Preparation method and application of solid electrolyte coated diaphragm

Abstract

The present invention relates to the technical field of battery separators, and discloses a preparation method and application of a solid electrolyte coated separator, comprising the following steps: (1) adding a dopant to a protonic acid solution, placing the solution in a 0-15°C ice-water bath and continuously stirring, and then sequentially adding 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; after drying, a coated modified solid electrolyte is obtained; and (2) the coated modified solid electrolyte and a binder are added to a solvent in a mass ratio of 4-6:1, mixed, and then coated on the surface of the separator. The present invention uses a conductive polymer to coat a modified solid electrolyte, and after coating the conductive polymer on the surface of the separator, a solid electrolyte coated separator with high ionic conductivity is obtained, which can enhance the energy efficiency of the battery while enhancing the safety performance of the battery by reducing the amount of liquid electrolyte used 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 mainstream lithium-ion batteries currently in use are liquid lithium-ion batteries. The electrolytes used contain organic solvents. Organic solvents may release gas during the reaction, causing battery bulging. Secondly, the flammability of organic solvents may lead to the possibility of fire or even explosion in the battery. 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, the metallic lithium in solid-state electrolyte batteries can be used as the negative electrode of the 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 batteries use all-solid-state electrolytes, the contact between the solid electrolyte and the electrode is far less thorough than that between the liquid electrolyte and the electrode. Gaps are easily formed between the interfaces of the two, which will lead to increased resistance in the solid-state battery, lower energy transmission efficiency, and poor battery cycle performance.

[0004] In order to solve the problem of high internal resistance caused by poor contact at the solid-solid interface of solid-state batteries, a solid-liquid mixing method is usually used to improve it. 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 system diaphragm is used. After a flexible polymer is added to a solid electrolyte material to form a composite material, this composite material is used to prepare a diaphragm to solve the interface problem. For example, the invention patent with announcement number CN112448100B discloses an organic-inorganic composite solid electrolyte diaphragm and its preparation and application. The organic-inorganic composite solid electrolyte diaphragm is composed of a lithium-ion polymer solid electrolyte and a lithium-ion inorganic solid electrolyte. However, the redox resistance and high conductivity of the composite system cannot be met at the same time, so a variety of substances are used in combination, which increases the process cost. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a preparation method and application of a solid electrolyte coated diaphragm, which adopts a conductive polymer to coat a modified solid electrolyte, and obtains a solid electrolyte coated diaphragm with high ionic conductivity after coating it on the surface of the diaphragm. It is used in a semi-solid battery of a solid-liquid system, which can enhance the energy efficiency of the battery while enhancing the safety performance of the battery by reducing the use of liquid electrolyte in the battery.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a solid electrolyte coated diaphragm, comprising the following steps:

[0008] (1) adding a dopant to a protonic acid solution, placing the solution in an ice-water bath at 0-15°C and continuously stirring, and then sequentially adding 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 amount of the conductive polymer added is 50-60% of the mass of the conductive polymer monomer; after drying, a coated modified solid electrolyte is obtained;

[0009] (2) The coated modified solid electrolyte and the binder are added to the solvent in a mass ratio of 4-6:1 and mixed, and then coated on the surface of the diaphragm.

[0010] Oxide solid electrolytes are usually used as diaphragm 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 diaphragm, and can also spontaneously exchange lithium ions between a small amount of electrolyte and solid electrolyte to enhance the transmission efficiency of lithium ions in solid-state batteries, so that solid-state batteries have good cycle efficiency and safety performance.

[0011] The use of conductive polymers to coat oxide solid electrolytes improves the conductivity of the oxide solid electrolytes. The strength of the diaphragm is then enhanced by coating it on the surface of the diaphragm. This improves the ion transmission efficiency of the semi-solid battery while also reducing the amount of liquid electrolyte used, thereby enhancing the battery's safety. Furthermore, the use of conductive polymer monomers and conductive polymers to coat the oxide solid electrolyte simultaneously can achieve deposition and coating during the polymerization process, but cannot guarantee complete coating continuity. The compatibility of conductive polymers on the surface of the oxide solid electrolyte is relatively poor, resulting in a poor coating effect for the conductive polymer alone. However, adding a small amount of conductive polymer as an auxiliary coating while coating the conductive polymer monomer can synergistically achieve a good coating effect, resulting in a more uniform and complete coating layer and a better bonding effect. Consequently, the resulting diaphragm has a higher ionic conductivity.

