CN114314697A - Single-crystal high-nickel lithium battery positive electrode material and preparation method thereof - Google Patents
Single-crystal high-nickel lithium battery positive electrode material and preparation method thereof Download PDFInfo
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Abstract
The invention provides a monocrystal high-nickel lithium battery positive electrode material and a preparation method thereof, wherein the preparation method comprises the following steps: (1) performing ball milling treatment on nickel oxide, cobaltosic oxide, manganese dioxide and lithium carbonate to obtain mixed powder; wherein the molar ratio of the elements of nickel, cobalt and manganese in the mixed powder is 8:1: 1; (2) and sintering the mixed powder to obtain the single crystal high nickel lithium battery positive electrode material. The preparation method of the single crystal high nickel lithium battery positive electrode material provided by the invention has the advantages of simple process, low cost, capability of effectively synthesizing the single crystal high nickel lithium battery positive electrode material and high compaction density.
Description
Technical Field
The invention relates to the technical field of battery materials, in particular to a single crystal high nickel lithium battery positive electrode material and a preparation method thereof.
Background
The lithium ion battery is widely applied to the fields of 3C products, transportation, aerospace and military because of the advantages of high energy density, long service life, high working voltage, wide working temperature range, no memory effect, environmental protection and the like. Among them, the new generation of lithium ion battery anode material, the high nickel ternary anode material, has high specific capacity and stable cycle performance and is widely applied to the field of electric automobiles.
The NCM811 positive electrode material is considered to be one of the most promising positive electrode materials because of its high specific capacity and low cost. In the prior art, the NCM811 material is mostly a polycrystalline secondary spherical particle anode material, the method uniformly mixes three elements of nickel, cobalt and manganese to fully exert the performance advantages of the material, however, the polycrystalline secondary spherical particle anode material has the defect of low compaction density due to gaps generated among primary particles after compaction, so that the volume energy density of the material is low; and cracks are easy to appear in the charging and discharging processes, so that the capacity is accelerated to be attenuated, and the stability is poor. With the higher demand for lithium ion battery capacity, further improvements in lithium ion battery energy density are needed.
The single crystal material can effectively improve the compaction density of the anode material, thereby improving the energy density of the battery, avoiding the occurrence of cracks in the charging and discharging process and expanding the application range of the lithium ion battery. However, the preparation process of the single crystal high nickel system is not mature, and the existing preparation processes mainly comprise three types: high-temperature calcination of precursor mixed lithium, multi-step calcination of precursor mixed lithium and molten salt synthesis. Wherein, high calcination temperature (for example 950 ℃) is needed for high-temperature calcination after lithium mixing of the precursor, so that more lithium is volatilized in the preparation process, the preparation cost is increased, and the particle agglomeration is serious at high temperature; although the multi-step calcination of the precursor lithium mixed can slightly reduce the synthesis temperature (for example 850 ℃), the process is complex, the parameter variables are more, and the operation difficulty is higher; the cost of molten salt synthesis is high; in addition, the preparation processes all need precursors prepared by a coprecipitation method, and the coprecipitation method for preparing the precursors can generate industrial wastewater, so that the treatment cost is high, the preparation procedures are further increased, and the precursors have great influence on the performance of the finally prepared cathode material. Therefore, a preparation method of a single crystal high nickel lithium battery positive electrode material with simple process and low cost is urgently needed.
Disclosure of Invention
The embodiment of the invention provides a single-crystal high-nickel lithium battery positive electrode material and a preparation method thereof.
In a first aspect, the invention provides a preparation method of a single-crystal high-nickel lithium battery positive electrode material, which comprises the following steps:
(1) carrying out ball milling on a nickel source, a cobalt source, a manganese source and lithium carbonate to obtain mixed powder; wherein the molar ratio of the elements of nickel, cobalt and manganese in the mixed powder is 8:1: 1;
(2) and sintering the mixed powder to obtain the single crystal high nickel lithium battery positive electrode material.
Preferably, in step (1), the nickel source is preferably nickel oxide;
the cobalt source is preferably cobaltosic oxide;
the manganese source is preferably manganese dioxide.
Preferably, in the step (1), the molar ratio of the elements of lithium, nickel, cobalt and manganese in the mixed powder is (10.5-11.4): 8:1: 1.
