Synthesis method of lithium nickel manganese oxide positive electrode material

Abstract

The application discloses a synthesis method of a lithium nickel manganese oxide positive electrode material and relates to the technical field of lithium ion battery materials, aiming at solving the problems of complex post-treatment after using nitrate raw materials, poor product morphology after spraying acetate raw materials and influence on performance; the method comprises the following steps: dissolving nickel acetate, manganese acetate and ammonium nitrate in deionized water to obtain a mixed solution; the mixed solution is spray dried to prepare mixed acetate of nickel and manganese; the mixed acetate is heat-treated in an oxygen atmosphere to obtain a nickel manganese oxide precursor; the nickel manganese oxide precursor is mixed with a lithium salt and then heat-treated in an oxygen atmosphere to obtain the lithium nickel manganese oxide positive electrode material; the spray drying method is adopted to prepare the precursor, thus avoiding the disadvantages of uneven precipitation and complex post-treatment of the reaction solution in the coprecipitation method, and the acetate is adopted to replace the nitrate, thus avoiding the complex post-treatment; in addition, the added ammonium nitrate can solve the problem of poor product morphology caused by the acetate raw material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium ion battery materials, in particular to a synthesis method of a lithium nickel manganese oxide positive electrode material. BACKGROUND

[0002] The global lithium battery industry is developing rapidly, and the main research direction is based on the original lithium iron phosphate (LiFePO4) route positive electrode material and nickel-cobalt-manganese ternary positive electrode material (NCM). In the ternary NCM positive electrode material system, in the face of future market competition, constantly improving the performance-price ratio and safety performance of the ternary product has become the development direction of the industry. The lithium salt consumption of various series of ternary positive electrode materials is relatively stable, and among the remaining raw material cost structure, cobalt resources are scarce, the price is high and fluctuates greatly, so the cobalt-free of the nickel-cobalt-manganese ternary positive electrode material is the current mainstream trend. As a typical representative of the binary positive electrode material, the spinel lithium nickel manganese oxide has a high-voltage working platform of 4.7V, which is much higher than the voltage platform of 3.4V of the current mainstream positive electrode material lithium iron phosphate; it also has a relatively high energy density and is considered to be one of the most promising next-generation high-energy-density positive electrode materials of lithium ion batteries.

[0003] The preparation method of lithium nickel manganese oxide can be divided into solid phase method and liquid phase method, and the biggest advantage of the liquid phase method is that the metal ions of raw materials can be uniformly mixed together at the molecular level, so as to prepare a material without or with few impurities. The coprecipitation method as the mainstream preparation method still has problems such as high waste liquid treatment cost, incomplete element precipitation and uneven precipitation. The spray drying method can realize high mixing of each component in the raw material, and at the same time, the liquid droplets are directly dried into spherical precursors in the drying process, avoiding the problem of waste water treatment, and is a green and efficient synthesis method with good application prospect.

[0004] The invention patent application with the publication number CN106328924A and the name of a carbon-coated high-potential lithium nickel manganese oxide positive electrode material and a preparation method thereof discloses that nickel salt, manganese salt, lithium salt and citric acid are mixed into a mixed solution according to a certain cation molar ratio, ultrasonic atomization and drying are carried out in an ultrasonic spray dryer with an ultrasonic device, and spherical precursors with uniform particle size are obtained. Then the obtained precursors are introduced into a high-temperature reactor for reaction and cracking, and lithium nickel manganese oxide microcrystal powder with uniform particle size is obtained; however, the metal salt used in the method is nitrate, and a large amount of nitrate will produce toxic nitrogen oxides in the subsequent heat treatment process, and the post-treatment is complex.

