Layered oxide material for sodium-ion battery, preparation method and application

Abstract

The invention relates to a sodium ion battery layered oxide material, a preparation method and application. The chemical formula of the sodium-ion battery layered oxide material is NaxLiaM1bNicMndM2eO2 + / -alpha, the space group is R-3m, and the corresponding structure is an O3 phase; wherein Li is an alkali metal element, Ni and Mn are transition metal elements, M1 is an element for replacing the transition metal Ni, and M2 is an element for replacing the transition metal Mn; m1 comprises at least two of B < 3 + >, Al < 3 + >, Fe < 3 + >, Sc < 3 + >, Y < 3 + > and La < 3 + >, and M2 comprises at least one of Si < 4 + >, Ti < 4 + >, Zr < 4 + > and Sn < 4 + >; x, a, b, c, d, e and 2 + / -alpha are mole percentages of corresponding elements respectively, and each component in the chemical formula satisfies charge conservation and stoichiometric ratio conservation, namely satisfies x + a + 3 * b + 2 * c + 4 * (d + e) = 2 * (2 + / -alpha) and a + b + c + d + e = 1, and satisfies 0.8 < = x < = 1.05, 0 < a < = 0.1, 0 < b < = 0.1, 0.3 < = c < 0.5, 0.2 < = d < 0.5, 0 < e < = 0.3, 0 < = alpha < = 0.05, a = b, a + b + c = 0.5, and d + e = 0.5.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion battery materials, and in particular to a sodium ion battery layered oxide material, a preparation method and applications thereof. Background Art

[0002] As lithium and cobalt resource constraints become increasingly severe, the cost of lithium-ion batteries has risen significantly. However, sodium is extremely abundant in the Earth's crust (23,000 ppm vs. Li 17 ppm), is widely distributed, and is inexpensive. Sodium-ion batteries have significant advantages in terms of cost, resources, and safety. In addition, sodium-ion batteries have good low-temperature performance and over-discharge resistance, making them an excellent choice for large-scale energy storage. They also have a broad market in two-wheeled electric vehicles and A00-class electric vehicles.

[0003] Due to their inherent properties, sodium-ion batteries have lower energy density than lithium-ion batteries, a key drawback of sodium-ion batteries. Cathode materials play a decisive role in achieving this energy density. Of the three major approaches to sodium-ion cathodes, layered oxides offer the highest specific capacity and the greatest potential for industrialization. Therefore, developing high-capacity cathodes is of great significance to sodium-ion batteries.

[0004] The specific capacity of layered oxide cathodes currently used in the industry is typically less than 140 mAh / g, which is detrimental to improving the energy density of sodium-ion batteries. To achieve high-capacity layered oxides, increasing the cutoff voltage and the content of variable-valence cations are key to improving the specific capacity. However, this is also accompanied by more severe phase transition behavior, capacity fade, voltage decay (referring to a decrease in the average discharge voltage), and polarization growth (polarization is quantified here as the difference between the average charge voltage and the average discharge voltage). The voltage decay problem of O3-phase cathode materials during cycling has not been effectively addressed. Especially at high voltages, it is accompanied not only by capacity fade but also by severe voltage decay and polarization growth. This voltage decay phenomenon typically originates from the irreversible migration of cations from the transition metal layer into the sodium layer, the dissolution of transition metal layer elements, and the growth of a surface rock salt phase. Doping and substitution of transition metal layer elements is a promising approach to address this problem, but current work has not yet resolved it. This is because the material experiences significant volume strain when charged to high voltages, and the effect of a single element is very limited. Small substitutions have no significant effect, while large substitutions can severely degrade the material's electrochemical performance. For example, the common use of Ti to replace Mn, although it can smooth the charge and discharge curves, will reduce the electronic conductivity of the material itself, produce greater polarization, and significantly reduce the material's specific capacity and first-cycle coulombic efficiency.

[0005] The industry has also adopted a scheme of multi-element doping of transition metal layer elements. Multi-element doping is of great help to capacity attenuation, but there is no outstanding or obvious improvement in suppressing voltage attenuation. The applicant of the present invention has conducted research on this issue and believes that: there are many factors that determine voltage attenuation. For example, the stability of the material surface is very important for suppressing transition metal dissolution and material rock salt transformation, but it is usually ignored. In common processes and material compositions, the elements are often evenly distributed on the surface. In addition, the existing Na-Ni-Mn-O based materials often provide charge compensation through the valence change of transition metal nickel during the charging and discharging process, but a small amount of manganese also changes valence at low voltage, generating Mn with severe Jan-Taylor effect. 3+ , which not only causes severe dissolution of transition metal manganese, but also causes interface instability of the material during the electrochemical process, resulting in the problem of discharge voltage decay that cannot be suppressed. Summary of the Invention

[0006] The purpose of the present invention is to address the defects of the prior art and provide a sodium ion battery layered oxide material, preparation method and application. The sodium ion battery layered oxide material of the present invention suppresses the migration and dissolution of transition metals by multi-element doping substitution of transition metal positions, and suppresses interfacial side reactions by surface doping, thereby having the characteristics of extremely low attenuation of average discharge voltage at high voltage (less than 0.2mV / week) and extremely high cycle retention rate. In addition, the average operating voltage of the material can be increased by doping substitution of transition metal elements, and the air stability and cycle stability of the material can be significantly improved.

[0007] To achieve the above objectives, in the first aspect, the present invention provides a sodium ion battery layered oxide material having the chemical formula Na x Li a M1 b Ni c Mn d M2 e O 2±α , the space group is R-3m, and the corresponding structure is O3 phase;

[0008] Wherein, Li is an alkali metal element, Ni and Mn are transition metal elements, M1 is an element that replaces the transition metal Ni, and M2 is an element that replaces the transition metal Mn; M1 includes B 3+ 、Al 3+ 、Fe 3+ Sc 3+ 、Y 3+ 、La 3+ At least two of M2 include Si 4+ 、Ti 4+ 、Zr 4+ 、Sn 4+at least one of; x, a, b, c, d, e and 2±α are respectively the molar percentages of the corresponding elements, and each component in the chemical formula satisfies the conservation of charge and the conservation of the stoichiometric ratio, that is, x+a+3×b+2×c+4×(d+e)=2×(2±α) and a+b+c+d+e=1, and satisfies 0.8≤x≤1.05, 0<a≤0.1, 0<b≤0.1, 0.3≤c<0.5, 0.2≤d<0.5, 0<e≤0.3, 0≤α≤0.05, a=b, a+b+c=0.5, d+e=0.5.

