Modified sulfide solid electrolyte as well as preparation method and application thereof

Abstract

The invention provides a modified sulfide solid electrolyte as well as a preparation method and application thereof. The modified sulfide solid electrolyte comprises a polyphosphazene coated sulfide solid electrolyte and a functional auxiliary agent formed on the polyphosphazene coated sulfide solid electrolyte. Wherein the functional auxiliary agent comprises a sulfydryl compound and / or an alcoholic hydroxyl compound. According to the invention, polyphosphazene is adopted to coat the sulfide solid-state electrolyte, the functional auxiliary agent is further introduced, and the sulfydryl compound and / or the alcoholic hydroxyl compound are / is crosslinked with polyphosphazene, so that the stability of the sulfide solid-state electrolyte to a lithium metal negative electrode can be enhanced, and the overall performance of the solid-state battery is further improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state batteries, and particularly relates to a modified sulfide solid-state electrolyte and a preparation method and application thereof. BACKGROUND

[0002] As the next generation of energy storage technology, all-solid-state lithium metal batteries are expected to solve the safety problem of commercial lithium-ion batteries and further improve the energy density thereof. As the core material of all-solid-state lithium metal batteries, a solid-state electrolyte not only needs to achieve excellent electrochemical properties, but also needs to have certain interface stability with a lithium metal negative electrode.

[0003] At present, sulfide solid-state electrolytes are considered as solid-state electrolyte materials with great potential due to their ultra-high lithium ion conductivity and low-temperature processability. However, it is found in actual research that when the sulfide solid-state electrolyte contacts with a lithium metal negative electrode, continuous interface side reactions occur, causing interface contact failure, triggering rapid growth of lithium dendrites and finally leading to a battery short circuit problem. Researchers use electrolyte doping or pressure regulation and other means, but only partial problems can be alleviated, and the interface stability problem cannot be fundamentally solved. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a modified sulfide solid-state electrolyte and a preparation method and application thereof. The modified sulfide solid-state electrolyte has good interface stability with lithium metal, so as to realize long cycle performance of a low-pressure sulfide-based solid-state lithium metal battery.

[0005] To achieve this purpose, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a modified sulfide solid-state electrolyte, comprising a polysiloxane-coated sulfide solid-state electrolyte and a functional additive formed on the polysiloxane-coated sulfide solid-state electrolyte.

[0007] The functional additive comprises a mercapto compound and / or an alcohol hydroxyl compound.

[0008] Preferably, the mass ratio of the sulfide solid-state electrolyte, polysiloxane and functional additive is 1g:(1-800)mg:(1-500)mg.

[0009] Preferably, the molecular weight M of the polysiloxane is 200-100000. w In 200-100000.

[0010] Preferably, the thiol-based compound is selected from any one or more of 2,3-dimercaptosulfonic acid sodium, thiol-PEG thiol, 1,6-hexanedithiol, 1,8-octanedithiol, 3,6-dioxa-1,8-octanedithiol, 1,4-butanediol bis(thioglycolate), or pentaerythritol tetrakis(3-mercaptopropionate).

[0011] Preferably, the alcohol hydroxyl-based compound is any one or more of BES sodium salt, 2,2,3,3-tetrafluoro-1,4-butanediol, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol, or hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol.

[0012] Preferably, the sulfide solid-state electrolyte is selected from any one or more of argyrodite-type sulfide solid-state electrolyte, glass-ceramic sulfide electrolyte, or glassy sulfide electrolyte.

[0013] Preferably, the argyrodite-type sulfide solid-state electrolyte comprises Li6PS5X, Li 11-n M 2-n P 1+n S 12 or Thio-LISICONs-type sulfide solid-state electrolyte; wherein X is selected from Cl, Br, or I, M is selected from Ge, Sn, or Si, and n = 0.2-0.8.

[0014] Preferably, the sulfide solid-state electrolyte is selected from Li6PS5Cl, Li7P3S 11 or Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 .

[0015] In a second aspect, the present application provides a preparation method of the modified sulfide solid-state electrolyte, comprising the following steps:

[0016] S1: providing a polyphosphazene-coated sulfide solid-state electrolyte;

[0017] S2: mixing the polyphosphazene-coated sulfide solid-state electrolyte with a functional additive, grinding, and then heating to obtain a modified sulfide solid-state electrolyte.

[0018] Preferably, the grinding time is 0.2-1.0 h.

[0019] Preferably, the heating temperature is 100-200 °C, and the heating time is 0.1-20 h.

[0020] Preferably, the mass ratio of the sulfide solid-state electrolyte to the functional additive is 1 g:(1-1000) mg.

[0021] Preferably, the polysiloxane-coated sulfide solid-state electrolyte is prepared by the following method:

[0022] The polysiloxane-coated sulfide solid-state electrolyte is obtained by mixing the phosphazene monomer with the sulfide solid-state electrolyte, grinding, and vacuum heating.

[0023] Preferably, the mass ratio of the sulfide solid-state electrolyte to the phosphazene monomer is 1g:(1-1000)mg.

[0024] Preferably, the phosphazene monomer is selected from any one or more of hexachlorotriphosphazene, phenoxy cyclotriphosphazene, or ethoxy (pentafluoro) cyclotriphosphazene.

[0025] Preferably, in the preparation of the polysiloxane-coated sulfide solid-state electrolyte, the grinding time is 0.3-2h.

[0026] Preferably, the vacuum heating temperature is 100-300℃, and the time is 0.5-48h.

