Battery cell, battery, and electric device

Abstract

The present application discloses a battery cell, a battery and an electric device. The battery cell comprises: a housing having an opening; and an electrode assembly accommodated in the housing and comprising a main body, a first tab and a second tab, the first tab and the second tab having opposite polarities and being arranged on the same side of the main body, wherein the first tab and the second tab extend from an open end of the housing, the housing comprises a bottom wall opposite to the opening, and an explosion-proof valve is arranged on the bottom wall. The battery cell provided by the present application has high capacity and high reliability.

Description

Battery cell, battery and electric device

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410430664.5, filed on April 10, 2024, entitled “Battery cell, battery and electric device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of battery technology, in particular to a battery cell, a battery and an electric device. BACKGROUND

[0004] With the increasingly wide range of applications of battery cells, people's demand for the use of battery cells is increasing, for example, the requirement for the capacity and fast charging performance of battery cells is becoming higher and higher. At present, in order to meet the high capacity and fast charging demand of battery cells, the tabs of the battery cell can be arranged on the same side, and the same side tab can reduce the space occupied by the internal mechanical parts of the battery cell, improve the space utilization rate of the active material, thereby shortening the electron transport path and reducing the internal resistance, which is beneficial to improve the fast charging performance and capacity of the battery cell. However, with the increase of the capacity of the battery cell, the gas production and heat release of the battery cell during thermal runaway also increase, which brings the reliability risk of the battery cell.

[0005] SUMMARY

[0006] The present application provides a battery cell, a battery and an electric device, which can have high energy density and high reliability.

[0007] In a first aspect, the embodiments of the present application provide a battery cell, comprising: a shell having an opening and a bottom wall opposite to the opening; an electrode assembly accommodated in the shell and comprising a main body part, a first tab and a second tab, the first tab and the second tab being opposite in polarity and arranged on the same side of the main body part; wherein the first tab and the second tab extend out from one end of the shell opening, and the bottom wall is provided with an explosion-proof valve.

[0008] The battery cell provided by the embodiments of the present application respectively arranges the explosion-proof valve and the electrical connection part (i.e. the first tab and the second tab) of the battery cell at opposite ends of the battery cell, thereby realizing the “thermal-electric separation” of the battery cell in the mechanical structure. After the battery cell appears thermal runaway, the spewing material spews out from the end far away from the first tab and the second tab, which can reduce the damage of the thermal gas spewing to the electrical connection part of the battery cell, and can reduce the risk of arc striking in the electrical connection part during the thermal gas spewing process, thereby improving the reliability of the battery cell.

[0009] In some embodiments, the area ratio of the explosion-proof valve based on the total area of the bottom wall is 20% to 60%, and the area of the explosion-proof valve is 300mm 2 to 1000mm 2 .

[0010] In some embodiments, the area ratio of the explosion-proof valve based on the total area of the bottom wall is 25% to 45%, and the area of the explosion-proof valve is 450mm 2 to 800mm 2 .

[0011] In some embodiments, the tab portion includes a positive electrode tab portion and a negative electrode tab portion, and the positive electrode tab portion and the negative electrode tab portion are extended out from the same end of the main body portion.

[0012] In some embodiments, the battery cell includes a cylindrical battery cell, and a length H in an axial direction of the cylindrical battery cell satisfies H≥70mm, and a diameter D of the cylindrical battery cell satisfies 40mm≤D≤60mm.

[0013] In some embodiments, a length H in an axial direction of the battery cell satisfies 80mm≤H≤120mm.

[0014] In some embodiments, the diameter D of the cylindrical battery cell satisfies 45mm≤D≤50mm.

[0015] In some embodiments, the main body portion includes a positive electrode tab, and a dimension L of the positive electrode tab in an axial direction of the battery cell and a length H in the axial direction of the battery cell satisfy 6mm≤H-L≤13mm.

[0016] In some embodiments, the main body portion includes a positive electrode tab, and the positive electrode tab includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a layered lithium-containing transition metal oxide.

[0017] In some embodiments, the positive electrode active material includes a Ni-containing layered lithium-containing transition metal oxide, and a molar content of Ni element based on a total molar amount of the Ni-containing layered lithium-containing transition metal oxide is greater than or equal to 80%.

[0018] In some embodiments, the main body portion further includes a negative electrode tab, and the negative electrode tab includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based composite material.

[0019] In some embodiments, the silicon-based composite material includes a carbon material matrix and a silicon material dispersed in the carbon material matrix, and the weight content of the silicon material is greater than or equal to 1% based on the total mass of the silicon-based composite material.

[0020] In some embodiments, the weight content of the silicon material is 2% to 20% based on the total mass of the silicon-based composite material.

[0021] In some embodiments, the carbon material includes graphite.

[0022] In some embodiments, the areal density of the negative electrode film layer is less than or equal to 0.2 g / 15 40.25 mm 2 .

