Double-site vacancy regulated manganese-iron-aluminum layered oxide sodium-ion battery positive electrode material and preparation method thereof

Abstract

The invention provides a double-site vacancy regulated manganese-iron-aluminum layered oxide sodium-ion battery positive electrode material and a preparation method thereof, and belongs to the technical field of sodium-ion batteries. According to the preparation method, partial vacancies are formed in transition metal sites and oxygen sites through reasonable means, and the manganese-iron-aluminum layered oxide composite material with the double-site vacancies is obtained. The chemical formula of the manganese-iron-aluminum layered oxide composite material is Na Fe < b-x > Mn < c > Al < d > MeO < 2-y >, b + x + c + d + e = 1, and 0.5 < = alt; 1, 0.2 < = b < = 0.35, 0.2 < = clt; 0.8, 0 lt; d < = 0.2, 0 < = e < = 0.4, 0lt; x is less than or equal to 0.15, 0lt; x is less than or equal to 0.05, y is less than or equal to 0.05,-is transition metal vacancy, x is the content of the transition metal vacancy, y is the content of oxygen vacancy, and values of x, a, b, c, d, e and y enable the general formula to meet valence balance. When the layered oxide composite material is used as the positive electrode material of the sodium-ion battery, the initial capacity is high, and the layered oxide composite material shows very excellent cycling stability and excellent rate capability and has a great development prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion batteries, and particularly to a cathode material for sodium-ion batteries based on manganese-iron-aluminum layered oxide with double-site vacancy regulation and a preparation method thereof. Background Art

[0002] In recent years, the rapid increase in energy consumption has accelerated the depletion of a large number of non-renewable energy sources, forcing the world to strive to promote renewable energy technologies and urgently requiring the development of cost-effective, safe and reliable large-scale energy storage systems. Among a series of energy storage solutions, lithium-ion batteries have become particularly effective due to their superior energy density and commendable cycle stability. However, the lack of lithium resources coupled with high costs has severely hindered the widespread deployment of lithium in energy storage infrastructure. Against this background, sodium-ion batteries (SIBs) have received considerable interest due to their cost-effectiveness and abundant sodium resources. Although significant progress has been made in SIBs technology in recent years, compared with lithium-ion batteries, their relatively low energy density still has serious deficiencies, and further research on their commercial feasibility is needed. In the constellation of SIBs components, the cathode material constitutes the main cost determinant. Therefore, determining the optimal cathode material is crucial. In this regard, layered Na x TMO 2 compounds have received extensive attention among various cathode materials due to their high energy density and high safety performance.

[0003] The cathode material plays a crucial role in improving the energy density of sodium-ion batteries. Currently, the main sodium-ion cathode materials include transition metal oxides, polyanion compounds, and Prussian blue. Among them, layered oxides are considered the most promising cathode materials for sodium-ion batteries due to their relatively high energy density; the general formula of layered transition metal oxides is Na x MO 2 , which can be divided into two types, P-type and O-type, according to the different coordination environments of sodium ions. In the P-type structure, sodium ions occupy the trigonal prism position, while in the O-type structure, sodium ions are in the octahedral position, and the numbers represent the stacking layers of oxygen layers in the minimum repeating unit. Among them, P2 manganese-based layered metal oxides have received extensive attention due to their high capacity, high cycle life, and good rate performance.

[0004] Mn~Ni-based layered oxide materials have good performance and have been widely studied. Among them, P2−Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O 2The most extensive, but the poor stability and high price of Ni-based materials have forced people to study non-Ni-based materials. On this basis, the research on Fe-based materials is the general trend. Fe-based materials have very low costs and common raw materials. However, Fe-based materials have an obvious disadvantage, that is, their stability is very poor.

[0005] Therefore, the present invention improves the cycle stability of iron-based layered oxide materials by regulating vacancies, and develops a layered metal oxide with high specific capacity, excellent cycle stability and rate performance as the positive electrode material of a sodium ion battery. Summary of the Invention

[0006] Aiming at the above deficiencies of the prior art, the present invention provides a positive electrode material for a sodium ion battery of a manganese-iron-aluminum layered oxide with double-site vacancy regulation and a preparation method thereof.

