Electrolyte additive, electrolyte, secondary battery, and electronic device

Abstract

The application provides an electrolyte additive, an electrolyte, a secondary battery and an electronic device. The electrolyte additive comprises a first component and a second component. The first component is selected from a compound shown in formula I; and the second component is selected from at least one of a compound shown in formula II, a compound shown in formula III and a compound shown in formula IV. The first component and the second component synergistically act to improve the high-temperature storage performance and the cycle life of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrolyte additive, an electrolyte, a secondary battery, and an electronic device. Background Technology

[0002] Lithium-ion batteries are characterized by high specific energy, high specific power, and long cycle life, and are currently widely used in consumer batteries and power batteries for new energy vehicles. With increasing demands for longer driving range, faster charging speeds, and adaptability to various application scenarios, there is an urgent need to improve the fast-charging cycle performance and stability of lithium-ion batteries under high pressure and high temperature.

[0003] However, increasing the operating voltage of lithium-ion batteries typically presents two major drawbacks: poor cycle performance and gas production / expansion. This is primarily because the cathode material is unstable under high voltage, making it prone to structural phase transitions, which promote oxygen evolution reactions and the dissolution of transition metal ions. This leads to decreased electrolyte stability, accelerating the formation of gases such as carbon dioxide and ethylene, resulting in battery gas production. Simultaneously, the cathode material structure collapses, hindering Li+ diffusion, leading to increased impedance, capacity decay, and decreased battery cycle performance. These processes become even more severe under high-temperature conditions, resulting in poor high-temperature performance of the battery.

[0004] Therefore, providing a solution that can improve the fast charging cycle and high-temperature storage performance of lithium-ion batteries is of great significance. Summary of the Invention

[0005] The purpose of this application is to provide an electrolyte additive, an electrolyte, a secondary battery, and an electronic device to improve the high-temperature storage performance and cycle life of the secondary battery. The specific technical solution is as follows:

[0006] A first aspect of this application provides an electrolyte additive comprising a first component and a second component;

[0007] The first component is selected from the compounds shown in Formula I;

[0008]

[0009] The second component is selected from at least one of the compounds shown in Formula II, Formula III, and Formula IV;

[0010]

[0011] R1 and R2 are each independently selected from fluorine or C1-C5 alkyl groups substituted with fluorine;

[0012] R3 is selected from hydrogen, C1-C6 alkyl, C6-C 18 Aryl, X is selected from n is selected from 0 or 1; each of the compounds shown in Formula II, Formula III, or Formula IV independently contains at least one S atom;

[0013] The mass ratio of the first component to the second component is 0.01 to 60:1, preferably 0.05 to 20:1.

[0014] In one embodiment of this application, R3 is selected from hydrogen, C1-C3 alkyl, phenyl,

[0015] In one embodiment of this application, the first component is selected from at least one of the following compounds;

[0016]

[0017] In one embodiment of this application, the second component is selected from at least one of the following compounds;

[0018]

[0019] A second aspect of this application provides an electrolyte comprising the electrolyte additive described in the first aspect of this application; the electrolyte additive having a mass percentage content of 0.1% to 6% based on the mass of the electrolyte.

[0020] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage of the first component is A, 0.1% ≤ A ≤ 2%, and the mass percentage of the second component is B, 0.1% ≤ B ≤ 2%.

[0021] In one embodiment of this application, the electrolyte further includes a lithium salt selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, lithium monofluorosulfonate, and lithium trifluoromethanesulfonate; the mass percentage of the lithium salt is C based on the mass of the electrolyte, where 10% ≤ C ≤ 15%.

[0022] A third aspect of this application provides a secondary battery comprising the electrolyte described in the second aspect of this application.

[0023] A fourth aspect of this application provides an electronic device comprising the secondary battery described in the third aspect of this application.

