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

Abstract

The invention discloses a positive active material and a preparation method thereof, a positive pole piece, a battery and a power utilization device, the positive active material comprises a substrate and a coating layer, the coating layer is formed on at least part of the surface of the substrate, the coating layer comprises a surface modifier and a hydrophobic protective agent, and the hydrophobic protective agent is formed on the surface of the substrate. The surface modifier comprises at least one of halogenated alkyl silane or alkyl silane, and the hydrophobic protective agent comprises a hydrophobic group. The surface modifier and the hydrophobic protective agent are arranged on at least part of the surface of the positive electrode active material provided by the invention, so that contact between an electrolyte and the positive electrode active material can be isolated, irreversible loss caused by side reaction of the positive electrode active material can be reduced, absorption of H2O and CO2 in air can be reduced, high-voltage durability of the positive electrode active material is improved, and the service life of the positive electrode active material is prolonged. The surface modifier and the hydrophobic protective agent act together, so that the battery has excellent cycle stability.

Description

Technical Field

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

[0002] Secondary batteries are not only applied to energy storage power systems such as hydroelectric power plants, thermal power plants, wind power plants, and solar power plants, but also widely used in electric transportation means such as electric bicycles, electric motorcycles, and electric vehicles, as well as in multiple fields such as military equipment and aerospace.

[0003] The positive electrode active material is a very important component of a secondary battery. However, the current positive electrode active material has poor stability, resulting in poor cycle performance of the battery containing it.

[0004] It should be noted that the above statements are only used to provide background technical information related to the present application, and do not necessarily constitute prior art. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present application provides a positive electrode active material, aiming to solve the problem of poor cycle performance of the battery containing it.

[0006] To achieve the above object, a first aspect of the present application provides a positive electrode active material, including a matrix and a coating layer. The coating layer is formed on at least a part of the surface of the matrix. The coating layer includes a surface modifier and a hydrophobic protective agent. The surface modifier includes at least one of a halogenated alkyl silane or an alkyl silane. The hydrophobic protective agent includes a hydrophobic group.

[0007] Thus, the surface modifier and the hydrophobic protective agent are provided on at least a part of the surface of the matrix, which can isolate the reaction between the electrolyte and the matrix of the positive electrode active material, improve the ionic conductivity of the coating layer, and reduce the absorption of H 2 O and CO 2 in the air by the positive electrode active material, improve the high-voltage durability of the positive electrode active material, and the combined action of the surface modifier and the hydrophobic protective agent will endow the battery containing it with excellent cycle stability.

[0008] In some embodiments, the surface modifier includes a hydrolyzable group. Optionally, the hydrolyzable group includes at least one of an ester group, an amide group, a carboxylate, or a sodium phenolate. Thus, the stability of the positive electrode active material can be improved, and the cycle performance of the battery containing it can be improved.

[0009] In some embodiments, the surface modifier includes at least one of heptadecafluorodecyltriethoxysilane, octadecylsilane, (trimethylsilyl)methyl trifluoromethanesulfonate, trimethylpentafluorophenylsilane, fluorooctylmethylsiloxane-dimethylsiloxane copolymer, N-methyl-N-(trimethylsilyl)trifluoroacetamide, or bis(3-trifluoropropyl)-1,1,3,3-tetramethyldisilazane.

[0010] In some embodiments, at least one of the following conditions is satisfied: the hydrophobic group includes at least one of a phenyl group, a halogen atom, a nitro group, an ester group, an ether group, or an alkyl group having 32 or fewer carbon atoms; the hydrophobic protecting agent further includes a first group, and the first group includes at least one of a phosphate group, a carbonate group, or a sulfonate group. Thereby, the stability of the cathode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0011] In some embodiments, the hydrophobic protecting agent includes at least one of distearyl phosphate, tributyl phosphate, trimethyl phosphate, triisopropyl phosphate, dibutyl phosphate, dimethyl phosphate, or diisopropyl phosphate. Thereby, the stability of the cathode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0012] In some embodiments, the matrix includes at least one of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide. Optionally, the matrix includes Li x Ni a Co b M c O 2-y , where M includes at least one of Mn or Al, 0.6 ≤ x ≤ 1.2, -0.1 ≤ y ≤ 0.1, 0.5 ≤ a < 1, 0.1 ≤ b ≤ 0.3, 0 < c ≤ 0.3, and a + b + c = 1. Thereby, the stability of the cathode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0013] In some embodiments, the volume average particle diameter D v 50 of the cathode active material is 10 μm - 20 μm, and can be optionally 10 μm - 15 μm. Thereby, the stability of the cathode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0014] In a second aspect of the present application, the present application provides a method for preparing a cathode active material, including: forming a coating layer on at least a part of the surface of a matrix, the coating layer including a surface modifier and a hydrophobic protecting agent, the surface modifier including at least one of a haloalkylsilane or an alkylsilane, and the hydrophobic protecting agent including a hydrophobic group.

[0015] Thus, the positive electrode active material prepared by the above method of the present application can improve the stability of the positive electrode active material and the cycle performance of the battery containing the same.

[0016] In some embodiments, it includes: preparing a surface modifier on at least part of the surface of the substrate by chemical vapor deposition to obtain an intermediate;

[0017] Soaking the intermediate in a solution containing a hydrophobic protecting agent to obtain the positive electrode active material.

[0018] Thus, the stability of the positive electrode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0019] In some embodiments, the temperature of the chemical vapor deposition is 130°C - 200°C. Thus, the stability of the positive electrode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0020] In some embodiments, at least one of the following conditions is satisfied: based on the total mass of the solution containing the hydrophobic protecting agent, the mass ratio of the hydrophobic protecting agent is 90% - 99%; the soaking time is 2 h - 6 h. Thus, the stability of the positive electrode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0021] In some embodiments, based on the total mass of the solution containing the hydrophobic protecting agent, the mass ratio of the hydrophobic protecting agent is 90% - 99%. Thus, the stability of the positive electrode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0022] In some embodiments, the soaking time is 2 h - 6 h. Thus, the stability of the positive electrode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0023] In some embodiments, the mass ratio of the substrate, the surface modifier, and the hydrophobic protecting agent is 1:(0.05 - 0.1):(0.02 - 0.05). Thus, the stability of the positive electrode active material can be improved, and the cycle performance of the battery containing the same can be improved.

[0024] In the third aspect of the present application, the present application provides a positive electrode sheet, including the positive electrode active material described in the first aspect of the present application or the positive electrode active material prepared by the method described in the second aspect. Thus, the positive electrode sheet has all the features and advantages of the foregoing positive electrode active material and the method for preparing the positive electrode active material, which will not be elaborated herein.

