Lithium-ion secondary battery, method of manufacturing, and electric device

Abstract

The application relates to a lithium ion secondary battery, a preparation method and an electric device. The lithium ion secondary battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, a separation film is arranged between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet comprises a positive electrode active layer, the positive electrode active layer comprises a positive electrode active material; the electrolyte comprises an electrolyte salt, a non-aqueous solvent and an additive; the positive electrode active material comprises a lithium transition metal oxide positive electrode material, the D v 3 of the positive electrode active material is greater than or equal to 1 mu m; and the additive comprises a first additive, the first additive being an alkyne base additive containing a Lewis base type nitrogen heterocycle. The lithium ion secondary battery has good normal temperature performance as well as higher energy density and significantly improved 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 batteries, preparation methods and power 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 various fields such as smartphones, tablets, laptops, power tools, electric bicycles, electric motorcycles, electric vehicles, and aerospace. They are also widely used in energy storage systems for hydropower, thermal power, wind power, and solar power plants. To meet the ever-increasing demand for extended battery life, battery systems with high energy density have remained a crucial research focus. The storage and use of lithium-ion rechargeable batteries involve not only ambient temperatures but also unavoidably high-temperature scenarios, such as elevated summer temperatures, direct sunlight exposure, and high-temperature storage and / or usage environments near the equator. High-temperature additives, such as alkyne-based additives, can improve the high-temperature performance of batteries by optimizing the solid electrolyte interphase (SEI) film at the negative electrode; however, this can lead to increased negative electrode interface impedance, affecting performance at room temperature.

[0004] Therefore, it is necessary to develop new methods to improve the high-temperature performance of high-energy-density battery systems while maintaining good room-temperature performance. Summary of the Invention

[0005] According to various embodiments and examples of this application, a lithium-ion secondary battery, a preparation method, and an electrical device are provided. This lithium-ion secondary battery exhibits high energy density and significantly improved high-temperature performance, as well as good room-temperature performance.

[0006] In some embodiments of the first aspect of this application, a lithium-ion secondary battery is provided, which includes a positive electrode, a negative electrode and an electrolyte, wherein a separator is disposed between the positive electrode and the negative electrode; the positive electrode includes a positive active layer, the positive active layer includes a positive active material; the electrolyte includes an electrolyte salt, a non-aqueous solvent and additives.

[0007] The positive electrode active material includes lithium transition metal oxide-based positive electrode materials, and the D of the positive electrode active material... v 3 is greater than or equal to 1 μm;

[0008] The additive includes a first additive, which is an alkylene base additive containing a Lewis base nitrogen heterocycle.

[0009] For high-energy-density battery systems with lithium transition metal oxide cathode materials, introducing a first additive containing carbon-carbon triple bonds and Lewis base nitrogen heterocycles into the electrolyte can significantly improve the battery's high-temperature performance. Furthermore, by increasing the D... v 3. Control the value within a relatively high range (e.g., D). v Within 3 μm (greater than or equal to 1 μm), the content of small particles with small particle size and large specific surface area in the positive electrode active material can be controlled at a low level, significantly reducing the interfacial side reactions of the positive electrode and significantly reducing the dissolution of transition metal ions in the positive electrode. Thus, through the aforementioned multiple synergistic effects, the high-temperature performance can be significantly improved while the increase in interfacial impedance that may be caused by the participation of the first additive in the negative electrode film formation can be significantly suppressed. Therefore, the high-temperature performance of the high-energy-density battery system can be significantly improved while also having good room-temperature performance.

[0010] The mechanism by which the first additive significantly improves the high-temperature performance of the battery includes, but is not limited to, the following aspects: The first additive can participate in the formation and repair of the solid electrolyte interphase (SEI) film at the negative electrode. The first additive and the SEI film it forms have high-temperature stability, which can significantly improve the stability of the SEI film and reduce the interfacial side reactions at the negative electrode at high temperatures. It can also absorb acid byproducts (such as hydrofluoric acid) generated by electrolyte side reactions from the source by using Lewis base nitrogen heterocycles, thereby inhibiting the damage of acid byproducts to the positive and negative electrode interfacial films and reducing the interfacial side reactions between the positive and negative electrodes. It can also inhibit the damage of acid byproducts to the positive electrode active material and reduce the dissolution of transition metal ions from the positive electrode. It can also adsorb transition metal ions that may dissolve from the positive electrode by using carbon-carbon triple bonds, thereby significantly reducing the deposition of transition metal ions at the negative electrode and significantly reducing the damage of transition metal ions that may dissolve from the positive electrode to the negative electrode SEI film. It can also inhibit the damage of acid byproducts to the negative electrode SEI film, further improving the stability of the negative electrode SEI film and reducing the interfacial side reactions at the negative electrode.

[0011] In some embodiments, the D of the positive electrode active material v 3 is 1μm~2μm, and can be selected as 1μm~1.6μm.

[0012] By using the D of the positive electrode active material v 3. Controlling the content of small particles with smaller particle size and larger specific surface area in the positive electrode active material is beneficial to better control the content of small particles with smaller particle size and larger specific surface area, thereby better reducing the interfacial side reactions of the positive electrode. Based on the multiple synergistic effects of the positive electrode active material and the first additive in the electrolyte, it is beneficial to better improve the high temperature performance while also taking into account the good room temperature performance.

[0013] In some embodiments, the average particle size of the primary particles in the positive electrode active material is 1.1 μm to 3.0 μm.

[0014] In some embodiments, the average particle size of the primary particles in the positive electrode active material is 1.2 μm to 2.5 μm.

[0015] By controlling the average particle size (denoted as D1) of the primary particles in the positive electrode active material within the aforementioned range, it is beneficial to ensure that the primary particles in the positive electrode active material have a more suitable size. This not only allows for the control of a more suitable ion transport path in the positive electrode active material, but also effectively suppresses the positive electrode interface reaction, reduces the dissolution of transition metal ions and their damage to the negative electrode SEI film, and thus controls the consumption of alkyne-based alkali additives in negative electrode film formation. This improves the cycle performance of lithium-ion secondary batteries and suppresses the increase in battery internal resistance. Based on the synergistic effects of the aforementioned factors, but not limited to the aforementioned theories, it is beneficial to better synergistically control the structural stability of the positive electrode active layer, the battery internal resistance, and the consumption of alkyne-based alkali additives in negative electrode film formation. It is also beneficial to better achieve both significantly improved high-temperature performance and good room-temperature performance.

[0016] In some embodiments, the D of the positive electrode active material v The ratio of 50 to the average particle size of the primary particles in the positive electrode active material is denoted as B1;

[0017] The positive electrode sheet satisfies one or more of the following characteristics:

[0018] (a1) The D of the positive electrode active material v 50 represents 2.5μm to 5μm;

[0019] (a2) B1 is 1~2.5.

[0020] In some embodiments, the positive electrode sheet satisfies one or more of the following characteristics:

[0021] (a1') D of the positive electrode active material v 50 is 3μm~4.5μm;

[0022] (a2')B1 is 1.8~2.3.

[0023] By using the D of the positive electrode active material v Controlling the particle size distribution of the positive electrode active material within the aforementioned range is beneficial for achieving a more suitable particle size distribution. This can indirectly adjust the contact area between the positive electrode active material and the electrolyte, which is conducive to better suppressing interfacial side reactions between the positive electrode active material and the electrolyte during cycling and / or storage, reducing the dissolution of positive electrode transition metal ions, thereby better improving the cycle performance of lithium-ion secondary batteries and suppressing the increase in battery internal resistance. It is also beneficial for better control of the overall ion transport path of the positive electrode active material particles. Based on the synergistic effect of the above-mentioned effects, but not limited to the aforementioned theory, it is beneficial to better achieve significant improvement in high-temperature performance while also maintaining good room-temperature performance.

[0024] By using the D of the positive electrode active material v Controlling the ratio (B1) of 50 to the average particle size of primary particles in the positive electrode active material within the aforementioned range is beneficial for making the median particle size of the positive electrode active material particles close to the average particle size of the primary particles, which are the basic unit of particles. This helps to reduce the agglomeration ratio of primary particles in the positive electrode active material, reduce the content of secondary particles as primary particle agglomerates, and correspondingly increase the proportion of non-agglomerated primary particles. Compared with secondary particles that have interfaces between primary particles, non-agglomerated primary particles do not have interfaces between primary particles in the secondary particles, allowing non-agglomerated primary particles to better resist the risk of particle cracking during cycling and / or storage. It also helps to better control the overall ion transport path of the positive electrode active material particles. By controlling B1 within the aforementioned range, the structural stability of the positive electrode active material can be better improved, which is more conducive to reducing positive electrode interface side reactions and slowing down electrolyte consumption, reducing the dissolution of positive electrode transition metal ions, improving battery life and suppressing the increase of battery internal resistance, and better achieving both significantly improved high-temperature performance and good room-temperature performance.

[0025] By synergistically controlling the D of the positive electrode active material v The average particle size of primary particles in the positive electrode active material (50 or B1) is beneficial to both the ion transport path of primary particles and the particle as a whole in the positive electrode active material, and at the same time, it can better suppress the side reactions at the positive electrode interface. Based on the synergy of the above effects, but not limited to the above theory, it is beneficial to better control the internal resistance of the battery, and to better improve the high temperature performance while also taking into account the good room temperature performance.

[0026] In some embodiments, the negative electrode sheet includes a negative electrode active layer, and the negative electrode active layer includes a negative electrode active material; the negative electrode active material has a D v 50 is 8μm~20μm.

[0027] In some embodiments, the D of the negative electrode active material v 50 represents 10μm~18μm.

[0028] By using the D of the negative electrode active material v By controlling the specific surface area of ​​the negative electrode active material within the aforementioned range, it is possible to keep the specific surface area of ​​the negative electrode active material within a relatively low range. This is beneficial for reducing side reactions at the negative electrode interface, reducing or delaying the consumption of the first additive at the negative electrode interface, and also for better controlling the overall ion transport path of the negative electrode active material particles. Based on the synergistic effect of the aforementioned effects, but not limited to the aforementioned theory, it is beneficial for better controlling the battery internal resistance and for better achieving both significantly improved high-temperature performance and good room-temperature performance.

[0029] In some embodiments, the negative electrode sheet includes a negative electrode active layer, and the negative electrode active layer includes a negative electrode active material; the negative electrode active material includes at least one of carbon-based materials and silicon-based materials;

[0030] The negative electrode sheet satisfies one or more of the following characteristics:

[0031] (b1) The silicon-based material accounts for 0-30% of the mass of the negative electrode active material;

[0032] (b2) The silicon-based material includes a silicon-carbon composite material, which includes a porous carbon matrix and elemental silicon located in 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.

[0033] By controlling the content and / or type of silicon-based materials in the negative electrode active material within the aforementioned range, it is beneficial to better control the expansion and contraction changes of the negative electrode, reduce the generation of fresh interfaces, suppress side reactions at the negative electrode interface, reduce the consumption rate of the first additive, decrease the rate of increase in battery internal resistance, and ultimately improve battery life. For example, in silicon-based materials, the volume expansion and contraction changes of silicon-carbon composite materials are relatively low.

[0034] In some embodiments, the first additive is present in the electrolyte at a mass percentage of less than 3.6%.

[0035] In some embodiments, the first additive is present in the electrolyte at a mass percentage of 0.02% to 3.6%.

[0036] In some embodiments, the first additive is present in the electrolyte at a mass percentage of 0.02% to 2%.

[0037] In some embodiments, the first additive is present in the electrolyte at a mass percentage of 0.1% to 1.6%, optionally 0.1% to 1.2%.

[0038] By controlling the mass ratio of the first additive in the electrolyte within the aforementioned range, the first additive can continuously play a role in repairing the SEI film during cycling and / or storage, which is more conducive to significantly improving high-temperature performance while also maintaining good room-temperature performance.

