Coating composition, separator, electrochemical device, and electronic device

Abstract

Provided are a coating composition, a separator, an electrochemical device, and an electronic device. The coating composition comprises a fiber material, filler particles, and a binder; the fiber material comprises at least one of first inorganic ceramic and an impurity element-containing first organic matter; the filler particles comprise at least one of second inorganic ceramic and an impurity element-containing second organic matter; at least one of the fiber material and the filler particles is an impurity element-containing organic matter; the impurity element includes a nitrogen element or / and a phosphorus element; and the mass percentage of the impurity element ranges from 10% to 60% on the basis of the mass of the coating composition. When the coating composition is applied to the separator, the coating composition is applied to the separator to form a coating, thereby improving the thermal safety performance and high-temperature cycle performance of the electrochemical device.

Description

Coating compositions, diaphragms, electrochemical devices, and electronic devices

[0001] This application claims priority to Chinese Patent Application No. 202411627506.5, filed on November 14, 2024, entitled "Coating Composition, Diaphragm, Electrochemical Device and Electronic Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrochemical energy storage, and in particular to a coating composition, a membrane using the coating composition, an electrochemical device using the membrane, and an electronic device using the electrochemical device. Background Technology

[0003] Electrochemical devices (such as lithium-ion batteries) are widely used in consumer electronics (such as mobile phones, laptops, cameras, etc.), energy storage products (such as home energy storage, energy storage power stations, UPS power supplies, etc.) and new energy vehicles as portable chemical energy sources due to their advantages such as high energy density, high operating voltage platform, low self-discharge, long service life and environmental friendliness.

[0004] Electrochemical devices include diaphragms, which are crucial to the safety of the device. Inorganic materials such as ceramic-coated diaphragms can improve their heat resistance. However, when a short circuit occurs between the positive and negative electrodes, a large amount of heat is generated instantaneously. This causes the diaphragm to shrink thermally, which may lead to continuous contact between the positive and negative electrodes and increase the short-circuit contact area, thus affecting the safety of the electrochemical device. Summary of the Invention

[0005] This application provides a coating composition, a diaphragm, an electrochemical device, and an electronic device.

[0006] This application provides a coating composition comprising a fiber material, filler particles, and a binder. The fiber material comprises at least one of a first inorganic ceramic or a first organic compound containing heterogeneous elements. The filler particles comprise at least one of a second inorganic ceramic or a second organic compound containing heterogeneous elements. At least one of the fiber material and the filler particles is an organic compound containing heterogeneous elements, including nitrogen and / or phosphorus. Based on the mass of the coating composition, the mass percentage of heterogeneous elements is 10% to 60%.

[0007] The coating composition provided in this application, when applied to a diaphragm, forms a coating on the diaphragm. The fibrous material in the coating acts as a supporting skeleton, improving the thermal shrinkage and stability of the diaphragm, enhancing its mechanical extrusion resistance, and increasing the overall hardness of the electrochemical device. The filler particles fill the gaps between the fibrous material, reducing the overall porosity of the diaphragm, improving its mechanical strength and thermal shrinkage, and facilitating the adhesive to fully bond the fibrous material and filler particles, thus improving the diaphragm's adhesion and interfacial stability between the diaphragm and the positive and negative electrode materials, thereby improving the rate performance of the electrochemical device. The combination of the aforementioned fibrous material and filler particles also helps reduce the coating's density, lowering the low-temperature impedance of the electrochemical device. Furthermore, the presence of nitrogen and / or phosphorus in the coating facilitates the construction of an organic coating framework structure, improving electrode stability and enhancing the thermal safety and high-temperature cycling performance of the electrochemical device. In this application, the content of impurity elements is in the range of 10% to 60%, which is beneficial to further improve the stability of the positive electrode and enable the electrochemical device to have good high-temperature cycling performance. If the mass percentage of impurity elements is large, such as greater than 60%, under a certain content, the increase in the mass percentage of impurity elements will increase the content of fiber materials or filler particles, thereby reducing the amount of binder used. This will increase the peel force between the diaphragm and the positive and negative electrode sheets, reduce the thermal shrinkage of the diaphragm, and reduce the thermal safety of the electrochemical device.

[0008] Based on the first aspect, in some embodiments, the impurity element accounts for 15% to 45% by mass in the coating composition. This further improves the thermal safety and high-temperature cycling performance of the electrochemical device.

[0009] Based on the first aspect, in some embodiments, the length-to-width ratio of the fiber material is (3-50):1. This facilitates easy dispersion during the preparation of the coating composition slurry and makes it easier to control the roughness of the coating composition applied to the diaphragm surface, ensuring the coating maintains a certain level of adhesion, thereby improving the high-temperature cycling performance and rate performance of the electrochemical device.

[0010] Based on the first aspect, in some embodiments, the length of the fiber material is from 2 μm to 50 μm. This facilitates improved dispersibility during the preparation of the coating composition slurry, and also allows for adjustment of the coating thickness when the coating composition is applied to the diaphragm. It reduces the increase in coating thickness due to the longer fiber material, thus decreasing the energy density of the electrochemical device. However, the longer fiber material also increases the roughness of the coating on the diaphragm surface, creating gaps on the diaphragm surface, thereby reducing the adhesion between the diaphragm and the positive and negative electrode plates, and consequently reducing the high-temperature cycling performance and rate performance of the electrochemical device.

[0011] Based on the first aspect, in some embodiments, the particle size Dv50 of the filler particles is from 0.1 μm to 3 μm. When the coating composition is applied to the diaphragm, it has a suitable thickness, which is beneficial for maintaining a high volumetric energy density in the electrochemical device and for reducing the probability of filler particles clogging the diaphragm pores, thereby improving the cycle performance of the electrochemical device.

[0012] Based on the first aspect, in some embodiments, the mass ratio of fiber material to filler particles is 1:(1 to 10). A mass ratio within this range is advantageous because the filler particles can fully fill the gaps in the fiber material in the coating composition. When the coating composition is applied to a diaphragm and forms a coating on the diaphragm, it helps to reduce the porosity of the coating, further improving the mechanical strength and thermal shrinkage of the diaphragm, and thus enhancing the thermal safety performance of the electrochemical device.

