Aluminum transition metal oxide with tetragonal structure as well as preparation method and application of aluminum transition metal oxide

Abstract

The invention belongs to the technical field of electrochemical energy storage, and discloses a tetragonal structure aluminum transition metal oxide and a preparation method and application thereof. The preparation method of the aluminum transition metal oxide with the tetragonal structure comprises the following steps: mixing aluminum salt, manganese salt, M salt, a precipitant solution and water, and reacting to obtain precursor powder; sintering the precursor powder to obtain an intermediate product; and mixing the intermediate product and N oxide powder, and sequentially carrying out ball milling, tabletting, medium-temperature sintering and high-temperature sintering to obtain the tetragonal structure aluminum transition metal oxide. According to the tetragonal-structure aluminum transition metal oxide, the tetragonal structure is used as a main body frame, charge and lattice environments are synergistically regulated and controlled through multiple metals of M and N, so that the influence of multivalent ion intercalation and deintercalation on a crystal structure is remarkably reduced, and the positive electrode material with stable structure, high specific capacity and excellent rate capability is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a tetragonal aluminum transition metal oxide and a preparation method and application thereof. Background Art

[0002] Under the current global "dual carbon" goals and new energy strategy, the development of safe, low-cost, environmentally friendly high-performance energy storage systems has become an important research direction in the field of electrochemistry. Aqueous batteries (such as aqueous multivalent ion batteries, lead-carbon batteries, lead-lithium batteries, etc.) use metals or oxides with abundant reserves and low prices in the earth's crust as electrode materials. They have the advantages of high theoretical energy density, high safety, non-toxic and non-flammable electrolytes, and have become ideal electrochemical energy storage devices. However, due to the high charge density and strong hydration of divalent or multivalent ions, the reversible insertion and extraction process of charged ions in the positive electrode materials in aqueous batteries always faces serious diffusion barriers and structural stability problems. Therefore, the development of a positive electrode material with high capacity, high stability and excellent charged ion migration ability is one of the key technical bottlenecks to break through the industrial application of aqueous batteries.

[0003] Transition metal oxides, due to their rich oxidation states and diverse crystal structures, are among the most promising cathode materials for aqueous batteries. However, common layered or tunnel-structured transition metal oxide cathode materials suffer from structural collapse and metal ion dissolution during charge and discharge, resulting in rapid capacity decay and severely limiting their long-term cycling and rate performance. To improve structural stability and electrochemical activity, researchers generally employ multi-metal doping strategies to enhance material stability.

[0004] Another approach to improving the performance of transition metal oxide cathode materials is to introduce metal elements such as aluminum and zinc to form metal oxides of aluminum and zinc, thereby improving the stability and cycle performance of the materials. The introduction of aluminum, in particular, has the following advantages: (1) trivalent aluminum ions have a high charge density, which stabilizes the crystal framework and inhibits Jahn-Teller distortion; (2) the introduction of aluminum helps to form oxygen vacancies, improving electron / ion migration performance; and (3) aluminum and transition metal elements have good compatibility, enabling a balance between high capacity and long cycle life while maintaining crystal stability.

[0005] In terms of crystal structure, traditional layered or tunnel-type manganese oxide structures are prone to severe volume changes or structural collapse due to the intercalation and deintercalation of multivalent ions. In contrast, tetragonal spinel and tetragonal perovskite structures have advantages such as high symmetry, three-dimensional continuous ion migration channels, and strong structural rigidity. They are more suitable for the reversible intercalation and deintercalation of multivalent ions and are less prone to phase transitions during cycling, demonstrating superior structural stability. Traditional synthesis methods currently used in most literature, such as hydrothermal, sol-gel, and solid-phase reaction methods, have problems such as cumbersome operations, narrow process windows, and poor material uniformity, which are not conducive to practical large-scale applications.

[0006] Therefore, the research on a tetragonal aluminum transition metal oxide with stable crystal structure, controllable particle size, excellent electrochemical performance and significantly improved specific capacity, rate performance and cycle stability and its preparation method are of great significance for the preparation of a new type of aqueous battery with high safety and high energy density. Summary of the Invention

[0007] In view of this, the present invention provides a tetragonal aluminum transition metal oxide and its preparation method and application, the purpose of which is to solve the technical problems of existing positive electrode materials in terms of poor structural stability, difficulty in intercalation and deintercalation of multivalent ions, and low electrical conductivity.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a tetragonal aluminum transition metal oxide, the chemical formula of which is: Al x Mn 2-y-z M y N z O4, where 1 / 6≤x<2, 0 <y≤2,0≤z≤1,2-y-z≥0;

[0010] The M is one or more of Co, Ni, Cu and Cr, and N is one or more of Ti, Mg, Fe, Zn, V, Sn, Y, Zr, Nb and Mo.

