Lithium-ion battery and electric apparatus

Abstract

A lithium-ion battery and an electric apparatus. The battery comprises a casing, an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are accommodated in the casing. The rated capacity of the battery is 70-180 Ah. The conductivity of the electrolyte at 25°C is 10-17 mS / cm. The electrode assembly comprises an electrode body and tabs arranged in a first direction. In a direction perpendicular to the first direction, the width of a single tab is 30-60 mm. The electrode body comprises a positive electrode sheet. The Dv50 of a positive electrode active material in the positive electrode sheet is less than or equal to 12 μm.

Description

Lithium-ion batteries and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application filed on January 24, 2025, with application number 202510120738X and entitled "Lithium-ion Battery and Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and more particularly to a lithium-ion battery and an electrical device. Background Technology

[0004] In recent years, lithium-ion batteries and other batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0005] As the application scope of batteries such as lithium-ion batteries continues to expand, higher demands are being placed on battery performance. For example, for lithium-ion batteries, it is often difficult to achieve a good balance between high-capacity charging and cycle performance. Summary of the Invention

[0006] A first aspect of this application provides a lithium-ion battery. The lithium-ion battery includes a casing, an electrode assembly, and an electrolyte; the electrode assembly and the electrolyte are housed within the casing. The rated capacity of the lithium-ion battery is 70 Ah to 180 Ah. The conductivity of the electrolyte at 25°C is 10 mS / cm to 17 mS / cm. The electrode assembly includes an electrode body and tabs arranged along a first direction. The width of a single tab is 30 mm to 60 mm perpendicular to the first direction. The electrode body includes a positive electrode sheet; the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, the positive active layer comprising a positive active material, the Dv50 of which is less than or equal to 12 μm.

[0007] This application, by combining a high-capacity lithium-ion battery with an electrolyte of high conductivity and a positive electrode active material with a low Dv50, can reduce the charge transfer resistance inside the battery, decrease polarization, and reduce internal side reactions, laying the foundation for high-rate charging and maintaining cycle performance. Simultaneously, by incorporating appropriately wide tabs in the battery, a larger current-carrying area can be provided, reducing internal heat generation during high-rate charging and resulting in better thermal safety performance. Therefore, the lithium-ion battery design in this application allows for a balance between high rated capacity, high charging rate, and good cycle performance while maintaining good thermal safety.

[0008] In some embodiments, the rated capacity of the lithium-ion battery is 80Ah to 150Ah.

[0009] In some embodiments, the Dv50 of the positive electrode active material is greater than or equal to 0.05 μm.

[0010] In some embodiments, the positive electrode active material comprises Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y A lithium-containing transition metal oxide, wherein 0.2≤x≤1.2, 0.5≤a≤1, 0≤b≤0.1, 0≤c≤0.1, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, W, Sb, Dy, and Te, and A includes one or more of N, P, S, and halogen elements; the Dv50 of the lithium-containing transition metal oxide is 1.5μm~12μm. The chemical formula is Li. x (Ni a Co b Mn c ) 1-d M d O 2-y A y Lithium-containing transition metal oxides have good specific capacity, which is beneficial to improving the energy density of lithium-ion batteries.

[0011] In some embodiments, 0.5 ≤ a ≤ 0.75, the Dv50 of the lithium-containing transition metal oxide is 1.5 μm to 4.5 μm. The lithium-containing transition metal oxide with 0.5 ≤ a ≤ 0.75 exhibits good structural stability, which is beneficial for improving battery cycle performance.

[0012] In some embodiments, 0.75 < a ≤ 1, and the Dv50 of the lithium-containing transition metal oxide is 1.5 μm to 12 μm. Lithium-containing transition metal oxides with 0.75 < a ≤ 1 have higher specific capacity, which is beneficial for improving battery energy density.

[0013] In some embodiments, the lithium-containing transition metal oxide accounts for 10% to 100% of the mass percentage of the positive electrode active material.

[0014] In some embodiments, the positive electrode active material comprises a lithium phosphate with a Dv50 of 0.05 μm to 2 μm. The lithium phosphate exhibits good cycle stability and can improve the cycle performance of lithium-ion batteries.

[0015] In some embodiments, the lithium phosphate comprises 1% to 90% of the mass percentage of the positive electrode active material.

[0016] In some embodiments, the positive electrode active material comprises single-crystal particles. Single-crystal particles have high lattice orientation uniformity, and can maintain good integrity and stability when affected by external forces, temperature changes, and other factors. When the battery is charged at high rates, the single-crystal particles can also maintain good stability. Therefore, the introduction of single-crystal particles can further improve the rate performance of lithium-ion batteries.

[0017] In some embodiments, the single-crystal particles account for 10% to 90% of the mass percentage of the positive electrode active material.

[0018] In some embodiments, the positive electrode active material further includes polycrystalline particles. Polycrystalline particles have good compaction properties, which is beneficial for increasing the compaction density of the positive electrode. The combination of polycrystalline and monocrystalline particles allows the positive electrode sheet to achieve both high compaction density and good stability, thereby enabling the battery to achieve both high energy density and good rate performance.

[0019] In some embodiments, the mass ratio of the polycrystalline particles to the single-crystal particles is 1:9 to 9:1.

[0020] In some embodiments, the polycrystalline particles account for 50% to 90% of the mass percentage of the positive electrode active material.

[0021] In some embodiments, the positive electrode active layer further comprises a conductive agent, which includes one or more of zero-dimensional, one-dimensional, and two-dimensional conductive agents. The conductive agent can construct a conductive network in the positive electrode active layer, promoting electron transport and further improving the rate performance of the battery.

[0022] In some embodiments, the mass ratio of the zero-dimensional conductive agent to the one-dimensional conductive agent is 1:1 to 100:1.

[0023] In some embodiments, the mass ratio of the two-dimensional conductive agent to the one-dimensional conductive agent is 0.01:1 to 0.5:1.

[0024] In some embodiments, the conductive agent accounts for 1% to 5% of the mass percentage of the positive electrode active layer.

[0025] In some embodiments, the zero-dimensional conductive agent includes one or more of Super P, Ketjen Black, and acetylene black.

[0026] In some embodiments, the one-dimensional conductive agent includes one or more of carbon nanotubes and carbon fibers.

[0027] In some embodiments, the two-dimensional conductive agent includes one or more of conductive graphite and graphene.

[0028] In some embodiments, the compaction density of the positive electrode active layer is 3.1 g / cm³. 3 ~3.7g / cm 3 At this point, lithium-ion batteries can exhibit high energy density.

[0029] In some embodiments, the electrolyte includes a solvent, which includes a carboxylic acid ester. The carboxylic acid ester can reduce the viscosity of the electrolyte, promote the transport of lithium ions in the electrolyte, and thus improve the rate performance of the battery. Simultaneously, the low-viscosity electrolyte can better wet the electrodes, improve the liquid phase diffusion transport rate, and further improve the rate performance of the battery.

[0030] In some embodiments, the carboxylic acid ester accounts for 5% to 80% of the solvent by mass. Within this range, the carboxylic acid ester's mass percentage in the solvent allows the electrolyte to maintain good stability while fully leveraging its ability to improve battery rate performance, thereby ensuring good cycle stability of the battery.

