A battery

Abstract

The utility model discloses a kind of batteries, it is related to battery technical field, including electric core and membrane shell, electric core is located in the accommodating cavity of membrane shell, electric core includes the first pole piece of multiple polarities same being stacked along Z axis direction, first pole piece includes the most top layer first pole piece of accommodating cavity's inner bottom surface away along Z axis direction and the most bottom layer first pole piece close to accommodating cavity's inner bottom surface;In X axis direction, the length of most top layer first pole piece is L1, the length of most bottom layer first pole piece is L2, the horizontal distance of the bottom surface linear edge of inner bottom surface to the top side linear edge of inner side surface is L3;And / or, in Y axis direction, the width of most top layer first pole piece is L1, the width of most bottom layer first pole piece is L2, the horizontal distance of the bottom surface linear edge of inner bottom surface to the top side linear edge of inner side surface is L3;L1, L2 and L3 satisfy: 0≤L1-L2≤L3;Wherein, L3 satisfies: 0.15mm≤L3≤0.5mm. By improving the space utilization of electric core in membrane shell, the energy density of battery is improved.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a battery. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, new energy vehicles, and energy storage power stations due to their advantages such as high energy density, good cycle performance, and small size.

[0003] During the cell design phase, to avoid mechanical interference between the electrode and the inner surface of the cavity, the electrode size is usually designed based on the narrower part of the cavity bottom. While this design effectively prevents the electrode from scratching the aluminum-plastic film or wrinkling during assembly, it leaves gaps between the electrode and the wider part of the cavity, resulting in underutilization of the battery's internal space and consequently energy density loss. Furthermore, if the electrode size is too large, it is prone to interfering with the cavity during cell installation, potentially breaking the membrane or causing edge damage to the electrode or membrane. This compromises the structural and encapsulation integrity of the electrode, posing safety hazards and compromising the overall battery safety performance. Utility Model Content

[0004] The purpose of this invention is to provide a battery that, by limiting the size of the electrode sheets in the housing cavity, allows some or all of the electrode sheets inside the membrane shell to be designed with different sizes, making the overall shape of the battery cell closer to the internal contour of the housing cavity, improving the space utilization rate of the battery cell inside the membrane shell, effectively improving the energy density of the battery, and solving the technical problem of energy density loss caused by low space utilization rate in existing batteries.

[0005] To achieve the above objectives, this utility model provides a battery, including a battery cell and a membrane housing. The battery cell is disposed within a receiving cavity of the membrane housing. The inner surface of the receiving cavity includes an inner bottom surface and an inner side surface surrounding the inner bottom surface and arranged at an angle to the inner bottom surface. The battery cell includes a plurality of first electrode plates of the same polarity stacked along the Z-axis direction. The first electrode plates include a topmost first electrode plate away from the inner bottom surface and a bottommost first electrode plate close to the inner bottom surface along the Z-axis direction.

[0006] The inner bottom surface and the inner side surface are connected by an inner arc surface. The inner bottom surface includes a bottom straight edge that intersects with the inner arc surface, and the inner side surface includes a top straight edge on the side away from the inner arc surface.

[0007] In the X-axis direction, the length of the first electrode plate of the top layer is L1, the length of the first electrode plate of the bottom layer is L2, and the horizontal distance from the straight edge of the bottom surface to the straight edge of the top surface is L3.

[0008] And / or, in the Y-axis direction, the width of the topmost first electrode is L1, the width of the bottommost first electrode is L2, and the horizontal distance from the bottom straight edge to the top straight edge is L3.

[0009] The following conditions must be met between L1, L2 and L3: 0 ≤ L1 - L2 ≤ L3; where L3 satisfies: 0.15 mm ≤ L3 ≤ 0.5 mm.

[0010] In some embodiments, L1 and L2 satisfy the following condition: 0.001 ≤ ≤0.035.

[0011] In some embodiments, in the X-axis direction, the distance between the side surface of the top first electrode and the inner surface is L4, and the distance between the side surface of the bottom first electrode and the inner surface is L5; and / or, in the Y-axis direction, the distance between the side surface of the top first electrode and the inner surface is L4, and the distance between the side surface of the bottom first electrode and the inner surface is L5.

[0012] The following condition must be met between L4 and L5: 0 ≤ L5 - L4 ≤ 0.7 mm.

[0013] In some embodiments, the battery cell includes at least one stacked core arranged along the Z-axis direction, the stacked core including a positive electrode and a negative electrode, and the first electrode is at least one of the positive electrode and the negative electrode.

[0014] Adjacent inner surfaces are connected by a side arc surface; along the diagonal direction of the inner bottom surface and / or along the symmetrical center line of the side arc surface, the diagonal of the inner bottom surface intersects with the symmetrical center line of the side arc surface to form a first intersection point A; the symmetrical center line of the side arc surface intersects with the top transition edge of the side arc surface away from the first intersection point A to form a second intersection point B; the symmetrical center line of the side arc surface intersects with the bottom transition edge of the side arc surface near the first intersection point A to form a third intersection point C; the first intersection point A, the third intersection point C, and the second intersection point B are connected in sequence.

[0015] Along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the topmost first electrode in the X-axis direction is greater than the length of the bottommost first electrode in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the topmost first electrode in the Y-axis direction is greater than the width of the bottommost first electrode in the Y-axis direction.

[0016] And / or, along the Z-axis away from the inner bottom surface, the length of multiple first pole pieces with the same polarity gradually increases in the X-axis direction; and / or, along the Z-axis away from the inner bottom surface, the width of multiple first pole pieces with the same polarity gradually increases in the Y-axis direction.

[0017] In some embodiments, the first electrode includes a first side extending along the X-axis direction and a second side extending along the Y-axis direction, the first side and the second side intersect to form a transition corner of the first electrode, and the radius of the transition corner of the first electrode is R;

[0018] The radius of the transition corner of the topmost first electrode is R1, and the radius of the transition corner of the bottommost first electrode is R2. Along the Z-axis, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy the following condition: R1 < R2.

