High-temperature-resistant sulfide electrolyte containing doping elements

Abstract

The present invention provides a high-temperature resistant sulfide electrolyte containing a doping element, including lithium (Li), phosphorus (P), sulfur (S), and doping element M. The material structure factor Δ is 468.7 ± 1 to 887.7 ± 1. Among them, Δ = {N(Li) × 312.5 + N(P) × 346} × 4, where N(Li) represents the atomic percentage of Li, and N(P) represents the atomic percentage of P.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, relates to solid electrolytes, and particularly relates to a sulfide solid electrolyte material with high temperature resistance. Background Art

[0002] With the rapid development of science and technology and human society, lithium-ion batteries are widely used in fields such as consumer electronics, medical electronics, electric vehicles, rail transit, mobile energy storage, smart grid, aerospace, and national defense due to their excellent performance. However, these fields have put forward higher requirements for the energy density, power density, and safety of batteries. Conventional lithium-ion batteries have reached the "bottleneck" of energy density. Scientists in China, the United States, Japan, etc. unanimously believe that the energy density of scalable lithium-ion batteries cannot exceed 350 W·h / Kg. Moreover, during the process of increasing their energy density, the volatile and flammable organic liquid electrolytes are extremely likely to induce safety accidents.

[0003] Since the currently commercially available lithium-ion batteries use electrolytes containing flammable organic solvents, it is necessary to install safety devices to suppress the temperature rise during short circuits or to improve the structure and materials for preventing short circuits. Solid-state batteries using non-volatile and non-flammable solid electrolytes to replace organic liquid electrolytes are one of the main solutions to solve the "bottleneck" problem of existing lithium-ion batteries, which can simplify the safety devices and have excellent manufacturing costs or productivity. Among them, sulfide solid electrolytes with high ionic conductivity and their solid electrolytes are the main development directions.

[0004] Although these sulfide solid electrolytes are non-volatile and non-flammable, at high temperatures, the sulfide solid electrolytes are not completely thermally safe. Phase transformation, thermal decomposition, and component volatilization processes will occur, which will have a huge impact on the ionic conductivity of the materials and seriously affect the performance of the materials. More importantly, the heated sulfide solid electrolytes will still release flammable sulfur, and flammable and highly toxic gases such as hydrogen sulfide will be generated in the air, causing huge safety risks. However, there are very few research reports in this regard, and there are few research results. Therefore, the need to improve the thermal stability of sulfide solid electrolytes and develop a series of high-temperature-resistant sulfide solid electrolytes is extremely urgent. Summary of the Invention

[0005] The present invention analyzes the "material-structure-performance" of sulfide solid electrolytes, summarizes an effective method for quickly designing and screening target sulfide solid electrolyte materials with good thermal stability by optimizing the material composition, and obtains a series of sulfide solid electrolytes with high-temperature stability according to this method, which are not easily decomposed, not easily sulfur-separated, and have good ionic conductivity. On this basis, a battery containing the sulfide solid electrolyte is proposed.

[0006] The present invention first provides a high-temperature resistant sulfide electrolyte containing a doping element. The material contains lithium (Li), phosphorus (P), sulfur (S), and doping element M. The structure factor Δ of the material is 468.7 ± 1 to 887.7 ± 1, where Δ = {N(Li) × 312.5 + N(P) × 346} × 4. In the formula, N(Li) represents the atomic percentage of Li, and N(P) represents the atomic percentage of P.

[0007] Among them, in the said material, the composition of lithium (Li), phosphorus (P), sulfur (S), and doping element M is: 0 < N(Li) ≤ 0.67, 0 < N(P) ≤ 0.375, 0.3125 ≤ N(S) ≤ 0.625, 0.03 ≤ N(M) ≤ 0.2. In the formula, N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P, N(S) represents the atomic percentage of S, and N(M) represents the atomic percentage of doping element M. The sum of each element is 100%. The thermal decomposition temperature of the material within this range is ≥ 300 °C.

[0008] Preferably, the structure factor Δ of the material is 600 ± 1 to 887.7 ± 1, where Δ = {N(Li) × 312.5 + N(P) × 346} × 4. In the formula, N(Li) represents the atomic percentage of Li, and N(P) represents the atomic percentage of P. In the said material, the composition of lithium (Li), phosphorus (P), sulfur (S), and doping element M is: 0.093 ≤ N(Li) ≤ 0.55, 0.12 ≤ N(P) ≤ 0.375, 0.33 ≤ N(S) ≤ 0.525, 0.12 ≤ N(M) ≤ 0.2. In the formula, N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P, N(S) represents the atomic percentage of S, and N(M) represents the atomic percentage of doping element M. The sum of each element is 100%. The thermal decomposition temperature of the material within this range is ≥ 500 °C.

[0009] Among them, in the sulfide solid electrolyte, the element M is at least one of non-metal elements such as oxygen (O), selenium (Se), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), or metal elements such as magnesium (Mg), calcium (Ca), strontium (Sr), zinc (Zn), scandium (Sc), antimony (Sb), silicon (Si), germanium (Ge), tin (Sn), boron (B), aluminum (Al), gallium (Ga), indium (In), titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), copper (Cu), nickel (Ni), manganese (Mn), chromium (Cr), silver (Ag), lanthanum (La), cerium (Ce), terbium (Tb), tellurium (Te), lead (Pb), arsenic (As), bismuth (Bi), etc.

