Secondary battery, battery module, battery pack, and electrical device

Abstract

The present application discloses a secondary battery, a battery module, a battery pack and an electrical device. The secondary battery includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The secondary battery further includes a functional layer located on at least one surface of the positive electrode sheet, the separator, and the negative electrode sheet. The functional layer includes hollow microspheres, and the hollow microspheres include a hollow cavity and a shell layer having a mesoporous structure. The shell layer includes a matrix and an organic group Y that is bonded to the outer surface of the matrix and the inner surface of the mesoporous structure and can complex transition metal ions. The present application can significantly improve the adsorption efficiency and adsorption capacity of transition metal ions, prevent the deposition of transition metals on the negative electrode, and significantly improve the cycle performance of the secondary battery.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and particularly relates to a secondary battery, a battery module, a battery pack, and an electrical device. Background Art

[0002] Secondary batteries rely on the reciprocating intercalation and deintercalation of active ions between the positive electrode and the negative electrode for charging and discharging. They have prominent characteristics such as high energy density, long cycle life, no pollution, and no memory effect. Therefore, as clean energy, secondary batteries have gradually spread from electronic products to energy storage power systems such as hydraulic, thermal, wind, and solar power stations, as well as multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace, to adapt to the sustainable development strategy of the environment and energy. However, during the charging and discharging process of secondary batteries, due to reasons such as the structural change of the positive electrode active material, transition metal ions in it are easily dissolved into the electrolyte and then deposited on the negative electrode, causing a series of side reactions, which leads to the continuous attenuation of the capacity of secondary batteries and deteriorates the cycle performance of secondary batteries. Summary of the Invention

[0003] The purpose of this application is to provide a secondary battery, a battery module, a battery pack, and an electrical device, aiming to significantly improve the adsorption efficiency and adsorption capacity of transition metal ions, prevent the deposition of transition metals on the negative electrode, and significantly improve the cycle performance of secondary batteries.

[0004] In a first aspect of this application, a secondary battery is provided, which includes a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate. The secondary battery further includes a functional layer, and the functional layer is located on at least one surface of the positive electrode plate, the separator, and the negative electrode plate. The functional layer includes hollow microspheres, and the hollow microspheres include a hollow cavity and a shell layer with a mesoporous structure. The shell layer includes a matrix and an organic group Y that binds to the outer surface of the matrix and the inner surface of the mesoporous structure and can complex with transition metal ions.

[0005] The functional layer of this application has a significantly improved adsorption efficiency and adsorption capacity of transition metal ions, can effectively prevent the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material, and effectively reduce the side reactions caused thereby. Therefore, the secondary battery of this application has a significantly improved cycle performance.

[0006] In any embodiment of the present application, the organic group Y has a lone pair of electrons. Since the organic group Y has a lone pair of electrons and the transition metal ion has an empty orbital, the organic group Y can better complex with the transition metal ions dissolved from the positive electrode active material, thereby improving the adsorption efficiency and adsorption capacity of the transition metal ions, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material, and effectively reducing the side reactions caused thereby.

[0007] In any embodiment of the present application, the organic group Y includes one or more of the following functional groups: -NH2, -SH, -OH, -COOH, -H2PO4, epoxyethyl group, -O-, -S-, -NR-, -NH-, -HPO4-, -CONH-, and acyloxy group, where R represents a C1-C6 alkyl group or -NH2. The organic group Y includes one or more of oxygen atoms, sulfur atoms, nitrogen atoms, and phosphorus atoms having a lone pair of electrons, so it can better complex with the transition metal ions dissolved from the positive electrode active material, thereby improving the adsorption efficiency and adsorption capacity of the transition metal ions, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material, and effectively reducing the side reactions caused thereby.

[0008] In any embodiment of the present application, the organic group Y includes -R 11 -O-R 21 、-R 12 -S-R 22 、-R 13 -NR-R 23 、-R 14 -NH-R 24 、-R 15 -HPO4-R 25 、-R 16 -CONH-R 26 、-R 17 -O-CO-R 27 、-R 31 -R 41 、-R 51 -O-R 61 -R 71 、-R 52 -S-R 62 -R 72 、-R 53 -NR-R 63 -R 73 、-R 54 -NH-R 64 -R 74 、-R 55 -HPO4-R 65 -R 75 、-R56 -CONH-R 66 -R 76 ,-R 57 -O-CO-R 67 -R 77 one or more of them, wherein, R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 each independently represents a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 31 represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 41 represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group, R 51 , R 52 , R 53 , R 54 , R 55 , R 56 , R 57 each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 61 , R 62 , R 63 , R 64 , R 65 , R 66 , R 67 each independently represents a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 71 , R 72 , R 73 , R 74 , R 75 , R 76 , R 77 each independently represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group.

[0009] In any embodiment of the present application, the number of carbon atoms of the organic group Y ≤ 10. Optionally, the number of carbon atoms of the organic group Y is 3-10. When the molecular chain of the organic group Y is within a suitable range, the adsorption effect of the shell mesoporous structure on transition metal ions can be fully exerted.

[0010] In any embodiment of the present application, the matrix is selected from inorganic oxides. Optionally, the matrix is selected from silica or alumina.

[0011] In any embodiment of the present application, the specific surface area of the hollow microspheres is 10 m 2 / g to 100 m 2 / g. When the specific surface area of the hollow microspheres is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the negative electrode plate and the surface of the negative electrode active material and effectively reducing the side reactions caused thereby, while significantly improving the cycle performance of the secondary battery.

[0012] In any embodiment of the present application, the volume average particle size Dv50 of the hollow microspheres is 80 nm to 5000 nm. Optionally, the volume average particle size Dv50 of the hollow microspheres is 200 nm to 5000 nm. When the Dv50 of the hollow microspheres is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the negative electrode plate and the surface of the negative electrode active material and effectively reducing the side reactions caused thereby, while significantly improving the cycle performance of the secondary battery.

[0013] In any embodiment of the present application, the radius of the hollow microspheres is R, the radius of the hollow cavity is r, and the ratio r / R of r to R is 0.70 to 0.95. Optionally, r / R is 0.75 to 0.90. When r / R is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the negative electrode plate and the surface of the negative electrode active material and effectively reducing the side reactions caused thereby.

[0014] In any embodiment of the present application, the thickness of the functional layer is 3 μm to 20 μm. When the thickness of the functional layer is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the negative electrode plate and the surface of the negative electrode active material and effectively reducing the side reactions caused thereby, thereby significantly improving the cycle performance of the secondary battery without affecting the kinetic performance of the secondary battery.

[0015] In any embodiment of the present application, the mesopore size of the shell layer is 5 nm to 50 nm. The shell layer has a mesopore size of 5 nm to 50 nm. On the one hand, the adsorption effect of the mesopore structure of the shell layer on the transition metal ions can be fully exerted, and on the other hand, the hollow microspheres can have an appropriate specific surface area, thereby effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the negative electrode plate and the surface of the negative electrode active material and effectively reducing the side reactions caused thereby.

[0016] In any embodiment of the present application, the functional layer further includes one or more of a conductive agent and a binder. The conductive agent can improve the electrical conductivity of the functional layer and increase the diffusion rate of active ions in the functional layer; the binder can bond the hollow microspheres and the conductive agent together to prevent powder shedding.

[0017] In any embodiment of the present application, based on the total mass of the functional layer, the mass percentage content of the hollow microspheres is 80% to 99%. Optionally, the mass percentage content of the hollow microspheres is 85% to 95%. The smaller the mass percentage content of the hollow microspheres, the worse the adsorption of the transition metal ions dissolved from the positive electrode active material, and most of the transition metal ions will still diffuse and deposit on the surface of the negative electrode plate and the negative electrode active material. Therefore, the improvement effect on the cycle performance of the secondary battery is limited; the higher the mass percentage content of the hollow microspheres, the better the adsorption of the transition metal ions dissolved from the positive electrode active material, which can effectively prevent the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material and effectively reduce the side reactions caused thereby, and the better the improvement effect on the cycle performance of the secondary battery.

