Battery cell, lithium-ion secondary battery and preparation method therefor, and electric device

Abstract

The present application provides a battery cell, a lithium-ion secondary battery and a preparation method therefor, and an electric device. The battery cell comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, and the positive electrode active layer comprises a lithium nickel cobalt manganese oxide. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, and the negative electrode active layer comprises graphite. The coating weight of the negative electrode active layer is 0.09 mg / 1540.25 mm2-0.15 mg / 1540.25 mm2. The battery cell satisfies: 0.12 mΩ≤DCR≤0.5 mΩ, wherein DCR is the direct current internal resistance of the battery cell at 25°C and 70% SOC under the conditions of a discharge rate of 4 C and a discharge duration of 10 s.

Description

Battery cells, lithium-ion secondary batteries and their preparation methods, and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. 2025100802621, filed on January 17, 2025, entitled "Battery cell, lithium-ion secondary battery and preparation method thereof, and power device thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of lithium-ion secondary battery technology, and in particular to a battery cell, a lithium-ion secondary battery and its preparation method, and an electrical device. Background Technology

[0004] In recent years, lithium-ion batteries and other lithium-ion rechargeable batteries have been used in a wide range of applications, including energy storage power systems for hydropower, thermal power, wind power and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace and many other fields.

[0005] With the significant development of lithium-ion rechargeable batteries, higher demands have been placed on their fast-charging performance. However, faster charging rates mean higher charging currents, which leads to more severe heat generation in the battery, causing a significant temperature rise and even safety issues. Summary of the Invention

[0006] Based on this, this application provides a battery cell, a lithium-ion secondary battery and its preparation method, and an electrical device, which can achieve both good fast charging performance and low temperature rise.

[0007] In a first aspect, this application provides a battery cell, the battery cell comprising a positive electrode and a negative electrode, the positive electrode comprising a positive current collector and a positive active layer disposed on at least one side of the positive current collector, the positive active layer comprising nickel-cobalt-manganese-lithium oxide, the negative electrode comprising a negative current collector and a negative active layer disposed on at least one side of the negative current collector, the negative active layer comprising graphite;

[0008] The coating weight of the negative electrode active layer is 0.09 mg / 1540.25 mm. 2 ~0.15mg / 1540.25mm 2 ;

[0009] The battery cell satisfies the following condition: 0.12mΩ≤DCR≤0.5mΩ, where DCR is the DC internal resistance of the battery cell at 25℃, 70% SOC, with a discharge rate of 4C and a discharge time of 10s.

[0010] The lithium-ion secondary battery described in this application has a negative electrode active layer comprising graphite with the aforementioned specific coating weight, and a positive electrode active layer comprising nickel-cobalt-manganese lithium oxide, which has a relatively stable layered crystal structure. This structure maintains structural integrity well under high current densities during fast charging, resulting in good fast-charging performance. Furthermore, the DC internal resistance (DCR) of the battery cell under the aforementioned specific conditions is within the aforementioned small range, thus exhibiting the advantage of low heat generation under high current densities during fast charging. Therefore, the lithium-ion secondary battery described in this application can achieve both good fast-charging performance and low temperature rise.

[0011] In some embodiments, one or more of the following features are satisfied:

[0012] (1) The graphite in the negative electrode active layer accounts for 88% to 97% of the total mass;

[0013] (2) The graphite includes artificial graphite;

[0014] (3) The coating weight of the negative electrode active layer is 0.1 mg / 1540.25 mm. 2 ~0.14mg / 1540.25mm 2 .

[0015] Graphite has a high specific capacity, enabling it to store more lithium ions during charging and accept more charge per unit time, which is beneficial for achieving fast charging. By controlling the mass percentage of graphite in the negative electrode active layer within this range, the negative electrode active layer can achieve a high capacity.

[0016] In some embodiments, the battery cell satisfies the following condition: 0.15mΩ ≤ DCR ≤ 0.4mΩ. This range indicates that the battery cell generates less heat at higher current densities during fast charging, which helps reduce the temperature rise of the battery cell under fast charging conditions.

[0017] In some embodiments, the molar percentage of cobalt in the nickel-cobalt-manganese lithium oxide is 10% to 15% of the total molar percentage of nickel, cobalt, and manganese. Thus, the nickel-cobalt-manganese lithium oxide used in the aforementioned battery cell has a high cobalt content, which is beneficial for improving the conductivity of the nickel-cobalt-manganese lithium oxide, reducing the DCR resistance of the battery cell, and thereby improving the fast-charging performance of the battery cell.

[0018] In some embodiments, the molar ratio of cobalt to nickel in the nickel-cobalt-manganese lithium oxide is 0.15 to 0.25. By controlling the molar ratio of cobalt to nickel, it is beneficial to reduce "lithium-nickel mixing" and improve the stability of the nickel-cobalt-manganese lithium oxide. This can help improve the stability of the nickel-cobalt-manganese lithium oxide during fast charging and improve the fast charging performance of the battery cell.

[0019] In some embodiments, the resistance of the positive electrode is 0.1Ω to 0.5Ω. Controlling the resistance of the positive electrode within this small range helps to reduce the internal resistance of the battery cell and reduce the temperature rise during high-current-density discharge during fast charging.

[0020] In some embodiments, the particle size Dv50 of the nickel-cobalt-manganese lithium oxide is 2 μm to 6 μm. By controlling the particle size Dv50 of the nickel-cobalt-manganese lithium oxide within this relatively small range, the diffusion distance of lithium ions from the surface to the interior of the nickel-cobalt-manganese lithium oxide material is significantly shortened, allowing lithium ions to reach the active sites more quickly to participate in the reaction, thus accelerating the electrode reaction rate and improving the fast-charging performance of the battery cell.

[0021] In some embodiments, one or more of the following features are satisfied:

[0022] (1) The particle size Dv10 of the nickel-cobalt-manganese lithium oxide is 1.1 μm to 1.9 μm;

[0023] (2) The particle size Dv99 of the nickel-cobalt-manganese lithium oxide is 5.0 μm to 8.5 μm;

[0024] (3) The particle sizes Dv10, Dv50 and Dv99 of the nickel cobalt manganese lithium oxide satisfy: 1.5≤(Dv99-Dv10) / Dv50≤3.5.

[0025] In some embodiments, the laser particle size distribution curve of the nickel-cobalt-manganese-lithium oxide has at least two peaks, wherein the particle size at the peak with the largest peak is recorded as the average particle size of the large particles, and the particle size at the peak with the smallest peak is recorded as the average particle size of the small particles, and the average particle size of the large particles is greater than the average particle size of the small particles.

[0026] Optionally, the average particle size of the large particles is 3μm to 4μm, and optionally 3.2μm to 3.7μm;

[0027] Optionally, the average particle size of the small particles is 2μm to 3μm, and optionally 2.3μm to 2.9μm.

[0028] By using a blend of nickel-cobalt-manganese lithium oxide particles of different sizes, with smaller particles filling the gaps between larger particles, the conductive network can be further improved, the internal resistance of the positive electrode sheet can be reduced, and the fast-charging performance of the battery cell can be enhanced.

[0029] In some embodiments, in the laser particle size distribution curve of the nickel-cobalt-manganese lithium oxide, the area of ​​the peak containing the large particles is less than or equal to the area of ​​the peak containing the small particles.

[0030] In some embodiments, the ratio of the area of ​​the peak containing the large particles to the area of ​​the peak containing the small particles is 1:9 to 5:5.

[0031] Furthermore, by controlling the proportion of large particles in nickel-cobalt-manganese lithium oxide to be small and the proportion of small particles to be dominant, it is beneficial to further reduce the internal resistance of the positive electrode. The lithium ion diffusion distance of small-particle nickel-cobalt-manganese lithium oxide materials is shorter, which allows lithium ions to reach the active site more quickly to participate in the reaction, thus accelerating the electrode reaction rate and improving the fast charging performance of the battery cell.

[0032] In some embodiments, one or more of the following features are satisfied:

[0033] (1) The mass percentage of the lithium nickel cobalt manganese oxide in the positive electrode active layer is 70% to 99%, and can be 85% to 96%;

[0034] (2) The nickel cobalt manganese lithium oxide includes nickel cobalt manganese lithium oxide in single-particle form, wherein the mass percentage of the nickel cobalt manganese lithium oxide in single-particle form is 80% to 100%, and optionally 90% to 99%.

[0035] (3) The coating weight of the positive electrode active layer is 0.15 mg / 1540.25 mm. 2 ~0.28mg / 1540.25mm 2 .

[0036] In some embodiments, the nickel-cobalt-manganese lithium oxide comprises lithium with the chemical formula Li y (Ni a Co b Mn c ) 1-d M 1 d O 2-x A x One or more of the compounds, where y is 0.2–1.2, a, b, and c are all non-zero, a + b + c = 1, a > 0.5, 0 ≤ d < 1, and 0 ≤ x < 2; M 1 It includes one or more of Zr, Sr, B, Ti, Mg, Sn, W, Sb, Nb, Zn and Al, where A includes one or more of S, N, F, Cl, Br and I.

[0037] In some embodiments, b is 0.1 to 0.15, and b / a is 0.15 to 0.25.

[0038] In some embodiments, the positive electrode active layer further includes lithium phosphate;

[0039] Optionally, the lithium-containing phosphate includes the chemical formula Liβ Fe α M 2 (1-α) One or more of the compounds containing PO4, wherein 0.2 ≤ α ≤ 1, 0.9 ≤ β ≤ 1.1, M 2 It includes at least one of Ti, V, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, and Sr. Further addition of lithium-containing phosphates to the positive electrode active layer, based on the aforementioned lithium nickel cobalt manganese oxides, helps to improve the DCR of the battery cell at low SOC.

[0040] In some embodiments, one or more of the following features are satisfied:

[0041] (1) The mass percentage of lithium phosphate in the positive electrode active layer is greater than 0 and ≤50%, and can be selected as 1% to 30%;

[0042] (2) The particle size of the lithium phosphate-containing Dv50 is 8μm to 20μm;

[0043] (3) The lithium phosphate includes secondary particles.

[0044] In some embodiments, the positive electrode sheet further includes at least one positive electrode tab, the positive electrode tab being connected to the positive current collector in a first direction, the total area of ​​the positive current collector in a cross-section perpendicular to the first direction being S1, and the total area of ​​the positive electrode tab in a cross-section perpendicular to the first direction being S2.

[0045] The ratio of S2 to S1 is ≥0.18, and can be selected from 0.18 to 1.

[0046] The ratio of the total cross-sectional area S2 of the positive electrode tab to the total cross-sectional area S1 of the positive electrode current collector is controlled to be above 0.18. The larger the cross-sectional area ratio, the larger the current transmission path of the positive electrode tab. At the same time, the resistance of the positive electrode tab is smaller, which can reduce the heat generation of the tab when the current is the same.

