Roll core, battery cell and electric equipment

Abstract

The utility model provides a roll core, a battery cell and electric equipment. The roll core comprises a first pole piece, a second pole piece and a diaphragm positioned between the first pole piece and the second pole piece, the first pole piece, the diaphragm and the second pole piece are laminated and wound to form a winding core; in the direction from the winding head of the first pole piece to the winding tail of the first pole piece, the first pole piece comprises a first area and a second area which are arranged in sequence; at least part of the second area is located at the winding tail of the first pole piece; in the first direction, the width d1 of the second area is smaller than the width d2 of the first area, so that the risk of corner cracking of the battery cell is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of battery cores, and in particular to a winding core, a battery core and electrical equipment. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, environmental protection and low pollution. Currently, they are not only widely used in portable electronic devices such as mobile phones and laptops, but also in electric equipment such as electric vehicles and electric bicycles.

[0003] Among them, the soft-pack lithium-ion battery cell includes a roll core and a soft-pack shell wrapped around the outside of the roll core. The soft-pack shell of the battery cell in the related art is an aluminum-plastic film. During the continuous charging and discharging process of the battery cell, the roll core will continue to expand and squeeze the aluminum-plastic film shell over time. The corners of the battery cell are more likely to have more concentrated stress, resulting in more obvious deformation of the aluminum-plastic film shell, and these are often the first locations where damage and cracks appear. The aluminum-plastic film with cracked corners cannot effectively prevent moisture and oxygen from entering the battery cell. In severe cases, it may cause leakage of the electrolyte, resulting in performance failure of the battery cell and even unsafe conditions such as combustion and explosion. Utility Model Content

[0004] In view of this, the embodiments of the present invention are dedicated to providing a winding core, a battery cell and an electrical device to improve the risk of corner cracking of the battery cell to a certain extent.

[0005] In a first aspect, the present invention provides a winding core, comprising a first pole piece, a second pole piece, and a diaphragm located between the first pole piece and the second pole piece; the first pole piece, the diaphragm, and the second pole piece are stacked and wound to form a winding core;

[0006] In a direction from a winding head portion to a winding tail portion of the first pole piece, the first pole piece includes a first region and a second region arranged in sequence; at least a portion of the second region is located at the winding tail portion of the first pole piece;

[0007] Along the first direction, a width d1 of the second region is smaller than a width d2 of the first region.

[0008] Optionally, a ratio of the width d1 of the second region to the width d2 of the first region satisfies: 90%≤d1 / d2<100%.

[0009] Optionally, a ratio of the width d1 of the second region to the width d2 of the first region satisfies: 90%≤d1 / d2≤95%.

[0010] Optionally, the total number of winding folds of the first pole piece is N1, N1 is a positive integer, and the second region is at least located in the region from the N1-1th fold to the N1th fold of the first pole piece;

[0011] And / or, the junction between the second area and the first area has a smooth transition.

[0012] Optionally, in a direction from an end of the second zone close to the first zone to an end of the second zone away from the first zone,

[0013] The width of the second zone decreases gradually in a linear trend;

[0014] Alternatively, the width of the second region gradually decreases, and the edge of the second region is an arc-shaped edge;

[0015] Alternatively, the widths of the second region at different positions are equal.

[0016] Optionally, in a direction from a winding head portion of the first pole piece to a winding tail portion of the first pole piece, the second region includes at least two first sub-segments connected in sequence;

[0017] In two adjacent first sub-sections, the width of the first sub-section close to the first region is greater than the width of the first sub-section far from the first region.

[0018] Optionally, in a direction from an end of the second region close to the first region to an end of the second region far from the first region, the width of each first sub-segment gradually decreases in a linear trend, and the slope of the straight line where the edges of two adjacent first sub-segments lie increases successively;

[0019] Alternatively, for any first sub-section, the widths of the first sub-section at different positions are equal.

[0020] Optionally, in a direction from the winding head to the winding tail of the second pole piece, the second pole piece includes a third region and a fourth region arranged in sequence, and at least a portion of the fourth region is located at the winding tail of the second pole piece;

[0021] Along the first direction, a width D1 of the fourth region is smaller than a width D2 of the third region.

[0022] Optionally, the width of the second pole piece at different positions in the winding core is greater than the width of the first pole piece at a position corresponding to the second pole piece;

[0023] And / or, the total number of folds of the second pole piece is N2, N2 is a positive integer, and the fourth region is at least located in the area from the N2-1th fold to the N2th fold of the second pole piece.

[0024] In a second aspect, the present invention provides a battery core, comprising a shell and the winding core as described above, wherein the shell is wrapped around the outside of the winding core.

[0025] In a third aspect, the present invention provides an electrical device comprising the battery cell as described above.

[0026] The winding core, battery cell and electrical equipment provided by the present invention are such that, in the direction from the winding head to the winding tail of the first electrode piece, the first electrode piece includes a first zone and a second zone arranged in sequence, at least a portion of the second zone is located at the winding tail of the first electrode piece, and the width of the second zone is smaller than the width of the first zone, that is, the width of at least the portion of the first electrode piece located at the winding tail is narrowed, thereby reducing the width of the entire winding core at the corners, that is, the width of the winding core at the corners is smaller than the width of the main body of the winding core, thereby providing more space margin for the corners of the winding core. For example, when the winding core expands and squeezes the shell during the charging and discharging process, the setting of the above-mentioned first electrode piece makes the corners of the winding core have more space margin, thereby effectively alleviating the extrusion deformation of the shell caused by the corners of the winding core, so that the corners of the shell can maintain a safer layer thickness, thereby avoiding the occurrence of corner cracks to a certain extent, ensuring the performance of the battery cell, and improving the safety of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a structural diagram of a winding core according to an embodiment of the present invention;

[0028] Figure 2 This is a side structural diagram of the first pole piece according to an embodiment of the present utility model;

[0029] Figure 3 This is a side structural diagram of the second pole piece according to an embodiment of the present utility model;