[0024] The beneficial effects of this application are:

[0025] This application provides an electrolyte additive, an electrolyte, a secondary battery, and an electronic device. The electrolyte additive includes a first component and a second component, wherein the second component reacts with a carbonate solvent and Li in the electrolyte. +The first component forms a four-coordinate compound, which can stabilize carbonate solvents and reduce the generation of gases such as carbon dioxide, olefins, and carbon monoxide during the decomposition of carbonate solvents during high-temperature storage. Simultaneously, the decomposition products of the second component during film formation can react with the decomposition products of the first component via free radical reactions, blocking the negative effects of the first component's decomposition products on the electrolyte and positive electrode. Furthermore, they can jointly construct an electrode-electrolyte interface film rich in LiF, Li3N, Li2SO4, and alkyl lithium sulfate, improving the cycle life of the secondary battery under high-voltage conditions and exhibiting good cycle life under high-rate charge-discharge conditions. The electrolyte additive of this application includes both the first and second components, and the mass ratio of the first and second components is limited to the range specified in this application. The synergistic effect of the first and second components can improve the high-temperature storage performance and cycle life of the secondary battery.

[0026] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Detailed Implementation

[0027] 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, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0028] A first aspect of this application provides an electrolyte additive comprising a first component and a second component;

[0029] The first component is selected from the compounds shown in Formula I;

[0030]

[0031] The second component is selected from at least one of the compounds shown in Formula II, Formula III, and Formula IV;

[0032]

[0033] R1 and R2 are each independently selected from fluorine or C1-C5 alkyl groups substituted with fluorine;

[0034] R3 is selected from hydrogen, C1-C6 alkyl, C6-C 18 Aryl, X is selected from n is selected from 0 or 1; each of the compounds shown in Formula II, Formula III, or Formula IV independently contains at least one S atom;

[0035] The mass ratio of the first component to the second component is 0.01 to 60:1, preferably 0.05 to 20:1. For example, the mass ratio of the first component to the second component can be 0.01:1, 0.03:1, 0.05:1, 0.1:1, 0.5:1, 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 60:1, or a range of any two values ​​therein.

[0036] The first component of this application, when used alone as an electrolyte additive, significantly improves the cycle performance and low-temperature discharge performance of secondary batteries. However, it cannot solve the problems of battery swelling and low capacity retention during high-temperature storage. The main reasons are as follows:

[0037] During the formation and cycling of a secondary battery, the reduction and decomposition process of the first component after being attacked by electrons is as follows:

[0038]

[0039] R1 and R2 are each independently selected from fluorine or fluorine-substituted C1-C5 alkyl groups. Decomposition product A has a strong electron-donating ability, specifically due to the lone electron on its nitrogen atom. Decomposition product A can be free in the electrolyte, attacking carbonate solvents and causing solvent decomposition to produce gases such as carbon dioxide, olefins, and carbon monoxide. This process becomes more intense at higher temperatures, leading to increased gas production in the secondary battery. Furthermore, decomposition product B is a relatively unstable "transition state" structure, which easily undergoes further decomposition at high temperatures to form F. - Hydrofluoric acid is formed in the electrolyte, which in turn corrodes the positive electrode active material, leading to ion dissolution and structural damage to the positive electrode active material. This, in turn, exacerbates the self-discharge phenomenon of the electrode and ultimately reduces the high-temperature storage performance of the secondary battery.

[0040] The electrolyte additive of this application also includes a second component, which reacts with the carbonate solvent and Li in the electrolyte. + The second component gains electrons during the formation process, undergoing a ring-opening reaction. The S=O and CO components in the ring-opening reaction products preferentially react with Li. +The process forms two / three-coordinate compounds, which then weakly interact with the C=O bonds in the carbonate solvent to form four-coordinate compounds. Therefore, it can stabilize carbonate solvents and reduce the generation of gases such as carbon dioxide, olefins, and carbon monoxide during high-temperature storage. Simultaneously, the decomposition product A of the first component during film formation can undergo a free radical reaction with the ring-opening decomposition product of the second component, blocking the negative effects of the first component's decomposition product A on the electrolyte. Furthermore, they can jointly construct an electrode-electrolyte interface film rich in LiF, Li3N, Li2SO4, and alkyl lithium sulfate, which not only suppresses the negative impact of the first component's decomposition product B on the positive electrode but also improves the cycle life and storage performance of the secondary battery under high-temperature conditions.

[0041] In summary, the electrolyte additive of this application includes both a first component and a second component, and the mass ratio of the first component and the second component is limited within the range of this application, which can improve the high-temperature storage performance and cycle life of secondary batteries.

