Conjugate extended lithium-containing organic positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium organic batteries, and provides a conjugate extended lithium-containing organic positive electrode material and a preparation method and application thereof. The synthesis process of the positive electrode material comprises the following steps: firstly, taking tetraamino p-benzoquinone as a raw material, and carrying out oximation modification reaction on the tetraamino p-benzoquinone to generate tetraamino p-oximic acid; then, carrying out composite treatment on the TAPO and a lithium source to obtain lithium tetraamino p-oximate; and finally, through a condensation polymerization reaction, further preparing to obtain the polybenzoquinone-pyrazine extended lithium oximate. Through specific chemical treatment, the organic material contains a lithium element, so that the dependence on an external lithium source (such as a metal lithium negative electrode or a lithium supplement agent) is eliminated. Through ingenious molecular design and synthesis strategies, the conductivity of the material is improved, and the rate capability, the solubility resistance, the high-temperature stability and the cycle life of the material are remarkably enhanced, so that a solid foundation is laid for long-term stable operation and high-performance expression of a battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium organic batteries, and in particular relates to a conjugated extended lithium-containing organic cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries are widely used. The performance of the cathode material determines the battery performance, so it is crucial to develop high-quality cathode materials. Although traditional inorganic cathode materials have the advantages of high potential and good cycle stability, they have problems such as scarce resources, high cost, and environmental pollution during recycling. Organic cathode materials have advantages such as high theoretical specific capacity, flexible structure design, easy availability of raw materials, low cost, and environmental friendliness. However, they also face problems such as poor conductivity and low voltage. Lithium-containing organic cathode materials are an important branch of organic electrode materials and have great potential. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a conjugated extended lithium-containing organic cathode material, a preparation method thereof, and an application thereof to solve the problems of low conductivity and solubility of traditional organic electrode materials. The synthesized conjugated extended lithium-containing organic cathode material can exhibit a specific capacity of about 260 mAh·g –1 , which is significantly higher than most existing inorganic electrode materials.

[0004] The technical solution of the present invention is as follows:

[0005] The first aspect of the present invention provides a conjugated extended lithium-containing organic cathode material based on the active functional group of lithium oxime (-C=N-OLi). The material structure contains the active functional group of lithium oxime, and the molecular skeleton is composed of extended benzene ring-pyrazine structures connected to each other. The structure is as follows:

[0006] n is 2 - 5.

[0007] The second aspect of the present invention provides a preparation method of the conjugated extended lithium-containing organic cathode material, including the following steps:

[0008] The first step: Synthesize tetraamino-p-oxime acid (TAPO)

[0009] Under an inert atmosphere, first disperse tetraamino-p-benzoquinone (TABQ) in a solvent, and then transfer it to a reaction vessel. At the same time, dissolve hydroxylamine hydrochloride (NH2OH·HCl) in the solvent. With the help of a constant pressure dropping funnel, slowly drop the hydroxylamine hydrochloride solution into the tetraamino-p-benzoquinone dispersion, react at 65 - 95 °C for 6 - 12 h. After the reaction system naturally cools to room temperature, wash the product with deionized water and then freeze-dry to obtain tetraamino-p-oxime acid;

[0010] The second step: Synthesize lithium tetraamino-p-oxime (Li_TAPO)

[0011] Under an inert atmosphere, add the tetraamino-p-oxime acid prepared in the first step to a lithium source solution, stir at room temperature for 24 to 48 h, then add an extractant to the solution to precipitate the sediment. Filter the sediment by suction, wash it repeatedly with the extractant, and dry it to obtain lithium tetraamino-p-oxime acid.

[0012] Step 3: Synthesize a conjugated extended lithium-containing organic cathode material (Li_pTAPO)

[0013] Under an inert atmosphere, dissolve the lithium tetraamino-p-oxime acid prepared in the second step in an aprotic solvent, stir and react at 100 to 130 °C for 12 to 24 h. After cooling to room temperature, add an extractant to the solution to precipitate the sediment. Wash it repeatedly with the extractant, filter by suction, and dry it to obtain the conjugated extended lithium-containing organic cathode material.

