CN114447425A

CN114447425A - Non-aqueous electrolyte and battery

Info

Publication number: CN114447425A
Application number: CN202110246923.5A
Authority: CN
Inventors: 邓永红; 张光照; 谢伟东; 胡时光; 吴成英; 江丽军; 邓晓岚; 王朝阳
Original assignee: Sanming Hexafluo Chemicals Co Ltd
Current assignee: Sanming Hexafluo Chemicals Co Ltd
Priority date: 2020-11-06
Filing date: 2021-03-05
Publication date: 2022-05-06
Also published as: WO2022095777A1

Abstract

In order to overcome the problems that the stability of a solvent in the existing electrolyte is insufficient and the cycle performance of a battery is influenced, the invention provides a non-aqueous electrolyte, which comprises an electrolyte and a solvent, wherein the solvent comprises a compound shown as a structural formula 1: r is₁‑R₂‑O‑R₃In the structural formula 1, R₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is selected from

Or a single bond, n is 1 or 2; r₃Selected from hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, aryloxy or

R₄Selected from alkyl and alkoxyAlkenyl, alkenyloxy, aryl, aryloxy, ether or polyether chain, R₅Is selected from

Or a single bond, m is 1 or 2, R₆Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl. Meanwhile, the invention also discloses a battery comprising the non-aqueous electrolyte. The non-aqueous electrolyte provided by the invention has higher cycle stability, can inhibit the growth of lithium dendrites and the shuttling effect of polysulfide, and improves the cycle performance of the battery.

Description

Non-aqueous electrolyte and battery

Technical Field

The invention belongs to the technical field of secondary batteries, and particularly relates to a non-aqueous electrolyte and a battery.

Background

The electrolyte is known as 'blood' in the lithium ion battery, and plays an important role in the capacity exertion of electrode materials in the lithium ion battery, the cycling stability of the battery, the safety of the battery and the like.

In the traditional lithium ion battery, because the theoretical specific capacity (372mAh/g) of the graphite negative electrode is lower, a lithium metal material (3860mAh/g, -3.04V vs. SHE) with higher specific capacity and lower potential is searched as a negative electrode material. Carbonate electrolyte solvents represented by Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and the like are not suitable for lithium metal batteries, mainly because lithium metal has a low potential and strong reducibility, and can react with most ester electrolytes, thereby easily causing growth of lithium dendrites and formation of dead lithium during charging and discharging, and finally causing rapid battery degradation and being difficult to meet requirements. In addition, since lithium polysulfide can also chemically react with an ester electrolyte, conventional ester electrolytes are also difficult to use in lithium sulfur batteries.

On the other hand, ether electrolytes represented by ethylene glycol dimethyl ether (DME) and 1, 3-cyclopentane (DOL) react slowly with lithium metal, and exhibit good stability to lithium metal, and thus have been used in the research of lithium metal batteries by many researchers. In addition, lithium polysulfide has better solubility in ether electrolyte and does not react with a solvent, so the ether electrolyte is also commonly used for lithium sulfur batteries, the classical formula is that 1M lithium bistrifluoromethylsulfonyl imide (LiTFSI) is dissolved in DME/DOL (1: 1v/v), and 1-2% LiNO is added at the same time₃As an additive. Although the ether electrolyte system has good stability to lithium metal and can relieve the growth of lithium dendrites, the oxidative decomposition potential is low, and the requirement of high-voltage cathode materials (such as ternary cathode materials NCM, spinel lithium nickel manganese oxide and other cathode materials) is difficult to meet. Meanwhile, the ether electrolyte is as flammable as the ester electrolyte, and brings a series of potential safety hazards to the lithium ion battery pack.

On the other hand, although the electrochemical performance of the battery can be improved to a small extent by adding the sulfone compound into the electrolyte, the existing sulfone compound additive, such as the sulfonamide compound or the sulfonate compound, does not have a good effect of improving the oxidation resistance of the electrolyte.

Disclosure of Invention

The invention provides a non-aqueous electrolyte and a battery, aiming at the problems that the stability of a solvent in the existing electrolyte is insufficient and the cycle performance of the battery is influenced.

The technical scheme adopted by the invention for solving the technical problems is as follows:

in one aspect, the present invention provides a nonaqueous electrolyte solution comprising an electrolyte and a solvent, wherein the solvent comprises a compound represented by formula 1:

R₁-R₂-O-R₃

structural formula 1

Wherein R is₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl;

R₂is selected from

Or a single bond, n is 1 or 2;

R₃selected from hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, aryloxy or

R₄Selected from the group consisting of hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, aryloxy, ether or polyether chains, R₅Is selected from

Or a single bond, m is 1 or 2, R₆Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl.

