Positive electrode active material and preparation method thereof, positive electrode plate, battery and electric device

Abstract

The invention discloses a positive electrode active material and a preparation method thereof, a positive electrode plate, a battery and a power utilization device, 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, and the polymer is formed on the surface of the inner core. Based on the total mass of the positive electrode active material, the mass ratio of silicon in the polymer is 0.05%-1%. The positive electrode active material disclosed by the invention has relatively high stability, so that the cycle performance and the direct-current resistance of the battery under high voltage can be improved.

Description

Technical Field

[0001] This application belongs to the field of batteries, and particularly relates to a positive electrode active material, a preparation method thereof, a positive electrode sheet, a preparation method thereof, a battery, and an electrical device. Background Art

[0002] In recent years, with the increasingly wide range of applications of batteries, batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, as well as in multiple fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As people's requirements for the energy density of batteries are getting higher and higher, increasing the operating voltage of the positive electrode material is an effective method. However, existing batteries have a relatively high DC resistance and poor cycle performance at high voltages. Summary of the Invention

[0003] In view of the technical problems in the background art, this application provides a positive electrode active material, aiming to improve the DC resistance and cycle performance of a battery containing the same at high voltages.

[0004] To achieve the above object, a first aspect of this application provides a positive electrode active material, including:

[0005] A core, the core includes a transition metal oxide;

[0006] A coating layer, the coating layer is formed on the surface of the core, the coating layer includes a polymer containing a silicon-oxygen bond, and based on the total mass of the positive electrode active material, the mass ratio of silicon in the polymer is 0.05%-1%.

[0007] This application has at least the following beneficial effects: The positive electrode active material of this application has high stability, thereby improving the cycle performance and DC resistance of the battery at high voltages.

[0008] In some embodiments, based on the total mass of the positive electrode active material, the mass ratio of silicon in the polymer is 0.1%-0.3%. Thereby, the cycle performance and DC resistance of the battery at high voltages can be improved.

[0009] In some embodiments, the thickness of the coating layer is 1nm-5nm, and can be 2nm-3nm. Thereby, the cycle performance and DC resistance of the battery at high voltages can be improved.

[0010] In some embodiments, the transition metal oxide includes Li x MO y or Na x MO yAt least one of them, 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.

[0011] 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, -N 3 , 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 alkylamino group, preferably at least one of a boron-containing group, a cyano group, -N 3 , an amino group, an amide group or an alkylthio group. Thereby, the battery cycle performance and DC resistance at high voltages can be improved.

[0012] In the second aspect of the present application, a method for preparing a cathode active material is proposed, including: mixing a transition metal oxide with a polysiloxane main chain material and a polysiloxane cross-linking material to form a coating layer including a polymer containing silicon-oxygen bonds on the surface of the transition metal oxide, wherein the polysiloxane main chain material includes at least 2 silicon atoms and at least 3 siloxane groups;

[0013] The polysiloxane cross-linking material includes 1 - 3 siloxane groups,

[0014] Based on the total mass of the cathode active material, the mass ratio of silicon in the polymer is 0.05% - 1%.

[0015] Thereby, the cathode active material with the above-mentioned high stability can be prepared by using this method, and thus the battery cycle performance and DC resistance at high voltages can be improved.

[0016] In some embodiments, the molecular weight of the polysiloxane main chain material is 300 - 10000, and can be optionally 500 - 1200. Thereby, a dense and stable coating layer can be formed on the surface of the transition metal oxide, and the battery cycle performance and DC resistance at high voltages can be improved.

[0017] In some embodiments, the structural formula of the polysiloxane main chain material includes:

[0018] where a is 1 - 6, R 1 , R 2 , R 3 , R 4 and R 5 each independently includes an alkyl group, and R 6 includes an alkyl group, an alkoxy group, a boron-containing group, a phosphorus-containing group, a halogen-containing group, a selenium-containing group, a cyano group, a hydroxyl group, -N 3 , 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, R7 including alkyl, alkenyl, alkoxy, phenyl, 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 voltages.

[0019] In some embodiments, R 1 , R 2 , R 3 , R 4 and R 5 each independently include ethyl, methyl, R 6 includes methoxy, ethoxy, R 7 includes 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 voltages.

[0020] In some embodiments, the main chain material containing siloxane includes

[0021] at least one of at least one of... 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 voltages.

[0022] In some embodiments, the molecular weight of the siloxane-containing crosslinking material is 90 - 500, optionally 100 - 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 voltages.

