Patent Publication Number: US-2022223979-A1

Title: Secondary battery, battery module, and apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of PCT Application No. PCT/CN2020/128472 filed on Nov. 12, 2020, which claims priority to Chinese Patent Application No. 202020819152.5, tilted “SECONDARY BATTERY, BATTERY MODULE AND APPARATUS” and filed on May 15, 2020, both of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a technical field of battery, and particularly relates to a secondary battery, a battery module and an apparatus. 
     BACKGROUND 
     With the development of science and technology, the application of rechargeable secondary batteries has become more and more extensive, and for example, the secondary batteries can be used in automobiles, electric bicycles, or wireless electric tools. The secondary battery includes a casing, an electrode assembly disposed in the casing, a cap cover connected with the casing, an electrode terminal disposed on the cap cover, and an adapting piece for connecting the electrode assembly and the electrode terminal. In some cases, the adapting piece may be fractured during the use of the secondary battery, which affects the service life of the secondary battery. 
     SUMMARY 
     The present disclosure provides a secondary battery, a battery module and an apparatus. The secondary battery can reduce the possibility of fatigue fracture of the adapting piece. 
     On one aspect, the present application provides a secondary battery, including: 
     an electrode assembly and a casing. The electrode assembly includes a main body portion and a tab portion, the tab portion extending out from the main body portion along an end of the main body portion and including an outer peripheral surface. The casing includes an accommodating hole for accommodating the electrode assembly. The casing includes a limiting protrusion. The outer peripheral surface extends around an axis of the accommodating hole. The limiting protrusion protrudes toward the tab portion and presses against the outer peripheral surface of the tab portion. The limiting protrusion is adapted to limit a position of the tab portion. 
     According to one embodiment of the present application, the electrode assembly further includes an insulating member, and at least part of the insulating member is disposed between the limiting protrusion and the tab portion. 
     According to one embodiment of the present application, the insulating member is wound into a tubular member along a circumferential direction of the accommodating hole to cover an outer peripheral surface of the electrode assembly. 
     According to one embodiment of the present application, a part of the insulating member extends beyond the tab portion in an axial direction of the accommodating hole. 
     According to one embodiment of the present application, the insulating member is formed as a sheet-like member. 
     According to one embodiment of the present application, the tab portion includes a first portion and a second portion, the second portion is connected to the main body portion, the tab portion is formed as a structure of multiple layers, a gap between two adjacent layers is smaller in the first portion than in the second portion, and the limiting protrusion presses against the second portion. 
     According to one embodiment of the present application, a surface of the limiting protrusion pressing against the tab portion is a smooth curved surface. 
     According to one embodiment of the present application, the limiting protrusion has a cross section in a shape of an arc or a triangle. 
     According to one embodiment of the present application, a surface of the limiting protrusion pressing against the tab portion is a flat surface. 
     According to one embodiment of the present application, the limiting protrusion has a cross section in a trapezoidal shape. 
     According to one embodiment of the present application, a portion of the casing is recessed toward the tab portion to form the limiting protrusion. 
     According to one embodiment of the present application, the limiting protrusion is formed in an annular shape, and the limiting protrusion is arranged around the tab portion. 
     According to one embodiment of the present application, the casing further includes a tubular body, the tubular body is sleeved on an outside of the limiting protrusion and is in an interference fit with the limiting protrusion. 
     According to one embodiment of the present application, two or more limiting protrusions are provided, and the two or more limiting protrusions are arranged at intervals around the tab portion. 
     According to one embodiment of the present application, the secondary battery further includes a cap member, the cap member includes a first disc body and a second disc body, the first disc body has a diameter larger than that of the second disc body, and an edge of the first disc body extending beyond the second disc body overlaps an end surface of the casing and is welded with the casing. 
     According to one embodiment of the present application, the casing is formed as a tubular structure and includes two openings, two cap members are provided, and the two cap members are respectively disposed on two ends of the casing to cover and close the respective openings. 
     According to one embodiment of the present application, the casing is formed as a cylindrical member. 
