A modified sodium supplement and a method for preparing the same

Abstract

This invention discloses a modified sodium supplement agent and its preparation method. The modified sodium supplement agent includes a core and a coating layer covering the surface of the core; wherein the core is a rare earth metal-doped sodium supplement agent, and the coating layer is a solid electrolyte. The modified sodium supplement agent of this invention exhibits a core-shell structure, wherein the core, being a rare earth metal-doped sodium supplement agent, can promptly absorb lattice oxygen, solving the oxygen generation problem; simultaneously, the solid electrolyte coating layer can effectively improve the conductivity of the material, thereby improving the initial coulombic efficiency, cycle performance, and energy density of sodium-ion batteries; furthermore, the preparation process of this modified sodium supplement agent is simple, easy to operate, and readily applicable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium replenishment agents for the positive electrode of sodium-ion batteries. Specifically, this invention relates to a modified sodium replenishment agent and its preparation method. Background Technology

[0002] In sodium-ion batteries, all the sodium ions required for cycling are provided by the positive electrode material. The negative electrode has a low initial efficiency, and a large amount of active sodium ions are irreversibly consumed during the first charge-discharge cycle, leading to a decrease in the reversible capacity and a shortened cycle life. Pre-sodiumification technology is the most direct and universal method to compensate for the loss of active sodium ions in the negative electrode. This involves adding sodium-rich materials (sodium replenishers) to the sodium-ion full cell to compensate for SEI losses, thereby improving the energy density and cycle life of the sodium-ion full cell.

[0003] Based on different pre-sodiuming principles, pre-sodiuming technologies can be divided into five categories: short-circuit pre-sodiuming, electrochemical pre-sodiuming, sodium metal physical pre-sodiuming, chemical pre-sodiuming, and cathode pre-sodiuming. Among these, short-circuit pre-sodiuming and sodium metal physical pre-sodiuming require the use of highly reactive metallic sodium as a reducing agent. However, metallic sodium readily reacts chemically with water and oxygen, thus requiring strictly anhydrous and oxygen-free conditions. Electrochemical pre-sodiuming involves battery disassembly and reassembly, a cumbersome process that limits its application. Chemical pre-sodiuming, to achieve true industrial application, still needs to address many practical large-scale production issues, such as electrode sampling location, electrode thickness, electrode porosity, and the uniformity of pre-sodiuming penetration depth. Furthermore, precise control of the pre-sodiuming reaction requires further in-depth research. In contrast, cathode pre-sodiuming only requires adding a small amount of sodium supplementer to the cathode slurry, which allows irreversible decomposition during the first week of charging, releasing sufficient active sodium. This method has received significant attention in recent years due to its simple operation and high process adaptability.

[0004] However, existing sodium-additive cathodes still have certain problems in use, such as: how to absorb the gases produced during decomposition; the impact of gas generation on electrode interface changes on subsequent cycles of sodium-ion batteries; and whether decomposition products will continue to participate in reactions. Furthermore, during sodium ion migration, the sodium-additive generates oxygen, which can then react with the sodium-containing anode, exacerbating side reactions with the electrolyte and cathode interface, ultimately leading to a deterioration in the high-temperature storage life of sodium-ion batteries. In addition, the high resistivity, low electronic conductivity, and slow decomposition of the sodium-additive powder limit its charge-discharge performance.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a modified sodium supplement and a method for its preparation.

[0007] In a first aspect, embodiments of the present invention provide a modified sodium supplement agent, comprising a core and a coating layer covering the surface of the core; wherein the core is a rare earth metal-doped sodium supplement agent, and the coating layer is a solid electrolyte.

[0008] The modified sodium supplement in this embodiment of the invention exhibits a core-shell structure, wherein the core is a rare earth metal-doped sodium supplement that can absorb lattice oxygen in a timely manner, thus solving the problem of oxygen production; at the same time, the solid electrolyte coating layer can effectively improve the conductivity of the material, thereby improving the first coulombic efficiency, cycle performance and energy density of sodium-ion batteries.

[0009] In some embodiments, the particle size D50 of the core is 100 nm to 50 μm;

[0010] And / or, the coating thickness of the coating layer is 1 nm to 100 nm.

