In-situ polymerized quasi-solid-state electrolyte, preparation method thereof and application thereof in lithium battery

Abstract

This invention relates to the field of energy storage technology, and more particularly to an in-situ polymerized quasi-solid-state electrolyte, its preparation method, and its application in lithium batteries. The in-situ polymerized quasi-solid-state electrolyte comprises a polymer matrix and a liquid electrolyte; the liquid electrolyte is confined within the polymer matrix network; the polymer matrix is ​​formed by copolymerization of 2,2,2-trifluoroethyl acrylate and 2-isocyanate ethyl methacrylate; the liquid electrolyte comprises a lithium salt and an ether-ester mixed solvent. This invention, by introducing specific functional monomers, establishes specific intermolecular interactions between the polymer backbone and the liquid components, synergistically solving the challenges of high-voltage stability and lithium-ion transport kinetics, demonstrating strong practicality.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to an in-situ polymerized quasi-solid electrolyte, its preparation method, and its application in lithium batteries. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With the increase in positive electrode operating voltage, the anodic stability of the electrolyte has become a bottleneck restricting the development of high-voltage lithium metal batteries. In traditional liquid electrolyte systems, ether-based electrolytes are prone to oxidative decomposition under high voltage; carbonate-based electrolytes undergo side reactions with the lithium metal anode, resulting in low coulombic efficiency and short cycle life; traditional liquid electrolytes also face safety hazards such as leakage, flammability, and difficulty in suppressing lithium dendrite penetration. Quasi-solid-state electrolytes can confine liquid components within a polymer network, improving battery safety and mechanical strength, but improvements are still needed in lithium-ion transport and high-voltage stability. Summary of the Invention

[0004] In view of this, the present invention provides an in-situ polymerized quasi-solid-state electrolyte, its preparation method, and its application in lithium batteries. The present invention addresses the challenges of balancing high-voltage stability and lithium-ion transport kinetics by introducing specific functional monomers to establish specific intermolecular interactions between the polymer backbone and the liquid components.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides an in-situ polymerized quasi-solid electrolyte, comprising a polymer matrix and a liquid electrolyte; The liquid electrolyte is confined within the polymer matrix network; The polymer matrix is ​​formed by copolymerization of 2,2,2-trifluoroethyl acrylate (TFEA) and 2-isocyanate ethyl methacrylate (IEM); The liquid electrolyte comprises a lithium salt and an ether-ester mixed solvent.

[0006] Further, the ether-ester mixed solvent is a mixture of tetraethylene glycol dimethyl ether (G4) and fluoroethylene carbonate (FEC), and the volume ratio of tetraethylene glycol dimethyl ether to fluoroethylene carbonate is 1-3:1; preferably 2:1.

[0007] Furthermore, the lithium salt is lithium hexafluorophosphate (LiPF6), and its concentration in the mixed solvent is 1.0-1.5 M, preferably 1.2 M.

[0008] Furthermore, the volume fraction of the polymer matrix in the quasi-solid electrolyte is 10%-20%, preferably 15%.

[0009] Further, the molar ratio of 2,2,2-trifluoroethyl acrylate to 2-isocyanoethyl methacrylate is (2-8):(8-2), preferably 5:5.

[0010] In a second aspect, the present invention provides a method for preparing the in-situ polymerized quasi-solid electrolyte described in the first aspect, comprising the following steps: A liquid electrolyte was prepared by dissolving lithium salt in an ether-ester mixed solvent. Add comonomers TFEA and IEM to the above liquid electrolyte, along with a crosslinking agent and an initiator, and mix thoroughly to obtain an electrolyte precursor solution; The electrolyte precursor solution is injected into the battery and subjected to in-situ thermal polymerization at a certain temperature to obtain the in-situ polymerized ether-ester hybrid quasi-solid electrolyte.

[0011] Further, the crosslinking agent is selected from one of polyethylene glycol diacrylate (PEGDA), trimethylolpropane triacrylate (TMPTA), divinylbenzene (DVB) or ethoxylated trimethylolpropane triacrylate (ETPTA), preferably polyethylene glycol diacrylate, and its addition amount is 0.8-1.2 mol of the total molar amount of the comonomer.

[0012] Further, the initiator is selected from one of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), azobisisobutyronitrile (ABVN), or dicumyl peroxide (DCP), preferably azobisisobutyronitrile (AIBN), and its addition amount is 0.4-0.6 mol of the total molar amount of the comonomer.

