High-magnification low-temperature-resistant lithium battery

Abstract

The application discloses a high-multiplying-rate low-temperature-resistant lithium battery and belongs to the technical field of lithium batteries. The lithium battery comprises a positive electrode, a negative electrode and an electrolyte. The preparation method of the electrolyte comprises the following steps: uniformly mixing acrylamide, imidazolyl propyl sulfonate, sodium acrylate, N-methyl pyrrolidone and deionized water, adding an initiator and a crosslinking agent, and obtaining a polyacrylamide gel after ultraviolet light irradiation and solidification; mixing 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone, stirring, and obtaining a precursor solution; and immersing the polyacrylamide gel in the precursor solution and heating to obtain the electrolyte. The lithium battery solves the problem of electrolyte freezing under a low-temperature environment and improves the low-temperature resistance of the lithium battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a high-rate, low-temperature resistant lithium battery. Background Technology

[0002] Traditional commercial electrolytes have relatively high melting points. Their viscosity increases significantly as the temperature decreases, thus affecting ionic conductivity and greatly inhibiting Li-ionization. + The ability to transmit signals is crucial. More importantly, as temperatures continue to drop, there is a risk of electrolyte freezing, leading to battery failure. Developing cryogenic electrolytes is essential to broaden the application scenarios of lithium batteries in low-temperature environments. Summary of the Invention

[0003] The purpose of this invention is to provide a high-rate, low-temperature resistant lithium battery to solve the problem of electrolyte freezing in lithium batteries under low-temperature conditions and improve the low-temperature resistance of lithium batteries.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A high-rate, low-temperature resistant lithium battery includes a positive electrode, a negative electrode, and an electrolyte;

[0006] The method for preparing the electrolyte includes the following steps:

[0007] S1. Mix acrylamide, imidazole propanesulfonate, sodium acrylate, N-methylpyrrolidone, and deionized water, stir for 30-40 min, add initiator and crosslinking agent, stir for 8-10 min, transfer to mold and cure under 365nm, 250W ultraviolet light for 2-3 h, wash with anhydrous ethanol and dry to obtain polyacrylamide gel.

[0008] S2. Mix 1,3-dioxolane, lithium bis(trifluoromethanesulfonylimide), lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methylpyrrolidone, and stir for 1-2 hours to obtain a precursor solution.

[0009] S3. Immerse the polyacrylamide gel in the precursor solution for 20-30 hours and heat at 40-50°C for 20-40 minutes to obtain the electrolyte.

[0010] As a preferred embodiment of the present invention, in step S1, the ratio of acrylamide, imidazole propanesulfonate, sodium acrylate, N-methylpyrrolidone, deionized water, initiator, and crosslinking agent is 2-4g: 0.1-0.2g: 0.1-0.3g: 10-12mL: 10-12mL: 0.014-0.018g: 0.002-0.004g.

[0011] In a preferred embodiment of the present invention, in step S1, the initiator is ammonium persulfate.

[0012] As a preferred embodiment of the present invention, in step S1, the crosslinking agent is N,N'-methylenebisacrylamide.

[0013] As a preferred embodiment of the present invention, the preparation method of the imidazolyl propanesulfonate includes the following steps:

[0014] Mix 1,3-propylsulfonyl lactone, 1-vinylimidazole, and acetone, stir in an ice-water bath for 2-3 days, filter, wash the solid phase, and dry under vacuum at 40°C for 24 hours to obtain the imidazole propanesulfonate.

[0015] As a preferred embodiment of the present invention, the molar ratio of 1,3-propylsulfonyl lactone, 1-vinylimidazole, and acetone is 1:1:10.

[0016] As a preferred embodiment of the present invention, in step S2, the ratio of 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water, and N-methylpyrrolidone is 1-2 mL: 0.45-0.47 g: 0.12-0.16 g: 0.04-0.06 g: 1-1.2 mL: 5-6 mL: 0.25-0.27 mL: 0.3-0.5 mL.

