CN113097460A - Ternary cathode material @ indium oxide core-shell structure composite material and preparation method thereof - Google Patents
Ternary cathode material @ indium oxide core-shell structure composite material and preparation method thereof Download PDFInfo
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- 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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Abstract
The invention discloses a preparation method of a ternary cathode material @ indium oxide core-shell structure composite material, and belongs to the technical field of lithium ion battery cathode materials. The preparation method comprises the steps of coating and roasting. The invention optimizes the coating process, and avoids the phenomenon of uneven coating caused by the fact that the condition of nuclear coating is easy to occur in the coating process. The crystallinity and purity of the coating layer are improved through the roasting step, and the performance of the composite material is further improved. Compared with the original ternary cathode material which is not subjected to coating treatment, the composite material has the characteristics of obviously improved conductivity and ionic property, higher specific capacity, good cycle stability, improved rate capability and obviously improved overall conductivity. The preparation process is simple, pollution-free, low in cost, short in flow and easy to industrially amplify.
Description
Technical Field
The invention relates to the technical field of lithium ion battery anode materials, in particular to a ternary anode material @ indium oxide core-shell structure composite material and a preparation method thereof, and the ternary anode material @ indium oxide core-shell structure composite material can be used for a lithium ion battery anode material.
Background
The high-nickel ternary cathode material has attracted wide attention in recent years, not only because the high-nickel ternary cathode material has the theoretical specific capacity of more than 200mAh/g, but also the cost is lower. However, the mixed-lithium-nickel-displacement effect of such materials during lithium intercalation can cause structural transformation, and the exposure to air causes the reduction of nickel element on the surface, so that the gelation of the materials can significantly influence the transfer of electron ions in the bulk phase.
The electrode active material is coated and modified, the coating layer can be used as an effective physical barrier layer to reduce the corrosion of the external electrode on the active material and reduce side reactions, and meanwhile, the high-ion electronic property can obviously improve the discharge property. Indium oxide (In)2O3) Is a superconductor material which is widely applied to various fields of photoelectric equipment such as solar batteries, photocatalysis, gas sensing and the like. It has excellent conductivity of about 103S/cm far higher than 10 of the body of the high nickel material-5S/cm. At the same time, In2O3The coating has good chemical stability and a stable body-centered cubic (bcc) structure, and can also play a role in resisting HF corrosion in electrolyte when being used as a coating layer. In2O3The related work for the high-nickel anode ternary anode material is less at present, and In (NO) is reported3)3The material is physically mixed with ternary cathode material powder and is coated by a high-speed mechanical fusion method (Liu Zeng, etc., power technology, 2020,44: 1417-. However, this method exists: 1) the coating is not uniform. Solid phase mixing is hindered by contact between interfaces and it is difficult to ensure coating uniformity due to density differences. Non-uniform coating can affect the effect of not fully resisting HF corrosion; 2) the cladding crystalline phase has been destroyed. High compression and shear tend to negatively affect the crystal structure, and the creation of defects can affect conductivity and ionicity.
Aiming at the problems, the invention aims to provide a ternary cathode material @ indium oxide core-shell structure composite material and a preparation method thereof. The prepared composite material has the characteristics of easily controlled indium oxide content, uniform coating and intact crystalline phase, and the battery prepared from the core-shell structure composite has higher specific capacity, good cycle stability, improved discharging capacity under large current and obviously improved integral conductivity. The preparation process is simple, pollution-free, low in cost, short in flow and easy to industrially amplify.
Disclosure of Invention
The embodiment of the invention provides a ternary cathode material @ indium oxide core-shell structure composite material and a preparation method thereof. The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed embodiments. This summary is not an extensive overview and is intended to neither identify key/critical elements nor delineate the scope of such embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.
The invention provides a preparation method of a ternary cathode material @ indium oxide core-shell structure composite material.
