Positive electrode active material and preparation method therefor, positive electrode sheet, battery, and electrical apparatus

Abstract

A positive electrode active material and a preparation method therefor, a positive electrode sheet, a battery, and an electrical apparatus. The positive electrode active material comprises an inner core and a coating layer; the inner core comprises a transition metal oxide; the coating layer is formed on the surface of the inner core; the coating layer comprises a polymer containing a silicon-oxygen bond; on the basis of the total mass of the positive electrode active material, the mass percentage of silicon in the polymer is 0.05%-1%.

Description

Positive electrode active material and preparation method thereof, positive electrode sheet, battery and electrical device

[0001] Priority information

[0002] This application requests priority to the Chinese patent application with patent application number 202311644278.8 filed with the State Intellectual Property Office of China on November 30, 2023, entitled “Positive electrode active material and preparation method thereof, positive electrode sheet, battery and electrical device”, and the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application belongs to the field of batteries, and specifically relates to a positive electrode active material and a preparation method thereof, a positive electrode sheet and a preparation method thereof, a battery and an electrical device. Background Art

[0004] In recent years, batteries have become increasingly widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As demand for battery energy density continues to rise, increasing the operating voltage of cathode materials is an effective approach. However, existing batteries suffer from high DC resistance and poor cycling performance at high voltages.

[0005] Summary of the Invention

[0006] In view of the technical problems existing in the background technology, the present application provides a positive electrode active material, aiming to improve the DC resistance and cycle performance of a battery containing the positive electrode active material at high voltage.

[0007] In order to achieve the above objectives, the present application provides, in a first aspect, a positive electrode active material, comprising:

[0008] an inner core comprising a transition metal oxide;

[0009] A coating layer is formed on the surface of the core, the coating layer comprises a polymer containing silicon-oxygen bonds, and based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%.

[0010] The present application at least includes the following beneficial effects: the positive electrode active material of the present application has high stability, thereby improving the battery cycle performance and DC resistance under high voltage.

[0011] In some embodiments, the mass proportion of silicon in the polymer is 0.1% to 0.3% based on the total mass of the positive electrode active material, thereby improving the battery cycle performance and DC resistance at high voltage.

[0012] In some embodiments, the coating layer has a thickness of 1 nm to 5 nm, thereby improving the battery cycle performance and DC resistance at high voltage.

[0013] In some embodiments, the coating layer has a thickness of 2 nm to 3 nm, thereby improving the battery cycle performance and DC resistance at high voltage.

[0014] In some embodiments, the transition metal oxide comprises Li x MO y Or Na x MO y At least one of, x is 1-2, y is 2-3, and M includes at least one of Ni, Co, Mn, Fe, Al, W, Nb, Ti, Sr, Zr or V.

[0015] In some embodiments, the polymer contains at least one of a boron-containing group, a phosphorus-containing group, a halogen-containing group, a selenium-containing group, a cyano group, a hydroxyl group, -N3, a nitroso group, an amino group, an ester group, an amide group, an aldehyde group, an acyl group, an alkyl group, an alkoxy group, an alkylthio group, or an alkylamine group. This can improve the battery's cycling performance and DC resistance at high voltages.

[0016] In some embodiments, the polymer contains at least one of a boron-containing group, a cyano group, a -N3 group, an amino group, an amide group, or an alkylthio group, thereby improving the battery cycle performance and DC resistance at high voltage.

[0017] In a second aspect of the present application, a method for preparing a positive electrode active material is proposed, comprising: mixing a transition metal oxide with a siloxane-containing main chain material and a siloxane-containing cross-linking material, and forming a coating layer comprising a polymer containing a silicon-oxygen bond on the surface of the transition metal oxide, wherein the siloxane-containing main chain material comprises at least 2 silicon atoms and at least 3 siloxane groups;

[0018] The cross-linked silicone material comprises 1-3 silicone groups,

[0019] Based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%.

[0020] Therefore, the method can be used to prepare the above-mentioned positive electrode active material with higher stability, thereby improving the battery cycle performance and DC resistance under high voltage.

[0021] In some embodiments, the molecular weight of the siloxane-containing main chain material is 300-10000. Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0022] In some embodiments, the molecular weight of the siloxane-containing main chain material is 500 to 1200. Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0023] In some embodiments, the structural formula of the siloxane-containing main chain material includes:

