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

Abstract

The application provides a sodium supplement material and a preparation method thereof, a positive electrode sheet and a sodium ion battery. The sodium supplement material has a core-shell structure. The core of the core-shell structure comprises a sodium supplement agent body. The shell of the core-shell structure comprises a coating layer formed by mixing a composite conductive carbon material and a metal oxide catalyst. 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.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, and in particular to a sodium supplementing 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 lithium ion battery in the energy storage field due to its low cost, abundant sodium resources and relatively high energy density.

[0003] Supplementing sodium to the positive electrode sheet by a sodium supplementing agent can reduce the adverse effects of sodium loss on the electrochemical performance of the sodium ion battery. The oxidation decomposition potential of the existing inorganic sodium supplementing agent still needs to be further reduced to achieve better sodium supplementing effect on the positive electrode sheet, thereby improving the performance of the sodium ion battery. SUMMARY

[0004] To solve the above technical problems, the present application discloses a sodium supplementing material, a preparation method thereof, a positive electrode sheet and a sodium ion battery to improve the sodium supplementing effect of the sodium supplementing material and thereby improve the performance of the sodium ion battery.

[0005] In a first aspect, the present application provides a sodium supplementing material, which has a core-shell structure, the core of the core-shell structure comprises a sodium supplementing agent body, and the shell of the core-shell structure comprises a coating layer formed by mixing a composite conductive carbon material and a metal oxide catalyst; wherein 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.

[0006] In some embodiments of the present application, the oxidation decomposition potential of the sodium supplementing material is E pa , 3.70V≤E pa ≤3.85V.

[0007] In some embodiments of the present application, the average particle size D50 of the sodium supplementing material is 1μm-3μm.

[0008] In some embodiments of the present application, the mass percentage content of the sodium supplementing agent body in the sodium supplementing material is 50%-90%.

[0009] In some embodiments of the present application, the organic complexing agent comprises at least one of polyvinylpyrrolidone, sodium nitrilotriacetic acid, disodium ethylenediaminetetraacetate, polyethylene glycol and polyether.

[0010] In some embodiments of the present application, the sodium supplementing material satisfies at least one of the following characteristics:

[0011] a) the material of the sodium supplementing agent body comprises at least one of Na2S, Na2Se and Na2N3;

[0012] b) the electrically conductive agent comprises at least one of electrically conductive carbon black, carbon nanotube, ketjen black, graphene and acetylene black;

[0013] c) the material of the metal oxide catalyst is selected from at least one of titanium dioxide, ruthenium dioxide, manganese dioxide, molybdenum dioxide, tricobalt tetroxide, triiron tetroxide and tin dioxide.

[0014] In a second aspect, the present application provides a preparation method of the sodium supplement material as described in the first aspect, comprising the following steps:

[0015] adding the sodium supplement agent and the catalyst precursor into the solvent to obtain a dispersion liquid after mixing;

[0016] adding the electrically conductive agent and the organic complexing agent into the dispersion liquid to mix, and drying to obtain a sodium supplement material precursor;

[0017] calcining the sodium supplement material precursor, wherein the calcination temperature is 300-700°C, and the calcination time is 1-10h, to obtain the sodium supplement material.

[0018] In some embodiments of the present application, the step of calcining the precursor comprises:

[0019] calcining the sodium supplement material precursor in an inert and / or reducing gas atmosphere, so that the catalyst precursor is converted into a metal oxide catalyst, and the organic complexing agent is converted into amorphous carbon.

[0020] In some embodiments of the present application, the mass ratio of the electrically conductive agent to the organic complexing agent is 1:0.15-1.

[0021] In some embodiments of the present application, the gas comprises at least one of nitrogen and argon.

[0022] In some embodiments of the present application, the material of the catalyst precursor comprises at least one of tetrabutyl titanate, manganese diethylhexanoate, iron diethylhexanoate, copper diethylhexanoate, cobalt diethylhexanoate, nickel diethylhexanoate and stannous diethylhexanoate.

[0023] In a third aspect, the present application provides a positive electrode tab, 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 supplement material as described in the first aspect, or comprises the sodium supplement material prepared by the preparation method as described in the second aspect.

[0024] In a fourth aspect, the present application provides a sodium ion battery, comprising the positive electrode tab as described in the third aspect.

[0025] In a fifth aspect, the application provides an energy storage device, comprising a box and at least one sodium ion battery of the fourth aspect, wherein the sodium ion battery is accommodated in the box.

[0026] In a sixth aspect, the application provides an electric device, comprising the energy storage device of the fifth aspect, wherein the energy storage device supplies power for the electric device.

