CN111048775A - In-situ sodium doping modification method for improving lithium storage performance of ternary cathode material - Google Patents

In-situ sodium doping modification method for improving lithium storage performance of ternary cathode material Download PDF

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CN111048775A
CN111048775A CN201911308056.2A CN201911308056A CN111048775A CN 111048775 A CN111048775 A CN 111048775A CN 201911308056 A CN201911308056 A CN 201911308056A CN 111048775 A CN111048775 A CN 111048775A
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ncm622
cathode material
ternary cathode
modification method
storage performance
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李昱
陈良丹
吴亮
周航
刘婧
陈丽华
王洪恩
苏宝连
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Wuhan University of Technology WUT
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
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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 discloses an in-situ sodium-doping modification method for improving lithium storage performance of a ternary cathode material, which uses CH3COONa is Na source, stirring and mixing with NCM622 precursor of nickelic ternary positive electrode material in absolute ethyl alcohol, directly drying the obtained material at high temperature, and then mixing the obtained material with excessive LiOH & H2Grinding and mixing O, and then calcining the mixed material at high temperature to obtain Na+And (4) doping. The results show that Na prepared by the method of the invention+The doped NCM622 shows excellent discharge specific capacity and cycling stability, and the invention has the advantages of wide source of raw materials, simple preparation process flow and suitability for commercial popularization and application.

Description

In-situ sodium doping modification method for improving lithium storage performance of ternary cathode material
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a modification method for in-situ sodium doping for improving lithium storage performance of a ternary cathode material.
Background
Currently, in the rapid development stage of electric vehicles and hybrid electric vehicles, Lithium Ion Batteries (LIBs) are receiving wide attention from people due to their characteristics of high capacity, high speed, low cost, and the like, and research on developing high-performance novel electrode materials is also getting more hot. The high nickel ternary positive electrode material has become a necessary trend for the development of power lithium battery materials due to the advantages of low cost, high capacity and environmental friendliness. Wherein the high nickel compound LiNi0.6Co0.2Mn0.2O2(NCM622) is considered to be one of the most promising commercial positive electrode materials.
However, the nickelic ternary positive electrode material still faces the problems of cation shuffling, capacity fading and rate capability. First, due to Ni2+(0.69A) and Li+(0.76A) have similar ionic radii, Ni is used in material synthesis and charge-discharge cycle engineering2+Easily migrate from the transition metal layer to the lithium layer and occupy Li+The position of (2) to make the material structure collapse, increase diffusion resistance and influence rate performance. In addition, when the electrode material is deeply delithiated, a large amount of Ni is present in order to maintain charge balance2+Occupy Li+Layer vacancies cause the transition of the positive electrode material from an ideal hexagonal layered structure to a spinel or cubic rock salt phase, resulting in the degradation of the layered structure and capacity fade, ultimately reducing cycle life. Na (Na)+Ionic radius and Li+Similarly, some Li can be replaced by high-temperature doping+. Thus, Na+The doped ternary cathode material can inhibit the lithium-nickel mixed discharge phenomenon and expand Li+Interlayer spacing, reduction of Li+Diffusion energy barrier and the function of slowing down the phase change of the layered structure of the ternary cathode material. Thus, a proper amount of Na+The doping has very important application significance for the research of the structure and the electrochemical performance of the ternary cathode material.
Disclosure of Invention
Based on the defects of the prior art, the technical problem to be solved by the invention is to provide an in-situ sodium-doping modification method for improving the lithium storage performance of a ternary cathode material, and anhydrous sodium acetate (CH)3COONa) is a Na source, the Na source is stirred and mixed with a high-nickel ternary positive electrode material NCM622 precursor sold in the market in deionized water, and the mixture is dried at high temperature and then is subjected to calcination reaction in a muffle furnace to obtain Na+The doped ternary cathode material can show excellent diffusion rate and stability, and the related raw materials have wide sources and simple preparation process, and is suitable for industrial popularization and application.