[0039] In some embodiments, the additive includes a negative electrode film-forming additive that is different from the first additive.

[0040] Unlike the first additive, the negative electrode film-forming additive can competitively participate in the negative electrode film formation, which can reduce or delay the consumption of the first additive in the negative electrode film formation and suppress the increase in negative electrode interface impedance caused by the participation of the first additive in the negative electrode film formation. This is beneficial to better improve the high-temperature performance of the high-energy-density battery system while also having good room-temperature performance.

[0041] In some embodiments, the additive includes one or more of a second additive, a third additive, and a fourth additive;

[0042] The second additive is one or more of silane additives and siloxane additives;

[0043] The third additive is one or more of isocyanate additives and acid anhydride additives;

[0044] The fourth additive is one or more of lithium salt additives and phosphate ester additives.

[0045] In some embodiments, the mass ratio of the second additive to the first additive in the electrolyte is 0.1 to 50.

[0046] In some embodiments, the mass ratio of the third additive to the first additive in the electrolyte is 0.01 to 50.

[0047] In some embodiments, the mass ratio of the fourth additive to the first additive in the electrolyte is 0.1 to 100.

[0048] In some embodiments, the mass ratio of the second additive, the third additive, the fourth additive and the first additive in the electrolyte is (0~0.5):(0~0.5):(0~1):1.

[0049] The second, third, and fourth additives can all be used as negative electrode film-forming additives. The second additive is a type of additive with low negative electrode film-forming impedance and a certain degree of acid removal effect, although its acid removal effect is lower than that of the first additive, and its negative electrode film-forming impedance is also lower than that of the first additive. The third additive is a type of additive with good acid removal effect, superior to that of the first additive, but its negative electrode film-forming impedance is higher than that of the first additive. The fourth additive has extremely low negative electrode film-forming impedance, far lower than that of the first additive.

[0050] By utilizing the synergistic effect of the first additive with one or more of the second, third, and fourth additives, it is beneficial to achieve a significant improvement in high-temperature performance while also maintaining good room-temperature performance.

[0051] In some embodiments, the electrolyte satisfies one or more of the following characteristics:

[0052] (c1) The molecular weight of the first additive is less than or equal to 500 Da;

[0053] (c2) The molecule of the first additive contains 1 to 4 carbon-carbon triple bonds;

[0054] (c3) The carbon-carbon triple bond is CH≡C-;

[0055] (c4) The molecule of the first additive contains 1 to 4 Lewis base nitrogen heterocycles;

[0056] (c5) The Lewis base nitrogen heterocycle includes an imidazole ring;

[0057] (c6) In the molecule of the first additive, the carbon-carbon triple bond and the Lewis base nitrogen heterocycle are connected by a linker L1, wherein the linker L1 contains a C-type carbon bond covalently bonded to the carbon-carbon triple bond. 1-3 Alkylene or containing fluorinated C atoms covalently bonded to a carbon-carbon triple bond 1-3 Alkylene.

[0058] In some embodiments, the first additive satisfies one or more of the following characteristics:

[0059] (d1) The molecular weight of the first additive is less than or equal to 300 Da;

[0060] (d2) The molecule of the first additive contains 1 to 4 imidazole rings;

[0061] (d3) The linker L1 contains C covalently bonded to the carbon-carbon triple bond. 1-3 Alkylene;

[0062] (d4) The Lewis base nitrogen heterocycle includes an imidazole ring; the imidazole ring in the Lewis base nitrogen heterocycle is substituted by 0, 1, or more substituents Q2, and each of the substituents Q2 in the substituted imidazole group is independently C. 1-3 Alkyl, cyano or fluorine atom.

[0063] In some embodiments, the first additive comprises compound II with the structure shown in formula (II): 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;

[0064] The mass percentage of compound II in the first additive is 80% to 100%.

[0065] By controlling the molecular weight of the first additive within the aforementioned lower range, the first additive can have a smaller molecular size, which is beneficial for better control of the low viscosity characteristics of the electrolyte, enabling the electrolyte to have higher conductivity and better control of the battery's internal resistance.

[0066] By controlling the number of carbon-carbon triple bonds in the first additive within the aforementioned range, it is beneficial to suppress the increase in interfacial impedance caused by the first additive participating in the formation and repair of the SEI film, and it is also beneficial to control the influence of the first additive on the liquid phase impedance; thus, the increase in battery internal resistance can be better suppressed.

[0067] By controlling the number of Lewis base nitrogen heterocycles in the first additive 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.

[0068] Examples of Lewis base nitrogen heterocycles include the imidazole ring in compound II.

[0069] In some embodiments of the second aspect of this application, a method for preparing a lithium-ion secondary battery is provided, comprising the following steps:

[0070] An electrode assembly comprising a positive electrode, a separator, and a negative electrode is placed within a battery casing; wherein the separator is disposed between the positive electrode and the negative electrode; wherein the positive electrode includes a positive active layer, the positive active layer includes a positive active material, the positive active material includes a lithium transition metal oxide-based positive electrode material, and the positive active material has a D... v 3 is greater than or equal to 1 μm;

[0071] An electrolyte is injected into the battery casing, and the casing is left to stand to allow the electrolyte to wet the positive electrode and the negative electrode, thus forming the battery. The electrolyte includes an electrolyte salt, a non-aqueous solvent, and an additive. The additive includes a first additive, which is an alkyne base additive containing a Lewis base nitrogen heterocycle.

[0072] The prepared lithium-ion secondary battery has the advantages of the lithium-ion secondary battery described in the first aspect of this application.

[0073] In some embodiments, the lithium-ion secondary battery described in the first aspect of this application is prepared.

[0074] In some embodiments of the third aspect of this application, an electrical device is provided, which includes the lithium-ion secondary battery described in the first aspect of this application.

[0075] 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

[0076] 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:

[0077] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0078] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0079] Figure 3 This is a schematic diagram of a battery device according to one embodiment of this application.

[0080] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0081] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0082] Figure 6 This is a schematic diagram of an electrical device that uses a lithium-ion secondary battery as a power source according to an embodiment of this application.

[0083] Explanation of reference numerals in the attached figures:

[0084] 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

[0085] The following describes in detail some embodiments and examples of the lithium-ion secondary battery, its preparation method, and its power application with appropriate reference to the accompanying drawings. However, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0086] 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.

[0087] 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.

[0088] 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".

[0089] 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.

[0090] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0091] 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.

[0092] Those skilled in the art will understand that, unless otherwise specified, the order in which the steps are written in the various embodiments or methods of this application does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but are preferably performed sequentially. For example, if method M includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, method M may also include step (c), meaning that step (c) can be added to method M in any order. For example, method M may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[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", "suitable method", etc., 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 not to limit 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," "example," and "exemplary" 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," 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," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0101] 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.

[0102] 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.

[0103] In this application, the term "room temperature" generally refers to 4℃~35℃, and may refer to 20℃±5℃. In some embodiments or examples of this application, room temperature refers to 20℃~30℃.

[0104] 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.

[0105] 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.

[0106] 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".

[0107] 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.

[0108] Unless otherwise stated, the improvements described in this application are not intended to be limited to any theoretical constraints.

[0109] To meet the ever-increasing demand for extended driving range, high-energy-density battery systems have always been an important research direction. The storage and use of lithium-ion rechargeable batteries involve not only room-temperature environments but also inevitably high-temperature scenarios, such as elevated summer temperatures, direct sunlight exposure, and high-temperature storage and / or use environments near the equator. High-temperature additives, such as alkynes, can improve the high-temperature performance of batteries by optimizing the solid electrolyte interphase (SEI) film at the negative electrode; however, they can increase the interface impedance of the negative electrode, affecting room-temperature performance. Therefore, it is necessary to develop new methods to improve the high-temperature performance of high-energy-density battery systems while maintaining good room-temperature performance.

[0110] For traditional lithium-ion rechargeable batteries, during charge and discharge, electrolyte side reactions easily produce acidic byproducts, such as hydrofluoric acid, leading to capacity decay and affecting battery life. For traditional lithium-ion rechargeable batteries with positive electrode materials including lithium transition metal oxides, these acidic byproducts can damage the positive electrode solid electrolyte interphase (CEI) film and corrode the positive electrode active material, causing transition metal ions to dissolve from the positive electrode, resulting in deterioration of battery cycle and / or storage performance. Furthermore, these acidic byproducts can easily damage the negative electrode SEI film, exposing fresh interfaces and exacerbating interface side reactions at the negative electrode, also worsening battery cycle and / or performance. In particular, 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 the negative electrode and depositing, can also easily damage the negative electrode solid electrolyte interphase (SEI) film, intensifying interface side reactions at the negative electrode and further deteriorating battery cycle and / or storage performance.

[0111] According to various embodiments and examples of this application, this application provides a lithium-ion secondary battery, a preparation method, and an electrical device. This lithium-ion secondary battery exhibits high energy density and significantly improved high-temperature performance, while also possessing good room-temperature performance.

[0112] 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.

[0113] 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.

[0114] In some embodiments, the lithium-ion secondary battery includes a positive electrode and an electrolyte; the electrolyte includes an electrolyte salt, a non-aqueous solvent, and additives; the positive electrode includes a positive active layer, and the positive active layer includes a positive active material; the electrolyte includes an electrolyte salt, a non-aqueous solvent, and additives; the positive active material includes a lithium transition metal oxide-based positive electrode material, and the positive active material has a D... v 3 is greater than or equal to 1 μm; the additives include a first additive, which is an alkyne base additive containing a Lewis base nitrogen heterocycle. This lithium-ion secondary battery exhibits high energy density and significantly improved high-temperature performance, while also demonstrating good room-temperature performance.

[0115] In some embodiments, a lithium-ion secondary battery is provided, comprising a positive electrode and an electrolyte; the positive electrode includes a positive active layer, the positive active layer including a positive active material; the electrolyte includes an electrolyte salt, a non-aqueous solvent, and an additive; the positive active material includes a lithium transition metal oxide positive electrode material, wherein the average particle size of the primary particles in the positive active material is 1.1 μm to 3.0 μm (see also appropriate values ​​or ranges in the context); the additive includes a first additive, which is an alkyne base additive containing a Lewis base nitrogen heterocycle.

[0116] 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 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.

[0117] 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."

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] In this application, unless otherwise specified, "separation membrane" and "diaphragm" have the same meaning and can be used interchangeably.

[0124] In a first aspect of this application, a lithium-ion secondary battery is provided, which has good room-temperature performance while having high energy density and significantly improved high-temperature performance.

[0125] 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 electrodes; the positive electrode includes a positive active layer comprising a positive active material; the electrolyte comprises an electrolyte salt, a non-aqueous solvent, and additives; the positive active material comprises a lithium transition metal oxide-based positive electrode material, and the positive active material has a D... v 3 is greater than or equal to 1 μm; the additives include the first additive, which is an alkyne base additive containing a Lewis base nitrogen heterocycle.

[0126] 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.

[0127] In this application, unless otherwise specified, "non-lithium metal element" refers to a metal element that is not lithium (Li).

[0128] 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. v50, 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.

[0129] In this application, unless otherwise specified, "non-aqueous solvent" means a solvent that is not water.

[0130] In this application, unless otherwise specified, a "carbon-carbon triple bond" is an unsaturated bond with a —C≡C— framework.

[0131] 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 are capable of donating 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.

[0132] 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.

[0133] In this application, unless otherwise specified, "first additive" refers to an alkyne-based base additive containing a Lewis base nitrogen heterocycle; it is understood that the first additive contains a carbon-carbon triple bond. It is understood that the first additive can attract and bind acidic substances, such as acid byproducts in the electrolyte (e.g., hydrofluoric acid). The first additive can participate in the formation of the negative electrode solid electrolyte interphase (SEI) film. The first additive can significantly improve the high-temperature performance of the battery, including extending high-temperature cycling and storage life, and can be used as a high-temperature additive; however, the introduction of the first additive can easily lead to a large negative electrode interfacial impedance at room temperature.