[0019] And / or, along the Z-axis away from the inner bottom surface, the radius R of the transition corner of all the first pole pieces gradually decreases.

[0020] In some embodiments, the battery cell includes at least one stacked core arranged along the Z-axis direction, the stacked core including a first stacked core and a second stacked core disposed on the side of the first stacked core near the inner bottom surface;

[0021] The first core stack includes at least two first electrode sheets stacked along the Z-axis direction and having the same polarity; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the topmost first electrode sheet in the X-axis direction is greater than the length of the bottommost first electrode sheet in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the topmost first electrode sheet in the Y-axis direction is greater than the width of the bottommost first electrode sheet in the Y-axis direction;

[0022] And / or, along the Z-axis away from the inner bottom surface, the length of all the first pole pieces of the first core gradually increases in the X-axis direction; and / or, along the Z-axis away from the inner bottom surface, the width of all the first pole pieces of the first core gradually increases in the Y-axis direction;

[0023] And / or, a single first electrode of the first stacked core includes a first side extending along the X-axis and a second side extending along the Y-axis, the first side and the second side intersecting to form a transition corner of the first electrode, the radius of the transition corner of the top first electrode is R1, and the radius of the transition corner of the bottom first electrode is R2; along the Z-axis, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy: R1 < R2;

[0024] And / or, along the Z-axis away from the inner bottom surface of the receiving cavity, the radius R of the transition corner of all the first pole pieces of the first stack gradually decreases.

[0025] In some embodiments, the second core stack includes at least two first pole pieces stacked along the Z-axis direction and having the same polarity; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the topmost first pole piece in the X-axis direction is greater than the length of the bottommost first pole piece in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the topmost first pole piece in the Y-axis direction is greater than the width of the bottommost first pole piece in the Y-axis direction; and / or, along the Z-axis direction away from the inner bottom surface, the length of all the first pole pieces in the X-axis direction gradually increases; and / or, the width of all the first pole pieces in the Y-axis direction gradually increases.

[0026] And / or, a single first electrode of the second stacked core includes a first side extending along the X-axis and a second side extending along the Y-axis. The first side and the second side intersect to form a transition corner of the first electrode. The radius of the transition corner of the topmost first electrode is R1, and the radius of the transition corner of the bottommost first electrode is R2. Along the Z-axis, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy the following condition: R1 < R2.

[0027] And / or, along the Z-axis away from the inner bottom surface, the radius R of the transition corner of all the first pole pieces of the second stack core gradually decreases.

[0028] In some embodiments, the thickness of the second core stack in the Z-axis direction is h2; the inner surface includes a bottom straight edge that intersects with the inner arc surface, and the vertical distance between the bottom straight edge and the bottom straight edge in the Z-axis direction is L6; h2 and L6 satisfy: h2≤L6.

[0029] And / or, a reference arc segment is formed between the first intersection point A and the third intersection point C, and the radius of the reference arc segment is R. AC h2 and R AC The condition is satisfied between: 0.6 ≤ ≤1.

[0030] In some embodiments, the thickness of the first core stack in the Z-axis direction is h1, and the thickness of the second core stack in the Z-axis direction is h2, where h1 and h2 satisfy: 2mm≤h1≤10mm, 2mm≤h2≤10mm;

[0031] The radius of the side arc surface is R. BC R BC Satisfies: 0.5mm≤R BC ≤5mm;

[0032] The radius of the reference arc segment is R. AC R AC Satisfies: 0.75mm≤R AC ≤8mm.

[0033] In some embodiments, both the first core stack and the second core stack include a second electrode sheet, the polarity of the first electrode sheet and the polarity of the second electrode sheet are opposite; the second electrode sheet includes a third side extending along the X-axis direction and a fourth side extending along the Y-axis direction, the third side and the fourth side intersect to form a transition corner of the second electrode sheet;

[0034] The second electrode is the negative electrode, and the first electrode is the positive electrode. The negative and positive electrodes are stacked together, and the radius of the transition corner of the positive electrode is R. 正， The radius of the transition angle of the negative electrode is R. 负 ;

[0035] Both the negative and positive electrode plates have outer rounded corners at their transition points; R 负 R 正 R BC With R AC The following conditions must be met between R: BC ≤R 正 ≤R 负 ≤R AC ; and / or, R 负 R 正 With R BC The following condition must be met: 0.7mm ≤ R 正 ≤R 负 ≤R BC ;

[0036] And / or, the transition corners of both the negative and positive electrodes are at least one of an inner rounded corner, a chamfer, or a composite chamfer, and the minimum distance from the transition edge of the transition corner of the negative electrode to its center point is R. 负 The minimum distance from the transition edge of the positive electrode's transition corner to its center point is R. 正 ;R 负 R 正 R BC With R AC The following conditions must be met between R: BC ≤R 负 ≤R 正 ≤R AC ; and / or, R 负 R 正 With R BC The following conditions must be met between R: BC ≤R 负 ≤R 正 .

[0037] Compared to the prior art, this utility model optimizes the structure of the battery cell in the housing cavity based on the draft angle of the housing cavity. The optimized battery cell includes multiple first electrode sheets with the same polarity stacked along the Z-axis direction. The first electrode sheets include the topmost first electrode sheet away from the inner bottom surface of the housing cavity along the Z-axis direction and the bottommost first electrode sheet close to the inner bottom surface of the housing cavity. The adjacent two inner surfaces of the housing cavity are connected by a side arc surface. Along the diagonal direction of the inner bottom surface of the housing cavity and / or along the symmetry center line direction of the side arc surface, the diagonal of the inner bottom surface of the housing cavity intersects with the symmetry center line of the side arc surface to form a first intersection point A. The symmetry center line of the side arc surface intersects with the top transition edge of the side arc surface away from the first intersection point A to form a second intersection point B.

