WO2022021146A1 - Solid electrolyte, electrochemical device, and electronic device - Google Patents

Abstract

Embodiments of the present application provide a solid electrolyte, an electrochemical device, and an electronic device. The solid electrolyte comprises a material of the formula Li_3+3xAs_1-xS_3-yO_y, wherein 0<x<1, and 0<y<3. The solid electrolyte provided by the present application has dual advantages of oxides and sulfides, and has good structural stability and high ionic conductivity.

Description

Solid State Electrolytes, Electrochemical Devices and Electronic Devices technical field

The present application relates to the technical field of electrochemistry, in particular to solid electrolytes, electrochemical devices and electronic devices.

Background technique

With the increasing volumetric energy density of electrochemical devices, traditional electrochemical devices (eg, lithium-ion batteries) using organic electrolytes face serious safety hazards. All-solid-state batteries assembled with solid-state electrolytes have excellent intrinsic safety, providing a feasible solution for improving the safety of electrochemical devices.

Solid-state batteries use solid electrolytes with high ionic conductivity for lithium ion conduction, which can eliminate the safety hazards of organic electrolytes from the root. So far, many types of solid electrolytes have been reported, among which oxide and sulfide inorganic ceramic materials have been studied relatively more. Oxide solid electrolytes have good chemical stability, wide electrochemical window, and large Young's modulus, which can effectively resist lithium dendrites, but their ionic conductivity is low at room temperature. Sulfide solid electrolytes have high ionic conductivity comparable to organic electrolytes. However, sulfides are generally very sensitive to moisture in the environment and have poor chemical stability in ordinary environments. In addition, sulfides have a narrow electrochemical window, relatively poor stability to lithium, and are easily oxidized when in contact with oxide cathode materials, resulting in large interfacial impedance.

Therefore, it is desirable to provide a solid electrolyte material that combines the advantages of oxide and sulfide solid electrolytes, has good chemical stability, and maintains high ionic conductivity.

SUMMARY OF THE INVENTION

The embodiments of the present application provide a solid electrolyte, which has the dual advantages of oxides and sulfides, and has both good structural stability and high ionic conductivity.

The present application provides a solid state electrolyte comprising a material with the chemical formula Li _3+3x As _1-x S _3-y O _y , wherein 0<x<1, 0<y<3.

In the above solid electrolyte, wherein, the Li _3+3x As _1-x S _3-y O _y contains two anions of S ^2- and O ^2- .

In the above solid electrolyte, wherein, 0.5≤x<1, 1≤y≤2.

In the above solid electrolyte, x is 0.5 and y is 1 or 2.

In the above solid electrolyte, the unit cell size of the Li _3+3x As _1-x S _3-y O _y is

In the above solid electrolyte, the unit cell size of the Li _3+3x As _1-x S _3-y O _y is

In the above solid electrolyte, the unit cell size of the Li _3+3x As _1-x S _3-y O _y is

In the above solid electrolyte, at least one of the following conditions is satisfied: the solid electrolyte has electronic insulation and ion conductivity; the lithium ion migration barrier in the solid electrolyte is less than or equal to 0.3 eV; the Li ₃₊ One As atom in _3x As _1-x S _3-y O _y is coordinated with two S atoms and one O atom to form a triangular pyramid structure; in the Li _3+3x As _1-x S _3-y O _y One As atom is coordinated with one S atom and two O atoms to form a triangular pyramid structure.

The present application also provides an electrochemical device comprising the above-mentioned solid electrolyte.

The present application also provides an electronic device comprising the above electrochemical device.

The solid electrolyte provided by the present application has the dual advantages of oxides and sulfides, and has both good structural stability and high ionic conductivity. In addition, the solid electrolyte also contains As element, which can coordinate with S and O to form a stable chemical structure, which further enhances the structural stability of the solid electrolyte relative to the chemical structure formed by other elements (for example, Al) and S and O. , while still having high ionic conductivity.

Description of drawings

1A is a schematic diagram of the crystal structure of the solid electrolyte material Li _4.5 As _0.5 S ₂ O according to an embodiment of the present application, and FIG. 1B is a schematic diagram of the crystal structure of the solid electrolyte material Li _4.5 As _0.5 SO ₂ according to an embodiment of the present application.