[0011] The present invention also provides a method for preparing a tetragonal aluminum transition metal oxide, comprising the following steps:

[0012] 1) mixing aluminum salt, manganese salt, M salt, precipitant solution and water and reacting them to obtain a precursor powder; or mixing aluminum salt, M salt, precipitant solution and water and reacting them to obtain a precursor powder;

[0013] 2) Sintering the precursor powder to obtain an intermediate product;

[0014] 3) The intermediate product and the oxide powder containing the nitrogen element are mixed and then subjected to ball milling, tableting, medium temperature sintering and high temperature sintering in sequence to obtain a tetragonal aluminum transition metal oxide; or the intermediate product is subjected to ball milling, tableting, medium temperature sintering and high temperature sintering in sequence to obtain a tetragonal aluminum transition metal oxide.

[0015] Preferably, in step 1), the aluminum salt is aluminum sulfate, the manganese salt is manganese sulfate, and the M salt is sulfate of M;

[0016] When adding the manganese salt, the molar ratio of the aluminum ion in the aluminum salt, the manganese ion in the manganese salt, and the M ion in the M salt is 1:1-1.25:0.5-2, the amount ratio of the aluminum ion in the aluminum salt to the precipitant is 1 mol:2.5-4 L, and the amount ratio of the aluminum ion in the aluminum salt to water is 1 mol:1-1.5 L;

[0017] When no manganese salt is added, the molar ratio of aluminum ions in the aluminum salt to M ions in the M salt is 1:1-2, the dosage ratio of aluminum ions in the aluminum salt to the precipitant is 1 mol:2.5-4 L, and the dosage ratio of aluminum ions in the aluminum salt to water is 1 mol:1-1.5 L.

[0018] Preferably, in step 1), the precipitant solution is a sodium hydroxide aqueous solution, and the concentration of the sodium hydroxide aqueous solution is 1.5 to 2.5 mol / L;

[0019] The reaction is a precipitation reaction, the temperature of the precipitation reaction is 45 to 55° C., and the time of the precipitation reaction is 4 to 8 hours.

[0020] Preferably, in step 2), the sintering temperature is 450-600° C., and the sintering time is 5-8 hours.

[0021] Preferably, in step 3), the molar ratio of N ions in the N-containing oxide powder to aluminum ions in the aluminum salt is ≤2.

[0022] Preferably, in step 3), the ball milling is plasma ball milling, the ball-to-material ratio of the ball milling is 8 to 12:1, the ball milling speed is 400 to 1400 rpm, and the ball milling time is 5 to 8 hours;

[0023] The tableting pressure is 10-20 MPa.

[0024] Preferably, in step 3), the medium-temperature sintering temperature is 750-850° C., the heating rate from room temperature to the medium-temperature sintering temperature is 4-6° C. / min, and the medium-temperature sintering time is 5-7 h.

[0025] Preferably, in step 3), the high-temperature sintering temperature is 900-1000° C., the heating rate from the medium-temperature sintering temperature to the high-temperature sintering temperature is 1.5-2.5° C. / min, and the high-temperature sintering time is 5-7 hours.

[0026] The present invention also provides an application of a tetragonal aluminum transition metal oxide in a positive electrode material for an aqueous battery.

[0027] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a method for preparing a tetragonal aluminum transition metal oxide through coprecipitation, plasma ball milling, and solid-phase sintering. The resulting tetragonal aluminum transition metal oxide uses a tetragonal structure as its main framework. Through the synergistic regulation of charge and lattice environment by multimetallic M and N elements, the effects of multivalent ion insertion and extraction on the crystal structure are significantly reduced, resulting in a positive electrode material with a stable structure, high specific capacity, and excellent rate performance.

[0029] The cathode material of this invention is suitable for aqueous batteries and has broad application prospects in large-scale safe energy storage, grid regulation, and portable energy devices. The preparation method of this invention features simple processes, readily available raw materials, and is environmentally friendly, suitable for low-cost, large-scale production and possesses excellent industrialization and promotion potential.

