Battery cell, battery device, and electric device

Abstract

The invention provides a battery cell, a battery device and a power utilization device. The battery monomer comprises an electrode assembly, the electrode assembly comprises a positive electrode piece, the positive electrode piece comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode piece, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises lithium-containing phosphate, and the diaphragm resistance of the positive electrode piece is 0.02-5 ohm; the shell and the electrode assembly are located in the containing space of the shell, the shell comprises an end plate, at least one electrode terminal is arranged on the end plate, and the ratio of the orthographic projection area of a terminal main body part of the electrode terminal with the single polarity on the end plate to the area of the surface of the side, away from the electrode assembly, of the end plate is 5%-70%.

Description

[0001] Cross-reference to related applications This application claims the priority of PCT patent application PCT / CN2025 / 071090 entitled "Battery Cell, Battery Device, and Electrical Device" filed on January 7, 2025, the entire content of which is incorporated herein by reference. Technical field

[0002] The present disclosure relates to the field of batteries, and specifically, to battery cells, battery devices, and electrical devices. Background art

[0003] Lithium-ion batteries are not only applied to energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, but also widely used in electric transportation means such as electric bicycles, electric motorcycles, and electric vehicles, as well as in multiple fields such as military equipment and aerospace. However, current batteries still have many problems in practical applications and need to be further improved.

[0004] It should be noted that the above statements are only used to provide background technical information related to the present application and do not necessarily constitute prior art. Summary of the invention

[0005] In the first aspect of the present application, a battery cell is proposed, including: an electrode assembly, the electrode assembly includes a positive electrode tab, the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode tab, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes a lithium-containing phosphate, wherein the film resistance of the positive electrode tab is 0.02 Ω - 5 Ω; a housing, including an accommodation space, the electrode assembly is located in the accommodation space of the housing, the housing includes an end plate, at least one electrode terminal is provided on the end plate, the electrode terminal includes a terminal main body portion, and the ratio of the area of the positive projection of the terminal main body portion of the electrode terminal of a single polarity on the end plate to the area enclosed by the outer contour of the end plate is 5% - 70%. Thereby, the heat generation of the battery cell during the rate charge and discharge process can be effectively reduced, so that the battery cell can maintain a relatively stable temperature during the rate charge and discharge process, and the battery cell has excellent rate charge and discharge performance.

[0006] In some embodiments, the ratio of the area of the positive projection of the terminal main body portion of the electrode terminal of a single polarity on the end plate to the area enclosed by the outer contour of the end plate is 15% - 65%, optionally 20% - 60%. Thereby, the electrode terminal can provide better overcurrent capacity and a larger heat dissipation area, and there is sufficient space on the end plate for arranging other structural components.

[0007] In some embodiments, the film resistance of the positive electrode sheet is 0.05 Ω - 1 Ω. Thereby, the heat generation of the positive electrode sheet during charge and discharge can be reduced.

[0008] In some embodiments, the positive active material layer includes a conductive agent, and the mass fraction of the conductive agent in the positive active material layer is 0.5% - 5%. Thereby, the heat generation of the positive electrode sheet can be further reduced by constructing a conductive network.

[0009] In some embodiments, the positive active material layer includes a conductive agent, the conductive agent includes carbon nanotubes, and the mass fraction of carbon nanotubes in the positive active material layer is 0.1% - 1.1%. Thereby, by adding a small amount of carbon nanotubes, the impedance of the positive electrode sheet can be effectively reduced, and the heat generation can be reduced.

[0010] In some embodiments, the diameter of the carbon nanotubes is 1 nm - 16 nm; optionally, 1 nm - 8 nm. Thereby, the carbon nanotubes have relatively excellent electronic conductivity.

[0011] In some embodiments, the conductive agent further includes carbon black. Thereby, by using a variety of conductive agents in combination, a more uniform and dense conductive network can be formed, which is beneficial to reducing the internal resistance of the positive electrode sheet and reducing heat generation.

[0012] In some embodiments, the lithium-containing phosphate satisfies the general formula: Li x1 A y1 Me a M b P 1-c X c Y z , where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes at least one of Na, K, and Mg, Me includes at least one of Mn, Fe, Co, and Ni, M includes at least one of Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes at least one of S, Si, Cl, B, C, and N, and Y includes one or both of O and F. Thereby, the structural stability of the lithium-containing phosphate particles is relatively high, and the cycle stability during charge and discharge is relatively excellent, which is beneficial to improving the cycle performance of the battery cell.

[0013] In some embodiments, at least a part of the surface of the lithium-containing phosphate has a carbon coating layer. Based on the total mass of the lithium-containing phosphate and the carbon coating layer, the mass fraction of carbon element in the positive electrode active material is 0.7% - 1.5%. Thereby, the conductivity of the positive electrode active material can be improved.

[0014] In some embodiments, the powder resistivity of the positive electrode active material is 2 S / cm - 60 S / cm, optionally 2 S / cm - 30 S / cm. Thereby, it helps to reduce the internal resistance of the positive electrode sheet and reduce heat generation.

[0015] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, and the mass fraction of the lithium-rich material in the positive electrode active material layer is 0.1% - 5%. Thereby, the addition of an appropriate amount of lithium-rich material can not only make up for the irreversible lithium ion loss in the battery cell, but also has a relatively small impact on the internal resistance of the positive electrode sheet, which is beneficial to reducing heat generation.

[0016] In some embodiments, the lithium-rich material includes at least one of lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, lithium citrate, lithium nickelate, and lithium ferrate. Thereby, the lithium-rich material can supplement the consumption of active lithium during the first charge and store an additional part of lithium ions in the negative electrode active material, improving the capacity of the battery cell.

[0017] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 - 370 mg / 1540.25 mm 2 。Thereby, by controlling the number of active lithium ions per unit area of the positive electrode sheet, the polarization during high-rate charge and discharge can be effectively reduced, and the polarization internal resistance can be reduced.

[0018] In some embodiments, the compaction density of the positive electrode active material layer corresponding to 100% SOC of the battery cell is 2.50 g / cm 3 - 2.80 g / cm 3 。Thereby, the particles in the positive electrode active material layer are relatively closely packed, and the contact resistance between particles is small, which is beneficial to reducing the resistance of the positive electrode sheet and improving the energy density of the battery cell.

[0019] In some embodiments, in the length direction of the positive electrode current collector, the coating length of the positive electrode active material layer is 200 mm - 700 mm. Thereby, the length of the positive electrode active material layer is appropriate, the electron migration path is appropriate, the polarization is weak, and the heat generation is small.

[0020] In some embodiments, the end plate is provided with a lead-out hole, the electrode terminal further comprises a first limit portion and a second limit portion, the terminal body connects the first limit portion and the second limit portion, the terminal body is passed through the lead-out hole, the first limit portion is located on the side of the end plate facing the electrode assembly, and the second limit portion is located on the side of the end plate away from the electrode assembly. Thus, the electrode terminal can be firmly fixed on the end plate and electrically connected to the electrode assembly and the external circuit.

[0021] In some embodiments, the ratio of the orthographic projection area of ​​the terminal body on the end plate to the orthographic projection area of ​​the first limiting portion on the end plate is 30%-90%. Thus, the internal resistance of the electrode terminal can be reduced and heat generation can be reduced.

[0022] In some embodiments, along a direction parallel to the end plate, the cross section of the terminal body is a rounded rectangle, thereby facilitating assembly of the electrode terminal.

[0023] In some embodiments, each end plate includes two electrode terminals, and the two electrode terminals have the same polarity, or the two electrode terminals have opposite polarities. Thus, the current density inside the battery cell can be effectively dispersed, thereby reducing the current load on a single electrode terminal, which helps reduce the risk of local overheating.

[0024] In some embodiments, each end plate includes two electrode terminals with opposite polarities, and the electrode terminals of a single polarity on different end plates are staggered along the length direction of the battery cell, and optionally, the electrode terminals of a single polarity on different end plates are diagonally arranged along the length direction of the battery cell, thereby facilitating electrical connection of multiple battery cells.

[0025] In some embodiments, the electrode assembly is a laminate structure, the laminate structure includes a plurality of positive electrode sheets and a plurality of negative electrode sheets stacked, each of the positive electrode sheets includes the positive current collector, the positive current collector includes a positive electrode body and a positive electrode ear, each of the negative electrode sheets includes a negative current collector and a negative electrode ear, the negative current collector includes a negative electrode body and a negative electrode ear, wherein the positive electrode body is electrically connected to the positive electrode ear, the positive electrode ear is electrically connected to the positive terminal, the negative electrode body is electrically connected to the negative electrode ear, and the negative electrode ear is electrically connected to the negative terminal. Thus, the electrode assembly can make more full use of the internal space of the battery cell, reduce the waste of internal space, and help to evenly distribute heat inside the battery cell, which is beneficial to improving heat dissipation efficiency and reducing the risk of local overheating.

[0026] In some embodiments, the ratio of the number of the positive electrode tab ears to the number of the positive electrode current collectors is 1-2; and / or, the ratio of the number of the negative electrode tab ears to the number of the negative electrode current collectors is 1-2. Thereby, it helps to disperse the current density on the current collector and helps to reduce the risk of local overheating.

[0027] In some embodiments, along the width direction of the positive electrode main body, the total width of the positive electrode tab ears accounts for 80%-100% of the total width of the positive electrode main body; and / or, along the width direction of the negative electrode main body, the total width of the negative electrode tab ears accounts for 80%-100% of the total width of the negative electrode main body. Thereby, by adopting a tab ear structure with a larger area, the current-carrying capacity of the tab ears can be effectively improved, and the temperature rise of the battery cell during fast charging can be alleviated.

[0028] In some embodiments, it further includes: an electrolyte, and the conductivity of the electrolyte at room temperature is 10 mS / cm - 18 mS / cm. Thereby, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and reduce heat generation.

[0029] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s - 5.5 mPa·s. Thereby, the migration rate of lithium ions in the electrolyte is relatively high, which is beneficial to improving the rate charge and discharge performance.

