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

Abstract

The application provides a sodium supplement material, a preparation method of the sodium supplement material, a positive electrode sheet and a sodium ion battery. The sodium supplement material has a first core-shell structure. The core of the first core-shell structure comprises a sodium supplement agent. The shell layer of the first core-shell structure comprises a composite catalytic material and a composite conductive carbon material. The composite catalytic material has a second core-shell structure. The core of the second core-shell structure comprises a metal oxide catalyst. The shell layer of the second core-shell structure comprises an electrochemically stable material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, and particularly relates to a sodium supplement material, a preparation method thereof, a positive electrode sheet and a sodium ion battery. BACKGROUND

[0002] The sodium ion battery is expected to replace the traditional sodium ion battery in the energy storage field due to low cost, rich sodium resources and relatively high energy density.

[0003] The negative electrode material used in the existing sodium ion battery is hard carbon. A solid electrolyte interface layer (SEI) is formed in the initial charging process of the hard carbon-based negative electrode. The formation of the SEI irreversibly consumes sodium ions from the positive electrode, resulting in low coulombic efficiency of the first cycle of the negative electrode, and reducing the capacity, energy density and cycle life of the sodium ion battery, which is not conducive to the improvement of the performance of the sodium ion battery. SUMMARY

[0004] To solve the above technical problems, the present application discloses a sodium supplement material, a preparation method thereof, a positive electrode sheet and a sodium ion battery, so as to improve the energy density and cycle performance of the sodium ion battery.

[0005] In a first aspect, the present application provides a sodium supplement material, the sodium supplement material having a first core-shell structure, the core of the first core-shell structure comprising a sodium supplement agent, and the shell layer of the first core-shell structure comprising a composite catalytic material and a composite conductive carbon material; the composite catalytic material having a second core-shell structure, the core of the second core-shell structure comprising a metal oxide catalyst, and the shell layer of the second core-shell structure comprising an electrochemically stable material.

[0006] In some embodiments of the present application, the composite conductive carbon material comprises a conductive agent and amorphous carbon, and the amorphous carbon is formed by carbonization of an organic complexing agent.

[0007] In some embodiments of the present application, the mass percentage content of the sodium supplement agent in the sodium supplement material is 50% to 90%.

[0008] In some embodiments of the present application, the electrochemically stable material comprises at least one of an electrochemically stable oxide material and an electrochemically stable carbide material.

[0009] In some embodiments of the present application, the electrochemically stable oxide material comprises at least one of Al2O3, ZrO2, MnO2, TiO2, Ni2O3 and ZnO; and the electrochemically stable carbide material comprises at least one of WC, TiC, TaC and MXene material.

[0010] In some embodiments of the present application, the organic complexing agent comprises at least one of polyvinylpyrrolidone, sodium nitrilotriacetate, disodium ethylenediaminetetraacetate, polyethylene glycol and polyethylene glycol ether.

[0011] In some embodiments of the present application, the sodium supplement material satisfies at least one of the following characteristics:

[0012] a) the material of the sodium supplement agent comprises at least one of Na2S, Na2Se and Na2N3;

[0013] b) the conductive agent comprises at least one of conductive carbon black, carbon nanotube, ketjen black, graphene and acetylene black;

[0014] c) the material of the metal oxide catalyst is selected from at least one of ruthenium dioxide, diiron trioxide, manganese dioxide, vanadium pentoxide, titanium dioxide, cobalt trioxide, nickel trioxide, nickel monoxide and tin dioxide.

[0015] In a second aspect, the present application provides a method for preparing the sodium supplement material according to the first aspect, comprising the following steps:

[0016] adding the sodium supplement agent and the composite catalytic material into a first solvent, and mixing to obtain a first dispersion liquid;

[0017] adding the conductive agent and the organic complexing agent into the first dispersion liquid for mixing, and drying to obtain a sodium supplement material precursor;

[0018] subjecting the sodium supplement material precursor to a first calcination treatment in an inert gas atmosphere to obtain a sodium supplement material with a first core-shell structure.

[0019] In some embodiments of the present application, the preparation process of the composite catalytic material comprises:

[0020] adding the metal oxide catalyst into a second solvent, and mixing to obtain a second dispersion liquid;

[0021] adding the electrochemically stable precursor material into the second dispersion liquid for mixing to obtain a mixed liquid, and subjecting the mixed liquid to a desolvation treatment to obtain a composite catalytic material precursor;

[0022] subjecting the composite catalytic material precursor to a second calcination treatment in an inert gas atmosphere, wherein the calcination temperature is 400-600°C, and the holding time is 4-6h, to obtain a composite catalytic material with a second core-shell structure.

[0023] In some embodiments of the present application, the electrochemically stable precursor material comprises at least one of Al2(SO4)3, AlCl3 and AlF3.

[0024] In some embodiments of the present application, the calcination temperature of the first calcination treatment is 300-700°C, and the holding time is 1-10h.

[0025] In a third aspect, the present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the sodium supplementing material according to the first aspect, or is prepared by the preparation method according to the second aspect.

[0026] In a fourth aspect, the present application provides a sodium ion battery, comprising the positive electrode sheet according to the third aspect.

[0027] In a fifth aspect, the present application provides an energy storage device, comprising a box body and at least one sodium ion battery according to the fourth aspect, wherein the sodium ion battery is accommodated in the box body.

