CN113363567A

CN113363567A - Halide solid electrolyte and preparation method and application thereof

Info

Publication number: CN113363567A
Application number: CN202110729896.7A
Authority: CN
Inventors: 孙学良; 王长虹; 徐国峰; 梁剑文; 王建涛; 李晓娜; 赵尚骞; 黄欢; 杨容
Original assignee: University of Western Ontario; China Automotive Battery Research Institute Co Ltd
Current assignee: University of Western Ontario; China Automotive Battery Research Institute Co Ltd
Priority date: 2021-06-29
Filing date: 2021-06-29
Publication date: 2021-09-07

Abstract

The invention provides a halide solid electrolyte and a preparation method and application thereof, wherein the chemical formula of the halide solid electrolyte is Li₃MX₆M is at least one of rare earth elements, and X is at least one of F, Cl, Br and I; the halide solid electrolyte has a structural microstress of 0.001 to 0.01. According to the halide solid electrolyte provided by the invention, the internal stress of the material is induced, so that the obvious structural micro stress reaches 0.001-0.01, the ionic conductivity is obviously improved and is 6-10 times higher than that of the electrolyte prepared by the traditional high-temperature solid phase method; furthermore, the electrochemical window and other properties are not affected, so that the solid-state secondary battery can be widely applied to the solid-state secondary battery.

Description

Halide solid electrolyte and preparation method and application thereof

Technical Field

The invention relates to the technical field of secondary batteries, in particular to a halide solid electrolyte and a preparation method and application thereof.

Background

The all-solid secondary battery has higher safety than the lithium ion secondary battery currently in commercial use. This is because the all-solid-state secondary battery employs a nonflammable inorganic fast-ion material as an electrolyte. With the development of recent years, several ion conductance higher than 1mS cm have been developed^-1The solid electrolyte material of (1). These materials are based on sulfide and oxide electrolytes, including Li₁₀Ge₂P₂S₁₂，Li₆PS₅Cl，Li₇P₃S₁₁And Li₃PS₄Etc.; the oxide electrolyte mainly contains Li_1.3Al_0.3Ti_1.7(PO₄)₃，Li₇La₃Zr₂O₁₂And the like. However, sulfide electrolytes are unstable in air and water, and are liable to generate toxic gases such as hydrogen sulfide, and therefore, the operation needs to be performed in an environment in which inert gas is a protective atmosphere; the oxide electrolyte can form a phase under the high-temperature condition, the phase forming temperature is over 1000 ℃, and the mass preparation and production are difficult.

In recent years, halide solid electrolytes have been used for their good mechanical properties and stability to high voltage positive electrode materials, and there is no sulfide electrolysisThe electrolyte generates hydrogen sulfide gas, oxide electrolyte is difficult to prepare in large quantity, and the like, and the electrolyte is gradually favored by people. However, the prior art halide solid state electrolytes, particularly halide electrolytes of hcp structure, have low room temperature ionic conductivity (10 to 10)^-5S/cm), poor dynamic conditions of the electrode process, and low lithium ion transmission efficiency, which may affect the rate characteristics of the solid-state secondary battery, and the battery may not maintain normal operation at high power.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a halide solid electrolyte, a preparation method and application thereof, and the halide solid electrolyte with high ionic conductivity is obtained, so that the electrochemical performance of a solid secondary battery is improved.

The invention provides a halide solid electrolyte with a chemical formula of Li₃MX₆M is at least one of rare earth elements, and X is at least one of F, Cl, Br and I; the halide solid electrolyte has a structural microstress of 0.001 to 0.01.

Further, the structural microstress of the halide solid electrolyte is expressed as compressive force in the a, b direction and tensile force in the c direction of the unit cell structure, and the unit cell structure is distorted under the structural microstress.

Further, the particle size D50 of the halide solid electrolyte is 10-500 nm.

Further, the anion arrangement of the halide solid state electrolyte is hexagonal close-packed or tetragonal close-packed.