Optionally, R₁Has 1 to 10 carbon atoms, R₃Selected from the group consisting of hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, and aryloxy₃Has 1 to 10 carbon atoms, R₄Has 1 to 10 carbon atoms, R₆The number of carbon atoms of (A) is 1 to 10.

Optionally, R₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is selected from

n is 1 or 2; r₃Selected from hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl or aryloxy groups.

Optionally, R₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is a single bond; r₃Selected from hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl or aryloxy groups.

n is 1 or 2; r₃Is selected from

R₄Selected from the group consisting of hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl or aryloxy, R₅Is selected from

m is 1 or 2, R₆Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl.

Optionally, R₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is a single bond; r₃Is selected from

R₄Selected from hydrocarbon radicals, ether radicals or polyether chains, R₅Is a single bond, R₆Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl.

Optionally, the compound shown in the structural formula 1 is selected from one or more of the following compounds:

optionally, the mass percentage of the compound shown in the structural formula 1 is 10-90% based on 100% of the total mass of the electrolyte.

Optionally, the solvent further comprises a cosolvent, and the volume ratio of the cosolvent to the compound shown in the structural formula 1 is 1: 100-90: 10;

the cosolvent comprises one or more of an ether solvent, a nitrile solvent, a carbonate solvent and a carboxylic ester solvent.

In another aspect, the present invention provides a battery comprising a positive electrode, a negative electrode, and the nonaqueous electrolytic solution described above.

According to the non-aqueous electrolyte provided by the invention, the solvent comprises the compound shown in the structural formula 1, and when the compound is added into the non-aqueous electrolyte to be used as the solvent, the direct contact between solvent molecules with high reactivity and positive and negative electrode interfaces can be effectively reduced, so that the side reaction which is unfavorable for electrochemical cycle in a battery is reduced.

Meanwhile, the compound shown in the structural formula 1 can be preferentially decomposed with other components in the electrolyte on the surface of the electrode to participate in passive film formation on the surface of the electrode, and an SEI/CEI film rich in metal fluoride is formed on the surface of the electrode, so that the growth of lithium dendrites is effectively inhibited, and the cycling stability of the battery is improved.

The compound shown in the structural formula 1 has higher oxidation resistance potential and flame retardance, and can reduce the flammability of the obtained electrolyte and improve the safety of the electrolyte. When the compound shown in the structural formula 1 is applied to a lithium-sulfur battery, the solubility of lithium polysulfide in electrolyte can be reduced, and the shuttle effect of the lithium polysulfide is slowed down.

Drawings

Fig. 1 is a graph of capacity retention of a lithium-sulfur half-cell provided in example 2 of the present invention after 100 cycles at 0.2C.

FIG. 2 shows a lithium copper half cell at 1mA/cm, provided in example 4 of the present invention²Current density, 1mAh/cm²Results of 400 cycles at face volume are shown.

FIG. 3 shows a 1mA/cm lithium copper half cell of comparative example 1 of the present invention²Current density, 1mAh/cm²The results of 100 cycles under the surface volume conditions are shown schematically.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

One embodiment of the present invention provides a nonaqueous electrolytic solution, including an electrolyte and a solvent, where the solvent includes a compound represented by formula 1:

R₁-R₂-0-R₃

structural formula 1

Wherein R is₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl;

R₂is selected from

Or a single bond, n is 1 or 2;

R₃selected from hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, aryloxy or

In the compound shown in the structural formula 1, R is included₁And R₆Exemplary fluoro groups are less polar and include the group represented by-R₂-O-or-R₅The polar group, the fluoro group and the polar group are combined to form a structure similar to a surfactant, the polar group can have better affinity with conventional solvents such as DME and DMC, the polarity of the fluoro group is lower, a stable shell-core structure is formed in the process of mixing with other electrolyte solvents, the inner core of the structure is the conventional solvents such as DME and DMC, lithium salt and the polar group of the compound shown in the structural formula 1, the outer layer is the fluoro group combined with the compound shown in the structural formula 1, the non-aqueous electrolyte is in a stable double-sheath-layer solution state, the direct contact between solvent molecules with higher reactivity and positive and negative electrode interfaces can be effectively reduced, the adverse side reaction to electrochemical cycle in the battery is further reduced, and the adverse side reaction to electrochemical cycle in the battery is improvedAnd (4) the cycling stability of the battery.