[0030] In some embodiments, the electrolyte includes a chain carboxylic ester solvent. Thereby, the chain carboxylic ester solvent can improve the solubility of the electrolyte lithium salt, thereby improving the migration rate of lithium ions in the electrolyte.

[0031] In some embodiments, the chain carboxylic ester solvent satisfies formula I: Formula I, wherein, R 1 includes a hydrogen atom, C 1 -C 5 alkyl, C 1 -C 5 haloalkyl, or at least one of them, and R 2 includes C 1 -C 5 alkyl, C 1 -C 5 haloalkyl, or at least one of them. Thereby, by adopting the aforementioned chain carboxylic ester solvent, the viscosity and conductivity of the electrolyte can be controlled within an appropriate range.

[0032] In some embodiments, the chain carboxylic ester solvent includes Formula I-1, Formula I-2, Formula I-3, Formula I-4, Formula I-5, Formula I-6, Formula I-7, at least one of Formula I-8.

[0033] In some embodiments, the battery cell is configured to take 5 min - 10.5 min to charge from 10% SOC to 80% SOC. Thus, the battery cell has excellent rate charge and discharge performance.

[0034] In the second aspect of the present application, the present application provides a battery device, including the aforementioned battery cell, and the battery device includes at least one of a battery module, a battery pack, and an energy storage device. Thus, the battery device has all the features and advantages of the aforementioned battery cell, which will not be elaborated herein.

[0035] In the third aspect of the present application, the present application provides an electrical device, including the aforementioned battery cell. Thus, the electrical device has all the features and advantages of the aforementioned battery cell, which will not be elaborated herein. Description of the Drawings

[0036] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, where: Figure 1 is a partial structural schematic diagram of an end plate according to an embodiment of the present application.

[0037] Figure 2 is a structural schematic diagram of a cover plate assembly according to an embodiment of the present application.

[0038] Figure 3 is Figure 2 an exploded view of the cover plate assembly in.

[0039] Figure 4 is a top view of a cover plate assembly according to an embodiment of the present application.

[0040] Figure 5 is Figure 4 a cross-sectional view of the cover plate assembly in the AA' direction in.

[0041] Figure 6 is a structural schematic diagram of a cover plate assembly according to another embodiment of the present application.

[0042] Figure 7 is Figure 6 an exploded view of the cover plate assembly in.

[0043] Figure 8 is a top view of a cover plate assembly according to another embodiment of the present application.

[0044] Figure 9 isFigure 8 Cross-sectional view of the middle cover plate assembly in the BB' direction.

[0045] Figure 10 Schematic structural diagram of the housing of an embodiment of the present application.

[0046] Figure 11 Schematic structural diagram of a battery cell of an embodiment of the present application.

[0047] Figure 12 Schematic structural diagram of the cover plate assembly of another embodiment of the present application.

[0048] Figure 13 It is Figure 12 Exploded view of the middle cover plate assembly.

[0049] Figure 14 Top view of the cover plate assembly of another embodiment of the present application.

[0050] Figure 15 It is Figure 14 Cross-sectional view of the middle cover plate assembly in the CC' direction.

[0051] Figure 16 Schematic structural diagram of the cover plate assembly of another embodiment of the present application.

[0052] Figure 17 It is Figure 16 Exploded view of the middle cover plate assembly.

[0053] Figure 18 Top view of the cover plate assembly of another embodiment of the present application.

[0054] Figure 19 It is Figure 18 Cross-sectional view of the middle cover plate assembly in the DD' direction.

[0055] Figure 20 Positive electrode tab of an embodiment of the present application.

[0056] Figure 21 Schematic structural diagram of the electrode assembly of an embodiment of the present application.

[0057] Figure 22 Schematic structural diagram of the positive current collector of an embodiment of the present application.

[0058] Figure 23 Schematic structural diagram of the positive current collector of another embodiment of the present application.

[0059] Figure 24 Schematic structural diagram of the positive current collector of another embodiment of the present application.

[0060] Figure 25It is a schematic structural diagram of an electrode assembly prepared by a lamination process according to an embodiment of the present application.

[0061] Figure 26 It is a schematic structural diagram of an electrical device according to an embodiment of the present application.

[0062] Explanation of reference numerals: 1 Battery cell; 2 Positive electrode tab; 3 Negative electrode tab; 4 Separator; 21 Positive current collector; 22 Positive active material layer; 211 Positive main body part; 212 Positive electrode ear part; 311 Negative main body part; 312 Negative electrode ear part; 11 Housing; 111 First opening; 112 Second opening; 12 First cover assembly; 121 First end plate; 122 Positive electrode terminal; 123 First insulating member; 124 First sealing member; 125 First positioning member; 126 Second insulating member; 127 Riveting block; 1211 First through hole; 1212 Liquid injection hole; 1221 First limiting part of the positive electrode terminal; 1222 Terminal main body part of the positive electrode terminal; 1223 Second limiting part of the positive electrode terminal; 1231 Second through hole; 13 Second cover assembly; 131 Second end plate; 132 Negative electrode terminal; 133 Third insulating member; 134 Second sealing member; 135 Second positioning member; 136 Fourth insulating member; 137 Pressure relief part; 1311 Third through hole; 1321 First limiting part of the negative electrode terminal; 1322 Terminal main body part of the negative electrode terminal; 1323 Second limiting part of the negative electrode terminal; 1231 Second through hole; 1331 Fourth through hole. Detailed description of the embodiments

[0063] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings, but there may be cases where unnecessary details are omitted. For example, there may be cases where the detailed description of well-known matters is omitted and the repeated description of actually identical structures is omitted. This is to avoid the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided 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.

[0064] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs; the terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application; unless otherwise stated, the numerical values of the various parameters mentioned in the present application can be measured by various commonly used measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of the present application).

[0065] The terms "comprising" and "having" and any variations thereof in the description and claims of this application are open expressions, that is, they include the content specified in this application, but do not exclude other aspects of the content.

[0066] In the description of this application, whether or not words such as "about" or "approximately" are used, all the numbers disclosed herein are approximate values. There may be a difference of less than 10% in the numerical value of each number or a reasonable difference considered by those skilled in the art, such as a difference of 1%, 2%, 3%, 4% or 5%.

[0067] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4 and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0068] In the description of this application, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of this application.

[0069] In the description of this application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. The "first feature" and "second feature" may include one or more of such features.

[0070] In the description of this application, the meaning of "a plurality of" is two or more.

[0071] In the description of the present application, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween.

[0072] In the description of the present application, a first feature being "above", "over" and "on top of" a second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature.

[0073] In the description of the present application, "A and / or B" may include the case of A alone, the case of B alone, and any one of the cases of A and B, where A and B are only used for illustration and may be any technical features connected by "and / or" in the present application.

[0074] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0075] If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0076] The fast charging performance of the battery enables the user to replenish a large amount of power for the device in a relatively short time, reducing the charging waiting time and improving the user experience. During the fast charging process, the chemical reaction rate inside the battery cell accelerates, and the current output by the battery cell is relatively large. Further, when the internal resistance of the battery cell is relatively large, according to Joule's law, as the battery cell continuously operates under a relatively large current, a large amount of heat will be generated inside the battery cell, resulting in an obvious temperature rise. High temperature will accelerate the aging process of the chemical substances inside the battery cell, especially the evaporation of the electrolyte and the degradation of the positive electrode active material, leading to a rapid decrease in the battery capacity and a poor cycling performance of the battery. In extreme cases, overheating may cause the battery to experience a thermal runaway phenomenon, even leading to combustion or explosion, posing a serious threat to the user and the surrounding environment.

[0077] Lithium-containing phosphates have both low cost and high theoretical specific capacity, which helps to improve the energy density of a single battery cell. However, the powder resistivity of lithium-containing phosphates themselves is relatively high. Under fast charging conditions, the heat generation of the positive electrode sheet caused by the relatively high powder resistivity of the positive electrode active material powder, and the heat generation of mechanical parts due to the large current passing through the electrode terminals are the main reasons for the temperature rise of the single battery cell. In this application, by improving the main heat source of heat generation under large current conditions inside the single battery cell, the internal heat generation of the single battery cell under fast charging conditions is effectively reduced. Specifically, when the sheet resistance of the positive electrode sheet 2 is 0.02 Ω - 5 Ω, the internal resistance of the positive electrode sheet is small, the conduction path of electrons in the positive electrode active material layer is short, and the heat generation of the positive electrode sheet under fast charging conditions is less; at the same time, when the ratio of the area of the positive projection of the terminal main body 1222 of the positive electrode terminal and the terminal main body 1322 of the negative electrode terminal on the end plate to the area surrounded by the outer contour of the end plate is 5% - 70%, the current-carrying area of the electrode terminal is large, which helps to reduce the internal resistance of the electrode terminal, thereby reducing the heat generation at the electrode terminal and improving the heat dissipation at the electrode terminal. Thus, the heat generation of the single battery cell 1 during the rate charge and discharge process can be effectively reduced, and the rapid diffusion of the heat accumulated inside the single battery cell 1 can be accelerated, so that the single battery cell 1 can maintain a relatively stable temperature during the rate charge and discharge process, and the single battery cell 1 has better rate charge and discharge performance. This application controls the heat generation of the chemical system of the lithium-containing phosphate single battery cell and the heat generation of mechanical parts to jointly reduce the internal temperature rise of the single battery cell and improve the cycle performance of the single battery cell under fast charging.

[0078] The single battery cell proposed in this application can be used in electrical equipment using the single battery cell as a power source or various energy storage systems using the single battery cell as an energy storage element. The electrical equipment may include, but is not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, etc. Among them, the electric toys may include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc., and the spacecraft may include airplanes, rockets, space shuttles, and spaceships, etc.

