will change during the charging and discharging process. That is, the molar subscript of Li in the positive electrode active material in the battery product will not always remain at 1, but will change.

[0151] In some embodiments, the composition of the nickel-containing positive electrode material satisfies: Li t Ni x Co y A h O z ;

[0152] Among them, A is selected from at least one of manganese, aluminum, copper, zinc, tin, magnesium and iron, 0<x<1, 0<y<1, 1.5≤y≤2.5, 0<h<1, 0.8≤t≤1.5, 1.5≤z≤2.5.

[0153] In some of the embodiments, the mass proportion of residual lithium in the composite positive electrode material is ≤2%, and the residual lithium includes Li2CO3, LiOH and Li2O.

[0154] Another embodiment of the present application provides a method for preparing a composite positive electrode material, comprising the following steps S10 to S20.

[0155] S10, mixing the nickel-containing positive electrode material, M element and the organic phosphonic acid compound to prepare a prefabricated positive electrode material.

[0156] S20, subjecting the prefabricated positive electrode material to a chemical formation treatment to prepare a composite positive electrode material.

[0157] The M element includes at least one of sulfur, selenium and tellurium; the organic phosphonic acid compound has a structure shown in formula (2):

[0158]

[0159] * represents the site where the structure represented by formula (2) is connected to other structures in the organic phosphonic acid compound.

[0160] During the preparation of the above-mentioned composite positive electrode material, the M element reacts with the layered oxide in the nickel-containing positive electrode material to form Li2M2O3, and at the same time forms a metal oxide-type rock salt phase to protect the surface of the positive electrode material particles, so that the organic phosphonic acid compound preferentially reacts with the residual lithium such as LiOH and Li2CO3 on the surface of the positive electrode material to form an organic phosphonate lithium compound, thereby absorbing the residual lithium on the surface of the nickel-containing positive electrode material and initially forming a coating layer on the surface of the positive electrode material; in the further formation process, Li2M2O3 further reacts with the residual lithium to be oxidized to Li2MO4, and finally forms a functional film layer whose components include inorganic component Li2MO4 and organic component organic phosphonate lithium compound, and the specific organic and inorganic components synergistically improve the strength and stability of the functional film layer, thereby reducing the probability of breakage of the positive electrode material particles, and the organic-inorganic hybrid functional film layer generated in situ on the particle surface improves the material's kinetic properties, cycle stability and thermal stability.

[0161] It can be understood that the organic phosphonic acid compound having the structure shown in formula (2) reacts with residual lithium such as LiOH and Li2CO3 on the surface of the positive electrode material to form an organic lithium phosphonate compound having the structure shown in formula (1).

[0162] Furthermore, in the process of M single substance reaction to form Li2MO4, Li + The released Li ions can be used to compensate for the loss of Li ions caused by the formation of the functional film layer. Taking the organic lithium phosphonate compound as hydroxyethylidene diphosphonic acid C2H8O7P2 (HEDP) and the M element as sulfur as an example, the main reaction processes that may be involved in the above preparation process are explained:

[0163] (1)4LiM1O2+2S→4M1O+Li2S2O3+Li2O;

[0164] (2)2Li2O+C2H8O7P2→Li4C2H4O7P2+2H2O;

[0165] (3)2Li2CO3+C2H8O7P2→Li4C2H4O7P2+2H2O+2CO2;

[0166] In reaction (1), the M element reacts with the layered oxide LiM1O2 in the nickel-containing positive electrode material to form Li2M2O3, and simultaneously generates a metal oxide-type rock salt phase M1O, where M1 is the metal in the nickel-containing positive electrode material, including but not limited to: Ni, Co or Mn; at the same time, the organic phosphonic acid compound preferentially reacts with residual lithium such as LiOH and Li2CO3 on the surface of the positive electrode material to form an organic lithium phosphonate compound.

[0167] (4)2LiMO2+S+2Li2O-4e - →2MO+Li2SO4+4Li + ;

[0168] (5)2LiMO2+S+2Li2CO3-4e - →2MO+Li2SO4+2CO2+4Li + ;

[0169] (6)Li2S2O3+5Li2O-8e - →2Li2SO4+8Li + ;

[0170] (7)Li2S2O3+Li2CO3-8e - →2Li2SO4+5CO2+8Li + ;

[0171] During the formation process, reactions (4) to (7) mainly occur. Li2M2O3 further reacts with residual lithium and is oxidized to Li2MO4, ultimately forming a functional membrane layer composed of inorganic component Li2MO4 and organic component lithium phosphonate compound, which further absorbs residual lithium and converts Li in the residual lithium into Li2MO4. + Release it.

[0172] It can be understood that when the above composite positive electrode material or the method for preparing the above composite positive electrode material is used to prepare a secondary battery, the formation step in the above step S20 can be directly performed in the battery.

[0173] In some embodiments, the mixing process in step S10 includes the following step S11.

[0174] Step S11, subjecting the nickel-containing positive electrode material and the M element to a first mixing treatment, and then adding an organic phosphonic acid compound to a second mixing treatment.

[0175] The researchers found that when organic phosphonic acid compounds come into direct contact with layered oxides in nickel-containing cathode materials, redox reactions occur to release oxygen, thereby damaging the structure of the cathode materials. Taking hydroxyethylidene diphosphonic acid C2H8O7P2 (HEDP) as an example, the reaction is as follows:

[0176] 4LiMO2+C2H8O7P2→Li4C2H4O7P2+4MO+2H2O+O2

[0177] Therefore, the nickel-containing positive electrode material and the M element are first mixed to deposit a metal oxide rock salt phase MO on the surface of the nickel-containing positive electrode material, which is equivalent to a "protective barrier" to reduce the probability of oxygen release due to redox reaction when the organic phosphonic acid compound directly contacts the layered oxide in the nickel-containing positive electrode material.

