Electrode sheet structure of battery, battery, and preparation method for electrode sheet

Abstract

An electrode sheet structure of a battery, comprising a metal layer. A transmission attenuation layer is provided on the edge of a first end portion of the metal layer; an active material layer is provided on the surface of the transmission attenuation layer away from the metal layer; the resistance value of the active material layer is R1; and the total resistance value of the metal layer, the active material layer, and the transmission attenuation layer is R2, and 1.3≤R2 / R1≤1.8. The transmission attenuation layer arranged between the metal layer and the active material layer reduces the transmission rate of electrons and inhibits the deintercalation speed of lithium ions, so that the safety problems such as lithium precipitation at the edge of electrode sheets, and ultra-thick head and tail parts of the electrode sheets are solved, and it is ensured that lithium precipitation does not occur at the head and tail parts of the electrode sheets, thereby improving the charging and discharging safety of the battery.

Description

A battery pole piece structure, battery and pole piece preparation method Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a battery pole piece structure, a battery and a method for preparing the pole piece. Background Art

[0002] Because the head and tail of existing lithium-ion batteries are close to the edge of the battery, when the battery kinetic window is insufficient or the process affects the interface between the cathode and anode and the separator, the edge effect of the battery will affect the rate of lithium ion insertion and extraction at the edge of the battery cell and the main part. As a result, lithium ions are easily deposited at the edge of the electrode, causing lithium deposition at the edge of the battery electrode, and causing the head and tail of the battery cell to be too thick, which in turn causes performance failure and safety risks of the battery cell. In the existing technology, there are currently no effective improvement measures in the industry for this anomaly. It can be seen that how to ensure that the battery electrode structure has sufficient safety has become one of the important difficulties in battery structure design. Therefore, it is urgent to propose a new technical solution to solve the above problems.

[0003] Summary of the Invention

[0004] One of the purposes of the present invention is to address the deficiencies in the prior art and provide a battery electrode structure that can effectively suppress the rate of lithium ion release from the edge of the electrode, thereby solving safety issues such as lithium deposition at the edge of the electrode and excessive thickness at the head and tail of the electrode, ensuring that lithium deposition will not occur at the head and tail of the electrode, and helping to improve the charge and discharge safety of the battery.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A battery electrode structure includes a metal layer, a first end edge of the metal layer having a weakened transmission layer, a side of the weakened transmission layer away from the metal layer having an active material layer, the resistance value of the active material layer is R1, and the total resistance value of the metal layer, the weakened transmission layer and the active material layer is R2, satisfying the relationship: 1.3≤R2 / R1≤1.8.

[0007] As an improvement to the electrode structure of the battery described in the present invention, the active material layer covers the surface of the weakened transmission layer and the metal layer, and the resistance value of at least part of the active material layer is 0.1Ω~10Ω, wherein the resistance value can be only the resistance value R1 of the area where the active material layer covers the weakened transmission layer, or it can be the resistance value of the entire area of ​​the active material layer that covers both the weakened transmission layer and the metal layer.

[0008] As an improvement to the electrode sheet structure of the battery according to the present invention, the thickness value of the active material layer embedded in the weakening transmission layer is d um, and the active material layer has active particles with an average particle size of d2 um, satisfying the relational expression: 0.05 ≤ d / d2 ≤ 0.3. In this numerical range, it can prevent the thickness of the active material layer embedded in the weakening transmission layer from being excessive, so as to ensure that the active particles of the active material layer do not contact and scratch the metal layer. Moreover, it is also necessary to prevent the thickness of the active material layer embedded in the weakening transmission layer from being too small, so as to prevent the situation that the adhesion between the active material layer and the weakening transmission layer is poor and easy to peel off.

[0009] As an improvement to the electrode sheet structure of the battery according to the present invention, the thickness value of the weakening transmission layer is D1 um, and D1, d, and d2 satisfy the relational expression: d < D1, 0.1 ≤ D1 / d2 ≤ 0.4. Within this thickness range, it can ensure that the effect of suppressing the lithium ion extraction speed at the edge part of the electrode sheet is the best, effectively overcome the safety problem of lithium deposition at the edge of the electrode sheet, and improve the charge-discharge safety of the battery.

[0010] As an improvement to the electrode sheet structure of the battery according to the present invention, the weakening transmission layer has particulate bodies with an average particle size of d1 um, and d1, d, and D1 satisfy the relational expression: d < d1 < D1 or d1 < d < D1. Among them, the particulate bodies can be ceramic particles. The ceramic particles can increase the resistance value of the weakening transmission layer, and the ceramic particles, as weakly conductive particles, have the effect of reducing electron transmission. The weakening transmission layer can be made by mixing a conductive agent and ceramic particles with an average particle size of d1 um.

