A sulfide electrolyte material, a solid-state electrolyte, an electrode sheet, a battery cell, or a solid-state battery

Abstract

The application relates to the technical field of sulfide electrolyte, in particular to a sulfide electrolyte material, a solid electrolyte, an electrode sheet, a battery cell or a solid-state battery. The sulfide electrolyte material comprises a sulfide base with ion conductivity and a coating layer, at least part of the surface of the sulfide base is coated by the coating layer, and the coating layer comprises iodine element. The material can inhibit the side reaction of the sulfide electrolyte and metal ions, and can inhibit the growth of dendrites, thereby inhibiting the deterioration failure of the battery.

Description

Technical Field

[0001] This invention relates to the field of sulfide electrolyte technology, specifically to a sulfide electrolyte material, a solid electrolyte, an electrode sheet, a battery cell, or a solid-state battery. Background Technology

[0002] Compared to traditional batteries, all-solid-state batteries use solid electrolytes instead of flammable and volatile organic electrolytes, thus offering a significant safety advantage. Sulfide solid electrolytes, in particular, exhibit high ionic conductivity and low Young's modulus compared to other electrolyte systems, making them one of the most promising choices for next-generation batteries.

[0003] However, sulfide electrolytes have low reduction potentials and are prone to reduction reactions with metal ions (such as lithium ions) in the positive electrode active material or with the negative electrode material (such as lithium metal anode), such as forming interface layers like lithium sulfide and lithium phosphide, which increases interfacial impedance. In addition, sulfide electrolytes have low Young's modulus, making them easily penetrated by metal dendrites, which can easily cause short circuits in the battery. Summary of the Invention

[0004] This invention provides a sulfide electrolyte material that can suppress side reactions between the sulfide electrolyte and metal ions, and can suppress the growth of metal dendrites, thereby suppressing battery deterioration and failure.

[0005] The present invention provides a sulfide electrolyte material comprising an ion-conductive sulfide matrix and a coating layer, wherein at least a portion of the surface of the sulfide matrix is ​​coated by the coating layer, and the coating layer comprises elemental iodine.

[0006] The sulfide electrolyte material described above has the general structural formula of the sulfide matrix as Li. a M b P c S d O e X f Where M is one or more of As, Sb, Sn, Si, and In, and X is one or more of F, Cl, and Br, 4≤a≤7, 0≤b≤1, 0≤c≤2, 3≤d≤8, 0≤e≤1, and 0≤f≤2.

[0007] The sulfide electrolyte material described above has a particle size D50 of 1-30 μm.

[0008] In the sulfide electrolyte material described above, the elemental iodine accounts for 2.5-10% of the mass of the sulfide matrix.

[0009] In the sulfide electrolyte material described above, the thickness of the coating layer is 5-400 nm.

[0010] The sulfide electrolyte material described above has a coating rate of ≥89%.

[0011] This invention also provides a method for preparing the above-mentioned sulfide electrolyte material, comprising: mechanically fusing a mixture of a sulfide matrix and elemental iodine under sealed conditions, causing the elemental iodine to sublimate and bind to the surface of the sulfide matrix, thereby obtaining the sulfide electrolyte material. This method is simple to implement, and the elemental iodine is tightly bound.

[0012] According to the preparation method described above, the linear velocity of the mechanical fusion treatment is 5-80 m / s, and the treatment time is 5-100 min.

[0013] The present invention also provides a solid electrolyte, comprising the sulfide electrolyte material described above or the sulfide electrolyte material prepared by the above preparation method. This solid electrolyte can reduce interfacial impedance and suppress dendrite growth.

[0014] The present invention also provides an electrode sheet comprising the above-described sulfide electrolyte material or the sulfide electrolyte material prepared by the above-described preparation method. This electrode sheet is less prone to dendrite penetration, thus preventing battery short circuits.

[0015] The electrode sheet described above comprises a lithium metal sheet and an electrolyte layer covering at least one surface of the lithium metal sheet, the electrolyte layer comprising the sulfide electrolyte material.