[0178] Optionally, the first mixing treatment lasts for 0.5 h to 6 h.

[0179] Optionally, the second mixing treatment time is 0.5h to 3h.

[0180] In the above "0.5h~6h", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h; or a range consisting of any two numerical values.

[0181] In the above "0.5h~3h", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.5h, 1h, 1.5h, 2h, 2.5h, 3h; or a range consisting of any two values.

[0182] In some of the embodiments, the first mixing process and the second mixing process are both performed under stirring conditions; further, the stirring speed is maintained at 400 r / s to 1000 r / s.

[0183] In some of the embodiments, the mass ratio of M element to the nickel-containing positive electrode material is (0.01-1):100.

[0184] Optionally, the mass ratio of M element and nickel-containing positive electrode material is (0.1-0.4):100.

[0185] In some of the embodiments, the mass ratio of the organic phosphonic acid compound to the nickel-containing positive electrode material is (0.01-1):100.

[0186] Optionally, the mass ratio of the organic phosphonic acid compound to the nickel-containing positive electrode material is (0.1-0.5):100.

[0187] By controlling the mass ratio of M element, organic phosphonic acid compound and nickel-containing positive electrode material, a stable inorganic-organic hybrid functional membrane layer is formed while absorbing residual lithium, and further avoiding the negative impact on battery cycle performance.

[0188] In the above “(0.01~1):100”, the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.01:100, 0.05:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.35:100, 0.4:100, 0.45:100, 0.5:100, 0.55:100, 0.6:100, 0.65:100, 0.7:100, 0.75:100, 0.8:100, 0.85:100, 0.9:100, 0.95:100, 1:100; or a range consisting of any two values.

[0189] In the above “(0.01~1):100”, the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.01:100, 0.05:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.35:100, 0.4:100, 0.45:100, 0.5:100, 0.55:100, 0.6:100, 0.65:100, 0.7:100, 0.75:100, 0.8:100, 0.85:100, 0.9:100, 0.95:100, 1:100; or a range consisting of any two values.

[0190] In some of the embodiments, after the mixing step and before the forming step, a drying step is further included.

[0191] Furthermore, the drying temperature is 80° C. to 110° C., and the drying time is 0.01 h to 5 h.

[0192] In some embodiments, the above-mentioned mixing treatment step is carried out in a solvent; further, the solvent includes N-methylpyrrolidone and a small molecule alcohol with 2 to 5 carbon atoms.

[0193] Furthermore, the small molecule alcohol having 2 to 5 carbon atoms includes ethanol.

[0194] In some of the embodiments, the M element is added in the form of a solution; specifically, the M element and N-methylpyrrolidone are mixed to form a solution; further, the concentration of the M element is 0.5 mol / L to 2 mol / L.

[0195] In some of the embodiments, the organic phosphonic acid compound is added in the form of a solution; specifically, the organic phosphonic acid compound and a small molecule alcohol having 2 to 5 carbon atoms are mixed to form a solution; further, the concentration of the organic phosphonic acid compound is 0.5 mol / L to 2 mol / L.

[0196] In some embodiments, the organic phosphonic acid compound contains a group represented by formula (1-2):

[0197]

[0198] Among them, R 1a Select from -OR 2a , any one of a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, and a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms; R 2a Any one selected from H, Li, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, and a substituted or unsubstituted alkylcarboxylic acid having 2 to 10 carbon atoms.

[0199] In some embodiments, R 1a Select from -OR 2a , an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by halogen, an alkyl group having 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 10 carbon atoms, and an alkynyl group having 2 to 10 carbon atoms.

[0200] In some embodiments, R 1a Select from -OR 2a , an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by halogen, an alkyl group having 1 to 10 carbon atoms substituted by hydroxy, an alkenyl group having 2 to 10 carbon atoms, and an alkynyl group having 2 to 10 carbon atoms.

[0201] In some embodiments, R 1aSelect from -OR 2a , an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by halogen, an alkyl group having 1 to 5 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 5 carbon atoms, and an alkynyl group having 2 to 5 carbon atoms.

[0202] In some embodiments, R 1a Select from -OR 2a , an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by halogen, an alkyl group having 1 to 5 carbon atoms substituted by hydroxy, an alkenyl group having 2 to 5 carbon atoms, and an alkynyl group having 2 to 5 carbon atoms.

[0203] In some embodiments, R 1a Select from -OR 2a , an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, an alkyl group having 1 to 3 carbon atoms substituted by hydroxy, an alkenyl group having 2 to 5 carbon atoms, and an alkynyl group having 2 to 5 carbon atoms.

[0204] In some embodiments, R 2a Any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by a halogen, an alkyl group having 1 to 10 carbon atoms substituted by a hydroxyl group, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and an alkylcarboxylic acid having 2 to 10 carbon atoms.

[0205] It is understood that: "alkyl carboxylic acid" refers to a group formed after at least one hydrogen in the alkyl group is replaced by a carboxylic acid group.

[0206] In some embodiments, R 2a Any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by halogen, an alkyl group having 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and an alkylcarboxylic acid having 2 to 10 carbon atoms.

[0207] In some embodiments, R 2a Any one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, an alkyl group having 1 to 5 carbon atoms substituted by a hydroxyl group, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, and an alkylcarboxylic acid having 2 to 5 carbon atoms.

[0208] In some embodiments, R 2aAny one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by halogen, an alkyl group having 1 to 5 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, and an alkylcarboxylic acid having 2 to 5 carbon atoms.

