Modified lithium metal and preparation method and application thereof

Abstract

The invention relates to modified lithium metal and a preparation method and application thereof, and belongs to the technical field of lithium metal batteries. The modified lithium metal includes: a matrix containing a lithium metal; the interface modification layer is attached to at least part of the surface of the matrix containing the lithium metal; and the interface modification layer is obtained by chemical reaction bonding of the lithium metal and functional molecules containing sulfydryl and nitrogen. The bonding strength between the matrix containing the lithium metal and the interface modification layer is high, so that the interface modification layer serves as a firm and uniform protection layer of the matrix containing the lithium metal, and the electrochemical stability of the lithium metal is improved.

Description

Technical Field

[0001] This application relates to the field of lithium metal battery technology, and in particular to a modified lithium metal, its preparation method and application. Background Technology

[0002] Lithium metal, with its highest theoretical specific capacity of 3860 mAh / g and lowest negative electrochemical potential (-3.040 V vs. standard hydrogen electrode), is widely considered the ultimate anode for lithium-based batteries. To further improve the energy density of lithium-based batteries, various next-generation lithium metal batteries have been proposed and extensively studied. These future technologies with extremely high energy densities include Li-LiNi... 1-x-y Co x Mn y The O2 (Li-NCM), Li-Li-rich cathode, Li-sulfur (Li-S), and lithium-air (Li-O2) systems largely depend on the stable cycling of lithium metal electrodes.

[0003] However, the electrochemical stability of lithium metal is not ideal. When lithium metal is used as the anode in batteries, the uneven deposition of lithium during charging and discharging results in dendritic crystal structures, known as lithium dendrites. These dendrite problems lead to serious safety issues and hinder the practical deployment of lithium metal batteries. Therefore, the use and development of practical lithium metal anodes in rechargeable systems are crucial for energy-dense lithium metal batteries. Summary of the Invention

[0004] This application provides a modified lithium metal, its preparation method, and its application to solve the following technical problem: how to improve the electrochemical stability of lithium metal. In a first aspect, embodiments of this application provide a modified lithium metal, the modified lithium metal comprising: A lithium metal matrix; An interface modification layer is attached to at least a portion of the surface of the lithium-containing metal substrate; The interface modification layer is obtained by chemically bonding the lithium metal with functional molecules containing thiol and nitrogen.

[0005] Optionally, the functional molecule includes at least one of the following: 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, and 5-mercapto-1-phenyl-tetrazazole.

[0006] Optionally, the thickness of the interface modification layer is 1 μm to 50 μm.

[0007] Optionally, the lithium metal-containing substrate includes one of the following: lithium metal with a thickness of 40 μm to 500 μm, and a current collector with a single-sided surface deposited with lithium metal thickness of 10 μm to 500 μm.

[0008] Secondly, embodiments of this application provide a method for preparing modified lithium metal as described in any embodiment of the first aspect. Preparation method, the method comprising: A solution is obtained by mixing functional molecules containing thiol and nitrogen with a solvent; The lithium metal-containing matrix is ​​immersed in the solution and allowed to stand, so that the lithium metal reacts with the mercapto- and nitrogen-containing functional groups. The molecules can undergo a chemical reaction to obtain modified lithium metal.

[0009] Optionally, the process parameters for the settling period include: a temperature of 25℃ to 45℃ and a time of 1 h to 24 h.

[0010] Optionally, the mixing time is 5 s to 2 h; and / or, The molar concentration of the solution is 0.001 mol / L to 10 mol / L.

[0011] Optionally, the solvent includes at least one of the following: ethylene glycol dimethyl ether, 1,3-dioxolane, dimethyl carbonate, tetrahydrogen ether, etc. Furan, dimethyl sulfoxide, N,N Dimethylformamide, ethanol.

[0012] Thirdly, embodiments of this application provide a negative electrode, the negative electrode comprising any embodiment of the first aspect. The modified lithium metal described above.

[0013] Fourthly, embodiments of this application provide a battery, the battery including the negative electrode as described in any one of the embodiments of the third aspect.