[0027] In a third aspect, the present application provides a full solid-state lithium metal battery, comprising a positive electrode, a lithium metal negative electrode, and an electrolyte.

[0028] The electrolyte is the modified sulfide solid-state electrolyte as described in the above technical solution; the active material of the positive electrode is selected from NCM ternary positive electrode material, lithium iron phosphate positive electrode material, or lithium manganate positive electrode material.

[0029] Preferably, the full solid-state lithium metal battery has a charge-discharge voltage of 3.0-4.3V.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] The present application provides a modified sulfide solid-state electrolyte, which comprises a polysiloxane-coated sulfide solid-state electrolyte and a functional additive formed on the polysiloxane-coated sulfide solid-state electrolyte. The functional additive comprises a mercapto compound and / or an alcohol hydroxyl compound. By using the polysiloxane-coated sulfide solid-state electrolyte, the present application can physically isolate the direct contact between lithium metal and the sulfide electrolyte, and at the same time form an electron insulating layer, such as lithium phosphide and lithium nitride. By further introducing the functional additive, the mercapto compound and / or the alcohol hydroxyl compound are crosslinked with the polysiloxane, which can improve the mechanical properties of the sulfide electrolyte.

[0032] The preparation method of the modified sulfide solid-state electrolyte provided by the present application has wide applicability and can be effectively applied to various sulfide solid-state electrolytes, further improving the overall performance of the solid-state battery. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 High resolution transmission electron micrograph of polydichlorophosphazene-coated sulfide solid state electrolyte powder A4 obtained in Example 4;

[0034] Figure 2 Infrared spectrum of surface-crosslinked Li6PS5Cl sulfide solid state electrolyte powder S4 obtained in Example 4;

[0035] Figure 3 Infrared spectrum of surface-crosslinked Li6PS5Cl sulfide solid state electrolyte powder S4 obtained in Example 4;

[0036] Figure 4 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G1-1;

[0037] Figure 5 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G1-1;

[0038] Figure 6 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G2-1;

[0039] Figure 7 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G2-1;

[0040] Figure 8 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G3-1;

[0041] Figure 9 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G3-1;

[0042] Figure 10 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G4-1;

[0043] Figure 11 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G4-1;

[0044] Figure 12 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G5-1;

[0045] Figure 13 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G6-1;

[0046] Figure 14 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G7-1;

[0047] Figure 15 Electrochemical impedance spectrogram of sulfide solid state electrolyte pellet G8-1;

[0048] Figure 16 Electrochemical impedance spectrogram of sulfide solid electrolyte sheet D-G1;

[0049] Figure 17 Electrochemical test result graph of full solid-state lithium metal battery C1;

[0050] Figure 18 Electrochemical test result graph of full solid-state lithium metal battery C2;

[0051] Figure 19 Electrochemical test result graph of full solid-state lithium metal battery C3. DETAILED DESCRIPTION

[0052] The technical solutions of the present application will be described in detail below in combination with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0053] In the prior art, the high activity of PS4 in sulfide solid electrolyte 3- The group is prone to irreversible reduction reaction with lithium metal, resulting in exponential growth of interface impedance. At the same time, the sulfide solid electrolyte formed by cold pressing has low density, which is difficult to inhibit the vertical growth of lithium dendrites. The volume expansion caused by repeated stripping / deposition of lithium metal in electrochemical cycling further aggravates the interface contact failure, eventually leading to battery short circuit or capacity decay, making it difficult for the sulfide-based full solid-state lithium battery to meet the commercialization needs in cycle life and safety.

[0054] In order to solve the above-mentioned difficulties, the present application modifies the surface of the sulfide solid electrolyte itself, which not only isolates it from the contact with the lithium metal anode, but also contains the mercapto (and / or alcohol hydroxyl) compound rich in nitrogen, phosphorus, oxygen and other elements, which can form interface components such as stable lithium nitride, lithium phosphide and lithium oxide during electrochemical cycling. These components form an electron insulating layer together, which inhibits the growth of lithium dendrites. At the same time, the cross-linking effect of the functional additives can improve the mechanical properties of the sulfide electrolyte and improve the interface contact with lithium metal, thereby improving the stability of the sulfide solid electrolyte to the lithium metal anode.

[0055] Specifically, the present application provides a modified sulfide solid-state electrolyte, comprising a polyphosphazene-coated sulfide solid-state electrolyte and a functional additive formed on the polyphosphazene-coated sulfide solid-state electrolyte. Wherein, the functional additive comprises a mercapto compound and / or an alcohol hydroxyl compound. In the present application, the mass ratio of the sulfide solid-state electrolyte, the polyphosphazene and the functional additive is 1g:(1-800)mg:(1-500)mg, preferably 1g:(1-600)mg:(1-350)mg, more preferably 1g:(1-400)mg:(1-200)mg.

[0056] In the present application, the polyphosphazene is generated after ring-opening polymerization of a phosphazene monomer selected from any one or more of hexachlorotriphosphazene, phenoxycyclophosphazene or ethoxyl(pentafluoro)cyclo-triphosphazene, preferably hexachlorotriphosphazene. The molecular weight of the polyphosphazene is 200-100000.

[0057] In the present application, the sulfide solid-state electrolyte is selected from any one or more of Argyrodites-type sulfide solid-state electrolyte, glass-ceramic sulfide electrolyte or glassy sulfide electrolyte; the Argyrodites-type sulfide solid-state electrolyte comprises Li6PS5X, Li 11-n M 2-n P 1+n S 12 (LGPS) or Thio-LISICONs-type sulfide solid-state electrolyte; wherein X is selected from Cl, Br or I, M is selected from Ge, Sn or Si, and n=0.2-0.8.

