Lithium ion battery electrode plate and lithium ion battery
By adding porous nanofibers and setting a gradient structure to the lithium-ion battery electrode, the problem of poor wettability of thick electrodes was solved, the electrolyte diffusion efficiency and battery performance were improved, and the capacity, rate and cycle performance were enhanced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- BEIJING CHEHEJIA AUTOMOBILE TECH CO LTD
- Filing Date
- 2025-03-28
- Publication Date
- 2026-05-08
AI Technical Summary
Thick lithium-ion battery electrodes have poor wettability, which prevents the electrolyte from penetrating effectively, limiting the charge transfer rate and reducing battery performance. In particular, during charging and discharging, this can lead to problems such as insufficient capacity, poor rate performance, and accelerated cycle life degradation.
Porous nanofibers are added to lithium-ion battery electrodes, and a multi-layer structure is set in the thickness direction of the electrode. The diameter and mass content of the porous nanofibers change in a gradient, which creates a fast electrolyte diffusion channel and improves the wettability and ionic conductivity of the electrode.
It improves the wettability of thick electrodes, reduces concentration polarization in the electrode thickness direction, and enhances the battery's capacity, rate performance, and cycle life, while also improving processing yield.
Smart Images
Figure CN224217465U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of lithium-ion battery technology, and particularly relates to a lithium-ion battery electrode sheet and a lithium-ion battery. Background Technology
[0002] During the operation of a lithium-ion battery, the electrolyte permeates into the electrode material and reacts chemically with the active substances therein, releasing electrons. The better the wettability of the electrode material with the electrolyte, the more effectively it can contact the electrolyte, thereby improving battery performance.
[0003] Electrode materials with good wettability can contact ions in the electrolyte more quickly, increasing charge transfer efficiency and improving the battery's energy density and charging speed. Conversely, electrode materials with poor wettability prevent the electrolyte from effectively penetrating, limiting charge transfer speed and reducing battery performance.
[0004] Therefore, electrode wettability is an important performance indicator that has a significant impact on battery capacity, cycle life, and charging speed.
[0005] When the thickness of the lithium-ion battery electrode is large, the tortuosity of the electrode is large, making it very difficult for the active material near the foil to be wetted, resulting in poor wetting. During charging and discharging, the liquid phase diffusion path of lithium ions in the electrode is long, and there is a large concentration polarization in the thickness direction of the electrode, which leads to insufficient capacity utilization, poor rate performance, and accelerated cycle life decay. Utility Model Content
[0006] The purpose of this invention is to provide a lithium-ion battery electrode sheet and a lithium-ion battery. The lithium-ion battery electrode sheet of this invention has better liquid absorption and retention performance, can increase the rapid diffusion channel of electrolyte, can greatly improve the wettability of thick electrodes (thickness > 50 μm), improve the ionic conductivity of the electrode sheet, reduce the concentration polarization in the thickness direction of the electrode sheet, and improve the SOC difference in the thickness direction of the electrode sheet and the problems of low capacity, poor rate capability and poor cycle performance of thick electrodes.
[0007] This utility model provides a lithium-ion battery electrode sheet, including a current collector and an active material layer;
[0008] The active material layer comprises active material particles, and porous nanofibers are distributed between the active material particles.
[0009] The active material layer comprises n sublayers, 2≤n≤10, from the electrode surface to the current collector, the diameter of the porous nanofibers in the n sublayers decreases sequentially and / or the mass content of the porous nanofibers in the n sublayers decreases sequentially.
[0010] The thickness of the active material layer is 40–100 μm.
[0011] This invention provides a lithium-ion battery, including the lithium-ion electrode sheet described above.
