Battery cell, preparation method therefor, battery device, and electrical device

Abstract

A battery cell, a preparation method therefor, a battery device, and an electrical device. The battery cell has a height of 200 mm or more. The battery cell comprises at least one electrode assembly, and the electrode assembly comprises electrode sheets and a separator. Each electrode sheet extends along a first direction, and the length of each electrode sheet along the first direction is greater than the length thereof along a second direction. The second direction is perpendicular to the first direction and is the same as the height direction of the battery cell. The electrode sheets and the separator are stacked in a third direction, and the third direction is perpendicular to the first direction and the second direction. The electrode assembly has a large-surface region in a cross section perpendicular to the height direction of the battery cell, and in the large-surface region, the average gap between each electrode sheet and the separator adjacent thereto along the third direction is 6.3 μm to 24 μm.

Description

Battery cells, their manufacturing methods, battery devices, and electrical devices

[0001] Cross-references to related applications

[0002] This disclosure is based on and claims priority to Chinese Patent Application No. 202510360440.6, filed on March 25, 2025, entitled “Battery Cell, Method of Preparation Thereof, Battery Device and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of battery technology, and in particular to a battery cell, a method for preparing the battery cell, a battery device, and an electrical device. Background Technology

[0004] In recent years, with the increasingly wide range of applications for battery cells, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, aerospace, and many other fields. With the rapid development of batteries, higher requirements have been placed on battery cycle performance, especially for taller battery cells.

[0005] Therefore, how to improve the cycle performance of high-density battery cells has become an urgent technical problem to be solved. Summary of the Invention

[0006] This disclosure is made in view of the above-mentioned problems, and its object is to provide a high-strength battery cell, a method for preparing the same, a battery device, and an electrical device, wherein the battery cell of this disclosure has excellent cycle performance.

[0007] To achieve the above objectives, the first aspect of this disclosure provides a battery cell with a height of 200 mm or more. The battery cell includes at least one cell, which includes an electrode and a separator. The electrode extends along a first direction, and its length along the first direction is greater than its length along a second direction. The second direction is perpendicular to the first direction and the same as the height direction of the battery cell. The electrode and separator are stacked along a third direction, which is perpendicular to both the first and second directions. The cell has a large surface area in a cross-section perpendicular to the height direction of the battery cell. In this large surface area, the average gap between the electrode and the adjacent separator along the third direction is 6.3 μm to 24 μm. This is beneficial for improving the cycle performance of the battery cell.

[0008] In some embodiments, the average gap between the third-direction electrode and the adjacent separator in the large area is 8.2 μm-20.3 μm. This is beneficial for further improving the electrolyte wettability of the cell, thereby improving the cycle performance of the battery cell.

[0009] In some embodiments, the battery cell is a wound cell. The wound cell includes a large surface area and bending areas on both sides of the large surface area along a first direction in a cross-section perpendicular to the height direction of the battery cell. In the bending areas, starting from the innermost bending position of the wound cell, the average gap between the electrode and the separator is 8.7 μm to 32.5 μm in a direction at a 45° angle to a third direction. This improves the wetting effect of the electrolyte, thereby enhancing the cycle performance of the battery cell.

[0010] In some embodiments, in the bending region, starting from the innermost bending position of the wound cell, the average gap between the electrode and the separator is 8.9 μm to 28.7 μm in a direction at 45° to a third direction. This further improves the cycle performance of the battery cell.

[0011] In some embodiments, in the bending region, starting from the innermost bending position of the wound cell, the gap between the electrode and the separator is 21.0 μm to 58.5 μm in a direction at 90° to a third direction. This helps to improve the wetting effect of the electrolyte and enhance the cycle performance of the battery cell.

[0012] In some embodiments, in the bending region, starting from the innermost bending position of the wound cell, the gap between the electrode and the separator is 23.5 μm to 55.5 μm in a direction at 90° to a third direction. This is beneficial for further improving the cycle performance of the battery cell.

[0013] In some embodiments, the separator includes a base membrane and a functional layer disposed on at least one side of the base membrane, the functional layer comprising porous ceramic particles. This improves the separator's ability to retain electrolyte, thereby enhancing the cycle performance of the battery cell.

[0014] In some embodiments, the porous ceramic particles include one or more of boehmite, alumina, titanium dioxide, silicon dioxide, silicon carbide, barium sulfate, calcium sulfate, and glass fiber. This is beneficial for improving the cycle performance of the battery.

[0015] In some embodiments, the air permeability of the separator is 156 s / 100 mL to 175.5 s / 100 mL. This is beneficial for improving the cycle performance and safety performance of the battery cells.

[0016] In some embodiments, the ionic conductivity of the separator is 0.6 mS / cm to 0.95 mS / cm. This is beneficial for improving the cycle stability of the battery cells.

[0017] In some embodiments, the areal density of the diaphragm is 3 g / m³. 2 ~7.6g / m 2This is beneficial for improving the energy density, cycle performance, and safety performance of individual battery cells.

[0018] In some implementations, the thickness of the functional layer is less than or equal to 5 μm. This is beneficial for improving the cycle performance of the battery.

[0019] In some implementations, the height of the individual battery cells is 200mm-300mm. This improves the energy storage capacity of the battery.

