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

Abstract

The invention discloses a positive electrode active material particle and a preparation method thereof, a positive electrode plate, a battery monomer, a battery and an electric device, the positive electrode active material particle has a polymer coating layer, and a polymer in the polymer coating layer comprises a structural unit represented by a formula (1); in the formula, R1, R2, R3 and R4 respectively and independently comprise any one of the following components:-H,-COOH,-COOR5,-CONH2,-CONHR5,-R6COOR5,-R6CONH2,-COR5,-R6COR5,-R5 and-R6CONHR5; wherein at least one group of R1, R2, R3 and R4 comprises-CONH2; r < 5 > independently comprises an unsubstituted C < 1 >-C < 4 > linear chain or branched chain alkyl group, and a C < 2 >-C < 4 > linear chain or branched chain alkenyl alkyl group; and R6 independently comprises an unsubstituted straight chain or branched chain alkylene group with 1 to 4 carbon atoms, and a straight chain or branched chain alkenyl alkylene group with 2 to 4 carbon atoms. The water content of the positive electrode active material particles is low, the stability of the positive electrode active material particles is improved, and the drying time in the battery preparation process is shortened, so that the cycle performance of the battery can be improved, and the service life of the battery can be prolonged.

Description

Technical Field

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

[0002] In recent years, with the widespread application of battery cells represented by lithium-ion batteries, their performance has received more and more attention, and the requirements for the water content of positive electrode active materials are getting higher and higher.

[0003] In the related art, the positive electrode active material is modified, and the modification method includes directly doping with components such as graphitized carbon; however, the effect of improving the water content of the positive electrode active material still needs to be further improved. Summary of the invention

[0004] The purpose of the present application is to provide a positive electrode active material particle and a preparation method thereof, a positive electrode plate, a battery cell, a battery and an electrical device. During the battery charging and discharging process, the positive electrode active material particles provided in the embodiments of the present application have a low water content during storage, which improves the stability of the positive electrode active material particles, thereby improving the cycle performance and service life of the battery; the present application also aims to include a positive electrode plate containing the positive electrode active material particles, which at least has the beneficial effects of the positive electrode active material particles. The present application provides a battery cell, a battery and an electrical device that can achieve the beneficial effects of the positive electrode plate.

[0005] In a first aspect, an embodiment of the present application provides a positive electrode active material particle having a polymer coating layer, wherein the polymer in the polymer coating layer comprises a structural unit represented by formula (1);

[0006]

[0007] Among them, R 1 , R 2 , R 3 , R 4 Each independently includes -H, -COOR 5 , -COOH, -CONH 2 ,-CONHR 5 , -R 6 COOR 5 , -R 6 CONH 2 、-COR 5 , -R 6 COR 5 , -R 5 , -R 6 CONHR 5 Any of the following:

[0008] Among them, R 1 , R 2 , R 3 , R 4 At least one group contains -CONH 2 , -R 6 CONH 2 ,-CONHR 5 , -R 6 CONHR 5 Any of the following;

[0009] R 5 independently including unsubstituted C 1 -C 4 Straight or branched alkyl, C 2 -C 4 Straight-chain or branched alkenyl alkyl;

[0010] R 6 independently including unsubstituted C 1 -C 4 Straight or branched chain alkylene, C 2 -C 4 Straight-chain or branched alkenylalkylene.

[0011] The polymer coating layer is mainly composed of polymer, which is a high molecular compound that can reduce its contact with air and reduce its absorption of moisture in air or solvent, thereby facilitating the preservation of positive electrode active material particles and keeping them at a lower water content. In addition, in the process of preparing batteries using positive electrode active material particles, the drying time of the battery is reduced.

[0012] Furthermore, the polymer may contain hydrophobic functional groups such as ketone groups and ester groups, which have a certain hydrophobic effect and further reduce the water content in the positive electrode active material particles.

[0013] According to the embodiment of the present application, the surface of the positive electrode active material particles in the positive electrode active material particles has a polymer coating layer, which can act as a barrier to reduce the penetration of water into the positive electrode active material particles, thereby reducing the chance of the positive electrode active material particles contacting with water, and maintaining the water content of the positive electrode active material particles at a low level. Since the surface contains a polymer, the battery containing the positive electrode active material particles reduces the drying time of the positive electrode active material particles during the preparation process, so that it meets the water content requirements.

[0014] When the positive electrode active material particles are used in the battery, the water in the electrolyte has a certain influence on the performance of the positive electrode active material particles. The polymer coating layer in the positive electrode active material particles can reduce the contact between the positive electrode active material particles and the electrolyte, reduce the positive electrode active material particles to obtain water in the electrolyte, reduce the probability of side reactions, and improve the stability of the positive electrode active material particles. The polymer itself has good stability, which can improve the stability of the positive electrode active material particles, which helps to extend the life and cycle life of the battery or energy storage system.

[0015] In the embodiments of the present application, the water content of the positive electrode active material particles can be measured using the Karl Fischer method known in the art. In some optional embodiments, the water content of the positive electrode active material particles is less than 300 ppm, and can be 10 ppm to 200 ppm.

[0016] According to the embodiment of the present application, the water content of the positive electrode active material particles during storage is within the above range, and the water content is relatively low, which improves the stability of the positive electrode active material particles.

[0017] In some optional embodiments, the positive electrode active material particles include one or more of layered metal oxide materials, olivine positive electrode active materials and spinel materials; optionally, the olivine positive electrode active material particles include lithium iron phosphate materials.

[0018] The positive electrode active material particles implemented in this application can be materials commonly used in the art, without obvious restrictions. Commonly used positive electrode active materials include the above types. The surface of the positive electrode active material particles of the above types is coated with a coating layer, which can reduce the overall moisture content of the positive electrode active material particles, reduce the occurrence of side reactions, and improve the stability of the positive electrode active material particles.

[0019] In some optional embodiments, the average particle size Dv of the positive electrode active material particles is 1 50 is 0.52μm~4.1μm, and can be optionally 1μm~1.8μm.

[0020] According to the embodiment of the present application, the positive electrode active material particles with the above average particle size have a higher specific surface area to increase the capacity of the battery, improve the energy density of the battery, and enable it to store more electrical energy. The positive electrode active material particles with the above average particle size facilitate the ion and electron transmission between the electrolyte and the positive electrode active material particles, and can increase the charge and discharge speed of the battery. The positive electrode active material particles with the above average particle size can reduce the stress of the electrode, reduce the volume expansion and contraction of the material, thereby reducing the loss of the battery during the cycle charge and discharge process and extending the life of the battery.

[0021] In some optional embodiments, the specific surface area of ​​the positive electrode active material particles is 7 m2 / g~15m 2 / g, optional 10m 2 / g~13m 2 / g.

[0022] According to the embodiments of the present application, the specific surface area of ​​the positive electrode active material particles is within the above range, which means that more active materials can participate in the electrochemical reaction, so the battery capacity is larger and the energy density of the battery can be improved; the above larger specific surface area has more active surface can accelerate the transmission of ions and electrons in the electrolyte, thereby reducing the charging and discharging time, which helps to increase the charging and discharging speed of the battery. The above larger specific surface area is usually accompanied by more uniform utilization of electrode materials, reducing material loss and helping to extend the life of the battery.

[0023] In some optional embodiments, the average thickness of the polymer coating layer is 10 nm to 1000 nm.

[0024] According to the embodiment of the present application, when the amount of the coating layer is controlled within a certain range, the contact between the positive electrode active material particles and the electrolyte can be reduced while taking into account the battery kinetic performance, which can reduce the amount of water in the electrolyte, reduce the occurrence of side reactions, and improve the stability and cycle life of the positive electrode active material particles. Compared with uncoated positive electrode active material particles, the positive electrode active material particles with the above coating layer have better surface elasticity, which can further improve the bonding force and cohesion of the positive electrode sheet. Therefore, by further controlling the coating amount, better battery cycle performance and low anti-expansion performance can also be obtained.

[0025] In some optional embodiments, the positive electrode active material particles include 0.1%-5% of the polymer coating layer based on the total mass of the positive electrode active material particles.

[0026] According to the embodiment of the present application, the polymer in the positive electrode active material particles is within the above-mentioned suitable range, which can reduce the contact between the positive electrode active material particles and the electrolyte on the basis of taking into account the battery kinetic performance, can reduce the water content in the electrolyte, reduce the occurrence of side reactions, and improve the stability and cycle life of the positive electrode active material particles. Compared with the positive electrode active material particles not coated with the polymer, the positive electrode active material particles with the above-mentioned polymer coating layer have better surface elasticity, which can further improve the bonding force and cohesion of the positive electrode sheet. Therefore, by further controlling the coating amount, better battery cycle performance and low anti-expansion performance can also be obtained.

[0027] In some optional embodiments, the weight average molecular weight of the polymer is 100,000 to 3,000,000, and optionally 500,000 to 1,500,000.

[0028] According to the embodiments of the present application, the weight average molecular weight of the polymer is within the above range, and it can have more molecular segments, which can increase the hydrophobicity of the polymer; the polymer with a weight average molecular weight within the above range can provide more molecular cross-linking points, thereby increasing the bonding strength with other components in the positive electrode active material film layer, helping to reduce the probability of positive electrode active material particles falling off during battery cycling, thereby improving the stability and cycle life of the battery.

[0029] In some optional embodiments, the glass transition temperature of the polymer is 120°C to 170°C, optionally 125°C to 150°C.

[0030] According to the embodiments of the present application, the glass transition temperature of the polymer can affect the interfacial stability between the polymer and the positive electrode active material particles. If the glass transition temperature of the polymer is suitable, it is relatively stable during battery operation, which can stabilize the interface between it and the positive electrode active material particles, and at the same time reduce the adverse effects of stress changes caused by volume changes of the positive electrode active material particles on the positive electrode active material film layer. Having a suitable glass transition temperature can provide better anti-cycling performance because they are less prone to physical changes during charging and discharging, reducing the risk of thermal runaway of the battery, which helps to extend the cycle life of the battery.

