Battery cell and electrochemical device comprising same

Abstract

A battery cell and an electrochemical device comprising same. The battery cell comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator located between the positive electrode sheet and the negative electrode sheet. Under the combined use of a single‑crystal nickel‑cobalt‑manganese ternary positive electrode material and a polycrystalline nickel‑cobalt‑manganese ternary positive electrode material, and by strictly controlling the interrelationship between the width A1 of first heat‑resistant strip layers and a gap width A2, the interrelationship between the proportion C of the two positive electrode materials and the width A1 of first heat‑resistant strip layers and the gap width A2, and the thickness difference between the first heat‑resistant strip layers and second heat‑resistant strip layers, the cycling stability of a battery system based on the ternary positive electrode materials is significantly enhanced while maintaining high thermal safety, so that a battery can ensure both excellent cycling performance and superior rate capability even under high‑rate fast charging and discharging conditions.

Description

A battery cell and an electrochemical device including the battery cell.

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510312755.3, filed on March 17, 2025, entitled "A battery cell and an electrochemical device including the battery cell", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery materials, specifically to a battery cell and an electrochemical device including the battery cell. Background Technology

[0004] Lithium-ion batteries are widely used in many fields, including 3C consumer products and electric vehicles. In an increasingly competitive market, battery technology is continuously advancing towards larger capacity and higher charging power, especially ternary lithium-ion batteries.

[0005] Nickel-cobalt-manganese ternary cathode material (chemical formula Li(Ni) x Co y Mn 1-x-y Nickel-cobalt-manganese (NCM) cathode materials, with their excellent high energy density, have been widely used in many key fields such as electric vehicles, mobile devices, and energy storage systems. However, the capacity decay rate of cells made of nickel-cobalt-manganese ternary cathode materials is relatively fast. Frequent charge-discharge cycles will accelerate the capacity decay, especially in high-rate fast charge-discharge scenarios. High-nickel ternary cathode materials are prone to cation mixing and microcracks caused by lattice stress, which makes the internal structure of the battery more fragile. The cycle stability problem urgently needs to be solved, which has become a key bottleneck restricting its further development. Summary of the Invention

[0006] This application provides a battery cell and an electrochemical device including the battery cell, which aims to solve to some extent the problem of poor cycle stability of existing lithium-ion batteries, which leads to rapid capacity decay under frequent charge-discharge cycles, especially under high-rate fast charge-discharge conditions.

[0007] In a first aspect, this application provides a battery cell, including a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrode. The separator includes a base film and a heat-resistant layer located on at least one surface of the base film. The heat-resistant layer includes a plurality of first heat-resistant strip layers spaced apart from each other and a second heat-resistant strip layer disposed between two adjacent first heat-resistant strip layers. The thickness H1 of the first heat-resistant strip layer and the thickness H2 of the second heat-resistant strip layer satisfy: 0 μm < H1 - H2 ≤ H1, where the units of H1 and H2 are both μm.

[0008] The positive electrode sheet includes a current collector and a positive active material layer disposed on at least one side surface of the current collector. The positive active material layer includes a positive active material, which includes a single-crystal nickel-cobalt-manganese ternary positive electrode material and a polycrystalline nickel-cobalt-manganese ternary positive electrode material.

[0009] The width A1 of the first heat-resistant strip layer, the spacing A2 between two adjacent first heat-resistant strip layers, and the weight ratio C of the single-crystal nickel-cobalt-manganese ternary cathode material to the polycrystalline nickel-cobalt-manganese ternary cathode material in the cathode active material layer satisfy the following relationship: 2.5≤(A1 / A2)×C≤20; where the units of A1 and A2 are both μm.

[0010] In one optional embodiment, the distance D mm between the edge of the negative electrode and the edge of the positive electrode on the same side in the direction of cell width and the tab distance L mm satisfy the following relationship: 10≤D×L≤100; where D is 0.1~3 and L is 6~50.

[0011] In one alternative implementation, 4.5 ≤ (A1 / A2) × C ≤ 15; and / or, 1 μm ≤ H1 - H2 ≤ 5 μm.

[0012] In one alternative implementation, A1 is 30μm-100μm; and / or, A2 is 6.7μm-20μm; and / or, C is 1-4; and / or, 0.5μm≤H1≤10μm; and / or, 0.5μm≤H2≤8μm.

[0013] In one alternative implementation, 1.5 ≤ A1 / A2 ≤ 4.5.

[0014] In one optional implementation, the battery cell satisfies one or more of the following conditions:

[0015] A. The first heat-resistant strip layer includes first heat-resistant particles;

[0016] B. The second heat-resistant strip layer includes second heat-resistant particles;

[0017] C. The diaphragm further includes an adhesive layer, which is located on the surface of the base film and / or the heat-resistant layer.

[0018] In one optional implementation, the battery cell satisfies one or more of the following conditions:

[0019] A. The particle size Dv50 of the first heat-resistant particle is 0.1μm to 2.5μm;

[0020] B. The first heat-resistant particle comprises at least one of the following: boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, diethylaluminum hypophosphite, pentaerythritol, and triazine charring agent;

[0021] C. Based on the total mass of the first heat-resistant strip layer, the first heat-resistant strip layer comprises 40wt% to 96wt% of first heat-resistant particles, 3wt% to 59.3wt% of binder, and 0.7wt% to 3wt% of dispersant;

[0022] D. The particle size Dv50 of the second heat-resistant particle is 0.1μm~2.5μm;

[0023] E. The second heat-resistant particle comprises at least one of the following: boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, diethylaluminum hypophosphite, pentaerythritol, and triazine charring agent;

[0024] F. Based on the total mass of the second heat-resistant strip layer, the second heat-resistant strip layer comprises 40wt% to 96wt% of second heat-resistant particles, 3wt% to 59.3wt% of binder, and 0.7wt% to 3wt% of dispersant;

[0025] G. The thickness of the adhesive coating layer is 0.5-3μm;

[0026] H. The adhesive layer comprises a polymer.

[0027] In one alternative embodiment, the adhesive layer comprises polymer particles, the polymer particles comprising at least one of a first polymer particle and a second polymer particle.

[0028] In one alternative embodiment, the polymer particles satisfy one or more of the following conditions:

[0029] A. The average particle size of the first polymer particles is 0.5μm-0.95μm;

[0030] B. The second polymer particle includes secondary particles formed by the agglomeration of primary particles, wherein the average particle size of the primary particles of the second polymer particle is 0.15μm-0.3μm, and the average particle size of the secondary particles of the second polymer particle is 2μm-18μm.

[0031] In one optional embodiment, the particle size of the single-crystal nickel-cobalt-manganese ternary cathode material is Dv10 of 0.8μm-4μm, Dv50 of 1μm-6μm, and Dv90 of 3μm-10μm.

[0032] In one optional embodiment, the BET of the single-crystal nickel-cobalt-manganese ternary cathode material is 0.5m. 2 / g-1.4m 2 / g.

[0033] In one optional embodiment, the particle size of the polycrystalline nickel-cobalt-manganese ternary cathode material is Dv10 of 3μm-13μm, Dv50 of 6μm-15μm, and Dv90 of 12μm-25μm.

[0034] In one optional embodiment, the BET of the polycrystalline nickel-cobalt-manganese ternary cathode material is 0.3m. 2 / g-1.0m 2 / g.

[0035] In one optional embodiment, the nickel element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 85%-98% of the total molar content of nickel, cobalt, and manganese metal elements.

[0036] In one optional embodiment, the nickel element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 80%-95% of the total molar content of nickel, cobalt, and manganese metal elements.

[0037] In one optional embodiment, the cobalt element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 1%-14% of the total molar content of nickel-cobalt-manganese metal elements.

[0038] In one optional embodiment, the cobalt element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%-19% of the total molar content of nickel-cobalt-manganese metal elements.

[0039] In one optional embodiment, the manganese element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 1%-10% of the total molar content of nickel-cobalt-manganese metal elements.

[0040] In one optional embodiment, the manganese element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%-10% of the total molar content of nickel-cobalt-manganese metal elements.

[0041] In one optional embodiment, in the single-crystal nickel-cobalt-manganese ternary cathode material, nickel accounts for 90%-95% of the total molar content of nickel, cobalt, and manganese metal elements.

[0042] In one optional embodiment, the nickel element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 87%-92% of the total molar content of nickel, cobalt, and manganese metal elements.

[0043] In one optional embodiment, the cobalt element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 2%-10% of the total molar content of nickel-cobalt-manganese metal elements.

[0044] In one optional embodiment, the cobalt element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 2%-10% of the total molar content of nickel-cobalt-manganese metal elements.

