A method for preparing self-healing polysilane gel electrolytes by in-situ polymerization at room temperature

Abstract

This invention belongs to the field of lithium-ion battery technology and discloses a method for preparing a self-healing polysiloxane gel electrolyte by in-situ polymerization at room temperature and its application. The gel electrolyte consists of glycidyl ether monomers containing two or more terminal ethylene oxide groups, amine monomers, an initiator, a solvent, and a lithium salt, wherein one of the two monomers contains at least a Si-O bond. This method can be used to prepare gel electrolytes in situ on the positive and negative electrode surfaces of lithium metal batteries. The method provided by this invention is simple and easy to implement, requiring only a temperature of around room temperature for polymerization, and can be used for large-scale production. Through the dynamic equilibrium property of siloxanes in the polysiloxane network, the gel electrolyte possesses a certain degree of self-healing capability. Furthermore, the gel electrolyte based on in-situ polymerization has good compatibility with commonly used cathode materials such as LiFePO4 and high-voltage NCM811, and the assembled coin cells exhibit excellent cycle performance and rate performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a method for preparing a room-temperature, green, in-situ polymerized self-healing polysilane gel electrolyte. Technical Background

[0002] Traditional liquid electrolytes exhibit poor compatibility with lithium metal anodes during cycling, easily leading to problems such as lithium dendrites puncturing the separator. Gel electrolytes, on the other hand, are network structures with good stability and cohesion, capable of encapsulating organic liquids and reducing the risk of leakage. Furthermore, the semi-solid elastomer properties of gels endow them with certain mechanical strength and processability, enabling them to suppress lithium dendrite growth at the interface and allowing for applications in flexible energy storage.

[0003] CN202310475209.2 describes a bicontinuous phase gel polymer electrolyte, its preparation method, and its application. This involves mixing ether-based small molecule plasticizers, lithium salts, amine monomers, and epoxy monomers to obtain a raw material mixture. A membrane is then introduced into this mixture for in-situ composite formation. The amine monomers and epoxy monomers, containing benzene rings or cyclohexyl rigid rings, react rapidly under lithium salt catalysis to construct a rigid cross-linked network. The resulting gel electrolyte has a rigid structure and lacks self-healing properties. 202110412045.X describes a self-healing polymer electrolyte membrane and its preparation method, and a battery. This membrane is prepared using polyamines and polyethylene glycol diglycidyl ether. It does not contain Si-O bonds, and the prepared membrane is an electrolyte membrane, which is inconsistent with gel electrolytes. Furthermore, the preparation conditions are complex, requiring an ice bath. All of the above methods involve non-in-situ polymerization to form gel electrolytes.

[0004] In-situ polymerization uses a liquid gel electrolyte to assemble the battery, directly polymerizing inside the battery through chemical cross-linking and thermally induced polymerization. This method preserves the Li + While maintaining high electrical conductivity, it also exhibits superior interfacial stability. Therefore, in-situ polymerization is a relatively preferred choice for gel electrolytes.

[0005] In conclusion, it is of great significance to develop a room-temperature, green, in-situ polymerizable method for preparing a self-healing polysilane gel electrolyte. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a room-temperature, green, in-situ polymerization method for preparing a self-healing polysilane gel electrolyte. This method simultaneously satisfies the requirements of in-situ polymerization, self-healing, no heating required, and solvent-free organic polymerization. This invention utilizes epoxy monomers or amine monomers containing Si-O bonds. The amine monomers form a cross-linked network with the epoxy monomers, and the unique dynamic balance between the Si-O bonds endows the gel electrolyte with self-healing capabilities, effectively suppressing lithium dendrite growth. The in-situ polymerization method further stabilizes the interface, thereby enabling safe and stable operation of lithium metal batteries. Furthermore, this invention offers advantages such as a simple manufacturing process, excellent electrochemical performance, compatibility with high-voltage cathodes, and solvent-free operation.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The steps include the following:

