Separators, electrochemical devices including the same, and electronic devices

Abstract

This application discloses a separator and an electrochemical and electronic device comprising the same. The separator includes a base membrane, on at least one surface of which are provided a first coating, a second coating, and a third coating. The first coating is located between the base membrane and the second coating, and the second coating is located between the first and third coatings. The first coating comprises a ceramic material, the second coating comprises a lithium-carbon material and fast-ion conductor nanowires, and the third coating comprises a polymer. The average thickness of the first coating is a μm, the average thickness of the second coating is b μm, and the lithium-carbon material loading in the second coating is c mg / cm³. 2 The fast ion conductor nanowire has an ionic conductivity of d S / cm, and the third coating has a porosity of e, with a value of 0.1 ≤ a × b × c × d × e ≤ 2.1. The membrane structure of this application, with the formula 0.1 ≤ a × b × c × d × e ≤ 2.1, can simultaneously improve the initial coulombic efficiency and cycle capacity retention of the electrochemical device.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and more specifically, to diaphragms and electrochemical and electronic devices comprising them. Background Technology

[0002] Silicon anodes, as anode materials in electrochemical devices such as lithium-ion batteries, offer up to eight times higher theoretical energy density compared to traditional graphite anodes, demonstrating excellent application potential. However, the use of silicon anodes leads to excessive loss of active lithium in these devices, reducing the initial coulombic efficiency (ICE). Furthermore, during cycling, silicon anodes cause continuous and irreversible loss of active lithium, decreasing the cycle capacity retention rate of these devices.

[0003] Therefore, it is of great significance to develop membranes that can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of electrochemical devices. Summary of the Invention

[0004] The purpose of this application is to solve the problem of simultaneously improving the first coulombic efficiency (ICE) and cycle capacity retention of electrochemical devices, and to provide a diaphragm and an electrochemical device and electronic device comprising the diaphragm.

[0005] To achieve the above objectives, this application provides a diaphragm, including a base membrane, on at least one surface of which a first coating, a second coating, and a third coating are provided; the first coating is located between the base membrane and the second coating, and the second coating is located between the first coating and the third coating; the first coating includes a ceramic material, the second coating includes a lithium-containing carbon material and fast ion conductor nanowires, and the third coating includes a polymer; The average thickness of the first coating is a μm, the average thickness of the second coating is b μm, and the lithium-carbon material loading in the second coating is c mg / cm³. 2 The ionic conductivity of the fast ion conductor nanowire is d S / cm, and the porosity of the third coating is e, 0.1≤a×b×c×d×e≤2.1.

[0006] When the membrane with a specific structure in this application is matched with the formula "0.1≤a×b×c×d×e≤2.1", the interfacial stability and ion transport kinetics of the electrochemical device are synergistically optimized, which can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device.

[0007] Specifically, when a, b, c, d, and e satisfy the formula "0.1≤a×b×c×d×e≤2.1", the lithium-containing carbon material in the second coating can effectively replenish the active lithium consumed during the first charge and discharge process due to the formation of the solid electrolyte interphase (SEI) film, thereby improving the first coulombic efficiency of the electrochemical device. At the same time, the fast ion conductor nanowires and the third coating work together to construct a stable and efficient lithium-ion transport channel, reducing electrode polarization and active material loss during cycling, and thus significantly improving the cycle capacity retention rate of the electrochemical device.

[0008] In some implementations, 0.6 ≤ a × b × c × d × e ≤ 1.4.

[0009] In some implementations, 5 ≤ a ≤ 20.

[0010] In some implementations, 3 ≤ b ≤ 10.

[0011] In some implementations, 1 ≤ c ≤ 2.

[0012] In some implementations, 0.0040 ≤ d ≤ 0.0060.

[0013] In some implementations, 0.65 ≤ e ≤ 0.85.

[0014] In some embodiments, the base film is made of at least one of polyethylene (PE), polypropylene (PP), polyimide (PI), polyphenylene sulfide, aramid, polyethylene terephthalate (PET), and polyether ether ketone (PEEK).

[0015] In some embodiments, the average thickness of the base film is 1-100 μm.

[0016] In some embodiments, the ceramic material includes at least one of alumina, silicon oxide, zirconium oxide, magnesium oxide, titanium oxide, aluminum nitride, and boehmite.

[0017] In some embodiments, the average particle size Dv50 of the ceramic material is 100-500 nm.

[0018] In some embodiments, the first coating also includes a first adhesive.

[0019] In some implementations, the mass percentage of the first adhesive is 1%-5% based on the mass of the first coating.

[0020] In some embodiments, the first adhesive in the first coating includes at least one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), ethyl polyacrylate (PEA), polyvinyl alcohol (PVA), polyurethane (PU), sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0021] In some embodiments, the molar ratio of lithium to carbon in the lithium-containing carbon material is 1:(3-8).

[0022] In some embodiments, the molar ratio of lithium to carbon in the lithium-containing carbon material is 1:(5-8).

[0023] In some embodiments, the average particle size Dv50 of the lithium-carbon material is 20-130 nm.

[0024] In some embodiments, the average particle size Dv50 of the lithium-carbon material is 20-100 nm.

[0025] In some embodiments, the average particle size Dv50 of the lithium-carbon material is 30-70 nm.

[0026] In this application, by further controlling the average particle size Dv50 of the lithium-containing carbon material, its dispersibility in the coating and its contact area with the electrolyte can be optimized, and the stability of the material's own structure during cycling can be ensured, thereby further improving the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device simultaneously.

[0027] In some embodiments, the fast ion conductor nanowires include at least one of LLZO (lithium lanthanum zirconium oxide) nanowires, LLTO (lithium lanthanum titanium oxide) nanowires, and LLZTO (lithium lanthanum zirconium titanium oxide) nanowires.

[0028] In some implementations, the fast ion conductor nanowires have an average diameter of 10-120 nm.

[0029] In some implementations, the fast ion conductor nanowires have an average diameter of 10-100 nm.

[0030] In some implementations, the fast ion conductor nanowires have an average diameter of 20-60 nm.

[0031] In this application, by further controlling the average diameter of the fast ion conductor nanowires, a more optimized and robust three-dimensional ion conduction network can be constructed in the coating, effectively balancing its electronic insulation and structural strength, thereby further improving the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device simultaneously.

[0032] In some implementations, the average aspect ratio of the fast ion conductor nanowire is ≥25.

[0033] In some implementations, the average aspect ratio of the fast ion conductor nanowire is ≥30.

