Positive electrode active material for sodium ion battery, sodium ion battery and power consumption device

Abstract

The present application provides a positive electrode active material for a sodium ion battery, a sodium ion battery, and a power consuming device, the positive electrode active material comprising a core and a shell layer covering the surface of the core, the core comprising sodium-containing positive electrode active material particles, and the shell layer having a pore structure and comprising a sodium-affinity material.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority from Chinese Patent Application No. 202310002450.3, entitled "Positive electrode active material for sodium ion battery, sodium ion battery and power consumption device," filed on January 3, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of battery technology, and in particular to positive electrode active materials for sodium ion batteries, sodium ion batteries, and power consuming devices. [Background technology]

[0003] Batteries are widely used in fields such as mobile phones, tablet computers, and electric vehicles, and are gradually becoming indispensable in people's lives. As batteries are widely used in various fields, the requirements for their performance are also increasing. However, the cycle performance and safety performance of batteries in related technologies still cannot meet the requirements, so there is a need to improve the cycle performance and safety performance of batteries. Summary of the Invention

[0004] The present application provides a positive electrode active material for a sodium ion battery, a sodium ion battery, and a power consumption device, which can improve the cycle performance and safety performance of the sodium ion battery.

[0005] A first aspect of the present application provides a positive electrode active material for a sodium-ion battery, comprising a core and a shell layer covering the surface of the core, wherein the core comprises sodium-containing positive electrode active material particles, and the shell layer has a pore structure and comprises a sodium-affinity material.

[0006] In the positive electrode active material for a sodium-ion battery according to the present application, the shell layer contains a sodium affinity material, thereby better covering the core containing sodium-containing positive electrode active material particles. When the positive electrode active material is used in a sodium-ion battery, the shell layer covering the surface of the core reduces the expansion of the core, further reducing deformation of the positive electrode active material and contributing to the insertion and desorption of sodium ions, thereby achieving the purpose of improving the cycle performance and safety of the sodium-ion battery.

[0007] According to any of the above-described embodiments of the first aspect of the present application, the average particle size D1 of the sodium-containing positive electrode active material particles and the average pore size D2 of the pore structure satisfy the relationship 5≦D1 / D2≦600. When the average particle size D1 of the sodium-containing positive electrode active material particles and the average pore size D2 of the pore structure satisfy the above relationship, the insertion and desorption of sodium ions can be made more rational, thereby improving the cycle performance and safety performance of the sodium-ion battery.

[0008] According to any of the above-described embodiments of the first aspect of the present application, the sodium-containing positive electrode active material particles have an average particle diameter D1 of 10 μm to 50 μm. By setting the average particle diameter D1 of the sodium-containing positive electrode active material particles within the above range, when the sodium-containing positive electrode active material particles are used in a sodium ion battery, the cycle performance and safety performance of the sodium ion battery can be improved, and the compressed density of the positive electrode active material layer can be improved, thereby improving the energy density of the sodium ion battery.

[0009] According to any of the above-described embodiments of the first aspect of the present application, the average pore diameter D2 of the pore structure is 0.1 μm to 1 μm. By setting the average pore diameter D2 of the pore structure within the above range, it can be matched with the average particle diameter of the positive electrode active material particles, and further contributes to the insertion and desorption of sodium ions from the positive electrode active material particles, thereby improving the rate performance of the sodium ion battery.

[0010] According to any of the above embodiments of the first aspect of the present application, the sodium-affinity material comprises one or more of a sodium-affinity carbon-based material and a sodium-affinity metal-based particle.

[0011] According to any of the above embodiments of the first aspect of the present application, the sodiophilic carbon-based material comprises one or more of graphene oxide and modified graphene oxide, modified carbon nanotubes, and modified carbon fibers.

[0012] According to any of the above embodiments of the first aspect of the present application, the sodium-affinity metal-based particles comprise one or more of sodium-affinity metal particles and sodium-affinity metal oxide particles.

[0013] According to any of the above embodiments of the first aspect of the present application, the sodium-affinity metal particles comprise one or more of copper, tin, gold, silver, aluminum, indium, zinc, lead, antimony, or alloys thereof.

[0014] According to any of the above embodiments of the first aspect of the present application, the sodium-affinity metal oxide particles include one or more of copper oxide, tin oxide, β-alumina, manganese dioxide, tricobalt tetroxide, zinc oxide, and nickel oxide.

[0015] According to any of the above embodiments of the first aspect of the present application, the shell layer has a thickness of 0.1 μm to 1 μm.

[0016] A second aspect of the present application provides a sodium ion battery including the positive electrode active material for a sodium ion battery according to the first aspect of the present application.

[0017] A third aspect of the present application provides a power consuming device including a sodium ion battery according to the second aspect of the present application.

[0018] The above description is only a summary of the technical solution of the present application, which can be implemented according to the content of the specification, in order to make the technical solution of the present application more clearly understood. In order to facilitate a clearer understanding of the above and other objectives, features and advantages of the present application, specific embodiments of the present application are listed below. [Brief explanation of the drawings]

[0019] Various other benefits and advantages will become apparent to those skilled in the art upon reading the following detailed description of alternative embodiments. The drawings are for illustrative purposes only and are not intended to limit the scope of the present application. Furthermore, like elements are designated by like reference numerals throughout the drawings. Reference is now made to the drawings, in which: [Figure 1] FIG. 1 is a schematic structural diagram of a sodium-ion battery according to some embodiments of the present application. [Figure 2] FIG. 2 is an exploded schematic view of the sodium-ion battery of FIG. 1. [Figure 3] 1 is a schematic structural diagram of a battery module according to some embodiments of the present application; [Figure 4] 1 is a schematic structural diagram of a battery pack according to some embodiments of the present application; [Figure 5] FIG. 5 is an exploded schematic view of the battery pack in FIG. 4. [Figure 6] 1 is a schematic structural diagram of a power consuming device according to some embodiments of the present application.The drawings are not necessarily drawn to scale. [Explanation of symbols]

[0020] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 sodium ion battery, 51 case, 52 electrode assembly, 53 cover plate DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, the embodiments of the technical solution of the present application will be described in detail with reference to the drawings. The following embodiments are merely provided for the purpose of more clearly explaining the technical solution of the present application, and are not intended to limit the scope of protection of the present application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are only for describing particular embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof contained in the specification, claims, and description of the drawings above of this application are intended to cover a non-exclusive inclusion.

