A conjugated extended lithium-containing organic positive electrode material and its preparation method and application

Abstract

The present invention belongs to the technical field of lithium-organic batteries, and provides a conjugated extended lithium-containing organic positive electrode material, a preparation method thereof, and an application thereof. The synthesis process of the positive electrode material is as follows: first, tetraaminobenzoquinone is used as a raw material, and an oximation modification reaction is performed on it to generate tetraaminobenzoxime; then, TAPO is composited with a lithium source to obtain lithium tetraaminobenzoxime; finally, polybenzoquinone-pyrazine extended oxime is further prepared through a condensation reaction. The present invention uses a specific chemical treatment to make the organic material itself contain lithium elements, thereby getting rid of dependence on an external lithium source (such as a metallic lithium negative electrode or a lithium supplement). Through ingenious molecular design and synthesis strategies, the electrical conductivity of the material is improved, and its rate performance, solubility resistance, high-temperature stability and cycle life are significantly enhanced, thereby laying a solid foundation for the long-term stable operation and high performance of the battery.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used, and the performance of their cathode materials determines their performance, making the development of high-quality cathode materials crucial. While traditional inorganic cathode materials offer advantages such as high potential and good cycle stability, they also face challenges such as limited resources, high costs, and environmental pollution during recycling. Organic cathode materials offer advantages such as high theoretical specific capacity, flexible structural design, readily available and low-cost raw materials, and environmental friendliness, but they also face challenges such as poor conductivity and low voltage. Lithium-containing organic cathode materials are an important branch of organic electrode materials and hold enormous potential. Summary of the Invention

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

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

[0005] The first aspect of the present invention provides a conjugated extended lithium-containing organic cathode material based on lithium oxime (-C=N-OLi) active functional groups. The material structure contains lithium oxime active functional groups, and the molecular skeleton is composed of interconnected extended benzene ring-pyrazine structures. The structure is as follows: n is 2~5.

[0006] The second aspect of the present invention is to provide a method for preparing the conjugated extended lithium-containing organic cathode material, comprising the following steps:

[0007] Step 1: Synthesis of tetraaminoparaoxime (TAPO)

[0008] Under an inert atmosphere, tetraaminobenzoquinone (TABQ) is first dispersed in a solvent and then transferred to a reaction vessel. Simultaneously, hydroxylamine hydrochloride (NH₂OH·HCl) is dissolved in the solvent. Using a constant-pressure dropping funnel, the hydroxylamine hydrochloride solution is slowly dripped into the tetraaminobenzoquinone dispersion. The reaction is carried out at 65–95°C for 6–12 hours. After the reaction system is naturally cooled to room temperature, the product is washed with deionized water and lyophilized to obtain tetraaminobenzoquinone.

[0009] Step 2: Synthesis of lithium tetraaminoparaoxime (Li_TAPO)

[0010] Under an inert atmosphere, the tetraaminoparaoxime prepared in the first step is added to a lithium source solution, and after stirring at room temperature for 24 to 48 hours, an extractant is added to the solution to precipitate, the precipitate is filtered, rinsed with the extractant multiple times, and dried to obtain lithium tetraaminoparaoxime;

[0011] Step 3: Synthesis of conjugated extended lithium-containing organic cathode material (Li_pTAPO)

[0012] Under an inert atmosphere, the tetraaminoparaoxime lithium prepared in the second step is dissolved in an aprotic solvent and reacted at 100-130°C with stirring for 12-24 hours. After cooling to room temperature, an extractant is added to the solution to precipitate, which is then rinsed multiple times with the extractant, filtered, and dried to obtain a conjugated extended lithium-containing organic cathode material.

[0013] Furthermore, the molar ratio of hydroxylamine hydrochloride to tetraaminobenzoquinone is 2:1 to 2.5:1, preferably 2.2:1 to 2.4:1.

[0014] More preferably, the first step reaction temperature is 65-95°C, and the reaction time is 6-12 h.

[0015] Furthermore, the solvent of the hydroxylamine hydrochloride solution and the solvent of the tetraaminobenzoquinone dispersion in the first step are the same, both of which are methanol, ethanol or a mixed solvent of alcohol and water. The concentration of the hydroxylamine hydrochloride solution is 0.01 ~ 0.02 g / mL, and the concentration of the tetraaminobenzoquinone dispersion is 0.01 ~ 0.02 g / mL.

[0016] Furthermore, the freeze-drying temperature in the first step is -20 to -40°C, and the freeze-drying time is 12 to 24 hours.