[0024] wherein a is 1-6, R1, R2, R3, R4 and R5 independently include alkyl groups, R6 includes alkyl, alkoxy, boron-containing group, phosphorus-containing group, halogen-containing group, selenium-containing group, cyano, hydroxyl, -N3, nitroso, amino, ester group, amide group, aldehyde group, acyl, alkylthio or alkylamino group, R7 includes alkyl, alkenyl, alkoxy, phenyl, In this way, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0025] In some embodiments, R1, R2, R3, R4 and R5 independently include ethyl and methyl, R6 includes methoxy and ethoxy, and R7 includes In this way, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0026] In some embodiments, the siloxane-containing backbone material comprises Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0027] In some embodiments, the siloxane-containing backbone material comprises Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0028] In some embodiments, the molecular weight of the siloxane-containing cross-linking material is 90 to 500. Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0029] In some embodiments, the molecular weight of the siloxane-containing cross-linking material is 100 to 300. Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0030] In some embodiments, the structural formula of the silicone-containing cross-linking material comprises: Wherein, R8 includes alkyl, R9 and R 10 Each independently includes a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group or a haloalkyl group, R 11 Including alkyl, Boron-containing groups, phosphorus-containing groups, halogen-containing groups, selenium-containing groups, cyano groups, hydroxyl groups, -N3, nitroso groups, amino groups, ester groups, amide groups, aldehyde groups, acyl groups, alkylthio groups or alkylamino groups. Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0031] In some embodiments, R8 and R9 are independently methyl, ethyl, methoxy, ethoxy, R 10 Including methyl, methoxy or ethoxy, R 11 Including methyl, In this way, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0032] In some embodiments, the cross-linked silicone material comprises Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0033] In some embodiments, the cross-linked silicone material comprises Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0034] In some embodiments, the mass ratio of the total mass of the siloxane-containing backbone material and the siloxane-containing crosslinking material to the transition metal oxide is 1:50-1000. This allows for the formation of a dense and stable coating layer on the surface of the transition metal oxide, thereby improving battery cycling performance and DC resistance at high voltages.

[0035] In some embodiments, the mass ratio of the total mass of the siloxane-containing backbone material and the siloxane-containing crosslinking material to the transition metal oxide is 1:100-200. This allows for the formation of a dense and stable coating layer on the surface of the transition metal oxide, thereby improving battery cycling performance and DC resistance at high voltages.

[0036] In some embodiments, the mass ratio of the siloxane-containing main chain material to the siloxane-containing crosslinking material is 1-50: 1. Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0037] In some embodiments, the mass ratio of the siloxane-containing main chain material to the siloxane-containing cross-linking material is 10-30: 1. Thus, a dense and stable coating layer can be formed on the surface of the transition metal oxide, which can improve the battery cycle performance and DC resistance at high voltage.

[0038] In the third aspect of the present application, the present application proposes a positive electrode plate, comprising the positive electrode active material described in the first aspect of the present application or the positive electrode active material obtained by the method described in the second aspect of the present application.

[0039] In a fourth aspect of the present application, the present application provides a battery comprising the positive electrode sheet described in the third aspect of the present application, thereby having high cycle performance and low DC resistance at high voltage.

[0040] In a fifth aspect of the present application, the present application provides an electrical device comprising the battery according to the fourth aspect of the present application, so that the electrical device has an excellent service life.

[0041] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0043] FIG1 is a cross-sectional view of a positive electrode active material according to one embodiment of the present application.

[0044] FIG2 is a schematic diagram of a battery according to an embodiment of the present application.

[0045] FIG3 is an exploded view of the battery shown in FIG2 according to one embodiment of the present application.

[0046] FIG4 is a schematic diagram of a battery module according to an embodiment of the present application.

[0047] FIG5 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0048] FIG. 6 is an exploded view of the battery pack shown in FIG. 5 according to an embodiment of the present application.

[0049] FIG7 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0050] FIG8 is a TEM image of the positive electrode active material obtained in Example 1.

[0051] FIG9 is a TEM image of the positive electrode active material obtained in Comparative Example 1.

[0052] FIG10 is a comparison chart of the cycle curves of the batteries obtained in Example 1 and Comparative Example 1.

[0053] FIG11 is a comparison diagram of the DCR after cycling of the batteries obtained in Example 1 and Comparative Example 1.

[0054] Explanation of reference numerals: 1000 positive electrode active material; 100 core; 200 coating layer; 1 battery cell; 11 housing; 12 electrode assembly; 13 cover plate; 2 battery module; 3 battery pack; 31 upper case; 32 lower case. DETAILED DESCRIPTION

[0055] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0056] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0057] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0058] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0059] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0060] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0061] Currently, market developments indicate that secondary batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As the application of secondary batteries continues to expand, market demand is also growing.

[0062] To further improve the energy density of the battery, the operating voltage of the cathode material can be increased. By increasing the operating voltage, the utilization rate of active ions in the cathode material can be increased, thereby increasing the energy density of the battery. However, the increase in the operating voltage accelerates side reactions on the surface of the cathode material and the release of lattice oxygen, causing the cathode surface to transform from a layered structure to a rock salt phase structure with sharply deteriorated kinetic performance. This reduces the kinetics of the active ion intercalation and deintercalation reaction, thereby seriously deteriorating the battery cycle life and DCR (direct current resistance).

[0063] The positive electrode active material of the present application includes a core and a coating layer, wherein the core includes a transition metal oxide, and the coating layer includes a polymer containing a silicon-oxygen bond (-Si-O-Si-). Based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%, that is, the coating layer has high stability and density, which can effectively alleviate the corrosion of HF in the electrolyte on the surface of the transition metal oxide, reduce the side reaction of the transition metal and the release of lattice oxygen, thereby stabilizing the surface of the transition metal oxide, that is, improving the stability of the positive electrode active material, and achieving the purpose of improving the battery cycle performance and DCR at high voltage.