Preferably, in step (1), the purity of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate is greater than 99%.
Preferably, in the step (1), the ball-to-material ratio of the ball-milling treatment is (4-6): 1;
the rotation speed of the ball milling treatment is 300-400 rpm, and the ball milling time is 4-6 h.
Preferably, in the step (1), a process control agent is further included in the ball milling treatment, and the amount of the process control agent is 100 to 250% of the sum of the mass of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate.
Preferably, the process control agent comprises ethanol.
Preferably, the particle size of the mixed powder is 1-5 μm.
Preferably, after the step (1) and before the step (2), further comprising: and carrying out standing treatment and drying treatment on the mixed powder in sequence, wherein the standing treatment time is 6-24 h.
Preferably, the drying treatment temperature is 80-100 ℃, and the time is not less than 6 h.
Preferably, in the step (2), the sintering treatment includes a pre-sintering treatment and a secondary sintering treatment;
the flow rate of the oxygen for sintering treatment is 40-120 mL/min;
the temperature of the pre-sintering treatment is 450-550 ℃, and the heat preservation time is 4-6 h;
the temperature of the secondary sintering treatment is 850-925 ℃, and the heat preservation time is 20-24 hours.
In a second aspect, the invention provides the single-crystal high-nickel lithium battery positive electrode material obtained by the preparation method of the single-crystal high-nickel lithium battery positive electrode material in the first aspect, wherein the molar ratio of elements of lithium, nickel, cobalt and manganese in the single-crystal high-nickel lithium battery positive electrode material is 10:8:1: 1.
Compared with the prior art, the invention at least has the following beneficial effects:
the preparation method successfully prepares the NCM811 monocrystal high-nickel lithium battery anode material by adopting the ball-milling mixed powder and high-temperature sintering preparation process. Compared with the existing preparation process of the single-crystal high-nickel lithium battery cathode material, the preparation method disclosed by the invention is simple in synthesis process, simple in equipment, easy in raw material obtaining, and free from precursor preparation, so that the preparation cost is low, and meanwhile, the component controllability in the preparation process is better, so that the preparation method is suitable for macro-preparation and large-scale production, and has a better application prospect.
Drawings
Fig. 1 is a flow chart of a method for preparing a single-crystal high-nickel lithium battery positive electrode material according to an embodiment of the invention;
fig. 2 is an XRD pattern of the NCM811 single-crystal high nickel lithium battery positive electrode material prepared in example 2 of the present invention;
FIG. 3 is a voltage profile of the NCM811 single crystal high nickel lithium battery positive electrode material prepared in example 2 of the present invention;
fig. 4 is an electron microscope image of the NCM811 single-crystal high-nickel lithium battery positive electrode material prepared in example 2 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention, and based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the scope of the present invention.
As shown in fig. 1, an embodiment of the present invention provides a preparation method of a single-crystal high-nickel lithium battery positive electrode material, where the preparation method includes the following steps:
(1) carrying out ball milling on a nickel source, a cobalt source, a manganese source and lithium carbonate to obtain mixed powder; wherein the molar ratio of the elements of nickel, cobalt and manganese in the mixed powder is 8:1: 1;
(2) and sintering the mixed powder to obtain the single crystal high nickel lithium battery positive electrode material.
According to the invention, a simple and easy-to-operate solid-phase sintering method is adopted, the raw materials are subjected to ball milling treatment to obtain mixed powder, then sintering treatment is carried out at high temperature, primary particle growth is promoted through sintering treatment to obtain a single crystal material, sufficient reaction and diffusion time are provided for three elements of nickel, cobalt and manganese through long-time sintering treatment, and finally the NCM811 single crystal high-nickel lithium battery anode material is prepared.
It is noted that the nickel source, the cobalt source and the manganese source are commonly used materials for preparing the nickel-cobalt-manganese ternary cathode material, and include, but are not limited to, nickel salt, cobalt salt and manganese salt, for example.
According to some preferred embodiments, in step (1), the nickel source is nickel oxide; the cobalt source is cobaltosic oxide; the manganese source is manganese dioxide.
