Interface modification layer, interface modification solid-state electrolyte and preparation method thereof

Abstract

The application provides an interface modification layer, an interface modification solid-state electrolyte and a preparation method thereof, and belongs to the technical field of solid-state electrolytes.The interface modification layer is a Li-M-C eutectic composite interface layer; wherein M is Mg, In, Sn or Al.The interface modification layer provided by the application can effectively improve the interface contact problem of a lithium negative electrode and a solid-state electrolyte, inhibit the formation of lithium dendrites, and prolong the cycle life of a battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state electrolyte, and particularly relates to an interface modification layer, an interface modified solid-state electrolyte and a preparation method thereof. BACKGROUND

[0002] In recent years, with the wide application of lithium ion batteries in electric vehicles, higher requirements are put forward for the energy density of lithium ion batteries, and the traditional graphite (the theoretical specific capacity of the negative electrode is 370 mAh / g) has been unable to meet the demand of practical application; lithium metal has a high theoretical specific capacity (3860 mAh / g) and a low electrochemical potential (3.04 V relative to the standard hydrogen electrode), and is suitable for replacing the widely used graphite negative electrode; however, in the process of practical application, there are problems such as the formation of lithium dendrites and the reaction with electrolyte, which exist great safety hazards.

[0003] The excellent mechanical properties of the solid-state electrolyte can protect the battery from being pierced by lithium dendrites, which provides the possibility for the application of lithium metal in solid-state batteries; especially the garnet solid-state electrolyte (such as Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ) has high lithium ion conductivity at room temperature, good air stability, and stability to metal lithium negative electrode, and is expected to be applied as a solid-state electrolyte in a full solid-state lithium battery. However, since the solid-state electrolyte and the lithium metal are in solid-solid contact, the interface contact between them is not good, and the interface impedance is large, especially after a plurality of charging and discharging, the "peeling and deposition" of the metal lithium itself will cause a large volume change, which will further deteriorate the interface contact between lithium and the solid-state electrolyte, so that the rate performance and the cycle performance of the solid-state lithium battery are sharply attenuated; therefore, the solid-state electrolyte needs to be interface modified to reduce the interface impedance.

[0004] Chinese patent CN109786675A discloses an interface modification method for a solid-state lithium battery metal lithium negative electrode, which needs to use a magnetron sputtering method to deposit a layer of LiPON film on the surface of the solid-state electrolyte, and the lithium symmetric battery cannot be stably cycled. In addition, the interface impedance between the existing interface modified solid-state electrolyte and the lithium metal is large, and the interface impedance at room temperature is generally greater than 60 Ω, the limiting current density of the lithium symmetric battery at room temperature is low, and is generally less than 0.4 mA / cm 2 , and the cycle performance of the lithium symmetric battery at room temperature is poor.

[0005] Therefore, it is urgent to provide an interface modification layer which can reduce the interface impedance between the solid-state electrolyte and the lithium metal and improve the cycle performance of the lithium symmetric battery. SUMMARY

[0006] In view of one or more technical problems in the prior art, the application provides an interface modification layer, an interface modification solid-state electrolyte and a preparation method thereof.The interface modification layer can effectively improve the interface contact problem of a lithium negative electrode and a solid-state electrolyte, inhibit the formation of lithium dendrites, and prolong the cycle life of a battery.

[0007] The application provides an interface modification layer in a first aspect, and the interface modification layer is a Li-M-C eutectic composite interface layer; wherein M is Mg, In, Sn or Al.

[0008] Preferably, in the Li-M-C eutectic composite interface layer, the content of Li is 5-20 wt%, the content of M is 50-80 wt%, and the content of C is 15-30 wt%; preferably, the content of Li is 9-15 wt%, the content of M is 55-73 wt%, and the content of C is 18-30 wt%.

[0009] Preferably, the thickness of the Li-M-C eutectic composite interface layer is 280-1000 nm.

[0010] The application provides a preparation method of the interface modification layer in the first aspect in a second aspect, and the preparation method comprises the following steps:

[0011] S1. forming a passivation layer containing lithium carbonate on the surface of a substrate to obtain a first modified substrate;

[0012] S2. forming a salt interface layer on the surface of the passivation layer to obtain a second modified substrate; the salt interface layer is an inorganic salt layer of M;

[0013] S3. forming a carbon black layer on the surface of the salt interface layer to obtain a third modified substrate;

[0014] S4. annealing the third modified substrate to form the interface modification layer on the surface of the substrate.

[0015] Preferably, in step S1, the substrate is placed in air for 24-120 h to form the passivation layer containing lithium carbonate on the surface of the substrate; wherein the substrate is a garnet-type solid-state electrolyte.

[0016] Preferably, the thickness of the passivation layer is 100-300 nm.

[0017] Preferably, in step S2, the first modified substrate is soaked in an inorganic salt solution of M in an inert gas atmosphere for 0.5-5 min to form the salt interface layer on the surface of the passivation layer.

[0018] Preferably, the thickness of the salt interface layer is 100-500 nm.

[0019] Preferably, the inorganic salt solution of M is obtained by dissolving an inorganic salt of M in an organic solvent; the concentration of the inorganic salt solution of M is 0.05-0.2 mol / L.

[0020] Preferably, the inorganic salt of M is one of indium chloride, aluminum nitrate, stannous chloride, and magnesium perchlorate, and preferably is indium chloride.

[0021] The organic solvent is one of acetonitrile, anisole, chloroform, dichloroethane, N,N-dimethylformamide, and isopropanol, and preferably is isopropanol.

[0022] Preferably, in step S3, the second modified substrate is burned at the outer flame of a candle for 9-30 s to form the carbon black layer on the surface of the salt interface layer; preferably, the burning is performed in 3-5 times, and the time of single burning is 3-6 s.

[0023] More preferably, the thickness of the carbon black layer is 100-600 nm.

[0024] Preferably, in step S4, the annealing treatment is performed in an inert gas atmosphere, the temperature of the annealing treatment is 500-700 ℃, and the time of the annealing treatment is 2-4 h.

[0025] In a third aspect, the application provides an interface-modified solid-state electrolyte, comprising the interface-modified layer of the first aspect; the interface-modified layer covers the surface of the solid-state electrolyte.

[0026] Preferably, the solid-state electrolyte is a garnet-type solid-state electrolyte; preferably, the garnet-type solid-state electrolyte is Li 6.4 La3Zr 1.4 Ta 0.6 O 12 solid-state electrolyte.