[0042] In one embodiment of this application, R3 is selected from hydrogen, C1-C3 alkyl, phenyl,

[0043] Applying an electrolyte containing the second component mentioned above to a secondary battery can improve the secondary battery's high-temperature storage performance and cycle life without affecting other performance characteristics.

[0044] In one embodiment of this application, the first component is selected from at least one of the following compounds;

[0045]

[0046] Applying an electrolyte containing the first component mentioned above to a secondary battery can improve the secondary battery's high-temperature storage performance and cycle life without affecting other performance characteristics.

[0047] In one embodiment of this application, the second component is selected from at least one of the following compounds;

[0048]

[0049] Applying an electrolyte containing the second component mentioned above to a secondary battery can further enhance the secondary battery's high-temperature storage performance and cycle life without affecting other performance characteristics.

[0050] The preparation method of the additives in this application is not particularly limited, as long as the purpose of this invention is achieved. For example, the two components can be directly mixed. The preparation method of the compounds used in this application is not particularly limited, and they can be prepared using methods known in the art or purchased directly from the market.

[0051] A second aspect of this application provides an electrolyte comprising the electrolyte additive described in the first aspect of this application; the mass percentage of the electrolyte additive is 0.1% to 6% based on the mass of the electrolyte. For example, the mass percentage of the electrolyte additive can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or a range of any two of these values, based on the mass of the electrolyte. Using electrolyte additives within the above range, without affecting other performance characteristics, enables the secondary battery to have higher high-temperature storage performance and cycle life.

[0052] In one embodiment of this application, based on the mass of the electrolyte, the mass percentage of the first component is A, where 0.1% ≤ A ≤ 2%, and the mass percentage of the second component is B, where 0.1% ≤ B ≤ 2%. For example, based on the mass of the electrolyte, the mass percentage A of the first component can be 0.1%, 0.5%, 1%, 1.5%, 2%, or a range of any two values ​​therein, and the mass percentage B of the second component can be 0.1%, 0.5%, 1%, 1.5%, 2%, or a range of any two values ​​therein. When the contents of the first and second components are within the above ranges, without affecting other performance characteristics, the secondary battery can further exhibit higher high-temperature storage performance and cycle life.

[0053] In one embodiment of this application, the electrolyte further includes a lithium salt selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, lithium monofluorosulfonate, and lithium trifluoromethanesulfonate. Based on the mass of the electrolyte, the mass percentage of the lithium salt is C, where 10% ≤ C ≤ 15%. For example, based on the mass of the electrolyte, the mass percentage C of the lithium salt can be 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two of these values. Adding the aforementioned lithium salt to the electrolyte within the above-mentioned range allows for better formation of tetracoordinate compounds with the second component and carbonate solvents, stabilizing the carbonate solvents, reducing the decomposition of carbonate solvents during high-temperature storage to produce gases such as carbon dioxide, olefins, and carbon monoxide, and jointly constructing an electrode-electrolyte interface film rich in substances such as LiF, Li3N, Li2SO4, and alkyl lithium sulfate, thereby improving the cycle life of the secondary battery under high-voltage conditions.

[0054] In one embodiment of this application, the electrolyte further includes a non-aqueous solvent. This application does not have any particular limitation on the non-aqueous solvent, as long as it can achieve the purpose of this application. For example, the non-aqueous solvent may be selected from, but is not limited to, ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, vinylene carbonate, methyl formate, ethyl formate, methyl acetate, ethyl propionate, ethyl butyrate, vinyl sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, dimethyl sulfite, dimethyl sulfite, sulfolane, and dimethyl sulfone.

[0055] This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application can be achieved. For example, based on the mass of the electrolyte, the mass percentage of non-aqueous solvents can be 79% to 89%, or, based on the mass of the electrolyte, the mass percentage of non-aqueous solvents can be 79%, 81%, 83%, 85%, 87%, 89%, or a range of any two of these values.

[0056] The preparation method of the electrolyte in this application is not particularly limited, as long as it can achieve the purpose of this invention. For example, various solvents in the electrolyte can be mixed, and then electrolyte lithium salt and additives can be added and mixed evenly.

