Sodium ion battery, preparation method thereof, and electronic device

Abstract

The present application provides a sodium-ion battery, a preparation method thereof, and an electronic device. The sodium-ion battery includes a negative electrode plate, a negative electrode current collector, and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a disordered carbon-based material, the disordered carbon-based material includes porous carbon and a disordered carbon layer, and the disordered carbon layer is disposed on the surface of the porous carbon. When the state of charge of the sodium-ion battery is 100%, the negative electrode plate includes sodium and carbon elements, and the ratio of the mass content of the sodium element to the mass content of the carbon element is 0.30 to 0.60 based on the mass of the negative electrode plate. By regulating the ratio of the mass content of the sodium element to the mass content of the carbon element in the negative electrode plate within the scope of the present application, the energy density of the sodium-ion battery is improved. In addition, the sodium-ion battery can also have a high first coulombic efficiency and good cycle performance.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a sodium ion battery, a preparation method thereof, and an electronic device. Background Art

[0002] Since Sony Corporation of Japan commercialized lithium-ion batteries in 1991, lithium-ion batteries have been rapidly used in consumer electronics, electric vehicles, energy storage and other fields due to their high energy density, high operating voltage, good load characteristics, fast charging speed, safety and pollution-free.

[0003] Due to the limited availability of lithium in the Earth's crust, the price of lithium carbonate has been rising recently, making lithium-ion batteries very expensive. Consequently, sodium-ion batteries, due to the abundant sodium reserves in the Earth's crust, have gained popularity in the industry. Their low theoretical cost offers the potential to replace lithium-ion batteries in some areas of the market, such as energy storage and low-speed electric vehicles.

[0004] Currently, the most commonly used negative electrode active material for sodium-ion batteries is hard carbon. Hard carbon materials have an internal structure composed of disordered carbon layers and contain numerous defects and pores. The hard carbon materials currently under research have low initial coulombic efficiency and compaction density, resulting in low energy density in sodium-ion batteries. Summary of the Invention

[0005] The purpose of the embodiments of the present application is to provide a sodium ion battery and its preparation method and electronic device to improve the energy density of the sodium ion battery. The specific technical solution is as follows:

[0006] In a first aspect, the present application provides a sodium-ion battery comprising a negative electrode plate, a negative electrode current collector, and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material comprising a disordered carbon-based material, the disordered carbon-based material comprising porous carbon and a disordered carbon layer, the disordered carbon layer disposed on the surface of the porous carbon; when the state of charge of the sodium-ion battery is 100%, the negative electrode plate comprises sodium and carbon, and the ratio of the mass content of the sodium element to the mass content of the carbon element is 0.30 to 0.60 based on the mass of the negative electrode plate. The mass content ratio of the sodium element to the carbon element in the negative electrode plate is within the range of the present application, indicating that the disordered carbon-based material has a high sodium storage capacity, and the provision of the disordered carbon layer can reduce the average potential of the negative electrode, thereby improving the energy density of the sodium-ion battery. Furthermore, the sodium-ion battery can also have a high first coulombic efficiency and good cycle performance.

[0007] In some embodiments of the present application, when the state of charge of the sodium-ion battery is 100%, the negative electrode plate includes sodium and carbon, and the ratio of the mass content of the sodium element to the mass content of the carbon element is 0.40 to 0.55. Controlling the mass content ratio of the sodium element to the carbon element within the above preferred range is beneficial for comprehensively further improving the energy density, first coulombic efficiency, and cycle performance of the sodium-ion battery.

[0008] In some embodiments of the present application, based on the mass of the negative electrode sheet, the mass content of the sodium element is 20% to 35%, indicating that the sodium storage capacity in the disordered carbon-based material is high, so that the sodium ion battery has a higher energy density.

[0009] In some embodiments of the present application, the single-side coating weight of the negative electrode active material layer is CW mg / cm 2 The single-side coating capacity of the negative electrode active material layer is B mAh / cm 2 , CW and B satisfy: 1.50≤CW / B≤3.00. Regulating the CW / B value within the above range is beneficial to comprehensively improve the energy density, first coulombic efficiency and cycle performance of sodium-ion batteries.

[0010] In some embodiments of the present application, 1.80≤B≤3.00 and / or 4.00≤CW≤9.00. Regulating the values of CW and B within the above ranges is beneficial to comprehensively improve the energy density, first coulombic efficiency, and cycle performance of sodium ion batteries.

[0011] In some embodiments of the present application, the compaction density of the negative electrode sheet is E g / cm 3 The porosity of the negative electrode sheet is F, E, and F satisfy the following conditions: 35% ≤ F / E ≤ 75%. Controlling the F / E value within the above range is beneficial to comprehensively improve the energy density, first coulombic efficiency, and cycle performance of sodium-ion batteries.

[0012] In some embodiments of the present application, 0.60≤E≤1.00 and / or 30%≤F≤55%. Regulating the values of E and F within the above ranges is beneficial to comprehensively improve the energy density, first coulombic efficiency and cycle performance of sodium ion batteries.