[0023] In some embodiments, the structural formula of the siloxane-containing crosslinking material includes: wherein, R 8 includes alkyl, R 9 and R 10 each independently include a hydrogen atom, alkyl, alkoxy, phenyl or haloalkyl, R 11 includes alkyl, boron-containing group, phosphorus-containing group, halogen-containing group, selenium-containing group, cyano group, hydroxyl group, -N 3 , nitroso group, amino group, ester group, amide group, aldehyde group, acyl group, alkylthio group or alkylamino group. 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 voltages.

[0024] In some embodiments, R 8and R 9 each independently includes methyl, ethyl, methoxy, ethoxy, and R 10 includes methyl, methoxy or ethoxy, and R 11 includes methyl, 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 voltages.

[0025] In some embodiments, the siloxane-containing crosslinking material includes at least one of, and optionally at least one of. 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 voltages.

[0026] In some embodiments, the mass ratio of the total mass of the siloxane-containing main chain material and the siloxane-containing crosslinking material to the mass of the transition metal oxide is 1:50 - 1000, and optionally 1:100 - 200. 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 voltages.

[0027] In some embodiments, the mass ratio of the siloxane-containing main chain material to the siloxane-containing crosslinking material is 1 - 50:1, and optionally 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 voltages.

[0028] In the third aspect of the present application, the present application provides a positive electrode sheet, 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.

[0029] In the fourth aspect of the present application, the present application provides a battery, which includes the positive electrode sheet described in the third aspect of the present application. Thus, the battery has high cycle performance and low DC resistance at high voltages.

[0030] In the fifth aspect of the present application, the present application provides an electrical device, which includes the battery described in the fourth aspect of the present application. Thus, the electrical device has excellent service life.

[0031] Additional aspects and advantages of the present application will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present application. Description of the Drawings

[0032] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0033] Figure 1 is a sectional view of the positive electrode active material of an embodiment of the present application.

[0034] Figure 2 is a schematic diagram of a battery of an embodiment of the present application.

[0035] Figure 3 is Figure 2 an exploded view of the battery of an embodiment of the present application shown.

[0036] Figure 4 is a schematic diagram of a battery module of an embodiment of the present application.

[0037] Figure 5 is a schematic diagram of a battery pack of an embodiment of the present application.

[0038] Figure 6 is Figure 5 an exploded view of the battery pack of an embodiment of the present application shown.

[0039] Figure 7 is a schematic diagram of an electrical device using the battery of an embodiment of the present application as a power source.

[0040] Figure 8 is a TEM image of the positive electrode active material obtained in Example 1.

[0041] Figure 9 is a TEM image of the positive electrode active material obtained in Comparative Example 1.

[0042] Figure 10 is a comparison chart of the cycling curves of the batteries obtained in Example 1 and Comparative Example 1.

[0043] Figure 11 is a comparison chart of the DCR after cycling of the batteries obtained in Example 1 and Comparative Example 1.

[0044] Description of reference numerals:

[0045] 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 box body; 32 Lower box body. Detailed embodiments

[0046] The embodiments of the technical solution of the present application will be described in detail below. The following embodiments are only used to more clearly illustrate the technical solution of the present application, so they are only examples and cannot be used to limit the protection scope of the present application.

[0047] As used herein, the term "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 present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0048] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a particular parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] If there is no special indication, all the implementation manners and optional implementation manners of the present application can be combined with each other to form a new technical solution.

[0050] If there is no special indication, all the technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0051] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0052] Currently, from the perspective of the development of the market situation, secondary batteries are more and more widely used. Secondary batteries are not only applied to energy storage power systems such as hydroelectric, thermal, wind and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in many fields such as military equipment and aerospace. With the continuous expansion of the application fields of secondary batteries, the market demand is also constantly increasing.

[0053] In order to further improve the energy density of the battery, the use voltage of the positive electrode material can be increased. By increasing the use voltage, the utilization rate of active ions in the positive electrode material can be improved, thereby improving the energy density of the battery. However, the increase in the use voltage accelerates the side reactions on the surface of the positive electrode material and the release of lattice oxygen, resulting in the transformation of the positive electrode surface from a layered structure to a rock salt phase structure with a sharp deterioration in kinetic performance, reducing the kinetics of the reaction for inserting and extracting active ions, and thus seriously deteriorating the battery cycle life and DCR (direct current resistance).

[0054] The positive electrode active material of this application includes a core and a coating layer. 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 ratio of silicon in the polymer is 0.05%-1%. That is, the coating layer has high stability and compactness, which can effectively alleviate the corrosion of the surface of the transition metal oxide by HF in the electrolyte, reduce the side reactions of transition metals 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 voltages.