According to some preferred embodiments, in the step (1), the molar ratio of the elements of lithium, nickel, cobalt and manganese in the mixed powder is (10.5 to 11.4):8:1:1 (for example, 10.5:8:1:1, 10.6:8:1:1, 10.7:8:1:1, 10.8:8:1:1, 10.9:8:1:1, 11:8:1:1, 11.1:8:1:1, 11.2:8:1:1, 11.3:8:1:1 or 11.4:8:1: 1).
In the invention, because lithium is partially volatilized in the sintering treatment process, the lithium element in the finally prepared single crystal high nickel lithium battery positive electrode material cannot meet the use requirement, in order to prepare the NCM811 single crystal high nickel lithium battery positive electrode material with the element molar ratio of lithium, nickel, cobalt and manganese being 10:8:1:1, a small excess of lithium carbonate needs to be added in the ball milling treatment process to make up for the loss of lithium in the sintering treatment, and the addition of the excess lithium carbonate can also accelerate the appearance of solid solution existing in the form of a single phase, promote the growth of fine particles, and accelerate the liquid-solid phase sintering diffusion process of the multi-element oxide, so that the distribution of the transition metal element in the product is more uniform, and the crystallization progress of the material is accelerated.
According to some preferred embodiments, in step (1), the purity of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate is greater than 99% (e.g., may be 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, etc.).
In the invention, the purity of raw materials such as nickel oxide, cobaltosic oxide, manganese dioxide, lithium carbonate and the like is limited, so that the existence of impurities can be reduced, and the performance of the prepared single-crystal high-nickel lithium battery positive electrode material is ensured.
According to some preferred embodiments, in the step (1), the ball milling treatment adopts a ball-to-material ratio of (4-6: 1) (for example, 4:1, 4.5:1, 5:1, 5.5:1 or 6: 1);
the rotation speed of the ball milling treatment is 300-400 rpm (for example, 300rpm, 320rpm, 340rpm, 350rpm, 360rpm, 380rpm or 400rpm), and the ball milling time is 4-6 h (for example, 4h, 4.5h, 5h, 5.5h or 6 h).
In the invention, the purpose of ball milling treatment is to disperse secondary particles or satellite balls existing in nickel oxide, cobaltosic oxide, manganese dioxide and lithium carbonate to obtain primary particles, so that the problem of low compaction density is avoided, and the prepared material is further ensured to have higher volume energy density; performing ball milling treatment on the raw material powder with different particle sizes to obtain mixed powder with smaller and uniform particle size; meanwhile, the three elements of nickel, cobalt and manganese are fully and uniformly mixed, so that the NCM811 monocrystal high-nickel lithium battery positive electrode material with uniform performance is obtained.
According to some preferred embodiments, in the step (1), a process control agent is further included in the ball milling treatment, and the amount of the process control agent is 100 to 250% (for example, may be 100%, 120%, 150%, 180%, 200%, 220%, or 250%) of the sum of the masses of the nickel oxide, the tricobalt tetroxide, the manganese dioxide, and the lithium carbonate.
According to some preferred embodiments, the process control agent comprises ethanol.
In the invention, the process control agent is added in the ball milling process, so that the cold welding of powder in the ball milling process can be prevented, the agglomeration of the powder can be prevented, the ball milling process is accelerated, and the powder yield is improved.
According to some preferred embodiments, the particle size of the mixed powder is 1 to 5 μm (for example, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm).
According to some preferred embodiments, after step (1) and before step (2), further comprising: and (2) carrying out standing treatment and drying treatment on the mixed powder in sequence, wherein the standing treatment time is 6-24 h (for example, 6h, 9h, 10h, 12h, 18h, 20h or 24 h).
According to some preferred embodiments, the mixed powder is dried at a temperature of 80 to 100 ℃ (for example, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃) for at least 6 hours (for example, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours).
In the invention, because the mixed powder just after ball milling treatment has higher temperature and higher activity, the activity of the mixed powder is reduced by standing treatment, namely, the mixed powder after ball milling treatment is cooled by standing. The process control agent added during the ball milling process can be further removed by the drying process.