     The secondary battery according to the embodiment of the present application includes a casing and an electrode assembly provided in the casing. The casing includes a limiting protrusion protruding toward the tab portion. The limiting protrusion presses against the outer peripheral surface of the tab portion, so that the limiting protrusion limits the position of the tab portion. As such, when the secondary battery is vibrated or impacted, the limiting protrusion can limit the position of the tab portion to prevent the tab portion from bending, thereby reducing the compressed amount of the tab portion, thus reducing the possibility of fatigue fracture of the adapting piece due to displacement of the electrode assembly and increasing the service life of the secondary battery. 
     On a further aspect, the present application provides a battery module, including a housing and the secondary battery as described above. The secondary battery is disposed in the housing. 
     On another further aspect, the present application provides an apparatus using a secondary battery as a power source, the apparatus includes the secondary battery as described above, and the secondary battery is adapted to provide electrical energy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to more clearly describe the technical solutions of the embodiments of the present application, the accompanying drawings that need to be used in the embodiments of the present application will be briefly introduced below; obviously, the accompanying drawings described below are only some implementations of the present application, and for the person skilled in the art, other drawings can be obtained based on the described accompanying drawings without expending creative labors. 
         FIG. 1  is a schematic structural diagram of a vehicle disclosed in an embodiment of the present application; 
         FIG. 2  is a schematic structural diagram of a battery module disclosed in an embodiment of the present application; 
         FIG. 3  is an explosive schematic diagram of a structure of the battery module of the embodiment shown in  FIG. 2 ; 
         FIG. 4  is a schematic structural diagram of a secondary battery disclosed in an embodiment of the present application; 
         FIG. 5  is a schematic cross-sectional view of the secondary battery of the embodiment shown in  FIG. 4 ; 
         FIG. 6  is an enlarged view of portion A in  FIG. 5 ; 
         FIG. 7  is a schematic structural diagram of a secondary battery disclosed in another embodiment of the present application; 
         FIG. 8  is a schematic partial cross-sectional view of a structure of the secondary battery of the embodiment shown in  FIG. 7 ; 
         FIG. 9  is a schematic structural diagram of a secondary battery disclosed in a further embodiment of the present application; 
         FIG. 10  is a schematic cross-sectional view of the secondary battery of the embodiment shown in  FIG. 9 ; 
         FIG. 11  is a schematic partial cross-sectional view of a structure of a secondary battery disclosed in another embodiment of the present application; 
         FIG. 12  is a schematic partial cross-sectional view of a structure of a secondary battery disclosed in a further embodiment of the present application; 
         FIG. 13  is a schematic partial cross-sectional view of a structure of a secondary battery disclosed in another further embodiment of the present application. 
     
    
    
     In the drawings, the drawings may not be drawn to an actual scale. 
     REFERENCE NUMERALS 
     
         
         
           
               1 , vehicle;  10 , battery module;  20 , housing;  30 , secondary battery;  31 , casing;  31   a , accommodating hole;  31   aa , axis;  311 , limiting protrusion;  312 , tubular body;  32 , cap member;  321 , the first disc body;  322 , second disc body;  33 , electrode assembly;  331 , main body portion;  332 , tab portion;  3321 , outer peripheral surface;  3322 , end surface;  332   a , first portion;  332   b , second portion;  333 , insulating member;  34 , electrode terminal;  35 , adapting piece;  40 , separating plate;  99 , channel; X, axial direction. 
           
         
       
    
     DETAILED DESCRIPTION 
     The implementations of the present application are described below in further detail with reference to the accompanying drawings and embodiments. The following detailed description of the embodiments and the accompanying drawings are used to exemplarily illustrate the principle of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments. 
     In the description of the present application, it should be noted that, unless otherwise stated, “multiple” means two or more; the orientation or positional relationship indicated by the terms “upper”, “lower”, “left”, “right”, “inside”, “outside” or the like is merely used for convenience of describing the application and simplifying the description, rather than indicating or implying that the device or element referred to must have a particular orientation, or be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms “first”, “second”, “third”, or the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance. “Perpendicularity” does not mean a strict perpendicularity, but allows an error within an allowed range. “Parallel” does not mean a strict parallel but allows an error within an allowed range. 
     The orientation words appearing in the following description all refer to the directions shown in the drawings, and are not intended to define the specific structure of the present application. In the description of the present application, it should also be noted that, unless otherwise clearly defined and specified, the terms “install”, “connect”, and “couple” should be understood in a broad sense, for example, may refer to a fixed connection, a detachable connection, or an integral connection, may refer to a direct connection or an indirect connection through an intermediate medium. For the person skilled in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to specific circumstances. 
