A non-newtonian fluid quasi-solid electrolyte, a preparation method and applications

Abstract

This invention provides a non-Newtonian fluid quasi-solid-state electrolyte, its preparation method, and its application. The raw materials for preparing the electrolyte include: a basic electrolyte, a shear-thickening material, a polymeric monomer, a crosslinking agent, and a thermal initiator. The mass ratio of the basic electrolyte to the shear-thickening material is 20:(1-10). This invention utilizes a quasi-solid-state electrolyte with non-Newtonian fluid properties to absorb the stress caused by lithium plating / delithiation in the battery, mitigating volume changes during charging and discharging. It also rapidly undergoes mechanical hardening during high-current pulse charging or sudden external loads, inhibiting lithium dendrite growth and preventing internal short circuits. The polymer network obtained through in-situ polymerization using polymeric monomers, crosslinking agents, and thermal initiators prevents battery leakage or oxidative decomposition and ensures more uniform lithium metal deposition and dissolution, further inhibiting lithium dendrite growth. Through the synergistic effect of the non-Newtonian fluid and the in-situ polymer network, the safety and cycle performance of the battery can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery technology, and in particular to a non-Newtonian fluid quasi-solid-state electrolyte, its preparation method, and its application. Background Technology

[0002] With the continuous advancement of global energy conservation and emission reduction, and the rapid development of new energy vehicles, the main source of energy utilization is gradually shifting from traditional fossil fuels to low-carbon renewable energy. Therefore, high-efficiency energy storage systems based on electrochemical reactions are not limited by geographical environment. Developing high-energy-density and high-safety electrochemical energy storage technologies is a crucial link in the energy revolution represented by renewable energy and new energy vehicle industries. Currently, lithium-ion battery technology is highly mature and plays a vital role in promoting the intelligentization and portability of society. After nearly thirty years of development, lithium-ion batteries based on electrochemical intercalation reactions have approached their theoretical energy density limit, but still cannot meet the energy storage needs of contemporary society. Therefore, the development of next-generation electrode materials with high safety and high specific capacity is imperative.

[0003] Lithium metal is considered one of the most promising anode materials due to its ultra-high theoretical specific capacity (3860 mAh / g) and very low standard negative electrochemical potential (-3.040 V). High-performance lithium metal rechargeable batteries can break through the energy density bottleneck of existing lithium-ion batteries (≤350 Wh / kg), achieving a single-cell energy density ≥500 Wh / kg. However, lithium metal batteries face safety issues, primarily lithium plating, dead lithium, and lithium dendrite formation caused by uneven deposition of lithium metal in the anode. Uneven deposition of lithium metal affects the battery's coulombic efficiency and cycle life, while lithium dendrite growth can puncture the separator, leading to internal short circuits and potentially causing battery combustion or explosion.

[0004] To address the issues of interfacial stability and dendrite growth in lithium metal anodes, these problems can be suppressed by understanding lithium deposition patterns and regulating metal deposition behavior. This can be achieved by reducing the current density at the electrode surface and inducing uniform lithium-ion deposition, thus reducing dendrite formation. Three-dimensional lithium metal anodes can mitigate volume effects during cycling and improve battery electrochemical performance. Optimizing the electrolyte and constructing artificial protective films can also suppress lithium dendrite growth and enhance battery performance. Solid-state electrolytes can reduce side reactions at the anode interface and improve battery safety. Furthermore, the mechanical and chemical compatibility between the electrolyte and electrode can be improved by preparing composite electrolytes and introducing interface modification layers. However, currently, optimizing the electrolyte has limited effectiveness in suppressing lithium dendrite growth, and the introduction of solid-state electrolytes significantly affects the ionic conductivity of the electrolyte, thereby impacting battery performance. Summary of the Invention

[0005] The purpose of this invention is to provide a non-Newtonian fluid quasi-solid electrolyte, its preparation method, and its application, in order to solve the problems in the background art mentioned above.

[0006] The technical solution adopted in this invention is: a non-Newtonian fluid quasi-solid electrolyte, wherein the raw materials for preparing the electrolyte include: a basic electrolyte, a shear thickening material, a polymer monomer, a crosslinking agent, and a thermal initiator, wherein: the mass ratio of the basic electrolyte to the shear thickening material is 20:(1-10).

