Long-circulation sodium ion battery positive electrode material, preparation method and application thereof, and sodium ion battery

Abstract

The invention provides a long-circulation sodium ion battery positive electrode material, a preparation method and application thereof, and a sodium ion battery. The long-circulation sodium-ion battery positive electrode material comprises an inner core and a coating layer coating the surface of the inner core, the chemical formula of the inner core is Na < x > A < y > B < z > Cu < 0.1 > Fe < 0.3 > C < 0.1 > Mn < 0.3 > D < 0.1 > O < 2 >; the coating layer is formed by compounding NaF, TiO2 and NaH2PO4 (sodium fluoride); according to the long-circulation sodium-ion battery positive electrode material, the core and the coating layer form a core-shell structure, the composite coating layer and the core interact in the charging process, a protective layer is formed on the surface layer, damage of side reaction of electrolyte to the positive electrode material is reduced, and in addition, through regulation and control and design of valence states of bulk phase elements, the long-circulation sodium-ion battery positive electrode material is obtained. Element dissolution and volume change of the positive electrode material in the charging and discharging process are reduced, and the cycle performance of the positive electrode material is remarkably improved by integrating the factors.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a long-cycle sodium ion battery positive electrode material, a preparation method and application thereof, and a sodium ion battery. Background Art

[0002] The advantages of sodium-ion batteries in terms of cost, low-temperature performance and safety have attracted more and more attention in the field of low-speed electric vehicles. However, the cycle performance of traditional sodium-ion batteries is inferior to that of mature lithium-ion batteries. The large volume change and drastic phase change during the insertion and extraction of the positive electrode and the damage to the positive electrode material by the electrolyte side reaction are one of the main reasons for the attenuation of the cycle performance. Therefore, it is urgent to develop a sodium-ion battery positive electrode material with excellent cycle performance. Summary of the invention

[0003] The present invention provides a long-cycle sodium ion battery positive electrode material and a preparation method and application thereof, and a sodium ion battery, so as to solve or at least partially solve the defects existing in the prior art.

[0004] In a first aspect, the present invention provides a long-cycle sodium-ion battery positive electrode material, comprising a core and a coating layer coated on the surface of the core;

[0005] The chemical formula of the core is: Na x A y B z Cu 0.1 Fe 0.3 C 0.1 Mn 0.3 D 0.1 O2;

[0006] Wherein, A is at least one of Li and K; B is at least one of Ni, Mg, Ca and Zn; C is at least one of Al and Y; D is at least one of Ti and Zr; 0.7≤x≤0.9, 0.01≤y≤0.1, z=((0.96~1)-xy)×0.5;

[0007] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0008] Preferably, the molar ratio of TiO2, NaF and NaH2PO4 is 1:(2-2.5):(1-1.5);

[0009] And / or, the mass of the coating layer is 0.1% to 1% of the mass of the core.

[0010] Preferably, the chemical formula of the core is Na 0.8 Li 0.05 Mg 0.025 Ni 0.05Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Ti 0.1 O2、Na 0.9 Li 0.01 Mg 0.035 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Zr 0.1 O2、Na 0.7 K 0.1 Mg 0.04 Ni 0.04 Cu 0.1 Fe 0.3 Y 0.1 Mn 0.3 Ti 0.1 Any of O2.

[0011] In a second aspect, a method for preparing a long cycle sodium ion battery positive electrode material of the present invention comprises the following steps:

[0012] Mixing a sodium source, a compound containing A, a compound containing B, a Cu source, a Fe source, a compound containing C, a Mn source, and a compound containing D to obtain a first precursor;

[0013] calcining the first precursor to obtain a calcined product;

[0014] Mixing NaF, TiO2 and NaH2PO4 to obtain a coating layer raw material, adding the calcined product to the coating layer raw material, and continuing to mix to obtain a second precursor;

[0015] The second precursor is calcined to obtain a long-cycle sodium-ion battery positive electrode material.

[0016] Preferably, in the step of calcining the first precursor to obtain a calcined product, the calcination temperature is 800 to 1000° C. and the calcination time is 10 to 20 hours.

[0017] Preferably, in the step of calcining the second precursor, the calcination temperature is 250-400° C. and the calcination time is 2-5 hours.

[0018] Preferably, NaF, TiO2 and NaH2PO4 are mixed to obtain a coating layer raw material, and the calcined product is added to the coating layer raw material and mixed continuously to obtain a second precursor, wherein the molar ratio of TiO2, NaF and NaH2PO4 is 1:(2-2.5):(1-1.5), and the mass ratio of the coating layer raw material to the calcined product is (0.1-1):100.