[0134] 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.

[0135] For high-energy-density battery systems with lithium transition metal oxide cathode materials, introducing a first additive containing carbon-carbon triple bonds and Lewis base nitrogen heterocycles into the electrolyte can significantly improve the battery's high-temperature performance. Furthermore, by increasing the D... v 3. Control the value within a relatively high range (e.g., D). v Within 3 μm (greater than or equal to 1 μm), the content of small particles with small particle size and large specific surface area in the positive electrode active material can be controlled at a low level, significantly reducing the interfacial side reactions of the positive electrode and significantly reducing the dissolution of transition metal ions in the positive electrode. Thus, through the aforementioned multiple synergistic effects, the high-temperature performance can be significantly improved while the increase in interfacial impedance that may be caused by the participation of the first additive in the negative electrode film formation can be significantly suppressed. Therefore, the high-temperature performance of the high-energy-density battery system can be significantly improved while also having good room-temperature performance.

[0136] The mechanism by which the first additive significantly improves the high-temperature performance of the battery includes, but is not limited to, the following aspects: The first additive can participate in the formation and repair of the solid electrolyte interphase (SEI) film at the negative electrode. The first additive and the SEI film it forms have high-temperature stability, which can significantly improve the stability of the SEI film and reduce the interfacial side reactions at the negative electrode at high temperatures. It can also absorb acid byproducts (such as hydrofluoric acid) generated by electrolyte side reactions from the source by using Lewis base nitrogen heterocycles, thereby inhibiting the damage of acid byproducts to the positive and negative electrode interfacial films and reducing the interfacial side reactions between the positive and negative electrodes. It can also inhibit the damage of acid byproducts to the positive electrode active material and reduce the dissolution of transition metal ions from the positive electrode. It can also adsorb transition metal ions that may dissolve from the positive electrode by using carbon-carbon triple bonds, thereby significantly reducing the deposition of transition metal ions at the negative electrode and significantly reducing the damage of transition metal ions that may dissolve from the positive electrode to the negative electrode SEI film. It can also inhibit the damage of acid byproducts to the negative electrode SEI film, further improving the stability of the negative electrode SEI film and reducing the interfacial side reactions at the negative electrode.

[0137] 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 vGrade 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.

[0138] 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.

[0139] 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.

[0140] The electrolyte sample can be obtained by disassembling the battery cell.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] In some embodiments, the D of the positive electrode active material v 3 is greater than or equal to 1μm, can be selected from 1μm to 2μm, can be further selected from 1μm to 1.6μm, and can also be any of the following values ​​or a range selected from any two of the following values: 1μm, 1.1μm, 1.2μm, 1.4μm, 1.5μm, 1.6μm, 1.8μm, 2μm, etc.

[0146] By using the D of the positive electrode active material v 3. Controlling the content of small particles with smaller particle size and larger specific surface area in the positive electrode active material is beneficial to better control the content of small particles with smaller particle size and larger specific surface area, thereby better reducing the interfacial side reactions of the positive electrode. Based on the multiple synergistic effects of the positive electrode active material and the first additive in the electrolyte, it is beneficial to better improve the high temperature performance while also taking into account the good room temperature performance.

[0147] In some embodiments, the average particle size of the primary particles in the positive electrode active material is 1.1 μm to 3.0 μm, optionally 1.2 μm to 2.5 μm, or any of the following values ​​or a range selected from any two of the following values: 1.1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.8 μm, 3.0 μm, etc.

[0148] In this application, the "average particle size of primary particles in the positive electrode active material" can be denoted as D1.

[0149] In this application, unless otherwise specified, the "average particle size of primary particles" in the positive electrode active material refers to the average particle size of all primary particles in the positive electrode active material. The "particle size of primary particles" refers to the maximum diameter of the primary particles in each direction.

[0150] In this application, unless otherwise specified, "primary particles" in the positive electrode active material refer to the basic particle unit in the positive electrode active material. It is understood that primary particles exist in the positive electrode active material. In the positive 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."

[0151] By controlling the average particle size (denoted as D1) of the primary particles in the positive electrode active material within the aforementioned range, it is beneficial to ensure that the primary particles in the positive electrode active material have a more suitable size. This not only allows for the control of a more suitable ion transport path in the positive electrode active material, but also effectively suppresses the positive electrode interface reaction, reduces the dissolution of transition metal ions and their damage to the negative electrode SEI film, and thus controls the consumption of alkyne-based alkali additives in negative electrode film formation. This improves the cycle performance of lithium-ion secondary batteries and suppresses the increase in battery internal resistance. Based on the synergistic effects of the aforementioned factors, but not limited to the aforementioned theories, it is beneficial to better synergistically control the structural stability of the positive electrode active layer, the battery internal resistance, and the consumption of alkyne-based alkali additives in negative electrode film formation. It is also beneficial to better achieve both significantly improved high-temperature performance and good room-temperature performance.

[0152] The particle morphology of the positive electrode active material can be used to statistically determine the particle size of the primary particles in the positive electrode active material, thereby obtaining the average particle size of the primary particles in the positive electrode active material. The particle morphology of the positive 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 positive electrode active material on conductive adhesive, or by performing SEM testing on the cross-section of the positive electrode sheet. Non-limitingly, SEM testing can refer to JY / T(001)-1996. One or more regions are randomly selected in the sample to be tested for scanning, and 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, thereby calculating the average particle size of each statistically analyzed primary particle. 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. The number of particles counted in a single operation can be several hundred, or even more than or equal to 1,000, or more than or equal to 2,000. Increasing the number of particles counted in a single operation helps improve the accuracy of the statistical results.

[0153] In this application, unless otherwise specified, the maximum diameter of the primary particles in each direction in the SEM morphology image of the positive electrode active material is denoted as "the particle size of the primary particles in the positive electrode active material".

[0154] In some embodiments, 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 and negative electrodes; the positive electrode includes a positive active layer comprising a positive active material; the electrolyte comprises an electrolyte salt, a non-aqueous solvent, and an additive; the positive active material comprises a lithium transition metal oxide positive electrode material, wherein the average particle size of the primary particles in the positive active material is 1.1 μm to 3.0 μm (see also appropriate values ​​or ranges in the context); the additive comprises a first additive, which is an alkyne base additive containing a Lewis base nitrogen heterocycle.

[0155] For high-energy-density battery systems with lithium transition metal oxide cathode materials, introducing a first additive containing carbon-carbon triple bonds and Lewis base nitrogen heterocycles into the electrolyte can significantly improve the high-temperature performance of the battery. Furthermore, by controlling the average particle size (D1) of the primary particles in the cathode active material within a suitable range (e.g., 1.1 μm to 3.0 μm), a suitable ion transport pathway can be maintained in the cathode active material. Simultaneously, the cathode interfacial reaction can be effectively suppressed, reducing the dissolution of cathode transition metal ions and their damage to the anode SEI film. This, in turn, controls the consumption of alkyne base additives in anode film formation, thereby improving the cycle performance of lithium-ion secondary batteries and suppressing the increase in battery internal resistance. Thus, through the aforementioned multiple synergistic effects, but not limited to the aforementioned mechanisms, the increase in interfacial impedance that may be caused by the participation of the first additive in anode film formation can be significantly suppressed while significantly improving high-temperature performance. This results in a high-energy-density battery system with good room-temperature performance while significantly improving high-temperature performance.

[0156] In this application, the D of the positive electrode active material is... v 50 (can be written as D) v 50 A The ratio of the particle size of the primary particles to the average particle size (D1) in the positive electrode active material is denoted as B1. Therefore, B1 = D... v 50 A / D1.

[0157] In some implementations, the positive electrode sheet satisfies one or more of the following characteristics:

[0158] (a1) D of the positive electrode active material v 50 is 2.5μm~5μm, can be selected from 3μm~4.5μm, and can also be any of the following values ​​or a range composed of any two of the following values: 2.5μm, 2.6μm, 2.8μm, 3.0μm, 3.2μm, 3.4μm, 3.5μm, 3.6μm, 3.8μm, 4.0μm, 4.2μm, 4.4μm, 4.5μm, 4.6μm, 4.8μm, 5μm, etc.;

[0159] (a2) B1 is 1~2.5, can be 1.8~2.3, or can be any of the following values ​​or a range of any two of the following values: 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2.0, 2.1, 2.2, 2.3, etc.

[0160] In some implementations, the positive electrode sheet satisfies one or more of the following characteristics:

[0161] (a1') D of the positive electrode active material v50 is 3μm~4.5μm, and can also be any of the following values ​​or a range selected from any two of the following values: 3μm, 3.2μm, 3.4μm, 3.5μm, 3.6μm, 3.8μm, 4.0μm, 4.2μm, 4.4μm, 4.5μm, etc.;

[0162] (a2') B1 is 1.8 to 2.3, and can also be any of the following values ​​or a range of any two of the following values: 1.8, 2.0, 2.1, 2.2, 2.3, etc.

[0163] By using the D of the positive electrode active material v Controlling the particle size distribution of the positive electrode active material within the aforementioned range is beneficial for achieving a more suitable particle size distribution. This can indirectly adjust the contact area between the positive electrode active material and the electrolyte, which is conducive to better suppressing interfacial side reactions between the positive electrode active material and the electrolyte during cycling and / or storage, reducing the dissolution of positive electrode transition metal ions, thereby better improving the cycle performance of lithium-ion secondary batteries and suppressing the increase in battery internal resistance. It is also beneficial for better control of the overall ion transport path of the positive electrode active material particles. Based on the synergistic effect of the above-mentioned effects, but not limited to the aforementioned theory, it is beneficial to better achieve significant improvement in high-temperature performance while also maintaining good room-temperature performance.

[0164] By using the D of the positive electrode active material v Controlling the ratio (B1) of 50 to the average particle size of primary particles in the positive electrode active material within the aforementioned range is beneficial for making the median particle size of the positive electrode active material particles close to the average particle size of the primary particles, which are the basic unit of particles. This helps to reduce the agglomeration ratio of primary particles in the positive electrode active material, reduce the content of secondary particles as primary particle agglomerates, and correspondingly increase the proportion of non-agglomerated primary particles. Compared with secondary particles that have interfaces between primary particles, non-agglomerated primary particles do not have interfaces between primary particles in the secondary particles, allowing non-agglomerated primary particles to better resist the risk of particle cracking during cycling and / or storage. It also helps to better control the overall ion transport path of the positive electrode active material particles. By controlling B1 within the aforementioned range, the structural stability of the positive electrode active material can be better improved, which is more conducive to reducing positive electrode interface side reactions and slowing down electrolyte consumption, reducing the dissolution of positive electrode transition metal ions, improving battery life and suppressing the increase of battery internal resistance, and better achieving both significantly improved high-temperature performance and good room-temperature performance.

[0165] In some embodiments, the D of the positive electrode active material v50 is 2.5μm~5μm, selectable from 3μm~4.5μm, and can also be any of the following values ​​or a range selected from any two of the following values: 2.5μm, 2.6μm, 2.8μm, 3.0μm, 3.2μm, 3.4μm, 3.5μm, 3.6μm, 3.8μm, 4.0μm, 4.2μm, 4.4μm, 4.5μm, 4.6μm, 4.8μm, 5μm, etc.; positive electrode The average particle size (D1) of the primary particles in the active material is 1.1μm to 3.0μm, and can be selected from 1.2μm to 2.5μm. It can also be any of the following values ​​or a range composed of any two of the following values: 1.1μm, 1.2μm, 1.4μm, 1.5μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.5μm, 2.6μm, 2.8μm, 3.0μm, etc.

