Solid electrolyte interface, preparation method thereof and lithium metal battery

Abstract

The invention relates to a solid electrolyte interface layer, a preparation method thereof and a lithium metal battery. The interface layer comprises a carbon nano tube, gallium-based liquid metal, an oxide of the gallium-based liquid metal, a gallium-based lithium alloy and a compound, wherein the gallium-based lithium alloy and the compound are formed by reaction of lithium metal and the gallium-based liquid metal. A gallium-based liquid metal reacts with a lithium metal to form an interface layer rich in Li2Ga, a Li2Ga (131) crystal face and a Li (110) crystal face have good lattice matching performance, a (110) single crystal lithium metal negative electrode is prepared through induction, the dispersity and the uniformity of the interface layer are improved due to the existence of a carbon nano tube, and the solid electrolyte interface layer reacts with the lithium metal to form a single orientation lithium negative electrode. Compared with other crystal faces, lithium stripping of the crystal face (110) can not change along with change of the number of layers, and the crystal face (110) has the characteristic of layer-by-layer deposition / stripping in the lithium deposition / stripping process. In the battery circulation process, the lithium (110) crystal face can be kept stable, the formation of cavities at the interface of the lithium metal and the solid electrolyte is effectively avoided, and the generation of lithium dendrites is remarkably inhibited, so that the long cycle life and the stability of the solid-state battery are realized.

Description

Technical Field

[0001] The present application relates to the technical field of lithium metal batteries, and in particular to a solid electrolyte interface, a preparation method thereof, and a lithium metal battery. Background Art

[0002] To meet the development requirements of portable electronic products, electric vehicles and renewable energy storage, lithium metal batteries (LMBs) have attracted widespread attention due to their high theoretical capacity and high energy density. However, their matching liquid electrolytes have many disadvantages such as poor electrochemical stability and thermal stability, poor safety, and short cycle life. On the one hand, when lithium dendrites grow, the negative electrode continuously exposes fresh surfaces and reacts with the electrolyte, irreversibly generating new SEI films, which reduces the coulombic efficiency and cycle stability of the battery. On the other hand, lithium dendrites formed by uneven deposition of metallic lithium may pierce the separator, causing internal short circuits and releasing a large amount of heat. In contrast, inorganic solid electrolytes (ISEs) have the intrinsic advantages of excellent mechanical properties, good safety, and a wide electrochemical window, and are considered to be one of the most promising electrolyte material systems.

[0003] However, lithium dendrites formed by the degradation of the interface between Li and ISE seriously hinder the practical application of solid-state lithium metal batteries. The main reason is that during long-term cycling, the interface degradation of the negative electrode / electrolyte forms voids, generating local large currents that lead to the nucleation of lithium dendrites. Commonly used lithium metal is polycrystalline, with an anisotropic structure of polycrystalline faces and completely different properties in different directions, which greatly affects the growth of lithium dendrites in lithium metal batteries. Specifically, the energy required for Li atoms to deposit / strip from different crystal planes varies greatly, resulting in the polycrystalline lithium metal negative electrode easily forming voids and dendrites during battery cycling, leading to battery failure.

[0004] It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0005] The main purpose of the present application is to overcome the defects of the above-mentioned background technology and provide a solid electrolyte interface, a preparation method thereof and a lithium metal battery.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] A solid electrolyte interface, comprising carbon nanotubes, gallium-based liquid metal and its oxide, and alloys and compounds formed by the reaction of lithium metal and gallium-based liquid metal, wherein the gallium-based lithium alloy acts as a template to induce lithium metal to crystallize along the Li (110) crystal plane to form a lithium metal negative electrode with a single orientation of the Li (110) crystal plane. 2 The (131) crystal plane of Ga has good lattice compatibility with the (110) crystal plane of Li. 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) has good contact.

[0008] Further:

[0009] In some optional embodiments, the gallium-based liquid metal includes gallium, and preferably also includes at least one of indium or tin, and more preferably includes: 70-75at.% Ga, 15-20at.% In, 5-10at.% Sn.

