Battery cell and electronic device

Abstract

The invention discloses a battery cell and an electronic device, the battery cell comprises a pole piece, and the pole piece comprises a current collector and an active material layer. The current collector includes a support layer, a first conductive layer, and a second conductive layer. Along the thickness direction of the pole piece, the first conductive layer is arranged on the first surface, and the second conductive layer is arranged on the second surface. The active material layer is arranged on the first conductive layer and / or the second conductive layer. The current collector comprises a first part, a second part and a third part which are arranged in sequence along the width direction of the unfolded pole piece; in the thickness direction, a first through hole is formed in the position, opposite to the second part, of the first conductive layer, and a second through hole is formed in the position, opposite to the second part, of the second conductive layer. The supporting layer is provided with a first hole channel, the first hole channel comprises a first section and a second section, the first section is located on the second part and penetrates through the first surface and / or the second surface, the first section is communicated with the first through hole and / or the second through hole, and the second section penetrates through the first end face and is communicated with the first section. The battery cell is beneficial to maintaining long cycle life of the battery cell.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a battery cell and an electronic device. Background Art

[0002] In order to increase the capacity of the battery cell, the existing battery cells usually use electrodes with larger thickness and width. After the battery cell is injected with electrolyte, the path of the electrolyte diffusion from the edge of the electrode to the middle of the electrode along the width direction of the electrode is extended, and the path of the electrolyte diffusion from the surface of the electrode to the middle of the electrode along the thickness direction of the electrode is extended, making it difficult for the electrolyte to infiltrate the middle of the electrode, and black spots and purple spots are prone to appear in the middle of the electrode. Lithium deposition will occur at the black and purple spots, resulting in significant capacity decay of the battery cell during the cycle. Summary of the invention

[0003] In view of the above situation, the present application provides a battery cell that is conducive to maintaining a long cycle life.

[0004] An embodiment of the present application provides a battery cell. The battery cell includes a pole piece, and the pole piece includes a current collector and an active material layer. The current collector includes a support layer, a first conductive layer, and a second conductive layer. Along the thickness direction of the pole piece, the support layer includes a first surface and a second surface arranged opposite to each other, the first conductive layer is arranged on the first surface, and the second conductive layer is arranged on the second surface. The active material layer is arranged on the first conductive layer and / or the second conductive layer. Along the width direction after the pole piece is unfolded, the current collector includes a first part, a second part, and a third part arranged in sequence. A first end face is provided on the side of the first part away from the second part. Along the thickness direction, a first through hole is provided at a position opposite to the first conductive layer and the second part, and a second through hole is provided at a position opposite to the second conductive layer and the second part. Among them, the support layer is provided with a first channel, and the first channel includes a first section and a second section, the first section is located in the second section and passes through the first surface and / or the second surface, and the first section is connected to the first through hole and / or the second through hole, and the second section passes through the first end face and is connected to the first section.

[0005] In the above-mentioned battery cell, the support layer is provided with a first channel, the first channel includes a first section and a second section, the first section is located in the second part and penetrates the first surface and / or the second surface, and the first section is connected with the first through hole and / or the second through hole, and the second section penetrates the first end face and is connected with the first section. When the battery cell is circulating, the electrolyte diffuses from the first end face through the second section to the first section, and then diffuses from the first section through the first through hole and / or the second through hole to the side of the active material layer close to the support layer, so as to increase the speed of the electrolyte diffusing to the middle position of the pole piece, and facilitate the electrolyte to fully infiltrate the middle position of the pole piece, reduce the probability of problems such as black spots and purple spots, and help the battery cell maintain a long cycle life.

[0006] In some embodiments of the present application, along the width direction, the width of the current collector is W1, the width of the second portion is W2, 0.05≤W2 / W1≤0.3, to facilitate the layout of the second section and the middle position of the second portion corresponding to the pole piece.

[0007] In some embodiments of the present application, along the width direction, the width of the first portion is W3, 0.35≤W3 / W1≤0.55, so that the second portion corresponds to the middle position of the pole piece by limiting the width of the first portion. The width of the third portion is W4, 0.35≤W4 / W1≤0.55, so that the second portion corresponds to the middle position of the pole piece by limiting the width of the third portion.

[0008] In some embodiments of the present application, along the width direction, a second end face is provided on the side of the third part far from the second part. The support layer is also provided with a second channel, and the second channel includes a third section and a fourth section, the third section is located in the second part and penetrates the first surface and / or the second surface, and the third section is connected with the first through hole and / or the second through hole, and the fourth section penetrates the second end face and is connected with the third section. When the battery cell is circulating, the electrolyte near the first end face diffuses to the first section through the second section, and then diffuses from the first section through the first through hole and / or the second through hole to the side of the active material layer near the support layer. The electrolyte near the second end face diffuses to the third section through the fourth section, and then diffuses from the third section through the first through hole and / or the second through hole to the side of the active material layer near the support layer. The first channel and the second channel cooperate to further increase the speed of the electrolyte diffusing to the middle position of the pole piece, and further facilitate the electrolyte to fully infiltrate the middle position of the pole piece, reduce the probability of problems such as black spots and purple spots, and further help the battery cell maintain a long cycle life.

