Cylindrical secondary battery and electronic device

Abstract

The invention provides a cylindrical secondary battery and an electronic device, the cylindrical secondary battery comprises a pole piece, the pole piece comprises a current collector and a material layer, and the material layer comprises a first edge region, a central region and a second edge region; based on the width of the material layer, the width ratio of the first edge area is 10%-30%, the width ratio of the central area is 40%-80%, and the width ratio of the second edge area is 10%-30%. Grooves are formed in the central area, stripes are arranged around the outer edge of each groove at intervals, and the stripes are communicated with the grooves respectively. The first projection area of each groove is S1 mm < 2 >, each stripe has a second projection, the sum of the second projection areas of the stripes is S2 mm < 2 >, 3 < = S1 / S2 < = 12, and 1.5 * 10 <-5 > < = S2 < = 0.45. Through the arrangement, the lithium precipitation performance and the cycle performance of the cylindrical secondary battery are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, in particular to a cylindrical secondary battery and an electronic device. BACKGROUND

[0002] Cylindrical secondary batteries, such as cylindrical lithium ion batteries, are applied in various high-rate discharge systems (such as a discharge rate greater than 3C), have characteristics such as high specific energy, high operating voltage, low self-discharge rate, small volume, light weight, and are widely used in the consumer electronics field.

[0003] Currently, the design of high-power cylindrical lithium ion batteries usually adopts a full-tab design, that is, the positive and negative tabs are extended from opposite directions, and a full-tab flattening or rubbing technology is used for preparation. However, the full-tab rubbing structure can cause tab infiltration problems, especially poor middle tab infiltration, which can cause lithium precipitation at the beginning or during the later cycle, thereby affecting the kinetic performance of the lithium ion battery. SUMMARY

[0004] The purpose of the present application is to provide a cylindrical secondary battery and an electronic device to improve the electrolyte infiltration performance of the tab, thereby improving the lithium precipitation performance and cycle performance of the cylindrical secondary battery.

[0005] It should be noted that the lithium ion battery is used as an example of the cylindrical secondary battery in the summary of the present application, but the cylindrical secondary battery of the present application is not limited to lithium ion batteries. The specific technical solutions are as follows:

[0006] The first aspect of the present application provides a cylindrical secondary battery, comprising a tab, the tab comprising a current collector and a material layer located on at least one surface of the current collector, along the width direction of the tab after being developed, the material layer comprises a first edge region, a center region and a second edge region in sequence; based on the width of the material layer, the width ratio of the first edge region is 10% to 30%, the width ratio of the center region is 40% to 80%, and the width ratio of the second edge region is 10% to 30%. The center region is provided with a plurality of grooves, and a plurality of stripes are respectively arranged at intervals around the outer edge of each groove and are respectively communicated with the grooves, and the plurality of stripes extend in a direction away from the outer edge; along the thickness direction of the tab, the first projection area of a single groove is S1 mm 2 , along the extension direction of a single stripe, the single stripe has a second projection, and the sum of the second projection areas of the plurality of stripes is S2 mm 2 , 3≤S1 / S2≤12, and optionally, 6≤S1 / S2≤8; 1.5×10 -5S2≤0.45, optionally, 0.0007≤S2≤0.15. By setting the grooves and the stripes in the central region of the pole piece and regulating the values of S1 / S2 and S2 within the scope of the present application, the grooves can store more electrolyte during the secondary battery cycle process, and the stripes can improve the flow of electrolyte on the pole piece, thereby improving the wettability of the electrolyte on the pole piece. The grooves and the stripes work together to improve the lithium precipitation performance and the cycle performance of the cylindrical secondary battery.

[0007] In one or more embodiments, along the width direction of the pole piece after being developed, the at least one stripe extends through the first end face of the first edge region away from the central region or the second end face of the second edge region away from the central region. By the above arrangement, it is beneficial to improve the wettability of the electrolyte on the pole piece while taking into account the processing performance and the active material loss, thereby improving the lithium precipitation performance and the cycle performance of the cylindrical secondary battery.

[0008] In one or more embodiments, along the thickness direction of the pole piece, the maximum depth of a single groove is D1 pm, the maximum depth of a single stripe is D2 pm, 0.5≤D2 / D1≤0.9, optionally, 0.6≤D2 / D1≤0.8; 3≤D1≤60, optionally, 10≤D1≤45. By regulating the values of D2 / D1 and D1 within the above ranges, the grooves and the stripes are arranged in combination, which is beneficial to improve the lithium precipitation performance and the cycle performance of the secondary battery.

[0009] In one or more embodiments, the thickness of the material layer is T pm, 0.5≤D1 / T≤0.9. By regulating the value of D1 / T within the above range, it is beneficial to improve the wettability of the electrolyte on the pole piece while reducing the risk of the material layer being punched by the grooves. While taking into account the safety performance of the secondary battery, the cycle performance and the lithium precipitation performance of the secondary battery are improved.

[0010] In one or more embodiments, along a direction perpendicular to the extension direction of a single stripe, the width of the second projection is W2 pm, 10≤W2≤400, optionally, 50≤W2≤200. By regulating the value of W2 within the above range, it is beneficial to the uniform distribution of the stripes on the surface of the pole piece. The flow of electrolyte on the pole piece through the stripes improves the lithium precipitation performance and the cycle performance of the secondary battery.

[0011] In one or more embodiments, along the thickness direction of the pole piece, the diameter of the maximum circumscribed circle of the first projection is W1 pm, 1.5≤W1 / W2≤8, optionally, 2≤W1 / W2≤5. By regulating the value of W1 / W2 within the above range, it is beneficial to improve the lithium precipitation performance and the cycle performance of the secondary battery.

[0012] In one or more embodiments, the plurality of stripes are distributed equiangularly around the outer edge of each groove, and the included angle formed by the extensions of the center lines of two adjacent stripes is A°, 20≤A≤180, and optionally, 60≤A≤120. By regulating the value of A within the above range, the number of stripes is moderate, which is conducive to the uniform distribution of the stripes on the pole piece, and the secondary battery has good lithium precipitation performance and cycle performance.

[0013] In one or more embodiments, the distance between two adjacent grooves along the length direction of the pole piece after being developed is R mm, 3≤R≤12, and optionally, 5≤R≤9. By regulating the value of R within the above range, the lithium precipitation performance and cycle performance of the secondary battery are improved.

[0014] In one or more embodiments, the pole piece is a positive pole piece; and / or, a negative pole piece. By providing the grooves and stripes on the central region of the positive pole piece and / or the central region of the negative pole piece, the lithium precipitation performance and cycle performance of the secondary battery are improved. When the grooves and stripes are provided on the central region of the negative pole piece, the lithium precipitation performance and cycle performance of the secondary battery are further improved.

[0015] The second aspect of the present application provides an electronic device comprising the cylindrical secondary battery in any of the foregoing embodiments. The cylindrical secondary battery of the present application has good lithium precipitation performance and cycle performance, and therefore, the electronic device of the present application has a longer service life.

