Electrolyte, secondary battery, method for manufacturing the same, and electric device

Abstract

The application discloses an electrolyte, a secondary battery and a preparation method and an electric device, and relates to the technical field of batteries, wherein the secondary battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte; the electrolyte comprises an electrolyte salt and a solvent; the electrolyte salt comprises an A metal salt; and at least before the first charging, the electrolyte further comprises an additive, wherein the additive comprises an aromatic compound with multiple substituents, and the structure general formula of the substituents is -S-A, wherein A is a metal element. The application can improve the first coulomb efficiency, the first discharge capacity and the cycle performance of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to an electrolyte, a secondary battery and its preparation method, and an electrical device. Background Technology

[0002] In recent years, with the increasing demand for clean energy, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, military equipment, aerospace, and many other fields. As the application areas of secondary batteries have greatly expanded, higher requirements have been placed on their performance.

[0003] However, during the first charge and discharge process of a secondary battery, a solid electrolyte membrane (SEI membrane) forms on the surface of the negative electrode, which consumes some of the active ions, leading to a decrease in the initial coulombic efficiency of the secondary battery and affecting its capacity and cycle performance. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte, a secondary battery and a method for preparing the same, and an electrical device thereof, to improve the initial coulombic efficiency, capacity and cycle performance of the secondary battery.

[0005] To achieve the above objectives, this application proposes an electrolyte, a secondary battery, a method for preparing the same, and an electrical device thereof.

[0006] In a first aspect, embodiments of this application propose a secondary battery, including a positive electrode, a negative electrode, and an electrolyte. At least before the first charge, the electrolyte includes an electrolyte salt and a solvent, wherein the electrolyte salt includes an A metal salt. At least before the first charge, the electrolyte also includes an additive, wherein the additive includes an aromatic compound having multiple substituents, wherein the general structural formula of the substituents is -SA, wherein A is a metal element.

[0007] Therefore, in the technical solution of this application embodiment, before at least the first charge, the electrolyte of the secondary battery contains an aromatic compound with multiple -SA substituents; during the first charge, the aromatic compound is oxidized at the positive electrode, and the substituents provide one molecule of electrons and one molecule of active ion (A ion) to form sulfur free radicals, which further couple to form disulfide bonds (-SS-), thereby polymerizing on the surface of the positive electrode to form a film layer, which can effectively avoid the occurrence of shuttle effect. The polymer of the film layer also has good conductivity and basically does not affect the performance of the secondary battery. Moreover, the active ions provided by the aromatic compound are embedded in the negative electrode to replenish the active ions; thereby improving the first coulombic efficiency, first discharge capacity and cycle performance of the secondary battery.

[0008] In any embodiment, A is any one of lithium, sodium, potassium, magnesium, and lead. When A is one of the aforementioned metallic elements, the secondary battery can be a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, a magnesium secondary battery, or an aluminum secondary battery.

[0009] In any embodiment, the aryl group of the aromatic compound includes at least one selected from phenyl, naphthyl, and anthraceneyl. Using the above-mentioned aryl group results in a simple structure of the aromatic compound and good electrical conductivity of the formed polymer; and / or,

[0010] A represents lithium. The substituent is lithium mercapto, which can be used for lithium replenishment in lithium secondary batteries.

[0011] In any embodiment, the aromatic compound includes at least one selected from lithium 1,4-phenylenedimercapto, lithium 1,3,5-phenyltrimercapto, lithium 1,3,5-naphthalenetrimercapto, and lithium 2,9,10-anthracitetrimercapto. Using the above aromatic compounds results in a simple structure, the formed polymer exhibits good conductivity, and its reaction voltage is more suitable, which is beneficial for improving the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary battery; and / or,

[0012] Before the first charge, the mass percentage of additives in the electrolyte is less than or equal to 6%. Maintaining the mass percentage of additives in the electrolyte within this range before the first charge can improve the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary battery, while also ensuring the kinetic performance of the secondary battery.

[0013] In any embodiment, the molar concentration of the electrolyte salt in the electrolyte is 1.0 mol / L to 2.0 mol / L. The molar concentration of the electrolyte salt in the electrolyte being within this range is beneficial for ensuring the performance of the secondary battery; and / or,

[0014] The solvent includes at least one selected from ethylene glycol dimethyl ether, 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, tetrahydrofuran, and 2-methyltetrahydrofuran. Using the above solvent helps to ensure the performance of the secondary battery.

