Lithium-ion secondary battery cell, method for producing the same, battery device, and electric device

Abstract

The application relates to a lithium ion secondary battery monomer, a preparation method thereof, a battery device and a power utilization device. The lithium ion secondary battery monomer comprises a negative electrode sheet and an electrolyte; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer on at least one side of the negative electrode current collector, and the negative electrode active layer comprises a negative electrode active material; the negative electrode active material comprises a graphite-based material, and the mass ratio of the graphite-based material in the negative electrode active material is 60%-100%; the electrolyte comprises one or more of a first alkyne compound and a second alkyne compound, and the sum of the mass ratios of the first alkyne compound and the second alkyne compound in the alkyne additive is 75%-100%; the negative electrode active layer has a relatively thin thickness (such as less than or equal to 60 mu m) on a single side of the negative electrode current collector, and the D v 50 is 3 mu m-15 mu m. The lithium ion secondary battery significantly improves the normal temperature performance while having good high temperature performance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion secondary battery technology, and further to lithium-ion secondary battery cells and their preparation methods, battery devices, and power-consuming devices. Background Technology

[0002] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0003] With the technological advancements in lithium-ion rechargeable batteries, they are increasingly being used in a wide range of fields, including smartphones, tablets, laptops, power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. They are also widely used in energy storage systems for hydropower, thermal power, wind power, and solar power plants. The storage and use of lithium-ion rechargeable batteries involves not only ambient temperatures but also unavoidable high-temperature environments. Non-limiting examples include high-temperature storage and / or use environments such as summer heat, direct sunlight, and locations near the equator. High-temperature additives, such as alkyne-based additives, can improve the battery's high-temperature performance by optimizing the solid electrolyte interphase (SEI) film at the negative electrode; however, this can increase the negative electrode interface impedance, affecting performance at room temperature.

[0004] Therefore, it is necessary to improve both the high-temperature performance and the room-temperature performance of lithium-ion secondary batteries. Summary of the Invention

[0005] According to various embodiments and examples of this application, this application provides a lithium-ion secondary battery cell, a method for preparing the same, a battery device, and an electrical device. This lithium-ion secondary battery exhibits good high-temperature performance while significantly improving room-temperature performance.

[0006] In some embodiments of the first aspect of this application, a lithium-ion secondary battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte, wherein a separator is disposed between the positive electrode and the negative electrode; the negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer comprising a negative active material; the negative active material comprises a graphite-based material, the graphite-based material comprising 60% to 100% by mass in the negative active material;

[0007] The electrolyte comprises an electrolyte salt, a non-aqueous solvent, and additives; the additives include acetylene additives, which are compounds containing carbon-carbon triple bonds; the acetylene additives include one or more of a first acetylene compound and a second acetylene compound; wherein the first acetylene compound consists of a carbon-carbon triple bond, a carbon-carbon triple bond, and a carbon-carbon triple bond connected in sequence. 1-3The second alkynyl compound consists of an alkylene group and -OC(=O)-R1, where R1 is a Lewis base nitrogen heterocycle; the second alkynyl compound consists of a carbon-carbon triple bond, C, and C bonds connected sequentially. 1-3 The structure consists of an alkylene group and -OC(=O)-O-R2, where R2 is C. 1-3 Alkyl group; the sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 75% to 100%;

[0008] The thickness of the negative electrode active layer on one side of the negative electrode current collector is less than or equal to 60 μm, and the D of the negative electrode active material is... v 50 is 3μm~15μm.

[0009] For lithium-ion secondary batteries where the negative electrode active material mainly includes graphite-based materials and the electrolyte contains specific alkyne additives (which can be referred to as "alkyne additive battery systems"), the electrolyte contains one or more of a first alkyne compound and a second alkyne compound with high interfacial impedance in negative electrode film formation. In this case, the negative electrode active layer of the negative electrode sheet is controlled to have a relatively thin thickness (e.g., ≤60μm) on one side of the negative electrode current collector through a thin coating process, and is combined with a suitable D... v The 50% negative electrode active material can balance the pressure resistance of the negative electrode active layer in the cold pressing process, the ion transport path within the overall particles of the negative electrode active material, and the appropriate specific surface area of ​​the negative electrode active material. It is more resistant to cold pressing than relatively small-diameter particles, and can also control the relatively short ion transport path. It can also better control the reaction area of ​​the negative electrode active material, thereby better controlling the consumption of acetylene additives in the negative electrode film formation, and better controlling the increase in negative electrode interface impedance caused by the introduction of acetylene additives. Based on the synergistic effect of the above, but not limited to the above theory, it can better synergistically control the structural stability of the negative electrode active layer, the battery internal resistance and the negative electrode interface reaction, and significantly improve the room temperature performance of the acetylene additive battery system.

[0010] In some embodiments, the thickness of the negative electrode active layer on one side of the negative electrode current collector is 40 μm to 55 μm.

[0011] In some embodiments, the thickness of the negative electrode active layer on one side of the negative electrode current collector is 45 μm to 55 μm.

[0012] By controlling the thickness of the negative electrode active layer on one side of the negative electrode current collector within the aforementioned range, the combined effects of the negative electrode liquid phase transport path and the negative electrode interface impedance on the battery internal resistance can be better balanced, and the room temperature performance of the acetylene additive battery system can be improved more significantly.

[0013] In some embodiments, the D of the negative electrode active material v 50 ranges from 3.5μm to 15μm.

[0014] By controlling the D of the negative electrode active material v 50 Within the aforementioned range, using a relatively small negative electrode active material is beneficial for the negative electrode sheet to have a lower tortuosity, which is beneficial for better balancing the pressure resistance of the negative electrode active layer in the cold pressing process, the ion transport path of the negative electrode active material and the reaction area, and is more beneficial for significantly improving the room temperature performance of the acetylene additive battery system.

[0015] In some embodiments, the negative electrode active material includes a coated negative electrode material, which includes a negative electrode active body and a carbon coating layer located on the negative electrode active body, comprising at least a portion thereof.

[0016] In some embodiments, the negative electrode active material D v 50 ranges from 5μm to 14μm.

[0017] In some embodiments, the negative electrode sheet satisfies one or more of the following characteristics:

[0018] (a1) The mass percentage of the coated negative electrode material in the negative electrode active material is 80%~100%;

[0019] (a2) The coated negative electrode material includes coated graphite, and the negative electrode active body in the coated graphite includes a graphite body.

[0020] In some embodiments, the coated graphite accounts for 80% to 100% of the mass of the negative electrode active material.

[0021] By incorporating a coated anode material (such as coated graphite) with a carbon coating layer into the anode active material, the lithium-ion transport channels on the surface of the anode active material can be optimized, promoting lithium-ion transport and improving the kinetics of lithium-ion secondary batteries. At the same time, it is also beneficial to suppress side reactions at the anode interface and suppress the increase in anode interface impedance caused by the participation of acetylene additives in anode film formation, which is conducive to better improving the room temperature performance of acetylene additive battery systems.

[0022] By incorporating a coated anode material (such as coated graphite) with a carbon coating layer into the anode active material, relatively small-sized anode active materials (such as D) can be combined. v 50 (5μm~14μm) optimizes rate performance.

[0023] In some embodiments, the porosity of the negative electrode active layer is 14% to 26%.

[0024] In some embodiments, the porosity of the negative electrode active layer is 18% to 22%.

[0025] By controlling the porosity (ε) of the negative electrode active layer within the aforementioned range, the tortuosity of the negative electrode sheet can be adjusted, which is beneficial for providing a better lithium-ion liquid phase transport channel, achieving better electrolyte wetting, and also taking into account the electrical contact network between the negative electrode active materials, which is beneficial for comprehensively improving the negative electrode dynamics and cycle performance.

[0026] In some embodiments, the additive further includes additive B, which is one or more of lithium salt additives and phosphate ester additives, and the mass ratio of additive B to the acetylene additive is 0.1 to 100.

[0027] Lithium salt additives and phosphate ester additives have low negative electrode film resistance. By introducing one or more of lithium salt additives and phosphate ester additives into the electrolyte, it is beneficial to reduce the resistance of the negative electrode SEI film and reduce the internal resistance of the battery. Furthermore, by controlling the mass ratio of additive B to alkyne additive within the aforementioned range, the room temperature performance of the alkyne additive battery system can be better improved.

[0028] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0029] (b1) The mass ratio of additive B to the acetylene additive is 0.3 to 50;

[0030] (b2) The lithium salt additive includes one or more of the following: lithium oxalate, lithium tetrafluoroborate, lithium difluorophosphate, lithium fluorosulfonic acid, and lithium perchlorate; the lithium oxalate includes one or more of the following: lithium difluorooxalateborate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, and lithium bis(oxalateborate); the lithium fluorosulfonic acid includes one or more of the following: lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonate.

[0031] (b3) The phosphate ester additives include one or more of silicon-based phosphate ester additives and alkyl phosphonate additives; the silicon-based phosphate ester additives include one or more of tris(trimethylsilane) phosphate and tris(trimethylsilyl) phosphite;

[0032] (b4) The additives include lithium salt additives, wherein the mass percentage of the lithium salt additives in the electrolyte is greater than 0 and less than or equal to 3%;

[0033] (b5) The additives include phosphate ester additives, wherein the mass percentage of the phosphate ester additives in the electrolyte is greater than 0 and less than or equal to 1%.

[0034] In some embodiments, the negative electrode sheet satisfies one or more of the following characteristics:

[0035] (c1) The negative electrode active material includes a silicon-based material, wherein the mass percentage of the silicon-based material in the negative electrode active material is less than or equal to 3%;

[0036] (c2) The negative electrode active material includes a silicon-based material, which includes a silicon-carbon composite material. The silicon-carbon composite material includes a porous carbon matrix and elemental silicon located within the pores of the porous carbon matrix. The silicon-carbon composite material accounts for 80% to 100% of the mass of the silicon-based material.

[0037] (c3) The graphite-based material accounts for 80% to 100% of the mass of the negative electrode active material.

[0038] By controlling the content and / or type of silicon-based materials in the negative electrode active material within the aforementioned range, the expansion and contraction changes of the negative electrode can be better controlled. This is beneficial for better matching the stability requirements of the negative electrode active layer in the thin coating process, reducing the generation of fresh interfaces, suppressing negative electrode interface side reactions, reducing the consumption rate of alkyne additives, and decreasing the rate of increase in battery internal resistance, thus improving battery cycle life. For example, in silicon-based materials, the volume expansion and contraction changes of silicon-carbon composite materials are relatively low.

[0039] In some embodiments, the positive electrode includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a positive active material, such as a lithium transition metal oxide positive electrode material. The thickness of the positive active layer on one side of the positive current collector is less than or equal to 50 μm. In this case, the positive electrode can provide a higher energy density, which corresponds to a thinner positive active layer, resulting in better capacity matching with the negative active layer. This is beneficial for suppressing lithium plating on the negative electrode and extending battery cycle life, including extended cycle life at room temperature.

[0040] In some embodiments, the positive electrode active material includes a lithium nickel-based oxide positive electrode material, which includes lithium, non-lithium metal elements, and oxygen; wherein the non-lithium metal elements include nickel; and in the lithium nickel-based oxide positive electrode material, the ratio of the atomic molar ratio of nickel to the sum of the atomic molar ratios of the non-lithium metal elements is denoted as R. Ni ;R Ni ≥0.8, the thickness of the positive electrode active layer on one side of the positive electrode current collector is 40μm~50μm. At this thickness, the capacity matching between the positive and negative electrode active layers is better, which is more conducive to extending the battery cycle life, including extending the cycle life at room temperature.

[0041] In some embodiments, the acetylene additive accounts for 0.001% to 3.2% of the mass of the electrolyte.

[0042] In some embodiments, the acetylene additive accounts for 0.01% to 1.8% of the mass of the electrolyte.

[0043] By controlling the mass ratio of acetylene additives in the electrolyte within the aforementioned range, the acetylene additives can continuously play a role in repairing the SEI film during cycling, which is more conducive to extending battery cycle life, including extending the cycle life at room temperature.

[0044] In some embodiments, the lithium-ion secondary battery cell satisfies one or more of the following characteristics:

[0045] (d1) The positive electrode sheet includes a positive active layer, the positive active layer includes a positive active material, and the positive active material includes a lithium transition metal oxide positive electrode material;

[0046] (d2) The negative electrode active material includes a silicon-based material, wherein the mass percentage of the silicon-based material in the negative electrode active material is less than or equal to 3%; the acetylene additive includes the first acetylene compound.

[0047] Alkyne additives can adsorb transition metal ions in electrolytes.

[0048] When the negative electrode active material includes the aforementioned amount of silicon-based material, a fresh interface is generated as the negative electrode volume expands and contracts, leading to interfacial side reactions and the production of acidic byproducts. The acidic byproducts can be adsorbed by a first alkynyl compound containing a Lewis base nitrogen heterocycle.

[0049] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0050] (e1) The molecular weight of the alkyne additive is less than or equal to 500 Da;

[0051] (e2) The carbon-carbon triple bond in the alkyne additive is CH≡C-;

[0052] (e3) The sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 80% to 100%;

[0053] (e4) The first alkynyl compound accounts for 80% to 100% of the mass of the alkynyl additive.

[0054] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0055] (f1) The molecular weight of the alkyne additive is less than or equal to 300 Da;

[0056] (f2) The Lewis base nitrogen heterocycle is a substituted or unsubstituted imidazole group, wherein the imidazole ring in the substituted or unsubstituted imidazole group is substituted by 0, 1 or more substituents Q2, and each substituent Q2 in the substituted imidazole group is independently C 1-3 Alkyl, cyano, or fluorine atom;

[0057] (f3) The sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 90% to 100%;

[0058] (f4) The first alkynyl compound accounts for 90% to 100% of the mass of the alkynyl additive.

[0059] In some embodiments, the acetylene additive includes one or more of compound II and compound III;

[0060] The structure of compound II is as follows: Among them, L 11 C 1-3 Alkylene, Q2 is independently C 1-3 Alkyl, cyano, or fluorine atom, p2 is 0, 1, 2, or 3;

[0061] The structure of compound III is as follows: Among them, L 21 C 1-3 Alkylene, R2 is C 1-3 alkyl.

[0062] By controlling the molecular weight of acetylene additives within the aforementioned lower range, acetylene additives can have smaller molecular sizes, which is beneficial for better control of the low viscosity characteristics of the electrolyte, resulting in higher conductivity of the electrolyte and better control of the battery's internal resistance.

[0063] By controlling the number of carbon-carbon triple bonds in acetylene additives within the aforementioned range, it is beneficial to suppress the increase in interfacial impedance caused by acetylene additives participating in the formation and repair of the SEI film, and also to control the influence of acetylene additives on liquid phase impedance. Thus, it is possible to better suppress the increase in battery internal resistance and better improve the room temperature performance of acetylene additive battery systems.

[0064] The first alkynyl compound, which includes both a carbon-carbon triple bond and a Lewis base nitrogen heterocycle, can promote the formation of an interface film with dual organic / inorganic properties during the negative electrode interface reaction, thereby improving the stability of the negative electrode SEI film. The Lewis base nitrogen heterocycle can also absorb acid byproducts in the electrolyte, which is beneficial to improving the stability of the negative electrode interface and the negative electrode active material, reducing the consumption rate of alkynyl additives, and decreasing the rate of increase in battery internal resistance. Based on the aforementioned multiple effects, but not limited to the aforementioned mechanisms, it is beneficial to better improve the room temperature performance of alkynyl additive battery systems.

[0065] By controlling the number of Lewis base nitrogen heterocycles in the acetylene additives within the aforementioned range, it is beneficial to better absorb acid byproducts in the electrolyte, and at the same time, it is also beneficial to control the steric hindrance effect of Lewis base nitrogen heterocycles on carbon-carbon triple bonds.

[0066] Examples of Lewis base nitrogen heterocycles include the imidazole ring in compound II.

[0067] According to some embodiments of the second aspect of this application, a method for preparing a lithium-ion secondary battery cell is provided, which includes the following steps:

[0068] An electrode assembly including a positive electrode and a negative electrode is placed inside a battery casing; wherein a separator is disposed between the positive electrode and the negative electrode; wherein the negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer includes a negative active material, the negative active material including a graphite-based material, the graphite-based material accounting for 60%~100% of the mass of the negative active material; the thickness of the negative active layer on one side of the negative current collector is less than or equal to 55 μm, and the D of the negative active material is... v 50 has a thickness of 3μm to 15μm;

[0069] An electrolyte is injected into the battery casing, and the mixture is allowed to stand to allow the electrolyte to wet the positive and negative electrode plates, thus forming the battery. The electrolyte comprises an electrolyte salt, a non-aqueous solvent, and additives. The additives include alkyne additives, which are compounds containing carbon-carbon triple bonds. The alkyne additives include one or more of a first alkyne compound and a second alkyne compound. The first alkyne compound consists of a carbon-carbon triple bond, a carbon-carbon triple bond, and a carbon-carbon triple bond connected sequentially. 1-3 The second alkynyl compound consists of an alkylene group and -OC(=O)-R1, where R1 is a Lewis base nitrogen heterocycle; the second alkynyl compound consists of a carbon-carbon triple bond, C, and C bonds connected sequentially. 1-3 The structure consists of an alkylene group and -OC(=O)-O-R2, where R2 is C. 1-3 Alkyl group; the sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 75% to 100%.

[0070] The prepared lithium-ion secondary battery has the advantages of the lithium-ion secondary battery described in the first aspect of this application.

[0071] In some embodiments, the lithium-ion secondary battery cell described in the first aspect of this application is prepared.

[0072] According to some embodiments of the third aspect of this application, a battery device is provided, which includes one or more of the lithium-ion secondary battery cells described in the first aspect of this application and lithium-ion secondary battery cells prepared by the preparation method of the lithium-ion secondary battery cells described in the second aspect of this application.

[0073] In some embodiments, the battery device includes one or more of the aforementioned lithium-ion secondary battery cells.

[0074] The number of lithium-ion secondary batteries in the battery device can be controlled according to capacity requirements.

[0075] In some embodiments of the fourth aspect of this application, an electrical device is provided, which includes at least one of the lithium-ion secondary battery cell described in the first aspect of this application, the lithium-ion secondary battery cell prepared by the method for preparing the lithium-ion secondary battery cell described in the second aspect of this application, and the battery device described in the third aspect of this application.

[0076] Details of one or more embodiments or examples of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0077] To better describe and illustrate the embodiments, examples, or models provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments, examples, or models, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0078] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0079] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0080] Figure 3 This is a schematic diagram of a battery device according to one embodiment of this application.

[0081] Figure 4This is a schematic diagram of a battery pack according to one embodiment of this application.

[0082] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0083] Figure 6 This is a schematic diagram of an electrical device that uses a lithium-ion secondary battery cell as a power source according to an embodiment of this application.

[0084] Explanation of reference numerals in the attached figures:

[0085] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery assembly; 5. Individual battery cell; 51. Battery housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0086] The following describes in detail, with appropriate reference to the accompanying drawings, some embodiments and examples of the lithium-ion secondary battery cell, its preparation method, battery device, and power-consuming device of this application. However, some 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 to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0087] The "range" disclosed in this application can be defined in the form of 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. Any endpoint can be included or excluded independently and can be combined arbitrarily; 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 ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also 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" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0088] In this application, the term "numerical value" includes the number itself and its reasonable approximations. The definition of "numerical value" can apply to discrete numerical points or to the endpoints of a numerical range. Unless otherwise specified, the term "approximation" covers a numerical interval based on a reasonable range of fluctuations of the number itself. This reasonable range of fluctuations can vary depending on the type and magnitude of the number. This reasonable range of fluctuations can be reasonably determined based on the accuracy of the testing or measurement method. Therefore, when referring to a numerical value or a numerical range, unless otherwise specified, it should be understood that the numerical value includes its reasonable approximation, and the numerical range includes reasonable approximations at both endpoints. Those skilled in the art will understand that acceptable fluctuation ranges of the relevant approximations can be included within the definition of the numerical value or the numerical range. In this application, unless otherwise specified, "N1" can be reasonably understood as "about N1," and "N1~N2" can be reasonably understood as "about N1 to about N2," where N1 and N2 are two unequal numerical values.

