Pretreatment composition for lithium metal electrode, method and lithium metal electrode

Abstract

The invention discloses a pretreatment composition and method for a lithium metal electrode and the lithium metal electrode. The pretreatment composition comprises a component (A) that is reactive with a lithium metal for a predetermined time of contact with the lithium metal; and a component (B) that does not substantially react with the lithium metal for a predetermined time of contact with the lithium metal and is miscible with the component (A). The invention further discloses a pretreatment method for the lithium metal electrode and the lithium metal electrode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries. Specifically, the present application relates to a pretreatment composition, a method and a lithium metal electrode for a lithium metal electrode. BACKGROUND

[0002] The information provided in this section is for the purpose of generally presenting the context of the disclosure. The work of the presently named inventors, to the extent the descriptions are described in this section, as well as aspects of the descriptions that can not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0003] Lithium metal electrode is an electrode material with high theoretical specific capacity and low electrochemical potential. However, lithium metal electrode is prone to form lithium dendrites during charging and discharging, which not only leads to battery capacity attenuation, but also may cause safety accidents in severe cases. The root cause of this problem is that there are various crystal face types on the surface of conventional commercial lithium metal electrode, and the ion diffusion energy barriers of different crystal faces are different, leading to uneven lithium ion deposition during deposition. The atomic arrangement of high-energy crystal face is sparse, and the lithium ion migration potential barrier is high, which easily leads to local ion accumulation and dendrite growth.

[0004] Therefore, there is still a need in the art for a method that can significantly alleviate dendrite growth and improve the performance of lithium metal electrode, and the process is simple and easy to realize precise control. SUMMARY

[0005] The present application provides a pretreatment composition, a method and a lithium metal electrode for a lithium metal electrode to solve one or more of the above problems and other aspects, or to provide an alternative technical solution to the prior art.

[0006] According to one aspect of the present application, a pretreatment composition for a lithium metal electrode is provided, comprising component (A) that can react with lithium metal within a predetermined time of contact with lithium metal; and component (B) that does not substantially react with lithium metal within the predetermined time of contact with lithium metal and is miscible with the component (A).

[0007] In some embodiments, in the pretreatment composition according to the present application, the predetermined time is 1-60 minutes.

[0008] In some embodiments, in the pretreatment composition according to the present application, the amount of the component (A) is 0.1% to 10% by volume, based on the total volume of the pretreatment composition.

[0009] In some embodiments, in the pretreatment composition according to the present application, the component (A) is selected from the group consisting of water, monohydric alcohol containing 1-6 carbon atoms, carboxylic acid containing 1-6 carbon atoms, primary and secondary amine containing 1-4 carbon atoms, aliphatic thiol containing 1-6 carbon atoms, monocyclic aromatic thiol, and mixtures thereof.

[0010] In some embodiments, in the pretreatment composition according to the present application, the component (B) is selected from the group consisting of dimethyl sulfoxide, acetonitrile, tetrahydrofuran, 1,2-dimethoxyethane, N-methylpyrrolidone, dimethylformamide, and mixtures thereof.

[0011] According to another aspect of the present application, there is provided a pretreatment method for a lithium metal electrode, comprising the steps in the following order: i) preparing a pretreatment composition according to the present application by mixing component (A) with component (B); and ii) contacting the lithium metal with the pretreatment composition under a protective atmosphere for a predetermined time to perform pretreatment.

[0012] In some embodiments, in the method according to the present application, the predetermined time is 1-60 minutes.

[0013] In some embodiments, in the method according to the present application, the method further comprises the step: iii) washing the lithium metal pretreated by step ii) with an organic solvent under a protective atmosphere, wherein the organic solvent is an electrolyte solvent used in a battery comprising the lithium metal electrode.

[0014] According to another aspect of the present application, there is provided a lithium metal electrode pretreated using the pretreatment method according to the present application.

[0015] In some embodiments, in the lithium metal electrode according to the present application, the lithium metal electrode has enhanced (100) crystal plane orientation.

