A new pole piece, a battery cell containing the new pole piece and a preparation method thereof

Abstract

The present application relates to the technical field of lithium ion batteries, and particularly relates to a novel pole piece, a battery cell containing the novel pole piece and a preparation method of the novel pole piece, the novel pole piece comprising a current collector, an active material layer and a tab, two end surfaces of the active material layer distributed along a length direction of the active material layer form two flow guide functional zones through setting of a plurality of flow guide grooves, and at least one surface of the active material layer located between the two flow guide functional zones forms a structure functional zone through setting of a three-dimensional structure array; the flow guide functional zone is used for accurately and rapidly transporting electrolyte to the structure functional zone and promoting rapid infiltration of the entire pole piece, the structure functional zone is used for stabilizing the electrolyte and accurately maintaining a gap between pole pieces of the battery cell, and the flow guide functional zone and the structure functional zone synergistically solve the problems of difficult control of a pole piece gap, poor interface stability, difficulty in electrolyte infiltration of a high-pressure density pole piece, long cycle stress mismatch and high short-circuit risk under mechanical abuse conditions in the prior art.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a novel electrode, a battery cell containing the novel electrode, and a method for preparing the same. Background Technology

[0002] The rapid development of the lithium battery industry has placed increasingly higher demands on the production efficiency of battery cells in consumer batteries. However, regardless of the cell structure, the safety and cycle performance of the cells are of paramount importance.

[0003] However, the safety and cycle performance of existing battery cells need further improvement for the following reasons: (1) Difficulty in controlling electrode gap: If the electrode gap is too large, it will cause relative slippage between the electrode and the separator, causing the positive and negative electrode coverage to deviate from the design standard, and even causing the electrode to flip. Moreover, the degree of relative slippage will intensify after long-term charging and discharging, which will seriously affect the appearance and performance of the cell, and affect the safety performance and cycle life of the cell. During the charging and discharging process of the battery, the electrode will expand and contract. If the electrode gap is too small, it will not only limit the expansion space and easily cause the active material to generate cycle cracks, but also increase the local pressure, causing the separator pores to close, hindering ion transport, and causing lithium plating, which will bring serious safety risks. (2) Poor interface stability: During vibration, impact or long-term cycling, micro-relative displacement easily occurs between the electrode and the separator. This instability not only causes the active material to fall off (powder) and increases the risk of micro short circuit, but also easily causes the overall deformation of the cell due to the mismatch of mechanical stress between the separator and the electrode. (3) Electrolyte wettability and interface contact issues: The continuous increase in electrode compaction density in pursuit of high energy density makes it increasingly difficult for the electrolyte to wet inside the electrode. Uneven wettability and poor electrode-separator interface contact lead to increased ion transport impedance, uneven internal battery reaction, inconsistent capacity performance, accelerated capacity decay and induction of lithium plating. (4) Long-cycle stress mismatch: During long-term cycling, the continuous "breathing" effect and heat generation of the battery will cause the electrode to expand and the separator to shrink. The mechanical stress generated between the two is different. Due to the mismatch of the thermal expansion coefficients, the electrode and the separator will generate internal stress, which will easily cause the electrode to wrinkle. Even the cell wrinkles will be wavy, which will seriously affect the cell's service life. (5) Short circuit risk: As the gap between the negative and positive electrodes of the battery cell is designed to be more and more extreme, the positive and negative electrodes are prone to contact under mechanical abuse conditions, causing short circuits or even fires.

[0004] Improving the structural design of the electrodes to solve the aforementioned technical problems is key to advancing lithium-ion battery technology. Therefore, this application is submitted. Summary of the Invention

[0005] Based on the background technology, this invention provides a novel electrode, a battery cell containing the novel electrode, and a method for preparing the same, aiming to solve the problems of existing technologies, such as difficulty in controlling electrode gaps, poor interface stability, difficulty in electrolyte wetting of high-voltage solid-density electrodes, high risk of short circuits under long-cycle stress mismatch and mechanical abuse.

[0006] To achieve the above objectives, the main technical solutions adopted by the present invention are as follows.

[0007] Firstly, the present invention proposes a novel electrode, comprising a current collector, an active material layer coated on the current collector, and an electrode tab electrically connected to the current collector. The active material layer has two end surfaces distributed along its length direction, which form two flow guiding functional areas by setting a plurality of flow guiding grooves. At least one surface of the active material layer located between the two flow guiding functional areas forms a structural functional area by setting a three-dimensional structural array, which is composed of a plurality of protrusions arranged in a sequence.

[0008] The aforementioned novel electrode has a current-guiding functional area used to precisely and rapidly deliver electrolyte to the structural functional area, promoting rapid wetting of the entire electrode. Its structural functional area is used to stably store the electrolyte delivered by the current-guiding functional area and precisely maintain the gap between the cell electrodes. The synergistic effect of the current-guiding functional area and the structural functional area significantly improves the battery's wetting efficiency, interface stability, reaction uniformity, and long cycle life. It fundamentally solves the problems of existing technologies, such as difficulty in controlling electrode gaps, poor interface stability, difficulty in wetting electrolyte in high-density electrodes, and high risk of short circuits under long-cycle stress mismatch and mechanical abuse.

[0009] It should be noted that the structural functional area can be set on a single surface of the active material layer (e.g., Figure 10 As shown), it can also be set on both surfaces of the active material layer (e.g. Figure 3 As shown, one surface of the active material layer has spherical protrusions arranged in a crown shape, and the other surface has spherical grooves arranged in a crown shape.

[0010] Furthermore, the protrusions are selected from any one of the following shapes: spherical, elongated, hexagonal prism, cylindrical, or flat-topped conical, while the drainage grooves are strip-shaped.