[0012] This invention provides a lithium-ion battery electrode sheet, comprising a current collector and an active material layer. The active material layer comprises active material particles, with porous nanofibers distributed between the particles. The active material layer comprises n sublayers, where 2 ≤ n ≤ 10. From the electrode surface to the current collector, the diameter of the porous nanofibers in the n sublayers decreases sequentially, and / or the mass content of the porous nanofibers in the n sublayers decreases sequentially. The thickness of the active material layer is 40–100 μm. For thicker electrodes with a thickness > 50 μm, this invention adds porous nanofibers to the electrode sheet and, based on the ion diffusion law, sets a multilayer structure of porous nanofibers with content gradients and / or diameter gradients in the thickness direction of the electrode sheet. This results in superior liquid absorption and retention performance, increases the rapid diffusion channels of the electrolyte, greatly improves the wettability of thick electrodes, enhances the ionic conductivity of the electrode sheet, reduces concentration polarization in the thickness direction of the electrode sheet, and improves the SOC difference in the thickness direction of the electrode sheet and the problems of low capacity, low rate capability, and poor cycle performance of thick electrodes. Furthermore, porous nanofibers possess excellent flexibility, which can improve the brittleness of thick electrode negative plates, alleviate high-voltage testing (Hi-pot) defects, and increase processing yield. Attached Figure Description
[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, 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 embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0014] Figure 1 This is a schematic diagram of the structure of the electrode sheet in one embodiment of the present invention. 1A is the current collector, 2A is the active material layer, 2A-1 is the first layer, and 2A-2 is the second layer in contact with the current collector 1A.
[0015] Figure 2 This is a schematic diagram of the structure of the electrode sheet in another embodiment of the present invention. 1B is the current collector, 2B is the active material layer, 2B-1 is the first layer, 2B-2 is the second layer, and 2B-3 is the third layer in contact with the current collector 1B.
[0016] Figure 3 This is a schematic diagram of the structure of the electrode sheet in another embodiment of the present invention. 1C is the current collector, 2C is the active material layer, 2C-1 is the first layer, and 2C-2 is the second layer in contact with the current collector 1C.
[0017] Figure 4 This is a schematic diagram of the structure of the electrode sheet in another embodiment of the present invention. 1D is the current collector, 2D is the active material layer, 2D-1 is the first layer, 2D-2 is the second layer, and 2D-3 is the third layer in contact with the current collector 1D.
[0018] Figure 5 This is a schematic diagram of the structure of the electrode sheet in another embodiment of the present invention. 1E is the current collector, 2E is the active material layer, 2E-1 is the first layer, 2E-2 is the second layer, 2E-3 is the third layer, and 2E-4 is the fourth layer in contact with the current collector 1E.
[0019] Figure 6 This is a schematic diagram of the structure of a sublayer in the active material layer of the electrode sheet in one embodiment of the present invention. 1 is an active material particle, 2 is a conductive agent, 3 is a binder, 4 is a porous nanofiber, and 5 is a current collector. Detailed Implementation
[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0021] The terms "first" and "second" in the specification and claims of this utility model may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.
[0022] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0023] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0024] This invention provides a lithium-ion battery electrode sheet, comprising a current collector and an active material layer;
[0025] The active material layer includes active material particles, and porous nanofibers are distributed between the active material particles. The porous nanofibers have a diameter of 5-500 nm, a length of 3-50 μm, and a porosity of 50-90%.
[0026] The active material layer comprises n sublayers, 2≤n≤10, from the electrode surface to the current collector, the diameter of the porous nanofibers in the n sublayers decreases sequentially and / or the mass content of the porous nanofibers in the n sublayers decreases sequentially.
[0027] The thickness of the active material layer is 40–100 μm.
[0028] In this invention, the lithium-ion battery electrode sheet can be either a positive electrode sheet or a negative electrode sheet, and the current collector is preferably a commonly used current collector such as copper foil or aluminum foil. There are no special limitations on the thickness of the current collector.
[0029] In this invention, the active material layer is obtained by coating an active material slurry onto the surface of the current collector and curing it. The active material slurry includes an active material, a conductive agent, a polymer binder, and porous nanofibers. The active material, conductive agent, and polymer binder are all commonly used positive / negative electrode active materials, conductive agents, and polymer binders in the art, and will not be described in detail here.
