Sodium secondary battery, positive electrode sheet, sodium supplement additive, and electric device

Abstract

The present application provides a sodium secondary battery, a positive electrode sheet, a sodium supplement additive, and an electric device. The sodium secondary battery of the present application comprises a sodium supplement additive, and the sodium supplement additive has a molecular formula of NawBxDyOz, wherein B comprises at least one of P, Sb, Ge, Ti, Sn, As, and Si, D comprises at least one of S, Se, and Cl, w is greater than 0 and less than or equal to 15, x is greater than 0 and less than or equal to 5, y is greater than 0 and less than or equal to 15, and z is greater than or equal to 0 and less than or equal to 5. The sodium secondary battery of the present application has good mass energy density and cycle performance.

Description

Sodium secondary battery, positive electrode sheet, sodium supplement additive and electrical device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202410177937.X filed on February 8, 2024, entitled “Sodium secondary battery, positive electrode sheet, sodium supplement additive and electrical device”, which is incorporated into this application in its entirety by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a sodium secondary battery, a positive electrode sheet, a sodium supplement additive, and an electrical device. Background Art

[0004] Sodium batteries have great application prospects in large-scale energy storage due to their abundant reserves, low price and wide operating temperature range.

[0005] Sodium secondary batteries suffer from sodium loss during the cycle process, which greatly affects their electrical performance.

[0006] Summary of the Invention

[0007] This application is made in light of the above-mentioned issues and aims to address at least one of the technical problems existing in the prior art. To this end, this application provides a sodium secondary battery, a positive electrode plate, a sodium supplement additive, and an electrical device. The sodium secondary battery of this application has good mass energy density and cycle performance.

[0008] The first aspect of the present application provides a sodium secondary battery, which includes a sodium supplement additive having a molecular formula of Na w B x D y O z , wherein B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

[0009] The positive electrode material of the sodium secondary battery will undergo phase change during the cyclic desodium process, which will cause the lattice spacing to shrink, thereby causing sodium loss. At the same time, the SEI film formed during the first charge and discharge of the negative electrode material of the sodium secondary battery will consume sodium ions, which will also cause sodium ion loss. The loss of sodium ions will reduce the mass energy density and cycle performance of the sodium secondary battery. w B x D y O zThe sodium supplement function is achieved. The sodium supplement additive of the present application can be decomposed and does not produce gas. The cationic part produced by the decomposition is sodium ions. On the one hand, the sodium ions produced can participate in the formation of the negative electrode SEI film, which is beneficial to improving the cycle performance of the sodium secondary battery. On the other hand, the sodium ions produced can directly supplement the sodium consumption of the positive electrode. Different from the existing sodium supplement agents, the anionic part produced by the decomposition of the sodium supplement additive of the present application will not produce gas, and most of it still maintains the original structure. At the same time, some sodium ions are still stored in the structure, which can provide reversible capacity for the sodium secondary battery, which is beneficial to improving the mass energy density of the sodium secondary battery. The sodium supplement additive of the present application has a good sodium supplement function and does not produce gas when decomposed. The sodium secondary battery containing the sodium supplement additive of the present application has good mass energy density and cycle performance.

[0010] In any embodiment, the decomposition voltage of the sodium supplement additive is 3.1V-4.0V.

[0011] The sodium-supplementing additive of the present application has an appropriate decomposition voltage that is highly compatible with the formation voltage of a sodium secondary battery. When the decomposition voltage of the sodium-supplementing additive of the present application is 3.1V-4.0V, the sodium-supplementing additive can decompose during the formation process of the sodium secondary battery to replenish sodium loss, without damaging the electrical performance of the sodium secondary battery during the decomposition process.

[0012] In any embodiment, B includes at least one of P, Sb, Ge, Ti, Sn, and As, D includes at least one of S, Se, and Cl, 0<w≤11, 0<x≤3, 0<y≤13, and 0≤z≤3.