[0009] In some embodiments of the present application, along the width direction, the projection of the third segment and the projection of the first segment are spaced apart along the length direction after the pole piece is unfolded, and the spacing between the projection of the third segment and the projection of the adjacent first segment is S1, 0.1mm≤S0≤5mm, so that the third segment and the first segment are dispersedly arranged in the middle of the pole piece, thereby facilitating the electrolyte to fully infiltrate the middle of the pole piece. Along the width direction, the projection of the fourth segment and the projection of the second segment are spaced apart along the length direction after the pole piece is unfolded, and the spacing between the projection of the fourth segment and the projection of the adjacent second segment is S0, 0.1mm≤S1≤5mm, so that the third segment and the first segment are dispersedly arranged in the middle of the pole piece, thereby facilitating the electrolyte to fully infiltrate the middle of the pole piece.

[0010] In some embodiments of the present application, along the width direction, the average pore size of the first channel is D1, and the average pore size of the second channel is D2, 0.6≤D1 / D2≤1.5, so that the average pore size of the first channel and the average pore size of the second channel can be adjusted according to the diffusion difficulty of the electrolyte.

[0011] In some embodiments of the present application, along the length direction of the electrode after unfolding, the spacing between two adjacent first channels is S2, and the spacing between two adjacent second channels is S3, 0.77≤S2 / S3≤1.3, so that the spacing between two adjacent first channels and the spacing between two adjacent second channels can be adjusted according to the diffusion difficulty of the electrolyte, and can adapt to the position tolerance between the first channel and the second channel.

[0012] In some embodiments of the present application, along the length direction after the pole piece is unfolded, the current collector includes a fourth part, a fifth part and a sixth part arranged in sequence. The end of the fourth part away from the fifth part is the winding starting end, and the end of the sixth part away from the fifth part is the winding ending end. The length of the current collector is L1, the length of the fourth part is L2, 0.1≤L2 / L1≤0.3, the length of the fifth part is L3, 0.3≤L3 / L1≤0.6, and the length of the sixth part is L4, 0.1≤L4 / L1≤0.3. The average pore size of the first and second pores located in the fourth part is D3, the average pore size of the first and second pores located in the fifth part is D4, and the average pore size of the first and second pores located in the sixth part is D5, D3≥D4≥D5. The average pore size of the first and second pores of the battery cell from the outside to the inside increases in a gradient, which is conducive to improving the electrolyte infiltration effect of the inner ring pole piece of the battery cell. In addition, the average pore sizes of the first and second channels of the battery cell decrease gradually from the inside to the outside, which is beneficial to reducing the impact of the first and second channels on the supporting layer of the outer ring electrode of the battery cell and improving the tensile strength of the outer ring electrode of the battery cell.

[0013] In some embodiments of the present application, the thickness of the support layer is T1, 1 / 6≤D4 / T1≤1 / 2, so as to facilitate the diffusion of the electrolyte and reduce the influence of the first pore and the second pore on the tensile strength of the support layer located in the fifth part. 0.6≤D4 / D3≤1, so that D3≥D4. 0.6≤D5 / D4≤1, so that D4≥D5.

[0014] In some embodiments of the present application, along the length direction, the number of the first and second holes per centimeter in the fourth part is N1, 30≤N1≤100; and / or, the number of the first and second holes per centimeter in the fifth part is N2, 20≤N2≤80; and / or, the number of the first and second holes per centimeter in the sixth part is N3, 10≤N3≤60. The number of the first and second holes per centimeter from the inside to the outside of the battery cell gradually increases, which is beneficial to improving the electrolyte infiltration effect of the inner ring electrode of the battery cell. In addition, the number of the first and second holes per centimeter from the outside to the inside of the battery cell gradually increases and decreases, which is beneficial to reducing the influence of the first and second holes on the support layer of the outer ring electrode of the battery cell and improving the tensile strength of the outer ring electrode of the battery cell.

[0015] In some embodiments of the present application, the pore size of the second section gradually decreases from the first end surface to the second end surface, so as to facilitate diffusion of the electrolyte from the first end surface to the first section.

[0016] In some embodiments of the present application, the first section includes a first subsection and a second subsection. The first subsection passes through the first surface and is connected to the second section, and the aperture of the first subsection gradually decreases from the first surface to the second surface, so that the electrolyte can fully infiltrate the middle part of the pole piece. The second subsection passes through the second surface and is connected to the second section, and the aperture of the second subsection gradually decreases from the second surface to the first surface, so that the electrolyte can fully infiltrate the middle part of the pole piece.

[0017] An embodiment of the present application further provides an electronic device, which includes any one of the battery cells in the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a battery cell in one embodiment of the present application.

[0019] Figure 2 yes Figure 1 Section view along section line Ⅱ-Ⅱ.

[0020] Figure 3 yes Figure 1 Section view along section line III-III.

[0021] Figure 4 yes Figure 1 Section view along section line IV-IV.

[0022] Figure 5 It is a schematic structural diagram of the first channel of the battery cell in another embodiment of the present application.

[0023] Figure 6 It is a schematic diagram of the structure of the second channel of the battery cell in another embodiment of the present application.

[0024] Figure 7 It is a schematic structural diagram of the first channel of the battery cell in another embodiment of the present application.

[0025] Figure 8 It is a schematic diagram of the structure of an electronic device in one embodiment of the present application.

[0026] Main component symbols Cells 100A, 100B, 100C Electronic device 200 Pole piece 10 Current collector 20 Part 1 20A Part 220B Part 3 20C The first end surface 201 Second end surface 202 Support layer 21 First surface 211 Second surface 212 First channel 213 Section 1 213A Section 213B Second channel 214 Section 3 214A Section 4, 214B First conductive layer 22 First through hole 221 The second conductive layer 23 The second through hole 231 First subsection 2131 Second subsection 2132 Active material layer 30 Thickness direction X Width direction Z Length direction Y.

