Composite solid-state polymer electrolyte, preparation method thereof and lithium ion battery

Abstract

The application discloses a composite solid-state polymer electrolyte and a preparation method and a lithium ion battery thereof, and relates to the technical field of lithium ion batteries. The composite solid-state polymer electrolyte comprises polyacrylonitrile-lithium polypropylene sulfonate, polydopamine and lithium bistrifluoromethylsulfonylimide. The polymer main chain in the composite solid-state polymer electrolyte contains lithium, can effectively reduce film crystallinity, improve molecular chain segment movement, and further improve lithium ion transmission capacity and ionic conductivity; meanwhile, the polymer main chain in the composite solid-state polymer electrolyte enhances material toughness and adhesion capacity, can improve system strength and electrochemical dynamics, so that the capacity retention rate and stability of the lithium ion battery are improved; in addition, the composite solid-state polymer electrolyte contains polydopamine, has excellent adhesion and film forming capacity, and further improves interface contact performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a composite solid-state polymer electrolyte, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] With the rapid development of clean energy market and electronic economy, the demand for electrochemical energy storage devices is increasing. Compared with traditional rechargeable secondary batteries, lithium ion batteries are widely used in portable electronic devices, new energy vehicles and grid energy storage systems due to their high energy density, excellent cycle stability and no memory effect. However, the safety performance of lithium ion batteries is insufficient, which brings safety hazards to consumers and limits the large-scale application of lithium ion batteries. Therefore, it is imperative to develop lithium ion batteries with high safety performance.

[0003] Since solid-state electrolyte has the characteristics of non-toxic, no leakage, and non-flammable, using solid-state electrolyte instead of liquid electrolyte provides an effective solution to the safety problem. Solid-state electrolyte mainly includes inorganic ceramic electrolyte, organic polymer electrolyte and organic-inorganic composite solid-state electrolyte, which can reduce the possibility of short circuit and thermal runaway of lithium ion batteries.

[0004] Among them, solid-state polymer electrolyte has the advantages of easy processing, high flexibility, low cost, low interfacial resistance and light weight, which provides a broad prospect for the next generation of lithium ion batteries. However, solid-state polymer electrolyte usually shows low ionic conductivity and slightly weak toughness and interface contact performance. Therefore, the present application designs a composite solid-state polymer electrolyte to improve the ionic conductivity and interface contact performance and mechanical properties of solid-state polymer electrolyte. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a composite solid-state polymer electrolyte, a preparation method thereof and a lithium ion battery.

[0006] The composite solid-state polymer electrolyte disclosed by the present application comprises polyacrylonitrile-lithium polyacrylate, polydopamine and lithium bistrifluoromethylsulfonylimide.

[0007] According to an embodiment of the present application, the mass ratio of polyacrylonitrile-lithium polyacrylate, polydopamine and lithium bistrifluoromethylsulfonylimide is (10-100):1:(1-10).

[0008] According to an embodiment of the present application, the structural formula of polyacrylonitrile-lithium polyacrylate is In the formula, a and b are both positive integers greater than or equal to 2.

[0009] According to an embodiment of the present application, the structural formula of polydopamine is n is a positive integer greater than or equal to 2.

[0010] The preparation method of the composite solid-state polymer electrolyte disclosed in the present application comprises the following steps:

[0011] The polyacrylonitrile-lithium polyacrylsulfonate and the polydopamine are added into N,N-dimethylformamide, stirred and dissolved to obtain an electrolyte mixed solution;

[0012] The lithium bistrifluoromethylsulfonylimide is added into the electrolyte mixed solution, heated and stirred uniformly to obtain an electrolyte mixed slurry;

[0013] The electrolyte mixed slurry is uniformly coated on a carrier, and after drying, the composite solid-state polymer electrolyte is obtained.

