Coating modification method of positive electrode material
By mixing boric acid, tungsten oxide and graphene to form a cladding raw material and performing secondary sintering with the positive electrode material, the problem of unsatisfactory charge and discharge specific capacity and cycle performance of the existing positive electrode materials is solved, and higher charge and discharge specific capacity and more stable cycle performance are achieved.
Patent Information
- Application Number
- CN202510225959.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-27
- Publication Date
- 2025-05-30
AI Technical Summary
The charge and discharge specific capacity and cycle performance of existing positive electrode materials are not ideal, and it is difficult to effectively improve.
The coated modified positive electrode material is prepared by mixing boric acid, tungsten oxide and graphene in the presence of a solvent to form a cladding raw material, and then mixing it with the positive electrode material for secondary sintering.
The charge-discharge specific capacity and cyclic stability of the positive electrode material are improved, the thermal stability and electrical conductivity of the cladding layer are enhanced, the Li+/Ni2+ mixed discharge is reduced, the H2-H3 phase transition is suppressed, and the interface between the positive electrode and the electrolyte is stabilized.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of cathode materials, and particularly relates to a method for coating and modifying a cathode material. Background Art
[0002] With the rapid development of the new energy industry, the demand for high-energy density batteries continues to rise. The technology of high-nickel ternary materials has been continuously broken through, gradually developing from NCM111 to NCM523, NCM622, and NCM811. Currently, NCM811 has become the mainstream of the development of high-nickel materials. However, due to the special nature of the surface of high-nickel materials, side reactions are easily triggered, and electrochemical reactions first occur on the surface and other factors, stabilizing the surface structure of the material is very important for improving the electrochemical performance of the electrode material. Currently, in the industry, most of the problems of interfacial side reactions and poor cycle stability are solved by technical means of coating and modification.
[0003] The prior art provides a preparation method for a graphene-coated nickel cobalt manganese lithium ion battery cathode material. By coating nickel cobalt manganese lithium with graphene to form a cathode material, the charge-discharge specific capacity and cycle performance of the cathode material can be improved, but the improvement effect is not ideal. Summary of the Invention
[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects that the charge-discharge specific capacity and cycle performance of the cathode material in the prior art are not ideal, so as to provide a method for coating and modifying a cathode material.
[0005] For this purpose, the present invention provides a method for coating and modifying a cathode material, including the following steps: in the presence of a solvent, boric acid, tungsten oxide, and graphene are mixed and sintered once to form a coating raw material; the cathode material and the coating raw material are mixed and sintered twice to form a coated and modified cathode material, and the mass ratio of the cathode material to the coating raw material is (500 - 1000):(4 - 10).
[0006] In some embodiments, the mass ratio of the boric acid, tungsten oxide, and graphene is (1 - 2):(0.3 - 0.5):(4 - 6).
[0007] In some embodiments, the step of mixing the boric acid, tungsten oxide, and graphene includes first forming a first mixed solution by ultrasonic treatment of graphene and a solvent, forming a second mixed solution by ultrasonic treatment of boric acid, tungsten oxide, and a solvent, and mixing the first mixed solution and the second mixed solution.
[0008] In some embodiments, the solvent includes an alcohol solvent. Preferably, the alcohol solvent includes an alcohol solvent of C1 - C6. More preferably, the alcohol solvent includes at least one of ethanol and isopropanol.
[0009] In some of these embodiments, the frequency of the ultrasonic treatment for forming the first mixture is 10 kHz - 22.5 kHz, the treatment time is 10 min - 30 min, and the number of ultrasonic treatment times is at least three times.
[0010] In some of these embodiments, the frequency of the ultrasonic treatment for forming the second mixture is 10 kHz - 22.5 kHz, and the treatment time is 5 min - 10 min.
[0011] In some of these embodiments, the first mixture and the second mixture are mixed under stirring, the stirring speed is 300 rpm - 400 rpm, and the stirring time is 8 min - 20 min.
[0012] In some of these embodiments, the temperature of the first sintering is 400 °C - 650 °C, and the time is 5 h - 7 h.
