A solid-state battery, its preparation method, and its electrical device

Abstract

This invention relates to the field of solid-state battery technology, and in particular to a solid-state battery, its preparation method, and an electrical device thereof. The solid-state battery provided by this invention includes a lithium metal anode, a sulfide solid electrolyte layer, and a cathode material layer stacked sequentially. The lithium metal anode includes a lithium metal layer and an amorphous lithium phosphate layer disposed on the surface of the lithium metal layer. This invention effectively improves the interface problem between the sulfide solid electrolyte and the lithium metal anode by using lithium phosphate to modify the surface of the lithium metal. The surface-modified lithium metal anode can effectively inhibit the reduction of the sulfide solid electrolyte by lithium metal, reduce interface impedance, improve the interface stability between the lithium metal anode and the sulfide solid electrolyte, and reduce phenomena such as lithium dendrite growth and interface deterioration during battery cycling, thereby significantly improving the cycle stability of the all-solid-state lithium metal battery.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and in particular to a solid-state battery, its preparation method, and an electrical device thereof. Background Technology

[0002] The performance of solid electrolytes plays a crucial role in the electrochemical performance of all-solid-state lithium batteries. Sulfide solid electrolytes exhibit high room-temperature ionic conductivity (10⁻⁶ Ω·cm). -4 ~10 -2 S cm -1 It has a wide electrochemical window. At the same time, sulfide solid electrolytes are soft and have excellent mechanical processing properties, and can provide low electrode / electrolyte interface impedance in solid-state lithium batteries, making them the most promising solid electrolytes for all-solid-state lithium batteries.

[0003] In recent years, sulfide solid electrolytes, such as binary and ternary sulfides, have been extensively studied. Sulfide solid electrolytes possess extremely high lithium-ion conductivity, meeting the ionic conductivity requirements of all-solid-state lithium batteries. However, the unstable interfacial reaction between sulfide solid electrolytes and lithium metal is a key factor limiting their application. The reduction products of sulfide solid electrolytes and lithium form an unstable interfacial phase. This phase has low ionic conductivity and high electronic conductivity, which not only increases interfacial impedance but also causes interfacial volume expansion, leading to stress and cracks within the electrolyte and easily resulting in the formation and diffusion of lithium dendrites.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The primary objective of this invention is to provide a solid-state battery that effectively improves the interface problem between the sulfide solid electrolyte layer and the lithium metal anode. The surface-modified lithium metal anode can effectively suppress the reduction of the sulfide solid electrolyte by lithium metal, reduce the interface impedance, and improve the cycle stability of the solid-state battery.

[0006] The second objective of this invention is to provide a method for preparing a solid-state battery as described above, which improves the interfacial stability between the lithium metal anode and the sulfide solid electrolyte layer by surface modification of the lithium metal anode, thereby improving the solid-solid interface contact problem between the two.

[0007] A third objective of this invention is to provide an electrical device.

[0008] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted:

[0009] The present invention provides a solid-state battery, comprising a lithium metal anode, a sulfide solid electrolyte layer and a positive electrode material layer stacked sequentially; the lithium metal anode includes a lithium metal layer and an amorphous lithium phosphate layer disposed on the surface of the lithium metal layer.

[0010] Furthermore, the thickness of the amorphous lithium phosphate layer is 0.2–1 μm.

[0011] Furthermore, the roughness of the amorphous lithium phosphate layer is less than or equal to 0.8 nm.

[0012] Furthermore, the ionic conductivity of the amorphous lithium phosphate layer is 1*10⁻⁶. -6 S / cm~9*10 -6 S / cm.

[0013] Furthermore, the roughness D2 of the sulfide solid electrolyte layer is 100 nm to 820 nm.

[0014] Furthermore, the roughness D1 of the amorphous lithium phosphate layer and the roughness D2 of the sulfide solid electrolyte layer satisfy: 300≤D2 / D1≤2700.

[0015] Furthermore, the amorphous lithium phosphate layer contains amorphous lithium phosphate but does not contain lithium phosphorus oxy nitrogen.

[0016] Furthermore, the sulfide solid electrolyte layer includes Li 10 GeP2S 12 Li6PS5Cl, β-Li3PS4 and Li7P3S 11 At least one of them.

