Sodium supplementing material and preparation method therefor, positive electrode sheet, and sodium-ion battery

Abstract

The present application provides a sodium supplementing material and a preparation method therefor, a positive electrode sheet, and a sodium-ion battery. The sodium supplementing material comprises an organic sodium supplementing agent body, and a conductive agent and a composite catalyst which are at least partially coated by the organic sodium supplementing agent body. The composite catalyst has a core-shell structure. The core layer of the core-shell structure comprises a metal oxide catalyst, the shell layer of the core-shell structure comprises an electrochemically stable material, and the electrochemically stable material is a material having electrochemical stability under charge and discharge test conditions from a first-cycle charging voltage of 4.1 V to a first-cycle discharging voltage of 1.5 V and from a cyclic charging voltage of 3.5 V to a cyclic discharging voltage of 1.5 V.

Description

Sodium-supplementing materials and their preparation methods, positive electrode sheets, sodium-ion batteries

[0001] Related cross-references

[0002] This application claims priority to Chinese Patent Application No. 202411829459.2, filed on December 12, 2024, entitled “Sodium Supplement Material and Preparation Method Thereof, Positive Electrode Sheet, Sodium-ion Battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of energy storage technology, and in particular to a sodium supplementation material and its preparation method, a positive electrode sheet, and a sodium-ion battery. Background Technology

[0004] Sodium-ion batteries, with their advantages of low cost, abundant sodium resources, and relatively high energy density, are expected to replace traditional lithium-ion batteries in the field of energy storage.

[0005] Adding sodium to the positive electrode using organic sodium replenishers can reduce the adverse effects of sodium loss on the electrochemical performance of sodium-ion batteries. However, conventional organic sodium replenishers have high oxidation decomposition potentials. Although combining organic sodium replenishers with metal oxide catalysts can lower their oxidation decomposition potentials, this also introduces a metal ion shuttle effect, leading to decreased stability of the organic sodium replenishers and affecting the cycle performance of sodium-ion batteries. Summary of the Invention

[0006] To address the aforementioned technical problems, this application discloses a sodium-supplementing material and its preparation method, a positive electrode sheet, and a sodium-ion battery, which reduces the oxidative decomposition potential of the sodium-supplementing material while suppressing the metal ion shuttle effect, thereby improving the energy density and cycle performance of the sodium-ion battery.

[0007] In a first aspect, this application provides a sodium supplement material, comprising an organic sodium supplement body and a conductive agent and a composite catalyst at least partially coated within the organic sodium supplement body; the composite catalyst has a core-shell structure, wherein the core layer of the core-shell structure comprises a metal oxide catalyst, and the shell layer of the core-shell structure comprises an electrochemically stable material, wherein the electrochemically stable material is a material that exhibits electrochemical stability under charge-discharge test conditions of an initial charge voltage of 4.1V to an initial discharge voltage of 1.5V and a cyclic charge voltage of 3.5V to a cyclic discharge voltage of 1.5V.

[0008] Secondly, this application provides a method for preparing the sodium-supplementing material as described in the first aspect, comprising the following steps:

[0009] Organic sodium supplementer, conductive agent and composite catalyst are mixed to obtain sodium supplement material precursor;

[0010] The sodium-supplementing material precursor was subjected to a first calcination treatment in an inert gas atmosphere at a temperature of 300℃ to 500℃ for 1h to 8h, and then cooled to obtain the sodium-supplementing material.

[0011] Thirdly, this application provides a positive electrode sheet, including a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a sodium-supplementing material as described in the first aspect, or the positive active material layer includes a sodium-supplementing material prepared by the preparation method described in the second aspect.

[0012] Fourthly, this application provides a sodium-ion battery, which includes the positive electrode sheet of the third aspect.

[0013] Fifthly, this application provides an energy storage device, including a housing and at least one sodium-ion battery, which is housed in the housing.

[0014] In a sixth aspect, this application provides an electrical appliance, including the energy storage device of the fifth aspect, which supplies power to the electrical appliance.

[0015] Compared with the prior art, this application has at least the following beneficial effects:

[0016] This application provides a sodium-supplementing material and its preparation method, a positive electrode sheet, and a sodium-ion battery. The sodium-supplementing material includes an organic sodium-supplementing agent body and a conductive agent and a composite catalyst at least partially coated in the organic sodium-supplementing agent body. The composite catalyst has a core-shell structure, the core layer of the core-shell structure includes a metal oxide catalyst, and the shell layer of the core-shell structure includes an electrochemically stabilizing material. The electrochemically stabilizing material is a material that has electrochemical stability under charge-discharge test conditions of 4.1V to 1.5V for the first charge cycle and 3.5V to 1.5V for the cycle charge cycle. In the sodium replenishment material of this application, the conductive agent and / or composite catalyst are at least partially coated within the organic sodium replenishment agent body, forming a coated or semi-coated structure on the conductive agent and / or composite catalyst. This facilitates electron transport to the organic sodium replenishment agent body, thereby reducing the oxidation decomposition potential of the sodium replenishment material. Simultaneously, the composite catalyst has a core layer and a shell layer. The core layer facilitates multi-electron transfer, further reducing the oxidation decomposition potential of the sodium replenishment material. The shell layer forms a protective layer for the metal oxide catalyst, reducing direct contact between the metal oxide catalyst and the electrolyte. This improves the structural stability of the metal oxide catalyst in the core layer, reduces the metal ion shuttle effect in the metal oxide catalyst of the sodium replenishment material, maintains the stability of the SEI (Solid Electrolyte Interphase) film, reduces irreversible sodium loss, and improves the cycle performance of the sodium-ion battery. Furthermore, the conductive agent in the sodium replenishment material further enhances its conductivity. The sodium replenishment material of this application possesses the above-mentioned structural and material properties, enabling it to reduce the oxidation decomposition potential of the sodium replenishment material while suppressing the metal ion shuttle effect, thereby improving the energy density and cycle performance of the sodium-ion battery. When this sodium-ion battery is used in energy storage devices, it can increase the capacity and lifespan of the energy storage devices, thereby reducing the operating costs of the energy storage devices. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is a cross-sectional structural diagram of a sodium supplement material according to one embodiment of this application;