[0010] In some optional embodiments, the carbon nanotubes include carbon nanotubes doped with a nitrogen content of 3 wt.% or pure carbon nanotubes.

[0011] In some optional embodiments, the mass ratio of the gallium-based liquid metal to the carbon nanotubes is (19-32):1.

[0012] The present application also provides a method for preparing a solid electrolyte interface, the preparation method comprising:

[0013] Mixing gallium-based liquid metal and carbon nanotubes to obtain a mixed liquid;

[0014] The mixed liquid is evenly coated on the solid electrolyte LLZTO to obtain a solid electrolyte containing a liquid metal interface;

[0015] In a nitrogen atmosphere, a lithium metal sheet is brought into contact with the solid electrolyte containing a liquid metal interface, and the solid electrolyte interface is obtained through a heat treatment process.

[0016] In some optional embodiments, the heat treatment process includes heating at 280-320° C. for 2-5 min, naturally cooling to room temperature, and naturally cooling to room temperature.

[0017] In some optional embodiments, the gallium-based liquid metal includes at least one of gallium, indium or tin, preferably including: 70-75 at.% Ga, 15-20 at.% In, 5-10 at.% Sn.

[0018] In some optional embodiments, the mass ratio of the gallium-based liquid metal to the carbon nanotubes is (19-32):1.

[0019] The present application also provides a lithium metal battery, comprising a solid electrolyte, wherein the solid electrolyte has the solid electrolyte interface.

[0020] This application has the following beneficial effects:

[0021] The solid electrolyte interface provided by the present application includes gallium-based liquid metal and its oxide and carbon nanotubes, and alloys and compounds formed by the reaction of lithium metal and gallium-based liquid metal. Gallium-based liquid metal and its oxide and lithium metal react fully at high temperature to form a Li-rich 2 Ga interfacial layer, Li 2 The Ga (131) crystal plane has a good lattice match with the Li (110) crystal plane, thereby inducing lithium to recrystallize along the (110) plane to form an oriented metal negative electrode. During the long cycle process, the Li (110) crystal plane structure is stable and realizes layer-by-layer lithium deposition / stripping, thereby avoiding the formation of voids and inhibiting the generation of lithium dendrites at the interface. At the same time, the carbon nanotubes provided in the present application are evenly dispersed in the interface as a framework, which can improve the dispersibility and uniformity of the interface layer and achieve excellent contact between the interface layer and the electrolyte. The solid electrolyte interface layer provided in the present application and the single crystal lithium metal negative electrode formed by its reaction with lithium can improve the cycle life and stability of the all-solid-state lithium metal battery.

[0022] Other beneficial effects of the embodiments of the present application will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 In the figure, (a) is a scanning electron micrograph of the LLZTO-GC surface, and (b) is a scanning electron micrograph of the LLZTO-GC cross section.

[0024] Figure 2 In the figure, (a) is a scanning electron microscope cross-section of LLZTO-GC, and (b) and (c) are X-ray photoelectron spectroscopy analyses of the top and bottom interfaces.

[0025] Figure 3 In the figure, (a) is the scanning electron microscope cross-sectional image of LLZTO-GC|Li, and (b) is the corresponding X-ray photoelectron spectroscopy analysis of LLZTO-GC|Li on the top and bottom layers.

[0026] Figure 4 (a) 2D-X-ray diffraction pattern of the texture of the original Li foil, and (b) 2D-X-ray diffraction pattern of Li-LLZTO prepared by recrystallization of lithium metal melted at 300°C on LLZTO.

[0027] Figure 5 In the figure, (a) is the 2D-X-ray diffraction pattern of LLZTO-GC|Li and the corresponding 1D-X-ray diffraction pattern, and (b) is the 2D-X-ray diffraction pattern of LLZTO-GC|Li without carbon nanotubes.

[0028] Figure 6 In the figure, (a) is the stress-strain curve of Li|LLZTO|Li, and (b) is the stress-strain curve of Li|G-LLZTO-G|Li and Li|GC-LLZTO-GC|Li.