[0010] Among them, for the sulfide electrolyte within the scope of the present invention, there will be no exothermic peak below 450 °C; or, there will be a phase transition peak near 210 - 320 °C, but there will be no exothermic peak of phase decomposition.

[0011] Among them, for the sulfide electrolyte within the scope of the present invention, in X-ray diffraction, there is a strong diffraction main peak before 2θ = 34 ± 0.5 deg, and the presented crystallization main peak will not appear after 2θ = 34 ± 0.5 deg.

[0012] Among them, for the sulfide electrolyte within the scope of the present invention, in X-ray diffraction above 300 °C, a crystallization peak of crystal phase A will appear near 2θ = 26.5 ± 0.5 deg; or a crystallization peak of crystal phase B will appear near 2θ = 32.5 ± 0.5 deg.

[0013] Among them, for the sulfide electrolyte within the scope of the present invention, the ionic conductivity is 3 mS / cm or more, and the electronic conductivity is not higher than 1×10 -10 S / cm.

[0014] Among them, for the sulfide electrolyte within the scope of the present invention, the brightness L* value in the L*a*b* colorimetric system is 50.0 - 80.0.

[0015] Among them, for the sulfide electrolyte within the scope of the present invention, the density is 1.5 - 3.0 g / cm 3 。

[0016] The present invention provides a battery containing the sulfide electrolyte within the selected range above.

[0017] The beneficial effects of the present invention are as follows: Based on the composition of traditional sulfide solid electrolytes, instead of using expensive and low-reserve rare elements, inexpensive and abundant conventional elements are used. Through the corresponding design of the correlation between the structure factor Δ and the thermal stability performance of the material, as the basis for optimizing the proportion of constituent elements, a selection method and a regional range of new materials different from traditional sulfide solid electrolytes can be obtained. The materials within the selected region have high thermal stability, do not decompose and do not precipitate sulfur at high temperatures. Moreover, the ionic conductivity is further improved by the addition of the doping element M, making it more secure and having a richer application scenario. More importantly, this invention will enrich the research on developing high-temperature-resistant sulfide solid electrolytes, making them more suitable for high-temperature extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0019] Figure 1 It is a graph showing the relationship between the structure factor Δ and the thermal decomposition temperature of high-temperature-resistant sulfide solid electrolytes with different atomic ratios.

[0020] Figure 2 It is a ternary composition diagram of LiPSM.

[0021] Figure 3It is a simplified projection LiPS ternary composition diagram.

[0022] Figure 4 It is the LiPSM quaternary composition diagram for Region II.

[0023] Figure 5 It is a simplified projection LiPS ternary composition diagram including Region II.

[0024] Figure 6 It is the DSC test spectrum of the sulfide solid electrolyte in Example 6.

[0025] Figure 7 It is the XRD test spectrum of the sulfide solid electrolyte in Example 6 after being treated at a high temperature of 500 °C.

[0026] Figure 8 It is the ionic conductivity of the sulfide solid electrolyte in Example 6.

[0027] Figure 9 It is the electronic conductivity of the sulfide solid electrolyte in Example 6.

[0028] Figure 10 It is the DSC test spectrum of the sulfide solid electrolyte in Example 7.

[0029] Figure 11 It is the XRD test spectrum of the sulfide solid electrolyte in Example 7 after being treated at a high temperature of 650 °C.

[0030] Figure 12 It is the distribution diagram of different examples in the LiPS ternary projection composition diagram in Table 2.

[0031] Figure 13 It is the distribution diagram of different preferred examples in the LiPS ternary projection composition diagram in Table 2.

[0032] Figure 14 It is the charge-discharge curve of the all-solid-state battery prepared with the sulfide solid electrolyte in Example 7 as the material.

[0033] Figure 15 It is the cycle curve of the all-solid-state battery prepared with the sulfide solid electrolyte in Example 7 as the material. Detailed implementation manners

[0034] The present invention will be further described below with reference to the accompanying drawings and specific examples. However, it should be understood that these examples are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0035] The thermal stability of a material is determined by its structure. Due to the large errors in the process of testing thermal information, it is impossible to accurately determine the thermal stability of sulfide solid electrolytes. Based on this background, we propose to measure the thermal stability of sulfide solid electrolytes by the bond energies contained in all the chemical bonds in the crystal structure of sulfide solid electrolytes.

[0036] In the microstructure of Li-P-S-M sulfide solid electrolytes, it can be considered to be composed of a corresponding number of [Li-S] bonds, [P-S] bonds, and chemical bonds of the doping element M, and these bonds form corresponding polyhedra and further form the macroscopic electrolyte material. The material decomposition process (physically measuring the decomposition temperature) is closely related to the essential structure of the material, that is, closely related to the number of corresponding polyhedra and the number of bonds that make up the electrolyte material.

[0037] Therefore, we define the structure factor δ of sulfide solid electrolytes, which reflects the energy possessed by all the polyhedra in the sulfide solid electrolyte, or the sum of the energies of all chemical bonds (Equation 1 and Equation 2).

