High-entropy O3-phase layered oxide material, preparation method, application and battery

Abstract

The invention discloses a high-entropy O3 phase layered oxide material, a preparation method, application and a battery. The chemical formula of the material is Na < 1-x-y > Ca < y > Li Ni Cu < c > Fe < d > Co < e > Mn < f > Ti < g > O < 2 >, the material belongs to a hexagonal system, and the space group is R-3m; wherein 0 lt; x is less than or equal to 0.1, 0lt; a + b + c + d + e + f + g = 1, 0 < a < = 0.1, 0.15 < = b < = 0.3, 0 < c < = 0.1, 0.08 < = d < = 0.25, 0 < e < = 0.08, 0.3 < = f < = 0.5, and 0 < g < = 0.1. The high-entropy O3-phase layered oxide material prepared by the invention has relatively good structural stability and air stability, and the preparation method is simple and easy for large-scale production; the sodium ion battery formed by using the lithium ion battery positive electrode material as a positive electrode active material has the characteristics of high cycling stability, high rate capability and fast charge.

Description

Technical Field

[0001] The present invention belongs to the field of sodium ion battery positive electrode materials, and specifically relates to a high-entropy O3 phase layered oxide material and a preparation method, application and battery. Background Art

[0002] Among various energy storage technologies, electrochemical energy storage, due to its high energy conversion efficiency, rapid response, and flexible deployment, has become an effective means of addressing issues such as unstable renewable energy generation. Currently, lithium-ion batteries (LIBs) dominate the electrochemical energy storage market, thanks to their high energy density, long cycle life, and mature industrial chain. In recent years, with the rapid development of electric vehicles and large-scale energy storage, demand for lithium resources has steadily increased. However, the concentration of lithium in the Earth's crust is low, approximately 0.0065%. Furthermore, lithium is unevenly distributed globally, with a primary concentration in South America. The scarcity and uneven distribution of lithium resources make LIBs unable to meet future large-scale energy storage technology needs. Sodium-ion batteries (SIBs) are considered an ideal low-cost alternative to LIBs due to their global availability, low cost, and high compatibility with current LIB production processes and equipment. Furthermore, LIBs offer advantages over LIBs in safety, fast charging performance, and low-temperature performance. These favorable factors hold promise for widespread application in new energy low-speed transportation and large-scale energy storage. Cathode materials for sodium-ion batteries primarily include polyanionic compounds, Prussian blue compounds, tunneling oxides, and layered transition metal oxides. Layered transition metal oxide cathodes are considered the most promising cathode materials for sodium-ion batteries due to their high capacity, simple preparation, environmental friendliness, and low cost.

[0003] Layered transition metal oxide cathode materials can be generally divided into P2 and O3 phases according to their structures. Compared with P2 phase materials, O3 phase materials have higher initial sodium content and can achieve higher full battery energy density when matched with hard carbon negative electrodes, thus receiving extensive research and attention. However, O3 phase materials still have complex phase transitions, slow Na + Key scientific issues such as diffusion kinetics and intrinsic air instability will reduce the cycle stability and rate performance of sodium-ion batteries, thus seriously restricting their commercial application.

[0004] High entropy oxides (HEOs) are emerging materials composed of five or more metal elements. The synergistic effect of these elements in the lattice produces a high entropy effect, a slow diffusion effect, severe lattice distortion, and a synergistic effect (cocktail effect), which gives the material a unique structure and excellent performance. Among them, the development of high entropy layered oxides is expected to solve the problems existing in the above-mentioned O3 phase positive electrode materials. However, the research on high entropy layered oxide positive electrodes is still in its infancy, and it still faces many challenges in overcoming cycle stability, rate performance, material structure stability, and conductivity. Therefore, how to design high entropy layered oxide sodium ion battery positive electrode materials with excellent performance is of great significance to this field. Summary of the Invention

[0005] The present invention addresses the deficiencies of the above-mentioned prior art and provides a high-entropy O3-phase layered oxide material, preparation method, application, and battery. The high-entropy O3-phase layered oxide material prepared by the present invention effectively suppresses phase transitions and drastic lattice parameter changes, exhibits good structural stability and air stability, and is simple to prepare and amenable to large-scale production. Sodium-ion batteries using this material as the positive electrode active material exhibit high cycle stability, high rate performance, and fast charging characteristics.

