Electrochemical device and electronic device

Abstract

The invention provides an electrochemical device and an electronic device, the electrochemical device comprises a pole piece, the pole piece comprises a current collector and an active material layer located on at least one surface of the current collector, the active material layer is internally provided with a hole, and the hole is connected with the surface of the current collector. Through the arrangement, infiltration of electrolyte in the pole piece is facilitated, lithium precipitation of the negative electrode is avoided, and the cycle performance of the electrochemical device is improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Art

[0002] With the booming development of emerging industries such as food delivery and sharing, the market has an urgent need for electrochemical devices with high energy density and long battery life (such as lithium-ion batteries and sodium-ion batteries). Cylindrical secondary batteries are widely used in industrial production and people's daily lives because of their advantages such as high energy density, good rate performance, high automation, low cost, and good consistency. However, the flattened structure of the full-tab structure of cylindrical secondary batteries will lead to poor electrolyte infiltration in the electrode, affecting the cycle performance of the cylindrical secondary battery. In addition, in order to make the electrochemical device have a high energy density, the thickness of the active material layer coated on the electrode is usually increased. The thick electrode also has the problem of poor electrolyte infiltration, which affects the cycle performance of the electrochemical device. Summary of the Invention

[0003] The purpose of the present application is to provide an electrochemical device and an electronic device to improve the wetting problem of the electrolyte in the electrode, thereby improving the cycle performance of the electrochemical device.

[0004] The specific technical solutions are as follows:

[0005] In a first aspect, the present application provides an electrochemical device comprising an electrode sheet, the electrode sheet comprising a current collector and an active material layer disposed on at least one surface of the current collector, the active material layer having holes disposed therein, the holes being connected to the surface of the current collector. The electrode sheets of the present application include a positive electrode sheet and a negative electrode sheet. This arrangement facilitates the infiltration of the electrolyte into the electrode sheet, thereby improving the cycling performance of the electrochemical device.

[0006] In one or more embodiments of the present application, the plurality of holes are provided along the length of the electrode sheet, and the spacing between adjacent holes is d mm, where 2 ≤ d ≤ 20. By regulating the distance d between adjacent holes within the above range, the electrolyte infiltration into the electrode sheet is facilitated, thereby improving the cycling performance of the electrochemical device.

[0007] In one or more embodiments of the present application, 4≤d≤10. By regulating the distance d between adjacent holes within the above range, the electrolyte is facilitated to penetrate into the electrode, thereby improving the cycle performance of the electrochemical device.

[0008] In one or more embodiments of the present application, the current collector surface is provided with protrusions, which are accommodated within the holes. The cross-section of the protrusions includes any of a rectangular, trapezoidal, curved-edge trapezoidal, pentagonal, hexagonal, triangular, or elliptical shape. This arrangement facilitates the infiltration of the electrolyte into the electrode sheet, improving the cycling performance of the electrochemical device. The protrusions also act as reinforcement ribs, improving the mechanical properties of the electrochemical device.

[0009] In one or more embodiments of the present application, the protrusion height is h μm, the active material layer thickness is T μm, and 2 ≤ h ≤ 0.45 T. By regulating the protrusion height within the above range, the electrolyte infiltration into the electrode is facilitated, improving the cycling performance of the electrochemical device. The protrusion also acts as a reinforcement, improving the mechanical properties of the electrochemical device.

[0010] In one or more embodiments of the present application, the thickness of the active material layer is T μm, the maximum height of the hole is H μm, 0.05T≤H≤0.5T, and by regulating the maximum height H of the hole within the above range, it is beneficial to the infiltration of the electrolyte in the electrode and improves the cycle performance of the electrochemical device.

[0011] In one or more embodiments of the present application, the thickness of the active material layer is T μm, 50 ≤ T ≤ 200. By regulating the thickness T of the active material layer within the above range, the electrolyte infiltration in the electrode is facilitated, and the cycle performance of the electrochemical device is improved.

[0012] In one or more embodiments of the present application, the width of the protrusion is X mm, 0.1≤X≤0.8. By adjusting the width X of the protrusion within the above range, it is beneficial to improve the infiltration of the electrolyte in the electrode and improve the cycle performance of the electrochemical device.

[0013] In one or more embodiments of the present application, the protrusion height is h μm, the maximum hole height is H μm, and 0.1 ≤ h / H ≤ 0.9. By regulating the ratio of the protrusion height to the maximum hole height, h / H, within the above range, electrolyte infiltration into the electrode is facilitated, improving the cycling performance of the electrochemical device. At the same time, the safety performance of the electrochemical device is not affected.

[0014] In one or more embodiments of the present application, 60≤T≤100. By regulating the thickness T of the active material layer within the above range, the electrolyte is facilitated to penetrate into the electrode sheet, thereby improving the cycle performance of the electrochemical device.

