Phosphorus-rich high-temperature resistant sulfide electrolyte

Abstract

The present invention provides a high-temperature resistant sulfide solid electrolyte rich in phosphorus, which contains at least lithium (Li), phosphorus (P), and sulfur (S) elements. The material structure factor Δ is 814 ± 1 to 1384 ± 1, where Δ = {N(Li) × 312.5 + N(P) × 346} × 4. In the formula, N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P, and N(P) ≥ 0.25. The sulfide solid electrolyte of the present invention has high thermal stability and can form a high-ion-conducting interface layer with the lithium metal negative electrode. Moreover, due to the enrichment of P in the material, it also has the ability to form a stable interface layer with the lithium metal negative electrode, effectively optimizing and improving the cycling performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, relates to solid electrolytes, and particularly relates to a phosphorus-rich high-temperature-resistant sulfide solid electrolyte material. On this basis, the phosphorus-rich high-temperature-resistant sulfide solid electrolyte and its solid-state battery are further described. Background Art

[0002] With the rapid development of science and technology and human society, lithium-ion batteries are widely used in consumer electronics, medical electronics, electric vehicles, rail transit, mobile energy storage, smart grid, aerospace, and national defense and military fields due to their superior performance. However, these fields have put forward higher requirements for the energy density, power density, and safety of batteries. The energy density of conventional lithium-ion batteries has reached a "bottleneck". 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 commercially available lithium-ion batteries currently use electrolytes containing flammable organic solvents, it is necessary to install a safety device to suppress the temperature rise during short circuits or 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 device 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, and processes such as phase transformation, thermal decomposition, and component volatilization will occur, which will have a huge impact on the ionic conductivity of the material and seriously affect the performance of the material. More importantly, the heated sulfide solid electrolyte will still release flammable sulfur, and flammable and highly toxic gases such as hydrogen sulfide will be produced in the air. Especially when there is a lithium metal anode, it will pose a huge safety risk. On the other hand, the electrochemical stability of sulfide solid electrolytes is poor. From the perspective of theoretical calculations, the voltage stability range of the Li-Ge-P-S-based crystal solid electrolyte system (ionic conductivity reaches 12 mS / cm) is only 1.71-2.14 V (vs. Li / Li+), and redox decomposition reactions will occur outside this voltage range. It can be seen that sulfide solid electrolytes are extremely unstable to lithium metal. For example, the reduction decomposition reaction of the Li-Ge-P-S-based crystal solid electrolyte system starts at 1.71 V, and LGPS is lithiated to form Li4GeS4, P, and Li2S; as the potential further decreases, multiple thermodynamic voltage platforms appear, corresponding to Li-P and Li-Ge alloys, and reduction reactions will continue to occur at 0 V. This makes it difficult to directly apply the lithium metal anode to the sulfide solid battery system, which is in great contradiction with the demand for high energy density. Therefore, at this stage, there is an urgent need to develop a high-temperature-resistant sulfide solid electrolyte material that is compatible with the lithium metal anode, so as to facilitate the compatibility of the lithium metal anode and the sulfide solid electrolyte, use lithium metal as the anode material, and then greatly improve the energy density of the battery while ensuring the safety of the battery. Summary of the Invention

[0005] Due to the urgent requirements for high thermal safety and high energy density of electrochemical energy storage devices, an electrolyte material that makes the lithium metal anode compatible with the sulfide solid electrolyte is developed, so that lithium metal can be used as the battery anode material while meeting high safety. Therefore, the present invention provides a phosphorus-rich sulfide solid electrolyte, which simultaneously has ultra-high thermal stability, high ionic conductivity, and high electrochemical stability. Through material selection and design of the sulfide solid electrolyte, and analysis of the "material-structure-performance" of the solid electrolyte material, it is summarized that target materials with good thermal stability can be quickly designed and screened by optimizing the composition, which are not easy to decompose, not easy to sulfurize, and have good ionic conductivity, and have ultra-high thermal stability performance.

