Preparation method of composite solid-state electrolyte and application thereof in all-solid-state lithium battery

Abstract

The application relates to a preparation method of a composite solid-state electrolyte. The composite solid-state electrolyte comprises Ta-doped LiNbO3, a polymer matrix (PVDF) and a lithium salt. The preparation method comprises the following steps: preparing LiNbO3 by a solid-phase sintering method x Ta (1‑x) O3 as an inorganic component, polyvinylidene fluoride (PVDF) and a lithium salt are mechanically mixed, ultrasonically dispersed and cast into a composite solid-state electrolyte with high ionic conductivity through a casting forming process. Trace doping of Ta reduces the magnetic domain size of LiNbO3, enhances the dielectric property of LiNbO3 and significantly improves the ionic conductivity of the composite solid-state electrolyte. The preparation method is simple in process and suitable for large-scale preparation, and the prepared composite solid-state electrolyte is suitable for a new generation of high-safety all-solid-state lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state lithium battery technology, and in particular to a method for preparing a composite solid-state electrolyte. Background Technology

[0002] With the rapid development of new energy and energy storage technologies, the requirements for energy density and safety of energy storage devices are constantly increasing. Although traditional liquid electrolytes have achieved large-scale application, their safety issues such as flammability, organic solvent leakage, and thermal runaway limit the further development of high-energy-density batteries. Solid-state electrolytes can effectively solve these problems. Polymer solid-state electrolytes have excellent flexibility and good film-forming properties, which are beneficial for reducing interfacial impedance, but their low ionic conductivity limits their application. Therefore, introducing inorganic components can improve ionic conductivity while retaining flexibility.

[0003] Lithium niobate (LiNbO3) possesses high ionic conductivity and a high dielectric constant, which can promote lithium salt dissociation through interfacial polarization, enhancing lithium-ion conductivity and improving the performance of composite solid electrolytes. Trace doping with Ta reduces the magnetic domain size of LiNbO3, further enhancing its dielectric properties and significantly improving the ionic conductivity of solid electrolytes. Therefore, a polyvinylidene fluoride (PVDF)-based compound with LiNbO3 was developed. 1-x Ta x The composite solid electrolyte made of O3 high dielectric material, and the proposed simple and efficient preparation process, are of great significance for realizing high-performance all-solid-state lithium batteries. Summary of the Invention

[0004] Based on this, and in response to the above problems, the present invention provides a composite solid electrolyte and its preparation method.

[0005] A method for preparing a composite solid electrolyte, comprising Ta-doped LiNO3 (LiNb) 1-x Ta x The composite solid electrolyte comprises O3, a polymer matrix (PVDF), and a lithium salt, and the preparation method includes the following steps:

[0006] S1, Preparation of LiNb 1-x Ta x O3:

[0007] S1-1. Calculate and weigh the lithium source, niobium source, and tantalum source according to their corresponding stoichiometric ratios.

[0008] S1-2. Add ethanol and grind thoroughly until the ethanol is completely dried.

[0009] S1-3. Place the ground raw material into an alumina crucible and dry it in an oven at 70℃-100℃ for 10-20 min.

[0010] S1-4. Place the dried raw material into a muffle furnace and calcine it at 1000-1200℃ for 8 h to obtain LiNb. 1- x Ta x O3 powder;

[0011] S2, LiNb 1-x Ta x O3 powder, polyvinylidene fluoride, and lithium salt were mixed with an organic solvent to obtain a composite electrolyte mixture.

[0012] S3. Coat the mixture prepared in step S2 into a film;

[0013] S4. Drying and curing;

[0014] S5. Demolding and cutting.

[0015] In some preferred embodiments of the present invention, in step S1-1, the lithium source is lithium carbonate, the niobium source is niobium pentoxide, and the tantalum source is tantalum pentoxide.

[0016] In some preferred embodiments of the present invention, the doping amount of the tantalum source in step S1-1 is 1 wt.%-5 wt.%.

[0017] In some preferred embodiments of the present invention, the lithium salt in step S2 includes one of LiClO4, LiTFSI, and LiFSI.

[0018] In some preferred embodiments of the present invention, the organic solvent in step S2 is N,N-dimethylformamide.

[0019] In some preferred embodiments of the present invention, the mixing process in step S2 includes at least one of mechanical mixing and ultrasonic dispersion.

[0020] In some preferred embodiments of the present invention, in step S3, the mixture obtained in S2 is uniformly coated onto the glass substrate by a doctor blade coating method, and the thickness is controlled between 150 and 200 μm.

[0021] In some preferred embodiments of the present invention, in step S4, the mixture after coating in step 3 is placed in a vacuum drying oven at 60°C-80°C for more than 24 hours to remove organic solvents and form a dense composite solid electrolyte.