[0025] In the fourth aspect of the present application, the present application provides a battery, including the positive electrode sheet described in the third aspect of the present application. Thus, the battery has excellent cycle performance.

[0026] In a fifth aspect of the present application, there is provided an electrical device including the battery described in the fourth aspect. Thus, the electrical device includes all the features and advantages of the aforementioned battery, which will not be elaborated herein again. Description of the Drawings

[0027] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0028] Figure 1 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0029] Figure 2 is Figure 1 an exploded view of the battery cell according to an embodiment of the present application shown in ;

[0030] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0031] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0032] Figure 5 is Figure 4 an exploded view of the battery pack according to an embodiment of the present application shown in ;

[0033] Figure 6 is a schematic diagram of an electrical device using the battery as a power source according to an embodiment of the present application;

[0034] Figure 7 are scanning electron microscope images of the positive electrode active material prepared in Example 1 of the present application when it is prepared, after being placed in air for 7 days, and after being placed in air for 14 days;

[0035] Figure 8 are scanning electron microscope images of the positive electrode active material prepared in Comparative Example 1 of the present application when it is prepared, after being placed in air for 7 days, and after being placed in air for 14 days.

[0036] Description of the Reference Numerals:

[0037] 1 battery pack; 2 upper box body; 3 lower box body; 4 battery module; 5 battery cell;

[0038] 51 housing; 52 electrode assembly; 53 top cover assembly. Detailed Embodiments

[0039] Hereinafter, embodiments of the lithium supplementing material, its preparation method, the positive electrode sheet, the battery, and the electrical device of the present application will be specifically described 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 detailed descriptions of well-known matters 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 to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0040] 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 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, 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 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. Additionally, when stating 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.

[0041] 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.

[0042] 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.

[0043] If there is no special instruction, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, if a method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, if 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 can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0044] In the description of the present application, the meaning of "a plurality of" is two or more than two.

[0045] In the description of the present application, "A and / or B" may include the case of A alone, the case of B alone, and any one of the cases of A and B. Here, A and B are only for example, and they may be any technical features connected by "and / or" in the present application.

[0046] Secondary batteries are not only applied to energy storage power systems such as hydroelectric power plants, thermal power plants, wind power plants, and solar power plants, but also widely applied to electric transportation means such as electric bicycles, electric motorcycles, and electric vehicles, as well as multiple fields such as military equipment and aerospace.

[0047] As an important component of a secondary battery, the positive electrode active material plays a role in providing active metal ions (such as lithium ions, sodium ions, etc.). However, on the one hand, during the charge and discharge of the battery, especially at high voltages, the interfacial film between the positive electrode active material and the electrolyte is easily damaged, and the positive electrode active material will continuously react with the electrolyte, resulting in irreversible loss of the positive electrode active material and affecting the cycle performance of the battery; on the other hand, existing positive electrode active materials have the problem of unstable chemical environment, and it is easy to absorb H 2 O and CO 2 on the surface of the positive electrode active material particles in the air, and H 2 O and CO 2 react with the positive electrode active material, and this process will consume active metal ions and produce an inactive rock salt phase. The irreversible inactive rock salt phase blocks the diffusion channels of active metal ions, increases the energy barrier for the reaction of active metal ions, and thus deteriorates the cycle performance of the battery containing it.

[0048] In the embodiment of the present application, a coating layer is provided on at least part of the surface of the substrate. The coating layer includes a surface modifier and a hydrophobic protective agent. The surface modifier and the hydrophobic protective agent act together. On the one hand, the setting of the coating layer can isolate the contact between the electrolyte and the substrate of the positive electrode active material, thereby reducing the side reaction between the two, reducing the irreversible consumption of the positive electrode active material, and the surface modifier containing haloalkylsilane and / or alkylsilane is provided on the surface of the substrate. Haloalkylsilane and / or alkylsilane have excellent ion conduction performance and can also reduce the formation of an overly thick interfacial film, so that the coating layer has little influence on the transport of active metal ions, and thus the battery impedance of the positive electrode active material containing the present application is relatively low; on the other hand, the hydrophobic protective agent in the coating layer can play a good hydrophobic role, which can reduce the absorption of H 2 O and CO 2 by the substrate, reduce the absorption of the substrate by H 2 O and CO 2The probability of the reaction enhances the stability of the cathode active material. In summary, the cathode active material proposed in this application has good stability and improves the cycling performance of the battery containing it.

[0049] The cathode active material disclosed in the embodiments of this application is applicable to secondary batteries, and the batteries disclosed in the embodiments of this application can be used in electrical devices using the battery as a power source or various energy storage systems using the battery as an energy storage element. The electrical devices may include, but are not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, and the like. 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.

[0050] In the first aspect of this application, a cathode active material is proposed. The cathode active material includes a matrix and a coating layer. The coating layer is formed on at least a part of the surface of the matrix, and the coating layer includes a surface modifier and a hydrophobic protective agent. The surface modifier includes at least one of haloalkylsilane or alkylsilane, and the hydrophobic protective agent includes a hydrophobic group.

[0051] This application has at least the following beneficial effects: For the cathode active material proposed in this application, the setting of the coating layer can isolate the contact between the electrolyte and the matrix of the cathode active material, thereby reducing the side reaction between the two, reducing the side reaction of the cathode active material. The surface modifier is provided on the surface of the matrix, has excellent ion conduction performance, and can also reduce the formation of an overly thick interfacial film, with little impact on the transport of active metal ions. Therefore, the battery containing it has a lower impedance. On the other hand, the hydrophobic protective agent can play a good hydrophobic role, which can reduce the absorption of H 2 O and CO 2 by the matrix, reduce the probability of the reaction between the matrix and H 2 O and CO 2 and enhance the stability of the cathode active material. In summary, the cathode active material proposed in this application has good stability and improves the cycling performance of the battery containing it.

[0052] It can be understood that alkylsilane is an organosilicon compound whose molecular structure contains an alkyl group and a silyl group. Haloalkylsilane refers to an alkylsilane containing a halogen atom, such as an alkylsilane containing an F atom, a Cl atom, a Br atom, or an I atom. The hydrophobic group refers to a lipophilic group, which has no affinity for water, is insoluble in water or has extremely low solubility, and can reduce the absorption of H 2 O and CO 2 by the matrix.

