Composite sodium supplement material and preparation method thereof, positive electrode sheet, battery and electrical device

Abstract

This application discloses a composite sodium-supplementing material, a preparation method thereof, a positive electrode plate, a battery, and an electrical device. The composite sodium-supplementing material comprises a substrate and a carbon coating layer located on at least a portion of the substrate's surface. The substrate comprises a sodium-supplementing material, and the carbon coating layer comprises an inorganic carbon material and an organic carbonized material. The sodium-supplementing material comprises one or more compounds represented by formula (I) or formula (II), where m represents an integer from 1 to 8, and n represents an integer from 2 to 20. The composite sodium-supplementing material provided herein has a low oxidation potential, a high theoretical capacity, and a high capacity utilization rate.

Description

Technical Field

[0001] The present application relates to a composite sodium supplement material and a preparation method thereof, a positive electrode sheet, a battery and an electrical device. Background Art

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. At present, lithium batteries still occupy the core position of batteries, but lithium batteries also face great challenges, such as the increasing shortage of lithium resources. Sodium resources are far more abundant than lithium resources, are more widely distributed, and have a much lower cost than lithium. Therefore, sodium batteries have become a new generation of electrochemical systems with great potential to replace lithium batteries. Similar to lithium batteries, when sodium batteries are charged for the first time, a solid electrolyte interface (SEI) film will form on the surface of the negative electrode. This process will irreversibly consume the active sodium of the positive electrode, thereby reducing the battery's first discharge capacity and first coulombic efficiency. Sodium supplementation of the positive electrode is one of the effective methods to solve the above problems. However, the positive electrode sodium supplements currently used have problems such as poor capacity performance and low capacity utilization. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0003] The present application provides a composite sodium-supplementing material and a preparation method thereof, a positive electrode plate, a battery and an electrical device. The composite sodium-supplementing material has a low oxidation potential, a high theoretical capacity and a high capacity utilization rate.

[0004] In a first aspect, the present application provides a composite sodium-supplementing material, comprising a matrix and a carbon coating layer located on at least a portion of the surface of the matrix, wherein the matrix comprises a sodium-supplementing material, and the carbon coating layer comprises an inorganic carbon material and an organic carbonized material.

[0005] The sodium supplement material includes one or more compounds represented by formula (I) and formula (II).

[0006]

[0007] m represents an integer of 1 to 8, and n represents an integer of 2 to 20.

[0008] The composite sodium-supplementing material provided in the embodiments of the present application can have a low oxidation potential, a high theoretical capacity, and a high capacity utilization rate. When applied to the positive electrode of a battery, it does not change the potential of the positive electrode active material, and can improve the battery's initial discharge capacity and initial coulombic efficiency, and can also make the battery have a high energy density. In addition, the active sodium is gradually consumed during the battery cycle. The composite sodium-supplementing material can also provide excess active sodium for storage in the negative electrode, thereby compensating for the loss of active sodium during the battery cycle, thereby reducing the probability of excessive release of sodium ions from the positive electrode active material, thereby improving the structural stability of the positive electrode active material and improving the battery's cycle stability and cycle life.

[0009] In any embodiment, the mass of the sodium-supplementing material is recorded as m1, the mass of the inorganic carbon material is recorded as m2, and the mass of the organic carbonized material is recorded as m3, m1:m2 is (1-4):1, which can be optionally (1-2):1; and / or, m3:(m1+m2) is (0.5-3):100, which can be optionally (1-2):100.

[0010] By adjusting m1:m2 within the above range, it is beneficial to improve the electronic conductivity of the sodium-supplementing material, reduce the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby helping to reduce the oxidation potential of the sodium-supplementing material, and also to maximize the capacity of the sodium-supplementing material and improve the capacity utilization rate of the sodium-supplementing material.

[0011] By adjusting m3:(m1+m2) within the above range, it is beneficial to improve the uniformity of the carbon coating layer, thereby improving the electronic conductivity of the sodium-supplementing material, reducing the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby helping to reduce the oxidation potential of the sodium-supplementing material, and also helping to exert the capacity of the sodium-supplementing material and improve the capacity utilization of the sodium-supplementing material.

[0012] In any embodiment, the powder resistivity of the composite sodium-supplementing material at 25° C. and 20 MPa is 0.2Ω.cm-2Ω.cm, and can be optionally 0.4Ω.cm-1Ω.cm.

[0013] In any embodiment, the specific surface area of ​​the composite sodium supplement material is 3.8m 2 / g-7.1m 2 / g, optional 4.5m 2 / g-6.8m 2 / g.

[0014] In any embodiment, the volume distribution particle size Dv50 of the composite sodium-supplementing material is 0.5 μm-10 μm, and optionally 1.5 μm-7.6 μm. When the volume distribution particle size Dv50 of the composite sodium-supplementing material is within the above range, the composite sodium-supplementing material can have a lower oxidation potential, thereby facilitating the utilization of the capacity of the sodium-supplementing material and improving the capacity utilization rate of the sodium-supplementing material.

[0015] In any embodiment, the inorganic carbon material includes one or more of conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, carbon nanotube, graphene, and reduced graphene oxide.

[0016] In any embodiment, the organic carbon source forming the organic carbonized material includes one or more of starch, glucose, fructose, maltose, sucrose, cellulose, hemicellulose, lignin, cyclodextrin, polyacrylonitrile, polyethylene glycol, polyvinyl alcohol, polyaniline, polypyrrole, polythiophene, phenolic resin, and epoxy resin.

[0017] In any embodiment, the sodium supplement material includes one or more of the following compounds:

[0018]

[0019]

[0020] The second aspect of the present application provides a method for preparing a composite sodium-supplementing material, comprising the following steps: mixing a sodium-supplementing material, an inorganic carbon material, and an organic carbon source to obtain a mixture, and sintering the obtained mixture at a preset temperature and a preset time to obtain a composite sodium-supplementing material.

[0021] The sodium supplement material includes one or more compounds represented by formula (I) and formula (II).

[0022]

[0023] m represents an integer of 1 to 8, and n represents an integer of 2 to 20.

[0024] The composite sodium-supplementing material prepared by the preparation method provided in the embodiments of the present application can have a low oxidation potential, a high theoretical capacity, and a high capacity utilization rate. When applied to the positive electrode of a battery, it will not change the potential of the positive electrode active material, and can improve the battery's initial discharge capacity and initial coulombic efficiency, and can also make the battery have a high energy density. In addition, the active sodium will gradually be consumed during the battery cycle. The composite sodium-supplementing material can also provide excess active sodium to be stored in the negative electrode, thereby compensating for the loss of active sodium during the battery cycle, thereby reducing the probability of excessive release of sodium ions from the positive electrode active material, thereby improving the structural stability of the positive electrode active material and improving the battery's cycle stability and cycle life.

