An organic electrode material, a positive electrode, a flexible positive electrode, and a battery

Abstract

The present invention relates to the field of batteries, and particularly to an organic electrode material, a positive electrode, a flexible positive electrode and a battery. The organic electrode material has a repeating structural unit represented by formula (I), so that the organic electrode material has a significantly improved discharge capacity and significantly improved cycling performance.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and particularly to an organic electrode material, a positive electrode, a flexible positive electrode, and a battery. Background Art

[0002] Due to the continuous consumption of traditional fossil fuels and global environmental problems, people are increasingly concerned about the development of sustainable clean energy. Secondary batteries, thanks to their high energy conversion efficiency and portability, have become one of the most promising energy storage devices. Among them, lithium-ion batteries have the advantages of high energy density, low self-discharge rate, long cycle life, and light weight, and are widely used in fields such as automobiles, power tools, and energy storage.

[0003] Compared with traditional inorganic electrode materials, organic electrode materials have many advantages, such as high theoretical capacity, low cost, low environmental pollution, and rich resources. So far, conjugated carbonyl compounds such as quinones, anhydrides, and ketones have become the most potential organic electrode materials due to their stable redox properties, structural diversity, multi-electron reactions, and fast reaction kinetics. However, most organic small molecules have solubility problems in electrolytes. Therefore, when used as lithium-ion battery electrode materials, they will show rapid capacity decay and poor cycle performance. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of poor cycle performance of organic electrode materials in the prior art, so as to provide an organic electrode material, a positive electrode, a flexible positive electrode, and a battery.

[0005] To this end, the present invention provides an organic electrode material having a repeating structural unit represented by formula (I):

[0006]

[0007] The present invention also provides a preparation method of an organic electrode material, comprising the following steps:

[0008] Taking 2,7-dinitro-pyrene-4,5,9,10-tetrone to carry out a polymerization reaction in the presence of a catalyst and a reducing agent to obtain the organic electrode material.

[0009] Furthermore, the preparation method satisfies at least one of the following (1)-(4):

[0010] (1) The catalyst is at least one of iodine, NH 4 Cl; and / or, the reducing agent is at least one of lithium flakes, zinc powder, and iron powder;

[0011] (2) The polymerization reaction is carried out at room temperature, and the reaction time is 6-8 h;

[0012] (3) After the reaction is completed, water is added to terminate the reaction, followed by solid-liquid separation. The solid is collected and dried to obtain the organic electrode material. Preferably, the drying temperature is 50 - 70 °C and the time is 24 - 48 h;

[0013] (4) The mass ratio of 2,7-dinitropyrene-4,5,9,10-tetrone to the catalyst and the reducing agent is 200:1 - 10:20 - 200.

[0014] Furthermore, the preparation method of the 2,7-dinitropyrene-4,5,9,10-tetrone includes dissolving pyrene-4,5,9,10-tetrone in a mixed solution of concentrated sulfuric acid and concentrated nitric acid, and heating for reaction to obtain it.

[0015] Furthermore, the preparation method of the 2,7-dinitropyrene-4,5,9,10-tetrone satisfies at least one of the following (1)-(4):

[0016] (1) The heating temperature is 80 - 100 °C and the time is 1 - 3 h;

[0017] (2) After the reaction is completed, the reaction solution is dropped into water to precipitate the solid. The solid is separated by solid-liquid separation, collected, and dried to obtain 2,7-dinitropyrene-4,5,9,10-tetrone. Preferably, the drying temperature is 60 - 70 °C and the time is 24 - 48 h;

[0018] (3) The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3 - 5:1;

[0019] (4) The molar amount of pyrene-4,5,9,10-tetrone to the volume of the mixed solution of concentrated sulfuric acid and concentrated nitric acid is 0.5 - 2 mmol:10 mL.

[0020] The present invention also provides a positive electrode, which includes a current collector and a positive electrode layer attached to the current collector. The positive electrode layer includes the organic electrode material described above or the organic electrode material obtained by any of the above preparation methods; preferably, by weight, the electrode layer includes 2 - 4 parts of the organic electrode material, 5 - 7 parts of the conductive agent, and 0.5 - 1.5 parts of the binder.

[0021] Among them, the conductive agent can be a conventional conductive agent, such as but not limited to conductive carbon black, conductive graphite, carbon fiber, carbon nanotube, acetylene black, and graphene, etc. The binder can also be a conventional binder, such as but not limited to styrene-butadiene rubber binder, carboxymethyl cellulose, carboxymethyl cellulose, sodium alginate, polyvinylidene fluoride, polyacrylic acid binder, styrene-butadiene rubber binder, polytetrafluoroethylene, polyamide, polyvinyl alcohol, polyethyleneimine, or polyimide, etc. The positive electrode is prepared by a conventional method, such as mixing the slurry, coating the slurry, drying (surface density 4 - 10 mg / cm 2 ), and rolling.

