A dithioamino compound and its use in electrolytes

Abstract

The application discloses a dithioamino compound and application thereof in electrolyte, and belongs to the technical field of batteries. The dithioamino compound has a low reduction potential, and when applied to electrolyte and corresponding secondary batteries, can be preferentially decomposed to organic solvents and form a stable SEI film, thereby helping to prevent the organic solvent from being reduced by a large number of electrons on the negative electrode surface; meanwhile, the unsaturated bond of the dithioamino compound can also undergo polymerization and crosslinking reactions in the film forming process, to generate a polymer with high molecules, thereby helping to form a more dense and stable film, and improving the mechanical strength and chemical stability of the SEI layer; in addition, the sulfur element in the dithioamino compound can generate a compound rich in sulfur and oxygen, further improving the toughness of the SEI film. Therefore, when the dithioamino compound is used to prepare a secondary battery, the obtained secondary battery has excellent cycle performance and low-temperature storage performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular to a dithioamino compound and its application in electrolytes. Background Technology

[0002] Film-forming additives play a crucial role in lithium-ion batteries, improving cycle life, capacity retention, and safety by forming stable SEI or CEI layers on the electrode surface. Currently, the most commonly used film-forming additive is fluoroethylene carbonate (FEC). However, FEC exhibits poor stability under high voltage conditions (>4.2V), easily decomposing on the positive electrode surface, leading to accelerated electrolyte decomposition and the generation of harmful byproducts. Furthermore, its decomposition process produces HF, a highly acidic substance that severely corrodes the positive electrode material, causing transition metal dissolution and reducing battery stability. Simultaneously, existing film-forming additives cannot effectively improve the stability of rechargeable batteries at low temperatures. Summary of the Invention

[0003] The purpose of this application is to overcome the technical problem that existing film-forming additives cannot effectively achieve excellent cycle performance and low-temperature storage performance of secondary batteries, and to propose a dithioamino compound and its application in electrolyte.

[0004] To achieve the above objectives, a first aspect of this application provides a dithioamino compound, the structural formula of which is shown in Formula A:

[0005]

[0006] R1 and R2 are each independently selected from any one of fluoroalkyl, fluoroaromatic, sulfonamide, cyano, vinyl, pyrazolyl, ester, aldehyde, ketone, and ether groups.

[0007] As an embodiment of this application, the fluoroalkyl group includes any one of fluoromethyl, fluoroethyl, fluorobutyl, and fluoroisobutyl.

[0008] As an embodiment of this application, the fluoroaromatic group includes fluorophenyl.

[0009] As an embodiment of this application, the ketone group includes an ethyl ketone group.

[0010] As an embodiment of this application, the ether group includes a methyl ether group.

[0011] As an embodiment of this application, the dithioamino compound includes any one of formulas 1 to 10:

[0012]

[0013] In a second aspect of this application, an electrolyte is provided, the electrolyte comprising a metal salt, an organic solvent, an additive, and the dithioamino compound described in this application.

[0014] As an embodiment of this application, the mass percentage of the dithioamino compound is 1% to 3% based on the electrolyte.

[0015] As an embodiment of this application, the mass ratio of the dithioamino compound to the additive is 1:

[0016] (2-5).

[0017] As an embodiment of this application, the molar concentration of the metal salt in the electrolyte is 0.5 mol / L to 2 mol / L.

[0018] As an embodiment of this application, the organic solvent includes at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl propyl carbonate, methyl ethyl carbonate, and methyl isobutyl carbonate.

[0019] As an embodiment of this application, the additive includes at least one selected from fluoroethylene carbonate, ethylene glycol dimethyl ether, trifluorophosphate, vinylene carbonate, 1,3-propane sulpholol, and methyl methacrylate.

[0020] As an embodiment of this application, the metal salt includes at least one of MClO4, MBF4, MPF6, MAsF6, MBOB, MFSI, MTFSI, MPF2O2, MCF3SO3, MCF3SO3, and MPF2(C2O4); wherein M includes any one of Li, Na, and K.

[0021] In a third aspect of this application, a secondary battery is provided, comprising the electrolyte described above.

[0022] In a fourth aspect of this application, an electrical device is provided, including the aforementioned secondary battery.

