Organic-inorganic composite solid-state electrolyte membrane, preparation method thereof and solid-state battery

Abstract

The invention relates to the technical field of solid-state batteries, and discloses a preparation method of an organic-inorganic composite solid-state electrolyte membrane, which comprises the following steps: step 1, preparing nano cellulose and an inorganic fast ion conductor into a mixed solution A, and preparing the mixed solution A into an inorganic electrolyte membrane by adopting a papermaking process; and 2, preparing a polymeric monomer, a lithium salt and an initiator into a mixed solution B, infiltrating the inorganic electrolyte membrane with the mixed solution B, and carrying out a polymerization reaction on the inorganic electrolyte membrane to prepare the organic-inorganic composite solid electrolyte membrane. The method has the advantages that: 1) uniform distribution of an inorganic phase is realized through a papermaking process, and the ionic conductivity (at room temperature: 1 * 10 <-6 >-8 * 10 <-4 > S / cm) is improved; 2) pores are filled through in-situ polymerization of an organic phase, and interfacial compatibility and mechanical strength are enhanced; and 3) the process is simple, low in cost and suitable for large-scale production. The electrolyte membrane can be applied to a solid-state battery with high energy density and high safety.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and particularly relates to an organic-inorganic composite solid electrolyte membrane, a preparation method thereof, and a solid-state battery. Background Art

[0002] With the increasing demand for high-energy density energy storage systems in electric vehicles and portable electronic devices, the liquid electrolytes used in traditional lithium-ion batteries have been unable to meet the development requirements of next-generation batteries due to their safety hazards such as flammability and easy leakage. Solid electrolytes have become a research hotspot due to their excellent thermal stability and high safety. Among them, organic-inorganic composite solid electrolytes combine the high ionic conductivity of inorganic materials and the good flexibility of organic materials, and are considered to be one of the most commercially promising technical routes. However, there are still many challenges in this field, especially how to achieve uniform dispersion of inorganic particles, optimize the organic-inorganic interface bonding, and balance the mechanical properties and electrochemical properties, etc. Innovative solutions are urgently needed.

[0003] Currently, the preparation of organic-inorganic composite electrolytes mainly uses methods such as physical blending, sol-gel method, and preformed polymer matrix filling, but these technologies all have obvious defects. Although the physical blending method has a simple process, the inorganic particles are prone to agglomeration, resulting in discontinuous ion transport paths, and the interfacial contact between the organic phase and the inorganic phase is poor, with a high interfacial impedance, seriously affecting the cycle performance of the battery. The sol-gel method can achieve uniform distribution of the inorganic phase, but the process is complex and usually requires high-temperature treatment, which not only has high energy consumption but also easily leads to an increase in the brittleness of the electrolyte membrane and a decrease in flexibility. The preformed polymer matrix filling method (such as infiltrating inorganic electrolyte into a porous PVDF membrane) can improve the interfacial contact, but the high crystallinity of the polymer matrix will limit the migration of lithium ions, and phase separation is prone to occur during long-term cycling, resulting in performance degradation. Therefore, it is of great significance to develop a preparation method for composite electrolytes that can simultaneously achieve uniform dispersion of inorganic particles, stable interfacial bonding, and excellent mechanical and electrochemical properties. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the prior art and provide a preparation method for an organic-inorganic composite solid electrolyte membrane, including:

[0005] Step 1: Prepare a mixed solution A by mixing nanocellulose and an inorganic fast ion conductor, and use a papermaking process to prepare an inorganic electrolyte membrane from the mixed solution A;

[0006] Step 2: Prepare a mixed solution B by mixing a polymerization monomer, a lithium salt, and an initiator, infiltrate the mixed solution B into the inorganic electrolyte membrane, and prepare an organic-inorganic composite solid electrolyte membrane on the inorganic electrolyte membrane through a polymerization reaction.

[0007] Further, the initiator is azobisisobutyronitrile (LiDFOB) or azobisisobutyronitrile (AIBN).

[0008] Further, the nanocellulose is one of bacterial cellulose, wood pulp cellulose, and chemically modified cellulose. The nanocellulose is preferably nanocellulose prepared by the TEMPO oxidation method, and secondarily preferably bacterial cellulose.

[0009] Further, the inorganic fast ion conductor is one of lithium aluminum titanium phosphorus oxide (LATP), lithium lanthanum zirconium oxide (LLZO), and lithium lanthanum zirconium tantalum oxide (LLZTO). The inorganic fast ion conductor is preferably lithium aluminum titanium phosphorus oxide, and secondarily preferably lithium lanthanum zirconium tantalum oxide.

