Lithium ion battery

Abstract

The invention relates to the technical field of all-solid-state batteries, in particular to a lithium ion battery which comprises a positive plate, a negative plate and a diaphragm, the diaphragm is located between the positive plate and the negative plate, and the positive plate, the diaphragm and the negative plate are stacked or wound to form a battery cell; the positive plate comprises a positive current collector and a positive active layer positioned on the surface of one side or two sides of the positive current collector, first coatings are also arranged at two ends of the positive active layer along the width and / or length direction of the positive current collector, and the positive active layer and the first coatings are coated on the surface of the positive current collector. The first coating with specific composition is arranged at the edge of the positive active layer, so that the problem of lithium precipitation at the edge of the negative electrode caused by doping the ion conductor material (such as LATP) into the positive electrode is effectively solved, and the safety performance and the cycle performance of the battery are also improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a lithium-ion battery. Background Technology

[0002] With the widespread adoption of electronic devices and the development of portable devices, lithium-ion batteries, thanks to their high energy density and long cycle life, have been widely used in various electronic products. However, lithium plating remains a key factor affecting battery safety and cycle life during battery use. This is especially true when ionic conductor materials (such as LATP) are incorporated into the positive electrode active layer. Because these materials are non-electronic conductors, they partially block the direct electron transport path, making electron transport more reliant on the contact between active material particles and the interface between the current collector and the active material. In this situation, the current density at the electrode edge increases significantly, leading to an increased lithium-ion concentration and making lithium plating at the negative electrode edge more likely, severely impacting the battery's cycle life. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a lithium-ion battery. The lithium-ion battery of this invention, by providing a first coating of a specific composition at the edge of the positive electrode active layer, can effectively improve the lithium deposition problem at the negative electrode edge caused by the mixing of ionic conductor materials into the positive electrode, and can also enhance the battery's safety and cycle performance.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, and the positive electrode, the separator, and the negative electrode are stacked or wound to form a battery cell; the positive electrode includes a positive current collector and a positive active layer located on one or both surfaces of the positive current collector, and a first coating is further provided at both ends of the positive active layer along the width and / or length direction of the positive current collector, wherein the positive active layer and the first coating are both coated on the surface of the positive current collector, and the first coating is adjacent to the edge of the positive active layer; the negative electrode includes a negative current collector and a negative active layer located on one or both surfaces of the negative current collector; The positive electrode active layer contains an ion conductor material; The first coating contains first particles, which include ceramic particles and / or organic particles, and the first particles contain at least one functional group selected from hydroxyl, amino, phosphate monoester, phosphate group, phosphite group or hypophosphite group. The average particle size of the first particle is 300nm~3000nm, and the average particle size of the ion conductor material is 80nm~500nm.

[0005] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: The lithium-ion battery of the present invention, by setting a first coating of a specific composition at the edge of the positive electrode active layer, can regulate the release rate of lithium ions in the edge region, reduce the accumulation of lithium ions in the electrode edge region, and reduce the current density in this region, thereby effectively improving the lithium deposition problem at the negative electrode edge caused by the mixing of ion conductor materials in the positive electrode active layer, and thus improving the cycle life and safety performance of the battery. Furthermore, by simultaneously controlling the average particle size of the first particles in the first coating and the average particle size of the ion conductor material particles in the positive electrode active layer, it is possible not only to effectively regulate the adsorption area of ​​the first particles for lithium ions and the contact area between the active material particles in the positive electrode active layer, thereby further optimizing the improvement of the lithium ion transport speed by the first particles; it also helps to form a stable interface structure, improve the adhesion and stability of the first coating, and effectively prevent electrolyte penetration and reduce electrochemical side reactions, thereby further improving the cycle life and safety of the battery.

[0006] 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

[0007] Figure 1 The diagram shown is a schematic diagram of the structure of a positive electrode sheet provided in an embodiment of the present invention.

[0008] Figure captions: 1. Positive current collector; 2. Positive active layer; 3. First coating layer. Detailed Implementation

[0009] 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.

[0010] 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.

[0011] Terminology Explanation In this invention, the terms "battery", "lithium battery", "lithium-ion battery" and "lithium-ion secondary battery" all have the same meaning and refer to lithium-ion secondary batteries.

[0012] In this invention, the length direction of the positive electrode current collector refers to the direction of the maximum side length of the functional surface of the positive electrode current collector, and the width direction of the positive electrode current collector refers to the direction of the minimum side length of the functional surface of the positive electrode current collector.

[0013] This invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, and the positive electrode, the separator, and the negative electrode are sequentially stacked or wound to form a battery cell. It is understood that a battery cell formed by sequentially stacking the positive electrode, the separator, and the negative electrode is a stacked battery cell, and a battery cell formed by sequentially winding the positive electrode, the separator, and the negative electrode is a wound battery cell.

[0014] In the lithium-ion battery of the present invention, such as Figure 1 As shown, the positive electrode sheet includes a positive current collector 1 and a positive active layer 2 located on one or both sides of the surface of the positive current collector 1. The positive active layer 2 is further provided with a first coating 3 at both ends along the width direction (and / or length direction) of the positive current collector. (Specifically, when the cell is a stacked cell, the first coating can be provided at both ends of the length and width directions of the positive active layer, or it can be provided only at both ends of the length or width directions; when the cell is a wound cell, the first coating is provided at both ends of the width direction of the positive active layer, and the first coating can be omitted at both ends of the length direction of the positive active layer.) The positive active layer 2 and the first coating 3 are both coated on the surface of the positive current collector 1. The first coating 3 can be adjacent to the edge of the positive active layer 2 or there can be a gap between them. It is understood that the surface of the positive electrode current collector is divided into a central region and an edge region. The positive electrode active layer is located in the central region, and the first coating layer is located in the edge region. The central region and the edge region are adjacent to each other and together constitute the entire surface area of ​​the positive electrode current collector. Furthermore, the edge of the positive electrode active layer and the edge of the first coating layer are adjacent to each other or there is a certain gap between them. This design of the position of the first coating layer, placing it at the edge of the positive electrode current collector, helps to improve the lithium plating problem at the edge of the positive electrode active layer. Further, in this invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on one or both sides of the surface of the negative electrode current collector. The positive electrode active layer contains an ion conductor material. The first coating layer contains first particles, which include ceramic particles and / or organic particles. The first particles contain hydroxyl (-OH), amino (-NH3), and phosphate monoester (-OPO3) groups. 2- ), phosphate group (PO4) 3- ), phosphate group (-PO3) 2- ) or hypophosphite group (-PO2) -The first particle has at least one functional group in the form of a molecule containing a known functional group; the average particle size of the first particle is 300 nm to 3000 nm, for example, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2000 nm, 2500 nm, or 3000 nm; the average particle size of the ionic conductor material is 80 nm to 500 nm, for example, 80 nm, 90 nm, 100 nm, 110 nm, or 120 nm. 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 370nm, 380nm, 390nm, 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, 460nm, 470nm, 480nm, 490nm, 500nm.