[0031] In some optional embodiments, the crystallinity of the polymer is 60% to 85%, and optionally 65-75%.

[0032] According to the embodiments of the present application, the crystallinity of the polymer is within the above range, which is often accompanied by a more ordered molecular arrangement, which helps to transfer charge more efficiently, reduce the resistance inside the battery, and thus improve the charge and discharge efficiency. The crystallinity of the polymer is within the above range, has higher mechanical stability, can better protect the positive electrode active material particles from external factors such as mechanical stress, expansion and contraction, and as the polymer has a lower free volume, there is a suitable gap between the polymer molecules.

[0033] In some optional embodiments, R 1 , R 2 , R 3 , R 4 Each independently includes H, -COOR 5 , -COOH, -CONH 2 ,-CONHR 5 , -R 6 COOR 5 , -R 6 CONH 2 、-COR 5 , -R 6 COR 5 , -R5 ,

[0034] -R 6 CONHR 5 Any of the following;

[0035] R 5 independently including unsubstituted C 1 ~C 3 Straight or branched alkyl, C 2 ~C 3 Straight-chain or branched alkenyl alkyl;

[0036] R 6 independently including unsubstituted C 1 ~C 3 Straight or branched chain alkylene, C 2 ~C 3 Straight-chain or branched alkenylalkylene.

[0037] According to the embodiment of the present application, the above polymer is coated on the surface of the positive electrode active material particles as a coating layer, which reduces the penetration of water into the positive electrode active material particles, thereby reducing the chance of the positive electrode active material particles contacting with water. Since the surface contains the polymer, the drying time of the positive electrode active material particles is reduced, so that the water content reaches the required range.

[0038] In some optional embodiments, the polymer includes a hydrophobic functional group, and the hydrophobic functional group includes one or more of a ketone group, an ester group, and an amide group.

[0039] According to the embodiments of the present application, the above-mentioned types of hydrophobic functional groups can reduce the adsorption of moisture in the air and electrolyte by the positive electrode active material particles containing the polymer, thereby reducing the drying time of the positive electrode active material particles and making them reach the required range of water content.

[0040] In some optional embodiments, the polymer includes at least one of (Formula I-1) to (Formula I-9):

[0041]

[0042] Wherein, n is a positive integer.

[0043] According to the embodiments of the present application, the polymer having the above-mentioned general structural formula has good hydrophobicity, can reduce the water content of the positive electrode active material particles, reduce the occurrence of side reactions, and improve the stability of the positive electrode active material particles.

[0044] In a second aspect, an embodiment of the present application provides a method for preparing positive electrode active material particles having a polymer coating layer, the method comprising:

[0045] A mixture comprising positive electrode active material raw material particles, a polymerizable monomer and a solvent is provided, wherein the polymerizable monomer has a structural formula (1a):

[0046]

[0047] Among them, R 1 , R 2 , R 3 , R 4 Each independently includes -H, -COOR 5 、-CONH 2 , -COOH, -CONHR 5 , -R 6 COOR 5 , -R 6 CONH 2 、-COR 5 , -R 6 COR 5 , -R 5 , -R 6 CONHR 5 Any of the following;

[0048] Among them, R 1 , R 2 , R 3 , R 4 At least one group contains -CONH 2 , -R 6 CONH 2 ,-CONHR 5 , -R 6 CONHR 5 Any of the following;

[0049] R 5 independently including unsubstituted C 1 -C 4 Straight or branched alkyl, C 2 -C 4 Straight-chain or branched alkenyl alkyl;

[0050] R 6 independently including unsubstituted C 1 -C 4 Straight or branched chain alkylene, C 2 -C 4 Straight-chain or branched alkenyl alkylene;

[0051] The polymerizable monomer is polymerized to form a polymer coating layer coating the positive electrode active material raw material particles.

[0052] According to an embodiment of the present application, polymerizable monomers and positive electrode active material particles are polymerized in a solvent by an initiator to obtain positive electrode active material particles having a polymer coating layer. This in-situ generated polymer coating layer can more evenly coat the positive electrode active material particles, the bonding force between the coating layer and the positive electrode active material particles is better, and the coating layer is not easy to fall off. In addition, the polymer on the surface of the positive electrode active material particles can reduce the water content of the electrolyte obtained by the positive electrode active material particles by reducing the contact between the positive electrode active material particles and the electrolyte, thereby reducing the occurrence of side reactions and improving the stability of the positive electrode active material particles. The coating layer contains a polymer itself with good stability, which can improve the stability of the positive electrode active material particles and help extend the life of the battery or energy storage system.

[0053] In some optional embodiments, the mass ratio of the polymerized monomer to the positive electrode active material raw material particles is (0.1-5):100.

[0054] According to the embodiments of the present application, controlling the mass ratio of the polymerization monomer and the positive electrode active material raw material particles within the above-mentioned range is conducive to forming a polymer coating layer on the surface of the positive electrode active material raw material particles. At the same time, controlling the thickness of the coating layer and the amount of polymer is conducive to improving the encapsulation rate and uniformity of the polymer coating layer formed in situ, thereby facilitating the charge and discharge performance and cycle performance of the battery.

[0055] In some optional embodiments, the initiator includes a photoinitiator. In some optional embodiments, the initiator includes one or more of azo compounds, organic sulfides, and pigment substances.

[0056] According to the embodiments of the present application, a photoinitiator is used to promote the polymerization reaction of the polymerizable monomer, so that the preparation method of the positive electrode active material particles is simple, fast, and convenient for industrial production. And the above-mentioned types of photoinitiators can achieve the polymerization reaction of the polymerizable monomer. The present application does not specifically limit the types of photoinitiators, and any photoinitiator in the field that can achieve in-situ generation of polymers is within the scope of protection of the present application.

[0057] According to the embodiments of the present application, the polymer initiated by the photoinitiator is usually deposited on the surface of the positive electrode active material particles in the form of a film layer. This film coating can provide effective isolation, prevent direct contact between the positive electrode active material particles and the electrolyte, reduce the chemical reaction between the positive electrode active material particles and the electrolyte, thereby reducing the self-discharge of the battery and the degradation of the electrolyte. The coating layer can reduce the solid-liquid interface problems between the positive electrode active material particles and the electrolyte, such as the formation of the SEI film and the expansion / contraction of the electrode; it can also reduce the risk of thermal runaway or short circuit of the battery, thereby improving the safety of the battery.

[0058] In some optional embodiments, the azo compound includes one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

[0059] According to the embodiments of the present application, the above-mentioned azo compounds undergo isomeric conversion under ultraviolet light, resulting in changes in the molecular structure, thereby initiating a polymerization reaction. This light responsiveness makes them very sensitive to light, enabling high-precision spatial and temporal control, and also enabling polymer control on a microscopic scale.

[0060] In some optional embodiments, the organic sulfide includes one or more of thiol and alkyl disulfide.

[0061] According to the embodiments of the present application, thiols and alkyl disulfides have sulfur-sulfur bonds, which can undergo photocrosslinking reactions under light initiation to form sulfide polymers. These sulfide polymers generally have good chemical resistance and can improve the stability of the positive electrode active material particles. Thiols and alkyl disulfides are relatively easy to obtain, so they can be more easily implemented in practical applications.

[0062] In some optional embodiments, the pigment substance includes one or more of tetrabromofluorescein, tetrabromofluoramine, riboflavin, and anthocyanin.

[0063] According to the embodiments of the present application, the above-mentioned types of pigments generally absorb light in the visible light range, so their spectral properties can be regulated by selecting different pigments. This makes it possible to select the appropriate wavelength to initiate the polymerization reaction as needed, thereby achieving more precise control. Pigments are generally more environmentally friendly and have less impact on the environment.

[0064] In some optional embodiments, the polymerizable monomer includes one or more of acrylic acid, acrylic ester, acrylamide, methacryloyl alkylene oxide, allyl vinyl, allyl ketone, acrolein, and vinyl sulfide.

[0065] According to the embodiments of the present application, the polymer generated by the above-mentioned type of polymer monomer through the initiator has a relatively lower specific surface area than directly coating the prepared polymer on the surface of the positive electrode active material particles, and the formed polymer is coated on the surface of the positive electrode active material particles, thereby reducing the water content in the positive electrode active material particles.

[0066] In some optional embodiments, the solvent includes one or more of water, tert-butanol, methanol, ethanol, n-butanol

[0067] According to the embodiments of the present application, the initiator, the polymerization monomer and the positive electrode active material particles undergo a polymerization reaction in the above-mentioned type of solvent. On the one hand, the polymerization monomer can be dissolved in the solvent, so that the polymer can be more evenly coated on the positive electrode active material particles, thereby improving the uniformity and encapsulation rate of the coating, and maintaining the water content of the positive electrode active material particles at a low level.

[0068] In a third aspect, an embodiment of the present application provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode active material film layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material film layer comprises the positive electrode active material particles of the first aspect or the positive electrode active material particles prepared by the preparation method of the second aspect.

[0069] According to the embodiments of the present application, the positive electrode active material particles have a low water content, which exists in the positive electrode active material film layer, can improve the stability of the positive electrode plate during battery use, and help extend the life of the battery or energy storage system. The polymer on the surface of the positive electrode active material particles can reduce the water content in the electrolyte obtained by the positive electrode active material particles by reducing the contact between the positive electrode active material particles and the electrolyte, reducing the occurrence of side reactions, which is beneficial to the cycle performance.

