Modified nano-aluminum oxide, preparation method and application thereof

Abstract

The application discloses a preparation method of modified nano-alumina, disperses nano-alumina in anhydrous ethanol, adds o-xylene, performs ultrasonic dispersion, then removes the ethanol through oil bath heating to obtain a suspension A; 3-aminopropyl triethoxysilane is added drop by drop into the suspension A, then the o-xylene in the suspension A is evaporated and removed through heating to obtain an intermediate product I; the intermediate product I is dispersed in anhydrous ethanol, 4,4'-diamino diphenyl sulfone and polyethylene glycol-2000 are added, ultrasonic dispersion is performed, filtration, washing and drying are performed to obtain an intermediate product II; the intermediate product II is mixed with carbon black and sesbania powder, then vacuum calcination is performed to obtain the modified nano-alumina. The application further discloses application of the modified nano-alumina in a nickel plating solution, and discloses technical content of obtaining a high-conductivity positive electrode material by modifying a positive electrode material in the nickel plating solution.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of battery materials, and particularly relates to modification of a positive electrode material of a lithium ion battery. BACKGROUND

[0002] The positive electrode material accounts for a large proportion in a lithium ion battery, and the performance of the positive electrode material will greatly affect the performance of the battery. At present, the research on the positive electrode material mainly focuses on lithium cobalt oxide and lithium nickel oxide electrode materials. In the charging and discharging process of the lithium battery positive electrode material, lithium ion deintercalation and electron transfer dual functions are realized. On the one hand, the diffusion rate of lithium ions needs to be fast, and on the other hand, good conductivity between particles is also a necessary condition for the formation of an effective conductive network of the powder electrode. However, the conductivity of most positive electrode materials belongs to the semiconductor property, which cannot meet the requirements of high conductivity materials.

[0003] In the prior art, a metal layer is usually coated on the surface of the electrode material to form a solid electrode material to meet the requirement of high conductivity. The existing coating mainly includes wet coating and dry coating, and is mainly physical coating. The coating uniformity is poor, and it is difficult to ensure the overall coating effect of the coating on the target. SUMMARY

[0004] A first object of the present application is to provide a modified nano-alumina and a preparation method thereof.

[0005] A second object of the present application is to provide a nickel plating solution and a preparation method thereof.

[0006] A third object of the present application is to provide a high-conductivity positive electrode material and a preparation method thereof.

[0007] To achieve the above objects, the present application provides the following specific technical solutions.

[0008] Firstly, the present application provides a preparation method of modified nano-alumina, comprising the following steps:

[0009] Step S1, dispersing nano-alumina in anhydrous ethanol, adding o-xylene, ultrasonic dispersion, and then heating to remove ethanol to obtain a suspension A;

[0010] Step S2, adding 3-aminopropyl triethoxysilane dropwise into the suspension A, and then heating to evaporate and remove o-xylene in the suspension A to obtain an intermediate product I;

[0011] Step S3, dispersing the intermediate product I in anhydrous ethanol, adding 4,4'-diamino diphenyl sulfone and polyethylene glycol-2000, ultrasonic dispersion, filtration, washing, and drying to obtain an intermediate product II;

[0012] Step S4, mixing the intermediate product II with carbon black and sesbania powder, and then vacuum roasting to obtain modified nano-alumina.

[0013] In a further preferred embodiment, the nano-alumina in step S1 has a particle size D50 of 10-150 nm.

[0014] In a further preferred embodiment, the oil bath in step S1 has a temperature of 80-120℃.

[0015] In a further preferred embodiment, the heating in step S2 is performed by first maintaining at 60-80℃ for 2-4 h, and then raising the temperature to above 140℃.

[0016] In a further preferred embodiment, the washing agent in step S3 is anhydrous ethanol.

[0017] In a further preferred embodiment, the vacuum calcination is performed at a temperature of 500-800℃.

[0018] In a further preferred embodiment of the preparation method, the amounts of the substances are as follows, in parts by weight: nano-alumina 35-85 parts, 3-aminopropyl triethoxysilane 2-5 parts, 4,4'-diamino diphenyl sulfone 0.2-0.8 parts, polyethylene glycol-2000 2-5 parts, carbon black 0.5-1 part, and sesbania powder 0.2-0.8 part.