[0015] When ion-conducting materials (such as lithium titanium aluminum phosphate (LATP)) are incorporated into the positive electrode active layer, the low ion conductivity of the active material itself can be compensated for. By constructing additional lithium-ion transport channels, the ion transport performance of the positive electrode can be optimized, ultimately improving the rate performance and cycle performance of the battery. However, since ion-conducting materials do not possess electronic conductivity, they partially block the direct electron transport path. This causes the electron transport path to rely more on the contact between active material particles and the interface between the current collector and the active material, resulting in a significant increase in current density at the electrode edge. Consequently, the lithium-ion concentration at the electrode edge increases, making it easier to trigger lithium plating at the negative electrode edge, severely impacting the battery's long-term performance. Cycle life; Based on the above problems, the lithium-ion battery of the present invention provides a first coating with a specific composition at the edge of the positive electrode active layer. The first coating contains first particles, and the first particles contain at least one functional group selected from hydroxyl, amino, phosphate monoester, phosphate, phosphite, or hypophosphite groups. These groups can adsorb lithium ions and regulate the release rate of lithium ions in the electrode edge region. Specifically, when the lithium ion concentration in the battery edge region is high, the functional groups adsorb excess lithium ions, reducing the release of free lithium ions and effectively reducing the accumulation of lithium ions in the electrode edge region. This effectively improves the lithium deposition problem at the negative electrode edge caused by the mixing of ion conductor materials into the positive electrode active layer, thereby improving the cycle life and safety performance of the battery. To determine the types of functional groups contained in the first particles, infrared spectroscopy can be used. The specific operation is as follows: Disassemble the finished lithium-ion battery, remove the positive electrode, soak and clean it with DMC, dry it, scrape off a powder sample of the first coating, and perform infrared spectroscopy on the powder sample. By analyzing the special absorption peaks of different functional groups, the types of functional groups contained in the first particles can be determined.

[0016] Furthermore, by simultaneously controlling the average particle size of the first particles in the first coating and the average particle size of the ion-conducting material particles in the positive electrode active layer within a suitable range, this invention can effectively regulate the adsorption area of ​​the first particles capable of adsorbing lithium ions and the contact area between the active material particles in the positive electrode active layer, thereby further improving the lithium ion transport speed. When the average particle size of the first particles in the first coating is too small, the adsorption area of ​​the first particles increases, and the number of functional groups capable of adsorbing lithium ions increases, resulting in excessive lithium ion adsorption in the first coating. This leads to a reduction in the number of lithium ions during the transport process in the negative electrode active layer, blocking lithium ion transport and affecting the rate performance of the battery. When the average particle size of the first particles in the first coating is too large, the adsorption area of ​​the first particles decreases, and the number of functional groups capable of adsorbing lithium ions decreases. The first particle size in the first coating layer is insufficient to adsorb excess lithium ions, resulting in a high lithium ion concentration at the electrode edge and causing lithium plating at the negative electrode edge. Therefore, the average particle size of the first particle needs to be controlled within a suitable range. Conversely, if the average particle size of the ion conductor material is too small, a good contact interface cannot be formed between the positive electrode active material particles, affecting the lithium ion transport speed and reducing the battery's rate charge / discharge performance. If the average particle size of the ion conductor material is too large, the contact area between the active material particles in the positive electrode active layer will be too small, and the excessively large particle size will also limit the lithium ion transport speed within the particles. Therefore, the average particle size of the ion conductor material in the positive electrode active layer needs to be set within a suitable range. Furthermore, controlling the average particle size of the first particle in the first coating layer and the average particle size of the ion conductor material in the positive electrode active layer within suitable ranges helps to form a stable interface structure, improves the adhesion and stability of the first coating, and effectively prevents electrolyte penetration, reduces electrochemical side reactions, and further improves the battery's cycle life and safety.

[0017] In this invention, the average particle size of the first particle and the ion conductor material can be measured by SEM. The specific measurement method is as follows: Disassemble the finished lithium-ion battery, take out the positive electrode sheet, soak and clean it with DMC and then dry it. Use SEM to observe the functional surface of the positive electrode sheet, take SEM images at an appropriate magnification, and then select 30 first particles and ion conductor material particles in the images respectively, measure their particle diameters, and take the average value, which is the average particle size of the first particle and the ion conductor material.

[0018] In one specific embodiment, the ratio of the average particle size of the first particle to that of the ionic conductor material is (0.8~15):1, for example, 0.8:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1. When the ratio of the average particle size of the first particle in the first coating to the average particle size of the ion conductor material in the positive electrode active layer is less than 0.8:1, it indicates that the average particle size of the first particle is too small and the average particle size of the ion conductor material is too large. The first particle that is too small is prone to forming a dense packing, which prevents the electrolyte from penetrating effectively, thus hindering lithium-ion transport, increasing polarization, and affecting the rate performance of the battery. On the other hand, the ion conductor material with an excessively large particle size will cause the ion diffusion path in the positive electrode active layer to become longer, which will restrict the lithium-ion transport kinetics and form a high-resistance region at the interface between the edge region and the ceramic layer, increasing the charge transport impedance and polarization, which will also affect the rate performance of the battery. When the average particle size ratio of the first particle to the ion conductor material in the first coating is greater than 15:1, it indicates that the average particle size of the first particle is too large and the average particle size of the ion conductor material is too small. The excessively large first particle reduces the contact area between particles, directly leading to increased porosity between the particles in the first coating, making it easier for the electrolyte to penetrate to the edge of the electrode. On the other hand, the excessively small particle size of the ion conductor material leads to an increase in the number of particles per unit volume. During cycling, the small volume expansion / contraction of each particle will have a cumulative effect, damaging the structural integrity of the positive electrode active layer, thus causing the positive electrode active layer to crack or fall off. After the positive electrode active layer fails, the edge of the electrode is exposed to the electrolyte, resulting in electrochemical side reactions, which seriously affect the cycle life of the battery.

[0019] In one specific embodiment, the average particle size of the first particle is 500nm~1500nm.

[0020] In one specific embodiment, the average particle size of the ion conductor material is 100 nm to 360 nm.

[0021] In one specific embodiment, the ratio of the average particle size of the first particle to that of the ion conductor material is (1.5~8):1.

[0022] In one specific embodiment, the ion conductor material includes at least one of lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), and lithium lanthanum titanium oxide (LLTO).

[0023] In one specific embodiment, the ceramic particles include at least one of boehmite, alumina, magnesium oxide, zirconium oxide, aluminum nitride, and silicon oxide. In a preferred embodiment, the first particles include at least two of the ceramic particles selected from boehmite, alumina, magnesium oxide, zirconium oxide, aluminum nitride, and silicon oxide. When the first coating includes two or more ceramic particles, a composite ceramic material is formed, which has a superior adsorption capacity for lithium ions and can effectively improve its mechanical properties. This helps to form a stable interface structure, improves the adhesion and stability of the first coating, and can further effectively prevent electrolyte penetration and reduce electrochemical side reactions, thereby further improving the cycle life and safety of the battery.

[0024] In one specific embodiment, the organic particles include at least one of 1,3,5-triazine-2,4,6-triamine, melamine cyanurate, and melamine trithiocyanate.