[0034] In some implementations, the average aspect ratio of the fast ion conductor nanowire is 30-300.

[0035] In some implementations, the average aspect ratio of the fast ion conductor nanowire is 50-150.

[0036] In some embodiments, the second coating also includes a second adhesive.

[0037] In some implementations, the mass percentage of the second adhesive is 1%-8% based on the mass of the second coating.

[0038] In some embodiments, the second adhesive in the second coating includes at least one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), ethyl polyacrylate (PEA), polyvinyl alcohol (PVA), polyurethane (PU), sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0039] In some embodiments, the polymer includes at least one of polyimide (PIA), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), aramid, polyvinyl alcohol (PVA), and polyurethane (PU).

[0040] In some implementations, the average thickness of the third coating is 2-6 μm.

[0041] This application also provides an electrochemical device comprising any of the diaphragms and negative electrodes described herein.

[0042] In some implementations, the negative electrode comprises a silicon-containing material.

[0043] In some embodiments, the silicon-containing material includes at least one of elemental silicon, silicon-carbon (Si-C) composite material, silicon-nitrogen (Si-N) composite material, silicon-oxygen (Si-O) composite material, and silicon alloy.

[0044] In some embodiments, the elemental silicon material includes at least one of amorphous silicon, porous silicon, crystalline silicon, and nano-silicon.

[0045] In some embodiments, the silicon-carbon (Si-C) composite material includes silicon carbide (SiC).

[0046] In some embodiments, the silicon-nitrogen (Si-N) composite material includes silicon nitride (Si3N4).

[0047] In some embodiments, the silicon-oxygen (Si-O) composite material includes silicon suboxide (SiO).

[0048] This application also provides an electronic device that includes the electrochemical device described above.

[0049] Compared with the prior art, the beneficial effects of this application are as follows: When the membrane with a specific structure in this application is matched with the formula "0.1≤a×b×c×d×e≤2.1", the interfacial stability and ion transport kinetics of the electrochemical device are synergistically optimized, which can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device.

[0050] Specifically, when a, b, c, d, and e satisfy the formula "0.1≤a×b×c×d×e≤2.1", the lithium-containing carbon material in the second coating can effectively replenish the active lithium consumed during the first charge and discharge process due to the formation of the solid electrolyte interphase (SEI) film, thereby improving the first coulombic efficiency of the electrochemical device. At the same time, the fast ion conductor nanowires and the third coating work together to construct a stable and efficient lithium-ion transport channel, reducing electrode polarization and active material loss during cycling, and thus significantly improving the cycle capacity retention rate of the electrochemical device. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] <General Definition> The term "polymer" refers to a polymeric compound prepared by polymerizing the same or different types of monomers. The general term "polymer" includes the terms "homopolymer," "copolymer," "trimer," and "interpolymer."

[0053] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0054] The term "porosity of the third coating" refers to the process of making at least five longitudinal cuts along the thickness direction of the third coating to obtain at least five flat cross-sections; then, calculating the ratio of the pore area of ​​the third coating to the cross-sectional area of ​​the third coating in each cross-section, and taking the arithmetic mean, which is the "porosity of the third coating".

[0055] The term "load of lithium-carbon material in the second coating" refers to the mass of lithium-carbon material per square centimeter of the second coating.

[0056] The term "ionic conductivity of fast ion conductor nanowires" refers to the ionic conductivity of fast ion conductor nanowires measured at 25°C, a frequency of 1MHz-0.1Hz, and a signal amplitude of 5mV.

[0057] The term "average particle size Dv50" refers to the particle size value that corresponds to a cumulative volume percentage of 50% in a particle group.

[0058] The term "average aspect ratio of fast ion conductor nanowires" refers to the ratio of the average length to the average diameter of fast ion conductor nanowires.

[0059] The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0060] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0061] In this application, a list of items connected by the term "at least one of" can 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" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and 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.

[0062] In the following description, all figures disclosed in this application are approximate values, regardless of whether the terms "about" or "approximately" are used in conjunction. They may vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a range of values ​​with a lower limit (RL) and an upper limit (RU) is disclosed, any values ​​falling within that range are specifically disclosed. Specifically, the following values ​​within this range are specifically disclosed: R = RL + k * (RU - RL), where k is a variable with a 1% increment from 1% to 100%, i.e., k is 1%, 2%, 3%, 4%, 5%, ..., 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any range of values ​​defined by the two R values ​​as defined above are also specifically disclosed.

[0063] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated.

[0064] Throughout this specification, references to "implementation," "partial implementation," "one implementation," "some implementations," "another implementation," "specific implementation," or "partial implementation" mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment.

[0065] I. Diaphragm This application provides a diaphragm, including a base membrane, on at least one surface of which a first coating, a second coating, and a third coating are provided; the first coating is located between the base membrane and the second coating, and the second coating is located between the first coating and the third coating; the first coating includes a ceramic material, the second coating includes a lithium-carbon material and fast ion conductor nanowires, and the third coating includes a polymer; The average thickness of the first coating is a μm, the average thickness of the second coating is b μm, and the lithium-carbon material loading in the second coating is c mg / cm³. 2 The ionic conductivity of the fast ion conductor nanowire is d S / cm, and the porosity of the third coating is e, 0.1≤a×b×c×d×e≤2.1.

[0066] When the membrane with a specific structure in this application is matched with the formula "0.1≤a×b×c×d×e≤2.1", the interfacial stability and ion transport kinetics of the electrochemical device are synergistically optimized, which can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device.

[0067] Specifically, when a, b, c, d, and e satisfy the formula "0.1≤a×b×c×d×e≤2.1", the lithium-containing carbon material in the second coating can effectively replenish the active lithium consumed during the first charge and discharge process due to the formation of the solid electrolyte interphase (SEI) film, thereby improving the first coulombic efficiency of the electrochemical device. At the same time, the fast ion conductor nanowires and the third coating work together to construct a stable and efficient lithium-ion transport channel, reducing electrode polarization and active material loss during cycling, and thus significantly improving the cycle capacity retention rate of the electrochemical device.

[0068] In this application, the ionic conductivity of the fast ion conductor nanowire is the ionic conductivity of the fast ion conductor nanowire measured at 25°C, a frequency of 1MHz-0.1Hz, and a signal amplitude of 5mV.

[0069] In some implementations, a×b×c×d×e can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, 2.04, 2.05, or 2.1, or fall within the range of any two of the above values.

[0070] In some implementations, 0.6 ≤ a × b × c × d × e ≤ 1.4.

