Lithium-ion battery and electrical device

Abstract

The present application discloses a lithium-ion battery and an electrical device. The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The positive electrode sheet comprises a layered lithium-containing transition metal oxide, the molar proportion of nickel in the layered lithium-containing transition metal oxide being in the range of 0.60 to 0.70, and the molar proportion of cobalt being in the range of 0.08 to 0.15. The negative electrode sheet comprises a negative electrode film layer. The negative electrode film layer comprises amorphous carbon and graphite. On the basis of the total mass of the negative electrode film layer, the mass proportion of the graphite is in the range of 80% to 98%, and the mass proportion of the amorphous carbon is in the range of 0.01% to 10%. In the embodiments of the present application, by regulating the specific components of the positive electrode active material and the negative electrode active material of the lithium-ion battery, the charging performance and cycle life of the lithium-ion battery are improved.

Description

Lithium-ion batteries and electrical equipment

[0001] This disclosure claims priority to Chinese patent application No. 2025100118251, filed on January 3, 2025, entitled “Lithium-ion Battery and Electrical Device”, which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to the field of new energy technology, and in particular to a lithium-ion battery and electrical equipment. Background Technology

[0003] This section provides only background information relevant to this application and is not necessarily prior art.

[0004] Lithium-ion batteries are widely used in wireless communication, transportation, aerospace, and many other fields. With continuous technological advancements, lithium-ion batteries will continue to play a vital role and drive innovation in energy storage technology. For lithium-ion batteries, charging performance and cycle life are crucial factors affecting their development.

[0005] Therefore, this invention is proposed. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a lithium-ion battery and electrical device, which aims to improve the charging performance and cycle life of lithium-ion batteries.

[0007] To achieve the above objectives, a first aspect of this application provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte.

[0008] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a nickel-cobalt compound, which includes a layered lithium-containing transition metal oxide. The ratio of the molar amount of nickel in the layered lithium-containing transition metal oxide to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide is in the range of 0.60 to 0.70, and the ratio of the molar amount of cobalt in the layered lithium-containing transition metal oxide to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide is in the range of 0.08 to 0.15.

[0009] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; the negative electrode film layer includes a negative electrode active material, which includes amorphous carbon and graphite; based on the total mass of the negative electrode film layer, the mass percentage of graphite is in the range of 80% to 98%, and the mass percentage of amorphous carbon is in the range of 0.01% to 10%.

[0010] The embodiments of this application improve the charging performance and cycle life of lithium-ion batteries by controlling the specific composition of the positive and negative electrode active materials.

[0011] In some embodiments, layered lithium-containing transition metal oxides include Li a Ni b Co c M d O e A f Wherein, 0<a≤1.2, 0.60≤b≤0.70, 0.08≤c≤0.15, 0.15≤d≤0.32, b+c+d=1; 1≤e≤2; 0≤f≤1, e+f=2; M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, W, Nb, Sb and B, and A includes one or more of N, F, S and Cl.

[0012] The embodiments of this application improve the structural stability of layered lithium-containing transition metal oxides using the above-described general chemical formula, thereby enabling lithium-ion batteries to have good cycle life.

[0013] In some embodiments, the nickel-cobalt compound includes nickel-cobalt compounds with a single crystal morphology.

[0014] The embodiments of this application improve the cycle life of lithium-ion batteries by using positive electrode active materials containing nickel-cobalt compounds with single-crystal morphology.

[0015] In some embodiments, the specific capacity of the positive electrode active material is in the range of 190 mAh / g to 200 mAh / g.

[0016] The embodiments of this application improve the cycle life of lithium-ion batteries by using positive electrode active materials within the above-mentioned specific capacity range.

[0017] In some embodiments, the mass percentage of nickel-cobalt compound is greater than or equal to 95% based on the total mass of the positive electrode active material.

[0018] The embodiments of this application improve the cycle life of lithium-ion batteries by adjusting the mass ratio of nickel-cobalt element compounds based on the total mass of the positive electrode active material.

[0019] In some embodiments, the compaction density of the positive electrode film is in the range of 3.1 g / cc to 3.6 g / cc.

[0020] The embodiments of this application improve the cycle life of lithium-ion batteries by using positive electrode film layers within the above-mentioned compaction density range.

[0021] In some embodiments, the coating weight of the positive electrode film is 225 mg / 1540.25 mm. 2 ~245mg / 1540.25mm 2 Within the range.

[0022] The embodiments of this application improve the cycle life of lithium-ion batteries by employing positive electrode film layers within the above-described coating weight range.

[0023] In some embodiments, graphite includes one or both of natural graphite and artificial graphite.

[0024] The embodiments of this application improve the cycle life and charging performance of lithium-ion batteries through the above-mentioned graphite.

[0025] In some embodiments, the specific capacity of the negative electrode active material is in the range of 350 mAh / g to 365 mAh / g.

[0026] The embodiments of this application improve the cycle life of lithium-ion batteries by using negative electrode active materials within the above-mentioned specific capacity range.

[0027] In some embodiments, the graphitization degree of graphite is in the range of 90% to 95%.

[0028] The graphite with the above-mentioned degree of graphitization has a highly ordered layered structure. Using graphite with the above-mentioned degree of graphitization is beneficial to reduce its volume expansion during charging and discharging, thereby improving the cycle life of lithium-ion batteries.

[0029] In some embodiments, the OI value of graphite is in the range of 8 to 25.

[0030] The expansion of graphite with the aforementioned orientation index (OI) value during lithium intercalation can be dispersed in all directions, which helps to reduce the volume expansion of lithium-ion batteries and improve their cycle life.

[0031] In some embodiments, the Dv50 of graphite is in the range of 9 μm to 20 μm.

[0032] The embodiments of this application improve the charging performance and cycle life of lithium-ion batteries by using graphite within the Dv50 range described above.

[0033] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.6 m². 2 / g~2.1m 2 Within the range of / g.

[0034] The embodiments of this application utilize negative electrode active materials within the aforementioned specific surface area range, which helps to reduce surface side reactions and improve the cycle life of lithium-ion batteries.

[0035] In some embodiments, at least a portion of amorphous carbon covers at least a portion of the surface of graphite.

[0036] The embodiments of this application improve the charging performance of lithium-ion batteries by using graphite with at least a portion of its surface covered with amorphous carbon.

[0037] In some embodiments, the porosity of the negative electrode film is in the range of 30% to 45%.

[0038] The embodiments of this application improve the charging performance and cycle life of lithium-ion batteries through the negative electrode film layer within the aforementioned porosity range.

[0039] In some embodiments, the compaction density of the negative electrode film is in the range of 1.5 g / cc to 1.8 g / cc.

[0040] The embodiments of this application improve the cycle life of lithium-ion batteries by using negative electrode film layers within the aforementioned compaction density range.

[0041] In some embodiments, the coating weight of the negative electrode film is 130 mg / 1540.25 mm. 2 ~150mg / 1540.25mm 2 Within the range.

[0042] The embodiments of this application improve the cycle life of lithium-ion batteries by employing negative electrode film layers within the above-described coating weight range.