[0011] In some embodiments, the rare earth metal includes at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0012] In some embodiments, the sodium supplement is one or a mixture of two of inorganic sodium supplements or organic sodium supplements;

[0013] Preferably, the inorganic sodium supplement includes at least one of Na3N, Na3P, Na2O, NaNO2, Na2CO3, Na2NiO2, NaCrO2, Na5FeO4, NaBH4, and NaNH2;

[0014] Preferably, the organic sodium supplement includes at least one of Na2C6O6, Na2C6H2O6, CH3COONa, PABZ-Na, EDTA-4Na, DTPA-5Na, Na2C4O4, Na2C2O4, and Na2C3O5.

[0015] In some embodiments, the solid electrolyte includes at least one of β-Al2O3 solid electrolyte, NASICON-type solid electrolyte, sulfide solid electrolyte, and complexed hydride solid electrolyte.

[0016] In some embodiments, the sodium supplementer accounts for 50% to 99% of the mass of the modified sodium supplementer;

[0017] And / or, the rare earth metal accounts for 0.05% to 10% of the mass of the modified sodium supplement;

[0018] And / or, the solid electrolyte accounts for 0.95% to 50% of the mass of the modified sodium supplement.

[0019] Secondly, embodiments of the present invention also provide a method for preparing the modified sodium supplement as described in the first aspect, comprising the following steps:

[0020] (1) The sodium supplement agent is mixed with a rare earth metal source and then calcined to obtain a rare earth metal doped sodium supplement agent.

[0021] (2) The rare earth metal doped sodium supplement is added to the solid electrolyte powder and mixed evenly. Then the mixture is subjected to high-temperature sintering once and high-temperature sintering twice to obtain the modified sodium supplement.

[0022] In some embodiments, in step (1), the rare earth metal source includes at least one of rare earth metal element, rare earth metal oxide, rare earth metal sulfide, rare earth metal phosphide, rare earth metal nitride, and rare earth metal halide; the calcination treatment is carried out in an air atmosphere or an oxygen atmosphere, the calcination treatment temperature is 500℃~600℃, and the calcination time is 1h~10h;

[0023] And / or, in step (2), the first high-temperature sintering and / or the second high-temperature sintering are carried out in an oxygen atmosphere, the temperature of the first high-temperature sintering is 600℃~800℃ and the sintering time is 3h~10h, and the temperature of the second high-temperature sintering is 1000℃~1200℃ and the sintering time is 3h~10h.

[0024] The features and advantages described above for modified sodium supplements also apply to the preparation method of modified sodium supplements, and will not be repeated here.

[0025] Thirdly, embodiments of the present invention also provide a sodium-ion battery positive electrode sheet, comprising a positive electrode active material, a conductive agent, a binder, a current collector, and the modified sodium supplement agent described in the first aspect;

[0026] The positive electrode active material includes Na2Fe2(SO4)3 and Na2Fe(SO4). 2.2 H2O, Na3V2(PO3), Na3MnTi(PO3)3, Na2FeP2O7, Na2CoP2O7, Na3(VPO4)2F3, Na4Fe3(PO4)2P2O7, Na2MnSiO4, Na3CoB5O 10 At least one of them;

[0027] And / or, the conductive agent includes at least one of Super P, Ketjen Black, acetylene black, carbon black, carbon nanotubes, graphene, conductive graphite, carbon fiber, conductive carbon nanotubes, and mesoporous carbon.

[0028] And / or, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, styrene-butadiene rubber, sodium carboxymethyl cellulose, polypropylene, polyethylene, polyacrylic acid, carboxymethyl cellulose, sodium alginate, and gelatin.

[0029] In this embodiment of the invention, by adding the above-mentioned modified sodium replenishing agent to the positive electrode of a sodium-ion battery, the sodium replenishing agent decomposes and releases active sodium ions during the battery charging process to replenish sodium for the sodium-ion battery. This can compensate for the irreversible sodium loss during the first charge and discharge cycle and improve the capacity and cycle life of the sodium-ion battery.

[0030] Fourthly, embodiments of the present invention also provide a sodium-ion battery, comprising a negative electrode, a separator, an electrolyte, and the sodium-ion battery positive electrode described in the third aspect; wherein the separator comprises any one of a polymer separator, a ceramic separator, or a polymer / ceramic composite separator. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the modified sodium supplement in an embodiment of the present invention. Detailed Implementation

[0032] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0034] In this article, the words “contain” and “include” and their various variations mean that other elements or wholes may be included but not specifically described.

[0035] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three kinds of relationships. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.

[0036] Firstly, such as Figure 1 As shown in the figure, an embodiment of the present invention proposes a modified sodium supplement agent, comprising a core and a coating layer covering the surface of the core; wherein, the core is a rare earth metal doped sodium supplement agent, and the coating layer is a solid electrolyte.

