Sulfide-based solid electrolyte, method for producing and using the same, and solid battery cell containing the same

Abstract

To provide a sulfide-based solid electrolyte that is free from Ge and exhibits superior electrochemical and chemical stability and high lithium ion conductivity.SOLUTION: There is provided a sulfide-based solid electrolyte comprising or consisting of the following general chemical formula: Li(4-x)[M'kM"1-k]1-xPxS4-zOz, where 0.33≤x≤0.65, 0.1≤k≤0.5, and 0≤z≤1.0; M' is selected from Si; and M" is selected from Sn. Here, the solid electrolyte is characterized in that the X-ray diffraction peak with CuKα radiation is at 2θ=29.58°±0.5°. This sulfide-based solid electrolyte exhibits particularly high ionic conductivity, high chemical and electrochemical stability, superior hydrolysis resistance, and extended cycle stability, thereby contributing to the longer cycle life in a solid battery cell.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to sulfide-based solid electrolytes, their production and use, and solid battery cells containing them.

Background Art

[0002] In battery technology, in recent years, lithium-ion battery systems have become increasingly widespread. This is particularly due to their high energy density and long predicted lifespan, which has enabled more efficient battery configurations. In this case, the high chemical reactivity, low mass, and high mobility of lithium ions play a central role. In solid batteries, both the electrodes and the electrolyte are made of solid materials. In lithium-ion batteries, lithium compounds are present in all three phases of the electrochemical cell, i.e., the positive electrode, the negative electrode, and the electrolyte solution contain lithium ions from a solid lithium-ion conductor. Here, a general advantage of lithium-based solid batteries is that the often flammable or highly toxic and easily decomposable liquid electrolyte is replaced, thus improving the safety and reliability of lithium-based batteries.

[0003] Particularly for electric vehicles, great interest has been focused on the development of high-power and high-capacity lithium-based solid batteries. For high battery performance, generally, from the perspective of maximizing the performance of the battery, a solid electrolyte material with good ion conductivity is desirable.

[0004] Already in 2011, Kamaya et al. discovered a sulfide-based solid electrolyte having the general chemical formula Li 10+x M 1+x P 2-x S 12 , where M is any element of Groups 13-16 of the periodic table (Non-Patent Document 1). Here, in particular, the solid electrolyte of the chemical formula Li 10 GeP2S 12 has received particular attention, which is the "LGPS-based sulfide solid electrolyte" or simply "LGPS" ( L ithium- G ermanium-P Phosphor- S sulfur, lithium germanium phosphorus sulfur) is called. This discovered material has a high ionic conductivity comparable to that of a 12×10 ―3 Scm ―1 electrolyte solution. In particular, this LGPS showed a high ionic conductivity of 10 ―2 S / cm, achieving a record ionic conductivity that exceeds the values of some liquids (see Patent Document 1).

[0005] However, LGPS has many drawbacks. That is, germanium (Ge) is expensive. Furthermore, germanium has low chemical stability, for example, low electrochemical reduction resistance. In the LGPS-based electrochemical solid material described in Patent Document 1, the reduction potential of germanium is (Li / Li + compared to) only about 0.25V. When this is used in a battery together with an active material for a negative electrode with an operating potential of less than 0.25V, there is a problem that the sulfide-based solid electrolyte material undergoes reductive decomposition, resulting in deterioration.

[0006] In tests using pure lithium metal, LGPS decomposed rapidly, and the products formed were ion-insulating. As a result, the cell already lost capacity and performance after only a few cycles.

[0007] One possibility to stabilize the LGPS material is to dope oxygen atoms into selective sulfur sites within the crystal structure (Non-Patent Document 2). However, this approach leads to a significant decrease in ionic conductivity, thereby severely limiting the usefulness of the LGPS material as an alternative to liquid electrolytes.

[0008] Furthermore, the LGPS material hydrolyzes when in contact with water, forming toxic H2S gas. This high sensitivity to moisture poses a risk to end-users when this material is exposed to the surrounding atmosphere and also causes problems during the processing of this material because extremely high sensitivity to moisture is considered and costly preventive measures must be taken.

[0009] Among the many proposals of the prior art, only the following will be described.