[0023] In some embodiments, the areal density of the negative electrode film layer is 0.07 g / 15 40.25 mm 2 to 0.14 g / 15 40.25 mm 2 .

[0024] In some embodiments, the electrolyte includes an organic solvent, and the organic solvent includes a chain carbonate, and the weight content of the chain carbonate is 50% to 90% based on the total weight of the organic solvent.

[0025] In some embodiments, the chain carbonate includes one or more of dimethyl carbonate and methyl ethyl carbonate.

[0026] In a second aspect, the embodiments of the present application provide a battery including the battery monomer of the first aspect of the present application.

[0027] In a third aspect, the embodiments of the present application provide a power consumption device including the battery of the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0029] FIG. 1 is a structural schematic diagram of a vehicle according to some embodiments of the present application.

[0030] FIG. 2 is an exploded schematic diagram of a battery according to some embodiments of the present application.

[0031] FIG. 3 is an exploded schematic diagram of a battery module shown in FIG. 2.

[0032] In the drawings, the drawings are not necessarily drawn according to the actual scale.

[0033] The reference signs are explained as follows: 1, vehicle; 2, battery; 3, controller; 4, motor; 5, case; 5a, first case portion; 5b, second case portion; 5c, accommodation space; 6, battery module; 7, battery cell. DETAILED DESCRIPTION

[0034] Hereinafter, embodiments of the battery cell, the battery, and the electric device of the present application are specifically disclosed while appropriately referring to the accompanying drawings. However, there are cases where unnecessary detailed explanations are omitted. For example, there are cases where detailed explanations of matters that are already well known, repeated explanations of actually identical structures are omitted. This is in order to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following explanations are provided in order for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0035] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is contained in the range between "a" and "b," wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing each and every numerical value that is contained in the range between "0" and "5." In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0036] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0037] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0038] If not specially specified, all steps in the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0039] If not specially specified, in the present application, the terms "first", "second", etc. are used to distinguish different objects, rather than to describe a specific sequence or primary and secondary relationship.

[0040] In the present application, the terms "a plurality of" and "a plurality of kinds" refer to two or more than two.

[0041] In the description of the embodiments of the present application, if not specially specified, the first feature is "on" or "under" the second feature, which can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature can be "above", "over" and "on" the second feature, which can mean that the first feature is directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature can be "under", "below" and "underneath" the second feature, which can mean that the first feature is directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is lower than that of the second feature.

[0042] Unless otherwise specified, the terms used in the present application have the commonly understood meanings understood by those skilled in the art.

[0043] Unless otherwise specified, the values of the parameters mentioned in the present application can be measured by various test methods commonly used in the art, for example, the test methods given in the examples of the present application. Unless otherwise specified, the test temperature of each parameter is 25℃.

[0044] The battery mentioned in the embodiments of the present application can be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application can include a battery cell, a battery module, or a battery pack, etc. The battery cell is the smallest unit that constitutes a battery, which can realize the function of charging and discharging by itself. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed connection through a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a box body and battery cells, and the battery cells or battery modules are contained in the box body. In some embodiments, the box body can be part of the chassis structure of the vehicle. For example, part of the box body can be at least part of the floor of the vehicle, or part of the box body can be at least part of the cross beam and longitudinal beam of the vehicle.

[0045] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0046] The technical solutions described in the embodiments of the present application are applicable to batteries and electric devices using batteries.

[0047] The battery can be used as a power source of an electric device, or as an energy storage unit of an electric device. The electric device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a notebook computer, etc.), a vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0048] The electric device can select the type of battery according to its use requirements, such as a battery cell, a battery module, or a battery pack.

[0049] The following embodiments are described for convenience with the electric device being a vehicle as an example.

[0050] FIG. 1 is a structural schematic diagram of a vehicle provided by some embodiments of the present application.

[0051] As shown in FIG. 1, the vehicle 1 is internally provided with a battery 2, which can be arranged at the bottom, head or tail of the vehicle 1. The battery 2 can be used for power supply of the vehicle 1, for example, the battery 2 can be used as an operating power source of the vehicle 1.

[0052] The vehicle 1 can further include a controller 3 and a motor 4, the controller 3 being used to control the battery 2 to supply power to the motor 4, for example, for the working power demand of the vehicle 1 during starting, navigation and driving.

[0053] In some embodiments, the battery 2 can not only serve as the power source for the operation of the vehicle 1, but also serve as the driving power source for the vehicle 1, replacing or partially replacing the fuel or natural gas to provide driving power for the vehicle 1.

[0054] FIG. 2 is an exploded schematic view of a battery according to some embodiments of the present application. As shown in FIG. 2, the battery 2 includes a box 5 and battery cells (not shown), and the battery cells are accommodated in the box 5.