[0013] In some of these embodiments, after mixing boric acid, tungsten oxide, and graphene, before the first sintering, it further includes a step of drying the mixture, the drying temperature is 60 °C - 100 °C, and the drying time is 10 h - 15 h.
[0014] In some of these embodiments, the temperature of the second sintering is 400 °C - 650 °C, and the time is 5 h - 7 h.
[0015] In some of these embodiments, the positive electrode material and the coating raw material are mixed by stirring. The specific steps include mixing the positive electrode material and the coating raw material at a speed of 800 rpm - 1200 rpm for 2 min - 4 min, then mixing at a speed of 1800 rpm - 2200 rpm for 2 min - 4 min, and finally mixing at a speed of 3500 rpm - 4500 rpm for 8 min - 12 min.
[0016] In some of these embodiments, the positive electrode material includes lithium nickel cobalt manganese oxide, and the positive electrode material is obtained by sintering a nickel cobalt manganese ternary precursor and a lithium source. The chemical formula of the nickel cobalt manganese ternary precursor is Ni a Co b Mn 1-a-b (OH) 2 , where 0.7 ≤ a ≤ 0.95, 0.01 ≤ b ≤ 0.1, and the molar ratio of the lithium source to the lithium nickel cobalt manganese oxide is (1 - 1.2):1.02.
[0017] The technical solution of the present invention has the following advantages:
[0018] The present invention provides a method for coating and modifying a cathode material, which includes the following steps: in the presence of a solvent, boric acid, tungsten oxide and graphene are mixed and sintered once to form a coating raw material; the cathode material and the coating raw material are mixed and sintered twice to form a coated and modified cathode material. Graphene can improve the electron transfer rate inside the battery. The introduction of boric acid, on the one hand, can form a boron oxide in a high-temperature environment to further form a protective layer and provide an isolation layer for the cathode material. On the other hand, boric acid with thermal stability can complement graphene to enhance the thermal stability and conductivity of the coating layer. At the same time, the boron element in boric acid can react with the residual lithium ions in the cathode material to form Li + / Ni 2+ mixing and discharging, which can inhibit the H2-H3 phase transition during the charge and discharge process, enhance the stability of the cycle performance. At the same time, Li formed in the reaction 2 WO 4 can reduce the corrosion of the electrolyte, resulting in a thinner solid electrolyte interface film and further stabilizing the interface between the cathode and the electrolyte. By using a mixture of boric acid, tungsten oxide and graphene as the coating raw material to coat the cathode material and defining the mass ratio of the coating raw material to the cathode material, the formed cathode material has a high charge-discharge specific capacity and strong cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.
[0020] Figure 1 It is a graph showing the test results of the cycle performance stability of the button cells formed by the cathode materials obtained in Example 1, Comparative Example 1 and Comparative Example 5 in the experimental examples of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0021] The following embodiments are provided to better further understand the present invention. They are not limited to the best embodiments, and do not limit the content and protection scope of the present invention. Any product that is the same or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.
[0022] For those examples where specific experimental procedures or conditions are not specified, the operations or conditions of the conventional experimental procedures described in the literature in this field can be followed. For reagents or instruments whose manufacturers are not specified, they are all conventional reagent products that can be obtained through commercial purchase.
[0023] Example 1
[0024] This example provides a method for coating and modifying a cathode material, and the specific steps and methods are as follows:
[0025] (1) Weigh 10 g of graphene, clean it with absolute ethanol to remove impurities. Mix the clean graphene with 30 mL of ethanol, and perform ultrasonic treatment at a frequency of 15 kHz for 10 min. The ultrasonic treatment is carried out three times in total to obtain a first mixed solution. Weigh 3 g of boric acid and 0.8 g of tungsten oxide, and mix them with 40 mL of absolute ethanol, and perform ultrasonic treatment at a frequency of 15 kHz for 5 min to form a second mixed solution. Mix the second mixed solution with the first mixed solution, and stir at a speed of 400 rpm for 10 min to obtain a third mixed solution. Dry the third mixed solution in a constant-temperature oven to remove the solvent. The drying temperature is 60 °C, and the drying time is 12 h to obtain a mixed powder. Put the mixed powder into a tubular furnace, sinter it in a nitrogen atmosphere. The sintering temperature is 400 °C, and the sintering time is 5 h to obtain a coating raw material. Wash the coating raw material with ethanol to remove impurities.
