Asymmetric barrier materials, preparation thereof and use in aqueous asymmetric zinc metal batteries

Abstract

The application belongs to the field of zinc metal batteries, and particularly relates to an asymmetric barrier material suitable for a zinc metal battery, which comprises a cellulose-based film and an organic coating layer combined on the surface of the film, wherein the organic coating layer comprises a PVDF-based polymer and conductive zinc salt distributed therein. The application also comprises preparation and application of the barrier material in asymmetry. The application provides the asymmetric barrier material with the novel physicochemical structure, which is based on the combination of the base film and the organic coating layer, can unexpectedly adapt to the application requirements of aqueous zinc metal batteries, can help to solve problems such as hydrogen evolution reaction of the zinc negative electrode, dendrite growth and dead zinc evolution, and can help to improve the long-term cycle stability of the zinc metal battery under large current.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of zinc metal batteries, and particularly relates to an asymmetric zinc metal battery designed by using an asymmetric barrier material. BACKGROUND

[0002] Zinc metal anode has the advantages of low redox potential (-0.76 V vs. standard hydrogen electrode SHE), high theoretical capacity (820 mAh / g, 5855 mAh / cm3) and safety. The rechargeable aqueous zinc battery using zinc metal anode is considered as the most potential energy storage battery technology of the next generation due to its inherent safety, low cost and sustainability. However, as a typical aqueous electrolyte system battery, one of the long-term challenges of zinc battery in practical application is the complex reaction of water on the negative side. On the negative side, water molecules will react with zinc metal to cause corrosion, hydrogen evolution reaction, etc., leading to dendrite growth and uneven distribution of Zn deposition. Therefore, it is necessary to develop reasonable strategies to solve this problem of aqueous zinc battery.

[0003] Electrolyte strategy is an important strategy to solve the above problems of aqueous zinc metal battery. For example, the invention patent CN118800980A designs a water-based electrolyte with silicate additives, which reduces the interface side reaction by inhibiting the activity of water; the invention patent designs a zinc battery organic electrolyte with chlorophyll derivatives as additives, which greatly promotes the transmission speed of zinc ions in organic electrolyte, improves the ionic conductivity, and improves the reversibility of zinc ions.

[0004] In addition, the Chinese patent document with publication number CN117712622A discloses an asymmetric separator and its preparation method and application. The asymmetric separator is prepared by layer-by-layer electrospinning or vacuum suction filtration method using waste animal / plant fibers as raw material combined with Leiws acid and Lewis base. The asymmetric separator has small pores on both sides and large pores in the middle. The two sides of the asymmetric separator are mainly Lewis acid or base, and the middle is mainly animal / plant fiber.

[0005] In summary, although the existing technology has some improvement schemes for electrolyte and separator, it is difficult to adapt to the application requirements of aqueous zinc battery, and it is difficult to fundamentally solve the problems of zinc anode hydrogen evolution reaction, dendrite growth and dead zinc evolution. SUMMARY

[0006] To solve the problems of zinc negative electrode hydrogen evolution reaction, dendrite growth, dead zinc evolution and the like, and to improve the service life of the zinc metal battery, the first object of the present application is to provide an asymmetric barrier material, which is designed to meet the application requirements of the asymmetric aqueous zinc battery, and can effectively solve the problems of zinc negative electrode hydrogen evolution reaction, dendrite growth, dead zinc evolution, and the like, thereby significantly improving the long-term cycle stability of the battery.

[0007] The second object of the present application is to provide the preparation of the asymmetric barrier material and the application thereof in the asymmetric aqueous zinc battery.

[0008] The third object of the present application is to provide an asymmetric aqueous zinc battery comprising the asymmetric barrier material.

