Ether-based electrolyte based on ionic liquid modification as well as preparation method and application of ether-based electrolyte

Abstract

The invention discloses an ether-based electrolyte based on ionic liquid modification and a preparation method and application thereof, and belongs to the technical field of lithium batteries. The ether-based electrolyte based on ionic liquid modification comprises a basic electrolyte and an ionic liquid additive, the basic electrolyte is a 1M bis (trifluoromethane sulfonimide) lithium solution, a solvent is ethylene glycol dimethyl ether and 1, 3-dioxolame in a volume ratio of 1: 1, and the basic electrolyte contains 1-5wt% of lithium nitrate; the addition amount of the ionic liquid additive is 0.5-5 wt%. The preparation method of the ether-based electrolyte based on ionic liquid modification comprises the following steps: in an argon glove box (H2O is less than 0.1 ppm, and O2 is less than 0.1 ppm), dropwise adding an ionic liquid additive into a basic electrolyte, and magnetically stirring for 2 hours at 500 rpm until a uniform and transparent solution is formed; the ether-based electrolyte based on ionic liquid modification is suitable for various lithium metal batteries, the coulombic efficiency, the cycle life and the safety of the lithium metal batteries can be effectively improved, and the lithium metal batteries can stably operate at a wider environment temperature range.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to an ether-based electrolyte modified by ionic liquid, and a preparation method and application thereof. Background Art

[0002] As a new generation of energy storage technology, lithium-ion batteries boast high energy density, excellent cycle performance, and high specific power. They are gaining increasing attention for applications in portable electronic devices, electric vehicles, grid peak regulation, and small backup power plants. Lithium-ion batteries consist of positive and negative electrode materials (electrode cores), an electrolyte, and a separator. The electrolyte, often called the "blood" of a lithium battery, serves as the migration medium for lithium ions and bridges the gap between the positive and negative electrodes. It significantly impacts the battery's cycle life, safety, operating temperature, rate capability, and reversible capacity.

[0003] However, the existing lithium-ion battery electrolyte has many problems and limitations.

[0004] The first is the compatibility issue between the electrolyte and the negative electrode interface. Conventional ether-based electrolytes show high interfacial reaction activity with lithium metal negative electrodes, which can easily trigger continuous side reactions. This not only destroys the stability of the interface, causing the impedance to continue to rise, but also significantly shortens the battery cycle life. What is more serious is that during the repeated charge and discharge process of the battery, lithium metal is very likely to grow dendrites, which not only reduces the coulomb efficiency, but also poses a huge safety hazard. Once the dendrites pierce the diaphragm, it will cause a short circuit in the battery, greatly limiting the wide range of practical applications of lithium metal batteries.

[0005] Secondly, insufficient temperature adaptability is another key issue. Existing electrolyte systems show a significant performance degradation in extreme temperature environments, which undoubtedly greatly restricts the application range of lithium metal batteries and makes it difficult to meet the needs of use in diverse and complex environments.

[0006] Furthermore, the existing improvement schemes have many limitations. Taking the additive scheme as an example, although some research teams have tried to use additives to optimize battery performance, the following defects are generally exposed: on the one hand, the compatibility between the additives and the electrolyte matrix is ​​not ideal, and it is difficult to achieve perfect fusion; on the other hand, the additives themselves have poor electrochemical stability and are prone to decomposition reactions, which is obviously not conducive to improving the overall stability of the electrolyte. At the same time, its regulatory effect on the SEI film is very limited, and it is difficult to construct an interface layer that is both stable and has good mechanical strength. Although the CN117691184A patent proposes a composite additive system, which has improved the interface stability and rate performance to a certain extent, it is still plagued by problems such as high cost, cumbersome process and poor long-term stability.