[0043] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the second negative electrode film layer being disposed between the first negative electrode film layer and the negative electrode current collector; the first negative electrode film layer includes a first negative electrode active material, the first negative electrode active material including amorphous carbon and graphite; the second negative electrode film layer includes a second negative electrode active material, the second negative electrode active material including graphite or the second negative electrode active material including amorphous carbon and graphite; based on the total mass of the first negative electrode film layer, the mass percentage of graphite in the first negative electrode film layer is in the range of 85% to 96%, and the mass percentage of amorphous carbon in the first negative electrode film layer is in the range of 1% to 9.7%; based on the total mass of the second negative electrode film layer, the mass percentage of graphite in the second negative electrode film layer is in the range of 91% to 97%, and the mass percentage of amorphous carbon in the second negative electrode film layer is in the range of 0% to 4%.

[0044] The embodiments of this application improve the charging performance of lithium-ion batteries while maintaining good cycle life by adjusting the mass ratio of amorphous carbon in each layer of the negative electrode film.

[0045] In some embodiments, the specific capacity of the first negative electrode active material is in the range of 350 mAh / g to 360 mAh / g, and / or the specific capacity of the second negative electrode active material is in the range of 355 mAh / g to 365 mAh / g.

[0046] The embodiments of this application, by layering the negative electrode film and differentially controlling the specific capacity of each layer of negative electrode active material, improve the charging performance of lithium-ion batteries while still maintaining good cycle life.

[0047] In some embodiments, the Dv50 of the first negative electrode active material is in the range of 9.8 μm to 14.8 μm, and / or the Dv50 of the second negative electrode active material is in the range of 11 μm to 18 μm.

[0048] The embodiments of this application, through the first and second negative electrode active materials within the Dv50 range described above, achieve good cycle life while improving the charging performance of lithium-ion batteries.

[0049] In some embodiments, the specific surface area of ​​the first negative electrode active material is 0.6 m². 2 / g~1.2m 2 Within the range of / g, and / or, the specific surface area of ​​the second negative electrode active material is within 1.5m². 2 / g~2.1m 2 Within the range of / g.

[0050] The embodiments of this application reduce side reactions on the negative electrode surface and improve the cycle life of lithium-ion batteries by using the first and second negative electrode active materials within the above-mentioned specific surface area range.

[0051] In some embodiments, the CB values ​​of the negative electrode and the positive electrode are in the range of 1.05 to 1.15.

[0052] The embodiments of this application, through lithium-ion batteries within the aforementioned CB value range, enable good wetting and reabsorption on both the positive and negative electrode plates, improve the liquid phase transport conditions of lithium ions, and provide more active sites for lithium ion insertion on the negative electrode, thereby improving the charging performance and cycle life of the lithium-ion battery.

[0053] Secondly, embodiments of this application provide an electrical device including any of the lithium-ion batteries provided in the first aspect.

[0054] The electrical devices provided by the embodiments of this application have at least the same advantages as lithium-ion batteries, which can improve the battery life of the electrical devices. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. Other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 is a schematic diagram of the vehicle structure provided in an embodiment of this application;

[0057] Figure 2 is an exploded structural diagram of a lithium-ion battery provided in an embodiment of this application;

[0058] Figure 3 is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0059] Explanation of icon numbers:

[0060] 1000-Vehicle, 100-Lithium-ion battery, 200-Controller, 300-Motor, 10-Box, 20-Battery cell, 11-First part, 12-Second part, 21-End cap, 22-Housing shell, 23-Electrode assembly, 21a-Electrode terminal.

[0061] Embodiments of the present invention

[0062] The present application will be further described below with reference to specific embodiments. It should be understood that these specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0063] For the sake of brevity, this article only discloses some specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0064] In this description, unless otherwise stated, the term "or" is inclusive. That is, the phrase "A or (or) B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0065] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0066] Unless otherwise stated, the terms used in this application have their common meanings in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0067] The type and structural stability of the positive electrode active material significantly impact the cycle life of lithium-ion batteries. The type of negative electrode active material and the number of insertion / extraction sites for active ions in the negative electrode active material significantly affect the charging capability of lithium-ion batteries. However, in some cases, as the charging capability of lithium-ion batteries increases, the stability of the positive and / or negative electrodes deteriorates, thereby negatively impacting the cycle life of the lithium-ion battery. Therefore, improving the charging performance and cycle life of lithium-ion batteries is of great significance to their development.

[0068] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use lithium-ion batteries, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0069] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device according to an embodiment of this application.

[0070] Please refer to Figure 1, which is a structural schematic diagram of a vehicle provided in an embodiment of this application.

[0071] Referring to Figure 1, vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A lithium-ion battery 100 is installed inside vehicle 1000, which can be located at the bottom, front, or rear of vehicle 1000. The lithium-ion battery 100 can be used to power vehicle 1000; for example, it can serve as the operating power source for vehicle 1000. Vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 controls the lithium-ion battery 100 to supply power to the motor 300, for example, to meet the power needs of vehicle 1000 during startup, navigation, and driving.

[0072] In some embodiments of this application, the lithium-ion battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0073] Please refer to Figure 2, which is a schematic diagram of the exploded structure of a lithium-ion battery provided in an embodiment of this application.

[0074] Referring to Figure 2, the lithium-ion battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, collectively defining a space for accommodating the battery cell 20. The second portion 12 can be a hollow structure with one open end, and the first portion 11 can be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 together define the space. Alternatively, both the first portion 11 and the second portion 12 can be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0075] In the lithium-ion battery 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 20 is housed within the casing 10. Alternatively, the lithium-ion battery 100 can also consist of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then these battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the casing 10. The lithium-ion battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0076] Among them, the battery cell 20 can be in the form of a cylinder, a flat shape, a cuboid, or other shapes.

[0077] Please refer to Figure 3, which is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0078] Referring to Figure 3, the battery cell 20 refers to the smallest unit that makes up the lithium-ion battery 100. The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0079] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, giving battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 to output or input electrical energy to battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0080] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The housing 22 can be made of various materials, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, and plastic.

[0081] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the cell assembly, while the portions of the positive and negative electrode sheets without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery cell 20, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0082] To achieve the above objectives, a first aspect of this application provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte.

[0083] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a nickel-cobalt compound, which includes a layered lithium-containing transition metal oxide. The ratio of the molar amount of nickel to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide is in the range of 0.60 to 0.70, and the ratio of the molar amount of cobalt to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide is in the range of 0.08 to 0.15.

[0084] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes amorphous carbon and graphite. Based on the total mass of the negative electrode film layer, the mass percentage of graphite is in the range of 80% to 98%, and the mass percentage of amorphous carbon is in the range of 0.01% to 10%.

[0085] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on one surface of the positive current collector. In some embodiments, the positive electrode includes a positive current collector and two positive electrode film layers, one of which is disposed on one surface of the positive current collector, and the other is disposed on the opposite surface of the positive current collector where the aforementioned positive electrode film layer is disposed. In some embodiments, the positive electrode film layer is a single-layer film layer. In some embodiments, the positive electrode film layer is a multilayer film layer, as specifically configured as needed.

[0086] Layered lithium-containing transition metal oxides have a well-known meaning. In some embodiments, examples of layered lithium-containing transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. In some embodiments, the modified compound may be a new compound formed by doping and / or surface coating modification of the above-mentioned layered lithium-containing transition metal oxides.

[0087] By controlling the ratio of the molar amount of nickel to the total molar amount of transition metal elements in layered lithium-containing transition metal oxides within the range of 0.60 to 0.70, nickel-lithium mixing can be reduced while maintaining high energy density in lithium-ion batteries. This improves the structural stability of layered lithium-containing transition metal oxides and thus enhances the cycle life of lithium-ion batteries.