[0031] In some embodiments, the carboxylic acid ester includes one or more of methyl formate, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0032] In some embodiments, the solvent further includes cyclic carbonates. Cyclic carbonates have a high dielectric constant, and the combination of cyclic carbonates and carboxylic acid esters can give the electrolyte a suitable viscosity while improving its conductivity, further promoting the improvement of battery rate performance. In addition, cyclic carbonates often have high boiling points and good stability; when combined with carboxylic acid esters, they can increase the boiling point and stability of the electrolyte. When the battery is charged at high rates, the combination of cyclic carbonates and carboxylic acid esters can help maintain the electrolyte's good stability, further improving the battery's rate performance.

[0033] In some embodiments, the cyclic carbonate accounts for 10% to 95% of the solvent by mass. Within this range, the cyclic carbonate's good stability is fully utilized, allowing for better compatibility between the cyclic carbonate and carboxylic acid esters, further promoting improved battery rate performance.

[0034] In some embodiments, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

[0035] In some embodiments, the electrode body includes a negative electrode sheet; the negative electrode sheet includes a negative current collector and a negative active layer located on at least one surface of the negative current collector, the negative active layer comprising a negative active material, the negative active material including modified graphite, the modified graphite including a graphite matrix and a coating layer located on at least a portion of the surface of the graphite matrix, the coating layer being made of amorphous carbon. The modified graphite including the coating layer can further reduce diffusion resistance and charge transfer resistance, improving the rate performance of the battery.

[0036] In some embodiments, the thickness of the coating layer is 1 nm to 50 nm.

[0037] In some embodiments, the modified graphite accounts for 10% to 100% of the mass percentage of the negative electrode active material.

[0038] In some embodiments, the Dv50 of the negative electrode active material is 5 μm to 16 μm.

[0039] In some embodiments, the lithium-ion battery further includes electrode terminals connected to the housing, and the electrode terminals are directly electrically connected to the tabs. This direct electrical connection between the electrode terminals and tabs eliminates the need for current-collecting components between them, shortening the current path, reducing the internal mechanical resistance of the battery, and further improving the battery's rate performance.

[0040] In some embodiments, the ratio of the number of tabs to the number of electrode body layers is 0.75 to 1. A larger number of tabs allows for parallel connection between the multiple electrode body layers, thereby reducing the battery's internal resistance and further improving its rate performance.

[0041] A second aspect of this application provides an electrical device including the lithium-ion battery of the first aspect. Attached Figure Description

[0042] 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:

[0043] Figure 1 is a schematic diagram of an electrode assembly according to an embodiment of this application.

[0044] Figure 2 is a schematic diagram of a lithium-ion battery according to an embodiment of this application.

[0045] Figure 3 is an exploded view of a lithium-ion battery according to an embodiment of this application, as shown in Figure 2.

[0046] Figure 4 is a schematic diagram of an electrical device using a lithium-ion battery as a power source according to an embodiment of this application.

[0047] Explanation of reference numerals in the attached drawings: 1. Lithium-ion battery; 11. Casing; 12. Electrode assembly; 121. Electrode body; 122. Tab; 13. Cover plate; 2. Electrical device. Detailed Implementation

[0048] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] 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 the specific range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be included or excluded independently, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 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 "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0051] 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.

[0052] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0053] 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.

[0054] 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. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may 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.

[0055] 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.

[0056] 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.

[0057] In this application, unless otherwise specified, "lithium-ion battery" refers to a basic unit capable of converting chemical energy into electrical energy, and more generally includes a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions repeatedly insert and extract between the positive and negative electrode.

[0058] High-capacity lithium-ion batteries can better meet consumers' demands for battery capacity. For high-capacity lithium-ion batteries, increasing the charging rate is particularly important. However, increasing the charging rate usually increases internal polarization within the battery, affecting its capacity utilization. Furthermore, high-rate charging often leads to greater heat generation and more side reactions, making it difficult for the battery to effectively balance high rated capacity and a high charging rate.

[0059] Based on this, one embodiment of this application provides a lithium-ion battery. The lithium-ion battery includes a casing, an electrode assembly, and an electrolyte; the electrode assembly and electrolyte are housed within the casing. The rated capacity of the lithium-ion battery is 70 Ah to 180 Ah. The conductivity of the electrolyte at 25°C is 10 mS / cm to 17 mS / cm. The electrode assembly includes an electrode body and tabs arranged along a first direction. The width of a single tab is 30 mm to 60 mm perpendicular to the first direction. The electrode body includes a positive electrode sheet; the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, the positive active layer comprising a positive active material, the Dv50 of which is less than or equal to 12 μm.

[0060] In this embodiment, for lithium-ion batteries with high rated capacity, using an electrolyte with high conductivity and a positive electrode active material with a low Dv50 can reduce the charge transfer resistance inside the battery, decrease polarization, and reduce internal side reactions, laying the foundation for high-rate charging and maintaining cycle performance. Simultaneously, providing appropriately wide tabs in the battery allows for a larger current-carrying area, reducing internal heat generation during high-rate charging and resulting in better thermal safety performance. Therefore, the lithium-ion battery design in this application achieves a balance between high rated capacity, high charging rate, and good cycle performance while maintaining good thermal safety.

[0061] In some embodiments, the lithium-ion battery of this application can maintain a high capacity at a charging rate of 4C or higher. Optionally, the charging rate can be 4C, 5C, 6C, etc.

[0062] Please refer to Figure 1, which shows a schematic diagram of an electrode assembly 12 according to one embodiment of this application. The electrode assembly 12 includes an electrode body 121 and a tab 122 arranged along a first direction. Understandably, the first direction refers to the direction from the electrode body 121 to the tab 122. In Figure 1, as an example, the Y direction represents the first direction, and the X direction represents the direction perpendicular to the first direction. The width of the tab perpendicular to the first direction can represent the width of the tab in the X direction. In Figure 1, the width of a single tab perpendicular to the first direction is represented by W, where W is 30mm to 60mm.

[0063] In this application, the rated capacity of the lithium-ion battery can be tested by the following method: the battery is charged at a constant current of 0.33C to the charging cutoff voltage, and then charged at a constant voltage to the cutoff current of 0.05C. Then it is discharged at 0.33C to the discharge cutoff voltage, and the discharge capacity is recorded as the rated capacity of the battery.

[0064] Understandably, the charging cut-off voltage can be selected based on the type of positive electrode active material. For example, when the positive electrode active material mainly consists of lithium-containing transition metal oxides, and the percentage of nickel in the total molar amount of transition metal elements in the lithium-containing transition metal oxides is less than or equal to 75%, the charging cut-off voltage can be 4.4V, and the discharging cut-off voltage can be 2.5V. When the positive electrode active material mainly consists of lithium-containing transition metal oxides, and the percentage of nickel in the total molar amount of transition metal elements in the lithium-containing transition metal oxides is greater than 75%, the charging cut-off voltage can be 4.25V, and the discharging cut-off voltage can be 2.5V. When the positive electrode active material mainly consists of lithium phosphate, the charging cut-off voltage can be 3.8V, and the discharging cut-off voltage can be 2.5V.