According to some preferred embodiments, in the step (2), the sintering process includes a pre-sintering process and a secondary sintering process;
the oxygen flow rate of the sintering treatment is 40-120 mL/min (for example, 40mL/min, 50mL/min, 60mL/min, 70mL/min, 80mL/min, 90mL/min, 100mL/min, 110mL/min or 120 mL/min);
the temperature of the pre-sintering treatment is 450-550 ℃ (for example, 450 ℃, 455 ℃, 460 ℃, 470 ℃, 480 ℃, 490 ℃, 500 ℃, 505 ℃, 510 ℃, 520 ℃, 525 ℃, 530 ℃, 540 ℃ or 550 ℃), and the heat preservation time is 4-6 h (for example, 4h, 4.5h, 5h, 5.5h or 6 h);
the temperature of the secondary sintering treatment is 850-925 ℃ (for example, 850 ℃, 855 ℃, 860 ℃, 865 ℃, 870 ℃, 875 ℃, 880 ℃, 885 ℃, 890 ℃, 895 ℃, 900 ℃, 905 ℃, 910 ℃, 915 ℃, 920 ℃ or 925 ℃), and the heat preservation time is 20-24 h (for example, 20h, 20.5h, 21h, 21.5h, 22h, 22.5h, 23h, 23.5h or 24 h).
The temperature increase rate of the pre-sintering treatment and the secondary sintering treatment is 4 to 6 ℃/min (for example, 4 ℃/min, 4.5 ℃/min, 5 ℃/min, 4.5 ℃/min, or 6 ℃/min).
According to the invention, a tubular furnace is used for sintering treatment, oxygen is introduced for sintering, firstly, pre-sintering is adopted to preliminarily mix nickel, cobalt, manganese and lithium elements, and then sintering is carried out at 850-925 ℃ for 20-24 h, so that all elements can be fully diffused by long-time sintering and oxygen introduction, and the NCM811 single-crystal high-nickel lithium battery anode material can be prepared through sintering treatment, and industrial wastewater and the like cannot be generated because a coprecipitation method is not used in the whole preparation process; the preparation process is simpler, no various experimental parameter variables exist, and the operation and the control are convenient, so that the preparation method of the single-crystal high-nickel lithium battery positive electrode material provided by the invention has wide popularization value.
In the present invention, when the oxygen flow rate is less than 40mL/min, the Ni element is not sufficiently oxidized; however, if the oxygen flow rate is higher than 120mL/min, the preparation cost will be increased, so the oxygen flow rate for sintering treatment is selected to be 40-120 mL/min.
The invention also provides a single crystal high nickel lithium battery anode material, which is obtained by the preparation method of the single crystal high nickel lithium battery anode material.
According to some preferred embodiments, the molar ratio of the elements lithium, nickel, cobalt and manganese in the single-crystal high-nickel lithium battery positive electrode material is 10:8:1: 1.
In the invention, by controlling the sintering temperature and time and the addition amount of lithium carbonate in the ball milling treatment, the monocrystal high nickel lithium battery positive electrode material with the element molar ratio of lithium, nickel, cobalt and manganese of 10:8:1:1 can be prepared. Meanwhile, experiments prove that the molar ratio of the elements of lithium, nickel, cobalt and manganese of the single-crystal high-nickel lithium battery anode material prepared by the preparation method is (9.7-10.4):8:1: 1.
In order to more clearly illustrate the technical scheme and advantages of the present invention, the following provides a detailed description of a method for preparing a single-crystal high-nickel lithium battery positive electrode material by using several embodiments.
Example 1
(1) Weighing nickel oxide with the purity of 99.5%, cobaltosic oxide, manganese dioxide and lithium carbonate powder as raw materials according to the element molar ratio of Li to Ni to Co to Mn of 11 to 8 to 1, putting the raw materials into a planetary ball mill (the ball-to-material ratio is 5 to 1), adding ethanol as a process control agent, and carrying out ball milling treatment for 6 hours at the rotating speed of 400rpm to obtain mixed powder; wherein the dosage of the ethanol is 200 percent of the sum of the mass of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate;
(2) standing the mixed powder obtained in the step (1) for 10h, then drying the mixed powder in a forced air drying oven at 80 ℃ for 10h, then placing the mixed powder in a tubular furnace, introducing oxygen (the flow is 40mL/min), pre-sintering the mixed powder at 500 ℃ for 5h, cooling the mixed powder, taking out the obtained powder, uniformly grinding the powder, then placing the powder in the tubular furnace, introducing oxygen (the flow is 40mL/min), heating the powder to 875 ℃ at the heating rate of 5 ℃/min, and sintering the powder for 18h at the temperature of 875 ℃ to obtain the NCM811 single-crystal high-nickel lithium battery anode material.