[0019] Preferably, the sodium source includes at least one of sodium carbonate, sodium bicarbonate, sodium acetate and sodium oxalate;

[0020] And / or, the Cu source includes at least one of copper carbonate, copper nitrate, copper oxalate, copper acetate, and copper oxide;

[0021] And / or, the Fe source includes at least one of ferric oxide, ferric nitrate, ferric oxalate and ferric acetate;

[0022] And / or, the Mn source includes at least one of manganese tetraoxide, manganese nitrate, manganese oxalate and manganese acetate;

[0023] And / or, the A-containing compound includes at least one of carbonate, nitrate, oxalate, acetate, and oxide containing A;

[0024] And / or, the B-containing compound includes at least one of carbonate, nitrate, oxalate, acetate and oxide containing B;

[0025] And / or, the C-containing compound includes at least one of a C-containing carbonate, a nitrate, an oxalate, an acetate, and an oxide;

[0026] And / or, the D-containing compound includes at least one of D-containing carbonates, nitrates, oxalates, acetates, and oxides.

[0027] In a third aspect, the present invention also provides an application of the long-cycle sodium-ion battery positive electrode material or the long-cycle sodium-ion battery positive electrode material prepared by the preparation method in the preparation of a sodium-ion battery.

[0028] In a fourth aspect, the present invention further provides a sodium ion battery, comprising a positive electrode, wherein the positive electrode comprises the long-cycle sodium ion battery positive electrode material or the long-cycle sodium ion battery positive electrode material prepared by the preparation method.

[0029] The long-cycle sodium ion battery positive electrode material, preparation method and application thereof, and sodium ion battery of the present invention have the following beneficial effects compared with the prior art:

[0030] The long-cycle sodium ion battery positive electrode material of the present invention comprises a core and a coating layer coated on the surface of the core, wherein the core and the coating layer form a core-shell structure, and a protective layer is formed on the surface through the interaction between the composite coating layer and the core during the charging process, thereby reducing the damage to the positive electrode material by the side reaction of the electrolyte, and further reducing the element dissolution and volume change of the positive electrode material during the charging and discharging process through the regulation and design of the valence state of the bulk elements, and the above factors are combined to significantly improve the cycle performance of the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 The first cycle charge and discharge curve of the sodium ion battery in Example 1 at a rate of 0.1C;

[0033] Figure 2 The capacity retention rate of the sodium ion battery in Example 1 and the sodium ion battery in Comparative Example 1 after different cycle times at 1C is shown in FIG.

[0034] Figure 3 This is a TEM image of the coating layer on the surface of the core of the long-cycle sodium-ion battery positive electrode material prepared in Example 1. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The following are described in detail. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and simplicity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values ​​within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the numbered ranges, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any quoted numbers (fractions or integers) within the indicated range.

[0037] The present invention provides a long-cycle sodium ion battery positive electrode material, comprising a core and a coating layer coated on the surface of the core;

[0038] The chemical formula of the core is: Na x A y Bz Cu 0.1 Fe 0.3 C 0.1 Mn 0.3 D 0.1 O2;

[0039] Wherein, A is at least one of Li and K; B is at least one of Ni, Mg, Ca and Zn; C is at least one of Al and Y; D is at least one of Ti and Zr; 0.7≤x≤0.9, 0.01≤y≤0.1, z=((0.96~1)-xy)×0.5 (i.e. z=(0.98-xy±0.02)×0.5);

[0040] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0041] The long-cycle sodium ion battery positive electrode material of the present invention comprises a core and a coating layer coated on the surface of the core, wherein the core and the coating layer form a core-shell structure, and a protective layer is formed on the surface of the coating layer through the interaction between the composite coating layer and the core during the charging process, thereby reducing the damage of the electrolyte side reaction to the positive electrode material, and further reducing the element dissolution and volume change of the positive electrode material during the charging and discharging process through the regulation and design of the valence state of the bulk elements, and the above factors are combined to significantly improve the cycle performance of the positive electrode material.

[0042] In some embodiments, the molar ratio of TiO2, NaF and NaH2PO4 is 1:(2-2.5):(1-1.5).

[0043] In some embodiments, the mass of the coating layer is 0.1% to 1% of the mass of the core.

[0044] In some embodiments, the chemical formula of the core is Na 0.8 Li 0.05 Mg 0.025 Ni 0.05 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Ti 0.1 O2、Na 0.9 Li 0.01 Mg 0.035 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Zr 0.1 O2、Na 0.7 K 0.1 Mg 0.04 Ni 0.04 Cu 0.1 Fe 0.3 Y0.1 Mn 0.3 Ti 0.1 Any of O2.

[0045] Based on the same inventive concept, the present invention also provides a method for preparing a long-cycle sodium ion battery positive electrode material, comprising the following steps:

[0046] S1, mixing a sodium source, a compound containing A, a compound containing B, a Cu source, a Fe source, a compound containing C, a Mn source, and a compound containing D to obtain a first precursor;

[0047] S2, calcining the first precursor to obtain a calcined product;

[0048] S3, mixing NaF, TiO2 and NaH2PO4 to obtain a coating layer raw material, adding the calcined product in S2 to the coating layer raw material, and continuing to mix to obtain a second precursor;

[0049] S4. calcining the second precursor to obtain a long-cycle sodium-ion battery positive electrode material.