[0057] A third aspect of this application provides a secondary battery comprising the electrolyte described in the second aspect of this application.

[0058] In this specific embodiment, a lithium-ion battery is used as an example of a secondary battery to explain the present application. The specific technical solution is as follows:

[0059] This application does not impose any particular restrictions on the conductive agent, as long as it can achieve the purpose of this application. For example, the conductive agent may be selected from, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0060] This application does not impose any particular limitation on the adhesive, as long as it can achieve the purpose of this application. For example, the adhesive may be selected from, but is not limited to, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, terpolymer of tetrafluoroethylene-hexafluoropropylene, and fluorinated acrylate resin.

[0061] In this application, the secondary battery further includes a positive electrode sheet, which includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The phrase "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that the term "surface" here can refer to the entire surface area of ​​the positive current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0062] This application does not impose any particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, aluminum foil or aluminum alloy foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0063] The positive electrode material layer includes a positive electrode active material. This application does not impose any particular limitation on the positive electrode active material, as long as it can achieve the purpose of this application. For example, the positive electrode active material can be selected from, but is not limited to, lithium nickel cobalt manganese oxide (e.g., NCM811, NCM622, NCM613, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, and lithium titanate.

[0064] Furthermore, when the cutoff voltage of the secondary battery is 4.25V or higher, the additives used in this application can significantly reduce the initial DCR of the lithium-ion battery, enhance the fast-charge cycle performance at room temperature, while also maintaining excellent high-temperature storage performance and exhibiting excellent high-temperature stability, which can significantly reduce battery expansion during high-temperature storage.

[0065] The positive electrode material layer may also include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, it may include at least one of the aforementioned conductive agents and binders. This application does not impose any particular restrictions on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0066] This application does not impose any particular limitations on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector is 15 μm to 20 μm, and the thickness of the single-sided positive electrode material layer is 40 μm to 50 μm.

[0067] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0068] This application does not impose any particular limitation on the preparation method of the positive electrode sheet, as long as it achieves the purpose of this application. For example, the positive electrode active material, conductive agent, and binder are mixed in a certain proportion, and N-methylpyrrolidone (NMP) is added and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on one surface of the positive electrode current collector, and after drying, a positive electrode sheet with a single-sided coating of positive electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the positive electrode current collector, and after drying, a positive electrode sheet with a double-sided coating of positive electrode material layer is obtained. After coating, the positive electrode sheet is obtained by cold pressing and cutting.

[0069] In this application, the secondary battery also includes a separator. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the material of the separator can be selected from, but is not limited to, at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. This application does not impose any particular limitation on the number of layers in the separator, as long as it achieves the purpose of this application; for example, the separator can be a single-layer thin film or a multi-layer composite thin film.

[0070] In some embodiments of this application, the diaphragm may include a substrate layer and a surface treatment layer. This application does not impose any particular limitation on the substrate layer, as long as it achieves the purpose of this application. For example, the substrate layer may be selected from, but is not limited to, at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0071] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. This application does not have any particular limitations on the surface treatment layer, as long as it can achieve the purpose of this application. For example, the surface treatment layer may be selected from, but is not limited to, at least one of high-purity alumina and boehmite.

[0072] In this application, there is no particular limitation on the thickness of the diaphragm, as long as it can achieve the purpose of this application. For example, the thickness of the diaphragm can be from 5 μm to 20 μm.

[0073] In this application, the secondary battery further includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "a negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the negative electrode current collector, or only a portion thereof; this application does not have any particular limitation, as long as the purpose of this application is achieved.

[0074] This application does not impose any particular limitation on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the negative electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, copper foil or aluminum alloy foil can be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0075] The negative electrode material layer includes a negative electrode active material. This application does not impose any particular limitation on the negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material can be selected from, but is not limited to, at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material can 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 can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.

[0076] In some embodiments of this application, the negative electrode material layer may further include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, it may be at least one of the aforementioned conductive agents and binders. This application does not impose any particular restrictions on the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0077] This application does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it can achieve the purpose of this application. For example, the thickness of the single-sided negative electrode material layer is 40 μm to 60 μm.

