A method for preparing manganese tetraoxide and positive electrode material

Abstract

The present invention relates to the field of battery technology, and discloses a method for preparing manganese tetraoxide and a positive electrode material. The present invention uses manganese acetate and the like as manganese source, urea as a precipitant, adds a star-shaped cardanol surfactant, and obtains manganese tetraoxide with a nano flower-like structure having a high specific surface area through hydrothermal reaction and calcination. Then, lithium carbonate is calcined by a high-temperature solid phase method to obtain lithium cobalt oxide with a nano flower-like structure. As a positive electrode active material for a lithium ion battery, the larger the specific surface area, the more active de- / insertion lithium sites are provided, and the diffusion rate of lithium ions is increased, thereby increasing the specific capacity of the battery, and the first discharge specific capacity reaches 139.6-159.1 mA h / g. After 100 cycles, the capacity retention rate reaches 94.85-96.42%. It has good cycle stability performance.

Description

Technical Field

[0001] The invention relates to the technical field of batteries, and in particular to a method for preparing manganese tetraoxide and a positive electrode material. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in new energy products such as automobiles, mobile phones, and computers. Improving the specific capacity and cycle stability of lithium-ion batteries has become a research trend. Among them, the positive electrode material plays a decisive role in the performance of lithium-ion batteries. At present, the commercial positive electrode materials are mainly lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, etc. Compared with lithium nickel cobalt manganese oxide ternary lithium, lithium manganese oxide has the advantages of lower cost and simple preparation method, and has broad application prospects.

[0003] Lithium manganate is usually obtained by reacting manganese tetraoxide and other materials as manganese precursors with lithium carbonate, lithium hydroxide, etc. Increasing the specific surface area of ​​positive electrode materials such as lithium manganate is conducive to promoting the transmission and migration of lithium ions during the charge and discharge process, thereby improving the specific capacity and charge and discharge efficiency of the battery. Patent CN104538623B discloses a method for preparing a spherical lithium nickel manganate positive electrode material, using urea as a uniform precipitant, CTAB and PVP as dual template agents, a flower-shaped spherical precursor can be obtained, and then a spherical lithium nickel manganate positive electrode material with pores and a large specific surface area is obtained after high-temperature lithiation. However, the lithium nickel manganate positive electrode material of this patent does not show good specific capacity and cycle stability. Summary of the invention

[0004] The invention solves the problems that manganese tetraoxide and lithium manganate have small specific surface areas, lithium manganate positive electrode materials have low specific capacity and poor cycle stability.

[0005] Technical solution: A nano-flower-shaped manganese tetraoxide, comprising 100 parts by weight of a manganese compound, 180-300 parts by weight of a star-shaped cardanol surfactant, and 32-48 parts by weight of urea. ;

[0006] The preparation method of nano flower-like manganese tetraoxide is as follows: add a manganese compound and a star-shaped cardanol surfactant to ethanol, add urea after stirring, and then pour the solution into a hydrothermal reactor to react, filter after cooling, wash with water and ethanol in turn, and put it into a tubular furnace for calcination after drying to obtain nano flower-like manganese tetraoxide.

[0007] The star-shaped cardanol surfactant has a chemical structure as shown in the following formula (I):

[0008]

[0009] Preferably, the manganese compound is manganese sulfate, manganese nitrate or manganese acetate.

[0010] Preferably, the reaction is carried out at 130-160° C. for 4-8 h; and the calcination is carried out at 250-300° C. for 3-4 h.

[0011] Preferably, the preparation method of the star-shaped cardanol surfactant is:

[0012] (1) Adding cardanol glycidyl ether and 1,4,7,10-tetraazacyclododecane in a molar ratio of (4.8-5.6):1 to tetrahydrofuran, heating to 60-65° C., condensing and refluxing for 24-36 hours, rotary evaporation, methanol washing, and drying to obtain a surfactant precursor.

[0013] (2) Adding a surfactant precursor, succinic anhydride, and 4-dimethylaminopyridine in a molar ratio of 1:(4-4.8):(4-4.8) to toluene, heating to 60-80° C., reacting for 24-48 hours, rotary evaporation, washing with methanol, and drying to obtain a star-shaped cardanol surfactant.

