Battery cells, batteries and electrical devices

Abstract

This application provides a battery cell, a battery, and an electrical device. The battery cell includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The separator is disposed between the positive and negative electrode cells. The positive active material layer, the negative active material layer, the separator, and the electrolyte satisfy the following relationship: this battery cell can achieve both rate performance and power performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0002] With the rapid development of battery technology, it has been widely used in electrical devices such as vehicles. Currently, the market demands increasingly higher rate performance and power performance from batteries. However, in current technologies, batteries cannot simultaneously achieve both high rate performance and high power performance. Summary of the Invention

[0003] This application provides a battery cell, a battery, and an electrical device, wherein the battery cell can balance rate performance and power performance.

[0004] In a first aspect, embodiments of this application provide a battery cell, including a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The separator is disposed between the positive electrode and the negative electrode. The positive active material layer, the negative active material layer, the separator, and the electrolyte satisfy the following relationship: Wherein, T1 is the thickness of the positive electrode active material layer, in cm; P1 is the porosity of the positive electrode active material layer. T2 is the thickness of the negative electrode active material layer, in cm; P2 is the porosity of the negative electrode active material layer. T3 is the thickness of the separator, in cm; P3 is the porosity of the separator. G is the ionic conductivity of the electrolyte at 25°C, in mS / cm.

[0005] In the battery cell provided in this application embodiment, the positive electrode active material layer, the negative electrode active material layer, the separator and the electrolyte satisfy the above-mentioned relationship, which can help the transport of ions in the battery cell, so that the battery cell has a lower resistance at high rate, thereby improving the power performance of the battery cell, and thus achieving a balance between rate performance and power performance of the battery cell.

[0006] In some embodiments of this application, the thickness T1 of the positive electrode active material layer satisfies: 0.0035cm ≤ T1 ≤ 0.0055cm; optionally, 0.0035cm ≤ T1 ≤ 0.0045cm. Setting the thickness T1 of the positive electrode active material layer within the above-mentioned suitable range can shorten the transport path of ions within the positive electrode active material layer, thereby further reducing the resistance of the battery cell and improving the power performance of the battery cell.

[0007] In some embodiments of this application, the porosity P1 of the positive electrode active material layer satisfies: 30% ≤ P1 ≤ 60%; optionally, 40% ≤ P1 ≤ 60%. Setting the porosity P1 of the positive electrode active material layer within the above-mentioned suitable range can facilitate the transport of ions within the positive electrode active material layer, thereby further reducing the resistance of the battery cell and improving the power performance of the battery cell.

[0008] In some embodiments of this application, the positive electrode active material layer comprises a positive electrode active material, and the BET specific surface area S1 of the positive electrode active material satisfies: 8m² 2 / g≤S1≤12m 2 / g. Setting the BET specific surface area S1 of the positive electrode active material within the above-mentioned suitable range can increase the ion transport rate in the positive electrode active material layer, thereby further improving the power performance of the battery cell.

[0009] In some embodiments of this application, the thickness T2 of the negative electrode active material layer satisfies: 0.003cm ≤ T2 ≤ 0.005cm; optionally, 0.0035cm ≤ T2 ≤ 0.005cm. Setting the thickness T2 of the negative electrode active material layer within the above-mentioned suitable range can shorten the transport path of ions within the negative electrode active material layer, thereby further reducing the resistance of the battery cell and improving the power performance of the battery cell.

[0010] In some embodiments of this application, the porosity P2 of the negative electrode active material layer satisfies:

[0011] 30% ≤ P2 ≤ 60%; optionally, 40% ≤ P2 ≤ 60%. Setting the porosity P2 of the negative electrode active material layer within the above-mentioned suitable range can facilitate the transport of ions within the negative electrode active material layer, thereby further reducing the resistance of the battery cell and improving the power performance of the battery cell.

[0012] In some embodiments of this application, the negative electrode active material layer comprises a negative electrode active material, and the BET specific surface area S2 of the negative electrode active material satisfies: 1.7m². 2 / g≤S2≤2.2m 2 / g. Setting the BET specific surface area S2 of the negative electrode active material within the aforementioned suitable range can increase the ion transport rate within the negative electrode active material layer, thereby further improving the power performance of the battery cell.

[0013] In some embodiments of this application, the thickness T3 of the separator satisfies: 0.0005cm ≤ T3 ≤ 0.0015cm. Setting the thickness T3 of the separator within the above range can shorten the transport path of ions within the separator, thereby further reducing the resistance of the battery cell and improving its power performance.

[0014] In some embodiments of this application, the porosity P3 of the separator satisfies: 30% ≤ P3 ≤ 80%. Setting the porosity P3 of the separator within the above range can facilitate ion transport, increase the ion transport rate, and thus reduce the ion concentration in the battery cell, thereby improving the power performance of the battery cell.

[0015] In some embodiments of this application, the air permeability of the separator is greater than or equal to 150s / 100cm. 3 Setting the air permeability of the separator within the above-mentioned range can facilitate ion transport, increase the ion transport rate, and thus reduce the resistance of the battery cell, thereby improving the power performance of the battery cell.

[0016] In some embodiments of this application, the ionic conductivity G of the electrolyte at 25°C satisfies: 13 mS / cm ≤ G ≤ 26 mS / cm; optionally, 14 mS / cm ≤ G ≤ 25 mS / cm. Setting the ionic conductivity G of the electrolyte at 25°C within the aforementioned suitable range enhances the conductivity of ions within the electrolyte, further reduces the resistance of the battery cell, and thus further improves the power performance of the battery cell.

[0017] In some embodiments of this application, the electrolyte retention coefficient N satisfies: 3g / Ah ≤ N ≤ 7g / Ah. Setting the electrolyte retention coefficient N within this range can reduce the resistance of the battery cell, thereby improving its power performance, and also improve its cycle performance.

[0018] In some embodiments of this application, the electrolyte comprises an electrolyte salt and an organic compound, wherein the viscosity μ of the organic compound satisfies the following condition: 0.1 mPa·s - 3.5 mPa·s. The electrolyte salt and the organic compound with viscosity μ satisfying the above relationship in the electrolyte result in a high conductivity, thereby reducing the resistance of the battery cell and further improving the power performance of the battery cell.