[0070] In a fourth aspect, the present invention provides a battery cell, comprising the positive electrode sheet of the third aspect. The battery cell of the present invention comprises the positive electrode sheet, which helps to extend the life and cycle performance of the battery.

[0071] In a fifth aspect, an embodiment of the present application provides a battery, comprising the battery cell of the fourth aspect.

[0072] In a sixth aspect, an embodiment of the present application provides an electrical device comprising the battery of the fifth aspect.

[0073] The positive electrode active material particles of the embodiment of the present application have a polymer coating layer, which improves the stability of the positive electrode active material particles. The surface polymer can reduce the contact between the positive electrode active material particles and the electrolyte, which can reduce the positive electrode active material particles from obtaining water in the electrolyte, reduce the occurrence of side reactions, and is beneficial to the cycle performance. The positive electrode sheet, battery cell and electrical device containing the positive electrode active material have at least the above advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some implementation methods of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0075] Figure 1It is a schematic diagram of an embodiment of a battery cell of the present application.

[0076] Figure 2 yes Figure 1 An exploded schematic diagram of a battery cell is shown.

[0077] Figure 3 It is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0078] In the drawings, the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0079] Below, the electrode assembly and its preparation method, battery cell, battery module, battery pack and electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0080] "Scope" disclosed in the present application is defined in the form of lower limit and upper limit, and 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 scope defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a scope of 60-120 and 80-110 is listed for a particular parameter, it is understood that the scope of 60-110 and 80-120 is also expected. 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 range can be fully expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, characterized in that a and b are all real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0081] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0082] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0083] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0084] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0085] If not specifically stated, 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) and B is true (or exists); or both A and B are true (or exist).

[0086] Unless otherwise specified, in this application, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0087] If not specifically stated otherwise, in this application, the term "attach" refers to connection by adhesion, coating or the like.

[0088] If not otherwise specified, in this application, the terms "first", "second", "third", "fourth", etc. are used to distinguish different objects rather than to describe a specific order or a primary and secondary relationship.

[0089] Unless otherwise specified, in this application, the term "active ions" refers to ions that can be inserted and removed back and forth between the positive and negative electrodes of a battery cell, including but not limited to lithium ions, sodium ions, etc.

[0090] The term "multiple" as used herein refers to two or more (including two). The term "multiple" or "several" as used herein refers to two or more (including two).

[0091] In the present application, the battery cell may include a lithium-ion battery, a sodium-ion battery, etc., which is not limited in the present embodiment. The battery cell may be an aqueous battery or an oil-based battery, which is not limited in the present embodiment. The battery cell may be a flat body, a rectangular parallelepiped, or other shapes, which is not limited in the present embodiment.

[0092] A battery cell, also known as a rechargeable battery or storage battery, refers to a battery that can be used continuously by recharging the active material after the battery is discharged. Typically, a battery cell includes an electrode assembly and an electrolyte, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0093] The main raw materials of the battery include positive electrode active material particles, negative electrode materials, separators and electrolytes. During the battery charging and discharging process, the positive electrode active material particles undergo electrochemical oxidation / reduction reactions, and active ions represented by lithium ions are repeatedly embedded in and removed from the positive electrode active material particles. The positive electrode active material particles mainly include layered structure materials, spinel structure materials, and olivine structure materials.

[0094] In order to ensure good electrochemical performance, strict requirements are placed on the performance of the positive electrode active material particles. One of the more important points is that the positive electrode active material particles have good chemical stability and do not react with electrolytes. Positive electrode active material particles are often exposed to a humid environment during preparation and storage, resulting in a certain amount of water on the surface. The presence of water reduces the chemical stability of the positive electrode active material particles and the side reactions with electrolytes.

[0095] How to reduce the water content of positive electrode active material particles during storage and preparation is very important for positive electrode active material particles and batteries. Before using the positive electrode active material particles or in the later battery preparation process, drying treatment is generally performed to reduce the water content in the positive electrode active material particles. However, it is difficult to completely dry the water in the positive electrode active material particles or reduce the water content to an extremely low level, and it takes a long time.

[0096] In view of this, the present application provides a positive electrode active material particle with a polymer coating layer to solve the above problems.

[0097] Positive electrode active material particles

[0098] In a first aspect, an embodiment of the present application provides a positive electrode active material particle having a polymer coating layer, wherein the polymer in the polymer coating layer comprises a structural unit represented by formula (1);

[0099]

[0100] Among them, R 1 , R 2 , R 3 , R 4 Each independently includes -H, -COOR 5 、-CONH 2 , -COOH, -CONHR 5 , -R 6 COOR 5 , -R 6 CONH 2 、-COR 5 , -R 6 COR 5 , -R 5 , -R 6 CONHR 5 Any of the following;

[0101] Among them, R 1 , R 2 , R 3 , R 4 At least one group contains -CONH 2 , -R 6 CONH 2 ,-CONHR 5 , -R 6 CONHR 5 Any of the following;

[0102] R 5 independently including unsubstituted C 1 -C 4 Straight or branched alkyl, C 2 -C 4 Straight-chain or branched alkenyl alkyl;

[0103] R 6 independently including unsubstituted C 1 -C 4 Straight or branched chain alkylene, C 2 -C 4 Straight-chain or branched alkenylalkylene.

[0104] The polymer coating layer is mainly composed of polymer, which is a high molecular compound that can reduce its contact with air and reduce its absorption of moisture in air or solvent, thereby facilitating the preservation of positive electrode active material particles and keeping them at a lower water content. In addition, in the process of preparing batteries using positive electrode active material particles, the drying time of the battery is reduced.

[0105] According to the embodiment of the present application, the positive electrode active material particles have a polymer coating layer, which can act as a barrier to prevent moisture from penetrating into the positive electrode active material particles, thereby reducing the chance of the positive electrode active material particles contacting with moisture, and maintaining the water content of the positive electrode active material particles at a low level. Since the surface contains a polymer and the polymer is prepared in situ, the battery containing the positive electrode active material particles reduces the drying time of the positive electrode active material particles during the preparation process, so that it meets the water content requirements.

[0106] When the positive electrode active material particles are used in the battery, the water in the electrolyte has a certain influence on the performance of the positive electrode active material particles. The polymer coating layer in the positive electrode active material particles can reduce the contact between the positive electrode active material particles and the electrolyte, reduce the positive electrode active material particles to obtain water in the electrolyte, reduce the occurrence of side reactions, and improve the stability of the positive electrode active material particles. The polymer itself has good stability, which can improve the stability of the positive electrode active material particles, which helps to extend the life and cycle life of the battery or energy storage system.

[0107] In some optional embodiments, the water content of the positive electrode active material particles is less than 300 ppm, and can be 10 ppm to 200 ppm. The water content of the positive electrode active material particles can be 1 ppm, 5 ppm, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm, 120 ppm, 130 ppm, 140 ppm, 150 ppm, 160 ppm, 170 ppm, 180 ppm, 190 ppm, 200 ppm, 210 ppm, 220 ppm, 230 ppm, 240 ppm, 250 ppm, 260 ppm, 270 ppm, 280 ppm, 290 ppm, 299 ppm, any value or a range thereof.

[0108] According to the embodiment of the present application, the water content of the positive electrode active material particles during storage is within the above range, and the water content is relatively low, which improves the stability of the positive electrode active material particles. In the embodiment of the present application, the water content of the positive electrode active material particles can be determined using the Karl Fischer method known in the art.

[0109] In some optional embodiments, the positive electrode active material particles include one or more of layered metal oxide materials, olivine positive electrode active materials and spinel materials; optionally, the olivine positive electrode active material particles include lithium iron phosphate materials.

[0110] The positive electrode active material particles implemented in this application can be materials commonly used in the art, without obvious restrictions. Commonly used positive electrode active materials include the above types. The surface of the positive electrode active material particles of the above types is coated with a coating layer, which can reduce the overall moisture content of the positive electrode active material particles, reduce the occurrence of side reactions, and improve the stability of the positive electrode active material particles.

[0111] For example, when the battery cell is a lithium-ion battery cell or a lithium metal battery cell, the positive electrode active material may include one or more of a lithium transition metal oxide, a lithium-containing phosphate with an olivine structure, and their respective modified compounds. Examples of lithium transition metal oxides may include 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 respective modified compounds. Examples of lithium-containing phosphates with an olivine structure may include one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds. The present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials may also be used.

[0112] In some embodiments, in order to further improve the energy density of the battery cell, the positive electrode active material may include a general formula of Li a Ni b Co c M d O e A f One or more of lithium transition metal oxides and modified compounds thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more selected from N, F, S and Cl.

[0113] As an example, the positive electrode active material may include LiCoO 2 、LiNiO 2 、LiMnO 2 、LiMn 2 O 4 、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.80 Co 0.15 Al 0.05 O 2 、LiFePO 4 and LiMnPO 4 One or more of .

[0114] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0115] In the list of positive electrode materials in this application, the molar content of O is only a theoretical value. 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.

[0116] When the battery cell is a sodium ion battery cell or a sodium metal battery cell, the positive electrode active material may include but is not limited to one or more of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.

[0117] As an example, the positive electrode active material may include NaFeO 2 、NaCoO 2 、NaCrO 2 、NaMnO 2 、NaNiO 2 、NaNi 1 / 2 Ti 1 / 2 O 2 、NaNi 1 / 2 Mn 1 / 2 O 2 、Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O 2 、NaNi1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , NaFePO 4 , NaMnPO 4 , NaCoPO 4 , Prussian blue-based materials, and one or more of the materials of the general formula X p M’ q (PO 4 ) r O x Y 3-x In the general formula X p M’ q (PO 4 ) r O x Y 3-x , 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, X includes one or more selected from H + , Li + , Na + , K + , and NH 4 + . M’ is a transition metal cation, optionally including one or more selected from V, Ti, Mn, Fe, Co, Ni, Cu, and Zn, and Y is a halogen anion, optionally including one or more selected from F, Cl, and Br.

