Preparation method and application of solid electrolyte coated diaphragm

Abstract

The invention relates to the technical field of battery diaphragms, and discloses a preparation method and application of a solid electrolyte coated diaphragm, and the preparation method comprises the following steps: (1) adding a dopant into a protonic acid solution, placing in an ice-water bath at 0-15 DEG C, continuously stirring, sequentially adding a conductive polymer monomer, an oxide solid electrolyte and a conductive polymer in the process, and continuously stirring, so as to obtain a solid electrolyte coated diaphragm; a mixed solution is obtained; the conductive polymer is one or more of polypyrrole, polyaniline, polythiophene and polyacetylene; and drying to obtain the coated modified solid electrolyte. And (2) adding the coated modified solid electrolyte and a binder into a solvent according to a mass ratio of (4-6): 1, mixing, and coating on the surface of the diaphragm. According to the invention, the conductive polymer is adopted to coat the modified solid electrolyte, and the surface layer of the diaphragm is coated with the modified solid electrolyte to obtain the solid electrolyte coated diaphragm with high ionic conductivity, so that the energy efficiency of the battery can be enhanced, and the safety performance of the battery can be enhanced by reducing the usage amount of the liquid electrolyte in the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separators, and in particular to a preparation method and application of a solid electrolyte-coated separator. Background Art

[0002] The currently used mainstream lithium-ion batteries are liquid lithium-ion batteries, and the electrolytes used contain organic solvents. The organic solvents may release gases during the reaction, resulting in battery swelling. Secondly, the flammability of the organic solvents may cause the battery to catch fire or even explode. Therefore, it is very necessary to develop new high-safety and high-performance batteries to gradually replace liquid batteries. Among them, the solid electrolyte in solid-state batteries has high safety and can be used to replace liquid electrolytes. In addition, metallic lithium can be used as the negative electrode of the solid electrolyte battery, which can improve the energy density of the battery. Therefore, solid-state batteries are an important development direction for future batteries.

[0003] However, since all-solid-state electrolytes are used in all-solid-state batteries, the contact between the solid electrolyte and the electrode is far less substantial than that between the liquid electrolyte and the electrode. There are easily gaps between the two interfaces, which will increase the resistance inside the solid-state battery, reduce the energy transfer efficiency, and deteriorate the battery cycle performance.

[0004] To address the problem of high internal resistance caused by poor contact at the solid-solid interface of solid-state batteries, a solid-liquid hybrid method is usually adopted for improvement. A certain amount of liquid is retained in the solid-state battery, and the fluidity of the liquid is used to solve the problem of poor contact at the solid-solid interface. At the same time, a composite separator is used. After adding a flexible polymer to the solid electrolyte material to form a composite material, the composite material is used to prepare a separator to solve the interface problem. For example, the invention patent with the publication number CN112448100B discloses an organic-inorganic composite solid electrolyte separator and its preparation and application. The organic-inorganic composite solid electrolyte separator is composed of a lithium-ion-containing polymer solid electrolyte and a lithium-ion-containing inorganic solid electrolyte. However, the redox resistance and high conductivity of the composite system cannot be satisfied simultaneously. Therefore, the use of multiple substances in combination increases the process cost. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a preparation method and application of a solid electrolyte-coated separator. The solid electrolyte is coated and modified with a conductive polymer, and after being coated on the surface layer of the separator, a solid electrolyte-coated separator with high ionic conductivity is obtained. When it is used in a semi-solid battery with a solid-liquid system, it can enhance the energy efficiency of the battery and, at the same time, enhance the safety performance of the battery by reducing the usage amount of the liquid electrolyte inside the battery.

[0006] The object of the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a solid electrolyte-coated separator, comprising the following steps: (1) Add a dopant to a protonic acid solution, place it in an ice-water bath at 0-15 °C and continuously stir. During the process, successively add a conductive polymer monomer, an oxide solid electrolyte, and a conductive polymer to obtain a mixed solution; the conductive polymer is one or more of polypyrrole, polyaniline, polythiophene, and polyacetylene, the average molecular weight of the conductive polymer is 2000-50000, the concentration of the conductive polymer monomer in the mixed solution is 0.001-1 mol / L, and the addition amount of the conductive polymer is 50-60% of the mass of the conductive polymer monomer; after drying, a coated and modified solid electrolyte is obtained; (2) Add the coated and modified solid electrolyte and a binder to a solvent in a mass ratio of 4-6:1, mix them, and coat the surface of the separator.

