An electrolyte additive, electrolyte and lithium-air battery or lithium-lithium symmetric battery

Abstract

The application discloses an electrolyte additive, an electrolyte and a lithium-air battery or a lithium-lithium symmetric battery, and relates to the technical field of battery materials. Components of the additive include a halogen Lewis acid and a halogen oxygen-containing cyclic compound. The application can reduce the charging overpotential of the lithium-air battery or the lithium-lithium symmetric battery, form an SEI film on the surface of a lithium negative electrode, inhibit the occurrence of a side reaction on the surface of the lithium negative electrode, inhibit the dendrite growth of the lithium negative electrode, and improve the cycle life of the lithium-air battery.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to an electrolyte additive, an electrolyte, and a lithium-air battery or a lithium-lithium symmetric battery. Background Technology

[0002] The lithium-air battery provides 13000Wh / kg. -1 The potential for mass energy density is up to nine times that of lithium-ion batteries. However, non-aqueous lithium-air batteries face many challenges in practical applications. Lithium metal, as a typical anode material in lithium-air batteries, is highly reducing and easily affected by the electrolyte and oxygen-rich environment. It can react with trace amounts of water in the electrolyte and system to form byproducts such as lithium hydroxide (LiOH) and lithium carbonate (Li2CO3). In addition, oxygen dissolves in the electrolyte and diffuses to the anode, further reacting with lithium metal. Another problem comes from the insulating discharge product lithium peroxide. The accumulation of lithium peroxide causes passivation of the positive electrode and prevents further discharge of the lithium-air battery, limiting the discharge capacity. At the same time, the insulating properties of lithium peroxide make it difficult to decompose, resulting in ultra-high overpotentials exceeding 1V during charging.

[0003] Currently, research on lithium metal anode protection and improved anode stability using artificial solid electrolyte interphase (SEI) membranes has been reported. However, batteries using only organic solid electrolyte interphase membranes (SEI) are still limited. + Low conductivity is detrimental to long-term battery cycling. Batteries using inorganic solid electrolyte interphase (SEI) membranes for lithium anode protection can improve the energy efficiency and cycle performance of lithium-air batteries. Batteries using only inorganic solid electrolyte interphase (SEI) membranes have higher mechanical strength, but their flexibility is poor and they are difficult to adapt to dendrite growth or volume changes during battery charging and discharging, which can lead to SEI membrane breakdown and battery short circuit. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, the present invention provides an electrolyte additive, an electrolyte, and a lithium-air battery or a lithium-lithium symmetrical battery, which can reduce the charging overpotential of the lithium-air battery or the lithium-lithium symmetrical battery and form an SEI film on the surface of the lithium anode, suppressing the occurrence of side reactions on the surface of the lithium anode, and at the same time suppressing the dendrite growth of the lithium anode, thereby improving the cycle life of the lithium-air battery.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides an electrolyte additive, wherein the additive comprises halogen Lewis acids and halogen oxygen-containing cyclic compounds.

[0007] The halogen Lewis acid is selected from one or more of aluminum chloride (AlCl3), zinc chloride (ZnCl2), magnesium chloride (MgCl2), indium chloride (InCl3), aluminum bromide (AlBr3), zinc bromide (ZnBr2), magnesium bromide (MgBr2), indium bromide (InBr3), aluminum iodide (AlI3), zinc iodide (ZnI2), magnesium iodide (MgI2), and indium iodide (InI3), and its general structural formula is XY. n ;

[0008] The halogen-containing oxygen-containing cyclic compounds include one or more of the structural formulas shown in formulas (1) to (5), wherein the hydrogen in formulas (1) to (5) can be substituted by any one or more of C1 to C12 alkyl, phenyl, C1 to C12 alkoxy, benzyl, hydroxyl, amino, C3 to C12 epoxy, urea, vinyloxy, mercapto, thio, nitro, piperidine, imidazole, and sulfoxide;

[0009] Wherein, X is a metallic element and Y is a halogen element.

[0010]

[0011] Preferably, Y is selected from one of fluorine, chlorine, bromine, and iodine.