[0053] In some embodiments, the surface modifier includes a hydrolyzable group. Herein, the hydrolyzable group refers to a group that can react with water and undergo hydrolysis. The above-mentioned hydrolyzable group is beneficial for consuming moisture, blocking the erosion of water vapor on the cathode active material, improving the stability of the cathode active material, and further enhancing the cycle performance of the battery containing the same. In other embodiments, the hydrolyzable group includes at least one of an ester group, an amide group, a carboxylate salt, or a sodium phenoxide.

[0054] In some embodiments, the surface modifier includes at least one of heptadecafluorodecyltriethoxysilane, octadecylsilane, (trimethylsilyl)methyl trifluoromethanesulfonate, trimethylpentafluorophenylsilane, fluorooctylmethylsiloxane-dimethylsiloxane copolymer, N-methyl-N-(trimethylsilyl)trifluoroacetamide, or bis(3-trifluoropropyl)-1,1,3,3-tetramethyldisilazane. Specifically, the above substances have the characteristics of high electronegativity, good dielectric properties, and good solubility, which contribute to the transport of active metal ions at the electrode / solid electrolyte interface (SEI film). When used in the positive electrode of a battery, it also reduces its activation energy; in addition, the above surface modifier can isolate the contact between the electrolyte and the matrix of the cathode active material, thereby reducing the side reaction between the two, reducing the irreversible consumption of the cathode active material. The surface modifier is provided on the surface of the matrix, has excellent ion-conducting properties, and can also reduce the formation of an overly thick interfacial film, with little impact on the transport of active metal ions. Therefore, the battery containing the same has a lower impedance and improved cycle performance.

[0055] It can be understood that (trimethylsilyl)methyl trifluoromethanesulfonate, also known as trimethylsilyl trifluoromethanesulfonate, is an important organic compound; fluorooctylmethylsiloxane-dimethylsiloxane copolymer is an organosilicon compound copolymerized from fluorooctylmethylsiloxane and dimethylsiloxane, and has excellent properties such as high temperature resistance, oxidation resistance, and chemical corrosion resistance; the molecular formula of N-methyl-N-(trimethylsilyl)trifluoroacetamide is H 2 C(OMe)N(SiMe 3 )CF 3 , where Me represents methyl; bis(3-trifluoropropyl)-1,1,3,3-tetramethyldisilazane is a chemical substance with the molecular formula C 10 H 12 F 6 NSi 2 N.

[0056] In some embodiments, the hydrophobic group includes at least one of a phenyl group, a halogen atom, a nitro group, an ester group, an ether group, or an alkyl group with a carbon atom number less than or equal to 32. The hydrophobic protective agent containing the above hydrophobic group on the surface of the matrix can reduce the water absorption of the matrix, making the matrix have good stability and improving the cycle performance of the battery containing the same.

[0057] In some embodiments, the hydrophobic protective agent further includes a first group, and the first group includes at least one of a phosphate group, a carbonate group, or a sulfonate group. Specifically, on the surface of the matrix, the hydrophobic group tends to be away from the matrix. On the outer surface of the coating layer, it can reduce the absorption of H 2 O and CO 2 by the surface of the matrix particles; taking the cathode active material of a lithium-ion battery as an example, the first group tends to be close to the matrix and combines with the Li element of the matrix to form an O=DOLi-group (D can be a P element, a C element, or an S element). Inside the coating layer, the O=DOLi-group can improve the transport coefficient of active metal ions during charge and discharge. In addition, the hydrophobic protective agent containing a hydrophobic group and a first group acts together with the surface modifier to endow the battery with excellent rate performance and cycle stability.

[0058] For example, the phosphate group can react with the matrix of the cathode active material of a lithium-ion battery to form an O=POLi - group, which improves the binding force between the hydrophobic protective agent and the matrix, reduces the risk of its detachment from the matrix surface, and can improve the ionic conductivity of the coating layer and enhance the cycle performance of the battery containing it.

[0059] In some embodiments, the hydrophobic protective agent includes at least one of distearyl phosphate, tributyl phosphate, trimethyl phosphate, triisopropyl phosphate, dibutyl phosphate, dimethyl phosphate, or isopropyl phosphate. Specifically, the above hydrophobic protective agents contain both a hydrophobic group and a first group, which can reduce the absorption of H 2 O and CO 2 by the surface of the matrix particles, and at the same time improve the transport coefficient of active metal ions during charge and discharge. In addition, the hydrophobic protective agent containing a hydrophobic group and a first group acts together with the surface modifier to endow the battery with excellent rate performance and cycle stability.

[0060] In some embodiments, the volume average particle size D v 50 of the cathode active material is 10 μm - 20 μm. For example, the volume average particle size D v 50 of the cathode active material can be 10 μm - 19 μm, 11 μm - 18 μm, 12 μm - 17 μm, 13 μm - 16 μm, 14 μm - 15 μm, etc. Specifically, when the volume average particle size D v 50 of the cathode active material is limited within the above range, it is beneficial to the rapid deintercalation and intercalation of active metal ions, and reduces the contact between the matrix and H 2 O and CO 2The probability of the reaction can also reduce the probability of side reactions between the positive electrode active material and the electrolyte, improve the stability of the positive electrode active material, and improve the cycle performance of the battery containing the same. In some other embodiments, the volume average particle size D v 50 of the positive electrode active material is 10 μm - 15 μm.

[0061] The aforementioned volume average particle size D v 50 means the particle size corresponding to when the cumulative volume distribution percentage of the particles reaches 50%.

[0062] The "volume average particle size D v 50" of the present application has a well-known meaning in the art and can be measured by well-known instruments and methods in the art. As an example, the volume average particle size D v 50 of the positive electrode active material can be measured by laser diffraction particle size analysis method. Specifically, the volume average particle size D v 50 of the positive electrode active material can be measured with reference to Standard GB / T 19077-2016 using a laser particle size analyzer (such as Malvern Master Size 3000).

[0063] In some embodiments, the matrix includes at least one of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide. Specifically, lithium nickel cobalt manganese oxide has a high capacity and can improve the energy density of the battery, and lithium nickel cobalt manganese oxide is easy to absorb H 2 O and CO 2 , resulting in the reduction of nickel. Using the above substances in combination with the coating layer to make the positive electrode active material not only improves the energy density of the battery, but also stabilizes the Mn-Mn bonds and O-O bonds on the surface of the matrix, improves the stability of the positive electrode active material, and improves the cycle performance of the battery containing the same.