[0009] S1: Glycidyl ether monomers containing Si-O bonds and amine monomers; or glycidyl ether monomers and amine monomers containing Si-O bonds are added to the corresponding solvent in a 1:1 ratio of epoxy group to amino group, stirred, and a uniform and transparent liquid A is obtained; wherein at least one of the glycidyl ether monomers or amine monomers contains a silicon-oxygen bond;

[0010] S2: Add lithium salt and initiator to a uniform and transparent liquid A to obtain a uniform and transparent liquid B, i.e., a gel electrolyte liquid;

[0011] S3: A uniform, transparent liquid B is placed at room temperature and polymerized for a period of time to obtain a gel electrolyte. According to the present invention, preferably, the glycidyl ether monomer is characterized by containing two or more terminal ethylene oxide groups, which include, but are not limited to, the following structures:

[0012]

[0013] According to the present invention, preferably, the glycidyl ether monomer containing Si-O bonds comprises, but is not limited to, the following structures: According to the present invention, preferably, the amine monomer comprises, but is not limited to, the following structures:

[0014]

[0015] According to the present invention, preferably, the amine monomer containing Si-O bonds comprises, but is not limited to, the following structures:

[0016]

[0017] Preferably, the initiator used is LiBF4 or FEC.

[0018] Preferably, the concentration of LiBF4 or FEC initiator is 0.01-3 mol / L.

[0019] Preferably, the solvent used is one or a mixture of several of DEC, EMC, DME, EC, EMC, DMC, diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; different solvents dissolve different numbers of lithium salts, and the present invention prefers ether solvents.

[0020] Preferably, the lithium salt is one or a mixture of several of LiPF6, LiTFSI, LiBF4 and LiODFB.

[0021] Preferably, the concentration of lithium salt is 0.01-4 mol / L.

[0022] Preferably, the glycidyl ether monomers and amine monomers account for 1-50% of the total weight of the gel electrolyte (i.e., the solid content of glycidyl ether monomers and amine monomers is 1-50%). More preferably, the solid content is 20%-50%. Most preferably, the solid content is 20%.

[0023] Preferably, the polymerization time is 1-120 hours.

[0024] Preferably, the application field of the gel electrolysis for lithium-ion batteries is lithium-ion batteries.

[0025] Preferably, in the self-healing polysilane gel electrolyte, the solution system of glycidyl ether monomers and amine monomers is polymerized between the positive and negative electrodes in an in-situ polymerization manner to form a gel electrolyte.

[0026] Specific applications of gel electrolytes in batteries: Battery assembly process: In a glove box filled with argon gas, a cellulose membrane is used as the separator. The prepared gel electrolyte liquid is dropped onto the separator and then assembled into a coin cell with the positive and negative electrodes. Polymerization is carried out at room temperature, resulting in in-situ polymerization inside the battery to form a cellulose membrane-supported gel polymer electrolyte. Preferably, the negative electrode material of the lithium-ion battery is lithium metal, graphite, silicon, or silicon-carbon composite materials, etc. The positive electrode material of the lithium-ion battery is LiCoO2, LiFePO4, or ternary materials, etc.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: it adopts an in-situ polymerization method with lower and more stable interfacial resistance; the self-healing ability formed can inhibit the growth of lithium dendrites; there is no solvent evaporation, no heating is required, and the operation is simple and easy; and it has the ability to match high voltage positive electrode. Attached Figure Description

[0028] Figure 1 These are optical polymerization images of gel electrolytes with different solid contents in Example 1.

[0029] Figure 2These are aggregated state images from different time periods in Example 1.

[0030] Figure 3 Infrared spectra of gel electrolyte and DME solvent in Example 1

[0031] Figure 4 The electrochemical impedance spectra (a) and conductivity performance (b) at different temperatures are shown in Example 1.

[0032] Figure 5 This is for testing the self-healing performance of gel electrolytes.

[0033] Figure 6 LSV test in gel electrolyte.

[0034] Figure 7 For battery cycle and rate performance testing.

[0035] Figure 8 Electrochemical impedance spectroscopy (a) and ionic conductivity (b) of electrolytes with different solid contents are shown.