[0007] Finally, new additives face significant technical challenges. For example, the "core-shell" composite additive proposed by the Shanghai Silicate Research Team improves interfacial stability through a synergistic mechanism of ion exclusion and enrichment. However, its prospects for industrial application are bleak. This is because its complex molecular structure relies on precise synthesis processes, and the high-purity raw materials lead to significantly increased costs. Scaling up production presents difficult technical bottlenecks, and the organic components pose numerous risks in terms of environmental safety and high-temperature stability.

[0008] Therefore, the field urgently needs a lithium battery electrolyte that improves interface stability and cycle life, inhibits lithium dendrite growth, enhances safety, improves coulombic efficiency, reduces lithium loss, and broadens the operating temperature range. Summary of the Invention

[0009] The purpose of the present invention is to provide an ether-based electrolyte modified by ionic liquid and its preparation method and application, so as to solve the problems existing in the above-mentioned prior art, so that the lithium battery based on the electrolyte has high energy density, high safety and wide temperature range applicability.

[0010] In order to achieve the above object, the present invention provides the following technical solutions:

[0011] The present invention provides an ether-based electrolyte modified by ionic liquid, comprising a basic electrolyte and an ionic liquid additive.

[0012] Preferably, the basic electrolyte is a 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution, the solvent is ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, and contains 1-5 wt% lithium nitrate.

[0013] Preferably, the ionic liquid additive includes: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide) ([EMIM][TFSI]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1-butyl-3-methylimidazolium bis(fluoromethanesulfonyl imide) ([BMIM][FSI]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl imide) ([EMIM][FSI]), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide) ([BMIM][TFSI]), N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl imide) ([Py13][TFSI]), and N-methyl-N-propylpyrrolidine bis(fluoromethanesulfonyl imide) ([Py13][FSI]).

[0014] Preferably, the amount of the ionic liquid additive added is 0.5-5 wt %, that is, 0.5-5 g of the ionic liquid additive is added to every 100 g of the basic electrolyte.

[0015] Preferably, the amount of the ionic liquid additive added is 1-2 wt%.

[0016] The present invention also provides a method for preparing the above-mentioned ether-based electrolyte modified by ionic liquid, comprising the following steps: in an argon glove box (H2O <0.1ppm, O2 <0.1ppm), adding the ionic liquid additive dropwise to the basic electrolyte, and magnetically stirring (500rpm, 2h) until a uniform transparent solution is formed.

[0017] The present invention also provides an application of the above-mentioned ether-based electrolyte modified by ionic liquid in a lithium metal battery.

[0018] Preferably, the lithium metal battery electrolyte is an ether-based electrolyte based on ionic liquid, the negative electrode is lithium metal, and the positive electrode is one of lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese base, lithium nickel manganese oxide, and lithium iron manganese phosphate.

[0019] The present invention discloses the following beneficial effects:

[0020] 1. The present invention enhances the compatibility of the electrolyte and the lithium metal negative electrode by adding an appropriate amount of ionic liquid additive to the basic electrolyte: Due to the characteristics of the ionic liquid additive, the side reactions between the electrolyte and the lithium metal negative electrode are effectively reduced, the interface stability is significantly improved, and the increase in interface impedance is suppressed, thereby improving the power density and energy efficiency of the lithium metal battery.

[0021] 2. Effectively inhibit the growth of lithium dendrites: Ionic liquid additives help form a more stable and uniform SEI film, which can effectively guide the uniform deposition of lithium, inhibit the growth of lithium dendrites, reduce battery short circuits caused by lithium dendrites piercing the diaphragm, and improve the coulombic efficiency of the battery, thereby extending the battery life.

[0022] 3. Improve battery safety and environmental friendliness: The non-flammable, low-volatile, safe and environmentally friendly properties of ionic liquid additives significantly improve battery safety, reduce safety risks during storage and use, reduce electrolyte volatilization and environmental pollution, and are in line with the concept of green environmental protection.

