CN112499696B - Method for reducing residual alkali content of high-nickel material and low-residual alkali high-nickel material prepared by method - Google Patents
Method for reducing residual alkali content of high-nickel material and low-residual alkali high-nickel material prepared by method Download PDFInfo
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- 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
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- 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
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Abstract
The invention provides a method for reducing the residual alkali content of a high-nickel materialA method, said method comprising: and mixing the high-nickel ternary positive electrode material precursor, the lithium salt and the additive, and then performing gradient sintering to obtain a high-nickel ternary primary sintering product with low residual alkali, wherein the additive is weak acid salt. The method comprises the steps of setting a low-temperature platform by adopting a gradient sintering mode, melting a weak acid salt additive in the low-temperature platform, and consuming LiOH and Li on the surface of a high-nickel ternary material through the melted weak acid salt additive 2 CO 3 And the like.
Description
Technical Field
The invention belongs to the technical field of high-nickel material preparation, and relates to a method for reducing residual alkali content of a high-nickel material and a low-residual alkali high-nickel material prepared by the method.
Background
In recent years, due to the excessive exploitation and use of traditional energy by human beings, not only the resource shortage of traditional energy is caused, but also various global problems such as environmental pollution and greenhouse effect are caused. Therefore, the development of new energy sources that are environmentally friendly and renewable is considered as an important way to replace traditional energy sources. The lithium ion battery as a novel battery in new energy sources has the advantages of high energy density, long cycle life, environmental friendliness, high safety and the like, is unique among numerous chemical power sources, and attracts wide attention of human society. The anode material is an important component of the lithium ion battery and is an important factor for restricting the development of the lithium ion battery with high power and long service life. Among them, nickel-cobalt-manganese ternary cathode materials (NCM), especially high-nickel ternary cathode materials, are considered to be the most powerful candidates among next-generation lithium ion battery cathode materials due to their high specific capacities. However, the high-nickel ternary material also has some intrinsic disadvantages, for example, as the content of nickel increases, the phenomenon of Li/Ni mixed-exclusion becomes more and more serious, which leads to the reduction of rate capability of the material; the higher the nickel content of the ternary material, the easier it is to react with CO in the air 2 And H 2 Reaction of O to Li 2 CO 3 And LiOH, which causes the excessive content of residual alkali on the surface of the material, thereby affecting the cycle performance of the material.
The preparation process of the high-nickel ternary cathode material comprises the following specific steps: 1. uniformly mixing a high-nickel ternary precursor nickel cobalt manganese hydroxide, a lithium salt and a dopant, and then performing primary high-temperature sintering in an atmosphere furnace. 2. And crushing, grinding and screening the sintered material. 3. And (3) stirring and mixing the screened materials with a certain proportion of water, and performing suction filtration and drying. 4. And uniformly mixing the dried material and the coating agent, and then performing secondary high-temperature sintering in an atmosphere furnace. 5. And screening and demagnetizing the sintered material to obtain the finished product of the high-nickel ternary cathode material.
Because the lithium salt can volatilize and lose a part in the high-temperature sintering process, the addition amount of the lithium salt is often increased during the compounding, namely the lithium salt ratio is increased, so that the reaction is fully performed. However, the addition of an excessive amount of lithium salt results in the remaining of lithium, which absorbs CO in the air 2 And H 2 O to Li 2 CO 3 And LiOH residual base. The situation is concentrated in one-time high-temperature sintering, and the total amount of residual alkali of a calcined product is as small as seven-eight-thousand, and more than ten thousand. Excessive residual alkali causes the slurry to form a jelly-like shape, resulting in difficulty in coating process, and secondly, lowering the cycle performance of the material, and also causing gas generation problem of soft package resulting in a decrease in the safety of the battery.
CN109768254A discloses a modified low residual alkali type high nickel ternary positive electrode material, which is obtained by uniformly dispersing a high nickel ternary positive electrode material and hydrogen phosphate in a solvent, drying the obtained mixed solution, and sintering the dried product to react residual alkali on the surface of the high nickel ternary positive electrode material with the hydrogen phosphate to generate phosphate.