[0013] Based on the first aspect, in some embodiments, the mass ratio of the sum of fiber material and filler particles to binder in the coating composition is 99:1 to 85:15. Adding an appropriate amount of binder to the coating composition enables the fiber material and filler to bond together, and also helps maintain a certain adhesion between the diaphragm and the positive and negative electrode plates when the coating composition is applied to the diaphragm, thereby improving the rate performance of the electrochemical device.

[0014] Based on the first aspect, in some embodiments, the first organic compound includes at least one selected from ammonium polyphosphate, piperazine pyrophosphate, melamine polyphosphate, polyacrylonitrile, melamine, melamine thiocyanate, or melamine cyanurate. All of the above organic compounds have a fibrous structure and contain heterogeneous elements. When the coating composition is applied to the diaphragm to form a coating, the organic compound acts as a supporting skeleton in the coating, improving the thermal shrinkage and stability of the diaphragm, enhancing the mechanical extrusion resistance of the diaphragm, and increasing the overall hardness of the electrochemical device. Simultaneously, the crystals of the above organic compound grow along the long axis of the fibers, which can reduce the thermal shrinkage of the diaphragm. Furthermore, at high temperatures, the above organic compound decomposes, providing a flame-retardant effect.

[0015] Based on the first aspect, in some embodiments, the first inorganic ceramic includes at least one selected from lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum zirconium oxide, alumina, boehmite, titanium dioxide, aluminum silicate, silicon carbide, or silicon nitride. All of the above inorganic ceramics have a fibrous structure, which, in addition to increasing the mechanical strength of the diaphragm, also serves as a supporting framework, thereby further improving the mechanical extrusion resistance performance of the diaphragm.

[0016] Based on the first aspect, in some embodiments, the second organic compound includes at least one selected from polyacrylonitrile, ammonium polyphosphate, melamine, dicyandiamide, melamine cyanurate, melamine trithiocyanate, or melamine polyphosphate. All of the above organic compounds contain heterogeneous elements and, in addition to containing heterogeneous elements, also serve as fillers to further improve the mechanical extrusion resistance performance of the diaphragm. Furthermore, the above organic compounds exhibit good thermal stability, which is beneficial for improving the thermal safety performance of the electrochemical device and reducing the high-temperature storage expansion of the electrochemical device.

[0017] Based on the first aspect, in some embodiments, the second inorganic ceramic includes at least one selected from lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium niobium oxide, alumina, boehmite, or magnesium hydroxide. Using a solid electrolyte in the aforementioned inorganic ceramic can improve the lithium-ion mobility in the electrochemical device, reduce the low-temperature impedance of the electrochemical device, and improve the low-temperature cycling performance of the electrochemical device; using alumina, boehmite, or magnesium hydroxide is more conducive to improving the mechanical strength of the membrane.

[0018] Based on the first aspect, in some embodiments, the binder includes at least one selected from polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene-butadiene rubber, isocyanate, polyvinyl alcohol, or sodium carboxymethyl cellulose. The aforementioned binders can effectively bond the fibrous material and filler particles, improving the adhesion of the diaphragm.

[0019] A second aspect of this application also provides a diaphragm, the diaphragm comprising a base membrane and a coating on at least one surface of the base membrane, the coating comprising the coating composition, which is capable of improving the thermal shrinkage and stability of the diaphragm.

[0020] Based on the second aspect, in some embodiments, the porosity of the membrane is 35% to 50%. This allows the electrochemical device to have both low internal resistance and good cycle retention.

[0021] Based on the second aspect, in some embodiments, the coating thickness is from 0.3 μm to 5 μm. This allows the diaphragm to reduce the internal resistance of the electrochemical device while maintaining a certain level of resistance to thermal shrinkage, thereby balancing the thermal safety and cycle performance of the electrochemical device.

[0022] A third aspect of this application also provides an electrochemical device, including a positive electrode and a negative electrode, and a diaphragm located between the positive and negative electrode. The diaphragm comprises a coating composition that improves the thermal safety and high-temperature cycling performance of the electrochemical device.

[0023] A fourth aspect of this application provides an electronic device including the aforementioned electrochemical device. The diaphragm comprising the above-described coating composition improves the thermal safety and high-temperature cycling performance of the electrochemical device, thereby enhancing the safety performance and service life of the electronic device. Attached Figure Description

[0024] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0025] Figure 1, (a) is a cross-sectional structural diagram of the coating composition of this application applied to a diaphragm; (b) is a surface structural diagram of the coating composition of this application applied to a diaphragm.

[0026] Figure 2 is a scanning electron microscope image of the coating on the surface of the base film in Embodiment 1-1 of this application.

[0027] Figure 3 is a scanning electron microscope image at the magnification of Figure 2.

[0028] Figure 4 is a scanning electron microscope image of the coating on the surface of the base film in Examples 1-2 of this application.

[0029] Figure 5 is a scanning electron microscope image of the coating on the surface of the base film in Comparative Example 2 of this application. Detailed Implementation

[0030] The technical solutions in the embodiments of this application are described clearly and in detail below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0031] As used herein, the term "about" is used to describe and indicate small variations. When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely and examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format herein. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0032] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" or "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" or "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0033] One embodiment of this application provides a coating composition comprising a fiber material, filler particles, and a binder. The fiber material comprises at least one of a first inorganic ceramic or a first organic compound containing heterogeneous elements. The filler particles comprise at least one of a second inorganic ceramic or a second organic compound containing heterogeneous elements. At least one of the fiber material and the filler particles is an organic compound containing heterogeneous elements, including nitrogen and / or phosphorus. Based on the mass of the coating composition, the mass percentage of heterogeneous elements is 10% to 60%.