[0025] In one specific embodiment, the surface of the ionic conductor material particles is provided with a carbon coating layer, the thickness of which is 1.5 nm to 40 nm, for example, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, or 40 nm. In a preferred embodiment, the thickness of the carbon coating layer is 3 nm to 20 nm. Ion conductor materials inherently have poor electronic conductivity. The core function of the carbon coating layer on the particle surface is to construct a continuous electron transport channel and isolate direct contact with the electrolyte / positive electrode active material to reduce side reactions. Setting the thickness of the carbon coating layer within the range of 1.5nm-40nm is crucial for balancing electron conduction and lithium-ion transport: 1.5nm is the minimum effective thickness; below this value, the carbon coating layer is prone to porosity or discontinuity, failing to completely cover the surface of the ion conductor material. This not only fails to stably improve electronic conductivity but also exposes part of the ion conductor, allowing it to react with the electrolyte. 40nm is the upper limit threshold; since the carbon coating layer is an ion insulator, exceeding this thickness significantly increases the transport path and energy barrier of lithium ions between the ion conductor and the positive electrode active material / electrolyte, leading to increased interfacial impedance and affecting battery rate performance. Therefore, carbon coating treatment on the particle surface of ion conductor materials can effectively improve the interfacial contact between them and the positive electrode active material, reduce interfacial impedance, and improve the high-rate performance of the battery. Furthermore, if the carbon coating thickness exceeds 40 nm, in addition to hindering lithium-ion transport, the slight volume changes of the ion conductor particles during cycling can lead to a decrease in the bonding force between the thicker carbon layer and the particle interface, making it prone to cracking and detachment. The detached carbon powder not only loses its electron conduction and protective functions but may also create micro-short circuit hazards inside the battery. At the same time, the exposed ion conductors exacerbate side reactions, ultimately leading to a significant reduction in battery cycle life. In this invention, the carbon coating thickness can be measured using TEM. The specific measurement method is as follows: Disassemble the finished lithium-ion battery, remove the positive electrode sheet, soak and clean it with DMC, and dry it. Use TEM to observe the positive electrode sheet and take TEM images at an appropriate magnification. Then, select 30 ion conductor material particles in the images and measure the thickness of the carbon coating on the particle surface (to avoid uneven thickness at different locations, the thickness can be measured at 3-5 points for each ion conductor material particle and the average value is taken). Then, take the average value of the 30 test results, which is the carbon coating thickness on the surface of the ion conductor material particle.

[0026] Further, in one specific embodiment, the ratio of the average particle size of the ion conductor material to the thickness of the carbon coating layer is (10~200):1, for example, 10:1, 30:1, 50:1, 70:1, 90:1, 110:1, 130:1, 150:1, 170:1, 190:1, 200:1. In a preferred embodiment, the ratio of the average particle size of the ion conductor material to the thickness of the carbon coating layer is (20~100):1. When the ratio of the average particle size of the ion conductor material to the surface carbon coating thickness is less than 10:1, the small-particle-size ion conductor material is more prone to structural instability, while the thick carbon coating layer may hinder lithium-ion transport. The combined effect of these two factors may lead to increased interfacial impedance and decreased cycle performance. The thick carbon coating layer may also form a "bottleneck effect" on the surface of the ion conductor material, hindering the rapid transport of lithium ions and affecting the rate performance of the battery. When the ratio of the average particle size of the ionic conductor material to the thickness of the surface carbon coating is greater than 200:1, the thin carbon coating layer cannot effectively improve electronic conductivity. At the same time, the large particle size of the ionic conductor material will lead to a longer lithium-ion diffusion path, which may reduce the rate performance of the battery. In addition, the large particle size of the ionic conductor material will lead to a longer lithium-ion diffusion path in the electrolyte, which may cause increased polarization and further affect the rate performance and energy density of the battery.

[0027] In one specific embodiment, the positive electrode, the separator, and the negative electrode are sequentially stacked to form the battery cell. The stacked structure design, with alternating positive and negative electrode layers, forms an electrode assembly; compared to a wound structure, the stacked structure offers higher energy density and better heat dissipation. In the stacked structure, the positive and negative tabs are located on opposite sides of the battery cell, forming a lithium-ion circulation pathway and preventing lithium-ion accumulation inside the battery.

[0028] In one specific embodiment, the negative electrode current collector includes a first surface near the center of the cell and a second surface away from the center of the cell along its thickness direction. The first surface of the negative electrode current collector located in the outermost layer / outermost ring of the cell is provided with the negative electrode active layer, while the second surface is not provided with the negative electrode active layer. The outermost negative electrode is designed with single-sided paste coating to ensure that lithium ions migrate back to the positive electrode sheet and avoid the formation of dead lithium on the negative electrode sheet. On the outermost negative electrode sheet of the cell, the side facing the positive electrode receives lithium ions from the positive electrode during charging; while the outermost negative electrode sheet, which is not facing the positive electrode, generally has difficulty receiving lithium ions from the positive electrode. In a fully charged lithium-ion battery, due to the significant concentration difference between the two sides of the outermost negative electrode sheet, lithium ions easily migrate from the high concentration area facing the positive electrode to the low concentration area on the side not facing the positive electrode during resting, forming ineffective lithium ions, causing capacity loss and seriously affecting the battery's capacity retention rate.

[0029] In one specific embodiment, the lithium-ion battery further includes a tab structure comprising multiple positive tabs and multiple negative tabs. The multiple positive tabs are integrally connected to the positive current collector, and the multiple negative tabs are integrally connected to the negative current collector. The multiple positive and negative tabs give the cell a multi-tab structure, improving the battery's high-rate charge and discharge capability.

[0030] In a preferred embodiment, all of the plurality of positive tabs and all of the plurality of negative tabs are led out from opposite ends of the battery cell. When all the tab structures of the positive and negative electrodes are located on both sides of the battery cell, it helps lithium ions to form a circulation path, avoids lithium ion accumulation and lithium plating near the tab side, and further solves the lithium plating problem of the negative electrode.

[0031] In one specific embodiment, the lithium-ion battery further includes a casing and a cover, the casing and the cover together forming an inner cavity, and the battery cell is located in the inner cavity.

[0032] In one specific embodiment, the lithium-ion battery further includes a first hard tab and a second hard tab, the plurality of positive tabs are connected to the first hard tab, the plurality of negative tabs are connected to the second hard tab, the first hard tab and the second hard tab are led out from opposite ends of the battery cell, and the lithium-ion battery includes a packaging film, the packaging film being an aluminum-plastic film.

[0033] In one specific embodiment, a transition region is formed between the positive electrode active layer and the first coating layer. The dimension of the transition region along the width direction of the positive electrode current collector is 0.2mm to 4mm, for example, 0.2mm, 0.5mm, 0.7mm, 1mm, 1.2mm, 1.4mm, 1.7mm, 2mm, 2.2mm, 2.5mm, 2.7mm, 3mm, 3.2mm, 3.5mm, 3.7mm, or 4mm. In a preferred embodiment, the dimension of the transition region along the width direction of the positive electrode current collector is 0.5mm to 3mm. When the positive electrode active layer slurry and the first coating layer slurry are simultaneously coated on the surface of the positive electrode current collector, a transition region is formed between the positive electrode active layer and the first coating layer, and the width of the transition region is 0.2mm to 4mm.