[0047] In some embodiments, the battery cell is a prismatic battery and the outer packaging is a rigid shell, with the ratio of S2 to S1 being 0.18 to 1.00, optionally 0.18 to 0.22. When the battery cell is a prismatic battery and the outer packaging is a rigid shell, using tabs with a large S2 / S1 ratio, such as full tabs, can easily lead to anode-cathode overlap problems. Therefore, further controlling it within this range can reduce the risk of anode-cathode overlap while also taking into account the low ohmic impedance of the positive tab.

[0048] In some embodiments, the battery cell includes an outer packaging, a first electrode terminal, and a second electrode terminal. The positive electrode and the negative electrode are disposed inside the outer packaging, and the first electrode terminal and the second electrode terminal are disposed on the outer packaging. The battery cell satisfies one or more of the following conditions:

[0049] (1) The positive electrode tab is directly connected to the first electrode terminal;

[0050] (2) The battery cell also includes a negative electrode tab, which is connected to the negative current collector and directly connected to the second electrode terminal.

[0051] Using a direct connection method can reduce the contact resistance between the tabs and electrode terminals, lower the DCR of the battery cell, and improve fast charging performance.

[0052] In some embodiments, the AC resistance IMP of the battery cell satisfies the following condition: 0.075mΩ ≤ IMP ≤ 0.24mΩ, where IMP is the AC resistance of the battery cell at 25°C, 70% SOC, a 1kHz current frequency, and a 5mV voltage amplitude. A smaller AC resistance IMP range is beneficial for improving the fast-charging performance of the battery cell and reducing heat generation, thereby reducing the temperature rise of the battery cell and improving its safety.

[0053] In some embodiments, the rated capacity of the battery cell at a 1C discharge rate is C0, where 130Ah ≤ C0 ≤ 170Ah.

[0054] In some embodiments, the battery cell has two larger surfaces disposed opposite to each other in its own thickness direction, and the distance between the outer surfaces of the two larger surfaces is the thickness of the battery cell;

[0055] The charging time for the battery cell from 10% SOC to 80% SOC at 25°C is 5 min to 14 min, and the thickness of the battery cell is ≤64 mm, which can be selected as 34 mm to 64 mm.

[0056] When the charging capacity of a single battery cell is such that the charging time from 10% SOC to 80% SOC at 25℃ is 5min to 14min, and the thickness of the battery cell is controlled, the battery cell has good thermal conductivity, and the heat inside the battery cell can be transferred to the external area of ​​the battery cell more quickly. This can reduce the temperature rise of the battery cell, and also help to reduce the temperature difference between the inside and outside of the battery cell, so that the overall performance of the battery cell has good consistency, which is conducive to maximizing the charging performance of the battery cell and improving the safety of the battery cell.

[0057] In some embodiments, the charging time of the battery cell from 10% SOC to 80% SOC at 25°C is 8 min to 14 min, and the thickness of the battery cell is 40 mm to 64 mm, optionally 40 mm to 48 mm.

[0058] When the charging capacity of a single battery cell is such that the charging time from 10% SOC to 80% SOC at 25℃ is 8min to 14min, further controlling the thickness of the battery cell within this range can reduce the temperature rise of the battery cell, thereby reducing the internal and external temperature differences and ensuring good consistency in the overall performance of the battery cell. This is beneficial for maximizing the charging performance of the battery cell and improving its safety. On the other hand, a thicker battery cell means more electrode layers, which can increase the capacity of the battery cell.

[0059] In some embodiments, the charging time of the battery cell from 10% SOC to 80% SOC at 25°C is 5 min to 8 min, and the thickness of the battery cell is 34 mm to 48 mm, optionally 34 mm to 42 mm.

[0060] When the charging capacity of a single battery cell is such that the charging time from 10% SOC to 80% SOC at 25℃ is 5-8 minutes, it exhibits good fast-charging performance. Further controlling the thickness of the battery cell within this smaller range can improve its thermal conductivity, allowing heat to be transferred more quickly from the inside to the outside, reducing temperature rise and minimizing temperature differences between the inside and outside of the cell. This results in better consistency in the overall performance of the battery cell, enhancing its charging performance and safety. On the other hand, a thicker battery cell means more electrode layers, which can increase the cell's capacity.

[0061] In a second aspect, this application provides a lithium-ion secondary battery, comprising at least one battery cell provided in the first aspect of this application.

[0062] In some embodiments, the lithium-ion secondary battery further includes a cooling plate, the battery cell having two larger surfaces disposed opposite to each other in its thickness direction, and the cooling plate being disposed on at least one side of the two larger surfaces of the battery cell;

[0063] Optionally, the cooling plate is provided with cooling channels.

[0064] In a third aspect, this application provides an electrical device, including at least one of the battery cell provided in the first aspect of this application and the lithium-ion secondary battery provided in the second aspect of this application.

[0065] The electrical device of this application includes the battery cell or lithium-ion secondary battery provided in this application, and therefore has at least the same advantages as the battery cell or the lithium-ion secondary battery.

[0066] Details of one or more embodiments 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

[0067] To better describe and illustrate the embodiments or examples 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 or examples, 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:

[0068] Figure 1 is a schematic diagram of the structure of the positive current collector and the positive electrode tab of the positive electrode sheet of a lithium-ion secondary battery according to an embodiment of this application.

[0069] Figure 2 is a schematic diagram of a lithium-ion secondary battery according to an embodiment of this application.

[0070] Figure 3 is an exploded view of a lithium-ion secondary battery according to an embodiment of this application, as shown in Figure 2.

[0071] Figure 4 is a schematic diagram of a battery device according to an embodiment of this application.

[0072] Figure 5 is a schematic diagram of a battery pack according to one embodiment of this application.

[0073] Figure 6 is an exploded view of the battery pack of one embodiment of this application shown in Figure 5.

[0074] Figure 7 is a schematic diagram of an electrical device using a lithium-ion secondary battery as a power source according to an embodiment of this application.

[0075] Explanation of reference numerals in the attached figures:

[0076] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery assembly; 5. Individual battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate. Detailed Implementation

[0077] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. 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.

[0078] 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 independently included or excluded, and they can be combined arbitrarily, meaning 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 "0-5" have been listed in this document; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, stating that a parameter is an integer ≥2 is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, stating that a parameter is an integer selected from "2-10" is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0079] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0080] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0081] 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.

[0082] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples 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, preferably sequentially. For example, if the method 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, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0083] In this application, unless otherwise specified, A (e.g., B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0084] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0085] With the significant advancements in lithium-ion rechargeable batteries, higher demands have been placed on their fast-charging performance. However, faster charging rates mean higher charging currents, leading to severe heat generation and potentially causing significant temperature rises or even safety issues. Specifically, increased battery temperature accelerates side reactions, such as lithium-ion consumption, thus accelerating capacity decay. Furthermore, increased temperature promotes gas production from these side reactions, causing battery swelling, degrading battery life, and in severe cases, even triggering the battery's safety valve to open. Therefore, improving the fast-charging performance of lithium-ion rechargeable batteries while simultaneously reducing their temperature rise is a pressing technical challenge.

[0086] The first aspect of this application provides a battery cell, the battery cell including a positive electrode and a negative electrode, the positive electrode including a positive current collector and a positive active layer disposed on at least one side of the positive current collector, the positive active layer including nickel cobalt manganese lithium oxide, the negative electrode including a negative current collector and a negative active layer disposed on at least one side of the negative current collector, the negative active layer including graphite.

[0087] The coating weight of the negative electrode active layer is 0.09 mg / 1540.25 mm. 2~0.15mg / 1540.25mm 2 .

[0088] The battery cell meets the following condition: 0.12mΩ≤DCR≤0.5mΩ, where DCR is the DC internal resistance of the battery cell at 25℃, 70% SOC, with a discharge rate of 4C and a discharge time of 10s.

[0089] The lithium-ion secondary battery described in this application has a negative electrode active layer comprising graphite with the aforementioned specific coating weight, and a positive electrode active layer comprising nickel-cobalt-manganese lithium oxide, which has a relatively stable layered crystal structure. This structure maintains structural integrity well under high current densities during fast charging, resulting in good fast-charging performance. Furthermore, the DC internal resistance (DCR) of the battery cell under the aforementioned specific conditions is within the aforementioned small range, thus exhibiting the advantage of low heat generation under high current densities during fast charging. Therefore, the lithium-ion secondary battery described in this application can achieve both good fast-charging performance and low temperature rise.

[0090] The coating weight of the negative electrode active layer refers to the coating weight per unit area of ​​the negative electrode active layer, calculated as the weight after drying without solvent. The coating weight of the positive electrode active layer is similar. As a non-limiting example, the negative electrode current collector has two surfaces opposite 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.

[0091] In this application, the coating weight of the electrode (positive electrode or negative electrode) is tested by the following method: the battery is disassembled, the electrode is removed, and it is punched into a piece with an area of ​​S = 1540.25 mm². 2 Take a small circular electrode, measure its weight M, and then take another electrode. Remove the film layer from the surface of the electrode to remove the remaining empty current collector foil. Similarly, punch it to a diameter S = 1540.25 mm. 2 The small round piece is weighed, and the mass of the empty aluminum foil is M0. Then the coating weight = (M-M0) / S / n, where n is the number of film layers coated on the current collector, which is 1 or 2, corresponding to single-sided coating or double-sided coating.

[0092] As an example, the coating weight of the negative electrode active layer is 0.09 mg / 1540.25 mm. 2 0.1mg / 1540.25mm 2 0.11mg / 1540.25mm 2 0.12mg / 1540.25mm 2 0.13mg / 1540.25mm 2 0.14mg / 1540.25mm 2 0.15mg / 1540.25mm 2Or it can be within the range defined by any two of the above point values ​​as endpoints. Further, the coating weight of the negative electrode active layer is 0.1 mg / 1540.25 mm. 2 ~0.14mg / 1540.25mm 2 .

[0093] As an example, the DC internal resistance (DCR) of a single battery cell at 25°C and 70% SOC, with a discharge rate of 4C and a discharge time of 10s, falls within the aforementioned range. For example, it could be 0.12mΩ, 0.13mΩ, 0.14mΩ, 0.15mΩ, 0.16mΩ, 0.17mΩ, 0.18mΩ, 0.19mΩ, 0.20mΩ, 0.21mΩ, 0.22mΩ, 0.23mΩ, 0.24mΩ, 0.25mΩ, 0.26mΩ, 0.27mΩ, or 0. 28mΩ, 0.29mΩ, 0.30mΩ, 0.31mΩ, 0.32mΩ, 0.33mΩ, 0.34mΩ, 0.35mΩ, 0.36mΩ, 0.37mΩ, 0.38mΩ, 0.39mΩ, 0.40mΩ, 0.41mΩ, 0.42mΩ, 0.43mΩ, 0.44mΩ, 0.45mΩ, 0.46mΩ, 0.47mΩ, 0.48mΩ, 0.49mΩ, 0.50mΩ, or any two of the above point values ​​as endpoints within the range.