[0018] In any embodiment of the present application, the coating surface density of the functional layer is 2 g / m 2 ~15 g / m 2 . When the coating surface density of the functional layer is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material and effectively reducing the side reactions caused thereby, so as to significantly improve the cycle performance of the secondary battery without affecting the kinetic performance of the secondary battery.

[0019] The second aspect of the present application provides a battery module, which includes the secondary battery of the first aspect of the present application.

[0020] The third aspect of the present application provides a battery pack, which includes the battery module of the second aspect of the present application.

[0021] The fourth aspect of the present application provides an electrical device, which includes at least one of the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, and the battery pack of the third aspect of the present application.

[0022] The secondary battery of the present application has a functional layer, in which the shell layer of the hollow microspheres has a large number of mesoporous structures. Thus, the functional layer of the present application has the characteristic of a high specific surface area and can efficiently adsorb transition metal ions dissolved from the positive electrode active material. An organic group Y capable of complexing with transition metal ions is also bonded to the outer surface of the hollow microspheres and the inner surface of the mesoporous structures in the shell layer of the hollow microspheres. It can adsorb the transition metal ions on the outer surface of the hollow microspheres and the inner surface of the mesoporous structures in the shell layer, thereby further improving the adsorption efficiency and adsorption capacity of the transition metal ions. Therefore, the functional layer of the present application has a significantly improved adsorption efficiency and adsorption capacity for transition metal ions, can effectively prevent the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode sheet and the negative electrode active material, and can effectively reduce the side reactions caused thereby. Thus, the secondary battery of the present application has significantly improved cycle performance.

[0023] The shell layer of the hollow microspheres in the functional layer of the present application has a large number of mesoporous structures. Thus, the functional layer of the present application also has the characteristic of a high porosity and does not hinder the extraction and insertion of active ions between the positive and negative electrodes of the secondary battery. Therefore, the functional layer of the present application can also significantly improve the cycle performance of the secondary battery without affecting other electrochemical performances of the secondary battery.

[0024] The battery module, battery pack, and electrical device of the present application include the secondary battery provided by the present application, and thus at least have the same advantages as the secondary battery. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the drawings without creative efforts.

[0026] Figure 1 It is a schematic diagram of an embodiment of the secondary battery of the present application.

[0027] Figure 2 is Figure 1 An exploded schematic diagram of the embodiment of the secondary battery shown.

[0028] Figure 3 It is a schematic diagram of an embodiment of the battery module of the present application.

[0029] Figure 4 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0030] Figure 5 is Figure 4 An exploded schematic diagram of the embodiment of the battery pack shown.

[0031] Figure 6 It is a schematic diagram of an embodiment of an electrical device using the secondary battery of the present application as a power source.

[0032] Figure 7 It is a scanning electron microscope (SEM) image of the hollow silica microspheres prepared in Example 1.

[0033] Figure 8 It is Figure 7 a partial enlarged view.

[0034] Figure 9 It is an infrared absorption spectrum of the hollow microspheres prepared in Example 1.

[0035] Figure 10 It is a scanning electron microscope (SEM) image of the cross-section of the functional layer prepared in Example 1.

[0036] Figure 11 and Figure 12 It is Figure 10 an enlarged view of the functional layer shown at different magnifications.

[0037] In the drawings, the drawings are not necessarily drawn to actual scale. Among them, the reference numerals are explained as follows:

[0038] 1 Battery pack, 2 Upper box body, 3 Lower box body, 4 Battery module, 5 Secondary battery, 51 Housing, 52 Electrode assembly, 53 Cover plate. Detailed implementation manners

[0039] Hereinafter, embodiments of the secondary battery, battery module, battery pack, and electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to 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 description 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.

[0040] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0042] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0043] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0044] If there is no special instruction, the "including" and "comprising" mentioned in this application mean open-ended or can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can also mean only including or comprising the listed components.

[0045] Unless otherwise specified, the term "or" is inclusive in this application. 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 present) and B is false (or absent); A is false (or absent) while B is true (or present); or both A and B are true (or present).

[0046] In this application, the term "hollow microsphere" refers to a class of spherical or quasi-spherical materials with a special core-shell structure. The difference from traditional core-shell structure materials is that the hollow microspheres in this application have a hollow core layer, that is, a hollow cavity. The term "quasi-spherical" means that the shape of the material is basically spherical, or the aspect ratio of the material is close to 1, for example, not greater than 1.3, optionally not greater than 1.2.

[0047] In this application, the term "alkyl" includes not only straight-chain alkyls but also branched-chain alkyls, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl and other similar alkyls. In various embodiments, C1-C6 alkyl, i.e., the alkyl can contain 1-6 carbon atoms.

[0048] In this application, the term "alkenyl" includes not only straight-chain alkenyls but also branched-chain alkenyls. The number of carbon-carbon double bonds in the alkenyl can be one or more, such as vinyl, n-propenyl, isopropenyl, 2-butenyl, 3-butenyl and other similar alkenyls. In various embodiments, C2-C6 alkenyl, i.e., the alkenyl can contain 2-6 carbon atoms.

[0049] Throughout this specification, the substituents of compounds are disclosed in groups or ranges. It is expressly contemplated that such description includes every individual sub-combination of the members of these groups and ranges. For example, it is expressly contemplated that the term "C1-C6 alkyl" discloses C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5, C5-C6 alkyls individually.

[0050] A secondary battery, also known as a rechargeable battery or storage battery, refers to a battery that can be reused by activating the active materials through charging after discharging. Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During the charge and discharge process of the secondary battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time allowing active ions to pass through. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. Currently, secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. In order to better adapt to the environmental and energy sustainable development strategies, secondary batteries need to meet the requirements of high energy density, high power density, high overall reliability, wide operating temperature range, strong environmental adaptability, and excellent cycle performance and storage performance.

[0051] Most of the positive electrode active materials used in secondary batteries include transition metal elements. For example, Fe, Mn, etc. After multiple charge and discharge cycles of the secondary battery, due to reasons such as the intrinsic structural defects of the positive electrode active materials, the repeated extraction and insertion of active ions, the introduction of soluble transition metal impurities during the synthesis process, and the erosion of acidic substances in the electrolyte, the transition metal ions in the positive electrode active materials are likely to dissolve into the electrolyte. Subsequently, under the driving force of the electric field, the dissolved transition metal ions will pass through the separator, diffuse through the electrolyte to the negative electrode, and undergo an electrochemical reaction to deposit on the surface of the negative electrode plate and the negative electrode active materials.

[0052] The transition metals deposited on the surface of the negative electrode plate and the negative electrode active materials will hinder the extraction and insertion of active ions, exacerbating the capacity decay of the secondary battery. The transition metals deposited on the surface of the negative electrode plate and the negative electrode active materials also have a significant destructive effect on the solid electrolyte interface (SEI) film on the surface of the negative electrode active materials, resulting in continuous damage and repair of the SEI film, further exacerbating the consumption of active ions and the capacity decay of the secondary battery. The transition metals deposited on the surface of the negative electrode plate and the negative electrode active materials will also increase the negative electrode impedance, further exacerbating the capacity decay of the secondary battery. In addition, when the secondary battery is in a high-temperature environment, the dissolution rate of transition metal ions will further accelerate, and the capacity decay of the secondary battery will also accelerate further, resulting in a significant reduction in the service life of the secondary battery.

[0053] To reduce the impact of transition metal ion dissolution on the performance of secondary batteries, current researchers mainly make improvements in the following directions: preparing electrolytes with the function of capturing transition metal ions; adding conductive carbon to the positive electrode paste, and using the high specific surface area of the conductive carbon to bind transition metal ions to prevent the dissolution of transition metal ions; optimizing the surface characteristics of the negative electrode active material to form a SEI film with high mechanical strength, high chemical stability and high thermal stability on the surface of the negative electrode active material; optimizing the structure of the secondary battery to slow down the rise of the internal temperature of the secondary battery and reduce the dissolution rate of transition metal ions, etc. The above solutions have all reduced the impact of transition metal ion dissolution on the performance of secondary batteries to a certain extent. However, the above solutions still have problems such as low adsorption efficiency of transition metal ions, easy deterioration of other electrochemical performances of secondary batteries (such as power performance, etc.), or easy occurrence of other adverse side reactions.