[0015] Secondly, embodiments of this application propose a method for preparing a secondary battery, comprising the following steps:

[0016] An electrolyte is prepared by combining an electrolyte salt, a solvent, and an additive. The electrolyte salt includes an A metal salt, and the additive includes an aromatic compound having multiple substituents. The general structural formula of the substituents is -SA, where A is a metal element.

[0017] The positive electrode, separator, negative electrode, and electrolyte are assembled to obtain a secondary battery.

[0018] An electrolyte is prepared by combining an additive containing the aromatic compound with an electrolyte salt and a solvent, and then assembled to obtain a secondary battery. The electrolyte of the assembled secondary battery contains an aromatic compound with multiple -SA substituents, which can polymerize on the surface of the positive electrode to form a film layer, effectively avoiding the occurrence of the shuttle effect. The polymer of the film layer also has good conductivity and will not affect the performance of the secondary battery. It can also replenish active ions, thereby improving the initial coulombic efficiency, initial discharge capacity and cycle performance of the secondary battery.

[0019] Thirdly, embodiments of this application provide an electrolyte comprising an electrolyte salt, a solvent, and an additive. The electrolyte salt comprises an A metal salt, and the additive comprises an aromatic compound having multiple substituents. The general structural formula of the substituents is -SA, wherein A is a metal element.

[0020] An additive containing the aromatic compound is added to the electrolyte. The aromatic compound has multiple -SA substituents and can be used in secondary batteries to polymerize on the surface of the positive electrode to form a film layer, effectively avoiding the shuttle effect. The polymer of the film layer also has good conductivity and will not affect the performance of the secondary battery. It can also replenish active ions, thereby improving the initial coulombic efficiency, initial discharge capacity and cycle performance of the secondary battery.

[0021] In any embodiment, A is any one of lithium, sodium, potassium, magnesium, and lead. Using the aforementioned metallic element, A can be applied to lithium secondary batteries, sodium secondary batteries, potassium secondary batteries, magnesium secondary batteries, or aluminum secondary batteries.

[0022] In any embodiment, the aryl group of the aromatic compound includes at least one selected from phenyl, naphthyl, and anthraceneyl. Using the above-mentioned aryl group results in a simple structure for the aromatic compound, which is suitable for use in secondary batteries, and the resulting polymer exhibits good conductivity; and / or,

[0023] A represents lithium. The substituent is lithium mercapto, and the aromatic compound can be used for lithium replenishment in lithium secondary batteries.

[0024] In any embodiment, the aromatic compound includes at least one selected from lithium 1,4-phenylenedimercapto, lithium 1,3,5-phenyltrimercapto, lithium 1,3,5-naphthalenetrimercapto, and lithium 2,9,10-anthracitetrimercapto. Using the above aromatic compounds results in a simple structure, which, when used in secondary batteries, leads to polymers with good conductivity and a more suitable reaction voltage, thus improving the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary battery; and / or,

[0025] In the electrolyte, the mass percentage of the additive is less than or equal to 6%. When the mass percentage of the additive in the electrolyte falls within the aforementioned range, its use in secondary batteries can improve the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary battery, while also ensuring the kinetic performance of the secondary battery.

[0026] In any embodiment, the molar concentration of the electrolyte salt in the electrolyte is 1.0 mol / L to 2.0 mol / L. The molar concentration of the electrolyte salt in the electrolyte being within this range is beneficial for ensuring the performance of the secondary battery; and / or,

[0027] The solvent includes at least one selected from ethylene glycol dimethyl ether, 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, tetrahydrofuran, and 2-methyltetrahydrofuran. Using the above solvent helps to ensure the performance of the secondary battery.

[0028] Fourthly, embodiments of this application propose an electrical device, including a secondary battery of the first aspect or a secondary battery prepared by the preparation method of the second aspect. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope (SEM) image of the positive electrode sheet after formation in Example 3 of this application.

[0030] Figure 2 This is a scanning electron microscope (SEM) image of the positive electrode sheet after formation in Comparative Example 1 of this application.

[0031] Figure 3 This is a transmission electron microscope (TEM) image of the positive electrode sheet after formation in Example 3 of this application.

[0032] Figure 4 for Figure 3 The distribution map of sulfur element.

[0033] Figure 5 This is a transmission electron microscope (TEM) image of the positive electrode sheet after formation in Comparative Example 1 of this application.

[0034] Figure 6 for Figure 5 The distribution map of sulfur element.