[0089] In this application, unless otherwise specified, "about" means within a reasonable range above and below the stated number, and the range of fluctuation may vary depending on the type and value of the stated number. For example, a range of ±10%, ±5%, ±2%, ±1% is permissible. For instance, taking "about 20°C" as an example, where the approximation is ±1°C, approximate values ​​such as 19°C and 19.5°C within the approximation range indicated by "about 20°C" should also be included in the range indicated by "about 20°C".

[0090] In this application, the terms "multiple," "various," or "multiple items" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one item or two or more (greater than or equal to) items. It can be understood that when "any number of" items are involved, it refers to any suitable combination of multiple items, that is, a combination of "any number of" items in a manner that does not conflict and enables the implementation of this application.

[0091] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0092] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0093] In this application, open-ended technical features or solutions described using terms such as "containing," "comprising," or "including" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if 'a' includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both features or solutions where "a consists of a1, a2, and a3" or "a is selected from a1, a2, and a3," and features or solutions where "a includes not only a1, a2, and a3, but also other members."

[0094] In this application, unless otherwise specified, M (e.g., m1) means that m1 is a non-limiting example of M, and it is understood that M is not limited to m1.

[0095] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. Unless otherwise specified, the descriptions such as "optionally include" and "optionally contain" in this application, taking "optionally include" as an example, mean "may include or not include."

[0096] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. Any and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "M and / or N" represents the group consisting of M, N, and "a combination of M and N". "Containing M and / or N" can mean "containing M, containing N, and containing both M and N", or "containing M, containing N, or containing both M and N", and can be appropriately understood according to the context.

[0097] In this document, the word "suitable" in "suitable combination" or "suitable method" refers to the technical solution that can implement this application.

[0098] In this document, terms such as "preferred," "better," and "good" are merely descriptions of implementation methods or embodiments that achieve better results, and should be understood as not constituting a limitation on the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "preferred" term shall be independent.

[0099] In this application, terms such as "further," "even more," "especially," "for example," "as," and "example" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0100] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0101] In the description of this application, it should be understood that the terms "thickness", "height", "upper", "lower", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0102] In this application, unless otherwise expressly specified and limited, terms such as "connected" and "joined" in relation to mechanical structures should be interpreted broadly, for example, they can refer to a fixed connection, a detachable connection, or an integral part. Those skilled in the art can understand the meaning of the above terms in this application according to the circumstances.

[0103] In this application, unless otherwise expressly specified and limited, the phrase "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. In this application, unless otherwise expressly specified and limited, the phrase "above" or "below" the second feature can indicate a horizontal positional relationship, or it can simply indicate the existence of an attachment relationship without specifying a horizontal positional relationship.

[0104] In this application, the terms "room temperature" or "normal temperature" generally refer to 4℃~35℃, and may refer to 20℃±5℃. In some embodiments or examples of this application, room temperature refers to 20℃~30℃. In some embodiments or examples of this application, "normal temperature" is 20℃~35℃, and may be selected as 20℃~30℃.

[0105] In this application, when a unit is specified for a data range, if it is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 3~5 μm or 3-5 μm both mean that the units for the left endpoint "3" and the right endpoint "5" are both μm (micrometers), and both have the same meaning as 3 μm ~ 5 μm. Furthermore, similar descriptions of other parameters such as temperature and size are interpreted in the same way.

[0106] In this application, unless otherwise stated, "molecular weight" refers to molecular mass measured in Daltons (Da), where 1 Dalton equals 12 One-twelfth of the mass of a carbon atom.

[0107] In this application, "greater than or equal to", "greater than or equal to", and "≥" have the same meaning and can be used interchangeably; "less than or equal to", "less than or equal to", and "≤" have the same meaning and can be used interchangeably; "greater than" can be equivalently represented as ">", and "less than" can be equivalently represented as "<". In this application, unless otherwise specified, "greater than or equal to" and "≥" can be considered as providing two additional solutions: "greater than" and "equal to". In this application, unless otherwise specified, "less than or equal to" and "≤" can be considered as providing two additional solutions: "less than" and "equal to".

[0108] In this application, the exemplary descriptions such as "in some implementations (or embodiments)" and "in one implementation (or embodiment)" may cover, but are not limited to, the following meanings: these solutions can be combined with other solutions in a suitable manner to form new technical solutions.

[0109] Unless otherwise stated, the improvements described in this application are not intended to be limited to any theoretical constraints.

[0110] The storage and use of lithium-ion rechargeable batteries involve not only ambient temperature environments but also, unavoidably, high-temperature scenarios. Non-limiting examples include high-temperature storage and / or use environments such as summer heat, direct sunlight, and locations near the equator. High-temperature additives, such as alkyne-based additives, can improve the high-temperature performance of the battery by optimizing the solid electrolyte interphase (SEI) film at the negative electrode; however, they can increase the interface impedance of the negative electrode, affecting its performance at room temperature. Therefore, it is necessary to improve both the high-temperature and room-temperature performance of lithium-ion rechargeable batteries simultaneously.

[0111] According to various embodiments and examples of this application, this application provides a lithium-ion secondary battery cell, a method for preparing the same, a battery device, and an electrical device. This lithium-ion secondary battery exhibits simultaneously improved high-temperature and room-temperature performance.

[0112] In some embodiments, a lithium-ion secondary battery cell includes a negative electrode sheet and an electrolyte; the negative electrode sheet includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer including a negative active material, the negative active material including a graphite-based material; the electrolyte includes one or more of a first alkynyl compound and a second alkynyl compound; the negative active layer has a relatively thin thickness (e.g., less than or equal to 60 μm) on one side of the negative current collector, and the D of the negative active material... v The thickness ranges from 3μm to 15μm. This lithium-ion secondary battery exhibits good high-temperature performance while significantly improving its room-temperature performance.

[0113] In some embodiments, a lithium-ion secondary battery cell includes a negative electrode sheet and an electrolyte; the negative electrode sheet includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer including a negative active material; the electrolyte includes one or more of a first alkynyl compound and a second alkynyl compound; the thickness Ds of the negative active layer on one side of the negative current collector is equal to the thickness D of the negative active material. v 50 (denoted as D) v 50 N The ratio of (R) x =Ds / D v 50 N The value can be less than 20, and further optionally, the D of the negative electrode active material can be less than 20. v The thickness of the electrode is 3μm to 15μm. In some embodiments, the negative electrode active material includes a graphite-based material. This lithium-ion secondary battery significantly improves its room-temperature performance while maintaining good high-temperature performance.

[0114] In some embodiments, a lithium-ion secondary battery cell includes a negative electrode sheet and an electrolyte; the negative electrode sheet includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer including a negative active material; the negative active material including a graphite-based material; the electrolyte including an alkyne additive, the alkyne additive including one or more of a first alkyne compound and a second alkyne compound; the negative active layer has a relatively thin thickness (e.g., less than or equal to 60 μm) on one side of the negative current collector, and the D of the negative active material... v The thickness of the graphite material ranges from 3 μm to 15 μm. This lithium-ion secondary battery exhibits good high-temperature performance while significantly improving room-temperature performance. In some embodiments, the graphite-based material accounts for 60% to 100% of the mass of the negative electrode active material.

[0115] In some embodiments, the sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 75% to 100%, and optionally 80% to 100%.

[0116] In some embodiments, the first alkynyl compound is composed of a carbon-carbon triple bond, a C-carbon triple bond, and a C-carbon triple bond connected in sequence. 1-3 It consists of an alkylene group and -OC(=O)-R1, where R1 is a Lewis base nitrogen heterocycle.

[0117] In some embodiments, the second alkynyl compound consists of a carbon-carbon triple bond, a C-carbon triple bond, and a C-carbon triple bond connected in sequence. 1-3 It consists of an alkylene group and -OC(=O)-O-R2, where R2 is an alkyl group, which can be C. 1-3 alkyl.

[0118] In some embodiments, a lithium-ion secondary battery cell includes a positive electrode, a negative electrode, and an electrolyte, with a separator between the positive and negative electrode. The negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector. The negative active layer includes a negative active material. The negative active material includes a graphite-based material, with the graphite-based material accounting for 60% to 100% of the negative active material by mass. The electrolyte includes an electrolyte salt, a non-aqueous solvent, and additives. The additives include acetylene additives, which are compounds containing carbon-carbon triple bonds. The acetylene additives include one or more of a first acetylene compound and a second acetylene compound. The negative active layer has a relatively thin thickness (e.g., less than or equal to 60 μm) on one side of the negative current collector. The negative active material has a D... v The thickness of the 50 is 3μm to 15μm. This lithium-ion secondary battery exhibits good high-temperature performance while significantly improving room-temperature performance. In some embodiments, the combined mass percentage of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 75% to 100%, optionally 80% to 100%.

[0119] In this application, unless otherwise specified, the "high temperature" referring to battery cycling and / or storage can be greater than 35°C and less than or equal to 80°C, optionally greater than 35°C and less than or equal to 60°C, further optionally 37°C to 60°C, further optionally 40°C to 60°C, and even more optionally 45°C to 60°C, but is not limited thereto. The "high temperature" referring to battery storage or cycling can also be any of the following temperatures or a range selected from any two of the following temperatures: 36°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc.

[0120] In this application, unless otherwise specified, "normal temperature" referring to battery cycling and / or storage can be 20℃~35℃, or optionally 20℃~30℃, but is not limited to this. "High temperature" referring to battery storage or cycling can also be any of the following temperatures or a range selected from any two of the following temperatures: 20℃, 22℃, 24℃, 25℃, 26℃, 28℃, 30℃, 32℃, 34℃, 35℃, etc.

[0121] In this application, unless otherwise specified, the term "lithium-ion secondary battery" refers to a secondary battery in which the active ions include lithium ions, and "lithium-ion secondary battery cell" refers to a battery cell in which the active ions include lithium ions. Typically, a lithium-ion secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. A separator is disposed between the positive and negative electrodes; the separator primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0122] In this application, unless otherwise specified, "electrode active material layer" includes at least one of the positive active material layer of the positive electrode sheet and the negative active material layer of the negative electrode sheet. Depending on the specific circumstances, the electrode active material layer may refer to either the positive active material layer or the negative active material layer. It is understood that the positive active material layer contains positive active material, and the negative active material layer contains negative active material. In this application, "electrode active material layer" may also be referred to as "active material layer," "positive active material layer" may also be referred to as "positive active layer," and "negative active material layer" may also be referred to as "negative active layer."

[0123] In this application, the terms "electrode sheet" and "electrode plate" have the same meaning and can be used interchangeably. An electrode sheet can be a positive electrode sheet or a negative electrode sheet, and the "active material" or "active substance" in the electrode sheet has the ability to reversibly insert and extract active ions.

[0124] In this application, the term "negative electrode sheet" includes a negative electrode active layer, which includes a negative electrode active material. The term "negative electrode active material" refers to a material used in a negative electrode sheet that is capable of reversibly inserting and de-inserting active ions.

[0125] In this application, unless otherwise specified, "negative electrode sheet" includes a negative electrode current collector. A "negative electrode current collector" refers to a structure responsible for collecting and conducting electrons at the negative electrode. In the negative electrode sheet, the negative electrode active layer is located on at least one side of the negative electrode current collector, and may be located on one or both sides of the negative electrode current collector.

[0126] In this application, the term "positive electrode sheet" includes a positive electrode active layer, and the positive electrode active layer includes a positive electrode active material. The term "positive electrode active material" refers to a material used in a positive electrode sheet that is capable of reversibly extracting and inserting active ions.

[0127] In this application, unless otherwise specified, "positive electrode sheet" includes a positive current collector. A "positive current collector" refers to a structure responsible for collecting and conducting electrons at the positive electrode. In the positive electrode sheet, the positive active layer is located on at least one side of the positive current collector, and may be located on one or both sides of the positive current collector.

[0128] In this application, unless otherwise specified, "separation membrane" and "diaphragm" have the same meaning and can be used interchangeably.

[0129] In a first aspect of this application, a lithium-ion secondary battery is provided that significantly improves room-temperature performance while maintaining good high-temperature performance.

[0130] In some embodiments, a lithium-ion secondary battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte, with a separator disposed between the positive and negative electrode. The negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer comprising a negative active material; the negative active material includes a graphite-based material; the electrolyte includes an electrolyte salt, a non-aqueous solvent, and additives; the additives include acetylene additives, which are compounds containing carbon-carbon triple bonds; the acetylene additives include one or more of a first acetylene compound and a second acetylene compound; the negative active layer has a relatively thin thickness (e.g., less than or equal to 60 μm) on one side of the negative current collector, and the D of the negative active material... v The thickness of the graphite material ranges from 3 μm to 15 μm. In some embodiments, the graphite-based material accounts for 60% to 100% of the mass of the negative electrode active material.

[0131] In some embodiments, the sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 75% to 100%, and optionally 80% to 100%.

[0132] In some embodiments, a lithium-ion secondary battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte, with a separator disposed between the positive and negative electrode. The negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer comprising a negative active material. The negative active material includes a graphite-based material, the graphite-based material comprising 60% to 100% of the negative active material by mass. The electrolyte includes an electrolyte salt, a non-aqueous solvent, and additives. The additives include acetylene additives, which are compounds containing carbon-carbon triple bonds. The acetylene additives include one or more of a first acetylene compound and a second acetylene compound. The sum of the mass percentages of the first acetylene compound and the second acetylene compound in the acetylene additives is 75% to 100%, optionally 80% to 100%. The thickness of the negative active layer on one side of the negative current collector is less than or equal to 60 μm, and the Do of the negative active material is... v 50 is 3μm~15μm.

[0133] In this application, unless otherwise specified, "graphite-based material" refers to a negative electrode active material containing a graphite matrix. Unless otherwise specified, "graphite matrix" refers to a matrix composed of graphite. Unless otherwise specified, the mass percentage of the graphite matrix in the graphite-based material can be 90% to 100%, or it can be any of the following percentages or a range selected from any two of the following percentages: 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%. Non-limitingly, the graphite-based material can include one or more of coated graphite-based materials and uncoated graphite. Coated graphite-based materials include a graphite matrix and a coating layer located on at least a portion of the surface of the graphite matrix; it is understood that the coating layer is a different material from that in the graphite matrix.

[0134] In some embodiments, the graphite-based material accounts for 60% to 100% of the mass of the negative electrode active material, optionally 70% to 100%, further optionally 75% to 100%, even further optionally 80% to 100%, even further optionally 90% to 100%, even further optionally 95% to 100%, even further optionally 97% to 100%, and may also be any of the following percentages or a range selected from any two of the following percentages: 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0135] In this application, unless otherwise specified, the "thickness of the negative electrode active layer on one side of the negative electrode current collector" in a lithium-ion secondary battery can be abbreviated as "thickness of the negative electrode active layer on one side"; the "total thickness of the negative electrode active layer on both sides of the negative electrode current collector" in a lithium-ion secondary battery can be abbreviated as "total thickness of the negative electrode active layer".

[0136] In this application, unless otherwise specified, "non-aqueous solvent" means a solvent that is not water.

[0137] In this application, unless otherwise specified, a "carbon-carbon triple bond" is an unsaturated bond with a —C≡C— framework.

[0138] In this application, unless otherwise specified, "acetylene additives" refers to additives containing carbon-carbon triple bonds. Acetylene additives can participate in the formation of the negative electrode solid electrolyte interphase (SEI) film. Acetylene additives can significantly improve the high-temperature performance of batteries, including extending high-temperature cycling and storage life, and can be used as high-temperature additives. However, the introduction of one or more of some acetylene additives, such as first acetylene compounds and second acetylene compounds, can easily lead to high negative electrode interfacial impedance at room temperature, thus affecting the battery's room-temperature performance.

[0139] In this application, unless otherwise specified, "first ynyl compound" refers to an ynylene additive containing a carbon-carbon triple bond and a Lewis base nitrogen heterocycle. The carbon-carbon triple bond and Lewis base nitrogen heterocycle in the first ynyl compound are linked by a linker L1, which typically contains a C-type carbon bond covalently bonded to the carbon-carbon triple bond. 1-3 Alkylene. Exemplarily, the first alkynyl compound is composed of a carbon-carbon triple bond, C... 1-3 It consists of an alkylene group and -OC(=O)-R1, where R1 is a Lewis base nitrogen heterocycle.

[0140] In this application, unless otherwise specified, "Lewis base nitrogen heterocycle" refers to a nitrogen heterocycle possessing Lewis base properties. This concept is based on the Lewis acid-base theory. Lewis base nitrogen heterocycles can donate electron pairs and are electron-rich. Therefore, Lewis base nitrogen heterocycles can attract and bind acidic substances. Non-limiting examples of Lewis base nitrogen heterocycles include imidazole rings, but are not limited to these.

[0141] In this application, unless otherwise specified, "nitrogen heterocyclic structure" refers to a ring structure in which the cyclic atoms include nitrogen atoms. The term "cyclic atom" refers to the constituent atom of the ring skeleton. As a non-limiting example, the three carbon atoms and two nitrogen atoms in an imidazole ring are cyclic atoms, and the imidazole ring is a 5-membered ring. "Ringed nitrogen atom" refers to the nitrogen atom in the cyclic atom.

[0142] In this application, unless otherwise specified, "second alkynyl compound" is an alkynyl additive containing a carbon-carbon triple bond and an alkyl carbonate group, wherein the structure of the alkyl carbonate group is R2-OC(=O)-O-*, where * is the bonding site attached to a carbon atom, and R2 is an alkyl group, which can further be C 1-3 Alkyl groups. In di-alkynyl compounds, the carbon-carbon triple bond and the alkyl carbonate group are linked by a linker L2, which typically contains a carbon group covalently bonded to the carbon-carbon triple bond. 1-3 Alkylene. Exemplarily, the second alkynyl compound may be composed of a carbon-carbon triple bond, C... 1-3 It is composed of an alkylene group and -OC(=O)-O-R2, where R2 is an alkyl group, and can be further C 1-3 alkyl.

[0143] In the lithium-ion secondary battery provided in this application, it is understood that the positive electrode and the negative electrode are wetted by the electrolyte.

[0144] The negative electrode of this lithium-ion secondary battery adopts a thin coating process, and the thickness of the negative electrode active layer is relatively thin, such as less than or equal to 60μm. This can improve the diffusion distance of lithium ions on the negative electrode and, to some extent, help to compensate for the increase in interfacial impedance caused by the introduction of acetylene additives. However, the cold pressing process of the thin coating process may face problems such as coating cracking. The negative electrode needs to have a certain mechanical strength. Smaller particles have better pressure resistance, but the larger specific surface area of ​​small particles will aggravate the side reactions at the negative electrode interface and thus easily exacerbate the increase in negative electrode interfacial impedance caused by acetylene additives.

[0145] For lithium-ion secondary batteries where the negative electrode active material mainly includes graphite-based materials and the electrolyte contains specific alkyne additives (which can be referred to as "alkyne additive battery systems"), the electrolyte contains one or more of a first alkyne compound and a second alkyne compound with high interfacial impedance in negative electrode film formation. In this case, the negative electrode active layer of the negative electrode sheet is controlled to have a relatively thin thickness (e.g., ≤60μm) on one side of the negative electrode current collector through a thin coating process, and is combined with a suitable D... v The 50% negative electrode active material can balance the pressure resistance of the negative electrode active layer in the cold pressing process, the ion transport path within the overall particles of the negative electrode active material, and the appropriate specific surface area of ​​the negative electrode active material. It is more resistant to cold pressing than relatively small-diameter particles, and can also control the relatively short ion transport path. It can also better control the reaction area of ​​the negative electrode active material, thereby better controlling the consumption of acetylene additives in the negative electrode film formation, and better controlling the increase in negative electrode interface impedance caused by the introduction of acetylene additives. Based on the synergistic effect of the above, but not limited to the above theory, it can better synergistically control the structural stability of the negative electrode active layer, the battery internal resistance and the negative electrode interface reaction, and significantly improve the room temperature performance of the acetylene additive battery system.

