Lithium ion battery electrolyte capable of ensuring low-temperature discharge characteristic and preparation method of lithium ion battery electrolyte

Abstract

The invention relates to the technical field of electrolyte preparation, and discloses a lithium ion battery electrolyte capable of ensuring low-temperature discharge characteristic, which comprises the following components in percentage by mass: 25% of propylene carbonate (PC), 35% of dimethyl carbonate (DMC), 20% of gamma-butyrolactone (GBL), 20% of ethyl acetate, 1.0 mol / L of lithium salt bis (trifluoromethanesulfonimide) (LiTFSI), 3% of additive 1, 3-propane sultone (PS) (mass fraction: 0.1% of sodium hydroxide (mass fraction: 0.1% of sodium hydroxide), and the balance of water. According to the present invention, the low temperature performance of the solution is improved, the unique solvent formula and the unique solvent ratio enable the electrolyte to have good fluidity in the low temperature environment, and the freezing point of the electrolyte is effectively reduced so as to ensure that the lithium ions can smoothly migrate between the electrodes at the low temperature, such that the lithium ion battery performance is improved, and the lithium ion battery performance is improved. The discharge performance of the battery under a low-temperature condition is obviously improved, and the application scene of the lithium ion battery is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of electrolyte preparation, in particular to a lithium ion battery electrolyte ensuring low-temperature discharge characteristics and a preparation method thereof. Background Art

[0002] With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, aerospace, polar scientific research and other fields, the requirements for their low-temperature performance are increasing. Traditional lithium-ion battery electrolytes often have problems such as increased viscosity, difficulty in ion migration, and even solidification at low temperatures, resulting in a sharp drop in battery capacity and poor discharge capacity in low-temperature environments, which cannot meet the use requirements under cold conditions. Common electrolyte solvent systems have insufficient performance at low temperatures. For example, some traditional solvents are prone to crystallization at low temperatures, which limits the movement of ions. At the same time, the ionic conductivity of traditional lithium salts at low temperatures is significantly reduced, and the SEI film formed by some electrolytes has poor stability at low temperatures and is easy to rupture, which leads to the intensification of side reactions between electrode materials and electrolytes, affecting the overall performance and life of the battery. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the deficiencies in the prior art, the present invention provides a lithium ion battery electrolyte and a preparation method thereof that ensure low-temperature discharge characteristics. The electrolyte has good fluidity in a low-temperature environment and effectively reduces the freezing point of the electrolyte, which ensures that lithium ions can smoothly migrate between electrodes at low temperatures, significantly improves the discharge performance of the battery under low-temperature conditions, and solves the problem that traditional lithium ion battery electrolytes often have increased viscosity, difficulty in ion migration, and even solidification at low temperatures, which causes the battery capacity to drop sharply in a low-temperature environment, the discharge capacity to deteriorate, and the problem of being unable to meet the use requirements under cold conditions.

[0005] (II) Technical solution

[0006] In order to achieve the above-mentioned electrolyte still has good fluidity under low temperature environment, the freezing point of the electrolyte is effectively reduced, which ensures that lithium ions can smoothly migrate between electrodes at low temperature and significantly improves the discharge performance of the battery under low temperature conditions. The present invention provides the following technical solution: a lithium ion battery electrolyte that ensures low-temperature discharge characteristics, including the following formula and ratio, solvent: propylene carbonate (PC) 25%, dimethyl carbonate (DMC) 35%, γ-butyrolactone (GBL) 20%, ethyl acetate 20%, lithium salt: lithium bistrifluoromethanesulfonyl imide (LiTFSI) 1.0 mol / L, additives: 1,3-propane sultone (PS) 3% (mass fraction, relative to the total amount of solvent), vinylene carbonate (VC) 2% (mass fraction, relative to the total amount of solvent).

[0007] Preferably, in the formula, the combination of multiple solvents can effectively reduce the freezing point of the electrolyte and improve the low-temperature fluidity. LiTFSI has good ionic conductivity at low temperatures. PS and VC as additives can optimize the interface between the electrode and the electrolyte and enhance the low-temperature discharge performance.