[0028] In a sixth aspect, the present application provides an electric device, comprising the energy storage device according to the fifth aspect, wherein the energy storage device supplies power to the electric device.

[0029] Compared with the prior art, the present application has at least the following beneficial effects:

[0030] The present application provides a sodium supplementing material, a preparation method thereof, a positive electrode sheet, and a sodium ion battery. The sodium supplementing material has a first core-shell structure. The core of the first core-shell structure comprises a sodium supplementing agent, and the shell of the first core-shell structure comprises a composite catalytic material and a composite conductive carbon material. The composite catalytic material has a second core-shell structure. The core of the second core-shell structure comprises a metal oxide catalyst, and the shell of the second core-shell structure comprises an electrochemically stable material. In the first core-shell structure, the composite catalytic material and the composite conductive carbon material are distributed in the shell layer of the first core-shell structure. The composite conductive carbon material in the shell layer can improve the electronic conductivity of the composite catalytic material, thereby improving the actual catalytic effect of the composite catalytic material. In the second core-shell structure, the composite catalytic material also has a core-shell structure, i.e., a second core-shell structure. The shell layer of the second core-shell structure comprises an electrochemically stable material, which can reduce the direct contact between the metal oxide catalyst and the electrolyte, maintain the structural stability of the metal oxide catalyst during charging and discharging, reduce the metal ion shuttle effect of the metal oxide catalyst in the sodium supplementing material, maintain the stability of the negative electrode SEI, reduce the irreversible loss of sodium, and improve the cycle performance of the sodium ion battery. In summary, the sodium supplementing material of the present application has a double-core-shell structure. This double-core-shell structure not only reduces the oxidative decomposition potential of the sodium supplementing material, but also inhibits the metal ion from shuttling to the negative electrode, thereby improving the energy density and cycle performance of the sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort.

[0032] Figure 1 Structure diagram of a sodium supplement material for an embodiment of the present application;

[0033] Figure 2 Structure diagram of a household energy storage system for an embodiment of the present application;

[0034] Figure 3 Structure diagram of an energy storage system for an embodiment of the present application.

[0035] Legend: 1-energy storage device, 2-electric energy conversion device, 3-first user load, 4-second user load, 10-first core-shell structure, 11-core of the first core-shell structure, 12-shell layer of the first core-shell structure, 20-second core-shell structure, 21-core of the second core-shell structure, 22-shell layer of the second core-shell structure, 400-energy storage system, 410-high-voltage cable, 420-first electric energy conversion device, 430-second electric energy conversion device. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0037] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", and the like indicate the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0038] In addition, in addition to indicating the orientation or positional relationship, the above-mentioned part of the terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. Those of ordinary skill in the art can understand the specific meaning of these terms in the present application according to the specific situation.

[0039] In addition, the terms "mount", "set", "provided with", "connect", "connected" should be understood broadly. For example, it can be fixed connection, detachable connection, or integral structure; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate media, or internal communication between two devices, elements or components. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0040] In addition, in this paper, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Unless otherwise stated, the meaning of "multiple" is two or more.

[0041] It should be noted that in the content of the present application, the present application is explained by taking sodium ion battery as an example of secondary battery, but the secondary battery of the present application is not limited to sodium ion battery.

[0042] In the related art, although the oxidation decomposition potential of the sodium supplement material can be reduced by introducing a metal oxide catalyst into the sodium supplement material, the metal oxide catalyst is prone to phase transition and structural change under high pressure when the metal oxide catalyst is introduced, and the generated metal cations shuttle to the negative electrode, that is, the metal ions produce a shuttle effect, which can induce the decomposition of the electrolyte and the change of the SEI structure, resulting in poor cycle stability of the sodium ion battery. How to reduce the oxidation decomposition potential of the sodium supplement material while inhibiting the shuttle effect to improve the energy density and cycle performance of the sodium ion battery has become a technical problem to be solved.

[0043] Therefore, the present application provides a sodium supplement material, which is characterized by Figure 1The sodium supplement material has a first core-shell structure 10, a core 11 of the first core-shell structure comprising a sodium supplement agent, and a shell layer 12 of the first core-shell structure comprising a composite catalytic material and a composite conductive carbon material, the composite conductive carbon material comprising a conductive agent and amorphous carbon; the composite catalytic material has a second core-shell structure 20, a core 21 of the second core-shell structure comprising a metal oxide catalyst, and a shell layer 22 of the second core-shell structure comprising an electrochemically stable material. In the first core-shell structure, the composite catalytic material and the composite conductive carbon material are distributed in the shell layer of the first core-shell structure, and the electronic conductivity of the composite catalytic material can be improved by the composite conductive carbon material in the shell layer, thereby improving the actual catalytic effect of the composite catalytic material. In the second core-shell structure, the composite catalytic material also has a core-shell structure, i.e., a second core-shell structure, and the shell layer of the second core-shell structure comprises an electrochemically stable material, which can reduce the direct contact between the metal oxide catalyst and the electrolyte, maintain the structural stability of the metal oxide catalyst during the charging and discharging process, reduce the metal ion shuttle effect of the metal oxide catalyst in the sodium supplement material, maintain the stability of the negative electrode SEI, reduce the irreversible loss of sodium, and improve the cycle performance of the sodium ion battery. In summary, the sodium supplement material of the present application has a double-core-shell structure, which can not only reduce the oxidative decomposition potential of the sodium supplement material, but also inhibit the metal ion from shuttling to the negative electrode, thereby improving the energy density and cycle performance of the sodium ion battery.