[0071] In some implementations, 5 ≤ a ≤ 20. For example, a can be 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, or 20, or fall within the range of any two of the above values.

[0072] In some implementations, 3 ≤ b ≤ 10. For example, b can be 3, 3.2, 3.5, 3.7, 4, 4.2, 4.5, 4.7, 5, 5.2, 5.5, 5.7, 6, 6.2, 6.5, 6.7, 7, 7.2, 7.5, 7.7, 8, 8.2, 8.5, 8.7, 9, 9.2, 9.5, 9.7 or 10, or fall within the range of any two of the above values.

[0073] In some implementations, 1 ≤ c ≤ 2. For example, c can be 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95 or 2, or fall within the range of any two of the above values.

[0074] In some implementations, 0.0040 ≤ d ≤ 0.0060. For example, d can be 0.0040, 0.0041, 0.0042, 0.0043, 0.0044, 0.0045, 0.0046, 0.0047, 0.0048, 0.0049, 0.0050, 0.0051, 0.0052, 0.0053, 0.0054, 0.0055, 0.0056, 0.0057, 0.0058, 0.0059, or 0.0060, or fall within the range of any two of the above values.

[0075] In some implementations, 0.65 ≤ e ≤ 0.85. For example, e can be 0.65, 0.66, 0.67, 0.68, 0.69, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8, 0.81, 0.82, 0.83, 0.84, or 0.85, or fall within the range of any two of the above values.

[0076] In some embodiments, the base film is made of at least one of polyethylene (PE), polypropylene (PP), polyimide (PI), polyphenylene sulfide, aramid, polyethylene terephthalate (PET), and polyether ether ketone (PEEK).

[0077] In some embodiments, the average thickness of the base film is 1-100 μm. Exemplarily, the average thickness of the base film is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm, or falls within the range of any two of the above values.

[0078] In some embodiments, the ceramic material includes at least one of alumina, silicon oxide, zirconium oxide, magnesium oxide, titanium oxide, aluminum nitride, and boehmite.

[0079] In some embodiments, the average particle size Dv50 of the ceramic material is 100-500 nm. For example, the average particle size Dv50 of the ceramic material can be 100 nm, 120 nm, 130 nm, 150 nm, 170 nm, 180 nm, 200 nm, 220 nm, 230 nm, 250 nm, 270 nm, 280 nm, 300 nm, 320 nm, 330 nm, 350 nm, 370 nm, 380 nm, 400 nm, 420 nm, 430 nm, 450 nm, 470 nm, 480 nm, or 500 nm, or fall within the range of any two of the above values.

[0080] In some embodiments, the first coating also includes a first adhesive.

[0081] In some embodiments, the mass percentage of the first adhesive is 1%-5% based on the mass of the first coating. For example, the mass percentage of the first adhesive, based on the mass of the first coating, can be 1%, 1.2%, 1.3%, 1.5%, 1.7%, 1.8%, 2%, 2.2%, 2.3%, 2.5%, 2.7%, 2.8%, 3%, 3.2%, 3.3%, 3.5%, 3.7%, 3.8%, 4%, 4.2%, 4.3%, 4.5%, 4.7%, 4.8%, 4.9%, or 5%, or fall within the range of any two of the aforementioned values.

[0082] In some embodiments, the first adhesive in the first coating includes at least one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), ethyl polyacrylate (PEA), polyvinyl alcohol (PVA), polyurethane (PU), sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0083] In some embodiments, the molar ratio of lithium to carbon in the lithium-containing carbon material is 1:(3-8). For example, the molar ratio of lithium to carbon in the lithium-containing carbon material can be 1:3, 1:3.2, 1:3.5, 1:3.7, 1:4, 1:4.2, 1:4.5, 1:4.7, 1:5, 1:5.2, 1:5.5, 1:5.7, 1:6, 1:6.2, 1:6.5, 1:6.7, 1:7, 1:7.2, 1:7.5, 1:7.7, or 1:8, or fall within the range of any two of the above values.

[0084] In some embodiments, the molar ratio of lithium to carbon in the lithium-containing carbon material is 1:(5-8).

[0085] In some embodiments, the average particle size Dv50 of the lithium-carbon material is 20-130 nm. For example, the average particle size Dv50 of the lithium-carbon material can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, or 130 nm, or fall within the range of any two of the above values.

[0086] In some embodiments, the average particle size Dv50 of the lithium-carbon material is 20-100 nm.

[0087] In some embodiments, the average particle size Dv50 of the lithium-carbon material is 30-70 nm.

[0088] In this application, by further controlling the average particle size Dv50 of the lithium-containing carbon material, its dispersibility in the coating and its contact area with the electrolyte can be optimized, and the stability of the material's own structure during cycling can be ensured, thereby further improving the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device simultaneously.

[0089] In some embodiments, the fast ion conductor nanowires include at least one of LLZO (lithium lanthanum zirconium oxide) nanowires, LLTO (lithium lanthanum titanium oxide) nanowires, and LLZTO (lithium lanthanum zirconium titanium oxide) nanowires.

[0090] In some embodiments, the average diameter of the fast ion conductor nanowire is 10-120 nm. Exemplarily, the average diameter of the fast ion conductor nanowire can be 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, or 120 nm, or fall within the range of any two of the aforementioned values.

[0091] In some implementations, the fast ion conductor nanowires have an average diameter of 10-100 nm.

[0092] In some implementations, the fast ion conductor nanowires have an average diameter of 20-60 nm.

[0093] In this application, by further controlling the average diameter of the fast ion conductor nanowires, a more optimized and robust three-dimensional ion conduction network can be constructed in the coating, effectively balancing its electronic insulation and structural strength, thereby further improving the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device simultaneously.

[0094] In some embodiments, the average aspect ratio of the fast ion conductor nanowire is ≥25. Exemplarily, the average aspect ratio of the fast ion conductor nanowire can be 25, 30, 40, 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, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, or 400, or fall within a range of any two of the above values.

[0095] In some implementations, the average aspect ratio of the fast ion conductor nanowire is ≥30.

[0096] In some implementations, the average aspect ratio of the fast ion conductor nanowire is 30-300.

[0097] In some implementations, the average aspect ratio of the fast ion conductor nanowire is 50-150.

[0098] In some embodiments, the second coating also includes a second adhesive.