[0006] The high entropy O3 phase layered oxide material Na prepared by the present invention 1-x-y Ca y Li a Ni b Cu c Fe d Co e Mn f M g O2 achieves excellent electrochemical performance and air / water stability by virtue of its high entropy effect and the interlayer pillar role of calcium ions. The designed structure can suppress the harmful phase transition and stress generated during the insertion / extraction of sodium ions. Among them, Ca ions can play a pillar role in the interlayer to stabilize the layered structure in the high sodium removal state and suppress the Na + / H + Ion exchange improves the air stability of the material (i.e., anti-deliquescence performance); Ni and Fe ions can provide charge compensation as redox centers, providing most of the capacity in the battery; Cu and Co ions can improve the electronic conductivity of the positive electrode material, improve the rate performance of the material and contribute to a part of the capacity; Li ions can inhibit Na + The Mn and Ti ions play a supporting role in the framework; and the Ti ions can inhibit the Jahn-Teller effect, stabilize the lattice oxygen, and improve the structural stability during the insertion / extraction of sodium ions.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] The present invention provides a high entropy O3 phase layered oxide material, the chemical formula of which is Na 1-x- y Ca y Li a Ni b Cu c Fe d Co e Mn f Ti g O2, belongs to the hexagonal system, the space group is R-3m; among them, 0 <x≤0.1,0<y≤0.05,a+b+c+d+e+f+g=1,0<a≤0.1,0.15≤b≤0.3,0<c≤0.1,0.08≤d≤0.25,0<e≤0.08,0.3≤f≤0.5,0<g≤0.1。

[0009] In the present invention, in the high entropy O3 phase layered oxide material, the stacking sequence of the transition metal layers is preferably ABCABC.

[0010] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.02≤x≤0.08, such as 0.05 or 0.06.

[0011] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.01≤y≤0.03, such as 0.01 or 0.02.

[0012] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.02≤a≤0.1, such as 0.03, 0.05, 0.06 or 0.07.

[0013] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.2≤b≤0.3, for example, 0.2, 0.22, 0.25 or 0.3.

[0014] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.02<c≤0.08, such as 0.03, 0.04, 0.05 or 0.06.

[0015] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.08≤d≤0.2, for example, 0.08, 0.1, 0.15 or 0.2.

[0016] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.01<e≤0.07, for example, 0.02, 0.03, 0.04, 0.05 or 0.06.

[0017] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.4≤f≤0.5, such as 0.44, 0.45 or 0.48.

[0018] In the present invention, in the chemical formula of the high entropy O3 phase layered oxide material, preferably, 0.01<g≤0.1, for example, 0.03, 0.04, 0.05 or 0.06.

[0019] In certain specific embodiments, the chemical formula of the high entropy O3 phase layered oxide material is Na 0.93 Ca 0.01 Li 0.06 Ni 0.25 Cu 0.05 Fe 0.1 Co 0.05 Mn 0.44 Ti 0.05 O2、Na 0.93 Ca 0.01 Li 0.07 Ni 0.2 Cu 0.03 Fe 0.2 Co 0.02 Mn 0.45 Ti 0.03 O2, or Na 0.93 Ca 0.01 Li 0.06 Ni 0.2 Cu 0.04 Fe 0.2 Co 0.02 Mn 0.45 Ti 0.03 O2.

[0020] The present invention also provides a method for preparing the high-entropy O3 phase layered oxide material, comprising the following steps:

[0021] A mixture containing a sodium source, a calcium source, a lithium source, a nickel source, a copper source, an iron source, a cobalt source, a manganese source and a titanium source is wet ball-milled, tableted and calcined to obtain the high-entropy O3 phase layered oxide material.

[0022] In the present invention, the amounts of the sodium source, calcium source, lithium source, nickel source, copper source, iron source, cobalt source, manganese source and titanium source are generally added in a stoichiometric ratio based on the chemical formula of the high-entropy O3 phase layered oxide material; preferably, the amounts of the sodium source and the lithium source are in excess of the theoretical addition amount by 1%-3% to compensate for volatilization during high-temperature calcination.

