Lithium-ion battery and electric device

Abstract

Disclosed are a lithium-ion battery and an electric device. The lithium-ion battery comprises an electrolyte; the electrolyte comprises a solvent; the solvent comprises a first solvent, the first solvent comprises one or two of a carboxylate solvent and an ether solvent, and based on the total weight of the solvent, the weight proportion of the first solvent is greater than or equal to 0 and less than or equal to 20%; the electrolyte has an electrolyte injection coefficient greater than or equal to 2.8 g / Ah and less than or equal to 3.6 g / Ah. By adjusting the weight proportion of the first solvent of the electrolyte in the solvent and the electrolyte injection coefficient of the electrolyte, the synergistic effect of different indexes is achieved, the situations of film formation side reactions between the solvent of the electrolyte and a negative electrode and gas generation during battery cycling are reduced, the stability of film formation of the electrolyte on a negative electrode sheet is improved, and the cycle life of the lithium-ion battery is prolonged.

Description

Lithium-ion batteries and electrical equipment

[0001] This disclosure claims priority to Chinese patent application No. 2024115274629, filed on October 29, 2024, entitled “Lithium-ion Battery and Electrical Device”, which is incorporated herein by reference in its entirety. Technical Field

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

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

[0004] Lithium-ion batteries, with their advantages of high energy density, long cycle life, low self-discharge rate, fast charging capability, and wide operating temperature range, are widely used in wireless communication, transportation, aerospace, and many other fields. With continuous technological advancements, lithium-ion batteries will continue to play a vital role and drive innovation in energy storage technology. For lithium-ion batteries, cycle life is one of the key factors in their development.

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

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

[0007] To achieve the above objectives, a first aspect of this application provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte; the electrolyte includes a solvent; the solvent includes a first solvent, which includes one or two of carboxylic acid ester solvents and ether solvents; based on the total weight of the solvent, the weight percentage of the first solvent is greater than or equal to 0 and less than or equal to 20%; the electrolyte injection coefficient is greater than or equal to 2.8 g / Ah and less than or equal to 3.6 g / Ah.

[0008] The embodiments of this application utilize the synergistic effect of various indicators by adjusting the weight ratio of the first solvent in the electrolyte and the electrolyte injection coefficient, thereby reducing the occurrence of film-forming side reactions and gas generation between the electrolyte solvent and the negative electrode during battery cycling, improving the film-forming stability of the electrolyte on the negative electrode sheet, and enhancing the cycle life of the lithium-ion battery.

[0009] In some embodiments, the carboxylic acid ester solvent includes one or more of ethyl acetate, methyl acetate, propyl acetate, propyl propionate, and ethyl propionate.

[0010] The embodiments of this application use one or more carboxylic acid ester solvents, including ethyl acetate, methyl acetate, propyl acetate, propyl propionate, and ethyl propionate, which is beneficial to improving the charging life of lithium-ion batteries.

[0011] In some embodiments, the ethers include one or more of tetrahydrofuran, 1,2-dimethoxyethylene, dimethoxymethane, dimethoxypropane, 2-methyltetrahydrofuran, and 1,3-dioxocyclopentane.

[0012] The embodiments of this application use the aforementioned ether solvents, which is beneficial for improving the charging life of lithium-ion batteries.

[0013] In some embodiments, the electrolyte further includes a second solvent, which includes a carbonate solvent; the weight percentage of the second solvent is greater than or equal to 60% and less than or equal to 65% based on the total weight of the solvents.

[0014] The embodiments of this application employ a second solvent including carbonate solvents, which is beneficial to improving the film-forming stability of the electrolyte on the negative electrode and improving the cycle life of the lithium-ion battery.

[0015] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl methacrylate.

[0016] The embodiments of this application employ the aforementioned second solvent, which is beneficial for improving the film-forming stability of the electrolyte on the negative electrode and enhancing the cycle life of the lithium-ion battery.

[0017] In some embodiments, the conductivity of the electrolyte is greater than or equal to 8 mS / cm and less than or equal to 14.5 mS / cm.

[0018] The embodiments of this application improve the charging performance of lithium-ion batteries by regulating the conductivity of the electrolyte and thus the migration rate of ions.

[0019] In some embodiments, the concentration of lithium salt in the electrolyte is 0.8 mol / L to 1.3 mol / L.

[0020] The embodiments of this application, by employing lithium salts of the above concentration, are beneficial for improving the film-forming stability of the electrolyte at the negative electrode, regulating the conductivity of the electrolyte, enhancing the migration rate of lithium ions, and improving the cycle life of lithium-ion batteries.

[0021] In some embodiments, the negative electrode sheet includes a negative current collector and a plurality of negative electrode film layers disposed on at least one surface of the negative current collector; the negative electrode film layers include a negative electrode active material; the negative electrode active material includes artificial graphite.

[0022] Artificial graphite has good compatibility with electrolytes, which is conducive to the formation of a good SEI film in contact with the electrolyte, thus giving lithium-ion batteries a good cycle life.

[0023] In some embodiments, the specific surface area of ​​artificial graphite is greater than or equal to 0.6 m². 2 / g, and less than or equal to 2.4m 2 / g.

[0024] The embodiments of this application utilize artificial graphite within the aforementioned specific surface area range, which helps to reduce surface side reactions and improve battery cycle life.

[0025] In some embodiments, the specific surface area of ​​artificial graphite is greater than or equal to 0.7 m². 2 / g, and less than or equal to 1.7m 2 / g.

[0026] The embodiments of this application utilize artificial graphite within the aforementioned specific surface area range, which helps to reduce surface side reactions and improve the cycle life of lithium-ion batteries.

[0027] In some embodiments, the grain size of the artificial graphite is Dv50 greater than or equal to 6 μm and Dv99 greater than or equal to 20 μm.

[0028] The artificial graphite within the aforementioned grain size range exhibits good structural stability, and its use is beneficial for improving the cycle life of lithium-ion batteries.

[0029] In some embodiments, the grain size of the artificial graphite is Dv50 greater than or equal to 8 μm and less than or equal to 18 μm; Dv99 is greater than or equal to 20 μm and less than or equal to 50 μm.

[0030] Artificial graphite within the aforementioned grain size range exhibits good structural stability, and its use is beneficial for improving battery cycle life.

[0031] In some embodiments, the degree of graphitization of the artificial graphite is greater than or equal to 85% and less than or equal to 99%.

[0032] The above-mentioned graphitization degree of artificial graphite has a highly ordered layered structure. Using artificial graphite with the above-mentioned graphitization degree is beneficial to reduce its volume expansion during charging and discharging, thereby improving the cycle life of lithium-ion batteries.

[0033] In some embodiments, the degree of graphitization of the artificial graphite is greater than or equal to 88% and less than or equal to 95%.

[0034] The above-mentioned graphitization degree of artificial graphite has a highly ordered layered structure. Using artificial graphite with the above-mentioned graphitization degree is beneficial to reduce its volume expansion during charging and discharging, thereby improving the cycle life of lithium-ion batteries.

[0035] In some embodiments, the OI value of the artificial graphite is less than or equal to 20.

[0036] The expansion of artificial graphite with the aforementioned orientation index (OI) value during lithium intercalation can be dispersed in all directions, which helps to reduce the volume expansion of lithium-ion batteries and improve their cycle life.

[0037] In some embodiments, the OI value of the artificial graphite is greater than or equal to 6 and less than or equal to 15.

[0038] The expansion of artificial graphite with the aforementioned orientation index (OI) value during lithium intercalation can be dispersed in all directions, which helps to reduce the volume expansion of lithium-ion batteries and improve their cycle life.

[0039] In some embodiments, the ratio of the full-charge thickness to the full-discharge thickness of the negative electrode sheet is greater than or equal to 1.1 and less than or equal to 1.3.

