Positive electrode material uniformly coated with high-entropy oxide and preparation method of positive electrode material

Abstract

The invention belongs to the field of electrochemical energy conversion and energy storage materials, and particularly relates to a high-entropy oxide uniformly-coated positive electrode material and a preparation method thereof.A layered metal oxide positive electrode material and a high-entropy oxide with the high lattice matching degree serve as a coating layer, and organic matter serves as a dispersing agent and a binding agent; and sintering at high temperature in the air to obtain the layered metal oxide positive electrode material uniformly coated with the high-entropy oxide. According to the method, the layered structure of the failed layered metal oxide positive electrode is repaired, the electrochemical performance of the failed layered metal oxide positive electrode is recovered, the ion transmission and structural stability of the electrode material under high voltage are improved by uniformly coating the high-entropy oxide, the problem of decommissioned battery treatment is solved to a great extent, and the method has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical energy conversion and energy storage materials, and specifically relates to a positive electrode material uniformly coated with a high entropy oxide and a preparation method thereof. Background Art

[0002] With the development of society and the continuous increase in demand for new energy, the output of lithium-ion batteries has continued to increase, and the treatment of waste lithium-ion batteries has become an inevitable problem. At present, layered metal oxide cathodes have become one of the most widely used cathode materials in lithium-ion batteries, especially accounting for more than 60% of the electric vehicle power battery market. In order to cope with the future wave of electric vehicle retirement, it is crucial to develop efficient layered metal oxide electrode recycling technology. Compared with the traditional pyrometallurgical and hydrometallurgical recycling based on structural destruction and element extraction, the emerging direct recycling method can be directly reused in new lithium-ion batteries after component supplementation and structural repair. It has a short process, low pollution, high recycling efficiency, and can greatly increase the profit margin. However, the direct recycling method still has the problem of only repairing but not improving the cathode material, which is difficult to meet the industry's growing demand for lithium-ion battery performance. In particular, during the continuous charging and discharging process, the bulk of the layered metal oxide electrode material will undergo cation mixing and irreversible phase change, and microcracks and interface side reactions will occur on the surface. Therefore, seeking an efficient lithium-ion battery cathode material recycling and modification method is an urgent problem to be solved. Summary of the invention

[0003] The present invention mainly provides a layered metal oxide electrode material coated with a high entropy oxide having a lattice matching and a preparation method thereof, so as to solve the problem that the existing layered metal oxide electrode material is easy to fail and difficult to be recycled after failure. The specific scheme is as follows:

[0004] A positive electrode material uniformly coated with a high entropy oxide is obtained by mixing raw materials including a metal compound corresponding to the high entropy oxide, an electrode material and a lithium-containing compound, respectively, until the solvent is evaporated to dryness, and then calcining to obtain the positive electrode material uniformly coated with the high entropy oxide; the electrode material is a layered metal oxide electrode material.

[0005] Furthermore, the mass ratio of the metal compound to the layered metal oxide electrode material is 0.03-1.03:100; the amount ratio of the layered metal oxide electrode material to the lithium-containing compound is 100:5-85.

[0006] Furthermore, the electrode material is a layered metal oxide electrode material with a failure rate of 0 to 80%; the layered metal oxide electrode material includes one of ternary lithium nickel cobalt manganese oxide, ternary lithium nickel cobalt aluminum oxide, lithium cobalt oxide, and lithium manganese oxide.

[0007] Furthermore, the metal compound corresponding to the high entropy oxide includes one or more of a lithium-containing compound, a lanthanum-containing compound, a nickel-containing compound, a cobalt-containing compound, a manganese-containing compound, a chromium-containing compound, an aluminum-containing compound or an iron-containing compound.

[0008] Further, the lithium-containing compound includes one or more of lithium nitrate, lithium hydroxide, lithium chloride, lithium citrate or lithium acetate; the lanthanum-containing compound includes one or more of lanthanum acetate, lanthanum nitrate, lanthanum chloride, lanthanum oxide or lanthanum citrate; the nickel-containing compound includes one or more of nickel nitrate, nickel hydroxide, nickel chloride, nickel citrate or nickel acetate; the cobalt-containing compound includes one or more of cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt citrate or cobalt acetate; the manganese-containing compound includes one or more of manganese nitrate, manganese chloride or manganese acetate; the chromium-containing compound includes one or more of chromium nitrate, chromium sulfate, cobalt citrate or chromium acetate; the aluminum-containing compound includes one or more of aluminum nitrate, aluminum acetate or aluminum chloride; the iron-containing compound includes one or more of ferric nitrate, ferric acetate, ferric sulfate or ferric chloride.