[0006] The present invention first provides a high-temperature resistant sulfide solid electrolyte rich in phosphorus, which contains at least lithium (Li), phosphorus (P), and sulfur (S) elements. The material structure factor Δ is 814 ± 1 to 1384 ± 1, where Δ = {N(Li) × 312.5 + N(P) × 346} × 4. In the formula, N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P, and N(P) ≥ 0.25.

[0007] Among them, the composition of the high-temperature resistant sulfide solid electrolyte rich in phosphorus is Li-P-S-M, and the content of each component is: 0 < N(Li) ≤ 0.375, 0.25 ≤ N(P) ≤ 1, 0 < N(S) ≤ 0.375, 0 ≤ N(M) ≤ 0.18. 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 the doping element M. The sum of the percentages of all elements is 100%. The thermal decomposition temperature of the material within this range is ≥ 400 °C.

[0008] Preferably, the structure factor Δ of the high-temperature resistant sulfide solid electrolyte rich in phosphorus is 1000 ± 1 to 1384 ± 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. The composition of the shell material elements is Li-P-S-M, and the content of each component is: 0 < N(Li) ≤ 0.27, 0.479 ≤ N(P) ≤ 1, 0 < N(S) ≤ 0.251, 0 ≤ N(M) ≤ 0.18. 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 the doping element M. The sum of the percentages of all elements is 100%. The thermal decomposition temperature of the material within this range is ≥ 700 °C.

[0009] Among them, the doping element M of the high-temperature resistant sulfide solid electrolyte rich in phosphorus 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, the phosphorus-rich high-temperature resistant sulfide solid electrolyte is stable to metallic lithium. After contacting with the metal, it can form an ion-conducting interface layer, which is a lithium-phosphorus compound or its composite compound. In powder X-ray diffraction using CuKα radiation, characteristic peaks appear at 2θ = 24.1 ± 0.5 deg and 26.8 ± 0.5 deg, belonging to crystalline phase A, or a characteristic peak appears at 2θ = 15.9 ± 0.5 deg, belonging to crystalline phase B. Crystalline phase A and crystalline phase B exist simultaneously or independently; near the metallic lithium negative electrode side, the composition is mainly crystalline phase A, while near the sulfide solid electrolyte, the composition is mainly crystalline phase B; in the electrochemical workstation alternating current impedance test, the ionic conductivity of the mixed interface layer is preferably 3 mS / cm or more.

[0011] Among them, the phosphorus-rich sulfide electrolyte within the scope of the present invention does not show an exothermic peak below 450 °C.

[0012] Among them, in the X-ray diffraction of the phosphorus-rich sulfide electrolyte within the scope of the present invention above 500 °C, a crystallization peak of crystalline phase C appears near 2θ = 27 ± 0.5 deg.

[0013] Among them, the phosphorus-rich sulfide electrolyte within the scope of the present invention has an ionic conductivity of not less than 1 mS / cm and an electronic ionic conductivity of not more than 1×10 -10 S / cm.

[0014] Among them, the phosphorus-rich sulfide electrolyte within the scope of the present invention has a brightness L* value in the L*a*b* chromaticity system of 60.0 - 80.0.

[0015] Among them, the phosphorus-rich sulfide electrolyte within the scope of the present invention has a density of 1.8 - 2.7 g / cm 3 .

[0016] The present invention provides a battery containing the above-mentioned phosphorus-rich sulfide electrolyte.

[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 adopted. Through the corresponding design of the correlation between the structural 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 range of regions for new materials different from traditional sulfide solid electrolytes can be obtained. The materials within the selected regions have high thermal stability, do not decompose or sulfurize at high temperatures, and exhibit good ionic conductivity, and are safer. At the same time, as the P content increases, the stability of the sulfide solid electrolyte towards metallic lithium gradually increases, and a stable crystalline phase interface layer can be formed with the metallic lithium negative electrode, which helps the long-term cycling of the metallic lithium all-solid-state battery. By increasing the content of P, a phosphorus-rich sulfide solid electrolyte is formed, further improving the electrochemical stability of the sulfide solid electrolyte. Description of the Drawings

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

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

[0020] Figure 2 It is a ternary composition diagram of LiPS for the phosphorus-rich high-temperature-resistant sulfide solid electrolyte of the present invention.