[0014] Furthermore, the molar ratio of hydroxylamine hydrochloride to tetraamino-p-benzoquinone is 2:1 to 2.5:1. Preferably 2.2:1 to 2.4:1.

[0015] Further preferably, the reaction temperature in the first step is 65 to 95 °C, and the reaction time is 6 to 12 h.

[0016] Furthermore, the solvents of the hydroxylamine hydrochloride solution and the tetraamino-p-benzoquinone dispersion in the first step are the same, both being methanol, ethanol, or an alcohol-water mixed solvent. The concentration of the hydroxylamine hydrochloride solution is 0.01 to 0.02 g / mL, and the concentration of the tetraamino-p-benzoquinone dispersion is 0.01 to 0.02 g / mL.

[0017] Furthermore, the temperature of freeze-drying in the first step is -20 to -40 °C, and the freeze-drying time is 12 to 24 h.

[0018] Furthermore, the molar ratio of the tetraamino-p-oxime acid to the lithium source in the second step is 1:2 to 1:2.2.

[0019] Further preferably, the reaction time in the second step is 36 to 48 h.

[0020] Furthermore, the lithium source in the second step is one or more of lithium carbonate, lithium hydroxide, lithium methoxide, lithium tert-butoxide, and lithium hydride. The solvent of the lithium source solution is one or more of methanol, ethanol, tert-butanol, and tetrahydrofuran. The concentration of the lithium source solution is 0.01 to 0.02 g / mL.

[0021] Furthermore, the extractants in the second and third steps are one or more of diethyl ether, isopropyl ether, acetone, methyl ethyl ketone, and ethyl acetate.

[0022] Further, the aprotic solvent described in the third step is one or more of N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), acetonitrile (CH3CN), and dimethyl sulfoxide (DMSO).

[0023] Further preferably, the reaction temperature in the third step is 110 - 125 °C, and the reaction time is 12 - 16 h.

[0024] Further, the concentration of lithium tetraaminopyroximic acid in the aprotic solvent is 0.01 - 0.02 g / mL.

[0025] The third aspect of the present invention is to provide the application of the conjugate extended lithium-containing organic cathode material in a lithium-ion battery. The anode uses metallic lithium or graphite, the electrolyte uses 3M LiTFSI, the solvent is tetraethylene glycol dimethyl ether, and the separator uses Celgard 2400.

[0026] The present invention focuses on the research and development of new organic energy storage materials, prepares lithium polyoxime acid (Li_pTAPO) organic molecules, and adopts a multi-dimensional molecular engineering strategy. With the active functional group of lithium pyroximic acid as the core, through collaborative innovation, the lithiation sites are precisely regulated, etc., to optimize the electron conduction and lithium ion diffusion characteristics of the material, break through the technical barriers of traditional organic materials, and provide support for a new generation of lithium-based organic energy storage devices. The present invention proposes a lithiated organic cathode material based on lithium pyroximic acid, its preparation method and application, and there are two innovation points: one is prelithiation, which enables the organic material to contain lithium itself, getting rid of the dependence on external lithium sources, avoiding the problem of lithium dendrites, improving the battery safety, simplifying the preparation process, reducing the cost, and also improving the initial Coulombic efficiency of the battery; the other is structural stability, which realizes π-π conjugate extension and molecular weight increase through molecular design and synthesis strategies, optimizes the benzene ring - pyrazine system, realizes double optimization of electron and ion conduction, improves the conductivity, rate performance, etc., and ensures the long-term stable operation of the battery. The present invention is committed to the research and development of new lithium-containing organic energy storage materials, prepares lithium polyoxime acid organic molecules with excellent performance and high-performance lithium-containing organic cathode materials, provides support for a new generation of lithium-based organic energy storage devices, can be applied to fields such as smart grids, and is expected to promote energy storage technology and energy transformation.

[0027] Advantages and beneficial effects of the present invention:

[0028] 1. Advantages of prelithiation

[0029] Get rid of the dependence on external lithium sources: Make it contain lithium itself through chemical treatment, without relying on external lithium sources such as metallic lithium anodes or lithium supplement agents.

[0030] Improve the battery safety: Avoid the problem of lithium dendrites caused by using external lithium sources and improve the battery safety.