[0013] Furthermore, the in-situ thermal polymerization temperature is 65-75 ℃, preferably 70 ℃; the polymerization time is 4-8 hours, preferably 6 hours.

[0014] Thirdly, the present invention provides the application of the quasi-solid-state electrolyte described in the first aspect in lithium batteries.

[0015] Furthermore, the lithium battery is a lithium iron phosphate lithium metal battery or a ternary lithium metal battery.

[0016] Fourthly, a battery, wherein the battery electrolyte is the quasi-solid-state electrolyte described in the first aspect.

[0017] Compared with the prior art, the present invention has achieved the following beneficial effects: The polymer matrix backbone of this invention contains strong electron-withdrawing groups, which can effectively reduce the electron cloud density of ester groups and promote Li + Desolvation and rapid transport impart high ionic conductivity to the electrolyte at room temperature; the polymer backbone of this invention effectively anchors free G4 solvent molecules and PF6 through hydrogen bonding. - Anions enhance the electrochemical stability window and lithium-ion transport kinetics of the system. The quasi-solid electrolyte prepared in this invention induces stable CEI and SEI films in situ on the high-voltage cathode surface and the lithium metal anode surface, respectively, which inhibits the harmful phase transition and lithium dendrite growth of the ternary cathode material.

[0018] The preparation method of this invention employs an in-situ polymerization process, resulting in good liquid wettability of the precursor, simple operation, and suitability for pouch batteries (achieving a capacity of 302.64 Wh / kg). -1 Large-scale preparation of energy density is highly practical. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 The infrared spectra of the polymer matrix and quasi-solid electrolyte prepared in the embodiments and comparative examples of the present invention are shown; wherein, (a) is the polymer matrix and (b) is the quasi-solid electrolyte. Figure 2 This is to compare the performance of pure solvent G4, G4 / FEC mixed solvent, comparative example LE, and G4 solvent in the electrolyte of Example c-TI55. 1 H NMR spectrum; Figure 3 PF6 in the quasi-solid electrolyte of Example 1 and the liquid electrolyte of Comparative Example 1 of this invention. - of 19 F nuclear magnetic resonance image; Figure 4 The conductivity diagram of the electrolyte prepared in Example 1 of this invention at different temperatures; Figure 5 This is a comparison chart of the cycle performance of the Li||Li symmetric battery assembled with electrolyte in Example 1 of the present invention; Figure 6 The images are scanning electron microscope images of the lithium deposition layer on the surface of the lithium anode after cycling in Example 1 and Comparative Examples 1-2 of the present invention; wherein, (a) is Comparative Example 1, (b) is Comparative Example 2, and (c) is Example 1. Figure 7 This is a test diagram of the cycle performance of the lithium iron phosphate lithium metal battery assembled in Embodiment 1 of the present invention; Figure 8This is a test diagram of the cycle performance of the ternary lithium metal battery assembled in Embodiment 1 of the present invention; Figure 9 This is a charge-discharge curve of a 2 Ah ternary lithium metal pouch battery assembled with a quasi-solid-state electrolyte prepared in Example 1 of the present invention. Figure 10 The images are scanning electron microscope images of the ternary cathodes after cycling in Example 1 and Comparative Examples 1-2 of the present invention; wherein, (a) is Comparative Example 1, (b) is Comparative Example 2, and (c) is Example 1. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] Energy density and power density are two key performance indicators for rechargeable batteries, closely related to electrode capacity and the voltage difference between the positive and negative electrodes. To meet the growing demands of portable electronic devices and electric vehicles, increasing the charging voltage threshold of commercial cathode materials such as lithium cobalt oxide and ternary materials, or developing high-voltage, high-capacity cathode systems, has become an important direction in battery research. Among these, lithium metal anodes, due to their extremely high theoretical specific capacity and lowest electrochemical potential, are considered the core technology for achieving high-energy-density lithium metal batteries. With the increase in cathode operating voltage, the anodic stability of the electrolyte has become a bottleneck limiting the development of high-voltage lithium metal batteries. How to design an electrolyte that can match the high-voltage cathode (relative to Li / Li) is a crucial challenge. + Developing an electrolyte system that can maintain a voltage of ≥4.3 V while simultaneously stabilizing the lithium metal anode is a major challenge in the field. This invention is proposed based on this challenge.