[0064] The positive electrode active materials disclosed in the embodiments of the present application are suitable for lithium-ion batteries and sodium-ion batteries, and the batteries disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0065] In a first aspect, the present application proposes a positive electrode active material. Referring to Figure 1, the positive electrode active material 1000 includes a core 100 and a coating layer 200. The core 100 includes a transition metal oxide. The coating layer 200 is formed on the surface of the core 100. The coating layer 200 includes a polymer containing silicon-oxygen bonds. Based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%.

[0066] The positive electrode active material of the present application includes a core 100 containing a transition metal oxide and a coating layer 200 formed on at least a portion of the surface of the core 100. The coating layer 200 includes a polymer containing a silicon-oxygen bond. Based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%. That is, the coating layer 200 of the present application contains a high content of silicon, which can improve the density and stability of the coating layer 200, effectively alleviate the corrosion of HF in the electrolyte on the surface of the transition metal oxide, reduce transition metal side reactions and lattice oxygen release, thereby stabilizing the transition metal oxide surface, that is, improving the stability of the positive electrode active material, and achieving the purpose of improving the battery cycle performance and DCR under high voltage.

[0067] In addition to active ions such as lithium ions and sodium ions, transition metal oxides may also include a variety of other metal ions. In some embodiments of the present application, the transition metal oxide includes Li x MO y Or Na x MO y At least one of , x is 1-2, y is 2-3, and M includes at least one of Ni, Co, Mn, Fe, Al, W, Nb, Ti, Zr, Sr, or V. As an example, when the battery is a lithium-ion battery, the transition metal oxide may include but is not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, 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 NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), LiNi 0.56 Co 0.05 Mn 0.39 O2, lithium nickel cobalt aluminum oxide (such as LiNi0.8 Co 0.15 Al 0.05 O2) or its modified compounds, etc. When the battery is a sodium ion battery, the transition metal oxide may include but is not limited to sodium cobalt oxide (such as NaCoO2), sodium nickel oxide (such as NaNiO2), sodium manganese oxide (such as NaMnO2, NaMn2O4), sodium nickel cobalt oxide, sodium manganese cobalt oxide, sodium nickel manganese oxide, sodium nickel cobalt manganese oxide (such as NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、NaNi 0.5 Co 0.2 Mn 0.3 O2、NaNi 0.5 Co 0.25 Mn 0.25 O2、NaNi 0.6 Co 0.2 Mn 0.2 O2、NaNi 0.8 Co 0.1 Mn 0.1 O2、NaNi 0.56 Co 0.05 Mn 0.39 O2, sodium nickel cobalt aluminum oxide (such as NaNi 0.8 Co 0.15 Al 0.05 O2) or at least one of its modified compounds, etc.

[0068] The above-mentioned transition metal oxides all include a layered structure, and their surfaces are in direct contact with the electrolyte, which may deteriorate the stability of the transition metal oxides. The present application forms a coating layer 200 of a polymer containing a silicon-oxygen bond on the surface of the core 100, and based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%. That is, the coating layer 200 of the present application contains a high content of silicon, which can improve the density and stability of the coating layer 200, effectively alleviate the corrosion of HF in the electrolyte on the surface of the transition metal oxide, reduce transition metal side reactions and lattice oxygen release, thereby stabilizing the surface of the transition metal oxide, that is, improving the stability of the positive electrode active material, and achieving the purpose of improving the battery cycle performance and DCR at high voltage.

[0069] It should be noted that the silicon content in the polymer in the present application can be quantitatively analyzed by inductively coupled plasma emission spectrometry (ICP).

[0070] In some embodiments of the present application, the mass percentage of silicon in the polymer is 0.05%-1%, based on the total mass of the positive electrode active material, for example, 0.05%-0.95%, 0.1%-0.9%, 0.15%-0.85%, 0.2%-0.8%, 0.25%-0.75%, 0.3%-0.7%, 0.35%-0.65%, 0.4%-0.6%, 0.45%-0.55%, 0.5%-0.55%, etc. As a result, the coating layer 200 formed on the surface of the core 100 has a dense structure and high stability, which can effectively alleviate the corrosion of the transition metal oxide surface by HF in the electrolyte, reduce transition metal side reactions and lattice oxygen release, thereby stabilizing the transition metal oxide surface, and achieving the purpose of improving the battery cycle performance and DCR at high voltage. In other embodiments of the present application, the mass percentage of silicon in the polymer is 0.1%-0.3%, based on the total mass of the positive electrode active material.

[0071] In some embodiments of the present application, the coating layer 200 may have a thickness of 1 nm to 5 nm, such as 2 nm, 3 nm, 4 nm, or 5 nm. Thus, by forming a coating layer 200 of this thickness on the surface of the core 100, HF corrosion of the transition metal oxide surface in the electrolyte is effectively alleviated, reducing transition metal side reactions and lattice oxygen release, thereby stabilizing the transition metal oxide surface and improving battery cycling performance and DCR at high voltages. In other embodiments of the present application, the coating layer may have a thickness of 2 nm to 3 nm.