[0079] In the first aspect of this application, a single battery cell is proposed, including: an electrode assembly, the electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode sheet, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes lithium-containing phosphate, wherein the sheet resistance of the positive electrode sheet is 0.02 Ω - 5 Ω; a housing, including an accommodation space, the electrode assembly is located in the accommodation space of the housing, the housing includes an end plate, and at least one electrode terminal is provided on the end plate, reference Figure 1, taking the positive electrode terminal as an example, the ratio of the orthographic projection area of the terminal main body portion 122 of the positive electrode terminal 122 on the end plate 121 to the area enclosed by the outer contour of the end plate 121 can be 5% - 70%. Taking the negative electrode terminal as an example, the ratio of the orthographic projection area of the terminal main body portion 1322 of the negative electrode terminal 132 on the end plate 131 to the area enclosed by the outer contour of the end plate 131 can be 5% - 70%. Thereby, the heat generation of the battery cell during the rate charge and discharge process can be effectively reduced, so that the battery cell can maintain a relatively stable temperature during the rate charge and discharge process, and the battery cell has better rate charge and discharge performance.

[0080] In some embodiments, the housing includes two end plates oppositely arranged along the length direction of the battery cell. For example, it may include a first end plate 121 and a second end plate 131.

[0081] As an example, the sheet resistance of the positive electrode plate 2 can be 0.02Ω, 0.05Ω, 0.1Ω, 0.5Ω, 1Ω, 1.5Ω, 2Ω, 2.5Ω, 3Ω, 3.5Ω, 4Ω, 4.5Ω or 5Ω.

[0082] As an example, the sheet resistance of the positive electrode plate can be measured by the following method: After discharging the battery to 0% SOC, disassemble the electrode plate, and use a solvent, such as dimethyl carbonate, to clean the electrode plate more than three times. 20 parallel samples can be taken along the central axis of the electrode plate. Each sample is symmetric along the central axis, and the size of each sample is 4cm×25cm. Among them, the central axis can be parallel to the length direction of the electrode plate. Use a sheet resistance tester (Yuaneng Technology, model BER2500) to test the above 20 parallel samples, and after calculating the average value, it is used as the sheet resistance of the electrode plate.

[0083] As an example, the ratio of the orthographic projection area of the terminal main body portion of the electrode terminal of a single polarity on the end plate to the area enclosed by the outer contour of the end plate can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or 70%.

[0084] It is understandable that the larger the ratio of the orthogonal projection area of ​​the terminal body of the single polarity electrode terminal on the end plate to the area of ​​the surface of the end plate on one side away from the electrode assembly, for example, when it is 80%, 90% or 100%, the larger the flow area of ​​the electrode terminal is, and the lower the internal resistance of the electrode terminal is. However, since the size of the first limiter needs to be larger than the size of the terminal body in order to play a role in limiting the movement of the electrode terminal, when the ratio of the orthogonal projection area of ​​the terminal body of the single polarity electrode terminal on the end plate to the area of ​​the surface of the end plate on one side away from the electrode assembly is too large, for example, when it is greater than 70%, the first limiter is more difficult to process, and the first limiter has a poor fixing effect on the electrode terminal, and cannot effectively achieve the effect of limiting the movement of the electrode terminal position.

[0085] It should be noted that the orthographic projection area of ​​the electrode terminal on the end plate refers to the projection area of ​​the area formed by the outer edge contour of the terminal body of the electrode terminal. When the end plate includes multiple electrode terminals, the orthographic projection area of ​​the terminal body of the electrode terminal of a single polarity on the end plate refers to the sum of the projection areas of the areas formed by the outer edge contours of the terminal body of the multiple electrode terminals. The area enclosed by the outer contour of the end plate refers to the projection area of ​​the area formed by the outer edge contour of the end plate.

[0086] In some embodiments, the end plate is provided with a lead-out hole, and the electrode terminal includes a terminal body, a first limiting part, and a second limiting part, the terminal body connects the first limiting part and the second limiting part, the terminal body is passed through the lead-out hole, the first limiting part is located on the side of the end plate facing the electrode assembly, and the second limiting part is located on the side of the end plate away from the electrode assembly. Thus, the electrode terminal can be firmly fixed on the end plate and electrically connected to the electrode assembly and the external circuit. In some embodiments, the first limiting part of the electrode terminal can be the lower seat of the electrode column of the electrode terminal, also called the inner column.

[0087] As an example, the electrode terminals include a positive electrode terminal 122 and a negative electrode terminal 132 .

[0088] In some embodiments, the first end plate 121 is provided with a through hole, such as Figure 3 The first through hole 1211 and the second through hole 1231 in the positive electrode terminal 122 include a terminal main body 1222 and a second stopper 1223. The terminal main body 1222 connects the second stopper 1223 and the first stopper 1221. The terminal main body 1222 sequentially passes through the second through hole 1231 and the first through hole 1211. The second stopper 1223 is located on the side of the first end plate 121 away from the electrode assembly. In this way, the positive electrode terminal can be fixed to the first end plate more firmly.

[0089] In some embodiments, the second end plate 131 is provided with through holes, such as Figure 7 the third through hole 1311 and the fourth through hole 1331 in . Further, the negative electrode terminal 132 includes a terminal main body portion 1322 and a second limiting portion 1323. The terminal main body portion 1322 connects the second limiting portion 1323 and the first limiting portion 1321. The terminal main body portion 1322 sequentially passes through the fourth through hole 1331 and the third through hole 1311, and the second limiting portion 1323 is located on the side of the second end plate 131 facing away from the electrode assembly. Thus, the negative electrode terminal can be relatively firmly fixed on the second end plate.

[0090] In some embodiments, the ratio of the orthographic projection area of the terminal main body portion of the electrode terminal of a single polarity on the end plate to the area enclosed by the outer contour of the end plate is 15% - 65%, optionally 20% - 60%. Thus, the electrode terminal can provide better overcurrent capacity and a larger heat dissipation area, and there is sufficient space on the end plate for arranging other structural components.

[0091] In some embodiments, the ratio of the orthographic projection area of the terminal main body portion on the end plate to the orthographic projection area of the first limiting portion on the end plate is 30% - 90%. Thus, the internal resistance of the electrode terminal can be reduced and heat generation can be decreased.

[0092] As an example, the ratio of the orthographic projection area of the terminal main body portion on the end plate to the orthographic projection area of the first limiting portion on the end plate can be 30%, 40%, 50%, 60%, 70%, 80% or 90%. The terminal main body portion is the smallest part of the cross-sectional area of the electrode terminal and has a great influence on the resistance of the electrode terminal. By controlling the area size of the terminal main body portion, the internal resistance of the electrode terminal can be effectively reduced and the overcurrent capacity of the electrode terminal can be improved.

[0093] In some embodiments, the battery cell includes a housing 11, a first cover assembly 12 and a second cover assembly 13. The housing, the first cover assembly and the second cover assembly define an accommodation cavity. The first cover assembly includes a first end plate 121 and at least one positive electrode terminal 122. The positive electrode main body portion is electrically connected to the positive electrode terminal 122 through the positive electrode ear portion; and / or, the second cover assembly includes a second end plate 131 and at least one negative electrode terminal 132. The negative electrode main body portion is electrically connected to the negative electrode terminal 132 through the negative electrode ear portion.

[0094] Specifically, referring to Figure 10, both ends of the housing 11 along its length direction have a first opening 111 and a second opening 112. The length direction of the housing 11 is the same as that of the positive current collector. The first cover assembly 12 is adapted to cover the first opening 111, and the second cover assembly 13 is adapted to cover the second opening 112 to isolate the internal environment of the battery cell from the external environment. The housing, the first cover assembly, and the second cover assembly define a receiving cavity, and the electrode assembly is disposed in the receiving cavity. The shapes of the first cover assembly and the second cover assembly can be adapted to the shape of the housing to cooperate with the housing. The first cover assembly and the second cover assembly can be independently made of a material with a certain hardness and strength (such as aluminum alloy), so that the first cover assembly and the second cover assembly have higher strength. Thus, when the first cover assembly and the second cover assembly are subjected to extrusion, the deformation of the first cover assembly and the second cover assembly is reduced, and the safety performance of the battery cell is improved.

[0095] In some embodiments, the first cover assembly, the second cover assembly, and the housing can be independent components.

[0096] In some embodiments, the first cover assembly, the second cover assembly, and the housing are integrated. Specifically, the first cover assembly, the second cover assembly, and the housing can form a common connection surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing, then the first cover assembly covers the first opening of the housing, and the second cover assembly covers the second opening of the housing.

[0097] In some embodiments, referring to Figures 2 - 5 , the first cover assembly 12 includes a first end plate 121 and a positive electrode terminal 122. The positive electrode terminal 122 is disposed on one side of the first end plate 121 close to the electrode assembly. A first through hole 1211 is provided on the first end plate 121; a first insulating member 123 is disposed between the first end plate 121 and the positive electrode terminal 122. The first insulating member 123 is adapted to isolate the electrical connection components in the housing from the first end plate 121 to reduce the risk of short circuit. A second through hole 1231 is provided on the first insulating member 123, and the positive electrode terminal 122 sequentially passes through the second through hole 1231 and the first through hole 1211; on the side of the first end plate 121 away from the electrode assembly, a first sealing member 124, a first positioning member 125, a second insulating member 126, and a riveting block 127 are sequentially disposed. The riveting block is adapted to fix the positive electrode terminal 122 on the first end plate 121.

[0098] In some embodiments, referring to Figures 6 - 9, the second cover plate assembly 13 includes a second end plate 131 and a negative electrode terminal 132. The negative electrode terminal 132 is disposed on one side of the second end plate 131 close to the electrode assembly. A third through hole 1311 is provided on the second end plate 131. A third insulating member 133 is disposed between the second end plate 131 and the negative electrode terminal 132. The third insulating member 133 is adapted to isolate the electrical connection components in the housing from the second end plate 131 to reduce the risk of short circuit. A fourth through hole 1331 is provided on the third insulating member 133. The negative electrode terminal 132 sequentially passes through the fourth through hole 1331 and the third through hole 1311. On the side of the second end plate 131 away from the electrode assembly, a second sealing member 134, a second positioning member 135, a fourth insulating member 136, and the riveting block 127 are sequentially disposed. The riveting block 127 is adapted to fix the negative electrode terminal 132 on the second end plate 131.

[0099] As an example, the first insulating member 123, the second insulating member 126, the third insulating member 133, and the fourth insulating member 136 can be independently plastics, rubbers, etc.

