Fluorine-nitrogen double-doped carbon quantum dot mediated in-situ cross-linked solid electrolyte material and preparation method thereof
By using fluorine-nitrogen dual-doped carbon quantum dots to mediate in-situ cross-linked solid electrolyte materials, the problems of ionic conductivity and interface compatibility of existing solid polymer electrolyte materials have been solved, achieving efficient lithium-ion transport and long-cycle stability of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHIHEZI UNIVERSITY
- Filing Date
- 2026-02-03
- Publication Date
- 2026-05-08
AI Technical Summary
Existing solid polymer electrolyte materials have shortcomings in terms of ionic conductivity, electrochemical stability window and interfacial compatibility, which affect their commercial application. In particular, they are prone to interfacial delamination and structural degradation under long-term cycling or high-temperature conditions.
A solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots was developed. Fluorine-nitrogen dual-doped carbon quantum dots were prepared by aldehyde-amine condensation reaction, and double-bonded functional groups were grafted onto the surface of carbon quantum dots by Hoffmann alkylation reaction. Subsequently, they were polymerized in situ with lithium salt and crosslinking agent to construct a three-dimensional continuous network framework.
It improves room temperature ionic conductivity and lithium-ion transference number, enhances lithium metal anode compatibility, reduces electrode-electrolyte interface impedance, and improves battery cycle life and safety.
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Figure CN122000450A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid electrolyte materials technology, specifically relating to an in-situ crosslinked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots and its preparation method. Background Technology
[0002] With the increasing demand for high-energy-density and high-safety batteries from electric vehicles and energy storage systems, solid-state batteries are widely regarded as an important development direction for next-generation energy storage technology due to their potential high energy density and excellent safety performance. Among them, solid polymer electrolytes (SPEs) prepared by in-situ polymerization have become an important technical path for realizing high-performance solid-state batteries due to their good interfacial contact properties and processing adaptability.
[0003] However, existing SPE materials still face many key technical challenges, mainly including low ionic conductivity, limited electrochemical stability window, and poor interfacial compatibility with lithium metal anodes and high-voltage cathodes, which severely restrict their commercial application. To improve the overall performance of SPEs, researchers have proposed various modification strategies, including the introduction of inorganic fillers (such as LLZO, LLTO, NASICON-type ceramics, etc.). Methods include interface engineering, surface modification, in-situ synthesis to regulate structure, and the synergistic use of plasticizers and fillers.
[0004] Although the above strategies have improved the ionic conductivity and interfacial stability of SPE to some extent, the following problems still need to be addressed: On the one hand, inorganic fillers are prone to agglomeration at high addition levels, leading to local stress concentration and discontinuous ion transport channels, which in turn increases interfacial impedance and reduces overall ionic conductivity; on the other hand, the interfacial thermodynamic compatibility between the polymer matrix and inorganic fillers is poor, and under long-term cycling or high-temperature conditions, interfacial peeling and structural degradation are likely to occur, affecting the cycle stability and safety of the battery.
[0005] In recent years, carbon quantum dots (CQDs) have shown great promise in the field of solid-state electrolytes due to their unique structural properties and tunable surface chemistry. Studies have shown that CQDs can not only serve as building blocks for ion-conducting networks, improving lithium-ion migration efficiency, but also as interface stabilizers, improving interfacial compatibility between organic and inorganic phases and enhancing the structural stability of electrolytes. For example, CQDs modified with oxygen-containing functional groups can promote the dissociation of lithium salts and selectively adsorb anions, while simultaneously reducing the crystallinity of the polymer matrix, thereby improving ionic conductivity. Furthermore, CQD-induced supramolecular physical crosslinking strategies have also been proven to effectively reduce the lithium-ion migration barrier, achieving high ionic conductivity at room temperature.
[0006] Although some progress has been made in the research of SPE based on CQDs, there are still many unsolved problems in terms of structural control, interface stability and performance synergy mechanism. It is urgent to establish a quantitative relationship between filler structure-interface-performance through the synergistic optimization of material design and interface engineering in order to promote its practical application in all-solid-state lithium batteries.
[0007] In view of this, the present invention proposes a new solid electrolyte material and its preparation method, which is an in-situ cross-linked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots, and is an in-situ composite high-performance solid electrolyte material. Summary of the Invention
[0008] The purpose of this invention is to provide a method for preparing an in-situ cross-linked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots. The method involves using amide-modified fluorine-nitrogen dual-doped carbon quantum dots as intermediate nodes and a cross-linking agent containing double bonds to construct a novel "dot-chain" three-dimensional continuous framework electrolyte material with carbon quantum dots as intermediate nodes and the cross-linking agent as polymer chains through a double-bond free radical polymerization reaction.
[0009] To achieve the above objectives, the technical solution adopted is as follows:
[0010] A method for preparing a fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material includes the following steps:
[0011] (1) Fluorine-nitrogen dual-doped carbon quantum dots were prepared by aldehyde-amine condensation reaction;
[0012] (2) The acyl chloride monomer was subjected to Hoffmann alkylation reaction with the prepared fluorine-nitrogen double-doped carbon quantum dots to obtain carbon quantum dots with double bond functional groups on the surface.
[0013] (3) The carbon quantum dots with double bond functional groups on the surface are subjected to in-situ polymerization reaction with lithium salt and crosslinking agent containing double bonds to obtain the in-situ crosslinked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots.