[0044] In the present application, the oxidative decomposition potential refers to the potential corresponding to the oxidative decomposition reaction of the sodium supplement material during the charging process.

[0045] In some embodiments of the present application, the composite conductive carbon material comprises a conductive agent and amorphous carbon, and the amorphous carbon is formed by carbonization of an organic complexing agent. This amorphous carbon has good uniformity, and can not only be uniformly distributed on the surface of the sodium supplement agent during the formation of the shell layer of the first core-shell structure, but also adsorb the conductive agent to improve the uniformity of the conductive agent, thereby improving the conductivity of the shell layer of the first core-shell structure, promoting the transmission of electrons to the sodium supplement agent to reduce the oxidative decomposition potential of the sodium supplement material, and improving the first-cycle sodium supplement effect of the sodium supplement material.

[0046] In some embodiments of the present application, the mass percentage content of the sodium supplement agent in the sodium supplement material is 45% to 90%. For example, the mass percentage content of the sodium supplement agent in the sodium supplement material is 45%, 60%, 70%, 80%, or 90%. By adjusting the mass percentage content of the sodium supplement agent in the sodium supplement material within the above range, a sodium supplement material with low oxidative decomposition potential and low shuttle effect can be obtained.

[0047] In some embodiments of the present application, the electrochemically stable material includes at least one of an electrochemically stable oxide material and an electrochemically stable carbide material, which can reduce the direct contact between the metal oxide catalyst and the electrolyte, maintain the structural stability of the metal oxide catalyst during the charging and discharging process, and thus reduce the metal ion shuttle effect of the metal oxide catalyst in the sodium supplement material.

[0048] In some embodiments of the present application, the electrochemically stable oxide material includes at least one of Al2O3, ZrO2, MnO2, TiO2, Ni2O3 and ZnO; and the electrochemically stable carbide material includes at least one of tungsten carbide (WC), titanium carbide (TiC), tantalum carbide (TaC) and MXene (transition metal carbon / nitride material with two-dimensional structure). The above-mentioned materials are beneficial to maintain the structural stability of the metal oxide catalyst during the charging and discharging process, and reduce the metal ion shuttle effect of the metal oxide catalyst in the sodium supplement material.

[0049] In some embodiments of the present application, the organic complexing agent includes at least one of polyvinylpyrrolidone (PVP), sodium nitrilotriacetic acid (TDA-Na), disodium ethylenediaminetetraacetate (EDTA-2Na), polyethylene glycol (PEG) and polyethylene glycol ether, which are beneficial to form the amorphous carbon of the present application.

[0050] In some embodiments of the present application, the material of the sodium supplement agent includes at least one of Na2S, Na2Se and Na2N3. The above-mentioned sodium supplement agent belongs to inorganic sodium supplement agent, which has a high theoretical specific capacity and does not generate gas during the cycle process.

[0051] In some embodiments of the present application, the conductive agent includes at least one of conductive carbon black, carbon nanotube, ketjen black, graphene and acetylene black.

[0052] In some embodiments of the present application, the material of the metal oxide catalyst is selected from at least one of ruthenium dioxide, diiron trioxide, manganese dioxide, vanadium pentoxide, titanium dioxide, cobalt trioxide, nickel trioxide, nickel monoxide and tin dioxide. The above-mentioned metal oxide can be used in the sodium supplement material of the present application as an electron acceptor to accept electrons, thereby achieving the function of catalyzing the oxidative decomposition of the sodium supplement agent.

[0053] In a second aspect, the present application provides a preparation method of the sodium supplement material according to the first aspect, which includes the following steps:

[0054] Step A, adding the sodium supplement agent and the composite catalyst material into a first solvent to obtain a first dispersion liquid after mixing;

[0055] Step B, the conductive agent and the organic complexing agent are added into the first dispersion liquid for mixing, and a sodium supplement material precursor is obtained after drying;

[0056] Step C, the sodium supplement material precursor is subjected to a first calcination treatment to obtain a sodium supplement material with a first core-shell structure.

[0057] In step A, the sodium supplement agent and the composite catalytic material are added into a solvent, and the sodium supplement agent and the composite catalytic material are dispersed in the solvent after stirring and mixing to obtain a first dispersion liquid. The adding ratio of the sodium supplement agent to the solvent can be 1 g:5 mL to 1 g:100 mL. The first solvent includes at least one of methanol, ethanol, ethylene glycol and diethyl ether.

[0058] In step B, the conductive agent and the organic complexing agent are added into the first dispersion liquid, and the organic complexing agent is dissolved in the first dispersion liquid to be uniformly distributed on the surface of the sodium supplement agent after stirring to form a sodium supplement material slurry. The dissolved organic complexing agent can adsorb the conductive agent in the first dispersion liquid, so that the conductive agent is also uniformly distributed on the surface of the sodium supplement agent. The drying method can be vacuum drying, and the temperature of the vacuum drying is 60°C to 100°C. After the sodium supplement material slurry is subjected to vacuum drying treatment, a sodium supplement material precursor is obtained.

[0059] In step C, the first calcination treatment of the sodium supplement material precursor in an inert gas atmosphere is beneficial to the carbonization of the organic complexing agent in the sodium supplement material precursor into amorphous carbon at high temperature. In addition, the product obtained after calcination can be subjected to crushing treatment by a crusher, and then the sodium supplement material with a desired particle size range is obtained after sieving.

