Preparation method of manganous-manganic oxide and positive electrode material

Abstract

The invention relates to the technical field of batteries, and discloses a preparation method of manganous-manganic oxide and a positive electrode material, manganese acetate and the like are used as a manganese source, urea is used as a precipitator, a star-shaped cardanol surfactant is added, and the manganous-manganic oxide with a high specific surface area and a nano flower-shaped structure is obtained through hydrothermal reaction and calcination. As a positive electrode active material of the lithium ion battery, the larger the specific surface area is, more active lithium intercalation / deintercalation sites can be provided, the diffusion rate of lithium ions can be improved, the specific capacity of the battery can be increased, the first discharge specific capacity can reach 139.6-159.1 mA.h / g, and after 100 cycles, the specific capacity of the lithium ion battery can reach 139.6-159.1 mA.h / g. And the capacity retention ratio reaches 94.85%-96.42%. And the material has good cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for preparing manganese 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 cycling stability of lithium-ion batteries has become a research trend. The positive electrode material plays a decisive role in the performance of lithium-ion batteries. Currently, commercially available positive electrode materials mainly include lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, and lithium cobalt oxide. Compared to ternary lithium nickel cobalt manganese oxide, lithium manganese oxide has the advantages of lower cost and simpler preparation methods, and has broad application prospects.

[0003] Lithium manganate is usually obtained by reacting manganese oxide or the like as a manganese precursor with lithium carbonate, lithium hydroxide or the like. Increasing the specific surface area of ​​positive electrode materials such as lithium manganate is beneficial 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 quasi-spherical lithium nickel manganate positive electrode material. Using urea as a uniform precipitant and CTAB and PVP as dual templates, a flower-shaped quasi-spherical precursor can be obtained, which is then subjected to high-temperature lithiation to obtain a quasi-spherical lithium nickel manganate positive electrode material with pores and a large specific surface area. 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 of small specific surface area of ​​manganese manganese tetroxide and lithium manganate, low specific capacity of lithium manganate positive electrode material 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-shaped manganese tetraoxide is as follows: a manganese compound and a star-shaped cardanol surfactant are added to ethanol, urea is added after stirring, and then the solution is poured into a hydrothermal reactor for reaction. After cooling, it is filtered, washed with water and ethanol in sequence, dried, and placed in a tubular furnace for calcination to obtain nano-flower-shaped manganese tetraoxide.

[0007] The star-shaped cardanol surfactant has the chemical structure 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 reflux reaction 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 tetraoxide is as follows: lithium carbonate and nano-flower-shaped manganese tetraoxide 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 manganese oxide is 1:2.

[0016] Preferably, 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.

[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 present invention uses manganese acetate, manganese nitrate, etc. as manganese sources, urea as a precipitant, and adds a star-shaped cardanol surfactant. The star-shaped cardanol surfactant contains a carboxyl group and can complex with manganese ions to disperse the manganese ions. At the same time, the star-shaped 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. The micelles are self-assembled to form a nanoscale phase structure through coordination with manganese ions, thereby acting as a structural template agent. After hydrothermal reaction and calcination, a manganese tetraoxide with a nano-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 after high-temperature solid-phase calcination retains the nano-flower-like structure of the precursor manganese tetraoxide and has a large specific surface area of ​​80.8-103.2m 2 / g. It provides great convenience for subsequent use as positive electrode material for lithium-ion batteries.

[0020] The present invention uses nano-flower-shaped lithium manganese oxide with a 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 it provides, which increases the diffusion rate of lithium ions in the positive electrode material, thereby increasing the specific capacity of the battery. The initial discharge specific capacity reaches 139.6-159.1 mA·h / g, and after 100 cycles, the discharge specific capacity remains at 134.6-150.9 mA·h / g, with a capacity retention rate of 94.85-96.42%. This battery has excellent cycle stability. 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 following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts 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 The product was heated to 65°C, refluxed under condensation for 24 hours, and then rotary evaporated, washed with methanol, and dried to obtain a surfactant precursor with a yield of 2.76 g.

[0027] (2) 1 mmol of surfactant precursor, 4 mmol of succinic anhydride, and 4 mmol of 4-dimethylaminopyridine were added to 20 mL of toluene. The mixture was heated to 80°C and reacted for 48 h. The mixture was rotary evaporated, washed with methanol, and dried to obtain a star-shaped cardanol surfactant. The yield was 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, reflux under condensation for 36 h, rotary evaporate, wash with methanol, and dry to obtain a surfactant precursor. Yield: 2.53 g.

[0030] (2) 1 mmol of surfactant precursor, 4.8 mmol of succinic anhydride, and 4.8 mmol of 4-dimethylaminopyridine were added to 30 mL of toluene. The mixture was heated to 60°C and reacted for 24 h. The mixture was rotary evaporated, washed with methanol, and dried to obtain a star-shaped cardanol surfactant. The yield was 1.49 g.

