A high-conductivity, high-mobility lithium metal battery gel electrolyte, its preparation method, and the lithium battery thereof.

Abstract

This invention relates to a high-conductivity, high-mobility lithium metal battery gel electrolyte and a lithium battery. The gel electrolyte comprises a gel and a lithium salt dissolved in the gel. The gel is prepared by polymerization of a polymerizable ionic liquid, a polymerizable zwitterionic monomer, an initiator, and a crosslinking agent in an organic solvent. In this invention, the positively charged centers in the ionic liquid and the zwitterionic monomer on the main chain of the gel electrolyte interact electrostatically with the anions in the electrolyte, restricting anion migration and achieving a high lithium-ion mobility number, thereby reducing dendrite formation and growth. Simultaneously, the negatively charged centers at the ends of the zwitterionic monomers promote the dissociation of the lithium salt, resulting in higher conductivity and improved electrochemical performance of lithium ions.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, and particularly to gel polymer electrolytes used in lithium metal battery technology, specifically to a high conductivity, high mobility number lithium metal battery gel electrolyte, its preparation method, and a lithium battery thereof. Background Technology

[0002] In electrochemical energy storage technology, lithium metal batteries are favored due to their low redox potential (-3.04V relative to the standard hydrogen electrode) and high theoretical specific capacity (3860mAh g). -1 This has attracted widespread attention. However, in practical applications, uneven lithium deposition leads to the formation of numerous dendrites on the surface of the lithium metal anode. Lithium dendrites significantly affect the stability of the electrode and electrolyte surfaces, and their growth can even eventually puncture the separator, causing battery short circuits and the risk of thermal runaway. Furthermore, the high reactivity between metallic lithium and the electrolyte generates numerous side reactions, reducing the cycle stability of lithium metal batteries.

[0003] A high lithium-ion transference number can alleviate concentration polarization on the electrode and electrolyte surfaces during charging and discharging, suppress the formation of an "ion depletion layer" on the negative electrode surface, and thus protect the negative electrode and reduce dendrite formation. Current methods to improve the lithium-ion transference number include using high-concentration lithium salts and single-ion conductors. Among these, single-ion conductor polymer electrolytes covalently link anions to the polymer backbone, resulting in only lithium ions moving, leading to a lithium-ion transference number close to 1, thus reducing lithium-ion concentration polarization. However, the interaction between lithium ions and anion groups reduces lithium-ion dissociation, resulting in a lower single-ion conductor polymer electrolyte level, which affects the actual electrochemical performance of lithium-ion batteries. Summary of the Invention

[0004] To address the aforementioned issues, a high-conductivity, high-mobility gel electrolyte for lithium metal batteries, its preparation method, and a lithium battery thereof are provided to meet the application requirements of high-mobility and high-conductivity gel electrolytes.

[0005] The specific technical solution is as follows:

[0006] The first aspect of the present invention is to provide a high-conductivity, high-mobility lithium metal battery gel electrolyte, the gel electrolyte comprising a gel and a lithium salt dissolved in the gel;

[0007] The gel is made by polymerizing polymerizable ionic liquid, polymerizable zwitterionic monomer, initiator, and crosslinking agent in an organic solvent.

[0008] Specifically, the molar ratio of ionic liquid to zwitterionic monomer is 1:(0.5-2).

[0009] Specifically, the ionic liquid is one or more of the following: 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-butylimidazolium hexafluorophosphate, 1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-methylimidazolium tetrafluoroborate, 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-vinyl-3-methylimidazolium hexafluorophosphate, 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-vinyl-3-ethylimidazolium hexafluorophosphate, and 1-vinyl-3-ethylimidazolium tetrafluoroborate.

[0010] Specifically, the zwitterionic monomer is one or more of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphocholine, and 1-propylsulfonic acid-3-vinylimidazolium inner salt.

[0011] Specifically, the lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, and lithium tetrafluoroborate.