[0013] In some embodiments of the present application, a half-cell is assembled using sodium metal as a counter electrode and a negative electrode sheet. In the charge-discharge curve, the capacity is C when the voltage is greater than or equal to 0V and less than 0.2V, and the capacity is D when the voltage is greater than or equal to 0.2V and less than or equal to 1.2V, where C and D satisfy the following: C / D>4. When the C / D value is greater than 4, the potential in the half-cell is low, the voltage in the sodium-ion battery is high, and the energy density of the sodium-ion battery is improved.

[0014] A second aspect of the present application provides a method for preparing a sodium ion battery according to any of the aforementioned embodiments, wherein the method for preparing a disordered carbon-based material comprises the following steps:

[0015] (1) ball-milling a phenolic compound and an amine compound to obtain a uniformly mixed powder; the mass ratio of the phenolic compound to the amine compound is 1:(1 to 4);

[0016] (2) solidifying the uniformly mixed powder at a temperature of 100° C. to 200° C., then calcining at a temperature of 850° C. to 950° C. for 1 to 5 hours under inert gas protection, then cooling to <100° C., crushing and grading, and sieving to obtain porous carbon;

[0017] (3) coating the surface of the porous carbon with a disordered carbon layer to obtain a disordered carbon-based material;

[0018] The coating treatment in step (3) comprises the following steps: heating the porous carbon to 850° C. to 950° C. in an inert atmosphere, keeping the temperature in a methane atmosphere for 1.5 to 8 hours, and then cooling to room temperature; or

[0019] The coating treatment in step (3) includes the following steps: heating the porous carbon to 850°C to 950°C in an inert atmosphere, keeping it warm in a carbon dioxide atmosphere for 1.5h to 2.5h, and then keeping it warm in a methane atmosphere for 3.5h to 4.5h before cooling it to room temperature.

[0020] In a third aspect, the present application provides an electronic device, which includes the sodium ion battery described in any of the preceding embodiments; or, includes the sodium ion battery prepared by the preparation method described in any of the preceding embodiments.

[0021] Beneficial effects of the embodiments of the present application:

[0022] The present invention provides a sodium-ion battery, a preparation method thereof, and an electronic device. The sodium-ion battery comprises a negative electrode plate, a negative electrode current collector, and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprising a disordered carbon-based material, the disordered carbon-based material comprising porous carbon and a disordered carbon layer, the disordered carbon layer disposed on the surface of the porous carbon. When the sodium-ion battery has a state of charge of 100%, the negative electrode plate comprises sodium and carbon, and the ratio of the mass content of sodium to the mass content of carbon is 0.30 to 0.60 based on the mass of the negative electrode plate. This mass content ratio of sodium to carbon in the negative electrode plate is within the range of the present invention, indicating that the disordered carbon-based material has a high sodium storage capacity, and the provision of the disordered carbon layer can reduce the average potential of the negative electrode, thereby improving the energy density of the sodium-ion battery. Furthermore, the sodium-ion battery can also have a high initial coulombic efficiency and good cycle performance.

[0023] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0025] Figure 1 1-4 is the charge and discharge curve of Example 1-4;

[0026] Figure 2 Schematic diagram of the test of the mass content of sodium and carbon elements in the negative electrode. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field based on this application are within the scope of protection of this application.

[0028] The first aspect of the present application provides a sodium ion battery, which includes a negative electrode plate, a negative electrode current collector of the negative electrode plate and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a disordered carbon-based material, the disordered carbon-based material includes porous carbon and a disordered carbon layer, and the disordered carbon layer is arranged on the surface of the porous carbon. The above-mentioned "surface" can be the entire surface of the porous carbon, or a part of the surface of the porous carbon, or the surface of the pores inside the porous carbon. When the state of charge (SOC) of the sodium ion battery is 100%, the negative electrode plate includes sodium and carbon elements, and the ratio of the mass content of the sodium element to the mass content of the carbon element is 0.30 to 0.60 based on the mass of the negative electrode plate. For example, the mass ratio of the sodium element to the carbon element is 0.30, 0.33, 0.36, 0.40, 0.44, 0.48, 0.50, 0.53, 0.55, 0.60, or any value between any two of the above numerical ranges. In the disordered carbon-based material of the present application, a disordered carbon layer is provided on the surface of the porous carbon. During the charge and discharge cycle of the sodium ion battery, the disordered carbon-based material uses part of the metalloid sodium to induce sodium metal deposition on the surface of the disordered carbon-based material to generate sodium storage behavior, thereby improving the first coulombic efficiency of the sodium ion battery. When the SOC of the sodium-ion battery is 100%, when the mass content ratio of sodium and carbon in the negative electrode is less than 0.30, the sodium content is too low, indicating that the sodium storage capacity in the disordered carbon-based material is reduced, which will affect the energy density of the sodium-ion battery and manifest as a low weight energy density of the sodium-ion battery; when the mass content ratio of sodium and carbon in the disordered carbon-based material is greater than 0.60, the sodium content is too high, specifically, excessive sodium metal is deposited on the surface of the particles of the disordered carbon-based material, and then frequently contacts with the electrolyte and consumes film formation, which will affect the cycle performance of the sodium-ion battery; when the mass content ratio of sodium and carbon in the negative electrode is controlled within the scope of this application, the sodium storage capacity in the disordered carbon-based material is high, and the provision of the disordered carbon layer can reduce the average potential of the negative electrode, thereby improving the energy density of the sodium-ion battery. At the same time, the sodium-ion battery can also have a high first coulombic efficiency and good cycle performance.

