CN112151862B - Application of halogenated substituted imidazole as redox mediator, electrolyte and lithium-oxygen battery - Google Patents

Application of halogenated substituted imidazole as redox mediator, electrolyte and lithium-oxygen battery Download PDF

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CN112151862B
CN112151862B CN202011021912.9A CN202011021912A CN112151862B CN 112151862 B CN112151862 B CN 112151862B CN 202011021912 A CN202011021912 A CN 202011021912A CN 112151862 B CN112151862 B CN 112151862B
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lithium
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substituted imidazole
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刘佳
李丹
谢海明
刘军
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Northeast Normal University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01—ELECTRIC ELEMENTS
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Abstract

The invention belongs to the battery technologyIn particular to an application of halogenated substituted imidazole as a redox medium, an electrolyte and a lithium-oxygen battery. The invention provides an application of halogenated substituted imidazole as a redox medium in a lithium-oxygen battery. In the application of the invention, halogenated substituted imidazole is used as a redox medium and can effectively promote Li2O2To generate and accelerate Li2O2The decomposition efficiency of the lithium-oxygen battery is reduced, the over potential of the lithium-oxygen battery is reduced, and a solid electrolyte interface film protective layer can be generated on the surface of the lithium metal negative electrode in situ, so that the shuttle effect is inhibited, and the cycle life of the lithium-oxygen battery is prolonged. The embodiment shows that the lithium-oxygen battery obtained by using the halogenated substituted imidazole as the redox medium has long cycle life and low charging voltage.

Description

Application of halogenated substituted imidazole as redox mediator, electrolyte and lithium-oxygen battery
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to application of halogenated substituted imidazole as a redox medium, electrolyte and a lithium-oxygen battery.
Background
A lithium-oxygen battery is a battery using lithium as a negative electrode and oxygen as a positive electrode reactant, and has an ultra-high theoretical energy density, but a discharge product (Li) due to poor stability of a lithium metal negative electrode2O2) The problems of slow kinetics of intrinsic decomposition reaction, poor reversibility of an oxygen positive electrode and the like result in large overpotential, poor cycle stability and poor rate performance of the lithium-oxygen battery.
The catalyst can improve the problem of larger overpotential of a lithium oxygen battery to a certain extent, but the active sites of the solid-phase catalyst are insulated by Li2O2After covering, the charge transport at the three-phase interface, especially at the solid/solid interface, is hindered and the catalytic ability is severely restricted. The development of Redox Mediators (RMs) is believed to avoid this problem. During the battery cycle, the RM as a hole agent firstly generates electrochemical reaction to generate reductive RM-Or oxidizing RM+(
Figure GDA0002755339720000011
Or
Figure GDA0002755339720000012
) Which diffuse through the electrolyte and further chemically reduce or oxidize Li2O2The charge transmission of the solid/solid interface is effectively transferred to the charge transmission of the solid/liquid interface, so that the interface through charge impedance of the oxygen electrode can be reduced, the reaction activation energy is reduced, and the continuous catalytic reaction is promoted, thereby achieving the purposes of reducing the polarization of the battery, and improving the charge-discharge capacity and the cycling stability of the battery.
However, RM-And RM+Inevitably, the positive electrode migrates to the surface of the lithium negative electrode to generate a side reaction with the lithium negative electrode, i.e., a "shuttle effect", which leads to the continuous consumption of the RM and the corrosion of the metallic lithium, and directly leads to the energy attenuation of the battery, even the battery fails.
Disclosure of Invention
In view of the above, the present invention provides a method for using halogenated substituted imidazoles as redox mediators, which can effectively promote Li2O2To generate and accelerate Li2O2The decomposition efficiency of the lithium-oxygen battery is reduced, the overpotential of the lithium-oxygen battery is reduced, and a solid electrolyte interface film protective layer can be generated on the surface of the lithium metal negative electrode in situ, so that the shuttle effect is inhibited, and the cycle life of the lithium-oxygen battery is prolonged.
In order to achieve the purpose of the invention, the invention provides the following technical scheme:
the invention provides an application of halogenated substituted imidazole as a redox medium in a lithium-oxygen battery.
Preferably, the molecular structure of the halogenated substituted imidazole comprises substituted imidazole positive ions and halogen ions;
the substituted imidazole positive ion is formed by substituting hydrogen in imidazole by a substituent; the substituent group comprises one or more of alkyl, cyano, benzene derivatives and imidazole derivatives.
Preferably, the substituted imidazole cation has any one of the following structures:
Figure GDA0002755339720000021
preferably, the halide ion is iodide or bromide.
The invention also provides an electrolyte for a lithium-oxygen battery, which comprises halogenated substituted imidazole, lithium salt and an aprotic solvent; the halogenated substituted imidazole is the halogenated substituted imidazole in the technical scheme.
Preferably, the concentration of the halogenated substituted imidazole in the electrolyte is 0.001-2.5 mol/L.