[0023] This invention provides an in-situ polymerized quasi-solid electrolyte, comprising a polymer matrix and a liquid electrolyte; The liquid electrolyte is confined within the polymer matrix network; The polymer matrix is ​​formed by copolymerization of 2,2,2-trifluoroethyl acrylate (TFEA) and 2-isocyanate ethyl methacrylate (IEM); The liquid electrolyte comprises a lithium salt and an ether-ester mixed solvent.

[0024] The polymer matrix backbone of this invention contains strong electron-withdrawing groups (-CF3 and -N=C=O), which can effectively reduce the electron cloud density of ester groups and promote Li + Desolvation and rapid transport endow the electrolyte with a temperature up to 2.2 × 10⁻⁶ at room temperature. -3 S cm -1High ionic conductivity. The polymer backbone effectively anchors free G4 solvent molecules and PF6 through hydrogen bonding. - The anions improved the electrochemical stability window and lithium-ion transport kinetics of the system, thus synergistically solving the problem between high-voltage stability and lithium-ion transport kinetics.

[0025] The quasi-solid electrolyte prepared by this invention induces stable CEI and SEI films in situ on the surface of the high-voltage positive electrode and the surface of the lithium metal negative electrode, respectively, which inhibits the harmful phase transition and lithium dendrite growth of the ternary positive electrode material.

[0026] Further, the ether-ester mixed solvent is a mixture of tetraethylene glycol dimethyl ether (G4) and fluoroethylene carbonate (FEC), wherein the volume ratio of tetraethylene glycol dimethyl ether to fluoroethylene carbonate is 1-3:1; the volume ratio of tetraethylene glycol dimethyl ether to fluoroethylene carbonate can be any value between 1-3:1, for example, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, ..., 2:1, 2.1:1, ..., 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1; preferably 2:1. G4 has a high flash point (141 °C) and good compatibility with lithium metal anodes, while FEC is used to increase the solubility of lithium salt in G4. When the volume ratio of the two is too large, it will reduce the dissolution rate of lithium salt; when it is too small, it may reduce the safety of the system.

[0027] Furthermore, the lithium salt is lithium hexafluorophosphate (LiPF6), and its concentration in the mixed solvent is 1.0-1.5 M. The concentration of LiPF6 in the mixed solvent can be any value between 1.0-1.5 M, such as 1.1 M, 1.2 M, 1.3 M, 1.4 M, etc.; preferably 1.2 M. Compared with other commonly used organic lithium salts (such as LiTFSI, which easily corrodes aluminum foil current collectors under high voltage), lithium hexafluorophosphate not only has a higher room temperature ionic conductivity, but also effectively passivates aluminum current collectors, has better high voltage withstand capability, and is more cost-effective, making it more conducive to commercial applications.

[0028] Furthermore, the volume fraction of the polymer matrix in the quasi-solid electrolyte is 10%-20%, and the volume fraction of the polymer matrix in the quasi-solid electrolyte can be any value between 10% and 20%, such as 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%; preferably 15%.

[0029] Further, the molar ratio of 2,2,2-trifluoroethyl acrylate to 2-isocyanate ethyl methacrylate is (2-8):(8-2), wherein the molar ratio of (2-8):(8-2) means that 2,2,2-trifluoroethyl acrylate can be any value between 2 and 8, such as 3, 4, 5, 6, 7, etc., and 2-isocyanate ethyl methacrylate can be any value between 8 and 2; preferably 5:5.

[0030] This invention provides a method for preparing an in-situ polymerized quasi-solid electrolyte, comprising the following steps: A liquid electrolyte was prepared by dissolving lithium salt in an ether-ester mixed solvent. Add comonomers TFEA and IEM to the above liquid electrolyte, along with a crosslinking agent and an initiator, and mix thoroughly to obtain an electrolyte precursor solution; The electrolyte precursor solution is injected into the battery and subjected to in-situ thermal polymerization at a certain temperature to obtain the in-situ polymerized ether-ester hybrid quasi-solid electrolyte.

