Solid-state electrolyte, preparation method thereof and solid-state lithium battery

Abstract

The application belongs to the technical field of lithium ion batteries, and particularly relates to a solid-state electrolyte, a preparation method thereof and a solid-state lithium battery. The molecular formula of the solid-state electrolyte is Li6PS 5‑x Cl 1‑y‑ O x F y Formula I; in the formula I, 0<=x<=1.5, and 0<=y<=0.35. The solid-state electrolyte has fast ion transmission capacity, low diffusion activation energy, high air stability and high interface stability. The solid-state lithium ion symmetrical battery assembled with the lithium metal negative electrode and the solid-state lithium ion full battery assembled with the lithium metal / lithium alloy negative electrode and the high-voltage intercalation positive electrode both have good electrochemical stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a solid electrolyte, its preparation method, and a solid lithium battery. Background Technology

[0002] Traditional lithium-ion batteries, which use liquid organic electrolytes, suffer from safety issues such as leakage, volatility, and flammability. All-solid-state batteries offer a crucial solution to these safety problems, and solid-state electrolytes are a key component of all-solid-state batteries.

[0003] Sulfide inorganic solid electrolytes are among the most commonly used solid electrolytes. Currently, most sulfide inorganic solid electrolytes (most notably Li6PS5Cl material with a lithium-silver-germanium sulfide structure) have achieved the lithium-ion conductivity standard of liquid electrolytes, i.e., a lithium-ion conductivity greater than 1 mS·cm. -1 However, due to the high reactivity of the lithium metal anode, the sulfide inorganic solid electrolyte undergoes a vigorous electrochemical reaction when in direct contact with the lithium metal anode, significantly impacting its stability and thus affecting the cycle stability of the solid-state lithium battery. Furthermore, when the sulfide inorganic solid electrolyte is matched with a high-voltage cathode material to form a full cell, the low oxidation voltage (~2.1V) of the sulfide inorganic solid electrolyte differs greatly from the charge / discharge voltage plateau (>3.5V) of the cathode active material. This leads to severe side reactions between the sulfide inorganic solid electrolyte and the cathode, causing battery failure. Additionally, the sulfide inorganic solid electrolyte is highly sensitive to humid air and is easily corroded by water, generating toxic gases such as hydrogen sulfide, which increases the production and storage costs. Therefore, to improve the air and interfacial stability of the sulfide inorganic solid electrolyte, a suitable structure needs to be constructed.

[0004] Existing technologies improve the air stability of sulfide inorganic solid electrolytes by introducing oxygen or preparing oxygen-rich core-shell structures. Furthermore, introducing lithium halide coatings can improve the interfacial stability of sulfide inorganic solid electrolytes. Undoubtedly, these methods are effective, but achieving improved air and interfacial stability while ensuring rapid lithium-ion transport remains a challenge. Additionally, traditional coating and core-shell structures are relatively expensive.

[0005] Chinese patent application CN115295874A discloses a solid polymer electrolyte membrane containing nano-lithium fluoride, its preparation method, and its application. This solid polymer electrolyte membrane comprises a polymer matrix, a conductive lithium salt, and nano-lithium fluoride, wherein the mass of the nano-lithium fluoride is 0.5% to 5% of the total mass of the polymer matrix, conductive lithium salt, and nano-lithium fluoride. However, this solid polymer electrolyte membrane containing nano-lithium fluoride, its preparation method, and its application can only improve the interfacial stability of the solid polymer electrolyte membrane, but cannot simultaneously improve its air stability.

[0006] Chinese patent application CN110459798A discloses a core-shell structured sulfide solid electrolyte, its preparation method, and a solid-state battery. This core-shell structured sulfide solid electrolyte includes core-shell particles, each comprising a core and a shell layer covering the core. The core is a sulfide solid electrolyte. The shell layer has a thickness of 5–100 nm and is obtained by oxidizing the sulfide solid electrolyte with an external oxide. In this shell layer, some or all of the PS bonds in the sulfide solid electrolyte are replaced by PO. While the replacement of all PS bonds in the shell layer of this core-shell structured sulfide solid electrolyte and its preparation method with PO improves the air stability of the solid electrolyte, it does not simultaneously improve the interfacial stability. Summary of the Invention

[0007] The purpose of this invention is to provide a solid electrolyte that has a fast lithium-ion transport capability and can effectively improve the air stability and interface stability of the solid electrolyte.

[0008] A second objective of this invention is to provide a method for preparing a solid electrolyte.

[0009] A third objective of this invention is to provide a solid-state lithium battery.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A solid electrolyte, the molecular formula of which is shown in Formula I:

[0012] Li6PS 5-x Cl 1-y- O x F y Equation I; in Equation I, 0 ≤ x ≤ 1.5, 0 ≤ y ≤ 0.35.

[0013] Furthermore, the solid electrolyte is a crystal.