[0166] In some embodiments, the B1 of the positive electrode active material is 1 to 2.5, optionally 1.8 to 2.3, and may also be any of the following values ​​or a range selected from any two of the following values: 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2.0, 2.1, 2.2, 2.3, etc.; the average particle size (D1) of the primary particles in the positive electrode active material is 1.1 μm to 3.0 μm, optionally 1.2 μm to 2.5 μm, and may also be any of the following values ​​or a range selected from any two of the following values: 1.1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.8 μm, 3.0 μm, etc.

[0167] By synergistically controlling the D of the positive electrode active material v The average particle size of primary particles in the positive electrode active material (50 or B1) is beneficial to both the ion transport path of primary particles and the particle as a whole in the positive electrode active material, and at the same time, it can better suppress the side reactions at the positive electrode interface. Based on the synergy of the above effects, but not limited to the above theory, it is beneficial to better control the internal resistance of the battery, and to better improve the high temperature performance while also taking into account the good room temperature performance.

[0168] In some embodiments, the negative electrode sheet includes a negative electrode active layer, and the negative electrode active layer includes a negative electrode active material; the negative electrode active material D v 50 is 8μm~20μm, can be selected as 10μm~20μm, further selectable as 10μm~18μm, and can also be any of the following values ​​or a range composed of any two of the following values: 8μm, 8.5μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc.

[0169] By using the D of the negative electrode active material v By controlling the specific surface area of ​​the negative electrode active material within the aforementioned range, it is possible to keep the specific surface area of ​​the negative electrode active material within a relatively low range. This is beneficial for reducing side reactions at the negative electrode interface, reducing or delaying the consumption of the first additive at the negative electrode interface, and also for better controlling the overall ion transport path of the negative electrode active material particles. Based on the synergistic effect of the aforementioned effects, but not limited to the aforementioned theory, it is beneficial for better controlling the battery internal resistance and for better achieving both significantly improved high-temperature performance and good room-temperature performance.

[0170] 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.

[0171] In some embodiments, the D of the negative electrode active material v 1 is greater than or equal to 1.5 μm.

[0172] By controlling the D of the negative electrode active material v 1. Within the aforementioned range, the negative electrode interface side reactions can be significantly suppressed, the consumption rate of the first additive can be reduced, and the growth rate of the battery internal resistance can be reduced.

[0173] In some embodiments, the specific surface area (BET) of the negative electrode active material is 0.5 m². 2 / g~2.8m 2 / g, optional 0.5m 2 / g~2.0m 2 / g, which can be further selected as 0.7m 2 / g~1.6m 2 / g, can also be any of the following values ​​or a range selected from any two of the following values: 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 1.0 m 2 / g, 1.2 m 2 / g, 1.4m 2 / g, 1.5 m 2 / g, 1.6 m 2 / g, 1.8 m 2 / g, 2.0 m 2 / g、2.2 m 2 / g、2.4 m2 / g, 2.5 m 2 / g, 2.6 m 2 / g, 2.8m 2 / g etc.

[0174] In this application, unless otherwise specified, the "specific surface area" of the negative electrode active material has a commonly known meaning in the art. It can be tested using nitrogen adsorption specific surface area analysis and calculated using the BET (Brunauer Emmett Teller) method. Nitrogen adsorption specific surface area analysis can be performed using a Tri Star II specific surface area and porosity analyzer from Micromeritics, USA. The test procedures can refer to GB / T 19587-2004. Detailed steps are as follows: Using nitrogen as the adsorbate gas, calculate the specific surface area of ​​the material using the BET method; add the sample to be tested into a BET test tube until it reaches 2 / 3 of the bottom bulb, degas the sample, and heat it; after cooling to room temperature, refill with nitrogen to remove the vacuum, and plug the sample tube opening with a stopper, recording the sample weight; remove the stopper, add a filling rod, install the sample tube onto the instrument analysis station, input the sample weight, and begin the test. Before testing, the sample can be dried.

[0175] In some embodiments, the negative electrode sheet includes a negative electrode active layer, which includes a negative electrode active material; the negative electrode active material includes at least one of carbon-based materials and silicon-based materials. In some embodiments, the negative electrode active material includes a carbon-based material. Non-limitingly, the carbon-based material may include one or more of graphite-based materials, soft carbon, and hard carbon. The carbon-based material may include one or more of artificial graphite, natural graphite, soft carbon, and hard carbon. Non-limitingly, the mass percentage of silicon-based material in the negative electrode active material may be 0-30%, optionally 1%-30%, further optionally 1%-25%, and may also be 0%-25%, or any of the following percentages or a range selected from any two of the following percentages: 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 26%, 28%, 30%, etc.

[0176] In some embodiments, the negative electrode active material includes a graphite-based material, and may further be a graphite-based material.

[0177] In this application, "graphite-based material" refers to a negative electrode active material containing graphite, and a graphite-based material includes at least a graphite bulk. Non-limitingly, the graphite-based material may include one or more of coated graphite-based materials and uncoated graphite. A coated graphite-based material includes a graphite bulk and a coating layer located on at least a portion of the surface of the graphite bulk; it is understood that the coating layer is a different material from the graphite bulk. Non-limitingly, the mass percentage of the graphite bulk in the graphite-based material may be 90% to 100%, and may also 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%. Graphite-based materials may include, but are not limited to, one or more of artificial graphite and natural graphite. In some embodiments, the carbon-based material is a graphite-based material. In some embodiments, the negative electrode active material is a graphite-based material.

[0178] In this application, the “graphite body” is composed of graphite.

[0179] In some embodiments, the graphite-based material accounts for 70% to 100% of the mass of the negative electrode active material, further preferably 75% to 100%, even more preferably 80% to 100%, even more preferably 90% to 100%, even more preferably 95% to 100%, even more preferably 97% to 100%, and may also be any of the following percentages or a range selected from any two of the following percentages: 70%, 75%, 80%, 85%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0180] In some embodiments, the negative electrode active material includes a carbon-based material. Non-limitingly, the carbon-based material constitutes 70% to 100% of the mass of the negative electrode active material, optionally 70% to 99%, further optionally 75% to 99%, and may also be 75% to 100%, 80% to 100%, further optionally 90% to 100%, or any of the following percentages or a range selected from any two of the following percentages: 70%, 75%, 80%, 85%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0181] 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.

[0182] Non-limitingly, the mass percentage of silicon-based material in the negative electrode active material can be 0% to 30%, optionally 0% to 25%, or any of the following percentages or a range selected from any two of the following percentages: 0, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 26%, 28%, 30%, etc.

[0183] In some embodiments, the negative electrode active material includes a silicon-based material. Non-limitingly, the silicon-based material may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Non-limitingly, the mass percentage of the silicon-based material in the negative electrode active material may be 1% to 30%, optionally 1% to 25%, and may also be any of the following percentages or a range selected from any two of the following percentages: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 26%, 28%, 30%, etc.

[0184] "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.

[0185] In some embodiments, the negative electrode sheet includes a negative electrode active layer, which includes a negative electrode active material; the negative electrode active material includes at least one of carbon-based materials and silicon-based materials.

[0186] The negative electrode sheet satisfies one or more of the following characteristics:

[0187] (b1) The mass percentage of silicon-based material in the negative electrode active material is 0-30%, and can be selected as 1%-30% (see also the appropriate values ​​or ranges in any of the embodiments in the context).

[0188] (b2) Silicon-based materials include silicon-carbon composite materials, which include a porous carbon matrix and elemental silicon located in the pores of the porous carbon matrix; without limitation, the mass percentage of silicon-carbon composite materials in silicon-based materials may 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.

[0189] By controlling the content and / or type of silicon-based materials in the negative electrode active material within the aforementioned range, it is beneficial to better control the expansion and contraction changes of the negative electrode, reduce the generation of fresh interfaces, suppress side reactions at the negative electrode interface, reduce the consumption rate of the first additive, decrease the rate of increase in battery internal resistance, and ultimately improve battery life. For example, in silicon-based materials, the volume expansion and contraction changes of silicon-carbon composite materials are relatively low.

[0190] In some embodiments, the positive electrode active material includes a positive electrode active body and a coating layer located on the positive electrode active body.

[0191] 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.

[0192] 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.

[0193] 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 this.

[0194] 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.

[0195] 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 in intensity between the D and G peaks in the Raman spectrum can be used to distinguish between graphite and hard carbon. Likewise, the difference in intensity between the D and G peaks in the Raman spectrum can be used to distinguish between natural graphite and synthetic graphite.

[0196] In some implementations, the first additive has a mass percentage of less than 3.6% in the electrolyte.

[0197] In some embodiments, the first additive has a mass percentage of 0.02% to 3.6% in the electrolyte.

[0198] In some embodiments, the first additive has a mass percentage of 0.02% to 2% in the electrolyte.

[0199] In some embodiments, the mass percentage of the first additive in the electrolyte is 0.1% to 1.6%, optionally 0.1% to 1.2%.

[0200] Non-limiting, the mass percentage of the first additive in the electrolyte 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%, 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.

[0201] By controlling the mass ratio of the first additive in the electrolyte within the aforementioned range, the first additive can continuously play a role in repairing the SEI film during cycling and / or storage, which is more conducive to significantly improving high-temperature performance while also maintaining good room-temperature performance.

[0202] In some embodiments, the additives include negative electrode film-forming additives that are different from the first additive.

[0203] "Negative electrode film-forming additives" refer to additives that can decompose at the negative electrode working potential and participate 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 the interface film (CEI film) at the positive electrode. Generally, those skilled in the art can determine whether an additive can participate in the formation of the negative electrode SEI film by methods such as reduction potential analysis, analysis of decomposition products and SEI film composition, and electrochemical performance verification. For example, the reduction potential of the additive can be measured by cyclic voltammetry in a simulated battery environment (such as lithium metal-pair working electrode); for example, the composition of the SEI film can be analyzed by 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.

[0204] Unlike the first additive, the negative electrode film-forming additive can competitively participate in the negative electrode film formation, which can reduce or delay the consumption of the first additive in the negative electrode film formation and suppress the increase in negative electrode interface impedance caused by the participation of the first additive in the negative electrode film formation. This is beneficial to better improve the high-temperature performance of the high-energy-density battery system while also having good room-temperature performance.

[0205] In some embodiments, the additive includes one or more of a second additive, a third additive, and a fourth additive.

[0206] Non-limiting, the sum of the mass percentages of the second, third and fourth additives in the electrolyte can be greater than or equal to 0.02%, optionally 0.02% to 5%, further optionally 0.02% to 3%, and further optionally 0.02% to 1.5%.

[0207] In some embodiments, the second additive is one or more of silane additives and siloxane additives.

[0208] Without limitation, the second additive may include tris(trimethylsilane)borate (TMSB).

[0209] Without limitation, silane additives may include tris(trimethylsilane)borate (TMSB).

[0210] In some embodiments, the third additive is one or more of isocyanate additives and acid anhydride additives.

[0211] In some embodiments, the fourth additive is one or more of lithium salt additives and phosphate ester additives.

[0212] Without limitation, isocyanate additives may include, but are not limited to, toluene diisocyanate.

[0213] Without limitation, acid anhydride additives may include one or more of maleic anhydride, citrate anhydride, trifluoromethyl maleic anhydride, succinic anhydride, glutaric anhydride, succinic anhydride, etc.

[0214] Non-limitingly, the mass percentage of acid anhydride additives in the electrolyte can be 0% to 1%, preferably 0.01% to 1%, and further preferably 0.1% to 1%.

[0215] Non-limitingly, lithium salt additives may include one or more of lithium oxalate, lithium tetrafluoroborate, lithium difluorophosphate, and fluorosulfonic acid lithium salts; non-limitingly, lithium oxalate may include one or more of lithium difluorooxalateborate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate; non-limitingly, fluorosulfonic acid lithium salts may include one or more of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide (LiFSI).

[0216] Non-limitingly, phosphate ester additives may include silicon-based phosphate ester additives; non-limitingly, silicon-based phosphate ester additives may include one or more of tris(trimethylsilane) phosphate, tris(trimethylsilyl) phosphite, etc.