[0011] In this technical solution, the specific structure of the protrusion can be spherical (flat sphere, hemisphere, etc.), elongated (such as...) Figure 5 As shown), hexagonal prism (such as...) Figure 6 As shown), cylindrical (such as) Figure 7 As shown), flat-topped cone shape (such as...) Figure 8 Any one of the following (as shown). Protrusions of different shapes have different mechanical and conductive properties, and can all provide the required support strength and anti-collapse properties for the electrode.

[0012] In this technical solution, the flow channel is a strip-shaped structure. The flow channel is located on both sides of the structural functional area and does not overlap with the structural functional area. It is used to promote the rapid flow of electrolyte along the flow channel to the structural functional area and to extend deeper into the electrode, thereby quickly wetting the entire electrode.

[0013] Furthermore, the protrusion is spherical, with a height H of 50-230μm, preferably 80-120μm, and a bottom diameter R of 800-2500μm, preferably 1300-2000μm, i.e., a flat spherical structure. At the same time, the aspect ratio H / R is preferably 0.05-0.08.

[0014] In existing technologies, the dry coating thickness of mainstream graphite anode active material layers is typically 50-150 μm, with 80-120 μm being the most common. In this technical solution, the height H of the spherical protrusion is 50-230 μm. Utilizing the porosity and compression resilience of the active material layer, flattened spherical protrusions (also known as "hill-like" protrusions) are formed through localized densification. The upper limit design is primarily to ensure structural integrity while maximizing the liquid storage space, while the lower limit design is to ensure that the protrusion is not flattened by the diaphragm, maintaining a minimum liquid storage space. The bottom diameter R of the spherical protrusion is 800-2500 μm. The lower limit control is to ensure sufficient contact area with the diaphragm, while the upper limit control is mainly to avoid localized stress concentration caused by excessively large individual protrusions.

[0015] In practice, H is preferably controlled within 80-120 μm. This ensures that the protrusion height does not exceed the thickness of the active material layer and avoids damage to the current collector or breakage of the conductive network caused by the pressure-through of the active material layer. R is preferably controlled within 1300-2000 μm. This effectively guarantees mechanical strength and guides the electrolyte to penetrate from the electrode surface to the interior, allowing the electrolyte to permeate the entire electrode. Combined with the limitation of an aspect ratio H / R of 0.05-0.08, this helps to comprehensively optimize the mechanical strength, wettability, and electrolyte storage performance of the structural functional areas.

[0016] Furthermore, the center-to-center distances of the spherical protrusions in the length and width directions of the current collector are A1 and A2, respectively, with A1 and A2 being equal and ranging from 1.1R to 1.4R.

[0017] In this technical solution, the spherical protrusions are uniformly distributed, meaning that the distribution density of the spherical protrusions on the electrode surface is consistent. The center-to-center distance between two adjacent spherical protrusions in both the length and width directions of the current collector is 1.1R-1.4R. This three-dimensional structural array, which meets this distribution requirement, not only maximizes the electrolyte storage space but also reduces the tortuosity of the electrolyte flow path. This solves the problem that the reduced porosity after traditional rolling makes it difficult for the electrolyte to penetrate the entire volume of the electrode. While ensuring the mechanical strength of the electrode, it helps to comprehensively optimize the electrolyte storage performance and wetting efficiency, facilitating the rapid wetting and effective storage of the electrolyte flowing out of the self-guiding functional area.

[0018] It should be noted that while the spherical protrusions can also be non-uniformly distributed, in the corner areas after the electrode is wound, the distribution density of the spherical protrusions should be appropriately increased by 10%-50%, or the height of the spherical protrusions should be appropriately increased by 5%-20%. This is to actively compensate for the reduced effective gap in the corner area due to increased curvature, thereby achieving uniform control of the gap across the entire electrode surface. Considering both process cost and process difficulty, a uniform distribution of the spherical protrusions is preferred.

[0019] Furthermore, the width B1 of the strip-shaped drainage channel is 60-120μm, the thickness B2 is 20%-80% of the thickness of the active material layer, and the gap B3 between two adjacent strip-shaped drainage channels is 1-2mm; preferably, the angle α between the strip-shaped drainage channel and the length direction of the collector is 30°-90°; preferably, the angle α between the strip-shaped drainage channel and the length direction of the collector is 45°-60°.

[0020] In this technical solution, the dimensions of the strip structure should not be too small or too large. If it is too small, the electrolyte will have difficulty penetrating into the guide groove; if it is too large, too much active material will be lost, reducing the cell capacity. Through repeated experiments, this invention has found that the guiding effect is better when the width B1 of the guide groove of the strip structure is 60-120μm, the thickness B2 is 20%-80% of the thickness of the active material layer, and the gap B3 between two adjacent strip structure guide grooves is 1-2mm. Note: The height of the strip structure is less than the height of the guiding functional area, and it extends from the free end of the guiding functional area to near the structural functional area without overlapping it.

[0021] In this technical solution, the strip-shaped drainage channel is inclined, and the angle α (referred to as the "inclination angle") between it and the length direction of the current collector is 30°-90°, preferably 45°-60°. The strip-shaped drainage channel with the aforementioned inclination allows the electrolyte to spread rapidly along the channel into the depth of the electrode under capillary action, thus quickly wetting the entire electrode. It also allows the electrolyte to be quickly guided to the structural functional area and stored in the protrusions. The inclination angle of the strip-shaped drainage channel significantly affects the uniformity of electrolyte distribution. Too small or too large an inclination angle will result in an inability to simultaneously achieve efficient lateral diffusion and longitudinal propagation of the electrolyte, thereby affecting the overall diffusion rate. Through repeated experiments, this invention has found that when the angle α between the drainage channel and the length direction of the current collector is 30°-90°, especially 45°-60°, it helps the electrolyte to more uniformly and quickly cover and fill the protrusions of the entire structural functional area, forming a storage grid, thereby achieving the lowest internal resistance and the highest capacity retention rate.

