CN107579191B - Preparation method and application of porous composite membrane of lithium-sulfur battery - Google Patents

Abstract

A preparation method and application of a lithium-sulfur battery porous composite membrane belong to the technical field of lithium-sulfur battery materials. The preparation method is as follows: (1) preparing polyimide solution and poly(p-phenylene terephthalamide) solution; (2) adding calcium salt; (3) introducing carbon dioxide gas; (4) pouring into a film maker , and vacuum drying to obtain a dry film; (5) pickling the dry film and drying to obtain a lithium-sulfur battery porous composite film. The prepared lithium-sulfur battery porous composite membrane is used as a lithium-sulfur battery separator. The advantages of the present invention are: the porous composite membrane prepared by the present invention has excellent high temperature resistance, safety and tensile properties, uniform distribution of the surface and internal pore structure of the porous composite membrane, adjustable pore size, excellent air permeability, charge-discharge During the process, a large number of amide bonds in the porous composite membrane interact strongly with polysulfide ions, inhibiting the migration of polysulfide ions, so it has excellent cycle performance. It is beneficial to large-scale production and has broad application prospects.

Description

Preparation method and application of porous composite membrane for lithium-sulfur battery

technical field

The invention belongs to the technical field of lithium-sulfur battery materials, relates to a preparation method and application of a lithium-sulfur battery porous composite membrane, and in particular relates to the preparation of a polyimide and poly(p-phenylene terephthalamide) porous composite membrane method and its application.

Background technique

With the rapid development of new energy electric vehicles, the demand for high specific energy batteries is more urgent. Limited by the specific capacity of traditional lithium cobalt oxide, lithium manganate and other materials, lithium ion batteries can no longer meet the current needs. It is imperative to seek a secondary battery with a higher specific capacity. Lithium-sulfur batteries have been highly valued by researchers in recent years. Due to their high specific capacity (1675mAh/g), low cost, wide source of elemental sulfur, and non-toxicity, they are promising to become the next generation of secondary batteries with high specific energy. system.

However, there are still many difficulties that restrict the commercial application of lithium-sulfur batteries. Elemental sulfur is non-conductive, which affects the electrochemical performance of the entire battery; the discharge potential is relatively low, only 2.1V; the intermediate product of discharge lithium polysulfide is easily soluble in ether electrolyte (shuttle effect), causing sulfur to migrate to the surface of the negative electrode through the electrolyte, The battery life is reduced; the volume expansion of elemental sulfur during discharge is serious, and elemental lithium is used as the negative electrode material, which has potential safety hazards. Among the above problems, the dissolution of lithium polysulfide is the biggest problem to be solved at present.

The usual solution to the shuttle effect is to use a carbon material to compound with elemental sulfur, and to encapsulate elemental sulfur and discharge intermediates in the pores of the carbon material. However, recent studies have shown that carbon materials are non-polar molecules, which are similar to lithium polysulfides. The effect of chemisorption cannot be formed between them, resulting in an insignificant effect of inhibiting the shuttle effect. Based on this point of view, the researchers selected element doping to modify the surface structure of carbon materials, but the active sites for doping were limited. Recently, the study of polar molecules as cathode materials for lithium-sulfur batteries has become a hot spot to suppress the shuttle effect. However, the focus of researchers is mainly on how to inhibit the shuttle effect, and few people consider the separator as the last channel of shuttle to prevent the flow of polysulfide ions. If the separator contains polar molecules and the formation of polysulfide ions during charging and discharging The strong interaction can inhibit the shuttle of polysulfide ions, thereby improving the cycle performance of lithium-sulfur batteries.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing a porous membrane containing polar molecules and its application in view of the deficiencies in the inhibition of polysulfide ion shuttling by the existing diaphragm, in particular to a method for preparing a porous composite membrane for lithium-sulfur batteries and the same application.

To achieve the above object, the technical scheme adopted by the present invention is as follows:

A preparation method of a lithium-sulfur battery porous composite membrane, the specific steps of the method are as follows:

Step 1: prepare a uniform polyimide solution and a poly(p-phenylene terephthalamide) solution, and the concentrations of the two solutions are both 10 mmol/L~10 mol/L;

Step 2: adding calcium salt to the poly(p-phenylene terephthalamide) solution obtained in step 1 to obtain a uniform mixed solution, and the amount of calcium salt added is 100 mg/L to 1 g/L;

Step 3: feed carbon dioxide into the mixed solution obtained in step 2;

Step 4: Pour the polyimide solution obtained in step 1 into a film maker, and put the film maker in a vacuum drying box to dry at 60-180°C to obtain a dry film;

Step 5: Pour the mixed solution obtained in step 3 into the film maker in step 4, and place the film maker in a vacuum drying box to dry at 60-180°C to obtain a dry composite film;

Step 6: Wash the dry composite membrane obtained in Step 5 with dilute acid, and place the dry composite membrane in an oven to dry for 10-18 hours, thereby obtaining a porous composite membrane for lithium-sulfur batteries.