[0012] Preferably, the molar concentration ratio of the halogen Lewis acid to the halogen oxygen-containing ring compound is 1:(1-3). More preferably, the molar concentration ratio of the halogen Lewis acid to the halogen oxygen-containing ring compound is 1:1.

[0013] Preferably, the water content of the electrolyte additive is less than or equal to 10 ppm.

[0014] In a second aspect, the present invention provides an electrolyte, wherein the components of the electrolyte include the electrolyte additive.

[0015] Preferably, the electrolyte comprises an organic solvent, a lithium salt, and electrolyte additives.

[0016] The organic solvent is selected from one or more of ethylene glycol dimethyl ether, dimethyl sulfoxide, tetraethylene glycol dimethyl ether, acetonitrile, tetrahydrofuran, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and 1,2-propanediol carbonate. Tetraethylene glycol dimethyl ether is preferred.

[0017] Preferably, the water content of the organic solvent is less than or equal to 10 ppm.

[0018] The lithium salt is selected from one or more of lithium trifluoromethanesulfonate (LiCF3SO3), lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiB(C2O4)2), and lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, i.e., LiTFSI). Lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, i.e., LiTFSI) is preferred.

[0019] Preferably, the water content of the lithium salt is less than or equal to 50 ppm. More preferably, the water content of the lithium salt is less than or equal to 10 ppm.

[0020] Preferably, the molar concentration of the lithium salt in the electrolyte is 0.5–4 mol / L. More preferably, the molar concentration of the lithium salt in the electrolyte is 0.8–3.5 mol / L.

[0021] Preferably, the molar concentration of halogen Lewis acids in the electrolyte additive is 0.01–1 mol / L, and the molar concentration of halogen oxygen-containing cyclic compounds is 0.01–1 mol / L.

[0022] Preferably, the water content of the electrolyte is less than 100 ppm. More preferably, the water content of the electrolyte is less than 50 ppm.

[0023] Thirdly, the present invention provides a lithium-air battery or a lithium-lithium symmetrical battery, comprising a positive electrode, a negative electrode and the electrolyte.

[0024] The beneficial effects of this invention are:

[0025] The electrolyte additive of this invention comprises halogen Lewis acids and halogen oxygen-containing ring compounds. One end of the halogen Lewis acid is an inorganic halogen element, which can dissociate to protect the metal anode or reduce polarization voltage. The other end is a metal cation that can open the ring of the halogen oxygen-containing ring compound through Lewis acidity, reacting with the metal to form an alloy layer that protects the anode and improves the battery's cycle life. One end of the halogen oxygen-containing ring compound is a halogen element, and the other end is an oxygen-containing ring. The oxygen-containing ring is dissociated from the halogen Lewis acid to release halide ions. The combined addition of these two compounds can protect the anode or reduce the battery's overcharge potential and form an SEI film on the anode surface, inhibiting side reactions on the anode surface, suppressing dendrite growth on the anode, and improving the battery's cycle life.

[0026] The electrolyte of this invention contains electrolyte additives, in which halogen ions dissociate and enter the electrolyte, thereby reducing the charging overpotential of lithium-air batteries or lithium-lithium symmetric batteries. Halogen Lewis acids react with metallic lithium to form an alloy protective layer. In addition, the metal cations in the Lewis acids undergo ring-opening reactions with halogen oxygen-containing rings, forming a dense organic-inorganic composite SEI film on the surface of the lithium anode. This effectively suppresses unfavorable electrolyte side reactions and dendrite growth problems in lithium-air batteries or lithium-lithium symmetric batteries, significantly improving the battery's cycle performance and discharge specific capacity.

[0027] The lithium-air battery or lithium-lithium symmetric battery of the present invention can stably cycle for more than 62 cycles, and can stably cycle for up to about 130 cycles. Moreover, after 90 cycles, its charging platform is still at about 4.0V, the voltage rises very slowly, the cycle life is significantly increased, the battery impedance decreases, and the stability of the lithium metal anode is improved. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the effect of the electrolyte additive of the present invention on the negative electrode material;

[0029] Figure 2 The graph shows the cycle performance of the lithium-air battery prepared in Example 1;

[0030] Figure 3 The graph shows the cycle performance of the lithium-air battery prepared in Example 3;

[0031] Figure 4 The cycling performance of the lithium-air battery prepared in Comparative Example 1 is shown in the figure.