[0022] Furthermore, the heights of the two flow guiding functional areas are H1 and H3, respectively, and the height of the structural functional area is H2, with 0.4≤H2 / (H1+H2+H3)≤0.8.

[0023] In this invention, the current-guiding functional area precisely and rapidly delivers the electrolyte to the structural functional area through capillary action. The structural functional area stably stores the electrolyte delivered by the current-guiding functional area and precisely maintains the gap between the cell electrodes. If the amount of electrolyte injected into the current-guiding functional area significantly exceeds the storage capacity of the structural functional area, excess electrolyte needs to be extracted during the second sealing process, which can easily lead to waste and pollution. If the amount of electrolyte injected is significantly less than the storage capacity, the electrodes will not be properly wetted, resulting in poor cell interface after cycling, increased risk of lithium plating, and deterioration of cycle performance.

[0024] Through creative effort, this invention has discovered that when the protrusion is spherical and its height H, bottom diameter R, and height-to-width ratio H / R meet the above requirements, the electrolyte storage performance of the structural functional area is good; when the drainage groove is strip-shaped and its width B1, thickness B2, gap B3, and tilt angle α meet the above requirements, the drainage performance of the flow guiding functional area is good. Under these conditions, when the structural functional area accounts for 0.4-0.8% of the total electrode height, the good flow guiding capacity of the flow guiding functional area results in a good match between the injection volume and the electrolyte storage space of the structural functional area, which helps to maximize the synergistic effect of the flow guiding functional area and the structural functional area. At this time, the electrolyte wetting effect and electrochemical performance are good. When the height of the structural functional area accounts for less than 0.4, the guiding capacity of the channel in the flow guiding functional area is excessive, and the amount of electrolyte injected far exceeds the storage space of the structural functional area. The super-strong guiding capacity is provided by the large-sized channel and is based on the sacrifice of active materials, thus reducing the cell capacity. When the height of the structural functional area accounts for more than 0.8, although the storage space of the structural functional area is large, the amount of electrolyte injected by the flow guiding functional area is small due to the poor guiding capacity of the channel, resulting in poor wetting effect. Both situations are not conducive to maximizing the synergistic effect between the flow guiding functional area and the structural functional area.

[0025] Furthermore, the protrusions are formed by rolling on the surface of the active material layer, while the drainage grooves are formed by laser etching or mechanical scratching on the surface of the active material layer.

[0026] Secondly, this invention proposes a battery cell containing novel electrode plates.

[0027] Thirdly, this invention proposes a method for preparing a battery cell, comprising the following steps: S1. Provides electrode sheet I, electrode sheet II, and diaphragm after roll pressing and slitting; S2. Form a flow-guiding functional area on electrode I by surface laser etching or mechanical scratching; S3. The electrode I obtained in S2 is hot-pressed together with the separator using a heated embossing roller, forming a structural functional region on the surface of at least one active material layer of the electrode I, resulting in a separator-electrode I-separator composite. The structural functional region can be set on only one surface of the active material layer (e.g., Figure 10 As shown), structural functional areas can also be set on both surfaces of the active material layer (e.g. Figure 3 As shown in the figure, whether to set it to single-sided or double-sided is specifically achieved by controlling the heating temperature of the embossing roller, i.e., the pressure during hot pressing. S4. The diaphragm-electrode-diaphragm composite is wound with electrode II to form a core.

[0028] In the above preparation method, electrode I and separator are first hot-pressed together to form a separator-electrode I-separator composite, which is then wound with electrode II to form a core. The separator-electrode I-separator composite has at least one side with several protrusions arranged in a spaced sequence, and the opposite side is a depression. When it is wound with electrode II to form a cell, the protrusions and depressions form a nested interlock, which not only specifically solves the problem of slippage during separator winding in the prior art, which leads to low coverage accuracy or even short circuit between positive and negative electrodes, but also ensures low interface impedance and enhances the mechanical stability of the interface.

[0029] It should be noted that: the above-mentioned electrode I can be a positive electrode or a negative electrode, but it is usually a negative electrode.

[0030] Furthermore, the heating temperature of the embossing roller is controlled near the softening point of the polymer binder of the diaphragm, and the width of the embossing roller is consistent with the width of the structural functional area. Preferably, the temperature difference between the heating temperature of the embossing roller and the softening point of the polymer binder of the diaphragm is -10°C to 10°C. Preferably, a structural functional region is formed on the surface of at least one active material layer of electrode I by controlling the pressure during hot-pressing composite to be 1.2-5 MPa.

[0031] In this technical solution, when a structural functional area is formed only on the surface of one active material layer of electrode I, hot pressing composite requires a hard embossing roller and a hard smooth roller to complete the process. Electrode I passes between the hard embossing roller and the hard smooth roller. Since both rollers are hard and only the embossing roller has protrusions, a structural functional area will only be formed on the surface of one active material layer of electrode I.

[0032] In this technical solution, when structural functional areas are formed simultaneously on the surfaces of the two active material layers of electrode I, hot pressing composite requires a hard embossing roller and a soft smooth roller with an HB of 50-75 to complete the process. Electrode I passes between the hard embossing roller and the soft smooth roller. Since the soft smooth roller will deform to a certain extent after the hard embossing roller is pressed down, structural functional areas will be formed on the surfaces of the two active material layers of electrode I.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects: 1. Precisely control the gap between electrodes to provide buffer space for electrode expansion stress; The raised structures arranged in a sequence within the functional area support the gaps between the electrodes, creating a stable and uniform physical spacing between the electrodes inside the cell. This provides a buffer space for the expansion of the electrodes during cycling, effectively alleviating expansion stress and fundamentally reducing the risk of lithium plating and electrode cracking.

