CN115411359A - Gel electrolyte and application method thereof in lithium ion battery - Google Patents
Gel electrolyte and application method thereof in lithium ion battery Download PDFInfo
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- CN115411359A CN115411359A CN202211272040.2A CN202211272040A CN115411359A CN 115411359 A CN115411359 A CN 115411359A CN 202211272040 A CN202211272040 A CN 202211272040A CN 115411359 A CN115411359 A CN 115411359A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0085—Immobilising or gelification of electrolyte
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Condensed Matter Physics & Semiconductors (AREA)
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- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention discloses a gel electrolyte and a use method thereof in a lithium ion battery. The gel electrolyte consists of lithium salt, a non-aqueous solvent, a film-forming additive, a polymer monomer and a thermal initiator; injecting electrolyte into the battery, standing, performing formation, performing vacuum pumping on the battery after formation, pumping out a solvent in the battery by controlling the vacuum degree, adding a thermal initiator, performing hot-pressing polymerization on the battery, performing secondary formation, performing secondary pumping after high-temperature aging, pumping out gas generated by formation, and packaging to obtain the gel battery. Compared with the conventional gel electrolyte, the gel electrolyte forms a gradient solid electrolyte membrane on the surfaces of the anode and the cathode, so that the side reaction between the electrode material and the electrolyte can be reduced, and the cycle service life of the battery is prolonged.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery electrolyte, and particularly relates to gel electrolyte and a use method thereof in a lithium ion battery.
Background
The liquid electrolyte is generally composed of a lithium salt, an organic solvent and an additive, and is a very important part of a lithium ion secondary battery. However, since the organic solvent is a flowing liquid, there is a risk of liquid leakage. In addition, the organic solvent used in the liquid electrolyte is generally substances such as carbonic ester and carboxylic ester, which leads to poor high-temperature performance of the battery, and the flammability of the organic solvent causes potential safety hazards such as explosion of the battery. Compared with liquid electrolyte, the gel polymer electrolyte has the advantages of no liquid leakage, high cell hardness and high safety.
The polymer gel electrolyte is generally obtained by in-situ thermal polymerization. The general preparation method of the gel polymer electrolyte is as follows: the polymer monomer, the liquid electrolyte and the initiator are uniformly mixed, injected into a battery cell, and heated to gel, so that the polymer monomer is crosslinked into a polymer matrix with a net structure under the initiation of the initiator, and the liquid electrolyte is bound in the polymer matrix. Gel electrolytes employing thermal polymerization generally suffer from the following disadvantages: after in-situ thermal polymerization in the cell, the solvent in the electrolyte is present in a large amount in the polymer matrix, and although the ion conduction performance of the battery can be optimized, the presence of a large amount of non-aqueous solvent causes the gel battery to still have the risk of fire and explosion. Therefore, it is necessary to reduce the amount of the non-aqueous solvent remaining in the polymer in the gel battery, which is required for ion conduction, while also achieving the safety of the battery.
Disclosure of Invention
The invention aims to provide a gel electrolyte and a using method thereof in a lithium ion battery. The electrolyte adopts a twice formation process, a step-shaped interface film can be formed on the positive electrode and the negative electrode of the battery, the cycle life of the battery is prolonged, the content of a solvent in the gel electrolyte is controlled by vacuum air extraction, and the safety of the gel electrolyte at high temperature is improved.
A gel electrolyte is composed of lithium salt, non-aqueous solvent, film-forming additive, polymer monomer and thermal initiator.
The lithium salt is one or more of lithium difluorophosphoryl imide, lithium bistrifluorophosphorylimide, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorophosphate, lithium hexafluorophosphate or lithium tetrafluoroborate.
The non-aqueous solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, ethyl propionate, 1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 1, 2-dimethoxyethane, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl propionate, tetrahydrofuran and 2-methyltetrahydrofuran.
The film forming additive comprises a positive electrode film forming additive and/or a negative electrode film forming additive; the positive film-forming additive is any one or any combination of more than two of carbonate additives, sulfonate additives, sulfone additives, phosphate additives and lithium additives; the negative electrode film forming additive is any one or any combination of more than two of additives such as vinylene carbonate, ethylene carbonate, fluoroethylene carbonate and ethylene sulfite.