[0055] The positive electrode active material disclosed in the embodiments of the present application is applicable to lithium-ion batteries and sodium-ion batteries, and the batteries disclosed in the embodiments of the present application can be used in electrical equipment using the battery as a power source or various energy storage systems using the battery as an energy storage element. The electrical equipment may include, but is not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, etc. Among them, the electric toys may include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc., and the spacecraft may include airplanes, rockets, space shuttles, and spaceships, etc.

[0056] In the first aspect of the present application, a positive electrode active material is proposed. 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 a silicon-oxygen bond. Based on the total mass of the positive electrode active material, the mass ratio of silicon in the polymer is 0.05%-1%.

[0057] 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 part 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 ratio of silicon in the polymer is 0.05%-1%. That is, the coating layer 200 of the present application contains a relatively high content of silicon, which can improve the density and stability of the coating layer 200, effectively relieve the corrosion of the surface of the transition metal oxide by HF in the electrolyte, reduce the transition metal side reaction and the lattice oxygen extraction, 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 voltages.

[0058] In addition to active ions such as lithium ions and sodium ions, the transition metal oxide may also include various 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 them, 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 LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O4 )), 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 O 2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ), LiNi 0.56 Co 0.05 Mn 0.39 O 2 , lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O 2 ), or at least one of 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 NaCoO 2 ), sodium nickel oxide (such as NaNiO 2 ), sodium manganese oxide (such as NaMnO 2 , NaMn 2 O 4 ), 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 O 2 , NaNi 0.5 Co 0.2 Mn 0.3 O 2 , NaNi 0.5 Co 0.25 Mn 0.25 O 2 , NaNi 0.6 Co0.2 Mn 0.2 O 2 、 NaNi 0.8 Co 0.1 Mn 0.1 O 2 、 NaNi 0.56 Co 0.05 Mn 0.39 O 2 、 sodium nickel cobalt aluminum oxide (such as NaNi 0.8 Co 0.15 Al 0.05 O 2 ) or at least one of its modified compounds, etc.

[0059] 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. In this application, a coating layer 200 containing a polymer with a silicon-oxygen bond is formed on the surface of the core 100, and based on the total mass of the positive electrode active material, the mass ratio of silicon in the polymer is 0.05%-1%. That is, the coating layer 200 in this application contains a relatively high content of silicon, which can improve the density and stability of the coating layer 200, effectively relieve the corrosion of the surface of the transition metal oxide by HF in the electrolyte, reduce the side reaction of the transition metal and the escape 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 voltages.

[0060] It should be noted that the content of silicon in the polymer in this application can be quantitatively analyzed for elements by an inductively coupled plasma emission spectrometer (ICP).

[0061] In some embodiments of this application, based on the total mass of the positive electrode active material, the mass ratio of silicon in the polymer is 0.05%-1%, such as 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. Thus, the coating layer 200 formed on the surface of the core 100 has a dense structure and high stability, which can effectively relieve the corrosion of the surface of the transition metal oxide by HF in the electrolyte, reduce the side reaction of the transition metal and the escape 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 voltages. In other embodiments of this application, based on the total mass of the positive electrode active material, the mass ratio of silicon in the polymer is 0.1%-0.3%.

[0062] In some embodiments of the present application, the thickness of the coating layer 200 can be 1 nm - 5 nm, such as 2 nm, 3 nm, 4 nm, 5 nm, etc. Thus, by forming the coating layer 200 with such a thickness on the surface of the core 100, the corrosion of the surface of the transition metal oxide by HF in the electrolyte is effectively alleviated, the side reactions of the transition metal and the release of lattice oxygen are reduced, thereby stabilizing the surface of the transition metal oxide and achieving the purpose of improving the battery cycle performance and DCR at high voltages. In some other embodiments of the present application, the thickness of the coating layer can be 2 nm - 3 nm.

[0063] It should be noted that the thickness of the coating layer 200 can be obtained by observing with a transmission electron microscope (TEM).

[0064] 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, -N 3 , 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 alkylamino group. Thus, such groups in the present application can further improve the compactness and / or antioxidant property of the coating layer 200, effectively alleviate the corrosion of the surface of the transition metal oxide by HF in the electrolyte, reduce the side reactions 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 voltages. In some other embodiments of the present application, the polymer contains at least one of a boron-containing group, a cyano group, -N 3 , an amino group, an amide group or an alkylthio group.

[0065] It should be noted that the "boron-containing group" refers to a group containing boron element, such as B 3+ , BO 3 3- , BO 2 - , etc.; the "phosphorus-containing group" refers to a group containing phosphorus element, such as P 3- , P 2- , P - , PO 4 3- , PO 3 - , etc.; the "halogen-containing group" refers to a group containing halogen element, such as F - , Cl - , Br-, CH 2 F-, CH 2 Cl-, etc.; the "selenium-containing group" refers to a group containing selenium element, such as Se 2- .

