A sulfide solid-state electrolyte, a preparation method and a full-solid-state lithium ion battery

Abstract

The application relates to a sulfide solid electrolyte, a preparation method and a full solid-state lithium ion battery, and belongs to the field of lithium ion batteries. The chemical general formula of the sulfide solid electrolyte is xAB-R y S z , wherein AB is an alkali metal halide, A is one of Li, Na and K, B is one of F, Cl, Br and I, R y S z is a metal sulfide, R is one or more of Ca, Sr, Ba, Mn, Fe, Pb, Ge, Cr, As, Sb, V, Ga, Sn, Bi, In, Gd, Cu, Zn and Cu, and 0.3<=x<=0.7; in the application, R y S z is ZnIn2S4. The sulfide solid electrolyte has high room-temperature ionic conductivity and good air stability, can realize the assembly of a solid-state battery in air, the required working pressure of the battery is smaller, and the preparation of a low-pressure or even pressure-free full solid-state battery can be realized.

Description

Technical Field

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

[0002] All-solid-state lithium batteries have become the core direction of next-generation rechargeable battery technology: by completely eliminating the flammability and explosion risks of liquid batteries through solid electrolytes, they achieve intrinsic safety; they are compatible with lithium metal anodes and high-voltage cathodes, with a theoretical energy density exceeding 500Wh / kg; they support ultra-fast charging (charging to 80% SOC in 10 minutes) and operation in extreme temperatures (-40~150℃); at the same time, they simplify battery structure and are expected to achieve a cycle life of tens of thousands of cycles. Despite challenges in interface impedance and cost, their technological characteristics will reshape the landscape of the electric vehicle, aerospace, and energy storage industries, and commercial breakthroughs are expected around 2030.

[0003] Currently, the most commercially viable solid electrolytes include sulfide-based electrolytes (such as Li6PS5Cl and Li7P3S). 11 Sulfide solid electrolytes include halogenated (Li3InCl6, Li2ZrCl6), oxide-based (such as LLZO, LATP), and polymer-based composite (such as PEO / LiTFSI, PVDF-HFP / LiTFSI). Among them, sulfide solid electrolytes have high ionic conductivity (10). -3 ~10 -2 S cm -1 With its core advantages such as being close to liquid electrolyte, excellent mechanical ductility (easy to process into a dense interface), and wide electrochemical window (above 5V), it is currently the closest all-solid-state battery technology path to practical application. However, it still needs to solve industrialization bottlenecks such as poor chemical stability (decomposition into toxic gas H2S upon contact with water / oxygen), deterioration of the electrode-electrolyte solid-solid interface contact (void caused by cycle volume changes), and high cost (dependence on rare metal germanium and high raw material costs).

[0004] The future focus of sulfide solid electrolytes will be on the large-scale production and cost reduction of key materials, including achieving mass production from gram to ton levels, preparation from micrometer to nanometer scales, and continuous production, while reducing costs through the development of new systems. In terms of performance improvement, efforts will be made to solve interface problems in the production of battery composite electrodes and electrode films to reduce internal resistance and increase capacity, as well as overcome large-scale production challenges such as dry electrodes, densification under pressure, and assembly in specific environments. Furthermore, development will move towards improving energy density, maintaining battery capacity, and extending cycle life for end-applications, to meet the demand for high-energy-density, high-safety batteries in fields such as new energy vehicles.

[0005] A careful study of existing sulfide solid electrolytes reveals that those prepared using current techniques still face severe air sensitivity issues. This poses significant challenges to material preparation and transfer, thereby increasing production costs. Therefore, researchers in this field aim to develop a novel air-stable sulfide solid electrolyte that can be prepared in air while ensuring that its ionic conductivity remains unaffected by air conditions. Summary of the Invention

[0006] The purpose of this invention is to solve the air stability problem of sulfide solid electrolytes. A sulfide solid electrolyte, a preparation method, and an all-solid-state lithium-ion battery have been developed. The all-solid-state lithium-ion battery has the characteristics of high ionic conductivity and air stability.