[0025] In any embodiment, the preset temperature is 350° C.-500° C., optionally 380° C.-480° C. The preset temperature during the sintering process is within the above range. On the one hand, the organic carbon source can be carbonized and form a uniform carbon coating layer with high electronic conductivity on the surface of the sodium-supplementing material matrix together with the inorganic carbon material. On the other hand, the decomposition of the sodium-supplementing material can be reduced.

[0026] In any embodiment, the preset time is 2 hours to 5 hours, and can be optionally 2.5 hours to 4 hours. The preset time during the sintering process is within the above range. On the one hand, the organic carbon source can be carbonized and, together with the inorganic carbon material, form a uniform carbon coating layer with high electronic conductivity on the surface of the sodium-supplementing material matrix. On the other hand, the decomposition of the sodium-supplementing material can be reduced.

[0027] In any embodiment, the step of mixing the sodium-supplementing material, the inorganic carbon material, and the organic carbon source to obtain a mixture includes the following steps: grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, and then mixing the obtained intermediate with the organic carbon source for a second dry grinding to obtain a mixture.

[0028] Dry grinding of the sodium-supplementing material and the inorganic carbon material can reduce the particle size of the sodium-supplementing material and improve the dispersibility of the inorganic carbon material on the surface of the sodium-supplementing material particles, thereby increasing the number of contact points between the inorganic carbon material and the sodium-supplementing material particles. Furthermore, dry grinding of the sodium-supplementing material and the inorganic carbon material can reduce agglomeration of the inorganic carbon material and limit the rapid grain growth of the sodium-supplementing material particles during sintering.

[0029] In any embodiment, in the step of grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, the grinding time is 0.5h-5h, and can be optionally 0.6h-3h.

[0030] In any embodiment, in the step of grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, the grinding speed is 200 r / min-600 r / min, and can be optionally 300 r / min-500 r / min.

[0031] In any embodiment, in the step of grinding the sodium-supplementing material and the inorganic carbon material by a dry grinding process to obtain an intermediate, the volume distribution particle size Dv50 of the obtained intermediate is less than or equal to 20 μm, and can be optionally 1.5 μm-10 μm.

[0032] In any embodiment, in the step of grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, the grinding is performed in a ball milling device.

[0033] In any embodiment, in the step of mixing the obtained intermediate with an organic carbon source and performing a second dry grinding, the grinding time is 0.5 h to 4 h, and optionally 0.6 h to 2 h.

[0034] In any embodiment, in the step of mixing the obtained intermediate with the organic carbon source and performing a second dry grinding, the grinding speed is 200 r / min-600 r / min, and can be optionally 300 r / min-500 r / min.

[0035] In any embodiment, the preparation method further includes the steps of grinding and screening the composite sodium-supplementing material obtained by sintering at a preset temperature and for a preset time. This helps to reduce the oxidation potential of the composite sodium-supplementing material, maximize the capacity of the sodium-supplementing material, and improve the capacity utilization rate of the sodium-supplementing material.

[0036] In any embodiment, the mass of the sodium-supplementing material is recorded as m1, the mass of the inorganic carbon material is recorded as m2, and the mass of the residual carbon sintered by the organic carbon source at a preset temperature and a preset time is recorded as m3, m1:m2 is (1-4):1, which can be optionally (1-2):1; and / or, m3:(m1+m2) is (0.5-3):100, which can be optionally (1-2):100.

[0037] By adjusting m1:m2 within the above range, it is beneficial to improve the electronic conductivity of the sodium-supplementing material, reduce the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby helping to reduce the oxidation potential of the sodium-supplementing material, and also to maximize the capacity of the sodium-supplementing material and improve the capacity utilization rate of the sodium-supplementing material.

[0038] By adjusting m3:(m1+m2) within the above range, it is beneficial to improve the uniformity of the carbon coating layer, thereby improving the electronic conductivity of the sodium-supplementing material, reducing the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby helping to reduce the oxidation potential of the sodium-supplementing material, and also helping to exert the capacity of the sodium-supplementing material and improve the capacity utilization of the sodium-supplementing material.

[0039] In any embodiment, the inorganic carbon material includes one or more of conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, carbon nanotube, graphene, and reduced graphene oxide.

[0040] In any embodiment, the specific surface area of ​​the inorganic carbon material is 20m 2 / g-1600m 2 / g, optional 60m 2 / g-1500m 2 / g. Grinding an inorganic carbon material with a high specific surface area with a sodium-supplementing material can increase the contact sites between the inorganic carbon material and the sodium-supplementing material particles, thereby reducing the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby reducing the oxidation potential of the sodium-supplementing material, and further facilitating the utilization of the sodium-supplementing material's capacity and capacity utilization.

[0041] In any embodiment, the organic carbon source includes one or more of starch, glucose, fructose, maltose, sucrose, cellulose, hemicellulose, lignin, cyclodextrin, polyacrylonitrile, polyethylene glycol, polyvinyl alcohol, polyaniline, polypyrrole, polythiophene, phenolic resin, and epoxy resin.

[0042] In any embodiment, the sodium supplement material includes one or more of the following compounds:

[0043]

[0044] In a third aspect, the present application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the composite sodium-supplementing material of the first aspect of the present application or the composite sodium-supplementing material prepared by the preparation method of the second aspect of the present application. This can improve the initial discharge capacity and initial coulombic efficiency of the battery, and can also provide the battery with a high energy density.

[0045] In any embodiment, the weight content of the composite sodium-supplementing material in the positive electrode film layer is 0.1%-5%, and optionally 0.5%-3%, based on the total weight of the positive electrode film layer. This can further improve the initial discharge capacity and initial coulombic efficiency of the battery, and can also enable the battery to have a high energy density.

[0046] In any embodiment, the positive electrode film layer further includes a positive electrode active material, and the positive electrode active material includes one or more of layered transition metal oxides, polyanion materials, and Prussian materials.

[0047] A fourth aspect of the present application provides a battery, comprising the positive electrode sheet of the third aspect of the present application.

[0048] In any embodiment, the battery comprises one or more of a sodium ion battery, a sodium metal battery, and a negative electrode-free sodium battery.

[0049] A fifth aspect of the present application provides an electrical device, comprising the battery of the fourth aspect of the present application, wherein the battery is used to provide electrical energy.

[0050] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0052] Figure 1 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0053] Figure 2 yes Figure 1 An exploded schematic diagram of an embodiment of a battery cell.

[0054] Figure 3 It is a schematic diagram of an embodiment of a battery module of the present application.

[0055] Figure 4 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0056] Figure 5 yes Figure 4 An exploded schematic diagram of an embodiment of a battery pack is shown.

[0057] Figure 6 It is a schematic diagram of an embodiment of an electric device including the battery of the present application as a power source.