[0030] Figure 4 This is a schematic diagram of the structure of the first pole piece in the unfolded state according to an embodiment of the present invention. Figure 1 ;

[0031] Figure 5 This is a schematic diagram of the structure of the first pole piece in the unfolded state according to an embodiment of the present invention. Figure 2 ;

[0032] Figure 6 This is a schematic diagram of the structure of the first pole piece in the unfolded state according to an embodiment of the present invention. Figure 3 ;

[0033] Figure 7 This is a schematic diagram of the structure of the first pole piece in the unfolded state according to an embodiment of the present invention. Figure 4 ;

[0034] Figure 8 This is a schematic diagram of the structure of the first pole piece in the unfolded state according to an embodiment of the present invention. Figure 5 ;

[0035] Figure 9 This is a schematic diagram of the structure of the second pole piece in the unfolded state according to an embodiment of the present invention. Figure 1 ;

[0036] Figure 10 This is a schematic diagram of the structure of the second pole piece in the unfolded state according to an embodiment of the present invention. Figure 2 ;

[0037] Figure 11 This is a schematic diagram of the structure of the second pole piece in the unfolded state according to an embodiment of the present invention. Figure 3 ;

[0038] Figure 12 This is a schematic diagram of the structure of the second pole piece in the unfolded state according to an embodiment of the present invention. Figure 4 .

[0039] Among them, 100, winding core; 1, first pole piece; 11, first zone; 12, second zone; 120, arc-shaped edge; 121, first sub-segment; 13, positive electrode collector; 14, positive electrode active layer; 2, second pole piece; 21, third zone; 22, fourth zone; 221, second sub-segment; 23, negative electrode collector; 24, negative electrode active layer; 10, corner; 3, pole ear. DETAILED DESCRIPTION

[0040] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present invention.

[0041] A soft-pack lithium-ion battery cell consists of a roll core, a soft-pack shell wrapped around the core, and an electrolyte solution filled within the shell. The roll core includes a positive electrode sheet, a negative electrode sheet, and a separator. Specifically, the positive electrode sheet, separator, and negative electrode sheet are stacked and wound from the inside out to form the roll core. The separator is located between the positive and negative electrodes, isolating them from contact.

[0042] The flexible packaging shell is typically made of aluminum-plastic film. As the battery cell continuously charges and discharges, the coiled core expands over time, squeezing the aluminum-plastic film shell. Stress is concentrated more intensely at the corners of the cell, leading to more pronounced deformation and often the first locations for cracks to appear. Aluminum-plastic film with cracks at the corners cannot effectively prevent moisture and oxygen from entering the cell. In severe cases, this can lead to electrolyte leakage, resulting in performance failure and even safety concerns such as combustion and explosion.

[0043] Based on this, an embodiment of the utility model provides a winding core, a battery cell and an electrical device, which provides more space margin for the corners of the winding core by narrowing the width of at least the part of the first pole piece located at the tail of the winding, so as to effectively alleviate the extrusion deformation of the shell caused by the corners of the winding core when the winding core expands and squeezes the shell, so that the corners of the shell can maintain a safer layer thickness, thereby avoiding the occurrence of corner cracks to a certain extent.

[0044] The winding core 100, the battery cell, and the electrical equipment provided by the present invention are described in detail below with reference to specific embodiments in conjunction with the accompanying drawings.

[0045] Reference Figures 1 to 12 As shown, this embodiment provides a winding core 100, which is applied to a battery cell. The battery cell includes the winding core 100 and a shell, which is wrapped around the outer side of the winding core 100. The battery cell can be, for example, a soft-pack lithium-ion battery cell.

[0046] The winding core 100 of this embodiment specifically includes: a first pole piece 1 , a second pole piece 2 , a pole tab 3 , and a separator located between the first pole piece 1 and the second pole piece 2 .

[0047] Illustratively, the first electrode 1 in this embodiment may be, for example, a positive electrode, and the second electrode 2 may be, for example, a negative electrode.

[0048] The positive electrode sheet includes a positive electrode current collector 13 and a positive electrode active layer 14 coated on at least one side of the positive electrode current collector 13. Figure 2 As shown, at least one side of the positive electrode current collector 13 can be specifically Figure 2 The upper side and / or lower side of the positive electrode current collector 13. The negative electrode sheet includes a negative electrode current collector 23 and a negative electrode active layer 24 coated on at least one side of the negative electrode current collector 23. Figure 3 As shown, at least one side of the negative electrode current collector 23 can be specifically Figure 3 The upper side and / or lower side of the negative electrode current collector 23.

[0049] Exemplarily, the positive electrode current collector 13 may be, for example, aluminum foil, and the thickness of the positive electrode current collector 13 may be set between 6μm and 20μm. The positive electrode active layer 14 may include a positive electrode active material, a conductive agent, and a binder. The content of the positive electrode active material is, for example, 0% to 98.3%, the content of the binder is, for example, 0.5% to 5%, and the content of the conductive agent is, for example, 0 to 3%. Among them, the active material of the positive electrode active layer 14 may include one or more of lithium cobalt oxide, lithium iron phosphate, nickel cobalt manganese lithium, nickel cobalt aluminum lithium, lithium manganese oxide, and lithium-rich manganese-based lithium. The positive electrode binder is, for example, mainly a polyvinylidene fluoride (PVDF)-based binder. The positive electrode conductive agent includes, for example, at least one of conductive carbon black (such as Ketjen black), single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0050] Exemplarily, the negative electrode current collector 23 may be, for example, copper foil, and the thickness of the negative electrode current collector 23 may be set between 4 μm and 20 μm. The negative electrode active layer 24 may include a negative electrode active material, a conductive agent, and a binder. The content of the negative electrode active material is, for example, 0% to 98%, the content of the binder is, for example, 0.5% to 5%, and the content of the conductive agent is, for example, 0 to 3%. The active material of the negative electrode active layer 24 includes, but is not limited to, one or more of natural graphite, artificial graphite, mesophase carbon microbeads, lithium titanate, silicon negative electrode, silicon-carbon negative electrode, and alloy negative electrode. The negative electrode binder is, for example, mainly styrene-butadiene rubber. The negative electrode conductive agent includes, for example, at least one of conductive carbon black (such as Ketjen black), single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0051] For example, the thickness of the separator may be, for example, 3 μm to 20 μm.

