Modified lithium nickel cobalt manganese oxide positive electrode material and preparation method therefor, lithium-ion battery, and electric device

Abstract

The present application relates to a modified lithium nickel cobalt manganese oxide positive electrode material and a preparation method therefor, a lithium-ion battery, and an electric device. The modified lithium nickel cobalt manganese oxide positive electrode material comprises a lithium nickel cobalt manganese oxide positive electrode material substrate and a perovskite coating layer that coats the surface of the lithium nickel cobalt manganese oxide positive electrode material substrate, wherein the chemical formula of the perovskite coating layer is LiμWαSrβOγ, where 0<μ≤1, the ratio of α to β is 0.3-0.7, and 3≤γ<6.

Description

Modified nickel-cobalt-manganese lithium manganate positive electrode material, preparation method thereof, lithium ion battery and electric device

[0001] Related applications

[0002] The present application claims priority to the Chinese patent application No. 202411254572.2, filed on September 9, 2024, entitled "Modified nickel-cobalt-manganese lithium manganate positive electrode material, preparation method thereof, lithium ion battery and electric device", the contents of which are hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present application belongs to the field of lithium ion batteries, and particularly relates to a modified nickel-cobalt-manganese lithium manganate positive electrode material, a preparation method thereof, a lithium ion battery and an electric device. BACKGROUND

[0004] New energy vehicles have developed to today, and people's demand for driving range, charging speed and cost is increasing, so it is crucial to develop high-energy, high-power density and lower-cost lithium battery positive electrode materials. The ternary nickel-cobalt-manganese lithium manganate positive electrode material has the advantages of low Co content, high capacity and high rate, and has obvious advantages in capacity and cost compared with lithium cobaltate. However, the impedance and rate performance of the nickel-cobalt-manganese lithium manganate positive electrode material gradually deteriorate with the decrease of Co content; the high-temperature cycle life, storage gas production performance and safety performance deteriorate with the increase of cut-off voltage and Ni content.

[0005] Currently, in the traditional technology, there are methods for improving the technical problems existing in the nickel-cobalt-manganese lithium manganate positive electrode material by doping modification, but the doping improvement effect is still poor, and the problems such as the deterioration of the rate and impedance performance caused by the introduction of doping substances still exist. Currently, the traditional technology also has a method for solving the above-mentioned problems by coating modification, which forms a point-like oxide coating substance on the surface of the material structure to improve the surface side reaction problem of the positive electrode material. However, the traditional oxide coating not only causes the impedance and rate to deteriorate, but also causes hidden dangers after high voltage or later cycle. As confirmed by non-patent document (Xinhe Yang, Zicheng Zuo, Haiyan Wang, Quanbin Chen, Hui Zhang, Zhenlei Huang, Borong Wu, Henghui Zhuo, Electrochimica Acta (180) 2015: 604-609), the layered material coated with simple tungsten oxide does not generate stable tungsten compounds, which causes it to accumulate in the graphite negative electrode during the electrochemical reaction process, thereby resulting in poor high-temperature cycle and storage performance.

[0006] Therefore, it is of great significance to study a ternary nickel-cobalt-manganese lithium manganate positive electrode material with a stable coating layer and low interface impedance on the surface. SUMMARY

[0007] The technical problem to be solved by the present application is to overcome the deficiencies and drawbacks mentioned in the background art, and to provide a modified lithium nickel cobalt manganese oxide positive electrode material, a preparation method thereof, a lithium ion battery and an electric device.

[0008] To solve the above technical problems, the technical solution provided by the present application is:

[0009] A modified lithium nickel cobalt manganese oxide positive electrode material, comprising a lithium nickel cobalt manganese oxide positive electrode material matrix and a perovskite coating layer wrapped on the surface of the lithium nickel cobalt manganese oxide positive electrode material matrix, the chemical formula of the perovskite coating layer is Li μ W α Sr β O γ , wherein 0 < μ ≤ 1, the ratio of α and β is 0.3-0.7, and 3 ≤ γ < 6.

[0010] Applicants have found that in the Li μ W α Sr β O γ coating layer, when the ratio of α:β < 0.3, the coating layer structure is unstable, and has no or poor improvement effect on the DCR and stability of the modified lithium nickel cobalt manganese oxide positive electrode material, and when the ratio of α:β > 0.7, the formed coating material has fewer oxygen vacancies, and has no improvement effect on storage and cycle gas production.

[0011] In some examples, the modified lithium nickel cobalt manganese oxide positive electrode material described above, after XRD testing, the ratio of the (111) crystal face peak intensity of Li μ W α Sr β O γ to the (220) crystal face peak intensity of Li μ W α Sr β O γ is 0.2 < I (111) / I (220) < 1.5; further, 0.4 < I (111) / I (220) < 1.3; in the research process of the applicant, it is found through testing XRD data that I (111) / I (220) in this range can indicate that the generated coating material Li μ W α Sr β O γ has good crystallinity, which is beneficial to the gas production performance and rate performance of the material.

[0012] In some examples, the modified lithium nickel cobalt manganese oxide positive electrode material described above, Liμ W α Sr β O γ The peak intensity of the (400) crystal plane and Li μ W α Sr β O γ The ratio of the peak intensities of the (111) crystal plane is 0.1 < I (400) / I (111) <2.0; further, 0.2 < I (400) / I (111) <1.2, During the applicant's research process, by testing XRD data, it was found that I (400) / I (111) Within this range, it can be explained that the resulting coating material Li... μ W α Sr β O γ Its good crystallinity is beneficial to the gas production performance and rate performance of the material.