[0037] The modified sodium supplement agent in this embodiment of the invention adopts a core-shell structure, with the core being a rare earth metal-doped sodium supplement agent and the coating layer being a solid electrolyte. The two have a synergistic effect, and compared with existing positive electrode sodium supplement agents, it has lower powder resistance and higher electronic conductivity. This will greatly improve the charge and discharge performance of sodium-ion batteries, thereby solving the problems of high powder resistance and low electronic conductivity of existing positive electrode sodium supplement agents. It has high application value and broad application prospects.

[0038] In some embodiments, the particle size D50 of the core is 100 nm to 50 μm;

[0039] And / or, the coating thickness of the coating layer is 1nm to 100nm; the inventors found through research that if the coating layer thickness is too large, it will affect the sodium ion insertion and extraction of the sodium supplement, thereby affecting the capacity performance; but if the coating layer thickness is too small, it will lead to uneven coating of the entire material, thereby affecting the conductivity of the material.

[0040] In some embodiments, the rare earth metal includes at least one of Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).

[0041] In some embodiments, the sodium supplement is one or a mixture of two of inorganic sodium supplements or organic sodium supplements;

[0042] Preferably, the inorganic sodium supplement includes at least one of Na3N, Na3P, Na2O, NaNO2, Na2CO3, Na2NiO2, NaCrO2, Na5FeO4, NaBH4, and NaNH2;

[0043] Preferably, the organic sodium supplement includes at least one of Na2C6O6, Na2C6H2O6, CH3COONa, PABZ-Na, EDTA-4Na, DTPA-5Na, Na2C4O4, Na2C2O4, and Na2C3O5.

[0044] In some embodiments, the solid electrolyte includes β-Al₂O₃ solid electrolyte and NASICON-type solid electrolyte (e.g., Na₃Zr₂PSi₂O). 12 Na 3.1 Zr 1.9 Nd 0.1 Si2PO 12 ), sulfide solid electrolytes (such as: Na3PS4, Na...), etc. 10 GeP2S 12 Na11 Sn2PS 12 Na 10 SiP2S 12 At least one of the following: (e.g., complexed hydride solid electrolytes such as Na2(BH4)(NH2)).

[0045] In some embodiments, the sodium supplementer accounts for 50% to 99% of the mass of the modified sodium supplementer;

[0046] And / or, the rare earth metal accounts for 0.05% to 10% of the mass of the modified sodium supplement;

[0047] And / or, the solid electrolyte accounts for 0.95% to 50% of the mass of the modified sodium supplement.

[0048] Secondly, embodiments of the present invention also provide a method for preparing the modified sodium supplement as described in the first aspect, comprising the following steps:

[0049] (1) The sodium supplement agent is mixed with a rare earth metal source and then calcined to obtain a rare earth metal doped sodium supplement agent.

[0050] (2) The rare earth metal doped sodium supplement is added to the solid electrolyte powder and mixed evenly. Then the mixture is subjected to high-temperature sintering once and high-temperature sintering twice to obtain the modified sodium supplement.

[0051] In some embodiments, in step (1), the rare earth metal source includes at least one of rare earth metal element, rare earth metal oxide, rare earth metal sulfide, rare earth metal phosphide, rare earth metal nitride, and rare earth metal halide; the calcination treatment is carried out in an air atmosphere or an oxygen atmosphere, the calcination treatment temperature is 500℃~600℃, and the calcination time is 1h~10h;

[0052] And / or, in step (2), the first high-temperature sintering and / or the second high-temperature sintering are carried out in an oxygen atmosphere. The temperature of the first high-temperature sintering is 600℃~800℃ and the sintering time is 3h~10h; the temperature of the second high-temperature sintering is 1000℃~1200℃ and the sintering time is 3h~10h. The inventors have found through research that if the sintering temperature is too high, the solid electrolyte coating will easily deteriorate; but if the sintering temperature is too low, uneven coating and non-dense coating are likely to occur.

[0053] Thirdly, embodiments of the present invention also provide a sodium-ion battery positive electrode sheet, comprising a positive electrode active material, a conductive agent, a binder, a current collector, and the modified sodium supplement agent described in the first aspect;

[0054] The positive electrode active material includes Na2Fe2(SO4)3 and Na2Fe(SO4). 2.2 H2O, Na3V2(PO3), Na3MnTi(PO3)3, Na2FeP2O7, Na2CoP2O7, Na3(VPO4)2F3, Na4Fe3(PO4)2P2O7, Na2MnSiO4, Na3CoB5O 10 At least one of them;

[0055] And / or, the conductive agent includes at least one of Super P, Ketjen Black, acetylene black, carbon black, carbon nanotubes, graphene, conductive graphite, carbon fiber, conductive carbon nanotubes, and mesoporous carbon.