[0023] In the present invention, the sodium source may be conventional in the art, preferably one or more of sodium carbonate, sodium hydroxide and sodium bicarbonate. The calcium source may be conventional in the art, preferably calcium carbonate and / or calcium hydroxide. The lithium source may be a lithium salt conventionally used in the art, preferably lithium carbonate. The nickel source is preferably nickel carbonate and / or nickel oxide. The copper source is preferably copper oxide and / or copper hydroxide. The iron source is preferably ferric oxide and / or ferrous oxide. The cobalt source is preferably cobalt oxide and / or cobalt hydroxide. The manganese source is preferably one or more of manganese trioxide, manganese dioxide and manganese carbonate. The titanium source is preferably titanium dioxide.

[0024] In a specific embodiment, the sodium source is sodium carbonate, the calcium source is calcium carbonate, the lithium source is lithium carbonate, the nickel source is nickel oxide, the copper source is copper oxide, the iron source is ferric oxide, the cobalt source is cobalt tetroxide, the manganese source is manganese trioxide, and the titanium source is titanium dioxide.

[0025] In the present invention, the preparation method of the mixture containing sodium source, calcium source, lithium source, nickel source, copper source, iron source, cobalt source, manganese source and titanium source generally includes the following steps: mixing the metal sources in a mortar until uniform.

[0026] In the present invention, the equipment used in the wet ball milling process can be conventional in the art, such as an agate jar. The liquid medium of the wet ball milling is generally anhydrous ethanol or acetone. The mass ratio of the volume of the liquid medium of the wet ball milling to the abrasive can be conventional in the art, generally (0.5-1.0) mL / mg, preferably (0.7-0.8) mL / mg. During the wet ball milling process, the diameter of the grinding balls used can be 1-5 mm, such as 3 mm; the rotation speed of the ball mill can be 150-500 r / min, preferably 300-400 r / min, such as 350 r / min; the time of the ball milling can be 4-8 h, such as 6 h; the ball-to-material ratio can be (5-15):1, such as 10:1, and the ball-to-material ratio refers to the mass ratio of the grinding balls and each metal source material.

[0027] In the present invention, according to conventional practices in the art, the wet ball milling generally requires drying, wherein the drying temperature may be 80-120°C, for example, 100°C, and the drying time may be 0.5-2 hours, for example, 1 hour.

[0028] In the present invention, according to conventional practice in the art, the tableting is generally performed in a powder tablet press. The tableting pressure can be 10-20 MPa, for example 15 MPa. The size of the tablet after tableting can be conventional in the art, for example, pressed into a disc with a diameter of 13 mm.

[0029] In the present invention, the calcination is generally performed in a muffle furnace. The calcination is generally performed in air. The rate of heating to the calcination temperature may be 3-5°C / min. The calcination temperature may be 700-1100°C, preferably 800-1000°C, for example, 850°C, 900°C, or 950°C. The calcination time may be 10-30 hours, preferably 15-25 hours, for example, 18 hours, 20 hours, or 22 hours.

[0030] The present invention also provides an application of the high-entropy O3 phase layered oxide material as a positive electrode active material in a sodium ion battery.

[0031] The present invention also provides a sodium ion battery, which includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator, wherein the positive electrode plate includes a current collector and the high-entropy O3 phase layered oxide material as described above.

[0032] In the present invention, according to the conventional art, the current collector is generally aluminum foil.

[0033] In the present invention, the method for preparing the positive electrode plate preferably includes the following steps: uniformly coating a slurry containing the high-entropy O3 phase layered oxide material, conductive carbon black and polyvinylidene fluoride on the surface of the current collector and drying it.

[0034] Among them, the weight ratio of the high entropy O3 phase layered oxide material, the conductive carbon black and the polyvinylidene fluoride can be conventional in the art, preferably (70-90): (5:15): (5-15), for example 80:10:10.

[0035] The solvent in the slurry can be conventional in the art, such as N-methylpyrrolidone. The concentration of the polyvinylidene fluoride N-methylpyrrolidone solution can be conventional in the art, generally 20-40 mg / mL, preferably 30 mg / mL.

[0036] The drying temperature may be 80-150° C., such as 100° C., 110° C. or 120° C. The drying time may be 6-24 h, such as 8 h, 10 h, 12 h or 18 h.