CN110071278A discloses a high-nickel ternary positive electrode material containing an active oxygen remover, which comprises an active oxygen remover and a high-nickel ternary material, wherein the active oxygen remover is coated on the surface of the high-nickel ternary positive electrode material, the invention also provides a preparation method of the high-nickel ternary positive electrode material coated with the active oxygen remover, the high-nickel ternary positive electrode material and the active oxygen remover are dissolved in absolute ethyl alcohol according to a certain mass ratio for ultrasonic dispersion, and a sample is dried in vacuum at 100 ℃ for 12-24 h after filtration, so that the high-nickel ternary positive electrode material can be obtained, active oxygen formed in the circulation or storage process can be eliminated, the oxidative decomposition and gas production of electrolyte can be inhibited, residual lithium on the surface of the high-nickel ternary positive electrode material can be eliminated, and the surface residual alkali can be reduced.
CN109360983A discloses a modified high-nickel ternary cathode material and a preparation method and application thereof. The preparation method of the modified high-nickel ternary cathode material comprises the following steps: preparing a high-nickel ternary intermediate phase solution, and dissolving an acidic solid in water to obtain an acidic solution; and uniformly mixing the two solutions, carrying out hydrothermal or solvothermal reaction, calcining, cooling, grinding and sieving to obtain the modified high-nickel ternary cathode material.
Although the residual alkali on the surface of the material is washed away by adopting a water washing method at present, a large amount of lithium ions are lost along with the removal of the residual alkali in the water washing process; meanwhile, the erosion of the particle surface by water can cause the reduction of the structural stability, and the conditions increase the irreversible capacity of the material and reduce the cycle performance of the material.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for reducing the residual alkali content of a high-nickel material and a low-residual alkali high-nickel material prepared by the method 2 CO 3 And the like. The method provided by the invention can obtain the low-residual-alkali calcined product, so that water washing treatment is not needed, the process period is greatly shortened, the process complexity is reduced, the production efficiency is improved, meanwhile, the damage to the surface structure of the material in the water washing process is reduced, and the structural stability of the material is favorably maintained.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for reducing residual alkali content of a nickel-rich material, the method comprising:
and mixing the high-nickel ternary positive electrode material precursor, lithium salt and an additive, and then performing gradient sintering to obtain a low-residual-alkali high-nickel ternary primary sintering product, wherein the additive is a weak acid salt.
The method radically solves the problem of overhigh residual alkali of the high-nickel ternary material calcined product, adopts a gradient sintering mode, arranges a low-temperature platform, melts a weak acid salt additive in the low-temperature platform, and consumes LiOH and Li on the surface of the high-nickel ternary material by the melted weak acid salt additive 2 CO 3 And the like. The method provided by the invention can obtain the low-residual-alkali calcined product, so that water washing treatment is not needed, the process period is greatly shortened, the process complexity is reduced, the production efficiency is improved, meanwhile, the damage to the surface structure of the material in the water washing process is reduced, and the structural stability of the material is favorably maintained. In addition, the residual alkali of the product obtained by the method meets the requirements of the finished product, and if the electrical property of the product is not greatly different from that of the finished product, the method can become a one-step sintering method to replace the traditional secondary sintering method or even a three-step sintering method, and has great advantages in production efficiency and energy consumption.
As a preferable technical scheme, the chemical formula of the precursor of the high-nickel ternary cathode material is Ni x Co y Mn 1-x-y (OH) 2 Wherein x is more than or equal to 0.6 and less than 1, y is more than 0 and less than or equal to 0.4<x+y<1, for example x may be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 0.95, y may be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4, but is not limited to the values listed, and other values not listed within this range of values are equally applicable.
As a preferred technical solution of the present invention, the lithium salt includes lithium hydroxide;
preferably, the molar ratio of the lithium element in the lithium salt to the nickel-cobalt-manganese element in the high-nickel ternary positive electrode material precursor is 1.02 to 1.06, and may be, for example, 1.02, 1.03, 1.04, 1.05, or 1.06, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
As a preferable technical scheme of the invention, the additive is one or the combination of at least two of ammonium dihydrogen phosphate, lithium metaphosphate, lithium dihydrogen phosphate, ammonium bisulfate, ammonium sulfate and lithium sulfate.
It should be noted that the additive used in the present invention is not limited to the weak acid salt exemplified above, and may be used in the present invention as long as it satisfies the melting point within the low temperature plateau range.
Preferably, the additive is added in an amount of 0.1 to 0.4wt% based on the mass of the high-nickel ternary positive electrode material precursor, and may be, for example, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, or 0.4wt%, but is not limited to the recited values, and other values not recited in the range of the recited values are also applicable.