[0058] In some embodiments of the present application, the sulfide solid-state electrolyte is selected from Li6PS5Cl, Li7P3S 11 or Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 .

[0059] In the present application, the mercapto compound each contains 2 mercapto groups, and can be selected from any one or more of 2,3-dimercaptopropanesulfonic acid sodium, mercapto PEG mercapto, 1,6-hexanedithiol, 1,8-octanedithiol, 3,6-dioxa-1,8-octanedithiol, 1,4-butanediol bis(mercaptoacetate) or tetra(3-mercaptopropionic acid) pentaerythritol ester, preferably one or several of 2,3-dimercaptopropanesulfonic acid sodium, 1,6-hexanedithiol and 1,8-octanedithiol.

[0060] In the present application, any one or more of the alcohol hydroxyl compound BES sodium salt, 2,2,3,3-tetrafluoro-1,4-butanediol, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol or hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol.

[0061] The present application also provides a preparation method of the modified sulfide solid electrolyte, comprising the following steps:

[0062] S1: providing a polysiloxane-coated sulfide solid electrolyte;

[0063] S2: mixing the polysiloxane-coated sulfide solid electrolyte with a functional additive, grinding and then heating to obtain a modified sulfide solid electrolyte.

[0064] According to the present application, a polysiloxane-coated sulfide solid electrolyte is first provided.

[0065] In the present application, the sulfide solid electrolyte preferably includes a pretreatment before surface modification. The specific pretreatment process includes: after simple grinding of the sulfide solid electrolyte powder, placing it in a muffle furnace at 100-250°C for 1-24h of drying treatment to ensure removal of all trace amounts of moisture.

[0066] In the present application, the polysiloxane-coated sulfide solid electrolyte is prepared according to the following method:

[0067] The polysiloxane-coated sulfide solid electrolyte is obtained after mixing the phosphazene monomer with the sulfide solid electrolyte, grinding and vacuum heating.

[0068] Preferably, the sulfide solid electrolyte and the phosphazene monomer are mixed in a mass ratio of 1g:(1-1000)mg, preferably 1g:(1-500)mg, and more preferably 1g:(1-200)mg. The mixing is preferably carried out under manual grinding conditions, and the grinding time is 0.3-2h, such as 0.3h, 0.6h, 1h or 2h, etc. The vacuum heating is preferably carried out in a muffle furnace at a temperature of 100-300°C, such as 100°C, 200°C or 300°C, etc.; and the time is 0.5-48h, such as 0.5h, 1h, 16h, 32h or 48h, etc.

[0069] In some embodiments of the present application, the phosphazene monomer is added to the sulfide solid electrolyte powder under the protection of an inert atmosphere, and after grinding and vacuum heating, the phosphazene monomer undergoes ring-opening polymerization to generate polysiloxane, which coats the surface of the sulfide solid electrolyte to obtain a polysiloxane-coated sulfide solid electrolyte powder.

[0070] After obtaining the polysilphosphazene-coated sulfide solid-state electrolyte, according to the present application, the polysilphosphazene-coated sulfide solid-state electrolyte is mixed with a functional additive in a mass ratio of 1g:(1-1000)mg, preferably 1g:(1-500)mg, and more preferably 1g:(1-100)mg, and after grinding, heating is performed to obtain a modified sulfide solid-state electrolyte. The grinding time is 0.2-1.0h, such as 0.2h, 0.3h, 0.5h or 1h, etc.; the heating is preferably performed in a muffle furnace, the heating temperature is 100-200℃, such as 100℃, 150℃ or 200℃, etc., and the heating time is 0.1-20h, such as 0.1h, 1h, 10h or 20h, etc.

[0071] In some embodiments of the present application, the functional additive is preferably added to the polysilphosphazene-coated sulfide solid-state electrolyte powder, and after manual grinding and heating treatment, a polysilphosphazene-coated and functional additive-crosslinked sulfide solid-state electrolyte powder material is obtained.

[0072] In the present application, the above grinding and heating are preferably performed under the protection of an inert atmosphere, such as high-purity argon (argon purity ≥ 99.999%), to prevent chemical side reactions such as hydrolysis of the sulfide solid-state electrolyte powder.

[0073] The above preparation method provided by the present application uses a grinding and heating method to realize a polysilphosphazene-coated and mercapto compound or alcohol hydroxyl compound crosslinked sulfide solid-state electrolyte powder, which is simple, inexpensive, reduces production energy consumption, and improves the interface stability of lithium metal and the sulfide solid-state electrolyte. In addition, appropriate extension of the grinding and heating time not only ensures uniform dispersion of the phosphazene monomer in the sulfide solid-state electrolyte powder, but also allows the phosphazene monomer to undergo ring-opening polymerization to form polysilphosphazene and uniformly coat the surface of the sulfide solid-state electrolyte powder. Secondly, the mercapto compound or alcohol hydroxyl compound can also be uniformly dispersed between the polysilphosphazene-coated sulfide solid-state electrolyte powder particles and crosslinked, and the structure of the sulfide electrolyte is prevented from being damaged due to uneven grinding or excessively high temperature.

