CN106129468A - A kind of preparation method of single-ion polymer gel electrolyte materials - Google Patents

Abstract

The invention relates to a preparation method of a single-ion polymer gel electrolyte material, which comprises dissolving boric acid and lithium hydroxide in deionized water and heating in an oil bath; adding dipropylene glycol aqueous solution into the solution, raising the temperature, and stirring to carry out polymerization Reaction; add cyclohexane to the polymerization system, use azeotrope to remove water in the system, and the obtained white precipitate is the polymerization product; collect the polymerization product by filtration and dry it in vacuum to obtain a white powder, which is the single-ion polymer electrolyte material Dissolve the polymer electrolyte material and polyvinylidene fluoride-hexafluoropropylene) copolymer in dimethylformamide, and then heat to volatilize the solvent to obtain an electrolyte membrane; soak the electrolyte membrane in the electrolyte propylene carbonate to obtain a single Ionic polymer gel electrolyte membrane. The preparation method of the invention is simple and easy, the ion conductivity is increased to 1.2-2.0 S·cm ^-1 , and the lithium ion migration number is increased to 0.85-0.91.

Description

A kind of preparation method of single ion polymer gel electrolyte material

technical field

The invention relates to a preparation method of a single-ion polymer gel electrolyte material, specifically, a preparation method in which dipropylene glycol, boric acid and lithium hydroxide are polymerized in an aqueous solution, and then go through the process of film formation and gelation.

technical background

Compared with traditional secondary batteries (Ni-MH batteries, Ni-Cd batteries, etc.), Li-ion secondary batteries have the advantages of high specific energy, long cycle life, and environmental friendliness, and thus become an important chemical power source. However, traditional lithium-ion batteries use volatile organic electrolytes, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), etc., although they have high ionic conductivity , but because it is flammable and volatile, there are many safety hazards (such as combustion, explosion, leakage, etc.) in the users of lithium-ion batteries. In order to overcome this defect, it has been proposed to replace the electrolyte with a polymer electrolyte (Wu Yuping, Dai Xiaobing, Ma Junqi, Cheng Yujiang "Lithium Ion Batteries-Application and Practice". Beijing Chemical Industry Press, 2004, pp.301 ).

However, there are two problems with the pure polymer electrolyte: one is that the lithium ion migration number of the polymer electrolyte is very low, and it is easy to produce a concentration difference during charging and discharging, forming lithium dendrites and causing a short circuit of the battery; the other is that the polymer electrolyte ion conduction The rate is very low, and the ionic conductivity of pure polymer electrolytes cannot meet the practical application of lithium batteries at present. In order to solve the problem of low migration number of lithium ions, the concept of single-ion polymer electrolyte is proposed, which means that anions are fixed on the polymer main chain, and only cations migrate. This kind of single-ion conductor anion is fixed on the polymer main chain, and there will be no concentration polarization due to the difference in the migration speed of anion and cation during the charge and discharge process, so it has a high lithium ion migration number and can effectively avoid lithium ions. The formation of dendrites improves the performance of lithium-ion batteries. In order to solve the problem of low ionic conductivity, the concept of gel polymer electrolyte is proposed, which is to add a very small amount of organic electrolyte to the polymer system to improve its ionic conductivity. Therefore, the emergence of single-ion polymer gel electrolyte materials can improve the performance of lithium batteries from two aspects of lithium ion migration number and ion conductivity.

At present, many researchers at home and abroad have done a lot of research work on single-ion polymer gel electrolytes. Zhu et al. used PVA, boric acid, and oxalic acid for complex polymerization to obtain single-ion polymers (Zhu YS, Wang XJ, Hou YY, et al. A new single-ion polymer electrolyte based on polyvinyl alcohol forlithium ion batteries[J]. Electrochimica Acta,2013,87(1):113-118.) However, due to the semi-crystalline structure of PVA, the migration number of lithium ions at room temperature is close to 1, and the ion conductivity can only reach 6.11×10 ^-6 s cm ^-1 . Wang et al. used tartaric acid and boric acid complexation reaction to obtain a single ion polymer (Wang X, Liu Z, Kong Q, et al.Asingle-ion gel polymer electrolyte based on polymeric lithium tartaric acidborate and its superior battery performance[J].Solid State Ionics, 2014, 262(9):747-753.). Because the ether oxygen bonds on the polymer exist on the ring, the mobility is poor, which is not conducive to the migration of lithium ions. At room temperature, the ionic conductivity can reach 1.4×10 ^-4 s cm ^-1 , and the lithium ion migration number is close to 1, but Magnification performance is poor. In order to make the polymerization process simple and the electrolyte performance excellent, the present invention synthesizes a single-ion polymer structure with ether oxygen bonds on the main chain for the first time in aqueous solution. The ether oxygen bonds have strong mobility and can prepare single-ion polymers with good performance. polymer gel electrolyte membrane.

