A solid-state sodium-ion electrolyte membrane and a preparation method thereof

Abstract

The application discloses a kind of solid sodium ion electrolyte membrane and preparation method thereof, with porous organic film as support matrix, inorganic solid electrolyte is used to prepare electrolyte solution and is coated on both sides of porous organic film, and is obtained by drying preparation.The electrolyte membrane provided in the application further reduces the film thickness while maintaining excellent mechanical properties, has good thermal stability, good mechanical properties.Both the mechanical properties and ionic conductivity of the organic solid electrolyte membrane can be improved, and the problems of poor processability and flexibility of the inorganic solid electrolyte membrane are also improved.The sodium ion battery internal resistance, capacity performance and cycle performance can be tested by extreme needle test without affecting sodium ion battery internal resistance, capacity performance and cycle performance.The preparation method of the solid electrolyte membrane is simple, the production efficiency is high, and batch production is easy to realize.

Description

Technical Field

[0001] This invention relates to the field of electrochemical membrane materials, and more specifically to a solid sodium ion electrolyte membrane and its preparation method. Background Technology

[0002] Both lithium-ion and sodium-ion batteries currently primarily use organic solvent electrolytes such as carbonates. Organic solvents are flammable, prone to leakage, and volatile. When thermal runaway occurs inside the battery due to short circuits, overcharging, or other reasons, the organic solvents will further exacerbate the accumulation of heat, increasing the possibility of fire.

[0003] Currently, most separators on the market use polyolefin-based separators. For example, PP materials typically have a melting point of 160-165℃, while PE materials typically have a melting point of 130-140℃. To improve the heat resistance of these separators, high-temperature resistant ceramics or polymer materials are usually coated onto the polyolefin separator. This method can improve the heat resistance of the separator to some extent, but the improvement is limited due to the inherent melting point of the base material. Alumina ceramic-coated PE separator, which performs relatively well, shows a heat shrinkage rate of 1-5% after heating at 150℃ for 1 hour. At 180℃ for 1 hour, the heat shrinkage is already very significant, failing to meet the requirements of high-safety batteries.

[0004] Solid-state batteries use solid electrolyte membranes with certain mechanical strength to replace commercially available polyolefin porous membranes and some organic solvent electrolytes, which is expected to solve and improve safety issues in liquid batteries such as electrolyte leakage, combustion, and short circuits caused by lithium dendrites piercing the membrane.

[0005] Solid electrolytes are mainly classified into inorganic solid electrolytes and organic polymer solid electrolytes. Organic polymer solid electrolytes (such as polyethylene oxide) have good film-forming properties and good contact with electrode materials. However, organic solid electrolytes have low ionic conductivity, poor mechanical strength, and low ion transport number at room temperature. Inorganic solid electrolytes (including oxide and sulfide electrolytes) generally exhibit high ionic conductivity, high ion transport number, good mechanical properties, and good thermal stability compared to organic solid electrolytes. However, inorganic solid electrolyte films have poor processability and flexibility, poor interfacial contact with the electrode, and currently used inorganic electrolyte film sintering processes cannot achieve very thin films, which increases the internal resistance of solid-state batteries and affects their electrochemical performance.

[0006] Chinese patent application CN114865072A discloses a composite gel sodium ion solid electrolyte comprising an inorganic electrolyte material, an organic gel polymer, and a liquid electrolyte to improve the mechanical strength of the electrolyte membrane and prevent sodium metal dendrites from piercing the membrane. However, the composite electrolyte membrane prepared by this technology cannot be made very thin, and the composite membrane obtained using the inorganic electrolyte as a substrate has poor toughness, making it unsuitable for mass production of battery cells. Furthermore, the low-temperature freezing and high-temperature sintering processes are energy-intensive and require sophisticated equipment.

[0007] Chinese patent application CN114927761A discloses a non-aqueous electrolyte for sodium-ion batteries, comprising sodium salt, a non-aqueous organic solvent, a phosphorus-containing inorganic salt, and 2,2,2-trifluoroethyl methanesulfonate, which improves the high-temperature cycle performance, rate performance, and safety performance of sodium-ion batteries. However, this technology essentially still uses a conventional separator combined with a liquid organic electrolyte, resulting in limited improvement in battery heat resistance and safety performance. In the embodiment, the battery hot box test temperature is only 60°C, which cannot meet the requirements for high-safety sodium-ion batteries.