[0017] The beneficial effects of this invention are:

[0018] (1) This invention modifies the hydrogen bond network structure of the gel electrolyte by copolymerizing acrylamide and the zwitterionic monomer imidazole propanesulfonate, reducing the proportion of strong hydrogen bonds, making the gel network softer and more porous, thus promoting lithium ion transport. By using the three-dimensional porous network of the gel to bind free water, its content and activity are reduced, which can reduce its freezing at low temperatures, avoid the electrolyte freezing and the resulting ion conduction obstruction, and improve the stability of the electrolyte in low-temperature environments.

[0019] (2) This invention utilizes the positive and negative charge centers of the zwitterionic monomer imidazolium propanesulfonate to form a dynamic electric double layer on the electrode surface. When the battery is under high voltage, these charged groups will guide Li through electrostatic attraction / repulsion. + Uniformly distributed on the electrode surface to avoid localized Li + When the concentration is too high, a uniform ion distribution can balance the electric field strength on the electrode surface, reduce electrolyte decomposition caused by local strong electric fields, block dendrite penetration, and further inhibit dendrite growth, thereby improving the interfacial stability of the electrolyte and enhancing voltage withstand capability.

[0020] (3) By adding lithium trifluoromethanesulfonate, the present invention provides weak anionic coordination ability, which can reduce Li + The degree to which Li was bound made + It maintains a high migration rate even at low temperatures, thus preserving a certain ionic conductivity; simultaneously, through synergistic interaction with lithium bis(trifluoromethanesulfonyl)imide, it improves the overall ionic environment and increases the free movement of Li. + The quantity reduces the system's tendency to crystallize and maintains unobstructed ion transport pathways.

[0021] (4) This invention utilizes in-situ polymerization of 1,3-dioxolane, whose polymer chains can grow and fill the micropores, defects, or rough structures on the surface of the gel skeleton, forming a continuous and void-free interfacial transition layer, which promotes the growth of Li + Interface migration reduces charge transfer impedance, ensures the continuity of ion transport paths, and maintains the stability of ion transport at low temperatures. Detailed Implementation

[0022] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0023] Example 1

[0024] A high-rate, low-temperature resistant lithium battery includes a positive electrode, a negative electrode, and an electrolyte;

[0025] The method for preparing the electrolyte includes the following steps:

[0026] S1. Mix acrylamide, imidazole propanesulfonate, sodium acrylate, N-methylpyrrolidone, and deionized water, stir for 30 min, add initiator and crosslinking agent, stir for 8 min, transfer to a mold, cure under 365 nm, 250 W UV light for 3 min, wash with anhydrous ethanol and dry to obtain a polyacrylamide gel with dimensions of 5 cm × 5 cm × 0.1 cm; the ratio of acrylamide, imidazole propanesulfonate, sodium acrylate, N-methylpyrrolidone, deionized water, initiator, and crosslinking agent is 2 g: 0.1 g: 0.1 g: 10 mL: 10 mL: 0.014 g: 0.002 g;

[0027] The initiator is ammonium persulfate; the crosslinking agent is N,N'-methylenebisacrylamide;

[0028] The preparation method of the imidazolium propanesulfonate includes the following steps:

[0029] Mix 1,3-propylsulfonyl lactone, 1-vinylimidazole, and acetone, stir in an ice-water bath for 2 days, filter, wash the solid phase, and dry under vacuum at 40°C for 24 hours to obtain the imidazole propanesulfonate; the molar ratio of 1,3-propylsulfonyl lactone, 1-vinylimidazole, and acetone is 1:1:10.

[0030] S2. Mix 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water, and N-methylpyrrolidone, and stir for 1 h to obtain a precursor solution; the ratio of the amounts of 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water, and N-methylpyrrolidone is 1 mL: 0.45 g: 0.12 g: 0.04 g: 1 mL: 5 mL: 0.25 mL: 0.3 mL;

[0031] S3. Cut the polyacrylamide gel into small pieces with dimensions of 1.2cm×1.2cm×0.1cm, soak them in the precursor solution for 20h, heat them at 40℃ for 20min, and then dry the heated electrolyte with supercritical carbon dioxide under the drying conditions of 45℃ and 10MPa pressure for 20h to obtain the electrolyte.

[0032] Lithium cobalt oxide cathode material, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone were mixed in a mass ratio of 8:1:1:2 and ground in an agate mortar for 30 minutes to obtain a well mixed slurry. The slurry was then evenly coated onto aluminum foil using a scraper and dried in a vacuum oven at 60°C for 24 hours. Subsequently, it was punched into a disc with a diameter of 12 mm to obtain a cathode sheet with a thickness of 1 cm.