[0035] Figure 7 This is a conductivity diagram of the electrolyte under different mass percentages of additives in this application.

[0036] Figure 8 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0037] Figure 9 yes Figure 8 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0038] Figure 10 This is a schematic diagram of a battery module according to one embodiment of this application.

[0039] Figure 11 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0040] Figure 12 yes Figure 11 An exploded view of a battery pack according to one embodiment of this application is shown.

[0041] Figure 13 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0044] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the electrolyte, secondary battery, preparation method thereof, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0045] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0048] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0050] In recent years, with the increasing demand for clean energy, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, military equipment, aerospace, and many other fields. As the application areas of secondary batteries have greatly expanded, higher requirements have been placed on their performance.

[0051] However, during the first charge and discharge process of a secondary battery, a solid electrolyte membrane (SEI membrane) forms on the surface of the negative electrode, which consumes some of the active ions, leading to a decrease in the initial coulombic efficiency of the secondary battery and affecting its capacity and cycle performance.

[0052] Based on this, this application proposes an electrolyte, a secondary battery, a method for preparing the same, and an electrical device thereof.

[0053] In a first aspect, embodiments of this application propose a secondary battery, including a positive electrode, a negative electrode, and an electrolyte. The electrolyte includes an electrolyte salt and a solvent, and the electrolyte salt includes an A metal salt. At least before the first charge, the electrolyte also includes an additive, which includes an aromatic compound having multiple substituents. The general structural formula of the substituents is -SA, where A is a metal element.

[0054] Therefore, in the technical solution of this application embodiment, before at least the first charge, the electrolyte of the secondary battery contains an aromatic compound with multiple -SA substituents; during the first charge, the aromatic compound is oxidized at the positive electrode, and the substituents provide one molecule of electrons and one molecule of active ion (A ion) to form sulfur free radicals, which further couple to form disulfide bonds (-SS-), thereby polymerizing on the surface of the positive electrode to form a film layer, which can effectively avoid the occurrence of shuttle effect. The polymer of the film layer also has good conductivity and basically does not affect the performance of the secondary battery. Moreover, the active ions provided by the aromatic compound are embedded in the negative electrode to replenish the active ions; thereby improving the first coulombic efficiency, first discharge capacity and cycle performance of the secondary battery.

[0055] It should be noted that, at least before the first charge, the electrolyte also includes additives, which include aromatic compounds having multiple substituents. This means that the electrolyte contains the aromatic compound before the first charge of the secondary battery. After multiple charge-discharge cycles of the secondary battery, the electrolyte may still contain the aromatic compound, or it may no longer contain the aromatic compound. The first charge refers to the first charge performed after the secondary battery is assembled (the initial charge of formation). The substituent A can be selected according to the type of secondary battery. For example, when the secondary battery is a lithium secondary battery, A is lithium; when the secondary battery is a sodium secondary battery, A is sodium; and so on. In the aromatic compound, multiple substituents are independently attached to the aryl group, and the number of substituents on the aryl group can be 2, 3, 4, etc.

[0056] In any embodiment, A is any one of lithium, sodium, potassium, magnesium, and lead. When A is one of the aforementioned metallic elements, the secondary battery can be a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, a magnesium secondary battery, or an aluminum secondary battery.

[0057] In any embodiment, the aryl group of the aromatic compound includes at least one selected from phenyl, naphthyl, and anthracene. Using the above-mentioned aryl group results in a simple structure of the aromatic compound and good electrical conductivity in the formed polymer. The aryl group of the aromatic compound can be any one or any combination of phenyl, naphthyl, and anthracene.

[0058] In any embodiment, A is lithium. The substituent is lithium mercapto, which can achieve lithium replenishment in lithium secondary batteries.

[0059] In any embodiment, the aromatic compound includes at least one selected from lithium 1,4-phenyldimercapto, lithium 1,3,5-phenyltrimercapto, lithium 1,3,5-naphthalenetrimercapto, and lithium 2,9,10-anthracenetrimercapto. Using the above aromatic compounds results in a simple structure, the formed polymer exhibits good conductivity, and its reaction voltage is more suitable, which is beneficial for improving the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary battery. The aromatic compound can be any one or any combination of lithium 1,4-phenyldimercapto, lithium 1,3,5-phenyltrimercapto, lithium 1,3,5-naphthalenetrimercapto, and lithium 2,9,10-anthracenetrimercapto.

