Hollow-structured functionalized microspheres and their application in all-solid-state lithium metal batteries

Abstract

This invention discloses a hollow-structured functional microsphere and its application in all-solid-state lithium metal batteries. The microsphere is constructed using a one-step self-emulsification process, consisting of a polymer backbone and a crosslinking agent. It possesses abundant tertiary amines and sulfonic acid groups, along with a unique spherical hollow structure. Through strong amino coordination and single-ion conduction by sulfonic acid groups, it can inhibit the crystallization of PEO segments and efficiently dissociate lithium salts. Furthermore, the unique spherical hollow structure of the microsphere allows for the pre-embedding of active guest molecules, thereby improving ionic conductivity and lithium-ion transference number without sacrificing electrolyte membrane performance. This makes it a promising candidate for application in all-solid-state lithium metal batteries.

Description

Technical Field

[0001] This invention belongs to the field of polymer electrolytes, specifically relating to a functionalized polyethyleneimine microsphere with a hollow structure and its application in all-solid-state lithium metal batteries. Background Technology

[0002] Energy is the lifeblood of my country's industrial development. Faced with the environmental problems caused by fossil fuels, electrochemical energy storage devices, through the mutual conversion of electrical and chemical energy, can store and release energy, playing a crucial role in my country's energy transition. All-solid-state lithium-ion batteries use solid electrolytes instead of traditional flammable organic electrolytes. Compared to traditional electrolytes, they possess superior mechanical properties, effectively suppressing lithium dendrite growth during cycling and preventing electrolyte volatilization and leakage. Furthermore, they exhibit excellent chemical and thermal stability, resulting in better safety and a longer service life. However, the biggest obstacle facing solid polymer electrolytes is their high crystallinity at room temperature, leading to low ionic conductivity. Therefore, it is necessary to provide a polymer electrolyte with high ionic conductivity and low interfacial impedance to overcome these problems. Summary of the Invention

[0003] This invention aims to overcome the shortcomings and deficiencies of existing key materials and technologies in the field of solid-state batteries, proposing a functionalized microsphere with a hollow structure and its application in all-solid-state lithium metal batteries. This functionalized microsphere can be mass-produced through a one-step self-emulsification spheroidization process, offering advantages such as low cost, simple synthesis, and good synergistic ion-conducting performance. The resulting functionalized polyethyleneimine microspheres, rich in tertiary amines and sulfonic acid groups and possessing a special spherical structure, can suppress the crystallization of polyether-based polyethylene oxide (PEO) segments and efficiently dissociate lithium salts through strong amino coordination and single-ion conduction by sulfonic acid groups. Furthermore, the special structure of the microspheres can improve ionic conductivity and lithium-ion transference number without sacrificing electrolyte membrane performance.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A hollow-structured functionalized microsphere is produced using a one-step self-emulsifying spheroidization process, comprising a polymer backbone and a crosslinking agent. The surface of the polymer backbone is modified with sulfonic acid groups.

[0006] The preparation of the functionalized microspheres includes the following steps:

[0007] (1) At 0 ℃ or below, 30 wt% monomer solution is added dropwise to 30 wt% lithium hydroxide solution, stirred for 1~12 h and then freeze-dried;

[0008] (2) Add water to the product obtained in step (1) to prepare a 40 wt% solution, and then drop it into a 40 wt% polyethyleneimine solution. Stir overnight at 40 °C under argon protection.

[0009] (3) After dialysis of the product obtained in step (2) for 3 days, most of the solvent was removed by rotary evaporation and then vacuum drying was performed;

[0010] (4) Add water to the dried product of step (3) to prepare a 10wt% solution, then add it to an oily solution, stir and emulsify at room temperature for 2 h, then add a crosslinking agent, stir at room temperature for 1 h, then stir at 60 ℃ for 5 h, then centrifuge, wash and dry to obtain the functionalized microspheres.

[0011] Further, the amounts of the monomer solution and lithium hydroxide solution used in step (1) are calculated according to the molar ratio of monomer to lithium hydroxide being 1:1; the monomer is selected from one or more of 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, vinylbenzenesulfonic acid, and allyl vinylsulfonic acid.

[0012] Further, the molar ratio of the product used in step (2) to polyethyleneimine (PEI) is 4:1; the molecular weight of the polyethyleneimine is 600~1,000,000.

[0013] Further, in step (3), dialysis is performed using a dialysis bag with a molecular weight cutoff of 3500~6000.

[0014] Further, in step (4), 1-5g of product is added per liter of oily solution; the oily solution is selected from one or more of olive oil, solvent oil, and liquid paraffin.

[0015] Further, in step (4), the mass ratio of the crosslinking agent to the product used is 1:1; the crosslinking agent is selected from one or more of glutaraldehyde, glyoxal, and polyethylene glycol methacrylate.