[0016] The beneficial effects of the embodiments of the present application are as follows:

[0017] By providing the grooves and stripes on the central region of the pole piece, and regulating the values of S1 / S2 and S2 within the ranges of the present application, the grooves can store more electrolyte, and the stripes can improve the flow of the electrolyte on the pole piece during the cycle of the secondary battery, thereby improving the wettability of the electrolyte on the pole piece. The grooves and stripes work together to improve the lithium precipitation performance and cycle performance of the cylindrical secondary battery.

[0018] Of course, implementing any product or method of the present application does not necessarily require achieving all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other embodiments can also be obtained by those skilled in the art based on these drawings.

[0020] Figure 1 Part of the front view of the pole piece in one embodiment of the present application;

[0021] Figure 2 A partial front view of a pole piece in another embodiment of the present application;

[0022] Figure 3 A cross-sectional view of a pole piece in the present application along the Q-Q direction. Figure 1

[0023] Reference signs: pole piece 001; current collector 10; material layer 20; first edge region 21; center region 22; second edge region 23; first end face 211; groove 221; stripe 222; second end face 231. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. All other embodiments obtained by a person skilled in the art based on the present application belong to the scope of protection of the present application.

[0025] It should be noted that in the specific embodiments of the present application, the present application is explained by taking a lithium ion battery as an example of a cylindrical secondary battery, but the cylindrical secondary battery of the present application is not limited to a lithium ion battery. The specific technical solutions are as follows:

[0026] A first aspect of the present application provides a cylindrical secondary battery, comprising a pole piece, the pole piece comprising a current collector and a material layer located on at least one surface of the current collector, along the width direction of the pole piece after being developed, the material layer comprises a first edge region, a center region and a second edge region in sequence; based on the width of the material layer, the width ratio L1 of the first edge region is 10% to 30%, the width ratio L2 of the center region is 40% to 80%, and the width ratio L3 of the second edge region is 10% to 30%, for example, the width ratio L1 of the first edge region can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or a range composed of any two of the above values, the width ratio L2 of the center region can be 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, or a range composed of any two of the above values, and the width ratio L3 of the second edge region can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or a range composed of any two of the above values. The center region is provided with a plurality of grooves, a plurality of stripes are respectively and separately arranged around the outer edges of each groove, and the plurality of stripes respectively communicate with the grooves and extend in a direction away from the outer edges. Along the thickness direction of the pole piece, the first projection area of a single groove is S1 mm 2 ​, along the extension direction of the single stripe, the single stripe has a second projection, the sum of the second projection areas of the plurality of stripes is S2 mm 2 , 3≤S1 / S2≤12, optionally, 6≤S1 / S2≤8; for example, the value of S1 / S2 can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or a range composed of any two of them. 1.5x10 -5 ≤S2≤0.45, optionally, 0.0007≤S2≤0.15; for example, the value of S2 can be 1.5x10 -5 , 1.8x10 -5 , 2x10 -5 , 5x10 -5 , 8x10 -5 , 1x10 -4 , 3x10 -4 , 5x10 -4 , 7x10 -4 , 8x10 -4 , 0.001, 0.003, 0.005, 0.008, 0.01, 0.03, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.3, 0.4, 0.42, 0.45 or a range composed of any two of them.

[0027] In this application, for the convenience of understanding, it is defined that, in the unfolded state of the pole piece, the length direction of the pole piece itself is the X direction, the width direction of the pole piece itself is the Y direction, and the thickness direction of the pole piece itself is the Z direction. A three-dimensional coordinate system is established along the X direction, the Y direction and the Z direction. As shown in FIGS. Figure 1 and Figure 3 , the pole piece profile in Figure 1 is cut along Q-Q to obtain Figure 3 . The pole piece 001 comprises a current collector 10 and a material layer 20 located on one surface of the current collector. Along the width direction Y of the unfolded pole piece 001, the material layer 20 comprises a first edge region 21, a center region 22 and a second edge region 23 in sequence. The center region 22 is provided with grooves 221, and the outer edges surrounding each groove 221 are respectively provided with a stripe 222 which is in communication with the groove 221, and the stripe 222 extends in a direction away from the outer edge. Along the thickness direction Z of the pole piece 001, the groove 221 has a first projection, and along the extension direction of the stripe 222, the stripe 222 has a second projection.

[0028] When the value of S1 / S2 is too small, for example, less than the lower limit of this application, the storage space of the electrolyte on the electrode is insufficient, resulting in poor wetting effect of the electrolyte on the electrode, easy lithium plating on the electrode, and decreased cycle performance of the secondary battery. When the value of S1 / S2 is too large, for example, greater than the upper limit of this application, excessive local accumulation of electrolyte on the electrode can easily lead to side reactions, increase impedance, cause lithium plating at the negative electrode interface, reduce the thermal stability of the secondary battery, and cause side reactions between the electrolyte and the active material in the material layer, resulting in loss of active lithium, thereby reducing the cycle stability of the secondary battery. At the same time, excessive loss of active material content in the material layer leads to a decrease in the energy density of the secondary battery. This application creates grooves in the central region of the electrode and stripes along the outer edge of each groove, allowing the stripes to communicate with the grooves. The grooves provide more space for electrolyte to accumulate on the electrode, storing more electrolyte and effectively reducing the risk of insufficient electrolyte wetting in the center of the electrode. The stripes facilitate rapid electrolyte diffusion on the electrode, improving electrolyte flow and enhancing the wetting effect, especially in the center. The combination of grooves and stripes works synergistically to better achieve electrolyte conduction and / or micro-area storage, effectively improving the electrolyte wetting efficiency and performance on the electrode, thus reducing the risk of lithium plating during cycling and improving the lithium plating performance and cycle performance of the cylindrical secondary battery. In this application, those skilled in the art will understand that "multiple stripes communicating with grooves" means that the stripes spaced around the outer edge of each groove are connected to the grooves they surround.

[0029] In one or more embodiments, along the width direction after the electrode is unfolded, at least one stripe penetrates the first end face of the first edge region away from the central region or the second end face of the second edge region away from the central region. For example... Figure 2 As shown, along the width direction Y of the unfolded electrode 001, there is a stripe 222 that penetrates the first end face 211 of the first edge region 21 away from the central region 22, and another stripe 222 that penetrates the second end face 231 of the second edge region 23 away from the central region 22. This arrangement facilitates the introduction of electrolyte into the center of the electrode, allowing the electrolyte to flow more effectively into the grooves through the stripes. The combination of grooves and stripes enhances electrolyte conduction and / or micro-area storage, effectively improving the wetting efficiency and performance of the electrolyte on the electrode. This significantly reduces the risk of lithium plating due to insufficient wetting of the negative electrode during cycling, thus improving the lithium plating performance and cycle performance of the cylindrical secondary battery.