[0055] The box 5 is used to accommodate the battery cells, and the box 5 can have various structures. In some embodiments, the box 5 can include a first box part 5a and a second box part 5b, the first box part 5a and the second box part 5b are mutually covered, and the first box part 5a and the second box part 5b jointly define an accommodation space 5c for accommodating the battery cells. The second box part 5b can be a hollow structure with one end open, and the first box part 5a is a plate-like structure, which is covered on the open side of the second box part 5b to form the box 5 with the accommodation space 5c; or the first box part 5a and the second box part 5b can both be hollow structures with one side open, and the open side of the first box part 5a is covered on the open side of the second box part 5b to form the box 5 with the accommodation space 5c. Of course, the first box part 5a and the second box part 5b can have various shapes, such as a cylinder, a cuboid, etc.

[0056] In order to improve the sealing performance of the first box part 5a and the second box part 5b after being connected, a sealing member such as sealing glue, a sealing ring, etc. can be arranged between the first box part 5a and the second box part 5b.

[0057] Suppose the first box part 5a is covered on the top of the second box part 5b, the first box part 5a can also be referred to as an upper box cover, and the second box part 5b can also be referred to as a lower box.

[0058] In the battery 2, the battery cells can be one or multiple. If the battery cells are multiple, the multiple battery cells can be connected in series, in parallel or in a mixed manner, and the mixed manner means that the multiple battery cells are connected in series and in parallel. The multiple battery cells can be directly connected in series, in parallel or in a mixed manner, and then the whole of the multiple battery cells is accommodated in the box 5; of course, the multiple battery cells can first be connected in series, in parallel or in a mixed manner to form a battery module 6, and then the multiple battery modules 6 are connected in series or in parallel or in a mixed manner to form a whole, which is accommodated in the box 5.

[0059] FIG. 3 is an exploded schematic view of the battery module shown in FIG. 2.

[0060] As shown in FIG. 3, in some embodiments, the battery cells 7 are multiple, and the multiple battery cells 7 are first connected in series, in parallel or in a mixed manner to form a battery module 6. The multiple battery modules 6 are then connected in series or in parallel or in a mixed manner to form a whole, which is accommodated in the box.

[0061] The plurality of battery cells 7 in the battery module 6 can be electrically connected through a busbar component to achieve parallel connection, series connection or mixed connection of the plurality of battery cells 7 in the battery module 6.

[0062] The battery cell mentioned in the embodiments of the present application can include a lithium ion battery cell.

[0063] The battery cell in the embodiments of the present application includes a shell, an opening and a bottom wall opposite to the opening; an electrode assembly accommodated in the shell and including a main body part, a first tab and a second tab, the first tab and the second tab being opposite in polarity and arranged on the same side of the main body part; wherein the first tab and the second tab extend out from one end of the opening of the shell, and the bottom wall is provided with an explosion-proof valve.

[0064] High energy density and high fast charging performance are generally pursued in the design of battery cells. In order to improve the energy density and fast charging performance of the battery cell, a feasible method is to design the structure of the battery cell with the positive and negative electrode tabs extending from the same side. This structure design with the tabs extending from the same side can avoid the transmission of electrons in the shell, shorten the electron transmission path and reduce the internal resistance, thereby improving the fast charging performance of the battery cell. At the same time, the structure design with the positive and negative electrode tabs extending from the same side of the battery cell can save the internal space of the battery cell and improve the proportion of active materials in the battery cell, thereby improving the energy density of the battery cell. However, this design is prone to heat diffusion problems. Higher energy density and fast charging performance can increase the gas production of the battery cell, and the battery cell is prone to thermal runaway problems. In the process of pressure relief through the explosion-proof valve after thermal runaway occurs in the battery cell, high-pressure gas is prone to arc striking phenomenon at the electrical connection position of the battery cell when it is ejected, and even explosion, resulting in reduced reliability of the battery cell. Therefore, the battery cell with this design is difficult to have high energy density, high fast charging and high reliability, which restricts the development of the battery cell.

[0065] In the embodiments of the present application, the positive and negative electrode tabs extend from the same end of the battery cell, so that the battery cell has higher energy density and fast charging performance. On this basis, the explosion-proof valve and the electrical connection part (i.e. the first tab and the second tab) of the battery cell are arranged at different ends of the battery cell, respectively, so as to realize "thermal-electric separation" of the battery cell in the mechanical structure. The ejection of the thermal gas from the end away from the tabs after thermal runaway of the battery cell can reduce the damage of the thermal gas ejection to the electrical connection part of the battery cell, and can reduce the risk of arc striking at the electrical connection part during the thermal gas ejection process, thereby improving the reliability of the battery cell.

[0066] The first and second tabs are collectively referred to as tab portions, which are used to lead out the current generated by the main body portion. The main body portion is the core part of the battery cell to realize the charging and discharging function, and generally includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0067] The first and second tabs are defined as positive and negative tab portions, respectively. The two tab portions are electrically connected to the positive and negative electrode terminals, respectively. The tab portions can be directly connected to the positive and negative electrode terminals by welding or the like, or indirectly connected to the positive and negative electrode terminals through other components.