[0007] Oxide solid electrolytes are usually used as separator coatings, which can delay the heat generation reaction of the electrolyte and the oxidation reaction of the battery, help improve the thermodynamic stability of the separator, and can also spontaneously perform lithium-ion exchange between a small amount of electrolyte and the solid electrolyte to enhance the lithium-ion transport efficiency in the solid-state battery, enabling the solid-state battery to have good cycle efficiency and safety performance.

[0008] Coating the oxide solid electrolyte with a conductive polymer improves the conductivity of the oxide solid electrolyte. Then, by coating it on the surface of the separator, the strength performance of the separator is enhanced. While improving the ion transport efficiency of the semi-solid battery, it also reduces the amount of liquid electrolyte used and enhances the safety performance of the battery. In addition, when both a conductive polymer monomer and a conductive polymer are used to coat the oxide solid electrolyte, the conductive polymer monomer can achieve deposition coating during the polymerization process, but it cannot guarantee the complete coherence of the coating. Moreover, the compatibility of the conductive polymer on the surface of the oxide solid electrolyte is relatively poor. Therefore, the coating effect of the single conductive polymer is poor. However, adding a small amount of conductive polymer to assist the coating while the conductive polymer monomer is coating can synergistically achieve a good coating effect. The coating layer is more uniform and complete, and the bonding effect is also better. Therefore, the ion conductivity of the obtained separator is higher.

[0009] Preferably, the outer coating material in the coated and modified solid electrolyte is a conductive polymer, and the coating amount is 0.05-8% of the mass of the oxide solid electrolyte, more preferably 2-8%.

[0010] Preferably, the mass concentration of the oxide solid electrolyte in the mixed solution is 25-50%; the oxide solid electrolyte includes one or more of garnet-type solid electrolytes, LISICON-type solid electrolytes, NASICON-type solid electrolytes, and perovskite-type solid electrolytes.

[0011] Preferably, the average molecular weight of the conductive polymer is 10,000 - 50,000.

[0012] Preferably, the stirring time after adding the dopant into the protonic acid solution is 1 - 3 min, more preferably 2 - 3 min.

[0013] The protonic acid serves as an acidic environment, and the dopant is also an oxidant, which is used for synthesizing the polymer from the monomer. Polymerization cannot occur without adding it.

[0014] Preferably, the stirring time after adding the conductive polymer monomer is 2 - 10 min; the stirring time after adding the oxide solid electrolyte is 10 - 60 min, more preferably 15 - 30 min; the stirring time after adding the conductive polymer is 120 - 360 min, more preferably 250 - 300 min.

[0015] Preferably, the concentration of the protonic acid in the obtained mixed solution is 0.01 - 2 mol / L, more preferably 0.02 - 0.28 mol / L; the protonic acid includes one or more of organic protonic acids and inorganic protonic acids; the organic protonic acid is one or more of benzenesulfonic acid, p - toluenesulfonic acid, 4 - chlorobenzenesulfonic acid, 4 - hydroxybenzenesulfonic acid, p - aminobenzenesulfonic acid, and dodecylbenzenesulfonic acid; the inorganic protonic acid is one or more of hydrochloric acid, perchloric acid, sulfuric acid, phosphoric acid, acetic acid, and oxalic acid.

[0016] Preferably, the concentration of the dopant in the obtained mixed solution is 0.01 - 2 mol / L, more preferably 0.02 - 0.28 mol / L; the dopant is one or more of ammonium persulfate, potassium dichromate, hydrogen peroxide, potassium iodate, and manganese dioxide.

[0017] Preferably, the binder is PVDF.

[0018] Preferably, the solvent is N - methylpyrrolidone (NMP).

[0019] Preferably, the separator is a single - polyolefin separator, a mixed - polyolefin separator, a cellulose separator, or a polyimide separator.

[0020] Preferably, the coating is single - sided coating or double - sided coating; the thickness of the coating is 1 - 3 μm.

[0021] In a second aspect, the present invention also provides an application of the solid - electrolyte - coated separator prepared by the above - mentioned preparation method in a semi - solid battery.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) Coating the oxide solid electrolyte with a conductive polymer improves the conductivity of the electrolyte; (2) The use of a coating layer enables the coated separator to better fit the electrode. While making the adhesion between the separator and the electrode more stable, it reduces the internal resistance caused by poor contact between the electrode and the electrolyte layer. Specific Embodiments

[0023] The following specific examples are used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto.