[0030] The present invention adopts a three-step route of co-precipitation + plasma ball milling + solid-phase sintering to achieve uniform doping at the atomic level, control particle size distribution, and construct stable tetragonal structure crystals, which has significant process advantages and industrial potential. 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 description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0032] Figure 1 This is the XRD pattern of the AlCo2O4 cathode material obtained in Example 1;

[0033] Figure 2 AlMn obtained in Example 2 1.5 Co 0.5 The first cycle charge and discharge curve of O4 positive electrode material. DETAILED DESCRIPTION

[0034] The present invention provides a tetragonal aluminum transition metal oxide, the chemical formula of which is: Al x Mn 2-y-z M y N zO4, where 1 / 6≤x<2, 0 <y≤2,0≤z≤1,2-y-z≥0;

[0035] The M is one or more of Co, Ni, Cu and Cr, and N is one or more of Ti, Mg, Fe, Zn, V, Sn, Y, Zr, Nb and Mo.

[0036] The present invention also provides a method for preparing a tetragonal aluminum transition metal oxide, comprising the following steps:

[0037] 1) mixing aluminum salt, manganese salt, M salt, precipitant solution and water and reacting them to obtain a precursor powder; or mixing aluminum salt, M salt, precipitant solution and water and reacting them to obtain a precursor powder;

[0038] 2) Sintering the precursor powder to obtain an intermediate product;

[0039] 3) The intermediate product and the oxide powder containing the nitrogen element are mixed and then subjected to ball milling, tableting, medium temperature sintering and high temperature sintering in sequence to obtain a tetragonal aluminum transition metal oxide; or the intermediate product is subjected to ball milling, tableting, medium temperature sintering and high temperature sintering in sequence to obtain a tetragonal aluminum transition metal oxide.

[0040] In the present invention, in step 1), the aluminum salt is preferably aluminum sulfate, the manganese salt is preferably manganese sulfate, and the M salt is preferably M sulfate;

[0041] When adding manganese salt, the molar ratio of aluminum ions in the aluminum salt, manganese ions in the manganese salt, and M ions in the M salt is preferably 1:1-1.25:0.5-2, more preferably 1:1.05-1.2:1-1.75, more preferably 1:1.1-1.15:1.25-1.5, the amount ratio of aluminum ions in the aluminum salt to the precipitant is preferably 1 mol:2.5-4 L, more preferably 1 mol:2.7-3.5 L, more preferably 1 mol:3-3.2 L, the amount ratio of aluminum ions in the aluminum salt to water is preferably 1 mol:1-1.5 L, more preferably 1 mol:1.1-1.4 L, more preferably 1 mol:1.2-1.3 L;

[0042] When no manganese salt is added, the molar ratio of aluminum ions in the aluminum salt to M ions in the M salt is preferably 1:1-2, more preferably 1:1.2-1.8, more preferably 1:1.5-1.6, the amount ratio of aluminum ions in the aluminum salt to the precipitant is preferably 1 mol:2.5-4 L, more preferably 1 mol:2.7-3.5 L, more preferably 1 mol:3-3.2 L, and the amount ratio of aluminum ions in the aluminum salt to water is preferably 1 mol:1-1.5 L, more preferably 1 mol:1.1-1.4 L, more preferably 1 mol:1.2-1.3 L.

[0043] In the present invention, in step 1), the precipitant solution is preferably an aqueous sodium hydroxide solution, and the concentration of the aqueous sodium hydroxide solution is preferably 1.5 to 2.5 mol / L, more preferably 1.7 to 2.3 mol / L, and more preferably 2 to 2.2 mol / L;

[0044] The reaction is preferably a precipitation reaction. The temperature of the precipitation reaction is preferably 45 to 55° C., more preferably 47 to 53° C., more preferably 48 to 50° C., and the time of the precipitation reaction is preferably 4 to 8 hours, more preferably 5 to 7 hours, more preferably 6 hours.

[0045] In the present invention, in the step 1), after the reaction, filter pressing, washing and drying are carried out in sequence; the filter pressing pressure is preferably 0.8-1.5 MPa, more preferably 1.0-1.3 MPa, more preferably 1.1-1.2 MPa, the filter pressing time is preferably 5-15 min, more preferably 8-12 min, more preferably 10-11 min, the washing reagent is preferably deionized water, the number of washings is preferably 3 times, the drying is preferably vacuum drying, the vacuum degree of vacuum drying is preferably 1.5-6.5 kPa, more preferably 1.5-5 kPa, more preferably 1.5-3 kPa, the vacuum drying temperature is preferably 80-150 ° C, more preferably 100-130 ° C, more preferably 110-120 ° C, the vacuum drying time is preferably 2-8 h, more preferably 3-6 h, more preferably 4-5 h.