[0034] The coating composition provided in this application, when applied to a diaphragm, forms a coating on the diaphragm. The fibrous material in the coating acts as a supporting skeleton, improving the thermal shrinkage and stability of the diaphragm, enhancing its mechanical extrusion resistance, and increasing the overall hardness of the electrochemical device. The filler particles fill the gaps between the fibrous material, reducing the overall porosity of the diaphragm, improving its mechanical strength and thermal shrinkage, and facilitating the adhesive to fully bond the fibrous material and filler particles, thus improving the diaphragm's adhesion and interfacial stability between the diaphragm and the positive and negative electrode materials, thereby improving the rate performance of the electrochemical device. The combination of the aforementioned fibrous material and filler particles also helps reduce the coating's density, lowering the low-temperature impedance of the electrochemical device. Furthermore, the presence of nitrogen and / or phosphorus in the coating facilitates the construction of an organic coating framework structure, improving the stability of the positive and negative electrode sheets and enhancing the thermal safety and high-temperature cycling performance of the electrochemical device.

[0035] Compared to a single sheet-like structure containing impurities in the filler coating, the combination of fiber material and filler particles, as well as at least one containing impurities, in this application reduces the thermal shrinkage of the diaphragm and lowers its impedance, thereby improving the discharge capacity and cycle performance of the electrochemical device. Furthermore, compared to a single fiber material containing impurities, the combination of fiber material and filler particles, as well as at least one containing impurities, reduces the thermal shrinkage of the diaphragm and improves the thermal safety performance of the electrochemical device.

[0036] In the scanning electron microscope, the morphology of the aforementioned fibrous materials can be columnar or rod-shaped. Each columnar or rod-shaped particle in the fibrous material has a length and a width.

[0037] The presence of impurity elements within the range of 10% to 60% is beneficial for further improving the stability of the positive electrode, resulting in good high-temperature cycling performance and thermal safety of the electrochemical device. If the mass percentage of impurity elements is large, such as greater than 60%, at a given content, this increased mass percentage will increase the content of fiber materials or filler particles, thereby reducing the amount of binder used, lowering the peel force between the separator and the positive and negative electrode sheets, reducing the thermal shrinkage of the separator, and ultimately decreasing the thermal safety performance of the electrochemical device. In some embodiments, the mass percentage of impurity elements in the coating composition is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any value within the range of any two of the above values.

[0038] In some embodiments, the heterogeneous element accounts for 15% to 45% by mass in the coating composition, and more preferably, the heterogeneous element accounts for 20% to 45% by mass.

[0039] In some embodiments, the length-to-width ratio of the fiber material is (3-50):1. A length-to-width ratio within this range facilitates dispersion during the preparation of the coating composition slurry and allows for easy control of the roughness of the coating composition applied to the diaphragm surface, maintaining a certain level of adhesion and thus improving the high-temperature cycling performance and thermal safety of the electrochemical device. If the length-to-width ratio of the fiber material is small, it increases the density of the coating composition applied to the diaphragm surface, affecting the impedance of the diaphragm in the electrochemical device and reducing the rate capability of the device. If the fiber material is too long, a small length-to-width ratio makes it difficult to disperse during the preparation of the coating composition slurry, and the fiber material is easily broken, affecting its supporting role in the coating composition and reducing the mechanical crush resistance test performance of the diaphragm. In some embodiments, the length-to-width ratio of the fiber material can be 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or any value within the range of any two of the above values. Preferably, the ratio of the length to the width of the fiber material is in the range of 3 to 30, and more preferably in the range of 3 to 20.

[0040] In some embodiments, the length of the fiber material is from 2 μm to 50 μm. This improves dispersibility during the preparation of the coating composition slurry and also facilitates adjusting the coating thickness when the coating composition is applied to the diaphragm, reducing the increase in coating thickness due to the longer fiber material and thus minimizing the reduction in energy density of the electrochemical device. However, a longer fiber material also increases the roughness of the coating on the diaphragm surface, creating gaps on the diaphragm surface and reducing the adhesion between the diaphragm and the positive and negative electrode plates, thereby reducing the thermal safety performance, high-temperature cycling performance, and rate performance of the electrochemical device. In some embodiments, the length of the fiber material can be 2 μm, 3 μm, 5 μm, 7 μm, 9 μm, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any value within the range of any two of the above values. In some embodiments, the length of the fiber material is from 2 μm to 30 μm, more preferably from 2 μm to 15 μm.

[0041] In some embodiments, the particle size Dv50 of the filler particles is from 0.1 μm to 3 μm. Maintaining a suitable particle size Dv50 ensures an appropriate thickness when the coating composition is applied to the membrane, which is beneficial for maintaining a high volumetric energy density in the electrochemical device and for reducing the probability of filler particles clogging the membrane pores, thereby improving the cycle performance of the electrochemical device. In some embodiments, the particle size Dv50 of the filler particles can be 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3 μm, or any value within the range of any two of the above values. Preferably, the particle size Dv50 of the filler particles can be from 0.2 μm to 2 μm, more preferably from 0.3 μm to 1 μm.

[0042] In some embodiments, the mass ratio of fiber material to filler particles is 1:(1 to 10). A mass ratio within this range facilitates the filling particles to fully fill the gaps in the fiber material in the coating composition. When the coating composition is applied to a diaphragm and forms a coating on the diaphragm, it helps reduce the porosity of the coating, further improving the mechanical strength and thermal shrinkage of the diaphragm, and thus enhancing the thermal safety performance of the electrochemical device. The mass ratio of fiber material to filler particles can be 1:1, 1:2, 1:4, 1:6, 1:7, 1:8, 1:9, 1:10, or any value within the range of any two of the above values.

[0043] In some embodiments, the mass ratio of the sum of fiber material and filler particles to binder in the coating composition is 99:1 to 85:15. Adding an appropriate amount of binder to the coating composition can bond the fiber material and filler, and also helps maintain a certain adhesion between the membrane and the positive and negative electrode plates when the coating composition is applied to the membrane, thereby improving the rate performance of the electrochemical device. If the binder accounts for a large proportion by mass, it may reduce the membrane's permeability, increase internal resistance, and affect the rate performance of the electrochemical device. In some embodiments, the mass ratio of the sum of fiber material and filler particles to binder in the coating composition can be 99:1, 99:5, 90:6, 90:10, 80:10, 85:15, or any ratio within the range of any two of the above values.