[0209] In some embodiments, R 2a Any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, an alkyl group having 1 to 3 carbon atoms substituted by hydroxy, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, and an alkylcarboxylic acid having 2 to 5 carbon atoms.

[0210] In some embodiments, the organic phosphonic acid compound includes at least one of (A) to (C):

[0211]

[0212] Among them, in (a), each R 2a Not selected from H at the same time.

[0213] In some embodiments, each R 3a are independently selected from any one of a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group, and a group represented by formula (1-2), and at least one R 3a is selected from the group shown in formula (1-2); L 1a The substituent is selected from a substituted or unsubstituted alkane subunit having 1 to 10 carbon atoms and a substituted or unsubstituted alkene subunit having 2 to 10 carbon atoms.

[0214] In some embodiments, each R 3a They are independently selected from any one of an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by halogen, an alkyl group having 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group and a group represented by formula (1-2), and at least one R3 is selected from the group represented by formula (1-2).

[0215] In some embodiments, each R 3a They are independently selected from any one of a chain alkyl group having 1 to 10 carbon atoms, a chain alkyl group having 1 to 10 carbon atoms substituted by halogen, a chain alkyl group having 1 to 10 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group and a group represented by formula (1-2), and at least one R3 is selected from the group represented by formula (1-2).

[0216] In some embodiments, each R 3a They are independently selected from any one of a chain alkyl group having 1 to 5 carbon atoms, a chain alkyl group having 1 to 5 carbon atoms substituted by halogen, a chain alkyl group having 1 to 5 carbon atoms substituted by hydroxyl, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group and a group represented by formula (1-2), and at least one R3 is selected from the group represented by formula (1-2).

[0217] In some embodiments, each L 2a Each of them is independently selected from any one of a single bond, an alkane subunit having 1 to 10 carbon atoms, an alkane subunit having 1 to 10 carbon atoms substituted by a hydroxyl group, an alkane subunit having 1 to 10 carbon atoms substituted by a halogen, and an alkene subunit having 2 to 10 carbon atoms.

[0218] In some embodiments, each L 2a Each of them is independently selected from a single bond, a paraffinic hydrocarbon subunit having 1 to 10 carbon atoms, a paraffinic hydrocarbon subunit having 1 to 10 carbon atoms substituted by a hydroxyl group, a paraffinic hydrocarbon subunit having 1 to 10 carbon atoms substituted by a halogen, and an alkene subunit having 2 to 10 carbon atoms.

[0219] In some embodiments, each L 2a Each is independently selected from the group consisting of a single bond, an alkane subunit having 1 to 5 carbon atoms, an alkane subunit having 1 to 5 carbon atoms substituted by a hydroxyl group, an alkane subunit having 1 to 5 carbon atoms substituted by a halogen, and an alkene subunit having 2 to 5 carbon atoms.

[0220] In some embodiments, each L 2a Each of them is independently selected from a single bond, a chain alkane subunit having 1 to 5 carbon atoms, a chain alkane subunit having 1 to 5 carbon atoms substituted by a hydroxyl group, a chain alkane subunit having 1 to 5 carbon atoms substituted by a halogen, and a chain alkene subunit having 2 to 5 carbon atoms.

[0221] In some embodiments, each R 4a are independently selected from substituted or unsubstituted alkyl having 1 to 10 carbon atoms, substituted or unsubstituted alkenyl having 2 to 10 carbon atoms, substituted or unsubstituted alkynyl having 2 to 10 carbon atoms, and -L 21a R 5a At least one of .

[0222] Each L 21a are independently selected from single bonds, substituted or unsubstituted alkane subunits having 1 to 10 carbon atoms, R 5a Selected from -N(R 6a )2, each R 6aThey are independently selected from H, a substituted or unsubstituted alkane subunit having 1 to 10 carbon atoms, a phosphonic acid group and any one of the structures represented by formula (1-1); and (c) contains at least one group represented by formula (1-2).

[0223] It is understood that (C) contains at least one group represented by formula (1-2) means that at least one R in formula (C) 4a Selected from -L 21a R 5a , and at least one L 21a -N(R 6a )2, and at least one R 6a It is a group represented by formula (1-2).

[0224] In some embodiments, each L 21a Each of them is independently selected from any one of a single bond, an alkane substituent having 1 to 10 carbon atoms, an alkane substituent having 1 to 10 carbon atoms substituted by a halogen, and an alkane substituent having 1 to 10 carbon atoms substituted by a hydroxyl group.

[0225] In some embodiments, each L 21a Each of them is independently selected from any one of a single bond, a paraffinic hydrocarbon substituent having 1 to 10 carbon atoms, a paraffinic hydrocarbon substituent having 1 to 10 carbon atoms substituted by a halogen, and a paraffinic hydrocarbon substituent having 1 to 10 carbon atoms substituted by a hydroxyl group.

[0226] In some embodiments, each L 21a Each of them is independently selected from any one of a single bond, an alkane substituent having 1 to 5 carbon atoms, an alkane substituent having 1 to 5 carbon atoms substituted by a halogen, and an alkane substituent having 1 to 5 carbon atoms substituted by a hydroxyl group.

[0227] In some embodiments, each L 21a Each of them is independently selected from any one of a single bond, a paraffinic hydrocarbon substituent having 1 to 5 carbon atoms, a paraffinic hydrocarbon substituent having 1 to 5 carbon atoms substituted by a halogen, and a paraffinic hydrocarbon substituent having 1 to 5 carbon atoms substituted by a hydroxyl group.