[0052] Specifically, the first pole piece 1, the diaphragm, and the second pole piece 2 are stacked and wound to form a wound core, i.e., a roll core. The roll core 100 is covered with a shell. The shell can be a soft-pack shell, such as an aluminum-plastic film shell, and the thickness of the aluminum-plastic film shell can be set, for example, between 70 μm and 200 μm.

[0053] In the direction from the winding head of the first pole piece 1 to the winding tail of the first pole piece 1 , the first pole piece 1 includes a first region 11 and a second region 12 that are sequentially arranged.

[0054] It should be noted that the winding head of the first pole piece 1 can be understood as the area where the first pole piece 1 starts to be wound during the winding process of the winding core 100, that is, the head area, which is located inside the winding core 100. Correspondingly, the winding tail of the first pole piece 1 can be understood as the area where the first pole piece 1 ends to be wound. Figures 4 to 8 As shown, the direction from the winding head of the first pole piece 1 to the winding tail of the first pole piece 1 can be specifically Figures 4 to 8 In the direction from left to right.

[0055] At least part of the second region 12 is located at the winding tail of the first pole piece 1. Along the first direction, the width d1 of the second region 12 is smaller than the width d2 of the first region 11. Figures 4 to 8 As shown, the first direction here is Figures 4 to 8 The up-down direction in the figure may specifically be the width direction of the first pole piece 1 .

[0056] By making at least part of the second region 12 located at the winding tail of the first pole piece 1 and making the width of the second region 12 smaller than the width of the first region 11, that is, making the width of at least the portion of the first pole piece 1 located at the winding tail narrower, referring to Figure 1As shown, such a setting reduces the width of the corner 10 of the entire core 100, that is, the width of the corner 10 of the core 100 is smaller than the width of the main part of the core 100, thereby providing more space margin for the corner 10 of the core 100.

[0057] In this way, if the core 100 expands and squeezes the shell, since there is more space margin at the corner 10 of the core 100, the extrusion deformation caused by the corner 10 of the core 100 on the shell is effectively alleviated, and the occurrence of corner cracks is avoided to a certain extent.

[0058] In a specific implementation, the first electrode piece 1 may be subjected to a secondary punching process so that the width d1 of the second region 12 of the first electrode piece 1 is smaller than the width d2 of the first region 11 .

[0059] The winding core 100 provided in this embodiment is configured such that the first electrode piece 1 includes a first region 11 and a second region 12 arranged in sequence along the direction from the winding head to the winding tail of the first electrode piece 1, so that at least a portion of the second region 12 is located at the winding tail of the first electrode piece 1, and the width of the second region 12 is smaller than the width of the first region 11. In other words, the width of at least the portion of the first electrode piece 1 located at the winding tail is narrowed, thereby reducing the width of the corner 10 of the entire winding core 100, that is, the width of the corner 10 of the winding core 100 is smaller than the width of the main part of the winding core 100. Width, thereby providing more space margin for the corners 10 of the core 100. For example, when the core 100 expands and squeezes the shell during the charging and discharging process, the setting of the first pole piece 1 makes the corners 10 of the core 100 have more space margin, thereby effectively alleviating the extrusion deformation of the shell caused by the corners 10 of the core 100, so that the corners of the shell can maintain a safer layer thickness, thereby avoiding the occurrence of corner cracks to a certain extent, ensuring the performance of the battery cell, and improving the safety and service life of the battery cell.

[0060] In a specific implementation, if the ratio of the width d1 of the second area 12 to the width d2 of the first area 11 is too large, the space margin at the corner 10 of the core 100 will be small. However, if the ratio of the width d1 of the second area 12 to the width d2 of the first area 11 is too small, the capacity of the core 100 will be affected. Based on this, in some embodiments, the ratio of the width d1 of the second area 12 to the width d2 of the first area 11 can satisfy the following relationship:

[0061] 90%≤d1 / d2<100%

[0062] This arrangement not only ensures that there is sufficient space margin at the corners 10 of the core 100, thereby effectively alleviating the extrusion deformation of the shell caused by the corners 10 of the core 100, thereby avoiding the occurrence of corner cracks in the shell to a certain extent, but also ensures the capacity of the core 100 to a certain extent, that is, while avoiding corner cracks in the battery cell, the capacity of the battery cell is taken into account.

[0063] Illustratively, the ratio of d1 / d2 may be, for example, 90%, 92%, 92.5%, 94%, 95%, 96%, etc.

[0064] Furthermore, the ratio of the width d1 of the second region 12 to the width d2 of the first region 11 may satisfy the following relationship: 90%≤d1 / d2≤95%.

[0065] This arrangement further prevents corner cracks from occurring on the shell of the winding core 100 while ensuring the capacity of the winding core 100 .

[0066] The total number of folds of the first pole piece 1 is N1, where N1 is a positive integer. In some embodiments, the second region 12 can be located at least in the region from the N1-1st fold to the N1th fold of the first pole piece 1.

[0067] Specifically, along the direction from the winding head to the winding tail of the first pole piece 1, that is, from the winding inner circle to the winding outer circle, the order is fold 1, fold 2, fold 3, fold 4, fold 5, fold N1-1, and fold N. For example, if the total number of folds of the winding of the first pole piece 1 is 5, then fold N1-1 is the 4th fold, that is, the 2nd fold from the bottom; and fold N1 is the 5th fold, that is, the 1st fold from the bottom.

[0068] That is to say, the second region 12 is at least located in the area corresponding to the last two folds of the first pole piece 1. 折数 ≥ 2. For example, the second region 12 is located at the second to last fold of the first pole piece 1, or the second region 12 is located at the third to last fold of the first pole piece 1, etc.