Further, the halide solid electrolyte is Li₃YCl₆、Li₃ErCl₆、Li₃YbCl₆、Li₃DyCl₆、Li₃TmCl₆。

The invention also provides a preparation method of the halide solid electrolyte, which adopts a liquid phase synthesis method to prepare and comprises the following steps:

MX is dissolved in polar solvent containing hydrolysis inhibitor₃Mixing with LiX for reaction, and pyrolyzing the obtained reaction product at 450-600 ℃ to obtain the halideA solid electrolyte.

Further, after the mixing reaction, the reaction system is dehydrated and dried under vacuum at 80 +/-5 ℃ to obtain the reaction product.

Further, the hydrolysis inhibitor is NH₄X and X are halogen.

Preferably, NH₄X、MX₃And the molar ratio of LiX is 3:1: 3.

Further, the polar solvent is water and/or ethanol.

The invention also provides application of the halide solid electrolyte, in particular to an electrolyte or electrode additive in a solid secondary battery.

According to the halide solid electrolyte provided by the invention, the internal stress of the material is induced, so that the obvious structural micro stress reaches 0.001-0.01, the ionic conductivity is obviously improved and is 6-10 times higher than that of the electrolyte prepared by the traditional high-temperature solid phase method; and does not affect the performances such as electrochemical window, etc., thereby being widely applied to solid secondary batteries.

Drawings

FIG. 1 shows nano-Li in an embodiment of the present invention₃YCl₆The structural microstress calculation schematic diagram of (1);

FIG. 2 shows Li in an example of the present invention₃YCl₆Schematic of the crystal structure of (a).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention are described clearly and completely below, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention provides a halide solid electrolyte with a chemical formula of Li₃MX₆M is at least one of rare earth elements, and X is at least one of F, Cl, Br and I; the halide solidThe structural microstress of the state electrolyte is 0.001-0.01.

Wherein the calculation formula of the structural micro stress is

In the formula: ε is the structural microstress, β_TIs the half-value width (unit rad) of the X-ray diffraction peak, and K is the shape factor

λ is the wavelength of the incident light (λ ═ 0.15405nm), θ is the diffraction angle (rad), D is the crystallite size (nm), a Williamson-Hall line can be fitted by correlation parameters of at least 5 diffraction peaks, with the abscissa 4sin θ and the ordinate β_TThe slope of the cos theta line is the micro stress magnitude epsilon, and the crystallite size D can be determined according to the intercept

And was obtained as shown in fig. 1.

According to the research of the invention, the internal stress of the halide solid electrolyte material obtained by the traditional high-temperature solid phase sintering is not obvious, and when a certain means is adopted to induce the internal stress of the material, the material has obvious structural micro stress which is 0.001-0.01, the ionic conductivity of the obtained halide solid electrolyte is obviously improved and is 6-10 times higher than that of the electrolyte prepared by the traditional high-temperature solid phase method.

Specifically, the structural microstress of the halide solid electrolyte is expressed as a compressive force in the a, b direction and an tensile force in the c direction of the unit cell structure, and the unit cell structure is lattice-distorted by the structural microstress. After the lattice distortion occurs, the a axis and the b axis are shortened, the c axis is prolonged, the transmission of ions in the ab plane is accelerated, and therefore the ion conductivity is improved.

With Li₃YCl₆For example, the schematic crystal structure is shown in fig. 2, which is a hexagonal close-packed (hcp) arrangement, and the transport of lithium ions in the ab direction is octahedral-tetrahedral-octahedral (O-T-O), which is significantly slower than the transport of O-O in the c direction. The material lattice is distorted by the structural micro-stress, the a axis and the b axis are shortened, and the c axisProlonging and accelerating the diffusion of lithium ions on an ab plane, which is equivalent to improving the lithium ion speed-dependent step of Li-Y-Cl. Example of the invention nanosized Li₃YCl₆With standard Li₃YCl₆The bond length comparison between them is shown in table 1 below.

TABLE 1 nanosized Li₃YCl₆With standard Li₃YCl₆Bond length comparison between

Further, the particle size D50 of the halide solid electrolyte is 10-500 nm. The nanocrystallization of the halide solid electrolyte is a prerequisite for inducing structural microstress.

