Separators, electrochemical devices and electronic devices

Abstract

The separator of the present invention comprises a subnanoporous material and a binder, the subnanoporous material comprising a metal-organic framework material or a molecular sieve material, and the pore size of the subnanoporous material is 0.01 nm to 1 nm. The separator of the present invention can confine the electrolyte within the pores of the subnanoporous material. On the one hand, the electrochemical device of the present invention is advantageous in reducing side reactions between lithium metal and the electrolyte during cycling of the electrochemical device, improving the lithium deposition density on the surface of the negative electrode strip, thereby alleviating problems such as SEI film fracture and peeling during cycling, improving the safety of the electrochemical device, and extending the cycle life of the electrochemical device. On the other hand, the electrochemical device of the present invention is advantageous in increasing the number of lithium ion migrations, thereby retarding the growth of lithium dendrites, improving the safety of the electrochemical device, and extending the cycle life of the electrochemical device.

Description

[Technical Field]

[0001] The present invention relates to the field of electrochemical technology, and more particularly to separators, electrochemical devices and electronic devices. [Background technology]

[0002] Electrochemical devices such as lithium metal batteries have advantages such as high energy density, high operating voltage, low self-discharge rate, small volume, and light weight, and are widely used in consumer electronics. Lithium metal has a high theoretical specific capacity, making lithium metal batteries suitable for a wide range of applications. Therefore, by using lithium metal as the anode and a cathode containing a high-energy-density cathode material, the energy density and operating voltage of lithium metal batteries can be significantly improved.

[0003] However, due to the extremely high activity of lithium metal, it constantly undergoes violent side reactions with the electrolyte during the cycling process of a lithium metal battery, resulting in the consumption of both the electrolyte and lithium metal. On the other hand, the formation of "lithium dendrites" during the cycling process of a lithium metal battery also leads to the loss of lithium metal. The continued loss of lithium metal reduces the capacity of the lithium metal battery, thereby shortening its cycle life. Summary of the Invention

[0004] The present invention aims to provide a separator, an electrochemical device, and an electronic device for extending the cycle life of the electrochemical device.

[0005] A first aspect of the present invention provides a separator comprising a subnanoporous material and a binder, the subnanoporous material comprising a metal-organic framework material or a molecular sieve material, and the pore size of the subnanoporous material being 0.01 nm to 1 nm. By using the separator provided by the present invention and controlling the pore size of the subnanoporous material within the above range, compatibility between the subnanopore size and the solvent molecules in the electrolyte can be improved, and the pore size of the subnanoporous material can be made equal to or larger than the solvent molecule size, thereby advantageously confining the electrolyte within the pores of the subnanoporous material. Application of the separator provided by the present invention to an electrochemical device can reduce side reactions between lithium metal and the electrolyte during the cycling process of the electrochemical device and slow the growth of lithium dendrites, thereby improving the safety of the electrochemical device and extending the cycle life of the electrochemical device.

[0006] In some embodiments of the present invention, the pore size of the separator is 20 nm to 500 nm. By controlling the pore size of the separator within the above range, the safety of the electrochemical device can be improved and the cycle life of the electrochemical device can be extended.

[0007] In some embodiments of the present invention, the metal-organic framework material includes at least one of MOF-69C, MOF-74, MOF-5, ZIF-67, ZIF-8, MIL-100(Cr), MIL-100(Fe), UIO-66, PCN-61, and CuBTC, and the molecular sieve material includes at least one of MCM-41, SAPO-34, 3A molecular sieve, 4A molecular sieve, 5A molecular sieve, and 13X molecular sieve. By selecting a metal-organic framework material or molecular sieve material within the above ranges, the separator can have good mechanical properties and liquid absorption properties, which are advantageous for confining the electrolyte within the pores of the subnanoporous material. Applying the separator to an electrochemical device can further improve the safety of the electrochemical device and extend the cycle life of the electrochemical device.

[0008] In some embodiments of the present invention, the separator has the following characteristics: (1) the pores of the subnanoporous material contain a polymer, and the polymer contains at least one of poly(sodium styrene sulfonate), poly(N-2-(dimethylaminopropyl) methacrylamide), and poly(acrylic acid); (2) the particle diameter D50 of the particles of the subnanoporous material is 50 nm to 5000 nm; and (3) the specific surface area of ​​the subnanoporous material is 200 m 2 / g~2000m 2 / g, and (4) the binder contains at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, polyimide, polyamide, polyamideimide, polyvinyl alcohol, polyacrylonitrile, polystyrene-butadiene copolymer, sodium alginate, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose. Applying a separator having the above characteristics to an electrochemical device is advantageous in further improving the safety of the electrochemical device and further extending the cycle life of the electrochemical device. Applying a separator having the above characteristics to an electrochemical device is advantageous in further improving the safety of the electrochemical device and further extending the cycle life of the electrochemical device.

[0009] In some embodiments of the present invention, the separator satisfies at least one of the following requirements: (1) the separator has a thickness of 5 μm to 200 μm, and (2) the separator has a porosity of 10% to 80%. Adjusting the separator's thickness and porosity within the above ranges can reduce the difficulty of the separator's manufacturing process and improve separator uniformity. The application of the separator to an electrochemical device is advantageous in preventing lithium dendrite penetration and better confining the separator's electrolyte, thereby providing the electrochemical device with high safety and cycle characteristics as well as high energy density.

[0010] In some embodiments of the present invention, the separator has the following characteristics: (1) the particle diameter of the subnanoporous material particles is 100 nm to 5000 nm; (2) the thickness of the separator is 10 μm to 50 μm; (3) the porosity of the separator is 10% to 30%; (4) the pore diameter of the separator is 20 nm to 100 nm; and (5) the specific surface area of ​​the subnanoporous material is 200 m 2 / g~1500m 2 / g. Applying a separator having the above characteristics to an electrochemical device is advantageous in further improving the safety of the electrochemical device and further extending the cycle life of the electrochemical device.

[0011] A second aspect of the present invention provides an electrochemical device comprising the separator provided by the first aspect of the present invention. The separator provided by the present invention can confine the electrolyte within the pores of the sub-nanoporous material, which is advantageous in improving the safety of the electrochemical device and extending the cycle life of the electrochemical device, and therefore the electrochemical device provided by the present invention has high safety and a relatively long cycle life.

[0012] In some embodiments of the present invention, the electrochemical device is subjected to a constant current charge of 0.2 C to 3.7 V, followed by a constant voltage charge of 0.025 C at 3.7 V, allowing to stand for 5 minutes, and a constant current discharge of 0.2 C to 2.8 V in an environment of 25±1° C., which is repeated 10 or more times. The Raman spectrum of the separator shows a peak at 730 cm -1 ~750cm -1 where the peak area of ​​the Raman peak before cycling is S1 and the peak area of ​​the Raman peak after cycling is S2, and the relationship between S2 / S1 is 1.1≦S2 / S1≦5. An electrochemical device having the above characteristic peaks and having an S2 / S1 ratio within the above range has high safety and a longer cycle life.