[0019] In some embodiments of this application, based on the mass of the electrolyte, the mass fraction A of the electrolyte salt satisfies: 10% ≤ A ≤ 20%, and the mass fraction B of the organic compound satisfies: 30% ≤ B ≤ 70%. Setting the mass fraction A of the electrolyte salt and the mass fraction B of the organic compound within the aforementioned suitable ranges can reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and thus reduce the resistance of the battery cell, thereby further improving the resistance of the battery cell.

[0020] In some embodiments of this application, the electrolyte salt comprises a lithium salt; optionally, the lithium salt is selected from lithium hexafluorophosphate, lithium bisfluorosulfonylimide, and lithium bistrifluoromethanesulfonylimide or combinations thereof.

[0021] In some embodiments of this application, the low-viscosity organic compound comprises sulfone organic compounds, ether organic compounds, ester organic compounds, and nitrile organic compounds; optionally, the sulfone organic compound is selected from dimethyl sulfoxide; optionally, the ether organic compound is selected from ethylene glycol dimethyl ether; optionally, the ester organic compound is selected from methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl acrylate, or combinations thereof; optionally, the nitrile organic compound is selected from acetonitrile.

[0022] In some embodiments of this application, the electrolyte further includes a high-temperature additive, and the mass fraction C of the high-temperature additive satisfies the following condition based on the mass of the electrolyte: 0.01% ≤ C ≤ 1%. The high-temperature additive and its content can help form a protective layer on the surface of the electrode, which can exist stably under high-temperature conditions, thereby protecting the electrode and enabling the battery cell to have better high-temperature performance.

[0023] In some embodiments of this application, the high-temperature additive is selected from lithium tetrafluoroborate, lithium difluorophosphate, lithium fluorosulfonate, lithium aminosulfonate, or combinations thereof. These high-temperature additives can help form an inorganic protective layer, thereby improving the mechanical strength of the protective layer and further enhancing the high-temperature performance of the battery.

[0024] In some embodiments of this application, the electrolyte further includes a film-forming additive, wherein the mass fraction D of the film-forming additive satisfies the following condition based on the mass of the electrolyte: 1% ≤ D ≤ 5%. The film-forming additive and its content can help improve the stability of the interfacial film, thereby improving the cycle performance of the battery cell.

[0025] In some embodiments of this application, the film-forming additive is selected from vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, or combinations thereof.

[0026] Secondly, embodiments of this application provide a battery, including the battery cell described in any embodiment of the first aspect of this application.

[0027] Thirdly, embodiments of this application provide an electrical device, including a battery cell as described in any embodiment of the first aspect of this application or a battery as described in an embodiment of the second aspect of this application. Attached Figure Description

[0028] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0029] Figure 1 The present application provides structural schematic diagrams of vehicles according to some embodiments;

[0030] Figure 2 The present application shows a schematic diagram of the structure of a battery pack provided in some embodiments;

[0031] Figure 3 It shows Figure 2 A schematic diagram of the exploded structure of a battery;

[0032] Figure 4 The present application provides schematic diagrams of the structure of a single battery cell according to some embodiments.

[0033] Figure 5 It shows Figure 4 A schematic diagram of the exploded structure of a single battery cell.

[0034] The accompanying drawings are not drawn to scale.

[0035] Marking Description:

[0036] 1000 vehicles;

[0037] Battery 100, controller 200, motor 300;

[0038] Box 10, first box 11, second box 12;

[0039] Battery cell 20, casing 21, electrode assembly 22, cover assembly 23. Detailed Implementation

[0040] The embodiments of this application will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative and should not be construed as limiting the scope of protection of this application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0042] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0043] 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 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.

[0044] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and A existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0045] Various modifications and variations can be made to this application without departing from its scope of protection, which will be obvious to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed scope) and their equivalents. It should be noted that the implementation methods provided in the embodiments of this application can be combined with each other without contradiction.

[0046] Before explaining the scope of protection provided by the embodiments of this application, in order to facilitate understanding of the embodiments of this application, this application first specifically describes the problems existing in the related art:

[0047] Batteries are widely used in vehicles and other electrical devices due to their high power output, rechargeability, and good cycle performance. Currently, the market demands increasingly higher rate and power performance from batteries. However, in related technologies, batteries exhibit higher resistance at high rates, causing their power performance to fall short of requirements. Therefore, there is an urgent need to develop batteries that can balance both rate and power performance.

[0048] In view of this, embodiments of this application provide a battery cell, a battery, and an electrical device, wherein the battery cell can balance rate performance and power performance.

[0049] Electrical appliances

[0050] In this application, the electrical device can be a mobile phone, portable device, laptop computer, ship, spacecraft, vehicle, electric toy, and power tool, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.; spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical devices.

[0051] 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.

[0052] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of this application is shown.

[0053] like Figure 1 As shown, 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 battery 100 is installed inside vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of vehicle 1000. The battery 100 can be used to power vehicle 1000; for example, the battery 100 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 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of vehicle 1000 during starting, navigation, and driving.

[0054] In some embodiments of this application, the 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.

[0055] Battery

[0056] Please refer to Figure 2 and Figure 3 , Figure 2 A schematic diagram of the structure of a battery provided in some embodiments of this application is shown. Figure 3 It shows Figure 2 A schematic diagram of the exploded structure of a battery.

[0057] In this application, battery 100 refers to a battery comprising at least one individual battery cell 20. Figure 2 and Figure 3 As shown, the battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10.

[0058] The housing 10 provides a space for housing the battery cell 20, and can adopt various structures. In some embodiments, the housing 10 may include a first housing 11 and a second housing 12, which overlap each other, and together define a space for housing the battery cell 20. The second housing 12 may be a hollow structure with one open end, and the first housing 11 may be a plate-like structure, with the first housing 11 covering the open side of the second housing 12 so that the first housing 11 and the second housing 12 together define the space; alternatively, the first housing 11 and the second housing 12 may both be hollow structures with one open side, with the open side of the first housing 11 covering the open side of the second housing 12. Of course, the housing 10 formed by the first housing 11 and the second housing 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0059] In battery 100, there can be multiple battery cells 20. These multiple battery cells 20 can be connected in series, in parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel. Multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and then the whole assembly of multiple battery cells 20 is housed in the housing 10.

