Low-temperature performance electrolyte, preparation method of electrolyte, battery and electronic equipment

Abstract

The invention relates to the technical field of battery electrolytes, and discloses a low-temperature performance electrolyte, a preparation method of the electrolyte, a battery and electronic equipment. The method comprises the following steps: uniformly mixing a solvent, a lithium salt, an ionic liquid and an additive to prepare the electrolyte with low-temperature performance; the ionic liquid is imidazole ionic liquid or pyridine ionic liquid; and the additive is polysiloxane. The mixed solution of polysiloxane and the ionic liquid is adopted as the mixed additive, the main chain structure of polysiloxane is formed by alternating silicon atoms and oxygen atoms, and the special structure has a transmission effect on transportation of lithium ions, so that the migration speed of the lithium ions between the positive electrode and the negative electrode is greatly increased, and the conductivity of the lithium ion battery is improved. And the ionic liquid has the advantages of low volatility, non-inflammability, good ionic conductivity, wide operable temperature range and the like, so that the prepared electrolyte has excellent electrochemical performance even in a low-temperature environment through combination of the ionic liquid and the electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrolytes, and in particular to a low-temperature performance electrolyte, a method for preparing the electrolyte, a battery and an electronic device. Background Art

[0002] Under low temperature conditions, the activity of active substances inside the battery weakens, the internal resistance of the battery increases, and the chemical reaction rate slows down, which slows down the diffusion of ions during the charging process. Under low temperature conditions, the interface stability will also be affected, and lithium precipitation may occur, causing internal short circuit or spontaneous combustion of the battery.

[0003] In order to reduce the impact of low temperature on the normal use of the battery, corresponding countermeasures should be taken to improve the battery's low temperature resistance and protect and extend the battery's service life.

[0004] The Chinese invention patent with announcement number CN103219544B, "A low-temperature electrolyte for ternary power lithium-ion batteries and preparation method", uses low-melting-point small-molecule linear esters as additives on the basis of conventional solvents and lithium salts, effectively solving the problem of low low-temperature discharge efficiency of current lithium-ion batteries, but other performance of lithium-ion batteries at low temperatures is still insufficient; the Chinese invention patent application with publication number CN 105811003 A, "A low-temperature electrolyte", uses cyclic carbonate and chain carboxylate as basic solvents, and mixes them with lithium to obtain an electrolyte with low-temperature resistance, but the performance of lithium-ion batteries of this technical solution at low temperatures still needs to be improved.

[0005] Therefore, there is an urgent need for a method for preparing a low-temperature performance electrolyte to solve the above-mentioned technical problems. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for preparing an electrolyte with low-temperature resistance. By introducing a mixed additive of polysiloxane and ionic liquid, lithium ions can be quickly transferred in the electrolyte even under low temperature conditions and have a higher ionic conductivity.

[0007] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0008] The method for preparing a low-temperature performance electrolyte comprises the following steps:

[0009] The solvent, lithium salt, ionic liquid and additive are uniformly mixed to prepare an electrolyte with low temperature performance;

[0010] The ionic liquid is an imidazole ionic liquid or a pyridine ionic liquid; and the additive is polysiloxane.

[0011] Specifically, the method for preparing the low temperature performance electrolyte comprises the following steps:

[0012] Stirring the solvent and the lithium salt uniformly to obtain a first mixed solvent;

[0013] The ionic liquid and the additive are mixed and then subjected to ultrasound to obtain a second mixed solvent; the ionic liquid is an imidazole ionic liquid or a pyridine ionic liquid; and the additive is polysiloxane;

[0014] The second mixed solvent is added to the first mixed solvent, stirred evenly and then allowed to stand to obtain an electrolyte with low temperature performance.

[0015] Preferably, the molar ratio of lithium salt to solvent is 1:(22.1-22.7).

[0016] Preferably, the solvent is at least one of EC (ethylene carbonate), PC (propylene carbonate), DMC (dimethyl carbonate), DEC (diethyl carbonate), and EMC (ethyl methyl carbonate).

[0017] Preferably, the lithium salt is at least one of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), and LiFSI (lithium bis(fluorosulfonyl)imide).