Example 2
(1) Weighing nickel oxide with the purity of 99.5%, cobaltosic oxide, manganese dioxide and lithium carbonate powder as raw materials according to the element molar ratio of Li to Ni to Co to Mn of 11 to 8 to 1, putting the raw materials into a planetary ball mill (the ball-to-material ratio is 5 to 1), adding ethanol as a process control agent, and carrying out ball milling treatment for 6 hours at the rotating speed of 400rpm to obtain mixed powder; wherein the dosage of the ethanol is 200 percent of the sum of the mass of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate;
(2) standing the mixed powder obtained in the step (1) for 10h, then drying the mixed powder in a forced air drying oven at 80 ℃ for 10h, then placing the mixed powder in a tubular furnace, introducing oxygen (the flow rate is 80mL/min), pre-sintering the mixed powder at 500 ℃ for 5h, cooling the mixed powder, taking out the powder, uniformly grinding the powder, placing the powder in the tubular furnace again, introducing oxygen (the flow rate is 80mL/min), heating the powder to 875 ℃ at the heating rate of 5 ℃/min, and sintering the powder for 24h at 875 ℃ to obtain the NCM811 single-crystal high-nickel lithium battery anode material.
Example 3
(1) Weighing nickel oxide with the purity of 99.5%, cobaltosic oxide, manganese dioxide and lithium carbonate powder as raw materials according to the element molar ratio of Li to Ni to Co to Mn of 11 to 8 to 1, putting the raw materials into a planetary ball mill (the ball-to-material ratio is 5 to 1), adding ethanol as a process control agent, and carrying out ball milling treatment for 6 hours at the rotating speed of 400rpm to obtain mixed powder; wherein the dosage of the ethanol is 200 percent of the sum of the mass of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate;
(2) standing the mixed powder obtained in the step (1) for 10h, then drying the mixed powder in a forced air drying oven at 80 ℃ for 10h, then placing the mixed powder in a tubular furnace, introducing oxygen (the flow rate is 80mL/min), pre-sintering the mixed powder at 500 ℃ for 5h, cooling the mixed powder, taking out the obtained powder, uniformly grinding the powder, then placing the powder in the tubular furnace again, introducing oxygen (the flow rate is 80mL/min), heating the powder to 925 ℃ at the heating rate of 5 ℃/min, and sintering the powder for 18h at the temperature of 925 ℃ to obtain the NCM811 single-crystal high-nickel lithium battery anode material.
Example 4
(1) Weighing nickel oxide with the purity of 99.5%, cobaltosic oxide, manganese dioxide and lithium carbonate powder as raw materials according to the element molar ratio of Li to Ni to Co to Mn of 10.5 to 8 to 1, putting the raw materials into a planetary ball mill (the ball-to-material ratio is 6 to 1), adding ethanol as a process control agent, and carrying out ball milling treatment for 6 hours at the rotating speed of 400rpm to obtain mixed powder; wherein the dosage of the ethanol is 150 percent of the sum of the mass of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate;
(2) standing the mixed powder obtained in the step (1) for 6h, then placing the mixed powder in a forced air drying oven to dry for 7h at 100 ℃, then placing the mixed powder in a tubular furnace, introducing oxygen (the flow is 100mL/min), pre-sintering at 450 ℃ for 6h, cooling, taking out the obtained powder, uniformly grinding, then placing the powder in the tubular furnace again, introducing oxygen (the flow is 100mL/min), heating to 850 ℃ at the heating rate of 6 ℃/min, and sintering at 850 ℃ for 24h to obtain the NCM811 single crystal high nickel lithium battery anode material.
