CN114684871A - Method for reducing sulfur content of sulfate system lithium ion battery positive electrode material precursor - Google Patents

Method for reducing sulfur content of sulfate system lithium ion battery positive electrode material precursor Download PDF

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CN114684871A
CN114684871A CN202110255246.3A CN202110255246A CN114684871A CN 114684871 A CN114684871 A CN 114684871A CN 202110255246 A CN202110255246 A CN 202110255246A CN 114684871 A CN114684871 A CN 114684871A
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sulfur content
mother liquor
reaction
precursor
reducing
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刘飞
陈勃涛
张�林
王孝钶
朱卫泉
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Tianjin Guoan Mengguli New Material Technology Co ltd
RiseSun MGL New Energy Technology Co Ltd
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Tianjin Guoan Mengguli New Material Technology Co ltd
CITIC Guoan Mengguli Power Technology Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/006—Compounds containing, besides nickel, two or more other elements, with the exception of oxygen or hydrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer

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Abstract

The invention provides a method for reducing sulfur content of a precursor of a lithium ion battery anode material in a sulfate system. The method for reducing the sulfur content is simple, simultaneously can keep a reaction system balanced in the replacement process, effectively avoids adverse effects on the morphology of the precursor, and the precursor prepared by the method has the advantages of low sulfur content, high tap density, good particle sphericity of the precursor and uniform particle size.

Description

Method for reducing sulfur content of sulfate system lithium ion battery positive electrode material precursor
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a precursor of a sulfate system in a lithium ion battery anode material and a preparation method thereof.
Background
With the continuous development of global economy, the consumption of traditional non-renewable resources is serious, and at present, the nation puts forward higher requirements on the use of energy sources, so that the energy source use efficiency is required to be improved, and the purposes of energy conservation and emission reduction are achieved. Therefore, the application of new energy field has been promoted to the national strategic level. The lithium ion battery is used as a secondary storage battery with the best comprehensive performance at present, and is widely applied to a plurality of fields of 3C products, electric automobiles, electric bicycles, energy storage and the like due to the characteristics of high specific energy, long cycle life, good safety and the like.
The anode material is used as a key material of the lithium ion battery, and the performance of the battery is determined to a great extent. Common lithium ion battery materials include lithium cobaltate, lithium manganate, lithium iron sulfate and ternary materials. The ternary material has the advantages of high energy density, cycle performance, safety performance and the like, and becomes a mainstream product in the lithium ion battery industry.
The ternary precursor is the most critical material for the performance of the anode of the lithium ion battery material, and the quality of the precursor directly influences the performance of the anode material. At present, sulfate is used as a main metal raw material of the ternary precursor, a coprecipitation method is adopted, nickel salt, cobalt salt and manganese salt are prepared into salt solution according to a certain proportion, a metal hydroxide system or a metal carbonate system precursor is formed under the action of a precipitator and a complexing agent, and a qualified product is obtained through processes of washing, filtering, drying and the like. During the coprecipitation reaction, sulfate radicals are present in the mother liquor mainly in the form of sodium sulfate. A large amount of sulfate radicals are adsorbed on the surface or inside of the crystal, and washing with pure water is required to reduce the sulfur content. Partial sulfate radicals remaining in the crystals become impurities in the positive electrode material, and the capacity and the cycle performance of the positive electrode material are affected, so that the overall performance of the battery is reduced. How to reduce the sulfur content in the precursor product becomes a problem to be solved urgently by the ternary precursor.
Chinese patent CN 110817975 a discloses a method for reducing the content of sulfate radicals in a precursor by using pure water to replace mother liquor in a coprecipitation reaction process. The method can relatively reduce the sulfate radical content in the precursor, but the adoption of pure water to replace the mother liquor can cause the drastic changes of the ammonia, metal ammonia complex ions and hydroxyl radical concentration in the mother liquor, can destroy the chemical balance of a coprecipitation reaction system in a reaction kettle, and can generate adverse effects on the crystallization and growth of precursor particles. Therefore, it is necessary to reduce the sulfur content in the ternary precursor while maintaining the balance of the original coprecipitation reaction system to promote crystallization and growth of the precursor particles.