[0040] The negative electrode sheet within the range of the above-mentioned ratio of full charge thickness to full discharge thickness has a smaller thickness change during the cycling process of lithium-ion battery, thus improving the cycle life of lithium-ion battery.

[0041] In some embodiments, the full charge margin of the lithium-ion battery is greater than or equal to 95% and less than or equal to 102%.

[0042] When the full charge margin of a lithium-ion battery is within the above range, it is beneficial for the casing to form a gap with the positive and negative electrode plates. This ensures that when the positive and negative electrode plates expand, they will not contact the inner wall of the casing, or if they do contact the inner wall, the resulting expansion force will be small. This improves the safety performance of the lithium-ion battery and thus enhances its cycle life.

[0043] In some embodiments, the negative electrode film layer further includes a carbon coating layer covering at least a portion of the surface of the artificial graphite.

[0044] Compared to artificial graphite, carbon coatings have a greater number of surface defects, which helps to increase the number of sites for the insertion and extraction of active ions in the negative electrode active material. This allows active ions to diffuse more quickly within the particles of the negative electrode active material, thereby improving the charging performance of lithium-ion batteries.

[0045] In some embodiments, the carbon coating layer comprises amorphous carbon.

[0046] The embodiments of this application increase the number of defects on the surface of the negative electrode active material and the number of sites for intercalation and deintercalation of active ions by using a carbon coating layer including the above-mentioned materials, thereby enabling active ions to diffuse more quickly in the particles of the negative electrode active material and thus improving the charging performance of lithium-ion batteries.

[0047] In some embodiments, the thickness of the carbon coating is less than or equal to 50 nm.

[0048] The embodiments of this application increase the number of defects on the surface of the negative electrode active material and the number of sites for intercalation and deintercalation of active ions by using a carbon coating layer of the above-mentioned thickness, thereby enabling active ions to diffuse more quickly in the particles of the negative electrode active material and thus improving the charging performance of lithium-ion batteries.

[0049] In some embodiments, the thickness of the carbon coating layer is greater than or equal to 2 nm and less than or equal to 20 nm.

[0050] The carbon coating layer of the above-mentioned thickness in the embodiments of this application is beneficial to improving the charging performance of lithium-ion batteries and reducing the impact of the carbon coating layer on the capacity of the negative electrode active material, thereby enabling lithium-ion batteries to have good energy density.

[0051] In some embodiments, the coating weight of the negative electrode film is greater than or equal to 100 mg / 1540.25 mm. 2 And less than or equal to 180mg / 1540.25mm 2 .

[0052] The embodiments of this application employ negative electrode film layers within the aforementioned coating weight range, which is beneficial for improving the energy density and charging performance of lithium-ion batteries.

[0053] In some embodiments, the coating weight of the negative electrode film is greater than or equal to 130 mg / 1540.25 mm. 2 And less than or equal to 150mg / 1540.25mm 2 .

[0054] The embodiments of this application employ negative electrode film layers within the aforementioned coating weight range, which is beneficial for improving the energy density and charging performance of lithium-ion batteries.

[0055] In some embodiments, the compaction density of the negative electrode film is greater than or equal to 1.25 g / cc.

[0056] The embodiments of this application employ the above-mentioned compacted density negative electrode film layer, which is beneficial for enabling lithium-ion batteries to have higher energy density.

[0057] In some embodiments, the compaction density of the negative electrode film is greater than or equal to 1.25 g / cc and less than or equal to 1.7 g / cc.

[0058] The embodiments of this application employ the above-mentioned compacted density negative electrode film layer, which is beneficial for the lithium-ion battery to have a higher energy density and for the negative electrode film layer to have appropriate porosity for sufficient electrolyte wetting, so that the capacity of the lithium-ion battery can be more effectively utilized.

[0059] In some embodiments, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector; the positive electrode film layer includes a positive electrode active material; the positive electrode active material includes one or two of lithium nickel cobalt manganese oxide and lithium phosphate with an olivine structure.

[0060] Lithium-containing phosphates with an olivine structure possess a stable layered structure, which is beneficial for improving the cycle life of lithium-ion batteries. Lithium nickel cobalt manganese oxides have high theoretical and actual capacities, which is beneficial for improving the energy density of lithium-ion batteries. The embodiments of this application employ positive electrode sheets comprising the above-mentioned positive electrode active materials, which is beneficial for improving the cycle life and / or energy density of lithium-ion batteries.

[0061] In some embodiments, the coating weight of the positive electrode film is greater than or equal to 280 mg / 1540.25 mm. 2 And less than or equal to 400mg / 1540.25mm 2 .

[0062] The embodiments of this application employ positive electrode film layers within the above-mentioned coating weight range, which is beneficial for improving the energy density of lithium-ion batteries.

[0063] Secondly, embodiments of this application provide an electrical device including any of the lithium-ion batteries provided in the first aspect.

[0064] The electrical devices provided by the embodiments of this application have at least the same advantages as lithium-ion batteries, which can improve the battery life of the electrical devices. Attached Figure Description

[0065] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. Other drawings can be obtained based on these drawings without creative effort.

[0066] Figure 1 is a schematic diagram of the vehicle structure provided in an embodiment of this application;

[0067] Figure 2 is an exploded structural diagram of a lithium-ion battery provided in an embodiment of this application;

[0068] Figure 3 is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0069] Explanation of reference numerals: 1000-vehicle, 100-lithium-ion battery, 200-controller, 300-motor, 10-box, 20-cell battery, 11-first part, 12-second part, 21-end cap, 22-housing, 23-electrode assembly, 21a-electrode terminal. Detailed Implementation

[0070] The present application will be further described below with reference to specific embodiments. It should be understood that these specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0071] For the sake of brevity, this article only discloses some specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0072] In this description, unless otherwise stated, the term "or" is inclusive. That is, the phrase "A or (or) B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0073] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0074] Unless otherwise stated, the terms used in this application have their common meanings in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0075] During cyclic use, lithium-ion batteries are prone to various physical and chemical changes, some of which can affect their cycle life. Among these changes, the film stability of the electrolyte at the negative electrode is one of the factors influencing the cycle life of lithium-ion batteries.

[0076] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use lithium-ion batteries, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0077] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device according to an embodiment of this application.

[0078] Please refer to Figure 1, which is a structural schematic diagram of a vehicle provided in an embodiment of this application.

[0079] Referring to Figure 1, vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A lithium-ion battery 100 is installed inside vehicle 1000, which can be located at the bottom, front, or rear of vehicle 1000. The lithium-ion battery 100 can be used to power vehicle 1000; for example, it can serve as the operating power source for vehicle 1000. Vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 controls the lithium-ion battery 100 to supply power to the motor 300, for example, to meet the power needs of vehicle 1000 during startup, navigation, and driving.

[0080] In some embodiments of this application, the lithium-ion battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0081] Please refer to Figure 2, which is a schematic diagram of the exploded structure of a lithium-ion battery provided in an embodiment of this application.

[0082] Referring to Figure 2, the lithium-ion battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, collectively defining a space for accommodating the battery cell 20. The second portion 12 can be a hollow structure with one open end, and the first portion 11 can be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 together define the space. Alternatively, both the first portion 11 and the second portion 12 can be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0083] In the lithium-ion battery 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 20 is housed within the casing 10. Alternatively, the lithium-ion battery 100 can also consist of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then these battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the casing 10. The lithium-ion battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0084] Among them, the battery cell 20 can be in the form of a cylinder, a flat shape, a cuboid, or other shapes.

[0085] Please refer to Figure 3, which is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0086] Referring to Figure 3, the battery cell 20 refers to the smallest unit that makes up the lithium-ion battery 100. The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0087] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, giving battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 for outputting or inputting electrical energy to battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0088] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The housing 22 can be made of various materials, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, and plastic.