[0014] The technical solutions provided in this application have the following advantages compared with the prior art: The modified lithium metal provided in this application embodiment comprises: a lithium metal-containing matrix; and an interface modification layer. The interface modification layer is attached to at least a portion of the surface of the lithium-containing metal substrate. The interface modification layer is obtained by chemically bonding the lithium metal with functional molecules containing thiol and nitrogen. The thiol (-SH) in the functional molecules is reactive and lithiophilic, promoting bonding with the lithium-containing metal substrate. Sulfur can chemically react with the lithium metal surface to form lithium sulfide, providing stable and sufficient chemical bond sites. Nitrogen in the functional molecules is lithiophilic, inducing uniform deposition of lithium ions on the substrate surface. Nitrogen can also chemically react with the lithium metal surface to form lithium nitride, providing stable and sufficient chemical bond sites. These sufficient chemical bond sites firmly connect the lithium-containing metal substrate and the interface modification layer, thereby increasing the bonding strength between them. This makes the interface modification layer a robust and uniform protective layer for the lithium-containing metal substrate, thus improving the electrochemical stability of the lithium metal. Functional molecules containing thiol and nitrogen can bind to active sites on the surface of lithium metal to form a dense interface modification layer. This modification layer can inhibit the growth of lithium dendrites and improve the uniformity of lithium ion deposition. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic flowchart illustrating a method for preparing modified lithium metal provided in this application embodiment; Figure 2 SEM image of a modified lithium metal provided in Embodiment 1 of this application; Figure 3 Electrochemical impedance spectroscopy of a modified lithium metal anode and a pure lithium metal anode provided in Example 1 of this application; Figure 4 The image shows the cycle performance of a modified lithium metal anode and a pure lithium metal anode in a symmetrical battery, as provided in Example 1 of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0020] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0021] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0022] In a first aspect, embodiments of this application provide a modified lithium metal, the modified lithium metal comprising: A lithium metal matrix; An interface modification layer is attached to at least a portion of the surface of the lithium-containing metal substrate; The interface modification layer is obtained by chemically bonding the lithium metal with functional molecules containing thiol and nitrogen.

[0023] During battery charging and discharging, the uneven deposition of lithium ions in lithium metal anodes can easily lead to the growth of lithium dendrites, potentially causing short circuits and safety issues. Therefore, forming an interface modification layer on the surface of the lithium metal anode through a chemical reaction can effectively mitigate this problem. In this embodiment, the lithium metal-containing substrate is the core of the modified lithium metal, serving as the basic carrier for the electrochemical function of lithium metal. It supports the subsequent interface modification layer and participates in electrochemical processes such as lithium ion deposition and dissolution during battery charging and discharging. The interface modification layer is attached to at least a portion of the surface of the lithium metal-containing substrate. This means that, depending on actual needs and process conditions, one side, two sides, or specific local surfaces of the substrate can be modified, flexibly controlling the contact interface between lithium metal and the external environment (such as electrolyte), thereby affecting its electrochemical stability and other properties. The formation method involves chemically bonding lithium metal with functional molecules containing thiol and nitrogen groups. This chemical synthesis method ensures a close chemical bond between the interface modification layer and the substrate, rather than simple physical adhesion. When lithium metal reacts chemically with functional molecules containing thiol and nitrogen, these functional molecules may bind to active sites on the lithium metal surface, forming a dense interface modification layer. This layer can inhibit lithium dendrite growth and improve the uniformity of lithium-ion deposition. The functions of the interface modification layer include: inhibiting lithium dendrite growth: Through physical and chemical interactions, the interface modification layer limits the uneven deposition of lithium ions, thereby inhibiting lithium dendrite growth. Improving battery safety: Lithium dendrite growth is a major cause of battery short circuits and safety issues; the presence of the interface modification layer can effectively reduce lithium dendrite formation, improving battery safety. Improving battery performance: The interface modification layer can also improve the battery's cycle stability and rate performance. By optimizing the lithium-ion deposition process, it can reduce polarization during charging and discharging, thereby improving battery efficiency and lifespan.

[0024] The reactivity of the thiol group (-SH) makes it readily react with lithium-containing metal matrices in chemical reactions, actively seeking suitable sites for binding. The lithiophilicity of the thiol group (-SH) primarily stems from its atomic structure and chemical properties. The sulfur atom (S) has a relatively large atomic radius and low electronegativity, enabling it to form a relatively strong interaction with lithium (Li) atoms. During bond formation, the electron cloud of the sulfur atom can overlap to some extent with the outer electrons of the lithium atom; this electron cloud interaction is the chemical basis of lithiophilicity. Therefore, lithiophilicity allows it to locate on the lithium metal surface, while reactivity ensures its ability to react chemically with the lithium metal surface. The chemical reaction between sulfur and the lithium metal surface to form lithium sulfide is not only a chemical transformation but, more importantly, generates stable and sufficient chemical bonds. These chemical bonds act as "anchors," firmly fixing the interface modification layer to the lithium-containing metal matrix, enhancing the bonding strength between the two, and playing a crucial role in maintaining the stability of the entire modified lithium metal structure.