[0014] According to an embodiment of the present application, the preparation of the polyacrylonitrile-lithium polyacrylsulfonate comprises the following steps:

[0015] The propylene sulfonic acid is added into deionized water, stirred and dissolved to obtain a propylene sulfonic acid aqueous solution; under ice bath conditions, the lithium hydroxide aqueous solution is added into the propylene sulfonic acid aqueous solution, stirred to obtain a mixed solution; wherein the material liquid ratio of the propylene sulfonic acid, the deionized water and the lithium hydroxide aqueous solution is (5-50) g:(100-1000) mL:(0.5-10) g;

[0016] The dilute hydrochloric acid is added into the mixed solution, and after solid is precipitated, the addition of the dilute hydrochloric acid is stopped, and the stirring is continued, and then the solid is obtained by filtration, and the solid is dried to obtain the lithium propylene sulfonate;

[0017] The acrylonitrile, the lithium propylene sulfonate and the azobisisobutyronitrile are added into dimethyl sulfoxide, stirred to obtain a crude product; wherein the material liquid ratio of the acrylonitrile, the lithium propylene sulfonate, the azobisisobutyronitrile and the dimethyl sulfoxide is (1-10) g:(1-2) g:(0.1-1) g:(50-1000) mL;

[0018] The crude product is precipitated in deionized water, and after washing, the polyacrylonitrile-lithium polyacrylsulfonate is obtained.

[0019] According to an embodiment of the present application, the preparation of the polydopamine comprises the following steps:

[0020] The dopamine and the tris-hydroxymethyl aminomethane hydrochloride are mixed, and stirred under light shielding conditions to obtain the polydopamine; wherein the mass ratio of the dopamine and the tris-hydroxymethyl aminomethane hydrochloride is (5-50):(1-10), and the concentration of the polydopamine is 0.1-5 mol / L.

[0021] According to an embodiment of the present application, the polyacrylonitrile-lithium polyacrylate and the polydopamine are stirred at 50-120°C for 8-24h after being added into N,N-dimethylformamide.

[0022] According to an embodiment of the present application, the mixed slurry is uniformly coated on the carrier and then dried at 40-90°C for 12-36h.

[0023] The present application discloses a lithium ion battery comprising the composite solid-state polymer electrolyte as described above.

[0024] Compared with the prior art, the composite solid-state polymer electrolyte, the preparation method thereof and the lithium ion battery have the following advantages:

[0025] The polymer main chain of the composite solid-state polymer electrolyte of the present application contains lithium and can effectively reduce the film crystallinity, improve the molecular chain segment movement, and further improve the lithium ion transmission capacity and ionic conductivity; at the same time, the polymer main chain in the composite solid-state polymer electrolyte enhances the material toughness and adhesion, can improve the system strength and electrochemical kinetics, so that the capacity retention rate and stability of the lithium ion battery are improved; in addition, the composite solid-state polymer electrolyte contains polydopamine, which has excellent adhesion and film forming capacity, and further improves the interface contact performance.

[0026] The preparation method of the composite solid-state polymer electrolyte of the present application has simple process and low cost, effectively improves the stability and electrical performance of the composite solid-state polymer electrolyte, and thus improves the service life of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0028] Figure 1 The figure is a lithium ion conductivity test result. DETAILED DESCRIPTION

[0029] The embodiments of the present application will be disclosed below. For clear description, many practical details will be described in the following description. However, it should be understood that these practical details should not be used to limit the present application. That is, in some embodiments of the present application, these practical details are unnecessary.

[0030] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0031] Example 1

[0032] This embodiment provides a composite solid polymer electrolyte comprising lithium polyacrylonitrile-lithium polypropylene sulfonate, polydopamine, and lithium bis(trifluoromethanesulfonyl)imide.

[0033] In this example, the mass ratio of polyacrylonitrile-lithium polypropylene sulfonate, polydopamine and lithium bis(trifluoromethanesulfonylimide) is (10-100):1:(1-10).

[0034] In this example, the structural formula of polyacrylonitrile-lithium polypropylene sulfonate is: In the formula, a and b are both positive integers greater than or equal to 2, and a > b.

[0035] In this example, the structural formula of polydopamine is: In the formula, n is a positive integer greater than or equal to 2.

[0036] In this example, the tensile strength of the composite solid polymer electrolyte is greater than 5 MPa.

[0037] In this composite solid polymer electrolyte, the polymer backbone contains lithium compounds, which can effectively reduce film crystallinity and improve molecular chain segment movement, thereby enhancing lithium-ion transport capacity and ionic conductivity. Simultaneously, the polymer backbone in this composite solid polymer electrolyte enhances material toughness and adhesion, improving system strength and electrochemical kinetics, thus improving the capacity retention and stability of the lithium-ion battery. Furthermore, this composite solid polymer electrolyte contains polydopamine, which has excellent adhesion and film-forming ability, further improving interfacial contact performance.