[0013] In any embodiment, the sodium supplementation additive includes Na3PS4, Na3PS3O, Na3PSO3, Na3PS3Cl, Na 2.9375 PS 3.9375 Cl 0.0625 、Na 2.9 PS 3.95 Se 0.05 、Na3PSe4、Na3SbSe4、Na 3.1 Ge 0.1 P 0.9 S4、Na 3.1 T i0.1 P 0.9 S4、Na 3.1 Sn 0.1 P 0.9 S4、Na3P 0.62 As 0.38 S4、Na 2.730 Ca 0.135 PS4、Na3SbS4、Na 10 SnP2S12 、Na 10 GeP2S 12 、Na 11 Sn2PS 12 、Na 11 Sn2PS 12 、Na 11 Sn2PSe 12 or at least one of its hydrates.

[0014] In any embodiment, the sodium supplementation additive includes Na3PS4, Na3PS3O, Na3PSO3, Na3PS3Cl, Na 11 Sn2PSe 12 At least one of .

[0015] In any embodiment, the sodium supplementing additive has a median particle size Dv50 of 2-75 μm. In any embodiment, the sodium supplementing additive has a median particle size Dv50 of 2-50 μm.

[0016] The sodium supplement additive of the present application has an appropriate Dv50. An appropriate Dv50 helps provide a suitable decomposition rate for the sodium supplement additive, and is also beneficial to the processing of the positive electrode slurry, reducing the gelation phenomenon of the positive electrode slurry caused by the sodium supplement additive having an excessively small Dv50.

[0017] In any embodiment, the median particle size Dv50 of the positive electrode active material is 4-15 μm. In any embodiment, the median particle size Dv50 of the positive electrode active material is 4-10 μm.

[0018] The positive electrode active material of the present application has a suitable Dv50, which helps to further improve the processing performance of the positive electrode slurry and improve the cycle performance of the sodium secondary battery.

[0019] In any embodiment, the mass percentage of the sodium supplement additive is 0.5-5% based on the total mass of the positive electrode film layer. In any embodiment, the mass percentage of the sodium supplement additive is 2-5% based on the total mass of the positive electrode film layer.

[0020] The appropriate content of sodium-supplementing additives helps to further improve the mass energy density and cycle performance of sodium secondary batteries.

[0021] The second aspect of the present application provides a positive electrode plate, the positive electrode plate includes a sodium supplement additive, the sodium supplement additive has a molecular formula Na w B x D y O z, wherein B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

[0022] The third aspect of the present application provides a sodium supplement additive having a molecular formula of Na w B x D y O z , wherein B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

[0023] A fourth aspect of the present application provides an electrical device, comprising a sodium secondary battery according to the present application, a positive electrode sheet according to the present application, or a sodium supplement additive according to the present application. The above description is merely an overview of the technical solution of the present application. To better understand the technical means of the present application, implementation may be based on the contents of the specification. To further clarify the above and other purposes, features, and advantages of the present application, the following specifically describes specific implementation methods of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0025] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

[0026] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0027] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0028] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0029] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0030] Description of reference numerals:

[0031] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0032] Below, the embodiments of the positive electrode active material and its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack and electrical device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0033] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0036] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0038] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0039] Sodium batteries have great application prospects in large-scale energy storage due to their abundant reserves, low price and wide operating temperature range. Sodium secondary batteries undergo phase transitions during the sodium removal process, which causes the lattice spacing to shrink, resulting in sodium loss. At the same time, the SEI film formed during the first charge and discharge of the negative electrode material of the sodium secondary battery consumes sodium ions, which also causes sodium ion loss. The loss of sodium ions will reduce the mass energy density and cycle performance of the sodium secondary battery. Most sodium supplements have a decomposition voltage that is too high and / or produce gas when decomposing to produce sodium ions. In the sodium secondary battery system, if the decomposition voltage of the sodium supplement is too high, it cannot be decomposed during the formation process, and thus the sodium supplement function cannot be achieved. The generated gas is prone to electrolyte side reactions, which will affect the electrical performance of the sodium secondary battery. Therefore, it is necessary to develop a sodium supplement that matches the sodium secondary battery system.

[0040] [Sodium secondary battery]

[0041] Based on this, the present application provides a sodium secondary battery, which includes a sodium supplement additive having a molecular formula of Na w B x D y O z, wherein B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

[0042] As used herein, the term "sodium secondary battery" refers to a secondary battery using sodium ions as charge carriers.

