阅读说明：本技术 一种单离子交替共聚物锂盐及其制备方法 (Single-ion alternating copolymer lithium salt and preparation method thereof ) 是由 封伟 陈绍山 李瑀 冯奕钰 梁子嘉 于 2019-09-10 设计创作，主要内容包括：本发明公开了一种单离子交替共聚物锂盐及其制备方法。该单离子交替共聚物锂盐在聚合物单体上引入强吸电子基团-OCF-3,形成超离域阴离子,Li+与该超离域阴离子高度离解,可以促进Li+传导,进一步提高电导率。同时与马来酸酐这一高介电常数单元共聚,可以促进Li+的解离,可以有效增加“自由”锂离子的浓度,提高室温Li+电导率和迁移数。该锂盐有望进一步应用于固态电解质领域的研究。(The invention discloses a single-ion alternating copolymer lithium salt and a preparation method thereof. The single-ion alternating copolymer lithium salt introduces strong electron-withdrawing group-OCF on the polymer monomer 3 And a super-delocalized anion is formed, and Li + is highly dissociated from the super-delocalized anion, so that Li + conduction can be promoted, and the conductivity can be further improved. And meanwhile, the copolymer is copolymerized with a high dielectric constant unit of maleic anhydride, so that the dissociation of Li < + >, the concentration of free lithium ions can be effectively increased, and the room-temperature Li < + > conductivity and transference number are improved. The lithium salt is expected to be further applied to the research in the field of solid electrolytes.)

1. A single-ion alternating copolymer lithium salt is characterized by having the following molecular structure

Wherein n is 150-.

2. The method of claim 1, wherein the 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer and maleic anhydride are uniformly dispersed in dimethyl sulfoxide solvent, and a thermal initiator is added to raise the temperature under the protection of argon gas to perform polymerization reaction.

3. The method of claim 2, wherein the molar ratio of 4- (trifluoromethoxy) -styryl bis-sulfonimide lithium salt monomer to maleic anhydride is 1: (1-1.3), preferably 1: (1.05-1.2).

4. The method of claim 2, wherein the thermal initiator is azobisisobutyronitrile or benzoyl peroxide.

5. The method according to claim 4, wherein the thermal initiator is present in an amount of 0.1 to 1% by mass, preferably 0.1 to 0.3% by mass, based on the sum of the amounts by mass of the 4- (trifluoromethoxy) -styryl bis-sulfonimide lithium salt monomer and maleic anhydride.

6. The process according to claim 2, wherein the polymerization is carried out at a temperature of from 70 to 90 ℃ and for a time of from 24 to 48 hours, preferably from 30 to 48 hours.

7. The method of claim 2, wherein the 4- (trifluoromethoxy) -styryl bis-sulfonimide lithium salt monomer is prepared by:

step 1: uniformly dispersing 4- (trifluoromethoxy) -benzenesulfonamide, triethylamine and 4-dimethylamino pyridine in acetonitrile to obtain a solution A;

step 2: uniformly dispersing p-styrene sulfonyl chloride in acetonitrile to obtain a solution B;

and step 3: dropwise adding the obtained solution B into the solution A in an ice bath at 0 ℃, standing for 0.5-1h after dropwise adding is finished, then heating to 20-25 ℃, reacting for 48h, and purifying to obtain 4- (trifluoromethoxy) -styryl bissulfonylimide;

and 4, step 4: and adding the obtained 4- (trifluoromethoxy) -styryl bissulfonyl imide and lithium hydroxide into distilled water, stirring until the materials are completely dissolved, and treating to obtain the 4- (trifluoromethoxy) -styryl bissulfonyl imide lithium salt monomer.

8. The process of claim 7, wherein the molar ratio of 4- (trifluoromethoxy) -benzenesulfonamide, p-styrenesulfonyl chloride, triethylamine, and 4-dimethylaminopyridine is 1: 1: (1-5): (1-3); the concentration of 4- (trifluoromethoxy) -benzenesulfonamide in acetonitrile is 0.2-1 mol/L.

9. The method according to claim 7, wherein in step 4, the molar ratio of 4- (trifluoromethoxy) -styryl bissulfonylimide to lithium hydroxide is 1:1.