[0060] In any embodiment, before the first charge, the mass percentage of the additive in the electrolyte is less than or equal to 6%. Maintaining the mass percentage of the additive in the electrolyte within this range before the first charge can improve the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary battery; as the mass percentage of the additive in the electrolyte increases, the conductivity of the electrolyte decreases (see...). Figure 7When the mass percentage of the additive in the electrolyte is 6%, the conductivity of the electrolyte decreases to approximately 7 mS / cm. Further increasing the mass percentage of the additive may affect the kinetic performance of the secondary battery. Before the first charge, the mass percentage of the additive in the electrolyte can be 0.5%, 1%, 2%, 3%, 4%, 5%, or 6%.

[0061] In any embodiment, the molar concentration of the electrolyte salt in the electrolyte is 1.0 mol / L to 2.0 mol / L. The molar concentration of the electrolyte salt in the electrolyte falling within this range is beneficial for ensuring the performance of the secondary battery. The molar concentration of the electrolyte salt in the electrolyte can be 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, or 2.0 mol / L.

[0062] In any embodiment, the solvent includes at least one selected from ethylene glycol dimethyl ether, 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, tetrahydrofuran, and 2-methyltetrahydrofuran. Using the above solvent helps to ensure the performance of the secondary battery. The solvent can be any one or any combination of ethylene glycol dimethyl ether and 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, tetrahydrofuran, and 2-methyltetrahydrofuran.

[0063] Secondly, embodiments of this application propose a method for preparing a secondary battery, comprising the following steps:

[0064] An electrolyte is prepared by combining an electrolyte salt, a solvent, and an additive. The electrolyte salt includes an A metal salt, and the additive includes an aromatic compound having multiple substituents. The general structural formula of the substituents is -SA, where A is a metal element.

[0065] The positive electrode, separator, negative electrode, and electrolyte are assembled to obtain a secondary battery.

[0066] An electrolyte is prepared by combining an additive containing the aromatic compound with an electrolyte salt and a solvent, and then assembled to obtain a secondary battery. The electrolyte of the assembled secondary battery contains an aromatic compound with multiple -SA substituents, which can polymerize on the surface of the positive electrode to form a film layer, effectively avoiding the occurrence of the shuttle effect. The polymer of the film layer also has good conductivity and will not affect the performance of the secondary battery. It can also replenish active ions, thereby improving the initial coulombic efficiency, initial discharge capacity and cycle performance of the secondary battery.

[0067] Thirdly, embodiments of this application provide an electrolyte comprising an electrolyte salt, a solvent, and an additive. The electrolyte salt comprises an A metal salt, and the additive comprises an aromatic compound having multiple substituents. The general structural formula of the substituents is -SA, wherein A is a metal element.

[0068] An additive containing the aromatic compound is added to the electrolyte. The aromatic compound has multiple -SA substituents and can be used in secondary batteries to polymerize on the surface of the positive electrode to form a film layer, effectively avoiding the shuttle effect. The polymer of the film layer also has good conductivity and will not affect the performance of the secondary battery. It can also replenish active ions, thereby improving the initial coulombic efficiency, initial discharge capacity and cycle performance of the secondary battery.

[0069] In any embodiment, A is any one of lithium, sodium, potassium, magnesium, and lead. Using the aforementioned metallic element, A can be applied to lithium secondary batteries, sodium secondary batteries, potassium secondary batteries, magnesium secondary batteries, or aluminum secondary batteries. It is understood that when A is lithium, it can be used in lithium secondary batteries; when A is sodium, it can be used in sodium secondary batteries; and so on.

[0070] In any embodiment, the aryl group of the aromatic compound includes at least one selected from phenyl, naphthyl, and anthracene. Using the above-mentioned aryl group results in a simple structure for the aromatic compound, which is suitable for use in secondary batteries, and the resulting polymer exhibits good conductivity. The aryl group of the aromatic compound can be any one or any combination of phenyl, naphthyl, and anthracene.

[0071] In any embodiment, A is lithium. The substituent is lithium mercapto, and the aromatic compound can be used for lithium replenishment in lithium secondary batteries.