[0030] In one or more embodiments, there is one stripe that extends through the first end surface of the first edge region away from the center region. In one or more embodiments, there is one stripe that extends through the second end surface of the second edge region away from the center region. In one or more embodiments, there is one stripe that extends through the first end surface of the first edge region away from the center region, and there is another stripe that extends through the second end surface of the second edge region away from the center region. In one or more embodiments, there are two or more stripes that extend through the first end surface of the first edge region away from the center region. In one or more embodiments, there are two or more stripes that extend through the second end surface of the second edge region away from the center region. In one or more embodiments, there are two or more stripes that extend through the first end surface of the first edge region away from the center region, and there are two or more stripes that extend through the second end surface of the second edge region away from the center region. With the above arrangement, the electrolyte can be introduced into the middle of the pole piece, and the electrolyte can flow into the groove through the stripe better. The groove and the stripe are arranged in combination, which better realizes the electrolyte flow guiding and / or micro-zone storage effect, and can effectively improve the wetting efficiency and performance of the electrolyte on the pole piece, thereby effectively reducing the risk of lithium precipitation of the pole piece due to insufficient wetting of the negative pole piece during the cycle process, and improving the lithium precipitation performance and cycle performance of the cylindrical secondary battery.

[0031] In the thickness direction of the pole piece, the single groove has a first projection, and the shape of the first projection is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the shape of the first projection can be at least one of a triangle, an arc (an area smaller than a semicircle with the same radius), a semicircle, a rectangle, a trapezoid, a square, or a pentagon and above polygon. In the extension direction of the single stripe, the single stripe has a second projection, which refers to a plane formed by the width direction and the depth direction of the stripe itself in the present application. The shape of the second projection is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the shape of the second projection can be a triangle, an arc (an area smaller than a semicircle with the same radius), a semicircle, a rectangle, a trapezoid, or a square.

[0032] In one or more embodiments, as Figure 3As shown, along the thickness direction Z of the pole piece 001, the maximum depth of the single groove 221 is D1 μm, the maximum depth of the single stripe 222 is D2 μm, 0.5≤D2 / D1≤0.9, optionally, 0.6≤D2 / D1≤0.8, for example, the value of D2 / D1 can be 0.5, 0.53, 0.55, 0.58, 0.6, 0.62, 0.65, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.83, 0.85, 0.88, 0.9 or a range formed by any two of them; 3≤D1≤60, optionally, 10≤D1≤45, for example, the value of D1 can be 3, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 48, 50, 52, 55, 58, 60 or a range formed by any two of them. By adjusting the value of D2 / D1 and the value of D1 within the above range, it is beneficial to reduce the risk of excessive electrolyte accumulation in the local part of the pole piece and insufficient storage space of the electrolyte on the pole piece, while reducing the side reaction between the electrolyte and the active material in the material layer, and the electrolyte can flow quickly on the pole piece through the stripe. The groove and the stripe are arranged in combination, which is beneficial to improve the infiltration efficiency and performance of the electrolyte to the pole piece, improve the infiltration effect of the electrolyte to the pole piece, thereby reducing the risk of lithium precipitation of the pole piece in the cycle process, and improving the lithium precipitation performance and cycle performance of the secondary battery.

[0033] In one or more embodiments, as Figure 3 As shown, the thickness of the material layer (not labeled) is T μm, 0.5≤D1 / T≤0.9, for example, the value of D1 / T can be 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.65, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9 or a range formed by any two of them. By adjusting the value of D1 / T within the above range, it is beneficial to improve the infiltration efficiency and performance of the electrolyte to the pole piece, improve the infiltration effect of the electrolyte to the pole piece, while it is also beneficial to reduce the risk of the material layer being punched by the groove when the groove and the stripe are arranged, improve the cycle performance and lithium precipitation performance of the secondary battery while considering the safety performance of the secondary battery. In the present application, the thickness T of the material layer can be adjusted by means known to those skilled in the art, for example, when the slurry is coated on the surface of the current collector, under the condition that the solid content of the slurry is constant, the thickness T of the material layer can be increased by increasing the coating weight or decreased by reducing the coating weight; the thickness T of the material layer can also be reduced by increasing the cold pressing pressure or increased by reducing the cold pressing pressure when the pole piece is cold pressed.

[0034] In one or more embodiments, as Figure 1As shown, along the direction perpendicular to the extension direction of the single stripe 222, the width of the second projection is W2 μm, 10≤W2≤400, optionally, 50≤W2≤200, for example, the value of W2 can be 10, 30, 50, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400 or a range formed by any two of them. By adjusting the value of W2 within the above range, it is beneficial to the uniform distribution of the stripes on the surface of the pole piece, the electrolyte flows through the stripes on the pole piece, improves the wetting effect of the electrolyte on the pole piece, especially the middle part of the pole piece, effectively improves the wetting efficiency and wetting performance of the electrolyte on the pole piece, while reducing the processing difficulty in the actual production process, and reducing the risk of more loss of active material, thereby reducing the risk of lithium precipitation of the pole piece in the cycle process, improving the lithium precipitation performance and cycle performance of the secondary battery.

[0035] In one or more embodiments, as Figure 1 As shown, along the thickness direction Z direction of the pole piece 001, the diameter of the maximum circumscribed circle of the first projection is W1 μm, 1.5≤W1 / W2≤8, optionally, 2≤W1 / W2≤5, for example, the value of W1 / W2 can be 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 6.8, 7, 7.2, 7.5, 7.8, 8 or a range formed by any two of them. By adjusting the value of W1 / W2 within the above range, it is beneficial to reduce the risk of electrolyte gathering too much in the local part of the pole piece, resulting in uneven distribution of electrolyte on the whole pole piece, and the risk of excessive side reactions between electrolyte and active material in the material layer, leading to the decline of the cycle performance of the secondary battery, while reducing the risk of insufficient storage space of electrolyte on the pole piece. The groove and the stripe are arranged in combination, which is beneficial to improve the wetting efficiency and wetting performance of the electrolyte on the pole piece, improve the wetting effect of the electrolyte on the pole piece, thereby reducing the risk of lithium precipitation of the pole piece in the cycle process, improving the lithium precipitation performance and cycle performance of the secondary battery.

[0036] In one or more embodiments, a plurality of stripes are distributed equiangularly around the outer edge of each groove, as Figure 1As shown, the included angle formed by the extension lines of the center lines of two adjacent stripes 222 is A°, and 20≤A≤180, and optionally, 60≤A≤120. For example, the value of A can be 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, or a range formed by any two of them. By adjusting the value of A within the above range, the number of stripes is moderate, which is conducive to the uniform distribution of the stripes on the pole piece, the flow of the electrolyte through the stripes on the pole piece, the improvement of the electrolyte infiltration efficiency and performance of the pole piece, and the reduction of the risk of excessive side reactions between the electrolyte enriched in the groove and the active material in the material layer, which leads to the decline of the cycle performance of the secondary battery. In addition, it reduces the processing difficulty in the actual production process and improves the manufacturability of the pole piece, so that the secondary battery has good lithium precipitation performance and cycle performance.

