Positive electrode material, secondary battery, and electric device

Abstract

A positive electrode material, a secondary battery, and an electric device. The secondary battery comprises a positive electrode sheet; the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector; the positive electrode film layer comprises a positive electrode material, and the positive electrode material comprises a positive electrode active material and a coating material located on the surface of the positive electrode active material; the coating material comprises a copolymer of a cyano-containing compound and acetoacetic acid 2-(methacryloyloxy)ethyl ester. The positive electrode sheet in the secondary battery has a high discharge capacity per gram, and the secondary battery has good cycle and storage performance.

Description

Cathode material, secondary battery and electric device

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411168165.X, filed on August 23, 2024, entitled "Cathode material, secondary battery and electric device", the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of batteries, in particular to a cathode material, a secondary battery and an electric device. BACKGROUND

[0004] The cathode sheet of the secondary battery has the problems of transition metal dissolution of lithium ion cathode active material and a large amount of side reactions releasing oxygen under high pressure, resulting in a decrease in the cycle storage performance of the secondary battery.

[0005] Therefore, it is essential to develop a secondary battery that can solve the above problems. SUMMARY

[0006] In view of the above problems, the present application provides a cathode material, a secondary battery and an electric device. The cathode material forms a cathode sheet with high discharge gram capacity, and the secondary battery has good cycle storage performance.

[0007] In a first aspect, the present application provides a secondary battery, which comprises a cathode sheet.

[0008] The cathode sheet comprises a cathode current collector and a cathode film layer arranged on at least one surface of the cathode current collector.

[0009] The cathode film layer comprises a cathode material, which comprises a cathode active material and a coating material on the surface of the cathode active material.

[0010] The coating material comprises a cyan group-containing compound and a copolymer of acetyl acetic acid methyl methacrylic acid ethylene glycol ester.

[0011] In the technical scheme of the present application, the copolymer of the cyan group-containing compound and acetyl acetic acid methyl methacrylic acid ethylene glycol ester (AAEM); the β diketone bidentate chelate coordination in the structural unit formed by AAEM forms a stable six-membered chelate ring, which can stabilize transition metal ions in multiple oxidation states and coordination numbers; the cyan group-containing compound provides strong electronegativity for the copolymer, which is conducive to the stability of the six-membered chelate ring, and the two work together to improve the problems of transition metal dissolution and a large amount of side reactions releasing oxygen, improve the discharge gram capacity of the cathode sheet, and improve the cycle storage performance of the secondary battery.

[0012] In some embodiments, the cyano-containing compound comprises acrylonitrile (AN).

[0013] In the technical solutions of the embodiments of the present application, the acrylonitrile has high reactivity, the structural unit formed after copolymerization has strong electronegativity, which further stabilizes the six-membered chelate ring, and the structural unit of the AAEM, thereby further improving the problems of transition metal elution and oxygen release in a large number of side reactions, improving the discharge gram capacity of the positive electrode sheet, and improving the cyclic storage performance of the secondary battery, especially the high-temperature cyclic storage performance and the like.

[0014] In some embodiments, the copolymer comprises a six-membered ring, the six-membered ring comprises an N atom arranged on the ring, and ＊ = NH substituent group, wherein * represents a substituent connection site.

[0015] In some embodiments, the six-membered ring in the copolymer is formed by a cyano group (-CN) in the cyano-containing compound, which provides strong electronegativity to the copolymer, is conducive to the stability of the six-membered chelate ring, and the two together improve the problems of transition metal elution and oxygen release in a large number of side reactions, improve the discharge gram capacity of the positive electrode sheet, and improve the cyclic storage performance of the secondary battery, especially the high-temperature cyclic storage performance and the like.

[0016] In some embodiments, the structural formula of the six-membered ring is as shown in Formula 1:

[0017] Wherein, n≥2, optionally selected from 2-4.

[0018] In some embodiments, the structural formula of the copolymer is as shown in Formula 2:

[0019] Wherein, n≥2, optionally selected from 2-4; m≥2.

[0020] In some embodiments, the mass ratio of the coating material and the positive electrode active material is (0.5-2):100; and / or;

[0021] The thickness of the shell layer formed by the coating material is 2-10 nm.

[0022] In the technical solutions of the embodiments of the present application, the mass ratio of the coating material and the positive electrode active material is in the above range, which can well adjust the thickness of the shell layer; the reason for controlling the thickness of the shell layer formed by the coating material to be 2-10 nm is that: within the thickness range, the positive electrode active material can be effectively coated, and the positive electrode active material has good conductivity, which is conducive to improving the cyclic storage performance of the secondary battery and the like.

[0023] In some embodiments, the copolymer has a copolymerization molar ratio of the cyano-containing compound and the acetoacetic acid methyl methacrylate glycol ester of (40-80):(20-60).

[0024] In the technical solution of the embodiments of the present application, the reason for controlling the copolymerization molar ratio of the cyano-containing compound and the AAEM in the copolymer within the range is that the molar ratio of the two is stable in the coordination of the β-diketone bidentate chelate, which is beneficial to improving the cycle storage performance of the secondary battery and the like.

[0025] In some embodiments, the weight average molecular weight of the copolymer is 10000-200000.

