Rare earth element doped sulfide solid electrolyte, preparation method thereof and all-solid-state lithium battery

Abstract

The invention relates to a rare earth element doped sulfide solid electrolyte, a preparation method thereof and an all-solid-state lithium battery. The chemical composition of the rare earth element doped sulfide solid electrolyte is Li < 5.4 + x > P < 1-x > A < x > S < 4.4-2x > B < 2x > Cl < 1.6 > or Li < 5.4 + x > P < 1-x > A < x > S < 4.4 > B < 2x > Cl < 1.6-2x >, wherein x is more than or equal to 0.01 and less than or equal to 0.1; wherein A comprises at least one of a lanthanum element, a cerium element, a neodymium element, a samarium element and an ytterbium element, and B comprises at least one of an oxygen element, a fluorine element, a bromine element and an iodine element.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state lithium batteries, and particularly relates to a rare earth element-doped sulfide solid electrolyte, a preparation method thereof, and an all-solid-state lithium battery. Background Art

[0002] With the continuous increase in the demand for electronic products and new energy vehicles, higher requirements are put forward for the energy density and safety of batteries. Traditional organic liquid lithium-ion batteries have safety hazards such as being flammable and explosive, while all-solid-state lithium batteries use non-flammable and stable solid electrolytes; in addition, using lithium metal instead of the traditional graphite negative electrode greatly improves the energy density of the battery. Therefore, all-solid-state lithium batteries with high safety and high energy density are considered the development direction in the energy storage field. Solid electrolyte is the core of all-solid-state lithium battery technology, which can be further divided into polymer electrolyte, oxide electrolyte, and sulfide electrolyte. Polymer electrolyte has good film-forming property and high flexibility, but its room-temperature ionic conductivity is low. Oxide electrolyte has good stability, but its grain boundary impedance is relatively high and the interface contact is poor. Sulfide electrolyte has high ionic conductivity and can even be comparable to liquid electrolyte under certain conditions. In addition, sulfide electrolyte also has good mechanical processability, which makes it one of the most promising solid electrolytes for realizing all-solid-state lithium batteries. Among sulfide solid electrolytes, thio-LISICON solid electrolyte not only has high ionic conductivity but also has good electrochemical stability, and the research on it is the most extensive.

[0003] However, in practical applications, sulfide solid electrolytes face two major challenges. The first problem is that sulfide solid electrolytes react severely with moisture in the air: in a humid environment, due to the weak bond force between P-S bonds, H 2 O molecules are extremely likely to attack the main structure PS of the sulfide electrolyte 4 3- units, resulting in structural damage and the release of toxic H 2 S gas, which greatly increases the cost of using sulfide electrolytes. The second problem is that due to the narrow electrochemical window of sulfide electrolytes, their interface compatibility with lithium metal is poor, resulting in uneven deposition of lithium ions at the interface, and thus the phenomenon of lithium dendrite growth inside the electrolyte, ultimately leading to the deterioration of battery performance.

[0004] Therefore, while maintaining the high ionic conductivity of sulfide solid electrolytes, it is necessary to improve their air stability and interfacial compatibility with lithium anodes. To address the above issues, researchers have improved them by adding surface coating layers and intermediate interfacial layers. In addition, doping a small amount of metal cations such as Sn, Sb, and their oxides in sulfide solid electrolytes can also improve the stability of the materials. However, the surface coating layer will hinder the ionic conduction of lithium ions at the solid electrolyte interface, resulting in a decrease in ionic conductivity; the intermediate interfacial layer will cause hindrance to ionic transport at the electrolyte / electrode interface, resulting in a relatively large overall impedance of the battery and affecting the electrochemical performance of the battery. Summary of the Invention

[0005] In view of the above technical problems, the purpose of the present invention is to provide a rare earth element-doped sulfide solid electrolyte with high stability and high ionic conductivity, as well as the application of the obtained sulfide electrolyte in all-solid-state lithium batteries. The sulfide solid electrolyte is simple to prepare, has good air stability and compatibility with lithium metal, and has high ionic conductivity, which is expected to promote the practical application of sulfide solid electrolytes in all-solid-state lithium batteries.