[0038] Example 2

[0039] This embodiment provides a method for preparing the composite solid polymer electrolyte according to the above description, which is used to prepare the composite solid polymer electrolyte described in Example 1.

[0040] The preparation method of this composite solid polymer electrolyte includes the following steps:

[0041] Polyacrylonitrile-lithium polypropylene sulfonate and polydopamine were added to N,N-dimethylformamide and stirred to dissolve, thus obtaining an electrolyte mixed solution.

[0042] Lithium bis(trifluoromethanesulfonyl)imide was added to the electrolyte mixture, heated and stirred until homogeneous to obtain an electrolyte slurry.

[0043] The electrolyte mixture slurry is uniformly coated onto a carrier and dried to obtain a composite solid polymer electrolyte.

[0044] In this example, the feed-liquid ratio of polyacrylonitrile-lithium polypropylene sulfonate, polydopamine, N,N-dimethylformamide and lithium bis(trifluoromethanesulfonylimide) is (10-100)g:(1-10)g:(50-1000)mL:(1-10)g.

[0045] In this example, polyacrylonitrile-lithium polypropylene sulfonate and polydopamine were added to N,N-dimethylformamide and stirred at 50–120°C for 8–24 hours to obtain complete dissolution.

[0046] In this example, the mixed slurry was uniformly coated onto the carrier and then dried at 40–90°C for 12–36 hours.

[0047] In this example, the preparation of polyacrylonitrile-lithium polypropylene sulfonate includes the following steps:

[0048] Acrylic sulfonic acid was added to deionized water and stirred to dissolve, thus obtaining an aqueous solution of acrylic sulfonic acid. Under ice bath conditions, an aqueous solution of lithium hydroxide was added to the aqueous solution of acrylic sulfonic acid and stirred to obtain a mixed solution. The ratio of acrylic sulfonic acid, deionized water, and aqueous solution of lithium hydroxide was (5-50) g: (100-1000) mL: (0.5-10) g.

[0049] Add dilute hydrochloric acid to the mixture. Stop adding dilute hydrochloric acid after solid precipitates out, continue stirring, filter to obtain solid, and dry the solid to obtain lithium propylene sulfonate.

[0050] Acrylonitrile, lithium propylene sulfonate, and azobisisobutyronitrile were added to dimethyl sulfoxide and stirred to obtain a crude product; wherein the ratio of acrylonitrile, lithium propylene sulfonate, azobisisobutyronitrile, and dimethyl sulfoxide was (1-10) g: (1-2) g: (0.1-1) g: (50-1000) mL.

[0051] The crude product was precipitated in deionized water and washed to obtain polyacrylonitrile-lithium polyacrylonitrile sulfonate.

[0052] In this example, under ice bath conditions of -10 to 0°C, an aqueous solution of lithium hydroxide was added to an aqueous solution of propylene sulfonic acid, and the mixture was stirred for 0.5 to 6 hours. The concentration of the aqueous solution of lithium hydroxide was 0.5 mol / L.

[0053] In this example, dilute hydrochloric acid was added to the mixture. Once a solid precipitated, the addition of dilute hydrochloric acid was stopped, and stirring was continued for 0.2–3 hours. The concentration of the dilute hydrochloric acid was 4 mol / L.

[0054] In this example, after filtering to obtain the solid, the solid was dried at 30–100°C for 6 hours.

[0055] In this example, acrylonitrile, lithium propylene sulfonate, and azobisisobutyronitrile were added to dimethyl sulfoxide and stirred at 30–90°C for 4–24 h under a nitrogen atmosphere.

[0056] In this example, the crude product was precipitated in 50–1000 mL of deionized water and then washed three times with deionized water.

[0057] In this example, the preparation of polydopamine includes the following steps:

[0058] Dopamine is mixed with tris(hydroxymethyl)aminomethane hydrochloride and stirred under light-shielding conditions to obtain polydopamine; wherein the mass ratio of dopamine to tris(hydroxymethyl)aminomethane hydrochloride is (5-50):(1-10), and the concentration of polydopamine is 0.1-5 mol / L.

