Electrolyte additive, electrolyte and method for its preparation, lithium metal battery and use

Abstract

This application relates to an electrolyte additive, an electrolyte and its preparation method, a lithium metal battery, and its applications, belonging to the field of lithium metal battery technology. The electrolyte additive provided in this application has an acrylate structure, a sterically hindered conjugated fused ring structure, or a polyaromatic ring structure. This electrolyte additive can inhibit the growth of lithium dendrites on the surface of lithium-containing anodes, thereby improving the cycle performance and safety performance of lithium metal batteries.

Description

Technical Field

[0001] This application relates to the field of lithium metal battery technology, and in particular to an electrolyte additive, an electrolyte and its preparation method, a lithium metal battery and its applications. Background Technology

[0002] With increasing societal progress and continuous technological development, new production and lifestyles are placing ever higher demands on energy storage, transportation, and efficient utilization. Currently, lithium-ion batteries have become the core category of rechargeable batteries, efficiently and conveniently addressing today's energy needs and are widely used in mobile electronic devices, electric transportation, and green energy stations. However, the actual energy density of lithium-ion batteries (especially those using graphite anodes) is gradually approaching its theoretical limit. Therefore, there is an urgent need to develop lithium metal batteries with higher energy density and lower electrode potential to meet future energy demands.

[0003] Although lithium metal is the most ideal anode material, the commercial application of lithium metal batteries still faces significant challenges. During cycling, lithium metal anodes can experience pulverization, solid electrolyte layer rupture, and dendrite growth, leading to capacity decay, increased internal resistance, a wider voltage window, and internal short circuits. These issues severely impact the cycle performance and safety of lithium metal batteries. Summary of the Invention

[0004] Therefore, it is necessary to provide an electrolyte additive, an electrolyte and its preparation method, a lithium metal battery and its application, to suppress the growth of lithium dendrites on the surface of lithium-containing anodes, thereby improving the cycle performance and safety performance of lithium metal batteries.

[0005] A first aspect of this application provides an electrolyte additive comprising at least one organic compound having a general structural formula shown in Formula I:

[0006]

[0007] In Formula I, R is selected from substituted or unsubstituted conjugated fused ring groups or substituted or unsubstituted polyaryl ring groups.

[0008] In some embodiments, R is selected from substituted or unsubstituted pyrene, substituted or unsubstituted anthraquinone, substituted or unsubstituted phenanthrene, substituted or unsubstituted pentaphenyl, substituted or unsubstituted tetraphenylphenyl, or substituted or unsubstituted 1,2,3,4,5-pentaphenylphenyl.

[0009] A second aspect of this application provides an electrolyte comprising an organic solvent, a lithium salt, and the electrolyte additives described in the first aspect of this application.

[0010] In some embodiments, the electrolyte additive constitutes 0.25% to 10% by mass in the electrolyte; preferably 0.5% to 5%; more preferably 1% to 2%.

[0011] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0012] In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5 mol / L to 2 mol / L.

[0013] In some embodiments, the organic solvent includes one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0014] A third aspect of this application provides a method for preparing the electrolyte described in the second aspect of this application, comprising the following steps: mixing the organic solvent, the lithium salt and the electrolyte additive to obtain the electrolyte.

[0015] The fourth aspect of this application provides a lithium metal battery, including a lithium-containing negative electrode and an electrolyte, wherein the electrolyte includes the electrolyte described in the second aspect of this application or the electrolyte prepared by the preparation method described in the third aspect of this application.

[0016] The fifth aspect of this application provides an electrical device including the lithium metal battery described in the fourth aspect of this application.