[0069] This arrangement at least ensures that the width of the two inverse folds of the first pole piece 1 is narrower than the width of the inner circle of the first pole piece 1, thereby ensuring that there is a certain amount of space margin at the corners 10 of the winding core 100, thereby effectively alleviating the squeezing of the shell when the winding core 100 expands, thereby effectively avoiding cracks at the corners of the shell.

[0070] In some embodiments, a smooth transition can be achieved at the junction of the second region 12 and the first region 11. This configuration avoids excessive stress at the junction of the first region 11 and the second region 12, improves the structural strength of the first pole piece 1, and also alleviates, to a certain extent, the compression of the shell by the expansion of the winding core 100.

[0071] Reference Figure 4As shown, in a first feasible implementation, the width d1 of the second region 12 decreases gradually in a linear trend along a direction from an end of the second region 12 close to the first region 11 to an end of the second region 12 away from the first region 11 .

[0072] That is to say, along Figure 4 In the direction from left to right in the figure, the width d1 of the second area 12 in the up-down direction decreases linearly, and the width d1 at any position of the second area 12 is smaller than the width d2 of the first area 11 .

[0073] For example, Figure 4 The first pole piece 1 in the figure can be regarded as a trapezoidal edge pole piece.

[0074] This arrangement makes the width of the first pole piece 1 relatively narrow at least at the end of the winding, providing a certain space margin for the corner 10 of the core 100, alleviating the squeezing of the shell by the expansion of the core 100, and improving the risk of corner cracking of the battery cell.

[0075] Reference Figure 5 As shown, in a second possible implementation, the width d1 of the second zone 12 gradually decreases in a direction from an end of the second zone 12 close to the first zone 11 to an end of the second zone 12 away from the first zone 11, and the edge of the second zone 12 is an arc-shaped edge 120.

[0076] That is to say, along Figure 5 From left to right in the figure, the width d1 of the second area 12 in the up-down direction gradually decreases, and the edge is arc-shaped, wherein the width d1 at any position of the second area 12 is smaller than the width d2 of the first area 11.

[0077] For example, Figure 5 The first pole piece 1 in the figure can be regarded as an arc-shaped edge pole piece.

[0078] This arrangement provides a certain amount of space margin at the corners 10 of the core 100, alleviating the impact of the core 100 expanding on the housing and reducing the risk of corner cracking in the battery cell. Furthermore, this arrangement makes the edge of the first pole piece 1 smoother, further improving the smoothness of the corners 10 of the core 100, thereby further alleviating the impact of the core 100 expanding on the housing and reducing the risk of corner cracking in the battery cell.

[0079] Reference Figure 6 As shown, in a third possible implementation, in a direction from an end of the second region 12 close to the first region 11 to an end of the second region 12 away from the first region 11 , the width d1 at different positions of the second region 12 is equal.

[0080] That is to say, along Figure 6In the direction from left to right, the width d1 of any position of the second area 12 along the up-down direction remains unchanged, and the width d1 of any position of the second area 12 is smaller than the width d2 of the first area 11 .

[0081] For example, Figure 6 The first pole piece 1 in the figure can be regarded as a single-step pole piece.

[0082] This arrangement provides a certain amount of space margin at the corners 10 of the core 100 , thereby alleviating the squeezing of the shell by the expansion of the core 100 and further improving the risk of corner cracking of the battery cell.

[0083] The junction between the second region 12 and the first region 11 can have a smooth transition, thereby improving the structural strength of the junction between the two, and further improving the structural strength of the first pole piece 1 .

[0084] Reference Figure 7 and Figure 8 As shown, in the direction from the winding head of the first pole piece 1 to the winding tail of the first pole piece 1, the second region 12 includes at least two sequentially connected first sub-segments 121. Of the two adjacent first sub-segments 121, the width d12 of the first sub-segment 121 close to the first region 11 is greater than the width d11 of the first sub-segment 121 away from the first region 11.

[0085] For example, along Figure 7 and Figure 8 From left to right in the figure, the second region 12 includes two first sub-segments 121. Of the two adjacent first sub-segments 121, the width d12 of the first sub-segment 121 on the left is greater than the width d11 of the first sub-segment 121 on the right, and both d11 and d12 are less than the width d2 of the first region 11. That is, d11 < d12 < d2. For example, d11 / d2 = 90%, and d12 / d2 = 95%.

[0086] Of course, the number of the first sub-sections 121 can also be set to three or more, which can be set according to actual conditions.

[0087] Continue to refer to Figure 7 As shown, in the fourth feasible implementation, in the direction from the end of the second zone 12 close to the first zone 11 to the end of the second zone 12 away from the first zone 11, the width of each first sub-segment 121 gradually decreases in a linear trend, and the slope of the straight line where the edges of two adjacent first sub-segments 121 are located increases successively.

[0088] For example, from left to right, the width d11 of the first sub-segment 121 on the right is smaller than the width d12 of the first sub-segment 121 on the left. The width d12 of the first sub-segment 121 on the left decreases linearly, while the width d11 of the first sub-segment 121 on the right decreases linearly. Moreover, the slope of the first sub-segment 121 on the left is smaller than the slope of the first sub-segment 121 on the right. Figure 7 As shown, it can be understood that, in two adjacent first sub-segments 121 , the angle a1 between the edge of the first sub-segment 121 on the left and the horizontal plane is smaller than the angle a2 between the edge of the first sub-segment 121 on the right and the horizontal plane.

[0089] For example, Figure 7 The first pole piece 1 in the figure can be regarded as a polygonal edge pole piece.

[0090] This arrangement makes the width of the second zone 12 smaller than the width d2 of the first zone 11, and the widths of the two adjacent first sub-segments 121 gradually decrease in sequence, thereby providing a certain amount of space margin for the corners 10 of the core 100, thereby effectively alleviating the squeezing of the shell by the expansion of the core 100 and effectively improving the corner cracking problem.

