High-conductivity and high-lithium-stability modified halide solid electrolyte material constructed by solid source plasma, and preparation method and application of high-conductivity and high-lithium-stability modified halide solid electrolyte material

Abstract

The invention belongs to the technical field of halide solid-state electrolyte, and relates to a high-conductivity and high-lithium-stability modified halide solid-state electrolyte material constructed by solid source plasma, and a preparation method and application of the high-conductivity and high-lithium-stability modified halide solid-state electrolyte material. According to the preparation method, a halide solid electrolyte is taken as a matrix, halogenated ammonium salt is taken as a solid source, and the halide solid electrolyte is subjected to synergistic doping modification of elements such as nitrogen, fluorine / chlorine / bromine and the like by utilizing a plasma technology, so that the modified halide solid electrolyte material is obtained. The modified halide solid electrolyte material shows excellent conductivity and lithium-lithium symmetrical battery performance, and has a wide market application prospect. Meanwhile, the preparation method provided by the invention is simple, rapid, efficient and convenient, is easy to control, and contributes to promoting the development and application of the high-performance halide solid electrolyte material.

Description

Technical Field

[0001] The present invention relates to the technical field of halide solid electrolyte materials, and in particular to a solid source plasma-constructed modified halide solid electrolyte material with high conductivity and high stability to lithium, as well as a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries, due to their high energy density and long cycle life, have been widely used in a variety of fields, including portable digital electronic products, electric vehicles, and renewable energy storage systems. However, the organic electrolytes used in traditional lithium-ion batteries are flammable and explosive, which poses a serious safety risk to the battery. In contrast, solid-state batteries, due to their use of solid electrolytes, not only have higher safety but also can provide higher energy density. Therefore, they are considered to be a key direction for the development of future battery technology. In the development of solid-state batteries, the lithium-ion conductivity, chemical / electrochemical stability, and processability of solid electrolyte materials are key factors that need to be considered.

[0003] At present, researchers are actively exploring a variety of potential candidate materials for all-solid-state electrolytes. Sulfide, oxide, boride and halide electrolytes among inorganic solid electrolytes are the main research objects. Among them, halide electrolytes perform well in terms of electrochemical stability, but the lithium ion conductivity is relatively low. Density functional theory (DFT) calculations show that the lithium ion conductivity of halide electrolytes can be further improved by element doping. However, the existing doping methods are mainly through mechanical ball milling and sintering, which have a long synthesis cycle, a cumbersome preparation process and high energy consumption. Therefore, the development of a simple, fast and clean synthesis method for halide solid electrolytes is considered to have high development potential and is expected to become an important part of future solid-state battery technology.

[0004] Based on this, the present invention proposes a solid-source plasma-constructed modified halide solid electrolyte material with high conductivity and high lithium stability, as well as its preparation method and application. The above strategies are effectively combined to dope and modify the halide solid electrolyte material, thereby improving the conductivity of the halide electrolyte and improving the interface stability between the halide electrolyte and the lithium negative electrode, which is helpful to promote the development and application of halide electrolyte materials. Summary of the Invention

[0005] The present invention mainly addresses the problems of low electronic conductivity, poor stability to lithium, and insufficient cycle stability of halide electrolyte materials, and provides a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma, as well as a preparation method and application thereof. By adopting plasma technology, a large number of highly active free radicals are excited by solid source plasma of ammonium salts, and nitrogen, fluorine / chlorine / bromine element doping and coating of the halide electrolyte are achieved at low temperature, thereby optimizing the conductivity and poor stability to lithium of the halide electrolyte material and improving the electrochemical performance of the material.

[0006] The technical solution adopted by the present invention to solve its technical problem is: A method for preparing a modified halide solid electrolyte material with high conductivity and high lithium stability constructed by solid source plasma. The method uses a halide solid electrolyte as a matrix and an ammonium halide salt as a solid source, and dopes the halide electrolyte with nitrogen and halogen elements fluorine / chlorine / bromine through a one-step plasma method to obtain the modified halide solid electrolyte material.