Contents of the invention

In order to solve the problems of the prior art, the present invention uses dipropylene glycol, boric acid and lithium hydroxide in aqueous solution for complex polymerization, and then prepares a single-ion polymer gel electrolyte through film-forming and gelation processes .

Concrete technical scheme of the present invention is as follows:

A preparation method of a single-ion polymer gel electrolyte material: comprising the steps of:

(1) Boric acid and lithium hydroxide are dissolved in deionized water, the ratio of the amount of boric acid and lithium hydroxide is 1:1, and heated in an oil bath;

(2) Dipropylene glycol aqueous solution is added in the solution obtained in step (1), the temperature is raised, and the polymerization reaction is carried out with stirring;

(3) Add cyclohexane in the polymerization system, utilize azeotropic removal of water in the system, and the white precipitate obtained is the polymerization product;

(4) The polymer product is collected by filtration, and dried in vacuum to obtain a white powder, which is a single-ion polymer electrolyte material;

(5) Dissolve the polymer electrolyte material and polyvinylidene fluoride-hexafluoropropylene copolymer in dimethylformamide at a molar ratio of 1:2, and then heat to volatilize the solvent to obtain an electrolyte membrane; soaked in liquid propylene carbonate to obtain a single-ion polymer gel electrolyte membrane.

The concentration of boric acid and lithium hydroxide aqueous solution in the step (1) is 0.1-2 mol/L, and the heating temperature is 40-60°C.

The concentration of the dipropylene glycol aqueous solution in the step (2) is 0.2 to 4 mol/L, and the moles of dipropylene glycol are equal to twice the moles of boric acid.

The polymerization reaction time in the step (2) is 16 to 24 hours, and the reaction temperature is 80°C to 100°C.

In the step (3), cyclohexane is added in a ratio of 60 to 80 mL of cyclohexane per 100 mL of water.

In the step (4), the vacuum drying temperature is 50-60° C., the vacuum degree is -0.1-0.08 MPa, and the time is 12-24 hours.

The electrical properties of the single-ion polymer gel electrolyte membrane were tested, and the ion conductivity was increased to 1.2-2.0 S·cm ^-1 , and the lithium ion migration number was increased to 0.85-0.91.

Beneficial effects of the present invention: the present invention is the first to use boric acid and diethylene glycol aqueous solution (monomer molar ratio is 1:2, solution concentration is 0.5-1mol/L) to synthesize a main The single-ion polymer structure with ether oxygen bonds on the chain is shown in accompanying drawing 1 and accompanying drawing 2. In the experiment, polyvinylidene fluoride-hexafluoropropylene copolymer was selected as film-forming agent and propylene carbonate as plasticizer. The preparation method is simple and easy to operate. Pure single-ion polymerization can be obtained by adjusting the concentration of reactants and reaction temperature. Through the process of film formation and gelation, a single-ion polymer gel electrolyte with good performance is obtained.

Description of drawings

Fig. 1 concentration is that boric acid and diethylene glycol of 0.5mol/L are polymerized under the condition of 80 ℃ to obtain the infrared characterization figure of single ion polymer;

Fig. 2 concentration is the NMR characterization diagram of the single-ion polymer obtained by polymerization of boric acid and diethylene glycol at 80°C with a concentration of 0.5mol/L;

Figure 3 is a characterization diagram of the ionic conductivity of the single-ion polymer gel electrolyte membrane obtained by polymerization of boric acid and diethylene glycol at a concentration of 0.5 mol/L at 80°C.

detailed description

In order to make the advantages, technical solutions and objectives of the present invention more clear, the present invention will be further described below in conjunction with examples. The following examples of the present invention are given to further illustrate the present invention, rather than limit the scope of the present invention.

Example 1

(1) Dissolve 0.01mol of boric acid and lithium hydroxide in 100ml of deionized water (concentration: 0.1mol/L), and stir at 60°C until completely dissolved;

(2) Add 100 ml of dipropylene glycol aqueous solution with a concentration of 0.2 mol/L dropwise into the solution obtained in step (1), raise the temperature to 80° C., stir for polymerization, and react for 16 hours;

(3) Add cyclohexane in the polymerization system at a ratio of 60 mL cyclohexane per 100 mL of water, and use the azeotropic principle to remove the water in the system, and the white precipitate obtained is the polymerization product;

(4) The polymerized product was collected by filtration, and vacuum-dried for 24 hours at 50°C and a vacuum degree of -0.08MPa to obtain a white powder, which is a single-ion polymer electrolyte material. The characterization of the results is shown in Figures 1 and 2.