[0118] The modified compounds of the above positive electrode active materials can be doping modification and / or surface coating modification of the positive electrode active materials.

[0119] In some alternative embodiments, the average particle size Dv of the positive electrode active material particles 1 is 0.52 μm to 4.1 μm, optionally 1 μm to 1.8 μm.

[0120] Optionally, any value or the range composed of 0.52 μm, 0.6 μm, 0.7 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.1 μm.

[0121] According to the embodiments of the present application, the cathode active material particles with the above average particle size have a higher specific surface area, which can increase the capacity of the battery, improve the energy density of the battery, and enable it to store more electrical energy. The cathode active material particles with the above average particle size contribute to the ion and electron transport between the electrolyte and the cathode active material particles, and can improve the charge and discharge speed of the battery. The cathode active material particles with the above average particle size can reduce the stress of the electrode, reduce the volume expansion and contraction of the material, thereby reducing the loss of the battery during the cyclic charge and discharge process and extending the life of the battery.

[0122] In some alternative embodiments, the specific surface area of the cathode active material particles is 7 m 2 / g to 15 m 2 / g, and can be optionally 10 m 2 / g to 13 m 2 / g.

[0123] Optionally, the specific surface area of the cathode active material particles can be 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g or any value within the range composed thereof.

[0124] According to the embodiments of the present application, the specific surface area of the cathode active material particles within the above range means that more active materials can participate in the electrochemical reaction, so the capacity of the battery is larger, and the energy density of the battery can also be improved; the above larger specific surface area has more active surfaces, which can accelerate the transport of ions and electrons in the electrolyte, thereby reducing the charging and discharging time and contributing to improving the charging and discharging speed of the battery. The above larger specific surface area is usually accompanied by more uniform utilization of the electrode material, reducing the loss of the material and contributing to extending the life of the battery.

[0125] The specific surface area of the cathode active material particles has the meaning well-known in the art and can be measured by the instruments and methods well-known in the art. For example, it can be measured with reference to the standard of GB / T 19587-2004 Gas Adsorption BET Method for Determining the Specific Surface Area of Solid Substances, using the nitrogen adsorption specific surface area analysis and test method, and calculated by the BET (Brunauer Emmett Teller) method. Among them, the nitrogen adsorption specific surface area analysis and test can be carried out by the Tri StarⅡ3020 specific surface area and pore size analyzer of Micromeritics Company of the United States.

[0126] In some optional embodiments, the average thickness of the coating layer is 10 nm to 1000 nm. Optionally, the average thickness of the coating layer can be any value of 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or a range thereof.

[0127] According to the embodiment of the present application, when the amount of the coating layer is controlled within a certain range, the contact between the positive electrode active material particles and the electrolyte can be reduced while taking into account the battery kinetic performance, which can reduce the amount of water in the electrolyte, reduce the occurrence of side reactions, and improve the stability and cycle life of the positive electrode active material particles. Compared with uncoated positive electrode active material particles, the positive electrode active material particles with the above coating layer have better surface elasticity, which can further improve the bonding force and cohesion of the positive electrode sheet. Therefore, by further controlling the coating amount, better battery cycle performance and low anti-expansion performance can also be obtained.

[0128] The average thickness of the coating layer can be determined by sampling and detecting the average thickness of the coating layer in the cross section of the negative electrode material, and the average thickness of the coating layer can be calculated by sampling and measuring its thickness under an electron microscope.

[0129] In some optional embodiments, the positive electrode active material particles include 0.1%-5% of the polymer coating layer based on the total mass of the positive electrode active material particles.

[0130] Alternatively, the positive electrode active material particles may have a polymer coating layer of any value among 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5% or a range of their compositions.

[0131] According to the embodiment of the present application, the polymer in the positive electrode active material particles is within the above-mentioned suitable range, which can reduce the contact between the positive electrode active material particles and the electrolyte on the basis of taking into account the battery kinetic performance, can reduce the amount of water in the electrolyte, reduce the occurrence of side reactions, and improve the stability and cycle life of the positive electrode active material particles. Compared with uncoated positive electrode active material particles, the positive electrode active material particles with the above-mentioned coating layer have better surface elasticity, which can further improve the bonding force and cohesion of the positive electrode sheet. Therefore, by further controlling the coating amount, better battery cycle performance and low anti-expansion performance can also be obtained.

[0132] According to the embodiments of the present application, the polymer coating layer in the positive electrode active material particles is within the above-mentioned suitable range, which ensures that the positive electrode active material particles have a higher proportion of positive electrode active material particles, so that the positive electrode plate has good lithium ion conductivity and electronic conductivity. Therefore, the positive electrode plate can be used in a lithium battery to significantly improve the battery's energy density, rate performance and cycle performance.

[0133] The mass content of the polymer coating layer in the positive electrode active material particles can be detected by stripping the polymer coating layer. As an example, a certain amount of positive electrode active material particles is weighed and recorded as M1, and then the positive electrode active material particles are placed in a mixed solution of water and ethanol, the volume ratio of water: ethanol is 1:1, and the mass ratio of the positive electrode active material particles to the mixed solution is about 1:10. The mixed solution containing the positive electrode active material particles is ultrasonicated for 20-40 minutes, the ultrasonic frequency is 20-40HZ, which can be 25HZ, and then washed and filtered, and the positive electrode active material particles after stripping the polymer coating layer are collected. After drying, the positive electrode active material particles after stripping the polymer coating layer are weighed and collected and recorded as M2. Then, the collected positive electrode active material particles after stripping the polymer coating layer are further placed in a mixed solution of water and ethanol, and ultrasonicated for 20-40 minutes, and then washed, filtered and separated, and the positive electrode active material particles after stripping the polymer coating layer are further collected. After drying, the collected silicon material particles are weighed and recorded as M3. When the mass difference between M2 and M3 is less than 0.1%, it means that the polymer coating layer is stripped cleanly. The test results show that the polymer coating layer content m = M1-M3. The calculation method of the mass content of the polymer coating layer is m / M1.

[0134] In some optional embodiments, the weight average molecular weight of the polymer is 100,000 to 3,000,000, and optionally 500,000 to 1,500,000.

[0135] According to the embodiments of the present application, the weight average molecular weight of the polymer is within the above range, and it can have more molecular segments, which can increase the hydrophobicity of the polymer; the polymer with a weight average molecular weight within the above range can provide more molecular cross-linking points, thereby increasing the bonding strength with other components in the positive electrode active material film layer, helping to reduce the probability of positive electrode active material particles falling off during battery cycling, thereby improving the stability and cycle life of the battery.

[0136] The weight average molecular weight of the polymer can be measured by methods known in the art. As an example, the weight average molecular weight of the polymer in this application can be determined by referring to the standard GB / T 21863-2008 gel permeation chromatography. Specifically, in this application, an ultra-high performance polymer chromatograph: ACQUITY APC (detector: ACQUITY differential refractive index detector) can be used, and the following test steps are followed: (1) Preheating: Install the chromatographic column and pipeline, turn on the console in turn, test the power supply, etc., and open the test software Empower; (2) Parameter setting, injection volume: 0μL to 50μL (depending on the sample concentration); pump flow rate: 0.2mL / min; mobile phase: 30mol / L LiBr in NMP solution; sealing cleaning liquid: isopropanol; pre-column: PL gel 10umMiniMIX-B Guard (size: 50mm×4.6mm×2); analytical phase: PL gel 10um MiniMIX-B (size: 250 mm × 4.6 mm); standard: polystyrene sleeve; running time: 30 min; detector: ACQUITY differential refractive index (RI) detector; column oven temperature: 90 °C; detector temperature: 55 °C; (3) sample testing: a. Standard sample and test sample configuration: weigh 0.002 g to 0.004 g of standard sample / test sample respectively and add 2 mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard, and place in a refrigerator for >8 h; b. Standard solution / sample testing: edit the sample group to be tested, select the established sample group method, and after the baseline is stable, click the run queue to start testing the sample; (4) Data processing: Based on the relationship between retention time and molecular weight, use the chemical workstation to establish a calibration curve, integrate and quantify the sample spectrum, and the chemical workstation automatically generates the molecular weight and molecular weight distribution results.

[0137] In some optional embodiments, the glass transition temperature of the polymer is 120-170°C, optionally 125-150°C.

[0138] According to the embodiments of the present application, the glass transition temperature of the polymer can affect the interfacial stability between the polymer and the positive electrode active material particles. If the glass transition temperature of the polymer is suitable, it is relatively stable during battery operation, which can stabilize the interface between it and the positive electrode active material particles, and at the same time reduce the adverse effects of stress changes caused by volume changes of the positive electrode active material particles on the positive electrode active material film layer. Having a suitable glass transition temperature can provide better anti-cycling performance because they are less prone to physical changes during charging and discharging, reducing the risk of thermal runaway of the battery, which helps to extend the cycle life of the battery.

[0139] The glass transition temperature (Tg) is one of the characteristic temperatures of polymer materials, which refers to the temperature at which the polymer material changes from a highly elastic state to a glassy state or from a glassy state to a highly elastic state. The glass transition temperature (Tg) can be detected by commonly used methods in the art, such as differential scanning calorimetry (DSC), thermomechanical analysis (TMA), dynamic thermomechanical analysis (DMA), etc. in thermal analysis. Taking the measurement of Tg by the DSC method as an example, it can be detected in accordance with the standard ISO11357-2-2013. According to the fact that the specific heat of the polymer changes greatly before and after Tg, it is a step in the endothermic direction on the DSC curve. The average value of the temperatures of the two intersection points of the two extrapolated baselines before and after the step with the tangent line at the inflection point of the curve is taken as Tg.