[0074] It should be noted that the phosphazene monomer and the polysilphosphazene produced by ring-opening polymerization, the mercapto compound or alcohol hydroxyl compound, and the sulfide solid-state electrolyte do not undergo significant chemical reactions, ensuring that when used as a surface modification layer material, they do not have a serious adverse impact on the ion conduction of the sulfide solid-state electrolyte. Secondly, due to the presence of nitrogen, phosphorus, oxygen and other elements, lithium nitride, lithium phosphide, lithium oxide and other interface components that are beneficial to the interface are formed during the electrochemical cycle process. This interface component forms an electron insulating layer, inhibiting the conduction of electrons. At the same time, the crosslinking of the mercapto compound or alcohol hydroxyl compound improves the mechanical properties of the sulfide electrolyte, enhances the interface contact with lithium metal, and ultimately enhances the stability of the sulfide solid-state electrolyte to lithium metal.

[0075] In summary, the application uses the polyphosphazene formed after ring-opening polymerization and the thiol-based compound (and / or alcohol hydroxyl-based compound) to form a coating layer for surface modification of the sulfide solid electrolyte powder, wherein the cross-linking effect of the polyphosphazene coating layer formed after ring-opening polymerization of the phosphazene monomer and the thiol-based (and / or alcohol hydroxyl-based compound) functional additive can isolate the direct contact between the sulfide solid electrolyte and the lithium metal negative electrode material, effectively inhibit the occurrence of interface side reactions, and improve the mechanical properties of the sulfide solid electrolyte.

[0076] Based on the advantages of the sulfide solid electrolyte, the application also provides a full-solid-state lithium metal battery, which comprises a positive electrode, a lithium metal negative electrode and the modified sulfide solid electrolyte described above.

[0077] The active material of the positive electrode is selected from one or more of NCM ternary positive electrode material, lithium iron phosphate positive electrode material and lithium manganate positive electrode material.

[0078] In some embodiments of the application, the full-solid-state lithium metal battery has a charge-discharge voltage of 3.0-4.3V and a charge-discharge current density of 0.2-0.4mA cm -2

[0079] Through research, it is found that the full-solid-state lithium metal battery prepared based on the sulfide solid electrolyte powder material coated with polyphosphazene formed after ring-opening polymerization of phosphazene monomers and cross-linked with thiol-based compounds (and / or alcohol hydroxyl-based compounds) can realize stable cycling under low external pressure and improve the stability to the lithium metal negative electrode.

[0080] In order to further illustrate the application, the following examples are used for detailed description. Lithium phosphorus sulfide chloride (Li6PS5Cl, Wuhan Tianshi Kefeng New Energy Technology Co., Ltd.) is used in the following examples of the application. Hexachlorotriphosphazene (Shanghai Aladdin Biochemical Technology Co., Ltd.), sodium 2,3-dimercaptosulfonate (Shanghai Aladdin Biochemical Technology Co., Ltd.), 1,6-hexanedithiol (Shanghai Aladdin Biochemical Technology Co., Ltd.), 1,8-octanedithiol (Shanghai Aladdin Biochemical Technology Co., Ltd.), 2,2,3,3-tetrafluoro-1,4-butanediol (Shanghai Aladdin Biochemical Technology Co., Ltd.), and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (Shanghai Aladdin Biochemical Technology Co., Ltd.) are used in the following examples.

[0081] The following examples use the following instruments and equipment: KSL-1100X muffle furnace from Hefei Kejing Material Technology Co., Ltd., DHG-9030A electric heating air drying oven from Shanghai Jinghong Experimental Equipment Co., Ltd., and natural agate mortar (MNYB-Φ80mm) from Shanghai Xinuo Instrument Group Co., Ltd.

[0082] The instrument and equipment used in the sulfide solid electrolyte ion conductivity test and the assembly of the all-solid-state lithium metal battery include: MJP-Y general cylindrical mold (Φ10 mm) from Shanghai Xinuo Instrument and Equipment Co., Ltd., YLJ-15T-LD manual tablet press from Hefei Kejing Material Technology Co., Ltd., MSK-SFM-12M micro-vibration mixer from Hefei Kejing Material Technology Co., Ltd., SD-900M magnetron sputtering instrument from Beijing Boyuan Micro-Nano Technology Co., Ltd., DH7001D electrochemical workstation from Jiangsu Donghua Analysis Instrument Co., Ltd., and CT-4008T-5V 20mA-164 battery detection system from Shenzhen Xinnier Electronics Co., Ltd. Among them, the assembly process of the all-solid-state lithium metal battery is carried out in a dry high-purity argon glove box (the purity of argon is ≥99.999%), and the content of oxygen and water is below 0.1 ppm.

[0083] Example 1

[0084] In this example, the phosphazene monomer (hexachlorotriphosphazene) is used for ring-opening polymerization to generate polyphosphazene (polydichlorophosphazene), and the sulfide solid electrolyte powder (Li6PS5Cl) is surface modified by using a thiol or hydroxyl compound (sodium 2,3-dimercaptosulfonate). The specific method is as follows:

[0085] In a dry argon-filled glove box, 1 g of Li6PS5Cl powder and 10 mg of hexachlorotriphosphazene were weighed in a agate mortar (MNYB-Φ80 mm), mixed uniformly, and then manually ground for 0.4 h. The mixture was placed in a 100°C electric heating air drying oven (DHG-9030A) for heating for 10 h, and then placed in a 250°C muffle furnace (KSL-1100X) for vacuum heating for 36 h to obtain polydichlorophosphazene-coated sulfide solid electrolyte powder A1. After adding 5 mg of sodium 2,3-dimercaptosulfonate, the mixture was manually ground for 0.3 h, and then placed in a 180°C electric heating air drying oven (DHG-9030A) for heating for 12 h to obtain the surface-modified Li6PS5Cl sulfide solid electrolyte powder S1. The powder was stored in a dry argon-filled glove box.