[0009] In view of the problems of zinc negative electrode hydrogen evolution reaction, dendrite growth, dead zinc evolution, and the like, and the unsatisfactory large-current long cycle performance of the zinc metal battery, the present application provides the following solutions after in-depth research:

[0010] An asymmetric barrier material comprises a cellulose-based film and an organic coating layer compounded on the surface of the film, wherein the organic coating layer comprises a PVDF-based polymer and a conductive zinc salt distributed therein.

[0011] The present application provides an asymmetric barrier material with a novel physicochemical structure, which is based on the combination of a base film and an organic coating layer, and can unexpectedly meet the application requirements of the aqueous zinc metal battery, can help to solve the problems of zinc negative electrode hydrogen evolution reaction, dendrite growth, dead zinc evolution, and the like, and can help to improve the long-term cycle stability of the zinc metal battery under large current.

[0012] In the present application, the cellulose-based film can be any cellulose-based separator recognized in the industry, for example, a common cellulose or glass cellulose base film, which can have a thickness of 10-50 μm, and further can have a thickness of 20-30 μm.

[0013] In the present application, the PVDF-based polymer comprises one or more of PVDF, P(VDF-TrFE), P(VDF-HFP), P(VDF-TrFE-CTFE), and the like; further comprises P(VDF-TrFE), P(VDF-HFP), P(VDF-TrFE-CTFE); and further comprises at least one of P(VDF-TrFE) and P(VDF-TrFE-CTFE) having a relaxor ferroelectric function. Research shows that the multiphase PVDF-based polymer is preferred, which can further improve the adaptability of the zinc metal battery, help to further solve the problems of the zinc metal battery, and help to further improve the long-term cycle performance of the zinc metal battery under large current.

[0014] In the present application, the conductive zinc salt includes one or more of zinc triflate, bis-trifluoromethanesulfonyl zinc, zinc acetate.

[0015] Preferably, the weight ratio of the PVDF-based polymer and the conductive zinc salt is 1:0.05-0.8, and further can be 1:0.1-0.5.

[0016] Preferably, the thickness of the organic coating layer is 1-20 μm, and further can be 1-5 μm.

[0017] In the preferred embodiment of the present application, the asymmetric barrier material is a material after polarization treatment.

[0018] Further preferably, the polarization electric field is 60-100 KV / mm, preferably 85-100 KV / mm, and further 94-96 KV / mm. Studies have shown that under the preferred polarization process, the problems faced by zinc metal batteries can be further solved, and the long-term cycle performance of zinc metal batteries under large current can be further improved.

[0019] Further preferably, the polarization time is 5-30 min, and further can be 10-15 min.

[0020] The present application also provides a preparation method of the asymmetric barrier material, which comprises the following steps: slurrying a PVDF-based polymer and a conductive zinc salt, coating the slurry on a cellulose-based film, and drying to obtain the asymmetric barrier material; or performing polarization treatment on the prepared asymmetric barrier material.

[0021] The present application also provides an application of the asymmetric barrier material, which is arranged between a positive electrode and a negative electrode to prepare the aqueous zinc metal battery.

[0022] The present application also provides an aqueous asymmetric zinc metal battery, which comprises a positive electrode, a barrier layer, and a negative electrode, and the barrier layer is the asymmetric barrier material of the present application.

[0023] The positive electrode is soaked in an aqueous electrolyte.

[0024] The negative electrode is not soaked in the aqueous electrolyte or is soaked in an organic electrolyte.

[0025] Studies have shown that by using the asymmetric barrier material of the present application and arranging the asymmetric structure, the synergy can be further strengthened, which can fundamentally solve the problems of zinc negative electrode hydrogen evolution reaction, dendrite growth, and dead zinc evolution, and can significantly improve the long-term cycle performance of the prepared battery.

[0026] In the present application, the aqueous electrolyte is a zinc ion aqueous solution.

[0027] Preferably, the concentration of zinc ions in the zinc ion aqueous solution is 0.5-3M.