[0025] Nitrogen's lithiophilicity induces uniform lithium-ion deposition. This affinity attracts and guides lithium ions, creating an environment on the substrate surface conducive to their uniform distribution. During battery charging, lithium ions migrate from the electrolyte to the lithium metal substrate and deposit. The presence of nitrogen prevents excessive local accumulation and deposition of lithium ions, reducing uneven deposition phenomena such as lithium dendrites, thus improving the electrochemical stability of lithium metal. Nitrogen reacts chemically with the lithium metal surface to form lithium nitride, generating stable and sufficient chemical bonds. These bonds, along with those formed by thiol groups, further strengthen the connection between the lithium metal substrate and the interface modification layer, allowing the interface modification layer to more robustly and uniformly cover the substrate surface, acting as a reliable protective layer.

[0026] Therefore, through the tight and stable bond between the lithium metal-containing substrate and the interface modification layer, the interface modification layer becomes a robust and uniform protective layer for the lithium metal-containing substrate. During battery charging and discharging, it can effectively prevent undesirable contact between the lithium metal substrate and the external environment such as the electrolyte, reducing the occurrence of side reactions, such as suppressing unnecessary chemical reactions between lithium metal and the electrolyte and preventing electrolyte decomposition. Simultaneously, by guiding uniform lithium ion deposition, it reduces the risk of lithium dendrite growth, thus improving the electrochemical stability of lithium metal from multiple aspects. This makes this modified lithium metal more promising for applications requiring high electrochemical stability, such as high-performance batteries.

[0027] In some embodiments, the functional molecule includes at least one of the following: 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, and 5-mercapto-1-phenyl-tetrazazole.

[0028] In the embodiments of this application, the functional molecule can be one or more combinations of 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, and 5-mercapto-1-phenyl-tetrazazole, all of which contain thiol and nitrogen. The lithiophilicity of thiol and nitrogen causes them to approach the lithium metal surface, where sulfur and nitrogen react chemically with lithium atoms on the lithium metal surface to form chemical bonds. Simultaneously, the electron cloud distribution characteristics of nitrogen and sulfur atoms in the molecule may influence the surrounding chemical environment, inducing uniform deposition of lithium ions on the lithium metal surface. Furthermore, the presence of phenyl structures in these functional molecules further enhances their chemical stability. Therefore, these functional molecules possess good chemical stability and electrochemical activity, maintaining structural stability during battery charging and discharging and promoting lithium ion transport.

[0029] In some embodiments, the thickness of the interface modification layer is 1 μm to 50 μm.

[0030] In this embodiment, the thickness of the interface modification layer can be from 1 μm to 50 μm. The interface modification layer contains sufficient sulfur and nitrogen, which can react with lithium in the lithium metal anode to form lithium sulfide and lithium nitride, providing sufficient chemical bond sites. These sufficient chemical bond sites will fix the lithium metal anode and the interface modification layer, thereby improving the bonding strength between them. If the thickness of the interface modification layer is greater than 50 μm, the lithium sulfide concentration may be too high, resulting in a large interface resistance. When modified lithium metal is used as the anode, this may increase the lithium deposition overpotential and easily lead to dendrite formation. If the thickness of the interface modification layer is less than 1 μm, the mechanical strength of the interface modification layer may decrease. When modified lithium metal is used as the anode, the lithium dendrites may penetrate the interface modification layer during the battery charge-discharge cycle, leading to interface modification failure. For example, the thickness of the interface modification layer can be 1μm, 2μm, 3μm, 4μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, etc.

[0031] In some embodiments, the lithium metal-containing substrate includes one of the following: lithium metal with a thickness of 40 μm to 500 μm and a current collector with a single-sided surface deposited with lithium metal thickness of 10 μm to 500 μm.

[0032] In this embodiment, the lithium metal matrix can be a lithium metal layer with a thickness of 40 μm to 500 μm. While ensuring a certain lithium content for the charge-discharge reaction, this reduces the volume ratio of the electrodes, leaving more space for other components in the battery (such as electrolyte and separator), which helps improve the overall energy density of the battery. Simultaneously, it ensures sufficient lithium reserves, better handling lithium consumption during long-term charge-discharge cycles. Even if lithium dendrite growth occurs, it can buffer the damage to the battery structure to a certain extent, enhancing electrode durability and battery cycle life. For example, the lithium metal layer can be 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, or 500 μm thick.