[0089] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the cell assembly, while the portions of the positive and negative electrode sheets without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery cell 20, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0090] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, which may include, but is not limited to, one or more of the following materials: lithium nickel cobalt manganese oxide, lithium phosphates with an olivine structure, and their respective modified compounds. These positive electrode active materials may be used alone or in combination. Examples of lithium nickel cobalt manganese oxide include, but are not limited to, LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 One or more of the following. Examples of lithium phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

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

[0092] A positive electrode conductive agent imparts conductivity to the positive electrode. The positive electrode conductive agent can include any conductive material, as long as it does not cause a chemical change. Positive electrode conductive agents include, but are not limited to: carbon-based materials (e.g., natural graphite, conductive graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

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

[0094] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector.

[0095] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include, but is not limited to, at least one of the following materials: artificial graphite.

[0096] In some embodiments, the negative electrode film layer may further include a negative electrode binder, a negative electrode conductive agent, and other optional additives. For example, the negative electrode conductive agent may be one or more of superconducting carbon, carbon black (examples may include acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. For example, the negative electrode binder may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), lithium-ionized polyacrylic acid (PAALi), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). For example, other optional additives may be thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials.

[0097] In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0098] To achieve the above objectives, a first aspect of this application provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte; the electrolyte includes a solvent; the solvent includes a first solvent, which includes one or two of carboxylic acid ester solvents and ether solvents; based on the total weight of the solvent, the weight percentage of the first solvent is greater than or equal to 0 and less than or equal to 20%; the electrolyte injection coefficient is greater than or equal to 2.8 g / Ah and less than or equal to 3.6 g / Ah.

[0099] The first solvent has the advantages of low viscosity and low freezing point, which helps to improve the migration speed of lithium ions and facilitates sufficient and effective contact between the active material and the electrolyte. Adding it to the electrolyte is beneficial to improving the charging performance of lithium-ion batteries. However, the first solvent is prone to film-forming side reactions with the negative electrode and gas generation during battery cycling, which affects the cycle performance of lithium-ion batteries. Therefore, the embodiments of this application balance the charging performance and cycle performance of lithium-ion batteries by adjusting the weight ratio of the first solvent.

[0100] In this application, the components and their contents of the electrolyte can be determined according to methods known in the art. For example, they can be determined by gas chromatography, gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), inductively coupled plasma optical emission spectrometry (ICP-OES), etc.

[0101] Based on the total weight of the solvent, the weight percentage of the first solvent can be 0%, 0.1%, 0.2%, 0.5%, 1%, 1.1%, 1.2%, 1.5%, 2%, 2.1%, 2.2%, 2.5%, 3%, 3.1%, 3.2%, 3.5%, 4%, 4.1%, 4.2%, 4.5%, 5%, 5.1%, 5.2%, 5.5%, 6%, 6.1%, 6.2%, 6.5%, 7%, 7.1%, 7.2%, 7.5%, 8%, 8.1%, 8.2%, 8.5%, 9%, 9.1%, 9.2%, 9.5%, 10%, 10.1%, 10.2%, 10.5%, 11%, 11.1%, 11.2%, 11.5%. The percentages are 12%, 12.1%, 12.2%, 12.5%, 13%, 13.1%, 13.2%, 13.5%, 14%, 14.1%, 14.2%, 14.5%, 15%, 15.1%, 15.2%, 15.5%, 16%, 16.1%, 16.2%, 16.5%, 17%, 17.1%, 17.2%, 17.5%, 18%, 18.1%, 18.2%, 18.5%, 19%, 19.1%, 19.2%, 19.5%, 20%, etc., or any range of any two of the above values, for example, 0% to 2%, 1% to 5%, 3% to 8%, 5% to 10%, 8% to 15%, 10% to 20%, etc.

[0102] The electrolyte filling coefficient refers to the ratio of the electrolyte filling amount to the rated capacity of a lithium-ion battery. In the embodiments of this application, the electrolyte filling amount can be approximated as the electrolyte retention amount. The rated capacity of the battery refers to the amount of electricity that the battery can release when discharged to the cutoff voltage under specified charge and discharge conditions. These specified charge and discharge conditions can refer to the ICE standard.

[0103] The electrolyte filling coefficient affects the wetting effect of the electrolyte, which in turn affects the film formation effect of the electrolyte on the negative electrode. Furthermore, the electrolyte filling coefficient also affects the overall weight of the lithium-ion battery, thus impacting its energy density.

[0104] The electrolyte injection coefficient can be 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah, 3.1 g / Ah, 3.2 g / Ah, 3.3 g / Ah, 3.4 g / Ah, 3.5 g / Ah, 3.6 g / Ah, or a range of any two of the above values. For example, it can be 2.8 g / Ah to 3.0 g / Ah, 2.9 g / Ah to 3.1 g / Ah, 3.0 g / Ah to 3.2 g / Ah, 3.1 g / Ah to 3.3 g / Ah, 3.2 g / Ah to 3.4 g / Ah, or 3.3 g / Ah to 3.6 g / Ah.

[0105] The embodiments of this application utilize the synergistic effect of various indicators by adjusting the weight ratio of the first solvent in the electrolyte and the electrolyte injection coefficient, thereby reducing the occurrence of film-forming side reactions and gas generation between the electrolyte solvent and the negative electrode during battery cycling, improving the film-forming stability of the electrolyte on the negative electrode sheet, and enhancing the cycle life of the lithium-ion battery.

[0106] In some embodiments, the carboxylic acid ester solvent includes one or more of ethyl acetate, methyl acetate, propyl acetate, propyl propionate, and ethyl propionate.

[0107] The embodiments of this application employ a first solvent including one or more of ethyl acetate, methyl acetate, propyl propionate, and ethyl propionate, which is beneficial for improving the charging performance of lithium-ion batteries.

[0108] In some embodiments, the ethers include one or more of tetrahydrofuran, 1,2-dimethoxyethylene, dimethoxymethane, dimethoxypropane, 2-methyltetrahydrofuran, and 1,3-dioxocyclopentane.

[0109] The embodiments of this application use the aforementioned ether solvents, which is beneficial for improving the charging performance of lithium-ion batteries.

[0110] In some embodiments, the electrolyte further includes a second solvent, which includes a carbonate solvent; the weight percentage of the second solvent is greater than or equal to 80% and less than or equal to 100% based on the total weight of the solvents.

[0111] Based on the total weight of the solvent, the weight percentage of the second solvent can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, etc., or a range of any two of the above values, for example, 80%–90%, 85%–95%, 90%–100%, etc.

[0112] The aforementioned second solvent has a high dielectric constant and good electrochemical stability, which is beneficial to improving the film-forming stability of the electrolyte at the negative electrode and thus improving the cycle life of lithium-ion batteries.

[0113] The embodiments of this application employ a second solvent including carbonate solvents, which is beneficial to improving the film-forming stability of the electrolyte on the negative electrode and improving the cycle life of the lithium-ion battery.

[0114] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl methacrylate.

[0115] The embodiments of this application employ the aforementioned second solvent, which is beneficial for improving the film-forming stability of the electrolyte on the negative electrode and enhancing the cycle life of the lithium-ion battery.

[0116] In some embodiments, the conductivity of the electrolyte is greater than or equal to 8 mS / cm and less than or equal to 14.5 mS / cm.

[0117] The conductivity of an electrolyte refers to the ability of active ions to conduct within the electrolyte.

[0118] The conductivity of the electrolyte at 25°C can be tested using any known method. As an example, the testing method for the electrolyte may include: heating the test sample and standard liquid to 25°C (±0.1°C); calibrating the testing instrument (Leici DDSJ-308F) using two standard liquids at an ambient temperature of 25°C (±0.5°C); after calibration and cleaning the electrodes, vertically immersing the test sample electrode in the test liquid to begin the test; and recording the test results after the data has stabilized for at least 10 seconds.