[0217] In some implementations, the additives include lithium salt additives.

[0218] Without limitation, the mass percentage of lithium salt additive in the electrolyte can be 0 to 3%, which can be greater than 0 and less than or equal to 3%, and can be further selected as 0.05% to 3%.

[0219] In this application, when the mass percentage of lithium salt additives (such as LiFSI) in the electrolyte is greater than 3%, the mass percentage of lithium salt additives (such as LiFSI) in the electrolyte in the second additive is recorded as 3%.

[0220] In some implementations, the additives include phosphate esters.

[0221] Without limitation, the mass percentage of phosphate ester additives in the electrolyte can be 0 to 2%, which can be greater than 0 and less than or equal to 2%, and can be further selected as 0.1% to 2%.

[0222] In some embodiments, the second additive has a mass percentage of 0% to 1% in the electrolyte, optionally 0.1% to 1%.

[0223] In some embodiments, the mass ratio of the second additive to the first additive in the electrolyte is 0.1 to 50, optionally 0.2 to 50, further optionally 0.3 to 50, even further optionally 0.3 to 20, and may also be 0.2 to 1, optionally 0.2 to 0.5, or may be any of the following values ​​or a range selected from any two of the following values: 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, etc.

[0224] In some embodiments, the third additive has a mass percentage of 0% to 1% in the electrolyte, and may be 0.1% to 1%.

[0225] In some embodiments, the mass ratio of the third additive to the first additive in the electrolyte is 0.01 to 50, optionally 0.1 to 50, further optionally 0.2 to 50, even further optionally 0.3 to 50, even further optionally 0.3 to 20, and may also be 0.01 to 1, optionally 0.01 to 0.5, further optionally 0.01 to 0.3, or may be any of the following values ​​or a range selected from any two of the following values: 0.01, 0.02, 0.04, 0.05, 0.06, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 2, 3, 4, 5, 6, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, etc.

[0226] In some embodiments, the fourth additive has a mass percentage of 0% to 2% in the electrolyte, optionally 0.1% to 2%.

[0227] In some embodiments, the mass ratio of the fourth additive to the first additive in the electrolyte is 0.1 to 100, optionally 0.2 to 100, further optionally 0.2 to 50, even further optionally 0.3 to 50, even further optionally 0.3 to 20, and may also be 0.2 to 1, or may also be 0.08 to 100, optionally 0.08 to 50, further optionally 0.08 to 20, or may be 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.

[0228] In some embodiments, the mass ratio of the second additive, third additive, fourth additive, and first additive in the electrolyte is (0~20):(0~20):(0:50):1, and may be combined with features of any suitable embodiment in the context. For example, the mass ratio of the second additive, third additive, fourth additive, and first additive in the electrolyte may be (0.1~20):(0~20):(0:50):1, (0~20):(0.1~20):(0:50):1, (0~20):(0.1~20):(0.1:50):1, (0~0.5):(0~0.5):(0~1):1, (0.2~0.5):(0.01~0.5):(0.2~1):1, etc.

[0229] The second, third, and fourth additives can all be used as negative electrode film-forming additives. The second additive is a type of additive with low negative electrode film-forming impedance and a certain degree of acid removal effect, although its acid removal effect is lower than that of the first additive, and its negative electrode film-forming impedance is also lower than that of the first additive. The third additive is a type of additive with good acid removal effect, superior to that of the first additive, but its negative electrode film-forming impedance is higher than that of the first additive. The fourth additive has extremely low negative electrode film-forming impedance, far lower than that of the first additive.

[0230] By utilizing the synergistic effect of the first additive with one or more of the second, third, and fourth additives, it is beneficial to achieve a significant improvement in high-temperature performance while also maintaining good room-temperature performance.

[0231] In some implementations, the electrolyte satisfies one or more of the following characteristics:

[0232] (c1) The molecular weight of the first additive is less than or equal to 500 Da;

[0233] (c2) The molecule of the first additive contains 1 to 4 carbon-carbon triple bonds; not limited thereto, the number of carbon-carbon triple bonds in the molecule of the first additive may be 1, 2, 3 or 4.

[0234] (c3) The carbon-carbon triple bond is CH≡C-;

[0235] (c4) The molecule of the first additive contains 1 to 4 Lewis base nitrogen heterocycles. Without limitation, the number of Lewis base nitrogen heterocycles in the first additive can be 1, 2, 3 or 4.

[0236] (c5) Lewis base nitrogen heterocycles include imidazole rings;

[0237] (c6) In the molecule of the first additive, the carbon-carbon triple bond and the Lewis base nitrogen heterocycle are linked by a linker L1, which contains a C-type carbon bond covalently bonded to the carbon-carbon triple bond. 1-3 Alkylene or containing fluorinated C atoms covalently bonded to a carbon-carbon triple bond 1-3 Alkylene.

[0238] In some embodiments, the first additive satisfies one or more of the following characteristics:

[0239] (d1) The molecular weight of the first additive is less than or equal to 300 Da;

[0240] (d2) The molecule of the first additive contains 1 to 4 imidazole rings. Non-limitingly, the number of imidazole rings in the first additive can be 1, 2, 3 or 4.

[0241] (d3) Linker L1 contains C covalently bonded to the carbon-carbon triple bond. 1-3 Alkylene;

[0242] (d4) Lewis base nitrogen heterocycles include imidazole rings; the imidazole ring in a Lewis base nitrogen heterocycle 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.

[0243] In some embodiments, the first additive consists of a carbon-carbon triple bond, C 1-3 Alkylene and -OC(=O)-R 10 It is formed by sequential covalent bonds, R 10 It is a Lewis base nitrogen heterocycle.

[0244] In some embodiments, the first additive comprises compound II with the structure shown in formula (II): Among them, L 11 C 1-3Alkylene, Q2 is independently C 1-3 Alkyl, cyano, or fluorine atom, p2 is 0, 1, 2, or 3;

[0245] Without limitation, the mass percentage of compound II in the first additive may 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.

[0246] 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.

[0247] 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.

[0248] In some implementations, L 11 It is a methylene group.

[0249] In some implementations, p2 is 0.

[0250] In some embodiments, compound II is (Compound IIa).

[0251] Without limitation, the mass percentage of compound IIa in the first additive may 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.

[0252] By controlling the molecular weight of the first additive within the aforementioned lower range, the first additive can have a smaller molecular size, which is beneficial for better control of the low viscosity characteristics of the electrolyte, enabling the electrolyte to have higher conductivity and better control of the battery's internal resistance.

[0253] By controlling the number of carbon-carbon triple bonds in the first additive within the aforementioned range, it is beneficial to suppress the increase in interfacial impedance caused by the first additive participating in the formation and repair of the SEI film, and it is also beneficial to control the influence of the first additive on the liquid phase impedance; thus, the increase in battery internal resistance can be better suppressed.

[0254] By controlling the number of Lewis base nitrogen heterocycles in the first additive 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.

[0255] Examples of Lewis base nitrogen heterocycles include the imidazole ring in compound II.

[0256] In some embodiments, the additives in the electrolyte include cyclic sulfates.

[0257] Non-limiting, the mass percentage of cyclic sulfate esters in the electrolyte can be 0 to 3%, preferably 0.1% to 3%.

[0258] 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.

[0259] In some embodiments, the additive includes a polycyclic sulfate ester, which contains a plurality of monocyclic sulfate ester units.

[0260] In some embodiments, the multiple monocyclic sulfate units in the polycyclic sulfate ester are linked in a chain-like manner.

[0261] 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.

[0262] 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.

[0263] 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.

[0264] 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.

[0265] In some embodiments, the additives in the electrolyte include fluorocarbonate additives.

[0266] Non-limitingly, the mass percentage of fluorocarbonate additives in the electrolyte can be 0 to 10%, preferably 0.1% to 10%.

[0267] In some embodiments, the fluorocarbonate additive may include fluoroethylene carbonate (FEC). Non-limitingly, the mass percentage of FEC in the electrolyte may be 0-10%, optionally 0-5%, and further optionally 0.1%-10%, and even more preferably 0.1%-5%.

[0268] 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 the first additive in the negative electrode film formation, and better control the negative electrode interfacial impedance and battery internal resistance.

[0269] 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.

[0270] In some embodiments, the molar volume concentration of lithium hexafluorophosphate in the electrolyte can be 0.5 mol / L to 1.2 mol / L, optionally 0.6 mol / L to 1.2 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: 0.5 mol / L, 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, etc.

[0271] 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.

[0272] 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.

[0273] 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.

[0274] 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 and the negative electrode active body have different chemical compositions. 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%.

[0275] "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).

[0276] 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.

[0277] 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.

[0278] 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.

[0279] In some implementations, the negative electrode sheet satisfies one or more of the following characteristics:

[0280] (a1) The mass percentage of the coated negative electrode material in the negative electrode active material can be 80%~100%, optionally 90%~100%, further optionally 92%~100%, even further optionally 95%~100%, even further optionally 95%~98%, and can 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%, 92%, 94%, 95%, 96%, 98%, 100%, etc.;

[0281] (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%, further optionally 92% to 100%, even further optionally 95% to 100%, even further optionally 95% to 98%, and can 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%, 92%, 94%, 95%, 96%, 98%, 100%, etc.

[0282] 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.

[0283] In this application, the “graphite body” is composed of graphite.

[0284] 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 the first additive in anode film formation.

[0285] In some embodiments, the coated negative electrode material is coated graphite, in which case the active negative electrode body is the graphite body.

[0286] In some embodiments, the non-aqueous solvent includes chain carbonates.

[0287] 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.

[0288] In some embodiments, the structure of the chain carbonate is R 21 -OC(=O)-OR 22 R 21 and R 22 Each is independently an alkyl group having 1 to 3 (which can be 1, 2, or 3) 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 independently.

[0289] 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%.

[0290] In some embodiments, the non-aqueous solvent includes chain-like carboxylic acid ester compounds. Non-limitingly, the chain-like carboxylic acid ester compounds may constitute 0% to 40% of the non-aqueous solvent by mass.

[0291] 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.

[0292] In some embodiments, the non-aqueous solvent includes dimethyl carbonate, and, without limitation, the mass percentage of dimethyl carbonate in the non-aqueous solvent can be 0% to 50%.

[0293] In some embodiments, the ionic conductivity of the electrolyte at 25°C is greater than or equal to 8 mS / cm, and can be selected from 8 mS / cm to 20 mS / cm, further selected from 9 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: 8 mS / cm, 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.

[0294] 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).

[0295] Unless otherwise specified, the following steps may be used for testing:

[0296] 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℃).

[0297] Test: The instrument was calibrated using two standard solutions at 25℃. After calibration and cleaning the electrode, the test sample electrode was vertically placed into the liquid to be tested. Click "Start Test" and record the test results after the data stabilized for more than 10 seconds.

[0298] In some embodiments, lithium transition metal oxide cathode materials have a layered crystal structure.

[0299] Non-limitingly, the mass percentage of lithium transition metal oxide cathode material in 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.

[0300] In some embodiments, lithium transition metal oxide cathode materials include lithium nickel-based oxide cathode materials.

[0301] 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.

[0302] 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 0.8Co 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.

[0303] In some embodiments, lithium transition metal oxide cathode materials include lithium nickel cobalt-based oxide cathode materials.

[0304] 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.

[0305] "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).

[0306] 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.

[0307] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese-based oxide positive electrode materials.

[0308] 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.

[0309] 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.

[0310] In some embodiments, the positive electrode includes a positive active layer, which includes a positive active material, including a lithium transition metal oxide-based positive electrode material. The thickness of the positive active layer on one side of the negative current collector is less than or equal to 50 μm. The thickness of the positive active layer on one side of the negative 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 room temperature cycle life.

[0311] In some embodiments, the positive electrode active material includes lithium nickel-based oxide positive electrode materials, which include lithium, non-lithium metal elements, and oxygen; wherein, the non-lithium metal elements include nickel.

