Modified sodium supplement and preparation method thereof

Abstract

The invention discloses a modified sodium supplementing agent and a preparation method thereof. The modified sodium supplementing agent comprises an inner core and a coating layer coating the surface of the inner core, wherein the inner core is a rare earth metal doped sodium supplement agent, and the coating layer is a solid electrolyte. The modified sodium supplementing agent is of a core-shell structure, an inner core is a rare earth metal doped sodium supplementing agent, lattice oxygen can be absorbed in time, and the problem of oxygen production is solved; meanwhile, the solid electrolyte coating layer can effectively improve the conductivity of the material, so that the first coulombic efficiency, the cycle performance and the energy density of the sodium ion battery are improved; and the modified sodium supplementing agent is simple in preparation process, easy to operate and easy for large-scale production and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery positive electrode sodium supplement, and in particular, the present invention relates to a modified sodium supplement and a preparation method thereof. Background Art

[0002] All the sodium ions required in the sodium-ion battery cycle are provided by the positive electrode material. The negative electrode has a low initial efficiency, and a large number of active sodium ions are irreversibly consumed during the first cycle of charge and discharge, which reduces the reversible capacity of the sodium-ion battery and shortens the cycle life. Pre-sodiumization technology is the most direct and universal method to compensate for the loss of active sodium in the negative electrode, that is, to add additional sodium-rich materials (sodium supplements) to the sodium-ion full battery to compensate for the SEI loss, thereby improving the energy density and cycle life of the sodium-ion full battery.

[0003] According to the different pre-sodiumization principles, pre-sodiumization technology can be divided into five categories: short-circuit pre-sodiumization, electrochemical pre-sodiumization, sodium metal physical pre-sodiumization, chemical pre-sodiumization and positive electrode pre-sodiumization. Among them, short-circuit pre-sodiumization and sodium metal physical pre-sodiumization require the use of active metallic sodium as a reducing agent, and metallic sodium is very easy to react chemically with water and oxygen, so it needs to be carried out under strictly anhydrous and oxygen-free conditions; while electrochemical pre-sodiumization involves the disassembly and assembly of batteries, and the process is cumbersome, which limits its expanded application; if chemical pre-sodiumization is to be truly industrialized, it still needs to consider many practical large-scale production issues, such as the sampling position of the electrode, the thickness of the electrode, the porosity of the electrode, whether the penetration depth of pre-sodiumization is uniform, and how to achieve precise control of the pre-sodiumization reaction still needs further research; in contrast, positive electrode pre-sodiumization only needs to add a small amount of sodium supplement to the positive electrode slurry, which can cause irreversible decomposition during the first week of charging and release sufficient active sodium. This method has been the focus of attention in recent years due to its simple operation and high process adaptability.

[0004] However, the existing positive electrode sodium supplement still has certain problems during use, such as: how to absorb the gas produced by its decomposition; the impact of changes in the electrode interface caused by gas production on the subsequent cycle of the sodium ion battery; whether the decomposition products will continue to participate in the reaction, etc. In addition, during the migration of sodium ions, the sodium supplement will produce oxygen, which will then react with the sodium-containing negative electrode, aggravating the side reactions at the interface of the electrolyte and the positive electrode, and ultimately leading to the deterioration of the high-temperature storage life of the sodium ion battery. In addition, due to the high resistance of the sodium supplement powder, low electronic conductivity, and slow decomposition, its charge and discharge performance is limited.

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

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the present invention provides a modified sodium supplement and a preparation method thereof.

[0007] In a first aspect, an embodiment of the present invention provides a modified sodium supplement, comprising a core and a coating layer coated on the surface of the core; wherein the core is a rare earth metal-doped sodium supplement, and the coating layer is a solid electrolyte.

[0008] The modified sodium supplementer in the embodiment of the present invention presents a core-shell structure, wherein the inner core is a rare earth metal-doped sodium supplementer, which can absorb lattice oxygen in time to solve 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 the sodium ion battery.

[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 an inorganic sodium supplement or an organic sodium supplement, or a mixture of both;

[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 a β-Al2O3 solid electrolyte, a NASICON solid electrolyte, a sulfide solid electrolyte, and a complex hydride solid electrolyte.

[0016] In some embodiments, the mass proportion of the sodium supplement in the modified sodium supplement is 50% to 99%;

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

[0018] And / or, the mass proportion of the solid electrolyte in the modified sodium supplement agent is 0.95% to 50%.

