Solid-state electrolyte and preparation method thereof, and all-solid-state battery

Abstract

The application discloses a kind of solid electrolyte and preparation method thereof, full solid battery, belong to electrochemistry technical field, powder is mixed ball milling according to molar ratio Li2S:Li3N=(1.00~2.34):1, obtain sulfide solid electrolyte, its chemical formula is Li (2+x) N x S (1‑x) , and wherein the value range of x is 0.35~0.55.The application adopts Li2S and Li3N powder mixing ball milling for a certain time, i.e.can form new Li-N-S phase, it has good compatibility to lithium metal, can solve the problem that traditional sulfide electrolyte is incompatible with lithium metal negative electrode, can construct high specific energy full solid lithium battery using lithium metal negative electrode;Lithium symmetrical battery can be realized stable cycle, lithium symmetrical battery using the solid electrolyte can be cycled more than 750 times.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and more specifically, to a solid electrolyte and its preparation method, and an all-solid-state battery. Background Technology

[0002] Lithium-ion batteries have garnered increasing attention from the industry due to the rapid expansion of the energy storage sector. However, to meet the energy storage demands of consumer electronics and electric vehicles, lithium-ion batteries still face challenges related to low energy density and safety. Replacing the flammable organic electrolyte in traditional lithium-ion batteries with a solid-state electrolyte to construct all-solid-state batteries promises to improve battery safety and unlock new electrode materials, such as high-capacity lithium metal anodes, which could significantly enhance battery energy density.

[0003] Solid-state electrolytes are the core of all-solid-state batteries. Among various existing solid-state electrolytes, sulfide solid-state electrolytes possess excellent lithium-ion conductivity (1–10 mS / cm) and are considered one of the most promising. However, most sulfide solid-state electrolytes have narrow electrochemical stability windows, particularly lacking compatibility with lithium metal anodes. For example, they are prone to chemical reactions with lithium metal anodes or the growth of lithium dendrites, affecting the introduction of lithium metal into the anode. Therefore, developing solid-state electrolyte materials that are stable against lithium anodes is crucial. Summary of the Invention

[0004] To overcome the problems of narrow electrochemical stability windows, particularly insufficient compatibility with lithium metal anodes, and easy chemical reactions or lithium dendrite growth in existing sulfide solid electrolytes that affect lithium metal anode introduction, this invention provides a solid electrolyte with the chemical formula Li. (2+x) N x S (1-x) The value of x ranges from 0.35 to 0.55. This solid electrolyte has good compatibility with lithium metal and can achieve stable cycling of lithium symmetric batteries. Lithium batteries using this solid electrolyte can cycle more than 750 times.

[0005] Here, the preferred value range for x is 0.48 to 0.52.

[0006] Preferably, its X-ray diffraction pattern (copper target, wavelength) Diffraction peaks exist at positions 2θ = 28.18 ± 0.50°, 32.54 ± 0.50°, 46.97 ± 0.50°, 55.75 ± 0.50°, and 58.57 ± 0.50°.

[0007] Preferably, the normalized full width at half maximum (FWHM) of the diffraction peak corresponding to 2θ = 28.18 ± 0.50° in its X-ray diffraction pattern is F. (111) / λ, and satisfy F(111) / λ>0.3, preferably, where F (111) / λ>0.42.

[0008] The present invention also provides a method for preparing the above-mentioned solid electrolyte, wherein the powders are mixed and ball-milled in a molar ratio of Li2S:Li3N=(1.00~2.34):1 to obtain a nitrogen sulfide solid electrolyte.

[0009] Preferably, the ball-to-material mass ratio used in the ball milling process is (1-60):1, and the mixture is ball-milled at a speed of 150-900 rpm for 1-24 hours to obtain a nitrogen sulfide solid electrolyte.

[0010] The present invention also provides an all-solid-state battery, comprising a negative electrode layer, an electrolyte layer and a positive electrode layer in sequence, wherein the electrolyte layer contains the aforementioned solid electrolyte.

[0011] Preferably, the negative electrode layer includes a negative electrode active material, which is selected from one or more of metallic materials, carbon materials, and silicon materials;

[0012] Preferably, the metallic material is selected from lithium metal or lithium alloy;

[0013] Preferably, the carbon material is selected from one or more of natural graphite, coke, spherical carbon, artificial graphite, and amorphous carbon;

[0014] Preferably, the negative electrode layer does not contain the first electrolyte material; or the negative electrode layer includes the first electrolyte material, and the weight of the first electrolyte material in the negative electrode layer does not exceed 70% of the total weight; the first electrolyte material includes the solid electrolyte.

