Solid electrolyte and solid lithium metal battery

Abstract

The invention discloses a solid-state electrolyte and a solid-state lithium metal battery. A preparation method of the solid-state electrolyte comprises the following steps: preparing a Li1. 3Al0. 3Ti1. 7( PO4) (LATP) solid-state electrolyte by adopting a solid-phase sintering method; the preparation method comprises the following steps: dissolving InCl3 and polyacrylic acid (PAA) in isopropanol to form a colorless precursor solution; dripping the solution on the surface of the LATP solid electrolyte and coating by using a spin coater; and the coated and dried LATP is put into a tubular furnace to be sintered, and the In2O3 coated LATP is obtained. Through in-situ electrochemical reaction of indium oxide and lithium metal, an interface layer composed of a Li2O phase and a LixIn alloy is constructed. Wherein the Li2O phase has relatively low lithium ion migration energy barrier and electronic insulation capability; the LixIn alloy can improve the ion diffusion coefficient of the lithium side, and has very high affinity to lithium metal and LATP. According to the Li2O / LixIn interface layer prepared by the preparation method disclosed by the invention, tight contact between lithium metal and LATP is maintained, side reaction is avoided, interface ion transmission kinetics is improved, and uniform dendrite-free lithium deposition is realized.

Description

Technical Field

[0001] The present invention belongs to the field of solid-state batteries, and specifically relates to a method for preparing an interface layer between a solid-state electrolyte and a metallic lithium negative electrode, and a solid-state lithium metal battery. Background Art

[0002] Solid-state batteries have been identified as a key technology for future energy storage systems due to their low cost, high safety, and high energy density. 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) solid electrolyte has high room temperature ionic conductivity (10 -4 ~ 10 -3 S cm -1 ), wide electrochemical window (>5V), low raw material cost, simple preparation process, excellent air stability and moisture resistance, etc., and is considered to be one of the most promising candidate materials for realizing solid-state batteries.

[0003] However, poor solid-solid contact, severe spontaneous side reactions, and uncontrolled dendrite growth are the problems that LATP must overcome in practical applications. When LATP contacts Li metal, the Ti in LATP is strongly reduced due to the strong reducibility of Li metal. 4+ Will be restored to Ti 3+ , forming an interfacial phase with high electronic conductivity. Electrons are injected along the conductive phase, side reactions occur, and LATP is consumed. Moreover, the formation of the interfacial phase is accompanied by a dramatic volume expansion, and the gradual accumulation of stress can cause cracks or even breakage in the electrolyte. The interface impedance is large, the ion transfer efficiency is poor, and the lithium dendrites grow rapidly, which will eventually lead to battery failure. Therefore, in order to achieve high-performance and long-life solid-state batteries, it is urgent to construct an interface protection strategy that can maintain dynamic close contact, isolate interfacial side reactions, and have high ion transfer efficiency. Summary of the invention

[0004] The present invention aims to solve the problems of poor stability of LATP / Li interface, dendrite growth and side reactions during the cycle, and provides a Li with super-lithiophilicity and fast ion transport. 2 O / Li x Solid electrolyte of In mixed interface and its preparation method and application.

[0005] A solid electrolyte, comprising an interface layer, wherein the interface layer is Li x In alloy and Li 2 O, namely Li 2 O / Li x In interface, the Li2 O / Li x The In interface is grown in situ on the surface of the solid electrolyte.

[0006] The solid electrolyte includes Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP)、Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP), Li 7 La 3 Zr 2 O 12 LLZO, Li 0.5 La 0.5 TiO 3 (LLTO).

[0007] By impregnating or coating the surface of the solid electrolyte with InCl 3 After the polymer solution is sintered at 600℃~700℃, Li-containing 2 O / Li x In interface solid electrolyte.

[0008] The polymer solution includes any one of polyacrylic acid, polyvinyl pyrrolidone, polyphenolic resin, polyvinyl alcohol, polyethylene glycol and polyacrylamide.

[0009] The present invention introduces a uniform indium oxide thin layer through a simple and controllable coordination-assisted deposition method, and constructs a Li metal with fast ion transport and electronic insulation through the in-situ electrochemical reaction of indium oxide and lithium metal. 2 O phase and superlithiophilic Li x In alloy interface layer. Li 2 Low Li O phase + Migration barrier, Li + Stable and rapid transport and interface diffusion balance are guaranteed. 2 The electronic insulation ability of O can block electron injection and eliminate side reactions. x In alloy has a very high affinity for both Li and LATP, and can act as a hinge to tightly connect the two together. Its high ion diffusion coefficient can also promote uniform lithium deposition. This interface layer achieves close contact between the Li / LATP interface, effectively reducing the interface impedance, promoting uniform and efficient non-porous lithium plating / stripping, and significantly improving the cycle stability of symmetrical cells and full cells.

