Preparation method of nickel manganese oxide precursor and preparation method of lithium nickel manganese oxide positive electrode material

Abstract

The invention discloses a preparation method of a nickel manganese oxide precursor and a lithium nickel manganese oxide positive electrode material, and relates to the technical field of lithium ion battery material preparation. The method comprises the following steps: adding water and ammonium salt into a reaction container, fully stirring to prepare an ammonium salt solution, adding nickel-manganese alloy powder, and fully dispersing to obtain a suspension; introducing air or oxygen under the condition of keeping full stirring, controlling the reaction temperature to fully oxidize manganese, and after the reaction is finished, carrying out suction filtration, water washing and drying to obtain a mixture of nickel and manganese oxides; placing the prepared mixture in a tubular furnace, and performing heat treatment in an oxygen or air atmosphere to oxidize nickel to obtain a nickel manganese oxide precursor; the method is simple in step, easy to operate, mild in preparation condition, green and pollution-free, meanwhile, the catalyst ammonium salt can be recycled, the preparation cost is relatively low, and the prepared product is excellent in performance and suitable for large-scale production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery material preparation, in particular to a method for preparing a nickel manganese oxide precursor and a nickel manganese oxide lithium positive electrode material. Background Art

[0002] With the rapid development of the new energy vehicle market, the demand for high-performance power batteries continues to increase. Among them, spinel nickel manganese oxide has a high voltage working platform of 4.7V, which makes its energy density reach 650Wh / kg, which is 20% higher than the traditional LiCoO2 material and reaches the level of ternary materials. On the other hand, its main components are nickel and manganese, which are lower in cost and more environmentally friendly than cobalt-containing ternary materials. Because lithium nickel manganese oxide has the advantages of high energy density, low cost and more environmental protection, it is considered to be one of the most promising next-generation lithium-ion battery positive electrode materials. Studies have shown that the morphological and structural characteristics of the precursor play a decisive role in the performance of the positive electrode material. On the other hand, as an important component of lithium battery materials, the cost of the precursor accounts for 40% of the positive electrode material. Due to the quality inheritance between the precursor and the positive electrode material and the large proportion of the precursor cost, the development of high-performance and low-cost precursor preparation process is particularly important for improving the performance of the positive electrode material and reducing the cost. As an important precursor of lithium nickel manganese oxide, the mainstream preparation methods of nickel manganese oxide precursor are coprecipitation method and solid phase method.

[0003] The coprecipitation method has the advantage of uniformly mixing the raw metal ions at the molecular level, and a precursor with high phase purity can be obtained. For example, patent JP6582824B2 discloses a nickel-manganese composite hydroxide and a method for manufacturing the same, specifically, a plurality of metal compounds containing at least a nickel compound and a manganese compound are dissolved in water in a specified ratio, and then a mixed solution of sodium hydroxide and ammonia water is supplied to a reaction tank and mixed, and the reaction conditions are controlled at a certain temperature to prepare a hydroxide precursor containing nickel and manganese. The prepared nickel-manganese composite hydroxide is ball-milled with a lithium compound to form a mixture, and then heat-treated in an oxidizing atmosphere. However, the coprecipitation method for preparing a nickel-manganese precursor has problems such as high waste liquid treatment cost, incomplete element precipitation, and easy embedding of anions such as sulfate.

[0004] The solid phase method is also a common method for preparing nickel manganese oxide. It has the advantages of simple process and convenient operation, and is more suitable for large-scale industrial production. For example, patent CN112960704A discloses a method for preparing a high-voltage lithium nickel manganese oxide positive electrode material, in which a nickel source compound and a manganese source compound are ball-milled and mixed evenly, and then sintered and crushed to obtain a precursor. The obtained precursor is then ball-milled with lithium carbonate and the material is secondary sintered to obtain the desired finished lithium nickel manganese oxide positive electrode material. However, the solid phase method generally has the problem of uneven distribution of nickel and manganese, which will directly affect the performance of the subsequent preparation of the lithium nickel manganese oxide positive electrode material.