[0065] In some embodiments, the rated capacity of the lithium-ion battery is 70Ah to 180Ah. In this case, the lithium-ion battery can adequately meet the capacity requirements. Optionally, the rated capacity of the lithium-ion battery can be 70Ah, 80Ah, 90Ah, 100Ah, 110Ah, 120Ah, 130Ah, 140Ah, 150Ah, 160Ah, 170Ah, 180Ah, or any value within the range of any two of the above values. For example, the rated capacity of the lithium-ion battery can be 70Ah to 90Ah, 100Ah to 130Ah, 120Ah to 150Ah, etc. More optionally, the rated capacity of the lithium-ion battery is 80Ah to 150Ah.

[0066] In some embodiments, the electrolyte has a conductivity of 10 mS / cm to 17 mS / cm. Electrolytes with conductivity within this range can effectively reduce the liquid phase transport impedance inside the battery, giving the battery better rate performance. Simultaneously, conductivity within this range can reduce side reactions inside the battery, improving its cycle performance. Optionally, the electrolyte conductivity can be 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 17 mS / cm, or any value within the range of any two of these values. For example, the electrolyte conductivity can be 10 mS / cm to 12 mS / cm, 11 mS / cm to 15 mS / cm, 13 mS / cm to 17 mS / cm, etc.

[0067] In this application, the lithium-ion conductivity of the electrolyte describes the ability of dissociated ions in the electrolyte solution to conduct electricity through directional movement in an electric field, and can be tested using any method known in the art. As an example, the lithium-ion conductivity of the electrolyte can be tested as follows: Disassemble the battery, take approximately 100 mL of electrolyte sample in a dry, clean, corrosion-resistant sample bottle, seal it, and place it in a constant-temperature water bath. Shake the sample and maintain the temperature at 25°C (deviation ±0.5°C). After the sample temperature stabilizes, use a commercially available conductivity meter to test its conductivity. Clean and dry the conductivity meter with calibration solution, then vertically immerse it in the liquid to be tested. Click "Start Test," and record the test results after the data has stabilized for at least 10 seconds.

[0068] In some embodiments, the Dv50 of the positive electrode active material is less than or equal to 12 μm. A smaller Dv50 can reduce the charge resistance and diffusion resistance inside the battery, reduce battery polarization, and help improve the battery's rate performance. Optionally, the Dv50 of the positive electrode active material can be 12 μm, 11 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, 0.1 μm, 0.05 μm, or any value within the range of any two of the above values. Further optionally, the Dv50 of the positive electrode active material is greater than or equal to 0.05 μm.

[0069] In this application, Dv50 represents the particle size corresponding to a cumulative volumetric distribution percentage of 50%. It can be determined using a laser particle size analyzer (such as a Malvern Master Size 3000) with reference to standard GB / T 19077-2016.

[0070] In some embodiments, the width of the tabs is 30mm to 60mm. When the battery is charged at a high rate, a significant amount of heat is often generated inside the battery. Tabs within this width range allow for a larger current-carrying area, reducing heat generation during high-rate charging and thus improving the battery's thermal safety performance. In other words, by setting the tab width in this application, less heat is generated during high-rate charging, reducing the internal temperature rise and improving the battery's thermal safety performance. This allows the battery to achieve both good thermal safety performance and a high rated capacity and a large charging rate. Optionally, the tab width can be 30mm, 32mm, 35mm, 38mm, 40mm, 42mm, 45mm, 48mm, 50mm, 52mm, 55mm, 58mm, 60mm, or any value within the range of any two of the above values. For example, the width of the electrode tab can be 30mm-40mm, 34mm-44mm, 36mm-50mm, 40mm-45mm, 43mm-50mm, 49mm-58mm, 50mm-60mm, etc.

[0071] In this application, the width of the tab can be tested by disassembling the lithium-ion battery, obtaining the electrode assembly, confirming the position of the electrode body and the tab, and then measuring the width of the tab.

[0072] It is understood that when the electrode body includes a positive electrode plate, the tab connected to the positive electrode plate is the positive electrode tab. Optionally, the material of the positive electrode tab includes at least one of aluminum and its alloys. When the electrode body includes a negative electrode plate, the tab connected to the negative electrode plate is the negative electrode tab. Optionally, the material of the negative electrode tab includes at least one of copper and its alloys.

[0073] In some embodiments, the positive electrode active material includes Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y Lithium-containing transition metal oxides, wherein 0.2≤x≤1.2, 0.5≤a≤1, 0≤b≤0.1, 0≤c≤0.1, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, W, Sb, Dy, and Te, and A includes one or more of N, P, S, and halogen elements; the Dv50 of lithium-containing transition metal oxides is 1.5~12μm. The chemical formula is Li. x (Ni a Co b Mnc ) 1-d M d O 2-y A y Lithium-containing transition metal oxides have good specific capacity, which is beneficial to improving the energy density of lithium-ion batteries.

[0074] Understandably, 'a' is typically used to represent the nickel content in lithium-containing transition metal oxides. A larger 'a' indicates a higher nickel content, while a smaller 'a' indicates a lower nickel content. As some possible examples of 'a', it can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or any value within the range of any two of these values. For example, 'a' can be 0.55–0.75, 0.65–0.85, 0.75–0.95, etc.

[0075] Understandably, 'b' is typically used to represent the cobalt content in lithium-containing transition metal oxides. A larger 'b' indicates a higher cobalt content, while a smaller 'b' indicates a lower cobalt content. As some possible examples of 'b', it can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value within the range of any two of these values. For example, 'b' can be 0.005–0.015, 0.025–0.055, 0.045–0.075, 0.055–0.095, etc.

[0076] Understandably, 'c' is typically used to represent the manganese content in lithium-containing transition metal oxides. A larger 'c' indicates a higher manganese content, while a smaller 'c' indicates a lower manganese content. As some possible examples of 'c', it can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value within the range of any two of these values. For example, 'c' can be 0.005–0.015, 0.025–0.055, 0.045–0.075, 0.055–0.095, etc.

[0077] Understandably, 'd' is typically used to represent the content of element M in lithium-containing transition metal oxides. A larger 'd' indicates a higher content of element M, while a smaller 'd' indicates a lower content of element M. As some possible examples of 'd', it can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or any value within the range of any two of these values. For example, 'd' can be 0.005–0.015, 0.025–0.055, 0.045–0.075, 0.055–0.095, 0.15–0.55, 0.35–0.85, 0.55–0.95, etc. Optionally, 0 ≤ d ≤ 0.05.

[0078] Understandably, x is typically used to represent the lithium content in lithium-containing transition metal oxides. A larger x indicates a higher lithium content, while a smaller x indicates a lower lithium content. As some possible 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 of any two of the above values. Optionally, x can be 0.25–0.45, 0.35–0.75, 0.55–0.95, 1.05–1.15, etc.

[0079] Understandably, y is typically used to represent the content of element A in lithium-containing transition metal oxides. A larger y indicates a higher content of element A, while a smaller y indicates a lower content of element A. As some possible examples of y, y can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, and any value within the range of any two of the above values. For example, y can be 0.005–0.015, 0.025–0.055, 0.045–0.075, 0.055–0.095, 0.15–0.55, 0.35–0.85, 0.55–0.95, 1.05–1.15, 1.25–1.55, 1.45–1.95, etc. Optionally, 0 ≤ y ≤ 0.05.