[0031] Example 3

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

[0033] 30mmol of lithium carbonate and 60mmol of nano-flower-like manganese tetraoxide were mixed and placed in 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 5g of manganese acetate and 9.8g of star-shaped cardanol surfactant to ethanol, stir and add 1.7g of urea, then pour the solution into a hydrothermal reactor, heat to 160℃ for 4h, filter after cooling, wash with water and ethanol in turn, put into a tubular furnace after drying, heat to 300℃, and calcine for 3h to obtain nano-flower-like manganese tetraoxide.

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

[0037] Example 5

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

[0039] 30mmol of lithium carbonate and 60mmol of nano-flower-like manganese tetraoxide were mixed and placed in a tubular furnace. The mixture was first calcined at 550°C for 5h, then at 650°C for 2h, and finally at 850°C for 10h. The mixture was cooled to obtain a nano-flower-like lithium manganate positive electrode material.

[0040] Example 6

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

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

[0043] Comparative Example 1

[0044] 5 g of manganese acetate was added to ethanol, and 1.7 g of urea was added after stirring. The solution was then poured into a hydrothermal reactor and heated to 160°C for 4 hours. After cooling, it was filtered, washed with water and ethanol in turn, dried, placed in a tubular furnace, heated to 300°C, and calcined at this temperature for 3 hours to obtain nano-manganese tetraoxide.

[0045] 30mmol of lithium carbonate and 60mmol of nano-manganese tetraoxide were mixed and placed in a tube furnace. They were first calcined at 550℃ for 4h, then at 700℃ for 2h, and finally at 800℃ for 12h. The mixture was cooled to obtain lithium manganate positive electrode material.

[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, cool and filter, wash with water and ethanol in turn, dry and put into a tubular furnace, heat to 300 ° C, and calcine for 3 hours to obtain nano-flower-like manganese tetraoxide.

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

[0049] Comparative Example 3

[0050] Add 5g of manganese acetate and 9.8g of surfactant precursor to ethanol, stir and add 1.7g of urea, then pour the solution into a hydrothermal reactor, heat to 160℃ for 4h, cool and filter, wash with water and ethanol in turn, dry and put into a tubular furnace, heat to 300℃, and calcine for 3h to obtain nano-flower-like manganese tetraoxide.

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

[0052] The N2 adsorption / desorption curve of manganese tetraoxide was measured using a surface area and particle size analyzer, 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 manganese tetraoxide in Example 3 to Example 6, a star-shaped cardanol surfactant was added, which contains a carboxyl group and can be complexed with manganese ions to disperse the 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 achieving the effect of a structural template agent. After hydrothermal reaction and calcination, a manganese tetraoxide with a nano-flower-like structure of high specific surface area is obtained. Further, the nano-flower-like manganese tetraoxide and lithium carbonate are calcined to obtain lithium cobaltate (LiMn2O4) by a high-temperature solid-phase method. The lithium cobaltate after high-temperature solid-phase calcination maintains the nano-flower-like structure of the precursor manganese 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 21.8m 2 / g, the specific surface area of ​​lithium cobalt oxide is only 15.0m 2 / g.

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

[0059]

[0060] Examples 3 to 6 use high-surface-area nanoflower-shaped lithium manganese oxide as the positive electrode active material for lithium-ion batteries. A larger surface area provides more active lithium insertion / extraction sites, increasing the diffusion rate of lithium ions in the positive electrode material and thus increasing the specific capacity of the battery. The initial discharge capacity reached 139.6-159.1 mA·h / g, significantly higher than that of Comparative Examples 1 to 3. After 100 cycles, the discharge capacity remained at 134.6-150.9 mA·h / g, with a capacity retention rate of 94.85-96.42%. This demonstrates excellent cycling stability.

[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 principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A nano flower-shaped manganese tetraoxide, characterized in that: The method 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):

2. The 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 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 nano-flower-shaped manganese tetraoxide according to claim 1, characterized in that: 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, performing rotary evaporation after the reaction, washing with methanol and drying to obtain a star-shaped cardanol surfactant.

5. The nano-flower-shaped manganese tetraoxide according to claim 4, characterized in that: In the step (1), the molar ratio of cardanol glycidyl ether to 1,4,7,10-tetraazacyclododecane is (4.8-5.6):

1.

6. The nano-flower-shaped manganese tetraoxide according to claim 4, characterized in that: In the step (2), the molar ratio of the surfactant precursor, succinic anhydride and 4-dimethylaminopyridine is 1:(4-4.8):(4-4.8).

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

8. A method for preparing a nano-flower-shaped lithium manganate positive electrode material using the nano-flower-shaped manganese oxide according to any one of claims 1 to 8, 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.

9. The method for preparing nano-flower-shaped lithium manganate positive electrode material using nano-flower-shaped manganese oxide according to claim 8, characterized in that: The molar ratio of the lithium carbonate to the nano-flower-shaped manganese tetraoxide is 1:

2.

10. The method for preparing nano-flower-shaped lithium manganate positive electrode material by using nano-flower-shaped manganese oxide according to claim 8, 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.

Images