[0088] By adjusting the ratio of the molar amount of cobalt to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide within the range of 0.08 to 0.15, the layered lithium-containing transition metal oxide can exhibit a higher voltage plateau and better structural stability, thereby improving the cycle life of lithium-ion batteries.

[0089] It should be noted that the ratios of the molar amount of nickel to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide, and the ratios of the molar amount of cobalt to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide, in the embodiments of this application, can be determined using instruments and methods known in the art. For example, an ICP inductively coupled plasma atomic emission spectrometer can be used to measure the elemental composition and content in the positive electrode active material, obtain the molar amounts of nickel, cobalt, and transition metal elements in the layered lithium-containing transition metal oxide, and calculate the ratios of the molar amounts of nickel and cobalt to the total molar amounts of transition metal elements in the layered lithium-containing transition metal oxide.

[0090] In some embodiments, the positive electrode active material may include, in addition to the nickel-cobalt-containing compounds provided above, other existing positive electrode active materials to regulate the battery performance of the lithium-ion battery. For example, other existing positive electrode active materials may be lithium phosphates with an olivine structure. In some embodiments, the nickel-cobalt-containing compounds may include, in addition to the layered lithium-containing transition metal oxides provided above, other existing nickel-cobalt-containing compounds.

[0091] In some embodiments, the positive electrode film layer further includes a positive electrode conductive agent and a positive electrode binder.

[0092] The positive electrode conductive agent imparts conductivity to the positive electrode. The positive electrode conductive agent can include any existing conductive material. For example, the positive electrode conductive agent includes, but is not limited to, one or more of the following: carbon-based materials (e.g., natural graphite, conductive graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), and conductive polymers (e.g., polyphenylene derivatives).

[0093] Positive electrode binders improve the adhesion stability of the positive electrode film and reduce the probability of powder shedding. For example, positive electrode binders may include one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), lithium-ionized polyacrylic acid (PAALi), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0094] Graphite is suitable for lithium-ion intercalation and deintercalation, and can form lithium-graphite intercalation compounds. It has advantages such as low cost, abundant reserves, low lithium intercalation voltage, and small volume change during intercalation and deintercalation. Graphite-based negative electrode active materials, when used in negative electrode sheets, are beneficial for improving the cycle life of lithium-ion batteries. In some embodiments, graphite includes one or both of natural graphite and / or artificial graphite.

[0095] Amorphous carbon refers to a transitional state of carbon, generally encompassing carbon elements other than graphite and diamond. In some embodiments, amorphous carbon includes one or both of hard carbon and soft carbon. Compared to graphite, amorphous carbon has a greater number of surface defects, which is beneficial for increasing the number of sites for the insertion and extraction of active ions in the negative electrode active material. This allows active ions to diffuse more quickly within the particles of the negative electrode active material, thereby improving the charging performance of lithium-ion batteries.

[0096] In some embodiments, graphite and amorphous carbon exist in a mixed form in the negative electrode film layer. In some embodiments, amorphous carbon covers part or all of the surface of the graphite in the negative electrode film layer. In some embodiments, amorphous carbon partially covers part or all of the surface of the graphite in the negative electrode film layer, and the amorphous carbon and uncoated graphite as well as graphite with amorphous carbon covering its surface are mixed together.

[0097] Based on the total mass of the negative electrode film, the mass percentage of graphite can be 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 98%, etc., or a range of any two of the above values, such as 80%~90%, 85%~95%, or 90%~98%, etc.

[0098] Based on the total mass of the negative electrode film, the mass percentage of amorphous carbon can be 0.01%, 0.05%, 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc., or a range of any two of the above values, such as 0.01%~2%, 1%~3%, 2%~6%, 4%~8%, or 5%~10%, etc.

[0099] In some embodiments, the negative electrode active material may include other negative electrode active materials in addition to the graphite mentioned above, in order to regulate the battery performance of the lithium-ion battery. For example, other negative electrode active materials may be at least one of silicon-based negative electrode active materials and titanium-based negative electrode active materials.

[0100] In some embodiments, the negative electrode film layer may further include one or more of a negative electrode binder, a negative electrode conductive agent, and other optional additives. In some embodiments, the negative electrode binder may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), lithium-ionized polyacrylic acid (PAALi), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). In some embodiments, the negative electrode conductive agent may be one or more of superconducting carbon, carbon black (examples may include one or more of acetylene black, Ketjen black, and Super P), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, other optional additives may be thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials.

[0101] In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0102] It should be noted that the various parameters of the positive or negative active materials provided in the embodiments of this application can be obtained by sampling and testing from the cold-pressed positive or negative film layer.

[0103] The embodiments of this application improve the charging performance and cycle life of lithium-ion batteries by controlling the specific composition of the positive and negative electrode active materials.

[0104] In some embodiments, layered lithium-containing transition metal oxides include Li a Ni b Co c M d O e A f Wherein, 0<a≤1.2, 0.60≤b≤0.70, 0.08≤c≤0.15, 0.15≤d≤0.32, b+c+d=1; 1≤e≤2; 0≤f≤1, e+f=2; M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, W, Nb, Sb and B, and A includes one or more of N, F, S and Cl.

[0105] As an example, layered lithium-containing transition metal oxides may include, but are not limited to, LiNi. 0.6 Co 0.15 Mn0.25 O2, LiNi 0.70 Co 0.15 Mn 0.15 O2, LiNi 0.70 Co 0.08 Mn 0.32 O2, LiNi 0.65 Co 0.15 Mn 0.20 One or more of O2.

[0106] The embodiments of this application improve the structural stability of layered lithium-containing transition metal oxides using the above-described general chemical formula, thereby enabling lithium-ion batteries to have good cycle life.

[0107] In some embodiments, the nickel-cobalt compound includes nickel-cobalt compounds with a single crystal morphology.

[0108] A single crystal refers to a single primary particle. In some embodiments, a single crystal also includes a quasi-single crystal, which refers to a particle formed by the aggregation of a small number (e.g., 2 to 10) of primary particles. Whether a nickel-cobalt compound has a single-crystal morphology can be determined by scanning electron microscopy or transmission electron microscopy.

[0109] In some embodiments, the positive electrode active material may include a nickel-cobalt compound with a single-crystal morphology, and may also include a nickel-cobalt compound with a polycrystalline morphology. Polycrystalline refers to secondary particles formed by the aggregation of multiple (e.g., 11 or more) primary particles.

[0110] Compared to polycrystalline nickel-cobalt compounds, single-crystal nickel-cobalt compounds have fewer grain boundary defects, higher structural stability, and fewer side reactions in the battery, thus having a positive impact on the cycle life of lithium-ion batteries.

[0111] The embodiments of this application improve the cycle life of lithium-ion batteries by using positive electrode active materials containing nickel-cobalt compounds with single-crystal morphology.

[0112] In some embodiments, the specific capacity of the positive electrode active material is in the range of 190 mAh / g to 200 mAh / g. The specific capacity of the positive electrode active material can be 190 mAh / g, 191 mAh / g, 192 mAh / g, 193 mAh / g, 194 mAh / g, 195 mAh / g, 196 mAh / g, 197 mAh / g, 198 mAh / g, 199 mAh / g, 200 mAh / g, etc., or a range consisting of any two of the above values, such as 190 mAh / g to 195 mAh / g, 193 mAh / g to 198 mAh / g, or 195 mAh / g to 200 mAh / g, etc.

