D-a type spiro-florentine-based conjugated polymer electrode material with excellent cycle stability

Abstract

A D-A type spirofluorene-based conjugated polymer electrode material with excellent cycle stability relates to the technical field of lithium ion battery organic electrode materials, and a D-A type organic spirobifluorene-dibenzothiophene sulfone conjugated polymer lithium ion battery positive electrode material with excellent cycle stability is synthesized, wherein spirobifluorene is used as an electron donor unit, and dibenzothiophene sulfone is used as an electron acceptor unit.The beneficial effects of the present application are that when the material is used as a lithium ion battery positive electrode, it exhibits excellent cycle stability and rate performance, and the capacity retention rate is 114.2% after 2500 cycles at 0.5 Ag ‑1 current.

Description

Technical Field

[0001] This invention relates to the field of organic electrode materials for lithium-ion batteries, specifically to a DA-type spirofluorene-based conjugated polymer electrode material with excellent cycle stability. Background Technology

[0002] Lithium-ion batteries have become an indispensable part of various consumer electronic devices such as smartphones, laptops, watches, and tablets. Finding new electrode materials is an urgent task in manufacturing the next generation of high-performance lithium-ion batteries to meet the growing demands of various consumer electronic devices.

[0003] Traditional lithium-containing transition metal oxide cathode materials suffer from limitations such as theoretical specific capacity, poor cycle performance due to SEI instability, and poor rate performance due to low electronic conductivity, which restricts their development. In the search for novel lithium-ion battery cathode materials, organic electrode materials have attracted increasing attention due to their advantages such as low cost, high theoretical capacity, structural diversity, environmental friendliness, and ease of synthesis, and are expected to become the preferred high-performance cathode materials for next-generation rechargeable lithium-ion batteries.

[0004] Among them, conjugated donor-acceptor (DA) polymers, due to the strong electronic interaction between the donor and acceptor, exhibit low redox potentials, which is beneficial for improving power density and makes them suitable as cathode materials for lithium-ion batteries. Therefore, designing commercially viable DA polymers with good rate performance and excellent cycle stability is an important research direction in the field of organic lithium-ion battery electrodes. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention constructs a DA-type spirofluorene-based conjugated polymer electrode material with excellent cycle stability, which is applied to lithium-ion battery cathode materials and exhibits excellent cycle stability and rate performance.

[0006] This invention provides a DA-type spirofluorene-based conjugated polymer electrode material with excellent cycling stability, using spirodifluorene as the electron donor unit and dibenzothiophene sulfone as the electron acceptor unit. Its molecular structure is as follows:

[0007]

[0008] In the formula: m:n = 1:8.

[0009] The synthetic route for the DA-type spirofluorene-based conjugated polymer, namely compound 1, is as follows:

[0010]

[0011] In the formula: m:n = 1:8.

[0012] The DA-type spirofluorene-based conjugated polymer, namely compound 1, is prepared by the following method:

[0013] Step 1: Under anaerobic conditions, 3,7-dibromo-dibenzothiophene sulfone, 3,7-diboronate-dibenzothiophene sulfone, 2,2',7,7'-tetrabromo-9,9'-spirodifluorene, catalyst, and anhydrous potassium carbonate were dissolved in a mixed solution of degassed N,N-dimethylformamide and water. The mixture was heated to 130°C and reacted for 48 hours. After cooling to room temperature, the mixture was filtered to obtain an insoluble solid product.

[0014] Step 2: The insoluble solid product is washed with water, methanol, dichloromethane, tetrahydrofuran and acetone in turn to remove low molecular weight compounds and residual palladium catalyst.

[0015] Step 3: The product obtained from washing in step 2 is extracted with tetrahydrofuran solvent using a Soxhlet extractor for 48 hours. The product is then vacuum dried at 60°C for 24 hours to obtain a yellow-green powdery solid, which is the DA-type spirofluorene conjugated polymer.