Disclosure of Invention
Based on the above technical background, the present inventors have made a keen search and, as a result, have found that: the mother liquor in the reaction kettle is replaced by the sodium sulfate-removed mother liquor, so that the consumption of pure water can be reduced, the system can be kept balanced in the replacement process, and adverse effects on the appearance of the prepared precursor are avoided.
One aspect of the present invention provides a method for reducing sulfur content in a precursor of a sulfate-based lithium ion battery positive electrode material, comprising the steps of:
step 1, adding a metal salt solution, a precipitator and a complexing agent into a reaction kettle for reaction;
step 2, pumping out the mother liquor in the reaction kettle, removing sodium sulfate, and adding the mother liquor with the sodium sulfate removed into the reaction kettle for reaction;
and 3, after the reaction is finished, carrying out post-treatment.
The second aspect of the present invention provides a low sulfur content sulfate system lithium ion battery positive electrode material precursor prepared by the preparation method according to the first aspect of the present invention.
The method for reducing the sulfur content of the sulfate system lithium ion battery positive electrode material precursor and the low-sulfur-content precursor prepared by the method have the following advantages:
(1) the method for reducing the sulfur content is simple, and the sulfur content of the prepared ternary precursor can be greatly reduced;
(2) the ternary precursor prepared by the method for reducing the sulfur content has the advantages of low sulfur content, high tap density, good particle sphericity and uniform particle size.
Drawings
FIG. 1 shows a scanning electron micrograph of a low sulfur precursor prepared in example 1 of the present invention;
FIG. 2 shows an enlarged scanning electron micrograph of a low sulfur precursor prepared in example 1 of the present invention.
Detailed Description
The present invention will be described in detail below, and features and advantages of the present invention will become more apparent and apparent with reference to the following description.
A first aspect of the present invention provides a method for reducing sulfur content in a precursor of a positive electrode material for a sulfate-based lithium ion battery, the method comprising the steps of:
step 1, adding a metal salt solution, a precipitator and a complexing agent into a reaction kettle for reaction;
step 2, pumping out the mother liquor in the reaction kettle, removing sodium sulfate, and adding the mother liquor with the sodium sulfate removed into the reaction kettle for reaction;
and 3, after the reaction is finished, carrying out post-treatment.
This step is specifically described and illustrated below.
Step 1, adding a metal salt solution, a precipitator and a complexing agent into a reaction kettle for reaction.
In step 1 of the present invention, a metal salt solution is prepared by dissolving a nickel-containing sulfate, a manganese-containing sulfate and a cobalt-containing sulfate in water. The concentration of the metal salt solution is 0.5-10 mol/L, preferably 1-5 mol/L, and more preferably 2-3 mol/L.
The concentration of the metal salt solution can influence the morphology and the particle size distribution of the finally prepared precursor particles, and the precursor prepared by the salt solution with the concentration has better sphericity and more uniform particle size.
The molar ratio of nickel element, cobalt element and manganese element in the metal salt solution is (0-20): (0-5) 1, preferably the molar ratio is (0.5-15): (1-2): 1, and the molar ratio is more preferably (1-10): 1:1.
The addition of the metal salt solution, the precipitant and the complexing agent is preferably carried out continuously. The feeding speed ratio of the metal salt solution, the precipitator and the complexing agent is (0.5-5): 1:1, preferably (1-3): 1:1, and more preferably (1-2): 1:1.
Taking a 5L reaction kettle as an example, the feeding speed of the metal salt solution is 1-30 ml/min, preferably 5-20 ml/min, and more preferably 10 ml/min.
The feeding speed of the precipitant is 1-20 ml/min, preferably 3-15 ml/min, and more preferably 5 ml/min.
The feeding speed of the complexing agent is 1-20 ml/min, preferably 3-15 ml/min, and more preferably 5 ml/min.
The complexing agent is selected from one or more of monoethanolamine, diethanolamine, diethylenetriamine pentacarboxylate, ammonia water, polyacrylic acid, hydrolyzed polymaleic anhydride and ammonium bicarbonate, preferably selected from one or more of diethanolamine, ammonia water, polyacrylic acid and ammonium bicarbonate, and more preferably selected from one or two of ammonia water and ammonium bicarbonate.
The precipitant is preferably sodium hydroxide.
The molar ratio of the metal salt solution to the complexing agent is 0.25-4, preferably 0.25-2, and more preferably 0.5-1.
