Pole piece, battery and electronic device

Abstract

The invention relates to the technical field of batteries, in particular to a pole piece, a battery and an electronic device.The pole piece comprises a current collector and an active material layer coating at least one surface of the current collector, the active material layer comprises active particles, and a plurality of grooves are formed in the surface, away from the current collector, of the active material layer; the grooves penetrate through the surface, away from the current collector, of the active material layer to form notches, the cross sections of the grooves in the width direction of the active material layer are triangular, and the grooves are arranged at intervals in the length direction of the active material layer; the pole piece meets the relational expression that d / c * sin theta is more than 0.363 and less than 15.91; d is the width of the notch, and the unit is [mu] m; theta is an included angle between one groove wall surface of the first bevel edge groove and a normal perpendicular to the surface of the active material layer; and c is the median particle diameter D50 of the active particles, and the unit is [mu] m. According to the pole piece structure, falling of pole piece dust can be reduced, and the self-discharge rate K value of a finished battery cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a pole piece, a battery and an electronic device. BACKGROUND

[0002] With the increasing demand of users for lithium ion batteries, in order to realize the coexistence of high energy density, fast charging technology and other performances, the industry currently mainly adopts the method of laser punching of the pole piece. The existing technology adopts laser etching punching technology, which is perpendicular to the pole piece to perform laser etching, destroys a part of the active material to form a groove position, and realizes the punching of the pole piece. However, the super-high temperature condition in the laser etching process will cause the deactivation of the adhesive at the edge of the groove position, and then the broken and loose active material will continue to have dust falling problems in the manufacturing process of the subsequent process. The existence of dust particles will worsen the self-discharge rate (K value) of the finished product battery, and affect the product manufacturability rate. SUMMARY

[0003] The present application provides a pole piece, which can reduce the falling of pole piece dust.

[0004] In order to solve the above technical problems, the present application adopts the following technical scheme:

[0005] A pole piece, comprising a current collector and an active material layer coated on at least one surface of the current collector, the active material layer comprising active particles;

[0006] The surface of the active material layer away from the current collector is provided with a plurality of grooves, the grooves penetrate the surface of the active material layer away from the current collector to form a notch, the cross section of a plurality of grooves in the width direction of the active material layer is triangular, and a plurality of grooves are arranged at intervals along the length direction of the active material layer.

[0007] The pole piece satisfies the following relationship:

[0008] 0.363 < d / c x sin theta < 15.91;

[0009] Wherein, d is the width of the notch, unit: um;

[0010] Theta is the included angle between one of the groove walls of the groove and the normal line perpendicular to the surface of the active material layer;

[0011] C is the median particle size D50 of the active particles, unit: um.

[0012] Wherein, the pole piece satisfies the following conditions: 50 < d < 70, 4 < c < 6.5, 5° < theta < 15°.

[0013] The electrode sheet satisfies the following conditions: 50≤d<70, 6.5<c≤12, 5°<θ≤30°.

[0014] The electrode satisfies the following conditions: 70≤d<90, 4<c≤12, 5°<θ≤45°.

[0015] The grooves are distributed in a Z-shape along the width of the active material layer.

[0016] The groove is formed by mechanical drilling.

[0017] Wherein, the vertical depth h of the groove accounts for 20%-60% of the thickness of the active material layer;

[0018] And / or, a plurality of the grooves are equally spaced on the surface of the active material layer, and the groove spacing between adjacent grooves is 1.2-1.6 mm.

[0019] The active particles are lithium cobalt oxide particles or silicon-containing particles.

[0020] The present invention also provides a battery comprising the above-described electrode.

[0021] The present invention also provides an electronic device comprising the battery described above.

[0022] The beneficial effects of this invention are as follows: The electrode of this invention has several grooves on the surface of the active material layer, and the cross-section of the grooves in the width direction of the active material layer is triangular. The groove opening width d, the angle θ between one of the groove walls and the normal perpendicular to the surface of the active material layer, and the median particle size c of the active particles satisfy the relationship 0.363 < d / c × sinθ < 15.91. By constructing the groove opening width d, the median particle size c of the active particles, and the inclination angle of one of the groove walls to satisfy the above relationship, this invention outputs the oblique angle window of the groove (i.e., the inclination of the two groove walls) through the groove opening width d and the D50 particle size of the active particles, minimizing the impact of electrode dust shedding, thereby improving the subsequent dust damage to the separator, avoiding the occurrence of internal short circuits in the battery, improving the self-discharge rate (K value) of the cell, and improving the manufacturability of the product. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a side view of the negative electrode sheet according to an embodiment of the present invention;

[0025] Figure 2 This is a side view of the negative electrode sheet according to another embodiment of the present invention;

[0026] Figure 3 This is a top view of the negative electrode sheet according to an embodiment of the present invention.

