CN116154300A - Electrolyte and battery - Google Patents

Electrolyte and battery Download PDF

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Publication number
CN116154300A
CN116154300A CN202310176872.2A CN202310176872A CN116154300A CN 116154300 A CN116154300 A CN 116154300A CN 202310176872 A CN202310176872 A CN 202310176872A CN 116154300 A CN116154300 A CN 116154300A
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electrolyte
fluorinated solvent
lithium
fluorinated
carbonate
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邱亚明
王海
李素丽
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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Priority to CN202310176872.2A priority Critical patent/CN116154300A/en
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Priority to PCT/CN2024/078136 priority patent/WO2024179363A1/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
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three solvents
    • 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)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)

Abstract

The application relates to the technical field of batteries, in particular to electrolyte and a battery. The electrolyte comprises an organic solvent and lithium salt, wherein the organic solvent comprises a fluorinated solvent and a non-fluorinated solvent; the fluorinated solvents include a first fluorinated solvent, a second fluorinated solvent, and a third fluorinated solvent; the first fluorinated solvent is fluoroethylene carbonate; the second fluorinated solvent is acetic acid 2, 2-difluoroethyl ester; the third fluorinated solvent comprises at least one of other fluorinated carbonates, other fluorinated carboxylates, fluoroethers, fluorobenzene. According to the invention, by controlling proper content of fluoroethylene carbonate and low-viscosity 2, 2-difluoroethyl acetate in the electrolyte as organic solvents, on one hand, the high-voltage oxidation resistance can be obviously improved through the high-fluorine solvent, and on the other hand, the battery has better high-voltage cycle performance, and meanwhile, the multiplying power performance is improved, so that the lithium precipitation during charging is reduced.

Description

Electrolyte and battery
Technical Field
The application relates to the technical field of batteries, in particular to electrolyte and a battery.
Background
The lithium ion battery technology is increasingly advanced towards higher energy density while maintaining long cycle performance, and has been widely applied to life aspects including communication related electronic products, as a source of traffic related power energy, energy storage related fields and the like. Further increases in energy density require increases in battery voltage or increases in battery capacity.
The current commercial lithium ion battery voltage is basically below 4.55V, when the voltage further reaches above 4.55V, the traditional commercial carbonate electrolyte is difficult to withstand such high voltage, the positive side reaction is obviously aggravated, and the sufficiently good improvement of long-cycle stability cannot be realized through an additive strategy. In addition to the significant deterioration of the cycle, cell gassing and cycle expansion are also significantly exacerbated.
Perfluorinated solvents or highly fluorinated solvent electrolytes at high voltages are important and hot spots in leading edge research, but fluorinated solvents suffer from a series of problems including low conductivity and poor kinetics in practical applications. In addition, the high content of FEC can lead to higher content of HF in electrolyte, serious gas generation in high-voltage circulation and easier gas generation at high temperature.
The problems of poor dynamics and high-voltage gas production of high-voltage fluoroelectrolyte are increasingly needed to be solved along with the gradual maturation and landing of high-voltage technology. Conventional strategies often use high levels of fluoroethylene carbonate in place of conventional fluorine-free cyclic carbonates and employ high levels of fluoroether diluents, which are known to lead to poor kinetics and to problems with easy gassing.
Disclosure of Invention
In view of this, the present invention provides an electrolyte and a battery. The invention can solve the problems of large side reaction between electrolyte and interface, serious cyclic gas production, poor multiplying power performance and the like in the battery under high voltage.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides an electrolyte, which comprises an organic solvent and lithium salt, wherein the organic solvent comprises a fluorinated solvent and a non-fluorinated solvent;
the fluorinated solvents include a first fluorinated solvent, a second fluorinated solvent, and a third fluorinated solvent;
the first fluorinated solvent is fluoroethylene carbonate;
the second fluorinated solvent is acetic acid 2, 2-difluoroethyl ester;
the third fluorinated solvent comprises at least one of other fluorinated carbonates, other fluorinated carboxylates, fluoroethers, fluorobenzene.
The term "other fluorocarbons" refers to fluorocarbons other than fluoroethylene carbonate; the term "other fluorocarboxylic acid esters" refers to fluorocarboxylic acid esters other than 2, 2-difluoroethyl acetate.
Preferably, the mass percentage of the fluorinated solvent in the electrolyte is not less than 70wt%.
Preferably, the mass percentage of the fluorinated solvent in the electrolyte is 70-85 wt%. Exemplary are 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, 79wt%, 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, 85wt%, or any value within the range of values and range values of any of the foregoing numerical compositions.