The complexing agent is mainly used for complexing metal ions, so that the purpose of controlling free metal ions is achieved, the supersaturation coefficient of a system is reduced, and the growth speed and the morphology of particles are controlled. The addition amount of the complexing agent is too small, the morphology of the prepared precursor particles is poor, the dosage of the complexing agent is too large, and too many metal ions such as nickel cobalt and the like are complexed in a reaction system, so that incomplete reaction can be caused. Experiments show that when the complex is used in the above range, the prepared precursor has good sphericity and uniform particle size.
The reaction temperature is 30-100 ℃, preferably 40-80 ℃, and more preferably 45-55 ℃.
The high reaction temperature is beneficial to improving the reaction rate, but the high temperature can cause the oxidation of the precursor, but is not beneficial to generating the precursor with good appearance.
The reaction is carried out in a protective atmosphere, preferably nitrogen.
In step 1 of the invention, the pH of the reaction system is controlled to be 10.5-13, preferably 11-12.5, and more preferably 11.4-12.
Tests show that the precursor prepared by controlling the pH value of the reaction system in the above range has more uniform particle size, better particle sphericity and higher tap density, and is more favorable for improving the capacity and cycle performance of the lithium ion battery prepared by the precursor.
According to the invention, the ammonia concentration in the reaction system in the step 1 is 2-12 g/L, preferably 3-11 g/L, and more preferably 5-10 g/L.
In the present invention, the reaction is carried out under stirring at a stirring speed of 200 to 800rpm, preferably at a stirring speed of 300 to 600rpm, more preferably at a stirring speed of 400 to 500rpm, 700rpm and 800 rpm.
The stirring speed can influence the tap density of the prepared precursor, and the inventor finds that the range is more favorable for improving the tap density of the prepared precursor.
And 2, pumping out the mother liquor in the reaction kettle, removing sodium sulfate, and adding the mother liquor with the sodium sulfate removed into the reaction kettle for reaction.
And continuously or discontinuously pumping a part of mother liquor from the full kettle in the precursor reaction process, preferably performing suction filtration or pressure filtration, and more preferably performing pressure filtration.
The mother liquor extracted each time is 10-60% of the total volume, preferably 20-50% of the total volume, and more preferably 30-40% of the total volume.
The volume of the primary replacement mother liquor is too large, which is not beneficial to the reaction, the precursor does not grow completely, if the volume of the replacement mother liquor is too small, multiple replacements are needed, the preparation of the precursor is complicated, and the production efficiency is low.
The mother liquor pumped out of the reaction kettle is treated to remove sodium sulfate, the main substance in the mother liquor is sodium sulfate, the content of sulfate radicals in the mother liquor can be greatly reduced by a method of replacing the mother liquor, the possibility that the sulfate radicals are coated inside particles in the reaction process is reduced, and therefore the lithium battery prepared from the precursor has high capacitance and good cycle performance.
The method for removing the sodium sulfate is to perform cooling crystallization by utilizing the principle that the solubility difference of the sodium sulfate is larger at different temperatures. Table 1 shows the solubility of sodium sulfate at different temperatures.
TABLE 1 solubility of sodium sulfate at different temperatures
Temperature/. degree.C 0 10 20 30 40 50 60 70
Solubility in g 4.5 9.5 20.5 40.8 48.4 46.2 45.3 44.3
The specific way of removing sodium sulfate is as follows: and cooling the mother liquor pumped out of the reaction kettle, preferably reducing the temperature to 0-30 ℃, and more preferably reducing the temperature to 0-20 ℃. The crystallization time is preferably 8 to 20 hours, and more preferably 8 to 12 hours.
As is clear from table 1 above, since sodium sulfate has a low solubility in the temperature range of 0 to 30 ℃ and a low solubility in the temperature range of 0 to 20 ℃, it is preferable that the solubility of sodium sulfate is lowered by lowering the temperature to the above temperature range, and that a large amount of sodium sulfate crystals are precipitated from the mother liquor, thereby lowering the sulfate group content in the mother liquor.
And filtering and separating sodium sulfate separated out from the mother liquor to obtain the sodium sulfate-removed mother liquor.
In step 2 of the present invention, the mother liquor from which sodium sulfate is removed is heated and then added to the reaction kettle again, preferably, the mother liquor from which sodium sulfate is removed is heated to 20 to 110 ℃, preferably to 30 to 90 ℃, and more preferably to 35 to 65 ℃.