[0034] In the transition region, the content of the positive electrode active material gradually decreases from the side closer to the positive electrode active layer to the side closer to the edge ceramic layer, while the content of the ceramic material gradually increases, forming a gradient transition structure. This structure can reduce the release rate of lithium ions at the edge of the positive electrode, avoiding excessive accumulation of lithium ions in the battery edge region and causing lithium plating. If the width of the transition region is too narrow (e.g., less than 0.2 mm), the gradient is insufficient, and lithium ion transport at the interface is prone to abrupt changes, which will still lead to accumulation and cause lithium plating. Moreover, the first coating will not be able to fully exert its protective function, exacerbating side reactions. If it is too wide (e.g., more than 4 mm), it will encroach on the space of the positive electrode active layer, reduce the battery energy density, and the excessive proportion of ceramic material will hinder electron conduction, increase polarization, and deteriorate cycle and rate performance. Controlling it within 0.2-4 mm (preferably 0.5-3 mm) can balance ion regulation, active layer utilization, and electron conduction, ensuring battery performance.

[0035] In one specific embodiment, the dimension of the first coating along the width direction of the positive current collector is 0.5mm to 5mm, for example, 0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm, 4.0mm, 4.5mm, or 5.0mm. In a preferred embodiment, the dimension of the first coating along the width direction of the positive current collector is 1mm to 4mm. The dimension of the first coating along the width direction of the positive current collector, i.e., the width of the first coating, refers to the width of the first coating on one side of the positive electrode sheet, including the width of the transition region. Similarly, the dimension of the positive active layer along the width direction of the positive current collector, i.e., the width of the positive active layer, also includes the width of the transition region.

[0036] It should be noted that, in this invention, the method for measuring the dimensions of the transition region and the first coating along the width direction of the positive electrode current collector is as follows: The finished lithium-ion battery is disassembled, the positive electrode sheet is taken out, and after being soaked and cleaned by DMC and dried, the surface of the positive electrode sheet is observed using SEM. SEM images are taken at an appropriate magnification. Using graphics software, the areas of the irregular transition region coating, the first coating, or the positive electrode active layer along a certain length (along the length direction of the positive electrode current collector) are summed. The summed area is then divided by the length to obtain the width of each coating. Then, positive electrode sheets in 10 regions are taken respectively, and their coating widths are measured. The average value is the dimension of the transition region and the first coating along the width direction of the positive electrode current collector.

[0037] Further, in one specific embodiment, the ratio of the size of the transition region to the size of the first coating along the width direction of the positive electrode current collector is (0.1~0.9):1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, or 0.9:1. In a preferred embodiment, the ratio of the size of the transition region to the size of the first coating along the width direction of the positive electrode current collector is (0.2~0.8):1. When the width ratio of the transition region to the first coating is less than 0.1:1, an excessively large first coating width will hinder the transport of electrons in the positive electrode, exacerbating polarization during charging and discharging, thus affecting the cycle performance of the lithium-ion battery. This results in the battery capacity decreasing faster after multiple charge-discharge cycles. At the same time, an excessively large first coating width will reduce the utilization rate of the battery's internal space, affecting the capacity and energy density of the lithium-ion battery. An excessively small width of the mixed transition region cannot fully utilize the first coating to block the structural changes and side reactions of the positive electrode active material during charging and discharging, leading to rapid performance degradation of the positive electrode active material and shortening the cycle life of the lithium-ion battery. When the width ratio of the mixed transition region to the width of the first coating is greater than 0.9:1, the excessively narrow width of the first coating cannot fully cover the positive electrode active material coating. This will cause changes in the contact environment between some positive electrode active materials and the electrolyte during the charging and discharging process of the lithium-ion battery, affecting the insertion and extraction of lithium ions, and thus reducing the capacity, energy density, and cycle life of the lithium-ion battery. Generally speaking, the first coating itself is non-conductive. After mixing with the coating, it will hinder the electron transport path in the electrode. An excessively large width of the first coating has a more obvious hindering effect, affecting the charging and discharging efficiency and rate performance of the lithium-ion battery.

[0038] In one specific embodiment, the Mohs hardness of the first coating is 3 to 7, for example, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, or 7. In a preferred embodiment, the Mohs hardness of the first coating is 5 to 6.5. The method for determining the Mohs hardness of the first coating is as follows: Disassemble the finished lithium-ion battery, remove the positive electrode sheet, soak and clean it with DMC, and then dry it. Select at least three different locations on the surface of the first coating sample, smooth them with sandpaper, remove the surface oxide layer or contaminant layer, press a standard Mohs hardness pen on the sample surface, and slowly scratch until a slight scratch appears but does not penetrate. Record the hardness of the Mohs hardness pen used at this time, and take the average value of the hardness at different locations, which is the Mohs hardness of the first coating.

[0039] In one specific embodiment, the dimension of the first coating along the thickness direction of the positive electrode current collector is 5μm to 50μm, for example, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm. In a preferred embodiment, the dimension of the first coating along the thickness direction of the positive electrode current collector is 8μm to 30μm. The dimension of the first coating along the thickness direction of the positive electrode current collector can be obtained from a cross-sectional SEM image of the positive electrode sheet. The finished lithium-ion battery is disassembled, the positive electrode sheet is removed, soaked and cleaned with DMC, and then dried. The cross-sectional image of the positive electrode sheet is observed using SEM, and the thickness of the first coating at different positions is measured. The average value is taken as the dimension of the first coating along the thickness direction of the positive electrode current collector.

[0040] In one specific embodiment, the ratio of the Mohs hardness of the first coating to its dimension along the thickness direction of the positive electrode current collector is (0.1~1):1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1. In a preferred embodiment, the ratio of the Mohs hardness of the first coating to its dimension along the thickness direction of the positive electrode current collector is (0.2~0.8):1.

[0041] The first coating has a Mohs hardness of 4-7 and a thickness of 5-50 μm. The ratio of Mohs hardness to thickness is (0.1-1):1, which helps prevent excessively hard ceramic particles from piercing the separator. When the ratio of Mohs hardness to thickness is less than 0.1:1, the excessively thick first coating reduces its flexibility, making it more prone to cracking under mechanical stress. Conversely, low material hardness means poor compressive and shear resistance, making it more susceptible to deformation or fracture under external force, further crack propagation, and increased risk of micro-short circuits in the battery. When the ratio of Mohs hardness to thickness is greater than 1:1, insufficient coating thickness results in weak adhesion, making it prone to detachment during manufacturing or use. Excessive hardness increases material brittleness, making it more susceptible to cracking or peeling under external force or thermal stress. Therefore, a thin and hard ceramic layer is more prone to crack propagation and coating detachment, leaving the electrode edges unprotected. Unprotected electrode edges undergo electrochemical side reactions during cycling, leading to accelerated battery capacity decay.