[0034] 2. Improved structural stability and enhanced interface stability; Within the current-conducting functional area, the electrode and the separator can achieve large-area, robust surface contact through hot-pressing, effectively suppressing relative displacement between the electrode and the separator and preventing powder shedding and cell deformation. Within the structural functional area, the protrusions and depressions of the separator and the electrode form a mechanical interlocking structure, providing excellent resistance to shear stress. This mechanical interlocking structure makes the interface more stable when subjected to complex stresses such as vibration and impact, and after long-term cycling, relative displacement between the electrode and the separator is not likely to occur.

[0035] 3. Improved wettability and cell uniformity; The guiding channels within the flow-guiding area allow the electrolyte to rapidly enter the cell and the bottom layer of the electrodes via capillary action. By changing the specifications and inclination of the guiding channels, the flow path and wetting speed of the electrolyte can be flexibly adjusted. This design is particularly beneficial for solving the wetting problem of high-pressure solid electrodes, addressing electrolyte wettability and interface contact issues, significantly reducing internal resistance, improving the uniformity of internal reactions, and resulting in more consistent battery capacity, thereby extending cycle life. Furthermore, the protrusions form stable channels between the electrodes and the separator, which not only help build stable inter-electrode gap support but also help store electrolyte, increasing the battery's electrolyte capacity, thus slowing lithium release and improving battery cycle performance.

[0036] 4. Long-cycle stress matching and effective release improve cycle life; The protrusions within the structural functional area give the diaphragm and cell a certain degree of elastic deformation performance and elastic deformation space. This allows them to absorb and release mismatched stress during long-term cycling, preventing stress from accumulating at the interface and causing interface failure or diaphragm stretching deformation. This maintains the structural integrity of the cell during long-term cycling and improves cycle life.

[0037] 5. It simplifies the process flow, improves manufacturing efficiency, and further reduces the risk of short circuits; This invention combines the two manufacturing steps of "gap control structure forming" and "electrode-diaphragm composite" into one, simplifying the production process, reducing equipment investment and manufacturing costs, while improving product consistency and yield. It also reduces the risk of short circuits or even fires caused by the increasingly extreme gap design between the positive and negative electrodes of the battery cell under mechanical abuse conditions. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of the novel electrode proposed in Example 1; Figure 2 for Figure 1 A schematic diagram of the diaphragm-electrode I-diaphragm composite obtained by hot-pressing with a diaphragm; Figure 3 for Figure 2 A sectional view; Figure 4 This is a schematic diagram of the structure of the battery cell obtained in Example 1; Figure 5 A schematic diagram of the structure of the novel electrode sheet when the protrusion is elongated; Figure 6 A schematic diagram of the structure of the novel electrode sheet when the protrusion is a hexagonal prism; Figure 7 A schematic diagram of the structure of the novel electrode sheet when the protrusion is cylindrical; Figure 8 A schematic diagram of the structure of a novel electrode sheet with a flat-topped conical protrusion; Figure 9 This is a schematic diagram of the structure of the novel electrode sheet proposed in Example 16; Figure 10 This is a cross-sectional view of the diaphragm-electrode I-diaphragm composite obtained when the protrusions are distributed only on one surface of the active material layer.

[0040] Among them: 1. Current collector; 2. Active material layer; 3. Structural functional area; 31. Three-dimensional structural array; 311. Protrusion; 4. Flow guiding functional area; 41. Flow channel; 5. Tab; 6. Diaphragm; 7. Diaphragm-Electrode I-Diaphragm composite; 8. Electrode II. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0042] All chemical raw materials used in the following examples and comparative examples are commercially available, and all apparatus and operations involved are conventional in the art.

[0043] It should be noted that: the novel electrode sheets described in the following embodiments and comparative examples are specifically negative electrode sheets. The negative electrode current collector is a 6μm thick copper foil. The active material layer on the copper foil is prepared by mixing graphite (10wt% silicon content), conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose in a mass ratio of 97.5:0.4:1.2:0.9 and uniformly dispersing them in deionized water to first prepare a negative electrode active slurry. Then, the negative electrode active slurry is coated onto both surfaces of the copper foil and finally dried. Electrode sheet II8 is a positive electrode sheet. The positive electrode current collector is an 11μm thick aluminum foil. The active material layer on it is prepared by mixing lithium cobalt oxide, graphite, and PVDF in a mass ratio of 97.5:1.4:1.1 and uniformly dispersing them in NMP to prepare a positive electrode active slurry. Then, the positive electrode active slurry is coated onto both surfaces of the aluminum foil and finally dried. When assembling the soft-pack battery, the electrolyte is 1 The LiPF6 solution in M ​​was prepared using a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) in a molar ratio of 1:1:1. The membrane was a 9 μm thick ceramic membrane. The compacted density of the negative electrode sheets obtained in Examples 10-18 and Comparative Examples 3-6 was controlled to be ≥1.7 g / cm³. 3 .