[0006] In the first aspect, the present invention provides a rare earth element-doped sulfide solid electrolyte, and the chemical composition of the rare earth element-doped sulfide solid electrolyte is: Li 5.4+x P 1-x A x S 4.4-2x B 2x Cl 1.6 or Li 5.4+x P 1-x A x S 4.4 B 2x Cl 1.6-2x , 0.01 ≤ x ≤ 0.1; wherein: A includes at least one of lanthanum element, cerium element, neodymium element, samarium element, and ytterbium element, and B includes at least one of oxygen element, fluorine element, bromine element, and iodine element.

[0007] Preferably, the ionic conductivity of the rare earth element-doped sulfide solid electrolyte at 25 °C is greater than 5 mS / cm and less than 2×10 -9 S / cm.

[0008] Preferably, the amount of H 2 S released by the rare earth element-doped sulfide solid electrolyte in a sealed container with air having a humidity of 30-50% within 30-60 minutes is less than 0.8 cm 3 / g.

[0009] Preferably, the critical current density of the lithium symmetric battery assembled with the rare earth element-doped sulfide solid electrolyte is greater than 0.5 mA / cm at 25 °C. 2 .

[0010] Preferably, the time of stable constant current long cycle of the lithium symmetric battery assembled with the rare earth element-doped sulfide solid electrolyte is greater than 2000 h at 25 °C and 0.1 mA / cm. 2 .

[0011] In a second aspect, the present invention provides a method for preparing the above-mentioned rare earth element-doped sulfide solid electrolyte. The preparation method includes the following steps: under an inert atmosphere, weighing raw materials according to the chemical composition ratio of the rare earth element-doped sulfide solid electrolyte, mixing and grinding them, and then performing solid-phase sintering to obtain the rare earth element-doped sulfide solid electrolyte.

[0012] Preferably, the Li source in the raw materials includes at least one of lithium sulfide, lithium chloride, lithium oxide, lithium bromide, lithium iodide, and lithium fluoride; the P source includes phosphorus pentasulfide; the S source includes at least one of phosphorus pentasulfide, lithium sulfide, cerium sulfide, and samarium sulfide; the Cl source includes lithium chloride; the A source includes at least one of lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, ytterbium oxide, lanthanum sulfide, cerium sulfide, neodymium sulfide, samarium sulfide, and ytterbium sulfide; the B source includes at least one of lithium oxide, lanthanum oxide, cerium oxide, lithium fluoride, lithium bromide, and lithium iodide.

[0013] Preferably, the temperature of the solid-phase sintering is 480 - 520 °C, and the time is 12 - 20 hours.

[0014] In a third aspect, the present invention provides a all-solid-state lithium battery, which includes a positive electrode, the above-mentioned rare earth element-doped sulfide solid electrolyte, and a metallic lithium negative electrode.

[0015] Preferably, the capacity retention rate of the all-solid-state lithium battery after 200 constant current long cycles at 25 °C and 0.1 C is greater than 95%.

[0016] Advantageous Effects (1) The rare earth element-doped sulfide solid electrolyte provided by the present invention forms coordination with sulfur ions through the hetero-valent substitution of rare earth elements and forms coordination with phosphorus ions through the homo-valent or hetero-valent substitution of anions, improving the air stability of the sulfide solid electrolyte. (2) The rare earth element-doped sulfide solid electrolyte provided by the present invention effectively improves the ionic conductivity of the sulfide solid electrolyte by regulating the types and doping ratios of doping elements. (3) The rare earth element-doped sulfide solid electrolyte provided by the present invention has a low electronic conductivity, can effectively inhibit the growth of lithium dendrites, enhance the compatibility between the sulfide solid electrolyte and lithium metal, achieve excellent electrochemical performance, and improve the cycle stability of all-solid-state lithium batteries. Description of the Drawings

[0017] Figure 1 It is a test chart of the air stability of the electrolytes prepared in Comparative Examples 1-2 and Examples 1-5 of the present invention; Figure 2 It is a current-time relationship chart of the sulfide solid electrolyte in Comparative Example 1 and Example 3 of the present invention at a constant external voltage of 0.5 V; Figure 3 It is for the lithium symmetric batteries in Comparative Example 1 and Example 4 of the present invention at 0.1 mA / cm 2 and a constant current long-cycle performance chart at 25 °C; Figure 4 It is a constant current long-cycle performance chart of the all-solid-state lithium batteries in Comparative Example 1 and Example 5 of the present invention. Detailed Embodiments

[0018] The present invention will be further described below through the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and do not limit the present invention.