[0029] Figure 7 (a) is the Li|GC-LLZTO-GC|Li and Li|G-LLZTO-G|Li at 0.1 mA cm -2 (a) 2D-X-ray diffraction pattern of LLZTO-GC|Li after 2400 h of cycling.

[0030] Figure 8 In the figure, (a) is Li(110) and Li 2 Atomic arrangement of Ga(131) crystal plane; (b) Li 2 Schematic diagram of the lattice matching between Ga(131) and Li(110).

[0031] Fig. 9 Li metal in Li 2 Simulation of melting / crystallization process on Ga(131) crystal plane.

[0032] Fig.10 Li|GC-LLZTO-GC|Li (a) and Li|LLZTO-GC|Li (b) batteries at 0.1 mA cm -2 In situ 1D-X-ray diffraction patterns after electroplating and stripping for 10 h.

[0033] Fig.11 In the figure, (a) is the stripping energy of different lithium crystal planes, (b) and (c) are schematic diagrams of lithium stripping behavior of (110) and (211) crystal planes.

[0034] Fig.12 It's Li 2 Calculation of surface energy of the main crystal planes of Ga.

[0035] Fig.13 LLZTO-GC|Li at 0.5mAcm -2 Scanning electron microscope cross-sectional images after different cycle numbers.

[0036] Fig.14 The positive electrode mass loading is 2 mg cm-2 , with a surface capacity of 0.34 mAh cm -2 The rate performance of the batteries of Example 1 and Comparative Example 2.

[0037] Fig.15 This is a cycle performance test chart of the lithium metal battery assembled in Example 1 at 25°C and 1C rate after 3000 cycles.

[0038] Fig.16 This is a cycle performance test chart of the lithium metal battery assembled in Example 1 at 25°C and 2C rate after 3000 cycles. DETAILED DESCRIPTION

[0039] The following is a detailed description of the implementation of the present application. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present application.

[0040] The present invention provides a method for preparing a solid electrolyte interface, and the method comprises the following steps:

[0041] S1. The gallium-based liquid metal and the carbon nanotubes are mixed in a vortex oscillator to obtain a mixed liquid; in the air, the mixed liquid is evenly scraped on the solid electrolyte LLZTO to obtain a solid electrolyte containing a liquid metal interface;

[0042] In some embodiments, the gallium-based liquid metal includes at least one of gallium, indium or tin.

[0043] In some embodiments, the mass ratio of the gallium-based liquid metal to the carbon nanotubes is (19-32):1.

[0044] In this step, the gallium-based liquid metal and the carbon nanotubes are oscillated and mixed for 10-20 minutes, so that the carbon nanotubes are completely and evenly dispersed in the gallium-based liquid metal to form a uniform mixed liquid.

[0045] S2. Under a nitrogen atmosphere, the solid electrolyte containing a liquid metal interface is placed on a heating plate, and the lithium metal sheet is placed on the solid electrolyte, heated at 300° C. for 2 min, and naturally cooled to room temperature.

[0046] In some embodiments, the lithium metal sheet is cut using a blade to remove an oxide layer on the surface of the lithium metal.

[0047] In this step, a gallium-based liquid metal interface is introduced between the solid electrolyte and the lithium metal. Compared with the system where the lithium metal and the electrolyte are in direct contact, the introduction of the interface can regulate the subsequent crystal morphology of the lithium metal, thereby obtaining a lithium metal negative electrode with different crystal orientations. The gallium element and its oxide rich in the interface component react with lithium to form Li 2 Ga and LiGaO2 , Li 2 The (131) crystal plane of Ga has a very low lattice mismatch with the (110) crystal plane of Li. Therefore, during the cooling and crystallization of lithium metal, Li 2 Ga can act as a template to induce lithium metal to crystallize along the (110) direction, ultimately forming a lithium metal negative electrode with a single (110) orientation. The (110)-oriented lithium crystal plane has a very stable structure and produces a layer-by-layer peeling / deposition behavior along the (110) surface, thereby fundamentally avoiding the generation of voids caused by uneven lithium peeling / deposition, thereby inhibiting the formation of lithium dendrites at the interface, and ultimately improving the long-cycle performance of all-solid-state lithium metal batteries.

