Battery cell, battery device and electric device

Abstract

Provided in the present disclosure are a battery cell, a battery device and an electric device. The battery cell comprises: an electrode assembly, which comprises a positive electrode sheet, wherein the positive electrode sheet comprises 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 comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing phosphate, and the film resistance of the positive electrode sheet ranges from 0.02 Ω to 5 Ω; and a casing, wherein the electrode assembly is located in an accommodating space of the casing, the casing comprises an end plate, at least one electrode terminal is provided on the end plate, and the ratio of the area of the orthographic projection, on the end plate, of a terminal body portion of an electrode terminal of a single polarity to the area of the surface of the side of the end plate away from the electrode assembly ranges from 5% to 70%.

Description

Battery cells, battery packs, electrical devices Technical Field

[0001] This disclosure relates to the field of batteries, specifically to battery cells, battery devices, and electrical devices. Background Technology

[0002] Lithium-ion batteries are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. However, current batteries still have many problems in practical applications and require further improvement.

[0003] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art.

[0004] Application content

[0005] In a first aspect, this application proposes a battery cell comprising: an electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active material layer located on at least one side of the positive electrode sheet, the positive active material layer including a positive active material containing lithium phosphate, wherein the film resistivity of the positive electrode sheet is 0.02Ω-5Ω; and a housing including a receiving space, the electrode assembly being located within the receiving space of the housing, the housing including an end plate, the end plate having at least one electrode terminal, the electrode terminal including a terminal body portion, the ratio of the projected area of ​​the terminal body portion of the single-polarity electrode terminal on the end plate to the area enclosed by the outer contour of the end plate being 5%-70%. This effectively reduces heat generation in the battery cell during high-rate charging and discharging, thereby allowing the battery cell to maintain a relatively stable temperature during high-rate charging and discharging, resulting in superior high-rate charging and discharging performance.

[0006] In some embodiments, the ratio of the projected area of ​​the terminal body portion 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%, optionally 20%-60%. Thus, the electrode terminal can provide superior current carrying capacity and a larger heat dissipation area, while the end plate has ample space for mounting other structural components.

[0007] In some embodiments, the film resistance of the positive electrode is 0.05Ω-1Ω. This reduces the heat generated by the positive electrode during charging and discharging.

[0008] 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%. Therefore, the heat generation of the positive electrode can be further reduced by constructing a conductive network.

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

[0010] In some embodiments, the diameter of the carbon nanotubes is 1 nm-16 nm; optionally, 1 nm-8 nm. Thus, the carbon nanotubes exhibit superior electronic conductivity.

[0011] In some embodiments, the conductive agent further includes carbon black. Thus, by using a mixture of multiple conductive agents, a more uniform and dense conductive network can be formed, which helps to reduce the internal resistance of the positive electrode and reduce 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 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 B, Mg, 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. Therefore, lithium phosphate particles exhibit high structural stability and excellent cycle stability during charge and discharge, which is beneficial for improving the cycle performance of individual battery cells.

[0013] In some embodiments, at least a portion of the surface of the lithium phosphate has a carbon coating layer, and the mass fraction of carbon in the positive electrode active material is 0.7%-1.5% based on the total mass of the lithium phosphate and the carbon coating layer. This improves the conductivity of the positive electrode active material.

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

[0015] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, wherein the mass fraction of the lithium-rich material in the positive electrode active material layer is 0.1%-5%. Thus, the addition of an appropriate amount of lithium-rich material can compensate for the irreversible lithium-ion loss in the battery cell, while having a small impact on the internal resistance of the positive electrode sheet, which is beneficial for reducing heat generation.

[0016] In some embodiments, the lithium-rich material includes at least one selected from lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, lithium trilithium citrate, lithium nickel oxide, and lithium ferrite. Thus, the lithium-rich material can replenish the active lithium consumed during the first charge and additionally store lithium ions in the negative electrode active material, thereby increasing the capacity of a single 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 -370mg / 1540.25mm 2 Therefore, by controlling the number of active lithium ions per unit area of ​​the positive electrode, polarization during high-rate charging and discharging can be effectively reduced, thus lowering the polarization resistance.

[0018] In some embodiments, the compaction density of the positive electrode active material layer of the battery cell at 100% SOC is 2.50 g / cm³. 3 -2.80g / cm 3 Therefore, the particles in the positive electrode active material layer are densely packed, and the contact resistance between particles is small, which helps to reduce the resistance of the positive electrode sheet and increase the energy density of the battery cell.

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

[0020] In some embodiments, the end plate is provided with a lead-out hole, and the electrode terminal further includes a first limiting portion and a second limiting portion. The terminal body portion connects the first limiting portion and the second limiting portion, and the terminal body portion 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. Thus, the electrode terminal can be securely fixed to the end plate and electrically connected to the electrode assembly and external circuitry.

[0021] In some embodiments, the ratio of the projected area of ​​the terminal body portion on the end plate to the projected area of ​​the first limiting portion on the end plate is 30%-90%. This reduces the internal resistance of the electrode terminal and decreases heat generation.

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

[0023] In some embodiments, each endplate includes two electrode terminals, the two electrode terminals having the same polarity or opposite polarities. This effectively disperses the current density within the battery cell, thereby reducing the current load on individual electrode terminals and helping to reduce the risk of localized overheating.

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

[0025] In some embodiments, the electrode assembly is a stacked structure, comprising multiple positive electrode sheets and multiple negative electrode sheets stacked together. Each positive electrode sheet includes a positive current collector, which includes a positive electrode body and a positive electrode tab. Each negative electrode sheet includes a negative current collector and a negative electrode tab, which includes a negative electrode body and a negative electrode tab. The positive electrode body and the positive electrode tab are electrically connected, the positive electrode tab is electrically connected to a positive terminal, the negative electrode body and the negative electrode tab are electrically connected, and the negative electrode tab is electrically connected to a negative terminal. Therefore, the electrode assembly can make more efficient use of the internal space of the battery cell, reducing wasted internal space and facilitating uniform heat distribution within the battery cell, thereby improving heat dissipation efficiency and reducing the risk of localized overheating.

[0026] In some embodiments, the ratio of the number of positive electrode tabs to the number of positive current collectors is 1-2; and / or, the ratio of the number of negative electrode tabs to the number of negative current collectors is 1-2. This helps to disperse the current density on the current collectors and helps to reduce the risk of localized overheating.

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

[0028] In some embodiments, the battery further includes an electrolyte having a conductivity of 10 mS / cm to 18 mS / cm at room temperature. This results in a high migration rate of lithium ions in the electrolyte, which can further reduce the internal resistance of the battery cells and decrease heat generation.

[0029] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s. This results in a high migration rate of lithium ions in the electrolyte, which is beneficial for improving rate charge / discharge performance.

[0030] In some embodiments, the electrolyte comprises a chain-like carboxylic acid ester solvent. This chain-like carboxylic acid ester solvent can thus increase the solubility of the lithium salt electrolyte, thereby increasing the migration rate of lithium ions in the electrolyte.

[0031] In some embodiments, the chain-like carboxylic acid ester solvent satisfies Formula I:

[0032] Wherein, R1 includes at least one of a hydrogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R2 includes at least one of a C1-C5 alkyl group and a C1-C5 haloalkyl group. Therefore, by using the aforementioned chain-like carboxylic acid ester solvent, the viscosity and conductivity of the electrolyte can be controlled within a suitable range.

[0033] In some embodiments, the chain carboxylic acid ester solvent includes At least one of them.

[0034] In some embodiments, the battery cell is configured to charge from 10% SOC to 80% SOC in 5-10.5 minutes. This results in superior rate charge / discharge performance for the battery cell.

[0035] In a second aspect, this application proposes a battery device comprising the aforementioned battery cell, wherein the battery device includes at least one of a battery module, a battery pack, and an energy storage device. Thus, this battery device possesses all the features and advantages of the aforementioned battery cell, which will not be repeated here.

[0036] In a third aspect, this application proposes an electrical device comprising the aforementioned battery cell. Therefore, this electrical device possesses all the features and advantages of the aforementioned battery cell, which will not be repeated here. Attached Figure Description

[0037] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0038] Figure 1 is a partial structural schematic diagram of an end plate according to an embodiment of this application.