[0027] Explanation of reference numerals in the attached drawings: 1. Current collector; 2. Active material layer; 3. Tank wall; 4. Groove. Detailed Implementation

[0028] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0029] The present invention provides an electrode sheet, such as Figures 1-3 As shown, it includes a current collector 1 and an active material layer 2 coated on at least one surface of the current collector 1. In an embodiment, as... Figure 1 As shown, the active material layer 2 can be disposed on one surface of the current collector 1, such as... Figure 2 As shown, the active material layer 2 can also be disposed on two opposite surfaces of the current collector 1, and the active material layer 2 includes active particles;

[0030] The surface of the active material layer 2 away from the current collector 1 is provided with a plurality of grooves 4. The grooves 4 penetrate the surface of the active material layer 2 away from the current collector 1 to form slots. The cross-section of the plurality of grooves 4 in the width direction of the active material layer 2 is triangular. The plurality of grooves 4 are spaced apart along the length direction of the active material layer 2.

[0031] Specifically, such as Figure 1 and Figure 2 As shown, the triangle formed by the cross-section of the groove 4 in the width direction of the active material layer 2 includes an intersecting first hypotenuse and a second hypotenuse, and the intersection of the first hypotenuse and the second hypotenuse faces the current collector 1.

[0032] Among them, electrode 5 satisfies the following relationship:

[0033] 0.363 < d / c × sinθ < 15.91;

[0034] Where d is the width of the slot, in μm;

[0035] θ is the angle between one of the groove walls 3 of the groove 4 and the normal perpendicular to the surface of the active material layer 2;

[0036] c represents the median particle size D50 of the active particles, in μm.

[0037] Specifically, the length direction of the active material layer 2 is the winding direction of the electrode sheet.

[0038] For battery cells, especially silicon-based cells, the wider the slot on the electrode, the easier it is for loose, broken dust to escape from the slot; while the larger the particle size of SiC particles on the electrode, the greater the damage to SiC particles caused by creating holes on the electrode surface, which will increase the amount of broken dust.

[0039] The electrode of the present invention has a plurality of grooves 4 formed on the surface of the active material layer 2, and the cross section of the grooves 4 in the width direction of the active material layer 2 is triangular. The groove opening width d, the angle θ between one of the groove wall surfaces 3 and the normal perpendicular to the surface of the active material layer 2, and the median particle size c of the active particles satisfy the relationship 0.363 < d / c × sinθ < 15.91. The present invention achieves the above relationship by constructing the groove opening width d, the median particle size c of the active particles, and the inclination angle θ of one of the groove wall surfaces 3. Then, the oblique angle window of the groove 4 (i.e., the inclination of the two intersecting groove wall surfaces 3) is output by the groove opening width d and the D50 particle size of the active particles. This minimizes the impact of electrode dust shedding, thereby improving the subsequent dust damage to the separator, avoiding the occurrence of short circuits inside the battery, improving the self-discharge rate (K value) of the cell, and improving the manufacturability of the product.

[0040] The electrode sheet satisfies the following conditions: 50≤d<70, 4<c≤6.5, 5°<θ≤15°.

[0041] The electrode sheet satisfies the following conditions: 50≤d<70, 6.5<c≤12, 5°<θ≤30°.

[0042] The electrode satisfies the following conditions: 70≤d<90, 4<c≤12, 5°<θ≤45°.