[0007] Preferably, the method comprises the following steps: (1) Placing the halide solid electrolyte inside the plasma reaction device and connecting it to the plasma generator, and vacuuming the reaction area of ​​the plasma reaction device; (2) Connecting to an external solid source, the solid source sublimates into the interior of the plasma reaction device to a certain vacuum degree, and controlling the ignition of the solid source plasma by adjusting the radio frequency power to react with the halide solid electrolyte material in a plasma. After a certain reaction time, the radio frequency power is turned off to obtain a modified halide solid electrolyte material doped with nitrogen and halogen elements fluorine / chlorine / bromine.

[0008] The following are the preferred technical solutions of the present invention: Preferably, in step (1), the halide solid electrolyte is a Li3MX6 solid electrolyte, wherein M is selected from at least one of In, Sc, Y, Er, Tb, Zr, Zn, Sn, Yb, or Lu, and X is selected from at least one of Cl, Br, or I.

[0009] Preferably, in step (1), the selected halide electrolyte sample is in at least one of a flake and a powder form. More preferably, the sample can be processed more uniformly by a rotating plasma device, and can react more fully with the introduced solid source plasma.

[0010] Preferably, in step (1), the vacuum is evacuated to a vacuum degree of 1-70 Pa, which is a vacuum state.

[0011] Preferably, in step (2), the solid source is at least one of ammonium fluoride, ammonium chloride, or ammonium bromide.

[0012] Preferably, in step (2), the solid source is heated to a sublimation state and sublimated into the interior of the plasma reaction device. If the solid source and the solid electrolyte are directly mixed and placed in the plasma reaction device for reaction, it will be difficult to control the reaction process and impurities are likely to remain. Therefore, the solid source is introduced into the plasma reaction device by sublimation of the solid source, so as to better excite the solid source into a plasma state and react with the solid electrolyte.

[0013] Preferably, in step (2), the vacuum degree of the system after the solid source is introduced is preferably 5-200 Pa.

[0014] Preferably, in step (2), the plasma reaction device may be heated before the solid source is introduced, and the system temperature is heated to the reaction temperature, specifically room temperature to 500 o C. By using this temperature range, especially heating, the introduced solid source can be more easily excited into a plasma state.

[0015] Preferably, in step (2), the reaction conditions are: RF power of 50-300 W, reaction temperature of room temperature to 500 °C, and reaction time of 1-30 min; furthermore, the vacuum degree is preferably 5-200 Pa.

[0016] Preferably, in step (2), nitrogen and halogen elements are synergistically doped and modified, and the halogen elements include at least one of fluorine, chlorine, and bromine; more preferably, the doping amount of nitrogen is 0.5-5% of the mass of the modified halide solid electrolyte material, and the doping amount of halogen elements is 0.5-5% of the mass of the modified halide solid electrolyte material.

[0017] Preferably, the room temperature in the present invention is 10-40°C, more preferably 15-25°C.

[0018] The present invention also provides a solid source plasma-constructed modified halide solid electrolyte material with high electrical conductivity and high stability to lithium, which is prepared by any of the above preparation methods.

[0019] Preferably, the halide solid electrolyte nitrogen and the halogen elements fluorine / chlorine / bromine are synergistically doped and modified.

[0020] The present invention also provides a method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium by solid source plasma in the field of lithium ion batteries.