Preferably, the lithium salt comprises one or more of lithium bistrifluoromethanesulfonylimide, lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate and lithium difluorooxalato borate.
Preferably, the concentration of the lithium salt in the electrolyte is 0.01-4.8 mol/L.
Preferably, the aprotic solvent comprises tetraglyme, diglyme or dimethyl sulfoxide.
The invention also provides a lithium-oxygen battery which comprises a porous oxygen anode, a lithium metal cathode, a diaphragm and the electrolyte, wherein the electrolyte is the electrolyte in the technical scheme.
The invention provides an application of halogenated substituted imidazole as a redox medium in a lithium-oxygen battery. In the application of the invention, halogenated substituted imidazole is used as a redox medium, and the halogen couple can promote Li in the charging process of a lithium-oxygen battery2O2The decomposition efficiency is reduced, the overpotential is reduced, and the service life of the battery is effectively prolonged; the imidazole cation can effectively adsorb an intermediate product, namely superoxide ion (O) in the discharging process of the lithium-oxygen battery2·-) Promoting Li2O2Thereby increasing the discharge capacity; in addition, in the charging and discharging process of the lithium-oxygen battery, the imidazole group can effectively form a compact solid electrolyte interface film protective layer on the surface of the lithium metal negative electrode in situ, thereby preventing the uncontrollable growth of lithium dendrite and protecting the lithium metal negative electrode, further inhibiting the shuttle effect and prolonging the cycle life of the lithium-oxygen battery.
The test result of the embodiment shows that the electrolyte containing the halogenated substituted imidazole provided by the invention has obvious oxidation reduction peaks; the lithium-oxygen battery using the halogenated substituted imidazole as the redox medium has high discharge capacity and good cycling stability.
Drawings
FIG. 1 is a CV scan of the electrolytes of example 1 and comparative examples 1 to 2;
FIG. 2 is a constant current full discharge diagram of the button cell obtained in application example 1 and comparative application examples 1-2;
FIG. 3 is a cycle performance test chart of the button cell obtained in application example 1 and comparative application examples 1-2, wherein a is comparative application example 1, b is comparative application example 2, and c is application example 1;
FIG. 4 is an SEM image of a lithium metal cathode after 5 charge-discharge cycles of the button cell obtained in application example 1 and comparative application examples 1-2, wherein a-1 is a plan view of comparative application example 1, a-2 is a sectional view of comparative application example 1, b-1 is a plan view of comparative application example 2, b-2 is a sectional view of comparative application example 2, c-1 is a plan view of application example 1, and c-2 is a sectional view of application example 1;
FIG. 5 is a CV scan of the electrolytes of example 2 and comparative examples 1 to 2;
FIG. 6 is a constant current full discharge diagram of the button cell obtained in application example 2 and comparative application examples 1-2;
fig. 7 is a cycle performance test chart of the button cell obtained in application example 2 and comparative application example 2, wherein a is comparative application example 2, and b is application example 2;
fig. 8 is SEM images of lithium metal cathodes after 5 charge-discharge cycles of the button cells obtained in application example 2 and comparative application example 2, wherein a is comparative application example 2, and b is application example 2;
FIG. 9 is a CV scan of the electrolytes of example 3 and comparative example 3;
fig. 10 is a constant current full discharge diagram of the button cell obtained in application example 3 and comparative application example 3;
fig. 11 is a cycle performance test chart of the button cell obtained in application example 3 and comparative application example 3, wherein a is comparative application example 3, and b is application example 3;
fig. 12 is SEM images of lithium metal negative electrodes after 5 charge-discharge cycles of the button cells obtained in application example 3 and comparative application example 3, wherein a is comparative application example 3, and b is application example 3.
Detailed Description
The invention provides an application of halogenated substituted imidazole as a redox medium in a lithium-oxygen battery.
In the present invention, the molecular structure of the halogenated substituted imidazole preferably includes a substituted imidazole cation and a halogen ion. In the present invention, the substituted imidazolium cation is preferably a cation in which hydrogen in imidazole is substituted with a substituent; the substituents preferably include one or more of alkyl, cyano, benzene, derivatives of benzene, and derivatives of imidazole.
In the present invention, the alkyl group preferably includes one or more of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl; the benzene derivative preferably comprises one or more of toluene, o-xylene, styrene, benzoquinone, halogenated benzene, naphthalene and anthracene; the derivatives of imidazole preferably include one or more of alkyl substituted imidazole, phenyl substituted imidazole, cyanoethylated salt imidazole and azabenzimidazol. In the present invention, the cyanoethylated imidazole is preferably 2- (2-methyl-1-acetonitrile-1-yl) acetonitrile; the cyanoethylated salt imidazole is preferably 1-benzyl-2- (thiocyanomethyl) -3-ethylimidazole; the azabenzimidazole is preferably 6- ((2-methyl-2H-114-imidazol-1-yl) methyl) -1,3, 5-triazine-2, 4-diamine.
