Composite capacity compensation agent, positive pole piece, secondary battery and electric device

Abstract

The invention relates to a composite capacity compensation agent, a positive pole piece, a secondary battery and a power utilization device, the composite capacity compensation agent comprises a first capacity compensation agent and a second capacity compensation agent, the first capacity compensation agent comprises a material with a chemical formula of MxCaObHc, M comprises one or more of Na and Li, 0 < x < = 4, 2 < = a < = 6, 2 < = b < = 7, 0 < = c < = 6, and the second capacity compensation agent comprises a material with a chemical formula of MxCaObHc. The second capacity compensation agent comprises a metal salt, the decomposition voltage of the metal salt in the second capacity compensation agent is lower than that of the material with the chemical formula of MxCaObHc in the first capacity compensation agent, and the first capacity compensation agent and the second capacity compensation agent are matched for use, so that the decomposition voltage of the composite capacity compensation agent can be reduced; and the discharge gram capacity and the cycle performance of the secondary battery are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a composite capacity compensation agent, a positive electrode sheet, a secondary battery and an electric device. BACKGROUND

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] Secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Due to the rapid development of secondary batteries, higher requirements are put forward for their capacity and cycle performance. How to improve the capacity and cycle performance of secondary batteries has become a technical problem to be solved at present. SUMMARY

[0004] The present application provides a composite capacity compensation agent, a positive electrode sheet, a secondary battery and an electric device to improve the discharge specific capacity and cycle performance of the secondary battery.

[0005] In a first aspect, the present application provides a composite capacity compensation agent, comprising a first capacity compensation agent and a second capacity compensation agent, the first capacity compensation agent comprising a material with a chemical formula of M x C a O b H c , wherein M comprises one or more of Na and Li, 0 x C a O b H c , and the second capacity compensation agent comprises a metal salt, the decomposition voltage of the metal salt in the second capacity compensation agent being lower than that of the material with a chemical formula of M x C a O b H c in the first capacity compensation agent.

[0006] The decomposition voltage of the metal salt in the second capacity compensation agent is lower than that of the material with a chemical formula of M x C a O b H c in the first capacity compensation agent. Such metal salt can produce a strong soluble oxidizing intermediate during the charging process of the secondary battery, and this oxidizing intermediate can react with the material with a chemical formula of M x C a O b H c with a higher decomposition voltage.The material can promote the oxidative decomposition of the material after contacting with the material, and reduce the decomposition potential thereof. Therefore, the first capacity compensation agent and the second capacity compensation agent are used in cooperation, which can reduce the decomposition voltage of the composite capacity compensation agent, improve the sodium compensation efficiency and / or lithium compensation efficiency of the composite capacity compensation agent, and thus improve the discharge gram capacity and the cycle performance of the secondary battery.

[0007] In some embodiments, the mass ratio of the second capacity compensation agent to the first capacity compensation agent is (7-30): 100. Controlling the mass ratio of the first capacity compensation agent and the second capacity compensation agent in the composite capacity compensation agent within a reasonable range can further promote the decomposition of the first capacity compensation agent, and can further consume the oxidizing intermediates formed by the metal salt in the second capacity compensation agent, thereby further improving the discharge gram capacity and the cycle performance of the secondary battery.

[0008] In some embodiments, the mass ratio of the second capacity compensation agent to the first capacity compensation agent is (10-25): 100. In this way, the decomposition of the first capacity compensation agent can be further promoted, and the oxidizing intermediates formed by the metal salt in the second capacity compensation agent can be further consumed, thereby further improving the discharge gram capacity and the cycle performance of the secondary battery.

[0009] In some embodiments, the volume average particle size Dv50 of the first capacity compensation agent is 30 nm-5 μm. Controlling the volume average particle size Dv50 of the first capacity compensation agent within the above range is conducive to the interaction between the first capacity compensation agent and the second capacity compensation agent, further promotes the decomposition of the first capacity compensation agent, and thus further improves the discharge gram capacity and the cycle performance of the secondary battery. Alternatively, the volume average particle size Dv50 of the first capacity compensation agent is 30 nm-2 μm.

[0010] In some embodiments, the volume average particle size Dv50 of the second capacity compensation agent is 100 nm-5 μm. Controlling the volume average particle size Dv50 of the second capacity compensation agent within the above range can increase the contact area between the second capacity compensation agent and the electrolyte in the secondary battery, improve the decomposition efficiency of the second capacity compensation agent, promote the rapid decomposition of the first capacity compensation agent, and further consume the oxidizing intermediates formed by the second capacity compensation agent, thereby further improving the discharge gram capacity and the cycle performance of the secondary battery. Alternatively, the volume average particle size Dv50 of the second capacity compensation agent is 100 nm-3 μm.

[0011] In some embodiments, the first capacity compensation agent and the second capacity compensation agent each independently comprises at least one of a spherical structure, a spherical-like structure, a rod-like structure, and a block-like structure. In this way, it is conducive to promoting the decomposition of the first capacity compensation agent and consuming the oxidizing intermediates formed by the second capacity compensation agent, and further improving the cycle performance of the secondary battery.

[0012] In some embodiments, the metal salt comprises one or more of NaNO2, Na2C4O4, Na5FeO4, Na2C6O6, LiNO2, Li2C4O4, Li5FeO4, and Li2C6O6. Oxidative intermediates generated by oxidative decomposition of the above-mentioned kinds of metal salt can dissolve into the electrolyte of the secondary battery, interact with the material of formula M x C a O b H c , and facilitate decomposition of the material of formula M x C a O b H c .

[0013] In some embodiments, the material of formula M x C a O b H c comprises one or more of sodium oxalate, sodium acetate, sodium propionate, sodium malonate, sodium carbonate, sodium citrate, lithium oxalate, lithium acetate, lithium propionate, lithium malonate, lithium carbonate, and lithium citrate. The decomposition potential of the above-mentioned kinds of material is high, and when used in combination with the above-mentioned second capacity compensator, the decomposition potential of the material can be reduced, and the sodium compensation efficiency and / or lithium compensation efficiency of the composite capacity compensator can be improved.

[0014] In a second aspect, the application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material and the composite capacity compensator of the first aspect of the application.

[0015] The positive electrode sheet of the application comprises the composite capacity compensator provided by the application, and thus has at least the same advantages as the composite capacity compensator.

[0016] In some embodiments, the mass fraction of the composite capacity compensator in the positive electrode film layer is 0.01% to 8%.

[0017] In some embodiments, the positive electrode film layer comprises a positive electrode active material layer, and the positive electrode active material layer comprises a positive electrode active material.

[0018] In some embodiments, the positive electrode active material layer further comprises the first capacity compensator and the second capacity compensator in the composite capacity compensator.

[0019] In some embodiments, the positive electrode film layer further comprises a first film layer arranged on at least one side surface of the positive electrode active material layer;

[0020] wherein the positive electrode active material layer further comprises a first capacity compensation agent of the composite capacity compensation agent, and the first film layer comprises a second capacity compensation agent of the composite capacity compensation agent; or,

[0021] the positive electrode active material layer further comprises a second capacity compensation agent of the composite capacity compensation agent, and the first film layer comprises a first capacity compensation agent of the composite capacity compensation agent; or,

[0022] the first film layer comprises a first capacity compensation agent and a second capacity compensation agent of the composite capacity compensation agent.

[0023] In some embodiments, the positive electrode film layer further comprises a first film layer and a second film layer which are arranged in a stacked manner on at least one side surface of the positive electrode active material layer, the first film layer comprises a first capacity compensation agent of the composite capacity compensation agent, the second film layer comprises a second capacity compensation agent of the composite capacity compensation agent, the first film layer is arranged between the positive electrode active material layer and the second film layer, or the first film layer is arranged on a surface of the second film layer which is away from the positive electrode active material layer.

[0024] In a third aspect of the present application, a secondary battery is provided, comprising at least one of the composite capacity compensation agent according to the first aspect of the present application and the positive electrode tab according to the second aspect of the present application.