[0007] Preferably, the basic electrolyte contains lithium salt, main solvent and diluent; the concentration of lithium salt in the main solvent is 3 to 10 mol / L, and the concentration in the basic electrolyte is 0.1 to 2.5 mol / L.

[0008] Preferably, the lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluoroarsenate, and lithium tetrafluoroborate; the main solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether; and the diluent includes at least one of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether.

[0009] Preferably, the polymeric monomer accounts for 0.5% to 5% of the total mass of the base electrolyte and the shear thickening raw material, the crosslinking agent accounts for 0.5% to 5% of the total mass of the base electrolyte and the shear thickening raw material, and the thermal initiator accounts for 0.1% to 0.5% of the total mass of the polymeric monomer and the crosslinking agent.

[0010] Preferably, the polymerizing monomer includes at least one selected from pentaerythritol tetraacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol diacrylate; the crosslinking agent includes at least one selected from pentaerythritol tetra-3-mercaptopropionate, methyl mercaptopropionate, ethyl 3-mercaptopropionate, and γ-methacryloyloxypropyltrimethoxysilane; and the thermal initiator includes at least one selected from azobisisobutyronitrile, benzoyl peroxide, and diphenoxyethyl peroxide.

[0011] Preferably, the shear-thickening material is nano-silica.

[0012] The technical solution of the present invention also includes: a method for preparing the non-Newtonian fluid quasi-solid electrolyte as described above, comprising the steps of:

[0013] The lithium salt, main solvent, and diluent are mixed in proportion to obtain the basic electrolyte.

[0014] Mix the shear thickening material and the base electrolyte in proportion to obtain a non-Newtonian fluid electrolyte.

[0015] After mixing the monomers, crosslinking agent, and non-Newtonian fluid electrolyte in proportion, add the thermal initiator and stir well. Allow to stand for in-situ polymerization to obtain a non-Newtonian fluid quasi-solid electrolyte.

[0016] Preferred conditions for in-situ polymerization: temperature 50–85°C, time 8–36 h.

[0017] The technical solution of the present invention also includes: the application of the non-Newtonian fluid quasi-solid-state electrolyte as described above in lithium metal batteries.

[0018] The beneficial effects of this invention are as follows: A quasi-solid-state electrolyte with non-Newtonian fluid properties absorbs the stress caused by lithium plating / delithiation in the battery, alleviating volume changes during charging and discharging. It also rapidly undergoes mechanical hardening under conditions such as high-current pulse charging or sudden external loads, inhibiting lithium dendrite growth and preventing internal short circuits. The polymer network obtained through in-situ polymerization using monomers, crosslinking agents, and thermal initiators can bind the base electrolyte within, preventing leakage or oxidative decomposition. It also improves the compatibility of the battery's internal interfaces, homogenizing the interfacial current and resulting in more uniform lithium deposition and dissolution, thus inhibiting lithium dendrite growth. Furthermore, the viscoelasticity of the in-situ polymer network helps mitigate volume changes during charging and discharging. Through the synergistic effect of the non-Newtonian fluid and the in-situ polymer network, the safety and cycle performance of the battery can be significantly improved. Attached Figure Description

[0019] Figure 1 This is the electrochemical impedance spectroscopy obtained in Example 1 of the present invention;

[0020] Figure 2 This is the electrochemical impedance spectroscopy obtained in Example 2 of the present invention;

[0021] Figure 3 These are charge-discharge cycle diagrams obtained from Embodiment 3 and Comparative Example 1 of the present invention. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] The first aspect of the present invention provides a non-Newtonian fluid quasi-solid electrolyte and a method for its preparation.