[0037] In one or more embodiments, as shown, Figure 3 As shown, the distance between two adjacent grooves 221 along the length direction X of the unfolded pole piece 001 is R mm, and 3≤R≤12, and optionally, 5≤R≤9. For example, the value of R can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or a range formed by any two of them. By adjusting the value of R within the above range, the distance between two adjacent grooves is moderate, which is conducive to reducing the risk of insufficient electrolyte infiltration of the pole piece, and reducing the risk of local collapse of the material layer in the processing process, improving the electrolyte infiltration efficiency and performance of the pole piece, and improving the electrolyte infiltration effect of the pole piece. Thus, the lithium precipitation performance and cycle performance of the secondary battery are improved. In this application, the distance between two adjacent grooves refers to the distance between the geometric centers of two adjacent grooves along the length direction of the unfolded pole piece.

[0038] The length of the stripe is not particularly limited in this application, and those skilled in the art can set it according to the actual specifications of the pole piece and the distance between two adjacent grooves, as long as the purpose of this application can be achieved. In an embodiment of the present application, the stripe arranged at intervals around the outer edge of each groove can also communicate with the adjacent groove along its extension direction.

[0039] In one or more embodiments, the pole piece is a positive pole piece; and / or, a negative pole piece. By arranging grooves and stripes on the central region of the positive pole piece and / or the central region of the negative pole piece, the electrolyte infiltration efficiency and performance of the positive pole piece and / or the negative pole piece, especially the central region, can be improved, the electrolyte infiltration effect of the positive pole piece and / or the negative pole piece can be improved, and the lithium precipitation performance and cycle performance of the secondary battery can be improved. When grooves and stripes are arranged on the central region of the negative pole piece, the lithium precipitation performance and cycle performance of the secondary battery can be further improved.

[0040] In one or more embodiments, the grooves arranged in the central region of the material layer are arranged in a matrix. In another embodiment of the present application, a plurality of rows of grooves are arranged in the central region of the material layer along the width direction of the developed electrode plate, and the spacing between adjacent rows is equal. The present application does not particularly limit the number of rows of grooves, and a person skilled in the art can set the number of rows of grooves according to the actual specifications of the electrode plate, as long as the purpose of the present application can be achieved. For example, the number of rows of grooves can be 1 to 6.

[0041] In the present application, when the electrode plate is a positive electrode plate, “the electrode plate comprises a current collector and a material layer on at least one surface of the current collector” means that the positive electrode plate comprises a positive current collector and a positive material layer on at least one surface of the positive current collector. The above-mentioned “a positive material layer on at least one surface of the positive current collector” means that the positive material layer can be arranged on one surface of the positive current collector along the thickness direction of the positive current collector, or can be arranged on both surfaces of the positive current collector along the thickness direction of the positive current collector. It should be noted that the “surface” here can be the entire region of the surface of the positive current collector, or can be part of the surface of the positive current collector, and the present application does not particularly limit it, as long as the purpose of the present application can be achieved. The present application does not particularly limit the positive current collector, as long as the purpose of the present application can be achieved. For example, the positive current collector can comprise an aluminum foil, an aluminum alloy foil, or a composite current collector (such as an aluminum-carbon composite current collector), etc. The positive material layer of the present application comprises a positive active material, and the present application does not particularly limit the type of positive active material, as long as the purpose of the present application can be achieved. For example, the positive active material can comprise lithium nickel cobalt manganese oxide (LiNi 0.90 Co 0.05 Mn 0.05at least one of O2 (NCM955), NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobaltate (LiCoO2), lithium manganate, lithium manganese iron phosphate, or lithium titanate, etc. In the present application, the positive active material can also include a non-metal element, for example, the non-metal element includes at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur. In the present application, the thickness of the positive current collector is not particularly limited as long as the purpose of the present application can be achieved. For example, the thickness of the positive current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. In the present application, the positive material layer can also include a positive binder and a conductive agent. The present application does not particularly limit the type of the positive binder in the positive material layer as long as the purpose of the present application can be achieved, for example, the positive binder can include but is not limited to at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. The present application does not particularly limit the type of the conductive agent in the positive material layer as long as the purpose of the present application can be achieved, for example, the conductive agent can include but is not limited to at least one of conductive carbon black (Super P), carbon nanotube (CNT), carbon fiber, flake graphite, ketjen black, graphene, metal material, or conductive polymer. The above-mentioned carbon nanotube can include but is not limited to single-walled carbon nanotube and / or multi-walled carbon nanotube. The above-mentioned carbon fiber can include but is not limited to vapor-grown carbon fiber (VGCF) and / or nanocarbon fiber. The above-mentioned metal material can include but is not limited to metal powder and / or metal fiber, and in particular, the metal can include but is not limited to at least one of copper, nickel, aluminum, or silver. The above-mentioned conductive polymer can include but is not limited to at least one of polyphenylene derivative, polyaniline, polythiophene, polyacetylene, or polypyrrole. The present application does not particularly limit the mass ratio of the positive active material, the conductive agent, and the positive binder in the positive material layer, and a person skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved.

[0042] In the present application, when the pole piece is a negative pole piece, "the pole piece includes a current collector and a material layer on at least one surface of the current collector" means that the negative pole piece includes a negative current collector and a negative material layer on at least one surface of the negative current collector. The above-mentioned "the negative material layer on at least one surface of the negative current collector" means that the negative material layer can be disposed on one surface of the negative current collector along the thickness direction of the negative current collector, or can be disposed on two surfaces of the negative current collector along the thickness direction of the negative current collector. It should be noted that the "surface" here can be the entire area of the surface of the negative current collector, or can be part of the area of the surface of the negative current collector, which is not particularly limited in the present application as long as the purpose of the present application can be achieved. The negative current collector in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the negative current collector can include a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, or a composite current collector (such as a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.), etc. The negative material layer in the present application includes a negative active material. The type of negative active material in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the negative active material can include at least one of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x < 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate Li4Ti5O 12 with a spinel structure, Li-Al alloy, or metallic lithium. In the present application, the thickness of the negative current collector is not particularly limited as long as the purpose of the present application can be achieved. For example, the thickness of the negative current collector is 4 μm to 20 μm. Optionally, the negative material layer can further include a conductive agent and a negative binder. The type of conductive agent in the negative material layer in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the conductive agent can be the same as the type of conductive agent in the above-mentioned positive material layer. The type of negative binder in the negative material layer in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the negative binder can be the same as the type of positive binder in the above-mentioned positive material layer. The mass ratio of the negative active material, the conductive agent, and the negative binder in the negative material layer in the present application is not particularly limited as long as the purpose of the present application can be achieved.

[0043] The preparation method of the pole piece is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the preparation method of the pole piece includes but is not limited to the following steps: (1) preparing slurry; (2) coating the slurry on one surface of the current collector, and drying to obtain a pole piece with a material layer on one surface; (3) coating the slurry on the other surface of the current collector, and drying to obtain a pole piece with a material layer on both surfaces; (4) after cold pressing and slitting, along the width direction of the unfolded pole piece, the first edge region, the center region and the second edge region of the material layer are determined, and grooves and stripes are arranged in the center region of the material layer of the pole piece, i.e. the pole piece is obtained. Wherein, when the slurry is coated on one surface of the current collector, the grooves and stripes are arranged only on one surface of the pole piece; when the slurry is coated on both surfaces of the current collector, the grooves and stripes can be arranged only on either surface of the pole piece, or on both surfaces of the pole piece.

