CN111934027A - Cylinder lithium cell rolls up core and cylinder lithium cell - Google Patents

Cylinder lithium cell rolls up core and cylinder lithium cell Download PDF

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Publication number
CN111934027A
CN111934027A CN202010878606.0A CN202010878606A CN111934027A CN 111934027 A CN111934027 A CN 111934027A CN 202010878606 A CN202010878606 A CN 202010878606A CN 111934027 A CN111934027 A CN 111934027A
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surface density
negative
positive
preset direction
plate
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李红娜
赵悠曼
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Dongguan Chuangming Battery Technology Co Ltd
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Dongguan Chuangming Battery Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a cylindrical lithium battery roll core and a cylindrical lithium battery. The cylindrical lithium battery roll core comprises a winding body formed by sequentially stacking a positive plate, a diaphragm and a negative plate and spirally winding the positive plate, the diaphragm and the negative plate along a preset direction, wherein the surface density of the negative plate is kept unchanged, and the surface density of the positive plate is gradually increased along the preset direction; or the surface density of the positive plate is kept unchanged, and the surface density of the negative plate is gradually reduced along the preset direction; or the surface density of the positive plate is gradually increased along the preset direction, and the surface density of the negative plate is gradually decreased along the preset direction. In this way, the surface density difference between the positive electrode sheet and the negative electrode sheet dynamically changes along the winding direction of the winding body, and the difference change can offset the influence of curvature change on the actual CB at different positions of the winding body, so that the actual CB value at different positions of the winding body is always larger than the designed CB value, and the negative electrode capacity at each position of the winding body is always ensured to be in an excessive state.

Description

Cylinder lithium cell rolls up core and cylinder lithium cell
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a cylindrical lithium battery roll core and a cylindrical lithium battery.
Background
As is well known, when a negative electrode of a lithium ion battery is charged for the first time, when the negative electrode is a graphite/carbon system, the negative electrode reacts with an electrolyte to form an SEI film (solid electrolyte interface film) on the surface of the negative electrode, the SEI film has the characteristic of an ion conductor electron insulator and can allow lithium ions to pass through but isolate electrons from passing through, and the SEI film is the basis for the operation of the lithium ion battery. In actual production, during the formation of the SEI film, the negative electrode needs to participate in the reaction with the electrolyte, and during the working process of the lithium ion battery, the fracture and repair processes of the SEI film are accompanied. Therefore, when designing a lithium ion battery, the negative electrode capacity needs to be over designed, that is, the actual CB value (the ratio of the product of the negative electrode surface density and the negative electrode gram capacity to the product of the positive electrode surface density and the positive electrode gram capacity) is greater than the designed CB value, so that sufficient graphite/carbon is provided to participate in the reaction to form the SEI film on the premise that the negative electrode capacity meets the embedding requirement of the lithium ion battery. In the actual manufacturing process, if the negative electrode is excessive and insufficient (the actual CB value is less than the designed CB value), a large potential safety hazard of short circuit exists in the battery.
However, in the process of actually manufacturing the cylindrical lithium ion battery, since the battery core of the cylindrical lithium ion battery is of a winding structure, the winding structure is characterized in that the curvatures of the positive plate and the negative plate change along with different positions in the winding core, and therefore, along with the change of the curvatures of the positive plate and the negative plate, the actual CB values of the plates at different positions are in a changing state. Because the influence of pole piece camber to the CB value is great, the core that normally convolutes appears the negative pole excessively not enough easily in the great position department of camber, can't guarantee promptly that actual CB is greater than design CB value, and the inside short circuit risk of battery can't effectively avoid.
Disclosure of Invention
The embodiment of the invention aims to provide a cylindrical lithium battery roll core and a cylindrical lithium battery, and aims to solve the technical problem that the roll core of the cylindrical lithium battery in the prior art is easy to have excessive and insufficient negative electrodes at a position with larger curvature, so that the risk of short circuit inside the battery cannot be effectively avoided.