[0064] In some embodiments, the matrix includes Li x Ni a Co b M c O 2-y, where M includes at least one of Mn or Al, 0.6 ≤ x ≤ 1.2, -0.1 ≤ y ≤ 0.1, 0.5 ≤ a < 1, 0.1 ≤ b ≤ 0.3, 0 < c ≤ 0.3, and a + b + c = 1. For example, 0.6 ≤ x ≤ 1.1, 0.7 ≤ x ≤ 1, 0.8 ≤ x ≤ 0.9, etc.; -0.1 ≤ y ≤ 0.09, -0.1 ≤ y ≤ 0, 0 ≤ y ≤ 0.1, etc.; 0.5 ≤ a ≤ 0.9, 0.6 ≤ a ≤ 0.8, 0.7 ≤ a ≤ 0.8, etc.; 0.1 ≤ b ≤ 0.2, 0.2 ≤ b ≤ 0.3, etc.; 0.05 ≤ c ≤ 0.3, 0.1 ≤ c ≤ 0.3, 0.2 ≤ c ≤ 0.3, etc. The nickel content of the above matrix is high, and the reversible capacity is high, which improves the energy density of the battery containing it.

[0065] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur. The molar content of Li is different when the battery is discharged to different states. Therefore, the above Li x Ni a Co b M c O 2-y , the situation where x is less than 1 will occur; in addition, when a lithium supplement agent is added to the matrix, the situation where x is greater than 1 will occur.

[0066] In the enumeration of the matrix in this application, the lattice oxygen release will cause the change of the molar content of oxygen. Therefore, the situation where y is greater than 0 will occur. In addition, the metal dissolution in the matrix will also cause the situation where y is less than 0.

[0067] In some other embodiments, the matrix includes LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.5 Co 0.25 Mn 0.25 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 or LiNi 0.8 Co 0.15 Al 0.05 O 2 at least one of them.

[0068] In some embodiments, when the battery is a lithium-ion battery, the matrix can also adopt the matrix for lithium-ion batteries well-known in the art.

[0069] As an example, the matrix may further include at least one of the following materials: lithium phosphate with olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include but are 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 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, other lithium nickel cobalt manganese oxides (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which can also be abbreviated as NCM 333 ) and at least one of their modified compounds. Examples of lithium phosphate with olivine structure may include but are not limited to lithium iron phosphate (such as LiFePO 4 (which can also be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), composite materials of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and composite materials of lithium manganese iron phosphate and carbon. The modified compounds of the above materials can be doping modification and / or surface coating modification of the materials.

[0070] During the charge and discharge process of the battery, the deintercalation and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the matrix in the present application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, after charge and discharge cycles, the molar content of Li will change.

[0071] In the listing of the matrix in the present application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0072] In some embodiments, when the battery is a sodium ion battery, the matrix can also adopt a matrix for sodium ion batteries well-known in the art.

[0073] As an example, the matrix may include but is not limited to at least one of layered transition metal oxides, polyanion compounds, and Prussian blue analogs.

[0074] As an example of the above layered transition metal oxides, for example, the following can be listed:

[0075] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , wherein M 1 is one or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 < x ≤ 0.33, 0 < h ≤ 0.24, 0 ≤ k ≤ 0.32, 0 < l ≤ 0.68, 0 ≤ m < 0.1, h + k + l + m = 1, 0 ≤ y < 0.2;

[0076] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O 2 , wherein M 2 is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn, and Ba, 0 < z ≤ 0.1;

[0077] Na a Li b Ni c Mn d Fe e O 2 , wherein 0.67 < a ≤ 1, 0 < b < 0.2, 0 < c < 0.3, 0.67 < d + e < 0.8, b + c + d + e = 1.

[0078] As an example of the above polyanion compound, for example, the following can be listed:

[0079] A 1 f M 3 g (PO 4 ) i O j X 1 3-j , wherein A 1 is one or more of H, Li, Na, K, and NH 4 , M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, X 1 is one or more of F, Cl, and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0080] Na n M 4 PO4 X 2 , where M 4 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, and X 2 is one or more of F, Cl, and Br; 0 < n ≤ 2;

[0081] Na p M 5 q (SO 4 ) 3 , where M 5 is one or more of Mn, Fe, Co, Ni, Cu, and Zn; 0 < p ≤ 2, 0 < q ≤ 2;

[0082] Na s Mn t Fe 3-t (PO 4 ) 2 (P 2 O 7 ), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0083] As an example of the above-mentioned Prussian blue analogues, for example, the following can be listed:

[0084] A u M 6 v [M 7 (CN) 6 w ·xH 2 O, where A is one or more of H + , NH 4 + , alkali metal cations, and alkaline earth metal cations, M 6 and M 7 are each independently one or more of transition metal cations; 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is one or more of H + , Li + , Na + , K + , NH 4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , and Ra 2+ ; M 6 ​and M 7 Each independently is a cation of one or more transition metal elements selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W.

[0085] The modified compounds of the above materials may be doping modification and / or surface coating modification of the materials.

[0086] In the second aspect of the present application, a method for preparing a cathode active material is proposed. Thus, the aforementioned cathode active material can be prepared by a relatively simple method. Specifically, the method for preparing a cathode active material includes:

[0087] S100: Form a coating layer on at least a part of the surface of the substrate. The coating layer includes a surface modifier and a hydrophobic protective agent. The surface modifier includes at least one of a haloalkylsilane or an alkylsilane, and the hydrophobic protective agent includes a hydrophobic group.

[0088] Specifically, for the cathode active material prepared by the method proposed in the embodiments of the present application, a coating layer is provided on at least a part of the surface of the substrate. The coating layer includes a surface modifier and a hydrophobic protective agent. The coating layer formed by the surface modifier and the hydrophobic protective agent can, on the one hand, isolate the contact between the electrolyte and the substrate of the cathode active material, thereby reducing the side reaction between the two and reducing the side reaction of the cathode active material. The surface modifier is provided on the surface of the substrate, has excellent ion conductivity, and can also reduce the formation of an overly thick interfacial film, with less impact on the transport of active metal ions, and thus the battery impedance containing it is lower; on the other hand, the hydrophobic protective agent can play a good hydrophobic role, which can reduce the absorption of H 2 O and CO 2 by the substrate, reducing the probability of reaction between the substrate and H 2 O and CO 2 and enhancing the stability of the cathode active material. In summary, the cathode active material proposed in the present application has good stability and improves the cycling performance of the battery containing it.

[0089] In some embodiments, the method for preparing a cathode active material includes:

[0090] S101: Prepare a surface modifier on at least a part of the surface of the substrate by chemical vapor deposition to obtain an intermediate;

[0091] S102: Immerse the intermediate in a solution containing a hydrophobic protective agent to obtain the cathode active material.