Meanwhile, the compound shown in the structural formula 1 can be preferentially decomposed with other components in the electrolyte on the surface of the electrode to participate in passive film formation on the surface of the electrode, an SEI/CEI film rich in metal fluoride is formed on the surface of the electrode, the growth of lithium dendrites is effectively inhibited, and simultaneously, after the SEI/CEI film is formed, a shell-core double-sheath-layer structure formed by the compound shown in the structural formula 1 enables DME, DMC and the like to easily react with the surface of the electrode (positive and negative electrodes) and generate a solvent which is not beneficial to battery circulation to be locked in the sheath layer as far as possible, so that the thickness increase of the SEI/CEI film in the long-term circulation process is avoided, and the impedance is further prevented from being improved. The metal fluoride may be lithium fluoride, sodium fluoride, potassium fluoride, or the like, depending on the choice of the electrolyte.

The compound shown in the structural formula 1 has high oxidation resistance potential and flame retardance, and can reduce the flammability of the obtained electrolyte and improve the safety of the electrolyte. When the compound shown in the structural formula 1 is applied to a lithium-sulfur battery, the solubility of lithium polysulfide in electrolyte can be reduced, and the shuttle effect of the lithium polysulfide is slowed down.

In some embodiments, in the compound of formula 1, R₁And R₆The fluoro group of (a) may be perfluoro or partially fluoro.

In addition, R is₁And R₆The fluorine substitution degree of the fluoro group is related to the polarity, the higher the fluorine substitution degree is, the lower the polarity is, and meanwhile, the shell-core double-sheath layer structure formed by the compound shown in the structural formula 1 depends on R₁And R₆In a preferred embodiment, in order to ensure the stability of the core-shell double-sheath structure formed by the compound shown in the structural formula 1 in the electrolyte, R₁And R₆The fluoro group of (a) is selected from perfluoro groups to ensure that it has relatively low polarity.

In a preferred embodiment, R₁And R₆Each independently selected from

Wherein n is 1-4.

In some casesIn the examples, R₁Has 1 to 10 carbon atoms, R₃Selected from the group consisting of hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, and aryloxy₃Has 1 to 10 carbon atoms, R₄Has 1 to 10 carbon atoms, R₆The number of carbon atoms of (A) is 1 to 10.

In a preferred embodiment, R₁Has 1 to 5 carbon atoms, R₃Selected from alkyl, alkoxy, alkenyl and alkenyloxy with 1-3 carbon atoms, R₄Has 1 to 3 carbon atoms, R₆The number of carbon atoms of (A) is 1 to 4.

In particular, R₁And R₆The fluorine radical is a fluorine radical, the relatively long carbon chain is beneficial to improving the oxidation resistance and the flame retardance of the electrolyte, and R₁And R₆Insufficient carbon chain length of (2) results in R₁The oxidation resistance and the flame retardance of the electrolyte are deteriorated, and meanwhile, the electron and density distribution of molecules are changed, so that the shell-core structure is not formed easily, and the performance of the battery is not improved sufficiently. At the same time, R₁And R₆The carbon chain of the compound shown in the structural formula 1 cannot be too long, and the too long carbon chain is not beneficial to improving the compatibility of the compound shown in the structural formula 1 and other solvents or electrolytes in the electrolyte.

In some embodiments, R₁And R₆The number of carbon atoms of (a) may each independently be selected from 2, 3, 4, 5.

R₃And R₄The carbon chain of the compound is relatively short, so that steric hindrance can be reduced, the approach of metal ions to O in the compound shown in the structural formula 1 is facilitated, and the metal ions are better complexed.

In some embodiments, R₃And R₄The number of carbon atoms of (a) may each independently be selected from 1,2, 3, 4.

In some embodiments, the fluoroalkyl, fluoroalkoxy, fluoroalkenyl, hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, aryloxy, ether, or polyether chain may be linear or branched.

In some embodiments, R₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is selected from

In this example, an exemplary structure of the compound of formula 1 is:

when the compound shown in the structural formula 1 is selected from structural formula 1-1, the structure mainly comprises two parts, wherein one part is represented by R₁Examples of the polar group include a fluorinated nonpolar group and the other part is a sulfonate or a sulfinate, and when the polar group forms a core-shell double-sheath structure with another solvent or an electrolyte, the polar group has affinity with the other solvent or the electrolyte, and is located inside the core-shell double-sheath structure, R₁For example, the fluorinated nonpolar group is positioned outside the shell-core double-sheath structure, so that a stable dispersed and isolated structure is formed, and the side reaction between the electrode and the electrolyte is favorably reduced.