[0043] This invention outputs the oblique angle window of the groove 4 (i.e., the inclination of the two intersecting groove wall surfaces 3) by controlling the groove width of the groove 4 and the D50 particle size of the active particles. When the groove width is larger, i.e., d is larger, the dust is more likely to fall off, so the inclination angle θ of one of the groove wall surfaces 3 of the groove 4 needs to be increased. When the D50 particle size of the active particles is larger, i.e., c is larger, the contact area of ​​the active particles is increased, and the active particles are more likely to be damaged and fall off, so the inclination angle θ of one of the groove wall surfaces 3 of the groove 4 of the electrode also needs to be increased. However, when the inclination angle θ of the groove wall surface 3 of the groove 4 increases to a certain extent, the effect of reducing dust falling off will tend to stabilize. Therefore, by controlling the width d of the groove, the median particle size c of the active particles, and the tilt angle θ of the groove wall 3 of the electrode groove 4 within the above range, the present invention can keep the dust that is about to fall off inside the electrode, reduce the impact of dust on the bare cell body, minimize the shedding of electrode dust, improve the subsequent damage of dust to the separator, avoid the occurrence of short circuits inside the battery, thereby improving the self-discharge rate (K value) of the cell and improving the manufacturability of the product.

[0044] Experimental verification shows that, under the same electrode thickness, material system, and compaction density, the angle θ between the groove sidewall and the normal increases positively with the increase of the median particle size c of the active particles. That is, the larger the particle size, the larger the required optimal θ, which can reduce dust fall. However, due to the different adaptability of different material systems, process parameters, and design conditions to θ, its increase is not a fixed linear relationship. For example, if the material system and process design adopt the optimal conditions, even if c is large, θ can still achieve the improvement target with a relatively small state. Therefore, when d is the same and c is different, the value of θ may overlap. When d, c, and θ are within the above-mentioned value range of the present invention, dust fall can be effectively suppressed and manufacturing yield can be guaranteed.

[0045] In one embodiment, the groove 4 extends along the width direction of the active material layer 2, and both ends of the groove 4 penetrate the two end faces of the active material layer 2 in the width direction.

[0046] Furthermore, in the width direction of the active material layer 2, the grooves 4 extend in a Z-shape along the width direction of the active material layer. The Z-shape will reduce the opening angle of the grooves at the corners of the bare battery cell. The smaller the angle, the greater the probability of dust falling into the grooves at the corners.

[0047] The groove 4 is formed by mechanical drilling. Specifically, it can be achieved by roller pressing. According to the desired shape and size of the groove 4, a corresponding pattern is set on the roller, and then the electrode is roller-pressed to form the corresponding groove 4 on the electrode surface. Compared with laser drilling, mechanical drilling avoids the problem of adhesive deactivation at high temperatures leading to edge dust detachment, thus further reducing electrode dust detachment.

[0048] The vertical depth h of the groove 4 is a percentage A of the thickness of the active material layer, which is 20%-60%. That is, the depth of the groove 4 in the thickness direction of the active material layer 2 is 20%-60% of the thickness of the active material layer. If the depth of the groove 4 is too large, it will affect the mechanical properties and energy density of the electrode. If the depth of the groove 4 is too small, the contact area between the electrolyte and the active material will be too small, and the electrolyte will not be able to fully wet the entire electrode, resulting in a decrease in ion transport efficiency.

[0049] In this configuration, several grooves 4 are evenly spaced on the surface of the active material layer 2, with a groove spacing of 1.2-1.6 mm between adjacent grooves 4. The groove spacing between adjacent grooves 4 is the shortest distance between the edges of two adjacent grooves 4 that are close to each other. If the spacing is too small, excessive active material will be lost, affecting the battery's energy density and reducing the mechanical properties of the electrode, thus leading to a decrease in battery performance. If the spacing is too large, the contact area between the electrolyte and the active material is too small, and the electrolyte cannot fully wet the entire electrode, resulting in a decrease in ion transport efficiency.

[0050] The electrode sheet of the present invention can be a positive electrode sheet or a negative electrode sheet.

[0051] In some embodiments, the electrode is a positive electrode, the current collector is a positive electrode current collector, the active material layer is a positive electrode active material layer, and the active particles are lithium cobalt oxide particles.

[0052] In other embodiments, the electrode is a negative electrode, the current collector is a negative electrode current collector, the active material layer is a negative electrode active material layer, and the active particles are silicon-containing particles. The silicon-containing particles can be at least one of elemental silicon, silicon-carbon, silicon oxide, and silicon-metal alloy composites. In the embodiments of the present invention, the electrode is a negative electrode, the active particles are silicon-carbon particles, and the current collector is copper foil.