[0028] In the present application, the organic electrolyte is a mixed solution of organic zinc salt-organic solvent, wherein the organic solvent is one or more of acetonitrile, dimethylacetamide, and dimethylformamide; and the organic zinc salt is one or more of zinc trifluoromethanesulfonate, bis-trifluoromethanesulfonyl zinc, and zinc acetate.

[0029] The concentration of the organic zinc salt is 0.5-3M.

[0030] In the present application, the positive electrode can be any known positive electrode sheet in the field of aqueous zinc batteries, for example, it can include a current collector and a positive electrode material compounded on the surface thereof, wherein the positive electrode material can contain a positive electrode active material of a zinc metal battery, a conductive agent, and a binder.

[0031] The negative electrode in the present application can be a zinc metal negative electrode.

[0032] Advantages

[0033] The present application provides an asymmetric barrier material suitable for aqueous zinc batteries, which, based on the combination of ingredients and structure, helps to solve the problems of zinc negative electrode hydrogen evolution reaction, dendrite growth, and dead zinc evolution; in addition, the present application pre-polarizes the ingredients of the organic coating, which can further strengthen the performance of the material in the aqueous zinc battery.

[0034] The present application research also shows that the combination of the barrier material and the physicochemical structure of the battery can further strengthen the synergy, which helps to further fundamentally solve the problems of zinc negative electrode hydrogen evolution reaction, dendrite growth, and dead zinc evolution, and can significantly improve the long-term cycle performance of the prepared battery. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Full battery cycle performance chart of Example 1 and Comparative Example 1;

[0036] Figure 2 Surface morphology chart of the asymmetric barrier material in Example 1; DETAILED DESCRIPTION

[0037] An optional asymmetric barrier material of the present application includes the following steps:

[0038] I. Mix PVDF-based polymer and organic solvent in a certain proportion to form solution A;

[0039] II. Dissolve the organic zinc salt into solution A to form a polymer electrolyte precursor solution B;

[0040] III. Coating the precursor solution B on the surface of the cellulose separator;

[0041] IV. Drying the electrolyte precursor coated separator in a closed vacuum environment, drying at high temperature, evaporating the organic solvent to obtain the asymmetric barrier material.

[0042] The PVDF-based polymer in step I comprises one or more of PVDF, P(VDF-TrFE), P(VDF-HFP), P(VDF-TrFE-CTFE), etc.

[0043] The organic solvent in step I is one or more of N,N-dimethylformamide DMF, N,N-dimethylacetamide DMA, N-methylpyrrolidone NMP, etc., preferably N,N-dimethylformamide DMF, N,N-dimethylacetamide DMA.

[0044] The mass ratio of the PVDF-based polymer to the organic solvent is (0.1-2):1.

[0045] The organic zinc salt in step II is one or more of zinc triflate Zn(CF3SO3)2, bis-trifluoromethanesulfonylimide Zn(TFSI)2, zinc acetate Zn(CH3COO)2, preferably zinc triflate Zn(CF3SO3)2, bis-trifluoromethanesulfonylimide Zn(TFSI)2, and the concentration is 0.5-3M.

[0046] The cellulose separator in step III is one of ordinary cellulose separator or glass cellulose separator, and in the following case, the thickness can be 20±2μm, preferably GFD glass cellulose separator;

[0047] The temperature in step IV is 45-100℃, and the vacuum environment.

[0048] Example 1:

[0049] The mass ratio of the polymer polyvinylidene fluoride-trifluoroethylene P(VDF-TrFE) to the organic N,N-dimethylformamide DMF is 0.5:1, mixed to form solution A; then 1M zinc triflate Zn(CF3SO3)2 is added to form mixed solution B (the weight ratio of the polymer to zinc triflate is 1:0.5), the mixed solution B is coated on one surface of the base film (GFD glass cellulose), the coating thickness is 3μm, then placed in a vacuum environment, dried at 60℃ for 10h, an organic coating layer is formed on the surface of the base film, then polarized at 95KV / mm for 10min to obtain the asymmetric barrier material.