[0228] In some embodiments, each L 21a Each of them is independently selected from any one of a single bond, an alkanediyl group having 1 to 3 carbon atoms, an alkanediyl group having 1 to 3 carbon atoms substituted by a halogen, and an alkanediyl group having 1 to 3 carbon atoms substituted by a hydroxyl group.

[0229] In some embodiments, each R 6a Each of them is independently selected from H, an alkane subunit having 1 to 10 carbon atoms, an alkane subunit having 1 to 10 carbon atoms substituted by a halogen, an alkane subunit having 1 to 10 carbon atoms substituted by a hydroxyl group, a phosphonic acid group, and any one of the structures represented by formula (1-2).

[0230] In some embodiments, each R 6a Each of them is independently selected from H, a chain alkane subunit having 1 to 10 carbon atoms, a chain alkane subunit having 1 to 10 carbon atoms substituted by a halogen, a chain alkane subunit having 1 to 10 carbon atoms substituted by a hydroxyl group, a phosphonic acid group, and any one of the structures represented by formula (1-2).

[0231] In some embodiments, each R 6a Each of them is independently selected from H, an alkane subunit having 1 to 5 carbon atoms, an alkane subunit having 1 to 5 carbon atoms substituted by a halogen, an alkane subunit having 1 to 5 carbon atoms substituted by a hydroxyl group, a phosphonic acid group, and any one of the structures represented by formula (1-2).

[0232] In some embodiments, each R 6a Each of them is independently selected from H, a chain alkane subunit having 1 to 5 carbon atoms, a chain alkane subunit having 1 to 5 carbon atoms substituted by a halogen, a chain alkane subunit having 1 to 5 carbon atoms substituted by a hydroxyl group, a phosphonic acid group, and any one of the structures represented by formula (1-2).

[0233] In some embodiments, the organic lithium phosphonate compound includes at least one of hydroxyethylidene diphosphonic acid, amino trimethylene phosphonic acid, ethylenediamine tetramethylene phosphonic acid, hexamethylene diamine tetramethylene phosphonic acid and diethylene triamine penta methylene phosphonic acid.

[0234] In one embodiment of the present application, a positive electrode sheet is further provided, characterized in that the positive electrode sheet comprises the composite positive electrode material as described above or a composite positive electrode material prepared by the method for preparing the composite positive electrode material as described above.

[0235] When the positive electrode sheet is used to prepare a battery, the cycle stability and dynamic performance of the battery can be improved.

[0236] Specifically, the positive electrode sheet includes a current collector and a positive electrode active layer disposed on the surface of the current collector, and the components of the positive electrode active layer include the composite positive electrode material as described above or the composite positive electrode material prepared by the preparation method of the composite positive electrode material as described above.

[0237] In any embodiment of the present application, in the positive electrode active layer, the mass proportion of the composite positive electrode material is 70% to 100%.

[0238] In any embodiment of the present application, the components of the positive electrode active layer further include a conductive agent and a binder.

[0239] The conductive agent may be any conductive agent commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black and graphene. Specifically, it may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor grown carbon fiber VGCF, carbon nanotubes CNTs and graphene and composite conductive agents thereof.

[0240] The binder of the binder can be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS) and fluorine-containing acrylate resin.

[0241] Optionally, in the positive electrode active layer, the mass proportion of the conductive agent is 1% to 20%.

[0242] Optionally, in the positive electrode active layer, the mass proportion of the binder is 1% to 10%.

[0243] In any embodiment of the present application, the current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on a polymer material substrate.

[0244] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0245] In some of the embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0246] In any embodiment of the present application, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet are dispersed in a solvent to form a positive electrode active slurry; the positive electrode active slurry is coated on a current collector, and after drying, cold pressing and other processes, a positive electrode sheet can be obtained. The positive electrode slurry has a solid content of 40wt% to 80wt%, and the viscosity at room temperature is adjusted to 5000mPa·s to 25000mPa·s, and after drying, it is cold-pressed by a cold rolling mill to form a positive electrode sheet.

[0247] In some embodiments, the solvent includes N-methylpyrrolidone.

[0248] In some embodiments, the surface density of the composite positive electrode material contained in the positive electrode sheet is 0.018 g / cm 2 ~0.05g / cm 2 .

[0249] The surface density of the composite positive electrode material = the mass of the composite positive electrode material / the area of ​​the positive electrode sheet.

[0250] Another embodiment of the present application provides a secondary battery, which includes the above-mentioned composite positive electrode material or the composite positive electrode material prepared by the above-mentioned method for preparing the composite positive electrode material or the above-mentioned positive electrode sheet.

[0251] In some embodiments, the secondary battery further comprises a negative electrode sheet, a separator and an electrolyte, which are described herein as non-limiting.

[0252] [Negative electrode]

[0253] The negative electrode sheet includes a current collector and a negative electrode active layer loaded on the surface of the current collector.

[0254] The components of the negative electrode active layer include a negative electrode active material.

[0255] The negative electrode active material mentioned above can adopt the commonly used negative electrode active materials in this application.

[0256] In any embodiment of the present application, the above-mentioned negative electrode active material includes at least one of mesophase carbon microbeads, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials and iron-based materials.

[0257] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to: at least one of mesophase carbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, and silicon-carbon composites.

[0258] In any embodiment of the present application, the battery is a lithium battery, and the mass proportion of the negative electrode active material in the negative electrode active layer is 70% to 100%.

[0259] In any embodiment of the present application, the components of the negative electrode active layer further include a negative electrode conductive agent and a negative electrode binder.

[0260] In any embodiment of the present application, the above-mentioned negative electrode conductive agent can be a conductive material commonly used in the art, including but not limited to: at least one of graphite, carbon nanotubes, nanofibers, carbon black and graphene. Specifically, it can be selected from SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs and graphene and their composite conductive agents.