[0086] In a dry, argon-filled glove box, the sulfide solid electrolyte powder A1 prepared in Example 1 was added to an MJP-Y type ordinary cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300 to 360 MPa to the mold. The mold was cold-pressed for 3 to 5 minutes and then withdrawn to obtain a sulfide solid electrolyte sheet G1 with a diameter of 10 mm. Then, the sulfide solid electrolyte powder S1 prepared in Example 1 was added to an MJP-Y type ordinary cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300 to 360 MPa to the mold. The mold was cold-pressed for 3 to 5 minutes and then withdrawn to obtain a sulfide solid electrolyte sheet G1-1 with a diameter of 10 mm.

[0087] Example 2

[0088] In a dry, argon-filled glove box, 1 g of Li6PS5Cl powder and 25 mg of hexachlorotriphosphazene monomer were weighed into an agate mortar (MNYB-Φ80 mm). The mixture was then manually ground for 0.4 h, heated in a 100°C electric forced-air drying oven (DHG-9030A) for 10 h, and then heated in a muffle furnace (KSL-1100X) at 250°C under vacuum for 36 h to obtain polydichlorophosphazene-coated sulfide solid electrolyte powder A2. 25 mg of sodium 2,3-dimercaptopropanesulfonate was then added, followed by manual grinding for 0.3 h and heating in a 180°C electric forced-air drying oven (DHG-9030A) for 12 h. This yielded surface-modified Li6PS5Cl sulfide solid electrolyte powder S2, which was then stored in a dry, argon-filled glove box.

[0089] In a dry, argon-filled glove box, the sulfide solid electrolyte powder A2 prepared in Example 2 was added to an MJP-Y type ordinary cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300 to 360 MPa to the mold. The mold was cold pressed for 3 to 5 minutes and then withdrawn to obtain a sulfide solid electrolyte sheet G2 with a diameter of 10 mm. Then, the sulfide solid electrolyte powder S2 prepared in Example 2 was added to an MJP-Y type ordinary cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300 to 360 MPa to the mold. The mold was cold pressed for 3 to 5 minutes and then withdrawn to obtain a sulfide solid electrolyte sheet G2-1 with a diameter of 10 mm.

[0090] Example 3

[0091] In a dry argon-filled glove box, 1 g of Li6PS5Cl powder and 50 mg of hexachlorotriphosphazene monomer were weighed into a corundum mortar (MNYB-Φ80 mm), mixed uniformly, and then manually ground for 0.4 h. The mixture was heated in a 100 °C electric heating drying oven (DHG-9030A) for 10 h, and then heated in a 250 °C muffle furnace (KSL-1100X) under vacuum for 36 h to obtain polydichlorophosphazene-coated sulfide solid electrolyte powder A3. After adding 30 mg of sodium 2,3-dimercaptopropanesulfonate, the mixture was manually ground for 0.3 h, and then heated in a 180 °C electric heating drying oven (DHG-9030A) for 12 h. Thus, surface-modified Li6PS5Cl sulfide solid electrolyte powder S3 was obtained, and was stored in a dry argon-filled glove box.

[0092] In a dry argon-filled glove box, the sulfide solid electrolyte powder A3 prepared in Example 3 was added to a MJP-Y general cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold. After cold pressing for 3-5 min, the mold was removed to obtain a sulfide solid electrolyte tablet G3 with a diameter of 10 mm. Then, the sulfide solid electrolyte powder S3 prepared in Example 3 was added to a MJP-Y general cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold. After cold pressing for 3-5 min, the mold was removed to obtain a sulfide solid electrolyte tablet G3-1 with a diameter of 10 mm.

[0093] Example 4

[0094] In a dry argon-filled glove box, 1 g of Li6PS5Cl powder and 100 mg of hexachlorotriphosphazene monomer were weighed into a corundum mortar (MNYB-Φ80 mm), mixed uniformly, and then manually ground for 0.4 h. The mixture was heated in a 100 °C electric heating drying oven (DHG-9030A) for 10 h, and then heated in a 250 °C muffle furnace (KSL-1100X) under vacuum for 36 h to obtain polydichlorophosphazene-coated sulfide solid electrolyte powder A4. After adding 60 mg of sodium 2,3-dimercaptopropanesulfonate, the mixture was manually ground for 0.3 h, and then heated in a 180 °C electric heating drying oven (DHG-9030A) for 12 h. Thus, surface-modified Li6PS5Cl sulfide solid electrolyte powder S4 was obtained, and was stored in a dry argon-filled glove box.

[0095] In a dry argon-filled glove box, the sulfide solid-state electrolyte powder A4 prepared in Example 4 was added to a MJP-Y type general cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold, and the cold pressure was kept for 3-5 min before the mold was removed, to obtain a sulfide solid-state electrolyte tablet G4 with a diameter of 10 mm. Then, the sulfide solid-state electrolyte powder S4 prepared in Example 4 was added to a MJP-Y type general cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold, and the cold pressure was kept for 3-5 min before the mold was removed, to obtain a sulfide solid-state electrolyte tablet G4-1 with a diameter of 10 mm.

