Negative electrode current collector applying two-dimensional polyamide to interface layer

Abstract

The invention discloses a negative current collector applying two-dimensional polyamide to an interface layer, which is mainly composed of a conductive metal sheet and a polymer interface layer on the surface of the conductive metal sheet, and the polymer interface layer is composed of two-dimensional polyamide or mainly composed of two-dimensional polyamide. The two-dimensional polyamide is applied to the interface layer of the negative electrode current collector, so that the cycling stability and the rate capability of the metal battery are synchronously improved. Especially, research finds that effective electron delocalization is realized due to existence of p-pi and pi-pi conjugated groups in two-dimensional polyamide, and distribution of lithium ions is further improved through electron-ion interaction, so that densification nucleation and deposition morphology of lithium metal is realized. By utilizing the negative current collector, the lithium metal battery with high energy density, high magnification and long cycle life, especially a negative-electrode-free lithium metal battery can be obtained, and a brand new thought and scheme are provided for developing a high-performance metal battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative current collectors for metal batteries, and relates to a negative current collector applying two-dimensional polyamide to the interface layer, specifically to a negative current collector applying two-dimensional polyamide to the interface layer and a preparation method thereof, and a metal battery, especially a non-aqueous lithium metal battery, prepared by using the negative current collector. Background Art

[0002] Due to the rapid development of consumer electronics, Internet of Things, electric vehicles and grid energy storage, rechargeable batteries with high energy density and high rate performance have become a research hotspot. In the preparation process of non-aqueous lithium metal batteries, only a conductive substrate (such as copper foil) is used without using any negative electrode active materials, showing significant advantages in terms of material cost, simplicity of production process and energy density. However, compared with traditional lithium-ion batteries and conventional lithium metal batteries, non-aqueous lithium metal batteries usually show poor cycle stability and rate performance, which is mainly attributed to the poor reversibility and bad kinetic characteristics of the lithium ion deposition / stripping reaction on the negative current collector. To improve the above problems, research has been carried out on aspects such as electrolyte composition, negative electrode - electrolyte interface layer, positive electrode sacrificial agent and battery cycling conditions. Among them, using a polymer interface layer to regulate the negative electrode - electrolyte interface is considered a promising solution because polymer materials have excellent processability and chemical designability. However, the reported polymer interface layers usually perform poorly in lithium ion adsorption, distribution and nucleation regulation, resulting in limited rate and cycle performance, far lower than the corresponding performance of traditional lithium-ion and lithium metal batteries. [1,2,3] 。

[0003] Therefore, if there can be a polymer material as the interface layer to regulate the negative electrode - electrolyte interface, which not only has advantages in lithium ion adsorption, distribution and nucleation, but also is convenient to realize a valuable non-aqueous lithium metal battery, it is full of hope and extremely challenging for the entire non-aqueous battery field. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a negative electrode current collector applying two-dimensional polyamide to the interface layer. By applying two-dimensional polyamide to the interface layer of the negative electrode current collector, the synchronous improvement of the cycle stability and rate performance of the metal battery is realized. The nitrogen- and oxygen-containing groups in two-dimensional polyamide generate ion-dipole interactions with lithium ions, constructing uniform lithium ion adsorption and nucleation sites at the molecular scale, and promoting the uniform adsorption of lithium ions at the negative electrode-electrolyte interface; in particular, it is found that the existence of p-π and π-π conjugated groups in two-dimensional polyamide realizes effective electron delocalization, and further improves the distribution of lithium ions through electron-ion interactions, thereby realizing the dense nucleation and deposition morphology of lithium metal. Based on the discovery of the "adsorption-conjugation" effect of the above two-dimensional polyamide, the reversibility and kinetics of the lithium metal deposition-stripping reaction can be greatly improved. The negative electrode current collector prepared by using it can obtain a lithium metal battery with high energy density, high rate and long cycle life, especially a lithium metal battery without a negative electrode, providing a new idea and solution for the development of high-performance metal batteries.

[0005] To achieve the above object, the present invention is realized by a technical solution composed of the following technical measures.

[0006] On the one hand, the present invention provides an application of two-dimensional polyamide in a negative electrode current collector.

[0007] The two-dimensional polyamide (2DPA) is a known polymer, and its preparation method can be obtained based on the following publicly disclosed technical literature: Zeng Y. et al. Irreversible synthesis of an ultrastrong two-dimensional polymeric material. Nature 602, 91-95 (2022).

[0008] On the other hand, the present invention provides a negative electrode current collector applying two-dimensional polyamide to the interface layer, which is mainly composed of a conductive metal sheet and a polymer interface layer on its surface, and the polymer interface layer is composed of two-dimensional polyamide or mainly composed of two-dimensional polyamide.

[0009] In this article, the conductive metal sheet is one of the common knowledge components in the negative electrode current collector. The specific selection of the metal can directly refer to the metals that can be applied to the negative electrode current collector in the existing technical literature in this field, such as copper, nickel or copper-carbon composite materials; its specific size specifications can be selected according to the requirements of the corresponding battery, referring to the common knowledge / existing technical literature / existing processes in this field, such as the copper foil sheet commonly used in lithium metal batteries without a negative electrode.

[0010] In this article, the polymer interface layer is composed of or mainly composed of two-dimensional polyamide. It should be noted that when the polymer interface layer is composed of two-dimensional polyamide, according to the conventional preparation process of the current collector interface layer in the art, it has been experimentally verified that two-dimensional polyamide can be directly used as a single component. For example, the polymer interface layer can be formed on the surface of the conductive metal sheet by conventional methods such as coating.

[0011] In one of the technical solutions, the polymer interface layer is composed of or mainly composed of two-dimensional polyamide. When the polymer interface layer is mainly composed of two-dimensional polyamide, additives commonly used in the preparation process of the current collector interface layer can also be added to further improve the performance / expand the function / assist the process of the prepared negative electrode current collector. For the specific selection of additives, those skilled in the art can refer to the prior art or existing literature. For example, ion transport additives, film-forming additives, anti-aging agents, heat stabilizers, antibacterial agents and other processing additives / functional additives. The addition amount of the additives can directly refer to the conventional dosage of the selected additives in the process of preparing the negative electrode current collector or according to the usage instructions of the additives.

[0012] Those skilled in the art should be aware that on the premise that the composition of the negative electrode current collector applying two-dimensional polyamide to the interface layer has been clearly described above, those skilled in the art can completely prepare a negative electrode current collector consistent with the above description under the guidance of the prior art of the negative electrode current collector with an interface layer in the common general knowledge or literature in the art. However, in order to better illustrate the present invention and provide a reference technical solution, a method for preparing the negative electrode current collector applying two-dimensional polyamide to the interface layer under laboratory conditions will be given below, but this does not mean a specific limitation on the above method for preparing the negative electrode current collector.

[0013] In one of the technical solutions, the method for preparing the negative electrode current collector applying two-dimensional polyamide to the interface layer mainly includes the following steps:

[0014] (A-1) Weigh two-dimensional polyamide and dissolve it in a volatile solvent to prepare a two-dimensional polyamide solution, where the mass concentration of two-dimensional polyamide is 0.1-50 mg / mL;

[0015] (A-2) Coat the two-dimensional polyamide solution obtained in step (A-1) on the conductive metal sheet, and then volatilize the solvent to form a polymer interface layer, that is, obtain the negative electrode current collector applying two-dimensional polyamide to the interface layer;

[0016] Or

[0017] (B-1) Weigh two-dimensional polyamide and additives and dissolve them in a volatile solvent to prepare a mixed solution containing two-dimensional polyamide, where the mass concentration of two-dimensional polyamide is 0.1-50 mg / mL;

[0018] (B-2) Coating the mixed solution obtained in step (B-1) on a conductive metal sheet, and then volatilizing the solvent to form a polymer interface layer, thus obtaining a negative current collector with two-dimensional polyamide applied to the interface layer.