[0014] A method for preparing a solid electrolyte includes the following steps:

[0015] 1) Under inert gas protection, LiA, lithium sulfide, lithium chloride, and phosphorus pentasulfide powder were mixed according to Li6PS. 5-x Cl 1-y- O x F y The chemical composition formulas of the molar ratios in the mixtures are weighed and mixed to obtain a mixed powder. The mixture is then ball-milled to achieve uniformity; x≠0 or y≠0.

[0016] 2) Under the protection of inert gas, the mixed powder after step 1) is heat-treated and then cooled.

[0017] Furthermore, the LiA mentioned in step 1) is one or both of lithium oxide and lithium fluoride.

[0018] Furthermore, in step 2), the heat treatment is carried out at a temperature of 520–540℃ for 7–9 hours, and the heating rate and the cooling rate after the heat treatment are both 1℃ / min.

[0019] Furthermore, the mixed powder in step 2) needs to be pressed into a ceramic blank before heat treatment and cooling.

[0020] Further, in step 1), the mixture is mixed by ball milling at 200 rpm for 2 hours, and then at 500 rpm for 8 hours.

[0021] A solid-state lithium battery containing the above-mentioned solid electrolyte.

[0022] Furthermore, the solid electrolyte, when used as a battery separator, has a loading of 30–100 mg / cm³. 2 Lithium metal or lithium alloy is used as the negative electrode, with a thickness of 20–100 μm; an electronically conductive agent, an ionicly conductive agent, and an intercalated positive electrode active material together constitute the composite positive electrode; the electronically conductive agent includes, but is not limited to, Super P, carbon black, and carbon nanotubes; the ionicly conductive agent is the solid electrolyte as described in claim 1; the intercalated positive electrode active material includes, but is not limited to, LiCoO2 and LiNi. a Co b Mn c O2, a+b+c=1; the composite positive electrode consisting of the electronic conductive agent, the ionic conductive agent, and the intercalated positive electrode active material has a loading of 5-25 mg / cm³. 2 .

[0023] The beneficial effects of this invention are:

[0024] In this invention, the unstable PS bonds in the solid electrolyte are replaced by PO bonds, which effectively improves the air stability of the solid electrolyte. Furthermore, when the fluorine content is high, the fluorine will form lithium fluoride passivation with the lithium anode or high voltage collector. The lithium fluoride in this solid electrolyte has an electrochemical stability window of 0 to 6.4 V, which can improve the interface stability of the solid electrolyte.

[0025] By limiting the content and type of fluorine and oxygen elements, this invention enables the solid electrolyte to have high lithium-ion conductivity, while simultaneously improving the interfacial stability and air stability of the solid electrolyte.

[0026] The solid electrolyte of this invention is a crystal, and the high degree of crystallinity can improve the conductivity of lithium ions.

[0027] When x = 1 and y = 0.25, through a reasonable heat treatment process, the solid electrolyte of the present invention can be constructed to have a nanoshell containing both oxygen and fluorine. This structure can further improve the air stability and interfacial stability of the solid electrolyte.

[0028] In step 2) of the present invention, the mixture is pressed into a ceramic body and then subjected to heat treatment and cooling. When the mixture is pressed into a ceramic body, the components of each raw material are more tightly combined, which helps to form new crystals and ion diffusion. Attached Figure Description

[0029] Figure 1 These are XRD diagrams of the solid electrolytes in Examples 1 to 7 and Comparative Example 1 of the present invention;

[0030] Figure 2 (a) is a schematic diagram of the dark field image of the solid electrolyte in Example 6 of the present invention using transmission electron microscopy;

[0031] Figure 2 (b) and Figure 2 (c) is a schematic diagram of the elemental distribution of the solid electrolyte in Example 6 of the present invention;

[0032] Figure 3 This is a schematic diagram showing the test results of the negative electrode cross-section stability of the solid electrolyte in Comparative Examples 2, 8, and 9 of the present invention;

[0033] Figure 4 This is a schematic diagram showing the rate performance test results of the solid electrolyte in Comparative Example 3 and Example 10 of the present invention;

[0034] Figure 5 This is a schematic diagram of the rate performance test results of the solid electrolyte in Example 11 of the present invention;

[0035] Figure 6This is a schematic diagram showing the results of the cycle stability test of the solid-state lithium-ion full battery in Example 12 of the present invention;

[0036] Figure 7 This is a schematic diagram showing the cycle performance test results of the solid-state lithium-ion full battery in Example 13 of the present invention under high voltage and high positive electrode load. Detailed Implementation

[0037] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0038] Example 1

[0039] The solid electrolyte Li6PS in this embodiment 4.5 Cl-O 0.5 The preparation method includes the following steps:

[0040] 1) Dry phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, and lithium oxide separately in a vacuum drying oven for 24 hours;

[0041] 2) Under the protection of argon atmosphere in the glove box, the dried phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder and lithium oxide powder are uniformly mixed in a molar ratio of 0.5:2:1:0.5 and then loaded into a ball mill jar. Then, 20 zirconia grinding balls with a diameter of 10 mm are loaded into the ball mill jar and then sealed.