[0100] In some embodiments, referring to Figures 1 - 5 , a liquid injection hole 1212 is provided on the first end plate 121. The liquid injection hole 1212 can be used to inject electrolyte; referring to Figures 6 - 9 , a pressure relief portion 137 is provided on the second end plate 131. When the pressure inside the housing exceeds a threshold value, the pressure relief portion 137 can release the pressure inside the housing.

[0101] As an example, the pressure relief portion 137 and the second end plate 131 are two separate components, which are separately formed and then installed together. The pressure relief portion 137 can be components such as an explosion-proof sheet, an explosion-proof valve, a safety valve, etc. The pressure relief portion 137 can be installed on the second end plate 131 by bonding, welding, etc. When the pressure inside the battery cell reaches the threshold value, the pressure relief portion 137 opens at least part of the pressure relief holes, and the discharge cut-off inside the battery cell is discharged through the pressure relief holes to release the pressure inside the battery cell.

[0102] In some embodiments, referring to Figure 3 and Figure 7 , along the direction parallel to the end plate, the cross section of the terminal main body portion 1222 / 1322 is a rounded rectangle. Thus, it is convenient for the assembly of the electrode terminals.

[0103] In some embodiments, each end plate includes two of the electrode terminals, and the two electrode terminals have the same polarity or the two electrode terminals have opposite polarities. Thus, the current density inside the battery cell can be effectively dispersed, thereby reducing the current load on a single electrode terminal and helping to reduce the risk of local overheating.

[0104] In some embodiments, when each of the end plates includes a plurality of electrode terminals, for example, two electrode terminals, the ratio of the area of the positive projection of the terminal body portion of each electrode terminal on the end plate to the area enclosed by the outer contour of the end plate is the same.

[0105] In some embodiments, referring to Figure 13 and Figure 17 , each of the end plates includes two of the electrode terminals, and the polarities of the two electrode terminals are opposite. Thereby, the current density inside the battery cell 1 can be effectively dispersed, thereby reducing the current load on a single electrode terminal, alleviating the uneven polarization inside the battery cell, and reducing the risk of local overheating.

[0106] In some embodiments, each of the end plates includes two electrode terminals with opposite polarities, and the electrode terminals of a single polarity on different end plates are arranged in a staggered manner along the length direction of the battery cell. Optionally, the electrode terminals of a single polarity on different end plates are arranged diagonally along the length direction of the battery cell. Thereby, it is convenient to electrically connect a plurality of battery cells. Thereby, it is convenient to electrically connect a plurality of battery cells 1 and helps to alleviate the uneven polarization inside the battery cell.

[0107] In some embodiments, the first cover assembly 12 includes one positive electrode terminal 122 and one negative electrode terminal 132; and / or, the second cover assembly 13 includes one positive electrode terminal 122 and one negative electrode terminal 132.

[0108] Specifically, referring to Figures 12 - 15 , the first cover assembly 12 includes a first end plate 121, the first end plate 121 includes one positive electrode terminal 122 and one negative electrode terminal 132, two first through holes are provided on the first cover assembly, a first insulating member 123 is provided between the first end plate 121 and the positive electrode terminal 122 and the negative electrode terminal 132, two second through holes 1231 are provided on the first insulating member 123, the positive electrode terminal 122 sequentially passes through the correspondingly arranged second through hole 1231 and the first through hole 1211, the negative electrode terminal 132 sequentially passes through the correspondingly arranged second through hole 1231 and the first through hole 1211, and a first sealing member 124, a first positioning member 125, a second insulating member 126 and a riveting block 127 are sequentially arranged on the side of the first end plate 121 away from the electrode assembly.

[0109] Specifically, referring to Figures 16 - 19, the second cover plate assembly 13 includes a second end plate 131. The second end plate 131 includes one of the positive electrode terminals 122 and one of the negative electrode terminals 132. Two third through holes 1311 are provided on the second end plate 131. A second insulating member 133 is provided between the second end plate 131, the negative electrode terminal 132, and the positive electrode terminal 122. Two fourth through holes 1331 are provided on the third insulating member 133. The positive electrode terminal 122 sequentially passes through the correspondingly arranged fourth through hole 1331 and the third through hole 1311. The negative electrode terminal 132 sequentially passes through the correspondingly arranged fourth through hole 1331 and the third through hole 1311. On the side of the second end plate 131 away from the electrode assembly, a second sealing member 134, a second positioning member 135, a fourth insulating member 136, and the riveting block 127 are sequentially arranged.

[0110] In some embodiments, referring to Figure 21 , the electrode assembly is a laminated structure. The laminated structure includes a plurality of positive electrode plates and a plurality of negative electrode plates stacked. Each positive electrode plate includes the positive current collector. The positive current collector includes a positive main body portion and a positive electrode ear portion. Each negative electrode plate includes a negative current collector and a negative electrode ear portion. The negative current collector includes a negative main body portion and a negative electrode ear portion. Among them, the positive main body portion is electrically connected to the positive electrode ear portion. The positive electrode ear portion is electrically connected to the positive terminal. The negative main body portion is electrically connected to the negative electrode ear portion. The negative electrode ear portion is electrically connected to the negative terminal. Thus, the positive electrode plate 2, the separator 4, and the negative electrode plate 3 can make more full use of the internal space of the battery cell 1, reduce the waste of internal space, and help the heat to be evenly distributed inside the battery cell 1, which is beneficial to improving the heat dissipation efficiency and reducing the risk of local overheating.

[0111] In some embodiments, the battery cell is configured to have a charging time from 10% SOC to 80% SOC of 5 min - 10.5 min. Thus, the battery cell has excellent rate charge and discharge performance.

[0112] Taking the electrical device as an automobile as an example, in the actual use scenario, for an automobile, the state of charge (SOC) of its battery is usually between 10% and 80%. Thus, when the charging time of the battery in this SOC range is short, the waiting time of the user for charging can be reduced, greatly improving the user experience.

[0113] Under normal circumstances, a battery cell includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0114] [Positive electrode plate] In some embodiments, the sheet resistance of the positive electrode plate is 0.05 Ω - 1 Ω. Thereby, heat generation of the positive electrode plate during the charging and discharging process can be reduced.

[0115] In some embodiments, the positive electrode active material layer includes a conductive agent, and the mass fraction of the conductive agent in the positive electrode active material layer is 0.5% - 5%. Thereby, by adding the conductive agent, a conductive network can be constructed, effectively connecting the positive electrode active material particles, shortening the electron conduction path, improving the overcurrent internal resistance of the electrode plate, and further reducing the heat generation of the positive electrode plate.

[0116] As an example, the mass fraction of the conductive agent in the positive electrode active material layer 22 can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0117] In some embodiments, the positive electrode active material layer includes a conductive agent, the conductive agent includes carbon nanotubes, and the mass fraction of the carbon nanotubes in the positive electrode active material layer is 0.1% - 1.1%. Thereby, by adding a small amount of carbon nanotubes, the impedance of the positive electrode plate can be effectively reduced, and heat generation can be reduced.

[0118] Thereby, by adding a small amount of carbon nanotubes, the impedance of the positive electrode plate 2 can be effectively reduced, and heat generation can be reduced.

[0119] As an example, the mass fraction of the carbon nanotubes in the positive electrode active material layer 22 can be 0.1%, 0.5%, 1% or 1.1%.

[0120] Carbon nanotubes have high electron conduction ability, can form a complex three-dimensional conductive network, improve the interfacial contact between the positive electrode active material particles and the current collector, significantly reduce the sheet resistance of the positive electrode plate, and contribute to improving the rate charge and discharge performance of the battery.

[0121] In some embodiments, the diameter of the carbon nanotubes is 1 nm - 16 nm; optionally, 1 nm - 8 nm. Thereby, the carbon nanotubes have better electron conductivity.

[0122] As an example, the diameter of the carbon nanotubes is 1 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm or 16 nm.

[0123] It should be noted that the tube diameter of the aforementioned carbon nanotubes refers to the sum of the inner diameter and the wall thickness of the carbon nanotubes.

[0124] As an example, the tube diameter of the carbon nanotubes can be measured by the following method: Using a scanning electron microscope (SEM), gold is sprayed on the surface of the carbon nanotube sample, and the morphology of the sample is directly observed and the tube diameter is measured.

[0125] In some embodiments, the conductive agent further includes carbon black. Thus, by mixing different forms and sizes of conductive agents, a more uniform and dense conductive network can be formed between the positive electrode active materials, which is beneficial to reducing the internal resistance of the positive electrode sheet 2, improving the charge and discharge efficiency, and reducing heat generation.

[0126] In some embodiments, the lithium-containing phosphate satisfies the general formula: Li x1 A y1 Me a M b P 1-c X c Y z , where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes at least one of Na, K, and Mg, Me includes at least one of Mn, Fe, Co, and Ni, M includes at least one of Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes at least one of S, Si, Cl, B, C, and N, and Y includes one or both of O and F. Thus, the lithium-containing phosphate has relatively high ionic conductivity and electronic conductivity, and the structural stability of the lithium-containing phosphate particles is relatively high, and the cycle stability during charge and discharge is relatively excellent, which is beneficial to improving the cycle performance of the battery cell.

[0127] During the charge and discharge process of the battery, the deintercalation and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, after charge and discharge cycling, the molar content of Li will change.

[0128] In the listing of the positive electrode active materials for lithium ion batteries in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will show fluctuations.

[0129] In some embodiments, at least a part of the surface of the lithium-containing phosphate has a carbon coating layer. Based on the total mass of the lithium-containing phosphate and the carbon coating layer, the mass fraction of carbon element in the positive electrode active material is 0.7% - 1.5%. Thus, the carbon coating layer can effectively alleviate the poor electronic conductivity of the lithium-containing phosphate, reduce the resistance of the positive electrode active material in the positive electrode active material layer, and improve the specific capacity of the positive electrode active material.

[0130] As an example, based on the total mass of the lithium-containing phosphate and the carbon coating layer, the mass fraction of carbon element in the positive electrode active material can be 0.7%, 0.9%, 1.1%, 1.3% or 1.5%.

