High-purity argyrodite-phase sulfide solid electrolyte and method for producing the same

Abstract

The present invention relates to the technical field of batteries, and more particularly to a high-purity argyrodite-phase sulfide solid electrolyte and a method for preparing the same. The molecular formula of the high-purity argyrodite-phase sulfide solid electrolyte is Li 6±i P 1-e E e S 5±i-g G g Cl 1±i±t T t In the formula I, 0≦i<1, 0≦e<1, 0

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a high-purity argyrodite-phase sulfide solid electrolyte and a method for manufacturing the same.

Background Art

[0002] Solid electrolytes are important components of all-solid-state batteries. Among them, argyrodite-phase sulfide solid electrolytes have higher ionic conductivity at room temperature and lower electronic conductivity, and have good mechanical properties, contributing to the formation of a good solid / solid contact interface between the electrodes and the electrolyte in all-solid-state batteries. However, currently, many argyrodite-phase sulfide solid electrolyte phases are not pure and contain impurity phases such as raw materials or intermediate products during firing, which affect the chemical stability of the electrolyte and the reaction products at the electrolyte / electrode interface. In addition, high-purity-phase argyrodite-phase sulfide solid electrolytes are generally manufactured by extending the ball milling time of the precursor and extending the heat treatment time. The manufacturing time is generally one to two weeks, and the ionic conductivity of the obtained electrolyte at room temperature is lower. The high-speed manufacturing of high-purity argyrodite-phase sulfide solid electrolytes and the improvement of ionic conductivity at room temperature play an important role in optimizing the performance of electrolytes and all-solid-state lithium batteries.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In view of the drawbacks of argyrodite-phase sulfide solid electrolytes in the prior art, the present invention provides a high-purity argyrodite-phase sulfide solid electrolyte in a pure phase and a method for manufacturing the high-purity argyrodite-phase sulfide solid electrolyte.

Means for Solving the Problems

[0004] In one aspect of the present invention, a high-purity argyrodite-phase sulfide solid electrolyte is provided. The molecular formula of the high-purity argyrodite-phase sulfide solid electrolyte is shown in the following formula I: Li 6±i P 1-e E e S5±i-g G g Cl 1±i±t T t Formula I In Formula I, 0 ≦ i < 1, 0 ≦ e < 1, 0 < g ≦ 0.5, 0.2 ≦ t < 1, E is one or more of Ge, Si, Sn, and Sb, G is a composite of Se and O or O, T is one or two of Br and I, The high-purity argyrodite-phase sulfide solid electrolyte is a pure phase, without a raw material phase, and has no impurity peaks in its X-ray diffraction spectrum.

[0005] The argyrodite-phase crystal structure is PS4 3- tetrahedrons form a framework, and Li + ions, halogen ions (Cl - , Br - , I - ) and some S 2- ions are regularly dispersed therein. Doped O preferentially replaces S in the PS4 3- tetrahedron, and some P-S bonds become P-O bonds. However, the bond distance of the P-O bond is smaller than that of the P-S bond. Therefore, due to O doping, the volume of the PS4 3- group shrinks, causing a change in the crystal structure. When the amount of O doping in Li6PS5Cl is too large, the volume of the PS4 3- group shrinks significantly, the crystal framework shrinks, and the Li + ions, S 2- ions, and Cl - ions are squeezed out, easily forming impurity phases of components such as Li2S and LiCl. Therefore, in order to avoid the generation of impurity phases, the present invention limits the number of atoms of G to 0 < g ≦ 0.5 to avoid too much O addition. At the same time, in order to ensure that the crystal structure maintains its original volume after O doping, the position of the halogen is also corresponding to Br - or I - ions with a larger radius of the doped ion. When the amount of O doping is larger, the larger halogen ions can compensate for the volume reduction caused by O doping to support the framework, ensuring that the Li +Ions, S 2- Avoid the formation of an impurity phase by squeezing out ions and halogen ions.

[0006] Preferably, the ionic conductivity of the high-purity argyrodite-phase sulfide solid electrolyte at room temperature is 1×10 -3 ~8×10 -2 S / cm. Room temperature in this specification refers to 15~35°C.

[0007] Preferably, the high-purity argyrodite-phase sulfide solid electrolyte has excellent stability against lithium.

[0008] Preferably, when the high-purity argyrodite-phase sulfide solid electrolyte is exposed at a dew point of -40°C for 4 hours in a drying chamber, the ionic conductivity is reduced by ≦15%.

