Modification method for improving needling safety of layered oxygen sodium ion battery

Abstract

The invention relates to the field of sodium-ion batteries, in particular to a modification method for improving acupuncture safety of a layered oxygen sodium-ion battery, which is used for solving the problems that thermal runaway of an existing layered oxygen positive electrode material is difficult to control, the sodium-ion battery is easy to explode and fire, and the sodium-ion battery cannot pass an acupuncture experiment. According to the modification method, by introducing the safety enhancer, under the synergistic effect of a benzene ring and an organic phosphorus-nitrogen-sulfur structure, the safety of the layered oxygen sodium ion battery under the needling condition is remarkably improved, the thermal runaway risk is reduced, and the safety and reliability of the battery in the using process are guaranteed to the maximum extent; the performance of the battery is effectively maintained, the service life of the battery is prolonged, and meanwhile, the risk of safety accidents is also reduced.

Description

Technical Field

[0001] The invention relates to the field of sodium ion batteries, and in particular to a modification method for improving the acupuncture safety of layered oxygen sodium ion batteries. Background Art

[0002] Among all energy storage, electrochemical energy storage has the highest conversion rate, which has led to the rapid development of lithium-ion batteries. However, the proportion of lithium resources in the earth's crust is low, and the distribution of resources is uneven, which limits its further development. The proportion of sodium in the earth's crust far exceeds that of lithium, and the resources are evenly distributed. Nowadays, the layered oxygen positive electrode material in sodium-ion batteries can achieve a high energy density and is an ideal positive electrode material. However, the thermal runaway of the layered oxygen positive electrode material is difficult to control, which can easily cause the sodium-ion battery to explode and catch fire, and cannot pass the puncture test. Therefore, modifying the layered oxygen material to improve the pass rate of the puncture is a key technology to promote the widespread application of layered oxygen sodium batteries in energy storage.

[0003] In view of the above technical defects, a solution is now proposed. Summary of the invention

[0004] In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide a modification method for improving the safety of layered oxygen sodium ion battery needle puncture, which solves the problem that the thermal runaway of the existing layered oxygen positive electrode material is difficult to control, which easily leads to the explosion and fire of the sodium ion battery and cannot pass the needle puncture test.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries comprises the following steps:

[0007] Step 1: DOPO and anhydrous toluene are added to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, and nitrogen is introduced for protection. The mixture is stirred for reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 20-30 min. Then, phosphorus pentasulfide is added and the temperature is raised to 60-65° C. and the stirring reaction is continued for 8-10 h. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation. Then, the mixture is poured into chloroform, and then washed with a saturated sodium bicarbonate solution for 2-3 times, and then the solvent is removed by rotary evaporation to obtain intermediate 1;

[0008] Step 2: 4-nitroresorcinol, 3-bromo-1-propylene, anhydrous potassium carbonate, benzoquinone, toluene and N,N-dimethylformamide are added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen is introduced for protection. The mixture is stirred for reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 20-30 min, and then the temperature is raised to reflux and the stirring reaction is continued for 7-8 h. After the reaction is completed, the reaction product is cooled to room temperature, and then washed with saturated brine and ice water for 2-3 times in sequence, and then the solvent is removed by rotary evaporation to obtain intermediate 2;

[0009] Step 3: Add intermediate 2, reduced iron powder, hydrochloric acid solution, anhydrous ethanol, anhydrous acetone and deionized water to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introduce nitrogen protection, stir the reaction at a temperature of 25-30°C and a stirring rate of 300-400r / min for 20-30min, then heat to 85-95°C and continue stirring the reaction for 4-5h. After the reaction is completed, cool the reaction product to room temperature, then vacuum filter, adjust the filtrate to pH 7.5-8 with sodium hydroxide solution, and then remove the solvent by rotary evaporation to obtain intermediate 3;