[0146] The thickness of the negative electrode active layer on one side or the total thickness in a lithium-ion secondary battery can be obtained by methods known in the art. For example, the surfaces of substrates with and without the negative electrode active layer can be compared, such as by using a profilometer. In this method, the probe of the profilometer gently glides across the sample surface with a very small force. The micron- or even nanometer-level undulations on the sample surface are amplified millions of times by a sensor connected to the probe, then converted into electronic signals, input into software, and finally displayed in digital and graphical form.

[0147] The thickness of the active layer of the negative electrode under test can also be statistically determined from the results of multiple locations of the scanning electron microscope (SEM) images of the cross-section in the thickness direction of the electrode.

[0148] Alternatively, a micrometer can be used for measurement. The thickness D can be obtained by disassembling the battery cell, removing the negative electrode, and measuring the electrode thickness D using a micrometer. ATake another negative electrode sheet, wipe away the negative electrode active layer on the side to be tested, leaving the remaining empty current collector foil, and measure the thickness D. 10 The thickness of the negative electrode active layer on one side of the negative electrode current collector is D. A -D 10 Take another negative electrode sheet, wipe away the negative electrode active layer on both sides of the remaining empty current collector foil, and measure the thickness D0. Then, the total thickness of the negative electrode active layer on both sides of the negative electrode current collector in the lithium-ion secondary battery is D. A -D0.

[0149] The types and concentrations of inorganic components in the electrolyte (including electrolyte salts and inorganic additives) can be tested with reference to relevant standards such as GB / T 34672-2017 General Rules for Determination of Chemical Reagents by Ion Chromatography, JY / T020-1996 General Rules for Ion Chromatographic Analysis, and GB / T 6040-2019 General Rules for Infrared Spectroscopic Analysis, and the latest version of the standard method can be preferred. The types and contents of organic components in the electrolyte (including non-aqueous solvents and organic additives) can be tested with reference to relevant standards such as GB / T 9722-2023 General Rules for Gas Chromatography of Chemical Reagents.

[0150] In addition, those skilled in the art can also identify the components of the electrolyte in a lithium-ion secondary battery using one or more of the following detection methods, including but not limited to: nuclear magnetic resonance hydrogen spectroscopy (NMR spectroscopy). 1 Methods such as 1H NMR, high-performance liquid chromatography (HPLC), matrix-assisted laser desorption / ionization mass spectrometry (MADI-TOF), Fourier transform infrared spectroscopy (FT-IR), ultraviolet spectroscopy, and gas chromatography (GC) are available. The sample preparation and testing methods for these methods are known to those skilled in the art, and the test parameters can be appropriately adjusted according to the structure of the material or substance and the characteristics of the sample. As a non-limiting example, FT-IR, ultraviolet spectroscopy, and other methods can be used. 1 One or more of the following methods may be used to detect the types and contents of electrolyte components: ¹H NMR, mass spectrometry, MADI-TOF, GC, etc., but not limited to these.

[0151] The electrolyte sample can be obtained by disassembling the battery cell.

[0152] In some embodiments, in the lithium-ion secondary battery, the thickness of the negative electrode active layer on either side of the negative electrode current collector is 40 μm to 60 μm, optionally 40 μm to 55 μm, further optionally 45 μm to 55 μm, and may also be any of the following thicknesses or a range selected from any two of the following thicknesses: 40 μm, 42 μm, 44 μm, 45 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, 55 μm, 56 μm, 58 μm, 60 μm. In some embodiments, in the lithium-ion secondary battery, the thickness of the negative electrode active layer on either side of the negative electrode current collector is less than or equal to any of the following thicknesses: 50 μm, 52 μm, 54 μm, 55 μm, 56 μm, 58 μm, 60 μm, etc. In some embodiments, in a lithium-ion secondary battery, the thickness of the negative electrode active layer on either side of the negative electrode current collector is greater than or equal to any of the following thicknesses: 40μm, 42μm, 44μm, 45μm, 46μm, 48μm, etc.

[0153] In some embodiments, in the lithium-ion secondary battery, the total thickness of the negative electrode active layer on both sides of the negative electrode current collector is 80μm to 120μm, optionally 80μm to 110μm, further optionally 90μm to 110μm, and may also be any of the following thicknesses or a range selected from any two of the following thicknesses: 80μm, 82μm, 84μm, 85μm, 86μm, 88μm, 90μm, 92μm, 94μm, 95μm, 96μm, 98μm, 110μm, 112μm, 114μm, 115μm, 116μm, 118μm, 120μm, etc.

[0154] In some embodiments, the areal density of the negative electrode active layer on one side of the negative electrode current collector is (0.05~0.15) g / 1540.25 mm. 2 The optional value is (0.05~0.12) g / 1540.25 mm. 2 It can be further selected as (0.08~0.12) g / 1540.25mm 2 It can also be (0.08~0.15) g / 1540.25mm 2 The optional value is (0.085~0.14) g / 1540.25 mm. 2 It can also be any of the following values ​​or a range consisting of any two of the following values: 0.05g / 1540.25mm 2 0.055 g / 1540.25 mm 2 0.06 g / 1540.25mm 2 0.065 g / 1540.25mm 2 0.07 g / 1540.25mm 20.075 g / 1540.25mm 2 0.08g / 1540.25mm 2 0.085 g / 1540.25mm 2 0.09g / 1540.25mm 2 0.095 g / 1540.25mm 2 0.10 g / 1540.25mm 2 0.11 g / 1540.25mm 2 0.12 g / 1540.25mm 2 0.13 g / 1540.25mm 2 0.135 g / 1540.25 mm 2 0.14 g / 1540.25mm 2 0.145 g / 1540.25 mm 2 0.148 g / 1540.25mm 2 0.15 g / 1540.25mm 2 This allows for further control over the mass ratio of graphite-based materials in the negative electrode active material within a more suitable range.

[0155] Graphite-based materials are a type of carbon-based material. It is understood that negative electrode active materials include carbon-based materials. Carbon-based materials can include one or more of graphite, soft carbon, and hard carbon. Graphite can include one or more of artificial graphite and natural graphite. Non-limitingly, the mass percentage of graphite-based materials in the carbon-based materials can be 60% to 100%, optionally 80% to 100%, further preferably 90% to 100%, and even more preferably 97% to 100%, or any of the following percentages or a range selected from any two of the following percentages: 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc. The areal density of the negative electrode active layer on one side of the negative electrode current collector can be further controlled to be (0.05~0.15) g / 1540.25 mm². 2 , or any suitable value or range within that range.

[0156] In some embodiments, the carbon-based material may include one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0157] In some implementations, the carbon-based material is a graphite-based material.

[0158] In some implementations, the negative electrode active material is a graphite-based material.

[0159] In this application, unless otherwise specified, "area density of the negative electrode active layer on one side of the negative electrode current collector" refers to the ratio of the mass of the negative electrode active layer on one side of the negative electrode current collector to the area of ​​the negative electrode active layer on that side, and the corresponding "area" is equal to the orthogonal projection area of ​​the negative electrode active layer along the thickness direction of the electrode sheet. "Area density of the negative electrode active layer on one side of the negative electrode current collector" can also be written as "one-sided density of the negative electrode active layer".

[0160] Non-limitingly, the areal density of the negative electrode active layer on one side of the negative electrode current collector can be tested using the following method: Disassemble the battery to obtain the negative electrode sheet, wipe off the negative electrode active layer on one side of the obtained negative electrode sheet, leaving only the negative electrode active layer on one side, and punch it into an area S0 (e.g., 1540.25 mm²). 2 The small circular disc is used to measure its mass M. B Take another negative electrode sheet from a different region, wipe off the negative active layer on the surface, and cut the remaining negative current collector foil (which can be denoted as empty negative current collector foil) into small circular pieces with an area of ​​S0. Weigh the empty negative current collector foil and record the mass as M0. Then, the areal density ρ of the negative active layer on one side of the negative current collector is... S =(M B -M0) / S0.

[0161] In some embodiments, the thickness of the negative electrode active layer on one side of the negative electrode current collector is less than or equal to 60 μm, and may also be less than or equal to any of the following thicknesses: 42 μm, 44 μm, 45 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, 55 μm, 56 μm, 58 μm, etc.

[0162] In some embodiments, the thickness of the negative electrode active layer on one side of the negative electrode current collector is 40 μm to 60 μm, optionally 40 μm to 55 μm, further optionally 45 μm to 55 μm, and may also be any of the following thicknesses or a range selected from any two of the following thicknesses: 40 μm, 42 μm, 44 μm, 45 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, 55 μm, 56 μm, 58 μm, 60 μm, etc.

[0163] By controlling the thickness of the negative electrode active layer on one side and / or the total thickness of the negative electrode current collector within the aforementioned range, the combined effects of the negative electrode liquid phase transport path and the negative electrode interface impedance on the battery internal resistance can be better balanced, and the room temperature performance of the acetylene additive battery system can be improved more significantly.

[0164] In some embodiments, the D of the negative electrode active material v50 is 3μm~15μm, can be selected from 3.5μm~15μm, further selectable from 3.8μm~10μm, and can also be any of the following values ​​or a range composed of any two of the following values: 3μm, 3.5μm, 3.8μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, etc.

[0165] In the context of this application, the volumetric cumulative distribution particle size D can be used. v N (where N represents any value selected from 0 to 100) is used to characterize the particle size of the material. It refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching N%, where the particle size is less than or equal to D. v N's volume percentage is N%. D v N can be obtained from the volumetric cumulative distribution curve of the material particles. Unless otherwise specified, the volumetric cumulative distribution curve is accumulated from zero on the smaller particle size side. Let D... v Taking 50 as an example for illustration. In this application, unless otherwise stated, D v 50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50% in the material. This parameter indicates that the particle size of 50% of the material's volume is less than or equal to D. v 50, and particles accounting for 50% of the material volume have a particle size greater than D. v 50. Those skilled in the art will understand D v 50. D v 3. D v The meaning of Grade 1 is that it can be determined using instruments and methods known in the field. For example, it can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer or the LS-909 laser particle size analyzer from Malvern Instruments Ltd. (UK). Furthermore, for equipment models such as the Malvern 2000 laser particle size analyzer, the standard procedure GB / T19077-2016 / ISO 13320:2009 can be referenced for testing.

[0166] By controlling the D of the negative electrode active material v 50 Within the aforementioned range, using a relatively small negative electrode active material is beneficial for the negative electrode sheet to have a lower tortuosity, which is beneficial for better balancing the pressure resistance of the negative electrode active layer in the cold pressing process, the ion transport path of the negative electrode active material and the reaction area, and is more beneficial for significantly improving the room temperature performance of the acetylene additive battery system.

[0167] In some embodiments, the D of the negative electrode active material or the positive electrode active material can be tested using the following methods. v 50. D v 3. D v Grade 1. A Malvern 2000 (MasterSizer 2000) laser particle size analyzer was used, following the standard procedure GB / T19077-2016 / ISO 13320:2009. The detailed test procedure included: taking an appropriate amount of the sample to be tested, adding a solvent (the solvent can be deionized water, and the sample concentration can be controlled at 8%~12% opacity), sonicating for 5 min (53KHz / 120W) to fully disperse the sample, and then measuring the sample according to GB / T19077-2016 / ISO 13320:2009. Non-limiting examples of solvents include deionized water and anhydrous ethanol. After the sample was poured into the injection tower, it circulated with the solution to the test optical path system. Under the irradiation of the laser beam, the particle size distribution characteristics of the particles could be obtained by receiving and measuring the energy distribution of the scattered light. Based on the test data, a particle size volume distribution map was plotted, and D was obtained from the distribution map. v Parameters such as 50 were used. To avoid agglomeration during the drying process affecting particle size testing, a dispersion test was performed on a washed and moistened sample.

[0168] Unless otherwise specified, the thickness of the negative electrode active layer on one side of the negative electrode current collector can be denoted as Ds, and the D of the negative electrode active material is... v 50 can be written as D v 50 N The thickness (Ds) of the negative electrode active layer on one side of the negative electrode current collector is compared with the D of the negative electrode active material. v The ratio of 50 is denoted as R. x R x =Ds / D v 50 N In some implementations, R x It can be less than 20, further selectable as 5~18, even further selectable as 6~18, even further selectable as 6.5~18, even further selectable as 8~18, even further selectable as 10~18, and can also be any of the following suitable values ​​or a suitable range selected from any two of the following values: 3, 3.1, 3.2, 3.4, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, etc.; R x It can also be any of the following ranges: 5~16, 6~16, 6.5~16, 8~16, 10~16, 5~16, etc.

[0169] In some embodiments, the D of the negative electrode active material v 1 is greater than or equal to 1 μm.

[0170] In some embodiments, the D of the negative electrode active material v 1 is greater than or equal to 1.5 μm.

[0171] By controlling the D of the negative electrode active material v 1. Within the aforementioned range, side reactions at the negative electrode interface can be significantly suppressed, the consumption rate of acetylene additives can be reduced, and the growth rate of battery internal resistance can be decreased.

[0172] The tortuosity of the negative electrode active layer is denoted as τ.

[0173] In some embodiments, 4 ≤ τ ≤ 6, optionally, 4 ≤ τ ≤ 5.4, and further optionally, 4 ≤ τ ≤ 5.1. Non-limitingly, the tortuosity (τ) of the negative electrode active layer can also be any of the following values ​​or a range selected from any two of the following values: 4, 4.1, 4.2, 4.4, 4.5, 4.6, 4.8, 5.0, 5.1, 5.2, 5.4, 5.5, 5.6, 5.8, 6, etc.

[0174] In this application, the "torsionalism" of the negative electrode active layer can also be described as the tortuosity or tortuosity of the negative electrode sheet. The tortuosity of the negative electrode active layer reflects the degree of tortuosity of the pore connectivity pathways traversed by active ions when passing through a negative electrode active layer of a certain thickness. Numerically, the tortuosity τ of the negative electrode active layer can be equal to the ratio of the actual path length of the pore connectivity pathway between the two surfaces of the negative electrode active material layer to the thickness of the negative electrode active material layer. The theoretical minimum value of the tortuosity is 1, at which point the pore connectivity pathway is a straight pore, and the corresponding actual path is the shortest, numerically consistent with the thickness of the negative electrode active layer. The larger the tortuosity, the higher the degree of tortuosity of the pore connectivity pathway; conversely, the smaller the tortuosity, the lower the degree of tortuosity of the pore connectivity pathway. The value of the tortuosity is related to factors such as the particle size and particle size distribution of the negative electrode active material, and porosity. "Torsionalism" is a dimensionless parameter.

[0175] In this application, the tortuosity of the negative electrode active layer can be calculated by the following test and analysis method: the ion diffusion resistance Rion inside the pores of the negative electrode sheet is tested by a symmetrical cell, and the tortuosity τ of the negative electrode active layer is calculated based on the porosity ε, the thickness d of the negative electrode active layer and the conductivity k of the electrolyte.

[0176] The negative electrode sheet to be tested can be obtained by disassembling the battery cell. The residual electrolyte needs to be removed beforehand. For example, the negative electrode sheet sample can be washed with dimethyl carbonate (DMC) and then dried to remove the DMC.

[0177] In this application, porosity, ionic impedance Rion, ionic conductivity, effective electrode area, and negative electrode active layer thickness all have well-known meanings in the art. Those skilled in the art can use conventional methods in the art to test and obtain the relevant parameters ε, k, Rion, A, and d, and can preferentially use the methods described above.

[0178] For example, the ion impedance Rion of the negative electrode sheet can be tested by the following method: a negative electrode sheet sample with a certain area A is cut out (that is, the effective area of ​​the electrode is A), and the ion diffusion impedance Rion inside the pores of the electrode sheet is tested by means of a symmetrical cell. It can be obtained by testing the EIS impedance of the electrode sheet.

[0179] In this application, the test temperatures for ε, k, and Rion can be performed at room temperature, or, unless otherwise specified, at 20°C to 30°C (e.g., 25°C), and further, at 25°C.

[0180] In some embodiments of this application, the tortuosity τ of the negative electrode active layer is numerically equal to the value calculated according to the following formula: ε×k×Rion×A / d; where ε is the porosity of the negative electrode active layer at 25°C; k is the ionic conductivity of the electrolyte at 25°C, in mS / cm; Rion is the ionic resistance of the negative electrode at 25°C, in Ω; and A is the effective area when Rion is tested, in cm². 2 d represents the total thickness of the negative electrode active layer, in μm.

[0181] In some embodiments, the average particle size of the primary particles in the negative electrode active material is 0.1 μm to 2 μm, optionally 0.2 μm to 1.5 μm, and may also be 0.1 μm to 1 μm, further optionally 0.2 μm to 1 μm, or any of the following values ​​or a range selected from any two of the following values: 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, etc.

[0182] In this application, unless otherwise specified, the "average particle size of primary particles" in the negative electrode active material refers to the average particle size of all primary particles in the negative electrode active material. The "particle size of primary particles" refers to the maximum diameter of the primary particles in each direction.

[0183] In this application, unless otherwise specified, "primary particles" in the negative electrode active material refer to the basic particle unit in the negative electrode active material. It is understood that primary particles exist in the negative electrode active material. In the negative electrode active material, primary particles can exist in a non-agglomerated state, or multiple primary particles can form aggregates. Non-agglomerated primary particles can be called "non-agglomerated primary particles," and aggregates formed by multiple primary particles can be called "secondary particles."

[0184] By controlling the average particle size (denoted as D1) of the primary particles in the negative electrode active material within the aforementioned range, it is possible to control the negative electrode active material to have a more suitable ion transport path and achieve a better rate capability. At the same time, it is also possible to better control the negative electrode interface reaction and control the consumption of alkyne additives in negative electrode film formation. Based on the synergy of the aforementioned effects, but not limited to the aforementioned theory, it is beneficial to better synergistically control the structural stability of the negative electrode active layer, the battery internal resistance, and the consumption of alkyne additives in negative electrode film formation. It is also more beneficial to significantly improve the room temperature performance of the alkyne additive battery system.

[0185] The particle morphology of the negative electrode active material can be used to statistically analyze the particle size and average value of the primary particles in the negative electrode active material. The particle morphology of the negative electrode active material can be obtained using scanning electron microscopy (SEM) results (e.g., ZEISS Sigma 300, JEOL SEM, Axia Chemi SEM, etc.). The sample to be tested can be obtained by laying a powder sample of the negative electrode active material on conductive adhesive. Non-limitingly, SEM testing can refer to JY / T(001)-1996. One or more regions are randomly selected from the sample to be tested for scanning. Based on the SEM image at a certain magnification, the particle size of each primary particle in the scanned region and the frequency of occurrence of different particle sizes are statistically analyzed, and the average particle size of the statistically analyzed primary particles can then be calculated. Non-limitingly, the magnification of a single scanned region can be, for example, 1000X, but is not limited to this. To improve the accuracy of the statistical results, multiple regions can be randomly selected for scanning.

[0186] In this application, unless otherwise specified, the maximum diameter of the primary particles in each direction in the SEM morphology image of the negative electrode active material is denoted as "the particle size of the primary particles in the negative electrode active material".

[0187] In some embodiments, the negative electrode active material includes a coated negative electrode material, which includes a negative electrode active body and a carbon coating layer located on at least a portion of the negative electrode active body. It is understood that the carbon coating layer in the coated negative electrode material has a different chemical composition from the negative electrode active body. The negative electrode active body can be selected from at least one material known in the art suitable for negative electrode active materials. Non-limitingly, the negative electrode active body can include one or more of graphite and silicon-based materials. Non-limitingly, graphite can include one or more of natural graphite and artificial graphite. Non-limitingly, silicon-based materials can include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Non-limitingly, the carbon coating layer in the coated negative electrode material can include one or more of soft carbon, hard carbon, and amorphous carbon. Non-limitingly, the average thickness of the carbon coating in the coated negative electrode material can be 1 nm to 500 nm, optionally 100 nm to 500 nm, and further optionally 100 nm to 200 nm. Non-limitingly, the mass percentage of the coating layer in the coating active material is 0.2% to 5%, and optionally 0.5% to 3%.