[0007] In a first aspect, the present invention provides a sulfide solid electrolyte with the general chemical formula xAB-R. y S z In this invention, AB is a halide, A is one of Li, Na, and K, B is one of F, Cl, Br, and I, and x represents the molar ratio of AB to the sulfide solid electrolyte material as x:1, 0.3≤x≤0.7; R is one or more of Ca, Sr, Ba, Mn, Fe, Pb, Ge, Cr, As, Sb, V, Ga, Sn, Bi, In, Gd, Cu, Zn, and Cu, and y and z depend on the average valence state of R, aiming to maintain the valence state balance of the chemical elements. In this invention, R... y S z It is ZnIn2S4.

[0008] Using the above technical solution, based on the hard and soft acid-base theory, we choose the acid that tends to react with the soft base S. 2- The tightly bound soft acid or interface acid, i.e., R, is a metal cation that is easily polarized, easily loses electrons, and easily forms strong covalent bonds, to resist the erosion and hydrolysis of H2O and improve the air stability of the electrolyte. This sulfide solid electrolyte has good air stability, which can realize the assembly of all-solid-state batteries in air, reduce the difficulty of material preparation and battery assembly, and facilitate the simplification of the process and large-scale production.

[0009] Furthermore, the room temperature ionic conductivity of this sulfide solid electrolyte is 10. -3 ~10 -2 S cm -1 Furthermore, its ionic conductivity remains essentially unchanged after 60 days of exposure to air.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned sulfide solid electrolyte, the steps of which are as follows:

[0011] 1) R y S z Powder preparation

[0012] Method 1: Prepare R using a simple hydrothermal method y S z powder

[0013] A metal salt containing R was dissolved in deionized water, and an excess of thioacetamide was added and stirred until homogeneous. The resulting mixture was transferred to a stainless steel high-pressure reactor lined with polystyrene, with the mixture occupying 60-80% of the total volume of the reactor liner. The high-pressure reactor was sealed and subjected to a hydrothermal reaction. After the hydrothermal reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting product was washed by centrifugation with deionized water and anhydrous ethanol, and then dried to obtain R. y S z powder;

[0014] Method 2: Preparation of R using solid-state method y S z powder

[0015] A metal salt containing R and sulfur powder were uniformly mixed according to a stoichiometric ratio, vacuum sintered, and then naturally cooled to room temperature to obtain R. y S z powder;

[0016] 2) xAB-R y S z Preparation

[0017] xAB-R was prepared by ball milling. y S z That is, weigh AB and R according to the stoichiometric ratio. y S z The powder was ground and then ball-milled to obtain xAB-R. y S z Sulfide solid electrolyte.

[0018] The sulfide solid electrolyte prepared using the above technical solution has excellent air stability. The entire material preparation process can be carried out in air, which simplifies the complex transfer process in the synthesis of air-sensitive materials and can also save costs.

[0019] Furthermore, in step 1) of method one, the metal salt containing R is a chloride, nitrate, sulfate, or ammonium salt;

[0020] Furthermore, in step 1) of method one, the concentration of the metal ion in the deionized aqueous solution containing the metal salt of R is 0.02~0.2 mol / L. -1 The amount of thioacetamide added is 120-150% of the stoichiometric ratio (molar ratio);

[0021] Furthermore, in step 1) of method one, the hydrothermal reaction temperature is 150~200℃ and the hydrothermal reaction time is 12~24 hours;

[0022] Furthermore, in step 1) of method one, the drying temperature is 60~100℃ and the drying time is 5~12 hours;

[0023] Furthermore, in step 1) of method two, the sintering temperature is 400~800℃ and the sintering time is 10~30 hours;

[0024] Furthermore, in step 2), the grinding time is 20-40 minutes; the ball mill speed is 300-500 rpm; the ball milling time is 5-20 hours; and the ball-to-material ratio is 15-20:1.

[0025] Thirdly, the present invention provides an all-solid-state battery, which is prepared using the sulfide solid electrolyte described in the present invention as an electrolyte and a positive electrode additive.

[0026] Using the above technical solution, the sulfide solid electrolyte provided by the present invention has good practicality. It can provide the ionic conductivity required for battery operation and has good air stability, enabling the assembly of solid batteries in air. At the same time, the battery requires a low operating pressure, which is expected to realize the preparation of low-pressure or even pressureless all-solid-state batteries. Attached Figure Description

[0027] Figure 1 The AC impedance spectra of the products from Examples 1 and 5 are shown.