[0014] Preferably, a method for preparing a nano-flower-shaped lithium manganate positive electrode material using nano-flower-shaped manganese oxide is as follows: lithium carbonate and nano-flower-shaped manganese oxide are mixed, placed in a tubular furnace, subjected to gradient temperature calcination, and cooled to obtain a nano-flower-shaped lithium manganate (LiMn2O4) positive electrode material.

[0015] Preferably, the molar ratio of lithium carbonate to nano-flower-shaped manganese tetraoxide is 1:2.

[0016] Preferably, the gradient temperature calcination is first carried out at 500-550° C. for 4-6 h, then at 650-700° C. for 2-3 h, and finally at 800-850° C. for 8-12 h.

[0017] Technical effect: The present invention uses cardanol glycidyl ether, 1,4,7,10-tetraazacyclododecane and succinic anhydride as reactants to prepare a new star-shaped cardanol surfactant containing a four-arm alkyl chain and a carboxyl structure.

[0018] The invention uses manganese acetate, manganese nitrate and the like as manganese sources, urea as a precipitant, and simultaneously adds a star-shaped cardanol surfactant, which contains a carboxyl group and can be complexed with manganese ions to achieve the effect of dispersing the manganese ions. At the same time, the cardanol surfactant contains a four-arm star-shaped long alkyl chain of cardanol, which forms micelles in water through hydrogen bonds and van der Waals forces, and self-assembles with manganese ions through coordination to form a nanometer-scale phase structure, thereby achieving the effect of a structural template agent. After hydrothermal reaction and calcination, manganese tetraoxide with a nanometer flower-like structure having a high specific surface area is obtained.

[0019] The present invention uses a high temperature solid phase method to calcine nano-flower-like manganese tetraoxide and lithium carbonate to obtain lithium cobalt oxide (LiMn2O4). The lithium cobalt oxide calcined at high temperature solid phase maintains the nano-flower-like structure of the precursor manganese tetraoxide, and has a large specific surface area of ​​80.8-103.2 m 2 / g. It provides great convenience for subsequent use as positive electrode material for lithium-ion batteries.

[0020] The invention uses nano flower-shaped lithium manganese oxide with high specific surface area as the positive electrode active material of the lithium ion battery. The larger the specific surface area, the more active lithium extraction / insertion sites are provided, and the diffusion rate of lithium ions in the positive electrode material is increased, thereby increasing the specific capacity of the battery. The first discharge specific capacity reaches 139.6-159.1 mA·h / g, and after 100 cycles, the discharge specific capacity is maintained at 134.6-150.9 mA·h / g, and the capacity retention rate reaches 94.85-96.42%. It has good cycle stability performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the reaction formula for preparing star-shaped cardanol surfactant.

[0022] Figure 2 This is a scanning electron microscope (SEM) image of nano-flower-like manganese manganese oxide.

[0023] Figure 3 This is a scanning electron microscope (SEM) image of the nano-flower-shaped lithium manganese oxide positive electrode material. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] (1) Add 9.6 mmol of cardanol glycidyl ether (structural formula: n is 25-31), 2mmol 1,4,7,10-tetraazacyclododecane (structural formula is CAS No. 294-90-6), heated to 65°C, condensed and refluxed for 24 hours, rotary evaporated, washed with methanol, and dried to obtain a surfactant precursor with a yield of 2.76 g.

[0027] (2) Add 1 mmol of surfactant precursor, 4 mmol of succinic anhydride, and 4 mmol of 4-dimethylaminopyridine to 20 mL of toluene, heat to 80°C, react for 48 hours, rotary evaporate, wash with methanol, and dry to obtain a star-shaped cardanol surfactant. Yield: 1.32 g.

[0028] Example 2

[0029] (1) Add 11.2 mmol of cardanol glycidyl ether and 2 mmol of 1,4,7,10-tetraazacyclododecane to 60 mL of tetrahydrofuran, heat to 60°C, condense and reflux for 36 h, rotary evaporate, wash with methanol, and dry to obtain a surfactant precursor. The yield is 2.53 g.

