Lithium manganate positive electrode material and preparation method thereof, positive electrode sheet and battery

Abstract

This invention relates to the field of lithium manganese oxide cathode materials, specifically to lithium manganese oxide cathode materials and their preparation methods, cathode sheets, and batteries, for addressing the issue of Mn content during cycling. 3+ The problems of Jahn-Teller distortion, Mn dissolution, and low conductivity were addressed. K / Al co-doped lithium manganese oxide powder was obtained by ball milling and sintering lithium carbonate, manganese tetroxide, potassium carbonate, aluminum nitrate, and anhydrous ethanol. This powder was then coated with an acetylferrocene / diphenylamine polymer and finally coated with an AlF3@CeF3 suspension to obtain the lithium manganese oxide cathode material. This lithium manganese oxide cathode material significantly improved electronic conductivity, rate performance, and cycle stability, exhibiting excellent cycle stability and rate performance.

Description

Technical Field

[0001] This invention relates to the field of lithium manganese oxide cathode materials, specifically to lithium manganese oxide cathode materials and their preparation methods, cathode sheets, and batteries. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and energy storage systems due to their high efficiency, low self-discharge, and long cycle life. As a key component of lithium-ion batteries, the cathode material has a crucial impact on battery performance. Currently, commonly used cathode materials include lithium cobalt oxide, nickel-cobalt-manganese ternary materials, and lithium iron phosphate. Among these, lithium manganese oxide, as a low-cost and environmentally friendly cathode material, has been widely researched and applied.

[0003] However, lithium manganese oxide cathode materials face several key challenges during charge-discharge cycling, which pose major obstacles to further performance improvements. Firstly, the Mn content during cycling... 3+ Jahn-Teller distortion leads to Mn 3+ Instability in the crystal structure leads to lattice distortion and structural degradation, which in turn affects the electrochemical performance of the material. Secondly, Mn dissolution is a serious problem, especially at high voltages. Dissolved Mn ions can deposit on the surface of the negative electrode material or in the electrolyte, causing irreversible capacity loss and potentially forming dendrites, increasing the risk of battery short circuits. Finally, low ionic / electronic conductivity affects the rapid transport of lithium ions and electrons within the material, limiting the battery's charge / discharge rate and overall efficiency.

[0004] Therefore, developing lithium manganese oxide cathode materials with higher performance and better cycle stability is a current research focus and hot topic. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the present invention aims to provide lithium manganese oxide cathode material, its preparation method, cathode sheet and battery.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In a first aspect, this application provides a method for preparing lithium manganese oxide cathode material, comprising the following steps:

[0008] Step 1: Add lithium carbonate, manganese tetroxide, potassium carbonate, aluminum nitrate, and anhydrous ethanol to a planetary ball mill at a ball-to-material ratio of 10:1. Ball mill for 4-5 hours at a speed of 250-300 r / min. Then place the mixture in a vacuum drying oven and dry it at 75-80℃ for 12-14 hours. After that, place it in a tube furnace and heat it to 450℃ in air at a heating rate of 3℃ / min. Hold it at that temperature for 2 hours. Then cool it to room temperature with the furnace and grind it through a 100-mesh sieve. Then heat it to 800℃ at a heating rate of 5℃ / min and hold it for 10 hours. Then cool it to room temperature with the furnace and grind it through a 200-mesh sieve to obtain K / Al co-doped lithium manganese oxide powder.

[0009] Step 2: Add acetylferrocene, N-phenyl-p-phenylenediamine and dichloromethane to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 25-30℃ and 300-400 r / min for 10-12 min. Add ferric chloride while stirring, and continue stirring for 24-25 h. After the reaction is complete, add methanol, then filter to collect the solid and wash with deionized water 4-6 times. Place in a vacuum drying oven and dry at 65-70℃ for 24-26 h to obtain acetylferrocene / diphenylamine polymer.

[0010] Step 3: Add K / Al co-doped lithium manganese oxide powder to anhydrous ethanol and ultrasonically disperse it for 30-32 minutes at a power of 170-200W to form a mixture.

[0011] Step 4: Dissolve the acetylferrocene / diphenylamine polymer in dichloromethane and ultrasonically disperse it for 10-12 minutes at a power of 170-200W. Then add the suspension and continue ultrasonic dispersion for 15-20 minutes. Transfer the solution to a three-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and gas delivery tube. Purge with nitrogen for protection. Under conditions of 25-30℃ and a stirring rate of 600-700 r / min, add the dichloromethane solution of ferric chloride dropwise while stirring, controlling the dropping rate to 1-2 drops / s. After the reaction is complete, continue stirring for 12-13 hours. After the reaction is complete, centrifuge at 9000-10000 r / min for 10 minutes, collect the solid and wash it with methanol 3-5 times. Then place it in a vacuum drying oven and dry it at atmospheric pressure at 45-50℃ for 8-9 hours. Then raise the temperature to 65-70℃ and vacuum dry it for 24-26 hours. After that, place it in a tube furnace and heat it to 240℃ at a heating rate of 5℃ / min under a nitrogen atmosphere. Hold it at this temperature for 3 hours and let it cool naturally to room temperature to obtain coated lithium manganese oxide.

[0012] Step 5: Add coated lithium manganese oxide, anhydrous ethanol and dispersant to a beaker, sonicate at 130-150W for 20-25 minutes, then place in a vacuum drying oven and dry at 50-60℃ for 8-9 hours to obtain pretreated coated lithium manganese oxide.

[0013] Step 6: Add aluminum nitrate, cerium nitrate, and deionized water to a three-necked flask equipped with a stirrer, thermometer, and constant pressure dropping funnel. Stir magnetically for 10-15 minutes at a temperature of 25-30℃ and a stirring rate of 250-300 r / min. Then, while stirring, add the fluorine source solution dropwise, controlling the dropping rate to 1-2 drops / s. After the addition is complete, continue stirring for 30-35 minutes to obtain an AlF3@CeF3 suspension.

[0014] Step 7: Add the pretreated coated lithium manganese oxide to the AlF3@CeF3 suspension and sonicate it for 15-20 min at a power of 130-150 W. Adjust the pH to 7-8 with 0.1 mol / L dilute nitric acid, transfer it to a hydrothermal reactor, seal it, and place it in an oven at 90-110℃ for 2-4 h. After that, allow it to cool naturally to room temperature, transfer it to a centrifuge tube, and centrifuge it at 10000-12000 r / min for 10-12 min. Collect the bottom solid and wash it 3-5 times with deionized water, then wash it 1-2 times with anhydrous ethanol. After that, place it in a vacuum drying oven and dry it at 50-60℃ for 20-22 h to obtain the lithium manganese oxide cathode material.

[0015] In a preferred embodiment of the present invention, the ratio of lithium carbonate, manganese tetroxide, potassium carbonate, aluminum nitrate and anhydrous ethanol in step one is 3.8-4.3g: 15-17g: 0.14-0.16g: 0.75-0.80g: 30-35mL.