[0066] In the second aspect of the present application, a method for preparing a cathode active material is proposed, including: mixing a transition metal oxide with a polysiloxane main chain material and a polysiloxane crosslinking material to form a coating layer containing a polymer with silicon-oxygen bonds on the surface of the transition metal oxide, where the polysiloxane main chain material includes at least 2 silicon atoms and at least 3 siloxane groups; the polysiloxane crosslinking material includes 1-3 siloxane groups, and based on the total mass of the cathode active material, the mass ratio of silicon in the polymer is 0.05%-1%.

[0067] Thus, by mixing the transition metal oxide with the polysiloxane main chain material and the polysiloxane crosslinking material, the alkoxy groups in the main chain material and the alkoxy groups in the crosslinking material are hydrolyzed under the action of environmental water and crosslinked sufficiently, so that a complete silicon-oxygen bond-containing coating layer with a high silicon content can be formed on the surface of the transition metal oxide, and the mass ratio of silicon in the polymer is controlled to be 0.05%-1%. This coating layer has a dense structure and high stability, can effectively relieve 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, stabilize the surface of the transition metal oxide, and achieve the purpose of improving the battery cycle performance and DCR at high voltages.

[0068] It should be noted that "siloxane" refers to the group of -SiO-R, where R is an alkyl group.

[0069] In some embodiments of the present application, the molecular weight of the polysiloxane main chain material is 300-10000, such as 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 polysiloxane main chain material is 500-1200.

[0070] In some embodiments of the present application, the structural formula of the polysiloxane main chain material includes: where a is 1-6, R 1 、R 2 、R 3 、R 4 and R 5 independently include alkyl groups respectively, and R 6 includes an alkyl group, an alkoxy group, a boron-containing group, a phosphorus-containing group, a halogen-containing group, a selenium-containing group, a cyano group, a hydroxyl group, -N 3 、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, and R 7 includes an alkyl group, an alkenyl group, an alkoxy group, a phenyl group, Therefore, mixing the main-chain material composed of this type with the cross-linking material can form a better coating layer on the surface of the transition metal oxide, and the silicon content in the coating layer is relatively high, effectively alleviating the corrosion of the surface of the transition metal oxide by HF in the electrolyte, reducing the side reactions of the transition metal and the release of lattice oxygen, stabilizing the surface of the transition metal oxide, and achieving the purpose of improving the battery cycle performance and DCR at high voltages.

[0071] It should be noted that the bent bond in the above-mentioned group refers to the connection site between the molecular structure and other structures.

[0072] In some embodiments of the present application, in the structural formula of the main-chain material containing siloxane, R 1 、R 2 、R 3 、R 4 and R 5 independently include ethyl and methyl respectively, R 6 includes methoxy and ethoxy, and R 7 includes

[0073] Therefore, the main-chain material composed of this type and the cross-linking material can be hydrolytically cross-linked 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, effectively alleviating the corrosion of the surface of the transition metal oxide by HF in the electrolyte, reducing the side reactions of the transition metal and the release of lattice oxygen, stabilizing the surface of the transition metal oxide, and achieving the purpose of improving the battery cycle performance and DCR at high voltages.

[0074] As an example, the main-chain material containing siloxane includes 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)) at least one of them. In some 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 At least one of bis-[3-(triethoxysilyl)propyl]-disulfide (CAS: 56706-10-6).

[0075] In some embodiments of the present application, the molecular weight of the siloxane-containing crosslinked material is 90 - 500, such as 100 - 400, 150 - 350, 200 - 300, 250 - 300, etc. In some other embodiments of the present application, the molecular weight of the siloxane-containing crosslinked material is 100 - 300.

[0076] In some embodiments of the present application, the structural formula of the siloxane-containing crosslinked material includes: Wherein, R 8 includes an alkyl group, R 9 and R 10 each independently include a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group or a haloalkyl group, and R 11 includes an alkyl group, a boron-containing group, a phosphorus-containing group, a halogen-containing group, a selenium-containing group, a cyano group, a hydroxyl group, -N 3 , 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. Thus, the crosslinked material composed of the present application can form a better coating layer on the surface of the transition metal oxide when mixed with the main chain material, and the silicon content in the coating layer is relatively high, effectively alleviating the corrosion of HF in the electrolyte on the surface of the transition metal oxide, reducing the transition metal side reaction and the release of lattice oxygen, stabilizing the surface of the transition metal oxide, and achieving the purpose of improving the battery cycle performance and DCR at high voltage.