[0016] The electrode sheet described above includes a lithium iodide interface layer generated in situ during the electrochemical reaction between the lithium metal sheet and the electrolyte layer.

[0017] The present invention also provides a battery cell and a solid-state battery, including the electrode sheets described above, wherein the battery cell or battery has a high first-cycle charge-discharge capacity, first-cycle efficiency, and capacity retention rate.

[0018] This invention uses elemental iodine as a coating layer. Elemental iodine can generate an interfacial layer of metal iodide in situ during the electrochemical reaction. Metal iodide has high interfacial energy and good wettability, thus inhibiting metal dendrite growth. Furthermore, metal iodide has a high electrochemical window, which can suppress side reactions between sulfide electrolytes and metal elements, thereby inhibiting battery deterioration and failure. Compared to directly adding metal iodide (such as lithium iodide), the inorganic metal iodide interfacial layer formed in situ by elemental iodine can self-repair and re-form metal iodide in situ even if it breaks due to volume expansion and contraction during battery operation, thus ensuring the integrity of the interfacial layer. Attached Figure Description

[0019] Figure 1The distribution results of I and S elements obtained by EDS detection of the sulfide electrolyte material in Example 1 are shown in Figure 1; where A is the distribution result of I element, B is the distribution result of S element, and C is the corresponding SEM image.

[0020] Figure 2 The image shows the XRD pattern of the sulfide electrolyte material in Example 1.

[0021] Figure 3 Here is a SEM image of the sulfide electrolyte material in Example 1;

[0022] Figure 4 This is a SEM image of the sulfide electrolyte material in Example 1 at another magnification.

[0023] Figure 5 The critical current density test results are for the lithium symmetric battery prepared with the sulfide electrolyte in Example 1.

[0024] Figure 6 The critical current density test results are for the lithium symmetric battery prepared with the sulfide electrolyte in Comparative Example 1. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] To address the problems of low reduction potential and poor dendrite suppression in existing sulfide electrolytes, this invention provides a sulfide electrolyte material comprising an ion-conducting sulfide matrix and a coating layer, wherein at least a portion of the surface of the sulfide matrix is ​​coated by the coating layer, and the coating layer comprises elemental iodine.

[0027] Using elemental iodine as the coating layer, iodine can generate an interfacial layer of metal iodide (such as lithium iodide) in situ during the electrochemical reaction. Metal iodide has high interfacial energy and good wettability, thus inhibiting metal dendrite growth. Furthermore, metal iodide has a high electrochemical window, which can suppress side reactions between sulfide electrolytes and metal elements, thereby preventing battery deterioration and failure. Compared to directly adding metal iodide (such as lithium iodide), the in-situ formed inorganic metal iodide interfacial layer can self-repair and re-form metal iodide in situ even if it breaks due to volume expansion and contraction during battery operation, thus ensuring the integrity of the interfacial layer.

[0028] It is understood that the phrase "at least a portion of the surface of the sulfide matrix is ​​covered by the coating layer" as described above means that the coating layer can be formed on at least a portion of the surface of the sulfide matrix, preferably on a larger area of ​​the sulfide matrix surface, and more preferably on the entire surface of the sulfide matrix.

[0029] The composition of the sulfide matrix mentioned above is not specifically limited, nor is the metal ion used for conduction. For example, the metal ion used for conduction can be Li ion, Na ion, K ion, Ca ion, etc.

[0030] In some specific embodiments of the present invention, the conductive metal ion is Li ion, and the composition of the sulfide matrix can be selected accordingly. Accordingly, the sulfide electrolyte material can meet the requirements for the preparation of lithium batteries.