[0027] Compared with the prior art, the application has at least the following beneficial effects:

[0028] The interface-modified layer (Li-M-C eutectic composite interface layer) of the application can effectively improve the interface contact problem of the lithium negative electrode and the solid-state electrolyte, inhibit the formation of lithium dendrites, and prolong the cycle life of the battery; in addition, the Li-M-C eutectic composite interface layer can also ensure the stability of the solid-state electrolyte, and reduce the subsequent complex process treatment; the solid-state electrolyte comprising the interface-modified layer is assembled into a button cell, the interface impedance of which is <30 Ω at 25 ℃, and the button cell can be stably cycled for more than 600 h at a current density of 0.4 mA / cm 2 . BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to make the technical solutions of the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0030] Figure 1 is a schematic diagram of the interface modified solid-state electrolyte before and after annealing treatment provided by the embodiments of the present application;

[0031] Figure 2 is an EDS spectrum of the interface modified solid-state electrolyte provided by embodiment 1 of the present application;

[0032] Figure 3 is an impedance diagram of the interface modified solid-state electrolyte provided by embodiment 1 of the present application before and after exposure in air for 0h and 360h;

[0033] Figure 4 is a limiting current density test diagram of the lithium symmetric battery assembled by embodiment 1 of the present application at 25℃;

[0034] Figure 5 is an impedance spectrum of the lithium symmetric battery assembled by embodiments 1-5 at 25℃;

[0035] Figure 6 is an impedance spectrum of the lithium symmetric battery assembled by comparative examples 1-9 at 25℃;

[0036] Figure 7 is a local enlarged view of the impedance spectrum of the lithium symmetric battery assembled by comparative example 1-9 at 25℃;

[0037] Figure 8 is a cycle spectrum of the lithium symmetric battery assembled by embodiment 1 at 25℃ constant temperature, 0.4mA / cm 2 current density;

[0038] Figure 9 is a cycle spectrum of the lithium symmetric battery assembled by embodiment 2 at 25℃ constant temperature, 0.4mA / cm 2 current density;

[0039] Figure 10 is a cycle spectrum of the lithium symmetric battery assembled by comparative example 1 at 25℃ constant temperature, 0.05mA / cm 2 current density;

[0040] Figure 11 is a cycle spectrum of the lithium symmetric battery assembled by comparative example 2 at 25℃ constant temperature, 0.05mA / cm 2 current density. DETAILED DESCRIPTION

[0041] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the technical solutions in the embodiments of the present application for clear and complete description. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0042] The present application provides, in a first aspect, an interface modification layer, which is a Li-M-C eutectic composite interface layer; wherein M is Mg, In, Sn or Al.

[0043] It should be noted that C in the Li-M-C eutectic composite interface layer is carbon element.

[0044] The interface modification layer (Li-M-C eutectic composite interface layer) of the present application can effectively improve the interface contact problem of lithium negative electrode and solid-state electrolyte, inhibit the formation of lithium dendrites, and prolong the cycle life of the battery; in addition, the Li-M-C eutectic composite interface layer can also ensure the stability of the solid-state electrolyte, reducing the subsequent complex process; the solid-state electrolyte containing the interface modification layer is assembled into a button cell, and the interface impedance at 25℃ is <30Ω, which can be stably cycled for more than 600h under a current density of 0.4mA / cm 2

[0045] ​According to some preferred embodiments, in the Li-M-C eutectic composite interface layer, the content of Li is 5-20wt% (for example, it can be 5wt%, 6wt%, 8wt%, 10wt%, 12wt%, 15wt%, 16wt%, 18wt% or 20wt%), the content of M is 50-80wt% (for example, it can be 50wt%, 55wt%, 58wt%, 60wt%, 62wt%, 65wt%, 68wt%, 70wt%, 72wt%, 75wt%, 78wt% or 80wt%), and the content of C is 15-30wt% (for example, it can be 15wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt% or 30wt%); preferably, the content of Li is 9-15wt% (for example, it can be 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%), the content of M is 55-73wt% (for example, it can be 55wt%, 58wt%, 60wt%, 62wt%, 65wt%, 68wt%, 70wt% or 73wt%), and the content of C is 18-30wt% (for example, it can be 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt% or 30wt%);

[0046] More preferably, the thickness of the Li-M-C eutectic composite interface layer is 280-1000nm (for example, it can be 280nm, 300nm, 350nm, 400m, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm or 1000nm).

[0047] The present application provides in a second aspect a preparation method of the interface modification layer of the first aspect, which comprises the following steps:

[0048] S1. forming a passivation layer containing lithium carbonate on the surface of the substrate to obtain a first modified substrate;

[0049] S2. forming a salt interface layer on the surface of the passivation layer to obtain a second modified substrate; the salt interface layer is an inorganic salt layer of M;

[0050] S3. forming a carbon black layer on the surface of the salt interface layer to obtain a third modified substrate;

[0051] S4. annealing the third modified substrate to form the interface modification layer on the surface of the substrate.

[0052] The application forms an interface modification layer (Li-M-C eutectic composite interface layer) on the surface of the substrate by sequentially introducing a passivation layer, a salt interface layer and a carbon black layer on the surface of the substrate, and then performing annealing treatment; the preparation method of the interface modification layer is simple in process and easy to operate, can greatly reduce the production cost, is suitable for industrial production, and can complete the interface modification of the solid electrolyte substrate without using thin film deposition technologies such as magnetron sputtering, atomic layer deposition and electron beam evaporation, thereby reducing the interface impedance and improving the interface contact between the Li metal and the solid electrolyte.

[0053] According to some preferred embodiments, in step S1, the substrate is placed in air for 24-120h to form a passivation layer containing lithium carbonate on the surface of the substrate; wherein the substrate is a garnet-type solid electrolyte.

[0054] Preferably, the thickness of the passivation layer is 100-300nm (for example, it can be 100nm, 120nm, 140nm, 150nm, 160nm, 180nm, 200nm, 220nm, 240nm, 250nm, 260nm, 280nm or 300nm).

[0055] In some preferred embodiments of the application, the substrate is a garnet-type solid electrolyte; in some more preferred embodiments, the substrate is Li 6.4 La3Zr 1.4 Ta 0.6 O 12 solid electrolyte; by placing the garnet-type solid electrolyte in air for 24-120h, a passivation layer containing lithium carbonate with a thickness of 100-300nm can be formed on the surface thereof, which is used for annealing treatment with the subsequently formed salt interface layer and carbon black layer to form an interface modification layer on the surface of the substrate.