[0010] A method for preparing a solid electrolyte comprises the following steps: Step 1: InCl 3 and polymer dissolved in isopropanol to form a colorless solution; Step 2: Apply the above solution dropwise on the surface of the solid electrolyte and spin coat evenly; Step 3: Sinter the solid electrolyte in step 2 to obtain an In-containing 2 O 3 layer of solid electrolyte; Step 4: Add the In 2 O 3 The solid electrolyte layer reacts with molten lithium to obtain Li 2 O / Li x In interface solid electrolyte.

[0011] The InCl 3 The amount is 30-50 mM; the polymer solution includes any one of polyacrylic acid, polyvinyl pyrrolidone, polyphenolic resin, polyvinyl alcohol, polyethylene glycol, and polyacrylamide; InCl 3 The mass ratio of the polymer is 1:1-5.

[0012] The amount of solution dropped on the surface of the solid electrolyte is 0.05-0.2 g cm -2 .

[0013] In some embodiments, spin coating or dipping is used to achieve that the surface of the solid electrolyte contains the above-mentioned colorless solution.

[0014] The solid electrolyte is selected from Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP)、Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP), Li 7 La 3 Zr 2 O 12 LLZO, Li 0.5 La 0.5 TiO 3 (LLTO).

[0015] The technical solution of the present invention is based on Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3For example, Li 2 CO 3 、Al 2 O 3 、TiO 2 and NH 4 H 2 PO 2 Li1.3Al0.3Ti1.7(PO 4 )(LATP) solid electrolyte.

[0016] In the step 1, InCl 3 Replaced by Al(NO 3 ) 3 Mg(CH 3 COO 2 、Zn(NO 3 ) 2 Any one of the above will get the corresponding Al 2 O 3 , MgO, and ZnO interface structure of the solid electrolyte.

[0017] Another technical solution of the present invention is to provide a solid-state lithium metal battery, comprising the solid-state battery electrolyte or the solid-state battery electrolyte prepared by the method.

[0018] The method for preparing the indium oxide layer provided by the present invention has the following beneficial effects: (1) Anhydrous indium chloride and carboxyl-rich polyacrylic acid are mixed to form a cross-linked polymer network, and then an indium oxide layer is introduced on the surface of the solid electrolyte by spin coating and sintering. The method is simple and controllable, and the resulting metal oxide layer is uniform and dense; (2) The dense indium oxide layer reacts with metallic lithium in situ to generate Li 2 O / Li x In phase, LATP effectively improves the stability of lithium, eliminates problems such as interface side reactions and cracks, and helps to obtain solid-state batteries with excellent cycle performance and good rate performance; (3) Li with high ionic conductivity 2 The O phase provides a channel for efficient lithium ion transmission at the interface, guiding the uniform and dense lithium deposition and avoiding the hole and contact loss of lithium during the deposition / stripping process. (4) Li at the interface x In alloy has a very high affinity for both metallic lithium and LATP, and can act as a hinge to tightly connect the two together, making the physical contact between LATP and metallic lithium closer. Its higher ion diffusion coefficient also promotes uniform and dendrite-free lithium deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The LATP solid electrolyte (A) prepared in Example 1 of the present invention, InCl 3 +PAA@LATP(B)and In 2 O 3 Surface SEM image of @LATP (C) (scale bars are 10 μm).

[0020] Figure 2 The LATP (A) and In prepared in Example 1 of the present invention 2 O 3 XRD pattern of @LATP (B).

[0021] Figure 3 In prepared in Example 1 of the present invention 2 O 3 @LATP high-resolution XPS images of In 3d and O1s before and after the reaction with metallic lithium.

[0022] Figure 4 Li / In prepared in Example 1 of the present invention 2 O 3 @LATP / Li symmetric battery EIS impedance spectrum before cycling.

[0023] Figure 5 Li / In prepared in Example 1 of the present invention 2 O 3 @LATP / Li symmetric battery critical current density (CCD) curve.