[0072] In any embodiment, the aromatic compound includes at least one selected from lithium 1,4-phenyldimercapto, lithium 1,3,5-phenyltrimercapto, lithium 1,3,5-naphthalenetrimercapto, and lithium 2,9,10-anthracenetrimercapto. Using the above aromatic compounds results in a simple structure, which is suitable for use in secondary batteries. The polymer formed exhibits good conductivity and a more suitable reaction voltage, which is beneficial for improving the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary battery. The aromatic compound can be any one or any combination of lithium 1,4-phenyldimercapto, lithium 1,3,5-phenyltrimercapto, lithium 1,3,5-naphthalenetrimercapto, and lithium 2,9,10-anthracenetrimercapto.

[0073] In any embodiment, the mass percentage of the additive in the electrolyte is less than or equal to 6%. When the mass percentage of the additive in the electrolyte falls within the aforementioned range, its use in secondary batteries can improve the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary battery, while also ensuring the kinetic performance of the secondary battery. The mass percentage of the additive in the electrolyte can be 0.5%, 1%, 2%, 3%, 4%, 5%, or 6%.

[0074] In any embodiment, the molar concentration of the electrolyte salt in the electrolyte is 1.0 mol / L to 2.0 mol / L. The molar concentration of the electrolyte salt in the electrolyte falling within this range is beneficial for ensuring the performance of the secondary battery. The molar concentration of the electrolyte salt in the electrolyte can be 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, or 2.0 mol / L.

[0075] In any embodiment, the solvent includes at least one selected from ethylene glycol dimethyl ether, 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, tetrahydrofuran, and 2-methyltetrahydrofuran. Using the above solvent helps to ensure the performance of the secondary battery. The solvent can be any one or any combination of multiple selected from ethylene glycol dimethyl ether, 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, tetrahydrofuran, and 2-methyltetrahydrofuran.

[0076] Fourthly, embodiments of this application propose an electrical device, including a secondary battery of the first aspect or a secondary battery prepared by the preparation method of the second aspect.

[0077] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0078] In one embodiment of this application, a secondary battery is provided.

[0079] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0080] [Positive electrode plate]

[0081] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0082] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0083] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0084] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0085] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0086] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0087] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0088] [Negative electrode plate]

[0089] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0090] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0091] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0092] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0093] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0094] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0095] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0096] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0097] Electrolyte

[0098] The electrolyte plays a role in conducting ions between the positive and negative electrode plates.

[0099] In some embodiments, the electrolyte salt may be selected from at least one 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.

[0100] In some embodiments, the solvent may be selected from at least one 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.

[0101] In some embodiments, the electrolyte may optionally include additives. For example, the additives may also include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0102] [Isolation membrane]

[0103] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0104] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0105] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0106] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0107] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 8 This is an example of a square-structured secondary battery 5.

[0109] In some implementations, refer to Figure 9The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0110] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0111] Figure 10 This is battery module 4, used as an example. (See reference...) Figure 10 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0112] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0113] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0114] Figure 11 and Figure 12 This is battery pack 1 as an example. (See reference...) Figure 11 and Figure 12 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0115] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0116] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0117] Figure 13 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0118] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0119] Example

[0120] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0121] Preparation of secondary batteries

[0122] (1) Preparation of positive electrode sheet

[0123] The active material lithium iron phosphate, conductive carbon, and binder polyvinylidene fluoride (PVDF) are mixed evenly in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 90:5:5 to prepare a positive electrode slurry with a solid content of 55%. The slurry is coated on aluminum foil, and after drying, cold pressing, slitting, and vacuum drying, a positive electrode sheet is obtained.

[0124] (2) Preparation of negative electrode sheet

[0125] The active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed evenly in deionized water at a weight ratio of 96.2:0.8:0.8:1.2 to prepare a negative electrode slurry with a solid content of 50%. The negative electrode slurry is uniformly coated onto the negative electrode current collector copper foil once or multiple times. After drying, cold pressing, and slitting, the negative electrode sheet is obtained.

[0126] (3) Preparation of electrolyte

[0127] Lithium hexafluorophosphate (LiPF6) electrolyte salt was dissolved in a solvent, and then additives were added and mixed in an argon-atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm) to prepare the electrolyte. The solvent was a mixed solvent obtained by mixing ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 1:1 (DME:DOL = 1:1).

[0128] (4) Separating membrane

[0129] Polypropylene film is used as the separator.

[0130] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The stacking process yields a bare cell. The cell is then packaged in an aluminum-plastic film casing, and the electrolyte is injected. The cell is then sealed, left to stand, subjected to hot and cold pressing, and formed to obtain a secondary battery. Specifically, the formed battery is charged at a constant current of 0.2C to 3.8V, and then charged at a constant voltage of 3.8V to 0.05C.

