Preparation method of modified manganese hydroxide, product and application thereof

文档序号：202923 发布日期：2021-11-05 浏览：7次中文

阅读说明：本技术 一种改性氢氧化锰的制备方法及其制品和应用 (Preparation method of modified manganese hydroxide, product and application thereof ) 是由李诗文徐健方刚谭崇梅钱庆仁农庭峰闵婷婷蒋凯沈家华于 2021-07-30 设计创作，主要内容包括：本发明提供了一种改性氢氧化锰的制备方法及其制品和应用,在锰的可溶性盐溶液中掺杂了含A元素的可溶性盐溶液,即在氢氧化锰的基础上掺杂A元素进行改性,A元素与Mn均匀沉淀,合成了雪花状片层结构的改性颗粒,改性颗粒产品晶相均一,杂质含量低。其中,掺杂的A元素可在氢氧化锰颗粒表面形成致密的包覆层,阻碍了氢氧化锰与空气中的氧气接触,进而避免了氢氧化锰被氧化导致相变,保护了氢氧化锰的晶体结构。由此解决了目前的制备方法存在杂质含量过高、洗涤效率低下且晶体结构被破坏的问题。(The invention provides a preparation method of modified manganese hydroxide, a product and application thereof, wherein soluble salt solution containing an element A is doped in soluble salt solution of manganese, namely, the element A is doped on the basis of the manganese hydroxide for modification, the element A and Mn are uniformly precipitated, modified particles with snowflake lamellar structures are synthesized, and the modified particles have uniform crystal phase and low impurity content. The doped element A can form a compact coating layer on the surface of the manganese hydroxide particles, so that the manganese hydroxide is prevented from contacting oxygen in the air, the phase change caused by oxidation of the manganese hydroxide is avoided, and the crystal structure of the manganese hydroxide is protected. Therefore, the problems of high impurity content, low washing efficiency and damaged crystal structure in the existing preparation method are solved.)

1. The preparation method of the modified manganese hydroxide is characterized by comprising the following steps:

s1, adding soluble salt containing an element A into soluble salt of manganese, and mixing to obtain a mixed manganese A solution, wherein the element A is at least one of yttrium, nickel, cobalt, magnesium, titanium, niobium, zirconium, bismuth, boron, antimony, cerium, aluminum, molybdenum and lanthanum; the molar ratio of the A element to Mn is x: (1-x), wherein x is more than 0 and less than or equal to 0.3;

s2, adding a surfactant solvent into the reaction kettle, stirring, and simultaneously adding the mixed manganese A solution obtained in the step S1 and a precipitator for reaction to obtain slurry;

s3, adjusting the pH value of the slurry obtained in the step S2 to 8-13, aging, washing and filtering to obtain a primary product;

s4, drying the primary product obtained in the step S3 to obtain the modified manganese hydroxide with the snowflake lamellar structure.

2. The method for preparing modified manganese hydroxide according to claim 1, wherein the particle structure of the modified manganese hydroxide is a snowflake lamellar single crystal structure.

3. The method for preparing modified manganese hydroxide according to claim 1, wherein in step S1, the concentration of manganese ions in the soluble salt solution of manganese is 1-4 mol/L.

4. The method for preparing modified manganese hydroxide according to claim 1 or 3, wherein said soluble salt of manganese is at least one of chloride, sulfate, nitrate, and acetate; the soluble salt solution containing the element A is at least one of chloride salt, sulfate, nitrate and acetate.

5. The method for preparing modified manganese hydroxide according to claim 1, wherein in step S2, the surfactant solution is added into deionized water, the mixture is stirred at a stirring speed of 200-1200 rpm for 30-100 min, and then the mixed manganese a solution and the precipitant are added at a feeding flow rate of 1-200 mL/min for reaction, so as to obtain slurry.

6. The method for preparing modified manganese hydroxide according to claim 1 or 5, wherein the surfactant is at least one of glycine, alanine, leucine; the precipitant is at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

7. The method for preparing modified manganese hydroxide according to claim 6, wherein the concentration of the surfactant solution is 1-50 g/L; the concentration of the precipitant is 0.5-6 mol/L.

8. The method for preparing modified manganese hydroxide according to claim 1, wherein in step S3, a pH adjusting agent is added at a feed flow rate of 1-200 mL/min to adjust the pH of the slurry to 8-13, and then the slurry is aged for 4-25 h, discharged, washed, and filtered to obtain an initial product.