[0050] The preparation method of the long-cycle sodium ion battery positive electrode material of the present invention comprises the following steps: mixing a sodium source, a compound containing A, a compound containing B, a Cu source, an Fe source, a compound containing C, a Mn source, and a compound containing D according to the molar ratio of each metal element in the chemical formula of the inner core to obtain a first precursor; placing the first precursor in a muffle furnace for calcining to obtain a calcined product; mixing NaF, TiO2 and NaH2PO4 to obtain a coating layer raw material, adding the calcined product to the coating layer raw material, and continuing to mix to obtain a second precursor; placing the second precursor in a muffle furnace for calcining again to obtain the long-cycle sodium ion battery positive electrode material.

[0051] In some embodiments, in the step of calcining the first precursor to obtain a calcined product, the calcination temperature is 800-1000° C. and the calcination time is 10-20 hours.

[0052] In some embodiments, in the step of calcining the second precursor, the calcination temperature is 250-400° C. and the calcination time is 2-5 hours.

[0053] In some embodiments, NaF, TiO2 and NaH2PO4 are mixed to obtain a coating layer raw material, and a calcined product is added to the coating layer raw material and mixed continuously to obtain a second precursor, wherein the molar ratio of TiO2, NaF and NaH2PO4 is 1:(2-2.5):(1-1.5), and the mass ratio of the coating layer raw material to the calcined product is (0.1-1):100.

[0054] In some embodiments, the sodium source includes at least one of sodium carbonate, sodium bicarbonate, sodium acetate, and sodium oxalate;

[0055] In some embodiments, the Cu source includes at least one of copper carbonate, copper nitrate, copper oxalate, copper acetate, and copper oxide.

[0056] In some embodiments, the Fe source includes at least one of ferric oxide, ferric nitrate, ferric oxalate, and ferric acetate.

[0057] In some embodiments, the Mn source includes at least one of manganese tetraoxide, manganese nitrate, manganese oxalate, and manganese acetate.

[0058] In some embodiments, the A-containing compound includes at least one of A-containing carbonates, nitrates, oxalates, acetates, and oxides.

[0059] In some embodiments, the B-containing compound includes at least one of a carbonate, a nitrate, an oxalate, an acetate, and an oxide containing B.

[0060] In some embodiments, the C-containing compound includes at least one of a C-containing carbonate, a nitrate, an oxalate, an acetate, and an oxide.

[0061] In some embodiments, the D-containing compound includes at least one of a D-containing carbonate, a nitrate, an oxalate, an acetate, and an oxide.

[0062] In some embodiments, A is Li, and the Li-containing compound is at least one of lithium carbonate, lithium nitrate, lithium oxalate, lithium acetate, and lithium oxide.

[0063] In some embodiments, A is K, and the compound containing K is at least one of potassium carbonate, potassium nitrate, potassium oxalate, potassium acetate, and potassium oxide.

[0064] In some embodiments, B is Ni, and the Ni-containing compound is at least one of nickel carbonate, nickel nitrate, nickel oxalate, nickel acetate, and nickelous oxide.

[0065] In some embodiments, B is Mg, and the Mg-containing compound is at least one of magnesium carbonate, magnesium nitrate, magnesium oxalate, magnesium acetate, and magnesium oxide.

[0066] In some embodiments, C is Al, and the compound containing Al is at least one of aluminum carbonate, aluminum nitrate, aluminum oxalate, aluminum acetate, and aluminum oxide (ie, aluminum oxide).

[0067] In some embodiments, C is Y, and the compound containing Y is at least one of yttrium carbonate, yttrium nitrate, yttrium oxalate, yttrium acetate, and yttrium oxide.

[0068] In some embodiments, D is Ti, and the compound containing Ti is at least one of titanium carbonate, titanium nitrate, titanium oxalate, titanium acetate, and titanium dioxide.

[0069] In some embodiments, D is Zr, and the Zr-containing compound is at least one of zirconium carbonate, zirconium nitrate, zirconium oxalate, zirconium acetate, and zirconium oxide.

[0070] Based on the same inventive concept, the present invention also provides an application of the above-mentioned long-cycle sodium-ion battery positive electrode material or the long-cycle sodium-ion battery positive electrode material prepared by the above-mentioned preparation method in the preparation of a sodium-ion battery.

[0071] Based on the same inventive concept, the present invention also provides a sodium ion battery, comprising a positive electrode, wherein the positive electrode comprises the above-mentioned long-cycle sodium ion battery positive electrode material or the long-cycle sodium ion battery positive electrode material prepared by the above-mentioned preparation method.

[0072] Specifically, the above-mentioned long-cycle sodium-ion battery positive electrode material is used as the positive electrode active material, and the long-cycle sodium-ion battery positive electrode material, the conductive agent and the binder are mixed, coated on the positive electrode current collector, and dried to obtain the positive electrode; the conductive agent is a conventional conductive agent in the art, for example, including any one or more of conductive carbon black, conductive graphite, graphene, carbon nanotubes, acetylene black, Ketjen black or Super PLi; the binder is a conventional binder in the art, for example, the binder includes at least one of PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), CMC (sodium carboxymethyl cellulose), SBR (styrene-butadiene rubber emulsion), PAN (polyacrylonitrile), PAA (polyacrylic acid), etc.

