A high cycle performance sodium ion battery electrolyte and preparation method thereof

Abstract

The invention discloses a sodium ion battery electrolyte with high cycle performance and a preparation method thereof, comprising the following steps: dissolving a sodium salt in an organic solvent, mixing to obtain a sodium salt solution; adding a film former, a flame retardant and an additive to the sodium salt solution, and mixing evenly to obtain the electrolyte; the additive is obtained by amino-propylene addition reaction of tri-n-butyl (1-propylene) tin and 2,3,5,6-tetra (amino) p-benzoquinone, and then reacting with 1,2-dimercapto-o-carborane to generate thiol-propylene addition reaction. The present invention optimizes the composition and preparation process of the electrolyte, and the obtained sodium ion battery electrolyte shows excellent stability in multiple cycle tests, and the capacity retention rate is significantly improved. When the number of cycles reaches more than 1000 times, the capacity decay is less than 5%. The electrolyte also has good low temperature performance and thermal stability, and can work normally in a wide temperature range of 20 ° C to 60 ° C.

Description

Technical Field

[0001] The invention relates to the technical field of sodium ion battery electrolyte, in particular to a sodium ion battery electrolyte with high cycle performance and a preparation method thereof. Background Art

[0002] As an alternative technology to lithium-ion batteries, sodium-ion batteries (SIBs) have the advantages of abundant resources and low cost. Sodium is much more abundant in the earth's crust than lithium and is widely distributed, which makes sodium-ion batteries potentially an affordable energy storage technology. In addition, the voltage platform and chemical properties of sodium-ion batteries are similar to those of lithium-ion batteries, so they have great compatibility in material systems and battery design.

[0003] The patent application with publication number CN103715453A discloses a sodium ion battery system, a method for using a sodium ion battery, and a method for manufacturing a sodium ion battery. The invention provides a sodium ion battery system capable of achieving high capacity. That is, the sodium ion battery system comprises a sodium ion battery and a charging control unit, and the negative electrode active material is Na2Ti6O 13 The charge control unit controls the current and the potential of the negative electrode active material so that in addition to the Na2Ti6O 13 In addition to the first Na insertion reaction in the crystal phase, a second Na insertion reaction on the lower potential side also occurs.

[0004] The patent application with publication number CN111354924A discloses a sodium ion battery positive electrode active material, a sodium ion battery positive electrode material, a sodium ion battery positive electrode and a sodium ion battery and a preparation method, and relates to the technical field of sodium ion battery positive electrode active material. The sodium ion battery positive electrode active material includes Na2Fe(C2O4)(SO4)•2H2O; it alleviates the technical problem that the existing layered oxides and organic positive electrode active materials cannot simultaneously meet the high theoretical capacity of sodium ion batteries and ideal structural stability.

[0005] Although sodium-ion batteries have significant advantages, they still face several technical challenges in commercial applications:

[0006] 1. Insufficient cycle performance: Sodium ions have low conductivity in the electrolyte and easily form an unstable passivation film on the electrode surface, which increases the internal resistance of the battery and causes capacity decay.

[0007] 2. Electrolyte stability: During long-term cycling, the solvents and additives in the electrolyte are easily decomposed or react with sodium salts to form an unstable interface layer, which poses challenges to the battery life and safety. Summary of the invention

[0008] In view of this, the present application provides a method for preparing a sodium ion battery electrolyte with high cycle performance, which is used to solve the problems of insufficient cycle performance and unstable electrolyte in the prior art.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for preparing a sodium ion battery electrolyte with high cycle performance, comprising the following steps:

[0011] (1) dissolving a sodium salt in an organic solvent and mixing the mixture to obtain a sodium salt solution;

[0012] (2) adding a film-forming agent, a flame retardant and an additive to the sodium salt solution in step (1), and mixing them evenly to obtain the sodium ion battery electrolyte with high cycle performance;

[0013] The additive is obtained by subjecting tri-n-butyl (1-propenyl) tin and 2,3,5,6-tetra(amino)-p-benzoquinone to an amino-propene addition reaction, and then reacting with 1,2-dimercapto-o-carborane to generate a mercapto-propene addition reaction.