[0026] In the technical solution of the embodiments of the present application, the reason for controlling the weight average molecular weight of the copolymer within the range is that the weight average molecular weight within the range is beneficial to the thickness control of the shell layer formed by the coating material, the industrial production, and the stability of the shell layer, and reduces the risk of swelling of the shell layer too large or even dissolving in the electrolyte.

[0027] In some embodiments, the positive electrode active material includes any one or a combination of at least two of a ternary positive electrode material, a lithium-rich manganese-based material, lithium manganate, or nickel lithium manganate; and / or;

[0028] The ternary positive electrode material includes a nickel-cobalt-manganese ternary positive electrode material; and / or;

[0029] The lithium-rich manganese-based positive electrode material includes Li2MnO3 and / or LiMnO2.

[0030] In a second aspect, the present application provides a positive electrode material,

[0031] The positive electrode material includes a positive electrode active material and a coating material located on the surface of the positive electrode active material.

[0032] The coating material includes a copolymer of a cyano-containing compound and acetoacetic acid methyl methacrylate glycol ester.

[0033] In some embodiments, the cyano-containing compound includes acrylonitrile.

[0034] In some embodiments, the copolymer includes a six-membered ring, the six-membered ring includes an N atom arranged on the ring, and ＊ =NH substituent, wherein * represents a substituent connection site.

[0035] In some embodiments, the structure of the six-membered ring is as shown in Formula 1:

[0036] wherein n≥2, and is optionally selected from 2-4.

[0037] In some embodiments, the structural formula of the copolymer is shown as Formula 2:

[0038] wherein n≥2, optionally selected from 2-4; m≥2.

[0039] In some embodiments, the thickness of the shell layer formed by the coating material is 2-10 nm.

[0040] In some embodiments, the copolymer has a copolymerization molar ratio of the cyan group-containing compound and the acetyl acetic acid glycol methacrylate of (40-80):(20-60).

[0041] In some embodiments, the copolymer has a weight average molecular weight of 10000-200000.

[0042] In some embodiments, the positive electrode active material comprises any one or a combination of at least two of a ternary positive electrode material, a lithium-rich manganese-based material, lithium manganate, or nickel lithium manganate; and / or;

[0043] The ternary positive electrode material comprises a nickel cobalt manganese ternary positive electrode material; and / or;

[0044] The lithium-rich manganese-based positive electrode material comprises Li2MnO3 and / or LiMnO2.

[0045] In a third aspect, the present application provides a preparation method of a positive electrode material, comprising the following steps:

[0046] The coating material is arranged on the surface of the positive electrode active material to obtain the positive electrode material;

[0047] The coating material comprises a copolymer of a cyan group-containing compound and acetyl acetic acid glycol methacrylate.

[0048] In some embodiments, the preparation method of the copolymer comprises the following steps:

[0049] The cyan group-containing compound and the acetyl acetic acid glycol methacrylate are copolymerized to obtain the copolymer.

[0050] In some embodiments, the copolymerization temperature is 70-90°C; and / or;

[0051] The copolymerization time is 1-20h.

[0052] In some embodiments, the copolymerization is carried out in a solvent, and the solvent comprises N-methyl pyrrolidone.

[0053] In some embodiments, the manner of arranging the copolymer on the surface of the positive electrode active material comprises spray drying.

[0054] In some embodiments, the spray drying process further includes pre-oxidation into rings; and / or;

[0055] The pre-oxidation cyclization temperature is 180-240℃; and / or;

[0056] The pre-oxidation cyclization time is 1-10 hours.

[0057] Fourthly, this application provides an electrical device comprising the secondary battery described in the first aspect, and / or the positive electrode material described in the second aspect, and / or the positive electrode material obtained by the preparation method described in the third aspect.

[0058] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0059] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0060] Figure 1 is a structural characterization diagram of the prepolymer (PAN-AAEM prepolymer) of acrylonitrile and ethylene glycol acetoacetate methacrylate obtained in step (1) of Example 1 of this application;

[0061] Figure 2 is a transmission electron microscope (TEM) image of the coated active material in Example 1 of this application at a scale of 10 nm;

[0062] Figure 3 is a TEM image of the coated active material of Example 1 of this application at a scale of 50 nm.

[0063] Figure 4 is a TEM image of the coated active material of Comparative Example 3 of this application at a scale of 10 nm. Detailed Implementation

[0064] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," or "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of" and variations thereof. Unless otherwise noted, the terms "plurality" and "a plurality" as used herein encompass both "multiple" and "two or more."

[0066] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that any of the embodiments described herein can be incorporated into any other embodiment in a manner known to those of ordinary skill in the art.

[0067] "Ranges" disclosed herein are defined, described and covered, either explicitly or implicitly, by the stated lower and upper boundary values of the range. Ranges are inclusive of their endpoints unless otherwise specifically stated. Ranges can be combined in any order, i.e., any lower value can be combined with any upper value to form a range, unless otherwise indicated. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Also, if a minimum range value of 1 and 2 are listed, and a maximum range value of 3, 4 and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, a numerical range "a-b" indicates a shorthand way of describing all the real combinations of values between "a" and "b", where "a" and "b" are both real numbers. For example, the numerical range "2-10" indicates that all the real numbers between "2" and "10" have been listed herein, and "2-10" is just a shorthand way of describing these combinations of values. In addition, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0068] In the description of the embodiments of the application, the term "and / or" is merely used to describe associated objects, and indicates that there can be three types of relationships between the associated objects, for example, A and / or B can indicate that there are A, A and B, and B. In addition, the character " / " in the text generally indicates that the front and rear associated objects are in an "or" relationship.