[0008] Preferably, a method for preparing a lithium-ion battery electrolyte that ensures low-temperature discharge characteristics comprises the following specific steps: S1 raw material preparation and pretreatment, in a drying room protected by high-purity argon (water and oxygen content is less than 0.05 ppm), the reactor, storage container, and pipeline are pre-baked at a temperature of 120-150° C. for 4-6 hours to remove adsorbed water;

[0009] S2 solvent mixing, using a combination of magnetic stirring and ultrasonic oscillation to mix the solvent, first stirring at a speed of 200-300 rpm for 20-30 minutes, then ultrasonic oscillation for 15-20 minutes, repeating this step 3 times to make the solvent mixing more uniform;

[0010] S3 lithium salt dissolution, slowly add LiTFSI into the mixed solvent, raise the temperature of the reactor to 30-40°C, and stir at 400-600 rpm for 1.5-2 hours to accelerate the dissolution of the lithium salt;

[0011] S4 additive addition, use a microinjection pump to slowly inject 1,3-propane sultone (PS) into the reactor at an injection rate of 0.5-1 ml / min, and stir for 20-30 minutes after the injection is completed;

[0012] S5 multi-stage filtration and impurity removal, first through the 0.45μm glass fiber filter membrane to remove large particles of impurities;

[0013] S6 packaging and storage: the electrolyte is packaged into special antistatic, light-proof, sealed packaging containers in a Class 100 purification environment, filled with high-purity argon gas for protection, and stored in a low-temperature dry environment below -20°C.

[0014] Preferably, the S1 raw material preparation and pretreatment further includes accurately weighing propylene carbonate (PC), dimethyl carbonate (DMC), γ-butyrolactone (GBL), and ethyl acetate, respectively, and putting them into the reactor after further removing water and impurities through a molecular sieve column.

[0015] Preferably, the S1 raw material preparation and pretreatment further includes accurately weighing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), drying it in a vacuum drying oven for later use, preparing 1,3-propane sultone (PS) and vinylene carbonate (VC), and drying them.

[0016] Preferably, the S4 additive is added by injecting vinylene carbonate (VC) with a microinjection pump at an injection speed of 0.3-0.8 ml / min, and stirring for 30-40 minutes after injection to ensure that the additive is evenly dispersed.

[0017] Preferably, the S5 multi-stage filtration removes impurities and large particles and then uses a 0.22 μm polytetrafluoroethylene (PTFE) filter membrane and a 0.1 μm ceramic filter membrane to filter in series to further improve the purity of the electrolyte.

[0018] (III) Beneficial effects

[0019] Compared with the prior art, the present invention provides a lithium ion battery electrolyte and a preparation method thereof that ensures low temperature discharge characteristics, and has the following beneficial effects:

[0020] 1. The lithium-ion battery electrolyte that ensures low-temperature discharge characteristics and its preparation method, the scheme has improved low-temperature performance, the unique solvent formula and ratio make the electrolyte still have good fluidity in a low-temperature environment, effectively reduce the freezing point of the electrolyte, which ensures that lithium ions can smoothly migrate between electrodes at low temperatures, significantly improves the discharge performance of the battery under low-temperature conditions, and expands the application scenarios of lithium-ion batteries, such as in electronic equipment and electric vehicles in cold areas.

[0021] 2. The lithium-ion battery electrolyte that ensures low-temperature discharge characteristics and its preparation method. The electrolyte produced by this solution has enhanced interface stability. The additives 1,3-propane sultone (PS) and vinylene carbonate (VC) interact with the electrode material to form a more stable, dense and ion-conductive solid electrolyte interface film (SEI film) on the electrode surface. This SEI film can not only effectively prevent further reaction between the electrode material and the electrolyte, reduce the capacity decay of the battery during the charge and discharge process, but also maintain stable electrochemical performance at low temperatures and improve the cycle life of the battery.

[0022] 3. The lithium-ion battery electrolyte that ensures low-temperature discharge characteristics and its preparation method, the electrolyte has excellent ionic conductivity, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is used as a lithium salt, which exhibits high ionic conductivity at low temperatures. At the same time, the optimized preparation process ensures that the lithium salt is completely and evenly dissolved in the solvent, further improving the overall ionic conductivity of the electrolyte, so that the battery can quickly and stably output electrical energy during low-temperature discharge.

[0023] 4. The lithium-ion battery electrolyte that ensures low-temperature discharge characteristics and its preparation method, the process achieves high purity and stability. The improved preparation process greatly reduces the impurity content in the electrolyte through strict raw material pretreatment and multi-stage filtration and impurity removal steps. The high-purity electrolyte reduces the interference of impurities on the internal electrochemical process of the battery, improves the consistency and stability of battery performance, and reduces the battery self-discharge rate and safety risks. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in 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 making creative work are within the scope of protection of the present invention.