In a preferred embodiment of the present invention, the sintering process is performed in an oxygen atmosphere furnace.
Preferably, the oxygen content in the oxygen atmosphere furnace is 97% or more, for example, 97.0%, 97.2%, 97.4%, 97.6%, 97.8%, 98%, 98.2%, 98.4%, 98.6%, 98.8% or 99% by volume, but not limited to the recited values, and other values not recited in the range of the values are also applicable.
As a preferred technical solution of the present invention, the gradient sintering process specifically comprises:
mixing the high-nickel ternary positive electrode material precursor, the lithium salt and the additive, sequentially performing high-temperature sintering and low-temperature sintering, and then cooling to room temperature.
As a preferred technical solution of the present invention, the high temperature sintering process comprises: the mixture is heated to the high-temperature sintering temperature at a heating rate of 1 to 5 ℃/min, for example, 1.0 ℃/min, 1.5 ℃/min, 2.0 ℃/min, 2.5 ℃/min, 3.0 ℃/min, 3.5 ℃/min, 4.0 ℃/min, 4.5 ℃/min, or 5.0 ℃/min, but is not limited to the values recited, and other values not recited within the range of values are also applicable.
Preferably, the high temperature sintering temperature is 700 to 900 ℃, for example 700 ℃, 720 ℃, 740 ℃, 760 ℃, 780 ℃, 800 ℃, 820 ℃, 840 ℃, 860 ℃, 880 ℃ or 900 ℃, but is not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the sintering temperature is maintained at the high temperature for 8 to 12 hours, such as 8.0 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours, or 12.0 hours, but not limited to the recited values, and other values not recited in the range of values are also applicable.
As a preferred technical solution of the present invention, the low-temperature sintering process comprises: the mixture after high temperature sintering is cooled to the low temperature sintering temperature at a cooling rate of 1-5 ℃/min, for example, 1.0 ℃/min, 1.5 ℃/min, 2.0 ℃/min, 2.5 ℃/min, 3.0 ℃/min, 3.5 ℃/min, 4.0 ℃/min, 4.5 ℃/min, or 5.0 ℃/min, but is not limited to the values listed, and other values not listed within the range of values are also applicable.
Preferably, the low-temperature sintering temperature is 200 to 400 ℃, for example, 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃, 300 ℃, 320 ℃, 340 ℃, 360 ℃, 380 ℃ or 400 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the sintering temperature is maintained at the low temperature for 3 to 5 hours, such as 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours or 5.0 hours, but not limited to the recited values, and other values not recited in the range of values are also applicable.
The method adopts a gradient sintering mode, a low-temperature sintering platform is additionally arranged after high-temperature sintering, a weak acid salt additive added in the low-temperature platform is melted, and LiOH and Li on the surface of the high-nickel ternary material are consumed through the melted weak acid salt additive 2 CO 3 And the like. Therefore, the technological parameters adopted in the low-temperature sintering process are very important. The invention particularly limits the sintering temperature of the low-temperature sintering process to be 200-400 ℃, and when the sintering temperature is lower than 200 ℃, the additive has weakened capability of reducing the residual alkali of the material, and the residual alkali is relatively high, because the additive can not exist in a molten state below the temperature; when the sintering temperature is higher than 400 ℃, the residual alkali content of the material is relatively high, and the production cost is increased, because the sintering temperature has a critical value on the influence of the residual alkali of the nickel-rich material, and is lower than or higher than the critical valueAt this critical value, the residual alkali content of the material will be relatively high. The invention particularly limits the sintering time of the low-temperature sintering process to be 3-5 h, when the sintering time is less than 3h, the residual alkali content of the material is relatively high, because the reaction of the additive and the residual alkali is not complete when the time is less than the time; when the sintering time is more than 5 hours, the residual alkali content of the material increases and the production cost of the material increases, because the metering of the additive is essentially complete and the material produces Li again as time goes on 2 CO 3 Resulting in an increase in residual base. The invention particularly limits the cooling rate of the low-temperature sintering process to be 1-5 ℃/min, and when the cooling rate is lower than 1 ℃/min, the residual alkali content of the material is relatively higher and the specific capacity of the material is reduced, because the temperature is lower than the cooling rate, the reconstruction phenomenon of the material surface is induced, such as Li 2 CO 3 The particles are easy to accumulate on the surfaces of the particles, and lithium-deficient layers are formed on the surfaces of the particles; when the temperature reduction rate is higher than 5 ℃/min, the content of residual alkali of the material cannot be obviously changed, but the specific capacity of the material can be reduced, because the crystal volume of the material particles is larger due to the higher temperature reduction rate, the improvement of the specific capacity of the material is not facilitated.