[0119] The conductivity of the electrolyte can be 8%, 8.1%, 8.2%, 8.5%, 9%, 9.1%, 9.2%, 9.5%, 10%, 10.1%, 10.2%, 10.5%, 11%, 11.1%, 11.2%, 11.5%, 12%, 12.1%, 12.2%, 12.5%, 13%, 13.1%, 13.2%, 13.5%, 14%, 14.1%, 14.2%, 14.5%, etc., or a range of any two of the above values, for example, 8%–10%, 9%–11%, 10%–12%, 11%–13%, 12%–14%, 13%–14.5%.

[0120] The embodiments of this application improve the charging performance of lithium-ion batteries by regulating the conductivity of the electrolyte and thus the migration rate of ions.

[0121] In some embodiments, the concentration of lithium salt in the electrolyte is 0.8 mol / L to 1.3 mol / L. The concentrations of lithium salts in the electrolyte can be 0.8 mol / L, 0.81 mol / L, 0.82 mol / L, 0.83 mol / L, 0.84 mol / L, 0.85 mol / L, 0.86 mol / L, 0.87 mol / L, 0.88 mol / L, 0.9 mol / L, 0.91 mol / L, 0.92 mol / L, 0.93 mol / L, 0.94 mol / L, 0.95 mol / L, 0.96 mol / L, 0.97 mol / L, 0.98 mol / L, 1.0 mol / L, 1.01 mol / L, 1.02 mol / L, 1.03 mol / L, 1.04 mol / L, 1.05 mol / L, 1.06 mol / L, 1.07 mol / L, 1.08 mol / L, 1.09 mol / L, and 1.1 mol / L. 0 mol / L, 1.11 mol / L, 1.12 mol / L, 1.13 mol / L, 1.14 mol / L, 1.15 mol / L, 1.16 mol / L, 1.17 mol / L, 1.18 mol / L, 1.19 mol / L, 1.2 mol / L, 1.21 mol / L, 1.22 mol / L, 1.23 mol / L, 1.24 mol / L, 1.25 mol / L, 1.26 mol / L, 1.27 mol / L, 1.28 mol / L, 1.29 mol / L, etc., or any range of two of the above values, for example, 0.8 mol / L to 1.0 mol / L, 0.9 mol / L to 1.1 mol / L, 1.0 mol / L to 1.2 mol / L, 1.1 mol / L to 1.3 mol / L, etc.

[0122] Lithium salts are compounds containing lithium ions that act as carriers of lithium ions in the electrolyte, migrating between the positive and negative electrodes.

[0123] The embodiments of this application, by employing lithium salts of the above concentration, are beneficial for improving the film-forming stability of the electrolyte at the negative electrode, regulating the conductivity of the electrolyte, enhancing the migration rate of lithium ions, and improving the cycle life of lithium-ion batteries.

[0124] In some embodiments, the negative electrode sheet includes a negative current collector and a plurality of negative electrode film layers disposed on at least one surface of the negative current collector; the negative electrode film layers include a negative electrode active material; the negative electrode active material includes artificial graphite.

[0125] Here, artificial graphite refers to graphite material obtained through organic carbonization followed by high-temperature graphitization treatment. In some embodiments, a plurality of negative electrode film layers are disposed on one side surface of the negative electrode current collector. In some embodiments, a plurality of negative electrode film layers are disposed on both sides surface of the negative electrode current collector.

[0126] Artificial graphite has good compatibility with electrolytes, which is conducive to the formation of a good SEI film in contact with the electrolyte, thus giving lithium-ion batteries a good cycle life.

[0127] In some embodiments, the specific surface area of ​​artificial graphite is greater than or equal to 0.6 m². 2 / g, and less than or equal to 2.4m 2 / g.

[0128] The specific surface area of ​​artificial graphite can be 0.6 m². 2 / g, 0.65m 2 / g, 0.7m 2 / g, 0.75m 2 / g, 0.8m 2 / g, 0.85m 2 / g, 0.9m 2 / g, 0.95m 2 / g, 1.0m 2 / g, 1.05m 2 / g, 1.1m 2 / g, 1.15m 2 / g, 1.2m 2 / g, 1.25m 2 / g, 1.3m 2 / g, 1.35m 2 / g, 1.4m 2 / g, 1.45m 2 / g, 1.5m 2 / g, 1.55m 2 / g, 1.6m 2 / g, 1.65m 2 / g, 1.7m 2 / g, 1.75m 2 / g, 1.8m 2 / g, 1.85m 2 / g, 1.9m 2 / g, 1.95m 2 / g, 2.0m 2 / g, 2.05m 2 / g、2.1m 2 / g, 2.15m 2 / g, 2.2m 2 / g, 2.25m 2 / g, 2.3m 2 / g, 2.35m 2 / g, 2.4m 2 / g, or a range consisting of any two of the above values, for example, 0.6m.2 / g~1.0m 2 / g, 0.8m 2 / g~1.2m 2 / g, 1.0m 2 / g~1.4m 2 / g, 1.2m 2 / g~1.6m 2 / g, 1.4m 2 / g~1.8m 2 / g, 1.6m 2 / g~2.0m 2 / g, 1.8m 2 / g~2.2m 2 / g, 2.0m 2 / g~2.4m 2 / g etc.

[0129] The specific surface area of ​​artificial graphite can be tested using methods known in the art. For example, it can be tested using the nitrogen adsorption specific surface area analysis method according to GB / T19587-2017, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc., USA.

[0130] The embodiments of this application utilize artificial graphite within the aforementioned specific surface area range, which helps to reduce surface side reactions and improve battery cycle life.

[0131] In some embodiments, the specific surface area of ​​artificial graphite is greater than or equal to 0.7 m². 2 / g, and less than or equal to 1.7m 2 / g.

[0132] The specific surface area of ​​artificial graphite can be 0.7 m². 2 / g, 0.75m 2 / g, 0.8m 2 / g, 0.85m 2 / g, 0.9m 2 / g, 0.95m 2 / g, 1.0m 2 / g, 1.05m 2 / g, 1.1m 2 / g, 1.15m 2 / g, 1.2m 2 / g, 1.25m 2 / g, 1.3m 2 / g, 1.35m 2 / g, 1.4m2 / g, 1.45m 2 / g, 1.5m 2 / g, 1.55m 2 / g, 1.6m 2 / g, 1.65m 2 / g, 1.7m 2 / g, or a range consisting of any two of the above values, for example, 0.7m. 2 / g~1.0m 2 / g, 0.8m 2 / g~1.2m 2 / g, 1.0m 2 / g~1.4m 2 / g, 1.2m 2 / g~1.6m 2 / g, 1.4m 2 / g~1.7m 2 / g etc.

[0133] The embodiments of this application utilize artificial graphite within the aforementioned specific surface area range, which helps to reduce surface side reactions and improve the cycle life of lithium-ion batteries.

[0134] In some embodiments, the grain size of the artificial graphite is Dv50 greater than or equal to 6 μm and Dv99 greater than or equal to 20 μm.

[0135] The Dv50 of artificial graphite grains can be 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, etc., or a range of any two of the above values, for example, 6μm~12μm, 9μm~18μm, 12μm~18μm, 16μm~26μm, etc. The Dv90 of artificial graphite grains can be 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, etc. μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, 51μm, 52μm, 53μm, 54μm, 55μm, 56μm, 57μm, 58μm, 59μm, 60μm, etc., or any range of two of the above values, for example, 20μm~40μm, 30μm~50μm, 40μm~60μm, etc.