[0017] The present invention also provides a method for preparing a solid-state battery as described above, comprising the following steps:

[0018] An amorphous lithium phosphate layer is deposited on the surface of a lithium metal foil using radio frequency magnetron sputtering to obtain a lithium metal anode; the lithium metal anode, a sulfide solid electrolyte, and a cathode material are stacked sequentially and then pressed to obtain the solid-state battery.

[0019] Furthermore, the sputtering target used in the radio frequency magnetron sputtering is a crystalline Li3PO4 ceramic target, and the sputtering gas is argon.

[0020] Furthermore, the RF magnetron sputtering has a sputtering power of 100–200 W, a substrate temperature of 25–300 °C, a target-substrate distance of 6–10 cm, and a sputtering gas pressure of 0.5–2 Pa.

[0021] Furthermore, the deposition time is 1 to 5 hours.

[0022] The present invention also provides an electrical device comprising a solid-state battery as described above.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The solid-state battery of the present invention effectively improves the interface problem between the sulfide solid electrolyte layer and the lithium metal anode by using amorphous lithium phosphate to modify the surface of the lithium metal anode. The surface-modified lithium metal anode can effectively suppress the reduction of the sulfide solid electrolyte by lithium metal, has a smaller interface impedance, and excellent interface stability, thereby enabling the all-solid-state lithium metal battery to have excellent cycle stability.

[0025] The interface modification layer between the lithium metal and the sulfide solid electrolyte layer in the lithium metal anode of the present invention, namely the amorphous lithium phosphate layer, has excellent lithium-ion conduction and electronic insulation properties. It can effectively suppress the reduction reaction between the sulfide solid electrolyte and lithium metal, reduce the interface impedance, and improve the interface stability. It can avoid phenomena such as lithium dendrite growth and interface deterioration during battery cycling, and significantly improve the stable cycling of all-solid-state lithium metal batteries. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the solid-state battery structure of the present invention.

[0028] Figure 2 The lithium metal anode and Li in Example 3 of this invention 10 GeP2S 12 EIS spectrum of a symmetric cell composed of a solid electrolyte.

[0029] Figure 3 The lithium metal anode and Li in Example 3 of this invention 10 GeP2S 12 Constant current cycling curve of a symmetrical battery composed of a solid electrolyte.

[0030] Figure 4 The lithium metal anode and Li in Comparative Example 1 of this invention 10 GeP2S 12 EIS spectrum of a symmetric cell composed of a solid electrolyte.

[0031] Figure 5The lithium metal anode and Li in Comparative Example 1 of this invention 10 GeP2S 12 Constant current cycling curve of a symmetrical battery composed of a solid electrolyte.

[0032] Explanation of reference numerals in the attached figures

[0033] 1-Lithium metal layer; 2-Amorphous lithium phosphate layer; 3-Sulfide solid electrolyte layer; 4-Positive electrode material layer. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0035] The following is a detailed description of a solid-state battery, its preparation method, and its electrical device according to an embodiment of the present invention.

[0036] See Figure 1 In some embodiments of the present invention, a solid-state battery is provided, comprising a lithium metal anode, a sulfide solid electrolyte layer 3 and a positive electrode material layer 4 stacked sequentially; the lithium metal anode includes a lithium metal layer 1 and an amorphous lithium phosphate layer 2 disposed on the surface of the lithium metal layer.

[0037] The solid-state battery of the present invention obtains a lithium metal anode by surface modification of lithium metal with amorphous lithium phosphate. The interface modification layer between the lithium metal layer 1 and the sulfide solid electrolyte layer 3 in the lithium metal anode, namely the amorphous lithium phosphate layer 2, has excellent lithium-ion conduction and electronic insulation properties. It can not only ensure the effective transport of lithium ions between the sulfide solid electrolyte 3 and the lithium metal anode, but also effectively suppress the reduction reaction between the sulfide solid electrolyte 3 and the lithium metal, reduce the interface impedance, avoid lithium dendrite growth and interface deterioration during battery cycling, improve the interface stability between the lithium metal anode and the sulfide solid electrolyte 3, improve the solid-solid interface contact problem between the two, and improve the cycle stability of the solid-state battery.