[0039] Figure 2 is a structural schematic diagram of a cover plate assembly according to an embodiment of this application.

[0040] Figure 3 is an exploded view of the cover plate assembly in Figure 2.

[0041] Figure 4 is a top view of a cover plate assembly according to an embodiment of this application.

[0042] Figure 5 is a cross-sectional view of the cover plate assembly in Figure 4 along the AA' direction.

[0043] Figure 6 is a structural schematic diagram of a cover plate assembly according to another embodiment of this application.

[0044] Figure 7 is an exploded view of the cover plate assembly in Figure 6.

[0045] Figure 8 is a top view of a cover plate assembly according to yet another embodiment of this application.

[0046] Figure 9 is a cross-sectional view of the cover plate assembly in Figure 8 along the BB' direction.

[0047] Figure 10 is a schematic diagram of the structure of the housing according to an embodiment of this application.

[0048] Figure 11 is a schematic diagram of the structure of a battery cell according to an embodiment of this application.

[0049] Figure 12 is a structural schematic diagram of a cover plate assembly according to another embodiment of this application.

[0050] Figure 13 is an exploded view of the cover plate assembly in Figure 12.

[0051] Figure 14 is a top view of a cover plate assembly according to yet another embodiment of this application.

[0052] Figure 15 is a cross-sectional view of the cover plate assembly in Figure 14 along the CC' direction.

[0053] Figure 16 is a structural schematic diagram of a cover plate assembly according to another embodiment of this application.

[0054] Figure 17 is an exploded view of the cover plate assembly in Figure 16.

[0055] Figure 18 is a top view of a cover plate assembly according to yet another embodiment of this application.

[0056] Figure 19 is a cross-sectional view of the cover plate assembly in Figure 18 along the DD' direction.

[0057] Figure 20 shows a positive electrode sheet according to an embodiment of this application.

[0058] Figure 21 is a schematic diagram of the structure of an electrode assembly according to an embodiment of this application.

[0059] Figure 22 is a schematic diagram of the structure of a positive current collector according to an embodiment of this application.

[0060] Figure 23 is a schematic diagram of the structure of the positive current collector according to another embodiment of this application.

[0061] Figure 24 is a schematic diagram of the structure of the positive current collector according to another embodiment of this application.

[0062] Figure 25 is a schematic diagram of the structure of an electrode assembly fabricated using a lamination process according to an embodiment of this application.

[0063] Figure 26 is a schematic diagram of the structure of an electrical device according to an embodiment of this application.

[0064] Explanation of reference numerals in the attached drawings: 1. Battery cell; 2. Positive electrode sheet; 3. Negative electrode sheet; 4. Separator; 21. Positive current collector; 22. Positive active material layer; 211. Positive electrode body; 212. Positive electrode tab; 311. Negative electrode body; 312. Negative electrode tab; 11. Housing; 111. First opening; 112. Second opening; 12. First cover plate assembly; 121. First end plate; 122. Positive electrode terminal; 123. First insulating component; 124. First sealing component; 125. First positioning component; 126. Second insulating component; 127. Riveting block; 1211. First through hole; 1212. Liquid injection hole; 1221. First limiting part of positive electrode terminal; 1222. Terminal body part of positive electrode terminal; 1223. Second limiting part of positive electrode terminal; 1231. Second through hole; 13 Second cover plate assembly; 131 Second end plate; 132 Negative electrode terminal; 133 Third insulating component; 134 Second sealing component; 135 Second positioning component; 136 Fourth insulating component; 137 Pressure relief part; 1311 Third through hole; 1321 First limiting part of negative electrode terminal; 1322 Terminal body part of negative electrode terminal; 1323 Second limiting part of negative electrode terminal; 1231 Second through hole; 1331 Fourth through hole. Detailed Implementation

[0065] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0066] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0067] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0068] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0069] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0070] In the description of this application, it should be understood that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0071] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "First feature" and "second feature" may include one or more of the indicated feature.

[0072] In the description of this application, "multiple" means two or more.

[0073] In the description of this application, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or the first and second features being in contact through another feature between them.

[0074] In the description of this application, the terms "above," "over," and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicate that the first feature is at a higher horizontal level than the second feature.

[0075] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0076] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0077] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0078] Fast charging capabilities allow users to quickly replenish a device's power, reducing charging wait time and improving user experience. During fast charging, the chemical reaction rate within the battery cell accelerates, resulting in a larger output current. Furthermore, when the internal resistance of the battery cell is high, according to Joule's law, as the cell continues to operate at a high current, a significant amount of heat is generated, leading to a substantial temperature increase. High temperatures accelerate the aging process of the chemical substances within the battery cell, especially electrolyte evaporation and degradation of the positive electrode active material, causing a rapid decline in battery capacity and poorer cycle performance. In extreme cases, overheating can lead to thermal runaway, even causing combustion or explosion, posing a serious threat to users and the surrounding environment.

[0079] Lithium phosphates offer both low cost and high theoretical specific capacity, contributing to improved energy density in battery cells. However, the high resistivity of lithium phosphate powder leads to heat generation on the positive electrode sheet under fast charging conditions due to the high resistivity of the positive electrode active material powder, as well as heat generation on mechanical components at the electrode terminals due to high current flow. This application addresses this by improving the main heat sources within the battery cell under high current conditions, effectively reducing internal heat generation during fast charging. Specifically, when the film resistance of the positive electrode sheet 2 is 0.02Ω-5Ω, the internal resistance of the positive electrode sheet is low, the electron conduction path in the positive electrode active material layer is short, and heat generation on the positive electrode sheet is reduced under fast charging conditions. Simultaneously, when the ratio of the projected area of ​​the terminal body 1222 / 1322 on the end plate to the area enclosed by the outer contour of the end plate is 5%-70%, the current-carrying area of ​​the electrode terminal is large, which helps reduce the internal resistance of the electrode terminal, thereby reducing heat generation at the electrode terminal and improving heat dissipation. Therefore, the heat generation of battery cell 1 during high-rate charging and discharging can be effectively reduced, and the rapid diffusion of heat accumulated inside battery cell 1 can be accelerated. This allows battery cell 1 to maintain a relatively stable temperature during high-rate charging and discharging, resulting in superior high-rate charging and discharging performance. This application reduces the internal temperature rise of battery cell by controlling the heat generation of the chemical system and mechanical components of the lithium phosphate battery cell, thereby improving the cycle performance of the battery cell under fast charging.

[0080] The battery cells proposed in this application can be used in electrical devices that use the battery cells as a power source or in various energy storage systems that use the battery cells as energy storage elements. Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0081] In a first aspect, this application proposes a battery cell, comprising: an electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active material layer located on at least one side of the positive electrode sheet, the positive active material layer including a positive active material containing lithium phosphate, wherein the film resistance of the positive electrode sheet is 0.02Ω-5Ω; and a housing including a receiving space, the electrode assembly being located within the receiving space of the housing, the housing including an end plate, the end plate having at least one electrode terminal. Referring to FIG1, taking a positive electrode terminal as an example, the ratio of the orthographic projection area of ​​the terminal body portion 1222 of the 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 a negative electrode terminal as an example, the ratio of the orthographic projection area of ​​the terminal body portion 1322 of the 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%. This effectively reduces the heat generated by individual battery cells during high-rate charging and discharging, allowing the cells to maintain a relatively stable temperature and exhibit superior high-rate charging and discharging performance.

[0082] In some embodiments, the housing includes two end plates disposed opposite to each other along the length direction of the battery cell, for example, it may include a first end plate 121 and a second end plate 131.

[0083] As an example, the film resistance of the positive electrode 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.

[0084] As an example, the film resistance of the positive electrode can be tested using the following method: After discharging the battery to 0% SOC, disassemble the electrode and clean it more than three times with a solvent, such as dimethyl carbonate. Take 20 parallel samples along the central axis of the electrode, each sample symmetrical along the central axis, with each sample measuring 4cm × 25cm. The central axis can be parallel to the length direction of the electrode. Use a film resistance tester (Yuaneng Technology, BER2500 model) to test the above 20 parallel samples, and calculate the average value as the film resistance of the electrode.

