Redox-active organic polymers for lithium-ion battery cathode materials and their preparation methods

Abstract

This invention belongs to the field of lithium-ion battery cathode material synthesis, and relates to redox-active organic polymer materials, their preparation methods, and applications. N,N-diamino-1,4,5,8-naphthalenetetraimide is subjected to a dehydration condensation reaction with hexaazabenzphenanthrene hexacarboxylic acid trianal. After the reaction, the mixture is washed with deionized water, centrifuged, and vacuum dried to obtain a redox-active organic polymer. Button-type lithium-ion batteries prepared using this polymer as a cathode material exhibit high specific capacity, good rate performance, and excellent cycle stability. Therefore, this type of organic polymer material has broad application prospects in the field of lithium-ion batteries. The synthesis method of the material in this invention is simple, the raw materials are abundant, and the reproducibility is good, making it suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrode material synthesis, and specifically relates to an organic polymer with redox activity for lithium-ion battery cathode materials and its preparation method. Background Technology

[0002] With societal progress and the development of science and technology, energy demand is gradually increasing, and the energy crisis is becoming increasingly severe. Over-reliance on fossil fuels has already caused catastrophic consequences such as global warming and environmental degradation. The world's energy system must shift from non-renewable fossil fuels to low-carbon and multi-energy integration. How to fully develop and efficiently utilize clean energy to achieve carbon emission reduction has become a common concern for countries worldwide. In recent years, high-efficiency electrochemical energy storage devices have received increasing attention and had a significant impact on the scientific and industrial communities. Lithium-ion batteries (LIBs), with their high energy density, wide operating temperature range, and excellent cycle stability, have become the most widely used energy storage technology in portable electronic products.

[0003] Lithium-ion batteries represent the cutting edge of battery technology, and numerous studies are underway, dedicated to discovering new materials to improve performance. Among these, inorganic materials such as transition metal oxides, metal alloys, phosphates, and silicates are widely used in the cathodes of lithium-ion batteries. However, from a sustainable development perspective, these electrode materials suffer from relatively low theoretical capacities; for example, the theoretical capacity of LiMn₂O₄ is only 147 mAh g⁻¹. -1 The theoretical capacity of LiFePO4 is 170 mAh g. -1 Furthermore, the limited availability of raw materials in nature and the environmental pollution caused by heavy metals make them unsuitable for future needs. Compared to inorganic materials, organic electrode materials derived from nature are abundant, environmentally friendly, structurally designable, and safe. Therefore, in recent decades, many researchers have focused on organic cathode materials with redox groups, which offer advantages such as strong functional designability, environmental friendliness, and low cost. However, many organic electrode materials suffer from problems such as easy solubility in electrolytes, low conductivity, and low ion mobility, thus limiting their development. For example, in 2013, Chen Jun et al. designed a high-capacity carbonyl compound C4Q, which, when used as a lithium battery cathode, provided 431 mAh g⁻¹ in liquid electrolyte. −1 It exhibited a high capacity of 96.6% of its theoretical capacity, but at 0.2C, due to the dissolution of C4Q, only about 100 mAh g was retained after five cycles. −1 ( Angew Chem Int Ed,2013, 52(35): 9162-9166). To resist dissolution, the polymerization of small molecules with redox activity is considered an effective method. In 2021, Mohamed et al. first synthesized a conjugated microporous polymer, TPE-A-CMP, coupled with 2,6-dibromoanthraquinone (A-Br2) and tetraethyltetraphenyl (TPE-T) units. Due to the presence of active C=O groups, insolubility in electrolytes, and highly conjugated structure, TPE-A-CMP provides 163.6 mAh g⁻¹ at 0.1 C as a cathode material for lithium-ion batteries. -1 High discharge capacity and excellent cycle performance ( ACS Applied Energy Materials 2021, 4(12): 14628-14639).