In order to achieve the purpose, the invention adopts the technical scheme that: the cylindrical lithium battery winding core comprises a winding body formed by sequentially stacking a positive plate, a diaphragm and a negative plate and spirally winding the positive plate, the diaphragm and the negative plate along a preset direction, wherein the surface density of the negative plate is kept unchanged along the preset direction, and the surface density of the positive plate is gradually increased along the preset direction;
or the surface density of the positive plate is kept unchanged along the preset direction, and the surface density of the negative plate is gradually reduced along the preset direction;
or the surface density of the positive plate is gradually increased along the preset direction, and the surface density of the negative plate is gradually decreased along the preset direction.
Optionally, the positive plate includes a positive current collector and a positive coating layer covering the surface of the positive current collector, and when the surface density of the positive plate is gradually increased along the preset direction, the thickness of the positive coating layer is gradually increased along the preset direction.
Optionally, the thickness of the positive coating layer is uniformly increased along a preset direction.
Optionally, the negative electrode plate includes a negative electrode current collector and a negative electrode coating layer covering the surface of the negative electrode current collector, and when the surface density of the negative electrode plate is gradually reduced along the preset direction, the thickness of the negative electrode coating layer is gradually reduced along the preset direction.
Optionally, the thickness of the negative coating layer is uniformly reduced along a preset direction.
Alternatively, the ratio of the actual CB value at the maximum curvature difference position of the wound body to the design CB value is 1.21 or more, and the actual CB value at the minimum curvature difference position of the wound body is equal to the design CB value.
Wherein, the CB value is: the product of the surface density of the negative plate and the gram capacity of the negative plate and the product of the surface density of the positive plate and the gram capacity of the positive plate.
Optionally, when the surface density X of the positive electrode sheet gradually increases along the preset direction and the surface density Y of the negative electrode sheet is maintained along the preset direction, the surface density X of the positive electrode sheet at the position of the maximum curvature difference of the wound body1And the surface density X of the positive electrode sheet at the position of the minimum curvature difference of the wound body2The following requirements are respectively met:
X1designing a CB value Y of less than or equal to 0.827, and the gram capacity of the negative electrode/the gram capacity of the positive electrode;
X2design CB value Y is less than or equal to 1.0, and gram capacity of negative electrode/gram capacity of positive electrode.
Optionally, the surface density of the negative plateWhen the degree Y is gradually reduced along the preset direction and the surface density X of the positive plate is kept unchanged along the preset direction, the surface density Y of the negative plate at the position of the maximum curvature difference of the winding body1And the surface density Y of the negative electrode sheet at the position of the minimum difference in curvature of the wound body2The following requirements are respectively met:
Y1design CB value Y not less than 1.21 negative gram capacity/positive gram capacity;
Y2design CB value Y negative gram capacity/positive gram capacity is more than or equal to 1.0.
Optionally, the positive plate has an areal density of 100g/m2～300g/m2。
Optionally, the surface density of the positive plate is 220.2g/m2～266.3g/m2。
One or more technical schemes in the cylindrical lithium battery roll core provided by the invention at least have one of the following technical effects: according to the cylindrical lithium battery roll core, the surface density of the positive plate is gradually increased along the winding direction (namely the preset direction) of the winding body on the premise that the surface density of the negative plate is always unchanged; or, on the premise of maintaining the surface density of the positive plate unchanged all the time, the surface density of the negative plate is set to be gradually reduced along the winding direction (i.e. the preset direction); alternatively, the surface density of the positive electrode sheet is gradually increased in the winding direction (i.e., the predetermined direction) of the wound body, and the surface density of the negative electrode sheet is gradually decreased in the winding direction (i.e., the predetermined direction). In this way, in the winding body, along the winding forming direction of the winding body, namely the radial direction of the winding body, the difference between the surface density of the positive plate and the surface density of the negative plate dynamically changes, namely along with the change of the curvatures of the negative plate and the positive plate, the surface densities of the positive plate and the negative plate synchronously change to offset the influence of the curvature change on the actual CB of the winding body, so that the actual CB values at different positions of the winding body are always larger than the designed CB value, the negative electrode capacity at each position of the winding body is ensured to be always in an excessive state, and the problem that the actual CB value at a certain position cannot meet the excessive requirement of the negative electrode to cause the short circuit of the cylindrical lithium battery winding core disclosed by the invention is avoided.