[0014] Furthermore, in step (1), the process of preparing fluorine-nitrogen dual-doped carbon quantum dots by aldehyde-amine condensation reaction is as follows: fluorine-containing benzaldehyde and ethylenediamine are added to a solvent, the pH of the acidic solution is adjusted to 6-8, and after hydrothermal reaction, water is precipitated.
[0015] Furthermore, the fluorinated benzaldehyde is one of 3-fluorobenzaldehyde, 3,4-difluorobenzaldehyde, 2,4,6-trifluorobenzaldehyde, 4-fluorobenzaldehyde, 4-trifluoromethylbenzaldehyde, 2-fluorobenzaldehyde, and 4-(1,1-difluoroethyl)benzaldehyde.
[0016] The acidic solution is one of acetic acid, citric acid, nitric acid, sulfuric acid, and hydrochloric acid;
[0017] The molar ratio of the fluorinated benzaldehyde to ethylenediamine is 3-1:1;
[0018] The solvent is one of methanol, ethanol, and toluene;
[0019] The hydrothermal reaction temperature is 80-180℃, and the time is 8-12h.
[0020] Furthermore, in step (2), the acyl chloride monomer is one of 2-fluoroacryloyl chloride, acryloyl chloride, methacryloyl chloride, (E)-2-methyl-2-butenoyl chloride, and 4-pentenoyl chloride;
[0021] In the Hoffmann alkylation reaction, the solvent is dichloromethane, and the catalyst is potassium carbonate, cesium carbonate, or triethylamine solution. The reaction is carried out at room temperature for 5-12 hours.
[0022] Furthermore, in step (3), the in-situ polymerization process is as follows: dissolve lithium salt in a crosslinking agent containing double bonds, add carbon quantum dots with double bond functional groups on the surface, use azobisisobutyronitrile as an initiator, and carry out in-situ polymerization at 50-80°C.
[0023] Furthermore, the lithium salt is one of lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.
[0024] The crosslinking agent containing double bonds is one of polyethylene glycol diacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, neopentyl glycol diacrylate, polyethylene glycol dimethacrylate, and isobornyl acrylate.
[0025] Furthermore, the lithium salt forms a 1-2 mol / L mixed solution with a crosslinking agent containing double bonds;
[0026] The amount of carbon quanta containing double bond functional groups on the surface is 10-30 wt% of the total amount of lithium salt and crosslinking agent containing double bonds.
[0027] The amount of the initiator azobisisobutyronitrile (AIBN) is 0.5-2 wt% of the total mass of the crosslinking agent containing double bonds, the lithium salt, and the carbon quantum dots with double-bonded functional groups on the surface.
[0028] Another objective of this invention is to provide a fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material, prepared by the above-described method, which exhibits excellent room-temperature ionic conductivity and lithium-ion transference number, and demonstrates good lithium metal compatibility in lithium symmetric batteries.
[0029] Another objective of this invention is to provide a polymer solid-state battery that uses the above-mentioned fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ cross-linked solid electrolyte material. Applying this electrolyte material to an all-solid-state battery can significantly reduce the interfacial impedance between the electrode and the electrolyte, as well as the adverse reactions between the electrode and the electrolyte, thereby improving the cycle life of the battery.
[0030] To achieve the above objectives, the technical solution adopted is as follows:
[0031] A polymer solid-state battery comprising the above-mentioned fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ cross-linked solid electrolyte material.
[0032] Furthermore, in the polymer solid-state battery, the positive electrode material and the negative electrode active material are respectively located on both sides of the in-situ cross-linked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots.
[0033] The cathode material is LiNi. x Co y M 1-x-y One or more of O2, LiCoO2, LiMn2O4, and LiFePO4; the LiNi x Co y M 1-x-y In O2, M is either Mn or Al, 0.2 <x<0.9,0.1<y<0.5;
[0034] The negative electrode active material is lithium metal, lithium alloy, carbon series materials, Si-containing carbon materials, or olivine structure transition metal materials.
[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0036] 1. In the technical solution of the present invention, the in-situ cross-linked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots introduces CF / NH2 dual functional groups on the surface of carbon dots to achieve the "push-pull electron" effect and reduce the Li transition energy barrier.
[0037] 2. In the technical solution of the present invention, fluorine-nitrogen dual-doped carbon quantum dot network nodes are used to construct a cross-linked framework with dynamic ion transport channels using polyethylene glycol, thereby constructing a three-dimensional continuous network of "dot-chain" and reducing the activation energy drop of ion transport.
[0038] 3. The technical solution of the present invention uses the in-situ cross-linked solid electrolyte material mediated by the fluorine-nitrogen dual-doped carbon quantum dots of the present invention to assemble a lithium symmetric battery, which exhibits excellent long-cycle stability and is compatible with lithium metal anodes.
[0039] 4. In the technical solution of the present invention, the in-situ cross-linked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots is applied to solid-state batteries, which can significantly reduce the interfacial impedance of the electrode electrolyte and the adverse reactions between the electrode and the electrolyte, thereby improving the cycle life of the battery. Attached Figure Description
[0040] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:
[0041] Test results are available Figure 1-10 :
[0042] Figure 1 Synthetic route diagram for fluorine-nitrogen dual-doped carbon quantum dot crosslinked solid electrolyte;
[0043] Figure 2 The image shows a TEM image of the NHCTFCDs material in Example 1.