[0033] The current collector's function is to collect current and support active materials. After lithium metal is deposited on one side, it not only continues to perform these functions but also becomes a carrier for lithium metal adhesion. A lithium metal-containing substrate can be used to deposit a current collector with a single-sided surface thickness of 10 μm to 500 μm. This allows lithium ions to diffuse more rapidly during charge and discharge, resulting in faster deposition and dissolution. This helps improve the battery's rate performance and provides a larger lithium reserve, ensuring sufficient lithium for continuous reactions during long-term use, extending battery life and improving cycle life. For example, the thickness of the lithium metal deposited on one side of the current collector can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, or 500 μm. The current collector can be made of one or more of the following materials: copper, boron, gold, silver, platinum, carbon, iron, titanium, nickel, and stainless steel.

[0034] Secondly, embodiments of this application provide a method for preparing modified lithium metal as described in any embodiment of the first aspect. Preparation method, Figure 1 A schematic flowchart illustrating a method for preparing modified lithium metal provided in this application embodiment; please refer to [link / reference]. Figure 1 The method includes: S1. Mix functional molecules containing thiol and nitrogen with a solvent to obtain a solution; S2. Immerse the lithium metal-containing matrix in the solution and allow it to stand, so that the lithium metal reacts with the mercapto- and nitrogen-containing matrix. The functional molecules undergo a chemical reaction to obtain modified lithium metal.

[0035] In some embodiments, the settling process parameters include: a temperature of 25°C to 45°C and a time of 1 h to 24 h.

[0036] In this embodiment, a lithium metal-containing matrix is ​​immersed in a solution and allowed to stand, so that the lithium metal reacts with the contained thiol groups. A chemical reaction occurs between the lithium metal and nitrogen-functional molecules, leading to monomolecular self-assembly on the lithium metal surface. This results in a monomolecular self-assembled layer, or a dense interface modification layer, formed in situ on the lithium metal surface, thereby improving the electrochemical stability of the lithium metal. The settling temperature can be between 25°C and 45°C to ensure the reaction proceeds fully and a uniform interface modification layer is formed. This layer covers defects and unevenness on the lithium metal-containing substrate surface, improving the electrochemical stability of the substrate. Consequently, when the modified lithium metal is used as the negative electrode, it reduces lithium dendrite growth and electrolyte reduction reactions, thus improving battery safety and cycle stability. For example, the temperature of the chemical reaction can be 25℃, 28℃, 30℃, 33℃, 35℃, 38℃, 40℃, 43℃, 45℃, etc.; the time corresponding to the temperature can be 1 h to 24 h, and a sufficiently thick interface modification layer can be obtained. The time can be 1 h, 2 h, 3 h, 4 h, 5 h, 7 h, 10 h, 13 h, 15 h, 18 h, 20 h, 22 h, 24 h, etc.

[0037] In some embodiments, the mixing time is 5 seconds to 2 hours; and / or, The molar concentration of the solution is 0.001 mol / L to 10 mol / L.

[0038] In the embodiments of this application, the mixing time can be 5 s to 2 h, and the molar concentration of the solution can be 0.001 mol / L to 10 mol / L, so that the thickness of the interface modification layer formed on the surface of the lithium metal substrate is moderate. If the mixing time is higher than 2 h or the molar concentration of the solution is higher than 10 mol / L, the formation of an excessively thick interface modification layer may increase the migration resistance of lithium ions and reduce the charge and discharge rate and energy density of the battery. If the mixing time is lower than 5 s or the molar concentration of the solution is lower than 0.001 mol / L, the interface modification layer formed on the surface of the lithium metal substrate will be incomplete or unstable, increasing the risk of lithium dendrite formation in the subsequent battery and reducing the safety and cycle stability of the battery. For example, the mixing time can be 5s, 6s, 7s, 8s, 9s, 10s, 15s, 20s, 25s, 40s, 1min, 2min, 3min, 4min, 5min, 10min, 20min, 30min, 1h, 1.5h, 2h, etc.; the molar concentration of the solution can be 0.001mol / L, 0.003mol / L, 0.005mol / L, 0.01mol / L, 0.05mol / L, 0.1mol / L, 0.3mol / L, 0.5mol / L, 0.8mol / L, 1mol / L, 5mol / L, 8mol / L, 10mol / L, etc.