[0028] Figure 2 The AC impedance spectra of the products from Examples 2-4 are shown.

[0029] Figure 3 The AC impedance spectrum of the product of Example 3 after being placed in air for 60 days;

[0030] Figure 4 The XRD patterns of the product of Example 3 before and after being exposed to air for 60 days;

[0031] Figure 5 Cyclic performance curves of the all-solid-state battery prepared in Example 1. Detailed Implementation

[0032] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the present invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the present invention, many specific details will be included in the following description. The present invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the present invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0033] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] Example 1

[0035] This embodiment provides a method for preparing a 0.1LiCl-ZnIn2S4 solid electrolyte, where all raw materials are commercially available. The preparation method includes the following steps:

[0036] (1) Preparation of ZnIn2S4: 1 mmol of ZnCl2 and 2 mmol of InCl3·4H2O were added to 10 mL of deionized water at a stoichiometric ratio of 1:2, and stirred for 10 minutes until the solution was clear. Then, 4.5 mmol of excess thioacetamide (150% of the sum of the molar amounts of ZnCl2 and InCl3·4H2O) was added to the mixed solution, and stirred continuously for 30 minutes. The above mixed solution was then transferred to a stainless steel high-pressure reactor lined with polystyrene, with the solution occupying 70% of the total volume of the reactor liner; the high-pressure reactor was sealed under hydrothermal conditions and kept at 180 °C for 24 hours. After the product was naturally cooled to room temperature, it was washed three times by centrifugation with deionized water and anhydrous ethanol, respectively. Finally, the washed sample was dried overnight in a vacuum oven at 60 °C to obtain approximately 0.42 g of ZnIn2S4 powder.

[0037] (2) Preparation of 0.1LiCl-ZnIn2S4: 1 mmol of LiCl and 9 mmol of ZnIn2S4 powder were mixed at a stoichiometric ratio (molar ratio) of 1:9 and manually ground in an agate mortar for 30 minutes; then transferred to a zirconia ball mill jar and ball-milled at 400 rpm for 16 hours. The diameter of the zirconia grinding balls was 5 mm, and the ball-to-material ratio was 20:1. The above process was carried out in an air atmosphere. After ball milling, 0.1LiCl-ZnIn2S4 sulfide solid electrolyte was obtained.

[0038] Example 2

[0039] Prepared in the same manner as in Example 1, except that in step (2), 3 mmol of LiCl and 7 mmol of ZnIn2S4 powder are mixed in a stoichiometric ratio (molar ratio) of 3:7 to obtain 0.3LiCl-ZnIn2S4 sulfide solid electrolyte.

[0040] Example 3

[0041] Prepared in the same manner as in Example 1, except that in step (2), 5 mmol of LiCl and 5 mmol of ZnIn2S4 powder are mixed in a stoichiometric ratio (molar ratio) of 1:1 to obtain 0.5LiCl-ZnIn2S4 sulfide solid electrolyte.

[0042] Example 4

[0043] Prepared in the same manner as in Example 1, except that in step (2), 7 mmol of LiCl and 3 mmol of ZnIn2S4 powder are mixed in a stoichiometric ratio (molar ratio) of 7:3 to obtain 0.7LiCl-ZnIn2S4 sulfide solid electrolyte.

[0044] Example 5

[0045] Prepared in the same manner as in Example 1, except that in step (2), 9 mmol of LiCl and 1 mmol of ZnIn2S4 powder are mixed in a stoichiometric ratio (molar ratio) of 9:1 to obtain 0.9LiCl-ZnIn2S4 sulfide solid electrolyte.

[0046] Comparative Example 1

[0047] This comparative example provides a method for preparing Li6PS5Cl, where all raw materials are commercially available. The preparation method includes the following steps:

[0048] (1) Preparation of precursor powder: LiCl, Li2S and P2S5 were mixed in a stoichiometric ratio (molar ratio) of 2:5:1 and then ball-milled. The ball milling speed was 200 rpm and the ball milling time was 2 hours. The diameter of the zirconia grinding balls was 5 mm and the ball-to-material ratio was 15:1.