[0044] Figure 3 XPS image of the NHCTFCDs material in Example 1;
[0045] Figure 4 The electrochemical impedance spectroscopy (EIS) of the PECTFCD electrolyte membrane in Example 1 is shown below.
[0046] Figure 5 The ionic conductivity of the electrolyte membranes in Examples 1-3 and Comparative Case 1;
[0047] Figure 6 The Li||Li symmetric cells assembled with electrolytes from Example 1 and Comparative Case 1.
[0048] Figure 7 The Li||Cu battery assembled with the electrolyte in Example 1.
[0049] Figure 8 The CV curve is for the LFP||Li solid lithium metal battery assembled with the electrolyte in Example 1.
[0050] Figure 9 The rate performance of the LFP||Li solid lithium metal batteries assembled with electrolyte membranes in Examples 1-3 and Comparative Case 1 is shown.
[0051] Figure 10 The long-cycle performance of the LFP||Li solid lithium metal battery assembled with the electrolyte membrane in Example 1 is shown. Detailed Implementation
[0052] To further illustrate the fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material and its preparation method according to the present invention, and to achieve the intended purpose of the invention, the following, in conjunction with preferred embodiments, details the specific implementation, structure, features, and effects of the fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material and its preparation method proposed in this invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.
[0053] The following will provide a more detailed description of the fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material and its preparation method, with reference to specific embodiments:
[0054] This invention first prepares fluorine-nitrogen dual-doped carbon quantum dots (NFCDs), then grafts acrylamide functional groups onto the surface of nanoscale carbon quantum dot microspheres to obtain an Amide-NFCD structure. The abundant amide groups have a dipole-charge anchoring effect on anions such as TFSI⁻, which can weaken the depletion of anions in the interface region and induce... A dual-enriched SEI / CEI layer. Furthermore, Amide-NFCDs are used to construct novel "dot-chain" three-dimensional continuous framework electrolyte materials (CD-SPEs) with carbon quantum dots as intermediate nodes and the crosslinking agent as the polymer chain via double-bond radical polymerization with a double-bond-containing crosslinking agent. The crosslinking agent containing double bonds has abundant CO / C=O structures, which can interact with... A dynamic coordination network is formed, which, with the assistance of micro-movements of polymer chain segments, provides... This invention provides continuous skip sites, forming a rapid conduction mechanism of "coordination-dissociation-recoordination". The technical solution adopted in this invention is as follows:
[0055] A method for preparing a fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material includes the following steps:
[0056] (1) Fluorine-nitrogen dual-doped carbon quantum dots (NFCDs) were prepared by aldehyde-amine condensation reaction;
[0057] (2) The acyl chloride monomer is subjected to Hoffmann alkylation reaction with the prepared fluorine-nitrogen double-doped carbon quantum dots to obtain carbon quantum dots Amide-NFCDs with acrylamide functional groups grafted on the surface, that is, carbon quantum dots Amide-NFCDs with double bond functional groups on the surface.
[0058] (3) The carbon quantum dots with double bond functional groups on the surface are subjected to in-situ polymerization reaction with lithium salt and crosslinking agent containing double bonds to obtain the in-situ crosslinked solid electrolyte material (CD-SPEs) mediated by fluorine-nitrogen double doped carbon quantum dots.
[0059] In the above technical solution, the construction of fluorine-nitrogen dual-doped carbon quantum dots mainly utilizes the aldehyde-amine condensation reaction of fluorinated benzaldehyde and ethylenediamine to generate carbon quantum dots with abundant amino functional groups on the surface of 3-5 nm. Then, acrylamide is grafted onto the surface of the carbon dots through a Hoffmann alkylation reaction to obtain Amide-NFCDs. Finally, based on a double-bond free radical polymerization reaction, novel electrolyte materials CD-SPEs are prepared by in-situ polymerization with a crosslinking agent containing double bonds. In this process, the fluorine-nitrogen dual-doped carbon quantum dots are not simply "nanofillers" in solid polymer electrolytes (SPEs), but rather multifunctional synergistic centers integrating "ion accelerator + interface solder + electrochemical shield." Using carbon quantum dots as crosslinking points in the electrolyte network can avoid the aggregation of nanoscale ions, and the solid-solid contact between the solid electrolyte and the electrode is optimized based on in-situ polymerization technology. It can continuously jump at the CDs / polymer interface, improving its ionic conductivity.
[0060] Preferably, in step (1), the process of preparing fluorine-nitrogen dual-doped carbon quantum dots by aldehyde-amine condensation reaction is as follows: fluorine-containing benzaldehyde and ethylenediamine are added to a solvent, the pH of the acidic solution is adjusted to 6-8, and after hydrothermal reaction, water is precipitated.
[0061] More preferably, the fluorinated benzaldehyde is one of 3-fluorobenzaldehyde, 3,4-difluorobenzaldehyde, 2,4,6-trifluorobenzaldehyde, 4-fluorobenzaldehyde, 4-trifluoromethylbenzaldehyde, 2-fluorobenzaldehyde, and 4-(1,1-difluoroethyl)benzaldehyde.
[0062] The acidic solution is one of acetic acid, citric acid, nitric acid, sulfuric acid, and hydrochloric acid;
[0063] The molar ratio of the fluorinated benzaldehyde to ethylenediamine is 3-1:1;
[0064] The solvent is one of methanol, ethanol, and toluene;
[0065] The hydrothermal reaction temperature is 80-180℃, and the time is 8-12h.