[0010] From Patent Document 2, for example, the following electrolytes are known, which are Li a SiSnP b S c O d -containing electrolytes, where 2 ≤ a ≤ 10, 4 ≤ c ≤ 12, and 0 ≤ d ≤ 3.4, and this electrolyte is characterized by XRD peaks of primary CuK alpha at 2θ = 30° ± 1°, 2θ = 33° ± 1°, and 2θ = 43° ± 1°. For b, for example, 0.5 ≤ b ≤ 2.5 is applicable. According to an embodiment, the electrolyte is Li 10 SiSnP2S4O d . The electrolyte Li a MP b S c is also described, where M = Si, Ge, and / or Sn. According to the present invention, germanium is absent, and the crystal structure here is completely different from that of the present invention.

[0011] Furthermore, it is further known from Patent Document 3 (corresponding to Patent Document 4) that a sulfide solid electrolyte material contains an M1 element, an M2 element, and an S element, where the M1 element contains at least Li, and the M2 element is at least one element selected from the group consisting of P, Sb, Si, Ge, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. This sulfide solid electrolyte material has a maximum value at a position of 2θ = 29.58° ± 0.50° in X-ray diffraction measurement using CuK alpha rays. When the diffraction intensity of the maximum value at 2θ = 29.58° ± 0.50° is IA and the diffraction intensity of the maximum value at 2θ = 27.33° ± 0.50° is IB, the value of IB / IA is less than 0.50. At this time, M2 contains at least P and Si. According to a preferred embodiment, the sulfide solid electrolyte material has the general formula Li (4-x) (Ge 1-δ Si δ ) (1-x) P x (S 1-y O y) It has 4, where 0 < x < 1, 0 ≤ y ≤ 0.25 and 0 < δ < 1, and thus clearly deviates from the scope of the solid electrolyte according to the present invention that does not contain germanium. Furthermore, all the solid electrolytes in the examples are outside the scope of the claims according to the present invention.

[0012] The disclosure of Patent Document 5 (corresponding to Patent Document 6) is very similar to Patent Document 3 and relates to a sulfide solid electrolyte material in which, in addition to the M1 element, M2 element and S element, an O element is present. According to a preferred embodiment, this sulfide solid electrolyte material has the general formula Li (4-x) Ge (1-x) P x (S 1-y O y )4, where 0 < x < 1 and 0 < y ≤ 0.25, or the general formula Li (4-x) Si (1-x) P x (S 1-y O y )4, where 0 < x < 1 and 0 < y ≤ 0.25. These preferred embodiments have compositions different from the solid electrolyte according to the present invention. Furthermore, the solid electrolytes in all the examples essentially contain germanium, which should not be present according to the present invention.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Non-Patent Literature

[0014]

Non-Patent Literature 1

Non-Patent Literature 2

Summary of the Invention

Problems to be Solved by the Invention

[0015] Therefore, an object of the present invention is to provide a sulfide-based solid electrolyte that avoids the drawbacks of the prior art, does not contain Ge, and has good electrochemical and chemical stability and high lithium ion conductivity.

Means for Solving the Problems

[0016] According to the present invention, the above problems are achieved by a sulfide-based solid electrolyte comprising, or consisting of, the general chemical formula (I): Li (4-x) [M’ k M“ 1-k 1-x P x (S 4-z O z ) (I) wherein 0.33 ≤ x ≤ 0.65, 0.1 ≤ k ≤ 0.5 and 0 ≤ z ≤ 1.0, M’ is selected from Si, and M“ is selected from Sn, and the characteristic of this solid electrolyte is that the X-ray diffraction peak of CuK alpha ray is at 2θ = 29.58° ± 0.5°.

[0017] ​​Therefore, a sulfide-based solid electrolyte that does not contain Ge, has excellent electrochemical and chemical stability, and also has high lithium ion conductivity is provided. The concept of "sulfide-based solid electrolyte" should be understood to be synonymous with the "oxysulfide-based solid electrolyte", and as a result, both concepts are synonymous and can be used interchangeably. Furthermore, the concepts of "sulfide solid electrolyte", "sulfide solid electrolyte", and "sulfide-based solid electrolyte" are synonymous and should be understood to be interchangeable.

[0018] Therefore, the sulfide-based solid electrolyte of the present invention has the general chemical formula (I) Li (4-x) [Sn k Si 1-k 1-x P x (S 4-z O z ) and has an LGPS-type structure, and oxygen can be doped at the position of sulfur. This is a modified LGPS type having double replacement (M = M'+M") at site M. This sulfide-based solid electrolyte preferably has a high ionic conductivity of 1.0×10 -3 S / cm or more at 25°C, and an ionic conductivity up to 5×10 -3 S / cm has been demonstrated.

