A laminated cell and a battery

Abstract

The present application relates to the field of battery, specifically relates to a laminated cell and battery. The laminated cell comprises positive electrode sheet, diaphragm and negative electrode sheet, the positive electrode sheet comprises single-sided positive electrode sheet and double-sided positive electrode sheet, the diaphragm comprises first diaphragm and second diaphragm, the first diaphragm comprises first substrate layer and first coating layer, the second diaphragm comprises second substrate layer and second coating layer, the second coating layer comprises heat-resistant layer and second polymer layer, the laminated cell satisfies the following relationship: 2 <= T / H <= 300, H is the difference between the thickness of the second coating layer and the thickness of the first coating layer, unit is mu m, T is the maximum thickness of single-sided positive electrode active layer in all positive electrode sheets in the laminated cell, unit is mu m. The laminated cell is sequentially first region, second region and third region along the thickness direction, the diaphragm in the first region and the third region is the first diaphragm, the diaphragm in the second region is the second diaphragm, and the number of the first diaphragm is >= 2. The cycle performance and rate property of the battery of the present application are improved.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more specifically to a laminated battery cell and a battery including the laminated battery cell. Background Technology

[0002] Lithium-ion batteries offer advantages over other rechargeable batteries, including high energy density, long cycle life, low self-discharge, and no memory effect. Therefore, they have been widely recognized and applied in the market since their introduction. As consumers use batteries more frequently, their demands for charging / discharging speed and lifespan are also increasing. However, the actual charging / discharging performance of current lithium-ion batteries still cannot simultaneously meet the requirements of multiple operating conditions. Summary of the Invention

[0003] Research has revealed that while stacked batteries already exhibit relatively low internal resistance and good charge / discharge performance, maintaining consistent charging speeds across different regions is challenging during high-rate charging and discharging. Further investigation found that due to their structural design, stacked batteries are more prone to lithium plating closer to the surface layer, impacting cycle performance and safety. Furthermore, they affect the lithium insertion / extraction transfer rate of adjacent surface layers, leading to lithium plating on adjacent surfaces and further reducing cycle performance.

[0004] To address the issue of lithium plating on the surface layer of stacked batteries, this invention provides a stacked battery cell and a battery comprising the stacked battery cell. The stacked battery cell of this invention enables a balance in the lithium insertion / extraction rate of the cell surface, thereby improving the lithium plating problem on the surface of the stacked battery. Simultaneously, it achieves kinetic differences in different regions, ensuring consistent charging speeds across all areas of the battery, thus improving the battery's cycle performance and rate performance.

[0005] To achieve the above objectives, a first aspect of the present invention provides a laminated battery cell, the laminated battery cell comprising stacked positive electrode plates, a separator, and a negative electrode plate, the separator being located between the positive electrode plates and the negative electrode plates, the positive electrode plates comprising two single-sided positive electrode plates located on the outermost sides of the laminated battery cell and a plurality of double-sided positive electrode plates located in the middle of the laminated battery cell, the single-sided positive electrode plate comprising a current collector and a positive active layer located on one side of the current collector, the double-sided positive electrode plate comprising a current collector and positive active layers located on both sides of the current collector; the separator comprising a first separator and a second separator, the first separator comprising a first substrate layer and a first coating layer, the first coating layer comprising a first polymer layer located on at least one side of the first substrate layer, the second separator comprising a first polymer layer and a second polymer layer located on at least one side of the first substrate layer, the second separator comprising a first polymer layer and a second polymer layer located on at least one side of the first substrate layer, the first polymer layer comprising a first polymer layer and a second polymer layer located on at least one side of the first substrate layer, the second separator comprising a first polymer layer and a second polymer layer located on at least one side of the first substrate layer, the first polymer layer comprising a first polymer layer and a second polymer layer located on at least one side of the first substrate layer, the second polymer layer ... second polymer layer comprising a The stacked cell has a substrate layer and a second coating layer. The second coating layer includes a heat-resistant layer and a second polymer layer. The heat-resistant layer is located on at least one side of the surface of the second substrate layer. The second polymer layer is located on the surface of the heat-resistant layer and / or the surface of the second substrate layer. The stacked cell satisfies the following relationship: 2≤T / H≤300, where H is the difference between the thickness of the second coating layer and the thickness of the first coating layer in μm, and T is the maximum thickness of the positive electrode active layer on one side of all the positive electrode sheets in the stacked cell in μm. The stacked cell is divided into a first region, a second region, and a third region along the thickness direction. The separator in the first region and the third region is the first separator, and the separator in the second region is the second separator. The number of first separators is ≥2.

[0006] A second aspect of the present invention provides a battery comprising the stacked cells described in the first aspect of the present invention.

[0007] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0008] (1) In the stacked cell of the present invention, the first separator does not include a heat-resistant layer, and the second separator includes a heat-resistant layer. With the above arrangement, the electrolyte enrichment in the first region and the third region can be improved, thereby balancing the distribution of electrolyte in the two end regions and the middle region, balancing the overall consistency of the stacked cell, and improving the cycle performance of the battery.

[0009] (2) The distribution of the first separator and the second separator in the stacked cell of the present invention can provide the lithium ion transport rate at both ends, realize the balance of the lithium insertion and extraction rate of the surface layer, improve the problem of lithium deposition on the surface layer, and improve the rate performance and cycle performance of the battery.

[0010] (3) The distribution of the first separator and the second separator and the number of the first separator in the stacked cell of the present invention can reduce or even overcome the adverse effects of the surface layer on the adjacent surface layer, while improving the consistency of the charging rate of the two end regions and the middle region, thereby further improving the cycle stability and rate performance of the battery.

[0011] (4) By controlling the stacked cells to satisfy the relationship: 2≤T / H≤300, the liquid storage capacity of the first separator can be matched with the thickness of the positive electrode active layer, ensuring that the lithium ion transport rate and the diffusion rate in the positive electrode active layer have a high degree of compatibility, so that the battery has both high energy density and high fast charging safety performance.

[0012] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0014] Figure 1 The diagram shown is a cross-sectional schematic of the laminated battery cell of the present invention.

[0015] Figure 2 The diagram shows the distribution of the first and second separators in the stacked cell of the present invention. Detailed Implementation

[0016] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Unless otherwise specified herein, data ranges include endpoints.