[0012] Preferably, the outer coating material in the coated 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%.

[0013] 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 a garnet-type solid electrolyte, a LISICON-type solid electrolyte, a NASICON-type solid electrolyte and a perovskite-type solid electrolyte.

[0014] Preferably, the conductive polymer has an average molecular weight of 10,000-50,000.

[0015] Preferably, the stirring time after adding the dopant to the protonic acid solution is 1-3 minutes, more preferably 2-3 minutes.

[0016] Protonic acid serves as an acidic environment, and the dopant is also an oxidant, which is used to synthesize polymers from monomers. Without it, polymerization cannot occur.

[0017] 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.

[0018] Preferably, the concentration of the proton acid in the obtained mixed solution is 0.01-2 mol / L, more preferably 0.02-0.28 mol / L; the proton acid includes one or more of an organic proton acid and an inorganic proton acid; the organic proton 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 proton acid is one or more of hydrochloric acid, perchloric acid, sulfuric acid, phosphoric acid, acetic acid and oxalic acid.

[0019] 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.

[0020] Preferably, the binder is PVDF.

[0021] Preferably, the solvent is N-methylpyrrolidone (NMP).

[0022] Preferably, the separator is a single polyolefin separator, a mixed polyolefin separator, a cellulose separator or a polyimide separator.

[0023] Preferably, the coating is single-sided coating or double-sided coating; the coating thickness is 1-3 μm.

[0024] In a second aspect, the present invention also provides an application of the solid electrolyte coated diaphragm prepared by the above preparation method in a semi-solid battery.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The oxide solid electrolyte is coated with a conductive polymer to improve the conductivity of the electrolyte;

[0027] (2) The use of a coating layer allows the coated diaphragm to better fit the electrode, making the adhesion between the diaphragm and the electrode more stable while reducing the internal resistance caused by poor contact between the electrode and the electrolyte layer. DETAILED DESCRIPTION

[0028] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0029] The method for preparing the solid electrolyte coated diaphragm of the present invention comprises the following steps:

[0030] (1) Add the dopant to the protonic acid solution, place it in an ice water bath at 0-15°C and stir for 1-3 minutes;

[0031] (2) Add conductive polymer monomers (one or more of pyrrole, aniline, thiophene, and acetylene), and continue to place in a 0-15°C ice water bath and stir for 2-10 minutes;

[0032] (3) Add oxide solid electrolyte and continue to place in a 0-15°C ice water bath and stir for 10-60 minutes;

[0033] (4) Adding a conductive polymer (one or more of polypyrrole, polyaniline, polythiophene and polyacetylene), continuously placing in an ice water bath at 0-15°C and stirring for 120-360 min to obtain a mixed solution, wherein the concentrations of proton acid and dopant in the mixed solution 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 amount of conductive polymer added 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%;

[0034] (5) The mixed solution was then washed and filtered three times with deionized water, and then dried in an oven at 30-40°C for 10-16 hours to obtain a coated modified solid electrolyte;

[0035] (6) The coated modified solid electrolyte and binder (PVDF) are added to a solvent (N-methylpyrrolidone) in a mass ratio of 4-6:1 and mixed, and then coated on one side or both sides of the membrane surface to obtain a solid electrolyte coated membrane with a coating thickness of 1-3 μm.

[0036] In a specific embodiment of the present invention, the proton acid includes one or more of an organic proton acid and an inorganic proton acid; the organic proton 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 proton acid is one or more of hydrochloric acid, perchloric acid, sulfuric acid, phosphoric acid, acetic acid and oxalic acid.

[0037] 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.

[0038] In a specific embodiment of the present invention, the average molecular weight of the conductive polymer is 2,000-50,000.

[0039] In a specific embodiment of the present invention, the oxide solid electrolyte includes one or more of a garnet-type solid electrolyte, a LISICON-type solid electrolyte, a NASICON-type solid electrolyte, and a perovskite-type solid electrolyte.

[0040] In a specific embodiment of the present invention, the outer coating material in the coated modified solid electrolyte is a conductive polymer, and the coating weight is 0.05-8% of the mass of the oxide solid electrolyte. Coating weight = (mass of coated modified solid electrolyte - mass of oxide solid electrolyte) / mass of oxide solid electrolyte × 100%.