More preferably, the mass percentage of the fluorinated solvent in the electrolyte is 75wt% to 80wt%.
In the specific embodiment provided by the invention, the mass percentage of the fluorinated solvent in the electrolyte is 78wt%.
Preferably, the mass percentage of the first fluorinated solvent in the electrolyte is 8-16 wt%; exemplary are 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, or any value in the range of any two of the foregoing values and any value in the range.
Preferably, the mass percentage of the first fluorinated solvent in the electrolyte is 9-14 wt%; exemplary are 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, or any value in the range of any two of the foregoing values and any value within the range.
Preferably, the mass percentage of the second fluorinated solvent in the electrolyte is 5-15 wt%. Exemplary are 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, or any value within the range of values and range values of any of the foregoing numerical compositions.
Preferably, the mass percentage of the second fluorinated solvent in the electrolyte is 7-13 wt%. Exemplary are 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, or any value within the range of any two of the foregoing values and ranges.
As a preferred alternative to this, the third fluorinated solvent comprises methyl trifluoroethyl carbonate (FEMC), 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether (TTE), diethyl Fluorocarbonate (FDEC) at least one of ethyl 2, 2-trifluoroacetate (FEA), 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether (HFE) and 1, 4-difluorobenzene.
In a specific embodiment provided herein, the third fluorinated solvent includes methyl trifluoroethyl carbonate (FEMC) and 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether (TTE). Preferably, the mass percentage of the methyl trifluoroethyl carbonate (FEMC) in the electrolyte is 30-40 wt%, and the mass percentage of the 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether in the electrolyte is 15-25 wt%. More preferably, the mass percentage of the methyl trifluoroethyl carbonate (FEMC) in the electrolyte is 33-39 wt%, and the mass percentage of the 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether in the electrolyte is 20wt%.
Preferably, the non-fluorinated solvent comprises a first non-fluorinated solvent, or comprises a first non-fluorinated solvent and a second non-fluorinated solvent; the first non-fluorinated solvent comprises a linear carbonate and/or a linear carboxylate; the second non-fluorinated solvent includes a cyclic carbonate and/or a cyclic carboxylate.
Preferably, the mass percentage of the non-fluorinated solvent in the electrolyte is 3-15 wt%. Exemplary are 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, or any value within the range of any two of the foregoing values and ranges.
Preferably, the mass percentage of the non-fluorinated solvent in the electrolyte is 8-10 wt%.
In the specific embodiment provided by the invention, the mass percentage of the non-fluorinated solvent in the electrolyte is 10wt%.
Preferably, the mass percentage of the second non-fluorinated solvent in the electrolyte is 0wt% to 5wt%. Exemplary are 0wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any value within the range of values and range values for any of the foregoing numerical compositions.
Preferably, the mass percentage of the second non-fluorinated solvent in the electrolyte is 0wt% to 4wt%.
Preferably, the linear carbonate includes at least one of dimethyl carbonate, diethyl carbonate (DEC), methylethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, dipropyl carbonate.
In a specific embodiment provided by the present invention, the linear carbonate is diethyl carbonate (DEC).
Preferably, the linear carboxylic acid ester includes at least one of methyl acetate, ethyl acetate, propyl acetate, n-pentyl acetate, isopentyl acetate, methyl propionate, ethyl Propionate (EP), propyl Propionate (PP), methyl butyrate, and ethyl n-butyrate.
Preferably, the cyclic carbonate includes at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), and butylene carbonate.
In a specific embodiment provided herein, the cyclic carbonate is Propylene Carbonate (PC).
Preferably, the cyclic carboxylic acid ester includes at least one of gamma-butyrolactone, gamma-valerolactone, delta-valerolactone.
Preferably, the lithium salt includes, but is not limited to, at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorosulfimide, lithium bistrifluoromethylsulfonyl imide, lithium difluorobisoxalato phosphate, lithium tetrafluoroborate, lithium bisoxalato borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (pentafluoroethylsulfonyl) imide, lithium tris (trifluoromethylsulfonyl) methylsulfide, lithium bis (trifluoromethylsulfonyl) imide.
Preferably, the mass percentage of the lithium salt in the electrolyte is 10-20 wt%. Exemplary are 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, or any value within the range of values and range values of any of the foregoing numerical compositions.
Preferably, the electrolyte of the present invention further comprises a sulfonic acid-based additive.