[0019] First, the present invention provides a rare earth element-doped sulfide solid electrolyte. Among them, the chemical composition of the rare earth element-doped sulfide solid electrolyte can be: Li 5.4+x P 1-x A x S 4.4-2x B 2x Cl 1.6 or Li 5.4+x P 1- x A x S 4.4 B 2x Cl 1.6-2x , 0.01 ≤ x ≤ 0.1; where: A can include at least one of lanthanum element, cerium element, neodymium element, samarium element, ytterbium element, and B can include at least one of oxygen element, fluorine element, bromine element, iodine element.

[0020] It should be noted that the doped matrix sulfide solid electrolyte Li 5.4 PS 4.4 Cl 1.6 is an electrolyte obtained by further improving Li 6 PS 5 Cl, and Li 6 PS 5The Cl electrolyte belongs to a different crystal structure from the conventional electrolyte matrix. For example, Li 10 P 2 S 12 has problems of poor air stability and interfacial compatibility. Li 10 GeP 2 S 12 has problems of poor compatibility with lithium metal. The Li 6 PS 5 Cl electrolyte adopted in the present invention has better air stability and interfacial compatibility, and its ionic conductivity is slightly lower. However, by increasing the Cl content, the ionic conductivity of the Li 6 PS 5 Cl electrolyte can be significantly improved. And Li 5.4 PS 4.4 Cl 1.6 has good interfacial compatibility, but it will lead to poor air stability. Therefore, doping rare earth elements on the Li 5.4 PS 4.4 Cl 1.6 matrix can obtain an electrolyte with higher ionic conductivity, better air stability, and excellent interfacial compatibility.

[0021] Furthermore, rare earth elements have rich electronic orbital characteristics. In the present invention, coordination is formed with sulfur ions through hetero-valent substitution of rare earth elements, and at the same time, coordination is formed with phosphorus ions by combining homo-valent or hetero-valent substitution of anions, enhancing the structural stability of the sulfide solid electrolyte, improving the air stability of the electrolyte, and realizing the possibility of mass production in an air environment / dry room. In addition, doping with rare earth elements with a larger ionic radius can increase the crystal plane spacing of the electrolyte, broaden the lithium ion transport channels, thereby promoting the rapid transport of lithium ions and increasing the ionic conductivity. At the same time, the electronegativity difference between rare earth elements with lower electronegativity than phosphorus and sulfur is larger, increasing the electron migration barrier, thus hindering the transfer of electrons at the grain boundaries, effectively suppressing the growth of lithium dendrites inside the electrolyte, and further improving the compatibility between the electrolyte and lithium metal.

[0022] The choice of A is a rare earth element. Rare earth elements have low electronegativity. After doping, they can reduce the ionic transport impedance at the grain boundaries of the electrolyte, improve the ionic conductivity, at the same time increase the electron transport barrier, reduce the electronic conductivity, and further improve the compatibility between the electrolyte and lithium metal. The element B is selected from oxygen element and halogen. As a hard base, the oxygen element can form a strong binding with the hard acid P after doping, improving the air stability of the electrolyte. Halogen doping can increase the anion disorder degree, improve the ionic conductivity, and can in-situ form a lithium halide intermediate layer with lithium metal in the battery, guiding the uniform deposition of lithium ions and improving the interfacial compatibility. The combination of A and B elements can improve the air stability, ionic conductivity and interfacial compatibility of the electrolyte at the same time.

[0023] It should also be noted that rare earth doping can improve the ionic conductivity of the electrolyte, promote the interfacial lithium ion transport, reduce the uneven deposition of lithium metal; reduce the electronic conductivity, inhibit the growth of lithium dendrites inside the electrolyte, and improve the interfacial compatibility with the lithium negative electrode. If the doping ratio of rare earth elements is too small, it is easy to cause the inability to incorporate into the lattice and fail to achieve the effect of improving its performance; if the doping ratio is too large, it is easy to cause the distortion of the electrolyte crystal structure and the appearance of impurity phases, which is not conducive to ion transport and the interfacial compatibility will also decrease.