As a preferred technical scheme, after sintering is finished, the sintering material is sequentially crushed, ground and sieved to obtain the high-nickel ternary primary-combustion product with low residual alkali.
Preferably, the particle size after crushing is 7 to 13 μm, and may be, for example, 7.0. Mu.m, 7.5. Mu.m, 8.0. Mu.m, 8.5. Mu.m, 9.0. Mu.m, 9.5. Mu.m, 10.0. Mu.m, 10.5. Mu.m, 11.0. Mu.m, 11.5. Mu.m, 12.0. Mu.m, 12.5. Mu.m or 13.0. Mu.m, but not limited to the values listed, and other values not listed in the numerical range are also applicable.
Preferably, the milled sinter material is screened through a 200-500 mesh screen, such as 200 mesh, 250 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh or 500 mesh, but not limited to the values recited, and other values not recited within this range are equally applicable.
In a second aspect, the invention provides a low residual alkali high nickel material prepared by the method of the first aspect, wherein the residual alkali content of the low residual alkali high nickel material is 3500ppm to 7000ppm, such as 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm, 6500ppm or 7000ppm, but not limited to the recited values, and other unrecited values in the range are also applicable.
Compared with the prior art, the invention has the beneficial effects that:
the invention aims to reduce residual alkali of a calcined product, and the calcined product with low residual alkali is prepared by adopting a gradient sintering mode, arranging a low-temperature platform and doping an additive. Firstly, fully reacting the precursor with lithium salt at a high temperature, and then, in a low-temperature platform, excessive lithium oxide and additives in a molten state react with LiOH and Li on the surface of a sintered product 2 CO 3 Acid-base neutralization reaction occurs, so that the residual alkali content on the surface of the high nickel material is reduced. Because the method can obtain the low residual alkali calcined product, the water washing treatment can be omitted, the process period is greatly shortened, the process complexity is reduced, the production efficiency is improved, meanwhile, the damage to the surface structure of the material in the water washing process is reduced, and the structural stability of the material is favorably maintained.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
Example 1
The embodiment provides a method for reducing the residual alkali content of a high nickel material, which specifically comprises the following steps:
(1) High-nickel ternary cathode material precursor Ni 0.6 Co 0.3 Mn 0.1 (OH) 2 The lithium hydroxide and the additive are uniformly mixed to obtain a mixed material, the molar ratio of lithium element in the lithium hydroxide to nickel-cobalt-manganese element in the high-nickel ternary positive electrode material precursor is 1.02, the additive comprises lithium sulfate and ammonium dihydrogen phosphate, the addition amount of the lithium sulfate accounts for 0.1wt% of the mass of the high-nickel ternary positive electrode material precursor, and the addition amount of the ammonium dihydrogen phosphate accounts for 0.4wt% of the mass of the high-nickel ternary positive electrode material precursor;
(2) Heating the mixed material to 700 ℃ at the heating rate of 1 ℃/min, and preserving the heat for 10 hours; then cooling to 200 ℃ at the cooling rate of 1 ℃/min, preserving heat for 5 hours, and finally cooling along with the furnace to obtain a sintering material;
(3) And (3) sequentially crushing and grinding the sintered materials, wherein the particle size of the crushed and ground materials is 8 mu m, and the crushed and ground materials pass through a 200-mesh screen to obtain a high-nickel ternary primary combustion product with low residual alkali.
The residual alkali content of the high nickel ternary-calcined product prepared in this example is shown in table 1.