[0009] Preferably, the sodium ion battery layered oxide material is used as a positive electrode active material for a sodium ion secondary battery;

[0010] By replacing the transition metal Ni and / or Mn with the element Li and M1, the migration of the transition metal is suppressed. At the same time, the surface doping of M1 element reduces the interface side reaction and suppresses the surface rock salt transformation. By replacing the transition metal Mn with the element M2, the structural stability of the material is improved and the Mn migration during the cycle is suppressed. 3+ The production of Li, M1, and M2 can be suppressed, and the dissolution of transition metals can be inhibited; through the synergistic effect of Li, M1, and M2 replacing the transition metal sites, the discharge voltage decay is suppressed, so that the average discharge voltage decay rate is less than 0.2mV / cycle, and the total decay after 800 cycles is no more than 1.7mV.

[0011] In a second aspect, an embodiment of the present invention provides a method for preparing the sodium ion battery layered oxide material according to the first aspect, wherein the preparation method is a solid phase method, comprising:

[0012] According to Na x Li a M1 b Ni c Mn d M2 e O 2±α The required stoichiometric ratio of each element is obtained by weighing 0 wt.% to 10 wt.% of the required stoichiometric sodium source and lithium source, the required stoichiometric nickel source, manganese source, the precursor containing M1 and the precursor containing M2 in proportion, adding liquid ball milling medium, and ball milling at a speed of 300-600 rpm for 1-12 hours to obtain a powder;

[0013] The powder is placed in a crucible, calcined at 600-1000° C. for 1-20 hours in an atmosphere of air or pure oxygen, and then ground after cooling to room temperature to obtain the sodium ion battery layered oxide material;

[0014] Wherein, the sodium source includes: at least one of sodium hydroxide, sodium carbonate, sodium nitrate, sodium oxide, sodium peroxide, sodium acetate and sodium oxalate; the lithium source includes: at least one of lithium oxide, lithium hydroxide, lithium carbonate and lithium nitrate; the nickel source includes: at least one of nickel-containing metal oxides, metal carbonates, metal nitrates, metal oxalates, metal acetates, metal sulfates and metal hydroxides; the manganese source includes: at least one of manganese-containing metal oxides, metal carbonates, metal nitrates, metal oxalates, metal acetates, metal sulfates and metal hydroxides; the precursor containing M1 includes: at least one of oxides, carbonates, nitrates, oxalates, acetates, sulfates and hydroxides containing M1; the precursor containing M2 includes: at least one of oxides, carbonates, nitrates, oxalates, acetates, sulfates and hydroxides containing M2; M1 includes B 3+ 、Al 3+ 、Fe 3+ Sc 3+ 、Y 3+ 、La 3+ At least two of M2 include Si 4+ 、Ti 4+ 、Zr 4+ 、Sn 4+ At least one of; the liquid milling medium includes: one or more of anhydrous ethanol, isopropanol or acetone.

[0015] In a third aspect, an embodiment of the present invention provides a method for preparing the sodium ion battery layered oxide material according to the first aspect, wherein the preparation method is a sol-gel method, comprising:

[0016] According to Na x Li a M1 b Ni c Mn d M2 e O 2±α The required stoichiometric ratio of each element in the mixture is obtained by weighing 100wt.%-110wt.% of a sodium source, a required stoichiometric lithium source, a nickel source, a manganese source, a precursor containing M1, and a precursor containing M2, and an appropriate amount of citric acid, and dissolving them in deionized water to form a mixed solution; wherein the sodium source, lithium source, nickel source, manganese source, precursor containing M1, and precursor containing M2 are soluble salts of sodium, lithium, nickel, manganese, M1, and M2, respectively; the soluble salts include one or more of nitrate, oxalate, acetate, or sulfate; M1 includes B 3+ 、Al 3+ 、Fe 3+ Sc 3+ 、Y 3+ 、La 3+At least two of M2 include Si 4+ 、Ti 4+ 、Zr 4+ 、Sn 4+ at least one of;

[0017] The mixed solution is evaporated in an oil bath at a constant temperature to form a gel;

[0018] The gel is placed in a crucible and pretreated at 300-600° C. for 1-20 hours. The powder obtained by the pretreatment is ground and placed in a crucible, and sintered at 600-1000° C. in air or oxygen atmosphere for 1-20 hours. After cooling to room temperature, the powder is ground in an inert atmosphere to obtain the sodium ion battery layered oxide material.

[0019] In a fourth aspect, an embodiment of the present invention provides a method for preparing the sodium ion battery layered oxide material according to the first aspect, wherein the preparation method is a coprecipitation-solid phase method, comprising:

[0020] The precursor of M1-Ni-Mn-M2 was obtained by coprecipitation;

[0021] The coprecipitation method specifically includes:

[0022] Press Na x Li a M1 b Ni c Mn d M2 e O 2±α A deionized water solution containing NiSO4·6H2O, MnSO4·H2O, sulfate of M1 and sulfate of M2 is prepared in the required stoichiometric ratio of each element to obtain a transition metal solution, wherein the concentration of cations in the transition metal solution is 1.5-2.5 mol / L;

[0023] Prepare alkali solution with sodium hydroxide, ammonia water and deionized water, wherein the concentration of sodium hydroxide is 4 mol / L and the concentration of ammonia water is 1 mol / L;

[0024] Add an appropriate amount of deionized water into the reactor and introduce nitrogen, heat to 50°C-70°C and keep warm, stir at a speed of 800-1200 r / min, add alkali solution dropwise during stirring to adjust the pH to between 11.5 and 12, then simultaneously add the transition metal solution and alkali solution dropwise to carry out a coprecipitation reaction, and maintain the pH between 11.5 and 12;

[0025] The precipitate generated by the reaction is filtered and washed, and the precipitate generated by the reaction is filtered to obtain an M1-Ni-Mn-M2 precursor in which each element is evenly distributed;

[0026] The corresponding proportion of M1-Ni-Mn-M2 precursor and excess 0wt.%-10wt.% of sodium source and lithium source are weighed, mixed and ball-milled for 1-20 hours, and sintered at 600°C-1000°C for 1-20 hours in air or oxygen atmosphere to obtain the sodium ion battery layered oxide material; the sodium source includes one or more of sodium hydroxide, sodium carbonate, sodium nitrate, sodium oxide, sodium peroxide, and sodium oxalate; the lithium source includes at least one of lithium oxide, lithium hydroxide, lithium carbonate, and lithium nitrate.