An application of the lithium-sulfur battery porous composite membrane prepared above, the porous composite membrane is used for a lithium-sulfur battery separator.

Compared with the prior art, the beneficial effects of the present invention are as follows: the porous composite membrane prepared by the present invention has excellent high temperature resistance, safety and tensile properties, the surface and internal pore structure of the porous composite membrane are evenly distributed, the pore diameter is adjustable, and has excellent During the charging and discharging process, a large number of amide bonds in the porous composite film interact strongly with polysulfide ions, inhibiting the migration of polysulfide ions, so it has excellent cycle performance. The active material of the invention has rich sources, low cost, no pollution, easy preparation, clean and environment-friendly preparation process, can effectively improve the performance of the lithium-sulfur battery, is beneficial to large-scale production, and has broad application prospects.

Description of drawings

Fig. 1 is the XRD pattern of the porous composite film of lithium-sulfur battery prepared by the present invention;

Fig. 2 is the first charge-discharge curve diagram of using the porous composite membrane of lithium-sulfur battery as the separator;

Figure 3 shows the 0.1C discharge cycle curve when the porous composite membrane of lithium-sulfur battery is used as the separator.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall cover within the protection scope of the present invention.

Embodiment 1: This embodiment describes a method for preparing a porous composite membrane for a lithium-sulfur battery. The specific steps of the method are as follows:

Step 1: prepare a uniform polyimide solution and a poly(p-phenylene terephthalamide) solution, and the concentrations of the two solutions are both 10 mmol/L~10 mol/L;

Step 2: adding calcium salt to the poly(p-phenylene terephthalamide) solution obtained in step 1 to obtain a uniform mixed solution, and the amount of calcium salt added is 100 mg/L to 1 g/L;

Step 3: feed carbon dioxide into the mixed solution obtained in step 2;

Step 4: Pour the polyimide solution obtained in step 1 into a film maker, and put the film maker in a vacuum drying box to dry at 60-180°C to obtain a dry film;

Step 5: Pour the mixed solution obtained in step 3 into the film maker in step 4, and place the film maker in a vacuum drying box to dry at 60-180°C to obtain a dry composite film;

Step 6: Wash the dry composite membrane obtained in Step 5 with dilute acid, and place the dry composite membrane in an oven to dry for 10-18 hours, thereby obtaining a porous composite membrane for lithium-sulfur batteries.

Embodiment 2: The method for preparing a porous composite membrane for a lithium-sulfur battery according to Embodiment 1, in step 1, the solvents of the polyimide solution and the poly(p-phenylene terephthalamide) solution are the same. It is one or a mixture of dimethyl sulfoxide, sulfolane, dimethyl formamide or nitrogen methyl pyrrolidone.

Embodiment 3: In the method for preparing a porous composite membrane for a lithium-sulfur battery according to Embodiment 1, in step 2, the calcium salt is one of calcium chloride, calcium sulfate or calcium nitrate.

Embodiment 4: The method for preparing a porous composite membrane for a lithium-sulfur battery according to Embodiment 1, in step 3, the carbon dioxide gas is introduced for a time of 60 to 120 minutes, and the introduction amount is 0.2 to 1 L/ min.

Embodiment 5: In the method for preparing a porous composite membrane for a lithium-sulfur battery according to Embodiment 1, in steps 4 and 5, the temperature of the drying oven is 100°C.

Embodiment 6: The method for preparing a porous composite membrane for a lithium-sulfur battery according to Embodiment 1, in step 6, the dilute acid is one or more of hydrochloric acid, boric acid, benzoic acid, sulfuric acid or nitric acid mixture.

Embodiment 7: An application of the porous composite membrane for lithium-sulfur batteries prepared in Embodiment 1, where the porous composite membrane is used as a separator for lithium-sulfur batteries.

Example 1:

(1) Take 0.15g of polyimide and 0.397g of poly(p-phenylene terephthalamide), respectively, dissolve them into 240 mL of dimethyl sulfoxide, stir until the dissolution is complete, and add to poly(terephthaloyl terephthalamide) Slowly add 0.05g calcium chloride to the amine solution, continue to stir until completely dissolved, and feed carbon dioxide gas into the above solution for 80 minutes;

(2) Put the polyimide solution obtained in (1) into a film maker, and vacuum dry for 12 hours to obtain a polyimide film;

(3) Put the poly(p-phenylene terephthalamide) mixed solution obtained in (1) into the film maker in (2), and vacuum dry for 12 hours to obtain a composite film;

(4) Rinse the membrane obtained in (3) with dilute hydrochloric acid, and dry at 60° C. to obtain a porous composite membrane for a lithium-sulfur battery.

