A glassy sulfide argyrodite composite solid-state electrolyte material, and a preparation method and application thereof

Abstract

The application discloses a glassy sulfide argyrodite composite solid electrolyte material and a preparation method and application thereof as an electrolyte of a full solid-state lithium battery. The glassy sulfide solid electrolyte has the characteristics of no grain boundary, high cold-pressing density, good mechanical property and difficulty in forming a complete channel of lithium dendrites in the glassy sulfide solid electrolyte in a cycle process, and the glassy sulfide solid electrolyte is used as a filler to fill the primary cracks in the argyrodite electrolyte layer. The preparation method is that the glassy sulfide solid electrolyte and the argyrodite type crystalline electrolyte are mechanically mixed uniformly, and the obtained glassy sulfide-argyrodite composite solid electrolyte material has excellent mechanical strength, good compatibility to a lithium negative electrode while ensuring ionic conductivity, and effectively inhibits the growth of lithium dendrites in the solid electrolyte layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery solid-state electrolyte materials, and particularly relates to a glassy sulfide-argyrodite composite solid-state electrolyte material and a preparation method and application thereof. BACKGROUND

[0002] All-solid-state lithium metal batteries use solid-state electrolytes to replace the organic electrolyte in traditional secondary lithium ion batteries, fundamentally solving the safety problem plagued by lithium ion batteries. In addition, by matching the lithium metal negative electrode with high theoretical specific capacity (3860 mAh g -1 ) and low reduction potential (-3.04 V vs. standard hydrogen electrode), and the battery pack structure feature based on internal stringing, all-solid-state lithium metal batteries can theoretically break through the energy density limit of existing secondary energy storage devices, and thus meet the endurance requirements of the next generation of electronic devices. At present, the electrolyte of all-solid-state lithium metal batteries includes oxides, sulfides, halides, nitrides, hydrides and polymers. Among them, sulfide solid-state electrolytes are highly concerned by the industry and academia due to their characteristics of ultra-high ionic conductivity (10 -3 ~ 10 -2 S cm -1 ), strong electrode wetting and soft and easy processing. However, the compatibility of metal lithium negative electrode with sulfide solid-state electrolyte is not ideal, and mainly has the following problems: (1) the chemical instability of sulfide solid-state electrolyte to metal lithium negative electrode. The high-valence cations (P 5+ , Ge 4+ , Sn 4+ , etc.) in the sulfide solid-state electrolyte are easily reduced by metal lithium, generating interface by-products with low ionic conductivity, resulting in increased internal resistance of the battery and decreased coulomb efficiency of metal lithium. (2) battery failure caused by lithium dendrite growth. During the deposition of metal lithium, lithium dendrites will grow along the grain boundaries, defects and cracks in the sulfide solid-state electrolyte layer due to the intrinsic electronic conductivity of the sulfide solid-state electrolyte or external pressure, etc. When the growing lithium dendrites form a path in the electrolyte layer, the working voltage of the battery will suddenly drop, and the battery will fail. Therefore, it is of great significance to develop a new type of sulfide solid-state electrolyte with high ionic conductivity and high lithium compatibility for the development and application of all-solid-state lithium metal batteries.

[0003] The system of sulfide solid-state electrolyte covers glassy, glass-ceramic and crystalline three states. Among them, the argyrodite-type electrolyte (Li 6-x PS 5-x Cl 1+x) and metal lithium negative electrode will tend to form a lithium ion-conducting and electron non-conducting solid-state electrolyte layer, which inhibits the continuous side reaction between metal lithium and solid-state electrolyte and enhances the compatibility of solid-state electrolyte and lithium negative electrode. Therefore, sulfide electrolyte with high ionic conductivity and high lithium compatibility is identified as one of the most likely electrolyte systems applied in all-solid-state lithium metal batteries. However, the thermodynamically stable solid-state electrolyte layer formed between metal lithium and sulfide cannot effectively inhibit the growth of lithium dendrites. After the sulfide electrolyte is cold-pressed into a sheet, the primary cracks present on the sheet will expand due to the stress generated by lithium growth during lithium symmetrical battery cycling, and lithium dendrites tend to grow along the expanded cracks, thereby causing battery failure. In addition, the intrinsic electronic conductivity of the solid-state electrolyte and the existing grain boundaries can also induce the growth of lithium dendrites. Therefore, to solve the problem of lithium dendrite growth in sulfide electrolyte, improving its mechanical properties and reducing its electronic conductivity while maintaining its high ionic conductivity is an effective method. SUMMARY