[0027] In a fifth aspect, an embodiment of the present invention provides an electrode material for a sodium ion secondary battery, comprising the sodium ion battery layered oxide material described in the first aspect above, or comprising the sodium ion battery layered oxide material prepared by any of the preparation methods described in the second, third, and fourth aspects above.

[0028] Preferably, the electrode material further comprises a conductive additive and a binder;

[0029] The conductive additive includes at least one of carbon black, acetylene black, graphite powder, carbon nanotubes, graphene, and nitrogen-doped carbon;

[0030] The binder includes at least one of polyvinylidene fluoride (PVDF), sodium alginate, sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR).

[0031] In a sixth aspect, an embodiment of the present invention provides a positive electrode sheet comprising the electrode material of the sodium ion secondary battery described in the fifth aspect.

[0032] In a seventh aspect, an embodiment of the present invention provides a sodium ion secondary battery comprising the positive electrode sheet described in the sixth aspect.

[0033] The layered oxide material provided by the embodiment of the present invention is simple to prepare. The migration of transition metals is suppressed by replacing the transition metals Ni and / or Mn with the elements Li and M1. At the same time, the interface side reaction is reduced by surface doping with M1 element, and the surface rock salt transformation is suppressed. The structural stability of the material is improved by replacing the transition metal Mn with the element M2, and the migration of Mn during the cycle is suppressed. 3+The production of transition metals is suppressed, and the dissolution of transition metals is suppressed; through the synergistic effect of Li, M1, and M2 multi-elements replacing the transition metal sites, the discharge voltage decay is suppressed, thereby achieving extremely small discharge voltage decay and extremely high cycle retention rate at high voltage. In the half-cell test, it was found that the material obtained by this method has a reversible specific capacity of more than 175mAh / g, high energy density, high average working voltage, and an average discharge voltage decay rate of less than 0.2mV / week, and the total attenuation after 800 cycles is no more than 1.7mV. It can be considered that there is basically no voltage decay during the cycle. At the same time, the polarization growth is low, and the growth rate is less than 0.4mV per week. The total growth after 800 cycles is 7mV, which is negligible. It is considered that there is basically no polarization growth. The layered oxide material provided by the embodiment of the present invention has a high energy retention rate during long cycles and has certain industrial value.

[0034] Sodium-ion secondary batteries using the sodium-ion battery layered oxide materials of the present invention can be used in large-scale energy storage devices for smart grid peak regulation, distributed power stations, backup power supplies, or communication base stations. Due to their high operating voltage, energy density, and power density, they can be used as power batteries for two-wheeled electric vehicles or A00-class electric vehicles, exhibiting excellent cycle and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 X-ray diffraction (XRD) patterns of the layered oxide positive electrode materials prepared in Examples 1, 4, 5, and 6 of the present invention;

[0036] Figure 2 This is a scanning electron microscope (SEM) image of the layered oxide positive electrode material prepared in Example 1 of the present invention;

[0037] Figure 3 This is an SEM image of the layered oxide positive electrode material prepared in Example 4 of the present invention;

[0038] Figure 4 This is an SEM image of the layered oxide positive electrode material prepared in Example 5 of the present invention;

[0039] Figure 5 This is an SEM image of the layered oxide positive electrode material prepared in Example 6 of the present invention;

[0040] Figure 6 Specific energy-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.2V before the first 500 cycles of testing;

[0041] Figure 7 The average discharge voltage-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.2V before the 500-week test;

[0042] Figure 8 Polarization (defined as the difference between the average charge voltage and the average discharge voltage)-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.2V before the 500-cycle test;

[0043] Figure 9 Specific energy-cycle diagram for the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.3V before the 222-week test;

[0044] Figure 10 The average discharge voltage-cycle diagram for 222 weeks before the 2-4.3V test of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention;

[0045] Figure 11 Polarization-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.3V before 222 weeks of testing;

[0046] Figure 12 Specific energy-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 5 of the present invention at 2-4.2V before the 600-cycle test;

[0047] Figure 13 The average discharge voltage-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 5 of the present invention at 2-4.2V before the 600-week test;

[0048] Figure 14 Specific energy-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 5 of the present invention at 2-4.3V before the 400-cycle test;

[0049] Figure 15 The average discharge voltage-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 5 of the present invention at 2-4.3V before the 400-week test;

[0050] Figure 16 The specific energy-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in the comparative example of the present invention at 2-4.2V before the 300-cycle test;

[0051] Figure 17 The average discharge voltage-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in the comparative example of the present invention at 2-4.2V before the 300-week test;

[0052] Figure 18 Polarization-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in the comparative example of the present invention at 2-4.2V before the 300-week test. DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some, not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0054] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0055] The embodiment of the present invention provides a sodium ion battery layered oxide material, the chemical formula of which is Na x Li a M1 b Ni c Mn d M2 e O 2±α , the space group is R-3m, and the corresponding structure is O3 phase;

[0056] Wherein, Li is an alkali metal element, Ni and Mn are transition metal elements, M1 is an element that replaces the transition metal Ni, and M2 is an element that replaces the transition metal Mn; M1 includes B 3+ 、Al 3+ 、Fe 3+ Sc 3+ 、Y 3+ 、La 3+ At least two of M2 include Si 4+ 、Ti 4+ 、Zr 4+ 、Sn 4+ at least one of; x, a, b, c, d, e and 2±α are respectively the molar percentages of the corresponding elements, and each component in the chemical formula satisfies the conservation of charge and the conservation of the stoichiometric ratio, that is, x+a+3×b+2×c+4×(d+e)=2×(2±α) and a+b+c+d+e=1, and satisfies 0.8≤x≤1.05, 0<a≤0.1, 0<b≤0.1, 0.3≤c<0.5, 0.2≤d<0.5, 0<e≤0.3, 0≤α≤0.05, a=b, a+b+c=0.5, d+e=0.5.

