Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device. The electrochemical device includes an electric core (10) formed by winding a first electrode sheet (100), a separator (200) and a second electrode sheet (300). The first electrode sheet (100) includes: a current collector (110), a tab (120) and an active material layer (130). The current collector (110) includes a first surface (111) facing the inside of the electric core (10) and a second surface (112) facing away from the inside of the electric core (10); the tab (120) is electrically connected to the current collector (110) and extends out of the current collector (110); the active material layer (130) is disposed on the first surface (111) and the second surface (112) of the current collector (110); wherein, the winding starting end of the first electrode sheet (100) is set as a single-sided area (101), an insulating coating (140) is disposed on the first surface (111) of the current collector (110) located in the single-sided area (101), and the active material layer (130) is disposed on the second surface (112) of the current collector (110) located in the single-sided area (101).

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of batteries, and in particular, to an electrochemical device and an electronic device. Background Art

[0002] As Figure 1 shown, currently, a wound-type battery cell is usually formed by winding and laminating an anode electrode sheet 11, a separator 12, and a cathode electrode sheet 13. The winding starting end 16 of the anode electrode sheet 11 has an empty foil area 17 and a single-sided area 18. Active material layers 15 are not provided on both surfaces of the current collector 14 in the empty foil area 17, and the active material layer 15 is not provided on the surface of the current collector 14 facing the inside of the battery cell in the single-sided area 18, while the active material layer 15 is provided on the other surface facing the anode electrode sheet 13. Since the single-sided area of the anode electrode sheet 12 has an active material layer 15 only on one side, wrinkles are likely to occur during winding. In order to reduce wrinkles, the common practice in the industry is to extend the length of the empty foil area of the anode electrode sheet or to provide reinforcing ribs in the empty foil area. However, neither of the above solutions can well solve the problem of wrinkles at the winding starting end of the anode electrode sheet during winding. In addition, Figure 1 in the process of preparing the electrode sheet of the battery cell shown, problems of battery cells A and B occur due to the existence of the single-sided area and the empty foil area, resulting in low production efficiency. Summary of the Invention

[0003] In view of the above problems, the embodiments of the present application provide an electrochemical device and an electronic device applying the electrochemical device that can preferably solve the problem of wrinkles easily occurring at the winding starting end of the electrode sheet.

[0004] According to one aspect of the present application, the present application provides an electrochemical device, including a battery cell formed by winding a first electrode sheet, a separator, and a second electrode sheet. The first electrode sheet includes a current collector, including a first surface facing the inside of the battery cell and a second surface facing away from the inside of the battery cell; a tab, electrically connected to the current collector and extending out of the current collector; an active material layer, provided on the first surface and the second surface of the current collector; wherein, the winding starting end of the first electrode sheet is set as a single-sided area, an insulating coating is provided on the first surface of the current collector in the single-sided area, and an active material layer is provided on the second surface of the current collector in the single-sided area.

[0005] By setting the winding starting end of the electrode sheet as a single-sided area and providing an insulating coating in the single-sided area, on the one hand, the curling force of the single-sided area during winding of the battery cell is offset by the insulating coating, thereby improving the cold pressing wrinkles of the single-sided area; on the other hand, compared with the prior art, the empty foil area is omitted, saving foil material and improving the energy density. And, due to the setting of this single-sided area, there are no problems of battery cells A and B during the production of the battery cell, and the production efficiency is greatly improved.

[0006] In some embodiments of the present application, along the winding direction of the first electrode tab, the insulating coating is adjacent to or partially overlaps with the active material layer. In this way, the current collector at the junction of the insulating coating and the active material layer can be prevented from being exposed, so as to ensure the coverage of the insulating coating on the current collector and improve the safety performance of the electrode tab.

[0007] In some embodiments of the present application, the thickness of the insulating coating is 1 to 100 μm, and the thickness of the active material layer is 25 to 150 μm.

[0008] In some embodiments of the present application, the thickness of the insulating coating is less than or equal to the thickness of the active material layer. In this way, the thickness of the insulating coating will not significantly affect the overall thickness of the electrode tab, and thus will not have an adverse impact on the energy density of the electrochemical device.

[0009] In some embodiments of the present application, the insulating coating is provided on a part of the first surface of the single-sided area, or the insulating coating is provided on the entire first surface of the single-sided area. In this way, while ensuring the improvement of the wrinkles in the single-sided area, the use of the insulating coating is reduced, and materials are saved.

[0010] In some embodiments of the present application, the insulating coating is distributed in a striped or island-like pattern on the first surface of the single-sided area.