[0056] And / or, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, styrene-butadiene rubber, sodium carboxymethyl cellulose, polypropylene, polyethylene, polyacrylic acid, carboxymethyl cellulose, sodium alginate, and gelatin.

[0057] Fourthly, embodiments of the present invention also provide a sodium-ion battery, comprising a negative electrode, a separator, an electrolyte, and the sodium-ion battery positive electrode described in the third aspect; wherein the separator comprises any one of a polymer separator, a ceramic separator, or a polymer / ceramic composite separator.

[0058] Furthermore, the polymer membrane includes a single-layer polymer membrane and a multi-layer polymer membrane; wherein the single-layer polymer membrane includes a polyethylene (PE) membrane and a polypropylene (PP) membrane.

[0059] The following are non-limiting embodiments and comparative examples of the present invention. It should be noted that the schemes in the comparative examples are not prior art, but are only set up for comparison with the schemes in the embodiments, and are not intended to limit the present invention. Unless otherwise stated, all raw materials used in the embodiments and comparative examples are conventional commercially available products, or can be prepared by known methods.

[0060] Example 1

[0061] This embodiment provides a method for preparing a modified sodium supplement, comprising the following steps:

[0062] (1) After mixing 10.58g Na5FeO4 and 1.77g Nd(NO3)3 evenly, the mixture was calcined at 600℃ for 5h in air atmosphere to obtain Nd-Na5FeO4 composite material.

[0063] (2) Mix 6.5g of the above Nd-Na5FeO4 composite material with 3.5g of Na3Zr2PSi2O 12After mixing at 1000 rpm for 30 minutes in a high-energy ball mill, the mixture is placed in a muffle furnace and sintered at 600℃ for 3 hours in an oxygen atmosphere. Then, it is sintered at 1000℃ for another 3 hours to obtain the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O. 12 .

[0064] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 Solid electrolytes are coated on the surface of Nd-Na5FeO4 composite materials, forming a core-shell structure; wherein, the core Nd-Na5FeO4 composite material has a D50 of 12.8 μm, and Na3Zr2PSi2O 12 The coating thickness is 95 nm. Furthermore, in this modified sodium supplement, the mass percentage of Nd-Na5FeO4 is 65%, the mass percentage of rare earth metal Nd is 5.5%, and the mass percentage of Na3Zr2PSi2O is [missing information]. 12 The quality percentage is 35%.

[0065] This embodiment also provides a sodium-ion battery positive electrode sheet, which is prepared by the following steps: combining the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Super P, the binder PVDF, and the above-mentioned modified sodium-supplementing agent Nd-Na5FeO4@Na3Zr2PSi2O 12 The positive electrode slurry is obtained by mixing the following proportions by mass: 94%: 2%: 1%: 3% until the system is homogeneous. The positive electrode slurry is then uniformly coated onto the positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for drying. After cold pressing and slitting, the positive electrode sheet of the sodium-ion battery is obtained.

[0066] Example 2

[0067] This embodiment provides a method for preparing a modified sodium supplement, comprising the following steps:

[0068] (1) After mixing 10.58g Na5FeO4 and 1.77g Nd(NO3)3 evenly, the mixture was calcined at 600℃ for 5h in air atmosphere to obtain Nd-Na5FeO4 composite material.

[0069] (2) Mix 6.5g of the above Nd-Na5FeO4 composite material with 3.5g of Na3Zr2PSi2O 12 After mixing at 1000 rpm for 30 minutes in a high-energy ball mill, the mixture is placed in a muffle furnace and sintered at 800℃ for 1 hour in an oxygen atmosphere, followed by high-temperature sintering at 1200℃ for 1 hour to obtain the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O. 12 .

[0070] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 A solid electrolyte is coated on the surface of the Nd-Na5FeO4 composite material, forming a core-shell structure; wherein, the core Nd-Na5FeO4 composite material has a D50 of 13.2 μm, and Na3Zr2PSi2O 12 The coating thickness is 78 nm. In this modified sodium supplement, Nd-Na5FeO4 accounts for 65% by mass, rare earth metal Nd accounts for 5.5% by mass, and Na3Zr2PSi2O... 12 The quality percentage is 35%.