[0019] Figure 2 is a structural schematic diagram of a residential energy storage system according to one embodiment of this application;

[0020] Figure 3 is a schematic diagram of the energy storage system according to one embodiment of this application.

[0021] Explanation of reference numerals in the attached drawings: 1-Energy storage device, 2-Electric power conversion device, 3-First user load, 4-Second user load, 10-Organic sodium supplement body, 20-Conductive agent, 30-Composite catalyst, 31-Core layer, 32-Shell layer, 400-Energy storage system, 410-High voltage cable, 420-First electric power conversion device, 430-Second electric power conversion device. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0024] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0025] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0026] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0027] In related technologies, although the oxidation decomposition potential of sodium-supplementing materials can be reduced by introducing metal oxide catalysts, these catalysts are prone to phase transitions and structural changes under high pressure. The resulting metal ions shuttle to the negative electrode, exhibiting a shuttle effect. This shuttle effect induces electrolyte decomposition and alters the SEI film structure, leading to decreased cycle stability of the sodium-ion battery. Therefore, how to reduce the oxidation decomposition potential of sodium-supplementing materials while suppressing the shuttle effect to improve the energy density and cycle performance of sodium-ion batteries has become a pressing technical problem.

[0028] In view of this, this application provides a sodium supplement material. Referring to Figure 1, the sodium supplement material includes an organic sodium supplement body 10 and a conductive agent 20 and a composite catalyst 30, which are at least partially coated in the organic sodium supplement body 10. Both the conductive agent and the composite catalyst can be in particulate form. The composite catalyst 30 has a core-shell structure. The core layer 31 of the core-shell structure includes a metal oxide catalyst, and the shell layer 32 of the core-shell structure includes an electrochemically stable material. The electrochemically stable material is a material that has electrochemical stability under charge-discharge test conditions of 4.1V to 1.5V for the first charge voltage and 3.5V to 1.5V for the cyclic charge voltage. In the sodium supplement material of this application, the conductive agent and / or composite catalyst are at least partially coated in the organic sodium supplement body. That is, the conductive agent and / or composite catalyst can be completely coated by the organic sodium supplement body, or the conductive agent and / or composite catalyst can be partially coated by the organic sodium supplement body. This results in the organic sodium supplement body forming a coated or semi-coated structure for the conductive agent and / or composite catalyst, which is beneficial for promoting electron transport to the organic sodium supplement body, thereby reducing the oxidation decomposition potential of the sodium supplement material. At the same time, the composite catalyst has a core layer and a shell layer. The core layer is beneficial for promoting multi-electron transfer, further reducing the oxidation decomposition potential of the sodium supplement material. The shell layer contains an electrochemically stabilizing material, forming a protective layer for the metal oxide catalyst. This reduces the direct contact between the metal oxide catalyst and the electrolyte, which is beneficial for improving the structural stability of the metal oxide catalyst in the core layer, reducing the metal ion shuttle effect in the metal oxide catalyst of the sodium supplement material, maintaining the stability of the SEI film, reducing irreversible sodium loss, and improving the cycle performance of the sodium-ion battery. Furthermore, the conductive agent in the sodium supplement material can further improve the conductivity of the sodium supplement material. The sodium-supplementing material of this application possesses the aforementioned structural and material properties, which can suppress the metal-ion shuttle effect while reducing the oxidative decomposition potential of the sodium-supplementing material, thereby improving the energy density and cycle performance of the sodium-ion battery. When this sodium-ion battery is applied in an energy storage device, it can increase the capacity and lifespan of the energy storage device, thereby reducing the operating cost of the energy storage device.

[0029] In this application, the oxidation decomposition potential refers to the potential corresponding to the oxidation decomposition reaction that occurs when the sodium supplement material undergoes an oxidation decomposition reaction during the charging process.

[0030] This application allows for charge-discharge testing of sodium-ion batteries containing the aforementioned electrochemically stable material. An exemplary charge-discharge test procedure is as follows: First, the sodium-ion battery is charged at a constant current of 0.1 times (C) to 4.1V, and then discharged at 0.1C to 1.5V. Subsequently, a cycle test is performed, i.e., charging at a constant current of 1C to 3.5V, and then discharging at 1C to 1.5V, constituting one charge-discharge cycle. After 300 charge-discharge cycles, the capacity retention rate of the sodium-ion battery is calculated. If the capacity retention rate is not less than 90%, the electrochemically stable material is considered to possess electrochemical stability.

