Lithium metal modification method, modified lithium metal and application thereof

Abstract

The invention relates to a lithium metal modification method, modified lithium metal and application thereof, and belongs to the technical field of electrochemical devices. The method comprises the following steps: soaking lithium metal in a metal-containing modification solution at a set temperature so as to form an alloy layer on the surface of the lithium metal to obtain modified lithium metal; wherein the metal-containing modification solution comprises one of the following components: a metal dispersion liquid and a metal salt solution. The surface of the prepared modified lithium metal is provided with a uniform and stable lithium alloy layer which serves as an effective physical barrier, and the electrochemical stability of the lithium metal is improved; the modified lithium metal is used as a negative electrode and has good chemical and electrochemical stability, and it is guaranteed that a uniform lithium ion transmission channel is formed at an electrode-solid electrolyte interface; the negative electrode is applied to the battery, the cycle performance of the battery is kept, continuous growth of lithium dendrites in the battery is inhibited, and lithium ions are uniformly deposited.

Description

Technical Field

[0001] This application relates to the field of electrochemical device technology, and in particular to a method for modifying lithium metal, modified lithium metal and its applications. Background Technology

[0002] The scarcity of traditional resources and energy, coupled with increasingly severe environmental problems, makes the development of next-generation energy storage systems with high specific energy and low cost, and the development of new energy conversion technologies, an urgent priority. Energy storage devices, represented by lithium metal batteries, have become an important research direction for novel energy storage systems in recent years. Lithium metal anodes possess extremely high theoretical specific capacity (3860 mAh / g), extremely low electrode potential (-3.045 V vs. standard hydrogen electrode), and relatively low density (0.534 g / cm³). 3 With its advantages such as high energy density, it is considered an ideal anode material for next-generation high-energy-density lithium batteries and has attracted widespread attention.

[0003] However, when using lithium metal as the negative electrode, the electrochemical stability of lithium metal is not ideal. The growth of dendrites on the surface of the negative electrode and the continuous loss of lithium metal make it impossible for lithium metal batteries to cycle stably. The continuous growth of dendrites can puncture the separator and cause internal damage to the battery, which can easily lead to safety accidents and poses safety hazards, thus hindering the practical application of lithium metal batteries. Summary of the Invention

[0004] This application provides a method for modifying lithium metal, modified lithium metal 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 method for modifying lithium metal, the method comprising: At a set temperature, lithium metal is immersed in a metal-modified solution to form a alloy on the surface of the lithium metal. A gold layer was formed, resulting in modified lithium metal; among which, The modified solution containing metal includes one of the following: a metal dispersion or a metal salt solution.

[0005] Optionally, the set temperature is 20℃~35℃; and / or, If the modified solution is a metal dispersion, the soaking time is 2h~20h; if the modified solution is a metal... If the solution is salt, the soaking time is 5s to 300s.

[0006] Optionally, the molar concentration of the modified solution is 0.05 mol / L to 1 mol / L.

[0007] Optionally, the metal dispersion may contain at least one of the following metals: gallium, zinc, aluminum, magnesium, silver, indium, or bismuth.

[0008] Optionally, the metal salt in the metal salt solution includes at least one of the following: gallium trichloride, gallium trifluoride, magnesium chloride, etc. Magnesium fluoride, silver nitrate.

[0009] Optionally, the solvent of the modified solution includes at least one of the following: 1,3-dioxolane, tetrahydrofuran, and dimethyl ether.

[0010] Optionally, the thickness of the alloy layer is greater than 0 and does not exceed 3 μm.

[0011] Optionally, the lithium metal includes at least one of the following characteristics: purity > 99% and thickness ≥ 25 μm.

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

[0013] Thirdly, embodiments of this application provide a battery, the battery comprising any embodiment of the third aspect. The negative electrode described.