[0023] Compared with the prior art, the beneficial effects of this application are:

[0024] The dithioamine compound provided in this application has three main advantages. First, it has a low reduction potential, allowing it to preferentially decompose and form a stable SEI film before organic solvents when used in electrolytes and corresponding secondary batteries. This helps prevent the organic solvent from being reduced by a large number of electrons on the negative electrode surface. Second, the unsaturated bonds in the dithioamine compound can undergo polymerization and cross-linking reactions during film formation, generating high-molecular-weight polymers. This helps form a denser and more stable film, improving the mechanical strength and chemical stability of the SEI layer. Third, the sulfur element in the dithioamine compound can generate sulfur- and oxygen-rich compounds, making the resulting SEI film more resilient. Due to these three advantages, when a secondary battery is prepared using an electrolyte containing the dithioamine compound described in this application, the resulting battery exhibits excellent cycle performance and low-temperature storage performance. Attached Figure Description

[0025] Figure 1 The Raman spectrum of the dithioamino compound described in Formula 1;

[0026] Figure 2 The Raman spectrum of the dithioamino compound described in Formula 2;

[0027] Figure 3 The Raman spectrum of the dithioamino compound described in Formula 3 is shown below.

[0028] Figure 4 The Raman spectrum of the dithioamino compound described in Formula 4;

[0029] Figure 5 The Raman spectrum of the dithioamino compound described in Formula 5;

[0030] Figure 6 The Raman spectrum of the dithioamino compound described in Formula 6;

[0031] Figure 7 The Raman spectrum of the dithioamino compound described in Formula 7;

[0032] Figure 8 The Raman spectrum of the dithioamino compound described in Formula 8;

[0033] Figure 9 The Raman spectrum of the dithioamino compound described in Formula 9;

[0034] Figure 10 The image shows the Raman spectrum of the dithioamino compound described in Formula 10. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] 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.

[0037] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0038] In one embodiment of this application, a dithioamino compound is provided, the structural formula of which is shown in Formula A:

[0039]

[0040] R1 and R2 are each independently selected from any one of fluoroalkyl, fluoroaromatic, sulfonamide, cyano, vinyl, pyrazolyl, ester, aldehyde, ketone, and ether groups.

[0041] This application reveals that, firstly, the dithioamine compound provided in this application has a low reduction potential. When applied to electrolytes and corresponding secondary batteries, it preferentially decomposes before organic solvents and forms a stable SEI film, thereby helping to prevent the organic solvent from being reduced by a large number of electrons on the negative electrode surface. Secondly, the unsaturated bonds of the dithioamine compound provided in this application can undergo polymerization and cross-linking reactions during film formation, generating high-molecular-weight polymers, thereby helping to form a denser and more stable film and improving the mechanical strength and chemical stability of the SEI layer. Thirdly, the sulfur element in the dithioamine compound provided in this application can generate sulfur- and oxygen-rich compounds, making the resulting SEI film more resilient. Due to the combined effects of these three aspects, when a secondary battery is prepared using an electrolyte containing the dithioamine compound described in this application, the resulting secondary battery exhibits excellent cycle performance and low-temperature storage performance.

[0042] In one embodiment, the fluoroalkyl group includes any one of fluoromethyl, fluoroethyl, fluorobutyl, and fluoroisobutyl.

[0043] In one embodiment, the fluoroaromatic group includes a fluorophenyl group.

[0044] In one embodiment, the ketone group includes an ethyl ketone group.

[0045] In one embodiment, the ether group includes a methyl ether group.

[0046] This application research found that when different substituent groups are selected in the dithioamino compounds provided in this application, the ability of the fluorinated groups in the resulting compounds to rapidly decompose at low temperatures varies, resulting in differences in the ability to form a lithium fluoride-rich SEI film at low temperatures, which in turn affects the decomposition of organic solvents in the electrolyte. Furthermore, the polymerization and cross-linking reactions of the dithioamino compounds provided in this application vary depending on the substituent groups selected, resulting in differences in the mechanical strength and interfacial stability of the formed SEI film. Therefore, when the corresponding substituent groups are further selected as the aforementioned groups, the dithioamino compounds obtained, when used in electrolytes to prepare secondary batteries, result in secondary batteries with better low-temperature storage performance and better cycle performance.