In some embodiments, R₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is a single bond; r₃Selected from hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl or aryloxy groups.

In this example, an exemplary structure of the compound of formula 1 is:

R₁-O-R₃

structural formula 1-2.

When the compound shown in the structural formula 1 is selected from structural formulas 1-2, the structure mainly comprises two parts, wherein one part is represented by R₁The polar group such as an ether has affinity with other solvents or electrolytes and is located inside the core-shell double-sheath structure, and R is a group having a fluorine atom, a nonpolar group, and the other part is a polar group such as an ether, and when the core-shell double-sheath structure is formed with other solvents or electrolytes, the polar group such as an ether has affinity with other solvents or electrolytes₁The fluorinated nonpolar groups are located outside the core-shell double-sheath structure, thereby forming a stable structureThe dispersed and isolated structure of (2) is beneficial to reducing side reactions between the electrode and the electrolyte.

n is 1 or 2; r₃Is selected from

m is 1 or 2, R₆Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl.

In this example, an exemplary structure of the compound of formula 1 is:

when the compound represented by formula 1 is selected from formula 1-3, the structure mainly comprises three parts, wherein two ends are represented by R₁And R₆The middle part of the fluorinated nonpolar group is a disulfonate or disulfinate polar group, and when the fluorinated nonpolar group forms a core-shell double-sheath structure with other solvents or electrolytes, the disulfonate or disulfinate polar group has affinity with other solvents or electrolytes and is located inside the core-shell double-sheath structure, and R is₁And R₆For example, the fluorinated nonpolar group is positioned outside the shell-core double-sheath structure, so that a stable dispersed and isolated structure is formed, and the side reaction between the electrode and the electrolyte is favorably reduced.

The compounds of formulae 1-3 can be prepared by the following routes:

in some embodiments, R₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r is₂Is a single bond; r₃Is selected from

In this example, an exemplary structure of the compound of formula 1 is:

wherein R is₇Selected from alkyl with 1-3 carbon atoms, and r is an integer of 0-2.

When the compound represented by formula 1 is selected from formula 1-4, the structure mainly comprises three parts, wherein two ends are represented by R₁And R₆The middle part of the fluorinated nonpolar group is the polar group of the polyether chain as an example, and when the core-shell double-sheath structure is formed with other solvents or electrolytes, the polar group of the polyether chain as an example has affinity with other solvents or electrolytes and is positioned inside the core-shell double-sheath structure, R₁And R₆The fluorinated nonpolar group is positioned outside the shell-core double-sheath structure, so that a stable dispersed and isolated structure is formed, and the side reaction between an electrode and electrolyte is reduced.

The compounds of formulae 1-4 can be prepared by the following route:

in different embodiments, the compounds of formula 1-1, formula 1-2, formula 1-3 and formula 1-4 may be added alone or in combination.

In some embodiments, the compound of formula 1 is selected from one or more of the following compounds:

the above is a part of the claimed compounds, but the invention is not limited thereto, and should not be construed as being limited thereto.

In some embodiments, the mass percentage of the compound represented by formula 1 is 10% to 90% based on 100% of the total mass of the electrolyte.

In a preferred embodiment, the mass percentage of the compound represented by the structural formula 1 is 40% to 80% based on 100% of the total mass of the electrolyte.

In a more preferred embodiment, the mass percentage of the compound represented by the structural formula 1 is 60% to 80% based on 100% of the total mass of the electrolyte.

In the electrolyte, when the addition amount of the compound shown in the structural formula 1 is in the range, a shell-core double-sheath structure can be effectively formed in the electrolyte, so that the occurrence of side reactions of the electrolyte in the battery circulation process is reduced, and the stability of the electrolyte is improved.

In this example, the compound represented by the formula 1 was used as a main solvent, and the compound represented by the formula 1 was mixed with another cosolvent.

In some embodiments, the solvent further comprises a co-solvent, and the volume ratio of the co-solvent to the compound shown in the structural formula 1 is 1: 100-90: 10.

In a more preferred embodiment, the volume ratio of the cosolvent to the compound shown in the structural formula 1 is 1: 9-1: 2.