After removing the sodium sulfate, the mother liquor from which the sodium sulfate is removed is heated, and the mother liquor from which the sodium sulfate is removed is heated to the temperature of +/-10 ℃ of the reaction temperature. The temperature rise treatment can maintain the characteristics of the mother liquor, such as volume, temperature, pH value, metal complex ion, ammonia concentration and the like, unchanged or slightly changed, thereby maintaining the balance of the original reaction system.
According to the invention, the replacement time interval of the mother liquor is 1-30 h, preferably 2-25 h, and more preferably 2-20 h.
In the production process of the ternary precursor, the reaction starting stage is a crystal nucleus forming stage, mother liquor is preferably extracted from a reaction kettle in a suction filtration or pressure filtration mode after crystals grow for 10 hours, sodium sulfate is removed from the extracted mother liquor, and then the mother liquor with the same volume of the sodium sulfate removed is added into the reaction kettle. The inventor finds that the normal growth of precursor crystals cannot be influenced after the sodium sulfate-removed mother liquor is used for replacement.
And stopping feeding and then carrying out post-treatment when the particle size of the precursor particles grows to 10-15 microns, preferably 11-13 microns, more preferably 11.5-12 microns.
In the prior art, after the mother liquor is pumped out of the reaction kettle, pure water is added into the reaction kettle, and the system is difficult to maintain balance in the mother liquor replacement process, so that adverse effects on the appearance of the prepared ternary precursor are generated.
And 3, after the reaction is finished, carrying out post-treatment.
The post-treatment comprises aging, washing, filtering, drying and sieving.
The aging time is 0.5-5 h, preferably 1-3 h, and more preferably 1-2 h.
Aging is to stand the solution for a period of time under certain conditions in order to allow the components inside the solution to react sufficiently or to allow suspended matter to settle. Experiments show that after aging for 0.5-5 h, the components in the reaction system can be fully reacted, and the prepared precursor has more uniform particle size and higher tap density.
The pH value in the reaction kettle is preferably increased to 12-14, preferably to 12-14, and more preferably to 12.5-13.5 before aging.
And (3) ageing, washing, wherein the washing agent is preferably water, the washing mode is preferably stirring washing, and filtering to obtain a filter cake after washing.
And drying the obtained filter cake, wherein the drying is preferably carried out in a vacuum oven, the drying temperature is 80-120 ℃, the drying time is 2-20 h, preferably the drying temperature is 100-120 ℃, the drying time is 5-15 h, more preferably the drying temperature is 100-110 ℃, and the drying time is 10 h.
And sieving the dried substances, preferably sieving the dried substances by a sieve of 100-800 meshes, and more preferably sieving the dried substances by a sieve of 300-500 meshes.
The second aspect of the present invention provides a sulfate-based lithium ion positive electrode material precursor with a low sulfur content prepared by the preparation method according to the first aspect of the present invention. The precursor with low sulfur content has the advantages of low sulfur content, high tap density, good sphericity, uniform particle size and the like, the sulfur content is 200-550 ppm, and the tap density is 1.98-2.1 g/cm3The particle size is 1 to 15 μm.
The lithium ion battery anode material prepared by using the lithium ion battery anode material as a precursor has improved specific discharge capacity and cycle performance.
The invention has the following beneficial effects:
(1) after the coprecipitation is carried out until the kettle is full, the sodium sulfate-free mother liquor is used for replacing the mother liquor in the reaction kettle in a continuous or discontinuous mode, so that the condition that the sulfur content of a ternary precursor exceeds the standard due to the fact that a large amount of sulfate radicals are adsorbed on the surface or the inner part of the precursor crystal is avoided;
(2) the method for reducing the sulfur content can remove 60-80% of sodium sulfate in the original system, greatly reduce the content of sulfate radicals in the mother solution, and control the sulfur content of the prepared ternary precursor to be 200-550 ppm;
(3) the method for reducing the sulfur content replaces the mother liquor in the reaction kettle with the sodium sulfate-free mother liquor, reduces the consumption of pure water, and simultaneously replaces the mother liquor in the reaction kettle with the sodium sulfate-free mother liquor to maintain the balance of a system in the replacement process, so that the method does not have any influence on the appearance of a precursor;
(4) the ternary precursor prepared by the method for reducing the sulfur content has high tap density of 1.98-2.1 g/cm3And has the advantages of good sphericity, uniform particle size and the like, and the particle size is 1-15 mu m.
