Patent Publication Number: US-2022223922-A1

Title: Jelly-roll battery cell and electrochemical device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national phase entry of International Application No. PCT/CN2020/079038, filed on Mar. 12, 2020 and entitled “JELLY-ROLL BATTERY CELL AND ELECTROCHEMICAL DEVICE”, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This application relates to the field of batteries, and in particular, to a jelly-roll battery cell and an electrochemical device. 
     BACKGROUND 
     Batteries have been widely used in various fields such as electronic products and electric vehicles. However, higher requirements are imposed on an energy density of the batteries in the market when the batteries are more commercialized. Therefore, a jelly-roll battery cell and an electrochemical device that have a relatively high energy density are required in the industry. 
     SUMMARY 
     One of the objectives of the embodiments of this application is to provide a jelly-roll battery cell and an electrochemical device to reduce a thickness of the jelly-roll battery cell and achieve a relatively high energy density and a relatively high space utilization rate. 
     According to an embodiment of this application, a jelly-roll battery cell is provided, including a first electrode plate, a second electrode plate, and a separator. The separator is disposed between the first electrode plate and the second electrode plate. The first electrode plate, the second electrode plate, and the separator are wound to form the jelly-roll battery cell. The jelly-roll battery cell has a thickness direction and a central region that is enclosed by the first electrode plate, the second electrode plate, and the separator. The first electrode plate includes: a first current collector, where the first current collector includes a first surface and a second surface opposite to the first surface, and the first surface is closer to the central region than the second surface. The first current collector comprises a first section and a second section, the first section has a first end and a second end, and the first end is a winding initiation end of the first electrode plate; the second section has a third end and a fourth end, the third end is connected to the second end, the second section is flat, and a first tab is disposed on the first surface in the second section. The second electrode plate includes: a second tab, where the second tab has a first side and a second side opposite to the first side. The first side is on the second electrode plate. The first end, the first tab, and the second tab do not overlap in the thickness direction. 
     In some embodiments of this application, the separator has a fifth end and a sixth end. The fifth end is a winding initiation end of the separator. The sixth end is a winding termination end of the separator. The fifth end does not overlap the first end, the first tab, or the second tab in the thickness direction. 
     In some embodiments of this application, the sixth end does not overlap the first tab or the second tab in the thickness direction. 
     In some embodiments of this application, the separator has a first boundary line. A part from the first boundary line to the fifth end constitutes a first part of the separator. A shape of the first part is curved or flat. The first part does not overlap the first tab or the second tab in the thickness direction. 
     In some embodiments of this application, the jelly-roll battery cell further includes a first insulation adhesive. The first insulation adhesive overlays a winding termination end of the second electrode plate, and the first insulation adhesive does not overlap the first tab or the second tab in the thickness direction. 
     In some embodiments of this application, the winding termination end of the second electrode plate does not overlap the first tab or the second tab in the thickness direction. 
     In some embodiments of this application, no first active material layer is disposed on the first surface or the second surface in the first section, no first active material layer is disposed on the first surface in the second section, and the first active material layer is disposed on the second surface in the second section. 
     In some embodiments of this application, the first current collector further includes a third section and a fourth section. The third section has a seventh end and an eighth end. The seventh end is connected to the fourth end. The fourth section has a ninth end and a tenth end. The ninth end is connected to the eighth end. The tenth end is a winding termination end of the first electrode plate. No first active material layer is disposed on the first surface in the third section, and the first active material layer is disposed on the second surface in the third section, and the first active material layer is disposed on the first surface and the second surface in the fourth section. 
     In some embodiments of this application, the separator located between the second section and the third section is provided with a coating or not provided with a coating. 
     In some embodiments of this application, the second electrode plate includes a second current collector. The second current collector includes a third surface and a fourth surface opposite to the third surface. The third surface is closer to the central region than the fourth surface. The second current collector further includes a fifth section, a sixth section, and a seventh section. The fifth section has an eleventh end and a twelfth end. The eleventh end is a winding initiation end of the second electrode plate. The sixth section has a thirteenth end and a fourteenth end. The thirteenth end is connected to the twelfth end. The seventh section has a fifteenth end and a sixteenth end. The fifteenth end is connected to the fourteenth end. The sixteenth end is a winding termination end of the second electrode plate. A second active material layer is disposed on the third surface and the fourth surface in the fifth section. The second active material layer is disposed on the third surface in the sixth section. No second active material layer is disposed on the third surface or the fourth surface in the seventh section. 
     In some embodiments of this application, the fifth section includes a first subsection, a second subsection, a third subsection, a fourth subsection, and a fifth subsection. The first subsection, the third subsection, and the fifth subsection are flat. The second subsection and the fourth subsection are curved. The first subsection is a starting subsection of the fifth section. The second subsection is connected to the first subsection. The third subsection is connected to the second subsection. The fourth subsection is connected to the third subsection. The fifth subsection is an ending subsection of the fifth section. The sixth section includes a sixth subsection, a seventh subsection, an eighth subsection, and a ninth subsection. The sixth subsection and the eighth subsection are curved. The seventh subsection and the ninth subsection are flat. The sixth subsection is a starting subsection of the sixth section. The seventh subsection is connected to the sixth subsection. The eighth subsection is connected to the seventh subsection. The ninth subsection is connected to the eighth subsection. The ninth subsection is an ending subsection of the sixth section. The seventh section includes a tenth subsection and an eleventh subsection. The tenth subsection is curved, and the eleventh subsection is flat. The tenth subsection is a starting subsection of the seventh section, and the eleventh subsection is an ending subsection of the seventh section. A second insulation adhesive is disposed on the fourth surface in the sixth subsection. An initiation end and a termination end of the second insulation adhesive overlap an initiation end and a termination end of the sixth subsection respectively. The initiation end of the sixth subsection is connected to the fifth section. A third insulation adhesive is disposed on the third surface in the tenth subsection. An initiation end and a termination end of the third insulation adhesive overlap an initiation end and a termination end of the tenth subsection respectively. The initiation end of the tenth subsection is connected to the sixth section. 