The polymer monomer is an ester monomer with unsaturated double bonds, and the addition amount is 0.5-6.5%.
The thermal initiator is selected from one or any combination of more than two of azodiisobutyronitrile, dibenzoyl peroxide, di (4-tert-butylcyclohexyl) peroxydicarbonate, lauroyl peroxide and diisopropyl peroxydicarbonate.
The application method of the gel electrolyte comprises the following steps:
(1) Preparing electrolyte with lithium salt solubility of 1-1.2mol/L of molar concentration; the electrolyte comprises a lithium salt, a non-aqueous solvent and a film-forming additive;
(2) Adding a polymer monomer, and uniformly stirring until the solution is clear to obtain a gel electrolyte containing the polymer monomer;
(3) Injecting the prepared gel electrolyte into a battery cell, standing, and performing formation step, wherein the upper limit of the formation voltage does not exceed the solvolysis voltage;
(4) Performing vacuum pumping on the formed gel electrolyte battery for 1-10s with the vacuum degree of the equipment being 50-100 kPa;
(5) Performing secondary liquid injection on the battery subjected to vacuum pumping in the step (4), wherein the electrolyte is a thermal initiator dissolved in a solvent, and the dosage of the thermal initiator accounts for 0.02-1% of the total dosage of the electrolyte;
(6) Standing at normal temperature for 24-72h, performing hot-pressing polymerization and secondary formation, wherein the hot-pressing temperature is 70-85 ℃, the hot-pressing time is 0.5-2h, the pressure is 450-750kg, and the formation voltage is the voltage of a battery platform;
(7) And (5) aging the secondary formed battery in the step (6), and performing vacuum pumping again after aging to finally finish battery packaging.
And (4) after the gel electrolyte is injected into the battery cell in the step (3), standing for 24-72h at the temperature of 25-45 ℃, and then performing a formation process step at the temperature of 25-45 ℃, wherein the formation voltage is less than 3.2V, and the formation current is 0.02C/0.05C/0.1C.
And (7) ageing the battery after secondary formation, wherein the ageing temperature is 45-55 ℃, the ageing time is 4-72h, the aged battery is subjected to a vacuum pumping step, the vacuum degree of equipment is 50-100kPa, and the vacuum pumping time is kept for 1-10s.
The invention has the beneficial effects that: compared with the conventional gel electrolyte, the gel electrolyte forms a gradient solid electrolyte membrane on the surfaces of the positive electrode and the negative electrode, so that the side reaction between the electrode material and the electrolyte can be reduced, and the cycle service life of the battery is prolonged. The gel electrolyte does not contain a large amount of non-aqueous solvent, is favorable for reducing the gas generation of the battery at high temperature and improving the safety of the battery at high temperature.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the following more detailed description. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Example 1
A preparation and application method of a battery gel electrolyte comprises the following specific steps:
(1) Preparing an EC and EMC mixed solvent according to a stoichiometric ratio, wherein the volume ratio is 3 6 The concentration of lithium salt is 1-1.2mol/L, and the lithium salt is stirred until the lithium salt is completely dissolved. Then adding film forming additives VC, PS and DTD into the electrolyte, wherein the mass fractions of the film forming additives VC, PS and DTD in the electrolyte are respectively 1%,1% and 1.5%, fully and uniformly stirring, and finally adding a polymer monomer PETEEA 1.5% into the electrolyte, fully and uniformly stirring to obtain a gel electrolyte containing the polymer monomer;
(2) Injecting the gel electrolyte obtained in the step (1) into a lithium ion battery, standing for 48 hours at room temperature, and then putting the battery on a cabinet to form the battery, wherein the upper limit of the formation voltage is 3.0V, and the charging current is 0.05C;
(3) Performing first vacuum air extraction on the formed battery, setting the vacuum degree to be 88kPa and the vacuum air extraction time to be 5s, checking film-forming potential data, checking the battery quality, and calculating the liquid absorption amount of the battery;
(4) Performing secondary liquid injection on the battery after vacuum extraction, wherein the electrolyte is a solvent for dissolving the thermal initiator reserved in the first step, standing, performing hot pressing for 0.5h at 85 ℃ in a formation cabinet, performing secondary formation after the battery is cooled to room temperature, wherein the upper limit of the formation voltage is 3.8V, and the charging current is 0.1C and 0.2C;
(5) Aging the secondarily formed battery at high temperature at 45 ℃ for 24 hours, performing secondary air extraction after aging, checking film-forming potential data, checking battery quality and calculating the liquid absorption amount of the battery, wherein the air extraction vacuum degree is the same as that of the first time, and the air extraction time is the same as that of the first time;
(6) And (3) carrying out capacity grading on the secondary formed battery, wherein the capacity grading currents are 0.2C and 0.5C respectively, completing the battery manufacturing process after circularly charging and discharging for 2 weeks, and carrying out other electrical property tests.