[0004] The purpose of the present application is to provide a glassy sulfide-argyrodite composite solid-state electrolyte and its preparation method and its application in all-solid-state lithium metal batteries. The composite solid-state electrolyte has high ionic conductivity and good negative electrode compatibility. The all-solid-state lithium metal battery assembled with the new composite solid-state electrolyte can operate stably under large current and large capacity working conditions.

[0005] A new glassy sulfide-argyrodite composite solid-state electrolyte material, the chemical composition of which comprises a glassy sulfide solid-state electrolyte and an argyrodite-type crystalline electrolyte.

[0006] Preferably, the glassy sulfide is a Li2S-P2S5 sulfide glassy system and a doped system based on Li2S-P2S5 glassy.

[0007] More preferably, the doping elements include one or more of Al, B, Si, Ge, Sn, In, O, Se, Cl, Br, I, and F.

[0008] More preferably, the chemical composition of the glassy sulfide solid-state electrolyte is 0.70 (0.75Li2S-0.25P2S5)-0.30LiI or 0.60 (0.7857Li2S-0.2143P2S5-0.0714SiS2)-0.40LiI.

[0009] Further preferably, the glassy sulfide-argyrodite composite solid-state electrolyte material is mixed according to the mass ratio of glassy sulfide: argyrodite = 1: x, wherein x = 5-15.

[0010] Further preferably, the argyrodite-type crystalline electrolyte comprises Li 6-y PS 5-y X 1+y , wherein X can be Cl, Br, and y is 0.3-0.6.

[0011] More preferably, the argyrodite-type crystalline electrolyte is Li 5.4 PS 4.4 Cl 1.6 .

[0012] The preparation method of the glassy sulfide-argyrodite composite solid-state electrolyte comprises the following steps:

[0013] (1) The following raw materials are weighed according to a certain mass ratio: Li2S-P2S5-based glassy sulfide and argyrodite-type crystalline electrolyte.

[0014] (2) The weighed raw materials are mechanically ball milled at a certain speed to obtain a uniformly mixed glassy sulfide-argyrodite composite solid-state electrolyte.

[0015] The following are preferred technical solutions of the present application:

[0016] In step (1), the mass ratio of Li2S-P2S5-based glassy sulfide to argyrodite is 1:(5-15);

[0017] In step (2), the speed of mechanical ball milling is 100-300 rpm, and the ball milling time is 30-120 minutes;

[0018] The application of the glassy sulfide-argyrodite composite solid-state electrolyte material in the preparation of a full solid-state lithium battery specifically includes:

[0019] The positive electrode of the full solid-state lithium metal battery is any one of NCM ternary material, lithium cobaltate, and sulfur, and is preferably NCM ternary material; the intermediate layer electrolyte of the full solid-state lithium metal battery is a glassy sulfide-argyrodite composite solid-state electrolyte material; and the negative electrode of the full solid-state lithium metal battery is metal lithium.

[0020] The application utilizes the characteristics of the glassy sulfide solid electrolyte, such as no grain boundary, high cold-pressing density, good mechanical property, and difficulty of lithium dendrite to form complete channels in the glassy sulfide solid electrolyte in the cycle process, fills the primary cracks in the argyrodite electrolyte layer by taking the glassy sulfide solid electrolyte as a filler, and prepares the glassy sulfide-argyrodite composite solid electrolyte by mechanically mixing the glassy sulfide solid electrolyte and the argyrodite-type crystalline electrolyte uniformly.

[0021] Compared with the prior art, the application has the following advantages:

[0022] The glassy sulfide solid electrolyte used has no grain boundary, high cold-pressing density, and good mechanical property, the glassy sulfide solid electrolyte is used as a filler to effectively fill the primary cracks in the argyrodite electrolyte layer, and the mechanical strength of the composite electrolyte is enhanced.