[0029] Preferably, when the state of charge of the sodium ion battery is 100%, the negative electrode plate includes sodium and carbon, and the mass content ratio of the sodium element to the carbon element is 0.40 to 0.55. For example, the mass content ratio of the sodium element to the carbon element is 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.55, or any value within a range consisting of any two of the above values. When the state of charge of the sodium ion battery is 100%, regulating the mass content ratio of the sodium element to the carbon element within the above preferred range is beneficial to comprehensively further improve the energy density, first coulombic efficiency, and cycle performance of the sodium ion battery.

[0030] The term "negative electrode active material layer disposed on at least one surface of the negative electrode current collector" refers to a negative electrode active material layer disposed on one surface of the negative electrode current collector, or a negative electrode active material layer disposed on both surfaces of the negative electrode current collector. The "surface" may refer to a portion of the surface of the negative electrode current collector or the entire surface.

[0031] The present application has no particular restrictions on the method for regulating the mass content ratio of sodium and carbon, as long as the purpose of the present application can be achieved. For example, the amount of disordered carbon layer coated on the porous carbon surface can be regulated by regulating the preparation parameters in the preparation process of the disordered carbon-based material, such as the mass ratio of phenolic compounds and amine compounds, the coating treatment time, the coating treatment method, etc., so that the specific surface area and pore size of the disordered carbon-based material can be regulated, and the mass content ratio of sodium and carbon changes with the change of the specific surface area and pore size of the disordered carbon-based material.

[0032] The specific surface area and pore size of the porous carbon are not particularly limited in this application, as long as the purpose of this application can be achieved. For example, the specific surface area of the porous carbon is 5m 2 / g to 80m 2 / g, and the pore size of the porous carbon is 0.1nm to 5nm.

[0033] In some embodiments of the present application, based on the mass of the negative electrode sheet, the mass content of the sodium element is 20% to 35%, indicating that the sodium storage capacity in the disordered carbon-based material is high, the sodium-ion battery has a higher energy density, and also helps to improve the rate performance and cycle performance of the sodium-ion battery.

[0034] The present application has no particular limitation on the mass content of carbon in the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, based on the mass of the negative electrode sheet, the mass content of carbon is 50% to 75%.

[0035] In some embodiments of the present application, the single-side coating weight of the negative electrode active material layer is CW mg / cm 2 The single-side coating capacity of the negative electrode active material layer is B mAh / cm 2 , CW and B satisfy: 1.50 ≤ CW / B ≤ 3.00. For example, the value of CW / B is 1.50, 1.60, 1.70, 1.80, 1.90, 2.00, 2.10, 2.20, 2.30, 2.40, 2.50, 2.60, 2.70, 2.80, 2.90, 3.00, or any value between any two of the above ranges. Controlling the CW / B value within the above range is beneficial for comprehensively balancing the energy density, rate performance, and cycle performance of sodium-ion batteries.

[0036] In this application, the single-side coating weight CW of the negative electrode active material layer refers to the unit weight (mg / cm2) of the negative electrode active material layer (single side) on the negative electrode sheet. 2 ); Single-side coating capacity of negative electrode active material layer B refers to the negative electrode sheet per unit area (cm 2 ) on a single side of the active material contribution to the capacity (i.e. mAh / cm 2 ).

[0037] In some embodiments of the present application, 1.80≤B≤3.00 and / or 4.00≤CW≤9.00. For example, the value of B is 1.80, 2.00, 2.10, 2.20, 2.30, 2.40, 2.50, 2.60, 2.70, 2.80, 2.90, 3.00, or any value between any two of the above numerical ranges. For example, the value of CW is 4.00, 4.50, 5.00, 5.50, 6.00, 6.50, 7.00, 7.50, 8.00, 8.50, 9.00, or any value between any two of the above numerical ranges. By regulating the values of CW and B within the above ranges, the negative electrode active material layer has more disordered carbon-based materials per unit area and has a larger sodium storage capacity. The negative electrode active material layer has a larger capacity contributed by the disordered carbon-based materials per unit area, which is beneficial to improving the energy density of the sodium ion battery.

[0038] In some embodiments of the present application, the compaction density of the negative electrode sheet is E g / cm 3 , the porosity of the negative electrode sheet is F, E and F satisfy: 35% ≤ F / E ≤ 75%. For example, the value of F / E is 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or any value between any two of the above numerical ranges. By regulating the value of F / E within the above range, the compaction density and porosity of the negative electrode sheet are matched, which is conducive to comprehensively improving the energy density and cycle performance of the sodium ion battery. In addition, the compaction density of the negative electrode sheet is relatively high, the porosity of the negative electrode sheet is relatively low, the thickness of the negative electrode sheet is thin, the volume energy density is increased and the sodium ion transmission distance is shortened, which can also improve the rate performance of the sodium ion battery.

