A method for preparing nano-scale sulfide solid electrolyte

Abstract

The present invention belongs to the technical field of solid-state batteries, and relates to a method for preparing a nano-scale sulfide solid electrolyte. The preparation method comprises the following steps: 1. configuring electrolyte raw materials according to the stoichiometric ratio in the chemical formula of the sulfide solid electrolyte, and adding a mixed solvent to the electrolyte raw materials for ball milling to obtain a precursor solution; 2. drying the precursor solution to obtain a complex electrolyte precursor; 3. sintering the complex electrolyte precursor to obtain the nano-scale sulfide solid electrolyte; wherein the mixed solvent comprises a complexing agent and a first organic solvent, and the complexing agent comprises an ether organic solvent having 3 or more ether bonds or cyclic ether bonds. Through the preparation method provided by the present invention, the preparation of nano-scale sulfide solid electrolyte can be achieved, and the ionic conductivity can also be high, which is conducive to contact with the positive electrode and improves the cycle performance of the whole battery.

Description

Technical Field

[0001] The invention belongs to the technical field of solid-state batteries and relates to a method for preparing a nano-scale sulfide solid electrolyte. Background Art

[0002] All-solid-state lithium batteries are considered to be the next generation of electrochemical energy storage devices with the most promising application prospects due to their higher energy density, safety performance and cycle life. Solid electrolytes, as the core components of all-solid-state batteries, have been widely studied. Among all solid electrolytes, sulfide solid electrolytes are considered to be the most likely to be used in practice due to their high ionic conductivity, excellent mechanical properties and other advantages.

[0003] At present, the synthesis method of sulfide solid electrolyte is mainly solid phase method or liquid phase ball milling method. The particle size of the prepared sulfide solid electrolyte is in the micron level. When applied to the composite positive electrode, it cannot be well dispersed around the positive electrode particles. There are many pores inside the sheet, and it is impossible to form a continuous three-dimensional conductive network, which is not conducive to the transmission of lithium ions and affects the electrochemical performance of the battery. Usually, the prepared electrolyte is mechanically crushed by dry method or re-solvent ball milling to make the electrolyte particle size reach the submicron level, but this preparation method will lead to a significant decrease in the electrolyte ion conductivity, resulting in the battery capacity cannot be fully utilized.

[0004] Based on this, the present invention aims to provide a method for preparing a nanoscale sulfide solid electrolyte, so as to achieve the preparation of a submicron-scale sulfide electrolyte while maintaining the high ionic conductivity of the electrolyte. Summary of the invention

[0005] The present invention aims to provide a method for preparing a nano-scale sulfide solid electrolyte, which can achieve the preparation of a submicron-scale sulfide electrolyte while maintaining high ionic conductivity of the electrolyte.

[0006] According to a first aspect of the present invention, the present invention provides a method for preparing a nanoscale sulfide solid electrolyte, the preparation method comprising the following steps:

[0007] 1. preparing electrolyte raw materials according to the stoichiometric ratio in the chemical formula of the sulfide solid electrolyte, and adding a mixed solvent to the electrolyte raw materials for ball milling to obtain a precursor solution;

[0008] 2. drying the precursor solution to obtain a complex electrolyte precursor;

[0009] 3. Sintering the complex electrolyte precursor to obtain the nanoscale sulfide solid electrolyte;

[0010] Wherein, the mixed solvent includes a complexing agent and a first organic solvent, and the complexing agent includes an ether organic solvent having three or more ether bonds or cyclic ether bonds.

[0011] Specifically, the complexing agent includes an ether organic solvent having 3 or more ether bonds or cyclic ether bonds, the general structural formula of the ether bond is expressed as ROR(R'), R and R' are independently selected from hydrocarbon groups; the general structural formula of the cyclic ether bond is expressed as ROR(R'), R and R' are carbon atoms at both ends of an organic group, and O and C in the cyclic ether bond are bonded by a single bond.