[0014] The technical solutions provided in this application have the following advantages compared with the prior art: The lithium metal modification method provided in this application includes: modifying lithium metal at a set temperature. The lithium metal is immersed in a metal-containing modification solution to form an alloy layer on its surface, thereby obtaining modified lithium metal; wherein, The modified solution containing metal includes one of the following: a metal dispersion or a metal salt solution. At a set temperature, lithium metal is immersed in the modified solution, causing surface alloying of the lithium metal. The rate of the surface alloying reaction and the uniformity of the alloy layer formation are controlled. The modified solution can directly or indirectly react chemically with lithium metal to form an alloy. The modified solution includes one of the following: a metal dispersion or a metal salt solution. The metal in the metal dispersion can form an alloy with lithium metal, and the metal salt in the metal salt solution can undergo a displacement reaction with lithium metal to form an alloy. Finally, a stable lithium metal alloy layer is formed on the surface of the lithium metal. This uniformly distributed alloy layer can serve as an effective physical barrier, improving the electrochemical stability of the lithium metal. 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 modifying lithium metal provided in this application embodiment; Figure 2 This is a scanning electron microscope image of the modified lithium metal provided in Example 1 of this application; Figure 3 X-ray energy dispersive spectroscopy (EDS) of modified lithium metal provided in Example 1 of this application; Figure 4 The cycling performance diagram of the modified lithium metal anode solid-state symmetric battery provided in Example 1 of this application; Figure 5 The cycling performance diagram is provided for the unmodified lithium anode solid-state symmetric battery of Comparative 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, "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 multiple 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 each be single or multiple.

[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 method for modifying lithium metal. Figure 1 Provided for the embodiments of this application A schematic flowchart of a method for modifying lithium metal; please refer to [link / reference]. Figure 1 The method includes: S1. At a set temperature, lithium metal is immersed in a modified solution to perform surface alloying of the lithium metal. Modified lithium metal was obtained; among which, The modified solution can react directly or indirectly with the lithium metal to form an alloy; The modified solution includes one of the following: a metal dispersion or a metal salt solution.

[0023] In this embodiment, the technical principle of this lithium metal modification method mainly involves an alloying process, that is, forming an alloy layer on the surface of lithium metal to improve its performance or change its surface properties. Alloying refers to the combination of two or more metallic (or non-metallic) elements through melting or other methods to form a substance with metallic properties. In this method, lithium metal undergoes an alloying reaction with the metal elements in the modification solution to form an alloy layer. Through the alloying process, the surface properties of lithium metal are changed, such as hardness, corrosion resistance, and electrochemical performance. Specific process: 1. Select a suitable metal dispersion or metal salt solution as the modification solution. Metal dispersions typically contain fine metal particles, while metal salt solutions contain soluble metal ions; the concentration, temperature, and other parameters of the modification solution need to be adjusted according to specific requirements. 2. Immerse lithium metal in a modified solution at a set temperature. The temperature must be chosen to ensure the alloying reaction proceeds smoothly while avoiding unnecessary phase transitions or corrosion of the lithium metal. The immersion time also affects the thickness and uniformity of the alloy layer; too short an immersion time may result in an excessively thin alloy layer, while too long an immersion time may result in an excessively thick alloy layer or unevenness. 3. During the immersion process, the metal elements in the modified solution undergo an alloying reaction with the lithium metal, forming an alloy layer. This alloy layer may have different physical and chemical properties than the lithium metal, thus altering the surface characteristics of the lithium metal. The formation of the alloy layer is a complex physicochemical process involving the diffusion, reaction, and phase transition of metal elements. After immersion, remove the lithium metal from the modified solution and perform necessary cleaning and drying. Further processing and treatment, such as cutting and stamping, can be performed on the modified lithium metal as needed. The negative electrode prepared from the modified lithium metal is suitable not only for traditional lithium-ion batteries but also for new battery systems such as all-solid-state batteries.

[0024] In some embodiments, the set temperature is 20°C to 35°C; and / or, If the modified solution is a metal dispersion, the soaking time is 2h~20h; if the modified solution is a metal... If the solution is salt, the soaking time is 5s to 300s.

[0025] In this embodiment, the set temperature directly determines the reaction rate between lithium metal and the modified solution. Temperature causes atoms and molecules to have different thermal energies. Within a suitable temperature range, collisions and chemical reactions between atoms can occur at an appropriate frequency. A suitable temperature setting helps form a uniform alloy layer. The diffusion and deposition of metal atoms (whether directly reacting from a metal dispersion or produced by metal salt substitution reactions) on the lithium metal surface can proceed in a relatively orderly manner.