[0044] Example 1

[0045] (1) such as Figure 1 As shown: A novel electrode includes a current collector 1, an active material layer 2 coated on the current collector 1 (the active material layer 2 has a thickness of 120 μm), and a tab 5 electrically connected to the current collector 1. The active material layer 2 has two flow-guiding functional areas 4 formed by several flow-guiding grooves 41 on its two end surfaces along its length. The active material layer 2 located between the two flow-guiding functional areas 4 forms a structural functional area 3 by a three-dimensional structural array 31, which is composed of several protrusions 311 arranged in a spaced sequence. The protrusions 311 are spherical cap-shaped, with a height H of 80 μm, a bottom diameter R of 1500 μm, and an aspect ratio H / R of 0.053. The center-to-center distances of the spherical cap-shaped protrusions in the length and width directions of the current collector 1 are A1 and A2, respectively, both A1 and A2 being 1900 μm (i.e., 1.27R). The drainage groove 41 is a strip structure with a width B1 of 100 μm and a thickness B2 of 60 μm (i.e., B2 is 50% of the thickness of the active material layer 2). The gap B3 between two adjacent drainage grooves 41 is 1.5 mm, and the angle α between the drainage groove 41 and the length direction of the current collector 1 is 45°.

[0046] Specifically, the total height of the novel electrode is 100mm, the heights H1 and H3 of the two flow guiding functional areas 4 are both 15mm, and the height H2 of the structural functional area 3 is 70mm.

[0047] (2) For example Figure 4 As shown, a winding core containing the above-mentioned novel electrode sheet is prepared by the following method: S1. Provides electrode sheet I, electrode sheet II 8 and diaphragm 6 after roll pressing and slitting; S2. The current-conducting functional area 4 is formed on electrode I by surface laser etching; S3. The electrode I obtained in S2 is hot-pressed together with the diaphragm 6 using a heated embossing roller, forming structural functional regions 3 on both surfaces of the active material layer 2 of the electrode I. The pressure during hot-pressing is 3 MPa, and the heating temperature of the embossing roller is 5°C higher than the softening point of the adhesive used in the diaphragm 6, resulting in the following... Figure 2 and Figure 3 The diaphragm-electrode I-diaphragm composite 7 is shown in the diagram. S4. The diaphragm-electrode-diaphragm composite 7 and electrode II 8 are wound together to form a core.

[0048] (3) Assemble the obtained core into a soft-pack battery.

[0049] Example 2

[0050] Compared to Example 1, the height of the protrusion was adjusted to 100 μm, while all other aspects remained the same as in Example 1.

[0051] Example 3

[0052] Compared to Example 1, the height of the protrusion was adjusted to 120 μm, while all other aspects remained the same as in Example 1.

[0053] Example 4

[0054] Compared with Example 1, the height of the protrusion was adjusted to 50 μm and the bottom diameter was adjusted to 2500 μm, while the rest remained the same as in Example 1.

[0055] Example 5

[0056] Compared with Example 1, the height of the protrusion was adjusted to 230 μm and the bottom diameter was adjusted to 800 μm, while the rest remained the same as in Example 1.

[0057] Example 6

[0058] Compared with Example 2, the height of the protrusion remains unchanged, the bottom diameter is adjusted to 1300μm, and everything else is the same as in Example 2.

[0059] Example 7

[0060] Compared with Example 2, the height of the protrusion remains unchanged, the bottom diameter is adjusted to 2000μm, and everything else is the same as in Example 2.

[0061] Example 8

[0062] Compared with Example 1, the center spacing A1 and A2 of the spherical protrusion in the length and width directions of the current collector are both adjusted to 1.1R, while the rest remain the same as in Example 1.

[0063] Example 9

[0064] Compared with Example 1, the center spacing A1 and A2 of the spherical protrusion in the length and width directions of the current collector are both adjusted to 1.4R, while the rest remain the same as in Example 1.

[0065] Comparative Example 1 Compared with Example 1, the height of the protrusion was adjusted from 80μm to 30μm, while all other aspects remained the same as in Example 1.

[0066] Comparative Example 2 Compared to Example 1, the height of the protrusion was adjusted from 80μm to 250μm, while all other aspects remained the same as in Example 1.

[0067] Examples 1-9, Comparative Examples 1 and 2 were used to investigate the influence of the specifications and arrangement of the spherical protrusions on the cell performance. The main technical parameters are shown in Table 1. The following performance tests were performed on the core and pouch cells obtained by the above embodiments: (1) Support strength and collapse resistance: the initial thickness T0 and the thickness T5 after standing for 5 hours were tested, and T5 / T0×100% was calculated to evaluate the support strength and collapse resistance; (2) 500-cycle capacity retention: 0.7C constant current and constant voltage charging to 4.53V, 0.025C cutoff, rest for 5 minutes, 1C constant current discharge to 3.0V, rest for 5 minutes, 500 cycles, the discharge capacity of the first cycle was recorded as the initial capacity C0, the discharge capacity of the 500th cycle was recorded as the initial capacity and the capacity after the cycle C0. 500 500-cycle capacity retention rate = C 500 / C0×100%. The specific performance test structure is shown in Table 1.

[0068]

[0069] As shown in Table 1, the test results of Examples 1-9 indicate that when the height H of the spherical protrusion is 50-230 μm, the bottom diameter R is 800-2500 μm, and the center spacing A1 and A2 in the length and width directions of the current collector are equal and 1.1R-1.4R, the three-dimensional structure array constructed by several spherical protrusions can stably store electrolyte and accurately maintain the gap between the cell electrodes. The resulting electrode has high support strength and can maintain good anti-collapse performance. However, when the protrusion height H is less than 50 μm, as in Comparative Example 1, the protrusion is too flat, resulting in insufficient support strength. During long cycles, it cannot effectively maintain the electrode gap, causing the gap to be filled too quickly by the expanding electrode, hindering ion transport, aggravating lithium plating, and drastically deteriorating cycle performance. When the protrusion strength H is greater than 230 μm, as in Comparative Example 2, the protrusion is too high. During static placement, it will bear a large tension, causing the top to be easily pressed down due to stress concentration, which is also detrimental to cycle performance.