[0031] Further, the crosslinking agent is selected from one of polyethylene glycol diacrylate (PEGDA), trimethylolpropane triacrylate (TMPTA), divinylbenzene (DVB), or ethoxylated trimethylolpropane triacrylate (ETPTA); preferably polyethylene glycol diacrylate, and its addition amount is 0.8-1.2 mol% of the total molar amount of the comonomer. The addition amount of polyethylene glycol diacrylate can be any value between 0.8-1.2 mol% of the total molar amount of the comonomer, such as 0.9 mol%, 1.0 mol%, 1.1 mol%, etc., preferably 1.0 mol%.

[0032] Further, the initiator is selected from one of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), azobisisobutyronitrile (ABVN), or dicumyl peroxide (DCP); preferably, it is azobisisobutyronitrile, and its addition amount is 0.4-0.6 mol% of the total molar amount of the comonomer. The addition amount of azobisisobutyronitrile can be any value between 0.4-0.6 mol% of the total molar amount of the comonomer, such as 0.45 mol%, 0.5 mol%, 0.55 mol%, etc., preferably 0.5 mol%.

[0033] Furthermore, the in-situ thermal polymerization temperature is 65-75 °C; the polymerization time is 4-8 hours. The in-situ thermal polymerization temperature can be any value between 65-75 °C, such as 66 °C, 67 °C, 68 °C, 69 °C, 70 °C, 71 °C, 72 °C, 73 °C, 74 °C, etc., preferably 70 °C; the polymerization time can be any value between 4-8 hours, such as 5 hours, 6 hours, 7 hours, etc., preferably 6 hours. The temperature and time of in-situ polymerization have a significant impact on the final performance of the electrolyte. When the temperature is too low or the time is too short, the monomer conversion rate is low, and the polymerization reaction is incomplete, resulting in the electrolyte failing to form a dense polymer matrix network, poor mechanical properties, and inability to lock in liquid components. When the temperature is too high or the time is too long, it easily leads to side reactions, causing the liquid solvent to evaporate or the lithium salt to decompose thermally, thereby significantly reducing the ionic conductivity of the system and destroying its electrochemical stability.

[0034] Further, the ether-ester mixed solvent is a mixture of tetraethylene glycol dimethyl ether (G4) and fluoroethylene carbonate (FEC), and the volume ratio of tetraethylene glycol dimethyl ether to fluoroethylene carbonate is 1-3:1; preferably 2:1.

[0035] Furthermore, the lithium salt is lithium hexafluorophosphate (LiPF6), and its concentration in the mixed solvent is 1.0-1.5 M, preferably 1.2 M.

[0036] Furthermore, the volume fraction of the polymer matrix in the quasi-solid electrolyte is 10%-20%, preferably 15%.

[0037] Further, the molar ratio of 2,2,2-trifluoroethyl acrylate to 2-isocyanoethyl methacrylate is (2-8):(8-2), preferably 5:5.

[0038] This invention provides the application of the aforementioned quasi-solid-state electrolyte in lithium batteries.

[0039] Furthermore, the lithium battery is a lithium iron phosphate lithium metal battery or a ternary lithium metal battery. The present invention provides a battery in which the electrolyte is the quasi-solid-state electrolyte described above.

[0040] The quasi-solid-state electrolyte provided in Example 1 of this invention has a room-temperature ionic conductivity of 2.21 × 10⁻⁶. -3 S cm -1 When applied to lithium iron phosphate full batteries, the initial discharge specific capacity of the battery is 130.54 mAh g. -1Subsequently, it exhibited a gradual increase in capacity and demonstrated excellent cycle stability, retaining a capacity of up to 93.4% after 1000 cycles. When applied to high-voltage ternary lithium-ion batteries, the battery exhibited a capacity of 205.6 mAh g⁻¹. -1 With a high initial discharge specific capacity, after 300 cycles at 0.5 C, the battery capacity still remained at 138.0 mAh g⁻¹. -1 The capacity retention rate is 80.4%. When applied to Ah-class pouch cells, this battery achieves an average discharge voltage of approximately 3.8 V and a discharge capacity of 1.96 Ah, with a high gravimetric energy density of 302.64 Wh / kg. -1 This demonstrates that the present invention has extremely high commercial application prospects.

[0041] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0042] Example 1 (1) Preparation of liquid electrolyte (LE): In a glove box filled with high-purity argon, tetraethylene glycol dimethyl ether (G4, 566 μL) and fluoroethylene carbonate (283 μL) were mixed at a volume ratio of 2:1. Then lithium hexafluorophosphate (0.182 g) was added and stirred to dissolve, so as to prepare a liquid electrolyte with a concentration of 1.2 M.