[0020] The second aspect of this disclosure also provides a method for preparing a battery cell with a height of 200 mm or more. The method includes a step of sequentially stacking electrodes and a separator and then cold-pressing them. The cold-pressing pressure is 20T to 50T, and the cold-pressing time is 20s to 150s. This is beneficial for improving the electrolyte creep height and wettability in the cell, thereby improving the cycle performance of the prepared battery cell.

[0021] In some implementations, the cold pressing pressure is 32T to 42.5T, and the cold pressing time is 20s to 60s. This is beneficial for further improving the cycle performance of the battery cells.

[0022] A third aspect of this disclosure also provides a battery device, comprising a battery cell according to the first aspect of this disclosure, or a battery cell prepared according to the preparation method of the second aspect of this disclosure. Thus, the battery device possesses at least the advantages of the battery cell of this disclosure.

[0023] The fourth aspect of this disclosure also provides an electrical device, and the battery device of the third aspect of this disclosure. Attached Figure Description

[0024] Figure 1 is a structural schematic diagram of a cross-section of a large area of ​​a battery cell according to an embodiment of the present disclosure, perpendicular to the height direction of the battery cell.

[0025] Figure 2 is a structural schematic diagram of a cross-section of a wound cell in an embodiment of the present disclosure, perpendicular to the height direction of the individual battery cell.

[0026] Figure 3 is a CT view of the interface of a wound cell in one embodiment of the present disclosure, perpendicular to the height direction of the battery cell, which includes two wound cells.

[0027] Figure 4 is a schematic diagram of a battery cell according to one embodiment of the present disclosure.

[0028] Figure 5 is an exploded view of a battery cell according to an embodiment of the present disclosure shown in Figure 4.

[0029] Figure 6 is a schematic diagram of a battery module according to one embodiment of the present disclosure.

[0030] Figure 7 is a schematic diagram of a battery pack according to one embodiment of the present disclosure.

[0031] Figure 8 is an exploded view of a battery pack according to an embodiment of the present disclosure, as shown in Figure 7.

[0032] Figure 9 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present disclosure.

[0033] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 521 Negative electrode; 522 Positive electrode; 523 Separator; 524 Gap; 53 Top cover assembly Detailed Implementation

[0034] The following detailed description of the battery cell, method for manufacturing the battery cell, battery device, and power-consuming device of this disclosure is provided with appropriate reference to the accompanying drawings. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts 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 disclosure and are not intended to limit the subject matter of the claims.

[0035] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the 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 expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​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 disclosure, 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.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this disclosure can be combined to form new technical solutions.

[0037] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions.

[0038] Unless otherwise specified, all steps of this disclosure may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if it is mentioned that the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] Unless otherwise specified, the terminology used in this disclosure has the common meaning as commonly understood by those skilled in the art.

[0040] Unless otherwise specified, the values ​​of the parameters mentioned in this disclosure can be determined using various test methods commonly used in the art, for example, according to the test methods given in this disclosure.

[0041] In this disclosure, the battery cell is a secondary battery, which can be reactivated by charging after discharge to continue its use. The battery cell can be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, a lithium metal battery, or a sodium metal battery; this disclosure does not limit it to any of these.

[0042] Currently, uneven electrolyte distribution is a common problem in large-size battery cells. During cell fabrication, after the initial electrolyte injection, the electrolyte wets from the periphery towards the center. Due to the stratification effect of electrolyte creep, the concentration of electrolyte salts and additives gradually decreases from the edges to the center, resulting in inferior quality of the initial anode film (SEI film) in the center of the cell compared to other areas. During battery operation, the continuous charging and discharging of the cell consumes electrolyte. In the later stages of cycle use, the electrolyte mainly resides at the bottom of the cell due to gravity. For large-size battery cells, the creeping path of the electrolyte from the bottom to the top of the cell is longer, leading to insufficient wetting at the top. Therefore, a method to improve the electrolyte wetting capacity of the electrodes is urgently needed.

[0043] To address the aforementioned issues, some reports suggest improving the electrolyte wetting rate by methods such as reducing the width and thickness of the electrodes and decreasing their compaction density. However, such treatments can negatively impact the overall performance of the battery cell, such as reducing its capacity. In particular, for taller battery cells, the middle / top portion remains difficult to wet with electrolyte, leading to uneven electrolyte distribution along the cell's height. This results in inconsistent film composition during formation, causing lithium plating during cycling and ultimately affecting the battery's cycle performance.

[0044] Based on this, this disclosure proposes a large-size battery cell, its preparation method, a battery device, and an electrical device. The battery cell of this disclosure has good electrolyte wettability in the middle and top, and exhibits excellent cycle performance. The following provides a more detailed description of this disclosure and optional embodiments.

[0045] battery cell

[0046] The first aspect of this disclosure provides a battery cell with a height of 200 mm or more. The battery cell includes at least one cell, which includes an electrode and a separator. The electrode extends along a first direction, and the length of the electrode along the first direction is greater than its length along a second direction. The second direction is perpendicular to the first direction and is the same as the height direction of the battery cell. The electrode and the separator are stacked along a third direction, which is perpendicular to the first and second directions. The cell has a large surface area in a cross-section perpendicular to the height direction of the battery cell. In the large surface area, the average gap between the electrode and the adjacent separator in the third direction is 6.3 μm to 24 μm.