[0041] 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.

[0042] Example 1

[0043] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0044] (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to a final concentration of 0.1 mol / L, and place in a 10°C ice-water bath and stir for 1 min;

[0045] (2) Add 0.12 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min;

[0046] (3) Add 4g of perovskite solid electrolyte Li 0.33 La0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min;

[0047] (4) Add 0.06 g of conductive polymer (polyaniline, average molecular weight of 10,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0048] (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 3.5 wt.%;

[0049] (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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0050] Example 2

[0051] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0052] (1) Prepare 200 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (manganese dioxide) to make the final concentration of dopant 0.22 mol / L, and place in a 10°C ice water bath and stir for 1 min;

[0053] (2) Add 0.34 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 2 min;

[0054] (3) Add 6g of LISICON solid electrolyte Li 0.8 Al 0.2 Ge 2.2 (PO4)3, continue stirring in an ice-water bath at 10°C for 15 min;

[0055] (4) Add 0.17 g of conductive polymer (polyaniline, average molecular weight of 10,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0056] (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 6 wt.%;

[0057] (6) Take 5g of coated modified solid electrolyte, add 3g of binder (PVDF), add 33g 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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.8 Al 0.2 Ge 2.2 The (PO4)3 type solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0058] Example 3

[0059] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0060] (1) Prepare 50 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (manganese dioxide) to a final concentration of 0.28 mol / L, and place in a 10°C ice-water bath and stir for 1 min;

[0061] (2) Add 0.08 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 2 min;

[0062] (3) Add 3g NASICON solid electrolyte Na3Zr2Si2PO 12 , continue stirring in an ice-water bath at 10°C for 15 min;

[0063] (4) Add 0.04 g of conductive polymer (polyaniline, average molecular weight of 10,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0064] (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 3.2 wt.%;

[0065] (6) Take 3g of coated modified solid electrolyte, add 1g of binder (PVDF), add 12g 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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Na3Zr2Si2PO 12 The diaphragm is coated with a solid electrolyte, and the diaphragm is coated on one side with a coating thickness of 3 μm.

[0066] Example 4

[0067] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0068] (1) Prepare 100 mL of 0.16 mol / L protonic acid solution (benzenesulfonic acid) and add dopant (ferric chloride) to a final concentration of 0.26 mol / L.

[0069] (2) Under nitrogen atmosphere, add 0.24 g of conductive polymer monomer (pyrrole) and place in a 10°C ice water bath and stir for 5 min.

[0070] (3) Add 6g of GARNET-type solid electrolyte Li7La3Zr2O 12 , continue stirring in a 10°C ice water bath for 1 min;

[0071] (4) Add 0.12 g of conductive polymer (polypyrrole, average molecular weight 20,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0072] (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 4.7 wt.%;

[0073] (6) Take 5g of coated modified solid electrolyte, add 3g of binder (PVDF), add 33g 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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li7La3Zr2O 12 The diaphragm is coated with a solid electrolyte, and the diaphragm is coated on one side with a coating thickness of 3 μm.

[0074] Example 5

[0075] The difference from Example 1 is that the conductive polymer is polythiophene.

[0076] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0077] (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to a final concentration of 0.1 mol / L, and place in a 10°C ice-water bath and stir for 1 min;

[0078] (2) Add 0.12 g of conductive polymer monomer (thiophene) and continue stirring in an ice-water bath at 10°C for 3 min;

[0079] (3) Add 4g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min;

[0080] (4) Add 0.06 g of conductive polymer (polythiophene, average molecular weight of 20,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0081] (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 3.5 wt.%;

[0082] (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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0083] Example 6

[0084] The difference from Example 1 is that double-sided coating is adopted.

[0085] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0086] (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to a final concentration of 0.1 mol / L, and place in a 10°C ice-water bath and stir for 2 min;

[0087] (2) Add 0.12 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min;

[0088] (3) Add 4g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min;

[0089] (4) Add 0.06 g of conductive polymer (polyaniline, average molecular weight of 10,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0090] (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 3.5 wt.%;

[0091] (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℃ and dry it 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 the diaphragm, and the diaphragm is coated on both sides, and the thickness of the coating layer on one side is 2 μm.

[0092] Comparative Example 1

[0093] The difference from Example 1 is that the solid electrolyte is not coated and modified.