[0024] In some embodiments, the ionic conductivity of the rare earth element-doped sulfide solid electrolyte at 25 °C can be greater than 5 mS / cm and less than 2×10 -9 S / cm.

[0025] In some embodiments, the amount of H 2 S released by the rare earth element-doped sulfide solid electrolyte in a sealed container with 30-50% humidity air within 30-60 minutes is less than 0.8 cm 3 / g.

[0026] In some embodiments, the critical current density of the lithium symmetric battery assembled with the rare earth element-doped sulfide solid electrolyte at 25 °C is greater than 0.5 mA / cm 2 .

[0027] In some embodiments, the stable constant current long cycle time of the lithium symmetric battery assembled with the rare earth element-doped sulfide solid electrolyte at 25 °C and 0.1 mA / cm 2 is greater than 2000 h.

[0028] That is, the present invention effectively improves the ionic conductivity of the sulfide solid electrolyte by regulating the types and doping ratios of doping elements, and at the same time has excellent air stability and stability to lithium metal, and can be applied to all-solid-state lithium batteries.

[0029] Hereinafter, an exemplary description of the preparation method of the rare earth element-doped sulfide solid electrolyte provided by the present invention is given. Among them, the preparation method may include the following steps: Under an inert atmosphere, weigh the raw materials according to the chemical composition ratio of the rare earth element-doped sulfide solid electrolyte, mix and grind them, and then perform solid-phase sintering to obtain the rare earth element-doped sulfide solid electrolyte.

[0030] In some embodiments, the inert atmosphere may be argon.

[0031] In some embodiments, the error in weighing the raw materials is controlled between 0 and +0.0005 grams.

[0032] In some embodiments, the Li source in the raw materials may include at least one of lithium sulfide, lithium chloride, lithium oxide, lithium bromide, lithium iodide, and lithium fluoride; the P source may include phosphorus pentasulfide; the S source may include at least one of phosphorus pentasulfide, lithium sulfide, cerium sulfide, and samarium sulfide; the Cl source may include lithium chloride; the A source may include at least one of lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, ytterbium oxide, lanthanum sulfide, cerium sulfide, neodymium sulfide, samarium sulfide, and ytterbium sulfide; and the B source may include at least one of lithium oxide, lanthanum oxide, cerium oxide, lithium fluoride, lithium bromide, and lithium iodide.

[0033] In some embodiments, the temperature of the solid-phase sintering may be 480 - 520 °C, and the time may be 12 - 20 h.

[0034] In addition, the present invention also provides a all-solid-state lithium battery. Among them, the all-solid-state lithium battery may include a positive electrode, the above-mentioned rare-earth element-doped sulfide solid electrolyte, and a metallic lithium negative electrode.

[0035] In some embodiments, the capacity retention rate of the all-solid-state lithium battery after 200 constant-current long cycles at 25 °C and 0.1C is greater than 95%.

[0036] The following further gives examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, rather than being limited to the specific values in the following examples. Unless otherwise specified, the technical means used in the examples are conventional means well-known to those skilled in the art.

[0037] Unless otherwise specified: The reagents and equipment used in the present invention can be obtained through conventional channels by commercial purchase; the present invention uses a Neware test system to test the performance of lithium symmetric batteries and all-solid-state lithium batteries.