[0016] In a preferred embodiment of the present invention, the ratio of acetylferrocene, N-phenyl-p-phenylenediamine, dichloromethane, ferric chloride and methanol in step two is 0.5-0.6g: 0.5-0.6g: 20-23mL: 5-6g: 30-35mL.

[0017] In a preferred embodiment of the present invention, the ratio of K / Al co-doped lithium manganese oxide powder to anhydrous ethanol in step three is 1-3g: 20-60mL.

[0018] In a preferred embodiment of the present invention, the ratio of the amount of acetylferrocene / diphenylamine polymer, dichloromethane, suspension and dichloromethane solution of ferric chloride in step four is 0.1-0.3g: 10-30mL: 20-60mL: 5-15mL.

[0019] In a preferred embodiment of the present invention, the ferric chloride dichloromethane solution in step four is a solution of ferric chloride and dichloromethane mixed in a ratio of 0.5g:5mL.

[0020] In a preferred embodiment of the present invention, the ratio of coated lithium manganese oxide, anhydrous ethanol and dispersant in step five is 1-2g: 25-50mL: 0.5-0.7mL.

[0021] In a preferred embodiment of the present invention, the dispersant in step five is PEG-400, CAS number 25322-68-3.

[0022] In a preferred embodiment of the present invention, the ratio of aluminum nitrate, cerium nitrate, deionized water and fluoride source solution in step six is ​​7.5-7.7g: 8.7-8.9g: 20-25mL: 10-12mL.

[0023] In a preferred embodiment of the present invention, the fluoride source solution in step six is ​​a solution of ammonium fluoride and deionized water mixed in a ratio of 4.4g:10mL.

[0024] In a preferred embodiment of the present invention, the ratio of the amount of pretreated lithium manganese oxide and AlF3@CeF3 suspension used in step seven is 1-2g:30-40mL.

[0025] Secondly, this application provides a lithium manganese oxide cathode material, which is prepared according to the preparation method of the lithium manganese oxide cathode material in the first aspect described above.

[0026] Thirdly, this application provides a positive electrode sheet, which is prepared from the lithium manganese oxide positive electrode material mentioned in the second aspect above, and the specific steps are as follows:

[0027] Lithium manganese oxide cathode material, conductive carbon black, polyvinylidene fluoride, and N-methylpyrrolidone were stirred using a magnetic stirrer at 1000-3000 rpm for 1-2 hours. The prepared slurry was then coated onto a pretreated aluminum foil current collector using a scraping method. The coated aluminum foil was transferred to a vacuum drying oven and pre-dried at 60-80℃ for 1-2 hours, followed by vacuum drying at 110-130℃ for 5-7 hours. After drying, the electrode sheet was rolled using a roller press at a pressure controlled at 6-12 MPa to achieve a compaction density of 2.2-2.3 g / cm³. 3 Ultimately, a positive electrode sheet is obtained.

[0028] In a preferred embodiment of the present invention, the ratio of lithium manganese oxide cathode material, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone is 40-42g: 3-5g: 2-3g: 90-95mL.

[0029] Fourthly, this application provides a battery comprising the positive electrode, negative electrode, separator, and electrolyte described in the third aspect above, with the specific steps as follows:

[0030] Using graphite as the negative electrode and Celgard 2400 polypropylene microporous membrane as the separator, the electrolyte was 1 mol / L LiPF6 (EC:DEC=1:1, v / v). The positive electrode, negative electrode, separator and electrolyte were assembled in an argon glove box with water and oxygen content of less than 1 ppm. After assembly, the battery was left to stand for 24 hours to obtain the battery.

[0031] The beneficial effects of this invention are:

[0032] The present invention relates to a lithium manganese oxide cathode material, its preparation method, cathode sheet, and battery. The method involves ball milling lithium carbonate, manganese tetroxide, potassium carbonate, aluminum nitrate, and anhydrous ethanol, followed by sintering to obtain K / Al co-doped lithium manganese oxide powder. This powder is then coated with an acetylferrocene / diphenylamine polymer, and finally coated with an AlF3@CeF3 suspension to obtain the final lithium manganese oxide cathode material. This preparation method uses K / Al co-doped lithium manganese oxide powder as the main raw material. The K / Al co-doped lithium manganese oxide powder simultaneously improves cycle stability and rate performance. Coating with the acetylferrocene / diphenylamine polymer significantly improves electronic conductivity, enhances rate performance, isolates direct contact between the electrolyte and the cathode, reduces particle agglomeration, and improves cycle stability. Coating with the AlF3@CeF3 suspension provides strong resistance to HF corrosion and suitability for high-temperature environments, improves interfacial ionic conductivity, and suppresses lattice phase transitions and electrolyte decomposition at high temperatures.

[0033] Al 3+ Ionic radius and Mn 4+ Highly compatible, capable of efficiently replacing part of Mn 3+ / Mn 4+ Entering the 16d lattice site, Mn 3+ This is the root cause of the Jahn-Teller effect, Mn 3+ 3D 4 Electronic configuration causes asymmetric deformation of the octahedral coordination structure, leading to lattice collapse in Al. 3+ For stable 3D 0 Configuration, no Jahn-Teller effect, substitutes for Mn 3+ This can reduce the amount of Mn in the crystal lattice. 3+The ratio fundamentally reduces irreversible lattice deformation during cycling, avoiding rapid capacity decay. Furthermore, the bond energy of Al-O bonds is much higher than that of Mn-O bonds. 3+ The replacement can strengthen the spinel lattice framework and reduce Li + The expansion / contraction of lattice volume during repeated insertion / extraction processes enhances structural stability; K + The ionic radius is much larger than that of Li. + Unable to access Li + Tetrahedral sites, but can selectively occupy interstitial or surface defect sites, K + The introduction of [something] will slightly expand the spinel lattice and broaden the Li [something]. + diffusion channels, reducing Li + Migration resistance within the crystal lattice, thereby improving the rate performance of the material, and K + The electropositivity can be related to the O on the crystal lattice surface. 2- This forms a strong interaction, inhibiting the desorption of surface lattice oxygen, while simultaneously reducing the interaction between HF in the electrolyte and surface O. 2﹣ The reaction further protects the surface structure; therefore, in Al 3+ Suppressing lattice distortion, K + Improve Li + The combined effect of both conductive and conductive processes can simultaneously improve the cycle stability and rate performance of lithium manganese oxide.

[0034] The polymer formed by the polymerization of acetylferrocene and diphenylamine is based on the reaction mechanism of the amino group of N-phenyl-p-phenylenediamine being converted by Fe. 3+ Oxidation generates an active intermediate, which then attacks the acetyl ferrocene ring to form a CN bond. Repeated oxidation-coupling processes achieve chain growth. Deactivation of the active intermediate leads to chain termination. The polymer is obtained after precipitation, washing, and drying.