[0039] In some embodiments, the solvent includes at least one of the following: ethylene glycol dimethyl ether, dioxolane, dicarbonate. Methyl ester, tetrahydrofuran, dimethyl sulfoxide, N,N Dimethylformamide, ethanol.

[0040] In the embodiments of this application, the solvent may be ethylene glycol dimethyl ether (DME), dioxolane (DOL), or dimethyl carbonate. (DMC), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), N,N One or more combinations of dimethylformamide (DMF) and ethanol are used as solvents. These solvents have good solubility and can fully dissolve functional molecules containing thiol and nitrogen to form a homogeneous solution system. Furthermore, these solvents themselves will not undergo violent side reactions with lithium metal, thereby damaging the structure of lithium metal or affecting the modification effect.

[0041] The preparation method of this modified lithium metal is based on the above-mentioned modified lithium metal, and the specific composition of this modified lithium metal can be determined by... Referring to the above embodiments, since the method for preparing modified lithium metal adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0042] Thirdly, embodiments of this application provide a negative electrode, the negative electrode comprising any embodiment of the first aspect. The modified lithium metal described above.

[0043] In this embodiment, lithium metal possesses an extremely high theoretical specific capacity, a crucial foundation for achieving high energy density in batteries. After modification, its electrochemical stability is enhanced while retaining its vital function as a lithium-ion source. During battery charging and discharging, it continuously provides and accepts lithium ions, ensuring normal electrochemical cycling and enabling the battery to output higher energy to meet the power demands of various applications. The modified lithium metal surface exhibits an interface modification layer formed by the reaction of functional molecules containing thiol and nitrogen, altering the original surface properties of lithium metal and significantly influencing lithium-ion deposition and dissolution behavior. During charging, lithium ions migrate from the positive electrode to the negative electrode via the electrolyte. The interface modification layer on the modified lithium metal surface guides lithium ions to deposit more uniformly on the lithium metal substrate, preventing rapid lithium dendrite growth due to excessively high local lithium-ion concentrations. During discharging, lithium ions smoothly desorb from the lithium metal substrate and migrate back to the positive electrode, resulting in a more stable and orderly process. This significantly improves key performance indicators such as electrochemical stability, cycle life, and charge / discharge efficiency of the negative electrode and the entire battery.

[0044] The negative electrode is based on the modified lithium metal described above, and the specific composition of the modified lithium metal can be found in the above embodiments. Since the negative electrode adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0045] Fourthly, embodiments of this application provide a battery, the battery including the negative electrode as described in any one of the embodiments of the third aspect.

[0046] In this embodiment, the negative electrode uses modified lithium metal. Lithium metal itself possesses an extremely high theoretical specific capacity, and even after modification, it retains a high lithium storage capacity. Compared to traditional graphite negative electrodes, this significantly increases the amount of electricity that can be stored per unit mass or unit volume of the battery, thereby improving the battery's energy density. In the negative electrode, the modified lithium metal, through its surface interface modification layer, effectively guides the uniform deposition and desorption of lithium ions, reducing the formation of lithium dendrites and adverse side reactions with the electrolyte. This allows the negative electrode structure to remain relatively intact during multiple charge-discharge cycles, and slows down the performance degradation of the electrode materials. For large-scale energy storage systems, a longer cycle life means a lower total lifespan cost, reducing the inconvenience and cost of frequent battery replacements. The modified lithium metal in this negative electrode can regulate lithium ion deposition behavior through its interface modification layer, suppressing the formation of lithium dendrites and reducing the risk of battery short circuits.

[0047] This battery can be an all-solid-state lithium metal battery, comprising a positive electrode, a modified lithium metal negative electrode, and a solid electrolyte. The positive electrode may include Li or compounds that reversibly insert and extract lithium ions. The solid electrolyte may include polymer electrolytes, inorganic solid electrolytes, and composite electrolytes. The compounds that reversibly insert and extract lithium ions are the positive electrode active materials, including lithium iron phosphate, lithium nickel manganese oxide, lithium manganese oxide, and lithium cobalt oxide.

[0048] The battery is based on the above-mentioned negative electrode. The specific composition of the negative electrode can be referred to the above embodiments. Since the battery adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0049] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0050] Example 1 A modified lithium metal, comprising: A lithium metal-containing substrate; the lithium metal-containing substrate is a lithium sheet with a thickness of 60 μm and a diameter of 8 mm; An interface modification layer is attached to at least a portion of the surface of a lithium-containing metal substrate, and the thickness of the interface modification layer is [missing information]. 20 µm; The interface modification layer is obtained by chemically bonding lithium metal with functional molecules containing thiol and nitrogen, the functional molecule being 2-mercaptobenzothiazole.