Example 5
(1) Weighing nickel oxide with the purity of 99.5%, cobaltosic oxide, manganese dioxide and lithium carbonate powder as raw materials according to the element molar ratio of Li to Ni to Co to Mn of 11.4 to 8 to 1, putting the raw materials into a planetary ball mill (the ball-to-material ratio is 5 to 1), adding ethanol as a process control agent, and carrying out ball milling treatment for 6 hours at the rotating speed of 300rpm to obtain mixed powder; wherein the dosage of the ethanol is 250 percent of the sum of the mass of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate;
(2) standing the mixed powder obtained in the step (1) for 12h, then placing the mixed powder in a forced air drying oven to dry for 8h at 90 ℃, then placing the mixed powder in a tube furnace, introducing oxygen (the flow is 60mL/min), pre-sintering at 550 ℃ for 4h, cooling, taking out the obtained powder, uniformly grinding, then placing the powder in the tube furnace again, introducing oxygen (the flow is 60mL/min), heating to 900 ℃ at the heating rate of 4 ℃/min, and sintering at 900 ℃ for 20h to obtain the NCM811 single crystal high nickel lithium battery anode material.
Example 6
(1) Weighing nickel oxide with the purity of 99.5%, cobaltosic oxide, manganese dioxide and lithium carbonate powder as raw materials according to the element molar ratio of Li to Ni to Co to Mn of 11 to 8 to 1, putting the raw materials into a planetary ball mill (the ball-to-material ratio is 4 to 1), adding ethanol as a process control agent, and carrying out ball milling treatment for 5 hours at the rotating speed of 350rpm to obtain mixed powder; wherein the dosage of the ethanol is 200 percent of the sum of the mass of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate;
(2) standing the mixed powder obtained in the step (1) for 12h, placing the mixed powder in a tubular furnace, then placing the mixed powder in a blast drying oven, drying the mixed powder for 10h at 70 ℃, introducing oxygen (the flow is 120mL/min), performing presintering treatment for 5.5h at 480 ℃, cooling, taking out the obtained powder, uniformly grinding, then placing the powder in the tubular furnace again, introducing oxygen (the flow is 120mL/min), heating to 875 ℃ at the heating rate of 4.5 ℃/min, and performing sintering treatment for 20h at 875 ℃ to obtain the NCM811 single-crystal high-nickel lithium battery anode material.
Comparative example 1
Preparing an NCM811 polycrystalline high-nickel lithium battery positive electrode material:
(1) mixing NiSO4·6H2O、CoSO4·7H2O and MnSO4·H2Preparing a 2mol/L sulfate mixed salt solution from three transition metal salts O according to the molar ratio of Ni to Co to Mn of 8 to 1, preparing a 10mol/L sodium hydroxide solution, and preparing the sodium hydroxide solution and 25% ammonia water into a mixed solution. Adjusting the temperature of circulating water in the reaction kettle to 50 ℃, adding ammonia water to adjust the pH value to 11.3, introducing inert gas nitrogen into the reaction kettle for 2 hours to remove air, setting the rotating speed of the reaction kettle to be 500rpm, pumping a salt solution into the reaction kettle by using a peristaltic pump when the reaction starts, and ensuring the complexation and precipitation of excessive metal ions by externally connecting an ammonia-alkali solution through the control of a built-in pH meter. After the reaction is finished, aging is carried out for 12h, and drying is carried out at 110 ℃ after washing and filtering to obtain hydroxide precursorA body;
(2) the hydroxide precursor is mixed with lithium hydroxide monohydrate LiOH H2And (3) completely grinding O, controlling the molar ratio of Li to TM (the sum of the molar ratios of the three elements of nickel, cobalt and manganese) to be 1.05:1, pre-sintering in a tube furnace at 500 ℃ for 6h, cooling to room temperature, taking out, fully grinding, placing in the tube furnace, controlling the oxygen flow to be 80ml/min, and preserving the temperature at 800 ℃ for 12h to obtain the NCM811 polycrystalline high-nickel lithium battery positive electrode material.