[0024] The preparation method of the solid electrolyte-coated separator in the present invention includes the following steps: (1) Add a dopant to the protonic acid solution, place it in an ice-water bath at 0 - 15 °C and stir for 1 - 3 min; (2) Add a conductive polymer monomer (one or more of pyrrole, aniline, thiophene, and acetylene), continuously place it in an ice-water bath at 0 - 15 °C and stir for 2 - 10 min; (3) Add the oxide solid electrolyte, continuously place it in an ice-water bath at 0 - 15 °C and stir for 10 - 60 min; (4) Add a conductive polymer (one or more of polypyrrole, polyaniline, polythiophene, and polyacetylene), continuously place it in an ice-water bath at 0 - 15 °C and stir for 120 - 360 min to obtain a mixed solution. In the mixed solution, the concentrations of the protonic acid and the dopant are 0.01 - 2 mol / L respectively, the concentration of the conductive polymer monomer in the mixed solution is 0.001 - 1 mol / L, the addition amount of the conductive polymer is 50 - 60% of the mass of the conductive polymer monomer, and the mass concentration of the oxide solid electrolyte in the mixed solution is 25 - 50%; (5) Then wash and filter the mixed solution three times with deionized water, and then dry it in an oven at 30 - 40 °C for 10 - 16 h to obtain the coated and modified solid electrolyte; (6) Add the coated and modified solid electrolyte and a binder (PVDF) in a mass ratio of 4 - 6:1 to a solvent (N-methylpyrrolidone), mix them, and then coat them on one side or both sides of the separator surface to obtain the solid electrolyte-coated separator, and the coating thickness is 1 - 3 μm.

[0025] In the specific embodiments of the present invention, the protonic acid includes one or more of organic protonic acids and inorganic protonic acids; the organic protonic acid is one or more of benzenesulfonic acid, p-toluenesulfonic acid, 4-chlorobenzenesulfonic acid, 4-hydroxybenzenesulfonic acid, p-aminobenzenesulfonic acid, and dodecylbenzenesulfonic acid; the inorganic protonic acid is one or more of hydrochloric acid, perchloric acid, sulfuric acid, phosphoric acid, acetic acid, and oxalic acid.

[0026] In a specific embodiment of the present invention, the dopant is one or more of ammonium persulfate, potassium dichromate, hydrogen peroxide, potassium iodate, and manganese dioxide.

[0027] In a specific embodiment of the present invention, the average molecular weight of the conductive polymer is 2000 - 50000.

[0028] In a specific embodiment of the present invention, the oxide solid electrolyte includes one or more of garnet-type solid electrolytes, LISICON-type solid electrolytes, NASICON-type solid electrolytes, and perovskite-type solid electrolytes.

[0029] In a specific embodiment of the present invention, the outer coating material of the coated and modified solid electrolyte is a conductive polymer, and the coating amount is 0.05 - 8% of the mass of the oxide solid electrolyte. Coating amount = (mass of coated and modified solid electrolyte - mass of oxide solid electrolyte) / mass of oxide solid electrolyte × 100%.

[0030] In a specific embodiment of the present invention, the separator is a single polyolefin separator, a mixed polyolefin separator, a cellulose separator, or a polyimide separator.

[0031] Example 1 The preparation of the solid electrolyte-coated separator includes the following steps: (1) Prepare 100 mL of a 0.5 mol / L protonic acid solution (hydrochloric acid), add a dopant (ammonium persulfate), and make the final concentration of the dopant 0.1 mol / L. Place it in an ice bath at 10°C and stir for 1 min. (2) Add 0.12 g of the conductive polymer monomer (aniline), and continue to stir in the ice bath at 10°C for 3 min. (3) Add 4 g of the perovskite-type solid electrolyte Li 0.33 La 0.56 TiO3, and continue to stir in the ice bath at 10°C for 15 min. (4) Add 0.06 g of the conductive polymer (polyaniline, average molecular weight of 10000), and continue to stir in the ice bath at 10°C for 240 min to obtain a mixed solution. (5) Then wash and filter the mixed solution three times with deionized water, and then dry it in an oven at 35°C for 12 h to obtain the coated and modified solid electrolyte, with a coating amount of 3.5 wt.%. (6) Take 4 g of the coated and modified solid electrolyte, add 3 g of binder (PVDF), add 30 g of N-methylpyrrolidone (NMP) solution, stir at room temperature and then coat it on one side of a polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, place it in an oven at 105 °C and dry for 12 h to remove the liquid solvent of the coating layer, obtaining a Li 0.33 La 0.56 TiO3-based solid electrolyte coated separator. The separator is coated on one side, and the thickness of the coating layer is 3 μm.