[0019] In this technical solution, the volatile solvent is a conventional solvent that can be removed at normal temperature or under heating conditions, and this solvent should be able to dissolve two-dimensional polyamide, such as N-methylpyrrolidone, N,N-dimethylformamide, or their mixtures, etc.

[0020] In this article, the conventional process specifications (such as thickness, etc.) of the polymer interface layer are the same as those of the interface layer of the current collector in the prior art. In one technical solution, to form an ultra-light and ultra-thin interface layer, the thickness of the polymer interface layer is not greater than 1 μm.

[0021] In one technical solution, the loading amount of the polymer interface layer is not greater than 0.1 mg / cm 2 .

[0022] Polyamide, commonly known as nylon, is a polymer with a wide range of uses and has various applications. The interaction between the abundant amide groups in polyamide and lithium ions is stronger than that of traditional polymers. However, due to the challenges in molecular engineering and material assembly of polyamide, the interface layer of the lithium metal-free battery based on polyamide has not been realized so far. On the one hand, this is because the molecular sequence of traditional polyamide leads to insufficient interaction between only the bare amide groups and lithium ions; on the other hand, one-dimensional polyamide chains are prone to entanglement and assemble into overly thick materials, prolonging the transport path of lithium ions inside the interface layer and resulting in a significant increase in interface impedance. [4,5] .

[0024] The inventive point of the present invention lies in using two-dimensional polyamide (2DPA) to form an interface layer. The nitrogen- and oxygen-containing groups in 2DPA generate ion-dipole interactions with lithium ions, constructing uniform lithium ion adsorption and nucleation sites at the molecular scale, and promoting the uniform adsorption of lithium ions at the negative electrode-electrolyte interface. On this basis, it is first found through research that the presence of p-π and π-π conjugated groups in 2DPA realizes effective electron delocalization, further improving the distribution of lithium ions through electron-ion interactions, thereby achieving dense nucleation and deposition morphology of lithium metal. Based on the above "adsorption-conjugation" effect of 2DPA, the reversibility and kinetics of the lithium metal deposition-stripping reaction can be greatly improved. The negative current collector prepared using it can obtain a lithium metal battery with high energy density, high rate, and long cycle life, especially a lithium metal-free battery.

[0025] Based on the above inventive points, in one preferred technical solution, in order to further improve the cycle stability and rate performance of the metal battery prepared using this negative current collector, the thickness of the polymer interface layer is preferably 50 - 240 nm, and more preferably 50 - 100 nm.

[0026] Based on the above inventive points, in one preferred technical solution, in order to further improve the cycle stability and rate performance of the metal battery prepared using this negative current collector, the mass concentration of two-dimensional polyamide in the two-dimensional polyamide solution or mixed solution is 0.1 - 20 mg / mL, more preferably 0.5 - 10 mg / mL, and most preferably 0.5 - 5 mg / mL.

[0027] Based on the above inventive points, in one preferred technical solution, in order to further improve the cycle stability and rate performance of the metal battery prepared using this negative current collector, the loading amount of the polymer interface layer in the negative current collector is 0.002 - 0.04 mg / cm 2 , and more preferably 0.005 - 0.02 mg / cm 2 .

[0028] In one preferred technical solution, the polymer interface layer is composed of two-dimensional polyamide (2DPA) and lithiated perfluorosulfonic acid polymer (LN), that is, in the step (B-1), two-dimensional polyamide and lithiated perfluorosulfonic acid polymer with a mass ratio of (1 - 20):1 are weighed and dissolved in a volatile solvent to prepare a mixed solution containing two-dimensional polyamide, where the mass concentration of two-dimensional polyamide is 0.1 - 50 mg / mL. By selecting lithiated perfluorosulfonic acid polymer (LN) as an auxiliary agent, the ionic conductivity performance and film-forming property of the polymer interface layer are further improved.

[0029] The above-provided negative current collector with two-dimensional polyamide applied to the interface layer can be applied to metal batteries, such as lithium metal batteries, sodium metal batteries, potassium metal batteries, magnesium metal batteries, aluminum metal batteries, etc.; more preferably, it is applied to lithium metal batteries without a negative electrode, including lithium metal secondary batteries without a negative electrode.

[0030] To better illustrate the present invention, the following will take a lithium metal battery as an example to demonstrate the specific application method of the above negative current collector with two-dimensional polyamide applied to the interface layer. However, it should be noted that the negative current collector with two-dimensional polyamide applied to the interface layer provided by the present invention is not only limited to being applied to lithium metal batteries, but can also be applied to other metal batteries.

[0031] First, based on the common knowledge of lithium metal batteries in the prior art, when applying the above negative electrode current collector to a lithium metal battery, the lithium metal battery generally further includes a negative electrode, a positive electrode, and an electrolyte. Moreover, the raw material selection / raw material ratio / preparation process of the negative electrode, positive electrode, and electrolyte all follow the conventional lithium metal battery process. A person skilled in the art can, according to the conventional preparation process of lithium metal batteries or the type of lithium metal battery required, select a suitable process based on the prior art to prepare a lithium metal battery based on the above negative electrode current collector.

[0032] To better illustrate the present invention and facilitate a more thorough interpretation of the beneficial effects of the negative electrode current collector applying two-dimensional polyamide to the interface layer provided by the present invention, on the other hand, the present invention also provides a lithium metal secondary battery without a negative electrode based on the negative electrode current collector, which is mainly composed of a positive electrode, an electrolyte, and the negative electrode current collector applying two-dimensional polyamide to the interface layer.

[0033] In this article, the positive electrode is one of the components well-known in the lithium metal secondary battery without a negative electrode, and it can be directly obtained through commercial channels or prepared by oneself according to the prior art literature / conventional process of lithium metal secondary batteries in this field.

[0034] To better illustrate the present invention and provide a reference technical solution, the positive electrode is mainly composed of a conventional positive electrode current collector and a positive electrode coating on its surface. The positive electrode coating is composed of a metal oxide for the positive electrode, a carbon-based particle for the positive electrode, and a binder.

[0035] Among them, the metal oxide for the positive electrode is a conventional component selection for the positive electrode coating in a lithium metal battery without a negative electrode. For example, it can be selected from any one of lithium iron phosphate, lithium cobaltate, and nickel cobalt manganese ternary materials.

[0036] Among them, the carbon-based particle for the positive electrode is a conventional component selection for the positive electrode coating in a lithium metal battery without a negative electrode. For example, it can be selected from any one of graphite, conductive carbon black, carbon nanotubes, and graphene.

[0037] Among them, the binder is a conventional component selection for the positive electrode coating in a lithium metal battery without a negative electrode. For example, it can be selected from any one of polyvinylidene fluoride solution, polytetrafluoroethylene emulsion, and carboxymethyl cellulose solution.

[0038] In this article, the electrolyte is one of the components well-known in the lithium metal secondary battery without a negative electrode, and it can be directly obtained through commercial channels or prepared by oneself according to the prior art literature / conventional process of lithium metal secondary batteries in this field.

[0039] To better illustrate the present invention and provide a reference technical solution, the electrolyte is composed of a metal fluoride for electrolyte, a metal nitride for electrolyte, and a solvent for electrolyte; the molar concentration of the metal fluoride for electrolyte is 0.1 to 5 mol / L, and the mass fraction of the metal nitride for electrolyte is 1 to 5%.