[0045] In one optional embodiment, the manganese element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 2%-7% of the total molar content of nickel-cobalt-manganese metal elements.

[0046] In one optional embodiment, the manganese element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 2%-7% of the total molar content of nickel-cobalt-manganese metal elements.

[0047] The technical solution of this application has the following advantages:

[0048] The battery cell provided in this application includes a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrode. The separator includes a base film and a heat-resistant layer located on at least one surface of the base film. The heat-resistant layer includes a plurality of first heat-resistant strip layers spaced apart from each other and a second heat-resistant strip layer disposed between two adjacent first heat-resistant strip layers. The thickness H1 of the first heat-resistant strip layer and the thickness H2 of the second heat-resistant strip layer satisfy: 0 μm < H1 - H2 ≤ H1, where the units of H1 and H2 are both μm. The positive electrode includes a current collector and a positive active material layer disposed on at least one surface of the current collector. The positive active material layer includes a positive active material, which includes a single-crystal nickel-cobalt-manganese ternary positive electrode material and a polycrystalline nickel-cobalt-manganese ternary positive electrode material. The width A1 of the first heat-resistant strip layer and the thickness H2 of two adjacent first heat-resistant strip layers are specified. The spacing width A2 between the strip layers and the weight ratio C of the single-crystal nickel-cobalt-manganese ternary cathode material to the polycrystalline nickel-cobalt-manganese ternary cathode material in the cathode active material layer satisfy the following relationship: 2.5≤(A1 / A2)×C≤20; where the units of A1 and A2 are both μm. By controlling the thickness difference between the first heat-resistant strip layer and the second heat-resistant strip layer, and controlling the relationship between the width A1 of the first heat-resistant strip layer, the spacing width A2, and the ratio C of the two cathode active materials to satisfy the above range, it is possible to avoid the heat-resistant layer forming too shallow a depression on the base film when the thickness difference is too small or (A1 / A2)×C is too large, which would cause the cathode active material to be unable to maintain the stability of the interface in the later stage of battery cycle expansion. It is also possible to avoid the heat-resistant layer forming too deep a depression on the base film when the thickness difference is too large or (A1 / A2)×C is too small, which would lead to a reduction in the rate performance, cycle life, and thermal safety of the battery. In summary, by combining monocrystalline nickel-cobalt-manganese ternary cathode materials with polycrystalline nickel-cobalt-manganese ternary cathode materials, and by strictly controlling the relationship between the width A1 and the spacing A2 of the first heat-resistant strip layer, the relationship between the ratio C of the two materials and the width A1 and the spacing A2 of the first heat-resistant strip layer, and the thickness difference between the first heat-resistant strip layer and the second heat-resistant strip layer, the cycle stability of the ternary cathode material battery system is significantly improved while maintaining high thermal safety. This allows the battery to maintain both high cycle performance and excellent rate performance even under high-rate fast charge and discharge scenarios.

[0049] Additional aspects and advantages of the embodiments of this application will be described and shown in part in the following description, or illustrated by practice of the embodiments of this application. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0051] Figure 1 is a schematic diagram of the diaphragm structure in Example 1;

[0052] Figure 2 is a schematic diagram of the diaphragm structure in Example 10;

[0053] Figure 3 is a schematic diagram of the diaphragm structure in Example 15;

[0054] Figure 4 is a schematic diagram of the diaphragm structure in Example 16;

[0055] Figure 5 is a schematic diagram of the diaphragm structure in Example 17;

[0056] Reference numerals: 1. Base film; 2. First heat-resistant strip layer; 3. Second heat-resistant strip layer; 4. First adhesive layer; 5. First adhesive strip layer; 6. Second adhesive strip layer. Detailed Implementation

[0057] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0058] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0059] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0060] Battery cells made with nickel-cobalt-manganese ternary cathode materials exhibit rapid capacity decay. Frequent charge-discharge cycles accelerate this decay, especially during high-rate fast charge-discharge scenarios. High-nickel ternary cathode materials are prone to cation mixing and microcracks caused by lattice stress, leading to rapid capacity decay. This application provides a battery cell designed to address, to some extent, the problem of rapid capacity decay during frequent charge-discharge cycles caused by poor cycle stability in existing lithium-ion batteries, particularly during high-rate fast charge-discharge processes. The technical solution adopted in this application is described below.

[0061] In a first aspect, this application provides a battery cell comprising a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrode. The separator comprises a base film and a heat-resistant layer located on at least one surface of the base film. The heat-resistant layer comprises a plurality of first heat-resistant strip layers spaced apart from each other and a second heat-resistant strip layer disposed between two adjacent first heat-resistant strip layers. The thickness H1 of the first heat-resistant strip layer and the thickness H2 of the second heat-resistant strip layer satisfy: 0 μm < H1 - H2 ≤ H1, where the units of H1 and H2 are both μm. The positive electrode includes a current collector. The current collector has a body and a positive electrode active material layer disposed on at least one side surface. The positive electrode active material layer includes a positive electrode active material, which includes a monocrystalline nickel-cobalt-manganese ternary positive electrode material and a polycrystalline nickel-cobalt-manganese ternary positive electrode material. The width A1 of the first heat-resistant strip layer, the spacing A2 between two adjacent first heat-resistant strip layers, and the weight ratio C of the monocrystalline nickel-cobalt-manganese ternary positive electrode material to the polycrystalline nickel-cobalt-manganese ternary positive electrode material in the positive electrode active material layer satisfy the following relationship: 2.5≤(A1 / A2)×C≤20; where the units of A1 and A2 are both μm.

[0062] In this application, the thickness H1 of the first heat-resistant strip layer, the thickness H2 of the second heat-resistant strip layer, the width A1 of the first heat-resistant strip layer, and the spacing width A2 between two adjacent first heat-resistant strip layers are all average values ​​calculated after measuring 20 data points respectively.

[0063] In this application, the first heat-resistant strip layer significantly improves the heat resistance of the separator and enhances the thermal safety of the battery cell. The thickness control between the first and second heat-resistant strip layers, specifically the spacing created between adjacent first ceramic strip layers, provides more ion transport channels during the battery's charge and discharge process, effectively increasing the migration rate of active ions. This, in turn, improves the battery's charge and discharge efficiency, effectively enhances the usable depth of discharge, reduces the minimum remaining charge (SOC) level for effective power supply, increases the battery's performance and reliability under high-rate operating conditions, and extends the cycle life of battery systems using ternary cathode materials. A second heat-resistant strip layer may or may not be provided between adjacent first heat-resistant strip layers. When a second heat-resistant strip layer is provided between adjacent first heat-resistant strip layers, it not only further enhances the heat resistance of the separator, thus significantly improving the battery's thermal safety, but also, by controlling the thickness of the second heat-resistant strip layer to be less than the thickness of the first heat-resistant strip layer, provides more ion transport channels during the battery's charge and discharge process, effectively increasing the migration rate of active ions and extending the cycle life of battery systems using ternary cathode materials.

[0064] The positive electrode active material on the positive electrode active material layer includes monocrystalline nickel-cobalt-manganese ternary cathode material and polycrystalline nickel-cobalt-manganese ternary cathode material. Monocrystalline nickel-cobalt-manganese ternary cathode material has excellent structural stability and cycle performance, especially under high voltage and high temperature conditions, but its specific capacity and rate performance are poor. Polycrystalline nickel-cobalt-manganese ternary cathode material is prone to lattice breakage during charge-discharge cycles, resulting in poor cycle performance, but it performs better in terms of specific capacity and rate performance. The combined use of monocrystalline and polycrystalline nickel-cobalt-manganese ternary cathode materials in a reasonable ratio can combine the advantages of both to meet different battery performance requirements. However, during battery cycling, polycrystalline ternary materials are prone to lattice breakage, resulting in a shorter discharge time at high rates under low SOC conditions, thus leading to a relatively short cell cycle life even under high-rate charge-discharge conditions.