[0016] The catalyst is described as follows: the molar ratio of tetra(triphenylphosphine)palladium to 2,2',7,7'-tetrabromo-9,9'-spirodifluorene is 8.7:100; the molar ratio of 3,7-dibromo-dibenzothiophene sulfone, 3,7-diboronate-dibenzothiophene sulfone, and 2,2',7,7'-tetrabromo-9,9'-spirodifluorene is 3:5:1; the molar amount of potassium carbonate used is 60 times that of 2,2',7,7'-tetrabromo-9,9'-spirodifluorene; and the volume ratio of N,N-dimethylformamide to water is 16:3.

[0017] The DA-type spirofluorene-based conjugated polymer electrode material has a nanosheet structure.

[0018] The process of applying the DA-type spirofluorene-based conjugated polymer to the positive electrode material of lithium-ion batteries is as follows: an organic spirofluorene-dibenzothiophene sulfone conjugated polymer, conductive carbon black and binder carboxymethyl cellulose (CMC) are mixed in a ratio of 6:3:1 to form a slurry, which is then coated on copper foil to successfully prepare an electrode sheet. The electrode sheet is then assembled with a lithium sheet to form a half-cell.

[0019] The polymer electrode material exhibits excellent cycle stability in batteries assembled with lithium sheets, maintaining 114.2% of the battery capacity after 2500 cycles at a current density of 500 mAg⁻¹.

[0020] When the polymer is used as the positive electrode of a lithium-ion battery, it exhibits a reversible capacity of 342.7 mAh g⁻¹ at a current density of 1 A g⁻¹.

[0021] The DA-type spirofluorene-based conjugated polymer can be used as a positive electrode material for recyclable polymer batteries.

[0022] The DA-type spirofluorene-based conjugated polymer can also be used as a positive electrode material in sodium, potassium, zinc, magnesium, aluminum, and calcium ion batteries.

[0023] The principle of applying the DA-type spirofluorene-based conjugated polymer electrode material with excellent cycle stability to the positive electrode material of lithium-ion batteries is as follows: (1) Since the polymer uses spirodifluorene as the electron donor unit (D) and dibenzothiophene sulfone as the electron acceptor unit (A), electrons can migrate in the DA polymer to form delocalized conduction electrons. (2) As an electrode material, due to the strong electron interaction between the donor and acceptor, it has a low redox potential, which is beneficial to improving the power density of the battery. (3) As an electrode material, the DA-type polymer has multiple reactive active sites, and there is a gradual activation process during charging and discharging. After the capacity continues to rise, it tends to stabilize.

[0024] The beneficial effects of this invention are as follows: Compared with existing organic polymer lithium-ion battery electrode materials, this application utilizes a DA-type polymer structure, which effectively improves the cycle performance of the electrode material. When the polymer is used as the positive electrode of a lithium-ion battery, at 1Ag... -1 At a current density of 342.7 mAh g, it exhibits a current density of 342.7 mAh g. -1 Reversible capacity. At 0.5 Ag -1 At the specified current density, the battery capacity retention rate was 114.2% after 2500 charge-discharge cycles, demonstrating excellent cycle stability. This organic polymer material can be used as a cathode material for lithium-ion batteries and has broad application prospects in long-life energy storage devices. Attached Figure Description

[0025] Figure 1 This is a 5000x scanning electron microscope image of compound 1;

[0026] Figure 2 This is a 20,000x scanning electron microscope image of compound 1.

[0027] Figure 3 The infrared spectrum of compound 1 was obtained experimentally.

[0028] Figure 4 The powder diffraction pattern of compound 1 was obtained experimentally.

[0029] Figure 5 The solid-state NMR spectrum of compound 1 was experimentally measured.

[0030] Figure 6 Cyclic voltammetry curves of a half-cell assembled with compound 1 and lithium foil, scan rate 0.1 mV / s. -1 ;

[0031] Figure 7 The galvanostatic charge-discharge curves of the half-cell assembled with compound 1 and lithium foil are shown, with a current density of 500 mAg. -1 ;

[0032] Figure 8 Cycle stability testing of a half-cell assembled with compound 1 and lithium foil was performed at a current density of 500 mAg. -1 Repeat 2500 times;

[0033] Figure 9 The rate performance curves of half-cells assembled with compound 1 and lithium foil are shown, with current densities of 50, 100, 200, 300, 500, and 1000 mAg. -1 ;

[0034] Figure 10 The non-in-situ paramagnetic resonance spectrum of the half-cell assembled with compound 1 and lithium sheet. Detailed Implementation

[0035] The following specific embodiments are intended to further illustrate the present invention, but these specific embodiments do not limit the scope of protection of the present invention in any way.

