CN116632344A - Electrolyte, preparation method thereof and secondary battery - Google Patents

Electrolyte, preparation method thereof and secondary battery Download PDF

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Publication number
CN116632344A
CN116632344A CN202310476835.3A CN202310476835A CN116632344A CN 116632344 A CN116632344 A CN 116632344A CN 202310476835 A CN202310476835 A CN 202310476835A CN 116632344 A CN116632344 A CN 116632344A
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China
Prior art keywords
electrolyte
additive
carbonate
lithium
methyl
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CN202310476835.3A
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Chinese (zh)
Inventor
李海杰
邵俊华
孔东波
张利娟
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Hunan Farnlet New Energy Technology Co ltd
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Hunan Farnlet New Energy Technology Co ltd
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Priority to CN202310476835.3A priority Critical patent/CN116632344A/en
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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
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • 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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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Secondary Cells (AREA)

Abstract

The application discloses an electrolyte, a preparation method thereof and a secondary battery, wherein the electrolyte comprises lithium salt, an organic solvent, an additive I and an additive II; the additive I comprises a compound with a structural formula shown in a formula (I); the additive II comprises a compound with a structural formula shown as a formula (II):wherein R is 1 Selected from C 1～6 Is a hydrocarbon group. The electrolyte provided by the application can greatly improve the low-temperature cycle efficiency and the low-temperature discharge capacity retention rate of the battery through the synergistic effect of the additive I and the additive II.