[0040] Among them, the metal fluoride for electrolyte is a conventional component selection for the electrolyte in a non-anode lithium metal battery. For example, any one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium difluoro(oxalato)borate, and lithium tetrafluoroborate can be selected.

[0041] Among them, the metal nitride for electrolyte is a conventional component selection for the electrolyte in a non-anode lithium metal battery. For example, any one of lithium nitride and lithium nitrate can be selected.

[0042] Among them, the solvent for electrolyte is a conventional component selection for the electrolyte in a non-anode lithium metal battery. For example, any one of 1,3-dioxolane, ethylene glycol dimethyl ether, diethyl carbonate, and fluoroethylene carbonate, or a mixture thereof, can be selected.

[0043] In this article, based on the common knowledge of non-anode lithium metal secondary batteries in the prior art, the non-anode lithium metal secondary battery may further include a conventional negative electrode case, a gasket, a shrapnel, a separator loaded with electrolyte, a positive electrode case, and other conventional structures / components / components. Those skilled in the art can select a suitable process based on the conventional preparation process of non-anode lithium metal secondary batteries or the required battery type to prepare the non-anode lithium metal secondary battery product based on the prior art.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. By applying two-dimensional polyamide to the interface layer of the negative electrode current collector, the present invention realizes the synergistic improvement of the cycle stability and rate performance of metal batteries, especially lithium metal batteries.

[0046] 2. In one of the technical solutions, a negative electrode current collector is prepared based on a polymer interface layer composed of two-dimensional polyamide (2DPA) and lithiated perfluorosulfonic acid polymer (LN), and a non-anode lithium metal battery is assembled. By optimizing and regulating the component ratio and thickness of the polymer interface layer, the further synchronous improvement of the cycle stability and rate performance of the battery is realized. When the surface current and surface capacity are 1 mA / cm 2 and 1 mAh / cm 2 , the Li||Cu half-cell can stably cycle 550 times, and the average Coulombic efficiency is 98.9%; the maximum surface current and surface capacity that the Li||Cu half-cell can withstand are 30 mA / cm 2and 10 mAh / cm 2 。

[0047] 3. In one of the technical solutions, a negative electrode current collector is prepared based on a polymer interface layer composed of two-dimensional polyamide (2DPA) and lithiated perfluorosulfonic acid polymer (LN), and a non-negative electrode LiFePO4 full cell is assembled. Its maximum volume energy density is 660 Wh / L, and when the actual areal capacity is about 3.0 mAh / cm 2 the cycle stability is increased to 200 cycles, and the average Coulombic efficiency is 98.8%.

[0048] 4. In one of the technical solutions, a negative electrode current collector is prepared based on a polymer interface layer composed of two-dimensional polyamide (2DPA) and lithiated perfluorosulfonic acid polymer (LN), and a non-negative electrode LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) soft-pack battery is assembled. Its maximum energy density and power density are 471 Wh / kg and 622 W / kg respectively (based on the mass of the full-component soft-pack battery, including active and non-active substances). BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 FIG. is a schematic diagram of a non-negative electrode lithium metal secondary battery applying a two-dimensional polyamide to the interface layer of a negative electrode current collector provided by the present invention, a microscopic image and an X-ray diffraction image of the polymer interface layer. Among them, on the left side of FIG. a is a schematic diagram of the structural principle of a non-negative electrode lithium metal secondary battery; in the middle is a schematic diagram of the lamellae of two-dimensional polyamide (2DPA) and the structure of lithiated perfluorosulfonic acid polymer (LN); on the right side is the chemical structural formula of 2DPA; FIG. b is an atomic force microscope image of 2DPA, showing its lamellar morphology; FIG. c is a transmission electron microscope image of 2DPA, showing its amorphous morphology; FIG. d is a grazing incidence wide-angle X-ray diffraction image of the interface layer composed of 2DPA and LN, showing its orientation mode relative to the matrix and amorphous morphology.

[0050] Figure 2 FIG. is a Coulombic efficiency curve diagram of the Li||Cu half cells assembled in Examples 1 to 3 of the present invention at different charge and discharge cycle numbers under the conditions of 1 mA / cm 2 and 1 mAh / cm 2 . Among them, 2DPA / LN-Cu (1 mg / mL) corresponds to the test sample prepared in Example 1, 2DPA / LN-Cu (3 mg / mL) corresponds to the test sample prepared in Example 2, and 2DPA / LN-Cu (5 mg / mL) corresponds to the test sample prepared in Example 3.

[0051] Figure 3Coulomb efficiency curves of the Li||Cu half-cells assembled in Example 1 and Comparative Example 1 of the present invention at 1 mA / cm 2 and 1 mAh / cm 2 under different charge-discharge cycle numbers. Among them, 2DPA / LN-Cu corresponds to the test sample prepared in Example 1.

[0052] Figure 4 Coulomb efficiency curves of the Li||Cu half-cells assembled in Example 1 and Comparative Example 1 of the present invention at 20 mA / cm 2 and 2 mAh / cm 2 under different charge-discharge cycle numbers. Among them, 2DPA / LN-Cu corresponds to the test sample prepared in Example 1.

[0053] Figure 5 Charge-discharge curves and voltage hysteresis curves of the Li||Cu half-cell assembled in Example 1 of the present invention at 20 mA / cm 2 and 2 mAh / cm 2 conditions. Among them, the inset is the voltage hysteresis curve of the Li||Cu half-cells assembled in Example 1 and Comparative Example 1 at 20 mA / cm 2 and 2 mAh / cm 2 under different charge-discharge cycles. 2DPA / LN-Cu corresponds to the test sample prepared in Example 1.

[0054] Figure 6 Charge-discharge curves of the Li||Cu half-cell assembled in Example 1 of the present invention at surface currents of 10, 20, 30 and 40 mA / cm 2

[0055] Figure 7 Charge-discharge curves of the Li||Cu half-cell assembled in Comparative Example 1 of the present invention at surface currents of 10, 20 and 30 mA / cm 2

[0056] Figure 8 Charge-discharge curves of the Li||Cu half-cell assembled in Example 1 of the present invention at 10 mA / cm 2 and 10 mAh / cm 2

[0057] Figure 9 Specific capacity curves of the non-aqueous anode LiFePO4 full-cells assembled in Example 4 and Comparative Example 2 of the present invention under different rate conditions (0.1 - 5C).

[0058] Figure 10 ​​​Capacity and Coulomb efficiency curves of the non-anode LiFePO4 full cells prepared in Example 4 and Comparative Example 2 of the present invention under different charge-discharge cycles.

[0059] Figure 11 Constant current charge-discharge curve of the non-anode LiFePO4 full cell prepared in Example 4 of the present invention under the conditions of a current density of 0.3C (charge rate) and 0.5C (discharge rate).

[0060] Figure 12 Cross-sectional scanning electron microscope image and optical picture of the negative electrode current collector used in Example 1 of the present invention. The scanning electron microscope image shows that the thickness of the polymer interface layer is 50nm, and the scale bar is 50nm.

[0061] Figure 13 Optical picture of the negative electrode current collector used in Example 1 of the present invention. It shows that the negative electrode current collector coated with the polymer interface layer can be industrially prepared by a large-scale scraping process.

[0062] Figure 14 Li||Cu half cell assembled in Example 1 of the present invention was analyzed by time-of-flight secondary ion mass spectrometry for Li - , CON - and LiF - Three-dimensional distribution result diagram of ion fragments.

[0063] Figure 15 Atomic force microscope mechanical modulus distribution diagram of the solid electrolyte interface on the copper foil surface of the Li||Cu half cell assembled in Example 1 of the present invention after 20 and 300 cycles of charge and discharge.