[0008] Chinese patent CN114006032A discloses a solid polymer electrolyte membrane and its preparation method. When tested at 150℃ for 1 hour, the thermal shrinkage rate is approximately 1-10%, and the ionic conductivity of the polymer electrolyte is generally less than 10. -4 S / cm. This patent mainly involves uniformly dispersing aramid fibers in a polymer electrolyte solution, coating and drying to obtain an aramid fiber-reinforced polymer electrolyte membrane, thereby improving the heat resistance and ionic conductivity of the polymer electrolyte membrane. However, this technology is an organic-organic composite electrolyte membrane, and the improvement in heat resistance and ionic conductivity is limited. Summary of the Invention

[0009] Purpose of the invention: The purpose of this invention is to provide a highly safe sodium-ion solid electrolyte membrane with controllable thickness, thin overall thickness, good mechanical properties, high mechanical strength, high ionic conductivity, and low thermal shrinkage at high temperatures.

[0010] Technical solution: In order to achieve the above-mentioned invention objective, the present invention provides a solid sodium-ion battery electrolyte membrane, comprising an organic porous membrane, a first electrolyte coating and a second electrolyte coating distributed on both sides of the organic porous membrane, wherein the first electrolyte coating and the second electrolyte coating are selected from aqueous electrolyte coatings, and the aqueous electrolyte coating is prepared by an aqueous electrolyte solution;

[0011] The aqueous electrolyte solution comprises, by mass percentage:

[0012] Inorganic solid electrolytes 85-98%,

[0013] Water-based adhesive 2-10%,

[0014] Additives 0-5%,

[0015] Solvent: water 65-400%;

[0016] The inorganic solid electrolyte is Na3Zr2PSi2O 12 The water-based adhesive is polyacrylic acid or polyacrylate.

[0017] The organic porous membrane has a porosity of 40-80%, a pore size of 0.1-20 μm, and a thickness of 5-20 μm;

[0018] The solid sodium-ion battery electrolyte membrane has a thickness of 10-30 μm and a thermal shrinkage rate of <1% after heating at 200°C for 2 hours.

[0019] The present invention provides a solid sodium-ion battery electrolyte membrane, comprising an organic porous membrane, a first electrolyte coating and a second electrolyte coating distributed on both sides of the organic porous membrane, wherein the first electrolyte coating and the second electrolyte coating are selected from oily electrolyte coatings, and the oily electrolyte coating is prepared from an oily electrolyte solution;

[0020] The oily electrolyte solution comprises, by mass percentage:

[0021] Inorganic solid electrolytes: 26.5-85%.

[0022] Polymer matrix 15-56%,

[0023] Sodium salt 5-25%,

[0024] Additives 0-5%,

[0025] Organic solvents 100-900%;

[0026] The inorganic solid electrolyte is Na3Zr2PSi2O 12 ;

[0027] The organic porous membrane has a porosity of 40-80%, a pore size of 0.1-20 μm, and a thickness of 5-20 μm;

[0028] The solid sodium-ion battery electrolyte membrane has a thickness of 10-30 μm and a thermal shrinkage rate of <1% after heating at 200°C for 2 hours.

[0029] Further: The organic porous membrane is selected from any one or more combinations of polyimide, aramid, polytetrafluoroethylene, nylon, and polyetheretherketone.

[0030] Furthermore, the polymer matrix is ​​selected from any one or more combinations of polyvinylidene fluoride, polymethyl methacrylate, nitrile rubber, polyimide, polycarbonate, and polyacrylonitrile.

[0031] The present invention discloses a method for preparing a solid electrolyte membrane, wherein a first electrolyte solution and a second electrolyte solution are respectively coated on both sides of an organic porous membrane and dried; the first electrolyte solution and the second electrolyte solution are selected from aqueous electrolyte coatings, and the aqueous electrolyte coatings are prepared from aqueous electrolyte solutions;

[0032] The aqueous electrolyte solution comprises, by mass percentage:

[0033] Inorganic solid electrolytes 85-98%,

[0034] Water-based adhesive 2-10%,

[0035] Additives 0-5%,

[0036] Solvent: water 65-400%;

[0037] The water-based adhesive is polyacrylic acid or polyacrylate;

[0038] Alternatively, the first electrolyte solution and the second electrolyte solution may be selected from an oily electrolyte coating, which is prepared from an oily electrolyte solution;

[0039] The oily electrolyte solution comprises, by mass percentage:

[0040] Inorganic solid electrolytes: 26.5-85%.