[0013] In some embodiments of the present invention, the infrared spectrum of the separator is -1 ~800cm -1, 1000cm -1 ~1260cm -1 , 1300cm -1 ~1500cm -1 where S3 is the sum of the peak areas of the infrared characteristic peaks before cycling and S4 is the sum of the peak areas of the infrared characteristic peaks after cycling, and 1.1≦S4 / S3≦100, preferably 1.1≦S4 / S3≦30. Electrochemical devices having the above characteristic peaks and with S4 / S3 within the above range have high safety and a longer cycle life.

[0014] A third aspect of the present invention provides an electronic device comprising the electrochemical device provided by the second aspect of the present invention. The electrochemical device provided by the present invention has high safety and a relatively long cycle life, and therefore the electronic device of the present invention has a relatively long service life.

[0015] Beneficial Effects of the Invention The present invention provides a separator, an electrochemical device, and an electronic device. The separator includes a subnanoporous material and a binder, the subnanoporous material including a metal-organic framework material or a molecular sieve material, and the pore size of the subnanoporous material is 0.01 nm to 1 nm. By using the separator provided by the present invention and controlling the pore size of the separator within the above range, it is advantageous to confine the electrolyte within the pores of the subnanoporous material. Furthermore, applying the separator provided by the present invention to an electrochemical device is advantageous in reducing side reactions between lithium metal and the electrolyte during the cycling process of the electrochemical device, improving the lithium deposition density on the surface of the negative electrode strip, thereby alleviating problems such as SEI film fracture and peeling during cycling, improving the safety of the electrochemical device, and extending the cycle life of the electrochemical device. On the other hand, applying the separator provided by the present invention to an electrochemical device can fix anions in the electrolyte within the pores of the subnanoporous material, which is advantageous in increasing the mobility of lithium ions, thereby retarding the growth of lithium dendrites, improving the safety of the electrochemical device, and extending the cycle life of the electrochemical device.Furthermore, by confining the electrolyte within the pores of the subnanoporous material, the amount of electrolyte used can be reduced, improving the Coulombic efficiency of the electrochemical device, and improving the cycle characteristics of the electrochemical device. [Brief explanation of the drawings]

[0016] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to interpret the present invention and do not constitute undue limitations on the present invention. [Figure 1] FIG. 1 is a schematic diagram of a separator provided by the present invention. [Figure 2] Figure 2 is a schematic diagram of the internal structure of a sub-nanoporous material. [Figure 3a] FIG. 3a is a scanning electron microscope (SEM) photograph of the separator prepared in Example 19. [Figure 3b]FIG. 3b is an SEM photograph of the separator prepared in Example 19. [Figure 3c] FIG. 3c is an SEM photograph of the separator prepared in Example 19. [Figure 4] FIG. 4 shows Raman spectra of the separator of the lithium metal battery of Example 1 before and after 10 cycles. [Figure 5] FIG. 5 is an infrared spectrum of the separator of the lithium metal battery of Example 1 before and after 10 cycles. [Figure 6] FIG. 6 is a graph showing the cycle characteristics of the lithium metal batteries prepared in Example 7 and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to clearly illustrate the objectives, technical solutions and advantages of the present invention, the present invention will be described in more detail below with reference to the drawings and examples. Obviously, the described examples are only some of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention fall within the protection scope of the present invention.

[0018] In the embodiments of the present invention, the present invention will be described using a lithium metal battery as an example of an electrochemical device, but the electrochemical device of the present invention is not limited to a lithium metal battery.

[0019] A first aspect of the present invention provides a separator. As shown in FIG. 1, the separator 10 includes a subnanoporous material 11 and a binder 12. In FIG. 1, the hexagon represents the subnanoporous material 11, and the rounded black lines represent the binder 12. The subnanoporous material 11 includes a metal-organic framework material or a molecular sieve material. As shown in FIG. 2, the subnanoporous material 11 contains well-ordered subnanopores 111. The pore diameter of the subnanoporous material is 0.01 nm to 1 nm. For example, the pore diameter of the subnanoporous material may be 0.01 nm, 0.05 nm, 0.1 nm, 0.3 nm, 0.5 nm, 0.7 nm, 0.9 nm, 1 nm, or a range consisting of any two of these values.

[0020] By using the separator provided by the present invention and controlling the pore size of the subnanoporous material within the above range, the compatibility between the subnanopore size and the solvent molecules in the electrolyte can be enhanced, and the pore size of the subnanoporous material can be made equal to or larger than the solvent molecule size, thereby confining the electrolyte within the pores of the subnanoporous material. The application of the separator provided by the present invention to electrochemical devices is advantageous, on the one hand, in reducing side reactions between lithium metal and the electrolyte during cycling of the electrochemical device, improving the lithium deposition density on the surface of the negative electrode strip, thereby alleviating problems such as SEI film fracture and peeling during cycling, improving the safety of the electrochemical device, and extending the cycle life of the electrochemical device. On the other hand, the application of the separator provided by the present invention to electrochemical devices is advantageous, on the other hand, in fixing anions in the electrolyte within the pores of the subnanoporous material, improving the mobility of lithium ions, thereby retarding the growth of lithium dendrites, improving the safety of the electrochemical device, and extending the cycle life of the electrochemical device. Furthermore, by confining the electrolyte within the pores of the subnanoporous material, the amount of electrolyte used can be reduced, the coulombic efficiency of the electrochemical device can be improved, and the cycle characteristics of the electrochemical device can be improved. The anion includes an anion in which a lithium salt is dissociated, for example, bistrifluoromethanesulfonylimide anion (TFSI -) may include, but are not limited to:

[0021] In some embodiments of the present invention, the pore size of the separator is 20 nm to 500 nm, preferably 20 nm to 100 nm. For example, the pore size of the separator may be 20 nm, 30 nm, 50 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, or a range consisting of any two of these values. Controlling the pore size of the separator within the above ranges results in the separator having good mechanical properties and liquid absorption characteristics. Application of the separator to an electrochemical device is beneficial for reducing side reactions between lithium metal and the electrolyte during the cycling process of the electrochemical device, improving the lithium deposition density and lithium ion migration rate on the surface of the negative electrode strip, and slowing the growth of lithium dendrites, thereby further improving the safety and cycle life of the electrochemical device. In the present invention, the pore size of the separator refers to the average pore size of the entire separator.