[0036] Example 1: A DA-type spirofluorene-based conjugated polymer electrode material with excellent cycle stability, the structural formula of which is:

[0037]

[0038] In the formula: m:n = 1:8.

[0039] In Example 2, under anaerobic conditions, 3,7-dibromo-dibenzothiophene sulfone (0.112 g, 0.30 mmol), 3,7-diboronate-dibenzothiophene sulfone (0.234 g, 0.50 mmol), 2,2',7,7'-tetrabromo-9,9'-spirodifluorene (0.0632 g, 0.10 mmol), tetrakis(triphenylphosphine)palladium (0.0125 g, 8.7 μmol), and anhydrous potassium carbonate (0.830 g, 6.0 mmol) were dissolved in a mixture of degassed N,N-dimethylformamide (16 mL) and water (3 mL), and the mixture was heated to 130 °C and reacted for 48 hours. After cooling to room temperature, the mixture was filtered to obtain an insoluble solid. The solid product was washed with water, methanol, dichloromethane, tetrahydrofuran, and acetone to remove residual palladium catalyst. The product was then extracted with tetrahydrofuran using a Soxhlet extractor for 48 hours, and finally dried under vacuum at 60°C for 24 hours. A yellow-green powdery solid was obtained, with a yield of 0.202 g and a productivity of 98%.

[0040] Figure 1 and Figure 2The 5000x and 20000x scanning electron microscope images of compound 1 show that the polymer exhibits a sheet-like morphology. Figure 3 The infrared spectrum of compound 1 showed symmetric and asymmetric stretching vibration peaks of the O=S=O bond in the sulfone group at 1300 cm⁻¹. -1 and 1155cm -1 And the stretching vibration peak of the aromatic ring C=C at 1600 cm⁻¹ -1 about. Figure 4 The powder diffraction pattern of compound 1 shows two distinct and sharp diffraction peaks at approximately 2θ = 12.7° and 2θ = 24.5°. Figure 5 The solid-state NMR spectrum of compound 1 shows that the chemical shifts of the C atoms bonded to the sulfone group O=S=O are approximately 140 ppm, 137, 130, 124, and 122 ppm, which are the chemical shifts of the aromatic carbons on the benzothiophene sulfone and spirofluorene groups.

[0041] Example 3: The polymer prepared in Example 1 was used as the positive electrode material for a lithium-ion battery. The specific application process was as follows: an organic spirodifluorene-dibenzothiophene sulfone conjugated polymer, conductive carbon black and carboxymethyl cellulose (CMC) binder were mixed in a ratio of 6:3:1 to form a slurry, which was then coated on a copper foil to successfully prepare an electrode sheet. The electrode sheet was then assembled with a lithium sheet to form a half-cell.

[0042] Figure 6 Cyclic voltammetry curves of a half-cell assembled with compound 1 and lithium foil, scan rate 0.1 mV / s. -1 It can be seen that compound 1 does not have obvious redox peaks.

[0043] Figure 7 The galvanostatic charge-discharge curves of the half-cell assembled with compound 1 and lithium foil were obtained at a current density of 500 mAg. -1 After 1500 cycles, the capacity increased by 27%, indicating that the battery exhibits a clear process of gradual capacity increase during charging and discharging. Figure 8 Cycle stability tests of half-cells assembled with compound 1 and lithium foil were conducted at a current density of 500 mAg. -1 After 2500 cycles, the battery capacity remained at 114.2%, demonstrating excellent cycle stability. Figure 9 Rate performance curves of half-cells assembled with compound 1 and lithium foil, with current densities of 50, 100, 200, 300, 500, and 1000 mAg. -1 At a current density of 1000 mAg -1 Maintain 103mAhg -1 Reversible capacity.