[0099] In some embodiments, the mass percentage of the second adhesive is 1%-8% based on the mass of the second coating. For example, the mass percentage of the second adhesive, based on the mass of the second coating, can be 1%, 1.2%, 1.3%, 1.5%, 1.7%, 1.8%, 2%, 2.2%, 2.3%, 2.5%, 2.7%, 2.8%, 3%, 3.2%, 3.3%, 3.5%, 3.7%, 3.8%, 4%, 4.2%, 4.3%, 4.5%, 4.7%, 4.8%, 4.9%, 5%, 5.2%, 5.3%, 5.5%, 5.7%, 5.8%, 6%, 6.2%, 6.3%, 6.5%, 6.7%, 6.8%, 7%, 7.2%, 7.3%, 7.7%, 7.8%, or 8%, or fall within the range of any two of the aforementioned values.

[0100] In some embodiments, the second adhesive in the second coating includes at least one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), ethyl polyacrylate (PEA), polyvinyl alcohol (PVA), polyurethane (PU), sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0101] In some embodiments, the polymer includes at least one of polyimide (PIA), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), aramid, polyvinyl alcohol (PVA), and polyurethane (PU).

[0102] In some embodiments, the average thickness of the third coating is 2-6 μm. Exemplarily, the average thickness of the third coating can be 2 μm, 2.2 μm, 2.3 μm, 2.5 μm, 2.7 μm, 2.8 μm, 3 μm, 3.2 μm, 3.3 μm, 3.5 μm, 3.7 μm, 3.8 μm, 4 μm, 4.2 μm, 4.3 μm, 4.5 μm, 4.7 μm, 4.8 μm, 5 μm, 5.2 μm, 5.3 μm, 5.5 μm, 5.7 μm, 5.8 μm, or 6 μm, or fall within the range of any two of the above values.

[0103] II. Electrochemical Device This application also provides an electrochemical device comprising any of the diaphragms described herein.

[0104] In this application, the electrochemical device includes any device in which an electrochemical reaction occurs to convert chemical energy into electrical energy and vice versa. Specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0105] In some embodiments, the electrochemical device also includes a positive electrode, a negative electrode, and an electrolyte.

[0106] 1. Positive electrode In some embodiments, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector.

[0107] In some embodiments, the positive current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is aluminum foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate. In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, activated carbon, and mesoporous carbon.

[0108] In some embodiments, the positive electrode active material layer may include a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent.

[0109] In some embodiments, the positive electrode active material is selected from LiCoO2, LiNiO2, and LiNi x Mn y O2, Li 1+ z Ni x Mn y Co 1-x-y O2, LiNi x Co y Al z The group consisting of O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, LiMnPO4, and combinations thereof, wherein each x is independently 0.2 to 0.9; each y is independently 0.1 to 0.45; and each z is independently 0 to 0.2. The positive electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as positive electrode active materials.

[0110] In some embodiments, the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF), poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone (PVP), acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer. The positive electrode binder of this application is not limited to the above materials, but also includes other materials that can be used as battery positive electrode binders.

[0111] In some embodiments, the positive electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The positive electrode conductive agent in this application is not limited to the above materials, but also includes other materials that can be used as positive electrode conductive agents in batteries.

[0112] 2. Negative electrode In some implementations, the negative electrode comprises a silicon-containing material.

[0113] In some embodiments, the silicon-containing material includes at least one of elemental silicon, silicon-carbon (Si-C) composite material, silicon-nitrogen (Si-N) composite material, silicon-oxygen (Si-O) composite material, and silicon alloy.

[0114] In some embodiments, the elemental silicon material includes at least one of amorphous silicon, porous silicon, crystalline silicon, and nano-silicon.

[0115] In some embodiments, the silicon-carbon (Si-C) composite material includes silicon carbide (SiC).

[0116] In some embodiments, the silicon-nitrogen (Si-N) composite material includes silicon nitride (Si3N4).

[0117] In some embodiments, the silicon-oxygen (Si-O) composite material includes silicon suboxide (SiO).

[0118] In some embodiments, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector.

[0119] In some embodiments, the negative current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is a copper foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate.

[0120] In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0121] In some embodiments, the negative electrode active material layer may include a silicon-containing material, a negative electrode binder, and a negative electrode conductive agent.

[0122] In some embodiments, the negative electrode binder may include at least one of polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryloyl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylic acid ester, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene. The negative electrode binder of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode binders.

[0123] In some embodiments, the negative electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The negative electrode conductive agent of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode conductive agents.

[0124] 3. Electrolytes In some embodiments, the electrolyte may include at least one of a gel electrolyte, a solid electrolyte, and a liquid electrolyte.

[0125] In some embodiments, the liquid electrolyte may include a non-aqueous solvent and a lithium salt.

[0126] In some embodiments, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate.

[0127] In some embodiments, the non-aqueous solvent may be at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds.

[0128] In some embodiments, the carbonate compound may include at least one of chain carbonate compounds, cyclic carbonate compounds, and fluorocarbonate compounds.

[0129] In some embodiments, the chain carbonate compound may include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and methyl ethyl carbonate (MEC).

[0130] In some embodiments, the cyclic carbonate compound may include at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), and vinylene carbonate (VC).

[0131] In some embodiments, the fluorocarbonate compound may include at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0132] In some embodiments, the carboxylic acid ester compound may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate (PP), γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonate lactone, caprolactone, and methyl formate.

[0133] In some embodiments, the ether compound may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

[0134] In some embodiments, the non-aqueous solvent may also include at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0135] III. Electronic Devices This application also provides an electronic device that includes the electrochemical device described above.

[0136] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. The electrochemical device described in this application is also not particularly limited in its use and can be used in any electronic device known in the prior art. According to some embodiments of this application, the electronic device includes, but is not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, and android robots.

[0137] IV. Testing Methods 1. Average thickness test of the first, second, or third coating. At least five plasma longitudinal cuts are performed along the thickness direction of the first, second, or third coating. The cuts are then polished using argon ion polishing technology to obtain at least five flat cross-sections. The cross-sections are then observed using a transmission electron microscope (TEM) to measure the thickness of the first, second, or third coating. The arithmetic mean of the measured values ​​is taken as the average thickness of the first, second, or third coating.

