A preparation method for improving high-temperature performance of lithium manganate material

Abstract

A preparation method for improving the high-temperature performance of a lithium manganate material of the present invention comprises the following specific steps: mixing a manganese source and a lithium source to obtain a mixed raw material; adding a dopant 1 to the mixed raw material, placing the mixed raw material in an air atmosphere after mixing, performing a sintering once, and screening the sintered product to obtain a first sintered material; adding a dopant 2 to the first sintered material, placing the mixed raw material in an air atmosphere after mixing, and performing a secondary sintering to obtain a second sintered material; mixing the second sintered material with a dopant 3 to obtain a solid-liquid mixture; heating and evaporating the solid-liquid mixture under stirring until crystals appear to obtain an intermediate product; adding a binder to the intermediate product, heating and evaporating the mixed raw material under stirring until the solvent is completely evaporated to obtain a semi-product; crushing, screening, and deironing the semi-product to obtain a product. The high-temperature performance and cycle performance of the lithium manganate material obtained by the preparation method of the present invention are both improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery positive electrode material production methods, and in particular to a preparation method for improving the high-temperature performance of lithium manganate materials. Background Art

[0002] With the increasing depletion of traditional energy sources and the increasing pollution they cause, governments around the world are increasingly looking to new energy vehicles, hoping that their emergence can alleviate the increasingly severe energy and environmental pressures we currently face. As the key to the development of new energy vehicles, battery materials have therefore been given a prominent position.

[0003] Currently, the primary active cathode material used in lithium-ion batteries is lithium cobalt oxide. Due to the scarcity and high price of cobalt, while easy to synthesize, this is not conducive to the widespread application of lithium-ion batteries. Furthermore, the poor safety performance of lithium cobalt oxide significantly limits its large-scale application in power batteries. Safe and inexpensive lithium manganese oxide batteries offer superior performance unmatched by nickel-metal hydride and lithium cobalt oxide batteries. The thermal decomposition temperature of 3V lithium manganese oxide in a charged state is 200°C higher than that of lithium cobalt oxide (the decomposition temperature in a charged state is approximately 430°C). Its excellent thermal stability makes it recognized as the most practical electrode material for electric vehicles. High-capacity power batteries using lithium manganese oxide as the positive electrode are expected to have significant application value in energy, transportation, environmental protection, communications, aerospace, and marine applications due to their abundant resources and excellent safety.

[0004] Currently, the main methods for synthesizing spinel lithium manganese oxide can be divided into two types: solid-phase method and liquid-phase method. The solid-phase method usually involves fully mixing manganese salts (such as manganese dioxide, etc.) and lithium salts (such as lithium carbonate, etc.) and then calcining them at a high temperature of 600-850°C for a long time. The lithium manganese oxide particles prepared by the conventional solid-phase method are uneven, irregular in morphology, and the product capacity decays rapidly. The liquid-phase method can solve some of the shortcomings of the solid-phase method. For example, lithium manganese oxide prepared by the sol-gel method and hydrothermal method has a more consistent particle size distribution and has a certain degree of controllability of particle morphology and size. However, the liquid-phase method often requires the use of expensive reaction reagents, requires a long drying time, and is accompanied by a complex reaction process. Therefore, the production process conditions of the liquid-phase method are difficult to control, the production cost is high, and it is not suitable for industrial production. Lithium manganese oxide is one of the most promising lithium-ion positive electrode materials. Compared with traditional positive electrode materials such as lithium cobalt oxide, lithium manganese oxide has the advantages of abundant resources, low cost, pollution-free, good safety, and good rate performance. It is an ideal positive electrode material for power lithium batteries. However, its poor cycle performance and electrochemical stability have greatly limited its industrialization. In view of this, the present invention is proposed. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a lithium manganate material with good high-temperature cycle performance and good electrochemical stability.