[0009] Preferably, when the high-purity argyrodite-phase sulfide solid electrolyte is immersed in an organic solvent at room temperature for 2 hours, the ionic conductivity is reduced by ≦20%.

[0010] Preferably, the organic solvent is one or more of ethylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, N-methylpyrrolidone, tetrahydrofuran, ethylene glycol dimethyl ether, anisole, 1,3-oxolane, toluene, xylene, chlorobenzene, and normal heptane.

[0011] In another aspect of the present invention, a method for manufacturing a high-purity argyrodite-phase sulfide solid electrolyte is provided. Step a) of manufacturing a lithium sulfide material; Step b) of weighing and mixing a raw material containing a lithium sulfide material and an oxidizing agent in a molar ratio to obtain an electrolyte precursor; Step c) of annealing and firing the precursor obtained in step b) to obtain a high-purity argyrodite-phase sulfide solid electrolyte.

[0012] Preferably, the method for manufacturing the lithium sulfide material includes the ball milling method, the carbon thermal reduction method, and one or more of the reactions of lithiated sulfur-containing chemicals, lithium metal sulfide nanoparticles, lithium-containing substances, and sulfur-containing substances.

[0013] Preferably, the oxidizing agent in step b) is one or more of Li2O, P2O5, Li3PO4, and I2. Adding an oxidizing agent to the raw materials contributes to obtaining a high-purity phase of the argyrodite phase sulfide solid electrolyte due to the oxidizing action of the oxidizing agent.

[0014] Preferably, the mixing method in step b) includes one or more of manual polishing, mechanical stirring, mechanical vibration, mechanical ball milling, high-energy ball milling, and roll milling.

[0015] When the mixing method in step b) is high-energy ball milling or roll milling, the ratio of balls to materials is (1 to 60):1, the rotation speed is 200 to 600 rpm, and the time is 4 to 24 hours.

[0016] Preferably, the annealing temperature in step c) is 400 to 600 °C and the time is 1 to 48 hours.

[0017] In another aspect of the present invention, a all-solid-state lithium secondary battery is provided, which includes a positive electrode, a negative electrode, and the high-purity argyrodite phase sulfide solid electrolyte.

Advantages of the Invention

[0018] Compared with the prior art, the present invention has the following beneficial effects. First, the argyrodite phase sulfide solid electrolyte according to the present invention is a pure phase, and there are no impurity peaks in its X-ray diffraction spectrum. Second, the high-purity argyrodite phase sulfide solid electrolyte according to the present invention has a higher ionic conductivity. Thirdly, the high-purity argyrodite-phase sulfide solid electrolyte according to the present invention has excellent stability against air, excellent stability against organic solvents, and excellent stability against lithium. Fourthly, the present invention realizes the production of a high-purity argyrodite-phase sulfide solid electrolyte by mixing and reacting a raw material containing a lithium sulfide material and an oxidizing agent and by the action of the oxidizing agent. Fifthly, when the high-purity argyrodite-phase sulfide solid electrolyte according to the present invention is applied to an all-solid-state lithium battery, the battery performance can be effectively improved.

Brief Description of the Drawings

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Figure 1

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Figure 8

Modes for Carrying Out the Invention

[0020] The technical solution of the present invention will be further described and explained below with specific examples and drawings. It should be understood that the specific examples described here are only for the convenience of understanding the present invention and do not specifically limit the present invention. Unless otherwise specified, all raw materials used in the embodiments of the present invention are raw materials commonly used in this field, and all methods used in the embodiments are normal methods in this field.

[0021] Example 1 The high-purity argyrodite-phase sulfide solid electrolyte in this example has a molecular formula of Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 and is manufacture of lithium sulfide material, manufactured by the mutual reaction of lithium-containing substances and sulfur-containing substances, dissolving metallic lithium and elemental sulfur in ether respectively, making the molar ratio of substances 2.1:1, and subjecting to reduced-pressure distillation after mixing to react to obtain Li2S a), weighing Li2S, P2S5, P2O5, LiCl, LiBr in a molar ratio and putting them into an agate mortar, manually grinding for 30 minutes to obtain an electrolyte precursor b), firing the electrolyte precursor in a vacuum at 550 °C for 4 hours to obtain Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 to obtain an electrolyte c), and is obtained by a manufacturing method including the above.

[0022] Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 The electrolyte phase is an argyrodite phase, the electrolyte is a pure phase, there is no raw material phase, its X-ray diffraction graph is shown in Figure 1, and it can be seen that there are no impurity peaks in the electrolyte.

[0023] Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5The original room temperature AC test impedance diagram of the electrolyte is shown in Figure 2, and its ionic conductivity at room temperature is shown in Table 1, which is 16 mS / cm.