[0094] Preparation of solid electrolyte coated separator:

[0095] Take 5g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, add 3g binder (PVDF), add 30g N-methylpyrrolidone (NMP) solution, and coat it on a polyolefin separator (PE separator, porosity 70%, thickness 20μm) on one side after stirring at room temperature. After coating, place it in an oven at 105℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0096] Comparative Example 2

[0097] The difference from Example 1 is that no conductive polymer is added.

[0098] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0099] (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to a final concentration of 0.15 mol / L, and place in a 10°C ice-water bath and stir for 1 min;

[0100] (2) Add 0.15 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min;

[0101] (3) Add 4g of perovskite solid electrolyte Li0.33 La 0.56 TiO3, and continue stirring in an ice-water bath at 10°C for 255 min to obtain a mixed solution;

[0102] (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.%;

[0103] (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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0104] Comparative Example 3

[0105] The difference from Example 1 is that no conductive polymer monomer is added.

[0106] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0107] (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;

[0108] (2) Add 4g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min;

[0109] (3) Add 0.14 g of conductive polymer (polyaniline, average molecular weight of 10,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0110] (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 3.4 wt.%;

[0111] (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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0112] Comparative Example 4

[0113] The difference from Example 1 is that no dopant is added.

[0114] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0115] (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;

[0116] (2) Add 0.12 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min;

[0117] (3) Add 4g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min;

[0118] (4) Add 0.06 g of conductive polymer (polyaniline, average molecular weight of 10,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0119] (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 3.4 wt.%;

[0120] (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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0121] Comparative Example 5

[0122] The difference from Example 1 is that the amount of conductive polymer added to the surface of the solid electrolyte is too much.

[0123] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0124] (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to a final concentration of 0.1 mol / L, and place in a 10°C ice-water bath and stir for 1 min;

[0125] (2) Add 0.12 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min;

[0126] (3) Add 4g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min;

[0127] (4) Add 0.84 g of conductive polymer (polyaniline, average molecular weight of 10,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0128] (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.%;

[0129] (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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0130] Comparative Example 6

[0131] 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.

[0132] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0133] (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to a final concentration of 0.1 mol / L, and place in a 10°C ice-water bath and stir for 1 min;

[0134] (2) Add 0.06 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min;

[0135] (3) Add 4g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min;

[0136] (4) Add 0.12 g of conductive polymer (polyaniline, average molecular weight of 10,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0137] (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 3.8 wt.%;

[0138] (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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0139] Comparative Example 7

[0140] The difference from Example 1 is that the average molecular weight of the conductive polymer is too large.

[0141] The preparation of the solid electrolyte coated diaphragm includes the following steps:

[0142] (1) Prepare 100 mL of 0.5 mol / L protonic acid solution (hydrochloric acid), add dopant (ammonium persulfate) to a final concentration of 0.1 mol / L, and place in a 10°C ice-water bath and stir for 1 min;

[0143] (2) Add 0.12 g of conductive polymer monomer (aniline) and continue stirring in an ice-water bath at 10°C for 3 min;

[0144] (3) Add 4g of perovskite solid electrolyte Li 0.33 La 0.56 TiO3, continue stirring in a 10℃ ice-water bath for 15min;

[0145] (4) Add 0.06 g of conductive polymer (polyaniline, average molecular weight 80,000) and continue stirring in an ice-water bath at 10°C for 240 min to obtain a mixed solution;

[0146] (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 3.4 wt.%;

[0147] (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℃ and dry it for 12h to remove the liquid solvent of the coating layer to obtain Li 0.33 La 0.56 The TiO3 solid electrolyte is coated on one side of the diaphragm, and the coating layer thickness is 3 μm.

[0148] Table 1 Performance data of solid electrolyte coated diaphragms prepared in Examples 1-6 and Comparative Examples 1-7

[0149]

[0150] Note: The test method for ionic conductivity is to place a solid electrolyte-coated diaphragm between the positive and negative electrodes (the electrode material is platinum electrode or graphite electrode).

[0151] As shown in Table 1, it can be seen from Examples 1-3 that the ionic conductivity formed by the four oxide solid electrolytes coated with different materials is different, among which Li7La3Zr2O 12 The ionic conductivity of the solid electrolyte is low, Li 0.33 La 0.56 TiO3 solid electrolyte and Li7La3Zr2O 12 The ionic conductivity of the solid electrolyte is high.