In order to solve the technical problems, the invention provides an in-situ sodium-doping modification method for improving the lithium storage performance of a ternary cathode material, which comprises the following steps:
1) will CH3Placing COONa in absolute ethyl alcohol, heating, stirring and dissolving to obtain a sodium-containing ethyl alcohol solution;
2) dissolving the NCM622 precursor into the solution obtained by the step 1), and then stirring at room temperature to obtain a mixed solution;
3) directly transferring the solution obtained by the treatment in the step 2) into an oven for drying treatment to obtain a sodium-containing mixed material, and obtaining the sodium-containing mixed material;
4) mixing the material obtained in the step 3) with excessive LiOH & H2Fully grinding and mixing O;
5) placing the mixed material obtained in the step 4) in a muffle furnace, and carrying out sectional high-temperature calcination to obtain the Na+Surface doped NCM622 ternary cathode material.
As a preferred aspect of the foregoing technical solution, the in-situ sodium doping modification method for improving lithium storage performance of a ternary cathode material provided by the present invention further includes a part or all of the following technical features:
as an improvement of the technical scheme, in the step 1), the mass ratio of CH3COONa to absolute ethyl alcohol is 1 (5000-.
As an improvement of the technical scheme, in the step 2), the mass ratio of the precursor material of NCM622 to CH3COONa is 100 (0.5-10), and the stirring time is 2-5 h.
As an improvement of the technical scheme, in the step 3), the drying temperature is 60-150 ℃, and the drying time is 8-12 h.
As an improvement of the technical proposal, in the step 4), LiOH & H2The O is 3-10% excessive relative to the precursor of NCM622, and the grinding time is 15-60 min.
As an improvement of the above technical solution, in the step 5), the step-by-step sintering condition is set: firstly presintering at 400-550 ℃ for 5-8 h; then, high-temperature calcination is carried out continuously, the temperature is 700-850 ℃, and the time is 12-18 h. In addition, the heating rate of calcination was 3 ℃/min.
In the technical scheme, the Na+Under the voltage range of 2.7-4.3V, the first turn of the doped NCM622 ternary cathode material has the coulombic efficiency of 70-90%, and the coulombic efficiency is maintained at 97.5-100% from the 2 nd turn to 100 turns; the capacity of the alloy is kept at 120-175mAh/g after 100 cycles of circulation under the current density of 0.5 ℃, and the capacity retention rate reaches 65-94 percent.
In the technical scheme, the Na+The doped NCM622 ternary positive electrode material has 3 percent of CH in the voltage range of 2.7-4.3V3The first turn of the NCM622 positive electrode material with the COONa doping amount achieves 85.4% of coulombic efficiency, the coulombic efficiency is kept at 99.99% from the 2 nd turn to 100 turns, the NCM622 positive electrode material is circulated for 100 turns under the current density of 0.5C, the capacity of the NCM622 positive electrode material is kept at 169.5mAh/g, and the capacity retention rate of the NCM622 positive electrode material achieves 92.55%. The EIS impedance test result shows that the charge transfer impedance of the background material can be effectively reduced by doping Na, which indicates that the sodium doping strategy is favorable for the diffusion of lithium ions and slows down the capacity attenuation.
The invention also provides the in-situ sodium-doped ternary cathode material obtained by the modification method.