[0011] In some embodiments of the present application, the insulating coating includes inorganic particles and a binder. The inorganic particles include at least one of alumina, zinc oxide, calcium oxide, silicon oxide, zirconium oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, yttrium oxide, silicon carbide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, and boehmite; the binder includes at least one of a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, polyphenylacetylene, sodium polyacrylate, potassium polyacrylate, polymethyl methacrylate, polyethylene, polypropylene, or polytetrafluoroethylene.

[0012] In some embodiments of the present application, the first electrode tab is an anode electrode tab.

[0013] In some embodiments of the present application, the thickness of the current collector is 4 to 6 μm. In this way, when the wrinkles in the single-sided area are improved, a thinner current collector can be selected to improve the energy density of the electrochemical device.

[0014] In some embodiments of the present application, along the width direction of the first electrode tab, the insulating coating covers up to the width edge of the first electrode tab. Along the length direction of the first electrode tab, a blank current collector is provided between the insulating coating and the active material layer, and / or the insulating coating to the length edge of the first electrode tab is provided as a blank current collector. By setting it in this way, while the insulating coating can already improve the wrinkling situation, the use of the insulating coating can be reduced, materials can be saved, and at the same time, the weight of the battery cell will not be excessively increased, and the energy density per unit weight of the battery cell can be improved.

[0015] In some embodiments of the present application, along the length direction of the first electrode tab, the insulating coating covers up to the length edge of the first electrode tab. Along the width direction of the first electrode tab, the insulating coating to the width edge of the first electrode tab is provided as a blank current collector. By setting it in this way, while the insulating coating can already improve the wrinkling situation, the use of the insulating coating can be reduced, materials can be saved, and at the same time, the weight of the battery cell will not be excessively increased, and the energy density per unit weight of the battery cell can be improved.

[0016] According to another aspect of the present application, the present application further provides an electronic device, including the above-mentioned electrochemical device, and the electrochemical device is used to supply power to the electronic device.

[0017] In the electrochemical device provided by the present application, by setting the winding starting end of the electrode tab as a single-sided area and providing an insulating coating in the single-sided area, on the one hand, the curling force of the single-sided area during winding of the battery cell is offset by the insulating coating, thereby improving the cold pressing wrinkles of the single-sided area; on the other hand, compared with the prior art, the empty foil area is omitted, the foil material is saved, and the energy density is improved. And because of the setting of this single-sided area, there is no problem of A and B battery cells during the production of the battery cell, and the production efficiency is greatly improved. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts do not necessarily draw according to the actual scale.

[0019] Figure 1 It is a schematic structural diagram of a traditional electrochemical device;

[0020] Figure 2 It is a schematic structural diagram of an embodiment of the electrochemical device of the present application;

[0021] Figure 3 It is a schematic structural diagram of an embodiment of the first electrode tab of the electrochemical device of the present application;

[0022] Figure 4 For Figure 3Side view of the first electrode sheet of the electrochemical device shown;

[0023] Figure 5 It is a side view of an embodiment of the first electrode sheet of the electrochemical device of the present application;

[0024] Figures 6 to 12 They are respectively schematic structural diagrams of different embodiments of the first electrode sheet of the present application;

[0025] Figures 13 to 16 They are respectively schematic structural diagrams of the production process of the first electrode sheet in Example 1;

[0026] Figures 17 to 18 They are respectively schematic structural diagrams of the production process of the first electrode sheet in Comparative Example 1. Specific embodiments

[0027] To facilitate the understanding of the present application, the present application will be described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is expressed as "fixed to" another element, it can be directly on the other element, or there can be one or more intermediate elements therebetween. When an element is expressed as "connected to" another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this specification are only for the purpose of illustration.

[0028] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in this specification in the description of the present application are only for the purpose of describing specific embodiments and are not used to limit the present application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0029] As Figure 2 shown, it is a schematic structural diagram of an embodiment of the electrochemical device of the present application.

[0030] The electrochemical device includes a wound battery cell 10 and a housing (not shown), and the wound battery cell is accommodated in the housing. The wound battery cell 10 is formed by winding a first electrode sheet 100, a separator 200, and a second electrode sheet 300 which are stacked, wherein the separator 200 is disposed between the first electrode sheet 100 and the second electrode sheet 300, and the polarities of the first electrode sheet 100 and the second electrode sheet 300 are different. Among them, the first electrode sheet 100 includes a current collector 110, a tab 120 electrically connected to the current collector 110 and extending out of the current collector, and an active material layer 130 disposed on the surface of the current collector. The current collector 110 has a first surface 111 facing the inside of the battery cell and a second surface 112 facing away from the inside of the battery cell, and the active material layer 130 is disposed on the first surface 111 and the second surface 112 of the current collector 110.