[0022] In some embodiments of the present invention, the metal-organic framework material comprises at least one of MOF-69C, MOF-74, MOF-5, ZIF-67, ZIF-8, MIL-100(Cr), MIL-100(Fe), UIO-66, PCN-61, and CuBTC, and the molecular sieve material comprises at least one of MCM-41, SAPO-34, 3A molecular sieve (2 / 3K2O·1 / 3Na2O·Al2O3·2SiO2·9 / 2H2O), 4A molecular sieve (Na2O·Al2O3·2SiO2·9 / 2H2O), 5A molecular sieve (3 / 4CaO·1 / 4Na2O·Al2O3·2SiO2·9 / 2H2O), and 13X molecular sieve (Na2O·Al2O3·2.45SiO2·6H2O). By selecting a metal-organic framework material or molecular sieve material within the above range, the separator has good mechanical properties and liquid absorption properties, and is more advantageous in confining the electrolyte within the pores of the sub-nanoporous material, reducing side reactions between lithium metal and the electrolyte during the cycling process of the electrochemical device, and improving the lithium deposition density and lithium ion migration rate on the surface of the negative electrode piece, thereby slowing down the growth of lithium dendrites, thereby further improving the safety of the electrochemical device and prolonging the cycle life of the electrochemical device.

[0023] In some embodiments of the present invention, the pores of the sub-nanoporous material contain a polymer, and the polymer includes at least one of poly(sodium styrene sulfonate) (PSS), poly(N-2-(dimethylaminopropyl)methacrylamide) (PDMAPMA), and poly(acrylic acid) (PAA). By modifying the interior of the pores of the sub-nanoporous material with a polymer within the above range, the adsorption capacity of the sub-nanopores for anions can be further improved, the lithium ion migration rate can be increased, and the growth of lithium dendrites can be further delayed, further improving the safety of the electrochemical device and further extending the cycle life of the electrochemical device.

[0024] In some embodiments of the present invention, the particle diameter D50 of the subnanoporous material particles is 50 nm to 5,000 nm, preferably 100 nm to 1,000 nm. For example, the particle diameter D50 of the subnanoporous material particles may be 50 nm, 100 nm, 300 nm, 500 nm, 1,000 nm, 2,500 nm, 4,000 nm, 5,000 nm, or a range consisting of any two of these values. Controlling the particle diameter D50 of the subnanoporous material particles within the above range is advantageous for obtaining a separator with a uniform thickness and a dense, flat structure, thereby improving the separator's ability to contain the electrolyte, further improving the safety of the electrochemical device, and further extending the cycle life of the electrochemical device. In the present invention, "D50" refers to the particle diameter at which the cumulative volume, from the smallest particle diameter side, becomes 50% in the volume-based particle size distribution of the material. In the present invention, the selection of the particle diameter D50 of the particles of the sub-nanoporous material is limited to the thickness of the separator, and the particle diameter D50 of the particles of the sub-nanoporous material is not more than half the thickness of the separator.

[0025] In some embodiments of the present invention, the specific surface area of ​​the sub-nanoporous material is 200 m 2 / g~2000m 2 / g, preferably 200m 2 / g~1500m 2 For example, the specific surface area of ​​a sub-nanoporous material is 200 m 2 / g, 400m 2 / g, 800m 2 / g, 1200m 2 / g, 1500m 2 / g, 1800m 2 / g, 2000m 2 / g, or a range consisting of any two of these values. Controlling the specific surface area of ​​the sub-nanoporous material within the above range is advantageous for obtaining a separator with a uniform thickness, which is dense and flat, thereby enabling the separator to better exert its electrolyte containment effect, further improving the safety of the electrochemical device, and further extending the cycle life of the electrochemical device.

[0026] In some embodiments of the present invention, the binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylate, polyimide, polyamide, polyamideimide, polyvinyl alcohol, polyacrylonitrile, polystyrene-butadiene copolymer, sodium alginate, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose. Selecting a binder within the above range can ensure that the separator has good ion transmission uniformity, mechanical properties, and stability. The application of the separator to an electrochemical device reduces side reactions between lithium metal and the electrolyte during the cycling process of the electrochemical device, which is beneficial for improving the lithium deposition density and lithium ion migration rate on the surface of the negative electrode strip, and slowing the growth of lithium dendrites, thereby further improving the safety and cycle life of the electrochemical device. The weight-average molecular weight of the binder is not particularly limited in the present invention and can be selected according to conventional standards as long as the objectives of the present invention are achieved. For example, the weight average molecular weight of the binder may be 150,000 to 1,000,000.

[0027] In the present invention, the characteristics of the above embodiment, that the pores of the subnanoporous material contain a polymer, and the characteristics such as the type of polymer, the particle diameter of the particles of the subnanoporous material, the specific surface area of ​​the subnanoporous material, or the type of binder, can be combined in any manner, and the separator satisfies at least one of the above characteristics.

[0028] In some embodiments of the present invention, the separator has a thickness of 5 μm to 200 μm, preferably 10 μm to 50 μm. For example, the separator may have a thickness of 5 μm, 10 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, or 200 μm, or a range consisting of any two of these values. Adjusting the separator thickness within the above range reduces the difficulty of the separator manufacturing process and improves separator uniformity. Application of the separator to an electrochemical device prevents penetration by lithium dendrites, thereby enabling the electrochemical device to have high safety and high energy density.

[0029] In some embodiments of the present invention, the porosity of the separator is 10% to 80%, preferably 10% to 30%. For example, the porosity of the separator may be 10%, 15%, 20%, 25%, 30%, 40%, 50%, 70%, 80%, or a range consisting of any two of these values. Adjusting the porosity of the separator to fall within the above range is advantageous in that the separator can better exert its ability to contain the electrolyte, further improving the safety of the electrochemical device and further extending the cycle life of the electrochemical device.

[0030] In the present invention, the separator can simultaneously satisfy the above-mentioned characteristics of the separator thickness and the separator porosity.

[0031] In the present invention, the electrical conductivity of the separator is 10 -10 This indicates that the separator of the present invention has good insulating properties, which is advantageous in improving short circuit prevention and safety of electrochemical devices.

[0032] The subnanoporous material of the present invention is a commercially available, general material, and by purchasing different model numbers of subnanoporous materials, subnanoporous materials with different pore sizes, particle sizes, or specific surface areas can be obtained. The present invention is not particularly limited to the source of the material, as long as the object of the present invention can be achieved.