[0011] As an improvement to the electrode sheet structure of the battery according to the present invention, the width value of the weakening transmission layer is W1, and W1 and D1 satisfy the relational expression: 0.005 ≤ D1 / W1 ≤ 0.025, 0.025 ≤ D1 / W1 ≤ 0.05. Within this ratio range, it can ensure that the effect of suppressing the lithium ion extraction speed at the edge part of the electrode sheet is the best, effectively overcome the safety problem of lithium deposition at the edge of the electrode sheet, and improve the charge-discharge safety of the battery.

[0012] As an improvement to the electrode sheet structure of the battery according to the present invention, the conductivity of the weakening transmission layer is not greater than 50% of the conductivity of the active material layer, and the conductivity of the weakening transmission layer is not less than 0.5×10 -5 S / cm to effectively regulate the performance of reducing electron transmission.

[0013] As an improvement to the electrode sheet structure of the battery described in the present invention, the conductivity of the weakening transmission layer is σ1, the conductivity of the active material layer is σ2, and the thickness value of the active material layer located on the surface of the weakening transmission layer is L2 um, satisfying the relationship: 100 ≤ (σ2 / σ1) × L2 ≤ 110, 0.05 ≤ σ1 / σ2 ≤ 0.5, d2 < L2, and σ2 is 1 × 10 -4 S / cm to 9 × 10 -2 S / cm. Within the above range, the effect of suppressing the lithium ion extraction speed at the edge of the electrode sheet can be guaranteed to be the best, effectively overcoming the safety problem of lithium deposition at the edge of the electrode sheet, and improving the charge and discharge safety of the battery.

[0014] As an improvement to the electrode sheet structure of the battery described in the present invention, when the active material layer is in a liquid state, the contact angle with the surface of the solid weakening transmission layer is θ°. The θ, the d, the D1, the R1, and the R2 satisfy the relationship: 2 ≤ (D1 - d) × θ × R2 / R1 ≤ 50. Within the above range, a better bonding effect and electrode sheet appearance between the active material layer and the weakening transmission layer can be guaranteed, and the charge and discharge safety of the battery is improved.

[0015] As an improvement to the electrode sheet structure of the battery described in the present invention, the active material layer has a first part and a second part connected to each other. The first part and the weakening transmission layer are stacked along the thickness direction of the electrode sheet structure to form a first stacking area. The second part and the first stacking area are arranged side by side on the metal layer. The thickness difference between the second part and the first stacking area is H, that is, there is a thickness difference of H um between the second part and the first stacking area. The H and the D1 satisfy the relationship: 0 ≤ H / D1 ≤ 3. Within the above range, the thickness uniformity of the electrode sheet can be guaranteed, and the charge and discharge uniformity of the battery is improved.

[0016] As an improvement to the electrode structure of the battery described in the present invention, the d2 is 10-30, the d1 is 0.5-3, the d is 1-3, the D1 is 1-4, the θ is 0.1-20, and the H is 0-10. Within the above numerical ranges, the active material layer has active particles with an average particle size of 10um-30um, the thickness of the active material layer embedded in the weakened transport layer is 1um-3um, the weakened transport layer has particles with an average particle size of 0.5um-3um, the thickness of the weakened transport layer is 1um-4um, and when the active material layer is in liquid state, it forms a contact angle with the surface of the solid weakened transport layer with a value of 0.1°-20°. The thickness difference between the second part and the first overlapping area is 0um-10um, which can ensure that the lithium ion escape rate is best suppressed at the edge of the electrode, effectively overcome the safety problem of lithium plating at the edge of the electrode, while ensuring the uniformity of the electrode and improving the charging and discharging safety of the battery.

[0017] A second object of the present invention is to provide a battery comprising the pole piece structure described above.

[0018] A third object of the present invention is to provide a method for preparing a pole piece, comprising the following steps:

[0019] S1. Prepare an active material layer with a resistance value of R1, select a desired metal layer, and make the total resistance of the metal layer, the transmission weakening layer, and the active material layer R2, and R1 and R2 satisfy the relationship: 1.3≤R2 / R1≤1.8, and prepare the desired transmission weakening layer;

[0020] S2. Coating the weakened transmission layer of step S1 on the edge of the first end of the metal layer, and coating the active material layer of step S1 on the side of the weakened transmission layer away from the metal layer to obtain the required electrode.