[0016] Compared with the prior art, the present application provides a technical solution with simple process, low cost and easy regulation. By using a pretreatment composition in which a component (A) that can react with lithium metal is uniformly mixed with a component (B) that does not substantially react with lithium metal, the present application realizes effective regulation of crystal orientation by using the selective reaction of component (A) diluted by component (B) with the crystal faces of the lithium metal electrode surface, inhibits the growth of dendrites on the lithium metal electrode, realizes more uniform lithium ion deposition, and at the same time forms an interface structure that is beneficial to lithium ion transmission during the pretreatment process, thereby improving the overall performance of the battery in which it is located from multiple aspects, including improving the coulombic efficiency and cycle performance. In addition, by controlling the content of component (A) in the pretreatment composition and the pretreatment time, the degree of reaction between component (A) and lithium metal can be accurately and controllably adjusted. BRIEF DESCRIPTION OF DRAWINGS

[0017] The disclosure of the present application will become more readily apparent from reference to the accompanying drawings. As will be readily appreciated, these drawings are merely intended to illustrate the subject application, and are not intended to act as a limitation thereon. Throughout the drawings, like referenced numerals are intended to represent like elements, wherein: Figure 1A X-ray diffraction (XRD) patterns of a lithium metal electrode pretreated according to one embodiment of the present application and a lithium metal electrode without pretreatment are shown.

[0018] Figure 1B XRD patterns of a lithium metal electrode pretreated according to another embodiment of the present application and a lithium metal electrode without pretreatment are shown.

[0019] Figure 1C XRD patterns of a lithium metal electrode pretreated according to another embodiment of the present application and a lithium metal electrode without pretreatment are shown.

[0020] Figure 2 XRD patterns of a lithium metal electrode pretreated according to one embodiment of the present application and a lithium metal electrode without pretreatment after 20 hours of cycling in a symmetric battery are shown.

[0021] Figure 3A SEM images of a lithium metal electrode pretreated according to one embodiment of the present application after 20 hours of cycling in a symmetric battery are shown.

[0022] Figure 3B SEM images of a lithium metal electrode without pretreatment after 20 hours of cycling in a symmetric battery are shown.

[0023] Figure 4A plot of voltage versus time is shown for a lithium copper half-cell comprising a lithium metal electrode pretreated according to one embodiment of the application, which shows the coulombic efficiency test results for the lithium copper half-cell.

[0024] Figure 5 A plot of discharge specific capacity and coulombic efficiency versus cycle number is shown for a lithium sulfur battery comprising a lithium metal electrode pretreated according to one embodiment of the application, which shows the cycling performance of the lithium sulfur battery.

[0025] Figure 6 Electrochemical impedance spectra (EIS) are shown for a symmetric cell comprising a lithium metal electrode pretreated according to one embodiment of the application and a symmetric cell comprising a lithium metal electrode that was not pretreated. DETAILED DESCRIPTION

[0026] In order that the foregoing and other objects, features and advantages of the present application can be more readily understood, a detailed description of the application follows. It should be understood that all descriptions are intended to be illustrative, and not restrictive, of the present application. To the extent that any individual technical feature of the embodiments described or implied in the various embodiments mentioned herein is described or implied, the present application still allows for any combination or sub-combination of these technical features (or equivalents thereof) to continue without any technical obstacles, and thus it should be considered that more embodiments according to the present application are also encompassed within the scope of the description as written herein.

[0027] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as those commonly understood by one of ordinary skill in the art to which this application belongs. If there is a conflict between the definitions provided in this application and those provided in the art, the definitions provided in this application control.

[0028] In this application, unless otherwise indicated, the numerical ranges are intended to include the end points, and all intermediate values and all sub-ranges of the ranges.

[0029] In this application, unless otherwise indicated, all numbers expressing quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about."

[0030] As used herein, the terms "comprising" and "including" encompass the case where the other elements are also present or are included, as well as the case where the other elements are not present or are excluded.

