Acrylate-based polymer solid electrolyte as well as preparation method and application thereof

Abstract

The invention provides an acrylate-based polymer solid electrolyte as well as a preparation method and application thereof. The preparation method comprises the following steps: adding dichloromethane into a flask filled with 2-hydroxyethyl acrylate, dropwise adding pyridine and glutaryl chloride, and stirring for reaction to obtain an acrylate-based polymer precursor; the preparation method comprises the following steps: uniformly mixing an acrylate-based polymer precursor and succinonitrile, adding a lithium salt into the mixed solution, and fully stirring until the lithium salt is dissolved; and adding azodiisobutyronitrile into the obtained solution, stirring to form a uniform solution, pouring the solution into a glass fiber support membrane, and carrying out polymerization reaction to obtain the acrylate-based polymer solid electrolyte membrane. The acrylate-based polymer solid electrolyte has a unique lithium ion solvation structure, can promote TFSI-to be decomposed on the surface of lithium metal to form LiF, and protects a lithium metal negative electrode interface. A lithium battery assembled based on the acrylate-based polymer solid electrolyte can realize 300-hour high-stability circulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to an acrylate-based polymer solid electrolyte and a preparation method and application thereof. Background Art

[0002] Under the dual carbon policy, reducing greenhouse gas emissions has become a key environmental protection measure. Replacing traditional fossil fuel vehicles with clean and sustainable electric vehicles is a crucial approach to reducing greenhouse gas emissions. However, lithium-ion batteries using conventional graphite anodes and conventional electrolytes are currently approaching their energy density limits. Lithium-ion batteries using lithium metal anodes are expected to exceed 500 Wh / kg in energy density, enhancing the practicality of electric vehicles. However, the flammability and leakage of conventional electrolytes, as well as their inability to effectively inhibit lithium dendrite growth, have hindered the practical application of lithium metal batteries. Therefore, the use of solid-state electrolytes with high mechanical strength, non-flammability, and non-leakage has become an effective solution. Among these, polymer solid-state electrolytes have become a promising candidate due to their flexibility and fabrication flexibility. However, current polymer electrolytes face technical challenges such as low room-temperature ionic conductivity, poor lithium metal-to-li metal interface stability, and a narrow electrochemical window.

[0003] To address the current situation of insufficient ionic conductivity, small molecule organic plasticizers, such as dimethyl carbonate (DMC) and ethylene glycol dimethyl ether (DME), are often added to polymer electrolyte systems in practical applications as electrolyte additives to improve the ionic conductivity of the electrolyte system. However, these additives often undergo various side reactions with the cathode material, affecting battery stability. Succinonitrile (SN) has excellent oxidation resistance due to its electron-withdrawing nitrile group, but it is significantly corrosive to lithium metal. Therefore, it is necessary to design a new polymer framework to improve the compatibility between the electrolyte membrane and lithium metal and establish a stable electrolyte-lithium metal interface.

[0004] Peng Hao et al. (Molecular Design for In-Situ Polymerized Solid Polymer Electrolytes Enabling Stable Cycling of Lithium Metal Batteries. First published: 05 March 2024) modified polyethylene glycol dimethacrylate polymer with various modifying groups and mixed it with succinonitrile (SN) to prepare a new polymer electrolyte. Due to the complex types and structures of the hexafluorobutyl acrylate (HFA) and vinylene carbonate (VC) modifying groups, the polymer electrolyte system is too complex and expensive. In addition, the preparation method of this polymer electrolyte is prone to residual liquid, which threatens the safety of battery operation, making it difficult to achieve large-scale industrial application. Summary of the Invention

[0005] To address the above issues, the present invention provides an acrylate-based polymer solid electrolyte, its preparation method, and its application. This method stabilizes the lithium metal anode-electrolyte system interface in a polymer electrolyte system using succinonitrile (SN) as a plasticizer, broadens the electrolyte decomposition voltage range, and simultaneously improves the system's ionic conductivity. This novel acrylate-based polymer solid electrolyte exhibits excellent performance in various electrochemical tests, including excellent charge-discharge capacity and long cycle life in button cells using lithium iron phosphate as the positive electrode material. It also demonstrates excellent interfacial compatibility in tests with lithium metal symmetric cells.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing an acrylate-based polymer solid electrolyte, comprising the following steps:

[0008] (1) Under a nitrogen atmosphere, dichloromethane is added to a flask containing 2-hydroxyethyl acrylate, pyridine and glutaryl chloride are added dropwise, and the mixture is stirred for reaction. The reaction product is washed, filtered, dried, concentrated under reduced pressure, and purified to obtain an acrylate-based polymer precursor;

[0009] (2) uniformly mixing the acrylate-based polymer precursor obtained in step (1) and succinonitrile (SN), and vacuum drying to remove residual moisture;

[0010] (3) adding lithium salt to the mixed solution of step (2) and stirring thoroughly until the lithium salt is dissolved;

[0011] (4) Adding azobisisobutyronitrile (AIBN) as a thermal initiator for free radical thermal polymerization to the solution obtained in step (3), stirring to form a uniform solution, pouring the obtained solution into a glass fiber support membrane, and performing polymerization reaction to obtain an acrylate-based polymer solid electrolyte membrane.