[0014] In some embodiments of the present invention, in step (1), the sodium salt is at least one of sodium hexafluorophosphate (NaPF6), sodium trifluoromethanesulfonate (NaCF3SO3), sodium perfluorobutane sulfonate (NaPFBS), sodium difluorosulfonimide (NaFSI), and sodium fluoroacetimide (NaTFSI).

[0015] The organic solvent is at least one of propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), and ethylene glycol dimethyl ether (DME).

[0016] In some embodiments of the present invention, in step (1) and step (2), the mixing method is stirring;

[0017] The stirring speed in step (1) is 300-500 rpm, and the stirring time is 30-60 min; the stirring speed in step (2) is 200-300 rpm, and the stirring time is 45-60 min.

[0018] In some embodiments of the present invention, the film former is at least one of ethylene carbonate (EC), vinyl sulfate (VC), and fluorosulfur carbonate (FEC).

[0019] The flame retardant is at least one of triethyl phosphate (TEP), trimethyl phosphate (TMP) and trimethyl sulfate.

[0020] Preferably, the addition reaction conditions in step (2) are: at a temperature of 60-70° C. and for 70-120 min.

[0021] Specifically, the preparation method of the additive is:

[0022] By weight, 33-66 parts of tri-n-butyl (1-propenyl) tin, 10-16 parts of sodium ethoxide, 200-300 parts of toluene, 10-18 parts of 2,3,5,6-tetrakis (amino) p-benzoquinone and 0.05-0.5 parts of 1,2-dimercapto-o-carborane are mixed, reacted at a temperature of 60-70° C. for 70-120 minutes, and toluene is removed by distillation to obtain the additive.

[0023] Reaction mechanism of electrolyte additives:

[0024] In the first reaction path, tri-n-butyl (1-propenyl) tin and 2,3,5,6-tetra(amino)-benzoquinone undergo an amino-propene addition reaction. This reaction not only increases the nitrogen content in the electrolyte, but also improves the solvation layer structure of sodium ions. This improvement helps to improve the cycle stability of the battery, making the migration of sodium ions in the electrolyte more efficient and reducing energy loss.

[0025] The second reaction pathway involves the introduction of 1,2-dimercapto-o-carborane, which is carried out through a mercapto-propylene addition reaction. This step increases the boron content in the electrolyte, significantly improving the thermal stability of the electrolyte and the transmission efficiency of sodium ions. The addition of boron also helps to optimize the overall performance of the electrolyte and ensure that the battery can operate stably over a wider temperature range.

[0026] The two key ingredients of this new additive: tin and benzoquinone. By promoting the formation of a more stable electrolyte interface (SEI), it further enhances the protection of electrode materials. This protection mechanism can effectively extend the service life of the battery, reduce the frequency of maintenance and replacement, and thus reduce the long-term use cost.

[0027] In some embodiments of the present invention, the high cycle performance sodium ion battery electrolyte obtained in step (2) is filtered through a microporous filter membrane to remove insoluble matter, and the obtained electrolyte can be sealed and stored under an inert atmosphere. The pore size of the microporous filter membrane is 0.20-0.22 μm, and the filtration pressure is 0.1-0.3 MPa.

[0028] In some embodiments of the present invention, 100-140 parts of organic solvent, 30-50 parts of sodium salt, 5-10 parts of film former, 7-12 parts of flame retardant and 3-6 parts of additives are used by weight.

[0029] The present invention also provides a sodium ion battery electrolyte with high cycle performance prepared by the preparation method.