[0031] As used herein, the term "substantially unreactive with" means that, from a chemical kinetics perspective, a particular substance does not undergo a significant chemical reaction, or its rate of reaction is so slow as to have a negligible reaction conversion, e.g., 0.1% or less, or the amount of reaction product is below the limit that can be detected by conventional analytical means, within a predetermined contact time.

[0032] In the present application, the term "water" refers to deionized water with conductivity no higher than 1.0 µS / cm at room temperature, unless otherwise specified.

[0033] As used herein, the term "miscible" refers to two or more materials capable of forming a uniform mixture, i.e., dissolving into each other to form a homogeneous reaction system.

[0034] In the present application, unless otherwise specified, each reaction is carried out at room temperature and normal pressure.

[0035] It is known to the inventors that the surface of untreated lithium metal electrode exists in multiple crystal facet types including lithium (110), (211) and (200). During charge-discharge cycles, lithium ions tend to deposit on the crystal facets with relatively high surface energy, which easily triggers dendrite growth. Since lithium (110) crystal facet has relatively low surface energy and relatively high chemical stability, it is relatively difficult to react with reactive substances, such as water, and is thus preserved.

[0036] In view of this, the present application provides a pretreatment composition and method for lithium metal electrode, by including a component reactive with lithium and diluted in the composition to pretreat lithium metal, the crystal facet orientation of the surface of lithium metal can be selectively regulated, in particular, the proportion of (110) crystal facet orientation of lithium metal is enhanced, so as to significantly inhibit dendrite growth on the surface of the electrode and improve the performance of the battery.

[0037] According to a first aspect of the present application, the present application provides a pretreatment composition for lithium metal electrode, which can comprise component (A) which can react with lithium metal within a predetermined time of contact with lithium metal; and component (B) which does not substantially react with lithium metal within the predetermined time of contact with lithium metal, and is miscible with the component (A).

[0038] In the present application, the "predetermined time" refers to the time condition for judging whether the component reacts when it is in contact with lithium metal. Specifically, when the component contained in the pretreatment composition can react when it is in contact with lithium metal within the predetermined time, the component can be component (A); when the component contained in the pretreatment composition does not react when it is in contact with lithium metal within the predetermined time, the component can be component (B).

[0039] In some embodiments, the predetermined time according to the present application can be 1 to 60 minutes.

[0040] The inventors have found that, on one hand, by using a component (A) having high reactivity with lithium metal as the active ingredient in the pretreatment composition, the crystal planes with higher surface energy, such as (200) and (211) crystal planes, can be selectively consumed, leaving the (110) crystal plane with lower surface energy, thus maximizing the proportion of (110) crystal plane relative to other crystal planes, and achieving the regulation of crystal plane orientation; on the other hand, the product of the reaction between component (A) and lithium metal can serve as an ion conduction layer, forming a solid electrolyte interface (SEI) film with high ionic conductivity, providing a favorable interface structure for the efficient and uniform transmission of lithium ions.

[0041] The inventors have further found that, in order to achieve the selective reaction described above and ensure the controllability of the reaction, it is necessary to introduce a component (B) that is well miscible with component (A) and does not substantially react with lithium metal within a predetermined time into the pretreatment composition. Component (B) can dilute the concentration of component (A) and form a uniform pretreatment composition with component (A), enabling component (A) to selectively react with specific crystal planes of lithium metal at a suitable rate and ensuring that the lithium metal surface obtains a controllable and uniform pretreatment.