[0136] In this application, the Dv50 and Dv99 of artificial graphite can be determined using a laser particle size analyzer (such as a Malvern Master Size 3000) in accordance with standard GB / T19077.1-2016. The physical definition of Dv50 is the particle size corresponding to a cumulative volume distribution percentage of artificial graphite reaching 50%; the physical definition of Dv90 is the particle size corresponding to a cumulative volume distribution percentage of artificial graphite reaching 90%.

[0137] The artificial graphite within the aforementioned grain size range exhibits good structural stability, and its use is beneficial for improving the cycle life of lithium-ion batteries.

[0138] In some embodiments, the grain size of the artificial graphite is Dv50 greater than or equal to 8 μm and less than or equal to 18 μm; Dv99 is greater than or equal to 20 μm and less than or equal to 50 μm.

[0139] The Dv50 of artificial graphite grains can be 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, etc., or a range of any two of the above values, for example, 8μm~12μm, 10μm~14μm, 12μm~18μm, etc. The Dv90 of artificial graphite grains can be 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, or any range of two of the above values, for example, 20μm~40μm, 30μm~50μm, etc.

[0140] Artificial graphite within the aforementioned grain size range exhibits good structural stability, and its use is beneficial for improving battery cycle life.

[0141] In some embodiments, the degree of graphitization of the artificial graphite is greater than or equal to 85% and less than or equal to 99%. The degree of graphitization of the artificial graphite can be 85%, 85.1%, 85.2%, 85.5%, 86%, 86.1%, 86.2%, 86.5%, 87%, 87.1%, 87.2%, 87.5%, 88%, 88.1%, 88.2%, 88.5%, 89%, 89.1%, 89.2%, 89.5%, 90%, 90.1%, 90.2%, 90.5%, 91%, etc. 91.1%, 91.2%, 91.5%, 92%, 92.1%, 92.2%, 92.5%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc., or a range consisting of any two of the above values, for example, 85%–89%, 87%–92%, 92%–94%, 93%–95%, 94%–96%, 95%–97%, 96%–99%, etc.

[0142] The degree of graphitization is an indicator of the extent to which carbon atoms form a close-packed hexagonal graphite crystal structure. The closer the lattice size of graphite is to the lattice constant of ideal graphite, the higher the degree of graphitization.

[0143] The degree of graphitization can be measured using methods known in the art. For example, the degree of graphitization can be measured using an X-ray diffractometer (such as a Bruker D8 Discover), and the measurement can be referenced in JB / T 4220-2011, to determine the interlayer spacing d of graphite (002) crystal planes. 002 The size is then determined according to the formula G = (0.344 - d). 002 The degree of graphitization is calculated by 0.344-0.3354, where G represents the degree of graphitization.

[0144] The above-mentioned graphitization degree of artificial graphite has a highly ordered layered structure. Using artificial graphite with the above-mentioned graphitization degree is beneficial to reduce its volume expansion during charging and discharging, thereby improving the cycle life of lithium-ion batteries.

[0145] In some embodiments, the degree of graphitization of the artificial graphite is greater than or equal to 88% and less than or equal to 95%.

[0146] The degree of graphitization of artificial graphite can be 88%, 89%, 90%, 90.1%, 90.2%, 90.5%, 91%, 91.1%, 91.2%, 91.5%, 92%, 92.1%, 92.2%, 92.5%, 93%, 94%, 95%, etc., or a range of any two of the above values, such as 88%–92%, 92%–94%, 93%–95%, etc.

[0147] The above-mentioned graphitization degree of artificial graphite has a highly ordered layered structure. Using artificial graphite with the above-mentioned graphitization degree is beneficial to reduce its volume expansion during charging and discharging, thereby improving the cycle life of lithium-ion batteries.

[0148] In some embodiments, the OI value of the artificial graphite is less than or equal to 20.

[0149] The OI value of artificial graphite can be 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, etc., or a range of any two of the above values, for example, 3~8, 8~10, 9~11, 10~12, 12~15, 14~18, 16~20, etc.

[0150] The OI value of artificial graphite refers to the orientation selectivity index of artificial graphite during the lithium intercalation process. The OI value is calculated based on X-ray diffraction (XRD) data, specifically by comparing the diffraction peak areas (C004 and (110) planes of graphite. 004 and C 110 The value is determined by the formula: OI value = C 004 / C 110 Artificial graphite has an OI value of less than or equal to 15, and the lithium intercalation expansion can be dispersed in all directions, thereby reducing the cyclic expansion of the electrode and the battery.

[0151] The expansion of artificial graphite with the aforementioned orientation index (OI) value during lithium intercalation can be dispersed in all directions, which helps to reduce the volume expansion of lithium-ion batteries and improve their cycle life.

[0152] In some embodiments, the OI value of artificial graphite is greater than or equal to 6 and less than or equal to 15. The OI value of artificial graphite can be 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, etc., or a range of any two of the above values, for example, 6 to 10, 9 to 11, 10 to 12, 11 to 15, etc.

[0153] The expansion of artificial graphite with the aforementioned orientation index (OI) value during lithium intercalation can be dispersed in all directions, which helps to reduce the volume expansion of lithium-ion batteries and improve their cycle life.

[0154] In some embodiments, the ratio of the full-charge thickness to the full-discharge thickness of the negative electrode sheet is greater than or equal to 1.1 and less than or equal to 1.3.

[0155] The ratio of the full-charge thickness to the full-discharge thickness of the negative electrode sheet can be 1.1, 1.15, 1.2, 1.25, 1.3, or any range of two of the above values, such as 1.1 to 1.25, 1.2 to 1.3, etc.

[0156] The full-charge thickness of the negative electrode refers to the thickness of the negative electrode after the lithium-ion battery is fully charged. The full-discharge thickness refers to the thickness of the negative electrode after the lithium-ion battery is discharged to zero charge. This indicator has a direct impact on the cycle life of lithium-ion batteries. By adjusting the ratio of the full-charge thickness to the full-discharge thickness of the negative electrode material, the cycle life of lithium-ion batteries can be effectively improved.

[0157] Understandably, the full-charge thickness can be tested using the following method: Measure the original thickness of the negative electrode sheet, denoted as H0. Then, disassemble the assembled lithium-ion battery after a full charge and measure the thickness of the negative electrode sheet after a full charge, denoted as H1. Finally, disassemble the assembled lithium-ion battery after a full discharge and measure the thickness of the negative electrode sheet after a full discharge, denoted as H2.

[0158] The negative electrode sheet within the range of the full charge thickness to full discharge thickness ratio mentioned above has a small thickness change during the cycling process of lithium-ion battery. Using the negative electrode sheet with the full charge thickness rebound rate mentioned above is beneficial to improving the cycle life of lithium-ion battery.

[0159] In some embodiments, the full charge margin of the positive and negative electrode plates is greater than or equal to 95% and less than or equal to 102%.

[0160] The full charge margin of the positive and negative electrode plates can be 95%, 96%, 97%, 98%, 99%, 100%, 101%, 102%, etc., or a range of any two of the above values, such as 95% to 100% or 98% to 102%.

[0161] Among them, the full charge margin refers to the ratio of the maximum size of the positive and negative electrode plates to the minimum size of the lithium-ion battery casing when the lithium-ion battery is fully charged.

[0162] The full charge margin of the positive and negative electrode plates is within the above range, which is beneficial for the shell to form a gap with the positive and negative electrode plates. This ensures that when the positive and negative electrode plates expand, they will not contact the inner wall of the shell, or if they do contact the inner wall of the shell, the resulting expansion force is small. This improves the safety performance of the lithium-ion battery and thus improves its cycle life.

[0163] In some embodiments, the negative electrode film layer further includes a carbon coating layer covering at least a portion of the surface of the artificial graphite.

[0164] Compared to artificial graphite, carbon coatings have a greater number of surface defects, which helps to increase the number of sites for the insertion and extraction of active ions in the negative electrode active material. This allows active ions to diffuse more quickly within the particles of the negative electrode active material, thereby improving the charging performance of lithium-ion batteries.