[0072] It should be noted that the thickness of the coating layer 200 can be measured by observation using a transmission electron microscope (TEM).

[0073] In some embodiments of the present application, the polymer contains at least one of a boron-containing group, a phosphorus-containing group, a halogen-containing group, a selenium-containing group, a cyano group, a hydroxyl group, -N3, a nitroso group, an amino group, an ester group, an amide group, an aldehyde group, an acyl group, an alkyl group, an alkoxy group, an alkylthio group or an alkylamine group. Thus, the group of the present application can further improve the compactness and / or oxidation resistance of the coating layer 200, effectively alleviate the corrosion of HF in the electrolyte on the surface of the transition metal oxide, reduce the side reaction of the transition metal and the release of lattice oxygen, thereby stabilizing the surface of the transition metal oxide, and achieving the purpose of improving the battery cycle performance and DCR at high voltage. In other embodiments of the present application, the polymer contains at least one of a boron-containing group, a cyano group, -N3, an amino group, an amide group or an alkylthio group.

[0074] It should be noted that "boron-containing group" refers to a group containing boron element, such as B 3+ , BO3 3- , BO2 -etc.; "Phosphorus-containing group" refers to a group containing phosphorus element, such as P 3- 、P 2- 、P - PO4 3- PO3 - etc.; "halogen-containing group" refers to a group containing halogen elements, such as F - 、Cl - , Br-, CH2F-, CH2Cl-, etc.; "Selenium-containing group" refers to a group containing selenium, such as Se 2- .

[0075] In the second aspect of the present application, the present application proposes a method for preparing a positive electrode active material, comprising: mixing a transition metal oxide with a siloxane-containing main chain material and a siloxane-containing cross-linking material, forming a coating layer comprising a polymer containing silicon-oxygen bonds on the surface of the transition metal oxide, wherein the siloxane-containing main chain material comprises at least 2 silicon atoms and at least 3 siloxane groups; the siloxane-containing cross-linking material comprises 1-3 siloxane groups, and based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%.

[0076] Thus, by mixing a transition metal oxide with a main chain material containing siloxane and a cross-linking material containing siloxane, the alkoxy groups in the main chain material and the alkoxy groups in the cross-linking material are hydrolyzed and fully cross-linked under the action of ambient water, thereby forming a complete silicon-oxygen bond-containing coating layer with a high silicon content on the surface of the transition metal oxide, and controlling the mass proportion of silicon in the polymer to be 0.05%-1%. The coating layer has a dense structure and high stability, can effectively alleviate the corrosion of HF in the electrolyte on the surface of the transition metal oxide, reduce transition metal side reactions and lattice oxygen release, stabilize the surface of the transition metal oxide, and achieve the purpose of improving the battery cycle performance and DCR under high voltage.

[0077] It should be noted that "siloxane" refers to a group of -SiO-R, wherein R is an alkyl group.

[0078] In some embodiments of the present application, the molecular weight of the main chain material containing silicone is 300-10000, for example, 500-10000, 800-10000, 1000-10000, 1500-10000, 2000-9000, 3000-8000, 4000-7000, 5000-6000, 5000-5500, etc. In some embodiments of the present application, the molecular weight of the main chain material containing silicone is 500-1200.

[0079] In some embodiments of the present application, the structural formula of the main chain material containing siloxane includes: wherein a is 1-6, R1, R2, R3, R4 and R5 independently include alkyl groups, R6 includes alkyl, alkoxy, boron-containing group, phosphorus-containing group, halogen-containing group, selenium-containing group, cyano, hydroxyl, -N3, nitroso, amino, ester group, amide group, aldehyde group, acyl, alkylthio or alkylamino group, R7 includes alkyl, alkenyl, alkoxy, phenyl, Therefore, by mixing the main chain material of this type with the cross-linking material, a better coating layer can be formed on the surface of the transition metal oxide, and the silicon content in the coating layer is relatively high, which effectively alleviates the corrosion of HF in the electrolyte on the surface of the transition metal oxide, reduces the side reaction of the transition metal and the release of lattice oxygen, stabilizes the surface of the transition metal oxide, and achieves the purpose of improving the battery cycle performance and DCR under high voltage.

[0080] It should be noted that the bent bonds in the above groups Refers to the connection site between a molecular structure and other structures.

[0081] In some embodiments of the present application, in the structural formula of the siloxane-containing main chain material, R1, R2, R3, R4 and R5 independently include ethyl and methyl, R6 includes methoxy and ethoxy, and R7 includes

[0082] Therefore, the main chain material of this type of composition is hydrolyzed and cross-linked with the cross-linking material to form a better coating layer on the surface of the transition metal oxide, and the silicon content in the coating layer is relatively high, which effectively alleviates the corrosion of HF in the electrolyte on the surface of the transition metal oxide, reduces the side reaction of the transition metal and the release of lattice oxygen, stabilizes the surface of the transition metal oxide, and achieves the purpose of improving the battery cycle performance and DCR under high voltage.