[0060] In some embodiments of the present application, the preparation process of the composite catalytic material includes:

[0061] Step I: a metal oxide catalyst is added into a second solvent to obtain a second dispersion liquid after mixing;

[0062] Step II: an electrochemically stable precursor material is added into the second dispersion liquid for mixing to obtain a mixed liquid, and a composite catalytic material precursor is obtained after desolventizing the mixed liquid;

[0063] Step III: the composite catalytic material precursor is subjected to a second calcination treatment in an inert gas atmosphere, the calcination temperature is 400°C to 600°C, and the holding time is 4h to 6h to obtain a composite catalytic material with a second core-shell structure.

[0064] In step I, the second solvent is water.

[0065] In step II, the desolventizing method is vacuum drying at 60°C to 110°C.

[0066] In Step III, by the second calcination process of the present application, i.e., the calcination temperature and the holding time are controlled within the above ranges, the metal oxide catalyst in the composite catalytic material precursor does not decompose, and the electrochemically stable precursor material decomposes to generate the corresponding oxide or carbide, which is conducive to obtaining the composite catalytic material of the present application.

[0067] In some embodiments of the present application, the electrochemically stable precursor material includes, but is not limited to, at least one of Al2(SO4)3, AlCl3, AlF3, Zr(SO4)2, ZrCl4, Ru(SO4)2, RuCl4, Ir(SO4)2, and IrCl4.

[0068] In some embodiments of the present application, the calcination temperature of the first calcination process is 300-700°C, and the holding time is 1-10h, which is conducive to converting the organic complexing agent in the sodium supplement material precursor into amorphous carbon by high-temperature carbonization, and forming a composite conductive carbon material from the amorphous carbon and the conductive agent, and forming a shell layer of the first core-shell structure from the composite catalytic material and the composite conductive carbon material.

[0069] The inert gas of the present application includes at least one of nitrogen and argon.

[0070] The preparation method of the sodium supplement material provided by the present application has the advantages of simple preparation process and wide source of raw materials. The prepared sodium supplement material has a double-core-shell structure, excellent sodium supplement performance, and low cost, thereby improving the energy density and cycle performance of the sodium ion battery while reducing the production cost of the sodium ion battery.

[0071] The present application also provides a positive electrode tab, which comprises a current collector and a positive electrode active material layer arranged on at least one surface of the current collector. The positive electrode active material layer comprises the sodium supplement material of any one of the above embodiments or the sodium supplement material prepared by the preparation method of any one of the above embodiments.

[0072] The positive electrode active material layer of the present application can be arranged on one surface or both surfaces in the thickness direction of the positive electrode current collector. In the present application, the positive electrode active material layer is arranged on the surface of the positive electrode current collector, i.e., the positive electrode active material layer can be arranged on part of the area of one surface of the positive electrode current collector, or can be arranged on the entire area of one surface of the positive electrode current collector. The positive electrode current collector of the present application is not particularly limited as long as it can achieve the purpose of the present application, for example, it can include but is not limited to aluminum foil, aluminum alloy foil, or composite current collector, etc. In the present application, the thickness of the positive electrode current collector is not particularly limited as long as it can achieve the purpose of the present application, for example, the thickness is 8-13μm. The single-sided thickness of the positive electrode active material layer of the present application can be 150-400μm.

[0073] In the present application, the positive electrode active material layer can further include a positive electrode active material, which is not particularly limited in the present application as long as the object of the present application can be achieved, and can include, for example, at least one of sodium nickel manganese acid, sodium nickel iron manganese acid, sodium iron sulfate, sodium vanadium phosphate, sodium copper manganese acid, sodium pyrophosphate, and sodium pyrophosphate.

[0074] In the present application, the positive electrode active material layer can further include a positive electrode conductive agent, which is not particularly limited in the present application as long as the object of the present application can be achieved, and can include, for example, at least one of Super P, carbon nanotube (CNT), Ketjen black (KB), graphene, graphene oxide, and acetylene black, but is not limited thereto. The mass percentage content of the conductive agent in the positive electrode active material layer is 10% to 40%. In the present application, the positive electrode active material layer can further include a positive electrode binder, which is not particularly limited in the present application as long as the object of the present application can be achieved, and can include, for example, at least one of fluorine-containing resin, polypropylene resin, fiber type binder, rubber type binder, polyimide type binder, and polyvinylidene fluoride (PVDF).

[0075] The present application also provides a sodium ion battery including the positive electrode sheet according to any one of the above embodiments.

[0076] The sodium ion battery according to the present application can further include a negative electrode sheet, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet to function as a separator.

[0077] The negative electrode sheet according to the present application is not particularly limited as long as the object of the present application can be achieved, and can include, for example, a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer can be disposed on the surface of the negative electrode current collector, i.e., the negative electrode active material layer can be disposed on a partial region of one surface of the negative electrode current collector or can be disposed on the entire region of one surface of the negative electrode current collector. The negative electrode current collector according to the present application is not particularly limited as long as the object of the present application can be achieved, and can include, for example, but is not limited to, a copper foil, a copper alloy foil, a nickel foil, or a composite current collector. In the present application, the thickness of the negative electrode current collector is not particularly limited as long as the object of the present application can be achieved, and can be, for example, 4 μm to 12 μm. The single-sided thickness of the negative electrode material layer according to the present application can be 70 μm to 200 μm.