     In some embodiments of this application, the sixth end extends beyond the termination ends of the second insulation adhesive and the third insulation adhesive, or the sixth end is flush with the termination ends of the second insulation adhesive and the third insulation adhesive. 
     In some embodiments of this application, the first side of the second tab is on the third surface in the eleventh subsection. 
     In some embodiments of this application, the first side of the second tab is on the fourth surface in the seventh subsection. 
     In some embodiments of this application, the jelly-roll battery cell further includes a fourth insulation adhesive overlaying the second side of the second tab. 
     In some embodiments of this application, a first insulation adhesive overlays the second side of the second tab. 
     In some embodiments of this application, the second tab is located below the eleventh subsection. 
     In some embodiments of this application, the third subsection has a first part, no second active material layer is disposed on the third surface or the fourth surface in the first part, and the first side of the second tab is on either the third surface or the fourth surface in the first part. Alternatively, the fifth subsection has a second part, no second active material layer is disposed on the third surface or the fourth surface in the second part, and the first side of the second tab is on either the third surface or the fourth surface in the second part; and the jelly-roll battery cell further includes: a fifth insulation adhesive, disposed on the second side of the second tab, and shielding a corresponding surface in the first part or the second part, where the surface is connected to the second side of the second tab; and a sixth insulation adhesive, disposed opposite to the fifth insulation adhesive, and shielding a surface in the first part or a surface in the second part, in each case the surface being not connected to the first side of the second tab. 
     In some embodiments of this application, the jelly-roll battery cell further includes a seventh insulation layer disposed at a corresponding position on the first electrode plate, the position being opposite to the fifth insulation adhesive and the sixth insulation adhesive. 
     According to another embodiment of this application, an electrochemical device is provided, including the jelly-roll battery cell disclosed in any of the foregoing embodiments. 
     The jelly-roll battery cell and the electrochemical device according to the embodiments of this application achieve a smaller thickness, a higher energy density, and a higher space utilization rate than conventional jelly-roll battery cells. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       For ease of describing the embodiments of this application, the following outlines the drawings necessary for describing the embodiments of this application. Apparently, the drawings outlined below are merely a part of embodiments in this application. Without making any creative efforts, a person skilled in the art can still obtain the drawings of other embodiments according to the structures illustrated in these drawings. 
         FIG. 1A  is a cross-sectional schematic view of a jelly-roll battery cell according to an embodiment of this application; 
         FIG. 1B  is a cross-sectional schematic view of a jelly-roll battery cell according to another embodiment of this application; 
         FIG. 1C  is a cross-sectional schematic view of a jelly-roll battery cell according to still another embodiment of this application; 
         FIG. 1D  is a cross-sectional schematic view of a jelly-roll battery cell according to another embodiment of this application; 
         FIG. 1E  is a cross-sectional schematic view of a jelly-roll battery cell according to still another embodiment of this application; 
         FIG. 1F  is a cross-sectional schematic view of a jelly-roll battery cell according to another embodiment of this application; 
         FIG. 1G  is a cross-sectional schematic view of a jelly-roll battery cell according to still another embodiment of this application; 
         FIG. 1H  is a cross-sectional schematic view of a jelly-roll battery cell according to another embodiment of this application; 
         FIG. 1I  is a cross-sectional schematic view of a jelly-roll battery cell according to still another embodiment of this application; 
         FIG. 1J  is a cross-sectional schematic view of a jelly-roll battery cell according to another embodiment of this application; 
         FIG. 1K  is a cross-sectional schematic view of a jelly-roll battery cell according to still another embodiment of this application; 
         FIG. 1L  is a cross-sectional schematic view of a jelly-roll battery cell according to another embodiment of this application; 
         FIG. 1M  is a cross-sectional schematic view of a jelly-roll battery cell according to still another embodiment of this application; and 
         FIG. 1N  is a cross-sectional schematic view of a jelly-roll battery cell according to another embodiment of this application. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of this application will be described in detail below. Throughout the specification of this application, the same or similar components and the components having the same or similar functions are denoted by similar reference numerals. The embodiments described herein with reference to the accompanying drawings are illustrative and graphical in nature, and are intended to enable a basic understanding of this application. The embodiments of this application are not to be construed as a limitation on this application. 
     In this specification, unless otherwise specified or defined, relativity terms such as “central”, “longitudinal”, “lateral”, “front”, “rear”, “right” “,” “left”, “internal”, “external”, “lower”, “higher”, “horizontal”, “perpendicular”, “higher than”, “lower than”, “above”, “under”, “top”, “bottom”, and derivative terms thereof (such as “horizontally”, “downwardly”, “upwardly”) shall be interpreted as a direction described in the context or a direction illustrated in the drawings. The relativity terms are used for ease of description only, and do not require that the construction or operation of this application should be in a specific direction. 
     The terms “about”, “roughly”, “substantially”, “substantively”, and “approximately” used herein are intended to describe and represent small differences. When used together an event or situation, such terms may represent an example in which the event or situation occurs exactly or an example in which the event or situation occurs very approximately. For example, when used together with a numerical value, such terms may represent a variation range falling within ±10% of the numerical value, such as ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.1%, or ±0.05% of the numerical value. For example, if a difference between two numerical values falls within ±10% of an average of the numerical values (such as ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.1%, or ±0.05% of the average), the two numerical values may be considered “substantially” the same. 
     Furthermore, for ease of description, “first”, “second”, “third”, and the like may be used herein to distinguish different components in one drawing or a series of drawings. “First”, “second”, “third”, and the like are not intended to describe corresponding components. 
     In this application, unless otherwise expressly specified or defined, the terms “dispose”, “connect”, “couple”, “fix”, and similar terms are used in a broad sense, and a person skilled in the art understands that, depending on the context, such terms may mean, for example, fixedly connecting, detachably connecting, or integrally connecting; or mechanically connecting or electrically connecting; or directly connecting or indirectly connecting through an intermediary structure; or internal communication between two components. 