[0009] Furthermore, the raw materials also include auxiliary agents; the auxiliary agents include one or more of polyvinyl pyrrolidone, dopamine, glucose, sucrose, guar gum, polyacrylic acid or polyacrylonitrile; the mass ratio of the auxiliary agent to the layered metal oxide electrode material is 1:3-10.

[0010] Furthermore, the lithium-containing compound includes one or more of lithium nitrate, lithium acetate, lithium hydroxide, lithium chloride, lithium citrate or lithium acetate.

[0011] A method for preparing the above-mentioned positive electrode material uniformly coated with high entropy oxide comprises the following steps:

[0012] (1) adding a metal compound corresponding to the high entropy oxide to ethanol and / or aqueous solution and uniformly mixing;

[0013] (2) adding an auxiliary agent to the system and mixing uniformly to obtain a mixed solution;

[0014] (3) adding the electrode material and the lithium-containing compound to the mixed solution while stirring, and mixing them evenly to obtain a precursor solution;

[0015] (4) heating the precursor solution while stirring until it is evaporated to dryness to obtain a precursor;

[0016] (5) The obtained precursor is calcined in a combustion-supporting atmosphere to obtain an electrode material uniformly coated with a high entropy oxide.

[0017] Furthermore, the temperature of heating and evaporating to dryness in step (4) is 80-100°C.

[0018] Furthermore, the calcination temperature in step (5) is 700-800° C., the heating rate is 3-8° C. / min, and the holding time is 4-14 h.

[0019] By adopting the above scheme, the method of the present invention has the following advantages:

[0020] 1. The present invention can effectively prevent the deterioration of performance fundamentally by strengthening the surface structure of the layered metal oxide positive electrode through surface coating. The coating can reduce the contact between the positive electrode and the electrolyte, thereby reducing the occurrence of interface side reactions. High entropy oxides have the advantages of good ionic conductivity and entropy stability, which can effectively improve the electrochemical performance of the material.

[0021] 2. The lattice matching degree between the coating material of the present invention and the layered metal oxide positive electrode and the uniformity of the coating have a great influence on the performance of the positive electrode material. The lattice of the high entropy oxide of the present invention matches the lattice of the layered metal oxide material, which will promote the diffusion of lithium ions at the interface.

[0022] 3. The auxiliary agent of the present invention acts as a dispersant and a binder, which can make the high entropy oxide evenly coated on the surface of the layered metal oxide material. Moreover, after high-temperature calcination in air or oxygen atmosphere, the organic matter serving as the dispersant and the binder will all volatilize, which will not affect the coating effect of the high entropy oxide.

[0023] 4. The high-temperature sintering in air of the present invention can not only generate a high-entropy phase and restore a layered structure, but also remove organic matter to avoid affecting the high-entropy coating.

[0024] 5. The present invention can not only restore the performance of failed layered metal oxide materials and solve the problem of handling retired batteries to a large extent, but also further improve the stability of failed layered metal oxides under high voltage.

[0025] 6. The present invention can not only improve the ion transport and structural stability of failed layered metal oxides under high voltage, but also has a significant performance improvement on commercial non-failed layered metal oxides, indicating that this method has great versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the NCM523 positive electrode material uniformly coated with high entropy oxide prepared in Example 1.

[0027] Figure 2 This is a TEM image of the NCM523 positive electrode material uniformly coated with high entropy oxide prepared in Example 1.

[0028] Figure 3 This is a rate performance diagram of the NCM523 positive electrode material uniformly coated with high entropy oxide prepared in Example 1.

[0029] Figure 4 This is a cycle performance diagram of the NCM523 positive electrode material uniformly coated with high entropy oxide prepared in Example 1. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Embodiment 1:

[0032] (1) Weigh 2.062 mg of LiNO3, 48.872 mg of La(NO3)3·6H2O, 1.404 mg of NiC4H6O4·4H2O, 1.644 mg of Co(NO3)2·6H2O, 1.616 mg of Mn(NO3)2·6H2O, 2.116 mg of Al(NO3)3·9H2O and 2.280 mg of Fe(NO3)3·9H2O and dissolve them in 60 mL of ethanol. Stir thoroughly until completely dissolved to obtain a mixed solution A.

[0033] (2) Weigh 1.6 g of polyvinyl pyrrolidone (PVP) and add it to mixed solution A. Stir thoroughly for 3 h to obtain mixed solution B.