[0073] In some embodiments, in addition to the above-mentioned positive electrode, the sodium ion battery also includes a negative electrode, an electrolyte, and a diaphragm; the negative electrode, the electrolyte, and the diaphragm are all conventional materials in the art; for example, the diaphragm is a PE diaphragm (polyethylene diaphragm), a PP diaphragm (polypropylene diaphragm), etc.; the electrolyte includes a sodium salt and an organic solvent; the sodium salt is any one or more of sodium hexafluorophosphate, sodium perchlorate, sodium trifluoromethylsulfonate, sodium tetrafluoroborate, sodium bis(fluorosulfonyl)imide and sodium bis(trifluoromethylsulfonyl)imide; the organic solvent is ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, diethylene glycol dimethyl ether, 1, Any one or more of 3-cyclopentanediol, ethylene glycol dimethyl ether and triethylene glycol dimethyl ether; the preparation method of the negative electrode is: mixing the negative electrode active material, the conductive agent and the binder, coating them on the negative electrode collector, and drying to obtain the negative electrode; the negative electrode active material includes hard carbon, soft carbon, Sn, Sb, Bi and other metals and their alloys, metal oxides and sulfides: such as TiO2, MnO2, FeS2, etc.; the conductive agent includes carbon nanotubes, graphene, conductive carbon black, etc.; the binder includes sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc.

[0074] The following further illustrates the long-cycle sodium ion battery positive electrode material and its preparation method and application, and the sodium ion battery of the present application with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as a limitation of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0075] Example 1

[0076] The embodiment of the present application provides a long-cycle sodium-ion battery positive electrode material, including a core and a coating layer coated on the surface of the core;

[0077] The chemical formula of the core is: Na 0.8 Li 0.05 Mg 0.025 Ni 0.05 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Ti 0.1 O2;

[0078] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0079] The method for preparing the above-mentioned long-cycle sodium ion battery positive electrode material comprises the following steps:

[0080] S1. According to the molar ratio of each metal element in the chemical formula of the core, sodium carbonate, lithium carbonate, magnesium carbonate, nickelous oxide, cupric oxide, ferric oxide, aluminum oxide, manganese tetraoxide, and titanium dioxide are mixed to obtain a first precursor;

[0081] S2, placing the first precursor in a muffle furnace, and calcining at 950° C. for 12 h to obtain a calcined product;

[0082] S3, mixing TiO2, NaF, and NaH2PO4 in a molar ratio of 1:2:1 to obtain a coating layer raw material, adding the calcined product in S2 to the coating layer raw material, and continuing to mix to obtain a second precursor; the mass of the coating layer raw material is 0.5% of the mass of the calcined product;

[0083] S4. Place the second precursor in a muffle furnace and calcine it at 300° C. for 2 h to obtain a long-cycle sodium-ion battery positive electrode material.

[0084] This embodiment also provides a sodium ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte;

[0085] The preparation method of the positive electrode is as follows: the long-cycle sodium ion battery positive electrode material prepared in Example 1, the conductive agent and the binder are mixed uniformly in a mass ratio of 90:5:5 and coated on an aluminum foil, dried at 120° C. for 6 h, and cut into discs to obtain a positive electrode; the conductive agent is conductive carbon black; the binder is PVDF (polyvinylidene fluoride);

[0086] The negative electrode is a sodium metal negative electrode sheet;

[0087] The electrolyte includes NaClO4, EC (ethylene carbonate) and DMC (dimethyl carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate) are used as solvents, and NaClO4 is a sodium salt; the volume ratio of EC to DMC is 1:1, and the concentration of NaClO4 in the electrolyte is 1.0 mol / L;

[0088] The diaphragm is a PE diaphragm;

[0089] Assemble the positive electrode, negative electrode, separator and electrolyte into a button battery.

[0090] Example 2

[0091] The embodiment of the present application provides a long-cycle sodium-ion battery positive electrode material, including a core and a coating layer coated on the surface of the core;

[0092] The chemical formula of the core is: Na 0.9 Li 0.01 Mg 0.035 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Zr 0.1 O2;

[0093] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0094] The method for preparing the above-mentioned long-cycle sodium ion battery positive electrode material comprises the following steps:

[0095] S1. According to the molar ratio of each metal element in the chemical formula of the core, sodium carbonate, lithium carbonate, magnesium carbonate, copper nitrate, ferric oxide, aluminum nitrate, manganese tetraoxide, and zirconium dioxide are mixed to obtain a first precursor;

[0096] S2, placing the first precursor in a muffle furnace, and calcining at 950° C. for 12 h to obtain a calcined product;

[0097] S3, mixing TiO2, NaF, and NaH2PO4 in a molar ratio of 1:2.5:1.5 to obtain a coating layer raw material, adding the calcined product in S2 to the coating layer raw material, and continuing to mix to obtain a second precursor; the mass of the coating layer raw material is 0.5% of the mass of the calcined product;

[0098] S4. Place the second precursor in a muffle furnace and calcine it at 300° C. for 2 h to obtain a long-cycle sodium-ion battery positive electrode material.

