High-rate low-temperature-resistant lithium battery

Abstract

The invention discloses a high-rate low-temperature-resistant lithium battery, and belongs to the technical field of lithium batteries. Comprising a positive electrode, a negative electrode and electrolyte, the preparation method of the electrolyte comprises the following steps: uniformly mixing acrylamide, imidazolyl propanesulfonate, sodium acrylate, N-methyl pyrrolidone and deionized water, adding an initiator and a cross-linking agent, and curing by ultraviolet irradiation to obtain polyacrylamide gel; the preparation method comprises the following steps: mixing 1, 3-dioxopentane, lithium bis (trifluoromethanesulfonimide), lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone, and stirring to obtain a precursor solution; and soaking the polyacrylamide gel in the precursor solution, and heating to obtain the electrolyte, the problem of electrolyte freezing of the lithium battery in a low-temperature environment is solved, and the low-temperature resistance of the lithium battery is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a high-rate and low-temperature-resistant lithium battery. BACKGROUND

[0002] Traditional commercial electrolytes have relatively high melting points. As the temperature decreases, their viscosity increases significantly, which affects the ionic conductivity and greatly inhibits the ability of Li + transport. More importantly, as the temperature continues to decrease, there is a risk of electrolyte freezing, which leads to battery failure. In order to expand the application scenarios of lithium batteries in low-temperature environments, it is necessary to develop low-temperature-resistant electrolytes. SUMMARY

[0003] The purpose of the present application is to provide a high-rate and low-temperature-resistant lithium battery, which is used to solve the problem of electrolyte freezing of lithium batteries in low-temperature environments and improve the low-temperature resistance of lithium batteries.

[0004] The purpose of the present application can be achieved by the following technical solutions:

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

[0006] The preparation method of the electrolyte comprises the following steps:

[0007] S1, acrylamide, imidazolyl propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water are mixed, stirred for 30-40 min, initiator and crosslinking agent are added, stirred for 8-10 min, transferred to a mold and irradiated with ultraviolet light at 365 nm and 250 W power for 2-3 h, washed with anhydrous ethanol and dried to obtain a polyacrylamide gel;

[0008] S2, 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone are mixed and stirred for 1-2 h to obtain a precursor solution;

[0009] S3, the polyacrylamide gel is soaked in the precursor solution for 20-30 h and heated at 40-50 DEG C for 20-40 min to obtain the electrolyte.

[0010] As a preferred technical solution of the present application, in step S1, the amount of acrylamide, imidazolyl propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water, initiator and crosslinking agent is 2-4 g: 0.1-0.2 g: 0.1-0.3 g: 10-12 mL: 10-12 mL: 0.014-0.018 g: 0.002-0.004 g.

[0011] As a preferred technical solution of the present application, in step S1, the initiator is ammonium persulfate.

[0012] As a preferred technical solution of the present application, in step S1, the crosslinking agent is N,N'-methylene bisacrylamide.

[0013] As a preferred technical solution of the present application, the preparation method of the imidazolyl propyl sulfonate salt comprises the following steps:

[0014] Take 1,3-propanesulfonic acid lactone, 1-vinylimidazole, acetone, stir in an ice water bath for 2-3d, filter, wash the solid phase, and dry at 40℃ under vacuum for 24h to obtain the imidazolyl propyl sulfonate salt.

[0015] As a preferred technical solution of the present application, the mass ratio of 1,3-propanesulfonic acid lactone, 1-vinylimidazole, and acetone is 1:1:10.

[0016] As a preferred technical solution of the present application, in step S2, the dosing ratio of 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, 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.

[0017] The beneficial effects of the present application are:

[0018] (1) The present application copolymerizes acrylamide and zwitterionic monomer imidazolyl propyl sulfonate salt, changes the hydrogen bond network structure of the gel electrolyte, reduces the proportion of strong hydrogen bonds, makes the gel network softer and the pore structure more abundant, and promotes the transmission of lithium ions. With the help of the three-dimensional porous network of the gel, the free water is bound, its content and activity are reduced, the freezing of the electrolyte at low temperature is avoided, the stability of the electrolyte in low temperature environment is improved.