[0021] The beneficial effects of the present invention are: 1) the weakened transmission layer of the present invention is equivalent to coating a weak conductive coating on the foil at the head and tail edges of the battery cell. The weakened transmission layer arranged between the metal layer and the active material layer inhibits the release rate of lithium ions, improves and regulates the release rate of lithium ions in different areas of the electrode, and can significantly reduce the transmission rate of electrons at the edge of the electrode; 2) by inhibiting the release rate of lithium ions, the release rate of lithium ions at the edge of the electrode is reduced, which can effectively solve the safety problems such as lithium deposition at the edge of the electrode, easy lithium deposition at the edge of the battery cell, and excessive thickness of the head and tail of the electrode, and ensure that lithium deposition will not occur at the head and tail of the electrode; 3) since lithium deposition no longer occurs during charging and discharging of the battery, the charging and discharging safety of the battery can be greatly improved, thereby effectively overcoming the problem of unsafe charging and discharging of the battery, effectively and significantly enhancing the charging and discharging performance of the battery and extending the service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Features, advantages, and technical effects of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0023] FIG1 is a schematic diagram of the structure of the metal layer, the transmission weakening layer and the active material layer of the present invention.

[0024] FIG2 is a second schematic structural diagram of the metal layer, the transmission weakening layer and the active material layer of the present invention.

[0025] FIG3 is a schematic structural diagram of a pole piece of the present invention.

[0026] FIG. 4 is a schematic diagram showing the difference in ion transport between the transport layer and the active material layer according to the present invention.

[0027] The description of the accompanying drawings is as follows:

[0028] 1-metal layer;

[0029] 2- transmission-reducing layer; 21- particle body; D1- thickness of the transmission-reducing layer;

[0030] 3-active material layer; 3a-first part; 3b-second part; 31-active particles;

[0031] d-thickness value of the active material layer embedded in the weakened transmission layer; H-thickness difference between the second part of the active material layer and the first overlapping area formed in the pole piece structure; T-thickness direction of the pole piece structure. DETAILED DESCRIPTION

[0032] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but rather use differences in the functions of the components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term and should be interpreted as "including but not limited to". In addition, "substantially" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve the desired technical effect.

[0033] The inventors have discovered that lithium deposition at the edges of the battery cell pole pieces poses a high safety risk to battery charging and discharging. Therefore, a new pole piece structure is needed to overcome the problem of lithium deposition at the edges of the pole pieces.

[0034] The present invention will be further described below in conjunction with Figures 1 to 4 , but they are not intended to limit the present invention.

[0035] The electrode structure of a battery, as shown in FIGS. 1 to 3, includes a metal layer 1. The first end edge of the metal layer 1 has a weakened transmission layer 2. On the side of the weakened transmission layer 2 away from the metal layer 1, there is an active material layer 3. The resistance value of the active material layer 3 is R1, and the total resistance value of the metal layer 1, the weakened transmission layer 2 and the active material layer 3 is R2, satisfying the relationship: 1.3 ≤ R2 / R1 ≤ 1.8. More preferably, it satisfies the relationship: 1.5 ≤ R2 / R1 ≤ 1.7.

[0036] Preferably, the active material layer 3 covers the surfaces of the weakened transmission layer 2 and the metal layer 1. The resistance value of at least part of the active material layer 3 is 0.1 Ω to 10 Ω. Among them, this resistance value can be only the resistance value R1 of the area where the active material layer 3 covers the weakened transmission layer 2, or the resistance value of the overall area where the active material layer 3 covers both the weakened transmission layer 2 and the metal layer 1.

[0037] Preferably, the thickness value of the active material layer 3 embedded in the weakened transmission layer 2 is d um, and the active material layer 3 has active particles 31 with an average particle size of d2 um, satisfying the relationship: 0.05 ≤ d / d2 ≤ 0.1, 0.1 ≤ d / d2 ≤ 0.15, 0.15 ≤ d / d2 ≤ 0.2, 0.2 ≤ d / d2 ≤ 0.25 or 0.25 ≤ d / d2 ≤ 0.3.