[0044] In some embodiments, the first organic compound includes at least one selected from ammonium polyphosphate, dicyandiamide, piperazine pyrophosphate, melamine polyphosphate, polyacrylonitrile, melamine, melamine thiocyanate, or melamine cyanurate. All of the above organic compounds have a fibrous structure and contain heterogeneous elements. When the coating composition is applied to the diaphragm to form a coating, the organic compound acts as a supporting skeleton in the coating, improving the thermal shrinkage and stability of the diaphragm, enhancing its mechanical extrusion resistance, and increasing the overall hardness of the electrochemical device. Simultaneously, the crystals of the organic compound grow along the long axis of the fibers, reducing the thermal shrinkage of the diaphragm. Furthermore, at high temperatures, the organic compound decomposes, providing a flame-retardant effect.

[0045] In some embodiments, the first inorganic ceramic includes at least one selected from lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum zirconium oxide, alumina, boehmite, titanium dioxide, aluminum silicate, silicon carbide, or silicon nitride. All of the above inorganic ceramics have a fibrous structure, which not only increases the mechanical strength of the diaphragm but also serves as a supporting framework, further improving the mechanical extrusion resistance performance of the diaphragm.

[0046] In some embodiments, the second organic compound includes at least one selected from polyacrylonitrile, ammonium polyphosphate, melamine, dicyandiamide, melamine cyanurate, melamine trithiocyanate, or melamine polyphosphate. All of the above organic compounds contain heterogeneous elements and, in addition to containing heterogeneous elements, also serve as fillers to further improve the mechanical extrusion resistance of the diaphragm. Furthermore, the above organic compounds exhibit good thermal stability, which is beneficial for improving the thermal safety performance of the electrochemical device and reducing the high-temperature storage expansion of the electrochemical device.

[0047] In some embodiments, the second inorganic ceramic includes at least one selected from lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium niobium oxide, alumina, boehmite, or magnesium hydroxide. Using a solid electrolyte in the aforementioned inorganic ceramics can improve the lithium-ion mobility in the electrochemical device, reduce the low-temperature impedance of the electrochemical device, and improve the low-temperature cycling performance of the electrochemical device; using alumina, boehmite, or magnesium hydroxide is more beneficial for improving the mechanical strength of the membrane.

[0048] In some embodiments, the binder includes at least one selected from polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene-butadiene rubber, isocyanate, polyvinyl alcohol, or sodium carboxymethyl cellulose. The above-mentioned binders can effectively bond the fibrous material and filler particles, improving the adhesion of the diaphragm.

[0049] This application also provides a diaphragm, comprising a base membrane and a coating on at least one surface of the base membrane, the coating comprising the coating composition. The diaphragm containing the coating has good heat retention, high porosity, and high ionic conductivity, resulting in electrochemical devices containing the diaphragm exhibiting low impedance, thermal safety throughput, high-temperature cycling performance, and low-temperature cycling performance.

[0050] In Figure 1(a), a coating is formed on the surface of the base membrane in the diaphragm. The coating contains a coating composition containing fibrous material (such as N-prism fibers) and filler particles (such as three-dimensional fillers). In Figure 1(b), the fibrous material and filler particles are uniformly distributed, and the filler particles fill the spaces between the fibrous materials.

[0051] In some embodiments, the membrane porosity is 35% to 50%. Within this range, the electrochemical device exhibits good cycle retention while maintaining low internal resistance. In some embodiments, the membrane porosity can be 35%, 38%, 40%, 43%, 45%, 48%, 50%, or any ratio within a range of any two of the above values.

[0052] In some embodiments, the coating thickness is from 0.3 μm to 5 μm. A coating thickness within this range allows the diaphragm to reduce the internal resistance of the electrochemical device while maintaining a certain level of heat shrinkage resistance, thereby balancing the thermal safety and cycle performance of the electrochemical device. In some embodiments, the coating thickness can be 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 1.8 μm, 2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any ratio within the range of any two of the above values. More specifically, the coating thickness is from 1 μm to 3 μm.

[0053] One embodiment of this application also provides an electrochemical device, including a housing, an electrode assembly, and an electrolyte, with the battery cell and electrolyte located inside the housing. The housing can be a packaging bag sealed with an encapsulating film (such as an aluminum-plastic film), such as a soft-pack secondary battery for the electrochemical device. In other embodiments, the electrochemical device can also be a steel-cased battery, an aluminum-cased battery, etc.

[0054] The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode. The electrode assembly can be a stacked structure, formed by layering the positive electrode, separator, and negative electrode. In other embodiments, the electrode assembly can also be a wound structure, formed by winding the stacked positive electrode, separator, and negative electrode.

[0055] Positive electrode sheet

[0056] The positive electrode includes a positive current collector and a positive active layer disposed on the positive current collector. The positive current collector can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, current collectors formed by combining the aforementioned conductive foil and polymer substrate. The positive active layer contains a positive active material, which includes compounds that reversibly insert and extract lithium ions (i.e., lithiation intercalation compounds). In some embodiments, the positive active material may include a lithium transition metal composite oxide. This lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel. In some embodiments, the positive active material may include, but is not limited to, lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganese oxide, spinel-type lithium nickel manganese oxide, and lithium titanate.

[0057] The positive electrode active layer also includes an adhesive for bonding the positive electrode active material particles to facilitate the formation of the film layer, and also to improve the bonding force between the positive electrode active layer and the positive electrode current collector. In some embodiments, the adhesive may include, but is not limited to, at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0058] The positive electrode active layer may also include a conductive material, including but not limited to carbon-based materials, metal-based materials, conductive polymers, or any combination thereof. In some embodiments, carbon-based materials may include, but are not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, metal-based materials may include, but are not limited to, metal powders or metal fibers, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0059] Negative electrode sheet

[0060] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector.

[0061] Negative current collectors include copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metal, or any combination thereof.

[0062] Negative electrode active materials include materials that reversibly insert / deintercalate lithium ions. In some embodiments, the materials that reversibly insert / deintercalate lithium ions include carbon materials. In some embodiments, the carbon material can be any carbon-based negative electrode active material commonly used in lithium-ion rechargeable batteries. In some embodiments, the carbon material includes, but is not limited to: crystalline carbon, amorphous carbon, or mixtures thereof. Crystalline carbon can be amorphous, flake-shaped, flake-shaped, spherical, or fibrous natural or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbides, calcined coke, etc.