[0026] The set temperature can be between 20℃ and 35℃, allowing the reaction between lithium metal and the modification solution (whether a metal dispersion or a metal salt solution) to proceed at a suitable rate. This also facilitates the orderly diffusion and deposition of metal atoms on the lithium metal surface, resulting in a more uniform and dense alloy layer, which better fulfills its subsequent function as a physical barrier. Furthermore, this temperature range is close to room temperature, eliminating the need for complex heating or cooling equipment to precisely maintain the temperature during actual operation, simplifying the process and reducing equipment costs and operational difficulties in experiments or production. If the set temperature is too high, exceeding 35℃, it becomes difficult to control the degree of alloying reaction, leading to decreased uniformity of the lithium alloy layer and potentially triggering adverse side reactions, such as rapid solvent evaporation causing sudden changes in solution concentration or unnecessary chemical reactions between lithium metal and the solvent or impurities in the environment, affecting the normal progress of the alloying reaction and the quality of the alloy layer. If the set temperature is too low, below 20℃, it slows down the alloying process and reduces modification efficiency. For example, the set temperature can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, etc.

[0027] In the embodiments of this application, if the modified solution is a metal dispersion, the metal contained therein is capable of reacting with lithium metal. A specific metal that forms an alloy. These metal atoms exist in a dispersed state in a solution. When lithium metal is immersed in it, based on the chemical activity of the metal atoms themselves and their compatibility with lithium metal in terms of atomic structure (such as matching atomic radius, complementary valence electron structure, etc.) and electrochemical properties, the metal atoms will gradually diffuse to the surface of lithium metal and undergo an alloying reaction with lithium metal atoms through interatomic interactions (such as sharing electrons, adjusting lattice structure, etc.).

[0028] If the modified solution is a metal dispersion, the soaking time can be 2 hours to 20 hours, which allows the metal in the dispersion to... The lithium alloy can be fully alloyed with metallic lithium. If the time is too long (more than 20 hours), the lithium alloy layer may become too thick, affecting ion transport performance. The metal may also excessively penetrate the lithium metal, altering its mechanical properties and potentially increasing its brittleness. If the time is too short (less than 2 hours), the reaction between lithium and the metal may be incomplete, resulting in poor uniformity of the lithium alloy layer, affecting its physical barrier effect and hindering the improvement of the electrochemical stability of the lithium metal. For example, if the modified solution is a metal dispersion, the soaking time can be 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, etc.

[0029] If the modification solution is a metal salt solution, the metal salt it contains can first undergo a displacement reaction with lithium metal. This is based on the high reactivity of lithium metal in the metal activity series; it can displace metal ions from the metal salt solution. The metal ions in the solution are replaced by lithium atoms, and the newly formed metal atoms, being in a highly reactive state, will then undergo an alloying reaction with the surrounding lithium metal atoms, forming an alloy layer on the lithium metal surface. This method of re-alloying through displacement reaction can utilize various metal salts to modify lithium metal, broadening the range of metals that can be used for modification. Therefore, metal salt solutions can form high-quality alloy layers on the lithium metal surface, and different metal salts can be selected to control the composition and properties of the alloy layer according to actual needs.

[0030] If the modified solution is a metal salt solution, the immersion time can be from 5s to 300s. A sufficiently strong metal salt solution allows the metal salt to undergo a displacement reaction with the lithium metal, followed by an alloying reaction to form a uniform alloy layer on the lithium metal surface. If the time is too long (more than 300s), the lithium metal may be excessively consumed, resulting in an overly high alloy composition and a porous structure. If the time is too short (less than 5s), a uniform and complete alloy layer may not form on the lithium metal surface. For example, the immersion time can be 5s, 10s, 15s, 20s, 25s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 150s, 200s, 250s, or 300s.

