3-(λ 1 -Aza-1-pyrazino[2,3-f][1,10]phenanthroline-diamine and its application

Abstract

The present invention discloses a 3-(λ 1 The present invention designs and synthesizes 3-(λ 1 ‑aza-pyrazino[2,3‑f][1,10]phenanthroline‑diamine, which uses the C=N bond as the redox active site, increases the density of redox active sites, and can simultaneously improve stability and specific capacity. Benefiting from its unique structure and low solubility as well as Fe 2+ / Fe 3+ The reversible redox shuttle of FCPD was realized, and the LIB with FCPD as the cathode exhibited excellent electrochemical performance, including a relatively high working potential of 3.26 V (vs. Li + / Li), at 100mAg ‑1 The lower has 240mAhg ‑1 High specific capacity, and at 1000mAg ‑1 150mAhg ‑1 High average specific capacity.

Description

Technical Field

[0001] The present invention relates to a 3-(λ 1 The invention relates to a lithium-ion battery positive electrode material and a method for using the invention to prepare a lithium-ion battery positive electrode material. Background Art

[0002] Against the backdrop of rapid industrial development around the world, people's demand for fossil fuels is increasing, leading to the depletion of limited fossil fuel energy resources and increasingly serious environmental pollution problems. Therefore, human society must seek renewable energy and clean energy to replace fossil energy. Batteries, as an energy storage system, can effectively store and convert these intermittent energy sources.

[0003] Lithium-ion batteries (LIBs) have shown great storage potential in consumer electronics due to their advantages such as high energy density, light weight, and long life. At the same time, problems such as resource scarcity and environmental pollution have forced people to develop and utilize sustainable green energy. Currently, organic polymer materials have been widely used as cathode materials for LIBs, among which redox-active small molecule organic compounds have been widely studied as promising LIB electrode materials due to their high theoretical capacity. However, severe dissolution problems and unfavorable electronic conductivity still limit their widespread application.

[0004] Bipolar materials have become a key research topic in lithium-ion battery cathode materials. Molecular structures can be tailored to the desired electrochemical properties. Therefore, the search for novel bipolar cathode materials with high specific capacity, excellent cycle stability, and high rate performance remains a challenging task. Summary of the Invention

[0005] The present invention aims to provide a 3-(λ 1 -Aza-pyrazino[2,3-f][1,10]phenanthroline-diamine (FCPD) and its application as a positive electrode material for lithium-ion batteries to solve the problems of high solubility and low conductivity.

[0006] The present invention designs and synthesizes a novel bipolar metal (FCPD) with maximized unit redox active sites through the condensation between ferrocenecarboxaldehyde (FCA) and pyrazino[2,3-f][1,10]phenanthroline-2,3. 2+ Part of it can be achieved by removing electrons from the electrolyte and combining anions (TFSI - ) and is oxidized, while the n-type C=N group can accept electrons and combine with cations (Li + ) and is restored, the theoretical capacity reaches 350mAhg -1 .

[0007] The present invention provides 3-(λ 1 -aza)pyrazino[2,3-f][1,10]phenanthroline-diamine (FCPD), the structure of which is shown below:

[0008]

[0009] The present invention designs and synthesizes a novel bipolar metal pyrrolidone (FCPD) with maximized unit redox active sites by condensing ferrocenecarboxaldehyde (FCA) and pyrazino[2,3-f][1,10]phenanthroline-2,3 (PPD), specifically comprising the following steps:

[0010] Step 1: Add 2-3 g of potassium phthalimide to N,N-dimethylformamide (DMF) and reflux at 120-160°C under protective gas for 1-2 hours. Then, slowly add 1-1.2 g of 3,4-dichloro-1,2,5-thiadiazole. Reflux the mixture for 0.3-0.6 hours and cool to room temperature. Pour the reaction mixture into water for 25-45 minutes, filter, wash with water and ether, and recrystallize from a mixture of chloroform and acetone. Next, reflux the resulting product and methylamine hydrochloride in a mixture of aqueous ammonia and N,N-dimethylformamide (DMF) at 120-160°C for 1-2 hours, cool to room temperature, remove the solution by vortexing, wash the solid with water, and dry overnight. Next, mix the resulting product and 1,10-phenanthroline-5,6-dione in ethanol, reflux at 60-80°C for 4-5 hours, and cool to room temperature to form a black solid. Finally, the black solid was stirred in aqueous ammonia to form a yellow solid, which was filtered, washed with water and ether, and dried in vacuo;

[0011] Step 2: n-BuOH is reacted at 120°C in the presence of a catalyst for 70-75h. 0.1mmol FCA and 0.1mmol PPD are added to a Pyrex tube, followed by 2-3mL n-BuOH and AcOH (0.5-1mL). Subsequently, the Pyrex tube is frozen and degassed with a liquid nitrogen bath at 70-90K. After three freeze-pump-thaw cycles, the tube is sealed under vacuum. The sealed Pyrex tube is ultrasonically treated to disperse the monomers and maintained at 120°C for 70-75h. The crude product of a reddish-brown precipitate is obtained by vacuum filtration. The reddish-brown product is washed with dimethylformamide (DMF) and acetone, and then dried in vacuo at 115-130°C.