[0078] This application does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the thickness of the negative electrode current collector is 5 μm to 15 μm.

[0079] In some embodiments of this application, the negative electrode material layer may further include a conductive agent, a binder, and a thickener. This application does not particularly limit the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, the conductive agent and binder may be at least one of the aforementioned conductive agents and binders. The thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose. This application does not particularly limit the mass ratio of the negative electrode active material, conductive agent, binder, and thickener in the negative electrode material layer; those skilled in the art can select them according to actual needs, as long as the purpose of this application is achieved.

[0080] Optionally, the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, which can be a conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0081] This application does not impose any particular limitation on the preparation method of the negative electrode sheet, as long as it achieves the purpose of this application. For example, the negative electrode active material, conductive agent, thickener, and binder can be mixed in a certain proportion, and deionized water can be added and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on one surface of the negative electrode current collector, and after drying, a negative electrode sheet with a single-sided negative electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode current collector, and after drying, a negative electrode sheet with a double-sided negative electrode material layer is obtained. After coating, the negative electrode sheet is obtained by cold pressing and cutting.

[0082] The secondary battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of secondary batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal; this application does not limit the type of metal and can use known metal rigid casings, as long as they achieve the purpose of this application. The flexible casing can be a metal plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0083] The fabrication process of the secondary battery described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the fabrication process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. Alternatively, stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the secondary battery.

[0084] A fourth aspect of this application provides an electronic device comprising the secondary battery described in the third aspect of this application. The secondary battery provided in the third aspect of this application has excellent high-temperature storage performance, thereby giving the electronic device of this application a long service life.

[0085] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries or lithium-ion capacitors, etc.

[0086] Example

[0087] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0088] Test methods and equipment:

[0089] ambient temperature cycling performance test

[0090] Place the lithium-ion battery in a 25°C constant temperature test chamber and let it stand for 30 minutes to allow it to reach a constant temperature. Charge it at a constant current of 3.0C to 4.4V, then charge it at a constant voltage until the cutoff current is 0.05C. Let it stand for 30 minutes, then discharge it at a constant current of 1.0C to 3.0V. Record this discharge capacity as C0. Repeat this process until the capacity decays to 80% of C0. Record the number of cycles, i.e., the number of cycles at room temperature.

[0091] High temperature stability test

[0092] The lithium-ion battery was placed in a 25°C constant temperature test chamber and left to stand for 30 minutes to allow it to reach a constant temperature. It was then charged at a constant current of 1.0C to 4.4V, followed by constant voltage charging until the cutoff current was 0.05C. After standing for 10 minutes, it was discharged at a constant current of 1.0C to 3.0V, and this discharge capacity was recorded as C2. The lithium-ion battery was removed, and its initial thickness was measured using a thickness meter and recorded as T1. The lithium-ion battery was then placed back in the 25°C constant temperature test chamber and left to stand for 30 minutes to allow it to reach a constant temperature. It was then charged at a constant current of 1.0C to 4.4V, followed by constant voltage charging until the cutoff current was 0.05C. The lithium-ion battery was then transferred to a 60°C chamber and left to stand for 15 days. The thickness after 15 days was measured using a thickness meter and recorded as T2. Then, it is discharged at a constant current of 1.0C to 3.0V, and recorded as the discharge capacity C3. The high-temperature storage capacity retention rate after 15 days of storage at 60℃ = C3 / C2 × 100%, and the high-temperature storage battery expansion rate = 100% × (T2-T1) / T1.

[0093] Initial DC Resistance (DCR) Test

[0094] Place the lithium-ion battery in a 25°C constant temperature chamber and let it stand for 30 minutes. Then, charge the lithium-ion battery at a constant current of 1.0C until the voltage reaches 4.4V. Next, discharge it at a constant current of 1.0C for 30 minutes, let it stand for 1 hour, and then discharge it at a current I1 corresponding to a 2.0C rate for 10 seconds. Record the corresponding voltage as V1. The DC resistance (DCR) of the lithium-ion battery at 50% state of charge (SOC) is initially DCR = V1 / I1, and the unit is mΩ.