[0068] The positive and negative tab portions extend from the same side and can share the tab folding space, thereby increasing the proportion of active materials in the battery cell, improving the energy density of the battery cell while maintaining high reliability, and further improving the fast charging performance of the battery cell.

[0069] In some embodiments, the explosion-proof valve can be provided in the form of a notch on the bottom wall of the battery cell.

[0070] In some embodiments, the area ratio of the explosion-proof valve to the total area of the bottom wall can be 20% to 60%, optionally 25% to 45%, and further optionally 30% to 40%; the area of the explosion-proof valve can be 300mm 2 to 1000mm 2 , optionally 450mm 2 to 800mm 2 , and further optionally 500mm 2 to 750mm 2 .

[0071] The size of the area of the explosion-proof valve affects the rate of gas discharge when the battery cell experiences thermal runaway and the strength of the shell. If the area of the explosion-proof valve is small, the gas inside the battery cell cannot be discharged in time, which can increase the risk of explosion and other reliability risks of the battery cell. If the area of the explosion-proof valve is large, the strength of the shell is reduced, which can affect the mechanical strength of the battery cell. By limiting the area of the explosion-proof valve and the area ratio of the explosion-proof valve to the bottom wall within the above range, the gas can be quickly discharged when the battery cell experiences thermal runaway, reducing the risk of explosion due to gas expansion of the battery cell and improving the reliability of the battery cell. At the same time, the shell has high mechanical strength, which is beneficial to the production and use of the battery cell.

[0072] As shown in FIG. 3, the battery cell can be a cylindrical battery cell.

[0073] In some embodiments, the axial length H of the cylindrical battery cell satisfies H ≥ 70 mm, optionally 80 mm ≤ H ≤ 120 mm; the diameter D of the cylindrical battery cell satisfies 40 mm ≤ D ≤ 60 mm, optionally 45 mm ≤ D ≤ 50 mm. This allows the battery cell to have a higher energy density.

[0074] In some embodiments, the axial length H of the cylindrical battery cell and the dimension L of the positive electrode tab along the axial direction of the cylindrical battery cell satisfy 6mm≤HL≤13mm. This increases the proportion of active material within the battery cell, further improving the energy density of the battery cell while maintaining high reliability.

[0075] The axial direction of a cylindrical battery cell refers to the direction of the cylinder's central axis of rotation, i.e., the same direction as the central axis. The radial direction of a cylindrical battery cell is perpendicular to the axial direction and is the direction of the diameter of the cylinder's end face. The axial dimension of a cylindrical battery cell is usually referred to as the length of the cylindrical battery cell.

[0076] The axial dimension of a cylindrical battery cell refers to the distance between the top and bottom outer surfaces of the battery cell. It is understood that the axial dimension of a cylindrical battery cell does not include the dimensions of the electrode terminals.

[0077] In some embodiments, the material of the battery cell housing may include but is not limited to hard plastic, aluminum, or steel, etc. In some embodiments, the material of the battery cell housing is steel.

[0078] In some embodiments, the thickness of the battery cell shell may be greater than or equal to 0.2 mm, and may be 0.25 mm to 0.6 mm.

[0079] [Positive electrode]

[0080] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0081] In some embodiments, the positive electrode active material may include one or more of a lithium-containing phosphate and a layered lithium-containing transition metal oxide. The lithium-containing phosphate may include one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their respective modified compounds. Examples of layered lithium-containing transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0082] In some embodiments, the layered lithium-containing transition metal oxide can include Ni element. The molar amount of the Ni element can account for more than 70% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide; alternatively, the molar amount of the Ni element can account for more than 80% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide; more alternatively, the molar amount of the Ni element can account for more than 90% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide.

[0083] The higher the content of the Ni element in the layered lithium-containing transition metal oxide, the higher the energy density of the battery cell.

[0084] In some embodiments, the layered lithium-containing transition metal oxide can include Li a Ni b Co c M d O e A f , wherein 0 < a < 1.2; 0.8 < b < 1; 0 < c < 1; 0 < d < 1; 1 < e < 2; 0 < f < 1; M includes but is not limited to one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B; A includes but is not limited to one or more of N, F, S and Cl. In this way, the energy density of the battery cell can be further improved.

[0085] In some embodiments, as an example, the layered lithium-containing transition metal oxide can include but is not limited to one or more of LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.9 Co 0.06 Mn 0.04 O2, LiNi 0.92 Co 0.06 Mn 0.02 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2.

[0086] During the charging and discharging process of the battery cell, Li will be deintercalated and consumed, and the molar content of Li is different when the battery cell is discharged to different states. In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of Li is the initial state of the material, i.e. the state before feeding, and the positive electrode active material is applied to the battery cell. After charging and discharging cycle, the molar content of Li can change.

[0087] In the examples of the present application regarding the positive electrode active materials, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0088] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0089] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin.

[0090] In some implementations, the weight percentage of the binder in the positive electrode film layer is greater than or equal to 0.5%, which is conducive to obtaining good bonding performance.