[0064] Figure 16 Physical picture of the non-anode NCM811 full cell prepared in Example 5 of the present invention.

[0065] Figure 17 Constant current charge-discharge curve of the non-anode NCM811 full cell prepared in Example 5 of the present invention under the conditions of a current density of 0.3C (charge rate) and 0.5C (discharge rate).

[0066] Figure 18 Constant current charge-discharge curve of the non-anode NCM811 full cell prepared in Example 5 of the present invention under different rate conditions (0.2 - 1.5C).

[0067] Figure 19 Li||Cu half cells assembled in Example 6 and Comparative Example 1 of the present invention at 1mA / cm 2 and 1mAh / cm 2Coulomb efficiency curve diagrams under different charge-discharge cycle numbers under certain conditions. Among them, 2DPA-Cu corresponds to the test sample prepared in Example 6.

[0068] Figure 20 Schematic diagram of the chemical reaction formula for synthesizing two-dimensional polyamide in the present invention. Detailed implementation manners

[0069] To further understand the present invention, the preferred implementation manners of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the invention. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and those skilled in the art can obviously make changes or appropriate modifications and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention. Although it is believed that those of ordinary skill in the art are fully aware of the following terms, the following definitions are still presented to help explain the subject matter disclosed in the present invention.

[0070] In one aspect, the present invention provides an application of two-dimensional polyamide in a negative electrode current collector.

[0071] The two-dimensional polyamide (2DPA) is a known polymer, and its preparation method can be obtained based on the following publicly available technical literature: Zeng Y. et al. Irreversible synthesis of an ultrastrong two-dimensional polymeric material. Nature 602, 91-95 (2022).

[0072] In another aspect, the present invention provides a negative electrode current collector applying two-dimensional polyamide to an interface layer, which is mainly composed of a conductive metal sheet and a polymer interface layer on its surface, and the polymer interface layer is composed of two-dimensional polyamide or mainly composed of two-dimensional polyamide.

[0073] In this article, the conductive metal sheet is one of the common knowledge components in the negative electrode current collector. The specific selection of the metal can directly refer to the metals that can be applied to the negative electrode current collector in the existing technical literature in the art. In one implementation manner, for example, copper, nickel or copper-carbon composite material; its specific size specifications can be selected according to the requirements of the corresponding battery, referring to the common knowledge in the art / existing technical literature / existing processes. For example, the copper foil sheet commonly used in lithium metal batteries without a negative electrode.

[0074] In this text, the polymer interface layer is composed of or mainly composed of two-dimensional polyamide. When the polymer interface layer is composed of two-dimensional polyamide, it should be noted that according to the conventional preparation process of the current collector interface layer in the art, it has been experimentally confirmed that two-dimensional polyamide can be directly used as a single component. For example, a polymer interface layer can be formed on the surface of a conductive metal sheet by conventional methods such as coating.

[0075] In one of the embodiments, the polymer interface layer is composed of or mainly composed of two-dimensional polyamide. When the polymer interface layer is mainly composed of two-dimensional polyamide, additives commonly used in the preparation process of the current collector interface layer can also be added to further improve the performance / expand the function / assist the process of the prepared negative electrode current collector. For the specific selection of additives, those skilled in the art can refer to the prior art or existing literature. For example, ion transport additives, film-forming additives, anti-aging agents, heat stabilizers, antibacterial agents and other processing additives / functional additives. The addition amount of the additives can directly refer to the conventional dosage of the selected additives in the process of preparing the negative electrode current collector or according to the usage instructions of the additives.

[0076] Those skilled in the art should be aware that on the premise that the composition of the negative electrode current collector with two-dimensional polyamide applied to the interface layer has been clearly described above, those skilled in the art can completely prepare a negative electrode current collector consistent with the above description under the guidance of the prior art of the negative electrode current collector with an interface layer in the common general knowledge or literature in the art. However, in order to better illustrate the present invention and provide a reference implementation method, a method for preparing the negative electrode current collector with two-dimensional polyamide applied to the interface layer under laboratory conditions will be given below, but this does not mean a specific limitation on the above method for preparing the negative electrode current collector.

[0077] In one of the embodiments, the method for preparing the negative electrode current collector with two-dimensional polyamide applied to the interface layer mainly includes the following steps:

[0078] (A-1) Weigh two-dimensional polyamide and dissolve it in a volatile solvent to prepare a two-dimensional polyamide solution, where the mass concentration of two-dimensional polyamide is 0.1 - 50 mg / mL;

[0079] (A-2) Coat the two-dimensional polyamide solution obtained in step (A-1) on a conductive metal sheet, and then volatilize the solvent to form a polymer interface layer, that is, obtain a negative electrode current collector with two-dimensional polyamide applied to the interface layer;

[0080] Or,

[0081] (B-1) Weigh two-dimensional polyamide and an additive and dissolve them in a volatile solvent to prepare a mixed solution containing two-dimensional polyamide, where the mass concentration of two-dimensional polyamide is 0.1 - 50 mg / mL;

[0082] (B-2) Coating the mixed solution obtained in step (B-1) on the conductive metal sheet, and then volatilizing the solvent to form a polymer interface layer, thus obtaining a negative electrode current collector with two-dimensional polyamide applied to the interface layer.

[0083] In this embodiment, the volatile solvent is a conventional solvent that can be removed at normal temperature or under heating conditions, and this solvent should be able to dissolve two-dimensional polyamide, such as N-methylpyrrolidone, N,N-dimethylformamide, or their mixtures, etc.

[0084] In this article, the conventional process specifications (such as thickness, etc.) of the polymer interface layer are the same as those of the interface layer of the current collector in the prior art. In one of the embodiments, to form an ultra-light and ultra-thin interface layer, the thickness of the polymer interface layer is not greater than 1 μm.

[0085] In one of the embodiments, the thickness of the polymer interface layer is not greater than 1 μm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 420 nm, 440 nm, 460 nm, 480 nm, 500 nm, 520 nm, 540 nm, 560 nm, 580 nm, 600 nm, 620 nm, 640 nm, 660 nm, 680 nm, 700 nm, 720 nm, 740 nm, 760 nm, 780 nm, 800 nm, 820 nm, 840 nm, 860 nm, 880 nm, 900 nm, 920 nm, 940 nm, 960 nm, 980 nm, 1000 nm, or any range or point value between them.

[0086] In one of the embodiments, the mass concentration of the two-dimensional polyamide is 0.1 to 50 mg / mL, such as 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL, 20 mg / mL, 21 mg / mL, 22 mg / mL, 23 mg / mL, 24 mg / mL, 25 mg / mL, 26 mg / mL, 27 mg / mL, 28 mg / mL, 29 mg / mL, 30 mg / mL, 31 mg / mL, 32 mg / mL, 33 mg / mL, 34 mg / mL, 35 mg / mL, 36 mg / mL, 37 mg / mL, 38 mg / mL, 39 mg / mL, 40 mg / mL, 41 mg / mL, 42 mg / mL, 43 mg / mL, 44 mg / mL, 45 mg / mL, 46 mg / mL, 47 mg / mL, 48 mg / mL, 49 mg / mL, 50 mg / mL or any range or point value therebetween.

[0087] Polyamide, commonly known as nylon, is a polymer with a wide range of uses and has various applications. The interaction between the abundant amide groups in polyamide and lithium ions is stronger than that of traditional polymers. However, due to the challenges in molecular engineering and material assembly of polyamide, the anode-free battery interface layer based on polyamide has not been realized so far. On the one hand, this is because the molecular sequence of traditional polyamide results in insufficient interaction between only the bare amide groups and lithium ions; on the other hand, one-dimensional polyamide chains are prone to entanglement and assemble into overly thick materials, extending the transmission path of lithium ions inside the interface layer and leading to a significant increase in the interface impedance. [4,5] .