[0031] In some embodiments of this application, the thickness of the shell layer is 1 nm to 5 nm. For example, the thickness of the shell layer is 1 nm, 2 nm, 3 nm, 4 nm, or 5 nm. When the thickness of the shell layer is too small (e.g., less than 1 nm), the electrolyte can still easily penetrate the shell layer and come into contact with the metal oxide catalyst, leading to the easy dissolution of metal ions under high voltage, which increases the metal ion shuttle effect of the metal oxide catalyst. When the thickness of the shell layer is too large (e.g., greater than 5 nm), the electron transfer resistance between the metal oxide catalyst and the organic sodium supplement increases, resulting in a decrease in the catalytic performance of the catalyst for the sodium supplement and hindering the reduction of the oxidation decomposition potential of the sodium supplement material. By controlling the thickness of the shell layer within the above range, it is possible to reduce the metal ion shuttle effect of the metal oxide catalyst in the sodium supplement material while lowering the oxidation decomposition potential of the sodium supplement material, which is beneficial to improving the energy density and cycle performance of sodium-ion batteries.

[0032] In some embodiments of this application, the mass percentage of the organic sodium supplement in the sodium supplement material is 'a', the mass percentage of the conductive agent in the sodium supplement material is 'b', and the mass percentage of the composite catalyst in the sodium supplement material is 'c', with 30% ≤ a ≤ 90%, 0 < b ≤ 70%, and 0 < c ≤ 30%. In other embodiments of this application, 50% ≤ a ≤ 80%, 5% ≤ b ≤ 50%, and 5% ≤ c ≤ 10%. For example, 'a' can be 30%, 40%, 50%, 60%, 70%, 80%, or 90%; 'b' can be 1%, 10%, 15%, 20%, 30%, 40%, 50%, or 70%; and 'c' can be 5%, 6%, 7%, 8%, 9%, or 10%. By controlling the content of organic sodium supplement agent, conductive agent, and composite catalyst in sodium supplement materials within the above-mentioned range, it is beneficial to obtain sodium supplement materials with low metal ion shuttle effect, low oxidation decomposition potential, and excellent conductivity, thereby improving the energy density and cycle performance of sodium-ion batteries.

[0033] In some embodiments of this application, the organic sodium supplement is made of at least one of CH3COONa, Na2C4O4, Na2C2O4, C6H5Na3O7, and Na2C6O6. The above-mentioned sodium supplement is an organic sodium supplement, which has the advantages of being environmentally friendly, widely available, and safe and non-toxic.

[0034] In some embodiments of this application, the conductive agent includes at least one selected from conductive carbon black, carbon nanotubes (CNTs), Ketjen black (KB), graphene, and acetylene black (ACET). These conductive agents possess good conductivity and a large specific surface area, which can improve the conductivity of the sodium-supplementing material and facilitate a reduction in the oxidative decomposition potential of the sodium-supplementing material.

[0035] In some embodiments of this application, the metal oxide catalyst includes at least one of ruthenium dioxide (RuO2), ferric oxide (Fe2O3), vanadium pentoxide (V2O5), titanium dioxide (TiO2), cobalt tetroxide (Co3O4), α-manganese dioxide (α-MnO2), δ-manganese dioxide (δ-MnO2), and γ-manganese dioxide (γ-MnO2). The aforementioned metal oxide catalysts are beneficial for reducing the oxidative decomposition potential of the sodium-supplementing material, thereby improving the sodium-supplementing effect of the material.

[0036] In some embodiments of this application, the electrochemical stabilizing material includes at least one of aluminum oxide (Al₂O₃), β-manganese dioxide (β-MnO₂), nickel oxide (Ni₂O₃), zinc oxide (ZnO), tungsten carbide (WC), titanium carbide (TiC), tantalum carbide (TaC), and MXene (a two-dimensional transition metal carbon / nitride material). These materials are beneficial for maintaining the structural stability of the metal oxide catalyst during charge and discharge, and for reducing the metal ion shuttle effect in the sodium-supplementing material.

[0037] Secondly, this application provides a method for preparing the sodium-supplementing material as described in the first aspect, comprising the following steps:

[0038] Step A: Mix the organic sodium supplement, conductive agent and composite catalyst to obtain the sodium supplement material precursor;

[0039] Step B: The sodium supplement material precursor is subjected to a first calcination treatment in an inert gas atmosphere. The calcination temperature is 300℃~500℃ and the holding time is 1h~8h. After cooling, the sodium supplement material is obtained.

[0040] In step A, raw materials such as organic sodium supplement, conductive agent and composite catalyst can be proportioned according to the component content of the designed sodium supplement material, and then mixed evenly to form a sodium supplement material precursor.

[0041] In step B, the inert gas includes at least one of inert gases such as nitrogen and argon; the calcination temperature is preferably 4 to 5 hours; and the cooling process can be natural cooling. Furthermore, after cooling to obtain the sodium-supplementing material, the material can be crushed using a crusher and then sieved to obtain sodium-supplementing materials within the desired particle size range; this application does not impose any particular limitations.

[0042] In some embodiments of this application, during the first calcination process, the organic sodium supplement melts, causing the conductive agent and composite catalyst to be coated within the molten sodium supplement; during the cooling process, the organic sodium supplement solidifies, causing the conductive agent and / or composite catalyst to be at least partially coated within the organic sodium supplement body. Through the above-described calcination and cooling processes of this application, the conductive agent and / or composite catalyst can be at least partially coated within the organic sodium supplement body, forming a coated or semi-coated structure for the conductive agent and / or composite catalyst, thereby forming a sodium supplement material with the structure of this application. The resulting sodium supplement material has a lower oxidation decomposition potential.

[0043] In some embodiments of this application, the preparation process of the composite catalyst includes:

[0044] Step i: Add the metal oxide catalyst to the solvent and mix to obtain a dispersion;

[0045] Step ii: Add the electrochemically stable precursor material to the dispersion and mix to obtain a mixture. After desolventizing the mixture, the composite catalyst precursor is obtained.