[0023] The introduced glassy sulfide solid electrolyte reduces the conduction of electrons along the grain boundary in the composite electrolyte layer, thereby reducing the intrinsic electronic conductivity of the composite electrolyte.

[0024] The glassy sulfide solid electrolyte and the argyrodite electrolyte have good chemical compatibility, and the composite structure can be effectively maintained in the cycle process.

[0025] The introduction of the glassy electrolyte greatly maintains the original ion conductivity of the argyrodite-type electrolyte, the ion conductivity of the high-performance composite sulfide solid electrolyte constructed by using the glassy sulfide solid electrolyte as a filler of the argyrodite-type electrolyte can be maintained at >5 mS cm -1 , which meets the requirements of industrialization on ion conductivity.

[0026] The prepared glassy sulfide-argyrodite composite solid electrolyte has better ability to inhibit the growth of lithium dendrites, and when it is applied to a full-solid-state lithium metal battery, the risk of short circuit of the battery can be effectively reduced, and the cycle stability of the battery is enhanced.

[0027] The full-solid-state lithium metal battery assembled by using the glassy sulfide-argyrodite composite solid electrolyte in the application has the advantages of large charge-discharge specific capacity and high cycle stability. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a micro-morphology graph of Comparative Example 1.

[0029] Figure 2 It is a micro-morphology graph of Example 4.

[0030] Figure 3 The lithium symmetric battery assembled for Example 4 was tested at 1 mA cm-2 -2 , 3 mA cm-2 -2 of constant current charge-discharge curves. DETAILED DESCRIPTION

[0031] The application will be described in detail below with reference to examples, but the application is not limited to the examples.

[0032] Example 1

[0033] 1 This example provides a novel glassy sulfide-AgGeS2 composite solid electrolyte material, which has a chemical composition comprising a glassy sulfide solid electrolyte and an AgGeS2 crystalline electrolyte. The chemical composition of the glassy sulfide solid electrolyte is 0.70(0.75Li2S-0.25P2S5)-0.30LiI, and the chemical composition of the AgGeS2-type crystalline electrolyte is Li 5.4 PS 4.4 Cl 1.6 .

[0034] 2 In an argon-protected glove box, 0.70(0.75Li2S-0.25P2S5)-0.30LiI and Li 5.4 PS 4.4 Cl 1.6 were weighed in a mass ratio of 1:9, respectively.

[0035] 3 The weighed materials were mixed by mechanical ball milling at a speed of 150 rpm for 25 minutes to obtain a uniformly mixed glassy sulfide-AgGeS2 composite solid electrolyte material.

[0036] 4 The obtained glassy sulfide-AgGeS2 composite solid electrolyte powder was pressed into a wafer by a tablet press at a pressure of 380 MPa, and aluminum foil coated with carbon was fixed on both sides of the wafer to form a sandwich structure. The alternating current impedance spectrum of the wafer was obtained by a Princeton electrochemical workstation, and the ionic conductivity of the wafer was calculated. The thickness of the electrolyte wafer was measured by a screw micrometer, and the actual density of the electrolyte wafer was calculated. The density of the wafer was obtained by comparing the actual density with the theoretical density.

[0037] 5 The obtained glassy sulfide-AgGeS2 composite solid electrolyte powder was pressed into a wafer by a tablet press at a pressure of 380 MPa, and a 0.1 mm thick lithium metal sheet was fixed on both sides of the wafer to form a sandwich structure. The anode stability and lithium dendrite inhibition ability of the obtained composite electrolyte were verified by constant current charge-discharge cycle test and critical current density test.

[0038] 6Mix the commercial NMC811 cathode and the commercial Li6PS5Cl electrolyte uniformly according to a ratio of 7:3 to obtain an NMC811 composite cathode material.

[0039] 7Press the obtained glassy sulfide argyrodite composite solid-state electrolyte powder into a wafer under a pressure of 380 MPa for 5 minutes by a tablet press; disperse 8 mg of the NMC811 composite cathode material on one side of the wafer, apply a pressure of 380 MPa again for 10 minutes by the tablet press; finally, place a metal lithium anode on the other side of the obtained wafer and apply a pressure of 20 MPa for 1 minute to prepare a full-solid-state lithium metal battery. Test the cycle stability and rate performance of the full-solid-state lithium metal battery by constant current charge-discharge cycle test and rate test.