[0070] Furthermore, a comparison of the test results from Examples 1-3, 6-9 and Examples 4 and 5 shows that when the height H of the spherical protrusion is 80-120 μm, the bottom diameter R is 1300-2000 μm, and the aspect ratio H / R is 0.05-0.08, a good balance is achieved between the support strength and structural integrity of the electrode. The electrode has both good mechanical support capability and structural durability, thus more effectively solving the problems of electrode gap control and long-cycle stress mismatch, resulting in better cell cycle performance.

[0071] Example 10

[0072] A novel electrode includes a current collector 1, an active material layer 2 coated on the current collector 1, and an electrode tab 5 electrically connected to the current collector 1. The active material layer 2 has two flow guiding functional areas 4 formed by a plurality of flow guiding grooves 41 on its two end surfaces along its length direction. The surface of the active material layer 2 located between the two flow guiding functional areas 4 forms a structural functional area 3 by a three-dimensional structural array 31. The three-dimensional structural array 31 is composed of a plurality of protrusions 311 arranged in a spaced sequence.

[0073] Specifically, the protrusion 311 is spherical, with a height H of 100 μm and a bottom diameter R of 1500 μm. The center-to-center distances of the spherical protrusions in the length and width directions of the current collector 1 are A1 and A2, respectively, and both A1 and A2 are 1800 μm (i.e., 1.2R).

[0074] Specifically, the drainage channel 41 is a strip structure with a width B1 of 80 μm and a thickness B2 of 36 μm (the active material layer 2 has a thickness of 120 μm, i.e., B2 is 30% of the thickness of the active material layer 2). The gap B3 between two adjacent drainage channels 41 is 1.5 mm, and the angle α between the drainage channel 41 and the length direction of the current collector 1 is 45°.

[0075] Specifically, the total height of the novel electrode is 100mm, the heights H1 and H3 of the two flow guiding functional areas 4 are both 15mm, and the height H2 of the structural functional area 3 is 70mm.

[0076] Example 11

[0077] Compared with Example 10, the width B1 of the strip structure is adjusted to 100 μm and the thickness B2 is adjusted to 60 μm, that is, the thickness B2 of the strip structure is 50% of the thickness of the active material layer 2, and the rest are consistent with Example 10.

[0078] Example 12

[0079] Compared with Example 10, the width B1 of the strip structure is adjusted to 120 μm and the thickness B2 is adjusted to 84 μm, that is, the thickness B2 of the strip structure is 70% of the thickness of the active material layer 2, and the rest are consistent with Example 10.

[0080] Example 13

[0081] Compared with Example 10, the width B1 of the strip structure is adjusted to 60 μm and the thickness B2 is adjusted to 24 μm, that is, the thickness B2 of the strip structure is 20% of the thickness of the active material layer 2, and the rest are consistent with Example 10.

[0082] Example 14

[0083] Compared with Example 10, the width B1 of the strip structure is adjusted to 120 μm and the thickness B2 is adjusted to 96 μm, that is, the thickness B2 of the strip structure is 80% of the thickness of the active material layer 2, and the rest are consistent with Example 10.

[0084] Example 15

[0085] Compared with Example 10, the included angle α between the drainage groove 41 and the current collector 1 along its length is adjusted to 60°, the width B1 of the strip structure is adjusted to 100μm and the thickness B2 is adjusted to 60μm, that is, the thickness B2 of the strip structure is 50% of the thickness of the active material layer 2, and the rest are consistent with Example 10.

[0086] Example 16

[0087] like Figure 9As shown, compared with Example 15, the included angle α between the diversion groove 41 and the collector 1 along the length direction is adjusted to 90°, while the rest remains the same as in Example 15.

[0088] Example 17

[0089] Compared with Example 15, the included angle α between the diversion groove 41 and the collector 1 along its length is adjusted to 55°, while the rest remains the same as in Example 15.

[0090] Example 18

[0091] Compared with Example 15, the included angle α between the diversion groove 41 and the collector 1 along the length direction is adjusted to 30°, while the rest remains the same as in Example 15.

[0092] Comparative Example 3 Compared with Example 13, the width B1 of the strip structure is adjusted to 50 μm and the thickness B2 of the strip structure is adjusted to 12 μm, which is 10% of the thickness of the active material layer 2. All other aspects remain the same as in Example 13.

[0093] Comparative Example 4 Compared with Example 10, the width B1 of the strip structure is adjusted to 150 μm and the thickness B2 is adjusted to 102 μm, which is 85% of the thickness of the active material layer 2. The rest are the same as in Example 10.

[0094] Comparative Example 5 Compared with Example 11, the included angle α between the flow channel 41 and the flow collector 1 along its length is adjusted to 20°, while the rest remains the same as in Example 11.

[0095] Comparative Example 6 Compared with Example 10, the flow channel 41 is not provided, but everything else is the same as Example 10.

[0096] Examples 10-18 and Comparative Examples 3-6 were used to investigate the influence of the structure (specifications and inclination) of the drain groove 41 on the cell performance. The main technical parameters are shown in Table 2. The following performance tests were performed on the core and pouch cells obtained by the above embodiments: (1) electrolyte complete immersion time; (2) DC internal resistance DCIR; (3) capacity retention rate after 100 cycles. The specific performance test results are shown in Table 2.