[0012] Specifically, the initiator is either an azo initiator or a peroxide initiator.

[0013] Specifically, the organic solvent is one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, tetrahydrofuran, 1,3-dioxolane, diethyl carbonate / ethylene carbonate, ethylene glycol dimethyl ether / 1,3-dioxolane, and ionic liquids.

[0014] A second aspect of the present invention is to provide a method for preparing the above-mentioned high conductivity, high mobility lithium metal battery gel electrolyte, comprising:

[0015] Add polymerizable ionic liquid, polymerizable zwitterionic monomer, lithium salt, initiator and crosslinking agent to organic solvent, and stir thoroughly to form a mixed solution;

[0016] A mixed solution is dropped onto a polypropylene separator, and after encapsulation and thermal polymerization, a high-conductivity, high-mobility lithium metal battery gel electrolyte is formed.

[0017] A third aspect of the present invention is to provide a lithium battery in which the electrolyte is the aforementioned high-conductivity, high-mobility lithium metal battery gel electrolyte.

[0018] The beneficial effects of the above scheme are:

[0019] Compared to single-ion monomers, the ionic liquid monomers and zwitterionic monomers in this invention have greater selectivity. Furthermore, the positively charged centers in the ionic liquid and zwitterionic monomers on the gel electrolyte backbone interact electrostatically with the anions in the electrolyte, restricting the migration of anions and thus obtaining a higher lithium-ion transference number. This reduces the growth of dendrites in lithium metal batteries, thereby reducing the generation and growth of dendrites. At the same time, the negatively charged centers at the ends of the zwitterionic monomers promote the dissociation of lithium salts, resulting in higher conductivity and improving the electrochemical performance of lithium ions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the preparation of a high-conductivity, high-mobility-number gel electrolyte provided in the examples;

[0021] Figure 2 This is a schematic diagram illustrating the principle by which the gel electrolyte provided in the embodiment achieves high conductivity and high mobility number;

[0022] Figure 3 The conductivity and migration data of the gel electrolyte provided in the embodiments of the present invention are shown in the figure.

[0023] Figure 4 The cyclic stability diagram of the gel electrolyte provided in the embodiments of the present invention;

[0024] Figure 5 The CV curve of the gel electrolyte provided in the embodiments of the present invention at a scan rate of 0.5 mV / s is shown. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0028] This invention provides a high conductivity, high mobility number lithium metal battery gel electrolyte, which includes a gel and a lithium salt dissolved in the gel; wherein the gel is prepared by polymerization of polymerizable ionic liquid and polymerizable zwitterionic monomer in a molar ratio of 1:(0.5-2) under the action of an initiator, a crosslinking agent and an organic solvent.

[0029] As a specific example, the ionic liquid in this invention is selected from, but not limited to, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-butylimidazolium hexafluorophosphate, 1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-methylimidazolium tetrafluoroborate, 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, and 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt. The zwitterionic monomer is selected from, but is not limited to, at least one of the following: methanesulfonyl imide salt, 1-vinyl-3-methylimidazolium hexafluorophosphate, 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-vinyl-3-ethylimidazolium hexafluorophosphate, and 1-vinyl-3-ethylimidazolium tetrafluoroborate; the zwitterionic monomer is selected from, but is not limited to, at least one of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphocholine, and 1-propylsulfonic acid-3-vinylimidazolium inner salt.

[0030] Example 1

[0031] In a 50 mL solution of dimethyl carbonate and ethylene carbonate (volume ratio 1:1), 20.16 g of 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 13.97 g of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide were added; subsequently, 14.35 g of lithium bis(trifluoromethanesulfonyl)imide, 0.68 g of azobisisobutyronitrile and 0.68 g of polyethylene glycol diacrylate were added to the solution, and the mixture was stirred thoroughly.

[0032] Add 1 ml of the mixed solution to the polypropylene separator and seal it using a battery sealing machine (all experimental operations were carried out in a glove box with a water content of less than 0.1 ppm and an oxygen content of less than 0.1 ppm); finally, place the sealed battery in an oven at 60°C and let it stand for 12 hours.