[0042] In one specific embodiment, the elongation of the separator is 50% to 300%, for example, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 210%, 220%, 230%, 240%, 250%, 260%, 270%, 280%, 290%, or 300%. In a preferred embodiment, the elongation of the separator is 80% to 280%. The method for determining the elongation of the separator is as follows: a sample is prepared from the separator disassembled from a lithium-ion battery, and the sample is placed on an electronic universal testing machine for stretching until it breaks. The elongation of the separator can be calculated based on the fracture length and the initial length.

[0043] In one specific embodiment, the thickness of the diaphragm is 5 μm to 25 μm, for example, 5 μm, 6 μm, 7 μm, 10 μm, 13 μm, 16 μm, 19 μm, 22 μm, or 25 μm. In a preferred embodiment, the thickness of the diaphragm is 9 μm to 20 μm. The thickness of the diaphragm can be obtained by obtaining its cross-sectional CP diagram.

[0044] In one specific embodiment, the ratio of the elongation of the diaphragm to the thickness of the diaphragm is (8~40):1, for example, 8:1, 12:1, 16:1, 20:1, 24:1, 28:1, 32:1, 36:1, or 40:1. In a preferred embodiment, the ratio of the elongation of the diaphragm to the thickness of the diaphragm is (12~28):1.

[0045] The separator has an elongation of 50% to 300% and a thickness of 5 μm to 25 μm. The ratio of elongation to thickness is (8 to 40):1. This ensures that the separator can slow down heat conduction and prevent excessive heat diffusion during battery thermal runaway or internal short circuits. It also helps the separator adapt to volume changes in the positive and negative electrode materials during battery charging and discharging, reducing poor contact between the electrodes and the separator. When the ratio of elongation to thickness is less than 8:1, the excessively low elongation prevents the separator from adapting to volume changes in the positive and negative electrode materials during charging and discharging, leading to poor contact between the electrodes and the separator. Conversely, an excessively thick separator increases internal resistance, making the battery more prone to increased internal resistance and enhanced polarization during cycling, thus shortening the battery's cycle life. When the ratio of the elongation to the thickness of the separator is greater than 40:1, the separator with excessively high elongation is prone to overstretching or rupture under mechanical stress, which significantly increases the risk of short circuit. On the other hand, the separator with too little thickness melts too quickly during battery thermal runaway, and cannot close the pores in time, resulting in excessively rapid heat diffusion and inability to effectively limit heat conduction, which seriously deteriorates the safety of the battery.

[0046] In one specific embodiment, the negative electrode active layer contains a negative electrode active material, which includes a carbon-based active material. The average particle size of the carbon-based active material is 800 nm to 16000 nm, for example, 800 nm, 1800 nm, 2800 nm, 3800 nm, 4800 nm, 5800 nm, 6800 nm, 7800 nm, 8800 nm, 9800 nm, 10800 nm, 11800 nm, 12800 nm, 13800 nm, 14800 nm, 15800 nm, or 16000 nm. In a preferred embodiment, the average particle size of the carbon-based active material is 1100 nm to 10000 nm. The average particle size of carbon-based active materials can be measured by referring to the measurement method of the average particle size of ion conductor materials. The specific measurement method is as follows: Disassemble the finished lithium-ion battery, take out the negative electrode sheet, soak and clean it with DMC and then dry it. Use SEM to observe the functional surface of the negative electrode sheet. Take SEM images at an appropriate magnification. Then select 30 carbon-based active material particles in the images and measure their particle diameter. Take the average value, which is the average particle size of the carbon-based active material.

[0047] In one specific embodiment, the ratio of the average particle size of the ion conductor material to the average particle size of the carbon-based active material is (0.01~0.6):1, for example, 0.01:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or 0.6:1. In a preferred embodiment, the ratio of the average particle size of the ion conductor material to the average particle size of the carbon-based active material is (0.05~0.3):1.

[0048] In one specific embodiment, the carbon-based active material includes at least one of artificial graphite, natural graphite, soft carbon, and hard carbon. In another specific embodiment, the negative electrode active material may further include a silicon-based active material, which includes at least one of silicon oxide, silicon carbon, silicon alloy, elemental silicon, and silicon sulfur.

[0049] The negative electrode sheet can use carbon-based active materials such as artificial graphite, natural graphite, graphite mixed with soft carbon, and graphite mixed with hard carbon as the negative electrode active material, or it can use a negative electrode active material that includes both carbon-based and silicon-based active materials. The choice of negative electrode active material is not limited in this invention. In one specific embodiment, the negative electrode active material is a small-particle-size carbon-based active material with an average particle size of 800 nm to 16000 nm. By changing the average particle size of the carbon-based active material to have a smaller particle size, the rate performance of the battery can be improved.

[0050] Furthermore, by adjusting the ratio of the average particle size of the ion conductor material to the negative electrode active material to achieve the optimal ratio, the lithium-ion transport rate can be matched with the lithium insertion rate of the carbon-based active material in the negative electrode, thereby further improving the battery's rate performance and cycle life. When the average particle size ratio of the ion conductor material to the carbon-based active material is less than 0.01:1, excessively small-sized ion conductor materials may lead to uneven distribution in the positive electrode, forming local high-concentration regions, affecting the uniformity and electrochemical activity of the positive electrode active material. At the same time, excessively large-sized carbon-based active material particles will cause uneven electron transport paths, affecting the lithium-ion insertion / extraction efficiency in the negative electrode, increasing interfacial impedance, leading to uneven charge transport paths, and affecting the battery's rate performance. When the average particle size ratio of the ion conductor material to the negative electrode carbon-based active material is greater than 0.6:1, the excessively large particle size of the ion conductor material forms a local ion transport bottleneck, affecting the diffusion rate of lithium ions at the positive electrode / electrolyte interface. This causes local charge concentration during charging and discharging, leading to local overcharging / over-discharging and affecting battery life. Conversely, the excessively small particle size of the carbon-based active material results in a large contact area with the electrolyte, easily triggering side reactions and further affecting the battery's cycle performance. This invention, by further controlling the ratio between the average particle sizes of the positive and negative electrode active materials, can further improve the battery's rate performance and cycle life.

[0051] In one specific embodiment, the negative electrode active layer further includes a negative electrode conductive agent and a negative electrode binder.

[0052] In one specific embodiment, the negative electrode conductive agent includes at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, graphene, and carbon nanotubes.

[0053] In one specific embodiment, the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, sodium polyacrylate, and lithium polyacrylate.

[0054] In one specific embodiment, the negative electrode active material layer further includes a negative electrode dispersant, which includes at least one of sodium carboxymethyl cellulose (CMC-Na) and lithium carboxymethyl cellulose (CMC-Li).

[0055] In one specific embodiment, the positive electrode active layer further comprises a positive electrode active material, including LiMn2O4 and Li4Ti5O4. 12 Li3V2(PO4)3, LiFe 1-x W x PO4, LiNi x Mny Co 1-x-y O2 and LiNi x Co y Al 1-x-y At least one of O2, wherein 0≤x≤1, 0≤y≤1, x+y≤1, and W is selected from at least one of Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, V, and Ti.

[0056] In one specific embodiment, the positive electrode active material layer further includes a positive electrode conductive agent and a positive electrode binder.