[0091] Continue to refer to Figure 8 As shown, in the fifth feasible implementation, in two adjacent first sub-segments 121, the width d12 of the first sub-segment 121 close to the first zone 11 is greater than the width d11 of the first sub-segment 121 away from the first zone 11, and for any first sub-segment 121, the widths at different positions of the first sub-segment 121 are equal.

[0092] Exemplarily, the width d11 of the first sub-segment 121 on the right side is smaller than the width d12 of the first sub-segment 121 on the left side. Furthermore, the width d12 of the first sub-segment 121 on the left side remains constant from left to right and is smaller than the width d2 of the first region 11. The width d11 of the first sub-segment 121 on the right side remains constant from left to right and is smaller than the width d2 of the first region 11.

[0093] For example, Figure 8 The first pole piece 1 in the figure can be regarded as a multi-step pole piece.

[0094] This arrangement makes the width of the second zone 12 smaller than the width d2 of the first zone 11, and the widths of the two adjacent first sub-segments 121 decrease successively, thereby providing a certain space margin for the corner 10 position of the core 100, thereby effectively alleviating the squeezing of the shell by the expansion of the core 100 and effectively improving the corner cracking problem.

[0095] Reference Figures 9 to 11As shown, in some embodiments, in a direction from the winding head of the second pole piece 2 to the winding tail of the second pole piece 2 , the second pole piece 2 includes a third region 21 and a fourth region 22 that are sequentially arranged.

[0096] Similarly, the winding head of the second pole piece 2 is the area where the second pole piece 2 starts to be wound during the winding process of the winding core 100, that is, the head area, which is located inside the winding core 100. The winding tail of the second pole piece 2 can be understood as the area where the second pole piece 2 ends to be wound. Figures 9 to 11 As shown, the direction from the winding head to the winding tail of the second pole piece 2 here can be specifically Figures 9 to 11 In the direction from left to right.

[0097] At least part of the fourth region 22 is located at the winding tail of the second pole piece 2. Along the first direction, the width D1 of the fourth region 22 is smaller than the width D2 of the third region 21. The first direction here can be specifically Figures 4 to 8 The up-down direction in , that is, the width direction of the second pole piece 2.

[0098] By making at least part of the fourth region 22 located at the winding tail of the second pole piece 2, and making the width D1 of the fourth region 22 smaller than the width D2 of the third region 21, that is, making the width of at least the portion of the second pole piece 2 located at the winding tail narrower, at the same time, because the width of at least the portion of the first pole piece 1 located at the winding tail is also narrowed, combined with Figure 1 As shown, this arrangement further reduces the width of the corners 10 of the entire core 100, that is, further making the width of the corners 10 of the core 100 smaller than the width of the main body of the core 100, thereby providing more space margin at the corners 10 of the core 100. If the core 100 expands and presses against the shell, the additional space margin at the corners 10 of the core 100 effectively alleviates the compression deformation caused by the corners 10 of the core 100 on the shell, further preventing the occurrence of corner cracks.

[0099] Reference Figure 9 As shown, in a feasible implementation, the width D1 of the fourth region 22 gradually decreases in a linear trend along a direction from an end of the fourth region 22 close to the third region 21 to an end of the fourth region 22 away from the third region 21 .

[0100] That is to say, along Figure 9 In the direction from left to right in the figure, the width D1 of the fourth region 22 in the up-down direction decreases linearly, and the width D1 at any position of the fourth region 22 is smaller than the width D2 of the third region 21 .

[0101] For example, Figure 9 The second pole piece 2 shown can be regarded as a trapezoidal edge pole piece.

[0102] This arrangement makes the width of the second pole piece 2 relatively narrower at least at the end of the winding, providing a certain space margin for the corner 10 of the core 100, further alleviating the squeezing of the shell by the expansion of the core 100, and improving the risk of corner cracking of the battery cell.

[0103] Reference Figure 10 As shown, in another possible implementation, in a direction from one end of the fourth region 22 close to the third region 21 to one end of the fourth region 22 away from the third region 21 , the width D1 of the fourth region 22 at different positions is equal.

[0104] That is to say, along Figure 10 In the direction from left to right, the width D1 of any position of the fourth region 22 remains unchanged, and the width D1 of any position of the fourth region 22 is smaller than the width D2 of the third region 21 .

[0105] For example, Figure 10 The pole piece shown can be considered as a single-step pole piece.

[0106] This arrangement provides a certain amount of space margin at the corners 10 of the core 100 , thereby alleviating the squeezing of the shell by the expansion of the core 100 and further improving the risk of corner cracking of the battery cell.

[0107] Reference Figure 11 As shown, in another possible implementation, in the direction from the winding head to the winding tail of the second pole piece 2, the fourth region 22 includes at least two sequentially connected second sub-segments 221. Of the two adjacent second sub-segments 221, the width D12 of the second sub-segment 221 closer to the third region 21 is greater than the width D11 of the second sub-segment 221 farther from the third region 21.

[0108] For example, along Figure 11 From left to right, the fourth region 22 includes two second sub-segments 221. Of the two adjacent second sub-segments 221, the width D12 of the second sub-segment 221 on the left is greater than the width D11 of the second sub-segment 221 on the right. Furthermore, both D11 and D12 are less than the width D2 of the third region 21, i.e., D11 < D12 < D2. For example, D11 / D2 = 90%, and D12 / D2 = 95%.

[0109] Of course, the number of the second sub-sections 221 can be set to three or more, and can be set specifically according to actual conditions.

[0110] In some examples, for any second sub-segment 221 , the widths of the second sub-segment 221 at different locations may be equal.

[0111] by Figure 11As shown in the example, the width D11 of the second sub-segment 221 on the right side is smaller than the width D12 of the second sub-segment 221 on the left side. The width D12 of the second sub-segment 221 on the left side remains constant from left to right and is smaller than the width D2 of the third region 21. The width D11 of the second sub-segment 221 on the right side remains constant from left to right and is smaller than the width D2 of the third region 21.