The principle of the invention is as follows: the invention relates to anhydrous sodium acetate (CH)3COONa) is Na source, and is mixed with the high nickel ternary positive electrode material LiNi0.6Co0.2Mn0.2O2(NCM622) precursor is stirred and mixed in absolute ethyl alcohol, and Na doping reaction is carried out in a muffle furnace after high-temperature drying treatment. The serious problems of lithium-nickel mixed discharge blocking lithium ion diffusion and capacity attenuation of the high-nickel ternary cathode material always restrict the wide application of the high-nickel ternary cathode material, although the problem cannot be completely eliminatedThe intrinsic lithium-nickel mixed-discharging phenomenon and structural change can improve the structural stability of the high-nickel ternary cathode material through an element-doped microstructure regulation and control means. CH (CH)3COONa has a relatively low melting point and sodium and lithium ions can enter the material lattice structure simultaneously, and therefore sodium is a preferred candidate for a useful doping material. In addition, the invention selects LiOH & H2O as Li source, LiOH H2The melting point of O is lower, the high-temperature calcination temperature designed by the invention is lower, the energy is low, the environment is protected, the source of the adopted raw materials is wide, the cost is low, and the method is suitable for large-scale commercial application.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1)CH3COONa has low melting point, and the invention adopts CH3COONa is a sodium source, and the Na source and the NCM622 precursor are efficiently and uniformly mixed in a solution environment, so that the Na is favorably realized+The homogeneous doping of the NCM622 material effectively dopes Na while not changing the layered structure of the NCM622 material+And the introduction of other impurities is avoided, so that the obtained modified ternary cathode material has excellent cycle stability. In addition, CH is compared to conventional NaCl3COONa is low in cost, and can be easily oxidized into residual simple substance carbon after high-temperature calcination, so that the surface conductivity of the anode material is enhanced, and the electrochemical performance of the ternary anode material is favorably improved.
2) The modified doping of the sodium metal element not only avoids other expensive elements and greatly reduces the cost, but also has wide raw material sources and is green and environment-friendly.
3) The invention adopts LiOH. H2O as Li source, compared with Li commonly used in industry2CO3，LiOH·H2O has the advantage of a lower melting point. Considering the requirement of the high-nickel ternary cathode material NCM622 on the calcining process, the Li/Ni mixed-discharging phenomenon of the high-nickel NCM622 material is more serious when the calcining temperature is higher, so that the structure is damaged, and the performance is finally influenced. Therefore, the high-temperature calcination conditions designed by us are 700-850 ℃ and LiOH H2O can be efficiently melt-diffused, while Li2CO3Incomplete decomposition due to high melting point, resulting in the production of trisThe surface of the meta-anode material has more residual lithium and large alkalinity, the surface impedance value is increased, and the electrochemical performance of the material is seriously influenced.
4) The modification method avoids the complex synthesis steps of the traditional ternary anode material doping, surface coating and other modification means, and no other pollutants are generated; the preparation method provided by the invention is simple, mild in reaction conditions, high in repetition rate and suitable for commercial popularization and application.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the contents of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following detailed description is given in conjunction with the preferred embodiments.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below.
FIG. 1 is an XRD pattern of the NCM622 positive electrode materials obtained in examples 1-2 and comparative examples 1-2;
FIG. 2 is a scanning electron micrograph of the NCM622 positive electrode material obtained in examples 1-2 and comparative examples 1-2, wherein a is a scanning image of the NCM622 positive electrode material obtained in comparative example 1; b is a scanned image of the NCM622 positive electrode material obtained in example 1; c is a scanned image of the NCM622 positive electrode material obtained in example 2; d is a scanned image of the NCM622 positive electrode material obtained in comparative example 2;
FIG. 3 is EDS energy spectrum test results of the NCM622 positive electrode materials obtained in examples 1-2 and comparative example 2, wherein a is a spectrum of all elements of the NCM622 positive electrode material obtained in example 1, and b is a distribution diagram of Na elements thereof; c is the whole element spectrum of the NCM622 positive electrode material obtained in example 2, and d is the Na element distribution diagram; e is the whole element spectrum of the NCM622 positive electrode material obtained in comparative example 2, and f is the Na element distribution diagram;
FIG. 4 is a graph showing the cycle stability test of the positive electrode materials obtained in examples 1 to 2 and comparative examples 1 to 2 at a rate of 0.2C;
FIG. 5 is a graph of discharge medium voltage-cycle at 0.2C rate for the products obtained in example 2 and comparative examples 1-2.
Detailed Description
Other aspects, features and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.