[0017] Compared with traditional technologies, the above-mentioned electrolyte additives, electrolytes and their preparation methods, lithium metal batteries and applications have at least the following advantages:

[0018] The acrylate structure in the above-mentioned electrolyte additive can realize the polymerization reaction and lithium-ion transport process. The substituted or unsubstituted conjugated fused ring group is a conjugated planar fused ring structure, and the substituted or unsubstituted polyaromatic ring group is a non-conjugated polyaromatic ring structure. Both have large steric hindrance, which can regulate the transport and deposition behavior of lithium ions. This allows the above-mentioned electrolyte additive to form a stable SEI film on the surface of the lithium-containing anode and to inhibit the growth of lithium dendrites on the surface of the lithium-containing anode, thereby improving the cycle performance and safety performance of lithium metal batteries. Attached Figure Description

[0019] Figure 1 This is the mass spectrum of organic compound A synthesized in Example 1 of this application.

[0020] Figure 2 This is the mass spectrum of organic compound B synthesized in Example 2 of this application.

[0021] Figure 3 The organic compound B synthesized in Example 2 of this application 1 H NMR spectrum.

[0022] Figure 4 The lithium metal batteries assembled for Examples 1-3 and Comparative Examples 1-4 of this application have a capacity of 1 mAh / cm². 2 The lithium metal anode interface diagrams after 20 charge-discharge cycles at the current density are shown in the figures: (a) Example 1; (b) Example 2; (c) Example 3; (d) Comparative Example 1; (e) Comparative Example 2; (f) Comparative Example 3; (g) Comparative Example 4.

[0023] Figure 5 The lithium metal battery assembled for Example 1 of this application has a capacity of 1 mAh / cm². 2 The current density is used to calculate the cycle performance after 20 charge-discharge cycles.

[0024] Figure 6 The lithium metal battery assembled for Example 2 of this application has a capacity of 1 mAh / cm². 2 The current density is used to calculate the cycle performance after 20 charge-discharge cycles.

[0025] Figure 7 The lithium metal battery assembled for Comparative Example 1 of this application has a capacity of 1 mAh / cm². 2 The current density is used to calculate the cycle performance after 20 charge-discharge cycles. Detailed Implementation

[0026] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0027] In this application, unless otherwise defined, all technical terms and jargon not explicitly stated have the same meaning as commonly understood by those skilled in the art and are common knowledge to those skilled in the art. Methods not explicitly stated are all conventional methods known to those skilled in the art. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0028] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0029] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0030] The term "conjugated fused ring group" refers to an aromatic hydrocarbon group derived from an aromatic ring compound that shares at least two carbon atoms by removing one hydrogen atom, and that the aromatic hydrocarbon group has a conjugated structure. Suitable examples include, but are not limited to: pyrene, anthracene, phenanthrene, and pentaphenyl.

[0031] The term "polycyclic aromatic group" refers to an aromatic hydrocarbon group derived from an aromatic ring compound having multiple aromatic rings by removing one hydrogen atom, and the aromatic hydrocarbon group is a non-conjugated structure. Suitable examples include, but are not limited to, tetraphenylphenyl and 1,2,3,4,5-pentaphenylphenyl.

[0032] The term "halogen" or "halogen group" refers to F, Cl, Br, or I.

[0033] The term "alkyl" refers to a saturated hydrocarbon containing a primary (normal) carbon atom, or a secondary carbon atom, or a tertiary carbon atom, or a quaternary carbon atom, or a combination thereof. Phrases containing this term include, for example, "C1-C1...". 10 "Alkyl" refers to an alkyl group containing 1 to 10 carbon atoms. Each time it appears, it can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, C9 alkyl, or C 10Alkyl groups. Suitable examples include, but are not limited to: methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(C H3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (- CH2CH2CH(CH3)2), 2-methyl-1-butyl(-CH2CH(CH3)CH2CH3), 1-hexyl(-CH2CH2CH2CH2CH2CH3), 2-hexyl(-CH(CH3)CH2CH2CH2CH3), 3-hexyl(-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl(-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl(-CH(CH3)CH( CH3)CH2CH3), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0034] The term "alkoxy" refers to a group having an -O-alkyl group, i.e., an alkyl group as defined above that is attached to the parent nucleus via an oxygen atom. Phrases containing this term include, for example, "C1~C1". 10 "Alkoxy" refers to an alkyl moiety containing 1 to 10 carbon atoms, and each occurrence can be independently C1 alkoxy, C4 alkoxy, C5 alkoxy, C6 alkoxy, C7 alkoxy, C8 alkoxy, C9 alkoxy, or C 10 Alkyl groups. Suitable examples include, but are not limited to: methoxy (-O-CH3 or -OMe), ethoxy (-O-CH2CH3 or -OEt), and tert-butoxy (-OC(CH3)3 or -OtBu).