[0004] Given that polymerizing small molecules is a very effective way to resist the dissolution of organic electrodes, researching such polymers as cathode materials for lithium-ion batteries is expected to lead to the discovery of organic cathode materials with high capacity and excellent cycle performance, thereby promoting the application and development of high-performance lithium batteries. Summary of the Invention

[0005] The purpose of this invention is to provide an organic polymer material with redox activity and its preparation method, and to test its performance as a cathode material for lithium-ion batteries.

[0006] This invention provides an organic polymer material with redox activity for use as a cathode material in lithium-ion batteries, wherein the structural formula of the organic polymer with redox activity is:

[0007] DNHH-polymer:

[0008] .

[0009] Specifically, DNHH-polymer is an organic polymer material with redox activity generated by the reaction of N,N-diamino-1,4,5,8-naphthalenetetraimide (DNTCB) and hexaazabenzophenanthrene hexacarboxylic trihydride (HHAT).

[0010] The present invention also provides a method for synthesizing the above-mentioned compound: the synthesis is carried out using a thick-walled reaction flask via a solvothermal method.

[0011] The synthetic reaction equations involved in this invention are as follows:

[0012]

[0013] The specific solvothermal synthesis method involves adding N,N-diamino-1,4,5,8-naphthalenetetraimide, hexaazabenzphenanthrene hexacarboxylic acid trihydride, and an organic solvent to a thick-walled reaction flask. After thorough dissolution and uniform dispersion, a dehydration condensation reaction is carried out via solvothermal method. After the reaction is completed and cooled to room temperature, the mixture is filtered, washed 2-3 times with deionized water, and dried under vacuum to obtain the product, which is the DNHH-polymer.

[0014] The molar ratio of N,N-diamino-1,4,5,8-naphthalenetetraimide and hexaazabenzophenanthrene hexacarboxylic acid trihydride is 1.5:1-1.6:1.

[0015] The reaction solvent is N,N-dimethylformamide or 1-methyl-2-pyrrolidone, and the volume of the solvent is controlled at 20-30 mL, generally not exceeding 2 / 3 of the volume of the thick-walled reaction flask. The concentration of N,N-diamino-1,4,5,8-naphthalenetetraimide in the organic solvent is controlled at 50-75 mmol / L. The reaction temperature for the dehydration condensation reaction is 120-165°C. The reaction time is 2-5 days.

[0016] After the reaction was completed, the mixture was cooled to room temperature and filtered through a sintered sand funnel. It was then washed 2-3 times with deionized water and dried under vacuum to obtain the organic polymer material with redox activity.

[0017] The aforementioned organic polymer materials with redox activity are used as cathode materials for lithium-ion batteries.

[0018] Furthermore, an electrode sheet made of an organic polymer material with redox activity was used as the positive electrode, lithium foil as the negative electrode, and porous polypropylene as the separator. (1.0 mol L) -1 LiTFSI was dissolved in a 1:1 (V:V) mixture of DME (dimethoxyethane):DOL (1,3-dioxolane) + 1 wt% LiNO3 as the electrolyte to assemble a coin cell.

[0019] The electrode sheet is prepared by mixing and grinding DNHH-polymer, battery conductive agent and binder in a mass ratio of 30%:60%:10%-60%:30%:10%. After adding an appropriate amount of dispersant (such as 1-methyl-2-pyrrolidone) and grinding again, it is uniformly coated on the current collector and vacuum dried to form the electrode sheet.