[0096] Example 5

[0097] In a dry argon-filled glove box, 1 g of Li6PS5Cl powder and 50 mg of hexachlorotriphosphazene monomer were weighed into a agate mortar (MNYB-Φ80 mm), mixed uniformly and then manually ground for 0.4 h, placed in a electric heating drying oven (DHG-9030A) at 100°C for heating for 10 h, and then placed in a muffle furnace (KSL-1100X) at 250°C for vacuum heating for 36 h, to obtain a polydichlorophosphazene-coated sulfide solid-state electrolyte powder A5. After adding 30 mg of 1,6-hexanedithiol, manual grinding was performed for 0.3 h, and then placed in an electric heating drying oven (DHG-9030A) at 180°C for heating for 12 h. The surface-modified Li6PS5Cl sulfide solid-state electrolyte powder S5 was obtained, and stored in a dry argon-filled glove box.

[0098] In a dry argon-filled glove box, the sulfide solid-state electrolyte powder S5 prepared in Example 5 was added to a MJP-Y type general cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold, and the cold pressure was kept for 3-5 min before the mold was removed, to obtain a sulfide solid-state electrolyte tablet G5-1 with a diameter of 10 mm.

[0099] Example 6

[0100] In a dry argon-filled glove box, 1 g of Li6PS5Cl powder and 50 mg of hexachlorotriphosphazene monomer were weighed into a corundum mortar (MNYB-Φ80 mm), mixed uniformly, and then manually ground for 0.4 h. The mixture was heated in a 100 °C electric heating drying oven (DHG-9030A) for 10 h, and then heated in a 250 °C muffle furnace (KSL-1100X) under vacuum for 36 h to obtain polydichlorophosphazene-coated sulfide solid electrolyte powder A6. After adding 30 mg of 1,8-octanedithiol, the mixture was manually ground for 0.3 h, and then heated in a 180 °C electric heating drying oven (DHG-9030A) for 12 h. Thus, surface-modified Li6PS5Cl sulfide solid electrolyte powder S6 was obtained, and was stored in a dry argon-filled glove box.

[0101] In a dry argon-filled glove box, the sulfide solid electrolyte powder S5 prepared in Example 6 was added to a MJP-Y type general cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold. After cold pressing for 3-5 min, the mold was removed to obtain a sulfide solid electrolyte tablet G6-1 with a diameter of 10 mm.

[0102] Example 7

[0103] In a dry argon-filled glove box, 1 g of Li6PS5Cl powder and 50 mg of hexachlorotriphosphazene monomer were weighed into a corundum mortar (MNYB-Φ80 mm), mixed uniformly, and then manually ground for 0.4 h. The mixture was heated in a 100 °C electric heating drying oven (DHG-9030A) for 10 h, and then heated in a 250 °C muffle furnace (KSL-1100X) under vacuum for 36 h to obtain polydichlorophosphazene-coated sulfide solid electrolyte powder A7. After adding 30 mg of 2,2,3,3-tetrafluoro-1,4-butanediol, the mixture was manually ground for 0.3 h, and then heated in a 180 °C electric heating drying oven (DHG-9030A) for 12 h. Thus, surface-modified Li6PS5Cl sulfide solid electrolyte powder S7 was obtained, and was stored in a dry argon-filled glove box.

[0104] In a dry argon-filled glove box, the sulfide solid electrolyte powder S7 prepared in Example 6 was added to a MJP-Y type general cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold. After cold pressing for 3-5 min, the mold was removed to obtain a sulfide solid electrolyte tablet G7-1 with a diameter of 10 mm.

[0105] Example 8

[0106] In a dry argon-filled glove box, 1 g of Li6PS5Cl powder and 50 mg of hexachlorotriphosphazene monomer were weighed into a corundum mortar (MNYB-Φ80 mm), mixed uniformly, and then manually ground for 0.4 h. The mixture was heated in a 100 °C electric heating drying oven (DHG-9030A) for 10 h, and then heated in a 250 °C muffle furnace (KSL-1100X) under vacuum for 36 h to obtain polydichlorophosphazene-coated sulfide solid electrolyte powder A8. After adding 30 mg of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol, the mixture was manually ground for 0.3 h, and then heated in a 180 °C electric heating drying oven (DHG-9030A) for 12 h. Thus, surface-modified Li6PS5Cl sulfide solid electrolyte powder S8 was obtained, and was stored in a dry argon-filled glove box.

[0107] In a dry argon-filled glove box, the sulfide solid electrolyte powder S8 prepared in Example 6 was added to a MJP-Y general cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold. After cold pressing for 3-5 min, the mold was removed to obtain a sulfide solid electrolyte tablet G8-1 with a diameter of 10 mm.

[0108] The polydichlorophosphazene-coated sulfide solid electrolyte powder A4 obtained in this example had a high-resolution transmission electron micrograph as shown in Figure 1 , and an infrared spectrum as shown in Figure 2 .

[0109] The infrared spectrum of the surface-crosslinked Li6PS5Cl sulfide solid electrolyte powder S4 obtained in this example is shown in Figure 3 .

[0110] As can be seen from Figure 1 , the contrast change in the high-resolution transmission electron micrograph shows that the polyphosphazene is coated on the surface of the sulfide electrolyte. As can be seen from the comparison of Figure 2 and Figure 3 , the hexachlorotriphosphazene undergoes ring-opening polymerization to form polydichlorophosphazene, and the characteristic vibration peak of the mercapto group at 2524 cm -1 disappears, indicating that crosslinking occurs.