[0035] "Alkenyl" refers to a group containing at least one unsaturated site, i.e., carbon-carbon sp. 2 Hydrocarbons with double bonds consisting of a positive, secondary, tertiary carbon atom, or a cyclic carbon atom. Phrases containing this term, such as "C2~C2". 10 "Alkenyl" refers to an alkenyl group containing 2 to 10 carbon atoms. Each time it appears, it can independently be C2 alkenyl, C3 alkenyl, C4 alkenyl, C5 alkenyl, C6 alkenyl, C7 alkenyl, C8 alkenyl, C9 alkenyl, or C... 10 Alkenyl. Suitable examples include, but are not limited to: vinyl (-CH=CH2), allyl (-CH2CH=CH2), cyclopentenyl (-C5H7) and 5-hexenyl (-CH2CH2CH2CH2CH=CH2).

[0036] One embodiment of this application provides an electrolyte additive, comprising at least one organic compound having the general structural formula shown in Formula I:

[0037]

[0038] In Formula I, R is selected from substituted or unsubstituted conjugated fused ring groups or substituted or unsubstituted polyaryl ring groups.

[0039] During cycling, electrolyte additives are crucial for improving the cycle performance of lithium metal batteries because they can decompose on the electrode surface and alter the stability of the solid electrolyte interphase (SEI) film. Traditional electrolyte additives include inorganic lithium salts such as lithium nitrate and lithium fluorophosphate, as well as organic electrolyte additives such as vinyl fluorocarbonate, fluoroboronate, and fluoronitrate. The aforementioned inorganic lithium salt additives can adjust the composition of the SEI film, while the fluorinated or nitrogen-containing groups in the aforementioned organic electrolyte additives can be converted into inorganic lithium fluoride or lithium nitride, which then enter the SEI film, thereby inhibiting lithium dendrite growth. However, traditional electrolyte additives rely heavily on the modifying power of fluorine or nitrogen, resulting in a single type of final decomposition product (lithium fluoride or lithium nitride). Furthermore, traditional electrolyte additives often improve electrode interface performance at the expense of certain properties; for example, traditional fluorinated additives corrode transition metals in the cathode material and are biotoxic; traditional nitrogen-containing additives have poor thermal stability and anti-explosion properties.

[0040] Unlike traditional electrolyte additives, the acrylate structure in the electrolyte additive provided in this application enables polymerization and lithium-ion transport processes. The substituted or unsubstituted conjugated fused ring groups form conjugated planar fused ring structures, while the substituted or unsubstituted polyaromatic ring groups form non-conjugated polyaromatic ring structures. Both exhibit significant steric hindrance, allowing for the regulation of lithium-ion transport and deposition behavior. This enables the electrolyte additive to suppress lithium dendrite formation without converting to lithium nitride or lithium fluoride, thereby optimizing the interface properties of the lithium-containing anode, stabilizing and improving the cycle performance and safety of lithium metal batteries. Furthermore, this electrolyte additive avoids the disadvantages of traditional fluorinated and nitrogen-containing additives. In other words, the electrolyte additive provided in this application can form a stable SEI film on the surface of the lithium-containing anode without interfering with the normal cycle performance of the lithium metal battery, and can suppress lithium dendrite growth on the surface of the lithium-containing anode, improving the cycle performance and safety of the lithium metal battery, and ultimately extending the battery's lifespan. It should be noted that when R is a substituted conjugated fused ring group or a substituted polyarylene ring group, this application does not impose any particular restrictions on the substitution positions on the conjugated fused ring group and the polyarylene ring group; and this application does not impose any particular restrictions on the preparation method of the organic compound with the general structure shown in Formula I, for example, it can be obtained commercially or prepared using methods commonly used in this technical field. Further, the organic compound with the general structure shown in Formula I can be prepared, for example, by an esterification reaction. Optionally, the above-mentioned organic compound may include, but is not limited to, the following organic compounds:

[0041]

[0042] In some embodiments, the substituents on the conjugated fused ring group and the polyarylene ring group are each independently selected from hydrogen atoms, halogens, substituted or unsubstituted C atoms. 1～10 Alkyl, substituted or unsubstituted C 1～10 Alkoxy, or substituted or unsubstituted C 2～10 Alkenyl group.

[0043] In some embodiments, R is selected from substituted or unsubstituted pyrene, substituted or unsubstituted anthraquinone, substituted or unsubstituted phenanthrene, substituted or unsubstituted pentaphenyl, substituted or unsubstituted tetraphenylphenyl, or substituted or unsubstituted 1,2,3,4,5-pentaphenylphenyl.

[0044] The aforementioned substituted or unsubstituted pyrene, substituted or unsubstituted anthracene, substituted or unsubstituted phenanthrene, and substituted or unsubstituted pentaphenyl are conjugated planar fused ring structures, while the aforementioned substituted or unsubstituted tetrastyrene and substituted or unsubstituted 1,2,3,4,5-pentaphenylphenyl are non-conjugated polyaromatic ring structures. Electrolyte additives with these groups and acrylate structures can achieve lithium dendrite suppression without conversion to lithium nitride or lithium fluoride, optimize the interfacial properties of lithium metal anodes, and stabilize and improve the cycle performance of lithium metal batteries.

[0045] Another embodiment of this application provides an electrolyte comprising an organic solvent, a lithium salt, and the above-described electrolyte additives.

[0046] The acrylate structure in the aforementioned electrolyte additive enables polymerization and lithium-ion transport. The substituted or unsubstituted conjugated fused-ring groups form conjugated planar fused-ring structures, while the substituted or unsubstituted polyaromatic ring groups form non-conjugated polyaromatic ring structures. Both exhibit significant steric hindrance, allowing for the regulation of lithium-ion transport and deposition behavior. This electrolyte additive can suppress lithium dendrite formation without converting to lithium nitride or lithium fluoride, thereby optimizing the interface properties of the lithium-containing anode and stabilizing and improving the cycle performance and safety of lithium metal batteries. Furthermore, this electrolyte additive avoids the disadvantages of traditional fluorinated and nitrogen-containing additives. Therefore, the electrolyte containing this additive can form a stable SEI film on the surface of the lithium-containing anode, inhibiting lithium dendrite growth, improving the cycle performance and safety of lithium metal batteries, and ultimately extending their lifespan. In some embodiments, the electrolyte may also include vinylene carbonate (VC), fluoroethylene carbonate (FEC), propane sulfonate lactone (PS), or vinyl sulfate (DTD), etc. In addition, the electrolyte may also include other electrolyte additives commonly used in this art. This application does not have any particular limitations.

[0047] In some embodiments, the electrolyte additive constitutes 0.25% to 10% of the electrolyte by mass; preferably 0.5% to 5%; more preferably 1% to 2%. It should be noted that when the mass percentage of the electrolyte additive in the electrolyte is 0.25% to 10%, it can significantly improve the lithium dendrite growth problem on the surface of the lithium-containing anode, and at the same time, significantly improve the cycle performance and safety performance of the lithium metal battery containing this electrolyte additive. It is understood that the mass percentage of the electrolyte additive in the electrolyte can be, for example, 0.25%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, etc.

[0048] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0049] In some embodiments, the concentration of lithium salt in the electrolyte is 0.5 mol / L to 2 mol / L. It is understood that the concentration of lithium salt in the electrolyte can be, for example, 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1.1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.7 mol / L, 2 mol / L, etc.