[0085] As an example, the ratio of the projected area of ​​the terminal body portion of the single-polarity electrode terminal 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%.

[0086] Understandably, the larger the ratio of the projected area of ​​the terminal body on the end plate to the area of ​​the surface of the end plate away from the electrode assembly (e.g., 80%, 90%, or 100%) of a single-polarity electrode terminal, the larger the current-passing area of ​​the electrode terminal and the lower its internal resistance. However, since the size of the first limiting part needs to be larger than the size of the terminal body to effectively restrict the movement of the electrode terminal, when the ratio of the projected area of ​​the terminal body on the end plate to the area of ​​the surface of the end plate away from the electrode assembly is too large (e.g., greater than 70%), the processing of the first limiting part becomes more difficult, and the fixing effect of the first limiting part on the electrode terminal is poor, failing to effectively restrict the positional movement of the electrode terminal.

[0087] It should be noted that the orthographic projection area of ​​the electrode terminal on the end plate refers to the projected area of ​​the region 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 single-polarity electrode terminal on the end plate refers to the sum of the projected areas of the regions formed by the outer edge contours of the terminal bodies of the multiple electrode terminals. The area enclosed by the outer contour of the end plate refers to the projected area of ​​the region formed by the outer edge contour of the end plate.

[0088] In some embodiments, the end plate is provided with a lead-out hole, and the electrode terminal includes a terminal body portion, a first limiting portion, and a second limiting portion. The terminal body portion connects the first limiting portion and the second limiting portion, and the terminal body portion 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. Thus, the electrode terminal can be securely fixed to the end plate and electrically connected to the electrode assembly and external circuitry. In some embodiments, the first limiting portion of the electrode terminal can be the lower post of the electrode terminal, also known as the inner post.

[0089] As an example, the electrode terminals include a positive electrode terminal 122 and a negative electrode terminal 132.

[0090] In some embodiments, the first end plate 121 is provided with through holes, such as the first through hole 1211 and the second through hole 1231 in FIG3. The positive electrode terminal 122 includes a terminal body portion 1222 and a second limiting portion 1223. The terminal body portion 1222 connects the second limiting portion 1223 and the first limiting portion 1221. The terminal body portion 1222 passes through the second through hole 1231 and the first through hole 1211 in sequence. The second limiting portion 1223 is located on the side of the first end plate 121 opposite to the electrode assembly. Thus, the positive electrode terminal can be more firmly fixed on the first end plate.

[0091] In some embodiments, the second end plate 131 is provided with through holes, such as the third through hole 1311 and the fourth through hole 1331 in FIG7. Further, the negative electrode terminal 132 includes a terminal body portion 1322 and a second limiting portion 1323. The terminal body portion 1322 connects the second limiting portion 1323 and the first limiting portion 1321. The terminal body portion 1322 passes through the fourth through hole 1331 and the third through hole 1311 in sequence. The second limiting portion 1323 is located on the side of the second end plate 131 opposite to the electrode assembly. Thus, the negative electrode terminal can be more securely fixed on the second end plate.

[0092] In some embodiments, the ratio of the projected area of ​​the terminal body portion 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%, optionally 20%-60%. Thus, the electrode terminal can provide superior current carrying capacity and a larger heat dissipation area, while the end plate has ample space for mounting other structural components.

[0093] In some embodiments, the ratio of the projected area of ​​the terminal body portion on the end plate to the projected area of ​​the first limiting portion on the end plate is 30%-90%. This reduces the internal resistance of the electrode terminal and decreases heat generation.

[0094] As an example, the ratio of the projected area of ​​the terminal body portion on the end plate to the projected area of ​​the first limiting portion on the end plate can be 30%, 40%, 50%, 60%, 70%, 80%, or 90%. The terminal body portion, being the smallest part of the electrode terminal's cross-sectional area, has a significant impact on the electrode terminal's resistance. By controlling the size of the terminal body portion, the internal resistance of the electrode terminal can be effectively reduced, and the current-carrying capacity of the electrode terminal can be improved.

[0095] In some embodiments, referring to FIG11, 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 a receiving cavity. The first cover assembly includes a first end plate 121 and at least one positive electrode terminal 122. The positive electrode body portion is electrically connected to the positive electrode terminal 122 through the positive electrode tab portion. And / or, the second cover assembly includes a second end plate 131 and at least one negative electrode terminal 132. The negative electrode body portion is electrically connected to the negative electrode terminal 132 through the negative electrode tab portion.

[0096] Specifically, referring to Figure 10, the housing 11 has a first opening 111 and a second opening 112 at both ends along its length direction. The length direction of the housing 11 is the same as the length direction of the positive electrode current collector. The first cover plate assembly 12 is adapted to cover the first opening 111, and the second cover plate 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 plate assembly, and the second cover plate assembly define a receiving cavity, and the electrode assembly is disposed within the receiving cavity. The shapes of the first cover plate assembly and the second cover plate assembly can be adapted to the shape of the housing to fit the housing. The first cover plate assembly and the second cover plate assembly can be made independently of materials with certain hardness and strength (such as aluminum alloy) to give the first cover plate assembly and the second cover plate assembly higher strength, thereby reducing the deformation of the first cover plate assembly and the second cover plate assembly when subjected to compression, and improving the safety performance of the battery cell.

[0097] In some embodiments, the first cover assembly, the second cover assembly, and the housing may be independent components.

[0098] In some embodiments, the first cover plate assembly, the second cover plate assembly, and the housing are integrated. Specifically, the first cover plate assembly, the second cover plate assembly, and the housing can form a common connection surface before other components are inserted into the housing. When it is necessary to enclose the interior of the housing, the first cover plate assembly covers the first opening of the housing, and the second cover plate assembly covers the second opening of the housing.

[0099] In some embodiments, referring to Figures 2-5, the first cover plate assembly 12 includes a first end plate 121 and a positive electrode terminal 122. The positive electrode terminal 122 is disposed on the side of the first end plate 121 near the electrode assembly. The first end plate 121 has a first through hole 1211. 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 disposed on the first insulating member 1231. The positive electrode terminal 122 passes through the second through hole 1231 and the first through hole 1211 in sequence. A first sealing member 124, a first positioning member 125, a second insulating member 126, and a riveting block 127 are disposed in sequence on the side of the first end plate 121 away from the electrode assembly. The riveting block is adapted to fix the positive electrode terminal 122 to the first end plate 121.

[0100] 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 the side of the second end plate 131 near the electrode assembly. The second end plate 131 has a third through hole 1311. 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 disposed on the third insulating member 133. The negative electrode terminal 132 passes through the fourth through hole 1331 and the third through hole 1311 in sequence. A second sealing member 134, a second positioning member 135, a fourth insulating member 136, and a riveting block 127 are disposed in sequence on the side of the second end plate 131 away from the electrode assembly. The riveting block 127 is adapted to fix the negative electrode terminal 132 to the second end plate 131.

[0101] As an example, the first insulating element 123, the second insulating element 126, the third insulating element 133 and the fourth insulating element 136 may each be made of plastic, rubber, etc.

[0102] In some embodiments, referring to Figures 1-5, the first end plate 121 is provided with an injection hole 1212, which can be used to inject electrolyte; referring to Figures 6-9, the second end plate 131 is provided with a pressure relief part 137, which can release the pressure inside the shell when the internal pressure exceeds a threshold.

[0103] As an example, the pressure relief section 137 and the second end plate 131 are two separate components, which are molded separately and then assembled together. The pressure relief section 137 can be a component such as an explosion-proof plate, explosion-proof valve, or safety valve, and can be installed on the second end plate 131 by means of bonding, welding, or other methods. When the internal pressure of the battery cell reaches a threshold, the pressure relief section 137 opens at least part of the pressure relief hole, and the internal pressure of the battery cell is released through the pressure relief hole to relieve the internal pressure of the battery cell.

