Positive electrode material and modification method thereof

Abstract

The invention relates to the technical field of positive electrode material modification, in particular to a positive electrode material and a modification method thereof. The modification method of the positive electrode material provided by the invention comprises the following steps: S1, mixing a precursor, a lithium source and a doping material, and carrying out primary sintering to obtain a primary sintered material, the doping material comprising an aluminum source, an antimony source and a zirconium source; s2, washing the first sintered material with water, and carrying out solid-liquid separation to obtain an intermediate; and S3, mixing the intermediate with boric acid and lithium metaaluminate, and carrying out secondary sintering to obtain the modified positive electrode material. The three elements of aluminum, zirconium and antimony are doped, so that the direct-current resistance is effectively reduced, the side reaction in the material is reduced, and the de-intercalation rate of lithium ions is improved. According to the invention, before coating, residual alkali on the surface of the material is washed off by setting the step of washing and coating, so that the cycle performance of the positive electrode material is further improved, and meanwhile, boric acid and lithium metaaluminate are used for isolating the contact between the positive electrode material and an electrolyte to a great extent, so that the cycle performance of the material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode material modification, and in particular to a cathode material and a modification method thereof. Background Art

[0002] With the urgent demand for renewable energy, electric vehicles, and portable electronic devices, the development of cyclic batteries is a key area of energy storage. Lithium nickel cobalt manganese oxide (LNCMnO) is one of the most popular cathode materials in lithium-ion batteries. It offers high energy density, long cycle life, and relatively manageable costs. High-nickel polycrystalline materials, in particular, offer greater specific capacity and superior performance. However, LNCMnO is prone to side reactions with the electrolyte, exacerbating material polarization and leading to reduced cycling performance.

[0003] Currently, cathode materials are mostly modified through element doping or coating to mitigate side reactions between the cathode material and the electrolyte. Coating materials typically use metal oxides, borates, or phosphates, but these materials can reduce the conductivity of the cathode material and affect the electron transfer rate. Furthermore, lithium batteries typically use lithium hydroxide as a lithium source. After sintering, the residual alkali content is high. Using water washing and coating methods can damage the material surface, causing a significant increase in DC resistance and poor cycling performance. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that the positive electrode material modification effect is poor, resulting in poor cycling performance of the positive electrode material, thereby providing a positive electrode material and a modification method thereof.

[0005] To this end, the present invention provides a method for modifying a positive electrode material, comprising the following steps: S1, mixing a precursor, a lithium source and a doping material, and performing a primary sintering to obtain a sintered material, wherein the doping material includes an aluminum source, an antimony source and a zirconium source; S2, washing the sintered material with water, performing solid-liquid separation, and obtaining an intermediate; S3, mixing the intermediate with boric acid and lithium aluminate, and performing a secondary sintering to obtain a modified positive electrode material.

[0006] In some embodiments, based on the mass of the precursor, the aluminum doping amount of the aluminum source is 1000-4000 ppm, the antimony doping amount is 1000-4000 ppm, and the zirconium doping amount is 1000-2000 ppm. Preferably, based on the mass of the precursor, the aluminum doping amount of the aluminum source is 3500-4000 ppm, the antimony doping amount is 3000-3500 ppm, and the zirconium doping amount is 1000-1500 ppm.

[0007] In some embodiments, the mass ratio of the intermediate, boric acid, and lithium metaaluminate is 300:0.2-0.4:0.2-0.4.

[0008] In some of these embodiments, the chemical formula of the precursor is Ni x Co y Mn z (OH)2, where 0.5 < x < 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, and x + y + z = 1.

[0009] In some of these embodiments, the specific surface area of the precursor is 5 - 10 m 2 / g.

[0010] In some of these embodiments, the tap density of the precursor is 1 - 3 g / cm 3 .

[0011] In some of these embodiments, the median particle size D50 of the precursor is 12 - 14 μm.

[0012] In some of these embodiments, the aluminum source includes at least one of aluminum oxide, aluminum hydroxide, aluminum nitrate, or aluminum phosphate.

[0013] In some of these embodiments, the zirconium source includes at least one of zirconium oxide, zirconium hydroxide, or zirconium nitrate.

[0014] In some of these embodiments, the antimony source includes at least one of antimony trioxide, antimony pentoxide, or antimony acetate.

[0015] In some of these embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, or lithium acetate.