[0033] The present invention is not particularly limited to a method for preparing the separator, as long as the object of the present invention can be achieved. For example, the separator can be prepared by a film-forming method commonly used in this field, which may include a wet film-forming method or a dry film-forming method, and may include, but is not limited to, methods such as cold pressing, hot pressing, scraping coating, spin coating, and electrospinning. The separator may be prepared by, but is not limited to, mixing a subnanoporous material and a binder, adding a solvent, and stirring to form a slurry. The slurry is then scraped with a doctor blade to form a film. The coated film is then activated by heating at 160°C to 200°C for 60 to 80 hours. The activated film is then subjected to high-pressure roll pressing, immersed in an electrolyte solution to ensure the separator is fully saturated with the electrolyte, and then wiped with dust-free paper to remove the liquid from the surface and dried to obtain the separator. Alternatively, the separator may be prepared by, but not limited to, mixing a subnanoporous material and a binder to form a film, applying high-pressure roll pressing, activating the film obtained by roll pressing, immersing in an electrolyte solution to ensure the separator is fully saturated with the electrolyte, and then wiped with dust-free paper to remove the liquid from the surface and dried to obtain the separator. The mass ratio of the subnanoporous material to the binder may be 7:1 to 11:1. The solvent may include, but is not limited to, N-methylpyrrolidine ketone. The solid content of the slurry may be 50 wt % to 80 wt %. The separator may be immersed in the electrolytic solution for 40 to 60 hours at room temperature, or the temperature of the electrolytic solution may be elevated, for example, to 40 to 70°C.

[0034] Typically, the pore size of the separator can be adjusted by changing the mass of the press roll used in the high-pressure roll press. The pore size of the separator can be decreased by increasing the mass of the press roll used in the high-pressure roll press. The pore size of the separator can be increased by decreasing the mass of the press roll used in the high-pressure roll press. The porosity of the separator can also be adjusted by changing the mass of the press roll used in the high-pressure roll press. The porosity of the separator can be decreased by increasing the mass of the press roll. The porosity of the separator can be increased by decreasing the mass of the press roll. The thickness of the separator can be adjusted by changing the doctor blade specifications. The thickness of the separator can be increased by selecting a doctor blade with a larger specification. The thickness of the separator can be decreased by selecting a doctor blade with a smaller specification. Specifically, for example, replacing a 30 μm doctor blade with a 150 μm doctor blade increases the separator thickness, but replacing a 30 μm doctor blade with a 20 μm doctor blade decreases the separator thickness.

[0035] A second aspect of the present invention provides an electrochemical device including the separator provided by the first aspect of the present invention. The separator provided by the present invention can confine an electrolyte within the pores of a sub-nanoporous material. The application of the separator to an electrochemical device is advantageous in improving the safety of the electrochemical device and extending the cycle life of the electrochemical device. Therefore, the electrochemical device provided by the present invention has high safety and a relatively long cycle life.

[0036] In some embodiments of the present invention, the electrochemical device is cycled 10 or more times, and the Raman spectrum of the separator shows a peak at 730 cm -1 ~750cm -1The Raman peaks are between 1.1 and 5, where S1 is the peak area of ​​the Raman peak before cycling and S2 is the peak area of ​​the Raman peak after cycling. An electrochemical device with the above characteristic peaks and an S2 / S1 ratio within the above range exhibits higher safety and longer cycle life. The increase in the peak area of ​​the Raman peak after cycling indicates that more lithium ions and anions have entered the pore structure of the subnanoporous material, thereby improving the safety and extending the cycle life of the electrochemical device. The above cycle involves constant current charging of the electrochemical device at 0.2 C to 3.7 V, followed by constant voltage charging at 3.7 V to 0.025 C, allowing to stand for 5 minutes, and constant current discharging at 0.2 C to 2.8 V in an environment of 25±1°C.

[0037] In some embodiments of the present invention, the electrochemical device is cycled 10 or more times, and the infrared spectrum of the separator is -1 ~800cm -1 , 1000cm -1 ~1260cm -1 , 1300cm -1 ~1500cm -1 The infrared characteristic peaks are between 1.1 and 1.1, and the sum of the peak areas of the infrared characteristic peaks before cycling is S3, and the sum of the peak areas of the infrared characteristic peaks after cycling is S4. The ratio S4 / S3 is 1.1≦S4 / S3≦100, preferably 1.1≦S4 / S3≦30. An electrochemical device having the above characteristic peaks and an S4 / S3 ratio within the above range exhibits higher safety and longer cycle life. An increase in the peak area of ​​the infrared characteristic peaks after cycling indicates that more solvent has entered the pore structure of the sub-nanoporous material, thereby improving the safety and extending the cycle life of the electrochemical device. The above cycle involves constant current charging of the electrochemical device at 0.2 C to 3.7 V, followed by constant voltage charging at 3.7 V to 0.025 C, allowing to stand for 5 minutes, and constant current discharging at 0.2 C to 2.8 V in an environment of 25±1°C.

[0038] The electrochemical device of the present invention further includes a positive electrode piece. The positive electrode piece is not particularly limited as long as the objective of the present invention is achieved. For example, the positive electrode piece includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode current collector is not particularly limited as long as the objective of the present invention is achieved. For example, the positive electrode current collector may include aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector). The thickness of the positive electrode current collector is not particularly limited as long as the objective of the present invention is achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm. In the present invention, the positive electrode active material layer includes a positive electrode active material. The type of positive electrode active material is not particularly limited as long as the objective of the present invention is achieved. For example, the positive electrode active material may include at least one of lithium nickel-cobalt manganese oxide (NCM), lithium nickel-cobalt aluminate, lithium iron phosphate (LiFePO4), lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, and lithium iron manganese phosphate. The present invention is not particularly limited by the type of NCM, as long as the objective of the present invention is achieved. For example, the type of NCM may include at least one of NCM811, NCM622, NCM523, and NCM111. In the present invention, the positive electrode active material may further include a nonmetallic element. For example, the nonmetallic element may include at least one of fluorine, phosphorus, boron, and chlorine. The present invention is not particularly limited by the thickness of the positive electrode active material layer, as long as the objective of the present invention is achieved. For example, the thickness of the positive electrode active material layer on one side is 30 μm to 120 μm. In the present invention, the positive electrode active material layer may be disposed on one surface of the positive electrode current collector in the thickness direction, or may be disposed on two surfaces of the positive electrode current collector in the thickness direction. Here, the "surface" may refer to the entire surface of the positive electrode current collector, or may refer to a partial surface of the positive electrode current collector; however, the present invention is not particularly limited as long as the object of the present invention is achieved. The positive electrode active material layer of the present invention may further contain a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent and the positive electrode binder are not particularly limited as long as the object of the present invention is achieved.For example, the positive electrode conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, graphene, metal materials, and conductive polymers. The carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or nanocarbon fibers. The metal material may include, but is not limited to, metal powder and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, and silver. The conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, and polypyrrole. The positive electrode binder may include at least one of, 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, polyacrylic acid, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, and nylon.