[0060] Each battery cell 20 can be a secondary battery cell or a primary battery cell, such as a lithium-ion secondary battery cell, a sodium-ion secondary battery cell, a magnesium-ion secondary battery cell, or a potassium-ion secondary battery cell, but is not limited to these. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes.

[0061] battery cell

[0062] This application provides a battery cell including a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The separator is disposed between the positive and negative electrode. The positive active material layer, the negative active material layer, the separator, and the electrolyte satisfy the following relationship: Where T1 is the thickness of the positive electrode active material layer in cm; P1 is the porosity of the positive electrode active material layer. T2 is the thickness of the negative electrode active material layer in cm; P2 is the porosity of the negative electrode active material layer. T3 is the thickness of the separator in cm; P3 is the porosity of the separator. G is the ionic conductivity of the electrolyte at 25℃ in mS / cm.

[0063] The positive electrode current collector can have a positive electrode active material layer disposed on one surface or on two surfaces. An isolation layer can also be disposed between the surface of the positive electrode current collector and the positive electrode active material layer, even if the positive electrode active material does not come into contact with the surface of the positive electrode current collector. This application does not impose any particular limitation on this embodiment. Similarly, the negative electrode current collector can also have a negative electrode active material layer disposed on one surface or on two surfaces. An isolation layer can also be disposed between the surface of the negative electrode current collector and the negative electrode active material layer. This application does not impose any particular limitation on this embodiment.

[0064] In this application, the thickness T1 of the positive electrode active material layer refers to the thickness of a single-sided positive electrode active material layer, and the thickness T2 of the negative electrode active material layer also refers to the thickness of a single-sided negative electrode active material layer.

[0065] Porosity refers to the percentage of the volume of pores in a material to its total volume, and it can be tested according to the method in GB / T 24586-2009.

[0066] The ionic conductivity G of an electrolyte refers to the conductivity of the electrolyte at 25°C. It can be tested using methods known in the art, and the testing instrument used can be a magnetic conductivity meter.

[0067] In the battery cell provided in this application embodiment, the inventors unexpectedly discovered through experiments that the actual ion transport path may be related not only to the thickness of the active material layer and the thickness of the separator, but also to the porosity of the active material layer and the separator. Therefore, in the embodiments of this application, the actual ion transport path in each layer is closer to the ratio of the thickness of each layer to its porosity. That is, the thickness T1 and porosity P1 of the positive electrode active material layer, the thickness T2 and porosity P2 of the negative electrode active material layer, the thickness T3 and porosity P3 of the separator, and the ionic conductivity G of the electrolyte satisfy the above relationship, which can help the ion transport in the battery cell, so that the battery cell has a lower resistance at high rates, thereby improving the power performance of the battery cell, and thus achieving a balance between rate performance and power performance in the battery cell.

[0068] In some embodiments of this application, the thickness T1 of the positive electrode active material layer satisfies: 0.0035cm≤T1≤0.0055cm.

[0069] In the above embodiments, the thickness T1 of the positive electrode active material layer is set within the above-mentioned suitable range, which can shorten the transport path of ions in the positive electrode active material, thereby further reducing the resistance of the battery cell and improving the power performance of the battery cell.

[0070] In some other embodiments of this application, the thickness T1 of the positive electrode active material layer satisfies: 0.0035cm ≤ T1 ≤ 0.0045cm. This further shortens the ion transport path within the positive electrode active material layer, thereby improving both the power performance and cycle performance of the battery cell.

[0071] In some examples, the thickness T1 of the positive electrode active material layer may be, but is not limited to, 0.0035cm, 0.0036cm, 0.0037cm, 0.0038cm, 0.0039cm, 0.0040cm, 0.0041cm, 0.0042cm, 0.0043cm, 0.0044cm, 0.0045cm, 0.0046cm, 0.0047cm, 0.0048cm, 0.0049cm, 0.0050cm, 0.0051cm, 0.0052cm, 0.0053cm, 0.0054cm, or 0.0055cm.

[0072] In some embodiments of this application, the porosity P1 of the positive electrode active material layer satisfies: 30% ≤ P1 ≤ 60%.

[0073] In the above embodiments, the porosity P1 of the positive electrode active material layer is set within the above-mentioned suitable range, which can facilitate the transport of ions in the positive electrode active material, thereby further reducing the resistance of the battery cell and improving the power performance of the battery cell.

[0074] In some other embodiments of this application, the porosity P1 of the positive electrode active material layer satisfies: 40% ≤ P1 ≤ 60%. This can further increase the ion transport rate within the positive electrode active material layer, further reduce the resistance of the battery cell, and improve the power performance of the battery cell.

[0075] In some examples, the porosity P1 of the positive electrode active material layer can be, but is not limited to, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%.

[0076] In some embodiments of this application, the positive electrode active material layer includes a positive electrode active material, and the BET specific surface area S1 of the positive electrode active material satisfies: 8m²2 / g≤S1≤12m 2 / g.

[0077] BET specific surface area is a well-known term in the art. It can be tested using the nitrogen adsorption specific surface area analysis method and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using the Tri Star II specific surface area and porosity analyzer from Micromeritics, Inc.

[0078] In the above embodiments, the BET specific surface area S1 of the positive electrode active material is set within the above-mentioned suitable range. This not only increases the ion transport rate in the positive electrode active material layer to further improve the power performance of the battery cell, but also reduces the contact area between the positive electrode active material and the electrolyte. Even under the action of high voltage or strong oxidation, the side reactions of the electrolyte on the surface of the positive electrode active material will decrease, thereby reducing gas production and heat generation, and improving the safety performance and cycle performance of the battery cell.