10. use of a single ion alternating copolymer lithium salt of claim 1 in a solid state electrolyte.

Technical Field

The invention relates to the technical field of energy materials, in particular to a single-ion alternating copolymer lithium salt and a preparation method thereof.

Background

The traditional liquid electrolyte has higher ionic conductivity, mainly is a mixed solution of LiPF6 dissolved in organic carbonate, so the traditional liquid electrolyte is widely applied, and at an elevated temperature, due to the instability of LiPF6 to trace proton species in the prepared electrolyte and the flammability of an organic solvent, the electrochemical performance and safety of a lithium ion battery are adversely affected. All-solid-state batteries based on polymer solid electrolytes can solve such safety problems well, and have been developed dramatically in recent years.

A typical polymer electrolyte is a bi-ionic conductor electrolyte, in which Li⁺And its counter anion are both mobile. In particular, Li⁺Generally less mobile than their corresponding anions because their motion is highly coupled to the motion of the lewis basic sites of the polymer matrix. This is also the exact reason why the Li + transport number (LTN) of a dual ion conducting solid polymer electrolyte is typically below 0.5. For conventional solid polymer electrolytes, during the battery discharge cycle, both Li + and anions move oppositely in the polymer matrix; however, anions tend to accumulate on the anode side and cause concentration gradients, leading to polarization, resulting in poor cell performance, voltage loss, increased internal impedance and adverse reactions, ultimately leading to cell failure. On the other hand, it has been demonstrated that when the LTN of the electrolyte is close to 1 (i.e., a single lithium ion conductor electrolyte), no concentration gradient occurs in the solution phase and the utilization of the active electrode material remains high.

The biggest limiting factors of the current lithium battery based on single-ion polymer lithium salt polymer electrolyte are low ionic conductivity and lithium ion transference number under the room temperature condition. Therefore, it has been a hot research direction to improve the ionic conductivity of the single-ion polymer lithium salt polymer electrolyte and increase the transference number of lithium ions to be as close to 1 as possible.

Disclosure of Invention

The purpose of the invention is to aim at Li in the prior art⁺The single-ion alternating copolymer lithium salt greatly promotes the conduction and the migration of lithium ions due to the special alternating structure and the trifluoromethoxy strong electron-withdrawing group,meanwhile, the anion has a structure with a benzene ring and the like with larger steric hindrance, is not easy to migrate, and effectively improves the transference number of the lithium ion.

The technical scheme adopted for realizing the purpose of the invention is as follows:

a single-ion alternating copolymer lithium salt has the following molecular structure

Wherein n is 150-.

In another aspect of the present invention, in the preparation method of the single-ion alternating copolymer lithium salt, 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer and maleic anhydride are uniformly dispersed in dimethyl sulfoxide solvent, and a thermal initiator is added to raise the temperature under the protection of argon gas to perform a polymerization reaction.

In the above preparation method, the molar ratio of the 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer to maleic anhydride is 1: (1-1.3), preferably 1: (1.05-1.2).

In the above preparation method, the thermal initiator is azobisisobutyronitrile or benzoyl peroxide.

In the above preparation method, the mass of the thermal initiator is 0.1 to 1%, preferably 0.1 to 0.3% of the total mass of the 4- (trifluoromethoxy) -styryl bis-sulfonimide lithium salt monomer and maleic anhydride.

In the preparation method, the reaction temperature of the polymerization reaction is 70-90 ℃, and the reaction time is 24-48h, preferably 30-48 h.

In the above preparation method, the preparation method of the 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer is as follows:

step 1: uniformly dispersing 4- (trifluoromethoxy) -benzenesulfonamide, triethylamine and 4-dimethylamino pyridine in acetonitrile to obtain a solution A;

step 2: uniformly dispersing p-styrene sulfonyl chloride in acetonitrile to obtain a solution B;

and step 3: dropwise adding the obtained solution B into the solution A in an ice bath at 0 ℃, standing for 0.5-1h after dropwise adding is finished, then heating to 20-25 ℃, reacting for 48h, and purifying to obtain 4- (trifluoromethoxy) -styryl bissulfonylimide;

and 4, step 4: and adding the obtained 4- (trifluoromethoxy) -styryl bissulfonyl imide and lithium hydroxide into distilled water, stirring until the materials are completely dissolved, and treating to obtain the 4- (trifluoromethoxy) -styryl bissulfonyl imide lithium salt monomer.