[0038] The solid-state battery of the present invention is an all-solid-state lithium metal battery. By modifying the surface of lithium metal with amorphous lithium phosphate, not only is the interface problem between the sulfide solid electrolyte layer 3 and the lithium metal anode improved and the interface stability is enhanced, but the original electrochemical performance of the surface-modified lithium metal anode is not affected, resulting in excellent high energy density.

[0039] It should be noted that the amorphous lithium phosphate layer can be tested using the following methods: X-ray diffraction (XRD) was used to characterize the microstructure of the prepared lithium phosphate film. The absence of obvious crystal peaks indicates that the lithium phosphate film obtained by magnetron sputtering deposition has an amorphous structure. Further characterization of the microstructure of the lithium phosphate film using scanning electron microscopy (SEM-EDS) revealed a dense surface and uniform distribution of Li, P, and O elements, indicating that the film contains lithium phosphate.

[0040] In some embodiments of the present invention, the thickness of the amorphous lithium phosphate layer 2 is 0.2 to 1 μm; typically, but not limitingly, for example, the thickness of the amorphous lithium phosphate layer 2 is 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm, etc.; preferably, the thickness of the amorphous lithium phosphate layer 2 is 0.6 to 0.8 μm.

[0041] The thinness of the amorphous lithium phosphate layer 2 in this invention leads to incomplete coverage of metallic lithium, and the thinner modification layer cannot suppress the violent side reactions between the sulfide solid electrolyte 3 and metallic lithium. If the thickness of the amorphous lithium phosphate layer 2 is too thick, it will reduce the ionic conductivity of the amorphous lithium phosphate film, affect the lithium-ion transport between the sulfide solid electrolyte 3 and the metallic lithium anode, thereby introducing additional interfacial impedance and accelerating battery cycle failure.

[0042] In some embodiments of the present invention, the roughness of the amorphous lithium phosphate layer 2 is less than or equal to 0.8 nm. Typically, but not limitingly, for example, the roughness of the amorphous lithium phosphate layer 2 is 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, or a range consisting of any two of the above values.

[0043] In some embodiments of the present invention, the ionic conductivity of the amorphous lithium phosphate layer 2 is 1*10⁻⁶. -6 S / cm~9*10 -6 S / cm. Typical, but not limiting, for example, the ionic conductivity of amorphous lithium phosphate layer 2 is 1*10⁻⁶. -6 S / cm, 3*10 -6 S / cm, 5*10 -6 S / cm, 6*10-6 S / cm, 8*10 -6 S / cm, 9*10 -6 S / cm or a range consisting of any two of the above values.

[0044] In some embodiments of the present invention, the roughness D2 of the sulfide solid electrolyte layer 3 is 100 nm to 800 nm. Typically, but not limitingly, the roughness D2 of the sulfide solid electrolyte layer 3 is 100 nm, 200 nm, 300 nm, 550 nm, 700 nm, 750 nm, 800 nm, or a range consisting of any two of the above values.

[0045] In some embodiments of the present invention, the roughness D1 of the amorphous lithium phosphate layer 2 and the roughness D2 of the sulfide solid electrolyte layer 3 satisfy: 300 ≤ D2 / D1 ≤ 2700. Typically, but not limitingly, D2 / D1 is, for example, 300, 500, 800, 1000, 1500, 1800, 2000, 2300, 2700, or a range consisting of any two of the above values.

[0046] In some embodiments of the present invention, the roughness of the amorphous lithium phosphate layer 2 and the sulfide solid electrolyte layer 3 is measured by AFM (atomic force microscopy).

[0047] The smaller roughness of the amorphous lithium phosphate layer 2 is conducive to dense contact between the sulfide solid electrolyte layer 3 and the lithium metal anode, effectively reducing interfacial impedance. If the roughness is larger, it is not conducive to interfacial contact between the sulfide solid electrolyte layer 3 and the lithium metal, significantly increasing the interfacial impedance.

[0048] In some embodiments of the present invention, the amorphous lithium phosphate layer 2 contains amorphous lithium phosphate but does not contain lithium phosphorus oxy nitrogen.

[0049] In some embodiments of the present invention, the sulfide solid electrolyte layer 3 includes Li 10 GeP2S 12 Li6PS5Cl, β-Li3PS4 and Li7P3S 11 At least one of them.