[0063] In some embodiments, the negative electrode active material layer includes a negative electrode active material. The specific type of negative electrode active material is not limited and can be selected according to requirements. In some embodiments, the negative electrode active material includes, but is not limited to: lithium metal, structured lithium metal, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Li-Al alloys or any combination thereof. The silicon-carbon composite refers to a silicon-carbon anode active material containing at least about 5 wt% silicon by weight.

[0064] In some embodiments, the negative electrode active material comprises at least one of artificial graphite, natural graphite, hard carbon, soft carbon, silicon alloy, or silicon oxide.

[0065] When the negative electrode includes silicon-carbon compounds, based on the total weight of the negative electrode active material, the silicon:carbon ratio is approximately 1:10-10:1, and the median particle size Dv of the silicon-carbon compounds is... 50The micrometer size ranges from approximately 0.1 micrometers to 20 micrometers. When the negative electrode comprises an alloy material, the negative electrode active material layer can be formed using methods such as vapor deposition, sputtering, or plating. When the negative electrode comprises lithium metal, the negative electrode active material layer is formed, for example, using a conductive framework with a spherical twisted structure and metal particles dispersed within the conductive framework. In some embodiments, the spherical twisted conductive framework may have a porosity of approximately 5% to approximately 85%. In some embodiments, a protective layer may also be provided on the lithium metal negative electrode active material layer.

[0066] In some embodiments, the negative electrode active material layer may include an adhesive and optionally a conductive material. The adhesive enhances the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector. In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0067] In some embodiments, the conductive material includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, or mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0068] In some embodiments, the current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and any combination thereof.

[0069] The negative electrode can be prepared by methods known in the art. For example, the negative electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then coating the active material composition onto a current collector. In some embodiments, the solvent may include, but is not limited to, water.

[0070] diaphragm

[0071] The material and shape of the diaphragm used in the electrochemical device of this application are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments, the diaphragm comprises a polymer or inorganic material formed from a material stable to the electrolyte of this application.

[0072] For example, the diaphragm may include a base membrane and a coating. The base membrane is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the base membrane is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be selected.

[0073] electrolyte

[0074] According to some embodiments of this application, the electrolyte includes an organic solvent, a lithium salt, and optional additives.

[0075] The organic solvent in the electrolyte of this application may be any organic solvent known in the prior art that can be used as an electrolyte solvent. There are no limitations on the electrolyte used in the electrolyte according to this application; it may be any electrolyte known in the prior art. The additives in the electrolyte according to this application may be any additives known in the prior art that can be used as electrolyte additives. In some embodiments, the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or ethyl propionate (EP).

[0076] In some embodiments, the organic solvent includes ether solvents, such as at least one selected from 1,3-dioxapentane (DOL) and dimethyl glycol ether (DME). In some embodiments, the lithium salt includes at least one selected from organic lithium salts or inorganic lithium salts. In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(fluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalatoborate)borate LiB(C2O4)2 (LiBOB), or lithium difluorooxalatoborate LiBF2(C2O4) (LiDFOB). In some embodiments, the additive includes at least one selected from fluoroethylene carbonate and adiponitrile.

[0077] One embodiment of this application also provides an electronic device, which includes an electrochemical device.

[0078] The electronic devices described in this application are not particularly limited. In some embodiments, the electronic devices described in this application include, but are not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0079] The present application will be described below through specific embodiments and comparative examples. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0080] Example 1-1

[0081] (1) Preparation of the diaphragm

[0082] solid electrolyte Li 1.3 Al 0.3 Ti 1.7 (PO4)3 [abbreviated as LATP], melamine polyphosphate fiber MPP, and styrene-butadiene rubber adhesive are mixed at a mass ratio of 60:30:10 to obtain a coating composition; deionized water is added to the coating composition and dispersed evenly to obtain a coating composition slurry. The particle size Dv50 of LATP is 500nm, the length of MPP fiber is 4μm, and the aspect ratio is 10:1.

[0083] The above-mentioned coating composition slurry is uniformly applied to one surface of a polyethylene film, and after drying in an oven, a diaphragm is obtained.

[0084] (2) Preparation of lithium-ion batteries

[0085] Preparation of the positive electrode sheet:

[0086] Lithium cobalt oxide (CCO), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) (a binder) were added to N-methylpyrrolidone (NMP) in a weight ratio of 96:2.5:1.5 and stirred until homogeneous to form a positive electrode slurry. The positive electrode slurry was then uniformly coated onto one side of an aluminum foil current collector and dried. The same steps were repeated on the other side of the aluminum foil to obtain a positive electrode sheet with a positive electrode active layer on both sides. After cold pressing and cutting, the positive electrode sheet was obtained.

[0087] Preparation of negative electrode sheet:

[0088] Artificial graphite (anode active material), sodium carboxymethyl cellulose (CMC) (thickener), and styrene-butadiene rubber (SBR) (binder) are added to deionized water in a weight ratio of 96:2:2 and stirred evenly to form a cathode slurry. The cathode slurry is then uniformly coated onto one side of a copper foil current collector and dried. The above steps are repeated on the other side of the copper foil to obtain a cathode sheet with a cathode active layer coated on both sides. After cold pressing and cutting, the cathode sheet is obtained.

[0089] Electrolyte preparation:

[0090] Preparation of the non-aqueous electrolyte: In a dry argon atmosphere glove box, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a weight ratio of 1:3:6 as a base solvent. Then, fluoroethylene carbonate and LiPF6 were dissolved in the base solvent to obtain the electrolyte. Based on the total mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, and the mass percentage of fluoroethylene carbonate was 5%.

[0091] Preparation of the diaphragm:

[0092] The diaphragm prepared in Example 1 above was selected.

[0093] Lithium-ion battery assembly:

[0094] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to obtain a stacked electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag, heat-sealed around the perimeter, leaving an injection port, and the electrolyte is injected. After vacuum sealing, settling, hot-pressing formation, degassing, and other processes, a lithium-ion battery is obtained.