In some embodiments, the ether solvent comprises a cyclic ether or a chain ether, and the cyclic ether may be, but is not limited to, 1, 3-Dioxolane (DOL), 1, 4-Dioxan (DX), crown ether, Tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH)₃-THF), 2-trifluoromethyltetrahydrofuran (2-CF)₃-THF); the chain ether may be, but is not limited to, one or more of Dimethoxymethane (DMM), 1, 2-Dimethoxyethane (DME), and diglyme (TEGDME). The nitrile solvent may specifically be, but is not limited to, one or more of acetonitrile, glutaronitrile, malononitrile. The carbonate solvent includes cyclic carbonate or chain carbonate, and the cyclic carbonate can be specifically but not limited to one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), gamma-butyrolactone (GBL) and Butylene Carbonate (BC); the chain carbonate may specifically be, but not limited to, one or more of dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC). The carboxylic ester solvent may be, but not limited to, one or more of Methyl Acetate (MA), Ethyl Acetate (EA), propyl acetate (EP), butyl acetate, Propyl Propionate (PP), and butyl propionate.

In some embodiments, the electrolyte includes one or more of a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt, and an aluminum salt.

In a preferred embodiment, the electrolyte comprises a lithium salt.

In a more preferred embodiment, the electrolyte comprises at least one of lithium hexafluorophosphate, lithium bistrifluoromethylsulfonyl imide, lithium bistrifluorosulfonimide, lithium tetrafluoroborate, lithium difluorooxalato borate.

In some embodiments, the concentration of the electrolyte in the nonaqueous electrolytic solution is 0.1mol/L to 8 mol/L.

In a preferred embodiment, the concentration of the electrolyte in the nonaqueous electrolytic solution is 0.5mol/L to 4 mol/L.

Specifically, the concentration of the electrolyte may be 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, 2.5mol/L, 3mol/L, 3.5mol/L, or 4 mol/L.

In some embodiments, the nonaqueous electrolyte further comprises an additive comprising one or more of biphenyl, fluorobenzene, vinylene carbonate, vinyl trifluoromethyl carbonate, ethylene carbonate, 1, 3-propanesultone, 1, 4-butanesultone, vinyl sulfate, vinyl sulfite, methylene methanedisulfonate, succinonitrile, adiponitrile, 1, 2-bis (2-cyanoethoxy) ethane, and 1,3, 6-hexanetrinitrile.

In some embodiments, the additive is added in an amount of 0.01 to 5.0% based on 100% by mass of the nonaqueous electrolytic solution.

Specifically, the additive may be added in an amount of 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 1.8%, 2%, 2.1%, 2.4%, 3%, 3.5%, 4%, 4.5%, or 5%.

Another embodiment of the present invention provides a battery including a positive electrode, a negative electrode, and the nonaqueous electrolytic solution described above.

The battery comprises the non-aqueous electrolyte, so that the battery has more excellent high-voltage stability and safety; the attenuation of the battery capacity is slowed down by inhibiting the growth of the metal dendrite, and when the lithium-sulfur battery is applied, the solubility of lithium polysulfide in electrolyte can be reduced, the shuttle effect that active substances and the capacity are irreversibly lost due to the fact that the lithium polysulfide is dissolved in the electrolyte and diffuses to a negative electrode is avoided, and the cycling stability of the obtained battery is remarkably improved.

In some embodiments, the battery is a secondary battery, which may be a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a magnesium secondary battery, a zinc secondary battery, an aluminum secondary battery, or the like.

In a preferred embodiment, the battery is a lithium metal battery, a lithium ion battery or a lithium sulphur battery.

In some embodiments, the positive electrode includes a positive electrode capable of reversibly intercalating/deintercalating metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.)Preferably, the positive active material is selected from the group consisting of NCM111, NCM622, NCM532, NCM811, LiFePO₄、LiCO₂、LiMnO₂、LiNiMnO₂Sulfur, and composites thereof.

In some embodiments, the anode includes an anode active material including one or more of a carbon-based anode, a silicon-based anode, a tin-based anode, a lithium anode, a sodium anode, a potassium anode, a magnesium anode, a zinc anode, and an aluminum anode. The carbon-based negative electrode can comprise graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads and the like; the silicon-based negative electrode can comprise silicon, silicon carbon, silicon oxygen, silicon metal compound and the like; the tin-based anode may include tin, tin carbon, tin oxide, tin metal compounds; the lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.

In a preferred embodiment, the negative active material is selected from at least one of metallic lithium and its alloys, graphite, mesocarbon microbeads.

In some embodiments, a separator is also included in the battery, the separator being positioned between the positive electrode and the negative electrode.

The separator may be an existing conventional separator, and may be a polymer separator, a non-woven fabric, and the like, including but not limited to a single layer PP (polypropylene), a single layer PE (polyethylene), a double layer PP/PE, a double layer PP/PP, and a triple layer PP/PE/PP, and the like.

The present invention will be further illustrated by the following examples.