[0071] This embodiment also provides a sodium-ion battery positive electrode sheet, which is prepared by the following steps: combining the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Super P, the binder PVDF, and the above-mentioned modified sodium-supplementing agent Nd-Na5FeO4@Na3Zr2PSi2O 12 The positive electrode slurry is obtained by mixing the following proportions by mass: 94%: 2%: 1%: 3% until the system is homogeneous. The positive electrode slurry is then uniformly coated onto the positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for drying. After cold pressing and slitting, the positive electrode sheet of the sodium-ion battery is obtained.

[0072] Example 3

[0073] This embodiment provides a method for preparing a modified sodium supplement, comprising the following steps:

[0074] (1) After mixing 10.58g Na5FeO4 and 1.77g Nd(NO3)3 evenly, the mixture was calcined at 600℃ for 5h in air atmosphere to obtain Nd-Na5FeO4 composite material.

[0075] (2) Mix 7g of the above Nd-Na5FeO4 composite material with 3g of Na3Zr2PSi2O 12 After mixing at 1000 rpm for 30 minutes in a high-energy ball mill, the mixture is placed in a muffle furnace and sintered at 600℃ for 3 hours in an oxygen atmosphere. Then, it is sintered at 1000℃ for another 3 hours to obtain the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O. 12 .

[0076] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12Solid electrolytes are coated on the surface of Nd-Na5FeO4 composite materials, forming a core-shell structure; wherein, the core Nd-Na5FeO4 composite material has a D50 of 13.8 μm, and Na3Zr2PSi2O 12 The coating thickness is 94 nm. Furthermore, in this modified sodium supplement, Na₅FeO₄ accounts for 70% by mass, rare earth metal Nd accounts for 5.5% by mass, and Na₃Zr₂PSi₂O₃ accounts for... 12 The quality percentage is 30%.

[0077] This embodiment also provides a sodium-ion battery positive electrode sheet, which is prepared by the following steps: combining the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Super P, the binder PVDF, and the above-mentioned modified sodium-supplementing agent Nd-Na5FeO4@Na3Zr2PSi2O 12 The positive electrode slurry is obtained by mixing the following proportions by mass: 94%: 2%: 1%: 3% until the system is homogeneous. The positive electrode slurry is then uniformly coated onto the positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for drying. After cold pressing and slitting, the positive electrode sheet of the sodium-ion battery is obtained.

[0078] Example 4

[0079] This embodiment provides a method for preparing a modified sodium supplement, comprising the following steps:

[0080] (1) After mixing 10.87g Na2NiO2 and 2.64g Nd(NO3)3 evenly, the mixture was calcined at 600℃ for 5h in air atmosphere to obtain Nd-Na2NiO2 composite material;

[0081] (2) Mix 6.5g of the above Nd-Na2NiO2 composite material with 3.5g of Na3Zr2PSi2O 12 After mixing at 1000 rpm for 30 minutes in a high-energy ball mill, the mixture is placed in a muffle furnace and sintered at 600℃ for 3 hours in an oxygen atmosphere. Then, it is sintered at 1000℃ for another 3 hours to obtain the modified sodium supplement Nd-Na2NiO2@Na3Zr2PSi2O. 12 .

[0082] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 A solid electrolyte is coated on the surface of the Nd-Na2NiO2 composite material, forming a core-shell structure; wherein, the core Nd-Na2NiO2 composite material has a D50 of 15.3 μm, and Na3Zr2PSi2O 12The coating thickness is controlled at 96 nm. Furthermore, in this modified sodium supplement, the mass percentage of Nd-Na2NiO2 is 65%, the mass percentage of rare earth metal Nd is 8%, and the mass percentage of Na3Zr2PSi2O is [missing information]. 12 The quality percentage is 35%.

[0083] This embodiment also provides a sodium-ion battery positive electrode sheet, which is prepared by the following steps: Na4Fe3(PO4)2P2O7 as the positive electrode active material, Super P as the conductive agent, PVDF as the binder, and the above-mentioned modified sodium-supplementing agent Nd-Na2NiO2@Na3Zr2PSi2O 12 The positive electrode slurry is obtained by mixing the following proportions by mass: 94%: 2%: 1%: 3% until the system is homogeneous. The positive electrode slurry is then uniformly coated onto the positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for drying. After cold pressing and slitting, the positive electrode sheet of the sodium-ion battery is obtained.