[0038] In the X-axis direction, the length of the topmost first electrode is L1, the length of the bottommost first electrode is L2, and the horizontal distance from the first intersection point A to the second intersection point B is L3; and / or, in the Y-axis direction, the width of the topmost first electrode is L1, the width of the bottommost first electrode is L2, and the horizontal distance from the first intersection point A to the second intersection point B is L3; L1, L2, and L3 satisfy: 0 ≤ L1 - L2 ≤ L3; where L3 satisfies: 0.15 mm ≤ L3 ≤ 0.5 mm.

[0039] This invention limits the dimensional difference of the electrodes at different positions in the cell thickness direction within the housing cavity. On one hand, it rationally controls the electrode size to better match the internal contour of the cavity without affecting the battery assembly, thereby improving the space utilization rate inside the housing cavity 21. This allows the limited-volume housing cavity to hold more active material, thus increasing the battery's energy density. On the other hand, the size limitation effectively prevents excessive dimensional margins between the top and bottom electrodes, which could lead to poor contact between the electrode edges during battery hot pressing and cause lithium plating. At the same time, it ensures that each electrode maintains a sufficient safe distance from the inner wall of the cavity, avoiding risks such as the film being ruptured or the electrode edges being damaged due to interference between the electrodes and the cavity wall after packaging, thus effectively improving the battery's safety performance. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 A schematic diagram of the battery provided in an embodiment of this utility model;

[0042] Figure 2 for Figure 1 Schematic diagram of the middle membrane shell;

[0043] Figure 3 for Figure 1 Another schematic diagram of the middle membrane shell;

[0044] Figure 4 for Figure 3 A magnified view of a portion of the image;

[0045] Figure 5 for Figure 1 Diagonal sectional view of the middle membrane shell;

[0046] Figure 6 for Figure 1 Half-sectional view of the middle membrane shell, the topmost first electrode plate, and the bottommost first electrode plate;

[0047] Figure 7 for Figure 1 Half-sectional view of the middle membrane shell;

[0048] Figure 8 for Figure 1 Half-sectional view of the middle membrane shell, the first core stack, and the second core stack;

[0049] Figure 9 for Figure 1 Half-sectional view of the middle membrane shell, the first core stack, the second core stack, and the second electrode;

[0050] Figure 10 for Figure 6 A schematic diagram of the topmost and bottommost first electrode plates;

[0051] Figure 11 for Figure 9 A schematic diagram of the second electrode plate;

[0052] Figure 12 This is a schematic diagram of the transition angle of the positive electrode plate;

[0053] Figure 13 This is a schematic diagram of the transition angle of the negative electrode.

[0054] The attached figures are labeled as follows:

[0055] Cell 1 and membrane housing 2;

[0056] First electrode 101 and second electrode 102;

[0057] The topmost first electrode plate 1011 and the bottommost first electrode plate 1012;

[0058] First core stack 11 and second core stack 12;

[0059] Receiving cavity 21;

[0060] Inner bottom surface 211 and inner side surface 212, side arc surface 213 and inner arc surface 214;

[0061] The straight edge of the bottom surface is 2111.

[0062] Top side straight edge 2121 and bottom side straight edge 2122;

[0063] Top transition edge 2131, left straight edge 2132, bottom transition edge 2133 and right straight edge 2134;

[0064] Outer bottom surface 221 and outer side surface 222. Detailed Implementation

[0065] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0066] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] First, it should be noted that, with the appendix Figure 1 Based on the coordinate system in the text, the X-axis is the length direction of cell 1 (i.e., the extension direction of the tab), the Y-axis is the width direction of cell 1, and the Z-axis is the thickness direction of cell 1.

[0068] Lithium-ion batteries are typically encapsulated using an aluminum-plastic film to form the battery casing, providing effective protection for the internal battery cells. The battery casing is generally formed using a stamping process, where a cavity of a certain depth is stamped into the aluminum-plastic film using a mold to accommodate the battery cells. To facilitate demolding after stamping and reduce tearing or deformation, the inner surface of the cavity is usually designed with a certain draft angle, meaning the inner surface of the cavity is at a certain angle to its inner bottom surface, rather than being completely perpendicular. This causes the cross-sectional dimensions of the cavity to change at different depths, resulting in the bottom width of the cavity being smaller than its opening width. To better match the internal contour of the cavity 21 of the casing 2 with the dimensions of the electrodes within it, this utility model embodiment discloses a battery, as shown in the attached figure. Figure 1 and 8 As shown, it includes a battery cell 1 and a membrane housing 2. The battery cell 1 is disposed in the receiving cavity 21 of the membrane housing 2. The receiving cavity 21 is formed by stamping process.

[0069] As attached Figures 2 to 5As shown, the inner surface of the receiving cavity 21 includes an inner bottom surface 211 and inner side surfaces 212 surrounding the inner bottom surface 211 and arranged at an angle to the inner bottom surface 211. The receiving cavity 21 includes four inner side surfaces 212 connected end to end in sequence, each inner side surface 212 is arranged at an angle to the inner bottom surface 211, and the angle between each inner side surface 212 and the inner bottom surface 211 is greater than 90 degrees.

[0070] As attached Figure 6 and 10 As shown, the battery cell 1 includes a plurality of first electrode sheets 101 of the same polarity stacked along the Z-axis direction. The first electrode sheet 101 includes a topmost first electrode sheet 1011 away from the inner bottom surface 211 along the Z-axis direction and a bottommost first electrode sheet 1012 close to the inner bottom surface 211.

[0071] As attached Figure 3 As shown, the inner bottom surface 211 and the inner side surface 212 are connected by the inner arc surface 214. The inner bottom surface 211 includes a bottom straight edge 2111 that intersects with the inner arc surface 214, and the inner side surface 212 includes a top straight edge 2121 on the side away from the inner arc surface 214.