[0066] Preferably, in step (2), the acyl chloride monomer is one of 2-fluoroacryloyl chloride, acryloyl chloride, methacryloyl chloride, (E)-2-methyl-2-butenoyl chloride, and 4-pentenoyl chloride;
[0067] In the Hoffmann alkylation reaction, the solvent is dichloromethane, and the catalyst is potassium carbonate, cesium carbonate, or triethylamine solution. The reaction is carried out at room temperature for 5-12 hours.
[0068] Preferably, in step (3), the in-situ polymerization process is as follows: dissolve lithium salt in a crosslinking agent containing double bonds, add carbon quantum dots with double bond functional groups on the surface, use azobisisobutyronitrile as an initiator, and carry out in-situ polymerization at 50-80°C.
[0069] More preferably, the lithium salt is one of lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.
[0070] The crosslinking agent containing double bonds is one of polyethylene glycol diacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, neopentyl glycol diacrylate, polyethylene glycol dimethacrylate, and isobornyl acrylate.
[0071] More preferably, the lithium salt forms a 1-2 mol / L mixed solution with a crosslinking agent containing double bonds;
[0072] The amount of carbon quanta containing double bond functional groups on the surface is 10-30 wt% of the total amount of lithium salt and crosslinking agent containing double bonds.
[0073] The amount of the initiator azobisisobutyronitrile (AIBN) is 0.5-2 wt% of the total mass of the crosslinking agent containing double bonds, the lithium salt, and the carbon quantum dots with double-bonded functional groups on the surface.
[0074] A fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material, prepared by the above-mentioned method, exhibits excellent room-temperature ionic conductivity and lithium-ion transference number, and demonstrates good lithium metal compatibility in lithium symmetric batteries.
[0075] A polymer solid-state battery comprising the above-mentioned fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ cross-linked solid electrolyte material.
[0076] Preferably, in the polymer solid-state battery, the positive electrode material and the negative electrode active material are respectively on both sides of the in-situ cross-linked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots;
[0077] The cathode material is LiNi. x Co y M 1-x-y One or more of O2, LiCoO2, LiMn2O4, and LiFePO4; the LiNi x Co y M 1-x-y In O2, M is either Mn or Al, 0.2 <x<0.9,0.1<y<0.5;
[0078] The negative electrode active material is lithium metal, lithium alloy, carbon series materials, Si-containing carbon materials, or olivine structure transition metal materials.
[0079] In the aforementioned technical solutions, CD-SPEs electrolytes exhibit excellent room-temperature ionic conductivity and lithium-ion transference number, and demonstrate good lithium metal compatibility in lithium-symmetric batteries. When applied to all-solid-state batteries, this electrolyte material can significantly reduce the interfacial impedance between the electrode and electrolyte, as well as adverse reactions between the electrode and electrolyte, thereby improving the battery's cycle life.
[0080] Figure 1 The synthesis route diagrams for the fluorine-nitrogen dual-doped carbon quantum dot crosslinked solid electrolytes in Examples 1-3 are shown below.
[0081] Example 1.
[0082] The specific operating steps are as follows:
[0083] (1) 4-trifluoromethylbenzaldehyde (30 mmol) and ethylenediamine (15 mmol) were added to 20 mL of anhydrous ethanol in a molar ratio. The pH was adjusted to 6 with acetic acid solution. The mixture was reacted at 180 °C for 8 h in a hydrothermal reactor to obtain yellow powdery fluorine-nitrogen double-doped carbon quantum dots, which were named NHCTFCDs.
[0084] (2) The 2-fluoroacryloyl chloride monomer was selected to carry out Hoffmann alkylation reaction with the amino groups on the surface of NHCTFCDs. The molar ratio of 2-fluoroacryloyl chloride monomer to NHCTFCDs was 1:1, the solvent was 20 mL of dichloromethane, the catalyst was potassium carbonate, the mass ratio of potassium carbonate to NHCTFCDs was 1:2, and the reaction was carried out at room temperature for 12 h.
[0085] After the reaction was completed, acrylamide functional groups were grafted onto the surface of the carbon dots to obtain carbon quantum dots with double bond functional groups on the surface, which were named CTFCDs.
[0086] (3) Carbon quantum dots (CTFCDs) with double-bonded functional groups on their surface were polymerized with ethylene glycol dimethacrylate (EGDMA), a crosslinking agent containing double bonds, to prepare a novel electrolyte material, PECTFCD. Specifically, 0.144 g of LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 0.55 g of EGDMA crosslinking agent and stirred until completely dissolved to prepare a 1 M LiTFSI / EGDMA solution. 10 wt% of CTFFCDs (based on the total mass of EGDMA and LiTFSI) and 0.5 wt% of azobisisobutyronitrile (AIBN) initiator (based on the total mass of EGDMA, LiTFSI, and CTFFCDs) were added to obtain a polymer electrolyte precursor solution. The solution was reacted at 60 °C for 12 h to obtain a polymer electrolyte tough film that was not easily deformed and could be bent without breakage, named PECTFCD.
[0087] (4) Using LFP as the positive electrode, the polymer electrolyte precursor solution from step 3 is uniformly coated onto the surface of the LFP positive electrode, and the Li sheet is used as the negative electrode to assemble a battery. The battery is reacted at 60℃ for 12 h to obtain a solid-state battery, and electrochemical tests are performed.
[0088] Example 2.