[0094] Furthermore, the battery cell satisfies: 0.15mΩ ≤ DCR ≤ 0.4mΩ. Within this range, the battery cell generates relatively little heat under high current density during fast charging, which helps reduce the temperature rise of the battery cell under fast charging conditions. Even further, the battery cell satisfies: 0.2mΩ ≤ DCR ≤ 0.3mΩ.

[0095] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric 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-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0096] Graphite has a high specific capacity, allowing it to store more lithium ions during charging and accept more charge per unit time, which is beneficial for achieving fast charging. Furthermore, graphite includes, but is not limited to, one or more of synthetic graphite and natural graphite. More specifically, graphite includes synthetic graphite.

[0097] In some embodiments, the mass percentage of graphite in the negative electrode active layer is 88% to 97%. Examples include 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, and 97%, or any two of these values ​​as endpoints. Controlling the mass percentage of graphite in the negative electrode active layer within this range allows the negative electrode active layer to have a higher capacity.

[0098] In some embodiments, the negative electrode active material, in addition to graphite, may also include one or more of the following materials: soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. 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, and other conventional materials that can be used as negative electrode active materials in batteries may also be used.

[0099] In some embodiments, the negative electrode active layer may optionally include a binder. 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).

[0100] Furthermore, the mass percentage of the binder in the negative electrode active layer is 0.1% to 10%, and can be selected as 0.5% to 5%. As an example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within the range formed by any two of the above point values ​​as endpoints.

[0101] In some embodiments, the negative electrode active layer may optionally include a conductive agent. 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.

[0102] Furthermore, the mass percentage of the conductive agent in the negative electrode active layer is 0.1% to 10%, and can be selected as 0.5% to 5%. As an example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within the range formed by any two of the above values ​​as endpoints.

[0103] In some embodiments, the negative electrode active layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0104] 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; coating the negative electrode slurry onto at least one surface of the negative electrode current collector, and then obtaining the negative electrode sheet after processes such as drying and cold pressing. 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.

[0105] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0106] 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. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be 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 one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0107] In some embodiments, the molar percentage of cobalt in the nickel-cobalt-manganese lithium oxide is 10% to 15% of the total molar percentage of nickel, cobalt, and manganese. Thus, the nickel-cobalt-manganese lithium oxide used in the aforementioned battery cell has a high cobalt content, which is beneficial for improving the conductivity of the nickel-cobalt-manganese lithium oxide, reducing the DCR resistance of the battery cell, and thereby improving the fast-charging performance of the battery cell.

[0108] As an example, the molar percentage of cobalt in nickel-cobalt-manganese lithium oxide can be 10%, 11%, 12%, 13%, 14%, or 15%, or within the range defined by any two of the above values.

[0109] In some embodiments, the molar ratio of cobalt to nickel in the nickel-cobalt-manganese lithium oxide is 0.15 to 0.25. By controlling the molar ratio of cobalt to nickel, it is beneficial to reduce "lithium-nickel mixing" and improve the stability of the nickel-cobalt-manganese lithium oxide. This can help improve the stability of the nickel-cobalt-manganese lithium oxide during fast charging and improve the fast charging performance of the battery cell.

[0110] As an example, the molar ratio of cobalt to nickel in nickel-cobalt-manganese lithium oxide is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, or 0.25, or any two of the above values ​​as endpoints.

[0111] In some embodiments, the particle size Dv50 of the nickel-cobalt-manganese lithium oxide is 2 μm to 6 μm. By controlling the particle size Dv50 of the nickel-cobalt-manganese lithium oxide within this relatively small range, the diffusion distance of lithium ions from the surface to the interior of the nickel-cobalt-manganese lithium oxide material is significantly shortened, allowing lithium ions to reach the active sites more quickly to participate in the reaction, thus accelerating the electrode reaction rate and improving the fast-charging performance of the battery cell.

[0112] As an example, the particle size Dv50 of the nickel-cobalt-manganese lithium oxide is 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or within the range defined by any two of the above values ​​as endpoints. Further, the particle size Dv50 of the nickel-cobalt-manganese lithium oxide is 2 μm to 4 μm, and more preferably 2.3 μm to 3.7 μm.

[0113] In some embodiments, the cobalt content in the nickel-cobalt-manganese lithium oxide is 10%–15% of the total molar ratio of nickel, cobalt, and manganese, the molar ratio of cobalt to nickel is 0.15–0.25, and the particle size (Dv50) of the nickel-cobalt-manganese lithium oxide is 2 μm–6 μm. Thus, the nickel-cobalt-manganese lithium oxide used in the aforementioned battery cell has a high cobalt content, which is beneficial for improving the conductivity of the nickel-cobalt-manganese lithium oxide, reducing the DCR resistance of the battery cell, and by controlling the molar ratio of cobalt to nickel, it helps to reduce "lithium-nickel mixing" and improve the stability of the nickel-cobalt-manganese lithium oxide. Simultaneously, by controlling the particle size (Dv50) of the nickel-cobalt-manganese lithium oxide within the aforementioned small range, the diffusion distance of lithium ions from the surface to the interior of the nickel-cobalt-manganese lithium oxide material is significantly shortened, allowing lithium ions to reach the active sites more quickly to participate in the reaction, accelerating the electrode reaction rate, thereby reducing the resistance caused by slow ion diffusion, and thus improving the fast-charging performance of the battery cell.

[0114] In some embodiments, the electrode resistance of the positive electrode is 0.1Ω to 0.5Ω. For example, the electrode resistance of the positive electrode can be 0.1Ω, 0.2Ω, 0.3Ω, 0.4Ω, 0.5Ω, or within a range defined by any two of the above values. Controlling the electrode resistance within this small range helps reduce the internal resistance of the battery cell and lowers the temperature rise during high-current-density discharge during fast charging. The electrode resistance of the positive electrode is related to the coating weight of the positive active layer, the type and content of the positive active material, its particle size, and the composition of the positive active layer. The electrode resistance can be controlled by adjusting one or more of these parameters. In some examples, the electrode resistance can be controlled by adjusting the coating weight of the positive active layer, the molar ratio of cobalt to nickel in the nickel-cobalt-manganese lithium oxide, the molar ratio of cobalt to nickel in the nickel-cobalt-manganese lithium oxide, and the particle size Dv50 of the nickel-cobalt-manganese lithium oxide. It can also be controlled by adjusting the composition of the positive electrode.

[0115] In some embodiments, the particle size Dv10 of the nickel-cobalt-manganese lithium oxide is 1.1 μm to 1.9 μm; as an example, the particle size Dv10 of the nickel-cobalt-manganese lithium oxide can be 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, or within a range formed by any two of the above values ​​as endpoints. Controlling the particle size Dv10 of the nickel-cobalt-manganese lithium oxide within a small particle size range results in a large contact area between the nickel-cobalt-manganese lithium oxide and the electrolyte, and Li + A shorter solid-phase transport path is beneficial for improving rate performance; in addition, controlling the particle size Dv10 of nickel-cobalt-manganese lithium oxide within a smaller particle size range can help increase the packing density and obtain a greater energy density.

[0116] In some embodiments, the particle size Dv99 of the nickel-cobalt-manganese lithium oxide is 5.0 μm to 8.5 μm; as an example, the particle size Dv99 of the nickel-cobalt-manganese lithium oxide can be 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.5 μm, or any two of the above values ​​as endpoints. Further, the particle size Dv99 of the nickel-cobalt-manganese lithium oxide is 6.0 μm to 8.5 μm. Controlling the particle size Dv99 of the nickel-cobalt-manganese lithium oxide within a small particle size range results in a large contact area between the nickel-cobalt-manganese lithium oxide and the electrolyte, and Li + A shorter solid-phase transport path is beneficial for improving rate performance; in addition, controlling the particle size Dv10 of nickel-cobalt-manganese lithium oxide within a smaller particle size range can help increase the packing density and obtain a greater energy density.

[0117] In some embodiments, the particle sizes Dv10, Dv50, and Dv99 of the nickel-cobalt-manganese lithium oxide satisfy the following condition: 1.5 ≤ (Dv99 - Dv10) / Dv50 ≤ 3.5. (Dv99 - Dv10) / Dv50 is used to measure the width of the particle size distribution. Controlling (Dv99 - Dv10) / Dv50 within this range results in a more uniform overall particle size of the nickel-cobalt-manganese lithium oxide, which improves the consistency of stirring and coating. Furthermore, a narrower particle size distribution can reduce polarization, improve lithium-ion diffusion efficiency and electron transport efficiency, thereby enhancing the charge-discharge performance of the material.

[0118] As an example, the value of (Dv99-Dv10) / Dv50 can be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, or any two of the above point values ​​as endpoints within the range.

[0119] In this application, Dv10, Dv50, and Dv99 have meanings known in the art and can be tested using methods known in the art. For example, they can be measured using a laser particle size analyzer (such as a Malvern Master Size 3000). Dv10, Dv50, and Dv99 respectively represent the particle sizes corresponding to the cumulative percentage of particle volume distribution reaching 10%, 50%, and 99% based on the particle size distribution, starting from the smallest particle size.

[0120] Particle size distribution can be obtained by the following method: Take a clean beaker, add an appropriate amount of the sample to be tested, and sonicate thoroughly to ensure complete dispersion. The testing instrument is a Malvern 2000 (USA). After the sample is poured into the injection tower, it circulates with the solution to the test optical path system. Under the illumination of the laser beam, the particle size distribution characteristics can be obtained by receiving and measuring the energy distribution of the scattered light (opause: 8%–12%). Particle size distribution diagrams are plotted based on the test data.

[0121] In some embodiments, the laser particle size distribution curve of the nickel-cobalt-manganese lithium oxide has at least two peaks. The particle size at the peak with the largest peak is denoted as the average particle size of the large particles, and the particle size at the peak with the smallest peak is denoted as the average particle size of the small particles. The average particle size of the large particles is greater than the average particle size of the small particles. By using nickel-cobalt-manganese lithium oxide particles of different sizes in this way, with small particles filling the gaps between large particles, the conductive network can be further improved, the internal resistance of the positive electrode sheet can be reduced, and thus the fast-charging performance of the battery cell can be improved.

[0122] The laser particle size distribution curve can be obtained by the following method: Take a clean beaker, add an appropriate amount of the sample to be tested, and sonicate thoroughly to ensure complete dispersion of the sample. The testing instrument is a Malvern 2000 (USA). After the sample is poured into the injection tower, it circulates with the solution to the test optical path system. Under the irradiation of the laser beam, the particle size distribution characteristics can be obtained by receiving and measuring the energy distribution of the scattered light (shading degree: 8%–12%). The laser particle size distribution curve is then plotted based on the test data.