[0027] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described below in conjunction with 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 of the embodiments.

[0029] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centrally disposed element at the same time. When an element is considered to be "disposed" on another element, it may be directly disposed on the other element or there may be a centrally disposed element at the same time.

[0030] When a value is considered to be "equal" to another value, it means that the two are equal within the set deviation, and the set deviation range is within 5%. In other words, when at least one of the two values ​​fluctuates within the set deviation range, even if their values ​​are not equal, they are still judged to be roughly equal. When a value is considered to be in a "1:1" ratio with another value, it means that the two are equal within the set deviation, and the set deviation range is within 5%. In other words, when at least one of the two values ​​fluctuates within the set deviation range, even if their values ​​are not equal, they are still judged to be equal in ratio.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items. The term "overlap" used herein refers to the overlap of the projections of two parts or the overlap of the projections of two parts.

[0032] An embodiment of the present application provides a battery cell. The battery cell includes a pole piece, and the pole piece includes a current collector and an active material layer. The current collector includes a support layer, a first conductive layer, and a second conductive layer. Along the thickness direction of the pole piece, the support layer includes a first surface and a second surface arranged opposite to each other, the first conductive layer is arranged on the first surface, and the second conductive layer is arranged on the second surface. The active material layer is arranged on the first conductive layer and / or the second conductive layer. Along the width direction after the pole piece is unfolded, the current collector includes a first part, a second part, and a third part arranged in sequence. A first end face is provided on the side of the first part away from the second part. Along the thickness direction, a first through hole is provided at a position opposite to the first conductive layer and the second part, and a second through hole is provided at a position opposite to the second conductive layer and the second part. Among them, the support layer is provided with a first channel, and the first channel includes a first section and a second section, the first section is located in the second section and passes through the first surface and / or the second surface, and the first section is connected to the first through hole and / or the second through hole, and the second section passes through the first end face and is connected to the first section.

[0033] In the above-mentioned battery cell, the support layer is provided with a first channel, the first channel includes a first section and a second section, the first section is located in the second part and penetrates the first surface and / or the second surface, and the first section is connected with the first through hole and / or the second through hole, and the second section penetrates the first end face and is connected with the first section. When the battery cell is circulating, the electrolyte diffuses from the first end face through the second section to the first section, and then diffuses from the first section through the first through hole and / or the second through hole to the side of the active material layer close to the support layer, so as to increase the speed of the electrolyte diffusing to the middle position of the pole piece, and facilitate the electrolyte to fully infiltrate the middle position of the pole piece, reduce the probability of problems such as black spots and purple spots, and help the battery cell maintain a long cycle life.

[0034] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0035] Example 1 See also Figure 1 One embodiment of the present application provides a battery cell 100A, which is used in a secondary battery. A secondary battery refers to a battery that can be used continuously by activating active materials by charging after the battery is discharged. The battery cell 100A includes a pole piece 10, which can be a positive pole piece or a negative pole piece. The battery cell 100A is a winding structure or a stacked structure, and the present application is described in terms of a winding structure.

[0036] The pole piece 10 includes a current collector 20 and an active material layer 30 . The active material layer 30 is used to generate current and collect the current onto the current collector 20 .

[0037] The current collector 20 is a composite current collector, and the current collector 20 includes a support layer 21, a first conductive layer 22, and a second conductive layer 23. Along the thickness direction X of the pole piece 10, the support layer 21 includes a first surface 211 and a second surface 212 that are oppositely arranged, the first conductive layer 22 is arranged on the first surface 211, and the second conductive layer 23 is arranged on the second surface 212.

[0038] The support layer 21 is made of a polymer insulating material, has high structural strength, low density and mass, and can reduce the thickness and weight of the current collector 20. Optionally, the polymer insulating material includes one or more of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyimide (PI), polyetherketone (PEK), and polyphenylene sulfide (PPS).

[0039] The first conductive layer 22 and the second conductive layer 23 are made of metal materials. Compared with the current collector made of traditional metal, the thickness of the first conductive layer 22 and the second conductive layer 23 arranged on both sides of the support layer 21 is thinner, which is conducive to reducing the generation of metal burrs when the current collector 20 is mechanically damaged by external impact, thereby reducing the risk of short circuit. Optionally, the metal material includes one or more of aluminum, copper, nickel, silver, gold, and iron.

[0040] Specifically, when the electrode 10 is a positive electrode, the metal material of the first conductive layer 22 and the second conductive layer 23 includes aluminum; when the electrode 10 is a negative electrode, the metal material of the first conductive layer 22 and the second conductive layer 23 includes copper.

[0041] The active material layer 30 is disposed on the first conductive layer 22 and the second conductive layer 23. Specifically, the active material layer 30 is coated on the first conductive layer 22 and the second conductive layer 23 by extrusion coating, transfer coating, spray coating or the like.

[0042] Please also read Figure 1 and Figure 2, along the width direction Z after the pole piece 10 is unfolded, the current collector 20 includes a first portion 20A, a second portion 20B and a third portion 20C arranged in sequence. The first portion 20A is provided with a first end surface 201 on a side away from the second portion 20B, and the third portion 20C is provided with a second end surface 202 on a side away from the second portion 20B. The second portion 20B and the part of the active material layer 30 close to the second portion 20B are the middle position of the pole piece 10.

[0043] It should be noted that the width direction Z of the current collector 20 is usually perpendicular to the coating direction of each material layer (eg, the active material layer 30 ) during the processing of the electrode sheet 10 .