[0025] The secondary battery of the present application comprises at least one of the composite capacity compensation agent provided by the present application and the positive electrode tab provided by the present application, and thus at least has the same advantages as the composite capacity compensation agent or the positive electrode tab.

[0026] In a fourth aspect of the present application, an electric device is provided, comprising the secondary battery according to the third aspect of the present application.

[0027] The electric device of the present application comprises the secondary battery provided by the present application, and thus at least has the same advantages as the secondary battery.

[0028] The details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to better describe and illustrate the embodiments or examples provided by the present application, reference can be made to one or more drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the presently described embodiments or examples, and any one of the best modes of these applications presently understood. Moreover, in all the drawings, the same reference numbers are used to represent the same components. In the drawings:

[0030] Figure 1 Structure diagram of a positive electrode tab according to an embodiment of the present application.

[0031] Figure 2 Structure diagram of a positive electrode tab according to an embodiment of the present application.

[0032] Figure 3 Structure diagram of a positive electrode tab according to an embodiment of the present application.

[0033] Figure 4 Structure diagram of a positive electrode tab according to an embodiment of the present application.

[0034] Figure 5 Structure diagram of a battery cell according to an embodiment of the present application.

[0035] Figure 6 Structure diagram of a battery cell according to an embodiment of the present application. Figure 5 Exploded view of a battery cell according to an embodiment of the present application.

[0036] Figure 7 Structure diagram of a battery module according to an embodiment of the present application.

[0037] Figure 8 Structure diagram of a battery pack according to an embodiment of the present application.

[0038] Figure 9 Structure diagram of a battery pack according to an embodiment of the present application. Figure 8 Exploded view of a battery pack according to an embodiment of the present application.

[0039] Figure 10 Structure diagram of an electric device powered by a secondary battery according to an embodiment of the present application.

[0040] Legend of reference numerals:

[0041] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 housing; 52 electrode assembly; 53 cover plate; 6 electric device; 7 positive electrode tab; 71 positive current collector; 72 positive film layer; 721 positive active material layer; 722 first film layer; 723 second film layer. DETAILED DESCRIPTION

[0042] Hereinafter, some embodiments of the composite capacity compensator, the positive electrode sheet, the secondary battery, and the power using device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters known well, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0043] The "ranges" disclosed in the present application can be defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, either end value can be included or excluded independently, and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are also listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise specified, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is within the range, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand manner of describing these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to listing the parameter as, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like. For example, when it is stated that a parameter is an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0044] In the present application, "a plurality of", "a plurality of kinds", and the like, unless otherwise specified, mean greater than or equal to 2 in number. For example, "one or more" means one or more than or equal to two.

[0045] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not otherwise specified.

[0046] Reference to "an embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily all referring to a common embodiment, or an embodiment that is independent of all other embodiments. One of skill in the art will understand that a reference to "an embodiment" in one part of this disclosure is not necessarily referring to the same embodiment as the reference to an embodiment in another part of this disclosure. Furthermore, the disclosure is not intended to be limited to the embodiments shown in the figures and described in this specification. As such, the disclosure is to be considered to encompass a variety of embodiments that can be derived from the disclosure with the spirit and scope of the disclosure being limited solely by the claims that can be issued in connection with this disclosure.

[0047] Those skilled in the art can understand that the sequence of writing each step in the method of each embodiment or embodiment does not mean a strict execution sequence and constitutes any limitation on the implementation process. The detailed execution sequence of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0048] In this application, the open technical features or technical solutions described by "containing", "including", "comprising" and the like, if not otherwise stated, do not exclude additional members from the listed members, which can be regarded as providing both the closed features or solutions composed of the listed members and the open features or solutions including additional members in addition to the listed members. For example, A includes a1, a2 and a3, if not otherwise stated, it can also include other members, or it can not include additional members, which can be regarded as providing the feature or solution that "A is composed of a1, a2 and a3", and also providing the feature or solution that "A includes a1, a2 and a3, and also includes other members". In this application, if not otherwise stated, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0049] In this application, "optionally", "optional" and "optional" mean that it can or can not be present, that is, it means to choose from the two parallel solutions of "yes" or "no". If there are multiple "options" in a technical solution, if not otherwise stated, and there is no contradiction or mutual restriction, each "option" is independent.

[0050] An embodiment of the present application provides a composite volume compensator, comprising a first volume compensator and a second volume compensator, the first volume compensator comprising a chemical formula of Mx C a O b H c The material, wherein M includes one or more of Na and Li, 0 < x ≤ 4, 2 ≤ a ≤ 6, 2 ≤ b ≤ 7, 0 ≤ c ≤ 6, and the second capacity compensator includes a metal salt, the decomposition voltage of which is higher than that of the first capacity compensator with chemical formula M. x C a O b H c The material has a low decomposition voltage.

[0051] The chemical formula of the first capacity compensator mentioned above is M. x C a O b H c The material has a relatively high decomposition voltage, for example, it can reach 4V~4.2V. When it is used as a capacity compensator in secondary batteries, there are problems such as incomplete decomposition in the first cycle, which affects the sodium replenishment efficiency and / or lithium replenishment efficiency of the material. Moreover, it cannot be applied to secondary batteries with a narrow voltage window, such as secondary batteries with a maximum operating voltage of 3.8V, which greatly limits the promotion and use of the material.

[0052] To solve the problem of chemical formula M x C a O b H c The problem of high decomposition voltage of materials can be addressed by reducing the particle size of the material, but this has little effect on improving the decomposition potential. On the other hand, the conductivity of the material can be improved by carbon coating or by incorporating conductive carbon during the material synthesis process. However, this method requires the addition of a large amount of conductive carbon and the two materials need to be mixed or incorporated evenly, which not only reduces the discharge capacity of the material and affects the energy density of the secondary battery, but also increases the manufacturing cost of the secondary battery.

[0053] Based on this, this application designs the aforementioned composite capacity compensator, wherein the decomposition voltage of the metal salt in the second capacity compensator is higher than that of the first capacity compensator containing the chemical formula M. x C a O b H c The materials have low decomposition voltages, and these metal salts can generate strong soluble oxidizing intermediates during secondary battery charging. These oxidizing intermediates react with a chemical formula M that has a higher decomposition voltage. x C a O b H cAfter the material contacts, the oxidation and decomposition of the material can be promoted, and the decomposition potential thereof is reduced. Therefore, the first capacity compensation agent and the second capacity compensation agent are used in combination, the decomposition voltage of the composite capacity compensation agent is reduced, the sodium compensation efficiency and / or the lithium compensation efficiency of the composite capacity compensation agent are improved, and thus the discharge gram capacity and the cycle performance of the secondary battery are improved, and the energy density of the secondary battery is also improved.

[0054] It should be noted that x includes but is not limited to 1, 2, 3, 4; a includes but is not limited to 2, 3, 4, 5, 6; b includes but is not limited to 2, 3, 4, 5, 6, 7; and c includes but is not limited to 0, 1, 2, 3, 4, 5, 6.

[0055] Optionally, XRD (X-ray diffraction method) and ICP (inductively coupled plasma technology) can be used to test the types of the first capacity compensation agent and the second capacity compensation agent in the composite capacity compensation agent. When the composite capacity compensation agent is reversely tested, the battery is first disassembled, the types of the first capacity compensation agent and the second capacity compensation agent in the battery are tested by using XRD and ICP, and then the same materials are used to assemble a button cell for measurement. Specifically, the same materials as the first capacity compensation agent and the second capacity compensation agent are used as the positive active material to prepare a positive electrode sheet, a sodium metal sheet or a lithium metal sheet is used as a negative electrode sheet, and a button cell is assembled, and then the button cell is charged at 0.1C constant current to 4.2V. The charging gram capacity of the battery under the same battery system is compared to determine the decomposition voltage of the above-mentioned materials. The higher the charging gram capacity of the battery is, the lower the decomposition voltage of the material is. When the first capacity compensation agent and the second capacity compensation agent contain Na + , a sodium ion battery is assembled for testing; and when the first capacity compensation agent and the second capacity compensation agent contain Li + , a lithium ion battery is assembled for testing. The above-mentioned same battery system means that, except that the positive active material is different, the other components of the positive electrode sheet, the composition of the negative electrode sheet, the composition of the electrolyte, and the composition of the separator are completely the same.