[0043] (2) Preparation of precursor solution: To the LE prepared above, add 2,2,2-trifluoroethyl acrylate (TFEA, 63.7 μL) and 2-isocyanate methacrylate (IEM, 71.7 μL) monomers in a molar ratio of 5:5 (polymer matrix accounts for 15% of the final system volume). Then, add 1 mol% of polyethylene glycol diacrylate (PEGDA, 1.52 μL) as a crosslinking agent and 0.5 mol% of azobisisobutyronitrile (AIBN, 0.0014 g) as an initiator, and mix evenly with magnetic stirring to obtain the precursor solution.

[0044] (3) In-situ thermal polymerization: The precursor solution is injected into the assembled battery casing, sealed, and the battery is moved into a 70 °C vacuum drying oven and heated for 6 hours to trigger the in-situ polymerization reaction, resulting in a dense and uniform ether-ester hybrid quasi-solid electrolyte, labeled as c-TI55.

[0045] Example 2 (1) Preparation of liquid electrolyte (LE): In a glove box filled with high-purity argon, tetraethylene glycol dimethyl ether (G4, 566 μL) and fluoroethylene carbonate (283 μL) were mixed at a volume ratio of 2:1. Then lithium hexafluorophosphate (0.182 g) was added and stirred to dissolve, so as to prepare a liquid electrolyte with a concentration of 1.2 M.

[0046] (2) Preparation of precursor solution: To the prepared LE, add 2,2,2-trifluoroethyl acrylate (TFEA, 115.3 μL) and 2-isocyanate methacrylate (IEM, 32.6 μL) monomers in a molar ratio of 8:2 (polymer matrix accounts for 15% of the final system volume). Then, add 1 mol% of polyethylene glycol diacrylate (PEGDA, 1.73 μL) as a crosslinking agent and 0.5 mol% of azobisisobutyronitrile (AIBN, 0.0023 g) as an initiator, and mix evenly with magnetic stirring to obtain the precursor solution.

[0047] (3) In-situ thermal polymerization: The precursor solution is injected into the assembled battery casing, sealed, and the battery is moved into a 70 °C vacuum drying oven and heated for 6 hours to trigger the in-situ polymerization reaction, resulting in a dense and uniform ether-ester hybrid quasi-solid electrolyte, labeled as c-TI82.

[0048] Example 3 (1) Preparation of liquid electrolyte (LE): In a glove box filled with high-purity argon, tetraethylene glycol dimethyl ether (G4, 566 μL) and fluoroethylene carbonate (283 μL) were mixed at a volume ratio of 2:1. Then lithium hexafluorophosphate (0.182 g) was added and stirred to dissolve, so as to prepare a liquid electrolyte with a concentration of 1.2 M.

[0049] (2) Preparation of precursor solution: To the prepared LE, add 2,2,2-trifluoroethyl acrylate (TFEA, 29 μL) and 2-isocyanate methacrylate (IEM, 127 μL) monomers in a molar ratio of 2:8 (polymer matrix accounts for 15% of the final system volume). Then, add 1 mol% of polyethylene glycol diacrylate (PEGDA, 1.73 μL) as a crosslinking agent and 0.5 mol% of azobisisobutyronitrile (AIBN, 0.0002 g) as an initiator, and mix evenly with magnetic stirring to obtain the precursor solution.

[0050] (3) In-situ thermal polymerization: The precursor solution is injected into the assembled battery casing, sealed, and the battery is moved into a 70 °C vacuum drying oven and heated for 6 hours to trigger the in-situ polymerization reaction, resulting in a dense and uniform ether-ester hybrid quasi-solid electrolyte, labeled as c-TI28.

[0051] Comparative Example 1 Perform only step (1) of Example 1, add 0.182 g LiPF6 to a mixed solvent of 666 μL G4 and 333 μL FEC (volume ratio 2:1) to prepare 1.2 M LiPF6 / G4+FEC as a blank liquid electrolyte control group. The pure liquid electrolyte is labeled as LE.

[0052] Comparative Example 2 The preparation steps are the same as in Example 1, except that in step (2), only TFEA (150 μL) is added and IEM monomer is not added at all, that is, the molar ratio of TFEA to IEM is 10:0.