[0092] Thus, the prepared cathode active material can isolate the contact between the electrolyte and the cathode active material, reduce the irreversible loss caused by the side reaction of the cathode active material, and can also reduce the absorption of H 2 O and CO2 The absorption can also play a role in hydrophobic protection and improve the ionic conductivity of the positive electrode active material. The combined action of the two substances can further improve the stability of the positive electrode active material and enhance the cycling performance of the battery containing it.

[0093] Specifically, in the coating layer formed by chemical vapor deposition, the surface modifier molecules form a monolayer molecular arrangement to form a self-assembled monolayer. The deposited surface modifier has good uniformity, can isolate the electrolyte from contacting the positive electrode active material, reduce the irreversible loss caused by side reactions of the positive electrode active material, and can also reduce the absorption of H 2 O and CO 2 by the substrate, reduce the probability of reaction between the substrate and H 2 O and CO 2 The probability of reaction, and can also reduce the probability of side reactions between the positive electrode active material and the electrolyte, improve the stability of the positive electrode active material, and improve the cycling performance of the battery containing it.

[0094] Specifically, the surface modifier is evaporated into a gas at a certain temperature and introduced into the reaction chamber. The substrate is placed in the reaction chamber so that the surface modifier is deposited on the outer surface of the substrate.

[0095] In some embodiments, the temperature of the chemical vapor deposition is 130°C - 200°C. For example, the temperature of the chemical vapor deposition can be 130°C - 199°C, 135°C - 195°C, 140°C - 190°C, 145°C - 185°C, 150°C - 180°C, 155°C - 175°C, 160°C - 170°C, etc. Within the above deposition temperature range, the surface modifier molecules form a monolayer molecular arrangement to form a self-assembled monolayer. The deposited surface modifier has good uniformity, can isolate the electrolyte from contacting the positive electrode active material, reduce the irreversible loss caused by side reactions of the positive electrode active material, and can also reduce the absorption of H 2 O and CO 2 by the substrate, reduce the probability of reaction between the substrate and H 2 O and CO 2 The probability of reaction, and can also reduce the probability of side reactions between the positive electrode active material and the electrolyte, improve the stability of the positive electrode active material, and improve the cycling performance of the battery containing it.

[0096] In some embodiments, the intermediate is immersed in a solution containing a hydrophobic protectant to obtain the positive electrode active material. Thus, the hydrophobic protectant can be evenly distributed on the surface of the substrate, improving the deintercalation rate of the active metal ions of the substrate, and can isolate the electrolyte from contacting the positive electrode active material, reduce the irreversible loss caused by side reactions of the positive electrode active material, and can also reduce the absorption of H 2 O and CO 2 by the substrate, reduce the probability of reaction between the substrate and H2 O and CO 2 The probability of reaction can also reduce the probability of side reactions between the positive electrode active material and the electrolyte, improve the stability of the positive electrode active material, and improve the cycle performance of the battery containing the same.

[0097] In some embodiments, based on the total mass of the solution containing the hydrophobic protective agent, the mass percentage of the hydrophobic protective agent is 90%-99%. For example, based on the total mass of the solution containing the hydrophobic protective agent, the mass percentage of the hydrophobic protective agent can be 90%-98.9%, 91%-98%, 92%-97%, 93%-96%, 94%-95%, etc. Controlling the mass percentage of the hydrophobic protective agent within the above range is beneficial for the hydrophobic protective agent molecules to form a monolayer molecular arrangement, form a self-assembled monolayer, improve the deintercalation rate of the active metal ions of the substrate, and is sufficient to isolate the contact between the electrolyte and the positive electrode active material, reduce the irreversible loss caused by side reactions of the positive electrode active material, and reduce the absorption of H 2 O and CO 2 by the substrate, and reduce the probability of reaction between the substrate and H 2 O and CO 2 The probability of reaction can also reduce the probability of side reactions between the positive electrode active material and the electrolyte, improve the stability of the positive electrode active material, and improve the cycle performance of the battery containing the same.

[0098] In some embodiments, the soaking time is 2h-6h. For example, the soaking time can be 2h-5.9h, 3h-5h, 3h-4h, 4h-5h, etc. Controlling the soaking time within the above range can make the thickness of the coating layer thinner, which is beneficial for the hydrophobic protective agent molecules to form a monolayer molecular arrangement, form a self-assembled monolayer, improve the deintercalation rate of the active metal ions of the substrate, and is sufficient to isolate the contact between the electrolyte and the positive electrode active material, reduce the irreversible loss caused by side reactions of the positive electrode active material, and reduce the absorption of H 2 O and CO 2 by the substrate, and reduce the probability of reaction between the substrate and H 2 O and CO 2 The probability of reaction can also reduce the probability of side reactions between the positive electrode active material and the electrolyte, improve the stability of the positive electrode active material, and improve the cycle performance of the battery containing the same.

[0099] In some embodiments, the mass ratio of the substrate, the surface modifier, and the hydrophobic protective agent is 1:(0.05 - 0.1):(0.02 - 0.05). For example, the mass ratio of the three can be 1:(0.05 - 0.09):(0.02 - 0.05), 1:(0.06 - 0.08):(0.02 - 0.05), 1:(0.05 - 0.1):(0.02 - 0.04), 1:(0.05 - 0.1):(0.03 - 0.04), etc. Thus, a relatively thin self-assembled monolayer can be formed on the surface of the substrate, which can improve the stability of the cathode active material and the cycling performance of the battery containing the same.

[0100] In the third aspect of the present application, a cathode electrode sheet is provided, which includes the cathode active material described in the first aspect of the present application, or the cathode active material prepared by the method described in the second aspect.

[0101] In some embodiments, the cathode electrode sheet includes a cathode current collector and a cathode active material layer located on at least one surface of the cathode current collector. The cathode active material layer includes the cathode active material, and the cathode active material includes the cathode active material described in the first aspect of the present application, or the cathode active material prepared by the method described in the second aspect. Thus, the cathode electrode sheet has all the features and advantages of the aforementioned cathode active material and the method for preparing the cathode active material, which will not be elaborated herein.

[0102] As an example, the cathode current collector has two surfaces opposite to each other in its own thickness direction, and the cathode active material layer is disposed on either one or both of the two opposite surfaces of the cathode current collector.

[0103] In some embodiments, the cathode 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 substrate layer and a metal layer formed on at least one surface of the polymer material substrate 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.).

