Secondary battery and electric device

Abstract

The invention provides a secondary battery and an electric device. The secondary battery comprises a positive pole piece, the positive pole piece comprises a positive active material, and the positive active material comprises a base material and a titanate coating layer at least partially covering the base material. The secondary battery has a high cycle capacity retention rate and a long service life.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to a secondary battery and an electrical device. Background Art

[0002] In recent years, with the increasingly wide application scope of secondary batteries represented by lithium-ion batteries, secondary batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the great development of secondary batteries, higher requirements are also put forward for their cycling performance. Summary of the Invention

[0003] The present application is made in view of the above problems, and its purpose is to provide a secondary battery and an electrical device, aiming to improve the cycling capacity retention rate of the secondary battery and improve the cycling performance of the battery.

[0004] A first aspect of the present application provides a secondary battery, including a positive electrode plate, the positive electrode plate including a positive electrode active material, and the positive electrode active material including a matrix material and a titanate coating layer at least partially covering the matrix material.

[0005] The present application uses a titanate coating layer to perform surface modification on the matrix material, which can improve the hydrophobicity of the positive electrode active material, effectively reduce the absorption of moisture in the environment by the positive electrode active material and the positive electrode plate during storage or production, reduce the influence of side reactions between moisture and the positive electrode active material or electrolyte on the cycling performance of the battery, improve the cycling performance of the battery. At the same time, the titanate coating layer can also reduce the possibility of side reactions of the electrolyte eroding the positive electrode active material, reduce the possibility of transition metal ion dissolution on the surface of the positive electrode active material, improve the cycling stability of the material, improve the cycling performance of the battery, and extend the service life of the battery.

[0006] In any embodiment, the titanate coating layer is connected to the matrix material through an -O- functional group.

[0007] The titanate coating layer is connected to the matrix material through an -O- functional group, that is, the titanate coating layer and the matrix material are connected by a chemical bond, which can improve the stability of the coating layer, achieve the purpose of isolating moisture or carbon dioxide in the air, reduce the influence of moisture or carbon dioxide in the air on the positive electrode active material and the positive electrode plate during the cycling process, and improve the cycling performance of the battery.

[0008] In any embodiment, based on the mass of the matrix material, the mass content of the titanate coating layer is 0.5% - 10%.

[0009] When the mass content of the titanate coating layer is within a suitable range, it can ensure that the coating layer with sufficient mass content densely coats the matrix material, achieving the purpose of improving the hydrophobic property of the cathode active material, effectively reducing the water absorption of the cathode active material or the cathode electrode during storage or production. At the same time, it is also necessary to avoid that an excessive titanate coating layer affects the energy density and kinetic performance of the battery.

[0010] In any embodiment, the thickness of the titanate coating layer is 1 nm - 10 nm.

[0011] When the thickness of the titanate coating layer is within a suitable range, it can ensure the dense coating of the matrix material, achieving the purpose of improving the hydrophobic property of the cathode active material, effectively reducing the water absorption of the cathode active material or the cathode electrode during storage or production. At the same time, it is also necessary to avoid that an overly thick titanate coating layer affects the energy density and kinetic performance of the battery.

[0012] In any embodiment, the matrix material includes Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 、Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 and one or more of its modified materials,

[0013] wherein, 0.6 ≤ a1 ≤ 1.2, 0 < x1 ≤ 1, 0 < y1 ≤ 1, -0.1 ≤ b1 ≤ 0.1; 0.6 ≤ a2 ≤ 1.2, 0 < x2 ≤ 1, 0 < y2 ≤ 1, -0.1 ≤ b2 ≤ 0.1.

[0014] In any embodiment, the Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 、Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 In

[0015] 0.6 ≤ a1 ≤ 1.2, 0.6 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.4, -0.1 ≤ b1 ≤ 0.1; 0.6 ≤ a2 ≤ 1.2, 0.6 < x2 ≤ 1, 0 < y2 ≤ 0.4, -0.1 ≤ b2 ≤ 0.1.

[0016] In any embodiment, the titanate coating layer includes one or more of a monoalkoxy titanate coating layer, a chelating titanate coating layer, and a coordination titanate coating layer.

[0017] In any embodiment, the titanate coating layer includes one or more of an isopropyltri(dioctylpyrophosphate acyloxy)titanate coating layer, a bis(dioctyloxyphosphate)ethylene titanate coating layer, an isopropyl dioleate acyloxy(dioctylphosphate acyloxy)titanate coating layer, and a tris(dodecylbenzenesulfonyl)isopropyl titanate coating layer.

[0018] In any embodiment, the method for preparing the positive electrode active material is as follows:

[0019] Prepare a matrix material solution;

[0020] Prepare a titanate coupling agent solution;

[0021] Mix the matrix material solution with the titanate coupling agent solution and carry out a chemical reaction to obtain the positive electrode active material.

[0022] The titanate coupling agent exists in a liquid form and has a low surface tension, so it can quickly spread on the surface of the matrix material. The matrix material is fully wetted by the titanate coupling agent. Subsequently, the alkoxy group of the titanate coupling agent reacts with the hydroxyl group on the surface of the matrix material, so that one end of the titanate coupling agent is connected to the surface of the matrix material with an -O- functional group, and the other end is a hydrophobic group, playing a hydrophobic role, which can effectively isolate water and carbon dioxide in the air and improve the cycle performance of the battery.

[0023] In any embodiment, the pH of the titanate coupling agent solution is 3 - 6.

[0024] The titanate coupling agent solution is in an acidic environment, which can activate the alkoxy group in the titanate coupling agent in advance, facilitating the reaction between the alkoxy group and the hydroxyl group on the surface of the matrix material to form a titanate coating layer.

[0025] In any embodiment, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on the positive electrode current collector. The positive electrode film layer includes additives, and the additives include one or more of aluminosilicate, hydrated oxide, polyvalent metal acid salt, heteropolyacid salt, and lithium titanate.

[0026] Introducing additives such as aluminosilicate, hydrated oxide, polyvalent metal acid salt, heteropolyacid salt, or lithium titanate into the positive electrode film layer can further improve the cycle performance of the battery.

[0027] In any embodiment, the additive includes lithium titanate.

[0028] The additive containing titanate in the positive electrode film layer can further improve the cycle capacity retention rate of the battery and extend the service life of the battery.