Examples
The invention is further illustrated by the following specific examples, which are intended to be illustrative only and not limiting to the scope of the invention.
Example 1
Continuously adding a metal salt solution with the solubility of 2mol/L (wherein the molar ratio of Ni, Co and Mn is 1:1:1), a complexing agent ammonia water (the concentration is 4mol/L) and a precipitator NaOH (the concentration is 6mol/L) into a 5L reaction kettle, introducing nitrogen as protective gas, setting the stirring speed of the reaction kettle to be 500rpm, the reaction temperature to be 50 ℃, the initial reaction pH value to be 11.8-12.0, the feeding speed of the metal salt solution to be 10ml/min, the flow rate of the precipitator to be 5ml/min and the flow rate of the complexing agent to be 5 ml/min.
After the reaction is completed, 2L of mother liquor in the reaction kettle is pressed out by a filter-pressing tank, the pressed mother liquor is cooled to 0 ℃ for crystallization for 8 hours, the precipitated sodium sulfate is filtered from the mother liquor, and then the sodium sulfate-removed mother liquor is heated to 50 ℃ and then is injected into the reaction kettle again to maintain the balance of the system in the reaction kettle. The mother liquor was replaced every 4 h.
Stopping feeding after the particle size of the precursor reaches 11.5 mu m, increasing the pH value in a reaction kettle to 13.5, aging for 1h, stirring and washing with pure water after aging to obtain a filter cake, drying the filter cake at 100 ℃ for 10h, sieving the dried powder with a 300-mesh sieve to obtain a ternary precursor, and detecting the sulfur content of the ternary precursor to be 217ppm by ICP analysis.
Example 2 preparation of ternary cathode Material
And (2) preparing a ternary cathode material by using the low-sulfur precursor prepared in the embodiment 1, uniformly mixing the obtained low-sulfur ternary precursor with LiOH according to a molar ratio of 1:1.05, placing the mixture in an atmosphere furnace, roasting at 800 ℃ for 12 hours at an oxygen flow rate of 10L/min and a heating rate of 2 ℃/min, cooling, grinding and sieving to obtain the ternary cathode material.
And (3) carrying out electrochemical performance test on the ternary cathode material, and measuring that the first discharge specific capacity of the ternary cathode material under the multiplying power of 0.1C is 205 mAh/g.
Example 3
Continuously adding a metal salt solution with the solubility of 2.5mol/L (wherein the molar ratio of Ni, Co and Mn is 6:2:2), complexing agent ammonia water (the concentration is 4mol/L) and precipitator NaOH (the concentration is 6mol/L) into a 5L reaction kettle, introducing nitrogen as protective gas, setting the stirring speed of the reaction kettle to be 700rpm, the reaction temperature to be 50 ℃, the initial reaction pH value to be 11.6-11.8, the feeding speed of the metal salt solution to be 30ml/min, the flow rate of the precipitator to be 20ml/min and the flow rate of the complexing agent to be 20 ml/min.
After the reaction is completed, pressing out 2L of mother liquor in the reaction kettle by using a filter-pressing tank, cooling the pressed out mother liquor to 5 ℃ for crystallization for 12h, filtering the precipitated sodium sulfate from the mother liquor, heating the sodium sulfate-removed mother liquor to 50 ℃, pumping the sodium sulfate-removed mother liquor into the reaction kettle again, and maintaining the balance of the system in the reaction kettle. The mother liquor was replaced every 2 h.
Stopping feeding after the particle size of the precursor reaches 11.5 mu m, increasing the pH value to 13 in a reaction kettle, aging for 1h, stirring and washing with pure water after aging to obtain a filter cake, drying the filter cake at 110 ℃ for 10h, sieving the dried powder with a 300-mesh sieve to obtain a ternary precursor, and detecting the sulfur content of the ternary precursor by ICP analysis to be 432ppm and the tap density to be 2.02g/cm3。
Example 4
Continuously adding a metal salt solution with the solubility of 3mol/L (wherein the molar ratio of Ni, Co and Mn is 8:1:1), a complexing agent ammonia water (the concentration is 4mol/L) and a precipitator NaOH (the concentration is 6mol/L) into a 5L reaction kettle, introducing nitrogen as protective gas, setting the stirring speed of the reaction kettle to be 800rpm, the reaction temperature to be 50 ℃, the initial reaction pH value to be 11.4-11.6, the feeding speed of the metal salt solution to be 1ml/min, the flow rate of the precipitator to be 1ml/min and the flow rate of the complexing agent to be 1 ml/min.