[0188] "Soft carbon" and "hard carbon" have well-known meanings in the art. Soft carbon can be graphitized by further high-temperature treatment, while hard carbon is difficult to graphitize even with further high-temperature treatment. In this application, unless otherwise specified, "amorphous carbon" refers to transitional carbon materials with a very low degree of graphitization and crystallization, which are approximately amorphous (or have no fixed shape and periodic structural regularity).

[0189] In some embodiments, the carbon coating layer in the coated negative electrode material is one of a soft carbon coating layer, a hard carbon coating layer, and an amorphous carbon coating layer. It can be understood that the material composition of the soft carbon coating layer is mainly soft carbon, the material composition of the hard carbon coating layer is mainly hard carbon, and the material composition of the amorphous carbon coating layer is mainly amorphous carbon.

[0190] In some embodiments, the negative electrode active material includes a coated negative electrode material, which comprises a negative electrode active body and a carbon coating layer, including at least a portion thereof, located on the negative electrode active body. The D of the negative electrode active material... v 50 is 5μm to 14μm, and can also be any of the following values ​​or a range composed of any two of the following values: 5μm, 5.5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, etc.

[0191] In some embodiments, the negative electrode active material includes a coated negative electrode material, which includes a negative electrode active body and a carbon coating layer located on at least a portion of the negative electrode active body. The average particle size of the primary particles in the negative electrode active material is 0.1 μm to 1.6 μm, and may also be any of the following values ​​or a range selected from any two of the following values: 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, etc.

[0192] In some implementations, the negative electrode sheet satisfies one or more of the following characteristics:

[0193] (a1) The mass percentage of the coated negative electrode material in the negative electrode active material can be 80%~100%, can be 90%~100%, or can be any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0194] (a2) The coated negative electrode material includes coated graphite, and the negative electrode active body in the coated graphite includes the graphite body. Non-limitingly, the mass percentage of coated graphite in the negative electrode active material can be 80% to 100%, optionally 90% to 100%, or any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0195] In this application, "coated graphite" is a coated anode material, wherein the anode active body in coated graphite includes a graphite body; coated graphite includes a graphite body and a carbon coating layer located on at least a portion of the surface of the graphite body.

[0196] In this application, the “graphite body” is composed of graphite.

[0197] By incorporating a coated anode material (such as coated graphite) with a carbon coating layer into the anode active material, the lithium-ion transport channels on the surface of the anode active material can be optimized, promoting lithium-ion transport and improving the kinetics of lithium-ion secondary batteries. At the same time, it is also beneficial to suppress side reactions at the anode interface and suppress the increase in anode interface impedance caused by the participation of acetylene additives in anode film formation, which is conducive to better improving the room temperature performance of acetylene additive battery systems.

[0198] By incorporating a coated anode material (such as coated graphite) with a carbon coating layer into the anode active material, rate performance can be optimized by using a relatively small average primary particle size (such as D1 of 0.1 μm to 1.6 μm).

[0199] In some embodiments, the coated negative electrode material is coated graphite, in which case the active negative electrode body is the graphite body.

[0200] In some embodiments, the porosity of the negative electrode active layer is 14% to 26%, optionally 15% to 25%, further optionally 18% to 22%, and may also be any of the following percentages or a range selected from any two of the following percentages: 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 26%, etc.

[0201] In this application, "porosity" has a meaning known in the art. The "porosity" of the negative electrode active layer refers to the percentage of pore volume in the negative electrode active layer relative to the total volume, and can be expressed as a percentage. The "porosity" of the negative electrode sheet can be denoted as ε.

[0202] The porosity of the negative electrode active layer can be determined using instruments and methods known in the art. For example, it can be tested using the AccuPyc II 1340 fully automatic true density analyzer from Micromeritics, USA, referring to the national standard GB / T 24586-2009 for the determination of apparent density, true density, and porosity of iron ore. This method involves cutting 30 small circular pieces with a diameter of 14 mm from the negative electrode sheet. Based on the principle of gas adsorption, using an inert gas such as helium or nitrogen as a medium, the true volume of the 30 small circular pieces with a diameter of 14 mm is measured. Then, based on the relationship between the apparent volume and true volume of the negative electrode sheet calculated using the area, thickness, and number of small circular pieces, the porosity of the negative electrode active layer is calculated.

[0203] The porosity ε of the negative electrode active layer can also be obtained by gas displacement testing. Using a small-molecule inert gas (such as He) displacement method, combined with Archimedes' principle and Bohr's law, the true volume V1 of the negative electrode active layer is accurately measured. Then, the apparent volume V2 of the negative electrode active layer is calculated through testing (V2 is calculated by multiplying the area of ​​the negative electrode active layer by its thickness d). Therefore, the porosity is calculated as (V2 - V1) / V2 × 100%.

[0204] True volume V1 test: Place the sample cup containing the negative electrode in the true density tester, seal the test system, and introduce helium gas according to the procedure. Calculate the true volume by detecting the gas pressure in the sample chamber and expansion chamber, and then using Bohr's law (PV=nRT).

[0205] By controlling the porosity (ε) of the negative electrode active layer within the aforementioned range, the tortuosity of the negative electrode sheet can be adjusted, which is beneficial for providing a better lithium-ion liquid phase transport channel, achieving better electrolyte wetting, and also taking into account the electrical contact network between the negative electrode active materials, which is beneficial for comprehensively improving the negative electrode dynamics and cycle performance.

[0206] In some embodiments, the active specific surface area of ​​the negative electrode active material is 2m². 2 / g~6m 2 / g, optional 2.5m 2 / g~5.5m 2 / g, further optional to 3m 2 / g~5m 2 / g, can also be any of the following values ​​or a range selected from any two of the following values: 2 m 2 / g、2.2 m 2 / g、2.4 m 2 / g, 2.5 m 2 / g, 2.6 m 2 / g、2.8 m 2 / g、3 m 2 / g, 3.5 m 2 / g、4m 2 / g, 4.5 m 2 / g、5 m 2 / g, 5.5 m 2 / g, 5.8 m 2 / g、6 m 2 / g etc.

[0207] In this application, unless otherwise specified, the "active specific surface area" of the negative electrode active material is a different concept from the "specific surface area" of traditional negative electrode active materials. The "specific surface area" of traditional negative electrode active materials is usually obtained using the gas adsorption BET method, representing the physical adsorption specific surface area of ​​the negative electrode active material. The active specific surface area of ​​the negative electrode active material corresponds to the active specific surface area during the actual reaction of the negative electrode active material, and can more accurately characterize the number of active sites during charging and discharging. A larger active specific surface area indicates more active sites in the negative electrode active material, a faster rate of charge exchange between active ions and electrons, and better kinetic performance of the negative electrode and the battery.

[0208] The physical adsorption specific surface area (BET) of the negative electrode active material may have some influence on its active specific surface area, but this is not absolute and is also affected by the type of negative electrode active material. Generally, for negative electrode active materials of the same material, the active specific surface area increases with the increase of the physical adsorption specific surface area. Furthermore, the larger the physical adsorption specific surface area of ​​the negative electrode active material, the higher its electrochemical activity, and the faster the charge exchange between active ions and electrons on its surface. However, this also leads to more side reactions between the negative electrode active material and the electrolyte.

[0209] For example, the active specific surface area of ​​the negative electrode active material can be tested using the following method.

[0210] (1) Extract the negative electrode active material sample and reconstitute it into the electrode to be tested.

[0211] The negative electrode sheet obtained from disassembling the battery cell is cleaned with a solvent (such as DMC) to remove residual electrolyte. A powder sample of the negative electrode active layer is extracted and resuspended in deionized water to form a homogeneous slurry, denoted as the resuspension slurry. The resuspension slurry is coated onto one side of the negative electrode current collector copper foil, dried, cold-pressed, and punched into a piece with an area of ​​S0 (e.g., 1540.25 mm²). 2 Small circular pieces were used as the electrode to be tested; the single-sided coating surface density and compaction density of the electrode to be tested were the same as in Example 1. The mass M of the negative electrode active layer... J =M B -M0, where M B M0 represents the mass of the electrode to be tested, and M0 represents the mass of the empty current collector foil.

[0212] (2) Using the electrode to be tested as the cathode and a lithium metal sheet as the anode, ferrocene with a concentration of 50 mmol / L was added to the electrolyte (the same as the electrolyte in Example 1), and then a coin cell was assembled. Four parallel samples were scanned at scan rates v of 0.1 mV / s, 0.3 mV / s, 0.5 mV / s, and 1 mV / s, respectively, to obtain cyclic voltammetry curves at different scan rates. The peak current ip of the cyclic voltammetry curves was extracted using EC-Lab software. A linear graph of the cyclic voltammetry curve ip and the square root of the scan rate v was plotted with the square root of the scan rate v as the abscissa and the peak current ip as the ordinate, and the slope K was obtained. The slope can be determined according to the Randles-Sevick equation, where n represents the number of electrons transferred, which is related to the type of probe molecule, and is taken as 1 here; c represents the concentration of ferrocene, which is taken as 50 mmol / L; and D is the diffusion coefficient of ferrocene, which is taken as 2.1 × 10⁻⁶. -6 cm 2 / s; then the active surface area of ​​the electrode to be tested, A = K / (2.69 × 10⁻⁶). 5 ×n 2 / 3 cD1 / 2 The active surface area A of the negative electrode sheet and the mass M of the negative electrode active layer are related. J The ratio can be recorded as the active specific surface area of ​​the negative electrode active material sample to be tested.

[0213] In some embodiments, the additive further includes additive B, which is one or more of lithium salt additives and phosphate ester additives. Non-limitingly, the mass ratio of additive B to the acetylene additive can be greater than 0 and less than or equal to 100, greater than 0 and less than or equal to 50, or 0.1 to 100, optionally 0.3 to 50, further optionally 0.3 to 20, or 0.08 to 100, optionally 0.08 to 50, further optionally 0.08 to 20, or any of the following values ​​or a range selected from any two of the following values: 0.05, 0.08, 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, 1, 2, 3, 4, 5, 6, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, etc.

[0214] Lithium salt additives and phosphate ester additives have low negative electrode film resistance. By introducing one or more of lithium salt additives and phosphate ester additives into the electrolyte, it is beneficial to reduce the resistance of the negative electrode SEI film and reduce the internal resistance of the battery. Furthermore, by controlling the mass ratio of additive B to alkyne additive within the aforementioned range, the room temperature performance of the alkyne additive battery system can be better improved.

[0215] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0216] (b1) The mass ratio of additive B to acetylene additive is 0.08 to 20, and may be selected from any suitable value or range in the context;

[0217] (b2) The lithium salt additives include one or more of the following: lithium oxalate, lithium tetrafluoroborate, lithium difluorophosphate, lithium fluorosulfonic acid, and lithium perchlorate; lithium oxalate includes one or more of the following: lithium difluorooxalateborate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, and lithium bis(oxalateborate); lithium fluorosulfonic acid includes one or more of the following: lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonate.

[0218] (b3) Phosphate ester additives include one or more of silicon-based phosphate ester additives and alkyl phosphonate additives; silicon-based phosphate ester additives include one or more of tris(trimethylsilane) phosphate and tris(trimethylsilyl) phosphite;

[0219] (b4) Additives include lithium salt additives. Non-limitingly, the mass percentage of lithium salt additives in the electrolyte may be greater than 0 and less than or equal to 3%, and may be any of the following percentages or a range selected from any two of the following percentages: 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, etc.

[0220] (b5) Additives include phosphate ester additives, the mass percentage of which in the electrolyte may be greater than 0 and less than or equal to 1%, and may be any of the following percentages or a range selected from any two of the following percentages: 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, etc.

[0221] In some implementations, the negative electrode active material includes a silicon-based material.

[0222] Non-limitingly, the mass percentage of silicon-based material in the negative electrode active material can be 0-40%, further preferably 0-30%, even more preferably 0-25%, even more preferably 0-20%, even more preferably 0-10%, even more preferably 0-5%, even more preferably 0-3%, even more preferably 0.1%-3%, and can also be any of the following percentages or a range selected from any two of the following percentages: 0, 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 4%, 5%, 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc.

[0223] Non-limitingly, the mass percentage of silicon-based material in the negative electrode active material can be 0.01% to 3%, optionally 0.1% to 3%, or any of the following percentages or a range selected from any two of the following percentages: 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, etc.

[0224] Non-limitingly, the mass percentage of carbon-based materials in the negative electrode active material can be 60% to 100%, optionally 70% to 100%, further optionally 80% to 100%, even further optionally 90% to 100%, even further optionally 97% to 100%, and can also be any of the following percentages or a range selected from any two of the following percentages: 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0225] In some embodiments, the negative electrode active material includes graphite, and further, the graphite may include one or more of artificial graphite and natural graphite.

[0226] In some implementations, the negative electrode sheet satisfies one or more of the following characteristics:

[0227] (c1) The mass percentage of silicon-based material in the negative electrode active material can be 0-3%. Optionally, the negative electrode active material includes silicon-based material, and the mass percentage of silicon-based material in the negative electrode active material is greater than 0 and less than or equal to 3% (see also suitable values ​​or ranges in any of the embodiments described in the context). For example, the mass percentage of silicon-based material in the negative electrode active material can also be any of the following percentages or a range selected from any two of the following percentages: 0, 0.01%, 0.02%, 0.04%. %, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, etc.;

[0228] (c2) The negative electrode active material includes silicon-based materials, which include silicon-carbon composite materials. The silicon-carbon composite materials include a porous carbon matrix and elemental silicon located in the pores of the porous carbon matrix. Non-limitingly, the mass percentage of silicon-carbon composite materials in the silicon-based materials can be 80% to 100%, optionally 90% to 100%, or any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0229] (c3) The mass percentage of graphite-based materials in the negative electrode active material is 60% to 100%, which can be selected as 80% to 100%, and any suitable value or range can be referred to in the context of this application.

[0230] "Silicon-carbon composite material" is a silicon-based material comprising a porous carbon matrix and elemental silicon located within the pores of the porous carbon matrix. Silicon-carbon composite materials can be obtained using vapor deposition methods. Those skilled in the art can prepare silicon-carbon composite materials using conventional methods in the field.

[0231] By controlling the content and / or type of silicon-based materials in the negative electrode active material within the aforementioned range, the expansion and contraction changes of the negative electrode can be better controlled. This is beneficial for better matching the stability requirements of the negative electrode active layer in the thin coating process, reducing the generation of fresh interfaces, suppressing negative electrode interface side reactions, reducing the consumption rate of alkyne additives, and decreasing the rate of increase in battery internal resistance, thus improving battery cycle life. For example, in silicon-based materials, the volume expansion and contraction changes of silicon-carbon composite materials are relatively low.

[0232] For traditional lithium-ion secondary batteries with positive electrode materials including lithium transition metal oxide (LiMeO) cathodes, on the one hand, these acidic byproducts can damage the solid electrolyte interphase (CEI) film and corrode the positive electrode active material, leading to the dissolution of transition metal ions from the positive electrode and thus deteriorating battery cycle performance. On the other hand, these acidic byproducts can easily damage the negative electrode SEI film, exposing fresh interfaces and exacerbating interfacial side reactions at the negative electrode, further worsening battery cycle performance. Specifically, the dissolution of transition metal ions from the positive electrode not only affects the structural stability of the positive electrode active material, but these dissolved transition metal ions, after migrating to and depositing at the negative electrode, can also easily damage the solid electrolyte interphase (SEI) film, intensifying interfacial side reactions at the negative electrode.

[0233] In some embodiments, the positive electrode includes a positive active layer, the positive active layer includes a positive active material, and the positive active material includes a lithium transition metal oxide positive electrode material.

[0234] In this application, unless otherwise specified, "lithium transition metal oxide cathode material" refers to a cathode active material containing lithium, transition metal elements, and oxygen. Therefore, lithium transition metal oxide cathode materials include non-lithium metal elements, and these non-lithium metal elements include transition metal elements. Non-limitingly, in lithium transition metal oxide cathode materials, the molar percentage of transition metal elements relative to non-lithium metal elements can be 90% to 100%, and can also be any of the following percentages or a range selected from any two of the following percentages: 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0235] In this application, unless otherwise specified, "non-lithium metal element" refers to a metal element that is not lithium (Li).

[0236] In some embodiments, lithium transition metal oxide cathode materials have a layered crystal structure.

[0237] In some embodiments, the positive electrode active material includes a lithium transition metal oxide (LiMe) positive electrode material. Non-limitingly, the LiMe is present in the positive electrode active material at a mass percentage of 80% to 100%, optionally 90% to 100%, further optionally 95% to 100%, and may also be any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0238] In some embodiments, lithium transition metal oxide cathode materials include lithium nickel-based oxide cathode materials.

[0239] In this application, unless otherwise specified, "lithium nickel-based oxide cathode material" refers to a lithium transition metal oxide cathode material containing nickel. It is understood that lithium nickel-based oxide cathode materials include lithium, non-lithium metal elements, and oxygen; the non-lithium metal elements include nickel. Non-limitingly, the mass percentage of the lithium nickel-based oxide cathode material in the cathode active material is 80% to 100%, optionally 90% to 100%, further optionally 95% to 100%, and may also be any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0240] Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 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 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.80 Co 0.15 Al 0.05 O2.

[0241] In some embodiments, lithium transition metal oxide cathode materials include lithium nickel cobalt-based oxide cathode materials.

[0242] In some embodiments, the positive electrode active material includes a lithium nickel cobalt-based oxide positive electrode material. Non-limitingly, the lithium nickel cobalt-based oxide positive electrode material constitutes 80% to 100% of the positive electrode active material by mass, optionally 90% to 100%, further optionally 95% to 100%, and may also be any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0243] "Lithium nickel cobalt-based oxide cathode material" refers to a lithium transition metal oxide cathode material containing nickel and cobalt elements, and is also a lithium nickel-based oxide cathode material containing cobalt elements. It is understood that in this application, "lithium nickel cobalt-based oxide cathode material" includes lithium (Li), nickel (Ni), cobalt (Co), and oxygen (O).

[0244] In some embodiments, the lithium nickel cobalt-based oxide cathode material may further include an M2 element, which can be either manganese (Mn) or aluminum (Al). When the M2 element is manganese (Mn), the lithium nickel cobalt-based oxide cathode material is a lithium nickel cobalt manganese-based oxide cathode material, which can be denoted as an NCM-based cathode material. When the M2 element is aluminum (Al), the lithium nickel cobalt-based oxide cathode material is a lithium nickel cobalt aluminum-based oxide cathode material, which can be denoted as an NCA-based cathode material.

[0245] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese-based oxide positive electrode materials.

[0246] In this application, unless otherwise specified, "lithium nickel cobalt manganese-based oxide cathode material" refers to a lithium transition metal oxide cathode material containing nickel, cobalt, and manganese; it is also a lithium nickel-based oxide cathode material containing cobalt and manganese; and a lithium nickel cobalt-based oxide cathode material containing manganese. It is understood that lithium nickel cobalt manganese-based oxide cathode material includes lithium, non-lithium metal elements, and oxygen; wherein the non-lithium metal elements include nickel, cobalt, and manganese. Non-limitingly, the mass percentage of the lithium nickel cobalt manganese-based oxide cathode material in the cathode active material is 80% to 100%, optionally 90% to 100%, further optionally 95% to 100%, and may also be any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0247] In some embodiments, the lithium transition metal oxide cathode material includes a ternary cathode material, which may be selected as a ternary cathode material. In this application, the "ternary cathode material" is composed of Li, nickel, cobalt, M2, and oxygen; wherein, M2 can be manganese or aluminum. When M2 is manganese (Mn), the ternary cathode material is lithium nickel cobalt manganese oxide, which can be denoted as NCM; when M2 is aluminum (Al), the ternary cathode material is lithium nickel cobalt aluminum oxide, which can be denoted as NCA.