[0046] Step iii: The composite catalyst precursor is subjected to a second calcination treatment in an inert gas atmosphere at a temperature of 400℃~600℃ and a holding time of 4h~6h to obtain a composite catalyst with a core-shell structure.

[0047] In step i, the solvent is water. For example, it can be distilled water or deionized water.

[0048] In step ii, the solvent removal process involves vacuum drying the mixture at 60°C to 110°C to evaporate the solvent.

[0049] In step iii, through the second calcination process of this application, that is, by controlling the calcination temperature and holding time within the above range, the metal oxide catalyst in the composite catalyst precursor does not decompose, while the electrochemically stable precursor material decomposes to generate corresponding oxides or carbides, forming an electrochemically stable material, which is beneficial to obtaining the composite catalyst of this application.

[0050] In some embodiments of this application, the electrochemically stable precursor material includes at least one of the sulfate, chloride, and fluoride salts corresponding to the metal ions in the electrochemically stable material. For example, when the electrochemically stable material is aluminum oxide, its corresponding electrochemically stable precursor material includes, but is not limited to, at least one of Al2(SO4)3, AlCl3, and AlF3.

[0051] The method for preparing sodium-supplementing materials provided in this application has the advantages of simple preparation process and wide availability of raw materials. The prepared sodium-supplementing materials have excellent sodium-supplementing performance and low cost, thereby improving the energy density and cycle performance of sodium-ion batteries while reducing the production cost of sodium-ion batteries, and thus reducing the operating cost of energy storage devices applied to sodium-ion batteries.

[0052] This application also provides a positive electrode sheet, including a current collector and a positive electrode active material layer disposed on at least one surface of the current collector. The positive electrode active material layer includes the sodium-supplementing material described in any of the above embodiments, or the positive electrode active material layer includes the sodium-supplementing material prepared by the preparation method described in any of the above embodiments.

[0053] The positive electrode active material layer of this application can be disposed on one or both surfaces of the positive electrode current collector in the thickness direction. In this application, the positive electrode active material layer is disposed on the surface of the positive electrode current collector; that is, the positive electrode active material layer can be disposed on a portion of one surface of the positive electrode current collector, or it can be disposed on the entire surface of one surface of the positive electrode current collector. This application does not have any particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application; for example, it can be, but is not limited to, aluminum foil, aluminum alloy foil, or composite current collectors. In this application, there is no particular limitation on the thickness of the positive electrode current collector, as long as it can achieve the purpose of this application; for example, a thickness of 8 μm to 13 μm. The single-sided thickness of the positive electrode active material layer in this application can be 150 μm to 400 μm.

[0054] In this application, the positive electrode active material layer also includes a positive electrode active material. This application does not have any particular restrictions on the positive electrode active material, as long as it can achieve the purpose of this application. For example, it may include at least one of sodium nickel manganate, sodium nickel iron manganate, sodium iron sulfate, sodium vanadium phosphate, sodium copper iron manganate, sodium iron pyrophosphate, and sodium iron pyrophosphate.

[0055] In this application, the positive electrode active material layer may further include a positive electrode conductive agent. This application does not impose any particular limitation on the positive electrode conductive agent, as long as it can achieve the purpose of this application. For example, it may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNT), Ketjen black (KB), graphene, graphene oxide, and acetylene black. The mass percentage of the conductive agent in the positive electrode active material layer is 10% to 40%. In this application, the positive electrode active material layer may further include a positive electrode binder. This application does not impose any particular limitation on the positive electrode binder, as long as it can achieve the purpose of this application. For example, it may include, but is not limited to, at least one of fluorinated resin, polypropylene resin, fiber-type binder, rubber-type binder, polyimide-type binder, and polyvinylidene fluoride (PVDF).

[0056] This application also provides a sodium-ion battery, including the positive electrode sheet described in any of the above embodiments.

[0057] The sodium-ion battery of this application also includes a negative electrode, a separator, and an electrolyte, wherein the separator is located between the positive electrode and the negative electrode and plays a role in isolation.

[0058] This application does not impose any particular limitation on the negative electrode sheet, as long as it achieves the purpose of this application. For example, the negative electrode sheet typically includes a negative current collector and a negative active material layer. The negative active material layer can be disposed on the surface of the negative current collector; that is, the negative active material layer can be disposed on a portion of the surface of the negative current collector, or it can be disposed on the entire surface of the negative current collector. This application does not impose any particular limitation on the negative current collector, as long as it achieves the purpose of this application. For example, it can include, but is not limited to, copper foil, copper alloy foil, nickel foil, or composite current collectors. In this application, there is no particular limitation on the thickness of the negative current collector, as long as it achieves the purpose of this application, for example, a thickness of 4μm to 12μm. The single-sided thickness of the negative material layer in this application can be 70μm to 200μm.

[0059] In this application, the negative electrode active material layer may also include a negative electrode binder. This application does not impose any particular limitation on the negative electrode binder, as long as it can achieve the purpose of this application. For example, it may include at least one of acrylate, polyamide, polyimide, polyamide-imide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose.