[0042] In the pretreatment composition according to the present application, component (A) can be selected as a species that can easily react with lithium metal within a predetermined time, such as 1-60 minutes, upon contact with lithium metal. In some embodiments, component (A) can be selected from the group consisting of: water; monohydric alcohols containing 1-6 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, t-butanol, n-pentanol, iso-pentanol, n-hexanol; carboxylic acids containing 1-6 carbon atoms, such as formic acid, acetic acid, propionic acid, isopropionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid; primary and secondary amines containing 1-4 carbon atoms, such as ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, dimethylamine, diethylamine; aliphatic and monocyclic aromatic thiols containing 1-6 carbon atoms, such as methyl mercaptan, ethyl mercaptan, n-propyl mercaptan, isopropyl mercaptan, n-butyl mercaptan, n-pentyl mercaptan, n-hexyl mercaptan, phenyl mercaptan; and mixtures thereof.

[0043] In some embodiments, in the pretreatment composition according to the present application, the amount of component (A) is 0.1% to 10% by volume, relative to the total volume of the pretreatment composition.

[0044] In some embodiments, in the pretreatment composition according to the present application, component (B) can include an aprotic polar solvent capable of forming a stable and uniform mixed solution with component (A) through intermolecular forces, such as hydrogen bonding forces or dipole-dipole forces. For example, component (B) can be selected from the group consisting of dimethyl sulfoxide (DMSO), acetonitrile, tetrahydrofuran (THF), 1,2-dimethoxyethane (DME), N-methyl pyrrolidone, dimethylformamide, and mixtures thereof.

[0045] According to a second aspect of the present application, the present application provides a pretreatment method for lithium metal electrode, which can comprise the following steps: i) preparing a pretreatment composition according to the present application by mixing component (A) with component (B); and ii) contacting lithium metal with the pretreatment composition under a protective atmosphere for a predetermined time for pretreatment.

[0046] In the pretreatment method according to the present application, the pretreatment process of lithium metal should be carried out under a protective atmosphere to avoid the adverse effects of moisture and oxygen in the air on lithium metal. The protective atmosphere can be argon, helium or other inert gases with sufficiently low (e.g. <0.1 ppm) oxygen and moisture content and no reaction with lithium, or a mixture thereof.

[0047] In addition, it should be understood that in the pretreatment method according to the present application, the contact between the pretreatment composition according to the present application and lithium metal can be achieved by any appropriate means that can allow the two to be in sufficient contact and achieve the desired pretreatment effect. For example, the lithium metal can be immersed in the pretreatment composition according to the present application for pretreatment in the form of immersion.

[0048] In some embodiments, in the pretreatment method according to the present application, the predetermined time for which the pretreatment composition according to the present application is contacted with lithium metal for pretreatment can be 1-60 minutes. The inventors have found that the time required for pretreatment is related to the type and amount of reactive component (A). For example, when the amount of component (A) is present in a lower amount, e.g. less than 1% by volume, in the pretreatment composition according to the present application, a prolonged contact time, e.g. greater than 20 minutes, can be selected to achieve the best pretreatment effect.

[0049] It should be understood that after the pretreatment of the surface of lithium metal in the pretreatment method according to the present application, the residue of the pretreatment composition present on the surface of lithium metal needs to be cleaned. Therefore, in some embodiments, the pretreatment method according to the present application can further comprise step iii) cleaning the lithium metal pretreated in step ii) under a protective atmosphere with an organic solvent.

[0050] In such embodiments, the organic solvent used to clean the lithium metal can be the electrolyte solvent used in the battery comprising the lithium metal electrode, to avoid introducing additional solvent components into the battery system. The organic solvent includes but is not limited to various alkyl carbonates, linear or cyclic ethers, etc. The skilled person can select the appropriate organic solvent for cleaning according to the type of electrolyte solvent in the electrolyte solution system of the battery used.

[0051] In some embodiments, the pre-treatment method according to the present application can be applied to various battery systems comprising lithium metal electrodes, including but not limited to lithium metal secondary batteries as well as various electrochemical systems using lithium metal as an electrode, such as test batteries for electrochemical performance evaluation and commercial battery systems employing different positive electrode materials such as lithium iron phosphate, lithium cobaltate, lithium manganate or ternary materials in combination with lithium metal negative electrodes.

[0052] According to a third aspect of the present application, the present application provides a lithium metal electrode, which can be pre-treated using the pre-treatment method according to the present application.