[0065] By combining monocrystalline nickel-cobalt-manganese ternary cathode materials with polycrystalline nickel-cobalt-manganese ternary cathode materials, and by strictly controlling the relationship between the width A1 and the spacing A2 of the first heat-resistant strip layer, the relationship between the ratio C of the two materials and the width A1 and the spacing A2 of the first heat-resistant strip layer, and the strict control of the thickness difference between the first heat-resistant strip layer and the second heat-resistant strip layer, the cycle stability of the ternary cathode material battery system is significantly improved while maintaining high thermal safety. This allows the battery to maintain both high cycle performance and excellent rate performance even in high-rate fast charge and discharge scenarios. Specifically, by controlling the thickness difference between the first and second heat-resistant strip layers to be within the range of 0μm < H1 - H2 ≤ H1, it can be avoided that when the thickness difference is too small, the depression formed by the heat-resistant layer on the base film is too shallow, resulting in reduced electrolyte storage and an inability to optimize electrolyte wetting on the electrode. This leads to insufficient electrolyte wetting of the monocrystalline and polycrystalline nickel-cobalt-manganese ternary cathode materials on the electrode, resulting in an excessively thin interfacial film that cannot maintain the battery's capacity under high-rate rapid charge-discharge conditions, thus shortening the battery's cycle life. Furthermore, it can also avoid the problem of excessively deep depressions formed by the heat-resistant layer on the base film when the thickness difference is too large. On the one hand, this exacerbates the uneven charge distribution on the electrode surface, reducing the lithium-ion insertion and extraction rate, thereby reducing the battery's rate performance. On the other hand, it reduces the continuity of the heat-resistant layer, weakens the bonding force between the separator and the electrode, and causes excessive stress concentration at the separator-electrode interface, worsening interface problems and easily leading to lithium plating, thus shortening the battery's cycle life. In addition, the reduced coating amount of ceramic material leads to a decrease in the thermal safety of the diaphragm.

[0066] By controlling the cell to meet the condition of 2.5≤A1 / A2×C≤20, not only can the electrolyte content at the interface be appropriate, forming a uniform CEI film and reducing interfacial impedance, but the interfacial performance between the separator and the cathode can also be improved. This mitigates the problem of grain boundary cracks that easily occur in polycrystalline ternary cathodes during charge and discharge, enhances the structural stability of ternary cathode materials, and slows down the capacity decay of ternary cathode materials. Furthermore, it effectively improves the rate performance of the battery, reduces the minimum remaining charge (SOC) level at which the battery can effectively supply power, improves the usable depth of discharge, and exhibits excellent cycle performance. The relationship A1 / A2×C should not be too large. If it exceeds 20, the electrolyte storage will be reduced due to an excessively wide first heat-resistant layer, leading to a decrease in the contact area between the free electrolyte and the cathode material, and / or the lithium-ion diffusion path will be longer due to an excessive proportion of single-crystal nickel-cobalt-manganese ternary cathode material. The combined effect leads to a decrease in the cell's rate performance and a shortened battery cycle life under high-rate charge and discharge conditions. The relationship A1 / A2×C should not be too small. If it is below 2.5, the excessive electrolyte storage due to the narrow width of the first heat-resistant strip layer will react with the highly active surface (especially the grain boundaries after cracking) of the excessive nickel-cobalt-manganese ternary cathode material, generating more gases (such as CO2 and CH4) and a thick and unstable CEI film (cathode-electrolyte interface film), leading to increased internal resistance and capacity decay. Furthermore, on the one hand, an excessively wide second heat-resistant strip layer will reduce the thermal safety of the separator, or a high proportion of polycrystalline nickel-cobalt-manganese ternary cathode material will increase side reactions, increasing the risk or amount of gas generation. Excessive internal pressure difference will also increase the risk of short circuits in the electrodes, further reducing the thermal safety of the battery. For example, H1-H2 can be 0.1μm, 0.5μm, 2μm, 5μm, 10μm, H1, or any two of these values. When "H1-H2=H1", it indicates that the second heat-resistant strip layer is absent. The value of A1 / A2×C can be 2.5, 4.5, 5, 6, 8, 10, 12, 15, 20, or any two of the above values.

[0067] In one optional embodiment, the distance D mm between the edge of the negative electrode and the edge of the positive electrode on the same side in the cell width direction satisfies the following relationship with the tab distance L mm: 10 ≤ D × L ≤ 100. By controlling D × L within the range of 10 to 100, the size of the tab distance and the negative electrode overhang area can be matched. On the one hand, this effectively improves the rate performance of the battery while providing excellent cycle performance; on the other hand, it ensures that the tab spacing and the negative electrode overhang area are appropriate, avoiding the need for the BMS to increase the minimum SOC (e.g., from 5% to 10%) due to unreasonable tab distance or overhang design to prevent lithium plating or over-discharge, thereby sacrificing some usable capacity to ensure safety. For example, D × L is 10, 20, 50, 60, 80, 100, or within any two of the above values.

[0068] When D×L < 10, the tab distance or excessive negative electrode area becomes too small, leading to significant manufacturing difficulties and challenges in achieving the required engineering precision. Even if these manufacturing challenges are overcome, during charging and discharging, lithium accumulation often occurs at the corresponding negative electrode position due to high-rate charging and discharging, preventing rapid lithium intercalation on the negative electrode side. This edge position is more prone to lithium plating, thus shortening the battery's lifespan. Alternatively, it can increase the battery's internal resistance, increasing voltage drop, reducing discharge performance, and increasing energy loss, further shortening the battery's lifespan. Furthermore, an excessively small tab distance can lead to excessively high local current density, especially at the end of charging and discharging (at low SOC), potentially causing lithium ion deposition on the negative electrode surface (lithium plating), resulting in active lithium loss and capacity decay. This forces the battery management system (BMS) to prematurely cut off discharge to protect the battery, indirectly increasing the minimum SOC value. Conversely, when D×L > 100, the battery's initial efficiency (first charge / discharge efficiency) decreases, and the battery capacity gradually decreases. This can result in excessively large tab spacing or negative electrode overhang. Excessively large overhang areas may generate uneven stress during battery cycling expansion / contraction, leading to electrode deformation or delamination. Excessively large tab spacing will increase the current transmission distance in the current collector, increasing local resistance (especially in the edge area), causing uneven current distribution. Increased internal resistance and uneven current distribution will aggravate battery polarization, especially at low SOC (remaining charge), which may trigger the voltage cutoff condition prematurely and shorten the usable capacity range.

[0069] In lithium-ion battery design, the overhang region refers to the distance Dmm between the edges of the negative electrode and the positive electrode on the same side of the cell. An increase in this distance leads to an increase in the overhang region, which in turn reduces the battery's initial charge / discharge efficiency and capacity. This is because during charging, some lithium ions diffuse into the overhang region, causing a decrease in initial efficiency and capacity. Therefore, a reasonable overhang design is crucial for optimizing battery performance and extending battery life. In this application, the distance Dmm between the edges of the negative and positive electrodes on the same side of the cell is between 0.1 and 3 mm, i.e., D is 0.1 to 3. For example, D is 0.1, 0.2, 0.5, 1, 2, 3, or any two of these values. When the D values ​​on both sides of the negative electrode are inconsistent, the minimum value is taken.

[0070] The tab distance refers to the distance from the tab to the edge of the battery cell. Changes in the tab position can significantly affect the battery's internal resistance. If the tab distance is too small, the distance between the positive and negative tabs will be too large, which may increase the internal resistance of the battery, thereby increasing the voltage drop and reducing the battery's discharge performance. This increases energy loss and shortens the battery's lifespan. Conversely, if the tab distance is too large, the distance between the positive and negative tabs will be too small, which may lead to a short circuit, causing the battery cell to catch fire. It may also lead to poor heat dissipation and imbalance inside the battery, directly affecting the battery's lifespan. In this application, the tab distance ranges from 6mm to 50mm, i.e., L is 6 to 50. For example, L is 6, 10, 20, 30, 40, 60, or any two of the above values.

[0071] In one alternative implementation, A1 is 30μm-100μm; and / or, A2 is 6.7μm-20μm. As an example, A1 can be 30μm, 50μm, 80μm, 100μm, or within any two of the above values. As an example, A2 can be 6.7μm, 8μm, 10μm, 15μm, 20μm, or within any two of the above values.

[0072] In one alternative implementation, by controlling A1 / A2 within the range of 1.5 to 4.5, the spacing region between the first heat-resistant strips provides more ion transport channels, effectively improving the migration rate of active ions. For example, the value of A1 / A2 can be 1.5, 1.8, 2, 2.5, 3, 3.5, 4, 4.5, or within any two of the above values.

[0073] In one optional embodiment, 0.5μm ≤ H1 ≤ 10μm. This configuration of the diaphragm enhances its affinity with the electrolyte, promotes uniform electrolyte distribution, reduces interfacial resistance, and prevents severe shrinkage of the diaphragm under high temperatures. For example, the thickness H1 of the first heat-resistant strip layer is 0.5μm, 2μm, 5μm, 10μm, or any two of these values. In another optional embodiment, 0.5μm ≤ H2 ≤ 8μm; for example, H2 is 0μm, 5μm, 8μm, or any two of these values.