Example 1
A modification method of in-situ sodium doping for improving lithium storage performance of a ternary cathode material comprises the following steps:
1) 0.002g of CH3COONa (accounting for 1 percent of the mass of the NCM622 precursor) is dissolved in 20ml of anhydrous ethanol, and the mixture is stirred at room temperature until the mixture is completely dissolved to obtain a sodium-containing ethanol solution;
2) dissolving 0.2g of NCM622 precursor in a sodium-containing ethanol solution, and stirring at room temperature for 3 hours to obtain a mixed solution;
3) directly transferring the solution obtained by the treatment of the step 2) into an electric heating constant temperature air blast drying oven, reacting for 12 hours at 100 ℃, and drying to obtain a mixed material;
4) mixing the material obtained in the step 3) with 5% excess LiOH & H2Grinding O in mortar for 30min to obtain Na-containing material+And Li+The mixed material of (1);
5) putting the material obtained in the step 4) into a muffle furnace, heating to 500 ℃ at 3 ℃/min, calcining for 6h, then heating to 740 ℃ at 3 ℃/min, continuously calcining for 12h, and taking out the obtained Na after the reaction is finished+NCM622 positive electrode material (Na1) was doped.
The product obtained in this example is shown in FIG. 1, and it can be seen from the figure that after doping with Na element, the NCM622 positive electrode material is α -NaFeO in a layered form2The crystal form structure belongs to an R-3m space group, and an XRD spectrogram has a relatively sharp diffraction peak and no impurity peak, which indicates that the crystal form structure of the modified ternary material is complete and the doping of elements has no influence on the crystal form structure of the material. (006) The splitting of two components at the positions of (102) and (108)/(110) is obvious, which indicates that the modified ternary cathode material has a good laminated structure. The cell parameter c was found to be 14.2209nm by further analysis using Rietveld fit analysis using GSAS software. Furthermore, in order toFurther understanding the degree of Li/Ni misclassification of the material, one generally considers the severity by whether the intensity ratio of the X-ray diffraction peaks at the (003) and (104) planes is greater than 1.2, when I (003): when the value of I (104) is more than 1.2, the lower the Li/Ni mixed-discharging degree of the material is, the more stable the material structure is, and the performance of the material is correspondingly improved. Therefore, we calculated I (003) for Na1 samples: the value of I (104) was 1.72, which is much greater than 1.2, indicating that the degree of Li/Ni miscarrying was suppressed to some extent.
The scanning of the product obtained in this example is shown in fig. 2b, and it can be seen that the NCM622 positive electrode material is composed of 100-300nm particles, and most of the nanoparticles have a tendency of agglomerating into spherical shapes.
The EDS energy spectrum test results of the product obtained in the example are shown in FIG. 3a and FIG. 3b, Na element is successfully detected by the surface energy spectrum test, and Na is confirmed+And the elements are uniformly distributed, indicating Na+Effectively incorporated into the ternary cathode material structure.
Example 2
Example 2 the modification method of in-situ sodium doping for improving lithium storage performance of ternary cathode material is substantially the same as example 1, except that CH in step 2)3The addition amount of COONa accounts for 3% of the mass of the NCM622 precursor, and the obtained Na+The doped NCM622 positive electrode material is labeled Na 2.
The products obtained in example 2 were subjected to X-ray diffraction analysis, and the results are shown in fig. 1, and the test results are substantially identical to those of example 1. By further adopting a Rietveld fitting analysis method and analyzing by using GSAS software, the unit cell parameter c value is 14.2216nm, the Li/Ni mixed-arrangement index is calculated by the intensity ratio of X-ray diffraction peaks at crystal faces (003) and (104) to obtain the value of a Na2 sample of 1.90, the Li/Ni mixed-arrangement phenomenon is inhibited to a certain degree, and the value is larger compared with a Na1 product, so that the electrochemical performance of Na2 is presumed to be more excellent.
The SEM scan test results are shown in fig. 2c and are substantially identical to the test results of example 1.
The EDS spectrum test results of the product obtained in this example are shown in FIGS. 2c and 2d, and the detection is performed by the surface energy spectrum testNa comes out and is uniformly distributed, which also indicates Na+Effectively incorporated into the ternary cathode material structure.