[0022] The present invention also provides a flexible positive electrode, the raw materials of which include the organic electrode material described above or the organic electrode material prepared by any of the preparation methods described above, and also include a carbon-based material. Preferably, the mass ratio of the organic electrode material to the carbon-based material is 1:1-3, more preferably 1:2-3.

[0023] Furthermore, the carbon-based material is selected from at least one of carbon nanotubes, graphene oxide, and carbon cloth.

[0024] The present invention also provides a preparation method of the flexible positive electrode. The organic electrode material and the carbon-based material are dispersed in a solvent to obtain a dispersion, which is then subjected to suction filtration and drying to obtain the flexible positive electrode in the form of a flexible self-supporting film. Among them, the solvent can be an organic solvent such as absolute ethanol. Ultrasonic dispersion can be used.

[0025] The present invention also provides a battery, including the positive electrode described above, or the flexible positive electrode described above, or the flexible positive electrode prepared by the preparation method described above.

[0026] The technical solution of the present invention has the following advantages:

[0027] 1. The organic electrode material provided by the present invention has a repeating structural unit shown in formula (I), so that the organic electrode material has a significantly improved discharge capacity and significantly improved cycling performance.

[0028] 2. The organic electrode material provided by the present invention uses iodine as a catalyst and lithium metal as a reducing agent, making the polymerization reaction easy to occur at room temperature, with a short reaction time and high yield, which is suitable for large-scale production.

[0029] 3. Compared with a conventional positive electrode, the flexible positive electrode provided by the present invention uses the organic electrode material and the carbon-based material in combination. Especially when the mass ratio of the organic electrode material to the carbon-based material is controlled to be 1:1-3, the discharge capacity and cycling performance can be further improved, especially when it is 1:2-3. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is a structural diagram of the flexible electrode provided in Embodiment 1 of the present invention;

[0032] Figure 2It is the cycling performance of the organic flexible cathode in Example 2 of the present invention at a current density of 50 mA / g. Detailed implementation mode

[0033] The following embodiments are provided to better understand the present invention further. They are not limited to the described optimal implementation mode, and do not constitute limitations on the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with those of other prior arts falls within the protection scope of the present invention.

[0034] For those not specifying specific experimental steps or conditions in the embodiments, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments not indicating the manufacturer, they are all conventional reagent products that can be obtained through commercial purchase. The carbon nanotubes are purchased from Tiannai, model LB107-44.

[0035] Example 1

[0036] This example provides a preparation method of an organic electrode material and a flexible electrode, including the following steps.

[0037] Synthesis of pyrene-4,5,9,10-tetrone: Dissolve pyrene (10 mmol) in a mixed solution of 80 mL of methanol and acetonitrile (volume ratio 1:1), and then successively add sodium periodate (82 mmol), 50 mL of deionized water, and ruthenium(III) chloride hydrate (0.12 mmol). After mixing evenly, place the above mixed solution in an oil bath at 40 °C and react for 12 h. After the reaction, cool to room temperature, collect the organic phase by dichloromethane extraction, and finally remove the solvent by a rotary evaporator to obtain a dark yellow powder. After vacuum drying, the obtained crude product is recrystallized and purified using dimethyl sulfoxide, and after vacuum drying, a yellow powder of pyrene-4,5,9,10-tetrone (yield 17.5%) is obtained, hereinafter referred to as pyrene tetrone. 1 H NMR(500MHz,DMSO-d 6 ,ppm):8.32(d,2H),7.74(t,1H). FT-IR(KBr,cm -1 ):1673(C=O),1561(C=C). UV-Vis(DMF,nm):267,293,373.

[0038] Synthesis of 2,7-dinitropyrene-4,5,9,10-tetrone: Pyrenetetrone (1 mmol) was dissolved in a mixed solution of 10 mL of concentrated sulfuric acid and concentrated nitric acid (volume ratio 4:1). Then, the above solution was sealed and placed in an oil bath, and the temperature was raised to 90 °C for reaction for 2 h. After the reaction was completed, the reaction solution was gradually added dropwise to 200 mL of deionized water for precipitation. It was clearly observed that yellow flocculates gradually precipitated. After standing overnight, the product was collected by centrifugation and dried in a vacuum drying oven at 60 °C for 24 h to obtain bright yellow 2,7-dinitropyrene-4,5,9,10-tetrone powder (yield 75.6%), hereinafter referred to as nitropyrenetetrone. 1 H NMR (500 MHz, DMSO-d 6 ): δ = 8.89 ppm (s); 13 C NMR (500 MHz, DMSO-d 6 ): 174.70, 149.19, 136.33, 134.58, 126.44 ppm; FTIR (KBr): 1687, 1590, 1531, 1350 cm -1 ; UV / Vis (DMF): 279, 343 nm.