Description

Electrolyte, preparation method thereof and secondary battery
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to electrolyte, a preparation method thereof and a secondary battery.
Background
The lithium ion battery has the advantages of wide working temperature range, large specific energy density, long cycle life, small self-discharge, no memory effect, environmental friendliness and the like, and is widely applied to various electronic equipment, such as the fields of mobile phones, notebook computers, electric tools and the like. Currently, with the increasing performance requirements of power batteries under low-temperature environmental conditions, the development of low-temperature batteries has very important significance
The low-temperature performance of the lithium battery is mainly related to the low-temperature conductivity of electrolyte, the diffusion capability of lithium ions in an active electrode material and the electrode interface property, the lithium battery electrolyte is a carrier for ion transmission in the battery and generally consists of lithium salt and an organic solvent, the electrolyte plays a role in conducting ions between the anode and the cathode of the lithium battery, the lithium battery is ensured to obtain the advantages of high voltage, high specific energy and the like, and the electrolyte is generally prepared from the raw materials of the high-purity organic solvent, the electrolyte lithium salt, necessary additives and the like according to a certain proportion under a certain condition.
However, the existing low-temperature lithium battery electrolyte has poor performance in a cold state, and the viscosity in the electrolyte is gradually increased and the fluidity is reduced along with the reduction of temperature, so that the performance of the electrolyte is seriously affected, and the low-temperature performance of the battery is deteriorated. Therefore, it is necessary to develop a low temperature lithium battery electrolyte.
Disclosure of Invention
The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the first aspect of the present application proposes an electrolyte such that its low-temperature discharge capacity retention rate and low-temperature cycle retention rate are high.
The second aspect of the application also provides a preparation method of the electrolyte.
The third aspect of the present application also provides a secondary battery.
According to an embodiment of the first aspect of the present application, there is provided an electrolyte comprising a lithium salt, an organic solvent, an additive I and an additive II;
the additive I comprises a compound with a structural formula shown in a formula (I); the additive II comprises a compound with a structural formula shown as a formula (II):
wherein R is 1 Selected from C 1～6 Is a hydrocarbon group.
The electrolyte provided by the embodiment of the application has at least the following beneficial effects:
the electrolyte provided by the application can greatly improve the low-temperature cycle efficiency and the low-temperature discharge capacity retention rate of the battery through the synergistic effect of the additive I and the additive II. Wherein the additive I is used for improving the conductivity of the electrolyte in a low-temperature state and reducing the resistance; the additive II has better conductivity and better stability at low temperature; the low-temperature discharge capacity retention rate and the low-temperature cycle retention rate of the battery are improved by the synergistic effect of the low-temperature discharge capacity retention rate and the low-temperature cycle retention rate of the battery.
According to some embodiments of the application, the R 1 At least one selected from methyl, ethyl and tert-butyl.
According to some embodiments of the application, the mass of the additive I is 0.1% -5% of the total mass of the electrolyte. Specifically, the mass of the additive i may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range of any two of these.
According to some embodiments of the application, the mass of the additive II is 0.1% -1% of the total mass of the electrolyte. Specifically, the mass of additive ii may be 0.1%, 0.2%, 0.3%, 0.4%, 0.6%, 0.8%, 1.0% or a combination of any two thereof, based on the total mass of the electrolyte.
According to some embodiments of the application, the mass ratio of additive I to additive II is 4-12. Therefore, when the mass content of the additive I and the additive II in the electrolyte is in the above range, the synergistic effect between the additive I and the additive II is further improved, and the low-temperature cycle performance is improved.
According to some embodiments of the application, the lithium salt is one or more of lithium bis (fluorosulfonyl) imide, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, or lithium perfluoroalkylsulfonate.
According to some embodiments of the application, the organic solvent is selected from one or more of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylethyl carbonate, methylpropyl carbonate, vinylene carbonate, fluoroethylene carbonate, methyl formate, ethyl acetate, ethyl propionate, propyl propionate, methyl butyrate, methyl acrylate, ethylene sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, 1, 3-propane sultone, vinyl sulfate, anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, N-dimethylformamide, sulfolane, dimethylsulfoxide, gamma-butyrolactone, and tetrahydrofuran.
According to some embodiments of the application, the mass of the organic solvent is 10-70% of the total mass of the electrolyte.
According to some embodiments of the application, the concentration of the lithium salt in the electrolyte is 0.5mol/L to 2mol/L. Too low a concentration of lithium salt in the electrolyte affects the conductivity of the electrolyte, too high a concentration of lithium salt in the electrolyte increases the viscosity of the electrolyte and also affects the conductivity of the electrolyte. When the concentration of the lithium salt in the electrolyte is in the above range, the conductivity of the electrolyte can be ensured, and the internal resistance of the secondary battery can be reduced.
According to some embodiments of the application, the mass of the lithium salt is 12-18% of the total mass of the electrolyte.
According to a second aspect of the present application, there is provided a method for preparing the above-mentioned electrolyte, comprising the steps of:
and in an argon protection glove box, adding the lithium salt, the additive I and the additive II into an organic solvent, and uniformly mixing to obtain the electrolyte.
A third aspect of the present application provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet and the above-described electrolyte.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.
Detailed Description
The following are specific embodiments of the present application, and the technical solutions of the present application will be further described with reference to the embodiments, but the present application is not limited to these embodiments.
The reagents, methods and apparatus employed in the present application, unless otherwise specified, are all conventional in the art.
The structural formulas of the additive I and the additive II used in the embodiment of the application are as follows:
the additive I is prepared by the following method:
4.26g of vinyl difluorophosphite (CAS 18133-42-1) was added to 6.1g of hexamethyldisiloxane under nitrogen protection, and after reacting at 75℃to 80℃for 2 hours, the system temperature was raised to 95℃to obtain the catalyst.
Additive II reference methods Arvai R, toulgoat F, M M edebielle, et al New aryl-containing fluorinated sulfonic acids and their ammonium salts, useful as electrolytes for fuel cells or ionic liquids [ J ]. Journal of Fluorine Chemistry,2009,129 (10): 1029-1035.
The lithium ion batteries of examples 1 to 3 and comparative examples 1 to 3 were each prepared as follows.
(1) Preparation of electrolyte
In a glove box filled with argon (water content < 10ppm, oxygen content < 1 ppm), adding additive I and additive II into non-aqueous organic solvent (EC: DEC=30:70, mass ratio), mixing uniformly, and slowly adding appropriate amount of lithium salt (LiPF) 6 ) After the lithium salt is completely dissolved, the electrolyte with the lithium salt concentration of 1mol/L is obtained. In table 1, the content of each additive of examples 1 to 3 and comparative examples 1 to 3 is a mass percentage calculated based on the total mass of the electrolyte.
(2) Preparation of positive plate
The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 Super P, conductive agent, adhesiveThe agent polyvinylidene fluoride (PVDF) was made into a positive electrode slurry in N-methylpyrrolidone (NMP). Wherein the solid content in the positive electrode slurry is 50wt%, and LiNi 0.8 Co 0.1 Mn 0.1 O 2 The mass ratio of Super P to PVDF is 8:1:1. And coating the positive electrode slurry on a positive electrode current collector aluminum foil, drying at 85 ℃, cold pressing, trimming, cutting pieces, splitting, and drying for 4 hours under a vacuum condition at 85 ℃ to prepare the positive electrode plate.
(3) Preparation of negative electrode sheet
And uniformly mixing the negative electrode active material artificial graphite, the conductive agent Super P, the thickener CMC and the adhesive Styrene Butadiene Rubber (SBR) in deionized water to prepare the negative electrode slurry. Wherein the solid content in the cathode slurry is 40wt%, and the mass ratio of graphite, super P, CMC and SBR is 89:6:3:2. And (3) coating the negative electrode slurry on a negative electrode current collector copper foil, drying at 85 ℃, cold pressing, trimming, cutting pieces, splitting, and drying for 12 hours at 120 ℃ under vacuum conditions to prepare a negative electrode plate.
(4) Preparation of a separator film
A Polyethylene (PE) film 16 μm thick was selected as the separator.
(5) Preparation of lithium ion batteries
And stacking the positive plate, the isolating film and the negative plate in sequence, enabling the isolating film to be positioned between the positive plate and the negative plate to play a role in isolating the positive plate from the negative plate, winding to obtain a bare cell, welding the electrode lug, placing the bare cell in an outer package, injecting the prepared electrolyte into the dried cell, packaging, standing, forming, shaping, testing capacity and the like, and thus completing the preparation of the lithium ion battery.
TABLE 1 electrolyte parameters for examples 1-3 and comparative examples 1-3
Additive I% Additive II% Additive I/additive II
Example 1 0.5 0.2 2.5
Example 2 1 0.2 5
Example 3 2 0.2 10
Comparative example 1 — — —
Comparative example 2 1 — —
Comparative example 3 — 0.2 —
Low-temperature discharge performance test of lithium ion battery
Placing a lithium ion battery in a high-low temperature box, regulating the temperature of a furnace to 25 ℃, charging to 4.2V by using a 1C constant current, charging to 0.05C by using a 4.2V constant voltage, discharging to 2.8V by using a 1C constant current after the surface temperature of the lithium ion battery is 25 ℃, and recording that the discharge capacity is C 0 Fully charging the lithium ion battery according to the charging mode, then regulating the high-low temperature box to minus 30 ℃, discharging to 2.8V with a constant current of 1C after the surface temperature of the lithium ion battery is minus 30 ℃, and recording the discharge capacity C 1 。
Lithium ion battery low-temperature discharge capacity retention (%) =c 1 /C 0 ×100％。
Low temperature cycle performance test:
at 0 ℃, the battery is subjected to a 200-week charge-discharge cycle test under the charge-discharge condition of 0.5C/1C, the charge-discharge voltage interval is 3.0V-4.6V, and the discharge capacities at the first week and the 200 th week are recorded respectively. The capacity retention rate at week 200 was calculated as: the 200 th week capacity retention (%) =200 th week discharge capacity/first week discharge capacity x 100%, and the results are shown in table 2.
Table 2: results of Performance test of examples 1 to 3 and comparative examples 1 to 3
Low-temperature discharge capacity retention% 200-week cycle retention at 0deg.C%
Example 1 35 85
Example 2 38 88
Example 3 39 89
Comparative example 1 23 65
Comparative example 2 26 75
Comparative example 3 27 76
As can be seen from examples 1 to 3 and comparative examples 1 to 3, comparative examples 1 to 3 are each free of additives and only have additive I added; or only additive II is added, but the low-temperature discharge capacity retention rate and the low-temperature cycle retention rate are relatively poor. In the embodiments 1 to 3 of the application, after the additive I and the additive II are added, the synergistic effect of the additive I and the additive II greatly improves the low-temperature performance.
The present application has been described in detail with reference to the above embodiments, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application.