[0021] Figure 3 It is an XRD test pattern of the sulfide solid electrolyte powder in Example 6.

[0022] Figure 4 It is an XRD test pattern of the sulfide solid electrolyte after being treated at a high temperature of 700 °C in Example 6.

[0023] Figure 5 It is an XRD test pattern of the powder on the A side of the interface layer after the sulfide solid electrolyte in Example 6 is contacted with metallic lithium.

[0024] Figure 6 It is an XRD test pattern of the powder on the B side of the interface layer after the sulfide solid electrolyte in Example 6 is contacted with metallic lithium.

[0025] Figure 7 It is the ionic conductivity test (AC impedance spectrum test result) of the crystalline phase A of the interface layer in Example 6.

[0026] Figure 8 It is the test result of the electronic conductivity of the crystalline phase A of the interface layer in Example 6 (DC polarization test result).

[0027] Figure 9It is the DSC test spectrum of the sulfide solid electrolyte in Example 6.

[0028] Figure 10 It is the cyclic test of the symmetric battery composed of the sulfide solid electrolyte and metallic lithium in Example 6.

[0029] Figure 11 It is the distribution diagram of different examples in Table 2 in the LiPS ternary projection composition diagram.

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

[0031] Figure 13 It is the charge-discharge curve of the all-solid-state battery prepared with the phosphorus-rich sulfide solid electrolyte as the material.

[0032] Figure 14 It is the cyclic curve of the all-solid-state battery prepared with the phosphorus-rich sulfide solid electrolyte as the material. Detailed implementation manners

[0033] The present invention will be further described below with reference to the accompanying drawings and specific examples, but 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.

[0034] Sulfide solid electrolytes are generally incompatible with metallic lithium and usually react with the metallic lithium negative electrode to form an interfacial layer. However, there are several situations for the interfacial layer: a. The interfacial layer will continuously react, resulting in the complete reduction of the solid electrolyte and the loss of the electron-blocking effect; b. The interfacial layer will generate components with poor ionic conductivity or no ionic transport ability, resulting in the loss of ionic transport ability of the interfacial layer and the inability of the battery to work. However, we found that the phosphorus-rich sulfide solid electrolyte has the following characteristics: after contacting with the metallic lithium negative electrode, it will form a phosphorus-rich interfacial layer, the main components of which are crystalline phase A and crystalline phase B, with high ionic transport ability, and at the same time can prevent the metallic lithium negative electrode from continuously reacting with the sulfide solid electrolyte. In this way, the compatibility between metallic lithium and the sulfide solid electrolyte can be achieved, and a battery with high energy density can be developed.

[0035] In the microstructure of the Li-P-S-M sulfide solid electrolyte, it can be considered to be composed of corresponding numbers of [Li-S] bonds, [P-S] bonds, and chemical bonds of the doping element M, and these bonds form corresponding polyhedra to 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.

[0036] Therefore, we define the structure factor δ of the sulfide solid electrolyte, which reflects the energy possessed by all polyhedra within the sulfide solid electrolyte, or the total energy of all chemical bonds (Equations 1 and 2).

[0037] δ = E{Li x P y S z M m} = ∑{E[Li-S]} + ∑{E[P-S]} + ∑{E[M]} (1)

[0038] δ = E{Li x P y S z M m} = ∑{E[LiS 4} + ∑{E[PS 3 + ∑{E[PS 4 + ∑{E[P 2 S 7 + ∑{E[P 2 S 6} + ∑{E[M]} (2)

[0040] In Equations 1 and 2, E{Li x P y S z M m} represents the energy value of Li x P y S z M m . E[Li-S] represents the energy contained in the [Li-S] bond, E[P-S] represents the energy contained in the [P-S] bond, E[M] represents the energy of the chemical bonds formed by the doping element M, and E[LiS 4 , E[PS 3 , E[PS 4 , E[P 2 S 7 , E[P 2 S 6 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 increase the ionic conductivity and minimize the disruption of the overall ratio with minimal impact on the overall energy of the material, the energy part E[M] can be ignored in subsequent calculations to simplify the model. Further, the number of [Li-S] and [P-S] bonds can be estimated through polyhedra, simplifying Equation 2 to:

[0042]

[0043] For comparison, normalization is carried out with one mole as a reference. We define the structure factor Δ of the normalized sulfide solid electrolyte. The structure factor Δ is obtained by normalizing δ in unit measurement and reflects the energy possessed by all polyhedra in the sulfide solid electrolyte under unit measurement, or the total energy of all chemical bonds.