[0018] More preferably, the lithium salt is LiPF6 or LiFSI.

[0019] Preferably, the polysiloxane is at least one of hydroxy polysiloxane, alkenyl polysiloxane and methyl polysiloxane.

[0020] Preferably, the solvent is a mixture of EC, DEC and EMC, and the molar ratio of EC:DEC:EMC is (1.78-1.91):(0.95-1.10):(1.60-1.72).

[0021] Preferably, the mass ratio of the additive to the ionic liquid is 1:(3-4).

[0022] Preferably, the cation of the imidazolium ionic liquid is R1R2Im, wherein R1 and R2 are alkyl substituents of the imidazolium cation, and Im represents an imidazole ring; the anion of the imidazolium ionic liquid is the same as the lithium salt anion;

[0023] The cation of the pyridine ionic liquid is RPy, wherein R represents a substituent (alkyl, alkoxy, etc.) on the pyridine ring, and Py represents the pyridine ring; the anion of the pyridine ionic liquid is the same as the anion of the lithium salt.

[0024] Preferably, the preparation process of the low-temperature performance electrolyte is carried out in a glove box environment; the glove box environment is: the atmosphere in the glove box is a mixture of argon and hydrogen, the moisture content in the glove box is less than 5ppm, and the oxygen content in the glove box is less than 5ppm.

[0025] Preferably, the preparation process of the second mixed solvent is: in a glove box environment, take the ionic liquid into an aluminum bottle, then add additives, seal it and transfer it out of the glove box, and perform ultrasound in a dry room environment; the dry room environment is: temperature 20-25°C, humidity 50%-60% RH; ultrasound frequency is 20-25kHz, and ultrasound time is 1-1.5h.

[0026] Preferably, the total mass of the ionic liquid and the additive is 4.0-5.3% of the mass of the solvent.

[0027] Preferably, the stirring is carried out by magnetic stirring, the stirring rate is 200-250 r / min, and the stirring time is 0.5 h.

[0028] The present invention also provides a low-temperature performance electrolyte, which is prepared by the above-mentioned preparation method.

[0029] The present invention also provides a battery comprising the above-mentioned low-temperature performance electrolyte.

[0030] The present invention also provides an electronic device comprising the battery.

[0031] Working principle:

[0032] The present invention provides a method for preparing a low-temperature resistant battery electrolyte. The method uses a mixed liquid of polysiloxane and ionic liquid as a mixed additive. The main chain structure of polysiloxane is composed of alternating silicon atoms and oxygen atoms. The special structure plays a transmission role in the transportation of lithium ions, greatly improving the speed of lithium ion migration between positive and negative electrodes. The ionic liquid has the advantages of low volatility, non-flammability, good ionic conductivity, wide operating temperature range, etc. The combination of the two enables the prepared electrolyte to have excellent electrochemical properties even in a low-temperature environment.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention adopts a mixed liquid of polysiloxane and ionic liquid as a mixed additive. The main chain structure of polysiloxane is composed of alternating silicon atoms and oxygen atoms. This special structure plays a transmission role in the transportation of lithium ions, greatly improving the migration speed of lithium ions between the positive and negative electrodes. The ionic liquid has the advantages of low volatility, non-flammability, good ionic conductivity, and a wide operating temperature range. The combination of the two enables the prepared electrolyte to have excellent electrochemical properties even in a low temperature environment. DETAILED DESCRIPTION

[0035] A method for preparing a low-temperature performance electrolyte comprises the following steps:

[0036] S1: In a glove box environment, EC, DEC and EMC are mixed in a certain proportion and stirred evenly to obtain a solvent; lithium salt is added and stirred evenly to obtain a first mixed solvent.

[0037] S2: In a glove box environment, take the ionic liquid into an aluminum bottle, then add a certain amount of polysiloxane to obtain a mixed additive, seal it and transfer it out of the glove box; in a dry room environment, perform ultrasound to obtain a second mixed solvent.