[0006] In order to solve the above problems, the present invention adopts the following technical solutions:

[0007] A preparation method of the present invention for improving the high-temperature performance of lithium manganate materials comprises the following specific steps:

[0008] (1) mixing a manganese source and a lithium source to obtain a mixed raw material;

[0009] (2) adding dopant 1 to the mixed raw material, placing the mixed raw material in an air atmosphere, performing a sintering operation, and screening the sintered product to obtain a first sintered material;

[0010] (3) adding the second dopant into the first sintered material, mixing, placing in an air atmosphere, and performing a second sintering to obtain a second sintered material;

[0011] (4) mixing the second sintered material with the third dopant to obtain a solid-liquid mixture; heating and evaporating the solid-liquid mixture while stirring until crystals appear to obtain an intermediate product;

[0012] (5) Adding a binder to the intermediate product and heating and evaporating the mixture under stirring until the solvent is completely evaporated to obtain a semi-product;

[0013] (6) The semi-product is crushed, screened, and iron removed to obtain the product.

[0014] Furthermore, the manganese source is any one or more of manganese sulfate, manganese dioxide, manganese acetate, manganese oxalate, and manganese chloride; and the lithium source is any one or more of lithium oxalate, lithium hydroxide, and lithium carbonate.

[0015] Furthermore, the dopant 1 is SiF4, and the addition amount of the dopant 1 is 1% to 1.5% of the mass of the mixed raw material.

[0016] Furthermore, the second dopant is aluminum hydroxide; the addition amount of the second dopant is 1% to 1.5% of the mass of the first sintered material.

[0017] Furthermore, the third dopant is a cobalt chloride solution; the mass ratio of the cobalt oxide in the third dopant to the mass ratio of the second sintered material is (3-5): (92-95).

[0018] Furthermore, the adhesive is any one or more of polyvinyl alcohol, epoxy resin, vinyl acetate resin, acrylic resin and chlorinated rubber.

[0019] Furthermore, during the primary sintering, a programmed temperature rising method is adopted, the temperature is raised to 400-700° C. at a heating rate of 20° C. / min, and the temperature is kept for 24-36 hours.

[0020] Furthermore, during the secondary sintering, a programmed temperature rising method is adopted, the temperature is raised to 800-1000° C. at a heating rate of 2-5° C. / min, and the temperature is kept for 8-24 hours.

[0021] Beneficial effects of the present invention: (1) SiF4 metal ions are used to harden the crystal structure of lithium manganate, so that lithium ions can be reversibly deintercalated from the spinel lattice, which is less likely to cause structural collapse and improves cycle performance.

[0022] (2) In the present invention, aluminum hydroxide is used as a dopant. The atomic radius of aluminum is small, which makes the bond energy of aluminum and oxygen large, resulting in a more stable crystal form of potassium manganate, which can improve the discharge cycle performance of potassium manganate to a certain extent. At the same time, the particle size of lithium aluminum manganate is smaller than that of lithium manganate, and the morphology is more regular, and it is not easy to agglomerate during subsequent mixing.

[0023] (3) In the present invention, cobalt chloride is used as a dopant in the secondary sintering material. Since the radius of Co ions is smaller than that of Mn ions and the Co-O bond energy is greater than that of Mn-O, Co doping reduces the unit cell parameter a of spinel. Moreover, the less a Co doping amount is in an appropriate proportion, the more stable the crystal structure is, thereby reducing the occurrence of the Jahn-Teller effect.

[0024] (4) The present invention improves the high temperature and cycle performance of the positive electrode material by adding dopants to adjust the proportion of metal elements in lithium manganese oxide. The difficulty of uneven solid phase mixing of lithium manganese oxide and cobalt lithium is improved by secondary sintering and primary wet mixing. At the same time, by secondary doping with compounds of aluminum, fluorine and cobalt elements, cobalt and aluminum-coated spinel lithium manganese oxide materials are synthesized, so that the product has strong M-O bonds, strong octahedral stability and metal ions with ionic radius similar to that of manganese ions, which can significantly improve its high temperature and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a comparison chart of battery voltage drop at 45°C. DETAILED DESCRIPTION

[0026] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form in conjunction with the following examples, but the protection scope of the present invention is not limited to the following specific examples.