[0057] Sodium ion battery layered oxide materials are used as positive electrode active materials for sodium ion secondary batteries.

[0058] By replacing the transition metal Ni and / or Mn with the element Li and M1, the migration of the transition metal is suppressed. At the same time, the surface doping of M1 element reduces the interface side reaction and suppresses the surface rock salt transformation. By replacing the transition metal Mn with the element M2, the structural stability of the material is improved and the Mn migration during the cycle is suppressed. 3+ The production of transition metals and the dissolution of transition metals are suppressed. In the layered oxide material proposed by the present invention, the solid solubility of the M1 element in the bulk phase is very low, so it tends to be enriched on the surface. Nickel and manganese are gradiently distributed around 100 nm on the surface, with the surface being rich in manganese and deficient in nickel. However, manganese does not change its valence during the charge and discharge process, which gives the material a strong surface during the electrochemical process, making the surface of the material highly stable and effectively suppressing the dissolution of transition metals and the rock salt transformation of the material. Through the synergistic effect of Li, M1, and M2 replacing the transition metal sites, the discharge voltage decay is suppressed, so that the average discharge voltage decay rate is less than 0.2 mV / cycle, and the total decay after 800 cycles is no more than 1.7 mV.

[0059] The embodiment of the present invention also provides a method for preparing the above-mentioned sodium ion battery layered oxide material, which can be prepared by any of the following methods: solid phase method, sol-gel method or coprecipitation-solid phase method.

[0060] The steps of the solid phase method preparation specifically include:

[0061] Step 110, according to Na x Li a M1 b Ni c Mn d M2 e O 2±α The required stoichiometric ratio of each element is obtained by weighing 0wt.%-10wt.% excess of the required stoichiometric sodium source and lithium source, the required stoichiometric nickel source, manganese source, M1-containing precursor and M2-containing precursor in proportion, adding liquid ball milling medium, and ball milling at a rotation speed of 300-600rpm for 1-12 hours to obtain powder.

[0062] The excess of sodium source and lithium source here is to compensate for the volatilization of sodium carbonate and lithium carbonate at high temperature.

[0063] In step 120 , the obtained powder is placed in a crucible, calcined at 600-1000° C. for 1-20 hours in an atmosphere of air or pure oxygen, and then ground after cooling to room temperature to obtain a layered oxide material for sodium ion batteries.

[0064] Wherein, the sodium source includes: at least one of sodium hydroxide, sodium carbonate, sodium nitrate, sodium oxide, sodium peroxide, sodium acetate and sodium oxalate; the lithium source includes: at least one of lithium oxide, lithium hydroxide, lithium carbonate and lithium nitrate; the nickel source includes: at least one of nickel-containing metal oxides, metal carbonates, metal nitrates, metal oxalates, metal acetates, metal sulfates and metal hydroxides; the manganese source includes: at least one of manganese-containing metal oxides, metal carbonates, metal nitrates, metal oxalates, metal acetates, metal sulfates and metal hydroxides; the precursor containing M1 includes: at least one of oxides, carbonates, nitrates, oxalates, acetates, sulfates and hydroxides containing M1; the precursor containing M2 includes: at least one of oxides, carbonates, nitrates, oxalates, acetates, sulfates and hydroxides containing M2; M1 includes B 3+ 、Al 3+ 、Fe 3 + Sc 3+ 、Y 3+ 、La 3+ At least two of M2 include Si 4+ 、Ti 4+ 、Zr 4+ 、Sn 4+ The liquid milling medium includes one or more of anhydrous ethanol, isopropyl alcohol or acetone.

[0065] The steps of preparing the sol-gel method specifically include:

[0066] Step 210, according to Na x Li a M1 b Ni c Mn d M2 e O 2±α The required stoichiometric ratio of each element is obtained by weighing 100wt.%-110wt.% of a sodium source, a required stoichiometric lithium source, a nickel source, a manganese source, a precursor containing M1, a precursor containing M2 and an appropriate amount of citric acid and dissolving them in deionized water to form a mixed solution.

[0067] Wherein, the sodium source, lithium source, nickel source, manganese source, precursor containing M1 and precursor containing M2 are soluble salts of sodium, lithium, nickel, manganese, M1 and M2 respectively; the soluble salts include one or more of nitrate, oxalate, acetate or sulfate; M1 includes B 3+ 、Al 3+ 、Fe 3+ Sc 3+ 、Y 3+ 、La 3+ At least two of M2 include Si4+ 、Ti 4+ 、Zr 4+ 、Sn 4+ At least one of.

[0068] Step 220: Evaporate the mixed solution in an oil bath at a constant temperature to form a gel.

[0069] The evaporation temperature is 150-500° C. and the evaporation time is 2-10 hours.

[0070] In step 230, the gel is placed in a crucible and pretreated at 300-600°C for 1-20 hours. The pretreated powder is then ground and placed in a crucible. The powder is sintered at 600-1000°C in air or oxygen atmosphere for 1-20 hours. After cooling to room temperature, the powder is ground in an inert atmosphere to obtain a layered oxide material for sodium ion batteries.

[0071] The method steps of preparing by coprecipitation-solid phase method specifically include:

[0072] Step 310: Obtain a precursor of M1-Ni-Mn-M2 by co-precipitation.