[0056] According to some preferred embodiments, in step S2, the first modified substrate is soaked in an inorganic salt solution of M in an inert gas atmosphere for 0.5-5min (for example, it can be 0.5min, 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min) to form the salt interface layer on the surface of the passivation layer; in the application, the inorganic salt solution of M is prepared in an inert gas atmosphere, and the first modified substrate is placed in the inorganic salt solution of M to avoid the influence of air on the formation of the salt interface layer; for example, indium chloride is hygroscopic and unstable in water, and the influence of air can be avoided in an inert gas atmosphere. It should be noted that the inert gas in the application is preferably argon, and the salt interface layer is an interface layer formed by one of indium chloride, aluminum nitrate, stannous chloride and magnesium perchlorate.

[0057] Preferably, the thickness of the salt interfacial layer is 100-500 nm (for example, it can be 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm or 500 nm).

[0058] According to some preferred embodiments, the inorganic salt solution of M is obtained by dissolving an inorganic salt of M in an organic solvent; the concentration of the inorganic salt solution of M is 0.05-0.2 mol / L (for example, it can be 0.05 mol / L, 0.06 mol / L, 0.08 mol / L, 0.10 mol / L, 0.12 mol / L, 0.14 mol / L, 0.15 mol / L, 0.16 mol / L, 0.18 mol / L or 0.2 mol / L).

[0059] Preferably, the inorganic salt of M is one of indium chloride, aluminum nitrate, stannous chloride and magnesium perchlorate, and preferably indium chloride.

[0060] The organic solvent is one of acetonitrile, anisole, chloroform, dichloroethane, N, N-dimethylformamide and isopropanol, and preferably isopropanol.

[0061] It should be noted that the inorganic salt in the present application is not limited to the above range, and other indium salts, aluminum salts, tin salts and magnesium salts that meet the conditions can also be used; the types of organic solvents are also not limited to the above range, and other organic solvents that can form a solution of the above indium salts, aluminum salts, tin salts and magnesium salts can also be used.

[0062] In the present application, the first modified substrate after passivation treatment is soaked in a salt solution to form a salt interfacial layer on the surface of the passivation layer; the concentration of the inorganic salt solution of M is controlled to be 0.05-0.2 mol / L, and the soaking time is controlled to be 0.5-5 min, so as to ensure that the thickness of the obtained salt interfacial layer is 100-500 nm; if the concentration of the inorganic salt solution is too large or too small, the thickness of the salt interfacial layer will be too large (greater than 500 nm) or too small (less than 100 nm), and finally the Li-M-C eutectic composite interfacial layer cannot be formed, and the interfacial modification layer formed cannot effectively reduce the interfacial impedance between the Li metal and the substrate, which is not conducive to the improvement of the interfacial contact performance between the Li metal and the substrate.

[0063] According to some preferred embodiments, in step S3, the second modified substrate is burned at the outer flame of a candle for 9-30 s to form the carbon black layer on the surface of the salt interfacial layer; preferably, the burning is performed for 3-5 times, and the time for each burning is 3-6 s.

[0064] More preferably, the thickness of the carbon black layer is 100-600 nm (for example, it can be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm or 600 nm).

[0065] In some preferred embodiments of the present application, a carbon black layer is formed on the surface of the salt interfacial layer by incomplete combustion of a candle by burning; by burning the candle at the outer flame for 9-30 s, the thickness of the generated carbon black layer can be ensured to be 100-600 nm; if the burning time is too long or too short, the thickness of the carbon black layer will be too large (greater than 600 nm) or too small (less than 100 nm), which will eventually fail to form a Li-M-C eutectic composite interfacial layer, and the interface modification layer obtained cannot effectively reduce the interfacial impedance between the Li metal and the matrix, which is not conducive to the improvement of the interfacial contact performance between the Li metal and the matrix.

[0066] In some more preferred embodiments of the present application, the burning is performed in 3-5 times, and the time for each single burning is 3-6 s, and the candle carbon black adhered to the surface is gently wiped off after each burning, so that the loose carbon black on the surface can be removed, and the pressure applied during the wiping process can further compact the remaining carbon black, so that a more compact carbon black layer can be finally obtained.

[0067] It should be noted that, in the process of burning the second modified matrix at the outer flame of the candle, only the plane finally in contact with the lithium electrode needs to be burned; if the matrix is a cylinder, the upper and lower surfaces of the cylinder can be burned; if the matrix is a square or a rectangular, the two closest symmetric planes can be selected for burning.

[0068] According to some preferred embodiments, in step S4, the annealing treatment is performed in an inert gas atmosphere, the temperature of the annealing treatment is 500-700°C (for example, it can be 500°C, 520°C, 540°C, 550°C, 560°C, 580°C, 600°C, 620°C, 640°C, 650°C, 660°C, 680°C or 700°C), and the time of the annealing treatment is 2-4 h (for example, it can be 2 h, 2.2 h, 2.5 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 h or 4 h); the annealing treatment is performed in an inert gas atmosphere to avoid oxidation of the carbon black layer and to obtain a Li-M-C eutectic composite interfacial layer. It should be noted that the inert gas of the present application is preferably argon.

[0069] The application forms an interface modification layer (Li-M-C eutectic composite interface layer) on the surface of the substrate after forming the lithium carbonate passivation layer, the salt interfacial layer and the carbon black layer on the surface of the substrate; the temperature and time of the annealing treatment are controlled in the above range, so that the Li-M-C eutectic composite interface layer can be obtained, and the interface impedance between the lithium negative electrode and the substrate is effectively reduced, the interface contact problem of the lithium negative electrode and the solid-state electrolyte is improved, the formation of lithium dendrites is inhibited, and the cycle life of the battery is prolonged; if the annealing temperature is too low, the Li-M-C eutectic composite interface layer cannot be obtained, and the interface layer formed on the surface will increase the contact impedance between Li and the substrate, which is not conducive to the interface contact between Li and the substrate.

[0070] The application provides an interface modification solid-state electrolyte in a third aspect, comprising the interface modification layer in the first aspect; the interface modification layer covers the surface of the solid-state electrolyte.

[0071] According to some preferred embodiments, the solid-state electrolyte is a garnet-type solid-state electrolyte; preferably, the garnet-type solid-state electrolyte is Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Solid-state electrolyte.

[0072] The application selects a garnet-type solid-state electrolyte (LLZO) with high lithium ion conductivity at room temperature, good air stability and stability to the metal lithium negative electrode, and performs interface modification and modification on the garnet-type solid-state electrolyte (LLZO), so as to form an interface modification layer (Li-M-C eutectic composite interface layer) on the surface of the LLZO, and obtain an interface modification solid-state electrolyte; in addition, the interface modification layer can ensure the air stability of the garnet-type solid-state electrolyte (LLZO), avoid the formation of a lithium carbonate passivation layer in the air, reduce the subsequent complex process treatment, improve the interface contact problem of the lithium negative electrode and the solid-state electrolyte, inhibit the formation of lithium dendrites, and prolong the cycle life of the battery; the interface modification solid-state electrolyte is assembled into a button cell, the interface impedance of which is less than 30 Ω at 25℃, and the button cell can be stably cycled for more than 600h under a current density of 0.4mA / cm 2 .