[0016] In some of these embodiments, under a stirring state, the precursor, the lithium source, and the doping material are mixed. The specific stirring steps include mixing at 900 - 1100 rpm for 1 - 3 min, mixing at 1800 - 2200 rpm for 2 - 4 min, and mixing at 3200 - 3800 rpm for 12 - 18 min in sequence.

[0017] In some of these embodiments, the steps of the first sintering include, in an oxygen atmosphere, raising the temperature to 450 - 520 °C at a heating rate of 1 - 3 °C / min and holding for 3 - 5 h, then raising the temperature to 750 - 800 °C at a heating rate of 1 - 3 °C / min and holding for 8 - 12 h. The flow rate of oxygen is 1.5 - 3 L / min. <\

[0018] In some of these embodiments, the steps of water washing include, under a stirring state, mixing the first sintered material and water for 8 - 12 min. The stirring speed is 3000 - 6000 rpm, and the mass ratio of water to the first sintered material is 1:0.5 - 0.8.

[0019] In some embodiments, the solid-liquid separation step includes filtering and drying, the drying temperature is 110-140° C., and the drying time is 8-12 minutes.

[0020] In some embodiments, the intermediate, boric acid and lithium aluminate are mixed under stirring, and the specific steps of stirring include mixing at a rotation speed of 800-1200 rpm for 1-3 min, mixing at a rotation speed of 1800-2400 rpm for 2-4 min, and mixing at a rotation speed of 3200-3800 rpm for 12-16 min.

[0021] In some embodiments, the secondary sintering step comprises increasing the temperature to 220-270° C. at a heating rate of 1-3° C. / min in an oxygen atmosphere and maintaining the temperature for 4-8 hours.

[0022] On the other hand, the present invention provides a positive electrode material, which is prepared by a method for modifying the positive electrode material including the above-mentioned method for modifying the positive electrode material.

[0023] The technical solution of the present invention has the following advantages:

[0024] The present invention provides a method for modifying a positive electrode material, comprising the following steps: S1, mixing a precursor, a lithium source and a doping material, and performing a sintering to obtain a sintered material, wherein the doping material includes an aluminum source, an antimony source and a zirconium source; S2, washing the sintered material with water, separating the solid and the liquid, and obtaining an intermediate; S3, mixing the intermediate with boric acid and lithium metaaluminate, and performing a secondary sintering to obtain a modified positive electrode material. The present invention uses aluminum, zirconium and antimony as doping elements, wherein the antimony element can improve the radial arrangement of the grains and ensure the performance of the material capacity. The doping of the aluminum element can not only reduce the mixing of cations inside the material, enhance the structural stability, and improve the cycle performance, but the doping of the zirconium element can further stabilize the crystal structure, inhibit phase change, and reduce interface side reactions. The present invention utilizes aluminum, zirconium and antimony as doping elements to effectively reduce DC resistance, reduce side reactions inside the material, and increase the deintercalation rate of lithium ions. Before coating, the present invention provides a water washing and coating step to wash away residual alkali on the surface of the material, thereby further improving the cycle performance of the positive electrode material. At the same time, the present invention utilizes boric acid and lithium aluminate to largely isolate the contact between the positive electrode material and the electrolyte, thereby improving the cycle performance of the material. At the same time, lithium aluminate can be combined with doping elements on the surface of the material to further improve the migration rate of lithium ions, and has good electron transmission performance. It can not only reduce the DC resistance of the positive electrode material but also inhibit the increase of the DC resistance during the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a microscopic morphology of the positive electrode material prepared in Example 1 of the present invention;

[0027] Figure 2 This is a graph showing the cycle performance results of batteries formed with the positive electrode materials prepared in Example 1 and Comparative Example 1 in the experimental examples of the present invention. DETAILED DESCRIPTION

[0028] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0029] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0030] Example 1

[0031] This embodiment provides a method for preparing a positive electrode material, and the specific steps and parameters are as follows:

[0032] (1) Weigh 1000g Ni 0.83 Co 0.11 Mn 0.06 (OH)2 precursor, 470.302g lithium hydroxide, 1.987g Al2O3, 5.037g Sb2O3 and 1.35g ZrO2, wherein the total amount of the precursor is 10.635mol / kg, and the specific surface area is 8.24m 2 / g, and the tap density is 1.99g / cm 3 The median particle size D50 is 13.04 μm, the purity of lithium hydroxide is 57.25%, and the purity of aluminum oxide, antimony oxide and zirconium oxide is above 99.9%. The above raw materials are mixed evenly in a high-speed mixer, the speed is set to 1000 r / min and mixed for 2 minutes, then the speed is set to 2000 r / min and mixed for 3 minutes, and the speed is set to 3500 r / min and mixed for 15 minutes, without setting a waiting time in the middle, to obtain a mixture.