[0031] In S1, the immersion process is carried out under a protective atmosphere, namely nitrogen and / or other inert gases, to prevent the oxidation of lithium and gallium. The solvent evaporation process of the immersion solution is carried out under vacuum conditions, allowing the solvent to leave the metal surface more completely. For obtaining the metal dispersion, the solid metal is dispersed in the solvent and mixed for 10-14 hours; for obtaining the metal salt solution, the solid metal salt is dispersed in the solvent and mixed for 25-45 minutes.

[0032] In some embodiments, the molar concentration of the modified solution is 0.05 mol / L to 1 mol / L.

[0033] In the embodiments of this application, the molar concentration of the modified solution can be from 0.05 mol / L to 1 mol / L. Sufficient supply of metal or metal salt ensures suitable kinetics for the modification reaction, enabling the formation of a uniform and dense lithium-gallium alloy layer on the lithium metal surface. If the molar concentration of the modified solution is too high (above 1 mol / L), excessive lithium salt will be introduced, making removal difficult. Simultaneously, the reaction rate will be too fast, making it difficult to control the soaking time. If the molar concentration of the modified solution is too low (below 0.05 mol / L), the kinetics of the modification reaction will be insufficient, resulting in a thin and uneven alloy layer. Furthermore, lower concentrations require longer soaking times to achieve the desired effect, reducing experimental efficiency. For example, the molar concentration of the modified solution can be 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, etc.

[0034] In some embodiments, the metal dispersion comprises at least one of the following metals: gallium, zinc, aluminum, magnesium, silver, etc. Indium and bismuth.

[0035] In this embodiment, the modified solution can be a metal dispersion, requiring that the metal contained therein be able to form an alloy with lithium metal. The metal in the metal dispersion can be one or more combinations of gallium, zinc, aluminum, magnesium, silver, indium, and bismuth. These metals, based on their own atomic structure characteristics (such as atomic radius matching, complementary valence electron structures, etc.) and chemical properties (such as differences in electrochemical potentials), can form an alloy on the surface of lithium metal after contact with it through processes such as interatomic diffusion and electron redistribution. The formation of this alloy changes the original surface state of lithium metal and endows it with new properties.

[0036] In some embodiments, the metal salt of the metal salt solution includes at least one of the following: gallium trichloride, trifluoride... Gallium, magnesium chloride, magnesium fluoride, silver nitrate.

[0037] In this embodiment, the modified solution can also be a metal salt solution, requiring that the metal salt can first react with lithium metal. A displacement reaction occurs, followed by alloying with lithium metal. The metal salt in the solution can be gallium trichloride or trifluoride. One or more combinations of gallium, magnesium chloride, magnesium fluoride, and silver nitrate, lithium metal, being an active metal, will displace the metal ions from these metal salts (according to the metal activity series, lithium has a stronger reducing power than many metals). The displaced metal atoms are in a highly active state and can then combine with the surrounding lithium metal atoms to form an alloy layer on the lithium metal surface.

[0038] In some embodiments, the solvent of the modified solution includes at least one of the following: 1,3-dioxolane, tetrahydrofuran Uranium, dimethyl ether.

[0039] In the embodiments of this application, the solvent of the modified solution can be 1,3-dioxolane (DOL) or tetrahydrofuran (THF). Dimethyl ether (DME) is a combination of one or more of the following: DOL is an organic solvent that exhibits good dispersing properties for metals in metal dispersions or good solubility for metal salts in metal salt solutions. The oxygen atoms in its molecular structure can coordinate with metal ions, thereby reducing the lattice energy of the metal salt and making it easier to dissolve. DOL itself possesses a certain degree of chemical stability; during lithium metal modification, it does not easily react with lithium metal or other metals in solution, ensuring the smooth progress of the modification process. Furthermore, its cyclic structure provides a relatively stable solvent environment for metal ions in solution, which is beneficial for maintaining the stability of the solution properties. THF is an excellent solvent; as a cyclic ether, its heterocyclic structure and oxygen atoms endow it with good solubility. It is miscible with water and most organic solvents, has a good solubility for metal salts, and exhibits good dispersing properties for metals. DME is a simple aliphatic ether, a colorless gas at room temperature and pressure, but can be used as a solvent under appropriate conditions. Its ether bond (-O-) structure gives it a certain solubility for metal salts. DME can undergo a solvation reaction with metal ions, encapsulating them within solvent molecules to form a stable solution. This solvation helps ensure the uniform distribution of metal ions in the solution, which is beneficial for subsequent reactions with lithium metal. DME is chemically relatively stable and does not readily react with metal particles, providing a favorable environment for the dispersion of metals or metal salts.