[0019] This sulfide-based solid electrolyte particularly preferably does not contain a transition metal element.

[0020] According to a preferred embodiment, for the general chemical formula (I), 0.4 ≦ x ≦ 0.6, more preferably 0.425 ≦ x ≦ 0.575 or 0.45 ≦ x ≦ 0.55, still more preferably 0.475 ≦ x ≦ 0.525.

[0021] According to a preferred embodiment, for the general chemical formula (I), 0.1 ≦ k ≦ 0.45, more preferably 0.1 ≦ k ≦ 0.4, still more preferably 0.1 ≦ k ≦ 0.35 or 0.1 ≦ k ≦ 0.3, and particularly very preferably 0.1 ≦ k ≦ 0.25 or 0.1 ≦ k ≦ 0.2 applies.

[0022] ​ According to a preferred embodiment, for the general chemical formula (I), with respect to z, 0 ≤ z ≤ 0.85, more preferably 0 ≤ z ≤ 0.8, still more preferably 0 ≤ z ≤ 0.67 or 0 ≤ z ≤ 0.6, particularly very preferably 0 ≤ z ≤ 0.5 or 0 ≤ z ≤ 0.4 or 0 ≤ z ≤ 0.35 or 0 ≤ z ≤ 0.3, especially 0 ≤ z ≤ 0.25 or 0 ≤ z ≤ 0.2 or 0 ≤ z ≤ 0.15 or 0 ≤ z ≤ 0.125 or 0 ≤ z ≤ 0.1 is applicable.

[0023] The sulfide-based solid electrolyte of this formula (I) has a peak at a position of 2θ = 29.58° ± 0.50° in X-ray diffraction measurement using CuK alpha rays. As is well known, the position of this peak in X-ray diffraction depends on the crystal structure. As a result, the presence of a peak at the position of 2θ = 29.58° ± 0.50° ensures the existence of the desired crystal structure of the sulfide-based solid electrolyte. An example of what this crystal structure looks like can be read from FIG. 2 of Patent Document 4.

[0024] Preferably, in X-ray diffraction measurement using CuK alpha rays, the diffraction spectrum does not have a peak at a position of 2θ = 27.33° ± 0.50°. When there is a peak at the above-mentioned position 2θ = 27.33° ± 0.50°, the diffraction intensity of the peak 2θ = 29.58° ± 0.50° having intensity A (abbreviated as IA) and the diffraction intensity of the peak 2θ = 27.33° ± 0.50° having intensity B (abbreviated as IB) satisfy the following equation, IB / IA < 0.50. In other words, the value of the quotient of the diffraction intensity of the second peak and the diffraction intensity of the first peak is less than 0.50. Similarly in this case, the crystal shape exists in the desired structure.

[0025] Some embodiments according to the present invention and particularly advantageous properties of the sulfide-based solid electrolyte will be described with particular reference to FIGS. 1 to 4 below.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0027] Figure 1 shows the diffraction spectra (XRD patterns) of various embodiments of a sulfide-based solid electrolyte according to the present invention, with different oxygen contents. The right column is an extracted and enlarged view of the main peak near 29 degrees. In this case, the displacement to a higher angle suggests the growth of the basic cell, indicates the insertion of an atom with a large ionic radius, in this case oxygen, and shows that the material composition is different from the original. The intensity (intensity (in arbitrary units)) is shown in arbitrary units. During XRD measurement, the peak intensity varies for each sample based on the measured amount. To obtain meaningful data, the spectra are normalized, which makes the unit of the y-axis meaningless.

[0028] Here, x, k, and z in the general chemical formula (I) were selected as follows, namely x = 0.55, k = 0.2, and 0.0 ≦ z ≦ 1.0. In particular, z is 0, 0.1, 0.2, 0.25, 0.3, 0.35, 0.67, and 1.0. As can be seen from the diffraction spectrum having a peak near 2θ = 29.58°, as the value of z increases, the peak no longer shifts to the higher angle side, indicating that there is a limit to the amount of oxygen incorporated into the mixed crystal. Therefore, this diffraction pattern shows that a fixed solution can be obtained up to z = 0.25 with the values of x and k given here. When the value of z > 0.67, the generation of impurities becomes visible.