[0038] Example 1

[0039] The preparation method of the rare-earth element-doped sulfide solid electrolyte and the lithium symmetric battery provided in this example includes the following steps: (1) Under an argon atmosphere, according to Li 5.41 P 0.99 La 0.01 S 4.38 O 0.02 Cl 1.6Weigh 1.3702 g (0.0323 mol) of LiCl, 2.2225 g (0.01 mol) of P 2 S 5 、1.7681 g (0.0385 mol) of Li 2 S, 0.0326 g (0.0001 mol) of La 2 O 3 ; (2) Pour the weighed raw materials into a mortar under an argon atmosphere and grind for 20 minutes; then pour the raw materials into a ball mill jar, add zirconia balls with a diameter of 5 mm, the ball-to-material ratio is 40:1, ball mill for 1 h, and the rotation speed is 300 rpm; load the ball-milled precursor into a quartz crucible under an argon atmosphere, and place the quartz crucible containing the precursor into a muffle furnace in a glove box (water < 0.01 ppm, oxygen < 0.01 ppm), set the temperature to 500 °C, and calcine for 20 h; after cooling, Li 5.41 P 0.99 La 0.01 S 4.3 8 O 0.02 Cl 1.6 rare earth element-doped sulfide solid electrolyte can be obtained; (3) Weigh 400 mg of Li 5.41 P 0.99 La 0.01 S 4.38 O 0.02 Cl 1.6 rare earth element-doped sulfide solid electrolyte powder, put it into a closed container with a humidity of 30%, the volume of the container is 3.806 L, place a hydrogen sulfide detector inside the container to monitor the hydrogen sulfide concentration (the detector is purchased from MSA Sensors (Shanghai) Co., Ltd.), and it is calculated that 1 ppm = 0.00095 cm 3 / g, after 30 min, data is obtained, and the data is exported through software for data plotting; (4) Use a solid-state mold battery to test Li 5.41 P 0.99 La 0.01 S 4.38 O 0.02 Cl 1.6 rare earth element-doped sulfide solid electrolyte: Weigh 100 mg of the above-mentioned rare earth element-doped sulfide solid electrolyte powder, pour it into a Φ10 mm mold, add Φ10 mm carbon-coated aluminum foil on both sides of the electrolyte, and press it under a powder press at a pressure of 360 MPa for 5 min; then conduct tests on ionic conductivity and electronic conductivity, and the test conditions are 25 °C; (5) The prepared Li 5.41 P0.99 La 0.01 S 4.38 O 0.02 Cl 1.6 Assemble a lithium symmetric battery with a rare earth element-doped sulfide solid electrolyte and test the critical current density of the battery at 25 °C; test the constant current long-term cycling performance of the battery at 25 °C and 0.1 mA / cm 2 below.

[0040] Example 2

[0041] The preparation methods of the rare earth element-doped sulfide solid electrolyte and the lithium symmetric battery provided in this example refer to Example 1. The main difference is that: In step (1), under an argon atmosphere, according to the stoichiometric ratio in Li 5.42 P 0.98 Ce 0.02 S 4.36 O 0.04 Cl 1.6 weigh the raw materials LiCl, P 2 S 5 , Li 2 S, CeO 2 .

[0042] Example 3

[0043] The preparation methods of the rare earth element-doped sulfide solid electrolyte and the lithium symmetric battery provided in this example refer to Example 1. The main difference is that: In step (1), under an argon atmosphere, according to the stoichiometric ratio in Li 5.45 P 0.95 Ce 0.05 S 4.4 Br 0.1 Cl 1.5 weigh the raw materials LiCl, P 2 S 5 , Li 2 S, Ce 2 S 3 , LiBr.

[0044] Example 4

[0045] The preparation methods of the rare earth element-doped sulfide solid electrolyte and the lithium symmetric battery provided in this example refer to Example 1. The main difference is that: In step (1), under an argon atmosphere, according to the stoichiometric ratio in Li 5.44 P 0.96 Sm 0.04 S 4.4 Br 0.04 I 0.04 Cl 1.52Weigh the raw materials LiCl and P according to the stoichiometric ratio in 2 S 5 、Li 2 S, Sm 2 S 3 、LiBr, LiI.

[0046] Example 5

[0047] The preparation methods of the rare earth element-doped sulfide solid electrolyte and the lithium symmetric battery provided in this example refer to Example 1. The main differences are as follows: In step (1), under an argon atmosphere, according to Li 5.46 P 0.94 La 0.04 Sm 0.02 S 4.4 F 0.12 Cl 1.48 Weigh the raw materials LiCl and P according to the stoichiometric ratio in 2 S 5 、Li 2 S, La 2 S 3 、Sm 2 S 3 、LiF; In step (6), weigh 100 mg of the prepared Li 5.46 P 0.94 La 0.04 Sm 0.02 S 4.4 F 0.12 Cl 1.48 Pour the rare earth element-doped sulfide solid electrolyte powder into a Φ10 mm mold and press it at a pressure of 250 MPa for 1 minute; for the positive electrode, mix it according to the ratio of LiNi 0.6 Co 0.2 Mn 0.2 O 2 : rare earth oxide sulfide solid electrolyte: VGCF = 7:2.5:0.5, weigh 3 mg of the composite positive electrode powder and add it to one side of the electrolyte layer. After spreading it evenly, perform a second pressing at a pressure of 360 MPa for 5 minutes; place a Φ10 mm lithium sheet on the negative electrode side and press it at a pressure of 50 MPa for 1 minute; the assembled all-solid-state lithium battery is subjected to a constant current charge-discharge test at 25 °C under a current density of 0.1 C, and the charge-discharge range is 2.8 - 4.3 V.