[0023] 4. Extending battery cycle life: By improving interface stability and inhibiting lithium dendrite growth and side reactions, the electrolyte of the present invention can significantly extend the cycle life of lithium metal batteries and improve battery reliability and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Graphs showing cycle tests of Li-Cu half-cells prepared using the electrolytes in Comparative Example 1, Examples 1, 2, and 3;

[0026] Figure 2 The SEM characterization images of lithium deposition on the Cu negative electrode surface after cycling of the Li-Cu half-cell prepared by the electrolyte in Comparative Example 1 (Figures ad) and Example 2 (Figures eh);

[0027] Figure 3 This is an EIS test graph of the Li-Cu half-cell prepared with the electrolyte in Comparative Example 1 and Example 2 after 100 cycles;

[0028] Figure 4 1 is a cycle test graph of a Li-Li symmetrical battery prepared using the electrolytes in Comparative Example 1 and Example 8;

[0029] Figure 5 1 is a cycle test chart of Li-LFP lithium metal full battery prepared with the electrolyte in Comparative Example 1 and Example 2;

[0030] Figure 6 This is an EIS analysis chart of the Li-LFP lithium metal full battery prepared with the electrolyte in Comparative Example 1 and Example 8 after 100 cycles;

[0031] Figure 7 This is a rate test graph of Li-LFP lithium metal full batteries prepared using the electrolytes in Comparative Example 1 and Example 2;

[0032] Figure 8 This is an analysis chart of the energy density and power density of Li-LFP lithium metal full batteries prepared using the electrolyte in Comparative Example 1 and Example 8. DETAILED DESCRIPTION

[0033] An embodiment of the present invention provides an ether-based electrolyte modified by an ionic liquid, comprising a basic electrolyte and an ionic liquid additive.

[0034] In some preferred embodiments, the basic electrolyte is a 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution, the solvent is ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, and contains 1-5 wt% lithium nitrate.

[0035] In some preferred embodiments, the ionic liquid additive includes: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide) ([EMIM][TFSI]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1-butyl-3-methylimidazolium bis(fluoromethanesulfonyl imide) ([BMIM][FSI]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl imide) ([EMIM][FSI]), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide) ([BMIM][TFSI]), N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl imide) ([Py13][TFSI]), and N-methyl-N-propylpyrrolidine bis(fluoromethanesulfonyl imide) ([Py13][FSI]).

[0036] In some more preferred embodiments, the amount of the ionic liquid additive added is 1-2 wt %. Optionally, the amount of the ionic liquid additive added is 0.5 wt %, or the amount of the ionic liquid additive added is 1 wt %, or the amount of the ionic liquid additive added is 2 wt %.

[0037] An embodiment of the present invention also discloses a method for preparing an ether-based electrolyte modified with an ionic liquid, comprising the following steps: in an argon glove box (H2O <0.1ppm, O2 <0.1ppm), adding an ionic liquid additive dropwise to a base electrolyte, and magnetically stirring (500rpm, 2h) until a uniform transparent solution is formed.

[0038] The present invention also provides an application of the above-mentioned ether-based electrolyte modified by ionic liquid in a lithium metal battery.

[0039] In a preferred embodiment, the lithium metal battery electrolyte is an ether-based electrolyte based on ionic liquid, the negative electrode is lithium metal, and the positive electrode is one of lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium-rich manganese base, lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, and lithium iron manganese phosphate.

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terms used in the present invention are only used to describe particular embodiments and are not intended to limit the present invention.

[0042] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0043] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0044] Example 1

[0045] An ether-based electrolyte modified by ionic liquid, the preparation method is as follows:

[0046] In an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), 0.5 wt% of the ionic liquid additive was added dropwise to the base electrolyte and magnetically stirred (500 rpm, 2 h) to form a homogeneous transparent solution, which was the ether-based electrolyte based on the ionic liquid.

[0047] The ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ([EMIM][TFSI]), the basic electrolyte is a 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution, the solvent is ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, and contains 2wt% lithium nitrate in the solution.

[0048] Example 2

[0049] An ether-based electrolyte modified by ionic liquid is prepared by the same method as in Example 1, except that the amount of the ionic liquid additive added is 1 wt%.