[0029] In any implementation manner, based on the mass of the positive electrode film layer, the mass content of the additive is 0.1%-1%.

[0030] The additive with a suitable mass content can achieve the purpose of consuming the moisture in the system, avoid the influence of moisture on the battery cycle performance, and also avoid the influence of excessive additives on the energy density of the battery.

[0031] In any implementation manner, the water contact angle of the positive electrode active material is greater than or equal to 85°.

[0032] In any implementation manner, the water contact angle of the positive electrode active material is greater than or equal to 100°.

[0033] In any implementation manner, the initial water content of the positive electrode plate is lower than 300 ppm.

[0034] In any implementation manner, the water content of the positive electrode plate after being stored in an environment with a humidity of 40% for 72 hours is lower than 990 ppm.

[0035] The second aspect of the present application provides an electrical device including the secondary battery described in the first aspect. Description of the Drawings

[0036] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0037] Figure 2 is Figure 1 the exploded view of the secondary battery according to an embodiment of the present application shown in

[0038] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0039] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0040] Figure 5 is Figure 4 the exploded view of the battery pack according to an embodiment of the present application shown in

[0041] Figure 6 is a schematic diagram of an electrical device using the secondary battery according to an embodiment of the present application as a power source;

[0042] Reference Signs:

[0043] 1 Battery pack; 2 Upper case; 3 Lower case; 4 Battery module; 5 Secondary battery; 51 Case; 52 Electrode assembly; 53 Cover plate. Detailed implementation mode

[0044] Hereinafter, embodiments of the secondary battery and the electrical device of the present application will be specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0045] 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 or exclude 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 specific 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, 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 specified, 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. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0048] 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), indicating 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, it is mentioned that the method may further include step (c), indicating 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 also include steps (c), (a), and (b), etc.

[0049] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application are open-ended and can also be closed-ended. For example, the terms "comprising" and "including" may mean that other components not listed can also be included or contained, or may only include or contain the listed components.

[0050] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0051] When the positive electrode active material is exposed to air, it is prone to absorb water in the air. The absorbed water will react with lithium ions in the positive electrode active material to generate lithium hydroxide, and lithium hydroxide will further react with carbon dioxide in the air to generate lithium carbonate, that is, lithium hydroxide and lithium carbonate are formed on the surface of the positive electrode active material. The above reactions will consume lithium ions in the material, resulting in capacity attenuation of the battery and affecting the cycle performance of the battery.

[0052] [Secondary battery]

[0053] Based on this, this application provides a secondary battery, including a positive electrode plate, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes a matrix material and a titanate coating layer at least partially covering the matrix material.

[0054] In this application, the matrix material is surface-modified with a titanate coating layer, which can improve the hydrophobicity of the cathode active material, effectively reduce the absorption of moisture in the environment by the cathode active material and the cathode electrode during storage or production, reduce the impact of side reactions between moisture and the cathode active material or electrolyte on the cycle performance of the battery, improve the cycle performance of the battery. At the same time, the titanate coating layer can also reduce the possibility of side reactions of the electrolyte eroding the cathode active material, reduce the possibility of transition metal ion dissolution on the surface of the cathode active material, improve the cycle stability of the material, improve the cycle performance of the battery, and extend the service life of the battery.

[0055] Compared with the silane coating layer, the coating effect of the titanate coating layer in this application is better than that of the silane coating layer. The coating layer is denser and has a more excellent hydrophobic effect, which is beneficial to improving the cycle performance of the battery.

[0056] In some embodiments, the titanate coating layer is connected to the matrix material through -O- functional groups.

[0057] The titanate coating layer is connected to the matrix material through -O-, that is, the titanate coating layer and the matrix material are connected by chemical bonds, which can improve the stability of the coating layer, achieve the purpose of isolating moisture or carbon dioxide in the air, reduce the influence of moisture or carbon dioxide in the air on the cathode active material and the cathode electrode during the cycle process, and improve the cycle performance of the battery.

[0058] In some embodiments, based on the mass of the matrix material, the mass content of the titanate coating layer is 0.5% - 10%.

[0059] In some embodiments, based on the mass of the matrix material, the mass content of the titanate coating layer is 1% - 5%.

[0060] In some embodiments, based on the mass of the matrix material, the mass content of the titanate coating layer can be selected as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the numerical range between any two of them.

[0061] When the mass content of the titanate coating layer is within a suitable range, it can ensure that the coating layer with sufficient mass content densely coats the matrix material, achieve the purpose of improving the hydrophobic performance of the cathode active material, effectively reduce the absorption of moisture by the cathode active material or the cathode electrode during storage or production. At the same time, it is also necessary to avoid excessive titanate coating layer affecting the energy density and kinetic performance of the battery.

[0062] In some embodiments, the thickness of the titanate coating layer is 1 nm - 10 nm. In some embodiments, the thickness of the titanate coating layer can be optionally 1 nm, 2 nm, 1 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm or the numerical range between any two of them.

[0063] In the present application, the titanate coating layer can be tested by instruments and methods known in the art. As an example, clean the sample preparation tool, mix the sample preparation glue (a jelly formed by dispersing polyvinylidene fluoride into N-vinylpyrrolidone, with the mass content of polyvinylidene fluoride being 8%) with the cathode active material powder (the powder weight is about 5 times that of the glue), coat it evenly on the copper foil after mixing, and dry it at 60 °C for 30 min. Cut the prepared sample into pieces of 6 mm × 6 mm with scissors, fix them on the sample stage, and put them into an ion polishing instrument (model: IB-19500CP) for cutting. According to JBT9352-1999, put the cut sample into a FEI Tecnai G2 transmission electron microscope device in the United States for thickness testing.

[0064] When the thickness of the titanate coating layer is within a suitable range, it can ensure a dense coating on the substrate material, achieve the purpose of improving the hydrophobic property of the cathode active material, effectively reduce the water absorption of the cathode active material or the cathode electrode during storage or production, and at the same time, avoid the influence of an overly thick titanate coating layer on the energy density and kinetic performance of the battery.