[0095] (3) Preparation of symmetric cells:

[0096] Different numbers of separators (1, 2, 3, 4, 5 layers) are stacked, with Cu foil as the positive and negative electrodes. The same electrolyte as that used in the lithium-ion battery is injected to obtain symmetrical batteries with different numbers of separators.

[0097] Examples 1-2

[0098] The difference between Examples 1-2 and Example 1-1 is that: melamine cyanurate particles, melamine cyanurate fibers, and styrene-butadiene rubber (SBR) adhesive are mixed at a mass ratio of 60:30:10, and deionized water is added to disperse them evenly to obtain a coating composition slurry. The remaining steps are the same as in Example 1-1.

[0099] Examples 1-3

[0100] The difference between Examples 1-3 and Examples 1-1 is that: dicyandiamide and solid electrolyte Li...1.3 Al 0.3 Ti 1.7 (PO4)3 fiber and styrene-butadiene rubber (SBR) adhesive are mixed at a mass ratio of 60:30:10, and deionized water is added to disperse the mixture evenly to obtain a coating composition slurry. The remaining steps are the same as in Examples 1-1.

[0101] Examples 1-4

[0102] The difference between Examples 1-4 and Example 1-1 is that: ammonium polyphosphate particles, alumina fibers, and styrene-butadiene rubber (SBR) adhesive are mixed in a mass ratio of 60:30:10, and deionized water is added to disperse them evenly to obtain a coating composition slurry. The remaining steps are the same as in Example 1-1.

[0103] Examples 1-5

[0104] The difference between Examples 1-5 and Example 1-1 is that: polyacrylonitrile particles, ammonium polyphosphate fibers, and styrene-butadiene rubber (SBR) adhesive are mixed in a mass ratio of 60:30:10, and deionized water is added to disperse them evenly to obtain a coating composition slurry. The remaining steps are the same as in Example 1-1.

[0105] Examples 1-6 to Examples 1-11

[0106] Adjust the type or quantity of fiber material in the coating composition slurry, wherein the mass ratio of the first inorganic ceramic and the first organic material contained in the fiber material is 1:1; or adjust the type or quantity of filler particles, wherein the mass ratio of the second inorganic ceramic and the second organic material contained in the filler particles is 1:1, thereby obtaining the corresponding coating composition slurry. Specific preparation parameters can be found in Table 1. The remaining steps are the same as in Examples 1-1.

[0107] Examples 1-12 to Examples 1-15

[0108] The ratio of the length to the width of the fiber material is changed, and the remaining steps are the same as in Examples 1-2.

[0109] Examples 1-16 to Examples 1-23

[0110] The types of fiber materials and filler particles in the coating composition were changed, and the mass ratio of impurities was also changed. The remaining steps were the same as in Examples 1-1.

[0111] Examples 1-24 to Examples 1-29

[0112] The length of the fiber material is changed, and the remaining steps are the same as in Examples 1-18.

[0113] Examples 1-30 to Examples 1-34

[0114] The types of fiber materials and filler particles in the coating composition were changed, and the particle size Dv50 of the filler particles was also changed. The remaining steps were the same as in Example 1-1.

[0115] Examples 1-35

[0116] The type of adhesive is changed, and the remaining steps are the same as in Example 1-1.

[0117] Examples 2-1 to 2-8

[0118] The thickness of the coating or the porosity of the diaphragm can be changed, and the remaining steps are the same as in Example 1-1.

[0119] Comparative Example 1

[0120] The difference between Comparative Example 1 and Example 1-1 is that: the solid electrolyte Li 1.3 Al 0.3 Ti 1.7 (PO4)3 particles and styrene-butadiene rubber (SBR) binder are mixed at a mass ratio of 90:10, and deionized water is added to disperse them evenly to obtain a coating composition slurry. The remaining steps are the same as in Examples 1-1.

[0121] Comparative Example 2

[0122] The difference between Comparative Example 2 and Example 1-1 is that melamine cyanurate particles and styrene-butadiene rubber (SBR) adhesive were mixed at a mass ratio of 90:10, and deionized water was added to disperse them evenly to obtain a coating composition slurry. The remaining steps were the same as in Example 1-1.

[0123] Comparative Example 3

[0124] The difference between Comparative Example 3 and Examples 1-1 is that melamine cyanurate fiber and styrene-butadiene rubber adhesive were mixed at a mass ratio of 90:10, and deionized water was added to disperse them evenly to obtain a coating composition slurry. The remaining steps were the same as in Examples 1-1.

[0125] Comparative Example 4

[0126] The difference between Comparative Example 4 and Examples 1-1 is that boehmite filler, alumina fiber, and styrene-butadiene rubber binder were mixed in a mass ratio of 60:30:10, and deionized water was added to disperse the mixture evenly to obtain a coating composition slurry. The remaining steps were the same as in Examples 1-1.

[0127] Relevant tests on coating compositions:

[0128] (1) Content of impurities

[0129] The separator was removed from the lithium-ion battery, specifically from the head, tail, or superanode region where it was not bonded to the electrode and the coating had not transferred to the electrode surface. The separator was cleaned with NMP to remove electrolyte and residual lithium salts, and the coating was detached from the base film surface and dried. Elemental analysis was used to determine the quantitative carbon and nitrogen content in the coating.

[0130] (2) Length and width of fiber material

[0131] The separator was removed from the lithium-ion battery. Separators were selected from the head, tail, or superanode region of the battery, where they were not bonded to the electrodes and the coating had not transferred to the electrode surface. The separator was cleaned with NMP to remove electrolyte and residual lithium salts. Morphological images of the separator coating were obtained using scanning electron microscopy. Thirty fiber materials were outlined with a rectangular frame, and their lengths and widths were calculated as averages to obtain the length and width of the fiber materials.

[0132] (3) Particle size of filler particles Dv50

[0133] The coating was removed from the lithium-ion battery, cleaned with NMP to remove electrolyte and residual lithium salt, dried, and then dispersed in deionized water to obtain a suspension of particles. The filler Dv50 was measured using a laser particle size analyzer.

[0134] Relevant performance tests of the diaphragm

[0135] (1) Test method for heat retention rate:

[0136] The dimensional changes of the diaphragm coated with the coating composition were detected at rated temperature and time.