Further, the halide solid electrolyte is nano-sized Li₃YCl₆、Li₃ErCl₆、Li₃YbCl₆、Li₃DyCl₆、Li₃TmCl₆. In a specific embodiment of the invention, nanosized Li₃YCl₆The ionic conductivity of the material can reach as high as 0.35mScm^-1Nano-sized Li₃ErCl₆The ionic conductivity of the material can reach as high as 0.47mScm^-1。

The embodiment of the invention also provides a preparation method of the halide solid electrolyte, which is prepared by adopting a liquid phase synthesis method and comprises the following steps:

MX is dissolved in polar solvent containing hydrolysis inhibitor₃And mixing and reacting with LiX, and pyrolyzing the obtained reaction product at 450-600 ℃ to obtain the halide solid electrolyte.

Due to the easy hydrolysis characteristic of halide precursors, the synthesis of halide materials is mainly based on high-energy ball milling and solid-phase high-temperature sintering at present. However, the solid electrolyte particles prepared by the traditional preparation method are micron-sized, and cannot induce structural micro-stress. The liquid phase synthesis method provided by the invention can synthesize the nano-scale halide solid electrolyte in a liquid phase. In addition, the nano-scale solid electrolyte material can improve the solid-solid interface contact between the nano-scale solid electrolyte material and the anode and cathode materials, and is beneficial to the energy exertion of the solid battery.

Wherein the hydrolysis inhibitor is NH₄X and X are halogen. May be in particular NH₄F、NH₄Cl、NH₄Br、NH₄And (I) one or more of. The polar solvent is water or ethanol, or a mixture of water and ethanol.

MX₃May be YX₃、ErX₃、ScX₃And one or more of rare earth metal halides.

The LiX can be one or more of LiCl, LiBr, LiI and LiF.

Preferably, NH₄X、MX₃And the molar ratio of LiX is 3:1: 3.

Further, after the mixing reaction, the reaction system is dried in vacuum at 80 +/-5 ℃ to remove water, so as to obtain the reaction product. The reaction product is in powder form and contains (NH) as the component₄)₃MX_3+aComplexes of (1 ≦ a ≦ 3) with LiX (e.g., (NH)₄)₃YCl₆And LiCl). Transferring the electrolyte to an inert atmosphere for pyrolysis/sintering, thereby cracking the hydrolysis inhibitor to obtain the halide solid electrolyte.

The pyrolysis temperature is more critical, influences the ionic conductivity of the final product, and is preferably 450-600 ℃, and more preferably 500 ℃.

The halide solid electrolyte prepared by the embodiment of the invention has the particle size D50 of 100-500 nm, more preferably 100-200 nm, the ionic conductivity is greatly improved, and the performances such as activation energy, an electrochemical window and the like are not influenced, so that the halide solid electrolyte can be widely applied to solid secondary batteries. Specifically, it can be applied to an electrolyte or electrode additive in a solid secondary battery.

Example 1

This example provides a halide solid electrolyte having the formula Li₃YCl₆The preparation method comprises the following steps:

3mol of NH₄Cl and 1mol YCl₃Dissolving in water, adding 3mol LiCl, mixing uniformly, removing water and drying at 80 ℃ in vacuum to obtain white powder, calcining the white powder in argon atmosphere (5 hours) at 450 ℃ to obtain nano Li₃YCl₆。

Example 2

3mol of NH₄Cl and 1mol YCl₃Dissolving in water, adding 3mol LiCl, mixing uniformly, removing water and drying at 80 ℃ in vacuum to obtain white powder, calcining the white powder in argon atmosphere (5 hours) at 500 ℃ to obtain nano Li₃YCl₆。

Example 3

3mol of NH₄Cl and 1mol YCl₃Dissolving in water, adding 3mol LiCl, mixing uniformly, removing water and drying at 80 ℃ in vacuum to obtain white powder, calcining the white powder in argon atmosphere (5 hours) at 550 ℃ to obtain nano Li₃YCl₆。

Example 4

This example provides a halide solid electrolyte having the formula Li₃ErCl₆The preparation method comprises the following steps:

3mol of NH₄Cl and 1mol of ErCl₃Dissolving in water, adding 3mol LiCl, mixing uniformly, removing water and drying at 80 ℃ in vacuum to obtain white powder, calcining the white powder in argon atmosphere (5 hours) at 500 ℃ to obtain nano Li₃ErCl₆。