[0059] In this example, after dopamine was mixed with tris(hydroxymethyl)aminomethane hydrochloride and stirred under light-shielding conditions for 6–18 hours, the solution turned brownish-black.

[0060] The preparation method of this composite solid polymer electrolyte is simple and low-cost, effectively improving the stability and electrical performance of the composite solid polymer electrolyte, thereby increasing the lifespan of lithium-ion batteries.

[0061] Example 3

[0062] This embodiment provides a lithium-ion battery, which includes the composite solid polymer electrolyte described in Embodiment 1.

[0063] To further illustrate the invention, this application provides nine samples of composite solid polymer electrolytes, which are described below.

[0064] Sample 1

[0065] The composite solid polymer electrolyte provided in Sample 1 comprises lithium polyacrylonitrile-polypropylene sulfonate, polydopamine, and lithium bis(trifluoromethanesulfonyl)imide. The mass ratio of lithium polyacrylonitrile-polypropylene sulfonate, polydopamine, and lithium bis(trifluoromethanesulfonyl)imide is 30:1:5. The structural formula of lithium polyacrylonitrile-polypropylene sulfonate is [insert structural formula here]. In the formula, a and b are both positive integers greater than or equal to 2, and a > b. The structural formula of polydopamine is: In the formula, n is a positive integer greater than or equal to 2.

[0066] The preparation method of this composite solid polymer electrolyte includes three processes: first, preparing polyacrylonitrile-lithium polypropylene sulfonate; second, preparing polydopamine; and third, using the prepared polyacrylonitrile-lithium polypropylene sulfonate and polydopamine to prepare the composite solid polymer electrolyte. The specific preparation method is as follows:

[0067] (1) Preparation of polyacrylonitrile-lithium polypropylene sulfonate

[0068] 20g of propylene sulfonic acid was added to 500mL of deionized water and stirred to dissolve, resulting in an aqueous solution of propylene sulfonic acid. Under ice bath conditions at 0℃, 5g of 0.5mol / L lithium hydroxide aqueous solution was added to the propylene sulfonic acid aqueous solution and stirred for 2h to obtain a mixed solution.

[0069] Add 4 mol / L dilute hydrochloric acid to the mixture. Stop adding dilute hydrochloric acid after solid precipitates. Continue stirring for 1 hour. Then filter to obtain solid. Dry the solid at 65°C for 6 hours to obtain lithium propylene sulfonate.

[0070] 7g acrylonitrile, 2g lithium propylene sulfonate and 0.3g azobisisobutyronitrile were added to 500mL dimethyl sulfoxide and stirred at 50℃ for 12h under nitrogen atmosphere to obtain crude product;

[0071] After precipitating the crude product in 500 mL of deionized water, the crude product was washed three times with deionized water to obtain polyacrylonitrile-lithium polyacrylonitrile sulfonate.

[0072] (2) Preparation of polydopamine

[0073] 20g of dopamine was mixed with 5g of tris(hydroxymethyl)aminomethane hydrochloride and stirred for 12h under light-shielding conditions to obtain polydopamine with a concentration of 2mol / L.

[0074] (3) Preparation of composite solid polymer electrolytes

[0075] Add 30g of polyacrylonitrile-lithium polyacrylonitrile sulfonate and 1g of polydopamine to 500mL of N,N-dimethylformamide, stir to dissolve, and obtain an electrolyte mixed solution;

[0076] 5g of lithium bis(trifluoromethanesulfonyl)imide was added to the electrolyte mixture and stirred at 80℃ for 12h to obtain the electrolyte mixture slurry.

[0077] The electrolyte mixture slurry was uniformly coated onto the carrier and dried at 60°C for 12 hours to obtain the composite solid polymer electrolyte.

[0078] Sample 2

[0079] The main difference between Sample 2 and Sample 1 is that the mass ratio of polyacrylonitrile-lithium polypropylene sulfonate, polydopamine and lithium bis(trifluoromethanesulfonyl)imide is 15:1:5, that is, the amount of acrylonitrile-lithium polypropylene sulfonate is 15g, the amount of polydopamine is 1g and the amount of lithium bis(trifluoromethanesulfonyl)imide is 5g.