[0033] Graphite powder, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone were mixed in a mass ratio of 8:1:1:2 and ground in an agate mortar for 30 minutes to obtain a well mixed slurry. The slurry was then evenly coated onto copper foil using a scraper and dried in a vacuum oven at 60°C for 24 hours. Subsequently, it was punched into a disc with a diameter of 12 mm to obtain a negative electrode sheet with a thickness of 1 cm.

[0034] In a glove box protected by an argon atmosphere (water content less than 0.1 ppm, oxygen content less than 0.1 ppm), using a Clegrad 2400 separator, the above-mentioned positive electrode, electrolyte, separator, electrolyte and negative electrode are stacked in sequence and formed into an electrode assembly through a winding process. The electrode assembly is then placed in an aluminum shell and sealed. Finally, after standing, formation and shaping processes, the lithium battery of this embodiment is obtained.

[0035] Example 2

[0036] A high-rate, low-temperature resistant lithium battery includes a positive electrode, a negative electrode, and an electrolyte;

[0037] The method for preparing the electrolyte includes the following steps:

[0038] S1. Mix acrylamide, imidazole propanesulfonate, sodium acrylate, N-methylpyrrolidone, and deionized water, stir for 35 min, add initiator and crosslinking agent, stir for 9 min, transfer to a mold, and cure under ultraviolet light at 365 nm and 250 W for 4 min. After washing with anhydrous ethanol and drying, a polyacrylamide gel with dimensions of 5 cm × 5 cm × 0.1 cm is obtained. The ratio of acrylamide, imidazole propanesulfonate, sodium acrylate, N-methylpyrrolidone, deionized water, initiator, and crosslinking agent is 3 g: 0.15 g: 0.2 g: 11 mL: 11 mL: 0.016 g: 0.003 g.

[0039] The initiator is ammonium persulfate; the crosslinking agent is N,N'-methylenebisacrylamide;

[0040] The preparation method of the imidazolium propanesulfonate includes the following steps:

[0041] Mix 1,3-propylsulfonyl lactone, 1-vinylimidazole, and acetone, stir in an ice-water bath for 2.5 days, filter, wash the solid phase, and dry under vacuum at 40°C for 24 hours to obtain the imidazole propanesulfonate; the molar ratio of 1,3-propylsulfonyl lactone, 1-vinylimidazole, and acetone is 1:1:10.

[0042] S2. Mix 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water, and N-methylpyrrolidone, and stir for 1.5 h to obtain a precursor solution; the ratio of the amounts of 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water, and N-methylpyrrolidone is 1.5 mL: 0.46 g: 0.14 g: 0.05 g: 1.1 mL: 5.5 mL: 0.26 mL: 0.4 mL;

[0043] S3. Cut the polyacrylamide gel into small pieces with dimensions of 1.2cm×1.2cm×0.1cm, soak them in the precursor solution for 25h, heat them at 45℃ for 30min, and then dry the heated electrolyte with supercritical carbon dioxide under the drying conditions of maintaining a pressure of 10MPa at 45℃ for 25h to obtain the electrolyte.

[0044] Lithium cobalt oxide cathode material, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone were mixed in a mass ratio of 8:1:1:2 and ground in an agate mortar for 30 minutes to obtain a well mixed slurry. The slurry was then evenly coated onto aluminum foil using a scraper and dried in a vacuum oven at 60°C for 24 hours. Subsequently, it was punched into a disc with a diameter of 12 mm to obtain a cathode sheet with a thickness of 1 cm.

[0045] Graphite powder, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone were mixed in a mass ratio of 8:1:1:2 and ground in an agate mortar for 30 minutes to obtain a well mixed slurry. The slurry was then evenly coated onto copper foil using a scraper and dried in a vacuum oven at 60°C for 24 hours. Subsequently, it was punched into a disc with a diameter of 12 mm to obtain a negative electrode sheet with a thickness of 1 cm.