[0010] Step 4: Add intermediate 3, hexachlorocyclotriphosphazene and ethyl acetate to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir and react for 20-30 minutes at a temperature of -5-0°C and a stirring rate of 300-400r / min, then heat to 25-30°C and continue stirring and reacting for 1-2 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain intermediate 4;

[0011] Step 5: Add intermediate 1, intermediate 4, triethylamine and dioxane to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir the reaction at a temperature of 40-45°C and a stirring rate of 300-400r / min for 40-60min, then heat to 85-90°C and continue stirring the reaction for 15-20h. After the reaction is completed, the reaction product is cooled to room temperature, then washed with distilled water 2-3 times, and then rotary evaporated to remove the solvent to obtain a safety enhancer;

[0012] Step 6: Layered oxide Na 0.44 MnO 2 , Super P conductive carbon black, polyvinylidene fluoride and safety enhancer are mixed evenly in a mass ratio of 7:2:1:0.2, and then N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry. The positive electrode slurry is then coated on the surface of the aluminum foil and dried completely to form a positive electrode sheet;

[0013] Step 7: Assemble the positive electrode, negative electrode, separator and electrolyte into a battery in a glove box filled with high-purity argon gas, and then subject the battery to a needle puncture test.

[0014] As a preferred embodiment of the present invention, the dosage ratio of the DOPO, anhydrous toluene and phosphorus pentasulfide in step 1 is 10 mmol: 30-35 mL: 10-12 mmol.

[0015] As a preferred embodiment of the present invention, the dosage ratio of the 4-nitroresorcinol, 3-bromo-1-propylene, anhydrous potassium carbonate, benzoquinone, toluene and N,N-dimethylformamide in step 2 is 10 mmol: 20 mmol: 22-25 mL: 0.01-0.03 g: 20-30 mL: 35-40 mL.

[0016] As a preferred embodiment of the present invention, the usage ratio of the intermediate 2, reduced iron powder, hydrochloric acid solution, anhydrous ethanol, anhydrous acetone and deionized water in step three is 5g:11-13g:2-3mL:8-10mL:8-10mL:8-10mL.

[0017] As a preferred embodiment of the present invention, the mass fraction of the hydrochloric acid solution in step three is 20-25%; the mass fraction of the sodium hydroxide solution is 10-15%.

[0018] As a preferred embodiment of the present invention, the usage ratio of the intermediate 3, hexachlorocyclotriphosphazene and ethyl acetate in step 4 is 60 mmol: 10 mmol: 70-80 mL.

[0019] As a preferred embodiment of the present invention, the usage ratio of the intermediate 1, intermediate 4, triethylamine and dioxane in step 5 is 60 mmol: 10 mmol: 2.5-3.5 g: 90-100 mL.

[0020] As a preferred embodiment of the present invention, the layered oxide Na in step 6 0.44 MnO 2 The mass ratio of Super P conductive carbon black, polyvinylidene fluoride, safety enhancer and N-methylpyrrolidone is 7:2:1:0.2:25.

[0021] As a preferred embodiment of the present invention, the negative electrode sheet in step seven is a sodium metal sheet;

[0022] The diaphragm is a glass fiber diaphragm;

[0023] The electrolyte is a solution of sodium hexafluorophosphate with a concentration of 1 mol / L dissolved in a mixed solvent.

[0024] As a preferred embodiment of the present invention, the mixed solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1.