[0054] In view of the above problems, the inventors of the present application have improved the structure of the secondary battery and proposed a secondary battery that not only has a significantly improved adsorption efficiency and adsorption capacity of transition metal ions but also has a significantly improved cycle performance.

[0055] The first aspect of the embodiment of the present application provides a secondary battery. The secondary battery includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The secondary battery further includes a functional layer located on at least one surface of the positive electrode sheet, the separator, and the negative electrode sheet. The functional layer includes hollow microspheres, and the hollow microspheres include a hollow cavity and a shell layer with a mesoporous structure. The shell layer includes a matrix and an organic group Y that binds to the outer surface of the matrix and the inner surface of the mesoporous structure and can complex with transition metal ions.

[0056] The secondary battery of the present application has a functional layer. The shell layer of the hollow microspheres in it has a large number of mesoporous structures. Therefore, the functional layer of the present application has the characteristic of a high specific surface area and can efficiently adsorb the transition metal ions dissolved from the positive electrode active material. The outer surface of the hollow microspheres and the inner surface of the mesoporous structure in the shell layer of the hollow microspheres are also combined with an organic group Y that can complex with transition metal ions, which can adsorb the transition metal ions on the outer surface of the hollow microspheres and the inner surface of the mesoporous structure of the shell layer, thereby further improving the adsorption efficiency and adsorption capacity of transition metal ions. Therefore, the functional layer of the present application has a significantly improved adsorption efficiency and adsorption capacity of transition metal ions, can effectively prevent the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode sheet and the negative electrode active material, and can effectively reduce the side reactions caused thereby. Therefore, the secondary battery of the present application has a significantly improved cycle performance.

[0057] The hollow microsphere shell layer in the functional layer of the present application has a large number of mesoporous structures, so the functional layer of the present application also has the characteristic of high porosity and does not prevent the extraction and insertion of active ions between the positive and negative electrodes of the secondary battery. Therefore, the functional layer of the present application can significantly improve the cycle performance of the secondary battery without affecting other electrochemical performances of the secondary battery, such as power performance, kinetic performance, etc.

[0058] The functional layer of the present application can utilize the high surface area of the hollow microspheres and the organic group Y bonded to the outer surface of the hollow microspheres and the inner surface of the mesoporous structures in the hollow microsphere shell layer to efficiently adsorb various transition metal ions dissolved from the positive electrode active material, such as Fe 2+ 、Fe 3+ 、Mn 2+ etc. Therefore, there is no particular limitation on the type of secondary battery in the present application. For example, the secondary battery can be a lithium-ion battery, a sodium-ion battery, etc.

[0059] In the secondary battery of the present application, the functional layer is located on at least one surface of the positive electrode sheet, the separator, and the negative electrode sheet. The positive electrode sheet has two surfaces opposite to each other in its own thickness direction, the negative electrode sheet has two surfaces opposite to each other in its own thickness direction, and the separator has two surfaces opposite to each other in its own thickness direction. Therefore, the functional layer can be located on at least one of the above 6 surfaces. For example, the functional layer is located on one or two surfaces of the positive electrode sheet, or the functional layer is located on one or two surfaces of the negative electrode sheet, or the functional layer is located on one or two surfaces of the separator, or the functional layer is simultaneously located on at least two of the positive electrode sheet, the negative electrode sheet, and the separator. Optionally, in some embodiments, the functional layer is located on one or two surfaces of the positive electrode sheet, or the functional layer is located on one or two surfaces of the separator, or the functional layer is simultaneously located on the positive electrode sheet and the separator. At this time, the adsorption effect of the functional layer on the transition metal ions dissolved from the positive electrode active material can be better exerted.

[0060] In some embodiments, the organic group Y has a lone pair of electrons. The organic group Y has a lone pair of electrons, and transition metal ions (such as Fe 2+ 、Fe 3+ 、Mn 2+ etc.) have empty orbitals. Therefore, the organic group Y can better complex with the transition metal ions dissolved from the positive electrode active material, thereby improving the adsorption efficiency and adsorption capacity of the transition metal ions, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode sheet and the negative electrode active material, and effectively reducing the side reactions caused thereby.

[0061] In some embodiments, the organic group Y has one or more of the following functional groups: -NH2, -SH, -OH, -COOH, -H2PO4, epoxyethyl group, -O-, -S-, -NR-, -NH-, -HPO4-, -CONH-, and acyloxy group (-O-CO-), where R represents a C1-C6 alkyl group or -NH2. The organic group Y includes one or more of oxygen atoms, sulfur atoms, nitrogen atoms, and phosphorus atoms having lone pairs of electrons, and thus can better complex with transition metal ions dissolved from the cathode active material, thereby improving the adsorption efficiency and adsorption capacity of the transition metal ions, effectively preventing the transition metal ions dissolved from the cathode active material from depositing on the surface of the anode electrode sheet and the anode active material, and effectively reducing the side reactions caused thereby.

[0062] As an example, the organic group Y includes -R 11 -O-R 21 , -R 12 -S-R 22 , -R 13 -NR-R 23 , -R 14 -NH-R 24 , -R 15 -HPO4-R 25 , -R 16 -CONH-R 26 , -R 17 -O-CO-R 27 , -R 31 -R 41 , -R 51 -O-R 61 -R 71 , -R 52 -S-R 62 -R 72 , -R 53 -NR-R 63 -R 73 , -R 54 -NH-R 64 -R 74 , -R 55 -HPO4-R 65 -R 75 , -R 56 -CONH-R 66 -R 76 , -R 57 -O-CO-R 67 -R 77 one or more of, where R 11 , R 12 , R 13 , R 14 , R 15, R 16 , R 17 Each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 Each independently represents a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 31 represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 41 represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group, R 51 , R 52 , R 53 , R 54 , R 55 , R 56 , R 57 Each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 61 , R 62 , R 63 , R 64 , R 65 , R 66 , R 67 Each independently represents a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 71 , R 72 , R 73 , R 74 , R 75 , R 76 , R 77 Each independently represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group.

[0063] In some embodiments, the number of carbon atoms of the organic group Y ≤ 10. Optionally, the number of carbon atoms of the organic group Y is 1-10, 2-10, 3-10, 4-10, 2-9, 3-9, 4-9, 2-8, 3-8, 4-8, 2-7, 3-7, or 4-7. When the molecular chain of the organic group Y is too long, it may affect the adsorption effect of the shell mesoporous structure on transition metal ions. When the molecular chain of the organic group Y is within a suitable range, the adsorption effect of the shell mesoporous structure on transition metal ions can be fully exerted.

[0064] In some embodiments, the matrix is selected from inorganic oxides. The present application does not particularly limit the type of inorganic oxides, and can be selected according to actual needs. Optionally, the matrix is selected from silica, or alumina.

[0065] In some embodiments, the specific surface area of the hollow microspheres is 10 m 2 / g to 100 m 2 / g. Optionally, the specific surface area of the hollow microspheres is 10 m 2 / g to 90 m 2 / g, 10 m 2 / g to 80 m 2 / g, 10 m 2 / g to 70 m 2 / g, 10 m 2 / g to 60 m 2 / g, 10 m 2 / g to 50 m 2 / g, 10 m 2 / g to 40 m 2 / g, 20 m 2 / g to 100 m 2 / g, 20 m 2 / g to 90 m 2 / g, 20 m 2 / g to 80 m 2 / g, 20 m 2 / g to 70 m 2 / g, 20 m 2 / g to 60 m 2 / g, 20 m 2 / g to 50 m 2 / g, 20 m 2 / g to 40 m 2 / g, 30 m 2 / g to 100 m 2 / g, 30 m 2 / g to 90 m 2 / g, 30 m 2 / g to 80 m 2 / g, 30 m 2 / g to 70 m 2 / g, 30 m 2 / g to 60 m 2 / g, 30 m 2 / g to 50 m 2 / g, or 30 m 2 / g to 40 m 2 / g.