[0038] S3: In a glove box environment, the second mixed solvent is added to the first mixed solvent, stirred evenly with a magnetic stirrer, and allowed to stand for 24 hours to obtain an electrolyte with low-temperature performance.

[0039] The EC, DEC and EMC mixed solvent is mixed according to the molar ratio of EC:DEC:EMC=(1.78-1.91):(0.95-1.10):(1.60-1.72); the molar ratio of LiPF6 (or LiFSI or other lithium salts) to the solvent is 1:(22.1-22.7); the mass ratio of polysiloxane to ionic liquid is 1:(3-4); the mass of the second mixed solvent is 4.0-5.3% of the mass of the solvent mixed with EC, DEC and EMC in step S1.

[0040] The ionic liquid is an imidazole ionic liquid or a pyridine ionic liquid, the imidazole ionic liquid cation is R1R2Im (R1 and R2 are alkyl substituents of the imidazole cation, and Im represents the imidazole ring); the pyridine ionic liquid cation is RPy, R represents a substituent (alkyl, alkoxy, etc.) on the pyridine ring, and Py represents the pyridine ring; the anions of the two types of ionic liquids are the same as the lithium salt anions.

[0041] The glove box environment is: a mixture of argon and hydrogen, with a moisture content of less than 5ppm and an oxygen content of less than 5ppm; the dry room environment is: a temperature of 20-25°C and a humidity of 50%-60%RH; the magnetic stirring has a stirring rate of 200-250r / min and a stirring time of 0.5h; during the ultrasonic process, the ultrasonic frequency is set to 20-25kHz and the ultrasonic time is 1-1.5h.

[0042] The present invention is further described below with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0043] In the following embodiments, the glove box environment is: a mixture of argon and hydrogen, with a moisture content of less than 5 ppm and an oxygen content of less than 5 ppm; the dry room environment is: a temperature of 20-25° C. and a humidity of 50%-60% RH.

[0044] Embodiment 1:

[0045] A method for preparing a low-temperature performance electrolyte comprises the following steps:

[0046] Step 1: In a glove box environment, weigh 27.14g EC, 20.03g DEC and 28.9g EMC respectively and add them into a 250ml container bottle. After stirring evenly, add 12.16g LiPF6 and stir evenly.

[0047] Step 2: In a glove box environment, weigh 15.04g of R1R2Im-PF6 ionic liquid (R1 is -CH3, R2 is -C3H7) into an aluminum bottle, add 4.81g of hydroxy polysiloxane to obtain a mixed additive, seal it and transfer it out of the glove box. In a dry room environment, perform ultrasound for 1h, and the ultrasound frequency is set to 21kHz.

[0048] Step 3: In a glove box environment, take 4.0g of the mixed additives in step 2 and add them to all the mixed solvents obtained in step 1. Stir with a magnetic stirrer for 0.5h at a stirring rate of 220r / min. Then, after standing for 24h, an electrolyte with low temperature resistance is obtained.

[0049] Embodiment 2:

[0050] A method for preparing a low-temperature performance electrolyte comprises the following steps:

[0051] Step 1: In a glove box environment, weigh 62.35g EC, 46.02g DEC and 66.39g EMC respectively and add them into a 500ml container bottle. After stirring evenly, add 33.67g LiFSI and stir evenly.

[0052] Step 2: In a glove box, weigh 21 g of R1R2Im-FSI ionic liquid (R1 is -CH3, R2 is -C5H 11 ) in an aluminum bottle, and then add 4.4 g of methyl polysiloxane and 2.2 g of hydroxy polysiloxane to obtain a mixed additive, which is sealed and transferred out of the glove box. In a dry room environment, ultrasonic treatment is performed for 1 h, and the ultrasonic frequency is set to 23 kHz.

[0053] Step 3: In a glove box environment, take 9.2g of the mixed additives in step 2 and add it to the mixed solvent in step 1. Stir with a magnetic stirrer for 0.5h at a stirring rate of 210r / min. Then, after standing for 24h, an electrolyte with low temperature resistance was obtained.