[0044]

[0045] In Equation 3 and Equation 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[LiS 4 , E[PS 3 , E[PS 4 , E[P 2 S 7 , E[P 2 S 6 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 for 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 represented 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 linking methods of two [PS4], and quantitatively can be equivalent to the structure of [PS4]. Therefore, Equation 4 can be further simplified to obtain Equation 5 by multiplying the number of central atoms by the product of the bonds included in the polyhedra derived from the central atoms. 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-property" 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-metallic 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] According to the derivation process of the above Equation 6, the above Equation 6 is also applicable to the Li-P-S sulfide solid electrolyte without the doping element M, which is equivalent to the M content being 0.

[0055] To verify the relationship between the structural factor Δ and thermal stability, we selected a series of phosphorus-rich 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 structural factor Δ of the device can be calculated. Electrochemical impedance spectroscopy tests were also carried out on the new sulfide solid electrolyte (the test instrument is Zahner Zennium Pro), and the ionic conductivities of the new sulfide solid electrolyte are also summarized in Table 1. During the calculation of the structural 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.

[0056] 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 CuKα radiation to obtain the phase decomposition temperature of the sulfide solid electrolyte. The structural factors Δ and their thermal decomposition temperatures of the high-temperature-resistant sulfide solid electrolytes with the above different atomic ratios are summarized in Figure 1 .

[0057] From the experimental results, the structural factor Δ changes synchronously with the thermal decomposition temperature of the sulfide solid electrolyte. The structural 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.

[0058] Table 1 Summary table of ionic conductivities and structural factors Δ of phosphorus-rich sulfide solid electrolytes with different atomic ratios

[0059] Chemical formula Ionic conductivity / (mS / cm) Structure factor Δ Thermal decomposition temperature / °C Example 1 Li2.8P2.88S2.32 4.8 935.74 798 Example 2 Li2.64P3.52S1.84 7.9 1021.46 871 Example 3 Li2.48P3.92S1.6 5.6 1065.66 909 Example 4 Li2.32P4.24S1.44 9.6 1096.02 935 Example 5 Li2.16P4.48S1.36 5.2 1112.54 949

[0060] According to the mutual change of the composition ratio relationship of the Li-P-S sulfide solid electrolyte, we established a ternary composition diagram of LiPS ( Figure 2 ), and combined with the experiment, a part of the phosphorus-rich region with a higher structural factor Δ result in the ternary composition diagram (the light shaded part in the figure) was selected. For the doping element M, since the content is very small, it can be regarded as the doping element replacing part of P and / or S in the ternary composition, and the energy fluctuation effect brought by the doping element M is also ignored during the calculation of the structural factor Δ. Therefore, the content of LiPS in the quaternary composition containing the doping element M can be regarded as the same as that of LiPS in the ternary composition without considering the doping element M, and the range of the phosphorus-rich region of LiPS in the quaternary composition can be regarded as the same as the above shaded part.

[0061] Specifically, in this region, the structure factor Δ is 814 ± 1 to 1384 ± 1, and the thermal decomposition temperature of the material in this region is greater than 400 °C. Specifically, the composition of the LiPSM material in this region is 0 < N(Li) ≤ 0.375, 0.25 ≤ N(P) ≤ 1, 0 < N(S) ≤ 0.375, 0 ≤ N(M) ≤ 0.18, 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. The sum of the elements is 100%. Among them, when N(M) = 0, it is a LiPS ternary composition material.

[0062] Furthermore, within the above-mentioned region, Region II (the dark shaded part) with a higher structure factor Δ result in the composition diagram was also selected through experiments. In this region, the structure factor Δ is 1000 ± 1 to 1384 ± 1, and through verification (specifically see the following series of examples), the materials in this region exhibit higher thermal stability and thermal decomposition temperature, and the decomposition temperature is greater than 700 °C. Specifically, the composition of the materials in this region is 0 < N(Li) ≤ 0.27, 0.479 ≤ N(P) ≤ 1, 0 < N(S) ≤ 0.251, 0 ≤ N(M) ≤ 0.18, 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. The sum of the elements is 100%.