[0012] From the perspective of the performance and manufacturing of all-solid batteries, it is expected that the particle size of the solid electrolyte is small and the ionic conductivity is high. On the one hand, by using the wet pulverization method of the existing solvent to prepare the sulfide solid electrolyte, although the electrolyte can be micronized to a certain extent, the prepared solid electrolyte is easily degraded by the solvent, and it is easy to condense during pulverization, and there is a problem of applying too much load to the pulverization; on the other hand, even if the solvent is not used and dry pulverization is performed, it is difficult to achieve the micronization of the electrolyte to the submicron level. At the same time, for the synthesis and preparation of the electrolyte, the electrolyte synthesized based on the method disclosed in the prior art needs to be further refined because the particles are too large, and the problem that it is easy to occur is that the finer the particles after refinement, the lower the ionic conductivity of the electrolyte. Based on this, in view of the problems existing in the preparation of sulfide solid electrolytes in the prior art, the present invention introduces a new type of complexing agent with multiple oxygen sites, especially a complexing agent with multiple ether bonds or cyclic ether bonds, in the ball milling process of the electrolyte raw material, and the complexing agent is allowed to react with all the raw materials through ball milling to form a complex, and then the required glass ceramic electrolyte is formed by annealing. While achieving the refinement of the electrolyte and preparing a nano-scale sulfide solid electrolyte, the ionic conductivity of the prepared electrolyte will not be greatly reduced, so that the prepared electrolyte maintains high ionic conductivity. In addition, by preparing a sulfide solid electrolyte through the method provided by the present invention, a nano-scale sulfide electrolyte can be synthesized in one step, without the need for multi-step ball milling, and without further refinement of the electrolyte. The generated sulfide particle size is small, and the ionic conductivity can also be high, which is conducive to contact with the positive electrode and improves the cycle performance of the full battery.

[0013] In some embodiments of the present invention, the complexing agent is selected from at least one of bis(2-methoxyethoxy)methane, bis(2-methoxyethoxy)ethane, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether. The ether substance having multiple oxygen sites is selected as the complexing agent in the ball milling process, and the nano-scale sulfide solid electrolyte is prepared without significantly reducing the ionic conductivity of the prepared electrolyte, so that the prepared electrolyte maintains high ionic conductivity.

[0014] In some embodiments of the present invention, the first organic solvent is an alkane organic solvent; the first organic solvent is selected from at least one of n-heptane, hexane, and octane. Selecting the above substances as the first organic solvent can further make the electrolyte raw material and the complexing agent react uniformly and be evenly dispersed in the first organic solvent in the form of a suspension, rather than being dissolved in the first solvent.

[0015] In some embodiments of the present invention, in the mixed solvent, the mixing volume ratio of the complexing agent to the first organic solvent is 1-60:99-40; preferably, the mixing volume ratio of the complexing agent to the first organic solvent is 10-40:90-60. Specifically, in the mixed solvent, the volume ratio of the complexing agent to the first organic solvent can be 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, 11:89, 12:88, 13:87, 14:86, 15:85, 16:84, 17:83, 18:82, 19:81, 20:80, 21:79, 22:78, 23:77, 24:76, 25:75, 26:74, 27:73, 28:72, 29:71, 30:70, 31:69, 32:68, 33:67, 34:66, 35:65, 36:64, 37:63, 38:62, 39:61, 40:60, 41:59, 42:58, 43:57, 44:56, 45:55, 46:54, 47:53, 48:52, 49:51, 50:50, 51:49, 52:48, 53:47, 54:46, 55:45, 56:44, 57:43, 58:42, 59:41, 60:40, or a range consisting of any two of the above values. Not limited to the listed values, other values ​​not listed within the numerical range are also applicable. In the technical solution provided by the present invention, by controlling the mixed volume ratio of the complexing agent and the first organic solvent within the above range, the particle size of the prepared sulfide solid electrolyte can be further significantly reduced while better maintaining the ionic conductivity of the prepared sulfide solid electrolyte.

[0016] In some embodiments of the present invention, in step 1, the chemical formula of the sulfide solid electrolyte is Li 7 P 2 S 8 X, wherein X comprises at least one of Cl, Br, and I. In some embodiments of the present invention, the electrolyte raw material comprises Li 2 S.P. 2 S 5, LiX; According to the stoichiometric ratio, the ratio of each electrolyte raw material is: Li 2 S:P 2 S 5 :LiX=3:1:1. Selecting the above method to prepare the sulfide solid electrolyte having the above chemical formula or preparing the electrolyte raw material having the above ratio can further make the prepared sulfide solid electrolyte have a crystalline phase of a fast ion conductor, and thus have a higher ion conductivity.