[0053] In some embodiments, the lithium metal electrode according to the present application has enhanced (100) crystal plane orientation. The type and intensity of the crystal plane of the lithium metal electrode can be determined by the position and intensity of the diffraction peak in the X-ray diffraction pattern by the conventional X-ray diffraction (XRD) method in the art.

[0054] The thickness of the lithium metal electrode used in the present application is not particularly limited. For example, the thickness of the lithium metal electrode can be in the range of several micrometers to several tens of millimeters. The person skilled in the art can select according to the specific application requirements, taking into account factors such as battery type, required capacity, working current density or space limitation, etc.

[0055] Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, suitable examples are described below. The examples are to be construed as resolving the technical problems of the present application, so that they are not limited to the explicitly stated combinations of features, but the features exemplified can be combined without limitation.

[0056] Examples The concepts of the present application and the resulting technical effects will be further illustrated below in conjunction with examples, so that those skilled in the art can fully understand the purposes, features and effects of the present application. Those skilled in the art will understand that the examples herein are for illustrative purposes only and are not intended to limit the scope of the present application. If not specifically stated, the raw materials used in the examples are commercially available conventional analytical grade reagents which are used directly without any purification.

[0057] Example 1 Preparation of the pre-treatment composition At room temperature, 1% by volume of water (component (A), 10 uL) was added dropwise into 99% by volume of dimethyl sulfoxide (DMSO) (component (B), 990 uL) relative to the total volume of the pre-treatment composition. Then, the resulting mixture was transferred to a magnetic stirrer for stirring for 5 minutes to obtain a uniformly mixed pre-treatment composition solution.

[0058] Pre-treatment of the lithium metal electrode After obtaining the above-mentioned pretreatment composition, the pretreatment method according to the present application further comprises the following steps in the following order: (1) A commercial lithium metal disc with a diameter of 16 mm and a thickness of 0.15 mm was immersed in the pretreatment composition solution prepared above under the protection of argon at room temperature for 20 minutes to allow the lithium metal to fully contact and react with the pretreatment composition; (2) The pretreated lithium metal was taken out and immersed in dimethyl carbonate (DMC) for 2 minutes to remove the residual pretreatment composition on the surface of the lithium metal under the protection of argon at room temperature, and then taken out and naturally dried to obtain the pretreated lithium metal.

[0059] Example 2 Preparation of the pretreatment composition At room temperature, 10% by volume of water (component (A), 100 uL) was added dropwise into 90% by volume of dimethyl sulfoxide (DMSO) (component (B), 900 uL) with respect to the total volume of the pretreatment composition. Then, the resulting mixture was transferred to a magnetic stirrer for stirring for 5 minutes to obtain a uniformly mixed pretreatment composition solution.

[0060] Pretreatment of the lithium metal electrode After obtaining the above-mentioned pretreatment composition, the pretreatment method according to the present application further comprises the following steps in the following order: (1) A commercial lithium metal disc with the same size as the lithium metal disc used in Example 1 was immersed in the pretreatment composition solution prepared above under the protection of argon at room temperature for 1 minute to allow the lithium metal to fully contact and react with the pretreatment composition; (2) The pretreated lithium metal was taken out and immersed in dimethyl carbonate (DMC) for 2 minutes to remove the residual pretreatment composition on the surface of the lithium metal under the protection of argon at room temperature, and then taken out and naturally dried to obtain the pretreated lithium metal.

[0061] Example 3 Preparation of the pretreatment composition At room temperature, 1% by volume of water (component (A), 10 uL) was added dropwise into 99% by volume of tetrahydrofuran (THF) (component (B), 990 uL) with respect to the total volume of the pretreatment composition. Then, the resulting mixture was transferred to a magnetic stirrer for stirring for 5 minutes to obtain a uniformly mixed pretreatment composition solution.