[0080] It is understandable that A includes one or more of N, P, S and halogen elements, where halogen elements can be F, Cl, Br, etc.

[0081] Optionally, the lithium-containing transition metal oxide includes LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.25 Mn 0.25 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.9 Co 0.09 Mn 0.01 O2, LiNi 0.92 Co 0.05 Mn 0.03 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2, etc.

[0082] In some embodiments, the lithium-containing transition metal oxide accounts for 10% to 100% of the mass percentage of the positive electrode active material. For example, the mass percentage of the lithium-containing transition metal oxide in the positive electrode active material can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or any value within the range of any two of the above values.

[0083] In some embodiments, 0.5 ≤ a ≤ 0.75, the Dv50 of the lithium-containing transition metal oxide is 1.5 μm to 4.5 μm. The lithium-containing transition metal oxide with 0.5 ≤ a ≤ 0.75 exhibits better structural stability, which is beneficial for improving battery cycle performance. Optionally, when 0.5 ≤ a ≤ 0.75, the Dv50 of the lithium transition metal oxide can be 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 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, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, or any value within the range of any two of the above values.

[0084] In some embodiments, 0.75 < a ≤ 1, and the Dv50 of the lithium-containing transition metal oxide is 1.5 μm to 12 μm. The lithium-containing transition metal oxide with 0.75 < a ≤ 1 has a higher specific capacity, which is beneficial for improving the energy density of the battery. Optionally, when 0.75 < a ≤ 1, the Dv50 of the lithium-containing transition metal oxide can be 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any value within the range of any two of the above values.

[0085] In some embodiments, the positive electrode active material includes a lithium phosphate, wherein the Dv50 of the lithium phosphate is 0.05 μm to 2 μm. The lithium phosphate exhibits good cycle stability and can improve the cycle performance of lithium-ion batteries. Optionally, the Dv50 of the lithium phosphate can be 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 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, 2 μm, or any value within the range of any two of the above values.

[0086] Optionally, lithium-containing phosphates may include at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Lithium-containing phosphates may also include one or more of lithium manganese phosphate and lithium manganese phosphate and carbon composites.

[0087] In some embodiments, the lithium phosphate content in the positive electrode active material is 1% to 90% by mass. Optionally, the lithium phosphate content in the positive electrode active material can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or any value within the range of any two of the above values.

[0088] In some embodiments, the positive electrode active material includes, in addition to, materials with the chemical formula Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y In addition to lithium-containing transition metal oxides and lithium-containing phosphates, it may also include positive electrode active materials known in the art for use in batteries.

[0089] Optionally, the positive electrode active material may also include one or more of the following materials: lithium transition metal oxides and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium manganese oxides, lithium manganese cobalt oxides, and their modified compounds. Non-limiting examples of lithium cobalt oxides may include LiCoO2. Non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.

[0090] In some embodiments, the positive electrode active material includes monocrystalline particles. Monocrystalline particles typically refer to particles composed of one or no more than five primary particles. Due to the smaller number of primary particles and grain boundaries in monocrystalline particles, they can maintain better integrity and stability when affected by external forces, temperature changes, and other factors. Monocrystalline particles also maintain good stability when the battery is charged at high rates. Therefore, the introduction of monocrystalline particles can further improve the rate performance of lithium-ion batteries. Optionally, the mass percentage of monocrystalline particles in the positive electrode active material is 10% to 90%. For example, the mass percentage of monocrystalline particles in the positive electrode active material can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or any value within the range of any two of the above values. It is understood that the mass percentage of monocrystalline particles in the positive electrode active material can also be 100%.

[0091] In some embodiments, the positive electrode active material also includes polycrystalline particles. Polycrystalline particles have good compaction properties, which is beneficial for increasing the compaction density of the positive electrode. The combination of polycrystalline and monocrystalline particles allows the positive electrode sheet to achieve both high compaction density and good stability, thereby enabling the battery to achieve both high energy density and good rate performance.

[0092] Optionally, the mass ratio of polycrystalline particles to monocrystalline particles is 1:9 to 9:1. For example, the mass ratio of polycrystalline particles to monocrystalline particles is 9:1, 8.5:1.5, 8:2, 7.5:2.5, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9, and any value within the range of any two of the above values.

[0093] In some embodiments, the polycrystalline particles account for 50% to 90% of the mass percentage of the positive electrode active material. For example, the mass percentage of polycrystalline particles in the positive electrode active material can be 50%, 60%, 70%, 80%, 90%, 100%, or any value within the range of any two of the above values.

[0094] In this application, the mass percentage of single-crystal particles in the lithium-containing transition metal oxide can be determined using testing methods known in the art. As an example, the mass percentage of single-crystal particles in the lithium-containing transition metal oxide can be tested as follows: The positive electrode active layer is sliced ​​along its thickness direction, and the crystal structure of the particles in the resulting cross-section is observed to determine the presence of single-crystal and polycrystalline particles (if any). The volumes of the single-crystal and polycrystalline particles are then calculated based on their dimensions in the cross-section. Since the density of single-crystal and polycrystalline particles is equal, the mass percentage of single-crystal particles in the lithium-containing transition metal oxide can be determined by the volume ratio of single-crystal particles to the total volume.

[0095] The mass percentage of polycrystalline particles in the lithium-containing transition metal oxide can be determined using methods known in the art. As an example, the mass percentage of polycrystalline particles in the lithium-containing transition metal oxide can be tested as follows: The positive electrode active layer is sliced ​​along its thickness direction, and the crystal structure of the particles in the resulting cross-section is observed to determine the presence of single-crystal and polycrystalline particles. The volumes of the single-crystal and polycrystalline particles are then calculated based on their dimensions in the cross-section. Since the density of single-crystal and polycrystalline particles is equal, the mass percentage of polycrystalline particles in the lithium-containing transition metal oxide can be determined by the volume ratio of polycrystalline particles to the total particles.

[0096] The mass ratio of polycrystalline particles to monocrystalline particles can be determined using testing methods known in the art. As an example, the mass ratio of polycrystalline particles to monocrystalline particles can be tested as follows: The positive electrode active layer is sliced ​​along its thickness direction, and the crystal structure of the particles in the resulting cross-section is observed to determine the number of monocrystalline and polycrystalline particles. Then, the volumes of the monocrystalline and polycrystalline particles are calculated based on their dimensions in the cross-section. Since monocrystalline and polycrystalline particles have the same density, their mass ratio can be determined by the volume ratio of polycrystalline and monocrystalline particles.

[0097] In some embodiments, the positive electrode active layer further comprises a conductive agent, which includes one or more of zero-dimensional, one-dimensional, and two-dimensional conductive agents. The conductive agent can construct a conductive network in the positive electrode active layer, promote electron transport, and further improve the rate performance of the battery.

[0098] In some embodiments, the mass ratio of the zero-dimensional conductive agent to the one-dimensional conductive agent is 1:1 to 100:1. In this case, the dot-like structure of the zero-dimensional conductive agent and the network structure of the one-dimensional conductive agent work together to provide a richer conductive network, further promoting electron transport and improving the rate performance of the battery. Optionally, the mass ratio of the zero-dimensional conductive agent to the one-dimensional conductive agent can be 1:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, or any value within the range of any two of the above ratios.