[0031] Furthermore, other elements can be doped into the sulfide matrix as needed. In some specific embodiments of the present invention, the general structural formula of the sulfide matrix is ​​Li. a M b P c S d O e X f In this process, M is one or more of As, Sb, Sn, Si, and In, and X is one or more of F, Cl, and Br, where 4≤a≤7, 0≤b≤1, 0≤c≤2, 3≤d≤8, 0≤e≤1, and 0≤f≤2. Specifically, the sulfide matrix can be doped with one or more of As, Sb, Sn, Si, and In, or with one or more of the halogens F, Cl, and Br. As, Sb, Sn, Si, and In dopants have larger electron radii, which can expand the lattice spacing and enhance lithium transport capacity, thereby improving ionic conductivity. Halogens F, Cl, and Br can form a lithium halide passivation layer in situ with lithium metal during electrochemical processes, improving interfacial stability and thus enhancing battery cycle stability.

[0032] There is no specific limitation on the particle size D50 of the sulfide electrolyte material. In practical applications, the particle size D50 of the electrolyte is typically 1-30 μm. Therefore, the particle size D50 of the aforementioned sulfide electrolyte material can also be controlled within the range of 1-30 μm. For example, it can be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or any range between two of the above values.

[0033] The mass ratio of elemental iodine to the sulfide matrix is ​​not specifically limited in the above description. However, the performance of the sulfide electrolyte material is better when the mass of elemental iodine is 2.5-10% of the sulfide matrix mass. For example, the mass of elemental iodine can be 2.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the sulfide matrix mass, or any two of the above values.

[0034] There is no specific limitation on the thickness of the coating layer. However, when the coating layer is too thick, the impedance between particles increases, the overall grain boundary resistance increases, and this will have a certain impact on the intrinsic ionic conductivity of the sulfide electrolyte. Therefore, the thickness of the coating layer is usually 5-400 nm. For example, it can be 5 nm, 10 nm, 50 nm, 90 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, or any two of the above values.

[0035] Further research indicates that sulfide electrolyte materials exhibit superior performance when the coating ratio is ≥89%. The coating ratio can be measured using EDS, calculated by dividing the iodine atomic concentration by the sum of all atomic concentrations. Even further, the coating ratio is ≥95%, and even more specifically, ≥97%.

[0036] It is understandable that the preparation method of the above-mentioned sulfide electrolyte material is not specifically limited, as long as the above-mentioned sulfide electrolyte material can be obtained. For example, the elemental iodine in the coating layer of the above-mentioned sulfide electrolyte material can be obtained by directly coating with elemental iodine or by in-situ substitution of iodine compounds.

[0037] The coating process is not specifically limited; it can be performed using liquid phase coating or mechanical grinding. Mechanical grinding is also not specifically limited. Examples include ball milling, vibratory milling, turbine milling, mechanical fusion, and disc milling.

[0038] In some embodiments of the present invention, the preparation method of the above-mentioned sulfide electrolyte material includes: mechanically fusing a mixture of a sulfide matrix and elemental iodine under sealed conditions, causing the elemental iodine to sublimate and bind to the surface of the sulfide matrix, thereby obtaining the sulfide electrolyte. This method is simple to operate, easy to implement, and the elemental iodine, through sublimation and binding to the sulfide matrix surface, exhibits stronger bonding force with the sulfide matrix, higher coating rate, and more uniform coating effect.

[0039] During the mechanical fusion process, as time goes on, the temperature of the grinding chamber increases, and elemental iodine sublimates in the chamber. It combines with the sulfide electrolyte precursor through intermolecular forces, thereby forming a uniform and dense coating layer, resulting in sulfide electrolyte materials with better performance.

[0040] For example, the linear speed during mechanical fusion can be controlled at 5-80 m / s, and the processing time is usually 5-100 min. Under these conditions, sulfide electrolyte materials with better coating effect can be obtained.

[0041] In detail, the rate of mechanical fusion can be controlled within the range of 5 m / s, 10 m / s, 20 m / s, 30 m / s, 40 m / s, 50 m / s, 60 m / s, 70 m / s, 80 m / s, or any two of the above values. The processing time can be within the range of 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, or any two of the above values. It can also be understood that when the rate of mechanical fusion is low, the degradation of elemental iodine can usually be ensured by extending the processing time.