[0019] (2) The present application utilizes the positive and negative charge centers of the zwitterionic monomer imidazolyl propyl sulfonate salt to form a dynamic double electric layer on the electrode surface. When the battery is at high voltage, these charged groups will guide Li + to be evenly distributed on the electrode surface, avoiding local Li + + concentration being too high. Uniform ion distribution can balance the electric field strength on the electrode surface, reduce the decomposition of electrolyte caused by local strong electric field, block dendrite penetration, further inhibit dendrite growth, thereby improving the interface stability of the electrolyte and the voltage resistance.

[0020] (3) The weak coordination ability of the anion provided by the lithium trifluoromethanesulfonate can reduce the Li + degree of constraint, so that the Li + can still maintain a high migration rate at low temperatures, thereby maintaining a certain ionic conductivity; at the same time, through the synergistic effect with lithium bis-trifluoromethanesulfonylimide, the overall ionic environment is improved, the number of free-moving Li + is increased, the crystallization tendency of the system is reduced, and the continuity of the ion transport path is maintained.

[0021] (4) The polymer chains of the 1,3-dioxolane can grow and fill the micropores, defects or rough structures on the surface of the gel skeleton through in-situ polymerization, forming a continuous and gap-free interface transition layer, promoting the interface migration of Li + , reducing the charge transfer impedance, ensuring the continuity of the ion transport path, and maintaining the stability of ion transport at low temperatures. DETAILED DESCRIPTION

[0022] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined object, the specific embodiments, structures, features and effects according to the present application are described in detail below.

[0023] Example 1

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

[0025] The preparation method of the electrolyte comprises the following steps:

[0026] S1, acrylamide, imidazolyl propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water are mixed, stirred for 30 min, initiator and crosslinking agent are added, stirred for 8 min, transferred to a mold and irradiated with ultraviolet light at 365 nm and 250 W power for 3 min, washed with anhydrous ethanol and dried to obtain a polyacrylamide gel with a size of 5 cm x 5 cm x 0.1 cm; the amount ratio of acrylamide, imidazolyl propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water, initiator and crosslinking agent is 2g:0.1g:0.1g:10mL:10mL:0.014g:0.002g;

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

[0028] The preparation method of the imidazolyl propyl sulfonate comprises the following steps:

[0029] S1, 1, 3-propanesultone, 1-vinylimidazole, acetone were mixed, stirred in an ice water bath for 2d, filtered, the solid phase was washed, and dried at 40℃ under vacuum for 24h to obtain the imidazolyl propanesulfonate; the mass ratio of 1, 3-propanesultone, 1-vinylimidazole, acetone was 1:1:10;

[0030] S2, 1, 3-dioxolane, lithium bis-trifluoromethanesulfonimide, lithium triflate, aluminum triflate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone were mixed and stirred for 1h to obtain a precursor solution; the amount ratio of 1, 3-dioxolane, lithium bis-trifluoromethanesulfonimide, lithium triflate, aluminum triflate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone was 1mL:0.45g:0.12g:0.04g:1mL:5mL:0.25mL:0.3mL;

[0031] S3, the polyacrylamide gel was cut into small pieces with a size of 1.2cm x 1.2cm x 0.1cm, soaked in the precursor solution for 20h, heated at 40℃ for 20min, and the heated electrolyte was supercritical carbon dioxide dried, the drying conditions were 45℃, 10MPa pressure for 20h, to obtain the electrolyte;

[0032] The lithium cobalt oxide positive electrode material, conductive carbon black, polyvinylidene fluoride and N-methyl pyrrolidone were mixed in a mass ratio of 8:1:1:2, ground in a marquis mortar for 30min to obtain a fully mixed slurry, uniformly coated on an aluminum foil using a scraper, and dried in a vacuum oven at 60℃ for 24h, then punched into a round sheet with a diameter of 12mm to obtain a positive electrode sheet with a thickness of 1cm;

[0033] The graphite powder, conductive carbon black, polyvinylidene fluoride and N-methyl pyrrolidone were mixed in a mass ratio of 8:1:1:2, ground in a marquis mortar for 30min to obtain a fully mixed slurry, uniformly coated on a copper foil using a scraper, and dried in a vacuum oven at 60℃ for 24h, then punched into a round sheet with a diameter of 12mm to obtain a negative electrode sheet with a thickness of 1cm;

[0034] In an argon atmosphere glove box (water content less than 0.1ppm, oxygen content less than 0.1ppm), the separator was Clegrad 2400, the above positive electrode sheet, electrolyte, separator, electrolyte and negative electrode sheet were stacked in order, and an electrode assembly was formed through a winding process, then the electrode assembly was placed in an aluminum shell and sealed, and finally, through processes such as standing, formation, shaping, etc., a lithium battery of the present embodiment was obtained.