[0050] In some embodiments, the organic solvent includes one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0051] Another embodiment of this application provides a method for preparing the above-mentioned electrolyte, comprising the following steps: mixing an organic solvent, a lithium salt, and an electrolyte additive to obtain an electrolyte. It is understood that the above mixing includes simple mixing, stirring mixing, ultrasonic mixing, etc., and this application does not impose any particular restrictions on the mixing method or the order in which the organic solvent, lithium salt, and electrolyte are added.

[0052] Another embodiment of this application provides a lithium metal battery, including a lithium-containing negative electrode and an electrolyte, wherein the electrolyte includes the electrolyte described above or the electrolyte prepared by the preparation method described above.

[0053] The aforementioned lithium metal batteries include, but are not limited to, lithium-oxygen batteries, lithium-sulfur batteries, and lithium-oxide batteries. The aforementioned lithium-containing anode includes anode active materials, which may include, but are not limited to, lithium metal, lithium alloys, mixtures of graphite and lithium metal, mixtures of graphite, silicon-carbon, and lithium metal, graphite chemical pre-intercalation materials, and graphite and silicon-carbon chemical pre-intercalation materials.

[0054] The aforementioned lithium metal battery also includes a positive electrode and a separator. Optionally, the positive electrode includes a positive electrode active material, which may include, but is not limited to, one or more of sulfur-containing compounds, lithium iron phosphate, lithium cobalt oxide, lithium iron manganese phosphate, lithium manganese oxide, lithium titanate, lithium nickel manganese oxide, and nickel-cobalt-manganese ternary materials; the separator may include, but is not limited to, glass fiber separators, polyethylene terephthalate separators, cellulose nonwoven separators, polyimide separators, polyolefin separators, etc.

[0055] Another embodiment of this application provides an electrical device including the aforementioned lithium metal battery. The aforementioned electrical device may include any device or apparatus powered by a lithium metal battery, such as mobile phones, laptops, electric vehicles, ships, satellites, energy storage devices, smart home appliances, etc., but is not limited thereto.

[0056] The present application will be further described in detail below with reference to specific embodiments and comparative examples.

[0057] Example 1

[0058] (1) Pyrene acrylate was synthesized by esterification reaction of 1-hydroxypyrene with acryloyl chloride. The structural formula of pyrene acrylate is shown in Formula IA:

[0059]

[0060] The synthesis method of pyrene acrylate includes the following steps:

[0061] 2.182 g of 1-hydroxypyrene (CAS No.: 5315-79-7) was dissolved in 20 mL of anhydrous tetrahydrofuran, and a small piece of metallic sodium was added. The mixture was stirred at room temperature for 2 h. Subsequently, 1.000 g of acryloyl chloride was slowly added dropwise under ice bath conditions, followed by stirring at room temperature for 24 h. After the reaction was completed, the reaction system was centrifuged to remove the solid insoluble matter, the solution was evaporated to dryness under vacuum, and washed with a small amount of ethyl acetate and saturated brine to separate the organic phase and obtain the crude product. The crude product was purified by silica gel chromatography (petroleum ether:dichloromethane = 5:1 solvent) to obtain organic compound A in 89.1% yield.

[0062] (2) Assembling lithium metal batteries

[0063] The lithium metal battery used is a Li|Li symmetrical coin cell, with lithium sheets as both the positive and negative electrodes. The electrolyte is 1 mol / L LiPF6 / EC+DEC+EMC (the mass ratio of EC, DEC, and EMC is 1:1:1). Pyrene acrylate is also added to the electrolyte, with a mass percentage of 1%. The separator is Celgard 2500.