[0024] The obtained Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 The obtained Li6PS

[0025] The obtained Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 After exposing the obtained Li6PS

[0026] Table 1 Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 Ionic conductivity of the electrolyte at room temperature JPEG0007693020000001.jpg33170

[0027] The produced Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 To further study the stability of the electrolyte material against the lithium metal electrode and consider the feasibility of using the lithium metal electrode as the negative electrode, a constant current charge-discharge test was performed on a symmetric battery assembled with the electrolyte and metallic lithium, and the test results are shown in Figure 3. Li / Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 / Li symmetric battery has a test current density of 1 mA / cm 2 and a charge-discharge time of 1 hour per cycle, and a test capacity density of 1 mAh / cm 2 According to the test results, Li / Li6PS4.8 O 0.2 Cl 0.5 Br 0.5 The O / Li symmetric battery can cycle for 12,000 hours at a current density of 1 mA / cm², and it is revealed that the polarization voltage does not change significantly. It is explained that the Li6PS 2 O 4.8 O 0.2 Cl 0.5 Br 0.5 electrolyte has excellent stability against lithium.

[0028] Using metallic lithium as the negative electrode and LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM) as the positive electrode, a full solid-state lithium primary battery is assembled and a battery charge-discharge test is conducted. Figure 4 shows the constant-current charge-discharge curve of the Li / Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 / NCM battery, and Figure 5 shows the cycle of the Li / Li6PS 4.8 O 0.2 Cl 0.5 Br 0.5 / NCM battery. The battery is tested at 0.5C. The initial discharge specific capacity is 3.31 mAh / cm² 2 , and the initial Coulomb efficiency is 80.7%. After 50 cycles, the discharge specific capacity becomes 3.04 mAh / cm² 2 .

[0029] Example 2 The high-purity argyrodite-phase sulfide solid electrolyte in this example has a molecular formula of Li 5.4 PS 4.3 O 0.1 Cl 1.4 I 0.2 and the production of lithium sulfide materials, which is produced by the ball milling method and the mutual reaction of lithium-containing substances and sulfur-containing substances. Metallic lithium and elemental sulfur are respectively dissolved in tetrahydrofuran, the molar ratio of the substances is 2.2:1, ball milled and mixed at 200 r / min for 24 hours, and then reacted by vacuum distillation to obtain Li2S in a) and Weigh Li2S, Li3PO4, LiCl, and I2 in a molar ratio and put them into a stirring tank for mechanical stirring. Stir at 300 r / min for 1 hour. After the above is completed, put them into a high-energy ball milling tank for high-energy ball milling. Set the ratio of balls to materials to 30:1 and perform high-energy ball milling at a rotational speed of 300 rpm for 24 hours to obtain a precursor electrolyte b), Bake the precursor electrolyte in a vacuum at 540 °C for 12 hours to obtain Li 5.4 PS 4.3 O 0.1 Cl 1.4 I 0.2 and obtain an electrolyte c). It is obtained by a manufacturing method including these steps.

[0030] Li 5.4 PS 4.3 O 0.1 Cl 1.4 I 0.2 The electrolyte phase is the argyrodite phase, the electrolyte is a pure phase, and there is no raw material phase.

[0031] Li 5.4 PS 4.3 O 0.1 Cl 1.4 I 0.2 The original ionic conductivity of the electrolyte at room temperature is 10.5 mS / cm.

[0032] The obtained Li 5.4 PS 4.3 O 0.1 Cl 1.4 I 0.2 Immerse the obtained Li

[0033] PS 5.4 O 4.3 Cl 0.1 I 1.4 electrolyte in an anisole + tetrahydrofuran solvent (the volume ratio of anisole to tetrahydrofuran is 1:2), immerse it at room temperature for 2 hours and then dry it. After immersion, the ionic conductivity of the electrolyte at room temperature becomes 9.03 mS / cm. 0.2 Place the obtained Li

[0034] Manufactured Li 5.4 PS 4.3 O 0.1 Cl 1.4 I 0.2 To further study the stability of the electrolyte material against the lithium metal electrode and consider the feasibility of using the lithium metal electrode as the negative electrode, a constant current charge-discharge test is performed on a symmetric cell assembled with the electrolyte and metallic lithium. Li / Li 5.4 PS 4.3 O 0.1 Cl 1.4 I 0.2 / Li symmetric cell has a test current density of 2 mA / cm 2 and a single charge-discharge time of 1 hour, and a test capacity density of 2 mAh / cm 2 According to the test results, Li / Li 5.4 PS 4.3 O 0.1 Cl 1.4 I 0.2 / Li symmetric cell can cycle 500 times at a current density of 2 mA / cm 2 and it is revealed that the polarization voltage does not change significantly, indicating that the electrolyte has excellent stability against lithium.