In some exemplary embodiments, in the preparation method of the ternary cathode material @ indium oxide core-shell structure composite material, the ternary cathode material is nickel-cobalt-manganese NCM or nickel-cobalt-aluminum NCA, and the preparation method includes: a coating step and a roasting step;
wherein the coating step comprises:
mixing the ternary cathode material powder with a solvent, stirring and ultrasonically dispersing to obtain a mixed solution A;
mixing an indium source precursor with a solvent, stirring and ultrasonically dispersing to obtain a mixed solution B;
mixing the mixed solution A and the mixed solution B to obtain a mixed solution C;
heating the mixed solution C to the hydrolysis reaction temperature for coating reaction, and cooling to obtain an intermediate product;
the roasting step comprises:
and roasting the intermediate product in the air to obtain the ternary cathode material @ indium oxide core-shell structure composite material.
The embodiment provides a preparation method of a novel ternary cathode material @ indium oxide core-shell structure composite material, wherein a uniform intermediate product can be generated on the surface of ternary cathode material particles through a coating step, and the intermediate product is converted into an indium oxide coating layer with high crystallinity through a roasting step. In the preparation method, how to obtain the intermediate product with uniform surface coating of the ternary cathode material is a technical difficulty.
Researches show that the mixing process of the ternary cathode material, the indium source precursor and the solvent has great influence on the uniform coating result. If the three materials are directly mixed, the problems of local agglomeration and difficult dispersion are easy to occur, the subsequent hydrolysis reaction is difficult to occur, and the uniform coating on the surface is difficult to achieve.
In the process of preparing the mixed solution a, the ternary cathode material powder is preferably added to the solvent for mixing, and needs to be added while stirring in the mixing process. In addition, after the ternary cathode material is completely added into the solvent, the stirring speed needs to be increased to realize rapid turbulence in the solution and break the ternary cathode material into small particle blocks which are agglomerated. Preferably, the stirring speed is controlled at 600-.
In the process of preparing the mixed solution B, it is also preferable to add the indium source precursor to the solvent, and after the indium source precursor is completely added, the stirring speed needs to be increased because the indium oxide is dissolved at a relatively low speed, and increasing the stirring speed can increase the energy input rate, facilitate faster dissolution, and increase the reaction efficiency. Preferably, the stirring speed is controlled at 600-.
Wherein the indium source precursor may include: indium nitrate (In (NO)3)3·H2O), indium acetate (In (C)2H4O2)3·H2O), indium trichloride (InCl)3·4H2O) any one or a combination of at least two; in (NO) therein3)3·6H2O powder is preferred.
In the process of preparing the mixed solution C, the mixed solution B is preferably slowly injected into the mixed solution a, and in the injection process, a combined stirring process is preferably adopted, so that the technical effects of more easily dispersing indium precursor molecules and the ternary cathode material more uniformly, not easily forming local agglomerates, and simultaneously improving the mixing efficiency can be achieved.
Through the limitation of the mixing process in the coating step, the solid-phase components can be fully mixed, the agglomeration problem easily occurring in the mixing process is avoided, precursor molecules are more uniformly dispersed on the surface of the ternary cathode material, and finally, the intermediate product is uniformly coated and formed on the surface of the ternary cathode material.
In the roasting step, the roasting is carried out in high-temperature air, so that the effect of improving the crystallinity of the coating layer material can be realized, and in the roasting process, a high-oxygen atmosphere is not needed, because if the coating is uniform enough, the high-oxygen environment with high oxygen partial pressure is not needed to avoid the problem of reduction of internal transition metal elements, and the common oxidizing atmosphere can also achieve the same purpose, so that the high-temperature air condition is milder, and the cost is lower.
The temperature of the high-temperature air is 150-300 ℃, the air is preheated, mainly residual water gas and other residual substances in the air are removed, and the residual dry air provides an oxidizing atmosphere, so that impurities can be prevented from being introduced in the roasting process.
Compared with the mechanical mixing process in the prior art, the preparation method provided by the invention solves the technical problem of uneven coating easily occurring in the prior art, has good crystallinity of the coating layer, and effectively avoids the damage of the crystal structure of the coating crystal layer caused by high compression and shearing action.
In some optional embodiments, between the step of raising the temperature to the hydrolysis reaction temperature for performing the coating reaction and the step of obtaining the intermediate product, further comprising:
adding a pH regulator to maintain the pH of the solution within a predetermined range.