[0050] The sulfide solid electrolyte layer 3 is mainly composed of Li 10 Ge2PS 12 (LGPS), sulfo-silver-germanium minerals Li6PS5Cl, β-Li3PS4 and Li7P3S 11 Mainly; Li 10 Ge2PS 12 (LGPS), Li6PS5Cl, β-Li3PS4 and Li7P3S 11Sulfide solid electrolyte powder is characterized by its soft texture, ease of molding, and excellent machinability. When the powder is in contact with lithium metal under certain pressure, good interfacial contact can be achieved, which can meet the requirements of solid electrolytes in all-solid-state lithium batteries. However, the interfacial stability between the aforementioned sulfide solid electrolyte 3 and lithium metal is poor, which can easily lead to problems such as low ionic conductivity, high electronic conductivity, large interfacial impedance, and the formation of lithium dendrites. This invention improves the interfacial problem between the aforementioned sulfide solid electrolyte 3 and lithium metal by using an amorphous lithium phosphate film to modify the surface of the lithium metal anode.

[0051] In some specific embodiments of the present invention, the sulfide solid electrolyte layer 3 includes Li 10 GeP2S 12 Li 10 GeP2S 12 The preparation method includes the following steps: ball milling and sieving a mixture of lithium sulfide, germanium sulfide, and phosphorus pentasulfide to obtain a uniformly sized mixed raw material powder; calcining the mixed raw material powder in an argon atmosphere and sieving to obtain Li 10 GeP2S 12 Solid electrolyte powder. Preferably, the molar ratio of lithium sulfide, germanium sulfide and phosphorus pentasulfide is 4-6:0.8-1.2:0.8-1.2.

[0052] In some specific embodiments of the present invention, Li 10 GeP2S 12 In the preparation method, the ball milling speed is 150-200 rpm / min, and the ball milling time is 2-5 h. Sieving includes using a 200-400 mesh sieve. Calcination includes heating to 500-650℃ and holding for 4-6 h; preferably, the heating rate is 5-10℃ / min.

[0053] The Li of the present invention 10 GeP2S 12 The preparation method is simple and yields Li 10 GeP2S 12 Solid electrolyte powders possess excellent ionic conductivity, chemical stability, and electrochemical stability, and can be used as solid electrolyte materials in all-solid-state lithium metal batteries.

[0054] In some embodiments of the present invention, the positive electrode material layer 4 includes lithium nickel cobalt manganese oxide and a sulfide solid electrolyte.

[0055] In some embodiments of the present invention, the content of nickel is greater than or equal to 0.5, with the sum of the molar amounts of nickel, cobalt and manganese in the lithium nickel cobalt manganese oxide being 1.

[0056] In some embodiments of the present invention, the mass ratio of lithium nickel cobalt manganese oxide to sulfide solid electrolyte is 6-8:2-4.

[0057] In some embodiments of the present invention, a method for preparing the above-mentioned solid-state battery is also provided, comprising the following steps:

[0058] Amorphous lithium phosphate was deposited on the surface of a lithium metal foil using radio frequency magnetron sputtering to obtain a lithium metal anode. The lithium metal anode, sulfide solid electrolyte, and cathode material were stacked sequentially and then pressed to obtain a solid-state battery.

[0059] This invention uses radio frequency magnetron sputtering to deposit an amorphous lithium phosphate layer 2, which has the advantages of uniform deposition and easy thickness control. The resulting amorphous lithium phosphate layer 2 has uniform composition, uniform and dense surface, strong adhesion to the surface of lithium metal foil, and high stability, which is beneficial to improving the performance of lithium metal anode and thus improving the performance of solid-state battery.

[0060] More importantly, lithium phosphate (Li3PO4) material itself has a crystalline structure composed of ordered atomic arrangements, providing electronic insulation, but also exhibiting extremely low lithium-ion conductivity. Lithium phosphate prepared by magnetron sputtering is an isotropic, amorphous structure formed by the accumulation of deposited atoms. Compared to crystalline lithium phosphate materials, amorphous lithium phosphate films exhibit significantly improved lithium-ion conductivity and electronic insulation. Therefore, when placed between a lithium metal layer and a sulfide solid electrolyte, they can significantly improve interface issues and enhance cycle stability.