[0015] In one or more embodiments of the present application, 0.2 ≤ h / H ≤ 0.6. By regulating the ratio of the protrusion height to the maximum hole height (h / H) within the above range, electrolyte infiltration into the electrode is facilitated, improving the cycling performance of the electrochemical device while maintaining the safety of the electrochemical device.

[0016] In one or more embodiments of the present application, 60 ≤ T ≤ 100, and 0.2 ≤ h / H ≤ 0.6. By regulating the active material layer thickness T and the ratio of the protrusion height to the maximum hole height h / H within the above ranges, the electrolyte infiltration into the electrode is facilitated, thereby improving the cycling performance of the electrochemical device.

[0017] In one or more embodiments of the present application, the holes include first holes and second holes. Along the width direction of the electrode sheet, the width of the active material layer is W, the width of the first hole is w1, and the width of the second hole is w2, w1 = W, 0.4 ≤ w2 / W ≤ 0.6; the number of first holes is N1, and the number of second holes is N2, 0.2 ≤ N2 / N1 ≤ 5. This arrangement facilitates the infiltration of the electrolyte into the electrode sheet and helps the active material layer maintain structural stability, further improving the cycling performance of the electrochemical device.

[0018] In one or more embodiments of the present application, 0.5 ≤ N2 / N1 ≤ 2. By regulating the ratio N2 / N1 of the second pores to the first pores within the above range, the electrolyte is facilitated to penetrate the electrode, while also facilitating the structural stability of the active material layer, thereby further improving the cycling performance of the electrochemical device.

[0019] In one or more embodiments of the present application, the first holes and the second holes are alternately distributed. This arrangement facilitates the infiltration of the electrolyte into the electrode, while also facilitating the structural stability of the active material layer, further improving the cycling performance of the electrochemical device.

[0020] The second aspect of the present application provides an electronic device, which includes the electrochemical device provided in the first aspect of the present application. The electrochemical device provided in the first aspect of the present application has good cycle performance, so the electronic device of the present application has a long service life.

[0021] Beneficial effects of this application:

[0022] The present application provides an electrochemical device and an electronic device, wherein the electrochemical device includes a pole piece, the pole piece includes a current collector and an active material layer located on at least one surface of the current collector, the active material layer is provided with holes inside, and the holes are connected to the surface of the current collector. The above-mentioned arrangement is conducive to the infiltration of the electrolyte into the pole piece, avoiding lithium deposition at the negative electrode, and improving the cycle performance of the electrochemical device. In particular, for cylindrical electrochemical devices and electrochemical devices using thick pole pieces, the use of pole pieces within the scope of the present application is more conducive to the infiltration of the electrolyte into the pole piece, avoiding lithium deposition at the negative electrode, and improving the cycle performance of the electrochemical device. "Thick pole piece" refers to a pole piece whose single-sided active material layer has a thickness greater than or equal to 80μm.

[0023] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0025] Figure 1 A schematic top view of a current collector according to an embodiment of the present application;

[0026] Figure 2 A schematic left view of a pole piece according to an embodiment of the present application;

[0027] Figure 3 A schematic diagram of a right side view of a pole piece according to an embodiment of the present application;

[0028] Figure 4 for Figure 3 A schematic cross-sectional view of the AA surface of an embodiment;

[0029] Figure 5 for Figure 3 A schematic cross-sectional view of the BB surface of an embodiment;

[0030] Figure 6 A schematic cross-sectional view of a pole piece according to an embodiment of the present application;

[0031] Figure 7 A schematic cross-sectional view of a pole piece according to an embodiment of the present application;

[0032] Figure 8 A schematic cross-sectional view of a pole piece according to an embodiment of the present application;

[0033] Figure 9 This is a schematic diagram of a cold-pressed special-shaped roller structure with protrusions provided on a current collector in accordance with an embodiment of the present application;

[0034] Description of reference numerals:

[0035] 1. Raised portion on the current collector; 2. Current collector; 3. Active material layer on the electrode; 4. Holes on the electrode; 4-1. First hole; 4-2. Second hole; H is the maximum height of the hole; h is the height of the protrusion; X is the width of the protrusion; d is the spacing between adjacent holes; T is the thickness of the active material layer; w1 is the width of the first hole; w2 is the width of the second hole. DETAILED DESCRIPTION

[0036] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0037] It should be noted that, in the specific embodiments of the present application, a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium-ion battery.

[0038] The first aspect of the present application provides an electrochemical device comprising an electrode, the electrode comprising a current collector and an active material layer located on at least one surface of the current collector, wherein the active material layer has holes disposed therein, the holes being connected to the surface of the current collector. The electrode of the present application comprises a positive electrode and a negative electrode, wherein the holes are disposed in at least one of the positive electrode or the negative electrode. Through such a configuration, the channels formed by the holes in the electrode facilitate the infiltration of the electrolyte into the electrode, preventing lithium deposition at the negative electrode, thereby improving the cycling performance of the electrochemical device.