It was found that the present process system is likely to have a problem of nuclear coating if the PH is not adjusted. The nuclear coating is mainly because the adsorbability of the particle interface and the coating molecules is not good enough, the coating molecules cannot be uniformly distributed on the particle surface, but are gathered at local sites, so that the concentration of other sites is low or the coating molecules are not adsorbed, and further the coating is non-uniform. And the film coating, the coating molecules and the particle interface are adsorbed more tightly, and the concentration of each part is uniform, so that the thickness of each part of the coating after the conversion reaction is uniform and the coating is in a film shape. In order to solve the technical problem, a PH regulator is added to ensure that the PH of a solution system is within a preset range, so that the charge of the system can be fully adjusted, the technical effect of inducing the conversion from the nuclear coating process to the film coating process is achieved, and the coating uniformity is greatly improved.
Further, the pH regulator is strong ammonia water, and the preset range is 5-10.
Concentrated ammonia water is selected as the pH regulator because the pH regulation speed is easier to control and the reaction is milder compared with strong alkaline substances such as NaOH and the like.
The research shows that when the pH value of the solution is in the range of 5-10, film-shaped coating can be well formed, if the pH value is beyond the range, the solution is easy to become nuclear coating, so that the coating is not uniform, and the technical problems of incomplete coating and exposed internal materials are easy to occur due to overhigh or overlow pH value. Preferably, the pH is in the range of 6 to 8.
In some alternative embodiments, in the coating step,
and in the process of heating to the hydrolysis reaction temperature for carrying out the coating reaction, continuously keeping the stirring state.
Researches show that the mixed solution C is heated and subjected to subsequent coating reaction under the condition of continuous stirring, so that the occurrence of local agglomeration can be avoided, and the coating uniformity is influenced; if the mixed solution C is not stirred in the processes of temperature rise and coating reaction, local agglomeration is easy to occur, and meanwhile, hydrolysis products are not easy to adsorb on the surfaces of particles, so that the coating is not uniform.
Further, the reactor for the coating reaction may be a beaker, a flask, a reaction vessel, or the like. Preferably, a reaction kettle is used as a reactor for the coating reaction.
In some alternative embodiments, the solvent comprises one or more combinations of water and/or polyols; in the mixed solution A, the mass ratio of the ternary cathode material to the solvent is 1: 5-1: 200.
preferably, the polyol is methanol or ethanol.
The mass fraction of the ternary cathode material in the solvent has a great influence on the dispersion, and if the proportion is too high, the ternary cathode material is not easy to disperse, and the technical problem of local agglomeration and blocking is easy to occur.
In some optional embodiments, in the mixed liquid B, the mass ratio of the indium source precursor powder to the solvent is 1: 10-1: 500.
the amount of the indium source precursor added has a large influence on the dispersion, and if the content is too low, the hydrolysis reaction becomes slow, and if the content is too high, a problem of local aggregation is likely to occur in the dispersion step, and the hydrolysis reaction product is likely to be agglomerated, and it is difficult to form a film-like coating on the particle surface.
Further, if the materials in the proportion are adopted for reaction, in the process of heating the mixed solution C to the hydrolysis reaction temperature, the heating speed is 10-30 ℃/min, the hydrolysis reaction temperature is 50-110 ℃, and the reaction time is 0.5-6 h.
Preferably, the hydrolysis reaction temperature is 60-100 ℃, and the reaction time is 1-4 h. This example shows the preferred reaction conditions for the hydrolysis reaction in the present process, with too low a temperature, insufficient hydrolysis, too slow a reaction, and reduced overall efficiency. Too high a temperature and too violent hydrolysis reaction for In2O3The coating quality of (2) has a negative influence, and the coating cannot be uniformly deposited on the surface of the nuclear layer, and the content is not easy to control.
The influence of the temperature rise speed on the coating process is that if the temperature rise speed is too low, the whole reaction process becomes slow, the energy consumption is improved, and the economical efficiency is poor. If the temperature rise rate is too high, the precursor molecules are not sufficiently adsorbed to the surface charge of the particles and then are converted, and the film-forming conversion process cannot be performed well.