[0041] Polymer matrix 15-56%,

[0042] Sodium salt 5-25%,

[0043] Additives 0-5%,

[0044] Organic solvents 100-900%;

[0045] The inorganic solid electrolyte is Na3Zr2PSi2O 12 ;

[0046] The organic porous membrane has a porosity of 40-80%, a pore size of 0.1-20 μm, and a thickness of 5-20 μm;

[0047] The solid electrolyte membrane has a thickness of 10-30 μm and a thermal shrinkage rate of <1% after heating at 200℃ for 2 hours.

[0048] The inorganic solid electrolyte is selected from Na-β″-Al2O3, Na 1+x Zr2P 3-x Si x O 12 Na3PS4, Na3SbS4, Na 11 Sn2PS12 Any one of the following, where 0 ≤ x ≤ 3.

[0049] This invention utilizes an organic porous membrane with excellent heat resistance as the supporting substrate for the electrolyte membrane. The organic porous membrane is selected from any one or more combinations of polyimide, aramid, polytetrafluoroethylene, nylon, and polyetheretherketone. Polyimide and aramid porous membranes are preferred.

[0050] Furthermore, the organic porous membrane has a porosity of 40-80%, a pore size of 0.1-20 μm, a thickness of 5-20 μm, and a heat resistance greater than 250℃. Excessive porosity or large pore size leads to poor mechanical properties of the porous membrane, while excessively low porosity or small pore size can block the conduction of sodium ions in inorganic and organic electrolytes, affecting the electrochemical performance of the battery. Therefore, more preferably, the organic porous membrane has a porosity of 40-70%, a pore size of 1-15 μm, and a thickness of 5-20 μm.

[0051] Furthermore, the solid sodium-ion battery electrolyte membrane provided by the present invention comprises, by mass percentage:

[0052] Organic porous membranes 20-70%,

[0053] Inorganic solid electrolytes: 5-80%.

[0054] As a preferred embodiment of the present invention, the inorganic solid electrolyte is selected from Na-β″-Al2O3 and Na 1+x Zr2P 3-x Si x O 12 (0≤x≤3), Na3PS4, Na3SbS4, Na 11 Sn2PS 12 Among them, sulfide electrolytes have the highest ionic conductivity (>10). -3 S / cm), Na-β″-Al2O3 and oxide Na 1+x Zr2P 3-x Si x O 12 Ionic conductivity close to (>10) -4 (S / cm), oxide electrolytes have the best stability.

[0055] This invention, based on the same inventive concept, provides two technical solutions: an aqueous electrolyte solution and an oil-based electrolyte solution. The aqueous system is more environmentally friendly and has a simpler process, eliminating the need for subsequent organic solvent recovery. However, some inorganic electrolyte materials are sensitive to water and may undergo side reactions, making them unsuitable for aqueous systems. The oil-based system has higher compatibility and is applicable to virtually all electrolyte materials. However, the organic solvent in the oil-based system requires an additional recovery process.

[0056] For electrolyte membranes prepared from aqueous electrolyte solutions, the following components are included by mass percentage:

[0057] Organic porous membranes 25%-70%,

[0058] Inorganic solid electrolytes: 30%-75%.

[0059] The remainder consists of dry-setting water-based binders. The preparation process also involves trace amounts of additives, generally not exceeding 5%.

[0060] Furthermore, the electrolyte membrane obtained by preparing the aqueous electrolyte solution comprises, by mass percentage:

[0061] Organic porous membranes 40%-55%,

[0062] Inorganic solid electrolytes: 45%-60%.

[0063] The solid electrolyte membrane has a thickness of 10-30 μm and a thermal shrinkage rate of <1% after heating at 200℃ for 2 hours.

[0064] The aqueous binder is selected from any one or more combinations of, but not limited to, polyacrylic acid, polyacrylate, polyacrylonitrile, polyoxyethylene, polyvinyl alcohol, styrene-butadiene rubber, and sodium carboxymethyl cellulose. Polyacrylic acid, polyacrylate, and polyacrylonitrile are preferred. During preparation, it is generally added at 2-10% (w / w) of the inorganic solid electrolyte, and after drying, it does not exceed 6% (w / w) of the total electrolyte membrane weight.