9. The method for preparing modified manganese hydroxide according to claim 1, wherein in step S4, the drying temperature is 60-120 ℃ and the drying time is 2-6 h.

10. The modified manganese hydroxide prepared by the preparation method of the modified manganese hydroxide according to any one of claims 1 to 9, wherein the chemical formula of the modified manganese hydroxide is [ A ]_xMn_(1-x)](OH)₂，0<x≤0.3。

11. The modified manganese hydroxide according to claim 10, wherein the median particle diameter D50 of the manganese hydroxide is 3 to 30 μm.

12. A positive electrode material comprising the lithium manganate produced from the modified manganese hydroxide according to claim 10 or 11 as a raw material.

13. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, and a separator spaced between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises the positive electrode material of claim 12.

Technical Field

The invention relates to the technical field of precursors of positive active materials, in particular to a preparation method of modified manganese hydroxide, a product and application thereof.

Background

Currently, lithium manganate sold in the market is mainly prepared by taking manganese dioxide (EMD) or manganous manganic oxide as a manganese source for electrolysis. The lithium manganate prepared by adopting electrolytic manganese dioxide as a raw material has poor high-temperature cycle performance and storage performance due to the uncontrollable impurities and morphology of EMD. While the problems of impurities and controllable appearance of manganese source materials are solved by using the trimanganese tetroxide as the raw material, the manganese element in the trimanganese tetroxide is in the valence states of +2 and +3, the valence state of the manganese element in the lithium manganate is +3, and the lithium element in the lithium carbonate can be embedded unevenly in the process of synthesizing the lithium manganate by using the trimanganese tetroxide as the raw material.

Based on the defects, the method for preparing the lithium manganate cathode material by using the manganese hydroxide as the raw material is also provided at present, and the problem of uneven valence state of the manganese element cannot exist in the preparation of the raw material. At present, the preparation method of manganese hydroxide is mainly prepared by reacting soluble manganese salt with sodium hydroxide, potassium hydroxide or ammonia water (ammonium monohydrate).

Chinese patent document (CN201110280431.4) mentions that spherical manganese hydroxide is continuously precipitated by ammonia water under the protection of nitrogen by using a manganese metal sheet and sulfuric acid to obtain a manganese sulfate solution, the precipitate is slurried by a stoichiometric lithium hydroxide solution and then is added into a high-pressure reaction kettle, the temperature and the oxygen partial pressure are controlled to react for a certain time so as to obtain pure-phase manganese dioxide, then carbon dioxide is introduced to react for a certain time so that lithium carbonate is uniformly precipitated on the surface of the manganese dioxide, the reaction is finished and then the lithium carbonate is filtered, and the precipitate is subjected to microwave drying, sintering and crushing classification to obtain the spherical lithium manganate positive electrode material with high tap density. However, the method is complex, the consistency of the product is low, and the method is not suitable for industrial production.

Chinese patent document (CN201110344396.8) proposes a preparation method of a spherical manganese hydroxide precursor of lithium manganate with good sphericity and strong oxidation resistance. The method is characterized in that the manganese hydroxide is prevented from being oxidized by atmosphere protection and adding a reducing agent in the synthesis process.

Chinese patent document (CN201810478501.9) mentions a new method for recovering manganese from titanium white waste acid, which extracts manganese from the waste acid by controlling the neutralization process of the waste acid and lime or carbide slag and by chemical oxidation and precipitation, so that the waste residue or waste water does not contain residual manganese, thereby achieving the purpose of protecting the environment.

However, the technical solutions involved in the above patents are based on the reaction of manganese sulfate solution with ammonia water or sodium hydroxide, and the hydrolysis into manganese hydroxide, all of which have the following problems: 1) in the synthesis process, inert gas atmosphere protection is required to be provided or a reducing agent is required to be added to prevent manganese hydroxide from being oxidized, so that the production cost is extremely high; 2) a large amount of sodium sulfate impurities are occluded in the synthesis process, the washing process is usually carried out in an inert atmosphere, the washing is difficult, and the performance of the lithium manganate anode material synthesized subsequently is easily influenced; 3) the obtained product is also easily oxidized by oxygen in the air when placed in the air, and phase change occurs, so that the defects of non-uniform crystal phase and disordered crystal structure of the product are caused.

In view of the above, it is necessary to provide a technical solution to the above problems.