[0069] At high voltage (e.g. 4.5V, etc.), the transition metal (e.g. Mn, etc.) in the positive electrode sheet (e.g. lithium ion positive electrode active material, such as lithium-rich manganese system) is dissolved and a large amount of side reactions release oxygen, which can cause the performance of the secondary battery, such as cycle storage, to decrease.

[0070] In the related art, in the face of the above technical problems, one of the traditional methods is to dope non-active cations (e.g. T i4+ , Se 6+ , Nb 5+ , etc.) in the coating layer formed on the outer surface of the positive electrode active material to enhance and combine with oxygen and thereby inhibit the release of oxygen, but the above-mentioned doped coating layer cannot isolate the positive electrode active material from contact with the electrolyte, and a large amount of transition metal is dissolved; the second traditional method is to form an inert coating layer on the outer surface of the positive electrode active material, and the inert coating layer is coated with inorganic metal oxides (e.g. Al2O3, MgO, etc.) or phosphates (e.g. NaPO3, β-NaCaPO4, etc.), but the above-mentioned inert coating layer has poor ion conduction ability, and the expansion of the positive electrode active material can cause the coating layer to crack, affecting the performance of the secondary battery.

[0071] If the dissolution of transition metal and a large amount of side reactions can be reduced, and the ion conduction of the positive electrode active material is not affected on the basis that the coating layer does not crack, the performance of the secondary battery can be further improved.

[0072] Based on the above considerations, in order to solve the problems of transition metal dissolution and a large amount of side reactions releasing oxygen in the positive electrode sheet (e.g. lithium ion positive electrode active material, such as lithium-rich manganese system) at high voltage, a positive electrode material, a secondary battery and an electric device are developed based on the above design concept through experimental research.

[0073] [Secondary battery]

[0074] The present application provides a secondary battery, which comprises a positive electrode sheet;

[0075] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one (e.g. one or two, etc.) surface of the positive electrode current collector;

[0076] The positive electrode film layer comprises a positive electrode material, and the positive electrode material comprises a positive electrode active material and a coating material arranged on the surface of the positive electrode active material;

[0077] The coating material comprises a copolymer of a compound containing a cyano group and acetyl acetic acid methyl methacrylate ethylene glycol ester;

[0078] In the technical scheme of the present application, the copolymer of the compound containing a cyano group and acetyl acetic acid methyl methacrylate ethylene glycol ester (AAEM) has a certain flexibility; wherein the structural formula of AAEM is Moreover, the β-diketone bidentate chelating coordination in the structural unit formed by AAEM forms a stable six-membered chelate ring, which can stabilize transition metal ions in multiple oxidation states and coordination numbers; the structural unit formed by the compound containing a cyano group provides strong electronegativity for the copolymer, which is conducive to the stability of the six-membered chelate ring, and the two work together to improve the problems of transition metal dissolution and a large amount of side reactions releasing oxygen, improve the discharge gram capacity of the positive electrode sheet, and improve the cycle storage performance of the secondary battery.

[0079] In some embodiments, the compound containing a cyano group includes acrylonitrile (AN). The structural formula of AN is

[0080] In the technical solution of the embodiments of the present application, acrylonitrile has high reactivity, and the structural unit formed after copolymerization has strong electronegativity, which further stabilizes the six-membered chelate ring. The structural unit of AAEM and the structural unit of the compound containing a cyano group work together to further improve the problems of transition metal dissolution and a large amount of side reactions releasing oxygen, improve the discharge gram capacity of the positive electrode sheet, and improve the cycle storage performance of the secondary battery, especially the high-temperature cycle storage performance and other performances.

[0081] In some embodiments, the copolymer includes a six-membered ring, and the six-membered ring includes an N atom arranged on the ring and ＊ =NH substituent group, wherein * represents a substituent connection site.

[0082] In the present application, the * represents a substituent connection site on the six-membered ring.

[0083] In some embodiments, the six-membered ring in the copolymer is formed by a cyano group (-CN) in the compound containing a cyano group, which provides strong electronegativity for the copolymer, which is conducive to the stability of the six-membered chelate ring. The two work together to improve the problems of transition metal dissolution and a large amount of side reactions releasing oxygen, improve the discharge gram capacity of the positive electrode sheet, and improve the cycle storage performance of the secondary battery, especially the high-temperature cycle storage performance and other performances.

[0084] In the technical solution of the embodiments of the present application, the structural formula of the six-membered ring is as shown in formula 1:

[0085] Wherein, n≥2, for example, 3, 4, 5, 6, etc., and can be selected from 2-4.

[0086] In the technical solution of the embodiments of the present application, the structural formula of the copolymer is as shown in formula 2:

[0087] Wherein, n≥2, for example, 3, 4, 5, 6, etc., and can be selected from 2-4.

[0088] m≥2, for example, 3, 4, 5, 6, etc.