[0039] In some embodiments of the present application, there are multiple holes along the length direction of the pole piece, and the spacing between adjacent holes is dmm (e.g. Figure 2 (as shown), 2≤d≤20, preferably 4≤d≤10. For example, the spacing between adjacent holes can be 2mm, 5mm, 8mm, 10mm, 12mm, 15mm, 18mm, 20mm, or a range consisting of any two of these values. By regulating the distance d between adjacent holes within the above range, it is beneficial to the infiltration of the electrolyte into the electrode sheet, avoiding lithium deposition at the negative electrode, and improving the cycle performance of the electrochemical device. At the same time, it is also beneficial to set holes in the electrode sheet to avoid the situation where d is too small and affects the hole arrangement.

[0040] In some embodiments of the present application, the current collector surface is provided with protrusions, which are accommodated in the holes, and the cross section of the protrusions includes any one of a rectangle, a trapezoid, a curved trapezoid, a pentagon, a hexagon, a triangle or an ellipse. Figure 2 As shown, the protrusion is rectangular, 1 is a protrusion, 4 is a hole, and the hole includes a gap part and a protrusion part. Figure 6 The cross section of the protrusion shown is trapezoidal. Figure 7 The cross section of the protrusion shown is a curved trapezoid. Figure 8 The protrusions shown have a hexagonal cross-section. Protrusions on the current collector surface facilitate the creation of holes in the electrode sheet, improving electrolyte wetting within the electrode sheet and thus improving the cycling performance of the electrochemical device. Furthermore, the protrusions act as reinforcing ribs within the electrode sheet, improving the mechanical properties of the electrochemical device.

[0041] In some embodiments of the present application, the height of the protrusion is h μm, the thickness of the active material layer is T μm, and 2 ≤ h ≤ 0.45 T. By regulating the protrusion height within the above range, it is convenient to set holes in the electrode and avoid the phenomenon of current collector metal exposure during the electrode coating process. It can effectively improve the infiltration of electrolyte in the electrode and improve the cycling performance of the electrochemical device. At the same time, the protrusion can act as a reinforcement and improve the mechanical properties of the electrochemical device.

[0042] In some embodiments of the present application, the maximum height of the hole is H μm, 0.05T≤H≤0.5T, preferably 0.1T≤H≤0.5T. Figure 2 As shown, the maximum height H of the hole is the distance from the top of the hole to the bottom of the protrusion. By adjusting the maximum height H of the hole within the above range, the electrolyte infiltration in the electrode is facilitated, and the cycle performance of the electrochemical device is improved.

[0043] In some embodiments of the present application, the thickness of the active material layer is T μm, 50 ≤ T ≤ 200, preferably 60 ≤ T ≤ 100. For example, the thickness of the active material layer can be 50 μm, 70 μm, 90 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, or a range consisting of any two of these values. By regulating the thickness T of the active material layer within the above range, it is beneficial for the electrolyte to set holes in the electrode, and it can also avoid the collapse of the active material after the holes are set in the electrode, thereby effectively improving the infiltration of the electrolyte in the electrode and improving the cycle performance of the electrochemical device.

[0044] In some embodiments of the present application, the width of the protrusion is X mm, 0.1 ≤ X ≤ 0.8. For example, the width of the protrusion can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, or a range consisting of any two of these values. By regulating the width X of the protrusion within the above range, it is advantageous to set holes in the electrode, and it can also avoid the collapse of the active material after the hole is set due to the protrusion being too large, thereby effectively improving the infiltration of the electrolyte in the electrode and improving the cycle performance of the electrochemical device.

[0045] In some embodiments of the present application, the height of the protrusion is hμm, the maximum height of the hole is Hμm, 0.1≤h / H≤0.9, preferably 0.2≤h / H≤0.6. For example, the value of h / H can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or a range consisting of any two values ​​therein. By regulating the ratio h / H of the protrusion height and the maximum height of the hole within the above range, it is beneficial to set holes in the electrode, avoiding damage to the current collector during the process of setting the holes, resulting in uneven stress, current collector breakage, fire and explosion, and other problems; it is also beneficial to the infiltration of the electrolyte in the electrode, avoiding lithium plating at the negative electrode, and improving the cycle performance of the electrochemical device.