[0024] Figure 6 Li / In prepared in Example 1 of the present invention 2 O 3 @LATP / Li symmetric cell at 0.1 mA cm -2 / 0.1 mAhcm -2 The voltage-time curve of the lower part.

[0025] Figure 7 Li / In prepared in Example 1 of the present invention 2 O 3 @LATP / Li symmetric cell at 0.2 mA cm -2 / 0.2 mAhcm -2 The voltage-time curve of the lower part.

[0026] Figure 8 Li / In prepared in Example 1 of the present invention 2 O 3 @LATP / LFP full battery rate performance (A) and long cycle performance (B).

[0027] Fig. 9 Li / In prepared in Example 1 of the present invention 2 O 3 @LATP / LMNO full battery rate performance (A) and long cycle performance (B).

[0028] Fig.10 This is the EIS impedance spectrum of the Li / LATP / Li symmetric battery prepared in Comparative Example 1 of the present invention before cycling.

[0029] Fig.11 CCD curve (A) of the Li / LATP / Li symmetric battery prepared in Comparative Example 1 of the present invention and the CCD curve (A) at 0.1 mA cm -2 / 0.1 mAh cm -2 The voltage-time curve of (B).

[0030] Fig.12 The rate performance (A) and long cycle performance (B) of the Li / LATP / LFP full battery prepared in Comparative Example 1 of the present invention.

[0031] Fig.13 Li / Al prepared in Example 2 of the present invention 2 O 3 @LATP / Li symmetric cell at 0.1 mA cm -2 / 0.1 mAhcm -2 The voltage-time curve of the lower part.

[0032] Fig.14 The Li / MgO@LATP / Li symmetric battery prepared in Example 3 of the present invention has a -2 / 0.1 mAhcm -2 The voltage-time curve of the lower part.

[0033] Fig.15 The Li / ZnO@LATP / Li symmetric battery prepared in Example 4 of the present invention has a -2 / 0.1 mAhcm -2 The voltage-time curve of the lower part. DETAILED DESCRIPTION

[0034] The present invention is described in detail below in conjunction with specific embodiments. The present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention. The experimental methods in the following embodiments are conventional methods unless otherwise specified. The test materials used in the following embodiments are all commercially available products. Unless otherwise specified, the reagents are assumed to be directly purchased.

[0035] Example 1 Li was prepared by solid phase sintering 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) solid electrolyte. 2 CO 3 (99%, Aladdin), Al 2 O 3 (99.99%, Aladdin), TiO 2 (99.8%, Aladdin) and NH 4 H 2 PO 4 (99%, MacLean) was weighed into the ball mill according to the stoichiometric ratio, and more than 10 wt% of Li 2 CO 3 To compensate for the loss of lithium during sintering. Zirconia ball milling beads of different sizes were placed in a jar, with a mass ratio of ball milling beads to raw materials of 10:1, and anhydrous ethanol was poured in as a dispersion liquid. A planetary ball mill was used to grind at 400 rpm for 9 h, and the slurry was taken out and dried in an oven at 80 °C for 8 h. The resulting powder was then placed in a crucible, heated to 900 °C in a muffle furnace at a heating rate of 2 °C / min, and calcined for 2 h. In order to reduce the particle size, the powder after the first calcination was ball milled again at 400 rpm for 9 h. The dried powder was sieved through a 500-mesh sieve, and 0.25 g of the powder was weighed and thoroughly mixed with 40 µL of a 5 wt% polyvinyl alcohol (PVA) aqueous solution, poured into a 10 mm steel mold, and pressed at a pressure of 8 MPa for 10 min to obtain a LATP embryo. The pressed LATP green body was placed in a porcelain boat and covered with mother powder, and sintered at 850 °C for 4 h in a muffle furnace with a heating rate of 2 °C / min to finally obtain a dense LATP solid electrolyte.

[0036] 50 mM InCl 3 (99.9%, Aladdin) and 3 mL (50 mg mL -1 ) polyacrylic acid PAA (1.8 K, Aladdin) was dissolved in isopropanol to form a colorless precursor solution. 6 µL (0.15 g cm -2 ) solution was applied to the surface of LATP solid electrolyte by spin coating three times at a speed of 2000 rpm for 30 s. After drying one side, the same process was repeated to modify the other side of LATP. 3 +PAA@LATP was transferred to a tube furnace and sintered at 650 °C for 2 h with a heating rate of 2 °C / min to obtain In 2 O 3@LATP solid electrolyte.