[0061] The solid-state battery preparation method of the present invention is simple in process, low in production cost, and short in production cycle, making it suitable for large-scale production.

[0062] In some embodiments of the present invention, the sputtering target used in radio frequency magnetron sputtering is a crystalline Li3PO4 ceramic target, and the sputtering gas is argon.

[0063] In some embodiments of the present invention, the sputtering power of radio frequency magnetron sputtering is 100-200W, the substrate temperature is 25-300°C, the target-substrate distance is 6-10cm, and the sputtering pressure is 0.5-2Pa. Typical but not limiting examples include, for instance, the sputtering power of radio frequency magnetron sputtering is 100W, 120W, 140W, 160W, 180W, or 200W, etc.; the substrate temperature is 25°C, 50°C, 100°C, 150°C, 200°C, 250°C, or 300°C, etc.; the target-substrate distance is 6cm, 7cm, 8cm, 9cm, or 10cm, etc.; and the sputtering pressure is 0.5Pa, 1Pa, 1.5Pa, or 2Pa, etc.

[0064] Radio frequency magnetron sputtering is a preparation method that is quite sensitive to preparation conditions. When the conditions of radio frequency magnetron sputtering are changed, such as when the conditions of radio frequency magnetron sputtering are not suitable, the prepared amorphous lithium phosphate layer 2 may have problems such as unevenness or partial exposure of the surface, which will affect the performance of the prepared lithium metal anode. The present invention uses the above-mentioned conditions for radio frequency magnetron sputtering, which can obtain a uniform and dense amorphous lithium phosphate layer 2.

[0065] In some embodiments of the present invention, the deposition time is 1 to 5 hours; typically, but not limitingly, the deposition time is 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours, etc. Different deposition times result in different thicknesses of the amorphous lithium phosphate layer 2. By controlling the deposition time, the present invention can obtain an amorphous lithium phosphate layer 2 of suitable thickness.

[0066] In some specific embodiments of the present invention, the method for preparing a solid-state battery includes the following steps: In a three-segment battery mold, a lithium metal anode is placed at the bottom of the sleeve of the battery mold, and then sulfide solid electrolyte powder is placed in. The surface of the amorphous lithium phosphate layer 2 of the lithium metal anode is in contact with the sulfide solid electrolyte powder. Pressure is applied to form the sulfide solid electrolyte powder and to ensure full contact between the lithium metal anode and the sulfide solid electrolyte 3. Finally, a positive electrode material is placed on top, and pressure is applied to assemble the solid-state battery.

[0067] In some specific embodiments of the present invention, the solid-state battery preparation method applies a pressure of 10 to 40 MPa when assembling the solid-state battery.

[0068] In some embodiments of the present invention, an electrical device is also provided, including the above-described solid-state battery.

[0069] The following describes a solid-state battery, its preparation method, and its electrical device provided by the present invention with reference to specific embodiments.

[0070] Example 1 provides a method for preparing a solid-state battery, comprising the following steps:

[0071] In a three-section battery mold, a lithium metal anode is placed at the bottom of the mold sleeve as the anode, and then Li is placed inside. 10 GeP2S 12 Solid electrolyte powder serves as the electrolyte layer. The surface of the amorphous lithium phosphate layer 2 of the lithium metal anode is in contact with the sulfide solid electrolyte powder. A pressure of 20 MPa is applied to the Li... 10 GeP2S 12 Solid electrolyte powder molding and lithium metal anode with Li 10 GeP2S 12 After the solid electrolyte is in full contact, the positive electrode material (composed of NCM622 and Li) is placed on top. 10GeP2S 12 Electrolyte powders were mixed at a mass ratio of 7:3 and assembled into a solid-state battery under a pressure of 40 MPa. The roughness of the sulfide solid electrolyte was 500 nm.

[0072] The preparation method of the lithium metal anode includes the following steps:

[0073] Using a polished lithium metal foil as a substrate, a crystalline lithium phosphate ceramic target with a purity of 99.99% was used as the sputtering target, and high-purity argon was used as the sputtering gas. An amorphous lithium phosphate layer 2 with a thickness of 0.6 μm and a roughness of 0.3 nm was deposited on the polished lithium metal foil surface using radio frequency magnetron sputtering, thus obtaining a lithium metal anode. The deposition conditions for radio frequency magnetron sputtering were: sputtering power of 200 W, substrate temperature of 50 °C, target-substrate distance of 6 cm, sputtering pressure of 0.5 Pa, and deposition time of 6 h.