[0140] In some alternative embodiments, the crystallinity of the polymer is 60% - 85%, and may be optionally 65 - 75%.

[0141] According to the embodiments of the present application, when the crystallinity of the polymer is within the above range, it is often accompanied by a more ordered molecular arrangement, which helps to more effectively transfer charges, reduce the resistance inside the battery, and thus improve the charge and discharge efficiency. When the crystallinity of the polymer is within the above range, it has higher mechanical stability, can better protect the positive active material particles from external factors such as mechanical stress, expansion and contraction, and due to the lower free volume of the polymer, there are appropriate gaps between polymer molecules.

[0142] Crystallinity refers to the proportion of the crystalline part in a partially crystalline polymer material at room temperature, and crystallinity = crystalline part / total part of the material (crystalline part + amorphous part). The crystallinity of the polymer can be detected by commonly used methods in the art, such as density method, X-ray diffraction method, calorimetry, etc.

[0143] In some alternative embodiments, R 1 、R 2 、R 3 、R 4 each independently includes any one of H, -COOR 5 、-COOH、-CONH 2 、-CONHR 5 、-R 6 COOR 5 、-R 6 CONH 2 、-COR 5 、-R 6 COR 5 、-R 5 、-R 6 CONHR 5 ;

[0144] R 5independently including unsubstituted C 1 ~C 3 Straight or branched alkyl, C 2 ~C 3 Straight-chain or branched alkenyl alkyl;

[0145] R 6 independently including unsubstituted C 1 ~C 3 Straight or branched chain alkylene, C 2 ~C 3 Straight-chain or branched alkenylalkylene.

[0146] According to the embodiment of the present application, the above polymer is coated on the surface of the positive electrode active material particles as a coating layer, which reduces the penetration of water into the positive electrode active material particles, thereby reducing the chance of the positive electrode active material particles contacting with water. Since the surface contains the polymer, the drying time of the positive electrode active material particles when preparing the battery is reduced, so that the water content reaches the required range.

[0147] For the purposes of this application, the above-mentioned "carboxylic acid groups" may refer to both the non-ionized (protonated) and ionized (carboxylate) forms of these groups. Other functional groups may also be exemplified in this manner.

[0148] In some optional embodiments, the polymer includes one or more functional groups selected from the group consisting of ketone group and ester group.

[0149] According to the embodiments of the present application, the above-mentioned types of functional groups have a certain hydrophobicity, which can reduce the adsorption of moisture in the air and electrolyte by the positive electrode active material particles containing the polymer coating layer, thereby reducing the drying time of the positive electrode active material particles and making them reach the required range of water content.

[0150] In some optional embodiments, the polymer includes at least one of (Formula I-1) to (Formula I-9):

[0151]

[0152]

[0153] Wherein, n is a positive integer, and n can be selected from 2 to 100000.

[0154] According to the embodiments of the present application, the polymer having the above-mentioned general structural formula has good hydrophobicity, can reduce the water content of the positive electrode active material particles, reduce the occurrence of side reactions, and improve the stability of the positive electrode active material particles.

[0155] Method for preparing positive electrode active material particles

[0156] In a second aspect, an embodiment of the present application provides a method for preparing positive electrode active material particles, the method comprising:

[0157] A mixture comprising positive electrode active material raw material particles, a polymerizable monomer and a solvent is provided, wherein the polymerizable monomer has a structural formula (1a):

[0158]

[0159] Among them, R 1 , R 2 , R 3 , R 4 Each independently includes -H, -COOR 5 、-CONH 2 , -COOH, -CONHR 5 , -R 6 COOR 5 , -R 6 CONH 2 、-COR 5 , -R 6 COR 5 , -R 5 , -R 6 CONHR 5 Any of the following:

[0160] Among them, R 1 , R 2 , R 3 , R 4 At least one group contains -CONH 2 , -R 6 CONH 2 ,-CONHR 5 , -R 6 CONHR 5 Any of the following:

[0161] R 5 independently including unsubstituted C 1 -C 4 Straight or branched alkyl, C 2 -C 4 Straight-chain or branched alkenyl alkyl;

[0162] R 6 independently including unsubstituted C 1 -C 4 Straight or branched chain alkylene, C 2 -C 4 Straight-chain or branched alkenyl alkylene;

[0163] The polymerizable monomer is polymerized to form a polymer coating layer coating the positive electrode active material raw material particles.

[0164] According to an embodiment of the present application, the polymerizable monomers and the positive electrode active material particles are polymerized in a solvent by an initiator to obtain positive electrode active material particles coated with a polymer on the surface. This in-situ generated polymer coating layer can more evenly coat the positive electrode active material particles, the bonding force between the coating layer and the positive electrode active material particles is better, and the coating layer is not easy to fall off. In addition, the polymer on the surface of the positive electrode active material particles can reduce the water content of the electrolyte obtained by the positive electrode active material particles by reducing the contact between the positive electrode active material particles and the electrolyte, thereby reducing the occurrence of side reactions and improving the stability of the positive electrode active material particles. The coating layer contains a polymer itself with good stability, which can improve the stability of the positive electrode active material particles and help extend the life of the battery or energy storage system.

[0165] In some optional embodiments, the average particle size Dv of the positive electrode active material particles is 1 50 and the average particle size Dv of the positive electrode active material raw material particles 2 The ratio of 50 is (1.03~1.95):1.

[0166] Alternatively, the average particle size Dv of the positive electrode active material particles 1 50 and the average particle size Dv of the positive electrode active material raw material particles 2 The ratio of 50 can be any value among 1.03:1, 1.10:1, 1.20:1, 1.30:1, 1.40:1, 1.50:1, 1.60:1, 1.70:1, 1.80:1, 1.90:1, 1.95:1 or a range thereof.

[0167] According to the embodiment of the present application, the average particle size Dv of the positive electrode active material particles is 1 50 and the average particle size Dv of the positive electrode active material raw material particles 2 The ratio of 50 is within the above range, which is beneficial to the deintercalation of active ions such as lithium ions in the positive electrode active material particles and is beneficial to the charge and discharge performance of the positive electrode active material particles.

[0168] In some optional embodiments, the average particle size Dv of the positive electrode active material raw material particles is 2 50 is 0.5μm~2.1μm, and can be optionally 0.7μm~1.5μm.

[0169] Alternatively, the average particle size Dv of the positive electrode active material raw material particles is 250 can be any value among 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.1μm or a range of their compositions.

[0170] According to the embodiment of the present application, the average particle size Dv50 of the positive electrode active material raw material particles is within the above range, so that the polymer can be better coated, and the positive electrode active material particles are more evenly dispersed, thereby improving the flexibility and cohesion of the positive electrode active material film layer, and reducing the surface fracture or cracking caused by winding or folding the positive electrode sheet containing the positive electrode active material film layer. 2 50 Within the above range, the positive electrode active material particles can have a suitable particle size and specific surface area, which is beneficial to the electrochemical performance of the positive electrode active material particles.

[0171] Average particle size distribution Dv of positive electrode active material particles 1 50. Average particle size distribution Dv of positive electrode active material raw material particles 2 50 is a well-known meaning in the art. Particle size distribution Dv 1 50.Dv 2 50, also known as the average particle size or median particle size, represents the particle size corresponding to 50% of the volume distribution of the positive electrode active material particles. The above particle size distributions can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer produced by Malvern Instruments Ltd., UK.

[0172] Any number of initiators may be used, such as photoinitiators (e.g., compounds containing phenone), thermal initiators, or chemical initiators. Examples of thermal initiators include, but are not limited to, azo compounds, peroxides (e.g., benzoyl peroxide), persulfates (e.g., potassium persulfate or ammonium persulfate), derivatives thereof, or combinations thereof. In some optional embodiments, the initiator includes a photoinitiator. In some optional embodiments, the initiator includes one or more of an azo compound, an organic sulfide, or a pigment.

[0173] According to the embodiments of the present application, a photoinitiator is used to promote the polymerization reaction of the polymerizable monomer, so that the preparation method of the positive electrode active material particles is simple, fast, and convenient for industrial production. And the above-mentioned types of photoinitiators can achieve the polymerization reaction of the polymerizable monomer. The present application does not specifically limit the types of photoinitiators, and any photoinitiator in the field that can achieve in-situ generation of polymers is within the scope of protection of the present application.

[0174] According to the embodiments of the present application, the polymer initiated by the photoinitiator is usually deposited on the surface of the positive electrode active material particles in the form of a film layer. This film coating can provide effective isolation, prevent direct contact between the positive electrode active material particles and the electrolyte, reduce the chemical reaction between the positive electrode active material particles and the electrolyte, thereby reducing the self-discharge of the battery and the degradation of the electrolyte. The coating layer can reduce the solid-liquid interface problems between the positive electrode active material particles and the electrolyte, such as the formation of the SEI film and the expansion / contraction of the electrode; it can also reduce the risk of thermal runaway or short circuit of the battery, thereby improving the safety of the battery.

[0175] In some optional embodiments, the azo compound includes one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

[0176] According to the embodiments of the present application, the above-mentioned azo compounds undergo isomeric conversion under ultraviolet light, resulting in changes in the molecular structure, thereby initiating a polymerization reaction. This light responsiveness makes them very sensitive to light, enabling high-precision spatial and temporal control, and also enabling polymer control on a microscopic scale.

[0177] In some optional embodiments, the organic sulfide includes one or more of thiol and alkyl disulfide.