[0058] In the accompanying drawings, which are not necessarily drawn to scale, reference numerals are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0059] Below, the embodiments of the composite sodium supplement material and its preparation method, positive electrode plate, battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0060] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0061] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0062] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0063] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0064] In this application, the terms "plurality" and "multiple" refer to two or more.

[0065] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0066] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0067] The powder resistivity of a material is well known in the art and can be measured using instruments and methods known in the art. For example, the test can be performed in accordance with GB / T 32993-2016. The test temperature is 25°C and the test pressure is 200 MPa.

[0068] The specific surface area of ​​a material is well known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis test method in accordance with GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using an ASAP 3020 surface area and pore size analyzer from Micromeritics, USA.

[0069] The volume distribution particle size Dv50 of a material is well known in the art and represents the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%. It can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer in accordance with GB / T19077-2016. The testing instrument can be a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd. in the UK.

[0070] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module, or a battery pack.

[0071] A battery cell is the smallest unit that makes up a battery and can independently realize the function of charging and discharging. A battery cell can be cylindrical, rectangular or other shapes, etc., which is not limited in the embodiments of the present application. Figure 1 As an example, a battery cell 5 having a rectangular parallelepiped structure is shown.

[0072] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0073] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0074] A battery cell generally includes an electrode assembly and an electrolyte. The electrode assembly typically includes a positive electrode sheet and a negative electrode sheet. The electrode assembly can be a wound structure or a stacked structure, which is not limited in the present application.

[0075] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging can also be a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0076] In some embodiments, as Figure 2 As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening, thereby sealing the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in a battery cell 5 can be one or more, and can be adjusted according to needs.

[0077] In some embodiments, battery cells may be assembled into a battery module. A battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the 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 manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0078] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0079] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0080] Figure 4 and Figure 5 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, a battery pack 1 may include a housing and multiple battery modules 4 disposed therein. The housing comprises an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the housing.

[0081] The battery provided in the embodiments of the present application is a sodium battery, which may include, for example, a sodium ion battery, a sodium metal battery, a negative electrode-free sodium metal battery, etc., and the embodiments of the present application are not limited to this.

[0082] A cathode-free sodium metal battery generally refers to a battery constructed without the active negative electrode layer being applied during the battery manufacturing process. For example, a sodium metal layer is not applied to the negative electrode through coating or deposition, or the negative electrode active material layer is formed from a carbonaceous active material layer. During initial charging, sodium ions gain electrons at the negative electrode and deposit on the surface of the negative electrode current collector, forming metallic sodium. During discharge, the metallic sodium can be converted into sodium ions and returned to the positive electrode, enabling cyclic charge and discharge. Compared to other batteries, cathode-free sodium metal batteries can achieve higher energy density due to the lack of an active negative electrode layer. In some embodiments, to improve battery performance, the cathode side of the cathode-free sodium metal battery can also be provided with some conventional negative electrode active materials, such as carbon materials. Although these materials have a certain capacity, their low content and their non-use as the primary negative electrode active material in the battery mean that such a battery can still be considered an cathode-free sodium metal battery. The CB (Cell Balance) value of a negative electrode-free sodium metal battery is typically very small. For example, in some embodiments, the CB value of a negative electrode-free sodium metal battery can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery divided by the unit area capacity of the positive electrode. Because a negative electrode-free sodium metal battery contains no or only a small amount of negative electrode active material, the unit area capacity of the negative electrode is small, and thus the CB value is very small, for example, typically less than or equal to 0.1.

[0083] The embodiments of the present application provide a composite sodium supplement material.

[0084] The composite sodium-supplementing material comprises a matrix and a carbon coating layer located on at least a portion of the surface of the matrix. The matrix comprises the sodium-supplementing material, and the carbon coating layer comprises an inorganic carbon material and an organic carbonized material.

[0085] The sodium supplement material includes one or more compounds represented by formula (I) and formula (II).

[0086]

[0087] m represents an integer of 1 to 8, and n represents an integer of 2 to 20.

[0088] The composite sodium supplement material provided in the embodiments of the present application includes a substrate and a carbon coating layer located on at least a portion of the surface of the substrate.

[0089] During the first charge of the battery (i.e., the first charge in the formation stage), the sodium supplement material matrix decomposes and releases active sodium ions and gases. The released active sodium ions can compensate for the loss of active sodium ions caused by the formation of the SEI film at the negative electrode, thereby improving the battery's first discharge capacity and first coulombic efficiency. The gases released by the decomposition of the sodium supplement material matrix can be removed during the battery formation stage.

[0090] Sodium-supplementing materials include one or more compounds represented by formula (I) or formula (II). These sodium-supplementing materials can have the advantages of high decomposition rate and high theoretical capacity. However, the sodium-supplementing materials represented by formula (I) or formula (II) have high oxidation potentials, resulting in low actual capacity and capacity utilization when used in batteries. This may affect the performance of the positive electrode active material in the battery and may also reduce the battery's energy density.

[0091] Inorganic carbon materials have high electronic conductivity, and coating them on the surface of the sodium-supplementing material matrix can improve the electronic conductivity of the sodium-supplementing material matrix; however, inorganic carbon materials are easy to agglomerate, which makes the carbon coating layer formed by the inorganic carbon materials on the surface of the sodium-supplementing material matrix usually uneven, which is not conducive to reducing the oxidation potential of the sodium-supplementing material, nor is it conducive to the capacity development of the sodium-supplementing material.

[0092] The organic carbonized material is obtained by carbonizing an organic carbon source. Upon heating, the organic carbon source softens, forming a uniform coating with the inorganic carbon material that coats the surface of the sodium-supplementing material particles. After carbonization, the organic carbon source in the coating ultimately forms the organic carbonized material. Furthermore, the carbonization treatment forms a uniform, highly electronically conductive carbon coating on the surface of the sodium-supplementing material matrix, thereby improving the sodium-supplementing material's electronic conductivity, reducing its charge transfer resistance and polarization resistance, and thereby lowering its oxidation potential. This also facilitates the utilization of the sodium-supplementing material's capacity and capacity utilization.

[0093] Therefore, the composite sodium-supplementing material provided in the embodiments of the present application can have a low oxidation potential, a high theoretical capacity, and a high capacity utilization rate. When applied to the positive electrode of a battery, it will not change the potential of the positive electrode active material, and can improve the battery's initial discharge capacity and initial coulombic efficiency, and can also make the battery have a high energy density. In addition, the active sodium will gradually be consumed during the battery cycle. The composite sodium-supplementing material can also provide excess active sodium to be stored in the negative electrode, thereby compensating for the loss of active sodium during the battery cycle, thereby reducing the probability of excessive release of sodium ions from the positive electrode active material, thereby improving the structural stability of the positive electrode active material and improving the battery's cycle stability and cycle life.