[0031] As Figure 3 , Figure 4 shown, a single-sided area 101 is provided at the winding start end of the first electrode sheet 100. An insulating coating 140 is provided on the first surface 111 of the current collector 110 located in the single-sided area 101, and an active material layer 130 is provided on the second surface 112 of the current collector 110 located in the single-sided area 101. It can also be understood that only one side of the current collector 110 located in the single-sided area 101 is provided with the active material layer 130, and the other side is provided with the insulating coating 140. It should be understood that the winding start end refers to the end where the electrode sheet starts to wind when forming the wound battery cell, which is a relative concept to the winding end. The winding end refers to the end where the electrode sheet ends winding when forming the wound battery cell.

[0032] By providing the winding start end of the first electrode sheet 100 as the single-sided area 101 and providing the insulating coating 140 in the single-sided area 101, on the one hand, the curling force of the single-sided area 101 during winding of the battery cell is offset by the insulating coating 140, thereby improving the cold pressing wrinkles of the single-sided area 101; on the other hand, the empty foil area (referring to the two sides of the current collector 110 where the active material layer is not coated) is eliminated, saving foil material and reducing the thickness occupied by the empty foil area, and improving the energy density. In addition, the presence of the insulating coating 140 will increase the contact impedance of the electrode sheet when a short circuit occurs inside the battery cell, thereby reducing the discharge power and the probability of thermal runaway when the battery cell is short-circuited, and improving the safety performance of the battery cell. Moreover, in the present application, one side of the current collector 110 is continuously coated, and it is not necessary to distinguish between A and B battery cells during electrode sheet winding, thus greatly improving the production efficiency.

[0033] In some embodiments of the present application, as Figure 3 , Figure 4As shown, in the winding direction of the first electrode sheet 100 (direction x in the figure), the insulating coating 140 is adjacently arranged to the active material layer 130, that is, the insulating coating 140 and the active material layer 130 do not overlap in the thickness direction of the electrode sheet and are not spaced in the winding direction of the electrode sheet. In this way, it is possible to prevent the contact area between the active material layer 130 and the insulating coating 140 from being too thick, which affects the local thickness of the first electrode sheet 100, thereby having an adverse impact on the flatness of the battery cell 10.

[0034] In some embodiments of the present application, as Figure 5 shown, in the winding direction of the first electrode sheet 100, the insulating coating 140 may also be partially overlapped with the active material layer 130. In the overlapping area, the active material layer 130 is arranged on the first surface 111 of the current collector 110, and the insulating coating 140 is laminated on the active material layer 130 to cover part of the active material layer 130. In this way, it is possible to prevent the current collector 110 at the junction of the insulating coating 140 and the active material layer 130 from being exposed, so as to ensure the coverage of the insulating coating 140 on the current collector 110 and improve the safety performance of the electrode sheet.

[0035] In some embodiments of the present application, as Figure 3 、 Figure 4 shown, the insulating coating 140 is arranged on the entire first surface 111 of the current collector 110 located in the single-sided area 101, that is, in the single-sided area 101, the insulating coating 140 completely covers the first surface 111 of the current collector 110 in the length direction and width direction of the first electrode sheet 100, and no blank current collector 110 is exposed.

[0036] In some embodiments of the present application, as Figures 6 - 12 shown, the insulating coating 140 may also be arranged only on a part of the first surface 111 of the current collector 110 located in the single-sided area 101, that is, in the single-sided area 101, the first surface 111 is partially covered by the insulating coating 140. In this way, while the insulating coating 140 can already improve the wrinkling situation, the use of the insulating coating 140 can be reduced, materials can be saved, and at the same time, the weight of the battery cell will not be increased excessively, and the energy density per unit weight of the battery cell can be improved.

[0037] In some embodiments, the coverage of the insulating coating 140 is 50% to 99.9%. For example, in some embodiments, the coverage of the insulating coating 140 is 65% to 95%; in some embodiments, the coverage of the insulating coating 140 is 75% to 85%; in some embodiments, the coverage of the insulating coating 140 is 50%, 60%, 70%, 80%, 90%, or within the range formed by any two of the above values. Within the above coverage, the insulating coating 140 can improve the wrinkling condition of the single-sided region 101 and also reduce the possibility of short circuit. Below the above coverage, the improvement of the wrinkling condition of the single-sided region 101 is not obvious, or the possibility of short circuit still exists.