[0060] In some embodiments, the diaphragm material can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular limitation. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0061] The sodium-ion battery of this application also includes an electrolyte. This application does not impose any particular limitation on the electrolyte; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. For example, at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), propyl propionate (PP), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC), or fluoroethylene carbonate (FEC) can be mixed in a certain mass or volume ratio to obtain a non-aqueous organic solvent, and then a sodium salt can be added to dissolve and mix evenly. This application does not limit the type of sodium salt, as long as the purpose of this application is achieved. For example, the sodium salt may include at least one of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium trifluoromethanesulfonate, and sodium p-toluenesulfonate. This application does not impose any particular limitation on the concentration of the sodium salt in the electrolyte, as long as the purpose of this application is achieved. For example, the concentration of the sodium salt is 1.0 mol / L to 2.0 mol / L.

[0062] The sodium-ion battery of this application also includes a casing. This application does not impose any particular restrictions on the casing, and those skilled in the art can choose one according to actual needs, as long as it can achieve the purpose of this application. For example, the casing may include an aluminum-plastic film.

[0063] This application does not impose any particular limitation on the preparation method of sodium-ion batteries. Any preparation method known in the art can be used, as long as it can achieve the purpose of this application. For example, the preparation method of sodium-ion batteries includes, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and winding and folding them as needed to obtain a bare cell with a wound structure; placing the bare cell in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain a sodium-ion battery.

[0064] This application also provides an energy storage device, including a housing and at least one sodium-ion battery as described in any of the above embodiments, the sodium-ion battery being housed within the housing. The energy storage device with this sodium-ion battery exhibits excellent performance, which is beneficial for its use. Housing the battery within the housing increases its stability and protection, thereby extending the lifespan of the energy storage device. It is understood that the energy storage device may contain one or more sodium-ion batteries, and when the energy storage device contains multiple sodium-ion batteries, the multiple sodium-ion batteries can be connected in at least one manner, such as parallel or series connection.

[0065] This application also provides an electrical device including the energy storage device in any of the above embodiments, which is beneficial to improving the product competitiveness and performance of the electrical device. In an optional embodiment, the electrical device includes an electrical device body, and the energy storage device is used to supply power to the electrical device body. In an optional embodiment, the electrical device body includes a positive electrode and a negative electrode, the positive electrode of the sodium-ion battery in the energy storage device is used to electrically connect to the positive electrode of the electrical device body, and the negative electrode of the sodium-ion battery in the energy storage device is used to electrically connect to the negative electrode of the electrical device body, so as to supply power to the electrical device.

[0066] The electrical equipment covered by this application may include, but is not limited to: containers, household energy storage systems, electric vehicles, electric cars, ships, spacecraft, electric toys, and power tools, etc. Among them, spacecraft include, for example, airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include, for example, stationary or mobile electric toys, specifically, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include, for example, metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, specifically, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0067] Please refer to Figure 2, which is a structural schematic diagram of a residential energy storage system according to one embodiment of this application. The embodiment in Figure 2 is illustrated using a residential energy storage scenario in user-side energy storage as an example. The energy storage device of this application is not limited to residential energy storage scenarios.

[0068] This application provides a residential energy storage system, which includes a power conversion device 2 (photovoltaic panel), a first user load 3 (streetlight), a second user load 4 (e.g., household appliances such as air conditioners), and an energy storage device 1. The energy storage device 1 is a small energy storage box that can be wall-mounted to an outdoor wall. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 1 is used to store this electrical energy and supply it to streetlights and household appliances during periods of high electricity prices, or to provide power during power outages / power failures.

[0069] Please refer to Figure 3, which is a structural schematic diagram of an energy storage system 400 according to one embodiment of this application. The embodiment in Figure 3 is illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 1 of this application is not limited to the energy storage scenario on the generation / distribution side.

[0070] This application provides an energy storage system 400, which includes a high-voltage cable 410, a first power conversion device 420, a second power conversion device 430, and the energy storage device 1 provided in this application. During power generation, the first power conversion device 420 and the second power conversion device 430 convert other forms of energy into electrical energy, which is then connected to the high-voltage cable 410 and supplied to the power consumption side of the distribution network. When the power load is low and the first power conversion device 420 and the second power conversion device 430 generate excess power, the excess power is stored in the energy storage device 1, reducing wind and solar curtailment rates and improving the absorption of new energy power generation. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 1, along with the high-voltage cable 410, in a grid-connected mode to supply power to the power consumption side. This provides various services such as peak shaving, frequency regulation, and backup for the power grid operation, fully leveraging the peak shaving function of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure on the power grid.

[0071] Optionally, the first power conversion device 420 and the second power conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electrical energy.

[0072] The number of energy storage devices 1 can be multiple, and these devices can be connected in series or in parallel. The multiple energy storage devices 1 are supported and electrically connected by an isolation plate (not shown). In this embodiment, "multiple" refers to two or more. An energy storage box can also be provided outside the energy storage device 1 to house it.

[0073] Optionally, the energy storage device 1 may include, but is not limited to, battery modules, battery packs, and battery systems. The battery module may be a battery module formed by connecting multiple sodium-ion batteries of this application in series or parallel; the battery pack may include multiple sodium-ion batteries of this application; and the battery system may be a charging and discharging system including sodium-ion batteries or battery packs of this application.

[0074] The actual application of the energy storage device 1 provided in this application can be, but is not limited to, the listed products, and can also be other application forms. This application does not strictly limit the application form of the energy storage device 1. This application only uses a multi-cell battery as an example for illustration. When the energy storage device 1 is a single cell battery, the energy storage device 1 can be at least one of cylindrical batteries, prismatic batteries, etc.

[0075] Example

[0076] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below.