[0042] 3) Remove the sealed ball mill jar from the glove box and place it into an all-around planetary ball mill for ball milling. During ball milling, the initial ball mill speed is 200 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 2 hours. After that, the ball mill speed is 500 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 8 hours. After ball milling, a mixed powder is obtained.

[0043] 4) After removing the mixed powder, weigh 0.2g and cold-press it into a ceramic blank with a diameter of 12mm. Then, perform heat treatment in a vacuum tube furnace under an argon atmosphere at a temperature of 530℃ for 8 hours. The heating and cooling rates are both 1℃ / min, thus obtaining crystalline Li6PS. 4.5 Cl-O 0.5 The crystals obtained in this embodiment can be crushed before use.

[0044] The solid electrolyte in this embodiment is the Li6PS obtained by the above method. 4.5 Cl-O 0.5 .

[0045] Example 2

[0046] The preparation method of the solid electrolyte Li6PS4Cl-O in this embodiment specifically includes the following steps:

[0047] 1) Dry phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, and lithium oxide separately in a vacuum drying oven for 24 hours;

[0048] 2) Under the protection of argon atmosphere in the glove box, the dried phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder and lithium oxide powder are uniformly mixed in a molar ratio of 0.5:1.5:1:1 and then loaded into the ball mill jar. Then, 20 zirconia grinding balls with a diameter of 10 mm are loaded into the ball mill jar and then sealed.

[0049] 3) Remove the sealed ball mill jar from the glove box and place it into an all-around planetary ball mill for ball milling. During ball milling, the initial ball mill speed is 200 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 2 hours. After that, the ball mill speed is 500 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 8 hours. After ball milling, a mixed powder is obtained.

[0050] 4) After removing the mixed powder, weigh 0.2g and cold-press it into a ceramic blank with a diameter of 12mm. Then, perform heat treatment in a vacuum tube furnace under an argon atmosphere at a temperature of 540℃ for 9 hours. The heating and cooling rates are 1℃ / min, thus obtaining crystalline Li6PS4Cl-O. In this embodiment, the obtained crystals can be pulverized before use.

[0051] The solid electrolyte in this embodiment is Li6PS4Cl-O obtained by the above method.

[0052] Example 3

[0053] The solid electrolyte Li6PS in this embodiment 3.5 Cl-O 1.5 The preparation method of [the substance] specifically includes the following steps:

[0054] 1) Dry phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, and lithium oxide separately in a vacuum drying oven for 24 hours;

[0055] 2) Under the protection of argon atmosphere in the glove box, the dried phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder and lithium oxide powder are uniformly mixed in a molar ratio of 0.5:1:1:1.5 and then loaded into the ball mill jar. Then, 20 zirconia grinding balls with a diameter of 10 mm are loaded into the ball mill jar and then sealed.

[0056] 3) Remove the sealed ball mill jar from the glove box and place it into an all-around planetary ball mill for ball milling. During ball milling, the initial ball mill speed is 200 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 2 hours. After that, the ball mill speed is 500 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 8 hours. After ball milling, a mixed powder is obtained.

[0057] 4) After removing the mixed powder, weigh 0.2g and cold-press it into a ceramic blank with a diameter of 12mm. Then, perform heat treatment in a vacuum tube furnace under an argon atmosphere at a temperature of 530℃ for 8 hours. The heating and cooling rates are both 1℃ / min, thus obtaining crystalline Li6PS. 3.5 Cl-O 1.5 The crystals obtained in this embodiment can be crushed before use.

[0058] The solid electrolyte in this embodiment is the Li6PS obtained by the above method. 3.5 Cl-O 1.5 .

[0059] Example 4

[0060] The solid electrolyte Li6PS4Cl in this embodiment 0.95 -OF 0.05 The preparation method of [the substance] specifically includes the following steps:

[0061] 1) Dry phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, and lithium oxide separately in a vacuum drying oven for 24 hours;

[0062] 2) Under the protection of argon atmosphere in the glove box, the dried phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, lithium oxide powder, and lithium fluoride powder are uniformly mixed in a molar ratio of 0.5:1.5:0.95:1:0.05 and then loaded into the ball mill jar. Then, 20 zirconia grinding balls with a diameter of 10 mm are loaded into the ball mill jar and then sealed.

[0063] 3) Remove the sealed ball mill jar from the glove box and place it into an all-around planetary ball mill for ball milling. During ball milling, the initial ball mill speed is 200 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 2 hours. After that, the ball mill speed is 500 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 8 hours. After ball milling, a mixed powder is obtained.