[0104] In some embodiments, the cathode active material layer may optionally further include a binder.

[0105] As an example, 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.

[0106] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent.

[0107] 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, and carbon nanofibers.

[0108] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the above-mentioned components for preparing the positive electrode plate, such as the positive electrode active material, 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.

[0109] In the fourth aspect of the present application, the present application proposes a battery including the positive electrode plate described in the third aspect. Thus, the battery includes all the features and advantages of the aforementioned positive electrode plate, which will not be elaborated herein.

[0110] Generally, a battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly serving to prevent short circuit between the positive electrode and the negative electrode, and at the same time allowing active metal ions to pass through.

[0111] [Negative electrode plate]

[0112] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0113] 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 any one or both of the two opposite surfaces of the negative electrode current collector.

[0114] In some embodiments, the negative electrode current collector can 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.).

[0115] In some embodiments, the negative electrode active material may be the negative electrode active material for batteries known in the art. By way of 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 include at least one of elemental silicon, silicon oxides, silicon nitride composites, and silicon alloys. The tin-based materials include 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 the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0116] In some embodiments, the negative electrode active material layer may also optionally include a binder. The binder includes 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).

[0117] In some embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0119] In some embodiments, the negative electrode plate can be prepared in the following manner: dispersing the 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.

[0120] [Electrolyte]

[0121] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The present application has no specific limitation on the type of the electrolyte, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid.

[0122] In some embodiments, the electrolyte uses an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0123] By way of example, when the battery is a lithium-ion battery, the electrolyte lithium salt may include lithium hexafluorophosphate (LiPF 6 )、lithium tetrafluoroborate (LiBF 4 )、lithium perchlorate (LiClO4 ) Lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP), or at least one of them.

[0124] As an example, when the battery is a sodium-ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluoro(oxalato)borate, sodium tetrafluoroborate, sodium bis(oxalato)borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0125] As an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0126] In some embodiments of the present application, the electrolyte further includes an additive. For example, the additive may include a negative electrode film-forming additive, or may include a positive electrode film-forming additive, or may also include an additive that can improve certain battery performance, such as an additive for improving the overcharge performance of the battery, an additive for improving the high-temperature performance of the battery, and an additive for improving the low-temperature performance of the battery.

[0127] [Separator film]

[0128] In some embodiments, the battery further includes a separator film. The present application does not particularly limit the type of the separator film, and any porous structure separator film with good chemical stability and mechanical stability can be selected.

[0129] In some embodiments, the material of the separator film includes at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0130] The battery of the present application includes the form of battery cells, battery modules, and battery packs. The battery, battery module, and battery pack of the present application will be described below with reference to the accompanying drawings as appropriate.

[0131] In some embodiments, the positive electrode plate, negative electrode plate, and separator can be made into an electrode assembly by a winding process or a stacking process.

[0132] In some embodiments, the battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0133] In some embodiments, the outer package of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the 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.

[0134] The present application places no particular restrictions on the shape of the battery, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 is a battery cell 5 with a square structure as an example.

[0135] In some embodiments, referring to Figure 2 , the outer package may include a housing 51 and a top cover assembly 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, negative electrode plate, and separator can form an electrode assembly 52 through 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 battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0136] In some embodiments, the battery can be assembled into a battery module. The number of batteries included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0137] Figure 3 is a battery module 4 as an example. Referring to Figure 3 , in the battery module 4, a plurality of battery cells 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 arbitrary manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0138] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of battery cells 5 are accommodated in the receiving space.

[0139] In some embodiments, the above battery modules can also be 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.

[0140] Figure 4 and Figure 5 is Battery Pack 1 as an example. Refer to Figure 4 and Figure 5 , in Battery Pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box can be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0141] In the fifth aspect of the present application, an electrical device is proposed, including the battery described in the fourth aspect of the present application. Thus, the electrical device includes all the features and advantages of the foregoing battery, which will not be elaborated herein.

[0142] The battery, battery module, and 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 are not limited thereto.

[0143] As the electrical device, the battery, battery module, or battery pack can be selected according to its usage requirements.

[0144] Figure 6 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 battery, a battery pack or battery module can be used.

[0145] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinness and lightness, and a battery can be used as the power source.

[0146] The solution of the present application will be described below through specific embodiments. It should be noted that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those embodiments where specific technologies or conditions are not indicated, the technologies or conditions described in the literature in the art or according to the product instructions are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0147] Example 1

[0148] Preparation of the positive electrode active material:

[0149] The original LiNi was synthesized by high-temperature solid-state reaction 0.8 Co 0.1 Mn 0.1 O 2 (NCM). Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The precursor was mixed with LiOH·H 2 O and thoroughly washed at a molar ratio of 1:1.05. Then, a sufficient amount of oxygen was introduced, and the mixture was heated to 600 °C / 5 h and then at 850 °C / 10 h. The heating rate and O 2 flow rate were 5 °C min -1 and 0.5 L min -1 respectively, and the obtained sample was labeled as the original NCM (matrix).

[0150] Preparation of the intermediate containing the surface modifier: Surface modifier: Heptadecafluorodecyltriethoxysilane (F 3 C(CF 2 ) 7 (CH 2 ) 3 Si(OCH 3 ) 3 ) and octadecylsilane (ODS: H 3 C(CH 2 ) 17 Si(OCH 3 ) 3 ) were subjected to chemical vapor deposition at a temperature of 150 °C and atmospheric pressure in a mass ratio of 1:1 to form an intermediate on the surface of NCM, and the mass ratio of NCM to the surface modifier was 1:0.08.

[0151] Preparation of the positive electrode active material: A uniform layer of dihexadecyl phosphate [CH 3 (CH 2 ) 15 O] 2 POOH (DHP)] was coated onto the surface of the intermediate. First, dihexadecyl phosphate was dissolved in tetrahydrofuran (THF, C 4 H 8(O) In a solvent, and stir well for 1 hour to obtain a THF solution of DHP (the mass ratio of DHP is 95% based on the total mass of the THF solution of DHP). Secondly, immerse the intermediate in a dipalmitoyl phosphate / THF solution and stir for 4 hours, and the mass ratio of NCM to dipalmitoyl phosphate is 1:0.04. Then, filter the obtained mixture by suction, and use an appropriate amount of tetrahydrofuran solution to remove excessive dipalmitoyl phosphate molecules several times. Finally, vacuum-dry the washed powder at 80 °C for 12 hours to remove the excess THF.