[0099] This embodiment also provides a sodium ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte;

[0100] The preparation method of the positive electrode is as follows: the long-cycle sodium ion battery positive electrode material prepared in Example 2, the conductive agent and the binder are mixed uniformly in a mass ratio of 90:5:5 and coated on an aluminum foil, dried at 120° C. for 6 h, and cut into discs to obtain a positive electrode; the conductive agent is conductive carbon black; the binder is PVDF (polyvinylidene fluoride);

[0101] The negative electrode is a sodium metal negative electrode sheet;

[0102] The electrolyte includes NaClO4, EC (ethylene carbonate) and DMC (dimethyl carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate) are used as solvents, and NaClO4 is a sodium salt; the volume ratio of EC to DMC is 1:1, and the concentration of NaClO4 in the electrolyte is 1.0 mol / L;

[0103] The diaphragm is a PE diaphragm;

[0104] Assemble the positive electrode, negative electrode, separator and electrolyte into a button battery.

[0105] Example 3

[0106] The embodiment of the present application provides a long-cycle sodium-ion battery positive electrode material, including a core and a coating layer coated on the surface of the core;

[0107] The chemical formula of the core is: Na 0.7 K 0.1 Mg 0.04 Ni 0.04 Cu 0.1 Fe 0.3 Y 0.1 Mn 0.3 Ti 0.1 O2;

[0108] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0109] The method for preparing the above-mentioned long-cycle sodium ion battery positive electrode material comprises the following steps:

[0110] S1. According to the molar ratio of each metal element in the chemical formula of the inner core, sodium carbonate, potassium carbonate, magnesium carbonate, nickelous oxide, copper nitrate, ferric oxide, yttrium nitrate, manganese tetraoxide, and titanium dioxide are mixed to obtain a first precursor;

[0111] S2, placing the first precursor in a muffle furnace, and calcining at 950° C. for 12 h to obtain a calcined product;

[0112] S3, mixing TiO2, NaF, and NaH2PO4 in a molar ratio of 1:2:1.5 to obtain a coating layer raw material, adding the calcined product in S2 to the coating layer raw material, and continuing to mix to obtain a second precursor; the mass of the coating layer raw material is 0.5% of the mass of the calcined product;

[0113] S4. Place the second precursor in a muffle furnace and calcine it at 300° C. for 2 h to obtain a long-cycle sodium-ion battery positive electrode material.

[0114] This embodiment also provides a sodium ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte;

[0115] The positive electrode preparation method is as follows: the long-cycle sodium ion battery positive electrode material prepared in Example 3, the conductive agent and the binder are mixed uniformly in a mass ratio of 90:5:5 and coated on an aluminum foil, dried at 120° C. for 6 h, and cut into discs to obtain a positive electrode; the conductive agent is conductive carbon black; the binder is PVDF (polyvinylidene fluoride);

[0116] The negative electrode is a sodium metal negative electrode sheet;

[0117] The electrolyte includes NaClO4, EC (ethylene carbonate) and DMC (dimethyl carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate) are used as solvents, and NaClO4 is a sodium salt; the volume ratio of EC to DMC is 1:1, and the concentration of NaClO4 in the electrolyte is 1.0 mol / L;

[0118] The diaphragm is a PE diaphragm;

[0119] Assemble the positive electrode, negative electrode, separator and electrolyte into a button battery.

[0120] Example 4

[0121] The embodiment of the present application provides a long-cycle sodium-ion battery positive electrode material, including a core and a coating layer coated on the surface of the core;

[0122] The chemical formula of the core is: Na 0.8 Li 0.05 Mg 0.025 Ni 0.05 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Ti 0.1 O2;

[0123] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0124] The method for preparing the above-mentioned long-cycle sodium ion battery positive electrode material comprises the following steps:

[0125] S1. According to the molar ratio of each metal element in the chemical formula of the core, sodium carbonate, lithium carbonate, magnesium carbonate, nickelous oxide, cupric oxide, ferric oxide, aluminum oxide, manganese tetraoxide, and titanium dioxide are mixed to obtain a first precursor;

[0126] S2, placing the first precursor in a muffle furnace and calcining at 800° C. for 20 h to obtain a calcined product;

[0127] S3, mixing TiO2, NaF, and NaH2PO4 in a molar ratio of 1:2:1 to obtain a coating layer raw material, adding the calcined product in S2 to the coating layer raw material, and continuing to mix to obtain a second precursor; the mass of the coating layer raw material is 0.5% of the mass of the calcined product;

[0128] S4. Place the second precursor in a muffle furnace and calcine at 400° C. for 5 h to obtain a long-cycle sodium-ion battery positive electrode material.

[0129] This embodiment also provides a sodium ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte;

[0130] The preparation method of the positive electrode is as follows: the long-cycle sodium ion battery positive electrode material prepared in Example 4, the conductive agent and the binder are mixed uniformly in a mass ratio of 90:5:5 and coated on an aluminum foil, dried at 120° C. for 6 h, and cut into discs to obtain a positive electrode; the conductive agent is conductive carbon black; the binder is PVDF (polyvinylidene fluoride);

[0131] The negative electrode is a sodium metal negative electrode sheet;

[0132] The electrolyte includes NaClO4, EC (ethylene carbonate) and DMC (dimethyl carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate) are used as solvents, and NaClO4 is a sodium salt; the volume ratio of EC to DMC is 1:1, and the concentration of NaClO4 in the electrolyte is 1.0 mol / L;

[0133] The diaphragm is a PE diaphragm;

[0134] Assemble the positive electrode, negative electrode, separator and electrolyte into a button battery.