[0064] Example 2

[0065] (1) Tetraphenyl acrylate was synthesized by esterification of 4-(1,2,2-tristyryl)phenol with acryloyl chloride. The structural formula of tetraphenyl acrylate is shown in Formula IB:

[0066]

[0067]

[0068] The synthesis method of tetraphenylethylene acrylate includes the following steps:

[0069] 3.482 g of 4-(1,2,2-tristyryl)phenol (CAS No.: 76115-06-5) was dissolved in 20 mL of anhydrous tetrahydrofuran, and a small piece of metallic sodium was added. The mixture was stirred at room temperature for 2 h. Subsequently, 1.000 g of acryloyl chloride was slowly added dropwise under ice bath conditions, followed by stirring at room temperature for 24 h. After the reaction was completed, the reaction system was centrifuged to remove the solid insoluble matter, the solution was evaporated to dryness under vacuum, and washed with a small amount of ethyl acetate and saturated brine to separate the organic phase and obtain the crude product. The crude product was purified by silica gel chromatography (petroleum ether:dichloromethane = 4:1 solvent) to obtain organic compound B in 52.2% yield.

[0070] (2) Assembling lithium metal batteries

[0071] The lithium metal battery used is a Li|Li symmetrical coin cell, with lithium sheets as both positive and negative electrodes. The electrolyte is 1 mol / L LiPF6 / EC+DEC+EMC (the mass ratio of EC, DEC, and EMC is 1:1:1). Tetraphenyl acrylate is also added to the electrolyte, with a mass percentage of 1%. The separator is Celgard 2500.

[0072] Example 3

[0073] (1) The synthesis method of tetraphenyl acrylate is the same as in Example 2.

[0074] (2) The assembly method of the lithium metal battery is basically the same as that in Example 2, except that the mass percentage of tetraphenyl acrylate in the electrolyte is 0.25%.

[0075] Example 4

[0076] (1) The synthesis method of tetraphenyl acrylate is the same as in Example 2.

[0077] (2) The assembly method of the lithium metal battery is basically the same as that in Example 2, except that the mass percentage of tetraphenyl acrylate in the electrolyte is 0.5%.

[0078] Example 5

[0079] (1) The synthesis method of tetraphenyl acrylate is the same as in Example 2.

[0080] (2) The assembly method of the lithium metal battery is basically the same as that in Example 2, except that the mass percentage of tetraphenyl acrylate in the electrolyte is 2%.

[0081] Example 6

[0082] (1) The synthesis method of tetraphenyl acrylate is the same as in Example 2.

[0083] (2) The assembly method of the lithium metal battery is basically the same as that in Example 2, except that the mass percentage of tetraphenyl acrylate in the electrolyte is 5%.

[0084] Example 7

[0085] (1) The synthesis method of tetraphenyl acrylate is the same as in Example 2.

[0086] (2) The assembly method of the lithium metal battery is basically the same as that in Example 2, except that the mass percentage of tetraphenyl acrylate in the electrolyte is 10%.

[0087] Example 8

[0088] (1) The synthesis method of pyrene acrylate is the same as in Example 1.

[0089] (2) The assembly method of the lithium metal battery is basically the same as that in Example 1, except that the mass percentage of pyrene acrylate in the electrolyte is 0.5%.

[0090] Example 9

[0091] (1) The synthesis method of pyrene acrylate is the same as in Example 1.

[0092] (2) The assembly method of the lithium metal battery is basically the same as that in Example 1, except that the mass percentage of pyrene acrylate in the electrolyte is 2%.

[0093] Example 10

[0094] (1) The synthesis method of pyrene acrylate is the same as in Example 1.

[0095] (2) The assembly method of the lithium metal battery is basically the same as that in Example 1, except that the mass percentage of pyrene acrylate in the electrolyte is 5%.

[0096] Comparative Example 1

[0097] The assembly method of the lithium metal battery is basically the same as that in Example 1, except that the additive pyrene acrylate is not added to the electrolyte.