[0089] The specific operating steps are as follows:
[0090] (1) Add 3,4-difluorobenzaldehyde (30 mmol) and ethylenediamine (15 mmol) in a molar ratio to 20 mL of anhydrous ethanol, adjust the pH to 6 with acetic acid solution, and react in a hydrothermal reactor at 180 °C. o After reacting at C for 8 hours, orange powdery fluorine-nitrogen dual-doped carbon quantum dots were obtained, which were named NHDFCDs.
[0091] (2) 2-fluoroacryloyl chloride monomer and amino groups on the surface of 3,4-difluorobenzaldehyde carbon dots (NHDFCDs) were selected for Hoffmann alkylation reaction; wherein the molar ratio of 3,4-difluorobenzaldehyde carbon dots (NHDFCDs) to 2-fluoroacryloyl chloride monomer was 1:1, the solvent was 20 mL of dichloromethane, the catalyst was potassium carbonate, wherein the mass ratio of potassium carbonate to NHDFCDs was 1:2, and the reaction was carried out at room temperature for 12 h.
[0092] After the reaction was completed, acrylamide functional groups were grafted onto the surface of the carbon dots to obtain carbon quantum dots with double bond functional groups on the surface, which were named DFCDs.
[0093] (3) A novel electrolyte material, PEDFCD, was prepared by polymerizing carbon quantum dots (DFCDs) with double-bonded functional groups on their surface with ethylene glycol dimethacrylate (EGDMA), a crosslinking agent containing double bonds. Specifically, 0.144 g of LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 0.55 g of crosslinking agent EGDMA and stirred until completely dissolved to prepare a 1 M LiTFSI / EGDMA solution. 10 wt% of DFCDs (based on the total mass of EGDMA and LiTFSI) and 0.5 wt% of azobisisobutyronitrile (AIBN) initiator (based on the total mass of EGDMA, LiTFSI, and DFCDs) were added to obtain a polymer electrolyte precursor solution. The solution was reacted at 60 °C for 12 h to obtain a polymer electrolyte tough film that was not easily deformed and could be bent without breakage, named PEDFCD.
[0094] (4) Using LFP as the positive electrode, the polymer electrolyte precursor solution from step 3 is uniformly coated onto the surface of the LFP positive electrode, and the Li sheet is used as the negative electrode to assemble a battery. The battery is reacted at 60 °C for 12 h to obtain a solid-state battery, and electrochemical tests are performed.
[0095] Example 3
[0096] The specific operating steps are as follows:
[0097] (1) 2,4,6-trifluorobenzaldehyde (30 mmol) and ethylenediamine (15 mmol) were added to 20 mL of anhydrous ethanol in a molar ratio. The pH was adjusted to 6 with acetic acid solution. The mixture was reacted at 180 °C for 8 h in a hydrothermal reactor to obtain reddish-brown powdery fluorine-nitrogen double-doped carbon quantum dots, which were named NHTFCDs.
[0098] (2) 2-fluoroacryloyl chloride monomer was selected to carry out Hoffmann alkylation reaction with the amino group on the surface of NHTFCDs; wherein the molar ratio of 2,4,6-trifluorobenzaldehyde (NHTFCDs) was 1:1, the solvent was 20 mL dichloromethane, the catalyst was potassium carbonate, the mass ratio of potassium carbonate to NHTFCDs was 1:2, and the reaction was carried out at room temperature for 12 h.
[0099] After the reaction was completed, acrylamide functional groups were grafted onto the surface of the carbon dots to obtain carbon quantum dots with double bond functional groups on the surface, which were named TFCDs.
[0100] (3) A novel electrolyte material, PETFCD, was prepared by polymerizing carbon quantum dots (TFCDs) with double-bonded functional groups on their surface with ethylene glycol dimethacrylate (EGDMA), a crosslinking agent containing double bonds. Specifically, 0.144 g of LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 0.55 g of crosslinking agent EGDMA and stirred until completely dissolved to prepare a 1 M LiTFSI / EGDMA solution. 10 wt% of TFCDs (based on the total mass of EGDMA and LiTFSI) and 0.5 wt% of azobisisobutyronitrile (AIBN) initiator (based on the total mass of EGDMA, LiTFSI, and TFCDs) were added to obtain a polymer electrolyte precursor solution. The solution was reacted at 60 °C for 12 h to obtain a polymer electrolyte tough film that was not easily deformed and could be bent without breaking, named PETFCD.
[0101] (4) Using LFP as the positive electrode, the polymer electrolyte precursor solution from step 3 is uniformly coated onto the surface of the LFP positive electrode, and the Li sheet is used as the negative electrode to assemble a battery. The battery is reacted at 60 °C for 12 h to obtain a solid-state battery, and electrochemical tests are performed.
[0102] Example 4.
[0103] The specific operating steps are as follows:
[0104] (1) Add 30 mmol of 4-trifluoromethylbenzaldehyde to 10 mmol of ethylenediamine in a molar ratio of 20 mL of methanol, adjust the pH to 6 with acetic acid solution, and react in a hydrothermal reactor at 100 °C for 12 h to obtain yellow powdery fluorine-nitrogen double-doped carbon quantum dots, named NHCTFCDs.
[0105] (2) The 2-fluoroacryloyl chloride monomer was selected to carry out Hoffmann alkylation reaction with the amino groups on the surface of NHCTFCDs. The molar ratio of 2-fluoroacryloyl chloride monomer to NHCTFCDs was 1:1, the solvent was 20 mL of dichloromethane, the catalyst was potassium carbonate, the mass ratio of potassium carbonate to NHCTFCDs was 2:2, and the reaction was carried out at room temperature for 5 h.