[0077] In some other embodiments of the present application, in the structural formula of the siloxane-containing crosslinked material, R 8 and R 9 each independently include a methyl group, an ethyl group, a methoxy group, an ethoxy group, and R 10 includes a methyl group, a methoxy group or an ethoxy group, and R 11 includes a methyl group,

[0078] As an example, the siloxane-containing crosslinked material includes (3-aminopropylmethyldimethoxysilane (CAS: 3663-44-3)), (3-glycidoxypropyltriethoxysilane (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)), at least one of them. In some other embodiments of the present application, the silicone-containing crosslinking material includes (3-Aminopropylmethyldimethoxysilane (CAS: 3663-44-3)), (3-Thiocyanatopropyltriethoxysilane (CAS: 34708-08-2)) or (3-Ureidopropyltriethoxysilane (CAS: 23779-32-0)), at least one of them.

[0079] In some embodiments of the present application, the mass ratio of the total mass of the silicone-containing backbone material and the silicone-containing crosslinking material to the mass of the transition metal oxide is 1:50 - 1000, such as 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, in the present application, the total mass of the silicone-containing backbone material and the silicone-containing crosslinking material is mixed with the transition metal oxide in this ratio, which can not only form a dense and stable coating layer on the surface of the transition metal oxide. The silicon content in this coating layer is relatively high, which can effectively alleviate the corrosion of HF in the electrolyte to the surface of the transition metal oxide, reduce the side reaction of the transition metal and the release of lattice oxygen, stabilize the surface of the transition metal oxide, and achieve the purpose of improving the battery cycle performance and DCR at high voltage, and moreover, it will not reduce the overall energy density of the battery. In some other embodiments of the present application, the mass ratio of the total mass of the silicone-containing backbone material and the silicone-containing crosslinking material to the mass of the transition metal oxide is 1:100 - 200.

[0080] In some embodiments of the present application, the mass ratio of the siloxane-containing main chain material to the siloxane-containing crosslinking material is 1-50:1, such as 5-45:1, 10-40:1, 15-35:1, 20-30:1, 25-30:1, etc. Thus, when the main chain material and the crosslinking material of the present application are mixed in this ratio, 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, effectively alleviating the corrosion of the surface of the transition metal oxide by HF in the electrolyte, reducing the side reaction of the transition metal and the release of lattice oxygen, stabilizing the surface of the transition metal oxide, and achieving the purpose of improving the battery cycle performance and DCR at high voltages. In some embodiments of the present application, the mass ratio of the siloxane-containing main chain material to the siloxane-containing crosslinking material is 10-30:1.

[0081] In some embodiments of the present application, the composition of the transition metal oxide is as described above and will not be elaborated here.

[0082] In the third aspect of the present application, a positive electrode sheet is proposed, and the positive electrode sheet 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.

[0083] 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.

[0084] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0085] In some embodiments of the present application, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can 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 can be formed by forming a metal material (such as 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.).

[0086] In some embodiments of the present application, the positive electrode active material layer may further include a positive electrode active material, and the positive electrode active material can be a positive electrode active material known in the art for batteries.

[0087] 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), vinylidene fluoride - tetrafluoroethylene - propylene terpolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene terpolymer, tetrafluoroethylene - hexafluoropropylene copolymer, or fluorinated acrylate resin.

[0088] In some embodiments of the present application, based on the total mass of the active material layer, the mass percentage of the binder is 0.5% - 3%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0089] 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.

[0090] In some embodiments of the present application, based on the total mass of the active material layer, the mass percentage of the conductive agent is 0.8% - 4%, such as 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0091] In some embodiments of the present application, the positive electrode plate can be prepared in the following manner: dispersing the components for preparing the positive electrode plate, 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, in a solvent (such as N - methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0092] In some embodiments of the present application, the positive electrode plate can also be prepared in the following manner: first mixing the main chain material containing siloxane and the cross - linking material containing siloxane with the transition metal oxide, then adding the conductive agent and / or the binder to obtain a mixed slurry, and then applying the mixed slurry on at least one side of the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate is obtained.

[0093] The fourth aspect of the present application provides a battery, and the battery includes the positive electrode plate 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 voltages.

[0094] In some embodiments of the present application, the battery further includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0095] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0096] In some embodiments of the present application, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper 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.).

[0097] In some embodiments of the present application, the negative electrode active material may be a negative electrode active material for a battery well-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 materials may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys. The tin-based materials may include at least one of elemental tin, tin oxides, or tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone, or two or more of them may be used in combination.