[0039] The electrochemical device of the present invention further includes a negative electrode piece. The present invention is not particularly limited to the negative electrode piece, as long as the objectives of the present invention are achieved. For example, the negative electrode piece may include a lithium-copper composite tape. The present invention is not particularly limited to the thickness of the lithium-copper composite tape, as long as the objectives of the present invention are achieved. For example, the lithium-copper composite tape may have a thickness of 30 μm to 80 μm. The negative electrode piece may further include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The present invention is not particularly limited to the negative electrode current collector, as long as the objectives of the present invention are achieved. For example, the negative electrode current collector may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector (e.g., a carbon-copper composite current collector, a nickel-copper composite current collector, or a titanium-copper composite current collector). The present invention is not particularly limited to the thickness of the negative electrode current collector, as long as the objectives of the present invention are achieved. For example, the thickness of the negative electrode current collector is 4 μm to 20 μm. In the present invention, the negative electrode active material layer includes a negative electrode active material. The present invention is not particularly limited to the negative electrode active material, as long as the object of the present invention can be achieved. For example, the negative electrode active material may be graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, or spinel-structured lithium titanate Li4Ti5O. 12The negative electrode active material layer may contain at least one of, but is not limited to, a lithium-ion conductive material ...

[0040] The electrochemical device of the present invention further includes an electrolyte. The electrolyte includes a lithium salt and a non-aqueous solvent. The lithium salt may include at least one of LiPF6, LiBF4, LiClO4, LiB(CH5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium difluoroborate. The present invention is not particularly limited to the non-aqueous solvent, as long as the objective of the present invention can be achieved. For example, the non-aqueous solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound, and another organic solvent, but is not limited to these. The carbonate compound may include at least one of a chain carbonate compound, a cyclic carbonate compound, and a fluorocarbonate compound, but is not limited to these. The linear carbonate compound may include, but is not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and ethyl methyl carbonate. The cyclic carbonate may include, but is not limited to, at least one of ethylene carbonate, propylene carbonate (PC), butylene carbonate, and vinyl ethylene carbonate. The fluorocarbonate compound may include, but is not limited to, at least one of fluoroethylene carbonate, 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.The carboxylate compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolactone, decalactone, valerolactone, and caprolactone. The ether compound may include, but is not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. The other organic solvent may include, but is not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, and trioctyl phosphate.

[0041] The electrochemical device of the present invention further includes a packaging bag for containing the positive electrode pieces, separator, negative electrode pieces, and electrolyte, as well as other components known in the art for electrochemical devices. The present invention does not limit the above-mentioned other components. The present invention is not particularly limited to the packaging bag, and any packaging bag known in the art may be used as long as the object of the present invention can be achieved.

[0042] The electrochemical device of the present invention is not particularly limited and may include any device in which an electrochemical reaction occurs. In one embodiment of the present invention, the electrochemical device may include, but is not limited to, a lithium ion secondary battery (lithium ion battery), a lithium metal secondary battery (lithium metal battery), a sodium ion secondary battery, a sodium metal secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. The present invention is not particularly limited to the shape of the electrochemical device, as long as the object of the present invention is achieved. For example, the shape of the electrochemical device may include, but is not limited to, a prismatic battery, a prismatic battery, or an irregular-shaped battery.

[0043] The process for preparing an electrochemical device is well known to those skilled in the art, and the present invention is not particularly limited thereto. For example, the process for preparing an electrochemical device may include, but is not limited to, stacking positive electrode pieces, separators, and negative electrode pieces in this order, securing the four corners of the entire stack with adhesive tape to obtain a stacked electrode assembly, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag, and sealing the bag to obtain an electrochemical device; or stacking positive electrode pieces, separators, and negative electrode pieces in this order, and optionally rolling or folding the stack to obtain a rolled electrode assembly, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag, and sealing the bag to obtain an electrochemical device. Furthermore, an overcurrent protection element, lead plates, etc. may be placed in the packaging bag as needed to prevent internal pressure buildup, overcharging, overdischarging, etc. within the electrochemical device.

[0044] A third aspect of the present invention provides an electronic device comprising the electrochemical device provided by the second aspect of the present invention. The electrochemical device provided by the present invention has high safety and a relatively long cycle life, and therefore the electronic device provided by the present invention has a relatively long service life.

[0045] The electronic device of the present invention is not particularly limited and may be used in any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-based computer, a mobile computer, an electronic book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headset, a video recorder, an LCD television, a portable vacuum cleaner, a portable CD player, a minidisc, a walkie-talkie, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electric bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household storage battery, or a lithium ion capacitor.

[0046] Example Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples and comparative examples. Each test and evaluation was carried out as follows. Unless otherwise specified, "parts" and "%" are based on mass.

[0047] Measurement methods and equipment Measurement of Raman spectra Separators prepared in the same example were divided into two groups, and one group was subjected to separator measurement before cycling. One was used as a test sample, and the other was assembled into a lithium metal battery. The lithium metal battery was cycled 10 times according to the following steps: At 25±1°C, the lithium metal battery was charged at a constant current of 0.2 C to 3.7 V, then charged at a constant voltage of 0.025 C from 3.7 V, allowed to stand for 5 minutes, and discharged at a constant current of 0.2 C to 2.8 V. The lithium metal battery was then disassembled, and the separator was removed. This was used as a post-cycle separator measurement sample. The Raman spectra of the separator before and after cycling were measured using a Raman spectrometer. The Raman spectra were then analyzed to calculate the Raman peak areas S1, S2, and S2 / S1.

[0048] Infrared spectrum measurement As in the Raman measurement described above, separator samples before and after cycling were obtained, and the infrared spectra of the separators before and after cycling were measured using an infrared spectrometer. The infrared spectra were then analyzed to calculate the areas S3, S4, and S4 / S3 of the characteristic infrared peaks.

[0049] Scanning electron microscope (SEM) measurements The surface morphology in the thickness direction of the separator and the cross-sectional morphology along the thickness direction were observed with a scanning electron microscope, and SEM photographs were taken.

[0050] Measurement of separator pore size and porosity The pore size and porosity of the separator were measured according to the Chinese national standard GB / T 21650.1-2008 "Measurement of pore size distribution and porosity of solid materials by mercury intrusion and gas adsorption methods."

[0051] Measuring flexibility The separator was folded so that the folding angle was 360° or less. If cracks occurred after folding, folding was stopped. The more times it was folded, the better its flexibility.

[0052] Measurement of thermal shrinkage The prepared separator was cut into 5 cm x 5 cm pieces, laid flat on a glass plate, and placed in a 200°C oven for 2 hours. The degree of curling at the edges of the separator was observed, and the corresponding length and width dimensions (A cm x B cm) were measured to calculate the longitudinal shrinkage (A1%) and transverse shrinkage (B1%), respectively. A1% = (5 - A) / 5 x 100%, and B1% = (5 - B) / 5 x 100%. The criteria for determining whether or not the separator experienced thermal shrinkage at 200°C were as follows: if A1% ≤ 10% and B1% ≤ 10%, the separator experienced thermal shrinkage at 200°C was deemed "absent"; if A1% ≥ 10% or B1% ≥ 10%, the separator experienced thermal shrinkage at 200°C was deemed "present."