[0021] The present invention uses the aforementioned plasma technology to excite a solid-source ammonium salt to form a large number of highly active free radicals. This allows for the coordinated doping and modification of the halide solid electrolyte with nitrogen and fluorine / chlorine / bromine elements under low-temperature heating conditions, thereby optimizing the halide solid electrolyte's conductivity and stability to lithium. The nitrogen and fluorine / chlorine / bromine doping levels prepared by the present invention can be controlled by parameters such as exposure time, radio frequency power, and heating temperature.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) Through the solid plasma effect, a one-step preparation method is achieved for nitrogen and fluorine / chlorine / bromine doped halide electrolyte materials. The preparation method is simple, fast, efficient, and under mild conditions; (2) Synergistic doping with nitrogen and fluorine / chlorine / bromine elements can simultaneously optimize the bulk structure and surface interface properties of the material, overcoming the limitations of single doping. It can improve the ionic conductivity of halide electrolytes, improve the material's stability to lithium, and effectively enhance material performance; (3) Through the synergistic effect of temperature and plasma, the nitrogen and fluorine / chlorine / bromine doping amounts can be precisely adjusted to improve the chemical composition and interface properties of halide electrolytes, thereby achieving the controllability of material properties and further expanding the application of materials; The present invention utilizes a one-step reaction between solid-source plasma excitation and a halide electrolyte material. Synergistic doping with nitrogen and fluorine / chlorine / bromine is a highly effective method for optimizing halide solid electrolyte materials, enhancing their ionic conductivity and lithium stability, resulting in excellent conductivity and lithium-lithium symmetric battery performance. Furthermore, the preparation method provided by the present invention is simple, rapid, efficient, convenient, and easy to control, contributing to the development and application of high-performance halide solid electrolyte materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 SEM images of the nitrogen and fluorine co-doped Li3InCl6 halide electrolyte in Example 1 and the unmodified Li3InCl6 halide electrolyte in Comparative Example 1; Figure 2 Element distribution diagram of the Li3InCl6 halide electrolyte co-doped with nitrogen and fluorine in Example 1; Figure 3 XRD patterns of the nitrogen and fluorine co-doped Li3InCl6 halide electrolyte prepared in Example 1 and Comparative Example 1; Figure 4 This is the ionic conductivity diagram of the Li3InCl6 halide electrolyte co-doped with nitrogen and fluorine elements prepared in Example 1. DETAILED DESCRIPTION

[0024] For ease of understanding, the technical solutions and implementation methods of the present invention are further described clearly, completely and in detail through specific examples and in combination with the accompanying drawings. It should be noted that the embodiments described in the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are given, but they are only part of the embodiments of the present invention, not all of the embodiments. The specific implementation methods described are limited to illustrating and explaining the present invention and do not limit the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] The experimental methods and conditions used in the following examples are conventional methods and conventional conditions unless otherwise specified. The materials, reagents, instruments, devices, etc. used in the examples are conventional substances or equipment known to those skilled in the art and can be obtained from commercial channels unless otherwise specified. The reaction conditions embodied in the summary of the invention are all capable of achieving the described reactions and obtaining products with the desired effects. Due to space limitations, only some examples are listed below to further illustrate the advantages of the technical solutions of the present invention.

[0026] Example 1

[0027] A powdered sample of a Li₃InCl₆ halide electrolyte (see the method in Comparative Example 1) was placed in the reaction zone of a rotating plasma reactor. Copper rings were attached to both ends of the plasma reactor and connected to the RF power generator (plasma generator) via wires. The plasma reactor was then evacuated to 10 Pa and maintained in this state. The temperature was then heated to 200°C. A solid ammonium fluoride source was then connected and heated and sublimated using a heating mantle, allowing the ammonium fluoride solid source to enter the plasma reactor, raising the vacuum to 40 Pa. The RF power was turned on, and the RF power was adjusted to 100 W. The vacuum pump was adjusted to maintain a vacuum of 20 Pa and a reaction temperature of 200°C. After ignition, the ammonium fluoride plasma reaction zone excited a large number of highly active free radicals, which reacted with the surface of the halide solid electrolyte. After a 5-minute plasma reaction, the RF power was turned off, yielding a Li₃InCl₆ halide electrolyte material co-doped with nitrogen and fluorine.