[0248] In some embodiments, the positive electrode includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a positive active material, which may include a lithium transition metal oxide (LiMe) positive electrode material. The thickness of the positive active layer on one side of the positive current collector is less than or equal to 50 μm. The thickness of the positive active layer on one side of the positive current collector can also be any of the following thicknesses or a range selected from any two of the following thicknesses: 40 μm, 42 μm, 44 μm, 45 μm, 46 μm, 48 μm, 50 μm, etc. In this case, the positive electrode can provide a higher energy density, which corresponds to a thinner positive active layer, resulting in better capacity matching with the negative active layer. This is beneficial for suppressing lithium plating on the negative electrode and extending battery cycle life, including extending cycle life at room temperature. The testing method for the thickness of the positive active layer on one side of the positive current collector is similar to the testing method for the thickness of the negative active layer on one side of the negative current collector.

[0249] In some embodiments, the positive electrode active material includes a lithium nickel-based oxide positive electrode material, which includes lithium, non-lithium metal elements, and oxygen; wherein the non-lithium metal elements include nickel; in the lithium nickel-based oxide positive electrode material, the ratio of the atomic molar ratio of nickel to the sum of the atomic molar ratios of the non-lithium metal elements is denoted as R. Ni .

[0250] In some implementations, R Ni ≥0.8, the thickness of the positive electrode active layer on one side of the positive electrode current collector is 40μm~50μm. The thickness of the positive electrode active layer on one side of the positive electrode current collector can also be any of the following thicknesses or a range selected from any two of the following thicknesses: 40μm, 42μm, 44μm, 45μm, 46μm, 48μm, 50μm, etc. In this case, the capacity matching between the positive and negative electrode active layers is better, which is more conducive to extending the battery cycle life, including extending the cycle life at room temperature.

[0251] Without limitation, R Ni It can be greater than or equal to 0.6, and can also be any of the following values ​​or a range consisting of any two of the following values: 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.92, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, etc.

[0252] Without limitation, R Ni It can be greater than or equal to 0.8, or it can be any of the following values ​​or a range consisting of any two of the following values: 0.8, 0.85, 0.9, 0.92, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, etc.

[0253] In some implementations, the lithium-ion secondary battery cell satisfies one or more of the following characteristics:

[0254] (d1) The positive electrode sheet includes a positive electrode active layer, the positive electrode active layer includes a positive electrode active material, and the positive electrode active material includes a lithium transition metal oxide positive electrode material; in some embodiments, the mass percentage of the acetylene additive in the electrolyte is 0.02% to 1.8%, and may also be any of the following percentages or a range selected from any two of the following percentages: 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, etc.;

[0255] (d2) The negative electrode active material includes silicon-based materials, wherein the mass percentage of silicon-based materials in the negative electrode active material is less than or equal to 3%, optionally 0.1% to 3%, further optionally 1% to 3%, and may also be any of the following percentages or a range selected from any two of the following percentages: 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%. The following percentages are specified: 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, etc.; acetylene additives include first acetylene compounds; in some embodiments, the first acetylene compound has a mass percentage of 0.05% to 2.5% in the electrolyte, and may also be any of the following percentages or a range selected from any two of the following percentages: 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 3.2%, etc.

[0256] Alkyne additives can adsorb transition metal ions in electrolytes.

[0257] When the negative electrode active material includes the aforementioned amount of silicon-based material, a fresh interface is generated as the negative electrode volume expands and contracts, leading to interfacial side reactions and the production of acidic byproducts. The acidic byproducts can be adsorbed by a first alkynyl compound containing a Lewis base nitrogen heterocycle.

[0258] In this application, the test sample of the "negative electrode active material" in the negative electrode sheet of a lithium-ion secondary battery can be obtained by disassembling the battery, removing the negative electrode sheet, and extracting the negative electrode active material from the negative electrode active layer of the negative electrode sheet using methods such as solvent washing, ultrasonic dispersion, centrifugation, and fractional sedimentation. The extracted material is then dried to obtain a powder sample. The obtained powder sample can be used for laser particle size analysis or other tests.

[0259] In this application, the test sample of the "positive electrode active material" in the positive electrode sheet of a lithium-ion secondary battery can be obtained by disassembling the battery, removing the positive electrode sheet, and extracting the positive electrode active material from the positive electrode active layer of the positive electrode sheet using methods such as solvent washing, ultrasonic dispersion, centrifugation, fractionation sedimentation, and sintering. The extracted powder sample is then dried to obtain a powder sample. The obtained powder sample can be used for laser particle size analysis or other tests. Furthermore, the powder material extracted from the positive electrode active layer can be sintered to remove organic components, thereby obtaining a powder sample of the positive electrode active material.

[0260] For example, the preparation of powder samples of positive electrode active materials can be carried out by the following method: disassemble the battery, take out the positive electrode sheet, soak and clean it with a solvent such as dimethyl carbonate to remove residual electrolyte; scrape the powder material of the positive electrode active layer, soak the powder material extracted from the positive electrode active layer with a solvent (such as N-methylpyrrolidone (NMP) etc.) to dissolve organic components such as binders in the solvent (ultrasonic dispersion and other methods can also be combined to promote dissolution), wash and filter, collect the solid phase, and then use density difference to centrifuge to separate the relatively low-density conductive agent from the suspension, collect the centrifuged precipitate to obtain the test powder of positive electrode active material.

[0261] The elemental composition of the positive electrode active material in the positive electrode active layer can be analyzed using methods known in the art, including but not limited to the following: inductively coupled plasma atomic emission spectrometry (ICP), X-ray diffraction (XRD), single-crystal X-ray diffraction (SCXRD), and energy dispersive spectroscopy (EDS). The sample preparation and testing methods for these methods are known to those skilled in the art, and the test parameters can be appropriately adjusted according to the sample characteristics. ICP can be used for quantitative analysis of the component content in the positive electrode active material.

[0262] The detection of positive electrode active material in the positive electrode active layer can be carried out by disassembling the battery after it is fully discharged, removing the positive electrode plate, scraping off the material of the positive electrode active layer, and using elemental analysis methods such as inductively coupled plasma (ICP) spectroscopy to test and analyze the types and proportions of elements, thereby confirming the elemental composition and chemical formula of the positive electrode active material.

[0263] In some embodiments, the positive electrode active material includes a positive electrode active body and a coating layer located on at least a portion of the surface of the positive electrode active material.

[0264] For positive or negative electrode active materials that include a coating layer (e.g., a carbon coating layer), a cross-section can be obtained using FIB (Focused Ion Beam) and the particle cross-sectional morphology can be observed under TEM (Transmission Electron Microscopy). A clear boundary can be observed at the coating interface, and the thickness and average thickness of the coating layer can be calculated based on the TEM image. Further analysis using one or more methods such as energy-dispersive spectroscopy (EDS) and Raman spectroscopy can identify the types of substances in the coating layer and the positive electrode active material, or vice versa.

[0265] Those skilled in the art can identify the components in the positive and negative active layers using one or more of the following detection methods known in the art, including but not limited to: Fourier transform infrared (FT-IR) spectroscopy, ultraviolet spectroscopy, and proton nuclear magnetic resonance (NMR) spectroscopy. 1 Methods include 1H NMR, gel permeation chromatography (GPC), high performance liquid chromatography (HPLC), mass spectrometry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, single crystal X-ray diffraction (SCXRD), inductively coupled plasma optical emission spectrometry (ICP), and energy dispersive spectroscopy (EDS). The sample preparation and testing methods for these methods are known to those skilled in the art, and the test parameters can be appropriately adjusted according to the structure of the material or substance and the characteristics of the sample.

[0266] As a non-limiting example, EDS can be used to distinguish between carbon and silicon, and thus between carbon-based and silicon-based materials. Similarly, EDS can be used to detect the type and content of conductive agents, but is not limited to these applications.

[0267] Using natural graphite and artificial graphite as non-limiting examples, the negative electrode active materials can be distinguished by the appearance and morphology of the particles. Further X-ray diffraction (XRD) analysis can be performed. In the XRD pattern, if the characteristic peak near 2θ 26.5° is very sharp and has high intensity, it is natural graphite; if the characteristic peak near 2θ 26.5° is relatively broad and has weak intensity, it is artificial graphite.

[0268] Taking graphite and soft carbon as examples of negative electrode active materials, Raman spectroscopy can be used to distinguish between them. More specifically, the characteristic peak information of carbon components in the spectrum (such as the intensity ratio of the D peak to the G peak, I) can be used. D / G The analysis focused on soft carbon. Both the D and G peaks are Raman characteristic peaks of carbon atom crystals. The D peak represents defects in the carbon atom crystal; the more defects, the greater the intensity of the D peak. The intensity of the D peak reflects the content of amorphous (randomly stacked) regions. The G peak represents the in-plane stretching vibrations of sp2 hybridized carbon atoms; the intensity of the G peak reflects the content of graphitized (layered structure) regions. As the degree of disorder in carbon atoms increases, the intensity ratio of the D peak to the G peak also increases. The Raman spectra can also be compared. D / G Standard Raman spectrum of graphite I D / G The difference between the two peaks can be used to determine whether the material being tested contains soft carbon. Similarly, the difference between the D and G peaks in the Raman spectrum can be used to distinguish between graphite and hard carbon. Likewise, the difference between the D and G peaks in the Raman spectrum can be used to distinguish between natural graphite and synthetic graphite.

[0269] In some embodiments, the mass percentage of the acetylene additive in the electrolyte is 0.001% to 3.2%, optionally 0.01% to 1.8%, and may also be any of the following percentages or a range selected from any two of the following percentages: 0.001%, 0.005%, 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 3.2%, etc.

[0270] By controlling the mass ratio of acetylene additives in the electrolyte within the aforementioned range, the acetylene additives can continuously play a role in repairing the SEI film during cycling, which is more conducive to extending battery cycle life, including extending the cycle life at room temperature.

[0271] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0272] (e1) The molecular weight of acetylene additives is less than or equal to 500 Da;

[0273] (e2) The carbon-carbon triple bond in acetylene additives is CH≡C-;

[0274] (e3) The sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive can be 75% to 100%, or more specifically 80% to 100%, or can be selected from any suitable value or range in the context of this application.

[0275] (e4) The mass percentage of the first alkynyl compound in the alkynyl additive is 75% to 100%, and may be 80% to 100%, or may be selected from any suitable value or range in the context of this application.

[0276] In some embodiments, the sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is greater than 50%, which can be 75% to 100%, further can be 80% to 100%, and even further can be 90% to 100%, or can be any of the following percentages or a range selected from any two of the following percentages: 75%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0277] In some embodiments, the mass percentage of the first alkynyl compound in the alkynyl additive may be 75% to 100%, further may be 80% to 100%, and even further may be 90% to 100%, or may be any of the following percentages or a range selected from any two of the following percentages: 75%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0278] In some embodiments, the mass percentage of the second alkynyl compound in the alkynyl additive can be 75% to 100%, further can be 80% to 100%, and even further can be 90% to 100%, or can be any of the following percentages or a range selected from any two of the following percentages: 75%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0279] In some embodiments, the acetylene additive is a combination of a first acetylene compound and a second acetylene compound; further, the acetylene additive may be the first acetylene compound.

[0280] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0281] (f1) The molecular weight of acetylene additives is less than or equal to 300 Da;

[0282] (f2) Lewis bases have a nitrogen heterocycle that is either substituted or unsubstituted imidazole, wherein the imidazole ring in the substituted or unsubstituted imidazole group is substituted by 0, 1 or more substituents Q2, and each substituent Q2 in the substituted imidazole group is independently C. 1-3 Alkyl, cyano (-CN), or fluorine atom;

[0283] (f3) The sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 90% to 100%, and may also be selected from any suitable value or range in the context of this application;

[0284] (f4) The first alkynyl compound accounts for 90% to 100% of the mass of the alkynyl additive, and may also be selected from any suitable value or range in the context of this application.

[0285] In this application, "C" is involved. 1-3 "alkylene" can be methylene, ethylene, or propylene unless otherwise specified, and can further be methylene, 1,2-ethylene, or 1,3-propylene.

[0286] In this application, "C" is involved. 1-3 "alkyl" can be methyl, ethyl, or propyl unless otherwise specified, and may further be methyl, ethyl, n-propyl, or isopropyl.

[0287] In some embodiments, R2 in the second alkynyl compound is a methyl group.

[0288] In some embodiments, the first alkynyl compound includes compound II, and may further be compound II.

[0289] In some embodiments, the second alkynyl compound includes compound III, and may further be compound III.

[0290] In some embodiments, the acetylene additive includes one or more of compounds II and III;

[0291] The structure of compound II is Among them, L 11 C 1-3 Alkylene, Q2 is independently C 1-3Alkyl, cyano, or fluorine atom, p2 is 0, 1, 2, or 3;

[0292] The structure of compound III is Among them, L 21 C 1-3 Alkylene, R2 is C 1-3 alkyl.

[0293] In some embodiments, L in compound II 11 It is a methylene group.

[0294] In some embodiments, p2 in compound II is 0.

[0295] In some embodiments, L in compound III 21 It is a methylene group.

[0296] In some embodiments, R2 in compound III is a methyl group.

[0297] In some embodiments, the sum of the mass percentages of compounds II and III in the acetylene additive can be 75% to 100%, further preferably 80% to 100%, and even further preferably 90% to 100%, or any of the following percentages or a range selected from any two of the following percentages: 75%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0298] In some embodiments, the mass percentage of compound II in the yne additive or the first yne group compound may be 75% to 100%, further preferably 80% to 100%, and even further preferably 90% to 100%. It may also be any of the following percentages or a range selected from any two of the following percentages: 75%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0299] In some embodiments, the mass percentage of compound III in the alkynyl additive or the second alkynyl compound may be 75% to 100%, further preferably 80% to 100%, and even further preferably 90% to 100%. It may also be any of the following percentages or a range selected from any two of the following percentages: 75%, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0300] In some embodiments, compound II is .

[0301] In some embodiments, compound III is .

[0302] By controlling the molecular weight of acetylene additives within the aforementioned lower range, acetylene additives can have smaller molecular sizes, which is beneficial for better control of the low viscosity characteristics of the electrolyte, resulting in higher conductivity of the electrolyte and better control of the battery's internal resistance.

[0303] The first alkynyl compound, which includes both a carbon-carbon triple bond and a Lewis base nitrogen heterocycle, can promote the formation of an interface film with dual organic / inorganic properties during the negative electrode interface reaction, thereby improving the stability of the negative electrode SEI film. The Lewis base nitrogen heterocycle can also absorb acid byproducts in the electrolyte, which is beneficial to improving the stability of the negative electrode interface and the negative electrode active material, reducing the consumption rate of alkynyl additives, and decreasing the rate of increase in battery internal resistance. Based on the aforementioned multiple effects, but not limited to the aforementioned mechanisms, it is beneficial to better improve the room temperature performance of alkynyl additive battery systems.

[0304] Examples of Lewis base nitrogen heterocycles include the imidazole ring in compound II.

[0305] In some embodiments, the acetylene additive includes compound II. Non-limitingly, the mass percentage of compound II in the acetylene additive can be 80% to 100%, optionally 90% to 100%, or any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0306] In some embodiments, the acetylene additive includes the structure of Compound IIa, without limitation, may constitute 80% to 100% of the mass of the acetylene additive, optionally 90% to 100%, or any of the following percentages or a range selected from any two of the following percentages: 80%, 82%, 84%, 85%, 86%, 88%, 90%, 94%, 95%, 96%, 98%, 100%, etc.

[0307] In some embodiments, the non-aqueous solvent includes chain carbonates.

[0308] In this application, unless otherwise specified, "chain carbonate" refers to a chain compound having a *-OC(=O)-O-* structure, where each * independently represents a bonding site with a carbon atom.

[0309] In some embodiments, the structure of the chain carbonate is R 21 -OC(=O)-OR22 R 21 and R 22 Each is independently an alkyl group having 1 to 4 (which can be 1, 2, 3, or 4) carbon atoms. In some embodiments, R 21 and R 22 Each is independently methyl, ethyl, or propyl. In some embodiments, R 21 and R 22 Each can be methyl or ethyl.

[0310] In some embodiments, the non-aqueous solvent includes dimethyl carbonate, and non-limitingly, the mass percentage of dimethyl carbonate in the non-aqueous solvent is greater than or equal to 20%, optionally 20% to 50%, and further optionally 20% to 40%.

[0311] In some embodiments, the non-aqueous solvent includes chain carboxylic acid ester compounds.

[0312] In this application, unless otherwise specified, "chain carboxylic acid ester" refers to a chain compound having a *-C(=O)-O-* structure, where each * independently represents a bonding site with a carbon atom. Chain carboxylic acid esters used in electrolytes for lithium-ion secondary batteries typically have low viscosity, which is beneficial for improving the lithium-ion conductivity of the electrolyte.

[0313] In some embodiments, the ionic conductivity of the electrolyte at 25°C is greater than or equal to 9 mS / cm, and can be selected from 9 mS / cm to 20 mS / cm, further selected from 10 mS / cm to 18 mS / cm, or can be any of the following conductivity values ​​or a range selected from any two of the following conductivity values: 9 mS / cm, 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 18 mS / cm, 20 mS / cm, etc.

[0314] In this application, unless otherwise specified, the term "ionic conductivity" of the electrolyte has a commonly known meaning in the art and can be tested and analyzed using existing methods in the field. Ionic conductivity can be obtained using a conductivity meter, such as the DDSJ-318 conductivity meter. The testing temperature can be 25±0.1℃. The testing method can be performed according to HG / T 4067-2015. Unless otherwise specified, the unit of ionic conductivity of the electrolyte is millisiemens per centimeter (mS / cm).

[0315] Unless otherwise specified, the following steps may be used for testing:

[0316] Pretreatment: Take the standard liquid and keep it at a constant temperature of 25℃ (deviation ±0.1℃), and take the test liquid and keep it at a constant temperature of the test temperature (deviation ±0.1℃).

[0317] Test: The instrument was calibrated using two standard solutions at 25℃. After calibration and cleaning of the electrode, the test sample electrode was vertically placed into the liquid to be tested. The test was started and the results were recorded after the data stabilized for more than 10 seconds.

[0318] The following is a description of the positive electrode sheet.

[0319] The positive electrode includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, the positive active layer including a positive active material.

[0320] Without limitation, the weight percentage of the positive electrode active material in the positive electrode active layer may be greater than or equal to 80 wt%, and may further be greater than or equal to 90 wt%.

[0321] As a non-limiting example, the positive current collector has two surfaces that are opposite to each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0322] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. In the positive electrode current collector, 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. In the positive electrode current collector, the composite current collector may be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. Non-limitingly, in the positive electrode current collector, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0323] The positive electrode active material may be any positive electrode active material known in the art for use in batteries. These positive electrode active materials may be used alone or in combination of two or more.

[0324] The types of positive electrode active materials in the positive electrode sheet can be referred to the description in the context of this application. Without limitation, other types of positive electrode active materials may also be introduced into the positive electrode active material. Other types of positive electrode active materials may include lithium phosphate-containing active materials.

[0325] In some embodiments, the positive electrode active material includes lithium phosphate-based positive electrode materials.

[0326] Non-limitingly, the mass percentage of lithium phosphate-containing cathode material in the cathode active material is 0% to 5%, optionally 0.1% to 5%, and may also be any of the following percentages or a range selected from any two of the following percentages: 0, 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0327] In this application, unless otherwise specified, "lithium phosphate-containing cathode material" refers to a class of cathode active materials containing lithium iron phosphate components, and more specifically, includes lithium, transition metal elements, and phosphate ions (PO4). 3- The positive electrode active material is lithium phosphate. Unless otherwise specified, "lithium phosphate positive electrode material" may be olivine structure.

[0328] In some embodiments, the positive electrode active material includes a lithium phosphate-based positive electrode material with an olivine structure. Non-limiting examples of lithium phosphate-based positive electrode materials with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium iron phosphate include LiFePO4. Examples of lithium manganese phosphate include LiMnPO4.

[0329] Non-limiting examples of lithium phosphate cathode materials include lithium iron phosphate cathode materials.

[0330] In this application, unless otherwise specified, "lithium iron phosphate cathode material" refers to a class of cathode active materials containing lithium iron phosphate components. Unless otherwise specified, "lithium iron phosphate cathode material" may have an olivine structure.