[0046] In the present invention, in order to ensure that the prepared tetragonal aluminum transition metal oxide material has excellent electrochemical properties, the selection of raw materials in step 1) is crucial. Among them, the aluminum salt is the source of aluminum element. Its solubility, reactivity and thermal decomposition behavior will directly affect the precipitation morphology of the precursor and the subsequent formation of the crystal structure. Water-soluble aluminum sulfate is preferably used as the aluminum salt; the manganese salt provides Mn 2+ , which mainly affects the oxidation state regulation of the material and the formation of a tetragonal structure lattice; the M is an electrochemically active transition metal, which participates in the redox reaction and can improve the specific capacity of the material. Preferably, the sulfate of M is used to ensure the precise ratio and crystal control consistency during the co-precipitation process.

[0047] In the present invention, in the step 1), the mixing is preferably performed by first mixing the aluminum salt, the manganese salt, the M salt, and water to obtain a mixed solution, and then mixing the mixed solution with the precipitant solution; wherein, to ensure the uniformity and controllability of the reaction, a peristaltic pump is used to synchronously pump the mixed solution and the precipitant solution into the reaction vessel in a set ratio, while mechanically stirring, and monitoring the acidity and alkalinity of the system by a pH meter to maintain the reaction system at a pH value of 11.5; the speed of the mechanical stirring is preferably 800 to 1500 rpm, more preferably 1000 to 1300 rpm, and more preferably 1100 to 1200 rpm.

[0048] In the present invention, in the step 2), the sintering temperature is preferably 450-600°C, more preferably 480-580°C, more preferably 500-550°C, and the sintering time is preferably 5-8h, more preferably 5.5-7h, more preferably 6-6.5h; the heating rate from room temperature to the sintering temperature is preferably 4-6°C / min, more preferably 4.2-5.6°C / min, more preferably 4.5-5°C / min.

[0049] In the present invention, in step 2), the sintering is preferably performed by placing the precursor powder in a high-temperature resistant ceramic crucible, and then placing the crucible in a muffle furnace or a tube furnace under an air atmosphere.

[0050] In the present invention, in the step 2), cooling is performed after sintering to room temperature.

[0051] In the present invention, in step 3), the molar ratio of N ions in the N-containing oxide powder to aluminum ions in the aluminum salt is preferably ≤2, more preferably ≤1.8, and even more preferably ≤1.6.

[0052] In the present invention, in step 3), the N oxide powder preferably includes one or more of TiO2, MgO, ZnO, V2O5, SnO2, ZrO2, Nb2O5, MoO3 and Y2O3; preferably ZnO+TiO2, Nb2O5+SnO2;

[0053] The purity of the N oxide powder is preferably ≥99%, more preferably ≥99.2%, and more preferably ≥99.5%. The particle size of the N oxide powder is preferably ≤10 μm, more preferably ≤9 μm, and more preferably ≤8 μm. The purity and particle size of the N oxide powder can ensure the uniformity and stability of the ball-milled particles.

[0054] In the present invention, in the step 3), the ball milling is preferably plasma ball milling, the ball-to-material ratio of the ball milling is preferably 8-12:1, more preferably 9-11:1, and more preferably 10:1, the medium of the ball milling is preferably cemented carbide balls, the diameter of the ball milling medium is preferably 5-10 mm, more preferably 6-9 mm, and more preferably 7-8 mm, the rotation speed of the ball milling is preferably 400-1400 rpm, more preferably 1100-1300 rpm, and more preferably 1200-1250 rpm, the ball milling time is preferably 5-8 h, more preferably 5.5-7 h, and more preferably 6-6.5 h, and the power supply frequency of the plasma ball milling is preferably 10-15 kHz, more preferably 11-14 kHz, and more preferably 12-13 kHz;

[0055] The tableting pressure is preferably 10 to 20 MPa, more preferably 12 to 18 MPa, and even more preferably 15 to 16 MPa.

[0056] In the present invention, in the step 3), the temperature of the medium-temperature sintering is preferably 750-850°C, more preferably 770-830°C, and more preferably 780-800°C. The heating rate from room temperature to the medium-temperature sintering temperature is preferably 4-6°C / min, more preferably 4.5-5.5°C / min, and more preferably 5-5.2°C / min. The medium-temperature sintering time is preferably 5-7h, more preferably 5.5-6.5h, and more preferably 6h.