[0023] In the description of the embodiments of the present application, technical terms such as "first" and "second" are merely used to distinguish different objects, and should not be understood to indicate or imply relative importance, or to imply the number or specific order of the indicated technical features, or their hierarchical relationship. In the description of the embodiments of the present application, "plurality" means two or more, unless otherwise clearly and specifically limited.

[0024] The term "embodiment" used herein means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The phrases appearing in various parts of the present specification do not necessarily refer to the same embodiment, nor are they mutually exclusive, independent, or alternative embodiments. Those skilled in the art may explicitly or implicitly understand that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the examples of this application, the term "and / or" only describes the relationship between related objects and indicates that three types of situations may exist, for example, A and / or B indicates that three cases may exist: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this specification generally indicates that the related objects before and after it are in an "or" relationship.

[0026] In describing the examples of the present application, the term "plurality" means two or more (including two); similarly, "multiple sets" means two or more sets (including two sets), and "plurality" means two or more (including two).

[0027] In describing the examples of the present application, the orientations or positional relationships indicated by technical terms such as "center," "longitudinal," "lateral," "length," "width," "wall thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are based on the orientations or positional relationships shown in the drawings, and are merely for the convenience and simplification of the description of the examples of the present application. They do not necessarily suggest or imply that the devices or elements shown have a specific orientation or are constructed and operated in a specific orientation, and therefore should not be understood as limiting the examples of the present application.

[0028] In the description of the embodiments of the present application, unless otherwise clearly specified or limited, technical terms such as "attached," "coupled," "connected," and "fixed" should be understood in a broad sense, and may refer to, for example, a fixed connection, a detachable connection, or integration, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediate medium, internal communication between two elements, or an interactive relationship between two elements. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application according to the specific circumstances.

[0029] Batteries are widely used in fields such as power tools and electric vehicles because they can be recycled through repeated charge and discharge. However, during the charge and discharge of a battery, irreversible changes can occur in the structure of the positive electrode active material. For example, the lattice of the positive electrode active material expands and deforms, resulting in the desorbed active ions being unable to be reinserted. In this way, dendrites can form in the battery, reducing the number of active ions, which can affect the cycle performance and safety of the battery.

[0030] In view of this, the present application provides a positive electrode active material for a sodium ion battery, a sodium ion battery, and a power consumption device that can improve the cycle performance and safety performance of the sodium ion battery. Positive electrode active material for sodium ion batteries

[0031] A first aspect of the present application provides a positive electrode active material for a sodium-ion battery, comprising a core and a shell layer covering the surface of the core, wherein the core comprises sodium-containing positive electrode active material particles, and the shell layer has a pore structure and comprises a sodium-affinity material.

[0032] In the positive electrode active material for a sodium-ion battery according to the present application, the shell layer contains a sodium affinity material, thereby better covering the core containing sodium-containing positive electrode active material particles. When the positive electrode active material is used in a sodium-ion battery, the shell layer covers the surface of the core, thereby reducing the expansion of the core and further reducing deformation of the positive electrode active material, contributing to the insertion and desorption of sodium ions, thereby achieving the objective of improving the cycle performance and safety of the sodium-ion battery.

[0033] In some embodiments of the present application, the average particle size D1 of the sodium-containing positive electrode active material particles and the average pore size D2 of the pore structure satisfy the relationship 5≦D1 / D2≦600. When the average particle size D1 of the sodium-containing positive electrode active material particles and the average pore size D2 of the pore structure satisfy the above relationship, the insertion and desorption of sodium ions becomes more rational, thereby improving the cycle performance and safety performance of the sodium ion battery.

[0034] In the present application, the average particle size of particles has a meaning known in the art and can be measured using instruments and methods known in the art. For example, a material is measured using a scanning electron microscope, a transmission electron microscope, or a particle size distribution device to obtain an image, a plurality of test particles (e.g., 100 or more) (e.g., sodium-containing positive electrode active material particles of the present application) are randomly selected from the image, and the average value of the shortest diagonal lengths of the particles can be statistically determined as the average particle size.

[0035] In the present application, the average pore size of the pore structure has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be calculated by the Brunauer Emmett Teller (BET) method with reference to GB / T21650.2-2008, and can be tested using a Tri-Star 3020 specific surface area and average pore size analysis tester manufactured by Micromeritics, Inc., USA.

[0036] In some examples, the ratio of the average particle size D1 of the sodium-containing positive electrode active material particles to the average pore size D2 of the pore structure is 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650, 660, 670, 680, 690, 700, 710, 720, 730, 740, 750, 760, 770, 780, 790, 800, 810, 820, 830, 840, 850, 860, 870, 880, 890, 900, 910, 920, 930, 940, 95 The ratio of the average particle size D1 of the sodium-containing positive electrode active material particles to the average pore size D2 of the pore structure may be, but is not limited to, 0, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, or a range consisting of any two of the above values. For example, the ratio of the average particle size D1 of the sodium-containing positive electrode active material particles to the average pore size D2 of the pore structure may be in the range of 6 to 580, 10 to 520, 20 to 480, 50 to 400, 80 to 360, 100 to 280, 120 to 240, or 150 to 210.

[0037] In some embodiments of the present application, the sodium-containing positive electrode active material particles have an average particle diameter D1 of 10 μm to 50 μm. By setting the average particle diameter D1 of the sodium-containing positive electrode active material particles within the above range, when used in a sodium ion battery, the cycle performance and safety performance of the sodium ion battery can be improved, and the compressed density of the positive electrode active material layer can be improved, thereby improving the energy density of the sodium ion battery.

[0038] In some examples, the average particle diameter D1 of the sodium-containing positive electrode active material particles may be, but is not limited to, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, or a range consisting of any two of the foregoing values. For example, the average particle diameter D1 of the sodium-containing positive electrode active material particles may be in the range of 11 μm to 48 μm, 15 μm to 42 μm, 20 μm to 38 μm, or 24 μm to 32 μm.

[0039] In some embodiments of the present application, the average pore diameter D2 of the pore structure is 0.1 μm to 1 μm. By setting the average pore diameter D2 of the pore structure within this range, it can be matched to the average particle diameter of the positive electrode active material particles, and further contributes to the insertion and desorption of sodium ions from the positive electrode active material particles, thereby improving the rate performance of sodium ion batteries when used in the sodium ion battery.