[0022] In some preferred embodiments of the present invention, step S5 involves peeling the dried composite solid electrolyte membrane from the glass substrate using antistatic tweezers and cutting it into round pieces with a diameter of 16 mm using a punching machine.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] This invention proposes for the first time a Ta-doped LiNbO3-based LiNb 1-x Ta x O3, as a composite solid electrolyte with inorganic components, significantly improves its ionic conductivity (>10). -4 S / cm);

[0025] Dielectric LiNbO3 can modulate the internal electric field in composite solid electrolytes, fundamentally promoting lithium-ion transport. Ta-doped LiNbO3 in LiNbO3... 1-x Ta x O3 enhances its original dielectric properties, making the composite solid electrolyte more conductive with stronger ions.

[0026] This invention retains the flexible matrix of polymer electrolytes while improving the deformation resistance of composite solid electrolytes by adding inorganic components, which is beneficial for the long cycle life of high energy density batteries.

[0027] The preparation process of this invention is simple to operate and the preparation conditions are mild, which facilitates large-scale industrial production. Attached Figure Description

[0028] Figure 1 This is a SEM image of the composite solid electrolyte membrane in this invention at 7000x magnification.

[0029] Figure 2 LiNb in this invention 1-x Ta x XRD pattern of O3;

[0030] Figure 3 The figure shows the test results of the all-solid-state lithium battery assembled with composite solid electrolyte in this invention. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing a composite solid electrolyte, comprising Ta-doped LiNO3 (LiNb) 1-x Ta x The composite solid electrolyte comprises O3, a polymer matrix (PVDF), and a lithium salt, and the preparation method includes the following steps:

[0034] S1, Preparation of LiNb 1-x Ta x O3:

[0035] S1-1. Weigh 0.1 mol lithium carbonate, 0.1 mol niobium pentoxide and 0.002 mol tantalum pentoxide, and put the weighed raw materials into a mortar;

[0036] S1-2. Add ethanol to the mortar and grind thoroughly until the ethanol is completely evaporated.

[0037] S1-3. Place the ground raw material into an alumina crucible and dry it in a 70℃ oven for 10 min.

[0038] S1-4. The dried raw material is placed in a muffle furnace and calcined at 1050℃ for 8 h to obtain LiNb. 0.98 Ta 0.02 O3 powder;

[0039] S2, Add 0.15 g LiNb 0.98 Ta 0.02 O3, 0.5 g polyvinylidene fluoride, and 0.2 g LiTFSI were added to 5 mL of N,N-dimethylformamide and mixed on a magnetic stirrer for 4 h to obtain a composite electrolyte mixture.

[0040] S3. The composite electrolyte mixture is uniformly coated onto the glass substrate using a doctor blade coating method, with the thickness controlled between 150 and 200 μm.

[0041] S4. After the mixture after coating in step 3 is placed in a vacuum drying oven at 60°C for 24 hours, a dense composite solid electrolyte is formed.

[0042] S5. Use antistatic tweezers to peel the dried and shaped composite solid electrolyte from the glass substrate, and use a punching machine to cut it into round sheets with a diameter of 16mm.

[0043] Example 2

[0044] A method for preparing a composite solid electrolyte, comprising Ta-doped LiNO3 (LiNb) 1-x Ta x The composite solid electrolyte comprises O3, a polymer matrix (PVDF), and a lithium salt, and the preparation method includes the following steps:

[0045] S1, Preparation of LiNb 1-x Ta x O3:

[0046] S1-1. Weigh 0.1 mol lithium carbonate, 0.1 mol niobium pentoxide and 0.003 mol tantalum pentoxide, and put the weighed raw materials into a mortar;

[0047] S1-2. Add ethanol to the mortar and grind thoroughly until the ethanol is completely evaporated.

[0048] S1-3. Place the ground raw material into an alumina crucible and dry it in an 80℃ oven for 15 min.

[0049] S1-4. The dried raw material is placed in a muffle furnace and calcined at 1050℃ for 8 h to obtain LiNb. 0.97 Ta 0.03 O3 powder;

[0050] S2, Add 0.15 g LiNb 0.97 Ta 0.03 O3, 0.5 g of polyvinylidene fluoride, and 0.2 g of LiTFSI were added to 5 mL of N,N-dimethylformamide and placed on an ultrasonic disperser for 2 h to obtain a composite electrolyte mixture.

[0051] S3. The composite electrolyte mixture is uniformly coated onto the glass substrate using a doctor blade coating method, with the thickness controlled between 150 and 200 μm.

[0052] S4. After placing the coated mixture from step 3 in an 80°C vacuum drying oven for 27 h, a dense composite solid electrolyte is formed.

[0053] S5. Use antistatic tweezers to peel the dried and shaped composite solid electrolyte from the glass substrate, and use a punching machine to cut it into round sheets with a diameter of 16mm.

[0054] Example 3

[0055] A method for preparing a composite solid electrolyte, comprising Ta-doped LiNO3 (LiNb) 1-x Ta x The composite solid electrolyte comprises O3, a polymer matrix (PVDF), and a lithium salt, and the preparation method includes the following steps:

[0056] S1, Preparation of LiNb 1-x Ta x O3:

[0057] S1-1. Weigh 0.1 mol lithium carbonate, 0.1 mol niobium pentoxide and 0.005 mol tantalum pentoxide, and put the weighed raw materials into a mortar;

[0058] S1-2. Add ethanol to the mortar and grind thoroughly until the ethanol is completely evaporated.