[0312] In lithium-nickel-based oxide cathode materials, the ratio of the atomic molar ratio of nickel to the sum of the atomic molar ratios of non-lithium metal elements is denoted as R. Ni When lithium-nickel-based oxide cathode materials also contain cobalt, the ratio of the atomic molar ratio of cobalt to the sum of the atomic molar ratios of non-lithium metal elements is denoted as R.Co When lithium-nickel-based oxide cathode materials also contain manganese, the ratio of the atomic molar ratio of manganese to the sum of the atomic molar ratios of non-lithium metal elements is denoted as R. Mn .

[0313] In some implementations, R Ni It can be 0.3 to 0.98, or any of the following values, or a range consisting of any two of the following values: 0.3, 0.33, 1 / 3, 0.34, 0.35, 0.5, 0.55, 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, etc.

[0314] 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.

[0315] 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.

[0316] In some implementations, R Co It can be 0.02 to 0.25, or any of the following values, or a range consisting of any two of the following values: 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.1, 0.12, 0.14, 0.15, 0.16, 0.18, 0.2, 0.22, 0.24, 0.25, etc.

[0317] In some implementations, R Mn It can be 0.1 to 0.35, or any of the following values, or a range consisting of any two of the following values: 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, 0.32, 0.34, 0.35, etc.

[0318] In some embodiments, the lithium nickel cobalt-based oxide cathode material contains an element M2, where M2 is manganese or aluminum; the sum of the atomic molar ratios of nickel, cobalt, and M2 relative to the sum of the atomic molar ratios of non-lithium metal elements in the nickel cobalt-based oxide cathode material is denoted as R. A R A The value is 0.42~1, and can be selected as 0.7~1.

[0319] The following is a description of the positive electrode sheet.

[0320] 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.

[0321] 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%.

[0322] 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.

[0323] 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).

[0324] The types of positive electrode active materials in the positive electrode sheet can be found in 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 materials in the cathode active material is 0% to 5%, and can be selected as 0.1% to 5%.

[0327] 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.

[0328] 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.

[0329] 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.

[0330] 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.

[0331] 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.

[0332] 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 the coating areal density on one side 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 .

[0333] In some embodiments, the positive electrode active material includes a lithium phosphate-containing active material. Further, the mass percentage of the lithium phosphate-containing 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) (based on the coating areal density of one side) can also be (0.1 ~ 0.5) g / 1540.25 mm². 2 The optional value is (0.2 ~ 0.4) g / 1540.25 mm. 2 However, this is not the only possibility. The compaction density of the positive electrode sheet can be 2.0 g / cm³. 3 ~2.8 g / cm 3 2.3g / cm³ is an option. 3 ~2.6 g / cm 3 .

[0334] 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.

[0335] The following are some other descriptions of the negative electrode plate.

[0336] 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.

[0337] 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%.

[0338] 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.

[0339] 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).

[0340] 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.

[0341] 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%.

[0342] For further information on the types of negative electrode active materials, please refer to the context of this application.

[0343] 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%.

[0344] 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%.

[0345] 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. When coating the negative electrode slurry, the surface density of the coating on one side of the negative electrode current collector, based on dry weight (excluding solvent), can be 7.5 mg / cm³. 2 ~22 mg / cm 2 The optional value is (0.12~0.2) g / 1540.25 mm. 2 The compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 ~ 2.0g / cm 3 1.0 g / cm³ is an optional value. 3 ~ 1.8 g / cm 3 .

[0346] The electrolyte is described below as an example.

[0347] The electrolyte serves to conduct ions between the positive and negative electrodes. The electrolyte consists of an electrolyte salt and a solvent.

[0348] In some embodiments, the electrolyte is a non-aqueous electrolyte. A non-aqueous electrolyte may include an electrolyte salt and a non-aqueous solvent.

[0349] 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 0.5 mol / L to 2 mol / L, further optionally 0.6 mol / L to 1.8 mol / L, and even more preferably 0.7 mol / L to 1.2 mol / L. It can also be 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, 2 mol / L, etc.

[0350] 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.

[0351] In some embodiments, the electrolyte salt includes an electrolyte lithium salt. Non-limitingly, the electrolyte lithium salt 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).

[0352] 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.

[0353] The electrolyte includes additives, including at least the first additive mentioned above.

[0354] 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.

[0355] The following is an exemplary description of the separator membrane.

[0356] In some embodiments, the lithium-ion secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0357] 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.

[0358] In some embodiments, the thickness of the separator is 6 μm to 40 μm, optionally 6 μm to 20 μm.

[0359] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0360] In some embodiments, the lithium-ion secondary battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0361] In some embodiments, the outer packaging of the lithium-ion secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the lithium-ion secondary battery can also be a soft pack, such as a pouch. The soft pack can be made of plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0362] A lithium-ion secondary battery includes at least one battery cell. A lithium-ion secondary battery may include one or more battery cells.

[0363] 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.

[0364] In some of these implementations, reference is made to... Figure 2 The 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.

[0365] The lithium-ion secondary battery can be a battery device 4 or a battery pack 1.

[0366] The battery device includes at least one battery cell. The number of battery cells in the battery device can be one or more, and those skilled in the art can select an appropriate number according to the application and capacity of the battery device.

[0367] 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.

[0368] Optionally, the battery device 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0369] 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.

[0370] 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.

[0371] 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.

[0372] In some embodiments, a method for preparing a lithium-ion secondary battery is provided, which includes the following steps:

[0373] S100: An electrode assembly including a positive electrode, a separator, and a negative electrode is placed inside a battery casing; wherein a separator is provided between the positive and negative electrode; wherein the positive electrode includes a positive active layer, the positive active layer includes a positive active material, the positive active material includes a lithium transition metal oxide-based positive electrode material, and the positive active material has a D... v 3 is greater than or equal to 1 μm;

[0374] S200: Inject electrolyte into the battery casing, allow it to stand to wet the positive and negative electrode plates, and form the battery; wherein, the electrolyte includes electrolyte salt, non-aqueous solvent and additives; the additives include a first additive, which is an alkyne base additive containing Lewis base nitrogen heterocycle.

[0375] The definitions of positive electrode active materials and additives can be found in the context of this application.

[0376] The prepared lithium-ion secondary battery has the advantages of the lithium-ion secondary battery described in the first aspect of this application.

[0377] In some embodiments, in step 200, after injecting electrolyte into the battery casing, a lithium-ion secondary battery assembly is obtained.

[0378] In some implementations, the lithium-ion secondary battery assembly may correspond to the state before formation treatment.

[0379] The transformation temperature can be 45°C, but is not limited to this.

[0380] 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):

[0381] S1) Charge at 0.05C for 14 minutes to 3V, then let stand for 10 minutes;

[0382] S2) Charge to 3.4V at 0.1C and let stand for 10 minutes;

[0383] S3) Charge to 3.65V at 0.2C and let stand for 10 minutes;

[0384] S4) Charge to 3.75V at 0.2C and let stand for 10 minutes;

[0385] The transformation ends.

[0386] 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.

[0387] In some embodiments, during the step of injecting electrolyte into the battery casing, the initial mass percentage of the first 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.

[0388] The first additive involved in this application is commercially available or can be synthesized using existing methods in the field of organic chemical synthesis. Once the structural formula of the first 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 first additive 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.

[0389] 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 may decrease 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 a first additive in the electrolyte is typically reduced after formation treatment compared to the electrolyte before formation treatment.

[0390] 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.

[0391] 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.

[0392] 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.

[0393] In some embodiments, the lithium-ion secondary battery described in the first aspect of this application is prepared.

[0394] In some embodiments of the third aspect of this application, an electrical device is provided, which includes at least one of the lithium-ion secondary batteries described in the first aspect of this application and lithium-ion secondary batteries prepared by the preparation method of the lithium-ion secondary batteries described in the second aspect of this application.

[0395] Electrical devices that include the aforementioned lithium-ion secondary batteries can have the advantages and benefits of the aforementioned lithium-ion secondary batteries.

[0396] In some embodiments, the electrical device includes a lithium-ion secondary battery according to any of the embodiments provided in this application.

[0397] Lithium-ion secondary batteries can be used as a power source for electrical devices or as an energy storage unit 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 type of electrical device can also be applied in aerospace and other fields, and can also be used in energy storage power systems such as hydroelectric, thermal, wind, and solar power plants.

[0398] As an electrical device, lithium-ion rechargeable batteries can be selected according to its usage requirements.

[0399] 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.

[0400] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a lithium-ion rechargeable battery as their power source.

[0401] In a fourth 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.

[0402] 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.

[0403] 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.

[0404] In the following examples, room temperature refers to 20 ℃ ~ 30 ℃.

[0405] In the following examples, unless otherwise specified, the parameters involved can be confirmed by referring to the test methods described above. For example, the parameters involving the positive electrode active material D... v 50 and D v 3. D of the negative electrode active material v 50 can be tested using a Malvern 2000 (MasterSizer 2000) laser particle size analyzer; for the specific surface area of ​​the negative electrode active material, a nitrogen adsorption specific surface area analysis method can be used, employing a Micromeritics Tri Star II specific surface area and porosity analyzer, and the specific surface area is calculated using the BET (Brunauer Emmett Teller) method. For the carbon coating layer, a transmission electron microscope (JEM-F200) combined with an energy dispersive spectrometer (EDS) 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, relevant standards such as GB / T 9722-2023 General Rules for Gas Chromatography of Chemical Reagents can be used for testing.

[0406] Among them, compound IIa ( Taking 2-propyn-1-yl 1H-imidazol-1-carboxylic acid ester as an example, the structure can be identified and quantitatively analyzed by the following methods:

[0407] In the 1H NMR spectrum, the H in the methylene group linked to the triple bond has a characteristic peak around 4.677 ppm; the hydrogen between the two nitrogen atoms in the imidazole ring has a characteristic peak around 8.095 ppm. By calculating the integrated area of ​​each characteristic peak and comparing it with the integrated area of ​​the internal standard trifluoromethylbenzene, the content of compound IIa can be quantitatively calculated.

[0408] The mass fraction of additives in the electrolyte can be determined using nuclear magnetic resonance (NMR) spectroscopy. The testing procedure is as follows: 500 μL of deuterated reagent is added to an NMR tube in a nitrogen-filled glove box. 100 μL of the non-aqueous electrolyte sample is then added to the NMR tube. The tube is shaken to dissolve the non-aqueous electrolyte in the deuterated reagent. The test is performed using an Oxford Instruments X-Pulse benchtop NMR spectrometer. Because the non-aqueous electrolyte is highly sensitive to moisture, both the proton NMR test and sample preparation are conducted under a nitrogen atmosphere (H₂O content less than 0.1 ppm, O₂ content less than 0.1 ppm). Simultaneously, all instruments used in the test must be pre-washed with pure water and dried in a vacuum environment at 60°C for at least 48 hours. The deuterated reagent was prepared as follows: Deuterated dimethyl sulfoxide (DMSO-d6), deuterated acetonitrile, and trifluoromethylbenzene were dried using a 4A molecular sieve at a temperature above 25°C for at least 3 days, ensuring that the water content of all reagents was less than 3 ppm. A Metrohm 831 KF coulometric moisture analyzer was used for moisture testing. Then, 10 mL of dried DMSO-d6 and 300 μL of dried trifluoromethylbenzene (internal standard) were mixed thoroughly in a nitrogen-filled glove box to obtain the first solution. 10 mL of dried deuterated acetonitrile and 300 μL of dried trifluoromethylbenzene (internal standard) were then mixed thoroughly to obtain the second solution. Finally, the first and second solutions were mixed thoroughly to obtain the deuterated reagent.

[0409] In the following embodiments, the electrolyte salt is an example of an electrolyte lithium salt, and compound IIa is a first additive as a non-limiting example.