[0065] In some embodiments, the substrate material includes cathode active substances for batteries well-known in the art. As a non-limiting example, the cathode active substance may include one or more of the following materials or substances: lithium transition metal oxides with an olivine structure and their respective modified compounds. However, the present application is not limited to these materials or substances, and other conventional materials or substances that can be used as cathode active substances for batteries can also be used. These cathode active substances can be used alone or in combination of two or more. Among them, non-limiting examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their modified compounds, etc. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (which can also be abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn0.3 O2 (which can also be abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM811), etc. Non-limiting examples of lithium nickel cobalt manganese oxides can include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0066] In some embodiments, the matrix material includes Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 、Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 and one or more of their modified materials,

[0067] where 0.6 ≤ a1 ≤ 1.2, 0 < x1 ≤ 1, 0 < y1 ≤ 1, -0.1 ≤ b1 ≤ 0.1; 0.6 ≤ a2 ≤ 1.2, 0 < x2 ≤ 1, 0 < y2 ≤ 1, -0.1 ≤ b2 ≤ 0.1.

[0068] In this article, the modified materials of Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 、Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 refer to the modification of Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 、Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2Doping modification or coating modification is carried out, where doping modification means doping the modifying element into the material body, and coating modification means the modifying element exists in the form of a coating layer on the surface of the material body. The modifying element includes one or more of Na, K, Ca, Ba, Sb, Ti, Zr, W, Sr, Nb, Mo, Si, Mg, B, Cr, Ta.

[0069] The above matrix material is a ternary layered transition metal oxide, which has advantages such as high specific capacity, high working voltage, and low cost. In order to further improve the energy density of the material, the molar content of nickel in the material will be increased. However, as the nickel content increases, the surface of the material is alkaline and easily absorbs water in the air. The water adsorbed on the surface of the material easily reacts with lithium on the surface of the material to form lithium hydroxide, and lithium hydroxide continues to react with carbon dioxide in the air to form lithium carbonate. Since the lithium ions on the surface of the material are consumed, the NiOOH phase formed in the surface lattice of the material belongs to a thermodynamically unstable phase, forming a surface reconstruction layer on the surface of the material, thereby increasing the impedance of the material and inducing the rapid growth of the cathode electrolyte interphase (CEI), resulting in a sharp decline in the cycling performance.

[0070] In this application, coating the ternary layered transition metal oxide with titanate can isolate water and carbon dioxide in the air, reduce the degree of side reactions occurring on the surface of the positive electrode active material. At the same time, the titanate coating layer seals the hydroxyl groups on the surface of the material, reduces the alkalinity of the material surface, and is also beneficial to reducing the water absorption performance of the material, reducing the phenomenon of side reactions of the material, and improving the cycling performance of the battery.

[0071] In some embodiments, in the chemical formula Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 a1 is any value among 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2 or a range composed of any two of these values.

[0072] In some embodiments, in the chemical formula Li a1 Ni x1 Co y Mn 1-x1-y1 O 2-b1 x1 is any value among 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.85, 0.9, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or a range composed of any two of these values.

[0073] In some embodiments, in the chemical formula Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 y1 is any value in 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.85, 0.9, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or a range formed by any two of these values.

[0074] In some embodiments, in the chemical formula Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 b1 is any value in -0.1, 0, 0.1 or a range formed by any two of these values.

[0075] In some embodiments, in the chemical formula Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 a2 is any value in 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2 or a range formed by any two of these values.

[0076] In some embodiments, in the chemical formula Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 x2 is any value in 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.85, 0.9, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or a range formed by any two of these values.

[0077] In some embodiments, in the chemical formula Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2Among them, y2 is any value in 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.85, 0.9, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or the range composed of any two of these values.

[0078] In some embodiments, the chemical formula Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 Among them, b2 is any value in -0.1, 0, 0.1 or the range composed of any two of these values.

[0079] In some embodiments, the Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 Among them,

[0080] 0.6 ≤ a1 ≤ 1.2, 0.6 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.4, -0.1 ≤ b1 ≤ 0.1; 0.6 ≤ a2 ≤ 1.2, 0.6 < x2 ≤ 1, 0 < y2 ≤ 0.4, -0.1 ≤ b2 ≤ 0.1.

[0081] In some embodiments, the Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 Among them,

[0082] 0.6 ≤ a1 ≤ 1.2, 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, -0.1 ≤ b1 ≤ 0.1; 0.6 ≤ a2 ≤ 1.2, 0.8 < x2 ≤ 1, 0 < y2 ≤ 0.2, -0.1 ≤ b2 ≤ 0.1.

[0083] If the matrix material has a high nickel (Ni) element content, the material is prone to absorb water. In this case, by coating a titanate coating on the surface of the matrix material, the positive electrode active material is prevented from adsorbing moisture on the surface, and the performance of the battery is improved.

[0084] In some embodiments, the titanate coating layer includes one or more of a monoalkoxy titanate coating layer, a chelating titanate coating layer, and a coordinating titanate coating layer.

[0085] In some embodiments, the monoalkoxy titanate coating layer contains one or more of the compounds represented by Formula I-1, Formula I-2, Formula I-3, Formula I-4, Formula I-5, and Formula I-6,

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092] wherein the wavy line indicates the bonding position of the monoalkoxy titanate coating layer to the matrix material, R1 includes any one of a substituted or unsubstituted C 1-20 alkyl group, a substituted or unsubstituted C 2-15 alkenyl group, R2 includes a substituted or unsubstituted C 6-30 aralkyl group, R3 includes at least one of -OCH2CH2NHCH2CH2NH2, C 1-20 alkoxy group, and R6, R7, R8, R9, R 15 , R 16 , R 17 each independently includes a substituted or unsubstituted C 1-20 alkyl group.

[0093] As used herein, the term "C 1-20 alkyl" refers to a straight-chain or branched-chain hydrocarbon chain group consisting only of carbon and hydrogen atoms, having no unsaturation in the group, having from 1 to 20 carbon atoms, and being attached to the rest of the molecule by a single bond.

[0094] As used herein, the term "substituted" means that at least one hydrogen atom of the compound or chemical moiety is replaced by another chemical moiety with a substituent, and the substituents are each independently selected from: hydroxyl group, mercapto group, amino group, cyano group, nitro group, aldehyde group, halogen atom, alkenyl group, alkynyl group, aryl group, heteroaryl group, C 1-6 alkyl group, C 1-6 alkoxy group.

[0095] As used herein, the term "C 2-15"Alkenyl" refers to a straight-chain or branched hydrocarbon chain containing 2 to 15 carbon atoms and having at least one carbon-carbon double bond.