[0074] In one optional embodiment, C is 1-4. As an example, C can be 1, 2, 3, 4, or any two of the above values. In this application, the weight ratio C of the monocrystalline nickel-cobalt-manganese ternary cathode material to the polycrystalline nickel-cobalt-manganese ternary cathode material in the cathode active material layer is controlled to be 1-4. That is, based on the total mass of the cathode active material, the mass percentage of the monocrystalline nickel-cobalt-manganese ternary cathode material is 50%-80%, and the mass percentage of the polycrystalline nickel-cobalt-manganese ternary cathode material is 20%-50%. For example, the mass percentage of the monocrystalline nickel-cobalt-manganese ternary cathode material is 50%, 60%, 70%, 80%, or any two of the above values, and the mass percentage of the polycrystalline nickel-cobalt-manganese ternary cathode material is 20%, 30%, 40%, 50%, or any two of the above values.

[0075] In one optional embodiment, the first heat-resistant strip layer includes first heat-resistant particles; specifically, the particle size of the first heat-resistant particles is 0.1 μm to 2.5 μm. Controlling the particle size of the first heat-resistant particles within this range not only helps to obtain a separator with a suitable porosity, thereby improving lithium-ion migration efficiency, but also helps to improve the heat resistance of the separator, thereby improving battery thermal safety. For example, the particle size of the first heat-resistant particles is 0.1 μm, 0.5 μm, 1 μm, 2 μm, 2.5 μm, or within any two of these values. For example, the first heat-resistant particle comprises at least one of boehmite (γ-AlOOH), alumina (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium dioxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, diethylaluminum hypophosphite, pentaerythritol, and triazine charring agent.

[0076] In one optional embodiment, when a second heat-resistant strip layer is disposed between two adjacent first heat-resistant strip layers, the second heat-resistant strip layer includes second heat-resistant particles; specifically, the particle size of the second heat-resistant particles is 0.1 μm to 2.5 μm. Controlling the particle size of the second heat-resistant particles within the above range not only helps to control and obtain a separator with a suitable porosity, thereby improving the migration efficiency of lithium ions, but also helps to improve the heat resistance of the separator, thereby improving the thermal safety of the battery. For example, the particle size of the second heat-resistant particles is 0.1 μm, 0.5 μm, 1 μm, 2 μm, 2.5 μm, or within any two of the above values. For example, the second heat-resistant particle comprises at least one of boehmite (γ-AlOOH), alumina (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium dioxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, diethylaluminum hypophosphite, pentaerythritol, and triazine charring agent.

[0077] In one optional embodiment, the first heat-resistant strip layer comprises, by weight, 40 wt% to 96 wt% of first heat-resistant particles, 3 wt% to 59.3 wt% of binder, and 0.7 wt% to 3 wt% of dispersant. By controlling the first heat-resistant particles, binder, and dispersant within the above ranges, the separator can have good wettability and low impedance. Applying the separator to the battery cell is beneficial for the battery cell to have good charge-discharge performance. For example, the first heat-resistant strip layer comprises 40 wt% first heat-resistant particles, 59.3 wt% binder, and 0.7 wt% dispersant; it may also comprise 60 wt% first heat-resistant particles, 37 wt% binder, and 3 wt% dispersant; or it may comprise 96 wt% first heat-resistant particles, 3 wt% binder, and 1 wt% dispersant.

[0078] In one optional embodiment, the second heat-resistant strip layer comprises, by weight, 40 wt% to 96 wt% of second heat-resistant particles, 3 wt% to 59.3 wt% of binder, and 0.7 wt% to 3 wt% of dispersant. By controlling the second heat-resistant particles, binder, and dispersant within the aforementioned ranges, the separator can achieve both good wettability and low impedance. Applying the separator to the battery cell is beneficial for improving the cell's charge-discharge performance. For example, the second heat-resistant strip layer may comprise 40 wt% second heat-resistant particles, 59.3 wt% binder, and 0.7 wt% dispersant; 60 wt% second heat-resistant particles, 37 wt% binder, and 3 wt% dispersant; or 96 wt% second heat-resistant particles, 3 wt% binder, and 1 wt% dispersant. For example, the binder includes at least one selected from polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, a copolymer of polyvinylidene fluoride and trichloroethylene, polyvinyl acetate, polyvinyl alcohol, polyethylene oxide, polyamide, polyacrylonitrile, acrylate polymers (e.g., polymethyl methacrylate), polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, styrene-butadiene rubber, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polytetrafluoroethylene, or polyhexafluoropropylene. The dispersant includes at least one selected from ethylene oxide, polyamide, polyvinyl alcohol, polyurethane, and polyvinylpyrrolidone.

[0079] In one optional embodiment, the thickness of the base film is 4–20 μm. For example, the thickness of the base film is 4 μm, 5 μm, 10 μm, 16 μm, 20 μm, or within any two of these values. In this application, the base film can be at least one of woven film, nonwoven film, polyolefin film, and separator paper. The polyolefin film can be one or more of polyethylene, polypropylene, or composites of polyethylene and polypropylene. The substrate has an elongation at break (TD) of 20%–200%, an elongation at break (MD) of 50%–300%, a puncture strength of 100 gf–600 gf, and a peel strength between the heat-resistant layer and the substrate layer of 30–200 N / m.

[0080] In one optional embodiment, the separator further includes an adhesive layer located on the surface of the base film and / or the heat-resistant layer. The adhesive layer enhances the adhesion between the separator and the electrode, shortens the lithium-ion migration path, and thus improves high-rate performance. Furthermore, during cycling, the active material of the electrode may develop microcracks due to volume expansion; the adhesive force of the adhesive layer can effectively fix the active particles, reducing capacity decay caused by detachment.

[0081] In one optional embodiment, the thickness of the adhesive layer is 0.5-3 μm. Such a thickness range effectively improves the adhesion between the separator and the electrode, preventing short circuits at the positive and negative electrode contacts and enhancing battery safety. For example, the thickness of the adhesive layer is 0.5 μm, 1 μm, 2 μm, 3 μm, or within any two of these values.

[0082] In one alternative embodiment, the adhesive layer is a porous layer comprising a polymer and optional filler particles, wherein the polymer accounts for 40%-100% of the total mass of the adhesive layer, and the filler particles account for 0%-60% of the total mass of the adhesive layer, wherein a filler particle mass percentage of 0% indicates that the coating contains no filler particles.

[0083] In one alternative embodiment, the adhesive layer is a porous layer comprising a polymer and optional filler particles, wherein the polymer accounts for 40%-60% of the total mass of the adhesive layer, and the filler particles account for 40%-60% of the total mass of the adhesive layer.

[0084] In another alternative embodiment, the adhesive layer includes polymer particles, the polymer particles including at least one of a first polymer particle and a second polymer particle, wherein the first polymer particle is dispersedly distributed in the adhesive layer and the second polymer particle is agglomerated in the adhesive layer.

[0085] In one alternative embodiment, the average particle size of the first polymer particles is 0.5 μm to 0.95 μm.

[0086] In one optional embodiment, the second polymer particle includes secondary particles formed by the agglomeration of primary particles, wherein the average particle size of the primary particles of the second polymer particle is 0.15 μm-0.3 μm, and the average particle size of the secondary particles of the second polymer particle is 2 μm-18 μm.

[0087] In this application, the average particle size of polymer particles refers to the average particle size of polymer particles in the adhesive layer. When the adhesive layer contains only one type of polymer particles, the average particle size of polymer particles refers to the average value of 100 particles of that type of polymer particles. When the adhesive layer contains two types of polymer particles, the average particle size of polymer particles refers to the average value of 100 particles of the first type of polymer particles and 100 particles of the second type of polymer particles.

[0088] In one alternative embodiment, the adhesive layer comprises a polymer, for example, including polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, polyacrylonitrile, poly(meth)acrylate, aramid resin, poly(meth)acrylic acid, styrene-butadiene rubber (SBR), polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), carboxyethyl cellulose, polyacrylamide, phenolic resin, epoxy resin, waterborne polyurethane, ethylene-vinyl acetate copolymer, multi-component acrylic copolymer, lithium polystyrene sulfonate, waterborne silicone resin, nitrile-polyvinyl chloride blend, styrene-acrylic latex, pure styrene latex, and one or more combinations of blends and copolymers derived from the aforementioned polymers through modification.

[0089] In one optional embodiment, the particle size Dv10 of the single-crystal nickel-cobalt-manganese ternary cathode material is 0.8μm-4μm, Dv50 is 1μm-6μm, and Dv90 is 3μm-10μm. By controlling the particle size distribution of the single-crystal nickel-cobalt-manganese ternary cathode material within the above range, the battery performance of the cell is improved. In particular, Dv10≥0.8μm avoids an excessively high proportion of ultrafine particles, and Dv90≤10μm inhibits the agglomeration of large particles, making the particle size distribution more concentrated and the filling more compact, thereby improving the volumetric energy density. For example, the particle size Dv10 of the single-crystal nickel-cobalt-manganese ternary cathode material is 0.8μm, 1.0μm, 2.0μm, 3.0μm, 4μm or within any two of the above values; Dv50 is 1μm, 2μm, 3μm, 4μm, 6μm or within any two of the above values; and Dv90 is 3μm, 4μm, 5μm, 6μm, 10μm or within any two of the above values.