[0048] In order to further study the mechanism of action of the solid electrolyte interface in this application, this application conducted a scanning electron microscope test on the interface layer (GC) coated with a mixture of gallium-based liquid metal and carbon nanotubes. Figure 1 , (a) is the surface scanning electron microscope image of the GC layer, and (b) is the cross-sectional image of the GC layer.

[0049] (a) shows that the GC layer has good dispersion and the resulting interface is smooth and flat. (b) shows that the thickness of the GC interface layer is about 3 μm and has a clear layered structure.

[0050] In order to further analyze the phase in the interface, X-ray photoelectron spectroscopy (XPS) tests were performed on the upper and lower surfaces of the interface. Figure 2 (a) and (c), a Ga-containing layer is formed at the bottom of the GC layer. 2 O 3 、In 2 O 3 and SnO 2 Based on this phenomenon, the present invention melts the Li sheet and GC layer on LLZTO at 300°C to form an interface, and performs XPS tests on the Li|GC layer at different positions to determine its composition. Figure 3 , Ga 2p near the Li|GC layer of LLZTO 3 / 2 The spectrum detected two peaks at 1117.5 and 1116.2 eV, which belong to LiGaO 2 and Li 2 Ga. The Ga in the Li|GC layer near lithium metal is converted to Li 2 Ga alloy.

[0051] In order to further analyze the crystal orientation of lithium metal under different conditions, the present invention conducted 2D-X-ray diffraction (XRD) analysis on the crystal orientation of original lithium foil and after melting lithium on different substrates (gallium-based liquid metal and carbon nanotube-modified LLZTO (LLZTO-GC) and gallium-based and carbon nanotube-modified LLZTO (labeled as LLZTO-Ga)). Figure 4 (a), the original lithium foil shows the <110> , <200> , <211> and <220> A typical polycrystal composed of multiple crystal orientations. Figure 4 As shown in (b), the recrystallized Li on pure LLZTO tends to form random orientations due to the lack of interfacial reaction. Therefore, although lithium metal has a body-centered cubic structure, the (110) plane, as the plane with the lowest energy and the most dense arrangement, does not form preferentially as expected.

[0052] Depend on Figure 5 As shown in (a), the melted and crystallized lithium metal on LLZTO-GC has only one strong Li <110> orientation, i.e., the crystal orientation of Li is changed by the GC layer during the melting / recrystallization process. Figure 5 In sharp contrast to (b), the inhomogeneous interfacial layer in LLZTO-G does not have this property. Therefore, the GC layer with a uniform and smooth surface and its low lattice mismatch with Li(110) are crucial for the precise regulation of the Li metal crystal orientation.

[0053] This application also conducted interface mechanical strength tests on LLZTO|Li, LLZTO-G|Li and LLZTO-GC|Li. Figure 6 Under the same conditions, the interfacial adhesion of LLZTO|Li and LLZTO-G|Li is 6N and 393N respectively, while the interfacial adhesion of LLZTO-GC|Li is increased to 863N. This also shows that Li <110> Orientation has smaller yield strength and elastic modulus, which improves the mechanical strength of the interface.

[0054] The Li|GC-LLZTO-GC|Li battery was further tested at a current density of 0.1 mA cm -2 , area capacity is 1 mAh cm -2 The effect of lithium crystal orientation on its cycling stability was investigated. Figure 7 (a), Li|GC-LLZTO-GC|Li battery has excellent cycling stability, and there is no short circuit even after 2400h cycling. Its stripping / deposition overpotential remains at around 5mV. 2D-XRD characterization of the crystal orientation of LLZTO-GC|Li after cycling, Figure 7(b) shows that even after 2400 h of cycling, Li <110> The orientation was well maintained.