[0019] In a second aspect, an embodiment of the present invention further provides a method for preparing the modified sodium supplement as described in the first aspect, comprising the following steps:

[0020] (1) mixing a sodium supplement agent with a rare earth metal source and then calcining the mixture to obtain a rare earth metal-doped sodium supplement agent;

[0021] (2) adding the rare earth metal-doped sodium supplement agent to the solid electrolyte powder and mixing them evenly, and then subjecting the mixture to high-temperature sintering once and high-temperature sintering twice in sequence to obtain the modified sodium supplement agent.

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

[0023] And / or, in step (2), the primary high-temperature sintering and / or the secondary high-temperature sintering are carried out in an oxygen atmosphere, the temperature of the primary high-temperature sintering is 600°C to 800°C, the sintering time is 3h to 10h, and the temperature of the secondary high-temperature sintering is 1000°C to 1200°C, and the sintering time is 3h to 10h.

[0024] The above-mentioned features and advantages described for the modified sodium supplementer are also applicable to the preparation method of the modified sodium supplementer, which will not be described in detail here.

[0025] In a third aspect, an embodiment of the present invention further provides a positive electrode sheet for a sodium ion battery, 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] Wherein, the positive electrode active material includes Na2Fe2(SO4)3, 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;

[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 binder 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] The embodiment of the present invention adds the modified sodium supplement agent to the positive electrode plate of the sodium ion battery, so that during the battery charging process, the sodium supplement agent decomposes and releases active sodium ions to supplement sodium for the sodium ion battery, thereby compensating for the irreversible sodium loss during the first charge and discharge, and improving the capacity and cycle life of the sodium ion battery.

[0030] In a fourth aspect, an embodiment of the present invention further proposes a sodium ion battery, comprising a negative electrode plate, a diaphragm, an electrolyte and the positive electrode plate of the sodium ion battery described in the third aspect; wherein the diaphragm comprises any one of a polymer diaphragm, a ceramic diaphragm or a polymer / ceramic composite diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of the modified sodium supplementer according to an embodiment of the present invention. DETAILED DESCRIPTION

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

[0033] Where values ​​are described herein as a range, it should be understood that such disclosure includes disclosure of all possible sub-ranges within that range, as well as specific values ​​falling within that range, regardless of whether a specific value or a specific sub-range is explicitly stated.

[0034] Herein, the words "comprises" and "includes" and variations thereof mean that other elements or integers which are permitted but not specifically described may be included.

[0035] In this article, the term "and / or" is merely a term used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0036] First, as Figure 1 As shown, an embodiment of the present invention proposes a modified sodium supplement, comprising a core and a coating layer coated on the surface of the core; wherein the core is a rare earth metal-doped sodium supplement, and the coating layer is a solid electrolyte.

[0037] The modified sodium supplementer in the embodiment of the present invention adopts a core-shell structure, wherein the core is a rare earth metal-doped sodium supplementer and the coating layer is a solid electrolyte. The two have a synergistic effect. Compared with the existing positive electrode sodium supplementer, the modified sodium supplementer has lower powder resistance and higher electronic conductivity, which will greatly improve the charge and discharge performance of the sodium ion battery, thereby solving the problems of high powder resistance and low electronic conductivity of the positive electrode sodium supplementer in the prior art, and 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 have found through research that if the coating layer thickness is too large, it will affect the sodium ion deintercalation of the sodium supplement agent, thereby affecting the capacity; but if the coating layer thickness is too small, it will cause 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 an inorganic sodium supplement or an organic sodium supplement, or a mixture of both;

[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, NASICON solid electrolyte (such as Na3Zr2PSi2O 12 、Na 3.1 Zr 1.9 Nd 0.1 Si2PO 12 etc.), sulfide solid electrolytes (such as: Na3PS4, Na 10 GeP2S 12 、Na11 Sn2PS 12 、Na 10 SiP2S 12 etc.), complex hydride solid electrolyte (such as: Na2(BH4)(NH2), etc.) or at least one of the following.

[0045] In some embodiments, the mass proportion of the sodium supplement in the modified sodium supplement is 50% to 99%;

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

[0047] And / or, the mass proportion of the solid electrolyte in the modified sodium supplement agent is 0.95% to 50%.