[0034] (3) Weigh 4.75 g of 30%-depleted NCM523 and 1.25 g of LiNO3 and add them to solution B. Stir thoroughly for 3 h to obtain a precursor solution.

[0035] (4) Solution C was heated and stirred at 80° C. until the alcohol was evaporated, and then placed in a vacuum drying oven for 12 h to obtain a NCM523 precursor uniformly coated with high entropy oxide.

[0036] (5) The precursor was placed in a box furnace, sintered at 700°C for 4 h, and then heated to 800°C and sintered for 10 h to obtain a NCM523 positive electrode material uniformly coated with high entropy oxide.

[0037] Figure 1 The SEM image of the cathode material shows the synthesized oxide particles. Figure 2 From the TEM image, we can see that a uniform high entropy oxide coating layer appears on the surface of the positive electrode material, with a thickness of 9nm, which is closely connected to the positive electrode material. Figure 3 and Figure 4It can be seen that after 200 cycles, the positive electrode material of the present invention still has a specific capacity of 88.6% compared with the first cycle, and has excellent cycle performance and good stability.

[0038] Embodiment 2:

[0039] (1) Weigh 2.062 mg of LiNO3, 48.872 mg of La(NO3)3·6H2O, 1.404 mg of NiC4H6O4·4H2O, 1.644 mg of Co(NO3)2·6H2O, 1.616 mg of Mn(NO3)2·6H2O, 2.116 mg of Al(NO3)3·9H2O and 2.280 mg of Fe(NO3)3·9H2O and dissolve them in 60 mL of ethanol. Stir thoroughly until completely dissolved to obtain a mixed solution A.

[0040] (2) Weigh 1.6 g of polyvinyl pyrrolidone (PVP) and add it to mixed solution A. Stir thoroughly for 3 h to obtain mixed solution B.

[0041] (3) Weigh 5.75 g of commercial NCM523 and 0.25 g of LiNO3 and add them to solution B. Stir thoroughly for 3 h to obtain a precursor solution.

[0042] (4) Solution C was heated and stirred at 80° C. until the alcohol was evaporated, and then placed in a vacuum drying oven for 12 h to obtain a NCM523 precursor uniformly coated with high entropy oxide.

[0043] (5) The precursor was placed in a box furnace, sintered at 700°C for 4 h, and then heated to 800°C and sintered for 10 h to obtain a NCM523 positive electrode material uniformly coated with high entropy oxide.

[0044] Embodiment 3:

[0045] (1) Weigh 2.062 mg of LiNO3, 48.872 mg of La(NO3)3·6H2O, 1.404 mg of NiC4H6O4·4H2O, 1.644 mg of Co(NO3)2·6H2O, 1.616 mg of Mn(NO3)2·6H2O, 2.116 mg of Al(NO3)3·9H2O and 2.280 mg of Fe(NO3)3·9H2O and dissolve them in 60 mL of ethanol. Stir thoroughly until completely dissolved to obtain a mixed solution A.

[0046] (2) Weigh 1.6 g of polyvinyl pyrrolidone (PVP) and add it to mixed solution A. Stir thoroughly for 3 h to obtain mixed solution B.

[0047] (3) Weigh 4.76 g of 30%-depleted NCM811 and 0.24 g of LiNO3 and add them to solution B. Stir thoroughly for 3 h to obtain a precursor solution.

[0048] (4) The precursor solution is heated and stirred at 80° C. until the alcohol is evaporated, and then placed in a vacuum drying oven for 12 h to obtain a NCM523 precursor uniformly coated with high entropy oxide.

[0049] (5) The precursor was placed in a box furnace, sintered at 700°C for 4 h, and then heated to 800°C and sintered for 10 h to obtain a NCM523 positive electrode material uniformly coated with high entropy oxide.

[0050] Embodiment 4:

[0051] (1) Weigh 2.062 mg of LiNO3, 48.872 mg of La(NO3)3·6H2O, 1.404 mg of NiC4H6O4·4H2O, 1.644 mg of Co(NO3)2·6H2O, 1.616 mg of Mn(NO3)2·6H2O, 2.116 mg of Al(NO3)3·9H2O and 2.280 mg of Fe(NO3)3·9H2O and dissolve them in 60 mL of ethanol. Stir thoroughly until completely dissolved to obtain a mixed solution A.

[0052] (2) Weigh 1.6 g of polyvinyl pyrrolidone (PVP) and add it to mixed solution A. Stir thoroughly for 3 h to obtain mixed solution B.

[0053] (3) Weigh 5.76 g of commercial NCM811 and 0.24 g of LiNO3 and add them to solution B. Stir thoroughly for 3 h to obtain a precursor solution.