[0047] In one embodiment, the dithioamino compound includes any one of Formula 1 to Formula 10:

[0048]

[0049] In one embodiment, the dithioamino compound includes compounds shown in Formula 1, Formula 3, Formula 5 and Formula 6.

[0050] This application research found that when dithioamino compounds, including any one of Formulas 1 to 10, especially those shown in Formulas 1, 3, 5 and 6, are further selected and applied to the preparation of secondary batteries, the overall performance of the resulting secondary batteries is better.

[0051] In one embodiment of this application, an electrolyte is provided, the electrolyte comprising a metal salt, an organic solvent, an additive, and the dithioamino compound described in this application.

[0052] This application research found that by adding the dithioamine compound described in this application to the electrolyte provided in this application, the compound exhibits a low reduction potential at low temperatures. This allows it to preferentially decompose before the organic solvent in the electrolyte and form an SEI film with high mechanical strength and strong interfacial stability, thereby preventing the organic solvent from being reduced by a large number of electrons on the negative electrode surface. Simultaneously, the unsaturated bonds in the dithioamine compound can undergo polymerization and cross-linking reactions to generate high molecular weight polymers, further improving the density and stability of the SEI film. Furthermore, the sulfur element in the dithioamine compound can also generate sulfur- and oxygen-rich compounds, enhancing the toughness and stability of the SEI film. Therefore, when this electrolyte is further applied to secondary batteries, the resulting secondary batteries exhibit excellent low-temperature storage and cycle performance.

[0053] In one embodiment, the mass percentage of the dithioamino compound is 1% to 3% based on the electrolyte.

[0054] It should be noted that the mass percentage of dithioamino compounds, based on the electrolyte, was obtained by gas chromatography. The testing and calculation method is as follows: The components in the sample are separated by passing through the chromatographic column at different times, forming different peaks. The peak area of ​​the sample is then converted into concentration. The mass percentage m of the sample is then calculated. 样品 =V 样品 *(A 样品 ) / m 电解液 V 样品 It is the volume of the sample, A 样品 It is the peak area of ​​the sample on gas chromatography, m 电解液 It is the total mass of the electrolyte.

[0055] For example, the mass percentage of the dithioamino compound, based on the electrolyte, can be any point value or any two-point range between 1% and 3%, such as one or any two of 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%.

[0056] This study found that dithioamine compounds within a suitable addition range can form a uniformly thick SEI film on the negative electrode surface without significantly affecting the electrolyte viscosity, thus avoiding any impact on lithium-ion transport within the electrolyte and improving the overall performance of the subsequently prepared secondary battery. Specifically, the dithioamine compound preferentially decomposes before the organic solvent and forms a stable SEI film on the negative electrode surface, effectively reducing the impact of organic solvent decomposition on the secondary battery performance. When the mass percentage of the dithioamine compound is further selected within the aforementioned range, a suitable SEI film formation rate can be achieved while ensuring the functionality of the dithioamine compound, thereby effectively improving the low-temperature storage performance and cycle performance of the subsequently prepared secondary battery.

[0057] In one embodiment, the mass ratio of the dithioamino compound to the additive is 1:(2-5).

[0058] It should be noted that the mass ratio of the dithioamino compound to the additive was obtained through titration testing and calculation. The calculation method is: C = C1 * V1 / V2, where C1 is the concentration of the standard solution, V1 is the volume of the standard solution during titration, and V2 is the volume of the electrolyte.

[0059] For example, the mass ratio of the dithioamino compound to the additive can be any point value or any two points within a range of 1:(2 to 5), such as one or any two of the following: 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8, 1:4, 1:4.2, 1:4.4, 1:4.6, 1:4.8, 1:5.

[0060] This study found that when the mass ratio of dithioamine compound to additive is within a suitable range, the two have a good interaction. The resulting SEI film not only contains relatively soft sulfur elements but also contains components rich in fluorides and other organic compounds. The SEI film formed has good toughness and stability under low temperature conditions, which can significantly improve the low-temperature storage performance of the secondary battery subsequently prepared. Furthermore, when the mass ratio of dithioamine compound to additive is within a suitable range, it can ensure that the thickness of the formed SEI film is uniform. Therefore, during the subsequent charge and discharge process of the secondary battery, the SEI film will not break and reform, thereby effectively improving the cycle performance of the secondary battery subsequently prepared.