[0073] In order to more clearly illustrate the technical solutions and advantages of the application, the application will be further described below with reference to the embodiments.

[0074] The materials and reagents in the application can be directly purchased on the market or synthesized by oneself, and the specific models are not limited.

[0075] Example 1

[0076] Li 6.4 La3Zr 1.4 Ta 0.6O 12 After the solid-state electrolyte (LLZTO) substrate is placed in air for 24 h, a lithium carbonate-containing passivation layer with a thickness of 300 nm is formed on the surface of the substrate, obtaining a first modified substrate; in an argon-filled glove box, the first modified substrate is immersed in an InCl3 solution for 1 min and then taken out, and is subjected to drying treatment at 70 DEG C, forming a salt interfacial layer with a thickness of 400 nm on the surface of the passivation layer, obtaining a second modified substrate; wherein, 0.1106 g of InCl3 is dissolved in 5 mL of anhydrous isopropanol in an argon-filled glove box, and stirring is continued for 2 h, obtaining a uniformly mixed InCl3 solution;

[0077] The second modified substrate is taken out of the glove box, is burned at the outer flame of a candle for 5 s, the candle soot attached to the surface is gently wiped off, and the process is repeated for 3 times, forming a soot layer with a thickness of 200 nm on the surface of the salt interfacial layer, obtaining a third modified substrate;

[0078] The third modified substrate is placed in an argon-filled box furnace, and is annealed at 600 DEG C for 2 h, forming a Li-In-C eutectic composite interfacial layer with a thickness of 750 nm on the surface of the LLZTO (wherein, the content of Li is 10 wt%, the content of In is 70 wt%, and the content of C is 20 wt%), obtaining an interfacially modified solid-state electrolyte;

[0079] Two lithium sheets are attached to the interfacially modified solid-state electrolyte, and are assembled into a button cell, and are subjected to 2 h of infiltration at 160 DEG C.

[0080] It can be known from Figure 2 that the peak values of Zr, La, Ta and O in the EDS spectrum of the interfacially modified solid-state electrolyte prepared in Example 1 are low, and all of them are elements of LLZTO itself, so they are spurious peaks, and the main peaks are C and In, and since Li element is invisible in the EDS spectrum, it can be confirmed that there is a Li-In-C eutectic composite interfacial layer on the surface of the interfacially modified solid-state electrolyte.

[0081] It can be known from Figure 3 that the impedance of the interfacially modified solid-state electrolyte prepared in Example 1 does not change substantially after being placed in air for 360 h, indicating that the Li-In-C eutectic composite interfacial layer can ensure the stability of LLZTO in air, and avoid the formation of lithium carbonate passivation layer in air.

[0082] It can be known from Figure 4 that the limiting current density of the lithium symmetric battery assembled in Example 1 is 0.7 mA / cm 2 , and has good charge-discharge cycle performance under a current density of 0.1-0.7 mA / cm 2 .

[0083] It can be known fromFigure 5 It can be seen that the interfacial impedance R of the lithium symmetric battery assembled by Example 1 is 14Ω at 25℃, which indicates that the Li-In-C eutectic composite interface layer greatly reduces the interfacial impedance between Li and LLZTO and improves the interfacial wettability between Li and LLZTO. Li-LLZTo

[0084] It can be seen that the constant current deposition / stripping curve of the lithium symmetric battery assembled by Example 1 can be stably cycled for more than 1000h at 25℃, which indicates that the Li-In-C eutectic composite interface layer can effectively inhibit the formation of lithium dendrites and avoid battery short circuit; and the polarization voltage does not change, which indicates that the Li-In-C eutectic composite interface layer can effectively deposit and strip lithium and maintain good battery cycle performance. Figure 8

[0085] Example 2

[0086] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid-state electrolyte (LLZTO) matrix is placed in the air for 24h, a passivation layer containing lithium carbonate with a thickness of 300nm is formed on the surface of the matrix to obtain a first modified matrix; in an argon-filled glove box, the first modified matrix is soaked in an Al(NO3)3 solution for 1min and then taken out, and a drying treatment is performed at 70℃, so that a salt interface layer with a thickness of 400nm is formed on the surface of the passivation layer to obtain a second modified matrix; wherein 0.1106g of Al(NO3)3 is dissolved in 5mL of anhydrous isopropyl alcohol in an argon-filled glove box, and stirring is continued for 2h to obtain a uniformly mixed Al(NO3)3 solution;

[0087] The second modified matrix is taken out of the glove box, burned at the outer flame of a candle for 5s, the candle soot attached to the surface is gently wiped off, and the process is repeated for 3 times, so that a carbon black layer with a thickness of 200nm is formed on the surface of the salt interface layer to obtain a third modified matrix;

[0088] The third modified matrix is placed in an argon-filled box furnace and annealed at 600℃ for 2h to form a Li-Al-C eutectic composite interface layer with a thickness of 600nm on the surface of the LLZTO (wherein the content of Li is 14wt%, the content of Al is 59wt%, and the content of C is 27wt%), to obtain an interface-modified solid-state electrolyte;

[0089] Two lithium sheets are attached to the interface-modified solid-state electrolyte to assemble a button cell, and the button cell is soaked at 160℃ for 2h.

[0090] It can be seen that the interfacial impedance R of the lithium symmetric battery assembled by Example 1 is 14Ω at 25℃, which indicates that the Li-In-C eutectic composite interface layer greatly reduces the interfacial impedance between Li and LLZTO and improves the interfacial wettability between Li and LLZTO. Figure 5 ​​It can be seen that the interfacial impedance R of the lithium symmetrical battery assembled by Example 2 at 25℃ is 25Ω, which indicates that the Li-Al-C eutectic composite interfacial layer greatly reduces the interfacial impedance between Li and LLZTO and improves the interfacial wettability between Li and LLZTO. Li-LLZTo 6.4 It can be seen that the interfacial impedance R of the lithium symmetrical battery assembled by Example 2 at 25℃ is 25Ω, which indicates that the Li-Al-C eutectic composite interfacial layer greatly reduces the interfacial impedance between Li and LLZTO and improves the interfacial wettability between Li and LLZTO.