[0053] A quasi-solid electrolyte, labeled p-TFEA, was obtained by in-situ polymerization at 70 °C for 6 hours.

[0054] Comparative Example 3 The preparation steps are the same as in Example 1, except that in step (2), TFEA (12.7 μL) and IEM (129.1 μL) monomers with a molar ratio of 1:9 are added to the prepared LE.

[0055] A quasi-solid electrolyte was obtained by in-situ polymerization at 70 °C for 6 hours and labeled as c-TI19.

[0056] Comparative Example 4 The preparation steps are the same as in Example 1, except that in step (2), TFEA (114.7 μL) and IEM (14.3 μL) monomers with a molar ratio of 9:1 are added to the prepared LE.

[0057] A quasi-solid electrolyte was obtained by in-situ polymerization at 70 °C for 6 hours and labeled as c-TI91.

[0058] Figure 1 The images show the infrared spectra of the polymer matrix and quasi-solid electrolyte prepared in the embodiments and comparative examples of this invention; where (a) is the polymer matrix and (b) is the quasi-solid electrolyte. As can be seen from the figures, after the reaction, the 1638 cm⁻¹... -1 The complete disappearance of the C=C tensile vibration peak at the point confirms that the polymerization reaction in each system was complete and there were no unreacted monomers or crosslinking agents remaining.

[0059] Figure 2 This is to compare the performance of pure solvent G4, G4 / FEC mixed solvent, comparative example LE, and G4 solvent in the electrolyte of Example c-TI55. 1 The H NMR spectrum shows that in the G4 / FEC mixed solvent, the G4-H signal appears at 3.51 and 3.25 ppm. Upon addition of 1.2 M LiPF6, the signal is influenced by Li... +The reduced electron cloud density caused by coordination significantly shifted these signals to lower fields, to 3.55 and 3.28 ppm. However, in the c-TI55 system, the G4-H signal shifted back to higher fields, to 3.51 and 3.24 ppm. This reversal of chemical shifts indicates that G4 reacts with Li... + The coordination between them weakens, while hydrogen bonding interactions are formed between G4 and the carbonyl oxygen atom of the polymer.

[0060] Figure 3 PF6 in the quasi-solid electrolyte of Example 1 and the liquid electrolyte of Comparative Example 1 of this invention. - of 19 The f-NMR spectrum shows that c-TI55 exhibits PF6. - The doublet peaks showed significant splitting and shifted to a lower field. This phenomenon indicates that the chemical environment of the fluorine atom has changed and is affected by the deshielding effect of electron-deficient hydrogen atoms in the polymer matrix, thus confirming the strong interaction between the polymer matrix and the anion.

[0061] Performance testing The ionic conductivity of the quasi-solid electrolyte, its stability on the lithium anode, and the performance of two lithium metal batteries were tested in the examples.

[0062] Ionic conductivity testing of quasi-solid electrolytes: A precursor solution based on the embodiment was added to two stainless steel electrodes for in-situ thermal polymerization to form a blocked cell. The AC impedance of the blocked cell was tested under different temperature conditions. The formula is as follows: ; Where σ is the ionic conductivity of the quasi-solid electrolyte, in units of S cm⁻¹. -1 L is the film thickness in cm, R is the bulk resistance of the quasi-solid electrolyte obtained by fitting the AC impedance spectrum in Ω, and S is the cross-sectional area of ​​the stainless steel in cm². -2 .

[0063] Figure 4 This is a conductivity graph of the electrolyte prepared in Example 1 of the present invention at different temperatures. The graph shows that the ionic conductivity at 25 °C is 2.21 × 10⁻⁶. -3 S cm -1 Different electrolytes were sandwiched between stainless steel sheets (SS) to assemble SS||SS blocked batteries, which were then subjected to electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) tests. The results showed that the room temperature ionic conductivity of Example 1 (c-TI55) was 2.21 × 10⁻⁶. -3 S cm -1 At the same time, the activation energy for ion migration was obtained as 0.16 eV.

[0064] Stability determination of lithium anode A precursor solution based on the embodiment was added to the space between two lithium wafers for in-situ thermal polymerization to form a lithium symmetric battery, with a current density of 0.2 mAh cm⁻¹. -2 Under these conditions, charging and discharging are performed.