[0027] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods. Example 1

[0028] A preparation method for improving the high-temperature performance of lithium manganate material in this embodiment includes the following specific steps:

[0029] (1) manganese sulfate as a manganese source and lithium oxalate as a lithium source are mixed to obtain a mixed raw material;

[0030] (2) Adding SiF4 as a dopant to the mixed raw materials in an amount of 1% by weight of the mixed raw materials, placing the mixed raw materials in an air atmosphere, and performing a single sintering. During the single sintering, the temperature is raised to 400-700°C at a heating rate of 20°C / min using a programmed temperature rise method, and the temperature is kept at this temperature for 24-36 hours. The sintered product is sieved to obtain a first sintered material;

[0031] (3) Aluminum hydroxide is added as a dopant to the first sintered material in an amount of 1% of the mass of the first sintered material. After mixing, the mixture is placed in an air atmosphere for secondary sintering. During the secondary sintering, the temperature is raised to 800-1000°C at a heating rate of 2-5°C / min using a programmed temperature rising method, and the temperature is kept at this temperature for 8-24 hours to obtain a second sintered material.

[0032] (4) mixing the second sintered material with the cobalt chloride solution to obtain a solid-liquid mixture; heating and evaporating the solid-liquid mixture while stirring until crystals appear, thereby obtaining an intermediate product; wherein the mass ratio of cobalt oxide in the cobalt chloride solution to the mass ratio of the second sintered material is 4:94.

[0033] (5) Adding polyvinyl alcohol as a binder to the intermediate product, heating and evaporating the mixture under stirring until the solvent is completely evaporated to obtain a semi-product;

[0034] (6) The semi-product is crushed, screened, and iron removed using an iron remover to obtain the product. Example 2

[0035] A preparation method for improving the high-temperature performance of lithium manganate material in this embodiment includes the following specific steps:

[0036] (1) mixing manganese dioxide as a manganese source and lithium hydroxide as a lithium source to obtain a mixed raw material;

[0037] (2) Adding SiF4 as a dopant to the mixed raw materials in an amount of 1.5% of the mixed raw materials' mass, placing the mixed raw materials in an air atmosphere for a single sintering. During the single sintering, the temperature is raised to 400-700°C at a rate of 20°C / min using a programmed temperature ramp and then maintained at that temperature for 24-36 hours. The sintered product is sieved to obtain a first sintered material.

[0038] (3) Aluminum hydroxide is added as a dopant to the first sintered material in an amount of 1.5% of the mass of the first sintered material. After mixing, the mixture is placed in an air atmosphere for secondary sintering. During the secondary sintering, the temperature is raised to 800-1000°C at a heating rate of 2-5°C / min using a programmed temperature rising method, and the temperature is kept at this temperature for 8-24 hours to obtain a second sintered material.

[0039] (4) mixing the second sintered material with the cobalt chloride solution to obtain a solid-liquid mixture; heating and evaporating the solid-liquid mixture while stirring until crystals appear, and stopping the heating to obtain an intermediate product; wherein the mass ratio of cobalt oxide in the cobalt chloride solution to the second sintered material is 4:93;

[0040] (5) Adding epoxy resin as a binder to the intermediate product, heating and evaporating the mixture under stirring until the solvent is completely evaporated to obtain a semi-product;

[0041] (6) The semi-product is crushed, screened, and iron removed using an iron remover to obtain the product. Example 3

[0042] A preparation method for improving the high-temperature performance of lithium manganate material in this embodiment includes the following specific steps:

[0043] (1) manganese acetate as a manganese source and lithium carbonate as a lithium source are mixed to obtain a mixed raw material;

[0044] (2) Adding SiF4 as a dopant to the mixed raw materials in an amount of 1.2% of the mixed raw materials' mass, placing the mixed raw materials in an air atmosphere for a single sintering. During the single sintering, the temperature is raised to 400-700°C at a rate of 20°C / min using a programmed temperature ramp and then maintained at that temperature for 24-36 hours. The sintered product is sieved to obtain a first sintered material.