One type of reactor for carrying out the calcination reaction may employ a fixed bed, a moving bed, a fluidized bed, or a combination thereof.
In some alternative embodiments, the reactor of the calcination step is a fluidized bed; the air speed of the roasting atmosphere is 10-2000 mL/min; the roasting temperature is 400-900 ℃, and the roasting time is 2-8 h.
A fluidized bed may be used as a reactor for the calcination step. The method adopts a fluidized bed to finish the roasting process, and the gas-solid strong convection mode is beneficial to effectively strengthening the heat and mass transfer rate, has no reaction contact dead zone and ensures the crystallization consistency.
Preferably, the air speed is 50-1000 mL/min; the roasting temperature is 500-800 ℃, and the roasting time is 3-7 h. The embodiment provides a better air speed range, the better air speed range needs to be determined according to the powder property, the C-type particles need to be fully fluidized at a higher air speed, and the crystallization consistency of the coating layer in the roasting process is ensured. Meanwhile, when the calcination temperature and time are controlled within the above ranges, amorphous In can be ensured2O3Is converted into crystalline In with higher crystallinity2O3. The roasting temperature is too low, sufficient crystallization cannot be achieved, and the crystallinity is not enough. The roasting temperature is too high, and the compound is easy to be deeply oxidized in an oxidizing atmosphere to generate impurities, so that the purity of the compound is influenced.
In summary, in the above embodiments, the coating step is combined with the baking step, the overall two-step preparation process is simple, the cost is low, and the flow is short, and tests show that the prepared ternary cathode material @ indium oxide core-shell structure composite material can realize uniform coating, and can ensure that the crystal phase of the coating layer is intact, the content of indium oxide in the prepared composite material is easy to control, the coating is uniform, and the crystal phase is intact, and the battery prepared from the core-shell structure composite material has the characteristics of higher specific capacity, good cycle stability, improved power output under large current, and significantly improved overall conductivity. The preparation process is simple, pollution-free, low in cost, short in flow and easy to industrially amplify.
The invention has the following advantages and improvement effects:
the ternary cathode material @ indium oxide core-shell structure composite material core prepared by the invention has the following advantages:
1) the product purity is high;
2)In2O3the content is easy to regulate and control;
3) the conductivity of the whole compound is obviously improved;
4) uniform coating and complete crystal phase;
5) the crystallization consistency is good;
6) the specific capacity is higher, the cycling stability is good, and the large-current discharge capacity is improved;
7) simple preparation process, no pollution, low cost, short process and easy industrial scale-up
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
FIG. 1 is a graph comparing the cycle performance of example 1 with that of comparative example 1.
FIG. 2 is a graph comparing the rate performance of example 1 and comparative example 1.
Fig. 3 is a TEM image of example 1.
Figure 4 is an XRD pattern of example 1 and comparative example 1.
FIG. 5 is a TEM image of the product prepared in comparative example 3 at pH < 5.
FIG. 6 is a TEM image of the product prepared in comparative example 3 at pH > 10.
Detailed Description
The invention is further illustrated by the following specific examples.