[0079] In some embodiments of this application, the positive electrode active material may include the following materials or combinations thereof: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al0.05 O2) and its modified compounds or combinations thereof. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also known as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites or combinations thereof.

[0080] Furthermore, in some embodiments of this application, the positive electrode active material layer may also include a conductive agent and a binder. This application does not impose specific limitations on the types of conductive agents and binders in the positive electrode active material layer; they can be selected according to actual needs. For example, the conductive agent may be, but is not limited to, one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder may be, but is not limited to, one or more of styrene-butadiene rubber (SBR), waterborne acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylic resin, and polyvinyl alcohol (PVA).

[0081] In some embodiments of this application, the positive current collector can be made of materials such as metal foil or porous metal plate. For example, the material of the positive current collector can be, but is not limited to, foil or porous plate of metals such as copper, nickel, titanium, or silver, or their alloys. Further, in some specific embodiments of this application, the positive current collector is made of aluminum foil.

[0082] The positive electrode sheet of this application embodiment can be prepared using conventional methods in the art. For example, the positive active material, conductive agent, and binder are thoroughly mixed in an appropriate amount of NMP at a certain mass ratio to form a uniform positive slurry. The positive slurry is coated on the surface of the positive current collector aluminum foil, and after drying, cold pressing, and cutting, the positive electrode sheet is obtained.

[0083] In some embodiments of this application, the thickness T2 of the negative electrode active material layer satisfies: 0.003cm≤T2≤0.005cm.

[0084] In the above embodiments, the thickness T2 of the negative electrode active material layer is set within the above-mentioned suitable range, which can shorten the transport path of ions in the negative electrode active material layer, thereby further reducing the resistance of the battery cell and improving the power performance of the battery cell.

[0085] In some other embodiments of this application, the thickness T2 of the negative electrode active material layer satisfies: 0.0035cm≤T2≤0.005cm.

[0086] In the above embodiments, the thickness T2 of the negative electrode active material layer is set within the above-mentioned suitable range, which can reduce the resistance of the battery cell to improve the power performance of the battery cell, and at the same time improve the cycle performance of the battery cell.

[0087] In some examples, the thickness T2 of the negative electrode active material layer may be, but is not limited to, 0.003cm, 0.0031cm, 0.0032cm, 0.0033cm, 0.0034cm, 0.0035cm, 0.0036cm, 0.0037cm, 0.0038cm, 0.0039cm, 0.0040cm, 0.0041cm, 0.0042cm, 0.0043cm, 0.0044cm, 0.0045cm, 0.0046cm, 0.0047cm, 0.0048cm, 0.0049cm, or 0.0050cm.

[0088] In some embodiments of this application, the porosity P2 of the negative electrode active material layer satisfies: 30% ≤ P2 ≤ 60%.

[0089] In the above embodiments, the porosity P2 of the negative electrode active material layer is set within the above-mentioned suitable range, which can facilitate the transport of ions in the negative electrode active material, thereby further reducing the resistance of the battery cell and improving the power performance of the battery cell.

[0090] In some other embodiments of this application, the porosity P2 of the negative electrode active material layer satisfies: 40% ≤ P2 ≤ 60%.

[0091] In the above embodiments, the porosity P2 of the negative electrode active material layer is set within the above-mentioned suitable range, which can further increase the transport rate of ions in the negative electrode active material layer, thereby further improving the power performance of the battery cell.

[0092] In some examples, the porosity P2 of the negative electrode active material layer can be, but is not limited to, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, and 60%.

[0093] In some embodiments of this application, the negative electrode active material layer includes a negative electrode active material, and the BET specific surface area S2 of the negative electrode active material satisfies: 1.7m². 2 / g≤S2≤2.2m 2 / g.

[0094] In the above embodiments, the BET specific surface area S2 of the negative electrode active material is set within the above-mentioned suitable range, which can increase the ion transport rate in the negative electrode active material layer and further improve the power performance of the battery cell.

[0095] In some embodiments of this application, the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Li-Al alloys or combinations thereof.

[0096] Furthermore, in some embodiments of this application, the negative electrode active material layer may also include a conductive agent and a binder. This application does not impose specific limitations on the types of conductive agents and binders in the negative electrode active material layer; they can be selected according to actual needs.

[0097] For example, the conductive agent may be, but is not limited to, one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the binder may be, but is not limited to, one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), waterborne acrylic resin, and carboxymethyl cellulose (CMC).

[0098] In some embodiments of this application, the negative electrode current collector can be made of materials such as metal foil or porous metal plate. For example, the material of the negative electrode current collector can be, but is not limited to, foil or porous plate of metals such as copper, nickel, titanium, or iron, or their alloys. Further, in some specific embodiments of this application, the negative electrode current collector is made of copper foil.

[0099] The negative electrode sheet of this application embodiment can be prepared using conventional methods in the art. For example, the negative electrode active material, conductive agent, binder and thickener are dispersed in an appropriate amount of deionized water at a certain mass ratio, and a pore-forming agent is added and stirred thoroughly to form a uniformly dispersed negative electrode slurry. The negative electrode slurry is coated on the surface of the negative electrode current collector copper foil, and after drying, cold pressing and cutting, the negative electrode sheet is obtained.

[0100] In some embodiments of this application, the thickness T3 of the separator membrane satisfies: 0.0005cm≤T3≤0.0015cm.

[0101] In the above embodiments, the thickness T3 of the separator is set within the above range, which can shorten the transport path of ions in the separator, thereby further reducing the resistance of the battery cell to improve its power performance.

[0102] In some examples, the thickness T3 of the separator may be, but is not limited to, 0.0005cm, 0.0006cm, 0.0007cm, 0.0008cm, 0.0009cm, 0.0010cm, 0.0011cm, 0.0012cm, 0.0013cm, 0.0014cm, or 0.0015cm.

[0103] In some embodiments of this application, the porosity P3 of the separator membrane satisfies: 30% ≤ P3 ≤ 80%.

[0104] In the above embodiments, the porosity P3 of the separator is set within the above range, which can facilitate ion transport, increase the ion transport rate, and thus reduce the ion concentration in the battery cell, thereby improving the power performance of the battery cell.