[0005] In summary, a method for preparing a nickel manganese oxide precursor and a nickel manganese oxide lithium positive electrode material is urgently needed to solve this problem. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a nickel manganese oxide precursor and a nickel manganese oxide lithium positive electrode material to solve the problems mentioned in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for preparing a nickel manganese oxide precursor, comprising the following specific steps:

[0008] S1. Raw material preparation: Add water and ammonium salt into a reaction container and stir thoroughly to prepare an ammonium salt solution, add nickel-manganese alloy powder and disperse thoroughly to obtain a suspension;

[0009] S2 Suspended oxidation: air or oxygen is introduced under sufficient stirring, and the reaction temperature is controlled to fully oxidize manganese. After the reaction is completed, a mixture of nickel and manganese oxides is obtained by filtration, washing with water, and drying;

[0010] S3 heat treatment: placing the mixture obtained in step S2 in a tube furnace and performing heat treatment in an oxygen or air atmosphere to oxidize nickel and obtain a nickel-manganese oxide precursor.

[0011] Preferably, in the above step S1, the concentration of the nickel-manganese alloy powder in the suspension is 100-300 g / L, and the concentration of the ammonium salt is 2-20 g / L.

[0012] In the above preferred embodiment, the ammonium salt is one of ammonium chloride, ammonium sulfate and ammonium nitrate; the nickel-manganese alloy powder is directly purchased from the market, and the molar ratio of nickel and manganese is selected according to production needs.

[0013] Preferably, in the above step S2, the stirring speed is 200-600 rpm, the reaction temperature is 30-90° C., and the reaction time is 6-36 h.

[0014] Preferably, in the above step S3, the heat treatment temperature is 300-700° C., and the heat treatment time is 2-10 hours.

[0015] Another technical solution provided by the present invention is a method for preparing a lithium nickel manganese oxide positive electrode material, wherein the nickel manganese oxide precursor prepared by the above method is added with lithium salt and mixed by ball milling, and then heat-treated in a tubular furnace under an oxygen or air atmosphere to obtain a lithium nickel manganese oxide positive electrode material.

[0016] Preferably, the molar ratio of lithium in the lithium salt to the metal in the precursor oxide is 1:(1.9-2.2), the heat treatment temperature is 700-1000° C., and the heat treatment time is 6-24 h.

[0017] Preferably, the above-mentioned lithium nickel manganese oxide positive electrode material is LiNi 0.5 Mn 1.5 O4, the molar ratio of nickel to manganese in the nickel-manganese alloy powder is 1:3.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The preparation method of the nickel manganese oxide precursor and the nickel manganese oxide lithium positive electrode material has simple steps and is easy to operate, and the preparation conditions are mild and green and pollution-free. At the same time, the catalyst ammonium salt can be recycled, the preparation cost is relatively low, and the obtained product has excellent performance and is suitable for large-scale production and application.

[0020] 2. The preparation method of the nickel-manganese oxide precursor and the nickel-manganese oxide lithium positive electrode material uses a raw material nickel-manganese alloy powder in which the nickel and manganese elements are theoretically evenly distributed at the atomic level. A mixture of nickel and manganese tetraoxide is first obtained by a suspended oxidation method, and then further heat-treated and oxidized to obtain nickel-manganese oxide. An oxide precursor with evenly distributed nickel and manganese can be obtained, and the obtained precursor has fewer impurities. The nickel-manganese oxide lithium positive electrode material obtained after mixing with lithium has better cycle performance.

[0021] 3. The preparation method of the nickel manganese oxide precursor and the nickel manganese oxide lithium positive electrode material adopts a two-step oxidation method to first oxidize the more active manganese, thereby avoiding safety problems caused by excessive oxidation in a one-step heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is the XRD image of lithium nickel manganese oxide prepared in Example 1 and Comparative Example 1.

[0023] Figure 2 is a scanning electron microscope (SEM) image of the lithium nickel manganese oxide prepared in Example 1.

[0024] Figure 3 This is the Mn element distribution diagram in the single particle of nickel manganese oxide precursor prepared in Example 1.

[0025] Figure 4 This is the distribution diagram of Ni element in the single particle of nickel manganese oxide precursor prepared in Example 1.

[0026] Figure 5 This is a capacity test diagram of the nickel manganese oxide lithium assembled button battery prepared in Example 1.