[0017] In some embodiments of the present invention, in step 1, in g / ml, the addition ratio of the electrolyte raw material to the mixed solvent is 1 to 10: 10-100. Specifically, in g / ml, the addition ratio of the electrolyte raw material to the mixed solvent can be 1:10, 2:10, 3:10, 4:10, 5:10, 6:10, 7:10, 8:10, 9:10, 10:10, 1:15, 2:15, 3:15, 4:15, 5:15, 6:15, 7:15, 8:15, 9:15, 10:15, 1:20, 2:20, 3:20, 4:20, 5:20, 6:20, 7:20, 8:20, 9:20, 10:20, 1:25, 2:25, 3:25, 4:25, 5:20, 6:20, 7:20, 8:20, 9:20, 10:20, 1:25, 2:25, 3:25, 4:25, 5:20, 6:20, 7:20, 8:20, 9:20, 10:20, 1:25, 2:25, 3:25, 4:25 25, 3:25, 4:25, 5:25, 6:25, 7:25, 8:25, 9:25, 10:25, 1:30, 2:30, 3:30, 4:30, 5:30, 6:30, 7:30, 8:30, 9:30, 10:30, 1:35, 2:35, 3:35, 4:35, 5:35, 6:35, 7:35, 8:35, 9:35, 10:35, 1:40, 2:40, 3:40, 4:40, 5:40, 6:40, 7:40, 8:40, 9:40, 10 :40, 1:45, 2:45, 3:45, 4:45, 5:45, 6:45, 7:45, 8:45, 9:45, 10:45, 1:50, 2:50, 3:50, 4:50, 5:50, 6:50, 7:50, 8:50, 9:50, 10:50, 1:60, 2:60, 3:60, 4:60, 5:60, 6:60, 7:60, 8:60, 9:60, 10:60, 1:70, 2:70, 3:70, 4:70, 5:70, 6:70, 7:70, 8 :70, 9:70, 10:70, 1:80, 2:80, 3:80, 4:80, 5:80, 6:80, 7:80, 8:80, 9:80, 10:80, 1:90, 2:90, 3:90, 4:90, 5:90, 6:90, 7:90, 8:90, 9:90, 10:90, 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, or a range consisting of any two of the above values. Not limited to the listed values, other values ​​not listed in the numerical range are also applicable. In the technical solution provided by the present invention, by controlling the addition ratio of the electrolyte raw material to the mixed solvent within the above range, the particle size of the prepared sulfide solid electrolyte can be further significantly reduced while better maintaining the ionic conductivity of the prepared sulfide solid electrolyte.

[0018] In some embodiments of the present invention, in step 1, the speed of the ball milling is 400-1000 rpm; and the time of the ball milling is 20-120 h. Specifically, the speed of the ball milling can be 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, 450 rpm, 460 rpm, 470 rpm, 480 rpm, 490 rpm, 500 rpm, 510 rpm, 520 rpm, 530 rpm, 540 rpm, 550 rpm, 560 rpm, 570 rpm, 580 rpm, 590 rpm, 600 rpm, 610 rpm, 620 rpm, 630 rpm, 640 rpm, 650 rpm, 660 rpm, 670 rpm, 680 rpm, 690 rpm, 700 rpm, 710rpm, 720rpm, 730rpm, 740rpm, 740rpm, 750rpm, 760rpm, 770rpm, 780rpm, 790rpm, 800rpm, 810rpm, 820rpm, 830rpm, 840rpm, 850rpm, 860rpm, 870rpm, 880rpm, 890rpm, 900rpm, 910rpm, 920rpm, 930rpm, 940rpm, 950rpm, 960rpm, 970rpm, 980rpm, 990rpm, 1000rpm or a range consisting of any two of the above values. Not limited to the listed values, other values ​​not listed in the numerical range are equally applicable. Specifically, the ball milling time can be 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h, 40h, 41h, 42h, 43h, 44h, 45h, 46h, 47h, 48h, 49h, 50h, 51h, 52h 1h, 52h, 53h, 54h, 55h, 56h, 57h, 58h, 59h, 60h, 61h, 62h, 63h, 64h, 65h, 66h, 67h, 68h, 69h, 70h, 75h, 80h, 85h, 90h, 95h, 100h, 105h, 110h, 115h, 120h or a range consisting of any two of the above values. It is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. Most of the ball milling operations in the preparation methods of sulfide electrolytes disclosed in the prior art are mainly for mixing the raw materials evenly, while the present invention uses a specific ball milling operation to allow the complexing agent to react with all the raw materials to form a complex, and then form the required glass ceramic electrolyte by annealing.The present invention has found through research that when the rotation speed and time of the ball mill are controlled within the above range, the prepared sulfide solid electrolyte can further have a smaller particle size and a relatively higher ionic conductivity.