[0029] As shown in FIG. 1, when the value of z > 0.25, a decrease in ionic conductivity is observed, suggesting that when oxygen is introduced in excess, impurities other than the conductive LGPS phase are formed. When z exceeds 0.25, oxygen is no longer incorporated into the mixed crystal.

[0030] Therefore, according to a preferred embodiment, the sulfide-based solid electrolyte contains oxygen because this brings a series of special advantages. Therefore, the sulfide-based solid electrolyte of the general chemical formula (I) can preferably be selected as follows, namely, 0 < z ≦ 0.85, more preferably 0 < z ≦ 0.8, still more preferably 0 < z ≦ 0.67 or 0 < z ≦ 0.6, particularly very preferably 0 < z ≦ 0.5 or 0 < z ≦ 0.4 or 0 < z ≦ 0.35 or 0 < z ≦ 0.3, especially 0 < z ≦ 0.25 or 0 < z ≦ 0.2 or 0 < z ≦ 0.15 or 0 < z ≦ 0.125 or 0 < z ≦ 0.1, and x and k are selected as already defined.

[0031] According to a further embodiment, the sulfide-based solid electrolyte of general chemical formula (I) can be selected as follows, that is, 0.1 ≦ z ≦ 0.85, more preferably 0.1 ≦ z ≦ 0.8, still more preferably 0.1 ≦ z ≦ 0.67 or 0.1 ≦ z ≦ 0.6, particularly very preferably 0.1 ≦ z ≦ 0.5 or 0.1 ≦ z ≦ 0.4 or 0.1 ≦ z ≦ 0.35 or 0.1 ≦ z ≦ 0.3, and especially 0.1 ≦ z ≦ 0.25 or 0.1 ≦ z ≦ 0.2 or 0.1 ≦ z ≦ 0.15 or 0.1 ≦ z ≦ 0.125, x and k are selected as already defined.

[0032] It has been found that increasing the oxygen content in formula (I) also improves the electrochemical performance and stability in a solid battery cell.

[0033] Figure 2 shows the charge-discharge cycles of cells using various embodiments of the sulfide-based solid electrolyte according to the present invention, where 0.0 ≦ z ≦ 0.20. The parameter z was 0, 0.1, 0.15, and 0.2. The cells employed for this purpose included LNO-LCO + the sulfide-based solid electrolyte according to the present invention (LNO = lithium niobate, LCO = lithium cobaltate) as the cathode, and Li-In as the anode, with a C / 5 charge-discharge rate up to 3.6 V. From Figure 2, it can be seen that increasing the oxygen content results in a better capacity retention rate in the first 20 cycles. For the sample with z = 0.2, a retention rate of approximately 96% can be observed, while for the sample with z = 0.0, the retention rate remains at 84%. Therefore, as z increases, the energy retention rate increases, thereby significantly extending the life of the cell.

[0034] Surprisingly, it has also been found that incorporating oxygen into the solid electrolyte of general formula (I) improves the stability against moisture. Figure 3(a) shows the general chemical formula (I) according to the present invention Li (4-x) [M’ k M“ 1-k 1-x P x (S 4-z O z ) ​The XRD patterns of the sulfide-based solid electrolytes are shown respectively. For z = 0.15, that is, the XRD pattern with oxygen doping, the XRD patterns before the action of moisture (upper spectrum) and after the action of moisture at a dew point of -30 °C (lower spectrum) are shown respectively. Other parameters are x = 0.525 and k = 0.3. Figure 3(b) is the general chemical formula (I) according to the present invention Li (4-x) [M’ k M“ 1-k 1-x P x (S 4-z O z ) The XRD pattern of the sulfide-based solid electrolyte is shown. For z = 0.0, that is, the XRD pattern without oxygen doping, the XRD patterns before the action of moisture (upper spectrum) and after the action of moisture at a dew point of -30 °C (lower spectrum) are shown respectively. Other parameters are x = 0.55 and k = 0.2.

[0035] Regarding the action of moisture, a known humidity test using argon saturated with water is adopted, which is described in detail in A. Hayashi, H. Muramatsu, T. Ohtomo, S. Hama, M. Tatsumisago, J. Mater. Chem. A, 2013, 1, pp. 6320 - 6326. Therefore, both samples were exposed to humid argon gas with a humidity dew point of -30 °C. The humidity test was conducted as follows.