[0040] In some examples, the average pore diameter D2 of the pore structure is 0.1 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm, 0.3 μm, 0.31 μm, 0.32 μm, 0.33 μm, 0.34 μm, 0.35 μm, 0.36 μm, 0.37 μm, 0.38 μm, 0.39 μm, 0.40 μm, 0.41 μm, 0.42 μm, 0.43 μm, 0.44 μm, 0.45 μm, 0.46 μm, 0.47 μm, 0.48 μm, 0.49 μm, 0.50 μm, 0.51 μm, 0.52 μm, 0.53 μm, 0.54 μm, 0.55 μm, 0.56 μm, 0.57 μm, 0.58 μm, 0.59 μm, 0.60 μm, 0.61 μm, 0.62 μm, 0.63 μm, 0.64 μm, 0.65 μm, 0.66 μm, 0.67 μm, 0.68 μm, 0.69 μm, 0.70 μm, 0.71 μm, μm, 0.32μm, 0.33μm, 0.34μm, 0.35μm, 0.36μm, 0.37μm, 0.38μm, 0.39μm, 0.4μm, 0.41μm, 0.42μm, 0.43μm, 0.44μm, 0.45μm, 0.46μm, 0.47μm, 0.48μm, 0.49μm, 0.5μm, 0.51μm, 0.52μm, 0.53μm, 0.54μm, 0.55μm, 0.5 6μm, 0.57μm, 0.58μm, 0.59μm, 0.6μm, 0.61μm, 0.62μm, 0.63μm, 0.64μm, 0.65μm, 0.66μm, 0.67μm, 0.68μm , 0.69μm, 0.7μm, 0.71μm, 0.72μm, 0.73μm, 0.74μm, 0.75μm, 0.76μm, 0.77μm, 0.78μm, 0.79μm, 0.8μm, 0.8 The average pore diameter D2 of the pore structure may be, but is not limited to, 1 μm, 0.82 μm, 0.83 μm, 0.84 μm, 0.85 μm, 0.86 μm, 0.87 μm, 0.88 μm, 0.89 μm, 0.9 μm, 0.91 μm, 0.92 μm, 0.93 μm, 0.94 μm, 0.95 μm, 0.96 μm, 0.97 μm, 0.98 μm, 0.99 μm, 1 μm, or a range consisting of any two of the above values. For example, the average pore diameter D2 of the pore structure may be in the range of 0.11 μm to 0.98 μm, 0.16 μm to 0.89 μm, 0.21 μm to 0.81 μm, 0.29 μm to 0.71 μm, or 0.35 μm to 0.6 μm.

[0041] In the above embodiment, the shape of the pores in the pore structure is not particularly limited, and may be any shape known in the art, such as a square, circular, or V-shaped pore.

[0042] Furthermore, in some embodiments of the present application, the porosity of the shell layer is 20% to 60%. By setting the porosity of the shell layer within the above range, the distribution of the pore structure can be made uniform, which further contributes to the insertion and desorption of sodium ions, thereby improving the cycle performance and safety performance of the sodium ion battery.

[0043] In this application, porosity has the meaning known in the art and refers to the ratio of the pore volume within a material to the total volume of the material. It can be measured using instruments and methods known in the art. For example, see Chinese National Standard GB / T24586-2009 entitled "Determination of Apparent Density, True Density, and Porosity of Iron Ore." Porosity can be measured using a fully automatic true density tester, model AccuPyc II 1340, manufactured by Micromeritics, Inc., USA. Porosity = (V1 - V2) / V1 * 100%, where V1 represents the apparent volume of the material and V2 represents the true volume of the material. V1 can be measured by mercury intrusion porosimetry, and V2 can be measured by nitrogen gas adsorption.

[0044] In some examples, the porosity of the shell layer may be, but is not limited to, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, or a range consisting of any two of the above values. For example, the porosity of the shell layer may be in the range of 21% to 58%, 25% to 52%, or 30% to 48%.

[0045] In the embodiments of the present application, a suitable sodium-affinity material can contribute to the insertion and desorption of sodium ions, thereby improving the cycle performance and safety performance of the sodium-ion battery.

[0046] In some embodiments of the present application, the sodium-affinity material includes one or more of a sodium-affinity carbon-based material and a sodium-affinity metal-based particle, which can further improve the coverage of the shell on the core to reduce the expansion of the core, and enable directional insertion and desorption of sodium ions, thereby improving not only the cycle performance and safety performance of the sodium-ion battery, but also the rate performance of the sodium-ion battery.

[0047] In some embodiments of the present application, the specific surface area of the sodium-affinitive carbon-based material is 80 m 2 / g~2500m 2 By setting the specific surface area of the sodium-affinity carbon-based material within the above range, a large interface with sodium affinity can be formed, the shell can better cover the core, and the directional insertion and desorption of sodium ions can be promoted.

[0048] In this application, the specific surface area of a material has the meaning known in the art and can be measured using instruments and methods known in the art. For example, the specific surface area can be measured according to the nitrogen gas adsorption specific surface area analysis test method in accordance with GB / T19587-2017 and calculated according to the Brunauer Emmett Teller (BET) method. Alternatively, the nitrogen gas adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area and average pore size analysis tester manufactured by Micromeritics, Inc., USA.

[0049] In some examples, the specific surface area of the sodium-philic carbon-based material is 80 m 2 / g, 90m 2 / g, 100m 2 / g, 110m 2 / g, 120m 2 / g, 130m 2 / g, 140m 2 / g, 150m 2 / g, 160m 2 / g, 170m 2 / g, 180m2 / g、190m 2 / g、200m 2 / g、210m 2 / g、220m 2 / g、230m 2 / g、240m 2 / g、250m 2 / g、260m 2 / g、270m 2 / g、280m 2 / g、290m 2 / g、300m 2 / g、310m 2 / g、320m 2 / g、330m 2 / g、340m 2 / g、350m 2 / g、360m 2 / g、370m 2 / g、380m 2 / g、390m 2 / g、400m 2 / g、410m 2 / g、420m 2 / g、430m 2 / g、440m 2 / g、450m 2 / g、500m 2 / g、550m 2 / g、600m 2 / g、650m 2 / g、700m 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g、1000m 2 / g、1050m 2 / g、1100m 2 / g、1150m 2 / g、1200m 2 / g、1250m 2 / g、1300m 2 / g、1350m 2 / g、1400m 2 / g、1450m 2 / g、1500m 2 / g、1550m 2 / g, 1600m 2 / g, 1650m 2 / g, 1700m 2 / g, 1750m 2 / g, 1800m 2 / g, 1850m 2 / g, 1900m 2 / g, 1950m 2 / g, 2000m 2 / g, 2050m 2 / g, 2100m 2 / g, 2150m 2 / g, 2200m 2 / g, 2250m 2 / g, 2300m 2 / g, 2350m 2 / g, 2400m 2 / g, 2450m 2 / g, 2500m 2 / g, or a range consisting of any two of the above values. For example, the specific surface area of the sodium-affinity carbon-based material may be in the range of 90 m 2 / g~2450m 2 / g, 100m 2 / g~2300m 2 / g, 180m 2 / g~2200m 2 / g, 240m 2 / g~1800m 2 / g, 350m 2 / g~1500m 2 / g, 600m 2 / g~1200m 2 / g.