Example 1

This example is illustrative of the nonaqueous electrolyte, battery and method of making the same disclosed in the present invention, and includes the following steps:

preparing a mixed solvent of fluoroethylene carbonate (FEC) and compound 1 in a volume ratio of 2:8, and dissolving LiFSI in the obtained mixed solventThe mixed solvent was adjusted to have a lithium salt concentration of 1M, and 0.5% by mass of DTD was added to obtain an electrolyte solution. The electrolyte is assembled into a lithium-copper half-cell, a lithium sheet is used as a negative electrode, copper foil is used as a positive electrode, electrochemical tests are carried out, and test results show that the lithium-copper half-cell is at 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency for 100 cycles under the condition of the area capacity is 98.5 percent.

Example 2

preparing a mixed solvent of ethylene glycol dimethyl ether (DME) and a compound 2 in a volume ratio of 3:7, dissolving LiFSI in the obtained mixed solvent to make the concentration of lithium salt be 2.5M, and adding 0.5% by mass of DTD to obtain an electrolyte. The electrolyte is assembled into a lithium-sulfur half-cell, a lithium sheet is used as a negative electrode, a sulfur-carbon composite is used as a positive electrode, a constant-current charge-discharge electrochemical test is carried out, the test result is shown in figure 1, and as can be seen from figure 1, the capacity retention rate of the lithium-sulfur half-cell is 85.6% after the lithium-sulfur half-cell is cycled for 100 cycles under the condition of 0.2C.

Example 3

This example illustrates a non-aqueous electrolyte, a battery and a method for preparing the same, comprising the following steps:

preparing a mixed solvent of ethylene glycol dimethyl ether (DME) and a compound 3 in a volume ratio of 3:7, dissolving LiFSI in the obtained mixed solvent to make the concentration of lithium salt be 2.0M, and adding 0.5% by mass of DTD to obtain an electrolyte. The electrolyte is assembled into a lithium metal battery, and an electrochemical test is carried out by using NCM622 as a positive electrode and a lithium sheet as a negative electrode, and the test result shows that the capacity retention rate of the lithium metal battery is 87% after 100 cycles under the condition of 0.5C current density.

Example 4

This example is intended to illustrate the nonaqueous electrolyte, battery and method of making the same disclosed in the present invention, and includes most of the operating steps of example 1, with the following differences:

ethylene glycol dimethyl ether (DME) and a compound 7 are mixed in a volume ratio of 2:8 to serve as a mixed solvent.

The electrochemical test of the obtained lithium copper half cell is carried out, the test result is shown in figure 2, and the test result shows that the concentration of the lithium copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of the battery is 99.24 percent after the battery is cycled for 400 circles under the condition of the area capacity.

Example 5

preparing a mixed solvent of fluoroethylene carbonate (FEC) and compound 1 in a volume ratio of 1: 10.

Electrochemical tests are carried out on the obtained lithium-copper half cell, and the test result shows that the lithium-copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 96.9 percent.

Example 6

a mixed solvent of fluoroethylene carbonate (FEC) and compound 1 in a volume ratio of 1:20 is prepared.

Electrochemical tests are carried out on the obtained lithium-copper half cell, and the test result shows that the lithium-copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 95.0 percent.

Example 7

preparing a mixed solvent of fluoroethylene carbonate (FEC) and a compound 9 in a volume ratio of 2:8, and dissolving 1M LiFSI.

Electrochemical test is carried out on the obtained electrolyte lithium copper half cell, and the test result shows that the lithium copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 99.1 percent.

Example 8

This example is intended to illustrate the nonaqueous electrolyte, battery and method of making the same disclosed in the present invention, and includes most of the steps of example 1, except that:

preparing a mixed solvent of fluoroethylene carbonate (FEC) and a compound 10 in a volume ratio of 2:8, and dissolving 1M LiFSI to prepare an electrolyte.

Electrochemical test is carried out on the obtained electrolyte lithium copper half cell, and the test result shows that the lithium copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 99.2 percent.

Example 9

preparing a mixed solvent of ethylene glycol dimethyl ether (DME) and a compound 11 in a volume ratio of 1:9, and dissolving 1M LiFSI to obtain the electrolyte.

The obtained electrolyte is subjected to electrochemical test of the lithium-copper half cell, and the test result shows that the lithium-copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 98.9 percent.

Example 10

preparing a mixed solvent of ethylene glycol dimethyl ether (DME) and a compound 12 in a volume ratio of 2:8, and dissolving 2M LiFSI to obtain the electrolyte.