[0017] It should be noted that the numerical designations such as "first" and "second" in this disclosure are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0018] The first aspect of the present invention provides a laminated battery cell, the laminated battery cell comprising stacked positive electrode plates, a separator, and a negative electrode plate, the separator being located between the positive electrode plates and the negative electrode plates, the positive electrode plates comprising two single-sided positive electrode plates located on the outermost sides of the laminated battery cell and a plurality of double-sided positive electrode plates located in the middle of the laminated battery cell, the single-sided positive electrode plate comprising a current collector and a positive active layer located on one side of the current collector, the double-sided positive electrode plate comprising a current collector and positive active layers located on both sides of the current collector; the first separator comprising a first substrate layer and a first coating layer, the first coating layer comprising a first polymer layer located on at least one side of the first substrate layer, the second separator comprising a second substrate layer and a second coating layer, the second coating layer comprising a heat-resistant layer and a second polymer layer, the heat-resistant layer being located on at least one side of the second substrate layer. The second polymer layer is located on the heat-resistant layer and on the surface of the heat-resistant layer and / or the surface of the second substrate layer. The stacked cell satisfies the following relationship: 2≤T / H≤300 (e.g., 2, 5, 10, 30, 50, 80, 100, 130, 150, 180, 200, 230, 250, 280 or 300), where H is the difference between the thickness of the second coating and the thickness of the first coating in μm, and T is the maximum thickness of the positive electrode active layer on one side of all the positive electrode sheets in the stacked cell in μm. The stacked cell is divided into a first region, a second region and a third region along the thickness direction. The separator in the first region and the third region is the first separator, and the separator in the second region is the second separator. The number of first separators is ≥2.

[0019] Figure 1 As shown, the stacked cell 30 includes a positive electrode, a separator, and a negative electrode 31 stacked in sequence. The positive electrode includes two single-sided positive electrode 321 located on the outermost side of the stacked cell 30 and multiple (e.g., ≥2) double-sided positive electrode 322 located in the middle of the stacked cell. The separator includes a first separator 33 and a second separator 34.

[0020] like Figure 2 As shown ( Figure 2 This only represents the distribution of the first and second separators; the positive and negative electrodes are shown in [the diagram]. Figure 2 (Not shown in the text) The stacked cell is divided into a first region 11, a second region 12 and a third region 13 along the thickness direction. The separator in the first region 11 and the third region 13 is the first separator 33, and the separator in the second region 12 is the second separator 34. It can be understood that at least the two separators located on the outermost side of the stacked cell are the first separators (that is, at least the separator corresponding to the single-sided positive electrode is the first separator), and the separator corresponding to the double-sided positive electrode can be the second separator or can be the first separator and the second separator.

[0021] The single-sided positive electrode has a positive active layer on one side of the positive current collector, while the double-sided positive electrode has positive active layers on both sides of the positive current collector. The thicknesses of any two positive active layers can be the same or different.

[0022] In this invention, the first region and the third region can be collectively referred to as the two end regions. The second region can be referred to as the middle region.

[0023] The second polymer layer is located on the surface of the heat-resistant layer and / or the surface of the second substrate layer. It is understood that when the heat-resistant layer is located on one side of the second substrate layer, the second polymer layer can be located on both the surface of the heat-resistant layer and the surface of the second substrate layer. When the heat-resistant layer is located on both sides of the second substrate layer, the second polymer layer can be located on the surface of the heat-resistant layer.

[0024] Research has revealed that due to its structural design, the outermost positive electrode in a stacked battery is a single-sided positive electrode. This single-sided positive electrode only has the positive electrode active material layer coated on one side of the positive current collector, which easily generates internal stress leading to curling. Furthermore, the curling direction deviates from the stacking direction of the battery cells, making it prone to detaching from the stacked cells. This results in an imbalance in the lithium insertion / extraction rate of the surface layer, causing purple spots and / or lithium plating, thus reducing the battery's cycle performance and safety. During cycling, it also gradually affects the lithium insertion / extraction transport rate of adjacent surface layers. The curling stress of the surface layer positive electrode also causes adjacent surface layers to gradually curl, leading to purple spots and / or lithium plating on those layers as well, further reducing the battery's cycle performance and safety.

[0025] Therefore, controlling the distribution of the first and second separators, with the first separator located at both ends and the second separator located in the middle region, can shorten the lithium-ion transport distance, effectively reduce the resistance to lithium-ion transport in the two ends, improve the lithium-ion transport performance in the two ends, and improve the lithium plating problem caused by the imbalance of lithium insertion / extraction rates on the surface layer, thereby improving the rate performance and cycle performance of the battery. At the same time, in the stacked cell, the amount of electrolyte is more distributed in the two ends and less in the middle region. By setting the first separator to not include a heat-resistant layer and the second separator to include a heat-resistant layer, the electrolyte enrichment in the first and third regions can be improved, balancing the electrolyte content distribution in the two ends and the middle region, further balancing the overall consistency of the stacked cell, improving the cycle performance of the battery, and controlling the number of first separators can also reduce or even overcome the adverse effects of the surface layer on adjacent surface layers, while improving the consistency of charging rates in the two ends and the middle region, thereby further improving the cycle stability and rate performance of the battery.

[0026] When the difference H between the thickness of the second coating and the thickness of the first coating is smaller, the difference between the first separator located at both ends and the second separator located in the middle region is smaller, the lithium-ion transport rate is closer, and the surface layer of the cell is more prone to lithium deposition. At this time, by increasing the thickness of the positive electrode active layer, the diffusion time of lithium ions from the inside to the surface of the positive electrode sheet is extended, which matches the low difference in lithium-ion transport rate between the first and second separators, and avoids lithium deposition on the negative electrode due to the rapid depletion of lithium ions on the surface of the positive electrode sheet. When the difference H between the thickness of the second coating and the thickness of the first coating is larger, the liquid storage capacity of the first separator is worse, which affects the subsequent replenishment of electrolyte. However, the liquid storage capacity of the second separator is higher. At this time, by reducing the thickness of the positive electrode active layer, the diffusion path of lithium ions in the positive electrode sheet is shortened, which adapts to the shortcoming of the reduced liquid storage capacity of the first separator and avoids polarization surge due to insufficient electrolyte replenishment. Therefore, controlling the ratio of the maximum thickness T of the single-sided positive active layer in all the positive electrode sheets in the stacked battery cell to the difference H between the thickness of the second coating and the thickness of the first coating can ensure that the thickness of the positive active layer of the positive electrode sheet is appropriate when the liquid storage capacity of the first separator decreases (the greater the thickness of the positive active layer, the longer the lithium ion transport path. When the above relationship is satisfied, it can ensure that the maximum thickness of the single-sided positive active layer in all the positive electrode sheets matches the liquid storage capacity of the first separator, so the thickness of all the positive active layers in the positive electrode sheet is appropriate). This avoids the electrolyte not being able to be effectively replenished to the positive electrode interface during cycling due to the excessive thickness of the positive active layer, delays the capacity decay caused by electrolyte drying in the later stage of cycling, and also prevents the excessively thick positive active layer from causing severe polarization at high rates, breaking through the compensation capacity of the separator homogenization ion transport, so that the battery has the advantages of high energy density and high fast charging safety performance. Therefore, this invention, while controlling the proportion of the first separator in the total number of separators, also controls the stacked cells to satisfy the relationship: 2≤T / H≤300. This achieves optimal performance balance between the first separator located at both ends and the second separator located in the middle region, improving lithium plating caused by insufficient surface layer kinetics. Simultaneously, it avoids short circuits caused by separator puncture due to negative electrode expansion and increases battery energy density. When T / H > 300, the lithium-ion conduction path is too long, leading to reduced battery cycle performance and a lower lithium plating window. When T / H < 2, it easily causes battery short circuits and has little effect on improving lithium plating on the surface layer of the stacked cells.