[0064] 4) After removing the mixed powder, weigh 0.2g and cold-press it into a ceramic blank with a diameter of 12mm. Then, perform heat treatment in a vacuum tube furnace under an argon atmosphere at a temperature of 530℃ for 8 hours. The heating and cooling rates are both 1℃ / min, thus obtaining crystalline Li6PS4Cl.0.95 -OF 0.05 The crystals obtained in this embodiment can be crushed before use.

[0065] The solid electrolyte in this embodiment is the Li6PS4Cl obtained by the above method. 0.95 -OF 0.05 .

[0066] Example 5

[0067] The solid electrolyte Li6PS4Cl in this embodiment 0.85 -OF 0.15 The preparation method of [the substance] specifically includes the following steps:

[0068] 1) Dry phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, and lithium oxide separately in a vacuum drying oven for 24 hours;

[0069] 2) Under the protection of argon atmosphere in the glove box, the dried phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, lithium oxide powder, and lithium fluoride powder are uniformly mixed in a molar ratio of 0.5:1.5:0.85:1:0.15 and then loaded into the ball mill jar. Then, 20 zirconia grinding balls with a diameter of 10 mm are loaded into the ball mill jar and then sealed.

[0070] 3) Remove the sealed ball mill jar from the glove box and place it into an all-around planetary ball mill for ball milling. During ball milling, the initial ball mill speed is 200 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 2 hours. After that, the ball mill speed is 500 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 8 hours. After ball milling, a mixed powder is obtained.

[0071] 4) After removing the mixed powder, weigh 0.2g and cold-press it into a ceramic blank with a diameter of 12mm. Then, perform heat treatment in a vacuum tube furnace under an argon atmosphere at a temperature of 530℃ for 8 hours. The heating and cooling rates are both 1℃ / min, thus obtaining crystalline Li6PS4Cl. 0.85 -OF 0.15 The crystals obtained in this embodiment can be crushed before use.

[0072] The solid electrolyte in this embodiment is the Li6PS4Cl obtained by the above method. 0.85 -OF 0.15 .

[0073] Example 6

[0074] The solid electrolyte Li6PS4Cl in this embodiment 0.75 -OF 0.25 The preparation method of [the substance] specifically includes the following steps:

[0075] (1) Phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, and lithium oxide were dried in a vacuum drying oven for 24 hours respectively;

[0076] (2) Under the protection of argon atmosphere in the glove box, the dried phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, lithium oxide powder and lithium fluoride powder are uniformly mixed in a molar ratio of 0.5:1.5:0.75:1:0.25 and then loaded into the ball mill jar. Then, 20 zirconia grinding balls with a diameter of 10 mm are loaded into the ball mill jar and then sealed.

[0077] (3) Take the sealed ball mill jar out of the glove box and put it into the all-around planetary ball mill for ball milling. When ball milling, the ball mill speed is 200 rpm. After each ball milling for 20 minutes, let it stand and cool for 5 minutes. The total effective ball milling time is 2 hours. After that, the ball mill speed is 500 rpm. After each ball milling for 20 minutes, let it stand and cool for 5 minutes. The total effective ball milling time is 8 hours. After ball milling, a mixed powder is obtained.

[0078] (4) After removing the mixed powder, weigh 0.2g and cold-press it into a ceramic blank with a diameter of 12mm. Then, perform heat treatment in a vacuum tube furnace under an argon atmosphere at a temperature of 530℃ for 8 hours. The heating and cooling rates are both 1℃ / min, thus obtaining crystalline Li6PS4Cl. 0.75 -OF 0.25 The crystals obtained in this embodiment can be crushed before use.

[0079] The solid electrolyte in this embodiment is the solid electrolyte Li6PS4Cl obtained by the above method. 0.75 -OF 0.25 .

[0080] Example 7

[0081] The solid electrolyte Li6PS4Cl in this embodiment 0.65 -OF 0.35 The preparation method of [the substance] specifically includes the following steps:

[0082] (1) Phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, and lithium oxide were dried in a vacuum drying oven for 24 hours respectively;

[0083] (2) Under the protection of argon atmosphere in the glove box, the dried phosphorus pentasulfide powder, lithium sulfide powder, lithium chloride powder, lithium oxide powder and lithium fluoride powder are uniformly mixed in a molar ratio of 0.5:1.5:0.65:1:0.35 and then loaded into the ball mill jar. Then, 20 zirconia grinding balls with a diameter of 10 mm are loaded into the ball mill jar and then sealed.

[0084] (3) Take the sealed ball mill jar out of the glove box and put it into the all-around planetary ball mill for ball milling. When ball milling, the ball mill speed is 200 rpm. After each ball milling for 20 minutes, let it stand and cool for 5 minutes. The total effective ball milling time is 2 hours. After that, the ball mill speed is 500 rpm. After each ball milling for 20 minutes, let it stand and cool for 5 minutes. The total effective ball milling time is 8 hours. After ball milling, a mixed powder is obtained.