[0051] A method for preparing modified lithium metal, the method comprising: A solution is obtained by mixing functional molecules containing thiol and nitrogen groups with a solvent; wherein the solvent is dimethyl carbonate, and the solution... The molar concentration was 0.01 mol / L, and the mixing time was 20 min. The lithium metal-containing matrix is ​​immersed in a solution and allowed to stand, allowing the lithium metal to react with functional molecules containing thiol and nitrogen groups. The reaction yields modified lithium metal; specifically, the lithium metal-containing matrix is ​​immersed in dimethyl carbonate solution and allowed to stand, then placed in a glove box for treatment at a temperature of 30 °C for 24 h.

[0052] Figure 2 SEM image of a modified lithium metal provided in Embodiment 1 of this application; please refer to Figure 2 This indicates that the lithium-containing metal substrate surface is covered by a continuous interface-modified phase and is uniformly distributed on the substrate surface. Figure 3 Electrochemical impedance spectroscopy (EIS) of a modified lithium metal anode and a pure lithium metal anode provided in Example 1 of this application; please refer to [link to EIS]. Figure 3 This indicates that the modified lithium anode has a smaller interfacial impedance, proving that the interfacial modification layer significantly improves the interfacial dynamics of the anode surface.

[0053] A battery comprising: using a conventional ester electrolyte, 1 M LiPF6+ EC-DMC (volume ratio 1:1), with LiTFSI added as a lithium salt and a photoinitiator; the electrolyte liquid is uniformly dropped onto a cellulose film and polymerized using ultraviolet light until the electrolyte completely solidifies; both the positive and negative electrodes are MBT@Li; and a symmetrical battery is assembled. The battery operates at a current density of 5 mA / cm². 2 Cyclic capacity is 5 mAh / cm³ 2 Under these conditions, the cycle lasts for more than 800 hours. Figure 4 A symmetrical battery cycle performance diagram of a modified lithium metal anode provided in Embodiment 1 of this application; please refer to... Figure 4 The polarization voltage is 14 mV, while if pure lithium is used, it exhibits a very large polarization voltage (55 mV).

[0054] Example 2 Based on the disclosure in Example 1, Example 2 differs from Example 1 in that the molar concentration of the solution is: 0.1 mol / L.

[0055] A modified lithium metal, comprising: A lithium metal-containing substrate; the lithium metal-containing substrate is a lithium sheet with a thickness of 60 μm and a diameter of 8 mm; An interface modification layer is attached to at least a portion of the surface of a lithium-containing metal substrate, and the thickness of the interface modification layer is [missing information]. 20 µm; The interface modification layer is obtained by chemically bonding lithium metal with functional molecules containing thiol and nitrogen, the functional molecule being 2-mercaptobenzothiazole.

[0056] A method for preparing modified lithium metal, the method comprising: A solution is obtained by mixing functional molecules containing thiol and nitrogen groups with a solvent; wherein the solvent is dimethyl carbonate, and the solution... The molar concentration was 0.1 mol / L, and the mixing time was 20 min. The lithium metal-containing matrix is ​​immersed in a solution and allowed to stand, allowing the lithium metal to react with functional molecules containing thiol and nitrogen groups. The reaction yields modified lithium metal; specifically, the lithium metal-containing matrix is ​​immersed in dimethyl carbonate solution and allowed to stand, then placed in a glove box for treatment at a temperature of 30 °C for 24 h.

[0057] Example 3 Based on the content disclosed in Example 1, Example 3 differs from Example 1 in that the settling time is 4 hours.

[0058] A modified lithium metal, comprising: A lithium metal-containing substrate; the lithium metal-containing substrate is a lithium sheet with a thickness of 60 μm and a diameter of 8 mm; An interface modification layer is attached to at least a portion of the surface of a lithium-containing metal substrate, and the thickness of the interface modification layer is [missing information]. 20 µm; The interface modification layer is obtained by chemically bonding lithium metal with functional molecules containing thiol and nitrogen, the functional molecule being 2-mercaptobenzothiazole.

[0059] A method for preparing modified lithium metal, the method comprising: A solution is obtained by mixing functional molecules containing thiol and nitrogen groups with a solvent; wherein the solvent is dimethyl carbonate, and the solution... The molar concentration was 0.01 mol / L, and the mixing time was 20 min. The lithium metal-containing matrix is ​​immersed in a solution and allowed to stand, allowing the lithium metal to react with functional molecules containing thiol and nitrogen groups. The reaction yielded modified lithium metal; specifically, the lithium metal-containing matrix was immersed in dimethyl carbonate solution and allowed to stand, then placed in a glove box for treatment at a temperature of 30 °C for 4 h.