[0048] In a second aspect, an embodiment of the present invention further provides a method for preparing the modified sodium supplement as described in the first aspect, comprising the following steps:

[0049] (1) mixing a sodium supplement agent with a rare earth metal source and then calcining the mixture to obtain a rare earth metal-doped sodium supplement agent;

[0050] (2) adding the rare earth metal-doped sodium supplement agent to the solid electrolyte powder and mixing them evenly, and then subjecting the mixture to high-temperature sintering once and high-temperature sintering twice in sequence to obtain the modified sodium supplement agent.

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

[0052] And / or, in the step (2), the primary high-temperature sintering and / or the secondary high-temperature sintering are carried out in an oxygen atmosphere, the temperature of the primary high-temperature sintering is 600°C to 800°C, and the sintering time is 3h to 10h; the temperature of the secondary high-temperature sintering is 1000°C to 1200°C, and the sintering time is 3h to 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, it will easily cause uneven and non-dense coating.

[0053] In a third aspect, an embodiment of the present invention further provides a positive electrode sheet for a sodium ion battery, 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] Wherein, the positive electrode active material includes Na2Fe2(SO4)3, 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;

[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 binder 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] In a fourth aspect, an embodiment of the present invention further proposes a sodium ion battery, comprising a negative electrode plate, a diaphragm, an electrolyte and the positive electrode plate of the sodium ion battery described in the third aspect; wherein the diaphragm comprises any one of a polymer diaphragm, a ceramic diaphragm or a polymer / ceramic composite diaphragm.

[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 examples and comparative examples of the present invention. It should be noted that the schemes of the comparative examples are not prior art and are only provided for comparison with the schemes of the embodiments and are not intended to limit the present invention. Unless otherwise specified, the various raw materials used in the embodiments and comparative examples are conventional commercial 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) 10.58 g Na5FeO4 and 1.77 g Nd(NO3)3 were mixed evenly, and then calcined at 600°C for 5 h in an air atmosphere to obtain a Nd-Na5FeO4 composite material;

[0063] (2) 6.5 g of the above Nd-Na5FeO4 composite material was mixed with 3.5 g of Na3Zr2PSi2O 12Place it in a high-energy ball mill, mix it at 1000 rpm for 30 minutes, then place it in a muffle furnace, and sinter it at 600 ° C for 3 hours in an oxygen atmosphere; then sinter it at 1000 ° C for 3 hours to obtain the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O 12 .

[0064] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 The solid electrolyte is coated on the surface of the Nd-Na5FeO4 composite material to form a core-shell structure; the D50 of the core Nd-Na5FeO4 composite material is 12.8 μm, and the Na3Zr2PSi2O 12 The thickness of the coating layer is 95nm. In the modified sodium supplement, the mass proportion of Nd-Na5FeO4 is 65%, the mass proportion of rare earth metal Nd is 5.5%, and the mass proportion of Na3Zr2PSi2O 12 The quality accounts for 35%.

[0065] This embodiment also provides a sodium ion battery positive electrode plate, which is prepared by the following steps: positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF and the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O 12 The mixture is stirred and mixed according to the mass percentage of 94%:2%:1%:3% until the system is uniform to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode aluminum foil, dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain a sodium ion battery positive electrode sheet.

[0066] Example 2

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

[0068] (1) 10.58 g Na5FeO4 and 1.77 g Nd(NO3)3 were mixed evenly, and then calcined at 600°C for 5 h in an air atmosphere to obtain a Nd-Na5FeO4 composite material;

[0069] (2) 6.5 g of the above Nd-Na5FeO4 composite material was mixed with 3.5 g of Na3Zr2PSi2O 12 Place it in a high-energy ball mill, mix it at 1000 rpm for 30 minutes, then place it in a muffle furnace, and sinter it at 800 ° C for 1 hour in an oxygen atmosphere; then sinter it at 1200 ° C 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 The solid electrolyte is coated on the surface of the Nd-Na5FeO4 composite material to form a core-shell structure; the D50 of the core Nd-Na5FeO4 composite material is 13.2 μm, and the Na3Zr2PSi2O 12 The thickness of the coating layer is 78nm. In the modified sodium supplement, the mass proportion of Nd-Na5FeO4 is 65%, the mass proportion of rare earth metal Nd is 5.5%, and the mass proportion of Na3Zr2PSi2O 12 The quality accounts for 35%.

[0071] This embodiment also provides a sodium ion battery positive electrode plate, which is prepared by the following steps: positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF and the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O 12 The mixture is stirred and mixed according to the mass percentage of 94%:2%:1%:3% until the system is uniform to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode aluminum foil, dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain a sodium ion battery positive electrode sheet.