[0035] A battery charge-discharge test is performed on an all-solid-state lithium primary battery assembled with lithium metal as the negative electrode and FeS2 as the positive electrode. The battery is tested at 2 mA / cm 2 After 500 cycles, the discharge specific capacity becomes 2.21 mAh / cm 2

[0036] Example 3 The high-purity argyrodite-phase sulfide solid electrolyte in this example has a molecular formula of Li 5.4 PS 4.2 O 0.2 Cl 1.1 Br 0.5 and ​Manufacture of a lithium sulfide material, which comprises: a) mixing dry sulfur powder and lithium hydride powder in a molar ratio of 1:1, putting them into a ball mill tank, and performing ball milling at 100 r / min under room temperature conditions for 24 hours to obtain Li2S; b) weighing Li2S, P2O5, LiCl, and LiBr in a molar ratio, putting them into a stirring tank, and mechanically stirring at 400 r / min for 8 hours to obtain a precursor electrolyte; c) firing the precursor electrolyte in a vacuum at 580 °C for 24 hours to obtain 5.4 Li 4.2 PS 0.2 O 0.5 Cl 0.5 Br 0.5 an electrolyte. The electrolyte is obtained by the manufacturing method including the above steps.

[0037] Li 5.4 PS 4.2 O 0.2 Cl 0.5 Br 0.5 The electrolyte phase is the argyrodite phase, the electrolyte is a pure phase, and there is no raw material phase.

[0038] Li 5.4 PS 4.2 O 0.2 Cl 0.5 Br 0.5 The original ionic conductivity of the electrolyte at room temperature is 19 mS / cm.

[0039] The obtained 5.4 Li 4.2 PS 0.2 O 0.5 Cl 0.5 Br

[0040] The obtained 5.4 Li 4.2 PS 0.2 O 0.5 Cl 0.5After placing the electrolyte in a drying chamber and exposing it at a dew point of -40°C for 4 h, its ionic conductivity at room temperature becomes 17.37 mS / cm.

[0041] The produced Li 5.4 PS 4.2 O 0.2 Cl 0.5 Br 0.5 To further study the stability of the electrolyte material against the lithium metal electrode and consider the feasibility of using the lithium metal electrode as the negative electrode, a constant current charge-discharge test is performed on a symmetric cell assembled with the electrolyte and metallic lithium. Li / Li 5.4 PS 4.2 O 0.2 Cl 0.5 Br 0.5 / Li symmetric cell has a test current density of 5 mA / cm 2 and a single charge-discharge time of 1 h, and a test capacity density of 5 mAh / cm 2 According to the test results, Li / Li 5.4 PS 4.2 O 0.2 Cl 0.5 Br 0.5 / Li symmetric cell can cycle 1000 times at a current density of 5 mA / cm 2 and it is revealed that the polarization voltage does not change significantly, indicating that the electrolyte has excellent stability against lithium.

[0042] A battery charge-discharge test is performed on an all-solid-state lithium primary battery assembled with a lithium boron alloy as the negative electrode and NCM as the positive electrode. The battery is tested at 5 mA / cm 2 After 1000 cycles, the discharge specific capacity becomes 5.71 mAh / cm 2 .

[0043] Example 4 The high-purity argyrodite-phase sulfide solid electrolyte in this example has a molecular formula of Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I 0.2 and The production of lithium sulfide material, which is produced by the lithium metal sulfide nanoparticle method, where metal lithium nanoparticles are dispersed in a tetrahydrofuran-normal hexane medium, and after reacting for 24 hours through a mixed gas of hydrogen sulfide gas and argon gas inside, Li2S is obtained a), Weigh Li2S, P2O5, LiCl, LiBr, and LiI in a molar ratio and put them into a mortar for grinding. After the above is completed, put them into a roll milling tank for roll milling, with the ratio of balls to material being 5:1, and roll mill for 24 hours at a rotational speed of 200 rpm to obtain a precursor electrolyte b), The precursor electrolyte is calcined in a vacuum at 420 °C for 48 hours to obtain Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I 0.2 It is obtained by a production method including c) to obtain an electrolyte.

[0044] Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I 0.2 The electrolyte phase is the argyrodite phase, the electrolyte is a pure phase, and there is no raw material phase.