[0178] According to the embodiments of the present application, thiols and alkyl disulfides have sulfur-sulfur bonds, which can undergo photocrosslinking reactions under light initiation to form sulfide polymers. These sulfide polymers generally have good chemical resistance and can improve the stability of the positive electrode active material particles. Thiols and alkyl disulfides are relatively easy to obtain, so they can be more easily implemented in practical applications.

[0179] In some optional embodiments, the pigment substance includes one or more of tetrabromofluorescein, tetrabromofluoramine, riboflavin, and anthocyanin.

[0180] According to the embodiments of the present application, the above-mentioned types of pigments generally absorb light in the visible light range, so their spectral properties can be regulated by selecting different pigments. This makes it possible to select the appropriate wavelength to initiate the polymerization reaction as needed, thereby achieving more precise control. Pigments are generally more environmentally friendly and have less impact on the environment.

[0181] In some optional embodiments, the polymerizable monomer includes one or more of acrylic acid, acrylic ester, acrylamide, methacryloyl alkylene oxide, allyl ketone, and acrolein.

[0182] According to the embodiments of the present application, the polymer generated by the above-mentioned type of polymer monomer through an initiator has a hydrophobic functional group and a certain hydrophobicity, and the polymer formed by it is coated on the surface of the positive electrode active material particles, reducing the water content in the positive electrode active material particles.

[0183] In some optional embodiments, the mass ratio of the dosage of the initiator to the polymerization monomer is (0.001-0.05):1, and can be optionally (0.005-0.01):1.

[0184] According to the embodiments of the present application, the mass ratio of the initiator to the polymerization monomer is within the above range, which is conducive to the polymerization of the polymerization monomer to form a polymer as completely as possible, and also reduces the waste of the initiator, so that the polymer can be more evenly coated on the positive electrode active material particles, thereby improving the uniformity and encapsulation rate of the coating, and maintaining the water content of the positive electrode active material particles at a low level.

[0185] In some optional embodiments, the solvent includes one or more of water, tert-butanol, methanol, ethanol, n-butanol

[0186] According to an embodiment of the present application, the initiator, the polymerization monomer and the positive electrode active material particles undergo a polymerization reaction in the above-mentioned type of solvent. On the one hand, the polymerization monomer can be dissolved in the solvent, so that the polymer can be more evenly coated on the positive electrode active material particles, improve the uniformity and encapsulation rate of the coating, and maintain the water content of the positive electrode active material particles at a low level. Other solvents that can be used in the method of the embodiment of the present application include (but are not limited to) the above-mentioned types and combinations of these types. Considering the solubility in the polymer phase, solvents with different degrees of swelling can be selected. The solubility of the components of the solvent and the material to be swollen can be obtained from polymer textbooks (such as The Polymer Handbook) or can be measured experimentally.

[0187] In some optional embodiments, the positive electrode active material particles allow the polymerization monomer to undergo a polymerization reaction under the action of the initiator to satisfy at least one of the following conditions:

[0188] 1) in a closed environment, allowing the polymerization monomer to undergo a polymerization reaction under the action of the initiator;

[0189] 2) Under heating conditions, the polymerization monomer undergoes a polymerization reaction under the action of the initiator;

[0190] 3) by means of energy ray radiation, the polymerizable monomer undergoes a polymerization reaction under the action of the initiator; optionally, the energy ray is ultraviolet light.

[0191] According to the embodiments of the present application, any of the above methods is used to cause the polymerization monomer to undergo a polymerization reaction under the action of the initiator, which can initiate the polymerization reaction, increase the reaction rate, and reduce the water content of the prepared positive electrode active material particles.

[0192] In some optional embodiments, after the polymerization monomer is polymerized under the action of the initiator, the step further includes: drying the mixture after the polymerization reaction.

[0193] According to the embodiment of the present application, after the polymerization monomer is polymerized by the initiator of the embodiment of the present application, the polymer is coated on the positive electrode active material particles, and the water content of the mixture is low. The solvent can be removed by drying the mixture. In the embodiment of the present application, the drying can be carried out by a drying method commonly used in the art, and the drying method can include placing the liquid mixture in a ventilated environment, allowing the solvent to evaporate naturally, heating, nitrogen purging, etc.

[0194] In some optional embodiments, drying satisfies at least one of the following conditions:

[0195] 1) The drying temperature is 90-130° C.;

[0196] 2) The dry environment is an inert atmosphere or a vacuum environment;

[0197] 3) The drying time is 20 to 40 hours.

[0198] According to the embodiments of the present application, drying at 90 to 130°C can improve the drying efficiency and accelerate the removal of the solvent; drying in an inert atmosphere or a vacuum environment can further maintain the low water content of the positive electrode active material particles and reduce the risk of the positive electrode active material particles reacting with water and oxygen in the air. The drying time can be 20 to 40 hours, which can improve the drying efficiency and also achieve the removal of the solvent. Inert gases are a class of relatively inactive gases that are not easily involved in most chemical reactions, such as nitrogen, helium, neon, and krypton.

[0199] As an example, the method of preparing positive electrode active material particles comprises the following steps:

[0200] (1) At 20-25°C, the polymerized monomer and the positive electrode active material are mixed uniformly in a certain ratio and added to the reaction container, and the mass ratio is controlled at 0.5-5.0% and 95-99.5% respectively; stirring is continued for 20-60 minutes; the solvent is a mixture of water and tert-butyl alcohol (volume ratio 3:7), and the solid content of the slurry is 53-67%

[0201] (2) Adding initiator to the reaction vessel, the total mass ratio (the content of initiator in all added substances, including polymerizable monomers, positive electrode active materials and initiator) is controlled at 0.01%, and stirring for 30 minutes;

[0202] (3) introducing nitrogen / argon for 10 to 50 minutes to remove oxygen from the reactor;

[0203] (4) placing the reaction container under an ultraviolet lamp, irradiating at 20-25°C for 20-120 minutes, and continuously stirring; the ultraviolet lamp used in the polymerization process is a high-pressure mercury lamp with a power of 100-2000W and a wavelength of 220nm-2000nm.

[0204] (5) Finally, the photopolymerized product is washed with anhydrous ethanol, dried at 60° C. for 2 h, and then crushed into a powdery solid, i.e., positive electrode active material particles.

[0205] Positive electrode

[0206] In a third aspect, an embodiment of the present application provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode active material film layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material film layer comprises the positive electrode active material particles of the first aspect or the positive electrode active material particles prepared by the preparation method of the second aspect.

[0207] According to the embodiments of the present application, the positive electrode active material particles have a low water content, which exists in the positive electrode active material film layer, can improve the stability of the positive electrode plate during battery use, and help extend the life of the battery or energy storage system. The polymer on the surface of the positive electrode active material particles can reduce the water content in the electrolyte obtained by the positive electrode active material particles by reducing the contact between the positive electrode active material particles and the electrolyte, reducing the occurrence of side reactions, which is beneficial to the cycle performance.

[0208] In some optional embodiments, based on the total weight of the positive electrode active material film layer, the positive electrode active material film layer includes: 85%-98.7% of positive electrode active material particles, optionally 91.5%-98.3%. Positive electrode active material particles having the above mass content can increase the total capacity of the battery, allowing the battery to store more electrical energy and extend the battery life.

[0209] In some optional embodiments, based on the total weight of the positive electrode active material film layer, the positive electrode active material film layer includes 0.7% to 6% of a polymer or 0.7% to 6% of a binder, optionally 1% to 2.5%; or 1% to 2.5% of a polymer or a binder. When the positive electrode active material film layer has the above polymer or binder, the positive electrode active material film layer has a certain cohesive strength, which can improve the flexibility of the positive electrode active material film layer and reduce the probability of fracture or cracking of the positive electrode active material film layer when it is wound or folded.

[0210] In some optional embodiments, the positive electrode active material film layer further includes a conductive agent. In some optional embodiments, based on the total weight of the positive electrode active material film layer, the positive electrode active material film layer includes: 0.4% to 10% of the conductive agent, optionally 0.7% to 5%. The internal resistance of the positive electrode plate can be reduced and the charge and discharge efficiency can be improved.

[0211] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0212] The positive electrode active material film layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material for a battery cell known in the art.

[0213] In some embodiments, the positive electrode active material film layer may further include a positive electrode conductive agent. The present application has no particular restrictions on the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0214] In some embodiments, the positive electrode active material film layer may further optionally include a positive electrode binder. The present application has no particular restrictions on the type of positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0215] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0216] The positive electrode active material film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0217] In some embodiments, the method for preparing the positive electrode active material film layer includes:

[0218] Providing a slurry containing a binder, a positive electrode active material, and a conductive agent;

[0219] The slurry is coated and dried to form a positive electrode active material film layer. In some embodiments, when the solid content of the slurry is ≥75%, the leveling property of the slurry disappears and the slurry can be rolled into a film by a roller press; the increase in solid content can effectively reduce drying energy consumption and reduce production costs.

[0220] In some embodiments, based on the total mass of the positive electrode active material, the conductive agent, and the binder, the total amount of the binder added is preferably 1 to 2.5wt%, for example, 1wt%, 1.5wt%, 2wt%, 2.5wt%. If the amount of polymer or binder added is too low, too little binder cannot support the strength of the positive electrode active material film layer, and thus cannot meet the requirements of rolling and thinning. If the amount of binder added is too large, the positive electrode active material film layer will have a large viscosity, which will easily cause the film to stick during rolling, and it will be impossible to perform thinning and current collector composite.

[0221] Battery Cell

[0222] In a fourth aspect, the present invention provides a battery cell, comprising the positive electrode sheet of the third aspect. The battery cell of the present invention comprises the positive electrode sheet, which helps to extend the life and cycle performance of the battery.

[0223] The present application has no particular restrictions on the type of battery cells, for example, the battery cells may be lithium-ion batteries, sodium-ion batteries, etc. Optionally, lithium-ion batteries may be used.