2A is an X-ray diffraction pattern of the solid electrolyte material Li _4.5 As _0.5 S ₂ O according to an embodiment of the present application, and FIG. 2B is an X-ray diffraction diagram of the solid electrolyte material Li _4.5 As _0.5 SO ₂ according to an embodiment of the present application Spectrum.

3A is a graph showing the overall density of states of the solid electrolyte material Li _4.5 As _0.5 S ₂ O according to an embodiment of the present application, and FIG. 3B is a graph showing the overall state of the solid electrolyte material Li _4.5 As _0.5 SO ₂ according to an embodiment of the present application. Density graph.

FIG. 4A is a graph of the lithium ion migration barrier of the solid electrolyte material Li _4.5 As _0.5 S ₂ O according to an embodiment of the present application, and FIG. 4B is a graph of the lithium ion migration barrier of the solid electrolyte material Li _4.5 As _0.5 SO ₂ according to an embodiment of the present application. Graph of the lithium ion migration barrier.

detailed description

The following examples may enable those skilled in the art to more fully understand the present application, but do not limit the present application in any way.

In general, the structure of fast ion conductor materials can be regarded as composed of stable anion and cation frameworks and freely mobile ions (such as Li ⁺ ). In common oxide and sulfide-type Li ⁺ fast ion conductors, since the ionic radius of S ^2- is much larger than that of O ^2- , the framework of sulfide is more "loose", and the space for Li ⁺ movement between frameworks is more "loose". At the same time, due to the smaller binding force of the nucleus of S ^2- to the surrounding electron cloud, the electron cloud is more easily polarized, and the charge distribution is more easily deformed during the movement of Li ⁺ , which can reduce the force on Li ⁺ , so the Li ⁺ conductivity of sulfides is generally higher than that of oxides with similar structures. Conversely, for oxides, O ^2- is more electronegative than S ^2- , and the interaction of Li ⁺ with framework O ^2- is stronger, making the framework structure of oxides more stable. In addition, O ^2- is less susceptible to oxidation than S ^2- , and at the same time makes the reduction barrier of framework cations higher, therefore, oxides generally exhibit better chemical and electrochemical stability than sulfides .

In this application, a composite anion strategy is adopted, namely introducing S ^2- in oxides to expand the ion diffusion channel or introducing O ^2- in sulfides to improve stability to develop fast ion conductors with both advantages. The present application provides an oxysulfide solid state electrolyte material Li _3+3x As _1-x S _3-y O _y by using O ^2- and S ^2- together as framework anions, wherein 0<x<1, 0<y<3, the solid electrolyte material combines the advantages of both oxides and sulfides, has both high ionic conductivity and good chemical stability, and can be used as a solid electrolyte material in electrochemical devices.

In addition, the solid electrolyte material also contains As element. As can coordinate with S and O to form a stable chemical structure. Compared with the chemical structure formed by other elements (for example, Al) and S and O, As can further enhance the solid electrolyte. Structural stability while still having high ionic conductivity.

In some embodiments, Li _3+3x As _1-x S _3-y O _y contains both S ^2- and O ^2- anions. Among them, the Li-O bond length is short, the bond energy is large, and the bond is tight, which is conducive to improving the structural stability of the solid electrolyte, while the Li-S bond length is long, the bond energy is small, and the binding of lithium ions is weak. It is conducive to the transport of lithium ions. Therefore, the solid electrolyte Li _3+3x As _1-x S _3-y O _y of the present application combines the advantages of both oxides and sulfides, and has both good stability and high ionic conductivity, Thus, it can be used for a high-safety solid-state battery.