[0050] Example 3

[0051] An ether-based electrolyte modified by ionic liquid is prepared by the same method as in Example 1, except that the amount of the ionic liquid additive added is 2 wt %.

[0052] Example 4

[0053] An ether-based electrolyte modified by ionic liquid is prepared by the same method as in Example 2, except that the amount of the ionic liquid additive added is 5 wt % and the content of lithium nitrate in the base electrolyte is 1 wt %.

[0054] Example 5

[0055] An ether-based electrolyte modified by ionic liquid is prepared by the same method as in Example 2, except that the content of lithium nitrate in the base electrolyte is 5 wt %.

[0056] Example 6

[0057] An ether-based electrolyte modified by ionic liquid is prepared by the same method as in Example 2, except that the type of ionic liquid additive is 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]).

[0058] Example 7

[0059] An ether-based electrolyte modified by ionic liquid is prepared by the same method as in Example 3, except that the type of ionic liquid additive is N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide ([Py13][TFSI]).

[0060] Example 8

[0061] An ether-based electrolyte modified by an ionic liquid is prepared by the same method as in Example 2, except that the ionic liquid additive is a mixture of 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide ([BMIM][FSI]) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), with a mixing mass ratio of 1:1.

[0062] Example 9

[0063] An ether-based electrolyte modified by ionic liquid is prepared by the same method as in Example 2, except that the ionic liquid additive is a mixture of N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide salt ([Py13][TFSI]) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonyl imide salt ([EMIM][FSI]), with a mixing mass ratio of 1:1.

[0064] Example 10

[0065] An ether-based electrolyte modified by an ionic liquid is prepared by the same method as in Example 3, except that the ionic liquid additive is a mixture of 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide ([BMIM][FSI]) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), with a mixing mass ratio of 1:1.

[0066] Comparative Example 1

[0067] An ether-based electrolyte is prepared in an argon glove box (H2O <0.1ppm, O2 <0.1ppm) with a 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution. The solvent is ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1, and the solution contains 2wt% lithium nitrate, which is an ether-based electrolyte (basic electrolyte).

[0068] Test Case

[0069] Electrochemical performance test

[0070] Li-Cu half-cell system (Coulombic efficiency test)

[0071] The electrolyte of Comparative Example 1 was used, lithium metal sheet was used as positive electrode, and Cu was used as negative electrode to assemble a Li-Cu half-cell. The charge and discharge test was carried out at room temperature. The results are as follows Figure 1 shown.

[0072] The electrolytes of Examples 1-3 were used respectively, lithium metal sheets were used as positive electrodes, and Cu was used as negative electrodes to assemble Li-Cu half-cells. The charge and discharge tests were carried out at room temperature. The results were as follows: Figure 1 shown. Figure 1 Reg+0% IL is the electrolyte of Comparative Example 1; Reg+0.5% IL is the electrolyte of Example 1; Reg+1% IL is the electrolyte of Example 2; and Reg+2% IL is the electrolyte of Example 3.

[0073] Results: The base electrolyte had an initial Coulombic efficiency (CE) of only 91.0%, which dropped to 59.2% after 50 cycles. The electrolyte containing 1 wt% ionic liquid achieved an initial CE of 96.8% and maintained 86.0% after 200 cycles. The results of Li-Cu half-cell tests assembled using Comparative Example 1 and Examples 1-3 demonstrate that adding an appropriate proportion of ionic liquid helps stabilize the Cu anode surface, significantly improving the CE of lithium deposition and cycling stability.

[0074] Interface characterization

[0075] (1) SEM analysis Figure 2 (a)~(h)):

[0076] Comparative Example 1 Electrolyte: Lithium deposition exhibits typical dendrite morphology ( Figure 2 (a) to (d));

[0077] Example 2 electrolyte: forming a dense block-shaped deposition morphology ( Figure 2 In (e) to (h), the surface flatness is greatly improved.