     In the description of specific embodiments and claims, a list of items referred to by using the terms such as “one of”, “one thereof”, “one type of” or other similar terms may mean any one of the listed items. For example, if items A and B are listed, the phrase “one of A and B” means A alone, or B alone. In another example, if items A, B, and C are listed, then the phrases “one of A, B, and C” and “one of A, B, or C” mean: A alone; B alone; or C alone. The item A may include a single element or a plurality of elements. The item B may include a single element or a plurality of elements. The item C may include a single element or a plurality of elements. 
     In the description of embodiments and claims, a list of items referred to by using the terms such as “at least one of”, “at least one thereof”, “at least one type of” or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrases “at least one of A and B” and “at least one of A or B” mean: A alone; B alone; or both A and B. In another example, if items A, B, and C are listed, the phrases “at least one of A, B, and C” and “at least one of A, B, or C” mean: A alone; B alone; C alone; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. The item A may include a single element or a plurality of elements. The item B may include a single element or a plurality of elements. The item C may include a single element or a plurality of elements. 
     When forming a jelly-roll battery cell in the prior art, a separator usually needs to be wound for an empty coil interiorly. Consequently, four layers of separators exist inside the jelly-roll battery cell. Therefore, a space utilization rate of the jelly-roll battery cell provided in the prior art is low. The interior of a battery cell structure and a separator winding technique may be improved to obtain a jelly-roll battery cell inside which only two layers of separators exist. However, high requirements on an energy density of the battery cell in the market are not fully satisfied by merely improving the space utilization rate of the battery cell by reducing the quantity of layers of separators inside the jelly-roll battery cell. Therefore, more technical solutions to effectively obtaining a jelly-roll battery cell with a higher energy density and a higher space utilization rate are required in the industry. 
     In view of the foregoing situation, embodiments of this application provide an improved jelly-roll battery cell and electrochemical device. In this application, only two layers of separators exist in a central region of the jelly-roll battery cell. In addition, by designing a positional relationship between the separator located in the central region of the jelly-roll battery cell and an electrode plate and/or a cell tab in the central region in a thickness direction of the battery cell, this application effectively reduces a thickness of the battery cell and thereby improves a space utilization rate and an energy density of the battery cell. 
       FIG. 1A  is a cross-sectional schematic view of a jelly-roll battery cell  101  according to an embodiment of this application. As shown in  FIG. 1A , the jelly-roll battery cell  101  according to an embodiment of this application includes a first electrode plate  100 , a second electrode plate  200 , and a separator  300 . The first electrode plate  100 , the second electrode plate  200 , and the separator  300  are wound to form the jelly-roll battery cell  101 . The jelly-roll battery cell  101  has a thickness direction X, a length direction Y perpendicular to the thickness direction, and a central region S enclosed by the first electrode plate  100 , the second electrode plate  200 , and the separator  300 . 
     The first electrode plate  100  may include a first current collector  101 . A material of the first current collector  101  may include any material applicable to a current collector in the art. The first current collector  101  may include, for example, but without limitation, a polymer layer and/or a metal layer. The first current collector  101  may include a first surface  101   a  and a second surface  101   b  opposite to the first surface  101   a . The first surface  101   a  is closer to the central region S than the second surface  101   b.    
     The first current collector  101  may include a first section  103 , a second section  105 , a third section  107 , and a fourth section  109 . The first section  103 , the second section  105 , the third section  107 , and the fourth section  109  each may be regarded as a part of the first current collector  101 . The first section  103 , the second section  105 , the third section  107 , and the fourth section  109  together constitute the entire first current collector  101 . 
     The first section  103  has a first end  103   a  and a second end  103   b . The first end  103   a  may be an initiation end of the first section  103 , that is, a winding initiation end of the first electrode plate  100 . The second end  103   b  may be a termination end of the first section  103 . The first surface  101   a  and the second surface  101   b  in the first section  103  may be not provided with an active material layer. To be specific, a part of the first current collector  101 , which is defined by the first section  103 , may be a current collector that is not provided with an active material layer. The first section  103  may include a curved current collector and/or a flat current collector. 
     The second section  105  is connected to the first section  103 . The second section  105  has a third end  105   a  and a fourth end  105   b . The third end  105   a  may be an initiation end of the second section  105  and is connected to the second end  103   b . The fourth end  105   b  may be a termination end of the second section  105 . The second section  105  may include merely a flat current collector. The first surface  101   a  in the second section  105  may be provided with a first tab  111 . A material of the first tab  111  may include a metal. In some embodiments, the material of the first tab  111  may include copper. In some embodiments, the material of the first tab  111  may include nickel. In some embodiments, the material of the first tab  111  may include an alloy material of nickel, silver, or copper. In some embodiments, the material of the first tab  111  may include any material applicable to a tab in the art. The first tab  111  may be connected to the first surface  101   a  in the second section  105  of the first current collector  101  by any appropriate means such as, but without limitation, resistance welding, ultrasonic welding, and conductive adhesive connection. The first tab  111  may be a negative tab. In other embodiments of this application, the first tab  111  may be a positive tab. When the first tab  111  is located in the second section  105  of the first electrode plate  100 , the separator  300  at the winding initiation end does not need to be wound for an empty coil. Therefore, the central region S may be provided with only two layers of separators  300 . The first surface  101   a  in the second section  105  may be not provided with an active material layer. The second surface  101   b  in the second section  105  may be provided with a first active material layer  113 . To be specific, a part of the first current collector  101 , which is defined by the second section  105 , may be a current collector of which only one surface is provided with the active material layer. The first active material layer  113  may include any material commonly used in the art as an active material layer, for example, but without limitation, silicon-carbon hybrid, conductive carbon black (Super P), styrene butadiene rubber (SBR) as a binder, or lithium cobalt oxide (LiCoO 2 ). 