[0090] The particle size of the single-crystal nickel-cobalt-manganese ternary cathode material can be obtained by conventional methods in the art, and this application does not impose specific limitations. As an example, the method for testing the average particle size of the single crystal particles in this application includes: taking pictures on the surface or cross-section of the cathode active material layer using a scanning electron microscope, randomly selecting at least 20 single crystal particles from the obtained SEM images, measuring the particle size, and taking the average value; if the number of single crystal particles in the field of view is less than 20, then another field of view is selected for measurement, until the particle size of at least 20 single crystal particles is measured.

[0091] In one optional embodiment, the BET of the single-crystal nickel-cobalt-manganese ternary cathode material is 0.5m. 2 / g-1.4m 2 / g. BET controlled between 0.5-1.4m. 2The BET value is 0.5m / g, ensuring sufficient active surface area of ​​the single-crystal nickel-cobalt-manganese ternary cathode material for reaction (avoiding insufficient reactivity due to excessively low BET) while avoiding side reactions caused by excessively high BET (such as electrolyte decomposition and gas generation), thereby improving the cycle performance of the cell. For example, the BET of the single-crystal nickel-cobalt-manganese ternary cathode material is 0.5m. 2 / g, 0.8m 2 / g, 1.0m 2 / g, 1.4m 2 / g or within the range of any two of the above values.

[0092] In one optional embodiment, the particle size Dv10 of the polycrystalline nickel-cobalt-manganese ternary cathode material is 3-13 μm, Dv50 is 6-15 μm, and Dv90 is 12-25 μm. By controlling the particle size distribution of the polycrystalline nickel-cobalt-manganese ternary cathode material within the above range, the battery performance of the cell is improved. In particular, controlling Dv90≤25 μm avoids stress concentration at the grain boundaries caused by the volume expansion of excessively large polycrystalline particles during cycling, reduces the generation of microcracks, reduces the risk of dissolution of transition metals (such as Ni and Co), and improves high-temperature cycling stability. For example, the particle size Dv10 of the polycrystalline nickel-cobalt-manganese ternary cathode material is 3μm, 4μm, 6μm, 10μm, 13μm or within any two of the above values; Dv50 is 6μm, 8μm, 10μm, 12μm, 15μm or within any two of the above values; and Dv90 is 12μm, 15μm, 20μm, 22μm, 25μm or within any two of the above values.

[0093] The particle size of polycrystalline nickel-cobalt-manganese ternary cathode material can be tested using conventional methods in the art, and this application does not impose specific limitations. As an example, the method for testing the average particle size of polycrystalline particles described in this application includes: taking images on the surface or cross-section of the cathode active material layer using a scanning electron microscope, randomly selecting at least 20 polycrystalline particles from the obtained SEM images, measuring the particle size, and taking the average value; if the number of polycrystalline particles in the field of view is less than 20, then another field of view is selected for measurement, until the particle size of at least 20 polycrystalline particles is measured.

[0094] In one optional embodiment, the BET of the polycrystalline nickel-cobalt-manganese ternary cathode material is 0.3m. 2 / g-1.0m 2 / g, by controlling the BET of the polycrystalline nickel-cobalt-manganese ternary cathode material to be ≥0.3m 2 / g ensures that the polycrystalline nickel-cobalt-manganese ternary cathode material has sufficient reactivity, while BET≤1.0m 2This avoids excessive exposure of the active surface, reduces the continuous decomposition of the electrolyte at grain boundaries, inhibits gas generation and SEI film thickening, and thus improves the cycle performance of the cell. For example, the BET of the polycrystalline nickel-cobalt-manganese ternary cathode material is 0.3m. 2 / g, 0.5m 2 / g, 0.8m 2 / g, 1.0m 2 / g or within the range of any two of the above values.

[0095] In one optional embodiment, the nickel content in the monocrystalline nickel-cobalt-manganese ternary cathode material accounts for 85%-98% of the total nickel-cobalt-manganese metal element content; preferably 90%-95%. The nickel content in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 80%-95% of the total nickel-cobalt-manganese metal element content; preferably 87%-92%. Based on controlling the weight ratio C of the monocrystalline and polycrystalline nickel-cobalt-manganese ternary cathode materials, by controlling the nickel content in the monocrystalline and / or polycrystalline nickel-cobalt-manganese ternary cathode materials within the above ranges, especially the preferred ranges, the specific capacity of the material is significantly improved while maintaining structural stability and thermal safety, thereby increasing the energy density of the battery. An excessively high nickel content can lead to an increased risk of gas generation, which in turn reduces thermal safety. For example, the nickel content in the monocrystalline nickel-cobalt-manganese ternary cathode material accounts for 85%, 90%, 95%, 97%, 98% of the total nickel-cobalt-manganese metal element content, or falls within any two of the above values. The nickel element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 80%, 85%, 89%, 92%, 95% of the total nickel-cobalt-manganese metal elements, or falls within any two of the above values.

[0096] In one optional embodiment, the cobalt element in the monocrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%-14% of the total molar content of nickel, cobalt, and manganese metals; preferably 2%-10%. The cobalt element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%-19% of the total molar content of nickel, cobalt, and manganese metals; preferably 2%-10%. Based on the control of the weight ratio C of the aforementioned monocrystalline nickel-cobalt-manganese ternary cathode material and polycrystalline nickel-cobalt-manganese ternary cathode material, by controlling the cobalt element in the monocrystalline and / or polycrystalline nickel-cobalt-manganese ternary cathode materials within the above ranges, especially the preferred ranges, the cycle performance and rate performance of the battery are significantly improved while maintaining a low cost. For example, the cobalt element in the monocrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%, 5%, 9%, 12%, 14% of the total molar content of nickel, cobalt, and manganese metals, or falls within the range of any two of the above values. The cobalt element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%, 5%, 9%, 12%, 15%, 19% of the total nickel-cobalt-manganese metal elements, or falls within any two of the above values.

[0097] In one optional embodiment, the manganese element in the monocrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%-10% of the total molar content of nickel, cobalt, and manganese metals; preferably 2%-7%. The manganese element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%-10% of the total molar content of nickel, cobalt, and manganese metals; preferably 2%-7%. Manganese mainly plays a role in reducing cost, improving material safety, and structural stability in ternary cathode materials. The electrochemical inertness of manganese ensures that the material maintains a stable structure. Excessive manganese content may also cause the material to transform from a layered structure to a spinel structure, increasing the material's instability. Based on the control of the aforementioned weight ratio C between monocrystalline and polycrystalline nickel-cobalt-manganese ternary cathode materials, by controlling the manganese element in the monocrystalline and / or polycrystalline nickel-cobalt-manganese ternary cathode materials within the above-mentioned range, especially the preferred range, it is possible to reduce costs and improve battery cycle performance and thermal stability. For example, in the single-crystal nickel-cobalt-manganese ternary cathode material, the molar content of manganese in the total nickel-cobalt-manganese metal elements is 1%, 5%, 9%, 10%, or within any two of the above values. In the polycrystalline nickel-cobalt-manganese ternary cathode material, the molar content of manganese in the total nickel-cobalt-manganese metal elements is 1%, 5%, 9%, 10%, or within any two of the above values.

[0098] In one optional embodiment, the adhesive layer includes a first adhesive layer disposed on the side of the base film opposite to the first heat-resistant strip layer; disposing the first adhesive layer on the side opposite to the first heat-resistant strip layer can improve the adhesion between the separator and the electrode, shorten the migration path of lithium ions, thereby improving high-rate performance; and during cycling, the active material of the electrode may generate microcracks due to volume expansion, and the adhesive force of the adhesive layer can effectively fix the active particles and reduce capacity decay caused by shedding.

[0099] In one alternative embodiment, the adhesive layer includes a first heat-resistant strip layer located on the side opposite to the base film.

[0100] In an optional embodiment, when a second heat-resistant strip layer is provided between two adjacent first heat-resistant strip layers, the adhesive layer further includes a second adhesive strip layer located on the side of the second heat-resistant strip layer away from the base film, and the sum of the thicknesses of the first adhesive strip layer and the first heat-resistant strip layer is greater than the sum of the thicknesses of the second adhesive strip layer and the second heat-resistant strip layer. This arrangement can prevent poor continuity of the adhesive coating of the diaphragm heat-resistant layer, avoid insufficient adhesion, and improve structural stability.