[0044] The solid content of the above-mentioned slurry is not particularly limited in the present application, as long as the purpose of the present application can be achieved. The temperature and time of the above-mentioned drying are not particularly limited in the present application, as long as the purpose of the present application can be achieved. The process parameters of the above-mentioned cold pressing and slitting are not particularly limited in the present application, as long as the purpose of the present application can be achieved. The way of arranging grooves and stripes is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the grooves and stripes can be arranged by pulse laser etching, the first projection area S1, the second projection area, the maximum depth D1 of a single groove, the maximum depth D2 of a single stripe, the diameter W1 of the maximum circumscribed circle of the first projection, and the width W2 of the second projection can be controlled by the power and defocusing amount of the pulse laser emitter; the included angle A formed by the extension lines of the center lines of the adjacent two stripes can be adjusted by adjusting the position of the pulse laser emitter; the pitch R of the adjacent two grooves can be controlled by adjusting the pitch between the pulse laser emitters or the laser emission frequency.

[0045] The cylindrical secondary battery in the present application includes an electrolyte including a lithium salt and a non-aqueous solvent. The lithium salt can include at least one of LiPF6, LiNO3, LiBF4, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), or lithium difluorophosphate. The present application does not limit the content of the lithium salt in the electrolyte, as long as the object of the present application is achieved. The present application does not particularly limit the non-aqueous solvent, as long as the object of the present application is achieved. For example, the non-aqueous solvent can include, but is not limited to, at least one of a carbonate compound, a carboxylic acid ester compound, an ether compound, or other organic solvents. The carbonate compound can include, but is not limited to, at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluorinated carbonate compound. The chain carbonate compound can include, but is not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, or methyl ethyl carbonate. The cyclic carbonate can include, but is not limited to, at least one of vinylene carbonate, propylene carbonate (PC), butylene carbonate, or vinyl ethylene carbonate. The fluorinated carbonate compound can include, but is not limited to, at least one of fluorinated vinylene carbonate, carbonic acid-1,2-difluoro ethylene ester, carbonic acid-1,1-difluoro ethylene ester, carbonic acid-1,1,2-trifluoro ethylene ester, carbonic acid-1,1,2,2-tetrafluoro ethylene ester, carbonic acid-1-fluoro-2-methyl ethylene ester, carbonic acid-1-fluoro-1-methyl ethylene ester, carbonic acid-1,2-difluoro-1-methyl ethylene ester, carbonic acid-1,1,2-trifluoro-2-methyl ethylene ester, or carbonic acid trifluoromethyl ethylene ester. The carboxylic acid ester compound can include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valerolactone, or caprolactone. The ether compound can include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, 1-ethoxy-1-methoxy ethane, 2-methyl tetrahydrofuran, or tetrahydrofuran. The other organic solvents can include, but is not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0046] The diaphragm according to the present application is not particularly limited as long as the object of the present application can be achieved. For example, the material of the diaphragm can include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of the diaphragm can include at least one of a woven film, a nonwoven film, a microporous film, a composite film, a calendered film, or a spunlaced film. The diaphragm according to the present application can have a porous structure, and the size of the pore diameter of the porous structure of the diaphragm according to the present application is not particularly limited as long as the object of the present application can be achieved. For example, the size of the pore diameter can be 0.01 µm to 1 µm. The thickness of the diaphragm according to the present application is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the diaphragm can be 5 µm to 50 µm.

[0047] The cylindrical secondary battery according to the present application further includes a case for accommodating the positive electrode tab, the negative electrode tab, the diaphragm, and the electrolyte solution, and other components known in the art in the cylindrical secondary battery, and the other components are not limited according to the present application. The case according to the present application is not particularly limited and can be a case known in the art as long as the object of the present application can be achieved.

[0048] The cylindrical secondary battery according to the present application is not particularly limited and can include any device in which an electrochemical reaction occurs. In an embodiment of the present application, the cylindrical secondary battery can include, but is not limited to, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery, etc.

[0049] The method of manufacturing the cylindrical secondary battery according to the present application is not particularly limited and can be selected from a method known in the art as long as the object of the present application can be achieved. For example, the method of manufacturing the cylindrical secondary battery includes, but is not limited to, the following steps: stacking the diaphragm, the positive electrode tab, the diaphragm, and the negative electrode tab in order, and performing an operation such as winding, folding, etc. as needed to obtain an electrode assembly having a wound structure, placing the electrode assembly in a case, injecting an electrolyte solution into the case and sealing the case to obtain the cylindrical secondary battery.

[0050] The second aspect of the present application provides an electronic device including the cylindrical secondary battery according to any one of the preceding embodiments. The cylindrical secondary battery according to the present application has good lithium precipitation performance and cycle performance, and thus the electronic device according to the present application has a long service life.

[0051] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the art. For example, the electronic device can include, but is not limited to, a notebook computer, a pen input type computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copying machine, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio player, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, a power tool, a flashlight, a camera, a household large storage battery, and a lithium ion capacitor.

[0052] Embodiment

[0053] Hereinafter, examples and comparative examples are cited to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are on a mass basis.

[0054] Test methods and apparatus:

[0055] Test of S1, S2, D1, D2, T, W1, W2, R, and A:

[0056] At an ambient temperature of 25°C, a lithium ion battery was disassembled, and a pole piece provided with grooves and stripes was taken out, immersed in dimethyl carbonate (DMC) for 20 min, and then placed in an oven for drying at 80°C for 12 h to obtain a pole piece sample.

[0057] In the thickness direction of the pole piece, scanning electron microscopy was used to take pictures of the pole piece, and the bottom area of a single groove was calculated using image recognition, and the average value was taken as the first projection area S1 of a single groove. At the same time, the diameter of the maximum circumscribed circle of a single groove was measured, and the average value was taken as the diameter W1 of the maximum circumscribed circle of the first projection. The angle formed by the extension lines of the center lines of every two adjacent stripes in a single groove was measured, and the average value was taken as the angle A formed by the extension lines of the center lines of the adjacent two stripes. Then, in the extension direction of each stripe connected to a single groove, scanning electron microscopy was used to take pictures of each stripe connected to a single groove, and the bottom area of each stripe connected to a single groove was calculated using image recognition and then summed up, and the average value of the five summation results was taken as the sum S2 of the second projection areas of the multiple stripes connected to a single groove. At the same time, in a direction perpendicular to the extension direction of a single stripe, the width of a single stripe was measured, and the average value was taken as the width W2 of the second projection.

[0058] The cross section of the pole piece along Q-Q is prepared, and the cross section of the pole piece along Q-Q is subjected to ion polishing treatment to obtain the cross section of the pole piece. The cross section of the pole piece is observed by a scanning electron microscope, and a clear boundary between the material layer and the current collector, the cross section shape of the groove, and the cross section shape of the stripe can be observed. Along the thickness direction of the pole piece, the distance between the surface of the pole piece and the boundary between the material layer and the current collector is measured, which is the thickness T of the material layer; five grooves are selected, the distance between the surface of the pole piece and the deepest part of a single groove is measured, and the average value is taken, which is the maximum depth D1 of a single groove; the distance between the surface of the pole piece and the deepest part of the stripe connected to the single groove is measured, and the average value is taken, which is the maximum depth D2 of a single stripe. Five grooves are selected, the distance between the geometric center of a single groove and the geometric center of an adjacent groove along the length direction of the pole piece after being unfolded is measured, and the average value is taken, which is the pitch R of the adjacent two grooves.