[0104] In some embodiments, referring to Figures 3 and 7, the cross-section of the terminal body portion 1222 / 1322 is a rounded rectangle along a direction parallel to the end plate. This facilitates the assembly of the electrode terminals.

[0105] In some embodiments, each endplate includes two electrode terminals, the two electrode terminals having the same polarity or opposite polarities. This effectively disperses the current density within the battery cell, thereby reducing the current load on individual electrode terminals and helping to reduce the risk of localized overheating.

[0106] In some embodiments, when each end plate includes a plurality of electrode terminals, such as two electrode terminals, the ratio of the orthographic projection area 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.

[0107] In some embodiments, referring to Figures 13 and 17, each end plate includes two electrode terminals with opposite polarities. This effectively disperses the current density within the battery cell 1, thereby reducing the current load on individual electrode terminals, mitigating polarization unevenness within the battery cell, and reducing the risk of localized overheating.

[0108] In some embodiments, each end plate includes two electrode terminals with opposite polarities, and the electrode terminals of single polarity on different end plates are staggered along the length of the battery cell. Optionally, the electrode terminals of single polarity on different end plates are diagonally arranged along the length of the battery cell. This facilitates the electrical connection of multiple battery cells and helps to alleviate polarization unevenness within the battery cells.

[0109] In some embodiments, the first cover plate assembly 12 includes a positive electrode terminal 122 and a negative electrode terminal 132; and / or, the second cover plate assembly 13 includes a positive electrode terminal 122 and a negative electrode terminal 132.

[0110] Specifically, referring to Figures 12-15, the first cover plate assembly 12 includes a first end plate 121, which includes a positive electrode terminal 122 and a negative electrode terminal 132. The first cover plate assembly is provided with two first through holes. 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. The first insulating member 123 is provided with two second through holes 1231. The positive electrode terminal 122 passes through the corresponding second through hole 1231 and the first through hole 1211 in sequence. The negative electrode terminal 132 passes through the corresponding second through hole 1231 and the first through hole 1211 in sequence. 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 provided in sequence.

[0111] Specifically, referring to Figures 16-19, the second cover plate assembly 13 includes a second end plate 131, which includes a positive electrode terminal 122 and a negative electrode terminal 132. The second end plate 131 has two third through holes 1311. A second insulating member 133 is provided between the second end plate 131, the negative electrode terminal 132, and the positive electrode terminal 122. The third insulating member 133 has two fourth through holes 1331. The positive electrode terminal 122 passes through the corresponding fourth through holes 1331 and the third through holes 1311 in sequence. The negative electrode terminal 132 passes through the corresponding fourth through holes 1331 and the third through holes 1311 in sequence. 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 provided in sequence.

[0112] In some embodiments, referring to FIG21, the electrode assembly is a stacked structure, which includes multiple positive electrode sheets and multiple negative electrode sheets stacked together. Each positive electrode sheet includes a positive current collector, which includes a positive electrode body portion and a positive electrode tab portion. Each negative electrode sheet includes a negative current collector and a negative electrode tab portion, which includes a negative electrode body portion and a negative electrode tab portion. The positive electrode body portion is electrically connected to the positive electrode tab portion, the positive electrode tab portion is electrically connected to the positive terminal, the negative electrode body portion is electrically connected to the negative electrode tab portion, and the negative electrode tab portion is electrically connected to the negative terminal. Therefore, the positive electrode sheet 2, the separator 4, and the negative electrode sheet 3 can make more full use of the internal space of the battery cell 1, reducing internal space waste and helping to distribute heat evenly within the battery cell 1, thereby improving heat dissipation efficiency and reducing the risk of local overheating.

[0113] In some embodiments, the battery cell is configured to charge from 10% SOC to 80% SOC in 5-10.5 minutes. This results in superior rate charge / discharge performance for the battery cell.

[0114] Taking automobiles as an example of electrical devices, in actual use scenarios, the state of charge (SOC) of a car battery is usually between 10% and 80%. Therefore, when the charging time of the battery within this SOC range is short, the user's waiting time for charging can be reduced, which greatly improves the user experience.

[0115] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0116] [Positive electrode plate]

[0117] In some embodiments, the film resistance of the positive electrode is 0.05Ω-1Ω. This reduces the heat generated by the positive electrode during charging and discharging.

[0118] 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%. Thus, the addition of the conductive agent can construct a conductive network, effectively connecting the positive electrode active material particles, shortening the electron conduction path, improving the overcurrent resistance of the electrode, and further reducing the heat generation of the positive electrode.

[0119] 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%.

[0120] In some embodiments, the positive electrode active material layer includes a conductive agent, which includes carbon nanotubes, and the mass fraction of carbon nanotubes in the positive electrode active material layer is 0.1%-1.1%. Therefore, by adding a small amount of carbon nanotubes, the impedance of the positive electrode sheet can be effectively reduced, thus reducing heat generation.

[0121] Therefore, by adding a small amount of carbon nanotubes, the impedance of the positive electrode 2 can be effectively reduced, thus reducing heat generation.

[0122] As an example, the mass fraction of carbon nanotubes in the positive electrode active material layer 22 can be 0.1%, 0.5%, 1%, or 1.1%.

[0123] Carbon nanotubes have high electronic conductivity and can form complex three-dimensional conductive networks, improving the interfacial contact between positive electrode active material particles and current collectors, significantly reducing the film resistance of the positive electrode sheet, and helping to improve the rate charge and discharge performance of the battery.

[0124] In some embodiments, the diameter of the carbon nanotubes is 1 nm-16 nm; optionally, 1 nm-8 nm. Thus, the carbon nanotubes exhibit superior electronic conductivity.

[0125] As an example, the diameter of the carbon nanotubes is 1nm, 4nm, 6nm, 8nm, 10nm, 12nm, 14nm or 16nm.

[0126] It should be noted that the aforementioned diameter of carbon nanotubes refers to the sum of the inner diameter and the wall thickness of the carbon nanotubes.

[0127] As an example, the diameter of carbon nanotubes can be measured by the following method: using a scanning electron microscope (SEM), gold is sputtered onto the surface of the carbon nanotube sample to directly observe the morphology of the sample and measure the diameter.

[0128] In some embodiments, the conductive agent further includes carbon black. Thus, by using conductive agents of different forms and sizes in combination, a more uniform and dense conductive network can be formed between the positive electrode active materials, which helps to reduce the internal resistance of the positive electrode 2, improve charge / discharge efficiency, and reduce heat generation.

[0129] 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 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 B, Mg, 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. Therefore, lithium phosphate has relatively high ionic and electronic conductivity, and the lithium phosphate particles have high structural stability, resulting in excellent cycle stability during charge and discharge, which is beneficial to improving the cycle performance of battery cells.

[0130] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Li content changes when the positive electrode active material is applied to the battery system.

[0131] In the examples of positive electrode active materials for lithium-ion batteries in this application, the molar content of O is only a theoretical state value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0132] In some embodiments, at least a portion of the surface of the lithium phosphate has a carbon coating layer, and the mass fraction of carbon in the positive electrode active material is 0.7%-1.5% based on the total mass of the lithium phosphate and the carbon coating layer. Thus, the carbon coating layer can effectively alleviate the poor electronic conductivity of the lithium 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.

[0133] As an example, based on the total mass of the lithium phosphate and the carbon coating layer, the mass fraction of carbon in the positive electrode active material can be 0.7%, 0.9%, 1.1%, 1.3%, or 1.5%.

[0134] As an example, based on the total mass of lithium phosphate and carbon coating, the mass fraction of carbon in the positive electrode active material can be determined by the following method: Turn on all power switches of the carbon-sulfur analyzer, press and hold the "zero" button, open the oxygen valve of the carbon-sulfur analyzer, and adjust the oxygen pressure to 0.02-0.04 MPa. Turn on "pre-oxygen" and "post-control," and adjust the flow meter to approximately 100 L / h. Add silicon molybdenum powder (approximately 0.3 g), the weighed sample (250 mg), tin granules (0.3 g), and pure iron (1 g) sequentially to the crucible, and close the crucible. Click the "test" button to start the test. The test result will be automatically displayed upon completion; record this result as the carbon content.