Example 1:
at normal temperature, mixing a certain amount of high-purity NCM powder and deionized water in a mass ratio of 1: 10, mixing, stirring at the speed of 600r/min, and ultrasonically dispersing for 0.5 hour, wherein the working frequency of ultrasonic dispersion is 40KHz, so as to obtain a mixed solution A; indium source precursor In (NO)3)3Powder and deionized water in a mass ratio of 1: 20, stirring and ultrasonically dispersing for 0.5 hour at the speed of 600r/min, wherein the working frequency of ultrasonic dispersion is 40KHz, and obtaining a mixed solution B. Mixing the mixed solution A and the mixed solution B, adding the mixed solution A and the mixed solution B into a reaction kettle, heating to 60 ℃ under the stirring state at the speed of 1200r/min for coating reaction for 1.5h, adding concentrated ammonia water to keep the pH of the solution to about 6, and obtaining an intermediate product; roasting the intermediate product In hot air In a fluidized bed reactor, wherein the temperature of the hot air is 150 ℃, the air introducing speed of the hot air is 100mL/min, heating to 550 ℃, keeping for 3h, naturally cooling to room temperature to obtain the final product NCM @ In2O3。
And (3) electrochemical performance testing:
polyvinylidene fluoride (PVDF) powder and N-methyl pyrrolidone are mixed at a ratio of 2:98 at normal temperature, and stirred at the normal temperature for 16 hours to obtain a transparent viscous colloid solution. According to the active substance (ternary cathode material @ indium oxide core-shell structure composite material): conductive agent super P: PVDF/NMP 84: 8: 8, adding each component substance according to the mass ratio, adding an active substance, stirring for 2 hours, adding a conductive agent super P, stirring for 0.25 hour, adding a solvent binder, mixing with a glue solution to enable the solid content to be 20 wt%, and stirring for 2 hours to enable the solution to be in a transparent black state, thereby obtaining the anode slurry. According to the conventional production process of the lithium ion button cell, oily positive electrode slurry is coated on a current collector by a wet film preparation method, and a positive electrode plate can be obtained by punching a dry film through punching equipment through drying and dehydrating and deoxidizing processes. And assembling the button half cell with a metal lithium sheet, a diaphragm, electrolyte, a positive and negative electrode shell, an elastic sheet and a gasket in a glove box, and standing for 15 hours to obtain the lithium ion button half cell with fully soaked interior.
Comparative example 1:
NCM powder without coating and roasting treatment.
Electrochemical performance tests were performed on the lithium ion button half cells prepared in example 1 and comparative example 1, and the results of comparing the charge and discharge cycle performance at 0.1C are shown in fig. 1.
Fig. 1 is a graph comparing the cycle performance of example 1 with that of comparative example 1, and it can be seen from fig. 1 that the cycle stability is significantly improved after coating.
Fig. 2 is a graph comparing the rate performance of example 1 with that of comparative example 1, and it can be seen from the data in fig. 2 that the rate performance of the coated material is significantly improved, and especially the discharging power is significantly enhanced at high rate.
FIG. 3 is a TEM image of the product prepared in example 1, and it can be seen from FIG. 4 that the coating is relatively uniform and in the form of a film.
FIG. 4 is XRD patterns of example 1 and comparative example 1, and In after coating can be seen from FIG. 42O3Without the presence of other impurity peaks.
Comparative example 2:
the difference from example 1 is that the stirring speed is less than 200r/min in the preparation of the mixed liquids A and B. The solution state was observed after stirring for the same time.
Comparative example 3:
the difference from example 1 is that no pH agent was added during the preparation, and an excess of the pH agent was added so that the pH was 11. FIGS. 5 and 6 show the coating state of the coated product, respectively, and thus it can be seen that the surface of the coated product is not uniform if pH is not added or is out of range.
Comparative example 4:
the difference from example 1 is that in the coating process, the mixed solution C was not stirred during the temperature rise and the coating reaction, and the solution state was observed.
Comparative example 5:
the difference from example 1 is that hydrolysis reaction was performed at normal temperature and 120 c to prepare a product, and a lithium ion button type half cell was prepared and subjected to electrochemical performance test according to the aforementioned electrochemical performance test method.