[0007] To achieve the above object, the specific technical solutions of the present invention are as follows:

[0008] In a first aspect, the present invention provides a manganese-iron-aluminum layered oxide composite material with double-site vacancy regulation, and its chemical formula is Na a Fe b □ x Mn c Al d M e O 2-y , where b + x + c + d + e = 1, 0.5 ≤ a < 1, 0.2 ≤ b ≤ 0.35, 0.2 ≤ c < 0.8, 0 < d ≤ 0.2, 0 ≤ e ≤ 0.4, 0 < x ≤ 0.15, 0 < y ≤ 0.05, □ is a transition metal vacancy, x is the content of the transition metal vacancy, y is the content of the oxygen vacancy, and the values of x, a, b, c, d, e, and y make the general formula satisfy the valence balance. M is selected from one or more of K, Zn, Mg, Li, Co, Ni, Cd, Ti, Ca, Ba, Sr, Cr, Si, Ge, Ga, In, Zr, Sb, Sn, Mo, W, Te, V, La, Ce, Pr, Ru, Nb, Gd, Dy, Er, Yb, B, Ag, Au, Y, Sc, Sb, Bi, Sb, Te.

[0009] The present invention improves the performance of the layered oxide and stabilizes its own structure by regulating the conditions and ratios of the transition metal vacancies and oxygen vacancies in the manganese-iron-aluminum-based layered oxide, thereby enhancing the structural stability during the cycle, so that the layered oxide composite material exhibits the characteristics of high capacity, high rate performance and excellent cycle stability as the positive electrode material of a sodium ion battery. The layered oxide composite material Na a Fe b □ x Mn c Ald M e O 2-y When used as the cathode material of a sodium-ion battery, it has a high initial capacity and exhibits very strong cycle stability and high-rate performance. At a current density of 0.01 A·g -1 , a reversible capacity of 208.9 mAh·g -1 can be achieved. At a current density of 1 A·g -1 , after 1000 cycles, there is a retention rate of 97%. At a large current density of 2 A·g -1 , after 2000 cycles, there is almost no obvious capacity decay. The layered oxide composite material of the present invention has a P2 structure. When used as the cathode material of a sodium-ion battery, this P2 structure not only provides a sodium-ion diffusion channel, accelerating the migration power of ions / electrons, but also alleviates the problem that O3-type materials are prone to failure when exposed to air. At the same time, the present invention uses two-site vacancy regulation to control the structure of the layered oxide composite material, reducing the voltage range, thereby enhancing the structural stability during the cycling process of the layered oxide composite material and solving the problem of poor stability brought by the P2 structure. When the layered oxide composite material is used as the cathode material of a sodium-ion battery, it exhibits the characteristics of high capacity, high-rate performance, and excellent cycle stability.

[0010] Preferably, the two-site vacancy-regulated manganese-iron-aluminum layered oxide composite material is prepared by a co-precipitation method.

[0011] Second, the present invention provides a preparation method of the two-site vacancy-regulated manganese-iron-aluminum layered oxide composite material, including the following steps:

[0012] S1. According to the molar ratio of each metal element in the chemical formula, mix the sodium source, iron source, manganese source, aluminum source, and M source evenly in a solvent to obtain a mixed solution. Add an excessive precipitating agent to the mixed solution to obtain a yellow suspension. After standing the suspension at room temperature for a period of time, filter, dry, and grind it. Place the ground powder in a furnace at 300-1000 °C and calcine it for 9-23 h to obtain a precursor.

[0013] S2. Calcinate the precursor obtained in step S1 in an atmosphere of a mixture of hydrogen and nitrogen at 250-600 °C for 2-6 h to obtain a layered oxide composite material containing two-site vacancies.

[0014] The present invention regulates the formation of two-site vacancies through a simple co-precipitation method and calcination in a mixed atmosphere to obtain a layered oxide composite material containing two-site vacancies. This method has the advantages of simple preparation process, low cost, environmental protection, and non-toxicity.

[0015] Preferably, in step S1, the powder is calcined in an air atmosphere at 300 - 650 °C for 3 - 8 h, and then heated to 750 - 1000 °C for calcination for 6 - 15 h to obtain a precursor.

[0016] Preferably, in step S1, the solvent is absolute ethanol.

[0017] Preferably, in step S1, the precipitant is an oxalic acid solution.