[0036] Figure 9 This is a schematic diagram of the in-situ polymerization of gel electrolyte between the positive and negative electrodes of a battery. Detailed Implementation

[0037] The technical solution and effects of the present invention will be further described below with reference to the embodiments. However, the specific methods, formulas and descriptions used are not intended to limit the present invention.

[0038] In the following embodiments, the stainless steel battery casing is model CR2032.

[0039] Example 1: 0.6 g of 1,3-bis(3-glycidyl etheroxypropyl)tetramethyldisiloxane and 0.1 g of anhydrous piperazine were added to 2.8 g of DME electrolyte, with the amount of polymer monomer in the entire gel electrolyte being 20%. The mixture was stirred uniformly for 1 hour. Subsequently, 0.8 g of lithium bis(trifluoromethanesulfonyl)imide and 0.5 g of lithium tetrafluoroborate were added, and the mixture was stirred uniformly for 1 hour to obtain a gel electrolyte liquid. Finally, 60 μl of the clear gel electrolyte liquid was dropped into the battery. After being left at room temperature for 3 days, the battery contained a gel polymer electrolyte supported by a cellulose membrane.

[0040] Based on the above method steps, gel electrolyte liquids containing glycidyl ether monomers and amine monomers at weights of 10%, 30%, and 40% of the total weight of the gel electrolyte were prepared, and then polymerized to observe whether the gel electrolytes could polymerize. Figure 1The image shown is an optical polymerization state image of gel electrolytes with different solid contents provided in Example 1. It can be seen that when the solid content of the polymer monomer is not less than 20%, the gel electrolyte can be cured, while it is difficult to polymerize gel electrolytes with a solid content of less than 20%. This shows the feasibility of the gel polymer electrolyte of this scheme.

[0041] Figure 8 Electrochemical impedance spectroscopy (EIS) spectra of gel electrolytes with different solid contents were obtained. Calculations showed that the conductivity of gel electrolytes with solid contents of 20%, 30%, and 40% were 0.153 mS / cm, 0.074 mS / cm, and 0.025 mS / cm, respectively. Considering that higher ionic conductivity is required for battery operation, subsequent battery tests were conducted using a gel electrolyte with a 20% solid content.

[0042] like Figure 2 The images shown are of the liquid polymerization state of the gel electrolyte at different time points provided in Example 1. It is easy to see that the liquid before solidification is a slightly greenish and transparent state with very low viscosity and fluidity. During the intermediate solidification state, the gel electrolyte turns brown and has a certain degree of viscosity. When fully solidified, the gel electrolyte is dark brown and does not flow when inverted. In summary, the prepared gel electrolyte demonstrates the feasibility of in-situ polymerization.

[0043] like Figure 3 The image shows the infrared spectra of the gel electrolyte and DME solvent. The black infrared spectra correspond to the DME solvent and are taken from an infrared spectral library; the red infrared spectra correspond to the polymerized gel electrolyte, using total reflectance infrared spectroscopy mode. The comparison reveals that the DME solvent is present in the gel electrolyte; 1095 cm⁻¹ -1 The corresponding Si-O-Si infrared absorption peak originates from 1,3-bis(3-glycidyl etheroxypropyl)tetramethyldisiloxane, which is consistent with the gel electrolyte formulation. In infrared measurements, the R-NH-R1 secondary amine infrared absorption peak corresponding to piperazine dissolved in the solvent is located at 3310-3350 cm⁻¹. -1 Observation reveals a weak infrared peak corresponding to this location in the gel electrolyte, indicating relatively complete polymerization. For example... Figure 4 As shown, the conductivity of the cellulose membrane-supported gel polymer electrolyte measured by the battery in Example 1 at different temperatures is shown. At room temperature, the conductivity of the gel electrolyte can reach 0.2 mS / cm, indicating that the gel electrolyte has high conductivity.

[0044] like Figure 5 The image shows the self-healing performance test of the gel electrolyte in Example 1. After the gel electrolyte is broken, it can recover its original state within a certain period (2-5 hours), indicating that it has good self-healing ability. Figure 6As shown, the LSV test of the gel electrolyte in Example 1 shows that the decomposition voltage of the basic electrolyte is about 4.5V, while the recomposition voltage of the gel electrolyte reaches more than 5V. This indicates that the prepared gel electrolyte has the ability to match the high voltage positive electrode.