[0091] It can be seen that the interfacial impedance R of the lithium symmetrical battery assembled by Example 2 at 25℃ is 25Ω, which indicates that the Li-Al-C eutectic composite interfacial layer greatly reduces the interfacial impedance between Li and LLZTO and improves the interfacial wettability between Li and LLZTO. Figure 9

[0092] Example 3

[0093] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid-state electrolyte (LLZTO) matrix is placed in the air for 24h, a lithium carbonate-containing passivation layer with a thickness of 300nm is formed on the surface of the matrix to obtain a first modified matrix; in an argon-filled glove box, the first modified matrix is immersed in an InCl3 solution for 1min and then taken out, and a drying treatment is performed at 70℃, so that a salt interfacial layer with a thickness of 230nm is formed on the surface of the passivation layer to obtain a second modified matrix; wherein, 0.0857g of InCl3 is dissolved in 5mL of anhydrous isopropanol in an argon-filled glove box, and stirring is continued for 2h to obtain a uniformly mixed InCl3 solution;

[0094] The second modified matrix is taken out of the glove box, burned at the outer flame of a candle for 5s, the candle soot attached to the surface is gently wiped off, and the process is repeated for 3 times, so that a carbon black layer with a thickness of 200nm is formed on the surface of the salt interfacial layer to obtain a third modified matrix;

[0095] The third modified matrix is placed in an argon-filled box furnace and annealed at 600℃ for 2h to form a Li-In-C eutectic composite interfacial layer with a thickness of 637nm on the surface of the LLZTO (wherein, the content of Li is 15wt%, the content of In is 56wt%, and the content of C is 29wt%), to obtain an interfacial modified solid-state electrolyte;

[0096] Two lithium sheets are attached to the interfacial modified solid-state electrolyte to assemble a button cell, and the button cell is soaked at 160℃ for 2h.

[0097] It can be seen that the interfacial impedance R of the lithium symmetrical battery assembled by Example 2 at 25℃ is 25Ω, which indicates that the Li-Al-C eutectic composite interfacial layer greatly reduces the interfacial impedance between Li and LLZTO and improves the interfacial wettability between Li and LLZTO. Figure 5 Li-LLZTo ​= 26Ω, which indicates that the Li-In-C eutectic composite interface layer greatly reduces the contact impedance between Li and LLZTO, improves the interface contact between Li and LLZTO, is conducive to inhibiting the growth of lithium dendrites, and prolongs the charge-discharge life of the battery.

[0098] The galvanostatic deposition / stripping curve of the lithium symmetrical battery assembled in Example 3 at 25°C can be stably cycled for 800h, indicating that the Li-In-C eutectic composite interface layer can effectively inhibit the formation of lithium dendrites and prolong the charge-discharge life of the battery.

[0099] Example 4

[0100] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid-state electrolyte (LLZTO) matrix is placed in the air for 24h, a lithium carbonate-containing passivation layer with a thickness of 300nm is formed on the surface of the matrix to obtain a first modified matrix; in an argon-filled glove box, the first modified matrix is immersed in a SnCl2 solution for 1min and then taken out, and a drying treatment is performed at 70°C to form a salt interface layer with a thickness of 400nm on the surface of the passivation layer to obtain a second modified matrix; wherein 0.1106g of SnCl2 is dissolved in 5mL of anhydrous isopropanol in an argon-filled glove box, and stirring is continued for 2h to obtain a uniformly mixed SnCl2 solution;

[0101] The second modified matrix is taken out of the glove box, burned at the outer flame of a candle for 5s, the candle soot attached to the surface is gently wiped off, and the process is repeated for 3 times to form a carbon black layer with a thickness of 200nm on the surface of the salt interface layer to obtain a third modified matrix;

[0102] The third modified matrix is placed in an argon-filled box furnace and annealed at 600°C for 2h to form a Li-Sn-C eutectic composite interface layer with a thickness of 723nm on the surface of the LLZTO (wherein the content of Li is 9wt%, the content of Sn is 73wt%, and the content of C is 18wt%) to obtain an interface-modified solid-state electrolyte;

[0103] Two lithium sheets are attached to the interface-modified solid-state electrolyte to assemble a coin battery, and the battery is soaked at 160°C for 2h.

[0104] From Figure 5 It can be seen that the interface impedance R Li-LLZTO = 18Ω of the lithium symmetrical battery assembled in Example 4 at 25°C indicates that the Li-Sn-C eutectic composite interface layer greatly reduces the interface impedance between Li and LLZTO, and improves the interface wettability between Li and LLZTO.

[0105] The constant current deposition / stripping curve of the lithium symmetrical battery assembled in Example 4 at 25℃ can be stably cycled for 900h, indicating that the Li-Sn-C eutectic composite interface layer can prolong the cycle life of the battery.

[0106] Example 5

[0107] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid-state electrolyte (LLZTO) substrate is placed in the air for 24h, a lithium carbonate-containing passivation layer with a thickness of 300nm is formed on the surface of the substrate, obtaining a first modified substrate; in an argon-filled glove box, the first modified substrate is soaked in a Mg (ClO4) 2 solution for 1min and then taken out, and a drying treatment is carried out at 70℃, forming a salt interface layer with a thickness of 400nm on the surface of the passivation layer, obtaining a second modified substrate; wherein 0.1106g of Mg (ClO4) 2 is dissolved in 5mL of anhydrous isopropanol in an argon-filled glove box, and the stirring is continued for 2h to obtain a uniformly mixed Mg (ClO4) 2 solution;

[0108] The second modified substrate is taken out of the glove box, burned at the outer flame of a candle for 5s, the candle soot attached to the surface is gently wiped off, and the process is repeated for 3 times, forming a carbon black layer with a thickness of 200nm on the surface of the salt interface layer, obtaining a third modified substrate;

[0109] The third modified substrate is placed in an argon-filled box furnace and annealed at 600℃ for 2h, forming a Li-Mg-C eutectic composite interface layer with a thickness of 830nm on the surface of the LLZTO (wherein the content of Li is 15wt%, the content of Mg is 55wt%, and the content of C is 30wt%), obtaining an interface modified solid-state electrolyte;

[0110] Two lithium sheets are attached to the interface modified solid-state electrolyte, and a button cell is assembled, and the infiltration is carried out at 160℃ for 2h.

[0111] From Figure 5 It can be seen that the interface impedance R Li-LLZTO = 23Ω of the lithium symmetrical battery assembled in Example 5 at 25℃, indicating that the Li-Mg-C eutectic composite interface layer greatly reduces the interface impedance between Li and LLZTO, and improves the interface wettability between Li and LLZTO.

[0112] The constant current deposition / stripping curve of the lithium symmetrical battery assembled in Example 5 at 25℃ can be stably cycled for 850h, indicating that the Li-Mg-C eutectic composite interface layer can improve the cycle performance of the battery.