[0038] Among them, the coverage represents the coating degree of the coating on the coated surface, which is the percentage of the total coated area of the area to be coated minus the area of the exposed area to be coated layer in the coating layer to the total coated area. For example, a coverage of 100% means that the coating completely covers the entire area of the coated surface. A coverage of 60% means that the coating only covers 60% of the coated surface area, and the other 40% of the coated surface area is in an exposed state.

[0039] In the first surface 111 of the part of the current collector 110 in the single-sided region 101 where the above-mentioned insulating coating 140 is provided, the present application provides various embodiments.

[0040] In one embodiment, as Figure 6As shown, along the width direction of the first electrode tab 100 (i.e., the direction in which the tab 120 extends from the current collector 110, direction y in the figure), the insulating coating 140 covers up to the width edge of the first electrode tab. Along the length direction of the first electrode tab 100 (i.e., the winding direction of the electrode tab, direction x in the figure), between the insulating coating 140 and the active material layer 130, and from the insulating coating 140 to the length edge of the first electrode tab 100 (the edge perpendicular to the length direction), a part of the blank current collector 110 is exposed. Specifically, along the length direction, the distance between the corresponding edges of the insulating coating 140 and the active material layer 130 is the first distance d1, and the distance between the insulating coating 140 and the length edge is the second distance d2. Both the first distance d1 and the second distance d2 are between 0 and 10 mm, and at least one of them is not 0. For example, the first distance d1 is 0, 1 mm, 3 mm, 5 mm, 7 mm, 9 mm, or within the range formed by any two of the above values. Another example is that the second distance d2 is 0, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, or within the range formed by any two of the above values. It should be understood that the specific values of the first distance d1 and the second distance d2 can be set independently, and d1 and d2 can be set to be equal or unequal. In some embodiments, the first distance d1 is selected to be 0, that is, the insulating coating 140 and the active material layer 130 are adjacent in the length direction of the first electrode tab 100. In this way, the insulating coating 140 and the active material layer 130 do not overlap in the thickness direction of the electrode tab and there is no gap in the length direction of the electrode tab, so that the thickness of the electrode tab is not increased and the blank current collector is not exposed, which will not have an adverse impact on the energy density and safety.

[0041] In one embodiment, as Figure 7 shown, along the length direction of the first electrode tab 100 (direction x in the figure), the insulating coating 140 and the active material layer 130 are adjacent or partially overlapped, and the insulating coating 140 covers up to the length edge of the first electrode tab 100, that is, no blank current collector is exposed at the winding starting end of the first electrode tab 100; along the width direction of the first electrode tab 100 (direction y in the figure), the insulating coating 140 does not cover up to the width edge of the first electrode tab 100 (the edge perpendicular to the width direction), that is, the width edge of the first electrode tab 100 exposes the blank current collector 110. As Figure 7As shown, on one side where the electrode tab extends beyond the tab 120, the distance between the edge of the insulating coating 140 and the edge of the electrode tab is the third distance d3. On the other side of the electrode tab, the distance between the edge of the insulating coating 140 and the edge of the electrode tab is the fourth distance d4. Both the third distance d3 and the fourth distance d4 are between 0 and 10 mm, and at least one of them is not 0. For example, the third distance d3 is 0, 1 mm, 3 mm, 5 mm, 7 mm, 9 mm, or within the range formed by any two of the above values. Again, for example, the fourth distance d4 is 0, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, or within the range formed by any two of the above values. It should be understood that the specific values of the third distance d3 and the fourth distance d4 can be set independently, and d3 and d4 can be set to be equal or unequal. In some embodiments, the third distance d3 is selected to be 0, that is, the insulating coating 140 completely covers the edge on the side where the electrode tab extends beyond the tab 120. In this way, on the wound battery cell, the head of the battery cell (i.e., the side where the tab 120 extends) will not become thinner due to the presence of the blank current collector 110 at the edge of the electrode tab, which affects the encapsulation.

[0042] In some other embodiments, such as Figure 8 As shown, along the length direction (direction x in the figure) and the width direction (direction y in the figure) of the first electrode tab 100, the insulating coating 140 does not completely cover the first surface 111 of the current collector 110 in the single-sided region 101, that is, there is a gap between the insulating coating 140 and the active material layer 130, exposing the blank current collector 110. The length edges and the width edges on both sides of the first electrode tab 100 expose the blank current collector 110 because the insulating coating 140 is not covered. Its coverage area and coverage region are similar to those in the above embodiments, and will not be repeated here.