[0027] Compared with the prior art, the application has at least the following beneficial effects:

[0028] The application provides a sodium supplement material, a preparation method thereof, a positive electrode sheet and a sodium ion battery. The sodium supplement material has a core-shell structure. The core of the core-shell structure comprises a sodium supplement agent body. The shell of the core-shell structure comprises a coating layer formed by mixing a composite conductive carbon material and a metal oxide catalyst. The composite conductive carbon material comprises a conductive agent and amorphous carbon. The amorphous carbon is formed by carbonization of an organic complexing agent. The amorphous carbon has good uniformity. In the process of forming the coating layer, the amorphous carbon can be uniformly distributed on the surface of the sodium supplement agent body and can adsorb the conductive agent, thereby improving the uniformity of the conductive agent and improving the conductivity of the coating layer. Therefore, the sodium supplement material with the core-shell structure, which has the composite conductive carbon material and the metal oxide catalyst as the shell and the sodium supplement agent body as the core, has good conductivity and catalytic ability, thereby improving the first-cycle sodium supplement effect of the sodium supplement material and further improving the energy density and the cycle performance of the sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort.

[0030] Figure 1 A structure schematic diagram of the sodium supplement material of an embodiment of the application;

[0031] Figure 2 A structure schematic diagram of the household energy storage system of an embodiment of the application;

[0032] Figure 3 A structure schematic diagram of the energy storage system of an embodiment of the application.

[0033] Explanation of reference numerals: 1 - energy storage device, 2 - electric energy conversion device, 3 - first user load, 4 - second user load, 10 - sodium agent body, 20 - coating layer, 400 - energy storage system, 410 - high-voltage cable, 420 - first electric energy conversion device, 430 - second electric energy conversion device. DETAILED DESCRIPTION

[0034] 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. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0035] 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 intended to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0036] 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. For those of ordinary skill in the art, the specific meaning of these terms in the present application can be understood according to the specific situation.

[0037] In addition, the terms "mount", "set", "provided with", "connect", "connect" should be broadly understood. For example, it can be fixedly connected, detachably connected, or integrally constructed; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific situation.

[0038] In addition, the terms "first", "second", and the like are mainly used to distinguish different devices, elements or components (the specific type and structure may be the same or different), and are not intended to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise stated, the meaning of "multiple" is two or more.

[0039] The present application provides a sodium supplement material, which is referred to as Figure 1The sodium supplement material has a core-shell structure, the core of the core-shell structure includes a sodium supplement agent body 10, and the shell of the core-shell structure includes a coating layer 20 formed by mixing a composite conductive carbon material and a metal oxide catalyst; wherein the composite conductive carbon material includes a conductive agent and amorphous carbon, the amorphous carbon is formed by carbonization of an organic complexing agent, and the amorphous carbon has good uniformity of distribution. In the process of forming the coating layer, on the one hand, the amorphous carbon can be uniformly distributed on the surface of the sodium supplement agent body, and on the other hand, the amorphous carbon can adsorb the conductive agent to improve the uniformity of distribution of the conductive agent, so that the conductivity of the coating layer is improved, thereby promoting the transmission of electrons to the inside of the sodium supplement agent body through the composite conductive carbon material in the coating layer to reduce the oxidative decomposition potential of the sodium supplement material. Moreover, the metal oxide catalyst in the present application is distributed in the shell structure (coating layer) rather than in the core structure. If the metal oxide catalyst is distributed in the core structure, when the electrons pass through the shell structure to the surface of the core structure, the poor conductivity of the sodium supplement agent and the metal oxide catalyst will cause the electrons to be unable to quickly transmit to the metal oxide catalyst in the core structure, thereby affecting the catalytic effect of the metal oxide catalyst. Therefore, the metal oxide catalyst in the present application is distributed in the shell structure, which can improve the electron conductivity of the metal oxide catalyst through the composite conductive carbon material in the shell structure, thereby improving the actual catalytic effect of the metal oxide catalyst, specifically, improving the oxidative decomposition catalytic effect of the metal oxide catalyst on the sodium supplement agent body.

[0040] Therefore, the core-shell structure sodium supplement material with the composite conductive carbon material and the metal oxide catalyst as the shell and the sodium supplement agent body as the core has good conductivity and catalytic ability, thereby improving the first-cycle sodium supplement effect of the sodium supplement material and further improving the energy density and cycle performance of the sodium ion battery. It can be understood that the coating layer in the present application can be fully coated on the surface of the sodium supplement agent body.

[0041] In some embodiments of the present application, the oxidative decomposition potential of the sodium supplement material is E pa , 3.70V≤E pa ≤3.85V. For example, the oxidative decomposition potential is 3.70V, 3.75V, 3.78V, 3.80V or 3.85V. The sodium supplement material in the present application has a lower oxidative decomposition potential than existing inorganic sodium supplement agents, which can promote the oxidative decomposition of the sodium supplement agent body, improve the first-cycle sodium supplement effect, improve the first-cycle irreversible capacity loss of the sodium ion battery, and thereby improve the first-cycle coulombic efficiency of the sodium ion battery.

[0042] 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.