[0037] Figure 1 For LATP solid electrolyte (A), InCl 3 +PAA@LATP(B)and In 2 O 3 Surface SEM image of @LATP (C) (scale bar is 10 μm). It can be seen that the surface of the original LATP solid electrolyte presents stacked cubic particles and identifiable grain boundaries. After the introduction of the polymer network, PAA+InCl 3 @LATP surface is very flat, without pores and cracks. In after sintering 2 O 3 @LATP has a dense coating on the surface, covering the grains and filling the grain boundaries.

[0038] Figure 2 For the LATP (A) and In 2 O 3 @LATP (B) XRD diagram, it can be seen that In 2 O 3 The XRD of @LATP pellets has a good correspondence with the original LATP, indicating that no impurities are formed during the sintering process. 2 O 3 (PDF#060416) has a strong diffraction peak, indicating that InCl 3 Successfully converted to In 2 O 3 .

[0039] Figure 3 For the In 2 O 3 High-resolution XPS images of In 3d and O1s before and after the reaction of @LATP with metallic lithium. The results confirm that In 2 O 3 In situ conversion to Li x In alloy and Li 2 In the In 3d XPS spectrum (A), the transitions of the In 3d XPS peaks from 451.3 and 443.8 eV to lower binding energies 449.9 and 442.5 eV can be clearly detected, proving that Li x In alloy formation. In the O1s XPS spectrum (B), the O 1s XPS peak at 530.3 eV shifted to 530.9 eV after the reaction, which is consistent with the Li 2 O matches. Li generated by in-situ reaction 2 O / Li x In interface can greatly improve the stability of the interface.

[0040] Electrochemical performance test: To assemble a symmetrical cell, lithium foil was used as electrode, In 2 O 3 @LATP is used as electrolyte. The positive electrode material LiFePO 4 or Li 1.2 Mn 0.6 Ni 0.2 O 2 (LFP or LMNO), conductive additive (Super P) and binder (PVDF) were dispersed in n-methylpyrrolidone (NMP) in a weight ratio of 8:1:1. The resulting slurry was coated on aluminum foil with an active material loading of 1.2 to 1.5 mg cm -2 . Place it in a vacuum oven at 110 °C for 12 h. Punch holes into small circles on the dried coated aluminum foil. Use LFP or LMNO and Li foil as the negative and positive electrodes, respectively, and In 2 O 3 @LATP is used as electrolyte. In order to ensure Li + For good transport at the LFP / LATP or LMNO / LATP interface, 4 μL of electrolyte (1 M LiPF 6 Finally, the cells were assembled in an Ar-filled glove box (MIKROUNA, Super 1220 / 750, H 2 O≤1ppm, O 2 ≤1 ppm).

[0041] The ionic conductivity and interfacial impedance of the symmetrical cells and full cells were measured using the AC impedance technique (CHI614C electrochemical workstation) in the range of 1 MHz to 1 Hz with an amplitude of 0.01 V. The symmetrical cells were subjected to constant current charge and discharge tests with each cycle lasting 2 h. The critical current density (CCD) of the symmetrical cells was measured in time constant mode, and the areal capacity of lithium plating or stripping gradually increased under a fixed cycle period (1 h per half cycle). At 2.4-4.2 V (LFP, 1 C =170 mAh g -1 ) and 2.4-4.8 V (LMNO, 1 C =200 mAh g -1 The cells were charged and discharged at different current rates (0.1, 0.2, 0.5, 1.0, and 2.0 C) over a potential range of 2.5 Å. All electrochemical measurements were performed at 25 °C.

[0042] like Figure 4 As shown, before the cycle, Li / In 2 O 3In the EIS impedance spectrum of the @LATP / Li symmetric battery, the initial interface resistance is 106.5 Ω cm -2 .like Figure 5 As shown, in Li / In 2 O 3 In the critical current density (CCD) test of @LATP / Li symmetric battery, its CCD can reach 1.9 mA cm -2 .like Figure 6 As shown, Li / In 2 O 3 @LATP / Li symmetric cell at 0.1 mA cm -2 / 0.1 mAhcm -2 Under the condition of , it can stably cycle for more than 3900 h, and the polarization voltage is stable at about 24 mV. Figure 7 As shown, at 0.2 mAcm -2 / 0.2 mAh cm -2 Under the condition of Li / In 2 O 3 @LATP / Li symmetric battery can maintain a polarization voltage of 38 mV and stably cycle for more than 3700 h. The corresponding voltage platform is relatively flat and the ion transfer kinetics is excellent.