Disclosure of Invention

One of the objects of the present invention is: provides a preparation method of modified manganese hydroxide, which solves the problems of high impurity content, low washing efficiency and damaged crystal structure in the existing preparation method.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of modified manganese hydroxide comprises the following steps:

s1, adding soluble salt containing an element A into soluble salt of manganese, and mixing to obtain a mixed solution A, wherein the element A is at least one of yttrium (Y), nickel (Ni), cobalt (Co), magnesium (Mg), titanium (Ti), niobium (Nb), zirconium (Zr), bismuth (Bi), boron (B), antimony (Sb), cerium (Ce), aluminum (Al), molybdenum (Mo) and lanthanum (La); the molar ratio of the A element to Mn is x: (1-x), wherein x is more than 0 and less than or equal to 0.3;

s2, adding a surfactant solvent into the reaction kettle, stirring, and simultaneously adding the mixed solution A obtained in the step S1 and a precipitator for reaction to obtain slurry;

s3, adjusting the pH value of the slurry obtained in the step S2 to 8-13, aging, washing and filtering to obtain a primary product;

s4, drying the primary product obtained in the step S3 to obtain the snowflake lamellar modified manganese hydroxide.

Preferably, the particle structure of the modified manganese hydroxide is a snowflake lamellar single crystal structure.

Preferably, in the step S1, the concentration of manganese ions in the soluble salt solution of manganese is 1-4 mol/L.

Preferably, the soluble salt of manganese is at least one of chloride salt, sulfate, nitrate and acetate; the soluble salt solution containing the element A is at least one of chloride salt, sulfate, nitrate and acetate.

Preferably, in step S2, the surfactant solution is added into deionized water, stirred at a stirring speed of 200-1200 rpm for 30-100 min, and then the mixed manganese a solution and the precipitant are added at a feeding flow rate of 1-200 mL/min to react, so as to obtain a slurry. More preferably, the stirring speed is 500-1000 rpm, the stirring time is 40-80 min, and the feeding flow rate of the mixed manganese A solution is 5-100 mL/min. Preferably, the stirring speed is 500-800 rpm, the stirring time is 40-60 min, and the feeding flow rate of the mixed manganese A solution is 10-50 mL/min. More preferably, the feeding flow rate of the mixed manganese A solution is 10-20 mL/min.

Wherein, the stirring speed in the step S2 is controlled within the above range, the high molecular surfactant is more uniformly dispersible, and the manganese a mixed solution is added at the stirring speed, so that Mn and a element a can be more uniformly dispersed and precipitated, so that Mn can better react with the precipitant to generate manganese hydroxide, and the element a is doped, thereby forming a dense coating layer on the surface of manganese hydroxide particles, preventing the manganese hydroxide from contacting oxygen in the air, and further obtaining the modified manganese hydroxide doped with the element a with uniform crystal phase and low impurity content.

Preferably, the surfactant is at least one of glycine, alanine and leucine; the precipitant is at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

Preferably, the concentration of the surfactant solution is 1-50 g/L; the concentration of the precipitant is 0.5-6 mol/L. More preferably, the concentration of the surfactant solution is 1-10 g/L; the concentration of the precipitant is 1-6 mol/L.

Preferably, in step S3, a pH regulator is added at a feed flow rate of 1-200 mL/min to regulate the pH value of the slurry to 8-13, and then the slurry is aged for 4-25 h, discharged, washed, and filtered to obtain a primary product. More preferably, the feeding flow rate of the pH regulator is 5-100 mL/min, the pH value is 9-11, and the aging time is 4-18 h. Preferably, the feeding flow rate of the pH regulator is 10-50 mL/min, the pH value is 9-11, and the aging time is 4-12 h. Further preferably, the feeding flow rate of the pH regulator is 10-20 mL/min, the pH value is 9-11, and the aging time is 6-8 h. Wherein the pH regulator can be at least one of sodium hydroxide, potassium hydroxide, ammonia water, sodium carbonate and sodium bicarbonate. Preferably, the pH regulator is ammonia water to avoid secondary pollution. Because the reaction of the manganese A mixed solution in the slurry and the precipitator is uniform and controllable, the generated manganese hydroxide has a complete crystal lattice structure, and impurities in the reaction process are basically blocked outside the manganese hydroxide crystal lattice structure by the coating of the element A, so that the washing difficulty is greatly reduced, and the washing efficiency and the washing effect are improved.