     The third section  107  is connected to the second section  105 . The third section  107  has a seventh end  107   a  and an eighth end  107   b . The seventh end  107   a  may be an initiation end of the third section  107  and is connected to the fourth end  105   b . The eighth end  107   b  may be a termination end of the third section  107 . The third section  107  may include curved and flat current collectors. The first surface  101   a  in the third section  107  may be not provided with an active material layer. The second surface  101   b  in the third section  107  may be provided with a first active material layer  113 . To be specific, a part of the first current collector  101 , which is defined by the third section  107 , may be a current collector of which only one surface is provided with the active material layer. 
     The fourth section  109  is connected to the third section  107 . The fourth section  109  has a ninth end  109   a  and a tenth end  109   b . The ninth end  109   a  may be an initiation end of the fourth section  109  and is connected to the eighth end  107   b . The tenth end  109   b  may be a termination end of the fourth section  109 , that is, a winding termination end of the first electrode plate  100 . The fourth section  109  may include a curved current collector and a flat current collector. Both the first surface  101   a  and a second surface  101   b  in the fourth section  109  may be provided with the first active material layer  113 . To be specific, a part of the first current collector  101 , which is defined by the fourth section  109 , may be a current collector of which both surfaces are provided with the active material layer. 
     The second electrode plate  200  may include a second current collector  201 . A material of the second current collector  201  may include any material applicable to a current collector in the art. The second current collector  201  may include, for example, but without limitation, a polymer layer and/or a metal layer. The second current collector  201  may include a third surface  201   a  and a fourth surface  201   b  opposite to the third surface  201   a . The third surface  201   a  is closer to the central region S than the fourth surface  201   b.    
     The second current collector  201  may include a fifth section  203 , a sixth section  205 , and a seventh section  207 . The fifth section  203 , the sixth section  205 , and the seventh section  207  each may be regarded as a part of the second current collector  201 . The fifth section  203 , the sixth section  205 , and the seventh section  207  together constitute the entire second current collector  201 . 
     The fifth section  203  has an eleventh end  203   a  and a twelfth end  203   b . The eleventh end  203   a  may be an initiation end of the fifth section  203 , that is, a winding initiation end of the second electrode plate  200 . The twelfth end  203   b  may be a termination end of the fifth section  203 . The third surface  201   a  and the fourth surface  201   b  in the fifth section  203  may be provided with a second active material layer  213 . To be specific, a part of the second current collector  201 , which is defined by the fifth section  203 , may be a current collector of which both surfaces are provided with the active material layer. The second active material layer  213  may include any material commonly used in the art as an active material layer, for example, but without limitation, silicon-carbon hybrid, conductive carbon black (Super P), styrene butadiene rubber (SBR) as a binder, or lithium cobalt oxide (LiCoO 2 ). The material of the second active material layer  213  may be identical to or different from the material of the first active material layer  113 . The fifth section  203  may include a curved current collector and/or a flat current collector. 
     The fifth section  203  may include a first subsection  2031 , a second subsection  2033 , a third subsection  2035 , a fourth subsection  2037 , and a fifth subsection  2039 . The first subsection  2031 , the second subsection  2033 , the third subsection  2035 , the fourth subsection  2037 , and the fifth subsection  2039  each may be regarded as a part of the fifth section  203 . The first subsection  2031 , the second subsection  2033 , the third subsection  2035 , the fourth subsection  2037 , and the fifth subsection  2039  together constitute the entire fifth section  203 . 
     The first subsection  2031  may be a starting subsection of the fifth section  203 . The first subsection  2031  has an initiation end  2031   a  and a termination end  2031   b . The initiation end  2031   a  of the first subsection  2031  overlaps the eleventh end  203   a  of the fifth section  203 . The initiation end  2031   a  is a winding initiation end of the second electrode plate  200 . The first subsection  2031  may be flat. The second subsection  2033  is connected to the first subsection  2031 . The second subsection  2033  has an initiation end  2033   a  and a termination end  2033   b . The initiation end  2033   a  of the second subsection  2033  is connected to the termination end  2031   b  of the first subsection  2031 . The second subsection  2033  may be curved. The third subsection  2035  is connected to the second subsection  2033 . The third subsection  2035  has an initiation end  2035   a  and a termination end  2035   b . The initiation end  2035   a  of the third subsection  2035  is connected to the termination end  2033   b  of the second subsection  2033 . The third subsection  2035  may be flat. The fourth subsection  2037  is connected to the third subsection  2035 . The fourth subsection  2037  has an initiation end  2037   a  and a termination end  2037   b . The initiation end  2037   a  of the fourth subsection  2037  is connected to the termination end  2035   b  of the third subsection  2035 . The fourth subsection  2037  may be curved. The fifth subsection  2039  is connected to the fourth subsection  2037 . The fifth subsection  2039  has an initiation end  2039   a  and a termination end  2039   b . The initiation end  2039   a  of the fifth subsection  2039  is connected to the termination end  2037   b  of the fourth subsection  2037 . The termination end  2039   b  overlaps the termination end  203   b  of the fifth section  203 . The fifth subsection  2039  is a termination subsection of the fifth section  203 . The fifth subsection  2039  may be flat. 
     The sixth section  205  is connected to the fifth section  203 . The sixth section  205  has a thirteenth end  205   a  and a fourteenth end  205   b . The thirteenth end  205   a  may be an initiation end of the sixth section  205  and is connected to the twelfth end  203   b . The fourteenth end  205   b  may be a termination end of the sixth section  205 . The third surface  201   a  in the sixth section  205  may be provided with the second active material layer  213 . The fourth surface  201   b  in the sixth section  205  may be not provided with the second active material layer  213 . To be specific, a part of the second current collector  201 , which is defined by the sixth section  205 , may be a current collector of which only one surface is provided with the active material layer. The sixth section  205  may include a curved current collector and/or a flat current collector. 
     The sixth section  205  may include a sixth subsection  2051 , a seventh subsection  2053 , an eighth subsection  2055 , and a ninth subsection  2057 . The sixth subsection  2051 , the seventh subsection  2053 , the eighth subsection  2055 , and the ninth subsection  2057  each may be regarded as a part of the sixth section  205 . The sixth subsection  2051 , the seventh subsection  2053 , the eighth subsection  2055 , and the ninth subsection  2057  together constitute the entire sixth section  205 . 