[0054] Embodiment 3:

[0055] A method for preparing a low-temperature performance electrolyte comprises the following steps:

[0056] Step 1: In a glove box environment, weigh 105g EC, 77.49g DEC and 111.81g EMC respectively and add them into a 500ml container bottle. After stirring evenly, add 45.57g LiClO4 and stir evenly.

[0057] Step 2: In a glove box environment, weigh 34.41g RPy-PF6 (R is -C4H9, Py represents pyridine ring) into an aluminum bottle, add 9.72g alkenyl polysiloxane to obtain a mixed additive, seal it and transfer it out of the glove box. In a dry room environment, perform ultrasound for 1h, and the ultrasound frequency is set to 23kHz.

[0058] Step 3: In a glove box environment, take 14.72g of the mixed additives in step 2 and add it to the mixed solvent in step 1. Stir with a magnetic stirrer for 0.5h at a stirring rate of 230r / min. Then, after standing for 24h, an electrolyte with low temperature resistance was obtained.

[0059] Embodiment 4:

[0060] A method for preparing a low-temperature performance electrolyte comprises the following steps:

[0061] Step 1: In a glove box, weigh 500g of DMC and add it to a 1L container bottle, stir evenly, then add 106.33g of a mixture of LiFSI and LiBF4 and stir evenly. The mass ratio of LiFSI to LiBF4 is 1:0.7.

[0062] Step 2: In a glove box, weigh 79.95 g of RPy-PF6 (R is -C5H 11 , Py represents pyridine ring) in an aluminum bottle, and then add 23.91g of methyl polysiloxane to obtain a mixed additive, which is sealed and transferred out of the glove box. In a dry room environment, ultrasonication is performed for 1.5h, and the ultrasonic frequency is set to 22kHz.

[0063] Step 3: In a glove box environment, take 34.62g of the mixed additives in step 2 and add it to the mixed solvent in step 1. Stir with a magnetic stirrer for 0.5h at a stirring rate of 210r / min. Then, after standing for 24h, an electrolyte with low temperature resistance was obtained.

[0064] Comparative Example 1:

[0065] Step 1: In a glove box environment, weigh 58g EC, 42.81g DEC and 61.76g EMC respectively and add them into a 250mL container bottle. After stirring evenly, add 24.7g LiPF6 and stir evenly.

[0066] Step 2: Add 8.13 g of R1R2Im-PF6 ionic liquid (R1 is -CH3, R2 is -C5H 11 ), stirred with a magnetic stirrer for 0.5 h, and then allowed to stand for 24 h to obtain comparative electrolyte 1.

[0067] Comparative Example 2:

[0068] Step 1: In a glove box environment, weigh 146.72g EC, 108.28g DEC and 156.23g EMC respectively and add them into a 500mL container bottle. After stirring evenly, add 76.9g LiFSI and stir evenly.

[0069] Step 2: Add 20.56 g of alkenyl polysiloxane to the mixed solution in step 1, stir with a magnetic stirrer for 0.5 h, and then let stand for 24 h to obtain comparative electrolyte 2.

[0070] Comparative Example 3:

[0071] Step 1: In a glove box environment, weigh 203.88g EC, 150.47g DEC and 217.1g EMC respectively and add them into a 1L container bottle. After stirring evenly, add 86.81g LiPF6 and stir evenly.

[0072] Step 2: Add 28.57 g DTD (vinyl sulfate) to the mixed solution in step 1, stir with a magnetic stirrer for 0.5 h, and then let stand for 24 h to obtain comparative electrolyte 3.

[0073] Comparative Example 4:

[0074] Step 1: In a glove box environment, weigh 93.47g EC, 68.99g DEC and 99.53g EMC respectively and add them into a 500mL container bottle. After stirring evenly, add 39.81g LiPF6 and stir evenly.

[0075] Step 2: Add 13.1 g FEC (fluoroethylene carbonate) to the mixed solution in step 1, stir with a magnetic stirrer for 0.5 h, and then let stand for 24 h to obtain comparative electrolyte 4.

[0076] Comparative Example 5:

[0077] Step 1: In a glove box environment, weigh 164.31g EC, 121.28g DEC and 174.96g EMC respectively and add them into a 1L container bottle. After stirring evenly, add 69.97g LiPF6 and stir evenly.