[0028] Example 2-25

[0029] On the basis of Example 1, the reaction conditions including solid source, reaction temperature, reaction power, reaction time, etc. were changed. The specific conditions are shown in Table 1 below.

[0030]

[0031] Examples 26-35

[0032] On the basis of Example 1, the precursor was changed to Li3InBr6 solid electrolyte (refer to the method of Comparative Example 9), and some reaction conditions in Table 1 were selected for the experiment. The specific conditions are shown in Table 2 below.

[0033]

[0034] Comparative Example 1

[0035] Lithium chloride and indium chloride were weighed in a molar ratio of 3:1, and ball-milled at a speed of 500 r / min for 24 h in an argon atmosphere. o C min -1 Heat up to 260 o C, keep warm for 5 h and cool naturally to obtain Li3InCl6 halide electrolyte powder.

[0036] Comparative Example 2

[0037] The Li3InCl6 halide electrolyte material in Comparative Example 1 was placed in a common tube furnace, nitrogen protective gas was introduced, and then o C min -1 The heating rate was increased to 200 °C, kept at this temperature for 2 h and then cooled naturally, but element doping was not successfully achieved.

[0038] Comparative Example 3

[0039] The Li3InCl6 halide solid electrolyte material in Comparative Example 1 was placed in an ordinary tube furnace, and ammonium fluoride solid with a mass of 5% of the Li3InCl6 halide solid electrolyte was added, and nitrogen protective gas was introduced, and then the mixture was heated at 5 o C min -1 The heating rate was increased to 200 o C, after keeping warm for 2 h and then cooling naturally, element doping was not successfully achieved.

[0040] Comparative Example 4

[0041] The Li3InCl6 halide electrolyte material in Comparative Example 1 was placed in a common tube furnace, and ammonium chloride solid with a mass of 5% of the Li3InCl6 halide solid electrolyte was added, and nitrogen protective gas was introduced, and then the mixture was heated at 5 o C min -1 The heating rate was increased to 200 o C, after keeping warm for 2 h and then cooling naturally, element doping was not successfully achieved.

[0042] Comparative Example 5

[0043] The Li3InCl6 halide electrolyte material in Comparative Example 1 was placed in an ordinary tube furnace, and 5% ammonium bromide solid was added with the mass of Li3InCl6 halide solid electrolyte, and nitrogen protective gas was introduced, and then 5 o C min -1 The heating rate was increased to 200 o C, after keeping warm for 2 h and then cooling naturally, element doping was not successfully achieved.

[0044] Comparative Example 6

[0045] The Li3InCl6 halide electrolyte material in Comparative Example 1 was placed in a hydrothermal high-pressure reactor, and 5% ammonium fluoride solid was added with the mass of Li3InCl6 halide solid electrolyte. It was placed in a hydrothermal oven at 180°C and kept warm for 10 hours. After natural cooling, element doping was not successfully achieved.

[0046] Comparative Example 7

[0047] The Li3InCl6 halide electrolyte material from Comparative Example 1 was placed in the reaction zone of a rotating plasma reactor. Copper rings were attached to both ends of the plasma reactor and connected to the RF power generator (plasma generator) with wires. The plasma reactor was then evacuated to 10 Pa and maintained in this state, and the temperature was heated to 200°C. A solid ammonium fluoride source was introduced, the RF power switch was turned on, the RF power was adjusted to 10 W, and the vacuum pump was adjusted to maintain a vacuum of 30 Pa. After 10 minutes of treatment, the material was naturally cooled to obtain a modified Li3InCl6 halide electrolyte material, but doping was not successfully achieved.