[0015] Preferably, the thickness of the negative electrode layer is 10–500 μm.

[0016] Preferably, the electrolyte layer comprises a second electrolyte material, and the second electrolyte material comprises the solid electrolyte;

[0017] Preferably, the second electrolyte material further includes a sulfide solid electrolyte material and / or a halide solid electrolyte material;

[0018] Preferably, the sulfide solid electrolyte material is selected from Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, Li₂S-GeS₂, Li₆PS₅Cl, and Li₂S-P₂S₅. 3.25 Ge 0.25 P 0.75 S4 and Li 10 GeP2S 12 One or more of the following;

[0019] Preferably, the halide solid electrolyte material is selected from one or more of Li3InCl6, Li2ZrCl6, Li3YCl6 and Li3ScCl6;

[0020] Preferably, the thickness of the electrolyte layer is 1–500 μm.

[0021] Preferably, the positive electrode layer includes a positive electrode active material and a third electrolyte material, wherein the third electrolyte material includes the solid electrolyte;

[0022] Preferably, the positive electrode active material is selected from one or more of lithium iron phosphate, lithium-containing transition metal oxides, transition metal sulfides, transition metal oxysulfides, transition metal fluorides, polyanionic materials, elemental sulfur, and lithium sulfide;

[0023] Preferably, the positive electrode layer contains 5-70% by weight of the third electrolyte material, and the third electrolyte material includes a solid electrolyte material different from the solid electrolyte.

[0024] Preferably, the third electrolyte material includes a sulfide solid electrolyte material and / or a halide solid electrolyte material;

[0025] Preferably, the sulfide solid electrolyte material is selected from Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, Li₂S-GeS₂, Li₆PS₅Cl, and Li₂S-P₂S₅. 3.25 Ge 0.25 P 0.75 S4 and Li 10 GeP2S 12 One or more of the following;

[0026] Preferably, the halide solid electrolyte material is selected from one or more of Li3InCl6, Li2ZrCl6, Li3YCl6 and Li3ScCl6;

[0027] Preferably, the thickness of the positive electrode layer is 10–500 μm.

[0028] Beneficial effects:

[0029] The beneficial effects of adopting the technical solution of this invention are as follows:

[0030] By ball milling Li2S and Li3N powders for a certain period of time, a novel Li-NS phase can be formed. It has good compatibility with lithium metal and can solve the problem of incompatibility between traditional sulfide electrolytes and lithium metal anodes. It can be used to construct high-energy-density all-solid-state lithium batteries using lithium metal anodes. It can achieve stable cycling of lithium symmetric batteries. Lithium symmetric batteries using this solid electrolyte can cycle more than 750 times. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the all-solid-state battery structure in this invention;

[0033] Figure 2 These are the X-ray diffraction patterns of the solid electrolytes obtained in Examples 1-2 and Comparative Examples 1-4 of the present invention;

[0034] Figure 3 These are the AC impedance spectra and lithium-ion conductivity of the solid electrolytes obtained in Examples 1-2 and Comparative Examples 1-3 of the present invention, measured at a temperature of 27°C.

[0035] Figure 4 This is the lithium-ion conductivity curve of the solid electrolyte obtained in Example 1 of the present invention as a function of temperature;

[0036] Figure 5 These are the results of constant current cycling tests on the lithium symmetric batteries obtained in Example 1 and Comparative Example 5 of this invention.

[0037] Figure 6 This is a charge-discharge curve of the all-solid-state lithium battery obtained in Example 1 of the present invention at a temperature of 27°C. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0039] The solid electrolyte in this embodiment has the chemical formula Li. (2+x) N x S (1-x) The value of x ranges from 0.35 to 0.55. This solid electrolyte exhibits good compatibility with lithium metal, enabling stable cycling of lithium symmetric batteries. Lithium symmetric batteries using this solid electrolyte can cycle more than 750 times.

[0040] Here, the preferred value range for x is 0.48 to 0.52.