[0048] Comparative Example 1

[0049] The preparation methods of the sulfide solid electrolyte, the lithium symmetric battery, and the all-solid-state lithium battery provided in this comparative example include the following steps: (1) Under an argon atmosphere, according to Li 5.4 PS4.4 Cl 1.6 Weigh the raw materials LiCl, P 2 S 5 , Li 2 S according to the stoichiometric ratio in (2) Pour the weighed raw materials into a mortar under an argon atmosphere and grind for 20 minutes; then pour the raw materials into a ball mill jar, add zirconia balls with a diameter of 5 mm, the ball-to-material ratio is 40:1, ball mill for 1 h, and the rotation speed is 300 rpm; load the ball-milled precursor into a quartz crucible under an argon atmosphere, and place the quartz crucible containing the precursor into a muffle furnace in a glove box (water < 0.01 ppm, oxygen < 0.01 ppm), set the temperature to 500 °C, calcine for 20 h, and after cooling, Li 5.4 PS 4.4 Cl 1.6 sulfide solid electrolyte can be obtained; (3) Weigh 400 mg of Li 5.4 PS 4.4 Cl 1.6 sulfide solid electrolyte powder, put it into a sealed container with a humidity of 30%, the volume of the container is 3.806 L, place a hydrogen sulfide detector inside the container to monitor the hydrogen sulfide concentration (the detector is purchased from MSA Sensing Instruments (Shanghai) Co., Ltd.), and it is calculated that 1 ppm = 0.00095 cm 3 / g. After 30 minutes, data is obtained, and the data is exported through software for data plotting; (4) Use a solid-state mold battery to test the Li 5.4 PS 4.4 Cl 1.6 sulfide solid electrolyte: Weigh 100 mg of the above-mentioned rare earth sulfide solid electrolyte powder, pour it into a Φ10 mm mold, add Φ10 mm carbon-coated aluminum foil on both sides of the electrolyte, and press it under a powder press at a pressure of 360 MPa for 5 minutes; then conduct tests on ionic conductivity and electronic conductivity, and the test conditions are 25 °C. The test results are shown in Table 1; (5) Assemble a lithium symmetric battery with the prepared Li 5.4 PS 4.4 Cl 1.6 sulfide solid electrolyte, and test the critical current density of the battery at 25 °C; test the long-term constant current cycling performance of the battery at 25 °C and 0.1 mA / cm 2 ; (6) Weigh 100 mg of the prepared Li 5.4 PS 4.4 Cl 1.6 sulfide solid electrolyte powder, pour it into a Φ10 mm mold, and press it at a pressure of 250 MPa for 1 minute; the positive electrode is prepared according to LiNi 0.6 Co0.2 Mn 0.2 O 2 : Sulfide solid electrolyte: mixed in a ratio of VGCF = 7:2.5:0.5. Weigh 3 mg of the composite cathode powder and add it to one side of the electrolyte layer. After spreading it evenly, perform a second pressing at a pressure of 360 MPa for 5 minutes. Place a Φ10 mm lithium sheet on the negative electrode side and press it at a pressure of 50 MPa for 1 minute. The assembled all-solid-state lithium battery is subjected to a constant current charge-discharge test at 25 °C under a current density of 0.1 C, and the charge-discharge range is 2.8 - 4.3 V.

[0050] Comparative Example 2

[0051] The preparation method of the sulfide solid electrolyte and the lithium symmetric battery provided in this comparative example refers to Comparative Example 1. The main difference is that: In step (1), under an argon atmosphere, according to the stoichiometric ratio in Li 5.6 P 0.8 Ce 0.2 S 4 O 0.4 Cl 1.6 weigh the raw materials LiCl, P 2 S 5 、Li 2 S、CeO 2 .