[0089] The above structural formula is merely exemplary and meets the actual needs of the present application.

[0090] In the technical solution of the embodiment of the present application, the β-diketone bidentate chelating coordination in the AAEM structural unit forms a stable six-membered chelate ring, and an exemplary structural formula is as follows:

[0091] In the formula, M represents a transition metal (such as Mn, etc.), and the wavy line represents an intermediate undefined structure.

[0092] In some embodiments, the mass ratio of the coating material and the positive electrode active material is (0.5-2):100, where 0.5-2 can be 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, etc.; and / or;

[0093] The thickness of the shell layer formed by the coating material is 2-10 nm, such as 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, etc.

[0094] In the technical solution of the embodiment of the present application, the mass ratio of the coating material and the positive electrode active material is within the above range, which can well adjust the thickness of the shell layer; the reason why the thickness of the shell layer formed by the coating material is controlled to be 2-10 nm is that the thickness range can form effective coating on the positive electrode active material, and the positive electrode active material has good conductivity, which is beneficial to improving the cycle storage performance and other performances of the secondary battery.

[0095] In some embodiments, in the copolymer, the copolymerization molar ratio of the compound containing a cyano group and the acetyl acetic acid methyl propylene glycol methacrylate is (40-80):(20-60), such as 50:50, 60:40, 70:30, etc.

[0096] In the technical solution of the embodiment of the present application, the reason why the copolymerization molar ratio of the compound containing a cyano group and the AAEM two monomers in the copolymer is controlled to be within the range is that the molar ratio of the two is within the range, the β-diketone bidentate chelating coordination is stable, and finally it is beneficial to improving the cycle storage performance and other performances of the secondary battery.

[0097] In some embodiments, the weight average molecular weight of the copolymer is 10000-200000, such as 20000, 40000, 60000, 80000, 100000, 120000, 140000, 160000, 180000, etc.

[0098] In the present application, the weight average molecular weight is tested by gel permeation chromatography (GPC), also known as size exclusion chromatography (SEC). The test instrument is a Malvern OMNISEC multi-detector GPC / SEC gel permeation chromatography system. The test method is as follows: the concentration of the copolymer sample to be tested is diluted to 2-5 mg / mL, filtered to an automatic sample bottle using a 0.22 μm-0.45 μm filter membrane, the device is started to start the automatic test process, and after completion, the weight average molecular weight of the copolymer is calculated.

[0099] In the technical scheme of the embodiments of the present application, the reason why the weight average molecular weight of the copolymer is controlled within the range is that the weight average molecular weight within the range is beneficial to the control of the shell layer thickness of the coating material, is beneficial to industrial production, and is also beneficial to the stability of the shell layer, reducing the risk of swelling of the shell layer too large or even dissolving in the electrolyte.

[0100] In some embodiments, the positive electrode active material includes any one or a combination of at least two of a ternary positive electrode material, a lithium-rich manganese-based material, lithium manganate, or nickel-lithium manganate; and / or;

[0101] The ternary positive electrode material includes a nickel-cobalt-manganese ternary positive electrode material; and / or;

[0102] The lithium-rich manganese-based positive electrode material includes Li2MnO3 and / or LiMnO2.

[0103] In some embodiments, the nickel-cobalt-manganese ternary positive electrode material can be, for example, NCM333, NCM523, NCM622, and NCM811, etc.

[0104] In some embodiments, the positive electrode current collector can use any known material, for example, the positive electrode current collector includes a metal foil or a composite current collector.

[0105] In some embodiments, the metal foil includes an aluminum foil.

[0106] In some embodiments, the composite current collector includes a polymer material substrate layer and a metal layer arranged on at least one side of the polymer material substrate layer, wherein the material of the polymer material substrate layer includes any one or a combination of at least two of polyethylene, polypropylene, polystyrene, or polyethylene terephthalate; and the material of the metal layer includes any one or a combination of at least two of aluminum, nickel, titanium, silver, aluminum alloy, nickel alloy, titanium alloy, or silver alloy.

[0107] In some embodiments, the positive electrode film layer further includes a binder and / or a conductive agent.

[0108] In some embodiments, the binder includes any one or a combination of at least two of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorine-containing acrylate resin.

[0109] In some embodiments, the conductive agent includes any one or a combination of at least two of acetylene black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0110] The present application provides a preparation method of the positive electrode tab, including the following steps:

[0111] coating raw materials of the positive electrode film layer on at least one surface of the positive electrode current collector, drying to obtain the positive electrode tab;

[0112] The raw materials of the positive electrode film layer include a positive electrode active material and a coating material.

[0113] The coating material includes a copolymer formed by acrylonitrile and ethylene glycol acrylate acetoacetate.

[0114] In some embodiments, the raw materials of the positive electrode film layer, such as the positive electrode active material, the coating material, the binder, the conductive agent, any other components, and the solvent (such as N-methylpyrrolidone NMP, etc.).

[0115] In some embodiments, the drying further includes cold pressing, slitting, and the like.

[0116] In some embodiments, the positive electrode material includes a positive electrode active material and a coating material located on the surface of the positive electrode active material.

[0117] The coating material includes a copolymer of a cyano-containing compound and ethylene glycol acrylate acetoacetate.