[0123] Further, the average particle size of the large particles is 3μm to 4μm, and can be selected as 3.2μm to 3.7μm. As an example, the average particle size of the large particles can be 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, or within the range formed by any two of the above point values ​​as endpoints.

[0124] Alternatively, the particle size Dv50 of the large particles is 3μm to 4μm, and can be selected as 3.2μm to 3.7μm. As an example, the particle size Dv50 of the large particles can be 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, or within the range formed by any two of the above point values ​​as endpoints.

[0125] Further, the average particle size of the small particles is 2μm to 3μm, optionally 2.3μm to 2.9μm. As an example, the average particle size can be 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, or 3.0μm, or within the range defined by any two of the above values ​​as endpoints. Alternatively, further, the particle size Dv50 of the small particles is 2μm to 3μm, optionally 2.3μm to 2.9μm. As an example, the particle size Dv50 of the small particles can be 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, or within the range formed by any two of the above point values ​​as endpoints.

[0126] The main difference between large and small nickel-cobalt-manganese-lithium oxide particles is that large particles primarily enhance long-range conductivity, while small particles can compensate for local conductivity defects.

[0127] In some embodiments, in the laser particle size distribution curve of the nickel-cobalt-manganese lithium oxide, the area of ​​the peak where the small particles are located accounts for 0 to 100% of the sum of the areas of the peaks where the large particles are located and the areas of the peaks where the small particles are located. Examples include 0, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%, or any two of the above point values ​​as endpoints, for example, 10% to 100%, optionally 50% to 100%, more preferably 50% to 90%, and even more preferably 50% to 70%.

[0128] In some embodiments, in the laser particle size distribution curve of the nickel-cobalt-manganese lithium oxide, the area of ​​the peak containing the large particles is less than or equal to the area of ​​the peak containing the small particles. The peak area represents the total particle size, and can also indirectly characterize the total mass; in other words, the area of ​​the peak containing the large particles represents the total particle size or the total mass of the large particles; the area of ​​the peak containing the small particles represents the total particle size or the total mass of the small particles. Furthermore, by controlling the proportion of large particles in the nickel-cobalt-manganese lithium oxide to be relatively small, with small particles predominating, it is beneficial to further reduce the internal resistance of the positive electrode. The lithium-ion diffusion distance of the small-particle nickel-cobalt-manganese lithium oxide material is shorter, allowing lithium ions to reach the active sites more quickly to participate in the reaction, accelerating the electrode reaction rate, thus improving the fast-charging performance of the battery cell.

[0129] Optionally, the ratio of the area of ​​the peak containing the large particles to the area of ​​the peak containing the small particles is 1:9 to 5:5, more preferably 3:7 to 5:5. As examples, this area ratio can be 1:9, 1.5:8.5, 2:8, 2.5:7.5, 3:7, 4:6, 5:5, or any two of the above values ​​as endpoints. Furthermore, by controlling the proportion of small nickel-cobalt-manganese lithium oxide particles within the above range, it is beneficial to further reduce the internal resistance of the positive electrode sheet, and also to better leverage the advantage of faster lithium-ion diffusion in small-particle nickel-cobalt-manganese lithium oxide materials, thereby better improving the fast-charging performance of the battery cell.

[0130] By controlling the mass ratio of large particles to small particles, the ratio of the area of ​​the peak containing the large particles to the area of ​​the peak containing the small particles can be controlled. In some embodiments, the mass percentage of small particles in the nickel-cobalt-manganese lithium oxide is 0% to 100%, and examples include 0, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or any two of the above values ​​as endpoints, for example, 10% to 100%, optionally 50% to 100%, more preferably 50% to 90%, and even more preferably 50% to 70%. In some embodiments, the mass percentage of small particles in the nickel-cobalt-manganese lithium oxide can be 50% to 70%.

[0131] In some embodiments, the nickel-cobalt-manganese lithium oxide comprises single-particle nickel-cobalt-manganese lithium oxide, wherein the mass percentage of the single-particle nickel-cobalt-manganese lithium oxide in the positive electrode active layer is 80% to 100%, optionally 90% to 99%. Single particles are beneficial for reducing lithium-nickel mixing and improving the stability of the nickel-cobalt-manganese lithium oxide, thereby exhibiting better material stability at higher charging rates.

[0132] As an example, the mass percentage of the single-particle form of nickel-cobalt-manganese lithium oxide in the nickel-cobalt-manganese lithium oxide can be 80%, 82%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, 99%, 100%, or within the range formed by any two of the above point values ​​as endpoints.

[0133] In some embodiments, the mass percentage of the lithium nickel cobalt manganese oxide in the positive electrode active layer is 70% to 99%, optionally 85% to 96%. Further, the mass percentage of the single-particle morphology of the lithium nickel cobalt manganese oxide can be 70% to 99%, optionally 85% to 96%.

[0134] As an example, the mass percentage of lithium nickel cobalt manganese oxide or the mass percentage of single-particle nickel cobalt manganese lithium oxide in the positive electrode active layer can be 70%, 72%, 75%, 76%, 78%, 80%, 82%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, or 99%, or within a range defined by any two of the above values. Further, the mass percentage of lithium nickel cobalt manganese oxide or the mass percentage of single-particle nickel cobalt manganese lithium oxide in the positive electrode active layer is 85% to 96%.

[0135] In some embodiments, the coating weight of the positive electrode active layer is 0.15 mg / 1540.25 mm. 2 ~0.28mg / 1540.25mm 2 .

[0136] As an example, the coating weight of the positive electrode active layer is 0.15 mg / 1540.25 mm. 2 0.16mg / 1540.25mm 2 0.17mg / 1540.25mm 2 0.18mg / 1540.25mm 2 0.20mg / 1540.25mm 2 0.22mg / 1540.25mm 2 0.25mg / 1540.25mm 2 0.26mg / 1540.25mm 2 0.28mg / 1540.25mm 2 Or it can be within the range defined by any two of the above point values ​​as endpoints. Further, the coating weight of the negative electrode active layer is 0.16 mg / 1540.25 mm. 2 ~0.24mg / 1540.25mm 2 .

[0137] In some embodiments, the nickel-cobalt-manganese lithium oxide comprises lithium with the chemical formula Li y (Ni a Co b Mn c ) 1-d M 1 d O 2-x A x One or more of the compounds, where y is 0.2–1.2, a, b, and c are all non-zero, a + b + c = 1, a > 0.5, 0 ≤ d < 1, and 0 ≤ x < 2; M 1It includes one or more of Zr, Sr, B, Ti, Mg, Sn, W, Sb, Nb, Zn and Al, where A includes one or more of S, N, F, Cl, Br and I.

[0138] As some alternative examples of x, x can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, and any value within the range consisting of any two of the above values.

[0139] Optionally, b is 0.1 to 0.15. As some optional examples of b, b can be 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, and any value within the range of any two of the above values. Further, b is 0.11 to 0.15.

[0140] Where b is the molar percentage of cobalt in the sum of nickel, cobalt and manganese in the nickel-cobalt-manganese lithium oxide. As mentioned above, the nickel-cobalt-manganese lithium oxide used in the above battery cells has a high cobalt content, which is beneficial to improve the conductivity of the nickel-cobalt-manganese lithium oxide, reduce the DCR resistance of the battery cells, and thus improve the fast charging performance of the battery cells.

[0141] Optionally, b / a is 0.15 to 0.24. As some optional examples of b / a, b / a can be 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, and any value within the range of any two of the above values. Further, b / a is 0.15 to 0.2.

[0142] Where b / a is the molar ratio of cobalt to nickel in nickel cobalt manganese lithium oxide. As mentioned above, by controlling the molar ratio of cobalt to nickel, it is beneficial to reduce "lithium-nickel mixing" and improve the stability of nickel cobalt manganese lithium oxide. This can help improve the stability of nickel cobalt manganese lithium oxide during fast charging and improve the fast charging performance of battery cells.

[0143] Furthermore, non-limiting examples of lithium nickel cobalt manganese oxides may include Li(Ni) 0.65 Co 0.10 Mn 0.25 O2, Li(Ni) 0.63 Co 0.12 Mn 0.25 O2, Li(Ni) 0.60 Co 0.15 Mn 0.25 One or more of O2.

[0144] In some embodiments, the positive electrode active layer further includes lithium phosphate. Adding lithium phosphate to the positive electrode active layer, based on the aforementioned lithium nickel cobalt manganese oxide, helps improve the DCR of the battery cell at low SOC.

[0145] Optionally, the lithium-containing phosphate includes the chemical formula Li β Fe α M 2 (1-α) One or more of the compounds containing PO4, wherein 0.2 ≤ α ≤ 1, 0.9 ≤ β ≤ 1.1, M 2 It includes at least one of Ti, V, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, and Sr.

[0146] As some alternative examples of α, α can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, and any value within the range consisting of any two of the above values.

[0147] As some alternative examples of β, β can be 0.9, 0.95, 1, 1.01, 1.02, 1.1, 1.1, and any value within the range consisting of any two of the above values.

[0148] Furthermore, lithium-containing phosphates include lithium-containing phosphates with an olivine structure. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and one or more of their respective modified or carbon-coated materials.

[0149] In some embodiments, the mass percentage of lithium phosphate in the positive electrode active layer is greater than 0 and ≤50%; for example, it can be 0%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any two of the above values ​​as endpoints. Optionally, the mass percentage of lithium phosphate in the positive electrode active layer is 0-30%, further 1%-30%, and even further 1%-25%, 3%-25%, or 1%-10%.

[0150] In some embodiments, the Dv50 particle size of the lithium phosphate is 8 μm to 20 μm; as an example, the Dv50 particle size of the lithium phosphate can be 8 μm, 9 μm, 10 μm, 12 μm, 15 μm, 16 μm, 18 μm, 20 μm, or within the range defined by any two of the above values ​​as endpoints. Controlling the Dv50 particle size of the lithium phosphate within this range results in a large contact area between the lithium phosphate and the electrolyte, and the Li... +The shorter solid-phase transport path improves rate performance. Furthermore, the Dv50 particle size containing lithium phosphate is controlled within the aforementioned range, resulting in higher packing density and greater energy density; simultaneously, its suitable side reaction sites with the electrolyte contribute to superior battery cycle performance stability.

[0151] In some embodiments, the lithium phosphate includes secondary particles. Secondary particles refer to larger particles formed by the aggregation of multiple primary particles (single particles) through physical or weak chemical processes.

[0152] In some embodiments, the positive electrode further includes at least one positive electrode tab, which is connected to the positive current collector in a first direction. The total cross-sectional area of ​​the positive current collector perpendicular to the first direction is S1, and the total cross-sectional area of ​​the positive electrode tab perpendicular to the first direction is S2. The ratio of S2 to S1, S2 / S1, is ≥ 0.18, and can be selected as 0.18 to 1. Controlling the ratio of the total cross-sectional area S2 of the positive electrode tab to the total cross-sectional area S1 of the positive current collector to be above 0.18 results in a larger current transmission path for the positive electrode tab, while simultaneously reducing the resistance of the positive electrode tab, thus reducing heat generation at the same current.