In the present invention, the substituted imidazole cation preferably has any one of the following structures:
Figure GDA0002755339720000041
Figure GDA0002755339720000051
in the present invention, the halogen ion is preferably an iodide ion or a bromide ion.
The chemical nomenclature of the substituted halogenated imidazoles is not particularly limited, and may be those known to those skilled in the art, specifically, according to the IUPAC organic nomenclature, such as the following:
Figure GDA0002755339720000052
the invention also provides an electrolyte for a lithium-oxygen battery, which comprises halogenated substituted imidazole, lithium salt and an aprotic solvent; the halogenated substituted imidazole is the halogenated substituted imidazole in the technical scheme.
In the invention, the concentration of the halogenated substituted imidazole in the electrolyte is preferably 0.001-2.5 mol/L, more preferably 0.01-2.3 mol/L, and still more preferably 0.1-2 mol/L.
In the present invention, the lithium salt preferably includes one or more of lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, and lithium difluorooxalatoborate. In the invention, the concentration of the lithium salt in the electrolyte is preferably 0.01-4.8 mol/L, more preferably 0.1-4.5 mol/L, and still more preferably 1-4 mol/L.
In the present invention, the aprotic solvent preferably includes Tetraglyme (TEGDME), Diglyme (DME), or dimethyl sulfoxide (DMSO).
In the present invention, the method for preparing the electrolyte preferably includes the steps of: and mixing the lithium salt and the aprotic solvent, and adding halogenated substituted imidazole into the obtained mixed system to obtain the electrolyte.
The invention also provides a lithium-oxygen battery, which comprises a porous oxygen anode, a lithium metal cathode, a diaphragm and the electrolyte, wherein the electrolyte is the electrolyte in the technical scheme.
In the present invention, the lithium-oxygen battery includes a lithium metal negative electrode, a porous oxygen positive electrode, a separator, and an electrolyte.
In the present invention, the electrolyte in the lithium-oxygen battery is the electrolyte in the above technical solution, and is not described herein again.
The lithium metal negative electrode of the present invention is not particularly limited, and a lithium metal negative electrode known to those skilled in the art may be used.
In the present invention, the porous oxygen positive electrode includes a substrate, and conductive carbon and a binder supported on the substrate. In the present invention, the substrate is preferably a stainless steel net, a carbon cloth, or a carbon paper. In the present invention, the conductive carbon preferably includes one or more of supp, acetylene black, ketjen black, porous carbon, graphene, amorphous carbon, and carbon nanotubes. In the present invention, the binder preferably includes one or more of Polytetrafluoroethylene (PTFE), Styrene Butadiene Rubber (SBR), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), and lithium-metallized nafion. In the invention, the mass ratio of the conductive carbon to the binder is preferably (1-9): 1, more preferably (2-8): 1, and preferably (2-7): the loading of the conductive carbon and binder on the substrate is not particularly limited in the present invention, and may be those known to those skilled in the art. In the invention, the total loading amount of the conductive carbon and the binder on the substrate is preferably 0.05-0.65 mg/cm2。
The preparation method of the porous oxygen anode is not particularly limited, and the preparation method of the porous oxygen anode in the field can be adopted.
In the present invention, the method for preparing the porous oxygen positive electrode preferably includes the steps of:
mixing and stirring conductive carbon, a binder and a solvent to obtain slurry;
and coating the slurry on the surface of a substrate, and drying to obtain the porous oxygen anode.
In the present invention, the solvent is preferably acetone, ethanol or N-methylpyrrolidone (NMP). In the invention, the mixing and stirring time is preferably 4-24 h, and more preferably 10-20 h; the stirring rate is not particularly limited in the present invention, and a stirring rate known to those skilled in the art may be used. In the invention, the drying temperature is preferably 40-150 ℃, and more preferably 50-130 ℃; the time is preferably 4 to 24 hours, and more preferably 5 to 20 hours.
In the present invention, the separator is preferably a glass fiber separator. In the invention, the thickness of the glass fiber diaphragm is preferably 0.3-3.5 mm, and more preferably 0.8-2 mm. The source of the separator is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used.
The method for assembling the lithium-oxygen battery is not particularly limited, and the lithium-oxygen battery can be assembled by adopting a structure of the lithium-oxygen battery well known to a person skilled in the art. In the invention, when the lithium-oxygen battery is assembled, the diaphragm is a diaphragm soaked with electrolyte. In the invention, the impregnation amount of the electrolyte on the diaphragm is preferably 110-180 mu L/cm2More preferably 120 to 170. mu.L/cm2。
In order to further illustrate the present invention, the application of a halogenated substituted imidazole as a redox mediator, an electrolyte and a lithium-oxygen battery provided by the present invention will be described in detail with reference to the following examples, which should not be construed as limiting the scope of the present invention. It is to be understood that the disclosed embodiments are merely exemplary of the invention, and are not intended to be exhaustive or exhaustive. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The formula of the halogenated substituted imidazole in this example is:
Figure GDA0002755339720000071
mixing LiTFSI and TEGDME to obtain a mixed solution with the LiTFSI concentration of 1mol/L, adding halogenated substituted imidazole into the mixed solution, and stirring for 72 hours to obtain an electrolyte, wherein the concentration of the halogenated substituted imidazole in the electrolyte is 0.1 mol/L.