     The sixth subsection  2051  may be a starting subsection of the sixth section  205 . The sixth subsection  2051  is connected to the fifth subsection  2039 . The sixth subsection  2051  has an initiation end  2051   a  and a termination end  2051   b . The initiation end  2051   a  is connected to the termination end  2039   b  of the fifth subsection  2039 . The fourth surface  201   b  in the sixth subsection  2051  is provided with the second insulation adhesive  215 . The second insulation adhesive  215  has an initiation end  215   a  and a termination end  215   b . The initiation end  215   a  and the termination end  215   b  overlap the initiation end  2051   a  and the termination end  2051   b  of the sixth subsection  2051  respectively. The material of the second insulation adhesive  215  may include any material applicable to an insulation adhesive in the art. The sixth subsection  2051  may be curved. The seventh subsection  2053  is connected to the sixth subsection  2051 . The seventh subsection  2053  has an initiation end  2053   a  and a termination end  2053   b . The initiation end  2053   a  of the seventh subsection  2053  is connected to the termination end  2051   b  of the sixth subsection  2051 . The seventh subsection  2053  may be flat. The eighth subsection  2055  is connected to the seventh subsection  2053 . The eighth subsection  2055  has an initiation end  2055   a  and a termination end  2055   b . The initiation end  2055   a  of the eighth subsection  2055  is connected to the termination end  2053   b  of the seventh subsection  2053 . The eighth subsection  2055  may be curved. The ninth subsection  2057  is connected to the eighth subsection  2055 . The ninth subsection  2057  has an initiation end  2057   a  and a termination end  2057   b . The initiation end  2057   a  of the ninth subsection  2057  is connected to the termination end  2055   b  of the eighth subsection  2055 . The termination end  2057   b  overlaps the termination end  205   b  of the sixth section  205 . The ninth subsection  2057  is a termination subsection of the sixth section  205 . The ninth subsection  2057  may be flat. 
     The seventh section  207  is connected to the sixth section  205 . The seventh section  207  has a fifteenth end  207   a  and a sixteenth end  207   b . The fifteenth end  207   a  may be an initiation end of the seventh section  207  and is connected to the fourteenth end  205   b . The sixteenth end  207   b  may be a termination end of the seventh section  207 , that is, a winding termination end of the second electrode plate  200 . The third surface  201   a  and the fourth surface  201   b  in the seventh section  207  may be not provided with the second active material layer  213 . To be specific, a part of the second current collector  201 , which is defined by the seventh section  207 , may be a current collector that is not provided with an active material layer. The seventh section  207  may include a curved current collector and a flat current collector. The sixteenth end  207   b  may overlap none of the first tab  100 , the second tab  200 , and the fifth end  301  of the separator  300  in the thickness direction X, so as to reduce the thickness of the jelly-roll battery cell  101 . 
     The seventh section  207  may include a tenth subsection  2071  and an eleventh subsection  2073 . The tenth subsection  2071  and the eleventh subsection  2073  each may be regarded as a part of the seventh section  207 . The tenth subsection  2071  and the eleventh subsection  2073  together constitute the entire seventh section  207 . 
     The tenth subsection  2071  may be a starting subsection of the seventh section  207 . The tenth subsection  2071  has an initiation end  2071   a  and a termination end  2071   b . The initiation end  2071   a  of the tenth subsection  2071  is connected to the termination end  2057   b  of the ninth subsection  2057 . The tenth subsection  2071  may be curved. The third surface  201   a  in the tenth subsection  2071  is provided with a third insulation adhesive  217 . A material of the third insulation adhesive  217  may include a material commonly used as an insulation adhesive in the art. The third insulation adhesive  217  has an initiation end  217   a  and a termination end  217   b . The initiation end  217   a  and the termination end  217   b  overlap the initiation end  2071   a  and the termination end  2071   b  of the tenth subsection  2071  respectively. The eleventh subsection  2073  is connected to the tenth subsection  2071 . The eleventh subsection  2073  has an initiation end  2073   a  and a termination end  2073   b . The initiation end  2073   a  of the eleventh subsection  2073  is connected to the termination end  2071   b  of the eleventh subsection  2071 . The eleventh subsection  2073  is a termination subsection of the seventh section  207 . The eleventh subsection  2073  may be flat. The third surface  201   a  in the eleventh subsection  2073  is provided with a second tab  211 . The second tab  211  has a first side  211   a  and a second side  211   b  opposite to the first side  211   a . The first side  211   a  is on the third surface  201   a  in the eleventh subsection  2073  of the second electrode plate  200 . A material of the second tab  211  may include a metal. In some embodiments, the material of the second tab  211  may include copper. In some embodiments, the material of the second tab  211  may include nickel. In some embodiments, the material of the second tab  211  may include an alloy material of nickel, silver, or copper. In some embodiments, the material of the second tab  211  may include any material applicable to a tab in the art. The second tab  211  may be connected to the third surface  201   a  in the eleventh subsection  2073  of the second current collector  201  by any appropriate means such as, but without limitation, resistance welding, ultrasonic welding, and conductive adhesive connection. The second tab  211  is disposed to the right of the first tab  111 , and does not overlap the first tab  111  in the thickness direction X. The eleventh subsection  2073  may overlap no first tab  111  in the thickness direction X. The second tab  211  may be a positive tab. In other embodiments of this application, the second tab  211  may be a negative tab. The second tab  211  is disposed to the right of the first tab  111 . In other embodiments of this application, the second tab  211  may be disposed to the left of the first tab  111 . The second tab  211  does not overlap the first end  103   a  of the first electrode plate  100  or the first tab  111  in the thickness direction X, so as to further reduce the thickness of the jelly-roll battery cell  10 I. 