[0080] Sample 3

[0081] The main difference between Sample 3 and Sample 1 is that the mass ratio of polyacrylonitrile-lithium polypropylene sulfonate, polydopamine, and lithium bis(trifluoromethanesulfonyl)imide is 60:1:5, meaning the amount of acrylonitrile-lithium polypropylene sulfonate is 60g, the amount of polydopamine is 1g, and the amount of lithium bis(trifluoromethanesulfonyl)imide is 5g.

[0082] Sample 4

[0083] The main difference between Sample 4 and Sample 1 is that the amount of acrylonitrile used is 3g and the amount of lithium propylene sulfonate used is 2g.

[0084] Sample 5

[0085] The main difference between Sample 5 and Sample 1 is that the amount of acrylonitrile used is 15g and the amount of lithium propylene sulfonate used is 2g.

[0086] Sample Six

[0087] The main difference between Sample 6 and Sample 1 is that the polyacrylonitrile-lithium polyacrylonitrile sulfonate is replaced with polyacrylonitrile, while the amount remains the same. That is, the composite solid polymer electrolyte provided by Sample 6 includes polyacrylonitrile, polydopamine, and lithium bis(trifluoromethanesulfonyl)imide, with a mass ratio of polyacrylonitrile, polydopamine, and lithium bis(trifluoromethanesulfonyl)imide of 30:1:5.

[0088] The preparation of polyacrylonitrile includes the following steps:

[0089] 20g of acrylonitrile and 0.3g of azobisisobutyronitrile were added to 500mL of dimethyl sulfoxide and stirred at 50℃ for 12h under nitrogen atmosphere to obtain crude product;

[0090] After precipitating the crude product in 500 mL of deionized water, the crude product was washed three times with deionized water to obtain polyacrylonitrile.

[0091] Sample 7

[0092] The main difference between Sample 7 and Sample 1 is that the composite solid polymer electrolyte does not include polydopamine. Specifically, the composite solid polymer electrolyte provided in Sample 7 includes lithium polyacrylonitrile-lithium polypropylene sulfonate and lithium bis(trifluoromethanesulfonyl)imide, with a mass ratio of 30:5 between lithium polyacrylonitrile-lithium polypropylene sulfonate and lithium bis(trifluoromethanesulfonyl)imide.

[0093] Sample 8

[0094] The composite solid polymer electrolyte provided in Sample 8 comprises polyacrylonitrile and lithium bis(trifluoromethanesulfonyl)imide. The mass ratio of polyacrylonitrile to lithium bis(trifluoromethanesulfonyl)imide is 5:5.

[0095] The preparation method of this composite solid polymer electrolyte includes two processes: first, preparing polyacrylonitrile; and second, using the prepared polyacrylonitrile to prepare the composite solid polymer electrolyte. The specific preparation method is as follows:

[0096] (1) Preparation of polyacrylonitrile

[0097] 20g of acrylonitrile and 0.3g of azobisisobutyronitrile were added to 500mL of dimethyl sulfoxide and stirred at 50℃ for 12h under nitrogen atmosphere to obtain crude product;

[0098] After precipitating the crude product in 500 mL of deionized water, the crude product was washed three times with deionized water to obtain polyacrylonitrile.

[0099] (2) Preparation of composite solid polymer electrolytes

[0100] Add 5g of polyacrylonitrile to 500mL of N,N-dimethylformamide, stir to dissolve, and obtain an electrolyte mixed solution;

[0101] 5g of lithium bis(trifluoromethanesulfonyl)imide was added to the electrolyte mixture and stirred at 80℃ for 12h to obtain the electrolyte mixture slurry.

[0102] The electrolyte mixture slurry was uniformly coated onto the carrier and dried at 60°C for 12 hours to obtain the composite solid polymer electrolyte.

[0103] Sample Nine

[0104] The composite solid polymer electrolyte provided in Sample Nine includes polyacrylonitrile.

[0105] The preparation method of this composite solid polymer electrolyte includes two processes: first, preparing polyacrylonitrile; and second, using the prepared polyacrylonitrile to prepare the composite solid polymer electrolyte. The specific preparation method is as follows:

[0106] (1) Preparation of polyacrylonitrile

[0107] 20g of acrylonitrile and 0.3g of azobisisobutyronitrile were added to 500mL of dimethyl sulfoxide and stirred at 50℃ for 12h under nitrogen atmosphere to obtain crude product;

[0108] After precipitating the crude product in 500 mL of deionized water, the crude product was washed three times with deionized water to obtain polyacrylonitrile.