[0065] Figure 5 This is a comparison of the cycle performance of the Li||Li symmetric battery assembled with electrolyte in Example 1 of this invention. As can be seen from the figure, the battery achieved stable operation for up to 2000 hours with minimal voltage hysteresis. This demonstrates that the c-TI55 system imparts excellent interfacial stability to the lithium metal anode, promoting uniform lithium ion deposition / stripping and thus suppressing lithium dendrite growth.

[0066] Figure 6 The images show scanning electron microscope (SEM) images of the lithium deposition layer on the surface of the lithium anode after cycling in Examples 1 and 1-2 of this invention; (a) Comparative Example 1, (b) Comparative Example 2, and (c) Example 1. The images show that the systems in these examples induced the formation of extremely dense and uniform lithium deposition layers, indicating that the optimized electrolyte composition helps to construct a stable SEI film and achieve uniform Li... + The flux effectively suppressed lithium dendrite growth.

[0067] The quasi-solid-state electrolyte from Example 1 was applied to two types of lithium metal batteries, as follows: Application in lithium iron phosphate full batteries Lithium iron phosphate, conductive carbon black, and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 8:1:1, with an appropriate amount of N-methylpyrrolidone (NMP) added as a solvent. The mixture was continuously stirred on a magnetic stirrer for 7 hours until homogeneous. This mixture was then coated onto the surface of a carbon-coated aluminum foil current collector, and subsequently dried in a vacuum oven at 80 °C for 12 hours. The dried electrode was cut into 10 mm diameter discs for button cell assembly. The lithium iron phosphate areal loading was 2 mg / cm³. -2 The negative electrode is a lithium metal sheet. Test conditions: test voltage 2.5-3.8 V, test rate: 1 C.

[0068] Figure 7 The graphs show the cycle performance test results of the lithium iron phosphate lithium metal batteries assembled in Example 1 and Comparative Examples 1 and 2 of this invention. As can be seen from the graphs, the initial discharge specific capacity of the battery in Example 1 is 130.54 mAh g⁻¹. -1Subsequently, the battery exhibited a gradual increase in capacity. This capacity recovery mechanism is mainly attributed to the reconstruction of the metastable SEI film formed in the initial stage during cycling, which eventually evolved into a dense and stable interface rich in inorganic components. Thanks to this optimized interface characteristic, the battery demonstrated excellent cycle stability, retaining up to 93.4% of its capacity after 1000 cycles.

[0069] Application in high-voltage ternary lithium batteries Ternary material (NCM811), conductive carbon black, and polyvinylidene fluoride (PVDF) binder were mixed at a mass ratio of 8:1:1, with an appropriate amount of N-methylpyrrolidone (NMP) added as a solvent. The mixture was continuously stirred on a magnetic stirrer for 7 hours until the slurry was homogeneous. This mixture was then coated onto the surface of a carbon-coated aluminum foil current collector, and the coated aluminum foil was placed in a vacuum oven and dried at 80 °C for 12 hours. The dried electrode was cut into 10 mm diameter discs for button cell assembly. The areal loading of the ternary material was 3 mg cm⁻¹. -2 Left and right. The negative electrode is a lithium metal sheet. Test conditions: test voltage 3.0-4.5 V, test rate: 0.5 C.

[0070] Figure 8 The figures show the cycle performance test results of the ternary lithium metal batteries assembled in Example 1 and Comparative Examples 1 and 2 of this invention. As can be seen from the figures, the battery based on Example 1 exhibits a cycle performance of 205.6 mAh g⁻¹. -1 The battery exhibited a high initial discharge specific capacity. Subsequently, it underwent long-cycle testing at 0.5 C, and after 300 cycles, the battery capacity remained at 138.0 mAh g⁻¹. -1 The capacity retention rate is 80.4% (based on the initial capacity of 171.6 mAh g at 0.5 C). -1 calculate).