[0043] In some embodiments of the present application, the average particle size D50 of the sodium supplement material is 1-3 μm, which can effectively shorten the transmission distance of electrons between the particles of the sodium supplement material, thereby promoting the oxidative decomposition process of the sodium supplement material body and facilitating the reduction of the oxidative decomposition potential of the sodium supplement material. The average particle size D50 of the sodium supplement material represents the particle size corresponding to the cumulative particle size distribution percentage of 50% of the sodium supplement material.

[0044] In some embodiments of the present application, the mass percentage of the sodium supplement material body in the sodium supplement material is 50-90%, and the balance is the content of the coating layer. For example, the mass percentage of the sodium supplement material body in the sodium supplement material is 50%, 60%, 70%, 80% or 90%. By adjusting the mass percentage of the sodium supplement material body in the sodium supplement material within the above range, the sodium supplement material with a core-shell structure of the sodium supplement material body as the core and the composite conductive carbon material and the metal oxide catalyst as the shell can be formed, and the composite conductive carbon material in the shell structure promotes the transmission of electrons to the inside of the sodium supplement material body, thereby reducing the oxidative decomposition potential of the sodium supplement material.

[0045] 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 conducive to the formation of the amorphous carbon of the present application.

[0046] In some embodiments of the present application, the material of the sodium supplement material body includes at least one of Na2S, Na2Se and Na2N3. The sodium supplement material body belongs to inorganic sodium supplement agent and has the characteristics of high theoretical specific capacity and no gas generation during the cycle.

[0047] 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.

[0048] In some embodiments of the present application, the material of the metal oxide catalyst includes at least one of titanium dioxide, ruthenium dioxide, manganese dioxide, molybdenum dioxide, cobalt trioxide, iron trioxide and tin dioxide. The metal oxide can be used as an electron acceptor in the coating layer of the sodium supplement material of the present application to catalyze the oxidative decomposition of the sodium supplement material body.

[0049] In a second aspect, the present application provides a preparation method of the sodium supplement material according to the first aspect, which comprises the following steps:

[0050] Step A, adding the sodium supplement agent and the catalyst precursor into the solvent to obtain a dispersion after mixing;

[0051] Step B, the conductive agent and the organic complexing agent are added into the dispersion liquid and mixed, and after drying, a sodium supplement material precursor is obtained;

[0052] Step C, the sodium supplement material precursor is calcined at a temperature of 300-700°C for 1-10 hours to obtain the sodium supplement material.

[0053] In Step A, the sodium supplement agent and the catalyst precursor are added into the solvent, and after stirring and mixing, the sodium supplement agent is dispersed in the solvent, and the catalyst precursor is dissolved in the solvent to obtain a dispersion liquid. The addition ratio of the sodium supplement agent to the solvent can be 1 g:5 mL-1 g:100 mL. The temperature of the dispersion liquid is not particularly limited in the present application, for example, it can be room temperature (25°C). The solvent includes at least one of methanol, ethanol, ethylene glycol and diethyl ether.

[0054] In Step B, the conductive agent and the organic complexing agent are added into the dispersion liquid, and after stirring and mixing, the organic complexing agent is dissolved in the dispersion liquid and uniformly distributed on the surface of the sodium supplement agent. At the same time, the dissolved organic complexing agent can adsorb the conductive agent in the dispersion liquid, so that the conductive agent is also uniformly distributed on the surface of the sodium supplement agent, forming a sodium supplement material slurry of the present application in which the conductive agent and the catalyst precursor are adhered to the surface of the sodium supplement agent. In order to further improve the uniformity of the sodium supplement material slurry, the sodium supplement material slurry can also be subjected to ultrasonic dispersion. After vacuum drying treatment of the sodium supplement material slurry, a sodium supplement material precursor is obtained, and the temperature of the vacuum drying is 60-100°C.

[0055] In Step C, by the calcination process of the present application, that is, by adjusting the calcination temperature and the calcination time within the above-mentioned ranges, the organic complexing agent in the sodium supplement material precursor is converted into amorphous carbon by high-temperature carbonization, and the catalyst precursor is decomposed into a metal oxide catalyst, so that the amorphous carbon, the metal oxide catalyst and the conductive agent form a coating layer on the surface of the sodium supplement agent body, that is, a shell structure is formed. In addition, the product obtained after calcination can be subjected to crushing treatment by a crusher, and then sieved to obtain a sodium supplement material with a desired particle size range.

[0056] In some embodiments of the present application, the method for preparing the sodium supplement material further comprises:

[0057] The sodium supplement material precursor is calcined in an inert and / or reducing gas atmosphere, so that the catalyst precursor is converted into a metal oxide catalyst, and the organic complexing agent is converted into amorphous carbon, so that the amorphous carbon, the metal oxide catalyst and the conductive agent form a coating layer on the surface of the sodium supplement agent body, which is beneficial to form the sodium supplement material with the core-shell structure of the present application, and such a sodium supplement material has good conductivity and catalytic ability.