[0030] Beneficial effects of the present invention:

[0031] By optimizing the composition and preparation process of the electrolyte, the sodium ion battery electrolyte of the present invention shows excellent stability in multiple cycle tests, and the capacity retention rate is significantly improved. When the number of cycles reaches more than 1,000 times, the capacity decay is less than 5%. In addition, the electrolyte of the present invention has good low-temperature performance and thermal stability, and can work normally in a wide temperature range of -20°C to 60°C. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0033] Performance evaluation:

[0034] 1.Battery assembly:

[0035] Positive electrode material: Sodium oxide layered structure material (NaNi 0.5 Mn 0.3 Co 0.2 O2, referred to as NMC). Negative electrode material: hard carbon material. Diaphragm: polypropylene diaphragm. Battery type: CR2032 button battery.

[0036] 2. Cycle performance test

[0037] Test equipment: Arbin battery test system was used.

[0038] Test temperature: Room temperature (25°C).

[0039] Charge and discharge conditions: The battery was tested for charge and discharge cycles at a rate of 0.2C in the voltage range of 2.5V to 4.0V.

[0040] Test objective: Perform 1000 cycle tests and record the change in battery capacity after each cycle.

[0041] 3. Low temperature performance test

[0042] Test temperature: Tested in -20°C environment.

[0043] Test conditions: The battery is charged and discharged in the voltage range of 2.5V to 4.0V at a rate of 0.1C.

[0044] Test objective: Conduct 50 cycle tests and record the capacity retention rate and charge and discharge efficiency of the battery at low temperatures.

[0045] 4. Thermal stability test

[0046] Test temperature: Tested at 25°C, 40°C, and 60°C.

[0047] Test conditions: The battery was cycled 100 times at 0.5C rate at the above temperature.

[0048] Test objective: Record the capacity retention rate of the battery at different temperatures and observe whether the electrolyte decomposes or the battery has internal short circuit.

[0049] Example 1

[0050] The preparation method of the additive in this embodiment is:

[0051] 33 g of tri-n-butyl(1-propenyl)tin, 10 g of sodium ethoxide, 200 g of toluene, 10 g of 2,3,5,6-tetrakis(amino)-p-benzoquinone, and 0.05 g of 1,2-dimercapto-o-carborane were mixed, reacted at 60° C. for 70 min, and toluene was removed by distillation to obtain an additive.

[0052] A method for preparing a sodium ion battery electrolyte with high cycle performance comprises the following steps:

[0053] At room temperature, 100 g PC and 30 g NaPF6 were added to the reaction container, stirring was started, and stirring was carried out at a stirring speed of 300 rpm for 30 min. Subsequently, 5 g EC, 7 g TEP and 3 g additives were added, and stirring was carried out at a stirring speed of 200 rpm for 45 min. The mixed solution was filtered through a microporous filter membrane with a pore size of 0.20 μm and a filtration pressure of 0.3 MPa to remove insoluble matter. The obtained electrolyte was sealed and stored under an inert atmosphere.

[0054] The test results of this embodiment are as follows:

[0055] 1. Cycle performance test results: 1000 times capacity retention rate: 95.2%;

[0056] 2. Low temperature performance test results: 50 times capacity retention rate: 95.6%, charge and discharge efficiency in low temperature environment: 98.1%;

[0057] 3. Thermal stability test: 25°C environment: capacity retention rate is 97.2%; 40°C environment: capacity retention rate is 95.4%, and the electrolyte remains stable; 60°C environment: capacity retention rate is 92.7%.

[0058] Example 2

[0059] The preparation method of the additive in this embodiment is:

[0060] 44 g of tri-n-butyl(1-propenyl)tin, 12 g of sodium ethoxide, 250 g of toluene, 13 g of 2,3,5,6-tetrakis(amino)-p-benzoquinone and 0.2 g of 1,2-dimercapto-o-carborane were mixed, reacted at 65° C. for 85 min, and toluene was removed by distillation to obtain an additive.