[0043] Further testing of the In 2 O 3 @LATP solid electrolyte assembled Li / LFP and Li / LMNO full battery rate cycling performance and cycle stability. Figure 8 As shown, Li / In 2 O 3 The @LATP / LFP full cell exhibits excellent rate capability and stable long-cycle performance, with discharge capacities of 164.1, 155.9, 140.4, 124.1, and 100.4 mAh g at 0.1, 0.2, 0.5, 1, and 2 C, respectively. -1 , the initial capacity at 0.8 C is 129.4 mAh g -1 After 600 cycles, the capacity retention rate reaches 91.3%. Fig. 9 As shown, Li / In 2 O 3 @LATP / LMNO full cell capacity remains at 210 mAh g after 200 cycles at 0.2 C -1 , almost no attenuation. 2 O 3 @LATP also has good adaptability to high-voltage LMNO cathodes, with high energy density and good cycle stability.

[0044] Embodiment 2: The process of preparing LATP solid electrolyte by solid phase sintering method is the same as that in Example 1.

[0045] 50 mM InCl 3 (99.9%, Aladdin) and 3 mL (50 mg mL -1 ) polyacrylic acid PAA (1.8 K, Aladdin) was dissolved in isopropanol to form a colorless precursor solution. 2 µL (0.05 g cm -2 ) solution was applied to the surface of LATP solid electrolyte by spin coating three times at a speed of 2000 rpm for 30 s. After drying one side, the same process was repeated to modify the other side of LATP. 3 +PAA@LATP was transferred to a tube furnace and sintered at 650 °C for 2 h with a heating rate of 2 °C / min to obtain 2-In 2 O 3 @LATP solid electrolyte.

[0046] Electrochemical performance test: To assemble a symmetrical cell, lithium foil was used as the electrode, 2-In 2 O 3 @LATP was used as the electrolyte. The interfacial impedance of the symmetrical cell was measured using the AC impedance technique (CHI614C electrochemical workstation) in the range of 1 MHz to 1 Hz with an amplitude of 0.01 V. The critical current density (CCD) of the symmetrical cell was measured in the time constant mode, and the area capacity of lithium plating or stripping gradually increased under a fixed cycle period (1 h per half cycle). Li / 2-In 2 O 3 The initial interfacial impedance of the LATP / Li symmetric cell is 187.4 Ω cm -2 , CCD is 1.4 mAh cm -2 .

[0047] Embodiment 3: The process of preparing LATP solid electrolyte by solid phase sintering method is the same as that in Example 1.

[0048] 50 mM InCl 3 (99.9%, Aladdin) and 3 mL (50 mg mL -1 ) polyacrylic acid PAA (1.8 K, Aladdin) was dissolved in isopropanol to form a colorless precursor solution. 4 µL (0.1 g cm -2) solution was applied to the surface of LATP solid electrolyte by spin coating three times at a speed of 2000 rpm for 30 s. After drying one side, the same process was repeated to modify the other side of LATP. 3 +PAA@LATP was transferred to a tube furnace and sintered at 650 °C for 2 h with a heating rate of 2 °C / min to obtain 4-In 2 O 3 @LATP solid electrolyte.

[0049] Electrochemical performance test: To assemble a symmetrical cell, lithium foil was used as electrode, 4-In 2 O 3 @LATP was used as the electrolyte. The interfacial impedance of the symmetrical cell was measured using the AC impedance technique (CHI614C electrochemical workstation) in the range of 1 MHz to 1 Hz with an amplitude of 0.01 V. The critical current density (CCD) of the symmetrical cell was measured in the time constant mode, and the area capacity of lithium plating or stripping gradually increased under a fixed cycle period (1 h per half cycle). Li / 4-In 2 O 3 The initial interfacial impedance of the LATP / Li symmetric cell is 134.4 Ω cm -2 , CCD is 1.8 mAh cm -2 .

[0050] Embodiment 4: The process of preparing LATP solid electrolyte by solid phase sintering method is the same as that in Example 1.