[0046] In some embodiments of the present application, the hole includes a first hole and a second hole. Along the width direction of the electrode, the width of the active material layer is W, and the width of the first hole is w1 (e.g., Figure 4 As shown), the width of the second hole is w2 (as shown Figure 5 As shown), w1=W, 0.4≤w2 / W≤0.6. For example, the value of w2 / W can be 0.4, 0.45, 0.5, 0.55, 0.6 or a range consisting of any two values ​​therein. The number of the first holes is N1, the number of the second holes is N2, 0.2≤N2 / N1≤5, preferably 0.5≤N2 / N1≤2. For example, the value of N2 / N1 can be 0.2, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or a range consisting of any two values ​​therein. Figure 3 As shown, the pole piece includes a first hole and a second hole; Figure 4 The first hole shown is a through hole; Figure 5 The above arrangement is conducive to the infiltration of the electrolyte into the electrode sheet, and is also conducive to maintaining the structural stability of the active material layer, further improving the cycle performance and mechanical properties of the electrochemical device.

[0047] In some embodiments of the present application, the first holes and the second holes are alternately distributed. This arrangement facilitates the infiltration of the electrolyte into the electrode sheet and helps the active material layer maintain structural stability, further improving the cycle performance of the electrochemical device.

[0048] This application does not specifically limit the method for preparing the current collector with protrusions, as long as the purpose of this application can be achieved. For example, a method of extruding the current collector surface using a mold can be used. This application does not specifically limit the method for providing holes in the electrode sheet, as long as the purpose of this application can be achieved, for example, a method of using laser burning and vaporization can be used.

[0049] The present application does not particularly limit the type of positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the type of positive electrode current collector can be aluminum foil or aluminum alloy foil. The present application does not particularly limit the thickness of the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5μm to 20μm, preferably 6μm to 18μm. The positive electrode active material layer of the present application contains positive electrode active material. The present application does not particularly limit the type of positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material can include at least one of lithium nickel cobalt manganese oxide (NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. In the present application, the positive electrode active material layer can be arranged on one surface in the thickness direction of the positive electrode current collector, or on both surfaces in the thickness direction of the positive electrode current collector. It should be noted that the “surface” here may refer to the entire area of ​​the positive electrode current collector or a partial area of ​​the positive electrode current collector.

[0050] The positive electrode active material layer of the present application may further include a positive electrode conductive agent and a positive electrode binder. There is no particular limitation on the positive electrode conductive agent and the positive electrode binder, as long as the purpose of the present application can be achieved. For example, the conductive agent may include at least one of acetylene black, conductive carbon black (Super P), carbon nanotubes (CNTs), carbon nanofibers, Ketjen black, flake graphite or graphene. The binder may include at least one of polypropylene alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyamide-imide, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, carboxymethyl cellulose (CMC) or sodium carboxymethyl cellulose (CMC-Na).

[0051] The present application has no particular restrictions on the type of negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the type of negative electrode current collector may include but is not limited to copper foil, copper alloy foil, nickel foil, titanium foil, foam nickel, foam copper or composite current collector, etc. The present application has no particular restrictions on the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4μm to 12μm. The negative electrode active material layer of the present application contains negative electrode active materials. The present application has no particular restrictions on the type of negative electrode active materials, as long as the purpose of the present application can be achieved. For example, the negative electrode active materials may include but are not limited to natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO xAt least one of (0 < x ≤ 2) or metallic lithium, etc. In the present application, the negative electrode active material layer can be disposed on one surface in the thickness direction of the negative electrode current collector, or can be disposed on two surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of the negative electrode current collector or a partial area of the negative electrode current collector. The negative electrode active material layer of the present application can also contain a conductive agent and a binder. The present application has no particular limitation on the conductive agent and the binder, as long as the purpose of the present application can be achieved. For example, the binder and the conductive agent can include, but are not limited to, at least one of the substances optional for the above-mentioned positive electrode active material layer.

[0052] The electrochemical device of the present application further includes a separator for separating the positive electrode sheet and the negative electrode sheet, preventing internal short circuit of the electrochemical device, allowing electrolyte ions to pass freely, and not affecting the progress of the electrochemical charge and discharge process. The present application has no particular limitation on the separator, as long as the purpose of the present application can be achieved. For example, the separator can include a substrate layer and a surface treatment layer. The substrate layer can be a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide, etc. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be used. Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder, and there is no particular limitation on the inorganic particles. For example, it can be selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate, etc. There is no particular limitation on the binder. For example, it can be selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyvinylpyrrolidone, polyethylene ether or polymethyl methacrylate. The polymer layer contains a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene, etc. In the present application, the thickness of the separator has no particular limitation, as long as the purpose of the present application can be achieved. For example, the thickness of the separator can be 5 μm to 500 μm.