[0042] The aforementioned sulfide matrix can be prepared using a suitable method depending on the type of matrix used. Taking lithium sulfide electrolyte as an example, the lithium sulfide matrix can be formed by mixing and sintering matrix raw materials. The parameters for mixing and sintering the matrix raw materials are not specifically limited. For example, the sintering temperature of the matrix raw materials is 200-1000℃, and the time is 2-10 hours. More specifically, the sintering temperature can be 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, or any range between two of the above values, and the sintering time can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any range between two of the above values.

[0043] To ensure uniform and thorough mixing of the raw materials, the matrix materials typically undergo a mechanical grinding process before sintering. The conditions for mechanical grinding are not specifically limited, as long as the raw materials are thoroughly and uniformly mixed. For example, ball milling can be used to grind the raw materials, with the ball mill speed controlled at 200-800 r / min, and the milling time at 0.5-10 hours.

[0044] To disperse the sintered particles and ensure uniform coating, while also considering the uniform particle size of the final product, the sintered sulfide electrolyte precursor is typically mechanically ground before being coated with iodine. For example, ball milling is used to grind the raw material, with the ball mill speed controlled at 200-800 r / min and the milling time at 0.5-10 h. Specifically, the ball mill speed can be 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, or any two of these values, and the milling time can be 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, or any two of these values.

[0045] The sulfide matrix raw materials mentioned above typically include P2S5, Li2S, and LiCl. When dopants are present, they are usually added before sintering.

[0046] The present invention also provides a solid electrolyte, which includes the sulfide electrolyte material described above or the sulfide electrolyte material prepared by the above preparation method.

[0047] The present invention also provides an electrode sheet comprising the above-described sulfide electrolyte material or the sulfide electrolyte material prepared by the above-described preparation method.

[0048] It is understood that the aforementioned electrode sheet can be either a positive electrode sheet or a negative electrode sheet. The sulfide electrolyte material can be used solely as an electrolyte raw material on the active layer, or as a raw material for the active layer, or simultaneously as a raw material for both the electrolyte and the active layer.

[0049] The sulfide electrolyte material provided by the present invention can be used in all-solid-state batteries, as well as in semi-solid-state batteries and liquid batteries, and is preferably used in all-solid-state batteries.

[0050] Furthermore, because all-solid-state batteries typically require the addition of electrolytes to both the positive and negative electrodes, they face the challenge of achieving high energy density. To address this issue, in addition to using high-energy-density positive electrodes, high-energy-density material systems should also be explored for the negative electrodes. Compared to graphite with low specific capacity and silicon-based materials with high volumetric strain, lithium metal negative electrodes, with their high specific capacity (3861 mAh / g) and low electrochemical potential (-3.04 V relative to the standard hydrogen electrode), are considered the most ideal and promising negative electrode materials.

[0051] The sulfide electrolyte material provided by this invention is particularly suitable for applications in this type of solid-state battery. It can form a lithium iodide interface layer on the surface of the lithium metal anode, suppressing the growth of lithium dendrites and the side reactions between the sulfide electrolyte and the lithium metal anode, thereby suppressing the deterioration and failure of the sulfide solid-state lithium metal battery. Specifically, the electrode sheet includes a lithium metal sheet and an electrolyte layer covering at least one surface of the lithium metal sheet, wherein the electrolyte layer includes the aforementioned sulfide electrolyte material.

[0052] Furthermore, a lithium iodide interface layer is also included between the lithium metal sheet and the electrolyte layer. This lithium iodide interface layer is formed in situ by the reaction of the sulfide electrolyte material and the lithium metal anode during the electrochemical reaction process.

[0053] The aforementioned lithium iodide interface layer can be confirmed by transmission electron microscopy (TEM) and energy dispersive X-ray diffraction (EDX).