[0039] Preparation of organic electrode material: 200 mg of nitropyrenetetrone was dissolved in 20 mL of anhydrous methanol, and then stirred at room temperature until completely dissolved. Subsequently, 5 mg of iodine was added as a catalyst. After the above substances were completely dissolved, 100 mg of lithium metal was added as a reducing agent for reaction. After reacting at room temperature for 6 h, 1 mL of deionized water was added to the reaction flask to terminate the reaction. The product was collected by centrifugation and washed repeatedly with methanol and deionized water. Finally, it was dried in a vacuum drying oven at 60 °C for 24 h to obtain the final dark blue product, which was the organic electrode material. 13 C NMR: 164.25, 144.19, 130.23, 115.21 ppm; FTIR (KBr): 1687, 1590, 1531, 1350 cm -1 ; UV / Vis (DMF): 279, 343 nm.

[0040] Preparation of flexible positive electrode: 20 mg of carbon nanotubes (CNTs) was dispersed in 20 mL of anhydrous ethanol, with an ultrasonic power of 150 W and ultrasonic treatment for 2 h. Then, 20 mg of the above organic electrode material was mixed in and ultrasonic treatment was continued for 1 h to obtain a uniformly dispersed suspension. Finally, the above suspension was filtered by vacuum filtration. After drying in a vacuum at 70 °C, a flexible self-supporting film was obtained and cut into circular discs with a diameter of 12 mm using a circular punching machine as the positive electrode of the lithium-ion battery.

[0041] Example 2

[0042] This embodiment provides a preparation method of a flexible electrode, which is prepared by using the organic electrode material obtained in Example 1. The raw materials and processes are basically the same as those in Example 1, except that in the preparation of the flexible positive electrode, the amount of carbon nanotubes used is 20 mg, and the mass ratio of the organic electrode material to CNTs is 1:2.

[0043] Example 3

[0044] This embodiment provides a preparation method of a flexible electrode, which is prepared by using the organic electrode material obtained in Example 1. The raw materials and processes are basically the same as those in Example 1, except that in the preparation of the flexible positive electrode, the amount of carbon nanotubes used is 20 mg, and the mass ratio of the organic electrode material to CNTs is 1:3.

[0045] Example 4

[0046] This embodiment provides a preparation method of an electrode, which is prepared by using the organic electrode material obtained in Example 1 according to the following method:

[0047] Take the organic electrode material obtained in Example 1, carbon nanotubes, and PVDF and mix them in a mass ratio of 3:6:1. Add 1000 μL of NMP as a solvent and grind for more than 1 h. Uniformly coat the obtained slurry on the Al foil and dry it in a vacuum drying oven at 100 °C for 24 h. The single-sided areal density is 6 mg / cm 2 . After rolling, cut the electrode material into circular wafers with a diameter of 12 mm using a circular punching machine as the positive electrode of the lithium-ion battery.

[0048] Comparative Example 1

[0049] This comparative example provides a preparation method of an electrode, including the following steps:

[0050] Take pyrene-4,5,9,10-tetrone, carbon nanotubes, and PVDF and mix them in a mass ratio of 3:6:1. Add 1000 μL of NMP as a solvent and grind for more than 1 h. Uniformly coat the obtained slurry on the Al foil and dry it in a vacuum drying oven at 100 °C for 24 h. The single-sided areal density is 6 mg / cm 2 . After rolling, cut the electrode material into circular wafers with a diameter of 12 mm using a circular punching machine as the positive electrode of the lithium-ion battery.

[0051] Comparative Example 2

[0052] This comparative example provides a preparation method of a flexible electrode, including the following steps:

[0053] Disperse 20 mg of carbon nanotubes (CNTs) in 20 mL of absolute ethanol. With an ultrasonic power of 150 W, after ultrasonic treatment for 2 h, a uniformly dispersed suspension is obtained. Finally, the above suspension is filtered by vacuum filtration. After drying in vacuo at 70 °C, a flexible self-supporting film is obtained, which is cut into circular discs with a diameter of 12 mm using a circular punching machine and used as the positive electrode of a lithium-ion battery.