[0045] Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I 0.2 The original ionic conductivity of the electrolyte at room temperature is 25 mS / cm.

[0046] The obtained Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I 0.2 The obtained Li6PS

[0047] The obtained Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I0.2 It is placed in a drying chamber and exposed at a dew point of -40 °C for 4 h, and then its ionic conductivity at room temperature becomes 24 mS / cm.

[0048] The manufactured Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I 0.2 To further study the stability of the electrolyte material against the lithium metal electrode and consider the feasibility of using the lithium metal electrode as the negative electrode, a constant current charge-discharge test is performed on a symmetric battery assembled with the electrolyte and metallic lithium. Li / Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I 0.2 / Li symmetric battery has a test current density of 15 mA / cm 2 and a charge-discharge time of 1 hour per cycle, and a test capacity density of 15 mAh / cm 2 According to the test results, Li / Li6PS 4.7 O 0.3 Cl 0.4 Br 0.4 I 0.2 / Li symmetric battery can cycle 1000 times at a current density of 15 mA / cm 2 and it is revealed that the polarization voltage does not change significantly, indicating that the electrolyte has excellent stability against lithium.

[0049] A battery charge-discharge test is performed on an all-solid-state primary lithium battery assembled with a lithium-indium alloy as the negative electrode and LFP as the positive electrode. The battery is tested at 15 mA / cm 2 After 1000 cycles, the discharge specific capacity becomes 16.3 mAh / cm 2

[0050] Comparative Example 1 The electrolyte in Comparative Example 1 has a molecular formula of Li6PS5Cl 0.5 Br 0.5 and ​Manufacture of lithium sulfide material, which is manufactured by the mutual reaction of a lithium-containing substance and a sulfur-containing substance, dissolving metallic lithium and elemental sulfur in ether respectively, making the molar ratio of the substances 2.1:1, subjecting to vacuum distillation after mixing to react and obtaining Li2S a), Weigh Li2S, P2S5, LiCl, and LiBr in a molar ratio and put them into an agate mortar, grind manually for 30 minutes, and then obtain a precursor electrolyte b), Bake the precursor electrolyte in a vacuum at 550 °C for 4 hours to obtain Li6PS5Cl 0.5 Br 0.5 Obtain an electrolyte c), and it is obtained by a manufacturing method including these steps.

[0051] Li6PS5Cl 0.5 Br 0.5 The electrolyte phase is an argyrodite phase, there is an impurity phase in the electrolyte, its X-ray diffraction graph is shown in Fig. 6, and it can be seen that there is a Li2S impurity peak in the electrolyte.

[0052] Li6PS5Cl 0.5 Br 0.5 The original room temperature AC test impedance diagram of the electrolyte is shown in Fig. 7, and its ionic conductivity at room temperature is shown in Table 2 and is 5 mS / cm.

[0053] The obtained Li6PS5Cl 0.5 Br 0.5 Immerse the obtained electrolyte in anisole solvent, immerse at room temperature for 2 hours and then dry. The room temperature AC test impedance diagram after immersion is shown in Fig. 7, and its electrolyte conductivity is shown in Table 2 and is 3.75 mS / cm.

[0054] The obtained Li6PS5Cl 0.5 Br 0.5 After exposing the obtained electrolyte in a drying chamber at a dew point of -40 °C for 4 hours, the room temperature AC test impedance diagram is shown in Fig. 7, and its ionic conductivity at room temperature is shown in Table 2 and is 3.5 mS / cm.

[0055] Table 2 Li6PS5Cl 0.5 Br 0.5 Ionic conductivity of the electrolyte at room temperature JPEG0007693020000002.jpg32170

[0056] Manufactured Li6PS5Cl 0.5 Br 0.5 To further study the stability of the electrolyte material against the lithium metal electrode and consider the feasibility of using the lithium metal electrode as the negative electrode, a constant current charge-discharge test was performed on a symmetric cell assembled with the electrolyte and metallic lithium, and the test results are shown in Figure 8. Li / Li6PS5Cl 0.5 Br 0.5 / Li symmetric cell has a test current density of 0.1 mA / cm 2 and a single charge-discharge time of 1 hour, and the test capacity density is 0.1 mAh / cm 2 . According to the test results, Li / Li6PS5Cl 0.5 Br 0.5 / Li symmetric cell can cycle for 1700 hours at a current density of 0.1 mA / cm 2 , and it is clear that the polarization voltage increases significantly, indicating that the stability of the electrolyte against lithium is lower.