[0057] In one specific embodiment, the positive electrode conductive agent includes at least one of carbon black, acetylene black, graphene, carbon nanotubes, Ketjen black, and carbon fiber.

[0058] In one specific embodiment, the positive electrode binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, and polyurethane.

[0059] In this invention, the lithium-ion battery further includes an electrolyte, which is a conventional electrolyte in the art. For example, the electrolyte includes a solvent, a solute, and additives. Specifically, the electrolyte may be a non-aqueous electrolyte. The solvent may include organic solvents, specifically carbonate solvents, such as one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC), and propyl propionate (PP). The additives may include one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and 1,3-propanesulfonyl lactone (PS). The solute may include lithium salts, such as lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0060] In this invention, conventional diaphragms in the art can be used. For example, the diaphragm may include one or more of the following: polypropylene (PP) diaphragm, polyethylene (PE) diaphragm, polypropylene / polyethylene (PP / PE) bilayer composite membrane, polyimide electrospun diaphragm (PI), polypropylene / polyethylene / polypropylene (PP / PE / PP) trilayer composite membrane, or cellulose nonwoven fabric diaphragm.

[0061] 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.

[0062] Example 1 (1) Preparation of positive electrode P1: Preparation of positive electrode active material slurry: Lithium aluminum titanium phosphate (LATP) (with a carbon coating layer on the particle surface), positive electrode active material NCM (LiNi) 0.33 Mn 0.33 Co 0.33 O2), positive electrode binder PVDF, and positive electrode conductive agent conductive carbon black are mixed by stirring to form a homogeneous and stable mixture. This mixture contains 1 wt% LATP, 92 wt% positive electrode active material NCM, 2 wt% positive electrode binder PVDF, and 5 wt% positive electrode conductive agent conductive carbon black as the solid components. Using NMP as a solvent, a positive electrode active material slurry is prepared, with a solid content of 63 wt%. Preparation of the first coating slurry: Boehmite particles containing hydroxyl and phosphate groups and alumina particles (mass ratio 1:1), binder polyacrylate, and NMP solvent were mixed to obtain a first coating slurry with a solid content of 39 wt%. Specifically, based on the total mass of the first coating slurry, the mass content of the boehmite ceramic particles containing hydroxyl and phosphate groups and the alumina particles was 95 wt%, and the mass content of the binder was 5 wt%.

[0063] The positive electrode active material slurry is uniformly coated on both sides of the aluminum foil to form a positive electrode active layer. At the same time, the first coating slurry is coated on the positive electrode active layer on the surface of the aluminum foil along both ends of the positive electrode current collector aluminum foil width direction. After drying, compaction by a roller press and cutting, the positive electrode sheet of this embodiment 1 is obtained, denoted as P1.

[0064] (2) Preparation of negative electrode N1: The negative electrode active material graphite, negative electrode binder SBR, and negative electrode conductive agent are mixed and stirred to form a homogeneous and stable mixture. This mixture contains 95 wt% graphite, 3 wt% SBR, and 2 wt% negative electrode conductive agent as solid components. Water is used as a solvent to prepare a negative electrode active material slurry with a solid content of 46 wt%. This slurry is uniformly coated on both sides of a copper foil, dried, and then compacted using a roller press to obtain the negative electrode sheet, denoted as N1.

[0065] (3) Assembly of battery C1: The positive electrode P1, negative electrode N1, and separator (polypropylene / polyethylene (PP / PE) double-layer composite film) are sequentially stacked to form a bare battery cell. After hot pressing, multiple positive tabs are set on one end face of the positive current collector aluminum foil of the positive electrode P1, and these tabs are welded to aluminum tabs. Similarly, multiple negative tabs are set on one end face of the negative current collector copper foil of the negative electrode N1, and these tabs are welded to nickel-plated copper tabs. The aluminum tabs and nickel-plated copper tabs are led out from opposite ends of the bare battery cell. After perforation in the aluminum-plastic film, the battery is encapsulated and vacuum-baked at 95℃ for 24 hours. The electrolyte used is a 1M lithium hexafluorophosphate electrolyte, with a solvent of ethylene carbonate / dimethyl carbonate / 1,2-propylene glycol carbonate in a 1:1:1 (volume ratio). After electrolyte injection, the battery undergoes formation, secondary sealing, sorting, and OCV testing to obtain a soft-pack battery, designated C1.

[0066] Among them, the average particle size of the first particle in the first coating of battery C1 was measured to be 1000 nm, the average particle size of LATP in the positive electrode active layer was 280 nm, and the ratio of the average particle size of the first particle to that of LATP was 3.57:1; the thickness of the carbon coating layer on the surface of the ion conductor material particles in the positive electrode active layer of battery C1 was measured to be 12 nm, and the ratio of the average particle size of the ion conductor material to the thickness of the carbon coating layer was 23.33:1; the dimension of the transition region formed between the positive electrode active layer and the first coating in the positive electrode sheet of battery C1 along the width direction of the positive electrode current collector was measured to be 1 mm, and the first coating... The dimension along the width direction of the positive electrode current collector is 3 mm, and the ratio of the two dimensions is 0.33:1; the Mohs hardness of the first coating in the positive electrode sheet of battery C1 is measured to be 6.1, and the dimension of the first coating along the thickness direction of the positive electrode current collector is 19 μm, with a ratio of 0.32:1; the elongation of the separator in battery C1 is measured to be 230%, and the thickness of the separator is 11 mm, with a ratio of 20.91:1; the average particle size of graphite in the negative electrode active layer of battery C is measured to be 5500 nm, and the ratio of the average particle size of LATP in the positive electrode active layer to the average particle size of graphite is 0.051:1.

[0067] Example 2 group This set of embodiments refers to the battery preparation method of Embodiment 1, except that the average particle size of the first particles in the first coating is changed, specifically: In Example 2-1, the average particle size of the first particle in the first coating of battery C1 was measured to be 300 nm, the ratio of the average particle size of the first particle to the average particle size of the ion conductor material became 1.07:1, and the Mohs hardness of the first coating became 6.9. In Example 2-2, the average particle size of the first particle in the first coating of battery C1 was measured to be 3000 nm, the ratio of the average particle size of the first particle to the average particle size of the ion conductor material became 10.71:1, and the Mohs hardness of the first coating became 3.1. In Examples 2-3, the average particle size of the first particle in the first coating of battery C1 was measured to be 500 nm, the ratio of the average particle size of the first particle to the average particle size of the ion conductor material became 1.79:1, and the Mohs hardness of the first coating became 6.4. In Examples 2-4, the average particle size of the first particle in the first coating of battery C1 was measured to be 1500 nm, the ratio of the average particle size of the first particle to that of the ion conductor material became 5.36:1, and the Mohs hardness of the first coating became 5.

[0068] See Table 1 for details.

[0069] Example 3 Group The embodiments in this group refer to the battery preparation method of Embodiment 1, except that the average particle size of the ion conductor material is changed. At this time, the ratio of the average particle size of the first particle to the average particle size of the ion conductor material, the thickness of the carbon coating layer, the ratio of the average particle size of the ion conductor material to the thickness of the carbon coating layer, the Mohs hardness of the first coating, and the ratio of the average particle size of the ion conductor material to the average particle size of the carbon-based active material will also change accordingly, as detailed in Table 1.