[0037] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0038] The reagents and raw materials used in the present invention are commercially available.

[0039] The positive progress effect of the present invention is:

[0040] (1) The configurational entropy of the high-entropy O3 phase layered oxide material prepared by the present invention is 1.56R, which is a high-entropy positive electrode material (configurational entropy is greater than 1.5R). According to the Gibbs free energy formula, the increase in configurational entropy reduces the Gibbs free energy, thereby improving the structural stability; the random arrangement of atoms and their synergistic effect can better exert the performance advantages of high-entropy materials.

[0041] (2) The preparation method of the high-entropy O3 phase layered oxide material of the present invention is simple and easy to produce on a large scale; it has good structural stability and air stability.

[0042] (3) The sodium ion battery assembled from the prepared high-entropy O3 phase layered oxide material has the characteristics of high cycle stability, high rate performance and fast charging. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The XRD pattern, refinement results and SEM image of the high entropy O3 phase layered oxide material prepared in Example 1;

[0044] Figure 2 The XRD pattern, refinement results and SEM image of the high entropy O3 phase layered oxide material prepared in Example 2;

[0045] Figure 3 The XRD pattern, refinement results and SEM image of the high entropy O3 phase layered oxide material prepared in Example 3;

[0046] Figure 4 This is a first cycle charge-discharge curve of the high-entropy O3 phase layered oxide material prepared in Example 1;

[0047] Figure 5 This is a first cycle charge-discharge curve of the high-entropy O3 phase layered oxide material prepared in Example 2;

[0048] Figure 6 This is a first cycle charge-discharge curve of the high-entropy O3 phase layered oxide material prepared in Example 3;

[0049] Figure 7 This is a rate performance diagram of the high entropy O3 phase layered oxide material prepared in Example 1;

[0050] Figure 8 This is a rate performance diagram of the high entropy O3 phase layered oxide material prepared in Example 2;

[0051] Figure 9 This is a rate performance diagram of the high entropy O3 phase layered oxide material prepared in Example 3;

[0052] Figure 10The cycling performance diagram of the high entropy O3 phase layered oxide material prepared in Example 1 at 2C and 10C;

[0053] Figure 11 The cycling performance diagram of the high entropy O3 phase layered oxide material prepared in Example 2 at 2C and 10C;

[0054] Figure 12 This is a cycling performance diagram of the high entropy O3 phase layered oxide material prepared in Example 3 at 2C and 10C.

[0055] Figure 13 This is the XRD pattern of the high entropy O3 phase layered oxide material prepared in Example 1 after exposure to air and immersion in water. DETAILED DESCRIPTION

[0056] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0057] The purity of the sodium carbonate, calcium carbonate, lithium carbonate, nickel oxide, copper oxide, ferric oxide, cobalt oxide, manganese oxide and titanium dioxide used in the following examples and comparative examples is not less than 99.5%.

[0058] Example 1

[0059] Prepare 40 mmol of Na 0.93 Ca 0.01 Li 0.06 Ni 0.25 Cu 0.05 Fe 0.1 Co 0.05 Mn 0.44 Ti 0.05 O2(LNCFCMT) high entropy O3 phase layered oxide material, the preparation process is as follows:

[0060] 19.16mmol sodium carbonate, 0.4mmol calcium carbonate, 1.23mmol lithium carbonate, 10mmol nickel oxide, 2mmol copper oxide, 2mmol iron oxide, 0.67mmol cobalt oxide, 8.8mmol manganese oxide and 2mmol titanium dioxide were weighed and mixed in a mortar. The mixed powder was added to an agate jar, 3mL of ethanol was added as a wet grinding medium, and zirconium dioxide grinding balls with a diameter of 3mm were used. The ball-to-material mass ratio (i.e., the mass ratio of grinding balls to powder) was 10:1. The ball milling was carried out at a speed of 350rmp for 6h. The ball-milled powder was dried at 100℃ for 1h to obtain a dry precursor powder. The powder was pressed into a 13mm diameter disc at a pressure of 15Mpa using a powder tablet press, and then calcined in a high-temperature muffle furnace at 3℃min -1 The temperature was raised to 900°C at a heating rate of 1000 ℃ and calcined for 20 hours; after naturally cooling to room temperature, the obtained powder was transferred to a glove box filled with argon (H2O, O2<0.1ppm) for storage.