[0135] In some embodiments, the resistivity of the positive electrode active material powder is 2S / cm-60S / cm, optionally 2S / cm-30S / cm. This helps to reduce the internal resistance of the positive electrode and reduce heat generation.

[0136] As an example, the powder resistivity of the positive electrode active material can be tested using the following method: according to the test standard GB / T30835-2014, a PRCD1100 powder resistivity meter is used for testing.

[0137] In some embodiments, the positive electrode active material layer 22 further includes a lithium-rich material, wherein 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 both compensate for the irreversible lithium-ion loss in the battery cell 1 and have a small impact on the internal resistance of the positive electrode 2, which is beneficial to reducing heat generation.

[0138] 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%.

[0139] 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 effectively compensate for the loss of active lithium ions, but also help to load a larger amount of positive electrode active material in the positive electrode active material layer, thereby improving the energy density of the battery cell.

[0140] During the first charge of a battery, an SEI film forms on the surface of the negative electrode active material. The breakdown and recombination of the SEI during charge-discharge cycles both cause irreversible lithium-ion consumption, leading to reduced efficiency and capacity loss in the first cycle of the battery cell. Adding lithium-rich materials can pre-replenish this lost lithium during battery manufacturing, mitigating or eliminating capacity decay caused by lithium loss and extending the battery's cycle life.

[0141] In some embodiments, the lithium-rich material includes at least one selected from lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, lithium trilithium citrate, lithium nickel oxide, and lithium ferrite. Thus, the lithium-rich material can replenish the active lithium consumed during the first charge and additionally store lithium ions in the negative electrode active material, thereby improving the capacity utilization of the battery cell 1.

[0142] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm. 2 -370mg / 1540.25mm 2 Therefore, by controlling the number of active lithium ions per unit area of ​​the positive electrode, polarization during high-rate charging and discharging can be effectively reduced, thus lowering the polarization resistance.

[0143] As an example, the single-sided coating weight of the positive electrode active material layer can be 200 mg / 1540.25 mm. 2 210mg / 1540.25mm 2 220mg / 1540.25mm 2 230mg / 1540.25mm 2 240mg / 1540.25mm 2 250mg / 1540.25mm 2 260mg / 1540.25mm 2 270mg / 1540.25mm 2 280mg / 1540.25mm 2 290mg / 1540.25mm 2 300mg / 1540.25mm 2 310mg / 1540.25mm 2 320mg / 1540.25mm2 330mg / 1540.25mm 2 340mg / 1540.25mm 2 350mg / 1540.25mm 2 360mg / 1540.25mm 2 Or 370mg / 1540.25mm 2 .

[0144] As an example, the single-sided coating weight of the positive electrode active material layer can be tested using the following method: Disassemble the positive electrode sheet from the battery cell, take a single-sided coated positive electrode sheet (if it is a double-sided coated positive electrode sheet, first wipe off the positive electrode active material layer on one side), cut it into a small circular piece with an area of ​​S1, weigh it, and record its weight as M1. Then wipe off the positive electrode active material layer of the weighed positive electrode sheet, weigh the positive electrode current collector, and record it as M0. The single-sided coating weight of the positive electrode active material layer = (M1 - M0) / S1.

[0145] In some embodiments, the compaction density of the positive electrode active material layer of the battery cell at 100% SOC is 2.50 g / cm³. 3 -2.80g / cm 3 Therefore, the particles in the positive electrode active material layer 22 are densely packed, and the contact resistance between the particles is small, which is beneficial to reducing the resistance of the positive electrode sheet 2 and increasing the energy density of the battery cell 1.

[0146] As an example, the compaction density of the positive electrode active material layer of the battery cell 1 at 100% SOC can be 2.50 g / cm³. 3 2.55g / cm 3 2.60g / cm 3 2.65g / cm 3 2.70 g / cm 3 2.75g / cm 3 Or 2.80g / cm 3 .

[0147] 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 relatively densely packed, and the positive electrode sheet has both high energy density and low film resistance.

[0148] As an example, the compaction density of the positive electrode active material layer at 100% SOC of a single battery cell can be tested using the following method: Charge the single 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 sheet from the single battery cell, for example, take a single-sided coated positive electrode sheet (if it is a double-sided coated electrode sheet, wipe off the positive electrode active material layer on one side first), cut it into a small circular piece with an area of ​​S1, weigh it, record its weight as M1, and measure its thickness H1. Then wipe off the positive electrode active material layer of the weighed positive electrode sheet, weigh the positive current collector, record its weight as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode active material layer = (M1-M0) / S1, the thickness of the positive electrode active material layer = H1-H0, and the compaction density of the positive electrode active material layer = single-sided coating weight of the positive electrode active material layer / thickness of the positive electrode active material layer.

[0149] In some embodiments, referring to FIG20, the coating length of the positive electrode active material layer 22 in the longitudinal direction of the positive electrode current collector 21 is 200mm-700mm. Therefore, the length of the positive electrode active material layer 22 is moderate, the electron migration path is moderate, the polarization is weak, and the heat generation is small.

[0150] As an example, in the length direction of the positive current collector 21, the coating length of the positive active material layer 22 can be 200mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm or 700mm.

[0151] When the coating length of the positive electrode active material layer 22 is 200mm-700mm, the battery cell 1 can be a long strip structure. The long strip battery cells can be arranged and combined to directly form a battery pack, eliminating the intermediate module structure. This makes it easier to arrange multiple battery cells 1 tightly in the battery device, reducing excess gaps and unnecessary structural components, thereby improving the space utilization rate of the battery device and increasing the energy density of the battery device.

[0152] In some embodiments, the positive current collector 21 includes a positive electrode body portion 211 and at least one positive electrode tab portion 212, wherein the positive electrode body portion 211 is connected to the positive electrode tab portion 212. Thus, the positive electrode plate 2 can be electrically connected to the electrode terminal through the corresponding tab portion.

[0153] In some embodiments, the electrode terminal can be electrically connected to the positive electrode tab via an adapter piece. Specifically, the first limiting portion 1221 of the electrode terminal can be electrically connected to the positive electrode tab via the adapter piece. This significantly improves the welding quality and connection reliability between the electrode terminal and the tab.

[0154] When using an adapter plate to achieve electrical connection between the electrode terminals and the positive electrode tab, the shape and size of the adapter plate can be adjusted as needed to adapt to different distances and positions. Furthermore, the welding process of the adapter plate has fewer defects, which can help to distribute the current more evenly, reduce local overheating and potential difference, and improve the fast charging performance of the battery.

[0155] In some embodiments, the electrode terminals 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. This helps to reduce the structural complexity inside the battery cell, shrink the battery cell size, and increase the energy density.

[0156] When the electrode terminals are directly electrically connected to the positive electrode tab, the connectors are eliminated, simplifying the internal structure of the battery cell, reducing assembly steps, and lowering the overall manufacturing cost.

[0157] In some embodiments, the ratio of the number of positive electrode tabs to the number of positive electrode current collectors is 1-2. This helps to disperse the current density on the current collectors and helps to reduce the risk of localized overheating.

[0158] Electrical connections are achieved between the tabs and terminals, thereby outputting the current inside the battery cell to the external circuit. The ratio of the number of positive electrode tabs 212 to the number of positive electrode current collectors 21 corresponds to the number of positive electrode tabs on each positive electrode current collector. The number of positive electrode tabs on a single positive electrode current collector corresponds to the number of electrode terminals on the end plate. Thus, by matching the design of multiple tabs with the design of multiple electrode terminals, multiple transfer paths for electrons can be realized within the electrode assembly, shortening the electron transfer path, reducing the internal resistance of the battery cell, and reducing heat generation.

[0159] As an example, referring to Figures 22-24, the ratio of the number of positive electrode tabs 212 to the number of positive electrode current collectors 21 can be 1, 2, 3 or 4.

[0160] As an example, referring to Figure 23, the positive current collector includes the positive electrode body portion 211 and a plurality of positive electrode tabs 212, with at least two positive electrode tabs 212 located on opposite sides of the positive electrode body portion 211. Similarly, the negative current collector may include the negative electrode body portion and a plurality of negative electrode tabs, with at least two negative electrode tabs located on opposite sides of the negative electrode body portion. This provides a more uniform heat distribution and reduces tab deformation caused by excessive force on one side.