[0073] The coprecipitation method specifically includes: x Li a M1 b Ni c Mn d M2 e O 2±α A deionized water solution containing NiSO4·6H2O, MnSO4·H2O, sulfate of M1 and sulfate of M2 is prepared in the required stoichiometric ratio of each element to obtain a transition metal solution, wherein the concentration of cations in the transition metal solution is 1.5-2.5 mol / L;

[0074] Prepare alkali solution with sodium hydroxide, ammonia water and deionized water, wherein the concentration of sodium hydroxide is 4 mol / L and the concentration of ammonia water is 1 mol / L;

[0075] Add an appropriate amount of deionized water into the reactor and introduce nitrogen, heat to 50°C-70°C and keep warm, stir at a speed of 800-1200 r / min, add alkali solution dropwise during stirring to adjust the pH to between 11.5 and 12, then simultaneously add the transition metal solution and alkali solution dropwise to carry out a coprecipitation reaction, and maintain the pH between 11.5 and 12;

[0076] The precipitate generated by the reaction is filtered and washed, and the precipitate generated by the reaction is filtered to obtain an M1-Ni-Mn-M2 precursor in which each element is evenly distributed.

[0077] Step 320 , weighing the corresponding proportion of the M1-Ni-Mn-M2 precursor and an excess of 0wt.%-10wt.% of the sodium source and the lithium source, mixing and ball milling for 1-20 hours, and sintering at 600°C-1000°C for 1-20 hours in air or oxygen atmosphere to obtain the sodium ion battery layered oxide material.

[0078] The sodium source includes at least one of sodium hydroxide, sodium carbonate, sodium nitrate, sodium oxide, sodium peroxide, and sodium oxalate; the lithium source includes at least one of lithium oxide, lithium hydroxide, lithium carbonate, and lithium nitrate.

[0079] The sodium ion battery layered oxide material proposed in the present invention or prepared by the above method can be used as an electrode material for a sodium ion secondary battery. For example, it can be used together with a conductive additive and a binder to form a positive electrode material for a sodium ion secondary battery.

[0080] Among them, the conductive additives that can be adapted include: at least one of carbon black, acetylene black, graphite powder, carbon nanotubes, graphene, and nitrogen-doped carbon; the binder includes: at least one of polyvinylidene fluoride (PVDF), sodium alginate, sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR).

[0081] The positive electrode sheet prepared using the above-mentioned sodium ion secondary battery positive electrode material has good air stability and cycle stability. When applied to sodium ion secondary batteries, it can have extremely low average discharge voltage decay and extremely high cycle retention rate even under high voltage and long cycle, and has good air stability and cycle stability.

[0082] The sodium ion battery layered oxide material of the present invention, its preparation method and performance are further described in detail below with reference to some specific examples.

[0083] Example 1

[0084] In this example, a solid phase method was used to prepare the layered oxide material NaLi for sodium ion batteries. 0.05 Fe 0.04 Al 0.01 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0085] The specific preparation steps include: weighing Na2CO3 (excess 2%), Li2CO3 (excess 2%), Fe2O3, Al2O3, NiO, MnO2, and TiO2 in a ball mill according to the stoichiometric ratio, adding an appropriate amount of zirconium dioxide ball milling beads (bead-to-material ratio of 5:1), then adding an appropriate amount of anhydrous ethanol and mixing them evenly, grinding at a speed of 600 rpm for 5 hours, and drying at 100°C for 5 hours to obtain a precursor, treating the precursor at 900°C in an air atmosphere for 15 hours to obtain a black powder, which is ground and set aside for use, namely the layered oxide positive electrode material NaLi prepared in this embodiment. 0.05 Fe 0.04 Al 0.01 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0086] The XRD pattern of the sodium ion battery layered oxide material prepared in this embodiment is as follows: Figure 1 As shown in the figure, compared with the standard card, it can be seen that the main phase is O3 phase material with space group R-3m and no impurity phase exists. The scanning electron microscope (SEM) image of the layered oxide material is shown in the figure. Figure 2 As shown, the single crystal particles are lamellar, with a particle size of 3-6um, a smooth surface, and no obvious residual alkali particles.

[0087] The sodium ion battery layered oxide material prepared in this example was tested.

[0088] Half-cell assembly: Sodium ion battery layered oxide material, conductive carbon black (Super P) and vinylidene fluoride (PVDF) are slurried in N-methylpyrrolidone (NMP) solution at a mass ratio of 80:10:10 and coated on aluminum foil, and then cut into 10mm diameter pole pieces (loading is about 4-5mg / cm 2 ), with sodium metal sheet as the negative electrode, 1 mol / L NaClO4 / polycarbonate (PC):ethylene carbonate (EC):dimethyl carbonate (DMC) (volume ratio 1:1:1) + 2% Vol fluoroethylene carbonate (FEC) solution as the electrolyte, and glass fiber separator, a CR2032 button battery half-cell was assembled in an argon glove box.

[0089] Charge and discharge testing: The button-type batteries were charged and discharged in the voltage ranges of 2.0-4.2V and 2.0-4.3V, respectively. Testing was conducted for 500 cycles at 2.0-4.2V and 222 cycles at 2.0-4.3V. Prior to the cycling test, the batteries were activated three times using a low current density of 15mA / g (0.1C). Subsequently, the batteries were cycled at a rate of 1C within the same voltage range. Electrochemical performance testing was conducted at room temperature. Figure 6Specific energy-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.2V before the first 500 cycles of testing; Figure 7 The average discharge voltage-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.2V before the 500-week test; Figure 8 Polarization (defined as the difference between the average charge voltage and the average discharge voltage)-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.2V before the 500-cycle test; Figure 9 Specific energy-cycle diagram for the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.3V before the 222-week test; Figure 10 The average discharge voltage-cycle diagram for 222 weeks before the 2-4.3V test of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention; Figure 11 Polarization-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 1 of the present invention at 2-4.3V before 222 weeks of testing.

[0090] Example 2

[0091] In this example, the sol-gel method was used to prepare the layered oxide material NaLi for sodium ion batteries. 0.05 Fe 0.04 Al 0.01 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0092] The specific preparation steps include: weighing sodium carbonate, lithium carbonate, ferric nitrate, nickel acetate, manganese acetate, tetrabutyl titanate and an appropriate amount of citric acid according to the required stoichiometric ratio and dissolving them in deionized water to form a mixed solution; stirring the obtained solution in an oil bath at 80°C and 300 rpm for evaporation for 5 hours to form a gel; collecting the obtained gel and heating it at 450°C for 5 hours, then grinding the powder obtained by pretreatment, calcining it at 900°C in an air atmosphere for 15 hours, cooling it to room temperature, and grinding it to obtain a layered oxide positive electrode material.