[0152] Preparation of the positive electrode sheet:

[0153] Mix the previously prepared positive electrode active material, conductive agent acetylene black, and binder in a mass ratio of 98:1:1, add the solvent N-methylpyrrolidone and stir until the system becomes homogeneous to obtain a positive electrode paste; uniformly coat the positive electrode paste on both sides of the positive electrode current collector aluminum foil, dry it at room temperature and then transfer it to an oven for further drying, and then cut it into a rectangle of 40 mm × 50 mm as the positive electrode sheet, and the positive electrode areal capacity is 3.5 mAh / cm 2 .

[0154] Preparation of the negative electrode sheet:

[0155] Mix the negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) in a weight ratio of 96.5:0.7:1.8:1, and stir well in a deionized water solvent system until evenly mixed to obtain a negative electrode paste. Coat the negative electrode paste on the negative electrode current collector copper foil, dry it and cold-press it to obtain the negative electrode sheet.

[0156] Preparation of the electrolyte:

[0157] At 25 °C, mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain a mixed solvent, and then dissolve LiPF 6 in the above mixed solvent to obtain an electrolyte, where the concentration of LiPF 6 is 1 mol / L.

[0158] Preparation of the battery:

[0159] Use a polypropylene film as the separator. Stack the positive electrode sheet, separator, and negative electrode sheet in sequence, make the separator be in the middle of the positive electrode sheet and the negative electrode sheet to play a role of isolation, and wind it to obtain a bare battery cell. Place the bare battery cell in an outer package, inject the electrolyte and seal it to obtain the battery.

[0160] The differences between Examples 2-18 and Example 1 are shown in Table 1.

[0161] Comparative Example 1 was the same as Example 1 in the preparation method except that the surface modifier was not prepared on the surface of the substrate.

[0162] Comparative Example 2 was the same as Example 1 in the preparation method except that the hydrophobic protective agent was not prepared on the intermediate containing the surface modifier.

[0163] Comparative Example 3 was the same as Example 1 in the preparation method except that the surface modifier and the hydrophobic protective agent were not added. See Table 1.

[0164] Table 1

[0165]

[0166]

[0167] The positive electrode active materials and batteries in Examples 1-18 and Comparative Examples 1-3 were tested as follows:

[0168] 1. Scanning electron microscope images of the positive electrode active material

[0169] Scanning electron microscope images were taken of the positive electrode active materials obtained in Example 1 and Comparative Example 3 respectively. After that, they were exposed to air for 7 days and 14 days respectively, and then scanning electron microscope images were taken again, obtaining Figure 7 and Figure 8 .

[0170] Figure 7 In, Figure a2 is the scanning electron microscope image of the positive electrode active material prepared in Example 1, and the right side of Figure a2 is the enlarged image within its square frame; Figure b2 is the scanning electron microscope image of the positive electrode active material of Example 1 after being placed in air for 7 days, and the right side of Figure b2 is the enlarged image within its square frame; Figure c2 is the scanning electron microscope image of the positive electrode active material of Example 1 after being placed in air for 14 days, and the right side of Figure c2 is the enlarged image within its square frame; From Figure 7 it can be seen that for the positive electrode active material of Example 1 of the present application, when it was prepared, after being placed in air for 7 days and 14 days, the morphological changes were not significant, and the small particles on the surface did not show obvious fragmentation.

[0171] Figure 8 In, Figure a1 is the scanning electron microscope image of the positive electrode active material prepared in Comparative Example 1, and the right side of Figure a1 is the enlarged image within its square frame; Figure b1 is the scanning electron microscope image of the positive electrode active material of Comparative Example 1 after being placed in air for 7 days, and the right side of Figure b1 is the enlarged image within its square frame; Figure c1 is the scanning electron microscope image of the positive electrode active material of Comparative Example 1 after being placed in air for 14 days, and the right side of Figure c1 is the enlarged image within its square frame; From Figure 8 it can be seen that compared with Figure 7The positive electrode active material of Example 1 in the present application and the positive electrode active material of Comparative Example 1 of the present application, when prepared, have smooth small particles on the surface and good morphology. After being placed in air for 7 days, the small particles on the surface are significantly broken, and after 14 days, the fragmentation of the small particles on the surface is even more obvious, which can be attributed to H 2 O and CO 2 reacting with the small particles on the surface of the positive electrode active material, causing microcracks and a corroded surface. It can be seen that the positive electrode active material prepared in Example 1 of the present application has good stability.

[0172] 2. Cycle performance test of the battery:

[0173] The battery is charged at a rate of 0.5C to a voltage of 4.4V at room temperature of 25°C, and then discharged at a rate of 0.5C to a voltage equal to 2.5V, and the reversible capacity is measured as E 0 . According to the above charge-discharge process, it is cycled 1000 times, and the reversible capacity is obtained and denoted as E n , where n = 1000. The capacity retention rate ε of the battery after 1000 cycles at 25°C is ε=(E n -E 0 ) / E 0 ×100%.

[0174] 3. Measurement of the impedance of the battery:

[0175] Preparation of a button cell:

[0176] a. Preparation of the negative electrode sheet:

[0177] 96.5 wt.% artificial graphite, 2.5 wt.% styrene-butadiene rubber latex (SBR) binder, and 1 wt.% SP conductive carbon black are dispersed evenly in a solvent of deionized water to form a negative electrode slurry. The negative electrode slurry is coated on one side surface of a copper foil (with a thickness of 6 μm) (coating surface density is 0.15 g / 1540.25 mm 2 ), and then dried and cold-pressed to form a negative electrode active material layer (with a thickness of 0.15 mm) on one side surface of the negative electrode current collector, and finally punched to obtain a negative electrode sheet;

[0178] b. Preparation of the positive electrode sheet:

[0179] The positive electrode active materials, conductive carbon (SP), and binder (polyvinylidene fluoride PVDF) prepared in the foregoing examples and comparative examples are dissolved in a solvent of N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2, and after being fully stirred and mixed evenly, a positive electrode slurry is prepared. The positive electrode slurry is coated on one side surface of an aluminum foil (coating surface density is 0.4 g / 1540.25 mm 2), and then through drying and cold pressing, a positive electrode active material layer (with a thickness of 0.2 mm) is formed on one surface of the aluminum foil (15 μm). Finally, through punching, a positive electrode plate is obtained;

[0180] c. Preparation of the separator:

[0181] Using a polyethylene porous polymer film as the separator (with a thickness of 7 μm);

[0182] d. Preparation of the electrolyte

[0183] Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a mass ratio of 1:1:1 to obtain a solvent. Dissolve the fully dried electrolyte salt LiPF 6 in the above solvent, and after mixing evenly, an electrolyte with a concentration of 1 mol / L is obtained.