[0036] The sample was placed in a sealed container with an initial moisture content (about 1 - 2 ppm of H2O) at a dew point of about -75 °C. Then, more H2O was gradually filled into this container through a vent to increase the moisture content, and it was left standing for 42 hours. Then, this sample was returned to -70 °C with a low humidity dew point to stop further decomposition. Subsequently, this sample was prepared for XRD measurement. Figure 3 is Li (4-x) [M’ k M“ 1-k 1-x P x S 4―z O z ​​) shows the XRD patterns, where z = 0.0 and z = 0.15, showing the XRD patterns before and after the action of moisture at a dew point of -30 °C (about 375 - 400 ppm of H2O). After the action of moisture, in the sample with z = 0.0, the decrease in peak intensity is greater, and the width at the base is wider compared to its peak intensity, indicating the loss of the LGPS crystal structure. On the other hand, in the oxygen-doped sample, the decrease in peak intensity and the broadening of the base width are not so large, indicating that the crystal structure of the LGPS phase is better maintained. By containing oxygen, the stability against moisture is also enhanced.

[0037] The XRD patterns of the sulfide-based solid electrolyte were recorded before and after the action of moisture, showing the crystallinity. After the action of moisture, in the sample with z = 0, the decrease in peak intensity is greater, and the peak width is larger compared to the peak intensity, suggesting that the crystal structure of LGPS is lost. On the other hand, in the oxygen-doped sample, the decrease in peak intensity is smaller, and the broadening is also shown to be smaller, suggesting that the crystal structure of the LGPS phase is better maintained even when moisture acts.

[0038] According to an embodiment, the diffraction peak 2θ = 29.58° ± 0.50°, which is characteristic of the sulfide-based solid electrolyte of the present invention, shows an increase in the full width at half maximum (peak width at half of the peak height) after the humidity test, which corresponds to up to 1.8 times the full width at half maximum before the humidity test. This is a surprising and particularly advantageous property of the solid electrolyte according to the present invention.

[0039] Furthermore, the general chemical formula (I) Li (4-x) [M’ k M“ 1-k 1-x P x (S 4-z O z ) ​It has also been found that a sulfide-based solid electrolyte containing or consisting of (where z > 0) has higher reduction stability against Li metal. This is shown in FIGS. 4(a) and 4(b). FIG. 4(a) shows cyclic voltammetry measurements of a sample with k = 0.2, x = 0.55, and z = 0.1, and FIG. 4(b) shows cyclic voltammetry measurements of a sample with k = 0.3, x = 0.525, and z = 0.15 against lithium metal. The sample with z = 0.15 has a smaller oxidation peak near 0.25 V and a smaller reduction peak near 0.5 V compared to the sample with z = 0.1. The fact that the oxidation peak and the reduction peak are smaller when the oxygen content is higher indicates that this material is more chemically stable against Li metal.

[0040] The present invention also relates to a method for producing a sulfide-based solid electrolyte including the following steps, that is, this method a) preparing starting materials for the sulfide-based solid electrolyte, preferably in the form of oxide salts and / or sulfide salts; b) weighing the above-mentioned starting materials in stoichiometric amounts according to the general formula (I) of the sulfide-based solid electrolyte of the present invention; c) pulverizing the weighed amount of this starting material for 1 to 100 hours; d) heating the pulverized mixture obtained in step (c) at a temperature in the range of 300°C to 1000°C for 1 to 100 hours; e) obtaining a sulfide-based solid electrolyte after cooling and including where steps (b), (c), and (d) are carried out in an inert gas atmosphere excluding moisture or in a vacuum excluding moisture.

[0041] In step (a), starting materials for the sulfide-based solid electrolyte are first prepared. These are, for example, commercially available salts, preferably salts in the form of oxide salts and / or sulfide salts. According to the present invention, for example, Li2S, P2S5, SiO2, P2O5, SnS2, and SiS2 are employed. The purity of each salt is preferably ≧98%, more preferably ≧98.5%, still more preferably ≧99.0%, particularly salts with ≧99.5% or ≧99.9% are employed.