[0052] Table 1 shows the test results of the ionic conductivity and critical current density of the solid electrolytes prepared in Examples 1 - 5 and Comparative Examples 1 - 2: Ionic conductivity (mS / cm) <![CDATA[Critical current density (mA / cm 2 )]]> Example 1 5.67 0.9 Example 2 7.13 1.2 Example 3 6.32 1.3 Example 4 5.97 1.1 Example 5 5.27 0.9 Comparative Example 1 4.26 0.5 Comparative Example 2 2.13 0.6

[0053] Figure 1 This is the air stability test chart of the electrolytes prepared in Comparative Examples 1 - 2 and Examples 1 - 5 of the present invention. It can be seen from the figure that the H 5.41 P 0.99 La 0.01 S 4.38 O 0.02 Cl 1.6 sulfide solid electrolyte in Example 1 released 0.75 cm 2 / g of H 3 S gas after being exposed to 30% humidity for 30 min. The H 5.42 P 0.98 Ce 0.02 S 4.36 O 0.04 Cl 1.6 sulfide solid electrolyte in Example 2 released 0.26 cm 2 / g of H 3 S gas after being exposed to 30% humidity for 30 min. The Li5.45 P 0.95 Ce 0.05 S 4.4 Br 0.1 Cl 1.5 The H₂S gas release amount of the sulfide solid electrolyte after being exposed to 30% humidity for 30 min is 0.08 cm³ / g. For Li₃PS₄ in Example 4 2 / g, for Li₃PS₄ in Example 4 3 / g, for Li₃PS₄ in Example 4 5.44 P 0.96 Sm 0.04 S 4.4 Br 0.04 I 0.04 Cl 1.52 The H₂S gas release amount of the sulfide solid electrolyte after being exposed to 30% humidity for 30 min is 0.36 cm³ / g. For Li₃PS₄ in Example 5 2 / g, for Li₃PS₄ in Example 5 3 / g, for Li₃PS₄ in Example 5 5.46 P 0.94 La 0.04 Sm 0.02 S 4. 4 F 0.12 Cl 1.48 The H₂S gas release amount of the sulfide solid electrolyte after being exposed to 30% humidity for 30 min is 0.13 cm³ / g. All have excellent air stability; for Li₃PS₄ in Comparative Example 1 2 / g, for Li₃PS₄ in Comparative Example 1 3 / g, for Li₃PS₄ in Comparative Example 1 5.4 PS 4.4 Cl 1.6 The H₂S gas release amount of the sulfide solid electrolyte after being exposed to 30% humidity for 30 min is 2.03 cm³ / g. For Li₃PS₄ in Comparative Example 2 2 / g, for Li₃PS₄ in Comparative Example 2 3 / g, for Li₃PS₄ in Comparative Example 2 5.6 P 0.8 Ce 0.2 S 4 O 0.4 Cl 1.6 The H₂S gas release amount of the sulfide solid electrolyte after being exposed to 30% humidity for 30 min is 1.27 cm³ / g. 2 / g. 3 / g.

[0054] Figure 2 This is the current-time relationship diagram of the sulfide solid electrolytes in Comparative Example 1 and Example 3 of the present invention at a constant external voltage of 0.5 V. It can be calculated from the figure that for Li₃PS₄ in Example 3 5.45 P 0.95 Ce 0.05 S 4.4 Br 0.1 Cl 1.5The electronic conductivity is 1.54×10 -9 S / cm. The relatively low electronic conductivity is beneficial to suppressing the transport of electrons within the solid electrolyte, thereby inhibiting the growth of lithium dendrites within the electrolyte and improving the cycle life of the battery. The electronic conductivity of the electrolyte in Comparative Example 1 is 3.24×10 -9 S / cm.

[0055] Figure 3 Figure 1 shows the constant current long cycle performance graphs of the lithium symmetric batteries in Comparative Example 1 and Example 4 of the present invention at 0.1 mA / cm 2 and 25 °C. It can be seen from the figure that the lithium symmetric battery in Example 4 can stably cycle for 5000 h, demonstrating excellent interfacial compatibility between the electrolyte and lithium metal. The polarization of the symmetric battery in Comparative Example 1 suddenly increases after 120 cycles, indicating that due to the poor compatibility between the electrolyte and lithium metal, uneven deposition of lithium metal occurs at the interface, resulting in a large gap between the lithium sheet and the electrolyte, leading to abnormal increase in battery polarization.