[0062] Pretreatment of the lithium metal electrode After obtaining the above-mentioned pretreatment composition, the pretreatment method according to the present application further comprises the following steps in the following order: (1) Under the protection of argon gas at room temperature, commercial lithium metal discs with the same size as the lithium metal discs used in Example 1 were immersed in the pretreatment composition solution prepared above for 5 minutes to allow the lithium metal to fully contact and react with the pretreated composition; (2) Under the protection of argon gas at room temperature, the pretreated lithium metal was taken out and immersed in dimethyl carbonate (DMC) for 2 minutes to remove the residual pretreatment composition on the surface of the lithium metal, and then taken out and naturally dried to obtain the pretreated lithium metal.

[0063] Comparative Example 1 Commercial lithium metal discs with the same size as the commercial lithium metal discs used in Examples 1-3 were provided without any pretreatment.

[0064] Characterization of lithium metal electrodes X-ray diffraction Crystal structure analysis was performed on the pretreated lithium metal electrodes prepared according to Examples 1-3 and the untreated lithium metal electrode of Comparative Example 1 by X-ray diffraction (XRD). The crystal plane orientation of the above lithium metal samples was analyzed by observing the position and intensity of the diffraction peaks in the X-ray diffraction pattern. Subsequently, using the same pretreated lithium metal according to Example 1 and the same untreated lithium metal electrode of Comparative Example 1 as the two side electrodes, respectively, symmetrical batteries were assembled under the protection of argon gas at room temperature. The two groups of symmetrical batteries completed were cycled at a current density of 0.5 mA / cm 2 with a capacity of 0.5 mAh / cm 2 for 20 hours. After the cycle was completed, the symmetrical batteries were disassembled and the cycled lithium metal electrodes were taken out under the protection of argon gas at room temperature, washed with DMC and dried, and then the crystal plane orientation of the above lithium metal samples after cycling was observed by XRD.

[0065] Electron microscopy The surface deposition morphology of the pretreated lithium metal electrode according to Example 1 and the untreated lithium metal electrode of Comparative Example 1 was observed by scanning electron microscopy (SEM). Subsequently, using the same each of the above lithium metal as the two side electrodes, symmetrical batteries were assembled under the protection of argon gas at room temperature. The two groups of symmetrical batteries completed were cycled at a current density of 0.5 mA / cm 2 with a capacity of 0.5 mAh / cm 2 for 20 hours. After the cycle was completed, the symmetrical batteries were disassembled and the cycled lithium metal electrodes were taken out under the protection of argon gas at room temperature, washed with DMC and dried, and then the surface deposition morphology of the pretreated lithium metal samples after cycling was observed by SEM.

[0066] Battery performance evaluation including lithium metal electrodes The following performance tests were performed on the lithium metal electrodes pre-treated according to Example 1 and on the untreated lithium metal electrodes of Comparative Example 1.

[0067] Coulombic efficiency test A lithium-copper half-cell was assembled using the above pre-treated and untreated lithium metal as the counter and reference electrodes, respectively, and copper metal as the working electrode, and galvanostatic charge-discharge tests were performed on the lithium-copper half-cell under room temperature and argon-protected environment. An exemplary procedure for the specific test included: (1) discharging at a current density of 0.5 mA cm -2 for 1 h, and measuring the discharge capacity as the lithium deposition capacity (Q p ); (2) charging at a current density of 0.1 mA cm -2 for 1 h, followed by discharging at the same current density for 1 h, and measuring the capacity for each charge / discharge cycle as Q c , repeating the above charge / discharge cycle for n times, and recording the total capacity of charging and discharging (nQ c ); and (3) charging at a current density of 0.1 mA cm -2 to a cut-off voltage of 1.0 V, and measuring the charge capacity as the lithium stripping capacity (Q s ).

[0068] From the above test data, the average value of the coulombic efficiency (CE ave ) of the battery including the pre-treated lithium metal electrode can be calculated based on the following equation: .