[0035] Acetylferrocene / diphenylamine polymers possess a conjugated π-electron system, allowing conjugated π-electrons to migrate freely within the polymer chain, forming continuous electron transport channels. However, pure lithium manganese oxide has extremely low electronic conductivity, failing to meet the electron transport requirements at high rates. The polymer coating layer covers the surface of lithium manganese oxide particles and the gaps between particles, forming a three-dimensional electron transport network, thereby improving electronic conductivity and significantly enhancing rate performance. Furthermore, the polymer coating layer is a dense organic film that isolates the HF in the electrolyte from direct contact with the lithium manganese oxide surface, preventing HF from reacting with Mn. 3+ / Mn 4+The reaction generates soluble MnF2, reducing the loss of active sites. Lithium manganese oxide is prone to catalyzing the oxidative decomposition of the electrolyte under high voltage, generating byproducts. The polymer coating layer can block the electrolyte from contacting the highly active lithium manganese oxide surface, reducing electrolyte decomposition and avoiding excessive growth of interfacial impedance. The polymer has a certain degree of elasticity, which can buffer the volume expansion / contraction of lithium manganese oxide particles during cycling, preventing particles from breaking and agglomerating due to repeated stress. At the same time, the coating layer can prevent small particles after breakage from reacting excessively with the electrolyte, further improving cycle stability. Acetylferrocene / diphenylamine polymer coating of lithium manganese oxide can significantly improve electronic conductivity, improve rate performance, isolate the direct contact between the electrolyte and the positive electrode, reduce particle agglomeration, and improve cycle stability.

[0036] Both AlF3 and CeF3 are chemically inert fluorides and do not react with HF. Compared to organic polymers, AlF3@CeF3 can completely isolate HF from the surface of lithium manganese oxide, fundamentally inhibiting Mn leaching. This makes it particularly suitable for high-temperature cycling scenarios. The fluoride coating can react with the O2 on the surface of lithium manganese oxide. 2- The formation of strong FO bonds inhibits the desorption of surface lattice oxygen, preventing the irreversible phase transformation from spinel to rock salt phase at high temperatures, thereby improving high-temperature cycling stability; both AlF3 and CeF3 possess certain Li... + Conductivity, Li in AlF3 + Although its conductivity is lower than that of the electrolyte, it can act as an "interfacial conduction bridge" to reduce Li. + Migration resistance at the electrode / electrolyte interface, Ce in CeF3 3+ It can form an electron transport channel, while Ce 3+ The presence of Li can promote + In terms of adsorption and desorption at the interface, the efficiency of interfacial ion / electron mixing is further optimized. Compared with single AlF3 or CeF3 coating, the core-shell structure AlF3@CeF3 can balance HF resistance and electronic conduction, thereby reducing interfacial impedance and improving rate performance and low-temperature performance; Ce 3+ It exhibits certain catalytic activity and can inhibit the oxidative decomposition of the electrolyte under high voltage. Carbonate molecules in the electrolyte are easily oxidized to generate byproducts under high voltage, such as Ce. 3+ The oxidation pathway of electrolyte molecules can be adjusted through electron transfer, reducing the generation of by-products and avoiding excessive thickening of the SEI film at the interface. AlF3@CeF3 coating material has strong resistance to HF corrosion and is suitable for high-temperature environments, improving the interfacial ionic conductivity and inhibiting lattice phase transitions and electrolyte decomposition at high temperatures. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. The following drawings are not drawn to scale according to the actual size, but are intended to illustrate the main idea of ​​the present invention.

[0038] Figure 1 The capacity retention rate versus cycle number curves for Examples 4-6 and Comparative Examples 1-3 are shown below.

[0039] Figure 2 The charge-discharge curves of Examples 4-6 and Comparative Examples 1-3 are shown below;

[0040] Figure 3 AC impedance spectroscopy-Nyquist plots for Examples 4-6 and Comparative Examples 1-3;

[0041] Figure 4 This is a schematic diagram of the lithium manganese oxide cathode material product of Example 1. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1:

[0044] This embodiment describes a method for preparing lithium manganese oxide cathode material, including the following steps:

[0045] Step s1: Add 3.8g lithium carbonate, 15g manganese tetroxide, 0.14g potassium carbonate, 0.75g aluminum nitrate and 30mL anhydrous ethanol to a planetary ball mill with a ball-to-material ratio of 10:1. Ball mill for 4 hours at 250r / min. Then place in a vacuum drying oven and dry at 75℃ for 12 hours. Then place in a tube furnace and heat to 450℃ in air at a heating rate of 3℃ / min. Hold at this temperature for 2 hours. Then cool to room temperature with the furnace and grind through a 100-mesh sieve. Then heat to 800℃ at a heating rate of 5℃ / min and hold at this temperature for 10 hours. Then cool to room temperature with the furnace and grind through a 200-mesh sieve to obtain K / Al co-doped lithium manganese oxide powder.

[0046] Step s2: Add 0.5g acetylferrocene, 0.5g N-phenyl-p-phenylenediamine and 20mL dichloromethane to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 10min. Add 5g ferric chloride while stirring and continue stirring for 24h. After the reaction is complete, add 30mL methanol, filter and collect the solid, wash with deionized water 4 times, and then place in a vacuum drying oven and dry at 65℃ for 24h to obtain acetylferrocene / diphenylamine polymer.

[0047] Step s3: Add 1g of K / Al co-doped lithium manganese oxide powder to 20mL of anhydrous ethanol and ultrasonically disperse it for 30min at a power of 170W to form a mixture.

[0048] Step s4: Dissolve 0.1g of acetylferrocene / diphenylamine polymer in 10mL of dichloromethane and sonicate for 10min at 170W. Then add 20mL of suspension and continue sonicating for 15min. Transfer the solution to a three-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and gas delivery tube. Purge with nitrogen for protection. While stirring at 25℃ and a stirring rate of 600r / min, add dropwise 5mL of a ferric chloride dichloromethane solution (ferric chloride and dichloromethane are added in a 0:1 ratio). A solution of 0.5 g and 5 mL was prepared, with a dropping rate of 1 drop / s. After the addition was complete, the mixture was stirred for 12 h. After the reaction was completed, the mixture was centrifuged at 9000 r / min for 10 min, the solid was collected and washed three times with methanol. Then it was placed in a vacuum drying oven and dried at 45 °C under normal pressure for 8 h. Then it was heated to 65 °C and vacuum dried for 24 h. After that, it was placed in a tube furnace and heated to 240 °C at a heating rate of 5 °C / min under a nitrogen atmosphere. The temperature was held for 3 h and then naturally cooled to room temperature to obtain coated lithium manganese oxide.