Preferably, in step S4, the drying temperature may be 60 to 70 ℃, 70 to 80 ℃, 80 to 90 ℃, 90 to 100 ℃, or 100 to 120 ℃, and the drying time may be 2 to 4 hours, 4 to 6 hours. More preferably, the drying temperature is 80-90 ℃, 90-100 ℃, or 100-120 ℃, and the drying time is 2-4 h. More preferably, the drying temperature is 100 ℃ and the drying time is 3 h.

The second object of the present invention is to provide a modified manganese hydroxide prepared by the method for preparing modified manganese hydroxide according to any one of the above formulas, wherein the modified manganese hydroxide has a chemical formula of [ A_xMn_(1-x)](OH)₂，0<x is less than or equal to 0.3. Wherein, the value range of x can be 0<x≤0.1，0.1<x≤0.2，0.2<x is less than or equal to 0.3. The specific value of x is related to the molar ratio of A to Mn in the adopted raw materials, namely the ratio of the molar mass of the element A in the soluble salt containing the element A to the molar mass of Mn in the soluble salt of manganese is considered to be x/(1-x). The element A may be yttrium (Y), nickel (Ni), cobalt (Co), magnesium (Mg), titanium (Ti), niobium (Nb), zirconium (Zr), bismuth (Bi), boron (B), antimony (Sb), cerium (Ce), aluminum (Al), molybdenum (Mo) and lanthanum (La) in various combinations, and the molar amount of the element A is the total molar amount of the various combinations. When the element A is a combination of two elements, the element A has a better effect compared with single element doping modification under a proper quality, and the synergistic effect of the two elements doped together is stronger.

Preferably, the median particle diameter D50 of the manganese hydroxide can be 3-5 μm, 5-10 μm, 10-15 μm, 15-20 μm, 20-25 μm, 25-30 μm. More preferably, the manganese hydroxide has a median particle diameter D50 of 5-10 μm, 10-15 μm, 15-20 μm, 20-25 μm. The particle size of the modified manganese hydroxide particles obtained by the preparation method is small, and when the modified manganese hydroxide particles and a lithium source are prepared into the lithium manganate cathode material, the modified manganese hydroxide particles are more favorable for diffusion and migration of lithium elements, and can also reduce the sintering temperature, reduce the sintering time and improve the sintering efficiency. In addition, because the surface of the manganese hydroxide is also doped with the element A, the element A can promote the grain growth in the lithium manganate synthesis process and simultaneously inhibit the appearance of an octahedral spinel structure.

The invention also aims to provide a positive electrode material which comprises the lithium manganate prepared by taking the modified manganese hydroxide as a raw material. And sintering the modified manganese hydroxide and a lithium source together to prepare the lithium manganate cathode material.

The invention also provides a lithium ion battery, which comprises a positive pole piece, a negative pole piece and a separation film which is arranged between the positive pole piece and the negative pole piece, wherein the positive pole piece comprises the positive pole material.

The positive pole piece comprises a positive current collector and a positive active substance layer coated on at least one surface of the positive current collector, and the lithium manganate positive material is made into slurry and coated on the surface of the positive current collector to form the positive active substance layer. The positive electrode current collector is generally a structure or part that collects current, and may be any of various materials suitable for use as a positive electrode current collector of a lithium ion battery in the art, for example, the positive electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, an aluminum foil, and the like.

The negative pole piece comprises a negative current collector and a negative active material layer coated on at least one surface of the negative current collector. The negative electrode active material layer may include, but is not limited to, one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate, or other metals capable of forming an alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy. While the negative electrode current collector is generally a structure or part that collects current, the negative electrode current collector may be any material suitable for use as a negative electrode current collector of a lithium ion battery in the art, for example, the negative electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, a copper foil, and the like.

And the separator may be any material suitable for a lithium ion battery separator in the art, and for example, may be one or a combination of more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like.

Compared with the prior art, the invention has the beneficial effects that:

1) according to the preparation method provided by the invention, the soluble salt solution containing the element A is doped in the soluble salt solution of manganese, namely the element A is doped on the basis of manganese hydroxide for modification, the element A and Mn are uniformly precipitated, modified particles with snowflake lamellar structures are synthesized, and the modified particle products are uniform in crystalline phase and low in impurity content. The doped element A can form a compact coating layer on the surface of the manganese hydroxide particles, so that the manganese hydroxide is prevented from contacting oxygen in the air, the phase change caused by oxidation of the manganese hydroxide is avoided, and the crystal structure of the manganese hydroxide is protected. Therefore, the problems of high impurity content, low washing efficiency and damaged crystal structure in the existing preparation method are solved.