[0041] The X-ray diffraction pattern of the solid electrolyte was analyzed, and its X-ray diffraction spectrum (copper target, wavelength) was obtained. Diffraction peaks exist at positions 2θ = 28.18 ± 0.50°, 32.54 ± 0.50°, 46.97 ± 0.50°, 55.75 ± 0.50°, and 58.57 ± 0.50°.

[0042] Furthermore, the normalized full width at half maximum (FWHM) of the diffraction peak corresponding to 2θ = 28.18 ± 0.50° in its X-ray diffraction pattern is F. (111) / λ, and satisfy F (111) / λ>0.3, preferably, where F (111) / λ>0.42.

[0043] This embodiment also provides a method for preparing the above-mentioned solid electrolyte, comprising the following steps:

[0044] Step 1: Weigh the Li2S and Li3N powders under low humidity conditions (dew point temperature below -60℃), and control the molar ratio of Li2S:Li3N = (1.00~2.34):1;

[0045] Step 2: Mix the powder with the grinding balls and place them in a grinding jar. The mass ratio of the powder to the balls is (1-60):1. Grind the powder in a planetary ball mill at a speed of 150-900 rpm for 1-24 hours to obtain a nitrogen sulfide solid electrolyte.

[0046] This embodiment also provides an all-solid-state battery, such as Figure 1 As shown, it includes a negative electrode layer 100, an electrolyte layer 200 and a positive electrode layer 300 in sequence, and the electrolyte layer 200 contains the above-mentioned solid electrolyte.

[0047] The negative electrode layer 100 includes a negative electrode active material 101. The negative electrode layer 100 may or may not include a first electrolyte material 102. The first electrolyte material 102 includes the solid electrolyte.

[0048] The negative electrode active material 101 is selected from one or more of metallic materials, carbon materials, and silicon materials; the metallic material is selected from lithium metal or lithium alloy; the carbon material is selected from one or more of natural graphite, coke, spherical carbon, artificial graphite, and amorphous carbon.

[0049] From the perspective of battery energy density and output, the content of the first electrolyte material 102 in the negative electrode layer 100 does not exceed 70%; and the thickness of the negative electrode layer 100 is 10 to 500 μm.

[0050] It should be further explained here that the first electrolyte material 102 is a material containing a solid electrolyte; the first electrolyte material 102 may be a material containing the above-mentioned solid electrolyte as a main component; the first electrolyte material 102 may also be a material composed of the above-mentioned nitrogen solid electrolyte.

[0051] In a preferred embodiment, the electrolyte layer 200 includes a second electrolyte material, which includes the solid electrolyte;

[0052] Here, the second electrolyte material contained in the electrolyte layer 200 may be composed solely of the aforementioned solid electrolyte; or the second electrolyte material contained in the electrolyte layer 200 may be composed of the aforementioned solid electrolyte and a solid electrolyte material different from the aforementioned solid electrolyte material.

[0053] The different solid electrolyte materials here can be sulfide solid electrolyte materials and halide solid electrolyte materials. Among them, the sulfide solid electrolyte materials are selected from Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, Li₂S-GeS₂, Li₆PS₅Cl, and Li₂S₅Cl. 3.25 Ge 0.25 P 0.75 S4 and Li 10 GeP2S 12 One or more of the following; the halide solid electrolyte material is selected from one or more of Li3InCl6, Li2ZrCl6, Li3YCl6 and Li3ScCl6; from the viewpoint of battery energy density and output, the thickness of electrolyte layer 200 is 1 to 500 μm.

[0054] In a preferred embodiment, the positive electrode layer 300 includes a positive electrode active material 301 and a third electrolyte material 302, wherein the electrolyte material 302 includes the solid electrolyte;

[0055] Here, the positive electrode active material 301 is selected from one or more of lithium iron phosphate, lithium-containing transition metal oxides, transition metal sulfides, transition metal oxysulfides, transition metal fluorides, polyanionic materials, elemental sulfur, and lithium sulfide;

[0056] The third electrolyte material 302 contained in the positive electrode layer 300 may be composed solely of a solid electrolyte material different from the aforementioned solid electrolyte material. Alternatively, the third electrolyte material 302 contained in the positive electrode layer 300 may also contain a solid electrolyte material different from the aforementioned nitrogen-sulfide solid electrolyte material.