[0331] In some embodiments, the positive electrode active material includes lithium iron phosphate-based positive electrode materials. Further, the lithium iron phosphate-based positive electrode material may include at least one of lithium iron phosphate and a composite material of lithium iron phosphate and carbon.

[0332] In some embodiments, the composite material of lithium iron phosphate and carbon is carbon-coated lithium iron phosphate.

[0333] In some implementations, lithium iron phosphate cathode materials include carbon-coated lithium iron phosphate.

[0334] In this application, the term "carbon-coated lithium iron phosphate" includes a lithium iron phosphate body and a carbon coating layer located on at least a portion of the surface of the lithium iron phosphate body, wherein the lithium iron phosphate body comprises lithium iron phosphate. Non-limitingly, the carbon coating layer in the carbon-coated lithium iron phosphate may include one or more of soft carbon, hard carbon, and amorphous carbon. Non-limitingly, the mass percentage of the carbon coating layer in the lithium iron phosphate cathode material may be 1% to 1.5%.

[0335] In some embodiments, lithium iron phosphate cathode materials include lithium iron phosphate-based cathode materials. Lithium iron phosphate-based cathode materials refer to a class of cathode active materials containing lithium iron phosphate.

[0336] In some implementations, the lithium iron phosphate body includes lithium iron phosphate.

[0337] In some embodiments, the lithium iron phosphate-based cathode material includes carbon-coated lithium iron phosphate. In this case, the carbon-coated lithium iron phosphate comprises carbon-coated lithium iron phosphate.

[0338] In this application, the term "carbon-coated lithium iron phosphate" includes lithium iron phosphate and a carbon coating layer located on at least a portion of the surface of the lithium iron phosphate. Further, the carbon coating layer may include one or more of soft carbon, hard carbon, and amorphous carbon.

[0339] In some embodiments, the carbon coating layer in carbon-coated lithium iron phosphate includes soft carbon. In some embodiments, the carbon coating layer is a soft carbon coating layer, and in this case, the carbon-coated lithium iron phosphate can be referred to as soft carbon-coated lithium iron phosphate. "Soft carbon coating layer" refers to a coating layer mainly composed of soft carbon, and the mass percentage of soft carbon in the coating layer can be close to 100%. The mass percentage of soft carbon in the soft carbon coating layer in the carbon-coated lithium iron phosphate can be 1% to 1.5%, optionally 1.4% to 1.5%, but is not limited to this.

[0340] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. In the exemplary description of the positive electrode active material in this application, unless otherwise specified, the Li content can be the initial state of the material or a non-initial state after charge-discharge cycles. When the positive electrode active material is applied to the positive electrode in a battery system, the Li content in the positive electrode active material at the positive electrode will usually change after charge-discharge cycles. The Li content can be measured in atomic molar content, but is not limited to this. Regarding "Li content is the initial state of the material," the initial state of the material refers to the state before it is formed into the positive electrode active layer. It is understood that new materials or substances obtained by appropriately modifying the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to an acceptable modification method for the positive electrode active material, and non-limiting examples include one or more of coating modification and doping modification.

[0341] In the exemplary description of the positive electrode active material in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the atomic molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in atomic molar content, but is not limited to this.

[0342] In some embodiments, the positive electrode active layer optionally includes a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. Typically, the binder may constitute 0-10 wt% of the weight of the positive electrode active layer, more commonly 0-8 wt%, and even more commonly 1 wt%-5 wt%, based on the total weight of the positive electrode active layer.

[0343] In some embodiments, the positive electrode active layer optionally includes a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Typically, the weight percentage of the conductive agent in the positive electrode active layer can be 0-10 wt%, more commonly 0-8 wt%, and even more commonly 0-5 wt%, based on the total weight of the positive electrode active layer.

[0344] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry. Further, the positive electrode slurry is coated onto at least one surface of the positive current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained. Cold pressing can be performed using a cold rolling mill. The solvent in the positive electrode slurry can be, but is not limited to, any of the solvents described in the foregoing embodiments, for example, it can include N-methylpyrrolidone (NMP), and more specifically, NMP. The surface of the positive current collector coated with the positive electrode slurry can be a single surface of the positive current collector or both surfaces of the positive current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s.

[0345] In some embodiments, the positive electrode active material includes a lithium transition metal oxide active material. Further, the mass percentage of the lithium transition metal oxide active material in the positive electrode active material can be greater than or equal to 50%, but is not limited thereto. When coating the positive electrode slurry, the coating areal density (based on dry weight, minus solvent) (measured on both sides of the positive electrode current collector) can be (0.05 ~ 0.6) g / 1540.25 mm². 2 The optional value is (0.1~0.3) g / 1540.25 mm. 2 The compaction density of the positive electrode sheet can be 3.0 g / cm³. 3 ~ 4.2 g / cm 3 The option is 3.3 g / cm³. 3 ~ 3.8 g / cm 3 .

[0346] The term "compacted density" as used in this application has a meaning known in the art and is one of the reference indicators for the energy density of materials. In this application, unless otherwise specified, the compacted density of the positive electrode refers to the ratio of the mass of the positive electrode active layer to its volume, and the compacted density of the negative electrode refers to the ratio of the mass of the negative electrode active layer to its volume.

[0347] The following are some other descriptions of the negative electrode plate.

[0348] The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, the negative active layer including a negative active material.

[0349] Without limitation, the weight percentage of the negative electrode active material in the negative electrode active layer may be greater than or equal to 80 wt%, and may further be greater than or equal to 90 wt%.

[0350] As a non-limiting example, the negative electrode current collector has two surfaces that are opposite to each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0351] 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. In the negative electrode current collector, 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. In the negative electrode current collector, the composite current collector may be formed by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limitingly, in the negative electrode current collector, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0352] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials or substances, 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.

[0353] In some embodiments, the negative electrode active layer optionally includes a binder. Non-limitingly, the binder may include one or more 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). Non-limitingly, the weight percentage of the binder in the negative electrode active layer may be 0 wt% to 20 wt%, more further 0 wt% to 10 wt%, even further 0 to 5 wt%, even further 1 wt% to 5 wt%, and even more preferably 1 wt% to 3 wt%.

[0354] For further information on the types of negative electrode active materials, please refer to the context of this application.

[0355] In some embodiments, the negative electrode active layer optionally includes a conductive agent. Non-limitingly, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Non-limitingly, the weight percentage of the conductive agent in the negative electrode active layer may be 0 wt% to 15 wt%, more preferably 0 wt% to 10 wt%, and even more preferably 0 wt% to 5 wt%.

[0356] In some embodiments, the negative electrode active layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). Without limitation, the weight percentage of other additives in the negative electrode active layer may be 0 wt% to 15 wt%, more preferably 0 wt% to 10 wt%, even more preferably 0 wt% to 5 wt%, even more preferably 0 wt% to 3 wt%, and even more preferably 0 wt% to 2 wt%.

[0357] 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 (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry. Further, the negative electrode slurry is coated onto at least one surface of the negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained. Cold pressing can be performed using a cold rolling mill. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 30 wt% to 70 wt%, optionally 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s, optionally 3000 mPa·s to 10000 mPa·s. The compacted density of the negative electrode sheet can be 1.0 g / cm³. 3 ~ 2.0 g / cm 3 1.0 g / cm³ is an optional value. 3 ~ 1.8 g / cm 3 .

[0358] The electrolyte is described below as an example.

[0359] The electrolyte serves to conduct ions between the positive and negative electrodes. The electrolyte consists of an electrolyte salt and a solvent.

[0360] In some embodiments, the electrolyte is a non-aqueous electrolyte. A non-aqueous electrolyte may include an electrolyte salt and a non-aqueous solvent.

[0361] For the description of non-aqueous solvent electrolyte salts in the electrolyte, please refer to the context of this application.

[0362] In some embodiments, the electrolyte salt includes an electrolyte lithium salt, and more particularly, it can be an electrolyte lithium salt. Non-limitingly, other types of electrolyte salts may also be introduced into the electrolyte.

[0363] In some embodiments, the molar volume concentration of the electrolyte salt in the electrolyte is typically 0.5 mol / L to 5 mol / L, optionally 0.6 mol / L to 1.8 mol / L, optionally 0.7 mol / L to 1.2 mol / L, or any of the following concentrations or a range selected from any two of the following concentrations: 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, etc.

[0364] Non-limitingly, the electrolyte includes an electrolyte lithium salt, which may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0365] In some embodiments, the electrolyte includes one or both of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and in some of these embodiments, the electrolyte includes at least lithium hexafluorophosphate.

[0366] In some embodiments, the molar volume concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 0~0.5 mol / L, optionally 0.01 mol / L~0.5 mol / L, or any of the following concentrations or a range selected from any two of the following concentrations: 0 mol / L, 0.01 mol / L, 0.02 mol / L, 0.025 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.075 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.12 mol / L, 0.14 mol / L, 0.15 mol / L, 0.16 mol / L, 0.18 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L. mol / L, 0.35mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, etc.

[0367] In some embodiments, the electrolyte includes lithium bis(fluorosulfonyl)imide (LiFSI). Lithium bis(fluorosulfonyl)imide can function as both a film-forming additive and an electrolyte salt in the electrolyte. Non-limitingly, the molar volume concentration of lithium bis(fluorosulfonyl)imide in the electrolyte can be from 0.01 mol / L to 0.5 mol / L, optionally from 0.01 mol / L to 0.3 mol / L, or any of the following concentrations or a range selected from any two of the following concentrations: 0.01 mol / L, 0.02 mol / L, 0.025 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.075 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.12 mol / L, 0.14 mol / L, 0.15 mol / L, 0.16 mol / L, 0.18 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L. mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5mol / L, etc.

[0368] In some embodiments, the electrolyte comprises lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Non-limitingly, the molar volume concentration of lithium bis(fluorosulfonyl)imide in the electrolyte may be greater than 0 mol / L and less than or equal to 0.5 mol / L, optionally from 0.01 mol / L to 0.5 mol / L, or may be selected from any suitable range or value in the context of any of the embodiments described above.

[0369] Lithium bisfluorosulfonylimide (LiFSI) can participate in the formation of a stable solid electrolyte interfacial film at both the positive and negative electrodes. On the one hand, the stability of the positive and negative electrode interfacial film can be improved by introducing LiFSI into the electrolyte; on the other hand, LiFSI has a better ability to dissociate lithium ions than lithium hexafluorophosphate (LiPF6), so the addition of LiFSI is also beneficial to improving the liquid phase conductivity.

[0370] The types of non-aqueous solvents in the electrolyte can be described in the context of this application. Non-limitingly, other types of non-aqueous solvents may also be introduced into the electrolyte. In some embodiments, the non-aqueous solvent may include ethylene carbonate (EC). ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), ), propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0371] The electrolyte includes additives, including at least the aforementioned acetylene additives (which may be referred to as the first additive).

[0372] The types of additives in the electrolyte can be found in the description within the context of this application. Without limitation, other types of additives may also be introduced into the electrolyte. These other types of additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance characteristics, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0373] In some embodiments, the additives in the electrolyte include a second additive. In this application, unless otherwise specified, "second additive" refers to a negative electrode film-forming additive that is different from alkyne additives. "Negative electrode film-forming additive" refers to an additive capable of decomposing at the negative electrode operating potential and participating in the formation of the negative electrode SEI film. The higher the reduction potential of the negative electrode film-forming additive, that is, the more positive the potential value relative to Li / Li⁺, the earlier the negative electrode film-forming additive decomposes and thus participates in the formation of the negative electrode SEI film. It is understood that some negative electrode film-forming additives can also participate in the formation of an interface film (CEI film) at the positive electrode. Typically, those skilled in the art can determine whether an additive can participate in the formation of the negative electrode SEI film based on methods such as reduction potential analysis, analysis of decomposition products and SEI film composition, and verification of electrochemical performance. For example, the reduction potential of the additive can be measured in a simulated battery environment (such as a lithium metal-pair working electrode) using cyclic voltammetry. For example, the composition of the SEI film can be analyzed using chemical composition analysis methods including but not limited to X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). For example, the change in performance indicators such as initial coulombic efficiency, cycle stability, and impedance spectrum when the additive is introduced can be used to determine whether an introduced additive can participate in the formation of the negative electrode SEI film.

[0374] In some embodiments, the second additive includes one or more of lithium salt additives, phosphate ester additives, vinylene carbonate, fluorocarbonate additives (such as fluoroethylene carbonate), saturated sulpholactones, cyclic sulfates, etc.

[0375] Non-limitingly, the mass ratio of the second additive to the acetylene additive can be greater than 0 and less than or equal to 100, greater than 0 and less than or equal to 50, or 0.1 to 100, optionally 0.3 to 50, further optionally 0.3 to 20, or 0.08 to 100, optionally 0.08 to 50, further optionally 0.08 to 20, or any of the following values ​​or a range selected from any two of the following values: 0.05, 0.08, 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, 1, 2, 3, 4, 5, 6, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, etc.

[0376] In some embodiments, the additives in the electrolyte include cyclic sulfates.

[0377] In this application, "cyclic sulfate" contains one or more monocyclic sulfate units, and "monocyclic sulfate unit" contains *-OS(=O)2-O-*, where each * independently represents a bonding site with a carbon atom.

[0378] In some embodiments, the additive includes a polycyclic sulfate ester, which contains a plurality of monocyclic sulfate ester units.

[0379] In some embodiments, the multiple monocyclic sulfate units in the polycyclic sulfate ester are linked in a chain-like manner.

[0380] In some embodiments, the number of monocyclic sulfate units in the polycyclic sulfate ester is 2 to 4, and may further be 2, 3 or 4.

[0381] In some embodiments, the monocyclic sulfate unit is a 5- to 7-membered monocyclic ring, which can be a 5-membered ring, a 6-membered ring, or a 7-membered ring, and more specifically, a 5-membered ring or a 6-membered ring.

[0382] In some embodiments, the monocyclic ring in the monocyclic sulfate unit is replaced by 0, 1, or more substituents Q3, each of which is independently a halogen, C, or C. 1-3 Alkyl or C 1-3 Alkoxy group. Optionally, the substituent Q3 in the monocyclic sulfate unit is each independently a fluorine atom, a methyl group, or a methoxy group.

[0383] By introducing cyclic sulfates into the electrolyte, the negative electrode interface film can be optimized, the stability of the negative electrode SEI film can be improved, the negative electrode interface side reactions can be reduced, and the negative electrode interface impedance and battery internal resistance can be better controlled.

[0384] In some embodiments, the additives in the electrolyte include vinyl sulfate.

[0385] In some embodiments, the additives in the electrolyte include vinylene carbonate (VC). Vinylene carbonate (VC) can optimize the SEI film. By introducing VC into the electrolyte, it is beneficial to reduce or delay the consumption of the negative electrode film by alkyne additives, and to better control the charge transfer impedance of the negative electrode surface and the internal resistance of the battery.

[0386] In some embodiments, the additives in the electrolyte include fluoroethylene carbonate (FEC). Fluoroethylene carbonate (FEC) can form a robust interfacial film with low ion transport impedance on the negative electrode surface at room temperature. By introducing fluorocarbonate additives (such as FEC) into the electrolyte, it is beneficial to reduce or delay the consumption of acetylene additives in the negative electrode film formation, and to better control the negative electrode interfacial impedance and battery internal resistance.

[0387] The following is an exemplary description of the separator membrane.

[0388] In some embodiments, the lithium-ion secondary battery cell 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.

[0389] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation.

[0390] In some embodiments, the thickness of the separator is 6 μm to 40 μm, optionally 6 μm to 20 μm.

[0391] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0392] In some embodiments, the lithium-ion secondary battery cell may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0393] In some embodiments, the outer packaging of a lithium-ion secondary battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of a lithium-ion secondary battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0394] One aspect of this application also provides a lithium-ion secondary battery. The lithium-ion secondary battery includes at least one battery cell. The lithium-ion secondary battery may include one or more battery cells. Further, the battery cell is a lithium-ion secondary battery cell.

[0395] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0396] In some embodiments, the structure of a lithium-ion secondary battery cell can be found in [reference needed]. Figure 1 and Figure 2 .

[0397] In some of these implementations, reference is made to... Figure 2The outer packaging may include a battery casing 51 and a cover plate 53. The battery casing 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 battery casing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, and a separator can be formed into electrode assemblies 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to actual needs. In some embodiments, the electrolyte injection coefficient is greater than or equal to 1.6 g / Ah.

[0398] The lithium-ion secondary battery can be a battery device 4 or a battery pack 1.

[0399] The battery device includes at least one battery cell, which is a lithium-ion rechargeable battery cell. The battery device may contain one or more battery cells, and those skilled in the art can select an appropriate number based on the application and capacity of the battery device.

[0400] Figure 3 This is battery device 4, used as an example. (See reference...) Figure 3 In the battery assembly 4, multiple battery cells 5 can be arranged sequentially along the length of the battery assembly 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0401] Optionally, the battery device 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0402] In some embodiments, the battery devices described above can also be assembled into a battery pack, and the number of battery devices contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0403] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery devices 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 devices 4. The multiple battery devices 4 can be arranged in any manner within the battery box.

[0404] In a second aspect of this application, a method for preparing a lithium-ion secondary battery is provided, which can be used to prepare the lithium-ion secondary battery of the first aspect of this application.

[0405] In some embodiments, a method for preparing a lithium-ion secondary battery is provided, which includes the following steps: immersing an electrode assembly, including a positive electrode, a separator, and a negative electrode, in an electrolyte to form a battery.

[0406] According to some embodiments of the second aspect of this application, a method for preparing a lithium-ion secondary battery cell is provided, which includes the following steps:

[0407] S100: An electrode assembly including a positive electrode and a negative electrode is placed inside a battery casing; wherein a separator is provided between the positive electrode and the negative electrode; wherein the negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer includes a negative active material, the negative active material includes a graphite-based material, optionally, the mass percentage of the graphite-based material in the negative active material can be 60% to 100%, and suitable values ​​or ranges can also be referred to the first aspect of this application; the thickness of the negative active layer on one side of the negative current collector is less than or equal to 55 μm, and the D of the negative active material is... v 50 has a thickness of 3μm to 15μm;

[0408] S200: Injecting electrolyte into the battery casing, allowing it to stand to wet the positive and negative electrode plates, thus forming the battery; wherein the electrolyte includes an electrolyte salt, a non-aqueous solvent, and additives; the additives include acetylene additives, which are compounds containing carbon-carbon triple bonds; the acetylene additives include one or more of a first acetylene compound and a second acetylene compound; optionally, the sum of the mass percentages of the first acetylene compound and the second acetylene compound in the acetylene additives is 75% to 100%, and suitable values ​​or ranges may also be referred to the first aspect of this application.

[0409] The definitions of the first and second alkynyl compounds can be found in the first aspect of this application.

[0410] For example, the first alkynyl compound consists of a carbon-carbon triple bond, a C-carbon triple bond, and a C-carbon triple bond connected in sequence. 1-3 It consists of an alkylene group and -OC(=O)-R1, where R1 is a Lewis base nitrogen heterocycle.

[0411] For example, the second alkynyl compound consists of a carbon-carbon triple bond, C, and C bonds connected in sequence. 1-3 It consists of an alkylene group and -OC(=O)-O-R2, where R2 is an alkyl group, which can be C. 1-3 alkyl.

[0412] The prepared lithium-ion secondary battery has the advantages of the lithium-ion secondary battery described in the first aspect of this application.

[0413] In some embodiments, in step 200, after injecting electrolyte into the battery casing, a lithium-ion secondary battery assembly is obtained.

[0414] In some implementations, the lithium-ion secondary battery assembly may correspond to the state before formation treatment.

[0415] The formation temperature can be 45°C, but is not limited to this.

[0416] In some embodiments, the formation can be performed at 45°C using a method comprising the following steps (steps S1, S2, S3, and S4 are performed sequentially):

[0417] S1) Charge at 0.05C for 14 minutes to 3V, then let stand for 10 minutes;

[0418] S2) Charge to 3.4V at 0.1C and let stand for 10 minutes;

[0419] S3) Charge to 3.65V at 0.2C and let stand for 10 minutes;

[0420] S4) Charge to 3.75V at 0.2C and let stand for 10 minutes;

[0421] The transformation ends.