[0066] Under the condition that other conditions are the same, the larger the specific surface area of the hollow microspheres, the better the adsorption effect on the transition metal ions dissolved from the positive electrode active material. However, the specific surface area of the hollow microspheres should not be too large. When the specific surface area is too large, the surface energy is relatively high. At this time, the functional layer has too strong an adsorption ability for the electrolyte, which easily leads to a decrease in the electrolyte content in the electrode sheet, an increase in the resistance of the active ions to escape and embed in the active material particles, and a deterioration of the kinetic performance of the secondary battery. As a result, the cycle performance of the secondary battery may also deteriorate. Therefore, when the specific surface area of the hollow microspheres is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode sheet and the negative electrode active material and effectively reducing the side reactions caused thereby, while significantly improving the cycle performance of the secondary battery.

[0067] In some embodiments, the volume average particle size Dv50 of the hollow microspheres is 80 nm to 5000 nm. Optionally, the volume average particle size Dv50 of the hollow microspheres is 150 nm to 5000 nm, 200 nm to 5000 nm, 400 nm to 5000 nm, 600 nm to 5000 nm, 800 nm to 5000 nm, 1000 nm to 5000 nm, 1200 nm to 5000 nm, 150 nm to 4000 nm, 200 nm to 4000 nm, 400 nm to 4000 nm, 600 nm to 4000 nm, 800 nm to 4000 nm, 1000 nm to 4000 nm, 1200 nm to 4000 nm, 150 nm to 3000 nm, 200 nm to 3000 nm, 400 nm to 3000 nm, 600 nm to 3000 nm, 800 nm to 3000 nm, 1000 nm to 3000 nm, 1200 nm to 3000 nm, 150 nm to 2000 nm, 200 nm to 2000 nm, 400 nm to 2000 nm, 600 nm to 2000 nm, 800 nm to 2000 nm, 1000 nm to 2000 nm, or 1200 nm to 2000 nm.

[0068] Under the condition that other conditions are the same, the smaller the Dv50 of the hollow microspheres, the larger the corresponding specific surface area, and the better the adsorption effect on the transition metal ions dissolved from the positive electrode active material. However, when the Dv50 of the hollow microspheres is too small and the specific surface area is too large, the surface energy is also relatively high. At this time, the functional layer has too strong an adsorption ability for the electrolyte, which easily leads to a decrease in the electrolyte content in the electrode sheet, an increase in the resistance of the active ions to escape and embed in the active material particles, a deterioration in the kinetic performance of the secondary battery, an increase in battery polarization, an increase in irreversible consumption of active ions, and a decrease in reversible capacity. As a result, the cycle performance of the secondary battery may also deteriorate. Therefore, when the Dv50 of the hollow microspheres is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode sheet and the negative electrode active material and effectively reducing the side reactions caused thereby, while significantly improving the cycle performance of the secondary battery.

[0069] In some embodiments, the radius of the hollow microspheres is R, the radius of the hollow cavity is r, and the ratio r / R of r to R is 0.70 to 0.95. For example, r / R is 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95 or any range composed of the above values. Optionally, r / R is 0.75 to 0.95, 0.80 to 0.95, 0.85 to 0.95, 0.70 to 0.90, 0.75 to 0.90, 0.80 to 0.90, or 0.85 to 0.90.

[0070] The smaller the r / R, the smaller the cavity of the hollow microspheres, the thicker the shell layer, the smaller the specific surface area of the hollow microspheres, and the worse the adsorption effect on the transition metal ions dissolved from the positive electrode active material; the larger the r / R, the larger the cavity of the hollow microspheres, the thinner the shell layer, the larger the specific surface area of the hollow microspheres, and the better the adsorption effect on the transition metal ions dissolved from the positive electrode active material. However, r / R should not be too large either. At this time, the shell layer is too thin, and the total number of substrates that can adsorb transition metal ions per unit thickness decreases, affecting the adsorption effect of the mesoporous structure of the shell layer on the transition metal ions, thereby affecting the adsorption effect on the transition metal ions dissolved from the positive electrode active material. Therefore, when r / R is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode sheet and the negative electrode active material and effectively reducing the side reactions caused thereby.

[0071] In some embodiments, the thickness of the functional layer is 3 μm to 20 μm. Optionally, the thickness of the functional layer is 3 μm to 18 μm, 3 μm to 16 μm, 3 μm to 14 μm, 3 μm to 12 μm, 3 μm to 10 μm, 3 μm to 8 μm, 3 μm to 6 μm, 4 μm to 18 μm, 4 μm to 16 μm, 4 μm to 14 μm, 4 μm to 12 μm, 4 μm to 10 μm, 4 μm to 8 μm, 4 μm to 6 μm, 5 μm to 18 μm, 5 μm to 16 μm, 5 μm to 14 μm, 5 μm to 12 μm, 5 μm to 10 μm, 5 μm to 8 μm, 5 μm to 6 μm, 6 μm to 18 μm, 6 μm to 16 μm, 6 μm to 14 μm, 6 μm to 12 μm, 6 μm to 10 μm, or 6 μm to 8 μm.

[0072] The thinner the functional layer, the worse the adsorption of the transition metal ions dissolved from the positive electrode active material. Most of the transition metal ions will still diffuse and deposit on the surface of the negative electrode plate and the negative electrode active material. Therefore, the improvement effect on the cycle performance of the secondary battery is limited. The thicker the functional layer, the better the adsorption of the transition metal ions dissolved from the positive electrode active material, which can effectively prevent the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material and effectively reduce the side reactions caused thereby, and the better the improvement effect on the cycle performance of the secondary battery. However, the functional layer should not be too thick. An overly thick functional layer may hinder the diffusion of active ions between the positive and negative electrodes of the secondary battery and affect the kinetic performance of the secondary battery. Further, after the kinetic performance of the secondary battery deteriorates, the active ions are likely to be reduced and precipitated on the surface of the negative electrode active material, further exacerbating the consumption of the active ions and the capacity decay of the secondary battery. In addition, the metal simple substances (such as metallic lithium, etc.) reduced and precipitated on the surface of the negative electrode active material by the active ions also have strong activity and will react with the electrolyte to generate a large amount of HF. HF will damage the structure of the positive electrode active material and accelerate the dissolution of the transition metal ions, thereby possibly further deteriorating the cycle performance of the secondary battery. Therefore, when the thickness of the functional layer is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material and effectively reducing the side reactions caused thereby, so as to significantly improve the cycle performance of the secondary battery without affecting the kinetic performance of the secondary battery.

[0073] In some embodiments, the thickness of the shell layer is 10 nm to 1000 nm. Under the same conditions, the thicker the shell layer, the smaller the specific surface area of the hollow microspheres, and the worse the adsorption effect on the transition metal ions dissolved from the positive electrode active material; the thinner the shell layer, the larger the specific surface area of the hollow microspheres, and the better the adsorption effect on the transition metal ions dissolved from the positive electrode active material. However, the shell layer should not be too thin. At this time, the total number of substrates that can adsorb transition metal ions per unit thickness decreases, affecting the adsorption of transition metal ions by the mesoporous structure of the shell layer, and thus affecting the adsorption effect on the transition metal ions dissolved from the positive electrode active material. Therefore, when the thickness of the shell layer is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material and effectively reducing the side reactions caused thereby.

[0074] In some embodiments, the mesopore size of the shell layer is 5 nm to 50 nm. The shell layer has a mesopore size of 5 nm to 50 nm. On the one hand, it can fully exert the adsorption effect of the mesoporous structure of the shell layer on the transition metal ions. On the other hand, it can make the hollow microspheres have an appropriate specific surface area, thereby effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material and effectively reducing the side reactions caused thereby.