[0153] As an example, the values ​​of S2 / S1 can be 0.18, 0.19, 0.20, 0.21, 0.22, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.90, 0.95, 1, or any two of the above values ​​forming the range of endpoints. Generally, the tab is directly led out through the electrode plate. One method is to set the length of the tab to be the same as the length of the electrode plate, and S2 / S1 is 1, which is called a full tab.

[0154] Please refer to Figure 1. In the specific example shown in Figure 1, the positive electrode includes a positive current collector 121 and a positive electrode tab 122. The positive electrode tab 122 is connected to the positive current collector 121 in the first direction Y. The total area of ​​the positive current collector 121 in the cross section perpendicular to the first direction Y is S1. As an example, S1 is equal to the area of ​​the positive current collector 121 in the cross section of line AA. The total area of ​​the positive electrode tab 122 in the cross section perpendicular to the first direction Y is S2. As an example, S2 is equal to the total area of ​​the positive electrode tab 122 in the cross section of line BB.

[0155] In some embodiments, the battery cell is a prismatic battery. Furthermore, the battery cell is a prismatic battery, and its outer packaging can be a rigid casing or an aluminum-plastic film soft-pack casing.

[0156] The battery cell is a prismatic cell with a rigid outer casing. Optionally, its S2 / S1 ratio is 0.18 to 0.22, for example, 0.18, 0.19, 0.20, 0.21, 0.22, or any two of the above values ​​as endpoints. When the battery cell is a prismatic cell with a rigid outer casing, using tabs with a large S2 / S1 ratio, such as full tabs, can easily lead to anode-cathode contact problems. Therefore, further controlling it within this range can reduce the risk of anode-cathode contact while also ensuring the lower ohmic impedance of the positive tab.

[0157] In some embodiments, the battery cell is a cylindrical battery.

[0158] In some embodiments, the battery cell further includes a negative electrode tab connected to the negative current collector. Further, the negative electrode tab can adopt the same or similar structural arrangement as the positive electrode tab. Specifically, the negative electrode tab and the negative current collector are also connected in a first direction, the total cross-sectional area of ​​the negative current collector perpendicular to the first direction is S3, and the total cross-sectional area of ​​the negative electrode tab perpendicular to the first direction is S4; wherein the ratio of S4 to S3, S4 / S3, is ≥ 0.18, and can be optionally 0.18 to 1. As an example, the battery cell is a prismatic battery with a rigid outer casing; optionally, its S4 / S3 is 0.18 to 0.22.

[0159] In some embodiments, the battery cell includes an outer packaging, a first electrode terminal, and a second electrode terminal. The positive electrode and the negative electrode are disposed within the outer packaging, and the first electrode terminal and the second electrode terminal are disposed on the outer packaging. The outer packaging can be used to encapsulate the aforementioned electrode assembly, and an electrolyte is disposed within the outer packaging to wet the electrode assembly. Furthermore, the positive electrode, the negative electrode, and the separator can be fabricated into the electrode assembly using a winding process or a stacking process.

[0160] Furthermore, the positive electrode tab is directly connected to the first electrode terminal. Furthermore, the negative electrode tab is directly connected to the second electrode terminal. This direct connection method reduces the contact resistance between the tabs and the electrode terminals, lowers the DCR of the individual battery cells, and improves fast charging performance.

[0161] Furthermore, the number of positive electrode tabs can be one or more. Furthermore, the number of negative electrode tabs can also be one or more. Furthermore, the number of tabs can be set according to a certain ratio based on the number of layers of the electrode sheets formed by stacking or winding, for example, one tab per layer of electrode sheets. Then, multiple positive electrode tabs are connected into one piece using processes such as ultrasonic welding, and then the positive electrode tabs are directly connected to the first electrode terminal using processes such as laser welding; the negative electrode tabs are similar; as an example, laser welding is performed directly on the ultrasonic welding stamp, thus directly connecting the tabs and the electrode terminal.

[0162] In some embodiments, the AC resistance IMP of the battery cell satisfies the following condition: 0.075mΩ ≤ IMP ≤ 0.24mΩ, where IMP is the AC resistance of the battery cell at 25°C, 70% SOC, a 1kHz current frequency, and a 5mV voltage amplitude. A smaller AC resistance IMP range is beneficial for improving the fast-charging performance of the battery cell and reducing heat generation, thereby reducing the temperature rise of the battery cell and improving its safety.

[0163] As an example, the AC resistance IMP of a single battery cell can be 0.075mΩ, 0.08mΩ, 0.09mΩ, 0.1mΩ, 0.12mΩ, 0.15mΩ, 0.16mΩ, 0.18mΩ, 0.20mΩ, 0.22mΩ, or 0.24mΩ, or any two of the above values ​​as terminal values.

[0164] In some embodiments, the rated capacity of the battery cell at a 1C discharge rate is C0, where 130Ah ≤ C0 ≤ 170Ah.

[0165] As an example, the rated capacity C0 of a single battery cell at a discharge rate of 1C can be 130Ah, 135Ah, 140Ah, 145Ah, 150Ah, 155Ah, 160Ah, 165Ah, or 170Ah, or any two of the above values ​​as end values.

[0166] In some embodiments, the battery cell has two larger surfaces arranged opposite each other in its thickness direction, and the distance between the outer surfaces of the two larger surfaces is the thickness of the battery cell.

[0167] The charging time for a single battery cell from 10% SOC to 80% SOC at 25℃ is 5 to 14 minutes, which means that the battery cell has a charging rate capability of 3C to 8C.

[0168] When the charging time of the battery cell from 10% SOC to 80% SOC at 25℃ is 5min to 14min, the thickness of the battery cell is ≤64mm, and can be selected as 34mm to 64mm. When the charging capacity of the battery cell is such that the charging time from 10% SOC to 80% SOC at 25℃ is 5min to 14min, controlling the thickness of the battery cell ensures good thermal conductivity, allowing heat to be quickly transferred from the inside of the battery cell to the outside. This reduces the temperature rise of the battery cell, also helps to reduce the temperature difference between the inside and outside of the battery cell, resulting in good consistency in the overall performance of the battery cell, which is beneficial for maximizing the charging performance of the battery cell and improving its safety.

[0169] As an example, the thickness of a single battery cell can be 20mm, 22mm, 24mm, 25mm, 26mm, 28mm, 30mm, 32mm, 34mm, 35mm, 36mm, 38mm, 40mm, 42mm, 44mm, 45mm, 46mm, 48mm, 49mm, 50mm, 52mm, 54mm, 55mm, 56mm, 58mm, 60mm, 62mm, or 64mm, or within the range formed by any two of the above point values ​​as end values, and so on below.

[0170] The charging time for a single battery cell from 10% SOC to 80% SOC at 25℃ is 8 to 14 minutes, which means that the battery cell has a charging rate capability of 3C to 5C.

[0171] Furthermore, when the charging time of the battery cell from 10% SOC to 80% SOC at 25°C is 8 min to 14 min, the thickness of the battery cell is 40 mm to 64 mm, optionally 40 mm to 48 mm. When the charging capacity of the battery cell is within this range (8 min to 14 min at 25°C), further controlling the thickness of the battery cell within this range can, on the one hand, reduce the temperature rise of the battery cell, which helps to reduce the internal and external temperature differences, resulting in better consistency in the overall performance of the battery cell, facilitating optimal charging performance and improving battery cell safety. On the other hand, a thicker battery cell means more electrode layers, thus increasing the capacity of the battery cell.

[0172] The charging time for a single battery cell from 10% SOC to 80% SOC at 25℃ is 5 to 8 minutes, which means that the battery cell has a charging rate capability of 5C to 8C.

[0173] Furthermore, when the charging time of the battery cell from 10% SOC to 80% SOC at 25°C is 5-8 minutes, the thickness of the battery cell is 34mm-48mm, optionally 34mm-42mm. When the charging capacity of the battery cell is such that the charging time from 10% SOC to 80% SOC at 25°C is 5-8 minutes, it has good fast-charging performance. Further controlling the thickness of the battery cell within this smaller range can improve the thermal conductivity of the battery cell, allowing heat inside the battery cell to be transferred to the external area more quickly, reducing the temperature rise of the battery cell, which is beneficial to reducing the temperature difference between the internal and external parts of the battery cell, resulting in good consistency in the overall performance of the battery cell, which is conducive to maximizing the charging performance of the battery cell and improving the safety of the battery cell. On the other hand, a thicker battery cell means that there are more electrode layers, which can increase the capacity of the battery cell.

[0174] In some embodiments, the battery cell includes an electrolyte that facilitates ion conduction between the positive and negative electrode plates. The positive and negative electrode plates are immersed in the electrolyte.

[0175] Furthermore, the conductivity of the electrolyte at 25°C ranges from 10 mS / cm to 17 mS / cm. As an example, the conductivity of the electrolyte at 25°C can be 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, or 17 mS / cm, or any two of the above values ​​as endpoints. Further, the conductivity of the electrolyte at 25°C is 13 mS / cm to 15 mS / cm. Thus, by using an electrolyte within this higher conductivity range in conjunction with the aforementioned positive electrode, it is beneficial to improve lithium-ion transport in the electrolyte, thereby improving fast-charging performance.

[0176] In some embodiments, the electrolyte comprises a lithium salt. Further, the lithium salt may comprise 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).

[0177] Optionally, the lithium salt may include lithium hexafluorophosphate (LiPF6). Further, the lithium salt may include one or more of lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), and lithium difluorooxalate borate (LiDFOB), which may be used as lithium salt additives in combination with lithium hexafluorophosphate (LiPF6).

[0178] Furthermore, the concentration of lithium salt in the electrolyte can be from 0.8 mol / L to 2 mol / L. For example, it can be 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, or within the range formed by any two of the above values ​​as endpoints.

[0179] In some embodiments, the electrolyte comprises a solvent. Further, the solvent of the electrolyte comprises a carboxylic acid ester solvent. Further, the carboxylic acid ester solvent comprises one or more compounds having the following structure: R1-(C=O)-O-R2, wherein R1 and R2 each independently comprise a substituted or unsubstituted alkyl group.

[0180] As an example, carboxylic acid ester solvents include, but are not limited to, one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate.

[0181] In some embodiments, the mass percentage of the carboxylic acid ester solvent in the solvent is 5% to 80%. As an example, the mass percentage of the carboxylic acid ester solvent in the solvent is 5%, 5.5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 18%, 20%, 25%, 28%, 30%, 35%, 38%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, or within a range formed by any two of the above values ​​as endpoints.

[0182] In some embodiments, the solvent also includes cyclic carbonate solvents.