[0098] 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).

[0099] In some embodiments of the present application, the negative electrode active material layer may further optionally include a conductive agent. 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.

[0100] In some embodiments of the present application, the negative electrode active material layer may further optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0101] In some embodiments of the present application, the negative electrode sheet can be prepared in the following manner: 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 current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained.

[0102] Generally, a battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are inserted and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0103] The present application has no specific limitation on the type of electrolyte, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0104] In some embodiments of the present application, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0105] 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(trifluoromethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalato)borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate.

[0106] 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 difluorooxalate borate, sodium tetrafluoroborate, sodium bis(oxalato)borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate, or sodium bis(trifluoromethylsulfonyl)imide.

[0107] 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, methyl propyl carbonate, ethyl propyl 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, sulfolane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone, or diethyl sulfone.

[0108] In some embodiments of the present application, the electrolyte may further optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0109] The present application does not particularly limit the type of separator. Any well-known porous separator with good chemical stability and mechanical stability can be selected.

[0110] 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 can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0111] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0112] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0113] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0114] The present application does not particularly limit the shape of the battery, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 is a battery cell 1 with a square structure as an example.

[0115] In some embodiments, referring to Figure 3 , the outer package may include a housing 11 and a cover plate 13. Among them, the housing 11 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 11 has an opening communicating with 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 separator can form an electrode assembly 12 through a winding process or a stacking process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte infiltrates into 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.

[0116] In some embodiments, the batteries can be assembled into battery modules. The number of batteries included in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.

[0117] Figure 4 is the battery module 2 as an example. Refer to Figure 4 , in the battery module 2, a plurality of battery cells 1 can be arranged in sequence along the length direction of the battery module 2. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells 1 can be fixed by fasteners.

[0118] Optionally, the battery module 2 can further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0119] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0120] Figure 5 and Figure 6 is the battery pack 3 as an example. Refer to Figure 5 and Figure 6 , the battery pack 3 can include a battery box and a plurality of battery modules 2 arranged in the battery box. The battery box includes an upper box body 31 and a lower box body 32. The upper box body 31 can cover the lower box body 32 to form a closed space for accommodating the battery modules 2. The plurality of battery modules 2 can be arranged in the battery box in any manner.

[0121] In addition, the present application also provides an electrical device, and the electrical device includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices (such as mobile phones, laptop computers, 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, satellites, energy storage systems, etc., but is not limited thereto.

[0122] As the electrical device, the secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0123] Figure 7It is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or a battery module can be adopted.

[0124] The device as another example can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a battery can be adopted as the power source.

[0125] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those without specific technologies or conditions noted in the embodiments, the technologies or conditions described in the literature in this field or according to the product specifications are followed. For the reagents or instruments without the producer noted, they are all conventional products that can be obtained through commercial purchase.

[0126] Embodiment 1

[0127] 1. Preparation of the positive electrode sheet

[0128] Mix the transition metal oxide Li(Ni 0.56 Co 0.05 Mn 0.39 )O 2 uniformly with the main chain material (compound shown in Formula 1), the crosslinking material (compound shown in Formula 11), and the organic solvent NMP (N-methylpyrrolidone), where the total mass ratio of the main chain material and the crosslinking material to the mass of the transition metal oxide is 1:150, and the mass ratio of the main chain material to the crosslinking material is 12:1. Then, add the conductive agent carbon black (Super P) and the binder polyvinylidene fluoride (PVDF) (the mass ratio of the total mass of the transition metal oxide, the main chain material, and the crosslinking material, the conductive agent, and the binder is 97:2:1) and further stir and mix to obtain a stable positive electrode slurry;

[0129] Coat the positive electrode slurry on both surfaces of the positive electrode current collector aluminum foil, and through drying and cold pressing, form a positive electrode active material layer on both surfaces of the positive electrode current collector, and then through the processes of strip cutting and trimming, obtain the positive electrode sheet.

[0130] 2. Preparation of the negative electrode sheet

[0131] Mix the negative electrode active material artificial graphite, the conductive agent carbon black (Super P), the binder styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC-Na) in a mass ratio of 96:1:1.5:1.5 in an appropriate amount of solvent deionized water to obtain a negative electrode slurry. Coat the negative electrode slurry on both surfaces of the negative electrode current collector copper foil, and through drying and cold pressing, form a negative electrode active material layer on both surfaces of the negative electrode current collector. Finally, through the processes of strip cutting and trimming, obtain the negative electrode sheet.