[0032] Example 2 The preparation of the solid electrolyte coated separator includes the following steps: (1) Prepare 200 mL of a protonic acid solution (hydrochloric acid) with a concentration of 0.5 mol / L, add a dopant (manganese dioxide), and make the final concentration of the dopant 0.22 mol / L. Place it in an ice-water bath at 10 °C and stir for 1 min; (2) Add 0.34 g of conductive polymer monomer (aniline), and continue to stir in the ice-water bath at 10 °C for 2 min; (3) Add 6 g of LISICON-based solid electrolyte Li 0.8 Al 0.2 Ge 2.2 (PO4)3, and continue to stir in the ice-water bath at 10 °C for 15 min; (4) Add 0.17 g of conductive polymer (polyaniline, average molecular weight of 10,000), and continue to stir in the ice-water bath at 10 °C for 240 min to obtain a mixed solution; (5) Then wash and filter the mixed solution three times with deionized water, and then place it in an oven at 35 °C and dry for 12 h to obtain the coated and modified solid electrolyte, with a coating amount of 6 wt.%; (6) Take 5 g of the coated and modified solid electrolyte, add 3 g of binder (PVDF), add 33 g of N-methylpyrrolidone (NMP) solution, stir at room temperature and then coat it on one side of a polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, place it in an oven at 105 °C and dry for 12 h to remove the liquid solvent of the coating layer, obtaining a Li 0.8 Al 0.2 Ge 2.2 (PO4)3-based solid electrolyte coated separator. The separator is coated on one side, and the thickness of the coating layer is 3 μm.

[0033] Example 3 The preparation of the solid electrolyte coated separator includes the following steps: (1)Prepare 50 mL of a protonic acid solution (hydrochloric acid) with a concentration of 0.5 mol / L, add a dopant (manganese dioxide), and make the final concentration of the dopant 0.28 mol / L. Place it in an ice bath at 10 °C and stir for 1 min; (2)Add 0.08 g of a conductive polymer monomer (aniline), and continue to stir in an ice bath at 10 °C for 2 min; (3)Add 3 g of NASICON-type solid electrolyte Na3Zr2Si2PO 12 and continue to stir in an ice bath at 10 °C for 15 min; (4)Add 0.04 g of a conductive polymer (polyaniline, average molecular weight of 10,000), and continue to stir in an ice bath at 10 °C for 240 min to obtain a mixed solution; (5)Then wash and filter the mixed solution three times with deionized water, and then dry it in an oven at 35 °C for 12 h to obtain a coated and modified solid electrolyte with a coating amount of 3.2 wt.%; (6)Take 3 g of the coated and modified solid electrolyte, add 1 g of a binder (PVDF), add 12 g of an N-methylpyrrolidone (NMP) solution, stir at room temperature, and then coat it on one side of a polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, place it in an oven at 105 °C and dry for 12 h to remove the liquid solvent of the coating layer to obtain a Na3Zr2Si2PO 12 type solid electrolyte-coated separator. The separator is coated on one side, and the thickness of the coating layer is 3 μm.

[0034] Example 4 The preparation of the solid electrolyte-coated separator includes the following steps: (1)Prepare 100 mL of a protonic acid solution (benzenesulfonic acid) with a concentration of 0.16 mol / L, add a dopant (iron chloride), and make the final concentration of the dopant 0.26 mol / L; (2)Under a nitrogen atmosphere, add 0.24 g of a conductive polymer monomer (pyrrole), place it in an ice bath at 10 °C and stir for 5 min; (3)Add 6 g of GARNET-type solid electrolyte Li7La3Zr2O 12 and continue to stir in an ice bath at 10 °C for 1 min; (4)Add 0.12 g of a conductive polymer (polypyrrole, average molecular weight of 20,000), and continue to stir in an ice bath at 10 °C for 240 min to obtain a mixed solution; (5) Then, wash and filter the mixed solution with deionized water three times, and then dry it in an oven at 35 °C for 12 h to obtain a coated and modified solid electrolyte with a coating amount of 4.7 wt.%; (6) Take 5 g of the coated and modified solid electrolyte, add 3 g of binder (PVDF), add 33 g of N-methylpyrrolidone (NMP) solution, stir at room temperature and then coat it on one side of a polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, place it in an oven at 105 °C and dry for 12 h to remove the liquid solvent of the coating layer, and obtain a 12 solid electrolyte-coated separator of Li7La3Zr2O

[0035] Example 5 The difference from Example 1 is that the conductive polymer is polythiophene.