[0040] Example 2

[0041] 1This embodiment provides a novel glassy sulfide-argyrodite composite solid-state electrolyte material, which has a chemical composition comprising a glassy sulfide solid-state electrolyte and an argyrodite-type crystalline electrolyte. The chemical composition of the glassy sulfide solid-state electrolyte is 0.70(0.75Li2S-0.25P2S5)-0.30LiI, and the chemical composition of the argyrodite-type crystalline electrolyte is Li 5.4 PS 4.4 Cl 1.6 .

[0042] 2In an argon-protected glove box, 0.70(0.75Li2S-0.25P2S5)-0.30LiI and Li 5.4 PS 4.4 Cl 1.6 .

[0043] 3Mix the weighed materials by mechanical ball milling at a speed of 150 rpm for 25 minutes to obtain a glassy sulfide-argyrodite composite solid-state electrolyte material.

[0044] 4Press the obtained 150 mg of glassy sulfide-argyrodite composite solid-state electrolyte powder into a wafer under a pressure of 380 MPa by a tablet press, fix carbon-coated aluminum foils on both sides of the wafer to form a sandwich structure, and obtain an alternating current impedance spectrum of the wafer by a Princeton electrochemical workstation to calculate the ionic conductivity of the wafer. Measure the thickness of the electrolyte wafer by a screw micrometer, calculate the actual density of the electrolyte wafer, and compare the actual density with the theoretical density to obtain the relative density of the electrolyte wafer.

[0045] 5The obtained 150 mg glassy sulfide-argyrodite composite solid-state electrolyte powder was pressed into a wafer by a tablet press at a pressure of 380 MPa, 0.1 mm thick lithium metal sheets were fixed on both sides of the wafer, a sandwich structure was prepared, and the obtained composite electrolyte was verified for negative electrode stability and lithium dendrite inhibition ability through constant current charge-discharge cycle test and critical current density test.

[0046] 6Commercial NMC811 cathode, Li 5.4 PS 4.4 Cl 1.6 The electrolyte was mixed uniformly at a ratio of 7:3 to obtain an NMC811 composite cathode material. The obtained glassy sulfide-argyrodite composite solid-state electrolyte powder was pressed into a wafer by a tablet press at a pressure of 380 MPa for 5 minutes; 8 mg of NMC811 composite cathode material was dispersed on one side of the wafer, and the wafer was pressed again by a tablet press at a pressure of 380 MPa for 10 minutes; finally, a lithium metal anode was placed on the other side of the obtained wafer, and a pressure of 20 MPa was applied for 1 minute to press a full solid-state lithium metal battery. The cycle stability and rate performance of the full solid-state lithium metal battery were tested through constant current charge-discharge cycle test and rate test.

[0047] Example 3

[0048] 1This embodiment provides a novel glassy sulfide-argyrodite composite solid-state electrolyte material, which has a chemical composition comprising a glassy sulfide solid-state electrolyte and an argyrodite-type crystalline electrolyte. The chemical composition of the glassy sulfide solid-state electrolyte is 0.60 (0.7857Li2S-0.2143P2S5-0.0714SiS2)-0.40LiI, and the chemical composition of the argyrodite-type crystalline electrolyte is Li 5.4 PS 4.4 Cl 1.6 .

[0049] 2In an argon-protected glove box, 0.60 (0.7857Li2S-0.2143P2S5-0.0714SiS2)-0.40LiI and Li 5.4 PS 4.4 Cl 1.6 .

[0050] 3The weighed materials were mixed by mechanical ball milling at a speed of 100 rpm for 60 minutes to obtain a uniformly mixed glassy sulfide-argyrodite composite solid-state electrolyte material.