Example 2
The embodiment provides a method for reducing the residual alkali content of a high nickel material, which specifically comprises the following steps:
(1) High-nickel ternary positive electrode material precursor Ni 0.65 Co 0.15 Mn 0.2 (OH) 2 The lithium hydroxide and the additive are uniformly mixed to obtain a mixed material, the molar ratio of lithium element in the lithium hydroxide to nickel-cobalt-manganese element in a high-nickel ternary positive electrode material precursor is 1.03, the additive comprises ammonium sulfate and lithium metaphosphate, the addition amount of ammonium bisulfate accounts for 0.1wt% of the mass of the high-nickel ternary positive electrode material precursor, and the addition amount of lithium metaphosphate accounts for 0.2wt% of the mass of the high-nickel ternary positive electrode material precursor;
(2) Heating the mixed material to 800 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 8 hours; then cooling to 300 ℃ at the cooling rate of 2 ℃/min, preserving heat for 5 hours, and finally cooling along with the furnace to obtain a sintered material;
(3) And (3) sequentially crushing and grinding the sintered materials, wherein the particle size of the crushed and ground materials is 9.5 mu m, and the crushed and ground materials pass through a 300-mesh screen to obtain a high-nickel ternary primary combustion product with low residual alkali.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
Example 3
The embodiment provides a method for reducing the residual alkali content of a nickel-rich material, which specifically comprises the following steps:
(1) High-nickel ternary positive electrode material precursor Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 The lithium hydroxide and the additive are uniformly mixed to obtain a mixed material, the molar ratio of lithium element in the lithium hydroxide to nickel-cobalt-manganese element in the high-nickel ternary cathode material precursor is 1.04, the additive comprises ammonium bisulfate and lithium metaphosphate, the addition amount of the ammonium bisulfate accounts for 0.3wt% of the mass of the high-nickel ternary cathode material precursor, and the addition amount of the lithium metaphosphate accounts for 0.2wt% of the mass of the high-nickel ternary cathode material precursor;
(2) Heating the mixed material to 850 ℃ at the heating rate of 3 ℃/min, and keeping the temperature for 8 hours; then cooling to 400 ℃ at the cooling rate of 3 ℃/min, preserving the heat for 4 hours, and finally cooling along with the furnace to obtain a sintered material;
(3) And (3) sequentially crushing and grinding the sintered materials, wherein the particle size of the crushed and ground materials is 10.3 mu m, and the crushed and ground materials pass through a 400-mesh screen to obtain a high-nickel ternary primary combustion product with low residual alkali.
The residual alkali content of the high nickel ternary-calcined product prepared in this example is shown in table 1.
Example 4
The embodiment provides a method for reducing the residual alkali content of a nickel-rich material, which specifically comprises the following steps:
(1) High-nickel ternary positive electrode material precursor Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The lithium hydroxide and the additive are uniformly mixed to obtain a mixed material, the molar ratio of lithium element in the lithium hydroxide to nickel-cobalt-manganese element in a high-nickel ternary positive electrode material precursor is 1.05, the additive comprises lithium sulfate and ammonium dihydrogen phosphate, the addition amount of the lithium sulfate accounts for 0.2wt% of the mass of the high-nickel ternary positive electrode material precursor, and the addition amount of the ammonium dihydrogen phosphate accounts for 0.3wt% of the mass of the high-nickel ternary positive electrode material precursor;
(2) Heating the mixed material to 900 ℃ at the heating rate of 4 ℃/min, and keeping the temperature for 9 hours; then cooling to 250 ℃ at the cooling rate of 4 ℃/min, preserving heat for 3 hours, and finally cooling along with the furnace to obtain a sintered material;
(3) And (3) sequentially crushing and grinding the sintering material, wherein the particle size of the crushed and ground material is 11.6 mu m, and the crushed and ground material passes through a 400-mesh screen to obtain a high-nickel ternary primary-combustion product with low residual alkali.
The residual alkali content of the high nickel ternary-calcined product prepared in this example is shown in table 1.