[0061] In one embodiment, the molar concentration of the metal salt in the electrolyte is 0.5 mol / L to 2 mol / L.

[0062] It should be noted that the molar concentration of the metal salt in the electrolyte was obtained by titration.

[0063] For example, the molar concentration of the metal salt in the electrolyte can be any point value or any two points between 0.5 mol / L and 2 mol / L, such as one or any two of 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, and 2 mol / L.

[0064] This study found that organic solvents can help separate lithium ions and anions in lithium salts, and during charging, the solvated structure moves towards the negative electrode. Dithioamine compounds and additives help the electrolyte form an SEI film on the negative electrode surface, thus protecting the organic solvent molecules in the solvated layer on the negative electrode surface. When the molar concentration of the metal salt is further selected within the above range, the cycle performance and low-temperature storage performance of the subsequently prepared secondary battery can be better improved.

[0065] In one embodiment, the organic solvent includes at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl propyl carbonate, methyl ethyl carbonate, and methyl isobutyl carbonate.

[0066] In one embodiment, the organic solvent includes ethylene carbonate and ethyl methyl carbonate.

[0067] In one embodiment, the mass ratio of ethylene carbonate to methyl ethyl carbonate is 1:(2-3).

[0068] This study found that the type of organic solvent affects its interaction with dithioamino compounds. When the aforementioned types of organic solvents are selected, especially when the organic solvent is a mixture of ethylene carbonate and ethyl methyl carbonate, the overall performance of the resulting secondary battery is superior. Specifically, ethylene carbonate has a high dielectric constant, which helps in the separation of metal salts and enhances the transport capacity of metal ions in the electrolyte; ethyl methyl carbonate has a low viscosity, which ensures the fluidity of the electrolyte at low temperatures. The combination of these two components can better improve the cycle performance and low-temperature storage performance of the subsequently prepared secondary battery.

[0069] In one embodiment, the additive includes at least one selected from fluoroethylene carbonate, ethylene glycol dimethyl ether, trifluorophosphate, vinylene carbonate, 1,3-propane sulpholol, and methyl methacrylate.

[0070] In one embodiment, the additive includes fluoroethylene carbonate.

[0071] This study found that the type of additives in the electrolyte not only interacts differently with dithioamino compounds, but also affects the gas generation of the electrolyte and the corrosion of the positive electrode; when the additives are further selected to include the above-mentioned types of substances, especially fluoroethylene carbonate, the cycle performance of the secondary battery is better.

[0072] In one embodiment, the metal salt includes at least one of MClO4, MBF4, MPF6, MAsF6, MBOB, MFSI, MTFSI, MPF2O2, MCF3SO3, MCF3SO3, and MPF2(C2O4); wherein M includes any one of Li, Na, and K.

[0073] In one embodiment, the metal salt includes MPF6, MPF2(C2O4), and MFSI, wherein M is Li.

[0074] This study found that when the above-mentioned types of metal salts are selected, they can interact well with other components in the electrolyte, and the metal ions have a strong migration ability in the electrolyte, thereby improving the overall performance of the secondary battery.

[0075] In one embodiment of this application, a secondary battery is provided, including the electrolyte described in this application.

[0076] The secondary battery provided in this application contains the electrolyte provided in this application, which can form a stable and dense SEI film at low temperatures, and the metal ions have a strong transport capacity in the electrolyte, thus the secondary battery has good low-temperature storage performance and cycle performance.

[0077] In one embodiment, the secondary battery further includes a positive electrode, a negative electrode, and a separator.

[0078] In one embodiment, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector; the positive active material layer includes a positive active material, a conductive agent, and a binder. This application does not limit the positive active material, conductive agent, and binder; any known positive active material, conductive agent, and binder may be used.

[0079] For example, the positive electrode active material includes LiMnO2, LiFeO2, LiMn2O4, Li2FeSiO4, LiNi5CO2Mn3O2, and Li z Ni (1-x-y) Co x M yO2 (0.01≤x≤0.20, 0≤y≤0.20, 0.97≤z≤1.20, M selected from at least one of Mn, V, Mg, B and Al), LiFePO4 and Li z CO (1-x) M x O2 (0≤x≤0.1 and 0.97≤z≤1.20, M is selected from at least one of Mn, V, Mg, B and Al), etc.