[0043] In some embodiments of the present application, the insulating coating 140 can be set on the first surface 111 in different shapes through different coating processes. Such as Figures 9 to 11 In the shown embodiment, the insulating coating 140 is distributed in a strip shape on the first surface 111. Among them, the distance between adjacent two strips can be designed according to the coverage. In some embodiments, the distance between adjacent two strips is 1 - 3 mm. In this way, it can prevent the exposed area of the blank current collector 110 from being too large and affecting the safety performance of the electrode tab. In some other embodiments, such as Figure 12 In the shown embodiment, the insulating coating 140 is distributed in an island shape on the first surface 111, that is, the insulating coating 140 is distributed in non - continuous regions on the first surface 111. On a plane, each region presents as a regular circle, triangle, polygon, etc., and each region can also present as an irregular figure, such as a region surrounded by irregular curves.

[0044] In some embodiments of the present application, the thickness of the insulating coating is 1 to 100 μm; for example, in some embodiments, the thickness of the insulating coating is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or within the range formed by any two of the above values. The thickness of the active material layer is 25 to 150 μm; for example, in some embodiments, the thickness of the insulating coating is 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, or within the range formed by any two of the above values.

[0045] In some embodiments, the thickness of the insulating coating is less than or equal to the thickness of the active material layer. In this way, the thickness of the insulating coating will not significantly affect the overall thickness of the first electrode sheet, and thus will not have an adverse effect on the energy density of the electrochemical device. Preferably, the thickness of the insulating coating is less than the thickness of the active material layer. In this way, the thickness of the starting end of the winding of the first electrode sheet can be reduced, thereby increasing the energy density of the electrochemical device.

[0046] For the above-mentioned thicknesses of the insulating coating and the active material layer, the following test method can be used: Cut a 100 mm long electrode sheet sample, and use a micrometer to measure the thickness values of the electrode sheet at 10 different positions respectively, and take the average value as the thickness value of the electrode sheet. Among them, the thickness value of the electrode sheet with the active material layer coated on both sides is measured as D1, and the thickness value of the electrode sheet with the active material layer coated on one side and the insulating coating coated on the other side is D2. Then the thickness of the active material layer Da = (D1 - D) / 2, and the thickness of the insulating coating Di = D2 - Da - D, where D refers to the thickness of the current collector.

[0047] In some embodiments of the present application, the thickness of the current collector of the first electrode sheet is 4 to 10 μm. Preferably, in some embodiments of the present application, the thickness of the current collector of the first electrode sheet is 4 to 6 μm. Because an insulating coating is provided in the single-sided area at the starting end of the winding, the curling force in the single-sided area of the first electrode sheet during the winding process can be offset. Therefore, even if the thickness of the current collector is thinner than that of the current collector of the traditional battery cell, the present application can improve the cold pressing wrinkles in the single-sided area, while the thickness of the current collector of the traditional battery cell, such as the anode copper foil, usually needs to be designed to be 8 to 10 μm. Further, the thinner current collector can save more battery cell space, thereby increasing the energy density of the battery cell.

[0048] In some embodiments of the present application, the composition of the insulating coating includes inorganic particles and a binder. Among them, based on the total weight of the insulating coating, the mass content of the inorganic particles is 70% to 99.7%. For example, the mass content of the inorganic particles is 75%, 80%, 85%, 90%, 95%, or within the range formed by any two of the above values. Based on the total weight of the insulating coating, the binder content is 0.3% to 30%. For example, the mass content of the binder is 0.5%, 0.7%, 1%, 5%, 10%, 15%, 20%, 25%, or within the range formed by any two of the above values. The inorganic particles and the binder within the above mass content ranges can ensure that the insulating coating has good adhesion on the surface of the current collector, is not easily detached during the winding process of the electrode sheet, and is not easily detached in the battery cell to affect the safety performance.

[0049] In some embodiments of the present application, the insulating coating further includes a thickener. Based on the total weight of the insulating coating, the mass content of the thickener is 0.3% to 20%. For example, the thickener content is 0.5%, 0.7%, 1%, 5%, 10%, 15%, or within the range formed by any two of the above values. The thickener can improve the viscosity of the insulating coating in the slurry state, which is beneficial to coating the insulating coating slurry on the current collector.

[0050] In some embodiments of the present application, the inorganic particles include at least one of alumina, zinc oxide, calcium oxide, silicon oxide, zirconium oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, yttrium oxide, silicon carbide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, and boehmite.