[0057] In the present invention, in the step 3), the temperature of the high-temperature sintering is preferably 900-1000°C, more preferably 920-980°C, and more preferably 950-960°C. The heating rate from the medium-temperature sintering temperature to the high-temperature sintering temperature is preferably 1.5-2.5°C / min, more preferably 1.7-2.4°C / min, and more preferably 2-2.2°C / min. The high-temperature sintering time is preferably 5-7h, more preferably 5.5-6.5h, and more preferably 6h.

[0058] In the present invention, in step 3), the sintering atmospheres for the medium-temperature sintering and the high-temperature sintering are independently preferably air, nitrogen or argon.

[0059] In the present invention, in the step 3), cooling and grinding are carried out in sequence after high-temperature sintering; the cooling is preferably furnace cooling to room temperature, the grinding is preferably mechanical grinding, the mechanical grinding speed is preferably 200-400 rpm, more preferably 250-350 rpm, more preferably 300 rpm, and the mechanical grinding time is preferably 10-50 min, more preferably 20-40 min, more preferably 25-35 min.

[0060] The present invention also provides an application of a tetragonal aluminum transition metal oxide in a positive electrode material for an aqueous battery.

[0061] In the present invention, the application of the tetragonal aluminum transition metal oxide in the positive electrode material of aqueous batteries comprises the following steps:

[0062] (1) mixing a tetragonal aluminum transition metal oxide, a conductive agent, a binder, and a solvent to obtain a positive electrode material slurry;

[0063] (2) coating the positive electrode material slurry on the titanium foil current collector and drying it to obtain a positive electrode sheet;

[0064] (3) Assemble the positive electrode sheet, negative electrode and electrolyte to obtain a water-washable battery.

[0065] In the present invention, in the step (1), the conductive agent is preferably super carbon black, the binder is preferably polyvinylidene fluoride, and the solvent is preferably N-methylpyrrolidone; the mass ratio of the tetragonal aluminum transition metal oxide, the conductive agent, the binder and the solvent is preferably 90-95:1-5:4-7:100-300, more preferably 91-94:2-4:5-6:120-250, and more preferably 92-93:3:5-6:150-200.

[0066] In the present invention, in the step (2), the coating thickness is preferably 80 to 150 μm, more preferably 100 to 130 μm, and more preferably 110 to 120 μm; the drying is preferably vacuum drying, the vacuum drying temperature is preferably 100 to 150°C, more preferably 110 to 140°C, and more preferably 120 to 130°C, the vacuum degree of vacuum drying is preferably 1.5 to 6.5 kPa, more preferably 1.5 to 5 kPa, and more preferably 1.5 to 3 kPa, and the vacuum drying time is preferably 6 to 15 h, more preferably 8 to 12 h, and more preferably 9 to 10 h.

[0067] In the present invention, in the step (3), the negative electrode is preferably an aluminum-zinc alloy sheet, wherein the mass fraction of aluminum is preferably 50-60%, more preferably 52-58%, and more preferably 55-56%; the electrolyte is preferably an aluminum chloride aqueous solution, and the concentration of the aluminum chloride aqueous solution is preferably 0.8-1.2 mol / L, more preferably 0.9-1.1 mol / L, and more preferably 1 mol / L.

[0068] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0069] Example 1

[0070] Preparation of tetragonal aluminum transition metal oxide AlCo2O4:

[0071] 0.25 mol Al2(SO4)3·18H2O, 1 mol CoSO4 and 650 mL of water were mixed to obtain a mixed solution. The mixed solution was mixed with 1760 mL of a sodium hydroxide aqueous solution (concentration of 2 mol / L) using a peristaltic pump at a stirring speed of 1200 rpm to make the pH value of the obtained liquid 11.5. The mixture was subjected to precipitation reaction at 50°C for 7 h. The reaction product was filter-filtered at a pressure of 1.2 MPa for 10 min. The solid product obtained by filtration was washed three times with water and then dried in vacuum at 110°C and a vacuum degree of 1.5 kPa for 4 h to obtain a precursor powder.

[0072] The precursor powder was placed in a high-temperature resistant ceramic crucible and placed in a tube furnace. The temperature was raised to 550°C at a heating rate of 5°C / min in an air atmosphere and sintered for 6 hours. The crucible was then cooled to room temperature to obtain an intermediate product.