[0061] A method for preparing a sodium ion battery electrolyte with high cycle performance comprises the following steps:

[0062] At room temperature, 110 g of DMC and 40 g of NaCF3SO3 were added to the reaction container, stirring was started, and stirring was carried out at a stirring speed of 400 rpm for 40 min. Subsequently, 6.5 g of VC, 8.5 g of TMP and 4 g of additives were added, and stirring was carried out at a stirring speed of 250 rpm for 50 min. The mixed solution was filtered through a microporous filter membrane with a pore size of 0.21 μm and a filtration pressure of 0.2 MPa to remove insoluble matter. The obtained electrolyte was sealed and stored under an inert atmosphere.

[0063] The test results of this embodiment are as follows:

[0064] 1. Cycle performance test results: 1000 times capacity retention rate: 96.0%;

[0065] 2. Low temperature performance test results: 50 times capacity retention rate: 96.3%, charge and discharge efficiency in low temperature environment: 98.5%;

[0066] 3. Thermal stability test: 25°C environment: capacity retention rate is 97.7%; 40°C environment: capacity retention rate is 96.0%, and the electrolyte remains stable; 60°C environment: capacity retention rate is 93.4%.

[0067] Example 3

[0068] The preparation method of the additive in this embodiment is:

[0069] 55 g of tri-n-butyl(1-propenyl)tin, 14.5 g of sodium ethoxide, 280 g of toluene, 16 g of 2,3,5,6-tetrakis(amino)-p-benzoquinone and 0.4 g of 1,2-dimercapto-o-carborane were mixed, reacted at 65° C. for 110 min, and toluene was removed by distillation to obtain an additive.

[0070] A method for preparing a sodium ion battery electrolyte with high cycle performance comprises the following steps:

[0071] At room temperature, 125 g DEC and 40 g NaPFBS were added to the reaction container, stirring was started, and stirring was carried out at a stirring speed of 400 rpm for 50 min. Subsequently, 8.5 g FEC, 10.5 g trimethyl sulfate and 5 g additive were added, and stirring was carried out at a stirring speed of 250 rpm for 55 min. The mixed solution was filtered through a microporous filter membrane with a pore size of 0.22 μm and a filtration pressure of 0.3 MPa to remove insoluble matter. The obtained electrolyte was sealed and stored under an inert atmosphere.

[0072] The test results of this embodiment are as follows:

[0073] 1. Cycle performance test results: 1000 times capacity retention rate: 96.2%;

[0074] 2. Low temperature performance test results: 50 times capacity retention rate: 96.4%, charge and discharge efficiency in low temperature environment: 98.7%;

[0075] 3. Thermal stability test: 25°C environment: capacity retention rate is 97.9%; 40°C environment: capacity retention rate is 96.2%, and the electrolyte remains stable; 60°C environment: capacity retention rate is 93.5%.

[0076] Example 4

[0077] The preparation method of the additive in this embodiment is:

[0078] 66 g of tri-n-butyl(1-propenyl)tin, 16 g of sodium ethoxide, 300 g of toluene, 18 g of 2,3,5,6-tetrakis(amino)-p-benzoquinone and 0.5 g of 1,2-dimercapto-o-carborane were mixed, reacted at 70° C. for 120 min, and toluene was removed by distillation to obtain an additive.

[0079] A method for preparing a sodium ion battery electrolyte with high cycle performance comprises the following steps:

[0080] At room temperature, 140 g of EMC and 50 g of NaFSI were added to the reaction container, stirring was started, and stirring was carried out at a stirring speed of 500 rpm for 60 min. Subsequently, 10 g of FEC, 12 g of trimethyl sulfate and 6 g of additives were added, and stirring was carried out at a stirring speed of 300 rpm for 60 min. The mixed solution was filtered through a microporous filter membrane with a pore size of 0.22 μm and a filtration pressure of 0.3 MPa to remove insoluble matter. The obtained electrolyte was sealed and stored under an inert atmosphere.