[0131] As an example, based on the total mass of the lithium-containing phosphate and the carbon coating layer, the mass fraction of carbon element in the positive electrode active material can be tested by the following method: Turn on all power switches of the carbon and sulfur analyzer, press the "zeroing" button, open the oxygen valve of the carbon and sulfur analyzer, and adjust the oxygen pressure to 0.02 - 0.04 MPa. Open the "front oxygen" and "back control", and adjust the flowmeter to control at about 100 L / h. Add silicon molybdenum powder (about 0.3 g), the weighed sample (250 mg), tin grains (0.3 g), and pure iron (1 g) into the crucible in sequence, and close the crucible. Click the "test" button to start the test. After the test is completed, the test result will be automatically displayed, and record this result as the C content.

[0132] In some embodiments, the powder resistivity of the positive electrode active material is 2 S / cm - 60 S / cm, optionally 2 S / cm - 30 S / cm. Thus, it helps to reduce the internal resistance of the positive electrode plate and reduce heat generation.

[0133] As an example, the powder resistivity of the positive electrode active material can be tested by the following method: According to the test standard GB / T30835 - 2014, use the PRCD1100 powder resistivity meter for testing.

[0134] In some embodiments, the positive electrode active material layer 22 further includes a lithium-rich material, and the mass fraction of the lithium-rich material in the positive electrode active material layer 22 is 0.1% - 5%. Thus, the addition of an appropriate amount of lithium-rich material can not only make up for the irreversible lithium ion loss in the battery cell 1, but also has a small impact on the internal resistance of the positive electrode plate 2, which is beneficial to reducing heat generation.

[0135] As an example, the mass fraction of the lithium-rich material in the positive electrode active material layer 22 can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0136] When the mass fraction of the lithium-rich material in the positive electrode active material layer 22 is within the aforementioned range, it can not only better supplement the loss of active lithium ions, but also help the positive electrode active material layer to carry more positive electrode active materials, thereby improving the energy density of the battery cell.

[0137] When the battery is charged for the first time, an SEI film will be formed on the surface of the negative electrode active material, and the rupture and recombination of the SEI during the charge-discharge cycle will both cause irreversible consumption of lithium ions, resulting in a decrease in the first-cycle efficiency and capacity loss of the battery cell. By adding the lithium-rich material, this part of the lost lithium can be pre-supplemented during the battery preparation process, reducing or eliminating the capacity attenuation caused by lithium loss and extending the cycle life of the battery.

[0138] In some embodiments, the lithium-rich material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganite, lithium tartrate, lithium citrate, lithium nickelate, and lithium ferrite. Thus, the lithium-rich material can supplement the consumption of active lithium during the first charge and store some additional lithium ions in the negative electrode active material, enhancing the capacity utilization of the battery cell 1.

[0139] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 -370 mg / 1540.25 mm 2 。Thus, by controlling the number of active lithium ions per unit area of the positive electrode plate, the polarization during high-rate charge and discharge can be effectively reduced, and the polarization internal resistance can be decreased.

[0140] As an example, the single-sided coating weight of the positive electrode active material layer can be 200 mg / 1540.25 mm 2 、210 mg / 1540.25 mm 2 、220 mg / 1540.25 mm 2 、230 mg / 1540.25 mm 2 、240 mg / 1540.25 mm 2 、250 mg / 1540.25 mm 2 、260 mg / 1540.25 mm 2 、270 mg / 1540.25 mm 2 、280 mg / 1540.25 mm 2 、290 mg / 1540.25 mm 2 、300 mg / 1540.25 mm 2 、310 mg / 1540.25 mm 2 、320 mg / 1540.25 mm2 、330 mg / 1540.25 mm 2 、340 mg / 1540.25 mm 2 、350 mg / 1540.25 mm 2 、360 mg / 1540.25 mm 2 or 370 mg / 1540.25 mm 2 。

[0141] As an example, the single-sided coating weight of the positive electrode active material layer can be obtained by the following method: disassemble the positive electrode plate from the battery cell, take the single-sided coated positive electrode plate (if it is a double-sided coated positive electrode plate, the positive electrode active material layer on one side can be wiped off first), and punch it into small round pieces with an area of S 1 , weigh it, and record it as M 1 . Then wipe off the positive electrode active material layer of the above-mentioned weighed positive electrode plate, weigh the weight of the positive electrode current collector, and record it as M 0 . The single-sided coating weight of the positive electrode active material layer = (M 1 - M 0 ) / S 1 .

[0142] In some embodiments, the compaction density of the positive electrode active material layer corresponding to 100% SOC of the battery cell is 2.50 g / cm 3 - 2.80 g / cm 3 . Thus, the particles in the positive electrode active material layer 22 are stacked relatively tightly, and the contact resistance between particles is small, which is beneficial to reducing the resistance of the positive electrode plate 2 and improving the energy density of the battery cell 1.

[0143] As an example, the compaction density of the positive electrode active material layer corresponding to 100% SOC of the battery cell 1 can be 2.50 g / cm 3 , 2.55 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.70 g / cm 3 , 2.75 g / cm 3 or 2.80 g / cm 3 .

[0144] When the compaction density of the positive electrode active material layer is within the aforementioned range, the particles in the positive electrode active material layer are stacked relatively tightly, and the positive electrode plate has both a high energy density and a low film resistance.

[0145] As an example, the compaction density of the positive electrode active material layer corresponding to 100% SOC of the battery cell can be obtained by the following method: Charge the battery cell at a constant current of 1 / 3C to 3.8V, then charge it at a constant voltage of 3.8V to 0.05C. Disassemble the positive electrode plate from the battery cell. For example, take a single-sided coated positive electrode plate (if it is a double-sided coated electrode plate, the positive electrode active material layer on one side can be wiped off first), and punch it into small circular pieces with an area of S 1 , weigh them, and record it as M 1 , and measure its thickness H 1 . Then wipe off the positive electrode active material layer of the above-mentioned weighed positive electrode plate, weigh the positive electrode current collector, record it as M 0 , and measure its thickness H 0 . The single-sided coating weight of the positive electrode active material layer = (M 1 - M 0 ) / S 1 , the thickness of the positive electrode active material layer = H 1 - H 0 , and the compaction density of the positive electrode active material layer = the single-sided coating weight of the positive electrode active material layer / the thickness of the positive electrode active material layer.

[0146] In some embodiments, referring to Figure 20 , in the length direction of the positive electrode current collector 21, the coating length of the positive electrode active material layer 22 is 200 mm - 700 mm. Thus, the length of the positive electrode active material layer 22 is appropriate, the electron migration path is appropriate, the polarization is weak, and the heat generation is small.

[0147] As an example, in the length direction of the positive electrode current collector 21, the coating length of the positive electrode active material layer 22 can be 200 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm or 700 mm.

[0148] When the coating length of the positive electrode active material layer 22 is 200 mm - 700 mm, the battery cell 1 can be in a strip-shaped structure. The strip-shaped battery cells can be directly arranged and combined to form a battery pack, eliminating the intermediate module structure. Thus, it is convenient to closely arrange multiple battery cells 1 in the battery device, reducing the extra gaps and unnecessary structural components, thereby improving the space utilization rate of the battery device and the energy density of the battery device.

[0149] In some embodiments, the positive electrode current collector 21 includes a positive electrode main body portion 211 and at least one positive electrode tab 212, and the positive electrode main body portion 211 is connected to the positive electrode tab 212. Thus, the positive electrode plate 2 can be electrically connected to the electrode terminal through the corresponding tab.

[0150] In some embodiments, the electrode terminal can be electrically connected to the positive electrode tab through a connecting piece. Specifically, the first limiting portion 1221 of the electrode terminal can be electrically connected to the positive electrode tab through the connecting piece. Thereby, the welding quality and connection reliability between the electrode terminal and the tab can be significantly improved.

[0151] When realizing the electrical connection between the electrode terminal and the positive electrode tab through a connecting piece, the shape and size of the connecting piece can be adjusted as needed to adapt to different distances and positions. Moreover, the connecting piece has fewer welding process defects, which can help distribute the current more evenly, reduce local overheating and potential difference, and improve the fast charging performance of the battery.

[0152] In some embodiments, the electrode terminal can be directly electrically connected to the positive electrode tab. Specifically, the first limiting portion 1221 of the electrode terminal can be directly electrically connected to the positive electrode tab. Thereby, it helps to reduce the structural complexity inside the battery cell, reduce the volume of the battery cell, and improve the energy density.

[0153] When the electrode terminal is directly electrically connected to the positive electrode tab, the connecting piece is omitted, the internal structure of the battery cell is simplified, the assembly steps are reduced, and the overall manufacturing cost is lowered.

[0154] In some embodiments, the ratio of the number of the positive electrode tabs to the number of the positive current collectors is 1-2. Thereby, it helps to disperse the current density on the current collector and helps to reduce the risk of local overheating.

[0155] The electrical connection between the tab and the terminal is realized, so as to output the current inside the battery cell to the external circuit. The ratio of the number of the positive electrode tabs 212 to the number of the positive current collectors 21 corresponds to the number of positive electrode tabs on each positive current collector. The number of positive electrode tabs on a single positive current collector corresponds to the number of electrode terminals on the end plate. Thus, through the design of multiple tabs matching the design of multiple electrode terminals, multiple electron transfer paths can be realized within the electrode assembly, shortening the electron transfer path, reducing the internal resistance of the battery cell, and reducing heat generation.

[0156] As an example, referring to Figures 22 - 24 , the ratio of the number of the positive electrode tabs 212 to the number of the positive current collectors 21 can be 1, 2, 3 or 4.

[0157] As an example, referring to Figure 23, the positive current collector includes the positive electrode main body portion 211 and a plurality of the positive electrode tab portions 212. At least two of the positive electrode tab portions 212 are located on opposite sides of the positive electrode main body portion 211. Similarly, the negative current collector may include the negative electrode main body portion and a plurality of the negative electrode tab portions, and at least two of the negative electrode tab portions are located on opposite sides of the negative electrode main body portion. Thereby, a more uniform heat distribution can be provided, and the deformation of the tabs caused by excessive force on one side can be reduced.