[0049] Step s5: Add 1g of coated lithium manganese oxide, 25mL of anhydrous ethanol and 0.5mL of dispersant (dispersant is PEG-400, CAS number is 25322-68-3) into a beaker, sonicate for 20min at 130W, and then place it in a vacuum drying oven and dry at 50℃ for 8h to obtain pretreated coated lithium manganese oxide;

[0050] Step s6: Add 7.5g aluminum nitrate, 8.7g cerium nitrate, and 20mL deionized water to a three-necked flask equipped with a stirrer, thermometer, and constant pressure dropping funnel. Stir magnetically for 10min at 25℃ and a stirring rate of 250r / min. Then, while stirring, add 10mL of fluorine source solution (fluorine source solution is a solution of ammonium fluoride and deionized water mixed in a ratio of 4.4g:10mL) dropwise, controlling the dropping rate to 1 drop / s. After the addition is complete, continue stirring for 30min to obtain an AlF3@CeF3 suspension.

[0051] Step s7: Add 1g of pretreated coated lithium manganese oxide to 30mL of AlF3@CeF3 suspension, sonicate for 15min at 130W, adjust pH to 7 with 0.1mol / L dilute nitric acid, transfer to a hydrothermal reactor, seal and place in an oven at 90℃ for 2h, then allow to cool naturally to room temperature, transfer to a centrifuge tube, centrifuge at 10000r / min for 10min, collect the bottom solid and wash three times with deionized water, then wash once with anhydrous ethanol, then place in a vacuum drying oven and dry at 50℃ for 20h to obtain lithium manganese oxide cathode material.

[0052] Example 2:

[0053] This embodiment describes a method for preparing lithium manganese oxide cathode material, including the following steps:

[0054] Step s1: Add 4.1g lithium carbonate, 16g manganese tetroxide, 0.15g potassium carbonate, 0.77g aluminum nitrate and 33mL anhydrous ethanol to a planetary ball mill with a ball-to-material ratio of 10:1. Ball mill for 4.5h at 270r / min. Then place in a vacuum drying oven and dry at 77℃ for 13h. Then place in a tube furnace and heat to 450℃ in air at a heating rate of 3℃ / min and hold for 2h. Then cool to room temperature with the furnace and grind through a 100-mesh sieve. Then heat to 800℃ at a heating rate of 5℃ / min and hold for 10h. Then cool to room temperature with the furnace and grind through a 200-mesh sieve to obtain K / Al co-doped lithium manganese oxide powder.

[0055] Step s2: Add 0.55g acetylferrocene, 0.55g N-phenyl-p-phenylenediamine and 22mL dichloromethane to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 27℃ and 350r / min for 11min. Add 5.5g ferric chloride while stirring and continue stirring for 24h. After the reaction is complete, add 32mL methanol, filter and collect the solid, wash with deionized water 5 times, and then place in a vacuum drying oven and dry at 67℃ for 25h to obtain acetylferrocene / diphenylamine polymer.

[0056] Step s3: Add 2g of K / Al co-doped lithium manganese oxide powder to 40mL of anhydrous ethanol and ultrasonically disperse it for 31min at a power of 180W to form a mixture.

[0057] Step s4: Dissolve 0.2g of acetylferrocene / diphenylamine polymer in 20mL of dichloromethane and sonicate for 11min at 180W. Then add 40mL of suspension and continue sonicating for 17min. Transfer the solution to a three-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and gas delivery tube. Purge with nitrogen for protection. While stirring at 27℃ and a stirring rate of 650r / min, add 10mL of ferric chloride dichloromethane solution dropwise (ferric chloride and dichloromethane are in a 0.5:1 ratio). A solution of 5g:5mL was prepared, with a dropping rate of 1 drop / s. After the addition was complete, the mixture was stirred for 12 hours. After the reaction was completed, the mixture was centrifuged at 9500 r / min for 10 minutes. The solid was collected and washed four times with methanol. Then it was placed in a vacuum drying oven and dried at 47℃ under normal pressure for 8.5 hours. Then it was heated to 67℃ and vacuum dried for 25 hours. After that, it was placed in a tube furnace and heated to 240℃ at a heating rate of 5℃ / min under a nitrogen atmosphere. The temperature was held for 3 hours and then naturally cooled to room temperature to obtain coated lithium manganese oxide.

[0058] Step s5: Add 1.5g of coated lithium manganese oxide, 38mL of anhydrous ethanol and 0.6mL of dispersant (dispersant is PEG-400, CAS number is 25322-68-3) into a beaker, sonicate for 23min at 140W, and then place it in a vacuum drying oven and dry at 55℃ for 8.5h to obtain pretreated coated lithium manganese oxide;

[0059] Step s6: Add 7.6g aluminum nitrate, 8.8g cerium nitrate, and 23mL deionized water to a three-necked flask equipped with a stirrer, thermometer, and constant pressure dropping funnel. Stir magnetically for 13min at 27℃ and a stirring rate of 270r / min. Then, while stirring, add 11mL of fluorine source solution (fluorine source solution is a solution of ammonium fluoride and deionized water mixed in a ratio of 4.4g:10mL) dropwise, controlling the dropping rate to 1 drop / s. After the addition is complete, continue stirring for 33min to obtain an AlF3@CeF3 suspension.

[0060] Step s7: Add 1.5g of pretreated coated lithium manganese oxide to 35mL of AlF3@CeF3 suspension, sonicate for 17min at 140W, adjust pH to 8 with 0.1mol / L dilute nitric acid, transfer to a hydrothermal reactor, seal and place in an oven, set temperature 100℃, keep warm for 3h, then cool naturally to room temperature, transfer to centrifuge tube, centrifuge at 11000r / min for 11min, collect the bottom solid and wash 4 times with deionized water, then wash 2 times with anhydrous ethanol, then place in a vacuum drying oven and dry at 55℃ for 21h to obtain lithium manganese oxide cathode material.

[0061] Example 3:

[0062] This embodiment describes a method for preparing lithium manganese oxide cathode material, including the following steps:

[0063] Step s1: Add 4.3g lithium carbonate, 17g manganese tetroxide, 0.16g potassium carbonate, 0.80g aluminum nitrate and 35mL anhydrous ethanol to a planetary ball mill with a ball-to-material ratio of 10:1. Ball mill for 5 hours at 300 r / min. Then place in a vacuum drying oven and dry at 80℃ for 14 hours. Then place in a tube furnace and heat to 450℃ in air at a heating rate of 3℃ / min. Hold for 2 hours. Then cool to room temperature with the furnace and grind through a 100-mesh sieve. Then heat to 800℃ at a heating rate of 5℃ / min and hold for 10 hours. Then cool to room temperature with the furnace and grind through a 200-mesh sieve to obtain K / Al co-doped lithium manganese oxide powder.

[0064] Step s2: Add 0.6g acetylferrocene, 0.6g N-phenyl-p-phenylenediamine and 23mL dichloromethane to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 30℃ and 400r / min for 12min. Add 6g ferric chloride while stirring and continue stirring for 25h. After the reaction is complete, add 35mL methanol, filter and collect the solid, wash with deionized water 6 times, and then place in a vacuum drying oven and dry at 70℃ for 26h to obtain acetylferrocene / diphenylamine polymer.