[0075] In some embodiments, the functional layer may further optionally include one or several of a binder and a conductive agent. The conductive agent can improve the conductivity of the functional layer and increase the diffusion rate of active ions in the functional layer; the binder can bond the hollow microspheres and the conductive agent together to prevent powder falling. As an example, the binder used for the functional layer may include one or several of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. As an example, the conductive agent used for the functional layer includes one or several of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0076] In some embodiments, based on the total mass of the functional layer, the mass percentage content of the hollow microspheres is 80% to 99%. Optionally, the mass percentage content of the hollow microspheres is 85% to 95%. The smaller the mass percentage content of the hollow microspheres, the worse the adsorption of the transition metal ions dissolved from the positive electrode active material, and most of the transition metal ions will still diffuse and deposit on the surface of the negative electrode plate and the negative electrode active material. Therefore, the improvement effect on the cycle performance of the secondary battery is limited; the higher the mass percentage content of the hollow microspheres, the better the adsorption of the transition metal ions dissolved from the positive electrode active material, which can effectively prevent the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode plate and the negative electrode active material and effectively reduce the side reactions caused thereby, and the better the improvement effect on the cycle performance of the secondary battery.

[0077] In some embodiments, the coating surface density of the functional layer is 2 g / m 2 ~15 g / m 2 . Optionally, the coating surface density of the functional layer is 2 g / m 2 ~14 g / m 2 ,2 g / m 2 ~13 g / m 2 ,2 g / m 2 ~12 g / m 2 ,2 g / m 2 ~11 g / m 2 ,2 g / m 2 ~10 g / m 2 ,4 g / m 2 ~15 g / m 2 ,4 g / m 2 ~14 g / m 2 ,4 g / m 2 ~13 g / m 2 ,4 g / m 2 ~14 g / m 2 ,4 g / m 2 ~11 g / m 2 ,4 g / m 2 ~10 g / m 2 ,6 g / m 2 ~15 g / m 2 ,6 g / m 2 ~16 g / m 2 ,6 g / m 2 ~13 g / m 2 ,6 g / m 2 ~16 g / m 2 ,6 g / m 2 ~11 g / m 2 ,or 6 g / m 2 ~10 g / m 2 。

[0078] Under the same conditions, the smaller the coating surface density of the functional layer, the thinner the functional layer, and the poorer the adsorption of the transition metal ions dissolved from the positive electrode active material. Most of the transition metal ions will still diffuse and deposit on the surface of the negative electrode sheet and the negative electrode active material, resulting in limited improvement in the cycle performance of the secondary battery. The larger the coating surface density of the functional layer, the thicker the functional layer, and the better the adsorption of the transition metal ions dissolved from the positive electrode active material. It can effectively prevent the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode sheet and the negative electrode active material and effectively reduce the side reactions caused thereby, and the better the improvement effect on the cycle performance of the secondary battery. However, the coating surface density of the functional layer should not be too large. Otherwise, the too thick functional layer may hinder the diffusion of active ions between the positive and negative electrodes of the secondary battery and affect the kinetic performance of the secondary battery. Further, after the kinetic performance of the secondary battery deteriorates, the active ions are easily reduced and precipitated on the surface of the negative electrode active material, further aggravating the consumption of the active ions and the capacity attenuation of the secondary battery. In addition, the metal simple substances (such as metallic lithium, etc.) reduced and precipitated on the surface of the negative electrode active material by the active ions also have strong activity and will react with the electrolyte to generate a large amount of HF. HF will damage the structure of the positive electrode active material and accelerate the dissolution of the transition metal ions, thereby possibly further deteriorating the cycle performance of the secondary battery. Therefore, when the coating surface density of the functional layer is within an appropriate range, the adsorption effect on the transition metal ions dissolved from the positive electrode active material can be fully exerted, effectively preventing the transition metal ions dissolved from the positive electrode active material from depositing on the surface of the negative electrode sheet and the negative electrode active material and effectively reducing the side reactions caused thereby, so as to significantly improve the cycle performance of the secondary battery without affecting the kinetic performance of the secondary battery.

[0079] In some embodiments, the secondary battery includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The secondary battery further includes a functional layer, and the functional layer is located on at least one surface of the positive electrode sheet, the separator, and the negative electrode sheet. The functional layer includes hollow microspheres, and the hollow microspheres include a hollow cavity and a shell layer having a mesoporous structure. The shell layer includes a matrix and an organic group Y combined on the outer surface of the matrix and the inner surface of the mesoporous structure and capable of complexing transition metal ions. The organic group Y has one or more of the following functional groups: -NH2, -SH, -OH, -COOH, -H2PO4, epoxyethyl group, -O-, -S-, -NR-, -NH-, -HPO4-, -CONH-, and acyloxy group (-O-CO-), R represents a C1-C6 alkyl group or -NH2, and the matrix is selected from silicon dioxide. The specific surface area of the hollow microspheres is 10m 2 / g~100m 2 / g, the volume average particle size Dv50 of the hollow microspheres is 200 nm to 5000 nm. The thickness of the functional layer is 3 μm to 20 μm.

[0080] In some embodiments, the secondary battery includes a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate. The secondary battery further includes a functional layer located on at least one surface of the positive electrode plate, the separator, and the negative electrode plate. The functional layer includes hollow microspheres, the hollow microspheres include a hollow cavity and a shell layer having a mesoporous structure, and the shell layer includes a matrix and an organic group Y that binds to the outer surface of the matrix and the inner surface of the mesoporous structure and can complex transition metal ions. The organic group Y includes -R 11 -O-R 21 、-R 12 -S-R 22 、-R 13 -NR-R 23 、-R 14 -NH-R 24 、-R 15 -HPO4-R 25 、-R 16 -CONH-R 26 、-R 17 -O-CO-R 27 、-R 31 -R 41 、-R 51 -O-R 61 -R 71 、-R 52 -S-R 62 -R 72 、-R 53 -NR-R 63 -R 73 、-R 54 -NH-R 64 -R 74 、-R 55 -HPO4-R 65 -R 75 、-R 56 -CONH-R 66 -R 76 、-R 57 -O-CO-R 67 -R 77 or one or more of them, where R 11 、R 12 、R 13 、R 14 、R 15 、R 16 、R 17Each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 、R 27 Each independently represents a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 31 represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 41 represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group, R 51 、R 52 、R 53 、R 54 、R 55 、R 56 、R 57 Each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 61 、R 62 、R 63 、R 64 、R 65 、R 66 、R 67 Each independently represents a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 71 、R 72 、R 73 、R 74 、R 75 、R 76 、R 77 Each independently represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group. The matrix is selected from silica. The specific surface area of the hollow microspheres is 10 m 2 / g to 100 m 2 / g, and the volume average particle size Dv50 of the hollow microspheres is 200 nm to 5000 nm. The thickness of the functional layer is 3 μm to 20 μm.

[0081] The functional layer can be prepared by methods known in the art. Generally, the coating slurry is coated on at least one surface of the positive electrode plate, the separator, and the negative electrode plate, and then vacuum dried. The coating slurry is usually formed by dispersing hollow microspheres, an optional binder, an optional conductive agent, etc. in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto. There is no particular limitation on the coating method of the coating slurry. For example, it can be dip coating, spin coating, blade coating, flow coating, unidirectional stretching coating, bidirectional stretching coating, etc. There is no particular limitation on the vacuum drying temperature of the coating slurry. For example, it can be vacuum dried at 50°C to 90°C.

[0082] The hollow microspheres can be prepared by methods known in the art, such as the template method, spray drying method, hydrothermal method, self-assembly method, etc. An exemplary preparation method is as follows: Prepare a mixed solvent of a certain volume from absolute ethanol and deionized water; add a templating agent to the mixed solvent and stir to dissolve the templating agent; slowly drop the hollow microsphere precursor into the above-mentioned mixed solvent and react for a period of time to obtain a precipitate; filter the precipitate, wash it thoroughly with deionized water and absolute ethanol alternately, and then place it in a vacuum oven for vacuum drying to obtain the hollow microspheres.

[0083] The hollow microspheres obtained by the above method have molecular sieve characteristics and are fully nano-sized and uniformly sized small spheres. When the hollow microspheres obtained by the above method are prepared into a coating slurry and coated on a substrate, such as coated on at least one surface of a positive electrode sheet, a separator, and a negative electrode sheet, these hollow microspheres can be completely spread out and form a dense coating, so that while completely covering the surface of the substrate, it also has a high porosity and does not hinder the diffusion of active ions. Therefore, it can improve the cycle performance of the secondary battery without affecting the kinetic performance of the secondary battery.