Comparative example 1
And mixing the LiTFSI and the TEGDME to obtain a mixed solution with the LiTFSI concentration of 1mol/L, thereby obtaining the electrolyte.
Comparative example 2
LiI is used as a redox mediator to replace halogenated substituted imidazole in example 1, and the other technical means are the same as those of example 1 to obtain the electrolyte.
In an argon atmosphere, adopting a three-electrode system to respectively perform CV scanning on the electrolytes of the example 1 and the comparative examples 1-2, wherein the CV scanning conditions are as follows: the working electrode is a glassy carbon electrode, the reference electrode is a silver electrode, the counter electrode is a platinum electrode, the scanning speed is 50mV/S, and the voltage range is-0.8-1.8V vs+The CV scan obtained is shown in fig. 1. As can be seen from fig. 1, the electrolyte system provided in example 1 also exhibits a low potential pair (ii) as well as the system containing LiI-/I3 -) Redox peak and high potential pair (I)3 -/I2) Redox peak of (a); while comparative example 1 had no redox peak.
Application example 1
According to the mass ratio of 9: 1, taking SuperP and PVDF from a material, and adding N-methyl pyrrolidone to obtain anode slurry; coating the obtained anode slurry on the surface of carbon paper, and drying at 120 ℃ for 12h to obtain a porous oxygen anode, wherein the total load amount of Super P and PVDF on the surface of the porous oxygen anode is 0.4-0.5 mg/cm2；
Adopting a glass fiber diaphragm as a battery diaphragm;
a lithium metal negative electrode and a separator impregnated with the electrolyte of example 1 were used (the impregnation amount of the electrolyte was 150. mu.L/cm)2) The order of assembly of the porous oxygen anode, under high purity argon atmosphere (H)2O<0.1ppm，O2<0.1ppm) assembly 2025 button cell.
And (3) testing: and (3) performing constant current charge and discharge test on the obtained 2025 type button battery by adopting a Land battery test system, wherein the test conditions are as follows: the constant temperature is 25 ℃, the current density is 200mA/g, the specific capacity is limited to 500mAh/g (calculated by taking the mass of the conductive carbon material in the oxygen anode as the standard), and the potential range is 2.2-4.0V vs+。
Comparative application example 1
The electrolyte of comparative example 1 was used in place of the electrolyte of example 1, and the remaining technical means were the same as in application example 1, to obtain a button cell.
Comparative application example 2
The electrolyte of comparative example 2 was used in place of the electrolyte of example 1, and the remaining technical means were the same as in application example 1, to obtain a button cell.
And (3) respectively carrying out constant current full discharge tests on the button batteries obtained in the corresponding application example 1 and the comparative application examples 1-2, and obtaining a constant current full discharge graph shown in a figure 2. As can be seen from fig. 2, the discharge capacity of application example 1 is 10161mAh/g, the discharge capacity of comparative application example 1 is 6746mAh/g, and the discharge capacity of comparative application example 2 is 8304mAh/g, and it can be seen that the button cell provided in application example 1 of the present invention exhibits a higher discharge capacity. The reason for the analysis is that the imidazole group contained in the electrolyte efficiently promotes the generation of lithium superoxide.
And (3) respectively carrying out cycle performance tests on the button batteries obtained in the corresponding application example 1 and the comparative application examples 1-2, and obtaining a cycle performance test chart shown in figure 3, wherein a is the comparative application example 1, b is the comparative application example 2, and c is the application example 1. As can be seen from fig. 3, the button cell provided in application example 1 of the present invention exhibited higher cycle stability.
And (3) after 5 times of charge and discharge cycles are respectively carried out on the button batteries obtained in the corresponding example 1 and the comparative application examples 1-2, disassembling the button batteries, stripping lithium metal cathodes, and respectively carrying out a scanning electron microscope test, wherein the obtained SEM pictures are shown in figure 4, wherein a-1 is a plan view of the comparative application example 1, a-2 is a sectional view of the comparative application example 1, b-1 is a plan view of the comparative application example 2, b-2 is a sectional view of the comparative application example 2, c-1 is a plan view of the application example 1, and c-2 is a sectional view of the application example 1. As can be seen from fig. 4, the lithium metal negative electrode was corroded to different degrees after 5 cycles for the coin cell without redox mediator and the coin cell with LiI; after the button battery provided by application example 1 is subjected to 5 charge-discharge cycles, a relatively uniform SEI film appears on the surface of the lithium metal negative electrode, which indicates that the addition of the halogenated substituted imidazole can generate an SEI protective layer in situ on the surface of the lithium metal negative electrode sheet in the battery cycle process, and the SEI protective layer can effectively prevent the shuttle effect, so that the lithium negative electrode is protected.