[0012] Furthermore, in step 1, the protective gas is argon.

[0013] Furthermore, in step 1, the volume ratio of chloroform to acetone in the mixture of chloroform and acetone is 3:8.

[0014] Furthermore, in step 2, AcOH is selected as the reaction catalyst.

[0015] The present invention 3-(λ 1 The application of 2-nitro-pyrazino[2,3-f][1,10]phenanthroline-diamine is to use it as a positive electrode material for lithium-ion batteries to solve the problems of high solubility and low conductivity.

[0016] The present invention designs and synthesizes an organic cathode material, namely 3-(λ 1 -aza)pyrazino[2,3-f][1,10]phenanthroline-diamine (FCPD). This bipolar material has a C=N bond and Fe 2+ As redox active sites, increasing the density of redox active sites can improve both stability and specific capacity. Benefiting from its unique structure and low solubility as well as Fe 2+ / Fe 3+ The reversible redox shuttle of FCPD was realized, and the LIB with FCPD as the cathode exhibited excellent electrochemical performance, including a relatively high working potential of 3.26 V (vs. Li + / Li), at 100mAg -1 The lower has 240mAhg -1 High specific capacity, and at 1000mAg -1 150mAhg -1 High average specific capacity.

[0017] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0018] 1. FCPD has a unique conjugated nitrogen heterocyclic structure. The redox active sites of FCPD are C=N and Fe 2+ The experiment also verified that the FCPD redox process is highly reversible.

[0019] 2. A nanosphere with a large specific surface area was constructed. The spherical structure can provide sufficient contact paths between the electrolyte and the material, while being conducive to the transfer of ions, thereby improving the electrochemical performance of FCPD.

[0020] 3. Small molecules undergo aldehyde-ammonia dehydration condensation reaction to generate organic molecules containing Schiff base structure, which can effectively solve the solubility problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the synthesis route of FCPD of the present invention;

[0022] Figure 2 is a scanning electron microscope (SEM) image of the FCPD obtained in an embodiment of the present invention;

[0023] Figure 3 is a transmission electron microscope (TEM) image of the present invention;

[0024] Figure 4 This is a scanning electron microscope (SEM) image of the FCA in step 2 of Example 1;

[0025] Figure 5 This is a scanning electron microscope (SEM) image of PPD in step 2 of Example 1;

[0026] Figure 6 The Fourier transform infrared absorption spectra of FCPD, PPD and FCA obtained in the embodiment of the present invention are shown;

[0027] Figure 7 Thermogravimetric curves of FCPD, PPD and FCA obtained in the examples of the present invention;

[0028] Figure 8 The UV absorbance spectra of FCPD, PPD and FCA obtained in the examples of the present invention are shown;

[0029] Figure 9 The FCPD obtained in the embodiment of the present invention is 0.1mV s -1 Cyclic voltammogram of the lithium-ion battery in the first three cycles in the electrochemical window of 1.2-3.8V at the scan rate;

[0030] Figure 10 This is a graph showing the rate performance of lithium-ion batteries at different current densities using FCPD, PPD, and FCA obtained in an embodiment of the present invention;

[0031] Figure 11 FCPD, PPD and FCA obtained in the embodiment of the present invention are in the presence of 0.1Ag -1 Electrochemical cycle diagram of lithium-ion batteries under conditions;

[0032] Figure 12 FCPD, PPD and FCA obtained in the embodiment of the invention are in 1Ag -1 Electrochemical cycle diagram of lithium-ion batteries under conditions;

[0033] Figure 13 The cathode material FCPD obtained by the invention was uniformly mixed with Ketjen black (KB) and polyvinylidene fluoride (PVDF) in a molar ratio of 3:6:1 and 6:3:1 and then heated to 1Ag. -1 Electrochemical cycle diagram of lithium-ion battery under conditions.

[0034] Figure 14-16 is the X-ray photoelectron spectrum of FCPD. DETAILED DESCRIPTION

[0035] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0037] Unless otherwise specified, the reagents and materials used in the following examples can be obtained from commercial sources.

[0038] The battery performance tests in the following examples were all conducted using a Xinwei battery testing system and a Princeton electrochemical workstation.