[0030] (2) Add 1 mmol of surfactant precursor, 4.8 mmol of succinic anhydride, and 4.8 mmol of 4-dimethylaminopyridine to 30 mL of toluene, heat to 60° C., react for 24 h, rotary evaporate, wash with methanol, and dry to obtain a star-shaped cardanol surfactant. Yield: 1.49 g.

[0031] Example 3

[0032] Add 5 g of manganese acetate and 9.8 g of star-shaped cardanol surfactant to ethanol, add 1.7 g of urea after stirring, and then pour the solution into a hydrothermal reactor, heat to 140 ° C for 6 hours, filter after cooling, wash with water and ethanol in turn, put into a tubular furnace after drying, heat to 250 ° C, and calcine for 4 hours to obtain nano-flower-like manganese tetraoxide.

[0033] 30mmol lithium carbonate and 60mmol nano-flower-like manganese oxide were mixed and put into a tubular furnace. They were first calcined at 500℃ for 6h, then at 650℃ for 3h, and finally at 850℃ for 8h. After cooling, nano-flower-like lithium manganate (LiMn2O4) positive electrode material was obtained.

[0034] Example 4

[0035] Add 5 g of manganese acetate and 9.8 g of star-shaped cardanol surfactant to ethanol, add 1.7 g of urea after stirring, and then pour the solution into a hydrothermal reactor, heat to 160°C for 4 hours, filter after cooling, wash with water and ethanol in turn, put into a tubular furnace after drying, heat to 300°C, and calcine for 3 hours to obtain nanoflower-like manganese tetraoxide.

[0036] 30mmol lithium carbonate and 60mmol nano-flower-like manganese oxide were mixed and put into a tubular furnace. They were first calcined at 550°C for 4h, then at 700°C for 2h, and finally at 800°C for 12h. After cooling, a nano-flower-like lithium manganate positive electrode material was obtained.

[0037] Example 5

[0038] Add 5 g of manganese nitrate and 9 g of star-shaped cardanol surfactant to ethanol, add 1.6 g of urea after stirring, and then pour the solution into a hydrothermal reactor, heat to 130 ° C for 8 hours, filter after cooling, wash with water and ethanol in turn, put into a tubular furnace after drying, heat to 250 ° C, and calcine for 4 hours to obtain nano-flower-like manganese tetraoxide.

[0039] 30mmol lithium carbonate and 60mmol nano-flower-like manganese oxide were mixed and put into a tubular furnace. They were first calcined at 550°C for 5h, then at 650°C for 2h, and finally at 850°C for 10h. After cooling, a nano-flower-like lithium manganate positive electrode material was obtained.

[0040] Example 6

[0041] Add 5 g of manganese sulfate and 15 g of star-shaped cardanol surfactant to ethanol, add 2.4 g of urea after stirring, and then pour the solution into a hydrothermal reactor, heat to 140°C for 8 hours, filter after cooling, wash with water and ethanol in turn, put into a tubular furnace after drying, heat to 300°C, and calcine for 3 hours to obtain nanoflower-like manganese tetraoxide.

[0042] 30mmol lithium carbonate and 60mmol nano-flower-like manganese oxide were mixed and put into a tubular furnace. They were first calcined at 500°C for 5h, then at 700°C for 3h, and finally at 800°C for 12h. After cooling, a nano-flower-like lithium manganate positive electrode material was obtained.

[0043] Comparative Example 1

[0044] Add 5 g of manganese acetate to ethanol, stir and then add 1.7 g of urea, then pour the solution into a hydrothermal reactor, heat to 160°C for 4 hours, filter after cooling, wash with water and ethanol in turn, put into a tubular furnace after drying, heat to 300°C, and calcine for 3 hours to obtain nano manganese tetraoxide.

[0045] 30mmol lithium carbonate and 60mmol nano manganese tetraoxide were mixed and put into a tubular furnace. They were first calcined at 550°C for 4h, then at 700°C for 2h, and finally at 800°C for 12h. After cooling, lithium manganate positive electrode material was obtained.