[0055] Based on this, this application compares Li 2 Crystal structures of Ga and Li. Figure 8 It can be seen that Li 2 The atomic arrangement of the Ga(131) crystal plane is very similar to that of the Li(110) plane. 2 The lattice mismatch between Ga(131) and Li(110) is 8.9%, which is much lower than the 15% required for epitaxial growth. 2 Ga(131) and Li(110) can form a semi-coherent interface to induce Li epitaxial growth.

[0056] This application simulates the Li metal in Li 2 Melting / crystallization processes on Ga(131). Fig. 9 As the temperature decreases, the arrangement of Li atoms gradually changes from amorphous to ordered crystals. This indicates that Li 2 Ga(131) acts as a template to allow the molten Li to form a <110> Direction recrystallization.

[0057] In order to investigate whether Li with (110) orientation is <110> Directional deposition / stripping, this application conducted in-situ XRD testing. Specifically, Li|GC-LLZTO-GC|Li and Li|LLZTO-GC|Li batteries were assembled at 0.1 mA cm -2 Charge and discharge for 10 hours at a current density of Fig.10 (a) In the Li|GC-LLZTO-GC|Li battery, only the intensity of the Li(110) peak changes during the electroplating / stripping process, and no other diffraction peaks appear. Fig.10 (b) shows that since the Li metal of the Li|LLZTO-GC|Li battery is multi-oriented, its electroplating / stripping process occurs simultaneously on multiple planes (110), (200), and (211). Therefore, it can be concluded that in randomly oriented Li metal, the deposition / stripping of Li(110) with the lowest thermodynamic energy does not proceed atomically layer by atomic layer as expected.

[0058] In order to study the intrinsic mechanism of lithium metal deposition, this application also calculated the thermodynamic properties of Li stripping from several common Li crystal planes through molecular dynamics simulation. Fig.11(a) For the (110) and (100) planes, the stripping energy of Li atoms is relatively high at the beginning of stripping, and the stripping energy gradually decreases as the number of stripped atoms increases. In contrast, the stripping energy of the (211) and (111) planes remains almost unchanged. Fig.11 (b), for the (110) surface, since the peeling energy of the remaining surface atoms that have not been peeled off is lower than that of the new layer, the remaining surface Li atoms are peeled off first, and the entire interface remains peeled layer by layer. For the Li (211) surface, Fig.11 (c), due to the similar stripping energy, the inner layer Li atoms and the surface layer Li atoms are stripped at the same time, which gradually leads to the formation of voids. Therefore, for polycrystalline Li with (110) and (211) planes parallel to the surface, Li atoms tend to strip from (211) due to the low initial stripping energy, forming voids, resulting in an uneven interface and poor contact with the interface. This uneven surface further leads to an uneven distribution of the local electric field, causing lithium ions to preferentially deposit on the "Li tip" with a higher charge density in the next cycle, thereby generating Li dendrites.

[0059] In some embodiments, the mass ratio of the gallium-based liquid metal to the carbon nanotubes is (19-32):1, such as 19:1, 22:1, 25:1, 28:1, and 32:1. If the mass ratio is greater than 32:1, the carbon nanotubes have an insignificant bridging effect on the solid electrolyte interface; if the molar ratio is less than 19:1, the carbon nanotube content is too high, and the carbon nanotubes will cover the gallium-based liquid metal, resulting in the inability to wet the solid electrolyte, thereby failing to form a uniform and smooth interface.

[0060] In some embodiments, the gallium-based liquid metal in the solid electrolyte interface includes at least one of gallium, indium or tin. Adding indium and tin to the liquid metal can further improve the wettability of the GC layer to LLZTO, ensure that the interface is as thin as possible while remaining uniform, and improve the cycle stability of the electrolyte.

[0061] The present invention provides a solid electrolyte interface, including carbon nanotubes, gallium-based liquid metal and its oxide, and alloys and compounds formed by the reaction of lithium metal and gallium-based liquid metal. 2 The (131) crystal plane of Ga has good lattice compatibility with the (110) crystal plane of Li. 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) has good contact.