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

[0026] A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries, comprising: reacting DOPO and phosphorus pentasulfide, and then replacing the phosphorus oxygen double bond in DOPO with a phosphorus sulfur double bond to obtain an intermediate 1, then reacting 4-nitroresorcinol and 3-bromo-1-propylene, the hydroxyl group on 4-nitroresorcinol reacts with the bromine atom on 3-bromo-1-propylene, introducing an olefin group to obtain an intermediate 2, then reducing the nitro group on the intermediate 2 to an amino group under the action of reducing iron powder to obtain an intermediate 3, then reacting the intermediate 3 with hexachlorocyclotriphosphazene, the amino group on the intermediate 3 reacts with the chlorine atom on the hexachlorocyclotriphosphazene, thereby forming an intermediate 4 containing a large number of olefin groups, then reacting the intermediate 1 with the intermediate 4, the PH bond on the intermediate 1 reacts with the olefin group on the intermediate 4, thereby introducing a large number of benzene rings and organic phosphorus and sulfur, and obtaining a safety enhancer; the molecular structure of the safety enhancer contains a large number of benzene rings and organic phosphorus and sulfur. The organic phosphorus-nitrogen-sulfur structure can effectively improve the thermal stability of the layered oxygen sodium ion battery and its cycle stability. The phosphorus element can react with oxygen to generate compounds such as phosphoric acid and phosphates during the combustion process. The sulfur element can release strong acids such as sulfuric acid under high temperature conditions, and promote the dehydration of the substrate into carbon under the synergistic effect with phosphoric acid, thereby forming a protective layer that can isolate oxygen and heat and prevent the spread of fire. The nitrogen element can generate non-combustible gases such as nitrogen and nitric oxide during the combustion process, which can dilute the concentration of combustible gases and reduce the oxygen concentration in the combustion area, thereby inhibiting combustion. The modification method introduces a safety enhancer, and under the synergistic effect of the benzene ring and the organic phosphorus-nitrogen-sulfur structure, it significantly improves the safety of the layered oxygen sodium ion battery under acupuncture conditions, reduces the risk of thermal runaway, and maximizes the safety and reliability of the battery during use, effectively maintains the performance of the battery and extends the service life of the battery, while also reducing the risk of safety accidents. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Embodiment 1:

[0029] This embodiment is a modification method for improving the safety of acupuncture of layered oxygen sodium ion batteries, comprising the following steps:

[0030] Step 1: 10 mmol DOPO and 30 mL anhydrous toluene were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 25° C. and a stirring rate of 300 r / min for 20 min. Then, 10 mmol phosphorus pentasulfide was added and the mixture was heated to 60° C. and the stirring reaction was continued for 8 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation. The mixture was then poured into chloroform, and then washed twice with a saturated sodium bicarbonate solution, and then the solvent was removed by rotary evaporation to obtain intermediate 1.

[0031] Step 2: 10 mmol 4-nitroresorcinol, 20 mmol 3-bromo-1-propylene, 22 mL anhydrous potassium carbonate, 0.01 g benzoquinone, 20 mL toluene and 35 mL N, N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred for reaction at a temperature of 25° C. and a stirring rate of 300 r / min for 20 min, and then the temperature was raised to reflux and the stirring reaction was continued for 7 h. After the reaction was completed, the reaction product was cooled to room temperature, and then washed with saturated brine and ice water twice in sequence, and then the solvent was removed by rotary evaporation to obtain intermediate 2;

[0032] Step 3: Add 5g of intermediate 2, 11g of reduced iron powder, 2mL of 20% hydrochloric acid solution, 8mL of anhydrous ethanol, 8mL of anhydrous acetone and 8mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introduce nitrogen protection, stir and react for 20min at a temperature of 25°C and a stirring rate of 300r / min, then heat to 85°C and continue stirring and reacting for 4h. After the reaction is completed, the reaction product is cooled to room temperature, then vacuum filtered, and the filtrate is adjusted to pH 7.5 with a 10% sodium hydroxide solution, and then the solvent is removed by rotary evaporation to obtain intermediate 3;

[0033] Step 4: 60 mmol of intermediate 3, 10 mmol of hexachlorocyclotriphosphazene and 70 mL of ethyl acetate were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at a temperature of -5 ° C and a stirring rate of 300 r / min for 20 min, and then the temperature was raised to 25 ° C and the stirring reaction was continued for 1 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 4;