[0038] Preferably, the thickness value of the weakened transmission layer 2 is D1 um, and D1, d and d2 satisfy the relationship: d < D1, 0.1 ≤ D1 / d2 ≤ 0.4. Among them, D1 and d2 satisfy the relationship: 0.1 ≤ D1 / d2 ≤ 0.15, 0.15 ≤ D1 / d2 ≤ 0.17, 0.17 ≤ D1 / d2 ≤ 0.195, 0.195 ≤ D1 / d2 ≤ 0.25, 0.25 ≤ D1 / d2 ≤ 0.3, 0.3 ≤ D1 / d2 ≤ 0.35 or 0.35 ≤ D1 / d2 ≤ 0.4.

[0039] Preferably, the weakened transmission layer 2 has granular bodies 21 with an average particle size of d1 um, and d1, d and D1 satisfy the relationship: d < d1 < D1 or d1 < d < D1.

[0040] Preferably, the width value of the weakened transmission layer 2 is W1, and W1 and D1 satisfy the relationship: 0.005 ≤ D1 / W1 ≤ 0.015, 0.015 ≤ D1 / W1 ≤ 0.025, 0.025 ≤ D1 / W1 ≤ 0.03, 0.03 ≤ D1 / W1 ≤ 0.035, 0.035 ≤ D1 / W1 ≤ 0.04, 0.04 ≤ D1 / W1 ≤ 0.045 or 0.045 ≤ D1 / W1 ≤ 0.05.

[0041] Preferably, the conductivity of the weakened transmission layer 2 is not greater than 50% of the conductivity of the active material layer 3, and the conductivity of the weakened transmission layer 2 is not less than 0.5×10-5 S / cm.

[0042] Preferably, the conductivity of the weakening transmission layer 2 is σ1, the conductivity of the active material layer 3 is σ2, and the thickness value of the active material layer 3 on the surface of the weakening transmission layer 2 is L2 um, satisfying the relationship: 100 ≤ (σ2 / σ1) × L2 ≤ 110, 0.05 ≤ σ1 / σ2 ≤ 0.5, d2 < L2, and σ2 is 1×10 -4 S / cm to 9×10 -2 S / cm.

[0043] Preferably, when the active material layer 3 is in a liquid state, it forms a contact angle of θ° with the surface of the solid weakening transmission layer 2. That is, when the slurry of the active material layer 3 is dropped onto the surface of the weakening transmission layer 2, a contact angle with a degree value of θ° is formed. This contact angle is formed by the contact of the liquid and solid before drying. Actually, it is the interfacial angle formed when the active material layer 3 is in a liquid state and the weakening transmission layer 2 is in a solid state. The solid content of the liquid active material layer 3 is 45-55%; the weight loss rate of the solid weakening transmission layer 2 is ≤1%.

[0044] More preferably, the degree value θ of the contact angle, the thickness value d of the active material layer 3 embedded in the weakening transmission layer 2, the thickness value D1 of the weakening transmission layer 2, the resistance value R1 of the active material layer 3, and the total resistance value R2 of the metal layer 1, the weakening transmission layer 2, and the active material layer 3 satisfy the relationship: 2 ≤ (D1 - d) × θ × R2 / R1 ≤ 15, 15 ≤ (D1 - d) × θ × R2 / R1 ≤ 30, 30 ≤ (D1 - d) × θ × R2 / R1 ≤ 50. The degree value of the contact angle can be 0.1° - 20°.

[0045] Preferably, the active material layer 3 has a first part 3a and a second part 3b connected to each other. The first part 3a overlaps with the weakening transmission layer 2 along the thickness direction T of the electrode structure to form a first overlapping area. The second part 3b is arranged side by side with the first overlapping area on the metal layer 1. The thickness difference H between the second part 3b of the active material layer 3 and the first overlapping area formed in the electrode structure satisfies the relationship: 0 ≤ H / D1 ≤ 1, 1 ≤ H / D1 ≤ 2, 2 ≤ H / D1 ≤ 3. H is the thickness difference between the first overlapping area on one side of the electrode and the second part 3b.

[0046] Preferably, the metal layer 1 has two opposite first end edges. Two weakening transmission layers 2 are relatively arranged on the same side of the metal layer 1. There are a total of four weakening transmission layers 2 on both the front and back sides of the metal layer 1. Among them, R2 can be the total resistance value of the entire system composed of the metal layer 1, the four weakening transmission layers 2 on the front and back sides of the metal layer 1, and the two active material layers 3 on the front and back sides of the metal layer 1.

[0047] The resistance value test method adopts the four-wire two-probe test principle, and the selected test area can be 154.025mm 2 The starting recording pressure can be 0.35~0.45T, and the time interval can be 1s; the contact angle test method is the sessile drop method, and the test is completed using an optical contact angle meter.