[0033] (2) The mixed powder in step S1 is heated to 500°C in a box furnace at a heating rate of 2°C / min, kept at 500°C for 4 hours, and then heated to 770°C at a heating rate of 2°C / min, kept at 770°C for 10 hours. The sintering atmosphere is oxygen with a flow rate of 2L / min, and the mixture is naturally cooled to room temperature and crushed to obtain a sintered material.

[0034] (3) The crushed burnt material was sieved through a filter with a pore size of 45 microns. After sieving, 500 g of the burnt material was weighed and washed with water at a water-to-material ratio of 1:0.6 and a stirring time of 10 minutes. The material was then filtered with a suction filter and dried in a box furnace at a temperature of 120°C for 10 hours to obtain a dried material.

[0035] (4) The dried material of step (3) was sieved through a filter with a pore size of 45 microns. After sieving, 300 g was weighed, and 0.3 g of boric acid and 0.3 g of lithium aluminate were taken and loaded into a high-speed mixer. The speed was set to 1000 r / min and mixed for 2 min, then set to 2000 r / min and mixed for 3 min, and set to 3500 r / min and mixed for 15 min, without setting a waiting time in between; then the material was calcined in a box furnace, the atmosphere was selected to be oxygen, and the temperature was increased to 250 ° C at a heating rate of 2 ° C / min, kept warm for 6 h, and naturally cooled and sieved to obtain the positive electrode material.

[0036] Take a photo of the microscopic morphology of the cathode material, see Figure 1 It can be seen that the positive electrode material prepared by the modification method provided in the embodiment of the present invention is evenly distributed and has uniform size.

[0037] Example 2

[0038] This embodiment provides a method for preparing a positive electrode material, and the specific steps and parameters are as follows:

[0039] (1) Weigh Ni 0.83 Co 0.11 Mn 0.06 (OH)2 precursor, lithium hydroxide, Al2O3, Sb2O3 and ZrO2, wherein, based on the mass of the precursor, the doping amount of aluminum is 1000ppm, the doping amount of antimony is 4000ppm, the doping amount of zirconium is 1000ppm, the ratio of the molar amount of lithium element in the lithium source to the molar sum of nickel, cobalt, manganese, aluminum, zirconium and antimony is 0.9, the total amount of the precursor is 10.635mol / kg, and the specific surface area is 8.24m 2 / g, and the tap density is 1.99g / cm 3The median particle size D50 is 12 μm, the purity of lithium hydroxide is 57.25%, and the purity of aluminum oxide, antimony oxide and zirconium oxide is above 99.9%. The above raw materials are mixed evenly in a high-speed mixer, the speed is set to 900 r / min and mixed for 3 minutes, then set to 1800 r / min and mixed for 4 minutes, and the speed is set to 3200 r / min and mixed for 18 minutes, without setting a waiting time in the middle, to obtain a mixture.

[0040] (2) The mixed powder in step S1 is heated to 450°C in a box furnace at a heating rate of 1°C / min, kept at 450°C for 5 hours, then heated to 800°C at a heating rate of 3°C / min, kept at 800°C for 8 hours, and sintered in an oxygen atmosphere with a flow rate of 3 L / min. The mixture is naturally cooled to room temperature and crushed to obtain a sintered material.

[0041] (3) The crushed burnt material was sieved through a filter with a pore size of 45 μm. After sieving, 500 g of burnt material was weighed and washed with water at a water-to-material ratio of 1:0.5 and a stirring time of 12 min. The material was then filtered with a suction filter and dried in a box furnace at a temperature of 110°C for 12 h to obtain a dried material.