[0093] Example 3

[0094] This example uses a coprecipitation-solid phase method to prepare the sodium ion battery layered oxide material NaLi 0.05 Fe 0.04 Al 0.0 1Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0095] The specific preparation steps include: 0.05 Fe0.04 Al 0.01 Ni 0.4 Mn 0.4 Ti 0.1 The ratio of Fe, Al, Ni and Mn in O2 was used to prepare deionized water solutions of FeSO4·7H2O, Al2(SO4)3·18H2O, NiSO4·6H2O and MnSO4·H2O, and the cation concentration of the resulting transition metal solution was 2 mol / L; alkali solution was prepared with sodium hydroxide, ammonia water and deionized water, wherein the concentration of sodium hydroxide was 4 mol / L and the concentration of ammonia was 1 mol / L; an appropriate amount of deionized water was added to the reactor and argon was introduced, which was heated to 60°C and kept warm, and then alkali solution was added to the reactor, and the pH was first adjusted to 11.8. The mixture was stirred at a speed of 750 r / min, and then the transition metal solution and the alkali solution were added dropwise at the same time, and the pH was maintained at about 11.8 during the whole process; after the reaction was completed, the precipitate was filtered and washed, and dried at 120°C for 10 hours to obtain a hydroxide precursor with uniformly distributed transition metal elements and doped elements; the obtained hydroxide precursor was mixed with an excess of 2% sodium carbonate and an excess of 2% sodium carbonate in a stoichiometric ratio, heated at 450°C for 5 hours in an air atmosphere, calcined at 900°C for 10 hours, and then cooled to room temperature to obtain the layered oxide positive electrode material prepared in this embodiment.

[0096] The XRD pattern of the layered oxide cathode material prepared in this example is as follows: Figure 1 As shown, compared with the standard card, it can be seen that it is a pure O3 phase substance with a space group of R-3m.

[0097] Example 4

[0098] In this example, a solid phase method was used to prepare the layered oxide material NaLi for sodium ion batteries. 0.05 Fe 0.03 Al 0.02 Ni 0.4 Mn 0.4 Ti 0.1 O2.

[0099] The specific preparation steps include: weighing Na2CO3 (excess 2%), Li2CO3 (excess 2%), Fe2O3, Al2O3, NiO, MnO2, and TiO2 in a ball mill according to the stoichiometric ratio, adding an appropriate amount of zirconium dioxide ball milling beads (bead-to-material ratio of 5:1), then adding an appropriate amount of anhydrous ethanol and mixing them evenly, grinding at a speed of 600 rpm for 5 hours, and drying at 100°C for 5 hours to obtain a precursor, treating the precursor at 900°C in an air atmosphere for 15 hours to obtain a black powder, which is ground and set aside for use, namely the layered oxide positive electrode material NaLi prepared in this embodiment. 0.05 Fe 0.03 Al 0.02 Ni0.4 Mn 0.4 Ti 0.1 O2.

[0100] The XRD pattern of the sodium ion battery layered oxide material prepared in this embodiment is as follows: Figure 1 As shown in the figure, compared with the standard card, it can be seen that the main phase is O3 phase material with space group R-3m and no impurity phase exists. The scanning electron microscope (SEM) image of the layered oxide material is shown in the figure. Figure 3 As shown, the single crystal particles are lamellar, with a particle size of 3-6um, a smooth surface, and no obvious residual alkali particles.

[0101] Example 5

[0102] In this example, a solid phase method was used to prepare the layered oxide material NaLi for sodium ion batteries. 0.05 Fe 0.04 Al 0.01 Ni 0.4 Mn 0.3 Ti 0.2 O2.

[0103] The specific preparation steps include: weighing Na2CO3 (excess 2%), Li2CO3 (excess 2%), Fe2O3, Al2O3, NiO, MnO2, and TiO2 in a ball mill according to the stoichiometric ratio, adding an appropriate amount of zirconium dioxide ball milling beads (bead-to-material ratio of 5:1), and then adding an appropriate amount of anhydrous ethanol to mix evenly, grinding at a speed of 600 rpm for 5 hours, and drying at 100°C for 5 hours to obtain a precursor, treating the precursor at 900°C in an air atmosphere for 15 hours to obtain a black powder, which is ground and set aside, namely the layered oxide positive electrode material NaLi prepared in this embodiment. 0.05 Fe 0.04 Al 0.01 Ni 0.4 Mn 0.3 Ti 0.2 O2.

[0104] The XRD pattern of the sodium ion battery layered oxide material prepared in this embodiment is as follows: Figure 1 As shown in the figure, compared with the standard card, it can be seen that the main phase is O3 phase material with space group R-3m and no impurity phase exists. The scanning electron microscope (SEM) image of the layered oxide material is shown in the figure. Figure 4 As shown, the single crystal particles are lamellar, with a particle size of 1-4um, a smooth surface, and no obvious residual alkali particles.

[0105] The sodium ion battery layered oxide material prepared in this example was tested, and the half-cell assembly was the same as in Example 1.

[0106] The charge and discharge tests were also conducted at 2.0-4.2V and 2.0-4.3V, with 600 cycles of testing at 2.0-4.2V and 400 cycles of testing at 2.0-4.3V. Figure 12 Specific energy-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 5 of the present invention at 2-4.2V before the 600-cycle test; Figure 13 The average discharge voltage-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 5 of the present invention at 2-4.2V before the 600-week test; Figure 14 Specific energy-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 5 of the present invention at 2-4.3V before the 400-cycle test; Figure 15 The average discharge voltage-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in Example 5 of the present invention at 2-4.3V before the 400-week test.

[0107] Example 6

[0108] In this example, a solid phase method was used to prepare the layered oxide material NaLi for sodium ion batteries. 0.05 Fe 0.04 Al 0.01 Ni 0.4 Mn 0.2 Ti 0.3 O2.