[0046] Comparative Example 2

[0047] Add 5 g of manganese acetate and 9.8 g of cardanol glycidol to ethanol, stir and add 1.7 g of urea, then pour the solution into a hydrothermal reactor, heat to 160 ° C for 4 hours, filter after cooling, wash with water and ethanol in turn, put into a tubular furnace after drying, heat to 300 ° C, and calcine for 3 hours to obtain nanoflower-like manganese tetraoxide.

[0048] 30mmol lithium carbonate and 60mmol nano-flower-like manganese oxide were mixed and put into a tubular furnace. They were first calcined at 550°C for 4h, then at 700°C for 2h, and finally at 800°C for 12h. After cooling, a nano-flower-like lithium manganate positive electrode material was obtained.

[0049] Comparative Example 3

[0050] Add 5 g of manganese acetate and 9.8 g of surfactant precursor to ethanol, add 1.7 g of urea after stirring, and then pour the solution into a hydrothermal reactor, heat to 160°C for 4 hours, filter after cooling, wash with water and ethanol in turn, put into a tubular furnace after drying, heat to 300°C, and calcine for 3 hours to obtain nanoflower-like manganese tetraoxide.

[0051] 30mmol lithium carbonate and 60mmol nano-flower-like manganese oxide were mixed and put into a tubular furnace. They were first calcined at 550°C for 4h, then at 700°C for 2h, and finally at 800°C for 12h. After cooling, a nano-flower-like lithium manganate positive electrode material was obtained.

[0052] The specific surface area and particle size analyzer were used to test the N2 adsorption / desorption curve of manganese tetraoxide, and the specific surface area was determined based on the BET equation. The test results are shown in the table below.

[0053]

[0054] As can be seen from the above table, when preparing trimanganese tetraoxide in Example 3 to Example 6, a star-shaped cardanol surfactant was added, which contains a carboxyl group, can be complexed with manganese ions, and has the effect of dispersing manganese ions. At the same time, it contains a four-arm star-shaped cardanol alkyl long chain, which forms micelles in water through hydrogen bonds and van der Waals forces, and self-assembles with manganese ions through coordination to form a nanoscale phase structure, thereby having the effect of a structural template agent. After hydrothermal reaction and calcination, trimanganese tetraoxide with a nano-flower-like structure of high specific surface area is obtained. Further, the nano-flower-like trimanganese tetraoxide and lithium carbonate are calcined by a high-temperature solid phase method to obtain lithium cobaltate (LiMn2O4). The lithium cobaltate after high-temperature solid phase calcination maintains the nano-flower-like structure of the precursor trimanganese tetraoxide, and the specific surface area is very large, reaching 80.8-103.2m 2 / g. It provides great convenience for subsequent use as positive electrode material for lithium-ion batteries.

[0055] The difference between Comparative Example 1 and Example 2 is that no star-shaped cardanol surfactant is added, and the specific surface area of ​​manganese tetraoxide is only 4.9 m 2 / g. The specific surface area of ​​the obtained lithium cobalt oxide is only 4.1m 2 / g.

[0056] The difference between Comparative Example 2 and Example 2 is that cardanol glycidyl ether is used as a surfactant, which contains only hydrophobic groups and no carboxyl hydrophilic groups, and cannot play a role as a surface active agent and a structural template agent. The specific surface area of ​​manganese tetraoxide is only 4.2 m 2 / g. The specific surface area of ​​the obtained lithium cobalt oxide is only 3.4m 2 / g.

[0057] The difference between Comparative Example 3 and Example 2 is that the surfactant precursor is used as the surfactant, does not contain a carboxyl hydrophilic group, has no surface activity and has a poor dispersion effect on manganese ions, and does not play a good structural template role. The specific surface area of ​​manganese tetraoxide is only 21.8 m 2 / g, the specific surface area of ​​lithium cobalt oxide is only 15.0m 2 / g.