Example 5
The embodiment provides a method for reducing the residual alkali content of a high nickel material, which specifically comprises the following steps:
(1) High-nickel ternary cathode material precursor Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 The lithium hydroxide and the additive are uniformly mixed to obtain a mixed material, the molar ratio of lithium element in the lithium hydroxide to nickel-cobalt-manganese element in the high-nickel ternary cathode material precursor is 1.06, the additive comprises ammonium bisulfate, lithium dihydrogen phosphate and lithium sulfate, the addition amount of the ammonium bisulfate accounts for 0.4wt% of the mass of the high-nickel ternary cathode material precursor, the addition amount of the lithium dihydrogen phosphate accounts for 0.1wt% of the mass of the high-nickel ternary cathode material precursor, and the addition amount of the lithium sulfate accounts for 0.2wt% of the mass of the high-nickel ternary cathode material precursor;
(2) Heating the mixed material to 750 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 10 hours; then cooling to 300 ℃ at a cooling rate of 5 ℃/min, preserving heat for 3 hours, and finally cooling along with the furnace to obtain a sintering material;
(3) And (3) sequentially crushing and grinding the sintered materials, wherein the particle size of the crushed and ground materials is 12.8 mu m, and the crushed and ground materials pass through a 500-mesh screen to obtain a high-nickel ternary primary combustion product with low residual alkali.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
Example 6
The comparative example differs from example 3 in that: in the step (2), after high-temperature sintering, the temperature is reduced to 150 ℃ at the cooling rate of 3 ℃/min, the temperature is kept for 4 hours, and finally the sintered material is obtained after furnace cooling. The rest of the process parameters and the operation steps are exactly the same as in example 1.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
Example 7
This comparative example differs from example 3 in that: in the step (2), after high-temperature sintering, the temperature is reduced to 450 ℃ at the cooling rate of 3 ℃/min, the temperature is kept for 4 hours, and finally, the sintered material is obtained by furnace cooling. The rest of the process parameters and the operation steps are completely the same as those of the example 1.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
Example 8
This comparative example differs from example 3 in that: in the step (2), after high-temperature sintering, the temperature is reduced to 400 ℃ at the cooling rate of 3 ℃/min, the temperature is kept for 2 hours, and finally the sintered material is obtained after furnace cooling. The rest of the process parameters and the operation steps are completely the same as those of the example 1.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
Example 9
This comparative example differs from example 3 in that: in the step (2), after high-temperature sintering, the temperature is reduced to 400 ℃ at the cooling rate of 3 ℃/min, the temperature is kept for 6 hours, and finally, the sintered material is obtained by furnace cooling. The rest of the process parameters and the operation steps are exactly the same as in example 1.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
Example 10
The comparative example differs from example 3 in that: in the step (2), after high-temperature sintering, the temperature is reduced to 400 ℃ at the cooling rate of 0.5 ℃/min, the temperature is kept for 4 hours, and finally, the sintered material is obtained by furnace cooling. The rest of the process parameters and the operation steps are completely the same as those of the example 1.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
Example 11
This comparative example differs from example 3 in that: in the step (2), after high-temperature sintering, cooling to 400 ℃ at a cooling rate of 6 ℃/min, preserving heat for 4h, and finally cooling along with a furnace to obtain a sintered material. The rest of the process parameters and the operation steps are completely the same as those of the example 1.
The residual alkali content of the high nickel ternary-calcined product prepared in this example is shown in table 1.
Comparative example 1
The embodiment provides a method for reducing the residual alkali content of a high nickel material, which specifically comprises the following steps:
(1) High-nickel ternary positive electrode material precursor Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 Uniformly mixing the lithium hydroxide with the lithium hydroxide to obtain a mixed material, wherein the molar ratio of lithium element in the lithium hydroxide to nickel, cobalt and manganese element in a precursor of the high-nickel ternary cathode material is 1.04;
(2) Heating the mixed material to 850 ℃ at the heating rate of 3 ℃/min, and keeping the temperature for 8 hours; then cooling to 400 ℃ at the cooling rate of 3 ℃/min, preserving the heat for 4 hours, and finally cooling along with the furnace to obtain a sintered material;
(3) And (3) sequentially crushing and grinding the sintering material, wherein the particle size of the crushed and ground material is 10.3 mu m, and the crushed and ground material passes through a 400-mesh screen to obtain a high-nickel ternary primary-combustion product with low residual alkali.
The residual alkali content of the high nickel ternary-calcined product prepared in this example is shown in table 1.