Example 2
The formula of the halogenated substituted imidazole in this example is:
Figure GDA0002755339720000101
mixing lithium perchlorate and DMSO to obtain a mixed solution with the lithium perchlorate concentration of 1mol/L, then adding halogenated substituted imidazole into the mixed solution, and stirring for 72 hours to obtain an electrolyte, wherein the concentration of the halogenated substituted imidazole in the electrolyte is 0.2 mol/L.
CV scanning was performed on the electrolytes of example 2 and comparative examples 1 to 2 using a three-electrode system in an argon atmosphere, and the obtained CV scanning patterns are shown in FIG. 5. As can be seen from fig. 5, the electrolyte system provided in example 2 also exhibits a low potential pair (ii) as well as the system containing LiI-/I3 -) Redox peak and high potential pair (I)3 -/I2) Redox peak of (a); while comparative example 1 had no redox peak.
Application example 2
According to the mass ratio of 8: 2, taking the carbon nano tube and the PVDF as materials, and adding N-methyl pyrrolidone to obtain anode slurry; coating the obtained anode slurry on the surface of carbon paper, and drying at 120 ℃ for 12 hours to obtain a porous oxygen anode, wherein the total load amount of the carbon nano tube and PVDF on the surface of the porous oxygen anode is 0.4-0.5 mg/cm2；
Adopting a glass fiber diaphragm as a battery diaphragm;
the lithium metal negative electrode, the separator impregnated with the electrolyte of example 2, and the porous oxygen positive electrode were assembled in this order under a high-purity argon atmosphere (H)2O<0.1ppm，O2<0.1ppm) assembly 2025 button cell.
And (3) testing: adopting a Land battery testing system to perform constant-current charge-discharge testing on the obtained 2025 type button battery, wherein the set testing conditions are as follows: the constant temperature is 25 ℃, the current density is 200mA/g, the specific capacity is limited to 500mAh/g (calculated by taking the mass of the conductive carbon material in the oxygen anode as the standard), and the potential range is 2.2-4.0V vs+。
And (3) respectively carrying out constant current full discharge tests on the button batteries obtained in the corresponding example 2 and the comparative application examples 1-2, and obtaining a constant current full discharge graph shown in figure 6. As can be seen from fig. 6, the discharge capacity of application example 2 was 9570mAh/g, and it can be seen that the button cell provided in application example 2 of the present invention exhibited a higher discharge capacity. The reason for the analysis is that the imidazole group contained in the electrolyte efficiently promotes the generation of lithium superoxide.
And (3) respectively carrying out cycle performance tests on the button batteries obtained in the corresponding application example 2 and the comparative application example 2, and obtaining a cycle performance test chart shown in figure 7, wherein a is the comparative application example 2, and b is the application example 2. As can be seen from fig. 7, the button cell provided in application example 2 of the present invention exhibited higher cycle stability.
After 5 times of charge-discharge cycles of the button cells obtained in the corresponding application example 2 and the comparative application example 2, the button cells were disassembled, the lithium metal negative electrodes were stripped, and then the scanning electron microscope tests were performed, and the obtained SEM images are shown in fig. 8, where a is the comparative application example 2, and b is the application example 2. As can be seen from fig. 8, the button cell containing LiI showed significant corrosion of the lithium metal negative electrode after 5 cycles of charging and discharging; after the button cell provided by the application example 2 is subjected to 5 charge-discharge cycles, a relatively uniform SEI film appears on the surface of the lithium metal negative electrode, which shows that the addition of the halogenated substituted imidazole provided by the invention can form a relatively uniform SEI protective layer with a self-defense function in situ on the surface of the lithium metal negative electrode in the electrochemical cycle process, so that the surface of the lithium metal can be kept smooth, no dendrite and no corrosion are generated, the shuttle effect is effectively inhibited, the lithium entering the negative electrode is protected, and the service life of the lithium oxygen battery is prolonged.
Example 3
The formula of the halogenated substituted imidazole in this example is:
Figure GDA0002755339720000111
mixing LiTFSI and TEGDME to obtain a mixed solution with the LiTFSI concentration of 1mol/L, adding halogenated substituted imidazole into the mixed solution, and stirring for 72 hours to obtain an electrolyte, wherein the concentration of the halogenated substituted imidazole in the electrolyte is 0.02 mol/L.
Comparative example 3
LiIBr is used as a redox medium to replace halogenated substituted imidazole, and other technical means are the same as those of the embodiment 3 to obtain the electrolyte.