[0019] In a further preferred embodiment of step S1, the mass-volume ratio of nano-alumina to o-xylene is 0.5-1.5 g:2.5-7.5 mL.

[0020] Based on the same inventive concept, the present application provides a modified nano-alumina prepared by the above preparation method.

[0021] The present application further provides the use of the above modified nano-alumina in a nickel plating solution.

[0022] Further, the present application provides a nickel plating solution comprising a nickel salt, a complexing agent, a reducing agent, a pH adjusting agent, a dispersing agent, and the above modified nano-alumina.

[0023] In a further preferred embodiment, the nickel salt is at least one of nickel sulfate, nickel acetate, nickel carbonate, nickel hypophosphite, nickel sulfamate, and nickel methylsulfonate; the complexing agent is at least one of EDTA, acetic acid, lactic acid, succinic acid, glycolic acid, malic acid, citric acid, and glycine; the reducing agent is hydrazine hydrate; the pH adjusting agent is at least one of lithium hydroxide and lithium carbonate; and the dispersing agent is one of OP-10, polyethylene glycol, polyvinyl alcohol, triethanolamine, Tween, and Span.

[0024] In a further preferred embodiment, the concentration of the nickel salt in the nickel plating solution is 20-50 g / L, the concentration of the complexing agent is 30-60 g / L, the concentration of the reducing agent is 55-80 mL / L, the concentration of the dispersing agent is 2-5 g / L, and the mass percentage of the modified nano-alumina in the nickel plating solution is 2.5-12 wt %.

[0025] In addition, the present application provides a preparation method of the above nickel plating solution, comprising the following steps:

[0026] Step S1, preparing a nickel salt solution;

[0027] Step S2, adding a complexing agent to the nickel salt solution, and after the complexing agent is completely dissolved, adding a pH adjuster and a dispersing agent, and ultrasonic dispersing to obtain a mixed solution;

[0028] Step S3, simultaneously adding a reducing agent and modified nano-alumina to the mixed solution, and ultrasonic dispersing to obtain a nickel plating solution.

[0029] In a further preferred embodiment, after the pH adjuster is added in step S2, the pH value of the nickel plating solution is 11-13.

[0030] The present application further provides a preparation method of high-conductivity lithium cobalt oxide, comprising the following steps:

[0031] adding lithium cobalt oxide into the above nickel plating solution, heating and stirring, carrying out nickel plating, and then vacuum freeze-drying to obtain high-conductivity lithium cobalt oxide.

[0032] In a further preferred embodiment, the temperature during the heating and stirring is 80-90℃, and the heating rate is 5-10℃ / min.

[0033] In a further preferred embodiment, the stirring speed during the nickel plating process is maintained at 200-600 rpm.

[0034] In a further preferred embodiment, the temperature of the vacuum freeze-drying is -120--80℃, and the vacuum degree is 1.2×10 -4 ~2.5×10 -1 Pa.

[0035] In a further preferred embodiment, the method further comprises a step of cleaning the positive electrode material of the lithium ion battery before the lithium cobalt oxide is added into the nickel plating solution.

[0036] Further, the cleaning method is as follows: the lithium cobaltate is placed in a 1.0-2.0 M concentration sulfuric acid solution for ultrasonic cleaning for 20-40 min, ultrasonic cleaning in an acetone solution for 2-20 min, ultrasonic cleaning in an ethanol solution for 10-100 min, and the frequency of ultrasonic cleaning is 25-60 kHz; then the lithium cobaltate is washed with deionized water for multiple times, and dried in a vacuum drying oven for 1-5 h, and the drying temperature is 40-100 DEG C.

[0037] The application also provides the high-conductivity lithium cobaltate prepared by the above preparation method.

[0038] Based on the same inventive concept, the application provides a lithium ion battery comprising the high-conductivity lithium cobaltate.