[0118] In some embodiments, the preparation method of the positive electrode material includes the following steps:

[0119] setting the coating material on the surface of the positive electrode active material to obtain the positive electrode material.

[0120] The coating material includes a copolymer of a cyano-containing compound and ethylene glycol acrylate acetoacetate.

[0121] In some embodiments, the preparation method of the copolymer includes the following steps:

[0122] copolymerizing the cyano-containing compound and ethylene glycol acrylate acetoacetate to obtain the copolymer.

[0123] In some embodiments, the temperature of the copolymerization is 70-90°C, such as 75°C, 80°C, 85°C, etc.; and / or,

[0124] The time of the copolymerization is 1-20h, such as 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, etc.

[0125] In some embodiments, the copolymerization is performed in a solvent, which optionally includes N-methylpyrrolidone.

[0126] In some embodiments, the solvent is added in an amount of 50%-400% based on 100% of the total moles of the cyan-containing compound and the ethylene glycol methacrylate acetoacetate, such as 100%, 150%, 200%, 250%, 300%, 350%, etc. In certain embodiments, the molecular weight of the copolymer of the cyan-containing compound and the ethylene glycol methacrylate acetoacetate can be adjusted by adjusting the amount of the solvent added.

[0127] In some embodiments, the copolymerization is performed under the action of an initiator, which optionally includes a peroxide initiator (such as benzoyl peroxide, etc.) and / or an azo initiator (such as azobisisobutyronitrile, azobisisoheptyl nitrile, or dimethyl azobisisobutyrate, etc.).

[0128] In some embodiments, the manner of disposing the copolymer on the surface of the positive electrode active material includes spray drying.

[0129] For example, using an industrial solvent spray drying device, the positive electrode active material, the copolymer, and the solvent are mixed uniformly, spray dried, and the cyclone separated material is collected to form a shell layer on the outer surface of the positive electrode active material, thereby obtaining a positive electrode material.

[0130] In some embodiments, the spray drying is further followed by pre-oxidation into a ring; and / or;

[0131] The temperature of the pre-oxidation into a ring is 180-240°C (such as 190°C, 200°C, 210°C, 220°C, 230°C, etc.); and / or;

[0132] The time of the pre-oxidation into a ring is 1-10h (such as 2h, 4h, 6h, 8h, etc.).

[0133] In some embodiments, the method for preparing the positive electrode material includes the following steps:

[0134] (1) copolymerizing a cyan-containing compound and ethylene glycol methacrylate acetoacetate in a molar ratio of (40-80):(20-60) in a solvent through an initiator, wherein the temperature of the copolymerization is 70-90°C, and the time of the copolymerization is 1-20h, thereby obtaining a first copolymer;

[0135] (2) the first copolymer is arranged on the surface of the positive active material by spray drying to form a shell layer, to obtain the positive material; optionally, after the spray drying, the second copolymer is obtained by pre-oxidizing into a ring at 180-240℃ for 1-10h.

[0136] In the present application, the first copolymer can be directly used as a coating material to form a shell layer on the surface of the positive active material to obtain the positive material; the first copolymer can also be pre-oxidized into a ring on the surface of the positive active material to obtain a second copolymer containing a six-membered ring as a coating material to form a shell layer while completing pre-oxidation to obtain the positive material. The first copolymer and the second copolymer differ in whether pre-oxidation into a ring is performed.

[0137] In the technical scheme of the embodiments of the present application, the six-membered ring is formed by at least two (for example, 3, 4, 5, etc.) cyano groups in a compound containing cyano groups, such as acrylonitrile; an example path formed by acrylonitrile is exemplarily as follows:

[0138] wherein n≥2, for example, 3, 4, 5, 6, etc., and is optionally selected from 2-4.

[0139] Taking n=4 as an example, the path of the six-membered ring is exemplarily as follows with acrylonitrile:

[0140] (1) AN forms an AN repeating unit

[0141] (2) the AN repeating unit is pre-oxidized into a ring

[0142] In the present application, the above AN forms an AN repeating unit is only exemplarily drawn for the convenience of showing the formation process of the six-membered ring, and in fact, the number of cyano groups in the structure of intermediate 1 is≥2, and is further preferably 2-4.

[0143] In the present application, in the process of pre-oxidizing the AN repeating unit into a ring, intermediate 1 first forms intermediate 2, and intermediate 2 can directly form the six-membered ring structure, and the pre-oxidation temperature is >180℃, such as 180℃

[0144] In some embodiments, the positive electrode tab can be prepared by a method comprising: forming a shell layer on the surface of the positive electrode active material by coating material, to obtain a positive electrode material; dissolving the raw materials of the positive electrode film layer, i.e. the positive electrode material, the binder, the conductive agent and other optional additives, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on one side or both sides of the positive electrode current collector, drying to form a positive electrode film layer, to obtain the positive electrode tab. Optionally, after drying, cold pressing, slicing and other operations are performed.

[0145] [the negative electrode tab]

[0146] As the negative electrode tab, the present application is not particularly limited, and any known negative electrode tab can be selected according to actual needs.