[0131] The electrolyte preparation parameters for the secondary batteries of Examples 1 to 8 and Comparative Examples 1 to 2 are as shown in Table 1. For the secondary batteries of Comparative Examples 1 to 2, no additives were added during the preparation of the electrolyte.

[0132]

[0133] Performance testing:

[0134] (1) Testing of the morphology of the positive electrode sheet

[0135] Scanning electron microscopy: In a glove box, the positive electrode sheet was pretreated by thoroughly washing it with dimethyl carbonate (DMC) solution to remove lithium salt residues adhering to the surface, and then dried. Subsequently, a ZEISS Sigma 300 scanning electron microscope (SEM) was used to perform detailed microstructure and surface morphology tests on the dried positive electrode sheet. The tests were conducted in accordance with industry standard JY / T010-1996 to obtain high-quality images of the microscopic properties of the positive electrode sheet, providing important data for subsequent material analysis and performance evaluation.

[0136] Lens scanning: The pretreatment steps for the positive electrode are the same as those for the positive electrode in electron microscopy scanning; subsequently, the dried positive electrode is tested using a Thermo Scientific-Talos F200S G2 transmission electron microscope, and the test is performed in accordance with the industry standard JY / T0581-2020; the positive electrode is bombarded with a dual-beam electron microscope to sputter the surface atoms to achieve fine processing of the sample, and the secondary electrons and secondary ions generated are collected by the corresponding detectors and used for imaging, as well as three-dimensional reconstruction analysis of morphology, structure, elemental chemistry, etc.

[0137] (2) Testing of lithium content in negative electrode sheet

[0138] The negative electrode sheet was pretreated in the same way as the positive electrode sheet in the electron microscopy scan, and then the lithium content of ICP was tested.

[0139] (3) Testing of initial coulombic efficiency and initial discharge capacity

[0140] Charging process: 1 / 3C constant current charging to 3.65V, 3.65V constant voltage charging, cut-off current 0.05C, the obtained capacity is the first charging capacity;

[0141] Discharge process: Charge at 1 / 3C constant current to 2.5V, discharge at 0.05C to 2.0V, and record the resulting capacity as the initial discharge capacity;

[0142] The initial coulombic efficiency is the ratio of the initial discharge capacity to the initial charge capacity.

[0143] (4) 500-cycle capacity retention test

[0144] Charged to 3.65V at 1 / 3C constant current and constant voltage, discharged to 2.5V at 1 / 3C constant current and constant voltage, cycled for 500 times. The capacity retention rate after 500 cycles is the ratio of the discharge capacity on the 500th cycle to the discharge capacity on the first cycle.

[0145] (5) Electrolyte conductivity testing

[0146] Different weights of additives were dissolved in 30 mL of a 0.1 mol / L LiPF6 electrolyte solution and placed in a constant temperature bath for 30 min to prepare electrolytes with different additive mass ratios. The electrolytes were tested using a conductivity meter (LEEQ024H) according to the HG / T406-2015 test standard.

[0147] The morphology of the positive electrode sheets after formation in Example 3 and Comparative Example 1 was measured. The scanning electron microscope (SEM) image of the positive electrode sheet after formation in Example 3 is shown below. Figure 1 The scanning electron microscope (SEM) image of the positive electrode after conversion in Comparative Example 1 is shown below. Figure 2 ; The transmission electron microscope (TEM) image of the positive electrode sheet after formation in Example 3 is shown below. Figure 3 , Figure 3 The sulfur element distribution diagram is shown below. Figure 4 The transmission electron microscope (TEM) image of the positive electrode after formation in Comparative Example 1 is shown below. Figure 5 , Figure 5 The sulfur element distribution diagram is shown below. Figure 6 Furthermore, the sulfur content of the positive electrode sheets after formation in Example 3 and Comparative Example 1 was measured to be 3.17% and 0.11%, respectively.

[0148] The lithium content (mass percentage) of the negative electrode sheets after formation in Examples 1 to 8 and Comparative Examples 1 to 2 was tested respectively, and the results are shown in Table 1.

[0149] The secondary batteries prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were tested for their initial coulombic efficiency, initial discharge capacity, and capacity retention after 500 cycles. The results are shown in Table 1.

[0150] The conductivity of the electrolytes prepared in Examples 1 to 5 and Comparative Example 1 was tested respectively, and the results are shown in [Figure Number]. Figure 7 .