[0013] In some of these examples, the modified lithium nickel cobalt manganese oxide cathode materials described above, as measured by XRD, show that Li μ W α Sr β O γ The (111) crystal plane half-width at half-maximum and Li μ W α Sr β O γ The half-maximum-to-width ratio of the (220) crystal plane is 0.5 < K. (111) / K (220) <1.0; further, 0.6 <K (111) / K (220) <0.8; During the applicant's research process, K was found to be <0.8 through testing XRD data. (111) / K (220) Materials within this range exhibit good gas production and rate capability.

[0014] In some of these examples, in the aforementioned modified lithium nickel cobalt manganese oxide cathode materials, Li μ W α Sr β O γ The (400) crystal plane half-width and Li μ W α Sr β O γ The half-maximum-to-width ratio of the (111) crystal plane is 0.3 < K. (400) / K (111) <1.0; further, 0.4 <K (400) / K (111) <0.7.

[0015] In some examples, the modified lithium nickel cobalt manganese oxide cathode material has a ratio of the peak intensity of the (111) crystal face of Li μ W α Sr β O γ to the peak intensity of the (003) crystal face of the modified lithium nickel cobalt manganese oxide cathode material is 0.01 < I (111) / I (003) < 0.05; further, 0.015 < I (111) / I (003) < 0.035.

[0016] In some examples, the modified lithium nickel cobalt manganese oxide cathode material has a ratio of the half-height width of the (111) crystal face of Li μ W α Sr β O γ to the half-height width of the (003) crystal face of the modified lithium nickel cobalt manganese oxide cathode material is 1.2 < K (111) / K (003) < 2.2; further, 1.4 < K (111) / K (003) < 1.8.

[0017] In some examples, the modified lithium nickel cobalt manganese oxide cathode material has a perovskite coating layer with a thickness of 1 nm to 20 nm.

[0018] In some examples, the modified lithium nickel cobalt manganese oxide cathode material has a chemical formula of Li x Ni y Co z Mn 1-y-z-a M a O2, wherein 0.95 ≤ x ≤ 1.2, 0.5 ≤ y < 1, 0 < z ≤ 0.2, 0 < a ≤ 0.02, 0 < 1-y-z-a ≤ 0.28, and M includes one or more of Mg, Ti, Zr, Ba, W, Nb, Sr, Ta, and La elements.

[0019] In some examples, the modified lithium nickel cobalt manganese oxide cathode material has a powder conductivity p of 0.0001 S / cm to 0.02 S / cm under a pressure of 190 MPa.

[0020] As a general inventive concept, the present application also provides a method for preparing the modified lithium nickel cobalt manganese oxide cathode material as described above, comprising the following steps:

[0021] (1) mixing the precursor containing nickel, cobalt and manganese elements, lithium salt, W-containing compound, Sr-containing compound and M-containing compound, and then performing first sintering treatment to obtain a sintered product; in the sintering process, part of the W element also enters the matrix, and the Sr element cannot enter the matrix due to its large particle radius, so W and Sr mainly distribute on the surface of the material;

[0022] (2) crushing and dissociating the sintered product obtained in step (1), then mixing with lithium salt, performing second sintering treatment, and screening to obtain a modified lithium nickel cobalt manganese oxide positive electrode material.

[0023] In some examples, the preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material, in step (1), the molar ratio of Li element in lithium salt to the precursor is 0.95-1.0:1; the mass of W element in W-containing compound accounts for 0.4%-2.0% of the mass of the precursor, the mass of Sr element in Sr-containing compound accounts for 0.25%-1.6% of the mass of the precursor, and the molar ratio of W element to Sr element is 2:5-4:5. When the amount of W element added is too low, below 0.4%, as the sintering temperature rises, part of the W element will penetrate into the positive electrode material, thus causing the content of W element on the surface of the material to be too low, and it is difficult to generate perovskite material with the surface Sr element; when the content of W element is too high, above 2%, as W element will inhibit the growth of positive electrode material particle size, the inhibition of particle size growth is obvious, and it is difficult to generate the required positive electrode material. When the content of Sr element is too low, below 0.25%, it is difficult to generate perovskite material with the surface W; when the content of Sr element is too high, above 1.6%, the surface coating material is too much, the capacity of the positive electrode material deteriorates obviously, and the material performance is affected.

[0024] In some examples, the preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material, in step (1), the first sintering treatment is performed in an oxygen or air atmosphere, and the air flow rate is 5m 3 / h-30m 3 / h.

[0025] In some examples, the preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material, in step (1), the first sintering treatment is multi-stage sintering: the first-stage sintering temperature is T1, the sintering time is t1, the heating rate is V1, the second-stage sintering temperature is T2, the sintering time is t2, the heating rate is V2, the third-stage sintering temperature is T3, the sintering time is t3, and the cooling rate is V3; wherein 450℃≤T1≤750℃, 850℃≤T2≤950℃, 600℃≤T3≤800℃, 3h≤t1≤8h, 1.5≤t2 / t1≤3, t1≤t3≤t2; 0.5℃ / min≤V1≤1.5℃ / min, 1<V2 / V1≤3, V1≤V3≤V2. The first-stage sintering has a slow heating rate, a low constant temperature, and a low sintering time, which is conducive to the reaction of lithium salt and the precursor, slows down the growth of the precursor, and only maintains partial lithium insertion into the precursor; the second-stage sintering has a fast heating rate, a high constant temperature, and a long sintering time, which is conducive to the rapid growth of the precursor, the growth of the internal structure of the material, and the full insertion of lithium, and at this time, the Li, W, and Sr on the surface of the material rapidly form a lithium-deficient perovskite-like coating layer; the third-stage sintering has a proper low temperature and a slow cooling rate, and a moderate constant temperature, which is conducive to the further insertion of lithium on the surface of the material into the lithium-deficient perovskite-like coating layer, and further improves the lithium content in the coating layer. If the first sintering process is not set according to the above, for example, the first-stage sintering is cancelled, then the lithium will react with the precursor, W, and Sr synchronously and rapidly, and thus a uniform coating layer cannot be formed on the surface of the material; if there is no third-stage sintering, then the perovskite coating layer generated will have a serious lithium deficiency, and the performance of the material will deteriorate.