[0051] 50 mM InCl 3 (99.9%, Aladdin) and 3 mL (50 mg mL -1 ) polyacrylic acid PAA (1.8 K, Aladdin) was dissolved in isopropanol to form a colorless precursor solution. 8 µL (0.2 g cm -2 ) solution was applied to the surface of LATP solid electrolyte by spin coating three times at a speed of 2000 rpm for 30 s. After drying one side, the same process was repeated to modify the other side of LATP. 3 +PAA@LATP was transferred to a tube furnace and sintered at 650 °C for 2 h with a heating rate of 2 °C / min to obtain 8-In 2 O 3 @LATP solid electrolyte.

[0052] Electrochemical performance test: To assemble the symmetrical cell, lithium foil was used as electrode, 8-In2 O 3 @LATP was used as the electrolyte. The interfacial impedance of the symmetrical cell was measured using the AC impedance technique (CHI614C electrochemical workstation) in the range of 1 MHz to 1 Hz with an amplitude of 0.01 V. The critical current density (CCD) of the symmetrical cell was measured in the time constant mode, and the area capacity of lithium plating or stripping gradually increased under a fixed cycle period (1 h per half cycle). Li / 8-In 2 O 3 The initial interfacial impedance of the LATP / Li symmetric cell is 141.1 Ω cm -2 , CCD is 1.6 mAh cm -2 .

[0053] Examples 2, 3 and 4 demonstrate that Li 2 O / Li x In layer can improve the battery performance. When the same process is used, if different amounts of precursor solution are used to spin coat the LATP solid electrolyte, the Li / In layer in Example 1 of the present invention cannot be achieved. 2 O 3 @LATP / Li symmetric battery has excellent electrochemical performance. It proves that the Li 2 O / Li x The In layer is the most appropriate. A proper interface layer can ensure good interface physical contact without affecting its own strength and ability to inhibit dendrites, and can also provide an efficient interface ion transmission channel. This can achieve a smaller interface impedance and a higher critical current density. 2 O / Li x The In layer comprehensively improves the chemical / electrochemical stability of the Li / LATP interface.

[0054] Comparative Example 1: The process of preparing LATP solid electrolyte by solid phase sintering method is the same as that in Example 1.

[0055] Electrochemical performance test: To assemble a symmetrical cell, lithium foil was used as the electrode and LATP was used as the electrolyte. 4 or Li 1.2 Mn 0.6 Ni 0.2 O 2 (LFP or LMNO), conductive additive (Super P) and binder (PVDF) were dispersed in n-methylpyrrolidone (NMP) in a weight ratio of 8:1:1. The resulting slurry was coated on aluminum foil with an active material loading of 1.2 to 1.5 mg cm-2 . Place it in a vacuum oven at 110 °C for 12 h. Punch holes into small circles on the dried coated aluminum foil. Use LFP or LMNO and Li foil as the negative electrode and positive electrode, respectively, and LATP as the electrolyte. In order to ensure that Li + For good transport at the LFP / LATP or LMNO / LATP interface, 4 μL of electrolyte (1 M LiPF 6 Finally, the cells were assembled in an Ar-filled glove box (MIKROUNA, Super 1220 / 750, H 2 O≤1 ppm, O 2 ≤1ppm).

[0056] The ionic conductivity and interfacial impedance of the symmetrical cells and full cells were measured using the AC impedance technique (CHI614C electrochemical workstation) in the range of 1 MHz to 1 Hz with an amplitude of 0.01 V. The symmetrical cells were subjected to constant current charge and discharge tests with each cycle lasting 2 h. The critical current density (CCD) of the symmetrical cells was measured in time constant mode, and the areal capacity of lithium plating or stripping gradually increased under a fixed cycle period (1 h per half cycle). At 2.4-4.2 V (LFP, 1 C =170 mAh g -1 ) and 2.4-4.8 V (LMNO, 1 C =200 mAh g -1 The cells were charged and discharged at different current rates (0.1, 0.2, 0.5, 1.0, and 2.0 C) over a potential range of 2.5 Å. All electrochemical measurements were performed at 25 °C.

[0057] like Fig.10 As shown in the EIS impedance spectrum of the Li / LATP / Li symmetric battery before cycling, its initial interface resistance is very large, 1211.4 Ω cm -2 .like Fig.11 As shown in the critical current density test of Li / LATP / Li symmetric battery, its CCD is only 0.1 mA cm -2 (A). At 0.1 mA cm -2 / 0.1 mAh cm -2 Under the condition of ionization, the polarization voltage of the Li / LATP / Li symmetric battery gradually increased during the cycle and failed after 145 h (B). The poor compatibility of the LATP / Li interface led to continuous spontaneous side reactions and crack evolution.