[0042] In step (b), using the general formula (I) Li (4-x) [M’ k M“ 1-k 1-x P x (S 4-z O z ) the starting materials are weighed in stoichiometric amounts, where 0.33 ≦ x ≦ 0.65, 0.1 ≦ k ≦ 0.5, and 0 ≦ z ≦ 1.0, M’ is selected from Si, and M“ is selected from Sn. The weighing is carried out in an inert gas atmosphere or in a vacuum, that is, in the absence of oxygen and in a state where moisture is removed. The inert gas atmosphere is, for example, a noble gas such as argon or nitrogen gas. Excluding moisture means, for example, a content of H2O < 0.6 ppm. It may also be appropriate to maintain an O2 content < 0.6 ppm.

[0043] After weighing in step (b), it is also possible to optionally mix the starting materials, or it is also possible to proceed directly to step (c). When mixing is carried out, it is carried out under an inert gas atmosphere or in a vacuum, that is, in the absence of oxygen, and in a state where moisture is excluded for each.

[0044] ​In the subsequent step (c), the weighed amount of the starting material is pulverized. The pulverization is carried out for 1 to 100 hours, for example, 15 to 50 hours. For this purpose, any type of mill can be employed, and in this mill, pulverization can be carried out under an inert gas atmosphere or under vacuum, that is, in the absence of oxygen and with moisture excluded. Particularly preferably, according to the present invention, a ball mill, particularly a planetary ball mill, is employed. Particularly preferably, the pulverization is carried out in the range of 200 rpm to 500 rpm.

[0045] If necessary, after step (c) and before step (d), the obtained pulverized mixture can be pressed into the form of pellets. This is also preferably carried out under an inert gas atmosphere or under vacuum, with moisture excluded.

[0046] In step (d), the pulverized mixture or pellets obtained in step (c) are heated to a temperature in the range of 300°C to 1000°C for 1 to 100 hours under an inert gas atmosphere or under vacuum and with moisture excluded. Preferably, 300°C to 800°C, particularly 300°C to 700°C, is employed. This temperature is maintained for 1 to 100 hours, particularly preferably 15 to 50 hours.

[0047] After cooling, a sulfide-based solid electrolyte is obtained in step (e). The cooling is preferably carried out by allowing the sulfide-based solid electrolyte to stand at room temperature (25°C).

[0048] The form in which the sulfide-based solid electrolyte can exist is not further limited. Preferably, the sulfide-based solid electrolyte obtained in step (e) is subjected to a further pulverization step to obtain a powder. Preferably, the average particle size (d50) of the powder is in the range of 0.1 μm to 50 μm. This pulverization is preferably carried out under an inert gas atmosphere or under vacuum and with moisture excluded.

[0049] The object of the present invention also relates to the use of a sulfide-based solid electrolyte in a solid battery cell.

[0050] The present invention also relates to a solid battery cell including a sulfide-based solid electrolyte according to the present invention. Preferably, this solid battery cell is a high-output cell.

[0051] The solid battery cell of the present invention can be a primary battery or a secondary battery, preferably a rechargeable secondary battery. A primary battery can only be discharged once and cannot be recharged thereafter. A secondary battery is also called a storage battery and can be recharged. For example, the solid battery cell according to the present invention can be mounted in an automobile.

[0052] Preferably, the solid battery cell has a cathode material layer, an anode material layer, and an electrolyte layer disposed therebetween, and the sulfide-based solid electrolyte according to the present invention is present in all of one layer, two layers, or three layers.

[0053] The anode material layer of the solid battery cell can have, for example, at least one anode active material and can contain a solid electrolyte material, a conductive material, and a binder. Preferably, the anode active material layer contains the sulfide-based solid electrolyte according to the present invention, for example, at a ratio of 0.1 to 80% by volume. Further, metals such as In, Al, Si, and Sn can be present as the anode active material. This anode material layer can further contain a conductive material, that is, a conductive material selected from carbon black, graphitized carbon black, graphite, carbon nanotubes, and carbon nanofibers, or a combination thereof. Further, this anode material layer may contain a binder such as polyvinylidene fluoride (PVDF). The thickness of this anode material layer is preferably in the range of 0.1 μm to 1000 μm.

[0054] The cathode material layer of the solid battery cell can have, for example, at least one cathode active material and can contain a solid electrolyte material, a conductive material, and a binder. Preferably, this cathode active material layer contains the sulfide-based solid electrolyte according to the present invention, for example, at a ratio of 0.1 to 80% by volume. For example, the cathode active material is LiCoO2, LiNiO2 or Li y Ni (1-p-w) Mp N w containing O₂, where 0.8 ≦ y ≦ 1.2, 0 ≦ p ≦ 0.33, 0 ≦ w ≦ 0.33, and M and N are selected from Mn, Co, and Al. Further, similar to the anode material layer, a conductive material and a binder are present. The thickness of the cathode material layer is preferably in the range of 0.1 μm to 1000 μm.