[0105] In some examples, the porosity P3 of the separating membrane can be, but is not limited to, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, and 80%.

[0106] In some embodiments of this application, the air permeability of the separator is greater than or equal to 150s / 100cm. 3 .

[0107] In this application, there is no particular limitation on the method for measuring the air permeability of the separator membrane; the air permeability can be measured using methods commonly used in the art. A non-limiting example of a method for measuring air permeability is as follows: In an environment with a temperature of 15°C to 28°C and humidity less than 80%, a test sample of 4cm × 4cm is prepared and measured using an air-permeability tester with the Gurleytest (100cc) method to directly obtain the air permeability value.

[0108] In the above embodiments, the air permeability of the separator is set within the above range, which can facilitate ion transport, increase the ion transport rate, and thus reduce the resistance of the battery cell, thereby improving the power performance of the battery cell.

[0109] In some embodiments of this application, the separator may be selected from polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), aramid, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyimide (PI), polyamide, polyester, and natural fibers or combinations thereof.

[0110] In some embodiments of this application, the ionic conductivity G of the electrolyte at 25°C satisfies: 13 mS / cm ≤ G ≤ 26 mS / cm.

[0111] In the above embodiments, the ionic conductivity G of the electrolyte at 25°C is set within the above-mentioned suitable range, which can enhance the conduction ability of ions in the electrolyte, further reduce the resistance of the battery cell, and thus further improve the power performance of the battery cell.

[0112] In some other embodiments of this application, the ionic conductivity G of the electrolyte at 25°C satisfies: 14 mS / cm ≤ G ≤ 25 mS / cm.

[0113] In these embodiments, the conductivity of ions in the electrolyte can be further enhanced, thereby reducing the resistance of the battery cell and further improving the power performance of the battery cell.

[0114] In some examples, the ionic conductivity G of the electrolyte at 25°C may be, but is not limited to, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 17 mS / cm, 18 mS / cm, 19 mS / cm, 20 mS / cm, 21 mS / cm, 22 mS / cm, 23 mS / cm, 24 mS / cm, 25 mS / cm, and 26 mS / cm.

[0115] In some embodiments of this application, the electrolyte retention coefficient N satisfies: 3g / Ah≤N≤7g / Ah.

[0116] In this application, the electrolyte retention coefficient N refers to the ratio of the electrolyte retention amount to the discharge capacity of the battery cell in the first cycle.

[0117] In the above embodiments, the electrolyte retention coefficient N is set within the above range, which can reduce the resistance of the battery cell to improve the power performance of the battery cell, and at the same time improve the cycle performance of the battery cell.

[0118] In some examples, the electrolyte retention factor N can be, but is not limited to, 3 g / Ah, 4 g / Ah, 5 g / Ah, 6 g / Ah, or 7 g / Ah.

[0119] In some embodiments of this application, the electrolyte includes an electrolyte salt and an organic compound, and the viscosity μ of the organic compound satisfies: 0.1 mPa·s-3.5 mPa·s.

[0120] In the above embodiments, the viscosity of organic compounds can be tested according to GB / T 10247-2008 "Viscosity Measurement Methods". A Bollefeld (DV-2TLV) viscometer is used, with an 18-gauge rotor at approximately 70 r / min. The electrolyte salts and organic compounds with viscosity μ satisfying the above relationship in the electrolyte result in a high conductivity, which in turn reduces the resistance of the battery cells, thereby further improving the power performance of the battery cells.

[0121] In some embodiments of this application, based on the mass of the electrolyte, the mass fraction A of the electrolyte salt satisfies: 10% ≤ A ≤ 20%, and the mass fraction B of the organic compound satisfies: 30% ≤ B ≤ 70%.

[0122] In the above embodiments, the mass fraction A of the electrolyte salt and the mass fraction B of the organic compound are respectively set within the above-mentioned suitable ranges, which can reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and thus reduce the resistance of the battery cell, thereby further improving the resistance of the battery cell.

[0123] In some embodiments of this application, the electrolyte salt comprises a lithium salt.

[0124] In some specific embodiments of this application, the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), or combinations thereof.

[0125] In some embodiments of this application, the organic compounds include sulfone organic compounds, ether organic compounds, ester organic compounds, and nitrile organic compounds, or combinations thereof.

[0126] For example, sulfone organic compounds are selected from dimethyl sulfoxide (DMSO). Ether organic compounds are selected from dimethyl glycol ether (DME). Esters organic compounds are selected from methyl formate (MF), ethyl formate, methyl acetate (MA), ethyl acetate (EA), methyl acrylate, or combinations thereof. Nitrile organic compounds are selected from acetonitrile (AN).

[0127] In some embodiments of this application, the electrolyte further includes a high-temperature additive, and the mass fraction C of the high-temperature additive satisfies the following condition based on the mass of the electrolyte: 0.01% ≤ C ≤ 1%.

[0128] In the above embodiments, the high-temperature additives and their content can help form a protective layer on the surface of the electrode, which can exist at high temperature, thereby protecting the electrode and enabling the battery cell to have better high-temperature performance.

[0129] In some embodiments of this application, the high-temperature additive is selected from lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium fluorosulfonate (LiFSO3), lithium aminosulfonate (LiH2NO3S), or combinations thereof. These high-temperature additives can help form an inorganic protective layer, thereby improving the mechanical strength of the protective layer and further enhancing the high-temperature performance of the battery.

[0130] In some embodiments of this application, the electrolyte further includes a film-forming additive, wherein the mass fraction D of the film-forming additive satisfies the following condition based on the mass of the electrolyte: 1% ≤ D ≤ 5%.

[0131] In the above embodiments, the film-forming additives and their content can help improve the stability of the interfacial film, thereby improving the cycle performance of the battery cell.

[0132] In some embodiments of this application, the film-forming additive is selected from vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, or combinations thereof.

[0133] Figure 4 This is a single battery cell used as an example. Figure 5 It shows Figure 4 A schematic diagram of the exploded structure of a single battery cell.