[0091] In some embodiments, the positive electrode film layer further includes a conductive agent, which may include, for example, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0092] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be made by forming a metal material, such as aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, on a polymer material substrate. The polymer material substrate may include a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0093] In some embodiments, the thickness of the positive electrode current collector is 4 μm to 20 μm, optionally 6 μm to 18 μm, and further optionally 8 μm to 16 μm.

[0094] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0095] [Negative electrode]

[0096] In some embodiments, the negative electrode tab includes a negative current collector and a negative film layer located on at least one side of the negative current collector, and the negative film layer includes a negative active material.

[0097] In some embodiments, the negative active material can include a silicon-based composite material. The silicon-based composite material can include a silicon-carbon composite material or a silicon-oxygen composite material.

[0098] The silicon-carbon composite material is a composite of a carbon material and a silicon material, and the silicon-carbon composite material has a high theoretical specific capacity, which can significantly improve the energy density of the battery cell.

[0099] In some embodiments, the silicon-based composite material includes a carbon material matrix and a silicon material dispersed in the carbon material matrix. In some embodiments, there can also be a gap between the silicon material and the carbon material matrix. When there is a gap between the silicon material and the carbon material matrix, the gap can serve as a space to accommodate the volume expansion of the silicon material and buffer the stress generated during the expansion of the silicon material, thereby better reducing the problem of fragmentation and pulverization of the silicon-based composite material, and thus enabling the battery cell to have a long cycle life.

[0100] In some embodiments, the carbon material can include graphite, which can include but is not limited to one or more of artificial graphite, natural graphite, modified graphite.

[0101] In some embodiments, the carbon material can also include one or more of porous carbon, hard carbon, graphene, carbon nanotubes.

[0102] In some embodiments, the silicon material can include one or more of single crystal silicon, polycrystalline silicon, amorphous silicon.

[0103] In some embodiments, the weight content of the silicon material in the silicon-based composite material can be greater than or equal to 1%, optionally 2% to 20%, and further optionally 5% to 15%. Limiting the silicon content in the silicon-based composite material to the above range can improve the capacity per unit area of the tab, while reducing the coating amount while the battery cell has a higher capacity.

[0104] In some embodiments, the volume distribution particle size Dv50 of the silicon-based composite material can be 3 μm to 15 μm, and optionally 5 μm to 12 μm. The volume distribution particle size of the silicon-based composite material in the above range helps to reduce the surface activity, reduce the interface side reaction, reduce the consumption of electrolyte, and enable the battery cell to have a long cycle life.

[0105] The volume distribution particle size Dv50 of the material is a meaning known in the art, which represents the particle size corresponding to the cumulative volume distribution percentage of 50%, and can be determined by using instruments and methods known in the art. For example, it can be conveniently determined by referring to GB / T 19077-2016, using a laser particle size analyzer. The testing instrument can be a Mastersizer 3000 laser particle size analyzer of Malvern Instruments Ltd., UK.

[0106] In some embodiments, the specific surface area of the silicon-based composite material can be 0.5 m 2 / g to 2 m 2 / g, and can be 0.8 m 2 / g to 1.8 m 2 / g. The specific surface area of the silicon-based composite material in the above range helps to reduce the interface side reaction, reduce the consumption of electrolyte, and make the battery cell have a long cycle life.

[0107] The specific surface area of the material is a meaning known in the art, and can be determined by using instruments and methods known in the art. For example, it can be tested by referring to GB / T 19587-2017, using a nitrogen adsorption specific surface area analysis test method, and calculated by using a BET (Brunauer Emmett Teller) method, and the nitrogen adsorption specific surface area analysis test can be performed by using a TRISTAR II 3020 specific surface area and porosity analyzer of Micromeritics Corporation, USA.

[0108] The silicon-based composite material can be prepared by a method known in the art. As an example, graphite and silicon material can be used as raw materials, and the silicon-based composite material can be prepared by a vapor deposition method.

[0109] In some embodiments, the negative electrode film layer can further include a negative electrode conductive agent. As an example, the negative electrode conductive agent can include, but is not limited to, one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the negative electrode film layer can further include a negative electrode binder. As an example, the negative electrode binder can include, but is not limited to, one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0111] In some embodiments, the negative electrode film layer can further include other auxiliary agents. As an example, the other auxiliary agents can include a thickening agent, such as carboxymethyl cellulose sodium (CMC), PTC thermistor material, etc.

[0112] In some embodiments, the areal density of the negative electrode film layer can be less than or equal to 0.2 g / 15 40.25 mm 2 , optionally 0.07 g / 15 40.25 mm 2 to 0.14 g / 15 40.25 mm 2 .

[0113] Areal density refers to the weight of the negative active material per unit area of the negative electrode tab, which can be obtained by the ratio of the weight of the coated negative active material to the coating area. The areal density of the negative electrode film layer is within the above range, the negative active material has a smaller coating amount, the electrolyte has good wettability, and lithium ions have a faster insertion and extraction rate, which can further improve the fast charging performance of the battery cell.