[0083] As an example, the main chain material containing siloxane includes (1,3,5-Tris(trimethoxysilylpropyl)isocyanurate (CAS: 26115-70-8)), (Bis-(3-(triethoxysilyl)propyl)-tetrasulfide (CAS: 40372-72-3)), (Bis-[3-(triethoxysilyl)propyl]-disulfide (CAS: 56706-10-6)) or (4,4'-bis(triethoxysilyl)-1,1'-biphenyl (CAS: 123640-93-7)). In other embodiments of the present application, the main chain material containing siloxane includes (1,3,5-Tris(trimethoxysilylpropyl)isocyanurate (CAS: 26115-70-8)), (Bis-(3-(triethoxysilyl)propyl)-tetrasulfide (CAS: 40372-72-3)) or (bis-[3-(triethoxysilyl)propyl]-disulfide (CAS: 56706-10-6)).

[0084] In some embodiments of the present application, the molecular weight of the cross-linked silicone material is 90-500, such as 100-400, 150-350, 200-300, 250-300, etc. In other embodiments of the present application, the molecular weight of the cross-linked silicone material is 100-300.

[0085] In some embodiments of the present application, the structural formula of the cross-linked silicone-containing material includes: Wherein, R8 includes alkyl, R9 and R 10 Each independently includes a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group or a haloalkyl group, R 11 Including alkyl, Boron-containing groups, phosphorus-containing groups, halogen-containing groups, selenium-containing groups, cyano groups, hydroxyl groups, -N3 groups, nitroso groups, amino groups, ester groups, amide groups, aldehyde groups, acyl groups, alkylthio groups or alkylamino groups. Therefore, the cross-linking material composed of the present application is mixed with the main chain material to form a better coating layer on the surface of the transition metal oxide, and the silicon content in the coating layer is high, which effectively alleviates the corrosion of the transition metal oxide surface by HF in the electrolyte, reduces the side reaction of the transition metal and the release of lattice oxygen, stabilizes the surface of the transition metal oxide, and achieves the purpose of improving the battery cycle performance and DCR under high voltage.

[0086] In some embodiments of the present application, R8 and R9 in the cross-linked silicone material structure independently include methyl, ethyl, methoxy, and ethoxy. 10 Including methyl, methoxy or ethoxy, R 11 Including methyl,

[0087] As an example, the cross-linked silicone material includes (3-aminopropylmethyldimethoxysilane (CAS: 3663-44-3)), (3-Glycidyloxypropyltriethoxysilane (CAS: 2602-34-8)), (3-thiocyanatopropyltriethoxysilane (CAS: 34708-08-2)), (3-Ureidopropyltriethoxysilane (CAS: 23779-32-0)), (cyclohexyltrimethoxysilane (CAS: 17865-54-2)), (3,3,3-Trifluoropropyltrimethoxysilane (CAS: 429-60-7)), (Methyltrimethoxysilane (CAS: 1185-55-3)) or (trimethylethoxysilane (CAS: 1825-62-3)). In some other embodiments of the present application, the cross-linking material containing silicone includes (3-aminopropylmethyldimethoxysilane (CAS: 3663-44-3)), (3-thiocyanatopropyltriethoxysilane (CAS: 34708-08-2)) or (3-ureidopropyltriethoxysilane (CAS: 23779-32-0)).

[0088] In some embodiments of the present application, the mass ratio of the total mass of the siloxane-containing main chain material and the siloxane-containing cross-linking material to the transition metal oxide is 1:50-1000, for example, 1:100-1000, 1:150-950, 1:200-900, 1:250-850, 1:300-800, 1:350-750, 1:400-700, 1:450-650, 1:500-600, 1:550-600, etc. Thus, the present application mixes the total mass of the siloxane-containing main chain material and the siloxane-containing cross-linking material with the transition metal oxide in this ratio, which not only forms a dense and stable coating layer on the surface of the transition metal oxide, but also has a high silicon content in the coating layer, which can effectively alleviate the corrosion of the transition metal oxide surface by HF in the electrolyte, reduce transition metal side reactions and lattice oxygen release, stabilize the transition metal oxide surface, and achieve the purpose of improving the battery cycle performance and DCR at high voltage without reducing the overall energy density of the battery. In other embodiments of the present application, the mass ratio of the total mass of the siloxane-containing main chain material and the siloxane-containing cross-linking material to the transition metal oxide is 1:100-200.

[0089] In some embodiments of the present application, the mass ratio of the siloxane-containing main chain material to the siloxane-containing cross-linking material is 1-50:1, for example 5-45:1, 10-40:1, 15-35:1, 20-30:1, 25-30:1, etc. Thus, the main chain material and the cross-linking material of the present application are mixed according to this ratio, and a better coating layer can be formed on the surface of the transition metal oxide, and the silicon content in the coating layer is high, which effectively alleviates the corrosion of the transition metal oxide surface by HF in the electrolyte, reduces the side reaction of the transition metal and the release of lattice oxygen, stabilizes the surface of the transition metal oxide, and achieves the purpose of improving the battery cycle performance and DCR under high voltage. In some embodiments of the present application, the mass ratio of the siloxane-containing main chain material to the siloxane-containing cross-linking material is 10-30:1.