Example 2:

(1) Take 0.15g of polyimide and 0.397g of poly(p-phenylene terephthalamide), respectively, dissolve them into 240 mL of sulfolane, stir until the dissolution is complete, and slowly add them to the poly-p-phenylene terephthalamide solution. Add 0.05g calcium chloride, continue to stir until completely dissolved, and feed carbon dioxide gas into the above solution for 80 minutes;

(2) Put the polyimide solution obtained in (1) into a film maker, and vacuum dry for 12 hours to obtain a polyimide film;

(3) Put the poly(p-phenylene terephthalamide) mixed solution obtained in (1) into the film maker in (2), and vacuum dry for 12 hours to obtain a composite film;

(4) Rinse the membrane obtained in (3) with dilute hydrochloric acid, and dry at 60° C. to obtain a porous composite membrane for a lithium-sulfur battery.

Example 3:

(1) Take 0.15g of polyimide and 0.397g of poly(p-phenylene terephthalamide), respectively, dissolve them into 240 mL of dimethyl sulfoxide, stir until the dissolution is complete, and add to poly(terephthaloyl terephthalamide) Slowly add 0.05g calcium nitrate to the amine solution, continue to stir until completely dissolved, and feed carbon dioxide gas into the above solution for 80 minutes;

(2) Put the polyimide solution obtained in (1) into a film maker, and vacuum dry for 12 hours to obtain a polyimide film;

(3) Put the poly(p-phenylene terephthalamide) mixed solution obtained in (1) into the film maker in (2), and vacuum dry for 12 hours to obtain a composite film;

(4) Rinse the membrane obtained in (3) with dilute hydrochloric acid, and dry at 60° C. to obtain a porous composite membrane for a lithium-sulfur battery.

Example 4:

(1) Take 0.15g of polyimide and 0.397g of poly(p-phenylene terephthalamide), respectively, dissolve them into 240 mL of dimethyl sulfoxide, stir until the dissolution is complete, and add to poly(terephthaloyl terephthalamide) Slowly add 0.05g calcium chloride to the amine solution, continue to stir until completely dissolved, and feed carbon dioxide gas into the above solution for 120 minutes;

(2) Put the polyimide solution obtained in (1) into a film maker, and vacuum dry for 12 hours to obtain a polyimide film;

(3) Put the poly(p-phenylene terephthalamide) mixed solution obtained in (1) into the film maker in (2), and vacuum dry for 12 hours to obtain a composite film;

(4) Rinse the membrane obtained in (3) with dilute hydrochloric acid, and dry at 60° C. to obtain a porous composite membrane for a lithium-sulfur battery.

Example 5:

(1) Take 0.15g of polyimide and 0.397g of poly(p-phenylene terephthalamide), respectively, dissolve them into 240 mL of dimethyl sulfoxide, stir until the dissolution is complete, and add to poly(terephthaloyl terephthalamide) Slowly add 0.05g calcium chloride to the amine solution, continue to stir until completely dissolved, and feed carbon dioxide gas into the above solution for 80 minutes;

(2) Put the polyimide solution obtained in (1) into a film maker, and vacuum dry for 24 hours to obtain a polyimide film;

(3) Put the poly(p-phenylene terephthalamide) mixed solution obtained in (1) into the film maker in (2), and vacuum dry for 12 hours to obtain a composite film;

(4) Rinse the membrane obtained in (3) with dilute hydrochloric acid, and dry at 60° C. to obtain a porous composite membrane for a lithium-sulfur battery.

Example 6:

(1) Take 0.15g of polyimide and 0.397g of poly(p-phenylene terephthalamide), respectively, dissolve them into 240 mL of dimethyl sulfoxide, stir until the dissolution is complete, and add to poly(terephthaloyl terephthalamide) Slowly add 0.05g calcium chloride to the amine solution, continue to stir until completely dissolved, and feed carbon dioxide gas into the above solution for 80 minutes;

(2) Put the polyimide solution obtained in (1) into a film maker, and vacuum dry for 12 hours to obtain a polyimide film;

(3) Put the poly(p-phenylene terephthalamide) mixed solution obtained in (1) into the film maker in (2), and vacuum dry for 24 hours to obtain a composite film;

(4) Rinse the membrane obtained in (3) with dilute hydrochloric acid, and dry at 60° C. to obtain a porous composite membrane for a lithium-sulfur battery.