[0039] The nickel plating solution provided by the application uses modified nano-alumina as a pore-forming agent, and in the process of preparing the modified nano-alumina, the nano-alumina with a particle size distribution of 10-150 nm is used, the nano-alumina is first dispersed in anhydrous ethanol, then o-xylene is added, the nano-alumina is dispersed in the whole system, then the anhydrous ethanol is removed by heating, and finally the nano-alumina suspension A dispersed in o-xylene is obtained, which is the first dispersion of the nano-alumina and the process of removing ethanol; 3-aminopropyl triethoxysilane is added dropwise into the suspension A, the temperature is raised for reaction, the nano-alumina is coarsely modified, and the agglomeration between the nano-alumina powders is reduced, then the o-xylene in the dispersion system is removed, and the coarsely modified nano-alumina is dispersed in anhydrous ethanol for secondary dispersion, 4,4'-diamino diphenyl sulfone and polyethylene glycol-2000 are used as dispersants to improve the dispersion effect of the nano-alumina, so that the modified nano-alumina powder with high dispersity is prepared, which lays a foundation for obtaining a nickel plating layer with uniform pore distribution and thickness on the surface of the positive electrode material, improves the uniformity of the nickel plating layer coated on the positive electrode material, and finally the modified nano-alumina is obtained by mixing carbon black and sesbania powder as physical pore-forming agents with the modified nano-alumina powder coarse material and calcining.

[0040] The sesbania powder has a polyhydroxy structure and is low in price, and can better act on alumina and carbon-containing functional groups, and effectively inhibit the agglomeration of alumina through a space fixation mechanism.

[0041] The modified nano-alumina with more uniform dispersion and smaller agglomeration can be more uniformly dispersed in the nickel plating solution, and the distribution of the modified alumina particles in the nickel plating layer is also more uniform during electroplating, and the distribution is not uneven and the thickness is not uneven. The modified nano-alumina after the above modification is used as a pore-forming agent and mixed with the nickel plating solution, and the nickel-plated high-conductivity positive electrode material prepared has more excellent conductivity, better cycle performance and rate performance.

[0042] The technical scheme provided by the present application has the following obvious beneficial effects:

[0043] The modified alumina has very good dispersing performance, and can be used as a pore-forming agent to lay a foundation for the positive electrode material surface to obtain a nickel plating layer with uniform pore distribution and thin and uniform thickness, thereby improving the uniformity of the nickel plating layer coated on the positive electrode material.

[0044] In the nickel plating solution, the modified nano-alumina will also form a plating layer together with nickel during the nickel plating process of the positive electrode material, thereby avoiding the nickel layer being too thick or too dense, and ensuring that there is a sufficient channel for lithium ions to enter and exit from the surface of the positive electrode material.

[0045] The high-conductivity lithium cobaltate has very excellent conductivity, and the lithium ion battery using the high-conductivity lithium cobaltate has very good cycle performance and rate performance.

[0046] The method for modifying the nano-alumina is simple and easy to operate, and the preparation method of the nickel plating solution and the high-conductivity positive electrode material are both very simple and easy to operate, and are easy to popularize and apply. DETAILED DESCRIPTION

[0047] In order to facilitate the understanding of the present application, the present application will be described in more detail below in combination with preferred embodiments, but the protection scope of the present application is not limited to the following specific embodiments.

[0048] Unless otherwise defined, all the professional terms used in the following are the same as those commonly understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the protection scope of the present application.

[0049] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0050] Example 1

[0051] I. Preparation of modified nano-alumina

[0052] 35 g of nano-alumina with a particle size D50 of 10 nm, 2 g of 3-aminopropyl triethoxysilane, 0.2 g of 4,4'-diamino diphenyl sulfone, 2 g of polyethylene glycol-2000, 0.5 g of carbon black, and 0.2 g of sesbania powder were weighed respectively.