[0132] 3. Preparation of Electrolyte

[0133] In a glove box under an argon atmosphere (H 2 O < 0.1 ppm, O 2 < 0.1 ppm), ethylene carbonate and ethyl methyl carbonate were mixed at a mass ratio of 30:70 to obtain a solvent. The fully dried electrolyte salt LiPF 6 was dissolved in the above solvent, and after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0134] 4. Separator

[0135] A polypropylene film was used as the separator.

[0136] 5. Preparation of Secondary Battery

[0137] The positive electrode plate, separator, and negative electrode plate were stacked in sequence, with the separator placed between the positive and negative electrode plates to play a separating role, and then wound to obtain an electrode assembly; the electrode assembly was placed in an outer package, and the prepared electrolyte was injected into the dried lithium-ion battery. After vacuum packaging, standing, forming, and shaping processes, a lithium-ion battery was obtained.

[0138] The preparation methods of the lithium-ion batteries in Examples 2 - 13 and Comparative Examples 1 - 3 were the same as those in Example 1, except that the process of preparing the positive electrode plate was different, as shown in Table 1 specifically.

[0139] The preparation method of the lithium-ion battery in Example 14 was the same as that in Example 1, except that in the method of preparing the positive electrode plate, the transition metal oxide Li(Ni 0.56 Co 0.05 Mn 0.39 )O 2 , conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were 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) were added and stirred to form a positive electrode paste.

[0140] Table 1

[0141]

[0142] The silicon content and coating thickness in 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 batteries, were characterized, and the characterization results are shown in Table 2.

[0143] (1) Test of silicon content in the coating layer of the positive electrode active material:

[0144] Element quantitative analysis was carried out using an inductively coupled plasma emission spectrometer (ICP): The powder on the positive electrode was scraped off, and a test sample was prepared through digestion treatment (mixing the powder with alcohol and dispersing it ultrasonically for 20 min), and then the silicon content was tested using the ICP-MS mode.

[0145] (2) Coating thickness test of the positive electrode active material:

[0146] The powder on the positive electrode was scraped off, and a test sample was prepared through digestion treatment (mixing the powder with alcohol and dispersing it ultrasonically for 20 min). The coating thickness of the positive electrode active material was observed using a transmission electron microscope (TEM).

[0147] (3) Cycle performance test of the battery:

[0148] The ambient temperature was controlled at 25 °C, and it was left standing for 1 h. It was discharged at 0.33C to 2.5V, left standing for 5 min, charged at 0.33C to 4.4V, left standing for 5 min, and then discharged at 0.33C to 2.5V. The discharge capacity was recorded as C 0 . The cycle temperature was adjusted to 45 °C, and 700 cycles were carried out according to the process of charging at 0.5C to 4.4V, leaving standing for 5 min, discharging at 1C to 2.5V, and leaving standing for 5 min. The discharge capacity of the 700th cycle was C 1 , and the cycle capacity retention rate of the battery cell = C 1 / C 0 *100%.

[0149] (4) Battery DCR test

[0150] The battery was placed at 25 °C, charged at 0.33C to 4.4V, then charged at a constant voltage to 0.05C, left standing for 5 min, then discharged at 0.33C for 1.5 h, left standing for 120 min, and the voltage V after standing was recorded 1 , then discharged at 4C for 30 s, with a sampling interval of 0.1S, and the voltage V at the end of discharge was recorded 2 , battery DCR (direct current internal resistance) = (V 1 -V 2 ) / I, I = 4C.

[0151] Figure 8 is the TEM image of the positive electrode active material obtained in Example 1, Figure 9 the TEM image of the positive electrode active material obtained in Comparative Example 1. It can be seen from Figure 8 and 9 that there is an obvious coating layer on the surface of the positive electrode active material obtained in Example 1, while there is no coating layer shown on the surface of the positive electrode active material in Comparative Example 1; Figure 10 is the comparison chart of the cycle curves of the batteries obtained in Example 1 and Comparative Example 1. It can be seen from Figure 10It can be seen that the capacity retention rate of the lithium-ion battery of Example 1 is significantly higher than that of Comparative Example 1 after 700 cycles. Figure 11 It is a comparative diagram of DCR after cycling of the batteries obtained in Example 1 and Comparative Example 1. Figure 11 It can be seen that the DCR of the lithium-ion battery of Example 1 is significantly lower than that of Comparative Example 1 after 700 cycles.