[0038] δ = E{Li x P y S z M m} = ∑{E[Li-S]} + ∑{E[P-S]} + ∑{E[M]} (1)

[0039] δ = E{Li x P y S z M m} = ∑{E[LiS4]} + ∑{E[PS3]} + ∑{E[PS4]} + ∑{E[P2S7]} + ∑{E[P2S6]} + ∑{E[M]} (2)

[0040] In Equation 1 and Equation 2, E{Li x P y S z M m} represents the energy value possessed by Li x P y S z M m . E[Li-S] represents the energy contained in the [Li-S] bond, W[P-S] represents the energy contained in the [P-S] bond, E[M] represents the energy contained in the chemical bonds formed by the doping element M, and E[LiS4], E[PS3], E[PS4], E[P2S7], E[P2S6] represent the energies contained in the [LiS4], [PS3], [P2S7], [PS4], and [P2S6] polyhedra respectively.

[0041] Since the purpose of introducing the doping element M is to improve the ionic conductivity, and as much as possible without disrupting the overall ratio and having less impact on the overall energy of the material, the energy part E[M] can be ignored in subsequent calculations to facilitate simplifying the model. Further, the number of [Li-S] bonds and [P-S] bonds can be estimated through polyhedra, simplifying Equation 2 to:

[0042]

[0043] For comparison purposes, a unit mole is used as a reference for normalization. We define the structure factor Δ of the normalized sulfide solid electrolyte. The structure factor Δ is obtained by normalizing δ with unit measurement, reflecting the energy possessed by all polyhedra within the sulfide solid electrolyte under unit measurement, or the total sum of the energies of all chemical bonds.

[0044]

[0045] In Equations 3 and 4, N[LiS4], N[PS3], N[P2S7], N[PS4], and N[P2S6] represent the numbers of [LiS4], [PS3], [P2S7], [PS4], and [P2S6] polyhedra respectively, and E[LiS4], E[PS3], E[PS4], E[P2S7], E[P2S6] represent the energies contained in the [LiS4], [PS3], [P2S7], [PS4], and [P2S6] polyhedra respectively. N Total refers to the total number of atoms in the unit cell and is used as a normalization coefficient to enable fair comparison between various systems with different unit cell sizes. For further simplifying the calculation, during the calculation process, the number of atoms of the doping element M can be ignored, and N Total is denoted as the sum of the numbers of atoms of Li, S, and P.

[0046] The numbers of N[LiS4], N[PS3], N[P2S7], N[PS4], and N[P2S6] can be expressed by the number of central atoms among them. For example, N[LiS4] is closely related to the number of central atom Li, and N[PS3] is closely related to the number of central atom P. Based on the crystal structure of the sulfide electrolyte, it can be known that [P2S7], [PS3], and [P2S6] can all be equivalent to different connection methods of two [PS4], and can be numerically equivalent to the structure of [PS4]. Therefore, Equation 4 can be further simplified by multiplying the number of central atoms by the bonds included in the polyhedra derived from the central atoms to obtain Equation 5. Equation 5 is conducive to quickly calculating the results without the aid of computer assistance, improving practicality.

[0047] Δ = {N(Li) × E[Li-S] + N(P) × E[P-S]} × 4 (5)

[0048] Where N(Li) represents the atomic percentage of the central atom Li, N(P) represents the atomic percentage of the central atom P, E[Li-S] represents the energy contained in the [Li-S] bond, and E[P-S] represents the energy contained in the [P-S] bond.

[0049] E[Li-S] and E[P-S] can be obtained from the Handbook of Chemistry and Physics. Thus, Equation 5 can be further simplified to Equation 6.

[0050] Δ = {N(Li) × 312.5 + N(P) × 346} × 4 (6)

[0051] Where N(Li) represents the atomic percentage of the central atom Li, and N(P) represents the atomic percentage of the central atom P.

[0052] Thus, we define the structure factor Δ (Equation 6) of the normalized sulfide solid electrolyte. The structure factor Δ represents the simplified calculation of the total energy of all Li-S bonds and all P-S bonds inside the sulfide solid electrolyte, reflecting the thermal stability performance in terms of the material structure. Since this structure factor Δ is a simplified result obtained from the analysis and induction of the three dimensions of "material - structure - performance" of the sulfide solid electrolyte, and this result is uniquely related to the composition of Li-P-S-M, we expect that by optimizing the composition ratio of Li-P-S-M in the sulfide solid electrolyte, the thermal stability of the sulfide solid electrolyte can be effectively improved, enabling the sulfide solid electrolyte to stably exist at high temperatures without obvious thermal decomposition process and sulfur evolution process, and having good ionic conductivity.

[0053] Among them, in the Li-P-S-M sulfide solid electrolyte, the element M is at least one of non-metal elements such as oxygen O, selenium Se, fluorine F, chlorine Cl, bromine Br, iodine I or metal elements such as magnesium Mg, calcium Ca, strontium Sr, zinc Zn, scandium Sc, antimony Sb, silicon Si, germanium Ge, tin Sn, boron B, aluminum Al, gallium Ga, indium In, titanium Ti, zirconium Zr, vanadium V, niobium Nb, copper Cu, nickel Ni, manganese Mn, chromium Cr, silver Ag, lanthanum La, cerium Ce, terbium Tb, tellurium Te, lead Pb, arsenic As, bismuth Bi, etc.