CV scans were performed on the electrolytes of example 3 and comparative example 3, respectively, using a three-electrode system under an argon atmosphere, and the obtained CV scans are shown in fig. 9. As can be seen in fig. 9, the electrolyte system provided in example 3 also exhibits a low potential pair (Br), as well as the system containing LiBr-/Br3 -) Redox peak and high potential pair (Br) of (C)3 -/Br2) Redox peak of (2); while comparative example 3 has no redox peak.
Application example 3
According to the mass ratio of 7: 3, taking the carbon nano tube and the lithium metallized nafion, and adding acetone to obtain anode slurry; coating the obtained anode slurry on the surface of carbon paper, and drying at 120 ℃ for 12h to obtain a porous oxygen anode, wherein the total load amount of the carbon nano tube and the lithium metallized nafion on the surface of the porous oxygen anode is 0.4-0.5 mg/cm2；
Adopting a glass fiber diaphragm as a battery diaphragm;
the lithium metal negative electrode, the separator impregnated with the electrolyte of example 3, and the porous oxygen positive electrode were assembled in this order under a high-purity argon atmosphere (H)2O<0.1ppm，O2<0.1ppm) assembly 2025 button cell.
And (3) testing: and (3) carrying out constant current charge and discharge test on the obtained 2025 type button battery by adopting a Land battery test system, wherein the set test conditions are as follows: the constant temperature is 25 ℃, the current density is 200mA/g, the specific capacity is limited to 500mAh/g (calculated by taking the mass of the conductive carbon material in the oxygen anode as the standard), and the potential range is 2.2-4.0V vs+。
Comparative application example 3
LiBr is used as a redox medium to replace halogenated substituted imidazole, and other technical means are consistent with those of application example 3, so that the button cell is obtained.
And (3) respectively carrying out constant current full discharge tests on the button cells obtained in the corresponding example 3 and the comparative example 3, and obtaining constant current full discharge graphs as shown in a figure 10. As can be seen from fig. 10, the discharge capacity of comparative example 3 was 7927mAh/g, and the discharge capacity of comparative application example 3 was 5319mAh/g, and it can be seen that the button cell provided in application example 3 of the present invention exhibited a higher discharge capacity. The reason for the analysis is that the imidazole group contained in the electrolyte efficiently promotes the generation of lithium superoxide.
And (3) respectively carrying out cycle performance tests on the button batteries obtained in the corresponding application example 3 and the comparative application example 3, and obtaining a cycle performance test chart shown in figure 11, wherein a is the comparative application example 3, and b is the application example 3. As can be seen from fig. 11, the button cell provided in application example 3 of the present invention exhibited higher cycle stability.
After 5 charge-discharge cycles of the button cells obtained in the corresponding application example 3 and the comparative application example 3 were performed, the button cells were disassembled, the lithium metal negative electrodes were stripped, and then the scanning electron microscope tests were performed, and the obtained SEM images are shown in fig. 12, where a is the comparative application example 3, and b is the application example 3. As can be seen in fig. 12, the lithium metal negative electrode showed corrosion after 5 cycles of charging and discharging for the cell containing LiBr; after the button cell provided by application example 3 is subjected to 5 charge-discharge cycles, a relatively uniform SEI film appears on the surface of the lithium metal negative electrode, which shows that the addition of the halogenated substituted imidazole provided by the invention can generate an SEI protective layer on the surface of the lithium metal negative electrode in situ in the cell cycle process, and the SEI protective layer can effectively prevent the occurrence of shuttle effect, so that the lithium negative electrode is protected, and the cycle life of the lithium oxygen cell is prolonged.
Example 4
The formula of the halogenated substituted imidazole in this example is:
Figure GDA0002755339720000131
mixing lithium perchlorate and DMSO to obtain a mixed solution with the lithium perchlorate concentration of 2.5mol/L, adding halogenated substituted imidazole into the mixed solution, and stirring for 72 hours to obtain an electrolyte, wherein the concentration of the halogenated substituted imidazole in the electrolyte is 0.005 mol/L.
Application example 4
According to the mass ratio of 8: 2, taking the SuperP and the PVDF from the raw materials, and adding N-methyl pyrrolidone to obtain positive slurry; coating the obtained anode slurry on the surface of carbon paper, and drying at 120 ℃ for 12h to obtain a porous oxygen anode, wherein the total load amount of Super P and PVDF on the surface of the porous oxygen anode is 0.4-0.5 mg/cm2；
Adopting a glass fiber diaphragm as a battery diaphragm;
the lithium metal negative electrode, the separator impregnated with the electrolyte of example 4, and the porous oxygen positive electrode were assembled in this order under a high-purity argon atmosphere (H)2O<0.1ppm，O2<0.1ppm) assembly 2025 button cell.