[0085] (4) After removing the mixed powder, weigh 0.2g and cold-press it into a ceramic blank with a diameter of 12mm. Then, perform heat treatment in a vacuum tube furnace under an argon atmosphere at a temperature of 530℃ for 8 hours. The heating and cooling rates are both 1℃ / min, thus obtaining crystalline Li6PS4Cl. 0.65 -OF 0.35 The crystals obtained in this embodiment can be crushed before use.

[0086] The solid electrolyte in this embodiment is the Li6PS4Cl obtained by the above method. 0.65 -OF 0.35 .

[0087] Example 8

[0088] A solid-state lithium-ion symmetric battery comprising the solid electrolyte of Example 2 was prepared. This solid-state lithium-ion symmetric battery consists of two 50μm lithium anodes and the solid electrolyte Li6PS4Cl-O of Example 2. The solid electrolyte powder of Example 2 was cold-pressed into a sheet, and then the two 50μm lithium anodes were respectively placed on both sides of the cold-pressed solid electrolyte sheet to obtain the solid-state lithium-ion battery of this example. The loading of the solid electrolyte in this example is 100 mg / cm³. 2 .

[0089] Example 9

[0090] A solid-state lithium-ion symmetric battery comprising the solid electrolyte of Example 6 was prepared. This solid-state lithium-ion symmetric battery consists of two 50 μm lithium anodes and the solid electrolyte Li6PS4Cl from Example 6. 0.75 -OF 0.25 The solid electrolyte powder from Example 6 was cold-pressed into a sheet, and then two 50μm lithium anode sheets were placed on either side of the cold-pressed solid electrolyte sheet to obtain the solid lithium-ion battery of this example. The loading of the solid electrolyte in this example is 100 mg / cm³. 2 .

[0091] Example 10

[0092] A solid-state lithium-ion full cell comprising the solid electrolyte of Example 6 was prepared. This solid-state lithium-ion full cell includes a 20 μm lithium anode and the solid-state electrolyte Li6PS4Cl from Example 6.0.75 -OF 0.25 And a composite cathode, wherein the composite cathode comprises 70 wt% LiCoO2, 5 wt% Super P and 25 wt% Li6PS4Cl 0.75 -OF 0.25 The solid electrolyte powder and composite cathode powder from Example 6 were cold-pressed together in upper and lower layers. Then, a 20μm lithium anode was placed on the side of the solid electrolyte opposite to the composite cathode, thus obtaining the solid-state lithium-ion battery of this example. The solid electrolyte loading in this example is 80 mg / cm³. 2 The loading of the composite cathode is 8 mg / cm³. 2 .

[0093] Example 11

[0094] A solid-state lithium-ion full cell comprising the solid electrolyte of Example 6 was prepared. This solid-state lithium-ion full cell includes a 100 μm lithium-indium alloy anode and the solid-state electrolyte Li6PS4Cl from Example 6. 0.75 -OF 0.25 And a composite cathode, wherein the composite cathode comprises 85 wt% LiCoO2, 5 wt% carbon black and 10 wt% Li6PS4Cl 0.75 -OF 0.25 The solid electrolyte powder and composite cathode powder from Example 6 were cold-pressed together in upper and lower layers. Then, a 100μm lithium-indium alloy anode was placed on the side of the solid electrolyte opposite to the composite cathode, thus obtaining the solid-state lithium-ion battery of this example. The solid electrolyte loading in this example is 30 mg / cm³. 2 The loading capacity of the composite cathode is 5 mg / cm³. 2 .

[0095] Example 12

[0096] A solid-state lithium-ion full cell comprising the solid electrolyte of Example 6 was prepared. This solid-state lithium-ion full cell includes an 80 μm lithium-indium alloy anode and the solid-state electrolyte Li6PS4Cl from Example 6. 0.75 -OF 0.25 And a composite cathode, wherein the composite cathode comprises 65 wt% LiCoO2, 10 wt% carbon nanotubes and 25 wt% Li6PS4Cl 0.75 -OF 0.25 The solid electrolyte powder and composite positive electrode powder from Example 6 were cold-pressed together in upper and lower layers. Then, a 100μm lithium-indium alloy negative electrode was placed on the side of the solid electrolyte opposite to the composite positive electrode, thus obtaining the solid-state lithium-ion battery of this example. The solid electrolyte loading in this example is 50 mg / cm³. 2 The loading capacity of the composite cathode is 5 mg / cm³. 2.

[0097] Example 13

[0098] A solid-state lithium-ion full cell comprising the solid electrolyte of Example 6 was prepared. This solid-state lithium-ion full cell includes a 50 μm lithium-indium alloy anode and the solid-state electrolyte Li6PS4Cl from Example 6. 0.75 -OF 0.25 And a composite cathode, wherein the composite cathode comprises 70 wt% LiCoO2, 5 wt% Super P and 25 wt% Li6PS4Cl 0.75 -OF 0.25 The solid electrolyte powder and composite positive electrode powder from Example 6 were cold-pressed together in upper and lower layers. Then, a 100μm lithium-indium alloy negative electrode was placed on the side of the solid electrolyte opposite to the composite positive electrode, thus obtaining the solid-state lithium-ion battery of this example. The solid electrolyte loading in this example is 70 mg / cm³. 2 The loading capacity of the composite cathode is 25 mg / cm³. 2 .