[0051] In some embodiments of the present application, the binder includes at least one of a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, polyphenylacetylene, sodium polyacrylate, potassium polyacrylate, polymethyl methacrylate, polyethylene, polypropylene, or polytetrafluoroethylene.

[0052] In some embodiments of the present application, the thickener includes at least one of carboxymethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose.

[0053] In some embodiments of the present application, the first electrode sheet is an anode electrode sheet. Correspondingly, the second electrode sheet is a cathode electrode sheet. In this way, the cathode electrode sheet can be arranged at the outermost layer of the battery cell for termination, because the electrochemical corrosion between the aluminum foil of the cathode current collector and the aluminum-plastic film of the packaging bag is relatively small, which can improve the safety of the electrochemical device. In some other embodiments of the present application, the first electrode sheet is a cathode electrode sheet, and correspondingly, the second electrode sheet is an anode electrode sheet.

[0054] In some embodiments of the present application, the anode electrode sheet generally includes an anode current collector and an anode active material layer. Among them, the anode current collector can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector. The anode active material layer includes a cathode active material, a conductive agent and a binder. There is no particular limitation on the type of the anode active material, as long as the purpose of the present application can be achieved. For example, it can include at least one of natural graphite, artificial graphite, mesophase microcarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiOx (0 < x < 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate Li4Ti5O12 with spinel structure, Li-Al alloy and metallic lithium, etc. The conductive material can include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (such as metal powder, metal fiber, etc., including for example copper, nickel, aluminum, silver, etc.), conductive polymers (such as polyphenylene derivatives) and mixtures thereof. The binder can include at least one of polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, alginic acid, sodium alginate. In the present application, there is no particular limitation on the thickness of the anode current collector and the anode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the anode current collector is 4 μm to 10 μm, and the thickness of the anode active material layer is 20 μm to 150 μm.

[0055] In some embodiments of the present application, the cathode electrode sheet includes a cathode current collector and a cathode active material layer. Among them, the cathode current collector can include aluminum foil, aluminum alloy foil or composite current collector, etc. The cathode active material layer includes a cathode active material. For example, it can include at least one of lithium nickel cobalt manganese oxide (811, 622, 523, 111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate or lithium titanate, etc. In the present application, there is no particular limitation on the thickness of the cathode current collector and the cathode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the cathode current collector is 4 μm to 20 μm, and the thickness of the cathode material layer is 20 μm to 150 μm.

[0056] In some embodiments of the present application, the cathode electrode sheet or the anode electrode sheet is provided with tabs by die-cutting. The cathode tab material includes at least one of aluminum (Al) or aluminum alloy, and the anode tab material includes at least one of nickel (Ni), copper (Cu) or nickel-plated copper (Ni-Cu). In other embodiments, the anode tab and the cathode tab are welded to the blank current collector.

[0057] In some embodiments of the present application, the separator is used to separate the first electrode and the second electrode to prevent them from contacting each other, thereby avoiding internal short circuit of the battery cell. The separator can be wetted by the electrolyte to allow charged ions to pass through, forming an electric circuit. Specifically, the separator includes a substrate and an adhesive layer disposed on the surface of the substrate. The adhesive layer can be wetted by the electrolyte and bond the separator to the cathode or anode electrode, suppressing the volume expansion of the battery cell during charge and discharge cycles.

[0058] In some embodiments of the present application, the substrate of the separator can be selected from at least one of polyolefin (PO) membranes mainly composed of polyethylene (PE) and polypropylene (PP), polyester membranes (such as polyethylene terephthalate (PET) membranes), cellulose membranes, polyimide membranes (PI), polyamide membranes (PA), spandex or aramid membranes, woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, separator papers, rolled membranes, spun membranes, etc. In some embodiments, the material of the substrate of the separator is selected as polypropylene, which has a good effect on preventing short circuits, can improve the stability of the battery through the shut-off effect, and polypropylene usually has good affinity with high molecular polymers, which is beneficial to improving the bonding effect between the substrate and the adhesive layer.