[0113] Comparative Example 1

[0114] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid electrolyte substrate was placed in air for 24 h, a passivation layer containing lithium carbonate with a thickness of 300 nm was formed on the surface of the substrate; it was transferred to a box furnace filled with argon and annealed at 600°C for 2 h to obtain a modified solid electrolyte;

[0115] Two lithium pieces were attached to the solid electrolyte to assemble a button cell, which was immersed at 160°C for 2 h.

[0116] By Figures 6-7 It can be seen that the interfacial impedance R Li-LLZTO = 640Ω of the lithium symmetric battery assembled by Comparative Example 1 at 25°C, the passivation layer on the surface of the solid electrolyte increases the interfacial impedance, resulting in very poor interfacial wettability between Li and LLZTO.

[0117] By Figure 10 It can be seen that the galvanostatic deposition / stripping curve of the lithium symmetric battery assembled by Comparative Example 1 can only be stably cycled for 50 h, and the polarization voltage is very high, indicating that the interfacial impedance is very large. Only by modifying the interface can the wettability between the electrolyte and lithium metal be improved, thereby improving the cycle performance of charging and discharging.

[0118] Comparative Example 2

[0119] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid electrolyte substrate was placed in air for 24 h, it was transferred to a glove box filled with argon and polished to remove the passivation layer produced in the air; then it was annealed at 600°C for 2 h in a box furnace filled with argon to obtain a modified solid electrolyte;

[0120] Two lithium pieces were attached to the solid electrolyte to assemble a button cell, which was immersed at 160°C for 2 h.

[0121] By Figures 6-7 It can be seen that the interfacial impedance R Li-ILZTO = 250Ω of the lithium symmetric battery assembled by Comparative Example 2 at 25°C, indicating that compared to retaining the surface passivation layer, removing the surface passivation layer can improve the interfacial wettability between Li and LLZTO to some extent.

[0122] By Figure 11It can be seen that the galvanostatic deposition / stripping curve of the lithium symmetric battery at 25°C can only be stably cycled for 100 h, and then the polarization voltage gradually increases, indicating that the interface layer cannot effectively perform lithium stripping / deposition after a period of charge / discharge cycling, and due to uneven lithium deposition, subsequent lithium dendrite growth occurs, leading to short circuit.

[0123] Comparative Example 3

[0124] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid-state electrolyte (LLZTO) substrate was placed in air for 24 h, a lithium carbonate-containing passivation layer with a thickness of 300 nm was formed on the surface of the substrate. In an argon-filled glove box, the substrate was immersed in an InCl3solution for 1 min and then taken out, forming a salt interface layer with a thickness of 400 nm on the surface of the passivation layer. Then, the substrate was dried at 70°C and placed in an argon-filled box furnace, followed by annealing at 600°C for 2 h, forming an interface modification layer with a thickness of 700 nm on the surface of the LLZTO, thereby obtaining an interface-modified solid-state electrolyte. In the argon-filled glove box, 0.1106 g of InCl3was dissolved in 5 mL of anhydrous isopropanol, and the mixture was continuously stirred for 2 h to obtain a uniformly mixed InCl3solution.

[0125] Two lithium pieces were attached to the modified solid-state electrolyte to assemble a coin cell, which was then soaked at 160°C for 2 h.

[0126] Since no carbon black layer was formed, the Li-In-C eutectic composite interface layer could not be formed.

[0127] From Figures 6-7 It can be seen that the interface resistance R Li-LLZTO = 3500 Ω of the lithium symmetric battery assembled in Comparative Example 3 at 25°C indicates that this interface treatment method greatly increases the interface resistance, which is not conducive to the interface wetting between Li and LLZTO, and seriously affects the interface contact between Li metal and the solid-state electrolyte.

[0128] Comparative Example 4

[0129] Li 6.4 La3Zr 1.4 Ta 0.6 O 12After the solid electrolyte (LLZTO) substrate was placed in air for 24 hours, a passivation layer containing lithium carbonate with a thickness of 300 nm was formed on the surface of the substrate. Then, it was burned in the outer flame of a candle for 5 seconds, and the candle black adhering to the surface was gently wiped off. This process was repeated 3 times to form a carbon black layer with a thickness of 200 nm on the surface of the passivation layer. Then, it was placed in a box furnace filled with argon and annealed at 600 °C for 2 hours to form an interface modification layer with a thickness of 500 nm on the surface of LLZTO, thus obtaining an interface-modified solid electrolyte.

[0130] Two lithium sheets were attached to an interface-modified solid electrolyte and assembled into a button cell, which was then immersed at 160°C for 2 hours.

[0131] Because a salt interface layer was not formed, a Li-In-C eutectic composite interface layer could not ultimately be formed.

[0132] Depend on Figures 6-7 It can be seen that the interfacial impedance R of the lithium symmetric battery assembled in Comparative Example 4 at 25℃ is... Li-LLZTO =5000Ω, indicating that this interface treatment method greatly increases the interface impedance, which is not conducive to the interface wettability between Li and LLZTO, and seriously affects the interface contact between Li metal and solid electrolyte.

[0133] Comparative Example 5

[0134] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid electrolyte (LLZTO) matrix was placed in air for 24 hours, a 300 nm thick passivation layer containing lithium carbonate was formed on the surface of the matrix. The matrix was then immersed in an InCl3 solution for 1 minute in an argon-filled glove box, removed, and dried at 70 °C, forming a 1200 nm thick salt interface layer on the surface of the passivation layer. The matrix was then burned in the outer flame of a candle for 5 seconds, and the attached candle black was gently wiped off. This process was repeated three times to form a 200 nm thick carbon black layer on the surface of the salt interface layer. Finally, the matrix was placed in an argon-filled box furnace and annealed at 600 °C for 2 hours, forming a 1450 nm thick interface modification layer on the surface of the LLZTO, thus obtaining an interface-modified solid electrolyte. In this process, 0.5 g of InCl3 was dissolved in 5 mL of anhydrous isopropanol in an argon-filled glove box and stirred continuously for 2 hours to obtain a homogeneous InCl3 solution.

[0135] Two lithium sheets were attached to an interface-modified solid electrolyte and assembled into a button cell, which was then immersed at 160°C for 2 hours.

[0136] Due to the excessive thickness of the salt interface layer (excessive indium chloride content), the interface modification layer obtained finally is an interface layer formed by mixing Li-In-C eutectic and indium chloride.