[0135] Example 5

[0136] The embodiment of the present application provides a long-cycle sodium-ion battery positive electrode material, including a core and a coating layer coated on the surface of the core;

[0137] The chemical formula of the core is: Na 0.8 Li 0.05 Mg0.025 Ni 0.05 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Ti 0.1 O2;

[0138] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0139] The method for preparing the above-mentioned long-cycle sodium ion battery positive electrode material comprises the following steps:

[0140] S1. According to the molar ratio of each metal element in the chemical formula of the core, sodium carbonate, lithium carbonate, magnesium carbonate, nickelous oxide, cupric oxide, ferric oxide, aluminum oxide, manganese tetraoxide, and titanium dioxide are mixed to obtain a first precursor;

[0141] S2, placing the first precursor in a muffle furnace and calcining it at 1000° C. for 10 h to obtain a calcined product;

[0142] S3, mixing TiO2, NaF, and NaH2PO4 in a molar ratio of 1:2:1 to obtain a coating layer raw material, adding the calcined product in S2 to the coating layer raw material, and continuing to mix to obtain a second precursor; the mass of the coating layer raw material is 0.5% of the mass of the calcined product;

[0143] S4. Place the second precursor in a muffle furnace and calcine at 250° C. for 2 h to obtain a long-cycle sodium-ion battery positive electrode material.

[0144] This embodiment also provides a sodium ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte;

[0145] The preparation method of the positive electrode is as follows: the long-cycle sodium ion battery positive electrode material prepared in Example 5, the conductive agent and the binder are mixed uniformly in a mass ratio of 90:5:5 and coated on an aluminum foil, dried at 120° C. for 6 h, and cut into discs to obtain a positive electrode; the conductive agent is conductive carbon black; the binder is PVDF (polyvinylidene fluoride);

[0146] The negative electrode is a sodium metal negative electrode sheet;

[0147] The electrolyte includes NaClO4, EC (ethylene carbonate) and DMC (dimethyl carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate) are used as solvents, and NaClO4 is a sodium salt; the volume ratio of EC to DMC is 1:1, and the concentration of NaClO4 in the electrolyte is 1.0 mol / L;

[0148] The diaphragm is a PE diaphragm;

[0149] Assemble the positive electrode, negative electrode, separator and electrolyte into a button battery.

[0150] Comparative Example 1

[0151] This comparative example provides a sodium ion battery positive electrode material, the chemical formula of which is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2;

[0152] The method for preparing the above-mentioned sodium ion battery positive electrode material comprises the following steps:

[0153] S1. According to the molar ratio of each metal element in the chemical formula of the sodium ion battery positive electrode material, sodium carbonate, nickelous oxide, ferric oxide and manganese tetraoxide are mixed to obtain a precursor;

[0154] S2. Place the precursor in S1 in a muffle furnace and calcine at 900° C. for 20 h to obtain a positive electrode material for a sodium ion battery.

[0155] This comparative example also provides a sodium ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte;

[0156] The preparation method of the positive electrode is as follows: the sodium ion battery positive electrode material prepared in Comparative Example 1, the conductive agent and the binder are mixed uniformly in a mass ratio of 90:5:5 and coated on an aluminum foil, dried at 120° C. for 6 hours, and cut into discs to obtain a positive electrode; the conductive agent is conductive carbon black; the binder is PVDF (polyvinylidene fluoride);

[0157] The negative electrode is a sodium metal negative electrode sheet;

[0158] The electrolyte includes NaClO4, EC (ethylene carbonate) and DMC (dimethyl carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate) are used as solvents, and NaClO4 is a sodium salt; the volume ratio of EC to DMC is 1:1, and the concentration of NaClO4 in the electrolyte is 1.0 mol / L;

[0159] The diaphragm is a PE diaphragm;

[0160] Assemble the positive electrode, negative electrode, separator and electrolyte into a button battery.

[0161] Comparative Example 2

[0162] This comparative example provides a sodium ion battery positive electrode material, comprising a core and a coating layer coated on the surface of the core;

[0163] The chemical formula of the core is: Na 0.95 Li 0.05 Mg 0.025 Ni 0.05 Cu 0.1 Fe 0.3 Al 0.1 Mn0.3 Ti 0.1 O2;

[0164] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0165] The method for preparing the above-mentioned long-cycle sodium ion battery positive electrode material comprises the following steps:

[0166] S1. According to the molar ratio of each metal element in the chemical formula of the core, sodium carbonate, lithium carbonate, magnesium carbonate, nickelous oxide, cupric oxide, ferric oxide, aluminum oxide, manganese tetraoxide, and titanium dioxide are mixed to obtain a first precursor;

[0167] S2, placing the first precursor in a muffle furnace, and calcining at 950° C. for 12 h to obtain a calcined product;

[0168] S3, mixing TiO2, NaF, and NaH2PO4 in a molar ratio of 1:2:1 to obtain a coating layer raw material, adding the calcined product in S2 to the coating layer raw material, and continuing to mix to obtain a second precursor; the mass of the coating layer raw material is 0.5% of the mass of the calcined product;

[0169] S4. Place the second precursor in a muffle furnace and calcine at 300° C. for 2 h to obtain a positive electrode material for a sodium ion battery.