[0027] Figure 6 This is a test chart of the cycle performance of the nickel manganese oxide assembled button battery prepared in Example 1. DETAILED DESCRIPTION

[0028] The preparation method of the present invention comprises:

[0029] Raw material preparation: Add water and ammonium salt into a reaction container and stir thoroughly to prepare an ammonium salt solution, add nickel-manganese alloy powder and disperse thoroughly to obtain a suspension;

[0030] For reference, the concentration of nickel-manganese alloy powder in the suspension can be 100-300 g / L, and the concentration of ammonium salt can be 2-20 g / L;

[0031] In the above raw material preparation work, the ammonium salt used as the catalyst can be one of ammonium chloride, ammonium sulfate and ammonium nitrate;

[0032] In addition, the nickel-manganese alloy powder is purchased directly from the market, and the nickel-manganese molar ratio is selected according to production needs, and the requirements for producing nickel-manganese oxide precursors or the requirements for lithium nickel manganese oxide positive electrode materials can be used. In a preferred embodiment, the lithium nickel manganese oxide positive electrode material to be prepared is LiNi 0.5 Mn 1.5 O4, the molar ratio of nickel to manganese in the purchased nickel-manganese alloy powder is 1:3.

[0033] Suspended oxidation: air or oxygen is introduced under sufficient stirring, and the reaction temperature is controlled to fully oxidize manganese. After the reaction is completed, a mixture of nickel and manganese oxides is obtained by filtration, washing with water, and drying;

[0034] The parameters are for reference only. The stirring speed can be controlled at 200-600 rpm, the reaction temperature is preferably controlled at 30-90°C, and the reaction time is preferably 6-36 hours.

[0035] Heat treatment: The mixture obtained in step S2 is placed in a tube furnace and heat treated in an oxygen or air atmosphere to oxidize nickel and obtain a nickel-manganese oxide precursor.

[0036] The parameters are for reference only. The heat treatment temperature should be controlled at 300-700°C, and the heat treatment time should be 2-10 hours.

[0037] Lithium mixing: Add lithium salt to nickel manganese oxide precursor and mix them by ball milling, then heat treat them in a tube furnace under oxygen or air atmosphere to obtain lithium nickel manganese oxide positive electrode material;

[0038] In a preferred embodiment, the molar ratio of lithium in the lithium salt to the metal in the precursor oxide is 1:(1.9-2.2), the heat treatment temperature is 700-1000° C., and the heat treatment time is 6-24 hours.

[0039] The contents of the present invention are further described below through several examples and comparative examples, wherein the examples are not all the examples of the present invention and should not be understood as absolute limitations of the present invention. The protection scope of the present invention should be based on the claims and the description in the above embodiments.

[0040] Example 1

[0041] Weigh 10g of ammonium chloride, add it to 1000ml of deionized water, and fully dissolve it to obtain an ammonium chloride solution. Add 200g of nickel-manganese alloy powder to the above ammonium chloride solution, and obtain a nickel-manganese powder suspension by homogenization or strong stirring. While maintaining the stirring speed at 400rpm, introduce air through an air compressor, control the reaction temperature to 50°C, and the reaction time to 12h. After the reaction is completed, the dispersion obtained is filtered, washed with water, and dried to obtain a nickel and manganese oxide mixture powder. The obtained nickel and manganese oxide mixture powder is placed in a crucible and heat treated at 500°C in an oxygen atmosphere for 6h to obtain a nickel-manganese oxide precursor.

[0042] Figure 3 and Figure 4 1 is a distribution diagram of Mn and Ni elements in a single particle of the nickel manganese oxide precursor prepared in Example 1. It can be seen from the figure that the elements in the prepared precursor are evenly distributed.

[0043] The obtained nickel manganese oxide precursor is then ball-milled and mixed with lithium carbonate in a molar ratio of nickel manganese metal to lithium of 2:1. The mixture is heat-treated in a tube furnace under an oxygen atmosphere at 800° C. for 12 hours to obtain a lithium nickel manganese oxide positive electrode material.