[0099] In some embodiments, the mass ratio of the two-dimensional conductive agent to the one-dimensional conductive agent is 0.01:1 to 0.5:1. In this case, the sheet-like structure of the two-dimensional conductive agent and the network structure of the one-dimensional conductive agent work together to provide a richer conductive network, further promoting electron transport and improving the rate performance of the battery. Optionally, the mass ratio of the two-dimensional conductive agent to the one-dimensional conductive agent can be 0.01:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or any value within the range of any two of the above ratios.

[0100] In some embodiments, the conductive agent accounts for 1% to 5% of the mass percentage of the positive electrode active layer. Optionally, the conductive agent accounts for 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value within the range of any two of the above values.

[0101] In this application, the mass percentage of the conductive agent in the positive electrode active layer can be tested as follows: Disassemble the battery to obtain the positive electrode sheet, weigh it as m1, remove the positive electrode active layer, weigh the positive electrode current collector as m2, then the mass of the positive electrode active layer is m1-m2. Disassemble another identical battery to obtain the positive electrode sheet, heat-treat the positive electrode sheet at 800℃ in an argon atmosphere to remove the binder, weigh the remaining mass of the positive electrode sheet as m3. Then heat-treat the positive electrode sheet again at 800℃ in an air atmosphere to remove the conductive agent, weigh the remaining mass of the positive electrode sheet as m4, calculate the mass of the conductive agent as m3-m4, and the mass percentage of the conductive agent in the positive electrode active layer is (m3-m4) / (m1-m2)×100%.

[0102] Optionally, the zero-dimensional conductive agent accounts for 0.5% to 3% of the mass percentage of the positive electrode active layer. For example, the mass percentage of the zero-dimensional conductive agent in the positive electrode active layer can be 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, or any value within the range of any two of the above values.

[0103] Optionally, the one-dimensional conductive agent accounts for 0.01% to 1% of the mass percentage of the positive electrode active layer. For example, the one-dimensional conductive agent can account for 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or any value within the range of any two of the above values.

[0104] Optionally, the two-dimensional conductive agent accounts for 0% to 1% of the mass percentage of the positive electrode active layer. For example, the mass percentage of the two-dimensional conductive agent in the positive electrode active layer can be 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any value within the range of any two of the above values. It is understood that a mass percentage of 0% for the two-dimensional conductive agent in the positive electrode active layer indicates that the positive electrode active layer does not contain the two-dimensional conductive agent.

[0105] Optionally, zero-dimensional conductive agents include one or more of Super P, Ketjen Black, and acetylene black. One-dimensional conductive agents include one or more of carbon nanotubes and carbon fibers. Two-dimensional conductive agents include one or more of conductive graphite and graphene.

[0106] In some embodiments, the compaction density of the positive electrode active layer is 3.1 g / cm³. 3 ~3.7g / cm 3 At this point, lithium-ion batteries exhibit high energy density. Simultaneously, the compaction density of the positive electrode active layer within this range can promote electrolyte wetting of the positive electrode sheet, further improving the battery's rate performance. Optionally, the compaction density of the positive electrode active layer can be 3.1 g / cm³. 3 3.2g / cm 3 3.3g / cm 3 3.4g / cm 3 3.5g / cm 3 3.6g / cm 3 3.7g / cm 3 And any value within the range formed by any two of the above values. For example, the compaction density of the positive electrode active layer could be 3.15 g / cm³. 3 ~3.35g / cm 3 3.25g / cm 3 ~3.55g / cm 3 3.45g / cm 3 ~3.65g / cm 3 wait.

[0107] In this application, the compaction density of the active layer of the electrode sheet can be tested using the following method: Disassemble the battery, take the electrode sheet, punch it into a small circular piece with an area of ​​S1, weigh it, and record its weight as M1; measure the thickness of the active layer and record it as T; then wipe off the weighed active layer, weigh the remaining electrode sheet, and record it as M0. The compaction density of the active layer PD = (M1 - M0) / (S1 × T). It is understood that when the electrode sheet is a positive electrode sheet, the compaction density of the positive electrode active layer can be tested. When the electrode sheet is a negative electrode sheet, the compaction density of the negative electrode active layer can be tested.

[0108] In some embodiments, the positive electrode active layer includes a binder. Optionally, the binder accounts for 1% to 2% of the mass percentage of the positive electrode active layer. The binder is typically a polymer material with poor conductivity; when its mass percentage of the positive electrode active layer is within this range, it can exhibit good bonding performance while simultaneously providing the positive electrode active layer with good conductivity, thereby enabling the battery to maintain good rate performance. Further optionally, the mass percentage of the binder in the positive electrode active layer can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any value within the range of any two of the above values.

[0109] In this application, the mass percentage of the binder in the positive electrode active layer can be tested as follows: Disassemble the battery to obtain the positive electrode sheet, weigh it as m1, remove the positive electrode active layer, weigh the positive electrode current collector as m2, then the mass of the positive electrode active layer is m1-m2. Disassemble another identical battery to obtain the positive electrode sheet, heat-treat the positive electrode sheet at 800℃ in an argon atmosphere to remove the binder, and weigh the remaining mass of the positive electrode sheet as m3. The mass percentage of the binder in the positive electrode active layer is (m1-m2-m3) / (m1-m2)×100%.

[0110] As a non-limiting example, the adhesive may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0111] It is understood that 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 a 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).

[0112] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive material, binder, etc., in a solvent to form a positive electrode slurry. The positive electrode slurry is coated onto at least one surface of the positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface or both surfaces of the positive electrode current collector. The surface of the positive electrode current collector printed with the primer slurry can be a single surface or both surfaces of the positive electrode current collector.

[0113] In some embodiments, the electrolyte includes a solvent, which may include a carboxylic acid ester. The carboxylic acid ester can reduce the viscosity of the electrolyte, promoting lithium-ion transport within the electrolyte and thus improving the battery's rate performance. Simultaneously, the low-viscosity electrolyte can better wet the electrodes, improving the liquid-phase diffusion transport rate and further enhancing the battery's rate performance.

[0114] Optionally, the carboxylic acid ester accounts for 5% to 80% of the solvent by mass. In this range, the carboxylic acid ester's mass percentage in the solvent can fully utilize its ability to improve battery rate performance while maintaining good electrolyte stability, thereby ensuring good battery cycle stability. Further, the carboxylic acid ester's mass percentage in the solvent can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any value within the range of any two of the above values. Further, the carboxylic acid ester includes one or more of methyl formate, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0115] In some embodiments, the solvent also includes cyclic carbonates. Cyclic carbonates have a high dielectric constant, and the combination of cyclic carbonates and carboxylic acid esters can give the electrolyte a suitable viscosity while improving its conductivity, further enhancing the battery's rate performance. Furthermore, cyclic carbonates often have high boiling points and good stability; when combined with carboxylic acid esters, they can increase the electrolyte's boiling point and stability. When the battery is charged at high rates, the combination of cyclic carbonates and carboxylic acid esters can maintain good electrolyte stability, further improving the battery's rate performance.