[0017] Furthermore, in the second step, the molar ratio of tetraaminoparaoxime to the lithium source is 1:2 to 1:2.2.

[0018] More preferably, the reaction time of the second step is 36 to 48 h.

[0019] 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, and the concentration of the lithium source solution is 0.01 to 0.02 g / mL.

[0020] Furthermore, the extracting agent in the second and third steps is one or more of diethyl ether, isopropyl ether, acetone, butanone, and ethyl acetate.

[0021] Furthermore, the aprotic solvent 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).

[0022] More preferably, the reaction temperature in the third step is 110-125° C., and the reaction time is 12-16 h.

[0023] Furthermore, the concentration of lithium tetraaminoxime in the aprotic solvent is 0.01 to 0.02 g / mL.

[0024] The third aspect of the present invention provides the use of the conjugated extended lithium-containing organic cathode material in a lithium-ion battery. The negative electrode uses metallic lithium or graphite, the electrolyte uses 3M LiTFSI, the solvent is tetraethylene glycol dimethyl ether, and the separator uses Celgard 2400.

[0025] This invention focuses on the development of novel organic energy storage materials, preparing polyoxime lithium (Li_pTAPO) organic molecules. Using a multidimensional molecular engineering strategy, centered around the active functional groups of lithium oxime, this method utilizes collaborative innovation to precisely control lithiation sites, optimizing the material's electronic conduction and lithium-ion diffusion properties. This breakthrough addresses the technological barriers of traditional organic materials and supports a new generation of lithium-based organic energy storage devices. This invention proposes a lithiated organic cathode material based on lithium oxime, as well as its preparation and application. The innovations are twofold: first, pre-lithiation allows the organic material to contain lithium, eliminating dependence on external lithium sources and avoiding the problem of lithium dendrites, improving battery safety, simplifying the preparation process, reducing costs, and boosting the initial coulombic efficiency. Second, structural stability is achieved. Through molecular design and synthetic strategies, π-π conjugation extension and molecular weight increase are achieved, optimizing the benzene ring-pyrazine system, achieving dual optimization of electronic and ionic conduction, improving conductivity and rate capability, and ensuring long-term stable battery operation. This invention is committed to the research and development of new lithium-containing organic energy storage materials, the preparation of excellent performance polyoxime lithium organic molecules and high-performance lithium-containing organic positive electrode materials, providing support for the new generation of lithium-based organic energy storage devices, which can be applied to fields such as smart grids and are expected to promote energy storage technology and energy transformation.

[0026] Advantages and beneficial effects of the present invention:

[0027] 1. Advantages of pre-lithiation

[0028] Get rid of dependence on external lithium sources: through chemical treatment, it contains lithium itself, without relying on external lithium sources such as metallic lithium negative electrodes or lithium supplements.

[0029] Improve battery safety: Avoid the lithium dendrite problem caused by using external lithium sources and improve battery safety.

[0030] Simplify the preparation process and reduce costs: It can be directly combined with commercial graphite negative electrodes to form a full battery, simplifying the preparation process and reducing manufacturing costs.

[0031] Improve initial coulombic efficiency: The pre-lithiation compensation mechanism effectively improves the initial coulombic efficiency of the battery and ensures efficient operation of the battery.

[0032] 2. Advantages of structural stability

[0033] π-π conjugation extension and molecular weight improvement: Through molecular design and synthesis strategies, π-π conjugation extension and molecular weight improvement are achieved.

[0034] Dual conduction optimization: Optimize and expand the benzene ring-pyrazine system to achieve dual optimization of electron and ion conduction.

[0035] Multiple performance enhancements: Improved material conductivity, enhanced rate performance, solubility resistance, high temperature stability and cycle life, ensuring long-term stable operation of the battery.

[0036] 3. Application value advantages

[0037] Applicable to energy storage needs in smart grids and other fields: Provide strong support for the new generation of lithium-based organic energy storage devices, especially suitable for smart grids, renewable energy storage and other fields, and promote the development of energy storage technology and energy transformation.

[0038] Environmentally friendly and cost-effective: As an organic cathode material, it has the advantages of easy access to raw materials, low cost, and environmental friendliness. It is more sustainable than traditional inorganic cathode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the synthesis route of Li_pTAPO of the present invention (oximation-lithiation-condensation);

[0040] Figure 2 IR spectra and local magnifications of TABQ, TAPO, Li_TAPO, and Li_pTAPO, with the right side showing the local magnification of the left side.