[0090] In some embodiments of the present application, the composition of the transition metal oxide is as described above and will not be repeated here.

[0091] In the third aspect of the present application, the present application proposes a positive electrode plate, which includes the positive electrode active material described in the first aspect of the present application or the positive electrode active material obtained by the method described in the second aspect of the present application.

[0092] In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is provided on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material.

[0093] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0094] In some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer 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 (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0095] In some embodiments of the present application, the positive electrode active material layer may further include a positive electrode active material. The positive electrode active material may be a positive electrode active material for batteries known in the art.

[0096] In some embodiments of the present application, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin.

[0097] In some embodiments of the present application, based on the total mass of the active material layer, the mass proportion of the binder is 0.5%-3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0098] In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0099] In some embodiments of the present application, based on the total mass of the active material layer, the mass proportion of the conductive agent is 0.8%-4%, for example, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0100] In some embodiments of the present application, the positive electrode sheet can be prepared by the following method: the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the main chain material containing siloxane, the cross-linking material containing siloxane, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0101] In some embodiments of the present application, the positive electrode sheet can also be prepared by the following method: first, a siloxane-containing main chain material and a siloxane-containing cross-linking material are mixed with a transition metal oxide, and then a conductive agent and / or a binder are added to obtain a mixed slurry, and then the mixed slurry is applied to at least one side of the positive electrode collector, and after drying, cold pressing and other processes, a positive electrode sheet is obtained.

[0102] A fourth aspect of the present application provides a battery, comprising the positive electrode sheet described in the third aspect of the present application. Thus, the battery of the present application has higher cycle performance and lower DCR at high voltage.

[0103] In some embodiments of the present application, the battery further comprises a negative electrode plate, the negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material.

[0104] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0105] In some embodiments of the present application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base layer (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments of the present application, the negative electrode active material may adopt the negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites or silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds or tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0107] In some embodiments of the present application, the negative electrode active material layer may further optionally include a binder. The binder may include 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), or carboxymethyl chitosan (CMCS).

[0108] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0109] In some embodiments of the present application, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0110] In some embodiments of the present application, the negative electrode sheet can be prepared by the following method: the 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 collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0111] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0112] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or solid.

[0113] In some embodiments of the present application, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0114] In some embodiments of the present application, when the battery is a lithium ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate or lithium tetrafluorooxalatophosphate.

[0115] In some embodiments of the present application, when the battery is a sodium ion battery, the electrolyte salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.

[0116] In some embodiments of the present application, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone or diethyl sulfone.

[0117] In some embodiments of the present application, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0118] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0119] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0120] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0121] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0122] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0123] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG2 shows a square-structured battery cell 1 as an example.

[0124] In some embodiments, referring to Figure 3, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 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 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0125] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0126] Figure 4 shows an example battery module 2. Referring to Figure 4 , within the battery module 2, multiple battery cells 1 may be arranged sequentially along the length of the battery module 2. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 1 may be secured together using fasteners.

[0127] Optionally, the battery module 2 may further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0128] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0129] Figures 5 and 6 illustrate an example battery pack 3. Referring to Figures 5 and 6 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 31 and a lower case 32. The upper case 31 can be positioned over the lower case 32 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0130] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include 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., but is not limited thereto.

[0131] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0132] Figure 7 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0133] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0134] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0135] Example 1

[0136] 1. Preparation of positive electrode sheet

[0137] The transition metal oxide Li(Ni 0.56 Co 0.05 Mn 0.39 )O2 is uniformly mixed with a main chain material (the compound shown in Formula 1) and a cross-linking material (the compound shown in Formula 11) and an organic solvent NMP (N-methylpyrrolidone), wherein the mass ratio of the total mass of the main chain material and the cross-linking material to the transition metal oxide is 1:150, and the mass ratio of the main chain material to the cross-linking material is 12:1, and then a conductive agent carbon black (Super P) and a binder polyvinylidene fluoride (PVDF) are added (the total mass of the transition metal oxide to the main chain material and the cross-linking material, the conductive agent and the binder are in a mass ratio of 97:2:1) and further stirred and mixed to obtain a stable positive electrode slurry;

[0138] The positive electrode slurry is coated on both sides of the positive electrode current collector aluminum foil, and the positive electrode active material layer is formed on both sides of the positive electrode current collector through drying and cold pressing, and the positive electrode sheet is obtained by striping and cutting.

[0139] 2. Preparation of negative electrode sheet

[0140] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 96:1:1.5:1.5 to obtain a negative electrode slurry. The negative electrode slurry is coated on both sides of the negative electrode current collector copper foil. A negative electrode active material layer is formed on both sides of the negative electrode current collector through drying and cold pressing. Finally, the negative electrode sheet is obtained through striping and cutting processes.