[0044] The XRD pattern of the lithium nickel manganese oxide positive electrode material prepared by the above method is shown in the attached Figure 1 , is spinel phase LiNi 0.5 Mn 1.5 O4, the sample has high phase purity and good crystallinity. The SEM electron microscope image of the prepared lithium nickel manganese oxide sample is attached. Figure 2 The sample particle size is uniform. The positive electrode material prepared in Example 1 has a discharge capacity of 142.4 mAh / g at 0.1C, and a capacity retention rate of 91.0% after 1000 cycles at 1C.

[0045] Comparative Example 1

[0046] This example is carried out with reference to patent CN112960704A. Nickel oxide and manganese tetraoxide powders of battery-grade purity are mixed evenly by ball milling at a nickel-manganese molar ratio of 1:3. The evenly mixed materials are put into a bowl and sintered at 500°C for 20 hours. The sintered materials are taken out of the furnace and crushed to obtain a precursor; the obtained precursor is mixed with battery-grade lithium carbonate at a metal / lithium molar ratio of 2:1, and sintered at 900°C for 5 hours to obtain the desired nickel manganese oxide positive electrode material product. This comparative example uses a ball milling method to prepare a precursor, and the XRD diagram of the nickel manganese oxide positive electrode material obtained is shown in the attached Figure 1 The prepared positive electrode material was assembled and charged, and the discharge capacity was 94.2 mAh / g at 0.1C, and the capacity retention rate after 1000 cycles at 1C was 51.4%.

[0047] Comparative Example 2

[0048] This embodiment is carried out with reference to patent JP6582824B2, specifically, nickel sulfate and manganese sulfate are dissolved in water at a nickel to manganese molar ratio of 1:3, and then a mixed solution of sodium hydroxide and ammonia water is supplied to a reaction tank and mixed, and the reaction conditions are controlled at a certain temperature to prepare a hydroxide precursor containing nickel and manganese. The prepared nickel manganese hydroxide is ball-milled with lithium carbonate to form a mixture, and heat-treated at 800°C for 12 hours in an oxidizing atmosphere to obtain a lithium nickel manganese oxide positive electrode material. The obtained positive electrode assembly is charged, and the discharge specific capacity under 0.1C conditions is 114.2mAh / g, and the capacity retention rate after 1C cycle of 1000 cycles is 73.4%

[0049] Example 2

[0050] This example is carried out with reference to Example 1, except that the mass of the added nickel-manganese powder is 100 g, that is, the concentration of the nickel-manganese powder in the suspended oxidation process is 100 g / L.

[0051] Example 3

[0052] This example is carried out with reference to Example 1, except that the mass of the added nickel-manganese powder is 300 g, that is, the concentration of the nickel-manganese powder in the suspended oxidation process is 300 g / L.

[0053] Example 4

[0054] This example is carried out with reference to Example 1, except that the reaction temperature of the suspended oxidation process is 30° C. and the reaction time is 36 h.

[0055] Example 5

[0056] This example is carried out with reference to Example 1, except that the reaction temperature of the suspended oxidation process is 90° C. and the reaction time is 6 h.

[0057] Example 6

[0058] This example is carried out with reference to Example 1, except that the ammonium salt catalyst added in the suspended oxidation process is ammonium sulfate.

[0059] Example 7

[0060] This example is carried out with reference to Example 1, except that the stirring speed of the suspended oxidation reaction is 600 rpm.

[0061] Example 8

[0062] This example is carried out with reference to Example 1, except that the reaction temperature of the heat treatment oxidation process is 300° C. and the reaction time is 10 h.

[0063] Example 9

[0064] This example is carried out with reference to Example 1, except that the reaction temperature of the heat treatment oxidation process is 700° C. and the reaction time is 2 h.

[0065] Example 10

[0066] This example is carried out with reference to Example 1, except that the molar concentration of metal and lithium in the process of preparing lithium nickel manganese oxide by mixing lithium is 1.9.

[0067] Embodiment 11

[0068] This example is carried out with reference to Example 1, except that the reaction time of the process of preparing lithium nickel manganese oxide by mixing lithium is 700° C. and the reaction temperature is 24 h.