Comparative example 2
The embodiment provides a method for reducing the residual alkali content of a high nickel material, which specifically comprises the following steps:
(1) High-nickel ternary positive electrode material precursor Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 The lithium hydroxide and the additive are uniformly mixed to obtain a mixed material, the molar ratio of lithium element in the lithium hydroxide to nickel-cobalt-manganese element in a high-nickel ternary positive electrode material precursor is 1.04, the additive comprises ammonium bisulfate and lithium metaphosphate, the addition amount of the ammonium bisulfate accounts for 0.3wt% of the mass of the high-nickel ternary positive electrode material precursor, and the addition amount of the lithium metaphosphate accounts for 0.2wt% of the mass of the high-nickel ternary positive electrode material precursor;
(2) Heating the mixed material to 850 ℃ at the heating rate of 3 ℃/min, preserving the heat for 8 hours, and cooling along with the furnace to obtain a sintered material;
(3) And (3) sequentially crushing and grinding the sintered materials, wherein the particle size of the crushed and ground materials is 10.3 mu m, and the crushed and ground materials pass through a 400-mesh screen to obtain a high-nickel ternary primary combustion product with low residual alkali.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
Comparative example 3
The embodiment provides a method for reducing the residual alkali content of a nickel-rich material, which specifically comprises the following steps:
(1) High-nickel ternary positive electrode material precursor Ni 0.7 Co 0.1 Mn 0.2 (OH) 2 Uniformly mixing the lithium hydroxide with the lithium hydroxide to obtain a mixed material, wherein the molar ratio of the lithium element in the lithium hydroxide to the nickel-cobalt-manganese element in the precursor of the high-nickel ternary positive electrode material is 1.04;
(2) Heating the mixed material to 850 ℃ at the heating rate of 3 ℃/min, preserving the heat for 8 hours, and cooling along with the furnace to obtain a sintered material;
(3) And (3) sequentially crushing and grinding the sintering material, wherein the particle size of the crushed and ground material is 10.3 mu m, and the crushed and ground material passes through a 400-mesh screen to obtain a high-nickel ternary primary-combustion product with low residual alkali.
The residual alkali content of the high nickel ternary monohydrate prepared in this example is shown in table 1.
TABLE 1
As can be seen from the data in table 1:
(1) The residual alkali content of the nickel-rich material is higher than that of the nickel-rich material in examples 6 and 7, which are shown in example 3, because the low-temperature sintering temperature in example 6 is too low, the low-temperature sintering temperature in example 7 is too high, and both too low and too high sintering temperatures can cause the residual alkali content to be increased, and when the sintering temperature is higher than 400 ℃, the residual alkali content of the material is relatively higher, and the production cost is also increased.
(2) The residual alkali content of examples 8 and 9 is greater than that of example 3, because too short a holding time for the low-temperature sintering process in example 8 results in an increase in the residual alkali content, because when the sintering time is less than 3 hours, the residual alkali content of the material is relatively high, because below this time, the reaction of the additive with the residual alkali is not complete enough; the reason why the sintering time is too long in example 9 results in the increase of the residual alkali content is that when the sintering time is more than 5 hours, the residual alkali content of the material is increased and the production cost of the material is increased, because the metering of the additive is basically completed and the material can generate Li again with the time being prolonged 2 CO 3 Resulting in an increase in residual base. Therefore, too long or too short heat preservation time in the low-temperature sintering process can affect the residual alkali content of the high-nickel material.
(3) The residual alkali content of examples 10 and 11 is greater than that of example 3, because the temperature reduction rate of the low-temperature sintering process in example 10 is too low, and when the temperature reduction rate is lower than 1 ℃/min, the residual alkali content of the material is relatively higher and the specific capacity of the material is reduced, because the temperature reduction rate is lower, the reconstruction phenomenon of the material surface is induced, such as Li 2 CO 3 The particles are easy to accumulate on the surfaces of the particles, and lithium-deficient layers are formed on the surfaces of the particles; in example 11, when the temperature reduction rate in the low-temperature sintering process is too high, the residual alkali content of the material does not change significantly, but the specific capacity of the material is reduced, because when the temperature reduction rate is higher than 5 ℃/min, the residual alkali content of the material does not change significantly, but the specific capacity of the material is reduced, which is because the faster temperature reduction rate increases the crystal volume of the material particles, which is not favorable for increasing the specific capacity of the material. Therefore, the cooling rate of the low-temperature sintering process is too fast or too slow, which affects the residual alkali content of the high-nickel material.