[0043] In some embodiments, a sodium secondary battery includes a positive electrode sheet and an electrolyte, the positive electrode sheet includes a positive electrode film layer, and the positive electrode film layer includes a positive electrode active material and a sodium supplement additive.

[0044] In some embodiments, the positive electrode active material includes at least one of a polyanionic compound, a layered oxide, and a Prussian blue compound.

[0045] In some embodiments, the sodium secondary battery does not include a solid-state sodium secondary battery.

[0046] In some embodiments, the electrolyte solution includes an electrolyte salt and a solvent.

[0047] In some embodiments, the sodium supplement has the formula Na w B x D y O z , a sodium supplement for sodium secondary batteries.

[0048] In some embodiments, the "sodium supplement additive has the molecular formula Na w B x D y O z " means that sodium supplements include those with the molecular formula Na w B x D y O z substances and their hydrates.

[0049] In some embodiments, the polyanionic compound may be a compound having metal ions, transition metal ions and tetrahedral (YO4) n A class of compounds with anionic units. The metal ion can be at least one of sodium ion, lithium ion, potassium ion, and zinc ion; the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4) n valence.

[0050] In some embodiments, the layered oxide comprises a layered transition metal oxide. In some embodiments, the transition metal in the layered transition metal oxide may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. In some embodiments, the layered transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0051] This application adds sodium supplement additive Na to sodium secondary battery w B x D y O z The sodium supplement function is realized. The sodium supplement additive of the present application can be decomposed and does not produce gas. The cationic part produced by the decomposition is sodium ions. On the one hand, the sodium ions produced can participate in the formation of the negative electrode SEI film, which is beneficial to improving the cycle performance of the sodium secondary battery; on the other hand, the sodium ions produced can directly supplement the sodium consumption of the positive electrode. Different from the existing sodium supplement agents, the anionic part produced by the decomposition of the sodium supplement additive of the present application will not produce gas, and part of it still maintains the spatial structure of the original configuration, and some sodium ions are still stored in the above-mentioned spatial structure. Sodium ions can be deintercalated through the spatial structure of the sodium supplement additive material, providing reversible capacity for the sodium secondary battery while also increasing the sodium ion conduction rate, which is beneficial to improving the mass energy density and kinetic performance of the sodium secondary battery.

[0052] The sodium-supplementing additive of the present application has a good sodium-supplementing function and does not generate gas upon decomposition. The sodium secondary battery containing the sodium-supplementing additive of the present application has good mass energy density and cycle performance.

[0053] In some embodiments, the decomposition voltage of the sodium supplement additive is 3.1V-4.0V.

[0054] Herein, the term "decomposition voltage of the sodium supplement additive" refers to the voltage at which the sodium supplement additive can begin to decompose and release cations and / or anions.

[0055] In some embodiments, the decomposition voltage of the sodium supplementing additive may be 3.1 V, 3.2 V, 3.3 V, 3.4 V, 3.5 V, 3.6 V, 3.7 V, 3.8 V, 3.9 V, 4.0 V, or a value in a range consisting of the decomposition voltages of any two sodium supplementing additives.

[0056] The decomposition voltage of the sodium supplementing additive can be measured by methods and equipment known in the art. For example, a charge-discharge tester can be used for testing. Specifically, the sodium supplementing additive, Ketjen black, and PVDF are mixed into a slurry in a certain ratio (e.g., 5:3:2), coated onto aluminum foil, and assembled with a sodium sheet in a glove box to form a sodium half-cell. The sodium half-cell is charged at a certain current density (e.g., 10 mA / g) in a charge-discharge tester to obtain a sodium supplementing additive decomposition voltage curve.

[0057] The sodium-supplementing additive of the embodiment of the present application has an appropriate decomposition voltage that is highly compatible with the formation voltage of the sodium secondary battery. When the decomposition voltage of the sodium-supplementing additive of the embodiment of the present application is 3.1V-4.0V, the sodium-supplementing additive can decompose during the formation process of the sodium secondary battery to replenish sodium loss.