[0098] Comparative Example 2

[0099] The assembly method of the lithium metal battery is basically the same as that in Example 1, except that the additive pyrene acrylate is replaced with methyl acrylate (CAS No.: 292638-85-8), and the structural formula of methyl acrylate is shown in Formula II:

[0100]

[0101] Comparative Example 3

[0102] The assembly method of the lithium metal battery is basically the same as that in Example 1, except that the additive pyrene acrylate is replaced with phenyl acrylate (CAS No.: 937-41-7), and the structural formula of phenyl acrylate is shown in Formula III:

[0103]

[0104] Comparative Example 4

[0105] The assembly method of the lithium metal battery is basically the same as that in Example 2, except that the additive pyrene acrylate is replaced with acryloyltetraphenylamine, the structural formula of which is shown in Formula IV:

[0106]

[0107] Structural determination

[0108] Depend on Figure 1 It can be seen that the mass-to-charge ratio of organic compound A synthesized in Example 1 is 272.1717; the theoretical mass-to-charge ratio of pyrene acrylate is 272.08, which effectively proves that the organic compound A synthesized in Example 1 is pyrene acrylate.

[0109] Depend on Figure 2 It can be seen that the mass-to-charge ratio of organic compound B synthesized in Example 2 is 401.1547; the theoretical mass-to-charge ratio of tetraphenyl acrylate is also 401.1547, effectively proving that the organic compound B synthesized in Example 2 is tetraphenyl acrylate. Furthermore, Figure 3 of 1 In the 1H NMR spectrum, the proton signals at chemical shifts of 7.14-7.04, 7.01-6.88, 6.46, 6.31, and 6.08 correspond to hydrogen atoms in five different chemical environments within tetraphenyl acrylate, respectively. The proton signals at chemical shifts of 7.14-7.04 and 7.01-6.88 correspond to hydrogen atoms in aromatic ring groups, while the proton signals at chemical shifts of 6.46, 6.31, and 6.08 correspond to hydrogen atoms in vinyl groups. This further confirms that the organic compound B synthesized in Example 2 is tetraphenyl acrylate.

[0110] Cyclic performance test

[0111] The assembled lithium metal battery was subjected to charge-discharge cycles using Blue Electric equipment. The charge-discharge program consisted of a 2-hour rest period followed by a charge-discharge cycle at 1 mAh / cm². 2 Charged at a current density of 1 mAh / cm for 1 hour. 2 The lithium metal battery was discharged at a current density for 1 hour and cycled 20 times to test its cycle performance. Afterwards, the lithium metal battery was disassembled and the negative electrode was removed to observe the interface. The results are shown in Table 1 and... Figures 1-4 As shown.

[0112] Table 1

[0113]

[0114]

[0115] Combining Table 1 and Figure 4 (d) It can be seen that after 20 cycles, the lithium metal anode of Comparative Example 1 has a rough and uneven surface and a darker color, indicating severe pulverization and a large amount of lithium dendrite growth; combined with Table 1 and Figure 4 (e)~ Figure 4 (g) It can be seen that after 20 cycles, the surface condition of the lithium metal anodes in Comparative Examples 2-4 is similar to that of Comparative Example 1, with little difference. (Referring to Table 1...) Figure 4 (a) and Figure 4 (b) It can be seen that the lithium metal anodes of Examples 1-2 exhibited a metallic luster after 20 cycles, and their interface roughness and pulverization were significantly improved compared with Comparative Examples 1-4; the interfaces of the lithium metal anodes of Examples 4-6 were similar to those of Example 2, and exhibited a metallic luster after 20 cycles, with significant improvements in interface roughness and pulverization; the lithium metal surface of Example 7 exhibited a metallic luster and no pulverization, but some lithium dendrites grew; the interfaces of the lithium metal anodes of Examples 8-10 were also similar to those of Example 1, and exhibited a metallic luster after 20 cycles, with significant improvements in interface roughness and pulverization. Figure 4 (c) Although the lithium metal anode interface in Example 3 still showed some pulverization and lithium dendrite growth after 20 cycles, it was an improvement compared to Comparative Example 1. In summary, it can be shown that both pyrene acrylate and tetraphenylethylene acrylate additives have a good inhibitory effect on lithium dendrite growth in lithium metal anodes.