[0072] Example 3

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

[0074] (1) 10.58 g Na5FeO4 and 1.77 g Nd(NO3)3 were mixed evenly, and then calcined at 600°C for 5 h in an air atmosphere to obtain a Nd-Na5FeO4 composite material;

[0075] (2) 7g of the above Nd-Na5FeO4 composite material and 3g of Na3Zr2PSi2O 12 Place it in a high-energy ball mill, mix it at 1000 rpm for 30 minutes, then place it in a muffle furnace, and sinter it at 600 ° C for 3 hours in an oxygen atmosphere; then sinter it at 1000 ° C for 3 hours to obtain the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O 12 .

[0076] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12The solid electrolyte is coated on the surface of the Nd-Na5FeO4 composite material to form a core-shell structure; the D50 of the core Nd-Na5FeO4 composite material is 13.8 μm, and the Na3Zr2PSi2O 12 The thickness of the coating layer is 94nm. In the modified sodium supplement, the mass proportion of Na5FeO4 is 70%, the mass proportion of rare earth metal Nd is 5.5%, and the mass proportion of Na3Zr2PSi2O 12 The quality accounts for 30%.

[0077] This embodiment also provides a sodium ion battery positive electrode plate, which is prepared by the following steps: positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF and the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O 12 The mixture is stirred and mixed according to the mass percentage of 94%:2%:1%:3% until the system is uniform to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode aluminum foil, dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain a sodium ion battery positive electrode sheet.

[0078] Example 4

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

[0080] (1) 10.87 g of Na2NiO2 and 2.64 g of Nd(NO3)3 were mixed evenly, and then calcined at 600°C for 5 h in an air atmosphere to obtain a Nd-Na2NiO2 composite material;

[0081] (2) 6.5 g of the above Nd-Na2NiO2 composite material was mixed with 3.5 g of Na3Zr2PSi2O 12 Place it in a high-energy ball mill, mix it at 1000 rpm for 30 minutes, then place it in a muffle furnace, and sinter it at 600 ° C for 3 hours in an oxygen atmosphere; then sinter it at 1000 ° C for 3 hours to obtain the modified sodium supplement Nd-Na2NiO2@Na3Zr2PSi2O 12 .

[0082] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 The solid electrolyte is coated on the surface of the Nd-Na2NiO2 composite material to form a core-shell structure; the D50 of the core Nd-Na2NiO2 composite material is 15.3 μm, and the Na3Zr2PSi2O 12The thickness of the coating layer is controlled to be 96nm. In the modified sodium supplement, the mass proportion of Nd-Na2NiO2 is 65%, the mass proportion of rare earth metal Nd is 8%, and the mass proportion of Na3Zr2PSi2O 12 The quality accounts for 35%.

[0083] This embodiment also provides a sodium ion battery positive electrode plate, which is prepared by the following steps: positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF and the modified sodium supplement Nd-Na2NiO2@Na3Zr2PSi2O 12 The mixture is stirred and mixed according to the mass percentage of 94%:2%:1%:3% until the system is uniform to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode aluminum foil, dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain a sodium ion battery positive electrode sheet.

[0084] Example 5

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

[0086] (1) 10.87 g Na5FeO4 and 2.68 g Ce(NO3)3 were mixed evenly, and then calcined at 600°C for 5 h in an air atmosphere to obtain a Ce-Na5FeO4 composite material;

[0087] (2) 6.5 g of the Ce-Na5FeO4 composite material and 3.5 g of Na3Zr2PSi2O 12 Place it in a high-energy ball mill, mix it at 1000 rpm for 30 minutes, then place it in a muffle furnace, and sinter it at 600 ° C for 3 hours in an oxygen atmosphere; then sinter it at 1000 ° C for 3 hours to obtain the modified sodium supplement Ce-Na5FeO4@Na3Zr2PSi2O 12 .

[0088] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 The solid electrolyte is coated on the surface of Ce-Na5FeO4 composite material to form a core-shell structure; the core Nd-Na5FeO4 composite material has a D50 of 14.6 μm, and the Na3Zr2PSi2O 12 The thickness of the coating layer is 98nm. In the modified sodium supplement, the mass proportion of Ce-Na5FeO4 is 65%, the mass proportion of rare earth metal Ce is 5.5%, and the mass proportion of Na3Zr2PSi2O 12 The quality accounts for 35%.