[0053] The electrochemical device of the present application also includes an electrolyte, and the electrolyte may include a lithium salt and an organic solvent. The present application has no particular restrictions on the type of lithium salt, as long as the purpose of the present application can be achieved. For example, the lithium salt may include but is not limited to lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalatoborate) (LiBOB) or lithium difluorooxalatoborate (LiDFOB). The present application does not limit the content of lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the type of the above-mentioned organic solvent, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of a carbonate compound, a carboxylate compound, an ether compound or other organic solvents. The above-mentioned carbonate compound may include but is not limited to at least one of a chain carbonate compound or a cyclic carbonate compound. The above-mentioned linear carbonate compound may include but is not limited to at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate or methylethyl carbonate. The above-mentioned cyclic carbonate compound may include but is not limited to at least one of ethylene carbonate, propylene carbonate, butylene carbonate or vinylethylene carbonate. The above-mentioned carboxylate compound may include but is not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid, valerolactone or caprolactone. The above-mentioned ether compound may include but is not limited to at least one of ethylene glycol dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate.

[0054] The electrochemical device of the present application also includes a housing for housing the positive electrode sheet, separator, negative electrode sheet, and electrolyte, as well as other components known in the art for secondary batteries. This application does not specifically limit these other components. This application does not specifically limit the housing; any housing known in the art can be used, as long as it can achieve the objectives of this application. For example, aluminum alloy housings and steel housings can be used.

[0055] The electrochemical device of the present application is not particularly limited and may include any device that undergoes an electrochemical reaction. In one embodiment of the present application, the electrochemical device may include, but is not limited to, a lithium-ion battery, a sodium-ion battery, a lithium polymer secondary battery, or a lithium-ion polymer secondary battery.

[0056] The preparation process of the electrochemical device of the present application is well known to those skilled in the art and is not particularly limited in the present application. For example, it may include but is not limited to the following steps: stacking the positive electrode sheets, the separator and the negative electrode sheets in sequence, and winding, folding and other operations as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain an electrochemical device; or stacking the positive electrode sheets, the separator and the negative electrode sheets in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly with a stacked structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain an electrochemical device.

[0057] The second aspect of the present application provides an electronic device, which includes the electrochemical device provided in the first aspect of the present application. The electrochemical device provided in the first aspect of the present application has good cycle performance, so the electronic device of the present application has a long service life.

[0058] The electronic device of the present application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device can include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0059] Example

[0060] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0061] Test methods and equipment:

[0062] Measurement of various characteristic quantities of the pole piece

[0063] The battery was disassembled and the electrodes were obtained. The electrodes were cleaned with dimethyl carbonate (DMC) for 10 min and air-dried for 2 h before use.

[0064] The air-dried electrode was prepared by liquid nitrogen fracturing or ion polishing to obtain a longitudinal cross-section. Using a ZEIS-SEM (Sigma-02-33) scanning electron microscope, the protrusion height h, protrusion width X, the gap height (Hh) between the maximum hole height H and the protrusion height h, and the spacing d between adjacent holes were measured. Each characteristic value was measured at five locations on the electrode, and the average value was taken.

[0065] The above-mentioned naturally air-dried electrode, with a size of 3cm×10cm, was cleaned with DMC to remove the active material layer on the surface of the electrode. The distribution of the first holes and the second holes was observed with an optical microscope, and the number of holes N1 and N2 was obtained.

[0066] Cycle performance test

[0067] The lithium-ion batteries of each embodiment and comparative example were placed in a constant temperature box at 25°C for charge and discharge cycle testing. The charge and discharge voltage range was 2.5V to 4.2V. First, they were charged to 4.2V at a constant current of 0.5C, then charged to 0.05C at a constant voltage of 4.2V and left to stand for 5 minutes. Then, they were discharged to 2.5V at a constant current of 0.5C. The initial discharge capacity C1 was recorded. The above charge and discharge process was repeated for 600 cycles, and the discharge capacity C after the 600th cycle was recorded. 600 , calculate the capacity retention rate.

[0068] Capacity retention rate (%) = C 600 / C1×100%; the capacity retention rate is used to characterize the infiltration effect of the electrolyte in the electrode. The higher the capacity retention rate, the better the infiltration effect of the electrolyte in the electrode, and the better the cycle performance of the lithium-ion battery.

[0069] Mechanical properties testing

[0070] After charging the lithium-ion batteries of each embodiment and comparative example to 4.2V at a constant current of 2C, charge them to 0.05C at a constant voltage of 4.2V to reach a fully charged state. Place the fully charged lithium-ion battery on the test table, and place a round rod with a diameter of φ15.8mm and a length of at least 6cm at the center of the wide surface of the lithium-ion battery. Wait until the longitudinal axis of the lithium-ion battery is parallel to the surface of the test table and perpendicular to the longitudinal axis of the round rod (in a cross shape). Use a 9.1kg hammer and drop it vertically from a height of 610mm in a free state, and drop it on the intersection of the round rod and the lithium-ion battery.

[0071] Judgment criteria: Pass if there is no fire or explosion.