[0095] Example 1

[0096] <Preparation of Electrolyte>

[0097] In an argon-atmosphere glove box with a water content of <10 ppm and an oxygen content of <1 ppm, non-aqueous organic solvents ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate are added and mixed evenly in a mass ratio of 3:5:2. Then, compound I-1 (component 1) and compound II-5 (component 2) are added and mixed evenly. Lithium hexafluorophosphate (lithium salt) is then added, dissolved, and mixed evenly to obtain the electrolyte. Based on the mass of the electrolyte, the mass percentage of lithium hexafluorophosphate is 12.5%, the mass percentage of compound I-1 (component 2) (A) is 0.05%, the mass percentage of compound II-1 (component 2) (B) is 3%, and the balance is 84.45% non-aqueous organic solvent.

[0098] <Preparation of the positive electrode>

[0099] LiNi, the positive electrode active material 0.6 Co 0.1 Mn 0.3 O2, polyvinylidene fluoride (PVDF) binder, and carbon black conductive agent are mixed uniformly at a mass ratio of 97:1.2:1.8. N-methylpyrrolidone (NMP) is added as a solvent, and the mixture is stirred under vacuum until a homogeneous and fluid positive electrode slurry is formed, with a solid content of 0.65 wt%. The positive electrode slurry is then uniformly coated onto one surface of an 18 μm thick aluminum foil current collector, with a coating weight of 2.5 g / m². 2 The positive electrode sheet is dried at 85℃ and coated with a positive electrode material layer on one side. Then, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode material layer on both sides. After drying at 85℃, it is cold-pressed, trimmed, cut, and slit. After slitting, it is dried at 85℃ under vacuum for 4 hours. The tabs are then welded to obtain a positive electrode sheet with a specification of 258mm×200mm for later use. The thickness of the positive electrode material layer on one side is 45μm.

[0100] <Preparation of Negative Electrode Sheets>

[0101] Artificial graphite (the negative electrode active material) was mixed with carbon black (a conductive agent), sodium carboxymethyl cellulose (CMC) (a thickener), and styrene-butadiene rubber (SBR) (a binder) at a mass ratio of 95.8:1.2:1.5:1.5. Deionized water was added, and a negative electrode slurry with a solid content of 50 wt% was obtained under vacuum stirring. The negative electrode slurry was then uniformly coated onto one surface of an 8 μm thick copper foil negative electrode current collector, with a coating weight of 1.5 g / m. 2The negative electrode sheet is dried at 85℃ to obtain a negative electrode sheet with a single-sided negative electrode material layer. Then, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided negative electrode material layer. After drying at 85℃, the negative electrode sheet is cold-pressed, trimmed, cut, and slit. After slitting, it is dried at 85℃ under vacuum for 4 hours. The tabs are then welded to obtain a negative electrode sheet with a specification of 260mm×198mm for later use. The thickness of the single-sided negative electrode material layer is 50μm.

[0102] <Preparation of the diaphragm>

[0103] A double-layer PP ceramic diaphragm with a thickness of 16μm is used.

[0104] <Preparation of Lithium-ion Batteries>

[0105] The prepared positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to act as a separator. They are then wound, with the positive tab connected to the positive electrode and the negative tab connected to the negative electrode, resulting in an electrode assembly. The electrode assembly is placed in an aluminum foil packaging bag, with the positive and negative tabs extended from the inside to the outside of the bag. Moisture is removed at 80°C, and the prepared electrolyte is injected at an injection rate of 3.0 g / Ah. After vacuum sealing, formation, aging, and capacity testing, a lithium-ion battery is obtained. The formation upper limit voltage is 4.4V, the formation temperature is 45°C, and the formation resting time is 24 hours. The aging temperature is 45°C, and the aging resting time is 24 hours. The capacity testing involves charging to 4.4V at 0.2C, resting for 5 minutes, then discharging to 3.0V at 0.2C, followed by repeating the above steps at 0.5C and 1C.

[0106] Examples 2 to 40

[0107] Except for adjusting the types and mass percentages of the first and second components according to Table 1 in the <Preparation of Electrolyte>, changing the mass percentage of the non-aqueous organic solvent accordingly, and keeping the mass percentage of the lithium salt unchanged, the rest is the same as in Example 1.