[0151] Depend on Figures 1 to 6 It can be seen that, compared with Comparative Example 1, a film layer is formed on the surface of the positive electrode after the formation of Example 3. The sulfur content on the surface of the positive electrode after the formation of Example 3 is significantly increased, indicating that the electrolyte of this application is used in a secondary battery. After the first charge, aromatic compounds with multiple thiol lithium substituents can polymerize on the surface of the positive electrode to form a film layer.

[0152] As shown in Table 1, compared to Comparative Examples 1 and 2, the lithium content of the negative electrode sheets after formation in Examples 1 to 8 improved the initial coulombic efficiency, initial discharge capacity, and 500-cycle retention rate of the secondary batteries. This indicates that the electrolyte of this application, when used in secondary batteries, can provide lithium active ions after the first charge by having aromatic compounds with multiple mercaptolith substituents, which can then be inserted into the negative electrode sheet to replenish lithium active ions, thereby improving the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary batteries. In addition, compared to Comparative Example 1, the lithium content of the negative electrode sheets after formation in Comparative Example 2 did not improve the initial coulombic efficiency, initial discharge capacity, and 500-cycle retention rate of the secondary batteries. This indicates that simply increasing the concentration of lithium salt in the electrolyte did not replenish lithium active ions, nor did it improve the initial coulombic efficiency, initial discharge capacity, and cycle performance of the secondary batteries.

[0153] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte includes an electrolyte salt and a solvent, and the electrolyte salt includes an A metal salt; At least prior to the first charge, the electrolyte also includes additives comprising aromatic compounds having multiple substituents of the general formula -SA, where A is a metal element.

2. The secondary battery as described in claim 1, characterized in that, A can be any one of lithium, sodium, potassium, magnesium, and lead.

3. The secondary battery as described in claim 1 or 2, characterized in that, The aryl group of the aromatic compound includes at least one selected from phenyl, naphthyl, and anthracene; and / or, A represents lithium.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The aromatic compound includes at least one selected from lithium 1,4-phenylenedimercapto, lithium 1,3,5-phenyltrimercapto, lithium 1,3,5-naphthalenetrimercapto, and lithium 2,9,10-anthracitetrimercapto; and / or, Prior to the first charge, the mass percentage of additives in the electrolyte is less than or equal to 6%.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The molar concentration of the electrolyte salt in the electrolyte solution is 1.0 mol / L to 2.0 mol / L; and / or, The solvent includes at least one of ethylene glycol dimethyl ether, 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, tetrahydrofuran, and 2-methyltetrahydrofuran.

6. A method for preparing a secondary battery, characterized in that, Includes the following steps: An electrolyte is prepared by combining an electrolyte salt, a solvent, and an additive. The electrolyte salt includes an A metal salt, and the additive includes an aromatic compound having multiple substituents. The general structural formula of the substituents is -SA, where A is a metal element. The positive electrode, separator, negative electrode, and electrolyte are assembled to obtain a secondary battery.

7. An electrolyte, characterized in that, It includes an electrolyte salt, a solvent, and an additive. The electrolyte salt includes an A metal salt, and the additive includes an aromatic compound having multiple substituents with the general structural formula -SA, where A is a metal element.

8. The electrolyte as described in claim 7, characterized in that, A can be any one of lithium, sodium, potassium, magnesium, and lead.

9. The electrolyte as described in claim 7 or 8, characterized in that, The aryl group of the aromatic compound includes at least one selected from phenyl, naphthyl, and anthracene; and / or, A represents lithium.

10. The electrolyte according to any one of claims 7 to 9, characterized in that, The aromatic compound includes at least one selected from lithium 1,4-phenylenedimercapto, lithium 1,3,5-phenyltrimercapto, lithium 1,3,5-naphthalenetrimercapto, and lithium 2,9,10-anthracitetrimercapto; and / or, The mass percentage of additives in the electrolyte is less than or equal to 6%.

11. The electrolyte according to any one of claims 7 to 10, characterized in that, The molar concentration of the electrolyte salt in the electrolyte solution is 1.0 mol / L to 2.0 mol / L; and / or, The solvent includes at least one of ethylene glycol dimethyl ether, 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, tetrahydrofuran, and 2-methyltetrahydrofuran.

12. An electrical appliance, characterized in that, This includes secondary batteries prepared by any one of the methods described in claims 1 to 5 or as described in claim 6.

Images