[0058] In some embodiments of the present application, the mass ratio of the conductive agent and the organic complexing agent in the coating layer is 1:0.15-1. For example, the mass ratio of the conductive agent and the organic complexing agent is 1:0.15, 1:0.25, 1:0.35, 1:0.5, 1:0.75 or 1:1. The inventors have found that when the relative content of the organic complexing agent is too high, the relative content of the conductive agent is too low, and it is difficult to improve the conductivity of the sodium supplement material; when the relative content of the organic complexing agent is too low, the relative content of the conductive agent is too high, and it is difficult to utilize the adsorption of the organic complexing agent to the conductive agent to make the conductive agent more uniformly distributed on the surface of the sodium supplement agent, which is not conducive to the formation of the sodium supplement material slurry of the conductive agent and the catalyst precursor adhered to the surface of the sodium supplement agent. By adjusting the mass ratio of the conductive agent and the organic complexing agent within the above range, not only the conductivity of the conductive material can be improved, but also the uniformity of the distribution of the conductive agent on the surface of the sodium supplement agent can be improved, and the organic complexing agent can be carbonized as a supplementary carbon source during subsequent calcination compared with inorganic complexing agents, further improving the conductivity of the conductive material.

[0059] In some embodiments of the present application, the gas includes at least one of inert gases such as nitrogen and argon, which is conducive to the conversion of the organic complexing agent into amorphous carbon at high temperature.

[0060] In some embodiments of the present application, the material of the catalyst precursor includes at least one of tetrabutyl titanate, manganese diethylhexanoate, iron diethylhexanoate, copper diethylhexanoate, cobalt 2-ethylhexanoate, nickel diethylhexanoate and stannous diethylhexanoate.

[0061] 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, and the prepared sodium supplement material has 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.

[0062] The present application also provides a positive electrode tab, which includes a current collector and a positive electrode active material layer arranged on at least one surface of the current collector, and the positive electrode active material layer includes 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.

[0063] The positive electrode active material layer of the present application can be provided on one surface or both surfaces of the positive electrode current collector in the thickness direction. In the present application, the positive electrode active material layer is provided on the surface of the positive electrode current collector, that is, the positive electrode active material layer can be provided on part of the area of one surface of the positive electrode current collector, or can be provided 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 the purpose of the present application can be achieved, and for example, can include but is not limited to an aluminum foil, an aluminum alloy foil, or a composite current collector, etc. In the present application, the thickness of the positive electrode current collector is not particularly limited as long as the purpose of the present application can be achieved, and for example, the thickness can be 8 μm to 13 μm. The thickness of the positive electrode active material layer of the present application can be 150 μm to 400 μm.

[0064] In the present application, the positive electrode active material layer further includes a positive electrode active material, and the positive electrode active material of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, can include 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.

[0065] In the present application, the positive electrode active material layer can further include a positive electrode conductive agent, and the positive electrode conductive agent of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, can include but is not limited to at least one of Super P conductive carbon black, carbon nanotube (CNT), Ketjen black (KB), graphene, graphene oxide, and acetylene black. 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, and the positive electrode binder of the present application is not particularly limited as long as the purpose of the present application can be achieved, and for example, can include but is not limited to at least one of fluorine-containing resin, polypropylene resin, fiber type binder, rubber type binder, polyimide type binder, and polyvinylidene fluoride (PVDF).

[0066] The present application also provides a sodium ion battery including the positive electrode sheet according to any one of the above embodiments.

[0067] The sodium ion battery of the present application further includes a negative electrode sheet, a separator, and an electrolyte, wherein the separator is between the positive electrode sheet and the negative electrode sheet, and functions as a separator.

[0068] The negative electrode sheet is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the negative electrode sheet generally includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer can be provided on the surface of the negative electrode current collector, i.e., the negative electrode active material layer can be provided on a partial region of one surface of the negative electrode current collector, or can be provided on the entire region of one surface of the negative electrode current collector. The negative electrode current collector is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, it can include, but is not limited to, a copper foil, a copper alloy foil, a nickel foil, or a composite current collector, etc. 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. For example, the thickness is 4 μm to 12 μm. The thickness of the negative electrode material layer of the present application can be 70 μm to 200 μm.

[0069] In the present application, the negative electrode active material layer can further include a negative electrode binder. The negative electrode binder is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, it can include at least one of an acrylate, a polyamide, a polyimide, a polyamide-imide, a polyvinylidene fluoride, a styrene butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, sodium carboxymethyl cellulose.

[0070] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0071] The sodium ion battery of the present application further includes an electrolyte. The electrolyte is not particularly limited in the present application, and can be selected by a person skilled in the art according to actual needs, as long as the object 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 object 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 trifluoromethylsulfonate, 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 object 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.

[0072] The sodium-ion battery of the present application further comprises a shell, and the present application does not have special restrictions on the shell, and the person skilled in the art can select according to the actual needs, as long as the purpose of the present application can be achieved. For example, the shell can comprise an aluminum plastic film.

[0073] The present application does not have special restrictions on the preparation method of the sodium-ion battery, and the 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 comprises but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations according to the needs 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.