[0032] Figure 5 The cycling performance diagram of the lithium-air battery prepared in Comparative Example 2;

[0033] Figure 6 The image shows a SEM image of the lithium-air battery prepared in Example 1 after 30 cycles.

[0034] Figure 7 SEM image of the lithium-air battery prepared in Comparative Example 1 after 30 cycles;

[0035] Figure 8 This is a comparison chart of the cycle life of lithium-lithium symmetric batteries prepared in Example 2 and Comparative Example 3;

[0036] Figure 9 Impedance diagrams of the lithium-lithium symmetric batteries prepared in Example 2 and Comparative Example 3 after 100 cycles. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of the invention, the invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in the embodiments of the invention can be obtained by purchasing them on the market or by existing methods.

[0038] In order to reduce the charging overpotential of lithium-air batteries or lithium-lithium symmetric batteries and form an SEI film on the surface of the lithium anode to suppress the occurrence of side reactions on the surface of the lithium anode, and at the same time suppress dendrite growth of the lithium anode and improve the cycle life of lithium-air batteries, the first aspect of the present invention provides an electrolyte additive, wherein the additive comprises halogen Lewis acids and halogen oxygen-containing cyclic compounds.

[0039] The halogen Lewis acid is selected from one or more of aluminum chloride (AlCl3), zinc chloride (ZnCl2), magnesium chloride (MgCl2), indium chloride (InCl3), aluminum bromide (AlBr3), zinc bromide (ZnBr2), magnesium bromide (MgBr2), indium bromide (InBr3), aluminum iodide (AlI3), zinc iodide (ZnI2), magnesium iodide (MgI2), and indium iodide (InI3), and its general structural formula is XY. n , where X n+ The element is a metal cation, and Y is a halogen element, preferably one of fluorine, chlorine, bromine, or iodine. This halogen-type Lewis acid has an inorganic halogen element at one end, which can dissociate to protect the lithium metal anode or reduce the polarization voltage of the lithium-air battery; the other end is a metal cation that can open the ring of the halogen-type oxygen-containing compound through Lewis acidity, reacting with lithium metal to form an alloy layer that protects the lithium anode and improves the cycle life of the lithium-air battery.

[0040] The halogen-based oxygen-containing ring compound includes one or more structures represented by formulas (1) to (5), wherein the hydrogen in formulas (1) to (5) can be substituted by any one or more of C1-C12 alkyl, phenyl, C1-C12 alkoxy, benzyl, hydroxyl, amino, C3-C12 epoxy, urea, vinyloxy, mercapto, thio, nitro, piperidine, imidazole, and sulfoxide; wherein Y is a halogen element, preferably one of fluorine, chlorine, bromine, and iodine. One end of the halogen-based oxygen-containing ring compound is a halogen element, and the other end is an oxygen-containing ring. The oxygen-containing ring is released by ring-opening dissociation of halide ions from the halogen-based Lewis acid, protecting the lithium anode or reducing the over-charge potential of the battery.

[0041]

[0042] In some embodiments of the present invention, the molar concentration ratio of the halogen Lewis acid to the halogen oxygen-containing ring compound is 1:1; in some embodiments of the present invention, the molar concentration ratio of the halogen Lewis acid to the halogen oxygen-containing ring compound is 1:3.

[0043] The electrolyte additive of the present invention has a water content of less than or equal to 10 ppm.

[0044] Secondly, the present invention provides an electrolyte comprising the electrolyte additive. In some embodiments of the present invention, the electrolyte comprises an organic solvent, a lithium salt, and the electrolyte additive.

[0045] The organic solvent used in this invention is selected from one or more of ethylene glycol dimethyl ether, dimethyl sulfoxide, tetraethylene glycol dimethyl ether, acetonitrile, tetrahydrofuran, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and 1,2-propanediol carbonate. Tetraethylene glycol dimethyl ether is preferred, as it is stable to lithium metal anodes, has an antioxidant stability potential higher than 4V, is safe, low in cost, has low volatility, and exhibits superior stability against oxygen reducing groups.