[0030] For thicker electrodes (positive electrode thickness > 50 μm, negative electrode thickness > 70 μm), the active material layer of this invention contains porous nanofibers. Specifically, the active material layer contains active material particles, and linear porous nanofibers are distributed between the active material particles. The porous nanofibers are one or more of the following: aramid porous nanofibers, polyimide porous nanofibers, modified polyolefin porous nanofibers, ceramic composite porous nanofibers, polyacrylonitrile porous nanofibers, and silica / polymer hybrid porous nanofibers.
[0031] In this invention, the diameter of the porous nanofibers is preferably 5–500 nm, more preferably 50–450 nm, such as 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, and 500 nm, preferably within a range where any of the above values is the upper or lower limit; the length of the porous nanofibers is preferably 3–50 μm, more preferably 10–40 μm. For example, the porous nanofibers have diameters of 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, and 50μm, preferably within the range of any of the above values as the upper or lower limit; the porosity of the porous nanofibers is preferably 50-90%, more preferably 60-80%; the mass content of the porous nanofibers in the active material layer is preferably 0.05-0.3%, more preferably 0.1-0.25%, such as 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, and 0.3%, preferably within the range of any of the above values as the upper or lower limit; the porous nanofibers are preferably porous nanofibers with regular pore cross-sections such as circular, triangular, and elliptical pores.
[0032] To further improve the liquid absorption and retention performance of the active material layer in the thickened electrode, the active material layer in this invention comprises n sublayers, where 2 ≤ n ≤ 10, preferably 2 ≤ n ≤ 5, such as n being 2, 3, 4, 5, 6, 7, 8, 9, 10, preferably within a range where any of the above values is the upper or lower limit. In the electrode thickness direction, from the electrode surface to the current collector, the diameter of the porous nanofibers in the n sublayers decreases sequentially and / or the porosity of each of the n sublayers decreases sequentially; preferably, from the electrode surface to the current collector, when the diameter of the porous nanofibers in the n sublayers decreases sequentially, the porosity of each of the n sublayers is the same or decreases sequentially, that is, the mass content of the porous nanofibers in the n sublayers is the same or decreases sequentially; when the porosity of each of the n sublayers is the same or decreases sequentially, that is, when the mass content of the porous nanofibers in the n sublayers decreases sequentially, the diameter of the porous nanofibers in the n sublayers is the same or decreases sequentially.
[0033] In one embodiment of this utility model, n = 2, such as Figure 1As shown, 1A is the current collector, 2A is the active material layer, 2A-1 is the first layer, and 2A-2 is the second layer in contact with the current collector 1A. The diameter of the porous nanofibers in the first layer 2A-1 to the second layer 2A-2 decreases sequentially, and the content of porous nanofibers is the same or decreases sequentially.
[0034] In this invention, the diameter of the porous nanofibers in the first layer 2A-1 is preferably 200-500 nm, more preferably 250-450 nm, such as 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, preferably within the range of any of the above values as the upper or lower limit. The thickness of the first layer 2A-1 is preferably 20-50 μm, more preferably 30-40 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, preferably within the range of any of the above values as the upper or lower limit.
[0035] The diameter of the porous nanofibers in the second layer 2A-2 is preferably 5-350 nm, more preferably 50-300 nm, such as 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, preferably within the range of any of the above values as the upper or lower limit. The thickness of the second layer 2A-2 is preferably 20-50 μm, more preferably 30-40 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, preferably within the range of any of the above values as the upper or lower limit.
[0036] In another embodiment of this utility model, n = 3, as shown below. Figure 2 As shown, 1B is the current collector, 2B is the active material layer, 2B-1 is the first layer, 2B-2 is the second layer, and 2B-3 is the third layer in contact with the current collector 1B. The diameter of the porous nanofibers in the first layer 2B-1 to the third layer 2B-3 decreases sequentially, and the content of porous nanofibers is the same or decreases sequentially.
[0037] In this invention, the diameter of the porous nanofibers in the first layer 2B-1 is preferably 300-500 nm, more preferably 350-450 nm, such as 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, and preferably within the range of any of the above values as the upper or lower limit. The thickness of the first layer 2B-1 is preferably 20-40 μm, more preferably 30-35 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, and preferably within the range of any of the above values as the upper or lower limit.