[0074] The present application also provides an energy storage device comprising a box body and at least one sodium-ion battery of any 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 fixing 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.

[0075] The present application also provides an electric equipment comprising the energy storage device of any of the above embodiments, which is beneficial to improve the product competitiveness and use performance of the electric equipment. In an alternative embodiment, the electric equipment comprises an electric equipment body, and the energy storage device is used to power the electric equipment body. In an alternative embodiment, the electric equipment body comprises a device positive electrode and a device negative electrode, and the positive electrode sheet of the sodium-ion battery in the energy storage device is used to electrically connect the device positive electrode of the electric equipment body, and the negative electrode sheet of the sodium-ion battery in the energy storage device is used to electrically connect the device negative electrode of the electric equipment body, so as to power the electric equipment.

[0076] The electric equipment of the present application can comprise but is not limited to: a container, a household energy storage system, an electric car, an electric vehicle, 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 and a spacecraft, etc., the electric toy comprises, for example, a fixed or mobile electric toy, and specifically comprises, for example, an electric car toy, an electric ship toy and an electric airplane toy, etc., and the electric tool comprises, for example, a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, and specifically comprises, for example, a power drill, a power grinder, a power wrench, a power screwdriver, an electric hammer, an impact drill, a concrete vibrator and an electric planer.

[0077] Please refer to Figure 2 , Figure 2A structural schematic diagram of a household energy storage system according to an embodiment of the present application, and the present application Figure 2 The embodiment takes a household energy storage scenario in user-side energy storage as an example for illustration, and the energy storage device of the present application is not limited to the household energy storage scenario.

[0078] The present 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 by a wall-mounted manner. Specifically, the photovoltaic panel can convert solar energy into electric energy during a low electricity price period, and the energy storage device 1 is used to store the electric energy and supply the street lamp and the household appliance for use during a high electricity price period, or supply power during a power grid outage.

[0079] Please refer to Figure 3 , Figure 3 A structural schematic diagram of an energy storage system 400 according to an embodiment of the present application, and the present application Figure 3 The embodiment takes a power generation / distribution side shared energy storage scenario as an example for illustration, and the energy storage device 1 of the present application is not limited to the power generation / distribution side energy storage scenario.

[0080] The present application provides an energy storage system 400, which comprises a high-voltage cable 410, a first electric energy conversion device 420, a second electric energy conversion device 430, and an energy storage device 1 provided by the present application. In a power generation condition, the first electric energy conversion device 420 and the second electric energy conversion device 430 are used to convert other forms of energy into electric energy, and are connected with the high-voltage cable 410 to supply a power distribution network for use. When the electric load is low, the first electric energy conversion device 420 and the second electric energy conversion device 430 generate excess power, which is stored in the energy storage device 1, so as to reduce the curtailment rate of wind power and solar power and improve the problem of new energy power generation consumption. When the electric load is high, the power grid issues an instruction to transmit the electric energy stored in the energy storage device 1 in a grid-connected mode together with the high-voltage cable 410 to supply the power distribution network for use, thereby providing various services such as peak shaving, frequency modulation, and backup for the power grid operation, fully playing the role of peak shaving of the power grid, promoting the peak shaving and valley filling of the power grid, and relieving the power supply pressure of the power grid.

[0081] 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.

[0082] The number of the energy storage devices 1 can be multiple, and the multiple energy storage devices 1 are connected in series or in parallel with each other and are supported and electrically connected by an isolation plate (not shown in the figure). In the embodiment, “multiple” means two or more. The energy storage device 1 can further be provided with an energy storage box outside for accommodating the energy storage device 1.

[0083] Optionally, the energy storage device 1 can include, but is not limited to, a single battery cell, a battery module, a battery pack, a battery system, etc. Among them, the single battery cell can be a sodium ion battery of the present application, the battery module can be a battery module formed by connecting a plurality of sodium ion batteries of the present application in series / parallel, the battery pack can include a plurality of sodium ion batteries of the present application, and the battery system can be a charging and discharging system including a sodium ion battery or a battery pack of the present application.

[0084] The actual application form of the energy storage device 1 provided by the present application can be, but is not limited to, the listed products, and can also be other application forms, and the present application does not strictly limit the application form of the energy storage device 1. The present application only takes the energy storage device 1 as an example to illustrate the multi-core battery. When the energy storage device 1 is a single battery cell, the energy storage device 1 can be at least one of a cylindrical battery, a square battery, etc.

[0085] Embodiment

[0086] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Various tests and evaluations are carried out according to the following methods.