[0053] Specifically, the negative electrode active material layer is formed by curing a negative electrode slurry. The negative electrode slurry includes a negative electrode active material, a binder, and a solvent. The negative electrode active material includes active particles and graphite; in this application, the active particles are silicon carbon particles. The binder can be any binder known in the art, and may include at least one of polyacryl alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyamide-imide, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride, polytetrafluoroethylene (PTFE), carboxymethyl cellulose, or sodium carboxymethyl cellulose (CMC-Na). For example, styrene-butadiene rubber (SBR) can be used as the binder. The solvent is deionized water or NMP.

[0054] In some embodiments, the negative electrode slurry may further include at least one of a thickener and a conductive agent. In this embodiment, the thickener is sodium carboxymethyl cellulose, and the conductive agent may include at least one of conductive carbon black (SuperP), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjen black, or graphene.

[0055] This invention also discloses a battery comprising the aforementioned negative electrode sheet, a positive electrode sheet, and a separator. Specifically, the positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, and then wound to obtain a bare battery cell. The bare battery cell is placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. The battery is then obtained through processes such as vacuum sealing, settling, formation, degassing, and edge trimming.

[0056] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The positive active material layer includes a positive active material, which may be, but is not limited to, a material with the chemical formula Li. a Ni x Co y M z O 2-b N b The compounds shown are one or more combinations thereof, wherein 0.95 ≤ a ≤ 1.2, x > 0, y ≥ 0, z ≥ 0, and x + y + z = 1, 0 ≤ b ≤ 1, M is selected from one or more combinations of Mn and Al, N is selected from one or more combinations of F, P, and S, and the positive electrode active material may also be, but is not limited to, LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 One or more combinations of O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, TiS2, etc.

[0057] The positive electrode active material can also be modified. The methods for modifying the positive electrode active material are known to those skilled in the art. For example, the positive electrode active material can be modified by coating, doping and other methods. The materials used for modification can be one or more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce and W, including but not limited to.

[0058] The positive electrode active material layer may also include a conductive agent, which may include at least one of conductive carbon black (SuperP), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjen black, or graphene.

[0059] The positive electrode active material layer may also include a binder, which may be any binder known in the art. The binder may include at least one of polyacrylamide, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyamide-imide, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose, or sodium carboxymethyl cellulose (CMC-Na). For example, polyvinylidene fluoride (PVDF) may be selected as the binder.

[0060] A positive current collector is typically a structure or component that collects current. The positive current collector can be any material suitable for use as a positive current collector in a lithium-ion battery. For example, the positive current collector can be, but is not limited to, metal foil, and more specifically, aluminum foil.

[0061] The separator can be any material suitable for lithium-ion battery separators in the art, such as, but not limited to, one or more combinations of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers.

[0062] The electrolyte comprises a lithium salt and a solvent. 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, LiTFSI, or lithium difluoroborate. The solvent may be at least one of a carbonate compound, a carboxylic acid ester compound, an ether compound, or other organic solvent. The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof. The chain carbonate compound may be dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), or a combination thereof. The cyclic carbonate compound may be ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), or a combination thereof. Fluorocarbonate compounds may be 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, trifluoromethylethylene carbonate, and combinations thereof. The aforementioned carboxylic acid ester compounds may be methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, caprolactone, and combinations thereof. The aforementioned ether compounds may be dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof. The other organic solvents mentioned above may be at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters.

[0063] This invention also discloses an electronic device comprising the battery described above.

[0064] The electronic device described in this application can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, mobile phones, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0065] To enable those skilled in the art to clearly understand the above-described implementation details and operations of the present invention, and to demonstrate the significant advancements in the performance of the embodiments of the present invention, the following examples illustrate the above technical solutions.

[0066] Example 1

[0067] Preparation of negative electrode sheet:

[0068] The negative electrode active material, styrene-butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC) thickener were dispersed in deionized water at a mass ratio of 97.8:1.1:1.1. After thorough mixing, a negative electrode slurry was obtained. This slurry was then coated onto a 5 μm thick copper foil and dried to obtain a negative electrode active material layer. Grooves were then rolled into the surface of the negative electrode active material layer, and the mixture was slit to obtain a 65 μm thick negative electrode sheet. The negative electrode active material was composed of a mixture of graphite and silicon carbide particles at a mass ratio of 95:5.