[0059] Lithium precipitation performance test:

[0060] The lithium ion batteries in the examples and comparative examples are placed in a thermostat at 10°C, and after being placed for 60 minutes, charged at 2C constant current to 4.2V, charged at 4.2V constant voltage to a current of 0.05C, and after standing for 5 minutes, discharged at 0.5C constant current to 2.5V, which is one cycle. After 10 cycles according to the above charging and discharging process, charged at 2C constant current to 4.2V, charged at 4.2V constant voltage to a current of 0.05C, and after standing for 5 minutes, the lithium ion battery is disassembled, and the lithium precipitation state on the surface of the pole piece is observed. The area of the pole piece surface where lithium is not precipitated is golden yellow, and the area where lithium is precipitated is grayish white.

[0061] The judgment standard of the degree of lithium precipitation of the lithium ion battery is as follows: the lithium precipitation area is 0% for no lithium precipitation, i.e. the degree of lithium precipitation is none, the lithium precipitation area is greater than 0% and less than or equal to 2% for mild lithium precipitation, i.e. the degree of lithium precipitation is mild, the lithium precipitation area is greater than 2% and less than or equal to 20% for moderate lithium precipitation, i.e. the degree of lithium precipitation is moderate, and the lithium precipitation area is greater than 20% and less than or equal to 100% for severe lithium precipitation, i.e. the degree of lithium precipitation is severe, wherein the percentage of the lithium precipitation area is calculated based on the total area of the material layer.

[0062] Cycle performance test:

[0063] The lithium ion batteries in the examples and comparative examples are placed in a thermostat at 25°C, and subjected to charge and discharge cycle test, the lithium ion battery is charged at 2C constant current to 4.2V, charged at 4.2V constant voltage to 0.05C, and after standing for 5 minutes, discharged at 6C constant current to 2.5V, which is the first cycle, and the first cycle discharge capacity C1 is recorded. After 600 cycles according to the above cycle process, the discharge capacity C 600, the cycle capacity retention rate of the 600th cycle is calculated as an index for evaluating the infiltration effect of the electrolyte on the positive and negative electrode sheets and the cycle performance of the lithium ion battery, and the formula is shown as formula (I). When the 600th cycle (cls) capacity retention rate is lower, it indicates that the infiltration effect of the electrolyte on the electrode sheet in the lithium ion battery is worse, and the cycle performance of the lithium ion battery is worse; when the 600th cycle capacity retention rate is higher, it indicates that the infiltration effect of the electrolyte on the electrode sheet in the lithium ion battery is better, and the cycle performance of the lithium ion battery is better.

[0064] 600th cycle capacity retention rate (%) = C 600 / C1 x 100%. (I)

[0065] Example 1

[0066] <Preparation of negative electrode sheet>

[0067] The electrode sheet is a negative electrode sheet. The negative electrode active material artificial graphite, carboxymethyl cellulose sodium (CMC-Na) and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 97.3:1.7:1.0, then deionized water is added as a solvent, and stirred and mixed uniformly to obtain a negative electrode slurry with a solid content of 50wt%. The negative electrode slurry is uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 8μm, and dried at 105°C to obtain a negative electrode sheet with a single-side coated negative electrode material layer. Then, repeat the above steps on the other surface of the negative electrode current collector copper foil to obtain a negative electrode sheet with a double-side coated negative electrode material layer. Then, after cold pressing and slitting, along the width direction of the electrode sheet after being unfolded, the first edge region, the center region and the second edge region of the negative electrode material layer are determined, wherein, based on the width of the negative electrode material layer, the width ratio L1 of the first edge region is 30%, the width ratio L2 of the center region is 50%, and the width ratio L3 of the second edge region is 20%, and the coating weight of the negative electrode material layer is 7.5mg / cm 2 , and the thickness T of the negative electrode material layer is 50μm.

[0068] The maximum depth D1 of a single groove is set to 30μm, the diameter W1 of the maximum circumscribed circle of the first projection of a single groove is 203.108μm along the thickness direction of the negative electrode sheet, and the first projection area S1 of a single groove is 0.0324mm 2, the distance R between the two adjacent grooves is 5 mm, the grooves are distributed in a matrix, the number of rows of the grooves along the width direction of the negative electrode tab after being unfolded is 3, the outer edges of each groove are respectively provided with a stripe at intervals, the stripe is respectively communicated with the groove surrounded by the stripe, the stripe extends in a direction away from the outer edge of the groove surrounded, the maximum depth D2 of the single stripe is 18 μm, the single stripe has a second projection along the extension direction of the single stripe, the width W2 of the second projection along the direction perpendicular to the extension direction of the single stripe is 50 μm, the stripes surrounding the outer edges of each groove are distributed at equal angles, the included angle A formed by the extension lines of the center lines of the two adjacent stripes is 60°, and the sum S2 of the second projection areas of the plurality of stripes surrounding each groove is 0.0054 mm 2 , and the value of S1 / S2 is 6. The grooves and the stripes are laser etched in the central region according to the above parameters, the shapes of the grooves and the stripes are as shown in Figure 1 , and a negative electrode tab with a specification of 1500 mm x 62 mm is obtained.

[0069] <Preparation of a positive electrode tab>

[0070] The positive active material lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2), the binder polyvinylidene fluoride (PVDF), and the conductive carbon black are dispersed in N-methyl pyrrolidone (NMP) solvent at a mass ratio of 94.8:2.8:2.4, and are fully stirred and mixed to obtain a positive electrode slurry with a solid content of 72 wt%. The positive electrode slurry is uniformly coated on one surface of a positive current collector aluminum foil with a thickness of 13 μm, and is dried at 105°C to obtain a positive electrode tab with a single-sided coated positive electrode material layer. Then, the above steps are repeated on the other surface of the positive current collector aluminum foil to obtain a positive electrode tab with a double-sided coated positive electrode material layer. Then, after cold pressing, tabbing, and slitting, the positive electrode tab is dried at 105°C under vacuum conditions for 4 h to obtain a positive electrode tab with a specification of 1490 mm x 60 mm for use. The coating weight of the positive electrode material layer is 16 mg / cm 2 , and the compacted density of the positive electrode material layer is 3.4 g / cm 3 .

[0071] <Separator>

[0072] A polypropylene (PP) film with a thickness of 12 μm is used as the separator.

[0073] <Preparation of an electrolyte>

[0074] In a glove box under a dry argon atmosphere, organic solvents ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) were mixed in a mass ratio of 30:50:20 to obtain a base solvent, and then lithium salt lithium hexafluorophosphate (LiPF6) was added to the above base solvent, and the mixture was uniformly mixed to obtain an electrolyte. The mass percentage of LiPF6 in the electrolyte was 12.5%, and the balance was the base solvent.