In some embodiments, x and y in Li _3+3x As _1-x S _3-y O _y satisfy 0.5≤x<1, 1≤y≤2. Generally, x and y in solid-state electrolyte Li _3+3x As _1-x S _3-y O _y can fluctuate arbitrarily within the range satisfying 0<x<1, 0<y<3, that is, atoms of Li element The fraction can be in the range of 3 to 6, the atomic fraction of the As element can be in the range of 0 to 1, the atomic fraction of the S element can be in the range of 0 to 3, and the atomic fraction of the O element can be in the range of 0 to 3. Scope. In particular, when both x and y are 0, the prototype of this material is Li ₃ AsS ₃ , which crystallizes in the Pna2 ₁ space group in the orthorhombic system, with all Li, As and S atoms occupying 4a Wyckoff sites, A three-dimensional network structure is formed. However, as mentioned above, the chemical and electrochemical stability of sulfides is poor, so this material is not within the scope of this application. Li ₃ AsS _{3 -y} O _y formed by introducing O ^2- into Li ₃ AsS 3 can significantly enhance the stability of the material, and the Li ₃ AsS _3-y O _y material can generally maintain the lattice structure of its prototype and is still crystallized in The Pna2 ₁ space group in the orthorhombic system forms a three-dimensional network structure with all atoms still occupying the 4a Wyckoff position. In order to further improve the Li ⁺ conduction performance, Li ⁺ can be used to replace part of As ³⁺ in Li ₃ AsS _3-y O _y to form a composite anion solid electrolyte Li _3+3x As _1-x S _3-y O _y . With more interstitial Li ⁺ , its structure will be transformed from orthorhombic to triclinic, with all atoms occupying 1a Wyckoff positions. In some embodiments, the atomic fraction of Li element in Li _3+3x As _1-x S _3-y O _y may be in the range of 4.5 to 6, the atomic fraction of As element may be in the range of 0.5 to 1, S The atomic fraction of the element can range from 1 to 2, and the atomic fraction of the O element can range from 1 to 2. The band gaps of different materials differ by no more than 1eV, and the Li ⁺ migration barriers differ by no more than 0.3eV. In some embodiments, x=0.5, y=1 or 2, and the solid electrolytes are Li _4.5 As _0.5 S ₂ O and Li _4.5 As _0.5 SO ₂ . The following description mainly takes Li _4.5 As _0.5 S ₂ O and Li _4.5 As _0.5 SO ₂ as examples to better understand the present application, but is not intended to limit the present application.

In some embodiments, the unit cell size of Li _3+3x As _1-x S _3-y O _y (0<x<1, 0<y<3) is

Figure 1A is a schematic diagram of the crystal structure of Li _4.5 As _0.5 S ₂ O, and its unit cell size is

The framework cation As of Li _4.5 As _0.5 S ₂ O coordinates with two S atoms and one O atom to form a [AsS ₂ O] ^3- triangular pyramid with an As-S bond length of

range, the As-O bond length is

range. Figure 1B is a schematic _diagram of the crystal structure of _{Li4.5As0.5SO2} , _whose unit cell size is

The framework cation As of Li _4.5 As _0.5 SO ₂ coordinates with one S atom and two O atoms to form a [AsSO ₂ ] ^3- triangular pyramid with an As-S bond length of

range, the As-O bond length is

range. Similarly, for other atomic ratios of Li _3+3x As _1-x S _3-y O _y (0<x<1, 0<y<3), by using As element, As coordinates with S and O to form a triangle Compared with other structures (eg, tetrahedral structure, etc.), the triangular pyramid structure greatly enhances the structural stability of solid electrolytes. In addition, Li _3+3x As _1-x S _3-y O _y (0<x<1, 0<y<3) has the dual advantages of sulfide and oxide.

Figure 2A and Figure 2B are the X-ray diffraction patterns of Li _4.5 As _0.5 S ₂ O and Li _4.5 As _0.5 SO ₂ , respectively. Since S ^2- and O ^2- have different X-ray scattering, it can be seen that these two materials have different X-ray diffraction patterns. X-ray diffraction patterns are different.