[0056] When the above-mentioned composite capacity compensation agent is reversely tested, a fresh battery is preferentially selected for disassembly and testing. The fresh battery can be a battery just out of the factory, or a battery assembled on an electric device just out of the factory. The battery just out of the factory refers to a battery that has not been subjected to charge and discharge cycles after formation.

[0057] In some embodiments, the mass ratio of the second capacity compensation agent to the first capacity compensation agent is (5-35): 100. By adjusting the mass ratio of the second capacity compensation agent to the first capacity compensation agent, the decomposition voltage of the composite capacity compensation agent can be adjusted to be within the appropriate voltage range of the secondary battery, which can effectively improve the capacity compensation value of the composite capacity compensation agent. In addition, controlling the mass ratio of the first capacity compensation agent and the second capacity compensation agent in the composite capacity compensation agent within a reasonable range can further promote the decomposition of the first capacity compensation agent, and at the same time can further consume the oxidizing intermediates formed by the metal salt in the second capacity compensation agent, so that the first capacity compensation agent and the second capacity compensation agent can simultaneously exert their respective advantages, thereby further improving the discharge gram capacity and cycle performance of the secondary battery. Further, the mass ratio of the second capacity compensation agent to the first capacity compensation agent is (7-30): 100. Further, the mass ratio of the second capacity compensation agent to the first capacity compensation agent is (10-25): 100.

[0058] The mass ratio of the second capacity compensation agent to the first capacity compensation agent described above includes but is not limited to 5:100, 7:100, 8:100, 9:100, 10:100, 12:100, 14:100, 16:100, 18:100, 20:100, 22:100, 24:100, 26:100, 28:100, 30:100, 35:100.

[0059] In some embodiments, the volume average particle size Dv50 of the first capacity compensation agent is 30 nm-7 μm. Controlling the volume average particle size Dv50 of the first capacity compensation agent to be within the above range is conducive to the interaction between the first capacity compensation agent and the second capacity compensation agent, further promotes the decomposition of the first capacity compensation agent, and thereby further improves the discharge gram capacity and cycle performance of the secondary battery. It can be understood that the volume average particle size Dv50 of the first capacity compensation agent includes but is not limited to 30 nm, 50 nm, 100 nm, 500 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm. Further, the volume average particle size Dv50 of the first capacity compensation agent is 30 nm-5 μm. Further, the volume average particle size Dv50 of the first capacity compensation agent is 30 nm-2 μm.

[0060] In some embodiments, the second capacity compensator has a volume average particle size Dv50 of 30 nm to 7 μm. Controlling the volume average particle size Dv50 of the second capacity compensator within the above range can increase the contact area between the second capacity compensator and the electrolyte in the secondary battery, increase the decomposition efficiency of the second capacity compensator, promote the rapid decomposition of the first capacity compensator, and further consume the oxidizing intermediates formed by the second capacity compensator, thereby further improving the discharge specific capacity and the cycle performance of the secondary battery. It is understood that the volume average particle size Dv50 of the second capacity compensator includes, but is not limited to, 30 nm, 50 nm, 100 nm, 500 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, and 7 μm. Further, the volume average particle size Dv50 of the second capacity compensator is 100 nm to 5 μm. Still further, the volume average particle size Dv50 of the second capacity compensator is 100 nm to 3 μm.

[0061] In some embodiments, the first capacity compensator and the second capacity compensator each independently includes at least one of a spherical structure, a spherical-like structure, a rod-like structure, and a block-like structure. In this way, the decomposition of the first capacity compensator is promoted, and the oxidizing intermediates formed by the second capacity compensator are consumed, thereby further improving the cycle performance of the secondary battery.

[0062] In some embodiments, the metal salt includes one or more of NaNO2 (sodium nitrite), Na2C4O4 (sodium oxalate), Na5FeO4, Na2C6O6, LiNO2, Li2C4O4, Li5FeO4, and Li2C6O6. The oxidizing intermediates produced by the oxidation and decomposition of the above-mentioned metal salts can dissolve into the electrolyte of the secondary battery, and interact with the material having the chemical formula M x C a O b H c in the first capacity compensator, thereby facilitating the decomposition of the material having the chemical formula M x C a O b H c . The above-mentioned oxidizing intermediates include, but are not limited to, C4O4 2- , NO2 - , C6O6 2- , and the like.

[0063] In some embodiments, the material having the chemical formula M x C a O b H cThe material includes one or more of sodium oxalate (Na2C2O4), sodium acetate (NaC2O2H3), sodium propionate (NaC3O2H5), sodium malonate (Na2C3O4H2), sodium carbonate (Na2CO3), sodium citrate (Na3C6O7H5), lithium oxalate (Li2C2O4), lithium acetate (LiC2O2H3), lithium propionate (LiC3O2H5), lithium malonate (Li2C3O4H2), lithium carbonate (Li2CO3), and lithium citrate (Li3C6O7H5). The decomposition potential of the above-mentioned material is high. When the above-mentioned second capacity compensator is used in combination, the decomposition potential of the material can be reduced, and the sodium compensation efficiency and / or lithium compensation efficiency of the composite capacity compensator can be improved.

[0064] In some embodiments, when the secondary battery is a sodium ion battery or a sodium metal battery, M includes Na. The metal salt can include one or more of NaNO2 (sodium nitrite), Na2C4O4 (sodium squarate), Na5FeO4, Na2C6O6, LiNO2, Li2C4O4, Li5FeO4, and Li2C6O6. In this way, the decomposition voltage of the material of formula Na x C a O b H c can be reduced, the sodium compensation efficiency of the composite capacity compensator can be improved, and the discharge gram capacity and cycle performance of the secondary battery can be improved.

[0065] In some embodiments, when the secondary battery is a lithium ion battery or a lithium metal battery, M includes Li. The metal salt can include one or more of NaNO2 (sodium nitrite), Na2C4O4 (sodium squarate), Na5FeO4, Na2C6O6, LiNO2, Li2C4O4, Li5FeO4, and Li2C6O6. In this way, the decomposition voltage of the material of formula Li x C a O b H c can be reduced, the lithium compensation efficiency of the composite capacity compensator can be improved, and the discharge gram capacity and cycle performance of the secondary battery can be improved.

[0066] Another embodiment of the present application provides a preparation method of the above-mentioned composite capacity compensator, which includes a step of preparing a first capacity compensator and a step of preparing a second capacity compensator.

[0067] The above-mentioned preparation method is simple and convenient, and is conducive to the large-scale production of the composite capacity compensator.

[0068] In some embodiments, in the step of preparing the first capacity compensator, the step includes: subjecting a raw material containing the first capacity compensator to recrystallization treatment. In this way, the purity, particle size, or morphology of the first capacity compensator can be controlled.

[0069] In some embodiments, the step of preparing the second capacity compensator includes recrystallizing the raw material containing the second capacity compensator. This allows for the control of the purity, particle size, or morphology of the second capacity compensator.

[0070] In some embodiments, the preparation method of the composite capacity compensator further includes the step of mixing a first capacity compensator and a second capacity compensator to obtain the composite capacity compensator.

[0071] Another embodiment of this application provides a positive electrode sheet, including a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein the positive electrode film layer contains a positive electrode active material and the composite capacity compensator described above in this application.

[0072] The positive electrode of this application includes the composite capacity compensator provided in this application, and therefore has at least the same advantages as the composite capacity compensator.