[0261] The weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0 to 20 wt % based on the total weight of the negative electrode active layer.

[0262] The above-mentioned negative electrode binder can be a commonly used binder in the art, and can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0263] The weight ratio of the negative electrode binder in the negative electrode active layer is 0 to 30 wt % based on the total weight of the negative electrode active layer.

[0264] In any embodiment of the present application, the negative electrode active layer may further include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC-Na), etc. Based on the total weight of the negative electrode active layer, the weight ratio of other additives in the negative electrode active layer is 0-15wt%.

[0265] In any embodiment of the present application, the current collector in the negative electrode sheet may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil.

[0266] The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate.

[0267] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0268] In some of the embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0269] In any embodiment of the present application, the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at room temperature is adjusted to 2000mPa·s to 10000mPa·s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing such as a roller, a negative electrode sheet is obtained.

[0270] In some embodiments, the surface density of the negative electrode active material contained in the negative electrode sheet is 0.005 g / cm 2 ~0.03g / cm 2 .

[0271] The surface density of the negative electrode active material = the mass of the negative electrode active material / the area of ​​the negative electrode sheet.

[0272] [Electrolyte]

[0273] The electrolyte includes electrolyte salt and solvent

[0274] In some embodiments, the electrolyte salt may be selected from lithium ion electrolyte salts commonly used in the art.

[0275] As an example, the lithium ion electrolyte salt includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0276] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), 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), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0277] In some embodiments, in the electrolyte solution, the concentration of the electrolyte salt is generally 0.5 mol / L to 15 mol / L.

[0278] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0279] [Isolation film]

[0280] The separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0281] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0282] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0283] The thickness of the diaphragm is controlled within a range of 2 μm to 15 μm; optionally, the thickness of the diaphragm is controlled within a range of 2 μm to 13 μm.

[0284] In some embodiments, the battery is a secondary battery; specifically, the battery is a lithium-ion battery.

[0285] The shape of the secondary battery of the present application is not particularly limited, and it can be cylindrical, square or any other shape. For example, Figure 1 The battery cell 4 is a square structure as an example.

[0286] In some embodiments, reference Figure 2 The housing may include a shell 41 and a cover plate 43. The shell 41 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 41 has an opening connected to the receiving cavity, and the cover plate 43 can be covered on the opening to close the receiving cavity.

[0287] The positive electrode sheet, the negative electrode sheet and the separator can be wound or laminated to form an electrode assembly 42. The electrode assembly 42 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 42. The number of electrode assemblies 42 contained in the battery cell 4 can be one or more, which can be adjusted according to needs.

[0288] The secondary battery includes one or more battery cells 4 .

[0289] The secondary battery may be a battery module or a battery pack; the battery module or battery pack includes at least one battery cell. The number of battery cells 4 included in the battery module may be one or more, and those skilled in the art may select a suitable number according to the application and capacity of the battery module.

[0290] Figure 3 and Figure 4 The battery pack 1 is used as an example. The battery pack 1 includes a battery box and one or more battery cells 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for the battery cells 4.

[0291] The plurality of battery cells 4 may be arranged in the battery box in any manner.

[0292] The present application also provides an electrical device, which includes the secondary battery mentioned above.

[0293] Furthermore, in the above-mentioned electrical device, the battery may exist in the form of a battery cell, or may be further assembled into a battery pack.

[0294] The secondary battery pack can be used as a power source for an electrical device, and can also be used as an energy storage unit for the electrical device.

[0295] The above-mentioned electrical devices may be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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.

[0296] Figure 5The power consumption device 5 is taken as an example. The power consumption device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device 5's requirements for high power and high energy density of the battery, a battery pack can be used.

[0297] As another example, the power-consuming device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and a battery may be used as a power source.

[0298] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, technical personnel in the field should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0299] The following are specific embodiments.

[0300] Example 1

[0301] (1) Preparation of positive electrode

[0302] S1: Add the M element (sulfur) additive to the organic solvent N-methylpyrrolidone (NMP), stir at a speed of 400 r / s to 1000 r / s for 0.5 h to dissolve, and prepare an M element solution with a concentration of 1 mol / L;

[0303] S2: Add the organic phosphoric acid compound hydroxyethylidene diphosphonic acid into the organic solvent ethanol, stir at a speed of 400 r / s to 1000 r / s for 0.5 h to dissolve, and prepare an organic phosphoric acid solution with a concentration of 0.5 mol / L.

[0304] S3: LiNi containing nickel positive electrode material 0.9 Co 0.7 Mn 0.3 O2 (NCM9 material), binder polyvinylidene fluoride (PVDF) and conductive agent SP are configured in a mass ratio of (97:1:2) and mixed with solvent N-methylpyrrolidone (NMP) to obtain a prefabricated cathode slurry with a solid content of 75%.

[0305] S3: Add the M single substance solution to the prefabricated cathode slurry and stir for 1 hour. After uniform mixing, add the organic phosphoric acid solution and stir for 0.5 hour to obtain a uniformly mixed cathode composite slurry.

[0306] The mass ratio of the M element to the nickel-containing positive electrode material is recorded as X1, and the mass ratio of the organic phosphoric acid compound to the nickel-containing positive electrode material is recorded as X2.

[0307] S4: The cathode composite slurry is coated on the current collector aluminum foil and dried at 110° C. for 30 minutes to form an active layer to obtain a prefabricated positive electrode sheet.

[0308] The compaction density of the prefabricated positive electrode sheet is 3.5g / cm 3 , the calculation formula of compaction density is:

[0309] Compacted density = surface density / (pole sheet thickness - current collector thickness).