[0063] The following further verifies the relationship between the selected structure factor Δ region of the present invention and the thermal stability of the phosphorus-rich material through a series of examples.

[0064] Example 6

[0065] A phosphorus-rich sulfide solid electrolyte provided by the present invention has high ionic conductivity and high thermal stability. After contacting with the lithium metal negative electrode, a phosphorus-rich interfacial layer will be formed, which can prevent the lithium metal negative electrode from continuously reacting with the sulfide solid electrolyte, and a metal lithium all-solid-state battery with a long service life can be manufactured.

[0066] The preferably phosphorus-rich sulfide solid electrolyte in this example is a sulfide solid electrolyte containing lithium Li, phosphorus P, and sulfur S. The sulfide solid electrolyte material has the following atomic numbers, where the atomic numbers are N(Li) = 0.375, N(P) = 0.25, N(S) = 0.375, and it is equivalently calculated and experimented as the chemical formula Li3P2S3.

[0067] 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; 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), and other lithium sources and sulfur sources are used as starting materials. These powders are weighed according to the above composition in a glove box under an Ar atmosphere (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 atmosphere). The pot is installed in a planetary ball mill and mechanically ground for 40 hours at a table rotation speed of 300 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 phosphorus-rich sulfide solid electrolyte material. Figure 3 The XRD test pattern of the sulfide solid electrolyte powder obtained by this synthesis method is shown.

[0068] ICP test: The sulfide solid electrolyte of the test sample is ground into a 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 mL 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 mL volumetric flask, make up the volume with ultrapure water, and mix well. Then take 5 mL of the volumetric sample solution and dilute it to 50 mL, 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 calculated is 814.75.

[0069] XRD Diffraction Test: XRD measured the sample using a sealed test sample stage without contacting air. The 2θ position of the diffraction peak was determined by the centroid method using the XRD analysis program JADE. The test was carried out under conventional test conditions using a powder X-ray diffractometer of Purkinje General (other brands are also acceptable). Since there are differences in test parameters for different instruments, the following are the setting parameters of the powder X-ray diffractometer 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 / min; during the process of analyzing the peak position 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 position. Figure 3 The XRD test pattern of the sulfide solid electrolyte in this embodiment is shown. The novel sulfide solid electrolyte was placed in a muffle furnace for heat treatment, heated to 700 °C, and then tested and analyzed by powder X-ray diffraction with CuKα ray. Figure 4 The XRD test pattern of the sulfide solid electrolyte after being treated at a high temperature of 700 °C in this embodiment is shown. It is found that a crystallization peak appears near 2θ = 27.5 deg, belonging to the crystalline phase C. The above-mentioned sulfide solid electrolyte powder rich in phosphorus was pressed into a sulfide solid electrolyte sheet under a pressure of 300 Mpa. Then, the sulfide solid electrolyte sheet was closely attached to the metal lithium negative electrode and kept for more than 20 h to allow it to fully react with the metal lithium at the interface. Then, the metal lithium foil was removed, and the interface layer on the surface of the sulfide solid electrolyte sheet was scraped off to obtain side A near the metal lithium negative electrode and side B far from the metal lithium negative electrode, respectively, and XRD tests were carried out on the powders on both sides. The sample was measured using an XRD sealed test sample stage without contacting air. Figure 5 The XRD test pattern of the powder on side A of the interface layer after the sulfide solid electrolyte in this embodiment was contacted with the metal lithium is shown. It is found that characteristic peaks appear at 2θ = 24.3 deg and 26.6 deg, and these characteristic peaks belong to the LiP compound (crystalline phase A); Figure 6 The XRD test pattern of the powder on side B of the interface layer after the sulfide solid electrolyte in this embodiment was contacted with the metal lithium is shown. It is found that a characteristic peak appears at 2θ = 15.8 deg, and these characteristic peaks belong to the LiP5 compound (crystalline phase B), indicating that the sulfide solid electrolyte and the metal lithium react to form a stable LiP compound, and the crystalline phase A and the crystalline phase B can coexist, preventing further reaction and achieving the compatibility between the sulfide solid electrolyte and the metal lithium negative electrode. Further, it can be obtained that near the metal lithium negative electrode side, the composition is mainly crystalline phase A, and near the sulfide solid electrolyte, the composition is mainly crystalline phase B.