(5) Dissolve the polymer electrolyte material and polyvinylidene fluoride-hexafluoropropylene copolymer in dimethylformamide at a molar ratio of 1:2, volatilize the solvent to obtain an electrolyte membrane, and place the electrolyte membrane in the electrolyte solution of propylene carbonate Soaked in ester to obtain single-ion polymer gel electrolyte.

The electrical properties of the single-ion polymer gel electrolyte were tested, and the ionic conductivity is shown in Figure 3. The calculated ionic conductivity at room temperature was 2.0×10 ^-4 S·cm ^-1 , and the lithium ion migration number was 0.91.

Example 2

(1) Dissolve 0.03mol of boric acid and lithium hydroxide in 60ml of deionized water (concentration: 0.5mol/L), and stir at 40°C until completely dissolved;

(2) Add 60 ml of dipropylene glycol aqueous solution with a concentration of 1 mol/L dropwise into the solution obtained in step (1), heat up to 100° C., stir for polymerization, and react for 24 hours;

(3) Add cyclohexane in the polymerization system at a ratio of 80 mL cyclohexane per 100 mL of water, and use the azeotropic principle to remove the water in the system, and the white precipitate obtained is the polymerization product;

(4) The polymerization reaction product was collected by filtration, and vacuum-dried for 12 hours at 60° C. and a vacuum degree of −0.01 MPa to obtain a white powder, which is a single-ion polymer electrolyte material.

(5) Dissolve the polymer electrolyte material and polyvinylidene fluoride-hexafluoropropylene copolymer in dimethylformamide at a molar ratio of 1:2, volatilize the solvent to obtain an electrolyte membrane, and place the electrolyte membrane in the electrolyte solution of propylene carbonate Soaked in ester to obtain single-ion polymer gel electrolyte.

The electrical properties of the single-ion polymer gel electrolyte were tested, and the calculated ionic conductivity at room temperature was 1.8×10 ^-4 S·cm ^-1 , and the lithium ion migration number was 0.88.

Example 3

(1) Dissolve 0.1mol boric acid and lithium hydroxide in 100ml deionized water (concentration is 1mol/L), stir at 60°C until completely dissolved;

(2) Add 100 ml of dipropylene glycol aqueous solution with a concentration of 2 mol/L dropwise into the solution obtained in step (1), heat up to 80° C., stir for polymerization, and react for 21 hours;

(3) Add cyclohexane in the polymerization system at a ratio of 60 mL cyclohexane per 100 mL of water, and use the azeotropic principle to remove the water in the system, and the white precipitate obtained is the polymerization product;

(4) The polymerized product was collected by filtration, and vacuum-dried for 20 hours at 60° C. and a vacuum degree of −0.04 MPa to obtain a white powder, which is a single-ion polymer electrolyte material.

(5) Dissolve the polymer electrolyte material and polyvinylidene fluoride-hexafluoropropylene copolymer in dimethylformamide at a molar ratio of 1:2, volatilize the solvent to obtain an electrolyte membrane, and place the electrolyte membrane in the electrolyte solution of propylene carbonate Soaked in ester to obtain single-ion polymer gel electrolyte.

The electrical properties of the single-ion polymer gel electrolyte were tested, and the calculated ionic conductivity at room temperature was 1.5×10 ^-4 S·cm ^-1 , and the lithium ion migration number was 0.89.

Example 4

(1) Dissolve 0.15mol of boric acid and lithium hydroxide in 100ml of deionized water (concentration: 1.5mol/L), and stir at 50°C until completely dissolved;

(2) Add 100 ml of dipropylene glycol aqueous solution with a concentration of 3 mol/L dropwise into the solution obtained in step (1), heat up to 90° C., stir for polymerization, and react for 24 hours;

(3) Add cyclohexane in the polymerization system at a ratio of 70 mL cyclohexane per 100 mL of water, and use the azeotropic principle to remove the water in the system, and the white precipitate obtained is the polymerization product;

(4) The polymerized product was collected by filtration, and vacuum-dried for 20 hours at 50° C. and a vacuum degree of −0.08 MPa to obtain a white powder, which is a single-ion polymer electrolyte material.