[0057] Comparative Example 2 The electrolyte in Comparative Example 2 has a molecular formula of Li6PS 4.4 O 0.6 Cl 0.5 Br 0.5 , and The production of lithium sulfide materials, which is produced by the mutual reaction of lithium-containing substances and sulfur-containing substances, dissolving metallic lithium and elemental sulfur in ether respectively, making the molar ratio of substances 2.1:1, and reacting by vacuum distillation after mixing to obtain Li2S a), Weighing Li2S, P2S5, P2O5, and LiCl in a molar ratio and putting them into an agate mortar, manually grinding for 30 minutes to obtain a precursor of the electrolyte b), Firing the precursor of the electrolyte in a vacuum at 550 °C for 4 hours to obtain Li6PS 4.4 O 0.6 Cl0.5 Br 0.5 It is obtained by a production method including c) obtaining an electrolyte.

[0058] Li6PS 4.4 O 0.6 Cl 0.5 Br 0.5 The electrolyte phase is an argyrodite phase, and there is a Li2S impurity phase in the electrolyte.

[0059] Li6PS 4.4 O 0.6 Cl 0.5 Br 0.5 The ionic conductivity of the electrolyte at room temperature is 4.2 mS / cm.

[0060] The obtained Li6PS 4.4 O 0.6 Cl 0.5 Br 0.5 The electrolyte is immersed in an anisole solvent, immersed for 2 hours at room temperature and then dried, and its ionic conductivity at room temperature is 3.07 mS / cm.

[0061] The obtained Li6PS 4.4 O 0.6 Cl 0.5 Br 0.5 After the electrolyte is exposed at a dew point of -40 °C for 4 hours in a drying chamber, its ionic conductivity at room temperature becomes 2.90 mS / cm.

[0062] The manufactured Li6PS 4.4 O 0.6 Cl 0.5 Br 0.5 To further study the stability of the electrolyte material against a lithium metal electrode and consider the feasibility of using a lithium metal electrode as a negative electrode, a constant current charge-discharge test is performed on a symmetric cell assembled with the electrolyte and metallic lithium. Li / Li6PS 4.4 O 0.6 The Cl / Li symmetric cell has a test current density of 0.1 mA / cm 2 and a single charge-discharge time of 1 hour, and a test capacity density of 0.1 mAh / cm 2 According to the test results, Li / Li6PS4.4 O 0.6 The Cl / Li symmetric battery can be cycled for 950 hours at a current density of 0.1 mA / cm 2 It is revealed that the polarization voltage increases significantly, and it is explained that the stability of the electrolyte against lithium is lower.

[0063] Comparative Example 3 The electrolyte in Comparative Example 3 has a molecular formula of Li6PSe 4.8 O 0.2 Cl 0.5 Br 0.5 and is obtained by a production method including a) weighing Li2Se, P2Se5, P2O5, LiCl, and LiBr in a molar ratio and putting them into an agate mortar, manually grinding for 30 minutes to obtain a precursor of the electrolyte, and b) firing the precursor of the electrolyte in a vacuum at 550 °C for 4 hours to obtain Li6PSe 4.8 O 0.2 Cl 0.5 Br 0.5 the electrolyte.

[0064] Li6PSe 4.8 O 0.2 Cl 0.5 Br 0.5 The electrolyte phase is an argyrodite phase, and there is a Li2Se impurity phase in the electrolyte.

[0065] Li6PSe 4.8 O 0.2 Cl 0.5 Br 0.5 The ionic conductivity of the electrolyte at room temperature is 1.7 mS / cm.

[0066] The obtained Li6PSe 4.8 O 0.2 Cl 0.5 Br 0.5 The electrolyte is immersed in an anisole solvent, immersed at room temperature for 2 hours and then dried, and its ionic conductivity at room temperature is 1.02 mS / cm.

[0067] The obtained Li6PSe 4.8 O 0.2 Cl0.5 Br 0.5 After exposing the electrolyte in a drying chamber at a dew point of -40°C for 4 hours, its ionic conductivity at room temperature becomes 0.85 mS / cm.

[0068] The produced Li6PSe 4.8 O 0.2 Cl 0.5 Br 0.5 To further study the stability of the electrolyte material against the lithium metal electrode and consider the feasibility of using the lithium metal electrode as the negative electrode, a constant current charge-discharge test is performed on a symmetric cell assembled with the electrolyte and metallic lithium. Li / Li6PSe 4.8 O 0.2 Cl 0.5 Br 0.5 / Li symmetric cell has a test current density of 0.1 mA / cm 2 and a single charge-discharge time of 1 hour, and a test capacity density of 0.1 mAh / cm 2 . According to the test results, Li / Li6PSe 4.8 O 0.2 Cl 0.5 Br 0.5 / Li symmetric cell can cycle at a current density of 0.1 mA / cm 2 for 50 hours, and it is revealed that the polarization voltage increases significantly, indicating that the stability of the electrolyte against lithium is lower.