The other technical scheme of the invention is as follows: the utility model provides a cylinder lithium cell, includes foretell cylinder lithium cell book core.
According to the cylindrical lithium battery, by using the cylindrical lithium battery roll core, the actual CB value of each position inside the roll core is always larger than the designed CB value, namely the negative electrode capacity of each position of the roll core is always in an excessive state, so that the actual CB value of each position inside the cylindrical lithium battery always meets the requirement of the roll core on excessive design of the negative electrode, the risk of short circuit of the roll core inside the cylindrical lithium battery is reduced, and the use reliability and safety of the cylindrical lithium battery are effectively improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a cross-sectional view of a winding body of a cylindrical lithium battery winding core according to an embodiment of the present invention;
fig. 2 is a schematic view of a partial structure of a positive electrode sheet and a negative electrode sheet of a wound body according to an embodiment of the present invention;
fig. 3 is a partial structural view of a positive electrode sheet and a negative electrode sheet of a jelly roll according to another embodiment of the present invention;
fig. 4 is a partial structural view of a positive electrode sheet and a negative electrode sheet of a jelly roll according to still another embodiment of the present invention;
fig. 5 is a partial view of the structure shown in fig. 1.
Wherein, in the figures, the respective reference numerals:
10-a winding; 101-winding center; 11-positive plate; 111-positive current collector; 112-positive electrode coating layer; 12-a membrane; 13-negative plate; 131-a negative current collector; 132-negative coating layer.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to fig. 1 to 5 and the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, as used herein, refer to an orientation or positional relationship indicated in the drawings, which is solely for the purpose of facilitating the description and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and is therefore not to be construed as limiting the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
Reference in the specification to "one embodiment," "some embodiments," or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the invention. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," or the like, in various places throughout this specification are not necessarily all referring to the same embodiment, but rather "one or more but not all embodiments" unless specifically stated otherwise. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
As shown in fig. 1 to 5, an embodiment of the invention provides a cylindrical lithium battery roll core, which is suitable for manufacturing a cylindrical lithium battery. Specifically, as shown in fig. 1 and 2, the cylindrical lithium battery roll core includes a wound body 10 formed by sequentially stacking a positive electrode sheet 11, a separator 12, and a negative electrode sheet 13 and spirally winding them in a predetermined direction, wherein the predetermined direction is a winding direction of the positive electrode sheet 11, the separator 12, and the negative electrode sheet 13, and is a direction indicated by an arrow F2 in fig. 2.
Further, as shown in fig. 2 to 4, in this wound body 10, the areal density of the negative electrode sheet 13 is maintained constant in the winding direction, which is a predetermined direction (the direction indicated by an arrow F2 in the drawing), and the areal density of the positive electrode sheet 11 is gradually increased in the winding direction, which is a predetermined direction, as shown in fig. 2; alternatively, the areal density of the positive electrode sheet 11 is maintained constant along the preset direction, i.e., the winding direction, and the areal density of the negative electrode sheet 13 is gradually reduced along the preset direction, i.e., the winding direction, as shown in fig. 3; alternatively, the areal density of the positive electrode sheet 11 gradually increases in the winding direction, which is a predetermined direction, and the areal density of the negative electrode sheet 13 gradually decreases in the winding direction, which is a predetermined direction, as shown in fig. 4. In this way, the difference between the areal density of the negative electrode sheet 13 and the areal density of the positive electrode sheet 11 in the preset direction (i.e., the radial direction of the wound body 10) is gradually reduced, that is, the areal density of the negative electrode sheet 13 is the largest in excess at the position close to the center of the wound body 10 and is gradually reduced in the winding direction, so that the actual negative electrode at the position close to the center of the wound body 10 can be ensured to meet the requirement in excess, and the short circuit caused by the excess and insufficient negative electrodes can be avoided.