[0070] Ionic conductivity test: Electrochemical impedance spectroscopy was performed on the interfacial layer (crystalline phase A) formed between the sulfide solid electrolyte and the lithium metal anode using a Zahner Zennium Pro to obtain the ionic conductivity of the interfacial layer. The crystalline phase A obtained in this example was pressed into a sheet (500 MPa) to obtain a sheet with a thickness of approximately 1.0 mm and a diameter of φ10 mm. At room temperature, the ionic conductivity was calculated by measuring the AC impedance using the two-terminal method. The measurement frequency range was from 100 mHz to 8 MHz, and the amplitude was 5 mV. Figure 7 The AC impedance spectroscopy test results of the interfacial layer crystalline phase A formed between the sulfide solid electrolyte and the lithium metal anode are shown. The ionic conductivity of this interfacial layer crystalline phase A was measured to be 6.36 mS / cm. The polarization voltage was adjusted to 500 mV, and the electronic conductivity of the interfacial layer crystalline phase A formed between the sulfide solid electrolyte and the lithium metal anode was obtained through DC polarization testing. Figure 8 The DC polarization test results of the interfacial layer crystalline phase A formed between the sulfide solid electrolyte and the lithium metal anode are shown. The electronic conductivity of this interfacial layer crystalline phase A was obtained to be 0.68×10 -10 S / cm.

[0071] DSC test: To accurately obtain the thermal stability parameters of this phosphorus-rich 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 to 5 °C / minute, and the termination temperature was set to 450 °C. Based on the DSC results, the onset temperature of heat generation and the peak temperature of heat generation were obtained. It should be noted that the onset temperature of heat generation refers to the temperature at which the heat flow rises, and the peak temperature of heat generation refers to the peak temperature (heat generation peak temperature) at the lowest (highest) point of the heat flow. Figure 9 is the DSC test spectrum of the sulfide solid electrolyte in this example; within the entire test temperature range, no phase transition peak or exothermic peak of phase decomposition was found for this sulfide solid electrolyte. This indicates that this sulfide solid electrolyte has a high thermal stability value and remains stable within the test range.

[0072] Stability experiment with lithium metal: A symmetric battery was constructed in the form of lithium metal - sulfide solid electrolyte - lithium metal, and long-term cyclic testing was performed on a charge-discharge instrument to evaluate its electrochemical stability towards lithium metal. Figure 10It is a symmetric battery composed of a sulfide solid electrolyte and metallic lithium in this embodiment. It can be learned from the test results that the sulfide solid electrolyte in this embodiment can work stably for more than 3000 h.

[0073] Ionic conductivity test: Electrochemical impedance spectroscopy test was carried out on the novel sulfide solid electrolyte. The test instrument is Zahner Zennium Pro. The novel sulfide solid electrolyte obtained in the embodiment was pressed into a sheet (500 MPa) to obtain a sheet with a thickness of about 1.24 mm and a diameter of φ12 mm. At room temperature, the alternating current impedance was measured by the two-terminal method to calculate the ionic conductivity. The measurement frequency range was from 100 mHz to 8 MHz, and the amplitude was 5 mV. It can be measured that the ionic conductivity of the novel sulfide solid electrolyte is 6.8 mS / cm. Similarly, the direct current polarization measurement by the two-terminal method was used to calculate the electronic conductivity. The polarization voltage was 500 mV, and it can be measured that the electronic conductivity of the novel sulfide solid electrolyte is 0.87×10 -10 S / cm.

[0074] Density test: The powder density test was carried out on the novel sulfide solid electrolyte. The test instrument is a true density meter, and its density was obtained as 1.88 g / cm 3 .