[0026] In some examples, the preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material, in step (2), the molar ratio of lithium in the lithium salt to the lithium nickel cobalt manganese oxide in the sintered product obtained in step (1) is 0.06-0.2:1.

[0027] In some examples, the preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material, in step (2), the second sintering treatment is carried out in an oxygen or air atmosphere, and the air flow rate is 1m 3 / h-5m 3 / h.

[0028] In some examples, the preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material, in step (2), the sintering temperature of the second sintering treatment is 600-850℃, the sintering time is 6-20h, and the heating rate is 0.2-0.5℃ / min. When the second sintering temperature is lower than 600℃, the sintering is lithium-deficient, the perovskite cannot react with lithium, and when the sintering temperature is higher than 850℃, the material particles are mutually adhered and agglomerated, which needs to be dissociated again, thereby increasing the cost. Moreover, the dissociation also damages the coating layer on the surface, thereby deteriorating the performance of the material. The heating rate cannot be too high, otherwise the added lithium cannot fully react with the perovskite coating layer obtained in the first sintering, thereby failing to repair the surface of the material. The heating rate also cannot be too low, otherwise the heating time is too long, the sintering capacity is low, the cost is high, and it is not conducive to industrial production.

[0029] In some examples, the preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material, the lithium salt is selected from one or more of lithium carbonate, lithium hydroxide or lithium acetate, and the Sr-containing compound includes one or more of strontium oxide, strontium hydroxide or strontium carbonate; and the W-containing compound includes one or more of tungsten oxide, ammonium metatungstate or ammonium paratungstate.

[0030] As a general inventive concept, the application also provides a lithium ion battery comprising the modified lithium nickel cobalt manganese oxide positive electrode material or comprising the modified lithium nickel cobalt manganese oxide positive electrode material prepared by the preparation method.

[0031] As a general inventive concept, the application also provides an electrical device comprising the lithium ion battery.

[0032] Compared with the prior art, the application has the following beneficial effects:

[0033] (1) The modified lithium nickel cobalt manganese oxide positive electrode material has a perovskite coating layer including Li, W and Sr elements on the surface of the lithium nickel cobalt manganese oxide positive electrode material substrate, which has multiple technical effects: improving the internal resistance, rate performance and low power of the low-Co material; improving the high-temperature cycle capacity retention rate of the material at a high charge cut-off voltage; improving the high-temperature storage internal resistance growth and gas production of the material at a high charge cut-off voltage; improving the surface properties of the lithium nickel cobalt manganese positive electrode material, reducing the residual Li content on the surface of the material, and reducing the side reactions with the electrolyte in the electrochemical process.

[0034] (2) The application prepares the modified lithium nickel cobalt manganese oxide positive electrode material by using the Sr-containing compound, the W-containing compound and the additional lithium salt in combination with the hierarchical regulation of the sintering process. Under the hierarchical regulation of the first sintering process, the Sr element and the W element form a lithium-deficient LiW α Sr β O γThe perovskite compound coating layer effectively slows down the W and Sr elements from entering the material interior, and promotes the W and Sr elements to form a Li μ W α Sr β O γ The perovskite compound coating layer stabilizes the material surface structure, and effectively improves the stability performance.

[0035] (3) The preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material in the application, through second high-temperature sintering and adding a small amount of lithium salt, not only repairs the Li μ W α Sr β O γ The perovskite compound coating layer makes it form a stable lithium-containing perovskite layered coating layer on the material surface, and also makes the material surface powder and rock salt phase components react with the residual lithium and additional lithium source on the surface, and integrate with the matrix particles, which cooperates to make the material surface more stable, and effectively improves the material interface resistance and stability performance.

[0036] (4) In the preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material in the application, a W-containing compound is used, which can form a stable lithium-containing coating on one hand, so that it itself has low impedance and high rate effect; on the other hand, it can also effectively reduce the dissolution of tungsten elements in the coating in the electrolyte, promote its close combination on the surface of the positive electrode material, and effectively improve the material interface stability, so that the impedance, rate, cycle and storage properties and other performances of the positive electrode material are further improved.

[0037] In summary, the capacity, internal resistance, rate, cycle and storage and other electrochemical performances of the modified lithium nickel cobalt manganese oxide positive electrode material in the application are all very excellent. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the application, and other drawings can be obtained by the person skilled in the art without creative labor on the basis of the disclosed drawings.