[0050] Test:

[0051] The V2O5: carbon black: PVDF mass ratio was 7:2:1, and the slurry was uniformly mixed to coat the titanium foil. The positive electrode sheet was cut into a diameter of 12 mm, and zinc metal foil was used as the negative electrode. The CR2025 type button cell was assembled in air, the positive electrode was assembled first, then the water-based electrolyte (1M zinc sulfate aqueous solution) was added to soak the positive electrode, and then the asymmetric barrier material was added, wherein the fiber membrane layer (base film) of the asymmetric barrier material was close to the positive electrode side, and the P(VDF-TrFE) based electrolyte (organic coating layer) faced the zinc negative electrode. The negative electrode shell was covered, and the battery was packaged by a press. This is the full battery of Example 1. The battery made of water-based electrolyte and ordinary GFD separator is the comparative battery.

[0052] Comparative Example 1

[0053] Compared with Example 1, the only difference is that when assembling the battery, the barrier layer is the base film (GFD glass cellulose before modification of Example 1) separator, and the positive electrode and the negative electrode are soaked in the water-based electrolyte, and the rest is the same as Example 1.

[0054] The above battery was subjected to charge-discharge cycle test under the same test equipment and test conditions, wherein the voltage range of the full battery test was 0.2~1.6V, and the test temperature was 25℃, as shown in Figure 1 , the capacity of the battery of Example 1 reached 260.8 mAh g -1 after 1500 cycles, the capacity remained 117.8 mAh g -1 , and the retention rate was 45.2%, while the initial capacity of the comparative battery 1 was 228.3 mAh g -1 , and the capacity remained only 10% after 365 cycles.

[0055] Example 2:

[0056] Compared with Example 1, the only difference is that the polarization conditions are changed, and the other operations, parameters and tests are the same as Example 1, specifically:

[0057] A: Polarized at 70KV / mm for 30min. Its capacity reached 248.3 mAh g -1 after 1500 cycles, the capacity retention rate was 33.8%.

[0058] B: Polarized at 90KV / mm for 10min. Its capacity reached 254.6 mAh g -1 after 1500 cycles, the capacity retention rate was 41.6%.

[0059] C: without polarization treatment;

[0060] 242.6 mAh g at a current density of 1 A / g -1 , and the capacity retention rate was 30.7% after 1500 cycles.

[0061] From Examples 1 and 2, it can be seen that the polarization treatment of the barrier layer can optimize the long cycle performance of the prepared asymmetric battery.

[0062] Example 3:

[0063] Compared with Example 1, the only difference is that the polymer is changed, and other operations, parameters and tests are the same as Example 1, and the experimental groups are respectively:

[0064] Group A: the polymer is P(VDF-TrFE-CTFE). The capacity reaches 257.9 mAh g at a current density of 1 A / g -1 , and the capacity retention rate was 44.8% after 1500 cycles.

[0065] Group B: the polymer is PVDF, and the mass ratio is unchanged. The capacity reaches 239.5 mAh g at a current density of 1 A / g -1 , and the capacity retention rate was 34.1% after 1500 cycles.

[0066] From Examples 1 and 3, it can be seen that the process described in the application, combined with the combination of the multiphase polymer, can further optimize the long cycle performance of the prepared asymmetric battery.

[0067] Example 4:

[0068] Compared with Example 1, the only difference is that the following conditions are changed, specifically: the organic solvent is replaced with N,N-dimethylacetamide DMA, the ratio of the polymer and the organic solvent is 1:1; the base film is GFA separator; the weight ratio of the polymer and the organic zinc salt is 1:0.2; the drying temperature after coating is 90°C, and the time is 10h; and other operations and parameters are the same as Example 1.

[0069] The results are: the capacity reaches 254.6 mAh g at a current density of 1 A / g -1 , and the capacity retention rate was 42.1% after 1500 cycles.