[0158] As an example, referring to Figure 24 , the positive current collector includes the positive electrode main body portion 211 and a plurality of the positive electrode tab portions 212 spaced apart along the length direction of the positive current collector. Similarly, the negative current collector may also include the negative electrode main body portion 311 and a plurality of the negative electrode tab portions 312 spaced apart along the length direction of the negative current collector.

[0159] When the positive current collector includes a plurality of the positive electrode tab portions 212 and the negative current collector includes a plurality of the negative electrode tab portions 312, the transmission path of electrons between the positive electrode tab portions and the negative electrode tab portions is shorter, which can reduce the heat generation of the battery and improve the fast charging performance.

[0160] In some embodiments, along the width direction of the positive electrode main body portion, the total width of the positive electrode tab portions accounts for 80% - 100% of the total width of the positive electrode main body portion. Thereby, by adopting a tab structure with a larger area, the current-carrying capacity of the tab portions can be effectively improved, and the temperature rise of the battery cell during fast charging can be alleviated.

[0161] As an example, the total width of the positive electrode tab portions 212 accounts for 80%, 85%, 90%, 95% or 100% of the total width of the positive electrode main body portion 211.

[0162] When the battery cell performs high-rate charge and discharge, both the current and voltage inside the battery cell will increase accordingly, and the current passing through the tabs increases. A larger positive electrode tab area means a lower resistance. On the one hand, according to Ohm's law, at the same voltage, a tab with a larger area can carry a higher current, that is, it has a stronger current-carrying capacity. On the other hand, when the resistance of the tab is small, the heat generated due to resistance loss after the current passes through the tab can be reduced, the heat generation of the battery under high current is reduced, and the heat dissipation efficiency of the battery is indirectly improved.

[0163] In some specific embodiments, referring to Figure 22, taking the preparation of an electrode assembly by a stacking process as an example, the positive electrode plate used is rectangular. At this time, one of the short sides of the positive current collector has a positive electrode tab 212 extending along the length direction of the positive current collector. The width of the positive electrode tab is W1. At this time, the total width of the positive electrode tabs is equal to the width W1 of the positive electrode tab, and the total width V1 of the positive electrode main body is the width of the positive current collector. Similarly, the corresponding negative current collector can also have a similar structure, which will not be elaborated here.

[0164] In some specific embodiments, referring to Figure 23 , taking the preparation of an electrode assembly by a stacking process as an example, the positive electrode plate used is rectangular. At this time, both short sides of the positive current collector have positive electrode tabs 212 extending along the length direction of the positive current collector, and the extending directions of the two positive electrode tabs 212 are opposite. Among them, the widths W1 of the multiple positive electrode tabs 212 can be the same or different. At this time, the total width of the positive electrode tabs is the sum of the widths W1 of the multiple positive electrode tabs, and the total width V1 of the positive electrode main body is the width of the positive current collector. Similarly, the corresponding negative current collector can also have a similar structure, which will not be elaborated here.

[0165] In some specific embodiments, referring to Figure 24 , taking the preparation of an electrode assembly by a stacking process as an example, the positive electrode plate used is rectangular. At this time, one of the long sides of the positive current collector has multiple positive electrode tabs 212 extending along the width direction of the positive current collector, and the multiple positive electrode tabs 212 are arranged at intervals along the length direction of the positive current collector. Among them, the width of each positive electrode tab can be the same or different. Taking three positive electrode tabs as an example, the widths of the three positive electrode tabs 212 are L1, L2, and L3 respectively. L1, L2, and L3 can all be the same, or all different, or any two of them can be the same. At this time, the total width of the positive electrode tabs is the sum of the widths of the multiple positive electrode tabs, that is, W1 = L1 + L2 + L3, and the total width V1 of the positive electrode main body is the length of the positive current collector. Similarly, the corresponding negative current collector can also have a similar structure. At this time, the total width of the negative electrode tabs is the sum of the widths of the multiple negative electrode tabs, and the width of the negative electrode main body is the length of the negative current collector.

[0166] It should be noted that when the electrode assembly is prepared by a stacking process, the electrode assembly can include a structure of multiple layers of continuously arranged positive electrode plates / separator membranes / negative electrode plates / separator membranes. At this time, the ratio of the total width of the aforementioned positive electrode tabs to the total width V1 of the positive electrode main body corresponds to the ratio of the width of the positive electrode tabs to the width of the positive electrode main body in any positive electrode plate. Similarly, the ratio of the total width of the aforementioned negative electrode tabs to the total width V2 of the negative electrode main body corresponds to the ratio of the width of the negative electrode tabs to the width of the negative electrode main body in any negative electrode plate.

[0167] In some embodiments, with reference to Figure 25 , in an electrode assembly prepared by a lamination process, a plurality of positive electrode tab portions 212 may be misaligned (at least partially overlapped between adjacent positive electrode tab portions). At this time, the total width W3 of the positive electrode tab portions 212 can be regarded as the total width after stacking of the plurality of positive electrode tab portions 212 after lamination of the corresponding positive electrode sheet, negative electrode sheet, and separator film. The total width V1 of the positive electrode main body portion is the width of the positive electrode current collector. Similarly, a plurality of negative electrode tab portions 312 may also be misaligned (at least partially overlapped between adjacent negative electrode tab portions). At this time, the total width W4 of the negative electrode tab portions 312 can be regarded as the total width after stacking of the plurality of negative electrode tab portions 22 after lamination of the corresponding positive electrode sheet, negative electrode sheet, and separator film. The total width V2 of the negative electrode main body portion is the width of the negative electrode current collector.

[0168] In some embodiments, the widths and total widths of the positive electrode tab portions and the negative electrode tab portions may be the same. When the widths of the positive electrode current collector and the negative electrode current collector are also the same, along the width direction of the positive electrode main body portion, the ratio of the total width of the positive electrode tab portions to the total width of the positive electrode main body portion is the same as the ratio of the total width of the negative electrode tab portions to the total width of the negative electrode main body portion along the width direction of the negative electrode main body portion.

[0169] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0170] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. 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 can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0171] In some embodiments, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0172] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0173] In some embodiments, the positive electrode plate can be prepared in the following manner: Dispersing the above-mentioned components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; Coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0174] In some embodiments, the positive electrode plate can be prepared in the following manner: Dispersing the above-mentioned components for preparing the positive electrode plate, such as the positive electrode active material, the lithium-rich material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; Coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0175] In some embodiments, the positive electrode plate can be prepared in the following manner: Dispersing the positive electrode active material, the conductive agent, the binder, and any other components in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; Coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, to form a positive electrode active material layer, and then on the surface of the positive electrode active material layer, by means such as spraying and secondary coating, the lithium-rich material is compounded with the positive electrode active material layer.

[0176] [Negative electrode plate] In some embodiments, the negative electrode plate 3 includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode current collector includes a negative electrode main body portion 311 and at least one negative electrode tab 312, and the negative electrode main body portion 311 is connected to the negative electrode tab 312. Thus, the negative electrode plate 3 can be electrically connected to the electrode terminal through the corresponding tab.

[0177] In some embodiments, the electrode terminal and the negative electrode tab can be electrically connected through a jumper. Specifically, the first limiting portion 1321 of the electrode terminal can be electrically connected to the negative electrode tab through the jumper. Thus, the welding quality and connection reliability between the electrode terminal and the tab can be significantly improved.

[0178] When realizing the electrical connection between the electrode terminal and the negative electrode tab through the jumper, the shape and size of the jumper can be adjusted as needed to adapt to different distances and positions, and the welding process defects of the jumper are less, which can help to more evenly distribute the current, reduce local overheating and potential difference, and improve the fast charging performance of the battery.

[0179] In some embodiments, the electrode terminal can be directly electrically connected to the negative electrode tab. Specifically, the first limiting portion 1321 of the electrode terminal can be directly electrically connected to the negative electrode tab. Thereby, it helps to reduce the structural complexity inside the battery cell, reduce the volume of the battery cell, and improve the energy density.

[0180] When the electrode terminal is directly electrically connected to the negative electrode tab, the connecting piece is omitted, the internal structure of the battery cell is simplified, the assembly steps are reduced, and the overall manufacturing cost is reduced.

[0181] In some embodiments, the ratio of the number of the negative electrode tabs to the number of the negative current collectors is 1-2. Thereby, it helps to disperse the current density on the current collector and helps to reduce the risk of local overheating.

[0182] In some embodiments, the ratio of the number of the negative electrode tabs 312 to the number of the negative current collectors can be 1, 2, 3 or 4.

[0183] In some embodiments, along the width direction of the negative electrode main body portion, the total width of the negative electrode tabs 312 accounts for 80%-100% of the total width of the main body portion 311. Thereby, by adopting a larger tab structure, the current-carrying capacity of the tab can be effectively improved, and the temperature rise of the battery cell 1 during fast charging can be alleviated.

[0184] As an example, the total width of the negative electrode tabs 312 accounts for 80%, 85%, 90%, 95% or 100% of the total width of the negative electrode main body portion 311.

[0185] When the battery cell performs high-rate charge and discharge, the current and voltage inside the battery cell will increase accordingly, and the current passing through the tab increases. A larger negative electrode tab area means lower resistance. On the one hand, according to Ohm's law, at the same voltage, a tab with a larger area can carry a higher current, that is, it has a stronger current-carrying capacity. On the other hand, when the resistance of the tab is small, the heat generated due to resistance loss after the current passes through the tab can be reduced, the heat generation of the battery under high current is reduced, and the heat dissipation efficiency of the battery is indirectly improved.

[0186] As an example, the negative current collector has two surfaces opposite to each other in its own thickness direction, and the negative active material layer is provided on any one or both of the two opposite surfaces of the negative current collector.

[0187] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. 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 substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0188] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. By way of example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials include at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0189] In some embodiments, the negative electrode active material layer may also optionally include a binder. The binder includes at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0190] In some embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0191] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0192] In some embodiments, the negative electrode plate can be prepared in the following manner: the components for preparing the negative electrode plate, such as the negative electrode active material, conductive agent, binder, and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0193] [Electrolyte] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. There is no specific limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0194] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0195] In some embodiments, it further includes: an electrolytic solution, and the conductivity of the electrolytic solution at room temperature is 10 mS / cm - 18 mS / cm. Thus, the migration rate of lithium ions in the electrolytic solution is relatively high, and the internal resistance of the battery cell 1 can be further reduced.