[0036] The preparation of the solid electrolyte-coated separator includes the following steps: (1) Prepare 100 mL of a protonic acid solution (hydrochloric acid) with a concentration of 0.5 mol / L, add a dopant (ammonium persulfate), and make the final concentration of the dopant 0.1 mol / L. Place it in an ice-water bath at 10 °C and stir for 1 min; (2) Add 0.12 g of the conductive polymer monomer (thiophene), and continue to stir in the ice-water bath at 10 °C for 3 min; (3) Add 4 g of the perovskite-type solid electrolyte Li 0.33 La 0.56 TiO3, and continue to stir in the ice-water bath at 10 °C for 15 min; (4) Add 0.06 g of the conductive polymer (polythiophene, average molecular weight of 20000), and continue to stir in the ice-water bath at 10 °C for 240 min to obtain a mixed solution; (5) Then, wash and filter the mixed solution with deionized water three times, and then dry it in an oven at 35 °C for 12 h to obtain a coated and modified solid electrolyte with a coating amount of 3.5 wt.%; (6) Take 4 g of the coated and modified solid electrolyte, add 3 g of binder (PVDF), add 30 g of N-methylpyrrolidone (NMP) solution, stir at room temperature and then coat it on one side of a polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, place it in an oven at 105 °C and dry for 12 h to remove the liquid solvent of the coating layer, and obtain a 0.33 La 0.56 solid electrolyte-coated separator of LiLaTiO3 type, with the separator coated on one side and the coating layer thickness of 3 μm.

[0037] Example 6 The difference from Example 1 is that double-sided coating is adopted.

[0038] The preparation of the solid electrolyte coated diaphragm includes the following steps: (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to make the final concentration of dopant 0.1 mol / L, place in a 10°C ice water bath and stir for 2 min; (2) Add 0.12 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min. (3) Add 4 g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min; (4) Add 0.06 g of conductive polymer (polyaniline, average molecular weight 10,000) and continue stirring in an ice water bath at 10°C for 240 min to obtain a mixed solution; (5) The mixed solution was then washed and filtered three times with deionized water, and then dried in an oven at 35°C for 12 hours to obtain a coated modified solid electrolyte with a coating amount of 3.5 wt.%; (6) Take 4g of coated modified solid electrolyte, add 3g of binder (PVDF), add 30g of N-methylpyrrolidone (NMP) solution, and coat it on a polyolefin diaphragm (PE diaphragm, porosity 70%, thickness 20μm) on one side after stirring at room temperature. After coating, place it in an oven at 105℃ to dry for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 type solid electrolyte coated diaphragm is coated on both sides, and the thickness of the coating layer on one side is 2 μm.

[0039] Comparative Example 1 The difference from Example 1 is that the solid electrolyte is not coated and modified.

[0040] Preparation of solid electrolyte coated separator: Take 5g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, add 3g of binder (PVDF), add 30g of N-methylpyrrolidone (NMP) solution, and coat it on a polyolefin diaphragm (PE diaphragm, porosity 70%, thickness 20μm) on one side after stirring at room temperature. After coating, place it in an oven at 105℃ to dry for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 type solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0041] Comparative Example 2 The difference from Example 1 is that no conductive polymer is added.

[0042] The preparation of the solid electrolyte coated diaphragm includes the following steps: (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to make the final concentration of dopant 0.15 mol / L, place in a 10°C ice water bath and stir for 1 min; (2) Add 0.15 g of conductive polymer monomer (aniline) and continue stirring in an ice water bath at 10°C for 3 min. (3) Add 4 g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in an ice-water bath at 10°C for 255 min to obtain a mixed solution; (4) The mixed solution was then washed and filtered three times with deionized water, and then dried in an oven at 35°C for 12 hours to obtain a coated modified solid electrolyte with a coating amount of 3.5 wt.%; (5) Take 4g of coated modified solid electrolyte, add 3g of binder (PVDF), add 30g of N-methylpyrrolidone (NMP) solution, and coat it on a polyolefin diaphragm (PE diaphragm, porosity 70%, thickness 20μm) on one side after stirring at room temperature. After coating, place it in an oven at 105℃ to dry for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 type solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0043] Comparative Example 3 The difference from Example 1 is that no conductive polymer monomer is added.