[0060] Example 4 Based on the content disclosed in Example 1, Example 4 differs from Example 1 in that the solvent is dioxolane.

[0061] A modified lithium metal, comprising: A lithium metal-containing substrate; the lithium metal-containing substrate is a lithium sheet with a thickness of 60 μm and a diameter of 8 mm; An interface modification layer is attached to at least a portion of the surface of a lithium-containing metal substrate, and the thickness of the interface modification layer is [missing information]. 20 µm; The interface modification layer is obtained by chemically bonding lithium metal with functional molecules containing thiol and nitrogen, the functional molecule being 2-mercaptobenzothiazole.

[0062] A method for preparing modified lithium metal, the method comprising: A solution is obtained by mixing a functional molecule containing thiol and nitrogen with a solvent; wherein the solvent is dioxolane, and the solution... The molar concentration was 0.01 mol / L, and the mixing time was 20 min. The lithium metal-containing matrix is ​​immersed in a solution and allowed to stand, allowing the lithium metal to react with functional molecules containing thiol and nitrogen groups. The reaction yields modified lithium metal; specifically, the lithium metal-containing matrix is ​​immersed in dimethyl carbonate solution and allowed to stand, then placed in a glove box for treatment at a temperature of 30 °C for 24 h.

[0063] Example 5 Based on the content disclosed in Example 1, Example 5 differs from Example 1 in that the functional molecule is 2-mercaptobenzimidazole.

[0064] A modified lithium metal, comprising: A lithium metal-containing substrate; the lithium metal-containing substrate is a lithium sheet with a thickness of 60 μm and a diameter of 8 mm; An interface modification layer is attached to at least a portion of the surface of a lithium-containing metal substrate, and the thickness of the interface modification layer is [missing information]. 20 µm; The interface modification layer is obtained by chemically bonding lithium metal with functional molecules containing thiol and nitrogen, the functional molecule being 2-mercaptobenzimidazole.

[0065] A method for preparing modified lithium metal, the method comprising: A solution is obtained by mixing functional molecules containing thiol and nitrogen groups with a solvent; wherein the solvent is dimethyl carbonate, and the solution... The molar concentration was 0.01 mol / L, and the mixing time was 20 min. The lithium metal-containing matrix is ​​immersed in a solution and allowed to stand, allowing the lithium metal to react with functional molecules containing thiol and nitrogen groups. The reaction yields modified lithium metal; specifically, the lithium metal-containing matrix is ​​immersed in dimethyl carbonate solution and allowed to stand, then placed in a glove box for treatment at a temperature of 30 °C for 24 h.

[0066] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that: unmodified lithium foil was used to assemble a symmetrical battery under the same conditions, at a current density of 5 mA / cm². 2 Cyclic capacity is 5 mAh / cm³ 2 Under these conditions, the polarization voltage is greater than 55 mV after 120 hours of cycling.

[0067] Using the modified lithium metal obtained in Examples 1-5 as the negative electrode and the unmodified lithium metal from Comparative Example 1 as the negative electrode, a symmetrical battery was assembled under the same conditions, with a current density of 5 mA / cm². 2 The conditional loop test was performed, and the results are shown in Table 1 below.

[0068] Table 1 Cyclic test results of symmetric cells

[0069] Table 1 shows that the lithium metal anode modified with the interface modification layer provided in this application exhibits a longer cycle time and a lower polarization voltage. This indicates that the interface modification layer induces uniform lithium deposition, reduces the lithium deposition overpotential, and the lithium sulfide-rich SEI improves the stability of lithium metal charge-discharge cycles, demonstrating that lithium metal modified with functional molecules has better cycle stability. A similar strategy was used to modify the surface of lithium metal with 2-mercaptobenzimidazole (MBM). Although this improved the electrochemical performance compared to pure lithium metal, it was not as effective as the modification effect of 2-mercaptobenzothiazole (MBT).