[0027] In this invention, the thickness of the positive electrode active layer can be measured using a micrometer. For example, the thickness can be measured at 10 arbitrary sites on the positive electrode active layer, and the average value of the 10 test sites can be taken as the test result. The thickness of the first coating and the thickness of the second coating can be measured by cross-sectional SEM images of the first and second separators, respectively. For example, taking the "thickness of the first polymer layer" as an example, in the cross-sectional SEM image of the first separator, starting from any point on the interface between the first substrate layer and the first polymer layer, the distance from the starting point to the end point along a direction perpendicular to the first substrate layer is recorded as the thickness of the first polymer layer at that point. The thickness can be measured at 10 arbitrary sites on the first polymer layer, and the average value of the 10 test sites can be taken as the test result. The cross-sectional SEM images of the first and second separators can be obtained using conventional methods in the art.

[0028] In this invention, by controlling the distribution of the first and second separators, the number of the first separators, and ensuring that the stacked cells satisfy 2≤T / H≤300, the cycle stability, rate performance, and safety performance of the battery can be improved compared to existing technologies. To further enhance the effect, one or more of the technical features can be further optimized.

[0029] In one example, the stacked cell satisfies the following relationship: 4≤T / H≤266, where H is the difference between the thickness of the second coating and the thickness of the first coating in μm, and T is the maximum thickness of the positive electrode active layer on one side of all the positive electrode sheets in the stacked cell in μm.

[0030] In one example, the difference between the thickness of the second coating and the thickness of the first coating is 0.3 μm-5 μm (e.g., 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm). It is understood that the thickness of the second coating is greater than the thickness of the first coating. The term "thickness of the second coating" refers to the thickness of the second coating in a single second diaphragm. It is understood that when the second coating is located on one side of the second substrate layer, the thickness of the second coating represents the total thickness of the second coating on that single side surface; when the second coating is located on both sides of the second substrate layer, the thickness of the second coating represents the sum of the total thicknesses of the second coatings on both sides. In this invention, if the number of second diaphragms is ≥2, then the thickness of the second coating is the thickness of the second coating with the smallest thickness among all the second coatings of the second diaphragms. The term "thickness of the first coating" refers to the thickness of the first coating in a single first diaphragm. It can be understood that when the first coating is located on one side of the first substrate layer, it represents the thickness of the first coating on that single side; when the first coating is located on both sides of the first substrate layer, the thickness of the first coating represents the sum of the thicknesses of the first coatings on both sides. In this invention, if the number of first diaphragms is ≥2, then the thickness of the first polymer layer is the thickness of the thickest first polymer layer among all the first polymer layers of the first diaphragms.

[0031] In one example, the thickness of the second coating differs from that of the first coating by 0.5 μm to 4.6 μm.

[0032] In one example, the maximum thickness of the positive active layer on one side of all the positive electrode sheets in the stacked cell is 10μm-150μm (e.g., 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm).

[0033] In one example, the maximum thickness of the positive active layer on one side of all the positive electrode sheets in the stacked cell is 12μm-138μm.

[0034] In this invention, the thickness of the positive active layer on one side of all the positive electrode sheets in the stacked battery cell can be the same or different. When the thickness of the positive active layer on one side of all the positive electrode sheets in the stacked battery cell is the same, the maximum thickness of the positive active layer on one side of all the positive electrode sheets in the stacked battery cell is the thickness of the positive active layer on one side of any positive electrode sheet in the stacked battery cell. When the thickness of the positive active layer on one side of all the positive electrode sheets in the stacked battery cell is different, the maximum thickness of the positive active layer on one side of all the positive electrode sheets in the stacked battery cell is the maximum value among the thicknesses of the positive active layers on one side of all the positive electrode sheets in the stacked battery cell.

[0035] According to a specific embodiment, H is 0.3-5, T is 10-150, and the stacked cell satisfies the following relationship: 2≤T / H≤300, where H is the difference between the thickness of the second coating and the thickness of the first coating in μm, and T is the thickness of the positive electrode active layer on one side of any of the positive electrode sheets in the stacked cell in μm.

[0036] According to a specific embodiment, H is 0.5-4.6, T is 12-138, and the stacked cell satisfies the following relationship: 4≤T / H≤266, where H is the difference between the thickness of the second coating and the thickness of the first coating, in μm, and T is the thickness of the positive electrode active layer on one side of any of the positive electrode sheets in the stacked cell, in μm.

[0037] In one example, the separator corresponding to the single-sided positive electrode is a first separator, and the separator corresponding to the double-sided positive electrode is a second separator, or a first separator and a second separator. By controlling the distribution of the first separator and the second separator, the lithium ion transport rate in and near the surface layer can be accelerated, thereby reducing the lithium ion transport resistance in the surface layer and further achieving a balance between lithium insertion / extraction in the surface layer. Simultaneously, it can also improve the lithium ion transport rate of adjacent surface layers, reduce or even overcome adverse effects on adjacent surface layers, and improve the consistency of charging rates between the two end regions and the middle region, thereby further improving the battery's cycle stability and rate performance.

[0038] In one example, the percentage (f%) of the first diaphragm in the diaphragm is 0% < f% ≤ 40% (e.g., 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, or 40%).

[0039] In one example, the proportion of the first diaphragm in the diaphragm is 2% ≤ f% ≤ 20%.

[0040] In one example, the separator corresponding to the single-sided positive electrode is the first separator, and the separator corresponding to the double-sided positive electrode is the second separator.

[0041] In one example, the separator corresponding to the single-sided positive electrode is the first separator, and the separator corresponding to the double-sided positive electrode is the first separator and the second separator.

[0042] In one example, the porosity of the second substrate layer is less than the porosity of the first substrate layer. A higher porosity in the first substrate layer than in the second substrate layer helps to improve the lithium-ion transport rate in the corresponding region of the first separator, reduce the risk of lithium plating, and improve the consistency of charging rates between the two end regions and the middle region, thereby further improving the cycle stability and rate performance of the battery.

[0043] In one example, the porosity of the first substrate layer is 25%-70% (e.g., 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%).

[0044] In one example, the porosity of the first substrate layer is 35%-60%.

[0045] In one example, the porosity of the second substrate layer is 30%-50% (e.g., 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48% or 50%).

[0046] According to one specific embodiment, the porosity of the first substrate layer is 25%-70%, the porosity of the second substrate layer is 30%-50%, and the porosity of the second substrate layer is less than that of the first substrate layer.