[0089] The inventive point of the present invention lies in forming an interfacial layer using two-dimensional polyamide (2DPA). The nitrogen- and oxygen-containing groups in 2DPA generate ion-dipole interactions with lithium ions, constructing uniform lithium-ion adsorption and nucleation sites at the molecular scale, and promoting the uniform adsorption of lithium ions at the anode-electrolyte interface. On this basis, it was first discovered that the presence of p-π and π-π conjugated groups in 2DPA enables effective electron delocalization, further improving the distribution of lithium ions through electron-ion interactions, thereby achieving dense nucleation and deposition morphology of lithium metal. Based on the above "adsorption-conjugation" effect of 2DPA, the reversibility and kinetics of the lithium metal deposition-stripping reaction can be greatly enhanced. The anode current collector prepared using it can obtain a lithium metal battery with high energy density, high rate, and long cycle life, especially a lithium metal battery without an anode.

[0090] Based on the above inventive points, in one preferred embodiment, in order to further improve the cycle stability and rate performance of the metal battery prepared using this anode current collector, the thickness of the polymer interfacial layer is preferably 50 - 240 nm, more preferably 50 - 100 nm.

[0091] Based on the above inventive points, in one preferred embodiment, in order to further improve the cycle stability and rate performance of the metal battery prepared using this anode current collector, the mass concentration of two-dimensional polyamide in the two-dimensional polyamide solution or mixed solution is 0.1 - 20 mg / mL, more preferably 0.5 - 10 mg / mL, and most preferably 0.5 - 5 mg / mL.

[0092] In one embodiment, the loading amount of the polymer interfacial layer is not greater than 0.1 mg / cm 2 , such as 0.001 mg / cm 2 , 0.002 mg / cm 2 , 0.004 mg / cm 2 , 0.005 mg / cm 2 , 0.006 mg / cm 2 , 0.008 mg / cm 2 , 0.009 mg / cm 2 , 0.01 mg / cm 2 , 0.011 mg / cm 2 , 0.012 mg / cm 2 , 0.013 mg / cm 2 , 0.014 mg / cm 2 , 0.015 mg / cm 2 , 0.016 mg / cm 2 , 0.017 mg / cm 2 , 0.018 mg / cm2 , 0.019 mg / cm 2 , 0.02 mg / cm 2 , 0.03 mg / cm 2 , 0.04 mg / cm 2 , 0.05 mg / cm 2 , 0.06 mg / cm 2 , 0.07 mg / cm 2 , 0.08 mg / cm 2 , 0.09 mg / cm 2 , 0.1 mg / cm 2 or any range or point value therebetween.

[0093] Based on the above inventive points, in one preferred embodiment, in order to further improve the cycle stability and rate performance of the metal battery prepared using the negative electrode current collector, the loading amount of the polymer interface layer in the negative electrode current collector is 0.002 - 0.04 mg / cm 2 , more preferably 0.005 - 0.02 mg / cm 2 .

[0094] In one preferred embodiment, the polymer interface layer is composed of two-dimensional polyamide (2DPA) and lithiated perfluorosulfonic acid polymer (LN), that is, in the step (B-1), two-dimensional polyamide and lithiated perfluorosulfonic acid polymer with a mass ratio of (1 - 20):1 are weighed and dissolved in a volatile solvent to prepare a mixed solution containing two-dimensional polyamide, where the mass concentration of two-dimensional polyamide is 0.1 - 50 mg / mL. By selecting lithiated perfluorosulfonic acid polymer (LN) as an auxiliary agent, the ionic conductivity performance and film-forming property of the polymer interface layer are further improved.

[0095] Based on the above embodiment, the mass ratio of the two-dimensional polyamide to the lithiated perfluorosulfonic acid polymer is (1 - 20):1, that is, the mass ratio value is 1 - 20, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or any range or point value therebetween.

[0096] The above-provided negative electrode current collector applying two-dimensional polyamide to the interface layer can be applied to metal batteries, such as applied to lithium metal batteries, sodium metal batteries, potassium metal batteries, magnesium metal batteries, aluminum metal batteries, etc.; more preferably applied to lithium metal batteries without a negative electrode, including lithium metal secondary batteries without a negative electrode.

[0097] To better illustrate the present invention, the following will take a lithium metal battery as an example to demonstrate the specific application method of the above-mentioned negative electrode current collector with two-dimensional polyamide applied to the interface layer. However, it should be noted that the negative electrode current collector with two-dimensional polyamide applied to the interface layer provided by the present invention is not only limited to being applied to lithium metal batteries, but can also be applied to other metal batteries.

[0098] First, based on the common knowledge of lithium metal batteries in the prior art, when applying the above-mentioned negative electrode current collector to a lithium metal battery, the lithium metal battery usually further includes a negative electrode, a positive electrode, and an electrolyte. Moreover, the raw material selection / raw material ratio / preparation process of the negative electrode, positive electrode, and electrolyte all follow the conventional lithium metal battery process. Those skilled in the art can select a suitable process based on the conventional preparation process of lithium metal batteries or the type of lithium metal battery required, and prepare a lithium metal battery based on the above-mentioned negative electrode current collector according to the prior art.

[0099] To better illustrate the present invention and facilitate a more comprehensive interpretation of the beneficial effects of the negative electrode current collector with two-dimensional polyamide applied to the interface layer provided by the present invention, on the other hand, the present invention also provides a lithium metal secondary battery without a negative electrode based on this negative electrode current collector, which is mainly composed of a positive electrode, an electrolyte, and the negative electrode current collector with two-dimensional polyamide applied to the interface layer.

[0100] In this article, the positive electrode is one of the components well-known in the lithium metal secondary battery without a negative electrode, and it can be directly obtained through commercial channels or prepared by oneself according to the prior art literature / conventional process of lithium metal secondary batteries in this field.

[0101] To better illustrate the present invention and provide a reference implementation method, the positive electrode is mainly composed of a conventional positive electrode current collector and a positive electrode coating on its surface. The positive electrode coating is composed of a metal oxide for the positive electrode, a carbon-based particle for the positive electrode, and a binder.

[0102] Among them, the metal oxide for the positive electrode is a conventional component selection for the positive electrode coating in a lithium metal battery without a negative electrode. For example, any one of lithium iron phosphate, lithium cobaltate, and nickel cobalt manganese ternary materials can be selected.

[0103] Among them, the carbon-based particle for the positive electrode is a conventional component selection for the positive electrode coating in a lithium metal battery without a negative electrode. For example, any one of graphite, conductive carbon black, carbon nanotubes, and graphene can be selected.

[0104] Among them, the binder is a conventional component selection for the positive electrode coating in a lithium metal battery without a negative electrode. For example, any one of polyvinylidene fluoride solution, polytetrafluoroethylene emulsion, and carboxymethyl cellulose solution can be selected.

[0105] In this text, the electrolyte is one of the common knowledge components in the non-aqueous lithium metal secondary battery, and can be directly obtained commercially, or can be prepared by oneself according to the existing technical literature / conventional process of non-aqueous lithium metal secondary batteries in this field.

[0106] To better illustrate the present invention and provide a reference implementation, the electrolyte is composed of a metal fluoride for electrolyte, a metal nitride for electrolyte, and a solvent for electrolyte; the molar concentration of the metal fluoride for electrolyte is 0.1 - 5 mol / L, and the mass fraction of the metal nitride for electrolyte is 1 - 5%.