[0019] In some embodiments of the present invention, in step 2, the drying is vacuum drying; the vacuum degree of the drying is -0.05-0.3 MPa; the drying temperature is 50-80°C; and the drying time is 10-40 hours. Specifically, the vacuum degree of the drying can be -0.05MPa, -0.06MPa, -0.07MPa, -0.08MPa, -0.09MPa, -0.1MPa, -0.11MPa, -0.12MPa, -0.13MPa, -0.14MPa, -0.15MPa, -0.16MPa, -0.17MPa, -0.18MPa, -0.19MPa, -0.2MPa, -0.21MPa, -0.22MPa, -0.23MPa, -0.24MPa, -0.25MPa, -0.26MPa, -0.27MPa, -0.28MPa, -0.29MPa, -0.30MPa. Specifically, the drying temperature can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C or a range consisting of any two of the above values. Not limited to the listed values, other values ​​not listed in the numerical range are also applicable. Specifically, the drying time can be 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h, 40h or the range composed of any two of the above numerical values. Not limited to the listed numerical values, other unlisted numerical values ​​in the numerical range are also applicable. In the preparation method provided by the present invention, the precursor solution is heated and dried by vacuum drying, and the organic solvent can be better removed. When the relevant parameters of the drying are further regulated within the above range, the residual solvent can be further removed, and the generated complex electrolyte precursor is not decomposed, so that the electrolyte prepared subsequently has higher ionic conductivity.

[0020] In some embodiments of the present invention, in step 3, the sintering temperature is 100-200°C; and the sintering time is 1-24h. Specifically, the sintering temperature can be 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C, 110°C, 111°C, 112°C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C, 119°C, 120°C, 121°C, 122°C, 123°C , 124℃, 125℃, 126℃, 127℃, 128℃, 129℃, 130℃, 131℃, 132℃, 133℃, 134℃, 135℃, 136℃, 137℃, 138℃, 139℃, 140℃, 141℃, 142℃, 143℃, 144℃, 145℃, 146℃, 147℃, 148℃, 149℃, 150℃ ℃、151℃、152℃、153℃、154℃、155℃、156℃、157℃、158℃、159℃、160℃、161℃、162℃、163℃、164℃、165℃、166℃、167℃、168℃、169℃、170℃、171℃、172℃、173℃、174℃、175℃、176℃、1 77°C, 178°C, 179°C, 180°C, 181°C, 182°C, 183°C, 184°C, 185°C, 186°C, 187°C, 188°C, 189°C, 190°C, 191°C, 192°C, 193°C, 194°C, 195°C, 196°C, 197°C, 198°C, 199°C, 200°C or a range consisting of any two of the above values. Not limited to the listed values, other unlisted values ​​within the numerical range are also applicable. Specifically, the sintering time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h. The range is composed of any two of the above values. It is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. When different sintering temperatures are used for sintering treatment, the crystal structure of the sulfide electrolyte finally generated will be different, so that the performance of the sulfide solid electrolyte finally generated is completely different. In the preparation method provided by the present invention, the sintering temperature is further controlled within the above range, which can better achieve the refinement of the sulfide solid electrolyte, while making the ionic conductivity of the prepared sulfide solid electrolyte and the cycle performance of the electrolyte higher. When the sintering temperature exceeds the above range, the performance of the prepared sulfide solid electrolyte will be significantly deteriorated. For example, if the sintering temperature is high, the crystal phase of the synthesized electrolyte will be incorrect and the ionic conductivity will be deteriorated.

[0021] According to the second aspect of the present invention, the present invention further provides a sulfide solid electrolyte, which is prepared by any preparation method as described in the first aspect of the present invention.

[0022] According to the third aspect of the present invention, the present invention further provides a battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is selected from the sulfide solid electrolyte as described in the second aspect of the present invention.

[0023] In some embodiments of the present invention, the positive electrode active material of the positive electrode is selected from high-nickel ternary materials; in some embodiments of the present invention, the positive electrode active material of the positive electrode is selected from at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, nickel cobalt lithium manganese oxide, and lithium-rich lithium manganese oxide; the negative electrode active material of the negative electrode is metallic lithium.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention introduces a new type of ether complexing agent having multiple oxygen sites, especially an ether complexing agent having multiple ether bonds or cyclic ether bonds, during the ball milling process of the electrolyte raw material. While achieving electrolyte refinement and preparing a nano-scale sulfide solid electrolyte, the ionic conductivity of the prepared electrolyte will not be significantly reduced, so that the prepared electrolyte maintains high ionic conductivity.