[0094] The mass of the sodium supplement material is recorded as m1, the mass of the inorganic carbon material is recorded as m2, and the mass of the organic carbonized material is recorded as m3.

[0095] In some embodiments, m1:m2 can be (1-4):1, and can optionally be (1-2):1. By adjusting m1:m2 within the above range, it is beneficial to improve the electronic conductivity of the sodium-supplementing material, reduce the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby facilitating the reduction of the oxidation potential of the sodium-supplementing material, and also facilitating the utilization of the capacity of the sodium-supplementing material and improving the capacity utilization rate of the sodium-supplementing material.

[0096] In some embodiments, m3:(m1+m2) can be (0.5-3):100, or optionally (1-2):100. By adjusting m3:(m1+m2) within the above range, the uniformity of the carbon coating layer is improved, thereby improving the electronic conductivity of the sodium-supplementing material, reducing the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby reducing the oxidation potential of the sodium-supplementing material, and further facilitating the utilization of the capacity of the sodium-supplementing material and improving the capacity utilization rate of the sodium-supplementing material.

[0097] The mass content of organic carbonized materials in the composite sodium supplement material can be obtained by high-frequency infrared carbon-sulfur analysis. The test standard can refer to GB / T 20123-2006.

[0098] In some embodiments, the powder resistivity of the composite sodium-supplementing material at 25° C. and 20 MPa may be 0.2 Ω.cm-2 Ω.cm, or optionally 0.4 Ω.cm-1 Ω.cm.

[0099] In some embodiments, the specific surface area of ​​the composite sodium supplement material can be 3.8 m 2 / g-7.1m 2 / g, optional 4.5m 2 / g-6.8m 2 / g.

[0100] In some embodiments, the volume distribution particle size Dv50 of the composite sodium-supplementing material can be 0.5 μm-10 μm, optionally 1.5 μm-7.6 μm. When the volume distribution particle size Dv50 of the composite sodium-supplementing material is within the above range, the composite sodium-supplementing material can have a lower oxidation potential, thereby facilitating the utilization of the capacity of the sodium-supplementing material and improving the capacity utilization rate of the sodium-supplementing material.

[0101] In some embodiments, the inorganic carbon material may include, but is not limited to, one or more of conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, carbon nanotube, graphene, and reduced graphene oxide.

[0102] In some embodiments, the organic carbon source forming the organic carbonized material may include, but is not limited to, one or more of starch, glucose, fructose, maltose, sucrose, cellulose, hemicellulose, lignin, cyclodextrin, polyacrylonitrile, polyethylene glycol, polyvinyl alcohol, polyaniline, polypyrrole, polythiophene, phenolic resin, and epoxy resin.

[0103] In some embodiments, m may represent an integer from 1 to 6, optionally an integer from 1 to 4, and more optionally 1 or 2.

[0104] In some embodiments, n may represent an integer from 2 to 10, optionally an integer from 2 to 6, and more optionally 2 or 3.

[0105] In some embodiments, sodium supplement materials may include, but are not limited to, one or more of the following compounds:

[0106]

[0107]

[0108] [Preparation method]

[0109] The present invention also provides a method for preparing a composite sodium-supplementing material.

[0110] The preparation method comprises the following steps: mixing a sodium-supplementing material, an inorganic carbon material and an organic carbon source to obtain a mixture, and sintering the obtained mixture at a preset temperature and a preset time to obtain a composite sodium-supplementing material.

[0111] The sodium supplement material includes one or more compounds represented by formula (I) and formula (II).

[0112]

[0113] m represents an integer of 1 to 8, and n represents an integer of 2 to 20.

[0114] The preparation method of the composite sodium supplement material provided in the embodiments of the present application is simple in process and suitable for large-scale production.

[0115] When the battery is charged for the first time (i.e., the first charge in the formation stage), the sodium-supplementing material matrix decomposes and releases active sodium ions and gas. The released active sodium ions can make up for the loss of active sodium ions caused by the formation of the SEI film at the negative electrode, thereby improving the battery's first discharge capacity and first coulomb efficiency; the gas released by the decomposition of the sodium-supplementing material matrix can be removed in the battery formation stage. The sodium-supplementing material includes one or more compounds represented by formula (I) and formula (II), so the sodium-supplementing material can have the advantages of high decomposition rate and high theoretical capacity. However, the sodium-supplementing materials represented by formula (I) and formula (II) have high oxidation potentials, low actual capacity when used in batteries, and low capacity utilization, which may affect the performance of the positive electrode active material in the battery and may also reduce the energy density of the battery.

[0116] Inorganic carbon materials have high electronic conductivity, and coating them on the surface of the sodium-supplementing material matrix can improve the electronic conductivity of the sodium-supplementing material matrix; however, inorganic carbon materials are easy to agglomerate, which makes the carbon coating layer formed by the inorganic carbon materials on the surface of the sodium-supplementing material matrix usually uneven, which is not conducive to reducing the oxidation potential of the sodium-supplementing material, nor is it conducive to the capacity development of the sodium-supplementing material.

[0117] In the embodiment of the present application, a mixture comprising a sodium-supplementing material, an inorganic carbon material, and an organic carbon source is sintered together at a preset temperature and for a preset time. The organic carbon source softens upon heating, thereby forming a uniform coating with the inorganic carbon material on the surface of the sodium-supplementing material particles. After sintering, the organic carbon source in the coating ultimately forms an organic carbonized material. Furthermore, after sintering, a uniform carbon coating with high electronic conductivity is formed on the surface of the sodium-supplementing material matrix, thereby improving the electronic conductivity of the sodium-supplementing material, reducing the charge transfer resistance and polarization resistance of the sodium-supplementing material, and further reducing the oxidation potential of the sodium-supplementing material. This is also beneficial for utilizing the capacity of the sodium-supplementing material and improving the capacity utilization rate of the sodium-supplementing material.

[0118] Therefore, the composite sodium-supplementing material prepared by the preparation method provided in the embodiment of the present application can have a low oxidation potential, a high theoretical capacity, and a high capacity utilization rate. When applied to the positive electrode of the battery, it will not change the potential of the positive electrode active material, and can improve the battery's initial discharge capacity and initial coulombic efficiency, and can also make the battery have a high energy density. In addition, the active sodium will gradually be consumed during the battery cycle. The composite sodium-supplementing material can also provide excess active sodium to be stored in the negative electrode, thereby compensating for the loss of active sodium during the battery cycle, thereby reducing the probability of excessive release of sodium ions from the positive electrode active material, thereby improving the structural stability of the positive electrode active material and improving the battery's cycle stability and cycle life.

[0119] In some embodiments, m may represent an integer from 1 to 6, optionally an integer from 1 to 4, and more optionally 1 or 2.

[0120] In some embodiments, n may represent an integer from 2 to 10, optionally an integer from 2 to 6, and more optionally 2 or 3.