[0048] Comparative Example 8

[0049] The Li3InCl6 halide electrolyte material from Comparative Example 1 was placed in the reaction zone of a rotating plasma reactor. Copper rings were attached to both ends of the plasma reactor and connected to the RF power generator (plasma generator) with wires. The plasma reactor was then evacuated to 10 Pa and maintained in this state, and the temperature was heated to 200°C. A solid ammonium fluoride source was introduced, the RF power switch was turned on, the RF power was adjusted to 500 W, and the vacuum pump was adjusted to maintain a vacuum of 30 Pa. After 10 minutes of treatment, the material was naturally cooled to obtain a modified Li3InCl6 halide electrolyte material, but doping was unsuccessful.

[0050] Comparative Example 9

[0051] Lithium bromide and indium bromide with a molar ratio of 3:1 were weighed and ball-milled at a speed of 500 r / min for 24 h in an argon atmosphere. o C min-1 Heat up to 260 o C, keep warm for 5 h and cool naturally to obtain Li3InBr6 halide electrolyte powder.

[0052] Performance Test 1

[0053] The Li3InCl6 halide electrolyte sample powders prepared in Examples 1-25 and Comparative Examples 1-8 were pressed into tablets. To test the ionic conductivity of the electrolyte, carbon-coated aluminum foil was placed at both ends of the tablets, which were then placed in a button cell to maintain pressure for testing. The tablets were connected to an electrochemical workstation, the test parameters were set, and the test was started. The AC impedance test frequency range was 1 MHz to 0.1 Hz, and the voltage amplitude was 5-10 mV. To test the electrolyte's lithium stability, the battery was assembled in the order of positive electrode shell, lithium sheet, halide electrolyte sheet, lithium sheet, and negative electrode shell, and sealed with a packaging machine. After the battery was allowed to rest for 24 hours, electrochemical testing was performed using a Xinwei testing system.

[0054] The performance test results are shown in Table 3 below.

[0055]

[0056] From the performance test results of each embodiment and comparative example in Table 3, it can be found that Examples 1-25 are modified by plasma doping, and the excitation source is an ammonium salt solid source. The electrochemical properties of the obtained halide solid electrolyte are generally excellent, and the ionic conductivity and lithium-lithium symmetrical battery cycle time are significantly improved. In Comparative Examples 1-8, after conventional interface treatment and other inorganic source plasma treatment, the electrochemical performance is also improved relative to the untreated halide solid electrolyte, but the effect is obviously not as good as the modified electrolyte after plasma treatment with nitrogen, fluorine / chlorine / bromine elements defined in the present invention. This shows that the halide solid electrolyte is more suitable for doping modification with nitrogen, fluorine / chlorine / bromine element plasma to improve various related electrochemical properties of the electrolyte.

[0057] Performance Test 2

[0058] The Li3InBr6 halide electrolyte sample powders prepared in Examples 26-35 and Comparative Example 9 were pressed into tablets, and the ionic conductivity and lithium stability were tested according to the method of Performance Test 1. The performance test results are shown in Table 4 below.

[0059]

[0060] From the performance test results of the various examples and comparative examples in Table 4, it can be found that Examples 26-35 use plasma doping modification, the excitation source is an ammonium salt solid source, and the precursor is a Li3InBr6 halide electrolyte. Compared with the untreated Comparative Example 9, the resulting halide solid electrolytes generally have excellent electrochemical properties, with significant improvements in ionic conductivity and lithium-lithium symmetric battery cycle time. This shows that not only Li3InCl6 halide solid electrolytes, but other halide solid electrolytes (such as the aforementioned Li3InBr6) can also be modified by nitrogen, fluorine / chlorine / bromine elemental plasma doping to improve various related electrochemical properties of the electrolyte.