[0040] In some embodiments, the thickness of the alloy layer is greater than 0 and does not exceed 3 μm.

[0041] In this embodiment, the modified lithium metal includes a lithium metal matrix and a lithium alloy layer attached to at least the surface of the lithium metal matrix. The thickness of the alloy layer can be greater than 0 and not more than 3 μm.

[0042] In this embodiment, the thickness of the alloy layer can be greater than 0 and not more than 3 μm. A thinner alloy layer ensures its functionality while minimizing the increase in overall material weight and cost. An alloy layer thickness of no more than 3 μm avoids excessive ion transport resistance that could negatively impact battery charge / discharge performance, while simultaneously enhancing electrode stability and cycle life through its synergistic effect with the lithium metal substrate. The alloy layer creates a unique interface effect with the external environment and other materials it contacts. For example, in preventing side reactions between lithium metal and the electrolyte, this thickness acts as a "protective barrier," effectively isolating some electrolyte corrosion of the lithium metal substrate without severely affecting normal lithium ion migration, thus ensuring the overall electrochemical performance of the system remains relatively ideal. For example, the thickness of the alloy layer can be 3 μm, 2.8 μm, 2.5 μm, 2.3 μm, 2.1 μm, 2.0 μm, 1.5 μm, 1 μm, etc.

[0043] In some embodiments, the lithium metal includes at least one of the following characteristics: purity > 99% and thickness ≥ 25 μm.

[0044] In the embodiments of this application, the purity of lithium metal can be >99%, which helps to reduce side reactions caused by impurities. When lithium... When the impurity content in the metal is high, these impurities may chemically react with the electrolyte during charging and discharging. A thickness of ≥25μm can provide more lithium reserves. During battery cycling, lithium consumption and deposition lead to changes in electrode thickness. A thicker lithium electrode can better withstand these changes, reducing performance degradation caused by electrode structure damage. For example, when lithium dendrites grow, a thicker lithium metal layer can buffer the damage to the electrode structure and separator caused by the dendrites to a certain extent, reducing the risk of battery short circuits. For example, the purity of the lithium metal can be 99.1%, 99.2%, 99.3%, etc.; the thickness of the lithium metal can be 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, etc.

[0045] Secondly, embodiments of this application provide a modified lithium metal, wherein the modified lithium metal is derived from any one of the components described in the first aspect. The method described in the above embodiment is used to prepare the product.

[0046] In this embodiment, the modified lithium metal is prepared by the aforementioned lithium metal modification method. The modified lithium metal includes a lithium metal matrix and a lithium alloy layer attached to at least a portion of the surface of the lithium metal matrix. The alloy layer is uniformly distributed on the lithium metal surface, enhancing its stability. This stability allows the lithium metal to better maintain its structural integrity in complex electrochemical environments. For example, under high current density charging and discharging conditions, the unmodified lithium metal surface may experience structural damage due to intense local reactions, while the modified lithium metal, protected by the alloy layer, can more stably cope with these situations. The battery can be a solid-state battery, which uses solid electrodes and a solid electrolyte. Solid-state batteries generally have lower power density and higher energy density. The solid electrolyte in a solid-state battery can be a polymer electrolyte or a sulfide electrolyte. The modified lithium metal anode significantly suppresses the growth of anode dendrites, achieving uniform lithium deposition, thereby reducing battery safety hazards, improving battery cycle performance, and extending battery life.

[0047] The modified lithium metal is achieved based on the above-described lithium metal modification method. The specific steps of the lithium metal modification method can be referred to the above embodiments. Since the 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 elaborated here.