[0062] In an embodiment, the gallium-based liquid metal reacts with lithium metal to form a Li-rich 2 Ga interfacial layer, Li 2 The Ga(131) crystal plane has good lattice matching with the Li(110) crystal plane, inducing the preparation of a (110) single crystal lithium metal negative electrode. The presence of carbon nanotubes improves the dispersion and uniformity of the interface layer. The solid electrolyte interface layer provided in the present application reacts with lithium metal to form a single-oriented lithium negative electrode. Compared with other crystal planes, the lithium stripping energy of the (110) crystal plane does not change with the number of layers, and has the characteristics of layer-by-layer deposition / stripping during the lithium deposition / stripping process. During the battery cycle, the lithium (110) crystal plane can maintain stability, effectively avoiding the formation of voids at the interface between lithium metal and the solid electrolyte, and significantly inhibiting the generation of lithium dendrites, thereby achieving a long cycle life and stability of the solid-state battery.

[0063] In the above solid electrolyte interface, gallium-based liquid metal and its oxide react fully with lithium metal at high temperature. Li 2 Ga prepared lithium metal anode with preferred orientation, Li 2 Ga(131) and Li(110) have good lattice matching, thereby inducing lithium to form an oriented metal negative electrode along the (110) plane. During the long cycle process, due to the layer-by-layer peeling / deposition characteristics of Li, the Li(110) crystal plane has a very stable structure, which can avoid the formation of voids and ultimately inhibit the generation of lithium dendrites at the interface. At the same time, the carbon nanotubes provided in the present application are evenly dispersed in the interface as a framework, which can improve the dispersibility and uniformity of the interface layer and achieve excellent contact between the interface layer and the electrolyte. Finally, the lithium metal negative electrode with a single (110) orientation formed by the reaction of the solid electrolyte interface layer provided in the present application with lithium can be well maintained during the long cycle process, which can improve the cycle life of the all-solid-state lithium metal battery during operation.

[0064] The present application also provides a lithium metal battery, comprising the solid electrolyte interface, a solid electrolyte, a lithium metal negative electrode and a positive electrode sheet, wherein the solid electrolyte is disposed between the lithium metal negative electrode and the positive electrode sheet. The active material in the positive electrode sheet is lithium iron phosphate.

[0065] The scheme of the present invention will be explained below in conjunction with the embodiments. Those skilled in the art will understand that the following examples are only used to explain the present invention and cannot be understood as limiting the present invention. Unless otherwise stated, the reagents, software and instruments not specifically stated in the following embodiments are all conventional commercial products or open source.

[0066] Example 1

[0067] This implementation is based on Li 6.4 La3 Zr 1.4 Ta 0.6 O 12 Taking the preparation method of (LLZTO) as an example, the preparation method comprises:

[0068] (1) 1.1 g of LLZTO powder was placed in a graphite mold with a diameter of 10 mm and assembled into a spark plasma sintering furnace (SPS). The sintering pressure was set to 50 MPa at 1100 °C.

[0069] Sinter for 10 min to obtain a sintered ceramic sheet.

[0070] (2) The ceramic sheet obtained in step (1) was polished with 180, 600, 2000, and 5000 mesh sandpaper to form a smooth ceramic sheet with a thickness of 500 μm.

[0071] A method for preparing a solid electrolyte interface and a lithium metal battery, comprising:

[0072] Step 1: First, weigh 100 mg of PVDF (binder) and place it in a stirring bottle, add 1 mL of NMP (N-methylpyrrolidone), and stir on a small stirrer for 1 hour until PVDF is completely dissolved. Then add 100 mg of Super P (conductive carbon black) and 1 mL of NMP, stir at room temperature for 1 hour, and add 800 mg of LiFePO4 active material and 1.5 mL of NMP, stir at room temperature for more than 6 hours to obtain a positive electrode slurry.

[0073] Step 2: coat the positive electrode slurry obtained in step 1 on aluminum foil, dry it at 80° C. for more than 6 hours, cut it into a suitable size to obtain an LFP positive electrode sheet, and place it in a vacuum oven for drying and storage.