[0069] Cycle performance test A lithium-sulfur battery was assembled using a sulfur / carbon (50 mass%:50 mass) composite electrode as the positive electrode, and the above pre-treated and untreated lithium metal as the negative electrode, respectively, and charge-discharge cycling was performed on the lithium-sulfur battery at a rate of 0.5 C and a voltage range of 1.7-2.8 V to evaluate the cycle life of the lithium-sulfur battery under room temperature and argon-protected environment. The test was continued for 100 cycles, and the discharge capacity and coulombic efficiency for each cycle were measured.

[0070] Electrochemical impedance test A symmetric cell was assembled using the same pre-treated lithium metal according to Example 1 and the same untreated lithium metal electrode of Comparative Example 1 as the two electrodes, respectively, and electrochemical impedance spectroscopy (EIS) test was performed on the symmetric cell under room temperature and argon-protected environment. The impedance value of the electrode / electrolyte interface of the battery including the pre-treated lithium metal electrode was determined by analyzing the obtained Nyquist plot.

[0071] Results Figure 1A XRD patterns of lithium metal electrodes obtained according to Example 1 and Comparative Example 1 of the present application are shown. As can be seen from the figure, lithium metal treated with 1% water mixed with 99% DMSO for 20 minutes according to Example 1 exhibited a significant increase in the intensity of the (110) crystal plane diffraction peak compared to the untreated lithium metal of Comparative Example 1, while the intensity of the diffraction peaks of the (211) and (200) crystal planes were significantly reduced to near baseline levels. This indicates that the lithium metal pretreated according to Example 1 has enhanced (110) crystal plane orientation and negligible (211) and (200) crystal plane orientation.

[0072] Figure 1B and Figure 1C XRD patterns of lithium metal electrodes obtained according to Example 2 and 3 and Comparative Example 1 of the present application are shown. As can be seen from the figure, lithium metal pretreated with 10% water mixed with 90% DMSO for 1 minute exhibited a significant decrease in the intensity of the diffraction peaks of the (211) and (200) crystal planes, indicating that even at a shorter pretreatment time, using a higher concentration of water can still effectively regulate the crystal plane orientation of lithium metal. Figure 1B Figure 1C As can be seen from the figure, when treated with 1% water mixed with 99% THF for 5 minutes, the pretreated lithium metal also exhibited a significantly higher intensity of the (110) crystal plane diffraction peak and lower intensity of the (200) and (211) crystal plane diffraction peaks relative to the untreated lithium metal, achieving effective regulation of the crystal plane of lithium metal. Figure 1A and Figure 1B

[0073] Figure 2 XRD patterns of lithium metal electrodes according to Example 1 and Comparative Example 1 of the present application after 20 hours of cycling in symmetric cells are shown. As can be seen from the figure, lithium metal pretreated by the pretreatment method of Example 1 still maintained a clear (110) crystal plane dominant orientation even after cycling in the battery relative to untreated lithium metal, indicating that the dominant crystal plane orientation formed by the pretreatment method of the present application has good electrochemical stability and can continue to play a role during actual battery operation.

[0074] Figure 3A and Figure 3B SEM images of lithium metal electrodes according to Example 1 and Comparative Example 1 of the present application after 20 hours of cycling in symmetric cells are shown. As can be seen from the figure, lithium metal pretreated by the pretreatment method of Example 1 ( Figure 3A ) exhibited a more uniform and smoother surface compared to the untreated lithium metal of Comparative Example 1 ( Figure 3B ​​) exhibited more uniform surface morphology with regular shaped lithium deposits, while Comparative Example 1 showed a large number of irregular dendritic structures. This indicates that the lithium metal after the pretreatment process deposits lithium ions mainly on the lithium (110) crystal plane during battery cycling.