[0026] (2) Mix the lithium source and the ternary precursor, and then under an oxygen atmosphere with a flow rate of 2 L / min, first heat it at a heating rate of 2 °C / min to 550 °C, sinter at 550 °C for 7 h, then heat it at a heating rate of 2 °C / min to 800 °C, and sinter at 800 °C for 10 h. Finally, obtain a first-fired product after pulverization and passing through a 325-mesh sieve. Among them, the lithium source is lithium hydroxide monohydrate, and the ternary precursor is Ni 0.83 Co 0.05 Mn 0.12 (OH) 2 , and the molar ratio of the lithium source to the ternary precursor is 1:1.02.
[0027] (3) Take 500 g of the first-fired product obtained in step (2) and 4 g of the coating raw material obtained in step (1) and place them in a high-speed mixer. Mix them at a speed of 1000 rpm for 2 min, then mix them at a speed of 2000 rpm for 3 min, and finally mix them at a speed of 4000 rpm for 10 min without setting a waiting time in the middle. Place the mixed material under an oxygen atmosphere, heat it at a heating rate of 2 °C / min to 400 °C, sinter at 400 °C for 5 h, then naturally cool to room temperature, and finally obtain the cathode material after passing through a 325-mesh sieve.
[0028] Example 2
[0029] This embodiment provides a method for coating and modifying a cathode material. The specific steps and methods are the same as those in Embodiment 1, except that in step (3), the mass of the coating raw material is 10 g.
[0030] Embodiment 3
[0031] This embodiment provides a method for coating and modifying a cathode material. The specific steps and methods are as follows:
[0032] (1) Weigh 8 g of graphene, clean it with absolute ethanol to remove impurities, and ultrasonically treat the clean graphene and 30 mL of isopropanol at a frequency of 10 kHz for 30 min. The ultrasonic treatment is carried out three times in total to obtain a first mixed solution; weigh 2 g of boric acid and 1 g of tungsten oxide, mix them with 40 mL of isopropanol, and ultrasonically treat them at a frequency of 10 kHz for 10 min to form a second mixed solution; mix the second mixed solution with the first mixed solution and stir at a speed of 300 rpm for 20 min to obtain a third mixed solution; dry the third mixed solution in a constant-temperature oven to remove the solvent. The drying temperature is 100 °C and the drying time is 10 h to obtain a mixed powder; put the mixed powder into a tubular furnace and sinter it in a nitrogen atmosphere. The sintering temperature is 650 °C and the sintering time is 6 h to obtain a coating raw material, and wash the coating raw material with ethanol to remove impurities.
[0033] (2) Mix the lithium source and the ternary precursor, and then, under an oxygen atmosphere with a flow rate of 2 L / min, first heat it at a heating rate of 2 °C / min to 550 °C, sinter it at 550 °C for 7 h, then heat it at a heating rate of 2 °C / min to 800 °C, and sinter it at 800 °C for 10 h. Finally, after pulverization and passing through a 325-mesh sieve, a first-fired product is obtained. Among them, the lithium source is lithium hydroxide monohydrate, and the ternary precursor is Ni 0.83 Co 0.05 Mn 0.12 (OH) 2 , and the molar ratio of the lithium source to the ternary precursor is 1:1.02.
[0034] (3) Take 100 g of the first-fired product obtained in step (2) and 10 g of the coating raw material obtained in step (1) and place them in a high-speed mixer. Mix them at a speed of 800 rpm for 4 min, then mix them at a speed of 1800 rpm for 4 min, and finally mix them at a speed of 3500 rpm for 12 min without setting a waiting time in the middle. Place the mixed material under an oxygen atmosphere and heat it at a heating rate of 2 °C / min to 650 °C. After sintering at 650 °C for 5 h, naturally cool it to room temperature, and finally pass it through a 325-mesh sieve to obtain the cathode material.