Comparative example 1
The NCM622 positive electrode material precursor described in comparative example 1 was obtained commercially, and in order to ensure consistency of the treatment process, 0.2g of the NCM622 precursor and 5% excess LiOH · H were added2Grinding for 30min, placing in a muffle furnace, and calcining at high temperature under the same conditions, wherein the obtained NCM622 after high-temperature treatment is marked as Na 0.
The results of the X-ray diffraction analysis test of comparative example 1 are shown in FIG. 1, and the results are in agreement with those of examples 1-2. The c value of the unit cell parameter was 14.2165nm upon analysis with GSAS software by further applying Rietveld fitting analysis, which was found to be larger than that of examples 1-2 for Na1 and Na2, indicating that Na+The introduction of the lithium ion battery can improve the lithium layer spacing, which is beneficial to the intercalation and deintercalation of lithium ions between layers. Similarly, the Li/Ni mixed-exclusion index is calculated by the intensity ratio of X-ray diffraction peaks at the (003) and (104) crystal planes, so that the value of the Na0 sample is 1.62, which is far less than the Li/Ni mixed-exclusion indexes of Na1 and Na2, and the result shows that the Li/Ni mixed-exclusion degree can be effectively inhibited by sodium doping.
Fig. 2a is a scan of a sample from comparative example 1. SEM scanning test results show that the primary particle size of the material obtained in comparative example 1 is in nanometer level, and the surface is smooth and clean. The size of the primary particles gradually increases with the increase of the sodium content, and the primary particles gradually grow in the radial direction.
Comparative example 2
The experimental method of the invention 'gradient sodium ion doped lithium nickel cobalt aluminate anode material, preparation method and lithium battery' adopted in the comparative example 2 comprises the following specific steps:
weigh 0.2g NCM622 precursor, 5% excess Li2CO3And 0.002g NaCl (accounting for 1 percent of the mass of the precursor of the NCM622) are fully and uniformly mixed, then the material is presintered in a muffle furnace at the temperature of 500 ℃ for 6h at the heating rate of 3 ℃/min, then the material is calcined at the temperature of 740 ℃ at the heating rate of 3 ℃/min for 12h, and finally the mixture is cooled to the room temperature to obtain Na+Doped NCM622 positive electrode material (Na 3).
The products obtained in comparative example 2 were subjected to X-ray diffraction analysis, and the results are shown in fig. 1, which are substantially identical to those of example 1. The cell parameter c was found to be 14.2188nm by further analysis using Rietveld fit analysis using GSAS software. Combining the test results of examples 1-2 and comparative example 1, we found that the order of magnitude of c values was Na2>Na1>Na3>Na0, the result shows that Na+Doping is beneficial to widening interlayer spacing, and Na prepared by the scheme of the invention+The advantages of the doping material are more obvious, probably because the method of directly grinding and mixing the precursor and the Na source is not beneficial to the dispersion of each element, but the invention firstly realizes the uniform mixing of the Na source and the precursor material in the solution, and finally obtains the product Na+It can be fully doped into the precursor, therefore, the results show that the c values of the Na1 and Na2 materials are larger. In addition, the Li/Ni misclassification index is calculated by the intensity ratio of X-ray diffraction peaks at the (003) and (104) crystal planes, so that the value of the Na3 sample is 1.69, and the Li/Ni misclassification phenomenon is also inhibited to a certain extent. Also, we combined the test results of examples 1-2 and comparative example 1 and found that the order of magnitude of Li/Ni shuffling index is Na2>Na1>Na3>Na0, the result shows that Na+The doping is beneficial to inhibiting the Li/Ni mixed discharging phenomenon, and the Na prepared by the invention+The Li/Ni mixed-discharging phenomenon of the doped material is lower, so the experimental scheme of the invention has more advantages, mainly because the invention adopts LiOH & H with lower melting point2O as a lithium source, and Li used in comparative example 22CO3The melting point is higher, the Li source can not be fully doped into the crystal structure of the material due to insufficient decomposition under the calcination condition of 740 ℃, but the existence of the material shows that the Na is reduced+The doping efficiency is not good for the structural stability, therefore, we speculate that the electrochemical performances of Na1 and Na2 are more excellent in combination with the above results.