[0044] Along the thickness direction X, a first through hole 221 is provided at a position of the first conductive layer 22 opposite to the second portion 20B, and a second through hole 231 is provided at a position of the second conductive layer 23 opposite to the second portion 20B.

[0045] The support layer 21 is provided with a first channel 213. The first channel 213 includes a first section 213A and a second section 213B. The first section 213A is located in the second portion 20B and passes through the first surface 211 and the second surface 212, and the first section 213A is connected to the first through hole 221 and the second through hole 231, and the second section 213B passes through the first end surface 201 and is connected to the first section 213A.

[0046] When the battery cell 100A is circulating, the electrolyte diffuses from the first end surface 201 through the second section 213B to the first section 213A, and then diffuses from the first section 213A through the first through hole 221 and the second through hole 231 to the side of the active material layer 30 close to the support layer 21, so as to increase the speed of the electrolyte diffusing to the middle position of the electrode sheet 10, and facilitate the electrolyte to fully infiltrate the middle position of the electrode sheet 10, thereby reducing the probability of problems such as black spots and purple spots, which is beneficial for the battery cell 100A to maintain a long cycle life.

[0047] In some embodiments, the first segment 213A extends along the thickness direction X, and the second segment 213B extends along the width direction Z.

[0048] Please continue reading Figure 1 and Figure 2 In some embodiments, along the width direction Z, the width of the current collector 20 is W1, the width of the second portion 20B is W2, 0.05≤W2 / W1≤0.3, when W2 / W1 is too small (less than 0.05), the narrow width of the second portion 20B is not conducive to the layout of the second section 213B, when W2 / W1 is too large, the width of the second portion 20B is wide (greater than 0.3), which easily leads to a deviation between the second portion 20B and the middle position of the pole piece 10. By limiting 0.05≤W2 / W1≤0.3, the layout of the second section 213B is facilitated, and the second portion 20B corresponds to the middle position of the pole piece 10.

[0049] Optionally, W2 / W1 is one of 0.05, 0.1, 0.15, 0.2, 0.25, 0.3 and any other value in the range of 0.05≤W2 / W1≤0.3.

[0050] In some embodiments, along the width direction Z, the width of the first portion 20A is W3, 0.35≤W3 / W1≤0.55, so that the second portion 20B corresponds to the middle position of the pole piece 10 by limiting the width of the first portion 20A.

[0051] In some embodiments, along the width direction Z, the width of the third portion 20C is W4, 0.35≤W4 / W1≤0.55, so that the second portion 20B corresponds to the middle position of the pole piece 10 by limiting the width of the third portion 20C.

[0052] Furthermore, W3 / W1 = W4 / W1, so that the second portion 20B corresponds to the middle position of the pole piece 10 .

[0053] It should be noted that W2 / W1+W3 / W1+W4 / W1=1. Optionally, W2 / W1=0.05, W3 / W1=W4 / W1=0.475, or W2 / W1=0.1, W3 / W1=W4 / W1=0.45, or W2 / W1=0.2, W3 / W1=W4 / W1=0.4, or W2 / W1=0.3, W3 / W1=W4 / W1=0.35.

[0054] Please also read Figure 1 , Figure 3 and Figure 4 In some embodiments, the support layer 21 is further provided with a second channel 214, and the second channel 214 includes a third section 214A and a fourth section 214B. The third section 214A is located in the second portion 20B and passes through the first surface 211 and the second surface 212, and the third section 214A is connected to the first through hole 221 and the second through hole 231, and the fourth section 214B passes through the second end surface 202 and is connected to the third section 214A.

[0055] When the battery cell 100A is cycled, the electrolyte near the first end face 201 diffuses to the first section 213A through the second section 213B, and then diffuses from the first section 213A to the side of the active material layer 30 near the support layer 21 through the first through hole 221 and the second through hole 231; the electrolyte near the second end face 202 diffuses to the third section 214A through the fourth section 214B, and then diffuses from the third section 214A to the side of the active material layer 30 near the support layer 21 through the first through hole 221 and the second through hole 231. The first channel 213 and the second channel 214 cooperate to further increase the speed of the electrolyte diffusing to the middle position of the electrode sheet 10, and further facilitate the electrolyte to fully infiltrate the middle position of the electrode sheet 10, reduce the probability of problems such as black spots and purple spots, and further help the battery cell 100A maintain a long cycle life.

[0056] It should be noted that the number of the first through holes 221 and the number of the second through holes 231 are respectively the sum of the number of the first channels 213 and the second channels 214 , so that each group of the first through holes 221 and the second through holes 231 is connected to a first channel 213 or a second channel 214 .

[0057] In some embodiments, the third segment 214A extends along the thickness direction X, and the fourth segment 214B extends along the width direction Z.

[0058] Please also read Figure 1 and Figure 4 In some embodiments, along the width direction Z, the projection of the third segment 214A and the projection of the first segment 213A are spaced apart along the length direction Y after the electrode 10 is unfolded, and the spacing between the projection of the third segment 214A and the projection of the adjacent first segment 213A is S0, 0.1mm≤S0≤5mm, so that the third segment 214A and the first segment 213A are dispersedly arranged in the middle position of the electrode 10, thereby facilitating the electrolyte to fully infiltrate the middle position of the electrode 10.

[0059] Optionally, S0 is 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, and any other value in the range of 0.1 mm ≤ S0 ≤ 5 mm.