[0072] As attached Figure 6 and 7 As shown, in the X-axis direction, the length of the topmost first electrode 1011 is L1, the length of the bottommost first electrode 1012 is L2, and the horizontal distance from the bottom straight edge 2111 to the top straight edge 2121B is L3; and / or, in the Y-axis direction, the width of the topmost first electrode 1011 is L1, the width of the bottommost first electrode 1012 is L2, and the horizontal distance from the bottom straight edge 2111 to the top straight edge 2121 is L3; L1, L2, and L3 satisfy: 0≤L1-L2≤L3; wherein, L3 satisfies: 0.15mm≤L3≤0.5mm; preferably, L3 satisfies: 0.2mm≤L3≤0.4mm.

[0073] This invention limits the size difference of the electrode sheets at different positions in the cell thickness direction within the housing cavity. On the one hand, it reasonably controls the electrode sheet size to better match the internal contour of the cavity without affecting the battery assembly, thereby improving the space utilization rate inside the housing cavity 21. This allows the limited-volume housing cavity to hold more active material, thus increasing the energy density of the battery. On the other hand, the size limitation effectively prevents excessive dimensional margins between the top and bottom first electrode sheets, ensuring that each electrode sheet maintains a sufficient safe distance from the inner wall of the cavity. This avoids risks such as the film being ruptured or the electrode sheet edges being damaged due to interference between the electrode sheets and the cavity wall after encapsulation, effectively improving the safety performance of the battery.

[0074] As attached Figure 6 As shown, in a preferred embodiment, L1 and L2 satisfy the following condition: 0.001 ≤ The size of the first electrode 1011 exceeding the first electrode 1012 by ≤0.035 has two advantages. First, it prevents the top electrode 1 from being too large beyond the bottom electrode 1012, which could cause interference between the cell 1 and the casing 2 when it is installed. Under extreme conditions (drop), it also prevents the electrodes from being squeezed against the casing 2, thus avoiding damage to the electrodes and affecting the cycle life and safety performance of the cell 1. Second, it prevents the top electrode 1011 from being too small beyond the bottom electrode 1012, which could lead to wasted space in the housing 21 and thus reduce the energy density of the battery due to low space utilization. By controlling the size of the top electrode 1011 exceeding the bottom electrode 1012, this invention reduces the risk of poor pressure on the edge of the first electrode 101 during hot pressing, thereby reducing black spots and lithium plating, which is beneficial to improving the safety performance of the battery.

[0075] As attached Figure 2 As shown, in a preferred embodiment, the outer surface of the membrane shell 2 includes an outer bottom surface 221 and an outer side surface 222 that is angled to the outer bottom surface 221. The outer bottom surface 221 is parallel to the inner bottom surface 211, and the outer side surface 222 is parallel to the inner side surface 212, thus ensuring that the contour shapes of the inner and outer surfaces of the membrane shell 2 are consistent.

[0076] As a preferred embodiment, as shown in the appendix Figure 6 As shown, in the X-axis direction, the distance between the side surface of the topmost first electrode 1011 and the inner surface 212 is L4, and the distance between the side surface of the bottommost first electrode 1012 and the inner surface 212 is L5; and / or, in the Y-axis direction, the distance between the side surface of the topmost first electrode 1011 and the inner surface 212 is L4, and the distance between the side surface of the bottommost first electrode 1012 and the inner surface 212 is L5; L4 and L5 satisfy the following condition: 0 ≤ L5 - L4 ≤ 0.7 mm. Meeting the above dimensional relationship ensures that the first electrode 101 is stacked more uniformly during the stacking process, effectively improving the space occupancy distribution of the cell 1 inside the membrane housing 2 and maximizing the utilization of the space inside the membrane housing 2. By controlling the difference between L4 and L5 within a reasonable range, it is possible to avoid wasting internal space in the receiving cavity 21 due to excessive misalignment of the electrodes, and also to prevent interference between the electrode size and the membrane housing 2. Therefore, while ensuring the reliability of the battery structure and cycle performance, the internal space of the cavity 21 can be fully utilized, thereby effectively improving the energy density of the cell 1.

[0077] As a preferred embodiment, as shown in the appendix Figure 8 and 9 As shown, the battery cell 1 includes at least one stacked core arranged along the Z-axis direction. The stacked core includes a positive electrode and a negative electrode, and the first electrode 101 is at least one of the positive electrode and the negative electrode.

[0078] As attached Figures 3 to 5 As shown, two adjacent inner surfaces 212 are connected by a side arc surface 213. Along the diagonal direction of the inner bottom surface 211 and / or along the symmetry center line of the side arc surface 213, the diagonal of the inner bottom surface 211 intersects the symmetry center line of the side arc surface 213 to form a first intersection point A. The symmetry center line of the side arc surface 213 intersects the top transition edge of the side arc surface 213 away from the first intersection point A to form a second intersection point B. The symmetry center line of the side arc surface 213 intersects the bottom transition edge of the side arc surface 213 near the first intersection point A to form a third intersection point C. The first intersection point A, the third intersection point C, and the second intersection point B are connected in sequence.

[0079] It should be noted that, as shown in the attached document... Figure 4 As shown, the side arc surface 213 includes an inner arc surface and an outer arc surface, which are arranged opposite each other along the wall thickness direction of the side arc surface 213. The inner arc surface faces the receiving cavity 21, and the outer arc surface is arranged away from the receiving cavity 21. The inner arc surface is formed by four side edges, including a sequentially connected 2131, a left straight edge 2132, a bottom transition edge 2133, and a right straight edge 2134. The left straight edge 2132 and the right straight edge 2134 are opposite each other and are straight edges that intersect with the adjacent inner surface 212 of the receiving cavity 21, respectively. The top transition edge 2131 is opposite to the bottom transition edge 2133 and is connected between the left straight edge 2132 and the right straight edge 2134. The top transition edge 2131 is the arc edge of the inner arc surface away from the inner bottom surface 211, and the bottom transition edge 2133 is the arc edge of the inner arc surface close to the inner bottom surface 211.