[0042] (4) The dried material of step (3) was sieved through a filter with a pore size of 45 microns. After sieving, 300 g was weighed, and 0.2 g of boric acid and 0.4 g of lithium aluminate were taken and loaded into a high-speed mixer. The speed was set to 1200 r / min and mixed for 1 min, then the speed was set to 2400 r / min and mixed for 2 min, and the speed was set to 3200 r / min and mixed for 16 min, without setting a waiting time in between; then the material was calcined in a box furnace, the atmosphere was selected to be oxygen, and the temperature was increased to 270 ° C at a heating rate of 2 ° C / min, kept warm for 4 h, and naturally cooled and sieved to obtain the positive electrode material.

[0043] Example 3

[0044] This embodiment provides a method for preparing a positive electrode material, and the specific steps and parameters are as follows:

[0045] (1) Weigh Ni 0.83 Co 0.11 Mn 0.06 (OH)2 precursor, lithium hydroxide, Al2O3, Sb2O3 and ZrO2, wherein, based on the mass of the precursor, the doping amount of aluminum is 4000ppm, the doping amount of antimony is 1000ppm, the doping amount of zirconium is 2000ppm, the ratio of the molar amount of lithium element in the lithium source to the molar sum of nickel, cobalt, manganese, aluminum, zirconium and antimony is 1.2, the total amount of the precursor is 10.25mol / kg, and the specific surface area is 9.8m 2 / g, and the tap density is 1.42g / cm 3The median particle size D50 is 14 μm, the purity of lithium hydroxide is 57.25%, and the purity of aluminum oxide, antimony oxide and zirconium oxide is above 99.9%. The above raw materials are mixed evenly in a high-speed mixer, the speed is set to 1100 r / min and mixed for 1 min, then set to 2200 r / min and mixed for 2 min, and the speed is set to 3800 r / min and mixed for 12 min, without setting a waiting time in the middle, to obtain a mixture.

[0046] (2) The mixed powder in step S1 is heated to 520°C in a box furnace at a heating rate of 3°C / min, kept at 520°C for 3 hours, and then heated to 750°C at a heating rate of 1°C / min, kept at 750°C for 12 hours. The sintering atmosphere is oxygen with a flow rate of 1.5 L / min, and the mixture is naturally cooled to room temperature and crushed to obtain a sintered material.

[0047] (3) The crushed burnt material was sieved through a filter with a pore size of 45 microns. After sieving, 500 g of the burnt material was weighed and washed with water at a water-to-material ratio of 1:0.8 and a stirring time of 8 minutes. The material was then filtered with a suction filter and dried in a box furnace at a temperature of 140°C for 8 hours to obtain a dried material.

[0048] (4) The dried material of step (3) was sieved through a filter with a pore size of 45 microns. After sieving, 300 g was weighed, and 0.4 g of boric acid and 0.2 g of lithium aluminate were taken and loaded into a high-speed mixer. The speed was set to 800 r / min and mixed for 3 min, then the speed was set to 1800 r / min and mixed for 4 min, and the speed was set to 3800 r / min and mixed for 12 min, without setting a waiting time in between; then the material was calcined in a box furnace, the atmosphere was selected to be oxygen, and the temperature was increased to 220 ° C at a heating rate of 3 ° C / min, kept warm for 8 h, and naturally cooled and sieved to obtain the positive electrode material.

[0049] Example 4

[0050] This embodiment provides a method for preparing a positive electrode material, and the specific steps and parameters are as follows:

[0051] (1) Weigh Ni 0.83 Co 0.11 Mn 0.06 (OH)2 precursor, lithium carbonate, aluminum hydroxide, antimony acetate and zirconium nitrate, wherein, based on the mass of the precursor, the doping amount of aluminum is 1000ppm, the doping amount of antimony is 4000ppm, the doping amount of zirconium is 1000ppm, the ratio of the molar amount of lithium element in the lithium source to the molar sum of nickel, cobalt, manganese, aluminum, zirconium and antimony is 0.9, the total amount of the precursor is 10.635mol / kg, and the specific surface area is 8.24m 2 / g, and the tap density is 1.99g / cm 3The median particle size D50 is 12 μm, the purity of lithium hydroxide is 57.25%, and the purity of aluminum oxide, antimony oxide and zirconium oxide is above 99.9%. The above raw materials are mixed evenly in a high-speed mixer, the speed is set to 900 r / min and mixed for 3 minutes, then set to 1800 r / min and mixed for 4 minutes, and the speed is set to 3200 r / min and mixed for 18 minutes, without setting a waiting time in the middle, to obtain a mixture.