[0025] The present invention provides a technical solution, specifically, a lithium-ion battery electrolyte that ensures low-temperature discharge characteristics, including the following formula and ratio, solvent: propylene carbonate (PC) 25%, dimethyl carbonate (DMC) 35%, γ-butyrolactone (GBL) 20%, ethyl acetate 20%, lithium salt: lithium bistrifluoromethanesulfonyl imide (LiTFSI) 1.0 mol / L, additives: 1,3-propane sultone (PS) 3% (mass fraction, relative to the total amount of solvent), vinylene carbonate (VC) 2% (mass fraction, relative to the total amount of solvent);

[0026] Among them, in this formula, the combination of multiple solvents can effectively reduce the freezing point of the electrolyte and improve the low-temperature fluidity. LiTFSI has good ionic conductivity at low temperatures. PS and VC as additives can optimize the interface between the electrode and the electrolyte and enhance the low-temperature discharge performance. In practical applications, further adjustments need to be made according to the specific battery system and use environment.

[0027] Furthermore, a method for preparing a lithium-ion battery electrolyte that ensures low-temperature discharge characteristics includes the following specific steps: S1 raw material preparation and pretreatment, in a drying room protected by high-purity argon gas (water and oxygen content is less than 0.05ppm), pre-baking the reactor, storage container, pipeline, etc., at a temperature of 120-150°C for 4-6 hours to remove adsorbed water;

[0028] Wherein, propylene carbonate (PC), dimethyl carbonate (DMC), γ-butyrolactone (GBL), and ethyl acetate are accurately weighed, passed through a molecular sieve column to further remove water and impurities, and then placed in a reaction kettle;

[0029] wherein, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is accurately weighed, dried in a vacuum drying oven and set aside; 1,3-propane sultone (PS) and vinylene carbonate (VC) are prepared and dried;

[0030] S2 solvent mixing, using a combination of magnetic stirring and ultrasonic oscillation to mix the solvent, first stirring at a speed of 200-300 rpm for 20-30 minutes, then ultrasonic oscillation for 15-20 minutes, repeating this step 3 times to make the solvent mixing more uniform;

[0031] S3 lithium salt dissolution, slowly add LiTFSI into the mixed solvent, raise the temperature of the reactor to 30-40°C, and stir at 400-600 rpm for 1.5-2 hours to accelerate the dissolution of the lithium salt;

[0032] S4 additive addition, use a microinjection pump to slowly inject 1,3-propane sultone (PS) into the reactor at an injection rate of 0.5-1 ml / min, and stir for 20-30 minutes after the injection is completed;

[0033] Among them, vinylene carbonate (VC) is also injected using a microinjection pump at an injection speed of 0.3-0.8 ml / min, and stirred for 30-40 minutes after injection to ensure that the additive is evenly dispersed;

[0034] S5 multi-stage filtration and impurity removal, first through the 0.45μm glass fiber filter membrane to remove large particles of impurities;

[0035] Among them, a 0.22 μm polytetrafluoroethylene (PTFE) filter membrane and a 0.1 μm ceramic filter membrane are used in series to further improve the purity of the electrolyte;

[0036] S6 packaging and storage: the electrolyte is packaged into special antistatic, light-proof, sealed packaging containers in a Class 100 purification environment, filled with high-purity argon gas for protection, and stored in a low-temperature dry environment below -20°C.

[0037] Furthermore, the low-temperature performance of this solution is improved. The unique solvent formula and ratio make the electrolyte still have good fluidity in low-temperature environment, effectively reducing the freezing point of the electrolyte, which ensures that lithium ions can migrate smoothly between electrodes at low temperatures, significantly improving the discharge performance of the battery under low-temperature conditions, and expanding the application scenarios of lithium-ion batteries, such as electronic equipment and electric vehicles in cold regions.

[0038] Furthermore, the electrolyte produced by this solution has enhanced interfacial stability. Through the interaction between the additives 1,3-propane sultone (PS) and vinylene carbonate (VC) and the electrode material, a more stable, dense and ion-conductive solid electrolyte interface film (SEI film) is formed on the electrode surface. This SEI film can not only effectively prevent further reaction between the electrode material and the electrolyte, reduce the capacity decay of the battery during the charge and discharge process, but also maintain stable electrochemical performance at low temperatures, thereby improving the cycle life of the battery.