[0054] To verify the relationship between the structure factor Δ and thermal stability, we selected a series of sulfide solid electrolyte materials with different compositions containing lithium (Li), phosphorus (P), sulfur (S), and other elements (M). The sulfide solid electrolytes with different atomic numbers are summarized in Table 1. Through ICP testing, the accurate Li and P atomic ratios of the sulfide solid electrolyte can be obtained, and then the structure factor Δ of the device can be calculated. Electrochemical impedance spectroscopy tests (the test instrument is Zahner ZenniumPro) were carried out on the new sulfide solid electrolyte, and the ionic conductivities of the new sulfide solid electrolyte are also summarized in Table 1. During the calculation of the structure factor Δ, when calculating the atomic percentages (N(P) and N(Li)), the total number of atoms (N Total ) does not include the number of atoms of the doping element.

[0055] Table 1 Summary table of ionic conductivities and structure factor Δ of new high-temperature-resistant sulfide solid electrolytes with different atomic ratios

[0056]

[0057]

[0058] The sulfide solid electrolytes in Table 1 were placed in a muffle furnace for heat treatment, and then the heat-treated sulfide solid electrolytes were tested and analyzed by powder X-ray diffraction with CuKd rays to obtain the phase decomposition temperature of the sulfide solid electrolyte. The structure factor Δ and their thermal decomposition temperatures of the new high-temperature-resistant sulfide solid electrolytes with the above different atomic ratios are summarized in Figure 1 . Through the XRD tests of the sulfide solid electrolyte and its decomposition products, and the analysis with the structure factor Δ of the corresponding sulfide solid electrolyte, from the experimental results, the structure factor Δ changes synchronously with the thermal decomposition temperature of the sulfide solid electrolyte. The structure factor Δ of the present invention is positively correlated with the thermal decomposition temperature (thermal stability) of the sulfide solid electrolyte and can be used as an important parameter to measure the thermal stability performance of the sulfide solid electrolyte.

[0059] In addition, Comparative Examples 1-4 without the doping element M (Cl) are provided in Table 1. It can be seen that since the content of the doping element Cl is very small, it is not considered in the calculation of the structure factor Δ. Therefore, the comparative examples without the doping element have the same calculated value of the structure factor Δ. Although the measured thermal decomposition temperatures fluctuate, the overall change is not significant, which also confirms that the addition of the doping element has little effect on the decomposition temperature. However, since the doping element changes the distribution of electron holes in the structure, it generally improves the ionic conductivity of the material.

[0060] Due to the mutual change of the composition ratio relationship of the Li-P-S-M sulfide solid electrolyte, we established a LiPSM quaternary composition diagram ( Figure 2), and combined with experiments, a region with a relatively high structural factor Δ in the quaternary composition diagram was selected. Since the content of the doping element M is very small, the region range in the quaternary composition diagram is basically the same as the region projected on the LiPS ternary phase diagram plane. Therefore, the quaternary composition diagram can be simplified and projected onto the LiPS ternary phase diagram ( Figure 3 ). This is also consistent with the simplified theory in the previous formula derivation that the influence of the doping element M on the structural factor can be ignored, simplifying the calculation of the structural factor Δ and the selection of the element composition range.

[0061] The range of the structural factor Δ selected in combination with experiments is 468.7±1 to 887.7±1, and through verification (see the following series of examples for details), the thermal decomposition temperature of the materials in this region is greater than 300°C. Specifically, the LiPSM quaternary composition in this region is 0 < N(Li) ≤ 0.67, 0 < N(P) ≤ 0.375, 0.3125 ≤ N(S) ≤ 0.625, 0.03 ≤ N(M) ≤ 0.2, where N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P, N(S) represents the atomic percentage of S, and N(M) represents the atomic percentage of the doping element M. Figure 2-3 (the gray area in

[0062] Further, within the above region range, a region with an even higher structural factor Δ in the ternary composition diagram was also selected in combination with experiments ( Figure 4 , Figure 5 ). In this region, the structural factor Δ is 600±1 to 887.7±1, and through verification (see the following series of examples for details), the materials in this region exhibit higher thermal stability and thermal decomposition temperature, with the decomposition temperature greater than 500°C. Specifically, the LiPSM quaternary composition in this region is 0.093 ≤ N(Li) ≤ 0.55, 0.12 ≤ N(P) ≤ 0.375, 0.33 ≤ N(S) ≤ 0.525, 0.12 ≤ N(M) ≤ 0.2, where N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P, N(S) represents the atomic percentage of S, and N(M) represents the atomic percentage of the doping element M. Figure 4-5 (region II in

[0063] The following further verifies the relationship between the region of the structural factor Δ selected by the present invention and the thermal stability of the materials through a series of examples.

[0064] Example 6

[0065] An example of a high-temperature-resistant sulfide solid electrolyte, which has high thermal stability and appropriate ionic conductivity, can meet the operation of all-solid-state batteries at higher ambient temperatures. It mainly contains lithium (Li), phosphorus (P), sulfur (S) and a doping element M. Among them, N(Li)=0.392, N(P)=0.125, N(S)=0.483, and N(Cl)=0.054 are preferably used. The sulfide solid electrolyte of this embodiment has a balanced comprehensive performance by satisfying the above atomic range and having good ionic conductivity and electrochemical stability.