[0081] The test results of this embodiment are as follows:

[0082] 1. Cycle performance test results: 1000 times capacity retention rate: 96.8%;

[0083] 2. Low temperature performance test results: 50 times capacity retention rate: 96.8%, charge and discharge efficiency in low temperature environment: 99.0%;

[0084] 3. Thermal stability test: 25°C environment: capacity retention rate is 98.3%; 40°C environment: capacity retention rate is 96.8%, and the electrolyte remains stable; 60°C environment: capacity retention rate is 94.0%.

[0085] Comparative Example 1

[0086] A method for preparing a sodium ion battery electrolyte with high cycle performance comprises the following steps:

[0087] At room temperature, 100 g PC and 30 g NaPF6 were added to the reaction container, stirring was started, and stirring was carried out at a stirring speed of 300 rpm for 30 min. Subsequently, 5 g EC and 7 g TEP were added, and stirring was carried out at a stirring speed of 200 rpm for 45 min. The mixed solution was filtered through a microporous filter membrane with a pore size of 0.20 μm and a filtration pressure of 0.3 MPa to remove insoluble matter. The obtained electrolyte was sealed and stored under an inert atmosphere.

[0088] The test results of this comparative example:

[0089] 1. Cycle performance test results: 1000 times capacity retention rate: 90.4%;

[0090] 2. Low temperature performance test results: 50 times capacity retention rate: 89.2%, charge and discharge efficiency in low temperature environment: 95.5%;

[0091] 3. Thermal stability test: 25°C environment: capacity retention rate is 94.3%; 40°C environment: capacity retention rate is 92.1%, and the electrolyte remains stable; 60°C environment: capacity retention rate is 87.6%.

[0092] Comparative Example 2

[0093] The preparation method of the additive in this comparative example is:

[0094] 33 g of tri-n-butyl(1-propenyl)tin, 10 g of sodium ethoxide, 200 g of toluene and 10 g of 2,3,5,6-tetra(amino)-p-benzoquinone were mixed, reacted at 60° C. for 70 min, and toluene was removed by distillation to obtain an additive.

[0095] A method for preparing a sodium ion battery electrolyte with high cycle performance comprises the following steps:

[0096] At room temperature, 100 g PC and 30 g NaPF6 were added to the reaction container, stirring was started, and stirring was carried out at a stirring speed of 300 rpm for 30 min. Subsequently, 5 g EC, 7 g TEP and 3 g additives were added, and stirring was carried out at a stirring speed of 200 rpm for 45 min. The mixed solution was filtered through a microporous filter membrane with a pore size of 0.20 μm and a filtration pressure of 0.3 MPa to remove insoluble matter. The obtained electrolyte was sealed and stored under an inert atmosphere.

[0097] The test results of this comparative example:

[0098] 1. Cycle performance test results: 1000 times capacity retention rate: 93.3%;

[0099] 2. Low temperature performance test results: 50 times capacity retention rate: 93.0%, charge and discharge efficiency in low temperature environment: 97.6%;

[0100] 3. Thermal stability test: 25°C environment: capacity retention rate is 96.2%; 40°C environment: capacity retention rate is 94.1%, and the electrolyte remains stable; 60°C environment: capacity retention rate is 91.2%.

[0101] Comparative Example 3

[0102] The preparation method of the additive in this comparative example is:

[0103] 33 g of tri-n-butyl(1-propenyl)tin, 10 g of sodium ethoxide, 200 g of toluene and 0.05 g of 1,2-dimercapto-o-carborane were mixed, reacted at 60° C. for 70 min, and toluene was removed by distillation to obtain an additive.