[0054] The present invention also provides a battery cell comprising the aforementioned electrode sheet. It is readily understood that when the aforementioned electrode sheet is a positive electrode sheet, the battery cell also includes at least a negative electrode sheet, and when the aforementioned electrode sheet is a negative electrode sheet, the battery cell also includes at least a positive electrode sheet. For example, if the aforementioned electrode sheet is a negative electrode sheet and includes a lithium metal sheet and an electrolyte layer covering at least one surface of the lithium metal sheet, and the electrolyte layer includes the aforementioned sulfide electrolyte material, then the battery cell also includes a positive electrode sheet.

[0055] This invention also provides a solid-state battery, including the aforementioned electrode sheet or battery cell. Exemplarily, this solid-state battery can be prepared by the following method: dissolving the positive electrode active material, the aforementioned sulfide electrolyte, and a conductive agent in an organic solvent at a certain mass ratio to obtain a positive electrode slurry; coating the positive electrode slurry onto an aluminum foil and drying it to obtain a positive electrode sheet; pressing the aforementioned sulfide electrolyte in a mold battery, and then pressing it together with the negative electrode sheet (Li) and the aforementioned positive electrode sheet in a mold battery to obtain the final product. The aforementioned positive electrode active material and conductive agent are not specifically limited; any raw materials commonly used in solid-state battery preparation can be selected. For example, the positive electrode active material can be at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate (LFP), lithium nickel manganese oxide, lithium-rich manganese-based materials, etc., and the conductive agent can be vapor-grown carbon fiber (VGCF), etc.

[0056] The sulfide electrolyte material of the present invention will be described in detail below with reference to specific embodiments.

[0057] Example 1

[0058] A specific molar mass of raw materials P₂S₅, Li₂S, and LiCl was added to a ball mill jar, and the ball mill speed was controlled at 500 r / min for 8 h. The ball-milled material was sintered at 500℃ for 5 h to obtain a sulfide electrolyte precursor. The sintered sulfide electrolyte precursor was then wet-milled at 400 rpm for 2 h to obtain the product Li. 5.5 PS 4.5 Cl 1.5 Electrolytes.

[0059] Li 5.5 PS 4.5 Cl 1.5 Electrolytes and elemental iodine are added to a mechanical fusion machine for coating treatment, wherein the amount of elemental iodine used is Li 5.5 PS 4.5 Cl 1.5 The electrolyte mass is 5%, the mechanical fusion linear speed is 20 m / s, the time is 30 min, and the sulfide electrolyte material is obtained after coating is completed.

[0060] Example 2

[0061] A specific molar mass of raw materials P₂S₅, Li₂S, and LiCl was added to a ball mill jar, and the ball mill speed was controlled at 500 r / min for 8 h. The ball-milled material was sintered at 500℃ for 5 h to obtain a sulfide electrolyte precursor. The sintered sulfide electrolyte precursor was then wet-milled at 400 rpm for 2 h to obtain the product Li. 5.5 PS 4.5 Cl 1.5 Electrolytes.

[0062] Li 5.5 PS 4.5 Cl 1.5 Electrolytes and elemental iodine are added to a mechanical fusion machine for coating treatment, wherein the amount of elemental iodine used is Li 5.5 PS 4.5 Cl 1.5 The electrolyte mass is 2.5%, the mechanical fusion linear speed is 20 m / s, the time is 30 min, and the sulfide electrolyte material is obtained after coating is completed.

[0063] Example 3

[0064] A specific molar mass of raw materials P₂S₅, Li₂S, and LiCl was added to a ball mill jar, and the ball mill speed was controlled at 500 r / min for 8 h. The ball-milled material was sintered at 500℃ for 5 h to obtain a sulfide electrolyte precursor. The sintered sulfide electrolyte precursor was then wet-milled at 400 rpm for 2 h to obtain the product Li. 5.5 PS 4.5 Cl1.5 Electrolytes.

[0065] Li 5.5 PS 4.5 Cl 1.5 Electrolytes and elemental iodine are added to a mechanical fusion machine for coating treatment, wherein the amount of elemental iodine used is Li 5.5 PS 4.5 Cl 1.5 The electrolyte mass is 10%, the mechanical fusion linear speed is 20 m / s, the time is 30 min, and the sulfide electrolyte material is obtained after coating is completed.