[0065] Step s3: Add 3g of K / Al co-doped lithium manganese oxide powder to 60mL of anhydrous ethanol and ultrasonically disperse for 32min at a power of 200W to form a mixture;

[0066] Step s4: Dissolve 0.3g of acetylferrocene / diphenylamine polymer in 30mL of dichloromethane and sonicate for 12min at 200W. Then add 60mL of suspension and continue sonicating for 20min. Transfer the solution to a three-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and gas delivery tube. Purge with nitrogen for protection. While stirring at 30℃ and a stirring rate of 700r / min, add 15mL of a ferric chloride dichloromethane solution dropwise (the ferric chloride dichloromethane solution is prepared by mixing ferric chloride and dichloromethane in a 0:1 ratio). A solution of 0.5g:5mL was prepared, with a dropping rate of 2 drops / s. After the addition was complete, the mixture was stirred for 13 hours. After the reaction was completed, the mixture was centrifuged for 10 minutes at a speed of 10000 r / min. The solid was collected and washed 5 times with methanol. Then it was placed in a vacuum drying oven and dried at 50℃ under normal pressure for 9 hours. Then it was heated to 70℃ and vacuum dried for 26 hours. After that, it was placed in a tube furnace and heated to 240℃ at a heating rate of 5℃ / min under a nitrogen atmosphere. The temperature was held for 3 hours and then naturally cooled to room temperature to obtain coated lithium manganese oxide.

[0067] Step s5: Add 2g of coated lithium manganese oxide, 50mL of anhydrous ethanol and 0.7mL of dispersant (dispersant is PEG-400, CAS number is 25322-68-3) into a beaker, sonicate for 25min at 150W, and then place it in a vacuum drying oven and dry at 60℃ for 9h to obtain pretreated coated lithium manganese oxide;

[0068] Step s6: Add 7.7g aluminum nitrate, 8.9g cerium nitrate, and 25mL deionized water to a three-necked flask equipped with a stirrer, thermometer, and constant pressure dropping funnel. Stir magnetically for 15min at 30℃ and a stirring rate of 300r / min. Then, while stirring, add 12mL of fluorine source solution (fluorine source solution is a solution of ammonium fluoride and deionized water in a ratio of 4.4g:10mL) dropwise, controlling the dropping rate to 2 drops / s. After the addition is complete, continue stirring for 35min to obtain an AlF3@CeF3 suspension.

[0069] Step s7: Add 2g of pretreated coated lithium manganese oxide to 40mL of AlF3@CeF3 suspension, sonicate for 20min at 150W, adjust pH to 8 with 0.1mol / L dilute nitric acid, transfer to a hydrothermal reactor, seal and place in an oven at 110℃ for 4h, then allow to cool naturally to room temperature, transfer to a centrifuge tube, centrifuge at 12000r / min for 12min, collect the bottom solid and wash 5 times with deionized water, then wash 2 times with anhydrous ethanol, then place in a vacuum drying oven and dry at 60℃ for 22h to obtain lithium manganese oxide cathode material.

[0070] Preparation Example 1:

[0071] This preparation example illustrates a method for preparing lithium manganese oxide cathode material, including the following steps:

[0072] Step s1: Add 3.8g lithium carbonate, 15g manganese tetroxide and 30mL anhydrous ethanol to a planetary ball mill with a ball-to-material ratio of 10:1. Ball mill for 4 hours at 250r / min. Then place in a vacuum drying oven and dry at 75℃ for 12 hours. Then place in a tube furnace and heat to 450℃ at a heating rate of 3℃ / min in air atmosphere. Hold at this temperature for 2 hours. Then cool to room temperature with the furnace and grind through a 100-mesh sieve. Then heat to 800℃ at a heating rate of 5℃ / min and hold at this temperature for 10 hours. Then cool to room temperature with the furnace and grind through a 200-mesh sieve to obtain lithium manganese oxide powder.

[0073] Step s2: Add 0.5g acetylferrocene, 0.5g N-phenyl-p-phenylenediamine and 20mL dichloromethane to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 10min. Add 5g ferric chloride while stirring and continue stirring for 24h. After the reaction is complete, add 30mL methanol, filter and collect the solid, wash with deionized water 4 times, and then place in a vacuum drying oven and dry at 65℃ for 24h to obtain acetylferrocene / diphenylamine polymer.

[0074] Step s3: Add 1g of lithium manganese oxide powder to 20mL of anhydrous ethanol and ultrasonically disperse for 30min at a power of 170W to form a mixture.

[0075] Step s4: Dissolve 0.1g of acetylferrocene / diphenylamine polymer in 10mL of dichloromethane and sonicate for 10min at 170W. Then add 20mL of suspension and continue sonicating for 15min. Transfer the solution to a three-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and gas delivery tube. Purge with nitrogen for protection. While stirring at 25℃ and a stirring rate of 600r / min, add dropwise 5mL of a ferric chloride dichloromethane solution (ferric chloride and dichloromethane are added in a 0:1 ratio). A solution of 0.5 g and 5 mL was prepared, with a dropping rate of 1 drop / s. After the addition was complete, the mixture was stirred for 12 h. After the reaction was completed, the mixture was centrifuged at 9000 r / min for 10 min, the solid was collected and washed three times with methanol. Then it was placed in a vacuum drying oven and dried at 45 °C under normal pressure for 8 h. Then it was heated to 65 °C and vacuum dried for 24 h. After that, it was placed in a tube furnace and heated to 240 °C at a heating rate of 5 °C / min under a nitrogen atmosphere. The temperature was held for 3 h and then naturally cooled to room temperature to obtain coated lithium manganese oxide.

[0076] Step s5: Add 1g of coated lithium manganese oxide, 25mL of anhydrous ethanol and 0.5mL of dispersant (dispersant is PEG-400, CAS number is 25322-68-3) into a beaker, sonicate for 20min at 130W, and then place it in a vacuum drying oven and dry at 50℃ for 8h to obtain pretreated coated lithium manganese oxide;

[0077] Step s6: Add 7.5g aluminum nitrate, 8.7g cerium nitrate, and 20mL deionized water to a three-necked flask equipped with a stirrer, thermometer, and constant pressure dropping funnel. Stir magnetically for 10min at 25℃ and a stirring rate of 250r / min. Then, while stirring, add 10mL of fluorine source solution (fluorine source solution is a solution of ammonium fluoride and deionized water mixed in a ratio of 4.4g:10mL) dropwise, controlling the dropping rate to 1 drop / s. After the addition is complete, continue stirring for 30min to obtain an AlF3@CeF3 suspension.