(4) The residual alkali amount of comparative examples 1 to 3 is much higher than that of example 3 because the additive was omitted in comparative example 1, only the gradient sintering process was maintained, and the gradient sintering process was omitted in comparative example 2Only the additive is reserved; in comparative example 3 both the additive and the gradient sintering process were omitted. As can be seen from the residual alkali amount data of comparative examples 1 to 3, the gradient sintering process and the additive need to be present together to function, and the additive needs to be in a molten state with LiOH and Li on the surface of the sintered product 2 CO 3 Acid-base neutralization reaction occurs to remove residual alkali, while the melting process is realized only in the low-temperature sintering section of the gradient sintering process, and the residual alkali can be removed only by adopting the gradient sintering process and adding additives.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (11)
1. A method for reducing the residual alkali content of a high nickel material is characterized by comprising the following steps:
mixing a high-nickel ternary positive electrode material precursor, a lithium salt and an additive, and then performing gradient sintering to obtain a high-nickel ternary primary sintering product with low residual alkali, wherein the additive is a weak acid salt;
the gradient sintering process specifically comprises the following steps:
mixing a high-nickel ternary positive electrode material precursor, a lithium salt and an additive, sequentially performing high-temperature sintering and low-temperature sintering, and then cooling to room temperature;
cooling the mixed material after high-temperature sintering to a low-temperature sintering temperature at a cooling rate of 1-5 ℃/min;
the low-temperature sintering temperature is 200-400 ℃, the sintering temperature is kept for 3-5 h, and the high-temperature sintering process comprises the following steps: the mixed material is heated to a high-temperature sintering temperature at a heating rate of 1-5 ℃/min, the high-temperature sintering temperature is 700-900 ℃, the mixed material is kept at the high-temperature sintering temperature for 8-12 h, and the additive is one or the combination of at least two of ammonium dihydrogen phosphate, lithium metaphosphate, lithium dihydrogen phosphate, ammonium bisulfate, ammonium sulfate or lithium sulfate.
2. The method of claim 1, wherein the high nickel ternary positive electrode material precursor has a chemical formula of Ni x Co y Mn 1-x-y (OH) 2 Wherein x is more than or equal to 0.6 and less than 1, y is more than 0 and less than or equal to 0.4<x+y<1。
3. The method of claim 1, wherein said lithium salt comprises lithium hydroxide.
4. The method of claim 1, wherein the molar ratio of the lithium element in the lithium salt to the nickel-cobalt-manganese element in the high-nickel ternary positive electrode material precursor is 1.02 to 1.06.
5. The method according to claim 1, wherein the single additive is added in an amount of 0.1-0.4 wt% based on the mass of the high-nickel ternary positive electrode material precursor.
6. The method of claim 1, wherein the gradient sintering process is performed in an oxygen atmosphere furnace.
7. The method as claimed in claim 6, wherein the oxygen atmosphere furnace has an oxygen content of 97% or more by volume.
8. The method of claim 1, wherein after the gradient sintering is completed, the sintered material is crushed, ground and sieved in sequence to obtain the low residual alkali high nickel ternary monohydrate product.
9. The method of claim 8, wherein the particle size after crushing is 7 to 13 μm.
10. The method of claim 8, wherein the milled sinter material is screened through a 200-500 mesh screen.
11. The low residual alkali high nickel material prepared by the method of any one of claims 1 to 10, wherein the residual alkali content in the low residual alkali high nickel material is 3500 to 7000ppm.
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| CN113725410B (en) * | 2021-08-05 | 2023-07-04 | 华中科技大学 | Ternary positive electrode material coated with lithium metaphosphate in situ, and preparation method and application thereof |
| CN113903884B (en) * | 2021-09-30 | 2022-07-22 | 清华大学深圳国际研究生院 | Positive electrode active material, preparation method thereof, positive electrode and lithium ion battery |
| CN114597395A (en) * | 2022-03-15 | 2022-06-07 | 昆明理工大学 | Preparation method of single crystal type high-nickel ternary cathode material |
| CN114349077A (en) * | 2022-03-18 | 2022-04-15 | 宜宾锂宝新材料有限公司 | Preparation method of ternary cathode material, ternary cathode material and application |
| CN114899391A (en) * | 2022-04-27 | 2022-08-12 | 天津巴莫科技有限责任公司 | Ultra-high nickel single crystal anode material and preparation method thereof |
| CN114682575B (en) * | 2022-05-31 | 2022-08-23 | 宜宾锂宝新材料有限公司 | Method for reducing residual alkali on surface of high-nickel anode material, obtained material and application |
| CN115710023B (en) * | 2022-10-21 | 2023-09-05 | 安徽天力锂能有限公司 | Preparation method of high-nickel cathode material of lithium ion battery and high-nickel cathode material of lithium ion battery prepared by using same |
| CN116031389A (en) * | 2023-02-15 | 2023-04-28 | 华鼎国联电池材料有限公司 | High-nickel ternary positive electrode material and preparation method thereof |
| CN116259748A (en) * | 2023-04-04 | 2023-06-13 | 浙江华友钴业股份有限公司 | Preparation method of low-residual-alkali ternary positive electrode material and low-residual-alkali ternary positive electrode material |
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