The cylindrical lithium battery winding core provided by the embodiment of the invention is designed by the above-mentioned surface densities of the positive electrode sheet 11 and the negative electrode sheet 13, so that in the winding body 10, along the winding direction of the positive electrode sheet 11, the negative electrode sheet 13 and the diaphragm 12 as shown by an arrow F2 in fig. 2-4, that is, along the radial direction of the winding body 10 as shown by an arrow F1 in fig. 1 and 5, the difference between the surface density of the positive electrode sheet 11 and the surface density of the negative electrode sheet 13 dynamically changes, that is, as the curvatures of the negative electrode sheet 13 and the positive electrode sheet 11 change, the surface densities of the positive electrode sheet 11 and the negative electrode sheet 13 synchronously change, so as to counteract the influence of the curvature change on each specific actual CB of the winding body 10, make the actual CB values at different positions of the winding body 10 always greater than the designed CB values, thereby ensuring that the negative electrode capacity at each position of the winding body 10 is always in an excessive state, and avoiding that the actual CB value at a certain position cannot meet the negative electrode, and the cylindrical lithium battery winding core of the invention is short-circuited.
In another embodiment of the present invention, as shown in fig. 2, the positive electrode sheet 11 includes a positive electrode current collector 111 and a positive electrode coating layer 112 covering the surface of the positive electrode current collector 111, wherein the positive electrode current collector 111 may be a copper foil or an aluminum foil, the upper surface and the lower surface of the positive electrode current collector 111 are both covered by the positive electrode coating layer 112, and when the surface density of the positive electrode sheet 11 is gradually increased along a preset direction (a direction indicated by an arrow F2 in the figure), the thickness of the positive electrode coating layer 112 is gradually increased along the preset direction. In the present embodiment, the positive electrode coating layer 112 is formed by coating the positive electrode slurry, and since the surface density of the positive electrode is determined by the positive electrode active material in the positive electrode slurry, the thickness of the positive electrode coating layer 112 determines the amount of the positive electrode active material, that is, the surface density of the positive electrode sheet 11, and therefore, the surface density of the positive electrode sheet 11 can be gradually increased by increasing the thickness of the positive electrode coating layer 112 along a predetermined direction (i.e., a winding direction).
Specifically, in the present embodiment, the negative coating is coated on the negative current collector 131 by a constant coating method, so as to form the negative coating layer 132 with a constant surface density on the surface of the negative current collector 131, and the positive coating layer 112 is coated on the positive current collector 111 by a gradient coating method, so as to realize the thickness variation of the positive coating layer 112.
Preferably, in the present embodiment, as shown in fig. 2, the thickness of the positive electrode coating layer 112 is uniformly increased along the preset direction, that is, the cross section of the positive electrode sheet 11 is trapezoidal, the thickness of the positive electrode coating layer 112 is uniformly changed, the surface is flat, and the adhesion degree with the separator 12 is higher during winding.
In another embodiment of the present invention, as shown in fig. 3, the negative electrode sheet 13 includes a negative electrode current collector 131 and a negative electrode paint layer 132 covering the surface of the negative electrode current collector 131, wherein the negative electrode current collector 131 may be a copper foil or an aluminum foil, the upper surface and the lower surface of the negative electrode current collector 131 are both covered by the negative electrode paint layer 132, and when the surface density of the negative electrode sheet 13 is gradually reduced along a predetermined direction (a direction indicated by an arrow F2 in the figure), the thickness of the negative electrode paint layer 132 is gradually reduced along the predetermined direction. In the present embodiment, the negative electrode coating layer 132 is formed by coating the negative electrode slurry, and since the surface density of the negative electrode is determined by the negative electrode active material in the negative electrode slurry, the thickness of the negative electrode coating layer 132 determines the amount of the negative electrode active material, that is, the surface density of the negative electrode sheet 13, and therefore, the thickness of the negative electrode coating layer 132 is gradually reduced along a predetermined direction (i.e., a winding direction), that is, the surface density of the negative electrode sheet 13 is gradually reduced along the winding direction.
Specifically, in the present embodiment, the positive coating is coated on the positive current collector 111 by a constant coating method, so as to form the positive coating layer 112 with a constant surface density on the surface of the positive current collector 111, and the negative coating layer 132 is coated on the negative current collector 131 by a gradient coating method, so as to realize a thickness variation of the negative coating layer 132.
Preferably, in this embodiment, as shown in fig. 3, the thickness of the negative electrode coating layer 132 is uniformly reduced along a predetermined direction, that is, the cross section of the negative electrode sheet 13 is trapezoidal, the thickness of the negative electrode coating layer 132 is uniformly changed, the surface is flat, and the degree of adhesion with the separator 12 is higher during winding.