[0073] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0074] In some implementations, please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a positive electrode sheet according to an embodiment of the present application is shown. The positive electrode sheet 7 includes a positive current collector 71 and a positive electrode film layer 72 disposed on two opposite surfaces of the positive current collector 71.

[0075] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0076] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co 0.15 Al 0.05 O2.

[0077] It can be understood that the battery will be accompanied by lithium (Li) deintercalation and consumption during charging and discharging, and the content of Li in the positive plate is different when the battery is discharged to different states. In the enumeration of the positive active material in this application, the content of Li is the initial state of the material unless otherwise stated. When the positive active material is applied to the positive plate in the battery system, the content of Li in the positive active material contained in the plate will usually change after charging and discharging cycle. Among them, the content of Li can be quantified by molar content, but not limited to this. As for "the content of Li is the initial state of the material", the initial state of the material refers to the state before being put into the positive slurry. It can be understood that the new material obtained by properly modifying the listed positive active material is also within the scope of the positive active material, and the foregoing proper modification refers to acceptable modification methods for the positive active material, and non-limiting examples include coating modification.

[0078] In the enumeration of the positive active material in this application, the content of oxygen (O) is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual content of O will fluctuate. Among them, the content of O can be quantified by molar content, but not limited to this.

[0079] The positive active material includes a sodium ion active material.

[0080] As an example, the sodium ion active material can include one or more of the following materials: one or more of sodium transition metal oxides, polyanionic compounds, and prussian blue compounds. However, the present application is not limited to these materials, and other conventional and well-known materials that can be used as positive active materials for sodium ion batteries can also be used.

[0081] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of sodium transition metal oxides can be Na x MO2, wherein M can include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0

[0082] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions, and tetrahedral (YO4) n- anion units. The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be one or more of P, S and Si; and n represents the valence state of (YO4) n- .

[0083] The polyanionic compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO4)n- Anionic units and halogen anions. The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si, n represents the valence of (YO4) n- ; and the halogen can be one or more of F, CI, and Br.

[0084] The polyanionic compound can also be a compound having sodium ions, tetrahedral (YO4) n- anionic units, polyhedral (ZO y ) m+ ; and optional halogen anions. Y can be one or more of P, S, and Si, n represents the valence of (YO4) n- ; Z represents a transition metal, which can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, m represents the valence of (ZO y ) m+ ; and the halogen can be one or more of F, CI, and Br.

[0085] The polyanionic compound can include one or more of NaFeP04, Na3V2(P04)3(Na3V2P04, or NVP), Na4Fe3(P04)2(P207), NaM’P04F, and Na3(VO y )2(P04)2F 3-2y (0 < y < 1). In NaM’P04F, M’ can include one or more of V, Fe, Mn, and Ni.

[0086] Prussian blue compounds can be a compound having sodium ions, transition metal ions, and cyanide ions (CN - ). The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Non-limiting examples of Prussian blue compounds can be Na a Me b Me’ c (CN)6, where Me and Me’ can each independently be one or more of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a < 2, 0 < b < 1, and 0 < c < 1.

[0087] In some embodiments, a binder can also be optionally included in the positive electrode film layer. As non-limiting examples, the binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0088] In some embodiments, a conductive agent can also be optionally included in the positive electrode film layer. As non-limiting examples, the conductive agent can include one or more of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0089] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the composite capacity compensation agent, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side surface of the positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab can be obtained. The type of the solvent can be selected from, but is not limited to, any of the aforementioned embodiments, such as N-methyl pyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector, or on both surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector, or on both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt%-80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000mPa·s-25000mPa·s.

[0090] In some embodiments, the mass ratio of the composite capacity compensation agent in the positive electrode film layer is 0.01%-8%. During discharging of the secondary battery, the active ions released from the composite capacity compensation agent can provide abundant active ions for the secondary battery, make up for the loss of active ions of the secondary battery due to the initial efficiency, and thus effectively improve the discharge specific capacity and the cycle performance of the secondary battery.

[0091] In some embodiments, the positive electrode film layer includes a positive electrode active material layer, and the positive electrode active material layer contains the positive electrode active material.

[0092] In some embodiments, please refer to Figure 2 , Figure 2 A cross-sectional structure schematic diagram of a positive electrode tab of an embodiment of the present application is shown. The positive electrode tab 7 includes a positive electrode current collector 71 and a positive electrode film layer 72 arranged on the two opposite surfaces of the positive electrode current collector 71. The positive electrode film layer 72 includes a positive electrode active material layer 721, and the positive electrode active material layer 721 contains the positive electrode active material.

[0093] In some embodiments, the positive electrode active material layer further comprises a first capacity compensation agent and a second capacity compensation agent in the composite capacity compensation agent.

[0094] In some embodiments, please refer to Figure 2 , the positive electrode active material layer 721 further comprises a first capacity compensation agent and a second capacity compensation agent in the composite capacity compensation agent. In this way, the positive electrode active material layer 721 contains both the positive electrode active material and the first capacity compensation agent and the second capacity compensation agent in the composite capacity compensation agent, and the composite capacity compensation agent can provide abundant active ions for the secondary battery to make up for the loss of active ions caused by the initial efficiency of the secondary battery.

[0095] In some embodiments, the positive electrode film layer further comprises a first film layer arranged on at least one side surface of the positive electrode active material layer;

[0096] In some embodiments, the positive electrode active material layer further comprises a first capacity compensation agent in the composite capacity compensation agent, and the first film layer comprises a second capacity compensation agent in the composite capacity compensation agent; or,

[0097] The positive electrode active material layer further comprises a second capacity compensation agent in the composite capacity compensation agent, and the first film layer comprises a first capacity compensation agent in the composite capacity compensation agent; or,

[0098] The first film layer comprises a first capacity compensation agent and a second capacity compensation agent in the composite capacity compensation agent. In this way, the composite capacity compensation agent can still provide abundant active ions for the secondary battery to effectively make up for the loss of active ions caused by the initial efficiency of the secondary battery.

[0099] In some embodiments, please refer to Figure 2 , the positive electrode film layer 72 further comprises a first film layer 722 arranged on the surface of the positive electrode active material layer 721 away from the positive electrode current collector 71;

[0100] In some embodiments, the positive electrode active material layer 721 further comprises a first capacity compensation agent in the composite capacity compensation agent, and the first film layer 722 comprises a second capacity compensation agent in the composite capacity compensation agent; or,

[0101] The positive electrode active material layer 721 further comprises a second capacity compensation agent in the composite capacity compensation agent, and the first film layer 722 comprises a first capacity compensation agent in the composite capacity compensation agent; or,

[0102] The first film layer 722 comprises a first capacity compensation agent and a second capacity compensation agent in the composite capacity compensation agent.

[0103] Compared with the positive electrode sheet 7 in which the composite capacity compensation agent is located in the positive electrode active material layer 721, the contact area of the composite capacity compensation agent, the first capacity compensation agent or the second capacity compensation agent in the positive electrode sheet 7 in the above-mentioned embodiment with the positive electrode active material is greatly reduced, but the composite capacity compensation agent containing the first capacity compensation agent and the second capacity compensation agent can still effectively function in the positive electrode sheet 7, which may be due to the second capacity compensation agent dissolving into the electrolyte and contacting the first capacity compensation agent to trigger effective decomposition of the first capacity compensation agent.

[0104] In some embodiments, the positive electrode film layer further comprises a first film layer and a second film layer which are sequentially arranged on the surface of the positive electrode active material layer, the first film layer contains the first capacity compensation agent in the composite capacity compensation agent, and the second film layer contains the second capacity compensation agent in the composite capacity compensation agent, the first film layer is arranged between the positive electrode active material layer and the second film layer, or the first film layer is arranged on the surface of the second film layer away from the positive electrode active material layer. In this way, the composite capacity compensation agent can still provide abundant active ions for the secondary battery, effectively making up for the loss of active ions of the secondary battery due to the initial efficiency.