[0044] The preparation of the solid electrolyte coated diaphragm includes the following steps: (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid) and place in a 10°C ice water bath and stir for 1 min; (2) Add 4 g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min; (3) Add 0.14 g of conductive polymer (polyaniline, average molecular weight 10,000) and continue stirring in an ice water bath at 10°C for 240 min to obtain a mixed solution; (4) Then, wash and filter the mixed solution with deionized water three times, and then dry it in an oven at 35 °C for 12 h to obtain a coated and modified solid electrolyte with a coating amount of 3.4 wt.%. (5) Take 4 g of the coated and modified solid electrolyte, add 3 g of binder (PVDF), add 30 g of N-methylpyrrolidone (NMP) solution, stir at room temperature and then coat it on one side of a polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, place it in an oven at 105 °C for 12 h to remove the liquid solvent of the coating layer, and obtain a 0.33 Li 0.56 La

[0045] Comparative Example 4 The difference from Example 1 is that no dopant is added.

[0046] The preparation of the solid electrolyte-coated separator includes the following steps: (1) Prepare 100 mL of a protonic acid solution (hydrochloric acid) with a concentration of 0.5 mol / L, place it in an ice bath at 10 °C and stir for 1 min; (2) Add 0.12 g of conductive polymer monomer (aniline), and continue to stir in the ice bath at 10 °C for 3 min; (3) Add 4 g of perovskite-type solid electrolyte Li 0.33 La 0.56 TiO3, and continue to stir in the ice bath at 10 °C for 15 min; (4) Add 0.06 g of conductive polymer (polyaniline, average molecular weight of 10,000), and continue to stir in the ice bath at 10 °C for 240 min to obtain a mixed solution; (5) Then, wash and filter the mixed solution with deionized water three times, and then dry it in an oven at 35 °C for 12 h to obtain a coated and modified solid electrolyte with a coating amount of 3.4 wt.%. (6) Take 4 g of the coated and modified solid electrolyte, add 3 g of binder (PVDF), add 30 g of N-methylpyrrolidone (NMP) solution, stir at room temperature and then coat it on one side of a polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, place it in an oven at 105 °C for 12 h to remove the liquid solvent of the coating layer, and obtain a 0.33 Li 0.56 La

[0047] Comparative Example 5 The difference from Example 1 is that the amount of conductive polymer added to the surface of the solid electrolyte is too much.

[0048] The preparation of the solid electrolyte coated diaphragm includes the following steps: (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to make the final concentration of dopant 0.1 mol / L, place in a 10°C ice water bath and stir for 1 min; (2) Add 0.12 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min. (3) Add 4 g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min; (4) adding 0.84 g of a conductive polymer (polyaniline, average molecular weight of 10,000) and continuing to stir in an ice water bath at 10°C for 240 min to obtain a mixed solution; (5) The mixed solution was then washed and filtered three times with deionized water, and then dried in an oven at 35°C for 12 h to obtain a coated modified solid electrolyte with a coating amount of 12.1 wt.%; (6) Take 4g of coated modified solid electrolyte, add 3g of binder (PVDF), add 30g of N-methylpyrrolidone (NMP) solution, and coat it on a polyolefin diaphragm (PE diaphragm, porosity 70%, thickness 20μm) on one side after stirring at room temperature. After coating, place it in an oven at 105℃ to dry for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 type solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0049] Comparative Example 6 The difference from Example 1 is that the ratio of the added amount of the conductive polymer to the conductive polymer single substance exceeds the specified range.

[0050] The preparation of the solid electrolyte coated diaphragm includes the following steps: (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to make the final concentration of dopant 0.1 mol / L, place in a 10°C ice water bath and stir for 1 min; (2) Add 0.06 g of conductive polymer monomer (aniline) and continue stirring in an ice water bath at 10°C for 3 min. (3) Add 4 g of perovskite solid electrolyte Li 0.33La 0.56 TiO₃ was continuously stirred in an ice-water bath at 10 °C for 15 min; (4) 0.12 g of a conductive polymer (polyaniline, average molecular weight of 10,000) was added, and the mixture was continuously stirred in an ice-water bath at 10 °C for 240 min to obtain a mixed solution; (5) Then, the mixed solution was washed and filtered three times with deionized water, and then dried in an oven at 35 °C for 12 h to obtain a coated and modified solid electrolyte with a coating amount of 3.8 wt.%; (6) 4 g of the coated and modified solid electrolyte was taken, 3 g of a binder (PVDF) was added, and 30 g of an N-methylpyrrolidone (NMP) solution was added. After stirring at room temperature, it was coated on one side of a polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, it was placed in an oven at 105 °C and dried for 12 h to remove the liquid solvent of the coating layer, obtaining a 0.33 La 0.56 TiO₃-based solid electrolyte-coated separator. The separator was coated on one side, and the thickness of the coating layer was 3 μm.