[0137] By Figures 6-7 It can be seen that the interface impedance R of the lithium symmetric battery assembled by Comparative Example 5 at 25°C is 350Ω, indicating that this interface treatment method can slightly improve the interface contact between Li and LLZTO. Li-LLZTO

[0138] Comparative Example 6

[0139] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid-state electrolyte (LLZTO) substrate was placed in the air for 24 h, a passivation layer containing lithium carbonate with a thickness of 300 nm was formed on the surface of the substrate. In an argon-filled glove box, the passivation layer was immersed in an InCl3 solution for 1 min and then taken out, and a drying treatment was performed at 70°C. A salt interface layer with a thickness of 400 nm was formed on the surface of the passivation layer, and then the salt interface layer was burned at the outer flame of a candle for 40 s. The candle soot attached to the surface was gently wiped off and repeated 3 times to form a carbon black layer with a thickness of 700 nm on the surface of the salt interface layer. Finally, the carbon black layer was placed in an argon-filled box furnace and annealed at 600°C for 2 h to form an interface modification layer with a thickness of 1300 nm on the surface of the LLZTO, thereby obtaining an interface modification solid-state electrolyte. In an argon-filled glove box, 0.1106 g of InCl3 was dissolved in 5 mL of anhydrous isopropanol, and the stirring was continued for 2 h to obtain a uniformly mixed InCl3 solution.

[0140] Two lithium pieces were attached to the interface modification solid-state electrolyte to assemble a coin cell, and the coin cell was immersed at 160°C for 2 hours.

[0141] Due to the excessive thickness of the carbon black layer (excessive carbon black content), the interface modification layer obtained finally is an interface layer formed by mixing Li-In-C eutectic and carbon black.

[0142] By Figures 6-7 It can be seen that the interface impedance R of the lithium symmetric battery assembled by Comparative Example 7 at 25°C is 184Ω, indicating that this interface treatment method can slightly improve the interface contact between Li and LLZTO. Li-LLZTo

[0143] Comparative Example 7

[0144] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ​​After the solid electrolyte (LLZTO) matrix was placed in air for 24 hours, a 300 nm thick passivation layer containing lithium carbonate was formed on the surface of the matrix. The matrix was then immersed in an InCl3 solution for 1 minute in an argon-filled glove box, removed, and dried at 70 °C, forming a 400 nm thick salt interface layer on the surface of the passivation layer. The matrix was then burned in the outer flame of a candle for 5 seconds, and the attached candle black was gently wiped off. This process was repeated three times, forming a 200 nm thick carbon black layer on the surface of the salt interface layer. Finally, the matrix was placed in an argon-filled box furnace and annealed at 300 °C for 2 hours, forming a 900 nm thick interface modification layer on the surface of the LLZTO, thus obtaining an interface-modified solid electrolyte. In this process, 0.1106 g of InCl3 was dissolved in 5 mL of anhydrous isopropanol in an argon-filled glove box and stirred continuously for 2 hours to obtain a homogeneous InCl3 solution.

[0145] Two lithium sheets were attached to a modified solid electrolyte and assembled into a button cell, which was then immersed at 160°C for 2 hours.

[0146] Due to the excessively low annealing temperature, the Li-In-C eutectic composite interface layer could not be formed.

[0147] Depend on Figures 6-7 It can be seen that the interfacial impedance R of the lithium symmetric battery assembled in Comparative Example 7 at 25℃ is... Li-LLZTO =850Ω, this interface layer greatly increases the contact resistance between Li and LLZTO, which is not conducive to the interface contact between Li and LLZTO.

[0148] Comparative Example 8

[0149] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid electrolyte (LLZTO) matrix was placed in air for 24 hours, a 300 nm thick passivation layer containing lithium carbonate was formed on the surface of the matrix. The matrix was then immersed in an InCl3 solution for 1 minute in an argon-filled glove box, removed, and dried at 70°C, forming a 400 nm thick salt interface layer on the surface of the passivation layer. The matrix was then burned in the outer flame of a candle for 0.5 seconds, and the attached candle black was gently wiped off. This process was repeated three times, forming an 80 nm thick carbon black layer on the surface of the salt interface layer. Finally, the matrix was placed in an argon-filled box furnace and annealed at 600°C for 2 hours, forming a 580 nm thick interface modification layer on the surface of the LLZTO, thus obtaining an interface-modified solid electrolyte. In this process, 0.1106 g of InCl3 was dissolved in 5 mL of anhydrous isopropanol in an argon-filled glove box and stirred continuously for 2 hours to obtain a homogeneous InCl3 solution.

[0150] Two lithium sheets were attached to an interface-modified solid electrolyte and assembled into a button cell, which was then immersed at 160°C for 2 hours.

[0151] Because the carbon black layer is too thin (the carbon black content is too low), the passivation layer and the salt interface layer cannot react completely. The final interface modification layer is an interface layer formed by a mixture of Li-In-C eutectic, lithium carbonate and indium chloride.

[0152] Depend on Figures 6-7 It can be seen that the interfacial impedance R of the lithium symmetric battery assembled in Comparative Example 8 at 25℃ is... Li-LLZTO =800Ω, indicating that this interface treatment method is not conducive to improving the interface contact between Li and LLZTO.

[0153] Comparative Example 9

[0154] Li 6.4 La3Zr 1.4 Ta 0.6 O 12 After the solid electrolyte (LLZTO) matrix was placed in air for 24 hours, a 300 nm thick passivation layer containing lithium carbonate was formed on the surface of the matrix. The matrix was then immersed in an InCl3 solution for 1 minute in an argon-filled glove box, removed, and dried at 70 °C, forming a 60 nm thick salt interface layer on the surface of the passivation layer. The matrix was then burned in the outer flame of a candle for 5 seconds, and the attached candle black was gently wiped off. This process was repeated three times, forming a 200 nm thick carbon black layer on the surface of the salt interface layer. Finally, the matrix was placed in an argon-filled box furnace and annealed at 600 °C for 2 hours, forming a 520 nm thick interface modification layer on the surface of the LLZTO, thus obtaining an interface-modified solid electrolyte. In this process, 0.0015 g of InCl3 was dissolved in 5 mL of anhydrous isopropanol in an argon-filled glove box and stirred continuously for 2 hours to obtain a homogeneous InCl3 solution.

[0155] Two lithium sheets were attached to an interface-modified solid electrolyte and assembled into a button cell, which was then immersed at 160°C for 2 hours.

[0156] Because the thickness of the salt interface layer is too small (the indium chloride content is too low), the passivation layer and the salt interface layer cannot react completely. The final interface modification layer is an interface layer formed by a mixture of Li-In-C eutectic, lithium carbonate and indium chloride.