[0046] In a glove box protected by an argon atmosphere (water content less than 0.1 ppm, oxygen content less than 0.1 ppm), using a Clegrad 2400 separator, the above-mentioned positive electrode, electrolyte, separator, electrolyte and negative electrode are stacked in sequence and formed into an electrode assembly through a winding process. The electrode assembly is then placed in an aluminum shell and sealed. Finally, after standing, formation and shaping processes, the lithium battery of this embodiment is obtained.

[0047] Example 3

[0048] A high-rate, low-temperature resistant lithium battery includes a positive electrode, a negative electrode, and an electrolyte;

[0049] The method for preparing the electrolyte includes the following steps:

[0050] S1. Mix acrylamide, imidazole propanesulfonate, sodium acrylate, N-methylpyrrolidone, and deionized water, stir for 40 min, add initiator and crosslinking agent, stir for 10 min, transfer to a mold, and cure under 365 nm, 250 W UV light for 5 min. After washing with anhydrous ethanol and drying, a polyacrylamide gel with dimensions of 5 cm × 5 cm × 0.1 cm is obtained. The ratio of acrylamide, imidazole propanesulfonate, sodium acrylate, N-methylpyrrolidone, deionized water, initiator, and crosslinking agent is 4 g: 0.2 g: 0.3 g: 12 mL: 12 mL: 0.018 g: 0.004 g.

[0051] The initiator is ammonium persulfate; the crosslinking agent is N,N'-methylenebisacrylamide;

[0052] The preparation method of the imidazolium propanesulfonate includes the following steps:

[0053] Mix 1,3-propylsulfonyl lactone, 1-vinylimidazole, and acetone, stir in an ice-water bath for 3 days, filter, wash the solid phase, and dry under vacuum at 40°C for 24 hours to obtain the imidazole propanesulfonate; the molar ratio of 1,3-propylsulfonyl lactone, 1-vinylimidazole, and acetone is 1:1:10.

[0054] S2. Mix 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water, and N-methylpyrrolidone, and stir for 2 hours to obtain a precursor solution; the ratio of the amounts of 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water, and N-methylpyrrolidone is 2 mL: 0.47 g: 0.16 g: 0.06 g: 1.2 mL: 6 mL: 0.27 mL: 0.5 mL;

[0055] S3. Cut the polyacrylamide gel into small pieces with dimensions of 1.2cm×1.2cm×0.1cm, soak them in the precursor solution for 30h, heat them at 50℃ for 40min, and then dry the heated electrolyte with supercritical carbon dioxide under the drying conditions of 10MPa pressure at 45℃ for 30h to obtain the electrolyte.

[0056] Lithium cobalt oxide cathode material, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone were mixed in a mass ratio of 8:1:1:2 and ground in an agate mortar for 30 minutes to obtain a well mixed slurry. The slurry was then evenly coated onto aluminum foil using a scraper and dried in a vacuum oven at 60°C for 24 hours. Subsequently, it was punched into a disc with a diameter of 12 mm to obtain a cathode sheet with a thickness of 1 cm.

[0057] Graphite powder, conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone were mixed in a mass ratio of 8:1:1:2 and ground in an agate mortar for 30 minutes to obtain a well mixed slurry. The slurry was then evenly coated onto copper foil using a scraper and dried in a vacuum oven at 60°C for 24 hours. Subsequently, it was punched into a disc with a diameter of 12 mm to obtain a negative electrode sheet with a thickness of 1 cm.

[0058] In a glove box protected by an argon atmosphere (water content less than 0.1 ppm, oxygen content less than 0.1 ppm), using a Clegrad 2400 separator, the above-mentioned positive electrode, electrolyte, separator, electrolyte and negative electrode are stacked in sequence and formed into an electrode assembly through a winding process. The electrode assembly is then placed in an aluminum shell and sealed. Finally, after standing, formation and shaping processes, the lithium battery of this embodiment is obtained.

[0059] Comparative Example 1

[0060] Similar to the preparation method in Example 2, except that imidazole propanesulfonate is not added during the preparation of this electrolyte.

[0061] Comparative Example 1

[0062] Similar to the preparation method in Example 2, except that imidazole propanesulfonate is not added during the preparation of this electrolyte.

[0063] Comparative Example 2

[0064] Similar to the preparation method in Example 2, except that lithium trifluoromethanesulfonate is not added during the preparation of this electrolyte.