[0134] like Figure 4 and Figure 5 As shown, the battery cell 20 includes a housing 21, an electrode assembly 22, and a cover assembly 23. The housing 21 has a chamber for accommodating the electrode assembly 22, and the cover assembly 23 is used to close the opening of the housing 21. The cover assembly 23 includes an end cap, which is connected to the housing 21 to form the outer shell of the battery cell 20. The electrode assembly 22 is disposed inside the housing 21, and the housing 21 is filled with electrolyte.

[0135] An end cap is a component that covers the opening of the housing 21 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the end cap can be adapted to the shape of the housing 21 to fit it. Optionally, the end cap can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap is less prone to deformation under pressure and impact, giving the battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals can be provided on the end cap. The electrode terminals can be used to electrically connect to the electrode assembly 22 for outputting or inputting electrical energy into the battery cell 20. In some embodiments, the end cap can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this application embodiment does not impose any special limitations on this. In some embodiments, an insulating element may be provided on the inner side of the end cap. The insulating element can be used to isolate the electrical connection components within the housing 21 from the end cap to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0136] The housing 21 is a component used to cooperate with the end cap to form the internal environment of the battery cell 20, wherein the formed internal environment can accommodate the electrode assembly 22, electrolyte, and other components. The housing 21 and the end cap can be independent components, with an opening provided on the housing 21. The end cap closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap and housing 21 can be integrated. Specifically, the end cap and housing 21 can form a common connecting surface before other components are inserted into the housing, and the end cap closes the housing 21 when it is necessary to encapsulate the interior. The housing 21 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc.

[0137] Electrode assembly 22 is the component in the battery cell 20 where electrochemical reactions occur. The casing 21 may contain one or more electrode assemblies 22. The electrode assembly 22 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 electrode assembly 22, while the portions 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. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0138] The battery cell provided in this application embodiment can be prepared using conventional methods, such as the following preparation method: A positive electrode active material, conductive agent, and binder are dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry. The positive electrode slurry is coated on two opposing surfaces of the positive electrode current collector. After drying, cold pressing, and cutting, a positive electrode sheet is obtained. A negative electrode active material, conductive agent, binder, and thickener are dispersed in a solvent (e.g., deionized water), and a pore-forming agent is added. After stirring, a uniformly dispersed negative electrode slurry is obtained. The negative electrode slurry is coated on two opposing surfaces of the negative electrode current collector. After drying, cold pressing, and cutting, a negative electrode sheet is obtained. The positive electrode sheet, separator, and negative electrode sheet are stacked sequentially to obtain an electrode assembly, or stacked sequentially and wound to obtain an electrode assembly. The electrode assembly is placed in a housing, an electrolyte is injected and sealed, and then an electrolyte is injected into the housing and sealed again. After high-temperature standing, formation, and capacity testing, a battery cell is obtained.

[0139] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. All reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing. Similarly, the instruments used in the embodiments are commercially available.

[0140] Example 1

[0141] Preparation of positive electrode sheet

[0142] Lithium iron phosphate (LFP) with olivine structure, polyvinylidene fluoride (PVDF), and carbon black (SP) are mixed with solvent in a mass ratio of 97:2:1. After stirring, a uniformly dispersed positive electrode slurry is obtained. The positive electrode slurry is evenly coated on both surfaces of an aluminum foil. After drying, cold pressing, and cutting, a positive electrode sheet is obtained.

[0143] Preparation of negative electrode sheet

[0144] Artificial graphite, carbon black (SP), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) are mixed with a solvent in a ratio of 97:0.5:1.5:1. The pore-forming agent is added, and the mixture is stirred to obtain a uniformly dispersed negative electrode slurry. The negative electrode slurry is then uniformly coated on both surfaces of a copper foil. After drying, cold pressing, and cutting, the negative electrode sheet is obtained.

[0145] Preparation of electrolyte

[0146] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), 30% ethylene carbonate (EC), 15% dimethyl carbonate (DMC), ethylene glycol dimethyl ether (DME), and 15% lithium hexafluorophosphate (LiPF6) were mixed by mass fraction to obtain the electrolyte.

[0147] Separating membrane

[0148] Polyethylene film is used as the separation membrane.

[0149] Preparation of battery cells:

[0150] The positive electrode, negative electrode, and separator are made into an electrode assembly by winding or stacking. The assembly is then placed in a housing made of aluminum shell, aluminum-plastic film, etc. Electrolyte is injected into the housing and it is then sealed. After high-temperature standing, formation, and capacity testing, a single battery cell is obtained.

[0151] Examples 2-28 and Comparative Example 1

[0152] The preparation methods of Examples 2-28 and Comparative Example 1 are similar to those of Example 1. The differences are shown in Tables 1 and 2.

[0153] Test section

[0154] (1) Tests for T1, T2 and T3

[0155] After discharging the battery cell to 2.5V at a rate of 0.1C, the positive electrode, negative electrode, and separator were obtained. At room temperature, the positive electrode, negative electrode, and separator were left to stand in a dry environment (humidity ≤2%) for 24 hours to allow the electrolyte to evaporate. The positive electrode, broken in the middle, was taken, and its thickness at the center was measured using a micrometer. The electrode was moved to a different location to measure the thickness at another point, collecting thickness data from 50 points. The average value, T1', was obtained. Simultaneously, the thickness of the current collector, T0, was measured. If the positive electrode is coated on one side, then T1 = T1' - T0; if the positive electrode is coated on both sides, then T1 = (T1' - T0) / 2. The test method for T2 is the same as that for T1.

[0156] Take the diaphragm that is broken in the middle, use a micrometer to measure the thickness at the middle position of the diaphragm, and move it to measure the next point. Collect the thickness data at 50 points and obtain the average value T3.

[0157] (2) Tests of P1, P2 and P3

[0158] Tested according to the method of GB / T 24586-2009.

[0159] (3) Test of G

[0160] The ionic conductivity of the electrolyte was tested at 25°C using a magnetic conductivity meter.