[0045] The specific application of the gel electrolyte prepared in Example 1 in the battery is described as follows: Battery assembly process: In a glove box filled with argon gas, using the LFePO4 or NCM811 electrode prepared above as the positive electrode, a lithium sheet as the negative electrode (diameter 15.6 mm), and a cellulose membrane (TBL4825) as the separator (25 micrometers thick), 60 μL of the gel electrolyte liquid prepared above was added dropwise, and a CR2023 coin cell was assembled. After being left at room temperature for 3 days, the gel electrolyte was polymerized in situ inside the battery.

[0046] The manufacturing process of the NCM811 electrode sheet is as follows: First, a PVDF adhesive with a solid content of 6% is prepared. Then, the positive electrode active material, conductive carbon black, and PVDF (in actual practice, the corresponding mass of PVDF adhesive) are mixed in a solid ratio of 96:2:2. Finally, an appropriate amount of NMP solvent is added to adjust the viscosity of the slurry to a suitable range. The mixed slurry is evenly coated onto aluminum foil and dried at 80°C for 3 hours. It is then cut into positive electrode sheets with a diameter of 12mm, transferred to a vacuum drying oven at 120°C for 12 hours, and placed in a high-purity argon glove box for later use. Before use, it is compacted and dried again for 12 hours.

[0047] The manufacturing process of the LiFePO4 electrode is as follows: First, a PVDF adhesive with a solid content of 6% is prepared. Then, the positive electrode active material, conductive carbon black, and PVDF (in actual practice, the corresponding mass of PVDF adhesive) are mixed in a solid ratio of 8:1:1. Finally, an appropriate amount of NMP solvent is added to adjust the viscosity of the slurry to a suitable range. The mixed slurry is evenly coated onto aluminum foil and dried at 80°C for 3 hours. It is then cut into positive electrode sheets with a diameter of 12mm, transferred to a vacuum drying oven at 120°C for 12 hours, and placed in a high-purity argon glove box for later use. Before use, it is compacted and dried again for 12 hours.

[0048] like Figure 7 As shown, this is the LiFePO4 and LiNi provided in Example 1. 0.8 Co 0.1 Mn 0.1 Cycle and rate performance of O2 batteries.

[0049] According to the test, in the LiFePO4||Li battery, the initial capacity is 143mAh / g at a current density of 1C. After 200 cycles, the capacity retention rate of the battery can reach about 90%, and the discharge specific capacity reaches 120mAh / g at a current density of 5C.

[0050] In LiNi 0.8 Co 0.1 Mn 0.1 In the O2||Li battery, the capacity retention rate can reach about 75% after 280 cycles at a current density of 1C, and the discharge specific capacity reaches 105mAh / g at a current density of 2C; this indicates that the gel electrolyte has excellent electrochemical performance and high voltage resistance.

[0051] Example 2:

[0052] 0.7 g of 1,3-bis(3-glycidyl etheroxypropyl)tetramethyldisiloxane and 0.2 g of propargylamine were added to the corresponding tetraethylene glycol dimethyl ether, with the amount of polymer monomer in the entire gel electrolyte being 20%. The mixture was stirred uniformly for 1 hour. Subsequently, 0.8 g of lithium bis(trifluoromethanesulfonyl)imide and 0.5 g of lithium tetrafluoroborate were added, and the mixture was stirred uniformly for 1 hour to obtain a gel electrolyte liquid. 60 μl of the transparent and clear gel electrolyte liquid was dropped into a cellulose membrane to assemble a coin cell. After being left to stand for a period of time, the gel electrolyte was polymerized inside the cell.

[0053] The conductivity of the gel electrolyte prepared in Example 2 was 0.22 mS / cm.

[0054] The LiFePO4||Li battery assembly method is the same as in Example 1. In the LiFePO4||Li battery, at a current density of 1C, the first discharge specific capacity is 142mAh / g, and the capacity retention rate of the battery can reach about 85% after 200 cycles.