[0054] Comparative Example 3

[0055] This comparative example provides a method for preparing an organic electrode material and a flexible electrode, including the following steps.

[0056] Synthesis of pyrene-4,5,9,10-tetrone: The same as in Example 1.

[0057] Synthesis of 2,7-dibromopyrene-4,5,9,10-tetrone: Dissolve pyrene tetrone (1 mmol) in a mixed solution of 2 mL of trifluoroacetic acid and 5 mL of concentrated sulfuric acid, and then slowly add 1 mL of concentrated sulfuric acid solution containing N-bromosuccinimide (3 mmol) dropwise. After stirring evenly at room temperature, seal the reaction flask and then place it in an oil bath at 40 °C for two days. After the reaction is completed, add 20 mL of deionized water to the system to terminate the reaction and continue stirring for 1 h. Finally, collect the product by vacuum filtration and wash it repeatedly with saturated sodium bicarbonate and deionized water until the washing liquid is neutral. Hereinafter referred to as brominated pyrene tetrone. 1 H NMR (500 MHz, DMSO-d 6 , ppm): 8.25 (d, 1H), 8.08 (d, 1H), 7.96 (q, 1H); FTIR (KBr, cm -1 ): 1678 (C=O), 1580 (C=C), 708 (C-Br); UV / Vis (DMF, nm): 276.

[0058] Preparation of the organic electrode material: In a glove box filled with nitrogen, dissolve bis(1,5-cyclooctadiene)nickel (2 mmol), bipyridine (2 mmol) and 1,5-cyclooctadiene (1.5 mmol) in 20 mL of N,N-dimethylformamide solution, and then slowly add 10 mL of N,N-dimethylformamide solution containing brominated pyrene tetrone (1.5 mmol). After sealing, take out the reaction device and place it in an oil bath at 60 °C for 7 d. After the reaction is completed, pour the product into 50 mL of a mixed solution of 1 M HCl and methanol with a volume ratio of 1:1. A dark brown precipitate slowly precipitates. Collect the product by centrifugation and wash it repeatedly with HCl and methanol. The final product is dried in a vacuum drying oven overnight. Hereinafter referred to as poly(pyrene tetrone) (PPT). FTIR (KBr, cm -1 ): 1666 (C=O), 1610 (C=C).

[0059] Preparation of flexible positive electrode: 20 mg of carbon nanotubes (CNTs) were dispersed in 20 mL of absolute ethanol, with an ultrasonic power of 150 W for 2 h. Then, 20 mg of the above-mentioned organic electrode material was mixed in and ultrasonic treatment continued for 1 h to obtain a uniformly dispersed suspension. Finally, the suspension was filtered by vacuum filtration. After drying in vacuum at 70 °C, a flexible self-supporting film was obtained and cut into discs with a diameter of 12 mm using a round punching machine as the positive electrode of the lithium-ion battery.

[0060] Comparative Example 4

[0061] This comparative example provides a method for preparing an electrode, which is prepared by using the organic electrode material obtained in Comparative Example 3 according to the following method:

[0062] Take the organic electrode material, carbon nanotubes, and PVDF obtained in Comparative Example 3 and mix them in a mass ratio of 3:6:1. Add 1000 μL of NMP as a solvent and grind for more than 1 h. The obtained slurry was uniformly coated on an Al foil and dried in a vacuum drying oven at 100 °C for 24 h, with a single-sided areal density of 6 mg / cm 2 . After rolling, the electrode material was cut into discs with a diameter of 12 mm using a round punching machine as the positive electrode of the lithium-ion battery.

[0063] Experimental Example 1

[0064] Take the positive electrodes prepared in each group of examples and comparative examples, use a lithium sheet as the negative electrode of lithium ions, use a Celgard 2400 porous polypropylene membrane as the separator, and use a mixed solution of DOL and DME containing 1 mol / L LiTFSI (volume ratio 1:1) as the electrolyte. Finally, a CR2025 coin cell was assembled in a glove box filled with argon. The electrochemical performance was tested using a BlueTEC test system and a Princeton electrochemical workstation. At 25 °C, the first discharge specific capacity of the battery at a current density of 50 mA / g and the discharge specific capacity after 80 cycles were tested within a charge-discharge voltage range of 1.0 V to 3.5 V. The results are shown in the following table.