2) The preparation method provided by the invention has the advantages that the protection of inert atmosphere is not needed in the reaction process and the washing process, the addition of a reducing agent is not needed, the vacuum drying is not needed, the preparation process is simple, and the production cost is greatly reduced.

3) In addition, the surface of the manganese hydroxide prepared by the method is doped with the element A, so that the element A can promote the growth of lithium manganate crystal grains in the process of synthesizing the lithium manganate positive active material, and simultaneously inhibit the occurrence of the lithium manganate with an octahedral spinel structure, thereby ensuring the electrochemical performance of the lithium manganate positive active material.

Drawings

FIG. 1 is an electron micrograph of a modified manganese hydroxide according to example 1 of the present invention.

FIG. 2 is an enlarged electron microscope image of the modified manganese hydroxide of FIG. 1.

Detailed Description

In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantages will be described in further detail below with reference to the following detailed description and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

A preparation method of modified manganese hydroxide comprises the following steps:

(1) preparing raw materials:

preparing a manganese A mixed solution: adding soluble salt containing an element A into soluble salt of manganese, and mixing to obtain a mixed solution A, wherein the element A is at least one of yttrium (Y), nickel (Ni), cobalt (Co), magnesium (Mg), titanium (Ti), niobium (Nb), zirconium (Zr), bismuth (Bi), boron (B), antimony (Sb), cerium (Ce), aluminum (Al), molybdenum (Mo) and lanthanum (La); the molar ratio of the A element to Mn is 2: 8. the preparation method comprises the following specific steps: 2543.5g of MnSO are weighed first₄·H₂O, dissolved in 4500g of deionized water at about 50 ℃, 28.91g of NiSO was weighed₄·7H₂O and 46.59g YSO₄·8H₂And adding O into the prepared manganese sulfate solution, and fixing the volume to 5L to obtain a manganese A mixed solution.

Preparing a high molecular surfactant solution: weighing 2g of high molecular surfactant glycine, and dissolving with 3L of deionized water to obtain a high molecular surfactant solution with the concentration of 0.7 g/L.

preparing a pH regulator: 700g of 25% ammonia water solution is weighed, and the volume is fixed to 2L, so that 10M ammonia water solution is obtained.

Preparing a precipitator: 1200g of sodium hydroxide solid is weighed and the volume is adjusted to 5L, thus obtaining 6M sodium hydroxide solution.

(2) Feeding and reacting: firstly, adding the prepared macromolecular surfactant solution into a reaction kettle, and stirring for 40min at the stirring speed of 800 rpm; then, the prepared manganese A mixed solution and the precipitant sodium hydroxide solution are added simultaneously by a peristaltic pump at a feeding rate of 10mL/min, and the materials are fed for 8.4 h.

(3) Aging and washing of slurry: after the feeding is finished, adding a prepared pH regulator ammonia water solution by using a peristaltic pump at a rate of 20mL/min, adjusting the pH to 10, keeping the stirring speed at 800rpm, aging for 6h, and then performing centrifugal filtration on the slurry by using a centrifugal machine with the model number of YLT-1200 to obtain a filter cake. Then, the slurry was washed 1 time with 6g/L sodium hydroxide solution at 35 ℃ and 1 time with pure water, followed by dehydration.

(4) Drying: and (3) putting the filter cake into an electric heating forced air drier (model 101-0ABS), drying at constant temperature of 100 ℃ for 3h, and taking out to obtain the snowflake lamellar modified manganese hydroxide.

The molecular formula of the snowflake lamellar modified manganese hydroxide prepared by the embodiment is [ Ni ]_0.1Y_0.1Mn_0.8](OH)₂The precursor particles of the modified manganese hydroxide consist of snowflake lamellar monocrystal structure particles. The median particle diameter D50 of the modified manganese hydroxide is 3-30 μm.

Example 2

Different from the example 1, the preparation of the manganese-aluminum mixed solution is carried out, and the mol (a) of the soluble salt containing the element a and the soluble salt of manganese: mol (mn) ═ 3: 7, the molecular formula of the modified manganese hydroxide prepared in this example is [ Ni ]_0.1 Y_0.2Mn_0.7](OH)₂。