     The separator  300  may be disposed between the first electrode plate  100  and the second electrode plate  200 . The separator  300  has a fifth end  301  and a sixth end  303 . The fifth end  301  is a winding initiation end of the separator  300 . The sixth end  303  is a winding termination end of the separator  300 . The fifth end  301  overlaps the first tab  100  in the thickness direction X. In other embodiments of this application, the fifth end  301  does not overlap the first tab  100  in the thickness direction X, so as to further reduce the thickness of the jelly-roll battery cell  10 I. The sixth end  303  of the separator  300  does not overlap the first tab  111  or the second tab  211  in the thickness direction X. The separator  300  may have a virtual first boundary line  305 . A part from the first boundary line  305  to the fifth end  301 , which constitutes a part of the separator  300 , is defined as a first part Q of the separator  300 . A shape of the first part Q may be flat. The first part Q overlaps the first tab  100  in the thickness direction X. In other embodiments of this application, the first part Q may overlap no first tab  100  in the thickness direction X, so as to further reduce the thickness of the jelly-roll battery cell  10 I. The separator  300  located between the second section  105  and the third section  107  may be provided with a coating to improve safety of the jelly-roll battery cell  10 I. In other embodiments of this application, the separator  300  located between the second section  105  and the third section  107  may be not provided with a coating, so as to reduce the thickness of the jelly-roll battery cell  10 I. A material of the separator  300  may include any material applicable to a separator in the art. The sixth end  303  of the separator  300  may be flush with the termination end  215   b  of the second insulation adhesive  215  and the termination end  217   b  of the third insulation adhesive  217 . Alternatively, the sixth end  303  may extend beyond the termination end  215   b  of the second insulation adhesive  215  and the termination end  217   b  of the third insulation adhesive  217 , so as to ensure safety of the jelly-roll battery cell  101 . 
     The jelly-roll battery cell  101  may further include a first insulation adhesive  400  overlaying the winding termination end  207   b  of the second electrode plate  200 , and the second electrode plate  200  is fixed above the fourth surface  201   b  in the seventh subsection  2053  of the jelly-roll battery cell  101 . The first insulation adhesive  400  may be made of a material commonly used as an insulation adhesive in the art, for example but without limitation, insulation tape, polyolefin hot-melt adhesive, hot-melt adhesive made of ethylene and a copolymer thereof, polyurethane hot-melt adhesive, or polyamide hot-melt adhesive. The first insulation adhesive  400  may overlap neither the first tab  111  nor the second tab  211  in the thickness direction X, so as to maximize a thickness space and further increase the energy density of the jelly-roll battery cell  101 . 
     Both the third surface  201   a  and the fourth surface  201   b  at the winding initiation end  203   a  of the second current collector  201  are provided with the second active material layer  213 . Therefore, the jelly-roll battery cell  101  according to this embodiment of this application is free from two empty coils of opposite current collectors, that is, two coils are not provided with an active material layer. In addition, by disposing the first tab  111  on the first surface  101   a  in the second section  105  of the first electrode plate  100 , the first tab  111  of the jelly-roll battery cell  101  according to this embodiment of this application may overlap no first end  103   a  of the first electrode plate  100  in the thickness direction X, thereby reducing the thickness of the battery cell  10 . The thickness in the thickness direction X at the position of the first tab  111  consists of thicknesses of two layers of separators  300  located in the central region S, the first tab  111 , and remaining components. The thickness in the thickness direction X at the position of the second tab  211  consists of thicknesses of the second current collector  201 , the second tab  211 , and remaining components. Therefore, compared with a conventional jelly-roll battery cell, the jelly-roll battery cell  101  according to this embodiment of this application reduces the thickness, and thereby achieves a higher energy density and a higher space utilization rate. 
       FIG. 1B  is a cross-sectional schematic view of a jelly-roll battery cell  10 II according to another embodiment of this application. As shown in  FIG. 1B , the jelly-roll battery cell  10 II according to another embodiment of this application differs from the jelly-roll battery cell  10 I shown in  FIG. 1  only in: the fifth end  301 II of the separator  300 II does not overlap the first tab  111 II in the thickness direction X. 
     The fifth end  301 II of the separator  300 II does not overlap the first end  103   a II of the first electrode plate  100 II, the first tab  111 II, or the second tab  211 II in the thickness direction X. Therefore, the thickness in the thickness direction X at the position of the first tab  111 II consists of the thicknesses of the first tab  111  and remaining components. The thickness in the thickness direction X at the position of the second tab  211 II consists of the thicknesses of the second current collector  201 II, the second tab  211 II, and remaining components. Therefore, the jelly-roll battery cell  10 II according to this embodiment of this application has even a smaller thickness in the thickness direction X than the jelly-roll battery cell  10 I shown in  FIG. 1A , thereby achieving a higher energy density. 
       FIG. 1C  is a cross-sectional schematic view of a jelly-roll battery cell  10 III according to still another embodiment of this application. As shown in  FIG. 1C , the jelly-roll battery cell  10 III according to still another embodiment of this application differs from the jelly-roll battery cell  10 II shown in  FIG. 1B  only in: a shape of the first part QIII defined by the first boundary line  305 III of the separator  300 III and the fifth end  301 III of the separator  300 III is curved. 
       FIG. 1D  is a cross-sectional schematic view of a jelly-roll battery cell  10 IV according to another embodiment of this application. As shown in  FIG. 1D , the jelly-roll battery cell  10 IV according to another embodiment of this application differs from the jelly-roll battery cell  10 II shown in  FIG. 1B  only in: the second tab  211 IV is located to the left of the first tab  111 IV. The first insulation adhesive  400 IV overlaps the fifth end  301 IV of the separator  300 IV in the thickness direction X. In other embodiments of this application, the first insulation adhesive  400 IV may overlap no fifth end  301 IV of the separator  300 IV in the thickness direction X, so as to further reduce the thickness of the jelly-roll battery cell  10 IV. The first insulation adhesive  400 IV does not overlap the first end  103   a IV of the first electrode plate  100 IV in the thickness direction X. The thickness in the thickness direction X at the position of the first tab  111 IV consists of the thicknesses of the first tab  111 IV, the second current collector  201 IV, and remaining components. The thickness in the thickness direction X at the position of the second tab  211 IV consists of the thicknesses of the second current collector  201 IV, the second tab  211 IV, and remaining components. 