[0074] Step 3: weigh 0.4 g of LiTFSI, place it in a stirring bottle, and heat it at 110°C for 30 min; weigh 2 g of succinonitrile (SN), place it in another stirring bottle, mix the heated LiTFSI with it, and heat it at 70°C for 30 min to obtain a succinonitrile electrolyte.

[0075] Step 4, weigh 100 mg of gallium-based liquid metal (Ga: 72.16 At%, In: 18.59 At%, Sn: 9.25 At%), put it in a stirring bottle, add 5 mg of carbon nanotubes doped with a nitrogen content of 3 wt.%, mix on a vortex oscillator, and oscillate for more than 10 minutes to obtain a mixed liquid.

[0076] Step 5, in the air, evenly scrape the mixed liquid obtained in step 4 on the solid electrolyte LLZTO to obtain a solid electrolyte containing a liquid metal interface (abbreviated as LLZTO-GC);.

[0077] Step 6: In an inert gas atmosphere, use a knife to remove the oxide layer on the surface of the lithium metal block, and then roll it into a sheet with a thickness of 300 μm. Then use a punch with a diameter of 8 mm to cut it into round lithium sheets.

[0078] Step seven, under an inert gas atmosphere, stack the circular lithium sheet obtained in step six and the LLZTO-GC obtained in step five, place them on a heating table, keep them at 300° C. for 2 minutes, and then naturally cool them to room temperature to obtain a solid electrolyte after melting lithium.

[0079] Step eight, drip 5 μl of succinonitrile electrolyte on the positive electrode side of the solid electrolyte after melting lithium obtained in step seven, and then assemble it with the LFP positive electrode sheet obtained in step two to obtain a lithium metal button battery.

[0080] Comparative Example 1

[0081] The difference between Comparative Example 1 and Example 1 is that the gallium-based liquid metal and carbon nanotubes are replaced by Cu, and the remaining steps are the same as Example 1. Comparative Example 1 replaces the interface between the liquid metal and the carbon nanotubes with the Cu interface, and successfully induces the growth of Li metal along the (211) on the Cu interface, and further proves that the battery performance and interface stability of Li (211) are not as good as the battery performance and interface stability of the Li (110) assembled under the interface of the liquid metal and the carbon nanotubes.

[0082] Comparative Example 2

[0083] The difference between Comparative Example 2 and Example 1 is that there is only gallium-based liquid metal in the interface, and the remaining steps are the same as those of Example 1.

[0084] Comparative Example 3

[0085] The difference between Comparative Example 3 and Example 1 is that the gallium-based liquid metal contains only gallium metal, and the remaining steps are the same as Example 1. In Comparative Example 3, the liquid metal composition only retains Ga, without In and Sn, and the battery performance, interface contact, and ability to induce lithium metal to grow along (110) when the interface does not contain In and Sn are mainly compared. The results show that the presence of In and Sn enhances the wettability of the liquid metal interface, makes the interface and the electrolyte contact good, and perfectly induces the growth of lithium metal along the (110) surface.

[0086] The present application also provides a method for the Li formed at the interface in Example 1. 2 The surface energies of different Ga crystal planes were calculated. Fig.12 , Li 2 The Ga(131) plane has the lowest surface energy and can therefore be preferentially formed on the top of the GC layer when reacting with Li, thereby inducing the crystalline growth of Li metal.

[0087] The present application also conducted scanning electron microscopy tests on the prepared solid electrolyte interface before and after cycling. Fig.13 , (a) is the Li|GC-LLZTO-GC|Li battery at 0.5 mA cm -2 The initial scanning electron microscopy cross-section image of the device after cycling for 0.5 h at a current density of , (b) and (c) are cross-section electron microscopy images after the 20th and 60th cycles. Fig.13 It can be seen that the solid electrolyte interface and lithium metal can maintain close contact during long-term cycling.