[0047] In this disclosure, for battery cells with a height of 200 mm or more, by making the average gap between the electrode and the adjacent separator in the stacking direction (third direction) of the large area of ​​the cell 6.3 μm to 24 μm, the capillary force effect between the positive and negative electrode and the separator in the cell can be improved, the electrolyte creep height in the cell can be increased, thereby improving the electrolyte wettability of the cell and the electrolyte wettability in the battery cell. This reduces the lithium plating problem caused by lack of electrolyte in the middle and / or top of the cell during later cycles, thereby improving the cycle performance of the battery cell.

[0048] In the large area of ​​the battery cell, the average gap between the electrode and the adjacent separator in the stacking direction (third direction) can be a value within a range of 6.3μm, 7.2μm, 8.21μm, 9.5μm, 11.0μm, 12.5μm, 14.0μm, 15.5μm, 16.52μm, 18.5μm, 19.5μm, 20.21μm, 20.3μm, 23.52μm, 24μm, or any combination thereof. Optionally, in the large area of ​​the battery cell, the gap between the electrode and the adjacent separator in the stacking direction (third direction) is 8.2μm-20.3μm. This is more conducive to improving the capillary force between the positive and negative electrodes and the separator in the battery cell, thereby further improving the electrolyte wettability of the battery cell and thus improving the cycle performance of the battery cell.

[0049] The battery cell of this disclosure has a height of 200mm or more, which increases the internal space of the battery cell, thereby accommodating more electrolyte and electrode materials and improving the energy storage capacity of the battery. Furthermore, it facilitates the optimization of electrode dimensions, improves material utilization, and enhances production efficiency. In this disclosure, the height of the battery cell can be measured using a micrometer or height gauge. Exemplarily, the height of the battery cell of this disclosure can be a value within the range of 200mm, 220mm, 240mm, 260mm, 280mm, 300mm, or any combination thereof. Optionally, the height of the battery cell is 200mm-300mm, and more preferably 210mm-280mm. By keeping the height of the battery cell within the above range, it is beneficial to improve the battery's capacity and energy density, optimize electrode dimensions, improve material utilization, and simultaneously maintain production efficiency.

[0050] The battery cell disclosed herein includes at least one cell, for example, one, two, three, or four cells. Each cell includes electrodes and a separator, which are stacked along a third direction (i.e., the stacking direction) perpendicular to the height direction of the battery cell. In some embodiments, the electrodes include a positive electrode and a negative electrode, with the separator disposed between the positive and negative electrodes. During battery charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through. In some embodiments, the positive electrode, negative electrode, and separator are stacked sequentially in the order of "separator-negative electrode-separator-positive electrode".

[0051] Figure 1 shows a schematic diagram of the structure of a large area of ​​a battery cell according to an embodiment of the present disclosure. As shown in Figure 1, the positive electrode 521, the negative electrode 522, and the separator 523 extend along a first direction (length direction), the length in the first direction being greater than the length in a second direction, and the second direction being perpendicular to the first direction and the same as the height direction of the battery cell. The positive electrode 521, the negative electrode 522, and the separator 523 are stacked along a third direction (stacking direction, perpendicular to the first and second directions), and a gap 524 exists between the electrode and the adjacent separator.

[0052] In some embodiments, the battery cell is a wound cell. As shown in Figure 2, the positive electrode, negative electrode, and separator extend along a first direction (length direction) and are wound into a wound structure. The wound structure includes a large surface area and bending areas located on both sides of the large surface area along the first direction in a cross section perpendicular to the height direction of the battery cell. In the large surface area, the electrode and separator are stacked in a third direction. In the bending areas, the stacking direction of the electrode and separator is at a certain angle to the stacking direction of the electrode and separator in the large surface area.

[0053] In this disclosure, the term "large area" refers to a region in a cross-section perpendicular to the height direction of the battery cell, where the extension directions of the electrode and the separator are parallel to each other and perpendicular to the stacking direction. The term "bending area" refers to the corner area formed at both ends of the length direction during cell winding. It is understood that the cell of this disclosure includes a large area and a bending portion, wherein the bending portion is located on both sides of the large area. In a cross-section perpendicular to the height direction of the battery cell, the cross-section of the large area corresponds to the large area, and the cross-section of the bending portion corresponds to the bending area.

[0054] In this disclosure, the average gap between the electrode and the adjacent separator in the stacking direction can be tested using computed tomography (CT) technology. CT testing generates a three-dimensional image of the internal structure of the battery cell through X-ray penetration and computer reconstruction techniques, clearly displaying the internal structures of the battery, such as the electrode, separator, and electrolyte, thereby allowing the measurement of the gap between the positive or negative electrode and the separator. The specific testing steps are as follows: The battery cell prepared during the battery cell manufacturing process or obtained from disassembling a battery cell is placed in a CT device (e.g., Zeiss Xradia). A computed tomography (CT) scan is performed on the battery cell to obtain a CT image of the cross-section perpendicular to the height direction. Image analysis tools, such as PowerPoint software, are used to assist in measuring the average gap between the electrodes and adjacent separators in the stacking direction of the CT image. Exemplary steps for analyzing the average gap include: marking the bottommost electrode (positive or negative) and the topmost electrode (negative or positive) in the stacking direction of the battery cell in the CT image, and measuring the vertical distance between them; converting the actual total thickness according to the scale of the CT image; recording the number of positive electrode layers, negative electrode layers, and separator layers between the bottommost and topmost electrodes, and their respective single-layer thicknesses. The average gap is calculated as: Average gap between electrode and adjacent separator = (Actual total thickness - Single-layer thickness of positive electrode × Number of positive electrode layers - Single-layer thickness of negative electrode × Number of negative electrode layers - Single-layer thickness of separator × Number of separator layers) / (Total number of positive electrode layers, negative electrode layers, and separator layers - 1).