[0070] Example 4 group This set of embodiments refers to the battery preparation method of Embodiment 1, except that the average particle size of the first particle and the average particle size of the ion conductor material are changed at the same time, so that the ratio of the average particle size of the first particle to the average particle size of the ion conductor material changes. At this time, the thickness of the carbon coating layer, the ratio of the average particle size of the ion conductor material to the thickness of the carbon coating layer, the Mohs hardness of the first coating, and the ratio of the average particle size of the ion conductor material to the average particle size of the carbon-based active material will also change accordingly, as detailed in Table 1.

[0071] Comparative Example 1 The comparative examples in this group refer to the battery preparation method of Example 1, except that the average particle size of the first particle and the average particle size of the ion conductor material are changed, so that the ratio of the average particle size of the first particle to the average particle size of the ion conductor material changes. At this time, the thickness of the carbon coating layer, the ratio of the average particle size of the ion conductor material to the thickness of the carbon coating layer, the Mohs hardness of the first coating, and the ratio of the average particle size of the ion conductor material to the average particle size of the carbon-based active material will also change accordingly, as detailed in Table 1.

[0072] Table 1 In Table 1, it should be noted that the thickness of the carbon coating layer in Examples 4-3 is 0, that is, there is no carbon coating layer. Therefore, it is impossible to calculate the ratio of the average particle size of the ion conductor material to the thickness of the carbon coating layer, so it is represented by " / ".

[0073] Comparative Example 2 This comparative example refers to the battery preparation method of Example 1, except that the positive electrode active layer is not coated with the first coating slurry at both ends of the positive electrode current collector aluminum foil width direction, and no first coating is provided.

[0074] Comparative Example 3 This comparative example refers to the battery preparation method of Example 1, except that the first particles used in the first coating slurry are boehmite particles and alumina particles that do not contain functional groups, while the other parameters of the first particles remain unchanged.

[0075] Example 5 group This comparative example refers to the battery preparation method of Example 1, except that the coating position and coating size of the first coating slurry are changed, thereby changing the size of the transition region along the width direction of the positive electrode current collector and the size of the first coating along the width direction of the positive electrode current collector. Specifically: In Example 5-1, the dimension of the transition region along the width direction of the positive electrode current collector is 0.9 mm, and the dimension of the first coating along the width direction of the positive electrode current collector is 1 mm. The ratio of the dimensions of the transition region to the first coating along the width direction of the positive electrode current collector is 0.9:1. At this time, the Mohs hardness of the first coating is measured to be 5.9, and the ratio of the Mohs hardness of the first coating to the dimension of the first coating along the thickness direction of the positive electrode current collector is calculated to be 0.31:1. In Example 5-2, the dimension of the transition region along the width direction of the positive electrode current collector is 1 mm, and the dimension of the first coating along the width direction of the positive electrode current collector is 5 mm. The ratio of the dimensions of the transition region to the first coating along the width direction of the positive electrode current collector is 0.2:1. At this time, the Mohs hardness of the first coating is measured to be 6.1, and the ratio of the Mohs hardness of the first coating to the dimension of the first coating along the thickness direction of the positive electrode current collector is calculated to be 0.32:1. In Example 5-3, the dimension of the transition region along the width direction of the positive electrode current collector is 3.2 mm, and the dimension of the first coating along the width direction of the positive electrode current collector is 4 mm. The ratio of the dimensions of the transition region to the first coating along the width direction of the positive electrode current collector is 0.8:1. At this time, the Mohs hardness of the first coating is measured to be 5.9, and the ratio of the Mohs hardness of the first coating to the dimension of the first coating along the thickness direction of the positive electrode current collector is calculated to be 0.31:1. In Example 5-4, the dimension of the transition region along the width direction of the positive electrode current collector is 0.5 mm, and the dimension of the first coating along the width direction of the positive electrode current collector is 5 mm. The ratio of the dimensions of the transition region to the first coating along the width direction of the positive electrode current collector is 0.1:1. At this time, the Mohs hardness of the first coating is measured to be 6, and the ratio of the Mohs hardness of the first coating to the dimension of the first coating along the thickness direction of the positive electrode current collector is calculated to be 0.32:1. In Example 5-5, the dimension of the transition region along the width direction of the positive electrode current collector is 0.93 mm, and the dimension of the first coating along the width direction of the positive electrode current collector is 1 mm. The ratio of the dimensions of the transition region to the first coating along the width direction of the positive electrode current collector is 0.93:1. At this time, the Mohs hardness of the first coating is measured to be 5.9, and the ratio of the Mohs hardness of the first coating to the dimension of the first coating along the thickness direction of the positive electrode current collector is calculated to be 0.31:1. In Examples 5-6, the dimension of the transition region along the width direction of the positive current collector is 0.4 mm, and the dimension of the first coating along the width direction of the positive current collector is 5 mm. The ratio of the dimensions of the transition region to the first coating along the width direction of the positive current collector is 0.08:1. At this time, the Mohs hardness of the first coating is measured to be 6, and the ratio of the Mohs hardness of the first coating to the dimension of the first coating along the thickness direction of the positive current collector is calculated to be 0.32:1.

[0076] Example 6 This embodiment refers to the battery preparation method of Example 1, except that the composition of the first particle is changed: the boehmite particles and alumina particles containing hydroxyl and phosphate groups are replaced with 1,3,5-triazine-2,4,6-triamine organic particles containing amino groups.

[0077] Example 7 This embodiment refers to the battery preparation method of Example 1, except that the composition of the first particle is changed: the boehmite particles and alumina particles containing hydroxyl and phosphate groups are replaced with boehmite particles containing hydroxyl and phosphate groups and 1,3,5-triazine-2,4,6-triamine organic particles containing amino groups (mass ratio 1:1).

[0078] Example 8 group The embodiments in this group refer to the battery preparation method of Embodiment 1, except that the thickness and elongation of the separator are changed. Specifically: in Embodiment 8-1, the elongation of the separator is changed to 280%, the thickness of the separator is 25 μm, and the ratio of the elongation of the separator to the thickness of the separator is changed to 11.2:1; in Embodiment 8-2, the elongation of the separator is changed to 300%, the thickness of the separator is 5 μm, and the ratio of the elongation of the separator to the thickness of the separator is changed to 60:1.

[0079] Test case The batteries obtained in the above embodiments and comparative examples were tested using the following test methods: 1. The cell rate test method is as follows: Under an environment of (25±2)℃, the batteries obtained in the above examples and comparative examples are discharged at a standard constant current of 1C to the discharge termination voltage of 2.7V and left to stand for 30 minutes; then charged at a standard constant current and constant voltage of 1C to the charging limit voltage of 4.2V, with a cutoff current of 0.05C, and left to stand for 30 minutes; discharged at a standard constant current of 1C to the discharge termination voltage of 2.7V to obtain the actual cell capacity C0, and left to stand for 30 minutes; charged at a standard constant current and constant voltage of 1C to the charging limit voltage of 4.2V, with a cutoff current of 0.05C; after standing at (25±2)℃ for 4 hours, discharged at a certain rate at a constant current for 10 seconds to the discharge limit voltage of 2.7V. This rate is the discharge rate of the cell (in C), and the test results are recorded in Table 2.