[0084] Among them, the mass ratio of absolute ethanol to deionized water can be 1:9 to 9:1; the templating agent can include but is not limited to dodecyltrimethylammonium bromide; the reaction temperature can be 75±5°C, and the reaction time can be 1h to 10h; the vacuum drying temperature can be 80±5°C, and the vacuum drying time can be 8h to 16h.

[0085] The hollow microsphere precursor can be selected from one or more of the compounds shown in Formula 1.

[0086]

[0087] In Formula 1, each R1 is independently selected from a C1-C6 alkyl group or a C2-C6 alkenyl group; each R2 is independently selected from a C1-C6 alkoxy group or a C2-C6 alkenyloxy group;

[0088] Y represents -R 11 -O-R 21 、-R 12 -S-R 22 、-R 13 -NR-R 23 、-R 14 -NH-R 24 、-R 15 -HPO4-R 25 、-R 16 -CONH-R 26 、-R 17 -O-CO-R 27 、-R 31 -R41 、 -R 51 -O-R 61 -R 71 、 -R 52 -S-R 62 -R 72 、 -R 53 -NR-R 63 -R 73 、 -R 54 -NH-R 64 -R 74 、 -R 55 -HPO4-R 65 -R 75 、 -R 56 -CONH-R 66 -R 76 、 -R 57 -O-CO-R 67 -R 77 One or more of the following, where R 11 、 R 12 、 R 13 、 R 14 、 R 15 、 R 16 、 R 17 each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, and R 21 、 R 22 、 R 23 、 R 24 、 R 25 、 R 26 、 R 27 each independently represents a C1-C6 alkyl group, or a C2-C6 alkenyl group, and R 31 represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, and R 41 represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group, and R 51 、 R 52 、 R 53 、 R 54 、 R 55 、 R 56 、 R 57 each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, and R 61 、 R 62 、 R 63 、 R 64 、 R 65 、 R 66 、 R 67 each independently represents a C1-C6 alkyl group, or a C2-C6 alkenyl group, and R 71 、 R 72, R 73 , R 74 , R 75 , R 76 , R 77 Each independently represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group.

[0089] m is 0 or 1. Optionally, m is 0.

[0090] As an example, the hollow microsphere precursor can be selected from one or more of γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, γ-glycidyletheroxypropyltrimethoxysilane, γ-glycidyletheroxypropyltriethoxysilane, methacryloxy silane, methacryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, methacryloxypropyltriisopropoxysilane, methacryloxymethyltriethoxysilane, 3-methacryloxypropyltris(isopropenyloxy)silane, 3-mercaptomethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, 3-[3-carboxyacrylamide]propyltriethoxysilane.

[0091] The organic group Y can be determined by infrared spectroscopy absorption method. For example, it can be tested by using a Nexus type Fourier transform microscopic infrared spectrometer with a resolution of 4 cm -1 , the number of scans is 64, and the test range is 4000 cm -1 ~400 cm -1 .

[0092] The volume average particle size Dv50 of the hollow microspheres has the meaning well known in the art, which represents the particle size corresponding to when the cumulative volume distribution percentage reaches 50%, and can be measured by the instruments and methods well known in the art. For example, it can be conveniently measured by referring to GB / T19077-2016 Laser diffraction method for particle size distribution, using a laser particle size analyzer, such as the Mastersizer 2000E type laser particle size analyzer of Malvern Instruments Limited, UK.

[0093] The specific surface area of the hollow microspheres has a meaning well-known in the art and can be measured using instruments and methods well-known in the art. For example, reference can be made to GB / T 19587-2017, and the nitrogen adsorption specific surface area analysis test method can be used for testing, and the BET (Brunauer Emmett Teller) method can be used for calculation. Among them, the nitrogen adsorption specific surface area analysis test can be carried out by a TriStarII 3020M specific surface area and pore size analyzer of Micromeritics Company in the United States.

[0094] [Positive electrode tab]

[0095] The positive electrode tab includes a positive electrode current collector and a positive electrode film layer provided 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 own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0096] The positive electrode active material can be a positive electrode active material well-known in the art for secondary batteries.

[0097] When the secondary battery is a lithium-ion battery, the positive electrode active material may include, but is not limited to, Li a Ni b Co c M d O e A f , one or more of olivine-structured lithium-containing phosphates and their respective modified compounds, wherein 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium manganese iron phosphate, composites of lithium manganese iron phosphate and carbon, and one or more of their respective modified compounds. The present application is not limited to these materials, and other conventionally well-known materials that can be used as positive electrode active materials for lithium-ion batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more.

[0098] For example, the positive electrode active material may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 One or more of O2, LiFePO4, and LiMnPO4.

[0099] When the secondary battery is a sodium-ion battery, the positive electrode active material may include, but is not limited to, Na x MO2 (M is a transition metal, preferably one or more of Mn, Fe, Ni, Co, V, Cu, Cr, 0 < x ≤ 1), polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), Prussian blue materials, etc. However, the present application is not limited to these materials, and other materials that can be used as the positive electrode active material of the sodium-ion battery can also be used. These positive electrode active materials can be used alone or in combination of two or more.

[0100] For example, the positive electrode active material may include NaFeO2, NaMnO2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, or one or more of them.

[0101] In the present application, the modified compounds of the above positive electrode active materials can be doping modification or surface coating modification of the positive electrode active materials.

[0102] The positive electrode film layer usually contains the positive electrode active material, an optional binder, and an optional conductive agent. The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector and drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto. As an example, the binder for the positive electrode film layer 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 fluorinated acrylate resin. As an example, the conductive agent for the positive electrode film layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] The positive current collector can be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil can be used. The composite current collector can include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. As an example, the metal material can be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material substrate can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0104] [Negative electrode plate]

[0105] The negative electrode plate includes a negative current collector and a negative electrode film layer provided on at least one surface of the negative current collector. For example, the negative current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative current collector.

[0106] The negative current collector can be a metal foil or a composite current collector. As an example of the metal foil, copper foil can be used. The composite current collector can include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. As an example, the metal material can be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material substrate can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0107] The negative electrode film layer generally contains a negative electrode active material, an optional binder, an optional conductive agent, and other optional additives. The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative current collector and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, the optional conductive agent, the optional binder, and other optional additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto. As an example, the binder used for the negative electrode film layer can 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). As an example, the conductive agent used for the negative electrode film layer can include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Other optional additives can include thickeners (e.g., sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.

[0108] The negative electrode active material can be the negative electrode active material for secondary batteries known in the art. As an example, the negative electrode active material can include one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials can include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloy materials. The tin-based materials can include one or more of elemental tin, tin oxides, and tin alloy materials. The present application is not limited to these materials, and other conventionally known materials that can be used as the negative electrode active material of the secondary battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0109] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet described in the present application further includes a conductive bottom coating (for example, composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer. In some other embodiments, the negative electrode sheet described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0110] [Electrolyte]

[0111] The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The present application has no specific limitation on the type of the electrolyte, and it can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolytic solutions).

[0112] In some embodiments, the electrolyte is an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0113] The type of the electrolyte salt is not specifically limited and can be selected according to actual requirements. When the secondary battery of the present application is a lithium-ion battery, as an example, the electrolyte salt can include but is not limited to lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP). When the secondary battery of the present application is a sodium-ion battery, as an example, the electrolyte salt can include but is not limited to NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0114] The types of solvents are not specifically limited and can be selected according to actual needs. In some embodiments, by way of example, the solvents may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE), either alone or in combination.

[0115] In some embodiments, the electrolyte may optionally further include additives. For example, the additives may include negative electrode film-forming additives, or may include positive electrode film-forming additives, or may also include additives that can improve certain battery performance, such as additives for improving battery overcharge performance, additives for improving battery high-temperature performance, additives for improving battery low-temperature power performance, and the like.