[0121] In some embodiments, sodium supplement materials may include, but are not limited to, one or more of the following compounds:

[0122]

[0123] In some embodiments, the preset temperature may be 350° C.-500° C., optionally 380° C.-480° C. When the preset temperature during the sintering process is within the above range, the organic carbon source can be carbonized and, together with the inorganic carbon material, form a uniform carbon coating layer with high electronic conductivity on the surface of the sodium-supplementing material matrix. On the other hand, the decomposition of the sodium-supplementing material can be reduced.

[0124] In some embodiments, the preset time can be 2 hours to 5 hours, and optionally 2.5 hours to 4 hours. When the preset time during the sintering process is within the above range, on the one hand, the organic carbon source can be carbonized and, together with the inorganic carbon material, form a uniform carbon coating layer with high electronic conductivity on the surface of the sodium-supplementing material matrix, and on the other hand, the decomposition of the sodium-supplementing material can be reduced.

[0125] In some embodiments, the step of mixing the sodium-supplementing material, the inorganic carbon material, and the organic carbon source to obtain a mixture includes the following steps: grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, and then mixing the obtained intermediate with the organic carbon source for a second dry grinding to obtain a mixture.

[0126] The particle size of the currently available sodium-supplementing materials is usually relatively large, and when used directly, there may be problems such as residue or reduced capacity utilization. The manufacturing cost of small-particle, nano-scale sodium-supplementing materials is high, which is not conducive to large-scale production. Therefore, after the sodium-supplementing material and the inorganic carbon material are ground by a dry grinding process, on the one hand, the particle size of the sodium-supplementing material can be reduced, and on the other hand, the dispersibility of the inorganic carbon material on the surface of the sodium-supplementing material particles can be improved, and the contact sites between the inorganic carbon material and the sodium-supplementing material particles can be increased. In addition, after the sodium-supplementing material and the inorganic carbon material are ground by a dry grinding process, the agglomeration of the inorganic carbon material can be reduced, and the problem of rapid grain growth of the sodium-supplementing material particles during the sintering process can also be limited.

[0127] In some embodiments, in the step of grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, the grinding time can be 0.5h-5h, and optionally 0.6h-3h.

[0128] In some embodiments, in the step of grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, the grinding speed can be 200 r / min-600 r / min, and can be optionally 300 r / min-500 r / min.

[0129] In the step of grinding the sodium-supplementing material and the inorganic carbon material by dry grinding to obtain an intermediate, the volume distribution particle size of the intermediate obtained can be adjusted by adjusting the grinding time and / or grinding speed.

[0130] In some embodiments, in the step of grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, the volume distribution particle size Dv50 of the intermediate obtained can be less than or equal to 20 μm, and can be optionally 1.5 μm-10 μm, or 1.5 μm-7 μm. This is beneficial for reducing the oxidation potential of the sodium-supplementing material and improving the capacity utilization of the sodium-supplementing material.

[0131] The volume distribution particle size Dv50 of the intermediate refers to the volume distribution particle size Dv50 of the sodium supplement material after grinding.

[0132] In some embodiments, in the step of grinding the sodium-supplementing material and the inorganic carbon material using a dry grinding process to obtain an intermediate, the grinding can be performed in a ball mill.

[0133] In some embodiments, in the step of mixing the obtained intermediate with an organic carbon source and performing a second dry grinding, the grinding time can be 0.5 h to 4 h, and optionally 0.6 h to 2 h.

[0134] In some embodiments, in the step of mixing the obtained intermediate with the organic carbon source and performing a second dry grinding, the grinding speed may be 200 r / min-600 r / min, and optionally 300 r / min-500 r / min.

[0135] In some embodiments, the preparation method may further include the steps of grinding and screening the composite sodium-supplementing material obtained by sintering at a preset temperature and for a preset time. This helps reduce the oxidation potential of the composite sodium-supplementing material, maximizes the capacity of the sodium-supplementing material, and improves the capacity utilization rate of the sodium-supplementing material.

[0136] In some embodiments, the inorganic carbon material may include, but is not limited to, one or more of conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, carbon nanotube, graphene, and reduced graphene oxide.

[0137] In some embodiments, the specific surface area of ​​the inorganic carbon material can be 20 m 2 / g-1600m 2 / g, optional 60m 2 / g-1500m 2 / g. Grinding an inorganic carbon material with a high specific surface area with a sodium-supplementing material can increase the contact sites between the inorganic carbon material and the sodium-supplementing material particles, thereby reducing the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby reducing the oxidation potential of the sodium-supplementing material, and further facilitating the utilization of the sodium-supplementing material's capacity and capacity utilization.

[0138] In some embodiments, the organic carbon source may include, but is not limited to, one or more of starch, glucose, fructose, maltose, sucrose, cellulose, hemicellulose, lignin, cyclodextrin, polyacrylonitrile, polyethylene glycol, polyvinyl alcohol, polyaniline, polypyrrole, polythiophene, phenolic resin, and epoxy resin.

[0139] The mass of the sodium-supplementing material is recorded as m1, the mass of the inorganic carbon material is recorded as m2, and the mass of the residual carbon when the organic carbon source is sintered at the corresponding preset temperature and preset time is recorded as m3. The mass of the residual carbon when the organic carbon source is sintered at the corresponding preset temperature and preset time is related to the type of organic carbon source. By selecting an appropriate organic carbon source and selecting an appropriate sintering temperature and / or time, the residual carbon mass m3 of the organic carbon source can be adjusted.

[0140] In some embodiments, m1:m2 can be (1-4):1, and can optionally be (1-2):1. By adjusting m1:m2 within the above range, it is beneficial to improve the electronic conductivity of the sodium-supplementing material, reduce the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby facilitating the reduction of the oxidation potential of the sodium-supplementing material, and also facilitating the utilization of the capacity of the sodium-supplementing material and improving the capacity utilization rate of the sodium-supplementing material.

[0141] In some embodiments, m3:(m1+m2) can be (0.5-3):100, or optionally (1-2):100. By adjusting m3:(m1+m2) within the above range, the uniformity of the carbon coating layer is improved, thereby improving the electronic conductivity of the sodium-supplementing material, reducing the charge transfer resistance and polarization resistance of the sodium-supplementing material, thereby reducing the oxidation potential of the sodium-supplementing material, and further facilitating the utilization of the capacity of the sodium-supplementing material and improving the capacity utilization rate of the sodium-supplementing material.

[0142] Unless otherwise specified, all raw materials used in the above preparation methods can be obtained commercially.

[0143] [Positive electrode]

[0144] The embodiment of the present application also provides a positive electrode plate.

[0145] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector. The positive electrode current collector has two surfaces that are opposite to each other in its thickness direction, and the positive electrode film layer is located on either or both of the two opposing surfaces of the positive electrode current collector.