[0078] Step 2: Add 23.03 g of RPy-PF6 (R is -C4H9, Py represents a pyridine ring) to the mixed solution in step 1, stir with a magnetic stirrer for 0.5 h, and then let stand for 24 h to obtain comparative electrolyte 5.

[0079] experiment

[0080] The 9 electrolytes of Examples 1-4 and Comparative Examples 1-5 were injected into a 4.8Ah soft-pack system with NCM613 / graphite as positive and negative electrodes under the same conditions to obtain a battery. The obtained battery was tested for the conductivity of the electrolyte (Table 1) and the capacity retention rate of the corresponding soft-pack battery (Table 2) at 25°C, 0°C, and -20°C.

[0081] Table 1 Conductivity test of electrolytes of Examples 1-4 and Comparative Examples 1-5 at different temperatures

[0082]

[0083] Table 2 Test results of soft-pack batteries corresponding to Examples 1-4 and Comparative Examples 1-5 at different temperatures

[0084]

[0085]

[0086] According to the test results of conductivity in Table 1, the conductivity of electrolytes with different formulations is not much different at room temperature. As the temperature decreases, the advantages of Examples 1-4 become gradually obvious. Electrolytes with different formulations are injected into soft-pack 4.8Ah NCM613 lithium-ion batteries, and the batteries are charged and discharged at 1C for 100 cycles at 25°C, 0°C, and -20°C. As the temperature decreases, the discharge capacity gradually decreases. When the battery is cycled to 500 cycles at -20°C, the capacity retention rate of the soft-pack battery corresponding to the mixed additive containing polysiloxane and ionic liquid can still be maintained at 76% ± 1%, while the capacity retention rate of the soft-pack battery corresponding to the comparative electrolyte is only 43% ± 3%.

[0087] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a low-temperature performance electrolyte, characterized in that: The following steps are included: The solvent, lithium salt, ionic liquid and additive are uniformly mixed to prepare an electrolyte with low temperature performance; The ionic liquid is an imidazole ionic liquid or a pyridine ionic liquid; and the additive is polysiloxane.

2. The method for preparing a low temperature performance electrolyte according to claim 1, characterized in that: The molar ratio of the lithium salt to the solvent is 1:(22.1-22.7); the mass of the ionic liquid and the additive is 4.0-5.3% of the mass of the solvent.

3. The method for preparing a low temperature performance electrolyte according to claim 1, characterized in that: The solvent is at least one of EC, PC, DMC, DEC, and EMC; the lithium salt is at least one of LiPF6, LiBF4, LiClO4, and LiFSI.

4. The method for preparing a low temperature performance electrolyte according to claim 1, characterized in that: The polysiloxane is at least one of hydroxy polysiloxane, alkenyl polysiloxane and methyl polysiloxane.

5. The method for preparing a low temperature performance electrolyte according to claim 1, characterized in that: The solvent is a mixture of EC, DEC and EMC, and the molar ratio of EC:DEC:EMC is (1.78-1.91):(0.95-1.10):(1.60-1.72).

6. The method for preparing a low temperature performance electrolyte according to claim 1, characterized in that: The mass ratio of the additive to the ionic liquid is 1:(3-4).

7. The method for preparing a low temperature performance electrolyte according to claim 1, characterized in that: The cation of the imidazolium ionic liquid is R1R2Im, wherein R1 and R2 are alkyl substituents of the imidazolium cation, and Im represents an imidazole ring; the anion of the imidazolium ionic liquid is the same as the anion of the lithium salt; The cation of the pyridinium ionic liquid is RPy, wherein R represents a substituent on the pyridine ring, and Py represents the pyridine ring; the anion of the pyridinium ionic liquid is the same as the anion of the lithium salt.

8. A low temperature performance electrolyte, characterized in that: The preparation method is described in any one of claims 1 to 7.

9. A battery, characterized in that: The electrolyte in the battery is the electrolyte according to claim 8.

10. An electronic device, characterized in that: The electronic device comprises the battery according to claim 9.

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