     When solving the problem of fracture of the adapting piece in the secondary battery in related technologies, Applicant optimized the thickness of the adapting piece to improve the overall strength. But after using a period of time, the fracture of the adapting piece may still occur. Therefore, Applicant conducted further research and analysis on various components of the secondary battery, and found that since the adapting piece is arranged between the electrode terminal and the electrode assembly, when the secondary battery is vibrated or impacted, the electrode assembly tends to displace close to or away from the electrode terminal, causing the tab to be stressed. The tab will bend after being stressed, causing size of the electrode assembly to become smaller and displacement space between the electrode assembly and the cap cover to be increased, and thus the electrode assembly is easy to displace relative to the casing. The adapting piece will be compressed and stretched many times under the driving of the electrode assembly, resulting in local fatigue fracture of the adapting piece. 
     Based on the above-mentioned problem found by Applicant, Applicant improved the configuration of the secondary battery, and the embodiments of the present application are further described below. 
     In order to better understand the present application, the embodiments of the present application are described below in combination with  FIG. 1  to  FIG. 13 . 
     Referring to  FIG. 1 , an embodiment of the present application provides an apparatus that uses a battery module  10  as a power source. The apparatus can be, but is not limited to, a vehicle, a ship, an aircraft, an electric tool, or the like. One embodiment of the present application provides a vehicle  1  including a vehicle body and a battery module  10 . The battery module  10  is disposed on the vehicle body. The vehicle  1  may be a pure electric vehicle, a hybrid electric vehicle or an extended-range vehicle. The vehicle body is provided with a drive motor electrically connected with the battery module  10 . The battery module  10  provides electric energy to the drive motor. The drive motor is connected to wheels on the vehicle body through a transmission mechanism to drive the vehicle to travel. Optionally, the battery module  10  may be horizontally disposed at the bottom of the vehicle body. 
     In an embodiment of the present application, referring to  FIG. 2  and  FIG. 3 , the battery module  10  includes a housing  20 , a secondary battery  30 , and a separating plate  40 . There may be multiple secondary batteries  30  provided in the housing  20 . The multiple secondary batteries  30  may be connected in series or in parallel with each other through a busbar (not shown in the drawings). The separating plate  40  is disposed between the housing  20  and the secondary batteries  30 . Two separating plates  40  are respectively disposed corresponding to two ends of the respective secondary batteries  30  and can compress the respective secondary batteries  30  so as to limit the positional displacement of the respective secondary batteries  30 . The separating plate  40  can insulate and isolate the secondary batteries  30  and other adjacent structural components, such as busbars, circuit boards, or wiring harnesses, thereby improving the safety of use of the secondary battery  30 . In one example, the separating plate  40  is an injection molded integral member. The housing  20  in the embodiment of the present application is formed in a square shape or in other shapes. The housing  20  may be made of materials such as aluminum, aluminum alloy, or plastic. 
     Referring to  FIG. 4  and  FIG. 5 , the secondary battery  30  includes a casing  31 , a cap member  32  connected to the casing  31  in a sealed manner, an electrode assembly  33  disposed in the casing  31 , an electrode terminal  34  provided on the cap member  32 , and an adapting piece  35  for connecting the electrode assembly  33  with the electrode terminal  34 . 
     The casing  31  according to an embodiment of the present application is formed as a cylindrical member. It can be understood that the casing  31  may be formed in a square shape or in other shapes. The casing  31  includes an accommodating hole  31   a  for accommodating the electrode assembly  33  and electrolyte, and an opening communicating with the accommodating hole  31   a . The accommodating hole  31   a  may be a circular hole or a square hole. The accommodating hole  31   a  may be a through hole or a blind hole. The electrode assembly  33  may be mounted into the accommodating hole  31   a  through the opening. The casing  31  may be made of materials such as aluminum, aluminum alloy, or plastic. 