[0070] Solid-state lithium metal battery performance testing Using the modified lithium metal obtained in Example 1 as the negative electrode and commercial NCM811 as the positive electrode, a conventional ester electrolyte 1 M LiPF6+ EC-DMC (volume ratio 1:1) was used, with LiTFSI added as the lithium salt and a photoinitiator added. The electrolyte liquid was uniformly dropped onto the cellulose film and polymerized using ultraviolet light until the electrolyte completely solidified. This polymer film can perform the dual functions of electrolyte and separator. Cyclic performance was tested at 1 C. Table 2 shows the cycle performance data of the lithium negative electrode obtained in Example 1 assembled into a full cell. The first discharge specific capacity was 191.8 mAh / g, the discharge specific capacity after 150 cycles was 179.1 mAh / g, and the capacity retention rate was 93.4%.

[0071] Similarly, Example 2 5. Using the negative electrode obtained in Comparative Example 1, a full cell was assembled according to the above method, and battery performance was tested. Example 1 The results of Example 5 and Comparative Example 1 are shown in Table 2 below.

[0072] Table 2 Performance test results of solid-state lithium metal batteries

[0073] As shown in Table 2, the unmodified solid-state lithium metal battery exhibits a first-cycle discharge specific capacity of 190.6 mAh / g under 1C conditions, but its capacity retention rate is only 46.4% after 150 cycles. In contrast, the solid-state lithium metal battery assembled using a 0.01 mol / L dimethyl carbonate solution and allowed to stand for 24 h demonstrates the best first-cycle discharge specific capacity and the highest capacity retention rate.

[0074] One or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: (1) The modified lithium metal preparation method provided in the embodiments of this application is widely applicable to various lithium metal anodes and can suppress the growth of lithium dendrites. It is simple to operate, has a wide range of applications, and has little impact on the energy density of the battery. The lithium battery based on this method exhibits good cycle stability. It is a metal lithium modification method with great industrial advantages. (2) The modified lithium metal provided in the embodiments of this application effectively improves the negative electrode / electrolyte interface and significantly enhances the electrochemical performance of lithium metal, especially the cycling stability at high current density, and has excellent rate performance. (3) The functional molecular layer provided in this application has good electrochemical stability and exhibits chemical inertness to solid electrolytes. It can effectively solve the problem of interfacial side reactions caused by direct contact between lithium metal anode and solid electrolyte. It can also induce uniform lithium deposition and inhibit the growth of lithium dendrites, thereby improving the cycle stability of the battery and improving the safety of all-solid-state lithium-ion batteries. It has better interfacial affinity to solid electrolytes, can achieve selective lithium-ion conduction, induce uniform lithium-ion deposition, effectively reduce the interfacial impedance between solid electrolyte and lithium metal anode, improve the coulombic efficiency and cycle stability of all-solid-state lithium-ion batteries during charge and discharge cycles, and extend the service life of all-solid-state lithium metal batteries.

[0075] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A modified lithium metal, said modified lithium metal comprising: A lithium metal matrix; An interface modification layer is attached to at least a portion of the surface of the lithium metal-containing substrate; The interface modification layer is obtained by chemically bonding the lithium metal with functional molecules containing thiol and nitrogen.

2. The modified lithium metal according to claim 1, characterized in that, The functional molecule includes at least one of the following: 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, and 5-mercapto-1-phenyl-tetrazazole.

3. The modified lithium metal according to claim 1, characterized in that, The thickness of the interface modification layer is 1 μm to 50 μm.

4. The modified lithium metal according to claim 1, characterized in that, The lithium metal-containing substrate includes one of the following: lithium metal with a thickness of 40 μm to 500 μm, and a current collector with a single-sided surface deposition thickness of 10 μm to 500 μm of lithium metal.

5. A method for preparing modified lithium metal according to any one of claims 1 to 4, the method comprising: A solution is obtained by mixing functional molecules containing thiol and nitrogen with a solvent; The lithium metal-containing matrix is ​​immersed in the solution and allowed to stand, so that the lithium metal reacts with the mercapto- and nitrogen-containing components. The functional molecules undergo a chemical reaction to obtain modified lithium metal.

6. The method according to claim 5, characterized in that, The settling process parameters include: temperature of 25℃~45℃ and time of 1 h~24 h.

7. The method according to claim 5, characterized in that, The mixing time is 5 seconds to 2 hours; and / or, The molar concentration of the solution is 0.001 mol / L to 10 mol / L.

8. The method according to claim 5, characterized in that, The solvent includes at least one of the following: ethylene glycol dimethyl ether, dioxolane, dimethyl carbonate, tetrahydrofuran, dimethyl sulfoxide, N,N Dimethylformamide, ethanol.

9. A negative electrode comprising the modified lithium metal according to any one of claims 1 to 4.

10. A battery comprising the negative electrode of claim 9.

Images