[0073] The obtained intermediate product was placed in a plasma ball mill (power supply frequency of 12kHz), 600g of 8mm diameter carbide balls were added at a ball-to-material ratio of 10:1, and the mixture was ball-milled at a speed of 1200rpm for 6h to obtain powder. The obtained powder was pressed into tablets at a pressure of 15MPa, and then the obtained tablets were heated to 800℃ in an air atmosphere at a heating rate of 5℃ / min and kept warm for 6h to complete medium-temperature sintering. After the medium-temperature sintering was completed, the temperature was still raised to 950℃ in an air atmosphere at a heating rate of 2.2℃ / min and kept warm for 6h to complete high-temperature sintering. The product was then cooled to room temperature with the furnace, and the cooled product was mechanically ground at a speed of 300rpm for 30min to obtain tetragonal aluminum transition metal oxide AlCo2O4.

[0074] Example 2

[0075] Tetragonal aluminum transition metal oxides AlMn 1.5 Co 0.5 Preparation of O4:

[0076] 0.25 mol Al2(SO4)3·18H2O, 0.75 mol MnSO4·H2O, 0.25 mol CoSO4 and 650 mL of water were mixed to obtain a mixed solution. The mixed solution was mixed with 1760 mL of a sodium hydroxide aqueous solution (concentration of 2 mol / L) using a peristaltic pump at a stirring speed of 1100 rpm to make the pH value of the obtained liquid 11.5, and a precipitation reaction was carried out at 50°C for 7 h. The reaction product was filter-filtered at a pressure of 1.2 MPa for 10 min. The solid product obtained by filter-filtering was washed three times with water and then dried in vacuum at 120°C under a vacuum degree of 1.5 kPa for 4 h to obtain a precursor powder.

[0077] The precursor powder is placed in a high-temperature resistant ceramic crucible, and placed in a tube furnace under air atmosphere, heated to 550°C at a heating rate of 5°C / min and sintered for 6 hours, and then cooled to room temperature in the furnace to obtain an intermediate product;

[0078] The obtained intermediate product was placed in a plasma ball mill (power frequency of 12kHz), 600g of 8mm diameter carbide balls were added at a ball-to-material ratio of 10:1, and the powder was ball-milled at a speed of 1200rpm for 6h to obtain a powder. The obtained powder was pressed into a tablet at a pressure of 15MPa, and then the obtained tablet was heated to 800℃ in an air atmosphere at a heating rate of 5℃ / min and kept warm for 6h to complete medium-temperature sintering. After the medium-temperature sintering was completed, the tablet was heated to 950℃ at a heating rate of 2.2℃ / min in an air atmosphere and kept warm for 6h to complete high-temperature sintering. The tablet was then cooled to room temperature with the furnace, and the cooled product was mechanically ground at a speed of 300rpm for 30min to obtain tetragonal aluminum transition metal oxide AlMn 1.5 Co 0.5 O4.

[0079] Example 3

[0080] Preparation of tetragonal aluminum transition metal oxide AlMnCoO4:

[0081] 0.25 mol Al2(SO4)3·18H2O, 0.5 mol MnSO4·H2O, 0.5 mol CoSO4 and 650 mL of water were mixed to obtain a mixed solution. The mixed solution was mixed with 1760 mL of a sodium hydroxide aqueous solution (concentration of 2 mol / L) using a peristaltic pump at a stirring speed of 1200 rpm to make the pH value of the obtained liquid 11.5, and a precipitation reaction was carried out at 50°C for 7 h. The reaction product was filter-filtered at a pressure of 1.2 MPa for 10 min. The solid product obtained by filtration was washed three times with water and then dried in vacuum at 120°C and a vacuum degree of 1.5 kPa for 4 h to obtain a precursor powder.

[0082] The precursor powder is placed in a high-temperature resistant ceramic crucible, and placed in a tube furnace under air atmosphere, heated to 550°C at a heating rate of 5°C / min and sintered for 6 hours, and then cooled to room temperature in the furnace to obtain an intermediate product;

[0083] The obtained intermediate product was placed in a plasma ball mill (power supply frequency of 12kHz), 600g of 8mm diameter carbide balls were added at a ball-to-material ratio of 10:1, and the mixture was ball-milled at a speed of 400rpm for 6h to obtain powder. The obtained powder was pressed into tablets at a pressure of 15MPa, and then the obtained tablets were heated to 800℃ in an air atmosphere at a heating rate of 5℃ / min and kept warm for 6h to complete medium-temperature sintering. After the medium-temperature sintering was completed, the temperature was still raised to 950℃ in an air atmosphere at a heating rate of 2.2℃ / min and kept warm for 6h to complete high-temperature sintering. The product was then cooled to room temperature with the furnace, and the cooled product was mechanically ground at a speed of 300rpm for 30min to obtain tetragonal aluminum transition metal oxide AlMnCoO4.