[0048] Thirdly, embodiments of this application provide a negative electrode, the negative electrode comprising any embodiment of the second aspect. The modified lithium metal described above.

[0049] In this embodiment, the negative electrode comprises the aforementioned modified lithium metal. Because a stable and uniformly distributed lithium metal alloy layer is formed on the surface of the modified lithium metal (achieved through modification operations such as immersion in a suitable modification solution at a set temperature), this alloy layer acts as an effective physical barrier. For the negative electrode, this significantly reduces lithium dendrite growth and puncture problems during battery charging and discharging. The disordered growth of lithium dendrites often damages the electrode structure and can even cause serious faults such as battery short circuits. The alloy layer of the modified lithium metal effectively resists these problems, significantly enhancing the stability of the negative electrode during cycling and improving the overall safety and lifespan of the battery.

[0050] The alloy layer on the modified lithium metal surface can also improve the uniformity of lithium-ion transport. During battery operation, lithium ions need to migrate smoothly and uniformly between the positive and negative electrodes. Traditional lithium metal anodes may exhibit localized uneven lithium-ion transport, leading to electrode polarization and other adverse phenomena, affecting the battery's charge and discharge efficiency. However, the modified lithium metal in this embodiment creates a more uniform transport channel for lithium ions, enabling more orderly and efficient deposition and deintercalation of lithium ions on the anode surface. This optimizes the electrochemical performance of the anode and helps improve the battery's charge and discharge efficiency as well as its overall energy conversion efficiency.

[0051] Due to the suppression of lithium dendrite growth and the improvement of lithium-ion transport uniformity by modified lithium metal, the entire anode exhibits excellent cycle performance in all-solid-state symmetric batteries and related battery systems when applied to it. During multiple charge-discharge cycles, the anode better maintains its structural integrity and electrochemical performance, reducing capacity decay and enabling the battery to operate stably for a longer period, further demonstrating the advantages of this anode in high-performance battery applications. The negative electrode is based on the modified lithium metal described above. The specific preparation steps of the modified lithium metal can be referred to 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 elaborated here.

[0052] Thirdly, embodiments of this application provide a battery, the battery comprising any embodiment of the third aspect. The negative electrode described.

[0053] In the embodiments of this application, the modified lithium metal anode exhibits excellent cycle performance in the battery. Capacity decay is effectively suppressed during multiple battery cycles. This is because the surface alloy layer inhibits the growth of lithium dendrites, avoiding internal short circuits and irreversible loss of active lithium caused by lithium dendrite growth. Simultaneously, due to the improved uniformity of lithium-ion transport, electrochemical polarization is reduced during each cycle, enabling the battery to maintain good performance through more cycles, extending battery life and improving battery reliability.

[0054] 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.

[0055] 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.

[0056] Example 1 A method for modifying lithium metal, wherein the lithium metal has a purity of 99.9% and a thickness of 35 μm, comprising: At a set temperature, lithium metal is immersed in a metal dispersion to allow for surface alloying of the lithium metal, resulting in modified lithium metal. Lithium metal; Specifically, 0.4 g (0.0057 mol) of gallium metal was weighed into a vial in a glove box, 10 mL of DOL was added, and the mixture was stirred for 12 h. Then, lithium sheets were added and soaked at 25°C for 12 h. After soaking, the lithium sheets were removed and soaked in a nitrogen atmosphere. The solvent was evaporated under vacuum to obtain modified lithium metal. The thickness of the alloy layer of the modified lithium metal was 1 μm.

[0057] A type of negative electrode, where modified lithium metal can be directly applied to negative electrode materials.

[0058] An all-solid-state symmetric battery was constructed using the modified lithium metal anode material obtained in Example 1. The battery was then assembled and subjected to constant current charge-discharge testing. The modified lithium metal anode material obtained in Example 1 was used as the anode, and polyvinyl carbonate was used as the electrolyte. The charge-discharge current density was 3.6 mA / cm². 2 The charge / discharge time is 48 minutes. Figure 2 This is a scanning electron microscope image of the modified lithium metal provided in Example 1 of this application; Figure 3 X-ray energy dispersive spectroscopy (EDS) of modified lithium metal provided in Example 1 of this application; please refer to [link to EDS]. Figures 2-3 This indicates that gallium is uniformly distributed on the lithium metal surface. Figure 4 This is a cycle performance diagram of the modified lithium metal anode solid-state symmetric battery provided in Example 1 of this application; please refer to... Figure 4 The polarization voltage of this negative electrode is less than 30 mV, and it can be stably cycled for more than 1,000 times, exhibiting stable cycling characteristics.