[0033] like Figure 2 As shown, in this invention, the positive charge centers of zwitterions and ionic liquids jointly confine TFSI. - The zwitterions enable the electrolyte to acquire a high lithium-ion transference number; furthermore, the negatively charged groups of the zwitterions can promote the dissociation of lithium salts and the movement of lithium, thereby achieving a high lithium-ion conductivity.

[0034] In this invention, following the provided method, gel electrolytes are prepared using PDAS (pure zwitterionic monomer), with molar ratios of zwitterionic monomer to ionic liquid of 1:2 (25%), 1:1 (50%), and 2:1 (75%), respectively, and PBT (pure ionic liquid). Figure 3As shown, when the ratio of zwitterions to pure ionic liquid is 1:1, the electrolyte obtains the largest transport number, indicating that the combination of the two has the best effect on anion migration and also makes the electrolyte obtain a high conductivity.

[0035] like Figure 4 As shown, when the ratio of zwitterionic ions to ionic liquid is 1:1, the gel electrolyte maintains cycling stability after 80 cycles at a current density of 0.1C, with a capacity of 145 mAh g. -1 .

[0036] like Figure 5 As shown, when the ratio of zwitterions to ionic liquid is 1:1, the gel electrolyte exhibits both an oxidation peak and a reduction peak. Furthermore, the peak currents are essentially identical, indicating that the gel electrolyte possesses good reversibility.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-conductivity, high-mobility lithium metal battery gel electrolyte, characterized in that, The gel electrolyte comprises a gel and a lithium salt dissolved in the gel; The gel is made by polymerizing a polymerizable ionic liquid, a polymerizable zwitterionic monomer, an initiator, and a crosslinking agent in an organic solvent. The molar ratio of the ionic liquid to the zwitterionic monomer is 1:(0.5-2), and the ionic liquid is 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-butylimidazolium hexafluorophosphate, 1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-allyl-3-methylimidazolium tetrafluoroborate, 1-vinyl-3 1-Methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-vinyl-3-methylimidazolium hexafluorophosphate, 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-vinyl-3-ethylimidazolium hexafluorophosphate, 1-vinyl-3-ethylimidazolium tetrafluoroborate, wherein the zwitterionic monomer is one or more of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphocholine, 1-propylsulfonic acid-3-vinylimidazolium inner salt.

2. The high conductivity, high mobility number lithium metal battery gel electrolyte according to claim 1, characterized in that, The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonylimide), lithium perchlorate, and lithium tetrafluoroborate.

3. The high conductivity, high mobility lithium metal battery gel electrolyte according to claim 1, characterized in that, The initiator is either an azo initiator or a peroxide initiator.

4. The high conductivity, high mobility number lithium metal battery gel electrolyte according to claim 1, characterized in that, The organic solvent is one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, tetrahydrofuran, 1,3-dioxolane, diethyl carbonate / ethylene carbonate, ethylene glycol dimethyl ether / 1,3-dioxolane, and ionic liquids.

5. A method for preparing a high-conductivity, high-mobility lithium metal battery gel electrolyte, characterized in that, The preparation of a high-conductivity, high-mobility lithium metal battery gel electrolyte according to any one of claims 1-4 comprises: Add polymerizable ionic liquid, polymerizable zwitterionic monomer, lithium salt, initiator and crosslinking agent to organic solvent, and stir thoroughly to form a mixed solution; A mixed solution is dropped onto the separator, encapsulated, and thermally polymerized to form a high-conductivity, high-mobility lithium metal battery gel electrolyte.

6. The preparation method according to claim 5, characterized in that, The diaphragm is a polypropylene diaphragm.

7. A lithium battery, characterized in that, The electrolyte in this lithium battery is the high-conductivity, high-mobility lithium metal battery gel electrolyte as described in any one of claims 1-4.

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