[0105] Compared with the positive electrode sheet in which the composite capacity compensation agent is located in the positive electrode active material layer, the contact area of the composite capacity compensation agent in the positive electrode sheet in the above-mentioned embodiment with the positive electrode active material is greatly reduced, but the composite capacity compensation agent can still effectively function in the positive electrode sheet, which may be due to the second capacity compensation agent in the composite capacity compensation agent dissolving into the electrolyte and contacting the first capacity compensation agent to trigger effective decomposition of the first capacity compensation agent.

[0106] Figure 3 For a cross-sectional structure schematic diagram of the positive electrode sheet of another embodiment of the present application, please refer to Figure 3 The positive electrode sheet 7 comprises a positive electrode current collector 71 and a positive electrode film layer 72 arranged on the opposite surfaces of the positive electrode current collector 71, the positive electrode film layer 72 comprises a positive electrode active material layer 721 and a first film layer 722 and a second film layer 723 which are sequentially arranged on the surface of the positive electrode active material layer 721, the positive electrode active material layer 721 contains a positive electrode active material, the first film layer 722 contains the first capacity compensation agent in the composite capacity compensation agent, and the second film layer 723 contains the second capacity compensation agent in the composite capacity compensation agent. In the above-mentioned embodiment, the first film layer 722 is arranged between the positive electrode active material layer 721 and the second film layer 723.

[0107] Figure 4 For a cross-sectional structure schematic diagram of the positive electrode sheet of another embodiment of the present application, please refer to Figure 4The positive electrode sheet 7 comprises a positive electrode current collector 71 and a positive electrode film layer 72 arranged on two opposite surfaces of the positive electrode current collector 71. The positive electrode film layer 72 comprises a positive electrode active material layer 721, a second film layer 723 and a first film layer 722 arranged in sequence on the surface of the positive electrode active material layer 721. The positive electrode active material layer 721 comprises a positive electrode active material. The first film layer 722 comprises a first capacity compensation agent in the composite capacity compensation agent. The second film layer 723 comprises a second capacity compensation agent in the composite capacity compensation agent. In the above embodiment, the first film layer 722 is arranged on the surface of the second film layer 723 away from the positive electrode active material layer 721, that is, the second film layer 723 is arranged between the positive electrode active material layer 721 and the first film layer 722.

[0108] Optionally, the mass ratio of the composite capacity compensation agent in the positive electrode film layer is determined by the following method: the positive electrode film layer on the surface of the positive electrode current collector in the positive electrode sheet is scraped off to obtain a powder, the mass of the powder is m1, the mass of the composite capacity compensation agent in the powder is m2 by XRD and ICP, and the mass ratio of the composite capacity compensation agent in the positive electrode film layer is m2 / m1*100%.

[0109] The secondary battery according to another embodiment of the present application comprises at least one of the composite capacity compensation agent and the positive electrode sheet according to the present application.

[0110] The secondary battery according to the present application comprises at least one of the composite capacity compensation agent and the positive electrode sheet according to the present application, and thus has at least the same advantages as the composite capacity compensation agent or the positive electrode sheet.

[0111] The electric device according to another embodiment of the present application comprises the secondary battery according to the present application.

[0112] The electric device according to the present application comprises the secondary battery according to the present application, and thus has at least the same advantages as the secondary battery.

[0113] Generally, the secondary battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charging and discharging of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing the short circuit of the positive electrode and the negative electrode, and at the same time allowing ions to pass through.

[0114] In some embodiments, the positive electrode sheet in the secondary battery is the positive electrode sheet according to the present application.

[0115] In some embodiments, the secondary battery further comprises a negative electrode sheet.

[0116] In some embodiments, the negative electrode tab includes an alkali metal. As a non-limiting example, the negative electrode tab can include sodium metal, lithium metal, or the like.

[0117] In other embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0118] As a non-limiting example, the negative electrode current collector has two opposing surfaces in a thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two opposing surfaces of the negative electrode current collector.

[0119] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material base layer. Non-limiting examples of the metal material in the negative electrode current collector can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, or the like. Non-limiting examples of the polymer material base layer in the negative electrode current collector can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), or the like.

[0120] In some embodiments, the negative electrode active material can employ a negative electrode active material for a battery known in the art. As a non-limiting example, the negative electrode active material can include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, or the like. The silicon-based material can include one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can include one or more of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery can also be used. The negative electrode active material can be used alone or in combination of two or more.

[0121] In some embodiments, the negative electrode active material layer can also optionally include a binder. The binder can include one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0122] In some embodiments, the negative active material layer can also optionally include a conductive agent. The conductive agent can include one or more of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0123] In some embodiments, the negative active material layer can also optionally include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0124] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one side surface of the negative electrode current collector, and after processes such as drying, cold pressing, and the like, the negative electrode sheet can be obtained. The surface of the negative electrode current collector to which the negative electrode slurry is coated can be either one surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa s to 10000 mPa s. When the negative electrode slurry is coated, the coating unit area density, in terms of dry weight (excluding the solvent), can be 75 g / m 2 -220 g / m 2 . The compaction density of the negative electrode sheet can be 1.0 g / cm 3 -1.8 g / cm 3 .

[0125] In some embodiments, the secondary battery further includes an electrolyte. The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not particularly limited in the present application and can be selected as needed. For example, the electrolyte can be liquid.

[0126] In some embodiments, the electrolyte uses an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0127] In some embodiments, the electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro-oxalato-borate (LiDFOB), lithium bis-oxalato-borate (LiBOB), lithium difluoro-bis-oxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0128] In some embodiments, the solvent can include ethylene carbonate (EC, ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BPC), ), one or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, methyl ethyl sulfone, and diethyl sulfone.

[0129] In some embodiments, the electrolyte can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0130] In some embodiments, the additive in the electrolyte can include, but is not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0131] In some embodiments, the secondary battery further includes a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0132] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0133] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and can be 12 μm to 20 μm.

[0134] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to make an electrode assembly through a winding process or a stacking process.

[0135] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0136] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0137] The secondary battery includes at least one battery cell. The secondary battery can include one or more battery cells.

[0138] In the present application, unless otherwise specified, the "battery cell" refers to a basic unit capable of realizing mutual conversion between chemical energy and electrical energy, and further, generally includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0139] The shape of the battery cell is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, Figure 5 is a battery cell 5 in a square structure as an example.

[0140] In some embodiments, referring to Figure 6 , the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by a person skilled in the art according to actual needs.

[0141] The secondary battery can be a battery module 4 or a battery pack 1.

[0142] The battery module includes at least one battery cell. The number of battery cells contained in the battery module can be one or more, which can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0143] Figure 7 is a battery module 4 as an example. Referring to Figure 7 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0144] Optionally, the battery module 4 can further include a case having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0145] In some embodiments, the above-described battery module can be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and a person skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0146] Figure 8 and Figure 9 is a battery pack 1 as an example. Referring to Figure 8 and Figure 9 In the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box can be included. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0147] In addition, the present application also provides a power utilization device, which includes the secondary battery provided by the present application. The secondary battery can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device can be a mobile phone, a notebook computer, etc.; the electric vehicle can be 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., but is not limited thereto.

[0148] As the power utilization device, the secondary battery can be selected according to the use requirement thereof.

[0149] Figure 10 is a power utilization device 6 as an example. The power utilization device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the secondary battery for the power utilization device, a battery pack or a battery module can be used.

[0150] As another example of the device, it can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a secondary battery can be used as a power supply.

[0151] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the technology or condition is not specified in the embodiments, it is carried out according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0152] Example 1

[0153] The secondary battery is prepared according to the following method:

[0154] (1) Preparation of the first capacity compensation agent

[0155] After 3 g of sodium oxalate Na2C2O4 is dissolved in 100 mL of solvent (deionized water) and stirred rapidly and vigorously at a stirring speed of 500 rpm / min, 200 mL of anti-solvent (anhydrous ethanol) is slowly added thereto, followed by a large amount of white precipitate, which is extracted and dried to obtain rod-shaped sodium oxalate Na2C2O4 (the first capacity compensation agent) with a Dv50 of 1 μm.