[0078] Step s7: Add 1g of pretreated coated lithium manganese oxide to 30mL of AlF3@CeF3 suspension, sonicate for 15min at 130W, adjust pH to 7 with 0.1mol / L dilute nitric acid, transfer to a hydrothermal reactor, seal and place in an oven at 90℃ for 2h, then allow to cool naturally to room temperature, transfer to a centrifuge tube, centrifuge at 10000r / min for 10min, collect the bottom solid and wash three times with deionized water, then wash once with anhydrous ethanol, then place in a vacuum drying oven and dry at 50℃ for 20h to obtain lithium manganese oxide cathode material.

[0079] Preparation Example 2:

[0080] This preparation example illustrates a method for preparing lithium manganese oxide cathode material, including the following steps:

[0081] Step s1: Add 3.8g lithium carbonate, 15g manganese tetroxide, 0.14g potassium carbonate, 0.75g aluminum nitrate and 30mL anhydrous ethanol to a planetary ball mill with a ball-to-material ratio of 10:1. Ball mill for 4 hours at 250r / min. Then place in a vacuum drying oven and dry at 75℃ for 12 hours. Then place in a tube furnace and heat to 450℃ in air at a heating rate of 3℃ / min. Hold at this temperature for 2 hours. Then cool to room temperature with the furnace and grind through a 100-mesh sieve. Then heat to 800℃ at a heating rate of 5℃ / min and hold at this temperature for 10 hours. Then cool to room temperature with the furnace and grind through a 200-mesh sieve to obtain K / Al co-doped lithium manganese oxide powder.

[0082] Step s2: Add 1g of K / Al co-doped lithium manganese oxide powder, 25mL of anhydrous ethanol and 0.5mL of dispersant (dispersant is PEG-400, CAS number is 25322-68-3) to a beaker, sonicate for 20min at a power of 130W, and then place it in a vacuum drying oven and dry at a temperature of 50℃ for 8h to obtain pretreated K / Al co-doped lithium manganese oxide powder;

[0083] Step s3: Add 7.5g aluminum nitrate, 8.7g cerium nitrate, and 20mL deionized water to a three-necked flask equipped with a stirrer, thermometer, and constant pressure dropping funnel. Stir magnetically for 10min at 25℃ and a stirring rate of 250r / min. Then, while stirring, add 10mL of fluorine source solution (fluorine source solution is a solution of ammonium fluoride and deionized water in a ratio of 4.4g:10mL) dropwise, controlling the dropping rate to 1 drop / s. After the addition is complete, continue stirring for 30min to obtain an AlF3@CeF3 suspension.

[0084] Step s4: Add 1g of pretreated K / Al co-doped lithium manganese oxide powder to 30mL of AlF3@CeF3 suspension, sonicate for 15min at 130W, adjust pH to 7 with 0.1mol / L dilute nitric acid, transfer to a hydrothermal reactor, seal and place in an oven, set temperature 90℃, keep warm for 2h, then cool naturally to room temperature, transfer to centrifuge tube, centrifuge at 10000r / min for 10min, collect the bottom solid and wash 3 times with deionized water, then wash once with anhydrous ethanol, then place in a vacuum drying oven and dry at 50℃ for 20h to obtain lithium manganese oxide cathode material.

[0085] Preparation Example 3:

[0086] This preparation example illustrates a method for preparing lithium manganese oxide cathode material, including the following steps:

[0087] Step s1: Add 3.8g lithium carbonate, 15g manganese tetroxide and 30mL anhydrous ethanol to a planetary ball mill with a ball-to-material ratio of 10:1. Ball mill for 4 hours at 250r / min. Then place in a vacuum drying oven and dry at 75℃ for 12 hours. Then place in a tube furnace and heat to 450℃ at a heating rate of 3℃ / min in air atmosphere. Hold at this temperature for 2 hours. Then cool to room temperature with the furnace and grind through a 100-mesh sieve. Then heat to 800℃ at a heating rate of 5℃ / min and hold at this temperature for 10 hours. Then cool to room temperature with the furnace and grind through a 200-mesh sieve to obtain lithium manganese oxide powder.

[0088] Step s2: Add 0.5g acetylferrocene, 0.5g N-phenyl-p-phenylenediamine and 20mL dichloromethane to a three-necked flask equipped with a stirrer, thermometer and gas delivery tube. Purge with nitrogen for protection and stir at 25℃ and 300r / min for 10min. Add 5g ferric chloride while stirring and continue stirring for 24h. After the reaction is complete, add 30mL methanol, filter and collect the solid, wash with deionized water 4 times, and then place in a vacuum drying oven and dry at 65℃ for 24h to obtain acetylferrocene / diphenylamine polymer.

[0089] Step s3: Add 1g of lithium manganese oxide powder to 20mL of anhydrous ethanol and ultrasonically disperse for 30min at a power of 170W to form a mixture;

[0090] Step s4: Dissolve 0.1g of acetylferrocene / diphenylamine polymer in 10mL of dichloromethane and sonicate for 10min at 170W. Then add 20mL of suspension and continue sonicating for 15min. Transfer the solution to a three-necked flask equipped with a stirrer, thermometer, constant pressure dropping funnel, and gas delivery tube. Purge with nitrogen for protection. While stirring at 25℃ and a stirring rate of 600r / min, add 5mL of ferric chloride dichloromethane solution dropwise (ferric chloride and dichloromethane are in a 0.5:1 ratio). A solution of 5g and 5mL was prepared, with a dropping rate of 1 drop / s. After the addition was complete, the mixture was stirred for 12 hours. After the reaction was completed, the mixture was centrifuged at 9000 r / min for 10 minutes. The solid was collected and washed three times with methanol. Then it was placed in a vacuum drying oven and dried at 45℃ under normal pressure for 8 hours. Then it was heated to 65℃ and vacuum dried for 24 hours. After that, it was placed in a tube furnace and heated to 240℃ at a heating rate of 5℃ / min under a nitrogen atmosphere. The temperature was held for 3 hours and then naturally cooled to room temperature to obtain lithium manganese oxide cathode material.

[0091] Example 4:

[0092] This embodiment is a method for preparing a battery, including the following steps:

[0093] Step s1: 40g of lithium manganese oxide cathode material from Example 1, 3g of conductive carbon black, 2g of polyvinylidene fluoride, and 90mL of N-methylpyrrolidone were stirred at 1000r / min for 1 hour using a magnetic stirrer. The prepared slurry was then coated onto the pretreated aluminum foil current collector using a scraping method. The coated aluminum foil was transferred to a vacuum drying oven and pre-dried at 60℃ for 1 hour, followed by vacuum drying at 110℃ for 5 hours. After drying, the electrode sheet was rolled using a roller press with a rolling pressure controlled at 6MPa to achieve a compaction density of 2.2g / cm³. 3 Finally, a positive electrode sheet is obtained;

[0094] Step s2: Using graphite as the negative electrode and Celgard 2400 polypropylene microporous membrane as the separator, the electrolyte is 1 mol / L LiPF6 (EC:DEC=1:1, v / v). The positive electrode, negative electrode, separator and electrolyte are assembled into a CR2032 coin cell in an argon glove box with water and oxygen content of less than 1 ppm. After assembly, the cell is left to stand for 24 hours to obtain the battery.