[0084] Example 5

[0085] This embodiment provides a method for preparing a modified sodium supplement, comprising the following steps:

[0086] (1) After mixing 10.87g Na5FeO4 and 2.68g Ce(NO3)3 evenly, the mixture was calcined at 600℃ for 5h in air atmosphere to obtain Ce-Na5FeO4 composite material.

[0087] (2) Mix 6.5g of the above Ce-Na5FeO4 composite material with 3.5g of Na3Zr2PSi2O 12 After mixing at 1000 rpm for 30 minutes in a high-energy ball mill, the mixture is placed in a muffle furnace and sintered at 600℃ for 3 hours in an oxygen atmosphere. Then, it is sintered at 1000℃ for another 3 hours to obtain the modified sodium supplement Ce-Na5FeO4@Na3Zr2PSi2O. 12 .

[0088] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 Solid electrolytes are coated on the surface of Ce-Na5FeO4 composite materials, forming a core-shell structure; wherein, the core Nd-Na5FeO4 composite material has a D50 of 14.6 μm, and Na3Zr2PSi2O 12 The coating thickness is 98 nm. Furthermore, in this modified sodium supplement, Ce-Na5FeO4 accounts for 65% by mass, rare earth metal Ce accounts for 5.5% by mass, and Na3Zr2PSi2O... 12 The quality percentage is 35%.

[0089] This embodiment also provides a sodium-ion battery positive electrode sheet, which is prepared by the following steps: combining the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Super P, the binder PVDF, and the aforementioned modified sodium-supplementing agent Ce-Na5FeO4@Na3Zr2PSi2O 12 The positive electrode slurry is obtained by mixing the following proportions by mass: 94%: 2%: 1%: 3% until the system is homogeneous. The positive electrode slurry is then uniformly coated onto the positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for drying. After cold pressing and slitting, the positive electrode sheet of the sodium-ion battery is obtained.

[0090] Example 6

[0091] This embodiment provides a method for preparing a modified sodium supplement, comprising the following steps:

[0092] (1) After mixing 10.58g Na5FeO4 and 1.77g Nd(NO3)3 evenly, the mixture was calcined at 600℃ for 5h in air atmosphere to obtain Nd-Na5FeO4 composite material.

[0093] (2) Mix 6.5g of the above Nd-Na5FeO4 composite material with 3.5g of Na 10 GeP2S 12 After mixing at 1000 rpm for 30 minutes in a high-energy ball mill, the mixture is placed in a muffle furnace and sintered at 600℃ for 3 hours in an oxygen atmosphere. Then, it is sintered at 1000℃ for another 3 hours to obtain the modified sodium supplement Nd-Na5FeO4@Na. 10 GeP2S 12 .

[0094] In the modified sodium supplement prepared in this embodiment, Na 10 GeP2S 122 A solid electrolyte is coated on the surface of the Nd-Na5FeO4 composite material, forming a core-shell structure; wherein, the core Nd-Na5FeO4 composite material has a D50 of 12.9 μm, and Na 10 GeP2S 12 The coating thickness is 95 nm. Furthermore, in this modified sodium supplement, the mass percentage of Nd-Na5FeO4 is 65%, the mass percentage of rare earth metal Nd is 5.5%, and the mass percentage of Na... 10 GeP2S 12 The quality percentage is 35%.

[0095] This embodiment also provides a sodium-ion battery positive electrode sheet, which is prepared by the following steps: combining the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Super P, the binder PVDF, and the aforementioned modified sodium-supplementing agent Nd-Na5FeO4@Na... 10 GeP2S 12 The positive electrode slurry is obtained by mixing the following proportions by mass: 94%: 2%: 1%: 3% until the system is homogeneous. The positive electrode slurry is then uniformly coated onto the positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for drying. After cold pressing and slitting, the positive electrode sheet of the sodium-ion battery is obtained.

[0096] Example 7

[0097] This embodiment provides a method for preparing a modified sodium supplement, comprising the following steps:

[0098] (1) After mixing 10.36g Na5FeO4 and 1.1g Nd(NO3)3 evenly, the mixture was calcined at 600℃ for 5h in air atmosphere to obtain Nd-Na5FeO4 composite material.

[0099] (2) Mix 6.5g of the above Nd-Na5FeO4 composite material with 3.5g of Na3Zr2PSi2O 12 After mixing at 1000 rpm for 30 minutes in a high-energy ball mill, the mixture is placed in a muffle furnace and sintered at 600℃ for 3 hours in an oxygen atmosphere. Then, it is sintered at 1000℃ for another 3 hours to obtain the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O. 12 .