[0039] In some embodiments of the present application, 0.60≤E≤1.00 and / or 30%≤F≤55%. For example, the value of E is 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00 or any value between any two of the above numerical ranges. For example, the value of F is 30%, 35%, 40%, 45%, 50%, 55% or any value between any two of the above numerical ranges. When the values of E and F are regulated within the above ranges, when the negative electrode active material layer provides a higher energy density, the appropriate gaps between the particles provide sufficient buffer space for the volume expansion of the sodium ion battery during charge and discharge, thereby helping to comprehensively improve the energy density, first coulombic efficiency and cycle performance of the sodium ion battery.

[0040] The present application does not particularly limit the method for controlling the compaction density E and porosity F of the negative electrode sheet, as long as the objectives of the present application can be achieved. For example, the compaction density E can be controlled by adjusting the pressure during the cold pressing process of the negative electrode sheet, and the porosity F changes with the compaction density E.

[0041] In some embodiments of the present application, sodium metal is used as a counter electrode and a negative electrode sheet to assemble a half-cell. In the charge-discharge curve, the capacity in the voltage range of greater than or equal to 0V to less than 0.2V is C, and the capacity in the voltage range of greater than or equal to 0.2V to less than or equal to 1.2V is D, and C and D satisfy: C / D>4. When the value of C / D is greater than 4, the potential in the half-cell is low, the potential in the sodium ion battery (unless otherwise specified, in this application, refers to the full battery) is high, and the energy density of the sodium ion battery is improved. When C / D>4, the larger the value, the higher the potential of the sodium ion battery and the higher the energy density of the sodium ion battery.

[0042] This application does not impose any particular restrictions on the negative electrode current collector, as long as the purpose of this application can be achieved. For example, the negative electrode current collector may include aluminum foil, aluminum alloy foil, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, or copper foam. In this application, there is no particular restriction on the thickness of the negative electrode current collector or the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector is 6μm to 15μm, and the thickness of the negative electrode active material layer is 30μm to 130μm.

[0043] In some embodiments of the present application, the negative electrode active material layer further includes at least one of a negative electrode conductive agent or a thickener. The present application does not particularly limit the types of the negative electrode conductive agent and the thickener, as long as the purpose of the present application can be achieved. The present application does not particularly limit the mass ratio of the negative electrode active material, the negative electrode conductive agent, the thickener, and the negative electrode binder in the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the mass ratio of the negative electrode active material, the negative electrode conductive agent, the thickener, and the negative electrode binder in the negative electrode active material layer is (95-98):(0-1.5):(0.5-1.5):(0.8-2).

[0044] In some embodiments of the present application, the sodium ion battery further includes a positive electrode sheet and a diaphragm, which is disposed between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet, prevent internal short circuit of the electrochemical device, allow electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process.

[0045] The present application has no special restrictions on the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The present application has no special restrictions on the type of positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the positive electrode current collector may include aluminum foil, aluminum alloy foil, etc. The positive electrode active material layer of the present application includes positive electrode active material, and the present application has no special restrictions on the type of positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include layered oxides (such as NaCu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 O2), Prussian blue series (such as NaFe[Fe(CN)6] or Na2Fe[Fe(CN)6]), or polyanion compounds (such as sodium vanadium phosphate), etc. In the present application, there is no particular restriction on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5μm to 20μm, preferably 6μm to 18μm. The thickness of the positive electrode active material layer is 30μm to 120μm. Optionally, the positive electrode active material layer may also include a positive electrode conductive agent and a positive electrode binder. The present application has no particular restriction on the types of positive electrode conductive agents and positive electrode binders in the positive electrode active material layer, as long as the purpose of the present application can be achieved. The present application has no particular restriction on the mass ratio of the positive electrode active material, positive electrode conductive agent, and positive electrode binder in the positive electrode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. For example, the mass ratio of the positive electrode active material, the positive electrode conductor, and the positive electrode binder in the positive electrode active material layer is (94-98):(0.5-2.5):(1.5-3.5).

[0046] The present application does not particularly limit the separator, as long as it can achieve the purpose of the present application. For example, the material of the separator may include, but is not limited to, at least one of polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of separator may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane, or a spun membrane.

[0047] The sodium-ion battery of the present application further includes a packaging bag and an electrolyte, wherein the electrolyte, positive electrode sheet, separator, and negative electrode sheet are contained in the packaging bag. The present application does not particularly limit the packaging bag and electrolyte, and they can be packaging bags and electrolytes known in the art, as long as they can achieve the purpose of the present application. For example, the packaging bag can be an aluminum-plastic film or a steel shell. The electrolyte can include a sodium salt and a non-aqueous solvent. In some embodiments of the present application, the sodium salt can include at least one of sodium perchlorate or sodium hexafluorophosphate (NaPF6). The non-aqueous solvent can be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof. The carbonate compound can include, but is not limited to, at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluorocarbon compound. The chain carbonate compound can include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), or ethylmethyl carbonate (MEC). Cyclic carbonate compounds may include but are not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). Fluorocarbonate compounds may include but are not limited to fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate or trifluoromethylethylene carbonate. The above-mentioned carboxylate compounds may include but are not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valerolactone, mevalonolactone or caprolactone. The ether compound may include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvent may include, but is not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or a phosphate ester.