[0053] Measurement of cycle capacity retention rate The lithium metal battery was placed in an incubator at 25°C ± 2°C and allowed to stand for 2 hours. The lithium metal battery was charged at a constant current of 0.2 C to 3.7 V, then charged at a constant voltage of 0.05 C from 3.7 V, allowed to stand for 5 minutes, and then discharged at a constant current of 0.2 C to 3.0 V. This cycle was designated cycle 1. The discharge capacity of the first cycle was recorded. The charge-discharge cycle was then repeated according to cycle 1. At the 50th, 100th, 150th, and 200th cycles, a charge-discharge cycle was performed according to cycle 2 below. The battery was charged at a constant current of 0.05 C to 3.7 V, then charged at a constant voltage of 0.05 C from 3.7 V, allowed to stand for 5 minutes, and then discharged at a constant current of 0.05 C to 3.0 V. This cycle was designated cycle 2. The discharge capacity after each cycle was recorded. Ten lithium metal batteries were taken from each group, and the average capacity retention rate of the ten lithium metal batteries was calculated. Lithium metal battery cycle capacity retention rate = discharge capacity after each cycle (mAh) / discharge capacity after the first cycle (mAh) x 100%

[0054] Measurement of cycle number The lithium metal batteries were placed in an incubator at 25°C ± 2°C and allowed to stand for two hours. One charge-discharge cycle consisted of a constant current charge at 0.1C to 3.7V, a constant voltage charge at 3.7V to 0.05C, a 5-minute hold, and a constant current discharge at 0.1C to 3.0V. The discharge capacity of the lithium metal batteries was recorded for the first cycle. The charge-discharge cycle was then repeated according to the above cycle, and the number of cycles at which the capacity retention of the lithium metal batteries was reduced to 80% was recorded. Ten lithium metal batteries were selected from each group, and the average number of cycles at which the capacity retention of the lithium metal batteries was reduced to 80% was calculated.

[0055] Coulombic efficiency measurement Using an electrochemical station (Shenzhen KEIJINGLAN Electrochemical Workstation) at 20°C, the lithium metal battery was charged at a constant current of 0.2C to 3.7V, then charged at a constant voltage of 0.025C, allowed to rest for 5 minutes, and then discharged at a constant current of 0.2C to 2.8V, allowed to rest for 5 minutes. This cycle constituted one cycle. The charge-discharge cycle was repeated according to the above procedure. The coulombic efficiency was calculated as the average ratio of the discharge capacity to the charge capacity for each cycle when the capacity of the lithium metal battery had decayed to 80% of its initial discharge capacity.

[0056] Example 1 <Preparation of negative electrode pieces> A lithium-copper composite tape (50 μm thick, provided by Tianjin Zhongneng Lithium Industry Co., Ltd.) was used as the negative electrode piece, which was directly punched out to a diameter of 18 mm and subjected to the next step.

[0057] <Preparation of electrolyte> In a glove box with a dry argon atmosphere, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a lithium salt, was added to propylene carbonate (PC), an organic solvent, and dissolved and mixed uniformly to obtain an electrolyte solution with a lithium salt concentration of 1 mol / L.

[0058] <Preparation of positive electrode piece> The positive electrode active material LiFePO4, conductive carbon black, and binder PVDF were mixed in a mass ratio of 97.5:1:1.5, and N-methylpyrrolidine ketone (NMP) was added as a solvent. The mixture was stirred uniformly to prepare a positive electrode slurry with a solids content of 75 wt%. The positive electrode slurry was uniformly coated onto one surface of a 13 μm-thick aluminum foil positive electrode current collector and dried at 90°C to obtain a positive electrode piece with a 50 μm-thick layer of positive electrode active material coated on one side. After coating, the electrode piece was cut to a diameter of 14 mm and immersed in the electrolyte prepared in the above <Preparation of Electrolyte Solution> for 2 hours. The liquid on the surface was wiped off with dust-free paper and then subjected to the next step.

[0059] <Preparation of separator> 2 g of CuBTC powder was dried in a vacuum oven at 100 °C for 12 hours. After polishing, the dried powder was mixed with the CuBTC powder and the binder PVDF in a mass ratio of 9:1. NMP was added as a solvent and stirred uniformly to prepare a slurry with a solids content of 50 wt%. The slurry was scraped and coated with a 30 μm doctor blade to form a film. The coated film was activated by drying in a vacuum oven at 180 °C for 72 hours. The activated film was then pressed under a high pressure of 1 ton (t) before being subjected to the next step. The film was then immersed in the electrolyte prepared in the above <Preparation of Electrolyte Solution> for 48 hours at 60 °C. The liquid on the surface was wiped off with dust-free paper and then dried in a vacuum oven at 60 °C for 3 minutes to obtain a separator. The separator was cut to a diameter of 22 mm and subjected to the next step.

[0060] <Preparation of button batteries> In a glove box under a dry argon atmosphere, the negative electrode case, negative electrode pieces, separator, positive electrode pieces, and positive electrode case were arranged in this order from bottom to top and packaged in a packaging machine to obtain a lithium metal button battery. No electrolyte was required during assembly.

[0061] Examples 2 and 3 The same as in Example 1, except that the type of sub-nanoporous material was adjusted according to Table 1.

[0062] Examples 4 to 6 The same as in Example 1, except that the preparation parameters were adjusted according to Table 1.

[0063] Example 7 The procedure was the same as in Example 1, except that a separator prepared according to the following <Preparation of Separator> was used.

[0064] <Preparation of separator> 24 mg of PSS was dissolved in 600 mL of ethanol solution (volume ratio of ethanol to water: 1:1), and then 2 g of CuBTC powder was added. The mixture was stirred at room temperature for 24 hours, then suction filtered, and then vacuum dried at 100 °C for 12 hours and polished to obtain CuBTC powder whose pores were modified with PSS, which was designated as CuBTC@PSS powder. CuBTC@PSS powder and PVDF binder were mixed at a mass ratio of 9:1, NMP was added as a solvent, and the mixture was stirred uniformly to prepare a slurry with a solids content of 50 wt%. The slurry was then scraped with a 30 μm doctor blade to form a film. The coated film was then activated by drying in a vacuum dryer at 180 °C for 72 hours. The activated film was then subjected to a 1-ton (t) high-pressure roll press and then subjected to the next step. The film was then immersed in the electrolyte solution prepared in the above <Preparation of Electrolyte Solution> for 48 hours at 60 °C. The liquid on the surface was then wiped off with dust-free paper and dried in a vacuum dryer at 60 °C for 3 minutes to obtain a separator. The separator was then cut to a diameter of 22 mm and subjected to the next step.