[0146] The positive electrode film layer includes the composite sodium-supplementing material or the composite sodium-supplementing material prepared by the above-mentioned preparation method, thereby improving the initial discharge capacity and initial coulombic efficiency of the battery and also enabling the battery to have a high energy density.

[0147] In some embodiments, the weight content of the composite sodium-supplementing material in the positive electrode film layer is 0.1%-5%, and optionally 0.5%-3%, based on the total weight of the positive electrode film layer. This can further improve the initial discharge capacity and initial coulombic efficiency of the battery, and can also provide the battery with a high energy density.

[0148] The positive electrode film layer includes a positive electrode active material, which includes a material capable of extracting and inserting sodium. As an example, the positive electrode active material may be one or more of a layered transition metal oxide (including but not limited to P2 type, O3 type, etc.), a polyanion material (such as phosphate, fluorophosphate, pyrophosphate, sulfate, etc.), and a Prussian material.

[0149] In some embodiments, as examples, the positive electrode active material may include but is not limited to NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67 MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0150] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0151] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0152] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylic resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and one or more of carboxymethyl chitosan (CMCS).

[0153] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include but is not limited to one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0154] The positive electrode film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, optional positive electrode conductive agent, optional positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0155] [Negative electrode]

[0156] The battery cell includes a negative electrode plate. The structure and composition of the negative electrode plate can be selected according to the type of battery cell, and the embodiments of the present application are not limited thereto.

[0157] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector may have two opposing surfaces in its thickness direction, and the negative electrode film layer may be disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0158] The negative electrode active material may be any material known in the art. For example, the negative electrode active material includes, but is not limited to, one or more of soft carbon, hard carbon, and mesophase microcarbon beads.

[0159] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. As examples, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0160] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. As examples, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0161] In some embodiments, the negative electrode film layer may further include other additives. For example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.

[0162] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0163] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate may further include a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer; in some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode film layer.

[0164] In some embodiments, the negative electrode plate may include a negative electrode current collector and a metal layer disposed on at least one surface of the negative electrode current collector. The metal material in the metal layer may include but is not limited to one or more of sodium element and sodium alloy.

[0165] Sodium alloys may be alloys of metallic sodium with other metallic elements or non-metallic elements. For example, the other metallic elements in the sodium alloy may include, but are not limited to, one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, and the non-metallic elements in the sodium alloy may include one or more of boron, carbon, and silicon.

[0166] In some embodiments, the negative electrode sheet may be a sodium sheet (foil) or a sodium alloy sheet (foil).

[0167] In some embodiments, the negative electrode sheet may include a negative electrode current collector to assemble into a negative electrode-free sodium metal battery cell.

[0168] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. As examples of metal foils, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil may be used. As examples of three-dimensional porous current collectors, copper mesh, nickel mesh, foam copper, foam nickel, and foam aluminum may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, aluminum, aluminum alloy, silver, and silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0169] [Electrolytes]

[0170] The battery cell includes an electrolyte. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected according to needs. For example, the electrolyte can include one or more selected from solid electrolytes and liquid electrolytes (i.e., electrolytes).

[0171] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and a solvent.

[0172] In some embodiments, as an example, the electrolyte salt may include, but is not limited to, one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorobis(oxalatophosphate) (NaDFOP), and sodium tetrafluorooxalatophosphate (NaTFOP).

[0173] In some embodiments, the solvent may include, but is not limited to, one or more of an ester solvent, a sulfone solvent, and an ether solvent. As an example, the solvent may include, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), diethyl sulfone (ESE), and one or more of ethylene glycol dimethyl ether (DME).

[0174] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0175] [Isolation film]

[0176] Battery cells using electrolytes, as well as some battery cells using solid electrolytes, also include a separator. The separator is placed between the positive and negative electrode sheets to prevent internal short circuits.

[0177] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0178] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0179] The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, separator, negative electrode sheet and electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, dried and injected with the above-mentioned electrolyte, and then subjected to packaging, standing, formation and other processes to obtain a battery cell. Multiple battery cells can also be further connected in series, in parallel or in a mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in a mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0180] Electrical devices

[0181] The embodiments of the present application also provide an electrical device, which includes a battery provided in the embodiments of the present application, and the battery is used to provide electrical energy. The battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0182] The electrical device can select a specific type of battery, such as a battery cell, a battery module, or a battery pack, according to its usage requirements.

[0183] Figure 6 The diagram is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0184] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0185] Example

[0186] The following examples describe the present disclosure in more detail. These examples are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are commercially available.

[0187] Example 1

[0188] Sodium oxalate (compound H1), a sodium supplement material with a volume distribution particle size Dv50 of 16 μm, and conductive carbon black (with a specific surface area of ​​60 m 2 / g) was dry ground for the first time in a grinding jar at a grinding speed of 450 r / min and a grinding time of 3 h to obtain an intermediate with a volume distribution particle size Dv50 of approximately 3 μm (herein, the volume distribution particle size Dv50 of the sodium oxalate supplement material obtained after the first grinding).

[0189] Glucose powder as an organic carbon source was added to the grinding tank and dry-grinded for the second time at a grinding speed of 400 r / min and a grinding time of 1 h to obtain a mixture.

[0190] The resulting mixture was sintered at 420°C for 3 hours, and then ground and sieved to obtain a composite sodium-supplementing material having a volume distribution particle size Dv50 of approximately 3.2 μm.

[0191] In the obtained composite sodium-supplementing material, the mass of the sodium-supplementing material matrix is ​​recorded as m1, the mass of the inorganic carbon material is recorded as m2, and the mass of the residual carbon after sintering the organic carbon source at 420°C for 3 hours is recorded as m3. m1:m2 is 2:1, and m3:(m1+m2) is 2:100.

[0192] Examples 2 to 3

[0193] The preparation method of the composite sodium-supplementing material is similar to that of Example 1, except that the grinding speed and / or grinding time of the first dry grinding are adjusted to obtain intermediates with different volume distribution particle sizes Dv50. The volume distribution particle size Dv50 of the obtained intermediates and the volume distribution particle size Dv50 of the composite sodium-supplementing material are detailed in Table 1.

[0194] Examples 4 to 7

[0195] The preparation method of the composite sodium-supplementing material is similar to that of Example 1, except that the sintering temperature is different. Specific parameters are shown in Table 1.

[0196] Examples 8 to 12

[0197] The preparation method of the composite sodium supplement material is similar to that of Example 1, except that m1:m2 is different. Specific parameters are shown in Table 1.

[0198] Examples 13 to 16

[0199] The preparation method of the composite sodium supplement material is similar to that of Example 1, except that m3:(m1+m2) is different. The specific parameters are shown in Table 1.