[0137] The diaphragm is cut to its rated size, with a length of A0 and a width of B0. The diaphragm is then placed in a forced-air drying oven at 130°C and left to stand for 1 hour. The length A1 and width B1 of the diaphragm are measured using a microscope. The length and width retention rates of the diaphragm are obtained according to the following formulas.

[0138] Length heat retention rate = A1 / A0 * 100%

[0139] Width heat retention rate = B1 / B0 * 100%

[0140] (2) Method for testing the porosity of the diaphragm:

[0141] The gas displacement method was used, and the testing instrument was a true density meter (AccuPyc II1340). The diaphragm was cut to the rated size with a length of A0, a width of B0, and a thickness of C0. The volume of the diaphragm, V0, was calculated as A0*B0*C0. The diaphragm was then placed in the true density meter, and the actual volume was measured as V1.

[0142] The porosity of the membrane = (V0 - V1) / V1 * 100%

[0143] (3) Diaphragm impedance test method:

[0144] EIS impedance test

[0145] (a) Before measuring EIS, symmetrical cells with different numbers of membrane layers were placed in a high and low temperature chamber at 0°C for half an hour, and the EIS impedance spectrum at the set temperature of 0°C was measured.

[0146] (b) The EIS conditions were set to 1MHz-1kHz, the perturbation voltage was set to 5mV, the test was completed, and the data were linearly fitted to obtain the ion impedance of the membrane.

[0147] (4) Test methods for coating thickness and diaphragm thickness:

[0148] The separator was removed from the lithium-ion battery, rinsed with NMP to remove the electrolyte and lithium salt, dried at 60°C, and the separator cross-section was plasma-cut. The cross-sectional morphology of the separator was obtained by scanning electron microscopy (SEM), and the thickness of the coating and base film layers was measured.

[0149] Performance testing of lithium-ion batteries

[0150] (1) Thermal safety performance test:

[0151] At room temperature, the lithium-ion battery is charged at a constant current of 0.5C until the voltage exceeds 4.45V, and then further charged at a constant voltage of 4.45V until the current drops below 0.05C. At this point, the lithium-ion battery is fully charged. The lithium-ion battery is then placed in an oven and heated at a rate of 10℃ / min until a specific temperature is reached, such as 130℃. This temperature is maintained for one hour. If the lithium-ion battery does not catch fire or explode, it has passed this temperature test. The specific temperature is then increased in increments of 2℃, and the lithium-ion battery is tested again at this temperature to see if it passes. This process continues until the thermal runaway temperature of the lithium-ion battery is determined.

[0152] (2) Low-temperature impedance test:

[0153] The lithium-ion battery was left to stand at 0°C for 30 minutes to reach a constant temperature state. It was then charged at a constant current of 1C until the voltage reached 4.45V, and then charged at a constant voltage until the current reached 0.05C to reach a fully charged state. The DC impedance of the lithium-ion battery was then measured.

[0154] (3) High-temperature cycling test:

[0155] The lithium-ion battery was left to stand at 45°C for 30 minutes to reach a constant temperature state. It was then charged at a constant current of 1C until the voltage reached 4.45V, then charged at a constant voltage until the current reached 0.05C, and then discharged at a constant current of 1C until the voltage reached 3.0V. The discharge capacity at this point was recorded as C0. The cycle test was repeated 100 times, and the discharge capacity at the 100th cycle was recorded as C1.

[0156] Capacity retention rate = C1 / C0 * 100%

[0157] (4) 2C discharge rate performance test:

[0158] The lithium-ion battery was left to stand at 25°C for 30 minutes to reach a constant temperature state. It was then charged at a constant current of 1C until the voltage reached 4.45V, charged at a constant voltage until the current reached 0.05C, and discharged at a constant current of 0.2C until the voltage reached 3.0V. The discharge capacity at this point was recorded as C0. Next, it was charged at a constant current of 1C until the voltage reached 4.45V, charged at a constant voltage until the current reached 0.05C, and then discharged at a constant current of 2C until the voltage reached 3.0V. The discharge capacity at this point was recorded as C1. The 2C discharge rate performance = C1 / C0 * 100%.

[0159] (5) Compression test:

[0160] The lithium-ion battery was left to stand at 25°C for 30 minutes to reach a constant temperature state. It was then charged at a constant current of 1C until the voltage reached 4.45V, and then charged at a constant voltage until the current reached 0.05C.

[0161] In a 25℃ testing environment, the lithium-ion battery was placed on the test platform. A blunt nail with a diameter of 6mm was used, and the falling speed was 300N / min. The test was conducted from the nickel tab of the sample (starting from the head step, 10±1mm from the top edge of the main body) until the lithium-ion battery exploded and caught fire. The compressive force at this time was recorded.

[0162] Referring to Figures 2 and 3, in the scanning electron microscope of the coating prepared in Example 1-1, the fiber material in the above coating composition exhibits a rod-like structure, the fiber material and filler particles are evenly distributed, and the filler particles fill the spaces between the fiber materials.

[0163] Referring to Figure 4, in the scanning electron microscope of the coatings prepared in Examples 1-2, the fiber material exhibits a columnar structure with filler particles filling the spaces between the fibers.

[0164] Referring to Figure 5, in the scanning electron microscope of the coating prepared in Comparative Example 2, the surface of the coating is dense, smooth, with few pores, and no fibrous material is present.

[0165] The lithium-ion batteries prepared in the above embodiments and comparative examples were subjected to the above performance tests, and the test data are recorded in the table below.

[0166] Table 1

[0167] Table 2

[0168] As can be seen from Tables 1 and 2, compared to Comparative Examples 1 to 3, the coating compositions in Examples 1-1 to 1-11 contain fibrous materials and filler particles. When applied to the separator, these improve the thermal safety performance of the separator. Furthermore, when the prepared separator is applied to a lithium-ion battery, the lithium-ion battery exhibits good rate performance, thermal safety performance, high-temperature cycle performance, and extrusion resistance, while also reducing the low-temperature impedance of the lithium-ion battery. Compared to Comparative Example 4, in Examples 1-1 to 1-11, the presence of impurity elements in the coating compositions significantly improves the rate performance, thermal safety performance, and high-temperature cycle performance of the lithium-ion battery.