[0061] Example 2

[0062] Prepare 40 mmol of Na 0.93 Ca 0.01 Li 0.07 Ni 0.2 Cu 0.03 Fe 0.2 Co 0.02 Mn 0.45 Ti 0.03 O2(LNCFCMT-2) high entropy O3 phase layered oxide material:

[0063] Weigh 19.16mmol sodium carbonate, 0.4mmol calcium carbonate, 1.44mmol lithium carbonate, 8mmol nickel oxide, 1.2mmol copper oxide, 4mmol ferric oxide, 0.27mmol cobalt oxide, 9mmol manganese oxide and 1.2mmol titanium dioxide and mix them evenly. Add the mixed powder into an agate jar, add 3mL of ethanol as a wet grinding medium, use zirconium dioxide grinding balls with a diameter of 3mm, and the ball-to-material mass ratio is 10:1. Ball milling is carried out at a speed of 350rmp for 6h. The ball-milled powder is dried at 100℃ for 1h to obtain a dry precursor powder; the powder is pressed into a disc with a diameter of 13mm using a press at a pressure of 15Mpa, and then calcined in a high-temperature muffle furnace at 3℃min -1 The temperature was raised to 900°C at a heating rate of 1000 ℃ and calcined for 20 hours; after naturally cooling to room temperature, the obtained powder was transferred to a glove box filled with argon (H2O, O2<0.1ppm) for storage.

[0064] Example 3

[0065] Prepare 40 mmol of Na 0.93 Ca 0.01 Li 0.06 Ni 0.2 Cu 0.04 Fe 0.2 Co 0.02 Mn 0.45 Ti 0.03 O2 (LNCFCMT-3) high entropy O3 phase layered oxide material, the preparation process is as follows:

[0066] Weigh 19.16mmol sodium carbonate, 0.4mmol calcium carbonate, 1.23mmol lithium carbonate, 8mmol nickel oxide, 1.6mmol copper oxide, 4mmol ferric oxide, 0.27mmol cobalt oxide, 9mmol manganese oxide and 1.2mmol titanium dioxide and mix them evenly. Add the mixed powder into an agate jar, add 3mL of ethanol as a wet grinding medium, use zirconium dioxide grinding balls with a diameter of 3mm, and the ball-to-material mass ratio is 10:1. Ball milling is carried out at a speed of 350rmp for 6h. The ball-milled powder is dried at 100℃ for 1h to obtain a dry precursor powder; the powder is pressed into a 13mm diameter disc at a pressure of 15Mpa using a press, and then calcined in a high-temperature muffle furnace at 3℃min -1 The temperature was raised to 900°C at a heating rate of 1000 ℃ and calcined for 20 hours; after naturally cooling to room temperature, the obtained powder was transferred to a glove box filled with argon (H2O, O2<0.1ppm) for storage.

[0067] Comparative Example 1

[0068] Preparation of 40 mmol of NaNi 0.36 Fe 0.1 Mn 0.54 O2(NFM) material, its preparation process is as follows:

[0069] Weigh 20.6mmol of sodium carbonate, 14.4mmol of nickel oxide, 2mmol of ferric oxide, and 10.8mmol of manganese oxide and mix them evenly. Add the mixed powder into an agate jar, add 3mL of ethanol as a wet grinding medium, use 3mm diameter zirconium dioxide grinding balls, and the ball-to-material ratio of the ball milling is 10:1. Ball milling is carried out at a speed of 350rmp for 6h. The obtained powder is dried at 100℃ for 1h to obtain a mixed precursor powder; the powder is pressed into a 13mm diameter disc with a press at a pressure of 15Mpa, and then calcined in a high-temperature muffle furnace at 3℃min -1 The temperature was raised to 900°C at a heating rate of 1000 °C and calcined for 20 h. After cooling to room temperature in the furnace, the obtained powder was transferred to a glove box filled with argon (H2O, O2 <0.1 ppm) for storage.