[0065] Most inorganic solid electrolyte membranes are prepared using high-temperature sintering processes, which limit their thickness. While these membranes exhibit high mechanical properties, they are relatively brittle and lack flexibility, making them unsuitable for arbitrary bending. For aqueous electrolyte solutions, this invention utilizes an inorganic electrolyte solution coating process that can be matched with existing conventional membrane ceramic coating processes. By using an organic porous membrane as the supporting substrate, the processability and film-forming properties of the inorganic solid electrolyte are improved. The coating thickness is controllable and can be made thin, resulting in a composite membrane with high mechanical strength and good flexibility.

[0066] The polymer matrix is ​​selected from any one or more combinations of polyvinylidene fluoride, polymethacrylate, nitrile rubber, polyimide, polycarbonate, and polyacrylonitrile. Polyvinylidene fluoride, nitrile rubber, polyimide, and polyacrylic acid are preferred.

[0067] The sodium salt is selected from any one or more combinations of, but not limited to, sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium fluorosulfonyl trifluoromethanesulfonylimide, sodium bis(fluorosulfonyl)imide, sodium bis(oxalateborate), and sodium difluorooxalateborate. Sodium hexafluorophosphate, sodium perchlorate, and sodium bis(trifluoromethanesulfonyl)imide are preferred.

[0068] For oily electrolyte solutions, the electrolyte solution coating process of this invention can be matched with existing conventional membrane ceramic coating processes. The organic-inorganic composite electrolyte improves both the ionic conductivity of the organic electrolyte and the flexibility of the inorganic electrolyte. Using an organic porous membrane as a supporting substrate improves the processability and film-forming properties of the composite solid electrolyte. The coating thickness of the composite electrolyte membrane is controllable and can be made thin. The composite membrane has high mechanical strength and good flexibility.

[0069] The present invention provides a method for preparing a solid electrolyte membrane, which involves coating a first electrolyte solution and a second electrolyte solution onto both sides of an organic porous membrane and then drying them; the first electrolyte solution and the second electrolyte solution are each independently selected from an aqueous electrolyte solution or an oil-based electrolyte solution.

[0070] The aqueous electrolyte solution comprises an inorganic solid electrolyte, an aqueous binder, and additives; the oily electrolyte solution comprises an inorganic solid electrolyte, a sodium salt, a polymer matrix, and an organic solvent.

[0071] The inorganic solid electrolyte is selected from Na-β″-Al2O3, Na 1+x Zr2P 3-x Si x O 12 Na3PS4, Na3SbS4, Na 11 Sn2PS 12 Any one of the following, where 0 ≤ x ≤ 3.

[0072] Furthermore, the coating method is any one of gravure roller coating, wire rod coating, blade coating, or extrusion coating.

[0073] The organic porous membrane, the aqueous binder in the aqueous electrolyte solution, the sodium salt in the oily electrolyte solution, and the polymer matrix have all been described above and will not be repeated here.

[0074] For aqueous electrolyte solutions, additives such as dispersants, film-forming flexibility improvers, defoamers, and wetting agents may also be included. Those skilled in the art can make adaptive modifications based on the principles of this invention.

[0075] For oily electrolyte solutions, the organic solvent is selected from any one or more combinations of N-methylpyrrolidone, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, acetone, and ethyl acetate. N-methylpyrrolidone, ethylene carbonate, propylene carbonate, and dimethyl carbonate are preferred.

[0076] Beneficial Effects: This invention provides a solid-state sodium-ion battery electrolyte membrane and a method for preparing the electrolyte membrane. The electrolyte membrane thickness is ≤40 micrometers, and the thermal shrinkage rate at 200℃ is <2%. The solid-state electrolyte membrane prepared by this invention has controllable thickness and can be made thin, exhibiting good thermal stability and excellent mechanical properties. It improves both the mechanical properties of organic solid-state electrolyte membranes and the poor processability and flexibility of inorganic solid-state electrolyte membranes. Replacing ordinary polyolefin separators and part of the organic electrolyte with a solid-state electrolyte membrane significantly improves the safety of the battery cell, allowing it to pass extreme needle penetration tests (piercing a steel needle at high temperature until it glows red-hot) without affecting the internal resistance, capacity utilization, and cycle performance of the sodium-ion battery cell. The preparation method of the solid-state electrolyte membrane is simple, has high production efficiency, and is easy to mass-produce. Attached Figure Description

[0077] Figure 1 Here is a SEM image of the surface of the solid electrolyte membrane prepared in Example 1;

[0078] Figure 2 This is a graph showing the capacity retention rate of sodium-ion batteries during 0.5C cycling at room temperature, as described in Example 1.