[0078] In the present application, the negative electrode active material layer can further include a negative electrode binder. The negative electrode binder according to the present application is not particularly limited as long as the object of the present application can be achieved, and can include, for example, at least one of acrylate, polyamide, polyimide, polyamide-imide, polyvinylidene fluoride, styrene butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose.

[0079] In some embodiments, the material of the diaphragm can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the diaphragm is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0080] The sodium-ion battery of the present application further comprises an electrolyte. The electrolyte of the present application is not particularly limited, and can be selected by those skilled in the art according to actual needs, as long as the purpose of the present application can be 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) is mixed in a certain mass ratio or volume ratio to obtain a non-aqueous organic solvent, and then a sodium salt is added, dissolved and uniformly mixed. The type of sodium salt is not limited in the present application, as long as the purpose of the present application can be achieved. For example, the sodium salt can include at least one of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium trifluoromethyl sulfonate, and sodium p-toluenesulfonate. The concentration of the sodium salt in the electrolyte is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the concentration of the sodium salt is 1.0 mol / L to 2.0 mol / L.

[0081] The sodium-ion battery of the present application further comprises a shell, and the shell of the present application is not particularly limited, and can be selected by those skilled in the art according to actual needs, as long as the purpose of the present application can be achieved. For example, the shell can include an aluminum plastic film.

[0082] The preparation method of the sodium-ion battery of the present application is not particularly limited, and a preparation method known in the art can be selected, as long as the purpose of the present application can be achieved. For example, the preparation method of the sodium-ion battery includes but is not limited to the following steps: stacking the positive electrode sheet, the diaphragm and the negative electrode sheet in order, and winding, folding or other operations as needed to obtain a bare battery with a winding structure, placing the bare battery into a packaging bag, injecting an electrolyte into the packaging bag and sealing the packaging bag to obtain a sodium-ion battery.

[0083] The present application also provides an energy storage device comprising a box body and at least one sodium-ion battery according to any one of the above embodiments, wherein the sodium-ion battery is accommodated in the box body. The energy storage device with the sodium-ion battery has excellent performance, which is beneficial to the use of the energy storage device. By accommodating the battery in the box body, the fixation and protection of the battery can be increased, and the service life of the energy storage device can be improved. It can be understood that the energy storage device can have 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 of parallel and series.

[0084] The application also provides a power utilization device comprising the energy storage device in any of the above embodiments, which is conducive to improving the product competitiveness and use performance of the power utilization device. In an alternative embodiment, the power utilization device comprises a power utilization device body, and the energy storage device is used to supply power to the power utilization device body. In an alternative embodiment, the power utilization device body comprises a device positive electrode and a device negative electrode, the positive electrode tab of the sodium-ion battery in the energy storage device is used to electrically connect the device positive electrode of the power utilization device body, and the negative electrode tab of the sodium-ion battery in the energy storage device is used to electrically connect the device negative electrode of the power utilization device body, so as to supply power to the power utilization device.

[0085] The power utilization device of the application can include, but is not limited to, a container, a household energy storage system, an electric vehicle, an electric automobile, a ship, a spacecraft, an electric toy, and an electric tool, etc., wherein the spacecraft is, for example, an airplane, a rocket, a space shuttle, a spacecraft, etc., the electric toy includes, for example, a fixed or mobile electric toy, and specifically, for example, an electric automobile toy, an electric ship toy, an electric airplane toy, etc., and the electric tool includes, for example, a metal cutting electric tool, a grinding electric tool, an assembling electric tool, and a railway electric tool, and specifically, for example, an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator, and an electric planer.

[0086] Please refer to Figure 2 , Figure 2 The structure diagram of the household energy storage system of an embodiment of the application is shown, and the energy storage device of the application is not limited to the household energy storage scenario. Figure 2 The embodiment takes the household energy storage scenario in the user side energy storage as an example for illustration, and the energy storage device of the application is not limited to the household energy storage scenario.

[0087] The application provides a household energy storage system, which comprises an electric energy conversion device 2 (a photovoltaic panel), a first user load 3 (a street lamp), a second user load 4 (for example, a household appliance such as an air conditioner), and an energy storage device 1. The energy storage device 1 is a small energy storage box, which can be installed on an outdoor wall in a wall-mounted manner. Specifically, the photovoltaic panel can convert solar energy into electric energy during the low electricity price period, the energy storage device 1 is used to store the electric energy and supply the street lamp and the household appliance for use during the high electricity price period, or supply power during the power grid outage.

[0088] Please refer to Figure 3 , Figure 3 The structure diagram of the energy storage system 400 of an embodiment of the application is shown, and the energy storage device of the application is not limited to the energy storage scenario of the power generation / distribution side. Figure 3 The embodiment takes the energy storage scenario of the power generation / distribution side as an example for illustration, and the energy storage device of the application is not limited to the energy storage scenario of the power generation / distribution side.

[0089] The application provides a kind of energy storage system 400, energy storage system 400 includes: high voltage cable 410, first electric energy conversion device 420, second electric energy conversion device 430 and the energy storage device 1 provided by the application, under the condition of power generation, first electric energy conversion device 420 and second electric energy conversion device 430 are used to convert other forms of energy into electric energy, connect with high voltage cable 410 and supply for distribution network electricity side use, when electricity load is low, first electric energy conversion device 420, second electric energy conversion device 430 generates excess, and the electric quantity of more generation is stored to energy storage device 1, reduces the rate of abandoned wind, abandoned light, improves new energy power generation consumption problem;When electricity load is high, grid issues instructions, the electric quantity stored in energy storage device 1 is transmitted to electricity side use by grid-connected mode with high voltage cable 410, provides peak shaving, frequency modulation, backup and other services for grid operation, fully plays the role of grid peak shaving, promotes grid peak clipping, relieves grid power supply pressure.