[0010] Further, the polymerization monomer is one of acrylate (AAS), vinylene carbonate (VEC), vinyl carbonate (VC), vinyl ether, dimethyl carbonate (DMC), and dioxolane (DOL). The polymerization monomer is preferably dioxolane. The polymerization reaction temperature and time are preferably 40 °C and 6 h, secondarily preferably 60 °C and 6 h, or secondarily preferably 80 °C and 2 h. Vinyl carbonate (VC) polymerizes to form a LiF-rich interfacial layer, improving the stability of the electrode / electrolyte interface; acrylate monomers are crosslinked to make the polymer elastic modulus > 1 GPa, inhibiting dendrite penetration; when using dioxolane (DOL) monomer, the oxidation potential reaches 4.8 V vs. Li / Li+, supporting high-voltage positive electrodes.

[0011] Further, the lithium salt is one of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(oxalato)borate (LiBOB). The lithium salt is preferably lithium bis(trifluoromethanesulfonyl)imide.

[0012] Further, the thickness of the inorganic electrolyte membrane is 20 μm to 500 μm, and the mass ratio of the inorganic fast ion conductor to the nanocellulose is 1:1 to 19:1. The mass ratio of 1:1 - 19:1 ensures a continuous inorganic phase pathway.

[0013] Further, the nanocellulose and the inorganic fast ion conductor are dispersed in one of water, dimethylformamide, and dimethylacetamide to prepare a mixed solution A.

[0014] Further, the specific steps of the papermaking process are as follows: After the mixed solution A is uniformly dispersed by ultrasonic treatment or stirring, it is transferred to a sintered filter for suction filtration to obtain a film. The film obtained by suction filtration is calendered and dried to obtain an inorganic electrolyte membrane.

[0015] An organic-inorganic composite solid electrolyte membrane obtained according to the preparation method of the organic-inorganic composite solid electrolyte membrane.

[0016] A solid-state battery having an organic-inorganic composite solid electrolyte membrane obtained by a method for preparing an organic-inorganic composite solid electrolyte membrane. The negative electrode of the solid-state battery is preferably lithium metal, the positive electrode of the solid-state battery is preferably lithium iron phosphate, and the second preference for the positive electrode of the solid-state battery is lithium nickel cobalt manganese oxide.

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

[0018] 1. Through the papermaking process, three-dimensional uniform distribution of inorganic fast ion conductors (such as LATP / LLZO, etc.) in the nanocellulose network is achieved. Combining with the continuous organic phase electrolyte channels formed by in-situ polymerization, a "inorganic skeleton - organic penetration" bicontinuous ion transport path is constructed. The data of the examples show that the room temperature ionic conductivity breaks through 4.8×10 -4 S / cm (Example 7).

[0019] 2. In-situ polymerization of the organic phase within the inorganic porous membrane forms a molecular-level interfacial bond. The polymerization shrinkage stress causes a "mortise and tenon" mechanical interlock between the organic phase and the inorganic particles. SEM images show that 400 nm LATP particles are embedded in the polymer matrix.

[0020] 3. The three-dimensional nanocellulose network and the inorganic particles form a multi-level topological structure. The heterogeneous structure of the polymer-inorganic electrolyte multi-phase interface can inhibit the formation of lithium dendrites and improve the cycling performance of the lithium metal battery.

[0021] 4. The introduction of nanocellulose can not only simplify the preparation process of the inorganic composite separator but also improve the toughness of the composite electrolyte. Description of the Drawings

[0022] Figure 1 Scanning electron microscope picture of the nanocellulose / LATP composite membrane prepared in Example 1.

[0023] Figure 2 Linear sweep curve of the nanocellulose / LATP / DOL electrolyte membrane prepared in Example 1.

[0024] Figure 3 Charge-discharge curve of the lithium metal battery assembled with the nanocellulose / LATP / DOL electrolyte in Example 9.

[0025] Figure 4 Charge-discharge curve of the lithium metal battery assembled with the nanocellulose / LLZTO / VC electrolyte in Example 10.

[0026] Figure 5 Charge-discharge curve of the sodium metal battery assembled with the nanocellulose / LLZTO / DOL electrolyte in Example 11.