[0035] Example 2

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

[0037] The preparation method of the electrolyte comprises the following steps:

[0038] S1, acrylamide, imidazole propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water are mixed, stirred for 35 min, initiator and crosslinking agent are added, stirred for 9 min, transferred to a mold, irradiated with ultraviolet light at 365 nm and 250 W power for 4 min, washed with anhydrous ethanol and dried to obtain a polyacrylamide gel with a size of 5 cm*5 cm*0.1 cm; the amount ratio of acrylamide, imidazole propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, 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'-methylene bisacrylamide;

[0040] The preparation method of the imidazole propyl sulfonate comprises the following steps:

[0041] 1,3-propane sulfonic acid lactone, 1-vinylimidazole, acetone are mixed, stirred in an ice water bath for 2.5 d, filtered, the solid phase is washed, and vacuum drying is carried out at 40℃ for 24 h to obtain the imidazole propyl sulfonate; the amount ratio of 1,3-propane sulfonic acid lactone, 1-vinylimidazole and acetone is 1:1:10;

[0042] S2, 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone are mixed, stirred for 1.5 h to obtain a precursor solution; the amount ratio of 1,3-dioxolane, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone 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, the polyacrylamide gel is cut into small pieces with a size of 1.2 cm*1.2 cm*0.1 cm, soaked in the precursor solution for 25 h, heated at 45℃ for 30 min, and the heated electrolyte is subjected to supercritical carbon dioxide drying, the drying condition is 45℃, 10 MPa pressure for 25 h, to obtain the electrolyte;

[0044] The lithium cobalt oxide positive electrode material, conductive carbon black, polyvinylidene fluoride and N-methyl pyrrolidone are mixed in a mass ratio of 8:1:1:2, ground in a agate mortar for 30 min to obtain a fully mixed slurry, uniformly coated on an aluminum foil using a scraper, dried in a vacuum oven at 60 DEG C for 24 h, and then punched into a disc with a diameter of 12 mm to obtain a positive electrode sheet with a thickness of 1 cm;

[0045] The graphite powder, conductive carbon black, polyvinylidene fluoride and N-methyl pyrrolidone are mixed in a mass ratio of 8:1:1:2, ground in a agate mortar for 30 min to obtain a fully mixed slurry, uniformly coated on a copper foil using a scraper, dried in a vacuum oven at 60 DEG C for 24 h, and then punched into a disc with a diameter of 12 mm to obtain a negative electrode sheet with a thickness of 1 cm;

[0046] In an argon atmosphere glove box (water content less than 0.1 ppm, oxygen content less than 0.1 ppm), the separator is Clegrad 2400, the above positive electrode sheet, electrolyte, separator, electrolyte and negative electrode sheet are stacked in order, and an electrode assembly is formed by a winding process, then the electrode assembly is placed in an aluminum shell and sealed, and finally the lithium battery of the embodiment is obtained after standing, formation, shaping and other processes.

[0047] Example 3

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

[0049] The preparation method of the electrolyte comprises the following steps:

[0050] S1, acrylamide, imidazole propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water are mixed, stirred for 40 min, initiator and crosslinking agent are added, stirred for 10 min, transferred to a mold and irradiated with 365 nm ultraviolet light with a power of 250 W for 5 min, washed with anhydrous ethanol and dried to obtain a polyacrylamide gel with a size of 5 cm x 5 cm x 0.1 cm; the amount ratio of acrylamide, imidazole propyl sulfonate, sodium acrylate, N-methyl pyrrolidone, deionized water, initiator and crosslinking agent is 4g:0.2g:0.3g:12mL:12mL:0.018g:0.004g;

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

[0052] The preparation method of the imidazole propyl sulfonate comprises the following steps:

[0053] S1, 1, 3-propanesultone, 1-vinylimidazole, acetone were mixed, stirred in an ice water bath for 3d, filtered, the solid phase was washed, and dried at 40℃ under vacuum for 24h to obtain the imidazolyl propanesulfonate; the mass ratio of 1, 3-propanesultone, 1-vinylimidazole, acetone was 1:1:10;