[0080] It should be added that the method for accurately locating the first intersection point A, the second intersection point, and the third intersection point C on the membrane shell 2 is as follows: First, use a 3D profilometer to scan the outer contour of the membrane shell 2. Then, draw lines along the diagonal direction of the inner bottom surface 211 of the receiving cavity 21 and / or along the symmetry center line of the side arc surface 213 to obtain the three points A, C, and D. Alternatively, the cell 1 can be directly cut along the diagonal direction of the inner bottom surface 211 of the receiving cavity 21 and / or along the symmetry center line of the side arc surface 213, and the membrane shell 2 and each electrode can be observed under a 2.5D microscope or a microscope.

[0081] As a preferred embodiment, as shown in the appendix Figure 6As shown, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the top first electrode 1011 in the X-axis direction is greater than the length of the bottom first electrode 1012 in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the top first electrode 1011 in the Y-axis direction is greater than the width of the bottom first electrode 1012 in the Y-axis direction; ensuring that the outer dimensions of the top first electrode 1011 are greater than the outer dimensions of the bottom first electrode 1012, so that the top first electrode 1011 makes full use of the larger space of the top layer of the cavity 21, and the bottom first electrode 1012 makes full use of the smaller space of the bottom layer of the cavity 21. Compared with the design of a single-size first electrode 101, the space of the cavity 21 can be utilized more effectively, and more active material can be loaded in a limited space, which is beneficial to improving the energy density of the battery.

[0082] And / or, as another preferred embodiment, along the Z-axis away from the inner bottom surface 211, the length of multiple first electrode sheets 101 with the same polarity gradually increases in the X-axis direction; and / or, along the Z-axis away from the inner bottom surface 211, the width of multiple first electrode sheets 101 with the same polarity gradually increases in the Y-axis direction. That is, the dimensions of all the first electrode sheets 101 are designed to gradually change along the Z-axis direction, so that the outer contour of the cell 1 matches the inner contour of the receiving cavity 21 better, making full use of every corner of the receiving cavity 21, effectively improving the space utilization rate inside the receiving cavity 21, and loading more active materials in a limited space, thereby increasing the energy density of the battery.

[0083] As a preferred embodiment, as shown in the appendix Figure 10 As shown, the radius of the transition corner of the topmost first electrode 1011 is R1, and the radius of the transition corner of the bottommost first electrode 1012 is R2. Along the Z-axis, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy the condition: R1 < R2. The larger radius of the transition corner of the bottommost first electrode 1012 effectively reduces interference or jamming between the bottommost first electrode 1012 and the separator and other electrodes during alignment, making the stacking process smoother and improving manufacturing yield. The smaller radius of the transition corner of the topmost first electrode 1011 maximizes the active area without increasing the process difficulty, which is beneficial for improving energy density.

[0084] And / or, as another preferred embodiment, the first electrode 101 includes a first side extending along the X-axis and a second side extending along the Y-axis. The first side and the second side intersect to form a transition corner of the first electrode 101, and the radius of the transition corner of the first electrode 101 is R. Along the Z-axis away from the inner bottom surface 211, the radius R of the transition corners of all the first electrodes 101 gradually decreases. That is, the radius of the transition corners of all the first electrodes 101 gradually increases from bottom to top along the Z-axis, so that the electrodes closer to the top layer adopt a smaller radius transition corner, so that they can extend more fully to the corner space at the top of the receiving cavity 21, maximizing the filling efficiency of the active material. Conversely, the electrodes closer to the bottom layer adopt a smaller radius transition corner, which helps to adapt to the bottom structure and alleviate stress concentration. This effectively avoids space waste caused by a single or mismatched rounded corner radius, and further improves the energy density of the battery.

[0085] As a preferred embodiment, as shown in the appendix Figure 8 and 9 As shown, the battery cell 1 includes at least one stacked core arranged along the Z-axis direction. The stacked core includes a first stacked core 11 and a second stacked core 12 disposed on the side of the first stacked core 11 near the inner bottom surface 211. The first stacked core 11 and the second stacked core 12 can be a Z-type stacked core structure or an E-type stacked core structure.

[0086] In a preferred embodiment, the first core stack 11 includes at least two first electrode sheets 101 stacked along the Z-axis direction and having the same polarity; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the topmost first electrode sheet 1011 in the X-axis direction is greater than the length of the bottommost first electrode sheet 1012 in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the topmost first electrode sheet 1011 in the Y-axis direction is greater than the width of the bottommost first electrode sheet 1012 in the Y-axis direction;

[0087] And / or, along the Z-axis away from the inner bottom surface 211, the length of all the first pole pieces 101 of the first stacked core 11 gradually increases in the X-axis direction; and / or, along the Z-axis away from the inner bottom surface 211, the width of all the first pole pieces 101 of the first stacked core 11 gradually increases in the Y-axis direction.

[0088] And / or, a single first electrode 101 of the first stacked core 11 includes a first side extending along the X-axis direction and a second side extending along the Y-axis direction. The first side and the second side intersect to form a transition corner of the first electrode 101. The radius of the transition corner of the topmost first electrode 1011 is R1, and the radius of the transition corner of the bottommost first electrode 1012 is R2. Along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy the following condition: R1 < R2.

[0089] And / or, along the Z-axis away from the inner bottom surface 211 of the receiving cavity 21, the radius R of the transition corner of all the first pole pieces 101 of the first stacked core 11 gradually decreases.

[0090] Therefore, it can be seen that the present invention performs gradient design on the outer dimensions of all the first electrode sheets 101 of the first stacked core 11 and the radius of the transition corner, so that the outer contour of the first stacked core 11 can be highly matched with the inner contour of the receiving cavity 21, which greatly improves the space utilization of the receiving cavity 21, and improves the safety performance of the battery while increasing the energy density.

[0091] As a preferred embodiment, as shown in the appendix Figure 8 and 9 As shown, the second core stack 12 includes at least two first electrode sheets 101 stacked along the Z-axis direction and having the same polarity; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the topmost first electrode sheet 1011 of the second core stack 12 in the X-axis direction is greater than the length of the bottommost first electrode sheet 1012 in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the topmost first electrode sheet 1011 of the second core stack 12 in the Y-axis direction is greater than the width of the bottommost first electrode sheet 1012 in the Y-axis direction; and / or, along the Z-axis direction away from the inner bottom surface 211, the length of all the first electrode sheets 101 of the second core stack 12 gradually increases in the X-axis direction; and / or, the width of all the first electrode sheets 101 of the second core stack 12 gradually increases in the Y-axis direction.