[0059] S1-3. Place the ground raw material into an alumina crucible and dry it in a 70℃ oven for 15 min.

[0060] S1-4. The dried raw material is placed in a muffle furnace and calcined at 1060℃ for 8 h to obtain LiNb. 0.95 Ta 0.05 O3 powder;

[0061] S2, 0.2 g LiNb 0.95 Ta 0.05 O3, 0.5 g polyvinylidene fluoride, and 0.2 g LiClO4 were added to 5.5 mL of N,N-dimethylformamide and mixed on a magnetic stirrer for more than 4 h to obtain a composite electrolyte mixture.

[0062] S3. The composite electrolyte mixture is uniformly coated onto the glass substrate using a doctor blade coating method, with the thickness controlled between 150 and 200 μm.

[0063] S4. After placing the coated mixture from step 3 in a vacuum drying oven at 60°C for 27 h, a dense composite solid electrolyte is formed.

[0064] S5. Use antistatic tweezers to peel the dried and shaped composite solid electrolyte from the glass substrate, and use a punching machine to cut it into round sheets with a diameter of 16mm.

[0065] Comparative Example 1

[0066] A method for preparing a composite solid electrolyte includes lithium niobate, a polymer matrix (PVDF), and a lithium salt. The method for preparing the composite solid electrolyte includes the following steps:

[0067] S1. Preparation of LiNbO3:

[0068] S1-1. Weigh 0.1 mol of lithium carbonate and 0.1 mol of niobium pentoxide, and put the weighed raw materials into a mortar;

[0069] S1-2. Add ethanol to the mortar and grind thoroughly until the ethanol is completely evaporated.

[0070] S1-3. Place the ground raw material into an alumina crucible and dry it in a 70℃ oven for 10 min.

[0071] S1-4. Place the dried raw material into a muffle furnace and calcine it at 1170℃ for 8 h to obtain LiNbO3 powder.

[0072] S2. Add 0.15 g LiNbO3, 0.5 g polyvinylidene fluoride and 0.2 g LiTFSI to 5 mL N,N-dimethylformamide, and mix on a magnetic stirrer for 4 h to obtain a composite electrolyte mixture.

[0073] S3. The composite electrolyte mixture is uniformly coated onto the glass substrate using a doctor blade coating method, with the thickness controlled between 150 and 200 μm.

[0074] S4. After placing the coated mixture from step 3 in a vacuum drying oven at 60°C for 26 hours, a dense composite solid electrolyte is formed.

[0075] S5. Use antistatic tweezers to peel the dried and shaped composite solid electrolyte from the glass substrate, and use a punching machine to cut it into round sheets with a diameter of 16mm.

[0076] Table 1

[0077] Example 1 2.300 Example 2 3.020 Example 3 1.715 Comparative Example 1 0.987

[0078] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a composite solid electrolyte, characterized in that, The preparation method includes the following steps: S1, Preparation of LiNb 1-x Ta x O3: S1-1. Calculate and weigh the lithium source, niobium source, and tantalum source according to their corresponding stoichiometric ratios. S1-2. Add ethanol and grind thoroughly until the ethanol is completely dried. S1-3. Place the ground raw material into an alumina crucible and dry it in an oven at 70℃-100℃ for 10-20 min. S1-4. Place the dried raw material into a muffle furnace and calcine it at 1000-1200℃ for 8 h to obtain LiNb. 1-x Ta x O3 powder; S2, LiNb 1-x Ta x O3 powder, polyvinylidene fluoride, and lithium salt were mixed with an organic solvent to obtain a composite electrolyte mixture. S3. Coat the mixture prepared in step S2 into a film; S4. Drying and curing; S5. Demolding and cutting.

2. The preparation method according to claim 1, characterized in that, In step S1-1, the lithium source is lithium carbonate, the niobium source is niobium pentoxide, and the tantalum source is tantalum pentoxide.

3. The preparation method according to claim 1, characterized in that, The doping amount of the tantalum source in step S1-1 is 1 wt.%-5 wt.%.

4. The preparation method according to claim 1, characterized in that, The lithium salt in step S2 includes at least one of LiClO4, LiTFSI, and LiFSI.

5. The preparation method according to claim 1, characterized in that, The organic solvent in step S2 is N,N-dimethylformamide.

6. The preparation method according to claim 1, characterized in that, The mixing process in step S2 includes at least one of mechanical mixing and ultrasonic dispersion.

7. The preparation method according to claim 1, characterized in that, In step S3, the mixture is uniformly coated onto the glass substrate using a doctor blade coating method, with the thickness controlled between 150 and 200 μm.

8. The preparation method according to claim 1, characterized in that, In step S4, the coated mixture is placed in a vacuum drying oven at 60℃-80℃ for more than 24 hours to remove organic solvents and form a dense composite solid electrolyte.

9. The preparation method according to claim 1, characterized in that, In step S5, the dried composite solid electrolyte membrane is peeled off from the glass substrate using antistatic tweezers and cut into round pieces with a diameter of 16mm using a punching machine.

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