[0048] Specifically, the preparation method of the electrode of the present invention includes the following steps: preparing an active material layer with a resistance value of R1, selecting the required metal layer 1, making the total resistance value of the metal layer 1, the weakened transmission layer 2 and the active material layer 3 R2, R1 and R2 satisfy the relationship: 1.3≤R2 / R1≤1.8, and then preparing the required weakened transmission layer 2, and then, coating the aforementioned weakened transmission layer 2 on the edge of the first end of the metal layer 1, and coating the active material layer 3 with a resistance value of R1 on the side of the weakened transmission layer 2 away from the metal layer 1 to obtain the required electrode.

[0049] Furthermore, the present invention also provides a battery comprising a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet of the battery is the electrode sheet structure comprising the metal layer 1, the reduced transmission layer 2, and the active material layer 3, and the battery can be used in vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools, etc. Among them, the vehicle can be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc.; the spacecraft includes airplanes, rockets, space shuttles, and spacecraft, etc.; the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc.

[0050] Preferably, the battery can be a lithium ion battery, a sodium ion battery, a magnesium ion battery, etc.

[0051] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects are further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present invention are not limited thereto.

[0052] Example 1

[0053] Positive electrode sheet: See Figures 1 to 3, comprising a metal layer 1, a weakened transport layer 2 and an active material layer 3, the metal layer 1 is an aluminum current collector, first coated with a weak conductive material on the aluminum current collector, the weak conductive material can be made by mixing a conductive agent and ceramic particles with an average particle size of d1, d1 is 1.5um, the weak conductive material is coated at the position corresponding to the head and tail of the battery cell, that is, the weakened transport layer 2 is coated on the edge of the first end of the metal layer 1 to obtain a weak conductive current collector, and then the positive electrode active material, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed in an N-methylpyrrolidone solvent system in a weight ratio of 97.8:0.6:0.4:1.2 to obtain a positive electrode active material slurry, the positive electrode active material slurry is the active material layer 3, wherein the positive electrode active material can be LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 One or more of O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, and TiS2; the active particles 31 are a mixture of positive electrode active material, conductive agent acetylene black, and conductive carbon nanotubes; and finally, the positive electrode active material slurry is coated on the weakly conductive current collector; the portion of the positive electrode active material slurry superimposed on the weakened transmission layer 2 is the first portion 3a, and the portion of the positive electrode active material slurry not superimposed on the weakened transmission layer 2 is the second portion 3b; and then the positive electrode sheet is obtained by cold pressing and stripping.

[0054] Negative electrode sheet: The negative electrode active material, sodium carboxymethyl cellulose, and styrene-butadiene rubber (SBR) emulsion are mixed in a weight ratio of 97.4:1.3:1.3 to prepare a negative electrode active material slurry. The negative electrode active material can be a silicon-carbon material; the active material slurry is coated on a copper current collector to obtain an active material layer, and then cold pressed and slit to obtain a negative electrode sheet.

[0055] Isolation film: The PE surface is coated with a ceramic mixture as an isolation film.

[0056] Electrolyte: Ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) are mixed in a volume ratio of 1:1:4:4, and then fully dried lithium salt LiPF6 is dissolved in a mixed organic solvent at a ratio of 1 mol / L to prepare an electrolyte.

[0057] Preparation of a full battery: The positive electrode sheet, separator, and negative electrode sheet are wound or stacked to produce a bare cell, which is then encapsulated and injected with electrolyte to produce a finished lithium-ion battery.

[0058] The resistance value R1 of the active material layer 3 in the positive electrode sheet is 2Ω, the total resistance value R2 of the metal layer 1, the weakened transmission layer 2 and the active material layer 3 is 3Ω, the thickness d of the first portion 3a of the active material layer 3 embedded in the weakened transmission layer 2 is 2.4μm, the thickness D1 of the weakened transmission layer 2 is 3.7μm, the average particle size d2 of the active particles 31 is 19μm, and the conductivity σ1 of the weakened transmission layer 2 is 4.6×10 -3 S / cm, and the conductivity σ2 of the active material layer 3 is 1×10 -2 S / cm, the thickness L2 of the active material layer 3 located on the surface of the weakened transmission layer 2 is 50um, and the first overlapping area formed by the overlapping of the weakened transmission layer 2 and the first part 3a of the active material layer 3 in the electrode structure and the second part 3b of the adjacent active material layer 3 form a thickness difference H of 4.6um. The slurry of the active material layer 3 is dripped onto the surface of the weakened transmission layer 2 to form a contact angle of degree θ°=5°, and by adjusting R1, R2, d, D1 and d2, the following Examples 2 to 4 and Comparative Examples 1 to 4 are obtained, and the specific parameters are as shown in Table 1.