[0114] In some embodiments, the negative current collector can use a metal foil or a composite current collector. As an example of a metal foil, a copper foil, a copper alloy foil, an aluminum foil, or an aluminum alloy foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one side of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0115] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab can further include a conductive primer layer sandwiched between the negative electrode current collector and the negative electrode film layer, located on the surface of the negative electrode current collector, which can be composed of a conductive agent and a binder; in some embodiments, the negative electrode tab can further include a protective layer covering the surface of the negative electrode film layer.

[0116] The negative electrode tab can be prepared by dispersing the negative active material, the negative binder, the negative conductive agent, and the optional other auxiliary agents in a solvent and stirring uniformly to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after drying, rolling, and other processes, forming the negative electrode tab. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0117] [Electrolyte]

[0118] In some embodiments, the electrolyte includes an organic solvent, and the organic solvent includes a chain carbonate.

[0119] In some embodiments, the chain carbonate can include one or both of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0120] In some embodiments, the mass percentage of the chain carbonate in the organic solvent can be 50% to 90%, and optionally 60% to 85%.

[0121] The chain carbonate has low viscosity and good flowability. By setting the weight content of the chain carbonate in the organic solvent of the electrolyte within the above range, the electrolyte can have low viscosity, facilitating the flow of the electrolyte, and the electrolyte wettability of the electrode assembly can be better improved.

[0122] In some embodiments, the organic solvent can further include a cyclic carbonate. The cyclic carbonate can include one or more of ethylene carbonate (EC) and fluoroethylene carbonate. The fluoroethylene carbonate can include one or both of monofluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC), and optionally include monofluoroethylene carbonate (FEC).

[0123] The chain carbonate can make the electrolyte have low viscosity and facilitate the flow of the electrolyte, but its dielectric constant is small and its ability to dissociate electrolyte salt is slightly weak. By mixing the chain carbonate with the cyclic carbonate, the electrolyte can have good flowability while also having high ionic conductivity and high ion migration rate, and thus the battery cell can have better cycle performance.

[0124] In some embodiments, the mass percentage of the cyclic carbonate in the organic solvent can be 10% to 50%, and optionally 15% to 40%.

[0125] In some embodiments, the electrolyte further includes an electrolyte salt.

[0126] In some embodiments, the electrolyte salt includes an anion. The anion can include one or more of a bisfluorosulfonylimide anion (FSI - ), a bistrifluoromethylsulfonylimide anion (TFSI - ), a dioxalate borate anion (BOB - ), a difluorooxalate borate anion (DFOB - ), a difluorodioxalate phosphate anion (DFOP - ), a tetrafluorooxalate phosphate anion (TFOP - ), a difluorophosphate anion (PO2F2 - ), a hexafluorophosphate anion (PF6 - ), a tetrafluoroborate anion (BF4 - ), a hexafluoroarsenate anion (AsF6 - ), a trifluoromethanesulfonate anion (CF3SO3 - ).

[0127] In some embodiments, the electrolyte salt includes a cation, which can include one or more of lithium ion, sodium ion.

[0128] In some embodiments, the concentration of the electrolyte salt can be 0.3 mol / L or more, optionally 0.7 mol / L or more, and the concentration of the electrolyte salt can further be 4 mol / L or less, optionally 2.5 mol / L or less, 1.7 mol / L or less. When the concentration of the electrolyte salt is within the above range, the electrolyte can have a suitable ionic conductivity.

[0129] In some embodiments, the electrolyte can further include an additive. The additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0130] [Separator]

[0131] In some embodiments, the electrode assembly includes a separator. The type of the separator is not particularly limited in the present application, and any known porous structure film having good chemical stability and mechanical stability can be used.

[0132] In some embodiments, the material of the separator can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0133] Embodiments

[0134] The following examples more specifically describe the present disclosure, which are merely illustrative and not restrictive, since various modifications and changes can be apparent to those skilled in the art within the scope of the present disclosure. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further purification, and the instruments used in the examples are commercially available.

[0135] Example 1

[0136] Preparation of positive electrode tab

[0137] The positive electrode active material LiNi 0.92 Co 0.06 Mn 0.02O2, adhesive polyvinylidene fluoride (PVDF), conductive agent Super P, conductive agent carbon nanotube are mixed in a mass ratio of 97.5:1:1:0.5, an appropriate amount of solvent N-methyl pyrrolidone (NMP) is added, and stirring is uniformly obtained to obtain a positive electrode slurry. The positive electrode slurry is coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0138] Preparation of negative electrode sheet

[0139] The silicon material monocrystalline silicon and the carbon material graphite are mixed in a mass ratio of 5:95 to obtain a mixed material. The mixed material, conductive agent Super P, adhesive styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.9:1.1 in an appropriate amount of solvent deionized water to obtain a negative electrode slurry. The negative electrode slurry is coated on both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained. The area density of the negative electrode film layer is 0.14 g / 1540.25 mm 2 .