Electronic insulating properties and ionic conductivity are important for materials that can act as solid-state electrolytes. The Li _3+3x As _1-x S _3-y O _y (0<x<1, 0<y<3) provided by the present application has electronic insulation and ion conductivity. In this application, the total density of states of two materials, Li _4.5 As _0.5 S ₂ O and Li _4.5 As _0.5 SO ₂ , was calculated using the PBE exchange correlation functional in the VASP software (Vienna Ab-initio Simulation Package). As shown in Fig. 3A and Fig. 3B, the PBE band gaps of Li _4.5 As _0.5 S ₂ O and Li _4.5 As _0.5 SO ₂ are about 2.76 and 3.06 eV, respectively, and the wide band gaps indicate that the bonding state energy is low, that is, the oxidation potential is high. , which means that the electrochemical stability will be better. In addition, it should be pointed out that the PBE exchange-correlation functional will seriously underestimate the optical band gap of the material, for example, the experimental band gap of Li ₂ In ₂ SiS ₆ reported by Yin et al. in 2012 is 3.61 eV (Yin et al., " Synthesis, Structure, and Properties of Li ₂ In ₂ MQ ₆ (M=Si,Ge; Q=S,Se): A New Series of IR Nonlinear Optical Materials", 2012, Inorganic Chemistry, Volume 51, Pages 5839-5843) , but the _{PBE bandgap} of _Li2In2SiS6 is only about 2.08 eV. From this, it can be inferred that the actual band gap of Li _4.5 As _0.5 S ₂ O and Li _4.5 As _0.5 SO ₂ will be higher, and the electrochemical stability will be better.

Li-ion transport properties are the most critical features of solid-state electrolytes. The lithium ion migration barrier in Li _3+3x As _1-x S _3-y O _y (0<x<1, 0<y<3) provided by the present application is less than or equal to 0.3 eV. In this application, first-principles calculations are used to calculate the Li ⁺ migration barriers of two materials, Li _4.5 As _0.5 S ₂ O and Li _4.5 As _0.5 SO ₂ . Through transition state calculations on the possible migration paths of Li ⁺ , the barrier curves corresponding to the transition mechanism with the lowest activation energy are drawn, as shown in Fig. 4A and Fig. 4B. Specifically, the Li ⁺ in the interstitial site pushes away the lattice Li ⁺ to reach the next interstitial site, while occupying the lattice site by itself. Through this "push-filler" method, the rapid migration of Li ⁺ can be achieved. The migration barriers of Li _4.5 As _0.5 S ₂ O and Li _4.5 As _0.5 SO ₂ are only about 0.04 eV, indicating that these two materials are very good Li ⁺ fast conductors. As a comparison, the Li ⁺ migration barrier of Li ₁₀ GeP ₂ S ₁₂ , which is regarded as a benchmark material in sulfide solid-state electrolytes, is about 0.2 eV. It can be seen that Li _3+3x As _1-x S _3-y O _y (0<x<1, 0<y<3) series of materials have good application prospects as solid electrolytes.

Table 1 below shows the PBE band gaps and lithium ion migration barriers of various solid electrolytes of Examples 1-5 and Comparative Examples 1-3.

Table 1

	solid electrolyte	PBE band gap	Lithium Ion Migration Barrier
Example 1	Li 4.5 As 0.5 S 2 O	2.76eV	0.04eV
Example 2	Li 5.25 As 0.25 S 2 O	2.82eV	0.02eV
Example 3	Li 4.5 As 0.5 SO 2	3.06eV	0.04eV
Example 4	Li 3.75 As 0.75 S 2 O	2.45eV	0.15eV
Example 5	Li 3.75 As 0.75 SO 2	2.96eV	0.19eV
Comparative Example 1	Li 4.5 As 0.5 S 3	1.26eV	0.04eV
Comparative Example 2	Li 4.5 As 0.5 O 3	3.48eV	0.21eV
Comparative Example 3	Li 3.75 As 0.75 O 3	3.05eV	0.30eV

Comparing Examples 1 and 3 and Comparative Examples 1 to 2, it can be seen that by containing two anions of O ^2- and S ^2- in the solid electrolyte, the solid electrolyte having only one of O ^2- and S ^2- , has both a wide PBE band gap and a low lithium ion migration barrier. The wide PBE band gap indicates that the solid electrolyte has good electrochemical stability, and the low lithium ion migration barrier indicates that the solid electrolyte is very suitable for for transporting lithium ions. The same results were obtained by comparing Examples 4 to 5 and Comparative Example 3. In addition, by comparing Examples 1 to 2 and 4, it can be seen that with the increase of lithium element content, the PBE of the obtained solid electrolyte is wider, and the lithium ion migration barrier is smaller.