[0066] Preparation method: In this embodiment, the synthesis method adopts the solid-phase sintering method, which is mainly divided into two steps. Among them, the raw material mixing process: using a raw material composition containing the constituent components of the sulfide solid electrolyte material, through mechanical grinding or mixing under the action of a liquid-phase solvent, a precursor material is synthesized; and the heat treatment crystallization process: by heating the precursor material, the novel high-temperature-resistant sulfide solid electrolyte material is obtained. Lithium sulfide (Li2S), phosphorus pentasulfide (P2S5), lithium chloride (LiCl) and other lithium sources, phosphorus sources, sulfur sources, and chlorine sources are used as starting materials. These powders are weighed according to the above composition in a glove box under an Ar gas environment (dew point -70°C) and mixed in an agate mortar to obtain a raw material precursor. Then, the obtained raw material precursor is put into a 45 ml zirconia jar, and further zirconia balls (φ10 mm, 15-20 pieces) are put in, and the jar is completely sealed (Ar gas environment). The jar is installed in a planetary ball mill and mechanically ground at a table rotation speed of 300 rpm for 20 hours to obtain a precursor of the novel sulfide solid electrolyte. By heating the precursor material, the heating temperature is 300-500 degrees Celsius, and the heat treatment time is 10-30 h, to obtain the high-temperature-resistant sulfide solid electrolyte material.

[0067] ICP testing will: Put the sulfide solid electrolyte of the test sample into a mortar and grind it into a fine powder. Transfer it into a crucible and place it in an oven at 105 °C for 1 hour, then move it into a desiccator to cool. Weigh 0.1 g of the sample (accurate to 0.1 mg) and place it into a 100 m beaker. Add 5 mL of the standard digestion solution and heat it on a hot plate (70 °C) until the sample is completely dissolved, then cool it to room temperature. Transfer the sample solution into a 250 m volumetric flask, make up the volume with ultrapure water, and mix well. Then take 5 m of the volumetric sample solution and dilute it to 50 m, that is, dilute it 10 times. Transfer the sample solution and the diluted solution into the testing instrument Thermofisher iCAP 7200 for testing. The carrier gas is N2, the gas flow rate is 0.5 L / min, the nebulizer pressure is 0.19 Mpa, and the high-frequency power is 1150 W. Through ICP testing, the accurate Li and P atomic ratios of the sulfide solid electrolyte can be obtained, and then the structure factor Δ of the sulfide solid electrolyte can be calculated to be 663 (calculated by Δ = {N(Li) × 312.5 + N(P) × 346} × 4, where N(Li) represents the atomic percentage of Li and N(P) represents the atomic percentage of P).

[0068] DSC testing: To accurately obtain the thermal stability parameters of the new sulfide solid electrolyte, differential scanning calorimetry is used for accurate testing and evaluation in this example. Add 5 mg of the sulfide solid electrolyte to be tested into a stainless-steel container for DSC (differential scanning calorimeter) and seal it. Place the sealed container in a DSC device (NETZSCH DSC214) and conduct the measurement. For the reference, use 5 mg of Al2O3, set the heating rate to 5 °C / minute, and set the termination temperature to 450 °C. According to the DSC results, obtain the onset temperature of heat release and the peak temperature of heat release. It should be noted that the onset temperature of heat release refers to the temperature when the heat flow rises, and the peak temperature of heat release refers to the peak temperature (peak temperature of heat release) at the lowest (highest) point of the HeatFlow. Figure 6 The DSC test spectrum of the sulfide solid electrolyte is shown. It is found that there is no phase transition peak in the sulfide solid electrolyte, but there is no exothermic peak of phase decomposition.

[0069] XRD Diffraction Test: The XRD used a sealed test sample stage to measure the specimen in a way that it was not in contact with air. The 2θ position of the diffraction peak was determined by the centroid method using the XRD analysis program JADE. The test was conducted under conventional test conditions using a powder X-ray diffractometer from Purkinje General Electric (other brands are also acceptable). Since there are differences in test parameters among different instruments, the following are the setting parameters of the powder X-ray diffractometer from Purkinje General Electric as an example: tube voltage: 36 kV; tube current: 20 mA; X-ray wavelength: Cu-Kα ray; detector: scintillation counter; measurement range: 2θ = 10 - 80 deg; step width, scanning speed: 0.02 deg, 1 deg / minute; during the process of analyzing the peak positions for confirming the existence of the crystal structure based on the measurement results, the XRD analysis program JADE was used to draw the baseline by fitting with a cubic equation to obtain the peak positions. The new sulfide solid electrolyte was placed in a muffle furnace for heat treatment, heated to 500 °C, and then tested and analyzed by powder X-ray diffraction with CuKα ray. Figure 7 The XRD test pattern of the sulfide solid electrolyte after being treated at 500 °C is shown. It was found that there was a strong diffraction main peak before 2θ = 34 deg, and the presented crystallization main peak did not appear after 2θ = 34 deg. Further, a crystallization peak appeared at 27 deg, belonging to crystalline phase A, with the main phase being Li2S, and a crystallization peak appeared at 32.5, belonging to crystalline phase B, with the main phase being Li2PS3.

[0070] Ionic Conductivity Test: The new sulfide solid electrolyte was tested by electrochemical impedance spectroscopy. The test instrument was Zahner Zennium Pro. The new sulfide solid electrolyte obtained in the example was pressed into a sheet (500 MPa) to obtain a sheet with a thickness of about 1.24 mm and a diameter of φ10 mm. At room temperature, the ionic conductivity was calculated by the two-terminal method of AC impedance measurement. The measurement frequency range was from 100 mHz to 8 MHz, and the amplitude was 5 mV. The ionic conductivity of the new sulfide solid electrolyte could be measured to be 9.5 mS / cm. Figure 8 These are the ionic conductivity data of the sulfide solid electrolyte. Similarly, the electronic conductivity was calculated by the two-terminal method of DC polarization measurement, with a polarization voltage of 500 mV. The electronic conductivity of the new sulfide solid electrolyte could be measured to be 2.3×10 -10 S / cm. Figure 9 These are the electronic conductivity data of the sulfide solid electrolyte.