[0116] [Separator membrane]

[0117] In secondary batteries using electrolytes, as well as some secondary batteries using solid electrolytes, a separator membrane is further included. The separator membrane is disposed between the positive electrode sheet and the negative electrode sheet and functions to isolate them. The present application places no particular limitation on the type of separator membrane, and any publicly known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0118] In some embodiments, the material of the separator membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane can be a single-layer film or a multi-layer composite film. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different.

[0119] In some embodiments, the positive electrode sheet, the separator membrane, and the negative electrode sheet can be made into an electrode assembly by a winding process or a stacking process.

[0120] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0121] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0122] The present application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, Figure 1 a secondary battery 5 with a square structure is shown as an example.

[0123] In some embodiments, for example, Figure 2 as shown, the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or several, which can be adjusted according to requirements.

[0124] The preparation method of the secondary battery of the present application is well-known. In some embodiments, the positive electrode plate, the separator, the negative electrode plate and the electrolyte may be assembled to form a secondary battery. As an example, the positive electrode plate, the separator and the negative electrode plate may be formed into an electrode assembly through a winding process or a stacking process, the electrode assembly is placed in the outer package, dried and then injected with electrolyte, and after processes such as vacuum packaging, standing, formation, and shaping, a secondary battery is obtained.

[0125] Battery Module and Battery Pack

[0126] In some embodiments of the present application, the secondary battery according to the present application can be assembled into a battery module, and the number of secondary batteries included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0127] Figure 3 A schematic diagram of a battery module 4 is shown as an example. For example, Figure 3 as shown, in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0128] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of secondary batteries 5 are received in the receiving space.

[0129] In some embodiments, the above battery module can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0130] Figure 4 and Figure 5It is a schematic diagram of a battery pack 1 as an example. As Figure 4 and Figure 5 shown, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0131] Electrically Operated Device

[0132] The embodiments of the present application also provide an electrical device, which includes at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may be, but is not limited to, a mobile device (such as a mobile phone, laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0133] The electrical device may select a secondary battery, battery module, or battery pack according to its usage requirements.

[0134] Figure 6 It is a schematic diagram of an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device for high power and high energy density, a battery pack or a battery module may be used.

[0135] Another example of an electrical device may be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires being thin and light, and a secondary battery may be used as the power source.

[0136] Embodiment

[0137] The following embodiments more specifically describe the content disclosed in the present application. These embodiments are only for illustrative purposes, because various modifications and changes within the scope of the present application disclosure are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the embodiments are all commercially available.

[0138] Example 1

[0139] Preparation of Hollow Microspheres

[0140] Mix absolute ethanol and deionized water according to a mass ratio of 4:3 to prepare a mixed solvent with a volume of 500 ml; add 3 g of the template agent dodecyltrimethylammonium bromide to the mixed solvent and stir to dissolve the template agent; slowly drip 22.5 ml of the hollow microsphere precursor γ-aminopropyltrimethoxysilane into the above-mentioned mixed solvent, and then react at 75 °C for 2.4 h to obtain a precipitate; filter the precipitate, wash it thoroughly with deionized water and absolute ethanol alternately, and then place it in a vacuum oven at 80 °C for drying for 12 h to obtain hollow microspheres.

[0141] Preparation of Separator

[0142] Mix the above-mentioned hollow microspheres, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) according to a mass ratio of 90:5:5 in an appropriate amount of the solvent NMP and stir well to form a uniform coating slurry, and the viscosity of the coating slurry is 4000 mPa·s to 30000 mPa·s; use a unidirectional film drawing machine to uniformly coat the above-mentioned coating slurry on one surface of a porous polyethylene film, and obtain a separator with a functional layer after vacuum drying at 60 °C. Among them, the coating surface density of the coating slurry is 7.5 g / m 2 , and the coating thickness is 11.2 μm.

[0143] Preparation of Positive Electrode Plate

[0144] Mix the positive electrode active material lithium iron phosphate, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) according to a mass ratio of 96:2:2 in an appropriate amount of the solvent NMP and stir well to form a uniform positive electrode slurry, and the solid content of the positive electrode slurry is 60% and the viscosity is 5000 mPa·s to 25000 mPa·s; uniformly coat the positive electrode slurry on the surface of the positive electrode current collector aluminum foil, and obtain a positive electrode plate after drying and cold pressing. Among them, the coating surface density of the positive electrode slurry is 350 mg / m 2 , and the compaction density of the positive electrode plate is 2.5 g / m 3 .

[0145] Preparation of Negative Electrode Plate

[0146] Mix the negative electrode active material graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) according to a mass ratio of 96.2:0.8:1.8:1.2 in an appropriate amount of the solvent deionized water and stir well to form a uniform negative electrode slurry, and the solid content of the negative electrode slurry is 50% and the viscosity is 2000 mPa·s to 10000 mPa·s; uniformly coat the negative electrode slurry on the surface of the negative electrode current collector copper foil, and obtain a negative electrode plate after drying and cold pressing. Among them, the coating surface density of the negative electrode slurry is 220 mg / m 2, the compaction density of the negative electrode plate is 2.0 g / m 3 .

[0147] Preparation of Electrolyte

[0148] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent; LiPF6 is uniformly dissolved in the above organic solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0149] Preparation of Secondary Battery

[0150] The above positive electrode plate, separator, and negative electrode plate are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in an outer package, the above electrolyte is added, and after processes such as encapsulation, standing, formation, and aging, a secondary battery is obtained.

[0151] Examples 2 to 20 and Comparative Examples 1 to 5

[0152] The preparation method of the secondary battery is similar to that of Example 1, except that the preparation parameters of the hollow microspheres and the preparation parameters of the functional layer slurry are different. For details, see Table 1.

[0153] Table 1

[0154]

[0155]

[0156] Test Section

[0157] (1) Energy density test

[0158] At 25 °C, the secondary battery is charged at a constant current of 1C to 3.65V, and then charged at a constant voltage until the current is 0.05C; after the secondary battery is allowed to stand for 5 minutes, it is discharged at a constant current of 1C to 2.0V to obtain the discharge energy Q.

[0159] The energy density (Wh / Kg) of the secondary battery = discharge energy Q / mass m of the secondary battery.

[0160] (2) Room temperature cycle performance test

[0161] At 25 °C, the secondary battery is charged at a constant current of 1C to 3.65V, and then charged at a constant voltage until the current reaches 0.05C. At this time, the secondary battery is in a fully charged state, and the charging capacity at this time is recorded as the charging capacity of the first cycle; after the secondary battery is left standing for 5 minutes, it is discharged at a constant current of 1C to 2.0V. This is a cycle of charge and discharge, and the discharge capacity at this time is recorded as the discharge capacity of the first cycle. The secondary battery is tested for cyclic charge and discharge according to the above method, and the discharge capacity after each cycle is recorded.

[0162] The capacity retention rate (%) of the secondary battery after 1000 cycles at 25 °C = the discharge capacity after 1000 cycles / the discharge capacity of the first cycle × 100%.

[0163] (3) High-temperature cycle performance test

[0164] At 45 °C, the secondary battery is charged at a constant current of 1C to 3.65V, and then charged at a constant voltage until the current reaches 0.05C. At this time, the secondary battery is in a fully charged state, and the charging capacity at this time is recorded as the charging capacity of the first cycle; after the secondary battery is left standing for 5 minutes, it is discharged at a constant current of 1C to 2.0V. This is a cycle of charge and discharge, and the discharge capacity at this time is recorded as the discharge capacity of the first cycle. The secondary battery is tested for cyclic charge and discharge according to the above method, and the discharge capacity after each cycle is recorded.

[0165] The capacity retention rate (%) of the secondary battery after 1000 cycles at 45 °C = the discharge capacity after 1000 cycles / the discharge capacity of the first cycle × 100%.