[0065] Comparative Example 3

[0066] Similar to the preparation method in Example 2, except that 1,3-dioxolane is not added during the preparation of this electrolyte.

[0067] Performance testing

[0068] 1) Ionic conductivity test:

[0069] Electrolytes prepared in Examples 1-3 and Comparative Examples 1-3 were placed between two stainless steel sheets with a diameter of 16 mm, forming a stainless steel / electrolyte / stainless steel symmetrical cell. The ionic conductivity of the electrolyte was determined by electrochemical impedance spectroscopy (EIS) using an electrochemical workstation with a voltage amplitude of 15 mV and a frequency range of 0.5 Hz-1.5 MHz. The ionic conductivity of the electrolyte was tested at -20 °C.

[0070] 2) Lithium-ion transference number test:

[0071] The electrolytes prepared in Examples 1-3 and Comparative Examples 1-3 were used to assemble Li / electrolyte / Li symmetric cells. The lithium-ion transference number of the electrolyte at -20℃ was determined by chronoamperometry using an electrochemical workstation, and a constant potential polarization process was performed at a potential of 0.01V.

[0072] 3) Room temperature cycling performance test:

[0073] At 25°C, the batteries prepared in Examples 1-3 and Comparative Examples 1-3 were charged to 4.5V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C, and then discharged to 3.0V at a constant current of 0.1C. This cycle was repeated for 300 charge-discharge cycles, and the capacity retention rate at the 300th cycle was calculated.

[0074] 4) Low-temperature cycling performance test:

[0075] At -25°C, the batteries prepared in Examples 1-3 and Comparative Examples 1-3 were charged to 4.5V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C, and then discharged to 3.0V at a constant current of 0.1C. This cycle was repeated for 300 charge-discharge cycles, and the capacity retention rate at the 300th cycle was calculated.

[0076] The test results are shown in Table 1 below.

[0077] Table 1

[0078]

[0079] According to Table 1, comparing the test results of Examples 1-3 and Comparative Examples 1-3, it can be seen that the embodiments of the present invention optimize the electrolyte preparation process, so that the prepared electrolyte still has better performance under low temperature conditions.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high rate and low temperature resistant lithium battery, characterized in that, The electrolyte comprises a positive electrode, a negative electrode and an electrolyte; The preparation method of the electrolyte comprises the following steps: S1, acrylamide, imidazolyl propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water are uniformly mixed, initiator and crosslinking agent are added, and after ultraviolet light irradiation and curing, a polyacrylamide gel is obtained; S2, 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium triflate, aluminum triflate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone are mixed and stirred to obtain a precursor solution; S3, the polyacrylamide gel is soaked in the precursor solution for 20-30h, and heated at 40-50℃ for 20-40min to obtain the electrolyte.

2. The high rate and low temperature resistant lithium battery according to claim 1, characterized in that, In step S1, the amount ratio of acrylamide, imidazolyl propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water, initiator and crosslinking agent is 2-4g:0.1-0.2g:0.1-0.3g:10-12mL:10-12mL:0.014-0.018g:0.002-0.004g.

3. The high rate and low temperature resistant lithium battery according to claim 1, characterized in that, In step S1, the initiator is ammonium persulfate.

4. The high rate and low temperature resistant lithium battery of claim 1, wherein, In step S1, the crosslinking agent is N,N'-methylene bisacrylamide.

5. The high rate and low temperature resistant lithium battery of claim 1, wherein, The preparation method of the imidazolyl propyl sulfonate comprises the following steps: 1,3-propane sulfonic acid lactone, 1-vinylimidazole, acetone are mixed, stirred in an ice water bath for 2-3d, filtered, the solid phase is washed, and vacuum dried at 40℃ for 24h to obtain the imidazolyl propyl sulfonate.

6. The high rate and low temperature resistant lithium battery according to claim 5, characterized in that, The amount ratio of 1,3-propane sulfonic acid lactone, 1-vinylimidazole and acetone is 1:1:

10.

7. The high rate and low temperature resistant lithium battery of claim 1, wherein, In step S2, the amount ratio of 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium triflate, aluminum triflate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone is 1-2mL:0.45-0.47g:0.12-0.16g:0.04-0.06g:1-1.2mL:5-6mL:0.25-0.27mL:0.3-0.5mL.

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