[0169] Table 3

[0170] Table 3 shows that changing the length-to-width ratio of the fiber material, within the aforementioned suitable range, is beneficial for further improving the high-temperature performance and thermal safety performance of lithium-ion batteries, and also for reducing the low-temperature impedance of lithium-ion batteries.

[0171] Table 4

[0172] Table 5

[0173] In Table 5, in Examples 1-16 to 1-23, the mass ratio of impurity elements was changed. When the mass ratio of impurity elements was within a suitable range, the separator had a good high-temperature heat retention rate, and the assembled lithium-ion battery had good rate performance, thermal safety performance, and mechanical crush resistance.

[0174] Table 6

[0175] Table 7

[0176] As shown in Tables 6 and 7, when the fiber material length is adjusted to a suitable range, the separator also exhibits good high-temperature heat retention. When applied to lithium-ion batteries, the lithium-ion batteries also demonstrate good rate performance, thermal safety performance, and mechanical extrusion resistance. When the fiber material length is between 2 μm and 50 μm, the lithium-ion battery can also maintain excellent rate performance, thermal safety performance, and mechanical extrusion resistance.

[0177] Table 8

[0178] Table 9

[0179] As can be seen from Tables 8 and 9 above, when the particle size Dv50 of the filler particles is within a suitable range, the separator also has a good heat retention rate. When applied to lithium-ion batteries, the lithium-ion batteries also have good rate performance, thermal safety performance and mechanical extrusion resistance.

[0180] When the type of binder in the coating composition is changed, the separator also has good heat retention. When applied to lithium-ion batteries, the lithium-ion batteries also have excellent rate performance, thermal safety performance, and mechanical extrusion resistance.

[0181] Table 10

[0182] Table 10 shows that by changing the coating thickness, the separator also exhibits good high-temperature heat retention and low impedance. When applied to lithium-ion batteries, the lithium-ion batteries also exhibit good rate performance, thermal safety performance, mechanical extrusion resistance, and low impedance performance.

[0183] By adjusting the mass ratio of the fiber material and filler particles to the binder, and adjusting the porosity of the separator, lithium-ion batteries exhibit good rate performance, thermal safety performance, mechanical extrusion resistance, and low impedance performance when applied to lithium-ion batteries.

[0184] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with this application are still within the scope of this application.

Claims

1. A coating composition, characterized in that, The coating composition includes fiber material, filler particles, and binder. The fiber material comprises at least one of a first inorganic ceramic or a first organic compound containing a heterogeneous element. The filler particles comprise at least one of a second inorganic ceramic or a second organic compound containing a heterogeneous element. At least one of the fiber material and the filler particles is an organic compound containing the heterogeneous element, which includes nitrogen and / or phosphorus. The heterogeneous element accounts for 10% to 60% of the mass percentage based on the mass of the coating composition.

2. The coating composition according to claim 1, characterized in that, The coating composition satisfies at least one of the following conditions: (1) The length to width ratio of the fiber material is (3-50):1; (2) The length of the fiber material is from 2 μm to 50 μm; (3) The particle size Dv50 of the filler particles is 0.1 μm to 3 μm; (4) The mass ratio of the fiber material to the filler particles is 1:(1~10); (5) Based on the mass of the coating composition, the mass percentage of the impurity element is 16.5% to 45%; (6) In the coating composition, the mass ratio of the sum of the mass of the fiber material and the mass of the filler particles to the mass of the binder is 99:1 to 85:

15.

3. The coating composition according to claim 1 or 2, characterized in that, The first organic compound includes at least one of ammonium polyphosphate, dicyandiamide, piperazine pyrophosphate, melamine polyphosphate, polyacrylonitrile, melamine, melamine thiocyanate, or melamine cyanurate.

4. The coating composition according to any one of claims 1 to 3, characterized in that, The first inorganic ceramic includes at least one of lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum zirconium oxide, alumina, boehmite, titanium dioxide, aluminum silicate, silicon carbide, and silicon nitride.

5. The coating composition according to any one of claims 1 to 4, characterized in that, The second organic compound includes at least one of polyacrylonitrile, ammonium polyphosphate, melamine, dicyandiamide, melamine cyanurate, melamine trithiocyanate, or melamine polyphosphate.

6. The coating composition according to any one of claims 1 to 5, characterized in that, The second inorganic ceramic includes at least one of lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium niobium oxide, alumina, boehmite, or magnesium hydroxide.

7. The coating composition according to any one of claims 1 to 6, characterized in that, The adhesive includes at least one of polyacrylic acid, polyacrylate, polyvinylidene fluoride, styrene-butadiene rubber, isocyanate, polyvinyl alcohol, or sodium carboxymethyl cellulose.

8. The coating composition according to any one of claims 1 to 7, characterized in that, The mass percentage of the impurity element is between 16.5% and 40.2%.

9. The coating composition according to any one of claims 1 to 7, characterized in that, The mass percentage of the impurity element is between 22.5% and 60%.

10. The coating composition according to any one of claims 1 to 9, characterized in that, The fiber material comprises the first inorganic ceramic and the first organic material, and the filler particles comprise the second organic material.

11. The coating composition according to any one of claims 1 to 9, characterized in that, The fiber material includes the first organic material, and the filler particles include the second inorganic ceramic.

12. A diaphragm, characterized in that, The diaphragm includes a base membrane and a coating on at least one surface of the base membrane, the coating comprising a coating composition as described in any one of claims 1 to 11.

13. The diaphragm as claimed in claim 12, characterized in that, The diaphragm satisfies at least one of the following conditions: (1) The porosity of the diaphragm is 35% to 50%; (2) The thickness of the coating is 0.3 μm to 5 μm.

14. An electrochemical device comprising a positive electrode and a negative electrode, characterized in that, The electrochemical device further includes a membrane as described in claim 12 or 13, the membrane being located between the positive electrode and the negative electrode.

15. An electronic device, characterized in that, Includes the electrochemical device as described in claim 14.

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