[0005] In the invention patent with the publication number CN105655574B and the name of a kind of lithium nickel manganese oxide positive material and its preparation method, the raw material of lithium nickel manganese oxide positive material is M source compound, lithium salt, nickel salt, manganese salt, citric acid, ammonia and carbon source solution, and it discloses that nickel salt can use any one of nickel acetate, nickel oxalate, nickel sulfate and nickel nitrate;Manganese salt is selected from any one of manganese acetate, manganese oxalate, manganese sulfate and manganese nitrate;Lithium salt is selected from any one of lithium acetate, lithium oxalate, lithium carbonate and lithium nitrate;That is, it can not use nitrate, sulfate and other materials that need complex post-processing or will produce toxic gas as raw material, so as to avoid the above-mentioned post-processing problem, however, when using other raw materials such as acetate except the above-mentioned nitrate, the morphology of the prepared lithium nickel manganese oxide product is different, and the uniformity is poor, and the morphology will affect the material performance.

[0006] In summary, a synthesis method of lithium nickel manganese oxide positive material is needed to solve this problem. SUMMARY

[0007] The purpose of the present application is to provide a synthesis method of lithium nickel manganese oxide positive material to solve the problem of complex post-processing of nitrate raw material, poor product morphology after spraying of acetate raw material, and affect the performance.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a synthesis method of lithium nickel manganese oxide positive material, comprising the following specific steps:

[0009] S1: dissolving nickel acetate, manganese acetate and ammonium nitrate in deionized water to obtain a mixed solution;

[0010] S2: the mixed solution is spray dried to obtain mixed acetate of nickel and manganese;

[0011] S3: the mixed acetate is heat treated in oxygen atmosphere to obtain nickel manganese oxide precursor;

[0012] S4: the nickel manganese oxide precursor and lithium salt are mixed and heat treated in oxygen atmosphere to obtain lithium nickel manganese oxide positive material.

[0013] Preferably, in the above step S1, the total molar concentration of the mixed solution metal salt is 0.5-1.0mol / L.

[0014] Preferably, the above nickel acetate uses nickel acetate tetrahydrate, and the amount of manganese acetate tetrahydrate is determined according to the molar ratio of nickel and manganese in the prepared lithium nickel manganese oxide positive material;The amount of lithium salt is added according to the molar ratio of the total molar amount of nickel and manganese to the molar amount of lithium in the prepared lithium nickel manganese oxide positive material.

[0015] Preferably, in the above step S1, the concentration of ammonium nitrate is 0.1-0.5mol / L.

[0016] Preferably, in the step S2, the inlet temperature of the spray dryer is controlled at 280-400 DEG C, the sample pressure of the spray drying gas is 0.2-0.4 MPa, and the rotation speed of the peristaltic pump is 2-10 rpm.

[0017] Preferably, in the step S3, the heat treatment is performed in a tube furnace, the heat treatment temperature is 400-600 DEG C, and the heat treatment time is 6-12 h.

[0018] Preferably, in the step S4, the heat treatment is performed in a tube furnace, the heat treatment temperature is 750-950 DEG C, and the heat treatment time is 12-24 h.

[0019] Preferably, in the step S4, the lithium salt is selected from lithium acetate, lithium carbonate and lithium oxalate.

[0020] Preferably, the lithium nickel manganese oxide positive electrode material prepared by the synthesis method is used to prepare a coin battery in the following manner:

[0021] The prepared lithium nickel manganese oxide positive electrode material, conductive agent Super P and binder PVDF are mixed in a weight ratio of 8:1:1 to prepare a positive electrode slurry, which is coated on one side of an aluminum foil, and then dried to obtain a positive electrode sheet.

[0022] The coin battery is assembled in the order of a negative electrode shell, a lithium sheet, a separator, an electrolyte, the positive electrode sheet, a gasket, a spring and the negative electrode shell, wherein the electrolyte is LiPF6, the solvent volume ratio is EC:DMC=1:1, and the separator is a polyethylene porous film.

[0023] The test voltage is 3.5-4.95 V, the charging is performed in a constant current mode, the discharging is performed in a constant current mode, and the capacity test charging and discharging current is 0.1 C.

[0024] The test results are as follows: tap density 1.8-2.2 g / cm 3 , 0.1 C battery capacity 120-140 mAh / g, and 1 C cycle capacity retention rate 95±4% after 100 cycles.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. The synthesis method of the lithium nickel manganese oxide positive electrode material uses a spray drying method to prepare a precursor, which can realize atomic-level mixing of nickel and manganese, and can overcome the disadvantages of uneven precipitation and complex post-treatment of the reaction solution in the coprecipitation method.