[0031] Simplify the preparation process and reduce costs: It can be directly combined with commercial graphite anodes to form a full battery, simplifying the preparation process and reducing manufacturing costs.

[0032] Improve the initial Coulomb efficiency: The prelithiation compensation mechanism effectively improves the initial Coulomb efficiency of the battery, ensuring the efficient operation of the battery.

[0033] 2. Structural stability advantages

[0034] π-π conjugate extension and molecular weight increase: Through molecular design and synthesis strategies, π-π conjugate extension and molecular weight increase are achieved.

[0035] Dual conduction optimization: Optimize the extended benzene ring-pyrazine system to achieve dual optimization of electron and ion conduction.

[0036] Enhance multiple properties: Improve the electrical conductivity of the material, enhance the rate performance, anti-solubility, high-temperature stability and cycle life, and ensure the long-term stable operation of the battery.

[0037] 3. Application value advantages

[0038] Meet the energy storage needs of fields such as smart grids: Provide strong support for a new generation of lithium-based organic energy storage devices, especially suitable for fields such as smart grids and renewable energy storage, and promote the development of energy storage technology and energy transformation.

[0039] Environmentally friendly and cost-effective: As an organic cathode material, it has the advantages of easy availability of raw materials, low cost, and environmental friendliness, and is more sustainable than traditional inorganic cathode materials. Description of the drawings

[0040] Figure 1 Schematic diagram of the synthesis route of Li_pTAPO of the present invention (oximation-lithiation-condensation);

[0041] Figure 2 IR spectra and partial enlarged views of TABQ, TAPO, Li_TAPO, and Li_pTAPO, where the right side is the partial enlarged view of the left side;

[0042] Figure 3 Raman spectrum of Li_pTAPO;

[0043] Figure 4 For 7 Li - ssNMR spectrum (lithium source MeOLi, Li_TAPO, Li_pTAPO);

[0044] Figure 5 XRD spectrum of Li_pTAPO;

[0045] Figure 6 SEM image of Li_pTAPO;

[0046] Figure 7 The Li_pTAPO cathode material prepared in Example 1 (lithiation first and then condensation) was applied to a lithium-ion battery, and the charge-discharge curve at a current density of 0.1 A·g -1 is shown in the figure;

[0047] Figure 8 The Li_pTAPO' cathode material prepared in Comparative Example 1 (condensation first and then lithiation) was applied to a lithium-ion battery, and the charge-discharge curve at a current density of 0.1 A·g -1 is shown in the figure. Detailed Description of the Invention

[0048] The present invention will be further described in detail below through specific examples. The following examples are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0049] Example 1:

[0050] A preparation method of a conjugated extended lithium-containing organic cathode material, comprising:

[0051] In the first step, under an inert atmosphere, tetraaminobenzoquinone (TABQ) was dispersed in ethanol, and the concentration of TABQ was 0.01 g / mL and transferred to a reaction vessel. According to the molar ratio M(TABQ):M(NH2OH·HCl)=1:2.2, hydroxylamine hydrochloride (NH2OH·HCl) was dissolved in ethanol, and the concentration of hydroxylamine hydrochloride was 0.01 g / mL. Using a constant-pressure dropping funnel, the hydroxylamine hydrochloride solution was slowly dropped into the TABQ ethanol dispersion, and the reaction was carried out at 75 °C for 6 h. After the reaction system was naturally cooled to room temperature, the product was washed with deionized water, and the obtained solid was freeze-dried at -40 °C for 24 h to obtain tetraaminoparaldoxime acid (TAPO).

[0052] In the second step, continuing the operation under an inert atmosphere, the obtained TAPO and lithium methoxide (MeOLi) were added to methanol according to the molar ratio M(TAPO):M(MeOLi)=1:2.1. After stirring at room temperature for 48 h, ether was added to the solution to precipitate. The precipitate was filtered by suction and repeatedly rinsed with ether, and finally dried to obtain lithium tetraaminoparaldoxime acid (Li_TAPO).