[0090] Optionally, the first electric energy conversion device 420 and the second electric energy conversion device 430 can convert at least one of solar energy, light energy, wind energy, heat energy, tidal energy, biomass energy and mechanical energy into electric energy.

[0091] The number of energy storage devices 1 can be multiple, and the multiple energy storage devices 1 are connected in series or parallel with each other, and the multiple energy storage devices 1 are supported and electrically connected by isolation plates (not shown in the figure). In the embodiment, "multiple" means two or more. The energy storage device 1 can also be provided with an energy storage box outside for accommodating the energy storage device 1.

[0092] Optionally, the energy storage device 1 can include but is not limited to a battery module, a battery pack, a battery system, etc. The battery module can be formed by connecting a plurality of sodium ion batteries in series / parallel, the battery pack can include a plurality of sodium ion batteries, and the battery system can be a charging and discharging system including the sodium ion batteries or the battery pack.

[0093] The actual application form of the energy storage device 1 provided by the application can be but is not limited to the listed products, and can also be other application forms, and the application form of the energy storage device 1 is not strictly limited. The application only takes the energy storage device 1 as a multi-core battery as an example for description. When the energy storage device 1 is a single battery, the energy storage device 1 can be at least one of a cylindrical battery and a square battery.

[0094] Embodiment

[0095] Hereinafter, examples and comparative examples are given to more specifically describe the embodiments of the application. Various tests and evaluations are carried out according to the following methods.

[0096] Example 1

[0097] Preparation of sodium supplementing material

[0098] 9.5 g of metal oxide catalyst titanium dioxide (TiO2) was added to 50 mL of water, and after mixing, a second dispersion was obtained; 0.5 g of Al2(SO4)3was dissolved in the prepared second dispersion to obtain a mixed solution, and the mixed solution was subjected to ultrasonic dispersion and stirring, and then the mixed solution was vacuum dried at 80°C for 12 h (i.e., solvent removal treatment) to obtain a composite catalytic material precursor; then the composite catalytic material precursor was subjected to a second calcination treatment under an argon atmosphere, with a calcination temperature of 500°C and a calcination time of 5 h, to obtain a composite catalytic material;

[0099] 3 g of commercially available sodium sulfide (Na2S) powder (i.e., a sodium supplement agent), 0.6 g of the prepared composite catalytic material, was added to 50 mL of anhydrous ethanol, stirred at room temperature for 12 h, and then left to stand for 1 h, and the supernatant was removed to obtain a first dispersion; 2 g of Ketjen black (KB) (i.e., a carbon material) and 0.5 g of polyvinylpyrrolidone (PVP) (i.e., a complexing agent) were added to the prepared first dispersion and ultrasonically dispersed for 1 h, and then stirred for 6 h to form a sodium supplement material slurry; the sodium supplement material slurry was vacuum dried at 80°C for 12 h to obtain a sodium supplement material precursor; the sodium supplement material precursor was subjected to a first calcination treatment under an argon atmosphere, with a calcination temperature of 500°C and a calcination time of 4 h, and a temperature rise rate of 5°C / min, to obtain a sodium supplement material.

[0100] <Preparation of sodium supplement material pole piece>

[0101] The prepared sodium supplement material, conductive agent Ketjen black (KB), and binder PVDF were mixed in a mass ratio of 60:30:10, a solvent N-methyl pyrrolidone (NMP) was added, and stirring was performed until uniform, to obtain a sodium supplement material slurry with a solid content of 60%, and then the sodium supplement material slurry was uniformly 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 supplement material pole piece. The obtained sodium supplement material pole piece was cut into a circular piece with a diameter of 14 μm for use.

[0102] <Preparation of positive electrode pole piece>

[0103] The positive electrode active material Na4Fe3(PO4)2(P2O7) (i.e., NFPP), the prepared sodium supplement material, conductive agent Ketjen black, and binder PVDF were mixed in a mass ratio of 75:5:10:10, and then NMP was added, and stirring was performed until uniform, to obtain a positive electrode slurry with a solid content of 60%, and then the positive electrode slurry was uniformly 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 positive electrode pole piece. The obtained positive electrode pole piece was cut into a circular piece with a diameter of 14 μm for use.

[0104] <Preparation of electrolyte>

[0105] In an argon atmosphere glove box with water content ≤ 1 ppm, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1, then sodium salt NaClO4 was added and dissolved in the above solvent, and the electrolyte was obtained after uniform mixing. The molar concentration of NaClO4 in the electrolyte was 1 mol / L.

[0106] <Preparation of the separator>

[0107] A glass fiber membrane with a thickness of 260 μm was selected as the separator.

[0108] <Assembly of the button cell>

[0109] <Assembly of the first button cell>

[0110] A circular sodium sheet with a diameter of 14 μm was used as the counter electrode, the circular sodium supplement material electrode prepared above, the separator, and the circular sodium sheet were stacked in order, with the separator in the middle of the circular sodium supplement material electrode and the circular sodium sheet to play a separating role, then the prepared electrolyte was injected to assemble the first button cell.