In the above preparation method, the molar ratio of 4- (trifluoromethoxy) -benzenesulfonamide, p-styrenesulfonyl chloride, triethylamine, and 4-dimethylaminopyridine is 1: 1: (1-5): (1-3); the concentration of 4- (trifluoromethoxy) -benzenesulfonamide in acetonitrile is 0.2-1 mol/L.

In the above preparation method, in step 4, the molar ratio of 4- (trifluoromethoxy) -styryl bissulfonylimide to lithium hydroxide is 1:1.

in another aspect of the present invention, the use of the above-mentioned lithium salt of a single-ion alternating copolymer in a solid electrolyte

Compared with the prior art, the invention has the beneficial effects that:

1. the single-ion alternating copolymer lithium salt prepared by the invention greatly promotes the conduction and migration of lithium ions due to the special alternating structure and the trifluoromethoxy strong electron-withdrawing group, and anions have structures with large steric hindrance, such as benzene rings and the like, and are not easy to migrate, so that the migration number of the lithium ions is effectively improved.

2. The single-ion alternating copolymer lithium salt prepared by the invention is copolymerized with maleic anhydride, which is a high dielectric constant unit, can promote the dissociation of Li +, effectively increase the concentration of free lithium ions and improve the room-temperature Li + conductivity and transference number.

3. The single-ion alternating copolymer lithium salt prepared by the invention is expected to be applied to the field of all-solid batteries to obtain the all-solid batteries based on the electrolyte.

Drawings

FIG. 1 is a Fourier infrared absorption spectrum of 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer.

FIG. 2 is a Fourier infrared absorption spectrum of a synthesized single-ion alternating copolymer lithium salt.

Detailed Description

The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

Preparation of 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer

4- (trifluoromethoxy) -benzenesulfonamide was dissolved in acetonitrile solution, and triethylamine (Et)₃N) and 4-Dimethylaminopyridine (DMAP) were added to an acetonitrile solution of 4- (trifluoromethoxy) -benzenesulfonamide in an amount of 3 times and 1 time, respectively, based on the molar amount of 4- (trifluoromethoxy) -benzenesulfonamide amine, and the mixture was placed in an ice bath at 0 ℃ for 30 minutes to 1 hour to be sufficiently stirred and dissolved. The temperature was raised to room temperature (20-25 ℃) and reacted for 48 hours. After completion of the reaction, acetonitrile in the system was removed by a rotary evaporator, and the obtained solid was redissolved in methylene chloride. A4% excess of saturated sodium bicarbonate (NaHCO) was then used₃) The solution was washed with an aqueous solution and 1mol/L hydrochloric acid. After washing, dichloromethane was again spin-dried with a rotary evaporator to obtain 4- (trifluoromethoxy) -styryl bissulfonylimide. Equivalent molar amounts of 4- (trifluoromethoxy) -styryl bis-sulfonimide and lithium hydroxide (LiOH) were placed in 20ml of distilled water and stirred to a transparent solution, after which the distilled water was spin-dried with a rotary evaporator to obtain 4- (trifluoromethoxy) -styryl bis-sulfonimide lithium salt monomer.

FIG. 1 is a Fourier infrared absorption spectrum of 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer. In the spectrum, the absorption peak at 1643cm-1 corresponds to stretching vibration of C ═ C bond, the absorption peak at 1288cm-1 corresponds to asymmetric stretching vibration of-SO 2, and 1163cm^-1The absorption peak at (A) corresponds to the symmetric stretching vibration of-SO 2, 804cm^-1The absorption peak at (B) corresponds to stretching vibration of-SN-bond, 563cm^-1The absorption peak corresponds to the vibration belonging to the-SNS-bond. In addition, absorption peaks at 1573, 1217 and 1095cm-1 correspond to skeletal vibrations of benzene rings. In conclusion, the FT-IR spectrogram showsThe characteristic absorption peak of the compound can preliminarily prove the structure of the 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer.