[0055] The electrolyte layer of the solid-state battery cell is located between the cathode material layer and the anode material layer and enables ion conduction. Preferably, this electrolyte layer contains a sulfide-based solid electrolyte according to the present invention, which is present in a proportion of 10 to 100% by volume. The thickness of this electrolyte layer is preferably in the range of 0.1 μm to 1000 μm, for example, in the range of 0.1 μm to 300 μm.

[0056] The solid-state battery cell has a separator, which spatially and electrically separates the anode and the cathode. According to a preferred embodiment, the separator of the solid-state battery cell has a sulfide-based solid electrolyte based on an argyrodite structure.

[0057] More preferably, the particle size (d50) of the sulfide-based solid electrolyte in the cathode composition is smaller than the particle size (d50) of the cathode active material. The particle size (d50) of the sulfide-based solid electrolyte used in the cathode composition is smaller than the particle size (d50) of the sulfide-based solid electrolyte used in the separator, and more preferably, this electrolyte has an argyrodite structure.

[0058] The advantages of the sulfide-based solid electrolyte according to the present invention are very diverse.

[0059] Therefore, as the oxygen content increases, that is, as the value of z increases, the material has higher chemical and electrochemical stability. Thereby, the cycle stability in the solid-state battery cell is maintained longer, thereby improving the cycle life and overall performance during discharge.

[0060] The inclusion of oxygen in the molecular structure of the solid electrolyte significantly improves the moisture resistance of the electrolyte. The resistance to hydrolysis leads to a reduction in H2S generation. Furthermore, the moisture conditions during cell construction can be configured with significantly lower requirements compared to the case of the prior art LGPS.

[0061] Furthermore, the chemical stability is improved compared to Li metal. Moreover, particularly high ionic conductivity can be obtained.

[0062] Thus, since the sulfide-based solid electrolyte exhibits particularly good characteristics, it can be particularly advantageously employed in a solid-state battery cell.

Example

[0063] Production Example : Chemical formula (I) Li (4-x) [M’ k M“ 1-k 1-x P x (S 4-z O z ) The sulfide-based solid electrolyte of the present invention according to (where 0.33 ≦ x ≦ 0.65, 0.1 ≦ k ≦ 0.5, 0 ≦ z ≦ 1.0, M’ = Si and M“ = Sn) was produced as described below using a mechanical ball mill and subsequently using a solid-state reaction at a higher temperature.

[0064] ​Therefore, stoichiometric amounts of Li2S (purity 99.9% or higher), P2S5 (purity 98% or higher), SiO2 (purity 99.9% or higher), P2O5 (purity 99.9% or higher), SnS2 (purity 98% or higher), and SiS2 (purity 98% or higher) were weighed in a glove box filled with argon gas and weighed with <0.6 ppm of H2O and <0.6 ppm of O2. The weighed chemicals were mixed and pulverized in a zirconia planetary ball mill (Pulverisette 7 Premium series from Fritsch) for 20 hours. The pulverized powder was formed into cylindrical pellets in a glove box filled with argon gas. This pellet was filled into a quartz glass ampule and brought to a vacuum state of less than 10 Pa. The sealed ampule was heated from 25 °C to 550 °C and then the temperature was maintained for 24 hours. After the reaction, the ampule was naturally cooled to room temperature to obtain the desired sulfide-based solid electrolyte.

Claims

1. General chemical formula (I) Li （４－ｘ） [M' ｋ M" １－ｋ ] １－ｘ P ｘ S ４－ｚ O ｚ A sulfide-based solid electrolyte comprising or consisting of: wherein 0.33≦x≦0.65, 0.1≦k≦0.5, and 0≦z≦1.0; M' is selected from Si; and M" is selected from Sn; Here, the solid electrolyte is characterized in that the X-ray diffraction peak of CuK alpha ray is 2θ=29.58°±0.5°. Sulfide solid electrolyte.