[0066] Example 4

[0067] A specific molar mass of raw materials P2S5, Li2S, and LiCl was weighed and added to a ball mill jar. The ball mill speed was controlled at 500 r / min, and the mixture was ball-milled for 8 hours. The ball-milled material was sintered at 500℃ for 5 hours to obtain a sulfide electrolyte precursor. The sintered sulfide electrolyte precursor was then wet-milled at 400 rpm for 2 hours to obtain the product Li6PS5Cl electrolyte.

[0068] Li6PS5Cl electrolyte and elemental iodine were added to a mechanical fusion apparatus for coating treatment, wherein the amount of elemental iodine used was Li 5.5 PS 4.5 Cl 1.5 The electrolyte mass is 5%, the mechanical fusion linear speed is 20 m / s, the time is 30 min, and the sulfide electrolyte material is obtained after coating is completed.

[0069] Example 5

[0070] A specific molar mass of raw materials P2S5, Li2S, LiCl, and Sb2S5 was weighed and added to a ball mill jar. The ball mill speed was controlled at 500 r / min, and the mixture was ball-milled for 8 hours. The ball-milled material was sintered at 500℃ for 5 hours to obtain a sulfide electrolyte precursor. The sintered sulfide electrolyte precursor was then wet-milled at 400 rpm for 2 hours to obtain the product Li. 5.5 P 0.9 Sb 0.1 S 4.5 Cl 1.5 Electrolytes.

[0071] Li 5.5 P 0.9 Sb 0.1 S 4.5 Cl 1.5 Electrolytes and elemental iodine are added to a mechanical fusion machine for coating treatment, wherein the amount of elemental iodine used is Li 5.5 P 0.9 Sb 0.1 S4.5 Cl 1.5 The electrolyte mass is 5%, the mechanical fusion linear speed is 20 m / s, the time is 30 min, and the sulfide electrolyte material is obtained after coating is completed.

[0072] Comparative Example 1

[0073] A specific molar mass of raw materials P₂S₅, Li₂S, and LiCl was added to a ball mill jar, and the ball mill speed was controlled at 500 r / min for 8 h. The ball-milled material was sintered at 500℃ for 5 h to obtain a sulfide electrolyte precursor. The sintered sulfide electrolyte precursor was then wet-milled at 400 rpm for 2 h to obtain the product Li. 5.5 PS 4.5 Cl 1.5 Electrolytes.

[0074] Comparative Example 2

[0075] A specific molar mass of raw materials P₂S₅, Li₂S, and LiCl was added to a ball mill jar, and the ball mill speed was controlled at 500 r / min for 8 h. The ball-milled material was sintered at 500℃ for 5 h to obtain a sulfide electrolyte precursor. The sintered sulfide electrolyte precursor was then wet-milled at 400 rpm for 2 h to obtain the product Li. 5.5 PS 4.5 Cl 1.5 Electrolytes.

[0076] Li 5.5 PS 4.5 Cl 1.5 The electrolyte and LiI were fed into a mechanical fusion machine for coating treatment, wherein the amount of LiI used was Li 5.5 PS 4.5 Cl 1.5 The electrolyte mass is 5%, the mechanical fusion linear speed is 20 m / s, the time is 30 min, and the sulfide electrolyte material is obtained after coating is completed.

[0077] (1) The coating rate of the sulfide electrolyte materials obtained in the above examples and comparative examples was detected and analyzed using SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy). The coating rate was calculated as: (Iodine atomic concentration / Sum of non-metallic element atomic concentrations) × 100%. For example, for LPSCl electrolyte, the coating rate was calculated as: (Iodine atomic concentration / (Iodine atomic concentration + Phosphorus atomic concentration + Sulfur atomic concentration + Chlorine atomic concentration)) × 100%. TEM (transmission electron microscopy) was used to penetrate the ultrathin sample with a high-energy electron beam, and images were formed by the difference in electron scattering within the sample's internal structure. The thickness of the coating layer could be directly measured using a ruler after observation. The detection results are as follows: Figures 1-3The results are shown in Table 1. Furthermore, the particle size of the sulfide electrolyte was determined using a dry laser particle size analyzer, and the results are shown in Table 1.