Preferably, the sulfonic acid additive includes, but is not limited to, at least one of 1, 3-Propane Sultone (PS), 1-propylene-1, 3-sultone (PST), 5-methyl oxathiolane 2, 2-dioxide, 1, 3-propenesulfonic acid lactone, 2, 4-butane sultone, 1, 4-butane sultone. The sulfonic acid additive can form a film on the negative electrode, so that the problems of battery circulation and gas production during storage are further reduced.
Preferably, the sulfonic acid additive accounts for 0 to 10wt% of the total mass of the organic solvent and the lithium salt. Exemplary are 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or any value within the range of values and range values of any of the foregoing numerical compositions.
Preferably, the sulfonic acid additive accounts for 0 to 5wt% of the total mass of the organic solvent and the lithium salt.
The invention also provides a battery, which comprises a positive plate, a negative plate and the electrolyte.
Preferably, the positive electrode charge cut-off voltage of the battery is not less than 4.55V.
In an embodiment of the invention, the battery is a lithium ion battery.
In an embodiment provided by the invention, the battery further comprises a separator.
In an embodiment provided by the present invention, a positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both side surfaces of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, a conductive agent, and a binder.
Preferably, the positive electrode active material layer comprises the following components in percentage by mass: 80 to 99.8 weight percent of positive electrode active material, 0.1 to 10 weight percent of conductive agent and 0.1 to 10 weight percent of binder.
Preferably, the positive electrode active material layer comprises the following components in percentage by mass: 90 to 99.6 weight percent of positive electrode active material, 0.2 to 5 weight percent of conductive agent and 0.2 to 5 weight percent of binder.
In an embodiment provided by the present invention, a negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both side surfaces of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, a conductive agent, and a binder.
Preferably, the mass percentage of each component in the anode active material layer is as follows: 80 to 99.8 weight percent of negative electrode active material, 0.1 to 10 weight percent of conductive agent and 0.1 to 10 weight percent of binder.
Preferably, the mass percentage of each component in the anode active material layer is as follows: 90 to 99.6 weight percent of negative electrode active material, 0.2 to 5 weight percent of conductive agent and 0.2 to 5 weight percent of binder.
Preferably, the conductive agent is at least one selected from conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, and carbon fiber.
Preferably, the binder is at least one selected from sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene and polyethylene oxide.
Preferably, the anode active material includes a carbon-based anode material.
Preferably, the carbon-based negative electrode material includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, and soft carbon.
Preferably, the anode active material may further include a silicon-based anode material.
Preferably, the silicon-based negative electrode material is selected from at least one of nano silicon, silicon oxygen negative electrode material (SiOx, 0< x < 2), or silicon carbon negative electrode material.
Preferably, in the negative electrode active material, the mass ratio of the carbon-based negative electrode material to the silicon-based negative electrode material is 10:0 to 1:19.
Preferably, the positive electrode active material is selected from one or more of transition metal lithium oxide, lithium iron phosphate and lithium-rich manganese-based materials; the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O 2 Wherein, -0.1 is less than or equal to x is less than or equal to 1; y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and y+z is more than or equal to 0 and less than or equal to 1; wherein M is Mg, zn, Ga. Ba, al, fe, cr, sn, V, mn, sc, ti, nb, mo, zr.
Compared with the prior art, the invention has the following beneficial effects:
(1) The electrolyte provided by the invention contains a high-content fluorinated solvent (more than 70 wt%) and has better oxidation resistance than a corresponding non-fluorinated solvent, so that compared with a non-fluorinated traditional carbonate electrolyte, the electrolyte provided by the invention can be used for preparing a high-voltage battery, and the oxidation resistance of the electrolyte can be greatly improved.
(2) The fluorosolvent in the electrolyte contains fluoroethylene carbonate (FEC) and 2, 2-difluoroethyl acetate (DFEA), wherein the FEC is a common high-dielectric-constant solvent and plays a key role in improving the conductivity of the electrolyte; DFEA is a low viscosity fluorinated solvent and is also critical to improving electrolyte conductivity. According to the invention, by controlling proper content of fluoroethylene carbonate (FEC) and low-viscosity 2, 2-difluoroethyl acetate (DFEA) in the electrolyte as organic solvents, on one hand, the high-voltage oxidation resistance can be obviously improved through the high-fluorine solvent, and on the other hand, the battery not only has better high-voltage cycle performance, but also has improved multiplying power performance, and lithium precipitation during charging is reduced.