[0113] The specific capacity of positive electrode active material refers to the ratio of the electrical capacity that the positive electrode active material inside a lithium-ion battery can release to the mass of the positive electrode active material. It is an important indicator for measuring the energy storage capacity of positive electrode active material in lithium-ion batteries, and is usually expressed in milliampere-hours per gram (mAh / g).

[0114] The specific capacity of the positive electrode active material can be tested using any known method. As an example, the method for testing the specific capacity of the positive electrode active material may include: disassembling the battery, taking the positive electrode sheet and assembling it with the lithium sheet to form a small coin cell, charging and discharging it to obtain the battery capacity, and then dividing the battery capacity by the mass of the positive electrode active material to obtain the specific capacity of the positive electrode active material, wherein the test voltage range is 2.8~4.3V, and the charge / discharge current is 0.1C.

[0115] The embodiments of this application improve the cycle life of lithium-ion batteries by using positive electrode active materials within the above-mentioned specific capacity range.

[0116] In some embodiments, the mass percentage of the nickel-cobalt compound is greater than or equal to 95% based on the total mass of the positive electrode active material. The mass percentage of the nickel-cobalt compound, based on the total mass of the positive electrode active material, can be 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 100%, or a range of any two of the above values, such as 95%~98%, 97%~100%, etc.

[0117] The embodiments of this application improve the cycle life of lithium-ion batteries by adjusting the mass ratio of nickel-cobalt element compounds based on the total mass of the positive electrode active material.

[0118] In some embodiments, the compaction density of the positive electrode film layer is in the range of 3.1 g / cc to 3.6 g / cc. The compaction density of the positive electrode film layer can be 3.1 g / cc, 3.15 g / cc, 3.2 g / cc, 3.25 g / cc, 3.3 g / cc, 3.35 g / cc, 3.4 g / cc, 3.45 g / cc, 3.5 g / cc, 3.55 g / cc, 3.6 g / cc, etc., or a range consisting of any two of the above values, such as 3.1 g / cc to 3.3 g / cc, 3.2 g / cc to 3.4 g / cc, or 3.3 g / cc to 3.6 g / cc, etc.

[0119] The compaction density of the positive electrode film refers to the weight per unit volume of the material forming the positive electrode film on the positive electrode current collector after compaction treatment, usually expressed in g / cc (grams per cubic centimeter). The compaction density of the positive electrode film reflects the degree of compaction of the material forming the positive electrode film. The compaction density of the positive electrode film can be tested using equipment and methods known in the art. The compaction density of the positive electrode film is equal to the ratio of the coating weight of the positive electrode film to the thickness of the positive electrode film. The coating weight of the positive electrode film refers to the weight per unit area of ​​the material forming the positive electrode film on the positive electrode current collector, and can be expressed as mg / 1540.25mm². 2 The weight of the positive electrode coating is measured in milligrams per 1540.25 square millimeters. The coating weight can be tested using equipment and methods known in the art, for example, by taking a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated positive electrode sheet, the coating on one side can be wiped off first), and cutting it into pieces with an area of ​​1540.25 mm². 2 Take the small circular electrode and weigh it; then wipe off the positive electrode film layer of the weighed positive electrode sheet and weigh the positive current collector. The coating weight of the positive electrode film layer is equal to the weight of the small circular electrode sheet minus the weight of the positive current collector.

[0120] The embodiments of this application improve the cycle life of lithium-ion batteries by using positive electrode film layers within the above-mentioned compaction density range.

[0121] In some embodiments, the coating weight of the positive electrode film is 225 mg / 1540.25 mm. 2 ~245mg / 1540.25mm 2 Within this range. The coating weight of the positive electrode film can be 225mg / 1540.25mm. 2 230mg / 1540.25mm 2 235mg / 1540.25mm 2 240mg / 1540.25mm 2 245mg / 1540.25mm 2 etc., or a range consisting of any two of the above values, for example, 225mg / 1540.25mm. 2 ~235mg / 1540.25mm 2 230mg / 1540.25mm 2 ~240mg / 1540.25mm 2 Or 235mg / 1540.25mm 2 ~245mg / 1540.25mm 2 wait.

[0122] The embodiments of this application improve the cycle life of lithium-ion batteries by employing positive electrode film layers within the above-described coating weight range.

[0123] In some embodiments, graphite includes one or both of natural graphite and artificial graphite.

[0124] The embodiments of this application improve the cycle life and charging performance of lithium-ion batteries through the above-mentioned graphite.

[0125] In some embodiments, the specific capacity of the negative electrode active material is in the range of 350 mAh / g to 365 mAh / g. The specific capacity of the negative electrode active material can be 350 mAh / g, 351 mAh / g, 352 mAh / g, 353 mAh / g, 354 mAh / g, 355 mAh / g, 356 mAh / g, 357 mAh / g, 358 mAh / g, 359 mAh / g, 360 mAh / g, 361 mAh / g, 362 mAh / g, 363 mAh / g, 364 mAh / g, 365 mAh / g, etc., or a range of any two of the above values, such as 350 mAh / g to 360 mAh / g, 355 mAh / g to 365 mAh / g, etc.

[0126] The specific capacity of negative electrode active material refers to the ratio of the electrical capacity that the negative electrode active material inside a lithium-ion battery can release to the mass of the negative electrode active material. It is an important indicator for measuring the energy storage capacity of the negative electrode active material in a lithium-ion battery, and is usually expressed in milliampere-hours per gram (mAh / g).

[0127] The specific capacity of the negative electrode active material can be tested using any known method. As an example, the method for testing the specific capacity of the negative electrode active material may include: disassembling the battery, taking the negative electrode sheet and assembling it with the lithium sheet to form a small coin cell, charging and discharging it to obtain the battery capacity, and then dividing the battery capacity by the mass of the negative electrode active material to obtain the specific capacity of the negative electrode active material, wherein the test voltage range is 0.005V~2V, and the charge / discharge current is 0.1C.

[0128] The embodiments of this application improve the cycle life of lithium-ion batteries by using negative electrode active materials within the above-mentioned specific capacity range.

[0129] In some embodiments, the graphitization degree of graphite is in the range of 90% to 95%. The graphitization degree of graphite can be 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, etc., or a range consisting of any two of the above values, such as 90% to 93%, 92% to 95%, etc.

[0130] The degree of graphitization is an indicator of the extent to which carbon atoms form a close-packed hexagonal graphite crystal structure. The closer the lattice size of graphite is to the lattice constant of ideal graphite, the higher the degree of graphitization.

[0131] The degree of graphitization can be measured using methods known in the art. For example, the degree of graphitization can be measured using an X-ray diffractometer (such as a Bruker D8 Discover), and the measurement can be referenced in JB / T 4220-2011, to determine the interlayer spacing d of the (002) crystal planes of graphite. 002 The size is then determined according to the formula G = (0.344 - d). 002 The degree of graphitization is calculated by 0.344-0.3354, where G represents the degree of graphitization.

[0132] The graphite with the above-mentioned degree of graphitization has a highly ordered layered structure. Using graphite with the above-mentioned degree of graphitization is beneficial to reduce its volume expansion during charging and discharging, thereby improving the cycle life of lithium-ion batteries.