[0161] (4) Test of BET specific surface area

[0162] Please refer to GB / T 19587-2004 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method". After testing, the BET of the positive electrode in each embodiment and comparative example is: 10m 2 / g, BET of the negative electrode: 1.9m 2 / g.

[0163] (5) Air permeability test

[0164] In an environment with a temperature of 15°C to 28°C and humidity less than 80%, test samples were prepared to a size of 4cm × 4cm and measured using an air-permeability tester with the Gurleytest (100cc) method to directly obtain the air permeability value. The test results showed that the air permeability in each example and comparative example was 150s / 100cm. 3 .

[0165] (6) Test of 10C discharge capacity retention

[0166] At room temperature (25℃±2℃), the battery cell was charged at a constant current of 0.3C to 3.65V, then charged at a constant voltage to a current of 0.05C, and allowed to stand for 10 minutes. It was then discharged at a constant current of 0.3C to 2.5V, and the discharge capacity was recorded as D1. Subsequently, the battery cell was charged at a constant current of 0.3C to 3.65V, then charged at a constant voltage to a current of 0.05C, and allowed to stand for 10 minutes. It was then discharged at a constant current of 10C to 2.5V, and the discharge capacity was recorded as D2. The 10C discharge capacity retention rate = D2 / D1.

[0167] (7) Capacity retention test

[0168] At room temperature (25℃±2℃), the battery cell was charged at a constant current of 5C to 3.65V, then charged at a constant voltage to a current of 0.05C, and allowed to stand for 10 minutes. It was then discharged at a constant current of 3C to 2.5V, and the discharge capacity was recorded as Q1. The process was allowed to stand for 10 minutes. This process was repeated 500 times, and the final discharge capacity Q2 was recorded. The battery cell capacity retention rate was calculated as Q2 / Q1.

[0169] (8) Test of liquid retention coefficient N

[0170] Weigh the individual battery cells to be disassembled to obtain M1. Disassemble the battery cells, pour out the free electrolyte, add dimethyl carbonate (DMC) to the casing for extraction three times, pour out the residual DMC, and place the electrode assembly and casing in an oven to thoroughly remove DMC. Weigh the remaining components to obtain M2. The electrolyte retention is equal to M1-M2, therefore the electrolyte retention coefficient N is equal to (M1-M2) / Q1.

[0171] Tables 1 and 2 list some parameters of the battery cells of Examples 1-28 and Comparative Example 1, respectively. In Table 1, Z represents... Table 3 lists the test results of the individual cells in Examples 1-28 and Comparative Example 1.

[0172] Table 1

[0173] Serial Number T1(cm) P1 T2(cm) P2 T3(cm) P3 G(mS / cm) <![CDATA[Z(MΩ·μm 2 )]]> Example 1 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.0 143.8 Example 2 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.9 136.3 Example 3 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.9 136.3 Example 4 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.9 136.3 Example 5 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.9 136.4 Example 6 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.9 136.4 Example 7 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.9 136.4 Example 8 0.0045 40％ 0.0035 40％ 0.0012 40％ 17.1 134.2 Example 9 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.9 136.2 Example 10 0.0045 40％ 0.0035 40％ 0.0012 40％ 25.1 91.5 Example 11 0.0045 40％ 0.0035 40％ 0.0012 40％ 16.6 138.2 Example 12 0.0045 40％ 0.0035 40％ 0.0012 40％ 17.1 134.4 Example 13 0.0045 40％ 0.0035 40％ 0.0012 40％ 14.3 160.8 Example 14 0.0045 40％ 0.0035 40％ 0.0012 40％ 17.6 130.7 Example 15 0.0035 40％ 0.0035 40％ 0.0012 40％ 16.9 121.6 Example 16 0.0055 40％ 0.0035 40％ 0.0012 40％ 16.9 151.2 Example 17 0.0045 30％ 0.0035 40％ 0.0012 40％ 16.9 158.7 Example 18 0.0045 60％ 0.0035 40％ 0.0012 40％ 16.9 114.2 Example 19 0.0045 40％ 0.0030 40％ 0.0012 40％ 16.9 129.0 Example 20 0.0045 40％ 0.0050 40％ 0.0012 40％ 16.9 158.7 Example 21 0.0045 40％ 0.0050 30％ 0.0012 40％ 16.9 183.4 Example 22 0.0045 40％ 0.0050 60％ 0.0012 40％ 16.9 133.9 Example 23 0.0045 40％ 0.0050 40％ 0.0005 40％ 16.9 148.3 Example 24 0.0045 40％ 0.0035 40％ 0.0015 40％ 16.9 140.9 Example 25 0.0045 40％ 0.0035 40％ 0.0012 30％ 16.9 142.3 Example 26 0.0045 40％ 0.0035 40％ 0.0012 80％ 16.9 127.5 Example 27 0.0045 60％ 0.0035 60％ 0.0012 70％ 17.1 88.1 Example 28 0.0055 30％ 0.0050 30％ 0.0015 30％ 13.5 297.2 Comparative Example 1 0.0045 40％ 0.0035 40％ 0.0012 40％ 10.8 213.0

[0174] Table 2

[0175]

[0176]

[0177] Table 3

[0178] Serial Number 10C discharge capacity retention (%) Capacity retention (25°C, 500 cycles) Example 1 91.2％ 82.1％ Example 2 90.9％ 95.6％ Example 3 91.4％ 95.7％ Example 4 91.6％ 95.7％ Example 5 91.4％ 96.1％ Example 6 91.5％ 96.3％ Example 7 91.5％ 96.2％ Example 8 91.6％ 96.7％ Example 9 91.4％ 96.6％ Example 10 95.9％ 98.9％ Example 11 91.3％ 95.9％ Example 12 91.5％ 96.2％ Example 13 90.0％ 95.4％ Example 14 91.8％ 96.3％ Example 15 92.5％ 96.7％ Example 16 90.5％ 95.6％ Example 17 90.1％ 95.4％ Example 18 93.2％ 97.0％ Example 19 91.9％ 96.4％ Example 20 90.1％ 95.4％ Example 21 89.1％ 94.9％ Example 22 91.6％ 96.2％ Example 23 90.7％ 95.7％ Example 24 91.1％ 95.9％ Example 25 91.0％ 95.9％ Example 26 92.0％ 96.4％ Example 27 96.4％ 98.7％ Example 28 86.5％ 93.5％ Comparative Example 1 45.7％ 64.3％

[0179] As shown in Table 1, in the battery cell provided in this application embodiment, the thickness T1 and porosity P1 of the positive electrode active material layer, the thickness T2 and porosity P2 of the negative electrode active material layer, the thickness T3 and porosity P3 of the separator, and the ionic conductivity G of the electrolyte satisfy the above relationship. This allows the battery cell to have a lower resistance at high rates, thereby improving the power performance of the battery cell and achieving a balance between rate performance and power performance.