[0047] In this invention, porosity can be obtained by testing using the following method: measuring the length, width, and thickness of the sample according to GB / T 6672-2001 and GB / T6673-2001, and calculating the apparent volume V. 表观 The membrane's true volume V was measured using an analytical balance with an accuracy ≥0.0001g, weighed m, and measured with a helium true density analyzer (Bestde 3H-2000PM1 high-performance specific surface area and micropore analyzer). 真 The porosity is (1-V) 真 / V 表观 )*100%

[0048] In one example, the areal density of the first polymer layer is 0.1 g / m³. 2 -1g / m 2 (For example, 0.1g / m 2 0.2g / m 2 0.3g / m 2 0.4g / m 2 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 0.9g / m 2 or 1g / m 2 ).

[0049] In one example, the areal density of the first polymer layer is 0.2 g / m³. 2 -0.8g / m 2 .

[0050] In this invention, the areal density of the first polymer layer refers to the areal density of the first polymer layer on one side. When the first substrate layer has a first polymer layer on one side surface, the areal density of the first polymer layer is the areal density of the first polymer layer on that side (i.e. the side with the first polymer layer). When the first substrate layer has first polymer layers on both sides surface, the areal densities of the first polymer layers on both sides are equal, and the areal density of the first polymer layer is the areal density of the first polymer layer on either side.

[0051] In one example, the areal density of the second coating is 0.25 g / m³. 2 -1.8g / m 2 (For example, 0.25g / m 2 0.5g / m 2 0.8g / m 2 1g / m 2 1.3g / m 2 1.5g / m 2 Or 1.8g / m 2 ).

[0052] In one example, the areal density of the second coating is 0.28 g / m³. 2 -1.65g / m 2 .

[0053] In this invention, the areal density of the second coating refers to the sum of the areal density of the second polymer layer on one side and the areal density of the heat-resistant layer. When the second coating is present on one side of the second substrate layer, the areal density of the second coating is the sum of the areal density of the second polymer layer on that side and the areal density of the heat-resistant layer. When the second coating is present on both sides of the second substrate layer, the areal densities of the second coatings on both sides are the same, and the areal density of the second coating is the sum of the areal density of the second polymer layer on either side and the areal density of the heat-resistant layer.

[0054] In one example, the areal density of the second polymer layer is 0.05 g / m³. 2 -1g / m 2 (For example, 0.05g / m 2 0.1g / m 2 0.2g / m 2 0.3g / m 2 0.4g / m 2 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 0.9g / m 2 or 1g / m 2 ).

[0055] In one example, the areal density of the second polymer layer is 0.1 g / m³. 2 -0.5g / m 2 .

[0056] In this invention, the areal density of the second polymer layer refers to the areal density of the second polymer layer on one side. When the second substrate layer has a second polymer layer on one side surface, the areal density of the second polymer layer is the areal density of the second polymer layer on that side (i.e. the side with the first polymer layer). When the second substrate layer has second polymer layers on both sides surface, the areal densities of the second polymer layers on both sides are equal, and the areal density of the second polymer layer is the areal density of the second polymer layer on either side.

[0057] In one instance, the total number of diaphragms N ≤ 100 (e.g., 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100).

[0058] In one instance, the total number of diaphragms N ≤ 50.

[0059] In one instance, the number of first diaphragms located in the first region may be the same as or different from the number of first diaphragms located in the third region.

[0060] According to one specific embodiment, the total number of diaphragms N≤100, and the proportion of the first diaphragm in the diaphragm is 0%<f%≤40%.

[0061] In one example, the permeability of the first diaphragm is 50s / 100ml to 350s / 100ml (e.g., 50s / 100ml, 80s / 100ml, 90s / 100ml, 100s / 100ml, 130s / 100ml, 150s / 100ml, 180s / 100ml, 200s / 100ml, 230s / 100ml, 250s / 100ml, 300s / 100ml, 330s / 100ml or 350s / 100ml).

[0062] In one example, the permeability of the first diaphragm is 80s / 100ml-300s / 100ml.

[0063] In one example, the air permeability of the second diaphragm is 80s / 100ml to 400s / 100ml (e.g., 80s / 100ml, 100s / 100ml, 130s / 100ml, 150s / 100ml, 180s / 100ml, 200s / 100ml, 230s / 100ml, 250s / 100ml, 280s / 100ml, 300s / 100ml, 330s / 100ml, 350s / 100ml, 380s / 100ml or 400s / 100ml).

[0064] In one example, the air permeability of the second diaphragm is 100s / 100ml-350s / 100ml.

[0065] In one instance, the air permeability of the second diaphragm is greater than that of the first diaphragm;

[0066] In one example, the difference between the permeability of the second membrane and the permeability of the first membrane is ≥5s / 100ml (e.g., 5s / 100ml, 10s / 100ml, 50s / 100ml, 100s / 100ml, 150s / 100ml, 200s / 100ml, 250s / 100ml, or 270s / 100ml). When the difference between the permeability of the second membrane and the first membrane meets the above range, the current density of the positive and negative electrodes corresponding to the first membrane in the two end regions is larger, reducing the permeability and enabling better lithium ion transport. This reduces the lithium ion transport resistance and overcomes the problem of easy lithium plating in the two end regions.

[0067] In one example, the difference between the air permeability of the second diaphragm and the air permeability of the first diaphragm is 5s / 100ml-200s / 100ml.

[0068] According to one specific embodiment, the air permeability value of the first diaphragm is 50s / 100ml-350s / 100ml, the air permeability value of the second diaphragm is 80s / 100ml-400s / 100ml, and the difference between the air permeability value of the second diaphragm and the air permeability value of the first diaphragm is ≥5s / 100ml.

[0069] According to one specific embodiment, the air permeability value of the first diaphragm is 80s / 100ml-300s / 100ml, the air permeability value of the second diaphragm is 100s / 100ml-350s / 100ml, and the difference between the air permeability value of the second diaphragm and the air permeability value of the first diaphragm is 5s / 100ml-200s / 100ml.

[0070] In this invention, the air permeability value can be obtained by testing using the following method: In this invention, the air permeability rate is defined according to GB / T 36363-2018, where air permeability represents the area through which 100 mL of air passes under normal temperature, humidity, and pressure conditions, with the testing instrument applying a pressure of 1.21 kPa, and the area is 6.45 cm². 2 The time required for the spinning layer. The applied pressure of 1.21 kPa is a constant pressure, and the distance traveled is 6.45 cm. 2 The area is a fixed area.

[0071] In one example, the thermal shrinkage rate of the first diaphragm and / or the second diaphragm in the TD direction at 130°C is 0.1%-50% (e.g., 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%).

[0072] In one example, the thermal shrinkage rate of the first diaphragm and / or the second diaphragm in the TD direction at 130°C is 1%-10%.

[0073] In one example, the thermal shrinkage rate of the first and second diaphragms in the MD direction at 130°C is 0.1%-50% (e.g., 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%).

[0074] In one example, the thermal shrinkage rate of the first diaphragm and / or the second diaphragm in the MD direction at 130°C is 1%-10%.