[0196] As an example, the test method for the conductivity of the electrolytic solution can refer to HG-T 4067-2015.

[0197] In some embodiments, the viscosity of the electrolytic solution at room temperature is 1.5 mPa·s - 5.5 mPa·s. Thus, the migration rate of lithium ions in the electrolytic solution is relatively high.

[0198] As an example, the viscosity of the electrolytic solution at room temperature can be 1.5 mPa·s, 2 mPa·s, 2.5 mPa·s, 3 mPa·s, 3.5 mPa·s, 4 mPa·s, 4.5 mPa·s, 5 mPa·s, or 5.5 mPa·s.

[0199] As an example, the viscosity of the electrolytic solution can be obtained by the following method: The viscosity is tested by a viscometer. Referring to the national standard GB / T10247-2008, at a certain temperature, when the rotor rotates continuously at a constant speed in the sample, the shear force received makes the spring generate torque, and the torque is proportional to the viscosity, thus obtaining the viscosity value.

[0200] In some embodiments, the electrolytic solution includes a chain carboxylic ester solvent. Thus, the chain carboxylic ester solvent can increase the solubility of the electrolyte lithium salt, thereby increasing the migration rate of lithium ions in the electrolytic solution.

[0201] The viscosity of the chain carboxylic ester solvent is relatively low, and further, the overall viscosity of the electrolytic solution mainly composed of organic solvents is relatively low. In the low-viscosity electrolytic solution, the intermolecular interaction force is weak, and the movement between molecules is more free, making the diffusion and migration speed of lithium ions in the electrolytic solution faster. Further, when the battery cell is charged and discharged rapidly, concentration polarization will occur inside the battery. When the ion migration rate of the electrolytic solution is relatively high, the concentration polarization inside the battery can be alleviated. The aforementioned low-viscosity electrolytic solution can effectively reduce the concentration polarization by increasing the ion migration rate and improve the fast charging performance of the battery.

[0202] As an example, the qualitative analysis method of the chain carboxylic acid ester solvent can adopt gas chromatography-ion chromatography coupling.

[0203] In some embodiments, the chain carboxylic acid ester solvent satisfies Formula I: Formula I, wherein, R 1 includes at least one of a hydrogen atom, an alkyl group of C 1 -C 5 and a halogenated alkyl group of C 1 -C 5 . R 2 includes at least one of an alkyl group of C 1 -C 5 and a halogenated alkyl group of C 1 -C 5 . Thus, by adopting the aforementioned chain carboxylic acid ester solvent, the viscosity and conductivity of the electrolyte can be controlled within an appropriate range.

[0204] As an example, R 1 may include at least one of a hydrogen atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, and a fluoropropyl group.

[0205] As an example, R 2 may be one or more of a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, and a fluoropropyl group.

[0206] In some embodiments, the chain carboxylic acid ester solvent includes Formula I-1, Formula I-2, Formula I-3, Formula I-4, Formula I-5, Formula I-6, Formula I-7, at least one of Formula I-8.

[0207] The chain carboxylic acid ester has good lithium salt solubility, can improve the conductivity of the electrolyte, accelerate the migration rate of lithium ions inside the battery, and enhance the charge and discharge efficiency of the battery. Moreover, the chain carboxylic acid ester exhibits good thermal stability and oxidation stability at high temperatures, which helps to improve the stability of the battery under fast charging conditions and reduce the risk of thermal runaway.

[0208] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalato)borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0209] In some embodiments, the electrolyte may further optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain performance of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0210] [Separator membrane] The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0211] In some embodiments, the material of the separator membrane includes at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0212] In the second aspect of the present application, the present application provides a battery device, including the aforementioned battery cell. The battery device includes at least one of a battery module, a battery pack, and an energy storage device. Thus, the battery device has all the features and advantages of the aforementioned battery cell, which will not be elaborated here.

[0213] The battery device mentioned in the embodiments of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include a plurality of battery cells, and the plurality of battery cells are connected in series, parallel, or in a hybrid connection through a busbar component.

[0214] In some embodiments, the battery cell assembly is generally formed by arranging a plurality of battery cells.

[0215] As an example, the battery cell assembly may be a battery module, and the battery module is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with cable ties.

[0216] In some embodiments, the battery device may be a battery pack, and the battery pack includes a box body and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body.

[0217] As an example, the battery cell assembly can also be accommodated in the box body by directly fixing a plurality of battery cells to the box body.

[0218] As an example, the box body may include a first box body and a second box body. The first box body and the second box body are snapped together so that a closed space is formed inside the box body to accommodate the battery cell assembly. Here, "closed" means covering or closing, which can be sealed or non-sealed. The first box body can be a top cover or a bottom plate.

[0219] As an example, the box body may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0220] In some embodiments, the box body may be part of the chassis structure of a vehicle. For example, part of the box body may become at least part of the floor of the vehicle, or part of the box body may become at least part of the cross beams and longitudinal beams of the vehicle.

[0221] In the third aspect of the present application, the present application proposes an electrical device including the aforementioned battery cell. Thus, the electrical device has all the features and advantages of the aforementioned battery cell, which will not be elaborated here.

[0222] The aforementioned battery cell or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0223] As the electrical device, the battery cell or battery pack can be selected according to its usage requirements.

[0224] Figure 26 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery, a battery pack or a battery module can be used.

[0225] Another example of the electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a battery cell can be used as the power source.

[0226] The solution of the present application will be described below through specific embodiments. It should be noted that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those technologies or conditions not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0227] Embodiment 1 1. Positive electrode tab The positive electrode tab includes a positive electrode current collector aluminum foil, and positive electrode active material layers are provided on both surfaces of the aluminum foil. In the state of 100% SOC, the tap density of the positive electrode active material layer is 2.65 g / cm 3; The coating weight of the single-sided positive electrode active material layer is 260 mg / 1540.25 mm 2 ; In the length direction of the positive electrode current collector, the coating length of the positive electrode active material layer is 585 mm. Along the width direction of the positive electrode main body part, the total width of the positive electrode tab accounts for 80% of the total width of the positive electrode main body part.

[0228] Based on the total mass of the single-sided positive electrode active material layer, the positive electrode active material layer includes lithium iron phosphate material with a mass fraction of 95.4% (based on the total mass of the lithium-containing phosphate and the carbon coating layer, the mass fraction of carbon element in the positive electrode active material is 1.1%, and the powder resistivity of the positive electrode active material is 10 S / m), 0.3% of carbon nanotubes (the diameter of the carbon nanotubes is 8 nm), 1.7% of lithium supplement agent lithium ferrite, 0.4% of conductive agent carbon black, 2.2% of binder polyvinylidene fluoride (PVDF). The surface of the lithium iron phosphate has a carbon coating layer, and based on the total mass of the lithium iron phosphate, the mass fraction of the carbon coating layer is 1.18%. The film resistance of the positive electrode plate is 0.1 Ω.

[0229] 2. Negative electrode plate The negative electrode plate includes a negative electrode current collector copper foil, and the coating weight of the single-sided negative electrode active material layer is 123 mg / cm 2 . Along the width direction of the negative electrode main body part, the total width of the negative electrode tab accounts for 80% of the total width of the negative electrode main body part. Based on the total mass of the single-sided negative electrode active material layer, the negative electrode active material layer includes artificial graphite with a mass fraction of 96%, 1.1% of conductive agent carbon black, 1.4% of binder styrene-butadiene rubber (SBR), and 1.5% of thickener sodium carboxymethyl cellulose (CMC-Na).

[0230] 3. Electrolyte The electrolyte includes a solvent and an electrolyte salt. The solvent includes methyl acetate or ethyl acetate, and the electrolyte salt is lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide salt. The concentration of the electrolyte salt in the electrolyte is 1.0 mol / L. 1. The conductivity of the electrolyte at room temperature is 11 S / m, and the viscosity of the electrolyte at room temperature is 3.5 mPa·s.

[0231] 4. Separator The separator is a porous polypropylene membrane.

[0232] 5. Preparation of battery cell The battery cell includes a housing (the length of the housing of the battery cell is 630 mm, the width is 99.6 mm, and the thickness is 15.7 mm), an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are disposed within the housing. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The electrode assembly is a stacked structure, and the separator is disposed between the positive electrode plate and the negative electrode plate. The housing includes two end plates oppositely disposed along the length direction of the battery cell. The first cover assembly adopts the structure as shown in Figure 2 shown, and the second cover assembly adopts the structure as shown in Figure 6 shown. Wherein, the ratio of the area of the main body portion of the electrode terminal in the orthographic projection on the end plate to the area of the surface of the end plate away from the electrode assembly is 5%.

[0233] For the differences between the remaining embodiments, comparative examples and Embodiment 1, see Table 1. Among them, in Embodiment 7, the first cover assembly adopts the structure as shown in Figure 12 shown, and the second cover assembly adopts the structure as shown in Figure 16 shown.

[0234] The fast charging performance of the battery cells in the foregoing embodiments and comparative examples was tested, and the maximum temperature of the top cover during the fast charging performance test was monitored. The test method is as follows, and the test results are shown in Table 1.