[0053] In the third step, also under an inert atmosphere, 0.5 g of Li_TAPO obtained in the second step was dissolved in 50 mL of dimethyl sulfoxide (DMSO). The reaction was carried out with stirring at 125 °C for 12 h. After the reaction system was cooled to room temperature, acetone was added to precipitate. The precipitate was repeatedly rinsed with acetone, filtered by suction, and finally dried to obtain the conjugated extended lithium-containing organic cathode material (Li_pTAPO).

[0054] Figure 2The infrared spectrogram covers TABQ, TAPO, Li_TAPO, and Li_pTAPO. By comparison, it can be seen that the C=O bond in TABQ disappears after the oximation reaction to form TAPO, and instead, the C=N bond in the oxime acid appears, and this bond remains after the lithiation and polycondensation reactions. In addition, the intensity of the -OH peak at approximately 3200 cm -1 decreases significantly after lithiation, indicating that the lithiation process eliminates the hydroxyl group.

[0055] Figure 3 The Raman spectrum shows characteristic peaks corresponding to the structural formula of Li_pTAPO.

[0056] Figure 4 7 The Li - ssNMR spectra involve the lithium source MeOLi, Li_TAPO, and Li_pTAPO. Among them, the chemical shift of Li_pTAPO continuously shifts to a lower field (δ = 0.72 ppm), which means that after the lithium ions dissociate from methoxyl lithium, they coordinate with the oxime acid group. Subsequently, Li_TAPO condenses to form Li_pTAPO, constructing a continuous conjugated network, which reduces the electron cloud density of the lithium ions and thus enhances the deshielding effect.

[0057] Figure 5 The XRD spectrum of Li_pTAPO is shown. It can be seen from the figure that the material is basically amorphous.

[0058] Figure 6 The SEM image of Li_pTAPO is shown. It can be seen from the figure that the material is a bulk with no fixed structure.

[0059] Comparative Example 1

[0060] The difference from Example 1 is that the second step and the third step are swapped, and the condensation reaction is carried out first, followed by the lithiation reaction.

[0061] The first step is the same as in Example 1;

[0062] In the second step, continue to operate in an inert atmosphere. Dissolve 0.5 g of the obtained TAPO in 50 mL of dimethyl sulfoxide (DMSO). Stir and react at 125 °C for 12 h. After the reaction system cools down to room temperature, add acetone to precipitate. The precipitate is washed with acetone multiple times, filtered by suction, and then dried to finally obtain the conjugated extended polyoxime acid material (pTAPO’).

[0063] In the third step, the obtained pTAPO' and lithium methoxide (MeOLi) were added to methanol at a molar ratio of M(TAPO): M(MeOLi) = 1:2.1 under an inert atmosphere. After stirring at room temperature for 24 h, ether was added to the solution to precipitate. The precipitate was filtered and repeatedly rinsed with ether, and finally dried to obtain lithium tetraaminoparaoxamic acid (Li_pTAPO').

[0064] Production of positive electrode of lithium organic battery:

[0065] The electrode sheet preparation work was carried out in a glove box (water ≤ 0.01ppm, oxygen ≤ 0.01ppm). First, the Li_pTAPO synthesized in Example 1 and the Li_pTAPO' synthesized in Comparative Example 1 were fully ground and mixed with Ketjen black (KB) and polyvinylidene fluoride (PVDF) in a mass ratio of 6:3:1. Then, N-methylpyrrolidone (NMP) was added to the ground mixture, and a uniform electrode slurry was formed through a homogenization operation. Subsequently, the prepared electrode slurry was evenly coated on the aluminum foil current collector using a scraper process. After coating, the aluminum foil current collector with the slurry coating was placed on a heating table and dried at 110°C. Finally, after the drying process is completed, the electrode sheet is cut into positive electrode sheets for subsequent battery testing.

[0066] Button battery assembly

[0067] In the glove box, the button battery assembly test was carried out in an environment where the oxygen and moisture concentrations did not exceed 0.01 ppm. The assembly steps are as follows: First, the negative electrode shell is placed on the work station, and a metal lithium sheet is placed inside as the negative electrode material. After that, the battery separator is stacked and 80 μL of electrolyte (3M LiTFSI, the solvent is tetraethylene glycol dimethyl ether) is dripped, and then the pre-prepared positive electrode sheet is placed on the separator. Subsequently, the gasket and the shrapnel are stacked on the positive electrode sheet in sequence to ensure the stability of the internal structure of the battery. Finally, the positive electrode shell is covered and sealed using a battery packaging machine. After the assembly is completed, the battery is left to stand for 6 hours to ensure that the components inside the battery are fully stable before the electrochemical performance test is carried out.