[0079] Figure 3 This is a comparison chart of the sodium electrocautery performance of experimental examples. Detailed Implementation

[0080] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, all percentage units are mass percentages.

[0081] Example 1

[0082] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0083] Electrolyte solution preparation: According to the mass percentage, 95% Na3Zr2PSi2O 12 4% aqueous binder and 1% additives are dissolved and dispersed in 150% deionized water and stirred until homogeneous. The inorganic solid electrolyte is Na3Zr2PSi2O. 12 The water-based binder is polyacrylic acid; the additive is dispersant CMC.

[0084] The electrolyte solution was coated onto both sides of a PI porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The PI porous flexible membrane had a porosity of 57%, a pore size of 1-15 micrometers, and a thickness of 16 micrometers. The resulting solid electrolyte membrane had a thickness of 26 micrometers and a longitudinal tensile strength of 398 kgf / cm². 2 Sodium ion conductivity > 6 × 10 -4 S / cm.

[0085] Sodium-ion battery cathode preparation: Sodium-ion battery layered ternary cathode material, PVDF, and conductive agent are dissolved and dispersed in solvent NMP in a certain proportion. After stirring and dispersing evenly, the mixture is coated on aluminum foil, dried, rolled, and cut into the designed size.

[0086] Preparation of sodium-ion battery negative electrode sheet: Hard carbon negative electrode, water-based binder, conductive agent and CMC are dissolved and dispersed in deionized water in a certain proportion. After stirring and dispersing evenly, the mixture is coated on aluminum foil, dried, rolled and cut into the design size.

[0087] Sodium-ion positive and negative electrodes and the solid electrolyte membrane obtained above are stacked to form a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid-state sodium-ion battery is obtained. The cell internal resistance is 2.81mΩ, and the capacity retention rate after 146 cycles at room temperature (0.5C) is 97.3%. Figure 2 This is a cyclic curve graph.

[0088] Solid-state sodium-ion batteries have excellent safety performance and can pass extreme nail penetration tests (needle penetration of steel needles at high temperatures until they are red-hot). They do not catch fire, burn, smoke, or swell. The highest temperature of the battery cell when punctured is only 40°C, and the voltage change is small.

[0089] General needle penetration test method: After the power battery cell is charged, the test shall be carried out under the following conditions: Needle penetration direction: perpendicular to the direction of the battery plate; Needle type: φ5mm-φ8mm high temperature resistant steel needle, the cone angle of the needle tip is 45°-60°, the surface of the needle is smooth, free of rust, oxide layer and oil stains, and cleaned with organic solvents such as acetone before the test and dried immediately before the test; Needle penetration speed: (25±5)mm / s; Needle penetration degree: the needle should penetrate perpendicular to the direction of the power battery plate, and the penetration position should be close to the geometric center of the pierced surface, and the steel needle should remain in the battery; Observe for 1 hour.

[0090] Example 2

[0091] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0092] Electrolyte solution preparation: According to the mass percentage, 92% Na3Zr2PSi2O 12 7% aqueous binder and 1% additives are dissolved and dispersed in 150% deionized water and stirred until homogeneous. The inorganic solid electrolyte is Na3Zr2PSi2O. 12 The water-based binder is polyacrylate; the additive is dispersant CMC.

[0093] The electrolyte solution was coated onto both sides of a PI porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The PI porous flexible membrane had a porosity of 57%, a pore size of 1-15 micrometers, and a thickness of 18 micrometers. The resulting solid electrolyte membrane had a thickness of 28 micrometers and a longitudinal tensile strength of 396 kgf / cm². 2 Sodium ion conductivity > 6 × 10 -4 S / cm.

[0094] The preparation method of the sodium-ion battery electrode is the same as in Example 1, resulting in a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid-state sodium-ion battery is obtained. The cell internal resistance is 2.8mΩ, and the capacity retention rate is 97.4% after 147 cycles at room temperature (0.5C).

[0095] Example 3

[0096] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0097] Electrolyte solution preparation: According to the mass percentage, 95% Na3Zr2PSi2O 12 4.5% aqueous binder and 0.5% additives are dissolved and dispersed in 185% deionized water and stirred until homogeneous. The inorganic solid electrolyte is Na3Zr2PSi2O. 12 The water-based binder is polyacrylic acid; the additive is dispersant PEO.