[0034] Step 5: Add 60 mmol intermediate 1, 10 mmol intermediate 4, 2.5 g triethylamine and 90 mL dioxane into a three-necked flask equipped with a stirrer, a thermometer and a gas duct, introduce nitrogen protection, stir the reaction at a temperature of 40 ° C and a stirring rate of 300 r / min for 40 minutes, then heat the temperature to 85 ° C and continue to stir the reaction for 15 hours. After the reaction is completed, the reaction product is cooled to room temperature, then washed with distilled water twice, and then rotary evaporated to remove the solvent to obtain a safety enhancer;

[0035] Step 6: 7g of layered oxide Na 0.44 MnO 2 , 2g Super P conductive carbon black, 1g polyvinylidene fluoride and 0.2g safety enhancer are mixed evenly, and then 25g N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of aluminum foil and dried completely to form a positive electrode sheet;

[0036] Using sodium metal sheet as negative electrode;

[0037] Use fiberglass diaphragms as diaphragms;

[0038] A solution of 1 mol / L sodium hexafluorophosphate dissolved in a mixed solvent (propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1) was used as the electrolyte;

[0039] Step 7: Assemble the positive electrode, negative electrode, separator and electrolyte into a 26700 battery in a glove box filled with high-purity argon gas, then charge and discharge the 26700 battery once at 0.5C, and then fully charge it and let it stand for 2 hours to pass the needle puncture test.

[0040] Embodiment 2:

[0041] This embodiment is a modification method for improving the safety of acupuncture of layered oxygen sodium ion batteries, comprising the following steps:

[0042] Step 1: 10 mmol DOPO and 32 mL anhydrous toluene were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 28° C. and a stirring rate of 350 r / min for 25 min. Then, 11 mmol phosphorus pentasulfide was added and the temperature was raised to 62° C. and the stirring reaction was continued for 9 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation. Then, the mixture was poured into chloroform, and then washed twice with a saturated sodium bicarbonate solution, and then the solvent was removed by rotary evaporation to obtain intermediate 1;

[0043] Step 2: 10 mmol 4-nitroresorcinol, 20 mmol 3-bromo-1-propylene, 24 mL anhydrous potassium carbonate, 0.02 g benzoquinone, 25 mL toluene and 38 mL N, N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at a temperature of 28° C. and a stirring rate of 350 r / min for 25 min, and then the temperature was raised to reflux and the stirring reaction was continued for 7.5 h. After the reaction was completed, the reaction product was cooled to room temperature, and then washed with saturated brine and ice water twice in sequence, and then the solvent was removed by rotary evaporation to obtain intermediate 2;

[0044] Step 3: Add 5 g of intermediate 2, 12 g of reduced iron powder, 2.5 mL of 22% hydrochloric acid solution, 9 mL of anhydrous ethanol, 9 mL of anhydrous acetone and 9 mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introduce nitrogen protection, stir and react for 25 min at a temperature of 28 ° C and a stirring rate of 350 r / min, then heat to 90 ° C and continue to stir and react for 4.5 h. After the reaction is completed, the reaction product is cooled to room temperature, then vacuum filtered, and the filtrate is adjusted to pH 7.5 with a mass fraction of 12% sodium hydroxide solution, and then the solvent is removed by rotary evaporation to obtain intermediate 3;

[0045] Step 4: 60 mmol of intermediate 3, 10 mmol of hexachlorocyclotriphosphazene and 75 mL of ethyl acetate were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at a temperature of -3 ° C and a stirring rate of 350 r / min for 25 min, and then the temperature was raised to 28 ° C and the stirring reaction was continued for 1.5 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 4;

[0046] Step 5: Add 60 mmol of intermediate 1, 10 mmol of intermediate 4, 3 g of triethylamine and 95 mL of dioxane to a three-necked flask equipped with a stirrer, a thermometer and a gas duct, introduce nitrogen protection, stir the reaction at a temperature of 42 ° C and a stirring rate of 350 r / min for 50 min, then heat to 88 ° C and continue stirring the reaction for 18 h. After the reaction is completed, the reaction product is cooled to room temperature, then washed with distilled water twice, and then rotary evaporated to remove the solvent to obtain a safety enhancer;