[0061] Figure 1 The SEM images of the nitrogen- and fluorine-co-doped Li3InCl6 halide electrolyte in Example 1 and the unmodified Li3InCl6 halide electrolyte in Comparative Example 1 are shown. Compared with the unmodified Li3InCl6 halide electrolyte, the nitrogen- and fluorine-co-doped Li3InCl6 halide electrolyte exhibits uniformly distributed small particles on its surface. Figure 2 This is an element distribution diagram of the Li3InCl6 halide electrolyte co-doped with nitrogen and fluorine elements in Example 1. Fluorine and nitrogen elements are evenly distributed in the Li3InCl6 halide electrolyte, achieving effective fluorine and nitrogen doping; Figure 3 XRD patterns of the nitrogen and fluorine co-doped Li3InCl6 (LIC-NH4F) halide electrolyte prepared in Example 1 and the unmodified Li3InCl6 halide electrolyte (LIC) of Comparative Example 1, as well as a PDF card diagram of Li3InCl6 numbered PDF#70-3274 in the standard powder diffraction database; the XRD test results of the nitrogen and fluorine co-doped Li3InCl6 halide electrolyte are not significantly different from those of the unmodified Li3InCl6 halide electrolyte, indicating that the plasma doping technology does not change the crystal structure of the Li3InCl6 halide, can well maintain the structure of the material, and effectively achieve elemental doping without changing the structure; Figure 4 This is the ionic conductivity diagram of the nitrogen and fluorine co-doped Li3InCl6 (LIC-NH4F) halide electrolyte prepared in Example 1 and the unmodified Li3InCl6 halide electrolyte (LIC) of Comparative Example 1. The ionic conductivity of the nitrogen and fluorine co-doped Li3InCl6 halide electrolyte is 0.58 mS / cm, and the ionic conductivity of the unmodified Li3InCl6 halide electrolyte is only 0.44 mS / cm. The ionic conductivity of the halide electrolyte after plasma treatment is significantly improved.

[0062] The present application uses solid source plasma technology to dope and modify halide electrolytes with nitrogen, fluorine / chlorine / bromine elements, thereby achieving higher ionic conductivity and stability to lithium.

[0063] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma, characterized in that: The method uses a halide solid electrolyte as a matrix and an ammonium halide salt as a solid source, and modifies the halide solid electrolyte through a one-step plasma method to obtain a modified halide solid electrolyte material.

2. The method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma according to claim 1, characterized in that: The halide solid electrolyte is a Li3MX6 solid electrolyte, wherein M is selected from at least one of In, Sc, Y, Er, Tb, Zr, Zn, Sn, Yb, or Lu, and X is selected from at least one of Cl, Br, or I.

3. The method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma according to claim 1, characterized in that: The solid source is at least one of ammonium fluoride, ammonium chloride, or ammonium bromide.

4. The method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Placing the halide solid electrolyte inside the plasma reaction device, connecting it to the plasma generator, and performing vacuum treatment; (2) Connecting to an external solid source, the solid source sublimates into the interior of the plasma reaction device to a certain vacuum degree, adjusting the radio frequency power, and reacting for a certain time after ignition to obtain a modified halide solid electrolyte material.

5. The method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma according to claim 4, characterized in that: In step (1), the vacuum is evacuated to a vacuum degree of 1-70 Pa.

6. The method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma according to claim 5, characterized in that: In step (2), after the solid source is introduced, the system vacuum degree is 5-200 Pa; And / or, the temperature of the reaction device is room temperature to 500° C. when the solid source is introduced.

7. The method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma according to claim 6, characterized in that: The radio frequency power in step (2) is 50-300 W, the reaction temperature is room temperature-500 ° C, and the reaction time is 1-30 min.

8. The method for preparing a modified halide solid electrolyte material with high conductivity and high stability to lithium constructed by solid source plasma according to claim 4, characterized in that: The doping amounts of nitrogen element and halogen element in the modified halide solid electrolyte material are 0.5-5% of the mass of the modified halide solid electrolyte material respectively.

9. A modified halide solid electrolyte material with high conductivity and high stability to lithium prepared by the preparation method according to any one of claims 1 to 8 and constructed by solid source plasma.

10. Use of the solid-source plasma-constructed modified halide solid electrolyte material with high conductivity and high lithium stability according to claim 9 in the field of lithium-ion batteries.

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