[0075] In this invention, the MD direction represents the length direction of the diaphragm. The thermal shrinkage rate in the MD direction can be obtained by the following method: cut the diaphragm into a square with a side length of 70cm and mark the MD side (length direction) of the diaphragm. Place it in an oven at 130℃ and bake for one hour. After taking it out, measure the length xcm of the MD side of the diaphragm and calculate (70-x) / 70, which is the thermal shrinkage rate in the MD direction (length direction) of the diaphragm after baking at 130℃ for 1 hour.

[0076] In one example, the tensile strength in the TD direction of the first diaphragm and / or the second diaphragm is ≥50 MPa.

[0077] In one example, the tensile strength of the first diaphragm in the TD direction is ≥50 MPa.

[0078] In one example, the tensile strength of the second diaphragm in the TD direction is ≥50 MPa.

[0079] In one example, the tensile strength of the first diaphragm and the second diaphragm in the TD direction is ≥50 MPa.

[0080] In one example, the tensile strength in the MD direction of the first diaphragm and / or the second diaphragm is ≥50 MPa.

[0081] In one example, the tensile strength of the first diaphragm in the MD direction is ≥50 MPa.

[0082] In one example, the tensile strength of the second diaphragm in the MD direction is ≥50 MPa.

[0083] In one example, the tensile strength in the MD direction of the first diaphragm and the second diaphragm is ≥50 MPa.

[0084] In one instance, the puncture strength of the first diaphragm and / or the second diaphragm is ≥150 kgf.

[0085] In one instance, the puncture strength of the first diaphragm is ≥150 kgf.

[0086] In one instance, the puncture strength of the second diaphragm is ≥150 kgf.

[0087] In one instance, the puncture strength of the first diaphragm and the second diaphragm is ≥150 kgf.

[0088] In one example, the thickness of the first substrate layer is 1 μm to 25 μm (e.g., 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 23 μm or 25 μm).

[0089] In one example, the thickness of the first substrate layer is 3 μm-20 μm.

[0090] In one example, the aperture of the first substrate layer is 5nm-100nm (e.g., 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm).

[0091] In one example, the pore size of the first substrate layer is 20nm-90nm.

[0092] In one example, the first substrate layer comprises at least one of polyethylene, polypropylene, polyethylene, polypropylene composite, polyamide, polyimide, and aramid.

[0093] In one example, the thickness of the first polymer layer is 0.3 μm to 5 μm (e.g., 0.3 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm).

[0094] In one example, the first polymer layer comprises first polymer particles having a median particle size of 0.1 μm to 10 μm (e.g., 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm). The first polymer particles are composed of a first polymer having a number-average molecular weight of 100,000 Da to 800,000 Da (e.g., 100,000 Da, 150,000 Da, 200,000 Da, 250,000 Da, 300,000 Da, 350,000 Da, 400,000 Da, 450,000 Da, 500,000 Da, 550,000 Da, 600,000 Da, 650,000 Da, 700,000 Da, 750,000 Da, or 800,000 Da).

[0095] In one example, the first polymer layer includes a first polymer, which is a polymer formed by polymerizing at least one monomer selected from styrene, vinyl chloride, perfluoropropylene, trifluorochloroethylene, tetrafluoroethylene, vinylidene chloride, tetrachloroethylene, acrylate, methacrylic acid, methacrylate and acrylonitrile.

[0096] In one example, the acrylate includes one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and isobutyl acrylate.

[0097] In one example, the methacrylate includes one or more of methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate.

[0098] In one example, the thickness of the second substrate layer is 3μm-12μm (e.g., 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm or 12μm).

[0099] In one example, the aperture of the second substrate layer is 5nm-100nm (e.g., 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm).

[0100] In one example, the pore size of the second substrate layer is 20nm-90nm.

[0101] In one example, the second substrate layer comprises at least one of polyethylene, polypropylene, polyethylene, polypropylene composite, polyimide, and aramid.

[0102] In one example, the heat-resistant layer includes first particles, the composition of which includes at least one of alumina, magnesium oxide, boehmite, barium sulfate, barium titanate, zinc oxide, calcium oxide, silicon dioxide, silicon carbide, nickel oxide, aramid, melamine cyanurate, and polyimide.

[0103] In one example, the heat-resistant layer further includes a first adhesive, which includes at least one of polyacrylate, polytetrafluoroethylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer (e.g., polyvinylidene fluoride-hexafluoropropylene copolymer), polyimide, polyacrylonitrile, and polymethyl methacrylate.

[0104] In one example, based on the total weight of the heat-resistant layer, the weight content of the first particles is 80%-99% (e.g., 80%, 83%, 85%, 88%, 90%, 93%, 95%, or 99%), and the weight content of the first adhesive is 1%-20% (e.g., 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, or 20%).

[0105] In one example, based on the total weight of the heat-resistant layer, the weight content of the first particles is 85%-95%, and the weight content of the first adhesive is 5%-15%.

[0106] In one example, the thickness of the heat-resistant layer is 0.2 μm to 5 μm (e.g., 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm).

[0107] In one example, the thickness of the second polymer layer is 0.3 μm to 5 μm (e.g., 0.3 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm).

[0108] In one example, the second polymer layer comprises second polymer particles having a median particle size of 0.1 μm to 10 μm (e.g., 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm), and the second polymer particles comprising a second polymer having a number-average molecular weight of 100,000 Da to 500,000 Da (e.g., 100,000, 200,000, 300,000, 400,000, or 500,000).

[0109] In one example, the areal density of the second polymer layer is 0.05 g / m³. 2 -1g / m 2 (For example, 0.05g / m 2 0.1g / m 2 0.2g / m 2 0.3g / m2 0.4g / m 2 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 0.9g / m 2 or 1g / m 2 When the areal density of the second polymer layer is too low (e.g., below 0.1 g / m³), 2 If the amount of the second polymer is insufficient, it cannot provide enough adhesive strength, causing the battery to become soft and easily leading to safety accidents; when the areal density of the second polymer layer is too high (e.g., above 1 g / m³), it may cause further problems. 2 Excessive coating of the second polymer can obstruct the electrolyte transport channels, hindering lithium-ion transport and affecting the battery's rate performance and cycle performance.

[0110] In one example, the areal density of the second polymer layer is 0.1 g / m³. 2 -0.5g / m 2 .

[0111] In one example, the second polymer layer includes a second polymer, which is a polymer formed by polymerizing at least one monomer selected from styrene, vinyl chloride, perfluoropropylene, trifluorochloroethylene, tetrafluoroethylene, vinylidene chloride, tetrachloroethylene, acrylate, methacrylic acid, methacrylate and acrylonitrile.

[0112] In one example, the acrylate includes one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and isobutyl acrylate.

[0113] In one example, the methacrylate includes one or more of methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate.

[0114] In one example, the softening point of the second polymer is between 30°C and 80°C (e.g., 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C). When the softening point of the second polymer is too low (e.g., below 30°C), the second polymer will self-adhere and stick to the rollers during use, affecting the performance of the separator. When the softening point of the second polymer is too high (e.g., above 80°C), the second polymer requires a higher temperature to achieve good adhesion, and the formation temperature of the battery needs to be increased accordingly. However, a higher formation temperature will affect the solid electrolyte interface film, thereby affecting the performance of the lithium-ion battery.