[0058] Lithium manganate positive electrode material, polyvinylidene fluoride, and conductive carbon black were added to N-methylpyrrolidone at a mass ratio of 8:1:1, mixed to form a slurry, then coated on the surface of aluminum foil, and dried to form an electrode sheet as the positive electrode of a lithium-ion battery. A metal lithium sheet was used as the negative electrode, the diaphragm was a polypropylene microporous membrane, and the electrolyte was a 1 mol / L solution of lithium hexafluorophosphate in ethylene carbonate / dimethyl carbonate. A button cell was assembled in an argon glove box. The battery system was used for constant current charge and discharge cycle testing, with a rate of 0.2C and a cycle number of 100 times. The test results are shown in the table below.

[0059]

[0060] In Examples 3 to 6, nano-flower-shaped lithium manganese oxide with a high specific surface area is used as the positive electrode active material of the lithium ion battery. The larger the specific surface area, the more active lithium extraction / insertion sites are provided, and the diffusion rate of lithium ions in the positive electrode material is increased, thereby increasing the specific capacity of the battery. The first discharge specific capacity reaches 139.6-159.1 mA·h / g, which is much higher than that of Comparative Examples 1 to 3. After 100 cycles, the discharge specific capacity remains at 134.6-150.9 mA·h / g, and the capacity retention rate reaches 94.85-96.42%. It has good cycle stability performance.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing nano flower-shaped manganese tetraoxide, characterized in that: The invention comprises 100 parts by weight of a manganese compound, 180-300 parts by weight of a star-shaped cardanol surfactant, and 32-48 parts by weight of urea; The preparation method of the nano flower-shaped manganese tetraoxide is as follows: add a manganese compound and a star-shaped cardanol surfactant to ethanol, add urea after stirring, and then pour the solution into a hydrothermal reactor to react, filter after cooling, wash with water and ethanol in turn, and put it into a tubular furnace for calcination after drying to obtain the nano flower-shaped manganese tetraoxide; The star-shaped cardanol surfactant has a chemical structural formula as shown in the following formula (I): Formula (I); The preparation method of the star-shaped cardanol surfactant is: Step (1): add cardanol glycidyl ether and 1,4,7,10-tetraazacyclododecane to tetrahydrofuran, heat to 60-65° C., condense and reflux for 24-36 hours, rotary evaporate, wash with methanol, and dry to obtain a surfactant precursor; Step (2): adding a surfactant precursor, succinic anhydride and 4-dimethylaminopyridine to toluene, and performing rotary evaporation after the reaction, washing with methanol, and drying to obtain a star-shaped cardanol surfactant; In the step (1), the molar ratio of cardanol glycidyl ether to 1,4,7,10-tetraazacyclododecane is (4.8-5.6):1; In the step (2), the molar ratio of the surfactant precursor, succinic anhydride and 4-dimethylaminopyridine is 1:(4-4.8):(4-4.8).

2. The method for preparing nano flower-shaped manganese tetraoxide according to claim 1, characterized in that: The manganese compound is manganese sulfate, manganese nitrate or manganese acetate.

3. The method for preparing nano flower-shaped manganese tetraoxide according to claim 1, characterized in that: The reaction is carried out at 130-160° C. for 4-8 h; and the calcination is carried out at 250-300° C. for 3-4 h.

4. The method for preparing nano flower-shaped manganese tetraoxide according to claim 1, characterized in that: The reaction in step (2) is carried out at 60-80° C. for 24-48 hours.

5. A method for preparing nano-flower-shaped lithium manganate positive electrode material using the nano-flower-shaped manganese oxide obtained by the preparation method according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: mixing lithium carbonate and nano-flower-shaped manganese oxide, placing the mixture in a tubular furnace, performing gradient temperature rise calcination, and cooling the mixture to obtain the nano-flower-shaped lithium manganate positive electrode material.

6. The method for preparing nano-flower-shaped lithium manganate positive electrode material using the nano-flower-shaped manganese oxide obtained by the preparation method according to claim 5, characterized in that: The molar ratio of the lithium carbonate to the nano-flower-shaped manganese tetraoxide is 1:

2.

7. The method for preparing nano-flower-shaped lithium manganate positive electrode material using the nano-flower-shaped manganese oxide obtained by the preparation method according to claim 5, characterized in that: The gradient temperature calcination is first carried out at 500-550° C. for 4-6 hours, then at 650-700° C. for 2-3 hours, and finally at 800-850° C. for 8-12 hours.

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