[0080] 2. The cell cycle test method is as follows: At 25°C, the batteries obtained in the above examples and comparative examples are discharged at 3C standard constant current to the discharge termination voltage of 2.7V and rested for 30 minutes; then charged at 3C standard constant current and constant voltage to the charging limit voltage of 4.2V and the cutoff current of 0.05C and rested for 30 minutes; discharged at 3C standard constant current to the discharge termination voltage of 2.7V and rested for 30 minutes; the above full charge and discharge steps are repeated until the capacity decays to 80% and the cutoff is reached. The number of repeated cycles is the cycle number (in T), which is used to evaluate the cycle performance of the battery after aging. The test results are recorded in Table 2.

[0081] 3. The test method for lithium plating in battery cells is as follows: At 45℃, the batteries obtained in the above examples and comparative examples are discharged at a 3C standard constant current to the discharge termination voltage of 2.7V and rested for 30 minutes; then charged at a 3C standard constant current and constant voltage to the charging limit voltage of 4.2V and the cutoff current of 0.05C and rested for 30 minutes; discharged at a 3C standard constant current to the discharge termination voltage of 2.7V and rested for 30 minutes; the above full charge and discharge steps are repeated until the cycle count reaches 2200T. The electrode plates are disassembled to observe whether lithium plating occurs on the surface of the negative electrode plate. The lithium plating situation of the battery is divided into three levels: Level 1: No lithium plating; Level 2: Slight lithium plating, lithium plating at the top and bottom edges of the electrode plate or slight lithium plating at the arc, but it does not affect the normal use of the battery; Level 3: Severe lithium plating, lithium plating on a large area of ​​the entire electrode plate. The test results are recorded in Table 2.

[0082] Table 2 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 lithium-ion battery, characterized in that, The battery cell includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode. The positive electrode, the separator, and the negative electrode are stacked or wound to form a battery cell. The positive electrode includes a positive current collector and a positive active layer located on one or both sides of the positive current collector. The positive active layer is further provided with a first coating at both ends along the width and / or length direction of the positive current collector. Both the positive active layer and the first coating are coated on the surface of the positive current collector. The negative electrode includes a negative current collector and a negative active layer located on one or both sides of the negative current collector. The positive electrode active layer contains an ion conductor material; The first coating contains first particles, which include ceramic particles and / or organic particles, and the first particles contain at least one functional group selected from hydroxyl, amino, phosphate monoester, phosphate group, phosphite group or hypophosphite group. The average particle size of the first particle is 300nm~3000nm, and the average particle size of the ion conductor material is 80nm~500nm.

2. The lithium-ion battery according to claim 1, wherein, The ratio of the average particle size of the first particle to that of the ionic conductor material is (0.8~15):

1.

3. The lithium-ion battery according to claim 1 or 2, wherein, The average particle size of the first particle is 500 nm to 1500 nm; and / or, the average particle size of the ion conductor material is 100 nm to 360 nm; Preferably, the ratio of the average particle size of the first particle to that of the ion conductor material is (1.5~8):

1.

4. The lithium-ion battery according to claim 1, wherein, The ion conductor material includes at least one of lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum titanium oxide. And / or, the ceramic particles include at least one of boehmite, alumina, magnesium oxide, zirconium oxide, aluminum nitride, and silicon oxide; preferably, the first particle includes at least two of the ceramic particles selected from boehmite, alumina, magnesium oxide, zirconium oxide, aluminum nitride, and silicon oxide. And / or, the organic particles include at least one of 1,3,5-triazine-2,4,6-triamine, melamine cyanurate, and melamine trithiocyanate.

5. The lithium-ion battery according to claim 1, wherein, The surface of the ion conductor material particles is provided with a carbon coating layer, the thickness of which is 1.5 nm to 40 nm, preferably 3 nm to 20 nm; Preferably, the ratio of the average particle size of the ion conductor material to the thickness of the carbon coating layer is (10~200):1, more preferably (20~100):

1.

6. The lithium-ion battery according to claim 1, wherein, The positive electrode, the separator, and the negative electrode are stacked sequentially to form the battery cell; And / or, the negative electrode current collector includes a first surface near the center of the cell and a second surface away from the center of the cell along the thickness direction, the first surface of the negative electrode current collector located in the outermost layer / outermost ring of the cell is provided with the negative electrode active layer, and the second surface is not provided with the negative electrode active layer; And / or, the lithium-ion battery further includes a tab structure, the tab structure including a plurality of positive tabs and a plurality of negative tabs, the plurality of positive tabs being integrally connected to the positive current collector, and the plurality of negative tabs being integrally connected to the negative current collector; preferably, all of the plurality of positive tabs and all of the plurality of negative tabs are led out from opposite ends of the cell.

7. The lithium-ion battery according to claim 1, wherein, A transition region is formed between the positive electrode active layer and the first coating layer. The dimension of the transition region along the width direction of the positive electrode current collector is 0.2 mm to 4 mm, preferably 0.5 mm to 3 mm. And / or, the dimension of the first coating along the width direction of the positive electrode current collector is 0.5mm to 5mm, preferably 1mm to 4mm; Preferably, the ratio of the size of the transition region to the size of the first coating along the width direction of the positive electrode current collector is (0.1~0.9):1, more preferably (0.2~0.8):

1.

8. The lithium-ion battery according to claim 1, wherein, The first coating has a Mohs hardness of 3 to 7, preferably 5 to 6.5; And / or, the dimension of the first coating along the thickness direction of the positive electrode current collector is 5μm~50μm, preferably 8μm~30μm; Preferably, the ratio of the Mohs hardness of the first coating to the dimension of the first coating along the thickness direction of the positive electrode current collector is (0.1~1):1, more preferably (0.2~0.8):

1.

9. The lithium-ion battery according to claim 1, wherein, The elongation of the diaphragm is 50%~300%, preferably 80%~280%; And / or, the thickness of the diaphragm is 5μm to 25μm, preferably 9μm to 20μm; Preferably, the ratio of the elongation of the diaphragm to the thickness of the diaphragm is (8~40):1, more preferably (12~28):

1.

10. The lithium-ion battery according to claim 1, wherein, The negative electrode active layer contains a negative electrode active material, which includes a carbon-based active material. The average particle size of the carbon-based active material is 800 nm to 16000 nm, preferably 1100 nm to 10000 nm. Preferably, the ratio of the average particle size of the ion conductor material to the average particle size of the carbon-based active material is (0.01 to 0.6):1, more preferably (0.05 to 0.3):

1. And / or, the positive electrode active layer further comprises a positive electrode active material, including LiMn2O4 and Li4Ti5O4. 12 Li3V2(PO4)3, LiFe 1-x W x PO4, LiNi x Mn y Co 1-x-y O2 and LiNi x Co y Al 1-x-y At least one of O2, wherein 0≤x≤1, 0≤y≤1, x+y≤1, and W is selected from at least one of Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, V, and Ti.

Images