[0111] Comparative Example 1

[0112] In this comparative example, the Li6PS5Cl solid electrolyte powder D1 was used directly without surface modification.

[0113] In a dry argon-filled glove box, sulfide solid electrolyte powder D1 was added to an MJP-Y type ordinary cylindrical mold (Φ10 mm), and a YLJ-15T-LD manual tablet press was used to apply a pressure of 300-360 MPa to the mold. The cold press was maintained for 3-5 minutes and then the mold was withdrawn to obtain a sulfide solid electrolyte sheet D-G1 with a diameter of 10 mm.

[0114] Current impedance test

[0115] Sulfide solid electrolyte sheets G1-4, G1-1-4-1, and D-G1 prepared in Examples 1-4 and Comparative Example 1 were subjected to gold sputtering on both sides in an SD-900M magnetron sputtering instrument. Ionic conductivity was then measured using a DH7001D electrochemical workstation. Test conditions: a test frequency of 7 MHz to 10 Hz and an applied bias voltage of 100 mV.

[0116] The test results are as follows Figures 4-16 Shown are the electrochemical impedance spectroscopy spectra of sulfide solid electrolyte sheets G1, G1-1, G2, G2-1, G3, G3-1, G4, G4-1, G5-1, G6-1, G7-1, G8-1 and D-G1, respectively.

[0117] Figures 4-16 The horizontal axis is the real impedance, and the vertical axis is the imaginary impedance. It can be observed that the ionic conductivity of the sulfide solid electrolyte sheet without surface modification can reach 3mS cm -1 The sulfide solid electrolyte sheet coated with polydichlorophosphazene and cross-linked with sodium 2,3-dimercaptopropanesulfonate has a certain obstruction on lithium ion transmission, resulting in a decrease in ionic conductivity, but it can still be maintained at 0.01-3 mS cm -1 within the range.

[0118] Application Example 1

[0119] An all-solid-state lithium metal battery was prepared based on the solid electrolyte powder S2 in Example 2.

[0120] First, 100 mg of the sulfide solid electrolyte powder S2 prepared in Example 2 was placed in a polyetheretherketone (PEEK) cylindrical mold with a diameter of 10 mm, and a pressure of 1.5 tons was applied to it for 2 minutes to form a sulfide solid electrolyte layer. Then, 40 mg of the halide electrolyte (Li 0.9 NbO 0.9 Cl 4.8 ) is evenly spread on the surface of the sulfide solid electrolyte layer, and then pressed under 2 tons of pressure for 2 minutes; then 7 mg of composite positive electrode powder (mass ratio, NCM9: halide solid electrolyte (Li 0.9 NbO 0.9 Cl4.8 ):PTFE = 70:27:3) were uniformly spread on the surface of the sulfide solid electrolyte layer, and it was pressed again under 2.5 tons of pressure for 2 min to obtain a composite layer of solid electrolyte and positive electrode material; then lithium metal was placed on the sulfide solid electrolyte layer side of the composite layer; finally, the composite layer and the lithium metal layer were placed as a whole into a customized stainless steel mold (Ningbo Zhengli New Energy Technology Co., Ltd.), and a pressure of 7.5 MPa was applied to obtain a full-solid-state lithium metal battery C1. The above preparation processes were all performed in a glove box filled with argon.

[0121] Application Example 2

[0122] A full-solid-state lithium metal battery was prepared based on the solid electrolyte powder S3 in Example 3.

[0123] First, 100 mg of the sulfide solid electrolyte powder S3 prepared in Example 3 was placed in a polyether ether ketone (PEEK) cylindrical mold with a diameter of 10 mm, and it was pressed under a pressure of 1.5 tons for 2 min to form a sulfide solid electrolyte layer, and then 40 mg of halide electrolyte (Li 0.9 NbO 0.9 Cl 4.8 ) were uniformly spread on the surface of the sulfide solid electrolyte layer, and it was pressed again under 2 tons of pressure for 2 min; then 7 mg of composite positive electrode powder (mass ratio: NCM92: halide solid electrolyte (Li 0.9 NbO 0.9 Cl 4.8 ):PTFE = 70:27:3) were uniformly spread on the surface of the sulfide solid electrolyte layer, and it was pressed again under 2.5 tons of pressure for 2 min to obtain a composite layer of solid electrolyte and positive electrode material; then lithium metal was placed on the sulfide solid electrolyte layer side of the composite layer; finally, the composite layer and the lithium metal layer were placed as a whole into a customized stainless steel mold (Ningbo Zhengli New Energy Technology Co., Ltd.), and a pressure of 7.5 MPa was applied to obtain a full-solid-state lithium metal battery C2. The above preparation processes were all performed in a glove box filled with argon.

[0124] Comparative Application Example 1

[0125] A full-solid-state lithium metal battery was prepared based on the solid electrolyte powder D1 in Comparative Example 1.