[0422] In this application, the concentrations of additives and electrolyte salts involved in "injecting electrolyte into the battery casing" correspond to the "initial concentrations," which can respectively correspond to the initial mass percentage of the additives in the electrolyte and the initial molar volume concentration of the electrolyte salts in the electrolyte.

[0423] In some embodiments, during the step of injecting electrolyte into the battery casing, the initial mass percentage of the acetylene additive in the electrolyte is 0.1% to 5%, optionally 0.1% to 3%, and may also be any of the following percentages or a range selected from any two of the following percentages: 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.6%, 0.75%, 0.8%, 0.9%, 1%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0424] The alkyne additives involved in this application are commercially available or synthesized using existing methods in the field of organic chemical synthesis. Once the structural formula of the alkyne additive is selected, those skilled in the art can choose a suitable organic synthesis method to prepare the target compound; furthermore, those skilled in the art can also identify the structure of the prepared alkyne additives using one or more of the following detection methods, including but not limited to: 1H NMR spectroscopy (…). 1 Methods include 1H NMR, high performance liquid chromatography (HPLC), matrix-assisted laser desorption / ionization mass spectrometry (MADI-TOF), and Fourier transform infrared (FT-IR) spectroscopy.

[0425] In some embodiments, the initial mass percentage of the chain carboxylic acid ester in the electrolyte is 10% to 30%, optionally 20% to 4%, and further optionally 20% to 30%.

[0426] In some embodiments, the initial mass percentage of dimethyl carbonate in the electrolyte is greater than or equal to 20%, and can be selected as 20% to 40%.

[0427] In some embodiments, the initial mass percentage of the lithium salt additive in the electrolyte is 0.3% to 3%. Non-limitingly, the lithium salt additive may include one or more of lithium oxalate salts, lithium tetrafluoroborate, lithium difluorophosphate, and fluorosulfonic acid lithium salts; lithium oxalate salts may include one or more of lithium difluorooxalateborate (LiDFOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP); fluorosulfonic acid lithium salts may include one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0428] In some implementations, the initial mass percentage of lithium difluorophosphate in the electrolyte is 0.1% to 1%.

[0429] In some implementations, the initial mass percentage of LiDFOB in the electrolyte is 0.05% to 1%.

[0430] In some embodiments, the initial mass percentage of the phosphate ester additive in the electrolyte is 0.1% to 1%. Without limitation, the phosphate ester additive may include silicon-based phosphate ester additives; silicon-based phosphate ester additives may include one or more of tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilyl) phosphite (TMSPi), etc.

[0431] In some implementations, the initial mass percentage of TMSP in the electrolyte is 0.1% to 0.3%.

[0432] In some embodiments, the initial mass percentage of the cyclic sulfate in the electrolyte is 0.1% to 2%. The cyclic sulfate may be vinyl sulfate (DTD).

[0433] In some embodiments, the initial mass percentage of vinylene carbonate (VC) in the electrolyte is 0.1% to 3%.

[0434] In some embodiments, the initial mass percentage of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 3%.

[0435] In some embodiments, the initial molar volume concentration of lithium bis(fluorosulfonyl)imide (LiFSI) in the electrolyte is 0.01 mol / L to 0.5 mol / L.

[0436] Those skilled in the art will understand that the content of some additive components in the electrolyte may change after formation treatment. As a non-limiting example, for instance, the content of some film-forming additive components decreases due to their participation in the formation of the solid electrolyte interface film of the positive and / or negative electrodes. As a non-limiting example, the content of alkyne additives in the electrolyte typically decreases after formation treatment compared to the electrolyte before formation treatment.

[0437] In some embodiments, after formation treatment, the content of each additive in the prepared lithium-ion secondary battery can be referred to the first aspect of this application.

[0438] In lithium-ion secondary battery components, the types of electrolyte salts and non-aqueous solvents in the electrolyte are described in the first aspect of this application. After formation treatment, the mass ratios of both electrolyte salts and solvents in the electrolyte may change.

[0439] In lithium-ion secondary battery modules, the material composition and dimensions of the positive electrode, negative electrode, and separator can be found in the first aspect of this application. The dimensions of the positive electrode, negative electrode, and separator in the lithium-ion secondary battery module may differ somewhat from those in the lithium-ion secondary battery of the first aspect.

[0440] In some embodiments, the lithium-ion secondary battery cell described in the first aspect of this application is prepared.

[0441] In some embodiments, the positive electrode active material in the prepared lithium-ion secondary battery includes a lithium nickel-based oxide positive electrode material, which contains Li, non-lithium metal elements and O, and the non-lithium metal elements include Ni.

[0442] In some embodiments, the positive electrode active material includes Li x (Ni a Cob M’ c M’’ d )O 2-e lithium nickel-based oxide, wherein, 0.6 ≤ x ≤ 1.2, 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 ≤ d < 1 (optionally, 0 < d < 1), a + b + c + d = 1, -0.4 ≤ e ≤ 0.1 (optionally, -0.2 ≤ e ≤ 0.1, further optionally, -0.1 ≤ e ≤ 0.1). M’ may include at least one of Mn and Al. M’’ may include one or more of Na, K, Ca, Ba, Sb, Ti, Zr, W, Sr, Nb, Mo, Si, Mg, B, Cr, and Ta. a can refer to the value or range of values of R Ni The value or range of values of b can be referred to, non-restrictively, as the value or range of values of R Co In some embodiments, M’ is the Mn element.

[0443] Non-restrictively, x can be any one of the following values, or selected from the range formed by any two of the following values: 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, etc.

[0444] Non-restrictively, (2 - e) can be any one of the following values, or selected from the range formed by any two of the following values: 1.6, 1.7, 1.8, 1.9, 2, 2.05, 2.06, 2.08, 2.1, etc.

[0445] According to some embodiments of the third aspect of the present application, a battery device is provided, which includes one or more of the lithium ion secondary battery monomers described in the first aspect of the present application and the lithium ion secondary battery monomers prepared by the preparation method of the lithium ion secondary battery monomers described in the second aspect of the present application;

[0446] In some embodiments, the battery device includes one or more lithium ion secondary battery monomers.

[0447] The number of lithium ion secondary batteries in the battery device can be controlled according to the capacity requirement.

[0448] In some embodiments of the fourth aspect of the present application, an electrical device is provided, which includes at least one of the lithium ion secondary battery monomers described in the first aspect of the present application, the lithium ion secondary battery monomers prepared by the preparation method of the lithium ion secondary battery monomers described in the second aspect of the present application, and the battery device described in the third aspect of the present application.

[0449] In some embodiments, the electrical device includes the lithium ion secondary battery monomers of any embodiment provided by the present application.

[0450] Lithium-ion rechargeable battery cells can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices can include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices can include, for example, mobile phones and laptops; electric vehicles can include, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric motorcycles, power tools, etc., but are not limited to these. This electrical device can also be applied to military equipment, aerospace, and other fields, and can also be applied to energy storage power systems such as hydroelectric, thermal, wind, and solar power plants.

[0451] As an electrical device, lithium-ion rechargeable battery cells can be selected according to their usage requirements.

[0452] Figure 6 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device for lithium-ion secondary batteries, a battery device or battery pack can be used.

[0453] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use lithium-ion rechargeable battery cells as their power source.

[0454] In a fifth aspect of this application, a lithium-ion secondary battery assembly is provided, which is the lithium-ion secondary battery assembly in the preparation method of the lithium-ion secondary battery described in the second aspect of this application.

[0455] The following describes some embodiments of this application. The described embodiments are only a part of the embodiments of this application, and not all of them. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application and its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0456] Unless otherwise specified in the examples, the procedures described above, or those described in the literature in this field, or those described in the product instructions, shall be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products, or products that can be synthesized using conventional methods from commercially available products.

[0457] In the following examples, room temperature refers to 20 ℃ ~ 30 ℃.

[0458] In the following examples, unless otherwise specified, the parameters involved can be confirmed by referring to the test methods described above. For example, the D parameters involving the negative electrode active material... v 50 and D v 1. A Malvern 2000 (MasterSizer 2000) laser particle size analyzer can be used for testing. The active specific surface area of ​​the negative electrode active material, as well as the single-sided thickness, porosity, tortuosity, and single-sided density of the negative electrode active layer, can all be obtained using the methods described above. For the carbon coating layer, a JEM-F200 transmission electron microscope combined with an EDS (Energy Dispersive Spectrometer) can be used for testing. For example, the ionic conductivity of the electrolyte can be tested using a DDSJ-318 conductivity meter, referring to the detection method in HG-T 4067-2015. For the various organic components in the prepared lithium-ion secondary battery, qualitative and quantitative analysis of the organic components in the electrolyte can be performed using gas chromatography, referring to the standard GB / T 9722-2023 General Rules for Gas Chromatography of Chemical Reagents.

[0459] In the following embodiments, the electrolyte salt is an example of an electrolyte lithium salt, and compound IIa is an alkyne additive as a non-limiting example.

[0460] I. Preparation of lithium-ion secondary batteries (lithium-ion secondary battery cells)

[0461] Example 1.

[0462] (1) Positive electrode plate

[0463] The positive electrode active material (NCM811), conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed uniformly in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 95:2.5:2.5 to obtain a positive electrode slurry with a solid content of 50 wt%. The positive electrode slurry was coated onto both sides of the positive electrode current collector aluminum foil, with a coating density of 0.26 g / 1540.25 mm². 2 Through processes such as drying, cold pressing, slitting, and cutting, positive electrode sheets are obtained, with a compacted density of 3.5 g / cm³. 3 .

[0464] In this example, the D of the positive electrode active material v 50 is 3μm.

[0465] (2) Negative electrode plate

[0466] A negative electrode slurry was prepared by uniformly mixing the negative electrode active material (coated graphite), conductive agent carbon black (Super P), styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) in deionized water at a weight ratio of 95:1.5:1.5:2, with a solid content of 70 wt%. The negative electrode slurry was coated on both sides of the copper foil of the negative electrode current collector (with the same coating weight on both sides), and the coating density on one side of the negative electrode current collector was 0.112 g / 1540.25 mm. 2 The negative electrode sheet is obtained through drying, cold pressing, slitting, and cutting processes. The compacted density of the negative electrode sheet is approximately 1.6 g / cm³. 3 .

[0467] In this example, the negative electrode active material is coated graphite, comprising a graphite body and a soft carbon coating layer on the surface of the graphite body. The graphite body is artificial graphite, and the soft carbon coating layer accounts for approximately 5% of the mass of the coated graphite.

[0468] In this example, the porosity of the negative electrode active layer is 20%, the tortuosity is 5, and the D of the negative electrode active material is... v 50 is 4μm, and the D of the negative electrode active material is... v The average particle size (D1) of the primary particles in the negative electrode active material is 1 μm, ranging from 0.1 μm to 1 μm, and the active specific surface area of ​​the negative electrode active material is approximately 4 m². 2 / g.

[0469] (3) Separator: Conventional PE film is used as the separator.

[0470] (4) Preparation of electrolyte: Add additives to non-aqueous solvent, mix evenly, add fully dried electrolyte lithium salt, mix thoroughly to dissolve the electrolyte lithium salt, and prepare electrolyte.

[0471] The electrolyte salt in the electrolyte is a lithium electrolyte salt, specifically lithium hexafluorophosphate, with an initial concentration of 1 mol / L. The non-aqueous solvents are EC (ethylene carbonate), DMC (dimethyl carbonate), and EMC (ethyl methyl carbonate) in a mass ratio of 2:3:5. The additives are 2-propynyl-1-yl1H-imidazolium-1-carboxylic acid ester and fluoroethylene carbonate (FEC). The structure of the alkyne additive (also referred to as the first additive) is shown in formula (IIa), and it is also designated as compound IIa. The initial mass percentage of compound IIa in the electrolyte is 3%.

[0472]

[0473] (5) Preparation of lithium-ion secondary battery: The positive electrode, separator and negative electrode are stacked and wound in sequence to obtain bare cell (electrode assembly); tabs are welded to the bare cell, and the bare cell is put into aluminum shell and baked at 80°C to remove water. Then the electrolyte is injected and sealed. Then the cell goes through the processes of standing, hot and cold pressing, formation, shaping and capacity testing to obtain lithium-ion secondary battery (lithium-ion secondary battery cell).

[0474] After injecting electrolyte, a lithium-ion secondary battery assembly is obtained.

[0475] In this example, the standing soaking parameters are: standing at room temperature for 18 hours, and then standing at 45°C for 6 hours.

[0476] In this example, the formation parameters are as follows: at 45℃,

[0477] Charge at 0.05C for 14 minutes to 3.0V, then let stand for 10 minutes;

[0478] Charge to 3.4V at 0.1C and let stand for 10 minutes;

[0479] Charge at 0.2C to 3.65V and let stand for 10 minutes;

[0480] Charge at 0.2C to 3.75V and let stand for 10 minutes;

[0481] The transformation has ended.

[0482] In this example, the lithium-ion secondary battery obtained by formation was disassembled, and the composition of the electrolyte was tested. The content of the components in the electrolyte was 1.7% by mass percentage.

[0483] In this example, the negative electrode sheet obtained after cold pressing has a single-sided thickness of 45 μm and a total thickness of 90 μm on both sides. Disassembling the prepared lithium-ion secondary battery, the negative electrode sheet was found to have a single-sided thickness of approximately 51 μm and a total thickness of approximately 102 μm for the negative electrode active layer.

[0484] Examples 2-4. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that: in the step of preparing the negative electrode sheet, the surface density of the coating on one side of the negative electrode active layer was changed, while maintaining the compaction density consistent with Example 1; the total thickness of the negative electrode active layer in the lithium-ion secondary battery after cold pressing and in the final product was also changed, with the thickness on both sides remaining essentially the same. The remaining operational steps were the same as in Example 1. See Table 1 for details.

[0485] In Example 2, the total thickness of the negative electrode active layer in the prepared lithium-ion secondary battery is 84 μm;

[0486] In Example 3, the total thickness of the negative electrode active layer in the prepared lithium-ion secondary battery was 92 μm;

[0487] In Example 4, the total thickness of the negative electrode active layer in the prepared lithium-ion secondary battery was 119 μm.

[0488] Examples 5-6. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that the compaction density was changed to adjust the porosity in the negative electrode preparation step, while maintaining the same coating surface density as in Example 1. The remaining operational steps were the same as in Example 1. The test data for the single-sided and total thickness of the negative electrode active layer, and the porosity of the negative electrode active layer in the prepared lithium-ion secondary batteries can be found in Table 1.

[0489] Examples 7-8. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that different negative electrode active materials were used in the negative electrode preparation step, and the compaction density was adjusted to control the porosity to be basically consistent with Table 1. The remaining operational steps were the same as in Example 1. The D of the negative electrode active material used... v 50. The parameter values ​​of the average particle size (D1) of the primary particles of the negative electrode active material can be found in Table 1. The test data of the single-sided thickness and total thickness of the negative electrode active layer and the porosity of the negative electrode active layer in the prepared lithium-ion secondary battery can be found in Table 1.

[0490] Examples 9-10. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that the electrolyte composition was different and the initial molar volume concentration of the lithium hexafluorophosphate electrolyte salt was changed. The remaining operational steps were the same as in Example 1. See Table 2 for details.

[0491] In Example 9, the initial molar volume concentration of lithium hexafluorophosphate in the electrolyte was 0.7 mol / L;

[0492] In Example 10, the initial molar volume concentration of lithium hexafluorophosphate in the electrolyte was 1.2 mol / L.

[0493] Examples 11-12. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that the composition of the electrolyte was different, and the initial concentration of the alkyne additive (compound IIa) in the electrolyte was different. The remaining operating steps were the same as in Example 1. See Table 2 for details.

[0494] In Example 11, the initial mass percentage of the acetylene additive (compound IIa) in the electrolyte was 0.1%.

[0495] In Example 12, the initial mass percentage of the acetylene additive (compound IIa) in the electrolyte was 5%.

[0496] Examples 13-17. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that the composition of the electrolyte and the composition of the additives in the electrolyte were different. The remaining operating steps were the same as in Example 1. See Table 2 for details.

[0497] In Example 13, the additive composition of the electrolyte, based on its initial mass percentage in the electrolyte, was: 3% of compound IIa and 0.5% of lithium difluorophosphate.

[0498] In Example 14, the additive composition of the electrolyte, based on the initial mass percentage in the electrolyte, was: 3% of compound IIa and 0.5% of LiDFOB (lithium difluorooxalate borate).

[0499] In Example 15, the additive composition of the electrolyte, based on the initial mass percentage in the electrolyte, was: 3% of compound IIa and 0.5% of TMSP (tris(trimethylsilane)phosphate).

[0500] In Example 16, the additive composition of the electrolyte, based on the initial mass percentage in the electrolyte, was: 3% of compound IIa and 0.5% of DTD (ethylene sulfate).

[0501] In Example 17, the additive composition of the electrolyte, based on its initial mass percentage in the electrolyte, was: 3% of compound IIa and 0.5% of VC (ethylene carbonate).

[0502] Example 18. A lithium-ion secondary battery was prepared using a method essentially the same as that in Example 1, except that the composition of the electrolyte, the composition of the additives in the electrolyte, and the composition of the lithium salt in the electrolyte were different. The remaining operating steps were the same as in Example 1. See Table 2 for details.

[0503] In Example 18, the additive composition of the electrolyte, based on the initial mass percentage in the electrolyte, was: 3% of compound IIa and 0.5% of FEC (fluoroethylene carbonate); the electrolyte lithium salts, based on the initial molar volume concentration in the electrolyte, were 0.3 mol / L LiFSI (lithium bis(fluorosulfonyl)imide) and 0.7 mol / L LiPF6 (lithium hexafluorophosphate).

[0504] Example 19. A lithium-ion secondary battery was prepared using essentially the same method as in Example 1, except that the composition of the electrolyte was different, and the type of alkyne additive in the electrolyte was different. The remaining operating steps were the same as in Example 1. See Table 2 for details.

[0505] In Example 19, the alkyne additive compound IIa was replaced with methylcarboxylic acid-2-propynyl ester ( ).

[0506] Comparative Example 1. A lithium-ion secondary battery was prepared using essentially the same method as in Example 1, except that the composition of the electrolyte was different, the alkyne additive was omitted from the electrolyte, and the initial concentration of the lithium salt in the electrolyte remained unchanged. The remaining operating steps were the same as in Example 1.

[0507] Comparative Example 2. A lithium-ion secondary battery was prepared using essentially the same method as in Example 17, except that the electrolyte composition was different, the alkyne additive was omitted from the electrolyte, and the initial concentrations of the remaining additives and the electrolyte lithium salt remained unchanged. The remaining operating steps were the same as in Example 17.

[0508] Comparative Example 3. A lithium-ion secondary battery was prepared using essentially the same method as in Example 18, except that the electrolyte composition was different, the alkyne additive was omitted from the electrolyte, and the initial concentrations of the remaining additives and the electrolyte lithium salt remained unchanged. The remaining operating steps were the same as in Example 18.

[0509] Comparative Example 4. A lithium-ion secondary battery was prepared using essentially the same method as in Example 19, except that the electrolyte composition was different, the alkyne additive was omitted from the electrolyte, and the initial concentration of the lithium salt remained unchanged. The remaining operating steps were the same as in Example 19.

[0510] Comparative Examples 5-6. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that: in the step of preparing the negative electrode sheet, the surface density of the coating on one side of the negative electrode active layer was changed, while maintaining the compaction density consistent with Example 1; the total thickness of the negative electrode active layer in the lithium-ion secondary battery after cold pressing and in the final product was also changed, with the thickness on both sides remaining essentially the same. The remaining operational steps were the same as in Example 1. See Table 1 for details.

[0511] In Comparative Example 5, the total thickness of the negative electrode active layer in the prepared lithium-ion secondary battery is approximately 50 μm.

[0512] In Comparative Example 6, the total thickness of the negative electrode active layer in the prepared lithium-ion secondary battery was approximately 150 μm.