[0071] Thermal decomposition experiment: The sulfide solid electrolyte was sealed in a quartz tube, and the quartz tube was placed in the central position of a muffle furnace. This part was heated, and at the same time, the morphological changes of the sulfide solid electrolyte during heating were observed. By cooling one end of the quartz tube sealed with the sulfide solid electrolyte, the sulfur precipitation situation could be obtained, and the observation of the sulfur evolution reaction of the sulfide solid electrolyte was realized. Through the whole-process thermal decomposition experiment on the new sulfide solid electrolyte, the results showed that the sulfur evolution temperature of this sulfide solid electrolyte was 564 °C. Further, it was shown that when the ambient temperature exceeded 564 °C, the sulfur evolution reaction process of this sulfide solid electrolyte would occur and partial decomposition would occur.

[0072] Density test: By performing powder density test on the new sulfide solid electrolyte, the test instrument was a true density meter, and its density was obtained as 1.89 g / cm 3 .

[0073] Chromaticity test: By performing whiteness test on the new sulfide solid electrolyte, the test instrument was a powder whiteness meter. The powder to be tested was put into the test chamber, and the sample to be measured was placed at the instrument reflection test port. Enter the measurement interface, press the measurement key briefly to start the measurement. The buzzer makes a "beep" sound, and at the same time, the LED indicator light flashes until the flashing stops, and the buzzer makes a "beep" sound again to complete the chromaticity measurement of the sulfide solid electrolyte. The brightness L* value in the L*a*b* chromaticity system was preferably 75.0.

[0074] Example 7

[0075] An example of a high-temperature-resistant sulfide solid electrolyte, which has high thermal stability and appropriate ionic conductivity, can meet the operation of all-solid-state batteries at a relatively high ambient temperature. It mainly contains lithium Li, phosphorus P, sulfur S and doping element M, where preferably N(Li)=0.479, N(P)=0.083, N(S)=0.438, N(Cl)=0.077. The sulfide solid electrolyte of this embodiment has good ionic conductivity and electrochemical stability by meeting the above atomic range, and the comprehensive performance is balanced.

[0076] Preparation method: In this embodiment, the synthesis method adopts the solid-phase sintering method, which is mainly divided into two steps. Among them, the raw material mixing process: using a raw material composition containing the constituent components of the sulfide solid electrolyte material, and synthesizing a precursor material through mechanical grinding or mixing under the action of a liquid-phase solvent; and the heat treatment crystallization process: obtaining the novel high-temperature-resistant sulfide solid electrolyte material by heating the precursor material. Lithium sulfide (Li2S), phosphorus pentasulfide (P2S5), lithium chloride (LiCl), and other lithium sources, phosphorus sources, sulfur sources, and chlorine sources are used as starting materials. These powders are weighed according to the above composition in a glove box under an Ar gas environment (dew point -70°C), and mixed in an agate mortar to obtain a raw material precursor. Then, the obtained raw material precursor is put into a 45 ml zirconia pot, and further put into zirconia balls (φ10 mm, 15 - 20 pieces), and the pot is completely sealed (Ar gas environment). The pot is installed in a planetary ball mill and mechanically ground for 60 hours at a table rotation speed of 250 rpm to obtain a precursor of the novel sulfide solid electrolyte. By heating the precursor material, the heating temperature is 400 - 600 °C, and the heat treatment time is 10 - 30 h, to obtain the novel high-temperature-resistant sulfide solid electrolyte material.

[0077] ICP test: The sulfide solid electrolyte of the test sample is ground into fine powder in a mortar, transferred into a crucible, placed in an oven at 105 °C for 1 hour, and then transferred into a desiccator to cool. Weigh 0.1 g of the sample (accurate to 0.1 mg) and place it in a 100 m beaker, add 5 mL of the standard digestion solution, heat it on a hot plate (70 °C) until the sample is completely dissolved, and cool it to room temperature. Transfer the sample solution into a 250 m volumetric flask, make up the volume with ultrapure water, and mix well. Then take 5 m of the volumetric sample solution and dilute it to 50 m, that is, dilute it 10 times. The sample solution and the diluted solution are transferred into the test instrument Thermofisher iCAP 7200 for testing. The carrier gas is N2, the gas flow rate is 0.5 L / min, the nebulizer pressure is 0.19 Mpa, and the high-frequency power is 1150 W. Through the ICP test, the accurate Li and P atomic ratios of the sulfide solid electrolyte can be obtained, and then the structure factor Δ of the sulfide solid electrolyte can be calculated to be 713.6 (calculated by Δ = {N(Li) × 312.5 + N(P) × 346} × 4, where N(Li) represents the atomic percentage of Li and N(P) represents the atomic percentage of P).