[0027] 2. The synthesis method of the lithium nickel manganese oxide positive electrode material uses acetate as a precursor, which does not produce toxic gas during heat treatment, and does not need further treatment, and the process is more green and environmentally friendly.

[0028] 3. The synthesis method of the lithium nickel manganese oxide cathode material, wherein the easily decomposable ammonium nitrate is added before spray drying, and by controlling the spray drying temperature, the ammonium nitrate can be rapidly decomposed to produce nitrogen, water and oxygen during the spray drying process, so that the spray drying process becomes a process for producing porous spherical mixed acetate, and in the subsequent pre-calcination process in an oxygen atmosphere, the acetate is decomposed violently, and the gas is discharged from a large number of pores of the spray-prepared product, so that the spherical structure is not damaged, and the product sphericity and particle size uniformity are maintained.

[0029] 4. The synthesis method of the lithium nickel manganese oxide cathode material, wherein the ammonium ion complexation is beneficial to further improving the mixing uniformity of nickel and manganese atoms in the mixed solution, and the prepared cathode material has better performance.

[0030] 5. The synthesis method of the lithium nickel manganese oxide cathode material, wherein the concentration of the ammonium nitrate is controlled to be less than 5%, and the low-concentration ammonium nitrate aqueous solution does not have an explosion risk in the thermal decomposition process of the spray drying. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The XRD image of the sample prepared for the embodiment 1 of the application;

[0032] Figure 2 The scanning electron microscope (SEM) image of the sample prepared for the embodiment 1 of the application;

[0033] Figure 3 The scanning electron microscope (SEM) image of the sample prepared for the comparative example 1 of the application. DETAILED DESCRIPTION

[0034] A synthesis method of a lithium nickel manganese oxide cathode material, comprising the following specific steps:

[0035] S1: dissolving nickel acetate, manganese acetate and ammonium nitrate in deionized water to obtain a mixed solution, wherein the total molar concentration of the metal salts is preferably 0.5-1.0 mol / L, and the concentration of the ammonium nitrate is 0.1-0.5 mol / L;

[0036] S2: spray drying the mixed solution to prepare a mixed acetate of nickel and manganese, for reference, the inlet temperature of the spray drying is preferably controlled to be 280-400℃, the spray drying gas sampling pressure can be 0.2-0.4 MPa, and the peristaltic pump speed can be 2-10 rpm;

[0037] S3: heat treating the mixed acetate in an oxygen atmosphere to obtain a nickel manganese oxide precursor, wherein the heat treatment temperature is preferably 400-600℃, and the heat treatment time is preferably 6-12 h;

[0038] S4: the nickel-manganese oxide precursor and the lithium salt are mixed, and then heat-treated in an oxygen atmosphere, preferably at a temperature of 750-950°C for 12-24h, to obtain the lithium nickel-manganese oxide positive electrode material.

[0039] In a preferred embodiment, the nickel acetate salt is nickel acetate tetrahydrate, and the manganese acetate salt is manganese acetate tetrahydrate, and the amount of each is determined according to the molar ratio of nickel to manganese in the lithium nickel-manganese oxide positive electrode material to be prepared; the amount of lithium salt is determined according to the molar ratio of the total amount of nickel and manganese to lithium in the lithium nickel-manganese oxide positive electrode material to be prepared, and is added in a sufficient amount or in excess.

[0040] The heat treatment can be performed in a tube furnace.

[0041] The lithium salt in step S4 can be further selected from one or more of lithium acetate, lithium carbonate, and lithium oxalate, and is preferably lithium carbonate.