[0109] The specific preparation steps include: weighing Na2CO3 (excess 2%), Li2CO3 (excess 2%), Fe2O3, Al2O3, NiO, MnO2, and TiO2 in a ball mill according to the stoichiometric ratio, adding an appropriate amount of zirconium dioxide ball milling beads (bead-to-material ratio of 5:1), and then adding an appropriate amount of anhydrous ethanol to mix evenly, grinding at a speed of 600 rpm for 5 hours, and drying at 100°C for 5 hours to obtain a precursor, treating the precursor at 900°C in an air atmosphere for 15 hours to obtain a black powder, which is ground and set aside, namely the layered oxide positive electrode material NaLi prepared in this embodiment. 0.05 Fe 0.04 Al 0.01 Ni 0.4 Mn 0.2 Ti 0.3 O2.

[0110] The XRD pattern of the sodium ion battery layered oxide material prepared in this embodiment is as follows: Figure 1 As shown in the figure, compared with the standard card, it can be seen that the main phase is O3 phase material with space group R-3m and no impurity phase exists. The scanning electron microscope (SEM) image of the layered oxide material is shown in the figure. Figure 5 As shown, the single crystal particles are lamellar, with a particle size of 1-4um, a smooth surface, and no obvious residual alkali particles.

[0111] Comparative Example

[0112] In this comparative example, the layered oxide material NaNi was prepared by solid phase method. 0.4 Fe 0.2 Mn 0.4 O2.

[0113] The specific preparation steps include: weighing Na2CO3 (2% excess), NiO, Fe2O3, and MnO2 in a ball mill according to the stoichiometric ratio, adding an appropriate amount of zirconium dioxide ball milling beads (bead to material ratio of 5:1), adding an appropriate amount of anhydrous ethanol and mixing evenly, grinding at a speed of 600 rpm for 5 hours, drying at 100°C for 5 hours to obtain a precursor, treating the precursor at 900°C in an air atmosphere for 15 hours to obtain a black powder, grinding and setting aside, and obtaining the NaNi comparative example of the present invention. 0.4 Fe 0.2 Mn 0.4 O2.

[0114] The charge and discharge tests were carried out at 2.0-4.2V to test its electrochemical performance for the first 300 cycles. Figure 16 The specific energy-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in the comparative example of the present invention at 2-4.2V before the 300-cycle test; Figure 17 The average discharge voltage-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in the comparative example of the present invention at 2-4.2V before the 300-week test; Figure 18 Polarization-cycle diagram of the sodium ion half-cell assembled with the layered oxide positive electrode material prepared in the comparative example of the present invention at 2-4.2V before the 300-week test.

[0115] Combine Figures 6-18 By comparing the test results of Example 1, Example 5 and the comparative example, it can be seen that the discharge specific energy decay of the comparative example is very obvious, while the discharge specific energy of Examples 1 and 5 of the present invention is only slightly attenuated even under the conditions of a high voltage of 4.3V or 4.2V cycle for 600 weeks. The average discharge voltage of the comparative example is reduced from about 3.2V in the first week to about 2.6V after 300 cycles, while the average discharge voltage of Examples 1 and 5 of the present invention is almost unchanged. Thus, it can be seen that the technical solution of the present invention achieves extremely low voltage decay and extremely high cycle retention rate of sodium ion batteries at high voltage. In addition, by comparison, it can be seen that the polarization growth of the comparative example during the cycle is very obvious, while Examples 1 and 5 of the present invention have basically no polarization growth during the cycle, which shows that the performance of the battery during the charge and discharge process remains good. Compared with the sodium ion battery using the O3 phase positive electrode material in the prior art, the application of the sodium ion battery layered oxide material of the present invention can enable the battery to have higher battery efficiency, longer cycle life and better power performance.

[0116] The sodium ion battery layered oxide material provided by the present invention is simple to synthesize and easy to produce on a large scale and continuously. When used as a sodium ion battery layered oxide positive electrode material, it has the advantages of high reversible specific capacity, high energy density, high reversible charge and discharge potential, stable cycling, high air stability, and good rate performance. The layered oxide material of the present invention is used to construct a sodium ion full battery, which can have the characteristics of high average energy storage voltage, high energy density, and high power density. It can be used as a green and clean energy storage device for power generation, smart grid peak regulation, distributed power stations, backup power supplies, communication base stations, two-wheeled electric vehicles or A00 electric vehicles, etc., and has excellent safety performance, rate performance, and cycle performance.

[0117] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sodium ion battery layered oxide material, characterized in that The chemical formula of the sodium ion battery layered oxide material is Na x Li a M1 b Ni c Mn d M2 e O 2±α , the space group is R-3m, and the corresponding structure is O3 phase; Wherein, Li is an alkali metal element, Ni and Mn are transition metal elements, M1 is an element that replaces the transition metal Ni, and M2 is an element that replaces the transition metal Mn; M1 includes B 3+ 、Al 3+ 、Fe 3+ Sc 3+ 、Y 3+ 、La 3+ At least two of M2 include Si 4+ 、Ti 4+ 、Zr 4+ 、Sn 4+ at least one of; x, a, b, c, d, e and 2±α are respectively the molar percentages of the corresponding elements, and each component in the chemical formula satisfies the conservation of charge and the conservation of the stoichiometric ratio, that is, x+a+3×b+2×c+4×(d+e)=2×(2±α) and a+b+c+d+e=1, and satisfies 0.8≤x≤1.05, 0<a≤0.1, 0<b≤0.1, 0.3≤c<0.5, 0.2≤d<0.5, 0<e≤0.3, 0≤α≤0.05, a=b, a+b+c=0.5, d+e=0.

5.

2. The sodium ion battery layered oxide material according to claim 1, characterized in that The sodium ion battery layered oxide material is used as a positive electrode active material for sodium ion secondary batteries; By replacing the transition metal Ni and / or Mn with the element Li and M1, the migration of the transition metal is suppressed. At the same time, the surface doping of M1 element reduces the interface side reaction and suppresses the surface rock salt transformation. By replacing the transition metal Mn with the element M2, the structural stability of the material is improved and the Mn migration during the cycle is suppressed. 3+ The production of Li, M1, and M2 can be suppressed, and the dissolution of transition metals can be inhibited; through the synergistic effect of Li, M1, and M2 replacing the transition metal sites, the discharge voltage decay is suppressed, so that the average discharge voltage decay rate is less than 0.2mV / cycle, and the total decay after 800 cycles is no more than 1.7mV.