[0141] 3. Preparation of electrolyte

[0142] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), ethylene carbonate and ethyl methyl carbonate were mixed in a mass ratio of 30:70 to obtain a solvent, and fully dried electrolyte salt LiPF6 was dissolved in the above solvent. After mixing evenly, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0143] 4. Isolation film

[0144] Polypropylene film is used as the isolation film.

[0145] 5. Preparation of secondary batteries

[0146] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium-ion battery. After vacuum packaging, standing, formation, and shaping processes, a lithium-ion battery is obtained.

[0147] The preparation methods of the lithium-ion batteries of Examples 2-13 and Comparative Examples 1-3 are the same as those of Example 1, except that the processes for preparing the positive electrode sheets are different, as shown in Table 1.

[0148] The preparation method of the lithium ion battery of Example 14 is the same as that of Example 1, except that in the method of preparing the positive electrode sheet, the transition metal oxide Li (Ni 0.56 Co 0.05 Mn 0.39 )O2, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed, and then the main chain material (the compound shown in Formula 1) and the cross-linking material (the compound shown in Formula 11) are added and stirred to form a positive electrode slurry.

[0149] Table 1

[0150] The silicon content and thickness of the coating layer of the positive electrode active materials obtained in Examples 1-14 and Comparative Examples 1-3, as well as the cycle performance and direct current resistance (DCR) of the battery were characterized. The characterization results are shown in Table 2.

[0151] (1) Test of silicon content in the coating layer of positive electrode active material:

[0152] Inductively coupled plasma emission spectrometry (ICP) was used for elemental quantitative analysis: the powder on the positive electrode was scraped off, and the test sample was prepared by digestion treatment (mixing the powder with alcohol and using ultrasonic dispersion for 20 minutes), and then the silicon content was tested using ICP-MS mode.

[0153] (2) Test of coating thickness of positive electrode active material:

[0154] The powder on the positive electrode sheet was scraped off and a test sample was prepared by digestion treatment (mixing the powder with alcohol and using ultrasonic dispersion for 20 minutes). The thickness of the coating layer of the positive electrode active material was observed using a transmission electron microscope (TEM).

[0155] (3) Battery cycle performance test:

[0156] Control the ambient temperature to 25°C, let it rest for 1 hour, discharge at 0.33C to 2.5V, let it rest for 5 minutes, charge at 0.33C to 4.4V, let it rest for 5 minutes, discharge at 0.33C to 2.5V, and record the discharge capacity as C0. Adjust the cycle temperature to 45°C, and perform 700 cycles according to the process of charging at 0.5C to 4.4V, letting it rest for 5 minutes, discharging at 1C to 2.5V, and letting it rest for 5 minutes. The discharge capacity at the 700th cycle is C1, and the cycle capacity retention rate of the battery cell = C1 / C0*100%.

[0157] (4) Battery DCR test

[0158] The battery was placed at 25°C, charged to 4.4V at 0.33C, then charged to 0.05C at constant voltage, left to stand for 5 minutes, then discharged at 0.33C for 1.5 hours, left to stand for 120 minutes, and the voltage V1 after standing was recorded. The battery was then discharged at 4C for 30 seconds with a sampling interval of 0.1S, and the voltage V2 at the end of discharge was recorded. The battery DCR (DC internal resistance) = (V1-V2) / I, I = 4C.

[0159] Figure 8 is a TEM image of the positive electrode active material obtained in Example 1, and Figure 9 is a TEM image of the positive electrode active material obtained in Comparative Example 1. As can be seen from Figures 8 and 9, the surface of the positive electrode active material obtained in Example 1 has an obvious coating layer, while the surface of the positive electrode active material of Comparative Example 1 does not show a coating layer. Figure 10 is a comparison of the cycle curves of the batteries obtained in Example 1 and Comparative Example 1. As can be seen from Figure 10, the capacity retention rate of the lithium-ion battery in Example 1 is significantly higher than that of Comparative Example 1 after 700 cycles. Figure 11 is a comparison of the DCR after cycling of the batteries obtained in Example 1 and Comparative Example 1. As can be seen from Figure 11, the DCR of the lithium-ion battery in Example 1 is significantly lower than that of Comparative Example 1 after 700 cycles.

[0160] Table 2

[0161] As can be seen from the data in Table 2, the silicon content in the coating layer of the positive electrode active material obtained in Examples 1-14 is 0.05%-1%, while the positive electrode active material in the battery of Comparative Example 1 does not have a coating layer, and the silicon content in the coating layer of the positive electrode active material in Comparative Example 2 is 0.03%. The capacity retention rate of the battery of Examples 1-14 is significantly higher than that of Comparative Example 1-2, and the DCR of the battery of Examples 1-14 is significantly lower than that of Comparative Example 1-2, while the silicon content in the coating layer of the positive electrode active material obtained in Comparative Example 3 is 1.3%. Although the battery has high cycle performance, the coating layer of the positive electrode active material is too thick, which affects the transmission of lithium ions, resulting in a low DCR after cycling. This shows that the present application controls the silicon content in the coating layer on the surface of the positive electrode active material to be 0.05%-1%, which can significantly improve the stability of the positive electrode active material, thereby improving the battery cycle performance and DC resistance under high voltage.