[0078] A more stable and uniform SEI film is formed on the surface of the lithium metal negative electrode using the electrolyte of the present invention, which effectively suppresses the uncontrollable growth of lithium dendrites.

[0079] (2) EIS test:

[0080] The Li-Cu half-cells prepared with the electrolytes in Comparative Example 1 and Example 2 were subjected to EIS tests after 100 cycles. Figure 3 shown.

[0081] Figure 3 Reg is the electrolyte of Comparative Example 1; Reg+1%IL is the electrolyte of Example 2.

[0082] Analysis of results: The electrolyte with the addition of ionic liquid in appropriate proportions exhibits smaller interfacial impedance. Ionic liquids achieve a significant reduction in SEI film impedance through component design (high concentration, functional ions), film formation kinetics regulation (fast and uniform), structural optimization (inorganic-dominated, multi-layer composite) and interfacial synergistic effects.

[0083] Li-Li symmetrical battery test

[0084] The electrolyte of Comparative Example 1 was used, and lithium metal sheets were used as positive and negative electrodes to assemble a Li-Li symmetrical battery. The charge and discharge test was carried out at room temperature. The results are as follows Figure 4 shown.

[0085] The electrolyte of Example 8 was used, and lithium metal sheets were used as positive and negative electrodes to assemble a Li-Li symmetrical battery. The charge and discharge test was carried out at room temperature. The results are as follows Figure 4 shown.

[0086] Figure 4 In the figure, Reg is the electrolyte of Comparative Example 1; Reg+1%IL is the electrolyte of Example 8.

[0087] Result analysis: Figure 4 The test results show that at 1mA / cm 2 The electrolyte modified by mixed ionic liquid additives ([BMIM][FSI] and [EMIM][TFSI] mixed in a mass ratio of 1:1) showed excellent cycle stability under the current density of 1:1. This is due to the following aspects: the high ionic conductivity of ionic liquids, the high lithium ion transference number of ionic liquids, which can promote the uniform transmission of lithium ions and reduce the concentration gradient on the electrode surface, thereby inhibiting the growth of lithium dendrites; the ionic liquids are preferentially adsorbed on the electrode surface, forming a stable SEI film on the electrode. The ionic liquids may repair the local damage of SEI through dynamic equilibrium, preventing the continuous decomposition of the electrolyte and the irreversible consumption of lithium; the ionic liquids can change the Li +The solvation sheath structure reduces side reactions between free solvent molecules (such as ether groups) and lithium metal; the ionic liquid promotes the two-dimensional layered deposition of lithium, reducing the formation of loose "dead lithium" and thus reducing interfacial impedance and polarization voltage fluctuations. In summary, the synergistic effect of these aspects enables the Li-Li symmetric battery to achieve ultra-long cycling stability and extremely low polarization voltage.

[0088] The electrolyte of Comparative Example 1 was used, lithium iron phosphate (LFP) was used as the positive electrode, and lithium metal was used as the negative electrode to assemble a Li-LFP lithium metal full battery. Constant current charge and discharge tests were conducted at room temperature, and EIS tests were conducted after 100 cycles. The results are as follows: Figure 5 、 6 shown.

[0089] The electrolyte of Example 2 was used, lithium iron phosphate (LFP) was used as the positive electrode, and lithium metal was used as the negative electrode to assemble a Li-LFP lithium metal full battery. The charge and discharge test was carried out at room temperature and the EIS test was carried out after 100 cycles. The results are as follows Figure 5 、 6 shown.

[0090] Figure 5 Reg is the electrolyte of Comparative Example 1; Reg+1%IL is the electrolyte of Example 2.

[0091] Figure 6 In the figure, Reg is the electrolyte of Comparative Example 1; Reg+1%IL is the electrolyte of Example 8.