[0027] Figure 6This is a schematic flow chart of the preparation method of the organic-inorganic composite solid electrolyte membrane of the present invention. Detailed implementation manners

[0028] The present invention will be further described below through examples and comparative examples. All raw materials used in the following examples are commercially available products without special instructions, and all methods used are conventional methods in the art without special instructions.

[0029] Figure 6 This is a schematic flow chart of the preparation method of the organic-inorganic composite solid electrolyte membrane of the present invention. Examples 1-11 were prepared according to this method.

[0030] Example 1: Prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LATP according to a nanocellulose / LATP mass ratio of 1:9 and stir for more than 3 days. Take 5 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LATP (1:9) electrolyte membrane with a thickness of 80 μm. Additionally, prepare a 1 M LiTFSI DOL solution and add 0.2 M LiDFOB. Assemble a stainless steel / stainless steel battery and a stainless steel / lithium metal battery: After placing the nanocellulose / LATP (1:9) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 40 °C for reaction for 6 hours to obtain a solid-state battery. After testing, it was found that the room-temperature ionic conductivity of the electrolyte was 6×10 –5 S / cm, and the oxidation decomposition voltage was 4.5 V vs. Li / Li + .

[0031] Example 2: Prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LLZTO according to a nanocellulose / LLZTO mass ratio of 1:9 and stir for more than 3 days. Take 20 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LLZTO (1:9) electrolyte membrane with a thickness of 320 μm. Additionally, prepare a 1 M LiTFSI DOL solution and add 0.2 M LiDFOB. Assemble a stainless steel / stainless steel battery and a stainless steel / lithium metal battery: After placing the nanocellulose / LLZTO (1:9) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 60 °C for reaction for 6 hours to obtain a solid-state battery. After testing, it was found that the room-temperature ionic conductivity of the electrolyte was 6.5×10 –5 S / cm, and the oxidation decomposition voltage was 4.5 V vs. Li / Li + .

[0032] Example 3: Prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LLZTO according to a nanocellulose / LLZTO mass ratio of 3:7 and stir for more than 3 days. Take 3 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LLZTO(3:7) electrolyte membrane with a thickness of 30 μm. Additionally, prepare a DOL solution of 1 M LiTFSI and add 0.2 M LiDFOB. Assemble a stainless steel / stainless steel battery and a stainless steel / lithium metal battery: After placing the nanocellulose / LLZTO(3:7) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 40 °C for 6 hours to obtain a solid-state battery. After testing, it is found that the room-temperature ionic conductivity of the electrolyte is 2.1×10 –5 S / cm, and the oxidation decomposition voltage is 4.4 V vs. Li / Li + .

[0033] Example 4: Prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LATP according to a nanocellulose / LATP mass ratio of 5:5 and stir for more than 3 days. Take 10 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LATP(5:5) electrolyte membrane with a thickness of 150 μm. Additionally, prepare a DOL solution of 1 M LiTFSI and add 0.3 M LiDFOB. Assemble a stainless steel / stainless steel battery and a stainless steel / lithium metal battery: After placing the nanocellulose / LATP(5:5) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 40 °C for 6 hours to obtain a solid-state battery. After testing, it is found that the room-temperature ionic conductivity of the electrolyte is 1.2×10 –5 S / cm, and the oxidation decomposition voltage is 4.5 V vs. Li / Li + .

[0034] Example 5: Prepare a nanocellulose / N,N-dimethylacetamide suspension with a mass fraction of 0.2%. Add LATP according to a nanocellulose / LLZTO mass ratio of 1:9 and stir for more than 3 days. Take 5 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LATP(1:9) electrolyte membrane with a thickness of 75 μm. Additionally, prepare a DOL solution of 1 M LiTFSI and add 0.2 M LiDFOB. Assemble a stainless steel / stainless steel battery and a stainless steel / lithium metal battery: After placing the nanocellulose / LATP(1:9) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 40 °C for 6 hours to obtain a solid-state battery. After testing, it is found that the room-temperature ionic conductivity of the electrolyte is 5.5×10 –5 S / cm, and the oxidation decomposition voltage is 4.4 V vs. Li / Li + .