[0200] Examples 17 to 27

[0201] The preparation method of the composite sodium-supplementing material is similar to that of Example 1, except that the types of the sodium-supplementing material, inorganic carbon material and / or organic carbon source are different. The specific types are detailed in Table 1.

[0202] Compound H1

[0203] Compound H2

[0204] Compound H3

[0205] Compound H4

[0206]

[0207] Comparative Example 1

[0208] Sodium oxalate (compound H1) with a volume distribution particle size Dv50 of 16 μm was used as the sodium supplement material.

[0209] Comparative Example 2

[0210] Sodium oxalate (Compound H1) with a volume distribution particle size Dv50 of 16 μm was dry-ground in a grinding jar to obtain sodium oxalate with a volume distribution particle size Dv50 of approximately 3.2 μm, which was used as a sodium supplement material.

[0211] Comparative Example 3

[0212] Sodium oxalate (Compound H1), a sodium-supplementing material with a volume distribution particle size (Dv50) of 11.2 μm, and conductive carbon black, an inorganic carbon material, were dry-ground in a grinding jar to obtain a mixture with a volume distribution particle size (Dv50) of 3.2 μm, which served as the sodium-supplementing material. The mass of the sodium-supplementing material was denoted as m1, and the mass of the inorganic carbon material was denoted as m2, with the ratio of m1:m2 being 4:1.

[0213] Performance Testing

[0214] (1) Oxidation potential test of sodium supplement materials

[0215] The binder polyvinylidene fluoride (PVDF) is fully dissolved in N-methylpyrrolidone (NMP), and then the conductive agent conductive carbon black and the prepared composite sodium-supplementing material are added to form a uniform slurry. The slurry is evenly coated on the surface of aluminum foil and then transferred to a vacuum drying oven for complete drying. The slurry is then roll-pressed and punched to produce a positive electrode sheet. Based on the total mass of the binder polyvinylidene fluoride, the conductive agent conductive carbon black, and the composite sodium-supplementing material as 100%, the mass content of the binder polyvinylidene fluoride is 10%, the mass content of the sodium-supplementing material matrix in the composite sodium-supplementing material is 50%, and the total mass content of the conductive agent conductive carbon black and the carbon coating layer in the composite sodium-supplementing material is 40%.

[0216] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), NaPF6 was dissolved in ethylene glycol dimethyl ether (DME) and stirred evenly to obtain an electrolyte with a concentration of 0.5 mol / L.

[0217] The positive electrode sheet, the isolation film (polypropylene film), the sodium sheet and the electrolyte are assembled into a button battery.

[0218] At 25°C, the assembled button battery was charged at a constant current of 0.02C to 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.02C to obtain the initial charge capacity of the button battery; then the button battery was discharged at a constant current of 0.02C to 1.5V to obtain the initial discharge capacity of the button battery.

[0219] The first charge gram capacity of the composite sodium-supplementing material (mAh / g) = the first charge capacity of the button battery / the mass of the composite sodium-supplementing material.

[0220] The first discharge capacity (mAh / g) of the composite sodium-supplementing material = the first discharge capacity of the button cell / the mass of the composite sodium-supplementing material.

[0221] The corresponding dQ / dV curve is calculated based on the differential of the first cycle charge and discharge curve, or the assembled button battery is subjected to cyclic voltammetry (CV) test with a test voltage of 1.5V-4.5V and a scan rate of 0.1mV / s. The voltage corresponding to the oxidation peak is the oxidation potential of the composite sodium-supplementing material.

[0222] (2) The first coulombic efficiency test of a negative electrode-free sodium metal battery

[0223] The composite sodium-supplementing materials prepared in the above-mentioned embodiments and comparative examples were mixed with the positive electrode active material Na4Fe3(PO4)2O7, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 2.1:67.9:20:10, and then an appropriate amount of NMP was added and stirred thoroughly to form a uniform positive electrode slurry; the positive electrode slurry was evenly coated on the surface of the aluminum foil, and then transferred to a vacuum drying oven and dried at 110°C for 5h-6h, and then rolled and punched to obtain a positive electrode sheet.

[0224] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), NaPF6 was dissolved in ethylene glycol dimethyl ether (DME) and stirred evenly to obtain an electrolyte with a concentration of 0.5 mol / L.

[0225] The positive electrode sheet, isolation film (polypropylene film), and carbon-coated copper foil prepared above are stacked in order to form a laminated electrode assembly. The electrode assembly is placed in an outer package, injected with the electrolyte prepared above, and then subjected to vacuum packaging, standing, formation, shaping and other processes to obtain a negative electrode-free sodium metal battery.

[0226] At 25°C, the negative electrode-free sodium metal battery was charged to 4.2V at a constant current of 1 / 3C, and then charged at a constant voltage of 4.2V to a current of 0.05C to obtain the first charging capacity of the negative electrode-free sodium metal battery; then the negative electrode-free sodium metal battery was discharged to 1.5V at a constant current of 1 / 3C to obtain the first discharge capacity of the negative electrode-free sodium metal battery.

[0227] The first coulombic efficiency of the negative electrode-free sodium metal battery = the first discharge capacity of the negative electrode-free sodium metal battery / the first charge capacity of the negative electrode-free sodium metal battery.

[0228] The test results are shown in Table 2.

[0229] Table 2

[0230]

[0231] It can be seen from the test results in Table 2 that the composite sodium supplement material provided in the examples of the present application has low oxidation potential, high capacity and high capacity utilization.

[0232] It can also be seen from the test results in Table 2 that the battery using the composite sodium supplement material provided in the embodiments of the present application has a high first coulombic efficiency.

[0233] Comparative Example 2 adopts the direct grinding method, which can improve the capacity of sodium oxalate to a certain extent, but the improvement effect is limited. At the same time, the oxidation potential of sodium oxalate is still very high. Therefore, when applied to the battery system, the actual capacity of sodium oxalate is still poor, and the first coulombic efficiency of the battery is still low.

[0234] In Comparative Example 3, sodium oxalate is ground together with an inorganic carbon material, thereby increasing the capacity of sodium oxalate. However, the oxidation potential of sodium oxalate is still very high. Therefore, when applied to a battery system, the capacity of sodium oxalate at high potential cannot be effectively released, resulting in the actual capacity of sodium oxalate still being poor, and the first coulombic efficiency of the battery is still low.

[0235] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite sodium supplement material, characterized in that: The composite sodium-supplementing material comprises a matrix and a carbon coating layer located on at least a portion of the surface of the matrix, wherein the matrix comprises a sodium-supplementing material, and the carbon coating layer comprises an inorganic carbon material and an organic carbonized material; The sodium supplement material includes one or more compounds represented by formula (I) and formula (II). ， m represents an integer of 1 to 8, and n represents an integer of 2 to 20.