[0024] In this embodiment, the raw materials for preparing the non-Newtonian fluid quasi-solid-state electrolyte include a basic electrolyte, a shear-thickening material, a polymer monomer, a crosslinking agent, and a thermal initiator. The shear-thickening material is used to construct the non-Newtonian fluid properties of the electrolyte. Since dendrite growth accelerates the volume change of the material, lithium metal will deposit at the negative electrode during charging, inevitably causing an increase in volume. Under conditions of uneven current density or uneven lithium nucleation sites on the negative electrode side, the lithium metal deposition will occur in a dendritic morphology. This results in an uneven and non-dense deposition layer surface, further increasing the volume change. Furthermore, dendrites may pierce the separator, leading to internal short circuits. The aforementioned quasi-solid-state electrolyte with non-Newtonian fluid properties can absorb the stress caused by lithium plating / delithiation in the battery, alleviating stress during charging and discharging. The volume change within the electrolyte and the rapid mechanical hardening that occurs during high-current pulse charging or sudden external loads inhibit lithium dendrite growth and prevent lithium dendrite penetration of the separator, thus preventing internal short circuits. The polymer network obtained through in-situ polymerization using monomers, crosslinking agents, and thermal initiators can bind the basic electrolyte within, preventing battery leakage or oxidative decomposition, and improving the compatibility of the battery's internal interfaces. This homogenizes the interfacial current, resulting in more uniform lithium metal deposition and dissolution, and inhibits lithium dendrite growth. Furthermore, the viscoelasticity of the polymer network obtained through in-situ polymerization helps mitigate volume changes during charging and discharging. Through the synergistic effect of non-Newtonian fluids and the in-situ polymer network, the safety and cycle performance of the battery can be significantly improved.

[0025] The basic electrolyte contains lithium salt, main solvent and diluent; the concentration of lithium salt in the main solvent is preferably 3 to 10 mol / L, and the concentration in the basic electrolyte is preferably 0.1 to 2.5 mol / L.

[0026] In this embodiment, the lithium salt can be one or more of lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonylimide) (LiTFSI), lithium hexafluoroarsenate (LiAsF6), and lithium tetrafluoroborate (LiBF4); the main solvent can be one or more of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), and triethylene glycol dimethyl ether (G3); and the diluent can be one or more of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OFE), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether (HFE).

[0027] The preferred mass ratio of the base electrolyte to the shear thickening material is 20:(1-10), and the shear thickening material is nano-silica, preferably silica particles with a diameter of 1-1000 nm.

[0028] The preferred amounts of polymeric monomer, crosslinking agent, and thermal initiator are as follows: polymeric monomer accounts for 0.5% to 5% of the total mass of the base electrolyte and shear thickening raw material, crosslinking agent accounts for 0.5% to 5% of the total mass of the base electrolyte and shear thickening raw material, and thermal initiator accounts for 0.1% to 0.5% of the total mass of the polymeric monomer and crosslinking agent.

[0029] In this embodiment, the polymerizable monomer can be one of pentaerythritol tetraacrylate (PETEA), triethylene glycol dimethacrylate (TEGDMA), or tetraethylene glycol diacrylate (TEGDA); the crosslinking agent can be one of pentaerythritol tetra-3-mercaptopropionate (PETMP), methyl mercaptopropionate, ethyl 3-mercaptopropionate, or γ-methacryloyloxypropyltrimethoxysilane; and the thermal initiator can be one of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), or diphenoxyethyl peroxide dicarbonate (BPPD).

[0030] The method for preparing the above-mentioned non-Newtonian fluid quasi-solid electrolyte includes the following steps:

[0031] (1) Mix lithium salt, main solvent and diluent in proportion, and stir at room temperature for 8-12 hours to obtain basic electrolyte;

[0032] (2) Mix the shear thickening raw material and the basic electrolyte in proportion, and stir at room temperature for 8-12 hours to obtain a non-Newtonian fluid electrolyte.

[0033] (3) After mixing the monomers, crosslinking agent and non-Newtonian fluid electrolyte in proportion, add the thermal initiator and stir (10-30 min), let stand to polymerize in situ, and obtain non-Newtonian fluid quasi-solid electrolyte.

[0034] In step (3), the preferred conditions for in-situ polymerization are: temperature 50–85°C and time 8–36 h.

[0035] The second aspect of the present invention provides the application of the non-Newtonian fluid quasi-solid-state electrolyte of the first aspect in a lithium metal battery.

[0036] The method for preparing a lithium metal battery using this electrolyte includes the following steps:

[0037] S1. The mixture obtained by adding the thermal initiator in step (3) and stirring evenly is dip-coated onto the surface of the positive electrode sheet;

[0038] S2. Cover the mixture on the positive electrode plate in step S1 with a diaphragm, and dip the diaphragm surface with the mixture after adding the thermal initiator in step (3) and stirring it evenly.