[0077] Example 1

[0078] <Preparation of Sodium Supplement Materials>

[0079] 9.5 g of the metal oxide catalyst titanium dioxide (TiO2) was added to 50 mL of water, and after mixing, a dispersion was obtained; 0.5 g of Al2(SO4)3 was dissolved in the prepared dispersion to obtain a mixed solution, and the mixed solution was subjected to ultrasonic dispersion and stirring. After solvent removal treatment (vacuum drying at 80 °C for 12 h), a composite catalyst precursor was obtained; then the composite catalyst precursor was subjected to a second calcination treatment under an argon atmosphere, with a calcination temperature of 500 °C and a holding time of 5 h, to obtain a composite catalyst; the composite catalyst obtained after calcination was subjected to crushing treatment by a crusher and then sieving treatment;

[0080] 4 g of commercially available Na2C4O4 powder, 0.5 g of the prepared composite catalyst material, and 0.5 g of conductive carbon black (Super P) were physically mixed and subjected to a first calcination treatment under an argon atmosphere, with a calcination temperature of 350 °C, a holding time of 5 h, and a heating rate of 5 °C / min, to obtain a sodium supplementation material; the sodium supplementation material obtained after calcination was subjected to crushing treatment by a crusher and then sieving treatment for later use.

[0081] <Preparation of Sodium-Supplemented Material Electrode>[

[0082] The prepared sodium supplementation material, conductive agent Ketjenblack (KB), and binder PVDF were mixed in a mass ratio of 60:30:10, solvent N-methylpyrrolidone (NMP) was added, and the mixture was stirred evenly to obtain a sodium supplementation material slurry with a solid content of 60%. Then, the sodium supplementation material slurry was evenly coated on an aluminum foil with a thickness of 10 μm, with a single-sided coating thickness of 20 μm, and then vacuum dried at 110 °C for 12 h to obtain a sodium supplementation material electrode. The obtained sodium supplementation material electrode was cut into circular pieces with a diameter of 14 μm for later use.

[0083] <Preparation of NFPP Positive Electrode>[

[0084] The positive electrode active material Na4Fe3(PO4)2(P2O7) (i.e., NFPP), the prepared sodium supplementation material, conductive agent Ketjenblack, and binder PVDF were mixed in a mass ratio of 75:5:10:10, then NMP was added, and the mixture was stirred evenly to obtain a positive electrode slurry with a solid content of 60%. Then, the positive electrode slurry was evenly coated on an aluminum foil with a thickness of 10 μm, with a single-sided coating thickness of 20 μm, and then vacuum dried at 110 °C for 12 h to obtain a NFPP positive electrode. The obtained NFPP positive electrode was cut into circular pieces with a diameter of 14 μm for later use.

[0085] <Preparation of Electrolyte>[

[0086] In an argon-atmosphere glove box with a moisture content ≤1ppm, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1. Then, sodium salt NaClO4 was added and dissolved in the solvent. After thorough mixing, an electrolyte was obtained. The molar concentration of NaClO4 in the electrolyte was 1 mol / L.

[0087] <Preparation of the diaphragm>

[0088] A glass fiber membrane with a thickness of 260μm was selected as the separator.

[0089] Assembly of button batteries

[0090] Assembly of the first button cell battery

[0091] Using a circular sodium sheet with a diameter of 14 μm as the counter electrode, the circular sodium-supplementing material electrode, the separator, and the circular sodium sheet prepared above are stacked in sequence, with the separator positioned between the circular sodium-supplementing material electrode and the circular sodium sheet to act as a separator. Then, the prepared electrolyte is injected to assemble the first coin cell.

[0092] Assembly of the second button cell battery

[0093] Using a hard carbon negative electrode disc with a diameter of 14 μm as the counter electrode, the ratio of the negative electrode capacity to the positive electrode capacity (i.e., the N / P ratio) of the battery is 1.3. The NFPP positive electrode disc, the separator and the hard carbon negative electrode disc prepared above are stacked in sequence, so that the separator is placed between the NFPP positive electrode disc and the hard carbon negative electrode disc to play a role in isolation. Then the prepared electrolyte is injected to assemble a second coin cell.

[0094] Examples 2 to 4

[0095] Except for adjusting the amount of metal oxide catalyst and electrochemically stable precursor material added according to Table 1 in the <Preparation of Sodium Supplement Material>, the rest is the same as in Example 1.

[0096] Examples 5 to 6

[0097] Except for the section on "Preparation of Sodium Supplement Material", where the type of metal oxide catalyst was adjusted according to Table 1, the rest of the steps were the same as in Example 1.

[0098] Examples 7 to 10

[0099] Except for adjusting the calcination temperature and holding time of the second temperature according to Table 1 in the <Preparation of Sodium Supplement Material>, the rest is the same as in Example 1.

[0100] Examples 11-12

[0101] Except for adjusting the amount of sodium supplement added according to Table 2 in the <Preparation of Sodium Supplement Material> section, the rest is the same as in Example 2.

[0102] Example 13

[0103] Except for adjusting the type of sodium supplement agent according to Table 2 in the section on <Preparation of Sodium Supplement Material>, the rest is the same as in Example 2.

[0104] Examples 14 to 16

[0105] Except for adjusting the relevant parameters of the first calcination treatment according to Table 3 in the <Preparation of Sodium Supplement Material>, the rest is the same as in Example 2.

[0106] Comparative Example 1

[0107] Except for replacing the composite catalyst with a TiO2 catalyst in the <Preparation of Sodium Supplement Material> section, the rest is the same as in Example 1.