[0051] 4 The obtained 150 mg glassy sulfide-argyrodite composite solid-state electrolyte powder was pressed into a wafer by a tablet press at a pressure of 500 MPa, and carbon-coated aluminum foil was fixed on both sides of the wafer to form a sandwich structure. The alternating current impedance spectrum of the wafer was obtained by a Princeton electrochemical workstation, and the ionic conductivity of the wafer was calculated. The thickness of the electrolyte wafer was measured by a screw micrometer, and the actual density of the electrolyte wafer was calculated. The density of the electrolyte wafer was compared with the theoretical density to obtain the relative density.

[0052] 5 The obtained 150 mg glassy sulfide-argyrodite composite solid-state electrolyte powder was pressed into a wafer by a tablet press at a pressure of 500 MPa, and 0.1 mm thick lithium metal sheets were fixed on both sides of the wafer to form a sandwich structure. The obtained composite electrolyte was verified for negative electrode stability and lithium dendrite inhibition ability by constant current charge-discharge cycle test and critical current density test.

[0053] 6 Commercial NMC811 positive electrode, Li 5.4 PS 4.4 Cl 1.6 The electrolyte was mixed uniformly at a ratio of 7:3 to obtain an NMC811 composite positive electrode material.

[0054] 7 The obtained 80 mg glassy sulfide-argyrodite composite solid-state electrolyte powder was pressed into a wafer by a tablet press at a pressure of 380 MPa for 5 minutes. 8 mg of NMC811 composite positive electrode material was dispersed on one side of the wafer, and the wafer was pressed again by a tablet press at a pressure of 380 MPa for 10 minutes. Finally, a lithium metal negative electrode was placed on the other side of the wafer, and a pressure of 20 MPa was applied for 1 minute to form a full solid-state lithium metal battery. The cycle stability and rate performance of the full solid-state lithium metal battery were tested by constant current charge-discharge cycle test and rate test.

[0055] Example 4

[0056] 1 This example provides a novel glassy sulfide-argyrodite composite solid-state electrolyte material, which has a chemical composition comprising a glassy sulfide solid-state electrolyte and an argyrodite type crystalline electrolyte. The chemical composition of the glassy sulfide solid-state electrolyte is 0.60 (0.7857 Li2S-0.2143 P2S5-0.0714 SiS2)-0.40 LiI, and the chemical composition of the argyrodite type crystalline electrolyte is Li 5.4 PS 4.4 Cl 1.6 .

[0057] 2 In an argon-protected glove box, 0.60 (0.7857 Li2S-0.2143 P2S5-0.0714 SiS2)-0.40 LiI and Li6PS5Cl were weighed at a mass ratio of 1:7, respectively.

[0058] 3. The weighed materials were mixed by mechanical ball milling at 100 rpm for 60 minutes to obtain a uniformly mixed glassy sulfide-silver germanium ore composite solid electrolyte material.

[0059] 4. Using a tablet press, 150 mg of the obtained glassy sulfide-germanium sulfide composite solid electrolyte powder was formed into thin sheets under a pressure of 380 MPa. Carbon-coated aluminum foil was fixed to both sides of the sheets to create a sandwich structure. The AC impedance spectrum was obtained using a Princeton electrochemical workstation, and its ionic conductivity was calculated. The thickness of the electrolyte sheet was measured using a micrometer, and the actual density of the electrolyte sheet was calculated and compared with its theoretical density to obtain its packing density. The microstructure of the cold-pressed sheets was observed using a scanning electron microscope. Figure 1 )

[0060] 5. Using a tablet press, the obtained 150mg vitreous tablets were...

[0061] The sulfide-silver germanium sulfide composite solid electrolyte powder was pressed into thin sheets under a pressure of 380 MPa. 0.1 mm thick lithium metal sheets were fixed on both sides of the sheet to create a sandwich structure. The negative electrode stability and lithium dendrite suppression capability of the obtained composite electrolyte were verified through constant current charge-discharge cycle testing and critical current density testing. Its performance at 1 mA / cm²... 2 The current density is 3 mA / cm². 2 It can operate stably for over 900 hours at the cutoff capacity. Figure 3 )

[0062] 6. Commercial NMC811 cathode and Li 5.4 PS 4.4 Cl 1.6 The electrolytes were mixed evenly in a 7:3 ratio to obtain the NMC811 composite cathode material.