[0055] In some embodiments, as shown in FIG3, in the bending region, starting from the innermost bending position of the wound cell, the average gap between the electrode and the separator in a direction at 45° to a third direction is 8.7 μm to 32.5 μm. Exemplarily, this gap is a value within the range of 8.7 μm, 8.9 μm, 9.9 μm, 10.5 μm, 15.5 μm, 18.30 μm, 20.5 μm, 25.5 μm, 28.65 μm, 30.5 μm, 32.31 μm, 32.5 μm, or any two of these values. By ensuring the gap between the electrode and the separator in the bending region is within the aforementioned range, it is beneficial to further enhance the capillary force between the positive and negative electrodes and the separator, thereby increasing the electrolyte's climbing height within the cell, improving the electrolyte's wetting effect, and ultimately enhancing the cycle performance of the battery cell. Optionally, in the bending region, starting from the innermost bending position of the wound cell, the gap between the electrode and the separator is 8.7μm-28.7μm in a direction at 45° to the third direction.

[0056] Figure 3 shows an example of a battery cell comprising two cells, but should not be construed as limiting the present disclosure. Those skilled in the art can adjust the number of cells in a battery cell as needed. As shown in Figure 3, in each cell, in the bending region on each side, there is a 45° angle to a third direction at the upper and lower parts of the bending region.

[0057] In some embodiments, as shown in FIG3, in the bending region, starting from the innermost bending position of the wound cell, the gap between the electrode and the separator in a direction at 90° to a third direction is 21.0 μm to 58.5 μm. Exemplarily, this gap can be a value between 21.0 μm, 23.72 μm, 25.23 μm, 25.65 μm, 28.5 μm, 30.5 μm, 35.5 μm, 40.5 μm, 45.5 μm, 50.5 μm, 55.23 μm, 58.23 μm, or any two of these values. By ensuring that the gap between the electrode and the separator within the aforementioned range, starting from the innermost bend in the winding cell and at a 90° angle to a third direction, it is beneficial to increase the capillary force between the positive and negative electrodes and the separator. This enhances the electrolyte's climbing height within the cell, thereby improving the electrolyte's wetting effect and enhancing the cycle performance of the battery cell. Optionally, the gap between the electrode and the separator, starting from the innermost bend in the winding cell and at a 90° angle to a third direction, is 23.5 μm to 55.5 μm.

[0058] In this disclosure, an exemplary method for measuring the average gap between the electrode and the adjacent separator in the bending region of a wound battery cell, starting from the innermost bending position of the wound battery cell and at a specific angle to a third direction, includes the following specific steps: Obtaining a CT image of the battery cell using the same method described above; marking rays in the bending region at a 45° or 90° angle to a third direction, starting from the innermost bending position of the wound battery cell; measuring the total thickness of the battery cell from the innermost winding starting position to the fourth winding position along the marked ray direction; calculating the average gap between the four measured layers: Average gap = (Actual total thickness - Single layer thickness of the positive electrode × Number of layers of the positive electrode - Single layer thickness of the negative electrode × Number of layers of the negative electrode - Single layer thickness of the separator × Number of layers of the separator) / (Total number of layers of the positive electrode, negative electrode, and separator - 1). Using the same method as above, continue counting 5 layers from the inside out, and calculate the average gap value between each 5-layer cell. The last part with less than 5 layers is treated as a group and its average gap is calculated. The average value of each calculated average gap value is taken as the average gap between the electrode and the adjacent separator.

[0059] In some embodiments, the separator includes a base membrane and a functional layer disposed on at least one side of the base membrane, the functional layer comprising porous ceramic particles. Due to their abundant pore structure, the porous ceramic particles can reduce electrolyte extrusion caused by the cell's respiration during cycling, thereby improving the separator's electrolyte retention capacity.

[0060] In some embodiments, the porous ceramic particles include one or more of boehmite, alumina, titanium dioxide, silicon dioxide, silicon carbide, barium sulfate, calcium sulfate, and glass fiber. These porous ceramic particles possess abundant pore structures and stable structural and chemical properties, exhibiting excellent electrolyte retention capabilities. This helps reduce electrolyte loss in the middle and / or top of the cell during cycling, thereby improving the battery's cycle performance.

[0061] In some embodiments, the porosity of the porous ceramic particles is 10%-80%. By keeping the porosity of the porous ceramic particles within this range, on the one hand, the pores in the porous ceramic particles help to increase the capillary force of the separator on the electrolyte, thereby increasing the climbing height of the electrolyte on the separator and improving the wettability of the electrolyte; on the other hand, the pores of the porous ceramic particles have a good electrolyte retention capacity, which helps to reduce electrolyte loss during cycling, thereby improving the cycle performance of the battery.