[0052] (2) The mixed powder in step S1 is heated to 450°C in a box furnace at a heating rate of 1°C / min, kept at 450°C for 5 hours, then heated to 800°C at a heating rate of 3°C / min, kept at 800°C for 8 hours, and sintered in an oxygen atmosphere with a flow rate of 3 L / min. The mixture is naturally cooled to room temperature and crushed to obtain a sintered material.

[0053] (3) The crushed burnt material was sieved through a filter with a pore size of 45 μm. After sieving, 500 g of burnt material was weighed and washed with water at a water-to-material ratio of 1:0.5 and a stirring time of 12 min. The material was then filtered with a suction filter and dried in a box furnace at a temperature of 110°C for 12 h to obtain a dried material.

[0054] (4) The dried material of step (3) was sieved through a filter with a pore size of 45 microns. After sieving, 300 g was weighed, and 0.3 g of boric acid and 0.3 g of lithium aluminate were taken and loaded into a high-speed mixer. The speed was set to 1200 r / min and mixed for 1 min, then the speed was set to 2400 r / min and mixed for 2 min, and the speed was set to 3200 r / min and mixed for 16 min, without setting a waiting time in between; then the material was calcined in a box furnace, the atmosphere was selected to be oxygen, and the temperature was increased to 270 ° C at a heating rate of 2 ° C / min, kept warm for 4 h, and naturally cooled and sieved to obtain the positive electrode material.

[0055] Example 5

[0056] This embodiment provides a method for preparing a positive electrode material, and the specific steps and parameters are as follows:

[0057] (1) Weigh Ni 0.83 Co 0.11 Mn 0.06 (OH)2 precursor, lithium acetate, aluminum nitrate, antimony pentoxide and zirconium hydroxide, wherein, based on the mass of the precursor, the doping amount of aluminum is 1000ppm, the doping amount of antimony is 4000ppm, the doping amount of zirconium is 1000ppm, the ratio of the molar amount of lithium element in the lithium source to the molar sum of nickel, cobalt, manganese, aluminum, zirconium and antimony is 1.2, the total amount of the precursor is 10.635mol / kg, and the specific surface area is 8.24m 2 / g, and the tap density is 1.99g / cm 3The median particle size D50 is 12 μm, the purity of lithium hydroxide is 57.25%, and the purity of aluminum oxide, antimony oxide and zirconium oxide is above 99.9%. The above raw materials are mixed evenly in a high-speed mixer, the speed is set to 900 r / min and mixed for 3 minutes, then set to 1800 r / min and mixed for 4 minutes, and the speed is set to 3200 r / min and mixed for 18 minutes, without setting a waiting time in the middle, to obtain a mixture.

[0058] (2) The mixed powder in step S1 is heated to 450°C in a box furnace at a heating rate of 1°C / min, kept at 450°C for 5 hours, then heated to 800°C at a heating rate of 3°C / min, kept at 800°C for 8 hours, and sintered in an oxygen atmosphere with a flow rate of 3 L / min. The mixture is naturally cooled to room temperature and crushed to obtain a sintered material.

[0059] (3) The crushed burnt material was sieved through a filter with a pore size of 45 μm. After sieving, 500 g of burnt material was weighed and washed with water at a water-to-material ratio of 1:0.5 and a stirring time of 12 min. The material was then filtered with a suction filter and dried in a box furnace at a temperature of 110°C for 12 h to obtain a dried material.

[0060] (4) The dried material of step (3) was sieved through a filter with a pore size of 45 microns. After sieving, 300 g was weighed, and 0.3 g of boric acid and 0.3 g of lithium aluminate were taken and loaded into a high-speed mixer. The speed was set to 1200 r / min and mixed for 1 min, then the speed was set to 2400 r / min and mixed for 2 min, and the speed was set to 3200 r / min and mixed for 16 min, without setting a waiting time in between; then the material was calcined in a box furnace, the atmosphere was selected to be oxygen, and the temperature was increased to 270 ° C at a heating rate of 2 ° C / min, kept warm for 4 h, and naturally cooled and sieved to obtain the positive electrode material.

[0061] Comparative Example 1

[0062] This comparative example provides a method for preparing a lithium nickel cobalt manganese oxide positive electrode material. The specific steps and parameters are the same as those in Example 1, except that antimony trioxide is not contained in step (1).