[0035] Embodiment 4
[0036] This embodiment provides a method for coating and modifying a cathode material, and the specific steps and methods are as follows:
[0037] (1) Weigh 12 g of graphene, clean it with anhydrous ethanol to remove impurities. Mix the clean graphene and 30 mL of ethanol, and perform ultrasonic treatment at a frequency of 22.5 kHz for 10 min. The ultrasonic treatment is carried out three times in total to obtain a first mixed solution; weigh 4 g of boric acid and 0.6 g of tungsten oxide, and mix them with 40 mL of anhydrous ethanol, and perform ultrasonic treatment at a frequency of 22.5 kHz for 5 min to form a second mixed solution; mix the second mixed solution with the first mixed solution, and stir at a speed of 400 rpm for 8 min to obtain a third mixed solution; dry the third mixed solution in a constant-temperature oven to remove the solvent. The drying temperature is 60 °C, and the drying time is 15 h to obtain a mixed powder; put the mixed powder into a tube furnace, sinter it in a nitrogen atmosphere. The sintering temperature is 400 °C, and the sintering time is 7 h to obtain a coating raw material. Wash the coating raw material with ethanol to remove impurities.
[0038] (2) Mix the lithium source and the ternary precursor, and then under an oxygen atmosphere with a flow rate of 2 L / min, first heat it at a heating rate of 2 °C / min to 550 °C, sinter at 550 °C for 7 h, then heat it at a heating rate of 2 °C / min to 800 °C, and sinter at 800 °C for 10 h. Finally, obtain a first-fired product after pulverization and passing through a 325-mesh sieve. Among them, the lithium source is lithium hydroxide monohydrate, and the ternary precursor is Ni 0.83 Co 0.05 Mn 0.12 (OH) 2 , and the molar ratio of the lithium source to the ternary precursor is 1.2:1.02.
[0039] (3) Take 500 g of the first-fired product obtained in step (2) and 4 g of the coating raw material obtained in step (1) and place them in a high-speed mixer. After mixing at a speed of 1000 rpm for 2 min, then mix at a speed of 2200 rpm for 2 min, and finally mix at a speed of 4500 rpm for 8 min without setting a waiting time in the middle. Place the mixed material under an oxygen atmosphere and heat it at a heating rate of 2 °C / min to 400 °C. After sintering at 400 °C for 7 h, naturally cool it to room temperature. Finally, obtain the cathode material after passing through a 325-mesh sieve.
[0040] Example 5
[0041] This embodiment provides a method for coating and modifying a cathode material, and the specific steps and methods are as follows:
[0042] (1) Weigh 9 g of graphene, clean it with anhydrous ethanol to remove impurities. Then, mix the clean graphene with 30 mL of ethanol and ultrasonically treat it at a frequency of 12 kHz for 10 min. Repeat the ultrasonic treatment three times to obtain the first mixed solution. Weigh 2.5 g of boric acid and 0.9 g of tungsten oxide, mix them with 40 mL of anhydrous ethanol, and ultrasonically treat the mixture at a frequency of 18 kHz for 8 min to form the second mixed solution. Mix the second mixed solution with the first mixed solution and stir it at a speed of 350 rpm for 12 min to obtain the third mixed solution. Dry the third mixed solution in a constant-temperature oven to remove the solvent. The drying temperature is 75 °C and the drying time is 12 h to obtain the mixed powder. Put the mixed powder into a tube furnace and sinter it in a nitrogen atmosphere. The sintering temperature is 500 °C and the sintering time is 6 h to obtain the coated raw material. Wash the coated raw material with ethanol to remove impurities.
[0043] (2) Mix the lithium source and the ternary precursor, and then, under an oxygen atmosphere with a flow rate of 2 L / min, first heat it at a heating rate of 2 °C / min to 550 °C, sinter it at 550 °C for 7 h, then heat it at a heating rate of 2 °C / min to 800 °C, and sinter it at 800 °C for 10 h. Finally, obtain the first-fired product after pulverization and passing through a 325-mesh sieve. Among them, the lithium source is lithium hydroxide monohydrate, and the ternary precursor is Ni 0.83 Co 0.05 Mn 0.12 (OH) 2 , and the molar ratio of the lithium source to the ternary precursor is 1:1.02.