[0065] Table 1 Performance results of lithium batteries

[0066]

[0067]

[0068] Compared with the flexible positive electrodes of Comparative Examples 2 and 3, the flexible positive electrodes made of the organic materials of Examples 1-3 of the present invention are more stable and exhibit longer cycle stability and higher capacity under the same assembly and test conditions.

[0069] Compared with the positive electrode sheets of Comparative Examples 1 and 4, the positive electrode sheet made of the organic material of Example 4 of the present invention is more stable, showing longer cycle stability and higher capacity under the same assembly test conditions.

[0070] Compared with Example 4, the organic materials prepared in Examples 2-3 of the present invention show higher capacity and cycle stability under the same assembly test conditions, especially Example 2.

[0071] Obviously, the above examples are only for clear illustration and not for limitation of the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. An organic electrode material, characterized in that, the organic electrode material has a repeating structural unit shown in formula (I):

2. A method for preparing the organic electrode material according to claim 1, characterized in that, it includes the following steps, taking 2,7-dinitropyrene-4,5,9,10-tetrone to carry out a polymerization reaction in the presence of a catalyst and a reducing agent to obtain the organic electrode material.

3. The method for preparing the organic electrode material according to claim 2, characterized in that, the preparation method satisfies at least one of the following (1)-(4): (1) The catalyst is at least one of iodine, NH 4 Cl; and / or, the reducing agent is at least one of lithium flakes, zinc powder, and iron powder; (2) The polymerization reaction is carried out at room temperature, and the reaction time is 6-8 h; (3) After the reaction is completed, water is added to terminate the reaction, solid-liquid separation is carried out, the solid is collected, and the organic electrode material is obtained after drying; (4) The mass ratio of 2,7-dinitropyrene-4,5,9,10-tetrone to the catalyst and the reducing agent is 200:1-10:20-200.

4. The method for preparing the organic electrode material according to claim 3, characterized in that, the drying temperature is 50-70 °C and the time is 24-48 h.

5. The method for preparing the organic electrode material according to claim 2 or 3, characterized in that, the preparation method of the 2,7-dinitropyrene-4,5,9,10-tetrone includes dissolving pyrene-4,5,9,10-tetrone in a mixed solution of concentrated sulfuric acid and concentrated nitric acid, and heating and reacting to obtain it.

6. The method for preparing the organic electrode material according to claim 5, characterized in that, the preparation method of the 2,7-dinitropyrene-4,5,9,10-tetrone satisfies at least one of the following (1)-(4): (1) The heating temperature is 80-100 °C and the time is 1-3 h; (2) After the reaction is completed, the reaction solution is dropped into water to precipitate a solid, solid-liquid separation is carried out, the solid is collected, and 2,7-dinitropyrene-4,5,9,10-tetrone is obtained after drying; (3) The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3-5:1; (4) The molar amount of pyrene-4,5,9,10-tetrone to the volume of the mixed solution of concentrated sulfuric acid and concentrated nitric acid is 0.5-2 mmol:10 mL.

7. The method for preparing the organic electrode material according to claim 6, characterized in that, the drying temperature is 60-70 °C and the time is 24-48 h.

8. A positive electrode, characterized in that, it includes a current collector and a positive electrode layer attached to the current collector, and the positive electrode layer includes the organic electrode material according to claim 1 or the organic electrode material prepared by the preparation method according to any one of claims 2-7.

9. The positive electrode according to claim 8, characterized in that, by weight, the positive electrode layer includes 2-4 parts of the organic electrode material, 5-7 parts of the conductive agent, and 0.5-1.5 parts of the binder.

10. A flexible positive electrode, characterized in that, its raw materials include the organic electrode material according to claim 1 or the organic electrode material prepared by the preparation method according to any one of claims 2-7, and also include a carbon-based material.

11. The flexible positive electrode according to claim 10, characterized in that, The mass ratio of the organic electrode material to the carbon-based material is 1:1 - 3.

12. The flexible positive electrode according to claim 11, wherein, the mass ratio of the organic electrode material to the carbon-based material is 1:2 - 3.

13. The flexible positive electrode according to claim 10, wherein, the carbon-based material is selected from at least one of carbon nanotubes, graphene oxide, and carbon cloth.

14. A method for preparing the flexible positive electrode according to any one of claims 10 - 13, wherein, the organic electrode material and the carbon-based material are dispersed in a solvent to obtain a dispersion, which is subjected to suction filtration and drying to obtain the flexible positive electrode of a flexible self-supporting film.

15. A battery, wherein, it includes the positive electrode according to claim 8 or 9, or the flexible positive electrode according to any one of claims 10 - 13, or the flexible positive electrode prepared by the preparation method according to claim 14.

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