[0078] DSC Test: To accurately obtain the thermal stability parameters of this new sulfide solid electrolyte, differential scanning calorimetry was used for accurate testing and evaluation in this example. 5 mg of the sulfide solid electrolyte to be tested was added to a stainless-steel container for DSC (differential scanning calorimeter) and sealed. The sealed container was placed in a DSC device (NETZSCH DSC214) and measured. For the reference, 5 mg of Al2O3 was used, the heating rate was set at 5 °C / minute, and the end temperature was set at 450 °C. Based on the DSC results, the onset temperature of heat release and the peak temperature of heat release were obtained. It should be noted that the onset temperature of heat release refers to the temperature when the heat flow rises, and the peak temperature of heat release refers to the peak temperature (heat release peak temperature) at the lowest (highest) point of the heat flow. Figure 10 The DSC test pattern of the sulfide solid electrolyte is shown. It was found that the sulfide solid electrolyte had a phase transition peak at 250 °C and no exothermic peak of phase decomposition.

[0079] XRD Diffraction Test: The sample was measured by an XRD sealed test stage without contact with air. The 2θ positions of the diffraction peaks were determined by the centroid method using the XRD analysis program JADE. The powder X-ray diffraction of Purkinje General (other brands are also acceptable) was used for testing under conventional test conditions. Since there are differences in test parameters for different instruments, taking the setting parameters of the powder X-ray diffraction of Purkinje General as an example, tube voltage: 36 kV; tube current: 20 mA; X-ray wavelength: Cu-Kα ray; detector: scintillation counter; measurement range: 2θ = 10 - 80 deg; step width, scanning speed: 0.02 deg, 1 deg / minute; during the process of analyzing the peak positions for confirming the existence of the crystal structure based on the measurement results, the XRD analysis program JADE was used to draw the baseline by fitting with a cubic equation to obtain the peak positions. The new sulfide solid electrolyte was placed in a muffle furnace for heat treatment, heated to 650 °C, and then tested and analyzed by powder X-ray diffraction with CuKd ray. Figure 11 The XRD test pattern of the sulfide solid electrolyte after heat treatment at 650 °C is shown. It was found that there was a strong diffraction main peak before 2θ = 34 deg, and the presented crystallization main peak did not appear after 2θ = 34 deg. Further, a crystallization peak appeared at 27 deg, belonging to crystalline phase A, with the main phase being Li2S, and a crystallization peak appeared at 32 deg, belonging to crystalline phase B, with the main phase being Li2PS3.

[0080] Thermal decomposition experiment: The sulfide solid electrolyte was sealed in a quartz tube, and the quartz tube was placed at the central position of a muffle furnace. This part was heated, and at the same time, the morphological changes of the sulfide solid electrolyte during the heating process were observed. By cooling one end of the quartz tube sealed with the sulfide solid electrolyte, the sulfur precipitation situation could be obtained, and the sulfur evolution reaction of the sulfide solid electrolyte could be observed. Through the whole-process thermal decomposition experiment on the new sulfide solid electrolyte, the results showed that the sulfur evolution temperature of this sulfide solid electrolyte was 607 °C. Further, it was shown that when the ambient temperature exceeded 607 °C, the sulfur evolution reaction process would occur in this sulfide solid electrolyte, and partial decomposition would occur.

[0081] Density test: The powder density of the new high-temperature resistant sulfide solid electrolyte was tested using a true density meter, and its density was obtained as 1.98 g / cm 3 。

[0082] Chromaticity test: The whiteness of the new sulfide solid electrolyte was tested using a powder whiteness meter. The powder to be tested was placed in the test chamber, and the sample to be measured was placed at the reflection test port of the instrument. Enter the measurement interface, press the measurement key briefly to start the measurement. The buzzer makes a "beep" sound, and at the same time, the LED indicator flashes until the flashing stops. Then the buzzer makes a "beep" sound again to complete the chromaticity measurement of the sulfide solid electrolyte. The brightness L* value in the L*a*b* chromaticity system is preferably 65.0.

[0083] Examples 8 - 61

[0084] In this embodiment, the solid-phase sintering method was adopted, which was mainly divided into two steps: the raw material mixing process and the heat treatment crystallization process. New high-temperature resistant sulfide solid electrolytes with different ratios were synthesized, and their structure factor Δ was measured to determine their stability at high temperatures. The ionic conductivities and structure factor Δ of these new high-temperature resistant sulfide solid electrolytes are summarized in Table 2. In addition, the schematic diagrams of the ternary projection phase diagrams of the new high-temperature resistant sulfide solid electrolytes with different atomic ratios are shown in Figure 12 。Further, in order to obtain a sulfide solid electrolyte with higher thermal stability, experiments were carried out to synthesize the sulfide solid electrolytes with atomic ratios in the range of Examples 45 - 61. These sulfide solid electrolytes have a higher structure factor Δ (structure factor Δ > 600), showing higher thermal stability and thermal decomposition temperature (decomposition temperature greater than 500 °C). The schematic diagrams of the ternary projection phase diagrams of this part of the new high-temperature resistant sulfide solid electrolytes are shown in Figure 13 。

[0085] Table 2 Summary table of ionic conductivities and structure factor Δ of high-temperature resistant sulfide solid electrolytes with different atomic ratios

[0086]

[0087]

[0088] Meanwhile, as verified by the above-mentioned experimental accumulations, the structure factor Δ varies synchronously with the thermal decomposition temperature of the sulfide solid electrolyte, shows a positive correlation, and can be used as an important parameter to measure the thermal stability performance of the sulfide solid electrolyte. By optimizing the composition ratio of Li-P-S-M in the sulfide solid electrolyte, the thermal stability of the sulfide solid electrolyte can be effectively improved, enabling the sulfide solid electrolyte to stably exist at high temperatures without obvious thermal decomposition and sulfur evolution processes, and having good ionic conductivity. New sulfide solid electrolytes with high temperature resistance can be developed by optimizing the material composition ratio and controlling it within a reasonable range.