[0058] In some embodiments, B includes at least one of P, Sb, Ge, Ti, Sn, and As, D includes at least one of S, Se, and Cl, 0<w≤11, 0<x≤3, 0<y≤13, and 0≤z≤3.

[0059] In some embodiments, B comprises at least one of P and Sn. In some embodiments, D comprises S. In some embodiments, w can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. In some embodiments, x can be 1, 2, 3, 4, or 5. In some embodiments, y can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. In some embodiments, z can be 0, 1, 2, 3, 4, or 5.

[0060] In some embodiments, the sodium supplementation additives include Na3PS4, Na3PS3O, Na3PSO3, Na3PS3Cl, Na 2.9375 PS 3.9375 Cl 0.0625 、Na 2.9 PS 3.95 Se 0.05 、Na3PSe4、Na3SbSe4、Na 3.1 Ge 0.1 P 0.9 S4、Na 3.1 T i0.1 P 0.9 S4、Na 3.1 Sn 0.1 P 0.9 S4、Na3P 0.62 As 0.38 S4、Na 2.730 Ca 0.135PS4、Na3SbS4、Na 10 SnP2S 12 、Na 10 GeP2S 12 、Na 11 Sn2PS 12 、Na 11 Sn2PS 12 、Na 11 Sn2PSe 12 or at least one of its hydrates.

[0061] In some embodiments, the sodium supplementation additives include Na3PS4, Na3PS3O, Na3PSO3, Na3PS3Cl, Na 11 Sn2PSe 12 At least one of .

[0062] Sodium Supplement Additive In some embodiments, the sodium supplement additive has a median particle size Dv50 of 2-75 μm.

[0063] In some embodiments, the sodium supplementing additive has a median particle size Dv50 of 2-50 μm. In some embodiments, the sodium supplementing additive has a median particle size Dv50 of 2-30 μm. In some embodiments, the sodium supplementing additive has a median particle size Dv50 of 2-20 μm. In some embodiments, the sodium supplementing additive has a median particle size Dv50 of 2-15 μm. In some embodiments, the sodium supplementing additive has a median particle size Dv50 of 2-12 μm.

[0064] As used herein, the term "Dv50" refers to the particle size at which the volume cumulative particle size distribution percentage in the particles reaches 50%.

[0065] In some embodiments, the median particle size Dv50 of the sodium supplementing additive can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75um, or a value in the range consisting of the median particle size Dv50 of any two positive electrode active materials.

[0066] An appropriate Dv50 helps provide a suitable decomposition rate for the sodium supplement additive, while also facilitating the processing of the cathode slurry and reducing the gelation of the cathode slurry caused by an excessively small Dv50 of the sodium supplement additive. When the Dv50 of the sodium supplement additive is 2-75 μm, it helps further improve the mass energy density and cycle performance of sodium secondary batteries.

[0067] In some embodiments, the positive electrode active material has a median particle size Dv50 of 4-15 μm. In some embodiments, the positive electrode active material has a median particle size Dv50 of 4-10 μm. In some embodiments, the positive electrode active material has a median particle size Dv50 of 4-8 μm.

[0068] In some embodiments, the median particle size Dv50 of the positive electrode active material can be 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or a value in a range consisting of the median particle size Dv50 of any two positive electrode active materials.

[0069] The Dv50 of the sodium supplement additive and the positive electrode active material can be measured by methods and equipment known in the art. For example, it can be measured using a laser particle size analyzer (Malvern Master Size 3000) with reference to GB / T19077.1-2016.

[0070] Controlling the Dv50 of the positive electrode active material of the embodiment of the present application within the above range is beneficial to further improving the processing performance of the positive electrode slurry and improving the cycle performance of the sodium secondary battery.

[0071] In some embodiments, the mass percentage of the sodium supplement additive is 0.5-5% based on the total mass of the positive electrode film layer. In some embodiments, the mass percentage of the sodium supplement additive is 2-5% based on the total mass of the positive electrode film layer. In some embodiments, the mass percentage of the sodium supplement additive is 3-5% based on the total mass of the positive electrode film layer.