[0054] (4) The precursor solution is heated and stirred at 80° C. until the alcohol is evaporated, and then placed in a vacuum drying oven for 12 h to obtain a NCM523 precursor uniformly coated with high entropy oxide.

[0055] (5) The precursor was placed in a box furnace, sintered at 700°C for 4 h, and then heated to 800°C and sintered for 10 h to obtain a NCM523 positive electrode material uniformly coated with high entropy oxide.

[0056] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A positive electrode material uniformly coated with a high entropy oxide, characterized in that: Raw materials including metal compounds corresponding to high entropy oxides, electrode materials and lithium-containing compounds are mixed until the solvent is evaporated to dryness, and then calcined to obtain a positive electrode material uniformly coated with high entropy oxides; the electrode material is a layered metal oxide electrode material.

2. The positive electrode material uniformly coated with high entropy oxide according to claim 1, characterized in that: The mass ratio of the metal compound to the electrode material is 0.03-1.03:100; the amount ratio of the electrode material to the lithium-containing compound is 100:5-85.

3. The positive electrode material uniformly coated with high entropy oxide according to claim 1, characterized in that: The electrode material is a layered metal oxide electrode material with a failure rate of 0 to 80%; the layered metal oxide electrode material includes one of ternary nickel cobalt lithium manganese oxide, ternary nickel cobalt aluminum lithium oxide, lithium cobalt oxide, and lithium manganese oxide.

4. The positive electrode material uniformly coated with high entropy oxide according to claim 1, characterized in that: The metal compound corresponding to the high entropy oxide includes one or more of a lithium-containing compound, a lanthanum-containing compound, a nickel-containing compound, a cobalt-containing compound, a manganese-containing compound, a chromium-containing compound, an aluminum-containing compound or an iron-containing compound.

5. The positive electrode material uniformly coated with high entropy oxide according to claim 4, characterized in that: The lithium-containing compound includes one or more of lithium nitrate, lithium hydroxide, lithium chloride, lithium citrate or lithium acetate; the lanthanum-containing compound includes one or more of lanthanum acetate, lanthanum nitrate, lanthanum chloride, lanthanum oxide or lanthanum citrate; the nickel-containing compound includes one or more of nickel nitrate, nickel hydroxide, nickel chloride, nickel citrate or nickel acetate; the cobalt-containing compound includes one or more of cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt citrate or cobalt acetate; the manganese-containing compound includes one or more of manganese nitrate, manganese chloride or manganese acetate; the chromium-containing compound includes one or more of chromium nitrate, chromium sulfate, cobalt citrate or chromium acetate; the aluminum-containing compound includes one or more of aluminum nitrate, aluminum acetate or aluminum chloride; the iron-containing compound includes one or more of ferric nitrate, ferric acetate, ferric sulfate or ferric chloride.

6. The positive electrode material uniformly coated with high entropy oxide according to claim 1, characterized in that: The raw materials also include auxiliary agents; the auxiliary agents include one or more of polyvinyl pyrrolidone, dopamine, glucose, sucrose, guar gum, polyacrylic acid or polyacrylonitrile; the mass ratio of the auxiliary agent to the electrode material is 1:3-10.

7. The positive electrode material uniformly coated with high entropy oxide according to claim 1, characterized in that: The lithium-containing compound includes one or more of lithium nitrate, lithium acetate, lithium hydroxide, lithium chloride, lithium citrate or lithium acetate.

8. A method for preparing a positive electrode material uniformly coated with a high entropy oxide according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) adding a metal compound corresponding to the high entropy oxide to ethanol and / or aqueous solution and uniformly mixing; (2) adding an auxiliary agent to the system and mixing uniformly to obtain a mixed solution; (3) adding the electrode material and the lithium-containing compound to the mixed solution while stirring, and mixing them evenly to obtain a precursor solution; (4) heating the precursor solution while stirring until it is evaporated to dryness to obtain a precursor; (5) The obtained precursor is calcined in a combustion-supporting atmosphere to obtain an electrode material uniformly coated with a high entropy oxide.

9. The method for preparing a positive electrode material uniformly coated with a high entropy oxide according to claim 8, characterized in that: The temperature of heating and evaporating to dryness in step (4) is 80-100°C.

10. The method for preparing a positive electrode material uniformly coated with a high entropy oxide according to claim 8, characterized in that: The calcination temperature in step (5) is 700-800° C., the heating rate is 3-8° C. / min, and the insulation time is 4-14 h.

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