[0116] from Figure 7 It can be seen that the lithium metal battery in Comparative Example 1 is prone to various defects such as voltage drift, increased impedance, and internal short circuits during cycling. Figures 5-6 The lithium metal batteries in Examples 1 and 2 exhibited more stable output voltage and cycle performance compared to... Figure 7 The lithium metal battery in Comparative Example 1 shows significant optimization; the cycle performance of the lithium metal batteries in Examples 4-7 is comparable to... Figure 6 Similar to Example 2, the cycle performance of the lithium metal batteries in Examples 8-10 is similar to that in Example 2. Figure 5 Similar to Example 1, the output voltage and cycle performance of the lithium metal batteries in Examples 4 to 10 are also relatively stable, indicating that the two additives, pyrene acrylate and tetrastyrene acrylate, have a protective effect on the lithium metal anode and can inhibit the growth of lithium dendrites, thereby improving the cycle performance and safety performance of the lithium metal battery.

[0117] Since pyrene acrylate in Example 1 and tetraphenyl acrylate in Example 2 have the function of inhibiting lithium dendrite growth and optimizing the electrode interface, but methyl acrylate in Comparative Example 2 and phenyl acrylate in Comparative Example 3 do not have the above effect, it shows that only when R in Formula I is an aromatic group with large steric hindrance can the growth of lithium dendrites on the lithium metal anode be inhibited and the electrode interface optimized. Tetraphenyl acrylate in Example 2 has the function of inhibiting lithium dendrite growth and optimizing the electrode interface, but acryloxytetraphenylamine in Comparative Example 4 does not have the above effect, it shows that ester bond and sterically hindered directional group have a synergistic effect in inhibiting lithium dendrites and optimizing the electrode interface. If the ester bond is replaced with other groups, the effect of Example 2 cannot be achieved.

[0118] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. An electrolyte, characterized in that, Including organic solvents, lithium salts, and electrolyte additives; The electrolyte additive includes at least one of the organic compounds having the general structural formula shown in Formula I: In Formula I, R is selected from substituted or unsubstituted pyrene, substituted or unsubstituted anthraquinone, substituted or unsubstituted phenanthrene, substituted or unsubstituted pentaphenyl, substituted or unsubstituted tetrastyrene, or substituted or unsubstituted 1,2,3,4,5-pentaphenylphenyl.

2. The electrolyte according to claim 1, characterized in that, The electrolyte additive accounts for 0.25% to 10% of the mass percentage of the electrolyte.

3. The electrolyte according to claim 1, characterized in that, The electrolyte additive accounts for 0.5% to 5% of the mass percentage of the electrolyte.

4. The electrolyte according to claim 1, characterized in that, The electrolyte additive accounts for 1% to 2% of the mass percentage of the electrolyte.

5. The electrolyte according to claim 1, characterized in that, The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

6. The electrolyte according to any one of claims 1 to 5, characterized in that, The concentration of the lithium salt in the electrolyte is 0.5 mol / L to 2 mol / L.

7. The electrolyte according to any one of claims 1 to 5, characterized in that, The organic solvent includes one or more of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

8. The electrolyte according to any one of claims 1 to 5, characterized in that, The R is selected from substituted or unsubstituted pyrene, substituted or unsubstituted pentaphenyl, substituted or unsubstituted tetraphenylpyrene, or substituted or unsubstituted 1,2,3,4,5-pentaphenylphenyl.

9. The method for preparing the electrolyte according to any one of claims 1 to 8, characterized in that, The process includes the following steps: mixing the organic solvent, the lithium salt, and the electrolyte additive to obtain the electrolyte.

10. A lithium metal battery, characterized in that, It includes a lithium-containing negative electrode and an electrolyte, wherein the electrolyte includes the electrolyte according to any one of claims 1 to 8 or the electrolyte prepared by the preparation method according to claim 9.

11. An electrical appliance, characterized in that, Including the lithium metal battery of claim 10.

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