[0072] Twenty lithium-ion batteries were tested in each embodiment or comparative example, and the impact test pass rate = the number of passed batteries / 20. A higher impact test pass rate indicates better mechanical properties of the lithium-ion battery.

[0073] Example 1

[0074] <Preparation of Current Collector>

[0075] Preparation of positive electrode current collector with protrusions: The positive electrode current collector substrate is made of aluminum foil of a certain thickness, and a cold-pressed special-shaped roller is used (the structural schematic diagram of the cold-pressed special-shaped roller is shown in FIG. Figure 9 As shown, the cold-pressed special-shaped roller has an extrusion roller and extrusion teeth) to produce protrusions on both surfaces of the current collector aluminum foil, where the extrusion tooth length corresponds to the spacing between the protrusions, that is, the spacing d between adjacent holes in the positive electrode sheet, the thickness of the extrusion gear corresponds to the height of the protrusion, that is, the maximum height H of the holes in the positive electrode sheet, the arc length between adjacent extrusion teeth corresponds to the width W of the protrusion, and the gap between the opposite extrusion teeth on the upper extrusion roller and the lower extrusion roller corresponds to the thickness of the positive current collector after extrusion. After passing through the extrusion teeth, the extruded aluminum foil will extend to the gap between the adjacent extrusion teeth, and the gap between the adjacent extrusion teeth will accommodate the extended aluminum of the extruded part, forming a protrusion (as shown Figure 1 As shown, the protrusions are evenly distributed along the length of the current collector, and the spacing between the protrusions is d). A positive electrode current collector with a thickness of 13 μm and protrusions on both surfaces is obtained. In this case, the height of the protrusions on the positive electrode current collector is 20 μm, the width is 600 μm, and the spacing between adjacent protrusions is 8 mm.

[0076] Preparation of a negative electrode current collector with protrusions: The negative electrode current collector substrate is made of copper foil. The process of setting the protrusions is the same as that of the positive electrode current collector. The copper foil is extruded using a cold-pressed special-shaped roller to obtain a negative electrode current collector with a thickness of 10 μm and protrusions on both surfaces. At this time, the height of the protrusions on the negative electrode current collector is 20 μm, the width is 600 μm, and the spacing between adjacent protrusions is 8 mm.

[0077] <Preparation of positive electrode sheet>

[0078] The positive electrode active material lithium nickel cobalt manganese oxide (NCM811), the conductive agent, and the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 94.8:2.4:2.8, wherein the conductive agent is a mixture of conductive carbon black (Super P) and carbon nanotubes (CNT) in a mass ratio of 2:1. N-methylpyrrolidone (NMP) is added as a solvent and stirred evenly to prepare a positive electrode slurry with a solid content of 73wt%. The positive electrode slurry is evenly coated on one surface of the above-mentioned positive electrode current collector with protrusions and dried at 85°C to obtain a positive electrode sheet with a thickness of 100μm and a single-sided positive electrode active material layer. The above coating steps are then repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet with a double-sided positive electrode active material layer. The positive electrode sheet is cold pressed and cut into sheets with a specification of 60mm×1422mm. The coating surface density of the positive electrode active material layer is 15mg / cm 2 , compacted density is 3.4g / cm3 .

[0079] A laser cutting machine (model: G4020H, manufacturer: Han's Laser) was used with the laser power set to 600 W to burn and gasify the protrusions of the positive electrode sheet to a specified height, thereby obtaining a positive electrode sheet with holes.

[0080] The relevant parameters of the positive electrode sheet are: H = 20 μm, h = 6 μm, h / H = 0.3, d = 8 mm, X = 0.6 mm, w2 / W = 0.5, N2 / N1 = 1.

[0081] <Preparation of negative electrode sheet>

[0082] The negative electrode active materials artificial graphite, styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) are mixed in a mass ratio of 97:1.7:1.3, and then deionized water is added as a solvent to prepare a negative electrode slurry with a solid content of 70wt%, and stirred evenly. The negative electrode slurry is evenly coated on one surface of the above-mentioned negative electrode current collector with protrusions, and dried at 110°C to obtain a negative electrode sheet with a thickness of 60μm and a single-sided negative electrode active material layer coated. Then, the above coating steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided negative electrode active material layer coated. The negative electrode sheet is cold pressed and cut into sheets with a specification of 62mm×1467mm. The compaction density of the negative electrode active material layer is 1.6g / cm 3 .

[0083] A laser cutting machine (model: G4020H, manufacturer: Han's Laser) was used with the laser power set to 400 W to burn and gasify the protrusions of the negative electrode sheet to a specified height, thereby obtaining a negative electrode sheet with holes.

[0084] The relevant parameters of the negative electrode are: H = 12 μm, h = 3.6 μm, h / H = 0.3, d = 8 mm, X = 0.6 mm, w2 / W = 0.5, N2 / N1 = 1.