[0075] Chromaticity test: The whiteness test was carried out on the novel sulfide solid electrolyte. The test instrument is a powder whiteness meter. The powder to be measured was put into the test cavity, 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 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 is preferably 80.0.

[0076] 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 the heating process were observed. By cooling one end of the quartz tube sealed with the sulfide solid electrolyte, the sulfur precipitation situation can be obtained to realize the observation of the sulfur evolution reaction of the sulfide solid electrolyte. Through the whole-process thermal decomposition experiment on the novel phosphorus-rich sulfide solid electrolyte, the results show that the morphology and state of the sulfide solid electrolyte remain stable within 600 °C, and the sulfur evolution temperature is 694 °C. Further, it shows that when the ambient temperature exceeds 694 °C, the sulfide solid electrolyte will undergo a sulfur evolution reaction process and partial decomposition will occur.

[0077] Example 7-55

[0078] In this embodiment, the solid-phase sintering method is adopted, which is mainly divided into two steps: the mixing process of raw materials and the heat treatment crystallization process. Sulfide solid electrolytes rich in phosphorus with different ratios are synthesized, and their structure factor Δ is measured to determine their stability at high temperatures. The ionic conductivities and structure factor Δ of these phosphorus-rich sulfide solid electrolytes are summarized in Table 2. In addition, the schematic ternary phase diagrams of the phosphorus-rich sulfide solid electrolytes with different atomic ratios in each example are shown in Figure 11 . Further, in order to obtain sulfide solid electrolytes with higher thermal stability, experiments were carried out and Examples 39 to 55 were synthesized. The sulfide solid electrolytes with atomic ratios in this range have a higher structure factor Δ (structure factor Δ > 1000), showing higher thermal stability and thermal decomposition temperature (decomposition temperature > 700 °C). The schematic ternary phase diagrams of this part of the novel phosphorus-rich sulfide solid electrolytes are shown in Figure 12 .

[0079] Table 2 Summary of ionic conductivities and structure factor Δ of phosphorus-rich sulfide solid electrolytes with different atomic ratios

[0080]

[0081]

[0082]

[0083] Example 56

[0084] This novel high-temperature resistant sulfide solid electrolyte can be used as a solid electrolyte layer of all-solid-state lithium secondary batteries or all-solid-state lithium batteries, or a solid electrolyte mixed in the positive / negative electrode binders, etc. By forming a layer composed of the above solid electrolyte between the positive electrode, the negative electrode, and between the positive electrode and the negative electrode, an all-solid-state battery can be constructed. Here, the layer composed of this novel 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 scraper or the like; cutting it with a gas knife after the slurry contacts; screen printing method; and so on. Or, for the powder of the sulfide solid electrolyte, a compact can be fabricated by pressing or the like and then appropriately processed. As the positive electrode material, a positive electrode material used as a positive electrode active material for lithium ion batteries can be appropriately used. Regarding the negative electrode material, a negative electrode material used as a negative electrode active material for lithium ion batteries can also be appropriately used. In this example, the positive electrode active material is mainly LiCoO2, the negative electrode is mainly natural graphite, and the solid electrolyte is a phosphorus-rich sulfide solid electrolyte (Example 6 Li3P2S3), Figure 13The charge-discharge curves of the all-solid-state battery prepared with the phosphorus-rich sulfide solid electrolyte in this embodiment are shown. The battery capacity performs normally, the discharge capacity reaches 170 mAh / g, and the initial efficiency reaches over 98%. Figure 14 The cycling curves of the all-solid-state battery prepared with the phosphorus-rich sulfide solid electrolyte in this embodiment are shown. After 800 cycles, the capacity retention rate is above 80%, and the all-solid-state battery with metallic lithium has an extremely long cycling life.

[0085] It can be verified through the accumulation of the above experiments that the structure factor Δ changes 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 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. By optimizing the material composition ratio in the phosphorus-rich region and selecting the optimized composition material rich in phosphorus under the condition of meeting the structure factor Δ, a set of sulfide solid electrolyte materials with ultra-high temperature stability is obtained, and due to the enrichment of P in the material, it also has the ability to form a stable interfacial layer with the metallic lithium anode, effectively optimizing and improving the cycling performance.