[0039] S3. Cover the mixture on the diaphragm in step S2 with a lithium foil and vacuum seal the whole thing using an aluminum-plastic film.

[0040] S4. Place the packaged battery at 50-85℃ for 12-48 hours to perform in-situ polymerization to obtain a lithium metal battery.

[0041] The present technical solution will be further illustrated below through examples and comparative examples.

[0042] Example 1: Preparation of a non-Newtonian fluid quasi-solid-state electrolyte

[0043] (1) Weigh 3.74g DME (diluent), 24.07g TTE (main solvent) and 5.61g LiFSI (lithium salt) in an argon-environment glove box, mix them and stir magnetically for 10h at room temperature to obtain the basic electrolyte;

[0044] (2) Add 3.71g of nano-silica (shear thickening material) to the basic electrolyte and stir mechanically for 12h to obtain a non-Newtonian fluid electrolyte; (3) Add 0.1857g of PETEA (polymer monomer) and 1.39g of γ-methacryloyloxypropyltrimethoxysilane (crosslinking agent) to the non-Newtonian fluid electrolyte and stir mechanically for 3h;

[0045] Add 2.37 mg AIBN (thermal initiator), stir for 15 min, then inject the mixture into a 20 mm diameter polytetrafluoroethylene mold and let it stand at 60 °C for 36 h for in-situ polymerization.

[0046] After cooling to room temperature, the sheet of non-Newtonian fluid quasi-solid electrolyte is obtained by demolding.

[0047] A blocking battery was assembled using a sheet of non-Newtonian fluid quasi-solid electrolyte, and the electrochemical impedance spectroscopy was measured as shown in the attached figure. Figure 1 As shown, its ionic conductivity was calculated to be 1.97 mS / cm.

[0048] Example 2: Preparation of a non-Newtonian fluid quasi-solid-state electrolyte

[0049] (1) Weigh 7.00g G3 (diluent), 20.43g OFE (main solvent) and 7.48g LiFSI (lithium salt) in an argon-environment glove box, mix them and stir magnetically for 12h at room temperature to obtain the basic electrolyte;

[0050] (2) Add 8.73g of nano-silica (shear thickening material) to the basic electrolyte and stir mechanically for 12h to obtain a non-Newtonian fluid electrolyte;

[0051] (3) Add 1.09g PEGMEA (polymer monomer) and 1.09g TEGDMA (crosslinking agent) to a non-Newtonian fluid electrolyte and stir mechanically for 2h;

[0052] Add 3.27 mg AIBN (thermal initiator), stir for 15 min, then inject the mixture into a 20 mm diameter polytetrafluoroethylene mold and let it stand at 80 °C for 10 h for in-situ polymerization;

[0053] After cooling to room temperature, the sheet of non-Newtonian fluid quasi-solid electrolyte is obtained by demolding.

[0054] A blocking battery was assembled using a sheet of non-Newtonian fluid quasi-solid electrolyte, and the electrochemical impedance spectroscopy was measured as shown in the attached figure. Figure 2 As shown, its ionic conductivity was calculated to be 0.85 mS / cm.

[0055] Example 3: Preparation of a lithium metal battery

[0056] Preparation of the positive electrode: The positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 The O2 ternary material is made by mixing the positive electrode active material, the conductive agent SuperP and the binder 6wt% polyvinylidene fluoride-hexafluoropropylene in a mass ratio of 90:5:5, adding an appropriate amount of NMP for dilution, stirring evenly, and then uniformly coating it onto a 12μm aluminum foil. After drying, rolling and punching, the positive electrode sheet is obtained.

[0057] Preparation of negative electrode sheet: Select lithium foil with a thickness of 60μm and cut it to obtain negative electrode sheet.

[0058] Separator: Select a double ceramic diaphragm with a thickness of 20μm.