[0048] A second aspect of the present application provides a method for preparing a sodium ion battery according to any of the aforementioned embodiments, wherein the method for preparing a disordered carbon-based material comprises the following steps:

[0049] (1) ball-milling a phenolic compound and an amine compound to obtain a uniformly mixed powder; the mass ratio of the phenolic compound to the amine compound is 1:(1 to 4); for example, the mass ratio of the phenolic compound to the amine compound is 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, or any ratio between any two of the above ratio ranges.

[0050] (2) solidifying the uniformly mixed powder at a temperature of 100° C. to 200° C., then calcining at a temperature of 850° C. to 950° C. for 1 to 5 hours under inert gas protection, then cooling to <100° C., crushing and grading, and sieving to obtain porous carbon;

[0051] (3) coating the surface of the porous carbon with a disordered carbon layer to obtain a disordered carbon-based material;

[0052] Wherein, the coating treatment in step (3) includes the following steps: heating the porous carbon to 850°C to 950°C in an inert atmosphere, keeping it warm in a methane atmosphere for 1.5h to 8h, and then cooling it to room temperature; or, the coating treatment in step (3) includes the following steps: heating the porous carbon to 850°C to 950°C in an inert atmosphere, keeping it warm in a carbon dioxide atmosphere for 1.5h to 2.5h, and then keeping it warm in a methane atmosphere for 3.5h to 4.5h, and then cooling it to room temperature.

[0053] The present application has no particular limitation on the size of the standard sieve used for screening in step (2), as long as the purpose of the present application can be achieved. For example, the size of the standard sieve is 200 to 600 mesh to obtain porous carbon with an average particle size of 5 μm to 60 μm.

[0054] The present application does not particularly limit the types of phenolic compounds and amine compounds, as long as the purpose of the present application can be achieved. For example, the phenolic compound may include, but is not limited to, at least one of bisphenol A, resorcinol, naphthol, or aminophenol, and the amine compound may include, but is not limited to, at least one of hexamethylenetetramine, melamine, urea, C1 to C20 alkylamine, cetyltrimethylammonium bromide (CTAB), or C6 to C20 aromatic amine.

[0055] The present application has no particular limitation on the type of inert atmosphere, as long as the purpose of the present application can be achieved. For example, the inert atmosphere includes but is not limited to at least one of nitrogen, argon, or helium.

[0056] The preparation steps of the sodium-ion battery of the present application may also include but are not limited to the following steps: stacking the positive electrode sheets, the separator and the negative electrode sheets in sequence, and performing operations such as winding and folding on them as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a sodium-ion battery; or stacking the positive electrode sheets, the separator and the negative electrode sheets in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly with a stacked structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a sodium-ion battery.

[0057] In a third aspect, the present application provides an electronic device comprising the sodium-ion battery described in any of the aforementioned embodiments; or comprising a sodium-ion battery prepared by the preparation method described in any of the aforementioned embodiments. Therefore, the electronic device has a high energy density.

[0058] The electronic device of the present application is not particularly limited and can be any electronic device known in the art. For example, the electronic device can include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a sodium ion capacitor.

[0059] Example

[0060] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods.

[0061] Test methods and equipment:

[0062] Tests on the mass content of sodium and carbon, and the mass content ratio of sodium and carbon:

[0063] The specific test method is as follows: the sodium ion battery is charged at a constant current of 0.2C to a voltage of 3.95V, and then charged at a constant voltage to 0.02C; at this time, the SOC of the sodium ion battery is 100%; the sodium ion battery with 100% SOC is disassembled, the fully charged negative electrode plate is taken out, and it is cleaned 3 times with dimethyl carbonate (DMC) in a drying room (humidity <1%) to wash away the residual electrolyte and then dried. Then, ion polishing is used to cut it in a direction perpendicular to the surface of the negative electrode plate to expose the cross section of the cut negative electrode active material layer. The cross section of the obtained negative electrode active material layer is transferred to a scanning electron microscope with an energy spectrometer, and the test area is selected for energy spectrum testing. The test elements are Na and C. The test method is surface scanning. Test area selection: see Figure 2 Schematic diagram of the test, an area of 25 μm × 25 μm is arbitrarily selected as the test area 40 in the cross-sectional area of the negative electrode active material layer 30 which is greater than or equal to 5 μm away from the surface of the negative electrode sheet 001 (including the negative electrode current collector 20 and the negative electrode active material layer 30 arranged on the surface of the negative electrode current collector 20), and the energy spectrum test time is 4 minutes of surface scanning. The mass contents of the Na element and the C element are obtained by test, and the mass content ratio of the Na element to the C element is calculated.

[0064] Compaction density E test of negative electrode sheet:

[0065] The negative electrode sheet in the sodium ion battery is punched into small discs with a diameter of D = 14 mm. The mass of the small discs is weighed and their thickness is measured. After deducting the mass and thickness of the negative electrode current collector, the mass and thickness of the negative electrode active material layer are obtained. The calculation formula for compaction density is: compaction density = mass of negative electrode active material layer / area of negative electrode sheet / thickness of negative electrode active material layer, negative electrode sheet area = π(D / 2) 2 .