[0183] In some embodiments, the cyclic carbonate solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC). Further, the cyclic carbonate solvent includes ethylene carbonate (EC) and propylene carbonate (PC).

[0184] In some embodiments, the mass percentage of the cyclic carbonate solvent in the solvent is 10% to 90%. As an example, the mass percentage of the cyclic carbonate solvent in the solvent is 10%, 11%, 12%, 13%, 14%, 15%, 18%, 20%, 25%, 28%, 30%, 35%, 38%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 85%, 90%, or within a range formed by any two of the above values ​​as endpoints.

[0185] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives and positive electrode film-forming additives. Film-forming additives can improve the film-forming performance of the interfacial film inside the battery, further improving the battery's cycle performance.

[0186] Optionally, the mass percentage of the negative electrode film-forming additive or the positive electrode film-forming additive in the electrolyte is 0.2% to 3%. More preferably, the mass percentage of the negative electrode film-forming additive or the positive electrode film-forming additive in the electrolyte can be 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, or 3%, or a range formed by any two of the above values ​​as endpoints.

[0187] Furthermore, the negative electrode film-forming additive includes one or more of ethylene sulfate (DTD), fluoroethylene carbonate (FEC), and difluoroethylene carbonate (DFEC).

[0188] Furthermore, the cathode film-forming additive includes one or more of tris(trimethylsilane)borate (TMSB) and tris(trimethylsilane)phosphite (TMSP).

[0189] In some embodiments, the electrolyte may also include 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. For example, the electrolyte may also include trifluoromethyl ethylene carbonate (TFPC), which can improve the battery's flame retardant and low-temperature performance.

[0190] In some embodiments, the electrolyte injection coefficient is 2.2 g / Ah to 2.5 g / Ah. For example, it can be 2.2 g / Ah, 2.3 g / Ah, 2.4 g / Ah, 2.5 g / Ah, or within the range formed by any two of the above values ​​as endpoints.

[0191] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and typically includes at least a positive electrode, a negative electrode, and an electrolyte. During battery charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of active ions between the positive and negative electrodes. Furthermore, the electrolyte may be the aforementioned electrolyte solution.

[0192] In some embodiments, this application does not have any particular limitation on the type of separator membrane, and any well-known porous structure separator membrane with good chemical and mechanical stability can be selected.

[0193] In some embodiments, the thickness of the isolation membrane is 5μm to 40μm. For example, it can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm, 15μm, 20μm, 25μm, 30μm, 32μm, 35μm, or 40μm, or within the range formed by any two of the above point values ​​as end values, and can be selected as 5μm to 10μm.

[0194] In some embodiments, the base film 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.

[0195] Furthermore, the separator includes a ceramic coating in addition to the base film, including but not limited to an alumina coating. Furthermore, the thickness of the base film can be from 5 μm to 15 μm; for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, or 15 μm, or within the range defined by any two of the above values, specifically 5 μm to 10 μm. Furthermore, the thickness of the ceramic coating can be from 0.5 μm to 3 μm; for example, it can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm, or within the range defined by any two of the above values.

[0196] A second aspect of this application provides a lithium-ion secondary battery comprising at least one of the aforementioned battery cells.

[0197] In some embodiments, the lithium-ion secondary battery further includes two or more battery cells.

[0198] A second aspect of this application provides an electrical device, including at least one of the battery cell described above and the lithium-ion secondary battery described above.

[0199] The electrical device of this application includes the battery cell or lithium-ion secondary battery provided in this application, and therefore has at least the same advantages as the battery cell or the lithium-ion secondary battery.

[0200] The following description, with appropriate reference to the accompanying drawings, describes the battery cell, lithium-ion secondary battery, and power device of this application.

[0201] 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, the battery cell shown in Figure 2 is an example of a square-structured battery cell.

[0202] In some embodiments, a single battery cell has two larger surfaces disposed opposite each other in its thickness direction. Adjacent battery cells are disposed opposite each other with their larger surfaces facing each other.

[0203] In some embodiments, the outer packaging of the battery cell 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-type soft pack. The material of the soft pack can be plastic, and further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0204] In some embodiments, referring to FIG3, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. The electrode assembly 52 is immersed in an electrolyte. The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to actual needs.

[0205] A lithium-ion secondary battery includes at least one battery cell. A lithium-ion secondary battery may include one or more battery cells.

[0206] In some embodiments, the lithium-ion secondary battery can be a battery device or a battery pack. A battery device includes at least one battery cell. The number of battery cells in a battery device can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery device.

[0207] Figure 4 shows a battery device 4 as an example of a lithium-ion secondary battery. Referring to Figure 4, in the battery device 4, multiple battery cells 5 can be arranged sequentially along the length of the battery device 4. Of course, they can also be arranged in any other arbitrary manner. Furthermore, the multiple battery cells 5 can be fixed in place by fasteners.

[0208] Optionally, the battery device 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0209] 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.

[0210] Figures 5 and 6 show an example battery pack 1 as a lithium-ion secondary battery. Referring to Figures 5 and 6, 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 box 2 and a lower box 3, the upper box 2 covering the lower box 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.

[0211] In some embodiments, multiple battery cells 5 can also be arranged in any way in the battery box to obtain a lithium-ion secondary battery.

[0212] Furthermore, multiple battery cells 5 are arranged sequentially with a larger surface area on the same plane to form a group of battery cells, and then multiple groups of battery cells are arranged by bonding the larger surfaces together to form a lithium-ion secondary battery.

[0213] In some embodiments, the lithium-ion secondary battery further includes a cooling plate. Each battery cell has two larger surfaces arranged opposite each other along its thickness direction, and a cooling plate is disposed on at least one side of each of the two larger surfaces. The cooling plate is located inside the battery case. This method of cooling the larger surfaces (referred to as "large surfaces") of the battery cell through contact with the cooling plate allows for rapid heat conduction within the battery cell, thereby reducing the temperature rise of the battery cell and effectively improving the temperature rise during fast charging. It also helps reduce the internal and external temperature differences of the battery cell, resulting in better consistency in the overall performance of the battery cell, which is beneficial for maximizing the charging performance of the battery cell and improving its safety.

[0214] Optionally, the cooling plate is provided with cooling channels. Cooling media such as water can flow into these channels to remove heat generated by the battery cells. Furthermore, the thickness of the battery cells allows their internal temperature to reach a lower temperature similar to or the same as the surface temperature near the cooling plate within a shorter time. This reduces the temperature difference between the internal and external parts of the battery cells, ensuring that the entire battery cell operates at a lower temperature. This results in better consistency in the overall performance of the battery cells, improving their charging performance and safety.

[0215] Thus, this application, on the one hand, reduces the heat generated by individual battery cells at high rates by optimizing their design; on the other hand, it further utilizes rapid cooling methods at the lithium-ion secondary battery level, such as the battery pack level, through cooling plates to quickly dissipate the heat generated by the individual battery cells. In this way, by addressing both heat generation and heat conduction at individual battery cells, the temperature rise of individual battery cells at high rates is reduced, thereby improving the high-rate charging capability of both individual battery cells and the lithium-ion secondary battery.

[0216] Furthermore, a cooling plate is disposed between the larger surfaces of two adjacent battery cells to cool the two larger surfaces of the two battery cells respectively.

[0217] Furthermore, the aforementioned cooling plates are provided on both larger surfaces of the same battery cell. Thus, both larger surfaces of the same battery cell are cooled by the aforementioned cooling plates, which can further accelerate the heat conduction of the battery cell, so that the internal temperature of the battery cell reaches a lower temperature similar to or the same as the surface of the battery cell near the cooling plate in a shorter time. This reduces the temperature difference between the inside and outside of the battery cell, and keeps the battery cell as a whole at a lower temperature.

[0218] As an example, the aforementioned cooling plates are provided on both larger surfaces of each battery cell.

[0219] As described above, multiple battery cells 5 are sequentially arranged with their larger surfaces on the same plane to form a group of battery cells. Then, multiple groups of battery cells are bonded together with their larger surfaces to form a lithium-ion secondary battery. Furthermore, a cooling plate can be placed between two adjacent groups of battery cells. The cooling plate simultaneously cools and lowers the temperature of both groups of battery cells.

[0220] In addition, one embodiment of this application also provides an electrical device, which includes the lithium-ion secondary battery provided in this application. The lithium-ion secondary battery can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0221] As an electrical device, lithium-ion rechargeable batteries can be selected according to its usage requirements.

[0222] Figure 7 shows 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 pack or battery device can be used as the power source.

[0223] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0224] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or 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.

[0225] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0226] Example 1

[0227] (1) Preparation of positive electrode sheet.

[0228] The positive electrode active material is nickel-cobalt-manganese lithium oxide (single particle, specifically composed of Li(Ni)). 0.65 Co 0.10 Mn 0.25 O2 (Dv50 particle size is shown in Tables 1 and 2), lithium iron phosphate material (positive electrode active material), carbon black (conductive agent), and polyvinylidene fluoride (PVDF) (binder) were mixed evenly in a weight ratio of 94:3:2:1 to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the positive electrode current collector aluminum foil, dried to form a positive electrode active layer, and then cold-pressed and slit to obtain the positive electrode sheet.

[0229] As shown in Figure 1, the positive current collector of the positive electrode sheet 12 is die-cut to form a positive electrode tab 121. The positive electrode tab 121 is connected to the positive current collector 121 with a positive active layer in the main body in the first direction Y. The area of ​​the positive current collector 121 in the cross section perpendicular to the first direction Y is S1 (i.e., the cross-sectional area of ​​the positive current collector 121 on line AA), and the area of ​​the positive electrode tab 122 in the cross section perpendicular to the first direction Y is S2 (i.e., the cross-sectional area of ​​the positive electrode tab 122 on line BB). The ratio of S2 to S1, S2 / S1, is 0.18, as shown in Table 5.

[0230] The coating weight of the positive electrode active layer is 0.12 mg / 1540.25 mm. 2 .

[0231] In this application, the coating weight of the electrode (positive electrode or negative electrode) is tested by the following method: the battery is disassembled, the electrode is removed, and it is punched into a piece with an area of ​​S = 1540.25 mm². 2 Take a small circular electrode, measure its weight M, and then take another electrode. Remove the film layer from the surface of the electrode to remove the remaining empty current collector foil. Similarly, punch it to a diameter S = 1540.25 mm. 2 The small round piece is weighed, and the mass of the empty aluminum foil is M0. Then the coating weight = (M-M0) / S / n, where n is the number of film layers coated on the current collector, which is 1 or 2, corresponding to single-sided coating or double-sided coating.

[0232] (2) Preparation of negative electrode sheet.