[0046] The organic solvent described in this invention has a water content of less than or equal to 10 ppm. Since water can undergo side reactions with the lithium anode, affecting battery performance, it is necessary to control the water content of each component. In practice, the organic solvent can be dried using the following method: reflux drying the organic solvent under normal or reduced pressure for 6–12 hours, followed by drying with molecular sieves for 2–4 days.

[0047] The lithium salt described in this invention is selected from one or more of lithium trifluoromethanesulfonate (LiCF3SO3), lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalatoborate) (LiB(C2O4)2), and lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, i.e., LiTFSI). LiTFSI is preferred.

[0048] The lithium salt concentration described in this invention is 0.5–4 mol / L, which offers advantages such as high ionic conductivity and good rate performance. If the lithium salt concentration is less than 0.5 mol / L, the conductivity may be insufficient; if the concentration exceeds 4 mol / L, the viscosity of the resulting electrolyte for lithium-air batteries increases, its impregnation decreases, and the electrical characteristics of the lithium-air battery may deteriorate. The preferred lithium salt concentration is 0.8–3.5 mol / L.

[0049] The water content of the lithium salt described in this invention can be less than or equal to 50 ppm, preferably less than or equal to 10 ppm. In actual operation, the lithium salt can be vacuum-treated at 120℃~180℃ for 12h~24h.

[0050] The electrolyte additive of this invention contains 0.01–1 mol / L of halogen Lewis acids and 0.01–1 mol / L of halogen oxygen-containing compounds. Further, the electrolyte additive contains 0.0167–0.05 mol / L of halogen Lewis acids and 0.05 mol / L of halogen oxygen-containing compounds. This range has the advantage of fewer side reactions.

[0051] The preparation method of the electrolyte of the present invention is as follows: the organic solvent is mixed with lithium salt, stirred and confirmed to be completely dissolved, the additive is added, stirred and confirmed to be completely dissolved, and the obtained electrolyte is dehydrated to reduce the water content in the electrolyte to less than 100 ppm, preferably less than 50 ppm.

[0052] Thirdly, the present invention provides a lithium-air battery or a lithium-lithium symmetrical battery, comprising a positive electrode, a negative electrode, and the electrolyte. It may also include a separator, a battery casing, etc.

[0053] The lithium-air battery or lithium-lithium symmetrical battery can be a button cell, a soft-pack battery, a hard-shell battery, etc.

[0054] In this invention, the positive electrode of the lithium-air battery is an air electrode, which can be carbon nanotubes coated on a substrate (e.g., carbon paper), porous carbon, carbon materials loaded with catalysts, or non-carbon materials; the negative electrode can be metallic lithium, and the electrolyte is the aforementioned electrolyte. For example, in the case of a coin cell, the amount of electrolyte added to the coin cell can be 60–200 μL.

[0055] The assembly of lithium-air batteries can include, for example, a button cell: the battery casing is of type 2032, with the negative electrode casing opening facing upwards, and is placed flat on a panel; a spring sheet is placed into the negative electrode casing; a spacer is placed on the spring sheet, and then a lithium sheet (15.6 mm in diameter) is placed in the center of the spacer; a separator is clamped to cover the lithium sheet, and 100 μL of electrolyte is dropped onto the separator using a pipette; the positive electrode is clamped and placed in the center of the separator, and a porous positive electrode casing is clamped and covered with plastic tweezers, and then pressed using a button cell packaging machine.

[0056] In this invention, both the positive and negative electrodes of the lithium-lithium symmetric battery are metallic lithium.

[0057] The assembly of a lithium-ion symmetric battery may include, for example, a button cell: the battery casing is of type 2032, with the negative electrode casing opening facing upwards, and is placed flat on a panel; a spring sheet is placed into the negative electrode casing; a spacer is placed on the spring sheet, and then a lithium sheet (15.6 mm in diameter) is placed in the center of the spacer; a separator is clamped to cover the lithium sheet, and 60 μL of electrolyte is dropped onto the separator using a pipette; the lithium sheet is clamped to the center of the separator, and the positive electrode casing is clamped and covered with plastic tweezers, and then pressed using a button cell packaging machine.