[0063] Comparative Example 2

[0064] This comparative example provides a method for preparing a lithium nickel cobalt manganese oxide positive electrode material. The specific steps and parameters are the same as those in Example 1, except that step (1) does not contain aluminum oxide.

[0065] Comparative Example 3

[0066] This comparative example provides a method for preparing a lithium nickel cobalt manganese oxide positive electrode material. The specific steps and parameters are the same as those in Example 1, except that zirconium oxide is not contained in step (1).

[0067] Comparative Example 4

[0068] This comparative example provides a method for preparing a lithium nickel cobalt manganese oxide positive electrode material. The specific steps and parameters are the same as those of Example 1, except that step (4) does not contain lithium metaaluminate and boric acid. That is, in step (4), the dried material of step (3) is sieved through a filter with a pore size of 45 microns. After sieving, 300 g is weighed and calcined in a box furnace with an oxygen atmosphere. The temperature is increased to 250° C. at a heating rate of 2° C. / min, maintained at this temperature for 6 hours, and naturally cooled and sieved to obtain a positive electrode material.

[0069] Comparative Example 5

[0070] This comparative example provides a method for preparing a positive electrode material of lithium nickel cobalt manganese oxide. The specific steps and parameters are the same as those in Example 1, except that step (4) does not contain lithium metaaluminate.

[0071] Comparative Example 6

[0072] This comparative example provides a method for preparing a lithium nickel cobalt manganese oxide positive electrode material. The specific steps and parameters are the same as those in Example 1, except that step (4) does not contain boric acid.

[0073] Comparative Example 7

[0074] This comparative example provides a preparation method of a nickel cobalt manganese oxide positive electrode material. The specific steps and parameters are the same as those in Example 1, except that step (3) is not set, that is, the calcined material obtained in step (2) is sieved through a filter with a pore size of 45 microns, 300 g is weighed after sieving, and 0.3 g of boric acid and 0.3 g of lithium aluminate are taken and loaded into a high-speed mixer together. The speed is set to 1000 r / min and mixed for 2 min, then the speed is set to 2000 r / min and mixed for 3 min, and the speed is set to 3500 r / min and mixed for 15 min, without setting a waiting time in between; then the material is calcined in a box furnace, oxygen is selected as the atmosphere, the temperature is increased to 250°C at a heating rate of 2°C / min, kept warm for 6 h, and naturally cooled and sieved to obtain a positive electrode material.

[0075] Experimental example

[0076] The positive electrode materials prepared in Example 1 and Comparative Examples 1-7 were subjected to electrical performance tests according to the following method: 95 (positive electrode material): 3 (polyvinylidene fluoride): 2 (conductive carbon black) mass ratio was used for homogenization, and aluminum foil was spread flat on a coating machine for coating (surface density 13.3-13.5 mg / cm 2 , compacted density 2.8mg / cm 2), placed in an 80℃ forced air drying oven and dried for 3 hours; then punched, weighed, and the electrode was baked to make a button battery. When the cut-off voltage was in the range of 2.5V-4.25V, the charge and discharge process was the first cycle (0.2C / 0.2C), the second cycle (0.2C / 1C), the third cycle (0.2C / 1C), and the fourth to 53rd cycles (1C / 1C). The electrical performance test was carried out using a blue electric test system. At the same time, a 10-second 1C discharge voltage was added in the 53rd cycle, and the DCR value of the button battery was obtained using the voltage / current. The test results are shown in Table 1 and Figure 2 .

[0077] Table 1 Electrical performance test results

[0078]

[0079] According to the data in Table 1, the doping materials in Comparative Examples 1-3 do not contain antimony, aluminum or zirconium, and the positive electrode materials in Comparative Examples 4-6 do not contain one or two of the coating materials. The battery DC resistance is greater than 22Ω, the highest capacity retention rate is only 96.58%, and the first discharge capacity is less than 205.4mAh / g. The battery DC resistance formed by the positive electrode material prepared in Example 1 of the present application is only 12.1Ω, the capacity retention rate is 98.57%, and the first discharge capacity is 208.2mAh / g, which proves that the use of antimony, aluminum and zirconium doping elements has a synergistic effect on the reduction of DC resistance, the improvement of capacity retention rate and the first discharge capacity. The DC resistance is further reduced by coating with boric acid and lithium metaaluminate, while the capacity retention rate and the first discharge capacity are improved. Furthermore, in Comparative Example 7, the battery formed by not washing the sintered material has a high DC resistance, a cross capacity retention rate, and a low first discharge capacity. It can be seen that before coating, by setting the step of washing and coating, the residual alkali on the surface of the material is washed away, thereby further improving the cycle performance of the positive electrode material.