[0042] Example 1

[0043] 110g of manganese acetate tetrahydrate, 37.3g of nickel acetate tetrahydrate, and 14.4g of ammonium nitrate were weighed out and added to 600ml of deionized water to form a mixed solution, which was spray dried to obtain a nickel-manganese mixed acetate salt. The spray drying process was performed at a peristaltic pump feeding speed of 5rpm, an air inlet temperature of 300°C, and a feeding pressure of 0.4MPa. The sample obtained by spray drying was heat-treated in a tube furnace in an oxygen atmosphere at 500°C for 8h to obtain a nickel-manganese oxide precursor, which was mixed with lithium carbonate at a metal molar ratio of 1:1.05 and heat-treated in a tube furnace in an oxygen atmosphere at 850°C for 10h to obtain a lithium nickel-manganese oxide positive electrode material. The XRD pattern of the sample is shown in FIG. 1. Figure 1 , which is spinel LiNi 0.5 Mn 1.5 O4, and has high phase purity and good crystallinity, as shown in FIG. 1. Figure 2 The microstructure of the lithium nickel-manganese oxide positive electrode material obtained in this example is spherical, and a sample with good sphericity has a higher tap density and better electrochemical performance.

[0044] Comparative Example 1

[0045] This example was performed according to Example 1, except that ammonium nitrate was not added during preparation of the mixed solution. The SEM of the sample obtained in this example is shown in FIG. 2. Figure 3 The sample has an irregular shape and a large difference in particle size.

[0046] Example 2

[0047] This example was performed according to Example 1, except that the amount of manganese acetate tetrahydrate was 55g and the amount of nickel acetate tetrahydrate was 18.7g, i.e., the metal ion concentration of the spray precursor solution was 0.5mol / L.

[0048] Example 3

[0049] This example is performed according to Example 1, except that the amount of ammonium nitrate is changed to 4.8 g, i.e. the concentration is 0.1 mol / L.

[0050] Example 4

[0051] This example is performed according to Example 1, except that the amount of ammonium nitrate is changed to 24 g, i.e. the concentration is 0.5 mol / L.

[0052] Example 5

[0053] This example is performed according to Example 1, except that the temperature of the inlet of the spray dryer is set to 400°C.

[0054] Example 6

[0055] This example is performed according to Example 1, except that the sample pressure of the inlet of the spray dryer is set to 0.2 MPa.

[0056] Example 7

[0057] This example is performed according to Example 1, except that the sample speed of the peristaltic pump is adjusted to 10 rpm.

[0058] Example 8

[0059] This example is performed according to Example 1, except that the temperature of the first heat treatment is adjusted to 600°C.

[0060] Example 9

[0061] This example is performed according to Example 1, except that the time of the first heat treatment is adjusted to 12 h.

[0062] Example 10

[0063] This example is performed according to Example 1, except that the temperature of the second heat treatment is adjusted to 750°C.

[0064] Example 11

[0065] This example is performed according to Example 1, except that the time of the second heat treatment is adjusted to 24 h.

[0066] The nickel-manganese lithium acid lithium positive electrode material prepared in each of the above examples and comparative examples is used to make a button cell by the following method:

[0067] The prepared nickel-manganese lithium acid lithium positive electrode material, conductive agent Super P and binder PVDF are mixed in a weight ratio of 8:1:1 to prepare a positive electrode slurry, which is coated on one side of an aluminum foil and dried to prepare a positive electrode sheet.

[0068] Assembled the button cell in the order of negative shell, lithium sheet, diaphragm, electrolyte, positive sheet, gasket, spring and positive shell, wherein the electrolyte is LiPF6, the volume ratio of the solvent is EC:DMC=1:1, and the diaphragm is a polyethylene porous film;

[0069] The test voltage is 3.5-4.95V, the charging is performed by using a constant current process, then the discharging is performed by using a constant current process, and the capacity test charging and discharging current is 0.1C.

[0070] The sample tap density, battery capacity test and cycle stability test results of each embodiment and the comparative example are compared as shown in the following table:

[0071]

[0072] The test results of each embodiment are as follows: the tap density is 1.8-2.2g / cm 3 , the 0.1C battery capacity is 120-140mAh / g, and the 1C cycle 100 cycle capacity retention rate is 95±4%;

[0073] In addition, compared with the embodiment 1, the comparative example 1 only lacks 0.3mol / L of ammonium nitrate in the mixed solution before spray drying, the tap density in the test results of the embodiment 1 is 2.2g / cm 3 , the 0.1C discharge specific capacity of the prepared button cell is 138mAh / g, the 1C cycle 100 cycle capacity retention rate is 98.5%, and the tap density in the test results of the comparative example 1 is 1.5g / cm 3 , the 0.1C discharge specific capacity of the prepared button cell is 104mAh / g, and the 1C cycle 100 cycle capacity retention rate is 62.1%.