[0089] This embodiment also provides a sodium ion battery positive electrode plate, which is prepared by the following steps: positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF and the modified sodium supplement Ce-Na5FeO4@Na3Zr2PSi2O 12 The mixture is stirred and mixed according to the mass percentage of 94%:2%:1%:3% until the system is uniform to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode aluminum foil, dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain a sodium ion battery positive electrode sheet.

[0090] Example 6

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

[0092] (1) 10.58 g Na5FeO4 and 1.77 g Nd(NO3)3 were mixed evenly, and then calcined at 600°C for 5 h in an air atmosphere to obtain a Nd-Na5FeO4 composite material;

[0093] (2) 6.5 g of the above Nd-Na5FeO4 composite material was mixed with 3.5 g of Na 10 GeP2S 12 Place it in a high-energy ball mill, mix it at 1000 rpm for 30 minutes, then place it in a muffle furnace, and sinter it at 600 ° C for 3 hours in an oxygen atmosphere; then sinter it at 1000 ° C for 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 The solid electrolyte is coated on the surface of the Nd-Na5FeO4 composite material to form a core-shell structure; the D50 of the core Nd-Na5FeO4 composite material is 12.9 μm, and the Na 10 GeP2S 12 The thickness of the coating layer is 95nm. In the modified sodium supplement, the mass proportion of Nd-Na5FeO4 is 65%, the mass proportion of rare earth metal Nd is 5.5%, and the mass proportion of Na 10 GeP2S 12 The quality accounts for 35%.

[0095] This embodiment also provides a sodium ion battery positive electrode plate, which is prepared by the following steps: positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF and the modified sodium supplement Nd-Na5FeO4@Na 10 GeP2S 12 The mixture is stirred and mixed according to the mass percentage of 94%:2%:1%:3% until the system is uniform to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode aluminum foil, dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain a sodium ion battery positive electrode sheet.

[0096] Example 7

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

[0098] (1) 10.36 g Na5FeO4 and 1.1 g Nd(NO3)3 were mixed evenly, and then calcined at 600°C for 5 h in an air atmosphere to obtain a Nd-Na5FeO4 composite material;

[0099] (2) 6.5 g of the above Nd-Na5FeO4 composite material was mixed with 3.5 g of Na3Zr2PSi2O 12 Place it in a high-energy ball mill, mix it at 1000 rpm for 30 minutes, then place it in a muffle furnace, and sinter it at 600 ° C for 3 hours in an oxygen atmosphere; then sinter it at 1000 ° C for 3 hours to obtain the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O 12 .

[0100] In the modified sodium supplement prepared in this embodiment, Na3Zr2PSi2O 12 The solid electrolyte is coated on the surface of the Nd-Na5FeO4 composite material to form a core-shell structure; the D50 of the core Nd-Na5FeO4 composite material is 13.2 μm, and the Na3Zr2PSi2O 12 The thickness of the coating layer is 97nm. In the modified sodium supplement, the mass proportion of Nd-Na5FeO4 is 65%, the mass proportion of rare earth metal Nd is 3.5%, and the mass proportion of Na3Zr2PSi2O 12 The quality accounts for 35%.

[0101] This embodiment also provides a sodium ion battery positive electrode plate, which is prepared by the following steps: positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF and the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O12 The mixture is stirred and mixed according to the mass percentage of 94%:2%:1%:3% until the system is uniform to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode aluminum foil, dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain a sodium ion battery positive electrode sheet.

[0102] Comparative Example 1

[0103] This comparative example is basically the same as Example 1, except that: in the preparation process of the positive electrode sheet of the sodium ion battery in this comparative example, the modified sodium supplement Nd-Na5FeO4@Na3Zr2PSi2O is not added 12 , and 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 plate of the sodium ion battery in this comparative example, the sodium supplement is not doped with rare earth metal (that is, the sodium supplement is Na5FeO4@Na3Zr2PSi2O 12 ), the positive electrode plate of the sodium ion battery is a positive electrode active material Na4Fe3(PO4)2P2O7, a conductive agent Super P, a binder PVDF and a sodium supplement Na5FeO4@Na3Zr2PSi2O 12 The positive electrode slurry is obtained by stirring and mixing according to the mass percentage of 94%:2%:1%:3 until the system is uniform; then the positive electrode slurry is evenly coated on the positive electrode aluminum foil, dried at room temperature, transferred to an oven for drying, and then subjected to cold pressing and slitting processes.