[0180] While this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all embodiments falling within the scope of the claims.

Claims

1. A single battery cell, comprising: A positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector; A negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative active material layer disposed on at least one side of the negative current collector; A separator is disposed between the positive electrode and the negative electrode; Electrolyte; The positive electrode active material layer, the negative electrode active material layer, the separator, and the electrolyte satisfy the following relationship: Wherein, T1 is the thickness of the positive electrode active material layer, in cm; P1 is the porosity of the positive electrode active material layer; T2 is the thickness of the negative electrode active material layer, in cm; P2 is the porosity of the negative electrode active material layer; T3 is the thickness of the separator, in cm; P3 is the porosity of the separator. G is the ionic conductivity of the electrolyte at 25°C, in mS / cm. The thickness T1 of the positive electrode active material layer satisfies: 0.0035cm ≤ T1 ≤ 0.0055cm; The porosity P1 of the positive electrode active material layer satisfies: 30% ≤ P1 ≤ 60%; The thickness T2 of the negative electrode active material layer satisfies: 0.003cm ≤ T2 ≤ 0.005cm; The porosity P2 of the negative electrode active material layer satisfies: 30% ≤ P2 ≤ 60%; The thickness T3 of the isolation membrane satisfies: 0.0005cm ≤ T3 ≤ 0.0015cm; The porosity P3 of the isolation membrane satisfies: 30% ≤ P3 ≤ 80%; The ionic conductivity G of the electrolyte at 25°C satisfies: 13mS / cm≤G≤26mS / cm.

2. The battery cell according to claim 1, wherein, The thickness T1 of the positive electrode active material layer satisfies 0.0035cm≤T1≤0.0045cm.

3. The battery cell according to claim 1, wherein, The porosity P1 of the positive electrode active material layer satisfies 40% ≤ P1 ≤ 60%.

4. The battery cell according to claim 1, wherein, The positive electrode active material layer includes a positive electrode active material, and the BET specific surface area S1 of the positive electrode active material satisfies: 8m² 2 / g≤S1≤12m 2 / g.

5. The battery cell according to claim 1, wherein, The thickness T2 of the negative electrode active material layer satisfies: 0.0035cm≤T2≤0.005cm.

6. The battery cell according to claim 1, wherein, The porosity P2 of the negative electrode active material layer satisfies: 40% ≤ P2 ≤ 60%.

7. The battery cell according to claim 1, wherein, The negative electrode active material layer includes a negative electrode active material, and the BET specific surface area S2 of the negative electrode active material satisfies: 1.7m². 2 / g≤S2≤2.2m 2 / g.

8. The battery cell according to claim 1, wherein, The air permeability of the isolation membrane is greater than or equal to 150s / 100cm. 3 .

9. The battery cell according to claim 1, wherein, The electrolyte has an ionic conductivity G at 25°C that satisfies 14 mS / cm ≤ G ≤ 25 mS / cm.

10. The battery cell according to claim 1, wherein, The electrolyte retention coefficient N satisfies: 3g / Ah≤N≤7g / Ah.

11. The battery cell according to claim 1, wherein, The electrolyte comprises an electrolyte salt and an organic compound, and the viscosity μ of the organic compound satisfies: 0.1 mPa·s-3.5 mPa·s.

12. The battery cell according to claim 11, wherein, Based on the mass of the electrolyte, the mass fraction A of the electrolyte salt satisfies: 10% ≤ A ≤ 20%, and the mass fraction B of the organic compound satisfies: 30% ≤ B ≤ 70%.

13. The battery cell according to claim 11 or 12, wherein, The electrolyte salt contains a lithium salt.

14. The battery cell according to claim 13, wherein, The lithium salt is selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide or combinations thereof.

15. The battery cell according to claim 11, wherein, The organic compounds include sulfone organic compounds, ether organic compounds, ester organic compounds, and nitrile organic compounds.

16. The battery cell according to claim 15, wherein, The sulfone organic compound is selected from dimethyl sulfoxide.

17. The battery cell according to claim 15, wherein, The ether organic compound is selected from ethylene glycol dimethyl ether.

18. The battery cell according to claim 15, wherein, The ester organic compound is selected from methyl formate, ethyl formate, methyl acetate, methyl acrylate, or combinations thereof.

19. The battery cell according to claim 15, wherein, The nitrile organic compound is selected from acetonitrile.

20. The battery cell according to claim 9, wherein, The electrolyte also includes a high-temperature additive, and the mass fraction C of the high-temperature additive satisfies the following condition based on the mass of the electrolyte: 0.01% ≤ C ≤ 1%.

21. The battery cell according to claim 20, wherein, The high-temperature additive is selected from lithium tetrafluoroborate, lithium difluorophosphate, lithium fluorosulfonate, lithium aminosulfonate, or combinations thereof.

22. The battery cell according to claim 9, wherein, The electrolyte also includes film-forming additives, and the mass fraction D of the film-forming additives satisfies the following condition based on the mass of the electrolyte: 1% ≤ D ≤ 5%.

23. The battery cell according to claim 22, wherein, The film-forming additive is selected from vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, or a combination thereof.

24. A battery comprising a battery cell according to any one of claims 1 to 23.

25. An electrical device comprising a battery cell according to any one of claims 1 to 23 or a battery according to claim 24.

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