The SEM scan test results are shown in fig. 2d, and the test results are substantially consistent with those of example 1, but small impurities appear on the surface of the Na3 material, which may be residual lithium-containing compounds on the surface.
Obtained in this exampleEDS energy spectrum test results of the product are shown in fig. 2e and fig. 2f, Na elements are detected through surface energy spectrum test and are uniformly distributed, and the result also shows that Na+Effectively incorporated into the ternary cathode material structure.
Application example
The NCM622 obtained in comparative example 1, Na obtained in examples 1-2 and Na obtained in comparative example 2 were added to the mixture+And respectively carrying out electrochemical cycling stability performance tests on the doped anode materials. The method comprises the following specific steps:
mixing the positive electrode material, Super P and PVDF according to the mass ratio of 8:1:1, dropwise adding a proper amount of N-methylpyrrolidone (NMP), grinding for about 15 minutes, uniformly coating the slurry on an aluminum foil, drying in an oven at 60 ℃ for 2 hours, placing in a vacuum drying oven, and reacting at 120 ℃ for 12 hours. The negative electrode adopts a metal lithium sheet, the diaphragm is a polypropylene porous membrane, and the electrolyte adopts LiPF6The battery adopts a 2025 type button type battery, and the cycling stability performance test is carried out in a voltage range of 2.7-4.3V.
The test chart of the cycling stability performance of all samples to be tested is shown in figure 3, and the test results show that compared with the comparative example 1, under the 0.5C multiplying power, the discharge specific capacity and the cycling stability of the products obtained in the examples 1-2 and the comparative example 2 are obviously improved, which indicates that Na+Doping is beneficial to improve the electrochemical performance of NCM 622. In particular, the product obtained in example 2 is cycled for 100 circles at a current density of 0.5C, the capacity of the product is kept at 169.5mAh/g, and the capacity retention rate of the product reaches 92.55%. In addition, the products obtained in examples 1-2 also exhibited better telephone performance than the product obtained in comparative example 2, and the results showed that CH is used as a CH3COONa is a sodium source, is more favorable for improving the electrochemical performance of NCM622 and accords with the expectation, so that the invention has more commercial popularization superiority.
The results of the EIS impedance test of example 2 and comparative examples 1-2 are shown in FIG. 4, which shows the impedance profile of the ternary positive electrode material measured in the charged state after 1 cycle at a frequency range of 10-10000 Hz. As can be seen from the figure, the curve is composed of semi-circles of the high frequency region and the middle frequency region corresponding to the surface film impedance and the oblique lines of the low frequency region. The results show that Na+The semicircles of both the doped Na2 and Na3 materials were much smaller than the undoped NCM622, indicating that sodium+Doping can reduce surface film resistance. Further, the surface film resistance of Na2 was lower than that of Na3, and the results showed LiOH. H2The O is used as the Li source, is more beneficial to the complete decomposition of the Li source, reduces the surface residue, can more effectively reduce the surface film impedance of the NCM622 and improve the electrochemical performance of the NCM622, and accords with the expectation of us, so the invention has practical significance of wide application.
The raw materials listed in the invention, the upper and lower limits and interval values of the raw materials of the invention, and the upper and lower limits and interval values of the process parameters (such as temperature, time and the like) can all realize the invention, and the examples are not listed.

Claims (9)

1. A modification method for in-situ sodium doping for improving lithium storage performance of a ternary cathode material is characterized by comprising the following steps:
1) will CH3Placing COONa in absolute ethyl alcohol, heating, stirring and dissolving to obtain a sodium-containing ethyl alcohol solution;
2) dissolving the NCM622 precursor into the solution obtained by the step 1), and then stirring at room temperature to obtain a mixed solution;
3) directly transferring the solution obtained by the treatment in the step 2) into an oven for drying treatment to obtain a sodium-containing mixed material;
4) mixing the material obtained in the step 3) with excessive LiOH & H2Fully grinding and mixing O;
5) placing the mixed material obtained in the step 4) in a muffle furnace, and carrying out sectional high-temperature calcination to obtain the Na+Surface doped NCM622 ternary cathode material.