[0233] A negative electrode slurry was prepared by dissolving graphite (artificial graphite, secondary particles, Dv50 particle size as shown in Table 1), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) in deionized water at a weight ratio of 97:0.4:1.5:1.1 and mixing them evenly. The negative electrode slurry was then uniformly coated onto copper foil (the negative electrode current collector), dried to form the negative electrode active layer, and finally cold-pressed and slit to obtain the negative electrode sheet.

[0234] The coating weight of the negative electrode active layer is 0.12 mg / 1540.25 mm. 2 .

[0235] The formation of the negative electrode tab is similar to that of the positive electrode tab. Therefore, the area of ​​the negative electrode current collector in the cross-section perpendicular to the first direction is S3, and the area of ​​the negative electrode tab in the cross-section perpendicular to the first direction is S4. The ratio of S4 to S3 (S4 / S3) is the same as the ratio of S2 to S1 (S2 / S1).

[0236] (3) Separation membrane.

[0237] A 7μm thick PE (polyethylene) membrane was selected as the base membrane, and an alumina ceramic coating with a thickness of 1μm was formed on each of the two surfaces of the base membrane.

[0238] (4) Preparation of electrolyte.

[0239] Preparation of electrolyte: In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvent ethylene carbonate (EC) / ethyl methyl carbonate (EMC) was mixed evenly at a volume ratio of 3:7, and 1 mol / L LiPF6 lithium salt was added and dispersed evenly. The mixture was stirred evenly to obtain the electrolyte.

[0240] The electrolyte conductivity at 25°C was 12.5 mS / cm. Measurements were performed using an electrochemical impedance spectroscopy (EIS) instrument.

[0241] Test steps:

[0242] Sample preparation: Pour the electrolyte to be tested into the conductivity cell, ensuring that the electrodes are completely immersed in the electrolyte.

[0243] Parameter settings: Select a suitable frequency range, typically from 0.03Hz to 500,000Hz. Set the disturbance voltage, typically 5mV.

[0244] Resistance measurement: The resistance (R) of the electrolyte is measured using an AC impedance spectrometer. The data is fitted using an equivalent circuit to obtain the values ​​of the components in the equivalent circuit, thus yielding the resistance value.

[0245] Calculating electrical conductivity: Electrical conductivity (σ) can be calculated using the following formula: σ=d / (Rs)

[0246] Where d is the distance between the two electrodes of the conductivity cell; R is the resistance of the electrolyte; and S is the electrode area.

[0247] (5) Battery fabrication:

[0248] The prepared positive and negative electrode sheets are stacked in the order of "separator-negative electrode sheet-separator-positive electrode sheet", wound in the same direction, and then subjected to hot pressing, assembly into the shell, drying and injection of electrolyte. After high-temperature standing, formation, electrolyte replenishment and aging, a wound lithium-ion secondary battery cell (also known as "cell") is obtained.

[0249] The electrolyte injection coefficient is 2.4 g / Ah. The cell thickness is 44 mm.

[0250] The five battery cells obtained above are arranged sequentially with their larger surfaces on the same plane to form a group of battery cells. Then, the four groups of battery cells are arranged by attaching their larger surfaces together. Cooling plates are set on the outermost larger surfaces of the four groups of battery cells and on the larger surfaces between adjacent groups of battery cells. Cooling water can be circulated into the cooling plates (the temperature of the cooling water is maintained at 25°C). Then, the battery is installed into a battery case to obtain a lithium-ion secondary battery.

[0251] The following are performance tests.

[0252] (1) IMP test.

[0253] The testing equipment for AC resistance IMP is a BT3562 internal resistance meter (four-wire, beryllium copper gold-plated probe).

[0254] The test method for AC resistance IMP is performed at 25°C, 70% SOC, with a 1kHz current frequency and a 5mV voltage amplitude. Detailed test procedures are as follows:

[0255] To access the software interface: Locate the icon shown in the image on your computer and double-click it to enter the test interface.

[0256] Data save path settings: Click the folder icon in the upper right corner to enter the storage path and name the files accordingly.

[0257] Test item selection: Click the icon in the red box to enter the test item selection, and select the test item impedance.

[0258] Test parameter settings: Select Impedance to enter the test parameter settings interface. Set the disturbance voltage to 5mV. The frequency can be set from 0.03Hz to 500000Hz; set it to 1kHz.

[0259] Channel protection parameter settings: Double-click the Pstst icon (circled in red) to enter the parameter settings interface. Check the voltage and current options in the parameter interface, set the voltage to 10V and the current to 4A.

[0260] The equipment test clamps contact the positive and negative electrode plates of the battery cell to directly measure the IMP.

[0261] (2) DCR test.

[0262] 2.1 Adjusting SOC: At an ambient temperature of 25℃, charge the battery cell to 4.4V with a constant current and constant voltage of 0.33C. After standing for 5 minutes, discharge it to 70% SOC with a current of 0.33C.

[0263] 2.2 Discharge DCR: At 25℃, the cell with 70% SOC was discharged for 10s at an equivalent discharge rate of 4C. The starting voltage and ending voltage were recorded. The DC internal resistance DCR of the cell at 25℃, 70% SOC, with a discharge rate of 4C and a discharge time of 10s was obtained by dividing the voltage difference between the starting voltage and the ending voltage by the discharge current, as shown in Table 1.

[0264] (3) Resistance test of the positive electrode.

[0265] The BER1300 multi-functional electrode resistance meter was used for testing. First, the positive electrode was cut into a small circular piece of a certain size (40mm in diameter) as the test sample. The test sample was placed between two probes, and the test results were recorded. To ensure the accuracy of the test results, multiple sets (e.g., 5 sets) of test samples can be taken simultaneously, and the average value of the multiple sets of test samples can be calculated as the test result.

[0266] (4) Fast charging performance test and temperature rise.

[0267] Rated capacity test. The cell is fully charged to 4.4V at a current of 0.33C, allowed to rest for 30 minutes, and then discharged to 2.5V at a current of 0.33C. This discharge capacity is recorded as the 0.33C capacity. Similarly, the cell is fully charged to 4.4V at a current of 0.33C, allowed to rest for 30 minutes, and then discharged to 2.5V at a current of 1C. This discharge capacity is recorded as the 1C capacity. The 1C capacity is the rated capacity of the battery cell at a discharge rate of 1C, denoted as C0, in Ah. Therefore, C0 = 140 Ah.

[0268] The charging time from 10% SOC to 80% SOC was obtained by charging and discharging at different rates at 25℃. The battery was tested at room temperature (35℃±2℃) with the charging window of the three electrodes tested starting from 0% SOC. Constant current charging was performed at 3C0, 3.5C0, 4C0, 4.5C0, 6C0, 7C0, and 8C0 until the battery charging cutoff voltage of 4.4V or 0V negative electrode cutoff potential (whichever comes first). After each charge, it was discharged at 0.33C0 to 2.5V. The charging time to 10%, 15%, 20%, ..., 80% SOC was recorded at different charging rates. The negative electrode potential corresponding to the state of charge (SOC) is plotted, and the charging rate-negative electrode potential curves for different SOC states are obtained. Linear fitting is used to obtain the charging rate corresponding to the negative electrode potential of 0V in different SOC states. This charging rate is the charging window for that SOC state, denoted as C10%SOC, C15%SOC, C20%SOC, C25%SOC, ..., C75%SOC, C80%SOC. The charging time T (assuming no lithium plating) from 10%SOC to 80%SOC is calculated using the following formula, in minutes. The shorter the time, the better the fast charging performance of the battery. T = (60 / C10%SOC + 60 / C15%SOC + 60 / C20%SOC + ... + 60 / C75%SOC + 60 / C80%SOC) × 5%.

[0269] Temperature rise refers to the temperature difference between the highest and lowest temperatures inside the battery cell during fast charging performance testing. The highest temperature point is generally the positive terminal of the battery cell, while the lowest temperature point is generally the side of the battery cell closest to the casing.

[0270] Comparative Example 1 is basically the same as Example 1, except that the preparation of the positive electrode sheet in step (1) is different. Specifically, the type of positive electrode active material is different, while other conditions remain unchanged, as shown in Table 1.

[0271] Comparative Example 2

[0272] Comparative Example 2 is basically the same as Example 1, except that the preparation of the negative electrode sheet in step (2) is different. Specifically, the coating weight of the negative electrode active layer is different, as shown in Table 1.

[0273] Examples 2-3

[0274] It is basically the same as Example 1, except that the preparation of the positive electrode sheet in step (1) is different. Specifically, the type of positive electrode active material is different, while other conditions remain the same, as shown in Table 1.

[0275] Examples 4-5

[0276] It is basically the same as Example 1, except that the preparation of the negative electrode sheet in step (2) is different. Specifically, the coating weight of the negative electrode active layer is different (the number of electrode layers remains the same, so the thickness of the battery cell changes), as shown in Table 1.

[0277] Simultaneously, when adjusting the coating weight of the negative electrode active layer, the N / P ratio remains constant. This is based on the formula: N / P = (specific capacity of negative electrode active material × areal density of negative electrode × content ratio of negative electrode active material) / (specific capacity of positive electrode active material × areal density of positive electrode × content ratio of positive electrode active material). With the types and content ratios of the positive and negative electrode active materials remaining constant, the coating weight of the positive electrode active layer increases with increasing coating weight of the negative electrode active layer and decreases with decreasing coating weight of the negative electrode active layer.

[0278] The following table shows some parameters and performance results of Examples 1-5 and Comparative Examples 1-2:

[0279] Table 1

[0280] As shown in Table 1, Comparative Example 1 and Comparative Example 2 have larger DCRs, therefore their lithium-ion secondary batteries have larger temperature rises during fast charging tests.

[0281] By controlling the DCR within a suitable range in Examples 1-5, the lithium-ion secondary batteries can achieve both good fast-charging performance and low temperature rise.

[0282] Examples 6-8

[0283] The process is basically the same as in Example 1, except that the preparation of the positive electrode sheet in step (1) is different. Specifically, the particle size parameters of the positive electrode active material, nickel-cobalt-manganese lithium oxide, are different (Dv10, Dv50, Dv99), while other conditions remain unchanged.

[0284] The parameters and performance results of Examples 1, 6-8 are shown in the table below:

[0285] Table 2

[0286] As shown in Table 2, controlling the Dv50, Dv10, and Dv99 of the nickel-cobalt-manganese lithium oxide within a suitable range in Examples 1 and 6-8 results in a lower DCR of the battery cells, which is beneficial for improving rate performance, i.e., enhancing fast charging performance. Furthermore, compared to Examples 7-8, Examples 1 and 6 further control 1.5 ≤ (Dv99 - Dv10) / Dv50 ≤ 3.5, which further enables the lithium-ion secondary battery to achieve both good fast charging performance and low temperature rise.

[0287] Examples 9-13

[0288] It is basically the same as Example 1, except that the preparation of the positive electrode sheet in step (1) is different. Specifically, the nickel-cobalt-manganese lithium oxide in the positive electrode active material includes not only the small particles in Example 1, but also large particles with the same composition. The Dv10, Dv50, Dv99 and content of the large particles are shown in Table 3.