[0166] (4) Test for the mass of transition metal dissolution from the negative electrode plate

[0167] The secondary battery that has been cycled 1000 times at 25 °C above is disassembled and the negative electrode plate is taken out, and then immersed in dimethyl carbonate (DMC) for 2 hours; the negative electrode plate is taken out and dried in vacuum at 60 °C for 4 hours; the dried negative electrode plate is further baked at 400 °C for 2 hours. Select an area from the baked negative electrode plate, and then scrape the powder for sampling with a blade; after weighing and recording the mass of the powder sample, put it into a digestion tank, slowly add 10 mL of aqua regia as the digestion reagent, and then put it into the Mars5 microwave digestion instrument of CEM Corporation in the United States for digestion at a microwave emission frequency of 2450 Hz; transfer the digested sample solution to a volumetric flask and shake well, take a sample and put it into the ICP-OES injection system, and test the mass percentage of transition metal Fe in the powder sample at an argon pressure of 0.6 MPa and a radio frequency power of 1300 W.

[0168] Table 2 shows the performance test results of Examples 1 to 20 and Comparative Examples 1 to 5.

[0169] Table 2

[0170]

[0171]

[0172] Figure 7 is the scanning electron microscope (SEM) image of the hollow silica microspheres prepared in Example 1. Figure 8 is Figure 7 the partial enlarged view. From Figure 7 and Figure 8 it can be seen that the hollow microspheres prepared in this application are fully nano-sized and uniformly sized small spheres. Figure 9 is the infrared absorption spectrum of the hollow microspheres prepared in Example 1. From Figure 9 it can be seen that the hollow silica microspheres in Example 1 have a stretching vibration peak of N-H at 3500 cm -1 ~3300 cm -1 , a stretching vibration peak of C-H at 3000 cm -1 ~2800 cm -1 and a bending vibration peak of N-H at 1650 cm -1 ~1500 cm -1 , indicating that -NH2 is successfully bonded to the surface of the hollow silica microspheres prepared in Example 1.

[0173] Figure 10 is the scanning electron microscope (SEM) image of the cross-section of the functional layer prepared in Example 1. Figure 11 and Figure 12 are Figure 10 the enlarged views of the functional layer shown at different magnifications. From Figures 10 to 12 it can be seen that the functional layer of this application contains a large number of uniformly sized hollow microspheres, and when the hollow microspheres are prepared into a coating slurry and coated on a substrate, they can completely spread out and form a tight coating.

[0174] From the test results in Table 2, it can be seen that the functional layer of this application can significantly improve the adsorption efficiency and adsorption capacity of transition metal ions, prevent the deposition of transition metals on the negative electrode, and significantly improve the cycle performance of the secondary battery, while not affecting the energy density of the secondary battery.

[0175] In Comparative Example 2, silica particles with a solid structure were used to prepare the functional layer, which could not adsorb transition metal ions. After 1000 cycles of the secondary battery, a large amount of transition metals were deposited on the negative electrode, and the cycle performance of the secondary battery was also poor.

[0176] In Comparative Example 3 and Comparative Example 4, conventional hollow silica microspheres and hollow silica microspheres with -CH3 bonded to the surface were used to prepare the functional layer respectively, which could reduce the influence of the dissolution of transition metal ions on the cycle performance of the secondary battery to a certain extent, but the improvement effect was limited.

[0177] Comparative Example 5 used silica microspheres with a solid structure having -NH2 bonded to the surface to prepare a functional layer, which could also reduce the influence of transition metal ion dissolution on the cycle performance of the secondary battery to a certain extent, but the improvement effect was limited.

[0178] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same effect as the technical idea within the technical scope of the present application are included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments and other modes constructed by combining some constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery, comprising: a positive electrode plate; a negative electrode plate; and a separator located between the positive electrode plate and the negative electrode plate, characterized in that the secondary battery further comprises: a functional layer located on at least one surface of the positive electrode plate, the separator and the negative electrode plate, the functional layer comprises hollow microspheres, the hollow microspheres comprise a hollow cavity and a shell layer with a mesoporous structure, the shell layer comprises a matrix and an organic group Y bonded to the outer surface of the matrix and the inner surface of the mesoporous structure and capable of complexing transition metal ions, and the organic group Y has one or more of the following functional groups: -NH2, -SH, -OH, -COOH, -H2PO4, epoxyethyl group, -O-, -S-, -NR-, -NH-, -HPO4-, -CONH-, and acyloxy group, where R represents a C1-C6 alkyl group or -NH2.

2. The secondary battery according to claim 1, wherein The organic group Y includes -R 11 -O-R 21 ,-R 12 -S-R 22 ,-R 13 -NR-R 23 ,-R 14 -NH-R 24 ,-R 15 -HPO4-R 25 ,-R 16 -CONH-R 26 ,-R 17 -O-CO-R 27 ,-R 31 -R 41 ,-R 51 -O-R 61 -R 71 ,-R 52 -S-R 62 -R 72 ,-R 53 -NR-R 63 -R 73 ,-R 54 -NH-R 64 -R 74 ,-R 55 -HPO4-R 65 -R 75 ,-R 56 -CONH-R 66 -R 76 ,-R 57 -O-CO-R 67 -R 77 one or more of Wherein R 11 、R 12 、R 13 、R 14 、R 15 、R 16 、R 17 each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group R 21 、R 22 、R 23 、R 24 、R 25 、R 26 、R 27 each independently represents a C1-C6 alkyl group or a C2-C6 alkenyl group R 31 represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group, R 41 represents -NH2, -SH, -OH, -COOH, -H2PO4, or an oxiranyl group R 51 、R 52 、R 53 、R 54 、R 55 、R 56 、R 57 each independently represents a single bond, a C1-C6 alkyl group, or a C2-C6 alkenyl group R 61 、R 62 、R 63 、R 64 、R 65 、R 66 、R 67 each independently represents a C1-C6 alkyl group or a C2-C6 alkenyl group R 71 、R 72 、R 73 、R 74 、R 75 、R 76 、R 77 Each independently represents -NH2, -SH, -OH, -COOH, -H2PO4, or an epoxyethyl group.

3. The secondary battery according to claim 2, characterized in that, the number of carbon atoms of the organic group Y ≤ 10.

4. The secondary battery according to claim 3, characterized in that, the number of carbon atoms of the organic group Y is 3-10.

5. The secondary battery according to claim 1, characterized in that, the matrix is selected from inorganic oxides.

6. The secondary battery according to claim 5, wherein the matrix is selected from silicon dioxide or aluminum oxide.

7. The secondary battery according to claim 1, characterized in that, The specific surface area of the hollow microspheres is 10 m 2 / g to 100 m 2 / g.

8. The secondary battery according to claim 1, characterized in that, the volume average particle size Dv50 of the hollow microspheres is 80 nm to 5000 nm.

9. The secondary battery according to claim 8, wherein the volume average particle size Dv50 of the hollow microspheres is 200 nm to 5000 nm.

10. The secondary battery according to claim 1, wherein the radius of the hollow microspheres is R, the radius of the hollow cavity is r, and the ratio r / R of r to R is 0.70 to 0.

95.

11. The secondary battery according to claim 10, wherein r / R is 0.75 to 0.

90.

12. The secondary battery according to claim 1, characterized in that, the thickness of the functional layer is 3 μm to 20 μm.

13. The secondary battery according to claim 1, characterized in that, the mesopore size of the shell layer is 5 nm to 50 nm.

14. The secondary battery according to claim 1, wherein the functional layer further comprises one or more of a conductive agent and a binder.

15. The secondary battery according to any one of claims 1-14, characterized in that, based on the total mass of the functional layer, the mass percentage content of the hollow microspheres is 80% to 99%.

16. The secondary battery according to claim 15, characterized in that, based on the total mass of the functional layer, the mass percentage content of the hollow microspheres is 85% to 95%.

17. The secondary battery according to claim 1, characterized in that, The coating surface density of the functional layer is 2 g / m 2 ~15 g / m 2 .

18. A battery module, comprising the secondary battery according to any one of claims 1-17.

19. A battery pack, comprising the battery module according to claim 18.

20. An electric device, comprising at least one of the secondary battery according to any one of claims 1-17, the battery module according to claim 18, and the battery pack according to claim 19.

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