[0018] Preferably, the sodium source includes at least one of sodium carbonate, sodium nitrate, and sodium acetate; the iron source includes at least one of iron acetate, iron nitrate, iron sulfate, iron oxalate, and nickel ironate; the manganese source includes at least one of manganese acetate, manganese nitrate, manganese sulfate, manganese oxalate, and manganese chloride; the aluminum source includes at least one of aluminum acetate, aluminum nitrate, aluminum sulfate, aluminum oxalate, and aluminum ironate; the M source includes at least one of acetate M, nitrate M, sulfate M, oxalate M, and ironate M.

[0019] Preferably, in step S2, in the mixed atmosphere, the hydrogen content is 4%.

[0020] In a third aspect, the present invention provides the application of the double-site vacancy-regulated manganese-iron-aluminum layered oxide composite material in the preparation of a cathode material for a sodium-ion battery.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] When the double-site vacancy-regulated manganese-iron-aluminum layered oxide composite material of the present invention is used as the cathode material of a sodium-ion battery, it has a high initial capacity, and exhibits very strong cycle stability and high-rate performance. At a current density of 0.01 A·g -1 , a reversible capacity of 208.9 mAh·g -1 can be achieved; at a current density of 1 A·g -1 , there is a retention rate of 97% after 1000 cycles; at a large current density of 2 A·g -1 , there is almost no obvious capacity decay after 2000 cycles. Description of the Drawings

[0023] Figure 1 SEM image of the composite material prepared in Example 1;

[0024] Figure 2 HR-TEM image of the composite material prepared in Example 1;

[0025] Figure 3 XRD pattern of the composite material prepared in Example 1;

[0026] Figure 4 For the composite material prepared in Example 1 at 1 A·g-1 Cycling performance graph at current density;

[0027] Figure 5 The composite material prepared for Example 1 at 2 A·g -1 Cycling performance graph at current density;

[0028] Figure 6 Rate performance graph of the composite material prepared for Example 1. Detailed implementation manners

[0029] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0030] The present invention provides a manganese-iron-aluminum layered oxide composite material with double-site vacancy regulation, and its chemical formula is Na a Fe b □ x Mn c Al d M e O 2-y , where b + x + c + d + e = 1, 0.5 ≤ a < 1, 0.2 ≤ b ≤ 0.35, 0.2 ≤ c < 0.8, 0 < d ≤ 0.2, 0 ≤ e ≤ 0.4, 0 < x ≤ 0.15, 0 < y ≤ 0.05, □ is a transition metal vacancy, x is the content of the transition metal vacancy, y is the content of the oxygen vacancy, and the values of x, a, b, c, d, e, and y make the general formula satisfy the valence balance. M is selected from one or more of K, Zn, Mg, Li, Co, Ni, Cd, Ti, Ca, Ba, Sr, Cr, Si, Ge, Ga, In, Zr, Sb, Sn, Mo, W, Te, V, La, Ce, Pr, Ru, Nb, Gd, Dy, Er, Yb, B, Ag, Au, Y, Sc, Sb, Bi, Sb, Te.

[0031] The preparation method of the manganese-iron-aluminum layered oxide composite material with double-site vacancy regulation includes the following steps:

[0032] S1. According to the molar ratio of each metal element in the chemical formula, mix the sodium source, iron source, manganese source, aluminum source, and M source evenly in absolute ethanol to obtain a mixed solution. Add an excessive amount of oxalic acid solution to the mixed solution to obtain a yellow suspension; let the suspension stand at room temperature for a period of time, then filter, dry, and grind. Place the ground powder in an air atmosphere and calcine it at 300 - 1000 °C for 9 - 23 h to obtain a precursor;

[0033] S2. Calcinate the precursor obtained in step S1 in an atmosphere of a mixture of 4% hydrogen and nitrogen at 250 - 600 °C for 2 - 6 h to obtain a layered oxide composite containing double-site vacancies.

[0034] In some examples, the sodium source includes at least one of sodium carbonate, sodium nitrate, and sodium acetate; the iron source includes at least one of iron acetate, iron nitrate, iron sulfate, iron oxalate, and nickel iron; the manganese source includes at least one of manganese acetate, manganese nitrate, manganese sulfate, manganese oxalate, and manganese chloride; the aluminum source includes at least one of aluminum acetate, aluminum nitrate, aluminum sulfate, aluminum oxalate, and aluminum iron; the M source includes at least one of acetate M, nitrate M, sulfate M, oxalate M, and iron M.