[0038] The diameter of the porous nanofibers in the second layer 2B-2 is preferably 200-400 nm, more preferably 250-350 nm, such as 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, and preferably within the range of any of the above values as the upper or lower limit; the thickness of the second layer 2B-2 is preferably 20-40 μm, more preferably 30-35 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, and preferably within the range of any of the above values as the upper or lower limit.
[0039] The diameter of the porous nanofibers in the third layer 2B-3 is preferably 5-300 nm, more preferably 50-250 nm, such as 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, preferably within the range of any of the above values as the upper or lower limit. The thickness of the third layer 2B-3 is preferably 20-40 μm, more preferably 30-35 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, preferably within the range of any of the above values as the upper or lower limit.
[0040] In another embodiment of this utility model, n = 2, as shown below. Figure 3 As shown, 1C is the current collector, 2C is the active material layer, 2C-1 is the first layer, and 2C-2 is the second layer in contact with the current collector 1C. The content of porous nanofibers in the first layer 2C-1 to the second layer 2C-2 decreases sequentially, and the diameter of the porous nanofibers is the same or decreases sequentially.
[0041] In this invention, the mass content of porous nanofibers in the first layer 2C-1 is preferably 0.15-0.3%, more preferably 0.2-0.25%, such as 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, preferably within the range of any of the above values as the upper or lower limit. The thickness of the first layer 2C-1 is preferably 20-50 μm, more preferably 30-40 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, preferably within the range of any of the above values as the upper or lower limit.
[0042] The mass content of porous nanofibers in the second layer 2C-2 is preferably 0.05-0.2%, more preferably 0.1-0.15%, such as 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, preferably within the range of any of the above values as the upper or lower limit. The thickness of the second layer 2C-2 is preferably 20-50 μm, more preferably 30-40 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, preferably within the range of any of the above values as the upper or lower limit.
[0043] In another embodiment of this utility model, n = 3, as shown below. Figure 4 As shown, 1D is the current collector, 2D is the active material layer, 2D-1 is the first layer, 2D-2 is the second layer, and 2D-3 is the third layer in contact with the current collector 1D. The content of porous nanofibers in the first layer 2D-1 to the third layer 2D-3 decreases sequentially, and the diameter of the porous nanofibers is the same or decreases sequentially.
[0044] In this invention, the mass content of porous nanofibers in the first layer 2D-1 is preferably 0.15-0.3%, more preferably 0.2-0.25%, such as 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, preferably within the range of any of the above values as the upper or lower limit; the thickness of the first layer 2B-1 is preferably 20-40 μm, more preferably 30-35 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, preferably within the range of any of the above values as the upper or lower limit.
[0045] The mass content of porous nanofibers in the second layer 2D-2 is preferably 0.1-0.2%, more preferably 0.12-0.18%, such as 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, preferably within the range of any of the above values as the upper or lower limit. The thickness of the second layer 2D-2 is preferably 20-40 μm, more preferably 30-35 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, preferably within the range of any of the above values as the upper or lower limit.
[0046] The mass content of porous nanofibers in the third layer 2D-3 is 0.05-0.15%, more preferably 0.05-0.1%, such as 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, preferably within the range of any of the above values as the upper or lower limit. The thickness of the third layer 2D-3 is preferably 20-40 μm, more preferably 30-35 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, preferably within the range of any of the above values as the upper or lower limit.
[0047] In another embodiment of this utility model, n = 4, as shown below. Figure 5 As shown, 1E is the current collector, 2E is the active material layer, 2E-1 is the first layer, 2E-2 is the second layer, 2E-3 is the third layer, and 2E-4 is the fourth layer in contact with the current collector 1E. The content of porous nanofibers in the first layer 2E-1 to the fourth layer 2E-4 decreases sequentially, and the diameter of the porous nanofibers is the same or decreases sequentially.