[0057] From the viewpoint of battery energy density and output, the positive electrode layer 300 contains the third electrolyte material 302, which accounts for 5 to 70% of its weight; the third electrolyte material 302 includes sulfide solid electrolyte material and / or halide solid electrolyte material.

[0058] Among them, the sulfide solid electrolyte material is selected from Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li6PS5Cl, and Li 3.25 Ge 0.25 P 0.75 S4 and Li 10 GeP2S 12 One or more of the following;

[0059] The halide solid electrolyte material is selected from one or more of Li3InCl6, Li2ZrCl6, Li3YCl6 and Li3ScCl6; the thickness of the positive electrode layer is 10 to 500 μm.

[0060] Example 1

[0061] Preparation of solid electrolytes:

[0062] 12.4 mmol of Li3N (431 mg) and 12.4 mmol of Li2S (568 mg) were weighed separately in an argon-atmosphere glove box, corresponding to x = 0.5. The raw materials were ground and mixed in an agate mortar and then placed in a 45 ml ball mill jar. Zirconia ball milling beads were used, with a ratio of small balls (3 mm in diameter) to large balls (8 mm in diameter) of 5:1, for a total mass of 45 g. The mixture was ground in a planetary ball mill (FRITSCH PULVERISETTE 7) at 500 rpm for 7.5 hours, with a 5-minute pause after every 15 minutes of milling. After the reaction was complete, the ball mill jar was opened in an argon-atmosphere glove box, and the material was removed. Thus, the solid electrolyte material of Example 1 was obtained.

[0063] X-ray diffraction, ionic conductivity testing, solid electrolyte activation energy testing, lithium symmetric cell testing, and full cell testing were performed on the solid electrolyte material in Example 1. The results are as follows:

[0064] (1) Ionic conductivity test

[0065] Lithium-ion conductivity was tested by AC impedance spectroscopy. The method was as follows: Solid electrolyte was weighed in an argon-atmospheric glove box. 100 mg of electrolyte was placed in a molded battery and pressed into a sheet at a pressure of 500 MPa for 5 minutes. The pressure was then reduced to 250 MPa, and a symmetrical battery ("stainless steel | solid electrolyte | stainless steel") was directly assembled inside the molded battery. The AC impedance of this battery in open circuit mode was measured. Measurements were performed using a Biologic VSP200 analyzer at a voltage of 50 mV, a frequency range of 1 Hz to 7 MHz, and a test temperature of 27 °C. After measurement, the solid electrolyte sheet was removed from the molded battery, and its thickness was measured using a micrometer.

[0066] The formula for calculating lithium-ion conductivity is as follows:

[0067]

[0068] Where σ is the ionic conductivity of the solid electrolyte being measured, and R se This represents the AC impedance value of the solid electrolyte material in the impedance measurement, where S is the contact area between the solid electrolyte and the stainless steel electrode, and d is the thickness of the solid electrolyte material. Specific results for lithium-ion conductivity are shown in Table 1. Figure 3 The AC impedance spectrum and lithium-ion conductivity were measured at 27°C.

[0069] The results show that the lithium-ion conductivity of the solid electrolyte in Example 1 is 2.1 × 10⁻⁶. -4 S / cm.

[0070] (2) X-ray diffraction

[0071] The X-ray diffraction pattern of the sample was measured using a Malvern Panalytical Empyrean X-ray diffractometer with the following parameters: voltage 40 kV, current 45 mA; 2θ range: 10–80°; scan rate: 7°min. -1 A polyimide film was used to isolate the sample from air. X-ray diffraction was performed using copper Kα rays (wavelength...). The X-ray diffraction pattern of the sample is shown in the figure. Figure 2 .

[0072] The results show that diffraction peaks exist in the X-ray diffraction pattern at positions of 2θ = 28.18°, 32.54°, 46.97°, 55.75°, and 58.57°. The F-value of the diffraction peak corresponding to 2θ = 28.18° is... (111) / λ=0.42.

[0073] (3) Solid electrolyte activation energy test

[0074] The activation energy test method in Example 1 is to measure the ionic conductivity of the solid electrolyte material at different temperatures. The test method is as follows: the aforementioned mold battery is placed in a high and low temperature chamber with a temperature range of 30 to 110°C and a heating rate of 10°C·h. -1 During the heating process, the AC impedance of the mold battery in open circuit mode was tested, and the formula for calculating the lithium-ion conductivity is as described above. Figure 4 Li, as in Example 1 2.5 N 0.5 S 0.5 The lithium-ion conductivity of a solid electrolyte changes with temperature.