[0069] Comparative Example 4 The high-purity argyrodite-phase sulfide solid electrolyte in Comparative Example 4 has a molecular formula of Li6PS 4.8 O 0.2 Cl, and In the production of the lithium sulfide material, it is produced by the mutual reaction of a lithium-containing substance and a sulfur-containing substance. Metallic lithium and elemental sulfur are respectively dissolved in ether, the molar ratio of the substances is 2.1:1, and after mixing, it is subjected to vacuum distillation to react to obtain Li2S a), and Weigh Li2S, P2S5, P2O5, and LiCl in a molar ratio and put them into an agate mortar, and manually grind them for 30 minutes to obtain a precursor of the electrolyte b), and The precursor of the electrolyte is calcined in a vacuum at 550°C for 4 hours to obtain Li6PS4.8 O 0.2 It is obtained by a manufacturing method including c) obtaining a Cl electrolyte.

[0070] Li6PS 4.8 O 0.2 The Cl electrolyte phase is an argyrodite phase, and there is a Li2S impurity phase in the electrolyte.

[0071] Li6PS 4.8 O 0.2 The ionic conductivity of the Li6PS O Cl electrolyte at room temperature is 9.8 mS / cm.

[0072] The obtained Li6PS 4.8 O 0.2 The Li6PS O Cl electrolyte is immersed in an anisole solvent, immersed at room temperature for 2 hours and then dried, and its ionic conductivity at room temperature is 6.86 mS / cm.

[0073] The obtained Li6PS 4.8 O 0.2 After the Li6PS O Cl electrolyte is exposed at a dew point of -40 °C in a drying chamber for 4 hours, its ionic conductivity at room temperature becomes 6.57 mS / cm.

[0074] The manufactured Li6PS 4.8 O 0.2 To further study the stability of the manufactured Li6PS O Cl electrolyte material against a lithium metal electrode and consider the feasibility of using the lithium metal electrode as a negative electrode, a constant current charge-discharge test is performed on a symmetric battery assembled with the electrolyte and metallic lithium. Li / Li6PS 4.8 O 0.2 The Li / Li6PS O Cl / Li symmetric battery has a test current density of 0.1 mA / cm 2 and a single charge-discharge time of 1 hour, and a test capacity density of 0.1 mAh / cm 2 According to the test results, the Li / Li6PS 4.8 O 0.2 Cl / Li symmetric battery can cycle for 1000 hours at a current density of 0.1 mA / cm 2 It is revealed that the polarization voltage increases significantly, and it is explained that the stability of the electrolyte against lithium is lower.

[0075] Comparative Example 5 The high-purity argyrodite-phase sulfide solid electrolyte in Comparative Example 5 has a molecular formula of Li6PS 4.8 O 0.2 Br, and in the production of a lithium sulfide material, produced by the mutual reaction of a lithium-containing substance and a sulfur-containing substance, dissolving metallic lithium and elemental sulfur in ether respectively, making the molar ratio of the substances 2.1:1, subjecting to vacuum distillation after mixing to react to obtain Li2S a), and weighing Li2S, P2S5, P2O5, and LiCl in a molar ratio and putting them into an agate mortar, manually grinding for 30 minutes to obtain a precursor electrolyte b), and firing the precursor electrolyte in a vacuum at 550 °C for 4 hours to obtain a Li6PS 4.8 O 0.2 Br electrolyte c), and is obtained by a production method including these steps.

[0076] Li6PS 4.8 O 0.2 The Br electrolyte phase is an argyrodite phase, and there is a Li2S impurity phase in the electrolyte.

[0077] Li6PS 4.8 O 0.2 The ionic conductivity of the Li6PS

[0078] Br electrolyte at room temperature is 1.1 mS / cm. 4.8 O 0.2 The obtained Li6PS

[0079] Br electrolyte is immersed in an anisole solvent, immersed at room temperature for 2 hours and then dried, and its ionic conductivity at room temperature is 0.71 mS / cm. 4.8 O 0.2 The obtained Li6PS

[0080] Br electrolyte is exposed in a drying chamber at a dew point of -40 °C for 4 hours, and its ionic conductivity at room temperature becomes 0.66 mS / cm. 4.8 O 0.2To further study the stability of the Br electrolyte material against the lithium metal electrode and consider the feasibility of using the lithium metal electrode as the negative electrode, a constant current charge-discharge test is performed on a symmetric cell assembled with the electrolyte and metallic lithium. Li / Li6PS 4.8 O 0.2 The Br / Li symmetric cell has a test current density of 0.1 mA / cm 2 and a single charge-discharge time of 1 hour, and a test capacity density of 0.1 mAh / cm 2 According to the test results, the Li / Li6PS 4.8 O 0.2 The Br / Li symmetric cell can cycle for 100 hours at a current density of 0.1 mA / cm 2 It is revealed that the polarization voltage increases significantly, indicating that the stability of the electrolyte against lithium is lower.