[0098] The electrolyte solution was coated onto both sides of an aramid porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The aramid porous flexible membrane had a porosity of 52%, a pore size of 0.5-10 micrometers, and a thickness of 12 micrometers. The resulting solid electrolyte membrane had a thickness of 24 micrometers and a longitudinal tensile strength of 319 kgf / cm². 2 Sodium ion conductivity > 6 × 10 -4 S / cm.

[0099] The sodium-ion battery electrode preparation method is the same as in Example 1, yielding a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid-state sodium-ion battery is obtained. The cell internal resistance is 2.8mΩ, and the capacity retention rate after 147 cycles at room temperature (0.5C) is 97.3%.

[0100] Example 4

[0101] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0102] Electrolyte solution preparation: Dissolve and disperse 95% inorganic solid electrolyte, 4% aqueous binder, and 1% additives in 150% deionized water according to their mass percentages, and stir until homogeneous. The inorganic solid electrolyte is Na3Zr2PSi2O. 12 The water-based binder is polyacrylate; the additive is dispersant CMC.

[0103] The electrolyte solution was coated onto both sides of a PI porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The PI porous flexible membrane had a porosity of 57%, a pore size of 1-15 micrometers, and a thickness of 16 micrometers. The resulting solid electrolyte membrane had a thickness of 26 micrometers and a longitudinal tensile strength of 396 kgf / cm². 2 Sodium ion conductivity > 6 × 10 -4 S / cm.

[0104] Sodium-ion positive and negative electrodes and the solid electrolyte membrane obtained above are stacked to form a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid sodium-ion battery is obtained. The cell internal resistance is 2.8mΩ, and the capacity retention rate is 97.4% after 146 cycles at room temperature (0.5C).

[0105] Example 5

[0106] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0107] Electrolyte solution preparation: 96% inorganic solid electrolyte and 4% polymer matrix were dissolved and dispersed in 400% organic solvent by mass percentage, and stirred until homogeneous. The inorganic solid electrolyte was Na-β″-Al2O3; the polymer matrix was polyvinylidene fluoride; and the organic solvent was NMP.

[0108] The electrolyte solution was coated onto both sides of a PI porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The PI porous flexible membrane had a porosity of 57%, a pore size of 1-15 micrometers, and a thickness of 16 micrometers. The resulting solid electrolyte membrane had a thickness of 25 micrometers and a longitudinal tensile strength of 394 kgf / cm². 2 Sodium ion conductivity > 5.5 × 10 -4 S / cm.

[0109] Sodium-ion positive and negative electrodes and the solid electrolyte membrane obtained above are stacked to form a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid sodium-ion battery is obtained. The cell internal resistance is 2.8mΩ, and the capacity retention rate is 97.7% after 145 cycles at room temperature (0.5C).

[0110] Example 6

[0111] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0112] Electrolyte solution preparation: 77% inorganic solid electrolyte, 19.2% polymer matrix, and 3.8% sodium salt were dissolved and dispersed in 400% organic solvent by mass percentage, and stirred until homogeneous. The inorganic solid electrolyte was Na-β″-Al2O3; the polymer matrix was polyvinylidene fluoride; the sodium salt was sodium hexafluorophosphate; and the organic solvent was NMP.

[0113] The electrolyte solution was coated onto both sides of a PI porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The PI porous flexible membrane had a porosity of 57%, a pore size of 1-15 micrometers, and a thickness of 16 micrometers. The resulting solid electrolyte membrane had a thickness of 24 micrometers and a longitudinal tensile strength of 401 kgf / cm². 2 Sodium ion conductivity > 4.5 × 10 -4 S / cm.

[0114] Sodium-ion positive and negative electrodes and the solid electrolyte membrane obtained above are stacked to form a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid sodium-ion battery is obtained. The cell internal resistance is 2.83mΩ, and the capacity retention rate is 97.6% after 148 cycles at room temperature (0.5C).

[0115] Example 7

[0116] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0117] Electrolyte solution preparation: 45.5% inorganic solid electrolyte, 45.5% polymer matrix, and 9% sodium salt were dissolved and dispersed in 400% organic solvent by mass percentage, and stirred until homogeneous. The inorganic solid electrolyte was Na-β″-Al2O3; the polymer matrix was polyvinylidene fluoride; the sodium salt was sodium hexafluorophosphate; and the organic solvent was NMP.