[0109] (2) Preparation of composite solid polymer electrolytes

[0110] Add 5g of polyacrylonitrile to 500mL of N,N-dimethylformamide, stir to dissolve, and obtain an electrolyte mixed solution;

[0111] The electrolyte mixture was stirred at 80°C for 12 hours to obtain an electrolyte slurry.

[0112] The electrolyte mixture slurry was uniformly coated onto the carrier and dried at 60°C for 12 hours to obtain the composite solid polymer electrolyte.

[0113] The composite solid polymer electrolytes of samples one through nine above were subjected to stress-strain tests using the same method. The specific test results are as follows:

[0114] Table 1. Stress-strain test results

[0115]

[0116]

[0117] Samples 1 to 7 are the composite solid polymer electrolytes of this invention, while samples 8 to 9 are existing composite solid polymer electrolytes. As can be seen from Table 1, the tensile strength of samples 1 to 7 is higher than that of samples 8 to 9, demonstrating that the modification of the polyacrylonitrile matrix and the addition of composite polydopamine can further enhance the mechanical strength of the system.

[0118] Specifically, compared to Sample 5, Sample 4 and Sample 1 show an increased proportion of lithium polyacrylonitrile in the composite solid polymer electrolyte, resulting in increased tensile strength. This indicates that modification of the polyacrylonitrile matrix is ​​beneficial for improving tensile strength. Compared to Sample 3, Sample 2 and Sample 1 show a decreased proportion of polydopamine in the composite solid polymer electrolyte, resulting in decreased tensile strength. This indicates that adding polydopamine is beneficial for improving tensile strength. Further comparing Sample 1, Sample 6, and Sample 7, Sample 1's composite solid polymer electrolyte has a modified polyacrylonitrile matrix, while Sample 6's composite solid polymer electrolyte does not. Therefore, Sample 1 has a higher tensile strength than Sample 6. Sample 1's composite solid polymer electrolyte contains polydopamine, while Sample 7's composite solid polymer electrolyte does not. Thus, Sample 1 has a higher tensile strength than Sample 7.

[0119] The composite solid polymer electrolytes of samples one through nine above were then used to fabricate coin cells using the same method. The resulting coin cells were then subjected to electrical performance tests (charge / discharge conditions of 0.5C, charge / discharge range of 3.0V-4.60V). The specific test results are as follows:

[0120] Table 2 Electrical performance test results

[0121]

[0122]

[0123] Samples 1 to 7 are the composite solid-state polymer electrolytes of this invention, while samples 8 to 9 are existing composite solid-state polymer electrolytes. As can be seen from Table 2, the coin cells prepared from samples 1 to 7 exhibit higher initial charge-discharge efficiency, capacity recovery rate after 6 hours of storage at 70°C, and capacity retention rate after 100 cycles at 25°C compared to the coin cells prepared from samples 8 to 9. This demonstrates that the composite solid-state polymer electrolyte effectively improves charge-discharge performance, high-temperature stability, and cycle stability.

[0124] Specifically, the mass ratio of polyacrylonitrile-lithium polypropylene sulfonate and polydopamine in Sample 1 was 30:1, the mass ratio of polyacrylonitrile-lithium polypropylene sulfonate and polydopamine in Sample 2 was 15:1, and the mass ratio of polyacrylonitrile-lithium polypropylene sulfonate and polydopamine in Sample 3 was 60:1. The coin cell prepared in Sample 1 showed a higher capacity retention rate and no deterioration in the first charge and discharge efficiency.

[0125] The mass ratio of acrylonitrile to lithium propylene sulfonate in Sample 1 was 7:2, the mass ratio of acrylonitrile to lithium propylene sulfonate in Sample 4 was 3:2, and the mass ratio of acrylonitrile to lithium propylene sulfonate in Sample 5 was 15:2. The coin cell prepared in Sample 1 showed a higher capacity retention rate and no deterioration in the first charge-discharge efficiency.

[0126] In addition, the lithium-ion conductivity of the coin cells prepared from samples one through five was tested, and the results are as follows:

[0127] Figure 1 The graph shows the results of the lithium-ion conductivity test. It can be seen from the graph that among the coin cells prepared by samples one to five, the coin cell prepared by sample one has the best lithium-ion conductivity. This indicates that the synthesis steps of sample one are optimal, resulting in the best lithium-ion conduction capacity of the lithium-ion battery.