[0224] In some embodiments, a battery cell includes a negative electrode sheet, a separator, and an electrolyte.

[0225] [Negative electrode]

[0226] The specific composition and structure of the negative electrode plate can be selected according to the type of battery cell, and the embodiments of the present application are not limited to this.

[0227] For example, when the battery cell is a lithium-ion battery cell or a sodium-ion battery cell, the negative electrode plate includes a negative electrode current collector and a negative electrode active material film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode active material film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0228] The negative electrode active material is a material that can extract and embed active ions (such as lithium ions, sodium ions, etc.), and the negative electrode active material can adopt materials known in the art. As an example, the negative electrode active material includes but is not limited to one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. Silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy materials. Tin-based materials may include one or more of elemental tin, tin oxide and tin alloy materials. The present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials may also be used.

[0229] In some embodiments, the negative electrode active material film layer may further optionally include a negative electrode conductive agent. The present application has no particular restrictions on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0230] In some embodiments, the negative electrode active material film layer may further optionally include a negative electrode binder. The present application has no particular restrictions on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0231] In some embodiments, the negative electrode active material film layer may further optionally include other additives. As an example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC-Na), a PTC thermistor material, and the like.

[0232] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0233] The negative electrode active material film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0234] The negative electrode plate does not exclude other additional functional layers besides the negative electrode active material film layer. For example, in some embodiments, the negative electrode plate of the present application may also include a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode plate of the present application may also include a protective layer covering the surface of the negative electrode active material film layer.

[0235] When the battery cell is a lithium metal battery cell, the negative electrode plate may not include negative electrode active materials capable of extracting and embedding active ions. For example, in some embodiments, the negative electrode plate may include a lithium plate or a lithium alloy plate; in other embodiments, the negative electrode plate includes a mesh or foam three-dimensional skeleton layer, such as foam copper (or copper alloy), foam nickel (or nickel alloy), copper (or copper alloy) mesh, nickel (or nickel alloy) mesh, etc.

[0236] When the battery cell is a sodium metal battery cell, the negative electrode plate may not include negative electrode active materials capable of extracting and embedding active ions. For example, in some embodiments, the negative electrode plate may include a sodium plate or a sodium alloy plate; in other embodiments, the negative electrode plate includes a mesh or foam three-dimensional skeleton layer, such as foam copper (or copper alloy), foam nickel (or nickel alloy), foam aluminum (or aluminum alloy), copper (or copper alloy) mesh, nickel (or nickel alloy) mesh, aluminum (or aluminum alloy) mesh, etc.

[0237] [Preparation method]

[0238] The preparation method of the battery of the present application is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying. After packaging, standing, forming, shaping and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0239] [Isolation film]

[0240] The separator is disposed between the positive electrode and the negative electrode, and mainly plays the role of preventing the positive and negative electrodes from short-circuiting. The present application has no particular restriction on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0241] In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.

[0242] [Electrolytes]

[0243] In some embodiments, the battery cell includes an electrolyte. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte).

[0244] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0245] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. For example, the electrolyte salt includes one or more selected from lithium salts for lithium ion batteries and sodium salts for sodium ion batteries. As an example, the lithium salt includes one or more selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2 F 2 ), lithium difluorobis(oxalate phosphate) (LiDFOP), lithium tetrafluorooxalate phosphate (LiTFOP). As an example, the sodium salt includes one or more selected from NaPF 6 、NaClO 4 、NaBCl 4 、NaSO 3 CF 3 、Na(CH 3 )C 6 H 4 SO 3 One or more of the .

[0246] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include one or more selected from 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), cyclopentane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0247] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature power performance.

[0248] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0249] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0250] The present application has no particular restrictions on the shape of the battery cell, which can be a flat body, a rectangular parallelepiped or other shapes. Figure 1 The battery cell 5 is a rectangular parallelepiped structure as an example.

[0251] In some embodiments, Figure 2 As shown, the outer packaging may include a shell 51 and a cover plate 53. It is characterized in that the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate together form a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 of the first aspect of the embodiment of the present application or the electrode assembly 52 prepared by the method according to the second aspect of the embodiment of the present application is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0252] The method for preparing the battery cell of the present application is well known, and the method at least includes the step of preparing the electrode assembly of the second aspect of the embodiment of the present application. In some embodiments, the electrode assembly can be placed in an outer package, injected with electrolyte after drying, and vacuum packaged, allowed to stand, formed, shaped, etc. to obtain a battery cell.

[0253] In a fifth aspect, an embodiment of the present application provides a battery, comprising the battery cell of the fourth aspect. The battery can be understood as a battery module or a battery pack.

[0254] In some embodiments of the present application, the battery cells according to the present application can be assembled into a battery module. The battery module can contain multiple battery cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0255] Optionally, the battery module may further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0256] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0257] Electrical devices

[0258] In a sixth aspect, an embodiment of the present application provides an electrical device comprising the battery of the fifth aspect.

[0259] A battery cell and an electrical device containing the positive electrode active material have at least the above advantages.

[0260] The battery cell or electrical device of the present application comprises the separator of the first aspect of the present application, and thus has at least the advantages of using the separator.

[0261] The battery cell can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0262] Figure 3 Schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module may be used.

[0263] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0264] Example

[0265] The following examples describe the disclosure of the present application in more detail, and these examples are only for illustrative purposes, as it is obvious to those skilled in the art that various modifications and variations are made within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0266] Example 1

[0267] This embodiment provides a method for preparing positive electrode active material particles, comprising the following steps:

[0268] (1) At 25°C, polymerized monomer acrylamide and positive electrode active material raw material particles LiFePO4 were mixed uniformly in a certain ratio and added to a reaction container, with the mass ratio controlled at 1.96 and 98.04; stirring was continued for 60 minutes; the solvent was tert-butyl alcohol, and the solid content of the slurry was 63%. The average particle size DV50 of the positive electrode active material raw material particles was 0.9 μm, and the specific surface area was 15.9 m 2 / g.

[0269] (2) Adding initiator to the reaction vessel, the total mass ratio (total mass of polymerizable monomer, positive electrode active material and initiator) is controlled at 0.1%, and stirring for 30 minutes;

[0270] (3) Pass nitrogen / argon for 30 min to remove oxygen from the reactor;

[0271] (4) The reaction vessel was placed under an ultraviolet lamp and irradiated at 25°C for 60 minutes with continuous stirring; the ultraviolet lamp used in the polymerization process was a high-pressure mercury lamp with a power of 1000W and a wavelength of 1200nm.

[0272] (5) Finally, the polymerized product was washed with anhydrous ethanol, dried at 60° C. for 2 h, and then crushed into a powdery solid, i.e., positive electrode active material particles.

[0273] Preparation of the battery:

[0274] Positive electrode sheet: The prepared positive electrode active material particles, the conductive agent is conductive carbon black, the binder is polyvinylidene fluoride PVDF, and N-methylpyrrolidone is added to prepare a slurry, wherein the mass ratio of the positive electrode active material particles, the conductive agent and the binder is 96:2:2. The solid content of the slurry is 63%. The slurry is stirred and coated on the Cu current collector and dried. Negative electrode sheet: A graphite negative electrode is used, the conductive agent is conductive carbon black; the binder is a mixture of styrene-butadiene rubber and sodium carboxymethyl cellulose in a ratio of 1:1. The ratio of graphite material: conductive carbon black: binder = 96:2:2. Electrolyte: 1M LiPF 6 The solvent is ethylene carbonate (EC) and ethyl methyl carbonate (EMC), wherein EC / DEC (volume ratio 3:7).

[0275] Isolation membrane: Use polyethylene membrane with a thickness of 7um.

[0276] Battery assembly: stack the above-mentioned positive electrode sheet, isolation film, and negative electrode sheet in order, so that the isolation film is between the positive and negative electrode sheets to play an isolating role, and then wind them to obtain a bare battery cell; place the bare battery cell in an outer packaging aluminum shell, dry it at a temperature of 85°C until the water content of the bare battery cell is less than 300ppm, and then inject electrolyte at an injection coefficient of 3.5g / Ah, and obtain a battery after vacuum packaging, standing, forming, shaping and other processes.

[0277] Example 2-1 to Example 2-5

[0278] The difference between this embodiment and embodiment 1 is that the mass ratio of the polymerized monomer to the positive electrode active material is different, and the coating layer thickness and the type and content of the polymer are different, as shown in Table 1.

[0279] Example 3-1 to Example 3-4

[0280] The difference between this embodiment and embodiment 1 is that the types of solvent and initiator are different, as shown in Table 1.

[0281] Example 4-1 to Example 4-3

[0282] The difference between this embodiment and embodiment 1 is that the type and particle size of the positive electrode active material particles are different, as shown in Table 1.

[0283] Comparative Example 1

[0284] The difference between this comparative example and Example 1 is that the positive electrode active material raw material particles in Example 1 are used as positive electrode active material particles.

[0285] Test Section

[0286] The positive electrode active material particles obtained in the examples and comparative examples were tested.

[0287] (1) Detection of water content of positive electrode active material particles: The Karl Fischer method is used to measure the water content. The following are the detailed test steps:

[0288] Prepare reagents and equipment: First, you need to prepare Karl Fischer reagent, which is a special titrant usually composed of iodine, sodium thiosulfate, and ascorbic acid. In addition, you will need an accurate burette and a constant temperature water bath.

[0289] Add Karl Fischer reagent to the sample and then place it in a 70℃ constant temperature water bath to ensure that the temperature is within the specified range. During the titration process, the color change of the solution needs to be closely observed. When the color of the test paper changes from blue to colorless or light yellow, it is generally considered that the titration is over and the water has been completely consumed.