[0099] Comparative Example 1

[0100] The preparation method of the solid electrolyte Li6PS5Cl in this comparative example specifically includes the following steps:

[0101] 1) Dry phosphorus pentasulfide powder, lithium sulfide powder, and lithium chloride powder separately in a vacuum drying oven for 24 hours;

[0102] 2) Under the protection of argon atmosphere in the glove box, the dried phosphorus pentasulfide powder, lithium sulfide powder and lithium chloride powder are uniformly mixed in a molar ratio of 0.5:2.5:1 and then loaded into the ball mill jar. Twenty zirconia grinding balls with a diameter of 10 mm are loaded into the ball mill jar and then sealed.

[0103] 3) Remove the sealed ball mill jar from the glove box and place it into an all-around planetary ball mill for ball milling. During ball milling, the initial ball mill speed is 200 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 2 hours. After that, the ball mill speed is 500 rpm, and after every 20 minutes of ball milling, allow it to stand and cool for 5 minutes. The total effective ball milling time is 7 hours. After ball milling, a mixed powder is obtained.

[0104] 4) After removing the mixed powder, weigh 0.2g and cold-press it into a ceramic blank with a diameter of 12mm. Then, perform heat treatment in a vacuum tube furnace under an argon atmosphere at a temperature of 520℃ for 7 hours. The heating and cooling rates are both 1℃ / min, thus obtaining crystalline Li6PS5Cl. In this embodiment, the obtained crystals can be pulverized before use.

[0105] The solid electrolyte in this comparative example is Li6PS5Cl obtained by the above method.

[0106] Comparative Example 2

[0107] A solid-state lithium-ion symmetric battery comprising the solid electrolyte of Comparative Example 1 was prepared. This solid-state lithium-ion symmetric battery consists of two 50 μm lithium anodes and the solid electrolyte Li6PS5Cl from Example 1. The solid electrolyte powder of Example 1 was cold-pressed into a sheet, and then the two 50 μm lithium anodes were respectively placed on both sides of the cold-pressed solid electrolyte sheet to obtain the solid-state lithium-ion battery of this example. The loading of the solid electrolyte in this example is 100 mg / cm³. 2 .

[0108] Comparative Example 3

[0109] A solid-state lithium-ion full cell comprising the solid electrolyte of Comparative Example 1 was prepared. This solid-state lithium-ion full cell includes a 20 μm lithium anode, the solid electrolyte Li6PS5Cl of Comparative Example 1, and a composite cathode, wherein the composite cathode comprises 70 wt% LiCoO2, 5 wt% Super P, and 25 wt% Li6PS5Cl. The solid electrolyte powder of Comparative Example 1 and the composite cathode powder were cold-pressed together in layers. Then, the 20 μm lithium anode was placed on the side of the solid electrolyte opposite to the composite cathode, thus obtaining the solid-state lithium-ion battery of this embodiment. The solid electrolyte loading in this embodiment is 80 mg / cm³. 2 The loading of the composite cathode is 8 mg / cm³. 2 .

[0110] Experimental Example 1

[0111] XRD tests were performed on the solid electrolytes of Examples 1-7 and Comparative Example 1. The test results are as follows: Figure 1 As shown, the solid electrolytes of Examples 1-7 and Comparative Example 1 all exhibit distinct characteristic peaks at 25.1°, 29.5°, and 31°. These are the main characteristic peaks of lithium silver sulfide germanium ore, indicating that the solid electrolytes of Examples 1-7 and Comparative Example 1 are based on the lithium silver sulfide germanium ore structure, which ensures rapid lithium-ion conduction. Furthermore, impurity peaks were observed at 26.8°, 33.7°, 34.7°, and 38.6°, mainly corresponding to Li₂S (PDF No. 26-1188), Li₂O (PDF No. 12-0254), Li₃PO₄ (PDF No. 48-0956), and LiF (PDF No. 45-1460).

[0112] Experimental Example 2

[0113] The solid electrolyte of Example 6 was subjected to dark-field transmission electron microscopy (TEM) imaging and elemental distribution analysis. The results are as follows: Figure 2 As shown. From Figure 2 As can be seen from Example 6, the solid electrolyte forms a nanoscale shell with obvious composite oxygen and fluorine elements. This nanoscale shell can further and effectively improve air and interface stability.

[0114] Experimental Example 3

[0115] The lithium-ion conductivity and calculated activation energy Ea of the solid electrolytes of Examples 1 to 7 and Comparative Example 1 of this invention were tested using an electrochemical workstation, and the results are shown in Table 1.