[0039] Example 1:

[0040] Step 1: Potassium phthalimide (2.59 g, 14 mmol) was added to N,N-dimethylformamide (DMF). After reflux at 140°C under argon for 1 hour, 3,4-dichloro-1,2,5-thiadiazole (1.1 g, 7 mmol) was slowly added. The mixture was refluxed for 0.5 hour and then cooled to room temperature. The reaction mixture was poured into water for 30 minutes, then filtered, washed with water and diethyl ether, and recrystallized from a mixture of chloroform and acetone (3:8 v / v). The resulting product (pale yellow needles, 474 mg, 1.26 mmol) and methylamine hydrochloride were then refluxed in a mixture of aqueous ammonia and N,N-dimethylformamide (DMF) at 140°C for 1 hour. The mixture was cooled to room temperature, the solvent was removed by vortexing, and the solid was washed with water and dried overnight. The resulting product was then mixed with 1,10-phenanthroline-5,6-dione (173 mg, 0.8 mmol) in 30 mL of ethanol, refluxed at 70°C for 4 h, and cooled to room temperature to form a black solid. Finally, the black solid was stirred in 75 mL of aqueous ammonia to form a yellow solid, which was filtered, washed with water and diethyl ether, and dried in vacuo. The resulting product was named pyrazino[2,3-f][1,10]phenanthroline-2,3-diamine (PPD).

[0041] Step 2: A simple one-step aldehyde-ammonia dehydration condensation reaction of ferrocenecarboxaldehyde (FCA) monomer with pyrazino[2,3-f][1,10]phenanthroline-2,3-diamine (PPD) in a solvent was designed and synthesized. n-BuOH was reacted with AcOH as a catalyst at 120°C for 72 h. 21.4 mg (0.1 mmol) of FCA and 26.33 mg (0.1 mmol) of PPD were added to a Pyrex tube, followed by 2 mL of n-BuOH and 0.5 mL of AcOH. The Pyrex tube was then frozen and degassed in a liquid nitrogen bath at 77 K. After three freeze-pump-thaw cycles, the tube was sealed under vacuum. The sealed Pyrex tube was sonicated to disperse the monomer and maintained at 120°C for 72 h. The crude product was obtained by vacuum filtration as a reddish-brown precipitate. The reddish-brown product was washed with N,N-dimethylformamide (DMF) and acetone, then dried under vacuum at 120°C.

[0042] Example 2:

[0043] The positive electrode material FCPD obtained in the above example was uniformly mixed with Ketjen black (KB) and polyvinylidene fluoride (PVDF) in a molar ratio of 3:6:1 and 6:3:1, and then ground uniformly in an agate mortar to form a well-dispersed slurry. The slurry was then evenly coated on an aluminum foil current collector and dried in a vacuum oven at 100°C for 24 hours to form a working electrode. The prepared working electrode was used as the positive electrode sheet, the metal lithium sheet as the negative electrode, the separator was an organic separator, and the electrolyte was a 1M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) solution (commercially available) containing ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) (volume ratio 1:1). 2032 button cells were assembled in an argon-filled glove box and tested in the voltage range of 1.2V-3.8V vs Li / Li. + .

[0044] Comparative Example 2:

[0045] The materials FCPD, FCA, and PPD obtained in the above examples were uniformly mixed with Ketjen black (KB) and polyvinylidene fluoride (PVDF) in a molar ratio of 3:6:1, ground uniformly in an agate mortar to form a well-dispersed slurry, which was then evenly coated on an aluminum foil current collector and dried in a vacuum oven at 100°C for 24 hours to form a working electrode. The prepared working electrode was used as the positive electrode, the metal lithium sheet as the negative electrode, the separator was an organic separator, and the electrolyte was a 1M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) solution (commercially available) containing ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) (volume ratio 1:1). 2032 button cells were assembled in an argon-filled glove box and tested in the voltage range of 1.2V-3.8V vs Li / Li. + .

[0046] Figure 1 The following is a schematic diagram of the synthetic route for FCPD obtained in an embodiment of the present invention. FCPD is synthesized by a one-step aldehyde-ammonia dehydration condensation reaction of ferrocenecarboxaldehyde (FCA) monomer and pyrazino[2,3-f][1,10]phenanthroline-2,3-diamine (PPD) at 120°C. The preparation method is simple.

[0047] Figure 2 and Figure 3 Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the FCPD obtained in this example of the present invention are shown. The FCPD exhibits a spherical morphology. TEM images reveal particles approximately 200 nm in diameter and in contact with each other. The small spherical size facilitates ion transport, thereby improving the electrochemical performance of the FCPD.

[0048] Figure 4 This is a scanning electron microscope (SEM) image of FCA in step 2 of Example 1.

[0049] Figure 5 This is a scanning electron microscope (SEM) image of PPD in step 1 of Example 1.