[0048] The mass content of porous nanofibers in the first layer 2E-1 is 0.2-0.3%, more preferably 0.22-0.28%, such as 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, preferably within the range of any of the above values as the upper or lower limit. The thickness of the second layer 2E-2 is preferably 15-30 μm, more preferably 20-25 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, preferably within the range of any of the above values as the upper or lower limit.
[0049] The mass content of porous nanofibers in the second layer 2E-2 is 0.15-0.25%, more preferably 0.18-0.22%, such as 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, preferably within the range of any of the above values as the upper or lower limit. The thickness of the second layer 2E-2 is preferably 15-30 μm, more preferably 20-25 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, preferably within the range of any of the above values as the upper or lower limit.
[0050] The mass content of porous nanofibers in the third layer 2E-3 is 0.08-0.18%, preferably 0.1-0.15%, such as 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, preferably within the range of any of the above values as the upper or lower limit. The thickness of the third layer 2E-3 is preferably 15-30 μm, more preferably 20-25 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, preferably within the range of any of the above values as the upper or lower limit.
[0051] The mass content of porous nanofibers in the fourth layer 2E-4 is 0.05-0.1%, more preferably 0.08-0.09%, such as 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, preferably within the range of any of the above values as the upper or lower limit. The thickness of the fourth layer 2E-4 is preferably 15-30 μm, more preferably 20-25 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, preferably within the range of any of the above values as the upper or lower limit.
[0052] This invention improves the wetting problem of thick electrodes by adding porous nanofiber additives to the electrode sheet and designing a gradient structure in the thickness direction to construct a rapid diffusion channel for the electrolyte in the thickness direction of the electrode sheet. The rapid ion diffusion channel constructed by porous nanofibers can reduce concentration polarization on the membrane side and foil side, improve the kinetics of thick electrodes, and improve capacity, DCR, and cycle performance.
[0053] This utility model also provides a lithium-ion battery, including the lithium-ion battery electrode sheet described above, wherein the lithium-ion battery electrode sheet is a positive electrode and / or a negative electrode, and the lithium-ion battery further includes a separator, an electrolyte and a casing. This utility model does not have any special restrictions on the type of separator and electrolyte, and commonly used separators and electrolytes in the field of lithium-ion batteries can be used.
[0054] In this invention, the separator is disposed between the positive and negative electrodes, separating them. The positive electrode, separator, and negative electrode can be stacked or wound together to form a battery cell. The battery cell is disposed inside the outer casing, and the space between the outer casing and the battery cell is filled with electrolyte. The porous nanofibers in the electrode sheet can improve the electrolyte absorption and retention performance, increase the rapid diffusion channels of the electrolyte, improve the wettability of thicker electrode sheets, and provide the electrode sheet with good flexibility. This improves the rate performance and cycle performance of the lithium-ion battery while also enhancing the processability of the electrode sheet.
[0055] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0056] Example 1:
[0057] (1) Preparation of negative electrode
[0058] Artificial graphite, conductive carbon (SP), porous nanofibers (300 nm in diameter and 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.12:1:0.18:0.3:2.4 and stirred until homogeneous to obtain slurry A; artificial graphite, conductive carbon (SP), porous nanofibers (300 nm in diameter and 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.2:1:0.1:0.3:2.4 and stirred until homogeneous to obtain slurry B.
[0059] Copper foil was used as the negative electrode current collector. Two layers were coated, with slurry A on the upper layer and B on the lower layer. The negative electrode was prepared by cold pressing, cutting, and slitting.
[0060] (2) Preparation of the positive electrode
[0061] NCM523, conductive carbon (SP), porous nanofibers (250 nm in diameter and 20 μm in length) and PVDF were mixed in N-methylpyrrolidone solvent at a weight ratio of approximately 95.9:2:0.1:2 and stirred until homogeneous to obtain positive electrode slurry A. NCM523, conductive carbon (SP), porous nanofibers (250 nm in diameter and 20 μm in length) and PVDF were mixed in N-methylpyrrolidone solvent at a weight ratio of approximately 95.95:2:0.05:2 and stirred until homogeneous to obtain positive electrode slurry B.