[0035] Example 1

[0036] A layered oxide composite with double-site vacancy regulation, whose chemical formula is: Na 0.78 Fe 0.25 □ 0.05 Mn 0.55 Al 0.05 Mg 0.1 O 2-y , which contains transition metal vacancies and oxygen vacancies, and 0 < y ≤ 0.05. The preparation steps are as follows:

[0037] S1. First, synthesize a layered oxide without oxygen vacancies. According to the molar ratio of each metal element in the chemical formula, dissolve the sodium source (sodium carbonate), iron source (iron acetate), manganese source (manganese sulfate), aluminum source (aluminum acetate), and M source (in this example, M is Mg and the M source is magnesium sulfate) in anhydrous ethanol, stir evenly at room temperature to obtain a mixed solution, then drop an excessive amount of oxalic acid solution into the mixed solution to obtain a yellow suspension; then let the suspension stand at room temperature for 16 h, filter, dry, and grind. Place the ground powder in an air atmosphere and calcine it at 500 °C for 5 h, then raise the temperature to 800 °C and calcine it for 10 h to obtain a layered oxide precursor containing transition metal vacancies and without oxygen vacancies;

[0038] S2. Place the precursor obtained in step S1 in a porcelain boat, place it in a tubular furnace with a mixed atmosphere of hydrogen and nitrogen, and calcine it at 400 °C for 4 h to obtain a layered oxide composite containing double vacancies.

[0039] Figure 1 SEM image of the layered oxide composite with double vacancies prepared in Example 1. It can be seen from the figure that the surface of the layered oxide composite with double vacancies is smooth and has good crystallinity.

[0040] Figure 2HR~TEM image of the double-vacancy layered oxide composite prepared in Example 1. It can be seen from the figure the existence of double vacancies in the double-vacancy layered oxide composite.

[0041] Figure 3 XRD pattern of the double-vacancy layered oxide composite prepared in Example 1. It can be seen from the figure that all the peaks of the double-vacancy layered oxide composite can well correspond to the standard card peaks of P2~(PDF#54~0894).

[0042] Example 2

[0043] Double-site vacancy-regulated manganese-iron-aluminum layered oxide composite, with the chemical formula: Na 0.82 Fe 0.2 □ 0.1 Mn 0.55 Al 0.05 Mg 0.1 O 2-y , which contains transition metal vacancies and oxygen vacancies, and 0 < y ≤ 0.05. The preparation steps are as follows:

[0044] S1. First, synthesize the layered oxide without oxygen vacancies. According to the molar ratio of each metal element in the chemical formula, dissolve the sodium source (sodium carbonate), iron source (iron acetate), manganese source (manganese sulfate), aluminum source (aluminum acetate) and M source (in this example, M is Mg and the M source is magnesium sulfate) in absolute ethanol. After stirring evenly at room temperature, a mixed solution is obtained. Then, add an excessive amount of oxalic acid solution to the mixed solution to obtain a yellow suspension; then let the suspension stand at room temperature for 16 h, filter, dry, and grind. Place the ground powder in an air atmosphere and calcine it at 500 °C for 5 h, and then raise the temperature to 800 °C and calcine it for 10 h to obtain a layered oxide precursor containing transition metal vacancies and no oxygen vacancies;

[0045] S2. Place the precursor obtained in step S1 in a porcelain boat and place it in a tube furnace with a mixed atmosphere of hydrogen and nitrogen, and calcine it at 400 °C for 4 h to obtain a layered oxide composite containing double vacancies.

[0046] Example 3

[0047] Double-site vacancy-regulated manganese-iron-aluminum layered oxide composite, with the chemical formula: Na 0.8 Fe 0.22 □ 0.08 Mn 0.65 Al 0.05 O 2-y , which contains transition metal vacancies and oxygen vacancies, and 0 < y ≤ 0.05. The preparation steps are as follows:

[0048] S1. First, synthesize a layered oxide without oxygen vacancies. According to the molar ratio of each metal element in the chemical formula, dissolve the sodium source (sodium carbonate), iron source (iron acetate), manganese source (manganese sulfate), aluminum source (aluminum acetate), and M source (in this example, M e where the value of e is 0) in absolute ethanol. After stirring evenly at room temperature, a mixed solution is obtained. Then, add an excessive amount of oxalic acid solution to the mixed solution to obtain a yellow suspension; then let the suspension stand at room temperature for 16 h, filter, dry, and grind. Place the ground powder in an air atmosphere and calcine it at 500 °C for 5 h, and then raise the temperature to 800 °C and calcine it for 10 h to obtain a layered oxide precursor containing transition metal vacancies and without oxygen vacancies;

[0049] S2. Place the precursor obtained in step S1 in a porcelain boat and place it in a tube furnace with a mixed atmosphere of hydrogen and nitrogen, and calcine it at 400 °C for 4 h to obtain a layered oxide composite material containing double vacancies.