[0092] And / or, a single first electrode 101 of the second stacked core 12 includes a first side extending along the X-axis direction and a second side extending along the Y-axis direction. The first side and the second side intersect to form a transition corner of the first electrode 101. The radius of the transition corner of the topmost first electrode 1011 is R1, and the radius of the transition corner of the bottommost first electrode 1012 is R2. Along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy the following condition: R1 < R2.

[0093] And / or, along the Z-axis away from the inner bottom surface 211, the radius R of the transition corner of all the first pole pieces 101 of the second stacked core 12 gradually decreases.

[0094] Similarly, this invention also performs gradient design on the outer dimensions of all the first electrode sheets 101 of the second core stack 12 and the radius of the transition corner, so that the outer contour of the second core stack 12 can be highly matched with the inner contour of the receiving cavity 21, which can also improve the energy density and the safety performance of the battery.

[0095] Furthermore, it should be noted that both the first core stack 11 and the second core stack 12 include multiple positive electrode sheets, negative electrode sheets, and multiple separators. The positive electrode sheets, separators, and negative electrode sheets are stacked sequentially, and their external dimensions are designed with a gradual change. Of course, the external dimensions of the positive electrode sheets, negative electrode sheets, and separators in the first core stack 11 can be the same or different, as long as they are designed with a gradual change; similarly, the external dimensions of the positive electrode sheets, negative electrode sheets, and separators in the second core stack can be the same or different, as long as they are designed with a gradual change. Naturally, the more diverse the electrode external dimensions of the first core stack 11 and the second core stack 12, the greater the increase in the energy density of the battery. Regardless of the variety of electrode shapes and sizes in the first stack 11 and the second stack 12, they must all meet the following rule: the electrode closer to the inner bottom surface 211 of the receiving cavity 21 has smaller dimensions in the X and Y directions, while the electrode farther from the inner bottom surface 211 of the receiving cavity 21 has larger dimensions in the X and Y directions. This avoids interference between each stack and the membrane shell 2 during packaging, and significantly improves the safety performance of the battery.

[0096] As a preferred embodiment, as shown in the appendix Figure 8 As shown, the thickness of the second stacked core 12 in the Z-axis direction is h2; the inner surface 212 includes a bottom straight edge 2122 that intersects with the inner arc surface 214, and the vertical distance between the bottom straight edge 2111 and the bottom straight edge 2122 in the Z-axis direction is L6; h2 and L6 satisfy: h2≤L6, ensuring that the first stacked core 11 and the second stacked core 12 are effectively separated by the third intersection point C, so that the outer dimensions of each electrode inside the first stacked core 11 and the second stacked core 12 follow different gradient rules, reducing the assembly and processing difficulty of the two stacked cores, thereby reducing production costs. At the same time, satisfying h2≤L6 allows the smaller second stacked core near the inner bottom surface 211 to have a sufficient proportion, preventing the electrode from being too large and easily squeezing the AC area of ​​the weakest part of the membrane shell 2 when dropped, leading to problems such as membrane shell 2 breakage and leakage, reducing the safety of battery use. It should be noted that the area between the first intersection point A and the third intersection point C is an arc segment; on the arc segment AC, the dimensions of each electrode can vary according to a parabolic function; on the straight line segment CB, the dimensions of each electrode vary according to a linear function.

[0097] And / or, as another preferred embodiment, as shown in the appendix Figure 4 and 8 As shown, a reference arc segment is formed between the first intersection point A and the third intersection point C, and the radius of the reference arc segment is R. AC h2 and R AC The condition is satisfied between: 0.6 ≤ ≤1; By controlling the size of the second stacked core 12, the proportion of the first stacked core 11 in the membrane shell 2 can be increased, thereby increasing the battery energy density. At the same time, it avoids the second stacked core 12 being too small, which would cause the first stacked core 11 to be too large, thereby increasing the risk of interference with the membrane shell 2 and avoiding affecting the encapsulation effect.

[0098] As a preferred embodiment, as shown in the appendix Figure 9 As shown, the thickness of the first core stack 11 in the Z-axis direction is h1, and the thickness of the second core stack 12 in the Z-axis direction is h2. h1 and h2 satisfy: 2mm ≤ h1 ≤ 10mm, 2mm ≤ h2 ≤ 10mm; as shown in the attached figure. Figure 4 and 5 As shown, the radius of the side arc surface 213 is R. BC R BC Satisfies: 0.5mm≤R BC ≤5mm; the radius of the reference arc segment is R. AC R AC Satisfies: 0.75mm≤R AC ≤8mm; By controlling the thickness of each stacked core and the radius of the transition corner of the receiving cavity 21, interference between each electrode and the membrane shell 2 is avoided, which helps to improve the safety performance of the cell 1.

[0099] As a preferred embodiment, as shown in the appendix Figure 9 As shown, both the first core stack 11 and the second core stack 12 include a second electrode 102. The polarity of the first electrode 101 is opposite to that of the second electrode 102. The second electrode 102 includes a third side extending along the X-axis and a fourth side extending along the Y-axis. The third side and the fourth side intersect to form a transition corner of the second electrode 102.

[0100] The second electrode 102 is the negative electrode, and the first electrode 101 is the positive electrode. The negative and positive electrodes are stacked together, and the radius of the transition corner of the positive electrode is R. 正 The radius of the transition corner of the negative electrode is R. 负 As attached Figure 12 and 13 As shown.