Changing the molar ratio of 4- (trifluoromethoxy) -benzenesulfonamide, p-styrenesulfonyl chloride, triethylamine and 4-dimethylaminopyridine to 1: 1: (1-5): (1-3) does not affect the yield and result of the reaction;

in order to ensure the reaction to be carried out smoothly, the concentration of the 4- (trifluoromethoxy) -benzenesulfonamide in acetonitrile is 0.2-1 mol/L.

Example 2

Preparation of a Single-ion alternating copolymer lithium salt

Pouring 4- (trifluoromethoxy) -styryl bissulfonyl imide lithium salt monomer and maleic anhydride into a polymerization tube according to a molar ratio of 1:1.05, adding a solvent dimethyl sulfoxide to dissolve the dimethyl sulfoxide, adding 0.1% (mass ratio) benzoyl peroxide, performing freezing-vacuumizing-argon introduction before reaction, performing cyclic operation for three times, removing oxygen, heating to 80 ℃ to perform polymerization reaction for 24 hours, after the reaction is finished, opening the polymerization tube, exposing the polymerization tube in air to terminate the reaction, pouring a polymer dimethyl sulfoxide solution into tetrahydrofuran, precipitating to remove impurities, and repeating the three times to obtain the single-ion alternating copolymer lithium salt.

FIG. 2 is a Fourier infrared absorption spectrum of a synthesized single-ion alternating copolymer lithium salt. By contrast, it can be found that several places appear in the infrared spectrogram which are different from those in fig. 1. As shown, the infrared spectrum of FIG. 2 is 2337cm^-1An absorption peak appears, which corresponds to-CH₂The vibrational peak of the bond, which indicates that copolymerization has occurred between SSPSILI and MA. In addition, 1643cm is shown in the IR spectrum of FIG. 2 in comparison with the IR spectrum of FIG. 1^-1The disappearance of the absorption peak belonging to C ═ C, confirms the cleavage of the C ═ C bond and thus further confirms the occurrence of copolymerization between the two monomers. At the same time, FIG. 2 shows the IR spectra at 1803 and 1718cm^-1Two absorption peaks corresponding to symmetric and asymmetric stretching vibrations of the C ═ O bond appear, indicating that maleic anhydride was successfully introduced. In summary, FTIR spectra of the polymers compared to that of SSPSILIiDisappearance of peak corresponding to bond, -CH in spectrum₂The appearance of peaks corresponding to the-bond and C ═ O bond demonstrated successful copolymerization between the 4- (trifluoromethoxy) -styryl bis-sulfonimide lithium salt monomer and maleic anhydride.

Example 3

Preparation of a Single-ion alternating copolymer lithium salt

Pouring 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer and maleic anhydride into a polymerization tube according to a molar ratio of 1:1.2, adding a solvent dimethyl sulfoxide to dissolve the monomer, adding 0.3% (mass ratio) of azobisisobutyronitrile, performing freezing-vacuumizing-argon introduction before reaction, performing cycle operation for three times, removing oxygen, heating to 70 ℃ to perform polymerization reaction for 30 hours, after the reaction is finished, opening the polymerization tube, exposing the polymerization tube in air to terminate the reaction, pouring a polymer dimethyl sulfoxide solution into tetrahydrofuran, precipitating to remove impurities, and repeating the three times to obtain the single-ion alternating copolymer lithium salt.

Example 4

Preparation of a Single-ion alternating copolymer lithium salt

Pouring 4- (trifluoromethoxy) -styryl bis-sulfonyl imide lithium salt monomer and maleic anhydride into a polymerization tube according to a molar ratio of 1:1.3, adding a solvent dimethyl sulfoxide to dissolve the monomer, adding 0.3% (mass ratio) of azobisisobutyronitrile, performing freezing-vacuumizing-argon introduction before reaction, performing cycle operation for three times, removing oxygen, heating to 90 ℃ to perform polymerization reaction for 48 hours, after the reaction is finished, opening the polymerization tube, exposing the polymerization tube in air to terminate the reaction, pouring a polymer dimethyl sulfoxide solution into tetrahydrofuran, precipitating to remove impurities, and repeating the three times to obtain the single-ion alternating copolymer lithium salt.

The single ion alternating copolymer lithium salt of the present invention was prepared according to the present disclosure with process parameter adjustments and exhibited substantially the same properties as example 2.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.