And (3) testing: and (3) carrying out constant current charge and discharge test on the obtained 2025 type button battery by adopting a Land battery test system, wherein the set test conditions are as follows: the constant temperature is 25 ℃, the current density is 50-500 mA/g, the specific capacity is limited to 500-2000 mAh/g (calculated by taking the mass of the conductive carbon material in the oxygen anode as the standard), and the potential range is 2.2-4.0V vs+. The test results were similar to application example 1, showing good capacity and cycling stability.
Example 5
The structural formula of the halogenated substituted imidazole in this example is:
Figure GDA0002755339720000141
lithium hexafluorophosphate and DMSO are mixed to obtain a mixed solution with the lithium hexafluorophosphate concentration of 1mol/L, and then halogenated substituted imidazole in the embodiment is added into the mixed solution and stirred for 72 hours to obtain an electrolyte, wherein the concentration of the halogenated substituted imidazole in the electrolyte is 0.25 mol/L.
Application example 5
According to the mass ratio of 9: 1 taking acetylene black and PVDF as raw materials and adding N-methyl pyrrolidone to obtain anode slurry; coating the obtained anode slurry on the surface of carbon paper, and drying at 120 ℃ for 12h to obtain a porous oxygen anode, wherein the total load amount of Super P and PVDF on the surface of the porous oxygen anode is 0.4-0.5 mg/cm2；
Adopting a glass fiber diaphragm as a battery diaphragm;
the lithium metal negative electrode, the separator impregnated with the electrolyte of example 5, and the porous oxygen positive electrode were assembled in this order under a high-purity argon atmosphere (H)2O<0.1ppm，O2<0.1ppm) assembly 2025 button cell.
And (3) testing: and (3) carrying out constant current charge and discharge test on the obtained 2025 type button battery by adopting a Land battery test system, wherein the set test conditions are as follows: the constant temperature is 25 ℃, the current density is 50-500 mA/g, the specific capacity is limited to 500-2000 mAh/g (calculated by taking the mass of the conductive carbon material in the oxygen anode as the standard), and the potential range is 2.2-4.0V vs+. The test results were similar to application example 1, showing good capacity and cycling stability.
Example 6
The formula of the halogenated substituted imidazole in this example is:
Figure GDA0002755339720000151
lithium hexafluorophosphate and DME are mixed to obtain a mixed solution with the lithium hexafluorophosphate concentration being 1.8mol/L, halogenated substituted imidazole in the embodiment is added into the mixed solution, and the mixed solution is stirred for 72 hours to obtain an electrolyte, wherein the concentration of the halogenated substituted imidazole in the electrolyte is 0.1 mol/L.
Application example 6
According to the mass ratio of 6: 4, taking the graphene and the PVDF, and adding N-methyl pyrrolidone to obtain positive electrode slurry; coating the obtained anode slurry on the surface of carbon paper, and drying at 120 ℃ for 12h to obtain a porous oxygen anode, wherein the total load amount of Super P and PVDF on the surface of the porous oxygen anode is 0.4-0.5 mg/cm2；
Adopting a glass fiber diaphragm as a battery diaphragm;
the lithium metal negative electrode, the separator impregnated with the electrolyte of example 6, and the porous oxygen positive electrode were assembled in this order under a high-purity argon atmosphere (H)2O<0.1ppm，O2<0.1ppm) assembly 2025 button cell.
And (3) testing: and (3) carrying out constant current charge and discharge test on the obtained 2025 type button battery by adopting a Land battery test system, wherein the set test conditions are as follows: the constant temperature is 25 ℃, the current density is 50-500 mA/g, the specific capacity is limited to 500-2000 mAh/g (calculated by taking the mass of the conductive carbon material in the oxygen anode as the standard), and the potential range is 2.2-4.0V vs+. The test results were similar to application example 1, showing good capacity and cycling stability.
Example 7
The formula of the halogenated substituted imidazole in this example is:
Figure GDA0002755339720000152
mixing lithium perchlorate and DME to obtain a mixed solution with the lithium perchlorate concentration of 2mol/L, adding halogenated substituted imidazole into the mixed solution, and stirring for 72 hours to obtain electrolyte, wherein the concentration of the halogenated substituted imidazole in the electrolyte is 0.2 mol/L.
Application example 7
According to the mass ratio of 8: taking amorphous carbon and PVDF as raw materials and adding N-methyl pyrrolidone to obtain anode slurry; coating the obtained anode slurry on the surface of carbon paper, and drying at 120 ℃ for 12h to obtain a porous oxygen anode, wherein the total load amount of Super P and PVDF on the surface of the porous oxygen anode is 0.4-0.5 mg/cm2；
Adopting a glass fiber diaphragm as a battery diaphragm;
the lithium metal negative electrode, the separator impregnated with the electrolyte of example 7, and the porous oxygen positive electrode were assembled in this order under a high-purity argon atmosphere (H)2O<0.1ppm，O2<0.1ppm) assembly 2025 button cell.