[0055] Example 3:

[0056] 0.55 g of 1,3-bis(3-glycidyl etheroxypropyl)tetramethyldisiloxane and 0.15 g of n-butylamine were added to DME, with the amount of polymer monomer in the entire gel electrolyte being 20%. The mixture was stirred uniformly for 1 hour. Subsequently, 0.75 g of lithium bis(trifluoromethanesulfonyl)imide and 0.35 g of lithium difluorooxalateborate were added, and the mixture was stirred uniformly for 1 hour to obtain a gel electrolyte liquid. Finally, 60 μl of the transparent and clear gel electrolyte liquid was dropped into a cellulose membrane and assembled into a coin cell. After being left to stand for a period of time, the gel electrolyte was polymerized inside the cell.

[0057] The conductivity of the gel electrolyte prepared in Example 3 was 0.12 mS / cm.

[0058] The LiFePO4||Li battery assembly method is the same as in Example 1. In the LiFePO4||Li battery, at a current density of 1C, the first discharge specific capacity is 141mAh / g, and the capacity retention rate of the battery can reach about 70% after 200 cycles.

[0059] Example 4:

[0060] 0.45 g of pentaerythritol glycidyl ether and 0.15 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane were added to the corresponding DME, with the amount of polymer monomer in the entire gel electrolyte being 20%. The mixture was stirred uniformly for 1 hour. Subsequently, 0.75 g of lithium bis(trifluoromethanesulfonyl)imide and 0.35 g of lithium tetrafluoroborate were added, and the mixture was stirred uniformly for 1 hour to obtain a gel electrolyte liquid. Finally, 60 μl of the transparent and clear gel electrolyte liquid was dropped into a cellulose membrane to assemble a coin cell. After being left to stand for a period of time, the gel electrolyte was polymerized inside the cell.

[0061] The conductivity of the gel electrolyte prepared in Example 4 was 0.24 mS / cm.

[0062] The LiFePO4||Li battery assembly method is the same as in Example 1. In the LiFePO4||Li battery, at a current density of 1C, the first discharge specific capacity is 138mAh / g, and the capacity retention rate of the battery can reach about 88% after 200 cycles.

[0063] Example 5:

[0064] 0.75 g of 4,4'-biphenyl bisphenol diglycidyl ether and 0.13 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane were added to 2 g of DEC, with the amount of polymer monomer in the entire gel electrolyte being 20%. The mixture was stirred uniformly for 1 hour. Subsequently, 0.75 g of lithium bis(trifluoromethanesulfonyl)imide and 0.35 g of lithium hexafluorophosphate were added, and the mixture was stirred uniformly for 1 hour to obtain a gel electrolyte liquid. 60 μl of the clear gel electrolyte liquid was dropped into a cellulose membrane to assemble a coin cell. After being left to stand for a period of time, the gel electrolyte was polymerized inside the cell.

[0065] The gel electrolyte prepared in Example 5 has a conductivity of 0.34 mS / cm. In a LiFePO4||Li battery (with the same assembly method as in Example 1), the capacity retention rate of the battery can reach about 78% after 200 cycles at a current density of 1C.

[0066] The self-healing properties of the gel electrolytes prepared in Examples 2-5 were tested using the same method as in Example 1. After being broken, the gel electrolytes all recovered to their original state within a certain period (2-5 hours), indicating that the gel electrolytes prepared in Examples 2-5 all have excellent self-healing capabilities.

[0067] Comparative Example 1:

[0068] 0.65 g of pentaerythritol glycidyl ether and 0.1 g of anhydrous piperazine were added to the corresponding DME electrolyte, with the amount of polymer monomer in the entire gel electrolyte being 20%. The mixture was stirred uniformly for 1 hour. Subsequently, 0.8 g of lithium bis(trifluoromethanesulfonyl)imide and 0.5 g of lithium tetrafluoroborate were added, and the mixture was stirred uniformly for 1 hour to obtain the gel electrolyte liquid. Finally, 60 μl of the transparent and clear gel electrolyte liquid was dropped into a cellulose membrane to assemble a coin cell. After being left at room temperature for 3 days, the gel electrolyte was polymerized inside the cell.