[0054] S2, 1, 3-dioxolane, lithium bis-trifluoromethanesulfonimide, lithium triflate, aluminum triflate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone were mixed and stirred for 2h to obtain a precursor solution; the amount ratio of 1, 3-dioxolane, lithium bis-trifluoromethanesulfonimide, lithium triflate, aluminum triflate, fluoroethylene carbonate, ethyl acetate, deionized water and N-methyl pyrrolidone was 2mL:0.47g:0.16g:0.06g:1.2mL:6mL:0.27mL:0.5mL;

[0055] S3, the polyacrylamide gel was cut into small pieces with a size of 1.2cm x 1.2cm x 0.1cm, soaked in the precursor solution for 30h, heated at 50℃ for 40min, and the heated electrolyte was supercritical carbon dioxide dried, the drying conditions were 45℃, 10MPa pressure for 30h, to obtain the electrolyte;

[0056] The lithium cobalt oxide positive electrode material, conductive carbon black, polyvinylidene fluoride and N-methyl pyrrolidone were mixed in a mass ratio of 8:1:1:2, ground in a marquis mortar for 30min to obtain a fully mixed slurry, uniformly coated on an aluminum foil using a scraper, and dried in a vacuum oven at 60℃ for 24h, then punched into a round sheet with a diameter of 12mm to obtain a positive electrode sheet with a thickness of 1cm;

[0057] The graphite powder, conductive carbon black, polyvinylidene fluoride and N-methyl pyrrolidone were mixed in a mass ratio of 8:1:1:2, ground in a marquis mortar for 30min to obtain a fully mixed slurry, uniformly coated on a copper foil using a scraper, and dried in a vacuum oven at 60℃ for 24h, then punched into a round sheet with a diameter of 12mm to obtain a negative electrode sheet with a thickness of 1cm;

[0058] In an argon atmosphere glove box (water content less than 0.1ppm, oxygen content less than 0.1ppm), the separator was Clegrad 2400, the above positive electrode sheet, electrolyte, separator, electrolyte and negative electrode sheet were stacked in order, and an electrode assembly was formed through a winding process, then the electrode assembly was placed in an aluminum shell and sealed, and finally, through processes such as standing, formation, shaping, etc., a lithium battery of the present embodiment was obtained.

[0059] Comparative Example 1

[0060] Similar to the preparation method of Example 2, except that no imidazolium propanesulfonate was added during the preparation of the electrolyte.

[0061] Comparative Example 1

[0062] Similar to the preparation method of Example 2, except that no imidazolium propanesulfonate was added during the preparation of the electrolyte.

[0063] Comparative Example 2

[0064] Similar to the preparation method of Example 2, except that no lithium triflate was added during the preparation of the electrolyte.

[0065] Comparative Example 3

[0066] Similar to the preparation method of Example 2, except that no 1,3-dioxolane was added during the preparation of the electrolyte.

[0067] Performance Test

[0068] 1) Ion conductivity test:

[0069] The electrolytes prepared in Example 1-3 and Comparative Examples 1-3 were respectively placed between two stainless steel sheets with a diameter of 16 mm to form a stainless steel / electrolyte / stainless steel symmetrical battery. The ion 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 0.5-1.5 MHz. The ion conductivity of the electrolyte was tested at -20°C.

[0070] 2) Lithium ion transference number test:

[0071] The electrolytes prepared in Example 1-3 and Comparative Examples 1-3 were respectively assembled into Li / electrolyte / Li symmetrical batteries, and the lithium ion transference number of the electrolyte at -20°C was determined by chronoamperometry using an electrochemical workstation, and the constant potential polarization process was carried out at a potential of 0.01 V.

[0072] 3) Normal temperature cycle performance test:

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

[0074] 4) Low temperature cycle performance test:

[0075] The batteries prepared in Example 1-Example 3 and Comparative Example 1-Comparative Example 3 were respectively charged at 0.5C constant current and constant voltage to 4.5V at -25℃, with a cutoff current of 0.05C, and then discharged at 0.1C constant current to 3.0V, and the cycle was repeated, and the capacity retention rate at the 300th cycle was calculated after 300 cycles of charging and discharging.

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

[0077] Table 1

[0078]

[0079] According to Table 1, the test results of Example 1-Example 3 and Comparative Example 1-Comparative Example 3 are compared, and it can be seen that the electrolyte prepared by optimizing the electrolyte preparation process in the embodiments of the present application still has better performance under low temperature conditions.

[0080] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any equivalent embodiments with equivalent changes and modifications made on the basis of the technical essence of the present application to the above embodiments are still within the scope of the technical solution of the present application.

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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