[0138] 2. Testing of the loading of lithium-carbon materials in the second coating (1) Preparation of independent coated samples: Referring to the preparation method of the diaphragm in Example 1, sample A with only a first coating on the base membrane, sample B with both a first and a second coating on the base membrane, and sample C with a first, a second, and a third coating on the base membrane (i.e., the diaphragm of Example 1) were prepared respectively. The first coating thickness of samples A, B, and C was the same, and the second coating thickness of samples B and C was the same. Then, five sections with an area of ​​S (unit: cm²) were cut from each of the base membrane, samples A, B, and C respectively. 2 The circular samples were designated as base film circular sample, circular sample A, circular sample B, and circular sample C, respectively. (2) Accurate weighing: Using an analytical balance with an accuracy of 0.01 mg, weigh all the circular base film samples, circular sample A, and circular sample B obtained in step (1), and take the average value to obtain the mass M0 (unit: mg) of the circular base film sample and the mass M of circular sample A. A (Unit: mg), Mass M of circular sample B B (Unit: mg), and calculate different areal densities using the following formula: The surface density ρ of the first coating A (Unit: mg / cm³) 2 )=(M A -M0) / S; The total areal density ρ of the first and second coatings B (Unit: mg / cm³) 2 )=(M B -M0) / S; The areal density ρ2 of the second coating (unit: mg / cm³) 2 )= ρ B - ρ A ; (3) Calculate the mass fraction W of lithium-carbon material in the second coating: Carefully scrape 0.2g from the second coating of sample B prepared in step (1) to obtain the test sample of the second coating; measure the mass percentage L of lithium element in the test sample of the second coating using inductively coupled plasma optical emission spectrometry (ICP-OES), and then calculate the mass fraction W of lithium-containing carbon material in the second coating according to the molar ratio of lithium element to carbon element in lithium-containing carbon material (this molar ratio is obtained by the method of "testing the molar ratio of lithium element to carbon element in lithium-containing carbon material" below); (4) Calculate the loading of lithium-carbon material in the second coating: The lithium-carbon material loading in the second coating (unit: mg / cm³) 2 It is calculated using the following formula: The lithium-carbon material loading in the second coating (unit: mg / cm³) 2 =ρ2×W.

[0139] 3. Ionic conductivity test of fast ion conductor nanowires in the second coating The standard powder pressing and electrochemical impedance spectroscopy were used for testing. First, the fast-ion conductor nanowire powder was pressed into a dense, circular preform under a specific pressure of 300 MPa. Then, the preform was sintered at 900℃ to obtain a dense ceramic sheet for testing. Inert electrodes (such as gold electrodes) to block lithium ions were fabricated on both sides of the ceramic sheet using magnetron sputtering to obtain a symmetrical cell (Au|ceramic sheet|Au). Next, the prepared symmetrical cell (Au|ceramic sheet|Au) was placed in a test fixture, and electrochemical impedance spectroscopy was performed using an electrochemical workstation at a constant temperature of 25℃. The test frequency range was 1 MHz–0.1 Hz, and the signal amplitude was 5 mV. In the obtained impedance spectrum, the intercept in the high-frequency region intersecting the real axis represents the bulk resistance R of the ceramic sheet. b (Ω). By measuring the thickness L (cm) of the ceramic sheet and the electrode area A (cm²), the ionic conductivity d (S / cm) of the fast ion conductor nanowire can be obtained using the formula d = L / (R). b The result is obtained by calculating ×A).

[0140] 4. Porosity test of the third coating At least five plasma longitudinal cuts were performed along the thickness direction of the third coating, and polished using argon ion polishing technology to obtain at least five flat cross-sections. The cross-sections were then observed using a transmission electron microscope (TEM). At a magnification of 5000x, the ratio of the pore area of ​​the third coating to the cross-sectional area of ​​the third coating in each cross-section was calculated using image processing software ImageJ, and the arithmetic mean was taken as the "porosity of the third coating".

[0141] 5. Average particle size Dv50 test of ceramic materials At least five transverse cuts were made along the thickness direction of the first coating using a focused ion beam (FIB) to obtain at least five flat cross-sections. These cross-sections were then observed using a scanning electron microscope (SEM). A 30 μm × 30 μm test area was randomly selected from each cross-section, and the average particle size Dv50 of the ceramic material in the test area was measured. The arithmetic mean of the at least five cross-sections was then calculated, which is the average particle size Dv50 of the ceramic material in the first coating.

[0142] 6. Average particle size Dv50 test of lithium-containing carbon materials At least five transverse cuts were made along the thickness direction of the second coating using a focused ion beam (FIB) to obtain at least five flat cross-sections. These cross-sections were then observed using a scanning electron microscope (SEM). A 30 μm × 30 μm test area was randomly selected from each cross-section, and the average particle size Dv50 of the lithium-carbon material in the test area was measured. The arithmetic mean of the at least five cross-sections was then calculated, which is the average particle size Dv50 of the lithium-carbon material in the second coating.

[0143] 7. Test of the molar ratio of lithium to carbon in lithium-containing carbon materials Elemental analysis was used for testing. First, the mass percentage of lithium (Li) in the lithium-containing carbon material was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Simultaneously, the mass percentage of carbon (C) in the lithium-containing carbon material was determined using a carbon-sulfur analyzer. Then, based on the measured mass percentage of each element, the molar number of lithium and carbon elements was calculated by dividing by the molar mass of each element. The ratio of the two is the molar ratio of lithium to carbon in the lithium-containing carbon material.

[0144] 8. Measurement of average diameter and average aspect ratio of fast ion conductor nanowires Scanning electron microscopy (SEM) was used for observation and statistical analysis. At least 50 fast ion conductor nanowires with good morphology were randomly selected and photographed with SEM to obtain SEM images. The diameter and length of each fast ion conductor nanowire were measured and the arithmetic mean was taken to obtain the average diameter and average length of the fast ion conductor nanowire. The ratio of the average length to the average diameter is the average aspect ratio of the fast ion conductor nanowire.

[0145] 9. First Coulomb Efficiency (ICE) Test In a 25°C environment, the electrochemical device (lithium-ion secondary battery) was charged to 4.4V at a constant current and constant voltage of 0.5C, and then charged at a constant voltage until the current dropped to 0.05C. The initial charge capacity was recorded at this point. After resting for 5 minutes, it was discharged to 3.0V at a constant current of 0.1C, and the initial discharge capacity was recorded at this point. The initial coulombic efficiency (ICE) was calculated using the following formula: ICE (%) = Initial discharge capacity / Initial charge capacity × 100%.

[0146] 10. Cyclic capacity retention test In an environment of 25℃, the electrochemical device (lithium-ion secondary battery) was charged to 4.4V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C, and then discharged to 3.0V at a constant current of 1C. This cycle was repeated 100 times. The discharge capacity of the first cycle and the discharge capacity of the 100th cycle were recorded. The experiment was repeated 5 times, and the average value was taken. The cycle capacity retention rate (%) was calculated according to the following formula: Cycle capacity retention (%) = (average discharge capacity at the 100th cycle / average discharge capacity at the first cycle) × 100%.