[0012] Furthermore, in step (1), pyridine and glutaryl chloride are added dropwise at 0-5°C, and then stirred at room temperature for 20-24 hours.

[0013] Furthermore, in step (1), the volume ratio of 2-hydroxyethyl acrylate to dichloromethane is 1.4 to 1.5.

[0014] Furthermore, in step (1), the mass ratio of pyridine to glutaryl chloride is 1.5 to 2.0.

[0015] Furthermore, in step (2), the mass ratio of the acrylate-based polymer precursor to succinonitrile is 0.5 to 0.8.

[0016] Furthermore, in step (2), the product is dried in a vacuum drying oven at 75-80° C. for 10-12 hours.

[0017] Furthermore, in step (4), the polymerization reaction temperature is 60-65° C., and the polymerization reaction time is 8-10 hours.

[0018] The present invention provides an acrylate-based polymer solid electrolyte membrane obtained by the above-mentioned preparation method. The polymer solid electrolyte membrane comprises an acrylate-based polymer skeleton, a plasticizer succinonitrile (SN), a lithium salt and a glass fiber membrane.

[0019] Among them, the glass fiber membrane is the supporting structure of the polymer electrolyte; the acrylate-based polymer skeleton is the framework for regulating the lithium ion solvation structure; and succinonitrile (SN) is responsible for dissociating and transporting lithium ions, thereby improving the ionic conductivity of the system.

[0020] The present invention also provides the use of the aforementioned acrylate-based polymer solid electrolyte in a lithium-ion secondary battery. The lithium-ion secondary battery is obtained by stacking the battery's negative electrode housing, gasket, current collector, lithium metal, acrylate-based solid polymer electrolyte membrane, lithium metal, current collector, and positive electrode housing in this order, placing the entire battery in a hydraulic press, and pressing it.

[0021] The acrylate-based polymer solid electrolyte prepared by the method of the present invention has excellent lithium metal compatibility, containing [Li + (TFSI - ) x ] 1-x Anion-rich solvation structure, the electrolyte membrane can promote TFSI -The acrylate-based polymer solid electrolyte prepared by the present invention can be used to form LiF on the surface of lithium metal, which protects the lithium metal negative electrode interface. A lithium metal symmetric battery assembled with the acrylate-based polymer solid electrolyte prepared by the present invention can achieve a high stability cycle of 300 hours.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The material is easy to synthesize through a simple esterification reaction with mild reaction conditions, which can be applied to large-scale production.

[0024] (2) The electrolyte membrane is easy to prepare and can be successfully synthesized through simple solution casting and free radical thermal polymerization methods. The preparation conditions are simple and no professional equipment or production line construction is required.

[0025] (3) The battery has excellent long-cycle stability. The button battery with lithium iron phosphate as the positive electrode material can run stably for 400 cycles at a rate of 1C, and the capacity retention rate is as high as 97.5%.

[0026] (4) Excellent lithium metal compatibility at a current density of 0.1 mA / cm -2 Under the working conditions, it can run stably for 300 hours without obvious polarization increase.

[0027] (5) The acrylate polymer solid electrolyte prepared by the present invention does not require any additional group modification, and no residual solvent is generated during the production process, which has practical application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a hydrogen nuclear magnetic resonance spectrum of the acrylate-based polymer precursor prepared in Example 1 of the present invention.

[0029] Figure 2 This is an optical photograph of the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention.

[0030] Figure 3 This is the EDS Mapping diagram of the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention.

[0031] Figure 4 This is an electrochemical window test diagram of the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention.

[0032] Figure 5 3 is a conductivity diagram of the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at different temperatures.

[0033] Figure 6This is a polarization current test and electrochemical impedance diagram of the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at 30°C.

[0034] Figure 7 This is a test chart of the capacity at different rates of a button-type battery of lithium iron phosphate positive electrode material assembled with an acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at 30°C.

[0035] Figure 8 The graph is a test graph of the long cycle capacity and coulombic efficiency of a button-type battery of lithium iron phosphate positive electrode material assembled with an acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at different rates at 30°C.

[0036] Figure 9 This is a long cycle test chart at 30° C. of a button-type battery using a lithium iron phosphate positive electrode material assembled with an acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention.

[0037] Figure 10 The lithium metal symmetrical battery assembled with the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention has a lithium metal symmetrical battery at 0.1 mA / cm at 30°C. 2 Long cycle test diagram under current density.