[0108] Comparative Example 1

[0109] Except that the first and second components are not added in the <Preparation of Electrolyte>, the mass percentage of the non-aqueous organic solvent is changed accordingly, and the mass percentage of lithium salt remains unchanged, the rest is the same as in Example 1.

[0110] Comparative Examples 2 to 3

[0111] Except for the fact that no second component is added in the <Preparation of Electrolyte>, the type and mass percentage of the first component are adjusted according to Table 1, the mass percentage of the non-aqueous organic solvent is changed accordingly, and the mass percentage of lithium salt remains unchanged, the rest is the same as in Example 1.

[0112] Comparative Examples 4 to 5

[0113] Except for the omission of the first component in the <Preparation of Electrolyte>, the adjustment of the type and mass percentage of the second component according to Table 1, the change in the mass percentage of the non-aqueous organic solvent, and the unchanged mass percentage of the lithium salt, the rest is the same as in Example 1.

[0114] Comparative Examples 6 to 7

[0115] Except for adjusting the types and mass percentages of the first and second components according to Table 1 in the <Preparation of Electrolyte>, changing the mass percentage of the non-aqueous organic solvent accordingly, and keeping the mass percentage of the lithium salt unchanged, the rest is the same as in Example 1.

[0116] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Table 1.

[0117]

[0118]

[0119] As can be seen from Examples 1 to 40 and Comparative Examples 1 to 7, when electrolytes without the first and second components, or with only the first or second component, or with a mass ratio of the first and second components outside the scope of this application, are used in lithium-ion batteries, the lithium-ion batteries exhibit higher initial DCR and high-temperature storage battery expansion rate, as well as lower room-temperature cycle count and high-temperature storage capacity retention. When electrolytes with both the first and second components are added simultaneously are used in lithium-ion batteries, and the mass ratio of the first and second components is limited to the scope of this application, the lithium-ion batteries exhibit lower initial DCR and high-temperature storage battery expansion rate, as well as higher room-temperature cycle count and high-temperature storage capacity retention. The above results demonstrate that the combined use of the first and second components, and limiting the mass ratio of the first and second components to the scope of this application, can improve the high-temperature storage performance and cycle life of lithium-ion batteries.

[0120] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0121] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrolyte additive, comprising a first component and a second component; The first component is selected from the compounds shown in Formula I; The second component is selected from at least one of the compounds shown in Formula II, Formula III, and Formula IV; in, R1 and R2 are each independently selected from fluorine or C1-C5 alkyl groups substituted with fluorine; R3 is selected from hydrogen, C1-C6 alkyl, C6-C 18 Aryl, X is selected from n is selected from 0 or 1; each of the compounds shown in Formula II, Formula III, or Formula IV independently contains at least one S atom; The mass ratio of the first component to the second component is 0.01 to 60:

1.

2. The electrolyte additive according to claim 1, wherein, The mass ratio of the first component to the second component is 0.05 to 20:

1.

3. The electrolyte additive according to claim 1, wherein, R3 is selected from hydrogen, C1-C3 alkyl, phenyl, 4. The electrolyte additive according to claim 1, wherein, The first component is selected from at least one of the following compounds; 5. The electrolyte additive according to claim 1, wherein, The second component is selected from at least one of the following compounds; 6. An electrolyte comprising the electrolyte additive according to any one of claims 1 to 5; wherein the electrolyte additive comprises 0.1% to 6% by mass based on the mass of the electrolyte.

7. The electrolyte according to claim 6, wherein, Based on the mass of the electrolyte, the mass percentage of the first component is A, 0.1% ≤ A ≤ 2%, and the mass percentage of the second component is B, 0.1% ≤ B ≤ 2%.

8. The electrolyte according to claim 6, wherein, The electrolyte further includes a lithium salt selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, lithium monofluorosulfonate, and lithium trifluoromethanesulfonate; based on the mass of the electrolyte, the mass percentage of the lithium salt is C, 10% ≤ C ≤ 15%.

9. A secondary battery comprising the electrolyte according to any one of claims 6 to 8.

10. An electronic device comprising the secondary battery of claim 9.

Images