[0039] FIG. 1 is a scanning electron microscope (SEM) image of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in Example 1 of the application;

[0040] FIG. 2 is a scanning electron microscope (SEM) image of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in Comparative Example 2 of the application;

[0041] FIG. 3 is a transmission electron microscope (TEM) image of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in Example 1 of the application;

[0042] Figure 4 is a transmission electron microscope (TEM) image of the modified lithium nickel cobalt manganese oxide cathode material prepared in Example 2 of the present application.

[0043] Figure 5 is an XRD pattern of the modified lithium nickel cobalt manganese oxide cathode material prepared in Example 1 and Comparative Examples 1-7 of the present application. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0045] In order to facilitate the understanding of the present application, the present application will be described more fully and completely below in conjunction with the drawings in the specification and the preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0046] Unless otherwise defined, all the professional terms used below have the same meaning as generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing the specific embodiments and are not intended to limit the scope of protection of the present application.

[0047] Unless otherwise specified, the various raw materials, reagents, instruments and equipment, etc. used in the present application can be purchased from the market or can be prepared by existing methods.

[0048] Example 1

[0049] A modified lithium nickel cobalt manganese oxide cathode material of the present application comprises a lithium nickel cobalt manganese oxide cathode material matrix Li 1.04 Ni 0.686 Co 0.07 Mn 0.24 Zr 0.004 O2 and a perovskite compound coating layer LiWSr2O 5.5 on the surface of the matrix, and the thickness of the coating layer is 5 nm-16.5 nm.

[0050] The preparation method of the modified lithium nickel cobalt manganese oxide cathode material of the present embodiment comprises the following steps:

[0051] (1) Take 2000 g of nickel cobalt manganese hydroxide precursor Ni 0.69 Co 0.07 Mn 0.24 O2 and a perovskite compound coating layer LiWSr2O(OH)2, and 11.4 g of nano-zirconium oxide was added according to the molar ratio of the precursor to Zr element being 1:0.004; 31.89 g of nano-tungsten oxide was added according to the mass of W element accounting for 1.2% of the mass of the precursor, and 24.9 g of nano-strontium oxide was added according to the mass of Sr element accounting for 1% of the mass of the precursor; the above materials were weighed and added in a mixing tank and mixed uniformly. Then the mixed material was placed in an oxygen atmosphere with an oxygen concentration of >98% to perform first sintering, wherein the oxygen flow rate was 8 m 3 / h, the first sintering was first heated from room temperature to 650°C at a heating rate of 0.5°C / min, and then heated to 930°C at a heating rate of 1.5°C / min for 18 h, and then cooled to 750°C at a cooling rate of 1°C / min for 12 h, and finally naturally cooled to room temperature to obtain a sintered material, which was crushed and sieved to obtain a sintered product.

[0052] (2) The sintered product obtained in step (1) and LiOH·H2O were mixed uniformly according to the molar ratio of lithium nickel cobalt manganese oxide to lithium element in the sintered product being 1:0.15, and then placed in a kiln to perform second sintering, the second sintering conditions were: performed in an air atmosphere, the air flow rate was 3 m 3 / h, and the temperature was increased to 820°C at a rate of 0.3°C / min and maintained for 12 h, and then naturally cooled to room temperature, and then treated by passing through a 200-mesh sieve to obtain LiWSr2O 5.5 perovskite coated lithium nickel cobalt manganese oxide positive electrode material.

[0053] The scanning electron microscope (SEM) of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in this example is shown in FIG. 1, the positive electrode material has a obvious coating layer on the surface, the particles are uniformly distributed and the sample surface has less fine powder particles, and there is no obvious adhesion phenomenon, and the Dv50 value is 3.6 μm.

[0054] Under room temperature conditions, 2 g of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in this example was placed in a specific mold for powder compaction determination, the pressure was set to 190 MPa, and the pressure holding time was 10 seconds, and the powder compaction determination showed that the powder conductivity of the positive electrode material was as high as 0.005 S / cm.

[0055] Uniform particle dispersion and uniform coating layer can slow down the corrosion of the electrolyte on the surface of the material, and high powder conductivity can improve the internal resistance of the material, thereby improving the power and gas production performance of the material. Residual lithium testing showed that the residual Li content on the surface of the modified lithium nickel cobalt manganese oxide positive electrode material sample prepared in this example was 0.05%, which was relatively low, and this was conducive to alleviating the occurrence of surface side reactions during the cycle process.

[0056] The modified lithium nickel cobalt manganese oxide anode material prepared in this embodiment is tested by transmission electron microscopy (TEM), and the test results are shown in FIG. 3. A stable nanometer-level LiWSr2O layer is formed on the surface of the anode material 5.5 The cladding layer (the cladding layer material is between the dotted lines) is formed by adjusting the multi-stage sintering process parameters in this embodiment. This process can dynamically repair the perovskite and finally form a stable and uniform nanometer-level cladding layer on the surface of the material. The cladding layer material LiWSr2O 5.5 is analyzed by selected area electron diffraction (SAED). The crystal structure is Fm-3m (225) layered lithium-containing perovskite material. The thickness of the cladding layer is distributed between 5 nm and 16.5 nm, with the thinnest part being 5 nm and the thickest part being 16.5 nm. The nanometer-scale lithium-containing perovskite cladding layer is rich in oxygen vacancies, which can significantly improve the oxygen release of the material during high-temperature storage and improve the storage performance.