[0161] As an example, referring to FIG24, the positive current collector includes a positive electrode body portion 211 and a plurality of positive electrode tabs 212 spaced apart along the length direction of the positive current collector. Similarly, the negative current collector may also include a negative electrode body portion 311 and a plurality of negative electrode tabs 312 spaced apart along the length direction of the negative current collector.

[0162] When the positive current collector includes multiple positive electrode tabs 212 and the negative current collector includes multiple negative electrode tabs 312, the electron transport path between the positive electrode tabs and the negative electrode tabs is shorter, which can reduce battery heat generation and improve fast charging performance.

[0163] In some embodiments, along the width direction of the positive electrode body, the total width of the positive electrode tab accounts for 80%-100% of the total width of the positive electrode body. Therefore, by employing a tab structure with a larger area, the current-carrying capacity of the tab can be effectively improved, mitigating the temperature rise of the battery cell during fast charging.

[0164] As an example, the total width of the positive electrode tab 212 accounts for 80%, 85%, 90%, 95%, or 100% of the total width of the positive electrode body 211.

[0165] When a battery cell undergoes high-rate charging and discharging, both the internal current and voltage increase accordingly, leading to a greater current flowing through the tabs. A larger positive electrode tab area means lower resistance. On one hand, according to Ohm's law, at the same voltage, a larger tab area can carry a higher current, meaning it has stronger overcurrent capability. On the other hand, lower tab resistance reduces the heat generated by resistive losses as current flows through the tab, lowering heat generation under high current and indirectly improving the battery's heat dissipation efficiency.

[0166] In some specific embodiments, referring to Figure 22, taking the fabrication of an electrode assembly using a stacking process as an example, the positive electrode sheet used is rectangular. In this case, 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 tab is equal to the width W1 of the positive electrode tab, and the total width V1 of the positive electrode 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 described in detail here.

[0167] In some specific embodiments, referring to Figure 23, taking the fabrication of an electrode assembly using a stacking process as an example, the positive electrode sheet used is rectangular. In this case, the short sides of the positive current collector each have a positive electrode tab 212 extending along the length direction of the positive current collector, and the two positive electrode tabs 212 extend in opposite directions. The width W1 of the multiple positive electrode tabs 212 can be the same or different. In this case, 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 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 described in detail here.

[0168] In some specific embodiments, referring to Figure 24, taking the fabrication of an electrode assembly using a stacking process as an example, the positive electrode sheet used is rectangular. In this case, 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. The multiple positive electrode tabs 212 are spaced apart along the length direction of the positive current collector. 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, all be different, or any two can be the same. In this case, the total width of the positive electrode tabs is the sum of the widths of the multiple positive electrode tabs, i.e., W1 = L1 + L2 + L3, and the total width V1 of the positive electrode body is the length of the positive current collector. Similarly, the corresponding negative electrode current collector can also have a similar structure. In this case, the total width of the negative electrode tab is the sum of the widths of multiple negative electrode tabs, and the width of the negative electrode body is the length of the negative electrode current collector.

[0169] It should be noted that when the electrode assembly is fabricated using a stacking process, the electrode assembly may include a multi-layered, continuously arranged positive electrode / separator / negative electrode / separator structure. In this case, the ratio of the total width of the aforementioned positive electrode tab to the total width V1 of the positive electrode body corresponds to the ratio of the width of the positive electrode tab to the width of the positive electrode body in any positive electrode sheet. Similarly, the ratio of the total width of the aforementioned negative electrode tab to the total width V2 of the negative electrode body corresponds to the ratio of the width of the negative electrode tab to the width of the negative electrode body in any negative electrode sheet.

[0170] In some embodiments, referring to FIG26, in an electrode assembly fabricated using a stacking process, multiple positive electrode tabs 212 may be misaligned (adjacent positive electrode tabs at least partially overlap). In this case, the total width W3 of the positive electrode tabs 212 can be considered as the total width of the multiple positive electrode tabs 212 after the corresponding positive electrode sheet, negative electrode sheet, and separator are stacked, and the total width V1 of the positive electrode body is the width of the positive electrode current collector. Similarly, multiple negative electrode tabs 312 may also be misaligned (adjacent negative electrode tabs at least partially overlap). In this case, the total width W4 of the negative electrode tabs 312 can be considered as the total width of the multiple negative electrode tabs 22 after the corresponding positive electrode sheet, negative electrode sheet, and separator are stacked, and the total width V2 of the negative electrode body is the width of the negative electrode current collector.

[0171] In some embodiments, the width and total width of the positive electrode tab and the negative electrode tab can be the same. When the widths of the positive current collector and the negative current collector are also the same, the ratio of the total width of the positive electrode tab to the total width of the positive electrode body is the same as the ratio of the total width of the negative electrode tab to the total width of the negative electrode body along the width direction of the negative electrode body.

[0172] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0173] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0174] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0175] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0176] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0177] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, lithium-rich material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0178] In some embodiments, the positive electrode sheet can be prepared by dispersing the positive electrode active material, conductive agent, binder and any other components in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and after drying, cold pressing and other processes, forming a positive electrode active material layer; and then using spraying, secondary coating and other methods to composite the lithium-rich material with the positive electrode active material layer.

[0179] [Negative electrode plate]

[0180] In some embodiments, the negative electrode 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 body portion 311 and at least one negative electrode tab portion 312, with the negative electrode body portion 311 connected to the negative electrode tab portion 312. Thus, the negative electrode 3 can be electrically connected to an electrode terminal through the corresponding tab portion.

[0181] In some embodiments, the electrode terminal can be electrically connected to the negative electrode tab via an adapter piece. Specifically, the first limiting portion 1321 of the electrode terminal can be electrically connected to the negative electrode tab via the adapter piece. This significantly improves the welding quality and connection reliability between the electrode terminal and the tab.

[0182] When using an adapter plate to achieve electrical connection between the electrode terminals and the negative electrode tab, the shape and size of the adapter plate can be adjusted as needed to adapt to different distances and positions. Furthermore, the welding process of the adapter plate has fewer defects, which can help to distribute the current more evenly, reduce local overheating and potential difference, and improve the fast charging performance of the battery.

[0183] In some embodiments, the electrode terminals 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. This helps to reduce the structural complexity inside the battery cell, shrink the battery cell size, and increase the energy density.

[0184] When the electrode terminals are directly electrically connected to the negative electrode tab, the connectors are eliminated, simplifying the internal structure of the battery cell, reducing assembly steps, and lowering the overall manufacturing cost.

[0185] In some embodiments, the ratio of the number of negative electrode tabs to the number of negative electrode current collectors is 1-2. This helps to disperse the current density on the current collectors and helps to reduce the risk of localized overheating.

[0186] As an example, the ratio of the number of negative electrode tabs 312 to the number of negative electrode current collectors can be 1, 2, 3 or 4.

[0187] In some embodiments, along the width direction of the negative electrode body portion, the total width of the negative electrode tab portion 312 accounts for 80%-100% of the total width of the body portion 311. Therefore, by employing a tab structure with a larger area, the current-carrying capacity of the tab portion can be effectively improved, mitigating the temperature rise of the battery cell 1 during fast charging.

[0188] As an example, the total width of the negative electrode tab 312 accounts for 80%, 85%, 90%, 95%, or 100% of the total width of the negative electrode body 311.

[0189] When a battery cell undergoes high-rate charging and discharging, both the internal current and voltage increase accordingly, leading to a greater current flowing through the tabs. A larger negative electrode tab area means lower resistance. On one hand, according to Ohm's law, at the same voltage, a larger tab area can carry a higher current, meaning it has stronger overcurrent capability. On the other hand, lower tab resistance reduces the heat generated by resistive losses as current flows through the tab, lowering heat generation under high current conditions and indirectly improving the battery's heat dissipation efficiency.

[0190] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0191] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0192] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an 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 material includes at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material includes at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0193] In some embodiments, the negative electrode active material layer may 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).