[0112] For example, Figure 11 The pole piece shown can be regarded as a multi-step pole piece.

[0113] Of course, the fourth zone 22 can also be set as follows Figure 7 The structure of the second zone 12 in the first pole piece 1 shown is that the width of each second sub-segment 221 decreases linearly, and the slope of the straight line where the edges of two adjacent second sub-segments 221 are located increases successively, that is, the slope of the edge of the second sub-segment 221 on the right is greater than the slope of the edge of the second sub-segment 221 on the left.

[0114] The above-mentioned arrangement of the second pole piece 2 can further provide a certain space margin for the corner 10 of the winding core 100, thereby further effectively alleviating the squeezing of the shell by the expansion of the winding core 100 and effectively improving the corner cracking problem.

[0115] In addition, the fourth area 22 can also be set as follows Figure 5 The arc structure of the second area 12 in the first pole piece 1 shown in FIG. 1 is also provided as follows: Figure 7 The polygonal edge structure of the second area 12 in the first pole piece 1 can also provide a certain amount of space margin for the corners of the winding core 100, thereby further effectively alleviating the squeezing of the shell by the expansion of the winding core 100 and effectively improving the corner cracking problem.

[0116] The total number of winding folds of the second pole piece 2 is N2, where N2 is a positive integer. In some embodiments, the fourth region 22 can be located at least in the region from the N2-1st fold to the N2th fold of the second pole piece 2.

[0117] Specifically, along the direction from the winding head to the winding tail of the second pole piece 2, that is, from the winding inner circle to the winding outer circle, the order is fold 1, fold 2, fold 3, fold ... fold, fold N2-1, and fold N2. For example, if the total number of folds of the winding of the second pole piece 2 is 5, then fold N2-1 is the 4th fold, that is, the 2nd fold from the bottom, and fold N2 is the 5th fold, that is, the 1st fold from the bottom.

[0118] That is to say, the fourth area 22 is at least located in the area corresponding to the last two folds of the second pole piece 2. 折数 ≥ 2. For example, the fourth region 22 is located at the second to last fold of the second pole piece 2, or the fourth region 22 is located at the third to last fold of the second pole piece 2, etc.

[0119] This arrangement at least ensures that the width of the two inverse folds of the second pole piece 2 is narrower than the width of the inner circle of the second pole piece 2, thereby ensuring that there is a certain amount of space margin at the corners 10 of the winding core 100, so as to effectively alleviate the squeezing of the shell when the winding core 100 expands, thereby effectively avoiding the occurrence of cracks at the corners 10 of the shell.

[0120] It should be noted that the various structures of the second pole piece 2 can be used in conjunction with the various structures of the first pole piece 1, for example Figure 4 The first pole piece 1 shown is Figure 9 The second pole piece 2 shown is matched with each other and stacked and wound to form a core, so that the corners 10 of the wound core form a certain space margin, which can effectively alleviate the squeezing of the shell by the expansion of the core 100, thereby effectively improving the risk of corner cracks in the battery cell.

[0121] In order to improve the risk of corner cracking of the battery cell while avoiding serious lithium plating, based on this, in some embodiments, the width of the second pole piece 2 at different positions in the winding core can be made greater than the width of the first pole piece 1 at the position corresponding to the second pole piece 2.

[0122] That is to say, at a certain position of the winding core, the width of the second electrode piece 2 is greater than the width of the first electrode piece 1 located at the corresponding position of the inner circle of the second electrode piece 2, and is greater than the width of the first electrode piece 1 located at the corresponding position of the outer circle of the second electrode piece 2, thereby ensuring the coverage effect of the second electrode piece 2 on the corresponding first electrode piece 1, ensuring the area of ​​the second electrode piece 2, and avoiding the occurrence of lithium plating of the second electrode piece 2. That is, while improving the problem of corner cracks in the battery cell, the risk of lithium plating is reduced to a certain extent.

[0123] Exemplarily, in a specific implementation, the third-to-last fold and the first-to-last fold of the first electrode 1 correspond to the first-to-last fold of the second electrode 2 at the same time. For example, the second zone 12 of the first electrode 1 is located in the area from the third-to-last fold to the first-to-last fold of the first electrode 1, and the fourth zone 22 of the second electrode 2 is located in the area of ​​the first-to-last fold of the second electrode 2. In order to improve the risk of corner cracking while reducing the risk of lithium plating, at this time, the width d1 of the second zone 12 of the first electrode 1 can be made smaller than the width d2 of the first zone 11, the width D1 of the fourth zone 22 of the second electrode 2 can be made smaller than the width D2 of the third zone 21, and the width D1 of the fourth zone 22 can be made greater than the width d1 of the second zone 12, and the width D2 of the third zone 21 can be made greater than the width d2 of the first zone 11.

[0124] Of course, in other embodiments, for the first pole piece 1 with different structures described above, the second pole piece 2 can also be configured as follows: Figure 12The normal pole piece shown, that is, the width D2 of the second pole piece 2 is constant in the direction from the winding head of the second pole piece 2 to the winding tail of the second pole piece 2 .

[0125] This embodiment also provides a battery cell, which may be, for example, a lithium-ion battery cell, specifically a soft-pack lithium-ion battery cell.

[0126] The battery cell specifically includes: a shell and a winding core. The shell can be, for example, a soft-pack shell, specifically, an aluminum-plastic film shell.

[0127] Among them, the structure and implementation principle of the core in this embodiment are the same as those of the core 100 provided in the above embodiment, and can bring the same or similar technical effects. They will not be described one by one here, and the details can be referred to the description of the above embodiment.

[0128] It has been verified that the battery cell provided in this embodiment can greatly extend the service life of the battery cell in daily or harsh extreme environments, increasing the charge and discharge cycle life of the battery cell by more than 50% and the cycle life of the battery cell in high temperature and high humidity environments by more than 200%.

[0129] This embodiment also provides an electrical device, which includes a battery cell.