[0075] The results showed that the activation energy Ea of the solid electrolyte in Example 1 was 0.38 eV in the experimental temperature range.

[0076] (4) Lithium-symmetric battery testing

[0077] A molded battery is used as the battery casing, which includes two metal pillars and an insulating liner; lithium metal sheets serve as the positive and negative electrodes of the battery, and the electrolyte is the solid electrolyte prepared in Example 1.

[0078] 100 mg of the solid electrolyte powder from Example 1 was placed in a molded battery cylinder and maintained at a pressure of 500 MPa for 5 minutes. The pressure was then released, and lithium plates and stainless steel pillars were added to both ends of the electrolyte plate. The cylinder was placed inside the molded battery flange, subjected to a pressure of 25 MPa, and the screws were tightened. After sealing, a lithium symmetric battery was obtained. In the constant current cycling test of the lithium symmetric battery, the battery was left to stand at 27°C for 2 hours, followed by cycles consisting of 30 minutes of charging and 30 minutes of discharging, with a constant cycle current density of 0.1 mA·cm⁻¹. -1 . Figure 5 The results are from constant current cycling tests on lithium symmetric batteries.

[0079] The results show that the lithium symmetric battery using the solid electrolyte of Example 1 can cycle for more than 750 cycles, which corresponds to the solid electrolyte of Example 1 having good compatibility with lithium metal and can achieve stable cycling of the lithium symmetric battery.

[0080] (5) Full battery test

[0081] Step 1: Weigh Li6PS5Cl solid electrolyte powder and commercial LiCoO2 cathode powder in a dry atmosphere and mix for 10-30 minutes to obtain a cathode material mixture. The solid electrolyte accounts for 10%-70% of the weight of the cathode mixture.

[0082] Step two: A molded battery comprising two metal pillars and an insulating liner is used as the battery casing. 80 mg of the solid electrolyte powder from Example 1 is placed in the molded battery cylinder and held at a pressure of 200 MPa for 2 minutes. The pressure is then released to obtain the first electrolyte layer. Subsequently, 120 mg of Li6PS5Cl solid electrolyte powder is added and held at a pressure of 400 MPa for 2 minutes. The pressure is then released to obtain the second electrolyte layer.

[0083] Step 3: Add 10 mg of positive electrode mixture to one side of the electrolyte layer, spread it evenly, and maintain it under a pressure of 200 MPa for 2 minutes to obtain the positive electrode layer. Add a lithium sheet and a stainless steel pillar to the other end of the electrolyte sheet; place the cylinder into the mold battery flange, apply a pressure of 50 MPa, tighten the screws, and seal the mold battery. After battery assembly, let it stand at 27°C for 12 hours, and then conduct charge-discharge tests at a rate of 0.1C within a voltage range of 2.5–4.2V (relative to Li / Li+). Figure 6 The image shows the charge-discharge curves of the all-solid-state battery using the solid electrolyte of Example 1 at 27°C.

[0084] The results show that using Li (2+x) N x S (1-x) Among them, the solid electrolyte with x = 0.5 exhibits an initial discharge capacity of up to 138 mAh·g. -1 .

[0085] Example 2

[0086] 9.6 mmol of Li3N (336 mg) and 114.4 mmol of Li2S (664 mg) were weighed out, corresponding to x = 0.4. Otherwise, the solid electrolyte material of Example 2 was obtained in the same manner as in Example 1.

[0087] The lithium-ion conductivity of the solid electrolyte in Example 2 at 27°C was measured in the same manner as in Example 1. Figure 3 As shown, the result is 9.4 × 10 -5 S / cm.

[0088] The X-ray diffraction pattern of Example 2 was measured in the same manner as in Example 1, and the results are shown in [Figure 1]. Figure 2 The results showed that diffraction peaks existed in the X-ray diffraction pattern at positions of 2θ = 28.10°, 32.38°, 46.67°, 55.40°, and 58.09°. The F-value of the diffraction peak corresponding to 2θ = 28.10° was... (111) / λ=0.43.