[0513] Comparative Examples 7-8 used essentially the same method as Example 1 to prepare lithium-ion secondary batteries, the difference being that different negative electrode active materials were used in the negative electrode preparation step, and the D of the negative electrode active material was different. v 50. The parameter values ​​of the average particle size (D1) of the primary particles of the negative electrode active material can be found in Table 1. The test data of the single-sided thickness and total thickness of the negative electrode active layer and the porosity of the negative electrode active layer in the prepared lithium-ion secondary battery can be found in Table 1.

[0514] II. Test and Analysis Methods

[0515] (a) Battery performance testing

[0516] 1. Thickness of one side of the negative electrode active layer

[0517] Measurements were taken using a micrometer.

[0518] The thickness D of the electrode was obtained through the following testing method: disassembling the battery cell, removing the negative electrode plate, and measuring the electrode plate thickness D using a micrometer. A .

[0519] Take another negative electrode sheet, wipe away the negative electrode active layer on the side to be tested to remove the remaining empty current collector foil, and measure the thickness D. 10 The thickness of the negative electrode active layer on one side of the negative electrode current collector is D. A -D 10 .

[0520] 2. Porosity of the negative electrode active layer

[0521] (1) Pretreatment: Take an appropriate amount of sample in a 1 / 2 sample tube, heat and degas for 2 hours, and weigh the total weight after cooling to room temperature. Subtract the mass of the sample tube to obtain the sample mass. (2) Test: Put the sample tube into the workstation, cover it with a filter plug, and measure the amount of gas adsorbed on the solid surface under different adsorption pressures at a constant low temperature. Calculate the monolayer adsorption amount of the sample based on the BET multilayer adsorption theory and its formula, and then calculate the specific surface area of ​​the solid sample per unit mass. (3) Adsorbed gas: nitrogen, adsorption pressure point: 0-0.01, and test the free space yourself. Test atmosphere: high-purity liquid nitrogen atmosphere.

[0522] The apparent density, true density, and porosity of iron ore were tested using an AccuPyc II 1340 fully automatic true density tester from Micromeritics, USA, in accordance with the national standard GB / T 24586-2009.

[0523] Test method: Thirty small circular pieces with a diameter of 14 mm were cut from the negative electrode sheet. Based on the principle of gas adsorption, helium gas was used as the medium to test the true volume of the 30 small circular pieces with a diameter of 14 mm. Then, the porosity of the negative electrode active layer was calculated based on the relationship between the apparent volume and the true volume of the negative electrode sheet obtained from the area, thickness and number of small circular pieces.

[0524] (III) Battery performance testing

[0525] 1. Battery DCR Test

[0526] Initial DC internal resistance (DCR0)

[0527] At 25℃, the battery under test was charged at a constant current of 1C to 3.65V, and then charged at a constant voltage until the current was 0.05C. The battery was then discharged at a constant current of 0.5C for 1 hour, and the battery was adjusted to 50% SOC. The voltage of the battery at this time was recorded as U1. The battery was then discharged at a constant current of 4C for 30 seconds, and the voltage at the end of the discharge was recorded as U2, using a sampling time of 0.1 seconds. The initial DCR of the battery is represented by the discharge DCR at 50% SOC. The initial DCR of the battery is calculated as (U1-U2) / I, where I is the current value corresponding to 4C.

[0528] The test results can be found in Table 3 under "Battery DCR0".

[0529] 2. Room temperature cycling performance

[0530] Test procedure: 25℃, 1C / 1C cycle, voltage range 2.5V~3.65V, capacity retention is measured after 600 cycles.

[0531] Detailed steps: At 25℃, charge the battery under test to 3.65V at a constant current of 1C, then charge it to a cutoff current of 0.05C at a constant voltage of 3.65V, let it rest for 10 minutes, and then discharge it to 2.5V at a constant current of 1C, let it rest for 5 minutes. This constitutes one charge-discharge cycle. Record the discharge capacity at this point as C0. Repeat this charge-discharge cycle for the same battery, recording the discharge capacity C of the 1st cycle, 2nd cycle, ..., nth cycle. n The number of cycles must be at least 600.

[0532] Record the battery's cycle capacity retention rate P600 = C after 600 cycles. 600 / C0×100%.

[0533] The test results can be found in Table 3, "Capacity Retention Rate after 600 Cycles at Room Temperature". The higher the test value, the better the cycle life at room temperature.

[0534] 3. High-temperature cycling performance (65℃)

[0535] Test procedure: 65℃, 1C / 1C cycle, voltage range is 2.5V~3.65V, capacity retention is measured after 600 cycles.

[0536] Detailed steps: At 65℃, charge the battery under test to 3.65V at a constant current of 1C, then charge it to a cutoff current of 0.05C at a constant voltage of 3.65V. Let it rest for 10 minutes, then discharge it to 2.5V at a constant current of 1C, and let it rest for 5 minutes. This constitutes one charge-discharge cycle. Record the discharge capacity at this point as C0. Repeat this charge-discharge cycle for the same battery, recording the discharge capacity C of the 1st cycle, 2nd cycle, ..., nth cycle. n The number of cycles must be at least 600.

[0537] Record the battery's cycle capacity retention rate P600 = C after 600 cycles. 600 / C0×100%.

[0538] The test results can be found in Table 3, "Capacity Retention Rate After 600 Cycles at 65°C". A higher test value indicates a better high-temperature cycle life.

[0539] III. Test Analysis Results

[0540] Table 1.

[0541]

[0542] Table 2.

[0543]

[0544] Table 3.

[0545]

[0546] The ionic conductivity of the electrolytes in Examples 1-19 at 25°C is greater than or equal to 9 mS / cm, and is within the range of 9 mS / cm to 20 mS / cm.

[0547] In Examples 1-19, the tortuosity of the negative electrode sheet is in the range of 4 to 6. The tortuosity of Examples 1, 7, and 8 is 5, 1.2, and 5.7, respectively.

[0548] In Examples 1-19, the active specific surface area of ​​the negative electrode active material is all above 2m². 2 / g~6m 2 Within the range of / g, the active specific surface areas of Examples 1, 7, and 8 are 4m², respectively. 2 / g, 5.8m 2 / g and 2.2m 2 / g.

[0549] In Examples 1-19, the Dv1 of the negative electrode active material is greater than or equal to 1 μm.

[0550] In Examples 1-19, the average particle size (D1) of the primary particles of the negative electrode active material is in the range of 0.1 μm to 2 μm, while in Example 1 it is in the range of 0.1 μm to 1 μm.

[0551] In the lithium-ion secondary batteries prepared by formation, the electrolyte composition was tested by disassembling the cells: the mass percentage of alkyne additives in the electrolytes of Examples 1-19 was in the range of 0.01% to 3.2%. After formation, the mass percentage of alkyne additives in the electrolyte of Example 1 was about 1.7% (initial concentration before formation was 3%), the mass percentage of alkyne additives in the electrolyte of Example 11 was about 0.02% (initial concentration before formation was 0.1%), and the mass percentage of alkyne additives in the electrolyte of Example 12 was about 3% (initial concentration before formation was 5%). The mass percentage of various secondary additives in the electrolytes of Examples 13-18 decreased to varying degrees and all still had residues.

[0552] The lithium-ion secondary batteries prepared in Examples 1-19 all exhibit good high-temperature performance while significantly improving room-temperature performance.

[0553] In Comparative Examples 1-4, omitting the alkyne additives in the electrolyte resulted in a significant deterioration in both high-temperature and room-temperature performance.

[0554] Comparative Examples 5-6 showed that changing the thickness of the negative electrode active layer significantly deteriorated both high-temperature and room-temperature performance.

[0555] Comparative Examples 7-8: Changing the D of the negative electrode active material v 50. Both high-temperature and room-temperature performance deteriorated significantly. The capacity retention rate after 600 cycles at room temperature was less than 85%, and the capacity retention rate after 600 cycles at 65°C was less than 70%.

[0556] The descriptions of the various implementation methods and embodiments above tend to emphasize the differences between them. Similarities or resemblances can be referenced interchangeably, and for the sake of brevity, they will not be repeated here. The technical features of the implementation methods and embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combinations of these technical features do not contradict each other, they should be considered within the scope of this specification.

[0557] It should be noted that this application is not limited to the above-described embodiments and examples. The above-described embodiments and examples are merely examples, and any embodiments and examples that have the same structure and achieve the same effect as the technical concept within the scope of this application are included in the technical scope of this application. The embodiments and examples described above only illustrate several embodiments and examples of this application, and although the descriptions are relatively detailed, they should not be construed as limiting the scope of the patent. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments or examples, and other ways of constructing embodiments or examples by combining some of the constituent elements of the embodiments or examples, are also included in the scope of this application without departing from the spirit of this application.

Claims

1. A lithium-ion secondary battery cell, characterized in that, The device includes a positive electrode, a negative electrode, and an electrolyte, with a separator between the positive and negative electrode. The negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector. The negative active layer includes a negative active material. The negative active material includes a graphite-based material, and the graphite-based material accounts for 60% to 100% of the total mass of the negative active material. The electrolyte comprises an electrolyte salt, a non-aqueous solvent, and additives; the additives include acetylene additives, which are compounds containing carbon-carbon triple bonds; the acetylene additives include one or more of a first acetylene compound and a second acetylene compound; wherein the first acetylene compound consists of a carbon-carbon triple bond, a carbon-carbon triple bond, and a carbon-carbon triple bond connected in sequence. 1-3 The second alkynyl compound consists of an alkylene group and -OC(=O)-R1, where R1 is a Lewis base nitrogen heterocycle; the second alkynyl compound consists of a carbon-carbon triple bond, C, and C bonds connected sequentially. 1-3 The structure consists of an alkylene group and -OC(=O)-O-R2, where R2 is C. 1-3 Alkyl group; the sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 75% to 100%; The thickness of the negative electrode active layer on one side of the negative electrode current collector is 40 μm to 60 μm, and the D of the negative electrode active material is... v 50 is 3μm~7μm, and the average particle size of the primary particles in the negative electrode active material is 0.1μm~2μm; the negative electrode active material includes a coated negative electrode material, which includes a negative electrode active body and a carbon coating layer located on the negative electrode active body, including at least a portion thereof.

2. The lithium-ion secondary battery cell according to claim 1, characterized in that, The thickness of the negative electrode active layer on one side of the negative electrode current collector is 40μm~55μm.

3. The lithium-ion secondary battery cell according to claim 1, characterized in that, The thickness of the negative electrode active layer on one side of the negative electrode current collector is 45μm~55μm.

4. The lithium-ion secondary battery cell according to claim 1, characterized in that, The negative electrode active material D v 50 is 3.5μm~6μm; and / or, the average particle size of the primary particles in the negative electrode active material is 0.1μm~1.6μm.

5. The lithium-ion secondary battery cell according to claim 1, characterized in that, The tortuosity of the negative electrode active layer is denoted as τ, where 4≤τ≤6.

6. The lithium-ion secondary battery cell according to claim 1, characterized in that, The negative electrode sheet satisfies one or more of the following characteristics: (a1) The mass percentage of the coated negative electrode material in the negative electrode active material is 80%~100%; (a2) The coated negative electrode material includes coated graphite, and the negative electrode active body in the coated graphite includes a graphite body.

7. The lithium-ion secondary battery cell according to claim 6, characterized in that, The coated graphite accounts for 80% to 100% of the mass of the negative electrode active material.

8. The lithium-ion secondary battery cell according to any one of claims 1 to 7, characterized in that, The porosity of the negative electrode active layer is 14%~26%.

9. The lithium-ion secondary battery cell according to claim 8, characterized in that, The porosity of the negative electrode active layer is 18%~22%.

10. The lithium-ion secondary battery cell according to any one of claims 1 to 7, characterized in that, The additive also includes additive B, which is one or more of lithium salt additives and phosphate ester additives, and the mass ratio of additive B to the acetylene additive is 0.1 to 100.

11. The lithium-ion secondary battery cell according to claim 10, characterized in that, The electrolyte satisfies one or more of the following characteristics: (b1) The mass ratio of additive B to the acetylene additive is 0.3 to 50; (b2) The lithium salt additive includes one or more of the following: lithium oxalate, lithium tetrafluoroborate, lithium difluorophosphate, lithium fluorosulfonic acid, and lithium perchlorate; the lithium oxalate includes one or more of the following: lithium difluorooxalateborate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, and lithium bis(oxalateborate); the lithium fluorosulfonic acid includes one or more of the following: lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonate. (b3) The phosphate ester additives include one or more of silicon-based phosphate ester additives and alkyl phosphonate additives; the silicon-based phosphate ester additives include one or more of tris(trimethylsilane) phosphate and tris(trimethylsilyl) phosphite; (b4) The additives include lithium salt additives, wherein the mass percentage of the lithium salt additives in the electrolyte is greater than 0 and less than or equal to 3%; (b5) The additives include phosphate ester additives, wherein the mass percentage of the phosphate ester additives in the electrolyte is greater than 0 and less than or equal to 1%.

12. The lithium-ion secondary battery cell according to any one of claims 1 to 7, characterized in that, The negative electrode sheet satisfies one or more of the following characteristics: (c1) The negative electrode active material includes a silicon-based material, wherein the mass percentage of the silicon-based material in the negative electrode active material is less than or equal to 3%; (c2) The negative electrode active material includes a silicon-based material, which includes a silicon-carbon composite material. The silicon-carbon composite material includes a porous carbon matrix and elemental silicon located within the pores of the porous carbon matrix. The silicon-carbon composite material accounts for 80% to 100% of the mass of the silicon-based material. (c3) The graphite-based material accounts for 80% to 100% of the mass of the negative electrode active material.

13. The lithium-ion secondary battery cell according to any one of claims 1, 2, 4 to 7, characterized in that, The positive electrode includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a positive active material, which includes a lithium transition metal oxide positive electrode material. The thickness of the positive active layer on one side of the positive current collector is less than or equal to 50 μm.

14. The lithium-ion secondary battery cell according to claim 13, characterized in that, The positive electrode active material includes a lithium nickel-based oxide positive electrode material, which comprises lithium, non-lithium metal elements, and oxygen; wherein the non-lithium metal elements include nickel; in the lithium nickel-based oxide positive electrode material, the ratio of the atomic molar ratio of nickel to the sum of the atomic molar ratios of the non-lithium metal elements is denoted as R. Ni ; R Ni ≥0.8, the thickness of the positive electrode active layer on one side of the positive electrode current collector is 40μm~50μm.

15. The lithium-ion secondary battery cell according to any one of claims 1 to 7, characterized in that, The acetylene additive accounts for 0.1% to 3.2% of the mass of the electrolyte.

16. The lithium-ion secondary battery cell according to claim 15, characterized in that, The acetylene additive accounts for 1% to 1.8% of the mass of the electrolyte.

17. The lithium-ion secondary battery cell according to claim 15, characterized in that, The lithium-ion secondary battery cell satisfies one or more of the following characteristics: (d1) The positive electrode sheet includes a positive active layer, the positive active layer includes a positive active material, and the positive active material includes a lithium transition metal oxide positive electrode material; (d2) The negative electrode active material includes a silicon-based material, wherein the mass percentage of the silicon-based material in the negative electrode active material is less than or equal to 3%; the acetylene additive includes the first acetylene compound; (d3) The mass percentage of the alkyne additive in the electrolyte is 0.2% to 1.8%.

18. The lithium-ion secondary battery cell according to any one of claims 1 to 7, characterized in that, The electrolyte satisfies one or more of the following characteristics: (e1) The molecular weight of the alkyne additive is less than or equal to 500 Da; (e2) The carbon-carbon triple bond in the alkyne additive is CH≡C-; (e3) The sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 80% to 100%; (e4) The first alkynyl compound accounts for 80% to 100% of the mass of the alkynyl additive; (e5) The mass percentage of the alkyne additive in the electrolyte is 0.2% to 3.2%.

19. The lithium-ion secondary battery cell according to claim 18, characterized in that, The electrolyte satisfies one or more of the following characteristics: (f1) The molecular weight of the alkyne additive is less than or equal to 300 Da; (f2) The Lewis base nitrogen heterocycle is a substituted or unsubstituted imidazole group, wherein the imidazole ring in the substituted or unsubstituted imidazole group is substituted by 0, 1 or more substituents Q2, and each substituent Q2 in the substituted imidazole group is independently C 1-3 Alkyl, cyano, or fluorine atom; (f3) The sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 90% to 100%; (f4) The first alkynyl compound accounts for 90% to 100% of the mass of the alkynyl additive; (f5) The mass percentage of the alkyne additive in the electrolyte is 0.5% to 1.8%.

20. The lithium-ion secondary battery cell according to claim 18, characterized in that, The alkyne additives include one or more of compounds II and III; The structure of compound II is as follows: Among them, L 11 C 1-3 Alkylene, Q2 is independently C 1-3 Alkyl, cyano, or fluorine atom, p2 is 0, 1, 2, or 3; The structure of compound III is as follows: Among them, L 21 C 1-3 Alkylene, R2 is C 1-3 alkyl.

21. A method for preparing a lithium-ion secondary battery cell, characterized in that, Includes the following steps: An electrode assembly including a positive electrode and a negative electrode is placed inside a battery casing; wherein a separator is disposed between the positive electrode and the negative electrode; wherein the negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer includes a negative active material, the negative active material includes a graphite-based material, and the graphite-based material accounts for 60% to 100% of the mass of the negative active material; An electrolyte is injected into the battery casing, and the mixture is allowed to stand to allow the electrolyte to wet the positive and negative electrode plates, thus forming the battery. The electrolyte comprises an electrolyte salt, a non-aqueous solvent, and additives. The additives include alkyne additives, which are compounds containing carbon-carbon triple bonds. The alkyne additives include one or more of a first alkyne compound and a second alkyne compound. The first alkyne compound consists of a carbon-carbon triple bond, a carbon-carbon triple bond, and a carbon-carbon triple bond connected sequentially. 1-3 The second alkynyl compound consists of an alkylene group and -OC(=O)-R1, where R1 is a Lewis base nitrogen heterocycle; the second alkynyl compound consists of a carbon-carbon triple bond, C, and C bonds connected sequentially. 1-3 The structure consists of an alkylene group and -OC(=O)-O-R2, where R2 is C. 1-3 Alkyl group; the sum of the mass percentages of the first alkynyl compound and the second alkynyl compound in the alkynyl additive is 75% to 100%; In the prepared lithium-ion secondary battery cell, the thickness of the negative electrode active layer on one side of the negative electrode current collector is 40 μm to 60 μm, and the D of the negative electrode active material is... v 50 is 3μm~7μm, and the average particle size of the primary particles in the negative electrode active material is 0.1μm~2μm; the negative electrode active material includes a coated negative electrode material, the coated negative electrode material includes a negative electrode active body and a carbon coating layer located on the negative electrode active body, including at least a portion thereof; the carbon coating layer in the coated negative electrode material includes one or more of soft carbon, hard carbon and amorphous carbon.

22. The method for preparing a lithium-ion secondary battery cell according to claim 21, characterized in that, In the step of injecting electrolyte into the battery casing, the initial mass percentage of the acetylene additive in the electrolyte is 1% to 5%.

23. The method for preparing a lithium-ion secondary battery cell according to claim 21, characterized in that, Prepare a lithium-ion secondary battery cell according to any one of claims 2 to 20; and / or, In the step of injecting electrolyte into the battery casing, the initial mass percentage of the alkyne additive in the electrolyte is 1.4% to 3.5%.

24. A battery device, characterized in that, Includes one or more of the lithium-ion secondary battery cells according to any one of claims 1 to 20 and the lithium-ion secondary battery cells prepared by the preparation method of the lithium-ion secondary battery cells according to claim 22 or 23. The battery device includes one or more of the aforementioned lithium-ion secondary battery cells.

25. An electrical appliance, characterized in that, It includes at least one of the following: the lithium-ion secondary battery cell according to any one of claims 1 to 20, the lithium-ion secondary battery cell prepared by the method of preparing the lithium-ion secondary battery cell according to claim 22 or 23, and the battery device according to claim 24.

Images