[0194] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent includes at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0195] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0196] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0197] Electrolyte

[0198] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0199] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0200] In some embodiments, the battery further includes an electrolyte having a conductivity of 10 mS / cm to 18 mS / cm at room temperature. This results in a high migration rate of lithium ions in the electrolyte, which can further reduce the internal resistance of the battery cell 1.

[0201] As an example, the test method for the conductivity of electrolyte can be found in HG-T 4067-2015.

[0202] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s. Therefore, the migration rate of lithium ions in the electrolyte is relatively high.

[0203] As an example, the viscosity of the electrolyte 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.

[0204] As an example, the viscosity of the electrolyte can be tested using the following method: the viscosity is measured using 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 it experiences causes the spring to generate torque. The torque is proportional to the viscosity, thus yielding the viscosity value.

[0205] In some embodiments, the electrolyte comprises a chain-like carboxylic acid ester solvent. This chain-like carboxylic acid ester solvent can thus increase the solubility of the lithium salt electrolyte, thereby increasing the migration rate of lithium ions in the electrolyte.

[0206] Chain-like carboxylic acid ester solvents have low viscosity, resulting in a lower overall viscosity for electrolytes primarily composed of organic solvents. Low-viscosity electrolytes exhibit weaker intermolecular forces, allowing for freer molecular movement. This accelerates the diffusion and migration of lithium ions within the electrolyte. Furthermore, during rapid charging and discharging of individual battery cells, concentration polarization occurs within the battery. A higher ion migration rate in the electrolyte can mitigate this concentration polarization. Therefore, the aforementioned low-viscosity electrolyte can effectively reduce concentration polarization by increasing ion migration rate, thereby improving the battery's fast-charging performance.

[0207] As an example, the qualitative analysis of chain carboxylic acid ester solvents can be performed using gas chromatography-ion chromatography.

[0208] In some embodiments, the chain-like carboxylic acid ester solvent satisfies Formula I:

[0209] Wherein, R1 includes at least one of a hydrogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R2 includes at least one of a C1-C5 alkyl group and a C1-C5 haloalkyl group. Therefore, by using the aforementioned chain-like carboxylic acid ester solvent, the viscosity and conductivity of the electrolyte can be controlled within a suitable range.

[0210] As an example, R1 may include at least one of hydrogen atom, methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl.

[0211] As an example, R2 can be one or more of methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl.

[0212] In some embodiments, the chain carboxylic acid ester solvent includes At least one of them.

[0213] Chain-like carboxylic acid esters exhibit good lithium salt solubility, which can improve the conductivity of the electrolyte, accelerate the migration rate of lithium ions inside the battery, and enhance the battery's charge and discharge efficiency. Furthermore, chain-like carboxylic acid esters demonstrate good thermal and oxidation stability at high temperatures, which helps improve battery stability under fast charging conditions and reduces the risk of thermal runaway.

[0214] 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 dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0215] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0216] [Isolation membrane]

[0217] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0218] In some embodiments, the material of the separator includes at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0219] In a second aspect, this application proposes a battery device comprising the aforementioned battery cell, wherein the battery device includes at least one of a battery module, a battery pack, and an energy storage device. Thus, this battery device possesses all the features and advantages of the aforementioned battery cell, which will not be repeated here.

[0220] The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0221] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0222] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0223] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cell assemblies housed within the housing.

[0224] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0225] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0226] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0227] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0228] In a third aspect, this application proposes an electrical device comprising the aforementioned battery cell. Therefore, this electrical device possesses all the features and advantages of the aforementioned battery cell, which will not be repeated here.

[0229] The aforementioned battery cells or battery packs can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0230] As the electrical device, a single battery cell or a battery pack can be selected according to its usage requirements.

[0231] Figure 26 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0232] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0233] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0234] Example 1

[0235] 1. Positive electrode sheet

[0236] The positive electrode sheet includes a positive current collector aluminum foil, with a positive active material layer on both surfaces of the aluminum foil. At 100% SOC, the compaction density of the positive active material layer is 2.65 g / cm³. 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, and in the width direction of the positive electrode body, the total width of the positive electrode tab accounts for 80% of the total width of the positive electrode body.

[0237] Based on the total mass of the single-sided positive electrode active material layer, the positive electrode active material layer comprises, by mass percentage, 95.4% lithium iron phosphate material (based on the total mass of the lithium-containing phosphate and the carbon coating layer, the mass fraction of carbon 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% carbon nanotubes (the diameter of the carbon nanotubes is 8 nm), 1.7% lithium iron phosphate supplementer, 0.4% carbon black conductive agent, and 2.2% polyvinylidene fluoride (PVDF) binder. The lithium iron phosphate surface has a carbon coating layer, and based on the total mass of the lithium iron phosphate, the mass percentage of the carbon coating layer is 1.18%. The film resistance of the positive electrode sheet is 0.1 Ω.

[0238] 2. Negative electrode plate

[0239] The negative electrode sheet includes a negative current collector copper foil, and the coating weight of the single-sided negative electrode active material layer is 123 mg / cm³. 2 Along the width direction of the negative electrode body, the total width of the negative electrode tab accounts for 80% of the total width of the negative electrode body. Based on the total mass of the single-sided negative electrode active material layer, the negative electrode active material layer comprises 96% artificial graphite, 1.1% conductive carbon black, 1.4% binder styrene-butadiene rubber (SBR), and 1.5% thickener sodium carboxymethyl cellulose (CMC-Na) by mass percentage.

[0240] 3. Electrolyte

[0241] The electrolyte comprises a solvent and an electrolyte salt. The solvent includes methyl acetate or ethyl acetate, and the electrolyte salt is lithium hexafluorophosphate and lithium difluorosulfonylimide 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.

[0242] 4. Separating membrane

[0243] The separator is a porous polypropylene membrane.

[0244] 5. Preparation of battery cells

[0245] The battery cell includes a casing (the casing of the battery cell is 630 mm long, 99.6 mm wide, and 15.7 mm thick), an electrode assembly, and an electrolyte, with the electrode assembly and electrolyte disposed within the casing. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The electrode assembly has a stacked structure, with the separator disposed between the positive and negative electrode. The casing includes two end plates arranged opposite each other along the length of the battery cell. The first end plate assembly adopts the structure shown in Figure 2, and the second end plate assembly adopts the structure shown in Figure 6. The ratio of the projected area of ​​the electrode terminal body on the end plate to the area of ​​the surface of the end plate furthest from the electrode assembly is 5%.

[0246] The differences between the remaining embodiments and comparative examples and Embodiment 1 are shown in Table 1. In Embodiment 7, the first cover plate assembly adopts the structure shown in Figure 12, and the second cover plate assembly adopts the structure shown in Figure 16.

[0247] Fast charging performance tests were conducted on the individual battery cells in the aforementioned embodiments and comparative examples, and the maximum temperature of the top cover was monitored during the fast charging performance test. The test method is as follows, and the test results are shown in Table 1.

[0248] Fast charging cycle performance (45℃@80% SOH): At an ambient temperature of 45℃, a single battery cell is charged to 3.65V using Step Charge, then charged at a constant voltage to 0.05C, rested for 30 minutes, and then discharged at a constant current of 0.5C to 2.5V, rested for 30 minutes. This constitutes one charge-discharge cycle. This cycle is repeated until the battery cell's capacity reaches 80% of its initial capacity. The number of charge-discharge cycles is the fast charging cycle performance of the battery cell.

[0249] The Stepcharge charging steps are as follows: charge from 0% SOC to 10% SOC at a constant current of 1C; charge from 10% SOC to 15% SOC at a constant current of 7.0C; charge from 15% SOC to 20% SOC at a constant current of 7.0C; charge from 20% SOC to 25% SOC at a constant current of 7.0C; charge from 25% SOC to 30% SOC at a constant current of 7.0C; charge from 30% SOC to 35% SOC at a constant current of 6.2C; charge from 35% SOC to 40% SOC at a constant current of 5.7C; and charge from 40% SOC to 4% SOC at a constant current of 5.2C. 5% SOC; charging from 45% SOC to 50% SOC at a constant current of 4.8C; charging from 50% SOC to 55% SOC at a constant current of 4.6C; charging from 55% SOC to 60% SOC at a constant current of 4.4C; charging from 60% SOC to 65% SOC at a constant current of 4.2C; charging from 65% SOC to 70% SOC at a constant current of 3.9C; charging from 70% SOC to 75% SOC at a constant current of 3.5C; charging from 75% SOC to 80% SOC at a constant current of 3.0C; charging from 80% SOC to 100% SOC at a constant current of 0.33C.