[0156] (2) Preparation of the second capacity compensation agent

[0157] After 3 g of sodium nitrite NaNO2 is dissolved in 100 mL of solvent (deionized water) and stirred rapidly and vigorously at a stirring speed of 800 rpm / min, 200 mL of anti-solvent (tetrahydrofuran) is slowly added thereto, followed by a large amount of white precipitate, which is extracted and dried to obtain spherical metal salt sodium nitrite NaNO2 (the second capacity compensation agent) with a Dv50 of 3 μm.

[0158] (3) Preparation of the secondary battery

[0159] (3.1) Preparation of the positive electrode sheet

[0160] The positive electrode active material layered oxide NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, the composite capacity compensation agent, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are stirred and mixed uniformly at a weight ratio of 90:5:2.5:2.5, and then a certain amount of N-methyl pyrrolidone (NMP) solvent is added to obtain a positive electrode slurry under the action of a vacuum stirrer; the positive electrode slurry is uniformly coated on an aluminum foil (a positive electrode current collector); the aluminum foil is dried at room temperature, transferred to a 120℃ oven for drying for 4 h, and then subjected to cold pressing and slitting to obtain a positive electrode sheet, and the coating amount per unit area of the positive electrode sheet is 0.25 g / 1540.25 mm 2 . The composite capacity compensation agent is formed by stirring and mixing the first capacity compensation agent and the second capacity compensation agent, and the mass ratio of the second capacity compensation agent to the first capacity compensation agent is 20:100. The mass proportion of the composite capacity compensation agent in the positive electrode film layer is 5%.

[0161] (3.2) Preparation of the negative electrode sheet

[0162] The negative active material hard carbon, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickening agent sodium hydroxymethyl cellulose (CMC) are dissolved in solvent deionized water according to the weight ratio of 95.2:1.8:1.8:1.2, and a negative electrode slurry is obtained under the action of a vacuum stirrer; the negative electrode slurry is uniformly coated on a copper foil (negative electrode current collector); the copper foil is dried at room temperature, then transferred to a 120°C oven for drying for 4h, and then cold-pressed and cut to obtain a negative electrode sheet, with a coating amount of 0.17g / 1540.25mm 2 .

[0163] (3.3) Preparation of electrolyte

[0164] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents ethylene carbonate (EC) and methyl ethyl carbonate (EMC) are mixed uniformly according to a volume ratio of 3:7, and sodium salt NaPF6 (the mass ratio of sodium salt to organic solvent is 12.5:100) is dissolved in the organic solvent, stirred uniformly, and an electrolyte is obtained.

[0165] (3.4) Separation film

[0166] A polypropylene film is used as a separation film.

[0167] (3.5) Preparation of battery

[0168] The positive electrode sheet, the separation film, and the negative electrode sheet are stacked in order, with the separation film between the positive and negative electrode sheets to play a separation role, then wound into a square bare cell, and then placed in an aluminum plastic film, and then baked at 80°C to remove water, and then injected with electrolyte and sealed, and then subjected to processes such as standing, hot and cold pressing, formation, clamp, and capacity distribution, to obtain a sodium ion secondary battery.

[0169] Examples 2-7

[0170] The preparation method of the secondary battery is basically the same as that of Example 1, except that the mass ratio of the second capacity compensation agent to the first capacity compensation agent in the composite capacity compensation agent used in step (3.1) is changed, as shown in Table 1.

[0171] Examples 8-13

[0172] The preparation method of the secondary battery is basically the same as that of Example 1, except that the preparation method of the first capacity compensation agent in step (1) is changed, thereby changing the volume average particle size Dv50 of the first capacity compensation agent in the composite capacity compensation agent, as shown in Table 1.

[0173] In Example 8, the amount of solvent deionized water is 100mL, the amount of antisolvent anhydrous ethanol is 300mL, and the stirring speed is 1500 rmp / min.

[0174] In Example 9, the amount of solvent deionized water was 100 mL, the amount of antisolvent absolute ethanol was 300 mL, and the stirring speed was 1000 rpm / min.

[0175] In Example 10, the amount of solvent deionized water was 150 mL, the amount of antisolvent absolute ethanol was 300 mL, and the stirring speed was 1000 rpm / min.

[0176] In Example 11, the amount of solvent deionized water was 150 mL, the amount of antisolvent absolute ethanol was 300 mL, and the stirring speed was 800 rpm / min.

[0177] In Example 12, the amount of solvent deionized water was 200 mL, the amount of antisolvent absolute ethanol was 300 mL, and the stirring speed was 500 rpm / min.

[0178] In Example 13, the amount of solvent deionized water was 200 mL, the amount of antisolvent absolute ethanol was 300 mL, and the stirring speed was 200 rpm / min.

[0179] Examples 14-18

[0180] The method for preparing the secondary battery was substantially the same as in Example 1, except that the method for preparing the second capacity compensator in step (2) was changed, thereby changing the volume average particle diameter Dv50 of the second capacity compensator in the composite capacity compensator, as described in Table 1.

[0181] In Example 14, the amount of solvent deionized water was 40 mL, the amount of antisolvent tetrahydrofuran was 500 mL, and the stirring speed was 1500 rpm / min.

[0182] In Example 15, the amount of solvent deionized water was 100 mL, the amount of antisolvent tetrahydrofuran was 500 mL, and the stirring speed was 1500 rpm / min.

[0183] In Example 16, the amount of solvent deionized water was 300 mL, the amount of antisolvent tetrahydrofuran was 500 mL, and the stirring speed was 1000 rpm / min.

[0184] In Example 17, the amount of solvent deionized water was 400 mL, the amount of antisolvent tetrahydrofuran was 50 mL, and the stirring speed was 800 rpm / min.

[0185] In Example 18, the amount of solvent deionized water was 400 mL, the amount of antisolvent tetrahydrofuran was 500 mL, and the stirring speed was 200 rpm / min.

[0186] Example 19

[0187] The preparation method of the secondary battery is basically the same as that in Embodiment 1, except that the method for preparing the positive electrode sheet in step (3.1) is different.

[0188] In step (3.1) of this embodiment, the positive electrode active material layered oxide NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, the composite capacity compensator, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are proportioned by weight ratio 90:5:2.5:2.5, the mass ratio of the second capacity compensator to the first capacity compensator in the composite capacity compensator is 20:100, and the second capacity compensator and the first capacity compensator are formed on the positive electrode active material layer by means of double-layer coating.

[0189] Specifically, the positive electrode active material layered oxide NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are stirred and mixed uniformly, and then a certain amount of N-methyl pyrrolidone (NMP) solvent is added to obtain a positive electrode slurry under the action of a vacuum stirrer; the positive electrode slurry is uniformly coated on an aluminum foil (positive electrode current collector); and the aluminum foil is transferred to a 120°C oven for drying for 4h after being air-dried at room temperature to obtain a positive electrode active material layer.

[0190] Then the first capacity compensator in the composite capacity compensator is dissolved in NMP, and the formed slurry is coated on the surface of the positive electrode active material layer away from the aluminum foil, and after drying, a first film layer containing the first capacity compensator is obtained.

[0191] The second capacity compensator in the composite capacity compensator is dissolved in NMP, and the formed slurry is coated on the surface of the first film layer away from the aluminum foil, and after drying, a second film layer containing the second capacity compensator is obtained. The positive electrode film layer includes the positive electrode active material layer, the first film layer, and the second film layer.

[0192] Embodiment 20

[0193] The preparation method of the secondary battery is basically the same as that in Embodiment 1, except that the preparation method of the second capacity compensator in step (2) and the type of the prepared second capacity compensator are changed, as described in detail in Table 1.