[0060] Please continue reading Figure 4 In some embodiments, along the width direction Z, the projection of the fourth segment 214B and the projection of the second segment 213B are spaced apart along the length direction Y after the electrode 10 is unfolded, and the spacing between the projection of the fourth segment 214B and the projection of the adjacent second segment 213B is S1, 0.1mm≤S1≤5mm, so that the end of the fourth segment 214B and the end of the second segment 213B are dispersedly arranged in the middle position of the electrode 10, thereby facilitating the electrolyte to fully infiltrate the middle position of the electrode 10.

[0061] Optionally, S1 is 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, and any other value in the range of 0.1 mm ≤ S1 ≤ 5 mm.

[0062] It should be noted that the length direction Y of the current collector 20 is usually aligned with the coating direction of each material layer (eg, active material layer 30) during the processing of the electrode sheet 10. The length direction Y, the width direction Z, and the thickness direction X are perpendicular to each other.

[0063] Please continue reading Figure 4 In some embodiments, along the length direction Y, the projection of the third segment 214A partially overlaps or is spaced apart from the projection of the first segment 213A along the width direction Z, so that the third segment 214A and the first segment 213A are dispersedly arranged in the middle of the electrode sheet 10, thereby facilitating the electrolyte to fully infiltrate the middle of the electrode sheet 10. Specifically, when the width W2 of the second portion 20B is narrow, along the length direction Y, the projection of the third segment 214A partially overlaps with the projection of the first segment 213A along the width direction Z; when the width W2 of the second portion 20B is wide, along the length direction Y, the projection of the third segment 214A and the projection of the first segment 213A are spaced apart from each other along the width direction Z.

[0064] Please continue reading Figure 4 In some embodiments, the average pore size of the first pore 213 is D1, the average pore size of the second pore 214 is D2, and 0.6≤D1 / D2≤1.5, so that the average pore size of the first pore 213 and the average pore size of the second pore 214 can be adjusted according to the diffusion difficulty of the electrolyte.

[0065] Specifically, when the diffusion difficulty of the electrolyte at the first end face 201 is higher than that of the electrolyte at the second end face 202 (such as when the first end face 201 faces upward and the second end face 202 faces downward), 1<D1 / D2≤1.5 is defined to increase the speed at which the electrolyte at the first end face 201 diffuses to the middle of the electrode 10. When the diffusion difficulty of the electrolyte at the first end face 201 is lower than that of the electrolyte at the second end face 202 (such as when the first end face 201 faces downward and the second end face 202 faces upward), 0.6≤D1 / D2<1 is defined to increase the speed at which the electrolyte diffuses to the middle of the electrode 10. When there is no significant difference between the diffusion difficulty of the electrolyte at the first end face 201 and the diffusion difficulty of the electrolyte at the second end face 202, D1 / D2=1.

[0066] Optionally, D1 / D2 is one of 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 and any other value in the range of 0.6≤D1 / D2≤1.5.

[0067] It should be noted that the average pore size of the first channel 213 is D1, which is the average of the average pore size of the first section 213A and the average pore size of the second section 213B. The average pore size of the second channel 214 is D2, which is the average of the average pore size of the third section 214A and the average pore size of the fourth section 214B.

[0068] Please continue reading Figure 4 In some embodiments, along the length direction Y, the spacing between two adjacent first channels 213 is S2, and the spacing between two adjacent second channels 214 is S3, 0.77≤S2 / S3≤1.3, so that the spacing between two adjacent first channels 213 and the spacing between two adjacent second channels 214 can be adjusted according to the diffusion difficulty of the electrolyte, and can adapt to the position tolerance between the first channel 213 and the second channel 214.

[0069] Specifically, when the diffusion difficulty of the electrolyte at the first end surface 201 is lower than that of the electrolyte at the second end surface 202, 1<S2 / S3≤1.3. When the diffusion difficulty of the electrolyte at the first end surface 201 is higher than that of the electrolyte at the second end surface 202, 0.77≤S2 / S3<1.

[0070] Optionally, S2 / S3 is one of 0.77, 0.8, 0.9, 1, 1.1, 1.2, 1.3 and any other value in the range of 0.77≤S2 / S3≤1.3.

[0071] Please continue reading Figure 4 In some embodiments, the battery cell 100A is a winding structure. Along the length direction Y, the current collector 20 includes a fourth portion 20D, a fifth portion 20E, and a sixth portion 20F arranged in sequence. The end of the fourth portion 20D away from the fifth portion 20E is the winding starting end, and the end of the sixth portion 20F away from the fifth portion 20E is the winding ending end. The length of the current collector 20 is L1, the length of the fourth portion 20D is L2, 0.1≤L2 / L1≤0.3, the length of the fifth portion 20E is L3, 0.3≤L3 / L1≤0.6, and the length of the sixth portion 20F is L4, 0.1≤L4 / L1≤0.3.

[0072] When the battery cell 100A is circulating, the electrolyte wetting effect of the inner circle electrode of the battery cell 100A is worse than that of the outer circle electrode, that is, the electrolyte wetting effect of the fourth part 20D is worse than that of the fifth part 20E, and the electrolyte wetting effect of the fifth part 20E is worse than that of the sixth part 20F.

[0073] It should be noted that L2 / L1+L3 / L1+L4 / L1=1. Optionally, L2 / L1=0.1, L3 / L1=0.6, L4 / L1=0.3, or L2 / L1=0.2, L3 / L1=0.6, L4 / L1=0.2, or L2 / L1=0.3, L3 / L1=0.6, L4 / L1=0.1, or L2 / L1=0.2, L3 / L1=0.5, L4 / L1=0.3, or L2 / L1=0.3, L3 / L1=0.4, L4 / L1=0.3.