[0097] The principle of the electrolyte complete immersion time test is as follows: A high-precision balance (accuracy of at least 0.1 mg) is used to detect the weight change of the electrode after the electrolyte is injected in real time. When the weight of the electrode reaches saturation and tends to stabilize, it is considered that the electrolyte has completely immersed the electrode. The time required from the start of the injection to the complete immersion state is recorded as the complete immersion time. The test environment temperature is 25±1℃. The specific operation steps are as follows: 1) Immerse the electrode completely in the electrolyte; 2) Remove the electrode every 5 minutes and shake it slightly to remove any electrolyte beads and make it heavy; 3) Repeat step 2) until the weight is consistent and stable for three consecutive tests. The time to reach the first stable weight is recorded as the complete immersion time.

[0098] The DC internal resistance (DCIR) test temperature is 25±3℃, and the voltage accuracy and current accuracy of the charging and discharging equipment are ±0.05%FS and ±0.05%FS, respectively. The test is conducted in a constant temperature room with a temperature deviation of ±3℃. The specific test operation is as follows: under the shipment voltage of 3.78-3.85V, discharge with a current of 0.1C for 10s and record the test voltage as V1. Then discharge with a current of 1C for 10s and record the voltage as V2. DC internal resistance (DCIR) = (V1-V2) / (I2-I1).

[0099] The test procedure for 100-week capacity retention is similar to that for 500-week capacity retention as shown in Table 1.

[0100]

[0101] As shown in Table 2: (1) Comparison of the test results of Examples 10-14 and Comparative Example 6 shows that when the channel 41 is a strip structure and the width B1 of the strip structure is 60-120 μm and the thickness B2 is 20%-80% of the thickness of the active material layer 2, the constructed flow-guiding functional area 4 helps to accurately and quickly deliver the electrolyte to the structural functional area 3. The electrolyte wetting time of the resulting core is significantly shortened from more than 120 min to less than 1 h, and it can be completely wetting in as little as 15 min. Moreover, the DC internal resistance is reduced to varying degrees and the 100-cycle capacity retention rate is significantly improved, indicating that its conductivity is optimized and its cycle performance is significantly improved. When the width B1 and thickness B2 of the strip structure are below the range defined by this invention, as shown in Comparative Example 3, the width of the channel 41 is too narrow and the depth is too shallow, resulting in insufficient flow conduction capacity, extremely slow and uneven wetting, leading to high internal resistance and poor cycle performance. When the width B1 and thickness B2 of the strip structure are above the range defined by this invention, as shown in Comparative Example 4, the width of the channel 41 is too wide and the depth is too deep. Although the flow conduction capacity is strong and the wetting speed is fast, too much active material is lost, directly sacrificing the specific capacity and initial efficiency of the cell, and damaging the energy density and long-term cycle performance.

[0102] (2) Comparison of the test results of Examples 11, 15-18 and Comparative Example 5 shows that, under the same conditions, when the angle α between the drain groove 41 and the current collector 1 along its length is controlled between 30° and 90°, the electrolyte can completely wet the cell within 21-35 minutes, and the cell has good conductivity and a 100-cycle capacity retention rate of 88% or higher. In particular, when α is controlled between 45° and 60°, the performance is even better. It can be seen that the drain groove 41 within this angle range helps to make the electrolyte cover and fill the protrusions 311 most uniformly and quickly to form a liquid storage grid, thereby achieving the lowest internal resistance and the highest capacity retention rate. When α is less than 30°, as shown in Comparative Example 5, although it is beneficial for longitudinal advancement, the efficiency of lateral diffusion to all the gaps between the protrusions 311 is low, which leads to increased internal resistance and deterioration of cycle performance.

[0103] Example 19

[0104] Compared with Example 2, the total height of the new electrode remains unchanged at 100mm, but the height H2 of the structural functional area 3 is adjusted from 70mm to 40mm, and the heights H1 and H3 of the two flow guiding functional areas are both adjusted from 15mm to 30mm. The rest are the same as in Example 2.

[0105] Example 20

[0106] Compared with Example 2, the total height of the new electrode remains unchanged at 100mm, but the height H2 of the structural functional area 3 is adjusted from 70mm to 50mm, and the heights H1 and H3 of the two flow guiding functional areas are both adjusted from 15mm to 25mm. The rest are the same as in Example 2.

[0107] Example 21

[0108] Compared with Example 2, the total height of the new electrode remains unchanged at 100mm, but the height H2 of the structural functional area 3 is adjusted from 70mm to 60mm, and the heights H1 and H3 of the two flow guiding functional areas are both adjusted from 15mm to 20mm. The rest are the same as in Example 2.

[0109] Example 22

[0110] Compared with Example 2, the total height of the new electrode remains unchanged at 100mm, but the height H2 of the structural functional area 3 is adjusted from 70mm to 80mm, and the heights H1 and H3 of the two flow guiding functional areas are both adjusted from 15mm to 10mm. The rest are the same as in Example 2.

[0111] Comparative Example 7 Compared with Example 2, the total height of the new electrode remains unchanged at 100mm, but the height H2 of the structural functional area 3 is adjusted from 70mm to 35mm, and the heights H1 and H3 of the two flow guiding functional areas are both adjusted from 15mm to 32.5mm. The rest are the same as in Example 2.

[0112] Comparative Example 8 Compared with Example 2, the total height of the new electrode remains unchanged at 100mm, but the height H2 of the structural functional area 3 is adjusted from 70mm to 85mm, and the heights H1 and H3 of the two flow guiding functional areas are both adjusted from 15mm to 7.5mm. The rest are the same as in Example 2.