[0194] In step (2) of this embodiment, sodium nitrate NaNO2 is replaced by sodium hypophosphite Na2C4O4, deionized water is used as the solvent, and anhydrous ethanol is used as the antisolvent, so that the spherical metal salt sodium hypophosphite Na2C4O4 (the second capacity compensator) with a Dv50 of 100nm is prepared.

[0195] Embodiment 21

[0196] The preparation method of the secondary battery is basically the same as that of Example 20, except that the mass ratio of the second capacity compensator to the first capacity compensator in the composite capacity compensator used in step (3.1) is changed, as shown in Table 1.

[0197] Example 22

[0198] The preparation method of the secondary battery is basically the same as that of Example 1, except that the preparation method of the second capacity compensator in step (2) and the type of the prepared second capacity compensator are changed, and the mass ratio of the second capacity compensator to the first capacity compensator in the composite capacity compensator used in step (3.1) is changed, as shown in Table 1.

[0199] In step (2) of this example, NaNO2 is replaced by Na2C6O6, deionized water is used as the solvent, and anhydrous ethanol is used as the anti-solvent, so that a cubic block-shaped metal salt Na2C6O6 (second capacity compensator) with a Dv50 of 2 μm is prepared.

[0200] Example 23

[0201] The preparation method of the secondary battery is basically the same as that of Example 1, except that the preparation method of the second capacity compensator in step (2) and the type of the prepared second capacity compensator are changed, and the mass ratio of the second capacity compensator to the first capacity compensator in the composite capacity compensator used in step (3.1) is changed, as shown in Table 1.

[0202] In step (2) of this example, Li2O and Fe2O3 are mixed in a molar ratio of 5:2, and then thoroughly ground. After being uniformly mixed, the mixture is heated to 700°C in an inert atmosphere for 5 hours of pre-sintering, and then heated to 900°C for 30 hours of sintering, so that a crystalline phase of Li5FeO4 is obtained. The crystalline phase is ball milled for 20 hours, so that a spherical metal salt Li5FeO4 (second capacity compensator) with a Dv50 of 5 μm is prepared.

[0203] Examples 24-27

[0204] The preparation method of the secondary battery is basically the same as that of Example 1, except that the preparation method of the first capacity compensator in step (1) and the type of the prepared first capacity compensator are changed, as shown in Table 1.

[0205] In step (1) of Example 24, Na2C2O4 is replaced by NaOAc, deionized water is used as the solvent, and tetrahydrofuran is used as the anti-solvent, so that a spherical sodium acetate (first capacity compensator) with a Dv50 of 3 μm is prepared.

[0206] In step (1) of Example 25, sodium oxalate Na2C2O4 is replaced by sodium propionate, the solvent is replaced by deionized water, and the anti-solvent is replaced by tetrahydrofuran, to thereby prepare spherical sodium propionate (first capacity compensator) having a Dv50 of 2 μm.

[0207] In step (1) of Example 26, sodium oxalate Na2C2O4 is replaced by sodium carbonate, the solvent is replaced by deionized water, and the anti-solvent is replaced by tetrahydrofuran, to thereby prepare blocky sodium carbonate (first capacity compensator) having a Dv50 of 4 μm.

[0208] In step (1) of Example 27, sodium oxalate Na2C2O4 is replaced by sodium citrate, the solvent is replaced by deionized water, and the anti-solvent is replaced by tetrahydrofuran, to thereby prepare irregular blocky sodium citrate (first capacity compensator) having a Dv50 of 3 μm.

[0209] Example 28

[0210] A secondary battery is prepared as follows:

[0211] (1) Preparation of a first capacity compensator

[0212] After 3 g of lithium oxalate Li2C2O4 is dissolved in 100 mL of a solvent (deionized water) with rapid and vigorous stirring at a stirring speed of 500 rpm / min, 200 mL of an anti-solvent (tetrahydrofuran) is slowly added thereto, and a large amount of white precipitate is then produced. After suction filtration and drying, cubic blocky lithium oxalate Li2C2O4 (first capacity compensator) having a Dv50 of 3.5 μm is obtained.

[0213] (2) Preparation of a second capacity compensator

[0214] After 3 g of lithium nitrite LiNO2 is dissolved in 100 mL of a solvent (deionized water) with rapid and vigorous stirring at a stirring speed of 500 rpm / min, 200 mL of an anti-solvent (tetrahydrofuran) is slowly added thereto, and a large amount of white precipitate is then produced. After suction filtration and drying, spherical metal salt lithium nitrite LiNO2 (second capacity compensator) having a Dv50 of 2.5 μm is obtained.

[0215] (3) Preparation of a secondary battery

[0216] (3.1) Preparation of a positive electrode sheet

[0217] After 100 g of a positive electrode active material LiNi0.5Co0.2Mn0.3O2 is mixed with 0.5 g of a first capacity compensator (cubic blocky lithium oxalate Li2C2O4 having a Dv50 of 3.5 μm) and 0.5 g of a second capacity compensator (spherical lithium nitrite LiNO2 having a Dv50 of 2.5 μm), the mixture is rolled to a thickness of 100 μm, to thereby prepare a positive electrode sheet. 0.8 Co 0.1 Mn 0.1O2, composite capacity compensator, conductive agent carbon black, binder polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 90:5:2.5:2.5, and then stirred and mixed uniformly, and then a certain amount of N-methyl pyrrolidone (NMP) solvent is added, and a positive electrode slurry is obtained under the action of a vacuum stirrer; the positive electrode slurry is uniformly coated on an aluminum foil (positive electrode current collector); the aluminum foil is dried at room temperature, then transferred to a 120°C oven for drying for 4h, to form a positive electrode film layer, and then cold-pressed and cut to obtain a positive electrode sheet, with a coating amount of 0.25g / 1540.25mm 2 The composite capacity compensator is formed by mixing the first capacity compensator and the second capacity compensator, and the mass ratio of the second capacity compensator to the first capacity compensator is 20:100.

[0218] (3.2) Preparation of a negative electrode sheet

[0219] The negative electrode active material graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickening agent sodium hydroxymethyl cellulose (CMC) are dissolved in a solvent deionized water in a weight ratio of 95.2:1.8:1.8:1.2, and a negative electrode slurry is obtained under the action of a vacuum stirrer; the negative electrode slurry is uniformly coated on a copper foil (negative electrode current collector); the copper foil is dried at room temperature, then transferred to a 120°C oven for drying for 4h, and then cold-pressed and cut to obtain a negative electrode sheet, with a coating amount of 0.17g / 1540.25mm 2 .

[0220] (3.3) Preparation of an electrolyte

[0221] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents ethylene carbonate (EC) and methyl ethyl carbonate (EMC) are mixed uniformly in a volume ratio of 3:7, and lithium salt LiPF6 (the mass ratio of lithium salt to organic solvent is 12.5:100) is dissolved in the organic solvent, and stirred uniformly to obtain an electrolyte.

[0222] (3.4) Isolation film

[0223] A polypropylene film is used as the isolation film.

[0224] (3.5) Preparation of a battery

[0225] The positive electrode sheet, the isolation film, and the negative electrode sheet are stacked in order, with the isolation film between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then wound into a square bare cell, and then placed in an aluminum plastic film, and then baked at 80°C to remove water, and then injected with an electrolyte and sealed, and then subjected to processes of standing, hot and cold pressing, formation, clamping, and capacity distribution, to obtain a lithium ion secondary battery.

[0226] Comparative Example 1

[0227] The preparation method of the secondary battery is basically the same as that of Example 1, except that the method for preparing the positive electrode sheet in step (3.1) is different.

[0228] In step (3.1) of the present comparative example, the positive electrode active material layered oxide NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were stirred and mixed uniformly at a weight ratio of 90:5:5, and then a certain amount of N-methyl pyrrolidone (NMP) solvent was added to obtain a positive electrode slurry under the action of a vacuum stirrer; the positive electrode slurry was uniformly coated on an aluminum foil; the aluminum foil was dried at room temperature, then transferred to a 120°C oven for drying for 4h, and then cold-pressed and cut to obtain a positive electrode sheet, with a coating amount per unit area of 0.25g / 1540.25mm 2 .