(5) Dissolve the polymer electrolyte material and polyvinylidene fluoride-hexafluoropropylene copolymer in dimethylformamide at a molar ratio of 1:2, volatilize the solvent to obtain an electrolyte membrane, and place the electrolyte membrane in the electrolyte solution of propylene carbonate Soaked in ester to obtain single-ion polymer gel electrolyte.

The electrical properties of the single-ion polymer gel electrolyte were tested, and the calculated ionic conductivity at room temperature was 1.8×10 ^-4 S·cm ^-1 , and the lithium ion migration number was 0.85.

Example 5

(1) Dissolve 0.2mol of boric acid and lithium hydroxide in 100ml of deionized water (concentration is 2mol/L), stir at 50°C until completely dissolved;

(2) Add 100ml of dipropylene glycol aqueous solution with a concentration of 4mol/L dropwise into the solution obtained in step (1), heat up to 80°C, stir and carry out polymerization reaction, and react for 22 hours;

(3) Add cyclohexane in the polymerization system at a ratio of 60 mL cyclohexane per 100 mL of water, and use the azeotropic principle to remove the water in the system, and the white precipitate obtained is the polymerization product;

(4) The polymerized product was collected by filtration, and vacuum-dried for 23 hours at 55° C. and a vacuum degree of −0.08 MPa to obtain a white powder, which is a single-ion polymer electrolyte material.

(5) Dissolve the polymer electrolyte material and polyvinylidene fluoride-hexafluoropropylene copolymer in dimethylformamide at a molar ratio of 1:2, volatilize the solvent to obtain an electrolyte membrane, and place the electrolyte membrane in the electrolyte solution of propylene carbonate Soaked in ester to obtain single-ion polymer gel electrolyte.

The electrical properties of the single-ion polymer gel electrolyte were tested, and the calculated ionic conductivity at room temperature was 1.2×10 ^-4 S·cm ^-1 , and the lithium ion migration number was 0.88.

The present invention discloses and proposes a method for preparing a single-ion polymer gel electrolyte by complexing and polymerizing dipropylene glycol, boric acid and lithium hydroxide in an aqueous solution, and then preparing a single-ion polymer gel electrolyte through the process of film formation and gelation. Personnel can realize by referring to the contents of this article, appropriately changing links such as raw materials and process routes, although the method and preparation technology of the present invention have been described through preferred implementation examples, those skilled in the art can obviously achieve this without departing from the content, spirit and scope of the present invention. The methods and technical routes described in this paper are modified or recombined to realize the final preparation technology. In particular, it should be pointed out that all similar substitutions and modifications will be obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

Claims (7)

1. a preparation method for single-ion polymer gel electrolyte materials, is characterized in that specifically comprising the following steps that

(1) boric acid and Lithium hydrate being dissolved in deionized water, the ratio of the amount of the material of boric acid and two kinds of materials of Lithium hydrate is 1:1, heats in oil bath pan；

(2) being added dropwise over by dipropylene glycol aqueous solution in step (1) gained solution, heat up, stirring carries out polyreaction；

(3) adding hexamethylene in polymerization system, utilize the water being azeotroped off in system, the white precipitate obtained is polymerizate；

(4) polymerizate is collected by filtration, in vacuum drying, obtains white powder, be single-ion polymer electrolyte；

(5) polymer electrolyte and Kynoar-hexafluoropropylene copolymer are dissolved in dimethyl methyl by the mol ratio of 1:2 In amide, reheat and make solvent volatilization obtain dielectric film；Dielectric film is soaked in electrolyte Allyl carbonate, obtains list Ionic polymer gel dielectric film.

2. method as claimed in claim 2, is characterized in that the concentration of described step (1) mesoboric acid and lithium hydroxide aqueous solution is 0.1～2mol/L, heating-up temperature is 40～60 DEG C.

3. method as claimed in claim 2, is characterized in that in described step (2), the concentration of dipropylene glycol aqueous solution is 0.2～4mol/L.

4. method as claimed in claim 2, is characterized in that the dipropylene glycol molal quantity twice equal to boric acid molal quantity.

5. method as claimed in claim 2, is characterized in that in described step (2), polymerization reaction time is 16～24h, reaction temperature Degree is 80 DEG C～100 DEG C.

6. method as claimed in claim 2, is characterized in that in described step (3) by adding 60～80mL rings in every 100mL water The ratio of hexane adds hexamethylene.

7. method as claimed in claim 2, is characterized in that described step (4) vacuum drying temperature is 50～60 DEG C, vacuum Degree is-0.1～-0.08MPa, the time is 12～24h.