[0152] By comparing Example 1 with Examples 4-5, changing the type of conductive polymer had no significant effect on the overall physical property test results. In Example 4, since the pyrrole used is relatively active and prone to a series of polymerization side reactions such as oxidation, the reaction was carried out under an inert gas such as nitrogen.

[0153] By comparing Example 1 with Example 6, the double-sided coating is adopted, the overall thickness is increased, the air permeability value is increased, but the thermal shrinkage is effectively reduced and the puncture resistance is increased.

[0154] By comparing Example 1 with Comparative Example 1, the ionic conductivity of the single oxide electrolyte is significantly improved by using a conductive polymer to modify the oxide electrolyte.

[0155] By comparing Example 1 with Comparative Examples 2-4, the oxide solid electrolyte is coated with a conductive polymer monomer or a conductive polymer alone. The overall coating amount is similar, but the coating effect is poor, resulting in poor ionic conductivity. Failure to add a dopant will cause the conductive polymer monomer to be unable to polymerize, and the unpolymerized conductive polymer monomer does not have good conductivity, which in turn leads to a significant decrease in the ionic conductivity of the diaphragm.

[0156] Comparing Example 1 with Comparative Examples 5-6, the excessive addition of conductive polymer resulted in preferential coating of the conductive polymer on the surface of the oxide solid electrolyte, resulting in poor coating uniformity and bonding. In particular, in Comparative Example 5, the excessive amount of conductive polymer coating on the surface of the oxide solid electrolyte clogged the diaphragm's microporous structure, significantly reducing the membrane's air permeability and ionic conductivity. While Comparative Example 6 employed the same total mass of conductive polymer and conductive polymer monomer as in Example 1, the ratio of the added conductive polymer to the conductive polymer monomer exceeded the specified range, similarly resulting in greater conductive polymer coating on the surface of the oxide solid electrolyte. Even though the final coating amount was higher than in Example 1, the poor coating uniformity and bonding resulted in poor thermal shrinkage TD / MD and poor ionic conductivity.

[0157] By comparing Example 1 with Comparative Example 7, it can be seen that an excessively large 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 the excessive molecular weight of the conductive polymer will cause excessive steric hindrance, even if some conductive polymer monomers can be deposited and coated during the polymerization process, some conductive polymer monomers will still be unable to be coated on the surface of the oxide solid electrolyte due to the conductive polymer having an excessively long molecular chain and excessive steric hindrance. The uniformity and bonding of the coating will be greatly reduced, and the thermal shrinkage TD / MD and ionic conductivity of the resulting diaphragm will also be significantly reduced.

[0158] 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 itself when coated alone, greatly enhancing the energy efficiency of the solid-state battery.

[0159] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a solid electrolyte coated diaphragm, characterized in that: The steps include: (1) adding a dopant to a protonic acid solution, placing the solution in an ice-water bath at 0-15°C and continuously stirring, and then sequentially adding 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, the amount of the conductive polymer added 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%; after drying, a coated modified solid electrolyte is obtained; (2) The coated modified solid electrolyte and the binder are added to the solvent in a mass ratio of 4-6:1 and mixed, and then coated on the surface of the diaphragm.

2. The method for preparing a solid electrolyte coated diaphragm according to claim 1, characterized in that: The oxide solid electrolyte includes one or more of a garnet-type solid electrolyte, a LISICON-type solid electrolyte, a NASICON-type solid electrolyte and a perovskite-type solid electrolyte.

3. The method for preparing a solid electrolyte coated diaphragm 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 method for preparing a solid electrolyte coated diaphragm according to any one of claims 1 to 3, characterized in that: The stirring time after adding the conductive polymer monomer is 2-10 minutes; the stirring time after adding the oxide solid electrolyte is 10-60 minutes; and the stirring time after adding the conductive polymer is 120-360 minutes.

5. The method for preparing a solid electrolyte coated diaphragm according to claim 1, characterized in that: The protonic acid includes one or more of an organic protonic acid and an inorganic protonic acid.

6. The method for preparing a solid electrolyte coated diaphragm 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 method for preparing a solid electrolyte coated diaphragm according to claim 1, characterized in that: The outer coating material in the coated 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 method for preparing a solid electrolyte coated diaphragm 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 method for preparing a solid electrolyte coated diaphragm according to claim 1, 7 or 8, characterized in that: The coating has a thickness of 1-3 μm.

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

Images