[0050] In some embodiments of the present application, the sodium-affinity carbon-based material includes one or more of graphene oxide, modified graphene oxide, modified carbon nanotube, and modified carbon fiber, which can form a good porous conductive network, enhance the conductivity of the positive electrode active material, and contribute to the insertion and desorption of sodium ions, thereby improving the cycle performance and safety performance of the sodium-ion battery.

[0051] In some embodiments of the present application, the modified carbon nanotubes include one or more of modified single-walled carbon nanotubes and modified multi-walled carbon nanotubes, which not only have excellent sodium affinity but also can form a stable porous conductive network, thereby improving the conductivity of the positive electrode active material and reducing the lateral growth of sodium dendrites, thereby improving the safety and cycle performance of sodium-ion batteries.

[0052] In some embodiments of the present application, the average length of the modified single-walled carbon nanotubes is 3 μm to 28 μm. By setting the modified single-walled carbon nanotubes within this range, a stable porous conductive network can be formed, improving the conductivity of the positive electrode active material and further improving the sodium affinity of the shell, thereby allowing the shell to better cover the core and reducing the expansion rate of the core, thereby further improving the safety performance and cycle performance of the sodium ion battery.

[0053] In some examples, the average length of the modified single-walled carbon nanotubes may be, but is not limited to, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, or a range consisting of any two of the above values. For example, the average length of the modified single-walled carbon nanotubes may be in the range of 4 μm to 27 μm, 5 μm to 25 μm, 8 μm to 22 μm, or 11 μm to 18 μm.

[0054] In some embodiments of the present application, the average diameter of the modified single-walled carbon nanotubes is 1.5 nm to 9.5 nm. Setting the average diameter of the modified single-walled carbon nanotubes within this range can contribute to the formation of a stable porous conductive network, easing the difficulty of manufacturing the carbon nanotubes, and further reducing the manufacturing costs of the current collector.

[0055] In some examples, the average diameter of the modified single-walled carbon nanotubes may be, but is not limited to, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, or a range consisting of any two of the above values. For example, the average diameter of the modified single-walled carbon nanotubes may be in the range of 2 nm to 9 nm, 2.5 nm to 8 nm, 3 nm to 7.5 nm, or 4 nm to 6.5 nm.

[0056] In some embodiments of the present application, the specific surface area of the modified single-walled carbon nanotubes is 210 m 2 / g~1900m 2 For example, the specific surface area of modified single-walled carbon nanotubes is 210 m 2 / g, 220m 2 / g, 230m 2 / g, 240m 2 / g, 250m 2 / g, 260m 2 / g, 270m 2 / g, 280m 2 / g, 290m 2 / g, 300m 2 / g, 310m 2 / g, 320m 2 / g, 330m 2 / g, 340m 2 / g, 350m 2 / g, 360m 2 / g, 370m 2 / g, 380m 2 / g, 390m 2 / g, 400m 2 / g, 410m2 / g, 420m 2 / g, 430m 2 / g, 440m 2 / g, 450m 2 / g, 500m 2 / g, 550m 2 / g, 600m 2 / g, 650m 2 / g, 700m 2 / g, 750m 2 / g, 800m 2 / g, 850m 2 / g, 900m 2 / g, 950m 2 / g, 1000m 2 / g, 1050m 2 / g, 1100m 2 / g, 1150m 2 / g, 1200m 2 / g, 1250m 2 / g, 1300m 2 / g, 1350m 2 / g, 1400m 2 / g, 1450m 2 / g, 1500m 2 / g, 1550m 2 / g, 1600m 2 / g, 1650m 2 / g, 1700m 2 / g, 1750m 2 / g, 1800m 2 / g, 1850m 2 / g, 1900m 2 / g, or a range consisting of any two of the above values. For example, the specific surface area of the modified single-walled carbon nanotubes may be in the range of 220 m 2 / g~1850m 2 / g, 300m 2 / g~1500m 2 / g, 550m 2 / g~1200m 2 / g, 750m 2 / g~1000m 2 / g.

[0057] In some embodiments of the present application, the average length of the modified multi-walled carbon nanotubes is 1 μm to 18 μm. For example, the average length of the modified multi-walled carbon nanotubes may be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, or a range consisting of any two of the above values. For example, the average length of the modified multi-walled carbon nanotubes may be in the range of 2 μm to 17 μm, 3 μm to 16 μm, 5 μm to 14 μm, or 8 μm to 12 μm.

[0058] In some embodiments of the present application, the average diameter of the modified multi-walled carbon nanotubes is 7 nm to 90 nm. For example, the average diameter of the modified multi-walled carbon nanotubes is 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, 70 nm, 71 nm, 72 nm, 73 nm, 74 nm, 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm The average diameter of the modified multi-walled carbon nanotubes may be, but is not limited to, 8 to 85 nm, 11 to 80 nm, 15 to 70 nm, 20 to 65 nm, 25 to 55 nm, or 30 to 50 nm.

[0059] In some embodiments of the present application, the specific surface area of the modified multi-walled carbon nanotubes is 260 m 2 / g~2900m 2 For example, the specific surface area of modified multi-walled carbon nanotubes is 260 m 2 / g、270m 2 / g、280m 2 / g、290m 2 / g、300m 2 / g、310m 2 / g、320m 2 / g、330m 2 / g、340m 2 / g、350m 2 / g、360m 2 / g、370m 2 / g、380m 2 / g、390m 2 / g、400m 2 / g、410m 2 / g、420m 2 / g、430m 2 / g、440m 2 / g、450m 2 / g、500m 2 / g、550m 2 / g、600m 2 / g、650m 2 / g、700m 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g、1000m 2 / g、1050m 2 / g、1100m 2 / g、1150m 2 / g、1200m 2 / g、1250m 2 / g、1300m 2 / g、1350m 2 / g、1400m 2 / g、1450m 2 / g、1500m 2 / g、1550m 2 / g、1600m 2 / g、1650m 2 / g、1700m 2 / g、1750m 2 / g、1800m 2 / g、1850m 2 / g、1900m 2 / g、1950m 2 / g, 2000m 2 / g, 2050m 2 / g, 2100m 2 / g, 2150m 2 / g, 2200m 2 / g, 2250m 2 / g, 2300m 2 / g, 2350m 2 / g, 2400m 2 / g, 2450m 2 / g, 2500m 2 / g, 2550m 2 / g, 2600m 2 / g, 2650m 2 / g, 2700m 2 / g, 2750m 2 / g, 2800m 2 / g, 2850m 2 / g, 2900m 2 / g, or a range consisting of any two of the above values, but is not limited thereto. For example, the specific surface area of the modified multi-walled carbon nanotubes may range from 270 m 2 / g~2850m 2 / g, 300m 2 / g~2400m 2 / g, 440m 2 / g~2000m 2 / g, 550m 2 / g~1700m 2 / g, 750m 2 / g~1550m 2 / g.