[0041] Figure 3 is the Li_pTAPO Raman spectrum;

[0042] Figure 4 for 7 Li-ssNMR spectra (lithium source MeOLi, Li_TAPO, Li_pTAPO);

[0043] Figure 5 is the XRD spectrum of Li_pTAPO;

[0044] Figure 6 is the SEM image of Li_pTAPO;

[0045] Figure 7 The Li_pTAPO cathode material prepared in Example 1 (lithiation followed by condensation) was applied to lithium-ion batteries. -1 Charge and discharge curves under current density;

[0046] Figure 8 The Li_pTAPO' cathode material prepared in Comparative Example 1 (condensation followed by lithiation) was applied to lithium-ion batteries. -1 Charge and discharge curves at different current densities. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the scope of protection of the present invention cannot be limited thereto. Example

[0048] A method for preparing a conjugated extended lithium-containing organic positive electrode material, comprising:

[0049] In the first step, under an inert atmosphere, tetraaminobenzoquinone (TABQ) was dispersed in ethanol at a TABQ concentration of 0.01 g / mL and transferred to a reaction vessel. Hydroxylamine hydrochloride (NH₂OH·HCl) was dissolved in ethanol at a molar ratio of M(TABQ): M(NH₂OH·HCl) = 1:2.2 to a concentration of 0.01 g / mL. Using a constant pressure dropping funnel, the hydroxylamine hydrochloride solution was slowly added dropwise to the TABQ ethanol dispersion. The reaction was carried out at 75°C for 6 h. After the reaction system was cooled to room temperature, the product was washed with deionized water, and the resulting solid was freeze-dried at -40°C for 24 h to produce tetraaminoparaoxime (TAPO).

[0050] In the second step, continuing under an inert atmosphere, the resulting TAPO and lithium methoxide (MeOLi) were added to methanol at a molar ratio of M(TAPO):M(MeOLi) = 1:2.1. After stirring at room temperature for 48 hours, diethyl ether was added to the solution to cause precipitation. The precipitate was filtered, rinsed repeatedly with diethyl ether, and finally dried to obtain lithium tetraaminoparaoxime (Li_TAPO).

[0051] In the third step, also under an inert atmosphere, 0.5 g of the Li_TAPO obtained in the second step was dissolved in 50 mL of dimethyl sulfoxide (DMSO). The reaction was stirred at 125°C for 12 h. After the reaction system cooled to room temperature, acetone was added to precipitate. The precipitate was rinsed with acetone multiple times, filtered, and dried to obtain the conjugated extended lithium-containing organic cathode material (Li_pTAPO).

[0052] Figure 2The infrared spectra of TABQ, TAPO, Li_TAPO, and Li_pTAPO are shown. By comparison, it can be seen that the C=O bond in TABQ disappears after the oximation reaction and is replaced by the C=N bond in the oxime. This bond is also retained after the lithiation and polycondensation reactions. In addition, the C=N bond at about 3200 cm -1 The -OH peak intensity at 370 nm weakened significantly after lithiation, indicating that the lithiation process eliminated the hydroxyl groups.

[0053] Figure 3 Raman spectrum showed characteristic peaks corresponding to the structural formula of Li_pTAPO.

[0054] Figure 4 7 The Li-ssNMR spectra involve the lithium source MeOLi, Li_TAPO, and Li_pTAPO. The chemical shift of Li_pTAPO continuously shifts downfield (δ = 0.72 ppm), indicating that after the lithium ion is separated from the lithium methoxide, it coordinates with the oxime group. Subsequently, Li_TAPO condenses to form Li_pTAPO, building a continuous conjugated network that reduces the lithium ion electron cloud density and enhances the deshielding effect.

[0055] Figure 5 The XRD spectrum of Li_pTAPO is shown, from which it can be seen that the material is basically amorphous.

[0056] Figure 6 The SEM image of Li_pTAPO is shown, from which it can be seen that the material is a block without a fixed structure.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that the second and third steps are swapped, and the condensation reaction is carried out first, and then the lithiation reaction is carried out.

[0059] The first step is the same as in Example 1;

[0060] In the second step, continuing the process under an inert atmosphere, 0.5 g of the resulting TAPO was dissolved in 50 mL of dimethyl sulfoxide (DMSO). The reaction was stirred at 125°C for 12 h. After the reaction system cooled to room temperature, acetone was added to precipitate. The precipitate was rinsed with acetone several times, filtered, and dried to obtain the conjugated extended polyoxime material (pTAPO').