[0081] Finally, it should be noted that the specific examples described in this specification are merely illustrative of the gist of the present invention and do not limit the embodiments of the present invention. A person skilled in the art can make various modifications or additions to the described specific examples or substitute them in a similar manner. It is not possible to cover all embodiments here, nor is it necessary. These obvious changes or modifications derived from the essence of the present invention still fall within the protection scope of the present invention, and any interpretation of them as additional limitations is contrary to the gist of the present invention.

Claims

1. A high-purity argyrodite-phase sulfide solid electrolyte, whose molecular formula is shown in the following formula I, Li ６ PS ５－ｇ G ｇ Cl １－ｔ T ｔ Formula I In formula I, 0 < g ≤ 0.5, 0.2 ≤ t < 1, G is a composite of Se and O or O, T is Br and I, The high-purity argyrodite-phase sulfide solid electrolyte is a pure phase and has no impurity peaks in the X-ray diffraction spectrum. A high-purity argyrodite-phase sulfide solid electrolyte characterized by this.

2. The ionic conductivity of the high-purity argyrodite-phase sulfide solid electrolyte at room temperature is 1.05×10 －２ ~ 8×10 －２ S / cm. The high-purity argyrodite-phase sulfide solid electrolyte according to claim 1, characterized by this.

3. When the high-purity argyrodite-phase sulfide solid electrolyte is exposed at a dew point of -40°C for 4 hours in a drying chamber, the ionic conductivity is reduced by ≤ 15%. The high-purity argyrodite-phase sulfide solid electrolyte according to claim 1, characterized by this.

4. When the high-purity argyrodite-phase sulfide solid electrolyte is immersed in an organic solvent at room temperature for 2 hours, the ionic conductivity is reduced by ≤ 20%. The high-purity argyrodite-phase sulfide solid electrolyte according to claim 1, characterized by this.

5. The organic solvent is one or more of ethylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, N-methylpyrrolidone, tetrahydrofuran, ethylene glycol dimethyl ether, anisole, 1,3-oxolane, toluene, xylene, chlorobenzene, normal heptane. The high-purity argyrodite-phase sulfide solid electrolyte according to claim 4, characterized by this.

6. The method for manufacturing a high-purity argyrodite-phase sulfide solid electrolyte according to claim 1, comprising: Step a) of manufacturing a lithium sulfide material; Step b) of weighing and mixing a raw material containing a lithium sulfide material and an oxidizing agent in a molar ratio; Step c) of annealing and firing the powder obtained in step b) to obtain a high-purity argyrodite-phase sulfide solid electrolyte. The oxidizing agent is P ２ O ５ or Li ３ PO ４ or I ２ or one or more of them, and the method for manufacturing a high-purity argyrodite-phase sulfide solid electrolyte according to claim 1.

7. The method for manufacturing a lithium sulfide material includes a ball milling method, a carbon thermal reduction method, or one or more of the mutual reactions of a lithium-containing sulfur compound, lithium metal sulfide nanoparticles, a lithium-containing substance, and a sulfur-containing substance, and the manufacturing method according to claim 6.

8. The mixing method in step b) includes one or more of manual polishing, mechanical stirring, mechanical vibration, mechanical ball milling, high-energy ball milling, and roll milling, and the manufacturing method according to claim 6.

9. When the mixing method in step b) is high-energy ball milling or roll milling, the ratio of balls to the material is (1 - 60):1, the rotation speed is 200 - 600 rpm, and the time is 4 - 24 hours, and the manufacturing method according to claim 8.

10. The annealing and firing temperature in step c) is 400 - 600 °C, and the time is 1 - 48 hours, and the manufacturing method according to claim 6.

11. An all-solid-state lithium secondary battery, A all-solid-state lithium secondary battery comprising a positive electrode, a negative electrode, and the high-purity argyrodite-phase sulfide solid electrolyte according to claim 1.

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