[0095] Example 5:

[0096] This embodiment is a method for preparing a battery, including the following steps:

[0097] Step s1: 41g of lithium manganese oxide cathode material from Example 2, 4g of conductive carbon black, 2.5g of polyvinylidene fluoride, and 93mL of N-methylpyrrolidone were stirred at 2000r / min for 1.5h using a magnetic stirrer. The prepared slurry was then coated onto the pretreated aluminum foil current collector using a scraping method. The coated aluminum foil was transferred to a vacuum drying oven and pre-dried at 70℃ for 1.5h, followed by vacuum drying at 120℃ for 6h. After drying, the electrode sheet was rolled using a roller press with a rolling pressure controlled at 9MPa to achieve a compaction density of 2.2g / cm³. 3 Finally, a positive electrode sheet is obtained;

[0098] Step s2: Using graphite as the negative electrode and Celgard 2400 polypropylene microporous membrane as the separator, the electrolyte is 1 mol / L LiPF6 (EC:DEC=1:1, v / v). The positive electrode, negative electrode, separator and electrolyte are assembled into a CR2032 coin cell in an argon glove box with water and oxygen content of less than 1 ppm. After assembly, the cell is left to stand for 24 hours to obtain the battery.

[0099] Example 6:

[0100] This embodiment is a method for preparing a battery, including the following steps:

[0101] Step s1: 42g of lithium manganese oxide cathode material from Example 3, 5g of conductive carbon black, 3g of polyvinylidene fluoride, and 95mL of N-methylpyrrolidone were stirred at 3000r / min for 2 hours using a magnetic stirrer. The prepared slurry was then coated onto the pretreated aluminum foil current collector using a scraping method. The coated aluminum foil was transferred to a vacuum drying oven and pre-dried at 80℃ for 2 hours, followed by vacuum drying at 130℃ for 7 hours. After drying, the electrode sheet was rolled using a roller press with a rolling pressure controlled at 12MPa to achieve a compaction density of 2.3g / cm³. 3 Finally, a positive electrode sheet is obtained;

[0102] Step s2: Using graphite as the negative electrode and Celgard 2400 polypropylene microporous membrane as the separator, the electrolyte is 1 mol / L LiPF6 (EC:DEC=1:1, v / v). The positive electrode, negative electrode, separator and electrolyte are assembled into a CR2032 coin cell in an argon glove box with water and oxygen content of less than 1 ppm. After assembly, the cell is left to stand for 24 hours to obtain the battery.

[0103] Comparative Example 1:

[0104] This comparative example illustrates a method for preparing a battery, comprising the following steps:

[0105] Step s1: 40g of lithium manganese oxide cathode material from Preparation Example 1, 3g of conductive carbon black, 2g of polyvinylidene fluoride, and 90mL of N-methylpyrrolidone were stirred at 1000r / min for 1h using a magnetic stirrer. The prepared slurry was then coated onto the pretreated aluminum foil current collector using a scraping method. The coated aluminum foil was transferred to a vacuum drying oven and pre-dried at 60℃ for 1h, followed by vacuum drying at 110℃ for 5h. After drying, the electrode sheet was rolled using a roller press with a rolling pressure controlled at 6MPa to achieve a compaction density of 2.2g / cm³. 3 Finally, a positive electrode sheet is obtained;

[0106] Step s2: Using graphite as the negative electrode and Celgard 2400 polypropylene microporous membrane as the separator, the electrolyte is 1 mol / L LiPF6 (EC:DEC=1:1, v / v). The positive electrode, negative electrode, separator and electrolyte are assembled into a CR2032 coin cell in an argon glove box with water and oxygen content of less than 1 ppm. After assembly, the cell is left to stand for 24 hours to obtain the battery.

[0107] Comparative Example 2:

[0108] This comparative example illustrates a method for preparing a battery, comprising the following steps:

[0109] Step s1: 40g of lithium manganese oxide cathode material from Preparation Example 2, 3g of conductive carbon black, 2g of polyvinylidene fluoride, and 90mL of N-methylpyrrolidone were stirred at 1000r / min for 1h using a magnetic stirrer. The prepared slurry was then coated onto the pretreated aluminum foil current collector using a scraping method. The coated aluminum foil was transferred to a vacuum drying oven and pre-dried at 60℃ for 1h, followed by vacuum drying at 110℃ for 5h. After drying, the electrode sheet was rolled using a roller press with a rolling pressure controlled at 6MPa to achieve a compaction density of 2.2g / cm³. 3 Finally, a positive electrode sheet is obtained;

[0110] Step s2: Using graphite as the negative electrode and Celgard 2400 polypropylene microporous membrane as the separator, the electrolyte is 1 mol / L LiPF6 (EC:DEC=1:1, v / v). The positive electrode, negative electrode, separator and electrolyte are assembled into a CR2032 coin cell in an argon glove box with water and oxygen content of less than 1 ppm. After assembly, the cell is left to stand for 24 hours to obtain the battery.

[0111] Comparative Example 3:

[0112] This comparative example illustrates a method for preparing a battery, comprising the following steps:

[0113] Step s1: 40g of lithium manganese oxide cathode material from Preparation Example 3, 3g of conductive carbon black, 2g of polyvinylidene fluoride, and 90mL of N-methylpyrrolidone were stirred at 1000r / min for 1h using a magnetic stirrer. The prepared slurry was then coated onto the pretreated aluminum foil current collector using a scraping method. The coated aluminum foil was transferred to a vacuum drying oven and pre-dried at 60℃ for 1h, followed by vacuum drying at 110℃ for 5h. After drying, the electrode sheet was rolled using a roller press with a rolling pressure controlled at 6MPa to achieve a compaction density of 2.2g / cm³. 3 Finally, a positive electrode sheet is obtained;

[0114] Step s2: Using graphite as the negative electrode and Celgard 2400 polypropylene microporous membrane as the separator, the electrolyte is 1 mol / L LiPF6 (EC:DEC=1:1, v / v). The positive electrode, negative electrode, separator and electrolyte are assembled into a CR2032 coin cell in an argon glove box with water and oxygen content of less than 1 ppm. After assembly, the cell is left to stand for 24 hours to obtain the battery.

[0115] Performance testing:

[0116] The batteries of Examples 4-6 and Comparative Examples 1-3 were tested at 55°C and a charge / discharge cutoff voltage of 3.0-4.3V. The amount of electricity released per unit mass of active material during the first charge / discharge cycle at 0.2C and 1C rates was tested. The capacity retention rate after 100 cycles at a 1C charge / discharge rate was tested. The conductivity was tested. The amount of manganese dissolved was tested.

[0117] The test results are shown in the table below:

[0118]

[0119] Referring to the table above, based on the comparison between Examples 4-6 and Comparative Examples 1-3, it can be seen that the battery made of the lithium manganese oxide cathode material of the present invention has improved conductivity, reduced manganese dissolution, and has excellent cycle performance and rate performance.