[0026] (2) The preparation method provided by the present invention simplifies the preparation process and can synthesize nano-scale sulfide electrolyte in one step. There is no need for multi-step ball milling and further refinement of the electrolyte. The generated sulfide particles have a small size and a high ionic conductivity, which is helpful for contact with the positive electrode and improves the cycle performance of the entire battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0028] Figure 1 This is a SEM microscopic morphology image of a crystalline nanoscale sulfide electrolyte prepared in one embodiment of the present application;

[0029] Figure 2 This is a SEM microscopic morphology of the crystalline sulfide electrolyte prepared in a comparative example of the present application. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below by specific embodiments, which do not limit the protection scope of the present invention. Some non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the protection scope of the present invention.

[0031] As used in the present invention, including as used in the examples and unless otherwise expressly provided, all numbers may be read as if beginning with the wording "substantially", "approximately" or "about", even if the term does not explicitly appear. The phrase "approximately" or "about" may be used when describing the magnitude and / or position to indicate that the described value and / or position is within a reasonable expected value and / or position range. For example, the value may be ±0.1% of the value (or value range), ±1% of the value (or value range), ±2% of the value (or value range), ±5% of the value (or value range), ±10% of the value (or value range), ±15% of the value (or value range), ±20% of the value (or value range), etc. Any numerical range described in the present invention is intended to include all subranges or intermediate values ​​contained therein.

[0032] The disclosure of the numerical values ​​and numerical ranges of specific parameters (such as temperature, weight percentage, weight fraction, etc.) does not exclude other numerical values ​​and numerical ranges useful to the present invention. It is conceivable that two or more specific example numerical values ​​of a given parameter can determine the endpoints of the numerical range that the parameter can require. For example, if parameter X is exemplified herein as having numerical value A and also exemplified as having numerical value Z, it is expected that parameter X can have a numerical range from about A to about Z. Similarly, it is expected that two or more numerical ranges of disclosed parameters (whether these ranges are nested, overlapped or distinct) include all possible combinations of numerical ranges that can be required using the endpoints of the disclosed ranges. For example, if parameter X is exemplified herein as having a value in the range of 1-10, it also describes a sub-range of parameter X, including only as an example, such as: 1-9, 1-8, 1-7, 2-9, 2-8, 2-7, 3-9, 3-8, 3-7, 2-8, 3-7, 4-6 or 7-10, 8-10 or 9-10. Ranges include their endpoints and values ​​within the endpoints, for example, the range 0-5 includes 0, >0, 1, 2, 3, 4, <5, and 5.

[0033] Example 1

[0034] This embodiment provides a method for preparing a nano-scale sulfide solid electrolyte, and the specific steps are as follows:

[0035] 1. The electrolyte raw material Li 2 S: P 2 S 5: LiI: LiBr is weighed at a stoichiometric ratio of 3: 1: 0.3: 0.7, and the total weight of the electrolyte raw materials is 2 g, which is placed in a ball mill, and 20 mL of a mixed solvent is added and sealed, and ball milled at a speed of 800 rpm / min for 48 hours to obtain a uniformly mixed precursor solution; wherein the mixed solvent is obtained by mixing bis(2-methoxyethoxy)methane and n-heptane at a volume ratio of 10:90;

[0036] 2. Dry the precursor solution prepared in step 1 under vacuum at 60° C. for 24 h with a vacuum degree of -0.1 MPa to obtain a complex electrolyte precursor;

[0037] 3. The complex electrolyte precursor obtained by vacuum drying in step 2 is sintered at 140° C. for 3 h in an argon atmosphere to obtain a crystalline nanoscale sulfide electrolyte.

[0038] Example 2

[0039] This embodiment further provides a method for preparing a nano-scale sulfide solid electrolyte, and the specific steps are as follows:

[0040] 1. The electrolyte raw material Li 2 S: P 2 S 5 : LiI: LiBr is weighed at a stoichiometric ratio of 3: 1: 0.3: 0.7, and the total weight of the electrolyte raw materials is 2 g, which is placed in a ball mill, and 20 mL of a mixed solvent is added and sealed, and ball milled at a speed of 800 rpm / min for 48 hours to obtain a uniformly mixed precursor solution; wherein the mixed solvent is obtained by mixing bis(2-methoxyethoxy)methane and n-heptane at a volume ratio of 20:80;

[0041] 2. Dry the precursor solution prepared in step 1 at 60° C. under vacuum for 24 h with a vacuum degree of -0.1 MPa to obtain a complex electrolyte precursor;

[0042] 3. The complex electrolyte precursor prepared in step 2 was sintered at 140°C for 3 hours in an argon atmosphere to obtain a crystalline nano-scale sulfide electrolyte. The SEM microscopic morphology of the crystalline nano-scale sulfide electrolyte prepared by the above method is as follows: Figure 1 shown.