[0140] Preparation of separator film

[0141] A polyethylene film with a thickness of 10 μm is used as the separator film.

[0142] Preparation of electrolyte

[0143] Dimethyl carbonate (DMC) and monofluoroethylene carbonate (FEC) are mixed in a mass ratio of 85:15 to obtain an organic solvent, and then LiPF6 is dissolved in the organic solvent to obtain an electrolyte. The concentration of LiPF6 is 1.1 mol / L.

[0144] Preparation of battery monomer

[0145] The positive electrode sheet, the separator film, and the negative electrode sheet are sequentially stacked and connected to the winding needle, and then the winding needle is rotated to wind the positive electrode sheet, the separator film, and the negative electrode sheet on the winding needle. After winding is completed, the winding needle is extracted to form a cylindrical electrode assembly. The first and second tabs extend from the same end of the electrode assembly. The electrode assembly is placed in a cylindrical shell with an open end, and an end cover assembly is welded to the open end of the cylindrical shell. The bottom wall is opposite to the open end of the cylindrical shell, and the explosion-proof valve is provided on the bottom wall. The explosion-proof valve exists in the form of a notch. The electrolyte is injected into the shell, and the processes of standing and formation are carried out to obtain a cylindrical battery monomer. The diameter D of the cylindrical battery monomer is 46 mm, the height H is 95 mm, the area of the explosion-proof valve is 615 mm 2 , the area ratio of the explosion-proof valve relative to the total area of the bottom wall is 37%, and the size L of the positive electrode sheet in the axial direction of the battery monomer is 86.5 mm.

[0146] Examples 2 to 11

[0147] The battery cell was prepared in the same manner as in Example 1, except that the specifications of the battery cell were different, as shown in Table 1.

[0148] Examples 12 to 13

[0149] The battery cell was prepared in the same manner as in Example 1, except that the positive electrode material was different, as shown in Table 1.

[0150] Examples 14 to 21

[0151] The battery cell was prepared in the same manner as in Example 1, except that the specifications of the negative electrode sheet were different, as shown in Table 1.

[0152] Examples 22 to 23

[0153] The battery cell was prepared in the same manner as in Example 1, except that the composition ratio of the electrolyte was different, as shown in Table 1.

[0154] Comparative Example 1

[0155] The battery cell was prepared in the same manner as in Example 1, except that the explosion-proof valve and the tab part were arranged on the same side, as shown in Table 1.

[0156] Test Part

[0157] 1. The energy density of the battery cell was tested by the following method:

[0158] The battery cell was charged at 0.33C constant current to 4.25V, and then charged at constant voltage to a current of 0.05C. After standing for 5 min, the battery cell was discharged at 0.33C constant current to 2.8V to obtain the discharge energy Q. The mass energy density (Wh / L) of the battery cell = discharge energy Q / volume of the battery cell.

[0159] 2. The fast-charging performance of the battery cell was tested by the following method:

[0160] The battery cell was charged at 0.33C constant current to 4.25V, and then charged at constant voltage to a current of 0.05C. After standing for 5 min, the battery cell was discharged at 0.33C constant current to 2.8V to obtain the discharge energy Q. The mass energy density (Wh / L) of the battery cell = discharge energy Q / volume of the battery cell.

[0161] The battery monomer is sequentially charged at 1C0, 1.3C0, 1.5C0, 1.8C0, 2C0, 2.3C0, 2.5C0, 3C0, 3.5C0, 4C0, 4.5C0, 5C0 constant current to 4.25V or negative electrode cutoff potential (whichever is reached first), after each charging is completed, discharge to 2.8V at 1C0, record the negative electrode potential corresponding to 10% SOC, 20% SOC, 30% SOC, 40% SOC, 50% SOC, 60% SOC, 70% SOC, 80% SOC charged at different charging rates respectively, draw the charging rate-negatve electrode potential curve at different SOC, linear fitting to obtain the charging rate corresponding to the negative electrode potential of 0 at different SOC state, which is the charging window at this SOC state, the corresponding charging rate is recorded as C10% SOC, C20% SOC, C30% SOC, C40% SOC, C50% SOC, C60% SOC, C70% SOC, C80% SOC.

[0162] The charging time T of the battery cell from 10% SOC to 80% SOC is calculated according to the formula (60 / C20% SOC+60 / C30% SOC+60 / C40% SOC+60 / C50% SOC+60 / C60% SOC+60 / C70% SOC+60 / C80% SOC) x 10%, unit min. The shorter the time, the better the fast charging performance of the battery cell.