[0066] Porosity test of negative electrode sheet:

[0067] First, cut the negative electrode active material layer into a size of 0.5cm×1cm, use conductive glue to stick the cut negative electrode material layer on a 1cm×1.5cm silicon wafer carrier, and then use argon ion polishing (parameters: 8KV acceleration voltage, 4h for each sample) to process one end of the negative electrode plate. Argon ion polishing uses a high-voltage electric field to ionize argon gas to produce an ion state. The generated argon ions bombard the surface of the negative electrode plate at high speed under the action of the acceleration voltage, and the negative electrode plate is eroded layer by layer to achieve the polishing effect. After the cross-section of the negative electrode active material layer is prepared, it is analyzed using a scanning electron microscope (SEM). The scanning electron microscope used in this application is the JSM-6360LV model of JEOL to analyze the morphology and structure of the sample.

[0068] A test area of 1000 μm × 100 μm was selected on the surface of the negative electrode active material layer. The surface of the negative electrode active material layer refers to the surface of the negative electrode active material layer on the side away from the negative electrode current collector. The gaps between all particles in the area were counted. The brightness and darkness between the particles and pores in the image were distinguished. The brighter ones were particles, and the darker ones were pores. Then, ImageJ software was used to process the image, and the particles were adjusted to a black background and the pores were adjusted to white. The area of the pores in the entire image was counted to obtain the surface porosity.

[0069] Charge and discharge test:

[0070] Preparation of half-cell (button cell):

[0071] Using metallic sodium as the counter electrode, a sodium sheet with a diameter of 18 mm and a thickness of 0.6 mm, a separator, and the negative electrode sheets in each embodiment and comparative example (cut into a diameter of 18 mm and used) were assembled and stacked together in sequence, and the electrolyte prepared in Example 1 was added. The positive and negative electrodes were placed in button-type stainless steel shells and encapsulated to obtain button-type batteries.

[0072] Charge and discharge test:

[0073] In an environment of 25°C, the assembled button battery was left to stand for 5 hours before the charge and discharge test. The test process was as follows: 2 After the battery is discharged at a constant current density of 0.1 mA / cm2 to a gram capacity of 600 mAh / g, the discharge (sodium insertion) process is completed; after 5 minutes of suspension, the battery is turned to the charge (sodium removal) test. The test process is as follows: 2 The current density is constant current charged to 2V.

[0074] Record the gram capacity of the first discharge and first charge respectively. The first coulombic efficiency (ICE) = first charge capacity / first discharge capacity × 100%;

[0075] Record the gram capacity and voltage during the charge and discharge process, and calculate the gram capacity distribution within each voltage range during the sodium removal process. For example, in the first sodium removal curve, record the capacity C in the first voltage range U1 (0V≤U1<0.2V) and the capacity D in the second voltage range U2 (0.2V≤U2≤1.2V).

[0076] Single-sided coating capacity B test of negative electrode active material:

[0077] After the negative electrode materials of each embodiment and comparative example were made into negative electrode sheets and assembled into button batteries (the preparation method was the same as that of "Preparation of Half-cell (Button Battery)" in "Charge and Discharge Test"), the assembled button batteries were left to stand for 5 hours in an environment of 25°C and then subjected to charge and discharge tests. The test process was as follows: 2After the battery is discharged at a constant current density of 1000 mAh / g to a gram capacity of 600 mAh / g, the discharge (sodium insertion) process ends. During the discharge process, the discharge protection voltage is set to -15 mV. If the discharge process does not reach 600 mAh / g and reaches -15 mV, the discharge (sodium insertion) process ends and turns to the charging process.

[0078] After the charge (sodium removal) test, the test process is: at 0.1mA / cm 2 The current density was set to 2 V. The capacity during the charging process was recorded and divided by the negative electrode area to obtain the single-side coating capacity B.

[0079] Energy density test:

[0080] In an environment of 25°C, the sodium ion battery was charged at a constant current of 0.2C to a voltage of 3.95V, and then charged at a constant voltage to 0.02C; discharged at a constant current of 0.2C to a voltage of 1.5V, which was recorded as one cycle, and the discharge capacity and discharge energy of the first cycle were recorded; the discharge energy was divided by the discharge capacity to obtain the average discharge voltage; and the sodium ion battery weight at 50% SOC was tested to obtain the weight of the sodium ion battery.

[0081] Energy density = discharge capacity × average discharge voltage / sodium ion battery weight.

[0082] Cyclic performance test:

[0083] In an environment of 25°C, the sodium ion batteries in each embodiment and comparative example were charged at a constant current of 1C to a voltage of 3.95V, then charged at a constant voltage of 0.05C; and discharged at a constant current of 1C to a voltage of 1.5V. This cycle was recorded as one cycle. This cycle was repeated for 5000 times, and the capacity retention rate of the sodium ion battery during the cycle was recorded. If the capacity of the sodium ion battery during the cycle was less than 80% of the initial cycle capacity, the cycle was terminated, and the final number of cycles was recorded to characterize the cycle performance.