[0074] Please continue reading Figure 4 In some embodiments, the average pore size of the first pore 213 and the second pore 214 located in the fourth portion 20D is D3, the average pore size of the first pore 213 and the second pore 214 located in the fifth portion 20E is D4, and the average pore size of the first pore 213 and the second pore 214 located in the sixth portion 20F is D5, and D3≥D4≥D5. The average pore size of the first pore 213 and the second pore 214 of the battery cell 100A increases from the outside to the inside in a gradient manner, which is beneficial to improving the electrolyte infiltration effect of the inner ring electrode of the battery cell 100A. In addition, the average pore size of the first pore 213 and the second pore 214 of the battery cell 100A decreases from the inside to the outside in a gradient manner, which is beneficial to reducing the influence of the first pore 213 and the second pore 214 on the support layer 21 of the outer ring electrode of the battery cell 100A, and improving the tensile strength of the outer ring electrode of the battery cell 100A.

[0075] In some embodiments, the thickness of the support layer 21 is T1, 1 / 6≤D4 / T1≤1 / 2, which facilitates diffusion of the electrolyte and helps reduce the impact of the first channel 213 and the second channel 214 on the tensile strength of the support layer 21 located in the fifth portion 20E.

[0076] Optionally, D4 / T1 is one of 1 / 6, 1 / 4, 1 / 3, 5 / 12, 1 / 2 and any other value in the range of 1 / 6≤D4 / T1≤1 / 2.

[0077] In some embodiments, 0.6≤D4 / D3≤1, such that D3≥D4.

[0078] Optionally, D4 / D3 is one of 0.6, 0.7, 0.8, 0.9, 1 and any other value in the range of 0.6≤D4 / D3≤1.

[0079] In some embodiments, 0.6≤D5 / D4≤1, such that D4≥D5.

[0080] Optionally, D5 / D4 is one of 0.6, 0.7, 0.8, 0.9, 1 and any other value in the range of 0.6≤D5 / D4≤1.

[0081] It can be understood that the average aperture of the first through hole 221 and the second through hole 231 located in the fourth part 20D is D6, the average aperture of the first through hole 221 and the second through hole 231 located in the fifth part 20E is D7, and the average aperture of the first through hole 221 and the second through hole 231 located in the sixth part 20F is D8, D6≥D7≥D8, so that the first through hole 221 and the second through hole 231 are adapted to the aperture of the corresponding first channel 213 or the second channel 214.

[0082] Please continue reading Figure 4 In some embodiments, along the length direction Y, the number of the first channels 213 and the second channels 214 per unit centimeter in the fourth portion 20D is N1, 30≤N1≤100, so as to facilitate diffusion of the electrolyte in the fourth portion 20D.

[0083] Optionally, N1 is one of 30, 40, 50, 60, 70, 80, 90, 100 and any other value in the range of 30≤N1≤100.

[0084] In some embodiments, along the length direction Y, the number of the first channels 213 and the second channels 214 per unit centimeter in the fifth portion 20E is N2, 20≤N2≤80, so as to facilitate diffusion of the electrolyte in the fifth portion 20E.

[0085] Optionally, N2 is one of 20, 30, 40, 50, 60, 70, 80 and any other value in the range of 20≤N2≤80.

[0086] In some embodiments, along the length direction Y, the number of the first channels 213 and the second channels 214 per unit centimeter in the sixth portion 20F is N3, 10≤N3≤60, so as to facilitate diffusion of the electrolyte in the sixth portion 20F.

[0087] Optionally, N3 is one of 10, 20, 30, 40, 50, 60 and any other value in the range of 10≤N3≤60.

[0088] The number of the first holes 213 and the second holes 214 per centimeter of the battery cell 100A gradually increases from the inside to the outside, which is beneficial to improving the electrolyte infiltration effect of the inner ring electrode of the battery cell 100A. In addition, the number of the first holes 213 and the second holes 214 per centimeter of the battery cell 100A gradually increases and decreases from the outside to the inside, which is beneficial to reducing the impact of the first holes 213 and the second holes 214 on the support layer 21 of the outer ring electrode of the battery cell 100A, and improving the tensile strength of the outer ring electrode of the battery cell 100A.

[0089] Example 2 See also Figure 5 One embodiment of the present application further provides a battery cell 100B. The battery cell 100B is different from the battery cell 100A in that the structures of the first hole 213 and / or the second hole 214 are different.

[0090] In some embodiments, the pore size of the second section 213B gradually decreases from the first end surface 201 to the second end surface 202 to facilitate diffusion of the electrolyte from the first end surface 201 to the first section 213A.

[0091] In some embodiments, the first section 213A includes a first subsection 2131 and a second subsection 2132. The first subsection 2131 passes through the first surface 211 and is connected to the second section 213B, and the aperture of the first subsection 2131 gradually decreases from the first surface 211 to the second surface 212, so that the electrolyte can fully infiltrate the middle part of the electrode 10. The second subsection 2132 passes through the second surface 212 and is connected to the second section 213B, and the aperture of the second subsection 2132 gradually decreases from the second surface 212 to the first surface 211, so that the electrolyte can fully infiltrate the middle part of the electrode 10.

[0092] See also Figure 6 In some embodiments, the fourth segment 214B has a similar structure to the first segment 213A, and the aperture of the fourth segment 214B gradually decreases to facilitate diffusion of the electrolyte from the second end surface 202 toward the third segment 214A.

[0093] In some embodiments, the third section 214A has a similar structure to the first section 213A, and includes two tapered sub-sections to facilitate the electrolyte to fully infiltrate the middle portion of the electrode 10 .