[0085] <Preparation of Separator>

[0086] A polypropylene (PP) porous membrane with a thickness of 12 μm (provided by Celgard) was used as the separator.

[0087] <Preparation of Electrolyte>

[0088] In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 70:30 to form a base solvent. Lithium hexafluorophosphate (LIPF) and fluoroethylene carbonate (FEC) were then added to the base solvent, dissolved, and mixed thoroughly to form an electrolyte. The electrolyte solution contained 15% LFP by mass, 2% FEC by mass, and the remainder comprised the base solvent.

[0089] <Preparation of lithium-ion batteries>

[0090] The negative electrode sheet, separator and positive electrode sheet prepared above are stacked and wound in sequence to obtain an electrode assembly with a wound structure; the electrode assembly is flattened, the current collecting plate is welded, the shell is put into the shell, the coding is sprayed, the vacuum drying is carried out, the electrolyte is injected, the sealing is carried out, and the high temperature of 45°C is allowed to stand for 12 hours, and then the capacity is formed to obtain a cylindrical lithium-ion battery.

[0091] Example 2 to Example 28

[0092] Except for adjusting the relevant preparation parameters in <Preparation of Current Collector>, <Preparation of Positive Electrode Sheet>, and <Preparation of Negative Electrode Sheet> according to Table 1, the rest is the same as Example 1.

[0093] Example 29

[0094] Except that in <Preparation of Current Collector>, the negative electrode current collector aluminum foil is not provided with protrusions, and in <Preparation of Negative Electrode Sheet>, the negative electrode sheet is not provided with holes, the rest is the same as Example 1.

[0095] Example 30

[0096] Except that in <Preparation of Current Collector>, the positive electrode current collector copper foil is not provided with protrusions, and in <Preparation of Positive Electrode Sheet>, the positive electrode sheet is not provided with holes, the rest is the same as Example 1.

[0097] Comparative Example 1

[0098] Except that in <Preparation of Current Collector>, the positive electrode current collector aluminum foil and the negative electrode current collector copper foil are not provided with protrusions, and in <Preparation of Positive Electrode Sheet> and <Preparation of Negative Electrode Sheet>, no holes are provided in the positive electrode collector and the negative electrode sheet, the rest is the same as Example 1.

[0099] Comparative Example 2

[0100] Except that in <Preparation of Current Collector>, the positive electrode current collector aluminum foil and the negative electrode current collector copper foil are not provided with protrusions, in <Preparation of Positive Electrode Sheet> and <Preparation of Negative Electrode Sheet>, no holes are provided in the positive electrode collector and the negative electrode sheet, and the thicknesses of the positive electrode active material layer and the negative electrode active material layer are adjusted according to Table 1, the rest are the same as Example 1.

[0101] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Table 1.

[0102]

[0103]

[0104]

[0105]

[0106] As can be seen from Examples 1 to 30, Comparative Examples 1 and 2, the provision of holes within the active material layer of the electrode facilitates electrolyte infiltration into the electrode, preventing lithium deposition at the negative electrode. Lithium-ion batteries employing such electrode sheets exhibit high capacity retention and high impact pass rates, demonstrating good cycling and mechanical properties. Furthermore, as can be seen from Examples 19, 21, and Comparative Example 2, provision of holes within thick electrode sheets effectively improves electrolyte infiltration into the electrode sheets, resulting in high capacity retention and improved cycling performance for lithium-ion batteries.

[0107] Researchers in this application have discovered that the distance d between adjacent holes in a pole piece affects the cycling performance of a lithium-ion battery. As can be seen from Examples 1 to 5 and Comparative Example 1, the inclusion of holes within the active material layer of the pole piece, with the distance between the holes within the range of this application, facilitates electrolyte infiltration into the pole piece, resulting in a high capacity retention rate for the lithium-ion battery, indicating good cycling performance.

[0108] Researchers in this application have discovered that the protrusion height h affects the cycling and mechanical properties of lithium-ion batteries. As can be seen from Examples 6 to 11 and Comparative Example 1, the presence of protrusions on the current collector surface, with protrusion heights within the range of this application, can result in lithium-ion batteries with high capacity retention and high impact pass rates, demonstrating good cycling and mechanical properties.

[0109] Researchers in this application have discovered that the maximum height H of the holes affects the cycling performance of lithium-ion batteries. As can be seen from Examples 12 to 17 and Comparative Example 1, providing holes within the active material layer of the electrode and regulating the maximum height of the holes within the scope of this application facilitates electrolyte infiltration into the electrode, resulting in a higher capacity retention rate for the lithium-ion battery, indicating good cycling performance.