[0310] The above compaction density and surface density are well known in the art. The surface density of the pole piece refers to the weight of the active layer loaded by the pole piece per unit area. The surface density per unit area = the weight of the active layer / the area of ​​the active layer. As an example, the compaction density can be obtained by testing the following steps:

[0311] The positive electrode sheet is cut into 1000mm long sheets; the negative electrode sheet is rolled with a certain pressure and then punched into 1540.25mm 2 By measuring the weight and thickness of the small disc, the compacted density can be calculated.

[0312] (2) Preparation of negative electrode

[0313] Silicon oxide material SiOx, artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber SBR, and thickener sodium hydroxymethyl cellulose CMC are added into deionized water in a weight ratio of 40:57:0.5:1.25:1.25, and mixed and stirred for 6 hours to obtain negative electrode slurry; the slurry is evenly coated on the negative electrode current collector and dried to obtain a negative electrode sheet.

[0314] The compaction density of the negative electrode sheet is 1.6g / cm 3 The test method refers to the test of the compaction density of the positive electrode as above.

[0315] (3) Preparation of electrolyte

[0316] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of EC:EMC:DEC=1:1:1 to obtain an organic solvent, and then fully dried lithium salt LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0317] (4) Isolation membrane: Polyethylene film is selected as the isolation membrane of lithium-ion batteries.

[0318] (5) Assembly of lithium-ion battery: The positive electrode sheet, separator, and negative electrode sheet to be assembled are stacked in sequence, with the separator placed between the positive and negative electrode sheets to play an isolating role, and then a bare cell is obtained by winding; the bare cell is placed in a battery casing, and after drying, an electrolyte is injected, and the lithium-ion battery to be tested is obtained through vacuum packaging, standing, forming, shaping, and other processes. The formation process is: constant current charging at a current of 0.05C until the cell voltage reaches 3.7V and then cut off.

[0319] During the formation process, the nickel-containing positive electrode material in the prefabricated positive electrode sheet reacts with the M element and the organic phosphate compound, forming a functional film layer on the surface of the nickel-containing positive electrode material to obtain a composite positive electrode material.

[0320] (6) Testing:

[0321] S1. Separate the positive electrode sheet from the lithium-ion battery, and separate the active layer components by the following method to obtain a nickel-containing positive electrode material, i.e., a composite positive electrode material:

[0322] Take the positive electrode sheet and soak it in DMC for 30 minutes to remove the electrolyte solvent and lithium salt, then scrape the powder to peel off the positive electrode active layer powder and the aluminum current collector, and dissolve the collected powder in NMP and stir for 30 minutes to obtain a mixed slurry. Then place the mixed slurry in a centrifugal device and centrifuge it for 15 minutes to remove the lower layer component, which is the composite positive electrode material.

[0323] The obtained composite positive electrode material is placed under a transmission electron microscope (TEM) for observation, and obvious stratification can be seen, including a nickel-containing positive electrode material and a functional film layer disposed on the surface of the nickel-containing positive electrode material. The thickness of the functional film layer can be obtained based on the transmission electron microscope image information, which is recorded as H.

[0324] Specifically, when obtaining the thickness of the functional film layer, 5 areas of the composite positive electrode material are marked for test thickness, and an average value is taken.

[0325] S2. Use XPS to conduct qualitative testing on the components of the functional film layer of the composite positive electrode material to confirm the main component types.

[0326] XPS test results show that the functional film contains MO4 in Li2MO4 2- Group characteristic peak (175Ev, when M is S) and phosphate LiPO2 2- Characteristic peak (55.8eV), and the MO4 in Li2MO4 is calculated based on the ratio of the characteristic peak intensities 2- The ratio of the molar number of the group to the phosphate group in the organic lithium phosphonate compound is recorded as Y1.

[0327] S3, using acid-base titration method to determine the residual lithium content Y2 of the composite positive electrode material, the residual lithium includes Li2CO3, LiOH and Li2O. The specific steps are as follows:

[0328] Pretreatment: Weigh 30g of composite cathode material powder, add 100mL of pure water and stir for 30min, let stand for 10min, filter and remove a certain amount of filtrate;

[0329] Test: Use 0.05 mol / L hydrochloric acid standard solution to titrate the filtrate and calculate the residual lithium amount Y2 based on the titration result. The test and analysis method refers to GB / T 9736-2008.

[0330] S4. The residual amount Y3 of M element in the composite positive electrode material is characterized by DSC thermogravimetric analysis.

[0331] S5, battery rate cycle test

[0332] (1) 0.33C cycle capacity retention test

[0333] At 25°C, the secondary ion battery is first charged to 4.25V at a constant current of 0.33C, and then further charged to a current of 0.05C at a constant voltage of 4.25V, left for 30 minutes, and then discharged to 2.8V at a constant current of 0.33C. This is a charge and discharge cycle process. The discharge capacity this time is the discharge capacity of the first cycle, recorded as Cap4.

[0334] The secondary battery is subjected to a cyclic charge and discharge test in the above manner, and the discharge capacity of the 100th cycle is taken as Cap5. The capacity retention rate of the lithium-ion battery after 100 cycles is M3 = [Cap5 / Cap4] × 100%. The larger the M3 value, the smaller the battery capacity loss and the better the rate cycle performance.