[0084] Example 1-1

[0085] <Preparation of disordered carbon-based materials>

[0086] (1) bisphenol A and hexamethylenetetramine were ball-milled in a mass ratio of 1:1 to obtain a uniformly mixed powder;

[0087] (2) solidifying the mixed powder at 160° C., calcining at 900° C. for 2 h under nitrogen protection, cooling to 50° C., crushing and classifying, and sieving through a 300-mesh standard sieve to obtain porous carbon;

[0088] (3) The porous carbon obtained by screening in step (2) is placed in a rotary kiln, heated to 900°C in a nitrogen atmosphere, kept warm for 6 hours in a methane atmosphere, and cooled to room temperature in a nitrogen atmosphere to complete the coating treatment of the disordered carbon layer to obtain a disordered carbon-based material, wherein the specific surface area BET of the disordered carbon-based material is 5m 2 / g, pore size is 0.4nm.

[0089] <Preparation of negative electrode sheet>

[0090] The disordered carbon-based material prepared above was used as the negative electrode active material and mixed with the negative electrode binder styrene-butadiene rubber (abbreviated as SBR) and the thickener sodium carboxymethyl cellulose (CMCNa) in a mass ratio of 97:2:1. Deionized water was then added as a solvent and stirred thoroughly to obtain a negative electrode slurry with a solid content of 40 wt% and a uniform system. The negative electrode slurry was evenly coated on one surface of a negative electrode current collector aluminum foil with a thickness of 10 μm and dried at 70 ° C to obtain a single-sided coated negative electrode active material layer (CW = 6.49 mg / cm 2 ) to form a negative electrode sheet. The above steps were then repeated on the other surface of the aluminum foil to obtain a negative electrode sheet coated on both sides with a negative electrode active material layer. After cold pressing, cutting, and slitting, the sheet was dried under vacuum at 120°C for 12 hours to obtain a negative electrode sheet measuring 76 mm x 851 mm for later use.

[0091] <Preparation of positive electrode sheet>

[0092] The positive electrode active material NaCu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 O2, positive electrode conductive agent conductive carbon black (Super P), positive electrode binder polyvinylidene fluoride (abbreviated as PVDF) were mixed in a mass ratio of 97:1.4:1.6, N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred thoroughly to obtain a positive electrode slurry with a solid content of 72wt% and a uniform system. The positive electrode slurry was evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 85℃ to obtain a single-sided positive electrode active material layer (CW=13mg / cm 2 ) positive electrode sheet. The above steps are then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated on both sides with a positive electrode active material layer. After cold pressing, cutting, and slitting, the sheet is dried under vacuum at 85°C for 4 hours to obtain a positive electrode sheet measuring 74 mm x 867 mm for later use.

[0093] <Preparation of Separator>

[0094] The diaphragm includes a 7μm thick polyethylene (PE) substrate and an inorganic layer with a thickness of 1μm arranged on both surfaces of the substrate along its own thickness direction (the inorganic layer includes aluminum oxide and binder polyvinylidene fluoride in a mass ratio of 90:10). The total thickness of the diaphragm is 9μm.

[0095] <Preparation of Electrolyte>

[0096] In a dry (H2O <1ppm) argon atmosphere glove box, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio. 1,3-Propane Sultone and fluoroethylene carbonate were then added, dissolved, and thoroughly stirred. Sodium hexafluorophosphate (SHP) was then added and mixed thoroughly to form an electrolyte. The mass percentage of 1,3-Propane Sultone in the electrolyte was 1.5%, the mass percentage of fluoroethylene carbonate was 2%, and the concentration of the sodium salt in the electrolyte was 1 mol / L. The remainder consisted of EC and DEC.

[0097] <Preparation of Sodium Ion Batteries>

[0098] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to act as a barrier. The electrodes are then wound to form an electrode assembly. The electrode assembly is then placed in an aluminum-plastic film packaging bag, dehydrated at 80°C, and injected with the aforementioned electrolyte. The sodium-ion battery is then produced through a series of processes, including vacuum packaging, standing, formation, degassing, shaping, and capacity testing.

[0099] Example 1-2

[0100] <Preparation of disordered carbon-based materials>

[0101] (1) to (2) are the same as in Example 1-1;

[0102] (3) The porous carbon obtained by screening in step (2) is placed in a rotary kiln, heated to 900°C in a nitrogen atmosphere and then kept warm for 6 hours. During the holding period, the first 2 hours are kept warm in a carbon dioxide atmosphere and the last 4 hours are kept warm in a methane atmosphere. After the holding period, the temperature is cooled to room temperature in a nitrogen atmosphere to complete the coating treatment of the disordered carbon layer, thereby obtaining a disordered carbon-based material, wherein the BET specific surface area of the disordered carbon-based material is 6m 2 / g, pore size is 0.4nm.

[0103] The rest is the same as Example 1-1.

[0104] Examples 1-3

[0105] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-2.

[0106] Examples 1-4

[0107] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0108] Examples 1-5

[0109] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-2.

[0110] Examples 1-6

[0111] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0112] Example 1-7 to Example 1-9

[0113] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-2.

[0114] Example 2-1 to Example 2-7

[0115] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 1-4.

[0116] Comparative Example 1

[0117] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0118] Comparative Example 2

[0119] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-2.

[0120] Comparative Example 3

[0121] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0122] Comparative Example 4

[0123] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-2.