[0089] Comparative Example 1

[0090] 7 mmol of Li3N (245 mg) and 16.4 mmol of Li2S (755 mg) were weighed out, corresponding to x = 0.3. Otherwise, the solid electrolyte material of Comparative Example 1 was obtained in the same manner as in Example 1.

[0091] The lithium-ion conductivity of the solid electrolyte in Comparative Example 1 at 27°C was measured in the same manner as in Example 1. Figure 3 As shown, the result is 4.4 × 10 -5 S / cm.

[0092] The X-ray diffraction pattern of Comparative Example 1 was measured in the same manner as in Example 1, and the results are shown in [Figure 1]. Figure 2 The results showed that diffraction peaks existed in the X-ray diffraction pattern at positions of 2θ = 27.60°, 31.88°, 45.96°, 54.47°, and 56.97°. The F-value of the diffraction peak corresponding to 2θ = 27.60° was... (111) / λ=0.42.

[0093] Comparative Example 2

[0094] 15.3 mmol of Li3N (532 mg) and 10.2 mmol of Li2S (468 mg) were weighed out, corresponding to x = 0.6. Otherwise, the solid electrolyte material of Comparative Example 2 was obtained in the same manner as in Example 1.

[0095] The lithium-ion conductivity of the solid electrolyte in Comparative Example 2 at 27°C was measured in the same manner as in Example 1. Figure 3 As shown, the result is 1.6 × 10⁻⁶. -4 S / cm.

[0096] The X-ray diffraction pattern of Comparative Example 2 was measured in the same manner as in Example 1, and the results are shown in [Figure 1]. Figure 2 The results showed that the X-ray diffraction pattern contained diffraction peaks at 2θ = 28.44°, 32.85°, 47.49°, 56.16°, and 59.19°; while impurity phase diffraction peaks were present at 2θ = 31.95°, 50.84°, and 52.10°, indicating that Comparative Example 2 was not a pure phase.

[0097] Comparative Example 3

[0098] 18.3 mmol of Li3N (639 mg) and 7.86 mmol of Li2S (361 mg) were weighed out, corresponding to x = 0.7. Otherwise, the solid electrolyte material of Comparative Example 3 was obtained in the same manner as in Example 1.

[0099] The lithium-ion conductivity of the solid electrolyte in Comparative Example 3 at 27°C was measured in the same manner as in Example 1. Figure 3 As shown, the result is 1.2 × 10⁻⁶. -4 S / cm.

[0100] The X-ray diffraction pattern of Comparative Example 3 was measured in the same manner as in Example 1, and the results are shown in [Figure 1]. Figure 2 The results showed that the X-ray diffraction pattern contained diffraction peaks at 2θ = 28.56°, 33.28°, 47.79°, 56.04°, and 59.21°; while impurity phase diffraction peaks were present at 2θ = 31.95°, 50.84°, and 52.10°, indicating that Comparative Example 3 was not a pure phase.

[0101] Comparative Example 4

[0102] The lithium-ion conductivity of Comparative Example 4 at 27°C was measured in the same manner as in Example 1, and the result was less than 1 × 10⁻⁶. -9 S / cm.

[0103] Commercially available Li2S powder was used. The X-ray diffraction pattern of Comparative Example 4 was measured in the same manner as in Example 1, and the results are shown below. Figure 2 The results showed that the X-ray diffraction pattern contained diffraction peaks at 2θ = 27.19°, 31.49°, 53.34°, 55.90° and 65.48°, 72.23°, 74.38°.

[0104] Comparative Example 5

[0105] Using a commercially available Li6PS5C1 solid electrolyte, the lithium-symmetric battery was assembled and tested in the same manner as in Example 1. The results of the lithium-symmetric battery under constant current cycling tests are shown in [Figure 1]. Figure 5 The results showed that the battery short-circuited after no more than 60 cycles.

[0106] Table 1. Conductivity test results for each embodiment and comparative example.

[0107]

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A solid electrolyte, characterized in that, Its chemical formula is Li (2+x) N x S (1-x) The value of x ranges from 0.35 to 0.

55. The X-ray diffraction pattern using a copper target and a wavelength of λ = 1.5405 Å shows diffraction peaks at positions of 2θ = 28.18 ± 0.50°, 32.54 ± 0.50°, 46.97 ± 0.50°, 55.75 ± 0.50°, and 58.57 ± 0.50°.