[0110] Researchers in this application have discovered that the thickness of the active material layer affects the cycling performance of lithium-ion batteries. As can be seen from Examples 1, 18, 21, and Comparative Example 2, adjusting the thickness of the active material layer within the range of this application facilitates electrolyte infiltration into the electrode, resulting in a higher capacity retention rate for the lithium-ion battery, indicating good cycling performance.

[0111] Researchers in this application have discovered that the width of the protrusions affects the cycling performance of lithium-ion batteries. As can be seen from Examples 1, 22, 23, and Comparative Example 1, when protrusions are provided on the current collector surface and their widths are within the range of this application, the lithium-ion battery can achieve a high capacity retention rate, demonstrating good cycling performance.

[0112] Researchers in this application have discovered that the ratio of the protrusion height to the maximum hole height (h / H) affects the cycling performance of lithium-ion batteries. As can be seen from Examples 1 to 30, Comparative Examples 1 and 2, regulating the ratio of the protrusion height to the maximum hole height (h / H) within the range of this application facilitates electrolyte infiltration into the electrode sheet, resulting in a higher capacity retention rate for the lithium-ion battery, indicating good cycling performance.

[0113] Researchers in this application have discovered that the ratio of the second hole width to the electrode width (w2 / W) affects the cycling and mechanical properties of lithium-ion batteries. As can be seen from Examples 1, 24, 25, and Comparative Example 1, regulating the ratio of the second hole width to the electrode width within the scope of this application facilitates electrolyte infiltration into the electrode and improves the structural stability of the active material layer, resulting in a lithium-ion battery with a higher capacity retention rate and a higher impact pass rate, demonstrating good cycling and mechanical properties.

[0114] Researchers in this application have discovered that the ratio N2 / N1 between the number of second holes and the number of first holes affects the cycling performance and mechanical properties of lithium-ion batteries. As can be seen from Examples 1, 26 to 28, and Comparative Example 1, regulating the ratio between the number of second holes and the number of first holes within the scope of this application facilitates electrolyte infiltration into the electrode sheet and improves the structural stability of the active material layer, resulting in a lithium-ion battery with a higher capacity retention rate and a higher impact pass rate, indicating that the lithium-ion battery has good cycling performance and mechanical properties.

[0115] Researchers in this application have discovered that providing holes in one of the positive or negative electrode sheets, or in both the positive and negative electrode sheets, can affect the cycling and mechanical properties of lithium-ion batteries. As can be seen from Examples 1, 29, 30, and Comparative Example 1, providing holes in one of the positive or negative electrode sheets, or in both the positive and negative electrode sheets, facilitates the infiltration of the electrolyte into the sheet and improves the structural stability of the active material layer, resulting in a lithium-ion battery with a higher capacity retention rate and a higher impact pass rate, indicating that the lithium-ion battery has good cycling and mechanical properties.

[0116] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An electrochemical device comprising a pole piece, wherein the pole piece comprises a current collector and an active material layer located on at least one surface of the current collector, wherein the active material layer has holes disposed therein, and the holes are connected to the surface of the current collector.

2. The electrochemical device according to claim 1, wherein There are a plurality of holes along the length direction of the pole piece, and the spacing between adjacent holes is d mm, 2≤d≤20.

3. The electrochemical device according to claim 2, wherein 4≤d≤10。 4. The electrochemical device according to claim 1, wherein The current collector surface is provided with a protrusion, the protrusion is accommodated in the hole, and the cross section of the protrusion includes any one of a rectangle, a trapezoid, a curved trapezoid, a pentagon, a hexagon, a triangle or an ellipse.

5. The electrochemical device according to claim 4, wherein The electrochemical device satisfies at least one of the following characteristics: (1) The height of the protrusion is h μm, the thickness of the active material layer is T μm, and 2≤h≤0.45T; (2) The thickness of the active material layer is T μm, the maximum height of the pores is H μm, and 0.05T≤H≤0.5T; (3) The thickness of the active material layer is T μm, 50 ≤ T ≤ 200; (4) The width of the protrusion is X mm, 0.1≤X≤0.8; (5) The height of the protrusion is h μm, the maximum height of the hole is H μm, and 0.1≤h / H≤0.

9.

6. The electrochemical device according to claim 5, wherein 60≤T≤100, and / or, 0.2≤h / H≤0.

6.

7. The electrochemical device according to any one of claims 1 to 6, wherein The holes include a first hole and a second hole. Along the width direction of the electrode, the width of the active material layer is W, the width of the first hole is w1, and the width of the second hole is w2, w1=W, 0.4≤w2 / W≤0.6; The number of the first holes is N1, the number of the second holes is N2, and 0.2≤N2 / N1≤5.

8. The electrochemical device according to claim 7, wherein 0.5≤N2 / N1≤2.

9. The electrochemical device according to claim 7, wherein The first holes and the second holes are distributed alternately. 10 . An electronic device comprising the electrochemical device according to claim 1 .

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