[0058] In this invention, by using the electrolyte in a lithium-air battery or a lithium-lithium symmetric battery, the over-charge potential of the lithium-air battery can be reduced and an SEI film can be formed on the surface of the lithium anode, suppressing the occurrence of side reactions on the lithium anode surface. At the same time, it can suppress dendrite growth of the lithium anode and improve the cycle life of the lithium-air battery.

[0059] Figure 1 This is a schematic diagram illustrating the effect of the electrolyte additive of the present invention on the negative electrode material. On one hand, Lewis acids can passivate the lithium metal negative electrode, forming X m Li n The alloy layer provides anodic protection for the negative electrode material. On the other hand, in the electrolyte, halogen-containing oxygen ring compounds are ring-opened by halogen-containing Lewis acids, causing the halogens to be released and become free halide ions, which act as soluble catalysts to reduce the charging overpotential of lithium-oxygen batteries. The Lewis acid cations and the remaining groups (such as alkyl groups) of halogen-containing oxygen ring compounds react with lithium metal to form a dense organic-inorganic composite SEI film that protects the lithium negative electrode and improves battery life.

[0060] The above is a detailed description of the present invention. The following are embodiments of the present invention.

[0061] In the following embodiments, unless otherwise specified, the reagents, materials and instruments used are all conventional reagents, materials and instruments, and are commercially available. The reagents involved can also be synthesized by conventional synthesis methods.

[0062] Example 1: Lithium-air battery prepared with an electrolyte containing 3-iodooxyheterobutane and aluminum chloride as additives.

[0063] (1) Preparation of basic electrolyte: The electrolyte is a mixture of tetraethylene glycol dimethyl ether (10 ppm water content) and lithium bis(trifluoromethanesulfonyl)imide (50 ppm water content). Lithium bis(trifluoromethanesulfonyl)imide is added to tetraethylene glycol dimethyl ether, stirred and confirmed to be completely dissolved to obtain the basic electrolyte, wherein the lithium bis(trifluoromethanesulfonyl)imide is 1 mol / L;

[0064] (2) Preparation of electrolyte for lithium-air batteries: In a glove box filled with argon (moisture content < 0.1 ppm, oxygen content < 0.1 ppm), 3-iodooxyhexacyclobutane and aluminum chloride (moisture content 10 ppm) were added to the basic electrolyte at a concentration of 0.05 mol / L. The structural formula of 3-iodooxyhexacyclobutane is as follows:

[0065]

[0066] (3) Battery assembly: The positive electrode active material of the lithium-air battery is carbon nanotubes coated on carbon paper, and the negative electrode is a circular lithium metal sheet with a diameter of 15.6 mm. The battery case is a 2032 type, with the negative electrode case opening facing upwards and placed flat on the panel; the spring sheet is placed into the negative electrode case; the pad is placed on the spring sheet, and then the lithium sheet (diameter of 15.6 mm) is placed in the center of the pad; the separator is covered with the lithium sheet, and 100 μL of electrolyte is dropped onto the separator with a pipette; the positive electrode sheet is placed in the center of the separator, and the porous positive electrode case is covered with plastic tweezers. The battery is pressed with a button battery packaging machine to obtain a button lithium-air battery. The amount of electrolyte added to the button battery is 100 μL.

[0067] Example 2: Lithium-lithium symmetric battery prepared with an electrolyte containing 3-iodooxyhexacyclobutane and aluminum chloride as additives.

[0068] Similar to Example 1, the difference lies in step (3). In this example, step (3) is the following steps:

[0069] Battery Assembly: The positive and negative electrodes of the lithium-ion symmetric battery are both circular lithium metal sheets with a diameter of 15.6 mm. The battery casing is type 2032, with the negative electrode casing opening upwards, placed flat on the panel. Place the spring sheet into the negative electrode casing; place the spacer on the spring sheet, then place the lithium sheet (15.6 mm in diameter) in the center of the spacer; cover the lithium sheet with the separator, and use a pipette to drop 60 μL of electrolyte onto the separator; place the positive electrode sheet in the center of the separator, use plastic tweezers to cover the porous positive electrode casing, and press it with a button cell packaging machine to obtain a button-type lithium-ion symmetric battery. The amount of electrolyte added to the button cell is 60 μL.