[0074] Li 10 GeP2S 12 The preparation method of solid electrolyte powder includes the following steps:

[0075] Lithium sulfide, germanium sulfide, and phosphorus pentasulfide were weighed in a molar ratio of 5:1:1 and added to a polyurethane container containing zirconium dioxide grinding beads. The mixture was ball-milled at 180 rpm for 5 hours. After sieving through a 400-mesh sieve, a uniformly sized raw material powder was obtained. The uniformly mixed raw material powder was then placed in an argon atmosphere Magee furnace for calcination. The calcination conditions were: heating to 500℃ at a rate of 5℃ / min and holding for 6 hours. After sieving through a 400-mesh sieve, Li was obtained. 10 GeP2S 12 Solid electrolyte powder.

[0076] The solid-state battery preparation methods provided in Examples 2 to 5 are the same as those in Example 1, except that the deposition time is adjusted to 4h, 2h, 8h and 10h respectively to obtain amorphous lithium phosphate layers 2 of different thicknesses, as shown in Table 1.

[0077] The solid-state battery preparation methods provided in Examples 6-8 are the same as those in Example 1, except that in the preparation method of the lithium metal anode, the sputtering gas pressure is adjusted to 1 Pa, 1.5 Pa and 2 Pa respectively to obtain amorphous lithium phosphate layers 2 with different roughness, as shown in Table 1.

[0078] The solid-state battery preparation methods provided in Examples 9-12 are the same as those in Example 1, except that the molding pressure of the sulfide solid electrolyte is adjusted to 23 MPa, 25 MPa, 30 MPa and 32 MPa respectively to obtain sulfide solid electrolyte layers with different roughness, as shown in Table 1.

[0079] The solid-state battery preparation methods provided in Examples 13-15 are the same as those in Example 1, except that Li is used. 10 GeP2S 12 The solid electrolyte powders were replaced with Li6PS5Cl, β-Li3PS4, and Li7P3S, respectively. 11 .

[0080] The solid-state battery preparation method provided in Comparative Example 1 is the same as that in Example 1, except that the lithium metal anode is an unmodified lithium metal foil.

[0081] Table 1

[0082]

[0083]

[0084] The method for testing ionic conductivity in Table 1 is as follows: In this experiment, metallic silver (Ag) electrodes were deposited on both sides of the lithium phosphate thin film layer as blocking electrodes (electronic conduction, ionic insulation) to form an Ag / lithium phosphate layer / Ag sandwich structure for testing the ionic conductivity of the lithium phosphate layer. The deposition substrate was a glass plate.

[0085] The specific testing method is as follows: the Ag / lithium phosphate layer / Ag sample is connected to an electrochemical workstation for electrochemical impedance spectroscopy (EIS) testing, with a test frequency range of 1–10 Hz. 6 The frequency is Hz, and the amplitude is 200 Mv. Substituting the AC impedance value of the measured lithium phosphate layer into δ = L / RS, its ionic conductivity can be obtained, where R is the AC impedance value of the lithium phosphate layer, L is the thickness of the lithium phosphate layer, and S is the effective area of ​​the blocking electrode (Ag).

[0086] The lithium metal anodes and Li prepared in Examples 1-15 and Comparative Example 1 were used. 10 GeP2S 12 A symmetrical battery composed of solid electrolyte powder was tested for AC impedance and stability at 25°C. The test results are recorded in Table 2.

[0087] Among them, the lithium metal anode and Li in Example 3 10 GeP2S 12 The EIS spectrum and constant current cycling curve of a symmetric cell composed of a solid electrolyte are shown below. Figure 2 and 3 As shown, the lithium metal anode described in Comparative Example 1 and Li 10 GeP2S 12 The EIS spectrum and constant current cycling curve of a symmetric cell composed of a solid electrolyte are shown below. Figure 4 and Figure 5 As shown.