[0038] Figure 11 This is an X-ray photoelectron spectroscopy (XPS) analysis chart of the lithium metal surface after the cycle performance test of the lithium metal symmetrical battery assembled with the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at 30°C is completed. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to the examples, but the embodiments and protection scope of the present invention are not limited thereto.

[0040] Example 1

[0041] A method for synthesizing an acrylate-based polymer precursor comprises the following steps:

[0042] (1) 2-Hydroxyethyl acrylate (9.88 g, 85.12 mmol) was added to a 250 ml three-necked round-bottom flask, and 40.00 ml of dry dichloromethane was added to the flask under a nitrogen atmosphere;

[0043] (2) Pyridine (6.80 g, 86.12 mmol) and glutaryl chloride (7.38 g, 42.56 mmol) were added dropwise to the solution obtained in step (1) at 0°C, and the mixture was stirred at room temperature for 24 hours;

[0044] (3) The product obtained in step (2) was treated with 1.0 mol L -1The residue was washed with HCl solution, filtered, dried over MgSO4, and concentrated under reduced pressure to obtain a yellow solution. The residue was purified by silica gel column (volume ratio, petroleum ether / ethyl acetate = 2 / 1) to obtain a yellow liquid.

[0045] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the acrylate-based polymer precursor prepared in Example 1. The nuclear magnetic peaks indicate that the acrylate-based polymer precursor was successfully synthesized.

[0046] Example 2

[0047] A method for preparing an acrylate-based polymer solid electrolyte membrane comprises the following steps:

[0048] (1) 100.0 mg of the acrylate-based polymer precursor obtained in Example 1 and 150.0 mg of succinonitrile (SN) were uniformly mixed and then dried in a vacuum drying oven at 80° C. for 12 hours to remove residual moisture;

[0049] (2) adding 120.0 mg of lithium salt (LiTFSI) to the homogeneous solution of the acrylate-based polymer precursor and succinonitrile (SN) and stirring thoroughly until the lithium salt is dissolved;

[0050] (3) 5.0 mg of azobisisobutyronitrile (AIBN) was added to the above solution as a thermal initiator for free radical thermal polymerization, and the mixture was stirred to form a uniform solution. The resulting solution was poured into a glass fiber support membrane and polymerized at 60°C for 8 hours to obtain an acrylate-based polymer solid electrolyte membrane.

[0051] Figure 2 This is an optical photograph of the acrylate-based solid polymer electrolyte membrane prepared in Example 2. The electrolyte membrane appears milky white and translucent.

[0052] Figure 3 This is the EDS Mapping diagram of the acrylate-based solid polymer electrolyte membrane prepared in Example 2. It can be seen that the prepared polymer electrolyte membrane is composed of elements such as F, S, C, and N, and the elements are evenly distributed, indicating that the uniformity of the sample obtained by this preparation process is guaranteed.

[0053] Figure 4 This is an electrochemical window test graph of the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention. As can be seen, the polymer electrolyte membrane has a decomposition voltage of 5.12V, which is higher than the operating voltage range (>4.5V) of most commercially available cathode materials. This demonstrates that the acrylate-based solid polymer electrolyte membrane prepared by the present method has excellent high-voltage resistance, compatible with higher-voltage cathode materials, and thus improving the battery's energy density.

[0054] Figure 5 This is a graph showing the conductivity of the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at different temperatures. From this, it can be calculated that the ionic conductivity of the solid polymer electrolyte membrane provided by this embodiment of the present invention at 30°C is 1.31 mS / cm, and the ion migration activation energy is 0.1055 eV. This demonstrates that the acrylate-based solid polymer electrolyte membrane prepared by the method of the present invention has excellent ion transport performance and can effectively improve the rate capability and power density of the battery.

[0055] Figure 6 The polarization current test and electrochemical impedance spectroscopy (EIS) plot of the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at 30°C are shown. From this, it can be calculated that the lithium ion transference number of the solid polymer electrolyte membrane provided in Example 2 of the present invention at 30°C is 0.56. This indicates that the acrylate-based solid polymer electrolyte membrane prepared by the method of the present invention has excellent lithium ion transport performance, can effectively improve the rate capability and power density of the battery, and effectively inhibit the formation of lithium dendrites.

[0056] Application Example 1

[0057] A lithium metal symmetrical battery, the specific preparation steps are as follows:

[0058] The battery negative electrode housing, gasket, current collector, lithium metal, the acrylate-based solid polymer electrolyte membrane obtained in Example 2, lithium metal, current collector, and battery positive electrode housing are stacked together in order. The entire battery is placed in a hydraulic press and pressed to obtain a symmetrical lithium metal battery.