[0115] In one example, the softening point of the second polymer is -40°C to 95°C.

[0116] In one example, the positive electrode includes a positive current collector and a positive active layer located on one or both sides of the surface of the positive current collector.

[0117] In one example, the single-sided positive electrode includes a current collector for the single-sided positive electrode and a first positive active layer located on one or both sides of the current collector surface of the single-sided positive electrode.

[0118] In one example, the current collector of the single-sided positive electrode includes one or more of aluminum foil, carbon fiber, carbon nanotubes, aluminum foil, and polymer film composite materials.

[0119] In one example, the first positive electrode active layer includes a first positive electrode active material, a first positive electrode binder, and a first positive electrode conductive agent.

[0120] In one example, the first positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

[0121] In one example, the first positive electrode conductive agent includes one or more of carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes.

[0122] In one example, the first positive electrode binder includes one or more of polyvinylidene fluoride, acrylic acid-modified polyvinylidene fluoride, carboxylic acid-modified polyvinylidene fluoride, polyacrylic acid, polyacrylic acid copolymer, polymethyl methacrylate, and polyimide.

[0123] In one example, based on the total weight of the first positive electrode active material layer, the weight content of the first positive electrode active material is 80%-99% (e.g., 80%, 83%, 85%, 88%, 90%, 93%, 95%, or 99%), the weight content of the first positive electrode conductive agent is 0.5%-10% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%), and the weight content of the first positive electrode binder is 0.5%-10% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%).

[0124] In one example, the double-sided positive electrode includes a current collector for the double-sided positive electrode and a first positive active layer located on one or both sides of the current collector surface of the double-sided positive electrode.

[0125] In one example, the current collector of the double-sided positive electrode includes one or more of aluminum foil, carbon fiber, carbon nanotubes, aluminum foil, and polymer film composite materials.

[0126] In one example, the second positive electrode active layer includes a second positive electrode active material, a second positive electrode binder, and a second positive electrode conductive agent.

[0127] In one example, the second positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

[0128] In one example, the second positive electrode conductive agent includes one or more of conductive carbon black acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes.

[0129] In one example, the second positive electrode binder includes one or more of polyvinylidene fluoride (PVDF), acrylic acid-modified polyvinylidene fluoride, carboxylic acid-modified polyvinylidene fluoride, polyacrylic acid, polyacrylic acid copolymer, polymethyl methacrylate, and polyimide.

[0130] In one example, based on the total weight of the second positive electrode active material layer, the weight content of the second positive electrode active material is 80%-99% (e.g., 80%, 83%, 85%, 88%, 90%, 93%, 95%, or 99%), the weight content of the second positive electrode conductive agent is 0.5%-10% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%), and the weight content of the second positive electrode binder is 0.5%-10% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%).

[0131] In one example, the negative electrode sheet includes a negative electrode current collector and a layer of negative electrode active material located on one or both surfaces of the negative electrode current collector.

[0132] In one example, the negative electrode active material layer includes a negative electrode active substance, a negative electrode conductive agent, and a negative electrode binder.

[0133] In one example, the negative electrode active material includes one or more of artificial graphite, natural graphite, hard carbon, mesophase carbon microspheres, silicon carbide, and silicon suboxide.

[0134] In one example, the negative electrode conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0135] In one example, the negative electrode binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), lithium polyacrylate (PAALi), sodium polymethyl cellulose (CMC-NA), and lithium polymethyl cellulose (CMC-Li).

[0136] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode active material is 80%-99% (e.g., 80%, 83%, 85%, 88%, 90%, 93%, 95%, or 99%), the weight content of the negative electrode conductive agent is 0.5%-10% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%), and the weight content of the negative electrode binder is 0.5%-10% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%).

[0137] Except for the laminated cells, all materials used in the battery can be manufactured in accordance with the methods described in this field, and all can achieve good cycle stability and high rate performance.

[0138] In one example, the battery further includes an electrolyte. The electrolyte can be a conventional electrolyte in the art.

[0139] In one example, the battery is a lithium-ion rechargeable battery.

[0140] The battery of the present invention includes the stacked cell described in the first aspect of the present invention, which improves the lithium plating situation and enhances both cycle performance and rate performance.

[0141] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0142] The following examples illustrate the stacked cell and battery described in this invention.

[0143] Example 1

[0144] (1) Diaphragm

[0145] First diaphragm: The first polymer particles (the first polymer is a polymethyl methacrylate copolymer) and auxiliary additives (thickener sodium carboxymethyl cellulose, wetting agent dimethylsiloxane, binder methacrylic acid, etc.) are added to deionized water at a solid content of 10% and stirred at a stirring speed of 1500 rpm for 60 min to obtain the first polymer layer slurry S1.

[0146] A first polymer layer slurry S1 is coated onto the first surface of the first substrate layer (polyethylene substrate) and the second surface opposite to the first surface to form a first polymer layer. After drying in an oven, a first diaphragm is obtained. The first coating consists only of the first polymer layer, and both surfaces of the first substrate layer are coated with the first polymer layer. Therefore, the thickness of the first coating is the sum of the thicknesses of the two first polymer layers, which is 1 μm.

[0147] Second membrane: The second polymer particles (the second polymer is a polymethyl methacrylate copolymer) and auxiliary additives (thickener sodium carboxymethyl cellulose, wetting agent dimethylsiloxane, binder methacrylic acid, etc.) are added to deionized water at a solid content of 15% and stirred at a stirring speed of 1500 rpm for 60 min to obtain the second polymer layer slurry S2.

[0148] A heat-resistant layer (comprising 92 wt% first particles (alumina), a first binder (4 wt% methacrylic acid, 4 wt% sodium polymethyl cellulose)) is coated on the first surface of the second substrate layer (polyethylene substrate). A second polymer layer slurry S2 is then coated on the second surface of the second substrate layer opposite to the first surface and on the surface of the heat-resistant layer to form a second polymer. After drying in an oven, a second diaphragm is obtained. The second coating comprises one heat-resistant layer (3 μm) and two second polymer layers (1 μm each). Therefore, the thickness of the second coating is the sum of the thickness of the heat-resistant layer and the two second polymer layers, which is 4 μm.

[0149] (2) Positive electrode plate

[0150] Lithium cobalt oxide, PVDF, and superconducting carbon black were mixed in N-methylpyrrolidone at a mass ratio of 97:2:1 to prepare a positive electrode slurry. The positive electrode slurry was then coated onto one side of a positive electrode current collector (aluminum foil). After drying and rolling, a single-sided positive electrode sheet was obtained, in which the current collectors of the two single-sided positive electrode sheets had the same thickness.

[0151] Lithium cobalt oxide, PVDF, and superconducting carbon black were placed in N-methylpyrrolidone at a mass ratio of 97:2:1 to prepare a positive electrode slurry. The positive electrode slurry was then coated on both sides of the positive electrode current collector (aluminum foil). After drying and rolling, a double-sided positive electrode sheet was obtained, wherein the current collector of all double-sided positive electrode sheets had the same thickness.