[0104] A method for preparing a sodium ion battery electrolyte with high cycle performance comprises the following steps:

[0105] At room temperature, 100 g PC and 30 g NaPF6 were added to the reaction container, stirring was started, and stirring was carried out at a stirring speed of 300 rpm for 30 min. Subsequently, 5 g EC, 7 g TEP and 3 g additives were added, and stirring was carried out at a stirring speed of 200 rpm for 45 min. The mixed solution was filtered through a microporous filter membrane with a pore size of 0.20 μm and a filtration pressure of 0.3 MPa to remove insoluble matter. The obtained electrolyte was sealed and stored under an inert atmosphere.

[0106] The test results of this comparative example:

[0107] 1. Cycle performance test results: 1000 times capacity retention rate: 93.0%;

[0108] 2. Low temperature performance test results: 50 times capacity retention rate: 93.1%, charge and discharge efficiency in low temperature environment: 97.3%;

[0109] 3. Thermal stability test: 25°C environment: capacity retention rate is 96.0%; 40°C environment: capacity retention rate is 93.8%, and the electrolyte remains stable; 60°C environment: capacity retention rate is 91.1%.

[0110] In summary, it can be seen from the test results of the above embodiments and comparative examples that the sodium ion battery electrolyte of the present invention is excellent in improving battery cycle performance, low temperature performance and thermal stability. The electrolyte can significantly improve the service life of the sodium ion battery and expand its applicable operating temperature range, thus having a wide range of application prospects.

[0111] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for preparing a sodium ion battery electrolyte with high cycle performance, characterized in that: The following steps are involved: (1) dissolving a sodium salt in an organic solvent and mixing the mixture to obtain a sodium salt solution; (2) adding a film-forming agent, a flame retardant and an additive to the sodium salt solution in step (1), and mixing them evenly to obtain the sodium ion battery electrolyte with high cycle performance; The preparation method of the additive is: By weight, 33-66 parts of tri-n-butyl (1-propenyl) tin, 10-16 parts of sodium ethoxide, 200-300 parts of toluene, 10-18 parts of 2,3,5,6-tetrakis (amino) p-benzoquinone and 0.05-0.5 parts of 1,2-dimercapto-o-carborane are mixed, reacted at a temperature of 60-70° C. for 70-120 minutes, and toluene is removed by distillation to obtain the additive.

2. The method for preparing a sodium ion battery electrolyte with high cycle performance according to claim 1, characterized in that: In step (1), the sodium salt is at least one of sodium hexafluorophosphate, sodium trifluoromethanesulfonate, sodium perfluorobutanesulfonate, sodium difluorosulfonimide, and sodium fluoroacetimide. The organic solvent is at least one of propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate and ethylene glycol dimethyl ether.

3. The method for preparing a sodium ion battery electrolyte with high cycle performance according to claim 1, characterized in that: In step (1) and step (2), the mixing method is stirring; The stirring speed in step (1) is 300-500 rpm, and the stirring time is 30-60 min; the stirring speed in step (2) is 200-300 rpm, and the stirring time is 45-60 min.

4. The method for preparing a sodium ion battery electrolyte with high cycle performance according to claim 1, characterized in that: The film-forming agent is at least one of ethylene carbonate, ethylene sulfate, and thiofluorocarbonate. The flame retardant is at least one of triethyl phosphate, trimethyl phosphate and trimethyl sulfate.

5. The method for preparing a sodium ion battery electrolyte with high cycle performance according to claim 1, characterized in that: The high cycle performance sodium ion battery electrolyte obtained in step (2) is filtered through a microporous filter membrane, wherein the pore size of the microporous filter membrane is 0.20-0.22 μm and the filtration pressure is 0.1-0.3 MPa.

6. The method for preparing a sodium ion battery electrolyte with high cycle performance according to claim 1, characterized in that: By weight, 100-140 parts of organic solvent, 30-50 parts of sodium salt, 5-10 parts of film former, 7-12 parts of flame retardant and 3-6 parts of additives are used.

7. A sodium ion battery electrolyte with high cycle performance prepared by the preparation method according to any one of claims 1 to 6.