[0044] (3) Take 1000 g of the first-fired product obtained in step (2) and 8 g of the coated raw material obtained in step (1) and place them in a high-speed mixer. Mix them at a speed of 1000 rpm for 2 min, then mix them at a speed of 2000 rpm for 3 min, and finally mix them at a speed of 4000 rpm for 10 min without setting a waiting time in between. Place the mixed material under an oxygen atmosphere and heat it at a heating rate of 2 °C / min to 400 °C. Sinter it at 400 °C for 5 h, then naturally cool it to room temperature. Finally, obtain the cathode material after passing through a 325-mesh sieve.
[0045] Comparative Example 1
[0046] This comparative example provides a method for coating and modifying a cathode material. The specific steps and methods are the same as those in Example 1, except that in step (3), the coating raw material is not included. That is, 500 g of the first-fired product is placed in a high-speed mixer and mixed for 2 min at a rotation speed of 1000 rpm, then mixed for 3 min at a rotation speed of 2000 rpm, and finally mixed for 10 min at a rotation speed of 4000 rpm, without setting a waiting time in between. The mixed material is placed in an oxygen atmosphere and heated to 400 °C at a heating rate of 2 °C / min, sintered at 400 °C for 5 h, naturally cooled to room temperature, and finally passed through a 325-mesh sieve to obtain the cathode material.
[0047] Comparative Example 2
[0048] This comparative example provides a method for coating and modifying a cathode material. The specific steps and methods are the same as those in Example 1, except that boric acid of equal mass is used to replace tungsten oxide in step (1). That is, only 3.8 g of boric acid is contained in the second mixed solution in step (1).
[0049] Comparative Example 3
[0050] This comparative example provides a method for coating and modifying a cathode material. The specific steps and methods are the same as those in Example 1, except that tungsten oxide of equal mass is used to replace boric acid in step (1). That is, only 3.8 g of tungsten oxide is contained in the second mixed solution in step (1).
[0051] Comparative Example 4
[0052] This comparative example provides a method for coating and modifying a cathode material. The specific steps and methods are the same as those in Example 1, except that alumina of equal mass is used to replace tungsten oxide in step (1). That is, 3 g of boric acid and 0.8 g of alumina are contained in the second mixed solution in step (1).
[0053] Comparative Example 5
[0054] This comparative example provides a method for coating and modifying a cathode material. The specific steps and methods are the same as those in Example 1, except that the mass of the coating raw material in step (3) is 0.1 g.
[0055] Experimental Example
[0056] The positive electrode materials prepared in Examples 1-5 and Comparative Examples 1-5 were used as the positive electrode materials of lithium-ion batteries to prepare button cells. The preparation method is as follows: The lithium nickel cobalt aluminate positive electrode material, the binder is polyvinylidene fluoride (PVDF), the conductive agent is conductive carbon black (SP), and the solvent is N-methylpyrrolidone (NMP) are mixed in a dosage ratio of 96.9 g: 1.9 g: 1.6 g: 220 mL, stirred to make a slurry, coated on a copper foil, and dried and rolled to obtain a positive electrode sheet; 6 Using lithium hexafluorophosphate (LiPF 6 ) as the electrolyte, a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of 1:1 as the solvent, an electrolyte solution with an electrolyte concentration of 1 mol / L was prepared; a metal lithium sheet was used as the counter electrode, and a polypropylene (PP) membrane was used as the separator, and a button cell was assembled in a glove box filled with argon.
[0057] The button cells containing the positive electrode materials prepared in Examples 1-5 and Comparative Examples 1-5 were respectively subjected to electrochemical performance tests. The tests were carried out using a Wuhan Blue Electric CT2001A battery tester. The charge-discharge voltage range was 2.5-4.25 V. The capacity retention rates after 50 cycles at charge-discharge rates of 0.2C and 0.5C were respectively tested. The test results are shown in Table 1.