Example 2
The content of the polymer monomer TPGDA in the step (1) was changed to 2%, and the other procedures were the same as in example 1.
Example 3
The lithium salt in the step (1) is changed into LIPF 6 + LIFSI, molar concentration 0.6+0.6mol/L, and the other procedures are the same as in example 1.
Example 4
The polymer monomer in step (1) was changed to PETEA, the content was changed to 5%, and the other procedures were the same as in example 1.
Example 5
The hot pressing temperature of 85 ℃ for 0.5h in the step (4) is changed to 85 ℃ for 1h, and the other processes are the same as those in the example 1.
Comparative example 1
Using EC and EMC as solvents, and adding LiPF slowly at a volume ratio of 3 6 And finally, adding film-forming additives VC, PS and DTD into the electrolyte, wherein the mass fractions of the additives VC, PS and DTD in the electrolyte are respectively 1%,1% and 1.5%, and fully and uniformly stirring to obtain the lithium salt electrolyte with the conventional concentration. The addition of the polymer monomer and the addition of the thermal initiator were omitted and the other steps were the same as in example 1.
The cells used in examples 1-5 and comparative example 1 were: the electrolyte provided by the invention is not only suitable for NCM811 system batteries, but also suitable for other system batteries, such as NCA, silicon carbon or rich lithium manganese base and the like.
Tables 1 and 2 show the electrolyte formulations and test results of examples 1-5 and comparative example 1.
TABLE 1 examples and comparative electrolyte formulations
Table 2 results of performance test of batteries of examples and comparative examples
From the cycle test results of example 1, it can be seen that as the normal temperature cycle performance of the gel electrolyte battery is reduced, the high temperature cycle performance is basically maintained to be equivalent, and the hot box test performance is better than that of comparative example 1.
From example 2, it is understood that the increase in the polymer concentration slightly lowers the cycle performance at normal and high temperatures, and the safety performance is improved.
From the test results of example 3, it can be seen that the lithium salt LIFSI + LIPF is a binary lithium salt 6 The cycle performance and the safety performance in the gel electrolyte are good.
From the test results of example 4, it can be seen that the cycle performance of the battery is reduced and the safety test can be passed by using the PETEA polymer monomer.
As can be seen from the test results of example 5, the extension of the hot pressing time has no significant effect on the electrical and safety properties of the battery.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. The gel electrolyte is characterized by comprising lithium salt, a non-aqueous solvent, a film-forming additive, a polymer monomer and a thermal initiator.
2. The gel electrolyte of claim 1, wherein the lithium salt is one or more of lithium bis-fluorophosphorylimide, lithium bis-trifluorophosphorylimide, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorophosphate, lithium hexafluorophosphate, or lithium tetrafluoroborate.
3. The gel electrolyte of claim 1, wherein the non-aqueous solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, ethyl propionate, 1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 1, 2-dimethoxyethane, acetone, acetonitrile, methyl acetate, ethyl acetate, methyl propionate, tetrahydrofuran, and 2-methyltetrahydrofuran.