[0290] Calculate the water content: According to the principle of Karl Fischer method, the water content in the sample can be calculated by calculating the required volume of Karl Fischer reagent and the titration time.

[0291] In Karl Fischer titration, the formula for calculating water content is as follows:

[0292] C1*V1=C2*V2

[0293] Wherein, C1 is the initial Karl Fischer reagent concentration, V1 is the initial Karl Fischer reagent volume, C2 is the final Karl Fischer reagent concentration, and V2 is the final Karl Fischer reagent volume.

[0294] By using this formula, the mass percentage of water content in the sample can be calculated. The concentration and volume of the initial Karl Fischer reagent can be calculated from the concentration and volume of the prepared reagent. Then the final concentration and volume of the Karl Fischer reagent are measured by titration experiment. Finally, the mass percentage of water content in the sample is calculated by the formula.

[0295] (2) Detection of water content of positive electrode active material particles after storage: The positive electrode active material particles were placed in an air environment at a temperature of 25 degrees Celsius and a humidity of 20%. After storage for 30 days, the water content of the positive electrode active material particles was detected using the above method.

[0296] (3) Detection of polymer types: Mass spectrometry: The molecular weight of the molecule can be determined by ionizing the polymer molecules and measuring their mass. First, the sample to be tested needs to be nitrolyzed and prepared into an appropriate solution. Ionization: Under the action of the electric field, the molecules in the sample solution will be ionized into charged ions. Mass analysis: The ionized ions will be sent to the mass spectrometer for mass analysis. In the mass spectrometer, the ions will be focused in a small area, and then the mass of the ions can be calculated by measuring the mass and velocity of the ions. Data processing: The ion mass data measured by the mass spectrometer can be processed and analyzed by a computer. For example, by searching the mass-abundance spectrum (Mass-to-Charge Ratio vs. Intensity Plot), the mass of various molecules in the sample can be determined. Result analysis: Based on the mass spectrometry data, the composition and structure of the sample can be analyzed. For example, the molecular weight and relative content of various molecules in the sample can be determined.

[0297] (4) Battery drying time test: During the battery preparation process, in the assembly stage, the bare battery cell is placed in an outer aluminum shell and dried at a temperature of 85°C until the water content of the bare battery cell is less than 300 ppm. The drying time is recorded.

[0298] (5) Battery cycle life test: The secondary battery cells in the above-mentioned embodiments and comparative examples were tested respectively. The prepared battery was charged at 0.04C to 30% residual capacity (SOC) to complete the formation treatment; the charge and discharge capacity of the first charging battery was recorded, and then the cycle test was performed by charging at 0.33C to 4.0V and discharging at 0.33C to 2.0V, and the number of cycles when the battery capacity decayed to 80% was recorded, that is, the cycle life.

[0299] The properties of the positive electrode active material particles are shown in Table 1.

[0300] From the test results in Table 1, it can be seen that after the positive electrode active material raw material particles in the embodiment are coated with the polymer coating layer, their water content is significantly lower than that of the comparative example 1 after being stored for 30; after the positive electrode active materials of the embodiment and the comparative example are prepared into battery cells, the drying time of the embodiment is significantly lower than that of the comparative example at a temperature of 85°C until the water content of the bare battery cell is less than 300ppm, which shows that the positive electrode active material particles prepared in the embodiment of the present application have low water content, saving the time for preparing the battery. And the number of cycles when the battery cell capacity of the battery in the embodiment decays to 80% is significantly higher than that of the comparative example, which improves the stability of the positive electrode active material particles and also improves the service life of the battery.

[0301] Studies have shown that the fast charge and discharge efficiency of the positive electrode active material particles of the embodiment and the comparative example in the battery is at a comparable level, and the coating layer does not significantly reduce the charge and discharge efficiency of the battery.

[0302] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

[0303]

[0304]

Claims

1. A positive electrode active material particle, It is characterized in that The positive electrode active material particles have a polymer coating layer, wherein the polymer in the polymer coating layer includes a structural unit represented by formula (1); Among them, R 1 , R 2、 R 3、 R 4 Each independently includes -H, -COOH, -COOR 5 、-CONH 2 ,-CONHR 5 , -R 6 COOR 5 , -R 6 CONH 2 、-COR 5 , -R 6 COR 5 , -R 5 , -R 6 CONHR 5 Any of the following: Among them, R 1 , R 2、 R 3、 R 4 At least one group contains -CONH 2 , -R 6 CONH 2 ,-CONHR 5 , -R 6 CONHR 5 Any of the following: R 5 independently including unsubstituted C 1 -C 4 Straight or branched alkyl, C 2 -C 4 Straight-chain or branched alkenyl alkyl; R 6 independently including unsubstituted C 1 -C 4 Straight or branched chain alkylene, C 2 -C 4 Straight-chain or branched alkenylalkylene.

2. The positive electrode active material particle according to claim 1, It is characterized in that The water content of the positive electrode active material particles is less than 300 ppm, and can be selected to be 10 ppm to 200 ppm.

3. The positive electrode active material particle according to claim 1 or 2, It is characterized in that The positive electrode active material particles satisfy at least one of the following conditions: 1) The positive electrode active material particles include metal oxide materials, one or more of the positive electrode active material particles; optionally, the metal oxide material includes one or more of layered metal oxide materials, olivine positive electrode active material particles and spinel materials; optionally, the olivine positive electrode active material particles include lithium iron phosphate materials; 2) The average particle size Dv of the positive electrode active material particles 1 50 is 0.52μm~4.1μm, and can be selected as 1μm~1.8μm; 3) The specific surface area of ​​the positive electrode active material particles is 7 m 2 / g~15m 2 / g, optional 10m 2 / g~13m 2 / g; 4) The average thickness of the polymer coating layer is 10nm to 1000nm; 5) The positive electrode active material particles include 0.1% to 5% of the polymer coating layer based on the total mass of the positive electrode active material particles.

4. The positive electrode active material particle according to any one of claims 1 to 3, in, The weight average molecular weight of the polymer is 100,000 to 3,000,000, and can be optionally 500,000 to 1,500,000.

5. The positive electrode active material particle according to any one of claims 1 to 4, It is characterized in that The glass transition temperature of the polymer is 120° C. to 170° C., and can be 125° C. to 150° C.; and / or, The crystallinity of the polymer is 60% to 85%, and can be 65-75%.

6. The positive electrode active material particle according to any one of claims 1 to 5, It is characterized in that R 1 , R 2、 R 3、 R 4 Each independently includes H, -COOH, -COOR 5 、-CONH 2 ,-CONHR 5 , -R 6 COOR 5 , -R 6 CONH 2 、-COR 5 , -R 6 COR 5 , -R 5 , -R 6 CONHR 5 Any of the following: R 5 independently including unsubstituted C 1 ~C 3 Straight or branched alkyl, C 2 ~C 3 Straight-chain or branched alkenyl alkyl; R 6 independently including unsubstituted C 1 ~C 3 Straight or branched chain alkylene, C 2 ~C 3 Straight-chain or branched alkenylalkylene.

7. The positive electrode active material particle according to any one of claims 1 to 6, It is characterized in that The polymer includes at least one of (Formula I-1) to (Formula I-9): Wherein, n is a positive integer.

8. A method for preparing positive electrode active material particles having a polymer coating layer, It is characterized in that The method comprises: A mixture comprising positive electrode active material raw material particles, a polymerizable monomer and a solvent is provided, wherein the mass ratio of the polymerizable monomer to the positive electrode active material raw material particles is (0.1-5):100, wherein the polymerizable monomer has a structural formula of formula (1a): Among them, R 1 , R 2、 R 3、 R 4 Each independently includes -H, -COOR 5 , -COOH, -CONH 2 ,-CONHR 5 , -R 6 COOR 5 , -R 6 CONH 2 、-COR 5 , -R 6 COR 5 , -R 5 , -R 6 CONHR 5 Any of the following: Among them, R 1 , R 2、 R 3、 R 4 At least one group contains -CONH 2 , -R 6 CONH 2 ,-CONHR 5 , -R 6 CONHR 5 Any of the following; R 5 independently including unsubstituted C 1 -C 4 Straight or branched alkyl, C 2 -C 4 Straight-chain or branched alkenyl alkyl; R 6 independently including unsubstituted C 1 -C 4 Straight or branched chain alkylene, C 2 -C 4 Straight-chain or branched alkenylalkylene; The polymerizable monomer is polymerized to form a polymer coating layer coating the positive electrode active material raw material particles.

9. The preparation method according to claim 8, It is characterized in that The initiator includes a photoinitiator; optionally, the initiator includes one or more of an azo compound, an organic sulfide, and a pigment substance; Optionally, the azo compound includes one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate; Optionally, the organic sulfide includes one or more of mercaptans and alkyl disulfides; Optionally, the pigment substances include one or more of tetrabromofluorescein, tetrabromofluoramine, riboflavin, and anthocyanin.

10. The preparation method according to claim 8 or 9, It is characterized in that The polymerizable monomers include one or more of acrylic acid, acrylic ester, acrylamide, methacryloyl alkylene oxide, allyl ketone and acrolein.

11. The preparation method according to any one of claims 8 to 10, It is characterized in that The solvent includes one or more of water, tert-butanol, methanol, ethanol and n-butanol.

12. A positive electrode sheet, It is characterized in that The invention comprises a positive electrode current collector and a positive electrode active material film layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material film layer comprises the positive electrode active material particles according to any one of claims 1 to 7 or the positive electrode active material particles prepared by the preparation method according to any one of claims 8 to 11.

13. A battery cell, It is characterized in that Including the positive electrode sheet as described in claim 12.

14. A battery, It is characterized in that Comprising the battery cell according to claim 13.

15. An electrical device, It is characterized in that Comprising the battery of claim 14.

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