[0130] Specifically, the electrical device has a battery cell compartment, in which the battery cells are installed. The battery cells can serve as a power source or energy storage unit for the electrical device. The electrical device may include, but is not limited to, portable electronic devices (such as mobile phones, laptops, tablets, etc.) and electric vehicles (such as pure electric vehicles, hybrid electric vehicles, electric bicycles, etc.).

[0131] The battery cell in this embodiment has the same structure and implementation principle as the battery cell provided in the above embodiment, and can bring the same or similar technical effects, which will not be described one by one here. For details, please refer to the description of the above embodiment.

[0132] The following further describes the battery cell provided by the embodiment of the present invention, taking the first electrode 1 as the positive electrode and the second electrode 2 as the negative electrode, in combination with the preparation method:

[0133] Example 1:

[0134] Step 1: Prepare the positive electrode active material slurry, coat the positive electrode active material on the surface of the aluminum foil, and obtain the positive electrode sheet through baking, rolling and cutting.

[0135] The preparation method of the positive electrode active material slurry is as follows: after the conductive agent and polyvinylidene fluoride PVDF glue are evenly mixed, lithium cobalt oxide is added and stirred evenly to obtain the positive electrode active layer slurry.

[0136] The positive electrode active layer is composed of 98.3% by mass of lithium cobalt oxide, 0.5% by mass of PVDF, and 1.2% by mass of a conductive agent, wherein the conductive agent is composed of conductive carbon black, single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0137] Step 2: Prepare the negative electrode slurry, apply the negative electrode slurry on the carbon-coated copper foil, and obtain the negative electrode sheet through baking, rolling and cutting.

[0138] The negative electrode slurry is prepared as follows: 0.5% by mass of a conductive agent and 97% by mass of graphite powder are mixed evenly, and then deionized water, 1.3% by mass of carboxymethyl cellulose and 1.2% by mass of styrene-butadiene rubber adhesive are added respectively and stirred evenly to obtain a negative electrode active layer slurry.

[0139] Step 3: Punch the positive electrode sheet twice through a punching die to make the trapezoidal positive electrode sheet. Set the fold number corresponding to the second area 12 to S. 折数 =2, that is, the second region 12 corresponds to the region between the first to last fold and the second to last fold of the second pole piece 2. Wherein, d1 / d2=90%.

[0140] Step 4: The positive and negative electrodes are made into cores through sheeting and winding, and the cores are packaged, baked, injected, formed, sealed, sorted, OCV and packaged to obtain lithium-ion batteries.

[0141] Step 5: Perform capacity test, 25℃ room temperature cycle test and 45℃ / 90% humidity cycle test on the lithium-ion battery cell. During the cycle test, pay attention to the appearance of the battery cell, such as the flatness of the core, corner damage, etc.

[0142] Example 2

[0143] In this embodiment, only the shape of the positive electrode sheet in the third step is changed from a trapezoidal-edge positive electrode sheet to an arc-edge positive electrode sheet, and the rest is the same as in embodiment 1.

[0144] Example 3

[0145] In this embodiment, only the shape of the positive electrode sheet is changed from the trapezoidal edge positive electrode sheet to the polygonal edge positive electrode sheet in the third step. Where d12 / d2=95%. The fold number corresponding to the second area 12 is set to S 折数 =2, that is, the folds corresponding to the two first sub-sections 121 are both S 折数 = 1. Other aspects are the same as in Example 1.

[0146] Example 4

[0147] In this embodiment, only the shape of the positive electrode sheet is changed from the trapezoidal edge positive electrode sheet to the single-step positive electrode sheet. At the same time, the negative electrode sheet is punched twice through the punching die to make a single-step negative electrode sheet. The number of folds corresponding to the second area 12 of the positive electrode sheet is set to S折数 =2, set the fold number corresponding to the fourth area 22 of the negative electrode sheet to S 折数 =2. Wherein, D1 / D2=90%, D1>d1, D2>d2. Other aspects are the same as those of Example 1.

[0148] Example 5

[0149] In this embodiment, only the shape of the positive electrode sheet is changed from the trapezoidal edge positive electrode sheet to the multi-step positive electrode sheet in the third step, where d12 / d2=95%. The fold number corresponding to the second area 12 of the positive electrode sheet is set to S 折数 =2, that is, the second area 12 corresponds to the first to last fold and the second to last fold of the second pole piece 2. The fold numbers corresponding to the two first sub-sections 121 are both S 折数 =1.

[0150] At the same time, the negative electrode sheet is punched out twice through a punching die to form a multi-step negative electrode sheet. The fold number corresponding to the fourth area 22 of the negative electrode sheet is set to S. 折数 =2, that is, the fourth area 22 corresponds to the first to last fold and the second to last fold of the second pole piece 2. The fold numbers corresponding to the two second sub-sections 221 are both S 折数 =1. Among them, D11 / D2=90%, D12 / D2=95%, D 11 >d 11 , D 12 >d 12 The rest is the same as in Example 1.

[0151] Comparative Example 1

[0152] In this comparative example, only d1 / d2=95%, and the others are the same as in Example 1.

[0153] Comparative Example 2

[0154] In this comparative example, only d1 / d2=100%, that is, the positive electrode sheet is a normal sheet, S 折数 =0, and the rest is the same as in Example 1.

[0155] Comparative Example 3

[0156] In this comparative example, only the second area 12 of the positive electrode sheet is set to correspond to the fold number S 折数 =4, and the rest is the same as in Example 1.

[0157] Comparative Example 4

[0158] In this embodiment, only the fold number S corresponding to the second area 12 of the positive electrode sheet is 折数 =2, change the total fold number of the positive electrode sheet to that of the positive electrode sheet, and the rest is the same as in Example 1.

[0159] Comparative Example 5

[0160] In this comparative example, only the fold number corresponding to the second area 12 of the positive electrode sheet is set to S 折数 =4, the fold number corresponding to the fourth area 22 of the negative electrode sheet is set to S 折数 =4, and the rest is the same as in Example 4.