[0147] In some embodiments, the preparation method of the negative electrode tab comprises: dissolving the negative electrode material, such as the negative electrode active material (e.g. graphite), the conductive agent (e.g. acetylene black), the binder (e.g. butadiene rubber), and other optional components (e.g. thickening agent, such as sodium carboxymethyl cellulose), in a solvent (e.g. deionized water), to form a negative electrode slurry, coating the negative electrode slurry on the negative electrode current collector (e.g. copper foil), and drying, cold pressing, and slicing to obtain the negative electrode tab.

[0148] [the electrolyte]

[0149] In some embodiments, the secondary battery further comprises an electrolyte.

[0150] As the electrolyte, the present application is not particularly limited, and any known electrolyte with ion conduction function can be selected according to actual needs. The electrolyte comprises an electrolyte salt, a solvent, and optional additives.

[0151] In some embodiments, the electrolyte salt is selected from lithium salts, including lithium hexafluorophosphate (LiPF6).

[0152] In some embodiments, the solvent comprises any one or a combination of at least two of ethylene carbonate (EC), methyl ethyl carbonate (EMC), or diethyl carbonate (DEC).

[0153] [the separator]

[0154] As the separator, the present application is not particularly limited, and any known porous structure separator with electrochemical stability and mechanical stability can be selected according to actual needs. For example, the separator can be a single-layer or multi-layer film comprising one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0155] In some embodiments, the secondary battery can be prepared by the following method: stacking and winding the above positive electrode sheet, separator, and negative electrode sheet in sequence to obtain a battery cell; placing the battery cell into an outer package, adding electrolyte, and then performing packaging, standing, formation, aging, and other processes to obtain the secondary battery.

[0156] [Battery module, battery pack]

[0157] In some embodiments, the battery can be assembled into a battery module, and the number of batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0158] In some embodiments, the battery can also be assembled into a battery pack.

[0159] In some embodiments, the battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0160] [Power consumption device]

[0161] The present application provides a power consumption device, which comprises the secondary battery.

[0162] In some embodiments, the power consumption device comprises at least one of the battery module or the battery pack provided in any of the embodiments of the present application.

[0163] The secondary battery, battery module, or battery pack described in the present application can be used as a power source of the power consumption device, or can be used as an energy storage unit of the power consumption device. The power consumption device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0164] [Embodiments]

[0165] Embodiment 1

[0166] Positive electrode sheet: the positive electrode sheet is obtained by the following preparation method:

[0167] (1) The AN and AAEM are added to the NMP solvent in a molar ratio of 80:20, the molar ratio of the solvent and the two monomers is 86:1, the mixture is stirred and heated to 75°C and nitrogen is introduced for 1 hour, 0.1% initiator (azobisisobutyronitrile) is added according to the molar ratio of the monomers, and the reaction is carried out for 12 hours, then the temperature is raised to 85°C, and 0.1% initiator is added according to the molar ratio of the monomers, and the reaction is carried out for 2 hours, to obtain the PAN-AAEM prepolymer, the weight average molecular weight is 200000, the structure characterization schematic diagram is shown in Figure 1, wherein 2242.83 is the characteristic peak of cyano group, and 1737.6 is the characteristic peak of ester carbonyl group, which proves that the PAN-AAEM prepolymer is successfully synthesized;

[0168] (2) The positive active material (lithium-rich manganese Li2MnO3) and NMP are mixed uniformly in a mass ratio of 1:1, stirred for 1 hour, and then 1% of the positive active material (calculated according to 100% solid content) PAN-AAEM prepolymer is added, and the mixture is stirred for 30 minutes, then fed, and then sprayed and dried in a nitrogen environment at 180°C, and then pre-oxidized at 230°C for 3h to obtain the PAN-AAEM copolymer, and the cyclone separated material is collected to obtain the positive electrode material, and the PAN-AAEM copolymer forms a shell layer of 5.7nm on the outer surface of the positive active material;

[0169] (3) The positive electrode material, the binder PVDF, and the conductive agent acetylene black are dissolved in the solvent NMP in a mass ratio of 97.3:2.4:0.3, and the mixture is stirred and mixed uniformly to obtain a positive electrode slurry; the positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and then the coated positive electrode current collector is obtained after drying, and then the coated positive electrode current collector is subjected to drying, cold pressing, and cutting to obtain the positive electrode sheet.

[0170] The negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber, and the thickening agent sodium carboxymethyl cellulose are dissolved in deionized water in a mass ratio of 95:2:1:2, and the mixture is stirred and mixed uniformly to obtain a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then the negative electrode sheet is obtained after drying, cold pressing, and cutting.

[0171] The separator film is a polyethylene film.

[0172] The electrolyte is prepared by mixing ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1, and then dissolving LiPF6 uniformly in the above solution. The concentration of LiPF6 in the electrolyte is 1 mol / L.

[0173] Assembly: The above positive electrode sheet, separator film, and negative electrode sheet are stacked and wound in sequence to obtain a battery cell; the battery cell is placed in an outer package, and the above prepared electrolyte is added, and then the battery cell is subjected to packaging, standing, formation, aging, and other processes to obtain the secondary battery.

[0174] Examples 2-10 and Comparative Examples 1-3

[0175] In addition to the parameters in Table 1 and Table 2, the secondary battery was prepared according to the method of Example 1.