[0035] Example 6: Prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LLZTO according to a nanocellulose / LLZTO mass ratio of 1:9 and stir for more than 3 days. Take 5 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LLZTO (1:9) electrolyte membrane with a thickness of 80 μm. Additionally, prepare a 1 M LiDFOB solution in VC-DMC (VC is vinylene carbonate, DMC is dimethyl carbonate, with a volume ratio of 5:5) and add 0.5% AIBN. Assemble a stainless steel / stainless steel battery and a stainless steel / lithium metal battery: After placing the nanocellulose / LLZTO (1:9) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 60 °C for 6 hours and then transfer it to 80 °C for 2 hours to obtain a solid-state battery. After testing, it is found that the room temperature ionic conductivity of the electrolyte is 4.8×10 –5 S / cm, and the oxidation decomposition voltage is 4.8 V vs. Li / Li + .

[0036] Example 7: Prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LATP according to a nanocellulose / LATP mass ratio of 1:9 and stir for more than 3 days. Take 5 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LATP (1:9) electrolyte membrane with a thickness of 80 μm. Additionally, prepare a 1 M LiDFOB solution in VEC (VEC is ethylene carbonate) and add 1% AIBN. Assemble a stainless steel / stainless steel battery and a stainless steel / lithium metal battery: After placing the nanocellulose / LATP (1:9) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 60 °C for 6 hours and then transfer it to 80 °C for 2 hours to obtain a solid-state battery. After testing, it is found that the room temperature ionic conductivity of the electrolyte is 4.8×10 –4 S / cm, and the oxidation decomposition voltage is 4.6 V vs. Li / Li + .

[0037] Example 8: Prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LLZTO according to a nanocellulose / LLZTO mass ratio of 1:9 and stir for more than 3 days. Take 5 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LLZTO(1:9) electrolyte membrane with a thickness of 80 μm. Additionally, prepare a DOL solution of 1 M NaTFSI and add 0.2 M NaDFOB. Assemble a stainless steel / stainless steel battery and a stainless steel / lithium metal battery: After placing the nanocellulose / LLZTO(1:9) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 40 °C for 6 hours. After testing, it is found that the room temperature ionic conductivity of the electrolyte is 1.5×10 –5 S / cm, and the oxidation decomposition voltage is 4.1 V vs. Na / Na + .

[0038] Example 9: According to Example 1, prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LATP according to a nanocellulose / LATP mass ratio of 1:9 and stir for more than 3 days. Take 5 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LATP(1:9) electrolyte membrane with a thickness of 80 μm. Additionally, prepare a DOL solution of 1 M LiTFSI and add 0.2 M LiDFOB. Assemble a Li / LiFePO4 battery: After placing the nanocellulose / LATP(1:9) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 40 °C for 6 hours to obtain a solid-state battery.

[0039] Example 10: According to Example 6, prepare a nanocellulose / water suspension with a mass fraction of 0.2%. Add LLZTO according to a nanocellulose / LLZTO mass ratio of 1:9 and stir for more than 3 days. Take 5 mL of the suspension and place it in a sintered glass filter with a diameter of 4.5 cm for suction filtration to obtain a nanocellulose / LLZTO(1:9) electrolyte membrane with a thickness of 80 μm. Additionally, prepare a VC-DMC solution of 1 M LiDFOB and add 1% AIBN. Assemble a Li / LiFePO4 battery: After placing the nanocellulose / LLZTO(1:9) electrolyte membrane between the two electrodes, inject the solution. Subsequently, place the battery at 60 °C for 6 hours and then transfer it to 80 °C for 2 hours to obtain a solid-state battery.

[0040] Example 11: According to Example 8, a nanocellulose / water suspension with a mass fraction of 0.2% was prepared. LLZTO was added according to a nanocellulose / LLZTO mass ratio of 1:9 and stirred for more than 3 days. 5 mL of the suspension was placed in a fritted filter with a diameter of 4.5 cm and filtered by suction to obtain a nanocellulose / LLZTO (1:9) electrolyte membrane with a thickness of 80 μm. Additionally, a DOL solution of 1 M NaTFSI was prepared and 0.2 M NaDFOB was added. Assembly of the Na / Na3V2(PO4)3 battery: After placing the nanocellulose / LLZTO (1:9) electrolyte membrane between the two electrodes, the solution was injected. Subsequently, the battery was reacted at 40 °C for 6 hours to obtain a solid-state battery.

[0041] Table 1 Composition and experimental data of Examples 1-8

[0042]

[0043]

[0044] Figure 1 This is a scanning electron microscope image of the nanocellulose / LATP composite membrane prepared in Example 1. It can be clearly seen from the scanning electron microscope that the inorganic electrolyte LATP is evenly dispersed in the composite membrane, and the dendrites of LATP are about 400 nm.