[0053] The nano-alumina was dispersed in anhydrous ethanol, and 175 mL of o-xylene was added, ultrasonic dispersion was performed for 20 min, the ultrasonic dispersion frequency was 20 kHz, the oil bath was heated to 90℃, and the ethanol was removed to obtain a suspension A;

[0054] The 3-aminopropyl triethoxysilane was added dropwise to the suspension A, after the dropwise addition was completed, the temperature was continuously increased to 120 DEG C and reacted for 2 h, and then the temperature was increased to above 140 DEG C, the o-xylene in the suspension was evaporated to obtain a crude modified nano-alumina powder;

[0055] The crude modified nano-alumina powder was dispersed in anhydrous ethanol, 4,4'-diamino diphenyl sulfone and polyethylene glycol-2000 were added, and ultrasonic dispersion was performed for 20 min at an ultrasonic frequency of 30 kHz, and then filtration, drying and repeated washing with anhydrous ethanol were performed to obtain a modified nano-alumina powder crude material;

[0056] The modified nano-alumina powder crude material was mixed with carbon black and sesbania powder, vacuum calcination was performed at a calcination temperature of 500 DEG C, and after cooling to room temperature, crushing was performed to obtain a modified nano-alumina.

[0057] II. Preparation of a nickel plating solution

[0058] 20 g of nickel sulfate, 30 g of ethylenediaminetetraacetic acid (EDTA), 55 mL of hydrazine hydrate, 2 g of polyethylene glycol and 25 g of modified nano-alumina were weighed respectively;

[0059] Deionized water was used to dissolve the nickel sulfate to obtain a solution A;

[0060] EDTA was added to the solution A, and stirring was performed to completely dissolve the EDTA, then lithium hydroxide was added, the pH of the solution was adjusted to 11, then polyethylene glycol was added, and ultrasonic dispersion was performed for 1 h at an ultrasonic frequency of 28 kHz to obtain a solution B;

[0061] Hydrazine hydrate and modified nano-alumina were simultaneously added to the solution B, the volume was adjusted to 1 L, ultrasonic dispersion was performed for 20 min at an ultrasonic frequency of 40 kHz to obtain a nickel plating solution.

[0062] III. Preparation of high-conductivity lithium cobalt oxide

[0063] The LiCoO2 lithium battery positive electrode material was ultrasonically cleaned, including: ultrasonic cleaning in a 1.5 M concentration of sulfuric acid solution for 30 min, ultrasonic cleaning in an acetone solution for 40 min, and ultrasonic cleaning in an ethanol solution for 50 min, all at a frequency of 45 kHz; then multiple washing with deionized water was performed, and drying was performed in a vacuum drying oven for 3 h at a drying temperature of 80 DEG C;

[0064] The cleaned and dried LiCoO2 was immersed in the nickel plating solution, the temperature was increased to 80 DEG C, and stirring was continuously performed at a speed of 200 rpm, nickel plating was performed, after the nickel plating was completed, the LiCoO2 with a nickel film plated on the surface was subjected to freeze vacuum drying, the freezing temperature was -120 DEG C, and the vacuum degree was 1.2 x 10 -4 Pa, to obtain a finished product LiCoO2 material.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 1 is that the step of “preparing modified nano-alumina” in Example 1 is not implemented, and the unmodified nano-alumina with a particle size D50 of 10 nm is used to replace the modified nano-alumina in the nickel plating solution.

[0067] Specifically:

[0068] I. Preparing the nickel plating solution

[0069] 20 g of nickel sulfate, 30 g of ethylenediaminetetraacetic acid (EDTA), 55 mL of hydrazine hydrate, 2 g of polyethylene glycol, and 25 g of nano-alumina with a particle size D50 of 10 nm were weighed respectively;

[0070] Dissolve the nickel sulfate in deionized water to obtain solution A;

[0071] Add EDTA to solution A and stir to completely dissolve EDTA, then add lithium hydroxide to adjust the pH of the solution to 11, then add polyethylene glycol, and ultrasonically disperse for 1 h at an ultrasonic frequency of 28 kHz to obtain solution B;

[0072] Simultaneously add hydrazine hydrate and nano-alumina to solution B, and dilute to 1 L, and ultrasonically disperse for 20 min at an ultrasonic frequency of 40 kHz to obtain the nickel plating solution.