2. The composite sodium supplement material according to claim 1, wherein The mass of the sodium supplement material is recorded as m1, the mass of the inorganic carbon material is recorded as m2, and the mass of the organic carbonized material is recorded as m3. m1:m2 is (1-4):1; and / or, m3:(m1+m2) is (0.5-3):

100.

3. The composite sodium supplement material according to claim 2, wherein m1:m2 is (1-2):1; and / or, m3:(m1+m2) is (1-2):

100.

4. The composite sodium supplement material according to any one of claims 1 to 3, characterized in that The powder resistivity of the composite sodium supplement material at 25° C. and 20 MPa is 0.2Ω.cm-2Ω.cm; and / or, The specific surface area of ​​the composite sodium supplement material is 3.8m 2 / g-7.1m 2 / g; and / or, The volume distribution particle size Dv50 of the composite sodium supplement material is 0.5 μm-10 μm.

5. The composite sodium supplement material according to claim 4, characterized in that The powder resistivity of the composite sodium supplement material at 25° C. and 20 MPa is 0.4 Ω.cm-1 Ω.cm; and / or, The specific surface area of ​​the composite sodium supplement material is 4.5 m 2 / g-6.8m 2 / g; and / or, The volume distribution particle size Dv50 of the composite sodium supplement material is 1.5 μm-7.6 μm.

6. The composite sodium supplement material according to claim 1, characterized in that The inorganic carbon material includes one or more of conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, carbon nanotube, graphene, and reduced graphene oxide; and / or, The organic carbon source forming the organic carbonized material includes one or more of starch, glucose, fructose, maltose, sucrose, cellulose, hemicellulose, lignin, cyclodextrin, polyacrylonitrile, polyethylene glycol, polyvinyl alcohol, polyaniline, polypyrrole, polythiophene, phenolic resin, and epoxy resin.

7. The composite sodium supplement material according to claim 1, characterized in that The sodium supplement material includes one or more of the following compounds: 。 8. A method for preparing a composite sodium supplement material, characterized in that: The steps include: A sodium supplement material, an inorganic carbon material, and an organic carbon source are mixed to obtain a mixture, wherein: The sodium supplement material includes one or more compounds represented by formula (I) and formula (II). ， m represents an integer from 1 to 8, and n represents an integer from 2 to 20; The obtained mixture is sintered at a preset temperature and a preset time to obtain a composite sodium supplement material.

9. The preparation method according to claim 8, characterized in that The preset temperature is 350°C-500°C; and / or, The preset time is 2h-5h.

10. The preparation method according to claim 9, characterized in that The preset temperature is 380°C-480°C; and / or, The preset time is 2.5h-4h.

11. The preparation method according to claim 8, characterized in that The step of mixing the sodium supplementing material, the inorganic carbon material, and the organic carbon source to obtain a mixture comprises the following steps: The sodium supplement material and the inorganic carbon material are ground by a dry grinding process to obtain an intermediate, and then the intermediate is mixed with an organic carbon source and dry ground for a second time to obtain a mixture.

12. The preparation method according to claim 11, characterized in that In the step of grinding the sodium supplement material and the inorganic carbon material using a dry grinding process to obtain an intermediate, The grinding time is 0.5h-5h; and / or, The grinding speed is 200r / min-600r / min; and / or, The volume distribution particle size Dv50 of the obtained intermediate is less than or equal to 20 μm; and / or, Grinding is carried out in a ball mill.

13. The preparation method according to claim 12, characterized in that In the step of grinding the sodium supplement material and the inorganic carbon material using a dry grinding process to obtain an intermediate, The grinding time is 0.6h-3h; and / or, The grinding speed is 300r / min-500r / min; and / or, The volume distribution particle size Dv50 of the obtained intermediate is 1.5 μm-10 μm.

14. The preparation method according to claim 11, characterized in that In the step of mixing the obtained intermediate with an organic carbon source and performing a second dry grinding, Grinding time is 0.5h-4h; and / or, The grinding speed is 200r / min-600r / min.

15. The preparation method according to claim 14, characterized in that In the step of mixing the obtained intermediate with an organic carbon source and performing a second dry grinding, The grinding time is 0.6h-2h; and / or, The grinding speed is 300r / min-500r / min.

16. The preparation method according to claim 8, characterized in that The preparation method further comprises the steps of: grinding and screening the composite sodium-supplementing material obtained by sintering at a preset temperature and a preset time.

17. The preparation method according to claim 8, characterized in that The mass of the sodium supplement material is recorded as m1, the mass of the inorganic carbon material is recorded as m2, and the mass of the residual carbon after sintering the organic carbon source at a preset temperature and a preset time is recorded as m3. m1:m2 is (1-4):1; and / or, m3:(m1+m2) is (0.5-3):

100.

18. The preparation method according to claim 17, characterized in that: m1:m2 is (1-2):1; and / or, m3:(m1+m2) is (1-2):

100.

19. The preparation method according to claim 8, characterized in that The inorganic carbon material includes one or more of conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, carbon nanotube, graphene, and reduced graphene oxide; and / or, The specific surface area of ​​the inorganic carbon material is 20 m 2 / g-1600m 2 / g; and / or, The organic carbon source includes one or more of starch, glucose, fructose, maltose, sucrose, cellulose, hemicellulose, lignin, cyclodextrin, polyacrylonitrile, polyethylene glycol, polyvinyl alcohol, polyaniline, polypyrrole, polythiophene, phenolic resin, and epoxy resin; and / or, The sodium supplement material includes one or more of the following compounds: 。 20. The preparation method according to claim 19, characterized in that The specific surface area of ​​the inorganic carbon material is 60 m 2 / g-1500m 2 / g.

21. A positive electrode plate, comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, characterized in that: The positive electrode film layer includes the composite sodium-supplementing material according to any one of claims 1 to 7 or the composite sodium-supplementing material prepared by the preparation method according to any one of claims 8 to 20.

22. The positive electrode sheet according to claim 21, characterized in that: The weight content of the composite sodium-supplementing material in the positive electrode film layer is 0.1%-5%, based on the total weight of the positive electrode film layer.

23. The positive electrode sheet according to claim 22, characterized in that: The weight content of the composite sodium-supplementing material in the positive electrode film layer is 0.5%-3%, based on the total weight of the positive electrode film layer.

24. The positive electrode sheet according to any one of claims 21 to 23, characterized in that: The positive electrode film layer further includes a positive electrode active material, and the positive electrode active material includes one or more of layered transition metal oxides, polyanion materials, and Prussian materials.

25. A battery, characterized in that: Including the positive electrode sheet according to any one of claims 21 to 24.

26. The battery according to claim 25, characterized in that The battery includes one or more of a sodium ion battery, a sodium metal battery, and a negative electrode-free sodium battery.

27. An electrical device, characterized in that: The battery according to any one of claims 25 to 26 is used to provide electrical energy.

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