[0075] <Preparation of a lithium ion battery>

[0076] The above-prepared separator, positive electrode sheet, separator, and negative electrode sheet were sequentially stacked in order, with the separator between the positive electrode and the negative electrode to serve as a separation function. After winding, rubbing, current collector disc welding, shell insertion, code spraying, vacuum drying, electrolyte injection, pot sealing, high-temperature standing, and formation capacity, a lithium ion battery was obtained. The upper limit voltage of formation was 3.6V, the formation temperature was 45℃, and the formation standing time was 2h.

[0077] Example 2

[0078] Except that the proportion of the central area of the negative electrode material layer was 80%, and the number of grooves was set to 6 rows, the rest was the same as example 1.

[0079] Example 3

[0080] Except that the proportion of the central area of the negative electrode material layer was 60%, and the number of grooves was set to 4 rows, the rest was the same as example 1.

[0081] Examples 4 to 30

[0082] Except that the preparation parameters were adjusted according to Table 1, the rest was the same as example 1.

[0083] Example 31

[0084] Except that the positive electrode sheet was prepared according to the following steps, the rest was the same as example 1.

[0085] <Preparation of a positive electrode sheet>

[0086] The electrode sheet was a positive electrode sheet. The positive electrode active material lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1O2), a binder polyvinylidene fluoride (PVDF) and conductive carbon black were dispersed in N-methyl pyrrolidone (NMP) solvent at a mass ratio of 94.8:2.8:2.4, mixed well under stirring to obtain a positive electrode slurry with a solid content of 72 wt%. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 13 μm, and dried at 105 °C to obtain a positive electrode tab with a single-sided coated positive electrode material layer. Then, the above steps were repeated on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode tab with a double-sided coated positive electrode material layer. Then, after cold pressing and slitting, the first edge region, the center region and the second edge region of the positive electrode material layer were determined along the width direction of the tab after unfolding, wherein the width ratio L1 of the first edge region was 30%, the width ratio L2 of the center region was 50%, and the width ratio L3 of the second edge region was 20% based on the width of the positive electrode material layer, and the coating weight of the positive electrode material layer was 12 mg / cm 2 , and the thickness T of the positive electrode material layer was 50 μm.

[0087] The maximum depth D1 of a single groove was set to 30 μm, the diameter W1 of the maximum circumscribed circle of the first projection of a single groove was 203.108 μm along the thickness direction of the positive electrode tab, and the first projection area S1 of a single groove was 0.0324 mm 2 , the pitch R of adjacent two grooves was 5 mm along the length direction of the positive electrode tab after unfolding, the grooves were distributed in a matrix, the number of rows of the grooves was 3 along the width direction of the positive electrode tab after unfolding, the outer edges of each groove were respectively provided with a stripe at intervals, and the stripe respectively communicated with the surrounded groove, the stripe extended in a direction away from the outer edge of the surrounded groove, the maximum depth D2 of a single stripe was 18 μm, the single stripe had a second projection along the extension direction of the single stripe, the width W2 of the second projection was 50 μm along the direction perpendicular to the extension direction of the single stripe, the stripes surrounding the outer edges of each groove were distributed at equal angles, the included angle A formed by the extension lines of the center lines of adjacent two stripes was 60°, and the sum S2 of the second projection areas of the plurality of stripes surrounding each groove was 0.0054 mm 2 , and the value of S1 / S2 was 6. The grooves and stripes were laser etched in the center region according to the above parameters, and the shapes of the grooves and stripes were as shown in Figure 1 , to obtain a positive electrode tab with a specification of 1490 mm x 60 mm.

[0088] Example 32

[0089] In addition to setting the grooves in a matrix distribution in the preparation of the negative electrode sheet, the number of rows of grooves along the width direction after the negative electrode sheet is unfolded is 3, and the outer edges surrounding each groove are respectively provided with a stripe, and the stripe is respectively communicated with the surrounded groove, the stripe extends in the direction away from the outer edge of the surrounded groove, and along the width direction after the negative electrode sheet is unfolded, there is a stripe penetrating the first end surface of the first edge away from the center area, in addition, there is another stripe penetrating the second end surface of the second edge area away from the center area, and the rest is the same as example 1.

[0090] Comparative example 1

[0091] In addition to not setting grooves and stripes in the preparation of the negative electrode sheet, the rest is the same as example 1.

[0092] Comparative example 2

[0093] In addition to not setting grooves in the preparation of the negative electrode sheet, only setting stripes, the rest is the same as example 1.

[0094] Comparative example 3

[0095] In addition to not setting stripes in the preparation of the negative electrode sheet, only setting grooves, the rest is the same as example 1.

[0096] Comparative example 4

[0097] In addition to setting the number of rows of grooves to 8 in the preparation of the negative electrode sheet, the rest is the same as example 1.

[0098] Comparative example 5 to comparative example 6

[0099] In addition to adjusting the relevant preparation parameters according to table 1, the rest is the same as example 1.

[0100] The preparation parameters and performance parameters of each example and comparative example are shown in table 1.

[0101]

[0102]

[0103]

[0104] As can be seen from Examples 1 to 32 and Comparative Examples 1 to 6, by setting the grooves and the stripes on the central region of the material layer and regulating the value of S1 / S2 and the value of S2 within the range of the present application, the degree of lithium precipitation of the lithium ion battery is lighter, the capacity retention rate of 600 cls of the lithium ion battery is improved, which indicates that the electrolyte has a good wetting effect on the electrode sheet of the present application, and the lithium ion battery has good lithium precipitation performance and cycle performance. In Comparative Example 1, no grooves and stripes are set on the central region of the positive material layer and the negative material layer; in Comparative Example 2, only stripes are set on the central region of the negative material layer; in Comparative Example 3, only grooves are set on the central region of the negative material layer; in Comparative Example 4, grooves and stripes are set on the entire negative material layer; in Comparative Examples 5 to 6, the value of S1 / S2 is not within the range of the present application. The lithium ion batteries in Comparative Examples 1 to 6 have a heavier degree of lithium precipitation; and / or, a lower capacity retention rate of 600 cls. While the lithium ion batteries in Examples 1 to 32 have a lighter degree of lithium precipitation and a higher capacity retention rate of 600 cls, which indicates that the electrolyte has a good wetting effect on the electrode sheet, and the lithium ion battery has good lithium precipitation performance and cycle performance.

[0105] The values of D2 / D1 and D1 usually affect the lithium precipitation performance and cycle performance of the lithium ion battery. As can be seen from Examples 1, 8 to 14, when the values of D2 / D1 and D1 are within the range of the present application, the degree of lithium precipitation of the lithium ion battery is lighter, and the capacity retention rate of 600 cls is higher, which indicates that the electrolyte has a good wetting effect on the electrode sheet in the present application, and the lithium ion battery has good lithium precipitation performance and cycle performance.