[0165] In some embodiments, the carbon coating layer comprises amorphous carbon.

[0166] The embodiments of this application increase the number of defects on the surface of the negative electrode active material and the number of sites for intercalation and deintercalation of active ions by using a carbon coating layer including the above-mentioned materials, thereby enabling active ions to diffuse more quickly in the particles of the negative electrode active material and thus improving the charging performance of lithium-ion batteries.

[0167] In some embodiments, the thickness of the carbon coating is less than or equal to 50 nm.

[0168] The thickness of the carbon coating can be 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, 40nm, 41nm, 42nm, 43nm, 44nm, 45nm, 46nm, 47nm, 48nm, 49nm, 50nm, or any range of any two of the above values, for example, 1nm~10nm, 10nm~30nm, 20nm~40nm, 30nm~50nm, etc.

[0169] The thickness of the amorphous carbon coating layer can be obtained by acquiring a transmission electron microscope (TEM) image of the negative electrode active material. Based on the thickness of the amorphous carbon coating layer and combined with the X-ray photoelectron spectroscopy (XPS) analysis of the negative electrode active material, the content of graphitized carbon in the negative electrode active material can be determined. The acquisition of the TEM image and XPS analysis spectrum includes the use of conventional instruments and testing methods in this field.

[0170] The embodiments of this application increase the number of defects on the surface of the negative electrode active material and the number of sites for intercalation and deintercalation of active ions by using a carbon coating layer of the above-mentioned thickness, thereby enabling active ions to diffuse more quickly in the particles of the negative electrode active material and thus improving the charging performance of lithium-ion batteries.

[0171] In some embodiments, the thickness of the carbon coating layer is greater than or equal to 2 nm and less than or equal to 20 nm.

[0172] The thickness of the carbon coating can be 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, etc., or a range of any two of the above values, such as 2nm to 10nm, 10nm to 20nm, etc.

[0173] The carbon coating layer of the above-mentioned thickness in the embodiments of this application is beneficial to improving the charging performance of lithium-ion batteries and reducing the impact of the carbon coating layer on the capacity of the negative electrode active material, thereby enabling lithium-ion batteries to have good energy density.

[0174] In some embodiments, the coating weight of the negative electrode film is greater than or equal to 100 mg / 1540.25 mm. 2 And less than or equal to 180mg / 1540.25mm 2 .

[0175] The coating weight of the negative electrode film can be 100mg / 1540.25mm. 2 110mg / 1540.25mm 2 120mg / 1540.25mm 2 130mg / 1540.25mm 2 140mg / 1540.25mm 2 150mg / 1540.25mm 2 160mg / 1540.25mm 2 170mg / 1540.25mm 2 180mg / 1540.25mm 2 etc., or a range consisting of any two of the above values, for example, 100mg / 1540.25mm. 2 ~130mg / 1540.25mm 2 120mg / 1540.25mm 2 ~140mg / 1540.25mm 2 130mg / 1540.25mm 2 ~150mg / 1540.25mm 2 140mg / 1540.25mm 2 ~160mg / 1540.25mm 2 150mg / 1540.25mm2 ~180mg / 1540.25mm 2 wait.

[0176] The coating weight of the negative electrode film refers to the weight of the material forming the negative electrode film per unit area coated on the current collector, which can be expressed as mg / 1540.25mm². 2 The unit is (mg per 1540.25 square millimeters).

[0177] Method for determining coating weight (CW): Using a negative electrode sheet as the substrate, a sheet is punched to obtain an area of ​​1540.25 mm². 2 The small discs are weighed using a balance to obtain their weight. Then, the weight of the current collector portion of the small discs is subtracted to obtain the coating weight of the negative electrode film.

[0178] The embodiments of this application employ negative electrode film layers within the aforementioned coating weight range, which is beneficial for improving the energy density and charging performance of lithium-ion batteries.

[0179] In some embodiments, the coating weight of the negative electrode film is greater than or equal to 130 mg / 1540.25 mm. 2 And less than or equal to 150mg / 1540.25mm 2 .

[0180] The coating weight of the negative electrode film can be 130mg / 1540.25mm. 2 140mg / 1540.25mm 2 150mg / 1540.25mm 2 etc., or a range consisting of any two of the above values, for example, 130mg / 1540.25mm. 2 ~140mg / 1540.25mm 2 140mg / 1540.25mm 2 ~150mg / 1540.25mm 2 wait.

[0181] The embodiments of this application employ negative electrode film layers within the aforementioned coating weight range, which is beneficial for improving the energy density and charging performance of lithium-ion batteries.

[0182] In some embodiments, the compaction density of the negative electrode film is greater than or equal to 1.25 g / cc.

[0183] The compaction density of the negative electrode film can be 1.25 g / cc, 1.3 g / cc, 1.35 g / cc, 1.4 g / cc, 1.45 g / cc, 1.5 g / cc, 1.55 g / cc, 1.6 g / cc, 1.65 g / cc, 1.7 g / cc, 1.75 g / cc, 1.8 g / cc, etc., or a range of any two of the above values, for example, 1.3 g / cc to 1.5 g / cc, 1.4 g / cc to 1.6 g / cc, 1.5 g / cc to 1.7 g / cc, 1.6 g / cc to 1.8 g / cc, etc.

[0184] The compaction density of the negative electrode film refers to the weight per unit volume of the material forming the negative electrode film on the current collector after compaction treatment. It is usually expressed in g / cc (grams per cubic centimeter). The compaction density of the negative electrode film reflects the degree of compaction of the material forming the negative electrode film.

[0185] The embodiments of this application employ the above-mentioned compacted density negative electrode film layer, which is beneficial for enabling lithium-ion batteries to have higher energy density.

[0186] In some embodiments, the compaction density of the negative electrode film is greater than or equal to 1.25 g / cc and less than or equal to 1.7 g / cc.

[0187] The compaction density of the negative electrode film can be 1.25 g / cc, 1.3 g / cc, 1.35 g / cc, 1.4 g / cc, 1.45 g / cc, 1.5 g / cc, 1.55 g / cc, 1.6 g / cc, 1.65 g / cc, 1.7 g / cc, or any range of two of the above values, such as 1.3 g / cc to 1.5 g / cc, 1.4 g / cc to 1.6 g / cc, 1.5 g / cc to 1.7 g / cc, etc.

[0188] The embodiments of this application employ the above-mentioned compacted density negative electrode film layer, which is beneficial for the lithium-ion battery to have a higher energy density and for the negative electrode film layer to have appropriate porosity for sufficient electrolyte wetting, so that the capacity of the lithium-ion battery can be more effectively utilized.

[0189] In some embodiments, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector; the positive electrode film layer includes a positive electrode active material; the positive electrode active material includes one or two of lithium nickel cobalt manganese oxide and lithium phosphate with an olivine structure.

[0190] Lithium-containing phosphates with an olivine structure possess a stable layered structure, which is beneficial for improving the cycle life of lithium-ion batteries. Lithium nickel cobalt manganese oxides have high theoretical and actual capacities, which is beneficial for improving the energy density of lithium-ion batteries. The embodiments of this application employ positive electrode sheets comprising the above-mentioned positive electrode active materials, which is beneficial for improving the cycle life and / or energy density of lithium-ion batteries.

[0191] In some embodiments, the coating weight of the positive electrode film is greater than or equal to 280 mg / 1540.25 mm. 2 And less than or equal to 400mg / 1540.25mm 2 .

[0192] The embodiments of this application employ positive electrode film layers within the above-mentioned coating weight range, which is beneficial for improving the energy density of lithium-ion batteries.

[0193] Secondly, embodiments of this application provide an electrical device including any of the lithium-ion batteries provided in the first aspect.

[0194] The electrical devices provided by the embodiments of this application have at least the same advantages as lithium-ion batteries, which can improve the battery life of the electrical devices.