[0089] The above-mentioned high temperature resistant sulfide solid electrolyte of the present invention can be used as the solid electrolyte layer of an all-solid-state lithium secondary battery or an all-solid-state lithium battery, or as a solid electrolyte mixed in a positive / negative electrode binder. An all-solid-state battery can be formed by forming a layer composed of the above-mentioned solid electrolyte between the positive electrode, the negative electrode, and between the positive and negative electrodes. Here, the layer composed of this new high temperature resistant sulfide solid electrolyte can be fabricated by the following methods: for example, dropping a slurry composed of a sulfide solid electrolyte, a binder, and a solvent onto a substrate and leveling it with a doctor blade or the like; a method of cutting it off with a gas knife after the slurry contacts; a screen printing method; and so on. Alternatively, for the powder of the sulfide solid electrolyte, it can be fabricated by appropriately processing after making a compact by pressing or the like. As the positive electrode material, a positive electrode material used as the positive electrode active material of a lithium ion battery can be appropriately used. Regarding the negative electrode material, a negative electrode material used as the negative electrode active material of a lithium ion battery can also be appropriately used. In this embodiment, the positive electrode active material is mainly LiCoO2, the negative electrode is mainly natural graphite, and the solid electrolyte is a new high temperature resistant sulfide solid electrolyte. Figure 14 Shown are the charge-discharge curves of an all-solid-state battery prepared using the high temperature resistant sulfide solid electrolyte as an example of Example 7. The battery capacity performs normally, the discharge capacity reaches 120 mAh / g, and the initial efficiency reaches over 80%. Figure 15 Shown are the cycle curves of an all-solid-state battery prepared using the new high temperature resistant sulfide solid electrolyte as an example of Example 7. After 200 cycles, the capacity retention rate is above 93%.

[0090] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-temperature resistant sulfide electrolyte containing a doping element, including lithium (Li), phosphorus (P), sulfur (S), and doping element M, characterized in that, The composition of lithium (Li), phosphorus (P), sulfur (S), and doping element M is: 0 < N(Li) ≤ 0.636, 0 < N(P) ≤ 0.375, 0.3125 ≤ N(S) ≤ 0.625, 0.03 ≤ N(M) ≤ 0.

2. In the formula, N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P, N(S) represents the atomic percentage of S, and N(M) represents the atomic percentage of doping element M. The sum of all elements is 100%; The material structure factor Δ is 825.6 - 887.7, where Δ = {N(Li) × 312.5 + N(P) × 346} × 4. In the formula, N(Li) represents the atomic percentage of Li, and N(P) represents the atomic percentage of P; during the calculation of the structure factor Δ, when calculating the atomic percentages (N(P) and N(Li)), the total number of atoms (NTotal) does not include the atomic number of the doping element; at this time, the thermal decomposition temperature of the material within the element composition range is ≥ 703 °C.

2. The high-temperature resistant sulfide electrolyte containing a doping element according to claim 1, characterized in that, The element M is at least one of non-metal elements such as oxygen (O), selenium (Se), fluorine (F), chlorine (Cl), bromine (Br), iodine (I), or metal elements such as magnesium (Mg), calcium (Ca), strontium (Sr), zinc (Zn), scandium (Sc), antimony (Sb), silicon (Si), germanium (Ge), tin (Sn), boron (B), aluminum (Al), gallium (Ga), indium (In), titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), copper (Cu), nickel (Ni), manganese (Mn), chromium (Cr), silver (Ag), lanthanum (La), cerium (Ce), terbium (Tb), tellurium (Te), lead (Pb), arsenic (As), bismuth (Bi).

3. The high-temperature resistant sulfide electrolyte containing a doping element according to claim 1, characterized in that, The sulfide electrolyte does not show an exothermic peak below 450 °C; or, it shows a phase transition peak at 210 - 320 °C, but does not show an exothermic peak of phase decomposition.

4. The high-temperature resistant sulfide electrolyte containing a doping element according to claim 1, characterized in that, In the X-ray diffraction of the sulfide electrolyte, there is a strong diffraction main peak before 2θ = 34, and the presented crystallization main peak does not appear after 2θ = 34.

5. The high-temperature resistant sulfide electrolyte containing a doping element according to claim 1, characterized in that, In the X-ray diffraction of the sulfide electrolyte above 300 °C, a crystallization peak of crystal phase A appears near 2θ = 26.5; or a crystallization peak of crystal phase B appears near 2θ = 32.

5.

6. The high-temperature resistant sulfide electrolyte containing a doping element according to claim 1, characterized in that, The ionic conductivity of the sulfide electrolyte is 3 mS / cm or more, and the electronic conductivity is not higher than 1×10 -10 S / cm; the value of luminance L* in the L*a*b* colorimetric system is 50.0 to 80.0; the density is 1.5 to 3.0 g / cm 3 .

7. A battery containing the high-temperature resistant sulfide electrolyte containing a doping element according to any one of claims 1 to 6.

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