[0152] (3) Negative electrode sheet

[0153] A negative electrode active material (graphite), styrene-diene rubber (SBR), sodium carboxymethyl cellulose, and conductive carbon black were mixed in a weight ratio of 94%:3%:2%:1%. The mixture was dispersed in water and then subjected to a double planetary mixing process to obtain a negative electrode slurry. This slurry was coated onto a copper current collector, followed by drying and rolling to obtain the negative electrode sheet.

[0154] (4) Electrolyte

[0155] In an argon-filled glove box (moisture content <10 ppm, oxygen content <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) were mixed uniformly in a mass ratio of 2:1.5:2. LiPF6 (14 wt.% based on the total mass of the non-aqueous electrolyte) and ethyl propionate (20 wt.% based on the total mass of the non-aqueous electrolyte) were slowly added to the mixed solution and stirred until homogeneous to obtain the non-aqueous electrolyte.

[0156] (5) Lithium-ion batteries

[0157] The single-sided positive electrode, double-sided positive electrode, first separator, second separator, and negative electrode obtained above are stacked in the following order to form a bare cell: first region (single-sided positive electrode, first separator, negative electrode), second region (second separator, double-sided positive electrode, second separator, negative electrode, in this order), third region (first separator, single-sided positive electrode); then, after processes such as encapsulation, cell baking, electrolyte injection (injecting the electrolyte from step (4)), and hot pressing formation, a lithium-ion battery is obtained. See Table 1 for details.

[0158] Example 2

[0159] This embodiment is used to illustrate the effects produced by different combinations of data for various technical features.

[0160] The same procedure was followed as in Example 1, except that the data for several technical features were changed, as detailed in Table 1.

[0161] Example 3 Group

[0162] This set of examples illustrates the effects that occur when the difference H between the thickness of the second coating and the thickness of the first coating changes.

[0163] This embodiment is based on Embodiment 1, except that the difference H between the thickness of the second coating and the thickness of the first coating is changed, as detailed in Table 1.

[0164] Example 4 group

[0165] This set of examples illustrates the effects of changing the maximum thickness T of the positive active layer on one side of all positive electrode sheets in a laminated battery cell.

[0166] This embodiment group is based on Embodiment 1, except that the maximum thickness T of the positive active layer on one side of all positive electrode sheets in the laminated cell is changed, as detailed in Table 1.

[0167] Example 5 group

[0168] This set of examples illustrates the effects of changes in T / H.

[0169] This embodiment group is carried out with reference to Embodiment 1, except that T / H is changed, as detailed in Table 1.

[0170] Example 6 group

[0171] This set of examples illustrates the effects of changes in the porosity of the first substrate layer.

[0172] This embodiment group is carried out with reference to Embodiment 1, except that the porosity of the first substrate layer is changed, as detailed in Table 1.

[0173] Example 7 group

[0174] This set of examples is used to illustrate the effects when the proportion f of the first diaphragm in the diaphragm changes.

[0175] This embodiment group is based on Embodiment 1, except that the proportion of the first diaphragm in the diaphragm is changed, as shown in Table 1.

[0176] Example 8 group

[0177] This set of examples illustrates the effects of changing the number N of diaphragms.

[0178] This embodiment group is based on Embodiment 1, except that the number of diaphragms N is changed, as detailed in Table 1.

[0179] Comparative Example 1

[0180] The procedure was carried out in accordance with Example 1, except that the T / H ratio was changed, as detailed in Table 1.

[0181] Comparative Example 2

[0182] The procedure was carried out in accordance with Example 1, except that the T / H ratio was changed, as detailed in Table 1. The volumetric energy density loss was 34.6%.

[0183] Comparative Example 3

[0184] The procedure was carried out in accordance with Example 1, except that a heat-resistant layer (composed of 92 wt% first particles (alumina), first binder (4 wt% polymethyl methacrylate, 4 wt% sodium polymethyl cellulose)) was coated on the first surface of the first substrate layer (polyethylene substrate). The first polymer layer slurry S1 was coated on the second surface of the first substrate layer opposite to the first surface and the surface of the heat-resistant layer to form the first polymer layer. After drying in an oven, the first diaphragm was obtained.

[0185] Comparative Example 4

[0186] The procedure was carried out in accordance with Example 1, except that the proportion of the first diaphragm in the diaphragm was changed, as detailed in Table 1.

[0187] Table 1

[0188]

[0189]

[0190] * indicates the same as in Example 1.

[0191] Test case

[0192] The laminated cells and batteries obtained in the examples and comparative examples were tested as follows.

[0193] 1. Testing of diaphragm thickness and current collector thickness

[0194] The thicknesses of the first diaphragm, the second diaphragm, the current collector of the single-sided positive electrode, and the current collector of the double-sided positive electrode were measured using a micrometer.

[0195] 2. 5C / 6C Direct Charging 20-Week Test

[0196] The lithium-ion battery was placed at 25℃±3℃ and charged at a constant current of 5C and 6C to the upper limit voltage (4.5V), then charged at a constant voltage of 4.5V to 0.05C and left to stand for 5 minutes. Next, it was discharged at a constant current of 0.5C to 3V, and the discharge capacity at this point was recorded as Q1. After standing for 5 minutes, this constituted one charge-discharge cycle. This charge / discharge cycle was repeated for 20 cycles. After 20 cycles, the battery was disassembled to check the lithium plating on the negative electrode plates in the first and third regions. When there was no lithium plating, it was considered no lithium plating; when the lithium plating area accounted for less than 3% of the total negative electrode area, it was considered slight lithium plating; when the lithium plating area accounted for more than 10.5% of the total negative electrode area, it was considered severe lithium plating; when the lithium plating area accounted for 3%-10% of the total negative electrode area, it was considered lithium plating.

[0197] 3. Room temperature cycling test

[0198] The lithium-ion battery was placed at 25℃±3℃, and its thickness was measured as H1. It was then charged at a constant current of 1C to the upper limit voltage (4.5V), followed by constant voltage charging at 4.5V to 0.05C, and allowed to stand for 5 minutes. Next, it was discharged at a constant current of 0.5C to 3V, and the discharge capacity was recorded as Q1. After another 5 minutes of rest, this constituted one charge-discharge cycle. This charge / discharge cycle was repeated 800 times. The discharge capacity Q2 and the battery thickness H2 at 800T cycles were recorded. The capacity retention rate (%) = (Q2 / Q1)×100%, and the thickness expansion rate (%) = [(H2-H1) / H1]×100%.

[0199] 4. Volumetric energy density loss

[0200] Energy density test: At 25℃±2℃, the battery is charged to full capacity (100% SOC) using a 0.5C current and then discharged to 3.0V using a 0.2C current. The capacity discharged is recorded as the battery discharge capacity, and the plateau voltage is read from the discharge curve. Energy density = (battery discharge capacity × plateau voltage) / battery volume.