[0108] Comparative Example 2

[0109] Except that no sodium-supplementing material is prepared, that is, no first coin cell is prepared, and the second coin cell prepared does not contain sodium-supplementing material in the NFPP positive electrode, the rest is the same as in Example 1.

[0110] Test methods and equipment:

[0111] Relative content test of sodium supplement in sodium supplement materials:

[0112] Quantitative analysis of sodium supplementation agents was performed on the sodium supplementation material using inductively coupled plasma optical emission spectrometry (ICP). The main elemental method was used to test the sodium supplementation material sample, and the elemental content of sodium (Na) was determined to be C0. Therefore, the content of sodium supplementation agent in the sodium supplementation material sample was... This refers to the relative content of sodium supplements.

[0113] Oxidative decomposition potential test:

[0114] The first charge-discharge test of the first coin cell was carried out using the LAND test system, and the differential capacity curve (dQ / dV curve) was obtained. The oxidation peak of the dQ / dV curve corresponds to the oxidation decomposition reaction of the sodium supplement material, and the potential corresponding to the oxidation peak of the dQ / dV curve is the oxidation decomposition potential of the sodium supplement material.

[0115] Morphological observation of sodium-supplemented materials:

[0116] The cross-section of the sodium-supplementing material or the cross-section of the positive electrode active material layer was subjected to ion beam profile grinding to obtain the sodium-supplementing material cross-section. The obtained sodium-supplementing material cross-section was tested by EDS (Energy Dispersive Spectroscopy) at a magnification of 10K to 50K. The sodium-supplementing material cross-section showed a uniform distribution of composite catalyst metal elements. At the same time, the surface of the sodium-supplementing material was tested by SEM (Scanning Electron Microscope) and EDS at a magnification of 10K to 50K. The surface of the sodium-supplementing material also showed a uniform distribution of composite catalyst metal elements. This indicates that in the sodium-supplementing material, the organic sodium-supplementing agent bulk formed a coating or semi-coating structure on the conductive agent and / or composite catalyst.

[0117] Composite catalyst shell thickness test:

[0118] The cross-section of the composite catalyst was observed using HRTEM (High-Resolution Transmission Electron Microscopy) at a magnification of 20 million to 50 million times. The interior of the cross-section was darker than the exterior. The thickness of the brighter area was measured, which is the thickness of the composite catalyst shell.

[0119] First charge capacity and first discharge capacity test:

[0120] The test temperature was 25℃. The coin cell battery was charged at a constant current of 0.1 times (C) to 4.1V, which is the charging stage. After resting for 10 minutes, it was discharged at a constant current of 0.5C to 1.5V, and then rested for 10 minutes, which is the discharging stage. The charging capacity of the first charging stage was recorded as the first-cycle charging capacity, in mAh / g; the discharging capacity of the first discharging stage was also recorded as the first-cycle discharging capacity, in mAh / g.

[0121] Cyclic performance test:

[0122] The test temperature was 25℃. The coin cell battery was charged to 3.5V at a constant current of 1C, left to stand for 10 minutes, and then discharged to 1.5V at 1C. The capacity obtained in this step is the initial discharge capacity C. i Perform n cycles of 1C charge / 1C discharge and record the discharge capacity of the nth cycle. Cycle capacity retention rate = (Discharge capacity of the nth cycle / Initial discharge capacity C) i )×100%.

[0123] Table 1: Preparation parameters of composite catalysts

[0124] Table 2: Preparation parameters of sodium supplementation materials

[0125] In Table 2, " / " indicates that no relevant preparation parameters exist.

[0126] Table 3: First calcination treatment parameters for Examples 2, 14-16

[0127] Table 4: Test data of the first button cell in each embodiment and comparative example

[0128] In Table 4, " / " indicates that there is no relevant test data.

[0129] Table 5: Test data of the second button cell in each embodiment and comparative example

[0130] Combining Tables 4 and 5, it can be seen from Examples 1 to 16 and Comparative Examples 1 to 2 that the sodium replenishment material in Comparative Example 1 simply uses a TiO2 catalyst without the composite catalyst of this application. Although its first-cycle discharge capacity is slightly improved compared to Comparative Example 2, it is still relatively low, and its capacity retention rate after 300 cycles is also low. This may be because the sodium replenishment material in Comparative Example 1 does not have the structure of this application, leading to a metal ion shuttle effect in the metal oxide catalyst of the sodium replenishment material. This shuttle effect induces the decomposition of the electrolyte and changes in the SEI structure, resulting in the sodium-ion battery... The cycle stability deteriorates, and the capacity retention decreases. Comparative Example 2 lacks sodium-supplementing material, resulting in lower first-cycle charge and first-cycle discharge capacities and lower energy density for its second coin cell. In contrast, the first coin cell of this application exhibits a higher first-cycle specific capacity and a lower oxidation decomposition potential. Furthermore, the first-cycle discharge capacity and capacity retention after 300 cycles of the second coin cell of this application are significantly improved compared to Comparative Example 1, and the first-cycle specific capacity and first-cycle discharge capacity of the second coin cell of this application are significantly improved compared to Comparative Example 2. Moreover, the capacity retention after 300 cycles is also somewhat improved compared to Comparative Example 2. Therefore, the sodium-supplementing material of this application not only has a low oxidation decomposition potential but also inhibits metal ions from shuttling to the negative electrode, thereby simultaneously improving the energy density and cycle performance of the sodium-ion battery.