[0101] In one alternative embodiment, the thickness of the first adhesive strip layer is the same as the thickness of the second adhesive strip layer.

[0102] The material and shape of the separator used in the lithium-ion secondary battery of this application are not particularly limited, and may include any technology disclosed in the prior art.

[0103] The electrolyte used in the lithium-ion secondary battery of this application may include any technology disclosed in the prior art.

[0104] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in this application. In all embodiments and comparative examples of this application, the unit wt% represents the mass percentage content.

[0105] Example 1

[0106] This embodiment provides a battery cell, including a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrodes.

[0107] The diaphragm comprises a base membrane 1 (a polyethylene microporous membrane with a thickness D of 7 μm, a porosity of 40%, an average pore size of 45 nm, and a needle penetration strength of 300 gf) and multiple parallel, spaced first heat-resistant strips 2 located on one side of the base membrane, as shown in Figure 1. The first heat-resistant strips, by their total mass, consist of 7.5 wt% heat-resistant particles (specifically boehmite with a Dv50 of 0.3 μm), 10 wt% binder (polymethyl methacrylate), and 2.5 wt% dispersant (ethylene oxide). No second heat-resistant strips are provided between adjacent first heat-resistant strips (i.e., the thickness of the second heat-resistant strip is 0 μm, H1-H2=H1). The thickness H1 of the first heat-resistant strips is 1.5 μm, the width A1 is 30 μm, and the spacing width A2 is 20 μm.

[0108] The positive electrode sheet includes a positive current collector and a positive active layer located on both surfaces of the positive current collector. The positive active material on the positive active material layer is composed of monocrystalline nickel-cobalt-manganese ternary positive electrode material and polycrystalline nickel-cobalt-manganese ternary positive electrode material. The mass ratio C of monocrystalline and polycrystalline nickel-cobalt-manganese ternary positive electrode materials and the relationships A1 / A2 and A1 / A2×C are shown in Table 1. The molar content of nickel (Ni), cobalt (Co), and manganese (Mn) in the monocrystalline and polycrystalline nickel-cobalt-manganese ternary positive electrode materials are shown in Table 2.

[0109] Its preparation method is as follows:

[0110] (1) Preparation of the diaphragm

[0111] 1) Weigh out the heat-resistant particles, binder and dispersant according to the above mass content and set aside. Mix the heat-resistant particles (specifically boehmite, Dv50 is 0.3μm), binder (polymethyl methacrylate), dispersant (ethylene oxide) and water at a mass ratio of 1.5 times the total mass of the heat-resistant particles, binder and dispersant to obtain ceramic slurry;

[0112] 2) A coating roller of the corresponding size is pre-carved according to the dimensions (width and thickness, see Table 1) and spacing width A2 of the first heat-resistant strip layer, and the coating roller is engraved with concave and convex patterns. During coating, the slurry enters the concave and convex parts of the coating roller, and then the slurry is coated onto the film surface due to contact with the film to be coated. That is, the ceramic slurry obtained in step 1) is coated on one side of the base film using a coating roller (roller coating method), and after high temperature baking (temperature is 60℃, time is 30min), a base film layer with multiple parallel and spaced first heat-resistant strip layers coated on one side is obtained; the finished diaphragm is obtained.

[0113] (2) Preparation of positive electrode

[0114] First, according to the mass ratio in Table 1, the molecular formula Li(Ni) 0.92 Co 0.05 Mn 0.03 Single-crystal nickel-cobalt-manganese ternary cathode material (particle size parameters and BET are shown in Table 2) and Li(Ni)O2) 0.9 Co 0.05 Mn 0.05 Polycrystalline nickel-cobalt-manganese ternary cathode material (particle size parameters and BET are shown in Table 2) was mixed to obtain the cathode active material. Super-P (conductive carbon black) and activated carbon were mixed at a 1:1 mass ratio to prepare a conductive agent. Next, the cathode active material, conductive agent, and binder were mixed at a mass ratio of 97.5% cathode active material, 1.35% conductive agent, and 1.15% binder (PVDF), and dispersed in N-methylpyrrolidone solvent to ensure uniform dispersion, resulting in a cathode slurry. The obtained cathode slurry was then uniformly coated onto both sides of an aluminum foil current collector and dried to form a cathode film. Finally, the lithium-ion battery cathode sheet was fabricated through cold pressing, cutting into sheets, and welding electrode tabs.

[0115] (3) Preparation of negative electrode sheet

[0116] First, Si-C composite material was used as the active material, with a silicon content of 4% and a graphite content of 96%. The active material was mixed with Super-P conductive agent, CMC thickener, and SBR binder in a mass ratio of 97.2% Si-C, 0.6% conductive agent, 1.0% thickener, and 1.2% binder. These materials were dissolved in deionized water and thoroughly stirred to form a negative electrode slurry. Then, the negative electrode slurry was uniformly coated on both sides of a copper foil current collector and dried to form a negative electrode film. Finally, the lithium-ion battery negative electrode sheet was prepared by cold pressing, cutting into sheets, and welding electrode tabs. The distance D mm between the edge of the negative electrode sheet and the edge of the positive electrode sheet on the same side in the cell width direction, the tab distance L mm, and the relationship D×L are shown in Table 3.

[0117] (4) Preparation of electrolyte

[0118] LiPF6 was selected as the lithium salt, and a mixed solvent was prepared by mixing ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, and vinylene carbonate in a mass ratio of 8:85:5:2. Subsequently, the lithium salt and solvent were mixed at a mass ratio of 8:92 to form the electrolyte, which is specifically designed for lithium-ion batteries.

[0119] (5) Preparation of lithium-ion batteries

[0120] The separator is selected from the separator made in step (1). The prepared positive electrode, negative electrode and the manufactured separator are wound and assembled into a cell. After drying, liquid injection and encapsulation, etc., a lithium-ion battery is obtained.

[0121] The cell preparation methods in Examples 2-4 and 6-8 are basically the same as those in Example 1. The only difference is that the width A1 or the spacing width A2 of the first heat-resistant strip layer is adjusted during the preparation of the separator. In Examples 3-5 and 7, the mass ratio C of single crystal and polycrystalline nickel-cobalt-manganese ternary cathode materials is also adjusted during the preparation of the cathode sheet, so that A1 / A2×C is different. See Table 1 for details.

[0122] The preparation method of the battery cell in Example 5 is basically the same as that in Example 1. The only difference is that the mass ratio C of the single crystal and polycrystalline nickel-cobalt-manganese ternary cathode materials is adjusted so that A1 / A2×C is different, as detailed in Table 1.

[0123] The method for preparing the battery cell in Example 9 is basically the same as that in Example 1, except that the thickness of the first heat-resistant strip layer is adjusted, as detailed in Table 1.

[0124] The cell preparation method in Example 10 is basically the same as that in Example 1, except for the second heat-resistant strip layer 3 between two adjacent first heat-resistant strip layers 2 in the separator, as shown in Figure 2. The thickness of the second heat-resistant strip layer is shown in Table 1, and the composition of the second heat-resistant strip layer is the same as that of the first heat-resistant strip layer. The separator preparation method in this example is as follows:

[0125] 1) Weigh out the heat-resistant particles, binder and dispersant according to the above mass content and set aside. Mix the heat-resistant particles (specifically boehmite, Dv50 is 0.3μm), binder (polymethyl methacrylate), dispersant (ethylene oxide) and water at a mass ratio of 1.5 times the total mass of the heat-resistant particles, binder and dispersant to obtain ceramic slurry;

[0126] 2) A coating roller of corresponding dimensions is pre-carved according to the dimensions of the first heat-resistant strip layer (width and thickness, see Table 1) and the second heat-resistant strip layer (thickness shown in Table 1, width is A2). The coating roller has raised and recessed patterns. During coating, the slurry enters the raised and recessed parts of the coating roller, and then the slurry is coated onto the film surface due to contact with the film being coated. That is, the ceramic slurry obtained in step 1) is coated on one side of the base film using a coating roller (roller coating method). After high-temperature baking (temperature 60℃, time 30min), a base film layer is obtained with parallel, spaced first heat-resistant strip layers on one side and a second heat-resistant strip layer between adjacent first heat-resistant strip layers; the finished separator is obtained.

[0127] The cell preparation method in Example 11 is basically the same as that in Example 9, except for the second heat-resistant strip layer between two adjacent first heat-resistant strip layers in the separator. The thickness of the second heat-resistant strip layer is shown in Table 1, and the composition of the second heat-resistant strip layer is the same as that of the first heat-resistant strip layer. The separator preparation method in this example is the same as that in Example 10.