[0057] The modified lithium nickel cobalt manganese oxide anode material prepared in this embodiment is tested by X-ray diffractometer (XRD), and the test results are shown in FIG. 5. In addition to the diffraction peak position corresponding to the standard lithium nickel cobalt manganese oxide, there are also characteristic peaks of (111), (220), (400), etc. Through automatic identification analysis by JADE6.0 and comparison with the PDF card, it is determined that the characteristic peaks are LiWSr2O 5.5 crystal structure, which also corresponds to the TEM characterization results; by analyzing the (111), (220), (400) characteristic peaks, the peak intensities are 477.8, 549.8 and 136.7, respectively, and the half-height widths are 0.132, 0.180 and 0.099, respectively; among them, I (111) / I (220) is 0.868, I (400) / I (111) is 0.286, K (111) / K (220) is 0.733, K (400) / K (111) is 0.55. By analyzing the intensity of the (003) characteristic peak of the lithium nickel cobalt manganese oxide, which is 18344.2, and the half-height width value, which is 0.088, the ratio I 5.5 / I (111) of the (111) crystal face peak intensity of LiWSr2O (003) to the (003) crystal face peak intensity of the modified lithium nickel cobalt manganese oxide anode material is 0.026, and the ratio K 5.5 of the (111) crystal face half-height width of LiWSr2O to the half-height width of the (003) crystal face of the modified lithium nickel cobalt manganese oxide anode material is(111) / K (003) The value was 1.5. XRD analysis showed that this application successfully prepared a perovskite-coated lithium nickel cobalt manganese oxide cathode. The material has high crystallinity and forms an ordered layered structure, which significantly improves its gas generation performance and impedance.

[0058] Example 2:

[0059] A modified lithium nickel cobalt manganese oxide cathode material according to this application includes a lithium nickel cobalt manganese oxide cathode material matrix Li. 1.04 Ni 0.686 Co 0.07 Mn 0.24 Ti 0.004 O2 and the perovskite compound coating layer on the substrate surface (Li) 0.4 W 0.6 SrO3, with a coating thickness of 3nm-7nm.

[0060] The preparation method of the modified lithium nickel cobalt manganese oxide cathode material in this embodiment includes the following steps:

[0061] (1) Weigh 2000g of nickel-cobalt-manganese hydroxide precursor Ni 0.69 Co 0.07 Mn 0.24 (OH)₂ was prepared, and 910g of LiOH·H₂O was weighed out according to a precursor-to-Li molar ratio of 1:1; 7.04g of nano-titanium oxide was weighed out according to a precursor-to-Ti molar ratio of 1:0.004; 26.58g of nano-tungsten oxide was weighed out according to W as 1.0% of the precursor mass; and 19.94g of nano-strontium oxide was weighed out according to Sr as 0.8% of the precursor mass. These materials were then weighed and added to a mixing tank and mixed thoroughly. The mixed material was then placed in an oxygen atmosphere with an oxygen concentration >98% for the first sintering, wherein the oxygen flow rate was 8 m³ / s. 3 The first sintering process involves raising the temperature from room temperature to 650℃ at a rate of 0.5℃ / min and holding it at that temperature for 6 hours. Then, the temperature is raised to 930℃ at a rate of 1.5℃ / min and held at that temperature for 18 hours. Finally, the temperature is lowered to 750℃ at a rate of 1℃ / min and held at that temperature for 12 hours. The material is then allowed to cool naturally to room temperature to obtain the sintered material. The sintered material is then crushed and sieved to obtain the sintered product.

[0062] (2) The sintered product obtained in step (1) and LiOH·H2O are mixed evenly according to the molar ratio of lithium nickel cobalt manganese oxide to lithium in the sintered product being 1:0.06; then the mixture is placed in a kiln for a second sintering. The conditions for the second sintering are: air atmosphere, with an air flow rate of 4 m³ / s. 3The temperature was increased to 820℃ at a rate of 0.3℃ / min and held for 12 hours. After naturally cooling to room temperature, the material was passed through a 200-mesh sieve to obtain lithium nickel cobalt manganese oxide cathode material coated with a perovskite coating.

[0063] The modified lithium nickel cobalt manganese oxide cathode material prepared in this embodiment was tested by transmission electron microscopy (TEM). The TEM image is shown in Figure 4. Stable nanoscale Li₂ layers are formed on the surface of this cathode material. 0.4 W 0.6 The SrO3 coating, as measured by a Nano Measurer, exhibits a thickness distribution between 3 nm and 7 nm, with the thinnest point at 3 nm and the thickest at 7 nm. This nanoscale lithium-containing perovskite coating not only improves the internal resistance of low-Co materials and enhances power output, but also prevents electrolyte corrosion, improves interfacial stability, and significantly reduces oxygen release during high-temperature storage, thereby improving storage performance.

[0064] The modified lithium nickel cobalt manganese oxide cathode material prepared in this embodiment was tested by X-ray diffraction. Besides corresponding to the standard lithium nickel cobalt manganese oxide, its diffraction peak positions also exhibited characteristic peaks such as (111), (220), and (400). Through automatic identification and analysis using JADE 6.0 and comparison with PDF cards, these characteristic peaks were determined to be Li... 0.4 W 0.6 The SrO3 crystal structure here also corresponds to the TEM characterization results; by analyzing the characteristic peaks (111), (220), and (400), their peak intensities are 612.47, 600.46, and 418.32, respectively, and their full width at half maximum (FWHM) are 0.1458, 0.180, and 0.0921, respectively; among which I (111) / I (220) It is 1.02, I (400) / I (111) K is 0.683. (111) / K (220) K is 0.812. (400) / K (111) The intensity was 0.632. Analysis showed that the characteristic peak intensity of lithium nickel cobalt manganese oxide (003) was 19139.6, and the full width at half maximum (FWHM) was 0.090. (Li...) 0.4 W 0.6 The ratio of the intensity of the (111) crystal plane peak of SrO3 to the intensity of the (003) crystal plane peak of the modified nickel cobalt manganese oxide cathode material is I (111) / I (003) Li is 0.032. 0.4 W 0.6 The ratio K of the full width at half maximum (FWHM) of the (111) crystal plane of SrO3 to that of the (003) crystal plane of the modified nickel cobalt manganese oxide cathode material is K (111) / K (003)is 1.62. Through XRD analysis, it is shown that the lithium-containing perovskite coated lithium nickel cobalt manganese oxide positive electrode is successfully prepared in the application example, the material has high crystallinity, forms an ordered layered structure, and obviously improves the gas production performance and impedance.