[0176] Table 1: Material and structure information of the positive electrode material

[0177] Table 2: Process parameters for preparing the positive electrode sheet

[0178] In the table, the polymer refers to the PAN-AAEM copolymer, the PAN homopolymer or the PAAEM homopolymer, which is consistent with the material of the shell in the examples or comparative examples.

[0179] “—” refers to data not involved.

[0180] Performance test

[0181] (1) Coating effect test:

[0182] 1) Transmission electron microscopy (TEM) test was used, and the test process was as follows: a small amount of powder sample was taken to a test tube, ethanol was added to about 2 / 3 of the test tube, ultrasonic dispersion was performed for about 15 min, and standing was performed for about 5 min. 1-2 drops of supernatant were taken by a pipette and dropped onto a copper mesh, and an infrared lamp was used for baking to complete the sample preparation. Finally, the sample was sent for TEM test, model Thermo Scientific-Talos F200S G2;

[0183] 2) The TEM equipment projects a high-voltage accelerated electron beam onto a thin sample (nm), and the electron interacts with the atoms in the sample to scatter; by collecting the scattered electrons after transmission, the angle, intensity and energy of the scattered electrons can be analyzed, and the size, morphology, structure and composition information of the sample can be obtained.

[0184] The test results are shown in Figures 2-4. As can be seen from Figures 2-4, according to the comparison between Figures 2-3 and Figure 4, it can be seen that the shell layer is successfully coated on the surface of the positive electrode active material according to the examples of the present application.

[0185] (2) 60°C high-temperature cycle storage performance test: in a 60°C constant temperature environment, the secondary battery is charged from 2.5V to the upper limit cut-off voltage (4.4V) at 0.33C, then charged to a current of ≤0.05mA at a constant voltage, discharged to 2.5V at 0.33C, and the discharge capacity D0 was recorded. Then the secondary battery was charged to a current of ≤0.05mA at a constant voltage with the upper limit cut-off voltage (4.4V), and the secondary battery was left to stand for 150 days. During the standing period, three cycles were performed continuously every 15 days, and each cycle was discharged to 2.5V at 0.33C and then charged to a current of ≤0.05mA at a constant voltage of 4.4V. The discharge capacity of the third cycle was recorded as Dn. n (n = 1, 2, 3…), n represents the n th 15-day standing. The value of Dn / D0 is the capacity retention rate, which is used as an evaluation index of the degree of cell attenuation at the n th 15-day high-temperature storage, and the capacity retention rate at the 90 th day is recorded. n

[0186] (3) First coulombic efficiency: according to the embodiments of the present application, the steps for determining the rated capacity can include: at 25°C, using a charge-discharge machine, first charging to 4.4V at 1 / 3C, then charging to a current of 0.05C at a constant voltage of 4.4V, and the total capacity of this charging is the charging capacity; then discharging to 2.5V at 1 / 3C, and the discharge capacity at this time is the discharge capacity of the battery. The first coulombic efficiency is the charging capacity divided by the discharge capacity.

[0187] (4) Discharge gram capacity: according to the embodiments of the present application, the steps for determining the rated capacity can include: at 25°C, using a charge-discharge machine, first charging to 4.25V at 1 / 3C, then charging to a current of 0.05C at a constant voltage of 4.25V; then discharging to 2.5V at 1 / 3C, and the discharge capacity at this time is the discharge capacity of the battery. The discharge gram capacity is the discharge capacity divided by the total mass of active material.

[0188] The test results are summarized in Table 3.

[0189] Table 3

[0190] In the table, Fading EOL, i.e. End of Life, refers to the state in which the secondary battery can no longer safely and effectively provide the required power.

[0191] ​As can be seen from the data in Table 3, the discharge gram capacity of the positive electrode sheet in the secondary battery described in the application is above 181.06 mAh / g, the first coulombic efficiency of the secondary battery is above 82.98%; under the test conditions of 60°C and 0.33C, after 90 days of cell decay, the capacity retention rate is above 81.76%, that is, the high-temperature storage time is above 90 days; the positive electrode sheet in the secondary battery described in the application has high discharge gram capacity, and the secondary battery has high capacity retention rate after 90 days of cell decay under the test conditions of 60°C and 0.33C, and has excellent cycle storage performance, especially excellent high-temperature cycle storage performance.

[0192] As can be seen from Comparative Examples 1-3 and Example 1, the performance of Comparative Examples 1-3 is not as good as that of Comparative Example 1, proving that the positive electrode sheet formed by using the shell layer described in the application is more beneficial to the performance improvement of the secondary battery.

[0193] As can be seen from Examples 4-7, the performance of Examples 6-7 is not as good as that of Examples 4-5, proving that the shell layer formed by using the coating material with a thickness in the range of 2-10 nm is more beneficial to the performance improvement of the secondary battery.

[0194] As can be seen from Examples 8-9 and Example 1, the performance of Examples 8-9 is not as good as that of Example 1, proving that the positive electrode sheet formed by using the copolymer described in the application with a co-molar ratio of the compound containing a cyano group to AAEM in the range of (40-80):(20-60) is more beneficial to the performance improvement of the secondary battery.

[0195] As can be seen from Example 10 and Example 1, the performance of Example 10 is not as good as that of Example 1, proving that the copolymer described in the application containing a six-membered ring is more beneficial to the performance improvement of the secondary battery.