[0092] Result analysis: Figure 5 、 6 The test results show that at a current density of 1C and at a large electrode load (>16mg / cm 2 ), the electrolyte modified with ionic liquid additives achieved an initial coulombic efficiency of 99.1%, and after 210 cycles, the capacity retention rate was as high as 95.92%. During the entire cycle, the coulombic efficiency was relatively stable. The initial coulombic efficiency of the benchmark electrolyte was 97.2%, and the capacity had decayed significantly after 90 cycles. In addition, after 100 cycles of testing, the interfacial impedance of the electrolyte modified with the mixed ionic liquid additive was significantly lower than that of the benchmark electrolyte. Tests have shown that ionic liquids can stabilize the lithium metal negative electrode (inhibit dendrites and optimize SEI); improve the LFP positive electrode kinetics (enhance wetting and reduce side reactions); and optimize the electrolyte stability (reduce decomposition and reduce polarization), thereby significantly improving the cycle life and lower interfacial impedance of the Li-LFP full battery.

[0093] The electrolyte of Comparative Example 1 was used, lithium iron phosphate (LFP) was used as the positive electrode, and lithium metal was used as the negative electrode to assemble a Li-LFP lithium metal full battery. The rate charge and discharge test was carried out at room temperature. The results are as follows Figure 7 、 8 shown.

[0094] The electrolyte of Example 2 was used, lithium iron phosphate (LFP) was used as the positive electrode, and lithium metal was used as the negative electrode to assemble a Li-LFP lithium metal full battery. The rate charge and discharge test was carried out at room temperature. The results are as follows Figure 7 、 8 shown.

[0095] Figure 7 Reg is the electrolyte of Comparative Example 1; Reg+1%IL is the electrolyte of Example 2.

[0096] Figure 8 In the figure, Reg is the electrolyte of Comparative Example 1; Reg+1%IL is the electrolyte of Example 8.

[0097] Result analysis: Figure 7 、 8 The test results show that at different current densities, the electrolyte modified with ionic liquid additives exhibits excellent rate performance. From the energy density and power density analysis diagrams, it can be seen that compared with the benchmark electrolyte, the addition of ionic liquid can improve the energy density and power density of the battery system.

[0098] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. An ether-based electrolyte modified by ionic liquid, characterized in that: Includes base electrolyte and ionic liquid additives.

2. The ether-based electrolyte modified by ionic liquid according to claim 1, characterized in that The basic electrolyte is a 1M lithium bis(trifluoromethanesulfonyl)imide solution, the solvent is ethylene glycol dimethyl ether and 1,3-dioxolane in a volume ratio of 1:1, and contains 1-5 wt% of lithium nitrate.

3. The ether-based electrolyte modified by ionic liquid according to claim 1, characterized in that The ionic liquid additive is selected from one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, and N-methyl-N-propylpyrrolidine bis(fluoromethanesulfonyl)imide salt.

4. The ether-based electrolyte modified by ionic liquid according to claim 1, characterized in that The amount of the ionic liquid additive added is 0.5-5 wt%.

5. The ether-based electrolyte modified by ionic liquid according to claim 4, characterized in that The amount of the ionic liquid additive added is 1-2 wt%.

6. A method for preparing an ether-based electrolyte modified by an ionic liquid according to claim 1, characterized in that: The following steps are involved: In an argon glove box, the ionic liquid additive was added dropwise to the base electrolyte and magnetically stirred until a homogeneous transparent solution was formed.

7. The method for preparing an ether-based electrolyte modified by ionic liquid according to claim 6, characterized in that: The environmental conditions of the argon glove box are H2O<0.1ppm, O2<0.1ppm; the specific steps of the magnetic stirring are 500rpm and stirring for 2h.

8. Use of the ether-based electrolyte modified with an ionic liquid according to any one of claims 1 to 5 in the preparation of a lithium metal battery.

9. A lithium metal battery, characterized in that: The electrolyte of the lithium metal battery is the ether-based electrolyte modified by ionic liquid according to any one of claims 1 to 5, the negative electrode is lithium metal, and the positive electrode is one of lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese base, lithium nickel manganese oxide, and lithium iron manganese phosphate.

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