[0058] The rate cycling performance and cycle stability of Li / LFP and Li / LMNO full batteries assembled with the LATP solid electrolyte were further tested. Fig.12 As shown in Figure 2, the rate capability and long cycle performance of the Li / LATP / LFP full cell are poor, with the discharge capacities at 0.1, 0.2, 0.5, 1, and 2 C being 151.4, 138.9, 115.2, 84.1, and 29.2 mAh g, respectively. -1 (A) The initial discharge capacity of the Li / LATP / LFP full cell at 0.8 C is 100.6 mAh g -1 , after 110 cycles, the capacity retention rate is only 33.2% (B).

[0059] Comparative Example 1 proves that when the LATP solid electrolyte has no indium oxide modification layer, the problems of loose contact with metallic lithium, severe side reactions, and poor interfacial ion transfer efficiency are very serious. In the present invention, the indium oxide layer is electrochemically reacted with metallic lithium in situ to form a Li 2 O / Li x In has an interface with fast ion transfer and electron blocking functions. 2 O has a low migration energy barrier and excellent electronic insulation properties, which can ensure the rapid transmission of ions at the interface, isolate side reactions and inhibit dendrite growth at the interface. x In has a high affinity for both metallic lithium and LATP, significantly enhancing the contact between LATP and Li metal. As a result, the electrochemical performance of symmetric cells and full cells is greatly improved.

[0060] Comparative Example 2: The process of preparing LATP solid electrolyte by solid phase sintering method is the same as that in Example 1.

[0061] 50 mM Al(NO 3 ) 3 (99.9%, Aladdin) and 3 mL (50 mg mL -1 ) polyacrylic acid PAA (1.8 K, Aladdin) was dissolved in isopropanol to form a colorless precursor solution. 6 µL (0.15 g cm -2 ) solution was applied to the surface of LATP solid electrolyte by spin coating three times at a speed of 2000 rpm for 30 s. After drying one side, the same process was repeated to modify the other side of LATP. 3 ) 3 +PAA@LATP was transferred to a tube furnace and sintered at 650 °C for 2 h with a heating rate of 2 °C / min. Finally, Al 2 O 3 @LATP solid electrolyte.

[0062] Electrochemical performance test: To assemble a symmetrical cell, lithium foil was used as the electrode, Al 2 O 3 @LATP was used as the electrolyte. The symmetrical battery was subjected to constant current charge and discharge tests, with each cycle lasting 2 h. Fig.13 As shown, Li / Al 2 O 3 @LATP / Li symmetric cell at 0.1 mA cm -2 / 0.1 mAh cm -2 Under the conditions of , it can stably cycle for more than 800 h, and the polarization voltage is stable at around 31 mV.

[0063] Comparative Example 3: The process of preparing LATP solid electrolyte by solid phase sintering method is the same as that in Example 1.

[0064] 50 mM Mg(CH 3 COO 2 (99.9%, Aladdin) and 3 mL (50 mg mL -1 ) polyacrylic acid PAA (1.8 K, Aladdin) was dissolved in isopropanol to form a colorless precursor solution. 6 µL (0.15 g cm -2 ) solution was applied to the surface of LATP solid electrolyte by spin coating three times at a speed of 2000 rpm for 30 s. After drying one side, the same process was repeated to modify the other side of LATP. Then Mg(CH 3 COO 2 +PAA@LATP was transferred to a tubular furnace and sintered at 650 °C for 2 h with a heating rate of 2 °C / min to obtain MgO@LATP solid electrolyte.

[0065] Electrochemical performance test: To assemble the symmetrical battery, lithium foil was used as the electrode and MgO@LATP was used as the electrolyte. The symmetrical battery was subjected to constant current charge and discharge tests, with each cycle lasting 2 h. Fig.14 As shown in the figure, the Li / MgO@LATP / Li symmetric battery has a -2 / 0.1 mAh cm -2 Under the conditions of , it can stably cycle for more than 750 h, and the polarization voltage is stable at about 32 mV.

[0066] Comparative Example 4: The process of preparing LATP solid electrolyte by solid phase sintering method is the same as that in Example 1.