[0195] The beneficial effects of this application are further illustrated below with reference to the embodiments.

[0196] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0197] Example 1

[0198] The preparation of a lithium-ion battery includes the following steps:

[0199] (1) Provide positive electrode plates:

[0200] The positive electrode active material (lithium iron phosphate), conductive agent (acetylene black), binder (polyvinylidene fluoride, PVDF), and dispersant (sodium carboxymethyl cellulose, CMC-Na) were mixed in a weight ratio of 97.3:0.4:1.8:0.5. Then, a solvent (N-methylpyrrolidone) was added, and after thorough mixing, the mixture was coated onto aluminum foil. Following drying and cold pressing, the positive electrode sheet was obtained. The coating weight of the positive electrode film was 150 mg / 1540.25 mm. 2 The compacted density is 2.6 g / cc.

[0201] (2) Provide negative electrode plates:

[0202] The negative electrode active material (artificial graphite), conductive agent (acetylene black), binder (styrene-butadiene rubber, SBR), and thickener (sodium carboxymethyl cellulose, CMC-Na) were mixed evenly in a solvent (deionized water) at a weight ratio of 97:1:1.5:0.5. This mixture was then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The specific surface area of ​​the artificial graphite in the negative electrode film layer was 1.3 m². 2 / g, Dv50 is 13μm, Dv99 is 33μm, graphitization degree is 93%, and OI value is 12. The coating weight of the negative electrode film is 150mg / 1540.25mm. 2 The compaction density is 1.65 g / cc; the ratio of the full-charge thickness to the full-discharge thickness of the negative electrode sheet is 114%.

[0203] (3) Provide a separating membrane:

[0204] Polyethylene film is used as the separation membrane.

[0205] (4) Provide electrolyte:

[0206] Ethylene carbonate, dimethyl carbonate, and diethyl carbonate were mixed in a weight ratio of 35:40:25. LiPF6 (lithium hexafluorophosphate) was dissolved in the above solvent to obtain an electrolyte with a lithium salt concentration of 1 mol / L.

[0207] (5) The electrodes are arranged in the order of "separator-negative electrode sheet-separator-positive electrode sheet". One end of the positive electrode sheet, negative electrode sheet, and two separators is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. The winding shaft is rotated by a motor to wind the positive electrode sheet, negative electrode sheet, and two separators to obtain a dry cell. The dry cell is subjected to one liquid injection, high-temperature settling, formation, second liquid injection, and high-temperature settling. The liquid injection coefficient is 3.1 g / Ah to obtain a lithium-ion battery. The full charge margin of the lithium-ion battery is 99%.

[0208] The steps for preparing lithium-ion batteries in Examples 2 to 5 are similar to those in Example 1. The difference is that a first solvent is introduced into the electrolyte in step (4) of Examples 2 to 5. The specific components of the first solvent introduced in step (4) of Examples 2 to 5 and their weight percentage in the solvent are different, and the weight percentage of each component of the second solvent in the solvent is different.

[0209] The steps for preparing lithium-ion batteries in Examples 6 and 7 are similar to those in Example 1. The difference is that the weight percentage of the second solvent in step (4) of Examples 6 and 7 is different.

[0210] The steps for preparing the lithium-ion battery in Example 8 are similar to those in Example 1, except that the concentration of the electrolyte in step (4) of Example 8 is different.

[0211] The steps for preparing the lithium-ion battery in Example 9 are similar to those in Example 1, except that the electrolyte injection coefficient in step (4) of Example 9 is different.

[0212] The steps for preparing the lithium-ion battery in Example 10 are similar to those in Example 1, except that the specific surface area of ​​the artificial graphite in step (2) of Example 10 is different.

[0213] The steps for preparing the lithium-ion battery in Example 11 are similar to those in Example 1, except that the degree of graphitization of the artificial graphite in step (2) of Example 11 is different.

[0214] The steps for preparing the lithium-ion battery in Example 12 are similar to those in Example 1, except that the OI value of the artificial graphite in step (2) of Example 12 is different.

[0215] The steps for preparing the lithium-ion battery in Example 13 are similar to those in Example 1. The difference is that in step (2) of Example 13, the negative electrode film layer also includes a carbon coating layer covering at least a portion of the surface of the artificial graphite. The carbon coating layer includes amorphous carbon and has a thickness of 40 nm.

[0216] The steps for preparing the lithium-ion battery in Example 14 are similar to those in Example 1, except that the coating weight of the negative electrode film is different in step (2) of Example 14.

[0217] The steps for preparing the lithium-ion battery in Example 15 are similar to those in Example 1, except that the compaction density of the negative electrode film is different in step (2) of Example 15.

[0218] The steps for preparing the lithium-ion battery in Example 16 are similar to those in Example 1, except that the positive electrode active material is different in step (1) of Example 16.

[0219] The steps for preparing the lithium-ion battery in Comparative Example 1 are similar to those in Example 1. The difference is that in step (4) of Comparative Example 1, a first solvent is introduced into the electrolyte. The weight percentage of the first solvent in the solvent is 30%, and the weight percentage of the second solvent in the solvent is 70%. The specific composition of the second solvent in step (4) of Comparative Example 1 is the same as that in Example 1, but the weight percentage of each component in the solvent is different from that in Example 1.

[0220] The steps for preparing the lithium-ion battery in Comparative Example 2 are similar to those in Example 1. The difference is that in step (4) of Comparative Example 2, a first solvent is introduced into the electrolyte. The weight percentage of the first solvent in the solvent is 30%, and the weight percentage of the second solvent in the solvent is 70%. Furthermore, the specific composition of the second solvent and the weight percentage of each component in the solvent in step (4) of Comparative Example 2 are different from those in Example 1.

[0221] The preparation steps of the lithium-ion battery in Comparative Example 3 are similar to those in Example 1, except that a first solvent is introduced into the electrolyte in step (4) of Comparative Example 3. The first solvent accounts for 30% of the total weight of the electrolyte, and the second solvent accounts for 70% of the total weight of the electrolyte. The specific components of the first and second solvents and the weight percentage of each component in the electrolyte in step (4) of Comparative Example 3 are the same as those in Comparative Example 2. In step (5), the electrolyte injection coefficient is 2.6 g / Ah.

[0222] The lithium-ion batteries prepared in Examples 1-16 and Comparative Examples 1-3 were tested for cycle life, energy density, and charging performance. The test results are shown in Table 1.

[0223] (1) Cyclic life test:

[0224] The prepared lithium-ion battery was charged at 25℃ with a constant current of 1C to the charging cutoff voltage of 3.8V, then charged with a constant voltage to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0. Then, it was discharged at a rate of 1C followed by a discharge at 0.33C, and the discharge capacity C of each cycle was recorded. n Until the battery's capacity retention rate reaches 80%, capacity retention rate = C n / C0*100%, records the number of cycles at this point. The more cycles, the better the cycle performance of the secondary battery.

[0225] (2) Charging performance test:

[0226] At 25°C, the prepared lithium-ion battery was charged at a constant current of 0.33C to the charging cutoff voltage of 3.8V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0.

[0227] Then, the lithium-ion battery was sequentially charged at constant currents of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 until the full-cell charging cutoff voltage or the 0V negative electrode cutoff potential (whichever comes first). After each charge, it was discharged at 1C0 until the full-cell discharge cutoff voltage. The negative electrode potentials corresponding to 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% SOC (State of Charge) were recorded at different charging rates. The rate-negative electrode potential curves under different SOC states were plotted. After linear fitting, the charging rate corresponding to the negative electrode potential of 0V under different SOC states was obtained. This charging rate is the charging window under that SOC state, denoted as C. 10％SOC C 20％SOC C 30％SOC C 40％SOC C 50％SOC C 60％SOC C 70％SOC C 80％SOC According to the formula (60 / C) 10％SOC +60 / C 30％SOC +60 / C 40％ SOC +60 / C 50％SOC +60 / C 60％SOC +60 / C 70％SOC +60 / C 80％SOC The charging time T for the secondary battery to charge from 10% SOC to 80% SOC is calculated by multiplying the value by 10%. The shorter the charging time, the better the charging performance.