[0047] Step 6: 7g of layered oxide Na 0.44 MnO 2, 2g Super P conductive carbon black, 1g polyvinylidene fluoride and 0.2g safety enhancer are mixed evenly, and then 25g N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of aluminum foil and dried completely to form a positive electrode sheet;

[0048] Using sodium metal sheet as negative electrode;

[0049] Use fiberglass diaphragms as diaphragms;

[0050] A solution of 1 mol / L sodium hexafluorophosphate dissolved in a mixed solvent (propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1) was used as the electrolyte;

[0051] Step 7: Assemble the positive electrode, negative electrode, separator and electrolyte into a 26700 battery in a glove box filled with high-purity argon gas, then charge and discharge the 26700 battery once at 0.5C, and then fully charge it and let it stand for 2 hours to pass the needle puncture test.

[0052] Embodiment 3:

[0053] This embodiment is a modification method for improving the safety of acupuncture of layered oxygen sodium ion batteries, comprising the following steps:

[0054] Step 1: 10 mmol DOPO and 35 mL anhydrous toluene were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 30° C. and a stirring rate of 400 r / min for 30 min. Then, 12 mmol phosphorus pentasulfide was added and the mixture was heated to 65° C. and the stirring reaction was continued for 10 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation. The mixture was then poured into chloroform, and then washed with a saturated sodium bicarbonate solution for 3 times. The solvent was then removed by rotary evaporation to obtain intermediate 1.

[0055] Step 2: 10 mmol 4-nitroresorcinol, 20 mmol 3-bromo-1-propylene, 25 mL anhydrous potassium carbonate, 0.03 g benzoquinone, 30 mL toluene and 40 mL N, N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred for 30 min at a temperature of 30° C. and a stirring rate of 400 r / min, and then the temperature was raised to reflux and the stirring reaction was continued for 8 h. After the reaction was completed, the reaction product was cooled to room temperature, and then washed with saturated brine and ice water three times in sequence, and then the solvent was removed by rotary evaporation to obtain intermediate 2;

[0056] Step 3: Add 5g of intermediate 2, 13g of reduced iron powder, 3mL of 25% hydrochloric acid solution, 10mL of anhydrous ethanol, 10mL of anhydrous acetone and 10mL of deionized water into a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introduce nitrogen protection, stir and react for 30min at a temperature of 30°C and a stirring rate of 400r / min, then continue to stir and react for 5h under the condition of heating to 95°C. After the reaction is completed, the reaction product is cooled to room temperature, then vacuum filtered, and the filtrate is adjusted to pH 8 with a mass fraction of 15% sodium hydroxide solution, and then the solvent is removed by rotary evaporation to obtain intermediate 3;

[0057] Step 4: 60 mmol of intermediate 3, 10 mmol of hexachlorocyclotriphosphazene and 80 mL of ethyl acetate were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 0°C and a stirring rate of 400 r / min for 30 min, and then the temperature was raised to 30°C and the stirring reaction was continued for 2 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 4;

[0058] Step 5: Add 60 mmol intermediate 1, 10 mmol intermediate 4, 3.5 g triethylamine and 100 mL dioxane to a three-necked flask equipped with a stirrer, a thermometer and a gas duct, introduce nitrogen protection, stir the reaction at a temperature of 45 ° C and a stirring rate of 400 r / min for 60 min, then heat to 90 ° C and continue stirring the reaction for 20 h. After the reaction is completed, the reaction product is cooled to room temperature, then washed with distilled water 3 times, and then rotary evaporated to remove the solvent to obtain a safety enhancer;