[0065] Examples 8 to 18 The same as in Example 7, except that the preparation parameters were adjusted according to Table 1.

[0066] Example 19 The procedure was the same as in Example 1, except that the separator prepared in the following <Preparation of separator> was used.

[0067] <Preparation of separator> 24 mg of PSS was dissolved in 600 mL of ethanol solution (volume ratio of ethanol to water: 1:1), and then 2 g of CuBTC powder was added. The mixture was stirred at room temperature for 24 hours, then suction filtered, and then vacuum dried at 100 °C for 12 hours and polished to obtain CuBTC powder whose pores were modified with PSS, which was designated as CuBTC@PSS powder. CuBTC@PSS powder and the binder PTFE were mixed in a mass ratio of 9:1 and polished to a uniform consistency. The mixture was then formed into a film using a 1-ton high-pressure roll press. The film obtained by roll pressing was then dried in a vacuum dryer at 180°C for 72 hours to activate it and then used in the next step. The film thus produced was then immersed in the electrolyte prepared in the above <Preparation of Electrolyte Solution> at 60°C for 48 hours. The liquid on the surface was then wiped off with dust-free paper, and the film was then dried in a vacuum dryer at 60°C for 3 minutes to obtain a separator. The separator was then cut to a diameter of 22 mm and used in the next step.

[0068] Example 20 The same as in Example 2, except that the preparation parameters were adjusted according to Table 1.

[0069] Example 21 The same as in Example 7, except that the preparation parameters were adjusted according to Table 1.

[0070] Comparative Example 1 The procedure was the same as in Example 1, except that a separator prepared according to the following <Preparation of Separator> was used.

[0071] <Preparation of separator> A PP film (provided by Entek) was immersed in the electrolyte solution prepared in the above <Preparation of electrolyte solution> at 60°C for 48 hours, the liquid on the surface was wiped off with dust-free paper, and then the film was dried for 3 minutes in a vacuum dryer at 60°C to obtain a separator. The separator was cut to a diameter of 22 mm and used in the next step.

[0072] Comparative Example 2 The same as Comparative Example 1 was performed except that a PE film (provided by Entek) was used instead of the PP film.

[0073] Comparative Example 3 The procedure was the same as in Comparative Example 1, except that a PE film (provided by Entek) was used instead of the separator PP produced in <Preparation of separator>, and 70 μL of the electrolyte solution prepared in <Preparation of electrolyte solution> above was added to <Preparation of button battery>.

[0074] The relevant parameters and property measurements for each example and comparative example are shown in Tables 1 and 2.

[0075] [Table 1]

[0076] [Table 2]

[0077] Overall, the lithium metal batteries of Examples 1 to 21 of the present invention have higher coulombic efficiencies and more cycle times than those of Comparative Examples 1 to 3. This indicates that the lithium metal batteries of the present invention have higher coulombic efficiencies and longer cycle lives.

[0078] As can be seen from Examples 1 to 3 and Example 20, by adjusting the pore size of the subnanoporous material within the range of the present invention, the Coulombic efficiency of the lithium metal battery can be improved and the number of cycles of the lithium metal battery can be increased, i.e., the lithium metal battery has high Coulombic efficiency and long cycle life.

[0079] The type of subnanoporous material generally affects the coulombic efficiency and cycle life of a lithium metal battery. As can be seen from Examples 1 to 3 and Example 20, by selecting a subnanoporous material within the scope of the present invention, the lithium metal battery has high coulombic efficiency and a long cycle life.

[0080] The specific surface area of ​​the sub-nanoporous material generally affects the coulombic efficiency and cycle life of the lithium metal battery. As can be seen from Examples 1 to 3, by adjusting the specific surface area of ​​the nanoporous material within the range of the present invention, the lithium metal battery has a high coulombic efficiency and a long cycle life.

[0081] The particle size of the subnanoporous material particles generally affects the coulombic efficiency and cycle life of the lithium metal battery. As can be seen from Examples 1 to 3, 15 to 16, 20, and 21, by adjusting the particle size of the nanoporous material particles within the range of the present invention, the lithium metal battery has high coulombic efficiency and a long cycle life.

[0082] The pore size of the separator generally affects the Coulombic efficiency and cycle life of a lithium metal battery. As can be seen from Examples 1, 3 to 6, and 19, by adjusting the pore size of the separator within the range of the present invention, the Coulombic efficiency of the lithium metal battery can be improved and the number of cycles of the lithium metal battery can be increased, i.e., the lithium metal battery has a high Coulombic efficiency and a long cycle life.

[0083] The thickness of the separator generally affects the coulombic efficiency and cycle life of a lithium metal battery. As can be seen from Examples 7 to 11 and 19, by adjusting the separator thickness within the range of the present invention, the lithium metal battery has a high coulombic efficiency and a long cycle life.

[0084] The porosity of the separator generally affects the coulombic efficiency and cycle life of the lithium metal battery. As can be seen from Examples 1 to 21, by adjusting the porosity of the separator within the range of the present invention, the lithium metal battery has a relatively high coulombic efficiency and a relatively high number of cycles, i.e., the lithium metal battery has a high coulombic efficiency and a long cycle life.

[0085] The inclusion of a polymer within the pores of a sub-nanoporous material generally affects the coulombic efficiency and cycle life of a lithium metal battery. As can be seen from the comparison between Example 1 and Example 7, by modifying the polymer within the pores of the sub-nanoporous material of the separator, the lithium metal battery has a higher coulombic efficiency and a higher cycle number, i.e., the lithium metal battery has a higher coulombic efficiency and a longer cycle life.

[0086] The type of polymer generally affects the coulombic efficiency and cycle life of a lithium metal battery. As can be seen from Examples 7 and 17, by selecting a polymer within the scope of the present invention, the lithium metal battery has a high coulombic efficiency and a long cycle life.

[0087] The type of binder generally affects the coulombic efficiency and cycle life of a lithium metal battery. As can be seen from Examples 7 and 18, by selecting a binder within the scope of the present invention, the lithium metal battery has a high coulombic efficiency and a long cycle life.

[0088] The value of S2 / S1 generally affects the coulombic efficiency and cycle life of a lithium metal battery. As can be seen from Examples 1 to 21, by adjusting the value of S2 / S1 within the range of the present invention, the lithium metal battery has high coulombic efficiency and a long cycle life.

[0089] The value of S4 / S3 generally affects the coulombic efficiency and cycle life of a lithium metal battery. As can be seen from Examples 1 to 21, by adjusting the value of S4 / S3 within the range of the present invention, the lithium metal battery has high coulombic efficiency and a long cycle life.