[0060] In this application, the average length of a material can be measured by a method known in the art. For example, the average length of a material can be measured by the following method. A solution of a material and carboxymethyl cellulose (CMC) in a weight ratio of 40:60 was added to water, and the solution was diluted 1000 times with water to obtain a diluted solution. 20 mL of the resulting diluted solution was then filtered through a filter, and the filter was dried with the filtered material still on it. More than 100 scanning electron microscope (SEM) images were taken of the dried filter, and the length of the material was measured using the ImageJ program. The average value of the measured lengths of the material was taken as the average length of the material.

[0061] In this application, the average diameter of a material can be measured by a method known in the art. For example, the average diameter of a material can be measured by the following method. A solution of the material and carboxymethyl cellulose (CMC) in a weight ratio of 40:60 was added to water and diluted 1000 times with water to obtain a diluted solution. One drop of the obtained diluted solution was placed on a mesh of a transmission electron microscope (TEM), and the TEM mesh was dried. The dried TEM mesh was observed using a TEM device (H-7650, manufactured by Hitachi High-Technologies Corporation), and the average diameter of the material was measured.

[0062] In the present application, carbon materials can be appropriately modified to form sodiophilic carbon-based materials, for example, by functionalization (hydroxyl, amino, carboxyl, carbonyl, mercapto, fluorination) or doping. These modifications can be performed by methods known in the art, such as fluorination or doping. These modifications can be performed by methods known in the art, such as by using strong oxidizing acids or chemicals with related functional groups to perform a correlated chemical reaction with carbon nanotubes, for example, by heating carbon nanotubes with different concentrated nitric acids for a certain period of time to produce hydroxylated or carboxylated carbon nanotubes.

[0063] In some embodiments of the present application, the modified single-walled carbon nanotubes include one or more of functionalized single-walled carbon nanotubes or doped single-walled carbon nanotubes. The resulting single-walled carbon nanotubes have excellent sodium affinity, and the shell better covers the core, reducing the swelling of the core. This contributes to the insertion and extraction of sodium ions into the positive electrode active material, further improving the cycle performance and safety of sodium-ion batteries.

[0064] In some embodiments of the present application, the functionalized single-walled carbon nanotubes include one or more of hydroxyl-functionalized single-walled carbon nanotubes and carboxyl-functionalized single-walled carbon nanotubes. Hydroxyl and carboxyl groups have good sodium affinity properties, and therefore, the single-walled carbon nanotubes functionalized therewith have good sodium affinity.

[0065] In some embodiments of the present application, the doped single-walled carbon nanotubes include one or more of phosphorus-doped single-walled carbon nanotubes, sulfur-doped single-walled carbon nanotubes, nitrogen-doped single-walled carbon nanotubes, oxygen-doped single-walled carbon nanotubes, and boron-doped single-walled carbon nanotubes, since the above elements have excellent sodium affinity, the single-walled carbon nanotubes doped with them have better sodium affinity.

[0066] The above-mentioned functionalizing groups and doping elements can also be applied to the modification of graphene oxide, multi-walled carbon nanotubes, and carbon fibers.

[0067] In some embodiments of the present application, the sodium-affinity metal-based particles include one or more of sodium-affinity metal particles and sodium-affinity metal oxide particles.

[0068] In some embodiments of the present application, the sodium-affinity metal particles have an average particle size of 0.1 μm to 5 μm.

[0069] In some embodiments of the present application, the sodium-affinity metal oxide particles have an average particle size of 0.1 μm to 5 μm.

[0070] In the above embodiment, by setting the average particle size of the sodium-affinity metal particles and the sodium-affinity metal oxide particles within the above range, the sodium affinity characteristics of the substrate can be improved, and the thickness of the positive electrode can be reduced, thereby improving the energy density of the sodium ion battery.

[0071] In some embodiments of the present application, the sodium-affine metal particles comprise one or more of copper, tin, gold, silver, aluminum, indium, zinc, lead, antimony, or alloys thereof.

[0072] In some embodiments of the present application, the sodium-affinitive metal oxide particles include one or more of copper oxide, tin oxide, beta-alumina, manganese dioxide, tricobalt tetroxide, zinc oxide, and nickel oxide.

[0073] In some embodiments of the present application, the thickness of the shell layer is 0.1 μm to 1 μm. By setting the thickness of the shell layer in this range, the core can be stably covered and the expansion of the core can be further reduced, thereby allowing sodium ions to be more easily inserted into and extracted from the core, thereby improving the cycle performance of the sodium ion battery.

[0074] In some examples, the shell layer thickness is 0.1 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm, 0.3 μm, 0.31 μm, 0.32μm, 0.33μm, 0.34μm, 0.35μm, 0.36μm, 0.37μm, 0.38μm, 0.39μm, 0.4μm, 0.41μm, 0.42μm, 0.43μm, 0. 44μm, 0.45μm, 0.46μm, 0.47μm, 0.48μm, 0.49μm, 0.5μm, 0.51μm, 0.52μm, 0.53μm, 0.54μm, 0.55μm, 0.56μ m, 0.57μm, 0.58μm, 0.59μm, 0.6μm, 0.61μm, 0.62μm, 0.63μm, 0.64μm, 0.65μm, 0.66μm, 0.67μm, 0.68μm, 0.69μm, 0.7μm, 0.71μm, 0.72μm, 0.73μm, 0.74μm, 0.75μm, 0.76μm, 0.77μm, 0.78μm, 0.79μm, 0.8μm, 0.81 The shell layer thickness may be, but is not limited to, 0.82 μm, 0.83 μm, 0.84 μm, 0.85 μm, 0.86 μm, 0.87 μm, 0.88 μm, 0.89 μm, 0.9 μm, 0.91 μm, 0.92 μm, 0.93 μm, 0.94 μm, 0.95 μm, 0.96 μm, 0.97 μm, 0.98 μm, 0.99 μm, 1 μm, or a range consisting of any two of the above values. For example, the shell layer thickness ranges are 0.11 μm to 0.99 μm, 0.15 μm to 0.91 μm, 0.2 μm to 0.85 μm, 0.28 μm to 0.72 μm, and 0.36 μm to 0.61 μm.