[0084] Example 4

[0085] Preparation of tetragonal aluminum transition metal oxide AlCoFeO4:

[0086] 0.25 mol Al2(SO4)3·18H2O, 0.5 mol CoSO4 and 500 mL of water were mixed to obtain a mixed solution. The mixed solution was mixed with 1260 mL of a sodium hydroxide aqueous solution (concentration of 2 mol / L) using a peristaltic pump at a stirring speed of 1200 rpm to make the pH value of the obtained liquid 11.5. The mixture was subjected to precipitation reaction at 50°C for 7 h. The reaction product was filter-filtered at a pressure of 1.2 MPa for 10 min. The solid product obtained by filtration was washed three times with water and then dried in vacuum at 120°C under a vacuum degree of 1.5 kPa for 4 h to obtain a precursor powder.

[0087] The precursor powder is placed in a high-temperature resistant ceramic crucible, and placed in a tube furnace under air atmosphere, heated to 550°C at a heating rate of 5°C / min and sintered for 6 hours, and then cooled to room temperature in the furnace to obtain an intermediate product;

[0088] The obtained intermediate product and 0.25 mol α-Fe2O3 were placed in a plasma ball mill (power frequency of 12 kHz), and 600 g of 8 mm diameter carbide balls were added at a ball-to-material ratio of 10:1. The mixture was ball-milled at a speed of 1200 rpm for 6 h to obtain powder. The obtained powder was pressed into tablets at a pressure of 15 MPa. The obtained tablets were then heated to 800°C in an air atmosphere at a heating rate of 5°C / min and kept warm for 6 h to complete medium-temperature sintering. After the medium-temperature sintering was completed, the temperature was still raised to 950°C in an air atmosphere at a heating rate of 2.2°C / min and kept warm for 6 h to complete high-temperature sintering. The tablets were then cooled to room temperature with the furnace, and the cooled product was mechanically ground at a speed of 300 rpm for 30 min to obtain tetragonal aluminum transition metal oxide AlCoFeO4.

[0089] The performance of the tetragonal aluminum transition metal oxides obtained in Examples 1 to 4 was tested respectively. The performance test results are shown in Table 1.

[0090] Aqueous batteries were prepared using the tetragonal aluminum transition metal oxides obtained in Examples 1 to 4 according to the following steps:

[0091] Tetragonal aluminum transition metal oxide, super carbon black, polyvinylidene fluoride, and N-methylpyrrolidone are mixed in a mass ratio of 92:3:5:150 to obtain a positive electrode material slurry;

[0092] The positive electrode material slurry was coated (thickness of 120 μm) on a titanium foil current collector, and then vacuum dried at 120°C with a vacuum degree of 2 kPa for 10 h to obtain a positive electrode sheet;

[0093] An aqueous battery was obtained by assembling an aluminum-zinc alloy sheet with an aluminum content of 55 wt% as the negative electrode, a 1 mol / L aluminum chloride aqueous solution as the electrolyte, and the above-mentioned positive electrode sheet as the positive electrode.

[0094] Table 1 Performance test results of aqueous batteries made from tetragonal aluminum transition metal oxides obtained in Examples 1 to 4

[0095]

[0096] As shown in Table 1, the tetragonal aluminum transition metal oxide obtained in the present invention, when used as a cathode material for aqueous batteries, achieves a maximum capacity of 205.7 mAh / g at a current density of 100 mA / g, and its capacity drop after 200 cycles is only 23%. This demonstrates that the tetragonal aluminum transition metal oxide obtained in the present invention exhibits excellent electrical properties.

[0097] The XRD pattern of the AlCo2O4 cathode material obtained in Example 1 is as follows Figure 1 As shown. Figure 1 It can be seen that the main diffraction peak of AlCo2O4 obtained in Example 1 is consistent with the standard card, and the diffraction peak is sharp, which indicates that the material has a tetragonal spinel structure and good crystallinity.