[0201] Taking the energy density loss of Comparative Example 1 as an example, the energy density of the battery prepared in Example 1 is T1, and the energy density of the battery prepared in the comparative example is T2. Volumetric energy density loss (%) = [(T1-T2) / T1]×100%.

[0202] The results are recorded in Table 2.

[0203] Table 2

[0204]

[0205]

[0206] As can be seen from Table 2, the comparative examples and embodiments show that the stacked battery prepared in the embodiments has a milder lithium plating, a higher cycle capacity retention rate, and a lower thickness expansion rate. This indicates that by controlling the distribution of the first and second separators, the number of first separators, and ensuring that the stacked cells meet the condition of 2≤T / H≤300, the lithium plating of the stacked cells is improved, thereby enhancing the cycle stability, rate performance, and safety performance of the battery.

[0207] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A laminated battery cell, characterized in that, The stacked battery cell includes stacked positive electrode plates, separators, and negative electrode plates. The separator is located between the positive and negative electrode plates. The positive electrode plates include two single-sided positive electrode plates located on the outermost sides of the stacked battery cell and multiple double-sided positive electrode plates located in the middle of the stacked battery cell. Each single-sided positive electrode plate includes a current collector and a positive active layer located on one side of the current collector. Each double-sided positive electrode plate includes a current collector and positive active layers located on both sides of the current collector. The separator includes a first separator and a second separator. The first separator includes a first substrate layer and a first coating layer. The first coating layer includes a first polymer layer located on at least one side of the first substrate layer. The second separator includes a second substrate layer and a second coating layer. The coating includes a heat-resistant layer and a second polymer layer. The heat-resistant layer is located on at least one side of the second substrate layer, and the second polymer layer is located on the surface of the heat-resistant layer and / or the surface of the second substrate layer. The stacked cell satisfies the following relationship: 2≤T / H≤300, where H is the difference between the thickness of the second coating and the thickness of the first coating in μm, and T is the maximum thickness of the positive electrode active layer on one side of all the positive electrode sheets in the stacked cell in μm. The stacked cell is divided into a first region, a second region, and a third region along the thickness direction. The separator in the first region and the third region is the first separator, and the separator in the second region is the second separator. The number of first separators is ≥2.

2. The laminated cell according to claim 1, wherein, The stacked cell satisfies the following relationship: 4≤T / H≤266, where H is the difference between the thickness of the second coating and the thickness of the first coating, in μm, and T is the maximum thickness of the positive electrode active layer on one side of all the positive electrode sheets in the stacked cell, in μm. And / or, the percentage of the first diaphragm in the diaphragm is 0% < f% ≤ 40%; And / or, the difference between the thickness of the second coating and the thickness of the first coating is 0.3 μm-5 μm; And / or, the maximum thickness of the positive active layer on one side of all the positive electrode sheets in the stacked cell is 10μm-150μm.

3. The laminated cell according to claim 2, wherein, In the diaphragm, the percentage of the first diaphragm is 2% ≤ f% ≤ 20%; And / or, the difference between the thickness of the second coating and the thickness of the first coating is 0.5 μm-4.6 μm; And / or, the maximum thickness of the positive active layer on one side of all the positive electrode sheets in the stacked cell is 12μm-138μm.

4. The laminated cell according to claim 1, wherein, The porosity of the second substrate layer is less than the porosity of the first substrate layer; And / or, the porosity of the first substrate layer is 25%-70%, preferably 35%-60%; And / or, the porosity of the second substrate layer is 30%-50%.

5. The laminated cell according to claim 1, wherein, The areal density of the first polymer layer is 0.1 g / m³. 2 -1g / m 2 The preferred value is 0.2g / m 2 -0.8g / m 2 ; And / or, the areal density of the second coating is 0.25 g / m³. 2 -1.8g / m 2 The preferred value is 0.28 g / m 2 -1.65g / m 2 ; And / or, the areal density of the second polymer layer is 0.05 g / m³. 2 -1g / m 2 Preferably 0.1g / m 2 -0.5g / m 2 .

6. The laminated cell according to claim 1, wherein, The total number of diaphragms is N≤100, preferably N≤50; And / or, the air permeability of the first diaphragm is 50s / 100ml-350s / 100ml, preferably 80s / 100ml-300s / 100ml; And / or, the air permeability of the second diaphragm is 80s / 100ml-400s / 100ml, preferably 100s / 100ml-350s / 100ml; And / or, the air permeability of the second diaphragm is greater than that of the first diaphragm; And / or, the difference between the air permeability of the second diaphragm and the air permeability of the first diaphragm is ≥5s / 100ml, preferably 5s / 100ml-200s / 100ml.

7. The laminated cell according to any one of claims 1-6, wherein, The thermal shrinkage rate of the first diaphragm and / or the second diaphragm in the TD direction at 130°C is 0.1%-50%, preferably 1%-10%; And / or, the thermal shrinkage rate of the first diaphragm and / or the second diaphragm in the MD direction at 130°C is 0.1%-50%, preferably 1%-10%; And / or, the tensile strength in the TD direction of the first diaphragm and / or the second diaphragm is ≥50 MPa; And / or, the tensile strength in the MD direction of the first diaphragm and / or the second diaphragm is ≥50 MPa; And / or, the puncture strength of the first diaphragm and / or the second diaphragm is ≥150 kgf.

8. The laminated cell according to any one of claims 1-6, wherein, The thickness of the first substrate layer is 1μm-25μm, preferably 3μm-20μm; And / or, the pore size of the first substrate layer is 5nm-100nm, preferably 20nm-90nm; And / or, the thickness of the first polymer layer is 0.3 μm-5 μm; And / or, the first polymer layer includes first polymer particles, the median particle size Dv50 of the first polymer particles is 0.1 μm-10 μm, the composition of the first polymer particles includes a first polymer, and the number average molecular weight of the first polymer is 100,000 Da-800,000 Da.

9. The laminated cell according to any one of claims 1-6, wherein, The thickness of the second substrate layer is 3μm-12μm; And / or, the pore size of the second substrate layer is 5nm-100nm, preferably 20nm-90nm; And / or, the thickness of the heat-resistant layer is 0.2μm-5μm, and the heat-resistant layer includes first particles, the composition of which includes at least one of alumina, magnesium oxide, boehmite, barium sulfate, barium titanate, zinc oxide, calcium oxide, silicon dioxide, silicon carbide, nickel oxide, aramid, melamine cyanurate and polyimide; And / or, the thickness of the second polymer layer is 0.3 μm-5 μm; And / or, the second polymer layer includes second polymer particles, the median particle size Dv50 of the second polymer particles is 0.1 μm-10 μm, the composition of the second polymer particles includes a second polymer, the number average molecular weight of the second polymer is 100,000 Da-500,000 Da, and the softening point temperature of the second polymer is 30℃-80℃.

10. A battery, characterized in that, The battery comprises stacked cells according to any one of claims 1-9.

Images