[0116] Optionally, the cyclic carbonate accounts for 10% to 95% of the solvent by mass. Within this range, the cyclic carbonate's mass percentage in the solvent allows for better compatibility between the cyclic carbonate and carboxylic acid esters while fully utilizing the good stability of the cyclic carbonate, further promoting improved battery rate performance. More preferably, the cyclic carbonate's mass percentage in the solvent can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any value within the range of any two of the above values. More preferably, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate.

[0117] Optionally, the solvent also includes chain carbonates. The chain carbonates constitute 10% to 30% of the solvent by mass. For example, the chain carbonates may constitute 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or any value within the range of any two of the above values. Further optionally, the chain carbonates include one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0118] It is understood that the electrolyte also includes an electrolyte salt. Optionally, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). Further optionally, the molar concentration of the electrolyte salt in the electrolyte is 1 mol / L to 1.3 mol / L. For example, the molar concentration of electrolyte salts in the electrolyte can be 1 mol / L, 1.05 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.25 mol / L, 1.3 mol / L, or any value within the range of any two of the above values.

[0119] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0120] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0121] In some embodiments, the electrode body includes a negative electrode sheet; the negative electrode sheet includes a negative current collector and a negative active layer located on at least one surface of the negative current collector, the negative active layer comprising a negative active material, the negative active material including modified graphite, the modified graphite including a graphite matrix and a coating layer located on at least a portion of the surface of the graphite matrix, the coating layer comprising amorphous carbon. The modified graphite including the coating layer can further reduce diffusion resistance and charge transfer resistance, improving the rate performance of the battery.

[0122] Optionally, the thickness of the coating layer is 1 nm to 50 nm. Optionally, the thickness of the coating layer can be 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, or any value within the range of any two of the above values.

[0123] Optionally, the modified graphite accounts for 10% to 100% of the mass of the negative electrode active material. For example, the mass percentage of modified graphite in the negative electrode active material can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or any value within the range of any two of the above values.

[0124] In some embodiments, the Dv50 of the negative electrode active material is 5 μm to 16 μm. Optionally, the Dv50 of the negative electrode active material can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, or any value within the range of any two of the above values.

[0125] In some embodiments, the compaction density of the negative electrode active layer is 1.4 g / cm³. 3 ~1.9g / cm 3 At this point, lithium-ion batteries exhibit high energy density. Simultaneously, the compaction density of the negative electrode active layer within this range can promote electrolyte wetting of the negative electrode sheet, further improving the battery's rate performance. Optionally, the compaction density of the negative electrode active layer can be 1.4 g / cm³. 3 1.45g / cm 3 1.6g / cm 3 1.65g / cm 3 1.7g / cm 3 1.75g / cm 3 1.8g / cm 3 1.85g / cm 3 1.9g / cm 3 And any value within the range consisting of any two of the above values.

[0126] In some embodiments, the graphite matrix includes one or more of artificial graphite matrix and natural graphite matrix.

[0127] In some embodiments, the negative electrode active material may also be a negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials include one or more of silicon oxide compounds and silicon-carbon composites. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. These negative electrode active materials may be used alone or in combination of two or more.

[0128] 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).

[0129] 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.

[0130] In some embodiments, the negative electrode active layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0131] 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 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 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 polymer 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).

[0132] 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, etc., in a solvent (a non-limiting example of the solvent is deionized water), to form a negative electrode slurry. The negative electrode slurry is then coated onto at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet is obtained. 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.

[0133] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0134] In some embodiments, the lithium-ion battery further includes electrode terminals connected to the casing, with the electrode terminals and tabs directly electrically connected. The electrode terminals are output components for discharging the electrical energy of the battery cells. There can be one or more electrode terminals, made of conductive materials such as copper, iron, aluminum, stainless steel, and aluminum alloys. The electrode terminals conduct the electrical energy generated by the electrode assembly to the electrical device by electrically connecting the tabs. The direct electrical connection between the electrode terminals and tabs eliminates the need for current collectors between them, shortening the current path, reducing the internal resistance of the battery's mechanical components, and further improving the battery's rate performance. Optionally, the electrode terminals and tabs are directly welded together.

[0135] As is understood, the electrode tabs include positive and negative electrode tabs. Correspondingly, the electrode terminals include positive and negative electrode terminals. The positive electrode terminal and the positive electrode tab are directly electrically connected, and the negative electrode terminal and the negative electrode tab are directly electrically connected.

[0136] In some implementations, the ratio of the number of tabs to the number of electrode body layers in a lithium-ion battery is 0.75 to 1. In this case, the large number of tabs allows for parallel connection between the multiple electrode body layers, thereby reducing the battery's internal resistance and further improving its rate performance.

[0137] It is understood that the number of electrode body layers refers to the number of layers in the electrode body stack. When the electrode assembly is a stacked structure, the number of electrode body layers refers to the number of stacked layers. When the electrode assembly is a wound structure, the number of electrode body layers refers to the number of large faces of the wound core. In some embodiments, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0138] In some embodiments, the outer packaging of the lithium-ion battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0139] This application does not impose any particular limitation on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 shows a square-structured lithium-ion battery 1 as an example.

[0140] In some embodiments, referring to FIG3, the outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, and a separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The lithium-ion battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to actual needs.

[0141] In some implementations, the lithium-ion battery can be a single cell, a battery module, or a battery pack.

[0142] The battery module includes at least one lithium-ion battery. The battery module may contain one or more lithium-ion batteries, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0143] In a battery module, multiple lithium-ion batteries can be arranged sequentially along the length of the module. Of course, they can also be arranged in any other manner. Furthermore, these multiple lithium-ion batteries can be secured using fasteners.

[0144] Optionally, the battery module may also include a housing with a receiving space in which multiple lithium-ion batteries are housed.

[0145] In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules 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.

[0146] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0147] In some implementations, top cooling and side cooling can be used in the battery pack to improve battery heat dissipation, reduce heat accumulation inside the battery, and further improve the battery's thermal safety and rate performance.

[0148] In addition, this application also provides an electrical device, which includes the lithium-ion battery provided in this application. The 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.

[0149] As an electrical device, lithium-ion batteries can be selected based on its usage requirements.

[0150] Figure 4 shows an example of an electrical device 2. 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, a battery pack or battery module can be used.

[0151] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0152] 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.

[0153] 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.

[0154] Example 1

[0155] (1) Positive electrode plate

[0156] LiNi, the positive electrode active material 0.6 Co 0.2 Mn 0.2O2, conductive carbon black Super P, carbon nanotubes, graphene, and polyvinylidene fluoride binder are mixed in a weight ratio of 96.8:1.7:0.4:0.1:1. N-methylpyrrolidone (NMP) solvent is added, and the mixture is stirred to prepare a positive electrode slurry. The positive electrode slurry is then coated onto a current collector aluminum foil, dried, and subjected to cold pressing, slitting, and cutting to form the positive electrode sheet. The positive electrode active material is a single-crystal particle, and the compaction density of the positive electrode active layer is 3.4 g / cm³. 3 .