[0090] The separators prepared in Examples 1 to 21 exhibited no thermal shrinkage and high heat resistance even when heated to 200°C, whereas the separators prepared in Comparative Examples 1 to 3 exhibited thermal shrinkage and relatively poor heat resistance when heated to 200°C. This indicates that the separators provided by the present invention can alleviate the short circuit problem caused by thermal shrinkage of the separator at high temperatures and improve the safety of electrochemical devices.

[0091] The inventors evaluated the flexibility of the separator as follows: The separators prepared in Examples 1 to 21 of the present invention were folded over 100 times, and no cracks occurred. This indicates that the separators provided by the present invention have good flexibility.

[0092] Figures 3a to 3c show SEM photographs of the separator prepared in Example 19. Figures 3a and 3b are SEM photographs of the surface of the separator prepared in Example 19 at different magnifications. As can be seen from Figure 3a, the surface of the separator prepared in Example 19 perpendicular to the thickness direction is flat and dense. In Figure 3b, the rounded linear structures are binder, and the binder is uniformly distributed in the sub-nanoporous material. Figure 3c is an SEM photograph of a cross section along the thickness direction of the separator prepared in Example 19. As can be seen from Figure 3c, the separator prepared in Example 19 is also dense in the thickness direction. From the above, the separator prepared in Example 19 of the present invention is dense and flat.

[0093] As can be seen from FIG. 4, in the Raman spectrum of the separator of the lithium metal battery of Example 1, -1 ~750cm-1 Between Li + -TFSI - When the peak area of ​​the Raman peak before cycling is S1 and the peak area of ​​the Raman peak after cycling is S2, the relationship S2 / S1=3.2 is satisfied.

[0094] As can be seen from FIG. 5, in the infrared spectrum of the separator of the lithium metal battery of Example 1, -1 ~800cm -1 , 1000cm -1 ~1260cm -1 and 1300 cm -1 ~1500cm -1 If the sum of the peak areas of the infrared characteristic peaks within the above range before cycling is S3 and the sum of the peak areas of the infrared characteristic peaks within the above range after cycling is S4, then S4 / S3 = 21. -1 ~800cm -1 , 1000cm -1 ~1260cm -1 and 1300 cm -1 ~1500cm -1 In the range of 770 cm, a peak characteristic of CuBTC appears. In the infrared spectrum after cycling, in addition to the above characteristic peaks, -1 ~800cm -1 and 1380 cm -1 ~1420cm -1 Between Li + -PC has an infrared characteristic peak at 1000 cm -1 ~1100cm -1 Between TFSI - This indicates that the electrolyte can penetrate into the pores of the separator and also into the sub-nanopores of the sub-nanoporous material, and the separator has good liquid absorption properties.

[0095] 6, under the same cycle conditions, the cycle capacity retention rate of the lithium metal battery of Comparative Example 2 decays to 80% or less at the 25th cycle, while that of the lithium metal battery prepared in Example 7 of the present invention decays to 80% or less at the 150th cycle. This indicates that the capacity decay of the lithium metal battery prepared in Example 7 of the present invention is slower and the number of cycles is longer, i.e., the lithium metal battery prepared in Example 7 of the present invention has better cycle characteristics and a longer cycle life.

[0096] The above description is only a preferred embodiment of the present invention, and does not limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A separator, the separator comprises a sub-nanoporous material and a binder; the sub-nanoporous material comprises a metal-organic framework material or a molecular sieve material; The pore size of the sub-nanoporous material is 0.01 nm to 1 nm.

2. The separator according to claim 1, wherein the pore size of the separator is 20 nm to 500 nm.

3. the metal-organic framework material comprises at least one of MOF-69C, MOF-74, MOF-5, ZIF-67, ZIF-8, MIL-100(Cr), MIL-100(Fe), UIO-66, PCN-61, and CuBTC; 10. The separator of claim 1, wherein the molecular sieve material comprises at least one of MCM-41, SAPO-34, 3A molecular sieve, 4A molecular sieve, 5A molecular sieve, and 13X molecular sieve.

4. The separator is (1) The pores of the sub-nanoporous material contain a polymer, and the polymer includes at least one of poly(sodium styrene sulfonate), poly(N-2-(dimethylaminopropyl) methacrylamide), and poly(acrylic acid); (2) the particle diameter D50 of the particles of the subnanoporous material is 50 nm to 5000 nm; (3) The specific surface area of ​​the sub-nanoporous material is 200 m ２ / g to 2000m ２ / g, and (4) The separator according to claim 1, wherein the binder satisfies at least one of the following: polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, polyimide, polyamide, polyamideimide, polyvinyl alcohol, polyacrylonitrile, polystyrene butadiene copolymer, sodium alginate, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium hydroxymethylcellulose, and potassium hydroxymethylcellulose.

5. The separator is (1) The thickness of the separator is 5 μm to 200 μm; and (2) The separator according to claim 1, which satisfies at least one of the following conditions: a porosity of the separator is 10% to 80%.

6. The separator is (1) the particle diameter D50 of the particles of the subnanoporous material is 100 nm to 1000 nm; (2) The thickness of the separator is 10 μm to 50 μm; (3) The porosity of the separator is 10% to 30%; (4) The pore diameter of the separator is 20 nm to 100 nm; and (5) The specific surface area of ​​the sub-nanoporous material is 200 m ２ / g~1500m ２ The separator according to any one of claims 1 to 5, which satisfies at least one of the following conditions:

7. An electrochemical device comprising the separator according to any one of claims 1 to 6.

8. In an environment of 25±1° C., the electrochemical device is charged at a constant current of 0.2 C to 3.7 V, then charged at a constant voltage of 3.7 V to 0.025 C, allowed to stand for 5 minutes, and discharged at a constant current of 0.2 C to 2.8 V, and this cycle is repeated 10 times or more; The Raman spectrum of the separator is at 730 cm －１ ~750cm －１ and the peak area of ​​the Raman peak before cycling is S １ The peak area of ​​the Raman peak after cycling is S ２ In this case, 1.1≦S ２ / S １ 8. The electrochemical device of claim 7, wherein ≦5.

9. The infrared spectrum of the separator is －１ ~800cm －１ , 1000 cm －１ ~1260cm －１ , 1380 cm －１ ~1500cm －１ The sum of the peak areas of the infrared characteristic peaks before cycling is S ３ The sum of the peak areas of the infrared characteristic peaks after cycling is S ４ In this case, 1.1≦S ４ / S ３ ≦100, preferably 1.1≦S ４ / S ３ 9. The electrochemical device of claim 8, wherein ≦30.

10. An electronic device comprising the electrochemical device according to any one of claims 7 to 9.

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