[0062] Then, aluminum foil was used as the positive electrode current collector for two-layer coating, with slurry A on the upper layer and B on the lower layer. The positive electrode current collector coated with slurry was baked at 120°C for 1 hour, and then cold-pressed, cut, and slit to prepare the positive electrode.
[0063] (3) Assemble bare battery cells
[0064] Stack the four layers of positive electrode, separator, negative electrode, and separator in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Then wind them up and attach finishing tape at the winding point to obtain the bare cell.
[0065] (4) Preparation of electrolyte
[0066] In an argon atmosphere, ethylene carbonate / ethyl methyl carbonate (3:7) was mixed and then lithium hexafluorophosphate was added at a concentration of 1.0 mol / L to obtain an electrolyte.
[0067] (5) Assemble lithium-ion batteries
[0068] The bare battery cell is placed into an aluminum shell, dried at 100°C, and then injected with the prepared electrolyte. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is completed.
[0069] (6) After assembling the battery, test its capacity, DCR, and cycle performance.
[0070] Example 2:
[0071] (1) Preparation of negative electrode
[0072] Artificial graphite, conductive carbon (SP), porous nanofibers (300 nm in diameter and 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.1:1:0.2:0.3:2.4 and stirred until homogeneous to obtain slurry A; artificial graphite, conductive carbon (SP), porous nanofibers (300 nm in diameter and 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.15:1:0.15:0.3:2.4 and stirred until homogeneous to obtain slurry B; artificial graphite, conductive carbon (SP), porous nanofibers, CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.2:1:0.1:0.3:2.4 and stirred until homogeneous to obtain slurry C;
[0073] Copper foil was used as the negative electrode current collector, and a three-layer coating was applied, with slurry A on the upper layer, B on the middle layer, and B on the lower layer. The negative electrode was prepared by cold pressing, cutting, and slitting.
[0074] (2) Other aspects are the same as in Example 1.
[0075] Example 3:
[0076] (1) Preparation of negative electrode
[0077] Artificial graphite, conductive carbon (SP), porous nanofibers A (400 nm in diameter and 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.15:1:0.15:0.3:2.4 and stirred until homogeneous to obtain slurry A; artificial graphite, conductive carbon (SP), porous nanofibers B (200 nm in diameter and 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.15:1:0.15:0.3:2.4 and stirred until homogeneous to obtain slurry B.
[0078] Copper foil was used as the negative electrode current collector. Two layers were coated, with slurry A on the upper layer and B on the lower layer. The negative electrode was prepared by cold pressing, cutting, and slitting.
[0079] (2) Other aspects are the same as in Example 1.
[0080] Example 4:
[0081] (1) Preparation of negative electrode
[0082] Artificial graphite, conductive carbon (SP), porous nanofibers A (450 nm in diameter, 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.15:1:0.15:0.3:2.4 and stirred until homogeneous to obtain slurry A; artificial graphite, conductive carbon (SP), porous nanofibers B (300 nm in diameter, 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.15:1:0.15:0.3:2.4 and stirred until homogeneous to obtain slurry B; artificial graphite, conductive carbon (SP), porous nanofibers C (100 nm in diameter, 25 μm in length), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.15:1:0.15:0.3:2.4 and stirred until homogeneous to obtain slurry C;
[0083] Copper foil was used as the negative electrode current collector, and a three-layer coating was applied, with slurry A on the upper layer, B on the middle layer, and B on the lower layer. The negative electrode was prepared by cold pressing, cutting, and slitting.
[0084] (2) Other aspects are the same as in Example 1.
[0085] Comparative example:
[0086] (1) Preparation of negative electrode
[0087] Artificial graphite, conductive carbon (SP), CMC-Na, and SBR were mixed in deionized water at a weight ratio of 96.3:1:0.3:2.4 and stirred until homogeneous. Copper foil was used as the negative electrode current collector, coated, cold-pressed, cut, and slit to prepare the negative electrode.