[0045] Figure 2 This is the linear sweep curve of the nanocellulose / LATP / DOL electrolyte membrane prepared in Example 1. The linear sweep curve shows that the oxidation decomposition voltage of the nanocellulose / LATP / DOL electrolyte membrane prepared in Example 1 reaches 4.5 V vs. Li / Li+, indicating that this electrolyte can be used in high-voltage lithium batteries, and the uniform distribution of the inorganic phase is achieved through the papermaking process, improving the ionic conductivity (at room temperature: 1×10 –6 ~8×10 –4 S / cm)

[0046] Figure 3 This is the charge-discharge curve of the lithium metal battery assembled with the nanocellulose / LATP / DOL electrolyte in Example 9. A lithium metal battery with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode was assembled according to the description in Example 9, and it was found that the battery could be charged and discharged stably, and the capacity of the battery could reach 168 mAh / g.

[0047] Figure 4 This is the charge-discharge curve of the lithium metal battery assembled with the nanocellulose / LLZTO / VC electrolyte in Example 10. A lithium metal battery with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode was assembled according to the description in Example 10, and it was found that the battery could be charged and discharged stably, and the capacity of the battery could reach 131 mAh / g.

[0048] Figure 5 Charge and discharge curves of the sodium metal battery assembled with nanocellulose / LLZTO / DOL electrolyte in Example 11. A lithium metal battery with sodium vanadium phosphate as the positive electrode and sodium metal as the negative electrode was assembled according to the description in Example 11. It was found that the battery could be charged and discharged stably, and the capacity of the battery could reach 91 mAh / g.

[0049] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A preparation method of an organic-inorganic composite solid electrolyte membrane, characterized in that, Including: Step 1: Prepare a mixed solution A by mixing nanocellulose and an inorganic fast ion conductor, and use a papermaking process to prepare an inorganic electrolyte membrane from the mixed solution A. Step 2: Prepare a mixed solution B by mixing a polymer monomer, a lithium salt, and an initiator. Infiltrate the mixed solution B into the inorganic electrolyte membrane, and prepare an organic-inorganic composite solid electrolyte membrane on the inorganic electrolyte membrane through a polymerization reaction.

2. The method for preparing an organic-inorganic composite solid electrolyte membrane according to claim 1, wherein: The nanocellulose is one of bacterial cellulose, wood pulp cellulose, and chemically modified cellulose.

3. The method for preparing an organic-inorganic composite solid electrolyte membrane according to claim 1, wherein: The inorganic fast ion conductor is one of lithium aluminum titanium phosphorus oxide, lithium lanthanum zirconium oxide, and lithium lanthanum zirconium tantalum oxide.

4. The method for preparing an organic-inorganic composite solid electrolyte membrane according to claim 1, wherein: The polymer monomer is one or more of acrylate, ethylene carbonate, vinylene carbonate, vinyl ether, dimethyl carbonate, and dioxolane.

5. The method for preparing an organic-inorganic composite solid electrolyte membrane according to claim 1, wherein: The lithium salt is one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalato)borate.

6. The method for preparing an organic-inorganic composite solid electrolyte membrane according to claim 1, wherein: The thickness of the inorganic electrolyte membrane is 20 μm to 500 μm, and the mass ratio of the inorganic fast ion conductor to the nanocellulose is 1:1 to 19:

1.

7. The method for preparing an organic-inorganic composite solid electrolyte membrane according to claim 1, wherein: Disperse the nanocellulose and the inorganic fast ion conductor in one of water, dimethylformamide, and dimethylacetamide to prepare the mixed solution A.

8. The method for preparing an organic-inorganic composite solid electrolyte membrane according to claim 1, wherein: The specific steps of the papermaking process are as follows: After uniformly dispersing the mixed solution A by ultrasonic treatment or stirring, transfer it to a sintered filter for suction filtration to obtain a thin film, and calender the suction-filtered thin film and dry it to obtain the inorganic electrolyte membrane.

9. An organic-inorganic composite solid electrolyte membrane obtained by the method for preparing an organic-inorganic composite solid electrolyte membrane according to any one of claims 1-8.

10. A solid-state battery, characterized in that: Having an organic-inorganic composite solid electrolyte membrane obtained by the method for preparing an organic-inorganic composite solid electrolyte membrane according to any one of claims 1-8.

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