[0100] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 A solid electrolyte is coated on the surface of the Nd-Na5FeO4 composite material, forming a core-shell structure; wherein, the core Nd-Na5FeO4 composite material has a D50 of 13.2 μm, and Na3Zr2PSi2O 12 The coating thickness is 97 nm. Furthermore, in this modified sodium supplement, the mass percentage of Nd-Na5FeO4 is 65%, the mass percentage of rare earth metal Nd is 3.5%, and the mass percentage of Na3Zr2PSi2O is [missing information]. 12 The quality percentage is 35%.

[0101] This embodiment also provides a sodium-ion battery positive electrode sheet, which is prepared by the following steps: combining the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Super P, the binder PVDF, and the above-mentioned modified sodium-supplementing agent Nd-Na5FeO4@Na3Zr2PSi2O12 The positive electrode slurry is obtained by mixing the following proportions by mass: 94%: 2%: 1%: 3% until the system is homogeneous. The positive electrode slurry is then uniformly coated onto the positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for drying. After cold pressing and slitting, the positive electrode sheet of the sodium-ion battery is obtained.

[0102] Comparative Example 1

[0103] This comparative example is basically the same as Example 1, except that: in the preparation process of the sodium-ion battery positive electrode sheet in this comparative example, the modified sodium supplement agent Nd-Na5FeO4@Na3Zr2PSi2O is not added. 12 The mass percentages of the positive electrode material Na4Fe3(PO4)2P2O7, the conductive agent Super P, and the binder PVDF are 97%:2%:1%.

[0104] Comparative Example 2

[0105] This comparative example is basically the same as Example 1, except that: in the positive electrode of the sodium-ion battery in this comparative example, the sodium replenishing agent is not doped with rare earth metals (i.e., the sodium replenishing agent is Na5FeO4@Na3Zr2PSi2O). 12 The positive electrode of this sodium-ion battery is made of positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF, and sodium supplementing agent Na5FeO4@Na3Zr2PSi2O. 12 The positive electrode slurry is obtained by mixing the following proportions by mass: 94%: 2%: 1%: 3% until the system is homogeneous. The positive electrode slurry is then uniformly coated onto the positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the final product is obtained.

[0106] Comparative Example 3

[0107] This comparative example is basically the same as Example 1, except that the modified sodium supplement in this comparative example has a solid electrolyte core and a rare earth metal-doped sodium supplement layer, namely Na3Zr2PSi2O. 12 @Nd-Na5FeO4.

[0108] Comparative Example 4

[0109] This comparative example is basically the same as Example 1, except that the modified sodium supplement in this comparative example is not coated with solid electrolyte, that is, the modified sodium supplement is Nd-Na5FeO4, in which the mass percentage of rare earth metal Nd is 5.5%.

[0110] The sodium-ion battery positive electrode sheet of this comparative example is prepared by mixing the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Super P, the binder PVDF, and the above-mentioned modified sodium supplement agent Nd-Na5FeO4 in a mass percentage of 94%:2%:1%:3% until the system is homogeneous, thus obtaining a positive electrode slurry. The positive electrode slurry is then uniformly coated onto a positive electrode aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the product is obtained.

[0111] Comparative Example 5

[0112] This comparative example is basically the same as Example 1, except that: in the preparation of the modified sodium supplement in this comparative example, the temperature of the first sintering in step (2) is 500°C and the temperature of the second sintering is 1200°C.

[0113] The positive electrode sheets from the above examples and comparative examples were assembled into bare cells by winding with the separator and negative electrode sheets, respectively. These cells were then encapsulated in an aluminum-plastic film and injected with electrolyte to obtain sodium-ion full cells. The negative electrode sheets were prepared by the following steps: The negative electrode was mixed according to the following ratio: main material: conductive agent 1: thickener: binder = hard carbon: Super P: CMC: SBR = 94.6%: 0.8%: 1.6%: 3.0% until the system was homogeneous, resulting in a negative electrode slurry. This slurry was then uniformly coated onto aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the sodium-ion battery negative electrode sheet was obtained. The separator had no special requirements. The electrolyte was prepared using a solvent of 1.0 mol / L NaPF6 dissolved in ethyl methyl carbonate (EMC): ethylene carbonate (EC): dimethyl carbonate (DEC) at a mass ratio of 1:1:1. The assembled sodium-ion full cells were placed in a Land... In the CT2001A testing system, cycle performance tests were conducted within a reasonable voltage range. After formation, the cell was tested for gas production using the water displacement method. The test results are shown in Table 1.