[0080] In one embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; the negative electrode active material layer includes a negative electrode active material. This application does not limit the negative electrode active material; any known negative electrode active material can be used.

[0081] For example, the negative electrode active material includes graphite-based materials, silicon-based materials, metal oxides, metal sulfides, metal alloys, lithium alloys, etc.

[0082] For example, the graphite-based materials include natural graphite, artificial graphite, hard carbon, and soft carbon; the silicon-based materials include silicon, silicon-carbon composites, and silicon oxides; the metal oxides include lithium titanate, tin oxide, zinc oxide, and vanadium dioxide; the metal sulfides include tin sulfide, molybdenum sulfide, and zinc sulfide; the metal alloy materials include alloys composed of tin, aluminum, gallium, and germanium; and the lithium alloy materials include lithium metal and lithium silicon metal.

[0083] This application does not impose any restrictions on the diaphragm, and any diaphragm conventionally used in the art can be selected; for example, the material of the diaphragm can be a single-layer or multi-layered microporous film of polyolefins such as polypropylene and polyethylene, a ceramic-coated diaphragm, a hydrogel diaphragm, or a non-woven fabric diaphragm, etc.

[0084] In a fourth aspect, this application provides an electrical device including the secondary battery described in this application.

[0085] For example, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0086] Example 1

[0087] This application provides a dithioamino compound (Formula 1), and the preparation method of the dithioamino compound includes the following steps:

[0088] 0.5 g of dithiooxazone was added to 10 mL of dichloromethane, followed by 0.25 mL of trifluoromethanesulfonyl chloride and 0.1 g of sodium carbonate for pH adjustment. The mixture was then stirred at 0–5 °C for 1 h to convert the amino terminus to a CF3 group. Finally, 0.2 mL of methanesulfonyl chloride was added and the mixture was stirred at 0–5 °C for 2 h to introduce a sulfonyl group. The reaction system was kept at 22–27 °C, and 0.3 mL of 25% ammonia solution was added dropwise while stirring for 2 h to complete the ammoniation reaction. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 1.

[0089] The Raman spectrum of the dithioamino compound shown in Formula 1 is as follows: Figure 1 As shown.

[0090] Example 2

[0091] This application provides a dithioamino compound (Formula 2), the preparation method of which includes the following steps:

[0092] 0.5 g of dithiooxazone was added to 10 mL of dichloromethane, followed by 0.3 mL of fluoroaniline and 0.1 g of sodium carbonate for pH adjustment. The mixture was then stirred at 0–5 °C for 1 h. Finally, 0.2 mL of cyanogen trifluoride was added and the mixture was reacted at 0–5 °C for 2 h. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 2.

[0093] The Raman spectrum of the dithioamino compound shown in Formula 2 is as follows: Figure 2 As shown.

[0094] Example 3

[0095] This application provides a dithioamino compound (Formula 3), the preparation method of which includes the following steps:

[0096] 0.5 g of dithiooxazone was added to 10 mL of dichloromethane, followed by 0.25 mL of trifluoromethanesulfonyl chloride and 0.1 g of sodium carbonate for pH adjustment. The mixture was then stirred at 0–5 °C for 1 h. Finally, 0.2 mL of cyanogen trifluoride was added and the mixture was reacted at 0–5 °C for 2 h. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 3.

[0097] The Raman spectrum of the dithioamino compound shown in Formula 3 is as follows: Figure 3 As shown.

[0098] Example 4

[0099] This application provides a dithioamino compound (Formula 4), the preparation method of which includes the following steps:

[0100] 0.5 g of dithiooxazone was added to 10 mL of anhydrous acetonitrile, followed by 0.3 mL of formyl chloride. The mixture was stirred at 0–5 °C for 0.5 h. Finally, 0.2 mL of vinyl bromide was added dropwise and the mixture was reacted at 0–5 °C for 2 h. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 4.

[0101] The Raman spectrum of the dithioamino compound shown in Formula 4 is as follows: Figure 4 As shown.