[0106] Comparative Example 3

[0107] This comparative example is basically the same as Example 1, except that the core of the modified sodium supplement in this comparative example is a solid electrolyte, and the coating layer is a rare earth metal doped sodium supplement, 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 a solid electrolyte, that is, the modified sodium supplement is Nd-Na5FeO4, in which the mass proportion of the 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 modified sodium supplement Nd-Na5FeO4 in a mass percentage of 94%:2%:1%:3% until the system is uniform to obtain a positive electrode slurry; then the positive electrode slurry is evenly coated on the positive electrode aluminum foil, dried at room temperature and transferred to an oven for drying, and then subjected to cold pressing and slitting processes to obtain the positive electrode slurry.

[0111] Comparative Example 5

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

[0113] The positive electrode sheets in the above embodiments and comparative examples are respectively assembled with the separator and the negative electrode sheet into bare cells by winding, encapsulated with aluminum-plastic film, and injected with electrolyte to prepare a sodium ion full battery (wherein, the negative electrode sheet is prepared by the following steps: the negative electrode is stirred and mixed according to the main material: conductive agent 1: thickener: binder = hard carbon: Super P: CMC: SBR = 94.6%: 0.8%: 1.6%: 3.0% until the system is uniform to obtain a negative electrode slurry; then the negative electrode slurry is evenly coated on aluminum foil, dried at room temperature and transferred to an oven for drying, and then cold pressed and cut to obtain a sodium ion battery negative electrode sheet; there is no special requirement for the separator; the electrolyte is 1.0 mol / LNaPF6 dissolved in ethyl methyl carbonate (EMC): ethylene carbonate (EC): dimethyl carbonate (DEC) mass ratio = 1:1:1 solvent. The assembled sodium ion full battery is placed in Land In the CT2001A test system, the cycle performance test was carried out in a reasonable voltage range, and the gas production of the battery cell after formation was tested by the drainage method. The test results are shown in Table 1.

[0114] Table 1

[0115]

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

[0117] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0118] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A modified sodium supplement, characterized in that: It comprises a core and a coating layer coated on the surface of the core; wherein the core is a rare earth metal-doped sodium supplement and the coating layer is a solid electrolyte.

2. The modified sodium supplement according to claim 1, characterized in that The particle size D50 of the core is 100nm to 50μm; And / or, the coating thickness of the coating layer is 1 nm to 100 nm.

3. The modified sodium supplement according to claim 1, characterized in that 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.

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

5. The modified sodium supplement according to claim 1, characterized in that The solid electrolyte includes at least one of a β-Al2O3 solid electrolyte, a NASICON solid electrolyte, a sulfide solid electrolyte, and a complex hydride solid electrolyte.

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

7. A method for preparing a modified sodium supplement as claimed in any one of claims 1 to 6, characterized in that: The steps include: (1) mixing a sodium supplement agent with a rare earth metal source and then calcining the mixture to obtain a rare earth metal-doped sodium supplement agent; (2) adding the rare earth metal-doped sodium supplement agent to the solid electrolyte powder and mixing them evenly, and then subjecting the mixture to high-temperature sintering once and high-temperature sintering twice in sequence to obtain the modified sodium supplement agent.

8. The preparation method of the modified sodium supplement according to claim 7, characterized in that: In the step (1), the rare earth metal source includes at least one of a rare earth metal element, a rare earth metal oxide, a rare earth metal sulfide, a rare earth metal phosphide, a rare earth metal nitride, and a rare earth metal halide; the calcination treatment is carried out in an air atmosphere or an oxygen atmosphere, the calcination treatment temperature is 500° C. to 600° C., and the calcination time is 1 h to 10 h; And / or, in step (2), the primary high-temperature sintering and / or the secondary high-temperature sintering are carried out in an oxygen atmosphere, the temperature of the primary high-temperature sintering is 600°C to 800°C, the sintering time is 3h to 10h, and the temperature of the secondary high-temperature sintering is 1000°C to 1200°C, and the sintering time is 3h to 10h.

9. A positive electrode plate for a sodium ion battery, characterized in that: It comprises a positive electrode active material, a conductive agent, a binder, a current collector and the modified sodium supplement agent according to any one of claims 1 to 6; Wherein, the positive electrode active material includes Na2Fe2(SO4)3, 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; 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 binder 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.

10. A sodium ion battery, characterized in that: It comprises a negative electrode plate, a separator, an electrolyte and the positive electrode plate of the sodium ion battery according to claim 9; wherein the separator comprises any one of a polymer separator, a ceramic separator or a polymer / ceramic composite separator.

Images