[0078] Table 1

[0079]

[0080] Figure 1 The distribution results of I and S elements in the sulfide electrolyte material of Example 1, obtained by EDS analysis, are shown in Figure A, where A represents the distribution of I element, B represents the distribution of S element, and C is the corresponding SEM image. Figure 1 It can be seen that iodine is distributed on the surface of sulfide electrolyte particles.

[0081] Furthermore, the sulfide electrolyte material in Example 1 was subjected to XRD analysis, and the test results are as follows: Figure 2 As shown, Figure 2 The blue and red baselines represent the standard cards for sulfide electrolytes and elemental iodine, respectively.

[0082] Depend on Figure 2 It can be seen that the diffraction peaks in the sulfide electrolyte material only contain the characteristic peaks of elemental iodine and sulfide electrolyte, and do not contain other impurity peaks. Therefore, iodine exists in the form of elemental iodine.

[0083] Observations of the sulfide electrolyte materials in each embodiment under a scanning electron microscope at different magnifications revealed that the sulfide electrolyte material has an irregular amorphous morphology. Some large-diameter particles in the electrolyte are aggregates composed of multiple small-diameter primary particles. The particle size distribution of the primary particles is approximately in the range of 1-50 micrometers, with a D50 of 1-30 μm. See [link to microscopic observations] for some of the observation results. Figure 3 , 4 , Figure 3 , 4 The images shown are partial SEM images of the sulfide electrolyte material in Example 1 at different magnifications, where the D50 of the sulfide electrolyte material is 18.5 μm.

[0084] (2) The ability of the sulfide electrolyte to suppress lithium dendrite formation was evaluated using a lithium metal symmetric battery. The stronger the ability to suppress lithium dendrite formation, the higher its critical current density (CCD). The specific detection method is as follows, and the detection results are as follows. Figure 5 , 6 As shown in Table 2 below.

[0085] The detection and analysis method for suppressing lithium dendrite formation is as follows: ① Weigh a certain mass of sulfide electrolyte powder and load it into the battery compartment of the mold; ② Place the battery in a press and press it under a certain pressure, then place the cut lithium sheets at both ends of the electrolyte sheet; ③ After assembling the battery, press it under a certain pressure on the press, fix the battery on the pressure display fixture, and apply a certain test pressure. A lithium metal symmetric battery is thus prepared. Then, a current density of 0.1 mA / cm² is applied to the symmetric battery for 1 hour in the forward direction and 1 hour in the reverse direction (2 hours is one cycle). The current increases by 0.1 mA / cm² in each cycle, and the voltage change is detected. The current value at which a voltage drop (ΔV > 50mV) or a short circuit occurs is the critical current density (CCD).

[0086] Table 2

[0087]

[0088] As shown in Table 2 above, the lithium symmetric batteries prepared with the sulfide electrolytes in the examples all have high critical current densities, indicating that the battery interfaces prepared with the sulfide electrolytes in the examples are more stable and can suppress dendrite growth.

[0089] Figure 5 , 6 The critical current density test results are shown for the lithium symmetric batteries prepared with sulfide electrolytes in Example 1 and Comparative Example 1, respectively.

[0090] (3) Prepare a positive electrode slurry by mixing and dissolving nickel cobalt manganese (NCM111), sulfide electrolyte, vapor-grown carbon fiber (VGCF), and nitrile rubber (NBR) in xylene at a ratio of 85:15:1:1, then coating the positive electrode slurry onto aluminum foil, and placing the electrode in a vacuum oven to dry it at 60°C for 12 hours to obtain a composite positive electrode.

[0091] Weigh 0.15g of the sulfide electrolyte from the above examples or comparative examples, pressurize it at 300 MPa for 1 minute in a mold battery, use a lithium sheet as the negative electrode and the coated composite positive electrode as the positive electrode, place it in the mold battery and pressurize it at 400 MPa for 1 minute to prepare a solid-state battery.