[0068] Figure 7 and Figure 8 The charge and discharge performance of Li_pTAPO prepared in Example 1 and Li_pTAPO' prepared in Comparative Example 1 as positive electrode materials for lithium organic batteries are shown. -1 The specific capacity is about 260 mAh g -1 However, the Li_pTAPO' prepared by condensation followed by lithiation in Comparative Example 1 has almost no electrochemical performance.

[0069] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. A conjugated extended lithium-containing organic cathode material, characterized in that, The structure is as follows: n is from 2 to 5.

2. The preparation method of the conjugated extended lithium-containing organic cathode material according to claim 1, wherein It includes the following steps: The first step: Synthesize tetraamino-p-oxime acid Under an inert atmosphere, drop the hydroxylamine hydrochloride solution into the tetraamino-p-benzoquinone dispersion, react at 65 - 95 °C for 6 - 12 h, cool to room temperature, wash the product and then freeze-dry to obtain tetraamino-p-oxime acid; The second step: Synthesize lithium tetraamino-p-oxime Under an inert atmosphere, add the tetraamino-p-oxime acid obtained in the first step to the lithium source solution, stir at room temperature for 24 - 48 h, then add an extractant to the solution to precipitate the precipitate, filter the precipitate by suction, wash it with the extractant, and dry it to obtain lithium tetraamino-p-oxime; The third step: Synthesize a conjugated extended lithium-containing organic cathode material Under an inert atmosphere, dissolve the lithium tetraamino-p-oxime obtained in the second step in an aprotic solvent, stir and react at 100 - 130 °C for 12 - 24 h, cool to room temperature, then add an extractant to the solution to precipitate the precipitate, wash it with the extractant, filter by suction and dry to obtain the conjugated extended lithium-containing organic cathode material.

3. The preparation method of the conjugated extended lithium-containing organic cathode material according to claim 2, characterized in that, The molar ratio of hydroxylamine hydrochloride to tetraamino-p-benzoquinone is 2:1 - 2.5:

1.

4. The preparation method of the conjugated extended lithium-containing organic cathode material according to claim 2, wherein The solvents of the hydroxylamine hydrochloride solution and the tetraamino-p-benzoquinone dispersion in the first step are the same, both are methanol, ethanol or an alcohol-water mixed solvent. The concentration of the hydroxylamine hydrochloride solution is 0.01 - 0.02 g / mL, and the concentration of the tetraamino-p-benzoquinone dispersion is 0.01 - 0.02 g / mL.

5. The preparation method of the conjugated extended lithium-containing organic cathode material according to claim 2, characterized in that, The temperature of the freeze-drying in the first step is -20 - -40 °C, and the freeze-drying time is 12 - 24 h.

6. The preparation method of the conjugated extended lithium-containing organic cathode material according to claim 2, characterized in that, The molar ratio of the tetraamino-p-oxime acid to the lithium source in the second step is 1:2 - 1:2.

2.

7. The preparation method of the conjugated extended lithium-containing organic cathode material according to claim 2, wherein, The lithium source in the second step is one or more of lithium carbonate, lithium hydroxide, lithium methoxide, lithium tert-butoxide, lithium hydride. The solvent of the lithium source solution is one or more of methanol, ethanol, tert-butanol, tetrahydrofuran. The concentration of the lithium source solution is 0.01 - 0.02 g / mL.

8. The preparation method of the conjugated extended lithium-containing organic cathode material according to claim 2, wherein The extractants in the second and third steps are one or more of diethyl ether, isopropyl ether, acetone, butanone, ethyl acetate.

9. The preparation method of the conjugated extended lithium-containing organic cathode material according to claim 2, wherein, The aprotic solvent in the third step is one or more of N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, acetonitrile, dimethyl sulfoxide.

10. Application of the conjugated extended lithium-containing organic cathode material according to claim 1 in a lithium-ion battery.

Images