[0133] In some embodiments, the OI value of graphite is in the range of 8 to 25. The OI value of graphite can be 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, etc., or a range of any two of the above values, such as 8~12, 10~15, 13~18, 15~20, 18~23, or 20~25, etc.

[0134] The OI value of graphite refers to the orientation selectivity of graphite during lithium intercalation. The OI value is calculated based on X-ray diffraction (XRD) data, specifically by comparing the diffraction peak areas (C004 and C110) of the (004) and (110) crystal planes of graphite. 004 and C 110 The value is determined by the formula: OI value = C 004 / C 110 .

[0135] The expansion of graphite with the aforementioned orientation index (OI) value during lithium intercalation can be dispersed in all directions, which helps to reduce the volume expansion of lithium-ion batteries and improve their cycle life.

[0136] In some embodiments, the Dv50 of graphite is in the range of 9 μm to 20 μm. The Dv50 of graphite can be 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc., or a range consisting of any two of the above values, such as 9 μm to 13 μm, 11 μm to 15 μm, 13 μm to 17 μm, or 15 μm to 20 μm, etc.

[0137] Wherein, the average volumetric particle size Dv50 of graphite refers to the median particle size of graphite, indicating that 50% of the particles by volume have a diameter greater than this value, and another 50% of the particles by volume have a diameter smaller than this value. The average volumetric particle size Dv50 of graphite in the embodiments of this application can be referenced to standard GB / T 19077.1. In 2016, particle size was determined using a laser particle size analyzer (such as Malvern Master Size 3000).

[0138] The embodiments of this application improve the charging performance and cycle life of lithium-ion batteries by using graphite within the Dv50 range described above.

[0139] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.6 m². 2 / g~2.1m 2 Within the range of / g, the specific surface area of ​​the negative electrode active material can be 0.6m². 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g、2.1m 2 / g, or a range consisting of any two of the above values, for example, 0.6m. 2 / g~1.0m 2 / g, 0.8m 2 / g~1.2m 2 / g, 1.0m 2 / g~1.6m 2 / g or 1.3m 2 / g~2.1m 2 / g etc.

[0140] The specific surface area of ​​the negative electrode active material can be measured using methods known in the art. For example, refer to GB / T19587. In 2017, the nitrogen adsorption specific surface area was measured using the nitrogen adsorption specific surface area analysis method and calculated using the BET (Brunauer-Emmett-Teller) method. The nitrogen adsorption specific surface area analysis can be performed using the Tri... (The sentence is incomplete and requires more context to translate accurately). The analysis was conducted using a Star3020 specific surface area and pore size analyzer.

[0141] The embodiments of this application utilize negative electrode active materials within the aforementioned specific surface area range, which helps to reduce surface side reactions and improve the cycle life of lithium-ion batteries.

[0142] In some embodiments, at least a portion of amorphous carbon covers at least a portion of the surface of graphite.

[0143] The presence of at least a portion of the surface of the graphite in this application covered with amorphous carbon can be tested using equipment and methods known in the art. As an example, the specific morphology of the negative electrode active material can be observed using a transmission electron microscope.

[0144] The embodiments of this application improve the charging performance of lithium-ion batteries by using graphite with at least a portion of its surface covered with amorphous carbon.

[0145] In some embodiments, the porosity of the negative electrode film layer is in the range of 30% to 45%. The porosity of the negative electrode film layer can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, etc., or a range consisting of any two of the above values, such as 30% to 35%, 33% to 38%, 35% to 40%, or 38% to 45%, etc.

[0146] The porosity of the negative electrode film has a well-known meaning in the art and can be tested using equipment or methods known in the art. Specifically, it can be obtained by the gas displacement method. The porosity of the negative electrode film is P = (V1) / (V1) V2) / V1×100%, where V1 represents the apparent volume and V2 represents the actual volume.

[0147] The porosity of the negative electrode film has a significant impact on the charging performance of lithium-ion batteries. The porosity affects the number of pores within the negative electrode film and its wettability with the electrolyte. This wettability, in turn, influences the liquid phase conduction velocity of active ions within the negative electrode film, ultimately affecting the charging performance of the lithium-ion battery. Specifically, higher porosity is beneficial for a larger number of pores within the negative electrode film and better wettability with the electrolyte, which in turn promotes higher liquid phase conduction velocities for active ions, thus contributing to better charging performance. Conversely, lower porosity negatively impacts charging performance but positively affects cycle life.

[0148] The embodiments of this application improve the charging performance and cycle life of lithium-ion batteries through the negative electrode film layer within the aforementioned porosity range.

[0149] In some embodiments, the compaction density of the negative electrode film layer is in the range of 1.5 g / cc to 1.8 g / cc. The compaction density of the negative electrode film layer can be 1.5 g / cc, 1.55 g / cc, 1.6 g / cc, 1.65 g / cc, 1.7 g / cc, 1.75 g / cc, 1.8 g / cc, etc., or a range consisting of any two of the above values, such as 1.5 g / cc to 1.7 g / cc or 1.6 g / cc to 1.8 g / cc, etc.

[0150] The compaction density of the negative electrode film refers to the weight per unit volume of the material forming the negative electrode film on the negative electrode current collector after compaction treatment, usually expressed in g / cc (grams per cubic centimeter). The compaction density reflects the degree of compaction of the material forming the negative electrode film. The compaction density of the negative electrode film can be tested using equipment and methods known in the art. The compaction density of the negative electrode film is equal to the ratio of the coating weight of the negative electrode film to the thickness of the negative electrode film. The coating weight of the negative electrode film refers to the weight of the material forming the negative electrode film per unit area coated on the negative electrode current collector, and can be expressed as mg / 1540.25mm². 2 The weight of the negative electrode coating is measured in milligrams per 1540.25 mm². The coating weight can be tested using equipment and methods known in the art, for example, by taking a single-sided coated negative electrode sheet that has been cold-pressed (if it is a double-sided coated negative electrode sheet, the negative electrode film on one side can be wiped off first), and cutting it into pieces with an area of ​​1540.25 mm². 2 Take the small disc and weigh it; then wipe off the negative electrode film layer of the weighed negative electrode sheet and weigh the negative electrode current collector. The coating weight of the negative electrode film layer is equal to the weight of the small disc minus the weight of the negative electrode current collector.

[0151] The embodiments of this application improve the cycle life of lithium-ion batteries by using negative electrode film layers within the aforementioned compaction density range.

[0152] In some embodiments, the coating weight of the negative electrode film is 130 mg / 1540.25 mm. 2 ~150mg / 1540.25mm 2 Within the range.

[0153] The coating weight of the negative electrode film can be 130mg / 1540.25mm. 2 135mg / 1540.25mm 2 140mg / 1540.25mm 2 145mg / 1540.25mm 2 150mg / 1540.25mm 2 etc., or a range consisting of any two of the above values, for example, 130mg / 1540.25mm. 2 ~140mg / 1540.25mm 2 135mg / 1540.25mm 2 ~145mg / 1540.25mm 2 Or 140mg / 1540.25mm 2 ~150mg / 1540.25mm 2 wait.

[0154] The embodiments of this application improve the cycle life of lithium-ion batteries by employing negative electrode film layers within the above-described coating weight range.