[0157] Depend on Figures 6-7 It can be seen that the interfacial impedance R of the lithium symmetric battery assembled in Comparative Example 9 at 25℃ is... Li-LLZTo =930Ω, indicating that this interface treatment method is not conducive to improving the interface contact between Li and LLZTO.

[0158] According to the comparison of the experimental data of the examples and the comparative examples, it can be known that: ① the interface modification layers of examples 1, 2, 4 and 5 are respectively Li-In-C, Li-Al-C, Li-Sn-C and Li-Mg-C eutectic composite interface layers, although the interface modification layers of the four meet the requirements, but comparing the four, it can be found that the interface impedance of example 1 is smaller, and the Li-In-C eutectic composite interface layer can more effectively improve the stable cycle life of lithium symmetric battery; ② from the comparison of examples 1, 2 and comparative examples 1 and 2, it can be known that the passivation layer generated on the surface of the solid-state electrolyte seriously affects the interface impedance and the cycle life of the battery, while the eutectic composite interface layer can greatly improve the interface wettability and the cycle life of the battery; ③ from examples 1 and comparative examples 3 and 4, it can be known that the generation of the eutectic composite interface layer needs the joint action of the lithium carbonate layer, the salt interface layer (such as the indium chloride layer) and the carbon black layer, and one of them is indispensable; if one component is missing, the interface layer obtained will seriously affect the interface contact between the Li metal and the solid-state electrolyte; ④ from examples 1 and comparative examples 5 and 9, it can be known that if the concentration of the indium chloride solution is too large or too small, it will lead to too large or too small content of In in the interface modification layer, and the interface modification layer obtained cannot effectively reduce the interface impedance between Li and LLZTO, which is not conducive to the interface contact between Li and LLZTO; from examples 1 and comparative examples 6 and 8, it can be known that if the calcination time is too long or too short, it will lead to too much or too little content of C in the interface modification layer, and the interface modification layer obtained cannot effectively reduce the interface impedance between Li and LLZTO, which is not conducive to the interface contact between Li and LLZTO. ⑤ from examples 1 and comparative example 7, it can be known that the annealing temperature of comparative example 7 is too low, although a layer of interface modification layer is also formed on the surface of LLZTO, but the interface modification layer is not a Li-In-C eutectic composite interface layer; the interface modification layer greatly increases the interface impedance between Li and LLZTO; it is explained that only when the annealing temperature is appropriate, the Li-In-C eutectic composite interface layer can effectively improve the interface impedance between the Li metal and the solid-state electrolyte; in summary, the solid-state electrolyte modified by the eutectic composite interface layer has lower interface impedance and better lithium symmetric cycle performance than the unmodified one, the reasons are as follows: (1) the interface modification layer isolates the lithium metal and the solid-state electrolyte, which can avoid the occurrence of side reactions and improve the cycle life of the battery; (2) the interface modification layer can improve the contact problem between the lithium metal and the solid-state electrolyte, greatly reduce the interface impedance, avoid the uneven deposition of lithium ions at the interface gap, thereby inhibit the generation of lithium dendrites and prolong the cycle life.

[0159] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An interface modification layer characterized by, The interface modification layer covers the surface of the solid-state electrolyte; the interface modification layer is a Li-M-C eutectic composite interface layer; wherein M is Mg, In, Sn or Al, and C is carbon black.

2. The interface modification layer of claim 1, wherein, In the Li-M-C eutectic composite interface layer, the content of Li is 5-20wt%, the content of M is 50-80wt%, and the content of C is 15-30wt%.

3. The interface modification layer of claim 2, wherein, In the Li-M-C eutectic composite interface layer, the content of Li is 9-15wt%, the content of M is 55-73wt%, and the content of C is 18-30wt%.

4. The interface modification layer of claim 2, wherein, The thickness of the Li-M-C eutectic composite interface layer is 280-1000nm.

5. A method for producing the interface modification layer as claimed in any one of claims 1 to 4, characterized by, The preparation method comprises the following steps: S1. Forming a passivation layer containing lithium carbonate on the surface of the substrate to obtain a first modified substrate; S2. Forming a salt interface layer on the surface of the passivation layer to obtain a second modified substrate; The salt interface layer is an inorganic salt layer of M; S3. Forming a carbon black layer on the surface of the salt interface layer to obtain a third modified substrate; S4. Annealing the third modified substrate to form the interface modification layer on the surface of the substrate.

6. The preparation method according to claim 5, characterized in that, In step S1, the substrate is placed in air for 24-120h to form a passivation layer containing lithium carbonate on the surface of the substrate; wherein the substrate is a garnet-type solid-state electrolyte.

7. The preparation method according to claim 6, characterized in that, The thickness of the passivation layer is 100-300nm.

8. The preparation method according to claim 5, characterized in that, In step S2, the first modified substrate is soaked in an inorganic salt solution of M in an inert gas atmosphere for 0.5-5min to form the salt interface layer on the surface of the passivation layer.

9. The production method according to claim 8, characterized by, The thickness of the salt interface layer is 100-500nm.

10. The preparation method according to claim 8, characterized in that, The inorganic salt solution of M is obtained by dissolving an inorganic salt of M in an organic solvent; the concentration of the inorganic salt solution of M is 0.05-0.2mol / L.

11. The method of claim 10, wherein, The inorganic salt of M is one of indium chloride, aluminum nitrate, stannous chloride, and magnesium perchlorate.

12. The method of claim 10, wherein, The organic solvent is one of acetonitrile, anisole, chloroform, dichloroethane, N,N-dimethylformamide, and isopropanol.

13. The preparation method according to claim 10, characterized in that, The inorganic salt of M is indium chloride, and the organic solvent is isopropanol.

14. The method of claim 5, wherein, In step S3, the second modified substrate is burned at the outer flame of a candle for 9-30s to form the carbon black layer on the surface of the salt interface layer.

15. The method of claim 14, wherein, The burning is performed in 3-5 times, and the time of single burning is 3-6s.

16. The method of claim 14, wherein, The thickness of the carbon black layer is 100-600nm.

17. The preparation method according to claim 5, characterized in that, In step S4, the annealing treatment is performed in an inert gas atmosphere, the temperature of the annealing treatment is 500-700℃, and the time of the annealing treatment is 2-4h.

18. An interphase-modified solid-state electrolyte, characterized by, The interface modification layer comprises the interface modification layer according to any one of claims 1-4.

19. The interface-modified solid-state electrolyte of claim 18, wherein, The solid-state electrolyte is a garnet-type solid-state electrolyte.

20. The interface-modified solid-state electrolyte of claim 19, wherein, The garnet solid state electrolyte is Li 6.4 La3Zr 1.4 Ta 0.6 O 12 solid state electrolyte.

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