[0147] V. Examples It should be noted that, in the specific embodiments of this application, lithium-ion secondary batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion secondary batteries.

[0148] Unless otherwise specified, all reagents, materials, and instruments used in the following examples and comparative examples are commercially available. Furthermore, unless otherwise specified, "parts" and "%" refer to mass measurements.

[0149] In the following examples and comparative examples, the use of some reagents and materials is as follows: Carbon black, Ketjenblack EC-600JD, Lion brand; Polyvinylpyrrolidone (PVP), average molecular weight 1,300,000, P816208, Maclean; Alumina, 5-6μm, A800195, Maclean; Polyvinylidene fluoride (PVDF), 768739, McLean; Polyimide (PIA), P874997, McLean; Polyacrylonitrile, P750088, McLean; The base film is made of polyethylene and has a thickness of 5μm. It is manufactured by Shenzhen Xingyuan Material Technology Co., Ltd. Styrene-butadiene rubber, SBR1502, Jilin Petrochemical; Ethylene carbonate (EC), CAS No.: 96-49-1; Diethyl carbonate (DEC), CAS No.: 105-58-8; Propylene carbonate (PC), CAS No.: 108-32-7; Propyl propionate (PP), CAS No.: 106-36-5; Vinyl carbonate (VC), CAS No.: 872-36-6.

[0150] Example 1 This embodiment provides a diaphragm, including a base membrane, on one surface of which are disposed a first coating, a second coating, and a third coating; the first coating is located between the base membrane and the second coating, and the second coating is located between the first coating and the third coating; the first coating includes a ceramic material (alumina) and a first binder (polyvinylidene fluoride, PVDF); the second coating includes a lithium-carbon material and fast ion conductor nanowires (LLZO nanowires) and a second binder (polyvinylidene fluoride, PVDF); and the third coating includes a polymer (polyimide, PIA). The average thickness of the first coating is a μm, where a = 17; the average thickness of the second coating is b μm, where b = 6; and the lithium-carbon material loading in the second coating is c mg / cm³. 2 c=1.5, the ionic conductivity of the fast ion conductor nanowire is d S / cm, d=0.0052, the porosity of the third coating is e, e=0.77, a×b×c×d×e=0.61; The base film is made of polyethylene and has an average thickness of 5μm; In the first coating, the ceramic material (alumina) has an average particle size Dv50 of 200 nm, which is obtained by grinding and crushing alumina (A800195, Maclean) with a particle size of 5-6 μm and then screening it; based on the mass of the first coating, the mass percentage of the first binder (PVDF) is 2%; In the second coating, the molar ratio of lithium to carbon in the lithium-containing carbon material is 1:6, the average particle size Dv50 of the lithium-containing carbon material is 70 nm, the average diameter of the fast ion conductor nanowires (LLZO nanowires) is 60 nm, the average length is 3000 nm, the average aspect ratio is 50, the mass ratio of the lithium-containing carbon material to the fast ion conductor nanowires is 1:1, and based on the mass of the second coating, the mass percentage of the second binder (PVDF) is 2%. The average thickness of the third coating is 3 μm.

[0151] This embodiment also provides a lithium-ion secondary battery (electrochemical device), the preparation method of which includes the following steps: 1. Preparation of the diaphragm (1) Preparation of lithium-containing carbon materials Under the protection of argon inert gas, carbon black (Ketjenblack EC-600JD, Lion King) was added to a 1.5 mol / L LiPF6 solution (solvent is ethylene carbonate), stirred and impregnated for 24 h, removed, cured at 60 °C for 12 h, and screened to obtain lithium-containing carbon material with an average particle size Dv50=70 nm for later use. The solid-liquid ratio of carbon black and LiPF6 solution is 1g:10mL.

[0152] (2) Preparation of fast ion conductor nanowires (LLZO nanowires) According to Li 6.25 La3Zr2Al 0.25 O 12 Weigh lithium nitrate, lanthanum nitrate, zirconium oxynitrate, and aluminum nitrate according to their stoichiometric ratios, and mix them to obtain an LLZO raw material mixture for later use; mix DMF (N,N-dimethylformamide) and ethanol at a volume ratio of 3:7 to obtain a mixed solvent for later use; The LLZO raw material mixture, polyvinylpyrrolidone (PVP) and mixed solvent were mixed in a mass ratio of 8:1:40 and magnetically stirred at 60°C for 12 h to obtain the precursor spinning solution. The precursor spinning solution was loaded into a plastic syringe, connected to a 23G stainless steel needle, and the pusher speed was set to 0.8 mL / h. A high voltage electric field of 20 kV was applied between the stainless steel needle and the grounded roller receiver, the receiving distance was 18 cm, the roller speed was 300 rpm, and electrospinning was carried out in an environment of 25℃ and humidity <30% to obtain an LLZO / PVP composite nanofiber membrane. The LLZO / PVP composite nanofiber membrane was placed in a muffle furnace and heated to 300℃ at a rate of 2℃ / min under air atmosphere, held for 2h, and then heated to 900℃ at a rate of 5℃ / min for sintering, held for 4h, and naturally cooled to obtain LLZO (lithium lanthanum zirconium oxide) nanowires (average diameter = 60nm, average length = 3000nm, average aspect ratio = 50).

[0153] (3) Ceramic material (alumina) and first binder (polyvinylidene fluoride, PVDF) are mixed at a mass ratio of 98:2 to obtain a first coating mixture. The first coating mixture and N-methylpyrrolidone (NMP) are mixed at a mass ratio of 1:2 to obtain a first coating slurry. The first coating slurry is uniformly coated on one surface of the base film by gravure coating and vacuum dried at 80°C for 3 hours to obtain a base film containing the first coating.

[0154] (4) The lithium-carbon material prepared above, the fast ion conductor nanowire (LLZO nanowire) prepared above, and the second binder (polyvinylidene fluoride, PVDF) are mixed in a mass ratio of 49:49:2 to obtain a second coating mixture. The second coating mixture and N-methylpyrrolidone (NMP) are mixed in a mass ratio of 1:3 to obtain a second coating slurry. The second coating slurry is uniformly coated on the surface of the first coating of the base film containing the first coating in step (3), and vacuum dried at 90°C for 3 hours to obtain a base film containing the second coating.

[0155] (5) Mix the polymer (polyimide, PIA) and N-methylpyrrolidone (NMP) in a mass ratio of 1:4 to obtain a third coating slurry. Apply the third coating slurry evenly to the surface of the second coating of the base film containing the second coating in step (4), and treat it at 80°C, 120°C and 250°C for 1 hour each to obtain the diaphragm.