[0074] In addition, since the main raw material in the application is manganese acetate and nickel acetate, the complicated post-treatment process can be effectively avoided, the production cost is reduced, and therefore the application is more suitable for mass production.

[0075] The above is only a preferred embodiment of the application, but the protection scope of the application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be limited by the protection scope defined by the claims.

[0076] The details not described in the application are the known technology of the person skilled in the art.

Claims

1. A method for synthesizing a lithium nickel manganese oxide cathode material, characterized in that, The method comprises the following specific steps: S1: dissolving nickel acetate, manganese acetate and ammonium nitrate in deionized water to obtain a mixed solution, the total molar concentration of metal salts in the mixed solution is 0.5-1.0 mol / L, and the concentration of ammonium nitrate is 0.1-0.5 mol / L; S2: the mixed solution is spray dried to obtain mixed acetate of nickel and manganese, the temperature of the inlet of the spray dryer is controlled to be 280-400 DEG C, the sampling pressure of the spray drying gas is 0.2-0.4 MPa, and the rotation speed of the peristaltic pump is 2-10 rpm; S3: the mixed acetate is heat-treated in an oxygen atmosphere to obtain a nickel-manganese oxide precursor; S4: the nickel-manganese oxide precursor and a lithium salt are mixed and then heat-treated in an oxygen atmosphere to obtain a lithium nickel-manganese oxide positive electrode material. 2.The method of claim 1, wherein: The nickel acetate is nickel acetate tetrahydrate, the manganese acetate is manganese acetate tetrahydrate, and the dosage ratio of the two is determined according to the molar ratio of nickel to manganese in the lithium nickel-manganese oxide positive electrode material to be prepared; the dosage of the lithium salt is determined according to the molar ratio of the total molar amount of nickel and manganese to the molar amount of lithium in the lithium nickel-manganese oxide positive electrode material to be prepared, and the lithium salt is added in a sufficient amount or an excess amount. 3.The method of claim 1, wherein: The heat treatment in step S3 is performed in a tube furnace, the heat treatment temperature is 400-600 DEG C, and the heat treatment time is 6-12 h. 4.The method of claim 1, wherein: The heat treatment in step S4 is performed in a tube furnace, the heat treatment temperature is 750-950 DEG C, and the heat treatment time is 12-24 h. 5.The method of claim 1, wherein the method further comprises: adding a lithium source to the mixture; and heating the mixture to a temperature of 700-800 ℃ for 10-20 hours. In step S4, the lithium salt is selected from lithium acetate, lithium carbonate and lithium oxalate.

6. The lithium nickel manganese oxide cathode material according to any one of claims 1 to 5, characterized in that, The tap density of the nickel-manganese lithium acid cathode material is 1.8-2.2 g / cm 3 ; The lithium nickel-manganese oxide positive electrode material is tested by the following method to form a button cell: The prepared lithium nickel-manganese oxide positive electrode material, a conductive agent Super P and a binder PVDF are mixed according to a weight ratio of 8:1:1 to form a positive electrode slurry, which is coated on one side of an aluminum foil, and then the positive electrode slurry is dried to obtain a positive electrode sheet; The button cell is assembled in the order of a negative electrode shell, a lithium sheet, a separator, an electrolyte, the positive electrode sheet, a gasket, an elastic sheet and the positive electrode shell, wherein the electrolyte is LiPF6, the volume ratio of the solvent is EC:DMC=1:1, and the separator is a polyethylene porous film; The test voltage is 3.5-4.95 V, the button cell is charged by a constant current process and then discharged by a constant current process, and the capacity test charging and discharging current is 0.1 C; Test results are 0.1 C battery capacity 120-140 mAh / g, 1 C cycle 100 cycles capacity retention 95 4%.

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