[0016] The resulting functionalized microspheres can be prepared into electrolyte membranes and further prepared into electrolytes for all-solid-state lithium metal batteries.

[0017] The beneficial effects of this invention are as follows:

[0018] This invention provides a simple one-step self-emulsification spheroidization process to prepare functionalized polyethyleneimine microspheres rich in tertiary amines and sulfonic acid groups, exhibiting a unique spherical structure. Applying these functionalized microspheres to all-solid-state polymer electrolytes can improve ionic conductivity and lithium-ion transference number without sacrificing electrolyte membrane performance, thereby enhancing the overall performance of the polymer electrolyte. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the functionalized microspheres from Example 1.

[0020] Figure 2 Rate curves of the all-solid-state polymer electrolytes prepared in Example 1 and Comparative Example 1 in lithium iron phosphate / Li batteries.

[0021] Figure 3 The image shows the long-cycle diagrams of the all-solid-state polymer electrolytes prepared in Example 1 and Comparative Example 1 in lithium iron phosphate / Li batteries at a 1 C rate. Detailed Implementation

[0022] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0023] Example 1

[0024] At temperatures below 0 °C, 0.1 mol of 2-acrylamide-2-methylpropanesulfonic acid and lithium hydroxide were dissolved in water to prepare 30 wt% solutions. The 2-acrylamide-2-methylpropanesulfonic acid solution was then added dropwise to the lithium hydroxide solution, stirred for 1 h, and then freeze-dried. 0.1 mol of polyethyleneimine was dissolved in water to prepare a 40 wt% solution, and 0.04 mol of the freeze-dried product was dissolved in water to prepare a 40 wt% solution. This solution was then added dropwise to the prepared polyethyleneimine solution, stirred overnight at 40 °C under argon protection, and the product was dialyzed for 3 days. After rotary evaporation to remove most of the solvent, the product was then vacuum-dried to obtain grafted lithium salt hyperbranched polyethyleneimine.

[0025] 0.05 g of grafted lithium salt hyperbranched polyethyleneimine (PEI-AMPSLi) was dispersed in 0.5 mL of water and dissolved by shaking or sonication. Then, it was added to 10 mL of olive oil and emulsified by stirring at room temperature for 2 h. 0.025 g of 50 wt% glutaraldehyde solution was added, and the mixture was stirred at room temperature for 1 h, then heated and stirred at 60 ℃ for 5 h. After the reaction was complete, the suspension was transferred to a centrifuge tube for centrifugation and washing. 10 mL of cyclohexane was added to the solid obtained after centrifugation and washing, and the mixture was thoroughly shaken and placed in a high-speed centrifuge. The mixture was centrifuged at 10,000 rpm for 3 minutes to remove the supernatant. The remaining solid product was washed three times, air-dried at room temperature for 12 h, and then transferred to a vacuum drying oven at 60 ℃ for 6 h to obtain functionalized PEI-AMPSLi microspheres with PEI as the main framework.

[0026] Weigh 0.01 g of functionalized PEI-AMPSLi microspheres and add them to acetonitrile. Sonicate for 30 minutes to ensure uniform distribution. Then transfer to a glove box, add 0.69 g of PEO (molecular weight 1,000,000) and 0.25 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), ensuring a molar ratio of ethylene oxide to lithium ions of 18:1. Stir for 12 h, then remove from the glove box. Transfer the solution to release paper using a dropper and coat it with a coating agent. Set the film thickness to 1 mm or 1.5 mm. Transfer the release paper to a sealed glass box to air dry for 6 h, then transfer it to an 80 ℃ vacuum drying oven to dry for 12 h. After drying, peel off the film with tweezers and sandwich it between two folded pieces of release paper (ensuring the smoother side of the release paper faces the film). Then place it in a manual hot press and press it at 70 ℃ for 3 minutes. After hot pressing, once cooled to room temperature, the film can be transferred to a die-cutting machine to be cut into circular electrolyte membranes with a diameter of 16.5 mm, which will then be used as the electrolyte for lithium metal batteries.

[0027] Example 2

[0028] An equimolar amount of acrylic-2-acrylamide-2-methylpropanesulfonic acid copolymer was used instead of 2-acrylamide-2-methylpropanesulfonic acid as the reaction monomer, and the rest of the operation was the same as in Example 1.

[0029] Example 3

[0030] Equimolar amounts of vinylbenzenesulfonic acid were used instead of 2-acrylamide-2-methylpropanesulfonic acid as the reaction monomer, and the remaining operations were the same as in Example 1.

[0031] Example 4

[0032] An equimolar amount of allyl vinyl sulfonic acid was used instead of 2-acrylamide-2-methylpropane sulfonic acid as the reaction monomer, and the rest of the operation was the same as in Example 1.

[0033] Example 5

[0034] An equal volume of solvent oil was used instead of olive oil as the oily solution, and the rest of the operation was the same as in Example 1.