[0045] (3) Aluminum hydroxide is added as a dopant to the first sintered material in an amount of 1.2% of the mass of the first sintered material. After mixing, the mixture is placed in an air atmosphere for secondary sintering. During the secondary sintering, the temperature is raised to 800-1000°C at a heating rate of 2-5°C / min using a programmed temperature rising method, and the temperature is kept at this temperature for 8-24 hours to obtain a second sintered material.

[0046] (4) mixing the second sintered material with the cobalt chloride solution to obtain a solid-liquid mixture; heating and evaporating the solid-liquid mixture while stirring until crystals appear, thereby obtaining an intermediate product; wherein the mass ratio of cobalt oxide in the cobalt chloride solution to the second sintered material is 5:95.

[0047] (5) Adding vinyl acetate resin as a binder to the intermediate product, heating and evaporating the mixture under stirring until the solvent is completely evaporated to obtain a semi-product;

[0048] (6) The semi-product is crushed, screened, and iron removed using an iron remover to obtain the product. Example 4

[0049] A preparation method for improving the high-temperature performance of lithium manganate material in this embodiment includes the following specific steps:

[0050] (1) mixing manganese oxalate as a manganese source and lithium oxalate as a lithium source to obtain a mixed raw material;

[0051] (2) Adding SiF4 as a dopant to the mixed raw materials in an amount of 1.3% of the mixed raw materials' mass, the mixed raw materials are placed in an air atmosphere and sintered once. During the first sintering, a programmed temperature is used to increase the temperature to 400-700°C at a heating rate of 20°C / min and keep the temperature for 24-36 hours. The sintered product is sieved to obtain a first sintered material;

[0052] (3) Aluminum hydroxide is added as a dopant to the first sintered material in an amount of 1.2% of the mass of the first sintered material. After mixing, the mixture is placed in an air atmosphere for secondary sintering. During the secondary sintering, the temperature is raised to 800-1000°C at a heating rate of 2-5°C / min using a programmed temperature rising method, and the temperature is kept at this temperature for 8-24 hours to obtain a second sintered material.

[0053] (4) mixing the second sintered material with the cobalt chloride solution to obtain a solid-liquid mixture; heating and evaporating the solid-liquid mixture while stirring until crystals appear, thereby obtaining an intermediate product; wherein the mass ratio of cobalt oxide in the cobalt chloride solution to the mass ratio of the second sintered material is 5:92.

[0054] (5) Adding acrylic resin as a binder to the intermediate product, heating and evaporating the mixture under stirring until the solvent is completely evaporated to obtain a semi-product;

[0055] (6) The semi-product is crushed, screened, and iron removed using an iron remover to obtain the product. Example 5

[0056] A preparation method for improving the high-temperature performance of lithium manganate material in this embodiment includes the following specific steps:

[0057] (1) mixing manganese chloride as a manganese source and lithium hydroxide as a lithium source to obtain a mixed raw material;

[0058] (2) Adding SiF4 as a dopant to the mixed raw materials in an amount of 1.3% of the mixed raw materials' mass, the mixed raw materials are placed in an air atmosphere and sintered once. During the first sintering, a programmed temperature is used to increase the temperature to 400-700°C at a heating rate of 20°C / min and keep the temperature for 24-36 hours. The sintered product is sieved to obtain a first sintered material;

[0059] (3) Aluminum hydroxide is added as a dopant to the first sintered material in an amount of 1.2% of the mass of the first sintered material. After mixing, the mixture is placed in an air atmosphere for secondary sintering. During the secondary sintering, the temperature is raised to 800-1000°C at a heating rate of 2-5°C / min using a programmed temperature rising method, and the temperature is kept at this temperature for 8-24 hours to obtain a second sintered material.