The safety of electrochemical devices is receiving unprecedented attention. Solid electrolytes replace flammable organic electrolytes, which can completely avoid the safety risks caused by thermal runaway in principle. It can be seen from the above description that the oxysulfide solid state electrolyte provided by the present application has both the advantages of conventional oxide and sulfide solid state electrolytes, and has great application potential.

The Li _3+3x As _1-x S _3-y O _y (0<x<1, 0<y<3) materials disclosed in the present application can be prepared by various conventional methods. For example, Li ₂ O, Li ₂ S, As ₂ O ₃ and As ₂ S ₃ can be used as source materials, mixed uniformly according to the required molar ratio, ball-milled into a uniform powder under the protection of an inert atmosphere, and compressed into a tablet. Then, sintering is carried out in an inert atmosphere or vacuum by a high-temperature solid-phase method (eg, 200°C to 700°C). It can be understood that other preparation methods, such as melt quenching method, can also be selected. Of course, an appropriate target material can also be selected, the solid electrolyte material can be prepared by a physical or chemical vapor deposition method, and the desired element molar ratio can be obtained by adjusting the relevant process parameters. Since these raw materials and preparation processes are well known to those skilled in the art, they will not be repeated here.

Some embodiments of the present application also provide an electrochemical device, which may include, but is not limited to, a lithium-ion battery or a lithium metal battery. In this electrochemical device, the previously described Li _3+3x As _1-x S _3-y O _y (0<x<1, 0<y<3) materials can be used, since the structure of these electrochemical devices is also the It is well known to those skilled in the art and will not be repeated here.

Some embodiments of the present application also provide electronic devices including the above electrochemical devices. The electronic device of the embodiments of the present application is not particularly limited, and may be used in any electronic device known in the prior art. In some embodiments, electronic devices may include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large storage batteries for household use and lithium-ion capacitors, etc.

The solid electrolyte provided by the present application has the dual advantages of sulfide and oxide, and has both electronic insulation and high lithium ion conductivity. In addition, by using As element, As can coordinate with S and O to form a stable triangular pyramid structure, compared with the chemical structure (for example, tetrahedron, etc.) formed by other elements (for example, Al) and S and O, the solid electrolyte More structural stability while still having high ionic conductivity.

The above description is only a preferred embodiment of the present application and an illustration of the applied technical principles. Those skilled in the art should understand that the scope of disclosure involved in this application is not limited to the technical solutions formed by the specific combination of the above technical features, but also covers other technical solutions formed by any combination of the above technical features or their equivalents. Technical solutions. For example, a technical solution is formed by replacing the above features with the technical features disclosed in the present application with similar functions.

Claims (10)

1. A solid electrolyte comprising a material of the formula Li _3+3x As _1-x S _3-y O _y , wherein 0<x<1 and 0<y<3.
2. The solid electrolyte according to claim 1, wherein the Li _3+3x As _1-x S _3-y O _y contains two anions of S ^2- and O ^2- .
3. The solid electrolyte according to claim 1, wherein 0.5≤x<1, 1≤y≤2.
4. The solid electrolyte according to claim 1, wherein x is 0.5 and y is 1 or 2.
5. The solid electrolyte according to claim 1, wherein the unit cell size of the Li _3+3x As _1-x S _3-y O _y is

   
6. The solid electrolyte according to claim 1, wherein the unit cell size of the Li _3+3x As _1-x S _3-y O _y is

   
7. The solid electrolyte according to claim 1, wherein the unit cell size of the Li _3+3x As _1-x S _3-y O _y is

   
8. The solid electrolyte according to claim 1, wherein at least one of the following conditions is satisfied:

   The solid electrolyte has electronic insulation and ionic conductivity;

   The lithium ion migration barrier in the solid electrolyte is less than or equal to 0.3 eV;

   One As atom in the Li _3+3x As _1-x S _3-y O _y coordinates with two S atoms and one O atom to form a triangular pyramid structure;

   One As atom in the Li _3+3x As _1-x S _3-y O _y is coordinated with one S atom and two O atoms to form a triangular pyramid structure.
9. An electrochemical device comprising the solid state electrolyte according to any one of claims 1 to 8.
10. An electronic device comprising the electrochemical device of claim 9 .

Images