[0050] Comparative Example 1

[0051] Manganese-iron-aluminum layered oxide composite material, whose chemical formula is: Na 0.78 Fe 0.25 □ 0.05 Mn 0.55 Al 0.05 Mg 0.1 O 2 , which contains transition metal vacancies and no oxygen vacancies. The preparation steps are as follows:

[0052] S1. First, synthesize a layered oxide without oxygen vacancies. According to the molar ratio of each metal element in the chemical formula, dissolve the sodium source (sodium carbonate), iron source (iron acetate), manganese source (manganese sulfate), aluminum source (aluminum acetate), and M source (in this example, M is Mg, and the M source is magnesium sulfate) in absolute ethanol. After stirring evenly at room temperature, a mixed solution is obtained. Then, add an excessive amount of oxalic acid solution to the mixed solution to obtain a yellow suspension; then let the suspension stand at room temperature for 16 h, filter, dry, and grind. Place the ground powder in an air atmosphere and calcine it at 500 °C for 5 h, and then raise the temperature to 800 °C and calcine it for 10 h to obtain a layered oxide layered oxide composite material containing transition metal vacancies and no oxygen vacancies.

[0053] Comparative Example 2

[0054] Manganese-iron-aluminum layered oxide composite material, whose chemical formula is: Na 0.78 Fe 0.3 Mn 0.55 Al 0.05 Mg 0.1 O 2-y, without transition metal vacancies, with oxygen vacancies, and 0 < y ≤ 0.05. The preparation steps are as follows:

[0055] S1. First, synthesize a layered oxide without oxygen vacancies. According to the molar ratio of each metal element in the chemical formula, dissolve a sodium source (sodium carbonate), an iron source (iron acetate), a manganese source (manganese sulfate), an aluminum source (aluminum acetate), and an M source (in this example, M is Mg and the M source is magnesium sulfate) in absolute ethanol. After stirring evenly at room temperature, a mixed solution is obtained. Then, add an excessive amount of oxalic acid solution to the mixed solution to obtain a yellow suspension; then let the suspension stand at room temperature for 16 h, filter, dry, and grind. Place the ground powder in an air atmosphere and calcine it at 500 °C for 5 h, and then raise the temperature to 800 °C and calcine it for 10 h to obtain a layered oxide precursor;

[0056] S2. Place the precursor obtained in step S1 in a porcelain boat and place it in a tubular furnace with a mixed atmosphere of hydrogen and nitrogen, and calcine it at 400 °C for 4 h to obtain a layered oxide composite material without transition metal vacancies and with oxygen vacancies.

[0057] Comparative Example 3

[0058] Manganese-iron-aluminum layered oxide composite material, whose chemical formula is: Na 0.95 Fe 0.2 □ 0.18 Mn 0.6 Al 0.02 O 2-y , which contains transition metal vacancies and oxygen vacancies, and 0 < y ≤ 0.05. The preparation steps are as follows:

[0059] S1. First, synthesize a layered oxide without oxygen vacancies. According to the molar ratio of each metal element in the chemical formula, dissolve a sodium source (sodium carbonate), an iron source (iron acetate), a manganese source (manganese sulfate), an aluminum source (aluminum acetate), and an M source (in this example, M is Mg and the M source is magnesium sulfate) in absolute ethanol. After stirring evenly at room temperature, a mixed solution is obtained. Then, add an excessive amount of oxalic acid solution to the mixed solution to obtain a yellow suspension; then let the suspension stand at room temperature for 16 h, filter, dry, and grind. Place the ground powder in an air atmosphere and calcine it at 500 °C for 5 h, and then raise the temperature to 800 °C and calcine it for 10 h to obtain a layered oxide precursor;

[0060] S2. Place the precursor obtained in step S1 in a porcelain boat and place it in a tubular furnace with a mixed atmosphere of hydrogen and nitrogen, and calcine it at 400 °C for 4 h to obtain a layered oxide composite material with transition metal vacancies and oxygen vacancies.