[0059] Example 2 A method for modifying lithium metal, wherein the lithium metal has a purity of 99.9% and a thickness of 35 μm, comprising: At a set temperature, lithium metal is immersed in a metal dispersion to allow for surface alloying of the lithium metal, resulting in modified lithium metal. Lithium metal; Specifically, in a glove box, 0.134 g (0.001 mol) of aluminum trichloride was weighed and placed in a vial. 10 mL of THF was added, and the mixture was stirred for 30 min. Then, lithium sheets were placed in the vial and immersed at 28°C for 30 s. The lithium sheets were then removed and immersed in a nitrogen atmosphere. The solvent was evaporated under vacuum to obtain modified lithium metal. The thickness of the alloy layer of the modified lithium metal was 3 μm.

[0060] A type of negative electrode, where modified lithium metal can be directly applied to negative electrode materials.

[0061] An all-solid-state symmetric battery was constructed using the modified lithium metal anode material obtained in Example 2. The battery was then assembled and subjected to constant current charge-discharge testing. The modified lithium metal anode material obtained in Example 2 was used as the anode, and polyvinyl carbonate was used as the electrolyte. The charge-discharge current density was 3.6 mA / cm². 2 The charge / discharge time was 48 minutes, and the result was that the symmetrical battery could be stably cycled for 150 times.

[0062] Example 3 A method for modifying lithium metal, wherein the lithium metal has a purity of 99.9% and a thickness of 50 μm, comprising: At a set temperature, lithium metal is immersed in a metal dispersion to allow for surface alloying of the lithium metal, resulting in modified lithium metal. Lithium metal; Specifically, 0.14 g (0.0057 mol) of magnesium metal was weighed into a vial in a glove box, 10 mL of DOL was added, and the mixture was stirred for 12 h. Lithium sheets were then added and soaked at 30°C for 12 h. After soaking, the lithium sheets were removed and soaked in a nitrogen atmosphere. The solvent was evaporated under vacuum to obtain modified lithium metal. The thickness of the alloy layer of the modified lithium metal was 1 μm.

[0063] A type of negative electrode, where modified lithium metal can be directly applied to negative electrode materials.

[0064] A fully solid-state symmetric battery, using the modified lithium metal anode material obtained in Example 3 for the assembly of a fully solid-state symmetric battery. The device was assembled and subjected to constant current charge-discharge tests, using the modified lithium metal anode material obtained in Example 3 as the anode and polyvinyl carbonate as the electrolyte, with a charge-discharge current density of 3.6 mA / cm². 2 The charge / discharge time was 48 minutes, and the result was that the symmetrical battery could be stably cycled for 100 times.

[0065] Example 4 A method for modifying lithium metal, wherein the lithium metal has a purity of 99.9% and a thickness of 50 μm, comprising: At a set temperature, lithium metal is immersed in a metal dispersion to allow for surface alloying of the lithium metal, resulting in modified lithium metal. Lithium metal; Specifically, in a glove box, 0.176 g (0.001 mol) of gallium trichloride was weighed and placed in a vial. 10 mL of THF was added, and the mixture was stirred for 30 min. Then, lithium sheets were placed in the vial and immersed at 28°C for 30 s. The lithium sheets were then removed and immersed in a nitrogen atmosphere. The solvent was evaporated under vacuum to obtain modified lithium metal. The thickness of the alloy layer of the modified lithium metal was 3 μm.

[0066] A type of negative electrode, where modified lithium metal can be directly applied to negative electrode materials.