[0061] In the third step, also under an inert atmosphere, the resulting pTAPO' and lithium methoxide (MeOLi) were added to methanol at a molar ratio of M(TAPO):M(MeOLi) of 1:2.1. After stirring at room temperature for 24 hours, diethyl ether was added to the solution to cause precipitation. The precipitate was filtered, rinsed repeatedly with diethyl ether, and finally dried to obtain lithium tetraaminoparaoxime (Li_pTAPO').

[0062] The electrode sheet preparation work was carried out in a glove box (water ≤ 0.01 ppm, oxygen ≤ 0.01 ppm). First, the Li_pTAPO synthesized in Example 1 and the Li_pTAPO' synthesized in Comparative Example 1 were respectively ground and mixed with Ketjen black (KB) and polyvinylidene fluoride (PVDF) in a mass ratio of 6:3:1. Next, 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 doctor blade process. After coating, the aluminum foil current collector with the slurry coating was placed on a heating table and dried at a temperature of 110 ° C. Finally, after the drying process is completed, the electrode sheet is cut into positive electrode sheets for subsequent battery testing.

[0063] In a glove box, where oxygen and moisture concentrations do not exceed 0.01 ppm, button cell assembly tests were carried out. 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, solvent is tetraethylene glycol dimethyl ether) is added dropwise, and the pre-prepared positive electrode sheet is placed on the separator. Subsequently, a gasket and a spring 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 assembly, 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.

[0064] 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 of the battery is about 260 mAh·g -1 However, the Li_pTAPO' prepared in Comparative Example 1 by condensation followed by lithiation has almost no electrochemical performance.

[0065] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention.

Claims

1. A conjugated extended lithium-containing organic cathode material, characterized in that: The structure is as follows: In the structural formula, n is 2~5.

2. The method for preparing a conjugated extended lithium-containing organic cathode material according to claim 1, wherein: The steps include: Step 1: Synthesis of tetraaminoparaoxime Under an inert atmosphere, add hydroxylamine hydrochloride solution dropwise to tetraaminobenzoquinone dispersion, react at 65-95°C for 6-12 hours, cool to room temperature, wash the product, and freeze-dry to obtain tetraaminobenzoquinone, whose structure is: Step 2: Synthesis of lithium tetraaminoparaoxime Under an inert atmosphere, the tetraaminoparaoxime prepared in the first step is added to a lithium methoxide solution. After stirring at room temperature for 24 to 48 hours, an extractant is added to the solution to precipitate. The precipitate is filtered, rinsed with the extractant, and dried to obtain lithium tetraaminoparaoxime, whose structure is: Step 3: Synthesis of conjugated extended lithium-containing organic cathode materials Under an inert atmosphere, the lithium tetraaminoparaoxime prepared in the second step is dissolved in an aprotic solvent and reacted at 100-130°C with stirring for 12-24 hours. After cooling to room temperature, an extractant is added to the solution to precipitate, which is then rinsed with the extractant, filtered, and dried to obtain a conjugated extended lithium-containing organic cathode material.

3. The method for preparing a conjugated extended lithium-containing organic cathode material according to claim 2, wherein: The molar ratio of hydroxylamine hydrochloride to tetraaminobenzoquinone is 2:1 to 2.5:

1.

4. The method for preparing a conjugated extended lithium-containing organic cathode material according to claim 2, wherein: The solvent of the hydroxylamine hydrochloride solution and the tetraaminobenzoquinone dispersion in the first step are the same, both of which are methanol, ethanol or a mixed solvent of alcohol and water. The concentration of the hydroxylamine hydrochloride solution is 0.01 ~ 0.02 g / mL, and the concentration of the tetraaminobenzoquinone dispersion is 0.01 ~ 0.02 g / mL.

5. The method for preparing a conjugated extended lithium-containing organic cathode material according to claim 2, wherein: The freeze-drying temperature in the first step is -20 to -40°C, and the freeze-drying time is 12 to 24 hours.

6. The method for preparing a conjugated extended lithium-containing organic cathode material according to claim 2, wherein: In the second step, the molar ratio of tetraaminoparaoxime to lithium methoxide is 1:2 to 1:2.

2.

7. The method for preparing a conjugated extended lithium-containing organic cathode material according to claim 2, wherein: The solvent of the lithium methoxide solution in the second step is one or more of methanol, ethanol, tert-butanol, and tetrahydrofuran, and the concentration of the lithium methoxide solution is 0.01 to 0.02 g / mL.

8. The method for preparing a conjugated extended lithium-containing organic cathode material according to claim 2, wherein: The extracting agent in the second and third steps is one or more of ether, isopropyl ether, acetone, butanone and ethyl acetate.

9. The method for preparing a 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, and dimethyl sulfoxide.

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

Images