[0087] Example 1

[0088] <Preparation of sodium supplementing material>

[0089] 3g of commercially available sodium sulfide (Na2S) powder and 1.3g of tetrabutyl titanate were added to 50mL of anhydrous ethanol, stirred at room temperature for 12h, then stood for 1h, and after removing the supernatant, a dispersion liquid was obtained; then 0.5g of Ketjenblack and 0.5g of polyvinylpyrrolidone (PVP) were added to the dispersion liquid and ultrasonically dispersed for 1h, and then stirred for 6h to form a uniform sodium supplementing material slurry; the sodium supplementing material slurry was vacuum dried at 80℃ for 12h to obtain a sodium supplementing material precursor, and then the sodium supplementing material precursor was calcined at 500℃ for 4h, obtaining a sodium supplementing material. During the calcination process, argon gas was used, and the heating rate was 5℃ / min; the calcined product was crushed by a crusher and sieved to obtain a sodium supplementing material with an average particle size D50 of 1.26μm.

[0090] <Preparation of sodium supplementing agent electrode sheet>

[0091] The prepared sodium supplementing material, conductive agent Ketjenblack (KB), and binder PVDF were mixed in a mass ratio of 60:30:10, a solvent N-methyl pyrrolidone (NMP) was added, and stirred uniformly to obtain a sodium supplementing agent slurry with a solid content of 60%, then the sodium supplementing agent slurry was uniformly coated on a 10μm thick aluminum foil, the single-sided coating thickness was 20μm, and then vacuum dried at 110℃ for 12h to obtain a sodium supplementing agent electrode sheet. The obtained sodium supplementing agent electrode sheet was cut into a circular sheet with a diameter of 14μm for use.

[0092] Preparation of NFPP positive electrode sheet

[0093] The positive active material Na4Fe3(P04)2(P207) (i.e. NFPP), the prepared sodium supplement material, the conductive agent Ketjen black, and the binder PVDF were mixed in a mass ratio of 75:5:10:10, then NMP was added and stirred uniformly to obtain a positive electrode slurry with a solid content of 60%, then the positive electrode slurry was uniformly coated on an aluminum foil with a thickness of 10 μm, the single-sided coating thickness was 20 μm, then vacuum drying was performed at 110°C for 12 h to obtain a NFPP positive electrode sheet. The obtained NFPP positive electrode sheet was cut into a circular sheet with a diameter of 14 μm for use.

[0094] Preparation of electrolyte

[0095] In an argon atmosphere glove box with a water content of ≤1 ppm, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1, then sodium salt NaCl04 was added and dissolved into the above solvent, and after uniform mixing, an electrolyte was obtained. The molar concentration of NaCl04 in the electrolyte was 1 mol / L.

[0096] Preparation of separator

[0097] A glass fiber membrane with a thickness of 260 μm was selected as the separator.

[0098] Assembly of button cell

[0099] Assembly of first button cell

[0100] A circular sodium sheet with a diameter of 14 μm was used as the counter electrode, the circular sodium supplement electrode sheet prepared above, the separator, and the circular sodium sheet were stacked in order, with the separator in the middle of the circular sodium supplement electrode sheet and the circular sodium sheet to play a role of isolation, then the prepared electrolyte was injected to assemble a first button cell.

[0101] Assembly of second button cell

[0102] A circular sodium sheet with a diameter of 14 μm was used as the counter electrode, the NFPP positive electrode sheet prepared above, the separator, and the circular sodium sheet were stacked in order, with the separator in the middle of the NFPP positive electrode sheet and the circular sodium sheet to play a role of isolation, then the prepared electrolyte was injected to assemble a second button cell.

[0103] Examples 2-7

[0104] Except that in the preparation of the sodium supplement material, the addition amount of the conductive agent and the organic complexing agent was adjusted according to Table 1 to adjust the mass ratio of the conductive agent to the organic complexing agent, the rest was the same as Example 1.

[0105] Examples 8-14

[0106] Except that in the <preparation of sodium supplement material>, the types of sodium supplement agent, conductive agent, organic complexing agent and catalyst precursor are adjusted according to Table 1, the rest is the same as Example 4.

[0107] Examples 15-17

[0108] Except that in the <preparation of sodium supplement material>, the calcination temperature, calcination time and gas atmosphere are adjusted according to Table 2, the rest is the same as Example 4.

[0109] Comparative Example 1

[0110] Except that the commercially available Na2S is directly used as the sodium supplement material, the rest is the same as Example 1.

[0111] Comparative Example 2

[0112] No preparation of sodium supplement material is performed, that is, no first button cell is prepared, and no sodium supplement material is contained in the NFPP positive electrode sheet, so that no sodium supplement material is contained in the prepared second button cell, and the rest is the same as Example 1.

[0113] Comparative Example 3

[0114] Except that in the <preparation of sodium supplement material>, no organic complexing agent is added, the rest is the same as Example 1.

[0115] Comparative Example 4

[0116] Except that in the <preparation of sodium supplement material>, no conductive agent is added, the rest is the same as Example 1.

[0117] Test methods and equipment:

[0118] Test of the relative content of the sodium supplement agent in the sodium supplement material:

[0119] Quantitative analysis of the sodium supplement agent in the sodium supplement material is performed by using an inductively coupled plasma emission spectrometer (ICP): the sample of the sodium supplement material is tested by using the 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 which is the relative content of the sodium supplement agent.