[0072] In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage of the sodium supplement additive can be 0.5%, 1%, 2%, 3%, 4%, 5%, or a value within a range consisting of the mass percentages of any two of the above sodium supplement additives.

[0073] An appropriate content of sodium-supplementing additive helps to provide sodium ions while also making the content of positive electrode active materials appropriate, which helps to further improve the mass energy density and cycle performance of sodium secondary batteries.

[0074] The present application has no particular limitation on the shape of the sodium secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a sodium secondary battery 5 having a square structure as an example.

[0075] In some embodiments, referring to FIG2 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the sodium secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0076] In some embodiments, sodium secondary batteries can be assembled into a battery module. The number of sodium secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0077] Figure 3 shows an example battery module 4. Referring to Figure 3 , within battery module 4, multiple sodium secondary batteries 5 may be arranged sequentially along the length of battery module 4. Of course, any other arrangement is also possible. Furthermore, these multiple sodium secondary batteries 5 may be secured using fasteners.

[0078] In some embodiments, the battery module 4 may further include a housing having a housing space, and the plurality of sodium secondary batteries 5 may be housed in the housing space.

[0079] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0080] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0081] [Positive electrode]

[0082] The present application also provides a positive electrode plate, wherein the positive electrode plate includes a sodium supplement additive, wherein the sodium supplement additive has a molecular formula Na w B x D y O z, wherein B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

[0083] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer further includes a binder and a conductive agent.

[0084] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0085] In some embodiments, the positive electrode current collector may be a conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet may be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate may each be independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector may be a composite current collector formed by combining a metal foil with a polymer base film.

[0086] In some embodiments, the positive electrode film layer further includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0087] In some embodiments, the positive electrode film layer further includes a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, additives, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0089] [Negative electrode]

[0090] In some embodiments, the sodium secondary battery further includes a negative electrode sheet.

[0091] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0092] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0093] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil or aluminum foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0094] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0095] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0096] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0098] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0099] [Electrolyte]

[0100] The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode. The electrolyte of the embodiment of the present application is liquid and includes an electrolyte salt and a solvent.

[0101] In some embodiments, the electrolyte salt may be selected from at least one of sodium hexafluorophosphate and sodium fluorosulfonimide.

[0102] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0103] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0104] [Isolation film]

[0105] In some embodiments, the sodium secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0106] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0107] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0108] In some embodiments, the sodium secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0109] In some embodiments, the outer packaging of the sodium secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the sodium secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0110] The present application also provides a sodium supplement additive having a molecular formula of Na w B x D y O z , wherein B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

[0111] [Electrical devices]

[0112] The present application also provides an electrical device, which includes the sodium secondary battery of the present application, the positive electrode plate of the present application, or the sodium supplement additive of the present application.

[0113] In some embodiments, the electrical device of the embodiments of the present application may further include at least one of a battery module or a battery pack. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0114] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0115] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0116] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0117] Example

[0118] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0119] 1. Preparation method

[0120] Example 1

[0121] 1) Preparation of sodium supplement additives

[0122] Na2S and P2S5 are mixed in a specific proportion and sintered at high temperature in the absence of oxygen to produce Na3PS4. Na3PS4 is dissolved in methanol, heated to 100°C, allowed to stand for approximately 6 hours, and then dried to produce Na3PS3O. Na3PS3O is dissolved in deionized water in a specific proportion. Once fully dissolved, it is freeze-dried and then crushed and sieved for later use. The sodium supplement Na3PS3O has a Dv50 value of 4 μm.

[0123] 2) Preparation of positive electrode materials

[0124] The positive electrode active material Na 0.82 Ni 0.33 Fe 0.33 Mn 0.33 O2, sodium supplement additive Na3PS3O, conductive carbon black, and binder polyvinylidene fluoride are fully stirred and mixed in N-methylpyrrolidone according to the mass percentage of 92:3:3:2 to form a uniform positive electrode slurry. The positive electrode slurry is poured into the mixture at a ratio of 0.3g / 1540.25mm 2 The single-side weight of the coating is coated on the aluminum foil. After the coating is completed, it is dried, cold pressed, and cut to obtain the positive electrode sheet.