[0075] Figure 4 shows the voltage versus time plots of lithium-copper half-cells including lithium metal electrodes pretreated according to Example 1 and untreated lithium metal electrodes of Comparative Example 1 during constant current charge-discharge tests. From the values of Q Figure 4 determined p , nQ c and Q s , the average coulombic efficiency (CE ave ) of lithium-copper half-cells including lithium metal electrodes pretreated according to Example 1 was calculated to be 92.0%, while the CE ave of lithium-copper half-cells including untreated lithium metal electrodes of Comparative Example 1 was 90.2%. Figure 5 shows the plots of discharge g-capacity and coulombic efficiency versus cycle number of lithium-sulfur batteries of pretreated lithium metal electrodes and untreated lithium metal electrodes of Comparative Example 1. From the values of Q Figure 5 , the average coulombic efficiency of lithium-sulfur batteries of pretreated lithium metal electrodes according to Example 1 and untreated lithium metal electrodes of Comparative Example 1 were 97.2% and 93.7%, respectively, and the cycle number of lithium-sulfur batteries including pretreated lithium metal electrodes was doubled compared to lithium-sulfur batteries including untreated lithium metal electrodes. Figure 4 and Figure 5 The results show that after the surface structure with dominant (110) crystal plane orientation is formed on the lithium metal electrode surface by the pretreatment method according to the present application, the lithium dendrite growth is effectively inhibited, resulting in an improved coulombic efficiency of the battery and an extended cycle life of the battery.

[0076] Figure 6 shows the EIS test results of symmetric batteries including lithium metal electrodes pretreated according to Example 1 and untreated lithium metal electrodes of Comparative Example 1. From the plots, it can be seen that the symmetric battery using lithium metal electrodes of Example 1 exhibits a smaller interfacial impedance compared to the lithium metal electrodes of Comparative Example 1, with a value reduced from 179 Ω to 92 Ω. This indicates that the pretreatment of lithium metal crystal plane can result in the formation of an interfacial structure that is more conducive to lithium ion transport, such as the generation of a dense and high ionic conductivity SEI film, thereby assisting in alleviating the growth of lithium dendrites and extending the service life of lithium metal batteries.

Claims

1. A pretreatment composition for lithium metal electrodes, characterized in that, Include Component (A), which reacts with lithium metal within a predetermined time of contact with lithium metal, said component (A) is selected from water, monohydric alcohols containing 1-6 carbon atoms, carboxylic acids containing 1-6 carbon atoms, primary and secondary amines containing 1-4 carbon atoms, aliphatic thiols containing 1-6 carbon atoms, monocyclic aromatic thiols, and mixtures thereof; and Component (B) does not react substantially with lithium metal during a predetermined period of contact with lithium metal and is miscible with component (A).

2. The pretreatment composition according to claim 1, characterized in that, The scheduled time is 1-60 minutes.

3. The pretreatment composition according to claim 1, characterized in that, The amount of component (A) is from 0.1 vol% to 10 vol% relative to the total volume of the pretreatment composition.

4. The pretreatment composition according to claim 1, characterized in that, The component (B) is selected from dimethyl sulfoxide, acetonitrile, tetrahydrofuran, 1,2-dimethoxyethane, N-methylpyrrolidone, dimethylformamide, and mixtures thereof.

5. A pretreatment method for lithium metal electrodes, characterized in that, Including the steps in the following order: i) By mixing component (A) with component (B) Prepare the pretreatment composition according to any one of claims 1-4; as well as ii) Under a protective atmosphere, lithium metal is contacted with the pretreatment composition for a predetermined time to perform pretreatment.

6. The pretreatment method according to claim 5, characterized in that, The scheduled time is 1-60 minutes.

7. The pretreatment method according to claim 5, characterized in that, Further steps include: iii) Under a protective atmosphere, the lithium metal pretreated in step ii) is cleaned with an organic solvent, wherein the organic solvent is an electrolyte solvent used in batteries comprising lithium metal electrodes.

8. A lithium metal electrode, characterized in that, The lithium metal electrode is pretreated using the pretreatment method according to any one of claims 5-7.

9. The lithium metal electrode according to claim 8, characterized in that, The lithium metal electrode has an enhanced (100) crystal plane orientation.

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