[0059] Moreover, H, θ, L2, σ1 and σ2 in Examples 1 to 4 and Comparative Examples 1, 2 and 4 are the same; R1, d and d2 in Example 1 and Example 2 are the same, and only R2 and D1 are different; R2 and d2 in Example 1 and Comparative Example 1 are the same, and only R1, d and D1 are different; d, D1 and d2 in Example 1 and Comparative Example 4 are the same, and only R1 and R2 are different; R1, R2, D1 and d2 in Example 3 and Example 4 are the same, and only d is different; R2, D1 and d2 in Example 3 and Comparative Example 2 are the same, and only R1 and d are different; L2, σ2, R1 and d2 in Example 3 and Comparative Example 3 are the same, and H, θ, σ1, d and D1 in Comparative Example 3 are all 0.

[0060] Table 1

[0061] Performance tests were conducted on Examples 1-4 and Comparative Examples 1-4. The charging window is the maximum rate at which lithium deposition does not occur when the battery cell is directly charged to the cutoff voltage after disassembly of the cell interface at 5.0C, 5.2C, 5.4C, 5.6C, 5.8C, and 6.0C. The lithium deposition windows for Examples 1-4 and Comparative Examples 1-4 were obtained as shown in Table 2 below.

[0062] Table 2

[0063] When there is no weakly conductive layer or when active material particles penetrate the weakly conductive layer and directly contact the foil, the electron transport rate cannot be effectively suppressed, resulting in an accelerated lithium ion release rate and the occurrence of lithium deposition. As shown in Figure 4, the weakened transport layer 2 effectively reduces the electron transport rate and suppresses the lithium ion release rate.

[0064] Therefore, one of the keys of the present invention is to control the resistance ratio of the electrode sheet with or without a weak conductive layer, the thickness of the active material layer embedded in the weak conductive coating, and the relationship between the thickness of the weak conductive coating and the average particle size of the active material layer, that is, to control the resistance value R1 of the active material layer 3 in the positive electrode sheet, the total resistance value R2 of the metal layer 1, the weakened transmission layer 2 and the active material layer 3, the thickness d of the active material layer 3 embedded in the weakened transmission layer 2, the thickness D1 of the weakened transmission layer 2 and the average particle size d2 of the active particles 31, so that 1.3R1 ≤R2≤1.8R1, 0.05d2≤d≤0.3d2, 0.1d2≤D1≤0.4d2 and d<D1; d is 1um~3um; D1 is 1um~4um; d2 is 10um~30um; R1 is 0.1Ω~10Ω; under these conditions, the weakly conductive coating reduces the transmission rate of electrons, inhibits the escape rate of lithium ions, and ensures that the particles of the active material layer will not pierce the weakly conductive layer, so as not to directly contact the foil and cause the effect of reducing the transmission rate of electrons to fail.

[0065] In addition, the present invention also demonstrates the effect of such a pole piece structure on charging time by changing only the value of L2 based on Example 1 to obtain Example 5, and by changing only L2, σ1, and σ2 based on Example 5 to obtain Examples 6-7 and Comparative Examples 5-8. That is, further exploring the relationship between the conductivity of the weakened transmission layer 2 being σ1, the conductivity of the active material layer 3 being σ2, and the thickness of the active material layer 3 located on the surface of the weakened transmission layer 2 being L2 to obtain the design parameters in Table 3 and the corresponding full charge times under 2C and 4C cycle conditions in Table 4 based on these parameters. At the same time, such testing can meet the single variable principle. Compared with Example 1 in Table 1, the variables in Examples 6-7 and Comparative Examples 5-8 are only L2, σ1, and σ2.

[0066] Table 3

[0067] The charging window is the maximum rate at which lithium deposition does not occur when the battery cell is directly charged at 2.0C, 2.5C, 3.0C, 3.5C, 4.0C, and 4.5C to the cutoff voltage after disassembly of the cell interface. The charging time is the time required for a full charge using the 2C and 4C cycle conditions. The following results were obtained by comparing Examples 5-7 with Comparative Examples 5-8.