[0102] Example 5

[0103] This application provides a dithioamino compound (Formula 5), ​​the preparation method of which includes the following steps:

[0104] 0.5 g of dithiooxazone was added to 15 mL of anhydrous ethanol, followed by 0.4 g of dimethylpyrazole. The mixture was stirred at 10 °C for 1 h, and then 0.3 g of dimethyl ether was added dropwise and the mixture was reacted at 25 °C for 2 h. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 5.

[0105] The Raman spectrum of the dithioamino compound shown in Formula 5 is as follows: Figure 5 As shown.

[0106] Example 6

[0107] This application provides a dithioamino compound (Formula 6), the preparation method of which includes the following steps:

[0108] 0.5 g of dithiooxazone was added to 10 mL of dichloromethane, followed by 0.25 mL of trifluoromethanesulfonyl chloride and 0.1 g of sodium carbonate to adjust the pH of the system. The mixture was then stirred at 0–5 °C for 1 h. Finally, 0.4 g of acetyl chloride was slowly added and the mixture was reacted at 25 °C for 2 h. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 6.

[0109] The Raman spectrum of the dithioamino compound shown in Formula 6 is as follows: Figure 6 As shown.

[0110] Example 7

[0111] This application provides a dithioamino compound (Formula 7), the preparation method of which includes the following steps:

[0112] 0.5 g of dithiooxazone was added to 10 mL of dichloromethane, followed by 0.25 mL of cyanogen trifluoride and 0.1 g of sodium carbonate to adjust the pH of the system. The mixture was then stirred at 0–5 °C for 1 h. Finally, 0.2 mL of methanesulfonyl chloride was added and the mixture was stirred at 0–5 °C for 2 h to introduce sulfonyl groups. The reaction system was kept at 22–27 °C and 0.3 mL of 25% ammonia solution was added dropwise while stirring for 2 h to complete the ammoniation reaction. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 7.

[0113] The Raman spectrum of the dithioamino compound shown in Formula 7 is as follows: Figure 7 As shown.

[0114] Example 8

[0115] This application provides a dithioamino compound (Formula 8), the preparation method of which includes the following steps:

[0116] 0.5 g of dithiooxazone was added to 10 mL of dichloromethane, followed by 0.3 mL of fluoroaniline and 0.1 g of sodium carbonate to adjust the pH of the system. The mixture was then stirred at 0–5 °C for 1 h. Finally, 0.3 g of dimethyl ether was added dropwise and the mixture was reacted at 25 °C for 2 h. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 8.

[0117] The Raman spectrum of the dithioamino compound shown in Formula 8 is as follows: Figure 8 As shown.

[0118] Example 9

[0119] This application provides a dithioamino compound (Formula 9), the preparation method of which includes the following steps:

[0120] 0.5 g of dithiooxazone was added to 10 mL of dichloromethane, followed by 0.25 mL of cyanogen trifluoride. The mixture was stirred at 0–5 °C for 0.5 h. Finally, 0.2 mL of vinyl bromide was slowly added and the mixture was reacted at 0–5 °C for 2 h. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 9.

[0121] The Raman spectrum of the dithioamino compound shown in Formula 9 is as follows: Figure 9 As shown.

[0122] Example 10

[0123] This application provides a dithioamino compound (Formula 10), and the preparation method of the dithioamino compound includes the following steps:

[0124] 0.5 g of dithiooxazone was added to 10 mL of anhydrous acetonitrile, followed by 0.3 mL of formyl chloride. The mixture was stirred at 0–5 °C for 0.5 h, and finally 0.2 mL of methanesulfonyl chloride was added and the mixture was stirred at 0–5 °C for 2 h to introduce sulfonyl groups. 0.3 mL of 25% ammonia solution was added dropwise while maintaining the reaction system at 22–27 °C and stirred for 2 h to complete the ammoniation reaction. After the reaction was completed, post-treatment was performed to obtain the dithioamino compound shown in Formula 10.

[0125] The Raman spectrum of the dithioamino compound shown in Formula 10 is as follows: Figure 10 As shown.

[0126] Application Example 1

[0127] This application provides a secondary battery, the preparation method of which includes the following steps:

[0128] (1) Preparation of electrolyte

[0129] In an argon-filled glove box (moisture < 0.1 ppm, oxygen < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a mass ratio of 3:7 to prepare an organic solvent. 3% fluoroethylene carbonate (FEC) and 1% dithioamide compound based on the total mass of the electrolyte were added to the organic solvent. Then, a metal salt (lithium hexafluorophosphate and lithium difluorooxalate phosphate at a mass ratio of 13:1.5) was slowly added and stirred until completely dissolved to obtain the electrolyte; wherein the molar concentration of the metal salt was 1 mol / L.