(3) The non-fluorinated solvent in the electrolyte comprises a first non-fluorinated solvent or comprises the first non-fluorinated solvent and a second non-fluorinated solvent; the first non-fluorinated solvent comprises a linear carbonate and/or linear carboxylate and the second non-fluorinated solvent comprises a cyclic carbonate and/or cyclic carboxylate. Because both the fluorinated or non-fluorinated cyclic carbonate and the fluorinated or non-fluorinated cyclic carboxylate have higher dielectric constants, the solvent with high dielectric constant is preferentially coordinated with lithium ions and preferentially enriched at the interface of the anode and the cathode. In order to coordinate the fluorinated cyclic carbonate and/or cyclic carboxylate with lithium ion preferentially, enrich in the interface of positive and negative electrodes preferentially and improve the oxidation resistance of the electrolyte, the invention controls the sum of the cyclic carbonate and cyclic carboxylate of the second non-fluorinated solvent to be low (less than or equal to 5 wt%). Therefore, the absence or addition of low levels of high dielectric constant cyclic carbonates and/or cyclic carboxylates is critical to improving the oxidation resistance of the electrolyte.
Detailed Description
The invention discloses an electrolyte and a battery, and a person skilled in the art can use the content of the electrolyte and the battery to properly improve the technological parameters. It is expressly noted that all such similar substitutions and modifications will be apparent to those skilled in the art, and are deemed to be included in the present invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the relevant art that the invention can be practiced and practiced with modification and alteration and combination of the methods and applications herein without departing from the spirit and scope of the invention.
The Chinese and English names are compared as follows:
FEC fluoroethylene carbonate
DFEA Acetic acid 2, 2-difluoroethyl ester
PC Propylene carbonate
DEC Diethyl carbonate
FEMC Methyl trifluoroethyl carbonate
TTE 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether
FDEC Fluorocarbonic acid diethyl ester
FEA 2, 2-Trifluoroacetic acid ethyl ester
HFE 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether
PS 1, 3-propane sultone
PST 1, 3-propenesulfonic acid lactone
The reagents, materials, etc. used in the present invention are commercially available.
The invention is further illustrated by the following examples:
examples 1 to 7 and comparative examples 1 to 8
1) Preparation of positive plate
Lithium cobalt oxide (LiCoO) as a positive electrode active material 2 ) Mixing polyvinylidene fluoride (PVDF), SP (super P) and Carbon Nano Tube (CNT) according to the mass ratio of 96:2:1.5:0.5, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until the mixed system becomes anode active slurry with uniform fluidity; uniformly coating anode active slurry on two surfaces of an aluminum foil; and drying the coated aluminum foil, and then rolling and slitting to obtain the required positive plate.
2) Preparation of negative plate
Mixing negative active materials of artificial graphite, sodium carboxymethylcellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) according to the mass ratio of 96:1.5:1.5:0.95:0.05, adding deionized water, and obtaining negative active slurry under the action of a vacuum stirrer; uniformly coating the anode active slurry on two surfaces of a copper foil; and (3) airing the coated copper foil at room temperature, transferring to an 80 ℃ oven for drying for 10 hours, and then carrying out cold pressing and slitting to obtain the negative plate.
3) Preparation of electrolyte
The electrolytes of examples 1-7 and comparative examples 1-5, 7-8 were formulated as follows:
in a glove box filled with argon (H 2 O<0.1ppm，O 2 <0.1 ppm), FEC/DFEA/PC/DEC/FEMC/TTE/LiPF 6 Uniformly mixing according to the mass ratio of A/B/C/10-C/58-A-B/20/12 (FEC, DFEA, PC, DEC, FEMC is shown in the specific dosage in table 1), adding 2wt% of 1, 3-propane sultone based on the total mass of the electrolyte after dissolution, uniformly stirring, and obtaining the required electrolyte after passing the detection of moisture and free acid.
Comparative example 6 is different from the above electrolyte in the ratio, and specifically includes the following:
FEC/DFEA/PC/DEC/FEMC/TTE/LiPF 6 the mass ratio is 12/10/3/32/11/20/12.
Table 1 ratio of components of electrolyte in lithium ion batteries of examples and comparative examples
Figure BDA0004101164300000091
4) Preparation of a Battery
Laminating the positive plate in the step 1), the negative plate in the step 2) and the isolating film according to the sequence of the positive plate, the isolating film and the negative plate, and then winding to obtain the battery cell; and (3) placing the battery cell in an outer packaging aluminum foil, injecting the electrolyte in the step (3) into the outer packaging, and performing the procedures of vacuum packaging, standing, formation, shaping, sorting and the like to obtain the battery. The charge and discharge range of the battery is 3.0-4.55V.