[0096] In this document, the term "C 1-20 "Alkoxy" refers to an alkyl group containing an oxygen atom, having no unsaturation in the group, having 1 to 20 carbon atoms, and being attached to the rest of the molecule by a single bond.

[0097] In some embodiments, R1 comprises at least one of, R2 comprises R3 comprises -OCH2CH2NHCH2CH2NH2, at least one of, R6, R7, R8, R9, R 15 , R 16 , R 17 each independently comprises C8H 17 or C 17 H 35 .

[0098] In some embodiments, the chelating titanate coating layer comprises the compound shown in II-1,

[0099]

[0100] wherein the wavy line indicates the bonding position of the chelating titanate coating layer to the substrate material, R4 comprises at least one of, R5 comprises -O-CH2CH2OH, -O-CH2CH2NHCH2CH2OH, at least one of, wherein R 18 comprises C 2-20 alkenyl, R 19 , R 20 , R 21 , R 22 , R 23 each independently comprises at least one of a hydrogen atom, a substituted or unsubstituted C 5-25 alkyl.

[0101] In some embodiments, R4 comprises at least one of.

[0102] In some embodiments, the coordination titanate coating layer comprises the compound shown in III-1,

[0103]

[0104] Among them, the wavy line indicates the bonding position of the coordination-type titanate coating layer and the matrix material, and R 13 and R 14 each independently include C 3-25 alkyl groups.

[0105] In some embodiments, the method for preparing the positive electrode active material is as follows:

[0106] Prepare a matrix material solution;

[0107] Prepare a titanate coupling agent solution;

[0108] Mix the matrix material solution and the titanate coupling agent solution and then carry out a chemical reaction to obtain the positive electrode active material.

[0109] In some embodiments, the titanate coupling agent includes one or more of a monoalkoxy-type titanate coupling agent, a chelating-type titanate coupling agent, and a coordination-type titanate coupling agent.

[0110] In some embodiments, the monoalkoxy-type titanate coating layer contains one or more of the compounds represented by Formula IV-1, Formula IV-2, Formula IV-3, Formula IV-4, Formula IV-5, and Formula IV-6,

[0111]

[0112]

[0113]

[0114]

[0115]

[0116]

[0117] Among them, X includes C 1-10 alkyl, R1 includes substituted or unsubstituted C 1-20 alkyl, substituted or unsubstituted C 2-15 alkenyl, any one of which, R2 includes substituted or unsubstituted C 6-30 aralkyl, R3 includes at least one of -OCH2CH2NHCH2CH2NH2 and C 1-20 alkoxy, and R6, R7, R8, R9, R 15 , R 16 , R 17 each independently include substituted or unsubstituted C 1-20 alkyl groups.

[0118] In some embodiments, X includes C3H7 and R1 includes at least one of, R2 contains R3 contains -OCH2CH2NHCH2CH2NH2, at least one of, R6, R7, R8, R9, R 15 、R 16 、R 17 each independently contains C8H 17 or C 17 H 35 .

[0119] In some embodiments, the chelating titanate coupling agent includes the compound shown in V-1,

[0120]

[0121] wherein, Y contains -CH2CH2-, -CH2CH2NHCH2CH2- at least one of, R4 includes at least one of, R 18 includes C 2-20 alkenyl, R 19 、R 20 、R 21 、R 22 、R 23 each independently contains a hydrogen atom, a substituted or unsubstituted C 5-25 alkyl at least one of.

[0122] In some embodiments, R4 includes at least one of.

[0123] In some embodiments, the coordination type titanate coupling agent includes tetraoctyloxytitanium bis(diphosphite) dilaurate.

[0124] In some embodiments, the titanate coupling agent includes one or more of isopropyl tris(dioctylpyrophosphatooxy) titanate coupling agent, bis(dioctyloxyphosphate) ethylene titanate coupling agent, isopropyl dioleoyl oxy(dioctylphosphatooxy) titanate coupling agent, tris(dodecylbenzenesulfonyl) titanium isopropyl titanate coupling agent.

[0125] The titanate coupling agent exists in a liquid form, has a low surface tension, can quickly spread on the surface of the matrix material, and the matrix material is fully wetted by the titanate coupling agent. Subsequently, the alkoxy group of the titanate coupling agent reacts with the hydroxyl group on the surface of the matrix material, so that at least one end of the titanate coupling agent is connected to the surface of the matrix material, and the other end is a hydrophobic group, which plays a hydrophobic role and can effectively isolate water and carbon dioxide in the air, improving the cycle performance of the battery.

[0126] Compared with the coating treatment with silane coupling agent, the titanate coupling agent has higher reactivity with the matrix material, the formed coating layer is denser, and the hydrophobic effect of the formed coating layer is better, which is beneficial to improving the cycle performance of the battery.

[0127] In some embodiments, the pH of the titanate coupling agent solution is 3 - 6. In some embodiments, the pH of the titanate coupling agent solution can be selected as 3, 4, 5, 6 or the numerical range between any two of them.

[0128] The titanate coupling agent solution is in an acidic environment, which can activate the alkoxy group in the titanate coupling agent in advance, facilitating the reaction of the alkoxy group in the titanate with the hydroxyl group on the surface of the matrix material to form a titanate coating layer.

[0129] In some embodiments, the reaction time of the chemical reaction is 1h - 3.5h. In some embodiments, the reaction time of the chemical reaction can be selected as 1h, 2h, 3h, 3.5h or the numerical range between any two of them.

[0130] The appropriate reaction time enables the titanate coupling agent to fully react with the hydroxyl group on the matrix material. While maximizing the blocking treatment of the hydroxyl group on the matrix material, it can also form a dense coating layer to achieve the purpose of isolating moisture and carbon dioxide in the air.

[0131] In some embodiments, the reaction temperature of the chemical reaction is 15°C - 35°C. In some embodiments, the reaction temperature of the chemical reaction can be selected as 15°C, 20°C, 25°C, 30°C, 35°C or the numerical range between any two of them.

[0132] The reaction between the titanate coupling agent and the matrix material does not require heat treatment and can be carried out at room temperature, which is beneficial to industrial production.

[0133] In some embodiments, the specific steps for preparing the matrix material solution are as follows:

[0134] Dissolve the matrix material in the first solvent to obtain the matrix material solution.

[0135] In some embodiments, the first solvent includes one or more of ethanol, isopropanol, and n-butanol.