And (3) testing: and (3) carrying out constant current charge and discharge test on the obtained 2025 type button battery by adopting a Land battery test system, wherein the set test conditions are as follows: the constant temperature is 25 ℃, the current density is 50-500 mA/g, the specific capacity is limited to 500-2000 mAh/g (calculated by taking the mass of the conductive carbon material in the oxygen anode as the standard), and the potential range is 2.2-4.0V vs+. The test results were similar to application example 1, showing good capacity and cycling stability.
Example 8
The formula of the halogenated substituted imidazole in this example is:
Figure GDA0002755339720000161
mixing lithium perchlorate and DME to obtain a mixed solution with the lithium perchlorate concentration of 1mol/L, adding halogenated substituted imidazole into the mixed solution, and stirring for 72 hours to obtain electrolyte, wherein the concentration of the halogenated substituted imidazole in the electrolyte is 0.5 mol/L.
Application example 8
According to the mass ratio of 9: 1, taking Ketjen black and PVDF, and adding N-methyl pyrrolidone to obtain anode slurry; coating the obtained anode slurry on the surface of carbon paper, and drying at 120 ℃ for 12h to obtain a porous oxygen anode, wherein the total load amount of Super P and PVDF on the surface of the porous oxygen anode is 0.4-0.5 mg/cm2；
Adopting a glass fiber diaphragm as a battery diaphragm;
the lithium metal negative electrode, the separator impregnated with the electrolyte, and the porous oxygen positive electrode were assembled in this order under a high-purity argon atmosphere (H)2O<0.1ppm，O2<0.1ppm) assembly 2025 button cell.
And (3) testing: and (3) carrying out constant current charge and discharge test on the obtained 2025 type button battery by adopting a Land battery test system, wherein the set test conditions are as follows: the constant temperature is 25 ℃, the current density is 50-500 mA/g, the specific capacity is limited to 500-2000 mAh/g (calculated by taking the mass of the conductive carbon material in the oxygen anode as the standard), and the potential range is 2.2-4.0V vs+。
In an argon atmosphere, CV scans were performed on the electrolytes obtained in examples 4 to 8 using a three-electrode system, and the obtained CV scan results were all expressed as: the electrolyte system exhibits a low potential pair redox peak and a high potential pair redox peak.
And respectively carrying out constant current full discharge tests on the button batteries obtained in the corresponding examples 4-8, wherein the obtained constant current full discharge test results are shown as follows: the button cell provided by application examples 4-8 of the invention shows higher discharge capacity, and the reason for analysis is that the imidazole group contained in the electrolyte efficiently promotes the generation of lithium superoxide.
And (3) respectively carrying out cycle performance tests on the button batteries obtained in the application examples 4-8, wherein the cycle performance test results show that the button batteries provided by the application examples 4-8 have high cycle stability.
After the button batteries obtained in the application examples 4-8 are subjected to charge-discharge cycles for 5 times respectively, the button batteries are disassembled, the lithium metal negative electrodes are stripped, and then scanning electron microscope tests are performed respectively, and the SEM image results show that after the button batteries provided in the application examples 4-8 are subjected to charge-discharge cycles for 5 times, uniform SEI films are formed on the surfaces of the lithium metal negative electrodes, so that an SEI protective layer can be generated on the surfaces of the lithium metal negative electrodes in situ in the battery cycle process due to the addition of halogenated substituted imidazole, and the SEI protective layer can effectively prevent the shuttle effect, so that the lithium negative electrodes are protected.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.

Claims (8)

1. The halogenated substituted imidazole is used as a redox medium and is applied to a lithium-oxygen battery;
the molecular structure of the halogenated substituted imidazole comprises substituted imidazole positive ions and halogen ions;
the substituted imidazole positive ion has any one of the following structures:
Figure FDA0003512047240000011
2. use according to claim 1, characterized in that the halide ion is iodide or bromide.
3. An electrolyte for use in a lithium oxygen battery, the electrolyte comprising a halogenated substituted imidazole, a lithium salt, and an aprotic solvent; the halogenated substituted imidazole is the halogenated substituted imidazole according to any one of claims 1 to 2.
4. The electrolyte of claim 3, wherein the halogenated substituted imidazole is present in the electrolyte at a concentration of 0.001 to 2.5 mol/L.
5. The electrolyte of claim 3, wherein the lithium salt comprises one or more of lithium bistrifluoromethanesulfonylimide, lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, and lithium difluorooxalatoborate.
6. The electrolyte of claim 5, wherein the concentration of the lithium salt in the electrolyte is 0.01-4.8 mol/L.
7. The electrolyte of claim 3, wherein the aprotic solvent comprises tetraglyme, diglyme, or dimethyl sulfoxide.
8. A lithium-oxygen battery, comprising a porous oxygen positive electrode, a lithium metal negative electrode, a separator and an electrolyte, wherein the electrolyte is the electrolyte according to any one of claims 3 to 7.
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