[0101] Both the negative and positive electrode plates have outer rounded corners at their transition points; R 负 R 正 R BC With R AC The following conditions must be met between R: BC ≤R 正 ≤R 负 ≤R AC ; and / or, R 负 R 正 With R BC The following condition must be met: 0.7mm ≤ R 正≤R 负 ≤R BC ;

[0102] And / or, the transition corners of both the negative and positive electrodes are at least one of an inner rounded corner, a chamfer, or a composite chamfer, and the minimum distance from the transition edge of the transition corner of the negative electrode to its center point is R. 负 The minimum distance from the transition edge of the positive electrode's transition corner to its center point is R. 正 ;R 负 R 正 R BC With R AC The following conditions must be met between R: BC ≤R 负 ≤R 正 ≤R AC ; and / or, R 负 R 正 With R BC The following conditions must be met between R: BC ≤R 负 ≤R 正 .

[0103] Meeting the above conditions can ensure the coverage between the positive and negative electrodes in the battery, reduce the occurrence of lithium plating during cycling, ensure that the positive and negative electrodes do not interfere with the corners of the membrane, and enhance the safety of battery use.

[0104] It should be noted that when comparing the transition angles of the positive and negative electrodes, the types of transition angles of the negative and positive electrodes are the same.

[0105] This invention establishes a reasonable matching relationship between the radius dimensions of the transition corners of the positive electrode, negative electrode, and receiving cavity 21, effectively avoiding mechanical interference between the electrode and the inner wall of the receiving cavity 21 during the cell stacking, casing, and packaging process. It also effectively prevents the sharp edges of the electrode from scratching the separator or hitting the inner surface of the receiving cavity during the packaging process of the cell 1 or during subsequent use, thereby reducing the risk of internal short circuits and leakage in the battery and improving the safety performance of the cell 1.

[0106] In a preferred embodiment, the second electrode 102 contains silicon. The silicon content in the active layer of the second electrode 102 is 1.5%-40% by mass. By controlling the silicon content of the electrode, the energy density of the battery is improved, and the overall expansion and contraction of the battery caused by the electrode during charging and discharging is controllable. The electrode will not be squeezed and punctured by the membrane shell 2 due to excessive expansion and extension of the electrode and the reduced internal distance between the electrode and the membrane shell 2.

[0107] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0108] This article uses specific examples to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principles of this utility model, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A battery, characterized in that, The device includes a battery cell (1) and a membrane housing (2). The battery cell (1) is disposed in a receiving cavity (21) of the membrane housing (2). The inner surface of the receiving cavity (21) includes an inner bottom surface (211) and an inner side surface (212) surrounding the inner bottom surface (211) and arranged at an angle to the inner bottom surface (211). The battery cell (1) includes a plurality of first electrode plates (101) of the same polarity stacked along the Z-axis direction. The first electrode plate (101) includes a topmost first electrode plate (1011) away from the inner bottom surface (211) along the Z-axis direction and a bottommost first electrode plate (1012) close to the inner bottom surface (211). The inner bottom surface (211) and the inner side surface (212) are connected by an inner arc surface (214). The inner bottom surface (211) includes a bottom straight edge (2111) that intersects with the inner arc surface (214). The inner side surface (212) includes a top straight edge (2121) on the side away from the inner arc surface (214). In the X-axis direction, the length of the topmost first electrode (1011) is L1, the length of the bottommost first electrode (1012) is L2, and the horizontal distance from the bottom straight edge (2111) to the top straight edge (2121) is L3. And / or, in the Y-axis direction, the width of the topmost first electrode (1011) is L1, the width of the bottommost first electrode (1012) is L2, and the horizontal distance from the bottom straight edge (2111) to the top straight edge (2121) is L3. The following conditions must be met between L1, L2 and L3: 0 ≤ L1 - L2 ≤ L3; wherein L3 satisfies: 0.15 mm ≤ L3 ≤ 0.5 mm.

2. The battery according to claim 1, characterized in that, The condition L1 and L2 satisfy: 0.001 ≤ ≤0.

035.

3. The battery according to claim 1, characterized in that, In the X-axis direction, the distance between the side surface of the topmost first electrode (1011) and the inner surface (212) is L4, and the distance between the side surface of the bottommost first electrode (1012) and the inner surface (212) is L5; and / or, in the Y-axis direction, the distance between the side surface of the topmost first electrode (1011) and the inner surface (212) is L4, and the distance between the side surface of the bottommost first electrode (1012) and the inner surface (212) is L5; The condition L4 and L5 satisfy the following: 0 ≤ L5 - L4 ≤ 0.7 mm.

4. The battery according to claim 3, characterized in that, The battery cell (1) includes at least one stacked core arranged along the Z-axis direction, the stacked core including a positive electrode and a negative electrode, and the first electrode (101) is at least one of the positive electrode and the negative electrode; The two adjacent inner surfaces (212) are connected by a side arc surface (213); along the diagonal direction of the inner bottom surface (211) and / or along the symmetry center line direction of the side arc surface (213), the diagonal of the inner bottom surface (211) intersects the symmetry center line of the side arc surface (213) to form a first intersection point A, the symmetry center line of the side arc surface (213) intersects the top transition edge (2131) of the side arc surface (213) away from the first intersection point A to form a second intersection point B; the symmetry center line of the side arc surface (213) intersects the bottom transition edge (2133) of the side arc surface (213) close to the first intersection point A to form a third intersection point C, the first intersection point A, the third intersection point C and the second intersection point B are connected in sequence; Along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the topmost first electrode (1011) in the X-axis direction is greater than the length of the bottommost first electrode (1012) in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the topmost first electrode (1011) in the Y-axis direction is greater than the width of the bottommost first electrode (1012) in the Y-axis direction; And / or, along the Z-axis away from the inner bottom surface (211), the length of the plurality of first pole pieces (101) with the same polarity gradually increases in the X-axis direction; and / or, along the Z-axis away from the inner bottom surface (211), the width of the plurality of first pole pieces (101) with the same polarity gradually increases in the Y-axis direction.