[0062] In this disclosure, the porosity of ceramic particles has a meaning known in the art. The porosity of ceramic particles can be tested using the following method: The tap density and true density of the ceramic particles are measured separately, and the porosity is calculated using the following formula: (1 - tap density / true density) × 100%. The tap density of the ceramic particles is tested as follows: The ceramic particles are placed in a container under specified conditions and tapped. The volume and mass after tapping are measured, and the tap density is calculated: Tap density = Sample mass / Tapped volume. The true density of the ceramic particles is measured using the gas adsorption method. The test method is as follows: The ceramic sample is placed in a true density meter. Under a closed testing system, helium gas is introduced according to a procedure. The gas pressure in the sample chamber and expansion chamber is detected. Then, the true volume of the sample is calculated according to Bohr's Law (PV = nRT). Finally, the true density of the ceramic particles is calculated based on the true volume and mass of the sample: True density = Sample mass / Sample true volume.

[0063] In some embodiments, the permeability of the separator is 156 s / 100 mL to 175.5 s / 100 mL. By maintaining the separator's permeability within this range, it is beneficial to improve the separator's adsorption rate and absorption rate of the electrolyte, enabling better adsorption and retention of the electrolyte and improving the cycle performance of the battery cell. Furthermore, it facilitates the passage of active ions in the electrolyte, improving the battery's ionic conductivity. Additionally, it helps to improve the separator's strength and thermal stability, enhancing battery safety. Exemplarily, the separator's permeability can be 156 s / 100 mL, 156.4 s / 100 mL, 160.3 s / 100 mL, 162.2 s / 100 mL, 174.4 s / 100 mL, 175.1 s / 100 mL, 175.5 s / 100 mL, or a value within a range of any two of these values.

[0064] In this disclosure, the air permeability of the diaphragm has a meaning known in the art and can be tested using methods known in the art. Exemplarily, an air permeability meter (e.g., the MODEL 4110N air permeability meter from Gurly, USA) is used to measure the permeability per unit area (e.g., 1 in) of the sample under constant temperature (e.g., 20°C-25°C) and unit pressure difference (e.g., 1.23 kPa). 2 Air permeability is the time required for a specific volume (e.g., 100 mL) of gas (e.g., air) to pass through. An exemplary test procedure includes: at room temperature (25°C), flattening the diaphragm obtained from a secondary battery, selecting a smooth, oil-free location, placing it at the air outlet of the air compressor cylinder of the air permeability meter, and tightening it securely. After fixing the diaphragm in place, the weight of the cylinder floating on the liquid is used to compress the air inside the cylinder, resulting in a pressure difference of 1.23 kPa across the diaphragm, with a test area of ​​one square inch (approximately 6.45 cm²). 2 As air passes through the sample, the cylinder falls smoothly. The time required for 100 mL of air to pass through the diaphragm is measured, and the air permeability is calculated accordingly.

[0065] In some embodiments, the ionic conductivity of the separator is 0.6 mS / cm to 0.95 mS / cm. By keeping the ionic conductivity of the separator within the above range, it is beneficial to improve the ionic conductivity of the separator to the electrolyte, reduce the internal resistance of the battery, reduce the polarization phenomenon inside the battery, and improve the cycle stability of the battery cells.

[0066] In this disclosure, the ionic conductivity of the separator has a meaning known in the art and can be tested using methods known in the art. Exemplarily, the specific testing steps are as follows: The separator is obtained by disassembling it from the secondary battery. The thickness of the separator is measured using a micrometer; multiple measurements can be taken and the average value taken to ensure the accuracy of the thickness data. The separator is sandwiched between two electrodes to assemble a test battery. The resistance value of a single-layer separator is measured using a resistance meter. The conductivity is calculated based on the measured resistance value and the separator thickness. The formula is as follows: Conductivity = 1 / (Resistance × Thickness), in mS / cm.

[0067] In some embodiments, the areal density of the diaphragm is 3 g / m³. 2 ~7.6g / m 2 By ensuring the areal density of the separator is within the aforementioned range, it is demonstrated that a lower areal density of the separator is beneficial in two ways: firstly, it helps reduce the overall volume and weight of the battery cells, thereby increasing the energy density of the battery cells; secondly, a lower areal density indicates a lower thermal shrinkage rate of the separator, which is beneficial for improving battery safety performance. Furthermore, a lower areal density helps improve the uniformity of separator thickness, enhances the mechanical strength of the separator, and also improves the cycle performance of the battery.

[0068] In this disclosure, the areal density of the separator refers to the mass per unit area of ​​the separator, which can be tested using methods known in the art. Exemplarily, the testing steps are as follows: The separator is obtained by disassembling it from a secondary battery, and a sample of a certain area of ​​the separator, for example, 100 cm², is cut. 2 The mass of the cut diaphragm sample is weighed using a high-precision electronic balance, and the areal density of the diaphragm is calculated according to the following formula: areal density = mass / area.

[0069] In some embodiments, the thickness of the functional layer is less than or equal to 5 μm. By keeping the thickness of the functional layer within this range, it is beneficial to improve the electrolyte seepage and retention capabilities of the separator, thereby enhancing the wettability of the electrolyte to the battery cell and improving the battery's cycle performance. For example, the thickness of the functional layer can be less than or equal to 5 μm, less than or equal to 4 μm, less than or equal to 3 μm, less than or equal to 2 μm, or less than or equal to 1 μm.

[0070] The battery cell disclosed herein also includes an electrolyte. The electrolyte acts as a conductor of ions between the positive and negative electrodes. This disclosure does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel-like, or solid.