[0155] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the second negative electrode film layer being disposed between the first negative electrode film layer and the negative electrode current collector; the first negative electrode film layer includes a first negative electrode active material, the first negative electrode active material including amorphous carbon and graphite; the second negative electrode film layer includes a second negative electrode active material, the second negative electrode active material including graphite or the second negative electrode active material including amorphous carbon and graphite; based on the total mass of the first negative electrode film layer, the mass percentage of graphite in the first negative electrode film layer is in the range of 85% to 96%, and the mass percentage of amorphous carbon in the first negative electrode film layer is in the range of 1% to 9.7%; based on the total mass of the second negative electrode film layer, the mass percentage of graphite in the second negative electrode film layer is in the range of 91% to 97%, and the mass percentage of amorphous carbon in the second negative electrode film layer is in the range of 0% to 4%.

[0156] Based on the total mass of the first negative electrode film layer, the mass percentage of graphite in the first negative electrode film layer can be 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, etc., or a range of any two of the above values, such as 85%~90%, 87%~94%, or 91%~96%, etc.

[0157] Based on the total mass of the first negative electrode film, the mass percentage of amorphous carbon in the first negative electrode film can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 9.7%, etc., or a range of any two of the above values, such as 1%~5%, 3%~7%, 5%~9%, or 7%~9.7%, etc.

[0158] Based on the total mass of the second anode film, the mass percentage of graphite in the second anode film can be 91%, 92%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, etc., or a range of any two of the above values, such as 91%~94%, 93%~96%, or 95%~97%.

[0159] Based on the total mass of the second anode film, the mass percentage of amorphous carbon in the second anode film can be 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or any range of two of the above values, such as 0%~1%, 0.5%~1.5%, 1%~3%, or 2%~4%.

[0160] Among them, in the first negative electrode film layer and the second negative electrode film layer, the mass proportion of amorphous carbon in the first negative electrode film layer is relatively large, the number of sites for intercalation and deintercalation of active ions in the first negative electrode active material is relatively large, the diffusion rate of active ions in the particles of the first negative electrode active material is relatively large, and the charging performance is relatively good. In the second negative electrode film layer, the mass proportion of amorphous carbon is relatively small, the surface defects of the second negative electrode active material are relatively few, the structural stability is relatively good, and the cycle life is relatively high.

[0161] The embodiments of this application improve the charging performance of lithium-ion batteries while maintaining good cycle life by adjusting the mass ratio of amorphous carbon in each layer of the negative electrode film.

[0162] In some embodiments, the specific capacity of the first negative electrode active material is in the range of 350 mAh / g to 360 mAh / g. The specific capacity of the first negative electrode active material can be 350 mAh / g, 351 mAh / g, 352 mAh / g, 353 mAh / g, 354 mAh / g, 355 mAh / g, 356 mAh / g, 357 mAh / g, 358 mAh / g, 359 mAh / g, 360 mAh / g, etc., or a range consisting of any two of the above values, such as 350 mAh / g to 354 mAh / g, 352 mAh / g to 356 mAh / g, or 354 mAh / g to 360 mAh / g, etc.

[0163] In some embodiments, the specific capacity of the second negative electrode active material is in the range of 355 mAh / g to 365 mAh / g. The specific capacity of the second negative electrode active material can be 355 mAh / g, 356 mAh / g, 357 mAh / g, 358 mAh / g, 359 mAh / g, 360 mAh / g, 361 mAh / g, 362 mAh / g, 363 mAh / g, 364 mAh / g, 365 mAh / g, etc., or a range consisting of any two of the above values, such as 355 mAh / g to 360 mAh / g, 359 mAh / g to 363 mAh / g, or 361 mAh / g to 365 mAh / g, etc.

[0164] Among the first and second negative electrode active materials, the second negative electrode active material has a larger specific capacity, contributing more to the cycle life of the lithium-ion battery, while the first negative electrode active material has a smaller specific capacity, contributing more to the charging performance of the lithium-ion battery.

[0165] The embodiments of this application, by layering the negative electrode film and differentially controlling the specific capacity of each layer of negative electrode active material, improve the charging performance of lithium-ion batteries while still maintaining good cycle life.

[0166] In some embodiments, the Dv50 of the first negative electrode active material is in the range of 9.8 μm to 14.8 μm. The Dv50 of the first negative electrode active material can be 9.8 μm, 9.9 μm, 10.0 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11.0 μm, 11.1 μm, 11.2 μm, 11.3 μm, 11.4 μm, 11.5 μm, 11.6 μm, 11.7 μm, 11.8 μm, 11.9 μm, 12.0 μm, 12.1 μm, 12.2 μm, 12.3 μm, 12.4 μm, 12.5 μm, 12.6 μm, or 12.7 μm. The values ​​are 12.8μm, 12.9μm, 13.0μm, 13.1μm, 13.2μm, 13.3μm, 13.4μm, 13.5μm, 13.6μm, 13.7μm, 13.8μm, 13.9μm, 14.0μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, etc., or any range of two of the above values, such as 9.8μm~11.8μm, 10.8μm~12.8μm, 11.8μm~13.8μm, or 12.8μm~14.8μm, etc.

[0167] In some embodiments, the Dv50 of the second negative electrode active material is in the range of 11 μm to 18 μm. The Dv50 of the second negative electrode active material can be 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, etc., or a range consisting of any two of the above values, such as 11 μm to 15 μm, 15 μm to 17 μm, or 16 μm to 18 μm, etc.

[0168] The embodiments of this application, through the first and second negative electrode active materials within the Dv50 range described above, achieve good cycle life while improving the charging performance of lithium-ion batteries.

[0169] In some embodiments, the specific surface area of ​​the first negative electrode active material is 0.6 m². 2 / g~1.2m 2 Within the range of / g. The specific surface area of ​​the first negative electrode active material can be 0.6m². 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, or a range consisting of any two of the above values, for example, 0.6m. 2 / g~1.0m 2 / g or 0.8m 2 / g~1.2m 2 / g etc.

[0170] In some embodiments, the specific surface area of ​​the second negative electrode active material is 1.5 m². 2 / g~2.1m 2 Within the range of / g. The specific surface area of ​​the second negative electrode active material can be 1.5m². 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g、2.1m 2 / g, or a range consisting of any two of the above values, for example, 1.5m. 2 / g~1.9m 2 / g or 1.7m 2 / g~2.1m 2 / g etc.

[0171] The specific surface area of ​​the first and second negative electrode active materials can be tested using methods known in the art. For example, GB / T19587 can be referenced. In 2017, the nitrogen adsorption specific surface area was measured using the nitrogen adsorption specific surface area analysis method and calculated using the BET (Brunauer-Emmett-Teller) method. The nitrogen adsorption specific surface area analysis can be performed using the Tri... (The sentence is incomplete and requires more context to translate accurately). The analysis was conducted using a Star3020 specific surface area and pore size analyzer.

[0172] The embodiments of this application reduce side reactions on the negative electrode surface and improve the cycle life of lithium-ion batteries by using the first and second negative electrode active materials within the above-mentioned specific surface area range.

[0173] In some embodiments, the CB values ​​of the negative and positive electrodes are in the range of 1.05 to 1.15. The CB values ​​of the negative and positive electrodes can be 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, etc., or a range consisting of any two of the above values, such as 1.05 to 1.12 or 1.10 to 1.15, etc.