[0088] Table 2 Performance test results of lithium-symmetric batteries

[0089]

[0090] from Figure 2 and Figure 3 It can be seen that the lithium metal anode and Li prepared in Example 3 are effective. 10 GeP2S 12 The interfacial impedance of a symmetric cell composed of solid electrolyte powder is reduced to 10Ω, and is within 0.05mA / cm. 2 No significant polarization occurred after 300 cycles at a given current density, indicating that the amorphous lithium phosphate layer between the metallic lithium and the sulfide solid electrolyte suppressed the reduction reaction at the interface, ensuring interface stability. Furthermore, from... Figure 4 and Figure 5 It can be seen that the lithium metal anode and Li prepared using Comparative Example 1 are... 10 GeP2S 12 The interfacial impedance of a symmetric battery composed of solid electrolyte powder reaches 240Ω, and is within 0.05mA / cm. 2 The polarization increases sharply after 50 cycles at a current density, indicating that the intense side reactions at the interface caused the polarization to form, leading to an increase in interfacial impedance.

[0091] As can be further seen from Table 1, in Examples 1 to 5, as the thickness of the amorphous lithium phosphate thin film layer 2 gradually increases, the stable cycling current density of the lithium symmetric battery gradually increases, while the increase in interface impedance is not significant. In Example 5, when the thickness of the amorphous lithium phosphate thin film layer 2 is 1 μm, the symmetric battery achieves a current density of 0.15 mA / cm². 2 It can still cycle stably without micro-short circuits even at current densities. This indicates that the appropriate thickness of the amorphous lithium phosphate thin film layer 2 can effectively suppress interfacial side reactions and improve interfacial stability.

[0092] Comparing Examples 1 and 6-8, it can be seen that as the roughness of the amorphous lithium phosphate thin film layer 2 increases, the interfacial impedance gradually increases and the number of stable battery cycles gradually decreases, but it is still better than Comparative Example 1. Furthermore, when the roughness of the amorphous lithium phosphate thin film layer 2 is less than or equal to 0.8 nm, the cycle performance can be further improved.

[0093] Comparative Examples 1 and 9-12 show that by increasing the molding pressure of the sulfide solid electrolyte, the surface roughness of the sulfide solid electrolyte gradually decreases, the internal resistance of the symmetrical battery decreases accordingly, and the cycle performance of the battery is improved.

[0094] As can be seen from Comparative Examples 13-15, conventional sulfide solid electrolytes in the art can all be used in this invention.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solid-state battery, characterized by, The solid-state battery comprises a metal lithium negative electrode, a sulfide solid electrolyte layer and a positive electrode material layer which are sequentially stacked; the metal lithium negative electrode comprises a metal lithium layer and an amorphous lithium phosphate layer arranged on the surface of the metal lithium layer; The thickness of the amorphous lithium phosphate layer is 0.3-1 μm; The roughness D1 of the amorphous lithium phosphate layer is less than or equal to 0.8 nm, the roughness D2 of the sulfide solid electrolyte layer is 100-820 nm, and 300≤D2 / D1≤2700.

2. The solid-state battery of claim 1, wherein, The ion conductivity of the amorphous lithium phosphate layer is 1*10 -6 S / cm~9*10 -6 S / cm.

3. The solid-state battery of claim 1, wherein, The amorphous lithium phosphate layer contains amorphous lithium phosphate and does not contain lithium phosphorus oxygen nitrogen.

4. The solid-state battery of claim 1, wherein, The sulfide solid electrolyte includes Li 10 GeP2S 12 , Li6PS5Cl, β-Li3PS4, and Li7P3S 11 at least one of them.

5. The method of producing a solid-state battery according to any one of claims 1 to 4, characterized by, The method comprises the following steps: An amorphous lithium phosphate layer is deposited on the surface of a metal lithium foil by a radio frequency magnetron sputtering method to obtain a metal lithium negative electrode; the metal lithium negative electrode, a sulfide solid electrolyte and a positive electrode material are sequentially stacked and then pressed to obtain the solid-state battery.

6. The method of producing a solid-state battery according to claim 5, characterized by, The sputtering power of the radio frequency magnetron sputtering is 100-200 W, the substrate temperature is 25-300℃, the target-substrate distance is 6-10 cm, and the sputtering gas pressure is 0.5-2 Pa.

7. The method of producing a solid-state battery according to claim 5, characterized by, The deposition time is 1-5 h.

8. An electric device, characterized by The solid-state battery of any one of claims 1-4.

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