[0118] The electrolyte solution was coated onto both sides of a PI porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The PI porous flexible membrane had a porosity of 57%, a pore size of 1-15 micrometers, and a thickness of 16 micrometers. The resulting solid electrolyte membrane had a thickness of 24 micrometers and a longitudinal tensile strength of 403 kgf / cm². 2 Sodium ion conductivity > 3 × 10 -4 S / cm.

[0119] Sodium-ion positive and negative electrodes and the solid electrolyte membrane obtained above are stacked to form a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid sodium-ion battery is obtained. The cell internal resistance is 2.85mΩ, and the capacity retention rate is 97.6% after 145 cycles at room temperature (0.5C).

[0120] Example 8

[0121] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0122] Electrolyte solution preparation: 17.2% inorganic solid electrolyte, 69% polymer matrix, and 13.8% sodium salt were dissolved and dispersed in 400% organic solvent by mass percentage, and stirred until homogeneous. The inorganic solid electrolyte was Na-β″-Al2O3; the polymer matrix was polyvinylidene fluoride; the sodium salt was sodium hexafluorophosphate; and the organic solvent was NMP.

[0123] The electrolyte solution was coated onto both sides of a PI porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The PI porous flexible membrane had a porosity of 57%, a pore size of 1-15 micrometers, and a thickness of 16 micrometers. The resulting solid electrolyte membrane had a thickness of 24 micrometers and a longitudinal tensile strength of 407 kgf / cm². 2 Sodium ion conductivity > 2 × 10 -4 S / cm.

[0124] Sodium-ion positive and negative electrodes and the solid electrolyte membrane obtained above are stacked to form a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid sodium-ion battery is obtained. The cell internal resistance is 2.87mΩ, and the capacity retention rate is 97.9% after 145 cycles at room temperature (0.5C).

[0125] Example 9

[0126] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0127] Electrolyte solution preparation: 96% inorganic solid electrolyte and 4% polymer matrix were dissolved and dispersed in 400% organic solvent by mass percentage, and stirred until homogeneous. The inorganic solid electrolyte was Na3PS4; the polymer matrix was polyvinylidene fluoride; and the organic solvent was NMP.

[0128] The electrolyte solution was coated onto both sides of a PI porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The PI porous flexible membrane had a porosity of 57%, a pore size of 1-15 micrometers, and a thickness of 16 micrometers. The resulting solid electrolyte membrane had a thickness of 25 micrometers and a longitudinal tensile strength of 393 kgf / cm². 2 Sodium ion conductivity > 8 × 10-4 S / cm.

[0129] Sodium-ion positive and negative electrodes and the solid electrolyte membrane obtained above are stacked to form a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid sodium-ion battery is obtained. The cell internal resistance is 2.81mΩ, and the capacity retention rate is 97.6% after 145 cycles at room temperature (0.5C).

[0130] Example 10

[0131] This embodiment provides a sodium ion solid electrolyte membrane, which is prepared by the following method:

[0132] Electrolyte solution preparation: 94% inorganic solid electrolyte and 6% polymer matrix were dissolved and dispersed in 550% organic solvent by mass percentage, and stirred until homogeneous. The inorganic solid electrolyte was Na3PS4; the polymer matrix was nitrile rubber; and the organic solvent was NMP.

[0133] The electrolyte solution described above was coated onto both sides of an aramid porous flexible membrane, dried in an oven tunnel, and then wound up to obtain a solid electrolyte membrane. The aramid porous flexible membrane has a porosity of 52%, a pore size of 0.5-10 micrometers, and a thickness of 12 micrometers. The resulting solid electrolyte membrane has a thickness of 23 micrometers and a longitudinal tensile strength of 320 kgf / cm². 2 Sodium ion conductivity > 8 × 10 -4 S / cm.

[0134] Sodium-ion positive and negative electrodes and the solid electrolyte membrane obtained above are stacked to form a 5.5Ah sodium-ion dry cell. A small amount of electrolyte is injected, and after formation activation, a 5.5Ah solid sodium-ion battery is obtained. The cell internal resistance is 2.8mΩ, and the capacity retention rate is 97.7% after 147 cycles at room temperature (0.5C).

[0135] Test case

[0136] In this experiment, the solid electrolyte membrane prepared in the above embodiments was heated at a specific temperature, and the area before and after heating was measured to calculate the shrinkage rate. The results were compared with products prepared from ordinary PE / PP membranes and ceramic materials (alumina and boehmite), and are shown in Table 1.