[0163] 3. The fast charging cycle life of the battery monomer is tested by the following method:

[0164] The charging rate at each SOC obtained by the fast charging capacity test is step-charged, that is, charged to 10% SOC at C10% SOC, charged to 20% SOC at C20% SOC, charged to 30% SOC at C30% SOC, charged to 40% SOC at C40% SOC, charged to 50% SOC at C50% SOC, charged to 60% SOC at C60% SOC, charged to 70% SOC at C70% SOC, charged to 80% SOC at C80% SOC, then charged to 100% SOC at 0.33C, and discharged to 2.5V at 0.33C, the battery monomer is cycled charged and discharged according to the above method until the capacity attenuation of the battery monomer is 80% of the first cycle discharge capacity, and the cycle number of the battery monomer is recorded.

[0165] 4. The reliability of the battery monomer is tested by the following method:

[0166] After the battery cell ends the cycle life test, it is charged to 4.25V at 0.33C, and then continuously charged at 0.33C until the battery cell thermal runaway, and whether the explosion-proof valve is normally opened when the battery cell thermal runaway is observed and recorded. If the explosion-proof valve is normally opened, there is no pole flying out, cover flying out, shell rupture and the like, which is normal opening; otherwise, if there is pole flying out, cover flying out, shell rupture and the like, which is not normal opening.

[0167] The performance test data of the battery cell are shown in Table 2.

[0168] Table 2:

[0169] Note: The "probability of passing" in Table 2 means that some experimental groups pass the test in the process of multiple parallel experiments, and the score represents the data passing the test.

[0170] It can be seen from the data in Table 2 that by optimizing and adjusting the structural design of the battery cell, and cooperating with the optimized electrolyte and negative electrode adjustment, the battery cell in the embodiments of the present application can have high energy density and fast charging performance, and at the same time, has high reliability.

[0171] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art, and other ways constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, comprising: a housing having an opening and a bottom wall opposite to the opening; The electrode assembly is housed in the housing and includes a main body, a first electrode tab, and a second electrode tab, wherein the first electrode tab and the second electrode tab have opposite polarities and are disposed on the same side of the main body; The first electrode tab and the second electrode tab extend from the open end of the shell, and an explosion-proof valve is provided on the bottom wall.

2. The battery cell according to claim 1, wherein: Based on the total area of ​​the bottom wall, the area of ​​the explosion-proof valve accounts for 20% to 60%, and the area of ​​the explosion-proof valve is 300mm 2 Up to 1000mm 2 .

3. The battery cell according to claim 2, wherein: Based on the total area of ​​the bottom wall, the area of ​​the explosion-proof valve accounts for 25% to 45%, and the area of ​​the explosion-proof valve is 450mm 2 Up to 800mm 2 .

4. The battery cell according to any one of claims 1 to 3, wherein: The battery cell includes a cylindrical battery cell, the length H of the cylindrical battery cell in the axial direction satisfies H≥70 mm, and the diameter D of the cylindrical battery cell satisfies 40 mm≤D≤60 mm.

5. The battery cell according to claim 4, wherein: The axial length H of the battery cell satisfies 80 mm ≤ H ≤ 120 mm; and / or The diameter D of the cylindrical battery cell satisfies 45 mm ≤ D ≤ 50 mm.

6. The battery cell according to claim 4 or 5, wherein: The main body includes a positive electrode tab, and a dimension L of the positive electrode tab along the axial direction of the battery cell and a length H of the battery cell in the axial direction satisfy 6 mm ≤ HL ≤ 13 mm.

7. The battery cell according to claim 6, wherein: The positive electrode plate includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a layered lithium-containing transition metal oxide.

8. The battery cell according to claim 7, wherein: The positive electrode active material includes a Ni-containing layered lithium-containing transition metal oxide, and the molar content of Ni element is greater than or equal to 80% based on the total molar amount of the Ni-containing layered lithium-containing transition metal oxide.

9. The battery cell according to any one of claims 1 to 8, wherein: The main body also includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based composite material.

10. The battery cell according to claim 9, wherein: The silicon-based composite material includes a carbon material matrix and a silicon material dispersed in the carbon material matrix. Based on the total weight of the silicon-based composite material, the weight content of the silicon material is greater than or equal to 1%.

11. The battery cell according to claim 10, wherein: The weight content of the silicon material is 2% to 20% based on the total weight of the silicon-based composite material; and / or The carbon material includes graphite.

12. The battery cell according to any one of claims 9 to 11, wherein: The surface density of the negative electrode film layer is less than or equal to 0.2g / 1540.25mm 2 .

13. The battery cell according to claim 12, wherein: The surface density of the negative electrode film layer is 0.07g / 1540.25mm 2 Up to 0.14g / 1540.25mm 2 .

14. The battery cell according to any one of claims 1 to 13, wherein: The battery cell further includes an electrolyte, the electrolyte includes an organic solvent, the organic solvent includes a chain carbonate, and the weight content of the chain carbonate is 50% to 90% based on the total weight of the organic solvent.

15. The battery cell according to claim 14, wherein: The chain carbonate includes one or more of dimethyl carbonate and ethyl methyl carbonate. 16 . A battery comprising the battery cell according to claim 1 .

17. An electrical device comprising the battery according to claim 16.

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