[0092] The solid-state batteries prepared above were subjected to first-cycle charge-discharge capacity test, first-cycle efficiency test, rate test, and 100-cycle cycle retention test. The specific test methods are as follows, and the test results are shown in Table 3.

[0093] First-week efficiency: Each battery was left to stand at 25°C for 4 hours before the first charge-discharge capacity test was conducted. The test conditions were: charging to 4.25V at 0.1C, standing for 3 minutes, and then discharging to 2.5V at 0.1C. The charge-discharge curves were obtained, and the first-week charge capacity C0 and the first-week discharge capacity D0 at 4.25V were recorded respectively. The first coulombic efficiency (i.e., first-week efficiency) was calculated according to D0 / C0.

[0094] 0.5C / 0.1C Rate: At 25°C, the battery is charged at a constant current rate of 0.1C to 4.25V, allowed to rest for 3 minutes, and then discharged at a constant current rate of 0.1C to 2.5V. The capacity retention rate at the 0.5C / 0.1C rate is then calculated by dividing the discharge capacity at 0.5C by the discharge capacity at 0.1C.

[0095] Cycle retention rate after 100 cycles: The battery prepared above was subjected to cycle performance test at room temperature of 25°C. The test process is as follows: first, it was charged at 1C constant current to 4.25V, and then discharged at 1C constant current to 2.5V. After 100 cycles, the discharge capacity after 100 cycles was divided by the discharge capacity after the first cycle to obtain the cycle retention rate after 100 cycles.

[0096] Table 3

[0097]

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sulfide electrolyte material, characterized in that, It includes an ion-conductive sulfide matrix and a coating layer, wherein at least a portion of the surface of the sulfide matrix is ​​covered by the coating layer, and the coating layer includes elemental iodine; The iodine content is 2.5-10% of the mass of the sulfide matrix; The thickness of the coating layer is 5-400 nm; The coating rate of the sulfide electrolyte material is ≥89%; In this process, under sealed conditions, a mixture of sulfide matrix and elemental iodine is mechanically fused to sublimate and bind the elemental iodine to the surface of the sulfide matrix, thereby obtaining the sulfide electrolyte material.

2. The sulfide electrolyte material according to claim 1, characterized in that, The general structural formula of the sulfide matrix is ​​Li a M b P c S d O e X f Where M is one or more of As, Sb, Sn, Si, and In, and X is one or more of F, Cl, and Br, 4≤a≤7, 0≤b≤1, 0≤c≤2, 3≤d≤8, 0≤e≤1, and 0≤f≤2; and / or The particle size D50 of the sulfide electrolyte material is 1-30 μm.

3. A method for preparing the sulfide electrolyte material according to claim 1 or 2, characterized in that, include: The step involves mechanically fusing a mixture of a sulfide matrix and elemental iodine under sealed conditions, causing the elemental iodine to sublimate and bind to the surface of the sulfide matrix, thereby obtaining the sulfide electrolyte material.

4. The preparation method according to claim 3, characterized in that, The linear velocity of the mechanical fusion process is 5-80 m / s, and the processing time is 5-100 min.

5. A solid electrolyte, characterized in that, Includes the sulfide electrolyte material as described in claim 1 or 2.

6. An electrode sheet, characterized in that, Includes the sulfide electrolyte material as described in claim 1 or 2.

7. The electrode sheet according to claim 6, characterized in that, The electrode sheet includes a lithium metal sheet and an electrolyte layer covering at least one surface of the lithium metal sheet, the electrolyte layer including the sulfide electrolyte material.

8. The electrode sheet according to claim 7, characterized in that, The lithium metal sheet and the electrolyte layer also include a lithium iodide interface layer generated in situ during the electrochemical reaction.

9. A battery cell, characterized in that, Includes the electrode sheet as described in any one of claims 6-8.

10. A solid-state battery, characterized in that, Includes the electrode sheet as described in any one of claims 6-8.

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