In another embodiment of the present invention, as shown in fig. 1, the ratio of the actual CB value at the position of the maximum curvature difference of the wound body 10 to the design CB value is 1.21 or more, and the actual CB value at the position of the minimum curvature difference of the wound body 10 is equal to the design CB value. Wherein, the CB value is: the curvature difference is a curvature difference value between adjacent negative electrode sheet 13 and positive electrode sheet 11 at a certain winding position after winding in the wound body 10, the maximum curvature difference position of the wound body 10 is an inner side closest to the winding center 101 of the wound body 10, and the minimum curvature difference position of the wound body 10 is an outer side farthest from the winding center 101.
In the present embodiment, the ratio of the actual CB value at the position of the maximum curvature difference of the wound body 10 to the designed CB value is set to be 1.21 or more, and the actual CB value at the position of the minimum curvature difference of the wound body 10 is set to be equal to the designed CB value, so that the actual CB value at the position close to the winding center 101 of the wound body 10 (at the position of the maximum curvature difference of the positive electrode sheet 11 and the negative electrode sheet 13) is greater than the designed CB value, and under the limitation of the ratio, the actual CB value at each position of the wound body 10 in the winding direction is ensured to be greater than the designed CB value along the winding direction, and the designed CB value gradually approaches the designed CB value to approach the designed CB value when the tail of the wound body 10 is far from the winding center 101, and it is ensured that the negative electrode excess at each position of the wound body 10 satisfies the design requirement and the negative electrode excess.
In the present embodiment, it can be understood that, in the winding core of the cylindrical lithium battery, as shown in fig. 5, the design CB value (CB) of the winding coreDesign of) The actual CB value (CB) of a certain position of the winding core is selected according to the functional characteristics, such as charging and discharging capacity, efficiency and the like, required by the winding corePractice of) After the winding core is wound to form the wound body 10, the following formula is used to calculate:
CBpractice of＝[(R+H1)-R2]/(R+H1+H2+H3)2-(R+H1+H2)2]×CBDesign of
Wherein R represents the radius of the roll body 10, and CB of different positions of the roll body 10 is calculated according to the selection of R values of different sizes in the actual calculation processPractice ofR specifically refers to the distance between the center of the jelly roll 10 and the negative electrode collector 131 of the negative electrode sheet 13 at that position;
h1 represents the thickness of the negative electrode coating layer 132 corresponding to a specific value of R, that is, corresponding to one side surface of the negative electrode sheet 13 at a specific radius position of the wound body 10;
h3 represents the thickness of the positive electrode paint layer 112 corresponding to a specific R value, i.e., corresponding to one side surface of the positive electrode sheet 11 at a specific radius position of the roll 10, and the negative electrode paint layer 132 and the positive electrode paint layer 112 corresponding to H1 and H3 are opposite to each other;
h2 represents the thickness of separator 12 sandwiched between two adjacent positive electrode coating layers 112 and negative electrode coating layers 132 corresponding to a specific value of R, and the thickness value includes the gap that may exist when positive electrode sheet 11, separator 12, and negative electrode sheet 13 are sequentially stacked.
As is apparent from the above formula, in the winding core of the cylindrical lithium battery, the actual CB value at a specific position thereof is related to the winding radius of the winding body 10 corresponding to the position, and the surface density of the negative electrode sheet 13 and the positive electrode sheet 11 at the position (i.e., the thickness of the positive electrode coating layer 112 of the positive electrode sheet 11, and the thickness of the negative electrode coating layer 132 of the negative electrode sheet 13), and at the inner side of the winding body 10 with a smaller radius, i.e., the position close to the winding center 101 of the winding body 10, since R is relatively small, the risk that the actual CB value is smaller than the designed CB value is relatively large, i.e., the closer to the winding center 101 of the winding body 10, the greater the risk that the negative electrode is excessively insufficient.