[0170] This comparative example also provides a sodium ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte;

[0171] The preparation method of the positive electrode is as follows: the sodium ion battery positive electrode material prepared in Comparative Example 2, the conductive agent and the binder are mixed uniformly in a mass ratio of 90:5:5 and coated on an aluminum foil, dried at 120° C. for 6 hours, and cut into discs to obtain a positive electrode; the conductive agent is conductive carbon black; the binder is PVDF (polyvinylidene fluoride);

[0172] The negative electrode is a sodium metal negative electrode sheet;

[0173] The electrolyte includes NaClO4, EC (ethylene carbonate) and DMC (dimethyl carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate) are used as solvents, and NaClO4 is a sodium salt; the volume ratio of EC to DMC is 1:1, and the concentration of NaClO4 in the electrolyte is 1.0 mol / L;

[0174] The diaphragm is a PE diaphragm;

[0175] Assemble the positive electrode, negative electrode, separator and electrolyte into a button battery.

[0176] Comparative Example 3

[0177] This comparative example provides a sodium ion battery positive electrode material, comprising a core and a coating layer coated on the surface of the core;

[0178] The chemical formula of the core is: Na 0.8 Li 0.2 Mg 0.025 Ni 0.05 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Ti 0.1 O2;

[0179] The coating layer is composed of NaF, TiO2 and NaH2PO4.

[0180] The method for preparing the above-mentioned long-cycle sodium ion battery positive electrode material comprises the following steps:

[0181] S1. According to the molar ratio of each metal element in the chemical formula of the core, sodium carbonate, lithium carbonate, magnesium carbonate, nickelous oxide, cupric oxide, ferric oxide, aluminum oxide, manganese tetraoxide, and titanium dioxide are mixed to obtain a first precursor;

[0182] S2, placing the first precursor in a muffle furnace, and calcining at 950° C. for 12 h to obtain a calcined product;

[0183] S3, mixing TiO2, NaF, and NaH2PO4 in a molar ratio of 1:2:1 to obtain a coating layer raw material, adding the calcined product in S2 to the coating layer raw material, and continuing to mix to obtain a second precursor; the mass of the coating layer raw material is 0.5% of the mass of the calcined product;

[0184] S4. Place the second precursor in a muffle furnace and calcine at 300° C. for 2 h to obtain a positive electrode material for a sodium ion battery.

[0185] This comparative example also provides a sodium ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte;

[0186] The preparation method of the positive electrode is as follows: the sodium ion battery positive electrode material prepared in Comparative Example 3, the conductive agent and the binder are mixed uniformly in a mass ratio of 90:5:5 and coated on an aluminum foil, dried at 120° C. for 6 hours, and cut into discs to obtain a positive electrode; the conductive agent is conductive carbon black; the binder is PVDF (polyvinylidene fluoride);

[0187] The negative electrode is a sodium metal negative electrode sheet;

[0188] The electrolyte includes NaClO4, EC (ethylene carbonate) and DMC (dimethyl carbonate), EC (ethylene carbonate) and DMC (dimethyl carbonate) are used as solvents, and NaClO4 is a sodium salt; the volume ratio of EC to DMC is 1:1, and the concentration of NaClO4 in the electrolyte is 1.0 mol / L;

[0189] The diaphragm is a PE diaphragm;

[0190] Assemble the positive electrode, negative electrode, separator and electrolyte into a button battery.

[0191] Performance Testing

[0192] The sodium ion batteries in Examples 1 to 5 and Comparative Examples 1 to 3 were charged and discharged in a voltage window of 2.0-4.0 V, cycled 2 times at 0.1 C, and then cycled 100 times at 1 C. The test results are shown in Table 1 below.

[0193] Table 1 - Performance of sodium ion batteries in different embodiments

[0194]

[0195] It can be seen from Table 1 that the sodium ion batteries in Examples 1 to 5 have significantly improved cycle performance compared to the sodium ion battery in Comparative Example 1. In addition, the sodium ion batteries in Comparative Examples 2 to 3 outside the design range cannot achieve the high cycle performance effect of the sodium ion batteries in Examples 1 to 5.

[0196] Figure 1 This is the first cycle charge and discharge curve of the sodium ion battery in Example 1 at a rate of 0.1C.

[0197] from Figure 1 It can be seen that the sodium ion battery in Example 1 has a discharge capacity of 130 mAh / g, which has a high practical value.

[0198] Figure 2 The figure is a graph showing the capacity retention rate changes of the sodium ion battery in Example 1 and the sodium ion battery in Comparative Example 1 after different cycle times at 1C.