[0128] The preparation method of the battery cell in Example 12 is basically the same as that in Example 1. The only difference is that the particle size Dv50 of the heat-resistant boehmite particles is adjusted during the preparation of the separator, as detailed in Table 1.

[0129] The cell preparation methods in Examples 13 and 14 are basically the same as in Example 1, except that the content of each substance in the first heat-resistant strip layer is adjusted during the separator preparation process. Specifically, in Example 13, the first heat-resistant strip layer is composed of 42.3 wt% heat-resistant particles (specifically boehmite, Dv50 of 0.3 μm), 55.1 wt% binder (polymethyl methacrylate), and 2.6 wt% dispersant (ethylene oxide). In Example 14, the first heat-resistant strip layer is composed of 95.8 wt% heat-resistant particles (specifically boehmite, Dv50 of 0.3 μm), 3.5 wt% binder (polymethyl methacrylate), and 0.7 wt% dispersant (ethylene oxide).

[0130] The preparation method of the battery cell in Example 15 is basically the same as that in Example 1. The difference is that, in the separator preparation process, after obtaining the base film layer with the first heat-resistant strip layer with parallel spacing on one side in step 2), the first adhesive layer 4 is coated on one side of the base film 1 away from the first heat-resistant strip layer 2 using a roller coating method. Specifically, polyvinylidene fluoride (PVDF) and dimethylacetamide (DMAC) are mixed and stirred and dissolved to obtain a mixed slurry with a mass concentration of 8wt%. The mixed slurry is coated on the substrate by a gravure roller. DMAC is extracted by water in a water bath and then dried in a multi-section oven at 60°C (temperature 60°C, time 20min) to form the first adhesive layer 4 with a thickness H3 of 1.8μm (see Figure 3).

[0131] The preparation method of the battery cell in Example 16 is basically the same as that in Example 1. The difference is that, in the separator preparation process, after obtaining the base film layer with the first heat-resistant strip layer with parallel spacing on one side in step 2), a double-sided coating is performed on the side of the base film away from the first heat-resistant strip layer and the side of the first heat-resistant strip layer away from the base film using a roller coating method. Specifically, polyvinylidene fluoride (PVDF) and dimethylacetamide (DMAC) are mixed and thoroughly stirred and dissolved to obtain a mixed slurry with a mass concentration of 8wt%. The mixed slurry is coated on the base film and the first heat-resistant strip layer using a gravure roller. DMAC is extracted by water in a water bath and then dried in a multi-section oven at 60°C (temperature 60°C, time 20min) to form a first adhesive layer 4 with a thickness of 1.8μm on the side of the base film 1 away from the first heat-resistant strip layer 2. At the same time, a first adhesive strip layer 5 with a thickness H4 of 1.8μm is formed on the side of the first heat-resistant strip layer 2 away from the base film 1 (see Figure 4).

[0132] The cell preparation method in Example 17 is basically the same as that in Example 10. The only difference is that, in the separator preparation process, after obtaining the base film layer with the first heat-resistant strip layer coated on one side in step 2), a roller coating method is used to coat both sides of the base film on the side away from the first heat-resistant strip layer and the side of the first heat-resistant strip layer on the side away from the base film. This results in a first adhesive layer being formed on the side of the base film away from the first heat-resistant strip layer, a first adhesive strip layer being formed on the side of the first heat-resistant strip layer away from the base film, and a second adhesive strip layer being formed between adjacent first adhesive strip layers, thus obtaining the finished separator. Specifically, polyvinylidene fluoride (PVDF) and dimethylacetamide (DMAC) are mixed and thoroughly stirred to obtain a mixed slurry with a mass concentration of 8 wt%. The mixed slurry is coated onto a base film, a first heat-resistant strip layer, and a second heat-resistant layer using a gravure roller. DMAC is extracted using water in a water bath and then dried in a multi-section oven at 60°C (temperature 60°C, time 20 min) to form a first adhesive layer 4 with a thickness of 1.8 μm on the side of the base film 1 opposite to the first heat-resistant strip layer 2. At the same time, a first adhesive strip layer 5 with a thickness of 1.8 μm (H4) is formed on the side of the first heat-resistant strip layer 2 opposite to the base film 1, and a second adhesive strip layer 6 with a thickness of 1.8 μm (H5) is formed on the side of the second heat-resistant strip layer 3 opposite to the base film 1 (see Figure 5).

[0133] The cell preparation methods in Examples 18-21 are basically the same as those in Example 1. The only difference is that the physical parameters of the single-crystal nickel-cobalt-manganese ternary cathode material and the polycrystalline nickel-cobalt-manganese ternary cathode material used in the preparation of the cathode sheet are adjusted, as detailed in Table 2.

[0134] The cell preparation methods in Examples 22-27 are basically the same as those in Example 1. The only difference is that the molar content of nickel, cobalt and / or manganese in the single crystal or polycrystalline nickel-cobalt-manganese ternary cathode material used in the preparation of the cathode sheet is adjusted, as detailed in Table 3.

[0135] The cell preparation methods in Examples 28 to 33 are basically the same as those in Example 1, except that the distance D mm and / or the tab edge distance L mm are adjusted, resulting in different D×L, as detailed in Table 4.

[0136] The preparation method of the battery cell in Comparative Example 1 is basically the same as that in Example 1. The only difference is that in the preparation process of the positive electrode sheet, only the single-crystal nickel-cobalt-manganese ternary positive electrode material is used as the positive electrode active material, and its preparation method is the same as that in Example 1.

[0137] The preparation method of the battery cell in Comparative Example 2 is basically the same as that in Example 1. The only difference is that in the preparation process of the positive electrode sheet, only polycrystalline nickel-cobalt-manganese ternary positive electrode material is used as the positive electrode active material, and its preparation method is the same as that in Example 1.

[0138] The preparation method of the battery cell in Comparative Example 3 is basically the same as that in Example 1. The only difference is that the mass ratio C of the single crystal and polycrystalline nickel-cobalt-manganese ternary cathode materials is adjusted, resulting in different A1 / A2×C, as detailed in Table 1.

[0139] The preparation method of the battery cell in Comparative Example 4 is basically the same as that in Example 1. The only difference is that the width A1 of the first heat-resistant strip layer, the spacing width A2, and the mass ratio C of single crystal and polycrystalline nickel-cobalt-manganese ternary cathode materials are adjusted during the preparation of the separator, resulting in different A1 / A2×C, as detailed in Table 1.

[0140] Table 1 Physical parameters of the separator and positive electrode active material " / " indicates that it does not exist.

[0141] Table 2 Physical parameters of positive electrode active materials

[0142] Table 3. Molar content of metal elements in positive electrode active materials

[0143] Table 4 Parameters of the negative electrode sheet

[0144] Test case

[0145] The lithium-ion batteries prepared in each embodiment and comparative example were subjected to the following tests:

[0146] 1. Minimum Remaining Battery Capacity (SOC) Test

[0147] The battery cell is wrapped with foam material, the surface temperature of the battery cell is monitored, and it is placed in a constant temperature chamber. The constant temperature chamber is adjusted to 25°C to carry out steps (1) to (5).

[0148] (1) Let it rest for 5 minutes; (2) Discharge at a constant current of 0.5C to the lower limit voltage; (3) Let it rest for 15 minutes; (4) Charge at a constant current of 1.8C to the upper limit voltage, with a cutoff current of 0.05C; let it rest for 30 minutes; (5) Repeat (2) to (4) to obtain the full charge capacity C0.

[0149] Then, proceed with steps (6) to (11) until the discharge cutoff voltage at the target temperature and SOC equals the lower limit voltage (2.5V ± 0.05V).

[0150] (6) Adjust the constant temperature chamber to 0℃ and let it stand for 120 min; (7) Discharge at 0℃ and 7.5C for 15s with constant current and sampling frequency (100ms) to test the discharge cutoff voltage; (8) Adjust the constant temperature chamber to 25℃ and let it stand for 30 min; (9) At 25℃, discharge at 1C to reduce SOC or charge at 1C to increase SOC (charge if SOC is lower than the target SOC, discharge if SOC is higher than the target SOC, the target SOC refers to the SOC at which the discharge cutoff voltage is equal to the lower limit voltage); (10) Adjust the constant temperature chamber to 25℃ and let it stand for 90 min; (11) Repeat (7) to (10) until the discharge cutoff voltage tested in (7) is equal to the lower limit voltage (2.5V±0.05V).