[0410] I. Preparation of Lithium-ion Secondary Batteries

[0411] Example 1.

[0412] (1) Positive electrode plate

[0413] The positive electrode active material (Ni55), 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 96:3:1 to obtain a positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was coated onto both sides of the positive electrode current collector aluminum foil, with a coating density of 0.27 g / 1540.25 mm² on one side of the positive electrode current collector. 2 Through processes such as drying, cold pressing, slitting, and cutting, positive electrode sheets are obtained, with a compacted density of approximately 3.4 g / cm³. 3 .

[0414] In this example, the positive electrode active material is a ternary positive electrode material with the chemical formula LiNi. 0.55 C O0.12 Mn 0.33O2, D of the positive electrode active material v 50 is 4μm, D v The average particle size (D1) of the primary particles in the positive electrode active material is 2 μm, and the D of the positive electrode active material is 1.2 μm. v The ratio of 50 to the average particle size (D1) of the primary particles in the positive electrode active material is approximately 2.

[0415] (2) Negative electrode plate

[0416] 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 97:0.5:1.5:1, with a solid content of 50 wt%. The negative electrode slurry was then coated on both sides of the copper foil of the negative electrode current collector, with a coating density of 0.16 g / 1540.25 mm² on one side of the negative electrode current collector. 2 The negative electrode sheet is obtained through drying, cold pressing, slitting, and cutting processes. The compacted density of the negative electrode sheet is 1.65 g / cm³. 3 .

[0417] In this example, the negative electrode active material is coated graphite, comprising a graphite bulk and an amorphous carbon coating layer on the surface of the graphite bulk. The graphite bulk is artificial graphite, and the amorphous carbon coating layer accounts for approximately 1.43% of the mass of the coated graphite. The D of the negative electrode active material... v 50 has a diameter of 11 μm and a specific surface area of ​​1.5 m². 2 / g.

[0418] (3) Separator: Conventional PE film is used as the separator.

[0419] (4) Preparation of electrolyte: Add additives to non-aqueous solvent, mix evenly, add fully dried electrolyte lithium salt, mix thoroughly to fully dissolve electrolyte lithium salt, and prepare electrolyte.

[0420] 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 solvent is 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 (the first additive) and FEC (fluoroethylene carbonate). The structure of the first additive is shown in formula (IIa), also denoted as compound IIa. Compound IIa has an initial mass percentage of 2% in the electrolyte, and FEC has an initial mass percentage of 1% in the electrolyte.

[0421]

[0422] (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 battery is subjected to the following processes in sequence: standing, hot and cold pressing, formation, shaping and capacity testing to obtain lithium-ion secondary battery.

[0423] After injecting electrolyte, a lithium-ion secondary battery assembly is obtained.

[0424] In this example, the standing soaking parameters are: standing at room temperature for 18 hours, and then standing at 45°C for 6 hours.

[0425] In this example, the formation parameters are as follows: at 45℃,

[0426] Charge at 0.05C for 14 minutes to 3.0V, then let stand for 10 minutes;

[0427] Charge to 3.4V at 0.1C and let stand for 10 minutes;

[0428] Charge at 0.2C to 3.65V and let stand for 10 minutes;

[0429] Charge at 0.2C to 3.75V and let stand for 10 minutes;

[0430] The transformation has ended.

[0431] In this example, the lithium-ion secondary battery was manufactured, the cell was disassembled, and the component content in the electrolyte was tested. The first additive (compound II) was 1.2% by mass percentage in the electrolyte.

[0432] Examples 2-3. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that the positive electrode active material used in the positive electrode preparation step was different, mainly changing D. v 3. The relevant parameters of the positive electrode active material can be found in Table 1. The remaining operating steps are the same as in Example 1.

[0433] In Example 2, the D of the positive electrode active material v 3 is approximately 1 μm;

[0434] In Example 3, the D of the positive electrode active material v 3 is approximately 1.5 μm.

[0435] Examples 4-5. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that the positive electrode active material used in the positive electrode preparation step was different, mainly changing D. v 50. The relevant parameters of the positive electrode active material can be found in Table 1. The remaining operating steps are the same as in Example 1.

[0436] In Example 4, the D of the positive electrode active material v 50 is 2.7μm;

[0437] In Example 5, the D of the positive electrode active material v 50 is 4.8μm.

[0438] Example 6. A lithium-ion secondary battery was prepared using a method essentially the same as that in Example 1, except that the positive electrode active material used in the positive electrode preparation step was different. The relevant parameters of the positive electrode active material can be found in Table 1. The remaining operating steps were the same as in Example 1.

[0439] In Example 6, the positive electrode active material is a ternary positive electrode material with the chemical formula LiNi. 0.55 C O0.10 Mn 0.35 O2.

[0440] Examples 7-8. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that the D of the negative electrode active material used in the step of preparing the negative electrode sheet was changed. v The specific surface area and the value of 50 are different. Please refer to Table 1. The remaining operating steps are the same as in Example 1.

[0441] In Example 7, the D of the negative electrode active material v The thickness of 50 is 8.1 μm, and the specific surface area is 2.8 m². 2 / g.

[0442] In Example 8, the D of the negative electrode active material v The thickness of 50 is 19.8 μm, and the specific surface area is 0.5 m². 2 / g.

[0443] Examples 9-10. Lithium-ion secondary batteries were prepared using essentially the same method as in Example 1, except that the electrolyte composition and the initial concentration of the first additive (compound IIa) in the electrolyte were different, while the initial concentration of FEC remained unchanged. The remaining operational steps were the same as in Example 1. See Table 2 for details.

[0444] In Example 9, the initial mass percentage of the first additive (compound IIa) in the electrolyte was 0.1%.

[0445] In Example 10, the initial mass percentage of the first additive (compound IIa) in the electrolyte was 5%.

[0446] Examples 11-17. 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.

[0447] A second additive was added in Examples 11 and 12.

[0448] In Example 11, the additive composition of the electrolyte, based on the initial mass percentage in the electrolyte, was: 2% of compound IIa and 0.3% of TDI (toluene diisocyanate).

[0449] In Example 12, the additive composition of the electrolyte, based on its initial mass percentage in the electrolyte, was: 2% of compound IIa and 0.3% of TMSP (tris(trimethylsilane) phosphate).

[0450] In Example 13, the additive composition of the electrolyte, based on its initial mass percentage in the electrolyte, was: 2% of compound IIa and 0.5% of lithium difluorophosphate.

[0451] In Example 14, the additive composition of the electrolyte, based on the initial mass percentage in the electrolyte, was: 1% of compound IIa and 0.5% of LiDFOB (lithium difluorooxalate borate).

[0452] In Example 15, the additive composition of the electrolyte, based on its initial mass percentage in the electrolyte, was: 1% of compound IIa and 0.3% of TMSB (tris(trimethylsilane)borate).

[0453] In Example 16, the additive composition of the electrolyte, based on the initial mass percentage in the electrolyte, was: 2% of compound IIa and 1% of DTD (ethylene sulfate).

[0454] In Example 17, the additive composition of the electrolyte, based on the initial mass percentage in the electrolyte, was: 1% of compound IIa and 2% of FEC (fluoroethylene carbonate).

[0455] 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.

[0456] In Example 18, the electrolyte composition, based on its initial mass percentage in the electrolyte, consisted of: 1% of the first additive (compound IIa), 0.3% of TMSP, and 2% of FEC; and based on its initial molar volume concentration in the electrolyte, the electrolyte lithium salts were 0.3 mol / L LiFSI (lithium bis(fluorosulfonyl)imide) and 0.7 mol / L LiPF6 (lithium hexafluorophosphate).

[0457] Example 19. A lithium-ion secondary battery was prepared using a method essentially the same as that in Example 4, except that the negative electrode active material was different in the step of preparing the negative electrode sheet; the remaining steps were the same as in Example 4. See Table 1 for details.

[0458] In Example 19, the negative electrode active material is a carbon-based material and a silicon-based material in a mass ratio of 97:3, meaning the silicon-based material accounts for 3% of the total mass of the negative electrode active material. The carbon-based material is the same as in Example 1; the silicon-based material is a silicon-carbon composite material, comprising a porous carbon matrix and elemental silicon deposited within the pores of the porous carbon matrix, with a silicon to carbon mass ratio of 1:1. The negative electrode active material's D... v 1 and D v 50 is similar to Example 1.

[0459] 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 first 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 1.

[0460] Comparative Example 2. A lithium-ion secondary battery was prepared using essentially the same method as in Example 17, except that the composition of the electrolyte was different, the first 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.

[0461] 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 first 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.

[0462] Comparative Example 4. A lithium-ion secondary battery was prepared using essentially the same method as in Example 19, except that the composition of the electrolyte was different, the first 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.

[0463] Comparative Example 5. 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 first additive in the electrolyte was replaced with methylcarboxylic acid-2-propynyl ester (MCA). The initial concentration of the electrolyte lithium salt remains unchanged. The remaining operating steps are the same as in Example 1.

[0464] Comparative Example 6. A lithium-ion secondary battery was prepared using essentially the same method as in Example 19, except that the positive electrode active material used in the preparation of the positive electrode sheet was different, mainly changing D. v 3. The relevant parameters of the positive electrode active material can be found in Table 1. The remaining operating steps are the same as in Example 1.

[0465] In Comparative Example 6, the D of the positive electrode active material v 3 is approximately 0.5 μm.

[0466] Comparative Example 7. A lithium-ion secondary battery was prepared using essentially the same method as in Example 7, except that the positive electrode active material used in the preparation of the positive electrode sheet was different; the positive electrode active material of Comparative Example 6 was used. The relevant parameters of the positive electrode active material can be found in Table 1. The remaining operating steps were the same as in Example 7.

[0467] II. Test and Analysis Methods

[0468] 1. Electrolyte conductivity

[0469] A DDSJ-318 conductivity meter was used. Reference was made to page 5 of the industry standard HG / T4067-2015, "Lithium Hexafluorophosphate Electrolyte".

[0470] Test procedure (densitometer method):

[0471] Take about 100 mL of sample in a dry, clean, corrosion-resistant sample bottle, seal it and place it in a constant temperature water bath at 25℃±0.5℃, shake it from time to time. When the sample temperature is constant, replace the bottle cap with a rubber stopper with an electrode inserted. When the temperature is within the range of 25℃±0.5℃, read the data in the conductivity meter, which is the conductivity of the tested sample.

[0472] 2. Initial DC internal resistance (DCR) test:

[0473] At 25℃, the battery under test was charged at a constant current of 0.5C 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 30 minutes to adjust the battery to 50% SOC, and the voltage 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 0.1-second sampling time. The initial DCR of the battery is represented by the discharge DCR at 50% SOC, and the initial DCR of the battery is calculated as (U1-U2) / I, where I is the current value corresponding to 4C.

[0474] The test results can be found in Table 3 under "Battery DCR0".

[0475] 3. Normal temperature cycling performance (25℃)

[0476] At 25℃, the battery under test was charged to 3.65V at a constant current of 1C, then charged to a cutoff current of 0.05C at a constant voltage of 3.65V, left to rest for 10 minutes, and then discharged to 2.5V at a constant current of 1C, left to rest for 5 minutes. This constitutes one charge-discharge cycle. The discharge capacity at this point is recorded as C0. This charge-discharge cycle is repeated for the same battery, and the discharge capacity C of the first, second, ..., nth cycle is recorded. n The number of cycles must be at least 300.

[0477] Record the battery's cycle capacity retention rate P300 = C after 300 cycles. 300 / C0×100%.

[0478] The test results can be found in Table 3, "Capacity Retention Rate After 300 Cycles at Room Temperature". The higher the test value, the better the cycle life at room temperature.