[0059] Step 6: 7g of layered oxide Na 0.44 MnO 2 , 2g Super P conductive carbon black, 1g polyvinylidene fluoride and 0.2g safety enhancer are mixed evenly, and then 25g N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of aluminum foil and dried completely to form a positive electrode sheet;

[0060] Using sodium metal sheet as negative electrode;

[0061] Use fiberglass diaphragms as diaphragms;

[0062] A solution of 1 mol / L sodium hexafluorophosphate dissolved in a mixed solvent (propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1) was used as the electrolyte;

[0063] Step 7: Assemble the positive electrode, negative electrode, separator and electrolyte into a 26700 battery in a glove box filled with high-purity argon gas, then charge and discharge the 26700 battery once at 0.5C, and then fully charge it and let it stand for 2 hours to pass the needle puncture test.

[0064] Comparative Example 1:

[0065] This comparative example is a modification method for improving the acupuncture safety of layered oxygen sodium ion batteries, comprising the following steps:

[0066] Step 1: 7g of layered oxide Na 0.44 MnO 2 , 2g Super P conductive carbon black and 1g polyvinylidene fluoride are mixed evenly, and then 25g N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of aluminum foil, and after drying, it is used as a positive electrode sheet;

[0067] Using sodium metal sheet as negative electrode;

[0068] Use fiberglass diaphragms as diaphragms;

[0069] A solution of 1 mol / L sodium hexafluorophosphate dissolved in a mixed solvent (propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1) was used as the electrolyte;

[0070] Step 2: Assemble the positive electrode, negative electrode, separator and electrolyte into a 26700 battery in a glove box filled with high-purity argon gas, then charge and discharge the 26700 battery once at 0.5C, and then fully charge it and let it stand for 2 hours to pass the needle puncture test.

[0071] Comparative Example 2:

[0072] This comparative example is a modification method for improving the acupuncture safety of layered oxygen sodium ion batteries, comprising the following steps:

[0073] Step 1: 7g of layered oxide Na 0.44 MnO 2 , 2g Super P conductive carbon black, 1g polyvinylidene fluoride and 0.2g sodium ferric pyrophosphate are mixed evenly, and then 25g N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of aluminum foil and dried completely to form a positive electrode sheet;

[0074] Using sodium metal sheet as negative electrode;

[0075] Use fiberglass diaphragms as diaphragms;

[0076] A solution of 1 mol / L sodium hexafluorophosphate dissolved in a mixed solvent (propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1) was used as the electrolyte;

[0077] Step 2: Assemble the positive electrode, negative electrode, separator and electrolyte into a 26700 battery in a glove box filled with high-purity argon gas, then charge and discharge the 26700 battery once at 0.5C, and then fully charge it and let it stand for 2 hours to pass the needle puncture test.

[0078] Comparative Example 3:

[0079] This comparative example is a modification method for improving the acupuncture safety of layered oxygen sodium ion batteries, comprising the following steps:

[0080] Step 1: 7g of layered oxide Na 0.44 MnO 2 , 2g Super P conductive carbon black, 1g polyvinylidene fluoride and 0.2g chlorinated paraffin-70 are mixed evenly, and then 25g N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of aluminum foil and dried completely to form a positive electrode sheet;

[0081] Using sodium metal sheet as negative electrode;

[0082] Use fiberglass diaphragms as diaphragms;

[0083] A solution of 1 mol / L sodium hexafluorophosphate dissolved in a mixed solvent (propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1) was used as the electrolyte;

[0084] Step 2: Assemble the positive electrode, negative electrode, separator and electrolyte into a 26700 battery in a glove box filled with high-purity argon gas, then charge and discharge the 26700 battery once at 0.5C, and then fully charge it and let it stand for 2 hours to pass the needle puncture test.