[0073] II. Modified positive electrode material

[0074] Ultrasonically clean the LiCoO2 lithium battery positive electrode material, including: ultrasonically cleaning in a 1.5 M concentration of sulfuric acid solution for 30 min, ultrasonically cleaning in an acetone solution for 40 min, and ultrasonically cleaning in an ethanol solution for 50 min, all at an ultrasonic frequency of 45 kHz; then wash multiple times with deionized water and dry in a vacuum drying oven for 3 h at a drying temperature of 80°C;

[0075] Immerse the cleaned and dried LiCoO2 in the nickel plating solution, heat to 80°C, and continuously stir at a speed of 200 rpm, and perform nickel plating. After the nickel plating is completed, the LiCoO2 with a nickel film on the surface is subjected to freeze vacuum drying, with a freeze temperature of -120°C and a vacuum degree of 1.2×10 -4 Pa, to obtain a modified LiCoO2 material.

[0076] Example 2

[0077] I. Preparing modified nano-alumina:

[0078] Take 60 g of nano-alumina with a particle size D50 of 150 nm, 3.5 g of 3-aminopropyl triethoxysilane, 0.6 g of 4,4'-diamino diphenyl sulfone, 3 g of polyethylene glycol-2000, 0.8 g of carbon black, and 0.6 g of sesbania powder, respectively.

[0079] Disperse the nano-alumina in anhydrous ethanol, add 300 mL of o-xylene, and ultrasonically disperse for 20 min at a frequency of 25 kHz. Heat the oil bath to 120°C, and remove the ethanol to obtain suspension A.

[0080] Add 3-aminopropyl triethoxysilane dropwise to suspension A, and continue to heat to 120°C after the addition is complete. After 2 h of reaction, heat to above 140°C, and evaporate the o-xylene in the suspension to obtain crude modified nano-alumina powder.

[0081] Disperse the crude modified nano-alumina powder in anhydrous ethanol, and simultaneously add 4,4'-diamino diphenyl sulfone and polyethylene glycol-2000. Ultrasonically disperse for 30 min at a frequency of 30 kHz, filter and dry, and repeatedly wash with anhydrous ethanol to obtain crude modified nano-alumina powder.

[0082] Mix the crude modified nano-alumina powder with carbon black and sesbania powder, and vacuum calcine at a temperature of 600°C. After cooling to room temperature, crush to obtain modified nano-alumina.

[0083] II. Preparation of a nickel plating solution

[0084] Take 35 g of nickel sulfate, 45 g of ethylenediaminetetraacetic acid (EDTA), 65 mL of hydrazine hydrate, 3 g of polyethylene glycol, and 50 g of modified nano-alumina, respectively.

[0085] Dissolve the nickel sulfate in deionized water to obtain solution A;

[0086] Add EDTA to solution A, and stir to completely dissolve the EDTA. Then add lithium hydroxide, adjust the pH of the solution to 12, and then add polyethylene glycol. Ultrasonically disperse for 3 h at a frequency of 50 kHz to obtain solution B;

[0087] Simultaneously add hydrazine hydrate and modified nano-alumina to solution B, and dilute to 1 L. Ultrasonically disperse for 40 min at a frequency of 30 kHz to obtain a nickel plating solution.

[0088] III. Preparation of a high-conductivity positive electrode material

[0089] The LiCoO2 positive electrode material is ultrasonically cleaned, including: being placed in a 1.5 M concentration sulfuric acid solution and ultrasonically cleaned for 30 min, being placed in an acetone solution and ultrasonically cleaned for 40 min, and being placed in an ethanol solution and ultrasonically cleaned for 50 min, the ultrasonic cleaning frequency being 45 kHz; then being washed with deionized water multiple times and being dried in a vacuum drying oven for 3 h, the drying temperature being 80℃;

[0090] The cleaned positive electrode material is immersed in a nickel plating solution, heated to 90℃, and continuously stirred at 400 rpm to perform nickel plating. After the nickel plating is completed, the lithium battery positive electrode material with a nickel film plated on the surface is subjected to freeze vacuum drying, the freezing temperature being -90℃, and the vacuum degree being 1.2×10 -4 Pa, to obtain a finished positive electrode material.