After the reaction kettle is full, pressing out 2L of mother liquor in the reaction kettle by using a filter-pressing tank, cooling the pressed out mother liquor to 10 ℃ for crystallization for 12 hours, filtering the precipitated sodium sulfate from the mother liquor, heating the sodium sulfate-removed mother liquor to 50 ℃, pumping the sodium sulfate-removed mother liquor into the reaction kettle again, and maintaining the balance of the system in the reaction kettle. The mother liquor was replaced every 20 h.
Stopping feeding after the particle size of the precursor reaches 11.5 mu m, increasing the pH value to 12.5 in a reaction kettle, aging for 1h, stirring and washing with pure water after aging to obtain a filter cake, drying the filter cake at 120 ℃ for 10h, sieving the dried powder with a 300-mesh sieve to obtain a ternary precursor, and detecting the sulfur content of the ternary precursor to be 505ppm and the tap density to be 1.98g/cm through ICP analysis3。
Example 5
And (2) preparing a ternary cathode material by using the low-sulfur precursor prepared in the embodiment 3, uniformly mixing the obtained low-sulfur ternary precursor with LiOH according to a molar ratio of 1:1.05, placing the mixture in an atmosphere furnace, wherein the oxygen flow is 10L/min, the heating rate is 2 ℃/min, roasting the mixture at 800 ℃ for 12 hours, cooling, grinding and sieving the mixture to obtain the ternary cathode material.
And (3) carrying out electrochemical performance test on the ternary cathode material, and measuring that the first discharge specific capacity of the ternary cathode material under the multiplying power of 0.1C is 202 mAh/g.
Example 6
And (2) preparing a ternary cathode material by using the low-sulfur precursor prepared in the embodiment 4, uniformly mixing the obtained low-sulfur ternary precursor with LiOH according to a molar ratio of 1:1.05, placing the mixture in an atmosphere furnace, roasting at 800 ℃ for 12 hours at an oxygen flow rate of 10L/min and a heating rate of 2 ℃/min, cooling, grinding and sieving to obtain the ternary cathode material.
And (3) carrying out electrochemical performance test on the ternary cathode material to obtain that the first discharge specific capacity of the ternary cathode material is 203mAh/g under the multiplying power of 0.1C.
Comparative example
Comparative example 1
Continuously adding a metal salt solution with the solubility of 2mol/L (wherein the molar ratio of Ni, Co and Mn is 1:1:1), a complexing agent ammonia water (the concentration is 4mol/L) and a precipitator NaOH (the concentration is 6mol/L) into a 5L reaction kettle, introducing nitrogen as protective gas, setting the stirring speed of the reaction kettle to be 500rpm, the reaction temperature to be 50 ℃, the initial reaction pH value to be 11.8-12.0, the feeding speed of the metal salt solution to be 10ml/min, the flow rate of the precipitator to be 5ml/min and the flow rate of the complexing agent to be 5 ml/min.
Stopping feeding after the particle size of the precursor reaches 11.5 mu m, increasing the pH value to 13.5 in a reaction kettle, aging for 1h, stirring and washing with pure water after aging to obtain a filter cake, drying the filter cake at 100 ℃ for 10h, sieving the dried powder with a 300-mesh sieve to obtain a ternary precursor, and detecting the sulfur content of the ternary precursor to be 1250ppm by ICP analysis.
Comparative example 2 preparation of ternary cathode Material
The procedure of example 2 was repeated except that: the low-sulfur precursor prepared in comparative example 1 was used to prepare a ternary positive electrode material.
And (3) carrying out electrochemical performance test on the prepared ternary cathode material, and measuring that the first discharge specific capacity of the cathode material under the multiplying power of 0.1C is 198 mAh/g. The specific first discharge capacity of the ternary cathode material is lower than that of the ternary cathode materials obtained in the embodiments 2, 5 and 6, and the ternary cathode material obtained from the low-sulfur precursor prepared by the method has better electrochemical performance.