The obtained electrolyte is subjected to electrochemical test of the lithium-copper half cell, and the test result shows that the lithium-copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 99.2 percent.

Example 11

The obtained electrolyte is subjected to electrochemical test of the lithium-copper half cell, and the test result shows that the lithium-copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 99.3 percent.

Example 12

preparing a mixed solvent of dimethyl carbonate (DMC) and a compound 14 in a volume ratio of 2:8, and dissolving 2M LiFSI to obtain the electrolyte.

The obtained electrolyte is subjected to electrochemical test of the lithium-copper half cell, and the test result shows that the lithium-copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 98.3 percent.

Example 13

and preparing a mixed solvent of dimethyl carbonate (DMC) and a compound 15 in a volume ratio of 2:8, and dissolving 2M LiFSI to obtain the electrolyte.

The obtained electrolyte is subjected to electrochemical test of the lithium-copper half cell, and the test result shows that the lithium-copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 98.0 percent.

Example 14

Preparing a mixed solvent of fluoroethylene carbonate (FEC) and a compound 18 in a volume ratio of 2:8, and dissolving 1M LiFSI to obtain the electrolyte.

Example 15

This example is intended to illustrate a nonaqueous electrolyte, a battery and a method for preparing the same, which includes most of the steps of example 7, except that:

preparing a mixed solvent of fluoroethylene carbonate (FEC) and a compound 19 in a volume ratio of 8:2, and dissolving 1M LiFSI to obtain the electrolyte.

Electrochemical tests are carried out on the obtained lithium copper half cell, and the test result shows that the lithium copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 99.1 percent.

Comparative example 1

This comparative example is for comparative illustration of the nonaqueous electrolytic solution, battery and method for preparing the same disclosed in the present invention, and includes most of the operational steps in example 1, except that:

fluoroethylene carbonate (FEC) was used as a solvent for the electrolyte.

Electrochemical tests are carried out on the obtained lithium copper half cell, and the test result shows that the lithium copper half cell is at 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 80 percent.

Comparative example 2

Fluoroethylene carbonate (FEC) and compound 20 were mixed in a volume ratio of 2:8 as a mixed solvent.

The electrochemical test of the obtained lithium copper half cell is carried out, the test result is shown in figure 3, and the test result shows that the lithium copper half cell is at 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of 100 cycles under the condition of surface capacity is 92 percent.

Comparative example 3

This comparative example, which is used for comparative illustration of the nonaqueous electrolytic solution, the battery and the method for producing the same disclosed in the present invention, includes most of the operating steps in example 4, except that:

ethylene glycol dimethyl ether (DME) and a compound 21 are mixed in a volume ratio of 2:8 to serve as a mixed solvent.

The obtained lithium copper half cell is subjected to electrochemical test, and the test result shows that the concentration of the lithium copper half cell is 1mA/cm²Current density, 1mAh/cm²The average coulombic efficiency of the cell is 60 percent after 25 cycles under the condition of surface capacity.

Comparative example 4

This comparative example, which is used for comparative illustration of the nonaqueous electrolytic solution, the battery and the method for producing the same disclosed in the present invention, includes most of the operating steps in example 2, except that:

ethylene glycol dimethyl ether (DME) was used as an electrolyte solvent, LiFSI was dissolved in the solvent so that the lithium salt concentration was 2.5M, and 0.5% by mass of DTD was added to obtain an electrolyte. The electrolyte is assembled into a lithium-sulfur half-cell, a lithium sheet is used as a negative electrode, a sulfur-carbon composite is used as a positive electrode, constant-current charge-discharge electrochemical tests are carried out, and test results show that the capacity retention rate of the lithium-sulfur half-cell is 48.1% after the lithium-sulfur half-cell is cycled for 100 cycles under the condition of 0.2C.

Description of the test results

The test results of the comparative examples 1 to 4, 7 to 11 and 1 show that the battery performance is improved to different degrees by adding the compound shown in the structural formula 1-1 or 1-2 provided by the invention into the electrolyte, which indicates that the improvement of the battery performance has better universality under the condition of adding the compound shown in the structural formula 1-1 or 1-2 provided by the invention, and that less part of the active lithium metal generating dead lithium in the electrochemical process is, namely lithium dendrite is not easy to generate, the reversibility of the lithium metal cathode is better, and the battery stability is higher.