[0070] Comparative Example 2

[0071] Compared with Example 1, the only difference is that when assembling the battery, the organic coating side of the asymmetric barrier material is close to the positive electrode, and other operations and parameters are the same as Example 1.

[0072] The result is: the capacity reaches 207.3 mAh g at a current density of 1 A / g -1 , and fails after 500 cycles.

[0073] Comparative Example 3

[0074] The asymmetric barrier material is used, and the same aqueous electrolyte as the positive electrode side is additionally added to the negative electrode side. The capacity reaches 227.5 mAh g at a current density of 1 A / g -1 , and fails after 400 cycles.

[0075] Comparative Example 4

[0076] The asymmetric barrier material is used, and the organic zinc salt is not added in the organic coating, and other operations and parameters are the same as in Example 1. The capacity reaches 201.5 mAh g at a current density of 1 A / g -1 , and the capacity retention rate is 10% after 1500 cycles.

[0077] Comparative Example 5

[0078] The asymmetric barrier material is used, and PAA is used as the polymer in the polymer coating, and other operations and parameters are the same as in Example 1. The capacity reaches 197.3 mAh g at a current density of 1 A / g -1 , and the capacity retention rate is 11% after 1500 cycles.

[0079] Comparative Example 6

[0080] The asymmetric barrier material is used, and the PP separator is used as the base film, and other operations and parameters are the same as in Example 1. The capacity reaches 223.5 mAh g at a current density of 1 A / g -1 , and fails after 150 cycles.

Claims

1. An aqueous asymmetric zinc metal battery comprising a positive electrode, a barrier layer, a negative electrode, and a core of mutual compounding, characterized in that, The barrier layer is an asymmetric barrier material, which comprises a cellulose-based film and an organic coating layer compounded on the surface of the cellulose-based film, the organic coating layer comprises a PVDF-based polymer and a conductive zinc salt distributed therein, the cellulose-based film of the asymmetric barrier material is arranged close to the positive electrode side, and the organic coating layer of the asymmetric barrier material is arranged close to the negative electrode side; The positive electrode is soaked in an aqueous electrolyte; The negative electrode is not soaked in the aqueous electrolyte; The cellulose-based film is a common cellulose or glass cellulose-based film, and the thickness of the cellulose-based film is greater than 20 μm; The PVDF-based polymer comprises one or more of PVDF, P(VDF-TrFE), P(VDF-HFP) and P(VDF-TrFE-CTFE); The conductive zinc salt comprises one or more of zinc triflate, bis-trifluoromethanesulfonyl zinc and zinc acetate; The weight ratio of the PVDF-based polymer to the conductive zinc salt is 1:0.05-0.8; The thickness of the organic coating layer is 1-20 μm; The asymmetric barrier material is a material obtained by polarization treatment of the asymmetric barrier material; The polarization electric field is 60-100 KV / mm.

2. The aqueous asymmetric zinc metal battery of claim 1, wherein, The polarization electric field is 85-100 KV / mm.

3. The aqueous asymmetric zinc metal battery of claim 2, wherein, The polarization electric field is 94-96 KV / mm.

4. The aqueous asymmetric zinc metal battery of claim 1, wherein, The polarization time is 5-30 min.

5. The aqueous asymmetric zinc metal battery of claim 1, wherein, The polarization time is 10-15 min.

6. The aqueous asymmetric zinc metal battery of any one of claims 1-5, wherein, The preparation steps of the asymmetric barrier material are as follows: the PVDF-based polymer and the conductive zinc salt are slurried and coated on the cellulose-based film, and then dried; and then the prepared asymmetric barrier material is subjected to polarization treatment.

7. The aqueous asymmetric zinc metal battery of claim 1, wherein, The aqueous electrolyte is a zinc ion aqueous solution.

8. The aqueous asymmetric zinc metal battery of claim 7, wherein, The concentration of zinc ions in the zinc ion aqueous solution is 0.5-3 M.

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