[0075] In the present application, the thickness of the shell layer has a meaning known in the art and can be measured by a method known in the art. For example, the thickness of the shell layer can be measured using a cross-sectional image obtained by a transmission electron microscope (TEM).

[0076] In some embodiments of the present application, the sodium-containing positive electrode active material particles may include one or more of a sodium transition metal oxide, a polyanion-type compound, and a Prussian blue-based compound. In other embodiments of the present application, other known materials, such as NaFePO4F and NaFePO4, may be used as the positive electrode active material for sodium-ion batteries.

[0077] In some examples, the transition metal in the sodium transition metal oxide may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide may include Na x In the case of MO2, M may be one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 <x≦1。

[0078] In some other examples, the polyanionic compound comprises sodium ions, transition metal ions, and tetrahedral (YO4) n- and n is a group of compounds consisting of anionic units, wherein the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may include one or more of P, S, and Si, and n is (YO4) n- represents the valence of

[0079] Polyanionic compounds include sodium ions, transition metal ions, and tetrahedral (YO4) n- and a halogen anion, wherein the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include one or more of P, S, and Si; and n may be selected from the group consisting of (YO4) n- The halogen may include one or more of F, Cl, and Br.

[0080] In some specific embodiments, the polyanionic compounds include NaFePO, NaV(PO), NaM'POF (where M' includes one or more of V, Fe, Mn, and Ni), and Na(VO)(PO)F. 2y (0≦y≦1) may be included.

[0081] In some examples, the Prussian blue-based compound contains sodium ions, transition metal ions, and cyanuric ions (CN - The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound may be, for example, Na a Me b Me' c (CN)6, wherein Me and Me' each independently comprise one or more of Ni, Cu, Fe, Mn, Co, and Zn; <a≦2、0<b<1、0<c<1。

[0082] In the present application, the method for producing the positive electrode active material may be a method known in the art. For example, the positive electrode active material may be produced by polishing a mixture of a core material and a shell material, adding a pore-forming agent to obtain a mixed raw material, and then sintering the mixed raw material to produce a positive electrode active material including a core and a shell layer covering the surface of the core. The core includes sodium-containing positive electrode active material particles, and the shell layer has a pore structure and includes a sodium-affinity material.

[0083] In the method for producing the positive electrode active material described above, the pore structure of the shell layer is formed using a pore-forming agent. In some embodiments of the present application, the pore-forming agent may include one or more of a thermally decomposable pore-forming agent and a porous material. For example, the thermally decomposable pore-forming agent may include one or more of ammonium carbonate and ammonium bicarbonate. The thermally decomposable pore-forming agent decomposes from a solid to a gas at a specific temperature, thereby generating a pore structure in the active material layer in situ. The type of pore-forming agent may also be selected based on the size of the pre-prepared pores and the sintering temperature. sodium-ion battery

[0084] A second aspect of the present application provides a sodium ion battery including the positive electrode active material for a sodium ion battery according to the first aspect of the present application.

[0085] As can be seen, a sodium ion battery typically includes an electrode assembly and an electrolyte, the electrode assembly consisting of a positive electrode sheet, a negative electrode sheet, and a separator, the sodium ion battery operates primarily by the movement of metal ions between the positive electrode sheet and the negative electrode sheet through the separator, and the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on one side of the positive electrode current collector and including the positive electrode active material according to the first aspect of the present application.

[0086] In some embodiments of the present application, the positive electrode current collector may be made of a material such as a metal foil or a porous metal plate. For example, the positive electrode current collector may be made of, but is not limited to, a foil or a porous plate made of a metal such as copper, nickel, titanium, or silver, or an alloy thereof. Furthermore, in some specific embodiments of the present application, aluminum foil is used as the positive electrode current collector.

[0087] In some embodiments of the present application, the positive electrode active material layer may further include a conductive agent and an adhesive. In the embodiments of the present application, the types of the conductive agent and adhesive included in the positive electrode active material layer are not particularly limited and can be selected according to actual needs.

[0088] For example, the conductive agent may be, but is not limited to, one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The adhesive may be, but is not limited to, one or more of styrene butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylic resin, and polyvinyl alcohol (PVA).

[0089] In an embodiment of the present application, a positive electrode active material, a conductive agent, and an adhesive are mixed at a certain mass ratio in an appropriate amount of N-methylpyrrolidone (NMP) by sufficient stirring to form a uniform positive electrode slurry, and the resulting positive electrode slurry is applied to the surface of an aluminum foil serving as a positive electrode current collector, followed by drying, cold pressing, and die cutting, thereby producing a positive electrode sheet.

[0090] In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a sodium-affinity layer disposed on one side of the negative electrode current collector, the sodium-affinity layer including a hollow sodium-affinity shell layer, the sodium-affinity shell layer including a sodium-affinity material, which can reduce the lateral growth of sodium dendrites and can also uniformly deposit sodium on the surface of the negative electrode current collector, thereby further improving the cycle performance and safety performance of the sodium-ion battery.

[0091] In the above embodiment, the sodium-affinity material includes materials similar to those used in the shell layer of the above-described positive electrode active material, such as sodium-affinity metal particles, sodium-affinity metal oxide particles, and sodium-affinity carbon-based materials.

[0092] In some embodiments of the present application, the sodium affinity layer further includes a negative electrode active material, but the type of the negative electrode active material is not particularly limited and can be selected by those skilled in the art according to actual needs. For example, the negative electrode active material may include one or more of a carbon material, an alloy material, a transition metal oxide, a transition metal sulfide, a phosphorus-based material, and a titanate material. In some specific embodiments, the negative electrode active material includes a carbon material.

[0093] In some examples, the carbon material may include one or more of natural graphite, artificial graphite, mesophase carbon microspheres (MCMB), hard carbon, and soft carbon. The alloy material may include one or more of alloy materials made of multiple elements of Si, Ge, Sn, Pb, and Sb. The chemical formula of the transition metal oxide is, for example, M 1 u O v where M 1 may be one or more selected from Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb and V, and au=2v, a is M 1 The chemical formula of a transition metal sulfide is, for example, M 2 i S j and M 2 may include one or more of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V, where b i = 2j, b is M 2 The phosphorus-based material may include one or more of red phosphorus, white phosphorus, and black phosphorus. The titanate material may include Na2Ti3O7, Na2Ti6O 13 , Na4Ti5O 12 , Li4Ti5O 12 , NaTi2(PO4)3.