[0020] Compared with the prior art, the features of this invention are:

[0021] The redox-active organic polymer material of this invention has a simple, easy-to-operate, low-cost, readily available raw materials, good reproducibility, and excellent performance. When used as a cathode material for lithium-ion batteries, it exhibits high specific capacity and excellent cycle stability. The DNHH-polymer at 0.05 A g... -1 The specific capacity is 224.5 mAh g. -1 At 0.05 Ag -1 The capacity retention rate after 500 cycles is 60.9%, which is an improvement over traditional inorganic materials and some organic polymer materials. The redox-active organic polymer material of this invention not only solves the problem of small organic molecules dissolving in the electrolyte, but also exhibits high stability. As a novel type of lithium-ion battery cathode material, the redox-active organic polymer material of this invention possesses high discharge specific capacity, long-term cycle stability, and good rate performance, showing broad application prospects in the field of lithium-ion battery electrode materials. Attached Figure Description

[0022] Figure 1 Here is a structural diagram of the DNHH-polymer material;

[0023] Figure 2 The NMR spectrum of the DNHH-polymer material is shown below.

[0024] Figure 3 The image shows the C-NMR spectrum of the DNHH-polymer material.

[0025] Figure 4 The infrared spectrum of the DNHH-polymer material is shown below.

[0026] Figure 5 The image shows the Raman spectrum of the DNHH-polymer material.

[0027] Figure 6 Thermogravimetric curve of the DNHH-polymer material;

[0028] Figure 7 The graph shows the nitrogen adsorption-desorption and pore size distribution of the DNHH-polymer material.

[0029] Figure 8 Cyclic voltammetry of DNHH-polymer coin cells at different scan rates;

[0030] Figure 9 The rate performance diagram of the DNHH-polymer coin cell is shown.

[0031] Figure 10 The charge-discharge curves of the DNHH-polymer material at different current densities are shown.

[0032] Figure 11 The material DNHH-polymer coin cell is used in 0.05 A g. -1 Cyclic stability plot at current density;

[0033] Figure 12 This is the AC impedance diagram of a DNHH-polymer coin cell. Detailed Implementation

[0034] The present invention will be further described below through specific embodiments. Example 1

[0035] 30 mL of N,N-dimethylformamide (DMF) was added to a 48 mL thick-walled reaction flask, along with N,N-diamino-1,4,5,8-naphthalenetetraimide (2.25 mmol, 0.668 g) and hexaazabenzophenanthrene hexacarboxylic acid trihydride (1.5 mmol, 0.6663 g) (purchased from Maclean). After thorough dissolution and dispersion, the thick-walled reaction flask was subjected to vacuum treatment and kept at 125 °C for 4 days. After the reaction was completed, the mixture was washed three times with deionized water, and the solid was collected by filtration and dried under vacuum at 100 °C for 12 h to obtain the redox-active organic polymer material DNHH-polymer, with a yield of 45%.

[0036] DNHH-polymer was used as the active material for the positive electrode, and mixed with acetylene black and PVDF binder in a certain ratio. The ratio of DNHH-polymer:acetylene black:PVDF binder was 30%:60%:10% (mass ratio). After mixing and grinding for 2 hours, an appropriate amount of 1-methyl-2-pyrrolidone (NMP) was added and grinding was repeated for 0.5 hours. The mixture was then uniformly coated onto an aluminum foil sheet with an area of ​​1×1 cm and vacuum dried overnight at 80 °C to form an electrode sheet. This electrode sheet was used as the positive electrode, a lithium sheet as the negative electrode, and porous polypropylene (Hangzhou Chuangwei Rubber & Plastics Technology Co., Ltd., hereinafter the same) as the separator. 1.0 mol L -1 LiTFSI was dissolved in a 1:1 (V:V) mixture of DME (dimethoxyethane):DOL (1,3-dioxolane) + 1 wt% LiNO3 as the electrolyte to assemble a coin cell, and its electrochemical performance was investigated. Figure 8 Cyclic voltammetry of a coin cell at different scan rates; Figure 9 This is a rate stability graph for coin cells. Figure 10 The graphs show the charge-discharge curves of a coin cell at different current densities, starting at 0.05 A g. -1 The capacity can reach 228.5 mAh g. -1 , in 2 A g -1 The capacity is still 44.5 mAh g. -1 ; Figure 11The graph shows the cycle stability of the coin cell, with a capacity retention of 60.9%. Example 2