[0126] First, 100 mg of the sulfide solid electrolyte powder D1 prepared in Comparative Example 1 was placed in a polyether ether ketone (PEEK) cylindrical mold with a diameter of 10 mm, and it was pressed under a pressure of 1.5 tons for 2 min to form a sulfide solid electrolyte layer, and then 40 mg of halide electrolyte (Li 0.9 NbO 0.9 Cl 4.8) is evenly spread on the surface of the sulfide solid electrolyte layer; then 7 mg of composite cathode powder (mass ratio, NCM92: halide solid electrolyte (Li 0.9 NbO 0.9 Cl 4.8 A composite of 100% PTFE (70:27:3) was evenly spread on the surface of the sulfide solid electrolyte layer, which was then pressed under 2.5 tons of pressure for 2 minutes to form a composite layer of solid electrolyte and cathode material. Lithium metal was then placed on the sulfide solid electrolyte layer side of the composite layer. Finally, the composite layer and lithium metal layer were placed in a custom stainless steel mold (Ningbo Zhengli New Energy Technology Co., Ltd.) and a pressure of 20 MPa was applied to obtain the all-solid-state lithium metal battery C3. All of the above preparation processes were performed in an argon-filled glove box.

[0127] Electrochemical testing

[0128] The prepared all-solid-state lithium metal batteries C1 to C3 were electrochemically tested using a CT-4008T-5V 20mA-164 battery testing system. During the test, the applied current density was 0.2 to 0.4 mA cm -2 , the charge and discharge voltage range is 3.0~4.3V.

[0129] The test results are as follows Figures 17-19 As shown, corresponding to all-solid-state lithium metal batteries C1, C2, and C3, respectively, it can be observed that all-solid-state lithium metal batteries C1 and C2 exhibit excellent low-external pressure cycling performance within the charge and discharge voltage range of 3.0 to 4.3 V compared to C3. The results indicate that the polydichlorophosphazene coating and sodium 2,3-dimercaptopropanesulfonate cross-linking strategy improves the interfacial compatibility between the sulfide solid electrolyte and the negative electrode lithium metal material, thereby enhancing the battery's stability and cycle life.

[0130] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A modified sulfide solid electrolyte, characterized in that: The invention comprises a polyphosphazene-coated sulfide solid electrolyte and a functional additive formed on the polyphosphazene-coated sulfide solid electrolyte; The functional auxiliary agent includes a thiol compound and / or an alcohol hydroxyl compound.

2. The modified sulfide solid electrolyte according to claim 1, characterized in that The mass ratio of the sulfide solid electrolyte, polyphosphazene and functional additive is 1g: (1-800)mg: (1-500)mg; The molecular weight M of the polyphosphazene w Between 200 and 100,000.

3. The modified sulfide solid electrolyte according to claim 1 or 2, characterized in that The thiol compound is selected from any one or more of sodium 2,3-dimercaptopropanesulfonate, thiol PEG thiol, 1,6-hexanedithiol, 1,8-octanedithiol, 3,6-dioxa-1,8-octanedithiol, 1,4-butanediol bis(thioglycolate) or pentaerythritol tetrakis(3-mercaptopropionate); Any one or more of the alcohol hydroxy compound BES sodium salt, 2,2,3,3-tetrafluoro-1,4-butanediol, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol or hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol; The sulfide solid electrolyte is selected from any one or more of an argyrodite-type sulfide solid electrolyte, a glass-ceramic sulfide electrolyte, or a glassy sulfide electrolyte; The argyrodite-type sulfide solid electrolyte includes Li6PS5X, Li 11-n M 2-n P 1+n S 12 Or any one or more of Thio-LISICONs type sulfide solid electrolytes; wherein X is selected from Cl, Br or I, M is selected from Ge, Sn or Si, and n=0.2-0.

8.

4. The modified sulfide solid electrolyte according to any one of claims 1 to 3, characterized in that The sulfide solid electrolyte is selected from Li6PS5Cl, Li7P3S 11 or Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 .

5. A method for preparing the modified sulfide solid electrolyte according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: providing a polyphosphazene-coated sulfide solid electrolyte; S2: The polyphosphazene-coated sulfide solid electrolyte is mixed with a functional additive, ground and then heated to obtain a modified sulfide solid electrolyte.

6. The preparation method according to claim 5, characterized in that The grinding time is 0.2 to 1.0 h; The heating temperature is 100-200°C and the heating time is 0.1-20h; The mass ratio of the sulfide solid electrolyte to the functional additive is 1g:(1-1000)mg.

7. The preparation method according to claim 5 or 6, characterized in that: The polyphosphazene-coated sulfide solid electrolyte is prepared according to the following method: The phosphazene monomer is mixed with the sulfide solid electrolyte, ground, and vacuum heated to obtain a polyphosphazene-coated sulfide solid electrolyte.

8. The preparation method according to claim 7, characterized in that The mass ratio of the sulfide solid electrolyte to the phosphazene monomer is 1g:(1-1000)mg; The phosphazene monomer is selected from any one or more of hexachlorotriphosphazene, phenoxy cyclophosphazene or ethoxy (pentafluoro) cyclotriphosphazene; In the preparation of the polyphosphazene-coated sulfide solid electrolyte, the grinding time is 0.3 to 2 hours; The vacuum heating temperature is 100-300° C., and the time is 0.5-48 hours.

9. An all-solid-state lithium metal battery, characterized in that: including a positive electrode, a lithium metal negative electrode, and an electrolyte; The electrolyte is the modified sulfide solid electrolyte according to any one of claims 1 to 4 or the modified sulfide solid electrolyte prepared by the preparation method according to any one of claims 5 to 8.

10. The all-solid-state lithium metal battery according to claim 9, characterized in that: The active material of the positive electrode is selected from NCM ternary positive electrode material, lithium iron phosphate positive electrode material or lithium manganate positive electrode material; The charge and discharge voltage of the all-solid-state lithium metal battery is 3.0 to 4.3V.

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