     The cap member  32  according to the embodiment of the present application is formed as a plate-like member. The cap member  32  can cover and close the opening of the casing  31  and is connected with the casing  31  in a sealed manner. The electrode terminal  34  is adapted to be welded with the busbar. In one embodiment, the casing  31  is formed as a tubular structure and includes two openings. Two cap members  32  are provided. The two cap members  32  are respectively disposed on two ends of the casing  31  to cover and close the corresponding openings. Two electrode terminals  34  with opposite polarities are respectively disposed on the corresponding cap members  32 . In one example, the cap member  32  includes a first disc body  321  and a second disc body  322 . The first disc body  321  has a diameter greater than that of the second disc body  322 . An edge of the first disc body  321  that extends beyond the second disc body  322  overlaps the end surface of the casing  31  and is welded to the casing  31 . The end of the casing  31  is formed in a straight tubular shape. 
     The electrode assembly  33  according to the embodiment of the present application may include a main body portion  331  formed by winding a first electrode plate, a second electrode plate and a separator disposed between the first electrode plate and the second electrode plate, wherein the separator is an insulator interposed between the first electrode plate and the second electrode plate. The main body portion  331  includes two ends opposite each other along an axial direction X of the accommodating hole  31   a . In the present embodiment, the description is made by exemplarily taking the first electrode plate as a positive electrode plate and taking the second electrode plate as a negative electrode plate. Active material of the positive electrode plate is coated on a coating region of the positive electrode plate, and active material of the negative electrode plate is coated on a coating region of the negative electrode plate. The main body portion  331  is formed by the coating regions, and the uncoated regions extending out from the main body portion  331  forms a tab portion  332 . The electrode assembly  33  includes two tab portions  332 , namely, a positive tab portion and a negative tab portion. The positive tab portion extends out from the coating region of the positive electrode plate, and the negative tab portion extends out from the coating region of the negative electrode plate. In the embodiment of the present application, the two tab portions  332  extends out from the two ends opposite each other of the main body portion  331  respectively. The tab portions  332  are connected to the electrode terminals  34  of the same polarities respectively. Each tab portion  332  includes an outer peripheral surface  3321  and an end surface  3322 . The outer peripheral surface  3321  extends in a circumferential direction of the accommodating hole  31   a , that is, extends around an axis  31   aa  of the accommodating hole  31   a . The end surface  3322  is perpendicular to the axial direction X of the accommodating hole  31   a . The adapting piece  35  is connected to the end surface  3322 . 
     The casing  31  according to the embodiment of the present application is adapted to accommodate the electrode assembly  33 . The casing  31  includes a limiting protrusion  311 . The limiting protrusion  311  protrudes toward the tab portion  332  and presses against the outer peripheral surface  3321  of the tab portion  332 . The limiting protrusion  311  is adapted to limit a position of the tab portion  332 . Here, the “presses” means that the limiting protrusion  311  exerts a predetermined compressive stress on the outer peripheral surface  3321  of the tab portion  332 . The direction of the compressive stress is directed to a center of the tab portion  332  in a radial direction of the accommodating hole  31   a . The radial direction of the accommodating hole  31   a  is perpendicular to the axial direction X of the accommodating hole  31   a.    
     The secondary battery  30  according to the embodiment of the present application includes a casing  31  and an electrode assembly  33  disposed in the casing  31 . The casing  31  includes a limiting protrusion  311  protruding toward the tab portion  332 . The limiting protrusion  311  presses against the outer peripheral surface  3321  of the tab portion  332 , so that the limiting protrusion  311  limits the position of the tab portion  332 . As such, when the secondary battery  30  is vibrated or impacted, the tab portion  332  does not tend to expand and deform in the radial direction of the accommodating hole  31   a  under the limiting in position provided by the limiting protrusion  311 , and thus the possibility that the tab portion  332  becomes smaller in the axial direction X of the accommodating hole  31   a , that is, is pressed in the axial direction X of the accommodating hole  31   a  to become flatter, due to that the electrode assembly  33  displaces and is subjected to a reaction force from the adapting piece  35 , is reduced. If the tab portion  332  becomes flatter in the axial direction X of the accommodating hole  31   a , the displacement amount of the electrode assembly  33  in the axial direction X of the accommodating hole  31   a  will become larger, and the deformation amount of the adapting piece  35  will become larger due to the displacement of the electrode assembly  33 , making it easier for the adapting piece  35  to reach a fatigue fracture limit. Further, the limiting protrusion  311  can limit the electrode assembly  33  from displacing along the axial direction X of the accommodating hole  31   a  through the tab portion  332 , thereby reducing the possibility of fatigue fracture of the adapting piece  35  caused by the repeat compressing and stretching applied by the adapting piece due to the displacement of the electrode assembly  33 , and thus improving the safety of use of the secondary battery  30  and increasing the service life of the secondary battery  30 . 