As such, in the present embodiment, in the radial direction (i.e., the preset direction) of the jelly roll 10, the areal density of the negative electrode sheets 13 (i.e., the thickness H1 of the negative electrode dope layer 132 is maintained constant) is kept to be gradually increased (i.e., the thickness H3 of the positive electrode dope layer 112 is gradually increased), or the areal density of the negative electrode sheets 13 (i.e., the thickness H1 of the negative electrode dope layer 132 is gradually decreased) is kept to be constant (i.e., the thickness H3 of the positive electrode dope layer 112 is maintained constant), and the areal density of the negative electrode sheets 13 is gradually decreased (i.e., the thickness H1 of the negative electrode dope layer 132 is gradually decreased) while the areal density of the positive electrode sheets 11 is gradually increased (i.e., the thickness H3. In this way, the difference between the positive electrode coating layer 112 and the negative electrode coating layer 132 is the largest near the winding center 101 of the wound body 10, so that the actual CB value of the wound body 10 at the position near the winding center 101 is made to meet the setting requirement of the negative electrode excess by balancing the decrease in the actual CB value caused by the excessively small setting of the curvature radius R; on the contrary, as the curvature radius increases gradually, since the curvature radius R becomes larger and larger, at this time, the requirement that the actual CB value is larger than the designed CB value needs to be reduced by balancing the difference between the positive coating layer 112 and the negative coating layer 132, and thus, the difference between the positive coating layer 112 and the negative coating layer 132 is set to be smaller and smaller along the radiation direction of the jelly roll 10.
Specifically, the relationship between the R, H1, H2, and H3 described above and the actual CB value of the roll body 10 is described below with reference to specific examples. In the embodiment, the value range of R is set to be 1-15 mm, the value range of H1 is set to be 0.05-0.2 mm, the value range of H2 is set to be 0.008-0.03, and the value range of H3 is set to be 0.05-0.2 mm. At this time, a position closest to the winding center 101 of the roll body 10 is selected, and an actual CB value of the position is calculated as follows:
when the nearest position from the winding center 101 is taken as R1, the thickness H1 of the paint layer of the negative electrode sheet 13 and the positive electrode sheet 11 as H3 as 0.2, and the thickness H2 of the separator 12 as 0.03, the actual CB value at that position is:
CBpractice of＝[(1+0.2)2-12]/[(1+0.2+0.03+0.2)2-(1+0.2+0.03)2]×CBDesign of＝0.827CBDesign of
In order to ensure that the negative electrode at the position nearest to the winding center 101 is excessive enough, it is necessary to ensure that the actual CB value of the wound body 10 at the position near the winding center 101 is 1.21 times or more the design CB value when the wound body 10 is actually manufactured.
In another embodiment of the present invention, as shown in fig. 2, when the areal density X of the positive electrode sheet 11 is gradually increased in the preset direction and the areal density Y of the negative electrode sheet 13 is maintained in the preset direction (the direction indicated by the arrow F2 in the figure), the areal density X of the positive electrode sheet 11 at the position of the maximum curvature difference of the wound body 10 is1And the areal density X of the positive electrode sheet 11 at the position of the minimum difference in curvature of the wound body 102The following requirements are respectively met:
X1designing a CB value Y of less than or equal to 0.827, and the gram capacity of the negative electrode/the gram capacity of the positive electrode;
X2design CB value Y is less than or equal to 1.0, and gram capacity of negative electrode/gram capacity of positive electrode.
That is, when negative electrode sheet 13 is coated with negative electrode coating layer 132 by constant coating method and positive electrode sheet 11 is coated with positive electrode coating layer 112 by gradient coating method, surface density X of positive electrode sheet 11 at the position closest to winding center 101 of wound body 101And the area density X at the position farthest from the winding center 101 of the wound body 102Respectively satisfy the numbers as aboveThe values required to ensure that the actual CB values at each location of the jelly roll 10 meet the negative excess demand.
Further, in the present embodiment, the surface density of the positive electrode sheet 11 may be 100g/m2～300g/m2And may specifically be 100g/m2、150g/m2、180g/m2、200g/m2、220g/m2、250g/m2、260g/m2、280g/m2Or 300g/m2And the like.