[0174] Cell Balance (CB) refers to the excess ratio of the negative electrode to the positive electrode. The formula for calculating the CB value is: (specific capacity of negative electrode active material × coating weight of negative electrode film × weight ratio of negative electrode active material based on negative electrode film) / (specific capacity of positive electrode active material × coating weight of positive electrode film × weight ratio of positive electrode active material based on positive electrode film).

[0175] The embodiments of this application, through lithium-ion batteries within the aforementioned CB value range, enable good wetting and reabsorption on both the positive and negative electrode plates, improve the liquid phase transport conditions of lithium ions, and provide more active sites for lithium ion insertion on the negative electrode, thereby improving the charging performance and cycle life of the lithium-ion battery.

[0176] Secondly, embodiments of this application provide an electrical device including any of the lithium-ion batteries provided in the first aspect.

[0177] The electrical devices provided by the embodiments of this application have at least the same advantages as lithium-ion batteries, which can improve the battery life of the electrical devices.

[0178] The beneficial effects of this application are further illustrated below with reference to the embodiments.

[0179] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0180] Example 1

[0181] The preparation of a lithium-ion battery includes the following steps:

[0182] (1) Provide the positive electrode: NCM (LiNi) 0.65 Co 0.12 Mn 0.23 O2, polyvinylidene fluoride (PVDF), and conductive agent Super P were added sequentially to N-methylpyrrolidone (NMP) in a mass ratio of 97%:1%:2%, and the mixture was thoroughly stirred to prepare a positive electrode slurry. The positive electrode slurry was coated onto a 13 μm thick aluminum foil, dried, and then rolled to prepare the positive electrode sheet; the coating weight of the positive electrode film was 235 mg / 1540.25 mm. 2 .

[0183] (2) Providing the negative electrode sheet: Weigh 1.5% styrene-butadiene rubber (SBR), 1% conductive agent super P, 0.5% sodium carboxymethyl cellulose (CMC), and 97% negative electrode active material (including amorphous carbon artificial graphite) by mass percentage, and add them sequentially to water. Stir and mix thoroughly to prepare a negative electrode slurry. Coat the negative electrode slurry onto a copper foil with a thickness of 6 μm, dry it, and then roll it to prepare the negative electrode sheet; the coating weight of the negative electrode film is 140 mg / 1540.25 mm. 2 .

[0184] (3) Provide a separation membrane: A 2µm thick Al2O3 coating and a 1µm thick PVDF adhesive layer are respectively coated on two opposite surfaces of an 8µm polyethylene film to form a separation membrane.

[0185] (4) Provide electrolyte: Mix ethyl methyl carbonate (EMC) and ethylene carbonate (EC) in a volume ratio of 3:7, and dissolve LiPF6 (lithium hexafluorophosphate) in the above solvent to obtain an electrolyte with a lithium salt concentration of 1.1M and a conductivity of 9mS / cm.

[0186] (5) The positive electrode, negative electrode, and two separators are placed in the order of "separator-negative electrode-separator-positive electrode". One end of the positive electrode, negative electrode, and two separators is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. The winding shaft is rotated by a motor to wind the positive electrode, negative electrode, and two separators to obtain a dry cell. The dry cell is subjected to one liquid injection, high-temperature standing, formation, second liquid injection, and high-temperature standing. The liquid injection coefficient is 2.45 g / Ah to obtain a lithium-ion battery.

[0187] The steps for preparing the lithium-ion battery in Example 2 are similar to those in Example 1. The difference is that the positive electrode active material in step (1) of Example 2 is polycrystalline.

[0188] The steps for preparing lithium-ion batteries in Examples 3 and 4 are similar to those in Example 1. The difference is that the positive electrode active material in step (1) of Examples 3 and 4 is different from that in Example 1.

[0189] The steps for preparing lithium-ion batteries in Examples 5 and 6 are similar to those in Example 1. The difference is that, in the negative electrode film layer formed in step (2) of Examples 5 and 6, the mass ratio of graphite and amorphous carbon based on the total mass of the negative electrode film layer is different from that in Example 1.

[0190] The steps for preparing lithium-ion batteries in Examples 7 to 9 are similar to those in Example 1. The difference is that in step (2) of Examples 7 to 9, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, and the graphite in the first negative electrode film layer and the second negative electrode film layer is a mixture of natural graphite and artificial graphite. Furthermore, the mass ratio of amorphous carbon in the first negative electrode film layer and the second negative electrode film layer is different from that in Example 1.

[0191] The steps for preparing the lithium-ion battery in Comparative Example 1 are similar to those in Example 1, except that the positive electrode active material in step (1) of Comparative Example 1 is different from that in Example 1.

[0192] The steps for preparing lithium-ion batteries in Comparative Example 2 are similar to those in Example 1. The difference is that amorphous carbon is not added in step (2) of Comparative Example 2, the amount of graphite added is different from that in Example 1, and the rest is the same as in Example 1.

[0193] The lithium-ion batteries prepared in Examples 1 to 9 and Comparative Examples 1 to 2 were tested for cycle life and charging performance. The test results are shown in Table 1.

[0194] (1) Cyclic performance test:

[0195] The prepared lithium-ion battery was charged at 2.1C at a constant current to the charging cutoff voltage of 4.4V at 25°C, then charged at a constant voltage to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.5V. Its actual capacity was recorded as C0. Then, it was discharged at a rate of 1C followed by a discharge at 0.33C, and the discharge capacity C of each cycle was recorded. n Until the battery's capacity retention rate reaches 80%, the capacity retention rate = C n / C0*100%, records the number of cycles at this point. The more cycles, the better the cycle performance of the secondary battery.

[0196] (2) Charging performance test:

[0197] At 25°C, the prepared lithium-ion battery was charged at a constant current of 0.33C to the charging cutoff voltage of 4.4V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.5V. Its actual capacity was recorded as C0.

[0198] Then, the lithium-ion battery was sequentially charged at constant current rates of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 until it reached the full-cell charging cutoff voltage or the 0V negative electrode cutoff potential (whichever comes first). After each charge, it was discharged at 1C0 until it reached the full-cell discharge cutoff voltage. The negative electrode potentials corresponding to the charging to 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% SOC (State of Charge) were recorded at different charging rates. The charging rates at different SOC states were plotted. The negative electrode potential curve, after linear fitting, yields the charging rate corresponding to a negative electrode potential of 0V under different SOC states. This charging rate is the charging window under that SOC state, denoted as C. 10％SOC C 20％SOC C 30％SOC C 40％SOC C 50％SOC C 60％SOC C 70％SOC C 80％SOC According to the formula (60 / C) 10％SOC +60 / C 30％SOC +60 / C 40％SOC +60 / C 50％SOC +60 / C 60％SOC +60 / C 70％SOC +60 / C 80％SOC The charging time T for the secondary battery to charge from 10% SOC to 80% SOC is calculated by multiplying the value by 10%. The shorter the charging time, the better the charging performance.

[0199] [Amended according to Rule 26, December 17, 2025] Table 1 shows the performance test results of the lithium-ion batteries in each embodiment and comparative example.

[0200] [Revised according to Rule 26, December 17, 2025]

[0201] As can be seen from Table 1:

[0202] Analysis of Examples 1 to 9 and Comparative Examples 1 to 2 shows that by controlling the specific composition of the positive and negative active materials of the lithium-ion battery, the charging performance and cycle life of the lithium-ion battery can be improved.