     In one embodiment, referring to  FIG. 6 , the electrode assembly  33  further includes an insulating member  333 . The insulating member  333  is wound into a tubular member along the circumferential direction of the accommodating hole  31   a  to cover an outer peripheral surface of the electrode assembly  33 . At least part of the insulating member  333  is disposed between the limiting protrusion  311  and the tab portion  332 , so that the insulating member  333  can isolate the limiting protrusion  311  from the tab portion  332 . In the axial direction X of the accommodating hole  31   a , a part of the insulating member  333  extends beyond the tab portion  332 . The insulating member  333  may be formed as a sheet-like member. 
     In one embodiment, referring to  FIG. 6 , the tab portion  332  according to the embodiment of the present application is formed as a structure of multiple layers. During the manufacturing process of the electrode assembly  33 , the tab portion  332  will undergo a flattening process by a flattening device. The tab portion  332  after the flattening process includes a first portion  332   a  and a second portion  332   b . A gap between two adjacent layers is smaller in the first portion  332   a  than in the second portion  332   b , so that the two adjacent layers are relatively dense in the first portion  332   a , while are relatively sparse in the second portion  332   b . The second portion  332   b  of the tab portion  332  is connected to the main body portion  331 , while the first portion  332   a  is disposed away from the main body portion  331 . Since the second portion  332   b  is relatively sparse, when the electrode assembly  33  displaces and is subjected to the reaction force from the cap member  34  or other components, the tab portion  332  is more likely to be bent and deformed in the second portion  332   b  and expand in size along the radial direction of the accommodating hole  31   a . In the present embodiment, the limiting protrusion  311  presses against the outer peripheral surface  3321  of the tab portion  332  at a region corresponding to the second portion  332   b , and can provide a lateral support to the second portion  332   b  of the tab portion  332 , so that the second portion  332   b  is unlikely to be bent and deformed when the tab portion  332  is pressed by an external force, thereby reducing the possibility that the tab portion  332  becomes smaller in the axial direction X of the accommodating hole  31   a  due to the pressing of the external force. 
     In one embodiment, referring to  FIG. 6 , a surface of the limiting protrusion  311  pressing against the tab portion  332  is a smooth curved surface, to reduce the possibility that a local stress concentration appears in the tab portion  332  due to the pressing of the limiting protrusion  311  against the tab portion  332 , thereby reducing the possibility that structural damage such as cracks occurs in the tab portion  332  due to the local stress concentration. Optionally, the surface of the limiting protrusion  311  pressing against the tab portion  332  is an arc surface. 
     In one embodiment, a portion of the casing  31  is recessed toward the tab portion  332  to form the limiting protrusion  311  to ensure an integrity and structural strength of the casing  31 . A recessed portion is formed on the casing  31  in a region corresponding to the limiting protrusion  311 . The limiting protrusion  311  has a cross section in a shape of an arc, which is beneficial to reduce the possibility of cracks appearing in the region where the limiting protrusion  311  is formed due to excessive tensile stress. In one example, after the electrode assembly  33  and the casing  31  are assembled, the casing  31  is rolled on an outside of the casing  31  by a roller press to form the limiting protrusion  311 . 
     In one embodiment, referring to  FIG. 4  and  FIG. 6 , the limiting protrusion  311  is formed in an annular shape. The limiting protrusion  311  extends along the circumferential direction of the accommodating hole  31   a  and is disposed around the tab portion  332 . The limiting protrusion  311  can provide the lateral support to the tab portion  332  through the entire outer peripheral surface  3321  of the tab portion  332 , so that the tab portion  332  can be restricted and limited by the limiting protrusion  311  at various portions. 
     In one embodiment, referring to  FIG. 7  and  FIG. 8 , two or more limiting protrusions  311  are provided. The two or more limiting protrusions  311  are arranged at intervals around the tab portion  332 . Optionally, the two or more limiting protrusions  311  are arranged at even intervals around the tab portion  332 . A channel  99  is formed between two adjacent limiting protrusions  311 , so that gas generated during use of the secondary battery  30  or the electrolyte injected into the secondary battery  30  can flow through the channels  99 , so as to ensure normal use of the burst valve of the secondary battery  30  or consistency of the electrode assembly  33  being infiltrated with the electrolyte. 