[0051] Comparative Example 7 The difference from Example 1 was that the average molecular weight of the conductive polymer was too large.

[0052] The preparation of the solid electrolyte-coated separator included the following steps: (1) 100 mL of a protonic acid solution (hydrochloric acid) with a concentration of 0.5 mol / L was prepared, a dopant (ammonium persulfate) was added, and the final concentration of the dopant was 0.1 mol / L. It was stirred in an ice-water bath at 10 °C for 1 min; (2) 0.12 g of a conductive polymer monomer (aniline) was added, and the mixture was continuously stirred in an ice-water bath at 10 °C for 3 min; (3) 4 g of a perovskite-type solid electrolyte Li 0.33 La 0.56 TiO₃ was continuously stirred in an ice-water bath at 10 °C for 15 min; (4) 0.06 g of a conductive polymer (polyaniline, average molecular weight of 80,000) was added, and the mixture was continuously stirred in an ice-water bath at 10 °C for 240 min to obtain a mixed solution; (5) Then, the mixed solution was washed and filtered three times with deionized water, and then dried in an oven at 35 °C for 12 h to obtain a coated and modified solid electrolyte with a coating amount of 3.4 wt.%; (6) Take 4 g of the coated and modified solid electrolyte, add 3 g of binder (PVDF), add 30 g of N-methylpyrrolidone (NMP) solution, stir at room temperature and then coat it on one side of the polyolefin separator (PE separator, porosity of 70%, thickness of 20 μm). After coating, place it in an oven at 105 °C and dry for 12 h to remove the liquid solvent of the coating layer, obtaining a 0.33 La 0.56 TiO3-based solid electrolyte-coated separator. The separator is coated on one side, and the thickness of the coating layer is 3 μm.

[0053] Table 1 Performance data of the solid electrolyte-coated separators prepared in Examples 1-6 and Comparative Examples 1-7

[0054] Note: The test method for ionic conductivity is to place the solid electrolyte-coated separator (the electrode material is a platinum electrode or a graphite electrode) between the positive and negative electrodes.

[0055] As shown in Table 1, it can be seen from Examples 1-3 that the ionic conductivities formed by coating different four kinds of oxide solid electrolytes are different. Among them, the ionic conductivity of the Li7La3Zr2O 12 -type solid electrolyte is relatively low, and the Li 0.33 La 0.56 TiO3-type solid electrolyte and the Li7La3Zr2O 12 -type solid electrolyte have relatively high ionic conductivities.

[0056] By comparing Example 1 with Examples 4-5, the type of conductive polymer was changed, and there was no obvious effect on the overall physical property test results. In Example 4, due to the relatively active nature of pyrrole used, a series of polymerization side reactions such as oxidation reactions were likely to occur, so the reaction was carried out under inert gases such as nitrogen.

[0057] By comparing Example 1 with Example 6, double-sided coating was used, the overall thickness increased, the air permeability value increased, but the thermal shrinkage was effectively reduced and the puncture resistance was increased.

[0058] By comparing Example 1 with Comparative Example 1, using a conductive polymer-modified oxide electrolyte significantly improved the ionic conductivity of the single-oxide electrolyte.

[0059] By comparing Example 1 with Comparative Examples 2-4, when using a conductive polymer monomer or a conductive polymer alone to coat the oxide solid electrolyte, the overall coating amount is similar, but the coating effect is poor, resulting in poor ionic conductivity. And the absence of a dopant will cause the conductive polymer monomer not to polymerize, and the unpolymerized conductive polymer monomer does not have good conductivity, thus resulting in a significant decrease in the ionic conductivity of the separator.