[0203] Analysis of Examples 1 and 2 shows that using positive electrode active materials containing nickel-cobalt elements, including single-crystal morphology, can improve the cycle life of lithium-ion batteries.

[0204] Analysis of Examples 1, 3, and 4 shows that by adjusting the ratio of the molar amount of nickel / cobalt to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide, the cycle life of the lithium-ion battery fluctuates within a certain range. This indicates that adjusting the elemental proportions of the positive electrode active material can regulate the cycle life of the lithium-ion battery.

[0205] Analysis of Examples 1, 5, and 6 shows that, within a certain range, as the mass proportion of amorphous carbon in the negative electrode film increases, the charging performance of the lithium-ion battery improves while the cycle life decreases. This indicates that the introduction of amorphous carbon needs to be controlled within a certain range in order to improve the charging performance within a certain cycle life of the lithium-ion battery.

[0206] Analysis of Examples 1 and 7 shows that introducing artificial graphite into the negative electrode film layer can improve the charging performance of lithium-ion batteries compared to the scheme without introducing artificial graphite; the layered coating scheme of the negative electrode film layer is beneficial to improving the design flexibility of the negative electrode film layer scheme compared to the non-layered scheme.

[0207] Analysis of Examples 7 to 9 shows that as the mass proportion of artificial graphite in the negative electrode film increases, the charging performance of the lithium-ion battery improves accordingly. This indicates that controlling the type of graphite in the negative electrode film is beneficial to improving the charging performance and cycle life of the lithium-ion battery.

[0208] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

Claims

1. A lithium-ion battery, wherein, It includes positive electrode, negative electrode, separator and electrolyte; The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a nickel-cobalt compound, which includes a layered lithium-containing transition metal oxide. The ratio of the molar amount of nickel in the layered lithium-containing transition metal oxide to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide is in the range of 0.60 to 0.70, and the ratio of the molar amount of cobalt in the layered lithium-containing transition metal oxide to the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide is in the range of 0.08 to 0.

15. The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; the negative electrode film layer includes a negative electrode active material, which includes amorphous carbon and graphite; based on the total mass of the negative electrode film layer, the mass percentage of graphite is in the range of 80% to 98%, and the mass percentage of amorphous carbon is in the range of 0.01% to 10%.

2. The lithium-ion battery according to claim 1, wherein, The layered lithium-containing transition metal oxide includes Li a Ni b Co c M d O e A f Wherein, 0<a≤1.2, 0.60≤b≤0.70, 0.08≤c≤0.15, 0.15≤d≤0.32, b+c+d=1; 1≤e≤2; 0≤f≤1, e+f=2; M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, W, Nb, Sb and B, and A includes one or more of N, F, S and Cl.

3. The lithium-ion battery according to claim 1 or 2, wherein, The nickel-cobalt compounds include nickel-cobalt compounds with single-crystal morphology.

4. The lithium-ion battery according to any one of claims 1 to 3, wherein, The specific capacity of the positive electrode active material is in the range of 190 mAh / g to 200 mAh / g.

5. The lithium-ion battery according to any one of claims 1 to 4, wherein, Based on the total mass of the positive electrode active material, the mass percentage of the nickel-cobalt compound is greater than or equal to 95%.

6. The lithium-ion battery according to any one of claims 1 to 5, wherein, The compaction density of the positive electrode film is in the range of 3.1 g / cc to 3.6 g / cc.

7. The lithium-ion battery according to any one of claims 1 to 6, wherein, The coating weight of the positive electrode film is 225 mg / 1540.25 mm. 2 ~245mg / 1540.25mm 2 Within the range.

8. The lithium-ion battery according to any one of claims 1 to 7, wherein, The graphite includes one or both of natural graphite and artificial graphite.

9. The lithium-ion battery according to any one of claims 1 to 8, wherein, The specific capacity of the negative electrode active material is in the range of 350 mAh / g to 365 mAh / g.

10. The lithium-ion battery according to any one of claims 1 to 9, wherein, The graphitization degree of the graphite is in the range of 90% to 95%.

11. The lithium-ion battery according to any one of claims 1 to 10, wherein, The OI value of the graphite is in the range of 8 to 25.

12. The lithium-ion battery according to any one of claims 1 to 11, wherein, The graphite has a Dv50 in the range of 9μm to 20μm.

13. The lithium-ion battery according to any one of claims 1 to 12, wherein, The specific surface area of ​​the negative electrode active material is 0.6 m². 2 / g~2.1m 2 Within the range of / g.

14. The lithium-ion battery according to any one of claims 1 to 13, wherein, At least a portion of the amorphous carbon covers at least a portion of the surface of the graphite.

15. The lithium-ion battery according to any one of claims 1 to 14, wherein, The porosity of the negative electrode film is in the range of 30% to 45%.

16. The lithium-ion battery according to any one of claims 1 to 15, wherein, The compaction density of the negative electrode film is in the range of 1.5 g / cc to 1.8 g / cc.

17. The lithium-ion battery according to any one of claims 1 to 16, wherein, The coating weight of the negative electrode film is 130 mg / 1540.25 mm. 2 ~150mg / 1540.25mm 2 Within the range.

18. The lithium-ion battery according to any one of claims 1 to 17, wherein, The negative electrode film layer includes a first negative electrode sub-film layer and a second negative electrode sub-film layer, the second negative electrode sub-film layer being disposed between the first negative electrode sub-film layer and the negative electrode current collector; the first negative electrode sub-film layer includes a first negative electrode active material, the first negative electrode active material including amorphous carbon and graphite; the second negative electrode sub-film layer includes a second negative electrode active material, the second negative electrode active material including graphite or the second negative electrode active material including amorphous carbon and graphite; based on the total mass of the first negative electrode sub-film layer, the mass percentage of graphite in the first negative electrode sub-film layer is in the range of 85% to 96%, and the mass percentage of amorphous carbon in the first negative electrode sub-film layer is in the range of 1% to 9.7%; based on the total mass of the second negative electrode sub-film layer, the mass percentage of graphite in the second negative electrode sub-film layer is in the range of 91% to 97%, and the mass percentage of amorphous carbon in the second negative electrode sub-film layer is in the range of 0% to 4%.

19. The lithium-ion battery according to claim 18, wherein, The specific capacity of the first negative electrode active material is in the range of 350 mAh / g to 360 mAh / g, and / or the specific capacity of the second negative electrode active material is in the range of 355 mAh / g to 365 mAh / g.

20. The lithium-ion battery according to claim 18 or 19, wherein, The Dv50 of the first negative electrode active material is in the range of 9.8 μm to 14.8 μm, and / or the Dv50 of the second negative electrode active material is in the range of 11 μm to 18 μm.

21. The lithium-ion battery according to any one of claims 18 to 20, wherein, The specific surface area of ​​the first negative electrode active material is in the range of 0.6 m² / g to 1.2 m² / g, and / or the specific surface area of ​​the second negative electrode active material is in the range of 1.5 m² / g. 2 / g~2.1m 2 Within the range of / g.

22. The lithium-ion battery according to any one of claims 1 to 21, wherein, The CB values ​​of the negative electrode and the positive electrode are in the range of 1.05 to 1.

15.

23. An electrical appliance, wherein, Including the lithium-ion battery as described in any one of claims 1 to 22.

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