Comparative example 2
Preparing a NCM811 monocrystal high-nickel lithium battery positive electrode material:
(1) mixing NiSO4·6H2O、CoSO4·7H2O and MnSO4·H2Preparing a 2mol/L sulfate mixed salt solution from three transition metal salts O according to the molar ratio of Ni to Co to Mn of 8 to 1, preparing a 10mol/L sodium hydroxide solution, and preparing the sodium hydroxide solution and 25% ammonia water into a mixed solution. Adjusting the temperature of circulating water in the reaction kettle to 50 ℃, adding ammonia water to adjust the pH value to 11.3, introducing inert gas nitrogen into the reaction kettle for 2 hours to remove air, setting the rotating speed of the reaction kettle to be 500rpm, pumping a salt solution into the reaction kettle by using a peristaltic pump when the reaction starts, and ensuring the complexation and precipitation of excessive metal ions by externally connecting an ammonia-alkali solution through the control of a built-in pH meter. After the reaction is finished, aging for 12h, washing, filtering and drying at 110 ℃ to obtain a hydroxide precursor;
(2) mixing the hydroxide precursor obtained in the step (1) with a lithium source (LiOH. H)2O) is weighed according to the proportion that Li/TM (the sum of the molar ratios of the three elements of nickel, cobalt and manganese) is 1.5:1, and a proper amount of Li is added2SO4As a molten salt, a hydroxide precursor is mixed with a lithium source and Li2SO4And (2) uniformly mixing, placing the mixed powder in a tube furnace, introducing oxygen (the flow is 80ml/min), preserving the temperature for 15h at 840 ℃, washing the mixed powder with water after cooling to remove redundant impurities and residual lithium, and carrying out postbaking for 3h at 750 ℃ to obtain the NCM811 single-crystal high-nickel lithium battery positive electrode material.
The NCM811 single-crystal high nickel lithium battery positive electrode materials prepared in examples 1 to 6 and the high nickel lithium battery positive electrode materials prepared in comparative examples 1 to 2 were respectively subjected to a compaction density test, and the test results are shown in table 1.
Specifically, XRD test was performed on the NCM811 single-crystal high nickel lithium battery positive electrode material prepared in example 2 to obtain an XRD pattern shown in fig. 2, and the NCM811 single-crystal high nickel lithium battery positive electrode material was successfully prepared on the surface; the NCM811 monocrystal high-nickel lithium battery positive electrode material prepared in example 2 is used as a positive electrode, metal lithium is used as a negative electrode, Celgard2400 is adopted as a diaphragm, and 1mol/L LiPF is adopted as electrolyte6EC. Assembling mixed solution of EMC and DEC (volume ratio is 1:1:1) to obtain a battery; the battery performance is tested to obtain a discharge voltage curve shown in fig. 3, and the curve shows that the initial specific capacity of the battery is 190mAh/g, the battery is discharged at a constant current, the voltage is reduced from 4.25V to about 3V as a termination voltage along with the time, and the discharge capacity is about 190 mAh; as can be seen from the electron microscope image of the NCM811 single-crystal high-nickel lithium battery positive electrode material prepared in example 2 shown in fig. 4, the morphology of the prepared material is that of a single-crystal material, and it is confirmed that the single-crystal high-nickel lithium battery positive electrode material is indeed prepared.
TABLE 1
As can be seen from Table 1, the NCM811 single-crystal high-nickel lithium battery positive electrode materials prepared by the invention all have higher compaction density. In the comparative example 1, the NCM811 polycrystalline high-nickel lithium battery positive electrode material obtained by the existing preparation process is low in compacted density, so that the material volume energy density is low; and cracks are easy to appear in the charging and discharging processes, so that the capacity is accelerated to be attenuated, and the stability is poor. In addition, the hydroxide precursor is prepared by adopting a coprecipitation method in the comparative example 1, and a high-concentration sodium hydroxide alkali solution and ammonia water are also needed in the preparation process, so that industrial wastewater is easily generated, the treatment of the industrial wastewater is increased, and the treatment cost is high; meanwhile, the process for preparing the precursor is complicated, long in time consumption, more equipment and instruments are needed, and the operation difficulty is high. The method has the advantages that the nickel source, the cobalt source, the manganese source and the lithium carbonate are directly subjected to ball milling treatment, the operation is simple, the consumed time is short, the energy consumption is low, the nickel, the cobalt, the manganese and the lithium can be uniformly mixed only through the ball milling treatment, and the NCM811 single crystal high-nickel lithium battery positive electrode material which is beneficial to large-scale industrial production is more realized.