[0061] Comparative Example 4

[0062] Manganese-iron-aluminum layered oxide composite material, with the chemical formula: Na 0.82 Fe 0.2 □ 0.1 Mn 0.55 Al 0.05 Mg 0.1 O 2-y , which contains transition metal vacancies and oxygen vacancies, and y > 0.05. The preparation steps are as follows:

[0063] S1. First, synthesize the layered oxide without oxygen vacancies. According to the molar ratio of each metal element in the chemical formula, dissolve the sodium source (sodium carbonate), iron source (iron acetate), manganese source (manganese sulfate), aluminum source (aluminum acetate), and M source (in this embodiment, M is Mg, and the M source is magnesium sulfate) in absolute ethanol. After stirring evenly at room temperature, a mixed solution is obtained. Then, add an excessive amount of oxalic acid solution to the mixed solution to obtain a yellow suspension. Then, let the suspension stand at room temperature for 16 h, filter, dry, and grind. Place the ground powder in an air atmosphere and calcine it at 500 °C for 5 h, and then raise the temperature to 800 °C and calcine it for 10 h to obtain a layered oxide precursor containing transition metal vacancies and no oxygen vacancies;

[0064] S2. Place the precursor obtained in step S1 in a porcelain boat and place it in a tubular furnace with a mixed atmosphere of hydrogen and nitrogen. Calcinate it at 500 °C for 8 h to obtain a layered oxide composite material with a very high proportion of oxygen vacancies.

[0065] Application Example

[0066] Mix the layered oxide composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride) according to a mass ratio of 7:2:1, add an appropriate amount of N-methylpyrrolidone, and form a slurry after ultrasonic dispersion. Coat it on an aluminum foil and vacuum dry it for 12 h, and then press it into a positive electrode sheet. Use the positive electrode sheet prepared from the layered oxide composite material as the positive electrode, a sodium sheet as the negative electrode, a glass fiber as the separator, and NaClO 4 as the electrolyte to assemble a button battery (CR2032) and use a Blue Power battery test system to test its electrochemical performance.

[0067] The test results of the layered oxide composite material of Example 1 at a current density of 1 A·g -1 are as follows Figure 4 shown. It can be seen from the figure that at a current density of 1 A·g -1 , the first-cycle discharge specific capacity of the layered oxide composite material of Example 1 is 81.1 mAh / g, the discharge specific capacity after 1000 cycles is 82.3 mAh / g, and the capacity retention rate is 100%; at a large current density of 2 A·g -1 the test results are asFigure 5 As shown, it can be seen from the figure that at a high current density of 2 A·g -1 , the layered oxide composite material of Example 1 still has a capacity retention rate as high as 100% after 2000 cycles.

[0068] Figure 6 Figure 1 is the rate performance diagram of the layered oxide composite material of Example 1. It can be seen from the figure that at a current density of 0.01 A·g -1 , the layered oxide composite material of Example 1 can reach a reversible capacity of 208.9 mAh·g -1 ; at a high current of 0.5 A·g -1 , the layered oxide composite material of Example 1 still has a reversible capacity of more than 80.8 mAh·g -1 , and when the current returns to a small value, the capacity is not lost.

[0069] From the above test results, it can be seen that when the layered oxide composite material prepared by the present invention is used as the cathode material of a sodium-ion battery, it has a high initial capacity and exhibits very excellent cycle stability and excellent rate performance.

[0070] Table 1 shows the first-cycle discharge specific capacity and capacity retention rate after 1000 cycles of the layered oxide composite materials of Examples 1 to 3 and Comparative Examples 1 to 4 at a current density of 1 A·g -1 .

[0071] Table 1: Electrochemical performance of the layered oxide composite material at a current density of 1 A·g -1

[0072]

[0073] From the data in Table 1, it can be seen that when the layered oxide composite material prepared by the present invention is used as the cathode material of a sodium-ion battery, it has a high initial capacity and very excellent cycle stability. In the layered oxide composite material, containing only transition metal vacancies (Comparative Example 1), only oxygen vacancies (Comparative Example 2), too much content of transition metal vacancies (Comparative Example 3), or too much content of oxygen vacancies (Comparative Example 4) will all lead to a significant decrease in the first-cycle discharge specific capacity and cycle performance.