It can be seen from the results of comparing example 1 and comparative example 2 that, as shown in comparative example 2, if the polar group part in the compound shown in structural formula 1-1 is fluorinated, the density of the sulfur-oxygen double bond electron cloud is reduced, the polarity of the sulfonate molecule is reduced, it is difficult to form an electrolyte with a core-shell double-sheath layer structure, and the solvent stability is poor, resulting in deterioration of the cycle performance of the battery.

As can be seen from the test results of comparative example 4 and comparative example 3, as shown in comparative example 3, if the polar group part in the compound represented by structural formula 1-2 is fluorinated, the polarity is reduced, it is difficult to form an electrolyte of a core-shell double-sheath structure, and the solvent stability is poor, resulting in deterioration of the cycle performance of the battery.

The test results of comparative example 1, examples 5 and 6 and comparative example 1 show that in the electrolyte solvent, the compound shown in the structural formula 1-1 can better improve the battery performance in a larger addition range.

The test results of the comparative examples 12 to 15 show that the battery performance is improved to different degrees by adding the compound shown in the structural formula 1-3 or the structural formula 1-4 provided by the invention into the electrolyte.

The test results of the comparative examples 14 to 15 show that in the electrolyte solvent, the compound shown in the structural formula 1-4 can better improve the battery performance in a larger addition range.

The solvent FEC, due to its excessive impedance, cannot complete multiple cycles of charging and discharging of the lithium sulfur battery/lithium metal battery as a single solvent.

Since both sides of the compounds 20 and 21 are substituted by fluorine, the polarity is low, which is not favorable for good mutual solubility with conventional solvents such as DME and the like, lithium salts and the like, and further, the whole nonaqueous electrolyte cannot be in a stable double-sheath solution state, so that multi-turn charge-discharge cycles of the lithium-sulfur battery/lithium metal battery cannot be completed.

When the solvent DME is used as a single solvent and applied to the lithium-sulfur battery, the polysulfide shuttling effect is obvious, and the capacity attenuation is serious when charge and discharge circulation is carried out; when the solvent DME is used as a single solvent and applied to a lithium metal battery, because the electrolyte seriously corrodes an anode current collector and solvent molecules are oxidized and decomposed under the condition of high voltage (>4V vs Li +/Li), multi-turn charge-discharge circulation cannot be completed.

The data of example 2 and comparative example 4 show that the compound shown in the structural formula 1-1 can effectively inhibit the polysulfide shuttling effect and remarkably improve the cycle capacity retention rate of the lithium-sulfur battery in an electrolyte solvent.

The data of example 3 show that the compound shown in the structural formula 1-1 can effectively inhibit corrosion of DME to a current collector in an electrolyte solvent, and improve the cycle performance of a lithium metal battery.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A nonaqueous electrolyte comprising an electrolyte and a solvent, wherein the solvent comprises a compound represented by formula 1:

R₁-R₂-O-R₃

structural formula 1

Wherein R is₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl;

R₂is selected from

Or a single bond, n is 1 or 2;

R₃selected from hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, aryloxy or

2. The nonaqueous electrolytic solution of claim 1, wherein R is R₁Has 1 to 10 carbon atoms, R₃Selected from the group consisting of hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl, and aryloxy₃Has 1 to 10 carbon atoms, R₄Has 1 to 10 carbon atoms, R₆The number of carbon atoms of (A) is 1 to 10.

3. The nonaqueous electrolytic solution of claim 1, wherein R is₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is selected from

4. The nonaqueous electrolytic solution of claim 1, wherein R is₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is a single bond; r₃Selected from hydrocarbyl, alkoxy, alkenyl, alkenyloxy, aryl or aryloxy groups.

5. The nonaqueous electrolytic solution of claim 1, wherein R is₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is selected from

n is 1 or 2; r₃Is selected from

m is 1 or 2, R₆Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl.

6. The nonaqueous electrolytic solution of claim 1, wherein R is₁Selected from fluoroalkyl, fluoroalkoxy or fluoroalkenyl; r₂Is a single bond; r₃Is selected from

7. The nonaqueous electrolytic solution of claim 1, wherein the compound represented by the structural formula 1 is selected from one or more of the following compounds:

8. the nonaqueous electrolytic solution of claim 1, wherein the mass percentage of the compound represented by the structural formula 1 is 10% to 90% based on 100% by mass of the total mass of the electrolytic solution.

9. The nonaqueous electrolytic solution of claim 1, wherein the solvent further comprises a cosolvent, and the volume ratio of the cosolvent to the compound represented by the structural formula 1 is 1: 100-90: 10;

10. A battery comprising a positive electrode, a negative electrode and the nonaqueous electrolytic solution according to any one of claims 1 to 9.