[0235] Cycling performance under fast charging conditions (45°C @ 80% SOH): At an ambient temperature of 45°C, the battery cell is charged to 3.65 V by Stepcharge, charged at a constant voltage to 0.05C, left standing for 30 min, discharged at a constant current of 0.5C to 2.5 V, and left standing for 30 min. This is one charge-discharge cycle. Repeat the above charge-discharge cycle until the capacity of the battery cell is 80% of the initial capacity, and the number of charge-discharge cycles obtained is the fast charging cycle performance of the battery cell. Among them, The Stepcharge charging steps are as follows: charge at a constant current of 1C from 0% SOC to 10% SOC; charge at a constant current of 7.0C from 10% SOC to 15% SOC; charge at a constant current of 7.0C from 15% SOC to 20% SOC; charge at a constant current of 7.0C from 20% SOC to 25% SOC; charge at a constant current of 7.0C from 25% SOC to 30% SOC; charge at a constant current of 6.2C from 30% SOC to 35% SOC; charge at a constant current of 5.7C from 35% SOC to 40% SOC; charge at a constant current of 5.2C from 40% SOC to 45% SOC; charge at a constant current of 4.8C from 45% SOC to 50% SOC; charge at a constant current of 4.6C from 50% SOC to 55% SOC; charge at a constant current of 4.4C from 55% SOC to 60% SOC; charge at a constant current of 4.2C from 60% SOC to 65% SOC; charge at a constant current of 3.9C from 65% SOC to 70% SOC; charge at a constant current of 3.5C from 70% SOC to 75% SOC; charge at a constant current of 3.0C from 75% SOC to 80% SOC; charge at a constant current of 0.33C from 80% SOC to 100% SOC.

[0236] Table 1

[0237] The test results show that the battery cells in this application can effectively reduce the heat generation during the rate charge and discharge process, so that the battery cells can maintain a relatively stable temperature during the rate charge and discharge process, and the battery cells have better rate charge and discharge performance.

[0238] Specifically, the ratio of the orthographic projection area of the terminal main body of the unipolar electrode terminal on the end plate to the area of the side surface of the end plate far from the electrode assembly is different in Examples 1-2. The current-carrying area of the electrode terminal is large and the internal resistance is small, and the battery cells have better cycle performance under fast charging conditions.

[0239] In Examples 3-5, the ratio of the orthographic projection area of the terminal main body on the end plate to the orthographic projection area of the first limiting part on the end plate is different. The electrode terminal can provide better current-carrying capacity and a larger heat dissipation area, and the battery cells have better cycle performance under fast charging conditions.

[0240] In Example 6, the film resistance of the positive electrode plate is low, the internal resistance of the positive electrode plate is small, the conduction path of electrons in the positive electrode active material layer is short, and the heat generation of the positive electrode plate under fast charging conditions is less.

[0241] In Example 7, each end plate assembly includes two electrode terminals with different polarities, which can effectively disperse the current density inside the battery cell, thereby reducing the current load on a single electrode terminal, alleviating the uneven polarization inside the battery cell, reducing the risk of local overheating, and improving the cycle performance under fast charging conditions.

[0242] Comparative Examples 1-3 show that when the film resistance of the positive electrode sheet and / or the size of the terminal main body do not meet the requirements, the cycle performance of the battery cell under fast charging conditions is poor and the temperature rises significantly.

[0243] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same effect as the technical idea within the technical solution scope of the present application are included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: include: An electrode assembly, the electrode assembly comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode sheet, the positive electrode active material layer comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate, wherein the sheet resistance of the positive electrode sheet is 0.02Ω-5Ω; The shell comprises a containing space, the electrode assembly is located in the containing space of the shell, the shell comprises an end plate, at least one electrode terminal is arranged on the end plate, the electrode terminal comprises a terminal body, and the ratio of the orthographic projection area of ​​the terminal body of the electrode terminal of a single polarity on the end plate to the area enclosed by the outer contour of the end plate is 5%-70%.

2. The battery cell according to claim 1, characterized in that: The film resistance of the positive electrode plate is 0.05Ω-1Ω.

3. The battery cell according to claim 1, characterized in that: The ratio of the orthographic projection area of ​​the terminal body of the single polarity electrode terminal on the end plate to the area enclosed by the outer contour of the end plate is 15%-65%.

4. The battery cell according to claim 1, characterized in that: The ratio of the orthographic projection area of ​​the terminal body of the single polarity electrode terminal on the end plate to the area enclosed by the outer contour of the end plate is 20%-60%.

5. The battery cell according to claim 1, characterized in that: The positive electrode active material layer includes a conductive agent, and the mass fraction of the conductive agent in the positive electrode active material layer is 0.5%-5%.

6. The battery cell according to claim 1, characterized in that: The positive electrode active material layer includes a conductive agent, the conductive agent includes carbon nanotubes, and the mass fraction of the carbon nanotubes in the positive electrode active material layer is 0.1%-1.1%.

7. The battery cell according to claim 6, characterized in that: The diameter of the carbon nanotubes is 1nm-16nm.

8. The battery cell according to claim 6, characterized in that: The diameter of the carbon nanotubes is 1nm-8nm.

9. The battery cell according to claim 5, characterized in that: The conductive agent also includes carbon black.

10. The battery cell according to claim 1, characterized in that: The lithium-containing phosphate satisfies the general formula: Li x1 A y1 Me a M b P 1-c X c Y z , wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes at least one of Na, K, and Mg, Me includes at least one of Mn, Fe, Co, and Ni, M includes at least one of Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes at least one of S, Si, Cl, B, C, and N, and Y includes one or two of O and F.

11. The battery cell according to claim 1, characterized in that: At least part of the surface of the lithium-containing phosphate has a carbon coating layer, and based on the total mass of the lithium-containing phosphate and the carbon coating layer, the mass fraction of carbon element in the positive electrode active material is 0.7%-1.5%.

12. The battery cell according to claim 1, characterized in that: The powder resistivity of the positive electrode active material is 2S / cm-60S / cm.

13. The battery cell according to claim 1, characterized in that: The powder resistivity of the positive electrode active material is 2S / cm-30S / cm.

14. The battery cell according to claim 1, characterized in that: The positive electrode active material layer further includes a lithium-rich material, and the mass fraction of the lithium-rich material in the positive electrode active material layer is 0.1%-5%.

15. The battery cell according to claim 14, characterized in that: The lithium-rich material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, trilithium citrate, lithium nickel oxide and lithium ferrite.

16. The battery cell according to claim 1, characterized in that: The single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 -370mg / 1540.25mm 2 .

17. The battery cell according to claim 1, characterized in that: When the battery cell is configured to 100% SOC, the compaction density of the positive electrode active material layer is 2.50 g / cm 3 -2.80g / cm 3 .

18. The battery cell according to claim 1, characterized in that: In the length direction of the positive electrode current collector, the coating length of the positive electrode active material layer is 200 mm to 700 mm.

19. The battery cell according to claim 1, characterized in that: The end plate is provided with a lead-out hole, the electrode terminal includes a first limiting portion and a second limiting portion, the terminal body connects the first limiting portion and the second limiting portion, the terminal body passes through the lead-out hole, the first limiting portion is located on the side of the end plate facing the electrode assembly, and the second limiting portion is located on the side of the end plate away from the electrode assembly.

20. The battery cell according to claim 19, characterized in that: The ratio of the orthographic projection area of ​​the terminal main body on the end plate to the orthographic projection area of ​​the first limiting portion on the end plate is 30%-90%.

21. The battery cell according to claim 1, characterized in that: Along a direction parallel to the end plate, the cross section of the terminal body is a rounded rectangle.

22. The battery cell according to claim 1, characterized in that: Each of the end plates includes two electrode terminals, and the two electrode terminals have the same polarity, or the two electrode terminals have opposite polarities.

23. The battery cell according to claim 22, characterized in that: Each of the end plates includes two electrode terminals with opposite polarities, and the electrode terminals of a single polarity on different end plates are staggered along the length direction of the battery cell.

24. The battery cell according to claim 23, characterized in that: The electrode terminals of a single polarity on different end plates are arranged diagonally along the length direction of the battery cell.

25. The battery cell according to claim 1, characterized in that The electrode assembly is a laminate structure, which includes a plurality of positive electrode sheets and a plurality of negative electrode sheets stacked together, each of the positive electrode sheets includes the positive electrode collector, the positive electrode collector includes a positive electrode body and a positive electrode ear, each of the negative electrode sheets includes a negative electrode collector and a negative electrode ear, the negative electrode collector includes a negative electrode body and a negative electrode ear, wherein the positive electrode body is electrically connected to the positive electrode ear, the positive electrode ear is electrically connected to the positive terminal, the negative electrode body is electrically connected to the negative electrode ear, and the negative electrode ear is electrically connected to the negative terminal.

26. The battery cell according to claim 25, characterized in that: The ratio of the number of the positive electrode ear portions to the number of the positive electrode current collectors is 1-2; and / or the ratio of the number of the negative electrode ear portions to the number of the negative electrode current collectors is 1-2.

27. The battery cell according to claim 26, characterized in that: Along the width direction of the positive electrode main body, the total width of the positive electrode ear portion accounts for 80%-100% of the total width of the positive electrode main body; and / or, along the width direction of the negative electrode main body, the total width of the negative electrode ear portion accounts for 80%-100% of the total width of the negative electrode main body.

28. The battery cell according to claim 1, characterized in that: include: The electrolyte has an electrical conductivity of 10 mS / cm-18 mS / cm at room temperature.

29. The battery cell according to claim 28, characterized in that: The viscosity of the electrolyte at room temperature is 1.5 mPa·s-5.5 mPa·s.

30. The battery cell according to claim 28, characterized in that The electrolyte includes a chain carboxylic acid ester solvent.

31. The battery cell according to claim 30, characterized in that: The chain carboxylic acid ester solvent satisfies Formula I: Formula I, Wherein, R1 includes at least one of a hydrogen atom, a C1-C5 alkyl group, and a C1-C5 halogenated alkyl group, R2 includes at least one of a C1-C5 alkyl group and a C1-C5 halogenated alkyl group.

32. The battery cell according to claim 31, characterized in that: The chain carboxylic acid ester solvent includes Formula I-1, Formula I-2, Formula I-3, Formula I-4, Formula I-5, Formula I-6, Formula I-7, At least one of formula I-8.

33. The battery cell according to any one of claims 1 to 32, characterized in that: The battery cells are configured to be charged from 10% SOC to 80% SOC in 5 min to 10.5 min.

34. A battery device, characterized in that: Comprising the battery monomer described in any one of claims 1-33, the battery device comprises at least one of a battery module, a battery pack, and an energy storage device.

35. An electrical device, characterized in that: A battery cell comprising any one of claims 1-33.

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