3. A method for preparing the layered oxide material for sodium ion batteries according to claim 1 or 2, characterized in that: The preparation method is a solid phase method, comprising: According to Na x Li a M1 b Ni c Mn d M2 e O 2±α The required stoichiometric ratio of each element is obtained by weighing 0 wt.% to 10 wt.% of the required stoichiometric sodium source and lithium source, the required stoichiometric nickel source, manganese source, the precursor containing M1 and the precursor containing M2 in proportion, adding liquid ball milling medium, and ball milling at a speed of 300-600 rpm for 1-12 hours to obtain a powder; The powder is placed in a crucible, calcined at 600-1000° C. for 1-20 hours in an atmosphere of air or pure oxygen, and then ground after cooling to room temperature to obtain the sodium ion battery layered oxide material; Wherein, the sodium source includes: at least one of sodium hydroxide, sodium carbonate, sodium nitrate, sodium oxide, sodium peroxide, sodium acetate and sodium oxalate; the lithium source includes: at least one of lithium oxide, lithium hydroxide, lithium carbonate and lithium nitrate; the nickel source includes: at least one of nickel-containing metal oxides, metal carbonates, metal nitrates, metal oxalates, metal acetates, metal sulfates and metal hydroxides; the manganese source includes: at least one of manganese-containing metal oxides, metal carbonates, metal nitrates, metal oxalates, metal acetates, metal sulfates and metal hydroxides; the precursor containing M1 includes: at least one of oxides, carbonates, nitrates, oxalates, acetates, sulfates and hydroxides containing M1; the precursor containing M2 includes: at least one of oxides, carbonates, nitrates, oxalates, acetates, sulfates and hydroxides containing M2; M1 includes B 3+ 、Al 3+ 、Fe 3+ Sc 3+ 、Y 3+ 、La 3+ At least two of M2 include Si 4+ 、Ti 4+ 、Zr 4+ 、Sn 4+ At least one of; the liquid milling medium includes: one or more of anhydrous ethanol, isopropanol or acetone.

4. A method for preparing the layered oxide material for sodium ion batteries according to claim 1 or 2, characterized in that: The preparation method is a sol-gel method, comprising: According to Na x Li a M1 b Ni c Mn d M2 e O 2±α The required stoichiometric ratio of each element in the mixture is obtained by weighing 100wt.%-110wt.% of a sodium source, a required stoichiometric lithium source, a nickel source, a manganese source, a precursor containing M1, and a precursor containing M2, and an appropriate amount of citric acid, and dissolving them in deionized water to form a mixed solution; wherein the sodium source, lithium source, nickel source, manganese source, precursor containing M1, and precursor containing M2 are soluble salts of sodium, lithium, nickel, manganese, M1, and M2, respectively; the soluble salts include one or more of nitrate, oxalate, acetate, or sulfate; M1 includes B 3+ 、Al 3+ 、Fe 3+ Sc 3+ 、Y 3+ 、La 3+ At least two of M2 include Si 4+ 、Ti 4+ 、Zr 4+ 、Sn 4+ at least one of; The mixed solution is evaporated at a constant temperature in an oil bath to form a gel; The gel is placed in a crucible and pretreated at 300-600° C. for 1-20 hours. The powder obtained by the pretreatment is ground and placed in a crucible, and sintered at 600-1000° C. in air or oxygen atmosphere for 1-20 hours. After cooling to room temperature, the powder is ground in an inert atmosphere to obtain the sodium ion battery layered oxide material.

5. A method for preparing the sodium ion battery layered oxide material according to claim 1 or 2, characterized in that: The preparation method is a coprecipitation-solid phase method, comprising: The precursor of M1-Ni-Mn-M2 was obtained by coprecipitation; The coprecipitation method specifically comprises: Press Na x Li a M1 b Ni c Mn d M2 e O 2±α A deionized water solution containing NiSO4·6H2O, MnSO4·H2O, sulfate of M1, and sulfate of M2 is prepared in the required stoichiometric ratios of the elements to obtain a transition metal solution, wherein the concentration of cations in the transition metal solution is 1.5-2.5 mol / L; an alkali solution is prepared with sodium hydroxide, ammonia water, and deionized water, wherein the concentration of sodium hydroxide is 4 mol / L and the concentration of ammonia water is 1 mol / L; Add an appropriate amount of deionized water into the reactor and introduce nitrogen, heat to 50°C-70°C and keep warm, stir at a speed of 800-1200 r / min, add alkali solution dropwise during stirring to adjust the pH to between 11.5 and 12, then simultaneously add the transition metal solution and alkali solution dropwise to carry out a coprecipitation reaction, and maintain the pH between 11.5 and 12; The precipitate generated by the reaction is filtered and washed, and the precipitate generated by the reaction is filtered to obtain an M1-Ni-Mn-M2 precursor in which each element is evenly distributed; The corresponding proportion of M1-Ni-Mn-M2 precursor and excess 0wt.%-10wt.% of sodium source and lithium source are weighed, mixed and ball-milled for 1-20 hours, and sintered at 600°C-1000°C for 1-20 hours in air or oxygen atmosphere to obtain the sodium ion battery layered oxide material; the sodium source includes at least one of sodium hydroxide, sodium carbonate, sodium nitrate, sodium oxide, sodium peroxide, and sodium oxalate; the lithium source includes at least one of lithium oxide, lithium hydroxide, lithium carbonate, and lithium nitrate.

6. An electrode material for a sodium ion secondary battery, characterized in that The electrode material includes the sodium ion battery layered oxide material according to claim 1 or 2, or includes the sodium ion battery layered oxide material prepared by the preparation method according to any one of claims 3 to 5.

7. The electrode material according to claim 6, characterized in that The electrode material also includes a conductive additive and a binder; The conductive additive includes at least one of carbon black, acetylene black, graphite powder, carbon nanotubes, graphene, and nitrogen-doped carbon; The binder includes at least one of polyvinylidene fluoride (PVDF), sodium alginate, sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR).

8. A positive electrode sheet comprising the electrode material for a sodium ion secondary battery according to claim 6 or 7.

9. A sodium ion secondary battery comprising the positive electrode sheet according to claim 8.

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