2. The modification method for improving the lithium storage performance of the ternary cathode material according to claim 1, which comprises the following steps: in the step 1), CH3The mass ratio of COONa to absolute ethyl alcohol is 1 (5000-15000), and the stirring time is 0.25-3 h.
3. The lifting ternary positive of claim 1The in-situ sodium-doping modification method for the lithium storage performance of the electrode material is characterized by comprising the following steps of: in the step 2), the precursor material of NCM622 and CH3The mass ratio of COONa is 100 (0.5-10), and the stirring time is 2-5 h.
4. The modification method for improving the lithium storage performance of the ternary cathode material according to claim 1, which comprises the following steps: in the step 3), the drying temperature is 60-150 ℃, and the drying time is 8-12 h.
5. The modification method for improving the lithium storage performance of the ternary cathode material according to claim 1, which comprises the following steps: in the step 4), LiOH. H2The O is 3-10% excessive relative to the precursor of NCM622, and the grinding time is 15-60 min.
6. The modification method for improving the lithium storage performance of the ternary cathode material according to claim 1, which comprises the following steps: in the step 5), setting a sectional sintering condition: firstly presintering at 400-550 ℃ for 5-8 h; then, high-temperature calcination is continuously carried out at the temperature of 700 ℃ and 850 ℃ for 12-18 h, and the temperature rising speed of calcination is 3 ℃/min.
7. The in-situ sodium-doping modification method for improving the lithium storage performance of the ternary cathode material as claimed in any one of claims 1 to 6, wherein: the Na is+Under the voltage range of 2.7-4.3V, the first turn of the doped NCM622 ternary cathode material has the coulombic efficiency of 70-90%, and the coulombic efficiency is maintained at 97.5-100% from the 2 nd turn to 100 turns; the capacity of the alloy is kept at 120-175mAh/g after 100 cycles of circulation under the current density of 0.5 ℃, and the capacity retention rate reaches 65-94 percent.
8. The in-situ sodium-doping modification method for improving the lithium storage performance of the ternary cathode material as claimed in any one of claims 1 to 6, wherein the modification method comprises the following steps: the Na is+The doped NCM622 ternary positive electrode material has 3 percent of CH in the voltage range of 2.7-4.3V3The first-turn coulombic efficiency of the NCM622 positive electrode material with the COONa mixing amount reaches 85.4 percent, and the coulombic efficiency is circulated from the 2 nd turn to the 100 turnsThe efficiency is kept at 99.99%, the capacity is kept at 169.5mAh/g after 100 cycles of circulation under the current density of 0.5C, and the capacity retention rate reaches 92.55%.
9. An in-situ sodium-doped ternary cathode material with high lithium storage performance is characterized by being prepared by the method of any one of claims 1-8.
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CN113443662A (en) * 2021-09-01 2021-09-28 中南大学 Preparation method of sodium and/or potassium doped high-nickel ternary positive electrode material
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Publication number Priority date Publication date Assignee Title
CN112279312A (en) * 2020-10-30 2021-01-29 合肥国轩高科动力能源有限公司 Preparation method of sodium-nitrogen in-situ doped ternary material
CN113443662A (en) * 2021-09-01 2021-09-28 中南大学 Preparation method of sodium and/or potassium doped high-nickel ternary positive electrode material
CN113443662B (en) * 2021-09-01 2022-02-01 中南大学 Preparation method of sodium and/or potassium doped high-nickel ternary positive electrode material
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CN114447309A (en) * 2022-02-15 2022-05-06 中南大学 Sodium ion doped lithium ion battery positive electrode material and preparation method thereof
CN114447309B (en) * 2022-02-15 2023-11-10 中南大学 Sodium ion doped lithium ion battery positive electrode material and preparation method thereof

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