[0067] 50 mM Zn(NO 3 ) 2(99.9%, Aladdin) and 3 mL (50 mg mL -1 ) polyacrylic acid PAA (1.8 K, Aladdin) was dissolved in isopropanol to form a colorless precursor solution. 6 µL (0.15 g cm -2 ) solution was applied to the surface of LATP solid electrolyte by spin coating three times at a speed of 2000 rpm for 30 s. After drying one side, the same process was repeated to modify the other side of LATP. 3 ) 2 +PAA@LATP was transferred to a tubular furnace and sintered at 650 °C for 2 h with a heating rate of 2 °C / min to finally obtain ZnO@LATP solid electrolyte.

[0068] Electrochemical performance test: To assemble the symmetrical battery, lithium foil was used as the electrode and ZnO@LATP as the electrolyte. The symmetrical battery was subjected to constant current charge and discharge tests, with each cycle lasting 2 h. Fig.15 As shown in the figure, the Li / ZnO@LATP / Li symmetric battery has a -2 / 0.1 mAh cm -2 Under the conditions of , it can stably cycle for more than 630 h, and the polarization voltage is stable at around 67 mV.

[0069] Through the above comparative examples, it can be concluded that: the Li metal battery with super lithium affinity and fast ion transport provided by the present invention for solid-state lithium metal batteries 2 O / Li x The preparation method of In interface can effectively improve the stability and compatibility of Li / LATP interface, so that solid-state lithium metal batteries have excellent rate performance and cycle stability. In particular, this method is effective for other common metal oxides, all of which form Li 2 O and different alloys to achieve stable interlayer. In addition, the cost of interface modification is low, simple and controllable, and the operability is strong. The product performance is stable and highly reproducible. The super-lithiophilic and fast ion transport Li prepared by the present invention 2 O / Li x In interface modification strategy has good application prospects.

[0070] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A solid electrolyte, characterized in that The solid electrolyte includes an interface layer, and the interface layer is Li x In alloy and Li2O, i.e. Li2O / Li x In interface, the Li2O / Li x The In interface is grown in situ on the surface of the solid electrolyte.

2. The solid electrolyte according to claim 1, characterized in that The solid electrolyte includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li7La3Zr2O 12 , Li 0.5 La 0.5 Any one of TiO3.

3. The solid-state battery electrolyte according to claim 2, characterized in that: The solid electrolyte surface is impregnated or coated with a polymer solution containing InCl3 and then sintered at 600℃~700℃ to obtain a Li2O / Li x In solid electrolyte at the interface.

4. The solid-state battery electrolyte according to claim 2, characterized in that: The polymer solution includes any one of polyacrylic acid, polyvinyl pyrrolidone, polyphenolic resin, polyvinyl alcohol, polyethylene glycol and polyacrylamide.

5. A method for preparing a solid electrolyte, characterized in that: The steps include: Step 1: Dissolve InCl3 and polymer in isopropanol to form a colorless solution; Step 2: Apply the above solution dropwise on the surface of the solid electrolyte and spin coat evenly; Step 3: Sintering the solid electrolyte in step 2 to obtain a solid electrolyte containing an In2O3 layer; Step 4: The solid electrolyte containing the In2O3 layer in step 3 is reacted with molten lithium to obtain a Li2O / Li x In solid electrolyte at the interface.

6. The method for preparing a solid electrolyte according to claim 5, characterized in that: The amount of InCl3 is 30-50mM; the polymer solution includes any one of polyacrylic acid, polyvinyl pyrrolidone, polyphenolic resin, polyvinyl alcohol, polyethylene glycol, and polyacrylamide; the mass ratio of InCl3 to polymer is 1:1-5.

7. The method for preparing a solid electrolyte according to claim 5, characterized in that: The amount of solution dropped on the surface of the solid electrolyte is 0.05-0.2 g cm -2 .

8. The method for preparing a solid electrolyte according to claim 7, characterized in that: The solid electrolyte is selected from Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li 1.5 Al 0.5 Ge 1.5 (PO4)3 (LAGP), Li7La3Zr2O 12 LLZO, Li 0.5 La 0.5 TiO3 (LLTO).

9. The method for preparing a solid electrolyte according to claim 7, characterized in that: In the step 1, if InCl3 is replaced by any one of Al(NO3)3, Mg(CH3COO)2, and Zn(NO3)2, a solid electrolyte having an interface structure of Al2O3, MgO, and ZnO is obtained accordingly.

10. A solid-state lithium metal battery, characterized in that: A solid-state battery electrolyte comprising any one of claims 1 to 4 or a solid-state battery electrolyte prepared by the method of any one of claims 5 to 9.

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