[0094] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent and an adhesive. In the embodiments of the present application, the types of the conductive agent and adhesive in the negative electrode active material layer are not particularly limited and can be selected according to actual needs.

[0095] For example, the conductive agent may be one or more of, but is not limited to, graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The adhesive may be one or more of, but is not limited to, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0096] In an embodiment of the present application, a mixture of a carbonate, a sodium affinity material, an adhesive, and a pore-forming agent in a certain mass ratio is thoroughly stirred with an appropriate amount of deionized water to form a uniform negative electrode slurry, and the obtained negative electrode slurry is applied to the surface of a negative electrode current collector, followed by firing, drying, and cold pressing to produce a negative electrode sheet.

[0097] In addition, in the sodium ion battery according to the present application, the electrolyte solution includes an organic solvent and an electrolyte sodium salt. The types of the electrolyte sodium salt and the organic solvent are not particularly limited and can be selected according to actual needs. The electrolyte solution may include an organic solvent and an electrolyte sodium salt.

[0098] In some embodiments of the present application, the organic solvent comprises an ether-based organic solvent, for example, the ether-based organic solvent comprises one or more of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether, tetrahydrofuran.

[0099] In some embodiments of the present application, the molar concentration of the electrolyte sodium salt in the electrolyte solution is 0.5 mol / L to 3 mol / L, and the electrolyte sodium salt may include one or more of sodium hexafluorophosphate, sodium fluoroborate, sodium bis(trifluoromethylsulfonyl)amide, sodium bis(fluorosulfonyl)amide, and sodium bis(oxalato)borate.

[0100] In some embodiments of the present application, the electrolyte solution may further include an optional additive, such as a film-forming additive for the negative electrode, a film-forming additive for the positive electrode, or an additive capable of improving some performance of the sodium ion battery, such as the overcharge performance, high-temperature performance, or low-temperature power performance of the sodium ion battery.

[0101] In the embodiments of the present application, the material of the separator is not particularly limited, and any known separator with excellent chemical and mechanical stability can be selected. For example, the separator can include one or more of a porous polyolefin resin film (e.g., one or more of polyethylene, polypropylene, and polyvinylidene fluoride), a porous glass fiber, and a porous nonwoven fabric. The porous separator may be a single-layer film or a multi-layer composite film. When the porous separator is a multi-layer composite film, the materials of the layers may be the same or different.

[0102] In some embodiments of the present application, the sodium-ion battery may further include an exterior structure, which may be used to package the electrode assembly and the electrolyte.

[0103] In some embodiments of the present application, the exterior structure of the sodium ion battery may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior structure of the sodium ion battery may be a soft pack, for example, a bag-shaped soft pack. The material of the soft bag may be plastic, for example, at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0104] In the present application, the shape of the sodium ion battery is not particularly limited, and it may be cylindrical, rectangular, or any other shape. Figure 1 shows an example of a sodium ion battery 5 with a rectangular structure.

[0105] In some embodiments of the present application, as shown in FIG. 2 , the exterior structure may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and a side plate connected to the bottom plate, and a storage cavity is formed by the bottom plate and the side plate. The case 51 has an opening communicating with the storage cavity, and the cover plate 53 covers the opening to seal the storage cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be wound and / or stacked to form an electrode assembly 52. The electrode assembly 52 is packaged within the storage cavity. The electrode assembly 52 is impregnated with an electrolyte. The sodium-ion battery 5 may include one or more electrode units 52, and the number may be increased or decreased according to needs.

[0106] The method for manufacturing the sodium ion battery of the present application is a known method. In some embodiments of the present application, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a sodium ion battery. For example, the sodium ion battery can be manufactured by winding and / or stacking the positive electrode sheet, the separator, and the negative electrode sheet to form an electrode assembly, placing the formed electrode assembly in an exterior structure, injecting an electrolyte after drying, and performing processes such as vacuum packaging, standing, chemical formation, and shaping.

[0107] In some embodiments of the present application, the sodium ion battery according to the present application may be assembled into a battery module, and the number of sodium ion batteries included in the battery module may be plural, and may be specifically increased or decreased according to the application and capacity of the battery module.

[0108] Fig. 3 is a schematic diagram of an example battery module. As shown in Fig. 3, a battery module 4 may have a plurality of sodium ion batteries 5 arranged in sequence along the longitudinal direction of the battery module 4. Of course, the batteries may be arranged in any other manner. Furthermore, the plurality of sodium ion batteries 5 may be fixed by fasteners.

[0109] Optionally, the battery module 4 may further include a housing having an accommodating space in which the plurality of sodium ion batteries 5 are accommodated.

[0110] In some embodiments of the present application, the above battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be increased or decreased depending on the application and capacity of the battery pack.

[0111] 4 and 5 are schematic diagrams of an example battery pack. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery case and a plurality of battery modules 4 provided in the battery case. The battery case includes an upper housing 2 and a lower housing 3, and the upper housing 2 is provided to cover the lower housing 3, forming an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in any manner within the battery case. power consumption equipment

[0112] A third aspect of the present application provides a power consuming device including one or more of the sodium ion batteries, battery modules, or battery packs according to the second aspect of the present application, which may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device.

[0113] In the present application, the power consuming devices may be, but are not limited to, mobile phones, tablet computers, laptops, electric toys, power tools, electric bicycles, electric vehicles, boats, aircraft, energy storage systems, etc. However, the electric toys may include stationary or portable electric toys, such as game consoles, electric vehicle toys, electric boat toys, and electric plane toys, and the spacecraft may include airplanes, rockets, space shuttles, spaceships, etc.

[0114] In addition, the power consuming device may select a sodium ion battery, a battery module, or a battery pack according to its usage needs.

[0115] 6 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or battery module can be used to meet the high power and high energy density requirements of the power consuming device.

[0116] The following examples are provided to more fully describe the contents disclosed in the present application, and are merely illustrative, as it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the contents disclosed in the present application. All reagents used in the examples may be commercially available or may be synthesized according to conventional methods and may be used as is without further treatment. All equipment used in the examples is commercially available. Example 1 Positive electrode sheet manufacturing

[0117] The positive electrode active material was manufactured by the following steps: Positive electrode active material particles (sodium iron phosphate) and hydroxyl-functionalized multi-walled carbon nanotubes were added to an agate mortar in a mass ratio of 18:1, thoroughly polished, and then a pore-forming agent (ammonium carbonate) was added at a mass fraction of 1% (the ratio of the mass of the pore-forming agent to the total mass of the positive electrode active material particles, sodium affinity material, and pore-forming agent) to obtain a mixed raw material; the mixed raw material was then placed in a muffle furnace (KSL-1100X-S) and calcined at 800°C for 12 hours to produce the positive electrode active material.