[0063] 7. Using a tablet press, 80 mg of the obtained glassy sulfide-germanium sulfide composite solid electrolyte powder was pressed into a thin sheet under a pressure of 380 MPa for 5 minutes. 8 mg of NMC811 composite cathode material was dispersed on one side of the sheet, and the sheet was pressed again under a pressure of 380 MPa for 10 minutes. Finally, a lithium metal anode was placed on the other side of the sheet and pressed under a pressure of 20 MPa for 1 minute to prepare an all-solid-state lithium metal battery. The cycle stability and rate performance of the all-solid-state lithium metal battery were tested through constant current charge-discharge cycle testing and rate testing.

[0064] The above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the spirit of the present application shall also fall within the scope of the present application.

[0065] Comparative Example

[0066] The classical argyrodite type crystalline electrolyte has a chemical composition of Li 5.4 PS 4.4 Cl 1.6 The rest is the same as Example 4. The micro-morphology of the cold-pressed sheet is shown in the scanning electron microscope as Figure 3 .

[0067] Performance Test

[0068] Table 1: Statistics of ion conductivity, electronic conductivity and density of the obtained solid-state electrolyte

[0069]

[0070] Table 2: Statistics of critical current density of the obtained solid-state electrolyte

[0071]

[0072] Table 3: Statistics of cycle performance of the full solid-state lithium metal battery assembled by the obtained solid-state electrolyte

[0073]

[0074] From the performance test results, compared with the original comparative example, the introduction of glassy sulfide solid-state electrolyte in the examples slightly reduces the ion conductivity, but still maintains above the commercial requirement of 5 mS / cm. At the same time, the introduction of low electronic conductivity, no grain boundary and high density glassy sulfide solid-state electrolyte greatly reduces the electronic conductivity of the composite solid-state electrolyte and greatly improves the density of the composite solid-state electrolyte. Therefore, Examples 1-4 all show different degrees of improvement in the critical current density of the symmetric battery and the cycle performance of the full solid-state lithium metal battery, among which Example 4 shows an ultra-high critical current density value (2.9 mA / cm 2 ). As shown in the scanning electron microscope images of the comparative example and Example 4 ( Figures 2-3 ), the introduction of glassy sulfide solid-state electrolyte in the examples greatly reduces the original cracks in the argyrodite type electrolyte, improving the density and flatness of the cold-pressed sheet. In particular, the symmetric battery assembled by the electrolyte prepared in Example 4 can be stably operated for more than 900 h under the current density and capacity cut-off that meet the actual battery operating conditions.

Claims

1. A glassy sulfide-germanium sulfide composite solid electrolyte material, characterized in that, It consists of a glassy sulfide solid electrolyte and a silver-germanium sulfide crystalline electrolyte; The chemical composition of the glassy sulfide solid electrolyte is 0.70(0.75Li2S-0.25P2S5)-0.30LiI or 0.60(0.7857Li2S-0.2143P2S5-0.0714SiS2)-0.40LiI; The glassy sulfide solid electrolyte and the silver sulfide-germanium ore-type crystalline electrolyte are mechanically ball-milled at a mass ratio of 1:x, where x = 5~15. The basic structural formula of the sulfide-germanium ore-type crystalline electrolyte is Li 6-y PS 5-y X 1+y Where X is Cl or Br, and y is 0 ~ 0.

6.

2. The preparation method of the glassy sulfide-germanium sulfide composite solid electrolyte material according to claim 1, characterized in that, Includes the following steps: Weigh the glassy sulfide solid electrolyte and the silver-germanium sulfide crystalline electrolyte according to their mass ratio; The weighed raw materials were mechanically ball-milled and mixed evenly to obtain a glassy sulfide-silver germanium ore composite solid electrolyte material.

3. The preparation method of the glassy sulfide-silver germanite composite solid electrolyte material according to claim 2, characterized in that, In step (2), the rotation speed of the mechanical ball mill is 100~500 rpm, and the mechanical ball milling time is 5~300 minutes.

4. The application of the glassy sulfide-silver germanite composite solid electrolyte material according to claim 1 in the preparation of all-solid-state lithium batteries.

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