[0060] (4) mixing the second sintered material with the cobalt chloride solution to obtain a solid-liquid mixture; heating and evaporating the solid-liquid mixture while stirring until crystals appear, thereby obtaining an intermediate product; wherein the mass ratio of cobalt oxide in the cobalt chloride solution to the mass ratio of the second sintered material is 3:92.

[0061] (5) Adding chlorinated rubber as a binder to the intermediate product, heating and evaporating the mixture under stirring until the solvent is completely evaporated to obtain a semi-product;

[0062] (6) The semi-product is crushed, screened, and iron removed using an iron remover to obtain the product.

[0063] Comparative Example:

[0064] The comparative example used a commercially available DXM-2000 modified lithium manganate material produced by Gansu Elephant Energy Technology Co., Ltd.

[0065] The products obtained in the above embodiments and the products in the comparative examples were tested, and the battery cycle capacity performance test results at 45°C are as follows:

[0066] 1C gram capacity 1C high temperature cycle (200-cycle capacity retention) Example 1 107 92% Example 2 108 91.70% Example 3 106 90.60% Example 4 107 90.50% Example 5 105 92.20% Comparative Example 96 78.50%

[0067] Comparison of battery voltage drop at 45°C Figure 1 shown.

[0068] According to the cycle capacity performance test results and the comparison results of the battery voltage drop in the above embodiment and the comparative example, it can be seen that the improved lithium manganese oxide material prepared by the preparation method of the present invention has improved high temperature performance and cycle performance.

Claims

1. A preparation method for improving the high temperature performance of lithium manganate material, characterized in that: The specific steps include: (1) mixing a manganese source and a lithium source to obtain a mixed raw material; (2) adding dopant 1 to the mixed raw material, placing the mixed raw material in an air atmosphere, performing a sintering operation, and screening the sintered product to obtain a first sintered material; (3) adding the second dopant into the first sintered material, mixing, placing in an air atmosphere, and performing a second sintering to obtain a second sintered material; (4) mixing the second sintered material with the third dopant to obtain a solid-liquid mixture; heating and evaporating the solid-liquid mixture while stirring until crystals appear, thereby obtaining an intermediate product; (5) Adding a binder to the intermediate product and heating and evaporating the mixture under stirring until the solvent is completely evaporated to obtain a semi-product; (6) Crushing, screening, and iron removal of the semi-product to obtain the product; The dopant 1 is SiF4, and the addition amount of the dopant 1 is 1% to 1.5% of the mass of the mixed raw material; The second dopant is aluminum hydroxide; the addition amount of the second dopant is 1% to 1.5% of the mass of the first sintered material; The third dopant is a cobalt chloride solution; the mass ratio of the cobalt oxide in the third dopant to the mass ratio of the second sintered material is (3-5): (92-95); During the primary sintering, a programmed temperature rising method is adopted, the temperature is raised to 400-700° C. at a heating rate of 20° C. / min, and the temperature is kept for 24-36 hours.

2. The method for preparing a lithium manganate material for improving high temperature performance according to claim 1, wherein: The manganese source is any one or more of manganese sulfate, manganese dioxide, manganese acetate, manganese oxalate, and manganese chloride; the lithium source is any one or more of lithium oxalate, lithium hydroxide, and lithium carbonate.

3. The method for preparing a lithium manganate material for improving high temperature performance according to claim 1, wherein: The adhesive is any one or more of polyvinyl alcohol, epoxy resin, vinyl acetate resin, acrylic resin and chlorinated rubber.

4. The method for preparing a lithium manganate material for improving high temperature performance according to claim 1, wherein: During the secondary sintering, a programmed temperature rising method is adopted, the temperature is raised to 800-1000°C at a heating rate of 2-5°C / min, and the temperature is kept for 8-24 hours.

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