[0116] Table 1. Lithium-ion conductivity and diffusion activation energy Ea of the solid electrolytes in Examples 1-7 and Comparative Example 1

[0117]

[0118] As shown in Table 1, the ionic conductivity of the solid electrolytes in Examples 1-7 continuously decreases while the diffusion activation energy continuously increases with the increase of oxygen or fluorine content. This is mainly because fluorine and oxygen have the strongest electronegativity, increasing the difficulty of lithium-ion diffusion. However, the solid electrolytes in Examples 1-7 all possess relatively fast ion conduction capabilities, with ionic conductivity much greater than 1 mS²cm. -1 This makes it possible to achieve higher rate capabilities in assembled solid-state lithium batteries.

[0119] Test Example 4

[0120] Air stability test

[0121] The solid electrolytes of Comparative Example 1, Example 2, and Example 6 were all exposed to air for half an hour at room temperature and relative humidity of 35±2%. After that, the exposed solid electrolytes were heat-treated in an argon protective atmosphere at a temperature of 150°C for 2 hours. The lithium-ion conductivity of the heat-treated solid electrolytes was then tested using an electrochemical workstation, and the lithium-ion conductivity retention rate was calculated based on the original lithium-ion conductivity. The results are shown in Table 2.

[0122] Table 2. Lithium-ion conductivity and retention rate of solid electrolytes after heat treatment in Comparative Examples 1, 2, and 6

[0123]

[0124] As shown in Table 2, the addition of oxygen in Example 2 can improve the air stability of the solid electrolyte. In addition, Example 6, which has a special structure with a nanoshell rich in oxygen and fluorine, can further improve the air stability.

[0125] Experimental Example 5

[0126] Negative electrode interface stability test

[0127] The solid-state lithium-ion symmetric batteries of Comparative Example 2, Example 8, and Example 9 were all tested using coin cells.

[0128] First, the limiting current density and limiting capacity density of each solid electrolyte were tested. An electrochemical workstation was used for the tests. The test conditions were: current density between 0 and 1 mA·cm⁻¹. -2 Each step increases by 0.1 mA·cm -2 Current density >1 mA·cm -2 Each step increases by 0.2 mA·cm -2 The charging and discharging times alternated every half hour, and the test temperature was 60℃.

[0129] The long-term cycling stability of each solid electrolyte was tested under the following conditions: current density of 0.2 mA·cm⁻¹. -2 The charging and discharging times alternated every half hour, and the test temperature was 60℃.

[0130] The limiting current density and limiting capacity density of each solid electrolyte are shown in Table 3, and the long-term cycling stability of each solid electrolyte is shown in Table 4. Figure 3 As shown.

[0131] Table 3 shows the limiting current density and limiting capacity density of the solid electrolytes in Comparative Examples 2, 8, and 9.

[0132]

[0133] As shown in Table 3, adding oxygen in Example 2 improves the stability of the solid electrolyte anode and increases the limiting current density and limiting capacity density. Furthermore, introducing fluorine into Example 2 results in a special structure with an oxygen- and fluorine-rich nanoshell, which further enhances the limiting current density and limiting capacity density. Figure 3 It can be seen that the voltage of Li6PS5Cl fluctuates significantly, with the polarization voltage continuously increasing, indicating that a stable interface cannot be formed and side reactions occur continuously. In contrast, the voltage of the electrolytes with the introduction of oxygen and the simultaneous introduction of oxygen and fluorine elements shows almost no fluctuation, indicating that a relatively stable interface can be formed. Furthermore, the cycle life of the electrolytes with the introduction of oxygen and the simultaneous introduction of oxygen and fluorine elements is significantly increased, further illustrating the necessity of introducing these two elements.

[0134] Experimental Example 6

[0135] Positive electrode interface stability test

[0136] The solid-state lithium batteries of Comparative Example 3 and Examples 10-13 were tested. An electrochemical workstation was used for the tests, and the test temperature was 60°C.

[0137] The test conditions for Comparative Example 3 and Example 10 were: voltage ranging from 2.5 to 4.3 V, with gradually changing current density, each current density being 0.05 mA·cm⁻¹. -2 0.1mA·cm -2 0.2mA·cm -2 0.5mA·cm -2 1mA·cm -2 2mA·cm -2 and 0.05mA·cm -2 The test was conducted using a button battery, and the results were as follows: Figure 4 .

[0138] The test conditions for Example 11 were: voltage ranging from 2.5 to 4V, with the current density gradually changing to 0.1 mA·cm⁻¹. -2 0.2mA·cm -2 0.5mA·cm -2 1mA·cm -2 2mA·cm -2 The test was conducted using a pressure mold with an additional pressure of 100 MPa, and the results were as follows: Figure 5 .