[0088] (2) Preparation of the positive electrode
[0089] NCM523, conductive carbon (SP) and PVDF were mixed in the solvent N-methylpyrrolidone at a weight ratio of approximately 96:2:2 and stirred evenly to obtain a positive electrode slurry. Then, aluminum foil was used as the positive electrode current collector. The positive electrode current collector coated with the slurry was baked at 120°C for 1 hour, and then cold-pressed, cut, and slit to prepare the positive electrode.
[0090] (3) Other aspects are the same as in Example 1.
[0091] The performance of the lithium-ion batteries obtained in Examples 1-4 and the comparative examples was tested, and the results are shown in Table 1.
[0092] Table 1 Performance tests of lithium-ion batteries in the examples and comparative examples.
[0093]
Claims
1. A lithium-ion battery electrode sheet, characterized in that, Includes current collector and active material layer; The active material layer comprises active material particles, and porous nanofibers are distributed between the active material particles. The active material layer comprises n sublayers, 2≤n≤10, from the electrode surface to the current collector, the diameter of the porous nanofibers in the n sublayers decreases sequentially and / or the mass content of the porous nanofibers in the n sublayers decreases sequentially. The thickness of the active material layer is 40–100 μm.
2. The lithium-ion battery electrode sheet according to claim 1, characterized in that, 2≤n≤4； The porous nanofibers in the active material layer have a mass content of 0.05–0.3%. The porous nanofibers have a diameter of 5–500 nm, a length of 3–50 μm, and a porosity of 50–90%.
3. The lithium-ion battery electrode sheet according to claim 1, characterized in that, From the electrode surface to the current collector, as the diameter of the porous nanofibers in the n sub-layers decreases sequentially, the mass content of the porous nanofibers in the n sub-layers is the same or decreases sequentially. When the mass content of porous nanofibers in the n sublayers decreases sequentially, the diameter of the porous nanofibers in the n sublayers is the same or decreases sequentially.
4. The lithium-ion battery electrode sheet according to claim 1, characterized in that, When n=2, the diameter of the porous nanofibers in the first layer of the active material layer is 200-500 nm. The diameter of the porous nanofibers in the second layer of the active material layer is 5–350 nm.
5. The lithium-ion battery electrode sheet according to claim 1, characterized in that, When n=3, the diameter of the porous nanofibers in the first layer of the active material layer is 300-500 nm; The diameter of the porous nanofibers in the second layer of the active material layer is 200-400 nm. The diameter of the porous nanofibers in the third layer of the active material layer is 5–300 nm.
6. The lithium-ion battery electrode sheet according to claim 1, characterized in that, When n=2, the mass content of porous nanofibers in the first layer of the active material layer is 0.15-0.3%. The second layer of the active material layer contains 0.05% to 0.2% porous nanofibers by mass.
7. The lithium-ion battery electrode sheet according to claim 1, characterized in that, When n=3, the mass content of porous nanofibers in the first layer of the active material layer is 0.15-0.3%; The second layer of the active material layer contains 0.1-0.2% porous nanofibers by mass. The porous nanofiber content in the third layer of the active material layer is 0.05–0.15% by mass.
8. The lithium-ion battery electrode sheet according to claim 1, characterized in that, When n=4, the mass content of the first layer of porous nanofibers in the active material layer is 0.2-0.3%; The second layer of the active material layer contains 0.15–0.25% porous nanofibers by mass. The mass content of porous nanofibers in the third layer of the active material layer is 0.08-0.18%. The fourth layer of the active material contains 0.05–0.1% porous nanofibers by mass.
9. The lithium-ion battery electrode sheet according to claim 1, characterized in that, When n=2, the thickness of the first layer in the active material layer is 20-30 μm; the thickness of the second layer is 20-30 μm. When n=3, the thickness of the first layer in the active material layer is 25-40 μm, the thickness of the second layer is 25-40 μm, and the thickness of the third layer is 25-40 μm; When n=4, the thickness of the first layer of the active material layer is 30-50 μm, the thickness of the second layer is 30-50 μm, the thickness of the third layer is 30-50 μm, and the thickness of the fourth layer is 30-50 μm.
10. A lithium-ion battery, characterized in that, Includes the lithium-ion electrode sheet as described in any one of claims 1 to 9.