Battery performance test
The lithium ion batteries obtained in the above examples and comparative examples were subjected to a 25 ℃ cycle performance test and a lithium precipitation performance test, respectively.
1) 25 ℃ cycle performance test
The batteries in table 1 were subjected to charge-discharge cycles at 25 ℃ in a charge-discharge cut-off voltage range at a rate of 0.5C, and the discharge capacity at the 1 st week was measured as x1 mAh and the discharge capacity at the N week was measured as y1 mAh; the capacity at week N is divided by the capacity at week 1 to obtain a cycle capacity retention rate r=y1/x 1 at week N, and the number of cycles corresponding to the cycle capacity retention rate R1 being 80% is recorded.
2) 25 ℃ 0.5C direct lithium charging test
The battery in table 1 is charged to a cut-off voltage according to a multiplying power of 0.5C at 10 ℃, the cut-off current is 0.025C, the battery is kept stand for 5min, then the battery is discharged to the cut-off voltage according to the multiplying power of 0.5C, the charging and discharging cycle is continuously carried out, after 50 weeks of the cycle, the battery is disassembled after the battery is kept stand for 1h, whether obvious lithium precipitation conditions occur at the negative electrode of the battery are observed, if the negative electrode of the battery has silver white substances, the lithium precipitation is indicated, and if the negative electrode of the battery does not have silver white substances, the lithium precipitation is indicated.
3) 25 ℃ cycle gas production test
For a 25 ℃ cycling cell, the thickness of the first cycle (initial thickness) was recorded; then, 100 charge and discharge cycles were performed, and the thickness after the 100 th cycle was recorded.
Cyclic gas production condition: expansion ratio of 100 cycles = [ (thickness after 100 th cycle-initial thickness)/initial thickness ] ×100%
The test results are shown in Table 2.
Table 2 results of cycle and lithium analysis performance tests of lithium ion batteries of examples and comparative examples
Figure BDA0004101164300000101
Figure BDA0004101164300000111
From the experimental results of examples 1-3 and comparative examples 1-2, the FEC in the fluorinated solvent is in the range of 8% -16% (preferably 9% -14%), the cycle capacity retention rate of the lithium ion battery is 80% and the cycle number is more, and lithium is not separated out by direct charging at 25 ℃ and 0.5 ℃; too high FEC significantly worsens cyclic gassing, and too low a worsening magnification leads to lithium evolution. It can be seen that the battery has better high-voltage cycle performance and rate performance by controlling the FEC with proper content.
From the experimental results of examples 1, 4-5 and comparative examples 3-4, it is known that DFEA in the fluorinated solvent is in the range of 5% -15% (preferably 7% -13%), the cycle capacity retention rate of the lithium ion battery is 80% and the cycle number is higher, and lithium is not separated by direct charging at 25 ℃ and 0.5 ℃; too high DFEA can deteriorate high voltage cycling and too low can deteriorate rate capability resulting in lithium evolution. It can be seen that the battery has better high-voltage cycle performance and rate performance by controlling the DFEA with proper content.
From the experimental results of examples 1, 6-7 and comparative example 5, it is known that when the PC content in the non-fluorinated solvent is low or no PC is added, the cycle capacity retention rate of the lithium ion battery is 80% and the cycle number is high, and lithium is not separated by direct charging at 25 ℃ and 0.5 ℃; when the PC content is more than 5wt%, the number of cycles is significantly reduced. Therefore, the battery has better high-voltage cycle performance and rate performance without adding PC or with adding a small amount of PC.
As is clear from the results of comparative example 6, the number of cycles is low when the DEC content in the non-fluorinated solvent is more than 10%. Therefore, when the content of DEC is less than or equal to 10%, the battery has better high-voltage cycle performance and rate capability.
From the experimental results of example 1 and comparative examples 7 to 8, it is understood that the fec+dfea+femc scheme of example 1 can achieve not only better high-voltage cycle performance but also improved rate performance and reduced lithium precipitation during charging, compared to the fec+femc scheme of comparative example 7 and the dfea+femc scheme of comparative example 8.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (10)

1. An electrolyte, characterized in that the electrolyte comprises an organic solvent and a lithium salt, wherein the organic solvent comprises a fluorinated solvent and a non-fluorinated solvent;
the fluorinated solvents include a first fluorinated solvent, a second fluorinated solvent, and a third fluorinated solvent;
the first fluorinated solvent is fluoroethylene carbonate;
the second fluorinated solvent is acetic acid 2, 2-difluoroethyl ester;
the third fluorinated solvent comprises at least one of other fluorinated carbonates, other fluorinated carboxylates, fluoroethers and fluorobenzene.