Example 2:
at normal temperature, mixing a certain amount of high-purity NCA powder and ethanol in a mass ratio of 1: 100, stirring and ultrasonically dispersing for 0.3 hour at the speed of 600r/min, wherein the working frequency of ultrasonic dispersion is 30KHz, and obtaining a mixed solution A; indium source precursor In (NO)3)3Mixing the powder and ethanol in a mass ratio of 1: 200 mixing, stirring at 600r/min and ultrasonic dispersing for 0.3 hrThe working frequency of the powder is 30KHz, and mixed liquid B is obtained. Mixing the mixed solution A and the mixed solution B, adding the mixed solution A and the mixed solution B into a reaction kettle, heating to 80 ℃ under a stirring state, carrying out coating reaction for 2.5 hours, adding concentrated ammonia water, and keeping the pH of the solution to be about 7 to obtain an intermediate product; roasting the intermediate product In hot air In a fluidized bed reactor, wherein the temperature of the hot air is 200 ℃, the air introducing speed of the hot air is 1000mL/min, heating to 650 ℃, keeping for 4h, naturally cooling to room temperature to obtain the final product NCA @ In2O3。
Example 3:
at normal temperature, mixing a certain amount of high-purity NCM powder and deionized water in a mass ratio of 1: 30, stirring and ultrasonically dispersing for 0.8 hour at the speed of 600r/min, wherein the working frequency of ultrasonic dispersion is 35KHz, and obtaining a mixed solution A; indium source precursor In (NO)3)3Powder and deionized water in a mass ratio of 1: 60, stirring and ultrasonically dispersing for 0.8 hour at the speed of 600r/min, wherein the working frequency of ultrasonic dispersion is 35KHz, and obtaining a mixed solution B. Mixing the mixed solution A and the mixed solution B, adding the mixed solution A and the mixed solution B into a reaction kettle, heating to 90 ℃ under a stirring state, carrying out coating reaction for 2 hours, adding concentrated ammonia water to keep the pH of the solution to be about 8, and obtaining an intermediate product; roasting the intermediate product In hot air In a fluidized bed reactor, wherein the temperature of the hot air is 250 ℃, the air introducing speed of the hot air is 300mL/min, heating to 750 ℃, keeping for 6h, naturally cooling to room temperature to obtain a final product NCM @ In2O3。
Example 4:
at normal temperature, mixing a certain amount of high-purity NCA powder and ethanol in a mass ratio of 1: 60, stirring and ultrasonically dispersing for 1 hour at the speed of 600r/min, wherein the working frequency of ultrasonic dispersion is 25KHz, and obtaining a mixed solution A; indium source precursor In (NO)3)3Mixing the powder and ethanol in a mass ratio of 1: 100, stirring and ultrasonically dispersing for 1 hour at the speed of 600r/min, wherein the working frequency of ultrasonic dispersion is 25KHz, and obtaining mixed liquor B. Mixing the mixed solution A and the mixed solution B, adding the mixed solution A and the mixed solution B into a reaction kettle, heating to 70 ℃ under a stirring state, carrying out coating reaction for 4 hours, adding concentrated ammonia water, and keeping the pH of the solution to be about 7.5 to obtain an intermediate product; in a fluidised bedRoasting the intermediate product In hot air In a reactor, wherein the temperature of the hot air is 300 ℃, the air speed of the hot air is 600mL/min, heating to 800 ℃, keeping for 7h, and naturally cooling to room temperature to obtain the final product NCA @ In2O3。
The following table shows the electrochemical performance test results for each example and comparative example:
TABLE 1 cycling Performance and high Current discharge test
The results of comparative examples 2, 3 and 4 are not shown in table 1 above, and this is due to the problems of coating unevenness or solution phase separation occurring during the production process when the methods of comparative examples 2, 3 and 4 are employed. In the comparative example 2, when the mixed solutions a and B are prepared, the mixed solution a has a relatively obvious phase separation phenomenon due to the low stirring speed, and it is seen that the stirring is insufficient, and the ternary cathode material cannot be uniformly dispersed in the solvent.
Research shows that if a pH regulator is not added in the coating process, the pH of the solution is easy to exceed a preset range along with the reaction, and then the problem of nuclear coating is easy to occur. Comparative example 3 shows the case where no PH adjuster was added and the PH was not adjusted within the preset range, and the state appeared as shown in fig. 5 and 6, the coating was significantly core-like, not uniform enough, and the aggregation was significant in local areas.
In addition, it was found that continuous stirring is preferable during the temperature rise and coating reaction of the mixed solution C, and if stirring is not performed, local agglomeration is likely to occur, and the hydrolysate is not easily adsorbed on the particle surface, resulting in uneven coating. The mixed solution C in comparative example 4 was not stirred during the temperature rise and coating reaction, the solution delamination phenomenon was significant, and the color of the upper and lower particles after the reaction was significantly different.