2. The solid electrolyte according to claim 1, characterized in that, The value of x ranges from 0.48 to 0.

52.

3. The solid electrolyte according to claim 1, characterized in that, The normalized full width at half maximum (FWHM) of the diffraction peak corresponding to 2θ = 28.18 ± 0.50° in its X-ray diffraction pattern is F. (111) / λ, and satisfy F (111) / λ>0.

3.

4. The solid electrolyte according to claim 3, characterized in that, F (111) / λ>0.42。 5. A method for preparing a solid electrolyte according to any one of claims 1-4, characterized in that, The powders were mixed and ball-milled in a molar ratio of Li2S:Li3N = (1.00~2.34):1 to obtain a nitrogen sulfide solid electrolyte.

6. The method for preparing a solid electrolyte according to claim 5, characterized in that, The ball milling process uses a ball-to-material mass ratio of (1~60):1, and the mixture is milled at a speed of 150~900 rpm for 1~24 hours to obtain a nitrogen sulfide solid electrolyte.

7. An all-solid-state battery, characterized in that, It comprises, in sequence, a negative electrode layer, an electrolyte layer and a positive electrode layer, wherein the electrolyte layer contains a solid electrolyte as described in any one of claims 1-4.

8. A solid-state battery according to claim 7, characterized in that, The negative electrode layer includes a negative electrode active material, which is selected from one or more of metal materials, carbon materials, and silicon materials.

9. A solid-state battery according to claim 8, characterized in that, The metallic material is selected from lithium metal or lithium alloy.

10. A solid-state battery according to claim 8, characterized in that, The carbon material is selected from one or more of natural graphite, coke, spherical carbon, artificial graphite, and amorphous carbon.

11. A solid-state battery according to claim 7, characterized in that, The negative electrode layer does not contain the first electrolyte material; or the negative electrode layer includes the first electrolyte material, and the weight of the first electrolyte material in the negative electrode layer does not exceed 70% of the total weight; the first electrolyte material includes the solid electrolyte.

12. A solid-state battery according to claim 7, characterized in that, The thickness of the negative electrode layer is 10~500μm.

13. A solid-state battery according to claim 7, characterized in that, The electrolyte layer includes a second electrolyte material, which includes the solid electrolyte.

14. A solid-state battery according to claim 13, characterized in that, The second electrolyte material also includes sulfide solid electrolyte materials and / or halide solid electrolyte materials.

15. A solid-state battery according to claim 14, characterized in that, The sulfide solid electrolyte material is selected from Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li6PS5Cl, and Li 3.25 Ge 0.25 P 0.75 S4 and Li 10 GeP2S 12 One or more of them.

16. A solid-state battery according to claim 14, characterized in that, The halide solid electrolyte material is selected from one or more of Li3InCl6, Li2ZrCl6, Li3YCl6 and Li3ScCl6.

17. A solid-state battery according to claim 13, characterized in that, The thickness of the electrolyte layer is 1~500μm.

18. A solid-state battery according to claim 7, characterized in that, The positive electrode layer includes a positive electrode active material and a third electrolyte material.

19. A solid-state battery according to claim 18, characterized in that, The positive electrode active material is selected from one or more of lithium-containing transition metal oxides, transition metal sulfides, transition metal oxysulfides, transition metal fluorides, polyanionic materials, elemental sulfur, and lithium sulfide.

20. A solid-state battery according to claim 18, characterized in that, The positive electrode layer contains 5-70% of the third electrolyte material by weight, and the third electrolyte material includes a solid electrolyte material that is different from the solid electrolyte.

21. A solid-state battery according to claim 18, characterized in that, The third electrolyte material includes sulfide solid electrolyte materials and / or halide solid electrolyte materials.

22. A solid-state battery according to claim 21, characterized in that, The sulfide solid electrolyte material is selected from Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li6PS5Cl, and Li 3.25 Ge 0.25 P 0.75 S4 and Li 10 GeP2S 12 One or more of them.

23. A solid-state battery according to claim 21, characterized in that, The halide solid electrolyte material is selected from one or more of Li3InCl6, Li2ZrCl6, Li3YCl6 and Li3ScCl6.

24. A solid-state battery according to claim 18, characterized in that, The thickness of the positive electrode layer is 10~500μm.

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