[0050] Figure 6 The Fourier transform infrared absorption spectra of FCPD, PPD and FCA obtained in the present invention are shown. -1 ) completely disappeared, while C=N(1560cm -1 ) appeared, indicating the successful synthesis of FCPD. In addition, -NH2 (≈3400cm -1 ), indicating that only one amino group of the PPD monomer participated in the reaction.

[0051] Figure 7 The thermogravimetric curves of FCPD, PPD, and FCA obtained in the examples of the present invention are shown below. Under the conditions of 0-300°C, FCPD decomposes less, indicating that it has good structural thermal stability.

[0052] Figure 8 Figure 2 shows the UV absorbance spectra of FCPD, PPD, and FCA obtained in an example of the present invention. FCA and PPD exhibit distinct peaks in the electrolyte, further demonstrating that FCA and PPD are completely dissolved in the electrolyte, while FCPD has very low solubility in the electrolyte.

[0053] Figure 9 The FCPD obtained in the embodiment of the present invention is 0.1mV s -1The cyclic voltammetry curve of the lithium-ion battery in the first three cycles in the electrochemical window of 1.2-3.8V at the scan rate. It can be observed that there are two pairs of redox peaks (vs. Li / Li) at 2.3-3.0V and 1.8-2.0V. + ). The former is due to Fe 2+ and Fe 3+ The first is a typical p-type redox reaction, while the second is an n-type redox reaction. This shows that FCPD has good stability and reversibility.

[0054] Figure 10 The FCPD, PPD and FCA obtained in the present invention are the rate performance diagrams of lithium-ion batteries at different current densities. -1 At different current densities, the FCPD showed excellent rate characteristics, with corresponding high capacities of 247, 231, 213, 194, 183, and 151 mAh g -1 Importantly, when the current density is restored to 0.1Ag -1 When the capacity is still up to 240mAhg -1 This shows that FCPD has more competitive rate performance.

[0055] Figure 11 FCPD, PPD and FCA obtained in the embodiment of the present invention are in the presence of 0.1Ag -1 Electrochemical cycling diagram of lithium-ion batteries under different conditions. During 100 cycles, the capacity retention rate of FCPD is as high as 249 mAh g -1 , the capacity retention rate is 98.4%, and the average Coulombic efficiency is close to 100%. In contrast, the capacity of PPD and FCA is relatively low, and the Coulombic efficiency is also very unstable, which may be caused by their solubility in the electrolyte.

[0056] Figure 12 FCPD, PPD and FCA obtained in the embodiment of the present invention are 1Ag -1 Electrochemical cycle diagram of lithium-ion batteries under conditions. Even at 1.0Ag -1 The FCPD can still achieve a high current density of 150 mAh g after 1000 cycles. -1 The capacity retention rate is as high as 81.9%, while the average Coulombic efficiency is almost 100%.

[0057] Figure 13 The FCPD in Example 2 is 1Ag -1Electrochemical cycle diagram of lithium-ion batteries under different conditions. A half-cell was assembled by uniformly mixing the obtained cathode material FCPD with KB and PVDF in molar ratios of 3:6:1 and 6:3:1. Testing revealed that the 3:6:1 ratio resulted in more stable battery cycling and a higher specific capacity.

[0058] Figure 14 、 15 , 16 is to use X-ray photoelectron spectroscopy (XPS) to detect the structure and chemical composition of FCPD. The XPS spectrum of FCPD shows the presence of C, N and Fe elements in FCPD ( Figure 14-16 The C1s peaks at 284.8, 285.7, and 288.2 correspond to C=C / C-C, CN, and C=N bonds, respectively. Furthermore, the N 1s spectrum also demonstrates characteristic peaks for CN (399.6 eV), C=N (398.8 eV), and NH (399.3 eV) bonds, consistent with the C1s spectrum and FT-IR spectra. The Fe 2p spectrum also exhibits peaks for Fe2+ (708.1 and 720.8 eV).

Claims

1.3-(λ 1 -aza)pyrazino[2,3-f][1,10]phenanthroline-diamine, characterized in that Its structure is as follows: 。 2. The 3-(λ) of claim 1 1 -aza-pyrazino[2,3-f][1,10]phenanthroline-diamine preparation method, characterized in that: It is synthesized by a simple one-step aldehyde-ammonia dehydration condensation reaction between ferrocene carboxaldehyde monomer and pyrazino[2,3-f][1,10]phenanthroline-2,3-diamine in a solvent. The synthetic route is as follows: 。 3. The 3-(λ) of claim 1 1 -aza-pyrazino[2,3-f][1,10]phenanthroline-diamine, characterized in that: Used as positive electrode material for lithium-ion batteries.

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