[0120] Based on the comparison between Example 4 and Comparative Example 1, it can be seen that the lattice strengthening and channel widening caused by K / Al co-doping can improve the cycle stability and rate performance of the battery. However, Comparative Example 1 only coated lithium manganese oxide with acetyl ferrocene / diphenylamine polymer and then with AlF3@CeF3 suspension, lacking the synergistic effect of K / Al co-doping. The battery obtained in Example 4 has significantly better performance than that in Comparative Example 1, indicating that the battery with K / Al co-doping can effectively improve the cycle stability and rate performance of the battery.

[0121] Based on the comparison between Example 4 and Comparative Example 2, it can be seen that the conjugated conductive network and organic physical barrier of the acetyl ferrocene / diphenylamine polymer can improve the electronic conduction and cycle stability of the battery. However, Comparative Example 2 only first performs K / Al co-doping on lithium manganese oxide and then coats it with AlF3@CeF3 suspension, lacking the assistance of acetyl ferrocene / diphenylamine polymer coating. Therefore, the battery prepared in Example 4 has better performance than that in Comparative Example 2, indicating that the battery coated with acetyl ferrocene / diphenylamine polymer can improve the electronic conduction and cycle stability of the battery.

[0122] Based on the comparison between Example 4 and Comparative Example 3, it can be seen that the lattice strengthening and channel widening of K / Al co-doping can improve the cycle stability and rate performance of the battery; the conjugated conductive network and organic physical barrier of the acetyl ferrocene / diphenylamine polymer can improve the electronic conduction and cycle stability of the battery; and the inorganic chemical barrier and ion / electron conduction interface of AlF3@CeF3 can improve the cycle stability and interface conduction efficiency of the battery. However, Comparative Example 3 only uses AlF3@CeF3 suspension to coat lithium manganese oxide, lacking the synergistic optimization of K / Al co-doping and acetyl ferrocene / diphenylamine polymer coating. The battery performance of Example 4 is significantly better than that of Comparative Example 3, indicating that coating lithium manganese oxide with AlF3@CeF3 suspension can effectively improve the cycle stability of the battery.

[0123] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0124] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing lithium manganese oxide cathode material, characterized in that, Includes the following steps: Step 1: Lithium carbonate, manganese tetroxide, potassium carbonate, aluminum nitrate and anhydrous ethanol are ball-milled, dried, sintered, cooled, ground and sieved to obtain K / Al co-doped lithium manganese oxide powder. Step 2: Stir acetylferrocene, N-phenyl-p-phenylenediamine and dichloromethane, add ferric chloride, continue stirring, add methanol, filter and wash, dry to obtain acetylferrocene / diphenylamine polymer; Step 3: Add K / Al co-doped lithium manganese oxide powder to anhydrous ethanol and disperse it ultrasonically to form a mixture; Step 4: Dissolve the acetylferrocene / diphenylamine polymer in dichloromethane, disperse it ultrasonically, then add the suspension, continue ultrasonic dispersion, then add the dichloromethane solution of ferric chloride, continue stirring, centrifuge, wash, dry, sinter, and cool to obtain coated lithium manganate. Step 5: Ultrasonic treatment of the coated lithium manganese oxide, anhydrous ethanol and dispersant, followed by drying, to obtain pretreated coated lithium manganese oxide; Step 6: Stir aluminum nitrate, cerium nitrate and deionized water, add fluorine source solution, and continue stirring to obtain AlF3@CeF3 suspension; Step 7: Add the pretreated coated lithium manganese oxide to the AlF3@CeF3 suspension, sonicate, adjust the pH, place in an oven for heat preservation, then cool, centrifuge, wash, and dry to obtain the lithium manganese oxide cathode material.

2. The method for preparing lithium manganese oxide cathode material according to claim 1, characterized in that, In step one, the ratio of lithium carbonate, manganese tetroxide, potassium carbonate, aluminum nitrate, and anhydrous ethanol is 3.8-4.3g: 15-17g: 0.14-0.16g: 0.75-0.80g: 30-35mL; in step two, the ratio of acetylated ferrocene, N-phenyl-p-phenylenediamine, dichloromethane, ferric chloride, and methanol is 0.5-0.6g: 0.5-0.6g: 20-23mL: 5-6g: 30-35mL; in step three, the ratio of K / Al co-doped lithium manganese oxide powder and anhydrous ethanol is 1-3g: 20-60mL; in step four, the ratio of acetylated ferrocene / diphenylamine polymer, dichloromethane, suspension, and dichloromethane solution of ferric chloride is 0.1-0.3g: 10-30mL: 20-60mL: 5-15mL.

3. The method for preparing lithium manganese oxide cathode material according to claim 1, characterized in that, The ferric chloride dichloromethane solution in step four is a solution made by mixing ferric chloride and dichloromethane in a ratio of 0.5g:5mL.

4. The method for preparing lithium manganese oxide cathode material according to claim 1, characterized in that, In step five, the ratio of coated lithium manganese oxide, anhydrous ethanol, and dispersant is 1-2g: 25-50mL: 0.5-0.7mL.

5. The method for preparing lithium manganese oxide cathode material according to claim 1, characterized in that, In step six, the ratio of aluminum nitrate, cerium nitrate, deionized water, and fluoride source solution is 7.5-7.7g: 8.7-8.9g: 20-25mL: 10-12mL; in step seven, the ratio of pretreatment-coated lithium manganese oxide and AlF3@CeF3 suspension is 1-2g: 30-40mL.

6. The method for preparing lithium manganese oxide cathode material according to claim 1, characterized in that, The fluoride source solution in step six is ​​a solution made by mixing ammonium fluoride and deionized water in a ratio of 4.4g:10mL.

7. A lithium manganese oxide cathode material, characterized in that, The lithium manganese oxide cathode material is prepared according to the preparation method of lithium manganese oxide cathode material according to any one of claims 1-6.

8. A positive electrode sheet, characterized in that, The lithium manganese oxide cathode material as described in claim 7 is prepared by the following specific steps: Lithium manganese oxide cathode material, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone are stirred and coated onto a pretreated aluminum foil current collector. After drying, the electrode sheet is rolled using a roller press to finally obtain the cathode electrode sheet.

9. The positive electrode sheet according to claim 8, characterized in that, The ratio of lithium manganese oxide cathode material, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone is 40-42g: 3-5g: 2-3g: 90-95mL.

10. A battery, characterized in that, Including the positive electrode sheet as described in any one of claims 8-9, the specific steps are as follows: Using graphite as the negative electrode and Celgard 2400 polypropylene microporous membrane as the separator, the electrolyte was 1 mol / L LiPF6 (EC:DEC=1:1, v / v). The positive electrode, negative electrode, separator and electrolyte were assembled into a battery. After assembly, the battery was left to stand for 24 hours to obtain the battery.

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