[0107] Among them, the metal fluoride for electrolyte is a conventional component selection for the electrolyte in the non-aqueous lithium metal battery. For example, any one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium difluoro(oxalato)borate, and lithium tetrafluoroborate can be selected.

[0108] Among them, the metal nitride for electrolyte is a conventional component selection for the electrolyte in the non-aqueous lithium metal battery. For example, any one of lithium nitride and lithium nitrate can be selected.

[0109] Among them, the solvent for electrolyte is a conventional component selection for the electrolyte in the non-aqueous lithium metal battery. For example, any one of 1,3-dioxolane, ethylene glycol dimethyl ether, diethyl carbonate, and fluoroethylene carbonate, or a mixture of them can be selected.

[0110] In this text, based on the common knowledge of non-aqueous lithium metal secondary batteries in the prior art, the non-aqueous lithium metal secondary battery may further include a conventional negative electrode case, a gasket, a spring piece, a separator for loading the electrolyte, a positive electrode case, and other conventional structures / components / components. Those skilled in the art can select a suitable process based on the prior art according to the conventional preparation process of non-aqueous lithium metal secondary batteries or the required battery type to prepare the non-aqueous lithium metal secondary battery product.

[0111] The following will further explain the present application with reference to the embodiments. However, those skilled in the art should understand that these embodiments are provided only for the purpose of illustration and are not intended to limit the present application.

[0112] Embodiments

[0113] The following will describe the implementation scheme of the present application in detail in combination with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase. The present application should not be construed as being limited by the specific embodiments described.

[0114] 1. Raw materials

[0115] Melamine (MA, 99%), 1,3,5-benzenetricarbonyl chloride (TMC, 98%), pyridine (99.5%), lithium hydroxide (LiOH, 99%), 1,3-dioxolane (DOL, 99%), ethylene glycol dimethyl ether (DME, 99%), N-methylpyrrolidone (NMP, 99.5%) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 98%) were purchased from Adamas. Lithium difluoro(oxalato)borate (LiDFOB, 99.9%), lithium tetrafluoroborate (LiBF4, 99.9%), diethyl carbonate (DEC, 99.99%) and fluoroethylene carbonate (FEC, 99.9%) were purchased from Dodo Chem. 10 wt% perfluorosulfonic acid polymer aqueous dispersion (10 wt% Nafion in H2O) was purchased from Macklin. Lithium nitrate (LiNO3) was purchased from Nanjing Mojiesi Energy Technology Co., Ltd. Glass fiber membrane (GF / D) was purchased from Whatman.

[0116] 2. Preparation method

[0117] 2.1 Preparation method of applying two-dimensional polyamide to the negative current collector of the interfacial layer, mainly including the following steps:

[0118] (1) Synthesis and preparation of two-dimensional polyamide (2DPA):

[0119] Two-dimensional polyamide (2DPA) is a known polymer and can be obtained based on the preparation methods disclosed in the following technical literature: Zeng Y. et al. Irreversible synthesis of an ultrastrong two-dimensional polymeric material. Nature 602, 91-95 (2022).

[0120] Or refer to the following preparation method of two-dimensional polyamide:

[0121] As Figure 20 shown, two-dimensional polyamide (2DPA) is prepared by a one-step polycondensation reaction: 2 mmol (252 mg) of melamine (MA), 2 mmol (530 mg) of 1,3,5-benzenetricarbonyl chloride (TMC) and 2 mL of pyridine are added to 18 mL of N-methylpyrrolidone (NMP), and stirred at 25 °C for 16 hours; then, the gel obtained from the reaction is ultrasonically dispersed in 100 mL of ethanol, washed and centrifuged three times with deionized water; the finally obtained yellow powder is dried under vacuum at 100 °C for 24 hours to prepare two-dimensional polyamide (2DPA).

[0122] (2) Preparation of lithiated perfluorosulfonic acid polymer (LN):

[0123] Lithium hydroxide (LiOH) was gradually added to a 10 wt% perfluorosulfonic acid polymer aqueous dispersion (5 g), and with vigorous stirring at 100 °C until the pH value of the solution was 7. Then the obtained lithiated perfluorosulfonic acid polymer solution was vacuum dried at 100 °C for 24 hours to prepare the lithiated perfluorosulfonic acid polymer, simply referred to as LN.

[0124] (3) Preparation of the negative electrode current collector:

[0125] The preparation of the negative electrode current collector can be carried out according to steps (A-1), (A-2) or steps (B-1), (B-2);

[0126] (A-1) Weigh two-dimensional polyamide and dissolve it in N-methylpyrrolidone solvent to prepare a two-dimensional polyamide solution, where the mass concentration of the two-dimensional polyamide is 0.1 - 50 mg / mL;

[0127] (A-2) The two-dimensional polyamide solution obtained in step (A-1) was spin-coated on a copper foil (100 cm × 20 cm, thickness 9 μm), and then the solvent was volatilized at 100 °C and under vacuum conditions to form a polymer interface layer, thus obtaining a negative electrode current collector with two-dimensional polyamide applied to the interface layer. It was punched into a circular sheet with a diameter of 12 mm, or cut into a rectangular sheet with dimensions of 84 × 63 mm for further electrochemical measurement and characterization;

[0128] Or,

[0129] (B-1) Weigh two-dimensional polyamide and lithiated perfluorosulfonic acid polymer and dissolve them in N-methylpyrrolidone solvent to prepare a mixed solution containing two-dimensional polyamide, where the mass concentration of the two-dimensional polyamide is 0.1 - 50 mg / mL;

[0130] (B-2) The mixed solution obtained in step (B-1) was spin-coated on a copper foil (100 cm × 20 cm, thickness 9 μm), and then the solvent was volatilized at 100 °C and under vacuum conditions to form a polymer interface layer, thus obtaining a negative electrode current collector with two-dimensional polyamide applied to the interface layer. It was punched into a circular sheet with a diameter of 12 mm, or cut into a rectangular sheet with dimensions of 84 × 63 mm for further electrochemical measurement and characterization.

[0131] 2.2 Preparation of Li||Cu half-cell (2032 type button cell):

[0132] In a glove box filled with argon atmosphere (oxygen content, water content less than 0.1ppm), lithium bis(trifluoromethanesulfonyl imide) and lithium nitrate were weighed, and 1,3-dioxolane and ethylene glycol dimethyl ether were added thereto, the concentration of lithium bis(trifluoromethanesulfonyl imide) was 1 mol / L, the mass fraction of lithium nitrate was 3wt%, and the volume ratio of 1,3-dioxolane to ethylene glycol dimethyl ether was 4:1. The mixture was placed on a magnetic stirrer and stirred for 12 hours to ensure that the solid was fully dissolved, thereby preparing an electrolyte.

[0133] The negative electrode current collector (circular sheet) prepared in 2.1 was paired with a commercially available lithium metal sheet and separated by a layer of glass fiber membrane (Whatman, GF / D) and a layer of polypropylene separator Celgard 2340. The electrolyte was then injected into the glass fiber membrane to assemble a Li||Cu half-cell.

[0134] 2.3 Preparation of negative electrode-free LiFePO4 full battery (2032 button battery):

[0135] LiFePO4 powder, conductive carbon black particles and polyvinylidene fluoride emulsion binder were mixed in an appropriate amount of N-methylpyrrolidone solvent according to a mass ratio of 9.3:0.4:0.3, and the mixture was ground until the particles were evenly dispersed to obtain a positive electrode slurry. The positive electrode slurry was then coated on a carbon-coated aluminum foil and dried overnight at 100°C. It was cut into round pieces with a diameter of 12 mm as positive electrode sheets; the surface capacity of the LiFePO4 positive electrode is 3.0 mAh / cm 2 .