[0035] Example 6

[0036] An equal volume of liquid paraffin was used instead of olive oil as the oily solution, and the rest of the operation was the same as in Example 1.

[0037] Example 7

[0038] Adjust the amount of olive oil added to 20 mL, and follow the same procedure as in Example 1.

[0039] Example 8

[0040] Adjust the amount of olive oil added to 30 mL, and follow the same procedure as in Example 1.

[0041] Example 9

[0042] Adjust the amount of olive oil added to 40 mL, and follow the same procedure as in Example 1.

[0043] Example 10

[0044] Glyoxal was used in place of glutaraldehyde as a crosslinking agent of equal mass, and the rest of the operation was the same as in Example 1.

[0045] Example 11

[0046] Equal mass of polyethylene glycol methacrylate was used instead of glutaraldehyde as the crosslinking agent, and the rest of the operation was the same as in Example 1.

[0047] Comparative Example 1

[0048] In Example 1, PEI-AMPSLi microspheres were not added to the PEO-based solid polymer electrolyte membrane.

[0049] Comparative Example 2

[0050] PEI was used instead of PEI-AMPSLi as the reaction monomer, and the rest of the operation was the same as in Example 1.

[0051] Comparative Example 3

[0052] PEI was used instead of PEI-AMPSLi microspheres as the inorganic filler to prepare PEO-based polymer solid electrolyte membranes, and the remaining operations were the same as in Example 1.

[0053] In a vacuum glove box, the all-solid electrolyte membrane prepared above is assembled into a lithium iron phosphate / Li metal half cell in the following order: negative electrode shell (facing up), lithium sheet, separator, gasket, spring sheet and positive electrode shell (facing down).

[0054] Table 1. Cycle performance test results of lithium iron phosphate / Li batteries assembled with all-solid-state electrolyte membranes made of different materials.

[0055]

[0056] As can be seen from Table 1, the lithium iron phosphate solid-state full battery assembled with the all-solid-state polymer electrolyte prepared using the functionalized microspheres synthesized in this invention has higher capacity, better capacity retention and better coulombic efficiency compared with the comparative example.

[0057] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A functionalized microsphere with a hollow structure, characterized in that: The microspheres are hollow spherical structures composed of a polymer main chain and a crosslinking agent by using a one-step self-emulsifying ball process; and the polymer main chain is modified with sulfonic acid groups on the surface. The preparation of the functionalized microspheres with hollow structures comprises the following steps: (1) drop the monomer solution into the lithium hydroxide solution at 0 ℃ or below, stir for 1-12 h, and then freeze-dry; (2) add water to the product obtained in step (1) to form a solution, then drop into a 40wt% polyethyleneimine solution, and stir overnight under argon protection at 40 ℃; (3) dialyze the product obtained in step (2) for 3 days, remove most of the solvent by rotary evaporation, and then vacuum dry; (4) add water to the dried product of step (3) to form a solution, then add an oily solution, stir for 2 h at room temperature, then add a crosslinking agent, stir for 1 h at room temperature, then stir for 5 h at 60 ℃, and then centrifugal wash and dry to obtain the functionalized microspheres; The monomer in step (1) is selected from one or more of 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid-2-acrylamide-2-methylpropane sulfonic acid copolymer, vinylbenzenesulfonic acid, and allyl vinyl sulfonic acid; The oily solution in step (4) is selected from one or more of olive oil, solvent oil, and liquid paraffin.

2. The functionalized microspheres with hollow structure according to claim 1, characterized in that: The concentration of the monomer solution and the lithium hydroxide solution in step (1) is 30wt%, and the amount of the two is calculated according to the molar ratio of the monomer to lithium hydroxide as 1:

1.

3. The functionalized microspheres with hollow structure according to claim 1, characterized in that: The molar ratio of the product to polyethyleneimine used in step (2) is 4:1; and the molecular weight of the polyethyleneimine is 600-1,000,000.

4. The functionalized microspheres with hollow structure according to claim 1, characterized in that: The dialysis bag with a molecular weight cut-off of 3,500-6,000 is used for dialysis in step (3).

5. The functionalized microspheres with hollow structure according to claim 1, wherein: In step (4), 1-5 g of the product is added per liter of the oily solution.

6. The functionalized microspheres with hollow structure according to claim 1, wherein: The mass ratio of the crosslinking agent to the product used in step (4) is 1:1; and the crosslinking agent is selected from one or more of glutaraldehyde, glyoxal, and polyethylene glycol methacrylate.

7. Use of the functionalized microspheres with hollow structure according to claim 1 in the preparation of all-solid-state lithium metal batteries. The functionalized microspheres with hollow structures are used to prepare electrolyte separators, which are used as electrolytes for full-solid-state lithium metal batteries.

Images