[0131] In the process of preparing composite catalysts, parameters such as the type and amount of metal oxide catalysts, the type and amount of electrochemically stable precursor materials, and the calcination temperature and holding time of the second calcination treatment usually affect the performance of sodium-supplementing materials. As can be seen from Examples 1 to 10, based on the structure of the sodium-supplementing material in this application, by adjusting the above parameters within the range of this application, it is beneficial to obtain sodium-supplementing materials with low shuttle effect and low oxidation decomposition potential, so as to improve the energy density and cycle performance of sodium-ion batteries at the same time.

[0132] In the process of preparing sodium-supplementing materials, the content of sodium-supplementing agent, the content of carbon material, the type of sodium-supplementing agent, the calcination temperature of the first calcination treatment, and the holding time usually affect the performance of the sodium-supplementing materials. As can be seen from Examples 11 to 13 and Examples 14 to 16, based on the structure of the sodium-supplementing materials in this application, by adjusting the above parameters within the range of this application, it is beneficial to obtain sodium-supplementing materials with low shuttle effect and low oxidation decomposition potential, so as to improve the energy density and cycle performance of sodium-ion batteries at the same time.

[0133] The above provides a detailed description of a sodium-supplementing material, its preparation method, the positive electrode sheet, and the sodium-ion battery disclosed in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A sodium supplement material, wherein, It includes an organic sodium supplement body and a conductive agent and a composite catalyst at least partially coated in the organic sodium supplement body; The composite catalyst has a core-shell structure, wherein the core layer of the core-shell structure includes a metal oxide catalyst, and the shell layer of the core-shell structure includes an electrochemically stabilizing material. The electrochemically stabilizing material is a material that exhibits electrochemical stability under charge-discharge test conditions ranging from an initial charging voltage of 4.1V to an initial discharging voltage of 1.5V and a cyclic charging voltage of 3.5V to a cyclic discharging voltage of 1.5V.

2. The sodium supplement material according to claim 1, wherein, The thickness of the shell is 1 nm to 5 nm.

3. The sodium supplement material according to claim 1, wherein, The organic sodium supplement has a mass percentage content of a in the sodium supplement material, the conductive agent has a mass percentage content of b in the sodium supplement material, and the composite catalyst has a mass percentage content of c in the sodium supplement material, wherein 30% ≤ a ≤ 90%, 0 < b ≤ 70%, and 0 < c ≤ 30%.

4. The sodium supplement material according to claim 3, wherein, 50% ≤ a ≤ 80%, 5% ≤ b ≤ 50%, 5% ≤ c ≤ 10%.

5. The sodium supplement material according to claim 1, wherein, The sodium supplement material satisfies at least one of the following characteristics: a) The organic sodium supplement is made of at least one of CH3COONa, Na2C4O4, Na2C2O4, C6H5Na3O7 and Na2C6O6; b) The conductive agent includes at least one of conductive carbon black, carbon nanotubes, Ketjen black, graphene, and acetylene black; c) The material of the metal oxide catalyst includes at least one of ruthenium dioxide, ferric oxide, vanadium pentoxide, titanium dioxide, cobalt tetroxide, α-manganese dioxide, δ-manganese dioxide and γ-manganese dioxide; d) The electrochemically stabilizing material includes at least one of aluminum oxide, β-manganese dioxide, nickel oxide, zinc oxide, tungsten carbide, titanium carbide, tantalum carbide, and MXene.

6. A method for preparing a sodium-supplementing material as described in any one of claims 1 to 5, wherein, Includes the following steps: Organic sodium supplementer, conductive agent and composite catalyst are mixed to obtain sodium supplement material precursor; The sodium-supplementing material precursor was subjected to a first calcination treatment in an inert gas atmosphere at a temperature of 300℃ to 500℃ for 1h to 8h, and then cooled to obtain the sodium-supplementing material.

7. The preparation method according to claim 6, wherein, During calcination, the organic sodium supplement melts, causing the conductive agent and the composite catalyst to be coated in the molten sodium supplement; during cooling, the organic sodium supplement solidifies, causing the conductive agent and / or the composite catalyst to be at least partially coated in the organic sodium supplement body.

8. The preparation method according to claim 6, wherein, The preparation process of the composite catalyst includes: A metal oxide catalyst is added to a solvent, and the mixture is then mixed to obtain a dispersion. An electrochemically stable precursor material is added to the dispersion and mixed to obtain a mixture. The mixture is then desolventized to obtain a composite catalyst precursor. The composite catalyst precursor was subjected to a second calcination treatment in an inert gas atmosphere at a temperature of 400℃ to 600℃ for a holding time of 4h to 6h to obtain the composite catalyst with a core-shell structure.

9. The preparation method according to claim 8, wherein, The electrochemically stable precursor material includes at least one of the sulfate, chloride, and fluoride salts corresponding to the metal ions in the electrochemically stable material.

10. A positive electrode plate, wherein, The device includes a current collector and a positive electrode active material layer disposed on at least one surface of the current collector, wherein the positive electrode active material layer includes a sodium-supplementing material as described in any one of claims 1 to 5, or the positive electrode active material layer includes a sodium-supplementing material prepared by the preparation method as described in any one of claims 6 to 9.

11. A sodium-ion battery, wherein, Includes the positive electrode sheet as described in claim 10.

12. An energy storage device, wherein, It includes a housing and at least one sodium-ion battery as described in claim 11, the sodium-ion battery being housed within the housing.

13. An electrical appliance, wherein, The device includes the energy storage device of claim 12, wherein the energy storage device supplies power to the electrical equipment.

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