[0071] Figure 9 The image shows the charge-discharge curves of a 2 Ah-level ternary lithium metal pouch battery assembled using the quasi-solid-state electrolyte prepared in Example 1 of this invention. The assembly method for the Ah-level pouch battery is as follows: First, a positive electrode sheet is prepared in a dry room (dew point -60℃). The active material content of the positive electrode sheet is 96.00%, and the bifacial density of the prepared positive electrode sheet is 48 mg cm⁻¹. -2 The compacted density is 3.30 g / cm³. -3Subsequently, in a glove box, the battery was fabricated using a stacking process with lithium-copper composite strips and a 2325 separator. Aluminum and nickel tabs were ultrasonically welded to the current collector. Finally, the resulting dry cell was packaged in an aluminum-plastic bag to produce an Ah-class soft-pack battery. The testing conditions were: cutoff voltage of 3-4.25 V, and charge / discharge rates of 0.1C charging / 0.2C discharging. As shown in the figure, the battery achieved an average discharge voltage of approximately 3.8 V and a discharge capacity of 1.96 Ah, with a high gravimetric energy density of 302.64 Wh / kg. -1 This demonstrates that the present invention has extremely high commercial application prospects.

[0072] Figure 10 The images show the scanning electron microscope (SEM) morphology of the ternary cathodes after cycling in Examples 1 and 1-2 of this invention; (a) Comparative Example 1, (b) Comparative Example 2, and (c) Example 1. As can be seen from the figures, in the example systems, the active particles maintained good structural integrity after cycling. In contrast, the particle surfaces in the two comparative example systems showed obvious cracks and severe particle pulverization, indicating that their cathode structures underwent significant mechanical degradation. This demonstrates that the quasi-solid-state electrolyte system of the examples effectively promoted the formation of a stable CEI film, thereby significantly suppressing interfacial side reactions.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An in-situ polymerized quasi-solid-state electrolyte, characterized in that, Includes polymer matrix and liquid electrolyte; The liquid electrolyte is confined within the polymer matrix network; The polymer matrix is ​​formed by copolymerization of 2,2,2-trifluoroethyl acrylate and 2-isocyanoethyl methacrylate; The liquid electrolyte comprises a lithium salt and an ether-ester mixed solvent.

2. The in-situ polymerized quasi-solid-state electrolyte as described in claim 1, characterized in that, The ether-ester mixed solvent is a mixture of tetraethylene glycol dimethyl ether and fluoroethylene carbonate, and the volume ratio of tetraethylene glycol dimethyl ether to fluoroethylene carbonate is 1-3:1; preferably 2:

1.

3. The in-situ polymerized quasi-solid electrolyte as described in claim 1, characterized in that, The lithium salt is lithium hexafluorophosphate, and its concentration in the mixed solvent is 1.0-1.5 M, preferably 1.2 M.

4. The in-situ polymerized quasi-solid electrolyte as described in claim 1, characterized in that, The volume fraction of the polymer matrix in the quasi-solid electrolyte is 10%-20%, preferably 15%.

5. The in-situ polymerized quasi-solid-state electrolyte as described in claim 1, characterized in that, The molar ratio of 2,2,2-trifluoroethyl acrylate to 2-isocyanate ethyl methacrylate is 2-8:8-2, preferably 5:

5.

6. The method for preparing the in-situ polymerized quasi-solid electrolyte as described in claim 1, characterized in that, A liquid electrolyte was prepared by dissolving lithium salt in an ether-ester mixed solvent. Add comonomers TFEA and IEM to the above liquid electrolyte, along with a crosslinking agent and an initiator, and mix thoroughly to obtain an electrolyte precursor solution; The electrolyte precursor solution is injected into the battery and subjected to in-situ thermal polymerization at a certain temperature to obtain the in-situ polymerized ether-ester hybrid quasi-solid electrolyte.

7. The preparation method according to claim 1, characterized in that, The crosslinking agent is selected from one of polyethylene glycol diacrylate, trimethylolpropane triacrylate, divinylbenzene (DVB), or ethoxylated trimethylolpropane triacrylate, preferably polyethylene glycol diacrylate, and its addition amount is 0.8-1.2 mol% of the total molar amount of the comonomer; or, the initiator is selected from one of azobisisobutyronitrile, benzoyl azobisisobutyronitrile, or diisopropylbenzene peroxide, preferably azobisisobutyronitrile, and its addition amount is 0.4-0.6 mol% of the total molar amount of the comonomer.

8. The preparation method according to claim 1, characterized in that, The in-situ thermal polymerization temperature is 65-75 ℃, preferably 70 ℃; the polymerization time is 4-8 hours, preferably 6 hours.

9. The application of the quasi-solid-state electrolyte as described in any one of claims 1 to 5 in lithium batteries.

10. A battery, characterized in that, The battery electrolyte is the quasi-solid-state electrolyte as described in any one of claims 1 to 5.

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