[0289] The following table shows some parameters and performance results for Examples 1, 9-13:

[0290] Table 3

[0291] As shown in Table 3, in Examples 1 and 9-13, using either large or small particles of nickel-cobalt-manganese lithium oxide, or a combination of both, resulted in lithium-ion secondary batteries that achieved both good fast-charging performance and low temperature rise. Furthermore, using a combination of large and small particles of nickel-cobalt-manganese lithium oxide further enhanced the fast-charging performance and lower temperature rise of the lithium-ion secondary battery. Moreover, controlling the mass percentage of small particles in the nickel-cobalt-manganese lithium oxide to 50%–90% further improved the fast-charging performance and lower temperature rise of the lithium-ion secondary battery.

[0292] Examples 14-15

[0293] It is basically the same as Example 1, except that the preparation of the positive electrode sheet in step (1) is different. Specifically, the positive electrode active material also includes lithium phosphate, the content of which is shown in Table 4. The content of nickel cobalt manganese lithium oxide is reduced accordingly, and the total amount of positive electrode active material remains unchanged. The mass content of lithium phosphate in the positive electrode active layer is shown in Table 4.

[0294] The following table shows some parameters and performance results for Examples 1, 14-15:

[0295] Table 4

[0296] As shown in Table 4, adding ≤50% lithium iron phosphate material to the positive electrode active layer results in a lithium-ion secondary battery that balances good fast-charging performance with low temperature rise. Furthermore, controlling the lithium iron phosphate material content in the positive electrode active layer to ≤30% results in a lithium-ion secondary battery that balances even better fast-charging performance with low temperature rise.

[0297] Examples 16-17

[0298] It is basically the same as Example 1, except that the S2 / S1 of the positive electrode and the S4 / S3 of the negative electrode are different. In each example, S2 / S1 and S4 / S3 are equal, as shown in Table 5.

[0299] The following table shows some parameters and performance results for Examples 1, 16-17:

[0300] Table 5

[0301] As shown in Table 5, when the S2 / S1 ratio of the positive electrode and the S4 / S3 ratio of the negative electrode are both above 0.18, the lithium-ion secondary battery can achieve both better fast charging performance and lower temperature rise.

[0302] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0303] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the scope of the claims.

Claims

1. A battery cell, wherein, The battery cell includes a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector. The positive active layer includes nickel cobalt manganese lithium oxide. The negative electrode includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector. The negative active layer includes graphite. The coating weight of the negative electrode active layer is 0.09 mg / 1540.25 mm. 2 ~0.15mg / 1540.25mm 2 ; The battery cell satisfies the following condition: 0.12mΩ≤DCR≤0.5mΩ, where DCR is the DC internal resistance of the battery cell at 25℃, 70% SOC, with a discharge rate of 4C and a discharge time of 10s.

2. The battery cell as described in claim 1, wherein, It meets one or more of the following characteristics: (1) The graphite in the negative electrode active layer accounts for 88% to 97% of the total mass; (2) The graphite includes artificial graphite; (3) The coating weight of the negative electrode active layer is 0.1 mg / 1540.25 mm. 2 ~0.14mg / 1540.25mm 2 .

3. The battery cell according to any one of claims 1 to 2, wherein, The battery cell meets the following requirements: 0.15mΩ≤DCR≤0.4mΩ.

4. The battery cell according to any one of claims 1 to 3, wherein, In the nickel-cobalt-manganese lithium oxide, the molar percentage of cobalt in the sum of nickel, cobalt, and manganese is 10% to 15%.

5. The battery cell according to any one of claims 1 to 4, wherein, The molar ratio of cobalt to nickel in the nickel-cobalt-manganese lithium oxide is 0.15 to 0.

25.

6. The battery cell according to any one of claims 1 to 5, wherein, The resistance of the positive electrode is 0.1Ω to 0.5Ω.

7. The battery cell according to any one of claims 1 to 6, wherein, The particle size Dv50 of the nickel-cobalt-manganese lithium oxide is 2μm to 6μm.

8. The battery cell according to any one of claims 1 to 7, wherein, It meets one or more of the following characteristics: (1) The particle size Dv10 of the nickel-cobalt-manganese lithium oxide is 1.1 μm to 1.9 μm; (2) The particle size Dv99 of the nickel-cobalt-manganese lithium oxide is 5.0 μm to 8.5 μm; (3) The particle sizes Dv10, Dv50 and Dv99 of the nickel cobalt manganese lithium oxide satisfy: 1.5≤(Dv99-Dv10) / Dv50≤3.

5.

9. The battery cell according to any one of claims 1 to 8, wherein, The laser particle size distribution curve of the nickel-cobalt-manganese-lithium oxide has at least two peaks, wherein the particle size at the peak with the largest peak is recorded as the average particle size of the large particles, and the particle size at the peak with the smallest peak is recorded as the average particle size of the small particles, wherein the average particle size of the large particles is greater than the average particle size of the small particles. Optionally, the average particle size of the large particles is 3μm to 4μm, and optionally 3.2μm to 3.7μm; Optionally, the average particle size of the small particles is 2μm to 3μm, and optionally 2.3μm to 2.9μm.

10. The battery cell as described in claim 9, wherein, In the laser particle size distribution curve of the nickel-cobalt-manganese-lithium oxide, the area of ​​the peak containing the large particles is less than or equal to the area of ​​the peak containing the small particles.

11. The battery cell as claimed in claim 10, wherein, The ratio of the area of ​​the peak containing the large particles to the area of ​​the peak containing the small particles is 1:9 to 5:

5.

12. The battery cell according to any one of claims 1 to 11, wherein, It meets one or more of the following characteristics: (1) The mass percentage of the lithium nickel cobalt manganese oxide in the positive electrode active layer is 70% to 99%, and can be 85% to 96%; (2) The nickel cobalt manganese lithium oxide includes nickel cobalt manganese lithium oxide in single-particle form, wherein the mass percentage of the nickel cobalt manganese lithium oxide in single-particle form is 80% to 100%, and optionally 90% to 99%. (3) The coating weight of the positive electrode active layer is 0.15 mg / 1540.25 mm. 2 ~0.28mg / 1540.25mm 2 .

13. The battery cell according to any one of claims 1 to 12, wherein, The nickel-cobalt-manganese-lithium oxide includes the chemical formula Li y (Ni a Co b Mn c ) 1-d M 1 d O 2-x A x One or more of the compounds, where y is 0.2–1.2, a, b, and c are all non-zero, a + b + c = 1, a > 0.5, 0 ≤ d < 1, and 0 ≤ x < 2; M 1 It includes one or more of Zr, Sr, B, Ti, Mg, Sn, W, Sb, Nb, Zn and Al, where A includes one or more of S, N, F, Cl, Br and I.

14. The battery cell as described in claim 13, wherein, It meets one or more of the following characteristics: (1) b is 0.1 to 0.15; (2) b / a is 0.15 to 0.

25.

15. The battery cell according to any one of claims 1 to 14, wherein, The positive electrode active layer also includes lithium phosphate; Optionally, the lithium-containing phosphate includes the chemical formula Li β Fe α M 2 (1-α) One or more of the compounds containing PO4, wherein 0.2 ≤ α ≤ 1, 0.9 ≤ β ≤ 1.1, M 2 It includes at least one of Ti, V, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, and Sr.

16. The battery cell as described in claim 15, wherein, It meets one or more of the following characteristics: (1) The mass percentage of lithium phosphate in the positive electrode active layer is greater than 0 and ≤50%, and can be selected as 1% to 30%; (2) The particle size of the lithium phosphate-containing Dv50 is 8μm to 20μm; (3) The lithium phosphate includes secondary particles.

17. The battery cell according to any one of claims 1 to 16, wherein, The positive electrode sheet further includes at least one positive electrode tab, which is connected to the positive current collector in a first direction. The total cross-sectional area of ​​the positive current collector perpendicular to the first direction is S1, and the total cross-sectional area of ​​the positive electrode tab perpendicular to the first direction is S2. The ratio of S2 to S1 is ≥0.18, and can be selected from 0.18 to 1.

18. The battery cell as claimed in claim 17, wherein, The battery cell is a square battery and the outer packaging is a rigid shell. The ratio of S2 to S1 is 0.18 to 1.00, and can be selected as 0.18 to 0.

22.

19. The battery cell as described in claim 17 or 18, wherein, The battery cell includes an outer packaging, a first electrode terminal, and a second electrode terminal. The positive electrode and the negative electrode are disposed inside the outer packaging, and the first electrode terminal and the second electrode terminal are disposed on the outer packaging. The battery cell satisfies one or more of the following conditions: (1) The positive electrode tab is directly connected to the first electrode terminal; (2) The battery cell also includes a negative electrode tab, which is connected to the negative current collector and directly connected to the second electrode terminal.

20. The battery cell according to any one of claims 1 to 19, wherein, The AC resistance IMP of the battery cell satisfies: 0.075mΩ≤IMP≤0.24mΩ, where IMP is the AC resistance of the battery cell at 25℃, 70% SOC, 1kHz current frequency, and 5mV voltage amplitude.

21. The battery cell according to any one of claims 1 to 20, wherein, The rated capacity of the battery cell at a discharge rate of 1C is C0, 130Ah≤C0≤170Ah.

22. The battery cell according to any one of claims 1 to 21, wherein, The battery cell has two larger surfaces arranged opposite each other in its own thickness direction, and the distance between the outer surfaces of the two larger surfaces is the thickness of the battery cell. The charging time for the battery cell from 10% SOC to 80% SOC at 25°C is 5 min to 14 min, and the thickness of the battery cell is ≤64 mm, which can be selected as 34 mm to 64 mm.

23. The battery cell as described in claim 22, wherein, The charging time for the battery cell from 10% SOC to 80% SOC at 25°C is 8 min to 14 min, and the thickness of the battery cell is 40 mm to 64 mm, optionally 40 mm to 48 mm.

24. The battery cell as claimed in claim 22, wherein, The charging time for the battery cell from 10% SOC to 80% SOC at 25°C is 5 min to 8 min, and the thickness of the battery cell is 34 mm to 48 mm, optionally 34 mm to 42 mm.

25. A lithium-ion secondary battery comprising at least one battery cell as described in any one of claims 1 to 24.

26. The lithium-ion secondary battery as described in claim 25, wherein, The lithium-ion secondary battery also includes a cooling plate. The battery cell has two larger surfaces that are arranged opposite to each other in its own thickness direction. The cooling plate is provided on at least one side of the two larger surfaces of the battery cell. Optionally, the cooling plate is provided with cooling channels.

27. An electrical device comprising at least one of the battery cell according to any one of claims 1 to 24 and the lithium-ion secondary battery according to claim 25 or 26.

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