[0125] 3) Preparation of negative electrode sheet

[0126] The negative electrode active material hard carbon, the conductive agent carbon black, the thickener carboxymethyl cellulose, and the binder styrene-butadiene rubber were added to deionized water in a mass ratio of 97:0.5:0.5:2 and stirred to obtain a negative electrode slurry;

[0127] Then the negative electrode slurry was mixed with 0.28g / 1540.25mm 2 The double-sided weight is evenly coated on the copper foil, and after the double-sided coating is completed, it is dried, cold pressed, and cut to obtain the negative electrode sheet;

[0128] 4) Preparation of isolation membrane

[0129] Polypropylene film is used as the isolation film.

[0130] 5) Preparation of electrolyte

[0131] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), sodium hexafluorophosphate NaPF6 was dissolved in an organic solvent of propylene carbonate (PC) with 5% by mass of FEC fluoroethylene carbonate, and stirred evenly to obtain an electrolyte with a sodium salt concentration of 1 mol / L.

[0132] 6) Preparation of batteries

[0133] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare battery cell, the bare battery cell is welded with a pole ear, and the bare battery cell is placed in an aluminum shell and baked in a vacuum oven at 100°C for 8 hours. Then, the electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery is then subjected to the processes of static standing, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the sodium secondary battery of Example 1.

[0134] The preparation methods of the batteries of Examples 2-4 are similar to those of Example 1, but the types of sodium supplement additives are adjusted, as shown in Table 1.

[0135] The preparation methods of the batteries of Examples 5-8 are similar to those of Example 1, but the median particle size Dv50 value of the sodium supplement additive is adjusted, as shown in Table 1.

[0136] The preparation method of the batteries of Examples 9-10 is similar to that of Example 1, but the median particle size Dv50 value of the positive electrode active material is adjusted, as shown in Table 1.

[0137] The preparation methods of the batteries of Examples 11-12 are similar to those of Example 1, but the mass percentages of the sodium supplement additive and the positive electrode active material are adjusted, as shown in Table 1.

[0138] The preparation method of the battery of Comparative Example 1 is similar to that of Example 1, but no sodium supplement additive is added to the positive electrode film layer.

[0139] The preparation method of the battery of Comparative Example 2-3 is similar to that of Example 1, but the type of sodium supplement additive is adjusted, as shown in Table 1.

[0140] 2. Battery performance test

[0141] 1. Performance test of sodium supplement additives and positive electrode active materials

[0142] 1) Sodium Supplement Additive Median Particle Size Dv50 Test

[0143] The median particle size Dv50 value of the sodium supplement additive can be determined with reference to GB / T19077.1-2016 using a laser particle size analyzer (Malvern Master Size 3000).

[0144] 2) Cathode active material median particle size Dv50 test

[0145] The median particle size Dv50 value of the positive electrode active material can be measured with reference to GB / T19077.1-2016 using a laser particle size analyzer (Malvern Master Size 3000).

[0146] 3) Sodium supplement decomposition voltage test

[0147] The sodium supplement additive, Ketjen black and PVDF were mixed into a slurry in a ratio of 5:3:2, coated on aluminum foil, and assembled with sodium sheets into a sodium half-cell in a glove box. The sodium supplement additive was charged at a current density of 10 mA / g in a charge and discharge tester to obtain a sodium supplement additive decomposition voltage curve, where the vertical axis is voltage and the horizontal axis is gram capacity.

[0148] 4) Detection of whether the decomposition of sodium supplement additives produces gas

[0149] After assembling into a stacked battery, charge it at 0.05C to 3.9V and observe whether there is any bag swelling. Collect the gas using the drainage method to confirm the specific gas production. If the difference between the gas production of the battery containing the sodium supplement additive and the control battery (the battery without the sodium supplement additive) is ≤3ml / Ah, it is judged as no gas production. The specific operation of the drainage method is as follows: connect the soft-pack battery cell air bag to the exhaust pipe, first fill the gas collecting bottle with water, cover the bottle mouth with a glass sheet, and then invert it in the sink. When bubbles are continuously and evenly released from the catheter mouth, extend the catheter mouth into the gas collecting bottle filled with water. When bubbles are seen emerging from the outer edge of the gas collecting bottle mouth and the liquid level in the gas collecting bottle drops to the bottle mouth, cover the bottle mouth with a glass sheet in the water, move the gas collecting bottle out of the water, and place it upright or upside down on the table.