[0156] 2. Preparation of the positive electrode The positive electrode active material LiCoO2, the positive electrode conductive agent acetylene black, and the positive electrode binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 98:1.2:0.8. N-methylpyrrolidone (NMP) was added, and the mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 60 wt%. Aluminum foil was used as the positive electrode current collector, and the positive electrode slurry was uniformly coated onto the current collector. After drying, cold pressing, and cutting, the positive electrode sheet was obtained.

[0157] 3. Preparation of the negative electrode Silicon carbide (SiC), a silicon-containing material, acetylene black, a negative electrode conductive agent, and styrene-butadiene rubber (SBR), a negative electrode binder, were mixed in a mass ratio of 98.1:0.5:1.4. N-methylpyrrolidone (NMP) was added, and the mixture was stirred evenly under vacuum to obtain a negative electrode slurry with a solid content of 25 wt%. Copper foil was used as the negative electrode current collector, and the negative electrode slurry was uniformly coated onto the current collector. After drying, cold pressing, and cutting, the negative electrode sheet was obtained.

[0158] 4. Preparation of electrolytes (electrolytes) In a dry argon atmosphere glove box, ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) are mixed in a mass ratio of EC:DEC:PC:PP:VC = 25:25:15:31:4 to obtain a non-aqueous solvent. Then, lithium salt LiPF6 is added to the non-aqueous solvent to dissolve and mix evenly to obtain an electrolyte.

[0159] The mass concentration of LiPF6 in the electrolyte is 8%.

[0160] 5. Preparation of lithium-ion secondary batteries (electrochemical devices) The positive electrode, separator (with the third coating of the separator close to the negative electrode) and negative electrode prepared above are stacked in sequence and wound to obtain an electrode assembly; the electrode assembly is placed in an aluminum-plastic film packaging bag, dried and then injected with electrolyte, and after vacuum sealing, standing, formation, degassing and edge trimming, a lithium-ion secondary battery is obtained.

[0161] Examples 2-5 and Comparative Examples 1-7 Examples 2-5 and Comparative Examples 1-7 differ from Example 1 in that the average thickness of the first coating is a μm, the average thickness of the second coating is b μm, and the loading of lithium-carbon material in the second coating is c mg / cm³. 2 The ionic conductivity dS / cm of the fast ion conductor nanowires (LLZO nanowires) and the porosity e of the third coating are different, as shown in Table 1; the rest are consistent with Example 1. The coating amount of the first coating slurry was adjusted to achieve the following results in examples or comparative examples (a) as shown in Table 1. The coating amount of the second coating slurry was adjusted to achieve the following results in examples or comparative examples (b) as shown in Table 1. Keeping the mass ratio of the second binder (PVDF) in the second coating constant, the mass ratio of lithium-carbon material to fast ion conductor nanowires (LLZO nanowires) was adjusted to achieve the following results in examples or comparative examples (c) as shown in Table 1. The sintering temperature and holding time during the preparation of the fast ion conductor nanowires (LLZO nanowires) were adjusted to achieve the following results in examples or comparative examples (d) as shown in Table 1. The mass ratio of polymer (polyimide, PIA) to N-methylpyrrolidone (NMP) was adjusted to achieve the following results in examples or comparative examples (e) as shown in Table 1. In Comparative Example 3, no lithium-containing carbon material was used in the second coating; in Comparative Example 4, no fast ion conductor nanowires were used in the second coating; in Comparative Example 5, no second coating was used; in Comparative Example 6, no first coating was used; and in Comparative Example 7, no third coating was used.

[0162] Examples 6-9 The difference between Examples 6-9 and Example 1 lies in the average particle size Dv50 of the lithium-carbon material in the second coating, as shown in Table 2. All other aspects are consistent with Example 1. The average particle size Dv50 of the lithium-carbon material in each example was achieved by adjusting the screening process in the preparation method of the lithium-carbon material, as shown in Table 2.

[0163] Examples 10-13 The difference between Examples 10-13 and Example 1 lies in the average diameter of the fast ion conductor nanowires (LLZO nanowires) in the second coating, as shown in Table 3. All other parameters are the same as in Example 1. The average diameter of the fast ion conductor nanowires (LLZO nanowires) in each example was adjusted by changing the propeller speed, applied voltage, and receiving distance parameters of the precursor spinning solution in the preparation method of the fast ion conductor nanowires (LLZO nanowires), as shown in Table 3.

[0164] Examples 14-16 The difference between Examples 14-16 and Example 1 lies in the molar ratio of lithium to carbon in the lithium-containing carbon materials, as shown in Table 4. All other aspects are consistent with Example 1. The molar ratios of lithium to carbon in the lithium-containing carbon materials of each example were adjusted by changing the concentration of the LiPF6 solution in the preparation method, as shown in Table 4.

[0165] Example 17 The difference between Example 17 and Example 1 is: (1) In the second coating, ceramic material (zirconia) with an average particle size Dv50=500nm was used instead of ceramic material (alumina) with an average particle size Dv50=200nm in Example 1. (2) In the third coating, the polymer polyvinylidene fluoride (PVDF) is used instead of the polymer polyimide (PIA) in Example 1; (3) Replace the LLZO nanowires in Example 1 with LLTO (lithium lanthanum titanium oxide) nanowires; The rest is consistent with Example 1; wherein, the ceramic material (zirconia) with an average particle size Dv50=500nm is obtained by grinding and crushing zirconia (Z916858, Maclean) with a particle size of 2μm and screening. The preparation method of LLTO (lithium lanthanum titanium oxide) nanowires is as follows: According to Li 0.33 La 0.557 Weigh lithium nitrate, lanthanum nitrate, and tetrabutyl titanate in stoichiometric proportions to obtain an LLTO raw material mixture for later use; mix DMF (N,N-dimethylformamide) and ethanol in a volume ratio of 3:7 to obtain a mixed solvent for later use. The LLTO raw material mixture, polyvinylpyrrolidone (PVP) and mixed solvent were mixed in a mass ratio of 8:1:40 and magnetically stirred at 60°C for 12 h to obtain the precursor spinning solution. The precursor spinning solution was loaded into a plastic syringe, connected to a 23G stainless steel needle, and the pusher speed was set to 0.8 mL / h. A high voltage electric field of 20 kV was applied between the stainless steel needle and the grounded roller receiver, the receiving distance was 18 cm, the roller speed was 300 rpm, and electrospinning was carried out in an environment of 25℃ and humidity <30% to obtain an LLTO / PVP composite nanofiber membrane. The LLTO / PVP composite nanofiber membrane was placed in a muffle furnace and heated to 300℃ at a rate of 2℃ / min under air atmosphere, held for 2h, and then heated to 900℃ at a rate of 5℃ / min for sintering, held for 4h, and naturally cooled to obtain LLTO (lithium lanthanum titanium oxide) nanowires (average diameter = 60nm, average length = 3000nm, average aspect ratio = 50). Everything else is the same as in Example 1.