[0111] <Assembly of the second button cell>

[0112] A circular hard carbon negative electrode with a diameter of 14 μm was used as the counter electrode, and the ratio of the capacity of the negative electrode to the capacity of the positive electrode (N / P ratio) was 1.1, the positive electrode prepared above, the separator, and the negative electrode were stacked in order, with the separator in the middle of the positive electrode and the circular hard carbon negative electrode to play a separating role, then the prepared electrolyte was injected to assemble the second button cell.

[0113] Examples 2-4

[0114] Except that in <Preparation of the sodium supplement material>, the addition amount of the metal oxide catalyst and the electrochemically stable precursor material was adjusted according to Table 1, the rest was the same as Example 1.

[0115] Examples 5-6

[0116] Except that in <Preparation of the sodium supplement material>, the type of the metal oxide catalyst was adjusted according to Table 1, the rest was the same as Example 1.

[0117] Examples 7-10

[0118] Except that in <Preparation of the sodium supplement material>, the calcination temperature and the holding time at the second temperature were adjusted according to Table 1, the rest was the same as Example 1.

[0119] Examples 11-12

[0120] The rest is the same as Example 2 except that the addition amount of the sodium supplement agent is adjusted according to Table 2 in the preparation of the sodium supplement material.

[0121] Examples 13-14

[0122] The rest is the same as Example 2 except that the relevant parameters of the first calcination treatment are adjusted according to Table 3 in the preparation of the sodium supplement material.

[0123] Comparative Example 1

[0124] The rest is the same as Example 1 except that the composite catalytic material is replaced by a TiO2 catalyst in the preparation of the sodium supplement material.

[0125] Comparative Example 2

[0126] The rest is the same as Example 1 except that the preparation of the sodium supplement material is not performed, i.e., the first button cell is not prepared, and the sodium supplement material is not contained in the positive electrode sheet and in the second button cell prepared.

[0127] Test method and equipment:

[0128] Test of the relative content of the sodium supplement agent in the sodium supplement material:

[0129] Quantitative analysis of the sodium supplement agent in the sodium supplement material is performed by an inductively coupled plasma emission spectrometer (ICP): the sample of the sodium supplement material is tested by a main element method, the element content of sodium (Na) element is C0, and the content of sodium sulfide in the sample of the sodium supplement material is i.e., the relative content of the sodium supplement agent.

[0130] Test of the oxidative decomposition potential:

[0131] First circle charge-discharge test of the first button cell is performed by a LAND test system to obtain a differential capacity curve (dQ / dV curve), the oxidative peak value of the dQ / dV curve corresponds to the oxidative decomposition reaction of the sodium supplement material, and the potential corresponding to the oxidative peak value of the dQ / dV curve is the oxidative decomposition potential of the sodium supplement material.

[0132] Test of the first circle charge capacity and the first circle discharge capacity:

[0133] The test temperature is 25°C, the button cell is charged at a rate of 0.1 times (C) to 3.9V, which is the charging stage; it is then discharged at a rate of 0.1C to 1.5V and is left standing for 10 min, which is the discharging stage. The charge capacity of the first charging stage is recorded as the first circle charge capacity, with the unit of mAh / g; and the discharge capacity of the first discharging stage is recorded as the first circle discharge capacity, with the unit of mAh / g.

[0134] Test of the cycle performance:

[0135] The test temperature was 25°C, the button cell was charged at 1C constant current to 3.5V, and then discharged at 1C to 1.5V after standing for 10 min. The capacity obtained in this way was the initial discharge capacity C i , and the discharge capacity of the 20th cycle was recorded. The cycle capacity retention rate = (discharge capacity of the 20th cycle / initial discharge capacity C i ) x 100%.

[0136] Table 1 Preparation parameters of composite catalytic materials

[0137]

[0138]

[0139] Table 2 Preparation parameters of sodium supplement materials

[0140]

[0141] In Table 2, " / " means that there is no relevant preparation parameter.

[0142] Table 3 First calcination treatment parameters of Example 2, Example 13 to Example 14

[0143]

[0144]

[0145] Table 4 Test data of the first button cell of each example and comparative example

[0146] Initial charge specific capacity (mAh g -1 ) dQ / dV oxidation peak potential Example 1 382 3.74 Example 2 381 3.75 Example 3 375 3.78 Example 4 371 3.80 Example 5 360 3.75 Example 6 352 3.74 Example 7 381 3.75 Example 8 367 3.78 Example 9 373 3.74 Example 10 381 3.74 Example 11 392 3.75 Example 12 370 3.90 Example 13 360 3.73 Example 14 365 3.75 Comparative Example 1 350 3.75 Comparative Example 2 / /

[0147] In Table 4, " / " means that there is no relevant test data.