[0074] In summary, the present invention regulates the conditions and proportions of transition metal vacancies and oxygen vacancies in the manganese-iron-aluminum-based layered oxide to improve the performance of the layered oxide and stabilize its own structure, thereby enhancing the structural stability during the cycle, so that the composite material exhibits the characteristics of high capacity, high rate performance, and excellent cycle stability when used as the cathode material of a sodium-ion battery.

[0075] The above specific embodiments have described the implementation of the present invention in detail. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple variations all fall within the protection scope of the present invention.

Claims

1. A manganese-iron-aluminum layered oxide composite material regulated by dual-site vacancies, characterized in that: Its chemical formula is Na a Fe b □ x Mn c Al d M e O 2-y , where b + x + c + d + e = 1, 0.5 ≤ a < 1, 0.2 ≤ b ≤ 0.35, 0.2 ≤ c < 0.8, 0 < d ≤ 0.2, 0 ≤ e ≤ 0.4, 0 < x ≤ 0.15, 0 < y ≤ 0.05, □ is a transition metal vacancy, x is the content of the transition metal vacancy, y is the content of the oxygen vacancy, and the values of x, a, b, c, d, e, and y make the general formula satisfy the valence balance. M is selected from one or more of K, Zn, Mg, Li, Co, Ni, Cd, Ti, Ca, Ba, Sr, Cr, Si, Ge, Ga, In, Zr, Sb, Sn, Mo, W, Te, V, La, Ce, Pr, Ru, Nb, Gd, Dy, Er, Yb, B, Ag, Au, Y, Sc, Sb, Bi, Sb, Te.

2. The dual-site vacancy-regulated manganese-iron-aluminum layered oxide composite material according to claim 1, characterized in that: The dual-site vacancy-regulated manganese-iron-aluminum layered oxide composite material is prepared by a co-precipitation method.

3. The method for preparing the dual-site vacancy-controlled manganese-iron-aluminum layered oxide composite material according to claim 1 or 2, characterized in that: The following steps are involved: S1. According to the molar ratio of each metal element in the chemical formula, a sodium source, an iron source, a manganese source, an aluminum source and an M source are uniformly mixed in a solvent to obtain a mixed solution, and a precipitant is added to the mixed solution to obtain a suspension solution; The suspension solution is allowed to stand at room temperature for a period of time, then filtered, dried, and ground, and the ground powder is calcined at 300-1000°C to obtain a precursor; S2. calcining the precursor obtained in step S1 at 250-600° C. in a mixed atmosphere of hydrogen and nitrogen to obtain a layered oxide composite material containing double site vacancies.

4. The method for preparing the dual-site vacancy-controlled manganese-iron-aluminum layered oxide composite material according to claim 3, characterized in that: In step S1, the powder is calcined at 300-650° C. in an air atmosphere for 3-8 h, and then heated to 750-1000° C. for 6-15 h to obtain a precursor.

5. The method for preparing the dual-site vacancy-controlled manganese-iron-aluminum layered oxide composite material according to claim 3, characterized in that: In step S2, the calcination time is 2 to 6 hours.

6. The method for preparing the dual-site vacancy-controlled manganese-iron-aluminum layered oxide composite material according to claim 3, characterized in that: In step S2, the content of hydrogen in the mixed atmosphere is 4%.

7. The method for preparing the dual-site vacancy-controlled manganese-iron-aluminum layered oxide composite material according to claim 3, characterized in that: In step S1, the solvent is anhydrous ethanol.

8. The method for preparing the dual-site vacancy-controlled manganese-iron-aluminum layered oxide composite material according to claim 3, characterized in that: In step S1, the precipitant is oxalic acid solution.

9. The method for preparing the dual-site vacancy-controlled manganese-iron-aluminum layered oxide composite material according to claim 3, characterized in that: The sodium source includes at least one of sodium carbonate, sodium nitrate, and sodium acetate; the iron source includes at least one of ferric acetate, ferric nitrate, ferric sulfate, ferric oxalate, and nickel ferride; the manganese source includes at least one of manganese acetate, manganese nitrate, manganese sulfate, manganese oxalate, and manganese chloride; the aluminum source includes at least one of aluminum acetate, aluminum nitrate, aluminum sulfate, aluminum oxalate, and aluminum ferride; the M source includes at least one of acetic acid M, nitric acid M, sulfuric acid M, oxalic acid M, and ferride M.

10. Use of the dual-site vacancy-regulated manganese-iron-aluminum layered oxide composite material as claimed in claim 1 or 2 in the preparation of a positive electrode material for a sodium ion battery.

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