[0091] Comparative Example 2

[0092] Comparative Example 2 and Example 2 differ in that the step of “preparing modified nano-alumina” in Example 2 is not performed, and the unmodified nano-alumina with a particle size D50 of 150 nm is used to replace the modified nano-alumina in the nickel plating solution.

[0093] Specifically:

[0094] I. Preparing the nickel plating solution:

[0095] 35 g of nickel sulfate, 45 g of ethylenediaminetetraacetic acid (EDTA), 65 mL of hydrazine hydrate, 3 g of polyethylene glycol, and 50 g of modified nano-alumina are weighed respectively;

[0096] Deionized water is used to dissolve the nickel sulfate to obtain solution A;

[0097] EDTA is added to solution A, and stirring is performed to completely dissolve the EDTA, then lithium hydroxide is added, the solution pH is adjusted to 12, then polyethylene glycol is added, and ultrasonic dispersion is performed for 3 h, the ultrasonic frequency being 50 kHz, to obtain solution B;

[0098] Hydrazine hydrate and modified nano-alumina are simultaneously added to solution B, the volume is made up to 1 L, ultrasonic dispersion is performed for 40 min, the ultrasonic frequency being 30 kHz, to obtain the nickel plating solution.

[0099] II. Modified positive electrode material

[0100] The LiCoO2 positive electrode material is ultrasonically cleaned, including: being placed in a 1.5 M concentration sulfuric acid solution and ultrasonically cleaned for 30 min, being placed in an acetone solution and ultrasonically cleaned for 40 min, and being placed in an ethanol solution and ultrasonically cleaned for 50 min, the ultrasonic cleaning frequency being 45 kHz; then being washed with deionized water multiple times and being dried in a vacuum drying oven for 3 h, the drying temperature being 80℃;

[0101] The cleaned positive electrode material is immersed in a nickel plating solution, heated to 90°C, and stirred at 400 rpm at the same time, nickel plating is carried out, and after the nickel plating is completed, the lithium battery positive electrode material with a nickel film plated on the surface is subjected to freeze vacuum drying, the freezing temperature is -90°C, and the vacuum degree is 1.2x10 -4 Pa, to obtain a modified positive electrode material.

[0102] Example 3

[0103] I. Preparation of modified nano-alumina oxide:

[0104] The preparation method of the modified nano-alumina oxide includes:

[0105] 85 g of nano-alumina with a particle size D50 of 100 nm, 5 g of 3- aminopropyl triethoxysilane, 0.8 g of 4,4'-diamino diphenyl sulfone, 5 g of polyethylene glycol-2000, 1 g of carbon black, and 0.8 g of sesbania powder are weighed respectively;

[0106] The nano-alumina is dispersed in anhydrous ethanol, and 400 mL of o-xylene is added, ultrasonic dispersion is performed for 20 min, the ultrasonic dispersion frequency is 30 kHz, the oil bath is heated to 80°C, the ethanol is removed, and a suspension A is obtained;

[0107] 3-aminopropyl triethoxysilane is added dropwise to the suspension A, after the dropwise addition is completed, the temperature is continuously increased to 120°C and reacted for 2 h, and then the temperature is increased to above 140°C, and the o-xylene in the suspension is evaporated and removed, to obtain a crude modified nano-alumina powder;

[0108] The crude modified nano-alumina powder is dispersed in anhydrous ethanol, 4,4'-diamino diphenyl sulfone and polyethylene glycol-2000 are added at the same time, ultrasonic dispersion is performed for 40 min, the ultrasonic frequency is 30 kHz, and the mixture is filtered, dried, and repeatedly washed with anhydrous ethanol to obtain a crude modified nano-alumina powder;

[0109] After the crude modified nano-alumina powder is mixed with carbon black and sesbania powder, vacuum calcination is performed at a calcination temperature of 800°C, and after cooling to room temperature, the modified nano-alumina is obtained by crushing.

[0110] II. Preparation of a nickel plating solution:

[0111] 50 g of nickel sulfate, 60 g of ethylenediaminetetraacetic acid (EDTA), 80 mL of hydrazine hydrate, 5 g of polyethylene glycol, and 80 g of modified nano-alumina are weighed respectively.