[0118] The positive electrode active material produced above, acetylene black as a conductive agent, and carboxymethyl cellulose as an adhesive were mixed in a mass ratio of 95:2:3, and the mixture was thoroughly stirred in an appropriate amount of N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry. The formed positive electrode slurry was applied to the surface of aluminum foil as a positive electrode current collector, followed by drying, cold pressing, and die cutting to produce a positive electrode sheet. Manufacture of negative electrode sheets

[0119] A mixture of sodium carbonate, acetylene black, and carboxymethyl cellulose as an adhesive in a mass ratio of 95:2:3 was thoroughly stirred in an appropriate amount of N-methylpyrrolidone (NMP), and 1% of ammonium carbonate as a pore-forming agent was further added to form a uniform negative electrode slurry. The formed negative electrode slurry was applied to the surface of aluminum foil as a negative electrode current collector, and then baked at 120°C, dried, and cold-pressed to produce a negative electrode sheet. Separator

[0120] A polyethylene film was used as the separator. electrolyte

[0121] In a glove box filled with argon gas with a water content of less than 1 ppm, sodium hexafluorophosphate (NaPF6) with a concentration of 1.0 mol / L was added to a mixture of diethylene glycol dimethyl ether and tetrahydrofuran in a mass ratio of 1:3, and the mixture was stirred uniformly to prepare an electrolyte. Sodium-ion battery manufacturing

[0122] The positive electrode sheet, separator, and negative electrode sheet were subjected to a winding process and / or a stacking process to form an electrode assembly, and the formed electrode assembly was placed in an exterior structure, dried, and then an electrolyte solution was injected. After that, processes such as vacuum packaging, standing, chemical formation, and shaping were carried out to manufacture a sodium ion battery. Examples 2 to 21

[0123] The manufacturing method is the same as that of Example 1, except that the shell layer-related parameters such as the material of the shell layer and the average pore size of the pores are changed. Comparative Examples 1-2

[0124] The manufacturing method was the same as in Example 1, except that the positive electrode active material particles were not covered with a shell layer and the shell layer did not have a pore structure. Testing part (1) Capacity retention test

[0125] At 25°C, the battery was charged at 1 / 3C to the upper cutoff voltage of 3.65V to 4.25V, and then discharged at 1 / 3C to the lower cutoff voltage of 1.5V to 2.5V. This process was repeated three times, and the discharge capacity at the third time was taken as the standard capacity C1. After this process was repeated 200 times, the battery was charged at 1C and then discharged at 1C, resulting in a discharge capacity C200. Capacity retention rate = C200 / C1. (2) Testing for sodium dendrites on the surface of the negative electrode sheet

[0126] After 100 charge-discharge cycles at 1C, the fully charged sodium-ion battery was disassembled, and the surface morphology of the metallic sodium anode was observed using an optical microscope. The cross-sectional shape of the metallic sodium was observed using an electron microscope. The thickness of the deposit was then compared with the theoretical deposit thickness. However, if the thickness increase rate is less than 140%, no sodium dendrites are observed; if the thickness increase rate is between 150% and 200%, slight dendrites are observed; if the thickness increase rate is between 200% and 230%, moderate dendrites are observed; and if the thickness increase rate is between 230% and 300%, severe dendrites are observed.

[0127] Table 1 shows the test results for Examples 1 to 21 and Comparative Examples 1 and 2, each of which contains a different positive electrode active material.

[0128] [Table 1]

[0129] As can be seen from Table 1 and comparing the tests of Examples 1 to 21 with Comparative Examples 1 and 2, the shell layer containing a sodium affinity material can better cover the core containing sodium-containing positive electrode active material particles. When the positive electrode active material is used in a sodium ion battery, the shell layer covering the surface of the core reduces the expansion of the core, further reducing deformation of the positive electrode active material and contributing to the insertion and desorption of sodium ions, thereby achieving the goal of improving the cycle performance and safety performance of the sodium ion battery.

[0130] It should be noted that the above embodiments do not limit the technical solution of the present application, but are merely illustrative. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications to the technical solutions described in the above embodiments, or equivalent substitutions for some or all of the technical features therein, are possible, and as long as the essence of the corresponding technical solution deviates from the scope of the technical solutions of the embodiments of the present application, all of these should be included within the scope of the claims and description of the present application. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural contradiction. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions included within the scope of the claims.

Claims

1. a core including sodium-containing positive electrode active material particles; a shell layer covering the surface of the core, the shell layer has a pore structure and includes a sodium-affinity material; Positive electrode active material for sodium ion batteries.

2. an average particle diameter D1 of the sodium-containing positive electrode active material particles and an average pore diameter D2 of the pore structure satisfy the relationship 5≦D1 / D2≦600; The positive electrode active material for a sodium ion battery according to claim 1 .

3. The sodium-containing positive electrode active material particles have an average particle diameter D1 of 10 μm to 50 μm, and / or The average pore diameter D2 of the pore structure is 0.1 μm to 1 μm. The positive electrode active material for a sodium ion battery according to claim 1 or 2.

4. the sodium-affinity material comprises one or more of a sodium-affinity carbon-based material and a sodium-affinity metal-based particle; Optionally, the sodium-philic carbon-based material comprises one or more of graphene oxide and modified graphene oxide, modified carbon nanotubes, and modified carbon fibers; Optionally, the sodium-affinity metal-based particles include one or more of sodium-affinity metal particles and sodium-affinity metal oxide particles; Optionally, the sodium-affine metal particles comprise one or more of copper, tin, gold, silver, aluminum, indium, zinc, lead, antimony, or alloys thereof; Optionally, the sodium-affinity metal oxide particles include one or more of copper oxide, tin oxide, β-alumina, manganese dioxide, tricobalt tetroxide, zinc oxide, and nickel oxide. The positive electrode active material for a sodium ion battery according to claim 1 .

5. The thickness of the shell layer is 0.1 μm to 1 μm. The positive electrode active material for a sodium ion battery according to any one of claims 1 to 4.

6. A sodium ion battery comprising the positive electrode active material for a sodium ion battery according to any one of claims 1 to 5.

7. 10. A power consuming device comprising the sodium ion battery of claim 6.

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