[0068] Table 4

[0069] As can be seen from the table, when the conductivity of the weak conductive coating does not match the conductivity of the active material layer and the thickness of the electrode sheet, it significantly affects the performance of the battery cell. When (σ2 / σ1)×L2 < 100, the rate of lithium ion deintercalation is too slow and the charging time increases. When (σ2 / σ1)×L2 > 110, the transmission rate of electrons cannot be effectively inhibited, resulting in an accelerated rate of lithium ion extraction and the phenomenon of lithium deposition. It can be seen that the conductivity of the weakening transmission layer 2 is σ1, the conductivity of the active material layer 3 is σ2, and the thickness of the active material layer 3 on the surface of the weakening transmission layer 2 is L2, satisfying the relationship: 100 ≤ (σ2 / σ1)×L2 ≤ 110, 0.05 ≤ σ1 / σ2 ≤ 0.5, d2 < L2, and σ2 is 1×10 -4 S / cm to 9×10 -2 S / cm, within the above range, it can ensure that the extraction speed of lithium ions is best inhibited at the edge of the electrode sheet, effectively overcoming the safety problem of lithium deposition at the edge of the electrode sheet and improving the charge-discharge safety of the battery.

[0070] On the other hand, the present invention also obtains Examples 8 to 11 by only changing the value of θ based on Examples 1 to 4, and obtains Comparative Examples 9 to 12 by only changing θ based on Comparative Examples 1 to 4, obtains Comparative Example 13 by only changing the value of θ based on Example 8, obtains Comparative Example 14 by only changing the value of D1 based on Example 8, and obtains Comparative Example 15 by only changing the value of d based on Example 8, to explore the relationship between the angle value θ of the contact angle formed when the slurry of the active material layer 3 is dropped onto the surface of the weakening transmission layer 2, the resistance value R1 of the active material layer 3 in the positive electrode sheet, the total resistance value R2 of the metal layer 1, the weakening transmission layer 2 and the active material layer 3, the thickness value d of the active material layer 3 embedded in the weakening transmission layer 2, and the thickness value D1 of the weakening transmission layer 2, to obtain the design parameters in Table 5 and the differences in Poweloss under the 2C cycle regime conditions in Table 6.

[0071] Table 5

[0072] Powerloss refers to the difference between the capacity ratio of standard charge-discharge per hundred cycle nodes and the capacity ratio of charge-discharge in the cycle regime of adjacent cycle weeks, which is used to characterize the polarization of the battery cell. The larger the powerloss, the greater the polarization of the battery cell, and vice versa. By comparing Examples 8 to 11 and Comparative Examples 9 to 15, the results in Table 6 below are obtained.

[0073] Table 6

[0074] It can be seen from the table that when the resistance ratio of the electrode film with or without a weak conductive layer, the thickness of the active material layer 3 embedded in the weak conductive coating, and the contact angle with a value of θ° formed when the slurry of the active material layer 3 is dropped to the surface of the weakened transmission layer 2 present an unmatched relationship, that is, (D1-d)×θ×R2 / R1 is too large or too small, it significantly affects the performance of the battery cell. When 2≤(D1-d)×θ×R2 / R1≤50, there is better bonding effect and electrode appearance between the active material layer 3 and the weakened transmission layer 2. As the cycle proceeds, the electrode is in a stable state and the polarization grows slowly. When 50<(D1-d)×θ×R2 / R1 or (D1-d)×θ×R2 / R1<2, the bonding effect between the active material layer 3 and the weakened transmission layer 2 is weak. As the cycle proceeds, the active material layer 3 and the weakened transmission layer 2 begin to separate, resulting in a significant increase in the polarization of the battery cell, affecting the cycle performance of the battery cell.

[0075] Finally, the present invention also demonstrates the effect of this electrode structure on charge and discharge uniformity by changing only the value of H based on Example 1 to obtain Example 12, and by changing only H and D1 based on Example 12 to obtain Examples 13-14 and Comparative Examples 16-18. This further explores the relationship between H and the thickness D1 of the weakened transmission layer 2 to obtain the design parameters in Table 7, and based on these parameters, the difference in capacity retention under the 5C cycling standard in Table 8 is obtained. At the same time, such testing can meet the single variable principle. Compared with Example 1 in Table 1, the variables in Examples 13-14 and Comparative Examples 16-18 are only H and D1.

[0076] Table 7

[0077] The following results were obtained by comparing Examples 12 to 14 with Comparative Examples 16 to 18.