[0065] Comparative Example 1:

[0066] The preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material of the comparative example is different from that of Example 1 only in that the addition amount of the W element in step (1) is different. In step (1) of the comparative example, 7.97 g of nano tungsten oxide is weighed according to 0.3% of the mass of the W element accounting for the mass of the precursor, and the remaining process parameters are the same as those of Example 1.

[0067] The X-ray diffraction XRD test result of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in the comparative example is shown in FIG. 5. No Li μ W α Sr β O γ characteristic peak is found, which indicates that when the surface W content is too low, no perovskite coating material is generated.

[0068] Comparative Example 2:

[0069] The preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material of the comparative example is different from that of Example 1 only in that the addition amount of the W element in step (1) is different. In step (1) of the comparative example, 55.83 g of nano tungsten oxide is weighed according to 2.1% of the mass of the W element accounting for the mass of the precursor, and the remaining process parameters are the same as those of Example 1.

[0070] The scanning electron microscope SEM photo of the modified lithium nickel cobalt manganese oxide positive electrode material of the comparative example is shown in FIG. 2. Too much W content leads to low material particle size, aggravated primary particle size agglomeration, and obvious material gas production performance deterioration.

[0071] The X-ray diffraction XRD test result of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in the comparative example is shown in FIG. 5. No Li μ W α Sr β O γ characteristic peak is found, which indicates that when the surface W content is too high, the material surface state changes during the sintering process, single crystal growth is difficult, the material interface state changes, and no perovskite coating material is generated.

[0072] Comparative Example 3:

[0073] The preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material of the present comparative example is different from that of example 1 only in that the addition amount of the Sr element in step (1) is different. In step (1) of the present comparative example, 31.89 g of nano tungsten oxide is weighed according to 1.2% of the mass of the precursor, and 39.88 g of nano strontium oxide is weighed according to 1.6% of the mass of the precursor, and the remaining process parameters are the same as those of example 1.

[0074] The XRD test result of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in the present comparative example is shown in FIG. 5. No Li μ W α Sr β O γ characteristic peak is found, which indicates that when the content of W on the surface is too low or the content of Sr is too high, both of them are not within the appropriate content range, resulting in no perovskite coating material generated in the reaction process.

[0075] Comparative example 4:

[0076] The preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material of the present comparative example is different from that of example 1 only in that the first sintering procedure in step (1) is different. In the present comparative example, the mixed material is placed in an oxygen atmosphere with an oxygen concentration of > 98% for the first sintering, wherein the oxygen flow is 8 m 3 / h, the first sintering is first heated from room temperature to 800℃ at a heating rate of 3℃ / min for 6h, then heated to 930℃ at a heating rate of 0.3℃ / min for 18h, and then cooled to 750℃ at a cooling rate of 5℃ / min for 12h, and finally naturally cooled to room temperature to obtain the sintered material. The sintered material is crushed and sieved to obtain the sintered material; the remaining process parameters are the same as those of example 1.

[0077] The XRD test result of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in the present comparative example is shown in FIG. 5. No Li μ W α Sr β O γ characteristic peak is found, which indicates that in the first sintering process, the heating rate is too fast and is not within the appropriate range, so that the additive does not have enough time to react, resulting in no obvious perovskite coating material on the surface.

[0078] Comparative example 5:

[0079] The preparation method of the modified lithium nickel cobalt manganese oxide positive electrode material of the present comparative example is different from that of example 1 only in that step (2) is different. In step (2) of the present comparative example, the sintered product obtained in step (1) is directly placed in a kiln for the second sintering, and the second sintering conditions are as follows: performed in an air atmosphere, and the air flow is 3 m 3 / h, to 820℃ at 0.3℃ / min, and kept for 12h, and then cooled to room temperature naturally, and then treated by a 200-mesh sieve to obtain the modified lithium nickel cobalt manganese oxide cathode material.

[0080] The XRD test result of the modified lithium nickel cobalt manganese oxide cathode material prepared in the present comparative example is shown in Fig. 5. No Li μ W α Sr β O γ characteristic peak was found, which indicates that the lithium supplement in the secondary sintering process was not performed, and the structure of the generated coating material was not complete, and the crystallinity was poor, and thus the XRD failed to identify.

[0081] Comparative Example 6:

[0082] The preparation method of the modified lithium nickel cobalt manganese oxide cathode material in the present comparative example is different from that in Example 1 only in that the heating rate in step (2) is different. In the present comparative example, the heating rate in step (2) is 3℃ / min, and the other process parameters are the same as those in Example 1.