[0039] Furthermore, the electrolyte has excellent ionic conductivity. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a lithium salt exhibits high ionic conductivity at low temperatures. At the same time, the optimized preparation process ensures that the lithium salt is completely and evenly dissolved in the solvent, further improving the overall ionic conductivity of the electrolyte, so that the battery can quickly and stably output electrical energy during low-temperature discharge.

[0040] Furthermore, the process achieves high purity and stability. The improved preparation process greatly reduces the impurity content in the electrolyte through strict raw material pretreatment, multi-stage filtration and impurity removal. The high-purity electrolyte reduces the interference of impurities on the internal electrochemical process of the battery, improves the consistency and stability of battery performance, and reduces the battery self-discharge rate and safety risks.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lithium ion battery electrolyte that ensures low temperature discharge characteristics, characterized in that: The invention comprises the following formula and proportion: solvent: propylene carbonate (PC) 25%, dimethyl carbonate (DMC) 35%, γ-butyrolactone (GBL) 20%, ethyl acetate 20%, lithium salt: lithium bistrifluoromethanesulfonyl imide (LiTFSI) 1.0 mol / L, additives: 1,3-propane sultone (PS) 3% (mass fraction, relative to the total amount of solvent), vinylene carbonate (VC) 2% (mass fraction, relative to the total amount of solvent).

2. The lithium-ion battery electrolyte for ensuring low-temperature discharge characteristics according to claim 1, characterized in that: In the formula, the combination of multiple solvents can effectively reduce the freezing point of the electrolyte and improve the low-temperature fluidity. LiTFSI has good ionic conductivity at low temperatures. PS and VC as additives can optimize the interface between the electrode and the electrolyte and enhance the low-temperature discharge performance.

3. A method for preparing a lithium ion battery electrolyte that ensures low temperature discharge characteristics, characterized in that: The method comprises the following specific steps: S1: raw material preparation and pretreatment: in a drying room protected by high-purity argon (water and oxygen content is less than 0.05 ppm), the reactor, storage container and pipeline are pre-baked at a temperature of 120-150° C. for 4-6 hours to remove adsorbed water; S2 solvent mixing, using a combination of magnetic stirring and ultrasonic oscillation to mix the solvent, first stirring at a speed of 200-300 rpm for 20-30 minutes, then ultrasonic oscillation for 15-20 minutes, repeating this step 3 times to make the solvent mixing more uniform; S3 lithium salt dissolution, slowly add LiTFSI into the mixed solvent, raise the temperature of the reactor to 30-40°C, and stir at a speed of 400-600 rpm for 1.5-2 hours to accelerate the dissolution of the lithium salt; S4 additive addition, use a microinjection pump to slowly inject 1,3-propane sultone (PS) into the reactor at an injection rate of 0.5-1 ml / min, and stir for 20-30 minutes after the injection is completed; S5 multi-stage filtration and impurity removal, first through the 0.45μm glass fiber filter membrane to remove large particles of impurities; S6 packaging and storage: the electrolyte is packaged into special antistatic, light-proof, sealed packaging containers in a Class 100 purification environment, filled with high-purity argon gas for protection, and stored in a low-temperature dry environment below -20°C.

4. The method for preparing a lithium ion battery electrolyte with low temperature discharge characteristics as claimed in claim 3, characterized in that: The S1 raw material preparation and pretreatment also includes accurately weighing propylene carbonate (PC), dimethyl carbonate (DMC), γ-butyrolactone (GBL), and ethyl acetate, respectively, and further removing water and impurities through a molecular sieve column before putting them into a reactor.

5. The method for preparing a lithium ion battery electrolyte with low temperature discharge characteristics as claimed in claim 3, characterized in that: The S1 raw material preparation and pretreatment also includes accurately weighing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), drying it in a vacuum drying oven and setting it aside, preparing 1,3-propane sultone (PS) and vinylene carbonate (VC), and drying them.

6. The method for preparing a lithium ion battery electrolyte with low temperature discharge characteristics as claimed in claim 3, characterized in that: The S4 additive is added by injecting vinylene carbonate (VC) with a microinjection pump at an injection speed of 0.3-0.8 ml / min. After injection, stirring is performed for 30-40 minutes to ensure that the additive is evenly dispersed.

7. The method for preparing a lithium ion battery electrolyte with low temperature discharge characteristics as claimed in claim 3, characterized in that: The S5 multi-stage filtration removes impurities and large particles and then uses a 0.22 μm polytetrafluoroethylene (PTFE) filter membrane and a 0.1 μm ceramic filter membrane in series to further improve the purity of the electrolyte.