2. The electrolyte according to claim 1, wherein the mass percentage of the fluorinated solvent in the electrolyte is not less than 70wt%;
and/or the mass percentage of the fluorinated solvent in the electrolyte is 70-85 wt%.
3. The electrolyte according to claim 1, wherein the mass percentage of the first fluorinated solvent in the electrolyte is 8-16 wt%;
and/or the mass percentage of the second fluorinated solvent in the electrolyte is 5-15 wt%.
4. The electrolyte according to claim 1, wherein the mass percentage of the first fluorinated solvent in the electrolyte is 9-14 wt%;
and/or the mass percentage of the second fluorinated solvent in the electrolyte is 7-13 wt%.
5. The electrolyte according to claim 1, wherein, the third fluorinated solvent comprises methyl trifluoroethyl carbonate (FEMC), 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether (TTE), diethyl Fluorocarbonate (FDEC) at least one of ethyl 2, 2-trifluoroacetate (FEA), 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether (HFE) and 1, 4-difluorobenzene.
6. The electrolyte of claim 1, wherein the non-fluorinated solvent comprises a first non-fluorinated solvent or comprises a first non-fluorinated solvent and a second non-fluorinated solvent;
the first non-fluorinated solvent comprises a linear carbonate and/or a linear carboxylate;
the second non-fluorinated solvent comprises a cyclic carbonate and/or cyclic carboxylate;
and/or the mass percentage of the non-fluorinated solvent in the electrolyte is 3-15 wt%;
and/or the mass percentage of the second non-fluorinated solvent in the electrolyte is 0-5 wt%.
7. The electrolyte of claim 6 wherein the linear carbonate comprises at least one of dimethyl carbonate, diethyl carbonate (DEC), ethylmethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, dipropyl carbonate;
and/or the linear carboxylic acid ester comprises at least one of methyl acetate, ethyl acetate, propyl acetate, n-pentyl acetate, isopentyl acetate, methyl propionate, ethyl Propionate (EP), propyl Propionate (PP), methyl butyrate and ethyl n-butyrate;
and/or the cyclic carbonate comprises at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), butylene carbonate;
and/or the cyclic carboxylic acid ester comprises at least one of gamma-butyrolactone, gamma-valerolactone and delta-valerolactone.
8. The electrolyte of claim 1 wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorosulfimide, lithium bistrifluoromethylsulfonyl imide, lithium difluorobisoxalato phosphate, lithium tetrafluoroborate, lithium bisoxalato borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (pentafluoroethylsulfonyl) imide, lithium tris (trifluoromethylsulfonyl) methyllithium, lithium bis (trifluoromethylsulfonyl) imide;
and/or the mass percentage of the lithium salt in the electrolyte is 10-20wt%.
9. The electrolyte of any one of claims 1-8 further comprising a sulfonic acid-based additive including, but not limited to, at least one of 1, 3-Propane Sultone (PS), 1-propene-1, 3-sultone (PST), 5-methyl oxathiolane 2, 2-dioxide, 1, 3-propenolactone, 2, 4-butane sultone, 1, 4-butane sultone;
and/or, the sulfonic acid additive accounts for 0-10wt% of the total mass of the organic solvent and the lithium salt.
10. A battery comprising a positive electrode sheet, a negative electrode sheet, the electrolyte of any one of claims 1-9;
and/or the positive electrode charge cut-off voltage of the battery is more than or equal to 4.55V.
CN202310176872.2A 2023-02-28 2023-02-28 Electrolyte and battery Pending CN116154300A (en)

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WO2024179363A1 (en) * 2023-02-28 2024-09-06 珠海冠宇电池股份有限公司 Electrolyte and battery

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KR102271004B1 (en) * 2014-08-14 2021-07-02 솔베이(소시에떼아노님) Nonaqueous electrolyte compositions comprising sultone and fluorinated solvent
EP4070396A1 (en) * 2019-12-03 2022-10-12 Solvay Sa Electrolyte composition with fluorinated acyclic ester and fluorinated cyclic carbonate
JP2023504467A (en) * 2019-12-03 2023-02-03 ソルヴェイ（ソシエテ アノニム） Electrolyte composition having fluorinated acyclic carbonate and fluorinated cyclic carbonate
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