[0106] After the reaction was completed, acrylamide functional groups were grafted onto the surface of the carbon dots to obtain carbon quantum dots with double bond functional groups on the surface, which were named CTFCDs.
[0107] (3) Carbon quantum dots CTFCDs with double bond functional groups on the surface and the crosslinker ethylene glycol dimethacrylate containing double bonds are polymerized to prepare a novel electrolyte material PECTFCD. Specifically: Take 0.144 g of LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), dissolve it in 0.28 g of the crosslinker polyethylene glycol dimethacrylate (EGDMA), stir until completely dissolved, and prepare a 2 M LiTFSI / EGDMA solution; Add 10 wt% of CTFCDs (based on the total mass of EGDMA and LiTFSI), and 0.8 wt% of the initiator azobisisobutyronitrile (AIBN) (based on the total mass of EGDMA, LiTFSI and CTFCDs) to obtain a polymer electrolyte precursor solution. React this solution at 50 °C for 12 h to obtain a polymer electrolyte tough film that is not easily deformed and can be bent without breaking, named PECTFCD.
[0108] (4) The polymer electrolyte precursor solution in step (3) is uniformly coated on the surface of the positive electrode and assembled into a battery with the negative electrode material. The positive electrode material is one or more of LiNi x Co y M 1-x-y O2, LiCoO2, LiMn2O4, LiFePO4; in LiNi x Co y M 1-x-y O2, M is Mn or Al, 0.2 < x < 0.9, 0.1 < y < 0.5. The negative electrode active material is metallic lithium, lithium alloy, carbon series materials, Si-containing carbon-based materials or olivine structure transition metal materials.
[0109] Example 5.
[0110] The specific operation steps are as follows:
[0111] (1) Add 4-trifluoromethylbenzaldehyde (20 mmol) and ethylenediamine (20 mmol) in a molar ratio to 20 mL of toluene, adjust the pH to 6 with acetic acid solution, and react in a hydrothermal reaction kettle at 150 °C for 10 h to obtain yellow powdery fluorine-nitrogen co-doped carbon quantum dots, named NHCTFCDs.
[0112] (2) Select 2-fluoropropionyl chloride monomer to carry out Hofmann alkylation reaction with the amino group on the surface of NHCTFCDs. Among them, the molar ratio of 2-fluoropropionyl chloride monomer to NHCTFCDs is 1:1, the solvent is 20 mL of dichloromethane, the catalyst is potassium carbonate, and the mass ratio of potassium carbonate to NHCTFCDs is 1.5:2, and react at room temperature for 10 h.
[0113] After the reaction was completed, acrylamide functional groups were grafted onto the surface of the carbon dots to obtain carbon quantum dots with double bond functional groups on the surface, which were named CTFCDs.
[0114] (3) Carbon quantum dots (CTFCDs) with double-bonded functional groups on their surface were polymerized with ethylene glycol dimethacrylate (EGDMA), a crosslinking agent containing double bonds, to prepare a novel electrolyte material, PECTFCD. Specifically, 0.144 g of LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 0.50 g of crosslinking agent EGDMA and stirred until completely dissolved to prepare a LiTFSI / EGDMA solution. 20 wt% of CTFFCDs (based on the total mass of EGDMA and LiTFSI) and 2 wt% of azobisisobutyronitrile (AIBN) initiator (based on the total mass of EGDMA, LiTFSI, and CTFFCDs) were added to obtain a polymer electrolyte precursor solution. The solution was reacted at 80 °C for 10 h to obtain a polymer electrolyte tough film that was not easily deformed and could be bent without breakage, named PECTFCD.
[0115] Example 6.
[0116] The operation steps of Example 6 are the same as those of Example 1, except that different fluorinated benzaldehydes are used, as detailed in Table 1.
[0117] Table 1
[0118]
[0119] Example 7.
[0120] The operation steps of Example 7 are the same as those of Example 1, except that different hydrothermal reaction conditions are used in step (1), as shown in Table 2.
[0121] Table 2
[0122]
[0123] Example 8.
[0124] The operation steps of Example 8 are the same as those of Example 1, except that different acyl chloride monomers are used, as detailed in Table 3.
[0125] Table 3
[0126]
[0127] Example 9.
[0128] The operation steps of Example 9 are the same as those of Example 1, except that different catalyst reaction conditions are used in step (2), as shown in Table 4.
[0129] Table 4
[0130]
[0131] Example 10.
[0132] The operation steps of Example 10 are the same as those of Example 1, except that different crosslinking agent reaction conditions are used in step (3), as shown in Table 5.
[0133] Table 5
[0134]
[0135] Example 11.
[0136] The operation steps of Example 11 are the same as those of Example 1, except that different lithium salt reaction conditions are used in step (3), as shown in Table 6.
[0137] Table 6
[0138]
[0139] Example 12.
[0140] The operation steps of Example 12 are the same as those of Example 1, except that different amounts of carbon dots are used in step (3) as shown in Table 7.
[0141] Table 7
[0142]
[0143] Comparative Example 1.