[0199] from Figure 2 It can be seen that the capacity retention rate of the sodium ion battery in Example 1 is higher than that in Comparative Example 1 under the same number of cycles, indicating that the sodium ion battery in Example 1 has better stability.

[0200] Figure 3 This is a TEM image of the coating layer on the surface of the inner core of the long-cycle sodium-ion battery positive electrode material prepared in Example 1.

[0201] from Figure 3It can be seen that the coating layer evenly covers the surface of the inner core, which can reduce the damage of the electrolyte side reaction to the positive electrode material and improve the stability of the positive electrode material.

[0202] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A long cycle sodium ion battery positive electrode material, characterized in that: It comprises a core and a coating layer coated on the surface of the core; The chemical formula of the core is: Na x A y B z Cu 0.1 Fe 0.3 C 0.1 Mn 0.3 D 0.1 O2; Wherein, A is at least one of Li and K; B is at least one of Ni, Mg, Ca and Zn; C is at least one of Al and Y; D is at least one of Ti and Zr; 0.7≤x≤0.9, 0.01≤y≤0.1, z=((0.96~1)-xy)×0.5; The coating layer is composed of NaF, TiO2 and NaH2PO4.

2. The long cycle sodium ion battery positive electrode material according to claim 1, characterized in that The molar ratio of TiO2, NaF and NaH2PO4 is 1:(2-2.5):(1-1.5); And / or, the mass of the coating layer is 0.1% to 1% of the mass of the core.

3. The long cycle sodium ion battery positive electrode material according to claim 1, characterized in that The chemical formula of the core is Na 0.8 Li 0.05 Mg 0.025 Ni 0.05 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Ti 0.1 O2、Na 0.9 Li 0.01 Mg 0.035 Cu 0.1 Fe 0.3 Al 0.1 Mn 0.3 Zr 0.1 O2、Na 0.7 K 0.1 Mg 0.04 Ni 0.04 Cu 0.1 Fe 0.3 Y 0.1 Mn 0.3 Ti 0.1 Any of O2.

4. A method for preparing a long-cycle sodium ion battery positive electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Mixing a sodium source, a compound containing A, a compound containing B, a Cu source, a Fe source, a compound containing C, a Mn source, and a compound containing D to obtain a first precursor; calcining the first precursor to obtain a calcined product; Mixing NaF, TiO2 and NaH2PO4 to obtain a coating layer raw material, adding the calcined product to the coating layer raw material, and continuing to mix to obtain a second precursor; The second precursor is calcined to obtain a long-cycle sodium-ion battery positive electrode material.

5. The method for preparing a long cycle sodium ion battery positive electrode material according to claim 4, characterized in that: In the step of calcining the first precursor to obtain a calcined product, the calcination temperature is 800 to 1000° C. and the calcination time is 10 to 20 hours.

6. The method for preparing a long-cycle sodium ion battery positive electrode material according to claim 4, characterized in that: In the step of calcining the second precursor, the calcination temperature is 250 to 400° C. and the calcination time is 2 to 5 hours.

7. The method for preparing a long-cycle sodium ion battery positive electrode material according to claim 4, characterized in that: NaF, TiO2 and NaH2PO4 are mixed to obtain a coating layer raw material, and the calcined product is added to the coating layer raw material and mixed continuously to obtain a second precursor, wherein the molar ratio of TiO2, NaF and NaH2PO4 is 1:(2-2.5):(1-1.5), and the mass ratio of the coating layer raw material to the calcined product is (0.1-1):

100.

8. The method for preparing a long-cycle sodium ion battery positive electrode material according to claim 4, characterized in that: The sodium source includes at least one of sodium carbonate, sodium bicarbonate, sodium acetate and sodium oxalate; And / or, the Cu source includes at least one of copper carbonate, copper nitrate, copper oxalate, copper acetate, and copper oxide; And / or, the Fe source includes at least one of ferric oxide, ferric nitrate, ferric oxalate and ferric acetate; And / or, the Mn source includes at least one of manganese tetraoxide, manganese nitrate, manganese oxalate and manganese acetate; And / or, the A-containing compound includes at least one of carbonate, nitrate, oxalate, acetate, and oxide containing A; And / or, the B-containing compound includes at least one of carbonate, nitrate, oxalate, acetate and oxide containing B; And / or, the C-containing compound includes at least one of a C-containing carbonate, a nitrate, an oxalate, an acetate, and an oxide; And / or, the D-containing compound includes at least one of D-containing carbonates, nitrates, oxalates, acetates, and oxides.

9. Use of the long-cycle sodium ion battery positive electrode material as claimed in any one of claims 1 to 3 or the long-cycle sodium ion battery positive electrode material prepared by the preparation method as claimed in any one of claims 4 to 8 in the preparation of a sodium ion battery.

10. A sodium ion battery, characterized in that: It comprises a positive electrode, wherein the positive electrode comprises the long-cycle sodium ion battery positive electrode material according to any one of claims 1 to 3 or the long-cycle sodium ion battery positive electrode material prepared by the preparation method according to any one of claims 4 to 8.

Images