[0137] Table 1. Thermal shrinkage rate test of sodium ion solid electrolyte membrane

[0138]

[0139] In this experiment, an extreme nail penetration test was also conducted on the batteries provided in Example 1 and Comparative Example 1 (the steel needle was pierced and heated to a high temperature until it turned red). Figure 3As shown, in Example 1, the highest temperature of the needle-punctured battery cell was only 40°C, and the voltage change was small. However, the product made using a traditional PE ceramic diaphragm showed that a short circuit and combustion occurred instantly after being punctured.

[0140] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A solid sodium-ion battery electrolyte membrane, characterized in that: The membrane includes an organic porous membrane, a first electrolyte coating and a second electrolyte coating distributed on both sides of the organic porous membrane, wherein the first electrolyte coating and the second electrolyte coating are selected from aqueous electrolyte coatings, and the aqueous electrolyte coating is prepared from an aqueous electrolyte solution. The aqueous electrolyte solution comprises, by mass percentage: Inorganic solid electrolytes 85-98%, Water-based adhesive 2-10%, Additives 0-5%, Solvent: water 65-400%; The inorganic solid electrolyte is Na3Zr2PSi 2 O 12 The water-based adhesive is polyacrylic acid or polyacrylate. The organic porous membrane has a porosity of 40-80%, a pore size of 0.1-20 μm, and a thickness of 5-20 μm; The solid sodium-ion battery electrolyte membrane has a thickness of 10-30 μm and a thermal shrinkage rate of <1% after heating at 200°C for 2 hours.

2. The solid sodium-ion battery electrolyte membrane according to claim 1, characterized in that: The organic porous membrane is selected from any one or more combinations of polyimide, aramid, polytetrafluoroethylene, nylon, and polyetheretherketone.

3. A solid sodium-ion battery electrolyte membrane, characterized in that: The membrane includes an organic porous membrane, a first electrolyte coating and a second electrolyte coating distributed on both sides of the organic porous membrane, wherein the first electrolyte coating and the second electrolyte coating are selected from oily electrolyte coatings, and the oily electrolyte coating is prepared from an oily electrolyte solution; The oily electrolyte solution comprises, by mass percentage: Inorganic solid electrolytes: 26.5-85%. Polymer matrix 15-56%, Sodium salt 5-25%, Additives 0-5%, Organic solvents 100-900%; The inorganic solid electrolyte is Na3Zr2PSi 2 O 12 ; The organic porous membrane has a porosity of 40-80%, a pore size of 0.1-20 μm, and a thickness of 5-20 μm; The solid sodium-ion battery electrolyte membrane has a thickness of 10-30 μm and a thermal shrinkage rate of <1% after heating at 200°C for 2 hours.

4. The solid sodium-ion battery electrolyte membrane according to claim 3, characterized in that: The organic porous membrane is selected from any one or more combinations of polyimide, aramid, polytetrafluoroethylene, nylon, and polyetheretherketone.

5. The solid sodium-ion battery electrolyte membrane according to claim 4, characterized in that: The polymer matrix is ​​selected from any one or a combination of polyvinylidene fluoride, polymethyl methacrylate, nitrile rubber, polyimide, polycarbonate, and polyacrylonitrile.

6. A method for preparing a solid electrolyte membrane, characterized in that: The first electrolyte solution and the second electrolyte solution are respectively coated on both sides of the organic porous membrane and dried; the first electrolyte solution and the second electrolyte solution are selected from aqueous electrolyte coatings, which are prepared from aqueous electrolyte solutions; The aqueous electrolyte solution comprises, by mass percentage: Inorganic solid electrolytes 85-98%, Water-based adhesive 2-10%, Additives 0-5%, Solvent: water 65-400%; The water-based adhesive is polyacrylic acid or polyacrylate; Alternatively, the first electrolyte solution and the second electrolyte solution may be selected from an oily electrolyte coating, which is prepared from an oily electrolyte solution; The oily electrolyte solution comprises, by mass percentage: Inorganic solid electrolytes: 26.5-85%. Polymer matrix 15-56%, Sodium salt 5-25%, Additives 0-5%, Organic solvents 100-900%; The inorganic solid electrolyte is Na3Zr2PSi 2 O 12 ; The organic porous membrane has a porosity of 40-80%, a pore size of 0.1-20 μm, and a thickness of 5-20 μm; The solid electrolyte membrane has a thickness of 10-30 μm and a thermal shrinkage rate of <1% after heating at 200℃ for 2 hours.

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