[0150] 5) Method for detecting the presence of sodium supplements

[0151] Charge the battery cell to 4.0V, then disassemble it in an inert atmosphere glove box, take out the positive electrode and negative electrode respectively, scrape the powder on the positive electrode, take out 50g, soak it in 100g of anhydrous methanol, stir and dissolve it for 4h, take 100mL of the supernatant, vacuum dry it at 100℃, and obtain powder (weight is W). Send the powder for XRD test, test 0-90℃ at a scan rate of 1℃ / min, and compare the peaks with standard substances. For example, Na3PS3O is used as the sodium supplement additive, and JCPDS No. 27-0800 is selected as the standard substance. For other sodium supplement additives, the corresponding PDF card can be used for comparison; the negative electrode is sent for XPS peak spectrum test to detect the presence of P and S peaks. Peak comparison results showed that it was basically the same as the corresponding PDF card; and the powder concentration in the supernatant (i.e., W / 100mL) was greater than or equal to 100ppm; the XPS peak spectrum showed the presence of both P and S peaks, indicating the presence of trace amounts of undecomposed sodium supplement additives, which can be used as a basis for reverse detection.

[0152] 2. Battery performance test

[0153] 1) Mass energy density

[0154] Place the battery cell at 25°C for 2 hours to ensure that the temperature of the battery cell is 25°C. Charge the battery cell at 0.33C at 25°C to a charge cut-off voltage of 3.95V, then continue constant voltage charging at this charge cut-off voltage until the current reaches 0.05C, at which point the charge is cut off (where C represents the rated capacity of the battery cell). Place the battery cell at 25°C for 1 hour, then discharge the battery cell at 0.33C at 25°C to a discharge cut-off voltage of 1.5V. Record the total discharge capacity (C0) of the battery cell, and the total discharge energy (E0).

[0155] Place the battery cell on an electronic balance until the weight stabilizes, and read the battery cell weight value M0;

[0156] Battery energy density = battery cell discharge energy E0 / battery cell weight M0.

[0157] 2) Cycle performance

[0158] At 25°C, the secondary batteries prepared in each example and comparative example were charged at a constant current rate of 1C to a charge cutoff voltage of 3.95V. They were then charged at a constant voltage to a current of ≤0.05C, allowed to rest for 5 minutes, and then discharged at a constant current rate of 0.33C to a discharge cutoff voltage of 1.5V, allowed to rest for 5 minutes. This constituted one charge-discharge cycle. The batteries were subjected to cyclic charge-discharge testing using this method until the battery capacity decayed to 80%. The number of cycles at this point was recorded, which was the battery's cycle life at 25°C.

[0159] 3. Analysis of test results of various embodiments and comparative examples

[0160] Batteries of various examples and comparative examples were prepared according to the above method, and various performance parameters were measured. The relevant parameters of the positive electrode active material and the sodium supplement additive are shown in Table 1, and the battery performance test results are shown in Table 2.

[0161] Table 1. Related parameters of positive electrode active materials and sodium supplement additives

[0162] Table 2. Battery performance test results

[0163] According to the results in the above table, it can be seen from Examples 1-12 and Comparative Example 1 that the sodium secondary battery to which the sodium supplement additive of the present application is added can effectively improve mass energy density and cycle performance.

[0164] It can be seen from Examples 1-12 and Comparative Example 2 that, compared with commonly used sodium supplements on the market, such as Na2CO3, the sodium supplement additives of the embodiments of the present application do not produce gas when decomposed, and the decomposition voltage range is suitable. While improving the mass energy density of the sodium secondary battery, it can also improve its cycle performance. However, Na2CO3 will affect the cycle performance of the battery to a certain extent due to its high decomposition voltage.