Example 5

This example provides a halide solid electrolyte having the formula Li₃LaI₆The preparation method comprises the following steps:

3mol of NH₄I and 1mol of LaI₃Dissolving in water, adding 3mol of LiI, uniformly mixing, removing water and drying at the temperature of 80 ℃ in vacuum to obtain white powder, calcining the white powder in the atmosphere of argon (5 hours) at the calcining temperature of 500 ℃ to obtain nano Li₃LaI₆。

Comparative example 1

This comparative example provides a Li prepared by a conventional solid-phase sintering process₃YCl₆The preparation method comprises the following steps:

1mol of YCl₃And 3mol LiCl are directly sealed in a quartz tube in vacuum, and then are calcined in vacuum at 650 ℃ for 24 hours to obtain high-temperature solid-phase synthesized Li₃YCl₆And after fully grinding, the particle size is micron-sized.

Comparative example 2

This comparative example provides a Li prepared by a conventional solid-phase sintering process₃ErCl₆The preparation method comprises the following steps:

1mol of ErCl₃And 3mol LiCl are directly sealed in a quartz tube in vacuum, and then are calcined in vacuum at 650 ℃ for 24 hours to obtain high-temperature solid-phase synthesized Li₃ErCl₆The particle size is micron-sized.

Comparative example 3

This comparative example provides a halide solid electrolyte of the formula Li₃YCl₆The preparation method comprises the following steps:

3mol of NH₄Cl and 1mol YCl₃Dissolving in water, adding 3mol LiCl, mixing uniformly, removing water and drying at 80 ℃ in vacuum to obtain white powder, calcining the white powder in argon atmosphere (5 hours) at 350 ℃ to obtain nano Li₃YCl₆。

Comparative example 4

3mol of NH₄Cl and 1mol YCl₃Dissolving in water, adding 3mol LiCl, mixing uniformly, removing water and drying at 80 ℃ in vacuum to obtain white powder, calcining the white powder in argon atmosphere (5 hours) at 400 ℃ to obtain nano Li₃YCl₆。

Performance testing

The solid electrolytes of the respective examples and comparative examples were subjected to performance tests, and the results are shown in table 2.

Table 2 results of performance test of each solid electrolyte

Note: n/a indicates that there is no XRD peak, so the stress level and grain size cannot be calculated.

As can be seen from table 2, the halide solid electrolyte provided in the embodiments of the present invention has excellent room temperature ion conductivity, activation energy, and electrochemical window, and can be applied to a solid secondary battery.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A halide solid electrolyte characterized by having the formulaLi₃MX₆M is at least one of rare earth elements, and X is at least one of F, Cl, Br and I; the halide solid electrolyte has a structural microstress of 0.001 to 0.01.

2. The halide solid state electrolyte of claim 1, wherein the structural microstress of the halide solid state electrolyte is manifested by compressive forces in the a, b and tensile forces in the c direction of the unit cell structure, the unit cell structure being lattice distorted by the structural microstress.

3. A halide solid electrolyte according to claim 1 or 2, wherein the anion arrangement of the halide solid electrolyte is hexagonal close-packed or tetragonal close-packed.

4. The halide solid electrolyte according to claim 1 or 2, wherein the particle size D50 of the halide solid electrolyte is 10 to 500 nm.

5. The halide solid state electrolyte of claim 4, wherein the halide solid state electrolyte is Li₃YCl₆、Li₃ErCl₆、Li₃YbCl₆、Li₃DyCl₆、Li₃TmCl₆。

6. The method for producing a halide solid electrolyte according to any one of claims 1 to 5, which comprises a liquid phase synthesis method comprising:

7. The preparation method according to claim 6, wherein after the mixing reaction, the reaction system is dried under vacuum at 80 ± 5 ℃ to remove water, thereby obtaining the reaction product.

8. The method of claim 6 or 7, wherein the hydrolysis inhibitor is NH₄X and X are halogen;

preferably, NH₄X、MX₃And the molar ratio of LiX is 3:1: 3.

9. The method of claim 6 or 7, wherein the polar solvent is water and/or ethanol.

10. Use of the halide solid electrolyte according to any one of claims 1 to 5 as an electrolyte or electrode additive in a solid secondary battery.