[0106] The value of D1 / T usually affects the lithium precipitation performance and cycle performance of the lithium ion battery. As can be seen from Examples 1, 15 to 16, when the value of D1 / T is within the range of the present application, the degree of lithium precipitation of the lithium ion battery is lighter, and the capacity retention rate of 600 cls is higher, which indicates that the electrolyte has a good wetting effect on the electrode sheet in the present application, and the lithium ion battery has good lithium precipitation performance and cycle performance.

[0107] The value of A usually affects the lithium precipitation performance and cycle performance of the lithium ion battery. As can be seen from Examples 1, 17 to 19, when the value of A is within the range of the present application, the degree of lithium precipitation of the lithium ion battery is lighter, and the capacity retention rate of 600 cls is higher, which indicates that the electrolyte has a good wetting effect on the electrode sheet in the present application, and the lithium ion battery has good lithium precipitation performance and cycle performance.

[0108] The value of W2 generally affects the lithium precipitation performance and cycle performance of the lithium ion battery. As can be seen from Example 1, Example 20 to Example 24, when the value of W2 is within the range of the present application, the lithium ion battery has a lighter degree of lithium precipitation and a higher capacity retention rate of 600 cls, indicating that the electrolyte has a better wetting effect on the pole piece in the examples of the present application, and the lithium ion battery has better lithium precipitation performance and cycle performance.

[0109] The value of R generally affects the lithium precipitation performance and cycle performance of the lithium ion battery. As can be seen from Example 1, Example 25 to Example 28, when the value of W2 is within the range of the present application, the lithium ion battery has a lighter degree of lithium precipitation and a higher capacity retention rate of 600 cls, indicating that the electrolyte has a better wetting effect on the pole piece in the examples of the present application, and the lithium ion battery has better lithium precipitation performance and cycle performance.

[0110] The value of W1 / W2 generally affects the lithium precipitation performance and cycle performance of the lithium ion battery. As can be seen from Example 1, Example 4 to Example 14, Example 17 to Example 30, when the value of W1 / W2 is within the range of the present application, the lithium ion battery has a lighter degree of lithium precipitation and a higher capacity retention rate of 600 cls, indicating that the electrolyte has a better wetting effect on the pole piece in the examples of the present application, and the lithium ion battery has better lithium precipitation performance and cycle performance.

[0111] The pole piece is generally a positive pole piece and / or a negative pole piece, which generally affects the cycle performance of the lithium ion battery. As can be seen from Example 1 and Example 31, when the pole piece is a positive pole piece and / or a negative pole piece, the lithium ion battery has a lighter degree of lithium precipitation and a higher capacity retention rate of 600 cls, indicating that the electrolyte has a better wetting effect on the pole piece in the examples of the present application, and the lithium ion battery has better lithium precipitation performance and cycle performance.

[0112] The position relationship between the length direction stripe after the pole piece is developed and the first end face and / or the position relationship between the stripe and the second end face generally affects the cycle performance of the lithium ion battery. As can be seen from Example 1 and Example 32, when the position relationship between the length direction stripe after the pole piece is developed and the first end face and / or the position relationship between the stripe and the second end face is within the range of the present application, the lithium ion battery has a lighter degree of lithium precipitation and a higher capacity retention rate of 600 cls, indicating that the electrolyte has a better wetting effect on the pole piece in the examples of the present application, and the lithium ion battery has better lithium precipitation performance and cycle performance.

[0113] It is to be noted that, in the present document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0114] Various embodiments are described herein with reference to particular applications with a specific configuration and contents for convenience. It is to be understood that the application is not limited to those embodiments but cover any technical solutions falling in the scope of the application. The same or similar parts and / or steps in different embodiments can be combined to form another embodiment.

[0115] The above description is merely preferred embodiments of the present application, and not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of the present application.

Claims

1. A cylindrical secondary battery, comprising an electrode, the electrode comprising a current collector and a material layer located on at least one surface of the current collector, wherein along the width direction of the unfolded electrode, the material layer sequentially comprises a first edge region, a central region, and a second edge region; based on the width of the material layer, the width of the first edge region accounts for 10% to 30%, the width of the central region accounts for 40% to 80%, and the width of the second edge region accounts for 10% to 30%; The central region is provided with a plurality of grooves, and a plurality of stripes are provided at intervals around the outer edge of each groove, and the plurality of stripes are respectively connected to the grooves, and the plurality of stripes extend in a direction away from the outer edge; Along the thickness direction of the electrode sheet, the first projected area of ​​a single groove is S1 mm. 2 Along the extension direction of each individual stripe, each individual stripe has a second projection, and the sum of the second projected areas of the plurality of stripes is S² mm. 2 , 3≤S1 / S2≤12, 1.5×10 -5 ≤S2≤0.

45.

2. The cylindrical secondary battery according to claim 1, wherein, Along the width direction of the unfolded electrode, at least one of the stripes penetrates the first end face of the first edge region away from the central region or the second end face of the second edge region away from the central region.

3. The cylindrical secondary battery according to claim 1 or 2, wherein, Along the thickness direction of the electrode sheet, the maximum depth of a single groove is D1μm, the maximum depth of a single stripe is D2μm, 0.5≤D2 / D1≤0.9, and 3≤D1≤60.

4. The cylindrical secondary battery according to claim 3, wherein, The thickness of the material layer is T μm, and 0.5 ≤ D1 / T ≤ 0.

9.

5. The cylindrical secondary battery according to claim 3, wherein, 0.6≤D2 / D1≤0.8; and / or, 10≤D1≤45.

6. The cylindrical secondary battery according to any one of claims 1 to 5, wherein, Along a direction perpendicular to the extension direction of the individual stripe, the width of the second projection is W2μm, 10≤W2≤400.

7. The cylindrical secondary battery according to claim 6, wherein, Along the thickness direction of the electrode sheet, the diameter of the largest circumcircle of the first projection is W1μm, and 1.5≤W1 / W2≤8.

8. The cylindrical secondary battery according to any one of claims 1 to 7, wherein, The multiple stripes are distributed at equal angles around the outer edge of each groove, and the included angle formed by the extensions of the center lines of two adjacent stripes is A°, where 20 ≤ A ≤ 180.

9. The cylindrical secondary battery according to any one of claims 1 to 8, wherein, Along the length of the unfolded electrode sheet, the distance between two adjacent grooves is R mm, where 3 ≤ R ≤ 12.

10. The cylindrical secondary battery according to any one of claims 1 to 9, wherein it satisfies at least one of the following characteristics: (1) 6≤S1 / S2≤8; (2)0.0007≤S2≤0.15； (3) The plurality of stripes are distributed at equal angles around the outer edge of each groove, and the included angle formed by the extensions of the center lines of two adjacent stripes is A°, 60≤A≤120; (4) Along the length direction of the unfolded electrode sheet, the distance between two adjacent grooves is R mm, where 5≤R≤9; (5) Along the thickness direction of the electrode sheet, the diameter of the largest circumcircle of the first projection is W1μm, and along the direction perpendicular to the extension direction of the individual stripe, the width of the second projection is W2μm, 2≤W1 / W2≤5; and / or, 50≤W2≤200; (6) The electrode is a positive electrode; and / or a negative electrode.

11. An electronic device comprising a cylindrical secondary battery as described in any one of claims 1 to 10.

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