[0113] Furthermore, to explore how the structural functional area and the flow guiding functional area can be designed to maximize their synergistic effect, this invention also conducted Examples 19-22, Comparative Example 7, and Comparative Example 8, the main technical parameters of which are shown in Table 3. The cores obtained in the above embodiments were subjected to the following performance tests: electrolyte complete wetting time, DC internal resistance (DCIR), and capacity retention rate after 100 cycles (the specific testing methods are the same as in Table 2).

[0114]

[0115] As shown in Table 3, a comparison of the test results of Examples 2, 19-22, Comparative Example 7, and Comparative Example 8 shows that when the proportion of the structural functional area in the height of the entire electrode is 0.4-0.8, the DC internal resistance is relatively low and the capacity retention rate after 100 cycles is above 90%. This indicates that this height ratio range is more conducive to the synergistic effect of the current-conducting functional area and the structural functional area, and the wetting efficiency, interface stability, and long cycle life of the battery are all improved. In particular, when the height ratio of the structural functional area is 0.7, the electrolyte complete wetting time is the shortest and the capacity retention rate after 100 cycles is the highest. When the height ratio of the structural functional regions exceeds the range defined in this invention, the wetting performance and electrochemical performance are unsatisfactory. For example, as shown in Comparative Example 7, when the height H2 ratio of the structural functional regions is 0.35, the conductivity of the current-conducting functional regions is too strong. Although the electrolyte wetting speed is fast, the long-term cycle performance of the battery is significantly degraded. Similarly, as shown in Comparative Example 8, when the height H2 ratio of the structural functional regions is 0.85, the conductivity of the current-conducting functional regions is too weak. The insufficient electrolyte injection volume leads to poor wetting effect, increased internal resistance, and similarly, poor long-term cycle performance of the battery. Clearly, both the current-conducting and structural functional regions need not only good conductivity and electrolyte storage capacity but also a certain height ratio. Only with an appropriate height ratio can the electrolyte injection volume generated by the good conductivity of the current-conducting functional regions match the electrolyte storage space constructed by the good electrolyte storage capacity of the structural functional regions, thereby maximizing the synergistic effect of the current-conducting and structural functional regions.

[0116] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

Claims

1. A novel electrode, characterized in that: The active material layer (2) is coated on the current collector (1) and the electrode (5) electrically connected to the current collector (1). The active material layer (2) is characterized in that: the two ends of the active material layer (2) distributed along its length direction form two flow guiding functional areas (4) by setting a plurality of flow guiding grooves (41), and at least one surface of the active material layer (2) located between the two flow guiding functional areas (4) forms a structural functional area (3) by setting a three-dimensional structural array (31). The three-dimensional structural array (31) is composed of a plurality of protrusions (311) arranged in a spaced sequence.

2. The novel electrode sheet according to claim 1, characterized in that: The protrusion (311) is selected from any one of the following: spherical crown shape, long strip shape, hexagonal prism, cylindrical shape, and flat-topped conical shape. The drainage groove (41) is a strip structure.

3. The novel electrode sheet according to claim 1, characterized in that: The protrusion (311) is spherical, and the height H of the spherical protrusion is 50-230μm and the bottom diameter R is 800-2500μm; Preferably, the height H of the spherical protrusion is 80-120 μm, the bottom diameter R is 1300-2000 μm, and the aspect ratio H / R is 0.05-0.

08.

4. The novel electrode sheet according to claim 3, characterized in that: The center-to-center distances of the spherical protrusions in the length and width directions of the current collector (1) are A1 and A2, respectively, with A1 and A2 being equal and 1.1R-1.4R.

5. The novel electrode sheet according to claim 2, characterized in that: The width B1 of the strip structure's drainage channel is 60-120μm, the thickness B2 is 20%-80% of the thickness of the active material layer (2), and the gap B3 between two adjacent strip structures' drainage channels is 1-2mm. Preferably, the angle α between the drainage channel of the strip structure and the length direction of the collector (1) is 30°-90°; Preferably, the angle α between the drainage channel of the strip structure and the length direction of the collector (1) is 45°-60°.

6. The novel electrode sheet according to any one of claims 1-5, characterized in that: The heights of the two flow guiding functional areas (4) are H1 and H3 respectively, and the height of the structural functional area (3) is H2, 0.4≤H2 / (H1+H2+H3)≤0.

8.

7. The novel electrode sheet according to claim 1, characterized in that: The protrusion (311) is formed by rolling on the surface of the active material layer (2), and the drainage groove (41) is formed by laser etching or mechanical scratching on the surface of the active material layer (2).

8. A battery cell comprising the novel electrode sheet according to any one of claims 1-7.

9. A method for preparing a battery cell as described in claim 8, characterized in that: The following steps are included: S1. Provide the roller-pressed and slit electrode I, electrode II (8) and diaphragm (6). S2. The electrode I is formed into a flow-guiding functional area by surface laser etching or mechanical scratching (4). S3. The electrode I obtained in S2 and the diaphragm (6) are hot-pressed together by a heated embossing roller and a structural functional region (3) is formed on at least one surface of the active material layer (2) of the electrode I to obtain a diaphragm-electrode I-diaphragm composite (7). S4. The diaphragm-electrode-diaphragm composite (7) and electrode II (8) are wound together to form a core.

10. The method for preparing a battery cell according to claim 9, characterized in that: The heating temperature of the embossing roller is controlled near the softening point of the polymer binder in the diaphragm. By controlling the pressure during hot pressing, a structural functional area (3) is formed on the surface of at least one active material layer (2) of electrode I. Preferably, the temperature difference between the heating temperature of the embossing roller and the softening point of the polymer binder of the diaphragm is -10°C to 10°C. Preferably, a structural functional region (3) is formed on the surface of at least one active material layer (2) of electrode I by controlling the pressure during hot pressing to be 1.2-5 MPa.

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