4. The gel electrolyte of claim 1, wherein the film forming additive comprises a positive electrode film forming additive and/or a negative electrode film forming additive; the positive film-forming additive is any one or any combination of more than two of carbonate additives, sulfonate additives, sulfone additives, phosphate additives and lithium additives; the negative film forming additive is any one or any combination of more than two of additives such as vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, ethylene sulfite and the like.
5. The gel electrolyte of claim 1, wherein the polymer monomer is an ester monomer with unsaturated double bonds, and the addition amount is between 0.5 and 6.5 percent.
6. The gel electrolyte of claim 1, wherein the thermal initiator is selected from one or any combination of two or more of azobisisobutyronitrile, dibenzoyl peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate, lauroyl peroxide, and diisopropyl peroxydicarbonate.
7. The method of using the gel electrolyte of claim 1, wherein the method comprises the steps of:
(1) Preparing electrolyte with lithium salt solubility of 1-1.2mol/L of molar concentration; the electrolyte comprises a lithium salt, a non-aqueous solvent and a film-forming additive;
(2) Adding a polymer monomer, and uniformly stirring until the solution is clear to obtain a gel electrolyte containing the polymer monomer;
(3) Injecting the prepared gel electrolyte into a battery cell, standing, and carrying out formation process steps, wherein the upper limit of the formation voltage does not exceed the solvolysis voltage;
(4) Performing vacuum pumping on the formed gel electrolyte battery for 1-10s with the vacuum degree of the equipment being 50-100 kPa;
(5) Performing secondary liquid injection on the battery subjected to vacuum pumping in the step (4), wherein the electrolyte is a thermal initiator dissolved in a solvent, and the dosage of the thermal initiator accounts for 0.02-1% of the total dosage of the electrolyte;
(6) Standing at normal temperature for 24-72h, performing hot-pressing polymerization and secondary formation, wherein the hot-pressing temperature is 70-85 ℃, the hot-pressing time is 0.5-2h, the pressure is 450-750kg, and the formation voltage is the voltage of a battery platform;
(7) And (4) aging the secondary formed battery in the step (6), and vacuumizing again after aging to finally finish battery packaging.
8. The use method of the gel electrolyte according to claim 7, wherein in the step (3), after the gel electrolyte is injected into the battery core, the battery core is kept stand for 24-72 hours at a temperature of 25-45 ℃, and then a formation step is performed, wherein the formation temperature is 25-45 ℃, the formation voltage is less than 3.2V, and the formation current is 0.02C/0.05C/0.1C.
9. The use method of the gel electrolyte according to claim 7, characterized in that in the step (7), the battery is aged after secondary formation, the aging temperature is 45-55 ℃, the aging time is 4-72h, the aged battery is subjected to a vacuum pumping step, the vacuum degree of equipment is 50-100kPa, and the vacuum pumping time is kept for 1-10s.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211272040.2A CN115411359A (en) | 2022-10-18 | 2022-10-18 | Gel electrolyte and application method thereof in lithium ion battery |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115692867A (en) * | 2022-12-30 | 2023-02-03 | 天能电池集团股份有限公司 | Solid-state battery and preparation method thereof |
| CN116014259A (en) * | 2023-03-28 | 2023-04-25 | 河南省动力电池创新中心有限公司 | Gel lithium ion battery and preparation method thereof |
| WO2024119544A1 (en) * | 2022-12-05 | 2024-06-13 | 天能电池集团股份有限公司 | Semi-solid state battery and preparation method therefor |
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2022
- 2022-10-18 CN CN202211272040.2A patent/CN115411359A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024119544A1 (en) * | 2022-12-05 | 2024-06-13 | 天能电池集团股份有限公司 | Semi-solid state battery and preparation method therefor |
| CN115692867A (en) * | 2022-12-30 | 2023-02-03 | 天能电池集团股份有限公司 | Solid-state battery and preparation method thereof |
| CN116014259A (en) * | 2023-03-28 | 2023-04-25 | 河南省动力电池创新中心有限公司 | Gel lithium ion battery and preparation method thereof |
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