[0067] An all-solid-state symmetric battery was assembled using the modified lithium metal anode material obtained in Example 4. Constant current charge-discharge tests were conducted, with the modified lithium metal anode material obtained in Example 4 used as the anode and polyvinyl carbonate as the electrolyte. The charge-discharge current density was 3.6 mA / cm². 2 The charge / discharge time was 48 minutes, and the result was that the symmetrical battery could cycle stably for 600 cycles.

[0068] Comparative Example 1 A type of negative electrode, lithium metal negative electrode is used directly as a negative electrode material.

[0069] An all-solid-state symmetric battery was assembled using an unmodified lithium metal anode and subjected to charge-discharge tests. The unmodified lithium metal from Comparative Example 1 was used as the anode, and polyvinyl carbonate was used as the electrolyte. The charge-discharge current density was 3.6 mA / cm². 2 The charge / discharge time is 48 minutes. Figure 5 The cycling performance diagram of the unmodified lithium anode solid-state symmetric battery provided in Comparative Example 1 of this application is shown below; please refer to [link / reference]. Figure 5 The cycle was found to be unstable due to the continuous growth of lithium dendrites.

[0070] The performance of the all-solid-state symmetric batteries assembled in Examples 1-4 was tested. The test procedure was as follows: modified lithium metal was used as the negative electrode, polyvinyl carbonate was used as the electrolyte, and the charge / discharge current density was 3.6 mA / cm². 2 The charging and discharging time was 48 minutes, and the test results are shown in Table 1.

[0071] Table 1 Performance of all-solid-state symmetric batteries

[0072] As shown in Table 1, the performance of the modified lithium metal anode has been improved.

[0073] One or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: (1) In the embodiments of this application, lithium is immersed to alloy the surface, and then the solvent is evaporated. It was found that the modified lithium metal anode can suppress the growth of anode dendrites, achieve uniform lithium deposition, reduce the safety hazards of the battery, improve the safety of the battery, and improve the cycle performance of the battery; (2) In this application embodiment, modified lithium metal is used as a negative electrode interface modification layer, which has good chemical and electrochemical stability and ensures that a uniform lithium ion transport channel is formed at the electrode-solid electrolyte interface; applying the modified lithium metal negative electrode to the all-solid battery can maintain the cycle performance of the battery, suppress the continuous growth of lithium dendrites in the all-solid battery, and make lithium ions deposit uniformly. (3) The embodiments of this application effectively solve the problems of short cycle life and lithium dendrite growth of lithium metal anode, reduce the interfacial reaction between electrolyte and lithium metal anode, and the method is simple, effective, easy to process, highly efficient and mild.

[0074] 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 method for modifying lithium metal, the method comprising: At a set temperature, lithium metal is immersed in a metal-containing modification solution to form an alloy layer on the surface of the lithium metal, thereby obtaining modified lithium metal; wherein, The modified solution containing metal includes one of the following: a metal dispersion or a metal salt solution.

2. The method according to claim 1, characterized in that, The set temperature is 20℃~35℃; and / or, If the modified solution is a metal dispersion, the soaking time is 2h to 20h; if the modified solution is a metal salt solution, the soaking time is 5s to 300s.

3. The method according to claim 1 or 2, characterized in that, The molar concentration of the modified solution is 0.05 mol / L to 1 mol / L.

4. The method according to claim 1 or 2, characterized in that, The metal dispersion contains at least one of the following metals: gallium, zinc, aluminum, magnesium, silver, indium, and bismuth.

5. The method according to claim 1 or 2, characterized in that, The metal salt in the metal salt solution includes at least one of the following: gallium trichloride, gallium trifluoride, magnesium chloride, magnesium fluoride, and silver nitrate.

6. The method according to claim 1 or 2, characterized in that, The solvent of the modified solution includes at least one of the following: 1,3-dioxolane, tetrahydrofuran, and dimethyl ether.

7. The method according to claim 1, characterized in that, The thickness of the alloy layer is greater than 0 and does not exceed 3 μm.

8. The method according to claim 1, characterized in that, The lithium metal has at least one of the following characteristics: purity > 99% and thickness ≥ 25 μm.

9. A negative electrode comprising modified lithium metal obtained by the method of any one of claims 1 to 8.

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

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