[0071] The second aspect of this disclosure provides a method for preparing a battery cell. The method includes a step of sequentially stacking electrodes and separators and then cold-pressing them. The cold-pressing pressure is 20T to 50T, and the cold-pressing time is 20s to 150s. By sequentially stacking the electrodes and separators and then cold-pressing them, and by keeping the cold-pressing pressure and time within the aforementioned ranges, the average gap between the electrodes and adjacent separators is 6.3μm to 24μm. This is beneficial for improving the capillary force between the electrodes and separators in the prepared cell, increasing the electrolyte creep height and wettability within the cell, thereby improving the cycle performance of the prepared battery cell. In this disclosure, cold pressing is a well-known cell preparation process in the art, including placing the stacked electrodes and separators in a cold press, applying a certain pressure, and cold-pressing for a period of time, typically at room temperature, such as 25°C. For example, the cold pressing pressure can be 20T, 24T, 26T, 28T, 30T, 32T, 33.0T, 34.0T, 35.0T, 36.0T, 37.0T, 37.5T, 38.0T, 38.5T, 39.0T, 40.0T, 42.0T, 42.5T, 44T, 46T, 48T, 50T, or a value within a range of any two of these values. The cold pressing time can be 20s, 30s, 40s, 50s, 60s, 70s, 90s, 110s, 130s, 150s, or a value within a range of any two of these values. In some optional embodiments, the cold pressing pressure is 32T to 42.5T, and the cold pressing time is 20s to 60s. This facilitates a suitable average gap between the positive and negative electrodes and the separator in the prepared battery cell, increasing the electrolyte's creep height and wettability within the cell, and improving the battery's cycle performance. Furthermore, it helps to compact the electrode and separator layers, reducing the separator's resistance, increasing adhesion between the electrodes and / or separator, and improving the surface quality of the electrodes and / or separator.

[0072] In some embodiments, the preparation method further includes injecting an electrolyte into the bare cell obtained after cold pressing.

[0073] The components of the battery cell disclosed herein will be described in detail below.

[0074] Negative electrode sheet

[0075] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0076] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0077] 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0078] 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. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this disclosure 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.

[0079] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from 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).

[0080] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0082] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the 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.

[0083] Positive electrode sheet

[0084] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes the positive electrode material disclosed herein, or the positive electrode material prepared according to the preparation method of the present disclosure.

[0085] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector. 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0086] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this disclosure is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.1 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0087] 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 disclosure, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0088] In the examples of positive electrode active materials in this disclosure, the molar content of O is only a theoretical 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.

[0089] In some embodiments, when the battery cell is a sodium-ion battery, the positive electrode active material may be a known positive electrode active material for sodium-ion batteries. As an example, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds, Prussian blue compounds, etc.

[0090] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0091] In some embodiments, the positive electrode film 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.

[0092] 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.

[0093] electrolytes

[0094] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This disclosure does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0095] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0096] In some embodiments, the electrolyte salt may be selected from 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.

[0097] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0098] 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.

[0099] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0100] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0101] This disclosure does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 shows a square battery cell 5 as an example.

[0102] In some embodiments, referring to FIG5, the outer packaging may include a housing 51 and a top cover assembly 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0103] Battery device

[0104] In addition, this disclosure also provides a battery device, which includes the battery cell of this disclosure.

[0105] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0106] Figure 6 shows a battery module 4 as an example. Referring to Figure 6, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0107] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0108] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0109] Figures 7 and 8 show a battery pack 1 as an example. Referring to Figures 7 and 8, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0110] Electrical appliances

[0111] In addition, this disclosure also provides an electrical device, which includes the battery device provided in this disclosure. The battery device can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, 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.

[0112] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0113] Figure 9 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 the secondary battery for this device, a battery pack or battery module can be used.

[0114] Another example 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.

[0115] Example

[0116] The following describes embodiments of this disclosure. The embodiments described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. 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 the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0117] Example 1

[0118] Preparation of battery cells

[0119] Preparation of the positive electrode: Lithium iron phosphate (LFP) active material, carbon black conductive agent, and PVDF binder were mixed in a weight ratio of 98.2:0.3:1.5. N-methylpyrrolidone (NMP) solvent was added, and the mixture was thoroughly stirred to obtain a homogeneous positive electrode slurry. This slurry was then coated onto both surfaces of the positive electrode current collector aluminum foil. The coating weight of the positive electrode slurry was 0.3196 g / 1540.25 mm. 2 (Based on weight excluding solvent), after drying and cold pressing, a positive electrode sheet is obtained.

[0120] Preparation of negative electrode sheet:

[0121] Artificial graphite (specific capacity 330 mAh / g), carbon black (conductive agent), carboxymethyl cellulose (binder), and water were mixed in a weight ratio of 97.9:0.4:1.7:100. The mixture was thoroughly stirred to obtain a uniform negative electrode slurry. This slurry was then coated onto both sides of the copper foil used as the negative electrode current collector, with a coating weight of 0.1563 g / 1540.25 mm. 2 (Based on weight excluding solvent), after drying and cold pressing, a negative electrode sheet is obtained.

[0122] Electrolyte preparation:

[0123] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then dissolved in the mixture to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0124] Preparation of the diaphragm:

[0125] Preparation of functional layer: Alumina porous ceramic particles, acrylic block polymer dispersant and polyvinylidene fluoride binder are mixed in a weight ratio of 93:0.5:6.5 and dispersed in acetone solvent to obtain functional layer slurry.