[0059] In some embodiments of the present application, the adhesive layer disposed on the substrate includes a polymer and ceramic particles. The polymer is selected from at least one of polyvinylidene fluoride, copolymers of vinylidene fluoride and hexafluoropropylene, styrene-butadiene polymers, polyamides, polyacrylonitriles, polyethylene oxides, polyacrylates, polyacrylic acids, polyacrylates, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ethers, polymethacrylates, polytetrafluoroethylene, and polyhexafluoropropylene. The above polymers have high adhesiveness, and there are certain pores between the polymer particles. Therefore, it is beneficial for the separator to bond to the electrode, and at the same time, it can ensure the ion passing rate of the separator. The ceramic particles are selected from at least one of silicon dioxide, aluminum oxide, magnesium oxide, titanium dioxide, zirconium dioxide, zinc oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The ceramic particles in the adhesive layer can support the pores and maintain the pores from being damaged, thereby reducing the probability of compression pore blocking and swelling pore blocking of the separator, enabling the battery cell to have higher ionic conductivity, greatly improving the rate performance and cycle performance of the battery cell. At the same time, the ceramic particles can also increase the heat resistance of the separator and improve the safety of the battery cell. In some embodiments of the present application, the inorganic particles of the insulating coating and the ceramic particles of the adhesive layer are independently provided, and the types, amounts, particle sizes, etc. of the inorganic particles and ceramic particles can be the same or different.

[0060] The electrochemical device of the present application further includes an electrolyte, and both the electrolyte and the battery cell are accommodated within a housing. Among them, the electrolyte may be at least one of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent. In some embodiments of the present application, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, or lithium difluoroborate, etc. For example, LiPF6 may be selected as the lithium salt because it can provide high ionic conductivity and improve the cycling characteristics. The non-aqueous solvent may be at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvents, etc. The carbonate compound may be at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluorinated carbonate compound, etc. The chain carbonate compound may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC), etc. The cyclic carbonate compound may include at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylene carbonate (VEC), etc. The fluorinated carbonate compound may include at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethyl ethylene carbonate, etc. The carboxylate compound may include at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, or caprolactone, etc. The ether compound may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran, etc. The above other organic solvents may include at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate ester, etc.

[0061] In some embodiments of the present application, the housing includes at least one of an aluminum-plastic film, an aluminum shell, a steel shell, and a plastic shell. The present application places no special restrictions on the housing, as long as the purpose of the present application can be achieved.

[0062] The following further elaborates on the present application in conjunction with specific embodiments. It should be understood that the embodiments are only used to illustrate the present application and not to limit the scope of the present application.

[0063] Example 1 Preparation of the first electrode

[0064] Prepare the anode active material layer slurry and the insulating coating slurry. Among them, artificial graphite as the anode active material, styrene-butadiene rubber as the binder, and carboxymethyl cellulose as the thickener are mixed in a mass ratio of 96:3:1 and stirred evenly to obtain the anode active material layer slurry; alumina particles as inorganic particles, styrene-butadiene rubber as the binder, and carboxymethyl cellulose as the thickener are mixed in a weight ratio of 85:10:5 and stirred evenly to obtain the insulating coating slurry.

[0065] As Figure 13 shown, continuously coat the active material layer slurry on the second surface of a copper foil 20 with a thickness of 5 μm. After coating the second surface of the copper foil, as Figure 14 shown, intermittently coat the active material layer slurry on the first surface of the copper foil 20 to expose the blank current collector 101, and intermittently coat the insulating coating slurry on the blank current collector 101, and obtain the intermediate form of the electrode as shown in Figure 15 wherein, the thickness of the electrode is 117.3 μm, the thickness of the insulating coating 140 is 35 μm, and the compaction density is 1.755 g / cc.

[0066] Then die-cut the tab and slit. As Figure 16 shown, after die-cutting the tab, slit from the middle of the electrode in the winding direction of the intermediate form of the electrode to form two first electrode strips A and B, namely the first electrode strip of cell A and the first electrode strip of cell B, wherein the first electrode strip of cell A is the same as the first electrode strip of cell B, and both include a plurality of first electrodes connected end to end. Therefore, after cutting the first electrode strip of cell A and the first electrode strip of cell B, the same first electrode of cell A and the first electrode of cell B can be obtained. Therefore, the first electrodes obtained by the above method are the same when used to make cell A and cell B.

[0067] Comparative Example 1 Preparation of the first electrode

[0068] Mix artificial graphite as the anode active material, styrene-butadiene rubber as the binder, and carboxymethyl cellulose as the thickener in a mass ratio of 96:3:1 and stir evenly to obtain the anode active material layer slurry. As Figure 17As shown, the active material layer slurry is applied by slot die coating on the first surface and the second surface of a copper foil with a thickness of 6 μm. After cold pressing, along the winding direction, an intermediate form of the electrode sheet with a single-sided area 101 and an empty foil area 102 is formed.