[0069] Example 12

[0070] This example is carried out with reference to Example 1, except that the reaction time of the process of preparing lithium nickel manganese oxide by mixing lithium is 1000° C. and the reaction temperature is 6 hours.

[0071] The samples obtained in the embodiments and comparative examples were assembled and charged, and the capacity test and cycle stability test were performed; the positive electrode material performance was tested by conventional button battery test, and the battery assembly and performance test mainly included the following steps:

[0072] ① Preparation of positive electrode sheet: The prepared lithium nickel manganese oxide material, conductive agent Super P, and binder PVDF are mixed in a weight ratio of 8:1:1 to prepare positive electrode slurry, which is coated on one side of the aluminum foil surface and dried to obtain a positive electrode sheet.

[0073] ②Button cell battery assembly: Assemble the button cell in the order of negative electrode shell, lithium sheet, diaphragm, electrolyte, positive electrode sheet, gasket, spring and positive electrode shell, where the electrolyte is 1M LiPF6, the solvent volume ratio is EC:DMC:DEC=1:1:1, and the diaphragm is a polyethylene porous membrane.

[0074] ③Battery capacity test: The test voltage is 3.5-4.95V. The constant current step is used for charging and then for discharging. The capacity test charge and discharge current is 0.1C, and the cycle test charge and discharge current is 1C.

[0075] As an example, Figure 5 and 6 The following are the capacity test graph and cycle performance test graph of the nickel manganese oxide lithium assembled buckle battery prepared in Example 1. The specific comparison of all data is shown in Table 1 below:

[0076] Table 1: Performance test of examples and comparative examples

[0077]

[0078] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0079] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for preparing a nickel-manganese oxide precursor, characterized in that: The specific steps include: S1. Raw material preparation: Add water and ammonium salt into a reaction container and stir thoroughly to prepare an ammonium salt solution, add nickel-manganese alloy powder and disperse thoroughly to obtain a suspension; S2 Suspended oxidation: air or oxygen is introduced under sufficient stirring, and the reaction temperature is controlled to fully oxidize manganese. After the reaction is completed, a mixture of nickel and manganese oxides is obtained by filtration, washing with water, and drying; S3 heat treatment: placing the mixture obtained in step S2 in a tube furnace and performing heat treatment in an oxygen or air atmosphere to oxidize nickel and obtain a nickel-manganese oxide precursor.

2. The method for preparing a nickel manganese oxide precursor according to claim 1, characterized in that: In the step S1, the concentration of the nickel-manganese alloy powder in the suspension is 100-300 g / L, and the concentration of the ammonium salt is 2-20 g / L.

3. The method for preparing a nickel manganese oxide precursor according to claim 2, characterized in that: In step S1, the ammonium salt is one of ammonium chloride, ammonium sulfate and ammonium nitrate; the nickel-manganese alloy powder is purchased from the market, and the molar ratio of nickel and manganese is selected according to production needs.

4. The method for preparing a nickel manganese oxide precursor according to claim 1, characterized in that: In the step S2, the stirring speed is 200-600 rpm, the reaction temperature is 30-90° C., and the reaction time is 6-36 h.

5. The method for preparing a nickel manganese oxide precursor according to claim 1, characterized in that: In the step S3, the heat treatment temperature is 300-700° C., and the heat treatment time is 2-10 hours.

6. A method for preparing a lithium nickel manganese oxide positive electrode material, characterized in that: A nickel manganese oxide precursor prepared by the method according to any one of claims 1 to 5 is added with a lithium salt and mixed by ball milling, and then heat-treated in a tube furnace under an oxygen or air atmosphere to obtain a lithium nickel manganese oxide positive electrode material.

7. The method for preparing a lithium nickel manganese oxide positive electrode material according to claim 6, characterized in that: The molar ratio of lithium in the lithium salt to metal in the precursor oxide is 1:(1.9-2.2), the heat treatment temperature is 700-1000° C., and the heat treatment time is 6-24 hours.

8. The method for preparing a lithium nickel manganese oxide positive electrode material according to claim 6, characterized in that: The lithium nickel manganese oxide positive electrode material is LiNi 0.5 Mn 1.5 O4, the molar ratio of nickel to manganese in the nickel-manganese alloy powder is 1:3.

Images