[0136] In a glove box filled with argon atmosphere (oxygen content, water content less than 0.1ppm), lithium bis(trifluoromethanesulfonyl imide) and lithium nitrate were weighed, and 1,3-dioxolane and ethylene glycol dimethyl ether were added thereto, the concentration of lithium bis(trifluoromethanesulfonyl imide) was 1 mol / L, the mass fraction of lithium nitrate was 3wt%, and the volume ratio of 1,3-dioxolane to ethylene glycol dimethyl ether was 4:1. The mixture was placed on a magnetic stirrer and stirred for 12 hours to ensure that the solid was fully dissolved, thereby preparing an electrolyte.

[0137] Place the spring and gasket in the negative electrode shell in sequence, and then place the negative electrode current collector (circular sheet) and diaphragm prepared in 2.1 on the gasket in sequence, then inject the electrolyte into the diaphragm, and then place the positive electrode sheet, seal it with the positive electrode shell, and assemble it into a negative electrode-free LiFePO4 full battery.

[0138] 2.4 Preparation of NCM811 full battery without negative electrode (soft pack battery):

[0139] The size of the NCM811 positive electrode is 80×60 mm, and the active material loading is 26.4 mg / cm 2 , purchased from Cluder.

[0140] In a glove box filled with argon atmosphere (oxygen content and water content are lower than 0.1 ppm), lithium difluoro(oxalato)borate and lithium tetrafluoroborate were weighed. Diethyl carbonate and fluoroethylene carbonate were added thereto. The concentration of lithium difluoro(oxalato)borate was 1.0 mol / L, the concentration of lithium tetrafluoroborate was 0.2 mol / L, and the volume ratio of diethyl carbonate to fluoroethylene carbonate was 2:1. It was placed on a magnetic stirrer and stirred thoroughly for 12 hours to ensure that the solid was fully dissolved, and an electrolyte was prepared.

[0141] The positive electrode sheet, separator, and negative current collector (rectangular sheet) were stacked in the order of negative current collector / separator / positive electrode sheet / separator / negative current collector to form a Z-shaped laminated structure. The laminated electrode was subjected to ultrasonic welding of the tabs, including tab pre-welding, tab cutting, and tab main welding, to ensure the electrical connection of the battery. The laminated electrode was placed in an aluminum-plastic bag, and top sealing and side sealing were performed to form a closed battery structure. Then, 1.3 g / Ah of the electrolyte was added to the PE separator through the reserved liquid injection port, and finally the aluminum-plastic bag was heat-pressed and sealed. The obtained non-negative electrode NCM811 full battery (soft package battery) was subjected to rate and cycle performance tests under a pressure of ~1.0 MPa.

[0142] 3. Test methods

[0143] The Fourier transform infrared spectrometer (FTIR, Nicolet IS10) was used to record the infrared spectrum with a spectral width of 4000 - 400 cm -1 at a resolution of 2 cm -1 .

[0144] The microscopic morphology was obtained by a field emission scanning electron microscope (ZEISS, Gemini300) at an acceleration voltage of 5 kV.

[0145] The high-resolution cryogenic transmission electron microscope (cryo-TEM) images were taken on a transmission electron microscope (Talos F200X G2) at liquid nitrogen temperature and 200 kV.

[0146] For time-of-flight secondary ion mass spectrometry (TOF-SIMS) studies, ION-TOF 5 - 100 was used under the condition that the pressure in the analysis chamber was lower than 1.1×10 -9 mbar.

[0147] The XPS spectra were obtained using a Thermo Fisher Scientific K-Alpha+ X-ray photoelectron spectrometer and a monochromatic Al Kα source operating at 6 mA and 12 kV. All the obtained binding energies were calibrated using the C1s peak at 284.8 eV.

[0148] The mechanical modulus map of the atomic force microscope and the two-dimensional flaky structure of 2DPA were tested using an Oxford MFP-3D AFM.

[0149] Unless otherwise specified, all electrochemical measurements were carried out at 25 °C in a thermostatic test chamber.

[0150] The electrochemical performance of the battery was tested using a Neware battery test system.

[0151] The energy / power density was calculated based on the total mass of all components in the soft-pack battery.

[0152] Example 1

[0153] Example 1 was prepared according to the above-mentioned "2. Preparation method" to obtain a Li||Cu half-cell (2032-type button cell) as a test sample, denoted as Li||2DPA / LN-Cu (1 mg / mL).

[0154] Among them, when preparing the negative electrode current collector, steps (B-1) and (B-2) were carried out. The mass concentration of 2DPA in the mixed solution was 1 mg / mL, the mass ratio of 2DPA:LN was 5:1, the thickness of the finally formed polymer interface layer was 50 nm, and the loading amount was 0.01 mg / cm 2 .

[0155] Comparative Example 1

[0156] Comparative Example 1 was prepared according to the above-mentioned "2. Preparation method" to obtain a Li||Cu half-cell (2032-type button cell). However, when preparing the negative electrode current collector, the mixed solution was not coated, and only copper foil was used as the negative electrode current collector. The prepared Li||Cu half-cell was used as a test sample, denoted as Li||Cu.

[0157] Example 2

[0158] Example 2 was prepared according to the above-mentioned "2. Preparation method" to obtain a Li||Cu half-cell (2032-type button cell) as a test sample, denoted as Li||2DPA / LN-Cu (3 mg / mL).

[0159] Among them, when preparing the negative electrode current collector, steps (B-1) and (B-2) were carried out. The mass concentration of 2DPA in the mixed solution was 3 mg / mL, the mass ratio of 2DPA:LN was 5:1, the thickness of the finally formed polymer interface layer was 100 nm, and the loading amount was 0.02 mg / cm 2 .

[0160] Example 3

[0161] Example 3 Referring to the above “2. Preparation method”, a Li||Cu half-cell (2032-type button cell) was prepared as a test sample, denoted as Li||2DPA / LN-Cu (5 mg / mL).

[0162] Among them, when preparing the negative electrode current collector, steps (B-1) and (B-2) were followed. The mass concentration of 2DPA in the mixed solution was 10 mg / mL, the mass ratio of 2DPA:LN was 5:1, the thickness of the finally formed polymer interface layer was 150 nm, and the loading amount was 0.03 mg / cm 2 .

[0163] Example 4

[0164] Example 4 Referring to the above “2. Preparation method”, a non-aqueous LiFePO4 full cell was prepared as a test sample, denoted as 2DPA / LN-Cu||LiFePO4.

[0165] Among them, when preparing the negative electrode current collector, steps (B-1) and (B-2) were followed. The mass concentration of 2DPA in the mixed solution was 1 mg / mL, the mass ratio of 2DPA:LN was 5:1, the thickness of the finally formed polymer interface layer was 50 nm, and the loading amount was 0.01 mg / cm 2 .

[0166] Comparative Example 2

[0167] Comparative Example 2 Referring to the above “2. Preparation method”, a non-aqueous LiFePO4 full cell was prepared. However, when preparing the negative electrode current collector, the mixed solution was not coated, and only copper foil was used as the negative electrode current collector. The prepared non-aqueous LiFePO4 full cell was used as a test sample, denoted as Cu||LiFePO4.

[0168] Example 5

[0169] Example 5 Referring to the above “2. Preparation method”, a non-aqueous NCM811 full cell was prepared as a test sample, denoted as 2DPA / LN-Cu||NCM811.