[0043] Example 3

[0044] This embodiment further provides a method for preparing a nano-scale sulfide solid electrolyte, and the specific steps are as follows:

[0045] 1. The electrolyte raw material Li 2 S: P 2 S5 : LiI: LiBr is weighed at a stoichiometric ratio of 3: 1: 0.3: 0.7, and the total weight of the electrolyte raw materials is 2 g, which is placed in a ball mill, and 20 mL of a mixed solvent is added and sealed, and ball milled at a speed of 800 rpm / min for 48 hours to obtain a uniformly mixed precursor solution; wherein the mixed solvent is obtained by mixing bis(2-methoxyethoxy)methane and n-heptane at a volume ratio of 30:70;

[0046] 2. Dry the precursor solution prepared in step 1 at 60° C. under vacuum for 24 h with a vacuum degree of -0.1 MPa to obtain a complex electrolyte precursor;

[0047] 3. The complex electrolyte precursor prepared in step 2 is sintered at 140° C. for 3 h under an argon atmosphere to obtain a crystalline nanoscale sulfide electrolyte.

[0048] Comparative Example 1

[0049] This comparative example is based on Example 2, and further provides a method for preparing a nano-scale sulfide solid electrolyte. The difference from Example 2 is that the specific solvent added is different. In this comparative example, only bis(2-methoxyethoxy)methane complexing agent is added to the ball mill, and the remaining steps and parameters are the same as those in Example 2. The specific steps are as follows:

[0050] 1. The electrolyte raw material Li 2 S: P 2 S 5 : LiI: LiBr was weighed at a stoichiometric ratio of 3: 1: 0.3: 0.7, and the total weight of the electrolyte raw materials was 2 g. The raw materials were placed in a ball mill, and 20 mL of pure bis(2-methoxyethoxy)methane complexing agent was added and sealed. The ball mill was performed at a speed of 800 rpm / min for 48 h to obtain a uniformly mixed precursor solution.

[0051] 2. The precursor solution prepared in step 1 was dried under vacuum at 60° C. for 24 h with a vacuum degree of -0.1 MPa to obtain a complex electrolyte precursor;

[0052] 3. The complex electrolyte precursor prepared in step 2 is sintered at 140° C. for 3 h under an argon atmosphere to obtain a crystalline nanoscale sulfide electrolyte.

[0053] Comparative Example 2

[0054] Based on Example 2, this comparative example further provides a method for preparing a nano-scale sulfide solid electrolyte. The difference from Example 2 is that the specific solvent added is different. In this comparative example, only n-heptane solvent is added to the ball mill, and the remaining steps and parameters are the same as those in Example 2. The specific steps are as follows:

[0055] 1. The electrolyte raw material Li 2 S: P 2 S 5 : LiI: LiBr was weighed according to the stoichiometric ratio of 3: 1: 0.3: 0.7, and the total weight of the electrolyte raw materials was 2 g, which was placed in a ball milling jar, and 20 mL of n-heptane solvent was added and sealed. The jar was ball milled at a speed of 800 rpm / min for 48 h to obtain a uniformly mixed precursor solution;

[0056] 2. The precursor solution prepared in step 1 was dried under vacuum at 60° C. for 24 h with a vacuum degree of -0.1 MPa to obtain a complex electrolyte precursor;

[0057] 3. The complex electrolyte precursor prepared in step 2 was sintered at 140°C for 3h under an argon atmosphere to obtain a crystalline sulfide electrolyte. The SEM microscopic morphology of the crystalline sulfide electrolyte prepared by the comparative example preparation method is as follows: Figure 2 shown.

[0058] Comparative Example 3

[0059] This comparative example is based on Example 2, and further provides a method for preparing a nano-scale sulfide solid electrolyte. The difference from Example 2 is that the specific solvent added is different. In this comparative example, a solvent obtained by mixing 1,2-dimethoxyethane and n-heptane is added to the ball mill, and the remaining steps and parameters are the same as those in Example 2. The specific steps are as follows:

[0060] 1. The electrolyte raw material Li 2 S: P 2 S 5 : LiI: LiBr is weighed at a stoichiometric ratio of 3: 1: 0.3: 0.7, and the total weight of the electrolyte raw materials is 2 g, which is placed in a ball mill jar, and 20 mL of a mixed solvent is added and sealed, and ball milled at a speed of 800 rpm / min for 48 hours to obtain a uniformly mixed precursor solution; wherein the mixed solvent is obtained by mixing 1,2-dimethoxyethane and n-heptane at a volume ratio of 20:80;

[0061] 2. The precursor solution prepared in step 1 was dried under vacuum at 60° C. for 24 h with a vacuum degree of -0.1 MPa to obtain a complex electrolyte precursor;

[0062] 3. The complex electrolyte precursor prepared in step 2 is sintered at 140° C. for 3 h in an argon atmosphere to obtain a crystalline sulfide electrolyte.