[0130] (2) Preparation of positive electrode sheet

[0131] The positive electrode active material lithium nickel cobalt manganese oxide (NCM523), the conductive agent acetylene black (Super P), and the binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of NCM523:Super P:PVDF = 8:1:1, and then evenly dispersed in N-methylpyrrolidone (NMP) to form a uniform black slurry. The mixed black slurry is coated on both sides of aluminum foil, and then baked, rolled, and cut into sheets to obtain the positive electrode sheet.

[0132] (3) Preparation of negative electrode sheet

[0133] The negative electrode active material silicon dioxide-carbon material, conductive agent acetylene black (Super P) and binder SBR are mixed evenly in a mass ratio of graphite:Super P:SBR=9:0.5:0.5 and evenly dispersed in deionized water to form a uniform black slurry. The mixed slurry is coated on both sides of copper foil, and then baked, rolled, and cut into sheets to obtain the negative electrode sheet.

[0134] (4) Preparation of secondary batteries

[0135] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes. After winding, hot pressing and shaping, and welding of the tabs, a 2Ah bare cell is obtained. The bare cell is placed in an outer packaging aluminum-plastic film and baked in an oven at 85±10℃ for 24 hours. 10g of the prepared electrolyte is injected into the dried battery. The battery is then left to stand at 45℃ for 24 hours for formation and capacity testing to obtain a secondary battery.

[0136] Application Examples 2-5

[0137] This application provides a secondary battery, the preparation method of which differs from that of Application Example 1 in that the amount of dithioamino compound added is different.

[0138] Application Examples 6-9

[0139] This application provides a secondary battery, the preparation method of which differs from that of Application Example 1 in that the mass ratio of dithioamine compound and additives is different.

[0140] Application Examples 10-11

[0141] This application provides a secondary battery, the preparation method of which differs from that of Application Example 1 in that the molar concentration of the metal salt is different.

[0142] Application Example 12

[0143] This application provides a secondary battery, the preparation method of which differs from that of Application Example 1 in that the type of organic solvent is different.

[0144] Application Example 13

[0145] This application provides a secondary battery, the preparation method of which differs from that of Application Example 1 in that the type of additive is different.

[0146] Application Example 14

[0147] This application provides a secondary battery, the preparation method of which differs from that of Application Example 1 in that the type of metal salt is different.

[0148] Application Examples 15-23

[0149] This application provides a secondary battery, the preparation method of which differs from that of Application Example 1 in that the type of dithioamino compound is different.

[0150] Comparative Application Example 1

[0151] This application provides a secondary battery in a comparative application example. The difference between the preparation method of the secondary battery and that in application example 1 is that no dithioamino compound is added.

[0152] Comparative Application Example 2

[0153] This application provides a secondary battery in a comparative application example. The difference between the preparation method of the secondary battery and that in application example 1 is that no additives are added.

[0154] Comparative Application Example 3

[0155] This application provides a secondary battery in a comparative application example. The difference between the preparation method of the secondary battery and application example 1 is that trifluorophosphate is used instead of dithioamino compound.

[0156] The types and amounts of dithioamino compounds in the electrolytes of the application examples and comparative application examples, the mass ratio of dithioamino compounds to additives (A), the molar concentration of metal salts (B), the mass percentage of additives (C), the types of organic solvents, the types of additives, and the types of metal salts are shown in Table 1.