[0144] This comparative example provides a polymer electrolyte material, prepared using a method essentially the same as in Example 1, except that 10 wt% CTFCD was not added in step 3. That is:
[0145] This comparative example provides a polymer electrolyte material, the preparation method of which is as follows:
[0146] Specifically, 0.144 g of LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) was dissolved in 0.55 g of crosslinking agent ethylene glycol dimethacrylate (EGDMA) and stirred until completely dissolved to prepare a 1M LiTFSI / EGDMA solution. Then, 0.5 wt% of azobisisobutyronitrile (AIBN) initiator (based on the mass of EGDMA) was added to the solution to obtain a polymer electrolyte precursor solution. This solution was reacted at 60 °C for 12 h to obtain a polymer electrolyte membrane named EGDMA.
[0147] Using LFP as the positive electrode, the polymer electrolyte precursor solution described above was uniformly coated onto the surface of the LFP positive electrode, and a Li sheet was used as the negative electrode to assemble a battery. The battery was reacted at 60 °C for 12 h to obtain a solid-state battery, and electrochemical tests were performed.
[0148] Comparative Example 2.
[0149] This comparative example provides a polymer electrolyte material, prepared using a method essentially the same as in Example 1, except that step 2 is not performed. The NHCTFCDs obtained in step 1 are used as fillers in the polymer electrolyte and physically mixed in step 3 to prepare a solid-state battery.
[0150] Example 11: Performance Testing
[0151] 1. Physical characterization
[0152] The NHCTFCDs material in Example 1 was characterized by TEM. The results are as follows: Figure 2 As shown in the diagram, the structure indicates that the prepared carbon quantum dots have a uniform size with a particle size distribution of 10-20 nm.
[0153] The NHCTFCDs material in Example 1 was characterized by XPS. The results are as follows: Figure 3 As shown, the spectra characterize the chemical composition and bonding state of the carbon dots in NHCTFCDs. The full spectrum reveals that the carbon dots contain four elements: C, N, O, and F, confirming successful nitrogen doping and fluorine modification. High-resolution C 1s spectra show multiple bond types on the carbon dot surface. The symmetrical singlet at 688 eV in the F 1s spectrum indicates that fluorine is stably bonded via CF bonds. The N 1s spectrum shows that nitrogen exists in multiple chemical forms, enriching the electronic structure of the carbon dots.
[0154] 2. Electrical properties
[0155] All-solid-state batteries assembled from the polymer electrolytes prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to electrochemical tests.
[0156] Test method:
[0157] Using 5 mg of LFP or NCM81 as the positive electrode, a polymer electrolyte precursor solution was uniformly coated onto the surface of the LFP positive electrode, and a Li sheet was used as the negative electrode to assemble a battery. The battery was reacted at 60 °C for 12 h to obtain a solid-state battery, which was then subjected to electrochemical testing. Its charge-discharge performance and cycle stability were tested. Charge-discharge test conditions: 1 C, 2 C, 5 C, 10 C; Cycling test condition: 10 C.
[0158] Test results:
[0159] Figure 4The image shows the electrochemical impedance spectroscopy of the PECTFCD electrolyte membrane in Example 1. The results indicate that the PECTFCD electrolyte exhibits high ionic conductivity in the temperature range of 30-70℃.
[0160] Figure 5 The ionic conductivity of the polymer electrolyte membranes PECTFCD, PEDFCD, and PETFCD in Examples 1-3 and the electrolyte membrane in EGDMA in Comparative Case 1 are shown. The results show that the EGDMA sample has the lowest conductivity, which is 3.17 mS / cm. The conductivity gradually increases after the introduction of carbon dots. The PECTFCD sample has the highest conductivity, which reaches 4.19 mS / cm.
[0161] Figure 6 The Li||Li symmetric cells assembled with the electrolytes from Example 1 and Comparative Case 1 are shown. At 30°C, the EGDMA sample exhibited significant voltage fluctuations within a current density range of 0.05–0.5 mA / cm², while the PECTFCD sample maintained stable voltage across different current densities. During subsequent long-term cycling exceeding 2000 h, the voltage curve of the PECTFCD showed no significant decay, demonstrating excellent rate performance and electrochemical stability.
[0162] Figure 7 The Li||Cu battery assembled with the electrolyte from Example 1 exhibits stable electrochemical behavior at a current density of 0.1 mA / cm². During the 80-h test period, the battery voltage remained near 0 mV, with minimal polarization. The magnified partial image shows a high degree of overlap between the charge-discharge curves, and the coulombic efficiency reaches 90.0%, indicating good reversibility of lithium deposition / stripping.
[0163] Figure 8 The first image shows the CV curve of the LFP||Li solid-state lithium metal battery assembled with the electrolyte in Example 1. The second image shows the cyclic voltammetry curve of the Li|PECTFCD|LFP battery, which was measured for a total of 5 cycles. A pair of distinct redox peaks can be observed in the voltage range of 2.8–3.6 V, representing the lithium insertion and extraction reactions in the LFP cathode material. The curves from the 5 tests almost overlap, indicating that the battery performance is very stable during multiple charge-discharge cycles without significant performance degradation.
[0164] Figure 9The table shows the rate performance of the LFP||Li solid-state lithium metal batteries assembled with electrolyte membranes in Examples 1-3 and Comparative Case 1; the capacity and coulombic efficiency curves of the Li|LFP batteries at different rates from 0.2C to 10C. The PECTFCD maintains a relatively better capacity, demonstrating its superior lithium-ion transport capability at high rates. The coulombic efficiency of all three materials remains above 80% across the entire rate range, with minimal curve fluctuations, indicating good reversibility of lithium insertion and extraction reactions at different rates. When the rate recovers from 10C to 0.2C, the capacity recovery of the PECTFCD is more significant, further demonstrating its stronger electrode structure stability.