[0049] (2) Preparation of sulfide solid electrolyte: The precursor powder was placed in a vacuum furnace for sintering at a heating rate of 1.5℃ / min. -1 The sintering temperature was 600℃ and the sintering time was 10 hours. After natural cooling to room temperature, Li6PS5Cl sulfide solid electrolyte was obtained.

[0050] Application Example 1

[0051] This embodiment provides a method for preparing an all-solid-state lithium-ion battery, and all raw materials used in the preparation are commercially available. The preparation method includes the following steps:

[0052] (1) Preparation of positive electrode powder: Ni90 ternary positive electrode active material, 0.5LiCl-ZnIn2S4 sulfide solid electrolyte prepared in Example 3, and conductive additive VGCF are mixed uniformly in a mass ratio of 70:30:3 for later use;

[0053] (2) Preparation of negative electrode: Under the protection of argon atmosphere, Li-In alloy is cut into circular pieces with a diameter of 1cm;

[0054] (3) Assembly of all-solid-state lithium-ion battery: First, press the 0.5LiCl-ZnIn2S4 sulfide solid electrolyte prepared in Example 3 into a dense disc in the battery. Then, place the positive electrode powder obtained in step (1) on one side of the solid electrolyte and apply pressure to make the positive electrode powder uniformly adhere to the surface of the solid electrolyte. Finally, place the negative electrode sheet obtained in step (2) on the other side of the solid electrolyte and apply pressure to make the negative electrode sheet tightly adhere to the surface of the solid electrolyte, and the all-solid-state lithium-ion battery can be obtained.

[0055] The sulfide solid electrolyte described in this invention only serves to improve ionic conductivity in the positive electrode and does not provide actual capacity.

[0056] like Figure 1 and Figure 2The figures show the room-temperature AC impedance spectra of xLiCl-ZnIn2S4 sulfide solid electrolytes (x = 0.1, 0.3, 0.5, 0.7, and 0.9, respectively) in Examples 1, 2, 3, 4, and 5. The comparison reveals that the ionic conductivity of the sulfide solid electrolyte is closely related to the ratio of LiCl to ZnIn2S4. LiCl provides charge carriers for the sulfide solid electrolyte; therefore, when the LiCl content is low, there are fewer charge carriers, resulting in lower conductivity. Conversely, when the LiCl content is too high, charge carriers occupy most of the ion mobility sites, thus blocking ion transport channels and limiting ion transport in the sulfide solid electrolyte. Therefore, when 0.3 ≤ x ≤ 0.7, the sulfide solid electrolyte exhibits higher ionic conductivity.

[0057] like Figure 3 The figure shows the AC impedance spectrum of 0.5LiCl-ZnIn2S4 in Example 3 after being exposed to air for 60 days. It can be observed that the impedance of the sulfide solid electrolyte remains essentially unchanged, indicating that this sulfide solid electrolyte material has good air stability and that exposure to air does not affect its ionic conductivity.

[0058] like Figure 4 The image shows the XRD patterns of 0.5LiCl-ZnIn2S4 in Example 3 before and after being exposed to air for 60 days. The image shows no change in the XRD diffraction peaks, further demonstrating the excellent air stability of this sulfide solid electrolyte.

[0059] To further highlight the effects of this invention, Table 1 summarizes the room-temperature ionic conductivity of different embodiments and comparative examples. As shown in Table 1, the ordinary sulfide solid electrolyte (the product of Comparative Example 1) has poor air stability, and its ionic conductivity decreases significantly after contact with air. In contrast, the novel sulfide solid electrolyte prepared by this invention exhibits excellent air stability, maintaining its original ionic conductivity level even after being placed in air for 60 days, thus providing a possibility for the preparation of sulfide solid electrolytes in air and the assembly of all-solid-state batteries.