[0126] A diaphragm is obtained by uniformly coating the functional layer slurry on both sides of the base membrane using a porous polyethylene membrane as the base membrane, and then drying and cold pressing. The thickness of the functional layer on one side of the base membrane is 2 μm.

[0127] Assembly of individual battery cells:

[0128] The negative electrode, positive electrode, and separator are stacked sequentially in the order of "separator-negative electrode-separator-positive electrode," with the separator positioned between the positive and negative electrodes to provide isolation. The layers are then wound to form a coil structure. This coil structure is placed in a cold press at a pressure of 38.5T for 30 seconds to obtain a coiled bare cell. The coiled bare cell is then placed in an outer packaging, injected with the electrolyte, and sealed for formation to obtain a battery cell with a height of L (239mm).

[0129] Parameter testing

[0130] Membrane parameter testing:

[0131] The separator was obtained by disassembling the secondary battery, and its performance was tested according to the following method.

[0132] (1) Breathability

[0133] Measurements were taken using a Gurly MODEL 4110N air permeability meter. The diaphragm was laid flat on a clean, oil-free surface and placed at the outlet of the air compressor cylinder of the air permeability meter. It was then tightened securely. After fixing the diaphragm in place, the weight of the cylinder floating on the liquid was used to compress the air inside the cylinder, resulting in a pressure difference of 1.23 kPa across the diaphragm. The test area was one square inch (approximately 6.45 cm²). 2 As air passes through the sample, the cylinder falls smoothly. The time required for 100 mL of air to pass through the diaphragm is measured as the air permeability (unit: s / 100 mL).

[0134] (2) Ionic conductivity

[0135] The thickness of the separator is measured using a micrometer. Multiple measurements can be taken and the average value taken to ensure accurate thickness data. The separator is then sandwiched between the two electrodes to assemble a test cell. The resistance of a single-layer separator is measured using a resistance meter. Based on the measured resistance and separator thickness, the conductivity is calculated. The formula is as follows: Conductivity = 1 / (Resistance × Thickness), in mS / cm.

[0136] (3) Surface density

[0137] Cut 100cm 2 For example, the mass of the diaphragm sample is weighed using a high-precision electronic balance, and the areal density of the diaphragm is calculated according to the following formula: areal density = mass / area.

[0138] Cell parameter testing

[0139] (1) Testing the gap between the electrode and the adjacent diaphragm in the large area.

[0140] The battery cells, obtained from disassembling individual battery cells, are placed in a CT scanner to obtain CT images. Using image analysis software, the bottommost positive (or negative) electrode and the topmost negative (or positive) electrode in the cell stacking direction are marked in the CT image, and the vertical distance between them is measured. The actual total thickness is calculated based on the scale of the CT image. The number of positive electrode plates, negative electrode plates, and separator layers between the bottommost positive electrode plate (or negative electrode plate) and the topmost negative electrode plate (or positive electrode plate) are recorded, along with their individual layer thicknesses. The average gap is calculated using the following formula:

[0141] Average gap between the electrode and the adjacent separator = (actual total thickness - single layer thickness of positive electrode × number of layers of positive electrode - single layer thickness of negative electrode × number of layers of negative electrode - single layer thickness of separator × number of layers of separator) / (total number of layers of positive electrode, negative electrode and separator - 1).

[0142] (2) Testing of the gap between the electrode and the adjacent diaphragm in the bending area

[0143] The battery cells disassembled from individual cells are placed in a CT scanner to obtain CT images. Using image analysis software, the bending areas in the CT images are marked, starting from the innermost bend of the wound cell. Along the marked ray direction at a 45° or 90° angle to the third direction, the total thickness of the cell is measured from the innermost winding start position to the fourth winding position. The average gap between the four measured layers is calculated as follows: Average gap = (Actual total thickness - Single layer thickness of positive electrode × Number of positive electrode layers - Single layer thickness of negative electrode × Number of negative electrode layers - Single layer thickness of separator × Number of separator layers) / (Total number of positive electrode, negative electrode, and separator layers - 1). Using the same method, this process is repeated, counting five layers from the inside out, and calculating the average gap between each group of five cells. The remaining cells with fewer than five layers are grouped together, and their average gap is calculated. The average of these calculated average gap values ​​is taken as the average gap between the electrode and the adjacent separator.

[0144] (3) Winding wetting rate

[0145] Hot air was circulated using a fan to maintain a uniform and stable temperature during the test, with an ambient temperature of 25±5℃. The prepared battery cells were placed in a tray containing electrolyte for immersion. The weight gain of the battery cells (i.e., the weight of the electrolyte) was recorded at regular intervals from placement in the tray to completion of immersion, resulting in a curve showing the change in electrolyte weight over time. The curve was fitted using data processing software to determine the slope, which is the winding immersion rate, expressed in g / s. 0.5 .

[0146] Battery cell performance testing

[0147] Cyclic performance test:

[0148] At 25℃, the battery cells are first charged at a constant current of 1C (the current value at which the theoretical capacity is completely discharged within 1 hour) to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After resting for 5 minutes, the battery is discharged at a constant current of 1C to a voltage of 2.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. The lithium-ion rechargeable battery is subjected to multiple charge-discharge cycles using the above method until the discharge capacity of the lithium-ion rechargeable battery decays to 80%, and the number of cycles is recorded.

[0149] Examples 2-6

[0150] The battery cells were prepared using the same method as in Example 1, except that the cold pressing pressure, cold pressing time, and height of the battery cells were adjusted according to Table 1 so that the gap between the electrode and the separator had the values ​​shown in Table 2.