[0229] Comparative Example 2

[0230] The preparation method of the secondary battery is basically the same as that of Example 1, except that in step (3.1) for preparing the positive electrode sheet, the first capacity compensation agent prepared in step (1) is directly used as the composite capacity compensation agent.

[0231] Comparative Example 3

[0232] The preparation method of the secondary battery is basically the same as that of Example 1, except that in step (3.1) for preparing the positive electrode sheet, the second capacity compensation agent prepared in step (2) is directly used as the composite capacity compensation agent.

[0233] Comparative Example 4

[0234] The preparation method of the secondary battery is basically the same as that of Example 28, except that the method for preparing the positive electrode sheet in step (3.1) is different.

[0235] In step (3.1) of the present comparative example, the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were stirred and mixed uniformly at a weight ratio of 90:5:5, and then a certain amount of N-methyl pyrrolidone (NMP) solvent was added to obtain a positive electrode slurry under the action of a vacuum stirrer; the positive electrode slurry was uniformly coated on an aluminum foil (positive electrode current collector); the aluminum foil was dried at room temperature, then transferred to a 120°C oven for drying for 4h, and then cold-pressed and cut to obtain a positive electrode sheet, with a coating amount per unit area of 0.25g / 1540.25mm 2 .

[0236] Test Example

[0237] (1) Morphology test

[0238] The morphology of the first capacity compensator and the second capacity compensator was observed using a scanning electron microscope.

[0239] (2) Test of volume average particle size Dv50

[0240] Referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, the volume average particle size Dv50 of the first capacity compensator and the second capacity compensator was tested by using a Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.

[0241] (3) Test of discharge gram capacity and cycle performance of the battery

[0242] At 60°C, the battery was charged at 1 / 3C constant current to 4.2V, then charged at 4.2V constant voltage to a current of 0.05C, rested for 5 min, and then discharged at 1 / 3C to 1.9V. The obtained discharge gram capacity was recorded as the initial capacity D0. The above steps were repeated for the same battery, and the discharge gram capacity Dn of the battery after the nth cycle was recorded at the same time. The capacity retention rate Pn (%) of the battery after each cycle was Dn / D0*100%. In the test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and the 500th cycle corresponds to n=500. The discharge gram capacity of the battery after the 500th cycle was obtained, and the capacity retention rate P500 of the battery after the 500th cycle, i.e. the cycle performance of the battery, was calculated.

[0243] The test results of each embodiment and each comparative example are shown in Table 1. In Table 1, " / " represents the absence of the substance or the parameter.

[0244] Table 1

[0245]

[0246]

[0247] As can be seen from Table 1, compared with Comparative Examples 1-3, the discharge gram capacity of the battery after the 500th cycle and the capacity retention rate after the 500th cycle of the battery of Examples 1-27 are relatively high. Compared with Comparative Example 4, the discharge gram capacity of the battery after the 500th cycle and the capacity retention rate after the 500th cycle of the battery of Example 28 are obviously improved, indicating that the first capacity compensator and the second capacity compensator in Examples 1-28 are used in combination, which can reduce the decomposition voltage of the composite capacity compensator, improve the sodium compensation efficiency and / or lithium compensation efficiency of the composite capacity compensator, thereby effectively improving the discharge gram capacity and cycle performance of the battery.

[0248] The above description of the various embodiments tends to emphasize differences between the various embodiments, and the same or similar parts or features can be mutually referred to for brevity, which will not be repeated here.

[0249] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, which achieves the same action and effect as the technical idea, within the scope of the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications that can be thought of by those skilled in the art to the embodiments, or by combining part of the constituent elements of the embodiments, within the scope of the gist of the present application are also included in the scope of the present application.

Claims

1. A composite capacity compensator, characterized in that, It includes a first volume compensator and a second volume compensator, wherein the first volume compensator comprises a substance with the chemical formula M x C a O b H c The material, wherein M includes one or more of Na and Li, 0 < x ≤ 4, 2 ≤ a ≤ 6, 2 ≤ b ≤ 7, 0 ≤ c ≤ 6, the second capacity compensator includes a metal salt, and the decomposition voltage of the metal salt in the second capacity compensator is higher than that of the first capacity compensator with the chemical formula M. x C a O b H c The material has a low decomposition voltage.

2. The composite capacity compensator according to claim 1, characterized in that, The mass ratio of the second volume compensator to the first volume compensator is (7~30):

100.

3. The composite capacity compensator according to claim 1 or 2, characterized in that, The mass ratio of the second volume compensator to the first volume compensator is (10~25):

100.

4. The composite capacity compensator according to any one of claims 1 to 3, characterized in that, The composite capacity compensator has one or more of the following characteristics (1) to (2): (1) The volume average particle size Dv50 of the first capacity compensator is 30nm~5μm; (2) The volume average particle size Dv50 of the second capacity compensator is 100nm~5μm.

5. The composite capacity compensator according to any one of claims 1 to 4, characterized in that, The composite capacity compensator has one or more of the following characteristics (1) to (2): (1) The volume average particle size Dv50 of the first capacity compensator is 30nm~2μm; (2) The volume average particle size Dv50 of the second capacity compensator is 100nm~3μm.

6. The composite capacity compensator according to any one of claims 1 to 5, characterized in that, The first capacity compensator and the second capacity compensator each independently include at least one of a spherical structure, a near-spherical structure, a rod-shaped structure, and a block-shaped structure.

7. The composite capacity compensator according to any one of claims 1 to 6, characterized in that, The metal salt includes one or more of NaNO2, Na2C4O4, Na5FeO4, Na2C6O6, LiNO2, Li2C4O4, Li5FeO4, and Li2C6O6.

8. The composite capacity compensator according to any one of claims 1 to 7, characterized in that, The chemical formula is M x C a O b H c The materials include one or more of sodium oxalate, sodium acetate, sodium propionate, sodium malonate, sodium carbonate, sodium citrate, lithium oxalate, lithium acetate, lithium propionate, lithium malonate, lithium carbonate, and lithium citrate.

9. A positive electrode sheet, characterized in that, It includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer comprising a positive electrode active material and a composite capacity compensator according to any one of claims 1 to 8.

10. The positive electrode sheet according to claim 9, characterized in that, The composite capacity compensator accounts for 0.01% to 8% of the mass of the positive electrode film.

11. The positive electrode sheet according to claim 9 or 10, characterized in that, The positive electrode film layer includes a positive electrode active material layer, and the positive electrode active material layer contains a positive electrode active material.

12. The positive electrode sheet according to claim 11, characterized in that, The positive electrode active material layer also includes a first capacity compensator and a second capacity compensator in the composite capacity compensator.

13. The positive electrode sheet according to claim 11, characterized in that, The positive electrode film layer further includes a first film layer disposed on at least one surface of the positive electrode active material layer; The positive electrode active material layer further includes a first capacity compensator in the composite capacity compensator, and the first film layer includes a second capacity compensator in the composite capacity compensator; or... The positive electrode active material layer further includes a second capacity compensator in the composite capacity compensator, and the first film layer includes a first capacity compensator in the composite capacity compensator; or... The first membrane layer contains a first capacity compensator and a second capacity compensator in the composite capacity compensator.

14. The positive electrode sheet according to claim 11, characterized in that, The positive electrode film layer further includes a first film layer and a second film layer stacked on at least one side surface of the positive electrode active material layer. The first film layer contains a first capacity compensator in the composite capacity compensator, and the second film layer contains a second capacity compensator in the composite capacity compensator. The first film layer is disposed between the positive electrode active material layer and the second film layer, or the first film layer is disposed on the surface of the second film layer away from the positive electrode active material layer.

15. A secondary battery, characterized in that, It includes at least one of the composite capacity compensator according to any one of claims 1 to 8 and the positive electrode sheet according to any one of claims 9 to 14.

16. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 15.

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