[0136] In some embodiments, the mass ratio of the matrix material to the first solvent is 1:2 - 1:10. In some embodiments, the mass ratio of the matrix material to the first solvent can be optionally 1:2, 1:4, 1:6, 1:8, 1:10 or the numerical range between any two of them.

[0137] In some embodiments, the specific steps for preparing the titanate coupling agent solution are as follows:

[0138] Dissolve the titanate coupling agent and the acid auxiliary agent in a second solvent to obtain the titanate coupling agent solution.

[0139] In some embodiments, the second solvent includes one or more of isopropyl alcohol, acetone, ethyl acetate, octyl phthalate, paraffin oil, and xylene.

[0140] In some embodiments, the mass ratio of the titanate coupling agent to the second solvent is 1:5 - 1:10. In some embodiments, the mass ratio of the titanate coupling agent to the second solvent can be optionally 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or the numerical range between any two of them.

[0141] When the mass ratio of the titanate coupling agent to the solvent is within a suitable range, it ensures the uniform dispersion of the titanate coupling agent, which is beneficial for the subsequent uniform coating of the titanate coupling agent on the surface of the matrix material.

[0142] In some embodiments, the acid auxiliary agent includes any one of citric acid, glacial acetic acid, and hydrochloric acid.

[0143] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on the positive electrode current collector. The positive electrode film layer includes an additive, and the additive includes one or more of aluminosilicate, hydrated oxide, polyvalent metal acidic salt, heteropolyacid salt, and lithium titanate.

[0144] In this text, the term "aluminosilicate" refers to a substance with the chemical formula zM2O·Al2O3·xSiO2·yH2O, where M is a monovalent cation, x > 0, y ≥ 0, including but not limited to Na2O·Al2O3·SiO2·6H2O, 0.4K2O·0.6Na2O·Al2O3·2SiO2·4.5H2O.

[0145] In this text, the term "hydrated oxide" refers to a hydrated oxide formed by the oxide of elements such as Be, Mg, Al, Fe, Zr, Ti, Si, Sn, Th, Mn, Ce, Sb, V, Ta, Nb, Mo, and W and water, including but not limited to ZrO2·nH2O, MgO·nH2O, Al2O3·nH2O, Sb5O2·nH2O, n > 0.

[0146] In this text, the term "polyvalent metal acid salt" refers to phosphates, arsenates, antimonates, vanadates, molybdates, tungstates, tellurates, silicates, oxalates formed by Zr, Th, Ti, Ce, Sn, Al, Fe, U, including but not limited to iron phosphate, zirconium antimonate, titanium arsenate, tin tungstate.

[0147] In this text, the term "heteropolyacid salt" refers to the chemical formula H m XY 12 O 40 ·nH2O, where n > 0, m is 3, 4 or 5, X includes P, Si, As, Ge, B, and Y includes Mo, W, Y, including but not limited to ammonium phosphomolybdate, thallium phosphotungstate, zirconium phosphosilicate.

[0148] During the preparation of secondary batteries, moisture is inevitably introduced. Moisture will not only undergo side reactions with active materials to consume lithium ions, affecting the cycle performance of the battery, but also react with electrolyte salts in the electrolyte to generate highly reducing hydrogen fluoride. Hydrogen fluoride will then react with the components of the solid electrolyte interphase (SEI), damaging the SEI structure, affecting the cycle performance of the battery, and at the same time generating gases, affecting the safety performance of the battery.

[0149] Using a titanate coating layer to modify the surface of the positive electrode active material can isolate a part of the influence of water on the positive electrode active material or the positive electrode plate. However, it cannot isolate the influence of moisture introduced during the preparation process or storage process on the electrolyte or the positive electrode plate.

[0150] To address the above technical problems, the present application adds additives such as aluminosilicate, hydrated oxide, polyvalent metal acid salt or heteropolyacid salt to the positive electrode film layer. These additives can adsorb water in the battery system, reduce the amount of hydrogen fluoride generated by the reaction of water with the electrolyte, reduce the damage of hydrogen fluoride to the SEI film of the battery, reduce the loss of active lithium, and improve the cycle performance of the battery. These additives can also effectively absorb carbon dioxide, relieve the increase in the internal pressure of the battery, and improve the safety performance of the battery.

[0151] Introducing an additive of lithium titanate into the positive electrode film layer, lithium titanate can react with moisture in the system prior to the electrolyte salt to form a stable compound, thereby removing moisture in the system, reducing the possibility of side reactions between moisture and electrolyte salts to generate hydrogen fluoride, effectively reducing the damage of hydrogen fluoride to the SEI, and being beneficial to improving the cycle performance of the battery.

[0152] Since the above additives are added during the preparation of the slurry, and the negative electrode slurry is generally an aqueous slurry, the additives will react with water or adsorb water during the slurry preparation process and become ineffective, affecting their water removal effect in the battery system. While the positive electrode slurry is generally an oil-based slurry, which can ensure the reaction activity of the additives during the early manufacturing process to the greatest extent, enabling them to fully play the role of water removal in the battery system. Therefore, in this application, adding additives to the positive electrode film layer can maximize their water removal utility and achieve the purpose of improving the battery cycle performance.

[0153] In some embodiments, the additive includes lithium titanate.

[0154] Compared with the physical adsorption of water in the battery system by aluminosilicate, hydrated oxide, polyvalent metal acidic salt or heteropolyacid salt, lithium titanate chemically reacts with the water in the battery system to form stable compounds, and the water removal effect is more excellent, which is beneficial to reducing the possibility of side reactions between moisture and electrolyte salt to generate hydrogen fluoride and is beneficial to improving the battery cycle performance.

[0155] In some embodiments, the additive includes one or more of aluminosilicate and lithium titanate.

[0156] In some embodiments, based on the mass of the positive electrode film layer, the mass content of the additive is 0.1%-1%, and can be optionally 0.3%-0.5%. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the additive can be optionally 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or any numerical range between any two of them.

[0157] An appropriate mass content of the additive can achieve the purpose of consuming the moisture in the system, avoid the influence of moisture on the battery cycle performance, and at the same time avoid the influence of excessive additives on the energy density of the battery.