[0069] like Figure 2 and Figure 3 As shown, the negative electrode includes a current collector 1 and an active material layer 2 coated on the surface of the current collector 1. The active material layer 2 includes active particles. Several grooves 4 are provided on the surface of the active material layer 2 away from the current collector 1. The grooves 4 penetrate the surface of the active material layer 2 away from the current collector 1 to form slots. The cross-section of the grooves 4 in the width direction of the active material layer 2 is triangular. The grooves 4 are evenly spaced along the length direction of the active material layer 2 with a spacing of 1.5 mm. The grooves 4 are distributed in a Z-shape in the width direction of the active material layer 2. The two ends of the grooves 4 in the length direction penetrate the two end faces in the width direction of the active material layer 2. The triangle formed by the cross-section of the grooves 4 in the width direction of the active material layer 2 includes intersecting first and second hypotenuses. The intersection of the first and second hypotenuses faces the copper foil. The vertical depth h of the groove accounts for 30% of the thickness A of the active material layer 2, and the value of h is 10 μm. The electrode satisfies the following relationship:

[0070] 0.363 < d / c × sinθ < 15.91;

[0071] Where d is the width of the slot, in μm;

[0072] θ is the angle between one of the groove walls 3 and the normal perpendicular to the surface of the active material layer 2;

[0073] c represents the median particle size D50 of the active particles, in μm.

[0074] Preparation of the positive electrode sheet:

[0075] Lithium cobalt oxide, carbon nanotube conductive agent, and PVDF binder were dispersed in an N-methylpyrrolidone solvent system at a mass ratio of 98:1:1. After thorough mixing, a positive electrode slurry was prepared. The slurry was coated on both surfaces of an Al foil, and after drying, rolling, and slitting, a positive electrode sheet was obtained.

[0076] Electrolyte preparation:

[0077] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0078] Battery assembly:

[0079] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain bare cells. Before feeding the cells into the winding process, dust falling off the electrodes is collected and quantified using a Keyence microscope. The amount of dust falling off is recorded in Table 1. The bare cells are then placed in aluminum-plastic film packaging bags, dried, and injected with electrolyte. After vacuum sealing, settling, formation, and secondary sealing, the finished cells are obtained.

[0080] The preparation methods of Examples 2-9 are the same as those of Example 1, except for the parameters of the negative electrode. The parameters of the negative electrode of Examples 1-9 are shown in Table 1 below.

[0081] Comparative Example 1

[0082] The difference between Comparative Example 1 and Example 1 is that the groove on the negative electrode of Comparative Example 1 is a rectangular groove with a vertical depth accounting for 30% of the electrode thickness, a spacing of 1.5 mm between adjacent grooves, a groove width of 60 micrometers, and a median particle size D50 of 5 micrometers in the silicon-carbon particles in the negative electrode active material. Other preparation methods of Comparative Example 1 are the same as those of Example 1 and will not be described in detail here.

[0083] Comparative Example 2

[0084] The difference between Comparative Example 2 and Example 1 is that the groove on the negative electrode of Comparative Example 2 is a rectangular groove with a vertical depth accounting for 30% of the electrode thickness, a spacing of 1.5 mm between adjacent grooves, a groove width of 60 micrometers, and a median particle size D50 of 10 micrometers for silicon-carbon particles in the negative electrode active material. The other preparation methods of Comparative Example 2 are the same as those of Example 1 and will not be described in detail here.

[0085] Performance testing:

[0086] 1. Dust falling quantity test: During the electrode winding stage, the dust falling from the electrode at the station before the material is fed in the winding process is collected. The quantity is quantified using a Keyence microscope. The dust falling quantity of Examples 1-9 and Comparative Examples 1-2 is recorded in Table 1.

[0087] 2. Kmean test of cell K value: K value is the voltage drop per unit time, with the unit being mV / h. The average value Kmean is calculated from the K values ​​of a certain number of finished batteries.