[0060] By comparing Example 1 with Comparative Examples 5-6, since too much conductive polymer is added, the conductive polymer will preferentially coat the surface of the oxide solid electrolyte, and the coating uniformity and binding property are poor. Especially in Comparative Example 5, the coating amount on the surface of the oxide solid electrolyte is too large, and the excessive added conductive polymer will also block the microporous structure of the separator, resulting in a significant decrease in the gas permeability and ionic conductivity of the separator. Although Comparative Example 6 uses the same total mass of conductive polymer and conductive polymer monomer as in Example 1, since the ratio of the addition amount of the conductive polymer to the conductive polymer monomer exceeds the defined range, the conductive polymer will also coat more on the surface of the oxide solid electrolyte. Even though the final coating amount is higher than that in Example 1, due to the poor coating uniformity and binding property at this time, the thermal shrinkage TD / MD and ionic conductivity are poor.

[0061] By comparing Example 1 with Comparative Example 7, too large an average molecular weight of the conductive polymer will also hinder the coating effect of the conductive polymer monomer on the surface of the oxide solid electrolyte. Since too large a molecular weight of the conductive polymer will cause too large steric hindrance, even if some conductive polymer monomers can be deposited and coated during the polymerization process, there will still be some conductive polymer monomers that cannot be coated on the surface of the oxide solid electrolyte due to the conductive polymer with too long molecular chains and too large steric hindrance. The coating uniformity and binding property will be greatly reduced, and the thermal shrinkage TD / MD and ionic conductivity of the obtained separator will also be significantly reduced.

[0062] In summary, the present invention uses a conductive polymer to coat and modify the oxide solid electrolyte, which can improve the conductivity of the electrolyte powder coated alone and greatly enhance the energy efficiency of the solid-state battery.

[0063] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A preparation method of a solid electrolyte-coated separator, characterized in that, It includes the following steps: (1) Add a dopant to a protonic acid solution, place it in an ice-water bath at 0 - 15 °C and continuously stir. During the process, successively add a conductive polymer monomer, an oxide solid electrolyte, and a conductive polymer to obtain a mixed solution; the conductive polymer is one or more of polypyrrole, polyaniline, polythiophene, and polyacetylene, the average molecular weight of the conductive polymer is 2000 - 50000, the concentration of the conductive polymer monomer in the mixed solution is 0.001 - 1 mol / L, and the addition amount of the conductive polymer is 50 - 60% of the mass of the conductive polymer monomer; after drying, a coated and modified solid electrolyte is obtained; (2) Add the coated and modified solid electrolyte and a binder to a solvent in a mass ratio of 4 - 6:1, mix them, and then coat the surface of the separator.

2. The preparation method of the solid electrolyte-coated separator according to claim 1, characterized in that The mass concentration of the oxide solid electrolyte in the mixed solution is 25 - 50%; the oxide solid electrolyte includes one or more of garnet-type solid electrolytes, LISICON-type solid electrolytes, NASICON-type solid electrolytes, and perovskite-type solid electrolytes.

3. The preparation method of the solid electrolyte-coated separator according to claim 1, characterized in that, The concentration of the protonic acid in the mixed solution is 0.01 - 2 mol / L; the concentration of the dopant in the mixed solution is 0.01 - 2 mol / L.

4. The preparation method of the solid electrolyte-coated separator according to any one of claims 1-3, characterized in that, The stirring time after adding the conductive polymer monomer is 2 - 10 min; the stirring time after adding the oxide solid electrolyte is 10 - 60 min; the stirring time after adding the conductive polymer is 120 - 360 min.

5. The preparation method of the solid electrolyte-coated separator according to claim 1, wherein The protonic acid includes one or more of organic protonic acids and inorganic protonic acids.

6. The preparation method of the solid electrolyte-coated separator according to claim 1 or 5, characterized in that, The dopant is one or more of ammonium persulfate, potassium dichromate, hydrogen peroxide, potassium iodate, and manganese dioxide.

7. The preparation method of the solid electrolyte-coated separator according to claim 1, characterized in that, The outer coating material in the coated and modified solid electrolyte is a conductive polymer, and the coating amount is 0.05 - 8% of the mass of the oxide solid electrolyte.

8. The preparation method of the solid electrolyte-coated separator according to claim 1, characterized in that, The separator is a single polyolefin separator, a mixed polyolefin separator, a cellulose separator, or a polyimide separator.

9. The preparation method of the solid electrolyte-coated separator according to claim 1 or 7 or 8, characterized in that, The thickness of the coating is 1 - 3 μm.

10. Application of a solid electrolyte-coated separator prepared by the preparation method according to any one of claims 1 - 9 in a semi-solid battery.

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