[0148] Table 5 Test data of the second button cell of each example and comparative example

[0149]

[0150]

[0151] From Tables 4 and 5, it can be seen from Examples 1-14 and Comparative Examples 1-2 that the sodium supplement material of Comparative Example 1 simply uses TiO2 catalyst without using the composite catalytic material of the present application, although the oxidation decomposition potential is low, but the capacity retention rate after 50 cycles is low, which may be due to the fact that the sodium supplement material of Comparative Example 1 does not contain the composite catalytic material of the present application, and therefore does not have the "double core-shell structure" of the present application, resulting in metal ion shuttle effect of the metal oxide catalyst material in the sodium supplement material, which induces decomposition of the electrolyte and changes in the SEI structure, resulting in poor cycle stability of the sodium ion battery; Comparative Example 2 does not have a sodium supplement material, so the first cycle charge capacity and the first cycle discharge capacity of the second button cell are both low, resulting in low first cycle coulombic efficiency, thus being not conducive to improving the energy density and cycle performance of the sodium ion battery; while the first charge specific capacity of the first button cell of each example of the present application is significantly improved compared to Comparative Example 1, and the oxidation decomposition potential is low, and the capacity retention rate after 50 cycles of the second button cell of each example of the present application is significantly improved compared to Comparative Example 1, and the first cycle charge capacity and the first cycle discharge capacity are significantly improved compared to Comparative Example 2. It can be seen that under the action of the "double core-shell structure" sodium supplement material of the present application, not only can the oxidation decomposition potential of the sodium supplement material itself be reduced, but also the metal ion shuttle to the negative electrode can be inhibited, so that the energy density and cycle performance of the sodium ion battery are improved at the same time.

[0152] In the process of preparing the composite catalytic material, the type and amount of the metal oxide catalyst in the composite catalytic material, the type and amount of the electrochemically stable precursor material, the calcination temperature and time of the second calcination treatment, etc. will also generally affect the performance of the sodium supplement material. From Examples 1-10, it can be seen that, on the basis of the sodium supplement material having the structure of the present application, by adjusting the above parameters within the scope of the present application, it is beneficial to obtain a sodium supplement material with low shuttle effect and low oxidation decomposition potential, so that the energy density and cycle performance of the sodium ion battery are improved at the same time.

[0153] In combination with Tables 2-3, in the process of preparing the sodium supplement material, the type of the sodium supplement agent, the calcination temperature and time of the first calcination treatment will also generally affect the performance of the sodium supplement material. From Examples 11-12 and Examples 13-14, it can be seen that, on the basis of the sodium supplement material having the structure of the present application, by adjusting the above parameters within the scope of the present application, it is beneficial to obtain a sodium supplement material with low shuttle effect and low oxidation decomposition potential, so that the energy density and cycle performance of the sodium ion battery are improved at the same time.

[0154] The above has carried on the detailed introduction to the sodium supplement material, the preparation method thereof, the positive pole piece and the sodium ion battery disclosed by the application, the principle and the implementation mode of the present application are described in the text by applying specific examples, the above example description is only used for helping understanding the technical scheme and the core invention point of the implementation mode of the present application: at the same time, for the general technical personnel in the art, according to the idea of the present application, the specific implementation mode and the application range will have the change, and on the basis of the above, the content of the specification should not be understood as the limitation of the present application.

Claims

1. A sodium supplement material, characterized in that, The sodium-supplementing material has a first core-shell structure, wherein the core of the first core-shell structure includes a sodium-supplementing agent, and the shell of the first core-shell structure includes a composite catalytic material and a composite conductive carbon material. The composite catalytic material has a second core-shell structure, wherein the core of the second core-shell structure comprises a metal oxide catalyst, and the shell of the second core-shell structure comprises an electrochemically stabilizing material. The electrochemically stable material includes at least one of electrochemically stable oxide materials and electrochemically stable carbide materials; The electrochemically stable oxide material includes at least one of Al2O3, ZnO and ZrO2; The electrochemically stable carbide material includes at least one of WC, TiC, and TaC.

2. The sodium supplement material according to claim 1, characterized in that, The composite conductive carbon material includes a conductive agent and amorphous carbon, wherein the amorphous carbon is formed by carbonization of an organic complexing agent.

3. The sodium supplement material according to claim 1, characterized in that, The sodium supplement agent has a mass percentage of 45% to 90% in the sodium supplement material.

4. The sodium supplement material according to claim 2, characterized in that, The organic complexing agent includes at least one of polyvinylpyrrolidone, sodium aminotriacetate, disodium ethylenediaminetetraacetate, polyethylene glycol, and polyethylene glycol ether.

5. The sodium supplement material according to claim 2, characterized in that, The sodium supplement material satisfies at least one of the following characteristics: a) The sodium supplement is made of at least one of Na2S, Na2Se and Na2N3; b) The conductive agent includes at least one of carbon nanotubes, Ketjen black, graphene, and acetylene black; c) The material of the metal oxide catalyst is selected from at least one of ruthenium dioxide, ferric oxide, manganese dioxide, vanadium pentoxide, titanium dioxide, cobalt tetroxide, nickel oxide, nickel oxide, and tin dioxide.

6. A method for preparing a sodium-supplementing material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The sodium supplement and the composite catalytic material are added to the first solvent and mixed to obtain the first dispersion. The conductive agent and the organic complexing agent were added to the first dispersion and mixed. After drying, the sodium supplement material precursor was obtained. The sodium-supplementing material precursor is subjected to a first calcination treatment in an inert gas atmosphere to obtain the sodium-supplementing material having a first core-shell structure.

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

8. The preparation method according to claim 7, characterized in that, The electrochemically stable precursor material includes at least one of Al2(SO4)3, AlCl3, and AlF3.

9. The preparation method according to claim 8, characterized in that, The calcination temperature of the first calcination treatment is 300℃~700℃, and the holding time is 1 h~10 h.

10. A positive electrode plate, characterized in that, 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 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, characterized in that, Includes the positive electrode sheet as described in claim 10.

12. An energy storage device, characterized in that, 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, characterized in that, 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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