[0037] The experimental method was the same as in Example 1, except that the reaction conditions of holding at 125 °C for 4 days were changed to holding at 140 °C for 3 days, and the material DNHH-polymer was obtained with a yield of 40%. Example 3

[0038] The experimental method was the same as in Example 1, except that the reaction conditions of holding at 125 °C for 4 days were changed to holding at 160 °C for 2 days, and the material DNHH-polymer was obtained with a yield of 42%. Example 4

[0039] The experimental method was the same as in Example 1, except that the reaction conditions were changed from vacuum treatment of the thick-walled reaction flask to evacuation followed by nitrogen gas purging, thus obtaining the material DNHH-polymer with a yield of 43%. Example 5

[0040] The experimental method was the same as in Example 1, except that the reaction conditions were changed from adding 30 mL of N,N-dimethylformamide (DMF) to adding 30 mL of 1-methyl-2-pyrrolidone (NMP), thus obtaining the material DNHH-polymer with a yield of 43%.

[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. The application of an organic polymer material with redox activity in the cathode material of lithium-ion batteries, characterized in that, The structural formula of the organic polymer material with redox activity is as follows: 。 2. The application of the redox-active organic polymer material according to claim 1, characterized in that, Application method: the electrode sheet of organic polymer material with oxidation-reduction activity is prepared as the positive electrode, lithium foil as the negative electrode, porous polypropylene as the separator, 1.0 mol L -1 LiTFSI is dissolved in V:V=1:1 dimethoxyethane DME:1,3-dioxolane + 1 wt% LiNO3 as electrolyte, and assembled into a button cell.

3. The application of the redox-active organic polymer material according to claim 2, characterized in that, The positive electrode sheet is prepared by mixing and grinding an organic polymer with oxidation-reduction activity, a battery conductive agent, and a binder, adding a dispersant and grinding again, then uniformly coating it onto a current collector and vacuum drying to form an electrode sheet.

4. The application of the redox-active organic polymer material according to claim 1 in the cathode material of lithium-ion batteries, characterized in that, The method for preparing the redox-active organic polymer material uses N,N-diamino-1,4,5,8-naphthalenetetraimide and hexaazabenzophenanthrene hexacarboxylic acid trihydride as raw materials, and synthesizes them using a solvothermal method in a thick-walled reaction flask.

5. The application of the redox-active organic polymer material according to claim 4 in the cathode material of lithium-ion batteries, characterized in that, The specific steps of the preparation method are as follows: N,N-diamino-1,4,5,8-naphthalenetetraimide, hexaazabenzphenanthrene hexacarboxylic acid trihydride and organic solvent are added to a thick-walled reaction flask. After being fully dissolved and dispersed evenly, a dehydration condensation reaction is carried out by a solvothermal method. After the reaction is completed and cooled to room temperature, the mixture is filtered, washed 2-3 times with deionized water, and dried under vacuum to obtain the product, which is an organic polymer with redox activity.

6. The application of the redox-active organic polymer material according to claim 5 in the cathode material of lithium-ion batteries, characterized in that, The molar ratio of N,N-diamino-1,4,5,8-naphthalenetetraimide to hexaazabenzophenanthrene hexacarboxylic acid trihydride is 1.5:1-1.6:

1.

7. The application of the redox-active organic polymer material according to claim 5 in the cathode material of lithium-ion batteries, characterized in that, The organic solvent is N,N-dimethylformamide or 1-methyl-2-pyrrolidone.

8. The application of the redox-active organic polymer material according to claim 5 in the cathode material of lithium-ion batteries, characterized in that, The concentration of N,N-diamino-1,4,5,8-naphthalenetetraimide in organic solvents is 50-75 mmol / L.

9. The application of the redox-active organic polymer material according to claim 5 in the cathode material of lithium-ion batteries, characterized in that, The dehydration condensation reaction is carried out at a temperature of 120-165°C for 2-5 days.

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