[0184] Assembly: Stack a single positive electrode plate, a single separator, and a single negative electrode plate in sequence (the side of the positive electrode plate where the positive electrode active material layer is formed contacts the separator, and the side of the negative electrode plate where the negative electrode active material layer is formed contacts the separator), so that the separator is in the middle of the positive and negative electrodes to play a role in isolation, and add the electrolyte. Through pressure encapsulation (50 MPa), a CR2032 button-type full cell (with a capacity ≤ 5 mAh) is obtained.

[0185] Using a VSP-300 electrochemical workstation (Bio-logic), connect the button cell to the electrochemical workstation, and use electrochemical impedance spectroscopy (EIS) to measure in the frequency range between 2 MHz and 1 mHz, scan the constant potential range of ±10 V, and test the impedance of the button cell. The measurement results are shown in Table 2.

[0186] Table 2

[0187] Impedance / Ω Capacity Retention Rate / % Example 1 0.5 63.2％ Example 2 0.4 66.1％ Example 3 0.3 68.3％ Example 4 0.5 63.1％ Example 5 0.4 66.3％ Example 6 0.3 68.1％ Example 7 0.3 68.2％ Example 8 0.5 63.3％ Example 9 0.4 66.4％ Example 10 0.45 65.0％ Example 11 0.46 64.8％ Example 12 0.58 62.1％ Example 13 0.5 63.5％ Example 14 0.53 62.7％ Example 15 0.53 62.8％ Example 16 0.4 66.5％ Example 17 0.56 62.4％ Example 18 0.6 60.6％ Comparative Example 1 0.8 46.5％ Comparative Example 2 0.9 45.1％ Comparative Example 3 1 40.5％

[0188] Conclusion: As can be seen from Table 2, in Examples 1-18 of the present application, when at least part of the surface of the positive electrode active material is provided with a surface modifier and a hydrophobic protective agent, the battery containing it has excellent cycle stability and low impedance. Compared with Examples 1-18, in Comparative Examples 1-3, the surface modifier and the hydrophobic protective agent are not added simultaneously, and the cycle performance of the battery is significantly reduced and the impedance increases. It can be seen that in the present application, the surface modifier and the hydrophobic protective agent act together to isolate the contact between the electrolyte and the positive electrode active material, reduce the irreversible loss caused by the side reaction of the positive electrode active material, and can also reduce the absorption of H 2 O and CO 2 by the matrix, improve the high-voltage durability of the matrix, and make the battery containing it have excellent cycle stability and low impedance.

[0189] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same structure and achieving the same effects as the technical idea within the scope of the technical solution of this application are all 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 of the 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 matrix and a coating layer, the coating layer is formed on at least a part of the surface of the matrix, the coating layer comprises a surface modifier and a hydrophobic protective agent, the surface modifier comprises at least one of a haloalkylsilane or an alkylsilane, and the hydrophobic protective agent comprises a hydrophobic group.

2. The positive electrode active material according to claim 1, characterized in that, the surface modifier comprises a hydrolyzable group, optionally, the hydrolyzable group comprises at least one of an ester group, an amide group, a carboxylate or a sodium phenolate.

3. The positive electrode active material according to claim 1 or 2, characterized in that, the surface modifier comprises at least one of heptadecafluorodecyltriethoxysilane, octadecylsilane, (trimethylsilyl)methyl trifluoromethanesulfonate, trimethylpentafluorophenylsilane, fluorooctylmethylsiloxane-dimethylsiloxane copolymer, N-methyl-N-(trimethylsilyl)trifluoroacetamide or bis(3-trifluoropropyl)-1,1,3,3-tetramethyldisilazane.

4. The positive electrode active material according to any one of claims 1-3, characterized in that, at least one of the following conditions is satisfied: the hydrophobic group comprises at least one of a phenyl group, a halogen atom, a nitro group, an ester group, an ether group or an alkyl group having 32 or less carbon atoms; the hydrophobic protective agent further comprises a first group, and the first group comprises at least one of a phosphate group, a carbonate group or a sulfonate group.

5. The positive electrode active material according to any one of claims 1-4, characterized in that, the hydrophobic protective agent comprises at least one of distearyl phosphate, tributyl phosphate, trimethyl phosphate, triisopropyl phosphate, dibutyl phosphate, dimethyl phosphate or diisopropyl phosphate.

6. The positive electrode active material according to any one of claims 1-5, characterized in that, The matrix includes at least one of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide. Optionally, the matrix includes Li x Ni a Co b M c O 2-y , where M includes at least one of Mn or Al, 0.6 ≤ x ≤ 1.2, -0.1 ≤ y ≤ 0.1, 0.5 ≤ a < 1, 0.1 ≤ b ≤ 0.3, 0 < c ≤ 0.3, and a + b + c = 1.

7. The positive electrode active material according to any one of claims 1-6, characterized in that, The volume average particle size D of the positive electrode active material v is 10 μm - 20 μm, and may be optionally 10 μm - 15 μm.

8. A method for preparing a positive electrode active material, characterized in that, comprises: forming a coating layer on at least a part of the surface of the matrix, the coating layer comprises a surface modifier and a hydrophobic protective agent, the surface modifier comprises at least one of a haloalkylsilane or an alkylsilane, and the hydrophobic protective agent has a hydrophobic group.

9. The method according to claim 8, characterized in that, comprises: preparing a surface modifier on at least a part of the surface of the matrix by chemical vapor deposition to obtain an intermediate; immersing the intermediate in a solution containing a hydrophobic protective agent to obtain a positive electrode active material.

10. The method according to claim 9, characterized in that, the temperature of the chemical vapor deposition is 130°C - 200°C.

11. The method according to claim 9 or 10, characterized in that, at least one of the following conditions is satisfied: based on the total mass of the solution containing the hydrophobic protective agent, the mass ratio of the hydrophobic protective agent is 90% - 99%; the immersion time is 2h - 6h.

12. The method according to any one of claims 9-11, characterized in that, The mass ratio of the matrix, the surface modifier, and the hydrophobic protective agent is 1:(0.05 - 0.1):(0.02 - 0.05).

13. A positive electrode sheet, characterized in that, it includes the positive electrode active material described in any one of claims 1 - 7 or the positive electrode active material prepared by the method described in any one of claims 8 - 12.

14. A battery, characterized in that, it includes the positive electrode sheet described in claim 13.

15. An electrical device, characterized in that, it includes the battery described in claim 14.

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