Comparative example 2A hydroxide precursor was prepared by the coprecipitation method, and LiOH. H was used as the hydroxide precursor2O and Li2SO4Uniformly mixing, keeping the temperature at 840 ℃ for 15h, removing impurities and residual lithium after cooling, and then carrying out postbaking at 750 ℃ for 3h to obtain the NCM811 monocrystal high-nickel lithium battery positive electrode material. Firstly, the comparative example 2 is the same as the comparative example 1, and the coprecipitation method is adopted, so that industrial wastewater is easy to generate, and the treatment cost is high; the process is complicated, the time consumption is long, and the operation difficulty is high; secondly, the comparative example 2 also needs to be subjected to two times of high-temperature treatment and operations for removing impurities and residual lithium, and the operation is also complex, and the time is long when the temperature is reduced to 750 ℃ from 840 ℃. According to the preparation method, the hydroxide precursor does not need to be prepared, the required monocrystal high-nickel lithium battery positive electrode material can be prepared only by high-temperature sintering treatment after the mixed powder is obtained, the operation is simpler, the consumed time is shorter, complex instruments and equipment are not needed, the cost is lower, and therefore the preparation method is suitable for large-scale production and has wide popularization value. In addition, the coprecipitation method requires that the adopted raw materials are soluble nickel salt, cobalt salt and manganese salt, but the coprecipitation method adopts ball milling treatment, so that the raw materials do not need to be limited to the soluble nickel salt, cobalt salt and manganese salt, and the sources of the adopted raw materials are wider, so that the preparation method of the single-crystal high-nickel lithium battery positive electrode material provided by the application is easier to be widely applied.
In conclusion, the NCM811 monocrystal high-nickel lithium battery positive electrode material with higher compaction density is successfully prepared by adopting a preparation process combining ball-milling mixed powder and high-temperature sintering. The preparation method disclosed by the invention is simple in synthesis process, simple in equipment, easy in raw material obtaining, and free from precursor preparation, so that the preparation cost is low, and meanwhile, the component controllability in the preparation process is better, so that the preparation method is suitable for macro preparation and large-scale production.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. The preparation method of the single-crystal high-nickel lithium battery positive electrode material is characterized by comprising the following steps of:
(1) carrying out ball milling on a nickel source, a cobalt source, a manganese source and lithium carbonate to obtain mixed powder; wherein the molar ratio of the elements of nickel, cobalt and manganese in the mixed powder is 8:1: 1;
(2) and sintering the mixed powder to obtain the single crystal high nickel lithium battery positive electrode material.
2. The production method according to claim 1, wherein in step (1):
the nickel source is preferably nickel oxide;
the cobalt source is preferably cobaltosic oxide;
the manganese source is preferably manganese dioxide; and/or;
the molar ratio of elements of lithium, nickel, cobalt and manganese in the mixed powder is (10.5-11.4) 8:1: 1.
3. The production method according to claim 1, wherein in step (1):
the purities of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate are all more than 99%.
4. The production method according to claim 1, wherein in step (1):
the ball-material ratio adopted in the ball milling treatment is (4-6): 1;
the rotation speed of the ball milling treatment is 300-400 rpm, and the ball milling time is 4-6 h.
5. The production method according to claim 1, wherein in step (1):
the ball milling treatment also comprises a process control agent, and the dosage of the process control agent is 100-250% of the sum of the mass of the nickel oxide, the cobaltosic oxide, the manganese dioxide and the lithium carbonate.
6. The method of claim 5, wherein:
the process control agent comprises ethanol.
7. The method of claim 1, wherein:
the particle size of the mixed powder is 1-5 μm.
8. The production method according to any one of claims 1 to 7, characterized in that:
after the step (1) and before the step (2), further comprising: carrying out standing treatment and drying treatment on the mixed powder in sequence, wherein the standing treatment time is 6-24 h;
preferably, the drying treatment temperature is 80-100 ℃, and the time is not less than 6 h.
9. The production method according to any one of claims 1 to 8, characterized in that, in step (2):
the sintering treatment comprises pre-sintering treatment and secondary sintering treatment;
the flow rate of the oxygen for sintering treatment is 40-120 mL/min;
the temperature of the pre-sintering treatment is 450-550 ℃, and the heat preservation time is 4-6 h;
the temperature of the secondary sintering treatment is 850-925 ℃, and the heat preservation time is 20-24 hours.
10. The single crystal high nickel lithium battery positive electrode material is characterized by being obtained by the preparation method of the single crystal high nickel lithium battery positive electrode material according to any one of claims 1 to 9, wherein the molar ratio of elements of lithium, nickel, cobalt and manganese in the single crystal high nickel lithium battery positive electrode material is 10:8:1: 1.
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