[0070] Comparative Example 2

[0071] Prepare 40 mmol of Na 0.95 Ni 0.31 Cu 0.05 Fe 0.1 Co 0.05 Mn 0.44 Ti 0.05 O2(NCFCMT) material, its preparation process is as follows:

[0072] Weigh 19.57mmol sodium carbonate, 12.4mmol nickel oxide, 2mmol copper oxide, 2mmol iron oxide, 0.67mmol cobalt oxide, 8.8mmol manganese oxide and 2mmol titanium dioxide and mix them evenly. Add the mixed powder into an agate jar, add 3mL of ethanol as a wet grinding medium, use zirconium dioxide grinding balls with a diameter of 3mm, and a ball-to-material ratio of 10:1. Ball milling is carried out at a speed of 350rmp for 6h. The obtained powder is dried at 100℃ for 1h to obtain a mixed precursor powder; the powder is pressed into a disc with a diameter of 13mm using a press at a pressure of 15Mpa, and then calcined in a high-temperature muffle furnace at 3℃min -1 The temperature was raised to 900°C at a heating rate of 1000 °C and calcined for 20 h. After cooling to room temperature in the furnace, the obtained powder was transferred to a glove box filled with argon (H2O, O2 <0.1 ppm) for storage.

[0073] Comparative Example 3

[0074] Prepare 40 mmol of Na 0.95 Li 0.06 Ni 0.30 Fe 0.1 Co 0.05 Mn 0.44 Ti 0.05 O2(LNFCMT) material, its preparation process is as follows:

[0075] Weigh 19.57mmol sodium carbonate, 1.23mmol lithium carbonate, 12mmol nickel oxide, 2mmol ferric oxide, 0.67mmol cobalt oxide, 8.8mmol manganese oxide and 2mmol titanium dioxide and mix them evenly. Add the mixed powder into an agate jar, add 3mL of ethanol as a wet grinding medium, use zirconium dioxide grinding balls with a diameter of 3mm, and a ball-to-material ratio of 10:1. Ball milling is carried out at a speed of 350rmp for 6h. The obtained powder is dried at 100℃ for 1h to obtain a mixed precursor powder; the powder is pressed into a disc with a diameter of 13mm using a press at a pressure of 15Mpa, and then calcined in a high-temperature muffle furnace at 3℃min -1The temperature was raised to 900°C at a heating rate of 1000 °C and calcined for 20 h. After cooling to room temperature in the furnace, the obtained powder was transferred to a glove box filled with argon (H2O, O2 <0.1 ppm) for storage.

[0076] Comparative Example 4

[0077] Prepare 40 mmol of Na 0.95 Li 0.06 Ni 0.25 Cu 0.05 Fe 0.1 Co 0.05 Mn 0.49 O2 (LNCFCM) material, its preparation process is as follows:

[0078] Weigh 19.57mmol sodium carbonate, 1.23mmol lithium carbonate, 10mmol nickel oxide, 2mmol ferric oxide, 0.67mmol cobalt oxide and 9.8mmol manganese oxide and mix them evenly. Add the mixed powder into an agate jar, add 3mL of ethanol as a wet grinding medium, use zirconium dioxide grinding balls with a diameter of 3mm, and a ball-to-material ratio of 10:1. Ball milling is carried out at a speed of 350rmp for 6h. The obtained powder is dried at 100℃ for 1h to obtain a mixed precursor powder; the powder is pressed into a disc with a diameter of 13mm using a press at a pressure of 15Mpa, and then calcined in a high-temperature muffle furnace at 3℃min -1 The temperature was raised to 900°C at a heating rate of 1000 °C and calcined for 20 h. After cooling to room temperature in the furnace, the obtained powder was transferred to a glove box filled with argon (H2O, O2 <0.1 ppm) for storage.

[0079] Effect embodiment

[0080] (1)ICP test

[0081] After the product was dissolved in nitric acid, ICP-OES test was performed to obtain the elemental composition, thereby calculating the specific molecular composition of the layered oxide materials prepared in Examples 1-3 and Comparative Examples 1-5.