[0094] Except for the above differences, the parameters of the battery cell 100B and the battery cell 100A are substantially the same, and reference may be made to the description of the battery cell 100A.

[0095] Example 3 See also Figure 7One embodiment of the present application further provides a battery cell 100C. The battery cell 100C is different from the battery cell 100A in that an active material layer is provided on a single surface of the current collector.

[0096] In some embodiments, the active material layer 30 is disposed on the first conductive layer 22 or the second conductive layer 23. Correspondingly, the first segment 213A is located in the second portion 20B and passes through the first surface 211 or the second surface 212, and the first segment 213A is connected to the first through hole 221 or the second through hole 231.

[0097] Optionally, the active material layer 30 is disposed on the first conductive layer 22, the first segment 213A is located in the second portion 20B and passes through the first surface 211, and the first segment 213A is connected to the first through hole 221; or the active material layer 30 is disposed on the second conductive layer 23, the first segment 213A is located in the second portion 20B and passes through the second surface 212, and the first segment 213A is connected to the second through hole 231.

[0098] Except for the above differences, the parameters of the battery cell 100C and the battery cell 100A are substantially the same, and reference may be made to the description of the battery cell 100A.

[0099] Example 4 See also Figure 8 One embodiment of the present application further provides an electronic device 200, which includes the battery cell (100A, 100B, 100C) in any of the above embodiments. Optionally, the electronic device 200 may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc.

[0100] In the above-mentioned battery cells (100A, 100B, 100C) and electronic device 200, the support layer 21 is provided with a first channel 213. The first channel 213 includes a first section 213A and a second section 213B. The first section 213A is located in the second portion 20B and passes through the first surface 211 and / or the second surface 212, and the first section 213A is connected to the first through hole 221 and / or the second through hole 231, and the second section 213B passes through the first end surface 201 and is connected to the first section 213A. When the battery cells (100A, 100B, 100C) are circulating, the electrolyte diffuses from the first end surface 201 through the second section 213B to the first section 213A, and then diffuses from the first section 213A through the first through hole 221 and / or the second through hole 231 to the side of the active material layer 30 close to the support layer 21, so as to increase the speed of the electrolyte diffusing to the middle position of the electrode sheet 10, and facilitate the electrolyte to fully infiltrate the middle position of the electrode sheet 10, reduce the probability of problems such as black spots and purple spots, and help the battery cells (100A, 100B, 100C) maintain a long cycle life.

[0101] The specific implementation of the battery cells in the embodiments and comparative examples are described below.

[0102] Battery cycle test: Charge the battery to 4.25V at 0.5C constant current at 25℃, charge to 0.05C cut-off at 4.25V constant voltage, let stand for 10min, discharge to 2.0V at 1.0C constant current, let stand for 15min. The above is one cycle. Cycle 500 times in the above way, calculate the capacity retention rate of the battery, disassemble the battery, and observe whether there are black or purple spots on the electrode. Embodiment 1: A battery cell with a rated capacity of 5000mAh, the assembly process is as follows: (1) Preparation of negative electrode sheet: Mix the negative electrode active material graphite, silicon-based material, adhesive and conductive carbon in a weight ratio of 74:20:5:1, add deionized water as a solvent, prepare a slurry with a weight percentage of 50wt%, and stir evenly. Pre-set the first channel on the support layer of the composite current collector of the negative electrode sheet, and stick foam glue on part of the surface of the conductive layer of the composite current collector (the conductive layer is made of copper foil), and then evenly coat the slurry on one surface of the copper foil, heat to make the foam glue fall off so that part of the surface of the copper foil is exposed, and then dry at 110°C to obtain a negative electrode sheet with a negative electrode active material layer coated on one side. The coating weight of the negative electrode active material layer is 8kg / cm 2 , compacted density is 1.6g / cm 3 When preparing a double-sided coated negative electrode sheet, the above steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. The copper foil is then roll-welded with the conductive layer of the composite current collector, and the copper foil is die-cut to obtain a plurality of first tabs.

[0103] (2) Preparation of positive electrode sheet: Mix the positive electrode active materials lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, add N-methylpyrrolidone (NMP) as a solvent, prepare a slurry with a solid content of 75wt%, and stir evenly. The slurry is evenly coated on one surface of the aluminum foil, and then dried at 90°C to obtain a positive electrode sheet coated with a positive electrode active material layer on one side. The coating weight of the positive electrode active material layer is 13kg / cm 2 , compacted density is 3.5g / cm 3 When preparing a double-sided coated positive electrode sheet, repeat the above coating steps on the other surface of the aluminum foil. Then, die-cut the second tab in the blank area at the edge of the aluminum foil.

[0104] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were first mixed in a mass ratio of EC:EMC:DEC:EMC = 20:30:40:10 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) was added to the basic organic solvent to dissolve and mix well to obtain an electrolyte.

[0105] (4) Preparation of isolation membrane: A 7 μm thick polyethylene porous polymer film was used as the isolation membrane.

[0106] (5) Preparation of electrode assembly: winding the positive electrode sheet, separator and negative electrode sheet.

[0107] (6) Electrode assembly: Place the aluminum-plastic film with the holes punched in the assembly fixture, with the holes facing upward, place the electrode assembly in the holes, and apply external force to press it. Then, cover the electrode assembly with another aluminum-plastic film with the holes punched in the holes facing downward, and heat-seal the two aluminum-plastic films around the edges by hot pressing to obtain an assembled electrode assembly.

[0108] (7) Liquid injection packaging: The assembled electrode assembly is injected with electrolyte, with an injection volume of 9g. After vacuum packaging, static standing, hot pressing, shaping and other processes, the battery cell is obtained.