[0120] Test of the oxidative decomposition potential:

[0121] The first button cell is tested for the first cycle charge and discharge by using a LAND test system, and a differential capacity curve (dQ / dV curve) is obtained, 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.

[0122] Material particle size test:

[0123] The average particle size D50 of the sodium-supplemented material was tested by using a laser particle size analyzer.

[0124] First cycle charge capacity and first cycle discharge capacity test:

[0125] The test temperature was 25℃, and the button cell was charged at 0.1C (C) to 4.0V, which was the charging stage; then it was discharged at 0.1C to 2.5V and rested for 10min, which was the discharging stage. The charge capacity of the first charging stage was recorded as the first cycle charge capacity, with the unit of mAh / g; the discharge capacity of the first discharging stage was recorded as the first cycle discharge capacity, with the unit of mAh / g.

[0126] Cycle performance test:

[0127] The test temperature was 25℃, and the button cell was charged at 0.1C to 4.0V, and then discharged at 0.1C to 2.5V after resting for 10min. The capacity obtained by this step was the initial discharge capacity C i , and the cycle test of 0.1C charging / 0.1C discharging was carried out for 20 cycles, and the discharge capacity of the 20th cycle was recorded. Cycle capacity retention rate = (discharge capacity of the 20th cycle / initial discharge capacity C i ) × 100%.

[0128] Table 1 Preparation parameters of examples 1-14 and comparative examples 1-4

[0129]

[0130] In table 1, “ / ” indicates that there is no relevant preparation parameter.

[0131] Table 2 Preparation parameters of examples 4 and 15-17

[0132] Calcination temperature (°C) Calcination time (h) Gas atmosphere Example 4 500 4 Argon Example 15 300 10 Argon Example 16 700 1 Argon Example 17 500 4 Nitrogen

[0133] Table 3 Test data of sodium-supplemented materials and first button cells of various examples and comparative examples

[0134]

[0135] In table 3, “ / ” indicates that there is no relevant test data.

[0136] As can be seen from Table 3, from Examples 1 to 7 and Comparative Examples 1, 3 and 4, since Comparative Example 1 only uses a commercially available Na2S as the sodium supplement agent as the sodium supplement material, it does not have the core-shell structure of the sodium supplement material of the present application, and thus the first cycle charge capacity of the first coin cell is very low, the oxidation decomposition potential of the sodium supplement material is high, and it is difficult to improve the first cycle sodium supplement effect of the sodium supplement material; since Comparative Example 3 only adds a conductive agent to the raw material without adding an organic complexing agent, the sodium supplement agent and the conductive agent are mixed together by physical dispersion, the electron transport path is long, and the corresponding oxidation decomposition potential is only reduced to 3.87 V; since Comparative Example 4 only adds an organic complexing agent to the raw material without adding a conductive agent, the obtained sodium supplement material has poor conductivity, and thus its oxidation decomposition potential is higher, reaching 3.90 V; while the sodium supplement material of the present application has a core-shell structure, and the composite conductive carbon material in the coating layer contains both a conductive agent and amorphous carbon, the obtained sodium supplement material has a low oxidation decomposition potential, and the first cycle charge capacity of the first coin cell is significantly improved, which shows that, on the basis of the sodium supplement material having the structure of the present application, the combination of the conductive agent and the organic complexing agent effectively improves the first cycle sodium supplement effect of the sodium ion battery.

[0137] The types of sodium supplement agent, conductive agent, organic complexing agent and catalyst also generally affect the performance of the sodium ion battery. As can be seen from Examples 8 to 14, 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 ion battery with high first cycle charge capacity.

[0138] The preparation parameters such as calcination time, calcination temperature and gas atmosphere during calcination also generally affect the performance of the sodium ion battery. As can be seen from Examples 4, 15 to 17, on the basis of the sodium supplement material having the structure of the present application, by adjusting the above preparation parameters within the scope of the present application, it is beneficial to obtain a sodium ion battery with high first cycle charge capacity.

[0139] Table 4: Performance data of the second coin cell of each example and comparative example

[0140]

[0141]

[0142] As can be seen from Table 4, from Example 1 to Example 7 and Comparative Example 1 to Comparative Example 4, because Comparative Example 1 only directly uses a commercially available Na2S sodium supplement as a sodium supplement material, and does not have the core-shell structure of the sodium supplement material of the present application, and Comparative Example 2 does not contain a sodium supplement material in the positive electrode plate, the first charge capacity and the first discharge capacity of the second button cell of Comparative Example 1 and Comparative Example 2 are both low; Comparative Example 3 only adds a conductive agent to the raw material without adding an organic complexing agent, and the sodium supplement material body and the conductive agent in the composite sodium supplement are mainly obtained by simple physical mixing, when applied to the positive half-electric system, the conductive agent will separate from the sodium supplement material and disperse in the positive active material, the actual utilization rate of the conductive agent is low, which further leads to a sharp decrease in the actual decomposition efficiency of the sodium supplement material. Therefore, the first charge capacity and the first discharge capacity of the second button cell of Comparative Example 3 are both low. Although Comparative Example 4 has a core-shell structure, Comparative Example 4 only adds an organic complexing agent to the raw material without adding a conductive agent, which leads to the first charge capacity and the first discharge capacity of the second button cell of Comparative Example 4 are both low; while the first charge capacity, the first discharge capacity and the capacity retention rate after 20 cycles of the second button cell of the present application are all significantly improved. It can be seen that, on the basis of the conductive material having the structure of the present application, the combination of the conductive agent and the organic complexing agent is beneficial to the improvement of the energy density and the cycle performance of the NFPP sodium ion battery.