[0158] In some embodiments, the water contact angle of the positive electrode active material is greater than or equal to 85°. In some embodiments, the water contact angle of the positive electrode active material is greater than or equal to 100°. In some embodiments, the water contact angle of the positive electrode active material can be optionally 85°, 90°, 95°, 100°, 105°, 110°, 115°, 120°, 125°, 130°, 135°, 140°, 125° or any numerical range between any two of them.

[0159] The larger the water contact angle of the positive electrode active material, the better the hydrophobic performance of the material, and the less likely the positive electrode active material and the positive electrode plate are to absorb water and undergo side reactions.

[0160] In the present application, the water contact angle of the positive electrode active material can be tested using instruments and methods known in the art. As an example, the positive electrode active material powder is added to a pre-mold and pressed into a shape. The size after molding only needs to be able to hold the liquid droplet. The measurement is carried out at 25°C ± 5°C using a contact angle tester (such as SDC-200S): A water droplet is dropped onto the surface of the positive electrode active material powder after molding. The amount of the water droplet is 10 μL ± 1 μL, and the water contact angle is measured 3 - 5 seconds after the water droplet is dropped. Specifically, the measurement of the water contact angle uses the average value of the angles on both sides of the liquid droplet, and the specific value is automatically read by the instrument through fitting.

[0161] In some embodiments, the initial water content of the positive electrode sheet is less than 300 ppm. In some embodiments, the initial water content of the positive electrode sheet can be selected as 50 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, or the numerical range between any two of them.

[0162] The lower the initial water content of the positive electrode sheet, the less moisture in the system, which reduces the occurrence of side reactions during the cycling process and is beneficial to improving the cycling performance of the battery.

[0163] In the present application, the initial water content of the positive electrode sheet can be tested using instruments and methods known in the art. As an example, the freshly prepared positive electrode sheet is tested for its water content. Referring to the test standard GB / T24533 - 2019, a Karl Fischer moisture meter is used to test the water content of the positive electrode sheet. The test parameters are as follows: the mass of the positive electrode sheet sample is 1.0 g, the gas flow rate is 35 mL / min, the heating temperature is 170°C, and the termination time is 400 s.

[0164] In some embodiments, the water content of the positive electrode sheet after being stored in an environment with a humidity of 40% for 72 h is less than 990 ppm.

[0165] In some embodiments, the water content of the positive electrode sheet after being stored in an environment with a humidity of 40% for 72 h can be selected as 400 ppm, 450 ppm, 500 ppm, 550 ppm, 600 ppm, 650 ppm, 700 ppm, 750 ppm, 800 ppm, 850 ppm, 900 ppm, 950 ppm, 990 ppm, or the numerical range between any two of them.

[0166] The lower the water content of the positive electrode sheet after being stored in an environment with a humidity of 40% for 72 h, the poorer the water absorption performance of the positive electrode active material or the positive electrode sheet, and the better the effect of isolating moisture in the air, which is beneficial to the cycling performance and storage performance of the secondary battery.

[0167] In this application, the water content of the positive electrode sheet after being stored in an environment with a humidity of 40% for 72 hours can be tested using instruments and methods known in the art. As an example, the freshly prepared wound core battery is placed in an environment with a relative humidity of 40% for moisture absorption treatment. After 3 days, the positive electrode sheet of the innermost layer of the wound core is taken for water content testing. Referring to the test standard of GB / T24533-2019, a Karl Fischer moisture meter is used to test the water content of the positive electrode sheet, and the test parameters are as follows: the mass of the positive electrode sheet sample is 1.0 g, the gas flow rate is 35 mL / min, the heating temperature is 170 °C, and the termination time is 400 s.

[0168] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposite surfaces of the positive electrode current collector.

[0169] In some embodiments, 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.).

[0170] In some embodiments, the positive electrode film layer includes a conductive agent, and the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0171] In some embodiments, the positive electrode film layer includes a binder, and the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0172] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components used for preparing the positive electrode sheet, such as the positive electrode active material, additives, conductive agent, 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 processes such as drying and cold pressing, the positive electrode sheet can be obtained.

[0173] [Negative electrode sheet]

[0174] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0175] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0176] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. 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 substrate. The composite current collector can 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.).

[0177] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries 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 material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0178] In some embodiments, the negative electrode film layer may also optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0179] In some embodiments, the negative electrode film layer may also optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0180] In some embodiments, the negative electrode film layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0181] In some embodiments, the negative electrode plate can be prepared in the following manner: dispersing the above components for preparing the negative electrode plate, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0182] [Electrolyte]

[0183] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. There is no specific limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0184] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0185] In some embodiments, the electrolyte salt can be selected from 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 difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0186] In some embodiments, the solvent can be selected from 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, methyl ethyl sulfone, and diethyl sulfone.

[0187] In some embodiments, the electrolytic solution may also optionally include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain battery performances, 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.

[0188] [Separator]

[0189] In some embodiments, the secondary battery further includes a separator. There is no particular limitation on the type of separator in this application, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0190] In some embodiments, the material of the separator membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0191] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator membrane can be made into an electrode assembly by a winding process or a stacking process.

[0192] In some embodiments, the secondary battery can include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0193] 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-type soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be cited, etc.

[0194] [Secondary battery]

[0195] In one embodiment of the present application, a secondary battery is provided, which includes a positive electrode sheet, a separator membrane, a negative electrode sheet, and an electrolyte. The binder in the active material layer of the positive electrode sheet includes the polymer of any embodiment of the present application.

[0196] In some embodiments, the secondary battery is a lithium-ion battery or a sodium-ion battery. During the charge and discharge process of the battery, active ions are embedded 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 membrane is disposed between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0197] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator membrane can be made into an electrode assembly by a winding process or a stacking process.

[0198] In some embodiments, the secondary battery can include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0199] 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-type soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be cited, etc.

[0200] The present application has no particular limitation on the shape of the secondary battery, and it can be cylindrical, square, or any other shape. For example,Figure 1 The secondary battery 5 is a square structure as an example.

[0201] In some embodiments, referring to Figure 2 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 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 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0202] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary 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.

[0203] Figure 3 The battery module 4 is an example. Referring to Figure 3 , in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0204] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of secondary batteries 5 are received in the receiving space.

[0205] In some embodiments, the above battery module can be further assembled into a battery pack, and 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.

[0206] Figure 4 and Figure 5 The battery pack 1 is an example. Referring to Figure 4 and Figure 5 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0207] In addition, the present application also provides an electrical device, which 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, 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, satellites, energy storage systems, etc., but is not limited thereto.