[0088] Table 1:

[0089] Group d / μm c / μm θ sinθ d / c x sinθ Dust drop number / gram Kmean / mV / h Example 1 60 5 10 0.174 2.088 7890 0.041 Example 2 60 5 15 0.259 3.108 6450 0.028 Example 3 60 5 20 0.342 4.104 6430 0.028 Example 4 60 10 30 0.5 3 6352 0.030 Example 5 60 10 35 0.574 3.444 6213 0.029 Example 6 80 5 15 0.259 4.144 6589 0.034 Example 7 80 10 35 0.574 4.592 6624 0.032 Example 8 80 12 45 0.707 4.713 6502 0.030 Example 9 80 12 55 0.819 5.46 6578 0.030 Comparative Example 1 60 5 0 0 0 12230 0.089 Comparative Example 2 60 10 0 0 0 15230 0.102 Comparative Example 3 100 4 45 0.707 17.68 11325 0.085 Comparative Example 4 80 3 45 0.707 18.86 10224 0.078

[0090] In this invention, the angle θ between one of the groove walls and the normal perpendicular to the surface of the active material layer, and the groove width d, can be detected by online laser or online spectroscopy on the instrument, or by offline spectroscopy equipment; the median particle size D50 or c value of the active particles is detected by a laser particle size analyzer.

[0091] The results measured in Table 1 show that, compared with Comparative Examples 1 and 2, the groove structure on the negative electrode of the present invention is more conducive to reducing electrode dust shedding, improving subsequent dust damage to the diaphragm, avoiding internal shorting, thereby improving the K value and enhancing product manufacturability. As shown in Examples 3, 5, and 9, when d and c are within the preferred range, but θ exceeds the preferred range (i.e., in Example 3, d and c are within the range of 50≤d<70, 4<c≤6.5, and θ is greater than 15°; in Example 5, d and c are within the range of 50≤d<70, 6.5<c≤12, and θ is greater than 30°; in Example 9, d and c are within the range of 70≤d<90, 4<c≤12, and θ is greater than 45°), although dust is slightly reduced, there is no significant difference. This indicates that the tilt angle within the preferred range defined by the present invention has reached the critical value for improvement. The present invention controls θ within the preferred range to avoid excessive tilt angle, which is beneficial to improving processing efficiency. As can be seen from Comparative Examples 3 and 4, when the value of d / c×sinθ is greater than 15.91, the amount of dust falling off increases compared to the amount of dust falling off in this invention. It can be seen that when the relationship between d, c and θ satisfies the relationship of this invention, the dust falling off of the electrode can be effectively reduced, the K value can be improved, and the manufacturability of the product can be enhanced.

[0092] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.

Claims

1. A pole piece characterized by: The active material layer includes active particles. The active material layer is provided with a plurality of grooves away from the surface of the current collector, the grooves penetrate the surface of the active material layer away from the current collector to form notches, the plurality of grooves are triangular in cross section in the width direction of the active material layer, and the plurality of grooves are arranged at intervals along the length direction of the active material layer. The pole piece satisfies the following relationship: 0.363 < d / c x sinθ < 15.

91. Wherein, d is the width of the notch, in units of μm; θ is the included angle between one of the groove walls and the normal line perpendicular to the surface of the active material layer; c is the median particle size D50 of the active particles, in units of μm.

2. The pole piece of claim 1, wherein: The pole piece satisfies the following conditions: 50 ≤ d < 70, 4 < c ≤ 6.5, and 5° < θ ≤ 15°.

3. The pole piece of claim 1, wherein: The pole piece satisfies the following conditions: 50 ≤ d < 70, 6.5 < c ≤ 12, and 5° < θ ≤ 30°.

4. The pole piece of claim 1, wherein: The pole piece satisfies the following conditions: 70 ≤ d < 90, 4 < c ≤ 12, and 5° < θ ≤ 45°.

5. The pole piece of claim 1, wherein: In the width direction of the active material layer, the grooves are distributed in a zigzag shape.

6. The pole piece of claim 1, wherein: The grooves are formed by mechanical punching.

7. The pole piece of claim 1, wherein: The vertical depth h of the grooves accounts for 20%-60% of the thickness of the active material layer. And / or, the plurality of grooves are arranged at equal intervals on the surface of the active material layer, and the groove spacing between adjacent grooves is 1.2-1.6 mm.

8. The pole piece of claim 1, wherein: The active particles are lithium cobalt oxide particles or silicon-containing particles.

9. A battery, characterized by: The battery includes the pole piece of any one of claims 1-8.

10. An electronic device, comprising: The battery includes the pole piece of claim 9.

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