[0059] Application Example 2

[0060] A lithium metal full battery using lithium iron phosphate as the positive electrode material, the specific preparation steps are as follows:

[0061] The battery negative electrode housing, gasket, current collector, lithium metal, the acrylate-based solid polymer electrolyte membrane obtained in Example 2, the lithium iron phosphate positive electrode, current collector, and battery positive electrode housing are stacked together in order. The entire battery is placed in a hydraulic press and pressed to obtain a lithium iron phosphate positive electrode button cell.

[0062] Figure 7 This chart shows the capacity of a lithium iron phosphate positive electrode button cell assembled with the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at different rates at 30°C. As can be seen, the button cell with lithium iron phosphate as the positive electrode material has a charge-discharge specific capacity of 161, 157, 148, 140, 123, 110, 95, and 66 mAh / g at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C, respectively, demonstrating its excellent rate performance.

[0063] Figure 8 The following graphs show the long-term capacity and coulombic efficiency of a lithium iron phosphate cathode material button cell assembled with an acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at different rates at 30°C. As can be seen, the battery exhibited no significant capacity decay during the 150-cycle long-term cycle test, demonstrating excellent cycling stability. Furthermore, the charge and discharge curves closely matched, and the average coulombic efficiency reached 99.89%.

[0064] Figure 9 This is a graph showing the long-term cycling test of a lithium iron phosphate cathode material button cell assembled with an acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention at 30°C. After 400 cycles, the battery still maintained a capacity retention rate of 95.56%, and the average coulombic efficiency was 99.91%.

[0065] Figure 10 The lithium metal symmetrical battery assembled with the acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention has a lithium metal symmetrical battery at 0.1 mA / cm at 30°C. 2 Long cycle test diagram under current density. The lithium metal symmetric battery is 0.1mA / cm 2 , 0.05mAh / cm 2 Under normal conditions, it can circulate stably for more than 300 hours.

[0066] Figure 11 This is an X-ray photoelectron spectroscopy (XPS) analysis of the lithium metal surface of a symmetrical lithium metal battery assembled with an acrylate-based solid polymer electrolyte membrane prepared in Example 2 of the present invention after cycling performance testing at 30°C. The red line in the figure represents CF, the purple line represents LiF, the blue line represents the fitted curve, and the green line represents the data baseline. After the test cycle, the XPS method detected a signal peak with a binding energy of 685.0 eV on the lithium metal surface, confirming that it is the LiF component. This demonstrates that the acrylate-based polymer electrolyte membrane prepared by the method of the present invention has an excellent lithium metal anode-electrolyte interface.

Claims

1. A method for preparing an acrylate-based polymer solid electrolyte, characterized in that: The specific steps are as follows: (1) Under a nitrogen atmosphere, dichloromethane is added to a flask containing 2-hydroxyethyl acrylate, pyridine and glutaryl chloride are added dropwise, and the mixture is stirred for reaction. The reaction product is washed, filtered, dried, concentrated under reduced pressure, and purified to obtain an acrylate-based polymer precursor; (2) uniformly mixing the acrylate-based polymer precursor obtained in step (1) and succinonitrile, and vacuum drying to remove residual moisture; (3) adding lithium salt to the mixed solution of step (2) and stirring thoroughly until the lithium salt is dissolved; (4) adding azobisisobutyronitrile to the solution obtained in step (3), stirring to form a uniform solution, pouring the obtained solution into a glass fiber support membrane, and performing a polymerization reaction to obtain an acrylate-based polymer solid electrolyte membrane.

2. The preparation method according to claim 1, characterized in that In step (1), pyridine and glutaryl chloride are added dropwise at 0-5°C, and then stirred at room temperature for 20-24 hours.

3. The preparation method according to claim 1, characterized in that In step (1), the mass volume ratio of 2-hydroxyethyl acrylate to dichloromethane is 1.4 to 1.

5.

4. The preparation method according to claim 1, characterized in that In step (1), the mass ratio of pyridine to glutaryl chloride is 1.5 to 2.

0.

5. The preparation method according to claim 1, characterized in that In step (2), the mass ratio of the acrylate-based polymer precursor to succinonitrile is 0.5 to 0.

8.

6. The preparation method according to claim 1, characterized in that In step (2), the product is dried in a vacuum drying oven at 75 to 80° C. for 10 to 12 hours.

7. The preparation method according to claim 1, characterized in that In step (4), the polymerization reaction temperature is 60-65° C., and the polymerization reaction time is 8-10 hours.

8. An acrylate-based polymer solid electrolyte obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the acrylate-based polymer solid electrolyte according to claim 8 in a lithium-ion secondary battery.

10. The use according to claim 9, characterized in that The battery negative electrode shell, gasket, current collector, lithium metal, acrylate-based solid polymer electrolyte membrane, lithium metal, current collector, and battery positive electrode shell are stacked together in order, and the entire battery is placed in a hydraulic press and pressed to obtain a lithium-ion secondary battery.

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