[0114] Table 1

[0115]

[0116] As can be seen from Table 1, compared with the comparative example, the sodium-ion battery prepared using the modified sodium supplement agent of the present invention exhibits better electrochemical performance.

[0117] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0118] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A modified sodium supplement, characterized in that, It includes a core and a coating layer covering the surface of the core; wherein the core is a rare earth metal doped sodium supplement, and the coating layer is a solid electrolyte, including β-Al₂O₃ solid electrolyte and Na₃Zr₂PSi₂O₃. 12 Solid electrolyte, Na 3.1 Zr 1.9 Nd 0.1 Si2PO 12 Solid electrolyte, Na3PS4 solid electrolyte, Na 10 GeP2S 12 Solid electrolyte, Na 11 Sn2PS 12 Solid electrolyte, Na 10 SiP2S 12 At least one of solid electrolyte and Na2(BH4)(NH2) solid electrolyte; the particle size D50 of the core is 100nm~50μm, and the coating thickness of the coating layer is 1nm~100nm; The modified sodium supplement is prepared by a method comprising the following steps: (1) The sodium supplement agent is mixed with a rare earth metal source and then calcined to obtain a rare earth metal doped sodium supplement agent; the calcination is carried out in an air atmosphere or an oxygen atmosphere, the calcination temperature is 500℃~600℃, and the calcination time is 1h~10h. (2) The rare earth metal doped sodium supplement is added to the solid electrolyte powder and mixed evenly. Then the mixture is subjected to a first high-temperature sintering and a second high-temperature sintering to obtain the modified sodium supplement. The first high-temperature sintering and / or the second high-temperature sintering are carried out in an oxygen atmosphere. The temperature of the first high-temperature sintering is 600℃~800℃ and the sintering time is 3h~10h. The temperature of the second high-temperature sintering is 1000℃~1200℃ and the sintering time is 3h~10h.

2. The modified sodium supplement according to claim 1, characterized in that, The rare earth metals include at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

3. The modified sodium supplement according to claim 1, characterized in that, The sodium supplement is one or a mixture of two of the following: inorganic sodium supplement and organic sodium supplement; the inorganic sodium supplement includes at least one of Na3N, Na3P, Na2O, NaNO2, Na2CO3, Na2NiO2, NaCrO2, Na5FeO4, NaBH4, and NaNH2; the organic sodium supplement includes at least one of Na2C6O6, Na2C6H2O6, CH3COONa, PABZ-Na, EDTA-4Na, DTPA-5Na, Na2C4O4, Na2C2O4, and Na2C3O5.

4. The modified sodium supplement according to claim 1, characterized in that, The sodium supplement agent comprises 50% to 99% of the modified sodium supplement agent by mass. And / or, the rare earth metal accounts for 0.05% to 10% of the mass of the modified sodium supplement; And / or, the solid electrolyte accounts for 0.95% to 50% of the mass of the modified sodium supplement.

5. The modified sodium supplement according to claim 1, characterized in that, In step (1), the rare earth metal source includes at least one of rare earth metal elements, rare earth metal oxides, rare earth metal sulfides, rare earth metal phosphides, rare earth metal nitrides, and rare earth metal halides.

6. A positive electrode sheet for a sodium-ion battery, characterized in that, Includes positive electrode active material, conductive agent, binder, current collector and the modified sodium supplement agent as described in any one of claims 1-5; The positive electrode active material includes Na2Fe2(SO4)3 and Na2Fe(SO4). 2.2 H2O, Na3V2(PO3), Na3MnTi(PO3)3, Na2FeP2O7, Na2CoP2O7, Na3(VPO4)2F3, Na4Fe3(PO4)2P2O7, Na2MnSiO4, Na3CoB5O 10 At least one of them; And / or, the conductive agent includes at least one of Super P, Ketjen Black, acetylene black, carbon black, carbon nanotubes, graphene, conductive graphite, carbon fiber, conductive carbon nanotubes, and mesoporous carbon. And / or, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, styrene-butadiene rubber, sodium carboxymethyl cellulose, polypropylene, polyethylene, polyacrylic acid, carboxymethyl cellulose, sodium alginate, and gelatin.

7. A sodium-ion battery, characterized in that, It includes a negative electrode, a separator, an electrolyte, and a sodium-ion battery positive electrode as described in claim 6; wherein the separator includes any one of a polymer separator, a ceramic separator, or a polymer / ceramic composite separator.

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