Claims (10)

1. An electrolyte is characterized by comprising lithium salt, an organic solvent, an additive I and an additive II;
the additive I comprises a compound with a structural formula shown in a formula (I); the additive II comprises a compound with a structural formula shown as a formula (II):
wherein R is 1 Selected from C 1～6 Is a hydrocarbon group.
2. The electrolyte of claim 1, wherein R 1 At least one selected from methyl, ethyl and tert-butyl.
3. The electrolyte according to claim 1, wherein the mass of the additive i is 0.1-5% of the total mass of the electrolyte.
4. The electrolyte according to claim 1, wherein the mass of the additive II is 0.1-1% of the total mass of the electrolyte.
5. The electrolyte according to claim 1, wherein the mass ratio of the additive I to the additive II is 4-12.
6. The electrolyte according to claim 1, wherein the lithium salt is one or more of lithium bis (fluorosulfonyl) imide, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perfluoroalkylsulfonate.
7. The electrolyte according to claim 1, wherein the organic solvent is selected from one or more of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylethyl carbonate, methylpropyl carbonate, vinylene carbonate, fluoroethylene carbonate, methyl formate, ethyl acetate, ethyl propionate, propyl propionate, methyl butyrate, methyl acrylate, ethylene sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, 1, 3-propane sultone, vinyl sulfate, acid anhydride, N-methylpyrrolidone, N-methyl formamide, N-methylacetamide, acetonitrile, N-dimethylformamide, sulfolane, dimethyl sulfoxide, methyl sulfide, γ -butyrolactone, and tetrahydrofuran.
8. The electrolyte of claim 1, wherein the concentration of the lithium salt in the electrolyte is 0.5mol/L to 2mol/L.
9. The method for producing an electrolytic solution according to any one of claims 1 to 8, comprising the steps of:
and in an argon protection glove box, adding the lithium salt, the additive I and the additive II into an organic solvent, and uniformly mixing to obtain the electrolyte.
10. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, and the electrolyte as defined in any one of claims 1 to 8.
CN202310476835.3A 2023-04-28 2023-04-28 Electrolyte, preparation method thereof and secondary battery Pending CN116632344A (en)

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Application Number Priority Date Filing Date Title
CN202310476835.3A CN116632344A (en) 2023-04-28 2023-04-28 Electrolyte, preparation method thereof and secondary battery

Publications (1)

Publication Number Publication Date
CN116632344A true CN116632344A (en) 2023-08-22

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