[0479] 4. High-temperature cycling performance (45℃)

[0480] At 45℃, the battery under test is charged to 3.65V at a constant current of 1C, then charged to a cutoff current of 0.05C at a constant voltage of 3.65V, left to rest for 10 minutes, and then discharged to 2.5V at a constant current of 1C, left to rest for 5 minutes. This constitutes one charge-discharge cycle. The discharge capacity at this point is recorded as C0. This charge-discharge cycle is repeated for the same battery, and the discharge capacity C of the first, second, ..., nth cycle is recorded. n The number of cycles must be at least 600.

[0481] Record the battery's cycle capacity retention rate P600 = C after 600 cycles. 600 / C0×100%.

[0482] The test results can be found in Table 3, "Capacity Retention Rate after 600 Cycles at 45℃". A higher test value indicates a better high-temperature cycle life.

[0483] III. Test Analysis Results

[0484] In Examples 1-19, the ionic conductivity of the electrolytes at 25°C was all in the range of 8 mS / cm to 20 mS / cm.

[0485] Table 1.

[0486]

[0487] In Table 1, B1 represents the D of the positive electrode active material. v 50 is the ratio of the average particle size (D1) of the primary particles in the positive electrode active material.

[0488] Table 2.

[0489]

[0490] In the lithium-ion secondary batteries prepared by formation, the electrolyte composition was tested by disassembling the cells: the mass percentage of the first additive in the electrolytes of Examples 1-19 was all in the range of 0.02% to 3.6%. After formation, the mass percentage of the first additive in the electrolyte of Example 1 was about 1.2% (initial concentration before formation was 2%), the mass percentage of the first additive in the electrolyte of Example 9 was about 0.02% (initial concentration before formation was 0.1%), and the mass percentage of the first additive in the electrolyte of Example 10 was about 3.6% (initial concentration before formation was 5%). The mass percentage of other additives in the electrolytes of Examples 11-18 decreased to varying degrees and all still had residues.

[0491] In the lithium-ion secondary batteries prepared by formation, the electrolyte composition was tested by disassembling the cells: In Example 15, the mass ratio of the second additive to the first additive was in the range of 0.1 to 50, and the mass percentage of the second additive in the electrolyte was in the range of 0.1% to 1%, further in the range of 0.1% to 0.3%; In Example 11, the mass ratio of the third additive to the first additive was in the range of 0.1 to 50, and the mass percentage of the second additive in the electrolyte was in the range of 0.1% to 1%, further in the range of 0.1% to 0.3%; In Examples 12-14, the mass ratio of the fourth additive to the first additive was in the range of 0.01 to 100, and the mass percentage of the fourth additive in the electrolyte was in the range of 0.1% to 2%, further in the range of 0.1% to 0.5%.

[0492] Table 3.

[0493]

[0494] The lithium-ion secondary batteries prepared in Examples 1-19 all exhibited significantly improved high-temperature performance as well as good room-temperature performance.

[0495] Compared with Examples 1 and 17-19, Comparative Examples 1-4 omitted the first additive, and the high-temperature performance and room-temperature performance of Comparative Examples 1-4 were significantly deteriorated.

[0496] In Comparative Example 5, the first additive in Example 1 was replaced with an alkyne additive that did not contain Lewis base nitrogen heterocycles. The high-temperature performance and room-temperature performance of Comparative Example 5 were significantly deteriorated.

[0497] Comparative Example 6 reduced the D of the positive electrode active material in Example 19 v3. The high-temperature and room-temperature performance of Comparative Example 6 deteriorated. Compared with Example 7, the high-temperature and room-temperature performance of Comparative Example 7 also deteriorated.

[0498] 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.

[0499] 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, 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 positive electrode includes a positive active layer, which includes a positive active material. The electrolyte includes an electrolyte salt, a non-aqueous solvent, and additives. The positive electrode active material includes a lithium transition metal oxide positive electrode material, wherein the average particle size of the primary particles in the positive electrode active material is 1.1 μm to 3.0 μm, and the D of the positive electrode active material is... v 50 is 2.5μm to 5μm, and the D of the positive electrode active material is... v The ratio of 50 to the average particle size of the primary particles in the positive electrode active material is denoted as B1, where B1 is 1.1 to 2.5; the D of the positive electrode active material v 3 is greater than or equal to 1 μm; The additive includes a first additive, which is an alkylene base additive containing a Lewis base nitrogen heterocycle.

2. The lithium-ion secondary battery according to claim 1, characterized in that, The positive electrode active material D v 3 is 1μm to 2μm.

3. The lithium-ion secondary battery according to claim 2, characterized in that, The positive electrode active material D v 3 is 1μm to 1.6μm.

4. The lithium-ion secondary battery according to claim 1, characterized in that, The average particle size of the primary particles in the positive electrode active material is 1.5 μm to 2.8 μm.

5. The lithium-ion secondary battery according to claim 4, characterized in that, The average particle size of the primary particles in the positive electrode active material is 1.8 μm to 2.5 μm.

6. The lithium-ion secondary battery according to claim 1, characterized in that, The positive electrode sheet satisfies one or more of the following characteristics: (a1') D of the positive electrode active material v 50 is 3.5μm~4.8μm; (a2')B1 is 1.8 to 2.

1.

7. The lithium-ion secondary battery according to claim 1, characterized in that, The lithium transition metal oxide cathode material accounts for 95% to 100% of the mass of the cathode active material.

8. The lithium-ion secondary battery according to claim 1, characterized in that, The positive electrode active material is a lithium transition metal oxide type positive electrode material.

9. The lithium-ion secondary battery according to any one of claims 1 to 8, characterized in that, The negative electrode sheet includes a negative electrode active layer, and the negative electrode active layer includes a negative electrode active material; the negative electrode active material has a D... v 50 is 8μm to 20μm, and the D of the negative electrode active material is... v 1 is greater than or equal to 1.5 μm.

10. The lithium-ion secondary battery according to claim 9, characterized in that, The negative electrode active material D v 50 represents 10μm to 18μm.

11. The lithium-ion secondary battery according to any one of claims 1 to 8, characterized in that, The negative electrode sheet includes a negative electrode active layer, and the negative electrode active layer includes a negative electrode active material; the negative electrode active material includes at least one of carbon-based materials and silicon-based materials; The negative electrode sheet satisfies one or more of the following characteristics: (b1) The silicon-based material accounts for 0-30% of the mass of the negative electrode active material; (b2) The silicon-based material includes a silicon-carbon composite material, which includes a porous carbon matrix and elemental silicon located in 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. (b3) The specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g~2.8m 2 / g.

12. The lithium-ion secondary battery according to any one of claims 1 to 8, characterized in that, The first additive constitutes 0.02% to 3.6% by mass in the electrolyte.

13. The lithium-ion secondary battery according to claim 12, characterized in that, The first additive has a mass percentage of 0.1% to 3.6% in the electrolyte.

14. The lithium-ion secondary battery according to claim 12, characterized in that, The first additive has a mass percentage of 1% to 3.6% in the electrolyte.

15. The lithium-ion secondary battery according to claim 12, characterized in that, The first additive has a mass percentage of 0.1% to 1.6% in the electrolyte.

16. The lithium-ion secondary battery according to any one of claims 1 to 8, characterized in that, The additives include negative electrode film-forming additives different from the first additives, and the additives include a third additive; the third additive is one or more of isocyanate additives and acid anhydride additives, and the mass percentage of the third additive in the electrolyte is 0.1% to 1%.

17. The lithium-ion secondary battery according to claim 16, characterized in that, The electrolyte satisfies at least one of the following characteristics: (1) The mass ratio of the third additive to the first additive is 0.04 to 2; (2) The additives include isocyanate additives, and the isocyanate additives include toluene diisocyanate; (3) The additives include acid anhydride additives, which include one or more of maleic anhydride, citrate anhydride, trifluoromethyl maleic anhydride, succinic anhydride, glutaric anhydride, and succinic anhydride. (4) The mass percentage of the acid anhydride additive in the electrolyte is 0% to 1%.

18. The lithium-ion secondary battery according to any one of claims 1 to 8, characterized in that, The additives include one or more of the second, third, and fourth additives; The second additive is one or more of silane additives and siloxane additives; The third additive is one or more of isocyanate additives and acid anhydride additives; The fourth additive is one or more of lithium salt additives and phosphate ester additives.

19. The lithium-ion secondary battery according to claim 18, characterized in that, The electrolyte satisfies at least one of the following characteristics: (1) In the electrolyte, the mass ratio of the second additive to the first additive is 0.1 to 10; (2) In the electrolyte, the mass ratio of the third additive to the first additive is 0.01 to 10; (3) In the electrolyte, the mass ratio of the fourth additive to the first additive is 0.1 to 20.

20. The lithium-ion secondary battery according to claim 18, characterized in that, In the electrolyte, the mass ratio of the second additive, the third additive, the fourth additive and the first additive is (0-0.5):(0-0.5):(0-1):

1.

21. The lithium-ion secondary battery according to any one of claims 1 to 8, characterized in that, The electrolyte satisfies one or more of the following characteristics: (c1) The molecular weight of the first additive is less than or equal to 500 Da; (c2) The molecule of the first additive contains 1 to 4 carbon-carbon triple bonds; (c3) The carbon-carbon triple bond is CH≡C-; (c4) The molecule of the first additive contains 1 to 4 Lewis base nitrogen heterocycles; (c5) The Lewis base nitrogen heterocycle includes an imidazole ring; (c6) In the molecule of the first additive, the carbon-carbon triple bond and the Lewis base nitrogen heterocycle are connected by a linker L1, wherein the linker L1 contains a C-type carbon bond covalently bonded to the carbon-carbon triple bond. 1-3 Alkylene or containing fluorinated C atoms covalently bonded to a carbon-carbon triple bond 1-3 Alkylene.

22. The lithium-ion secondary battery according to claim 21, characterized in that, The first additive satisfies one or more of the following characteristics: (d1) The molecular weight of the first additive is less than or equal to 300 Da; (d2) The molecule of the first additive contains 1 to 4 imidazole rings; (d3) The linker L1 contains C covalently bonded to the carbon-carbon triple bond. 1-3 Alkylene; (d4) The Lewis base nitrogen heterocycle includes an imidazole ring; the imidazole ring in the Lewis base nitrogen heterocycle is substituted by 0, 1, or more substituents Q2, wherein each substituent Q2 in the substituted imidazole group is independently C. 1-3 Alkyl, cyano or fluorine atom.

23. The lithium-ion secondary battery according to claim 21, characterized in that, The first additive comprises compound II with the structure shown in formula (II): 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 mass percentage of compound II in the first additive is greater than or equal to 80% and less than 100%, or is 100%.

24. A method for preparing a lithium-ion secondary battery, characterized in that, Includes the following steps: An electrode assembly comprising a positive electrode, a separator, and a negative electrode is placed within a battery casing; wherein the separator is disposed between the positive electrode and the negative electrode; wherein the positive electrode includes a positive active layer, the positive active layer includes a positive active material, the positive active material is a lithium transition metal oxide positive electrode material, the average particle size of the primary particles in the positive active material is 1.1 μm to 3.0 μm, and the D of the positive active material is... v 50 is 2.5μm to 5μm, and the D of the positive electrode active material is... v The ratio of 50 to the average particle size of the primary particles in the positive electrode active material is denoted as B1, where B1 is 1.1 to 2.5; the D of the positive electrode active material v 3 is greater than or equal to 1 μm; An electrolyte is injected into the battery casing, and the casing is left to stand to allow the electrolyte to wet the positive electrode and the negative electrode, thus forming the battery. The electrolyte includes an electrolyte salt, a non-aqueous solvent, and an additive. The additive includes a first additive, which is an alkyne base additive containing a Lewis base nitrogen heterocycle.

25. The method for preparing a lithium-ion secondary battery according to claim 24, characterized in that, The lithium-ion secondary battery according to any one of claims 2 to 23 is prepared.

26. An electrical appliance, characterized in that, Includes the lithium-ion secondary battery as described in any one of claims 1 to 23.

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