[0060] Table 1. Room temperature ionic conductivity of different embodiments and comparative examples

[0061]

[0062] Figure 5 This is the cycle performance curve of the all-solid-state lithium-ion battery in Application Example 1 of the present invention. The all-solid-state lithium-ion battery can provide 197 mA hg. -1The reversible specific capacity and almost no capacity decay after 100 stable cycles demonstrate that the sulfide solid electrolyte provided by this invention can provide the high ionic conductivity required for the operation of all-solid-state lithium-ion batteries, while also ensuring good stability and compatibility with the electrodes, thereby ensuring stable cycling of solid-state lithium-ion batteries and further verifying its good practicality.

[0063] In summary, the sulfide solid electrolyte of this invention exhibits high room temperature ionic conductivity, good air stability, and good compatibility with electrode materials, making it suitable for all-solid-state battery systems. Based on the hard-soft acid-base theory, this invention selects an electrolyte that tends to react with soft bases (S0). 2- The tightly bound soft acids, i.e., metal cations with low positive charge and high polarizability, form strong covalent bonds to resist the erosion and hydrolysis by H2O, thereby improving the air stability of the sulfide solid electrolyte. The sulfide solid electrolyte of this invention can be synthesized in air without atmosphere control; the preparation method is simple, feasible, and easily scalable.

[0064] While the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the invention to these descriptions. Various changes in form and detail can be made by those skilled in the art, including several simple deductions or substitutions, without departing from the spirit and scope of the invention.

Claims

1. A sulfide solid electrolyte, characterized in that, The general chemical formula of the sulfide solid electrolyte is xAB-R. y S z Where AB is a halide, A is one of Li, Na, and K, and B is one of F, Cl, Br, and I; x represents the molar ratio of AB to the sulfide solid electrolyte material as x:1, 0.3≤x≤0.7; R y S z It is ZnIn2S4.

2. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that: The steps are as follows: 1) R y S z Powder preparation Method 1: Prepare R using a simple hydrothermal method y S z powder A metal salt containing R was dissolved in deionized water, and an excess of thioacetamide was added and stirred until homogeneous. The resulting mixture was transferred to a stainless steel high-pressure reactor lined with polystyrene, with the mixture occupying 60-80% of the total volume of the reactor liner. The high-pressure reactor was sealed and subjected to a hydrothermal reaction. After the hydrothermal reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting product was washed by centrifugation with deionized water and anhydrous ethanol, and then dried to obtain R. y S z powder; Method 2: Preparation of R using solid-state method y S z powder A metal salt containing R and sulfur powder were uniformly mixed according to a stoichiometric ratio, vacuum sintered, and then naturally cooled to room temperature to obtain R. y S z powder; 2) xAB-R y S z Preparation xAB-R was prepared by ball milling. y S z That is, weigh AB and R according to the stoichiometric ratio. y S z The powder was ground and then ball-milled to obtain xAB-R. y S z Sulfide solid electrolyte.

3. The method for preparing a sulfide solid electrolyte as described in claim 2, characterized in that: In step 1) of method one, the metal salt containing R is a chloride, nitrate, sulfate or ammonium salt.

4. The method for preparing a sulfide solid electrolyte as described in claim 2, characterized in that: In step 1) of method one, the concentration of metal ions in the deionized aqueous solution containing the metal salt of R is 0.02~0.2 mol / L. -1 The amount of thioacetamide added is 120-150% of the stoichiometric ratio.

5. The method for preparing a sulfide solid electrolyte as described in claim 2, characterized in that: In step 1) of method one, the hydrothermal reaction temperature is 150~200℃ and the hydrothermal reaction time is 12~24 hours; the drying temperature is 60~100℃ and the drying time is 5~12 hours.

6. The method for preparing a sulfide solid electrolyte as described in claim 2, characterized in that: In step 1) of method two, the sintering temperature is 400~800℃ and the sintering time is 10~30 hours.

7. The method for preparing a sulfide solid electrolyte as described in claim 2, characterized in that: In step 2), the grinding time is 20-40 minutes; the ball mill speed is 300-500 rpm; the ball milling time is 5-20 hours; and the ball-to-material ratio is 15-20:

1.

8. An all-solid-state lithium-ion battery, characterized in that: The all-solid-state lithium-ion battery was prepared using the sulfide solid electrolyte of claim 1 as the electrolyte and the positive electrode additive.

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