2. In the general chemical formula (I), 2. The solid electrolyte according to claim 1, characterized in that 0.4≦x≦0.6, more preferably 0.425≦x≦0.575 or 0.45≦x≦0.55, and even more preferably 0.475≦x≦0.

525.

3. In the general chemical formula (I), k is 0.1≦k≦0.45, more preferably 0.1≦k≦0.4; More preferably, 0.1≦k≦0.35 or 0.1≦k≦0.3, 3. The solid electrolyte according to claim 1 or 2, characterized in that 0.1≦k≦0.25 or 0.1≦k≦0.2 applies very particularly preferably.

4. In the general chemical formula (I), z is 0≦z≦0.85, more preferably 0≦z≦0.8; More preferably, 0≦z≦0.67 or 0≦z≦0.6, 4. The solid electrolyte according to claim 1 , wherein the following applies: 0≦z≦0.5 or 0≦z≦0.4 or 0≦z≦0.35 or 0≦z≦0.3, in particular 0≦z≦0.25 or 0≦z≦0.2 or 0≦z≦0.15 or 0≦z≦0.125 or 0≦z≦0.

1.

5. In the general chemical formula (I), oxygen is present and z is 0<z≦0.85, more preferably 0<z≦0.8; More preferably, 0<z≦0.67 or 0<z≦0.

6. Very particularly preferably, 0<z≦0.5 or 0<z≦0.4 or 0<z≦0.35 or 0<z≦0.3, in particular 0<z≦0.25 or 0<z≦0.2 or 0<z≦0.15 or 0<z≦0.125 or 0<z≦0.1 or 0.1≦z≦0.85; 5. The solid electrolyte according to claim 1 , wherein 0.1≦z≦0.8, even more preferably 0.1≦z≦0.67 or 0.1≦z≦0.6, very particularly preferably 0.1≦z≦0.5 or 0.1≦z≦0.4 or 0.1≦z≦0.35 or 0.1≦z≦0.3, and in particular 0.1≦z≦0.25 or 0.1≦z≦0.2 or 0.1≦z≦0.15 or 0.1≦z≦0.

125.

6. In an X-ray diffraction measurement using CuK alpha radiation, the diffraction spectrum has no peak at 2θ=27.33°±0.50°; or 6. The solid electrolyte according to claim 1, wherein the diffraction spectrum has a peak at 2θ=27.33°±0.50° in an X-ray diffraction measurement using CuK alpha rays, and in this case, a diffraction intensity (IA) having intensity A at peak 2θ=29.58°±0.50° and a diffraction intensity (IB) having intensity B at peak 2θ=27.33°±0.50° satisfy the following formula, IB / IA<0.

50.

7. A method for producing a sulfide-based solid electrolyte according to any one of claims 1 to 6, comprising the steps of: a) providing starting materials for the sulfide-based solid electrolyte, preferably in the form of oxides and / or sulfide salts; b) weighing out the starting materials in stoichiometric amounts according to the general formula (I) of claim 1; c) milling the weighed amount of the starting material for 1 to 100 hours; d) heating the ground mixture obtained in step (c) to a temperature ranging from 300° C. to 1000° C. for a period of time ranging from 1 to 100 hours; e) obtaining the sulfide-based solid electrolyte after cooling; Including, A method wherein steps (b), (c) and (d) are carried out in an inert gas atmosphere with the exclusion of moisture or in a vacuum with the exclusion of moisture.

8. After step (b) and before step (c), a step of mixing the starting materials under an inert gas atmosphere and the exclusion of moisture or under vacuum and the exclusion of moisture is carried out; and / or 8. The method according to claim 7, characterized in that after step (c) and before step (d), the obtained ground mixture is pressed into the form of pellets under an inert gas atmosphere and exclusion of moisture or under vacuum and exclusion of moisture.

9. 7. Use of the sulfide-based solid electrolyte according to claim 1 in a solid-state battery cell.

10. A solid-state battery cell comprising the sulfide-based solid electrolyte according to any one of claims 1 to 6, said solid-state battery cell being in particular a high-power cell.

11. 11. The solid-state battery cell according to claim 10, characterized in that the solid-state battery cell has a cathode material layer, an anode material layer, and an electrolyte layer disposed therebetween, and the sulfide-based solid electrolyte according to any one of claims 1 to 6 is present in one layer, two layers, or all three layers.

12. 12. The solid-state battery cell according to claim 10 or 11, in the form of a primary or secondary battery.

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