[0109] Comparative Example 1: The current collector of the battery cell is a metal current collector. It should be noted that, except for the different structure of the current collector, other parameters of Comparative Example 1 are the same as those of Example 1.

[0110] Comparative Example 2: The current collector of the battery cell is a composite current collector without pores. It should be noted that, except for the different structure of the current collector, other parameters of Comparative Example 2 are the same as those of Example 1.

[0111] It can be seen from Comparative Examples 1-2 and Example 1 that the support layer is provided with the first channel, which is beneficial to reducing the probability of black spots or purple spots appearing on the electrode after multiple cycles, and can reduce capacity loss.

[0112] The above description is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the disclosure scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises a pole piece, and the pole piece comprises a current collector and an active material layer; The current collector comprises a support layer, a first conductive layer and a second conductive layer. Along the thickness direction of the electrode sheet, the support layer comprises a first surface and a second surface arranged opposite to each other. The first conductive layer is arranged on the first surface, the second conductive layer is arranged on the second surface, and the active material layer is arranged on the first conductive layer and / or the second conductive layer. Along the width direction of the pole piece after unfolding, the current collector comprises a first portion, a second portion and a third portion arranged in sequence, and a first end surface is provided on a side of the first portion away from the second portion; Along the thickness direction, a first through hole is provided at a position of the first conductive layer opposite to the second portion, and a second through hole is provided at a position of the second conductive layer opposite to the second portion; Among them, the supporting layer is provided with a first channel, the first channel includes a first section and a second section, the first section is located in the second part and passes through the first surface and / or the second surface, and the first section is connected to the first through hole and / or the second through hole, and the second section passes through the first end surface and is connected to the first section.

2. The battery cell according to claim 1, characterized in that: Along the width direction, the width of the current collector is W1, the width of the second portion is W2, and 0.05≤W2 / W1≤0.

3.

3. The battery cell according to claim 2, characterized in that: Along the width direction, the width of the first portion is W3, 0.35≤W3 / W1≤0.55; and / or the width of the third portion is W4, 0.35≤W4 / W1≤0.

55.

4. The battery cell according to any one of claims 1 to 3, characterized in that: Along the width direction, a second end surface is provided on a side of the third portion away from the second portion; The supporting layer is also provided with a second channel, the second channel includes a third section and a fourth section, the third section is located in the second part and passes through the first surface and / or the second surface, and the third section is connected to the first through hole and / or the second through hole, and the fourth section passes through the second end surface and is connected to the third section.

5. The battery cell according to claim 4, characterized in that: Along the width direction, the projection of the third segment and the projection of the first segment are spaced apart along the length direction of the unfolded pole piece, and the spacing between the projection of the third segment and the adjacent projection of the first segment is S1, 0.1mm≤S0≤5mm; and / or, Along the width direction, the projection of the fourth segment and the projection of the second segment are spaced apart along the length direction of the unfolded pole piece, and the spacing between the projection of the fourth segment and the adjacent projection of the second segment is S0, 0.1mm≤S1≤5mm.

6. The battery cell according to claim 4 or 5, characterized in that: The average pore size of the first channel is D1, the average pore size of the second channel is D2, and 0.6≤D1 / D2≤1.

5.

7. The battery cell according to claim 4 or 5, characterized in that: Along the length direction of the pole piece after unfolding, the spacing between two adjacent first holes is S2, the spacing between two adjacent second holes is S3, and 0.77≤S2 / S3≤1.

3.

8. The battery cell according to any one of claims 4 to 7, characterized in that: Along the length direction of the unfolded pole piece, the current collector includes a fourth portion, a fifth portion and a sixth portion arranged in sequence, an end of the fourth portion away from the fifth portion is a winding start end, an end of the sixth portion away from the fifth portion is a winding end end, the length of the current collector is L1, the length of the fourth portion is L2, 0.1≤L2 / L1≤0.3, the length of the fifth portion is L3, 0.3≤L3 / L1≤0.6, and the length of the sixth portion is L4, 0.1≤L4 / L1≤0.3; The average pore size of the first channel and the second channel located in the fourth part is D3, the average pore size of the first channel and the second channel located in the fifth part is D4, and the average pore size of the first channel and the second channel located in the sixth part is D5, D3≥D4≥D5.

9. The battery cell according to claim 8, characterized in that: The thickness of the support layer is T1, 1 / 6≤D4 / T1≤1 / 2, 0.6≤D4 / D3≤1, 0.6≤D5 / D4≤1.

10. The battery cell according to claim 8, characterized in that: Along the length direction, the number of the first holes and the second holes per unit centimeter in the fourth portion is N1, 30≤N1≤100; and / or, Along the length direction, the number of the first holes and the second holes per unit centimeter in the fifth portion is N2, 20≤N2≤80; and / or, Along the length direction, the number of the first holes and the second holes per unit centimeter in the sixth portion is N3, 10≤N3≤60.

11. The battery cell according to claim 1, characterized in that: The aperture of the second section gradually decreases from the first end surface to the second end surface.

12. The battery cell according to claim 1, characterized in that: The first section includes a first sub-section and a second sub-section, the first sub-section passes through the first surface and is connected to the second section, the aperture of the first sub-section gradually decreases from the first surface to the second surface, the second sub-section passes through the second surface and is connected to the second section, and the aperture of the second sub-section gradually decreases from the second surface to the first surface.

13. An electronic device, characterized in that: The electronic device comprises the battery cell as claimed in any one of claims 1 to 12.

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