[0085] Comparative Example 4:

[0086] This comparative example is a modification method for improving the acupuncture safety of layered oxygen sodium ion batteries, comprising the following steps:

[0087] Step 1: 7g of layered oxide Na 0.44 MnO 2 , 2g Super P conductive carbon black, 1g polyvinylidene fluoride and 0.2g DOPO are mixed evenly, and then 25g N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of aluminum foil and dried completely to form a positive electrode sheet;

[0088] Using sodium metal sheet as negative electrode;

[0089] Use fiberglass diaphragms as diaphragms;

[0090] A solution of 1 mol / L sodium hexafluorophosphate dissolved in a mixed solvent (propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1) was used as the electrolyte;

[0091] Step 2: Assemble the positive electrode, negative electrode, separator and electrolyte into a 26700 battery in a glove box filled with high-purity argon gas, then charge and discharge the 26700 battery once at 0.5C, and then fully charge it and let it stand for 2 hours to pass the needle puncture test.

[0092] Comparative Example 5:

[0093] This comparative example is a modification method for improving the acupuncture safety of layered oxygen sodium ion batteries, comprising the following steps:

[0094] Step 1: 10 mmol DOPO and 35 mL anhydrous toluene were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 30° C. and a stirring rate of 400 r / min for 30 min. Then, 12 mmol phosphorus pentasulfide was added and the mixture was heated to 65° C. and the stirring reaction was continued for 10 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation. The mixture was then poured into chloroform, and then washed with a saturated sodium bicarbonate solution for 3 times. The solvent was then removed by rotary evaporation to obtain intermediate 1.

[0095] Step 2: 7g of layered oxide Na 0.44 MnO 2 , 2g Super P conductive carbon black, 1g polyvinylidene fluoride and 0.2g intermediate 1 are mixed evenly, and then 25g N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of aluminum foil and dried completely to form a positive electrode sheet;

[0096] Using sodium metal sheet as negative electrode;

[0097] Use fiberglass diaphragms as diaphragms;

[0098] A solution of 1 mol / L sodium hexafluorophosphate dissolved in a mixed solvent (propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1) was used as the electrolyte;

[0099] Step 3: Assemble the positive electrode, negative electrode, separator and electrolyte into a 26700 battery in a glove box filled with high-purity argon gas, then charge and discharge the 26700 battery once at 0.5C, and then fully charge it and let it stand for 2 hours to pass the needle puncture test.

[0100] The test results of the needle puncture test of Examples 1-3 and Comparative Examples 1-5 are shown in the following table:

[0101]

[0102] Referring to the data in the above table, according to the comparison between Examples 1-3 and Comparative Examples 1-5, it can be seen that the addition of sodium ferric pyrophosphate, chlorinated paraffin-70, DOPO, intermediate 1 and safety enhancer greatly improves the stability of the battery, thereby effectively solving the problem of needle puncture explosion of layered oxygen sodium ion batteries and significantly improving their safety.

[0103] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0104] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined in this application, they shall all fall within the protection scope of the present invention.