Examples of the experiments
Experimental example 1 SEM test
The low sulfur precursor prepared in example 1 was subjected to scanning electron microscope test, and the test results are shown in fig. 1 and 2.
As can be seen from the figures 1 and 2, the low-sulfur precursor prepared by the method has good sphericity and uniform particle size of 1-15 μm.
Experimental example 2 ICP test
ICP tests were performed on the low-sulfur precursors prepared in example 1 and comparative example 1, and the results are shown in table 2 below.
TABLE 2 Sulfur content test results
Sulfur content (ppm)
Example 1 217
Example 3 432
Example 4 505
Comparative example 1 1250
As can be seen from Table 2, the sulfur content of the low-sulfur precursor prepared by the preparation method of the present invention is only 200-550 ppm, while the sulfur content of the low-sulfur precursor prepared by replacing the mother solution of sodium sulfate with pure water is 1250ppm, which confirms that the precursor prepared by the preparation method of the present invention has lower sulfur content.
Experimental example 3 tap Density test
Tap density tests were performed on the low-sulfur precursors obtained in examples 1, 3, 4 and comparative example 1, and the tap density of the low-sulfur precursor obtained in test example 1 was 2.0g/cm3Example 3 the tap density of the low sulphur precursor obtained was 2.02g/cm3Example 4 the tap density of the low sulfur precursor was 1.98g/cm3Comparative example 1 the tap density of the low-sulfur precursor prepared was 1.96g/cm3. Description of the inventionThe low-sulfur precursor prepared by the preparation method has higher tap density.
The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims (10)

1. A method for reducing the sulfur content of a sulfate system lithium ion battery positive electrode material precursor is characterized by comprising the following steps:
step 1, adding a metal salt solution, a precipitator and a complexing agent into a reaction kettle for reaction;
step 2, pumping out the mother liquor in the reaction kettle, removing sodium sulfate, and adding the mother liquor with the sodium sulfate removed into the reaction kettle for reaction;
and 3, after the reaction is finished, carrying out post-treatment.
2. The method for reducing the sulfur content according to claim 1, wherein, in step 1,
the concentration of the metal salt solution is 0.5-10 mol/L;
the addition mode is preferably continuous addition, and the feeding speed ratio of the metal salt solution, the precipitator and the complexing agent is (0.5-5): 1:1.
3. The method for reducing the sulfur content according to claim 1, wherein, in step 1,
the complexing agent is selected from one or more of monoethanolamine, diethanolamine, diethylenetriamine pentacarboxylate, ammonia water, polyacrylic acid, hydrolyzed polymaleic anhydride and ammonium bicarbonate.
4. The method for reducing the sulfur content according to claim 1, wherein in the step 1, the reaction temperature is 30 to 100 ℃, and the pH of the reaction system is 10.5 to 13;
the reaction is carried out under stirring at a speed of 200 to 800 rpm.
5. The method for reducing the sulfur content according to claim 1, wherein, in the step 2,
the mother liquor extracted each time is 10-60% of the total volume, and the way of removing sodium sulfate is cooling crystallization.
6. The method for reducing the sulfur content according to claim 5, wherein, in the step 2,
the temperature for cooling and crystallization is 0-30 ℃, and the crystallization time is 8-20 h.
7. The method for reducing the sulfur content according to claim 1, wherein, in the step 2,
and heating the mother liquor from which the sodium sulfate is removed, adding the mother liquor into the reaction kettle again, and heating the mother liquor from which the sodium sulfate is removed to 20-110 ℃.
8. The method for reducing the sulfur content according to claim 1, wherein, in the step 2,
the replacement time interval of the mother liquor is 1-30 h;
and stopping feeding after the particle size of the precursor particles grows to 10-15 mu m.
9. The method for reducing the sulfur content according to claim 1, wherein, in step 3,
the post-treatment comprises aging, washing, filtering, drying and sieving;
the aging time is 0.5-5 h, and the pH value in the reaction kettle is preferably increased to 12-14 before aging.
10. A low sulfur sulfate system lithium ion positive electrode material precursor prepared according to the method of any one of claims 1 to 9.
CN202110255246.3A 2020-12-28 2021-03-09 Method for reducing sulfur content of sulfate system lithium ion battery positive electrode material precursor Pending CN114684871A (en)

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