     In one embodiment, referring to  FIG. 9  and  FIG. 10 , the secondary battery  30  of the present embodiment will be described mainly regarding the different aspects from the secondary battery  30  of the embodiment as shown in  FIG. 4  and  FIG. 5 , with the same configurations not repeated here. In the present embodiment, the casing  31  includes two limiting protrusions  311 . Each end of the casing  31  is provided with one limiting protrusion  311 , so that the two limiting protrusions  311  respectively apply the compressive stress to the tab portions  332  on both sides of the main body portion  331  at the same time, which increases the restriction and limit to the electrode assembly  33 , and further reduces the possibility of displacement of the electrode assembly  33  in the casing  31 . 
     In one embodiment, referring to  FIG. 11 , the secondary battery  30  of the present embodiment will be described mainly regarding the different aspects from the secondary battery  30  of the embodiment as shown in  FIG. 6 , with the same configurations not repeated here. In the present embodiment, the limiting protrusion  311  has a cross section in a trapezoidal shape. A top surface of the limiting protrusion  311  pressing against the tab portion  322  is a flat surface, which reduces the possibility that a local stress concentration appears in the tab portion  332  due to the pressing of the limiting protrusion  311  against the tab portion  332 , and thus reduces the possibility that the structural damage such as cracks occurs in the tab portion  332  due to the local stress concentration. 
     In one embodiment, referring to  FIG. 12 , the secondary battery  30  of the present embodiment will be described mainly regarding the different aspects from the secondary battery  30  of the embodiment as shown in  FIG. 6 , with the same configurations not repeated here. In the present embodiment, the limiting protrusion  311  has a cross section in a triangular shape. A top surface of the limiting protrusion  311  pressing against the tab portion  322  is a smooth curved surface, which reduces the possibility that a local stress concentration appears in the tab portion  332  due to the pressing of the limiting protrusion  311  against the tab portion  332 , and thus reduces the possibility that the structural damage such as cracks occurs in the tab portion  332  due to the local stress concentration. 
     In one embodiment, referring to  FIG. 13 , the secondary battery  30  of the present embodiment will be described mainly regarding the different aspects from the secondary battery  30  of the embodiment as shown in  FIG. 6 , with the same configurations not repeated here. In the present embodiment, the casing  31  further includes a tubular body  312 . The tubular body  312  and the limiting protrusion  311  are formed separately, and then can be sleeved on and connected to each other. The tubular body  312  is sleeved on an outside of the limiting protrusion  311  and is in an interference fit with the limiting protrusion  311 . The limiting protrusion  311  is formed as an annular member. The limiting protrusion  311  is sleeved on an outside of the tab portion  332  in advance and presses against the outer peripheral surface  3321  of the tab portion  332 . Then, the limiting protrusion  311  and the electrode assembly  33  are both assembled into the tubular body  312 . 
     The secondary battery  30  according to the embodiments of the present application includes a casing  31  and an electrode assembly  33  received in the casing  31 . The casing  31  includes a limiting protrusion  311 . The limiting protrusion  311  can press against the outer peripheral surface  3321  of the tab portion  332  to exert a compressive stress to the tab portion  332 , so that the limiting protrusion  311  can restrict and limit the position of the electrode assembly  33  through the tab portion  332 , and reduce the possibility of displacement of the electrode assembly  33  in the casing  31 , thereby reducing the possibility that the electrode assembly  33  displaces and repeatedly compresses and stretches the adapting piece  35  and thus causes the fatigue fracture of the adapting piece  35 , which is beneficial to improve the safety of use of the secondary battery  30  and increase the service life of the secondary battery  30 . 
     Although the present application has been described with reference to the optional embodiments, various improvements can be made to the present application and the components therein can be replaced with equivalents, without departing from the scope of the present application. In particular, as long as there is no structural conflict, various technical features mentioned in the various embodiments can be combined in any manner. The present application is not limited to the specific embodiments disclosed in the context, but includes all technical solutions falling within the scope of the claims.