[0124] The preparation parameters of Examples 1-1 to 1-9 and Comparative Examples 1 to 4 are shown in Table 1.

[0125] Table 1

[0126]

[0127] The preparation parameters of Example 2-1 to Example 2-7 are shown in Table 2.

[0128] Table 2

[0129]

[0130] The characteristic parameters and performance parameters of each embodiment and comparative example are shown in Table 3 and Table 4.

[0131] Table 3

[0132]

[0133]

[0134] It can be seen from Examples 1-1 to 1-9 and Comparative Examples 1 to 4 that the embodiments of the present application, by regulating the mass content ratio of sodium and carbon in the negative electrode sheet within the scope of the present application, enable the sodium ion battery of the present application to have high first coulombic efficiency, energy density and cycle performance. However, the mass content ratio of sodium and carbon in the negative electrode active material in the comparative example is not within the scope of the present application. At least one of the first coulombic efficiency, energy density and cycle performance of the sodium ion battery in the comparative example is low, and the first coulombic efficiency, energy density and cycle performance cannot be improved simultaneously. Among them, although the sodium ion batteries of Comparative Examples 1 and 2 have high first coulombic efficiency and cycle performance, their energy density is low.

[0135] Table 4

[0136]

[0137]

[0138] It can be seen from Examples 1-4 and 2-1 to 2-7 that sodium ion batteries with CW / B values, CW and B values, F / E values, F and E values, and C / D values within the ranges of this application have higher first coulombic efficiency, energy density, and cycle performance. Figure 1 The charge and discharge curves of Examples 1-4 are shown. Figure 1 It can be seen from the charge and discharge curves that in the half-cell prepared from the negative electrode sheets of Examples 1-4, the capacity C is 449 mAh / g, the capacity D is 79, and the C / D is 5.7.

[0139] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0140] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0141] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application are included in the scope of protection of the present application.

Claims

1. A sodium ion battery comprising a negative electrode plate, the negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material comprising a disordered carbon-based material, the disordered carbon-based material comprising porous carbon and a disordered carbon layer, the disordered carbon layer disposed on a surface of the porous carbon; When the state of charge of the sodium ion battery is 100%, the negative electrode plate includes sodium and carbon elements, and based on the mass of the negative electrode plate, the ratio of the mass content of the sodium element to the mass content of the carbon element is 0.30 to 0.

60.

2. The sodium ion battery according to claim 1, wherein The single-side coating weight of the negative electrode active material layer is CW mg / cm 2 The single-sided coating capacity of the negative electrode active material layer is B mAh / cm 2 , CW and B satisfy: 1.50≤CW / B≤3.

00.

3. The sodium ion battery according to claim 1, wherein Based on the mass of the negative electrode plate, the mass content of the sodium element is 20% to 35%.

4. The sodium ion battery according to claim 2, wherein 1.80≤B≤3.00 and / or 4.00≤CW≤9.

00.

5. The sodium ion battery according to claim 1, wherein The compaction density of the negative electrode sheet is E g / cm 3 The porosity of the negative electrode sheet is F, E and F satisfy: 35%≤F / E≤75%.

6. The sodium ion battery according to claim 5, wherein 0.60≤E≤1.00 and / or 30%≤F≤55%.

7. The sodium ion battery according to claim 1, wherein Sodium metal is used as the counter electrode and the negative electrode sheet is assembled into a half-cell. In the charge and discharge curve, the capacity when the voltage is greater than or equal to 0V to less than 0.2V is C, and the capacity when the voltage is greater than or equal to 0.2V to less than or equal to 1.2V is D. C and D satisfy: C / D>4.

8. The sodium ion battery according to claim 1, wherein When the state of charge of the sodium ion battery is 100%, the negative electrode plate includes sodium and carbon, and the ratio of the mass content of the sodium element to the mass content of the carbon element is 0.40 to 0.

55.

9. A method for preparing a sodium ion battery according to any one of claims 1 to 8, wherein: The preparation method of the disordered carbon-based material comprises the following steps: (1) ball-milling the phenolic compound and the amine compound to obtain a uniformly mixed powder; The mass ratio of the phenolic compound to the amine compound is 1:(1 to 4); (2) solidifying the uniformly mixed powder at a temperature of 100° C. to 200° C., then calcining at a temperature of 850° C. to 950° C. for 1 to 5 hours under inert gas protection, then cooling to <100° C., crushing and grading, and sieving to obtain porous carbon; (3) performing a coating treatment of a disordered carbon layer on the surface of the porous carbon to obtain the disordered carbon-based material; Wherein, the coating treatment in step (3) comprises the following steps: heating the porous carbon to 850° C. to 950° C. in an inert atmosphere, keeping the temperature in a methane atmosphere for 1.5 h to 8 h, and then cooling to room temperature; or, The coating treatment in step (3) includes the following steps: heating the porous carbon to 850°C to 950°C in an inert atmosphere, keeping it warm in a carbon dioxide atmosphere for 1.5h to 2.5h, and then keeping it warm in a methane atmosphere for 3.5h to 4.5h before cooling to room temperature.

10. An electronic device comprising the sodium ion battery according to any one of claims 1 to 8; or comprising the sodium ion battery prepared by the preparation method according to claim 9.

Images