[0083] The XRD test result of the modified lithium nickel cobalt manganese oxide cathode material prepared in the present comparative example is shown in Fig. 5. No Li μ W α Sr β O γ characteristic peak was found, which indicates that the heating rate in the secondary sintering process was too fast and was not within the appropriate range, and thus the initially generated coating material could not be repaired, and its structure was not complete, and the crystallinity was poor, and thus the XRD failed to identify.

[0084] Comparative Example 7:

[0085] The preparation method of the modified lithium nickel cobalt manganese oxide cathode material in the present comparative example is different from that in Example 1 only in that the amount of LiOH·H2O added in step (2) is different. In the present comparative example, the lithium nickel cobalt manganese oxide and LiOH·H2O are mixed in a molar ratio of 1:0.02 of lithium in the lithium nickel cobalt manganese oxide to lithium in LiOH·H2O, and the other process parameters are the same as those in Example 1.

[0086] The XRD test result of the modified lithium nickel cobalt manganese oxide cathode material prepared in the present comparative example is shown in Fig. 5. No Li μ W α Sr β O γ characteristic peak was found, which indicates that the lithium supplement content in the secondary sintering process was too low and was not within the appropriate range, and thus the initially generated coating material could not be repaired, and its structure was not complete, and the crystallinity was poor, and thus the XRD failed to identify.

[0087] Electrochemical performance test:

[0088] Positive electrode sheet: the battery positive electrode material prepared in each of the above examples and comparative examples was added to NMP solvent with conductive carbon black, graphite, and binder PVDF in a mass ratio of 94:2:2:2, mixed uniformly, coated on an Al foil, dried at 120°C for 12h, and rolled to prepare a positive electrode sheet.

[0089] Negative electrode sheet: graphite, conductive carbon black, CMC, and SBR were added to NMP solvent in a mass ratio of 97:1:1:1, mixed uniformly, coated on a Cu foil, dried at 120°C for 12h, and rolled to prepare a negative electrode sheet.

[0090] Assembled battery: the above positive electrode sheet was assembled with the negative electrode sheet into a 1.5 Ah soft-pack battery.

[0091] The electrochemical performance test was carried out at 25°C in a voltage window of 2.8-4.4V, and the specific test system was as follows: the capacity test was 0.33C charging and 0.33C discharging; the high-temperature cycle and gas production test system was as follows: 1C charging to 4.4V and 1C discharging to 2.8V at 45°C, cycled to 1000 cycles, and the capacity retention rate and gas content were calculated; the high-temperature storage gas production test system was as follows: 1C charging to 4.4V at 25°C, then the battery was placed in a 60°C constant-temperature oven, and left for 56d, and the gas content was calculated by the drainage method.

[0092] The materials obtained in the above examples and comparative examples were assembled into soft-pack batteries, and the electrochemical performance data of the batteries, such as 0.33C specific capacity, internal resistance at 25°C and -20°C under 10% SOC charge state, 45°C cycle capacity retention rate at 1000 cycles, 45°C cycle gas production at 1000 cycles, and 60°C storage gas production, are shown in Table 1, wherein the 1000 cycle gas production refers to the difference between the battery volume after 1000 cycles and the initial battery volume, and the 60°C storage gas production refers to the difference between the battery volume after 56d storage at 60°C and the initial battery volume.

[0093] Table 1: Electrochemical data of each example and comparative example

[0094] From the test data of Table 1, comparing Example 1 and Comparative Example 1, in Comparative Example 1, the lithium-containing perovskite coating layer is not formed due to insufficient W content, and in Example 1, the lithium-containing perovskite coating layer is formed, which brings better performance, and the material has better internal resistance, rate and gas production performance; comparing Example 1 and Comparative Example 2, in Comparative Example 2, the material is difficult to form a single crystal due to too high W content, and the small particle size brings obvious short-term performance improvement, but the gas production performance deteriorates obviously, which is difficult to meet the demand; comparing Example 1 and Comparative Example 3, in Comparative Example 3, the material surface is coated with too much material due to high strontium content, which leads to obvious deterioration of material capacity and short-term performance loss, which does not meet the demand; comparing Example 1 and Comparative Example 4, it is shown that the multi-stage sintering process, the heating rate / sintering time and other parameters affect the formation of the lithium-containing perovskite coating layer, further indicating that the sintering process can repair the formation of the lithium-containing perovskite coating layer, and thus bring performance improvement. Comparing Example 1 and Comparative Example 5, in Comparative Example 5, no additional lithium is added, which leads to the fact that the secondary sintering cannot repair the lithium-containing perovskite coating layer, resulting in unstable coating layer structure, although the material internal resistance and gas production performance are improved, but the improvement is weak compared with Example 1. Comparing Example 1 and Comparative Example 6, in Comparative Example 6, although lithium is added in the secondary sintering, the heating rate of the secondary sintering is too fast, which leads to the fact that the added lithium does not react with the perovskite coating layer, and the repair is not performed, and the material performance improvement is insufficient. Comparing Example 1 and Comparative Example 7, in Comparative Example 7, although lithium is added in the secondary sintering, the added lithium content is too low, which leads to the fact that the added lithium does not fully react with the perovskite coating layer, and the repair is not completely performed, and the material performance improvement is insufficient.

[0095] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the description.