[0165] Figure 10 The image shows the long-cycle performance of the LFP||Li solid-state lithium metal battery assembled with the electrolyte membrane in Example 1; the capacity and coulombic efficiency curves of the Li|PECTFCD|LFP battery under 5C long-cycle conditions. During 1500 cycles, the initial capacity of the battery was approximately 138 mAh / g, and the capacity remained above 120 mAh / g after the cycle, with a capacity retention of approximately 81.8%, demonstrating excellent long-cycle stability. The coulombic efficiency was 98%, with no significant fluctuations, indicating that almost no side reactions occurred during long-term charge-discharge processes, and the lithium insertion and extraction were highly reversible.
[0166] The results show that the electrolyte materials prepared in Examples 1-3 of this invention, when applied to solid-state batteries, can significantly reduce the interfacial impedance between the electrode and electrolyte, as well as the adverse reactions between the electrode and the electrolyte, thereby improving the cycle life of the battery.
[0167] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A method for preparing a fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material, characterized in that, Includes the following steps: (1) Fluorine-nitrogen dual-doped carbon quantum dots were prepared by aldehyde-amine condensation reaction; (2) The acyl chloride monomer was subjected to Hoffmann alkylation reaction with the prepared fluorine-nitrogen double-doped carbon quantum dots to obtain carbon quantum dots with double bond functional groups on the surface. (3) The carbon quantum dots with double bond functional groups on the surface are subjected to in-situ polymerization reaction with lithium salt and crosslinking agent containing double bonds to obtain the in-situ crosslinked solid electrolyte material mediated by fluorine-nitrogen double doped carbon quantum dots.
2. The preparation method according to claim 1, characterized in that, In step (1), the process of preparing fluorine-nitrogen dual-doped carbon quantum dots by aldehyde-amine condensation reaction is as follows: fluorine-containing benzaldehyde and ethylenediamine are added to a solvent, the pH is adjusted to 6-8, and after hydrothermal reaction, water is precipitated.
3. The preparation method according to claim 2, characterized in that, The fluorinated benzaldehyde is one of 3-fluorobenzaldehyde, 3,4-difluorobenzaldehyde, 2,4,6-trifluorobenzaldehyde, 4-fluorobenzaldehyde, 2-fluorobenzaldehyde, 4-trifluoromethylbenzaldehyde, and 4-(1,1-difluoroethyl)benzaldehyde. The acidic solution is one of acetic acid, citric acid, nitric acid, sulfuric acid, and hydrochloric acid. The molar ratio of the fluorinated benzaldehyde to ethylenediamine is 3-1:1; The solvent is one of methanol, ethanol, and toluene; The hydrothermal reaction temperature is 80-180℃, and the time is 8-12h.
4. The preparation method according to claim 1, characterized in that, In step (2), the acyl chloride monomer is one of 2-fluoroacryloyl chloride monomer, acryloyl chloride, methacryloyl chloride, (E)-2-methyl-2-butenoyl chloride, and 4-pentenoyl chloride; In the Hoffmann alkylation reaction, the solvent is dichloromethane, and the catalyst is potassium carbonate, cesium carbonate, or triethylamine solution. The reaction is carried out at room temperature for 5-12 hours.
5. The preparation method according to claim 1, characterized in that, In step (3), the in-situ polymerization process is as follows: after dissolving the lithium salt in a crosslinking agent containing double bonds, carbon quantum dots with double bond functional groups on the surface are added, and azobisisobutyronitrile is used as an initiator to carry out the in-situ polymerization reaction at 50-80℃.
6. The preparation method according to claim 5, characterized in that, The lithium salt is one of lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. The crosslinking agent containing double bonds is one of polyethylene glycol diacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, neopentyl glycol diacrylate, polyethylene glycol dimethacrylate, and isobornyl acrylate.
7. The preparation method according to claim 5, characterized in that, The lithium salt forms a 1-2 mol / L mixed solution with a crosslinking agent containing double bonds; The amount of carbon quanta containing double bond functional groups on the surface is 10-30 wt% of the total amount of lithium salt and crosslinking agent containing double bonds. The amount of the initiator azobisisobutyronitrile (AIBN) is 0.5-2 wt% of the total mass of the crosslinking agent containing double bonds, lithium salt, and carbon quantum dots with double bond functional groups on the surface.
8. A fluorine-nitrogen dual-doped carbon quantum dot-mediated in-situ crosslinked solid electrolyte material, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.
9. A polymer solid-state battery, characterized in that, The in-situ crosslinked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots as described in claim 8.
10. The polymer solid-state battery according to claim 9, characterized in that, In the polymer solid-state battery, the positive electrode material and the negative electrode active material are located on both sides of the in-situ cross-linked solid electrolyte material mediated by fluorine-nitrogen dual-doped carbon quantum dots. The cathode material is LiNi. x Co y M 1-x-y One or more of O2, LiCoO2, LiMn2O4, and LiFePO4; the LiNi x Co y M 1-x-y In O2, M is either Mn or Al, 0.2 <x<0.9,0.1<y<0.5; The negative electrode active material is lithium metal, lithium alloy, carbon series materials, Si-containing carbon materials, or olivine structure transition metal materials.