[0335] (2) Cyclic capacity retention test at 1C

[0336] At 25°C, the lithium-ion battery is first charged to 4.25V at a constant current of 1C, and then further charged to a current of 0.05C at a constant voltage of 4.25V, and then left for 30 minutes, and then discharged to 2.8V at a constant current of 1C. This is a charge and discharge cycle process, and the discharge capacity this time is the discharge capacity of the first cycle, recorded as Cap6. The lithium-ion battery is subjected to a cyclic charge and discharge test in the above manner, and the discharge capacity of the 100th cycle is taken, recorded as Cap7. The capacity retention rate (%) of the lithium-ion battery after 100 cycles is M4 = [Cap7 / Cap6] × 100%.

[0337] The larger the M4 value, the smaller the battery capacity loss and the better the rate cycle performance.

[0338] S8, battery impedance test

[0339] At 25°C, the prepared secondary battery was charged at a constant current of 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V to a current of 0.05C. After standing for 30 minutes, the voltage U1 was recorded; then it was discharged at 1 / 3C for 30 seconds, the voltage U2 was recorded, and then the internal resistance DCR of the secondary battery before storage was calculated based on the formula DCR = (U2-U1) / 1 / 3C.

[0340] Please see Table 1 for specific parameters and test results.

[0341] Embodiments 2 to 5

[0342] Examples 2 to 5 are basically the same as Example 1, except that in step (1) of preparing the positive electrode sheet, the type and amount of the organic phosphoric acid compound used are different from those in Example 1, as shown in Table 1. The electron microscope image of the composite positive electrode material prepared in Example 4 is as follows: Figure 6 shown.

[0343] The other steps and conditions are the same as those in Example 1.

[0344] Embodiment 6-7

[0345] Examples 6 to 7 are basically the same as Example 1, except that in step (1) of preparing the positive electrode sheet, the type and amount of the M element used are different from those in Example 1. For details, please see Table 1.

[0346] The other steps and conditions are the same as those in Example 1.

[0347] Embodiments 8 to 15

[0348] Examples 8 to 15 are basically the same as Example 1, except that in step (1) of preparing the positive electrode sheet, the amount of the M element and the organic phosphoric acid compound is adjusted differently from that in Example 1. For details, see Table 1.

[0349] The other steps and conditions are the same as those in Example 1.

[0350] Comparative Example 1

[0351] Comparative Example 1 is substantially the same as Example 1, except that in step (1) of preparing the positive electrode sheet, no M single substance is added. For details, please see Table 1.

[0352] The other steps and conditions are the same as those in Example 1.

[0353] Comparative Example 2

[0354] Comparative Example 2 is basically the same as Example 1, except that: in the preparation of the positive electrode sheet in step (1), no organic phosphoric acid compound is added. For details, please see Table 1.

[0355] The other steps and conditions are the same as those in Example 1.

[0356] The process conditions and test results of each embodiment and comparative example are shown in Table 1, wherein the mass ratio of M element and nickel-containing positive electrode material is recorded as X1, the mass ratio of the organic phosphoric acid compound and the nickel-containing positive electrode material is recorded as X2, the molar ratio of Li2MO4 to the organic lithium phosphonate compound is recorded as Y1, the residual lithium amount of the composite positive electrode material is Y2, the residual amount of S element in the composite positive electrode material is Y3, and the thickness of the functional film layer in the composite positive electrode material is recorded as H.

[0357] Table 1

[0358]

[0359]

[0360] Note: " / " indicates that the substance or parameter does not exist. When "Y3<0.01%", it means that the residual lithium content is very small and is lower than the lower limit that can be accurately determined by acid-base titration.

[0361] By analyzing the data in Table 1 and comparing the test results of Examples 1 to 15 with Comparative Examples 1 to 2, it can be seen that: by using the composite positive electrode material of the present application, a functional film layer with specific components is formed on the surface of the positive electrode material substrate: the inorganic component Li2MO4 and the organic component organic lithium phosphonate compound work together to improve the cycle stability of the battery and reduce the internal resistance of the battery, that is, it can promote the transmission and diffusion of ions or electrons between the two electrodes in the battery, reduce the energy consumed when charging and discharging the battery, so as to improve the battery kinetic performance.

[0362] It can be seen that the technical solution of the present application can improve the cycle life of the battery while maintaining good dynamic performance.

[0363] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0364] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims, and the description and drawings may be used to interpret the contents of the claims.

Claims

1. A composite positive electrode material, characterized in that: The composite positive electrode material comprises a nickel-containing positive electrode material and a functional film layer disposed on the surface of the nickel-containing positive electrode material, wherein components of the functional film layer include Li2MO4 and an organic lithium phosphonate compound; Wherein, M is selected from at least one of sulfur, selenium and tellurium; and the organic lithium phosphonate compound has a structure shown in formula (1): * represents the site where the structure represented by formula (1) is connected to other structures in the organic lithium phosphonate compound.

2. The composite positive electrode material according to claim 1, characterized in that In the functional film layer, MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound is (0.6-5):1; Optionally, in the functional film layer, MO4 in Li2MO4 2- The molar ratio of the group to the structure represented by formula (1) in the organic lithium phosphonate compound is (1-5):

1.

3. The composite positive electrode material according to claim 1, characterized in that In the composite positive electrode material, the content of the single substance of the M element is ≤0.1%.

4. The composite positive electrode material according to any one of claims 1 to 3, characterized in that: The thickness of the functional film layer is 5nm to 20nm; Optionally, the thickness of the functional film layer is 5nm to 10nm.