[0162] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode active material, characterized in that: include: an inner core, the inner core comprising a transition metal oxide; A coating layer is formed on the surface of the core, the coating layer comprises a polymer containing silicon-oxygen bonds, and based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%.

2. The positive electrode active material according to claim 1, characterized in that Based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.1%-0.3%.

3. The positive electrode active material according to claim 1 or 2, characterized in that: The coating layer has a thickness of 1 nm to 5 nm.

4. The positive electrode active material according to any one of claims 1 to 3, characterized in that The coating layer has a thickness of 2nm-3nm.

5. The positive electrode active material according to any one of claims 1 to 4, characterized in that The transition metal oxide includes Li x MO y Or Na x MO y At least one of, x is 1-2, y is 2-3, and M includes at least one of Ni, Co, Mn, Fe, Al, W, Nb, Ti, Zr, Sr or V.

6. A method for preparing a positive electrode active material, characterized in that: include: Mixing a transition metal oxide with a siloxane-containing main chain material and a siloxane-containing cross-linking material to form a coating layer including a polymer containing a silicon-oxygen bond on the surface of the transition metal oxide, wherein the siloxane-containing main chain material includes at least 2 silicon atoms and at least 3 siloxane groups; The cross-linked silicone-containing material comprises 1 to 3 silicone groups, Based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%.

7. The method according to claim 6, characterized in that The molecular weight of the main chain material containing siloxane is 300-10000.

8. The method according to claim 6 or 7, characterized in that: The molecular weight of the main chain material containing siloxane is 500-1200.

9. The method according to any one of claims 6 to 8, characterized in that: The structural formula of the main chain material containing siloxane includes: wherein a is 1-6, R1, R2, R3, R4 and R5 independently include alkyl groups, R6 includes alkyl groups, alkoxy groups, boron-containing groups, phosphorus-containing groups, halogen-containing groups, selenium-containing groups, cyano groups, hydroxyl groups, -N3, nitroso groups, amino groups, ester groups, amide groups, aldehyde groups, acyl groups, alkylthio groups or alkylamino groups, R7 includes alkyl groups, alkenyl groups, alkoxy groups, Phenyl, 10. The method according to claim 9, characterized in that R1, R2, R3, R4 and R5 independently include ethyl and methyl, R6 includes methoxy and ethoxy, and R7 includes 11. The method according to any one of claims 6 to 10, characterized in that: The main chain material containing siloxane includes At least one of .

12. The method according to any one of claims 6 to 11, characterized in that: The main chain material containing siloxane includes At least one of .

13. The method according to any one of claims 6 to 12, characterized in that: The molecular weight of the silicone-containing cross-linking material is 90-500.

14. The method according to any one of claims 6 to 13, characterized in that: The molecular weight of the silicone-containing cross-linking material is 100-300.

15. The method according to any one of claims 6 to 14, characterized in that: The structural formula of the cross-linked silicone-containing material includes: Wherein R8 includes alkyl, R9 and R 10 Each independently includes a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group or a haloalkyl group, R 11 Including alkyl, A boron-containing group, a phosphorus-containing group, a halogen-containing group, a selenium-containing group, a cyano group, a hydroxyl group, -N3, a nitroso group, an amino group, an ester group, an amide group, an aldehyde group, an acyl group, an alkylthio group or an alkylamino group.

16. The method according to claim 15, characterized in that R8 and R9 independently include methyl, ethyl, methoxy, ethoxy, 10 Including methyl, methoxy or ethoxy, R 11 Including methyl, 17. The method according to any one of claims 6 to 16, characterized in that The cross-linked silicone-containing material comprises At least one of .

18. The method according to any one of claims 6 to 17, characterized in that: The cross-linked silicone-containing material includes At least one of .

19. The method according to any one of claims 6 to 18, characterized in that: The mass ratio of the total mass of the siloxane-containing main chain material and the siloxane-containing cross-linking material to the transition metal oxide is 1:50-1000.

20. The method according to any one of claims 6 to 19, characterized in that The mass ratio of the total mass of the siloxane-containing main chain material and the siloxane-containing cross-linking material to the transition metal oxide is 1:100-200.

21. The method according to any one of claims 6 to 20, characterized in that: The mass ratio of the main chain material containing silicone to the cross-linking material containing silicone is 1-50:

1.

22. The method according to any one of claims 6 to 21, characterized in that The mass ratio of the main chain material containing silicone to the cross-linking material containing silicone is 10-30:

1.

23. A positive electrode plate, characterized in that: The invention comprises the positive electrode active material according to any one of claims 1 to 5 or the positive electrode active material obtained by the method according to any one of claims 6 to 22.

24. A battery, characterized in that: Including the positive electrode sheet as described in claim 23.

25. An electrical device, characterized in that: Comprising the battery of claim 24.

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