[0058] Table 1 Test results of the electrical performance of button cells formed by positive electrode materials
[0059]
[0060]
[0061] According to Table 1 and Figure 1 , it can be seen that compared with the positive electrode materials formed in Comparative Example 1 without coating raw materials, Comparative Example 2 with only boric acid as the coating material, Comparative Example 3 with only tungsten oxide as the coating material, Comparative Example 4 with alumina replacing tungsten oxide, and Comparative Example 5 with 0.1 g of coating material, the positive electrode material formed by the coating modification method of the positive electrode material provided in the embodiments of the present invention has a higher charge-discharge specific capacity and stable cycling ability, effectively improving the capacity retention rate at different charge-discharge rates.
[0062] Obviously, the above embodiments are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.
Claims
1. A coating modification method for a positive electrode material, characterized in that: The following steps are included: In the presence of a solvent, boric acid, tungsten oxide and graphene are mixed and sintered once to form a coating raw material; The positive electrode material and the coating raw material are mixed and sintered twice to form a coated modified positive electrode material, wherein the mass ratio of the positive electrode material to the coating raw material is (500-1000):(4-10).
2. The coating modification method of the positive electrode material according to claim 1, characterized in that: The mass ratio of the boric acid, tungsten oxide and graphene is (1-2):(0.3-0.5):(4-6).
3. The coating modification method of the positive electrode material according to claim 2, characterized in that: The step of mixing boric acid, tungsten oxide and graphene includes firstly subjecting graphene and solvent to ultrasonic treatment to form a first mixed solution, subjecting boric acid, tungsten oxide and solvent to ultrasonic treatment to form a second mixed solution, and mixing the first mixed solution and the second mixed solution.
4. The coating modification method of the positive electrode material according to claim 3, characterized in that: The solvent includes an alcohol solvent.
5. The coating modification method of the positive electrode material according to claim 4, characterized in that: The alcohol solvent includes a C1-C6 alcohol solvent; and / or, The frequency of the ultrasonic treatment for forming the first mixed solution is 10kHz-22.5kHz, the treatment time is 10min-30min, and the number of ultrasonic treatments is at least three times; and / or, The frequency of the ultrasonic treatment for forming the second mixed solution is 10kHz-22.5kHz, and the treatment time is 5min-10min; and / or, The first mixed liquid and the second mixed liquid are mixed under stirring at a speed of 300-400 rpm and a stirring time of 8-20 min.
6. The coating modification method of the positive electrode material according to claim 5, characterized in that: The alcohol solvent includes at least one of ethanol and isopropanol.
7. The coating modification method of the positive electrode material according to claim 6, characterized in that: The primary sintering temperature is 400°C-650°C and the time is 5h-7h; and / or, After the boric acid, tungsten oxide and graphene are mixed and before the first sintering, the mixed solution is dried at a temperature of 60° C. to 100° C. and for a drying time of 10 h to 15 h.
8. The coating modification method of the positive electrode material according to claim 7, characterized in that: The secondary sintering is carried out at a temperature of 400° C.-650° C. and for a time of 5 h-7 h.
9. The coating modification method of the positive electrode material according to any one of claims 1 to 8, characterized in that: The positive electrode material and the coating raw material are mixed by stirring. The specific steps include mixing the positive electrode material and the coating raw material at a rotation speed of 800rpm-1200rpm for 2min-4min, then mixing at a rotation speed of 1800rpm-2200rpm for 2min-4min, and finally mixing at a rotation speed of 3500rpm-4500rpm for 8min-12min.
10. The coating modification method of the positive electrode material according to claim 9, characterized in that: The positive electrode material includes nickel cobalt manganese oxide, and the positive electrode material is obtained by sintering a nickel cobalt manganese ternary precursor and a lithium source. The chemical formula of the nickel cobalt manganese ternary precursor is Ni a Co b Mn 1-a-b (OH)2, where 0.7≤a≤0.95, 0.01≤b≤0.1, The molar ratio of the lithium source to the lithium nickel cobalt manganese oxide is (1-1.2):1.02.