5. The battery according to claim 4, characterized in that, The first electrode (101) includes a first side extending along the X-axis direction and a second side extending along the Y-axis direction. The first side and the second side intersect to form a transition corner of the first electrode (101). The radius of the transition corner of the first electrode (101) is R. The radius of the transition corner of the topmost first electrode (1011) is R1, and the radius of the transition corner of the bottommost first electrode (1012) is R2; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy the following condition: R1 < R2. And / or, along the Z-axis away from the inner bottom surface (211), the radius R of the transition corner of all the first pole pieces (101) gradually decreases.

6. The battery according to claim 4, characterized in that, The battery cell (1) includes at least one stacked core arranged along the Z-axis direction, the stacked core including a first stacked core (11) and a second stacked core (12) disposed on the side of the first stacked core (11) near the inner bottom surface (211). The first stacked core (11) includes at least two first pole pieces (101) stacked along the Z-axis direction and having the same polarity; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the topmost first pole piece (1011) of the first stacked core (11) in the X-axis direction is greater than the length of the bottommost first pole piece (1012) in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the topmost first pole piece (1011) of the first stacked core (11) in the Y-axis direction is greater than the width of the bottommost first pole piece (1012) in the Y-axis direction; And / or, along the Z-axis away from the inner bottom surface (211), the length of all the first pole pieces (101) of the first stacked core (11) gradually increases in the X-axis direction; and / or, along the Z-axis away from the inner bottom surface (211), the width of all the first pole pieces (101) of the first stacked core (11) gradually increases in the Y-axis direction; And / or, a single first electrode (101) of the first stack (11) includes a first side extending along the X-axis direction and a second side extending along the Y-axis direction, the first side and the second side intersecting to form a transition corner of the first electrode (101), the radius of the transition corner of the topmost first electrode (1011) is R1, and the radius of the transition corner of the bottommost first electrode (1012) is R2; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy: R1 < R2; And / or, along the Z-axis away from the inner bottom surface (211) of the receiving cavity (21), the radius R of the transition corner of all the first pole pieces (101) of the first stacked core (11) gradually decreases.

7. The battery according to claim 6, characterized in that, The second stacked core (12) includes at least two first pole pieces (101) stacked along the Z-axis direction and having the same polarity; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the length of the topmost first pole piece (1011) of the second stacked core (12) in the X-axis direction is greater than the length of the bottommost first pole piece (1012) in the X-axis direction; and / or, along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, the width of the topmost first pole piece (1011) of the second stacked core (12) in the Y-axis direction is greater than the width of the bottommost first pole piece (1012) in the Y-axis direction; And / or, along the Z-axis away from the inner bottom surface (211), the length of all the first pole pieces (101) of the second stacked core (12) gradually increases in the X-axis direction; and / or, the width of all the first pole pieces (101) of the second stacked core (12) gradually increases in the Y-axis direction; And / or, a single first electrode (101) of the second stacked core (12) includes a first side extending along the X-axis direction and a second side extending along the Y-axis direction, the first side and the second side intersecting to form a transition corner of the first electrode (101), the radius of the transition corner of the topmost first electrode (1011) is R1, and the radius of the transition corner of the bottommost first electrode (1012) is R2; along the Z-axis direction, on the path from the first intersection point A to the second intersection point B, R1 and R2 satisfy: R1 < R2; And / or, along the Z-axis away from the inner bottom surface (211), the radius R of the transition corner of all the first pole pieces (101) of the second stacked core (12) gradually decreases.

8. The battery according to claim 6, characterized in that, The thickness of the second core stack (12) in the Z-axis direction is h2; the inner surface (212) includes a bottom straight edge (2122) that intersects with the inner arc surface (214), and the vertical distance between the bottom straight edge (2111) and the bottom straight edge (2122) in the Z-axis direction is L6; h2 and L6 satisfy the following condition: h2≤L6; And / or, a reference arc segment is formed between the first intersection point A and the third intersection point C, the radius of the reference arc segment being R. AC h2 and R AC The condition is satisfied between: 0.6 ≤ ≤1.

9. The battery according to claim 8, characterized in that, The thickness of the first stacked core (11) in the Z-axis direction is h1, and the thickness of the second stacked core (12) in the Z-axis direction is h2. The thickness of h1 and the thickness of h2 satisfy: 2mm≤h1≤10mm, 2mm≤h2≤10mm; The radius of the side arc surface (213) is R. BC The R BC Satisfies: 0.5mm≤R BC ≤5mm; The radius of the reference arc segment is R. AC The R AC Satisfies: 0.75mm≤R AC ≤8mm.

10. The battery according to claim 9, characterized in that, Both the first core stack (11) and the second core stack (12) include a second pole piece (102), the polarity of the first pole piece (101) and the polarity of the second pole piece (102) are opposite; the second pole piece (102) includes a third side extending along the X-axis direction and a fourth side extending along the Y-axis direction, the third side and the fourth side intersect to form a transition corner of the second pole piece (102); The second electrode (102) is a negative electrode, and the first electrode is a positive electrode. The negative electrode and the positive electrode are stacked together, and the radius of the transition corner of the positive electrode is R. 正 The radius of the transition corner of the negative electrode is R. 负 ; The transition corners of both the negative electrode and the positive electrode are externally rounded; the R 负 The R 正 The R BC With the R AC The following conditions must be met between R: BC ≤R 正 ≤R 负 ≤R AC ; and / or, the R 负 The R 正 With the R BC The following condition must be met: 0.7mm ≤ R 正 ≤R 负 ≤R BC ; And / or, the transition corners of both the negative electrode and the positive electrode are at least one of an inner rounded corner, a chamfer, or a composite chamfer, and the minimum distance from the transition edge of the transition corner of the negative electrode to its center point is R. 负 The minimum distance from the transition edge of the transition corner of the positive electrode to its center point is R. 正 The R 负 The R 正 The R BC With the R AC The following conditions must be met between R: BC ≤R 负 ≤R 正 ≤R AC ; and / or, the R 负 The R 正 With the R BC The following conditions must be met between R: BC ≤R 负 ≤R 正 .

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