[0112] Deionized water is used to dissolve the nickel sulfate to obtain a solution A;

[0113] EDTA was added to solution A, and stirred to completely dissolve the EDTA, then lithium hydroxide was added, the pH value of the solution was adjusted to 13, then polyethylene glycol was added, and ultrasonic dispersion was performed for 5 h at an ultrasonic frequency of 80 kHz to obtain solution B;

[0114] Hydrazine hydrate and modified nano-aluminum oxide were simultaneously added to solution B, and the volume was adjusted to 1 L, and ultrasonic dispersion was performed for 60 min at an ultrasonic frequency of 60 kHz to obtain a nickel plating solution.

[0115] III. Preparation of high-conductivity positive electrode material

[0116] The LiCoO2 positive electrode material was ultrasonically cleaned, including: ultrasonic cleaning in a 1.5 M concentration of sulfuric acid solution for 30 min, ultrasonic cleaning in an acetone solution for 40 min, and ultrasonic cleaning in an ethanol solution for 50 min, all at a frequency of 45 kHz; then washed with deionized water multiple times, and dried in a vacuum drying oven for 3 h at a drying temperature of 80℃;

[0117] The cleaned positive electrode material was immersed in the nickel plating solution, heated to 90℃, and simultaneously stirred at 600 rpm, nickel plating was performed, and after the nickel plating was completed, the lithium battery positive electrode material with a nickel film on the surface was subjected to freeze vacuum drying, the freezing temperature was -80℃, and the vacuum degree was 1.2×10 -4 , to obtain the finished positive electrode material.

[0118] The unmodified LiCoO2 positive electrode material, the finished positive electrode material prepared in Examples 1-3, and the modified positive electrode material prepared in Comparative Examples 1-2 were subjected to GITT testing, respectively, to obtain the electrical conductivity of the materials, and the results are shown in Table 1.

[0119] Table 1

[0120]

[0121] It can be seen that the nickel plating solution containing modified nano-aluminum oxide enables the positive electrode material to have more excellent electrical conductivity.

[0122] The unmodified LiCoO2 positive electrode material, the finished positive electrode material prepared in Examples 1-3, and the modified positive electrode material prepared in Comparative Examples 1-2 were respectively made into electrode sheets and assembled into half-batteries for constant current charge and discharge testing to evaluate the electrochemical performance of the electrode materials, specifically: the positive electrode material was assembled with a lithium metal negative electrode into a 2025 type button cell for electrochemical performance testing, and the electrolyte was 1.0 mol L -1 LiPF6 in ethylene carbonate and methyl ethyl carbonate (EC and EMC, volume ratio of 3:7). The loading of all half-battery positive electrodes was 5 mg·cm -2The test temperature was room temperature 25℃, and the voltage interval was 2.7~4.5 V. The discharge specific capacity of the batteries assembled by the positive electrode materials prepared in application examples 1-3, the modified positive electrode materials prepared in comparative examples 1-2 and the LiCoO2 positive electrode material without modification was respectively measured at the 300th cycle, and the results are shown in Table 2.

[0123] Table 2

[0124]

[0125] The capacity retention rate of the battery of the positive electrode material obtained in application examples 1-3 was 82.5%, 81.9% and 82.2% respectively, which was obviously superior to comparative example 1, comparative example 2 and the LiCoO2 positive electrode material without modification. It can be seen that the positive electrode material prepared by the method of the present application not only has higher electrical conductivity, but also has better cycle performance and rate performance.

[0126] The above only describes the preferred embodiments of the present application, and it should be pointed out that for those skilled in the art, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing modified nanometer alumina, characterized in that, The method comprises the following steps: Step S1, dispersing nano-alumina in anhydrous ethanol, adding o-xylene, ultrasonic dispersion, then heating to remove ethanol to obtain suspension A; Step S2, adding 3-aminopropyl triethoxysilane dropwise into suspension A, then heating to evaporate and remove o-xylene in suspension A to obtain intermediate product I; Step S3, dispersing intermediate product I in anhydrous ethanol, adding 4,4'-diamino diphenyl sulfone and polyethylene glycol-2000, ultrasonic dispersion, filtering, washing, and drying to obtain intermediate product II; Step S4, mixing intermediate product II with carbon black and sesbania powder, then vacuum roasting to obtain modified nano-alumina.