[0070] Example 3

[0071] Same as Example 1, except that 3-iodooxycyclobutane and aluminum bromide (with a water content of 10 ppm) are added to the basic electrolyte in step (2), with 3-iodooxycyclobutane at 0.05 mol / L and aluminum bromide at 0.0167 mol / L.

[0072] Example 4

[0073] Same as Example 1, except that in step (1), the tetraethylene glycol dimethyl ether (water content less than 10 ppm) and lithium bis(trifluoromethanesulfonylimide) (water content 10 ppm) are used, and the lithium bis(trifluoromethanesulfonylimide) is 0.5 mol / L.

[0074] Example 5

[0075] Same as Example 1, except that in step (1), the tetraethylene glycol dimethyl ether (water content less than 10 ppm) and lithium bis(trifluoromethanesulfonylimide) (water content less than 10 ppm) are used, and the lithium bis(trifluoromethanesulfonylimide) is 4 mol / L.

[0076] Example 6

[0077] Similar to Example 1, except that zinc chloride and a compound with the following structural formula (containing less than 10 ppm of water) are added to the basic electrolyte in step (2), with an addition amount of 0.01 mol / L.

[0078]

[0079] Example 7

[0080] Similar to Example 1, except that magnesium chloride and a compound with the following structural formula (containing less than 10 ppm of water) are added to the basic electrolyte in step (2), with an addition amount of 1 mol / L.

[0081]

[0082] Example 8

[0083] Same as Example 1, except that aluminum bromide and a compound with the following structural formula are added to the basic electrolyte in step (2):

[0084]

[0085] Example 9

[0086] Same as Example 1, except that magnesium bromide and a compound with the following structural formula are added to the basic electrolyte in step (2):

[0087]

[0088] Comparative Example 1: Lithium-air battery prepared with an electrolyte containing lithium iodide as an additive

[0089] Same as Example 1, except that in step (2), lithium iodide (containing 10 ppm water) is added to the basic electrolyte at a rate of 0.05 mol / L.

[0090] Comparative Example 2: Lithium-air battery prepared with an electrolyte containing 3-iodooxyheptacyclobutane as an additive.

[0091] Same as Example 1, except that in step (2), 3-iodooxyhexacyclobutane (containing 10 ppm water) is added to the basic electrolyte at a concentration of 0.05 mol / L.

[0092] Comparative Example 3: Lithium-lithium symmetric batteries prepared with lithium iodide as the additive in the electrolyte.

[0093] Same as Example 2, except that in step (2), lithium iodide (containing 10 ppm water) is added to the basic electrolyte at a rate of 0.05 mol / L.

[0094] Example 1

[0095] Figures 2-5 The electrochemical performance of lithium-air batteries were compared with those of Example 1 (electrolyte with 3-iodooxy-butane and aluminum chloride), Example 3 (electrolyte with 3-iodooxy-butane and aluminum bromide), Comparative Example 1 (electrolyte with lithium iodide), and Comparative Example 2 (electrolyte with 3-iodooxy-heterocyclic butane alone).

[0096] from Figure 5 It can be seen that lithium-air batteries using 3-iodooxyheterobutane alone cannot effectively dissociate iodine ions; the polarization voltage in the first cycle already reaches 4.1V. Figure 4 It can be seen that although the lithium-air battery using lithium iodide can maintain a low initial potential, it can only cycle 34 times. However, the performance of the lithium-oxygen batteries in Examples 1 and 3 of this invention can be effectively improved. Example 3 can stably cycle 62 times, and its lifespan is nearly doubled compared to Comparative Example 1. Example 1 can stably cycle about 130 times, and its cycle lifespan is nearly four times that of Comparative Example 1. Moreover, after 90 cycles, its charging platform is still at about 4.0V, and the voltage rise is very slow.