[0059] Assembly of lithium metal battery: The mixture obtained by adding thermal initiator and stirring evenly in step (3) of Example 1 is coated on the surface of the positive electrode sheet, and a separator is covered on the mixture at this time; the mixture obtained by adding thermal initiator and stirring evenly in step (3) of Example 1 is dipped onto the surface of the separator, and lithium metal foil is covered on the mixture at this time. The whole is vacuum sealed using aluminum-plastic film. During vacuum sealing, the battery is placed in a vacuum oven and vacuumed 3 times, each time for 10 minutes (vacuum degree 0.08MPa) to remove residual air inside the electrode; the sealed battery is left to stand at room temperature for 12 hours to achieve further wetting, and then placed in an oven at 60°C for 36 hours for in-situ polymerization to obtain a lithium metal battery.

[0060] The lithium metal battery was subjected to 70 charge-discharge cycles, and the charge-discharge curves are shown in the attached figure. Figure 3 As shown, its capacity retention rate reaches 93.54%.

[0061] Comparative Example 1: Preparation of Lithium Metal Batteries

[0062] The only difference from Example 3 is that Comparative Example 1 did not use the non-Newtonian fluid quasi-solid electrolyte of Example 3, but instead used the basic electrolyte in step (1) of Example 1.

[0063] The lithium metal battery was subjected to 70 charge-discharge cycles, and the charge-discharge curves are shown in the attached figure. Figure 3 As shown, its capacity retention rate is 85.96%.

[0064] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the claims, or equivalent forms of such scope and boundaries.

Claims

1. A non-Newtonian fluid quasi-solid-state electrolyte, characterized in that, The raw materials for preparing the electrolyte include: a basic electrolyte, a shear thickening material, a polymer monomer, a crosslinking agent, and a thermal initiator, wherein: the mass ratio of the basic electrolyte to the shear thickening material is 20:(1~10); the shear thickening material is nano-silica used to construct the non-Newtonian fluid properties of the electrolyte.

2. The non-Newtonian fluid quasi-solid-state electrolyte according to claim 1, characterized in that, The basic electrolyte contains lithium salt, main solvent and diluent; the concentration of lithium salt in the main solvent is 3~10 mol / L and the concentration in the basic electrolyte is 0.1~2.5 mol / L.

3. The non-Newtonian fluid quasi-solid-state electrolyte according to claim 2, characterized in that, The lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluoroarsenate, and lithium tetrafluoroborate; the main solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether; the diluent includes at least one of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether.

4. The non-Newtonian fluid quasi-solid-state electrolyte according to any one of claims 1-3, characterized in that, The polymeric monomer accounts for 0.5% to 5% of the total mass of the base electrolyte and the shear thickening raw material, the crosslinking agent accounts for 0.5% to 5% of the total mass of the base electrolyte and the shear thickening raw material, and the thermal initiator accounts for 0.1% to 0.5% of the total mass of the polymeric monomer and the crosslinking agent.

5. The non-Newtonian fluid quasi-solid-state electrolyte according to claim 4, characterized in that, The polymerizing monomer includes at least one of pentaerythritol tetraacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol diacrylate; the crosslinking agent includes at least one of pentaerythritol tetra-3-mercaptopropionate, methyl mercaptopropionate, ethyl 3-mercaptopropionate, and γ-methacryloyloxypropyltrimethoxysilane; and the thermal initiator includes at least one of azobisisobutyronitrile, benzoyl peroxide, and diphenoxyethyl peroxide.

6. A method for preparing the non-Newtonian fluid quasi-solid-state electrolyte according to any one of claims 1-5, characterized in that, Including the following steps: The lithium salt, main solvent, and diluent are mixed in proportion to obtain the basic electrolyte. Mix the shear thickening material and the base electrolyte in proportion to obtain a non-Newtonian fluid electrolyte. After mixing the monomers, crosslinking agent, and non-Newtonian fluid electrolyte in proportion, add the thermal initiator and stir well. Allow to stand for in-situ polymerization to obtain a non-Newtonian fluid quasi-solid electrolyte.

7. The method for preparing a non-Newtonian fluid quasi-solid-state electrolyte according to claim 6, characterized in that, Conditions for in-situ polymerization: temperature 50~85℃, time 8~36h.

8. The application of the non-Newtonian fluid quasi-solid-state electrolyte according to any one of claims 1-5 in lithium metal batteries.

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