[0078] Table 8

[0079] The table shows that when H and the thickness of the weakened transport layer 2, D1, do not match, the cell performance is significantly affected. When 3 ≤ H / D1, the electrode thickness uniformity is poor, local polarization is uneven, resulting in poor charge and discharge uniformity, which in turn affects the cycle retention rate. It can be seen that when H and the thickness of the weakened transport layer 2, D1, satisfy the relationship of 0 ≤ H / D1 ≤ 3, within the above range, the electrode charge and discharge uniformity can be guaranteed, thereby improving the corresponding electrical performance.

[0080] Based on the disclosure and teachings of the above description, those skilled in the art will be able to make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments. Any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention fall within the scope of protection of the present invention. In addition, although certain specific terms are used in this description, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A battery pole piece structure, characterized in that: Comprising: A metal layer (1), the first end edge of the metal layer (1) having a weakened transmission layer (2); On a side of the weakened transmission layer (2) away from the metal layer (1), there is an active material layer (3); The resistance value of the active material layer (3) is R1, and the total resistance value of the metal layer (1), the weakened transmission layer (2), and the active material layer (3) is R2, satisfying the relation: 1.3 ≤ R2 / R1 ≤ 1.

8.

2. The battery electrode structure according to claim 1, wherein: The active material layer (3) covers the surfaces of the weakened transmission layer (2) and the metal layer (1), and at least part of the resistance value of the active material layer (3) is 0.1 Ω to 10 Ω.

3. The battery electrode structure according to claim 1 or 2, characterized in that: The thickness value of the active material layer (3) embedded in the weakened transmission layer (2) is d um, and the active material layer (3) has active particles (31) with an average particle size of d2 um, satisfying the relation: 0.05 ≤ d / d2 ≤ 0.

3.

4. The battery electrode structure according to claim 3, wherein: The thickness value of the weakened transmission layer (2) is D1 um, and D1, d, and d2 satisfy the relation: d < D1, 0.1 ≤ D1 / d2 ≤ 0.

4.

5. The battery electrode structure according to claim 4, characterized in that: The weakened transmission layer (2) has particulate bodies (21) with an average particle size of d1 um, and d1, d, and D1 satisfy the relation: d < d1 < D1 or d1 < d < D1.

6. The battery electrode structure according to claim 3, characterized in that: The conductivity of the weakened transmission layer (2) is not greater than 50% of the conductivity of the active material layer (3), and the conductivity of the weakened transmission layer (2) is not less than 0.5×10 -5 S / cm.

7. The battery electrode structure according to claim 6, characterized in that: The conductivity of the weakened transmission layer (2) is σ1, the conductivity of the active material layer (3) is σ2, and the thickness value of the active material layer (3) on the surface of the weakened transmission layer (2) is L2 um, satisfying the relation: 100 ≤ (σ2 / σ1) × L2 ≤ 110, 0.05 ≤ σ1 / σ2 ≤ 0.5, d2 < L2.

8. The battery electrode structure according to claim 4, characterized in that: When the active material layer (3) is in a liquid state, it forms a contact angle with a value of θ° with the surface of the solid weakened transmission layer (2), and θ, d, D1, R1, and R2 satisfy the relation: 2 ≤ (D1 - d) × θ × R2 / R1 ≤ 50.

9. The battery electrode structure according to claim 4, characterized in that: The active material layer (3) has a first part (3a) and a second part (3b) connected to each other. The first part (3a) and the weakened transmission layer (2) are stacked in the thickness direction of the electrode structure to form a first stacked area, and the second part (3b) is arranged side by side with the first stacked area on the metal layer (1). The thickness difference between the second part (3b) and the first stacked area is H, and H and D1 satisfy the relation: 0 ≤ H / D1 ≤ 3.

10. The battery electrode structure according to claim 4, wherein: The width value of the weakened transmission layer (2) is W1, and W1 and D1 satisfy the relation: 0.005 ≤ D1 / W1 ≤ 0.

05.

11. A battery, characterized in that: Comprising the electrode structure according to any one of claims 1 to 10.

12. A method for preparing a pole piece, characterized in that: Comprising the following steps: S1. Prepare an active material layer (3) with a resistance value of R1, select the required metal layer (1), make the total resistance value of the metal layer (1), the weakened transmission layer (2), and the active material layer (3) be R2, and R1 and R2 satisfy the relation: 1.3 ≤ R2 / R1 ≤ 1.8, and prepare the required weakened transmission layer (2); S2. Coating the weakened transmission layer (2) in step S1 on the edge of the first end of the metal layer (1), and coating the active material layer (3) in step S1 on the side of the weakened transmission layer (2) away from the metal layer (1) to obtain the required pole piece.

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