[0063] Comparative Example 4

[0064] This comparative example is based on Example 2 and further provides a method for preparing a nano-scale sulfide solid electrolyte. The difference from Example 2 is that the added solvent and the processing steps are different. The specific steps are as follows:

[0065] The electrolyte raw material Li 2 S: P 2 S 5 : LiI: LiBr was weighed according to the stoichiometric ratio of 3: 1: 0.3: 0.7, and the total weight of the electrolyte raw materials was 2 g, which was placed in a ball milling jar, and 20 mL of n-heptane solvent was added and sealed. The jar was ball milled at a speed of 800 rpm / min for 48 h to obtain a uniformly mixed precursor solution;

[0066] The precursor solution prepared in step 1 is dried under vacuum at 60° C. for 24 h with a vacuum degree of -0.1 MPa to obtain an electrolyte precursor;

[0067] The electrolyte precursor prepared in step 2 is sintered at 140° C. for 3 h in an argon atmosphere to obtain a crystalline micron-sized sulfide electrolyte;

[0068] The crystalline micron-sized sulfide electrolyte prepared in step 3 and a certain amount of n-heptane solvent are placed in a ball mill and ball-milled for 24 hours to obtain a refined electrolyte slurry, which is then vacuum-dried at 60° C. for 24 hours to obtain a submicron-sized sulfide electrolyte powder.

[0069] Effect example

[0070] The particle size, ion conductivity / (mS / cm), full battery cycle stability and other properties of the electrolytes prepared by the above examples and comparative examples were further tested. The specific testing methods are as follows:

[0071] Particle size test method: The test was performed using a laser diffraction / scattering particle size distribution measuring device ("Mastersizer 3000+ Laser Particle Size Analyzer (Model)"). The specific test steps were as follows: a dehydrated isobutyl isobutyrate solvent was used as a dispersion medium, 50 mL of the dispersion medium was injected into the flow cell of the device, and after the dispersion medium was circulated, the measurement object was added and ultrasonic treatment was performed, and then the particle size distribution was measured.

[0072] Ionic conductivity: The electrolytes prepared in the above embodiments and comparative examples were respectively assembled into blocking cells with carbon-coated aluminum foil on both sides, and the EIS impedance was measured. The test method was as follows: the assembled blocking battery was placed in a constant temperature box at 25°C for 1 hour to make the temperature of the electrolyte inside the battery reach 25°C, and the battery was connected to Su Liqiang's electrochemical workstation to measure the constant voltage AC impedance at a frequency range of 1 MHz to 1 Hz, and the ionic conductivity of the corresponding electrolyte was obtained after conversion.

[0073] Cyclic stability of all-solid-state lithium metal battery: The assembly process of all-solid-state lithium metal battery is as follows: high nickel ternary NCM811, sulfide electrolyte prepared in the above embodiments and comparative examples, conductive agent VGCF and adhesive SBS are weighed in a certain mass ratio and added to isobutyl isobutyrate, and then placed in a slurry mixer and set to mix at a set speed. After the slurry is mixed, the slurry is scraped to obtain a positive electrode sheet, and then punched to obtain a positive electrode sheet with a diameter of 10 mm. Weigh 150 mg of the above-prepared electrolyte powder and put it into a PEEK mold with a diameter of 10 mm, and press it at a pressure of 100 MPa for 1 min by a tablet press; then put the prepared 10 mm positive electrode sheet into one side, and press it again at a pressure of 500 MPa for 10 minutes by a tablet press; finally, place the metal lithium negative electrode on the other side of the obtained thin sheet, and press it at a pressure of 20 MPa for 1 minute to make an all-solid-state lithium metal battery. The cycle stability of the above-mentioned all-solid-state lithium metal battery was verified by constant current charge and discharge cycle test (capacity retention rate / % after 100 cycles of the whole battery).

[0074] The particle size, ionic conductivity, and capacity retention rate of the electrolytes prepared in the embodiments and comparative examples tested by the above test method are shown in Table 1.