       FIG. 1E  is a cross-sectional schematic view of a jelly-roll battery cell  10 V according to still another embodiment of this application. As shown in  FIG. 1E , the jelly-roll battery cell  10 V according to still another embodiment of this application differs from the jelly-roll battery cell  10 II shown in  FIG. 1B  only in: the first side  211   a V of the second tab  211 V is disposed on the fourth surface  201   b V in the seventh subsection  2053 V. The thickness in the thickness direction X at the position of the first tab  111 V consists of the thicknesses of the first tab  111 V and remaining components. The thickness in the thickness direction X at the position of the second tab  211 IV consists of the thicknesses of the second tab  211 IV and remaining components. Therefore, the jelly-roll battery cell  10 V according to this embodiment of this application has even a smaller thickness in the thickness direction X than the jelly-roll battery cells shown in  FIG. 1A  to  FIG. 1D , thereby achieving a higher energy density. 
     In other embodiments of this application, the jelly-roll battery cell  10 V may further include a fourth insulation adhesive (not shown in the drawing) overlaying the second side  211   b V of the second tab  211 V, so as to prevent the second tab  211 V from piercing a package of the jelly-roll battery cell  10 V and avoid corrosion. 
       FIG. 1F  is a cross-sectional schematic view of a jelly-roll battery cell  10 VI according to another embodiment of this application. As shown in  FIG. 1F , the jelly-roll battery cell  10 IV according to another embodiment of this application differs from the jelly-roll battery cell  10 V shown in  FIG. 1E  only in: a shape of the first part QVI defined by the first boundary line  305 VI of the separator  300 VI and the fifth end  301 VI of the separator  300 VI is curved. 
       FIG. 1G  is a cross-sectional schematic view of a jelly-roll battery cell  10 VII according to still another embodiment of this application. As shown in  FIG. 1G , the jelly-roll battery cell  10 VII according to still another embodiment of this application differs from the jelly-roll battery cell  10 V shown in  FIG. 1E  only in: the second tab  211 VII is located to the left of the first tab  111 IVII, and the first insulation adhesive  400 VII overlaps the first tab  111 VII in the thickness direction X. The thickness in the thickness direction X at the position of the first tab  111 VII consists of the thicknesses of the first tab  111 VII, the first insulation adhesive  400 VII, and remaining components. The thickness in the thickness direction X at the position of the second tab  211 VII consists of the thicknesses of the second tab  211 VII and remaining components. 
     In other embodiments of this application, the first insulation adhesive  400 VII may overlap no first tab  111 VII in the thickness direction X. The thickness in the thickness direction X at the position of the first tab  111 VII consists of the thicknesses of the first tab  111 VII and remaining components. The thickness in the thickness direction X at the position of the second tab  211 VII consists of the thicknesses of the second tab  211 VII and remaining components. 
       FIG. 1H  is a cross-sectional schematic view of a jelly-roll battery cell  10 VIII according to another embodiment of this application. As shown in  FIG. 1H , the jelly-roll battery cell  10 VIII according to another embodiment of this application differs from the jelly-roll battery cell  10 VII shown in  FIG. 1G  only in: a shape of the first part QVIII defined by the first boundary line  305 VIII of the separator  300 VIII and the fifth end  301 VIII of the separator  300 VIII is curved. The first part QVIII partially overlaps the second tab  211 VIII in the thickness direction X. The thickness in the thickness direction X at the position of the first tab  111 VIII consists of the thicknesses of the first tab  111 VIII, the first insulation adhesive  400 VIII, and remaining components. The thickness in the thickness direction X at the position of the second tab  211 VIII consists of the thicknesses of the second tab  211 VIII, two layers of separators  300 , and remaining components. 
     In other embodiments of this application, the first insulation adhesive  400 VIII may overlap no first tab  111 VIII in the thickness direction X, and the first part QVIII may overlap no second tab  211 VIII in the thickness direction X. The thickness in the thickness direction X at the position of the first tab  111 VIII consists of the thicknesses of the first tab  111 VIII and remaining components. The thickness in the thickness direction X at the position of the second tab  211 VIII consists of the thicknesses of the second tab  211 VIII and remaining components. 
       FIG. 1I  is a cross-sectional schematic view of a jelly-roll battery cell  10 IX according to still another embodiment of this application. As shown in  FIG. 1I , the jelly-roll battery cell  10 IX according to still another embodiment of this application differs from the jelly-roll battery cell  10 V shown in  FIG. 1E  only in: the first insulation adhesive  400 IX overlays the second side  211   b IX of the second tab  2111 X, so as to prevent the second tab  211 IX from piercing the package of the jelly-roll battery cell  10 IX and avoid corrosion. 
       FIG. 1J  is a cross-sectional schematic view of a jelly-roll battery cell  10 X according to another embodiment of this application. As shown in  FIG. 1J , the jelly-roll battery cell  10 X according to another embodiment of this application differs from the jelly-roll battery cell  10 V shown in  FIG. 1E  only in: the second tab  211 X is located below the eleventh subsection  2073 X. The thickness in the thickness direction X at the position of the first tab  111 X consists of the thicknesses of the first tab  111 X and remaining components. The thickness in the thickness direction X at the position of the second tab  211 X consists of the thicknesses of the second tab  211 X, the second current collector  201 X, and remaining components. 