[0080] according to Figure 2 It can be seen that the cycle performance of the battery formed by the positive electrode material prepared in Example 1 of the present invention is much better than that of the battery formed by the positive electrode material prepared in Comparative Example 1.

[0081] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for modifying a positive electrode material, characterized in that: The following steps are included: S1, mixing a precursor, a lithium source and a doping material, and performing a sintering operation to obtain a sintered material, wherein the doping material includes an aluminum source, an antimony source and a zirconium source; S2, washing the burnt material with water, separating the solid and the liquid, and obtaining an intermediate; S3, mixing the intermediate with boric acid and lithium aluminate, and performing secondary sintering to obtain a modified positive electrode material.

2. The method for modifying the positive electrode material according to claim 1, wherein: Based on the mass of the precursor, the doping amount of the aluminum element in the aluminum source is 1000-4000 ppm, the doping amount of the antimony source is 1000-4000 ppm, and the doping amount of the zirconium source is 1000-2000 ppm; The mass ratio of the intermediate, boric acid and lithium aluminate is 300:0.2-0.4:0.2-0.

4.

3. The method for modifying the positive electrode material according to claim 2, wherein: Based on the mass of the precursor, the doping amount of the aluminum element in the aluminum source is 3500-4000 ppm, the doping amount of the antimony source is 3000-3500 ppm, and the doping amount of the zirconium source is 1000-1500 ppm.

4. The method for modifying the positive electrode material according to claim 2, wherein: The chemical formula of the precursor is Ni x Co y Mn z (OH)2, 0.5 < x < 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, and x + y + z = 1; and / or, The specific surface area of the precursor is 5-10m 2 / g; and / or, The tap density of the precursor is 1-3 g / cm 3 and / or, The median particle size D50 of the precursor is 12 to 14 μm.

5. The method for modifying the positive electrode material according to claim 2, wherein: The aluminum source includes at least one of aluminum oxide, aluminum hydroxide, aluminum nitrate or aluminum phosphate; The zirconium source includes at least one of zirconium oxide, zirconium hydroxide or zirconium nitrate; The antimony source includes at least one of antimony trioxide, antimony pentoxide or antimony acetate.

6. The method for modifying the positive electrode material according to claim 1, wherein: The lithium source includes at least one of lithium carbonate, lithium hydroxide or lithium acetate.

7. The method for modifying the positive electrode material according to claim 1, wherein: The precursor, lithium source, and doping material are mixed under stirring. Specifically, the stirring steps include mixing at a rotation speed of 900-1100 rpm for 1-3 minutes, mixing at a rotation speed of 1800-2200 rpm for 2-4 minutes, and mixing at a rotation speed of 3200-3800 rpm for 12-18 minutes. The primary sintering steps include, in an oxygen atmosphere, successively increasing the temperature to 450-520°C at a heating rate of 1-3°C / min, maintaining for 3-5 hours, increasing the temperature to 750-800°C at a heating rate of 1-3°C / min, maintaining for 8-12 hours, and the oxygen flow rate is 1.5-3L / min.

8. The method for modifying the positive electrode material according to claim 1, wherein: The water washing step includes mixing the first burnt material and water for 8-12 minutes under stirring, the stirring speed is 3000-6000 rpm, and the mass ratio of water to the first burnt material is 1:0.5-0.8; The solid-liquid separation steps include filtration and drying. The drying temperature is 110-140° C. and the drying time is 8-12 minutes.

9. The method for modifying the positive electrode material according to claim 1, wherein: The intermediate, boric acid and lithium metaaluminate are mixed under stirring, wherein the stirring comprises mixing at a rotation speed of 800-1200 rpm for 1-3 min, mixing at a rotation speed of 1800-2400 rpm for 2-4 min, and mixing at a rotation speed of 3200-3800 rpm for 12-16 min; The secondary sintering step includes increasing the temperature to 220-270° C. at a heating rate of 1-3° C. / min in an oxygen atmosphere and maintaining the temperature for 4-8 hours.

10. A positive electrode material, characterized in that The positive electrode material is prepared by the method for modifying the positive electrode material according to any one of claims 1 to 9.

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