From table 1, it can be seen that the ternary cathode material @ indium oxide core-shell structure composite material prepared by the method has good specific capacity, the cycle stability is improved, the power output under large current is enhanced, and the requirements of the next generation cathode material on the contrast capacity, the cycle stability and the rate capability are met.
The ternary cathode material @ indium oxide core-shell structure composite material core prepared by the invention has the following advantages:
1) the product purity is high;
adopts high-purity raw materials, and impurities are not easy to introduce in the process.
2)In2O3The content is easy to regulate and control;
the hydrolysis reaction rate is moderate, which is beneficial to adjusting the thickness of the coating layer.
3) The conductivity of the whole compound is obviously improved;
the indium oxide layer is intact in crystal form, and the conductivity of the composite is remarkably improved.
4) Uniform coating and complete crystal phase;
under the appropriate PH, the precursor is coated evenly. Meanwhile, the liquid phase coating has no strong physical mixing effect, and the crystalline phase is well retained.
5) The crystallization consistency is good;
good fluidization conditions ensure crystallization consistency.
6) The specific capacity is higher, the cycling stability is good, and the large-current discharge capacity is improved;
7) simple preparation process, no pollution, low cost, short flow and easy industrial amplification.
In conclusion, the ternary cathode material @ indium oxide core-shell structure composite material has the characteristics that the content of indium oxide is easy to control, the cladding is uniform, the crystal phase is intact, and the battery prepared from the core-shell structure composite has high specific capacity and good cycle stability, the power output under large current is improved, and the overall conductivity is obviously improved. The preparation process is simple, pollution-free, low in cost, short in flow and easy to industrially amplify.
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention, and not for all the purposes of the present invention, and that the changes and modifications of the above embodiments are within the scope of the present invention as long as they are within the scope of the present invention.
Claims (9)
1. A preparation method of a ternary cathode material @ indium oxide core-shell structure composite material is characterized in that the ternary cathode material is nickel-cobalt-manganese NCM or nickel-cobalt-aluminum NCA, and the preparation method comprises the following steps: a coating step and a roasting step;
wherein the coating step comprises:
mixing the ternary anode material powder with a solvent, and stirring at the stirring speed of 400-1600r/min to obtain a mixed solution A;
mixing the indium source precursor with a solvent, and stirring at the stirring speed of 400-;
mixing the mixed solution A and the mixed solution B to obtain a mixed solution C;
heating the mixed solution C to the hydrolysis reaction temperature for coating reaction, and cooling to obtain an intermediate product;
the roasting step comprises:
and roasting the intermediate product in high-temperature air to obtain the ternary cathode material @ indium oxide core-shell structure composite material, wherein the temperature of the high-temperature air is 150-300 ℃.
2. The method according to claim 1, wherein between the step of raising the temperature to the hydrolysis reaction temperature to perform the coating reaction and the step of obtaining the intermediate product, the method further comprises:
adding a pH regulator to maintain the pH of the solution within a predetermined range.
3. The method according to claim 1, wherein, in the coating step,
and in the process of heating to the hydrolysis reaction temperature for carrying out the coating reaction, continuously keeping the stirring state.
4. The method of claim 2, wherein the PH adjusting agent is ammonia water, and the predetermined range is PH 5-10.
5. The method of any one of claims 1-4, wherein the solvent comprises one or more combinations of water and/or a polyol; in the mixed solution A, the mass ratio of the ternary cathode material to the solvent is 1: 5-1: 200.
6. the production method according to claim 5, wherein a mass ratio of the indium source precursor powder to the solvent in the mixed solution B is 1: 10-1: 500.
7. the method according to claim 6, wherein the temperature of the mixture C is increased to the hydrolysis reaction temperature at a rate of 10-30 ℃/min, the hydrolysis reaction temperature is 50-110 ℃, and the reaction time is 0.5-6 h.
8. The method of claim 5, wherein the reactor of the roasting step is a fluidized bed; the air speed of the roasting atmosphere is 10-2000 mL/min; the roasting temperature is 400-900 ℃, and the roasting time is 2-8 h.
9. A ternary cathode material @ indium oxide core-shell structure composite material is characterized by being prepared by the preparation method of any one of claims 1-8.
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