[0069] The gel electrolyte prepared in Comparative Example 1 has a conductivity of 0.05 mS / cm. In a LiFePO4||Li battery, at a current density of 1C, the initial discharge specific capacity is 112 mAh / g, and the capacity retention rate after 200 cycles reaches approximately 73%. Comparing Example 1 and Example 4, the polymer system lacks self-healing properties due to the absence of Si-O bonds. It can also be seen that the presence of Si-O bonds affects electrochemical performance.

[0070] Comparative Example 2:

[0071] 0.6 g of 1,3-bis(3-glycidyl etheroxypropyl)tetramethyldisiloxane and 0.1 g of anhydrous piperazine were added to the corresponding DME electrolytes, with the amount of polymer monomer in the total gel electrolyte being 20%. The mixture was stirred uniformly for 1 hour. Subsequently, 0.8 g of lithium bis(trifluoromethanesulfonyl)imide and 0.5 g of lithium tetrafluoroborate were added, and the mixture was stirred uniformly for 1 hour. Finally, 60 μl of the clear gel electrolyte liquid was dropped into a cellulose membrane to assemble a coin cell. After heating at 60 °C for polymerization, the gel electrolyte was polymerized inside the cell.

[0072] The LiFePO4||Li battery assembly method is the same as in Example 1. Compared with Example 1, the capacity retention rate of the battery in Comparative Example 2 decreased significantly after 200 cycles. This is because the heating polymerization in Comparative Example 2 leads to reduced solvent evaporation, resulting in a significant degradation in the battery's cycle performance.

[0073] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing self-healing polysilane gel electrolyte by in-situ polymerization, characterized in that: (1) Add glycidyl ether monomers and amine monomers to a solvent at a molar ratio of 1:1 for epoxy groups and amino groups, stir, and obtain a uniform and transparent liquid A; wherein at least one of the glycidyl ether monomers and amine monomers contains a silicon-oxygen bond; and the glycidyl ether monomer contains two or more terminal ethylene oxide groups. (2) Add lithium salt and initiator to uniform and transparent liquid A to obtain uniform and transparent liquid B, which is gel electrolyte liquid; (3) After polymerizing liquid B at room temperature, a self-healing polysilane gel electrolyte is obtained.

2. The method for preparing self-healing polysilane gel electrolyte by in-situ polymerization according to claim 1, characterized in that: Glycidyl ether monomers have one of the following structures: 。 3. The method for preparing self-healing polysilane gel electrolyte by in-situ polymerization according to claim 1, characterized in that: The amine monomer is one of the following: 。 4. The method for preparing self-healing polysilane gel electrolyte by in-situ polymerization according to claim 1, characterized in that: The initiator is LiBF4 or FEC; the concentration of the initiator is 0.01-3 mol / L.

5. The method for preparing self-healing polysilane gel electrolyte by in-situ polymerization according to claim 1, characterized in that: The solvent is one or a mixture of several of DEC, EMC, DME, EC, DMC, diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

6. The method for preparing self-healing polysilane gel electrolyte by in-situ polymerization according to claim 1, characterized in that: The concentration of lithium salt is 0.01-4 mol / L.

7. The method for preparing self-healing polysilane gel electrolyte by in-situ polymerization according to claim 1, characterized in that: Glycidyl ether monomers and amine monomers account for 20-50% of the total weight of the gel electrolyte.

8. The method for preparing self-healing polysilane gel electrolyte by in-situ polymerization according to claim 1, characterized in that: The polymerization time at room temperature is 1-120 h.

9. The application of the self-healing polysilane gel electrolyte prepared according to any one of claims 1-8 in lithium-ion batteries, characterized in that: The self-healing polysilane gel electrolyte is polymerized in situ between the positive and negative electrodes of a lithium-ion battery to form a gel electrolyte.

10. The application according to claim 9, characterized in that: after the prepared gel electrolyte liquid is dropped onto the separator, it is assembled with the positive electrode and the negative electrode, and then polymerized at room temperature, forming a gel electrolyte in situ inside the battery.

Images