       FIG. 1K  is a cross-sectional schematic view of a jelly-roll battery cell  10 XI according to still another embodiment of this application. As shown in  FIG. 1K , the jelly-roll battery cell  10 XI according to still another embodiment of this application differs from the jelly-roll battery cell  10 X shown in  FIG. 1J  in: the first side  211   a XI of the second tab  211 XI is located on the fourth surface  201   b XI in the first part  2035   c XI of the third subsection  2035 XI. Neither the third surface  201   a XI nor the fourth surface  201   b XI in the first part  2035   c XI is provided with the first or second active material layer. The jelly-roll battery cell  10 XI further includes a fifth insulation adhesive  500 XI that is disposed on a second side  211   b XI of the second tab  211 XI and that shields a surface in the first part  2035   c XI, where the surface is connected to the first side  211   a XI of the second tab  211 XI, so as to prevent welding burrs of the second tab  211 XI from piercing the separator  300  and bringing risks of short circuits. The jelly-roll battery cell  10 XI may further include a sixth insulation adhesive  600 XII that is opposite to the fifth insulation adhesive  500 XII and that shields a surface in the first part, where the surface is not connected to the first side  211   a XI of the second tab  211 XI, so as to prevent the welding burrs of the second tab  211 XI from piercing the separator  300 XI and bringing risks of short circuits. Materials of the fifth insulation adhesive  500 XI and the sixth insulation adhesive  600 XI may include a material that is commonly used as an insulation adhesive in the art. 
     In other embodiments of this application, the first side  211   a XI of the second tab  211 XI may be located on the fourth surface  201   b XI in the second part of the fifth subsection  2039 XI. The second part in the fifth subsection  2039 XI is similar to the first part  2035   c XI, and neither the third surface  201   a XI nor the fourth surface  201   b XI in the second part is provided with an active material layer. In addition, the fifth insulation adhesive  500 XI is disposed on the second side  211   b XI of the second tab  211 XI and shields a surface in the second part, where the surface is connected to the second side  211   b XI of the second tab  211 XI. The sixth insulation adhesive  600 XI is opposite to the fifth insulation adhesive  500 XI and shields a surface in the second part, where the surface is not connected to the first side  211   a XI of the second tab  211 XI. 
       FIG. 1L  is a cross-sectional schematic view of a jelly-roll battery cell  10 XII according to another embodiment of this application. As shown in  FIG. 1L , the jelly-roll battery cell  10 XII according to another embodiment of this application differs from the jelly-roll battery cell  10 XI shown in  FIG. 1K  in: the first side  211   a XII of the second tab  211 XII is located on the third surface  201   a XII in the first part  2035   c XII of the third subsection  2035 XII. Neither the third surface  201   a XII nor the fourth surface  201   b XII in the first part  2035   c XII is provided with an active material layer. The jelly-roll battery cell  10 XII further includes a fifth insulation adhesive  500 XII that is disposed on the second side  211   b XII of the second tab  211 XII and that shields a surface in the first part  2035   c XII, where the surface is connected to the second side  211   b XII of the second tab  211 XII. The jelly-roll battery cell  10 XII may further include a sixth insulation adhesive  600 XII that is opposite to the fifth insulation adhesive  500 XII and disposed on a surface in the first part  2035   c XII, where the surface is not connected to the first side  211   a XII of the second tab  211 XII. A shape of the first part QXII defined by the first boundary line  305 XII of the separator  300 XII and the fifth end  301 XII of the separator  300 XII is curved. 
     In other embodiments of this application, the first side  211   a XII of the second tab  211 XII may be located on the third surface  201   a XII in the second part of the fifth subsection  2039 XII. The second part in the fifth subsection  2039 XII is similar to the first part  2035 Cxii. Neither the third surface  201   a XII nor the fourth surface  201   b XII in the second part is provided with an active material layer. The fifth insulation adhesive  500 XII is disposed on the second side  211   b XII of the second tab  211 XII and shields a surface in the second part, where the surface is connected to the second side  211   b XII of the second tab  211 XII. The sixth insulation adhesive  600 XII is opposite to the fifth insulation adhesive  500 XII and shields a surface in the second part, where the surface is not connected to the first side  211   a XII of the second tab  211 XII, so as to prevent the welding burrs of the second tab  211 XII from piercing the separator  300 XII and bringing risks of short circuits. 
       FIG. 1M  is a cross-sectional schematic view of a jelly-roll battery cell  10 XIII according to still another embodiment of this application. As shown in  FIG. 1M , the jelly-roll battery cell  10 XIII according to still another embodiment of this application differs from the jelly-roll battery cell  10 XII shown in  FIG. 1L  in: the jelly-roll battery cell  10 XIII further includes a seventh insulation layer  700 XIII disposed at a corresponding position on the first electrode plate  111 XIII, where the position is opposite to the fifth insulation adhesive  500 XIII and the sixth insulation adhesive  600 XIII. The fifth insulation adhesive  500 XIII and the sixth insulation adhesive  600 XIII can further prevent the welding burrs of the second tab  211 XIII from piercing the separator and bringing risks of short circuits, so as to further improve safety performance. The thickness of the fifth insulation adhesive  500 XIII, the sixth insulation adhesive, and the seventh insulation layer  700 XIII in the thickness direction X may be smaller than the thickness of the tab. A material of the seventh insulation layer  700 XIII may include a material that is commonly used as an insulation adhesive in the art. A shape of the first part QXIII defined by the first boundary line  305 XIII of the separator  300 XIII and the fifth end  301 XIII of the separator  300 XIII is flat. 
       FIG. 1N  is a cross-sectional schematic view of a jelly-roll battery cell  10 XIV according to another embodiment of this application. As shown in  FIG. 1N , the jelly-roll battery cell  10 XIV according to another embodiment of this application differs from the jelly-roll battery cell  10 XIII shown in  FIG. 1M  only in: the second tab  211 XIV is located to the left of the first tab  111 XIV. 
     An embodiment of this application further provides an electrochemical device, including the jelly-roll battery cell according to any embodiment of this application. 
     The technical content and technical features of this application have been disclosed above, but a person skilled in the art may still make various substitutions and modifications based on the teachings and disclosure of this application without departing from the spirit of this application. Therefore, the protection scope of this application is not limited to the content disclosed in the embodiments, but includes various substitutions and modifications made without departing from this application, and is covered by the claims of this application.