Example 7:

(1) Take 0.15g of polyimide and 0.397g of poly(p-phenylene terephthalamide), respectively, dissolve them into 240 mL of dimethyl sulfoxide, stir until the dissolution is complete, and add to poly(terephthaloyl terephthalamide) Slowly add 0.05g calcium chloride to the amine solution, continue to stir until completely dissolved, and feed carbon dioxide gas into the above solution for 80 minutes;

(2) Put the polyimide solution obtained in (1) into a film maker, and vacuum dry for 12 hours to obtain a polyimide film;

(3) Put the poly(p-phenylene terephthalamide) mixed solution obtained in (1) into the film maker in (2), and vacuum dry for 12 hours to obtain a composite film;

(4) Rinse the membrane obtained in (3) with dilute nitric acid, and dry at 60° C. to obtain a porous composite membrane for a lithium-sulfur battery.

Electrode preparation and performance test: Mix the electrode material, Super P and PVDF in a mass ratio of 8:1:1, use NMP as a solvent to form a slurry, stir for 12 hours, coat on aluminum foil as a positive electrode, and use metal lithium as a For the negative electrode, the porous composite film of polyimide and poly(p-phenylene terephthalamide) prepared in this example was used as the separator, and 1 mol/L LiTFSI was dissolved in DOL/DME (volume ratio of 1:1) to make The electrolyte, 1 mol/L LiNO ₃ as additive, was assembled into a button cell in a glove box. The Neware battery test system was used for constant current charge and discharge tests, and the charge and discharge voltage range was 1.7 V-2.8 V. As shown in FIG. 1, the XRD pattern of the polyimide and poly(p-phenylene terephthalamide) porous membrane prepared in this example is shown; FIG. 2 is a button cell assembled in this example at a current density of 0.1 The charge-discharge curve at C, it can be seen that the initial discharge capacity is 1543 mAh/g; Figure 3 is a curve diagram of the charge-discharge cycle of the coin-type battery assembled in this example at a current density of 0.1C for 100 cycles, it can be seen that The capacity retention rate was 89.7% after 50 cycles and 84.8% after 100 cycles.

Claims (7)

1. A preparation method of a lithium-sulfur battery porous composite membrane is characterized by comprising the following steps: the method comprises the following specific steps:

preparing a uniform polyimide solution and a poly-p-phenylene terephthalamide solution, wherein the concentrations of the two solutions are both 10 mmol/L-10 mol/L;

step two, adding calcium salt into the poly-p-phenylene terephthalamide solution obtained in the step one to obtain a uniform mixed solution, wherein the amount of the added calcium salt is 100 mg/L-1 g/L;

step three: introducing carbon dioxide gas into the mixed solution obtained in the step two;

step four: pouring the polyimide solution obtained in the step one into a film making device, and drying the film making device in a vacuum drying oven at the temperature of 60-180 ℃ to obtain a dry film;

step five: pouring the mixed solution obtained in the third step into the membrane making device obtained in the fourth step, and drying the membrane making device in a vacuum drying oven at the temperature of 60-180 ℃ to obtain a dry composite membrane;

step six: and (5) washing the dried composite membrane obtained in the fifth step with dilute acid, and drying the dried composite membrane in a drying oven for 10-18h to obtain the lithium-sulfur battery porous composite membrane.

2. The method of claim 1, wherein the porous composite membrane comprises: in the first step, the solvents of the polyimide solution and the poly-p-phenylene terephthalamide solution are one or a mixture of more of dimethyl sulfoxide, sulfolane, dimethylformamide or N-methylpyrrolidone.

3. The method of claim 1, wherein the porous composite membrane comprises: in the second step, the calcium salt is one of calcium chloride, calcium sulfate or calcium nitrate.

4. The preparation method of the porous composite membrane for the lithium-sulfur battery according to claim 1, wherein in the third step, the carbon dioxide gas is introduced for 60 to 120 minutes at an amount of 0.2 to 1L/min.

5. The method of claim 1, wherein the porous composite membrane comprises: in the fourth and fifth steps, the drying oven temperature was 100 ℃.

6. The method of claim 1, wherein the porous composite membrane comprises: in the sixth step, the dilute acid is one or a mixture of more of hydrochloric acid, boric acid, benzoic acid, sulfuric acid or nitric acid.

7. Use of a porous composite membrane for a lithium-sulphur battery prepared according to claim 1, characterized in that: the porous composite membrane is used for a lithium-sulfur battery diaphragm.

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