[0044] Figure 10The in-situ paramagnetic resonance (PMR) spectrum of the half-cell assembled with compound 1 and lithium foil shows the formation of free radical intermediates and lithium ion insertion during discharge. As the discharge level increases, the free radical concentration increases, and the paramagnetic signal strengthens accordingly, reaching its strongest point during complete discharge. During charging, lithium ions are gradually removed, and the paramagnetic signal gradually decreases to near the open-circuit voltage level.

Claims

1. An electrode based on a DA-type spirofluorene-based conjugated polymer with excellent cycling stability, characterized in that, With spirodifluorene as the electron donor unit and dibenzothiophene sulfone as the electron acceptor unit, its molecular structure is as follows: ； In the formula: m:n = 1:

8.

2. The electrode based on a DA-type spirofluorene-based conjugated polymer with excellent cycling stability according to claim 1, characterized in that, The preparation method of the DA-type spirofluorene-based conjugated polymer includes the following steps: ； Step 1: Under anaerobic conditions, 3,7-dibromo-dibenzothiophene sulfone, 3,7-diboronate-dibenzothiophene sulfone, 2,2',7,7'-tetrabromo-9,9'-spirodifluorene, catalyst, and anhydrous potassium carbonate were dissolved in a mixed solution of degassed N,N-dimethylformamide and water. The mixture was heated to 130°C and reacted for 48 hours. After cooling to room temperature, the mixture was filtered to obtain an insoluble solid product. Step 2: The insoluble solid product is washed sequentially with water, methanol, dichloromethane, tetrahydrofuran, and acetone to remove low molecular weight compounds and residual palladium catalyst. Step 3: The product obtained from washing in step 2 is extracted with tetrahydrofuran solvent using a Soxhlet extractor for 48 hours. The product is then dried under vacuum at 60°C for 24 hours to obtain a yellow-green powdery solid.

3. The electrode based on a DA-type spirofluorene-based conjugated polymer with excellent cycling stability according to claim 2, characterized in that, The catalyst is described as follows: the molar ratio of tetra(triphenylphosphine)palladium to 2,2',7,7'-tetrabromo-9,9'-spirodifluorene is 8.7:100; the molar ratio of 3,7-dibromo-dibenzothiophene sulfone, 3,7-diboronate-dibenzothiophene sulfone, and 2,2',7,7'-tetrabromo-9,9'-spirodifluorene is 3:5:1; the molar amount of potassium carbonate used is 60 times that of 2,2',7,7'-tetrabromo-9,9'-spirodifluorene; and the volume ratio of N,N-dimethylformamide to water is 16:

3.

4. The electrode based on a DA-type spirofluorene-based conjugated polymer with excellent cycling stability according to claim 3, characterized in that, The DA-type spirofluorene-based conjugated polymer electrode material has a nanosheet structure.

5. The application of an electrode based on a DA-type spirofluorene-based conjugated polymer with excellent cycling stability according to any one of claims 1-4, characterized in that, The process of applying the DA-type spirofluorene-based conjugated polymer to lithium-ion battery anode materials is as follows: an organic spirofluorene-dibenzothiophene sulfone conjugated polymer, conductive carbon black and binder carboxymethyl cellulose are mixed in a ratio of 6:3:1 to form a slurry, which is then coated on copper foil to successfully prepare an electrode sheet. The electrode sheet is then assembled with a lithium sheet to form a half-cell.

6. The application of an electrode based on a DA-type spirofluorene-based conjugated polymer with excellent cycling stability according to claim 5, characterized in that, The DA-type spirofluorene-based conjugated polymer exhibits performance at a current density of 500 mA g in batteries assembled with lithium sheets. -1 After 2500 cycles, the battery capacity remains at 114.2%.

7. An electrode based on a DA-type spirofluorene-based conjugated polymer with excellent cycling stability according to any one of claims 1-4, characterized in that, The DA-type spirofluorene-based conjugated polymer can also be used as a negative electrode material in sodium, potassium, zinc, magnesium, aluminum, and calcium ion batteries.

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