[0152] Table 2

[0153]

[0154]

[0155] As can be seen from the data in Table 2, the silicon content in the coating layer of the positive active materials obtained in Examples 1-14 is 0.05%-1%. The positive active materials in the batteries of Comparative Example 1 do not have a coating layer, and the silicon content in the coating layer of the positive active materials in Comparative Example 2 is 0.03%. The capacity retention rates of the batteries of Examples 1-14 are significantly higher than those of Comparative Examples 1-2, and the DCRs of the batteries of Examples 1-14 are significantly lower than those of Comparative Examples 1-2. The silicon content in the coating layer of the positive active materials obtained in Comparative Example 3 is 1.3%. Although its battery has high cycling performance, due to the too thick coating layer of the positive active materials, it affects the transport of lithium ions, resulting in a lower DCR after cycling. This shows that by controlling the silicon content in the coating layer on the surface of the positive active materials to be 0.05%-1% in this application, the stability of the positive active materials can be significantly improved, thereby improving the cycling performance and DC resistance of the battery under high voltage.

[0156] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples. Embodiments with the same structure and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope not departing from the gist of this application, various deformations that those skilled in the art can think of applied to the embodiments and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A positive electrode active material, characterized in that, it comprises: a core, the core comprising a transition metal oxide; a coating layer, the coating layer formed on the surface of the core, the coating layer comprising a polymer containing a silicon-oxygen bond, 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 thickness of the coating layer is 1 nm - 5 nm, and can be optionally 2 nm - 3 nm.

4. The positive electrode active material according to any one of claims 1-3, characterized in that, The transition metal oxide includes Li x MO y or Na x MO y wherein 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.

5. A method for preparing a positive electrode active material, characterized in that, it comprises: mixing a transition metal oxide with a silicon-oxane-containing main chain material and a silicon-oxane-containing crosslinking material to form a coating layer comprising a polymer containing a silicon-oxygen bond on the surface of the transition metal oxide, the silicon-oxane-containing main chain material comprising at least 2 silicon atoms and at least 3 siloxane groups; the silicon-oxane-containing crosslinking material comprises 1-3 siloxane groups, based on the total mass of the positive electrode active material, the mass proportion of silicon in the polymer is 0.05%-1%.

6. The method according to claim 5, characterized in that, the molecular weight of the silicon-oxane-containing main chain material is 300-10000, and can be optionally 500-1200.

7. The method according to claim 5 or 6, characterized in that, the structural formula of the silicon-oxane-containing main chain material comprises: where a is 1 - 6, R 1 , R 2 , R 3 , R 4 and R 5 each independently includes an alkyl group, R 6 includes an alkyl group, an alkoxy group, a boron - containing group, a phosphorus - containing group, a halogen - containing group, a selenium - containing group, a cyano group, a hydroxyl group, -N 3 , 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, R 7 includes an alkyl group, an alkenyl group, an alkoxy group, a phenyl group, 8. The method according to claim 7, characterized in that, R 1 、R 2 、R 3 、R 4 and R 5 each independently includes ethyl, methyl, R 6 includes methoxy, ethoxy, R 7 includes 9. The method according to any one of claims 5-8, characterized in that, The silicone-containing main chain material includes at least one of, and may optionally be at least one of.

10. The method according to any one of claims 5-9, characterized in that, the molecular weight of the silicon-oxane-containing crosslinking material is 90-500, and can be optionally 100-300.

11. The method according to any one of claims 5-10, characterized in that, The structural formula of the silicone-containing crosslinked material includes: Among them, R 8 includes alkyl groups, R 9 and R 10 each independently includes a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group or a haloalkyl group, and R 11 includes an alkyl group, a boron-containing group, a phosphorus-containing group, a halogen-containing group, a selenium-containing group, a cyano group, a hydroxyl group, -N 3 , 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.

12. The method according to claim 11, characterized in that, R 8 and R 9 each independently includes methyl, ethyl, methoxy, ethoxy, and R 10 includes methyl, methoxy or ethoxy, and R 11 includes methyl, 13. The method according to any one of claims 5-12, characterized in that, The silicone-containing crosslinked material includes at least one of, and optionally at least one of.

14. The method according to any one of claims 5-13, characterized in that, the mass ratio of the total mass of the silicon-oxane-containing main chain material and the silicon-oxane-containing crosslinking material to the mass of the transition metal oxide is 1:50-1000, and can be optionally 1:100-200.

15. The method according to any one of claims 5-14, characterized in that, the mass ratio of the silicon-oxane-containing main chain material and the silicon-oxane-containing crosslinking material is 1-50:1, and can be optionally 10-30:

1.

16. A positive electrode plate, characterized in that, it comprises the positive electrode active material according to any one of claims 1-4 or the positive electrode active material obtained by the method according to any one of claims 5-15.

17. A battery, characterized in that, it comprises the positive electrode plate according to claim 16.

18. An electrical device, characterized in that, it includes the battery described in claim 17.

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