[0075] Table 1 Electrolyte particle size, ionic conductivity, and full battery cycle stability results of each embodiment and comparative example

[0076]

[0077] According to the results presented in Table 1, it can be seen that the mixed solvent obtained by mixing the complexing agent with multiple oxygen sites and the alkane solvent is mixed with the electrolyte raw material and then subjected to ball milling treatment, which can effectively reduce the particle size of the prepared electrolyte without significantly reducing the ionic conductivity of the electrolyte.

[0078] Specifically, by comparing Examples 1, 2, 3 and Comparative Examples 1 and 2, it can be seen that when only a complexing agent with multiple oxygen sites is added to the ball mill, although the particle size of the prepared electrolyte can be significantly reduced, the corresponding conductivity of the electrolyte is also significantly reduced. At the same time, when only an alkane solvent is added to the ball mill, although its ion conductivity is relatively high, the particle size of the electrolyte is large, and the capacity retention rate of the electrolyte for 100 cycles of full battery cycles is also significantly reduced. It can be seen that when a complexing agent with multiple oxygen sites is mixed and used in combination with an alkane solvent, the particle size of the prepared electrolyte can be lower while the electrolyte can also maintain a higher ion conductivity. Comparative Example 2 and Comparative Example 3 show that when the complexing agent is replaced by bis(2-methoxyethoxy)methane with 1,2-dimethoxyethane, that is, when the complexing agent is replaced by 4 oxygen functional groups with 2 oxygen functional groups, the particle size of the prepared electrolyte is not significantly improved, and the corresponding ionic conductivity of the electrolyte is also significantly reduced. This is mainly because when the number of oxygen functional groups of the complexing agent is small, all lithium-containing raw materials cannot be complexed together, resulting in the segregation of the electrolyte components, and ultimately the desired electrolyte cannot be obtained. At the same time, by comparing Example 2 and Comparative Examples 2 and 4, it can be seen that the nano-refining of large particles by ball milling will lead to a significant reduction in the ionic conductivity of the electrolyte, and by introducing a suitable complexing agent, the particle size of the electrolyte can be nano-refined while the electrolyte can maintain a higher ionic conductivity.

[0079] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing a nano-scale sulfide solid electrolyte, characterized in that: The preparation method comprises the following steps:

1. preparing electrolyte raw materials according to the stoichiometric ratio in the chemical formula of the sulfide solid electrolyte, and adding a mixed solvent to the electrolyte raw materials for ball milling to obtain a precursor solution; 2. drying the precursor solution to obtain a complex electrolyte precursor; 3. Sintering the complex electrolyte precursor to obtain the nanoscale sulfide solid electrolyte; Wherein, the mixed solvent comprises a complexing agent and a first organic solvent, the complexing agent is selected from at least one of bis(2-methoxyethoxy)methane, bis(2-methoxyethoxy)ethane, and triethylene glycol dimethyl ether; the first organic solvent is an alkane organic solvent; In step 1, the electrolyte raw materials are Li2S, P2S5, and LiX. According to the stoichiometric ratio, the ratio of each electrolyte raw material is: Li2S:P2S5:LiX=3:1:1, and X is at least one of Cl, Br, and I; in step 3, the sintering temperature is 100~200°C; and the sintering time is 1~24h.

2. The preparation method according to claim 1, characterized in that: The first organic solvent is selected from at least one of n-heptane, hexane and octane.

3. The preparation method according to claim 1, characterized in that: In the mixed solvent, the mixing volume ratio of the complexing agent to the first organic solvent is 1:99-60:40; or, the mixing volume ratio of the complexing agent to the first organic solvent is 10:90-40:

60.

4. The preparation method according to claim 1, characterized in that: In step 1, the chemical formula of the sulfide solid electrolyte is Li7P2S8X, wherein X is at least one of Cl, Br, and I; and / or, In step 1, the addition ratio of the electrolyte raw material to the mixed solvent is 1-10:10-100 in g / ml.

5. The preparation method according to claim 1, characterized in that: In step 1, the rotation speed of the ball mill is 400-1000 rpm; the time of the ball mill is 20-120 h.

6. The preparation method according to claim 1, characterized in that: In step 2, the drying is vacuum drying; the drying temperature is 50-80° C.; and the drying time is 10-40 hours.

7. The preparation method according to claim 1, characterized in that: In step three, the sintering temperature is 100-170° C. and the sintering time is 1-24 hours.

8. A sulfide solid electrolyte, characterized in that: The sulfide solid electrolyte is prepared by the preparation method according to any one of claims 1 to 7.

9. A battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The electrolyte is selected from the sulfide solid electrolyte as claimed in claim 8.

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