[0250] Table 1

[0251] Test results show that the battery cells in this application can effectively reduce heat generation during the high-rate charging and discharging process, thereby enabling the battery cells to maintain a relatively stable temperature during the high-rate charging and discharging process, and the battery cells have superior high-rate charging and discharging performance.

[0252] Specifically, in Examples 1-2, the ratio of the projected area of ​​the unipolar electrode terminal body on the end plate to the area of ​​the surface of the end plate away from the electrode assembly is different. The electrode terminal has a larger overcurrent area and a smaller internal resistance, and the battery cell has better cycle performance under fast charging conditions.

[0253] In Examples 3-5, the ratio of the projected area of ​​the terminal body on the end plate to the projected area of ​​the first limiting part on the end plate is different. The electrode terminal can provide better overcurrent capacity and larger heat dissipation area, and the battery cell has better cycle performance under fast charging conditions.

[0254] In Example 6, the positive electrode has a low film resistance, a low internal resistance, a short electron conduction path in the positive active material layer, and generates less heat under fast charging conditions.

[0255] In Example 7, each endplate 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 polarization unevenness inside the battery cell, reducing the risk of local overheating, and improving cycle performance under fast charging conditions.

[0256] Comparative Examples 1-3 show that when the film resistance of the positive electrode and / or the size of the terminal body do not meet the requirements, the cycle performance of the battery cell under fast charging conditions is poor and the temperature rise is more obvious.

[0257] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, wherein, include: An electrode assembly, the electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active material layer located on at least one side of the positive electrode sheet, the positive active material layer including a positive active material, the positive active material including a lithium phosphate, wherein the film resistance of the positive electrode sheet is 0.02Ω-5Ω; The housing includes a receiving space, the electrode assembly is located within the receiving space of the housing, the housing includes an end plate, the end plate is provided with at least one electrode terminal, the electrode terminal includes a terminal body portion, and the ratio of the orthographic projection area of ​​the terminal body portion of the single polarity electrode terminal 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, wherein, The film resistance of the positive electrode is 0.05Ω-1Ω.

3. The battery cell according to claim 1 or 2, wherein, The ratio of the projected area of ​​the terminal body portion 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%, optionally 20%-60%.

4. The battery cell according to any one of claims 1-3, wherein, 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%.

5. The battery cell according to any one of claims 1-4, wherein, The positive electrode active material layer includes a conductive agent, which includes carbon nanotubes, and the mass fraction of carbon nanotubes in the positive electrode active material layer is 0.1%-1.1%.

6. The battery cell according to claim 5, wherein, The diameter of the carbon nanotubes is 1nm-16nm; optionally, 1nm-8nm.

7. The battery cell according to claim 5 or 6, wherein, The conductive agent also includes carbon black.

8. The battery cell according to any one of claims 1-7, wherein, 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 B, Mg, 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.

9. The battery cell according to any one of claims 1-8, wherein, The lithium phosphate has at least a portion of its surface covered with a carbon coating layer, and the mass fraction of carbon in the positive electrode active material is 0.7%-1.5% based on the total mass of the lithium phosphate and the carbon coating layer.

10. The battery cell according to any one of claims 1-9, wherein, The resistivity of the positive electrode active material is 2S / cm-60S / cm, optionally 2S / cm-30S / cm.

11. The battery cell according to any one of claims 1-10, wherein, The positive electrode active material layer further includes a lithium-rich material, wherein the mass fraction of the lithium-rich material in the positive electrode active material layer is 0.1%-5%.

12. The battery cell according to claim 11, wherein, The lithium-rich material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickel oxide, and lithium ferrite.

13. The battery cell according to any one of claims 1-12, wherein, The single-sided coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm. 2 -370mg / 1540.25mm 2 .

14. The battery cell according to any one of claims 1-13, wherein, When the battery cell is configured to have a state of 100% SOC, the compaction density of the positive electrode active material layer is 2.50 g / cm³. 3 -2.80g / cm 3 .

15. The battery cell according to any one of claims 1-14, wherein, In the longitudinal direction of the positive electrode current collector, the coating length of the positive electrode active material layer is 200mm-700mm.

16. The battery cell according to any one of claims 1-15, wherein, The end plate is provided with a lead-out hole, and the electrode terminal further includes a first limiting part and a second limiting part. The terminal body part is connected to the first limiting part and the second limiting part. The terminal body part passes 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.

17. The battery cell according to claim 16, wherein, The ratio of the projected area of ​​the terminal body on the end plate to the projected area of ​​the first limiting part on the end plate is 30%-90%.

18. The battery cell according to any one of claims 1-17, wherein, Along the direction parallel to the end plate, the cross-section of the terminal body is a rounded rectangle.

19. The battery cell according to any one of claims 1-18, wherein, Each of the end plates includes two electrode terminals, the two electrode terminals having the same polarity or the two electrode terminals having opposite polarities.

20. The battery cell according to claim 19, wherein, Each of the end plates includes two electrode terminals with opposite polarities. The electrode terminals of single polarity on different end plates are staggered along the length of the battery cell. Optionally, the electrode terminals of single polarity on different end plates are diagonally arranged along the length of the battery cell.

21. The battery cell according to any one of claims 1-20, wherein, The electrode assembly is a stacked structure, which includes multiple positive electrode plates and multiple negative electrode plates stacked together. Each positive electrode plate includes a positive current collector, which includes a positive electrode body and a positive electrode tab. Each negative electrode plate includes a negative current collector and a negative electrode tab, which includes a negative electrode body and a negative electrode tab. The positive electrode body is electrically connected to the positive electrode tab, the positive electrode tab is electrically connected to the positive terminal, the negative electrode body is electrically connected to the negative electrode tab, and the negative electrode tab is electrically connected to the negative terminal.

22. The battery cell according to claim 21, wherein, The ratio of the number of positive electrode tabs to the number of positive electrode current collectors is 1-2; and / or, the ratio of the number of negative electrode tabs to the number of negative electrode current collectors is 1-2.

23. The battery cell according to claim 22, wherein, Along the width direction of the positive electrode body portion, the total width of the positive electrode tab portion accounts for 80%-100% of the total width of the positive electrode body portion; and / or, along the width direction of the negative electrode body portion, the total width of the negative electrode tab portion accounts for 80%-100% of the total width of the negative electrode body portion.

24. The battery cell according to any one of claims 1-23, wherein, Further includes: The electrolyte has a conductivity of 10 mS / cm to 18 mS / cm at room temperature.

25. The battery cell according to claim 24, wherein, The viscosity of the electrolyte at room temperature is 1.5 mPa·s-5.5 mPa·s.

26. The battery cell according to claim 24 or 25, wherein, The electrolyte includes chain-like carboxylic acid ester solvents.

27. The battery cell according to claim 26, wherein, The chain-like carboxylic acid ester solvent satisfies Formula I: Wherein, R1 includes at least one of hydrogen atom, C1-C5 alkyl group, and C1-C5 haloalkyl group, and R2 includes at least one of C1-C5 alkyl group and C1-C5 haloalkyl group.

28. The battery cell according to claim 27, wherein, The chain-like carboxylic acid ester solvent includes At least one of them.

29. The battery cell according to any one of claims 1-28, wherein, The battery cell is configured to charge from 10% SOC to 80% SOC in 5 min to 10.5 min.

30. A battery device, wherein, The battery device includes the battery cell of any one of claims 1-29, and the battery device includes at least one of battery module, battery pack, and energy storage device.

31. An electrical device, wherein, Includes the battery cell as described in any one of claims 1-29.

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