For example, in this embodiment, the gram capacity of the positive electrode is 154mAh/g, the gram capacity of the negative electrode is 355mAh/g, and the constant areal density of the negative electrode sheet 13 is 110g/cm2Design CB value (design CB)Design of) 1.05, then:
the areal density of the positive electrode sheet 11, i.e., X, at the position of the maximum difference in curvature of the wound body 101≥0.827×1.05×110×355/154＝220.2g/m2；
And the surface density X of the positive electrode sheet 11 at the position of the minimum difference in curvature of the wound body 102I.e. X2≥1*1.05*110*355/154＝266.3g/m2。
In another embodiment of the present invention, as shown in fig. 3, when the areal density Y of the negative electrode sheet 13 is gradually reduced in the preset direction and the areal density X of the positive electrode sheet 11 is maintained in the preset direction (the direction indicated by the arrow F2 in the figure), the areal density Y of the negative electrode sheet 13 at the position of the maximum curvature difference of the wound body 10 is maintained1And the areal density Y of the negative electrode sheet 13 at the position of the minimum difference in curvature of the wound body 102The following requirements are respectively met:
Y1design CB value Y not less than 1.21 negative gram capacity/positive gram capacity;
Y2design CB value Y negative gram capacity/positive gram capacity is more than or equal to 1.0.
That is, when positive electrode sheet 11 is coated with positive electrode coating layer 112 by constant coating and negative electrode sheet 13 is coated with negative electrode coating layer 132 by gradient coating, surface density Y of negative electrode sheet 13 at the position closest to winding center 101 of wound body 101And the areal density Y at the position farthest from the winding center 101 of the wound body 102Respectively satisfy the above numerical requirementsThe selection of the area density of the negative electrode sheet 13 within this requirement ensures that the actual CB values at the respective positions of the wound body 10 satisfy the negative electrode excess demand.
The invention further provides a cylindrical lithium battery which comprises the cylindrical lithium battery winding core.
According to the cylindrical lithium battery, by using the cylindrical lithium battery roll core, the actual CB value of each position inside the roll core is always larger than the designed CB value, namely the negative electrode capacity of each position of the roll core is always in an excessive state, so that the actual CB value of each position inside the cylindrical lithium battery always meets the requirement of the roll core on excessive design of the negative electrode, the risk of short circuit of the roll core inside the cylindrical lithium battery is reduced, and the use reliability and safety of the cylindrical lithium battery are effectively improved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. The utility model provides a cylinder lithium cell rolls up core, includes by positive plate, diaphragm and negative plate according to the preface stack establish and along the winding body of presetting orientation spiral winding formation, its characterized in that:
the surface density of the negative plate is kept unchanged along the preset direction, and the surface density of the positive plate is gradually increased along the preset direction;
or the surface density of the positive plate is kept unchanged along the preset direction, and the surface density of the negative plate is gradually reduced along the preset direction;
or the surface density of the positive plate is gradually increased along the preset direction, and the surface density of the negative plate is gradually decreased along the preset direction.
2. The cylindrical lithium battery jelly roll of claim 1, wherein: the positive plate comprises a positive current collector and a positive coating layer covering the surface of the positive current collector, wherein the surface density of the positive plate is along when the preset direction is gradually increased, the thickness of the positive coating layer is gradually increased along the preset direction.
3. The cylindrical lithium battery jelly roll of claim 2, wherein: the thickness of the positive coating layer is uniformly increased along the preset direction.
4. The cylindrical lithium battery jelly roll of claim 1, wherein: the negative plate comprises a negative current collector and a negative coating layer covering the surface of the negative current collector, and when the surface density of the negative plate is gradually reduced along the preset direction, the thickness of the negative coating layer is gradually reduced along the preset direction.
5. The cylindrical lithium battery jelly roll of claim 4, wherein: the thickness of the negative coating layer is uniformly reduced along the preset direction.
6. The cylindrical lithium battery roll core according to any one of claims 1 to 5, characterized in that: the ratio of the actual CB value at the position with the maximum curvature difference of the winding body to the designed CB value is more than or equal to 1.21, and the actual CB value at the position with the minimum curvature difference of the winding body is equal to the designed CB value;
wherein, the CB value is: the product of the surface density of the negative plate and the gram capacity of the negative plate and the product of the surface density of the positive plate and the gram capacity of the positive plate are in a ratio.