[0157] (2) Negative electrode plate

[0158] Modified graphite (anode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) were mixed in a weight ratio of 96.8:0.7:1.3:1.2, and added to deionized water as a solvent. The mixture was stirred to prepare a cathode slurry. The cathode slurry was then coated onto a copper foil current collector, dried, and subsequently cold-pressed, slit, and cut into sheets to form the cathode electrode. The modified graphite comprises a synthetic graphite matrix and an amorphous carbon coating layer with a thickness of 2 nm on the surface of the synthetic graphite matrix.

[0159] (3) Separating membrane

[0160] A composite membrane is constructed by coating both sides of a PE-based film with an alumina ceramic coating and a PVDF adhesive layer. The thickness of the PE-based film is 3 μm, the thickness of the alumina ceramic coating is 1 μm, and the coating weight of the PVDF adhesive layer is 0.1 mg / cm³. 2 The thickness is 1μm.

[0161] (4) Electrolyte

[0162] In an argon-atmosphere glove box with a water content <1 ppm and an oxygen content <1 ppm, methyl formate, dimethyl carbonate, and ethylene carbonate were mixed in a mass ratio of 14:71:15. Film-forming additive FEC was added to the mixed solvent, followed by lithium salt LiPF6. The mixture was stirred until dissolved to obtain the electrolyte. The mass percentage of FEC was 5%, and the molar concentration of LiPF6 was 1 mol / L, based on the total mass of the electrolyte.

[0163] (5) Lithium-ion batteries

[0164] The positive electrode, separator, and negative electrode are prepared in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain a bare cell, and tabs are welded on. The ratio of the number of tabs to the number of electrode body layers is 1. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0165] Examples 2-16 and Comparative Examples 1-6 were manufactured using a similar preparation method to Example 1, and specific design information is shown in Table 1. It is understood that the specific capacity of different types of positive electrode active materials in the examples and comparative examples differs, and the thickness of the electrode active layer may differ even with the same rated capacity. Therefore, batteries using the same type of positive electrode active material are compared when comparing performance.

[0166] Test case

[0167] The temperature rise of the batteries prepared in Examples 1-16 and Comparative Examples 1-6 under 6C charging conditions was tested, and the results are shown in Table 1. Fast charging cycle performance of Examples 1, 5, 6 and Comparative Examples 1 and 2 was tested, and the results are shown in Table 2.

[0168] The specific test conditions are as follows:

[0169] (1) Examples 1-12, Comparative Examples 1-4:

[0170] ① Rated capacity: After the battery is left to stand in an environment of 25℃ for 2 hours, it is charged to 4.4V at 0.33C, charged to 0.05C at constant voltage, left to stand for 30 minutes, and then discharged to 2.5V at a constant current of 0.33C to obtain the discharge capacity, which is taken as the rated capacity C0.

[0171] ② Charge the battery sequentially at constant current rates of 0.33C0, 0.5C0, 1.0C0, 1.5C0, 2.0C0, 2.5C0, 3.0C0, 4.0C0, 6.0C0, 8.0C0, and 10.0C0 to a negative electrode cutoff potential of 4.4V or 0V (whichever comes first). After each charge, discharge the battery to 2.5V at 1C0. Record the negative electrode potential corresponding to the state of charge (SOC) at different rates: 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80%. Plot the charge rate-negative electrode potential curves for different SOC states. After linear fitting, obtain the charge rate corresponding to a negative electrode potential of 0V for each SOC state. This charge rate is the charging window for that SOC state, equivalent to a 6C charge.

[0172] ③ Record the temperature rise of the battery during the charging process in step ②. Temperature rise test method: Use a temperature-sensing wire cell, with a temperature-sensing wire placed at the center of the battery to detect the temperature rise during the charging process.

[0173] ④ Cyclic test: According to the charge rate-negative electrode potential curves plotted in ② under different SOC states, charge and discharge the battery within the corresponding upper and lower limit cutoff voltage ranges, and record the number of cycles when the capacity retention rate decays to 80% of the initial capacity.

[0174] (2) Examples 13-15, Comparative Example 5:

[0175] ① Rated capacity: After the battery is left to stand in an environment of 25℃ for 2 hours, it is charged to 4.25V at 0.33C, charged to 0.05C at constant voltage, left to stand for 30 minutes, and then discharged to 2.5V at a constant current of 0.33C to obtain the discharge capacity, which is taken as the rated capacity C0.

[0176] ② Charge the battery sequentially at constant current rates of 0.33C0, 0.5C0, 1.0C0, 1.5C0, 2.0C0, 2.5C0, 3.0C0, 4.0C0, 6.0C0, 8.0C0, and 10.0C0 to either 4.25V or 0V (whichever comes first). After each charge, discharge the battery to 2.5V at 1C0. Record the corresponding negative electrode potentials at different charging rates when the battery reaches 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% SOC. Plot the charging rate-negative electrode potential curves for different SOC states. After linear fitting, obtain the charging rate corresponding to a negative electrode potential of 0V at different SOC states. This charging rate is the charging window for that SOC state, and is equivalent to a 6C charge.

[0177] ③ Record the temperature rise of the battery during the charging process in step ②. Temperature rise test method: Use a temperature-sensing wire cell, with a temperature-sensing wire placed at the center of the battery to detect the temperature rise during the charging process.

[0178] ④ Cyclic test: According to the charge rate-negative electrode potential curves plotted in ② under different SOC states, charge and discharge the battery within the corresponding upper and lower limit cutoff voltage ranges, and record the number of cycles when the capacity retention rate decays to 80% of the initial capacity.

[0179] (3) Example 16, Comparative Example 6:

[0180] ① Rated capacity: After the battery is left to stand in an environment of 25℃ for 2 hours, it is charged to 3.8V at 0.33C, charged at a constant voltage to 0.05C, left to stand for 30 minutes, and then discharged to 2.5V at a constant current of 0.33C to obtain the discharge capacity, which is taken as the rated capacity.

[0181] ② Charge the battery sequentially at constant current rates of 0.33C0, 0.5C0, 1.0C0, 1.5C0, 2.0C0, 2.5C0, 3.0C0, 4.0C0, 6.0C0, 8.0C0, and 10.0C0 to a negative electrode cutoff potential of 3.8V or 0V (whichever comes first). After each charge, discharge the battery to 2.0V at 1C0. Record the negative electrode potential corresponding to the state of charge (SOC) at different rates: 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80%. Plot the charge rate-negative electrode potential curves for different SOC states. After linear fitting, obtain the charge rate corresponding to a negative electrode potential of 0V for each SOC state. This charge rate is the charging window for that SOC state, equivalent to a 6C charge.

[0182] ③ Record the temperature rise of the battery during the charging process in step ②. Temperature rise test method: Use a temperature-sensing wire cell, with a temperature-sensing wire placed at the center of the battery to detect the temperature rise during the charging process.

[0183] ④ Cyclic test: According to the charge rate-negative electrode potential curves plotted in ② under different SOC states, charge and discharge the battery within the corresponding upper and lower limit cutoff voltage ranges, and record the number of cycles when the capacity retention rate decays to 80% of the initial capacity.

[0184] Table 1

[0185] In Table 1, the crystal form "polycrystalline:monocrystalline" indicates the mass ratio of polycrystalline particles to monocrystalline particles. Dv50 is in μm. Conductivity is in mS / cm. Tab width is in mm. Battery rated capacity is in Ah. Temperature rise is in °C. The columns for methyl formate, dimethyl carbonate, and ethylene carbonate represent the mass percentage of methyl formate, dimethyl carbonate, and ethylene carbonate in the solvent, respectively.