[0228] (3) Energy density test:

[0229] The lithium-ion batteries prepared in each embodiment and comparative example were placed at 25°C and charged to 3.8V with a constant current of 0.33C, allowed to stand for 1 minute, and then charged to 0.05C with a constant voltage of 3.8V, allowed to stand for 30 minutes. They were then discharged to 2.0V with a constant current of 0.33C, and the discharge capacity A0 was recorded at this point, in Ah. The length, width, and height of the outer surface of the lithium-ion battery were measured using calipers, and the volume of a single cell V0 was calculated, in L. The volumetric energy density of the lithium-ion battery, VED, is calculated as (A0 × discharge plateau voltage of the lithium-ion battery) / V0, in Wh / L. It should be understood that the discharge plateau voltage of lithium-ion batteries with different positive and negative electrode systems varies, and can be obtained by testing their charge-discharge curves or referring to existing literature.

[0230] Table 1. Performance test results of lithium-ion batteries in the examples and comparative examples.

[0231] Table 1 (continued) Performance test results of lithium-ion batteries in the examples and comparative examples

[0232] Table 1 (continued) Performance test results of lithium-ion batteries in the examples and comparative examples

[0233] Table 1 (continued) Performance test results of lithium-ion batteries in the examples and comparative examples

[0234] As shown in Table 1, compared with the lithium-ion batteries of Comparative Examples 1 to 3, the lithium-ion batteries of Examples 1 to 16 significantly improved the cycle life of lithium-ion batteries by adjusting the weight ratio of the first solvent in the electrolyte and the electrolyte injection coefficient.

[0235] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0236] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0237] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A lithium-ion battery, wherein, The device includes a positive electrode, a negative electrode, a separator, and an electrolyte; the electrolyte includes a solvent; the solvent includes a first solvent, which includes one or both of carboxylic acid ester solvents and ether solvents; based on the total weight of the solvent, the weight percentage of the first solvent is greater than or equal to 0 and less than or equal to 20%; the electrolyte injection coefficient is greater than or equal to 2.8 g / Ah and less than or equal to 3.6 g / Ah.

2. The lithium-ion battery according to claim 1, wherein, The carboxylic acid ester solvents include one or more of ethyl acetate, methyl acetate, propyl acetate, propyl propionate, and ethyl propionate.

3. The lithium-ion battery according to claim 1, wherein, The ethers include one or more of tetrahydrofuran, 1,2-dimethoxyethylene, dimethoxymethane, dimethoxypropane, 2-methyltetrahydrofuran, and 1,3-dioxocyclopentane.

4. The lithium-ion battery according to any one of claims 1 to 3, wherein, The solvent also includes a second solvent, which includes a carbonate solvent; based on the total weight of the solvent, the weight percentage of the second solvent is greater than or equal to 80% and less than or equal to 100%.

5. The lithium-ion battery according to claim 3 or 4, wherein, The carbonate solvents include one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl methacrylate.

6. The lithium-ion battery according to any one of claims 1 to 5, wherein, The conductivity of the electrolyte is greater than or equal to 8 mS / cm and less than or equal to 14.5 mS / cm.

7. The lithium-ion battery according to any one of claims 1 to 6, wherein, The concentration of the lithium salt in the electrolyte is 0.8 mol / L to 1.3 mol / L.

8. The lithium-ion battery according to any one of claims 1 to 7, wherein, The negative electrode sheet includes a negative current collector and a plurality of negative electrode film layers disposed on at least one surface of the negative current collector; the negative electrode film layer includes a negative electrode active material; the negative electrode active material includes artificial graphite.

9. The lithium-ion battery according to claim 8, wherein, The specific surface area of ​​the artificial graphite is greater than or equal to 0.6 m². 2 / g, and less than or equal to 2.4m 2 / g.

10. The lithium-ion battery according to claim 8 or 9, wherein, The specific surface area of ​​the artificial graphite is greater than or equal to 0.7 m². 2 / g, and less than or equal to 1.7m 2 / g.

11. The lithium-ion battery according to any one of claims 8 to 10, wherein, The artificial graphite has a grain size Dv50 greater than or equal to 6 μm and a grain size Dv99 greater than or equal to 20 μm.

12. The lithium-ion battery according to any one of claims 8 to 11, wherein, The artificial graphite has a grain size Dv50 greater than or equal to 8 μm and less than or equal to 18 μm; and a grain size Dv99 greater than or equal to 20 μm and less than or equal to 50 μm.

13. The lithium-ion battery according to any one of claims 8 to 12, wherein, The degree of graphitization of the artificial graphite is greater than or equal to 85% and less than or equal to 99%.

14. The lithium-ion battery according to any one of claims 8 to 13, wherein, The degree of graphitization of the artificial graphite is greater than or equal to 88% and less than or equal to 95%.

15. The lithium-ion battery according to any one of claims 8 to 14, wherein, The OI value of the artificial graphite is less than or equal to 20.

16. The lithium-ion battery according to any one of claims 8 to 15, wherein, The OI value of the artificial graphite is greater than or equal to 6 and less than or equal to 15.

17. The lithium-ion battery according to any one of claims 8 to 16, wherein, The ratio of the full-charge thickness to the full-discharge thickness of the negative electrode sheet is greater than or equal to 1.1 and less than or equal to 1.

3.

18. The lithium-ion battery according to any one of claims 1 to 17, wherein, The full charge margin of the lithium-ion battery is greater than or equal to 95% and less than or equal to 102%.

19. The lithium-ion battery according to any one of claims 1 to 18, wherein, The negative electrode film layer also includes a carbon coating layer covering at least a portion of the surface of the artificial graphite.

20. The lithium-ion battery according to claim 19, wherein, The carbon coating layer comprises amorphous carbon.

21. The lithium-ion battery according to claim 19 or 20, wherein, The thickness of the carbon coating layer is less than or equal to 50 nm.

22. The lithium-ion battery according to any one of claims 19 to 21, wherein, The thickness of the carbon coating layer is greater than or equal to 2 nm and less than or equal to 20 nm.

23. The lithium-ion battery according to any one of claims 8 to 22, wherein, The coating weight of the negative electrode film layer is greater than or equal to 100 mg / 1540.25 mm. 2 And less than or equal to 180mg / 1540.25mm 2 .

24. The lithium-ion battery according to any one of claims 8 to 23, wherein, The coating weight of the negative electrode film layer is greater than or equal to 130 mg / 1540.25 mm. 2 And less than or equal to 150mg / 1540.25mm 2 .

25. The lithium-ion battery according to any one of claims 8 to 24, wherein, The compaction density of the negative electrode film is greater than or equal to 1.25 g / cc.

26. The lithium-ion battery according to any one of claims 8 to 25, wherein, The compaction density of the negative electrode film is greater than or equal to 1.25 g / cc and less than or equal to 1.7 g / cc.

27. The lithium-ion battery according to any one of claims 1 to 26, wherein, The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector; the positive electrode film layer includes a positive electrode active material; the positive electrode active material includes one or two of lithium nickel cobalt manganese oxide and lithium phosphate with an olivine structure.

28. The lithium-ion battery according to any one of claims 8 to 27, wherein, The coating weight of the positive electrode film is greater than or equal to 280 mg / 1540.25 mm. 2 And less than or equal to 400mg / 1540.25mm 2 .

29. An electrical appliance, wherein, Including the lithium-ion battery as described in any one of claims 1 to 28.

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