[0161] Table 1 Comparison of performance data of various embodiments and comparative examples

[0162]

[0163] From the data comparison of the above examples, it can be seen that:

[0164] 1. The energy density (ED) loss of the pole pieces corresponding to Examples 1 to 3 is generally better than that of the stepped pole pieces of Examples 4 and 5.

[0165] 2. The stepped pole pieces corresponding to Examples 4 and 5 are more conducive to improving the risk of corner cracking during battery cell cycling than the pole pieces corresponding to Examples 1 to 3.

[0166] 3. From the perspective of improving the risk of corner cracking during battery cell cycling, among Examples 1 to 3, the trapezoidal edge electrode of Example 1 is significantly better than the polygonal edge electrode of Example 3, and the polygonal edge electrode of Example 3 is better than the arc-shaped edge electrode of Example 2.

[0167] 4. From the perspective of improving the risk of corner cracking during battery cell cycling, among the stepped pole pieces of Example 4 and Example 5, the single-step pole piece of Example 4 is superior to the multi-step pole piece of Example 5.

[0168] From the data comparison of the above examples and comparative examples, it can be seen that:

[0169] 1. It can be seen from Example 1 and Comparative Example 1 that the smaller the ratio of the width d1 of the second zone to the width d2 of the first zone, the more conducive it is to improving the risk of corner cracking during battery cell cycling.

[0170] 2. From Example 1, Comparative Example 3 and Comparative Example 4, it can be seen that the fold number S corresponding to the narrowed width area 折数 The more it is, the better it is for improving the risk of battery cell cracking during cycling.

[0171] 3. From Comparative Examples 3 and 5, it can be seen that the ratio of the width d1 of the second zone to the width d2 of the first zone is the same, and the fold number S corresponding to the area with narrower width is 折数 Under the same conditions, single-step pole pieces are more conducive to improving the risk of corner cracking during battery cell cycling than trapezoidal edge pole pieces.

[0172] The above data comparison shows that from the perspectives of "lower ED loss" and "longer cycle performance," trapezoidal edge plates offer the best solution for cell corner cracking, balancing larger core corner margins with lower ED loss. This is followed by stepped plates, followed by curved and polygonal edge plates.

[0173] From the above performance data, it can be seen that the special-shaped punching processing of the positive electrode sheet makes the width d1 of the second area 12 of the positive electrode sheet smaller than the width d2 of the first area 11, which significantly improves the ability of the battery cell to resist the risk of corner cracking and greatly extends the service life of the battery cell.

[0174] In this document, it should be noted that, unless otherwise expressly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application.

[0175] In this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0176] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A winding core, characterized in that: The invention comprises a first pole piece (1), a second pole piece (2) and a diaphragm located between the first pole piece (1) and the second pole piece (2); the first pole piece (1), the diaphragm and the second pole piece (2) are stacked and wound to form a winding core; In a direction from a winding head portion of the first pole piece (1) to a winding tail portion of the first pole piece (1), the first pole piece (1) comprises a first region (11) and a second region (12) arranged in sequence; at least a portion of the second region (12) is located at the winding tail portion of the first pole piece (1); Along the first direction, a width d1 of the second region (12) is smaller than a width d2 of the first region (11).

2. The winding core according to claim 1, characterized in that The ratio of the width d1 of the second area (12) to the width d2 of the first area (11) satisfies: 90%≤d1 / d2<100%.

3. The winding core according to claim 2, characterized in that The ratio of the width d1 of the second area (12) to the width d2 of the first area (11) satisfies: 90%≤d1 / d2≤95%.

4. The winding core according to claim 1, wherein: The total number of winding folds of the first pole piece (1) is N1, N1 is a positive integer, and the second region (12) is at least located in the region from the N1-1th fold to the N1th fold of the first pole piece (1); And / or, the junction between the second area (12) and the first area (11) has a smooth transition.

5. The winding core according to claim 1, characterized in that In a direction from an end of the second zone (12) close to the first zone (11) to an end of the second zone (12) away from the first zone (11), The width of the second region (12) decreases gradually in a linear trend; Alternatively, the width of the second area (12) gradually decreases, and the edge of the second area (12) is an arc-shaped edge (120); Alternatively, the widths of the second region (12) at different positions are equal.

6. The winding core according to claim 1, characterized in that In a direction from a winding head portion of the first pole piece (1) to a winding tail portion of the first pole piece (1), the second region (12) comprises at least two first sub-segments (121) connected in sequence; In two adjacent first sub-sections (121), the width of the first sub-section (121) close to the first area (11) is greater than the width of the first sub-section (121) far from the first area (11).

7. The winding core according to claim 6, characterized in that In a direction from an end of the second area (12) close to the first area (11) to an end of the second area (12) far from the first area (11), the width of each first sub-section (121) gradually decreases in a linear trend, and the slope of the straight line where the edges of two adjacent first sub-sections (121) lie increases successively; Alternatively, for any first sub-section (121), the widths of the first sub-section (121) at different positions are equal.

8. The winding core according to any one of claims 1 to 7, characterized in that: In a direction from the winding head of the second pole piece (2) to the winding tail of the second pole piece (2), the second pole piece (2) comprises a third region (21) and a fourth region (22) arranged in sequence, and at least a portion of the fourth region (22) is located at the winding tail of the second pole piece (2); Along the first direction, a width D1 of the fourth region (22) is smaller than a width D2 of the third region (21).

9. The winding core according to claim 8, characterized in that The width of the second pole piece (2) at different positions in the winding core is greater than the width of the first pole piece (1) at a position corresponding to the second pole piece (2); And / or, the total number of winding folds of the second pole piece (2) is N2, N2 is a positive integer, and the fourth region (22) is at least located in the region from the N2-1st fold to the N2th fold of the second pole piece (2).

10. A battery cell, characterized in that: It comprises a shell and the winding core according to any one of claims 1 to 9, wherein the shell is wrapped around the outside of the winding core.

11. An electrical device, characterized in that: Comprising the battery cell as claimed in claim 10.

Images