5. The composite positive electrode material according to any one of claims 1 to 3, characterized in that: The organic lithium phosphonate compound contains a group represented by formula (1-1): Among them, R1 is selected from any one of -OR2, substituted or unsubstituted alkyl having 1 to 10 carbon atoms, substituted or unsubstituted alkenyl having 2 to 10 carbon atoms, and substituted or unsubstituted alkynyl having 2 to 10 carbon atoms; R2 is selected from any one of H, Li, substituted or unsubstituted alkyl having 1 to 10 carbon atoms, substituted or unsubstituted alkenyl having 2 to 10 carbon atoms, substituted or unsubstituted alkynyl having 2 to 10 carbon atoms, and substituted or unsubstituted alkylcarboxylic acid having 2 to 10 carbon atoms.

6. The composite positive electrode material according to claim 5, characterized in that The organic lithium phosphonate compound includes at least one of (a) to (c): Wherein, in (a), each R2 is not simultaneously selected from H; Each R3 is independently selected from any one of a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group, and a group represented by formula (1-1), and at least one R3 is selected from a group represented by formula (1-1); L1 is selected from a substituted or unsubstituted alkane subunit having 1 to 10 carbon atoms and a substituted or unsubstituted alkene subunit having 2 to 10 carbon atoms; Each L2 is independently selected from any one of a single bond, a substituted or unsubstituted alkane subunit having 1 to 10 carbon atoms, and a substituted or unsubstituted alkene subunit having 2 to 10 carbon atoms; each R4 is independently selected from a substituted or unsubstituted alkyl subunit having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl subunit having 2 to 10 carbon atoms, a substituted or unsubstituted alkynyl subunit having 2 to 10 carbon atoms, and -L 21 At least one of R5; Each L 21 They are independently selected from a single bond, a substituted or unsubstituted alkane subunit with 1 to 10 carbon atoms, R5 is selected from -N(R6)2, and each R6 is independently selected from H, a substituted or unsubstituted alkane subunit with 1 to 10 carbon atoms, a phosphonic acid group and any one of the structures shown in formula (1-1); and (c) contains at least one group shown in formula (1-1).

7. The composite positive electrode material according to claim 6, characterized in that The organic lithium phosphonate compound satisfies at least one of the following conditions (3) to (5): (3) each R2 is independently selected from any one of H, Li, an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by a halogen, an alkyl group having 1 to 10 carbon atoms substituted by a hydroxyl group, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkylcarboxylic acid having 2 to 10 carbon atoms, and an alkylcarboxylic acid having 2 to 10 carbon atoms substituted by a hydroxyl group; (4) Each R3 is independently selected from any one of an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms substituted by a halogen, an alkyl group having 1 to 10 carbon atoms substituted by a hydroxyl group, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, a phosphonic acid group, and a group represented by formula (1-1); (5) Each R4 is independently selected from an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and -L 21 At least one of R5; each R6 is independently selected from any one of an alkane subunit having 1 to 10 carbon atoms, a phosphonic acid group and a group represented by formula (1-1).

8. The composite positive electrode material according to any one of claims 1 to 3, characterized in that: The components of the functional film layer also include a metal oxide type rock salt phase; Optionally, the metal in the metal oxide type rock salt phase includes at least one of Ni, Co and Mn.

9. The composite positive electrode material according to any one of claims 1 to 5, characterized in that: The components of the nickel-containing positive electrode material satisfy: Li t Ni x Co y A h O z ; Among them, A is selected from at least one of manganese, aluminum, copper, zinc, tin, magnesium and iron, 0<x<1, 0<y<1, 1.5≤y≤2.5, 0<h<1, 0.8≤t≤1.5, 1.5≤z≤2.

5.

10. The composite positive electrode material according to any one of claims 1 to 5, characterized in that: The mass proportion of residual lithium in the composite positive electrode material is ≤2%, and the residual lithium includes Li2CO3, LiOH and Li2O.

11. A method for preparing a composite positive electrode material, characterized in that: The steps include: The nickel-containing positive electrode material, M element and an organic phosphonic acid compound are mixed to prepare a prefabricated positive electrode material; The prefabricated positive electrode material is subjected to a chemical formation treatment to prepare the composite positive electrode material; The M element includes at least one of sulfur, selenium and tellurium; the organic phosphonic acid compound has a structure shown in formula (2): * represents the site where the structure represented by formula (2) is connected to other structures in the organic phosphonic acid compound.

12. The method for preparing a composite positive electrode material according to claim 11, characterized in that: The mixing process comprises the following steps: The nickel-containing positive electrode material and the M element are subjected to a first mixing treatment, and then the organic phosphonic acid compound is added to perform a second mixing treatment; Optionally, the first mixing treatment time is 0.5h to 6h; Optionally, the second mixing treatment time is 0.5h to 3h.

13. The method for preparing a composite positive electrode material according to any one of claims 11 to 12, characterized in that: The mixing process satisfies at least one of the following conditions (6) to (7): (6) The mass ratio of the M element to the nickel-containing positive electrode material is (0.01-1):100; Optionally, the mass ratio of the M element to the nickel-containing positive electrode material is (0.1-0.4):100; (7) The mass ratio of the organic phosphonic acid compound to the nickel-containing positive electrode material is (0.01-1):100; Optionally, the mass ratio of the organic phosphonic acid compound to the nickel-containing positive electrode material is (0.1-0.5):

100.

14. A positive electrode sheet, characterized in that: The positive electrode sheet comprises the composite positive electrode material according to any one of claims 1 to 10 or a composite positive electrode material prepared by the method for preparing the composite positive electrode material according to any one of claims 11 to 13.

15. A secondary battery, characterized in that: The battery comprises the composite positive electrode material according to any one of claims 1 to 10 or the composite positive electrode material prepared by the method for preparing the composite positive electrode material according to any one of claims 11 to 13 or the positive electrode sheet according to claim 14.

16. An electrical device, characterized in that: The electric device comprises the secondary battery as claimed in claim 15 .

Images