[0088] The present application also conducts rate performance tests on the lithium metal batteries assembled in Example 1 and Comparative Example 2. Fig.14 , Fig.14 The figure is a rate performance test graph of the lithium metal battery assembled in Example 1 and Comparative Example 2 at room temperature, and cycled 5 times at 0.1C, 0.2C, 0.5C, 1C, 3C, and 5C respectively, and finally returned to the 1C rate cycle. Under the same conditions, the lithium metal battery assembled with the solid electrolyte prepared in Example 1 can provide 120 mAhg at 5C. -1 The discharge capacity is 154 mAh g when the rate returns to 1C. -1 The capacity of the lithium metal battery assembled with solid electrolyte without carbon nanotubes added to the interface is almost 0 at 5C. When the rate returns to 1C, the battery immediately overcharges due to short circuit. This is because the growth of lithium dendrites causes destructive damage to LLZTO, forming cracks and eventually causing the battery to short circuit.

[0089] The present application also conducts a cycle performance test on the lithium metal battery assembled in Example 1. Fig.15 , Fig.15 This is a cycle performance test chart of the lithium metal battery assembled in Example 1 at room temperature and 1C rate after 3000 cycles. The lithium metal battery assembled with the solid electrolyte prepared in Example 1 can stably cycle 3000 cycles with a capacity retention rate of 83%.

[0090] See also Fig.16 , Fig.16 This is a cycle performance test chart of the lithium metal battery assembled in Example 1 at room temperature and 3C rate after 10,000 cycles. The lithium metal battery assembled with the solid electrolyte prepared in Example 1 can stably cycle 10,000 cycles with a capacity retention rate of 62%, and the capacity retention rate after 6,000 cycles is 92%.

[0091] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A solid electrolyte interface, characterized in that The invention comprises carbon nanotubes, gallium-based liquid metal and its oxide, and gallium-based lithium alloy and compound formed by the reaction of lithium metal and gallium-based liquid metal. The gallium-based lithium alloy acts as a template to induce lithium metal to crystallize along the Li (110) crystal plane to form a lithium metal negative electrode with a single orientation of the Li (110) crystal plane.

2. The solid electrolyte interface according to claim 1, characterized in that The gallium-based liquid metal includes gallium, and preferably also includes at least one of indium or tin, and more preferably includes: 70-75 at.% Ga, 15-20 at.% In, and 5-10 at.% Sn.

3. The solid electrolyte interface according to claim 1, characterized in that The carbon nanotubes include carbon nanotubes doped with 3 wt.% nitrogen or pure carbon nanotubes.

4. The solid electrolyte interface according to any one of claims 1 to 3, characterized in that The mass ratio of the gallium-based liquid metal to the carbon nanotubes is (19-32):

1.

5. A method for preparing a solid electrolyte interface, characterized in that: include: Mixing gallium-based liquid metal and carbon nanotubes to obtain a mixed liquid; The mixed liquid is evenly coated on the solid electrolyte LLZTO to obtain a solid electrolyte containing a liquid metal interface; In a nitrogen atmosphere, a lithium metal sheet is brought into contact with the solid electrolyte containing a liquid metal interface, and the solid electrolyte interface is obtained through a heat treatment process.

6. The method for preparing a solid electrolyte interface according to claim 5, characterized in that: The heat treatment process includes heating at 280-320° C. for 2-5 minutes and naturally cooling to room temperature.

7. The method for preparing a solid electrolyte interface according to claim 5, characterized in that: The gallium-based liquid metal includes at least one of gallium, indium or tin, and preferably includes: 70-75 at.% Ga, 15-20 at.% In, and 5-10 at.% Sn.

8. The method for preparing a solid electrolyte interface according to claim 5, characterized in that: The carbon nanotubes include carbon nanotubes doped with 3 wt.% nitrogen or pure carbon nanotubes.

9. The method for preparing a solid electrolyte interface according to claim 5, characterized in that: The lithium metal sheet is prepared by using a blade to remove the oxide layer on the surface of the lithium metal.

10. A lithium metal battery, characterized in that: The invention comprises a solid electrolyte having a solid electrolyte interface as claimed in any one of claims 1 to 4.

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