7. The cylindrical lithium battery jelly roll of claim 6, wherein: the surface density X of the positive plate is gradually increased along the preset direction, and when the surface density Y of the negative plate is kept unchanged along the preset direction, the surface density X of the positive plate at the position of the maximum curvature difference of the winding body is positioned1And the surface density X of the positive electrode sheet at the position of the minimum curvature difference of the wound body2The following requirements are respectively met:
X1designing a CB value Y of less than or equal to 0.827, and the gram capacity of the negative electrode/the gram capacity of the positive electrode;
X2design CB value Y is less than or equal to 1.0, and gram capacity of negative electrode/gram capacity of positive electrode.
8. The cylindrical lithium battery jelly roll of claim 7, wherein: the surface density Y of the negative plate is gradually reduced along the preset direction, and when the surface density X of the positive plate is kept unchanged along the preset direction, the surface density Y of the negative plate at the position of the maximum curvature difference of the winding body is positioned1And the areal density Y of the negative electrode sheet at the position of the minimum curvature difference of the wound body2The following requirements are respectively met:
Y1design CB value Y not less than 1.21 negative gram capacity/positive gram capacity;
Y2design CB value Y negative gram capacity/positive gram capacity is more than or equal to 1.0.
9. The cylindrical lithium battery roll core according to any one of claims 1 to 5, characterized in that: the surface density of the positive plate is 100g/m2～300g/m2。
10. A cylindrical lithium battery, characterized in that, comprises the cylindrical lithium battery roll core of any one of claims 1 to 9.
CN202010878606.0A 2020-08-27 2020-08-27 Cylinder lithium cell rolls up core and cylinder lithium cell Pending CN111934027A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112542616A (en) * 2020-12-04 2021-03-23 东莞新能安科技有限公司 Electrochemical device and electronic device
WO2022252093A1 (en) * 2021-05-31 2022-12-08 宁德时代新能源科技股份有限公司 Lithium ion battery, battery module, battery pack and electric apparatus
CN115498247A (en) * 2022-10-27 2022-12-20 欣旺达电动汽车电池有限公司 Secondary battery and electric equipment
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WO2023028888A1 (en) * 2021-08-31 2023-03-09 宁德时代新能源科技股份有限公司 Lithium-ion battery, battery module, battery pack, and electrical device
WO2023236598A1 (en) * 2022-06-06 2023-12-14 宁德时代新能源科技股份有限公司 Electrode sheet structure and preparation method therefor, battery cell, and secondary battery

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112542616A (en) * 2020-12-04 2021-03-23 东莞新能安科技有限公司 Electrochemical device and electronic device
WO2022252093A1 (en) * 2021-05-31 2022-12-08 宁德时代新能源科技股份有限公司 Lithium ion battery, battery module, battery pack and electric apparatus
EP4145582A4 (en) * 2021-05-31 2023-08-09 Contemporary Amperex Technology Co., Limited Lithium ion battery, battery module, battery pack and electric apparatus
WO2023028888A1 (en) * 2021-08-31 2023-03-09 宁德时代新能源科技股份有限公司 Lithium-ion battery, battery module, battery pack, and electrical device
WO2023236598A1 (en) * 2022-06-06 2023-12-14 宁德时代新能源科技股份有限公司 Electrode sheet structure and preparation method therefor, battery cell, and secondary battery
CN115498247A (en) * 2022-10-27 2022-12-20 欣旺达电动汽车电池有限公司 Secondary battery and electric equipment
CN115566255A (en) * 2022-10-27 2023-01-03 欣旺达电动汽车电池有限公司 Secondary battery and electric equipment
CN115498247B (en) * 2022-10-27 2023-08-15 欣旺达电动汽车电池有限公司 Secondary battery and electric equipment
CN115566255B (en) * 2022-10-27 2023-08-15 欣旺达电动汽车电池有限公司 Secondary battery and electric equipment
WO2024087383A1 (en) * 2022-10-27 2024-05-02 欣旺达动力科技股份有限公司 Secondary battery and electric device
WO2024087389A1 (en) * 2022-10-27 2024-05-02 欣旺达动力科技股份有限公司 Secondary battery and electrical device

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