Claims

1. A modification method for improving the safety of acupuncture of layered oxygen sodium ion batteries, characterized in that: The following steps are involved: Step 1: DOPO and anhydrous toluene are added to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, and nitrogen is introduced for protection. The mixture is stirred for reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 20-30 min. Then, phosphorus pentasulfide is added and the temperature is raised to 60-65° C. and the stirring reaction is continued for 8-10 h. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation. Then, the mixture is poured into chloroform, and then washed with a saturated sodium bicarbonate solution for 2-3 times, and then the solvent is removed by rotary evaporation to obtain intermediate 1; Step 2: 4-nitroresorcinol, 3-bromo-1-propylene, anhydrous potassium carbonate, benzoquinone, toluene and N,N-dimethylformamide are added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen is introduced for protection. The mixture is stirred for reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 20-30 min, and then the temperature is raised to reflux and the stirring reaction is continued for 7-8 h. After the reaction is completed, the reaction product is cooled to room temperature, and then washed with saturated brine and ice water for 2-3 times in sequence, and then the solvent is removed by rotary evaporation to obtain intermediate 2; Step 3: Add intermediate 2, reduced iron powder, hydrochloric acid solution, anhydrous ethanol, anhydrous acetone and deionized water to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introduce nitrogen protection, stir the reaction at a temperature of 25-30°C and a stirring rate of 300-400r / min for 20-30min, then heat to 85-95°C and continue stirring the reaction for 4-5h. After the reaction is completed, cool the reaction product to room temperature, then vacuum filter, adjust the filtrate to pH 7.5-8 with sodium hydroxide solution, and then remove the solvent by rotary evaporation to obtain intermediate 3; Step 4: Add intermediate 3, hexachlorocyclotriphosphazene and ethyl acetate to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir and react for 20-30 minutes at a temperature of -5-0°C and a stirring rate of 300-400r / min, then heat to 25-30°C and continue stirring and reacting for 1-2 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain intermediate 4; Step 5: Add intermediate 1, intermediate 4, triethylamine and dioxane to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir the reaction at a temperature of 40-45°C and a stirring rate of 300-400r / min for 40-60min, then heat to 85-90°C and continue stirring the reaction for 15-20h. After the reaction is completed, the reaction product is cooled to room temperature, then washed with distilled water 2-3 times, and then rotary evaporated to remove the solvent to obtain a safety enhancer; Step 6: Layered oxide Na 0.44 MnO2, Super P conductive carbon black, polyvinylidene fluoride and safety enhancer are mixed evenly in a mass ratio of 7:2:1:0.2, and then N-methylpyrrolidone is added and mixed evenly to form a positive electrode slurry. The positive electrode slurry is then coated on the surface of aluminum foil and dried completely to form a positive electrode sheet; Step 7: Assemble the positive electrode, negative electrode, separator and electrolyte into a battery in a glove box filled with high-purity argon gas, and then subject the battery to a needle puncture test.

2. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 1, characterized in that: The usage ratio of the DOPO, anhydrous toluene and phosphorus pentasulfide in step 1 is 10 mmol: 30-35 mL: 10-12 mmol.

3. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 1, characterized in that: The usage ratio of the 4-nitroresorcinol, 3-bromo-1-propylene, anhydrous potassium carbonate, benzoquinone, toluene and N,N-dimethylformamide in step 2 is 10 mmol: 20 mmol: 22-25 mL: 0.01-0.03 g: 20-30 mL: 35-40 mL.

4. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 1, characterized in that: The dosage ratio of the intermediate 2, reduced iron powder, hydrochloric acid solution, anhydrous ethanol, anhydrous acetone and deionized water in step 3 is 5g:11-13g:2-3mL:8-10mL:8-10mL:8-10mL.

5. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 1, characterized in that: The mass fraction of the hydrochloric acid solution in step 3 is 20-25%; the mass fraction of the sodium hydroxide solution is 10-15%.

6. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 1, characterized in that: The usage ratio of the intermediate 3, hexachlorocyclotriphosphazene and ethyl acetate in step 4 is 60mmol:10mmol:70-80mL.

7. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 1, characterized in that: The usage ratio of the intermediate 1, intermediate 4, triethylamine and dioxane in step 5 is 60 mmol: 10 mmol: 2.5-3.5 g: 90-100 mL.

8. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 1, characterized in that: The layered oxide Na in step 6 0.44 The mass ratio of MnO2, Super P conductive carbon black, polyvinylidene fluoride, safety enhancer and N-methylpyrrolidone is 7:2:1:0.2:

25.

9. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 1, characterized in that: The negative electrode sheet in step seven is a sodium metal sheet; The diaphragm is a glass fiber diaphragm; The electrolyte is a solution of sodium hexafluorophosphate with a concentration of 1 mol / L dissolved in a mixed solvent.

10. A modification method for improving the acupuncture safety of layered oxygen sodium ion batteries according to claim 9, characterized in that: The mixed solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:2:1.

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