[0096] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

The application discloses a modified lithium nickel cobalt manganese oxide positive electrode material, which comprises a lithium nickel cobalt manganese oxide positive electrode material base and a perovskite coating layer wrapped on the surface of the lithium nickel cobalt manganese oxide positive electrode material base; the chemical formula of the perovskite coating layer is Li μ W α Sr β O γ , wherein, 0 < μ ≤ 1, the ratio of α and β is 0.3-0.7, 3 ≤ γ < 6. The modified lithium nickel cobalt manganese oxide cathode material as claimed in claim 1, wherein, Li μ W α Sr β O γ (111) crystal face peak intensity ratio of Li μ W α Sr β O γ (220) crystal face peak intensity is 0.2 < I (111) / I (220) < 1.

5. The modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 1-2, wherein, Li μ W α Sr β O γ of Li μ W α Sr β O γ is 0.1 < I (400) / I (111) < 2.

0. The modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 3, wherein, Li μ W α Sr β O γ of Li μ W α Sr β O γ is 0.5 (111) / K (220) <1.

0. The modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 4, wherein, Li μ W α Sr β O γ The ratio of the half-height width of the (400) crystal face of Li μ W α Sr β O γ to the half-height width of the (111) crystal face of Li (400) / K (111) is 0.3 The modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 5, wherein, Li μ W α Sr β O γ the ratio of the (111) crystal face peak intensity of Li (111) / I (003) <0.

05. The modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 6, wherein, According to XRD testing, Li μ W α Sr β O γ The ratio of the full width at half maximum (FWHM) of the (111) crystal plane to that of the (003) crystal plane in the modified lithium nickel cobalt manganese oxide cathode material is 1.2 < K. (111) / K (003) <2.

2. The modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 7, wherein, The perovskite coating layer has a thickness of 1-20 nm. The modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 8, wherein, The chemical formula of the nickel cobalt manganese lithium cathode material matrix is Li x Ni y Co z Mn 1-y-z-a M a O2, wherein, 0.95≤x≤1.2, 0.5≤y<1, 0<z≤0.2, 0<a≤0.02, 0<1-y-z-a≤0.28, M includes one or more of Mg, Ti, Zr, Ba, W, Nb, Sr, Ta and La elements. The modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 1 to 9, wherein, The modified nickel-cobalt-manganese lithium acid anode material has a powder conductivity ρ of 0.0001 S / cm-0.02 S / cm under a pressure of 190 MPa. A preparation method of the modified nickel-cobalt-manganese lithium acid anode material according to any one of claims 1-10, comprising the following steps: (1) mixing a precursor containing nickel-cobalt-manganese elements, a lithium salt, a W-containing compound, a Sr-containing compound and an M-containing compound, and then performing first sintering treatment to obtain a sintered product; (2) crushing and dissociating the sintered product obtained in step (1), then mixing with a lithium salt, performing second sintering treatment, and screening to obtain the modified nickel-cobalt-manganese lithium acid anode material. The method for preparing the modified lithium nickel cobalt manganese oxide cathode material as described in claim 11, wherein, In step (1), the molar ratio of Li element in the lithium salt to the precursor is 0.95-1.0:1, the mass of W element in the W-containing compound accounts for 0.4%-2.0% of the mass of the precursor, the mass of Sr element in the Sr-containing compound accounts for 0.25%-1.6% of the mass of the precursor, and the molar ratio of W element to Sr element is (2-4):

5. The method for producing the modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 11 to 12, wherein In step (1), the first sintering treatment is carried out under an oxygen or air atmosphere at a gas flow rate of 5 m 3 / h-30 m 3 / h. The method for producing the modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 11 to 13, wherein In step (1), the first sintering treatment is multi-stage sintering: the first-stage sintering temperature is T1, the sintering time is t1, the heating rate is V1, the second-stage sintering temperature is T2, the sintering time is t2, the heating rate is V2, the third-stage sintering temperature is T3, the sintering time is t3, and the cooling rate is V3; wherein 450℃ ≤ T1 ≤ 750℃, 850℃ ≤ T2 ≤ 950℃, 600℃ ≤ T3 ≤ 800℃, 3h ≤ t1 ≤ 8h, 1.5 ≤ t2 / t1 ≤ 3, t1 ≤ t3 ≤ t2; 0.5℃ / min ≤ V1 ≤ 1.5℃ / min, 1 < V2 / V1 ≤ 3, V1 ≤ V3 ≤ V2. The method for producing the modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 11 to 14, wherein In step (2), the molar ratio of lithium element in the lithium salt to the nickel-cobalt-manganese lithium acid in the sintered product obtained in step (1) is 0.06-0.2:

1. The method for producing the modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 11 to 15, wherein In step (2), the second sintering treatment is performed under an oxygen or air atmosphere at a gas flow rate of 1 m 3 / h-5 m 3 / h. The method for producing the modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 11 to 16, wherein In step (2), the second sintering treatment has a sintering temperature of 600℃-850℃, a sintering time of 6h-20h, and a heating rate of 0.2℃ / min-0.5℃ / min. The method for producing the modified lithium nickel cobalt manganese oxide cathode material according to any one of claims 11 to 17, wherein The lithium salt is selected from one or more of lithium carbonate, lithium hydroxide or lithium acetate, the Sr-containing compound includes one or more of strontium oxide, strontium hydroxide or strontium carbonate, and the W-containing compound includes one or more of tungsten oxide, ammonium metatungstate or ammonium paratungstate. A lithium ion battery comprising the modified nickel-cobalt-manganese lithium acid anode material according to any one of claims 1-10 or comprising the modified nickel-cobalt-manganese lithium acid anode material prepared by the preparation method according to any one of claims 11-18. An electric device comprising the lithium ion battery according to claim 19.

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