[0128] In summary, the composite solid polymer electrolyte of the present invention further enhances the mechanical strength of the system by modifying the polyacrylonitrile matrix and adding composite polydopamine, effectively improving the cycle stability of lithium-ion batteries and enhancing their charge-discharge performance.

[0129] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A composite solid-state polymer electrolyte, characterized by, The polyacrylonitrile-polypropylene sulfonic acid lithium, the polydopamine and the lithium bis-trifluoromethanesulfonimide; The polyacrylonitrile-polypropylene sulfonic acid lithium has a structural formula of , wherein a and b are both positive integers greater than or equal to 2. The polydopamine has a structural formula of , wherein n is a positive integer greater than or equal to 2.

2. The composite solid-state polymer electrolyte according to claim 1, wherein The mass ratio of the polyacrylonitrile-polypropylene sulfonic acid lithium, the polydopamine and the lithium bis-trifluoromethanesulfonimide is (10-100):1:(1-10).

3. A method for producing the composite solid-state polymer electrolyte according to any one of claims 1 to 2, characterized by, The method comprises the following steps: The polyacrylonitrile-polypropylene sulfonic acid lithium and the polydopamine are added into N,N-dimethylformamide, stirred and dissolved to obtain an electrolyte mixed solution; The lithium bis-trifluoromethanesulfonimide is added into the electrolyte mixed solution, heated and stirred uniformly to obtain an electrolyte mixed slurry; The electrolyte mixed slurry is uniformly coated on a carrier, and after drying, a composite solid-state polymer electrolyte is obtained.

4. The method for preparing a composite solid-state polymer electrolyte according to claim 3, characterized by, The preparation of the polyacrylonitrile-polypropylene sulfonic acid lithium comprises the following steps: The propylene sulfonic acid is added into deionized water, stirred and dissolved to obtain a propylene sulfonic acid aqueous solution; under ice bath conditions, the lithium hydroxide aqueous solution is added into the propylene sulfonic acid aqueous solution, stirred to obtain a mixed solution; wherein the material liquid ratio of the propylene sulfonic acid, the deionized water and the lithium hydroxide aqueous solution is (5-50) g:(100-1000) mL:(0.5-10) g; The dilute hydrochloric acid is added into the mixed solution, and after solid is precipitated, the addition of the dilute hydrochloric acid is stopped, and then the stirring is continued, and then the solid is obtained by filtration, and the solid is dried to obtain lithium propylene sulfonate; The acrylonitrile, the lithium propylene sulfonate and the azobisisobutyronitrile are added into dimethyl sulfoxide, stirred to obtain a crude product; wherein the material liquid ratio of the acrylonitrile, the lithium propylene sulfonate, the azobisisobutyronitrile and the dimethyl sulfoxide is (1-10) g:(1-2) g:(0.1-1) g:(50-1000) mL; The crude product is precipitated in deionized water, and after washing, the polyacrylonitrile-polypropylene sulfonic acid lithium is obtained.

5. The method for preparing a composite solid-state polymer electrolyte according to claim 3, characterized by, The preparation of the polydopamine comprises the following steps: The dopamine and the tris-hydroxymethyl aminomethane hydrochloride are mixed, and stirred under light shielding conditions to obtain the polydopamine; wherein the mass ratio of the dopamine and the tris-hydroxymethyl aminomethane hydrochloride is (5-50):(1-10), and the concentration of the polydopamine is 0.1-5 mol / L.

6. The method for preparing a composite solid-state polymer electrolyte according to claim 3, characterized by, The polyacrylonitrile-polypropylene sulfonic acid lithium and the polydopamine are added into N,N-dimethylformamide, and stirred at 50-120 DEG C for 8-24 h.

7. The method of claim 3, wherein the solid-state polymer electrolyte is prepared by mixing the polymer and the electrolyte solution at a temperature of 30°C to 100°C. After the mixed slurry is uniformly coated on the carrier, the drying is performed at 40-90 DEG C for 12-36 h.

8. A lithium-ion battery, characterized by The composite solid-state polymer electrolyte as claimed in any one of claims 1-2.

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