[0151] 2. Cyclic performance test

[0152] At an ambient temperature of 25±2℃, charge at 0.5C to the upper cutoff voltage, maintain constant voltage to 0.05C, let stand for 10 minutes, then discharge at 1C to the lower cutoff voltage. The initial discharge capacity is recorded as C0, and let stand for 10 minutes. Cyclic mode: Charge at 3C to the upper cutoff voltage, maintain constant voltage to 0.05C, let stand for 10 minutes, then discharge at 10C to the lower cutoff voltage, let stand for 20 minutes. After 600 cycles, charge at 0.5C to the upper cutoff voltage, maintain constant voltage to 0.05C, let stand for 10 minutes, then discharge at 1C to the lower cutoff voltage. The final discharge capacity is recorded as C1.

[0153] Capacity retention rate: C = C1 / C0 * 100%.

[0154] 3. Ratio Performance Test

[0155] The lithium-ion battery was placed at 25°C for 5 minutes; discharged at 0.5C to 2.5V, charged at 1C to 4.2V, kept constant at 0.05C, and discharged at 0.2C to obtain the initial capacity; placed at 25°C for 30 minutes; charged at 1C to 100% SOC at room temperature; placed at 25 minutes; placed at 0°C for 2 hours; discharged at 15C rate to the lower limit voltage and the discharge capacity was recorded. The 15C discharge capacity retention rate of the battery was calculated using the following formula.

[0156] 15C discharge capacity retention rate (%) = discharge capacity / initial capacity × 100%.

[0157] 4. Thermal stability safety test

[0158] The lithium-ion battery is discharged at 0.5C and fully charged at 1C. The lithium-ion battery is placed in a hot box and heated to 130°C at a rate of (5°C±2°C) / min and maintained for 60 minutes. The experiment ends, and the state of the lithium-ion battery before and after the test is recorded. If the lithium-ion battery catches fire, it is considered that the furnace temperature test has failed. 20 cells are tested at a time. The furnace temperature pass rate is expressed as "number of lithium-ion batteries that pass the furnace temperature test / total number of lithium-ion batteries".

[0159] Please see Table 5 for the test results.

[0160] Table 5 Performance Test Results

[0161] The results show that, compared with Comparative Examples 1-4, the battery cells provided in each embodiment of this application, by using a combination of monocrystalline nickel-cobalt-manganese ternary cathode material and polycrystalline nickel-cobalt-manganese ternary cathode material, and by strictly controlling the relationship between the weight ratio C of the two materials and the width A1 and spacing width A2 of the first heat-resistant strip layer, significantly improve the cycle stability of the ternary cathode material battery system while maintaining high thermal safety. This allows the battery to maintain both high cycle performance and excellent rate performance even in scenarios of rapid charging and discharging at high rates.

[0162] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. An electric cell, characterized by, The device includes a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrode. The separator includes a base film and a heat-resistant layer located on at least one surface of the base film. The heat-resistant layer includes a plurality of first heat-resistant strips spaced apart from each other and a second heat-resistant strip between two adjacent first heat-resistant strips. The thickness H1 of the first heat-resistant strip and the thickness H2 of the second heat-resistant strip satisfy: 0 μm < H1 - H2 ≤ H1, where the units of H1 and H2 are both μm. The positive electrode sheet includes a current collector and a positive active material layer disposed on at least one side surface of the current collector. The positive active material layer includes a positive active material, which includes a single-crystal nickel-cobalt-manganese ternary positive electrode material and a polycrystalline nickel-cobalt-manganese ternary positive electrode material. The width A1 of the first heat-resistant strip layer, the spacing A2 between two adjacent first heat-resistant strip layers, and the weight ratio C of the single-crystal nickel-cobalt-manganese ternary cathode material to the polycrystalline nickel-cobalt-manganese ternary cathode material in the cathode active material layer satisfy the following relationship: 2.5≤(A1 / A2)×C≤20; where the units of A1 and A2 are both μm.

2. The electric cell of claim 1, wherein, The distance D mm between the edge of the negative electrode and the edge of the positive electrode on the same side in the direction of cell width and the tab distance L mm satisfy the following relationship: 10≤D×L≤100; where D is 0.1~3 and L is 6~50.

3. The electric cell of claim 1, wherein, 4.5≤(A1 / A2)×C≤15; And / or, 1μm≤H1-H2≤5μm.

4. The electric cell of claim 1, wherein, A1 ranges from 30μm to 100μm; And / or, A2 is 6.7μm-20μm; And / or, C is 1-4; And / or, 0.5μm≤H1≤10μm; And / or, 0.5μm≤H2≤8μm.

5. The electric cell of claim 1, wherein, 1.5≤A1 / A2≤4.

5.

6. The electric cell of any one of claims 1-5, wherein, The battery cell meets one or more of the following conditions: A. The first heat-resistant strip layer includes first heat-resistant particles; B. The second heat-resistant strip layer includes second heat-resistant particles; C. The diaphragm further includes an adhesive layer, which is located on the surface of the base film and / or the heat-resistant layer.

7. The electric cell of claim 6, wherein, The battery cell meets one or more of the following conditions: A. The particle size Dv50 of the first heat-resistant particle is 0.1μm to 2.5μm; B. The first heat-resistant particle comprises at least one of the following: boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, diethylaluminum hypophosphite, pentaerythritol, and triazine charring agent; C. Based on the total mass of the first heat-resistant strip layer, the first heat-resistant strip layer comprises 40wt% to 96wt% of first heat-resistant particles, 3wt% to 59.3wt% of binder, and 0.7wt% to 3wt% of dispersant; D. The particle size Dv50 of the second heat-resistant particle is 0.1μm~2.5μm; E. The second heat-resistant particle comprises at least one of the following: boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, diethylaluminum hypophosphite, pentaerythritol, and triazine charring agent; F. Based on the total mass of the second heat-resistant strip layer, the second heat-resistant strip layer comprises 40wt% to 96wt% of second heat-resistant particles, 3wt% to 59.3wt% of binder, and 0.7wt% to 3wt% of dispersant; G. The thickness of the adhesive coating layer is 0.5-3μm; H. The adhesive layer comprises a polymer.

8. The electric cell of claim 6, wherein, The adhesive layer comprises polymer particles, which include at least one of a first polymer particle and a second polymer particle.

9. The electric cell of claim 8, wherein, The polymer particles satisfy one or more of the following conditions: A. The average particle size of the first polymer particles is 0.5μm-0.95μm; B. The second polymer particle includes secondary particles formed by the agglomeration of primary particles, wherein the average particle size of the primary particles of the second polymer particle is 0.15μm-0.3μm, and the average particle size of the secondary particles of the second polymer particle is 2μm-18μm.

10. The electric cell of any one of claims 1-5, wherein, The particle size of the single-crystal nickel-cobalt-manganese ternary cathode material is Dv10 of 0.8μm-4μm, Dv50 of 1μm-6μm, and Dv90 of 3μm-10μm. And / or, the BET of the single-crystal nickel-cobalt-manganese ternary cathode material is 0.5m. 2 / g-1.4m 2 / g; And / or, the particle size of the polycrystalline nickel-cobalt-manganese ternary cathode material is 3μm-13μm for Dv10, 6μm-15μm for Dv50, and 12μm-25μm for Dv90; And / or, the BET of the polycrystalline nickel-cobalt-manganese ternary positive electrode material is 0.3m 2 / g-1.0m 2 / g.

11. The battery cell of any one of claims 1-5, wherein, The nickel element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 85%-98% of the total molar content of nickel, cobalt, and manganese metal elements; And / or, the nickel element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 80%-95% of the total molar content of nickel, cobalt, and manganese metal elements; And / or, the cobalt element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 1%-14% of the total molar content of nickel-cobalt-manganese metal elements; And / or, the cobalt element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%-19% of the total molar content of nickel-cobalt-manganese metal elements; And / or, the manganese element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 1%-10% of the total molar content of nickel-cobalt-manganese metal elements; And / or, the manganese element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 1%-10% of the total molar content of nickel-cobalt-manganese metal elements.

12. The electric cell of claim 11, wherein, In the single-crystal nickel-cobalt-manganese ternary cathode material, nickel accounts for 90%-95% of the total molar content of nickel, cobalt, and manganese metal elements; And / or, the nickel element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 87%-92% of the total molar content of nickel-cobalt-manganese metal elements; And / or, the cobalt element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 2%-10% of the total molar content of nickel-cobalt-manganese metal elements; And / or, the cobalt element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 2%-10% of the total molar content of nickel-cobalt-manganese metal elements; And / or, the manganese element in the single-crystal nickel-cobalt-manganese ternary cathode material accounts for 2%-7% of the total molar content of nickel-cobalt-manganese metal elements; And / or, the manganese element in the polycrystalline nickel-cobalt-manganese ternary cathode material accounts for 2%-7% of the total molar content of nickel-cobalt-manganese metal elements.

13. An electrochemical device, characterized by, Includes the battery cell described in any one of claims 1-12.

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