[0056] Figure 4 Figure 2 shows the constant current long cycle performance graphs of the all-solid-state lithium batteries in Comparative Example 1 and Example 5 of the present invention. It can be seen from the figure that the battery capacity in Comparative Example 1 rapidly decays after 200 cycles, and the capacity retention rate is only 56.62%. The all-solid-state lithium battery assembled in Example 5 has a higher discharge capacity and better cycle stability, and the capacity retention rate of the battery is 98.44% after 200 cycles.

[0057] The above research shows that: within a certain doping ratio range (0.01 ≤ x ≤ 0.1), the ionic conductivity of rare earth element doped sulfide solid electrolytes is improved to varying degrees, and the critical current density is also increased, indicating that rare earth element doping can improve the ionic conductivity of sulfide electrolytes and their compatibility with lithium metal, thereby enhancing the electrochemical performance of all-solid-state lithium batteries. In addition, the air stability of rare earth element doped sulfide electrolytes is significantly improved, providing the possibility for realizing batch production of sulfide solid electrolytes in an air environment / dry room.

[0058] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A rare earth element doped sulfide solid electrolyte, characterized in that: The chemical composition of the rare earth element doped sulfide solid electrolyte is: Li 5.4+x P 1-x A x S 4.4-2x B 2x Cl 1.6 or Li 5.4+x P 1-x A x S 4.4 B 2x Cl 1.6-2x , 0.01≤x≤0.1; Wherein: A includes at least one of lanthanum, cerium, neodymium, samarium and ytterbium; and B includes at least one of oxygen, fluorine, bromine and iodine.

2. The rare earth element doped sulfide solid electrolyte according to claim 1, characterized in that: The ionic conductivity of the rare earth element doped sulfide solid electrolyte at 25°C is greater than 5 mS / cm and less than 2×10 -9 S / cm.

3. The rare earth element-doped sulfide solid electrolyte according to claim 1 or 2, characterized in that: The amount of H2S released by the rare earth element doped sulfide solid electrolyte in a closed container containing air with a humidity of 30 to 50% for 30 to 60 minutes is less than 0.8 cm 3 / g.

4. The rare earth element-doped sulfide solid electrolyte according to any one of claims 1 to 3, characterized in that: The critical current density of the lithium symmetric battery assembled with the rare earth element doped sulfide solid electrolyte at 25°C is greater than 0.5 mA / cm 2 .

5. The rare earth element-doped sulfide solid electrolyte according to any one of claims 1 to 4, characterized in that: The lithium symmetric battery assembled with the rare earth element doped sulfide solid electrolyte has a high conductivity at 25°C and 0.1 mA / cm 2 The stable constant current long cycle time under this condition is greater than 2000h.

6. A method for preparing a rare earth element-doped sulfide solid electrolyte according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: in an inert atmosphere, raw materials are weighed according to the chemical composition ratio of the rare earth element doped sulfide solid electrolyte, and the raw materials are mixed and ground, and then solid-phase sintering is performed to obtain the rare earth element doped sulfide solid electrolyte.

7. The preparation method according to claim 6, characterized in that: The Li source in the raw material includes at least one of lithium sulfide, lithium chloride, lithium oxide, lithium bromide, lithium iodide, and lithium fluoride, the P source includes phosphorus pentasulfide, the S source includes at least one of phosphorus pentasulfide, lithium sulfide, cerium sulfide, and samarium sulfide, the Cl source includes lithium chloride, the A source includes at least one of lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, ytterbium oxide, lanthanum sulfide, cerium sulfide, neodymium sulfide, samarium sulfide, and ytterbium sulfide, and the B source includes at least one of lithium oxide, lanthanum oxide, cerium oxide, lithium fluoride, lithium bromide, and lithium iodide.

8. The preparation method according to claim 6 or 7, characterized in that: The solid phase sintering is carried out at a temperature of 480-520° C. and for a time of 12-20 hours.

9. An all-solid-state lithium battery, characterized in that: The all-solid-state lithium battery comprises a positive electrode, a rare earth element-doped sulfide solid electrolyte according to any one of claims 1 to 5, and a metallic lithium negative electrode.

10. The all-solid-state lithium battery according to claim 9, characterized in that: The capacity retention rate of the all-solid-state lithium battery after 200 cycles of constant current long cycle at 25° C. and 0.1C is greater than 95%.

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