[0165] It can be seen from Examples 1-12 and Comparative Example 3 that, compared with other types of sodium-containing compounds, such as Na3PO4, the sodium-supplementing additive of the present application can be decomposed to supplement sodium at a suitable decomposition voltage, thereby improving the mass energy density of the sodium secondary battery, while Na3PO4 cannot be decomposed and thus cannot supplement the sodium loss of the sodium secondary battery.

[0166] It can be seen from Examples 1-4 that different types of sodium supplement additives in the present application can improve the mass energy density and cycle performance of sodium secondary batteries, among which Na3PS3O has a better effect.

[0167] It can be seen from Examples 1 and 5-8 that when the Dv50 of the sodium supplement additive in the examples of the present application is 2-75 μm, it helps to better improve the mass energy density and cycle performance of the sodium secondary battery.

[0168] It can be seen from Examples 1, 9-10 that when the Dv50 of the positive electrode active material of the examples of the present application is 4-15 μm, it helps to better improve the mass energy density and cycle performance of the sodium secondary battery.

[0169] It can be seen from Examples 1 and 11-12 that when the mass percentage of the sodium supplement additive in the examples of the present application is 0.5-5%, it is beneficial to better improve the mass energy density and cycle performance of the sodium secondary battery.

[0170] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A sodium secondary battery, wherein: The sodium secondary battery includes a sodium supplement additive having a molecular formula of Na w B x D y O z , wherein B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

2. The sodium secondary battery according to claim 1, wherein The decomposition voltage of the sodium supplement additive is 3.1-4.0V.

3. The sodium secondary battery according to claim 1 or 2, wherein The B includes at least one of P, Sb, Ge, Ti, Sn, and As, the D includes at least one of S, Se, and Cl, 0<w≤11, 0<x≤3, 0<y≤13, and 0≤z≤3.

4. The sodium secondary battery according to any one of claims 1 to 3, wherein The sodium supplement additives include Na3PS4, Na3PS3O, Na3PSO3, Na3PS3Cl, Na 2.9375 PS 3.9375 Cl 0.0625 、Na 2.9 PS 3.95 Se 0.05 、Na3PSe4、Na3SbSe4、Na 3.1 Ge 0.1 P 0.9 S4、Na 3.1 T i0.1 P 0.9 S4、Na 3.1 Sn 0.1 P 0.9 S4、Na3P 0.62 As 0.38 S4、Na 2.730 Ca 0.135 PS4、Na3SbS4、Na 10 SnP2S 12 、Na 10 GeP2S 12 、Na 11 Sn2PS 12 、Na 11 Sn2PS 12 、Na 11 Sn2PSe 12 or at least one of its hydrates.

5. The sodium secondary battery according to any one of claims 1 to 4, wherein The sodium supplement additives include Na3PS4, Na3PS3O, Na3PSO3, Na3PS3Cl, Na 11 Sn2PSe 12 At least one of .

6. The sodium secondary battery according to any one of claims 1 to 5, wherein Meet at least one of the following characteristics: (1) The median particle size Dv50 of the sodium supplement additive is 2-75 μm; (2) The median particle size Dv50 of the positive electrode active material is 4-15 μm; (3) Based on the total mass of the positive electrode film layer, the mass percentage of the sodium supplement additive is 0.5-5%.

7. The sodium secondary battery according to any one of claims 1 to 6, wherein: Meet at least one of the following characteristics: (1) The median particle size Dv50 of the sodium supplement additive is 2-50 μm; (2) The median particle size Dv50 of the positive electrode active material is 4-10 μm; (3) Based on the total mass of the positive electrode film layer, the mass percentage of the sodium supplement additive is 2-5%.

8. A positive electrode plate, comprising a sodium supplement additive having a molecular formula of Na w B x D y O z ,in, B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

9. A sodium supplement additive having a molecular formula of Na w B x D y O z ,in, B includes at least one of P, Sb, Ge, Ti, Sn, As, and Si, D includes at least one of S, Se, and Cl, 0<w≤15, 0<x≤5, 0<y≤15, and 0≤z≤5.

10. An electrical device, wherein: The electrical device comprises the sodium secondary battery according to any one of claims 1 to 7, the positive electrode sheet according to claim 8, or the sodium supplement additive according to claim 9.

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