[0208] As the electrical device, the secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0209] Figure 6 Take an electrical device as an example. The electrical device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be adopted.

[0210] Another example of the device can be a mobile phone, tablet computer, laptop, etc. This device usually requires thin and light design, and a secondary battery can be used as the power source.

[0211] Embodiment

[0212] 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 not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0213] I. Preparation Method

[0214] Example 1

[0215] 1) Preparation of the positive electrode active material

[0216] First, weigh 100 g of LiNi 0.8 Co 0.1 Mn 0.1O2 (NCM811) was added to 500 g of absolute ethanol to obtain Solution A; 5 g of isopropyltri(dioctylpyrophosphato)titanate was dispersed in 20 g of isopropanol to obtain Solution B, and then glacial acetic acid was added dropwise to adjust the pH of Solution B to 4. Solution B was added to Solution A to obtain Solution C; Solution C was dispersed using a high-shear disperser at a shear rate of 5000 r / min for 120 min; the solution was continuously stirred for 60 min and then the reaction was stopped; the resulting reaction product was dried to obtain the positive electrode active material.

[0217] 2) Preparation of the positive electrode sheet

[0218] The positive electrode active material, conductive agent (Super P), and binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone according to a weight ratio of 97:1.2:1.8, and after mixing evenly, a positive electrode slurry was prepared; the positive electrode slurry was evenly coated on the surfaces of both sides of the positive electrode current collector aluminum foil, and the coating areal density was 25.3 mg / cm 2 , and then after drying, cold pressing, and slitting, a positive electrode sheet was obtained.

[0219] 3) Preparation of the negative electrode sheet

[0220] The negative electrode active material graphite, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na), and conductive agent carbon black (SuperP) were dissolved in deionized water according to a weight ratio of 96.2:1.8:1.2:0.8, and after mixing evenly, a negative electrode slurry was prepared; the negative electrode slurry was evenly coated on the surfaces of both sides of the negative electrode current collector copper foil, and the coating areal density was 8.6 mg / cm 2 , and after drying, cold pressing, and slitting, a negative electrode sheet was obtained.

[0221] 4) Separator

[0222] A polyethylene film was used as the separator.

[0223] 5) Preparation of the electrolyte

[0224] In an environment with a water content of less than 10 ppm, ethylene carbonate EC and diethyl carbonate DMC, non-aqueous organic solvents, were mixed in a volume ratio of 1:1 to obtain an electrolyte solvent, and then a lithium salt was mixed with the mixed solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0225] 6) Preparation of the battery

[0226] Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and then wind to obtain a wound battery cell; place the wound battery cell in an outer packaging case, inject electrolyte after drying, and obtain a lithium-ion battery through processes such as vacuum packaging, standing, forming, and shaping.

[0227] Example 2 - 4

[0228] Compared with Example 1, isopropyl tris(dioctylpyrophosphate acyloxy) titanate was adjusted to bis(dioctyloxyphosphate) ethylene titanate, isopropyl dioleoyl dioctylphosphate titanate, and isopropyl tris(dodecylbenzenesulfonyl) titanate. Specific parameters are shown in Table 1.

[0229] Example 5 - 7

[0230] Compared with Example 1, the mass of isopropyl tris(dioctylpyrophosphate acyloxy) titanate was adjusted to 10 g, 1 g, and 0.5 g. Specific parameters are shown in Table 1.

[0231] Example 8

[0232] Compared with Example 1, the preparation method of the positive electrode sheet in Example 8 was adjusted as follows:

[0233] Dissolve the positive electrode active material, conductive agent (Super P), binder polyvinylidene fluoride (PVDF), and additive Li2TiO3 in the solvent N-methylpyrrolidone according to a weight ratio of 96.9:1.2:1.8:0.1, mix evenly, and prepare a positive electrode paste; evenly coat the positive electrode paste on the surfaces of both sides of the positive electrode current collector aluminum foil, and the coating surface density is 25.3 mg / cm 2 , and then obtain the positive electrode sheet through drying, cold pressing, and slitting.

[0234] Example 9 - 11

[0235] Compared with Example 8, the mass content of the additive Li2TiO3 in Examples 9 - 11 was adjusted. Specific parameters are shown in Table 1.

[0236] Example 12 - 13

[0237] Compared with Example 10, the types of additives in Examples 12 - 13 were adjusted. Specific parameters are shown in Table 1.

[0238] Comparative Example 1

[0239] Compared with Example 1, the positive electrode active material in Comparative Example 1 was LiNi that was not coated with a titanate coupling agent 0.8 Co 0.1 Mn 0.1O2 (NCM811), specific parameters are shown in Table 1.

[0240] Comparative Example 2

[0241] Compared with Example 1, isopropyltris(dioctylpyrophosphato)titanate was adjusted to octadecyltrimethoxysilane, and specific parameters are shown in Table 1.

[0242] II. Test Methods

[0243] 1. Normal-temperature cycle capacity retention rate of the battery

[0244] At 25 °C, the secondary batteries prepared in each example and comparative example were charged at a constant current of 1C to the charging cut-off voltage of 4.4V, then charged at a constant voltage until the current was 0.05C, left standing for 5 minutes, and then discharged at a constant current of 1C to the discharging cut-off voltage of 2.5V, and left standing for 5 minutes. This was one charge-discharge cycle. The battery was tested for cyclic charge and discharge according to this method. Taking the capacity of the first discharge as 100%, the capacity retention rate of the battery after 800 cycles was calculated. Capacity retention rate of the battery after 800 cycles (%) = Discharge capacity of the 800th cycle / Capacity of the first discharge × 100%.

[0245] III. Analysis of Test Results of Each Example and Comparative Example

[0246] The secondary batteries of each example and comparative example were prepared according to the above method, and various parameters were measured. The results are shown in the following table.

[0247] Table 1

[0248]

[0249]

[0250]

[0251]

[0252] As can be seen from the above table, the secondary batteries in Examples 1 - 13 of the present application include a positive electrode plate, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes a matrix material (LiNi 0.8 Co 0.1 Mn 0.1 O2) and an isopropyltris(dioctylpyrophosphato)titanate coating layer, a bis(dioctyloxyphosphato)ethylene titanate coating layer, an isopropyl dioleoyloxy(dioctylphosphato)titanate coating layer, or an isopropyl tris(dodecylbenzenesulfonyl)titanate coating layer that at least partially covers the matrix material.