[0098] AlMn obtained in Example 2 1.5 Co 0.5 The first cycle charge and discharge curve of O4 positive electrode material is as follows Figure 2 As shown. Figure 2 It can be seen that at a current density of 100 mA / g, the AlMn 1.5 Co 0.5 The initial capacity of the aqueous battery assembled by O4 is 136mAh / g.

[0099] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A tetragonal aluminum transition metal oxide, characterized in that: The chemical formula of the tetragonal aluminum transition metal oxide is: Al x Mn 2-y-z M y N z O4, where 1 / 6≤x<2,0 <y≤2,0≤z≤1,2-y-z≥0; The M is one or more of Co, Ni, Cu and Cr, and N is one or more of Ti, Mg, Fe, Zn, V, Sn, Y, Zr, Nb and Mo.

2. The method for preparing a tetragonal aluminum transition metal oxide according to claim 1, characterized in that: The steps include: 1) mixing aluminum salt, manganese salt, M salt, precipitant solution and water and reacting them to obtain a precursor powder; or mixing aluminum salt, M salt, precipitant solution and water and reacting them to obtain a precursor powder; 2) Sintering the precursor powder to obtain an intermediate product; 3) The intermediate product and the oxide powder containing the nitrogen element are mixed and then subjected to ball milling, tableting, medium temperature sintering and high temperature sintering in sequence to obtain a tetragonal aluminum transition metal oxide; or the intermediate product is subjected to ball milling, tableting, medium temperature sintering and high temperature sintering in sequence to obtain a tetragonal aluminum transition metal oxide.

3. The method for preparing a tetragonal aluminum transition metal oxide according to claim 2, wherein: In the step 1), the aluminum salt is aluminum sulfate, the manganese salt is manganese sulfate, and the M salt is sulfate of M; When adding the manganese salt, the molar ratio of the aluminum ion in the aluminum salt, the manganese ion in the manganese salt, and the M ion in the M salt is 1:1-1.25:0.5-2, the amount ratio of the aluminum ion in the aluminum salt to the precipitant is 1 mol:2.5-4 L, and the amount ratio of the aluminum ion in the aluminum salt to water is 1 mol:1-1.5 L; When no manganese salt is added, the molar ratio of aluminum ions in the aluminum salt to M ions in the M salt is 1:1-2, the dosage ratio of aluminum ions in the aluminum salt to the precipitant is 1 mol:2.5-4 L, and the dosage ratio of aluminum ions in the aluminum salt to water is 1 mol:1-1.5 L.

4. The method for preparing a tetragonal aluminum transition metal oxide according to claim 2, wherein: In the step 1), the precipitant solution is a sodium hydroxide aqueous solution, and the concentration of the sodium hydroxide aqueous solution is 1.5 to 2.5 mol / L; The reaction is a precipitation reaction, the temperature of the precipitation reaction is 45 to 55° C., and the time of the precipitation reaction is 4 to 8 hours.

5. The method for preparing a tetragonal aluminum transition metal oxide according to claim 3 or 4, characterized in that: In the step 2), the sintering temperature is 450-600° C., and the sintering time is 5-8 hours.

6. The method for preparing a tetragonal aluminum transition metal oxide according to claim 5, characterized in that: In the step 3), the molar ratio of nitrogen ions in the nitrogen-containing oxide powder to aluminum ions in the aluminum salt is ≤2.

7. The method for preparing a tetragonal aluminum transition metal oxide according to claim 6, characterized in that: In the step 3), the ball milling is plasma ball milling, the ball-to-material ratio of the ball milling is 8 to 12:1, the ball milling speed is 400 to 1400 rpm, and the ball milling time is 5 to 8 hours; The tableting pressure is 10-20 MPa.

8. The method for preparing a tetragonal aluminum transition metal oxide according to claim 6 or 7, characterized in that: In the step 3), the medium-temperature sintering temperature is 750-850° C., the heating rate from room temperature to the medium-temperature sintering temperature is 4-6° C. / min, and the medium-temperature sintering time is 5-7 hours.

9. The method for preparing a tetragonal aluminum transition metal oxide according to claim 8, characterized in that: In step 3), the high-temperature sintering temperature is 900-1000° C., the heating rate from the medium-temperature sintering temperature to the high-temperature sintering temperature is 1.5-2.5° C. / min, and the high-temperature sintering time is 5-7 hours.

10. Use of the tetragonal aluminum transition metal oxide according to claim 1 in a positive electrode material for aqueous batteries.

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