[0143] The types of sodium supplement materials, the types of conductive agents, the types of organic complexing agents, and the types of catalysts usually also have an impact on the performance of sodium ion batteries. As can be seen from Example 7 to Example 14, 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 NFPP sodium ion battery with high first charge capacity.

[0144] The preparation parameters such as calcination time, calcination temperature, and gas atmosphere during calcination usually also have an impact on the performance of sodium ion batteries. As can be seen from Example 1, Example 15 to Example 17, on the basis of the sodium supplement material having the structure of the present application, by adjusting the above preparation parameters within the scope of the present application, it is beneficial to obtain a NFPP sodium ion battery with high first charge capacity.

[0145] The above has introduced in detail a kind of sodium supplement material and its preparation method, positive electrode plate and sodium ion battery disclosed by the present application, specific examples are applied in this paper to explain the principle and implementation mode of the present application, the above example is only used to help understanding the technical scheme and core invention point of the embodiment of the present application: at the same time, for the general technical personnel in the art, according to the idea of the present application, in specific implementation mode and application range will have the change, 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 core-shell structure, wherein the core of the core-shell structure includes a sodium-supplementing agent body, and the shell of the core-shell structure includes a coating layer formed by mixing a composite conductive carbon material and a metal oxide catalyst as an electron acceptor; The composite conductive carbon material comprises a conductive agent and amorphous carbon, wherein the amorphous carbon is formed by carbonization of an organic complexing agent.

2. The sodium supplement material according to claim 1, characterized in that, The oxidation decomposition potential of the sodium supplement material is E. pa 3.70V≤E pa ≤3.85V.

3. The sodium supplement material according to claim 1, characterized in that, The average particle size D50 of the sodium-supplementing material is 1 μm to 3 μm.

4. The sodium supplement material according to claim 1, characterized in that, The sodium supplement body has a mass percentage of 50% to 90% in the sodium supplement material.

5. The sodium supplement material according to claim 1, characterized in that, The organic complexing agent includes at least one of polyvinylpyrrolidone, sodium aminotriacetate, disodium ethylenediaminetetraacetate, polyethylene glycol, and polyethylene glycol ether.

6. The sodium supplement material according to any one of claims 1 to 5, characterized in that, The sodium supplement material satisfies at least one of the following characteristics: a) The material of the sodium supplement body includes at least one of Na2S, Na2Se and Na2N3; 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 is selected from at least one of titanium dioxide, ruthenium dioxide, manganese dioxide, molybdenum dioxide, cobalt tetroxide, iron tetroxide and tin dioxide.

7. A method for preparing a sodium-supplementing material as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Sodium supplement and catalyst precursor are added to solvent and mixed to obtain dispersion; The conductive agent and organic complexing agent were added to the dispersion and mixed, and then dried to obtain the sodium supplement material precursor. The sodium-supplementing material precursor is calcined at a temperature of 300℃ to 700℃ for 1 h to 10 h to obtain the sodium-supplementing material.

8. The preparation method according to claim 7, characterized in that, The step of calcining the precursor includes: The sodium-supplementing material precursor is calcined in an inert and / or reducing gas atmosphere to transform the catalyst precursor into a metal oxide catalyst and the organic complexing agent into amorphous carbon.

9. The preparation method according to claim 7, characterized in that, The mass ratio of the conductive agent to the organic complexing agent is 1:0.15~1.

10. The preparation method according to claim 8, characterized in that, The gas includes at least one of nitrogen and argon.

11. The preparation method according to claim 7, characterized in that, The catalyst precursor material includes at least one of tetrabutyl titanate, manganese diethylhexanoate, iron diethylhexanoate, copper diethylhexanoate, cobalt 2-ethylhexanoate, nickel diethylhexanoate, and stannous diethylhexanoate.

12. 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 6, or includes a sodium-supplementing material prepared by the preparation method as described in any one of claims 7 to 11.

13. A sodium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 12.

14. An energy storage device, characterized in that, It includes a housing and at least one sodium-ion battery as described in claim 13, the sodium-ion battery being housed within the housing.

15. An electrical appliance, characterized in that, The device includes the energy storage device of claim 14, which supplies power to the electrical equipment.

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