[0253] As can be seen from the comparison between Examples 1-13 and Comparative Example 1, compared with the positive electrode active material without a titanate coating layer, in the present application, the matrix material is coated with titanate, which can increase the water contact angle of the positive electrode active material, improve the hydrophobic property of the positive electrode active material, reduce the initial water content of the positive electrode sheet and the water content after storing for 72 h in an environment with a humidity of 40%, increase the cycle capacity retention rate of the battery, and extend the service life of the battery.

[0254] As can be seen from the comparison between Examples 1-4 and Comparative Example 2, compared with the silane coating layer using octadecyltrimethoxysilane, in the present application, the titanate coating layer is used, which can increase the water contact angle of the positive electrode active material, improve the hydrophobic property of the positive electrode active material, reduce the initial water content of the positive electrode sheet and the water content after storing for 72 h in an environment with a humidity of 40%, increase the cycle capacity retention rate of the battery, and extend the service life of the battery.

[0255] As can be seen from Examples 1 and 5-7, based on the mass of the matrix material, the mass content of the titanate coating layer is 0.5%-10%. The positive electrode active material has a large water contact angle, good hydrophobic effect, small initial water content of the positive electrode sheet and water content after storing for 72 h in an environment with a humidity of 40%. The battery has a high cycle capacity retention rate and excellent cycle performance.

[0256] As can be seen from the comparison between Examples 8-13 and Example 1, the positive electrode film layer includes additives. The additives include one or more of Na2O·Al2O3·SiO2·6H2O or 0.4K2O·0.6Na2O·Al2O3·2SiO2·4.5H2O aluminosilicate, lithium titanate (Li2TiO3), which can further reduce the initial water content of the positive electrode sheet and the water content after storing for 72 h in an environment with a humidity of 40%, increase the cycle capacity retention rate of the battery, and extend the service life of the battery. As can be seen from the comparison between Example 10 and Examples 12-13, the additive contains lithium titanate (Li2TiO3), which can further reduce the initial water content of the positive electrode sheet and the water content after storing for 72 h in an environment with a humidity of 40%, increase the cycle capacity retention rate of the battery, and extend the service life of the battery.

[0257] As can be seen from Examples 8-11, based on the mass of the positive electrode film layer, the mass content of the additive is 0.1%-1%. The initial water content of the positive electrode sheet and the water content after storing for 72 h in an environment with a humidity of 40% are both small. The battery has a high cycle capacity retention rate and excellent cycle performance.

[0258] It should be noted that this application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the scope of the technical solution of this application are included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art 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 secondary battery, comprising a positive electrode plate, characterized in that, The positive electrode plate includes a positive active material, and the positive active material includes a matrix material and a titanate coating layer at least partially covering the matrix material.

2. The secondary battery according to claim 1, characterized in that, The titanate coating layer is connected to the matrix material through -O- functional groups.

3. The secondary battery according to claim 1 or 2, characterized in that, Based on the mass of the matrix material, the mass content of the titanate coating layer is 0.5% - 10%.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The thickness of the titanate coating layer is 1 nm - 10 nm.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The matrix material includes Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 、Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 and one or more of its modified materials, Wherein, 0.6 ≤ a1 ≤ 1.2, 0 < x1 ≤ 1, 0 < y1 ≤ 1, -0.1 ≤ b1 ≤ 0.1; 0.6 ≤ a2 ≤ 1.2, 0 < x2 ≤ 1, 0 < y2 ≤ 1, -0.1 ≤ b2 ≤ 0.

1.

6. The secondary battery according to claim 5, wherein The Li a1 Ni x1 Co y1 Mn 1-x1-y1 O 2-b1 、Li a2 Ni x2 Co y2 Al 1-x2-y2 O 2-b2 Among them, 0.6 ≤ a1 ≤ 1.2, 0.6 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.4, -0.1 ≤ b1 ≤ 0.1; 0.6 ≤ a2 ≤ 1.2, 0.6 < x2 ≤ 1, 0 < y2 ≤ 0.4, -0.1 ≤ b2 ≤ 0.

1.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, The titanate coating layer includes one or more of a monoalkoxy titanate coating layer, a chelating titanate coating layer, and a coordination titanate coating layer.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The titanate coating layer includes one or more of an isopropyl tri(dioctylpyrophosphate acyloxy) titanate coating layer, a bis(dioctyloxy pyrophosphate) ethylene titanate coating layer, an isopropyl dioleate acyloxy (dioctyl phosphate acyloxy) titanate coating layer, and a tris(dodecylbenzenesulfonyl) titanate isopropyl coating layer.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The preparation method of the positive active material is as follows: Prepare a matrix material solution; Prepare a titanate coupling agent solution; Mix the matrix material solution and the titanate coupling agent solution and carry out a chemical reaction to obtain the positive active material.

10. The secondary battery according to claim 9, characterized in that, The pH of the titanate coupling agent solution is 3 - 6.

11. The secondary battery according to any one of claims 1 to 10, characterized in that, The positive electrode plate includes a positive current collector and a positive electrode film layer provided on the positive current collector. The positive electrode film layer includes an additive, and the additive includes one or more of aluminosilicate, hydrated oxide, polyvalent metal acid salt, heteropolyacid salt, and lithium titanate.

12. The secondary battery according to claim 11, characterized in that, The additive includes lithium titanate.

13. The secondary battery according to claim 11 or 12, characterized in that, Based on the mass of the positive electrode film layer, the mass content of the additive is 0.1% - 1%.

14. The secondary battery according to any one of claims 1 to 13, characterized in that, The water contact angle of the positive active material is greater than or equal to 85°.

15. The secondary battery according to any one of claims 1 to 13, characterized in that, The water contact angle of the positive active material is greater than or equal to 100°.

16. The secondary battery according to any one of claims 1 to 15, characterized in that, The initial water content of the positive electrode plate is lower than 300 ppm.

17. The secondary battery according to any one of claims 1 to 16, characterized in that, The water content of the positive electrode plate after being stored in an environment with a humidity of 40% for 72 h is lower than 990 ppm.

18. An electrical device, characterized in that, A secondary battery including any one of claims 1 to 17.

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