[0082] (2) XRD and SEM characterization

[0083] The high entropy O3 phase layered oxide materials prepared in Examples 1-3 were subjected to XRD test and SEM characterization, and the test results are as follows: Figure 1-Figure 3 As shown in Figure 2, XRD results show that the prepared high-entropy O3-phase layered oxide material exhibits a highly crystalline O3-phase α-NaFeO2 structure belonging to the R-3m space group. SEM images show that the microstructure of the prepared high-entropy O3-phase layered oxide material exhibits polyhedral / horseshoe-shaped particles with a particle size of 2 to 8 μm.

[0084] (3) Deliquescence resistance test

[0085] The high entropy O3 layered oxide materials prepared in Examples 1-3 were immersed in water for half an hour, filtered, and dried at 100°C for 2 hours, and then subjected to XRD testing. The test results are shown in FIG. Figure 13 The test results show that the XRD pattern has not changed and the original O3 phase structure is still maintained, indicating that it has excellent air / water stability.

[0086] (4) Battery performance test:

[0087] a. Preparation of positive electrode sheet:

[0088] The materials prepared in Examples 1-3 and Comparative Examples 1-4, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were dissolved in N-methylpyrrolidone (NMP) at a weight ratio of 80:10:10, mixed to form a slurry, and evenly coated on aluminum foil to prepare an electrode. The slurry was then vacuum-dried at 110°C for 10 hours and cut into 12 mm diameter discs. The active material loading was 3 mg cm -2 .

[0089] b. Assembling sodium ion batteries:

[0090] The positive electrode prepared in step a was assembled with a metal sodium negative electrode into a sodium ion battery. The diameter of the metal sodium negative electrode was 15.6 mm and the thickness was 0.5 mm. The electrolyte composition was 1 M NaClO4 dissolved in PC, the additive was 5 vol% fluoroethylene carbonate (FEC), and the separator was porous glass fiber (GF / D). CR2016 button cells were assembled in a glove box filled with argon (H2O, O2 <0.1 ppm).

[0091] c. Electrochemical performance test:

[0092] The prepared sodium ion battery was subjected to constant current charge and discharge tests in the voltage range of 2-4.2V. The electrochemical test was performed using the LAND-CT2001C battery test system of Wuhan Landian Company, with 1C = 200mAg -1 , test results see Figure 4-Figure 12 and Tables 1-2.

[0093] Table 1

[0094]

[0095]

[0096] Among them, the high entropy O3 layered oxide materials prepared in Examples 1-3 can still recover to 144.9 mAh g at a rate of 0.2C after rate testing. -1 、143.8mAh g -1 、144.4mAh g -1 reversible specific capacity.

[0097] Table 2

[0098]

[0099] It can be seen from the above test data that the high-entropy O3 phase layered oxide material prepared by the present invention has excellent cycle stability and rate performance. The capacity retention rates of Examples 1-3 are all higher than 74% after 500 cycles at a rate of 2C, and the capacity retention rates of Examples 1-3 are all higher than 80% after 1200 cycles at a rate of 10C.

[0100] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A high entropy O3 phase layered oxide material, characterized in that: Its chemical formula is Na 1-x- y Ca y Li a Ni b Cu c Fe d Co e Mn f Ti g O2, belongs to the hexagonal system, the space group is R-3m; among them, 0 <x≤0.1,0<y≤0.05,a+b+c+d+e+f+g=1,0<a≤0.1,0.15≤b≤0.3,0<c≤0.1,0.08≤d≤0.25,0<e≤0.08,0.3≤f≤0.5,0<g≤0.1。 2. The high entropy O3 phase layered oxide material according to claim 1, wherein: The high entropy O3 phase layered oxide material satisfies one or more of the following conditions: (1) In the high entropy O3 phase layered oxide material, the stacking order of the transition metal layers is ABCABC; (2) In the chemical formula of the high entropy O3 phase layered oxide material, 0.02≤a≤0.1, such as 0.03, 0.05, 0.06 or 0.07; (3) In the chemical formula of the high entropy O3 phase layered oxide material, 0.2≤b≤0.3, such as 0.2, 0.22, 0.25 or 0.3; (4) In the chemical formula of the high entropy O3 phase layered oxide material, 0.02<c≤0.08, such as 0.03, 0.04, 0.05 or 0.06; (5) In the chemical formula of the high entropy O3 phase layered oxide material, 0.08≤d≤0.2, such as 0.08, 0.1, 0.15 or 0.2; (6) In the chemical formula of the high entropy O3 phase layered oxide material, 0.01 < e ≤ 0.07, such as 0.02, 0.03, 0.04, 0.05 or 0.06; (7) In the chemical formula of the high entropy O3 phase layered oxide material, 0.4≤f≤0.5, such as 0.44, 0.45 or 0.48; (8) In the chemical formula of the high entropy O3 phase layered oxide material, 0.01 < g ≤ 0.08, such as 0.03, 0.04, 0.05 or 0.06; (9) In the chemical formula of the high entropy O3 phase layered oxide material, 0.02≤x≤0.08, such as 0.05 or 0.06; (10) In the chemical formula of the high entropy O3 phase layered oxide material, 0.01≤y≤0.03, for example, 0.01 or 0.