[0186] As can be seen from Table 1, when the rated capacity of the battery, the conductivity of the electrolyte, the width of a single tab, and the Dv50 of the positive electrode active material are within a suitable range, the battery exhibits a low temperature rise under a 6C high-rate charging.

[0187] Furthermore, the cyclic performance of Examples 1, 5, 6, Comparative Example 1, and Comparative Example 2 is shown in Table 2.

[0188] Table 2

[0189] In Table 2, the unit for the number of cycles is cycles.

[0190] As shown in Tables 1 and 2, increasing the electrolyte conductivity reduces the battery temperature rise, but may decrease the battery's cycle performance. Furthermore, when the electrolyte conductivity is between 10 mS / cm and 17 mS / cm, the battery can achieve a balance between good cycle performance and low temperature rise.

[0191] 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.

[0192] 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.

Claims

1. A lithium-ion battery, comprising: Housing, electrode assembly, and electrolyte; The electrode assembly and the electrolyte are housed within the housing; The rated capacity of the lithium-ion battery is 70Ah to 180Ah; the conductivity of the electrolyte at 25°C is 10mS / cm to 17mS / cm. The electrode assembly includes an electrode body and a tab arranged along a first direction; the width of a single tab is 30mm to 60mm perpendicular to the first direction. The electrode body includes a positive electrode sheet; the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, the positive active layer contains a positive active material, and the Dv50 of the positive active material is less than or equal to 12 μm.

2. The lithium-ion battery according to claim 1, wherein, The rated capacity of the lithium-ion battery is 80Ah to 150Ah.

3. The lithium-ion battery according to any one of claims 1 to 2, wherein, The Dv50 of the positive electrode active material is greater than or equal to 0.05 μm.

4. The lithium-ion battery according to any one of claims 1 to 3, wherein, The positive electrode active material includes Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y The lithium-containing transition metal oxide, wherein 0.2≤x≤1.2, 0.5≤a≤1, 0≤b≤0.1, 0≤c≤0.1, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, W, Sb, Dy and Te, and A includes one or more of N, P, S and halogen elements; the Dv50 of the lithium-containing transition metal oxide is 1.5μm~12μm.

5. The lithium-ion battery according to claim 4, wherein, 0.5≤a≤0.75, the Dv50 of the lithium-containing transition metal oxide is 1.5μm~4.5μm.

6. The lithium-ion battery according to claim 4, wherein, 0.75<a≤1, the Dv50 of the lithium-containing transition metal oxide is 1.5μm~12μm.

7. The lithium-ion battery according to any one of claims 4 to 6, wherein, The lithium-containing transition metal oxide accounts for 10% to 100% of the mass percentage of the positive electrode active material.

8. The lithium-ion battery according to any one of claims 1 to 7, wherein, The positive electrode active material includes lithium phosphate, and the Dv50 of the lithium phosphate is 0.05μm to 2μm.

9. The lithium-ion battery according to claim 8, wherein, The lithium phosphate comprises 1% to 90% of the mass of the positive electrode active material.

10. The lithium-ion battery according to any one of claims 1 to 9, wherein, The positive electrode active material includes single crystal particles.

11. The lithium-ion battery according to claim 10, wherein, The single-crystal particles account for 10% to 90% of the mass percentage of the positive electrode active material.

12. The lithium-ion battery according to any one of claims 10 to 11, wherein, The positive electrode active material also includes polycrystalline particles.

13. The lithium-ion battery according to claim 12, wherein, The mass ratio of the polycrystalline particles to the single-crystal particles is 1:9 to 9:

1.

14. The lithium-ion battery according to any one of claims 12 to 13, wherein, The polycrystalline particles account for 50% to 90% of the mass percentage of the positive electrode active material.

15. The lithium-ion battery according to any one of claims 1 to 14, wherein, The positive electrode active layer further comprises a conductive agent, which includes one or more of zero-dimensional conductive agents, one-dimensional conductive agents, and two-dimensional conductive agents.

16. The lithium-ion battery according to claim 15, wherein, The mass ratio of the zero-dimensional conductive agent to the one-dimensional conductive agent is 1:1 to 100:

1.

17. The lithium-ion battery according to any one of claims 15-16, wherein, The mass ratio of the two-dimensional conductive agent to the one-dimensional conductive agent is 0.01:1 to 0.5:

1.

18. The lithium-ion battery according to any one of claims 15 to 17, wherein, The conductive agent satisfies one or more of the following characteristics: (1) The conductive agent accounts for 1% to 5% of the mass percentage of the positive electrode active layer; (2) The zero-dimensional conductive agent includes one or more of Super P, Ketjen Black and acetylene black; (3) The one-dimensional conductive agent includes one or more of carbon nanotubes and carbon fibers; (4) The two-dimensional conductive agent includes one or more of conductive graphite and graphene.

19. The lithium-ion battery according to any one of claims 1 to 18, wherein, The compaction density of the positive electrode active layer is 3.1 g / cm³. 3 ~3.7g / cm 3 .

20. The lithium-ion battery according to any one of claims 1 to 19, wherein, The electrolyte includes a solvent, and the solvent includes a carboxylic acid ester.

21. The lithium-ion battery according to claim 20, wherein, The carboxylic acid ester accounts for 5% to 80% of the mass percentage of the solvent.

22. The lithium-ion battery according to any one of claims 20 to 21, wherein, The carboxylic acid esters include one or more of methyl formate, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

23. The lithium-ion battery according to any one of claims 20 to 22, wherein, The solvent also includes cyclic carbonates.

24. The lithium-ion battery according to claim 23, wherein, The cyclic carbonate accounts for 10% to 95% of the mass of the solvent.

25. The lithium-ion battery according to any one of claims 23 to 24, wherein, The cyclic carbonates include one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

26. The lithium-ion battery according to any one of claims 1 to 25, wherein, The electrode body includes a negative electrode sheet; the negative electrode sheet includes a negative current collector and a negative active layer located on at least one surface of the negative current collector, the negative active layer contains a negative active material, the negative active material includes modified graphite, the modified graphite includes a graphite matrix and a coating layer located on at least a portion of the surface of the graphite matrix, the material of the coating layer includes amorphous carbon.

27. The lithium-ion battery according to claim 26, wherein, The thickness of the coating layer is 1 nm to 50 nm.

28. The lithium-ion battery according to any one of claims 26 to 27, wherein, The modified graphite accounts for 10% to 100% of the mass of the negative electrode active material.

29. The lithium-ion battery according to any one of claims 26 to 28, wherein, The Dv50 of the negative electrode active material is 5μm to 16μm.

30. The lithium-ion battery according to any one of claims 1 to 29, wherein, The lithium-ion battery also includes electrode terminals, which are connected to the housing and are directly electrically connected to the tabs.

31. The lithium-ion battery according to any one of claims 1 to 30, wherein, The ratio of the number of tabs to the number of electrode body layers is 0.75 to 1.

32. An electrical appliance, wherein, The lithium-ion battery includes any one of claims 1 to 31.

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