[0069] Then, the tab is die-cut and the strip is cut. As Figure 18 shown, after die-cutting the tab, the strip is cut from the middle of the intermediate form of the electrode sheet along the winding direction to form two first electrode sheet strips A and B, namely the first electrode sheet of cell A and the first electrode sheet of cell B. Among them, the winding starting ends of the first electrode sheet of cell A and the first electrode sheet of cell B are opposite at the winding starting end of the electrode sheet. Specifically, Figure 18 when the tab directions are both downward in the figure, the winding starting end of the first electrode sheet of cell A is located on the right side, and the winding starting end of the first electrode sheet of cell B is located on the left side. Therefore, the winding starting ends of the first electrode sheet of cell A and the first electrode sheet of cell B obtained after cutting are opposite, and the first electrode sheets obtained by the above method are made into different cells A and B.

[0070] It should be noted that the preparation parameters of Comparative Example 1 are the same as the corresponding preparation parameters in Embodiment 1.

[0071] Please refer to Table 1 together, which shows the test data of the wound cell of Example 1 and the electrochemical device of Comparative Example 1. It can be seen from Table 1 that after winding the first electrode sheet of the wound cell of Example 1, the proportion of the single-sided area with wrinkles is significantly smaller than that of the wound cell of Comparative Example 1 with wrinkles in the single-sided area. Example 1 can significantly improve the phenomenon of wrinkles at the winding starting end of the first electrode sheet.

[0072] Group Number of battery cells / piece Number of wrinkles in single-sided area / piece Wrinkle ratio Comparative example 1 586 61 10.4％ Example 1 671 0 0

[0073] Table 1

[0074] In addition, it can be seen from the above preparation process that the winding starting ends of the first electrode sheet of cell A and the first electrode sheet of cell B in Comparative Example 1 are different. When preparing the wound cell, it is necessary to classify them to wind them from different directions to form cell A and cell B. However, the first electrode sheets of cell A and cell B in Example 1 are the same. When preparing the wound cell, there is no need to classify them, and they can be wound from the same direction, which can improve the production efficiency and reduce the production cost.

[0075] The above is only the implementation mode of this application, and it does not limit the patent scope of this application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, is similarly included in the patent protection scope of this application.

Claims

1. An electrochemical device, comprising an electric core formed by winding a first pole piece, a separator and a second pole piece, characterized in that, the first pole piece includes: a current collector, including a first surface facing the inside of the electric core and a second surface facing away from the inside of the electric core; an active material layer, disposed on the first surface and the second surface of the current collector; wherein, the winding starting end of the first pole piece is set as a single-sided area, the single-sided area is located at the winding center of the electric core, an insulating coating is disposed on the first surface of the current collector located in the single-sided area, and the active material layer is disposed on the second surface of the current collector located in the single-sided area; a tab, disposed in an area where the active material layer is provided on both side surfaces of the current collector, and the tab is electrically connected to the current collector.

2. The electrochemical device according to claim 1, characterized in that, along the winding direction of the first pole piece, the insulating coating is adjacent to or partially overlaps with the active material layer.

3. The electrochemical device according to claim 1, characterized in that, the thickness of the insulating coating is 1 to 100 μm, and the thickness of the active material layer is 25 to 150 μm.

4. The electrochemical device according to claim 3, characterized in that, the thickness of the insulating coating is less than or equal to the thickness of the active material layer.

5. The electrochemical device according to claim 1, characterized in that, the insulating coating is disposed on a part of the first surface of the single-sided area, or, the insulating coating is disposed on the entire first surface of the single-sided area.

6. The electrochemical device according to claim 5, characterized in that, the insulating coating is distributed in a stripe shape or an island shape on the first surface of the single-sided area.

7. The electrochemical device according to claim 1, characterized in that, the insulating coating includes inorganic particles and an adhesive, the inorganic particles include at least one of alumina, zinc oxide, calcium oxide, silicon oxide, zirconium oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, yttrium oxide, silicon carbide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, boehmite, and the adhesive includes at least one of a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride, a copolymer of hexafluoropropylene, polystyrene, poly(phenylacetylene), sodium polyacrylate, potassium polyacrylate, polymethyl methacrylate, polyethylene, polypropylene or polytetrafluoroethylene.

8. The electrochemical device according to claim 1, characterized in that, the first pole piece is an anode pole piece.

9. The electrochemical device according to claim 1, characterized in that, the thickness of the current collector is 4 to 10 μm.

10. An electronic device, characterized in that, comprising the electrochemical device according to any one of claims 1 to 9, and the electrochemical device is used to supply power to the electronic device.

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