02.

3. The high entropy O3 phase layered oxide material according to claim 1, wherein: The chemical formula of the high entropy O3 phase layered oxide material is Na 0.93 Ca 0.01 Li 0.06 Ni 0.25 Cu 0.05 Fe 0.1 Co 0.05 Mn 0.44 Ti 0.05 O2、Na 0.93 Ca 0.01 Li 0.07 Ni 0.2 Cu 0.03 Fe 0.2 Co 0.02 Mn 0.45 Ti 0.03 O2, or Na 0.93 Ca 0.01 Li 0.06 Ni 0.2 Cu 0.04 Fe 0.2 Co 0.02 Mn 0.45 Ti 0.03 O2.

4. A method for preparing a high entropy O3 phase layered oxide material as claimed in any one of claims 1 to 3, characterized in that: The steps include: A mixture containing a sodium source, a calcium source, a lithium source, a nickel source, a copper source, an iron source, a cobalt source, a manganese source and a titanium source is wet ball-milled, tableted and calcined to obtain the high-entropy O3 phase layered oxide material.

5. The method for preparing a high entropy O3 phase layered oxide material according to claim 4, wherein: The amounts of the sodium source, calcium source, lithium source, nickel source, copper source, iron source, cobalt source, manganese source and titanium source are added in a stoichiometric ratio according to the chemical formula of the high entropy O3 phase layered oxide material; Preferably, the amount of the sodium source and the lithium source used is 1% to 3% in excess of the theoretical addition amount.

6. The method for preparing a high entropy O3 phase layered oxide material according to claim 4, wherein: Each raw material in the mixture satisfies one or more of the following conditions: (1) The sodium source is one or more of sodium carbonate, sodium hydroxide and sodium bicarbonate; (2) The calcium source is calcium carbonate and / or calcium hydroxide; (3) The lithium source is lithium carbonate; (4) The nickel source is nickel carbonate and / or nickel oxide; (5) The copper source is copper oxide and / or copper hydroxide; (6) The iron source is ferrous oxide and / or ferrosoferric oxide; (7) The cobalt source is cobalt tetroxide and / or cobalt hydroxide; (8) The manganese source is one or more of manganese trioxide, manganese dioxide and manganese carbonate; (9) The titanium source is titanium dioxide.

7. The method for preparing a high entropy O3 phase layered oxide material according to claim 4, wherein: The wet ball milling satisfies one or more of the following conditions: (1) The diameter of the grinding balls used in the wet ball milling is 1-5 mm; (2) The ball-to-material ratio of the wet ball milling is (5-15):1, for example, 10:1; (3) The rotation speed of the wet ball mill is 150-500 r / min, preferably 300-400 r / min, for example 350 r / min; (4) The wet ball milling time is 4-8 hours, for example 6 hours.

8. The method for preparing a high entropy O3 phase layered oxide material according to claim 4, wherein: The calcination temperature is 700-1100°C, preferably 800-1000°C, such as 850°C, 900°C or 950°C; And / or, the calcination time is 10-30 hours, preferably 15-25 hours, such as 18 hours, 20 hours or 22 hours.

9. Use of the high-entropy O3 phase layered oxide material as claimed in any one of claims 1 to 3 as a positive electrode active material in a sodium ion battery.

10. A sodium ion battery, characterized in that: It comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. The positive electrode sheet comprises a current collector and a high-entropy O3 phase layered oxide material as described in any one of claims 1 to 3.

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