[0170] Among them, when preparing the negative electrode current collector, steps (B-1) and (B-2) were followed. The mass concentration of 2DPA in the mixed solution was 1 mg / mL, the mass ratio of 2DPA:LN was 5:1, the thickness of the finally formed polymer interface layer was 50 nm, and the loading amount was 0.01 mg / cm 2 .

[0171] Example 6

[0172] Example 6: Referring to the above "2. Preparation method", a Li||Cu half-cell (2032 type button cell) was prepared as a test sample, denoted as Li||2DPA-Cu (1 mg / mL).

[0173] Among them, when preparing the negative electrode current collector, steps (A-1) and (A-2) were followed. The mass concentration of 2DPA was 1 mg / mL, the thickness of the finally formed polymer interface layer was 50 nm, and the loading amount was 0.01 mg / cm 2 .

[0174] 4. Test results

[0175] The Li||Cu half-cell prepared in Example 1 was subjected to battery charge-discharge performance testing. As Figure 2 shown, after comparing the Li||Cu half-cells prepared in Examples 1 to 3, it was found that when the thickness of the 2DPA / LN interface layer was 50 nm, the half-cell exhibited the best cycle stability and a higher average Coulombic efficiency. As Figure 3 shown, under the conditions of 1 mA / cm 2 and 1 mAh / cm 2 , after 550 charge-discharge cycles, the Coulombic efficiency remained at 98.9%.

[0176] As Figure 4 and 5 shown, under the conditions of 20 mA / cm 2 and 2 mAh / cm 2 , it was able to cycle stably for 40 cycles, and the voltage hysteresis could be maintained at a low and stable level; as Figure 6 and 8 shown, even under the conditions of 30 mA / cm 2 and 2 mAh / cm 2 or 10 mA / cm 2 and 10 mAh / cm 2 , the battery could still be effectively charged and discharged; while the comparative sample Li||Cu in Comparative Example 1 short-circuited under the conditions of 30 mA / cm 2 and 2 mAh / cm 2 ( Figure 7 ).

[0177] As Figure 9 shown, the non-aqueous negative electrode LiFePO4 full cell prepared in Example 4 was subjected to battery charge-discharge performance testing. When the actual areal capacity was 3.0 mAh / cm 2 , the non-aqueous negative electrode LiFePO4 full cell exhibited excellent rate performance of up to 5C, and compared with that at 0.1C, it maintained about 63.4% of the specific capacity. In addition, as Figure 10 and 11As shown, the non-aqueous anode LiFePO4 full cell far exceeds Comparative Example 2 and can cycle 89 times at the same capacity retention rate during 200 cycles.

[0178] As Figure 12 shown, the cross-sectional scanning electron microscope image and optical picture of the anode current collector used in Example 1 of the present invention are presented. The scanning electron microscope image shows that the thickness of the polymer interface layer is 50 nm, and the scale bar is 50 nm. As Figure 13 shown by the optical picture, the anode current collector loaded with the polymer interface layer can be industrially prepared by a large-scale doctor blade coating process.

[0179] As Figure 14 、 15 shown, the discharge products on the positive electrode of the non-aqueous anode LiFePO4 full cell prepared in Example 4 are analyzed. Figure 14 is the three-dimensional distribution of Li - , CON - and LiF - ion fragments on the positive electrode after discharge detected by time-of-flight secondary ion mass spectrometry; Figure 15 is the atomic force microscope mechanical modulus map of the positive electrode after 20 and 300 charge-discharge cycles of the battery.

[0180] As Figures 16 - 18 shown, the 8 Ah non-aqueous anode NCM811 full cell prepared in Example 5 can stably cycle 20 times, with a Coulombic efficiency above 99.2% and an energy density reaching 471 Wh / kg. Moreover, it can achieve a maximum rate of 1.5 C, corresponding to a power density of 622 W / kg.

[0181] The Li||Cu half cell prepared in Example 6 is subjected to battery charge-discharge performance testing. As Figure 19 shown, in the absence of LN, the half cell with the polymer interface layer can stably cycle 550 charge-discharge cycles under the conditions of 1 mA / cm 2 and 1 mAh / cm 2 , and the Coulombic efficiency is maintained at 98.3%.

[0182] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

[0183] The references cited in the present invention are as follows:

[0184] [1] Assegie A, Cheng J, Kuo L, Su W, & Hwang B. Polyethylene oxide film coating enhances lithium cycling efficiency of an anode-free lithium-metal battery. Nanoscale 10, 6125 - 6138 (2018).

[0185] [2] Hu A et al. N, F-enriched inorganic / organic composite interphases to stabilize lithium metal anodes for long-life anode-free cells. J. Colloid Interface Sci. 648,

[0186] 448 - 456 (2023).

[0187] [3] Fedorov R, Maletti S, Heubner C, Michaelis A, & Ein-Eli Y. Molecular engineering approaches to fabricate artificial solid-electrolyte interphases on anodes for Li-ion batteries: a critical review. Adv. Energy Mater. 11, 2101173 (2021).

[0189] [4] Liu P et al. Ultra-long-life and ultrathin quasi-solid electrolytes fabricated by solvent-free technology for safe lithium metal batteries. Energy Storage Mater.

[0190] 58, 132 - 141 (2023).

[0191] [5] Payamyar P, King BT, HC., & Schlüter AD. Two-dimensional polymers: concepts and perspectives. Chem. Commun. 52, 18 - 34 (2016).

Claims

1. Application of two-dimensional polyamide in negative current collector.

2. A negative current collector applying a two-dimensional polyamide to an interface layer, characterized in that It is mainly composed of a conductive metal sheet and a polymer interface layer on its surface, and the polymer interface layer is composed of two-dimensional polyamide or mainly composed of two-dimensional polyamide.

3. The negative electrode current collector according to claim 2, wherein: The polymer interface layer is mainly composed of two-dimensional polyamide and also includes additives.

4. The negative current collector according to claim 2, wherein: The preparation method of the negative current collector applying two-dimensional polyamide to the interface layer mainly includes the following steps: (A-1) Weigh two-dimensional polyamide and dissolve it in a volatile solvent to prepare a two-dimensional polyamide solution, wherein the mass concentration of two-dimensional polyamide is 0.1-50 mg / mL; (A-2) Coat the two-dimensional polyamide solution obtained in step (A-1) on the conductive metal sheet, and then volatilize the solvent to form a polymer interface layer, that is, obtain the negative current collector applying two-dimensional polyamide to the interface layer; Or (B-1) Weigh two-dimensional polyamide and additives and dissolve them in a volatile solvent to prepare a mixed solution containing two-dimensional polyamide, wherein the mass concentration of two-dimensional polyamide is 0.1-50 mg / mL; (B-2) Coat the mixed solution obtained in step (B-1) on the conductive metal sheet, and then volatilize the solvent to form a polymer interface layer, that is, obtain the negative current collector applying two-dimensional polyamide to the interface layer.

5. The negative electrode current collector according to claim 2, wherein: The thickness of the polymer interface layer is not more than 1 μm.

6. The negative electrode current collector according to claim 2, characterized in that: The loading amount of the polymer interface layer is not more than 0.1 mg / cm 2 .

7. The negative electrode current collector according to claim 2, wherein: The polymer interface layer is composed of two-dimensional polyamide and lithiated perfluorosulfonic acid polymer.

8. The negative current collector according to any one of claims 2-7 is applied to a metal battery.

9. The application according to claim 8, wherein: The metal battery is a lithium metal battery without a negative electrode.

10. A non - negative - electrode lithium - metal secondary battery uses the negative - electrode current collector as described in any one of claims 2 to 7 as one of its components, and is characterized in that: It is mainly composed of a positive electrode, an electrolyte and the negative current collector applying two-dimensional polyamide to the interface layer.

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