[0139] The test conditions for Example 12 were: voltage of 2.5–4V and current density of 0.5 mA·cm. -2 The test was conducted using a pressure mold with an additional pressure of 100 MPa, and the results were as follows: Figure 6 .

[0140] The test conditions for Example 13 were as follows: the voltage was 2.5–3.9V for the first two weeks of cycling, and after two weeks of cycling, the voltage changed to 2.5–4.3V, with a current density of 0.2 mA·cm⁻¹. -2 The test was conducted using a pressure mold with an additional pressure of 100 MPa, and the results were as follows: Figure 7 .

[0141] Depend on Figure 4 It is evident that, with the introduction of oxygen and fluorine, solid-state lithium-ion full cells composed of solid electrolytes at different current densities can release higher specific capacity than solid-state lithium-ion full cells composed of Li6PS5Cl electrolytes, and exhibit higher capacity retention when the current returns to a low level. Figure 5 It can be seen that solid-state lithium-ion full batteries composed of solid electrolytes with the introduction of oxygen and fluorine elements can achieve high performance at 0.1 mA·cm⁻¹ under certain pressure. -2 Achieving an ultra-high specific capacity, with a specific capacity of 187 mAh·g -1Even at 2mA·cm -2 It can also reach close to 80mAh·g under ultra-high current. -1 Specific capacity. (From) Figure 6 It can be seen that solid-state lithium-ion full batteries composed of solid electrolytes with the introduction of oxygen and fluorine elements can achieve stable cycling at a relatively high current density, achieving 129 mAh·g after 100 cycles. -1 Specific capacity and near 100% capacity retention. (By...) Figure 6 It is evident that solid-state lithium-ion full batteries composed of electrolytes containing oxygen and fluorine can achieve high areal capacity and specific capacity under high voltage and high positive electrode load, with an areal capacity of 2.7 mAh·cm³. -2 Specific capacity is 155mAh·g -1 Therefore, it can be concluded that the introduction of oxygen and fluorine can improve the stability of the cathode interface, provide higher specific capacity and high capacity retention, and achieve excellent electrochemical performance under high voltage and high cathode load.

[0142] For ease of comparison, the molecular formula of the solid electrolyte is Li6PS. 5-x Cl 1-y- O x F y 0≤x≤1.5, 0≤y≤0.35 in Figures 1-7 In Chinese, it is simplified to LPSC-OxFy.

[0143] Based on the above discussion, it can be demonstrated that the introduction of oxygen and fluorine can effectively improve the air stability of the electrolyte and the interface stability of the negative and positive electrodes.

Claims

1. A method for preparing a solid electrolyte, characterized in that, The molecular formula of the solid electrolyte is shown in Formula I: Li6PS 5-x Cl 1-y- O x F y Equation I; in Equation I, x=1, y=0.25; The method for preparing the solid electrolyte includes the following steps: 1) Under inert gas protection, LiA, lithium sulfide, lithium chloride, and phosphorus pentasulfide powder were mixed according to Li6PS. 5-x Cl 1-y- O x F y The chemical composition formulas of the molar ratios in the mixtures are weighed and mixed to obtain a mixed powder. The mixture is then ball-milled to achieve uniformity; x≠0 or y≠0. 2) Under inert gas protection, the mixed powder from step 1) is heat-treated and then cooled. In step 2), the heat treatment is carried out at a temperature of 520–540 °C for 7–9 h, and the heating rate and the cooling rate after heat treatment are both 1 °C / min. The LiA is one or both of lithium oxide and lithium fluoride.

2. The method for preparing a solid electrolyte according to claim 1, characterized in that, The solid electrolyte is a crystal.

3. The method for preparing a solid electrolyte according to claim 1, characterized in that, The mixed powder in step 2) needs to be pressed into a ceramic blank before heat treatment and cooling.

4. The method for preparing a solid electrolyte according to claim 1, characterized in that, In step 1), the mixture is mixed by ball milling at 200 rpm for 2 hours, and then at 500 rpm for 8 hours.

5. A solid electrolyte, characterized in that, It was prepared using the solid electrolyte preparation method described in claim 1.

6. A solid-state lithium battery containing the solid electrolyte as described in claim 5.

7. The solid-state lithium battery according to claim 6, characterized in that, When the solid electrolyte is used as a battery separator, the loading is 30–100 mg / cm³. 2 Lithium metal or lithium alloy is used as the negative electrode, with a thickness of 20–100 μm; an electronically conductive agent, an ionicly conductive agent, and an intercalated positive electrode active material together constitute the composite positive electrode; the electronically conductive agent includes carbon black and carbon nanotubes; the ionicly conductive agent is the solid electrolyte as described in claim 1; the intercalated positive electrode active material includes LiCoO2 and LiNi. a Co b Mn c O2, a+b+c=1; the composite cathode loading of the electronic conductive agent, ionic conductive agent and intercalated positive electrode active material is 5-25 mg / cm³. 2 .

Images