[0097] Example 2

[0098] Figure 6 The image shows a SEM image of the lithium anode of the lithium-air battery prepared in Example 1 after 30 cycles. It can be seen that there is no obvious particulate byproduct formation on the surface of the lithium sheet, and the surface of the lithium sheet is relatively smooth. This proves that the halogen Lewis acid and halogen oxygen-containing cyclic compound have a protective effect on the lithium anode. Therefore, the discharge specific capacity and cycle life of the lithium-air battery obtained by using the electrolyte of the present invention are greatly improved.

[0099] Figure 7 The SEM image of the lithium anode of the lithium-air battery prepared in Comparative Example 1 after 30 cycles shows many particulate byproducts on the lithium sheet surface. This is due to the erosion of the lithium anode by redox intermediates and electrolyte byproducts, which leads to a reduction in the cycle life of the lithium-air battery. Figure 6 There are obvious differences.

[0100] Example 3

[0101] Figure 8 The graph shows a comparison of the cycle life of lithium-lithium symmetric batteries prepared in Example 2 (3-iodooxyhexacyclobutane and aluminum chloride) and Comparative Example 3 (lithium iodide), indicating that the addition of the additives of the present invention reduces the polarization voltage and increases the cycle life of the lithium-lithium symmetric batteries.

[0102] Figure 9The impedance diagrams of the lithium-lithium symmetric batteries prepared in Example 2 (3-iodooxyheterobutane and aluminum chloride) and Comparative Example 3 (lithium iodide) after 100 cycles show that the addition of halogen Lewis acids and halogen oxygen-containing cyclic compounds in this invention reduces the impedance of the lithium-lithium symmetric battery and improves the stability of the lithium metal anode.

[0103] According to various exemplary embodiments of the present invention, the protective layer on the lithium metal anode can prevent the reaction between the redox mediator in the electrolyte and the lithium metal, thereby inhibiting the growth of lithium dendrites and the rapid consumption of the redox mediator.

[0104] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrolyte, characterized by, The components of the electrolyte include an organic solvent, a lithium salt, and an electrolyte additive, the components of the electrolyte additive include a halogen Lewis acid and a halogen oxygen-containing ring compound; The halogen Lewis acid is selected from one or more of aluminum chloride, zinc chloride, magnesium chloride, indium chloride, aluminum bromide, zinc bromide, magnesium bromide, indium bromide, aluminum iodide, zinc iodide, magnesium iodide, and indium iodide; The halogen oxygen-containing ring compound includes one or more of the structural formulas shown in formulas (1)-(5), wherein the hydrogen in the formulas (1)-(5) is replaced by any one or several of C1-C12 alkyl, phenyl, C1-C12 alkoxy, benzyl, hydroxyl, amino, C3-C12 epoxy, urea, acryloxy, mercapto, sulfide, nitro, piperidine, imidazole, and sulfoxide; The Y is selected from one of fluorine, chlorine, bromine, and iodine.

2. The electrolyte according to claim 1, characterized in that, The Y is selected from one of fluorine, chlorine, bromine, and iodine.

3. The electrolyte of claim 1, wherein The molar concentration ratio of the halogen Lewis acid and the halogen oxygen-containing ring compound is 1: (1-3).

4. The electrolyte according to claim 1, characterized in that, The water content of the electrolyte additive is less than or equal to 10 ppm.

5. The electrolyte according to claim 1, characterized in that, The molar concentration of the halogen Lewis acid in the electrolyte additive is 0.01-1 mol / L, and the molar concentration of the halogen oxygen-containing ring compound is 0.01-1 mol / L.

6. The electrolyte of claim 1, wherein The organic solvent is selected from one or more of ethylene glycol dimethyl ether, dimethyl sulfoxide, tetraethylene glycol dimethyl ether, acetonitrile, tetrahydrofuran, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and 1,2-propanediol carbonate.

7. The electrolyte of claim 1, wherein The lithium salt is selected from one or more of lithium trifluoromethyl sulfonate, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalate borate, and lithium bis-trifluoromethanesulfonimide.

8. A lithium-air battery or lithium-lithium symmetric battery, characterized by, The electrolyte includes a positive electrode, a negative electrode, and the electrolyte of any one of claims 1-7.

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