2. The production method according to claim 1, wherein The heating mode in step S2 is: first, heat at 60-80℃ for 2-4h, then heat to above 140℃.

3. The production method according to claim 1, wherein The vacuum roasting temperature is 500-800℃.

4. The production method according to any one of claims 1 to 3, wherein In steps S1-S4, the amount of each substance is by weight parts, wherein the amount of nano-alumina is 35-85 parts, the amount of 3-aminopropyl triethoxysilane is 2-5 parts, the amount of 4,4'-diamino diphenyl sulfone is 0.2-0.8 parts, the amount of polyethylene glycol-2000 is 2-5 parts, the amount of carbon black is 0.5-1 part, and the amount of sesbania powder is 0.2-0.8 part.

5. The production method according to claim 4, wherein In step S1, the mass-volume ratio of nano-alumina to o-xylene is 0.5-1.5 g:2.5-7.5 mL.

6. The modified nano-alumina prepared by the preparation method according to any one of claims 1-5.

7. A nickel plating solution, characterized by comprising: The plating solution comprises a nickel salt, a complexing agent, a reducing agent, a pH adjusting agent, a dispersing agent, and the modified nano-alumina according to claim 6.

8. The nickel plating solution of claim 7, wherein The nickel salt is at least one of nickel sulfate, nickel acetate, nickel carbonate, nickel hypophosphite, nickel sulfamate, and nickel methylsulfonate; the complexing agent is at least one of EDTA, acetic acid, lactic acid, succinic acid, glycolic acid, malic acid, citric acid, and glycine; the reducing agent is hydrazine hydrate; the pH adjusting agent is at least one of lithium hydroxide and lithium carbonate; and the dispersing agent is at least one of OP-10, polyethylene glycol, polyvinyl alcohol, triethanolamine, Tween, and Span.

9. The nickel plating solution according to claim 7 or 8, wherein The concentration of the nickel salt in the plating solution is 20-50 g / L, the concentration of the complexing agent is 30-60 g / L, the concentration of the reducing agent is 55-80 mL / L, the concentration of the dispersing agent is 2-5 g / L, and the mass percentage of the modified nano-alumina in the plating solution is 2.5-12 wt %.

10. The method of preparing a nickel plating solution according to any one of claims 7 to 9, wherein The method comprises the following steps: Step S1, preparing a nickel salt solution; Step S2, adding a complexing agent into the nickel salt solution, and after the complexing agent is completely dissolved, adding a pH adjusting agent and a dispersing agent, and ultrasonic dispersion to obtain a mixed solution; Step S3, simultaneously adding a reducing agent and the modified nano-alumina into the mixed solution, and ultrasonic dispersion to obtain a plating solution.

11. The method of claim 10, wherein the nickel plating solution is prepared by adding the nickel salt to the aqueous solution, and then adding the complexing agent, the reducing agent, and the pH adjuster. After adding the pH adjusting agent in step S2, the pH value of the plating solution is 11-13.

12. A method for producing high-conductivity lithium cobaltate, characterized by, The method comprises the following steps: Adding lithium cobaltate into the plating solution according to any one of claims 7-9 or the plating solution prepared by the preparation method according to any one of claims 10-11, heating and stirring to perform nickel plating, and then vacuum freeze-drying to obtain high-conductivity lithium cobaltate.

13. The production method according to claim 12, wherein The temperature during the temperature-increasing stirring is 80-90℃, and the temperature-increasing rate is 5-10℃ / min.

14. The production method according to claim 12 or 13, characterized by, The method further comprises a step of cleaning the lithium cobaltate before the lithium cobaltate is added into the nickel plating solution.

15. The high-conductivity lithium cobaltate prepared by the preparation method according to any one of claims 12-14.

16. A lithium-ion battery, characterized by The high-conductivity lithium cobaltate according to claim 15.

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