[0086] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-temperature resistant sulfide electrolyte rich in phosphorus, containing at least lithium (Li), phosphorus (P), and sulfur (S) elements, with the material structure factor Δ being 814 - 1384. Among them, Δ = {N(Li) × 312.5 + N(P) × 346} × 4, where N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P, and N(P) ≥ 0.25; during the calculation of the structure factor Δ, when calculating the atomic percentages N(Li) and N(P), the total number of atoms does not include the atomic number of the doping element.

2. The high-temperature resistant sulfide electrolyte rich in phosphorus according to claim 1. It is characterized in that The composition of the high-temperature resistant sulfide solid electrolyte rich in phosphorus is Li - P - S - M, and the content of each component is: 0 < N(Li) ≤ 0.375, 0.25 ≤ N(P) < 1, 0 < N(S) ≤ 0.375, 0 ≤ N(M) ≤ 0.18, 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, and the sum of each element is 100%; the thermal decomposition temperature of the material within the element composition range ≥ 400 °C.

3. The high-temperature resistant sulfide electrolyte rich in phosphorus according to claim 1. It is characterized in that The structure factor Δ of the high-temperature resistant sulfide solid electrolyte rich in phosphorus is 1000 - 1384, where Δ = {N(Li) × 312.5 + N(P) × 346} × 4, where N(Li) represents the atomic percentage of Li, N(P) represents the atomic percentage of P; the composition of the high-temperature resistant sulfide solid electrolyte rich in phosphorus is Li - P - S - M, and the content of each component is: 0 < N(Li) ≤ 0.27, 0.479 ≤ N(P) < 1, 0 < N(S) ≤ 0.251, 0 ≤ N(M) ≤ 0.18, 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, and the sum of each element is 100%; the thermal decomposition temperature of the material within the element composition range ≥ 700 °C; during the calculation of the structure factor Δ, when calculating the atomic percentages N(Li) and N(P), the total number of atoms does not include the atomic number of the doping element M.

4. The high-temperature resistant sulfide electrolyte rich in phosphorus according to claim 1. It is characterized in that The doping 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).

5. The high-temperature resistant sulfide electrolyte rich in phosphorus according to claim 1. It is characterized in that Stable to metallic lithium, after contacting with metal, it can form an ion-conducting interface layer, which is a lithium-phosphorus compound or its composite compound.

6. The high-temperature resistant sulfide electrolyte rich in phosphorus according to claim 5, characterized in that in the powder X-ray diffraction using CuKα radiation, the ion-conducting interface layer shows characteristic peaks at 2θ = 24.1 ± 0.5 deg and 26.8 ± 0.5 deg, belonging to crystal phase A, or shows a characteristic peak at 2θ = 15.9 ± 0.5 deg, belonging to crystal phase B. Crystal phase A and crystal phase B exist simultaneously or independently; near the metallic lithium negative electrode side, the composition is mainly crystal phase A, while near the sulfide solid electrolyte, the composition is mainly crystal phase B; in the AC impedance test by an electrochemical workstation, the ionic conductivity of the mixed interface layer is above 3 mS / cm.

7. The high-temperature resistant sulfide electrolyte rich in phosphorus according to claim 1, characterized in that the sulfide electrolyte rich in phosphorus does not show an exothermic peak below 450 °C; in the X-ray diffraction above 500 °C, a crystal peak of crystal phase C appears near 2θ = 27.

8. The high-temperature resistant sulfide electrolyte rich in phosphorus according to claim 1, characterized in that The phosphorus-rich sulfide electrolyte has an ionic conductivity of not less than 1 mS / cm and an electronic ionic conductivity of not more than 1×10 -10 S / cm.

9. The high-temperature resistant sulfide electrolyte rich in phosphorus according to claim 1, characterized in that for the sulfide electrolyte rich in phosphorus, the lightness L* value in the L*a*b* colorimetric system is 60.0 - 80.0; the sulfide electrolyte rich in phosphorus has a density of 1.8 - 2.7 g / cm3.

10. A battery containing the sulfide electrolyte rich in phosphorus according to any one of claims 1 - 9.

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