[0151] Comparative Example 1

[0152] The battery cells were prepared using the same method as in Example 1, except that the cold pressing pressure and cold pressing time were adjusted according to Table 1 so that the gap between the electrode and the adjacent separator in the large area of ​​the cell was less than 6.3 μm.

[0153] Comparative Example 2

[0154] The battery cells were prepared using the same method as in Example 1, except that the cold pressing pressure and cold pressing time were adjusted according to Table 1 so that the gap between the electrode and the adjacent separator in the large area of ​​the cell was greater than 24 μm.

[0155] Table 1

[0156] The same test methods as in Example 1 were used to test Examples 1 to 6 and Comparative Examples 1 and 2, and the results are shown in Table 2 below.

[0157] Table 2

[0158] The results show that in Examples 1-6, by controlling the cold pressing pressure within the range of 20T-50T and the cold pressing time within the range of 20s-150s during battery preparation, the average gap between the positive and negative electrodes and the adjacent separator in the large area of ​​the battery cell in the third direction is within the range of 6.3μm-24μm. This is beneficial to improving the electrolyte wetting rate, thereby improving the cycle performance of the battery. In contrast, Comparative Example 1 used a cold pressing time exceeding 150s during battery cell preparation, resulting in an average gap between the electrode and the adjacent separator in the large area of ​​the prepared battery cell being less than 6.3μm. Comparative Example 2 used a cold pressing pressure less than 20T to prepare the battery cell, resulting in an average gap between the electrode and the adjacent separator in the large area of ​​the prepared battery cell being greater than 24μm. The winding wetting rate of the cells in Comparative Examples 1 and 2 is low, and the electrolyte wetting effect is poor, resulting in poor cycle performance of the battery cells.

[0159] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in the technical scope of this disclosure. 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, are also included in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A battery cell, The height of the battery cell is 200mm or more. The battery cell includes at least one battery cell, and the battery cell includes electrodes and a separator. The electrode extends along a first direction, and the length of the electrode along the first direction is greater than its length along a second direction. The second direction is perpendicular to the first direction and is the same as the height direction of the battery cell. The electrode and the separator are stacked along a third direction, which is perpendicular to both the first and second directions. The cell has a large surface area in a cross-section perpendicular to the height direction of the battery cell, and the average gap between the electrode and the adjacent separator in the third direction of the large surface area is 6.3μm-24μm.

2. The battery cell of claim 1, wherein, In the large area, the average gap between the electrode and the adjacent diaphragm in the third direction is 8.2 μm-20.3 μm.

3. The battery cell of claim 1 or 2, wherein, The battery cell is a wound battery cell, and the wound battery cell includes a large surface area and bending areas located on both sides of the large surface area along the first direction in a cross section perpendicular to the height direction of the battery cell. In the bending region, starting from the innermost bending position of the wound cell, the average gap between the electrode and the separator is 8.7 μm to 32.5 μm in a direction at 45° to the third direction.

4. The battery cell of claim 3, wherein, In the bending region, starting from the bending position of the innermost layer of the wound cell, the average gap between the electrode and the separator is 8.9 μm to 28.7 μm in a direction at 45° to the third direction.

5. The battery cell of claim 3 or 4, wherein, In the bending region, starting from the innermost bending position of the wound cell, the average gap between the electrode and the separator is 21.0 μm to 58.5 μm in a direction at 90° to the third direction.

6. The battery cell of claim 5, wherein, In the bending region, starting from the innermost bending position of the wound cell, the average gap between the electrode and the separator is 23.5 μm to 55.5 μm in a direction at 90° to the third direction.

7. The battery cell of any one of claims 1 to 6, wherein, The diaphragm includes a base membrane and a functional layer disposed on at least one side of the base membrane, the functional layer comprising porous ceramic particles.

8. The battery cell of claim 7, wherein, The porous ceramic particles include one or more of boehmite, aluminum oxide, titanium dioxide, silicon dioxide, silicon carbide, barium sulfate, calcium sulfate, and glass fiber.

9. The battery cell of claim 7 or 8, wherein, The air permeability of the diaphragm is 156s / 100mL-175.5s / 100mL.

10. The battery cell of any one of claims 7-9, wherein, The ionic conductivity of the membrane is 0.6 mS / cm to 0.95 mS / cm.

11. The battery cell of any one of claims 7-10, wherein, The face density of the separator is 3 g / m 2 ~ 7.6 g / m 2 .

12. The battery cell of any one of claims 7-11, wherein, The thickness of the functional layer is less than or equal to 5 μm.

13. The battery cell of any one of claims 1-12, wherein, The height of the battery cell is 200mm-300mm.

14. A method for preparing a battery cell, wherein the height of the battery cell is 200 mm or more, and the method includes a step of sequentially stacking an electrode and a separator and then cold pressing the stack, wherein the cold pressing pressure is 20 T to 50 T and the cold pressing time is 20 s to 150 s.

15. The method of manufacturing according to claim 14, wherein, The cold pressing pressure is 32T to 42.5T, and the cold pressing time is 20s to 60s.

16. A battery device comprising the battery cell according to any one of claims 1 to 13, or, comprising the battery cell prepared according to the preparation method of claim 14 or 15.

17. An electric device comprising the battery device of claim 16.

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