[0196] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application, but not to limit them; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application, and they should be covered in the scope of the claims and the description of the application. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, wherein, The secondary battery comprises a positive electrode sheet; The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector; The positive electrode film layer comprises a positive electrode material, and the positive electrode material comprises a positive electrode active material and a coating material arranged on a surface of the positive electrode active material; The coating material comprises a cyan-containing compound and a copolymer of acetyl acetic acid glycol methacrylate.

2. The secondary battery according to claim 1, wherein The cyan-containing compound comprises acrylonitrile.

3. The secondary battery according to claim 1 or 2, wherein The copolymer includes a six-membered ring including an N atom disposed on the ring and ＊ = NH substituent, wherein * represents a substituent attachment site.

4. The secondary battery according to claim 3, wherein The structural formula of the six-membered ring is shown as Formula 1: n is greater than or equal to 2, and is optionally selected from 2 to 4.

5. The secondary battery according to any one of claims 1 to 4, wherein The structural formula of the copolymer is shown as Formula 2: n is greater than or equal to 2, and is optionally selected from 2 to 4.

6. The secondary battery according to any one of claims 1 to 5, wherein The mass ratio of the coating material to the positive electrode active material is (0.5-2):100; and / or; The thickness of the shell layer formed by the coating material is 2-10 nm.

7. The secondary battery according to any one of claims 1 to 6, wherein In the copolymer, the copolymerization molar ratio of the cyan-containing compound to acetyl acetic acid glycol methacrylate is (40-80):(20-60).

8. The secondary battery according to any one of claims 1 to 7, wherein The weight average molecular weight of the copolymer is 10000-200000.

9. The secondary battery according to any one of claims 1 to 8, wherein The positive electrode active material comprises any one or a combination of at least two of a ternary positive electrode material, a lithium-rich manganese-based material, lithium manganate or nickel manganate; and / or; The ternary positive electrode material comprises a nickel-cobalt-manganese ternary positive electrode material; and / or; The lithium-rich manganese-based positive electrode material comprises Li2MnO3 and / or LiMnO2.

10. A positive electrode material, wherein, The positive electrode material comprises a positive electrode active material and a coating material arranged on a surface of the positive electrode active material; The coating material comprises a cyan-containing compound and a copolymer of acetyl acetic acid glycol methacrylate.

11. The cathode material of claim 10, wherein, The cyan-containing compound comprises acrylonitrile.

12. The positive electrode material according to claim 10 or 11, wherein The copolymer includes a six-membered ring including an N atom disposed on the ring and ＊ = NH substituent, wherein * represents a substituent attachment site.

13. The cathode material of claim 12, wherein, The structural formula of the six-membered ring is shown as Formula 1: n is greater than or equal to 2, and is optionally selected from 2 to 4.

14. The cathode material of any one of claims 10-13, wherein, The structural formula of the copolymer is shown as Formula 2: n is greater than or equal to 2, and is optionally selected from 2 to 4. m≥2。 15. The cathode material of any one of claims 10-14, wherein, The thickness of the shell layer formed by the coating material is 2-10 nm.

16. The cathode material of any one of claims 10-15, wherein, In the copolymer, the copolymerization molar ratio of the cyan-containing compound to acetyl acetic acid glycol methacrylate is (40-80):(20-60).

17. The cathode material of any of claims 10-16, wherein, The weight average molecular weight of the copolymer is 10000-200000.

18. The cathode material of any of claims 10-17, wherein, The positive electrode active material comprises any one or a combination of at least two of a ternary positive electrode material, a lithium-rich manganese-based material, lithium manganate or nickel manganate; and / or; The ternary positive electrode material comprises a nickel-cobalt-manganese ternary positive electrode material; and / or; The lithium-rich manganese-based positive electrode material comprises Li2MnO3 and / or LiMnO2.

19. A method of producing a positive electrode material, wherein, The preparation method comprises the following steps: arranging the coating material on the surface of the positive electrode active material to obtain the positive electrode material; The coating material comprises a cyan-containing compound and a copolymer of acetyl acetic acid glycol methacrylate.

20. The method of making according to claim 19, wherein, The preparation method of the copolymer comprises the following steps: copolymerizing the cyan-containing compound and acetyl acetic acid glycol methacrylate to obtain the copolymer.

21. The method of making according to claim 20, wherein, The copolymerization temperature is 70-90°C; and / or; The copolymerization time is 1-20h.

22. The method of manufacturing according to claim 20 or 21, wherein, The copolymerization is carried out in a solvent, and the solvent optionally comprises N-methyl pyrrolidone.

23. The method of making according to any one of claims 20-22, wherein, The way of arranging the copolymer on the surface of the positive electrode active material comprises spray drying.

24. The method of making according to any one of claims 20-23, wherein, The spray drying is followed by pre-oxidation into a ring; and / or; The pre-oxidation into a ring is carried out at a temperature of 180-240°C; and / or; The pre-oxidation ring formation time is 1-10h.

25. An electrical device, comprising: The electric device comprises the secondary battery according to any one of claims 1-9, and / or the positive electrode material according to any one of claims 10-18, and / or the positive electrode material obtained by the preparation method according to any one of claims 19-24.

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