[0157] Among them, metal salt 1 is a mixture of lithium hexafluorophosphate and lithium difluorodioxarate phosphate in a mass ratio of 13:1.5;

[0158] Metal salt 2 is lithium hexafluorophosphate;

[0159] Organic solvent 1 is a mixture of ethylene carbonate and ethyl methyl carbonate in a 3:7 ratio;

[0160] Organic solvent 2 is a mixture of ethylene carbonate and methyl ethyl carbonate in a 3:7 ratio;

[0161] Additive 1 is fluoroethylene carbonate;

[0162] Additive 2 is ethylene glycol dimethyl ether;

[0163] Table 1. Results of Material and Parameter Selection for Application Examples and Comparative Application Examples

[0164]

[0165]

[0166] The performance of the secondary batteries prepared according to the corresponding use cases and comparative application examples was tested, including the following aspects:

[0167] 1. Room Temperature Cycling Performance Test: At 25℃, the manufactured battery was charged to 4.5V at a constant current of 0.5C, then charged at a constant voltage of 4.5V (cutoff current 0.01C); then discharged to 3.0V at a constant current of 0.5C. After 500 charge-discharge cycles, the capacity retention rate after the 500th cycle was calculated. The calculation formula is as follows: Capacity retention rate after 500 cycles = (Discharge capacity after the 500th cycle / Discharge capacity after the 1st cycle) × 100%;

[0168] 2. Low-Temperature Storage Performance Test: At -20℃, the manufactured battery was charged to 4.5V at a constant current of 0.5C, and then charged at a constant voltage of 4.5V (cutoff current 0.01C); then discharged to 3.0V at a constant current of 0.5C, and the discharge capacity was recorded as the initial discharge capacity. The battery was then charged to 4.5V at a constant current of 0.5C, and then charged at a constant voltage of 4.5V (cutoff current 0.01C). The battery was then stored in a -20℃ freezer for 10 days, and then allowed to naturally warm to 25℃. At 25℃, it was discharged to 3.0V at a constant current of 0.5C, and the discharge capacity was recorded as the retention capacity. Then, at 25℃, it was cycled once at the same 0.5C rate, and the discharge capacity was recorded as the recovery capacity. The low-temperature storage performance of the battery was calculated as follows: Battery capacity retention rate = Retention capacity / Initial capacity × 100%; Battery capacity recovery rate = Recovery capacity / Initial capacity × 100%.

[0169] The results are shown in Table 2;

[0170] Table 2 Performance Data of Secondary Batteries

[0171]

[0172]

[0173] As can be seen from Table 2, when the technical solution provided in this application is adopted, the obtained secondary battery has excellent cycle performance and low temperature storage performance; specifically, the capacity retention rate of the obtained secondary battery at 25℃ / 500 cycles is above 74.31%, the capacity retention rate at low temperature storage (-20℃, 10 days) is above 56.83%, and the capacity recovery rate is above 62.47%.

[0174] As can be seen from Application Examples 1-23 and Comparative Application Example 1, when no dithioamine compound is added, the cycle performance and low-temperature storage performance of the obtained secondary battery show a significant downward trend; as can be seen from Application Examples 1-23 and Comparative Application Example 2, when no additive is added, the overall performance of the obtained secondary battery also shows a certain downward trend; as can be seen from Application Examples 1-23 and Comparative Application Example 3, when other substances are used to replace the dithioamine compound, the effect of this application cannot be achieved.

[0175] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this application and not to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A dithioamino compound, characterized in that, The dithioamino compound includes any one of Formula 1 to Formula 10: 。 2. An electrolyte, characterized in that, The electrolyte comprises a metal salt, an organic solvent, an additive, and a dithioamino compound as described in claim 1.

3. The electrolyte according to claim 2, characterized in that, The mass percentage of dithioamino compounds is 1% to 3% based on the electrolyte.

4. The electrolyte according to claim 3, characterized in that, The mass ratio of the dithioamino compound to the additive is 1:(2~5).

5. The electrolyte according to claim 3, characterized in that, The molar concentration of the metal salt in the electrolyte is 0.5 mol / L to 2 mol / L.

6. The electrolyte according to claim 2, characterized in that, The organic solvent includes at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, and methyl propyl carbonate. And / or, the additives include at least one of fluoroethylene carbonate, ethylene glycol dimethyl ether, trifluorophosphate, vinylene carbonate, 1,3-propane sulpholol and methyl methacrylate; And / or, the metal salt includes at least one of MClO4, MBF4, MPF6, MAsF6, MBOB, MFSI, MTFSI, MPF2O2, MCF3SO3, MCF3SO3, and MPF2(C2O4); wherein M includes any one of Li, Na, and K.

7. A secondary battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte as described in any one of claims 2 to 6.

8. An electrical device, characterized in that, Includes the secondary battery as described in claim 7.

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