[0166] Example 18 The difference between Example 18 and Example 1 is: (1) In the second coating, a ceramic material (magnesium oxide) with an average particle size Dv50=100nm was used instead of the ceramic material (alumina) with an average particle size Dv50=200nm in Example 1. (2) In the third coating, the polymer polyacrylonitrile (PAN) is used instead of the polymer polyimide (PIA) in Example 1; (3) Replace the LLZO nanowires in Example 1 with LLZTO (lithium lanthanum zirconium titanium oxide) nanowires; The rest is consistent with Example 1; wherein, the ceramic material (magnesium oxide) with an average particle size Dv50=100nm is magnesium oxide (M761792, Maclean) with an average particle size of 100nm, and the preparation method of LLZTO (lithium lanthanum zirconium titanium oxide) nanowires is as follows: According to Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Lithium nitrate, lanthanum nitrate, zirconium oxynitrate, and tantalum nitrate were weighed according to their stoichiometric ratios and mixed to obtain an LLZTO raw material mixture for later use; DMF (N,N-dimethylformamide) and ethanol were mixed in a volume ratio of 3:7 to obtain a mixed solvent for later use. The LLZTO raw material mixture, polyvinylpyrrolidone (PVP) and mixed solvent were mixed in a mass ratio of 8:1:40 and magnetically stirred at 60°C for 12 h to obtain the precursor spinning solution. The precursor spinning solution was loaded into a plastic syringe, connected to a 23G stainless steel needle, and the pusher speed was set to 0.8 mL / h. A high voltage electric field of 20 kV was applied between the stainless steel needle and the grounded roller receiver, the receiving distance was 18 cm, the roller speed was 300 rpm, and electrospinning was carried out in an environment of 25℃ and humidity <30% to obtain an LLZTO / PVP composite nanofiber membrane. The LLZTO / PVP composite nanofiber membrane was placed in a muffle furnace and heated to 300℃ at a rate of 2℃ / min under air atmosphere, held for 2h, and then heated to 950℃ at a rate of 5℃ / min for sintering, held for 3h, and naturally cooled to obtain LLZTO (lithium lanthanum zirconium titanium oxide) nanowires (average diameter = 60nm, average length = 3000nm, average aspect ratio = 50). Everything else is the same as in Example 1.

[0167] Table 1. Condition parameters and performance test results for Examples 1-5 and Comparative Examples 1-7 As shown in Table 1, the diaphragm of this application can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device.

[0168] Table 2. Condition parameters and performance test results for Examples 1 and 6-9 As shown in Table 2, the diaphragm of this application can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device.

[0169] Table 3. Condition parameters and performance test results for Examples 1 and 10-13 As shown in Table 3, the diaphragm of this application can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device.

[0170] Table 4. Condition parameters and performance test results for Examples 1 and 14-16 As shown in Table 4, the diaphragm of this application can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device.

[0171] Table 5. Condition parameters and performance test results for Examples 1 and 17-18 As shown in Table 5, the diaphragm of this application can simultaneously improve the first coulombic efficiency (ICE) and cycle capacity retention of the electrochemical device.

[0172] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A diaphragm, characterized in that, Includes a base film, wherein at least one surface of the base film is provided with a first coating, a second coating and a third coating; The first coating is located between the base film and the second coating, the second coating is located between the first coating and the third coating, the first coating includes a ceramic material, the second coating includes a lithium-carbon material and fast ion conductor nanowires, and the third coating includes a polymer; The average thickness of the first coating is a μm, the average thickness of the second coating is b μm, and the lithium-carbon material loading in the second coating is c mg / cm³. 2 The ionic conductivity of the fast ion conductor nanowire is d S / cm, and the porosity of the third coating is e, 0.1≤a×b×c×d×e≤2.1; 5≤a≤20； 3≤b≤10； 1≤c≤2； 0.0040≤d≤0.0060； 0.65≤e≤0.85。 2. The diaphragm as described in claim 1, characterized in that, 0.6≤a×b×c×d×e≤1.

4.

3. The diaphragm as described in claim 1, characterized in that, At least one of the following conditions (1)-(2) must be satisfied: (1) The average particle size Dv50 of the lithium-containing carbon material is 20-100 nm; (2) The molar ratio of lithium to carbon in the lithium-containing carbon material is 1:(3-8).

4. The diaphragm as described in claim 3, characterized in that, At least one of the following conditions (1)-(2) must be satisfied: (1) The average particle size Dv50 of the lithium-containing carbon material is 30-70 nm; (2) The molar ratio of lithium to carbon in the lithium-containing carbon material is 1:(5-8).

5. The diaphragm as described in claim 1, characterized in that, At least one of the following conditions (1)-(2) must be satisfied: (1) The average diameter of the fast ion conductor nanowire is 10-100 nm; (2) The average aspect ratio of the fast ion conductor nanowire is ≥25.

6. The diaphragm as described in claim 5, characterized in that, At least one of the following conditions (1)-(2) must be satisfied: (1) The average diameter of the fast ion conductor nanowire is 20-60 nm; (2) The average aspect ratio of the fast ion conductor nanowire is ≥30.

7. The diaphragm as described in claim 1, characterized in that, At least one of the following conditions (1)-(4) must be satisfied: (1) The ceramic material includes at least one of alumina, silicon oxide, zirconium oxide, magnesium oxide, titanium oxide, aluminum nitride, and boehmite; (2) The average particle size Dv50 of the ceramic material is 100-500 nm; (3) The fast ion conductor nanowires include at least one of LLZO nanowires, LLTO nanowires, and LLZTO nanowires; (4) The polymer includes at least one of polyimide, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, aramid, polyvinyl alcohol, and polyurethane.

8. An electrochemical device, characterized in that, Includes the diaphragm and negative electrode as described in any one of claims 1-7.

9. The electrochemical device as described in claim 8, characterized in that, The negative electrode comprises a silicon-containing material.

10. An electronic device, characterized in that, Includes the electrochemical device as described in claim 9.

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